Stressed rivers project
- Environmental flow study
Glenelg River System
Stressed rivers project Environmental flows study
Glenelg River System
April 2003
Sinclair Knight Merz Pty Limited
ACN 001 024 095
ABN 37 001 024 095
590 Orrong Road
Armadale VIC 3143
PO Box 2500
Malvern VIC 3144
Australia
Telephone: +61 3 9248 3100
Facsimile: +61 3 9248 3364
COPYRIGHT: The concepts and information contained in
this document are the property of Glenelg Hopkins
Catchment Management Authority. Use or copying of this
document in whole or in part without the written permission
of Glenelg Hopkins Catchment Management Authority
constitutes an infringement of copyright.
Contents
PART A
1. Introduction...............................................................................................1
1.1
Project scope ......................................................................................1
2. Catchment description...........................................................................2
2.1
2.2
2.3
2.4
Physiography ......................................................................................2
Landuse ..............................................................................................6
Hydrology ............................................................................................7
Water quality .....................................................................................10
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.5
2.6
Salinity.................................................................................... 10
Dissolved oxygen..................................................................... 11
Nutrients ................................................................................. 11
pH........................................................................................... 11
Turbidity.................................................................................. 11
Biota ..................................................................................................12
Summary...........................................................................................14
3. Key issues .............................................................................................. 16
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Potential environmental issues ........................................................16
Sand slugs ........................................................................................19
Water quality .....................................................................................20
Flow regulation..................................................................................22
Channel condition .............................................................................24
Current flora and fauna values of the Glenelg River system ...........25
The heritage reach............................................................................26
4. Methods................................................................................................... 28
5. Site descriptions................................................................................... 31
6. Objectives ............................................................................................... 37
6.1
6.2
6.3
Policy and strategy objectives ..........................................................37
Catchment objectives .......................................................................38
Environmental objectives..................................................................38
7. Discussion.............................................................................................. 40
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Seasonal timing of releases .............................................................40
Periods of cease to flow ...................................................................41
Baseflows .........................................................................................41
Freshes during periods of cease to flow/low flow ............................41
Spring freshes...................................................................................42
Flow variability...................................................................................42
High flows .........................................................................................42
8. Recommendations ............................................................................... 43
8.1
Flow Recommendations ...................................................................44
8.1.1
8.1.2
8.1.3
8.2
Reach 1 – Rocklands Reservoir – Chetwynd River..................... 44
Reach 2 – Chetwynd River to Wannon River ............................. 52
Reach 3 – Wannon River to Tidal Extent ................................... 61
Supporting recommendations ..........................................................67
9. References ............................................................................................. 71
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE i
PART B
1. Introduction...............................................................................................1
1.1
1.2
Project scope ......................................................................................1
Report structure..................................................................................2
2. Catchment description...........................................................................3
2.1
2.2
2.3
2.4
Physiography ......................................................................................3
Landuse ..............................................................................................3
Hydrology ............................................................................................7
Water quality .....................................................................................10
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.5
2.6
Salinity.................................................................................... 10
Dissolved oxygen..................................................................... 11
Nutrients ................................................................................. 11
pH........................................................................................... 11
Turbidity.................................................................................. 12
Biota ..................................................................................................12
Summary...........................................................................................14
3. Key issues .............................................................................................. 16
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Potential environmental issues ........................................................16
Sand slugs ........................................................................................19
Water quality .....................................................................................20
Regulation .........................................................................................22
Channel condition .............................................................................23
Current flora and fauna values of the Glenelg River system ...........24
The heritage reach............................................................................25
4. Environmental objectives................................................................... 27
4.1
4.2
Preliminary umbrella objectives........................................................27
Preliminary specific objectives .........................................................27
5. Outcomes................................................................................................ 28
5.1
Assessment framework....................................................................28
5.1.1
5.1.2
5.1.3
5.2
Technical panel........................................................................ 28
Study reaches ......................................................................... 28
Use of existing data and information.......................................... 30
Reporting...........................................................................................30
6. References ............................................................................................. 31
Appendix A
A.1
A.2
A.3
A.4
A.5
A.6
A.7
Appendix B
B.1
B.2
B.3
B.4
B.5
Hydrology.......................................................................... 34
Streamflows......................................................................................34
Licensed water use...........................................................................36
System operation..............................................................................37
Summary...........................................................................................38
Flow plots ..........................................................................................39
Flow duration curves.........................................................................42
Rocklands Reservoir discharge .......................................................54
Geomorphology............................................................... 55
Introduction .......................................................................................55
Stream network.................................................................................55
Hydrology ..........................................................................................56
Landuse ............................................................................................56
Sand slugs ........................................................................................57
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE ii
B.6
Summary...........................................................................................58
Appendix C
C.1
C.2
C.3
C.4
C.5
C.6
C.7
Appendix D
D.1
D.2
Biota
77
Condition of instream and riparian habitat........................................77
Fish, decapod crustacea and molluscs............................................77
D.2.1
D.2.2
D.2.3
D.3
D.4
D.5
D.6
D.7
Water quality..................................................................... 59
Salinity...............................................................................................60
Nutrients ............................................................................................61
pH......................................................................................................62
Dissolved oxygen..............................................................................63
Turbidity.............................................................................................63
Summary...........................................................................................64
Water quality plots indicating guideline values ................................65
Fish ........................................................................................ 77
Decapod Crustacea ................................................................. 82
Macroinvertebrates .................................................................. 82
Birds ..................................................................................................83
Amphibians and reptiles ...................................................................83
Other vertebrates ..............................................................................84
Instream and riparian flora................................................................85
The Glenelg Heritage River and Lower Glenelg National Park. ......86
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE iii
Document History and Status
Issue
Rev.
Issued To
Qty
Date
Reviewed
Approved
Draft
1
Project Team
1
20/9/01
P. Close
M. Shirley
Draft
2
Alex Marshall GHCMA
1
24/9/01
M. Shirley
M. Shirley
Draft
3
Tranter
1
28/4/02
R Nathan
R Nathan
Draft
4
Tranter
1
16/10/02
S Hannon
M Shirley
Final
4
Melanie
GHCMA
Melanie
GHCMA
Melanie
GHCMA
Tranter
1
23/1/03
R. Nathan
R. Nathan
Printed:
Last Saved:
File Name:
7 May, 2003
7 May, 2003
Project Manager:
Name of Organisation:
Name of Project:
Name of Document:
Document Version:
Project Number:
Michael Shirley
Glenelg Hopkins Catchment Management Authority
Wimmera, Avoca and Glenelg Rivers Environmental Flows
Glenelg River – Final Report
Final
WC01432
\\SKMMELB8\VOL1\DATA\PROJECT\Wcms\Wc01432\500_Analysis_Reporting\Reporting\Released
Reports\Glenelg\R04_Mjs_Glenelg_Final.Doc
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE iv
1.
Introduction
There is an increasing awareness in water resource management of the need to
incorporate the environmental requirements of ecosystems into the water resource
planning process. Alteration to flow regimes can have significant impacts on riverine
aquatic ecosystems. Under the 1994 Council of Australian Governments (COAG)
agreement, the environment is recognised as a legitimate water user and
environmental water requirements must be assessed and provided. As a result the
determination of the water regime required to sustain the physical and ecological
processes of aquatic ecosystems is a key process.
The Victorian Water for the Environment Program, implemented by Department of
Sustainability and Environment, aims to implement measures that provide water for
environmental needs. The objective of the program is to increase environmental flows
to maintain and, where possible, restore the environmental values of rivers and
wetlands, whilst recognising existing entitlements.
The Glenelg River was examined by the Scientific Panel as part of the Stressed Rivers
assessment of priority rivers for the development of restoration plans. The Stressed
Rivers Scientific Panel noted that the effect of Rocklands Reservoir was likely to have
caused a decline in the health of the aquatic ecosystems of the Glenelg River. It was
not specified as a high priority river because at the time it was considered that the
system, with Rocklands Reservoir in its current operational condition, did not include
capacity to deliver the water required for further environmental enhancement (Stressed
Rivers Scientific Panel, 1998). Recent developments to increase the extent of the
Wimmera-Mallee Pipeline mean that there may be additional water made available to
meet the environmental needs of the Glenelg River.
1.1 Project scope
A range of flow related issues have prompted this study to determine environmental
water requirements of the Glenelg River.
The current project examines the environmental water requirements of the surface
water systems of the main stem of the Glenelg River, excluding the Wannon River and
the estuarine ecosystem.
The aim of this project is to provide a scientific basis for the implementation of
provisions for water dependent ecosystems, and in doing so, meet the objective of the
State's Water for the Environment Program and objectives of the Glenelg Hopkins
Catchment Management Authority. The staff of the Catchment Management
Authority and the members of the Project Group made a significant contribution to the
project and the outcomes, and we thank them for this input.
The project includes a clear scientific process for the determination of environmental
water requirements and recommendations to maximise the implementation of these
provisions.
This report is the final report of the project. It includes a synopsis of the key issues in
the Glenelg River system, environmental flow objectives, detailed environmental flow
recommendations and key supporting recommendations. The Appendices of the
report provide the detailed assessment of the flow related issues for the system.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 1
2.
Catchment description
The study area specified for this report is the main channel of the Glenelg River. No
tributaries are included in the study area.
2.1 Physiography
The Glenelg River rises in the Grampians and flows to the Southern Ocean (Figure 2-1
Glenelg River catchment). On leaving the Grampians the river flows along the
northern and then the western edge of the Dundas Tablelands, between Rocklands
Reservoir and Casterton. Near Casterton the Wannon River joins the Glenelg River
and from there the Glenelg River meanders across broad coastal plains towards
Dartmoor. Below Dartmoor the river follows a generally southerly course becoming
increasingly incised in limestone (Erskine 1994). At the confluence of Moleside
Creek the river turns west north west and runs parallel to the coast before flowing
south into South Australia, then back south south east to enter the sea at Nelson,
Victoria.
The catchment is approximately 120 km wide and 100 km from north to south,
covering a total area of 1,266,030 ha (Department of Water Resources Victoria 1989).
The topography of the catchment varies substantially from the rugged escarpments of
the Grampians in the northeast to the coastal plains in the southwest. The Victoria and
Serra Ranges of the Grampians drain into both the Glenelg and the Wannon Rivers;
the former drains the north and west of the catchment and the latter the east and south.
The central portion of the catchment is composed of the deeply dissected Dundas and
Merino tablelands. Towards the southeast the tablelands drop down to the flat basal
plains around Hamilton. Near Nelson there is an estuarine lagoon at the mouth of the
Glenelg River and a line of calcareous sand dunes fringes the coastline. During low
flow conditions salt water penetrates upstream beyond the boundary of the Lower
Glenelg National Park. At over 70 km, the Glenelg estuary is one of the State’s
longest (Sherwood et al. 1998).
In 1986, the Department of Water Resources conducted a survey of the environmental
condition of Victorian streams. Within the Glenelg River catchment the condition or
health of 58 sites located on both the Glenelg River and its tributaries was described
using both biological and physical assessment criteria (Mitchell 1990). In general,
approximately 45% of the Glenelg River and 70% of tributaries within the catchment
were described as poor to very poor environmental condition. In 1994 seven of the
original 58 sites were resurveyed. While some sites had improved as a result of
exclusion of stock from riparian zones, stream condition was still described as
generally poor (Davidson et al. 1994).
Davidson et al. (1994) suggested that flow regulation, sedimentation, salinisation and
extensive snag removal were the main factors leading to poor channel condition. Our
field observations support those of Mitchell et al. (1996) that the riparian vegetation is
continuous to discontinuous along both banks of the river but is generally restricted to
the bankface and the immediate bank verge (Figure 2-2, Figure 2-3). The lower
section in the Lower Glenelg National Park is in good condition with excellent bank
and verge vegetation (Figure 2-6). The banks are generally stable with only isolated
examples of bank erosion (Figure 2-4). In some locations, bank instability is
associated with stock traffic.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 2
The main issue associated with physical condition of the Glenelg River is the high
sand load that occupies a large proportion of the channel (Figure 2-5). The sediment
has created a sandy bed and reduced the occurrence of deep holes (>2m) in sections of
the river. Areas of sediment build-up are most obvious are around Casterton and
Harrow.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 3
n
Figure 2-1 Glenelg River catchment.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Draft
PAGE 4
n
n
Figure 2-2 Glenelg River at Fulham Hole Streamside Reserve (note typical
riparian vegetation, consisting of patchy overstorey and little or no
understorey).
Figure 2-3 Glenelg River at Dartmoor.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 5
2.2 Landuse
The Department of Water Resources Victoria (1989) reports that European settlement
of the Glenelg catchment began in 1837. The merino wool industry was established
quickly and today wool is still the main product of the region with prime lamb
production also important. The beef industry is well established and a small amount
of dairying occurs in the catchment. Since 1837, two-thirds of the catchment has been
cleared for pasture to graze sheep and cattle and today only two main forested areas
remain. The northeast of the catchment is forested and includes the Grampians
National Park, as well as State Forest where a small amount of hardwood is logged. In
the west there is a mixture of native hardwood forests (the Glenelg National Park) and
intensive softwood plantations. In addition to the intensive forested areas there are
occasional extensive blue gum plantations found in the catchment (Department of
Water Resources Victoria 1989). Hamilton is the major urban centre within the
catchment, located in the southeast.
n
Figure 2-4 Glenelg River at Wannon River confluence (note erosion of left
bank).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 6
n
Figure 2-5 Sand slug in the Glenelg River downstream of Chetwynd River
confluence.
2.3 Hydrology
Rainfall varies seasonally and spatially within the catchment. While winter months
are wetter throughout the catchment, there is a gradual decline in mean annual rainfall
from the coast near Nelson (approximately 750 mm) to the centre of the catchment
(approximately 550 mm). In the northeast of the catchment, in the vicinity of the
Grampians, annual rainfall increases with elevation to more than 900 mm on the
Victoria Range. Rainfall is relatively reliable along the coast and in the higher parts of
the Grampians (Department of Water Resources Victoria, 1989).
Reflecting rainfall distribution, flows are strongly seasonal with 70% of average
annual flow in the Glenelg River above the Wannon River junction occurring in the
three months August to October. At Dartmoor (Station 238206), the residual mean
annual flow of the Glenelg River, post Rocklands Reservoir construction, is 639,000
ML. Although only 1.5 % of that total occurs in the months January to March, there
are reliable base flows rarely falling below 30 ML per day during this period
(Department of Water Resources Victoria 1989).
Wimmera Mallee Water (WMW) and Southern Rural Water Authority (SRW) both
have jurisdiction over water flow in the Glenelg River. The Glenelg River upstream
of Mooree Bridge is the responsibility of WMW, while downstream of Moree Bridge
is the responsibility of SRW.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 7
n
Figure 2-6 Lower Glenelg River
There are three notable water storages within the Glenelg River basin. These are
Konong Wootong Reservoir, Moora Moora Reservoir and Rocklands Reservoir.
Konong Wootong is a small reservoir constructed on Den Hills Creek, a tributary of
the Wannon River, to supply the townships of Casterton and Coleraine. The capacity
of this storage is 1,920 ML and diverts approximately 852 ML/year out of the system
(Ingeme 1996). Moora Moora Reservoir is located in the upper reaches of the Glenelg
River. The reservoir is a small, offstream storage with a capacity of only 6,300 ML
(Department of Water Resources Victoria 1989). Lake Bellfield diverts water from
the upper Wannon River. Rocklands Reservoir is the largest storage in the catchment
with a total capacity of 348,000 ML. The primary purpose of the storage is to provide
domestic and stock supply to the Wimmera Mallee Water channel system (Godoy
1996).
Rocklands Reservoir has a significant impact on the seasonal flow pattern downstream
of the reservoir, although the impact decreases with distance from the dam.
Rocklands has a storage capacity about three times its average annual inflow and has
spilled once every four years on average since construction. Downstream of the
Chetwynd River, flows are continuous due to natural inflow from the catchment
adding to the river flows. However, in December 2000, the Glenelg River ceased
flowing below Casterton (M. Tranter pers. comm.). Current releases from Rocklands
Reservoir do not appear to exert an influence below Casterton due to the limited
availability of water for release (Mitchell et al. 1996). Rather streamflow at Casterton
is influenced by inflow from other sources including tributaries and rainfall near
Casterton.
The Glenelg River, under natural conditions, commonly ceased to flow at Balmoral
over the three months February to April, sometimes for months longer (Godoy 1996).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 8
The deep pools through the river would have allowed the key biota to persist during
the cease to flow periods. However, the cease to flow does not occur within the
current flow regime, which is a summer autumn flow release. Under low flow
conditions transit times for releases from Rocklands Reservoir are approximately 7
days to Balmoral, 14 days to Fulham Bridge and 21 days to Harrow. According to
Mitchell et al. (1996) a 20-25 ML/day release at Rocklands delivers 10 ML/day at
Fulham Bridge and 2 ML/day at Harrow.
The total licensed volume for water extraction from the main channel of the Glenelg
River is 68.2 ML/year which is a very small proportion of licensed water entitlement
in the Glenelg River system. All licences on the Glenelg River extract upstream of the
Wannon River confluence (J Donovan, pers. comm.). An additional 878.6 ML/year is
licensed for extraction from the remainder of the catchment. Of the 68.2 ML/year
available for extraction from the Glenelg River, 66 ML/year is extracted through two
irrigation licences. These licences are generally used sometime between September
and February, although the specific timing of such use is dependent on the crops being
irrigated. The remaining 2.2 ML/year is a dairy licence, which is used throughout the
year for dairy washing and stock watering.
Further information on the licensed entitlement within the Glenelg River system is
presented in Appendix A. The licensed volume is distinct from the total volume that
is actually extracted each year due to a number of factors including the availability of
flow and water quality.
The Rocklands Outlet channel passes from Rocklands Reservoir in the Glenelg River
Basin to Toolondo Reservoir in the Wimmera Catchment. Water is also lost from the
Glenelg River due to evaporation at Frasers Swamp and tributary plugs restrict the rate
of inflow into the Glenelg River mainstem. In addition, losses due to seepage from the
river can lead to lower streamflows. To reduce losses along the river to Fulham
Bridge, Wimmera Mallee Water can release water from the 5 and 12 Mile channel
outfalls, although this is generally only done when there are concurrent transfers to
Toolondo Reservoir. There is some leakage from the Rocklands Outlet channel that
reaches the Glenelg River and helps offset some of the losses in this reach.
A compensation flow from Rocklands Reservoir down the Glenelg River is currently
fixed at 3,300 ML/year. This was previously a sliding scale between 2,500 ML and
3,700 ML/year, but at the request of the Glenelg Hopkins CMA, a new formula has
been developed being the average of the historic releases, (3,300 ML/year; Table 2-1)
(R Leeson, pers. comm.). Wimmera Mallee Water is required to maintain a reserve
volume in Rocklands to guarantee this compensation flow. The compensation flows,
released in summer and autumn, are aimed to maintain a target flow of 5-10 ML/d at
Fulham Bridge and 1-2 ML/day at Harrow. Commencement of compensation flows is
timed to take advantage of the wet river channel and thus prevent the flow from
ceasing altogether (Godoy 1996) and the releases to the river are based on the flow
measured at Fulham Bridge (Gauge 238224). The compensation flows are generally
released between mid November to late April, depending on the weather.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 9
n
Table 2-1 Summary of environmental flow releases for the Glenelg River
(Source Wimmera Mallee Water)
Season
Compensation Flow
ML
Environmental Flow
ML
Total Release
ML
1996-97
3,700
4,119
7,819
1997-98
3,210
6,167
9,377
1998-99
3,300
5,736
9,036
1999-2000
3,300
1,994
5,294
2.4 Water quality
The key parameters that influence ecological processes and water use are salinity,
nutrients (TN and TP), pH, dissolved oxygen (DO), and turbidity (SKM 2001a).
2.4.1
Salinity
Salinity varies along the length of the Glenelg River and depends on the structure of
the channel and groundwater intrusions. The section of the Glenelg River between
Rocklands Reservoir and Fulham Bridge was characterised by Sherwood et al. (1998)
as shallow sections (<3 m deep) interspersed with deep elongated pools (>8.5 m deep).
This section of the river has been identified as a major source of salt. Salinity
increases with distance downstream from Rocklands Reservoir through this reach
(Sherwood et al. 1998).
McGuckin et al. (1991) also documented salinity in the 15 km section downstream of
Rocklands Reservoir. They found surface and bottom salinities were between 3,500
µS/cm and 7000 µS/cm with surface salinities approximately 2000 µS/cm less than
that at the bottom. Further downstream, conductivity declined to approximately 2000
µS/cm with the exception of Fulham Bridge, where bottom conductivity was 10,380
µS/cm. In the reach between Casterton and Dartmoor, McGuckin et al. (1991) found
no significant difference in surface and bottom salinities.
Deoxygenation also prevailed in the section of the river between Rocklands Reservoir
and Fulham Bridge with the lowest concentrations of dissolved oxygen coinciding
with high bottom conductivities (McGuckin et al. 1991). Adverse temperature was
also closely associated with saline pools in this reach. The persistence of such
conditions greatly affects the amount of suitable available habitat for aquatic
organisms. If the deeper areas of the pool habitats are highly deoxygenated it may
cause a significant reduction in useable habitat, and also reduce access to the benthos
which is a significant source of food and resources. Although stratification and
deoxygenation would have occurred naturally in pools, particularly in low flow
events, the current reduced flow conditions exacerbate this effect.
At times of low flow, saline groundwater is a major source of salt (Glenelg Regional
Catchment Strategy, 1997). At higher flows, fresh surface water masks the effect of
groundwater (Sherwood et al. 1998). A decrease in salinity that occurs between
Myaring Bridge to Dartmoor, approximately 20 km downstream, is likely to be due to
dilution that results from inflow of less saline surface or groundwater. The change in
catchment dynamics, as a result of the impact of Rocklands and Moora Moora
Reservoirs, has exacerbated the salinity effects because of the reduction in winter
freshes in the system.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 10
2.4.2
Dissolved oxygen
Severe deoxygenation has been found throughout the length of the Glenelg River
(McGuckin et al. 1991). McGuckin et al. found that deoxygenation was closely
associated with the presence of saline pools in the reach from Rocklands Reservoir to
Fulham Bridge with each pool registering a bottom dissolved oxygen concentration of
less than 10% saturation. Sites between Casterton and Dartmoor were only slightly
better than upstream with values ranging between 10-40% saturation. McGuckin et al.
suggested that the temperature gradient in this section of the river was most likely
associated with the depth of the pool and was the governing factor controlling DO at
conductivities less than 500 µS/cm.
Although low dissolved oxygen does not appear to be of concern at the VWQMN
sampling sites, isolated locations do exhibit low DO concentrations. Of particular
concern is the significant reduction in DO at depth in the deep pools along the Glenelg
River, especially in the reach from Rocklands Reservoir to Fulham Bridge. Low
levels of DO also occur at depth in the estuarine section of the river.
2.4.3
Nutrients
Nutrient enrichment of the waterways within the catchment has also been recognised
as a significant issue. To date there have been no blue green algal blooms reported in
the Glenelg River although eutrophication of the farm dams and lakes has been
recorded (Dixon et al. 1998). Blooms have, however been recorded in Rocklands
Reservoir in 1991.
Sources of nutrients within the Glenelg River are varied. For example, contrary to the
norm, active erosion in the subcatchment of Sandford contributes to total nitrogen
(TN) loads but no total phosphorus (TP). Nitrogen may be from decaying organic
material and animal wastes. Until 1996/97, the Casterton Wastewater Treatment Plant
was contributing an unknown load of nutrients to the river, which would be having a
major impact. This practice of discharging has now ceased (Wagg 1997). Septic tank
effluent at Dartmoor may also contribute to nitrogen concentrations in the river
(Sherwood et al. 1998). At Dartmoor, total Kheldahl nitrogen associated with organic
material is also positively related to flow, similarly for TP, which is attached to
sediments (Wagg 1997).
Although TP rarely exceeds the guideline values (SKM 2001a) in the Glenelg River,
values of TN progressively exceed the ANZECC guideline values for the river with
distance downstream. The occurrence of high nitrogen values can potentially lead to
the growth of algal blooms.
2.4.4
pH
With few exceptions, monitored values of pH within the catchment over the past
decade have been within guidelines. Median pH values have only been outside the
two guidelines at Big Cord where water was slightly acidic. This indicates that pH is
not an issue in terms of water quality in the Glenelg River below Rocklands Reservoir.
2.4.5
Turbidity
Median turbidity values have been recorded as excellent for the past 10 years at all
sites presented. The 90th percentile values for turbidity at Henty, Dartmoor and
Sandford have frequently indicated degraded conditions that correlate with periods of
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 11
high flow during winter (Department of Water Resources Victoria 1989). Turbidity at
Fulham Bridge has been shown to correlate positively with discharge at flows greater
than 10 ML/day (Mitchell et al. 1996). Turbidity is not of concern in the Glenelg
River system as the high winter turbidity levels are not prolonged and return to
acceptable levels.
2.5 Biota
The native freshwater fauna of the Glenelg River system represent a diverse
assemblage with high conservation significance. Twenty species of native freshwater
fish and 26 estuarine species have been recorded from the Glenelg River system
(SKM 2001a, DNRE 2000c). Eight species have conservation significance and of
these, five are protected through their listing on the Victorian Flora and Fauna
Guarantee Act 1988. Four species are protected through their listing on the List of
Threatened Australian Vertebrate Fauna (ANZECC 2000). Of the 20 species of
native freshwater fish, seven are known to migrate between freshwater and
estuarine/marine habitats at some stage in their life cycle (Koehn and O’Connor
1990).
Seven species of decapod crustacea and at least three species of bivalve mollusc have
also been recorded (SKM 2001a). Of these, the Glenelg freshwater mussel (Hyridella
glenelgensis) and the western swamp cray (Gramastacus insolitus) are suspected of
being rare, with restricted distributions and low abundances (Tarmo Raadik pers.
comm.). Consequently, these species may in the near future be rated as highly
threatened fauna in Victoria.
The EPA (1999) recorded a total of 86 families of macroinvertebrates from a total of
61 survey sites throughout the Glenelg River catchment (SKM 2001a). Mitchell et al.
(1996) and EPA (1999) report a dominance of insects (such as beetles, mayflies and
true bugs) in the macroinvertebrate community, as is commonly the case in fresh
waters. Based on the macroinvertebrate communities present, the health of sites in the
Glenelg River was assessed as good to excellent in both pools and shallow habitats
based on ratings presented in OCE (1988). Increased community complexity and
abundance of macroinvertebrates was reported at sites with macrophytes and organic
debris (Mitchell et al. 1996).
There have been 271 species of bird recorded along the Glenelg River of which 50
species have conservation significance either in Victoria or nationally (DNRE 2000a,
DNRE 2000b). Of the threatened species, 20 are reliant directly upon the instream
environment for their survival (SKM 2001a).
The warty bell frog (Litoria raniformis), has been recorded in the Glenelg catchment
and is listed as vulnerable by DNRE (2000b). Two species of threatened reptile, the
swamp skink (Egernia coventryi) and tree goanna (Varanus varius), have been
recorded from the Glenelg catchment (DNRE 2000a). Although the tree goanna does
not directly depend on the riparian environment, such areas often provide the only
remaining habitat. It should be noted that the latest recorded sightings of these species
date from the early 1980’s.
Other vertebrates present in the catchment and known to depend directly on the
instream environment for food and shelter include the platypus (Ornithorhynchus
anatinus) and water rat (Hydromys chrysogaster). Platypus have been recorded in the
Glenelg River near Casterton and Dartmoor and in the vicinity of Fulham Hole at 5
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 12
Mile Channel Outfall. The species has also been recorded in the Wannon River near
Coleraine and Hamilton, Mackinnon Creek and Grange Burn (unpublished database
Australian Platypus Conservancy; Melanie Tranter pers. comm.). The water rat has
been observed in south west Victoria and was observed during the field work for this
project. Locations of recorded sightings are listed in the Atlas of Victorian Wildlife
(DNRE, 2000a). The Long-footed Mouse eared Bat (Myotis adversus) is also found in
the catchment. They are known to take insects from the water surface and
consequently would directly and indirectly benefit from the provision of
environmental flows.
Of the 63 threatened flora species that occur in the Glenelg River catchment (SKM
2001a), 15 of them rely directly on the instream environment or temporary inundation
for their survival (DNRE, 2000; Dale Tonkinson pers. comm.). Thirty species of
aquatic and semi-terrestrial macrophyte have been recorded in the mid to upper
reaches of the Glenelg River (Mitchell 1996). Species richness within sites ranged
from 7-11. Emergent aquatic macrophyte species were dominant and represent
between 67 and 100% of species present at sites surveyed.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 13
2.6 Summary
n
Table 2-2 Summary of environmental issues, reach by reach.
Reach
Headwaters to backwater
of Rocklands Reservoir
Rocklands Reservoir to
Chetwynd River
Geomorphology
Sediment buildup
Harrow
around
Regulation of Rocklands
Reservoir is inpart
responsible for the low
transport rate
60% loss of capacity due to
sand slugs at Harrow
and Burkes Bridge
Flora and Fauna
Low flows and sediment deposition in mid to
upper reaches of Glenelg have been
shown to promote excessive growth of
Typha spp. and Phragmites australis
Water Quality
Hydrology
Low flows and sediment deposition in mid to
upper reaches of Glenelg have been
shown to promote excessive growth of
Typha spp. and Phragmites australis
Salinity increases with distance downstream
from this reach
70% of annual flow occurs Aug to Oct
to Wannon
For
Significant impact on streamflows
caused by Rocklands and spills
only once every four years
Rocklands
Dam
significantly
impedes
upstream movement of migratory fish
species.
A large proportion of high and moderate value
with only one sub-reach requiring
rehabilitation
a distance 15km downstream of
Rocklands salinity varies greatly
between the surface and bottom of the
river.
Very low Dissolved oxygen and temperature
is associated with saline pools for the
above distance
Glenelg R used to dry at Balmoral Feb
to Apr under natural conditions
but current conditions do not
lead to drying
Water lost due to evaporation at
Fraser’s Swamp
There is a significant reduction in peak
flows,
due
to
Rocklands
Reservoir, down to Casterton
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 14
Reach
Chetwynd River to
Wannon River
Geomorphology
Sediment buildup around
Casterton
20% loss of capacity due to
sand
slugs
at
Casterton
Flora and Fauna
Platypus recorded near Casterton
Variegated pygmy perch endemic to Glenelg
catchment and found in reach between
Harrow and Strathdownie
Water Quality
Erosion in the Sandford subcatchment
contributes to increased nitrogen loads
Hydrology
70% of annual flow occurs Aug to Oct
to Wannon
Deoxygenated pools present
Continuous streamflow due to natural
inflows
A large proportion of this reach is comprised
of moderate value sub-reaches with a
similar number but smaller length of
high value sub-reaches. Two small subreaches requiring rehabilitation occur in
this region
Wannon River to tidal
extent
10% loss of capacity due to
sand slugs at Dartmoor
Lower Glenelg National Park in good
condition with excellent bank and verge
vegetation
There is a significant reduction in peak
flows,
due
to
Rocklands
Reservoir, down to Casterton
High nitrogen due to septic inflows
No licences for extraction in this reach
Deoxygenated pools present
Platypus recorded near Dartmoor
This reach contains a larger proportion of high
value than moderate value subreaches. There are not any sub-reaches
requiring rehabilitation in this reach
Tidal extent to river mouth
WC01432:R04_MJS_GLENELG_FINAL.DOC
No licences for extraction in this reach
Final
PAGE 15
3.
Key issues
In common with other river basins around Australia, the hydrology of the Glenelg
River catchment has undergone substantial change in the past 200 years. Extensive
clearing of native vegetation for agriculture and the introduction of rabbits has resulted
in a number of primary impacts on the Glenelg River such as salinisation, erosion and
sedimentation. These modifications to the channel system have been further
exacerbated as a result of system regulation by Rocklands Reservoir and water
harvesting.
3.1 Potential environmental issues
Rocklands Reservoir in the upper Glenelg River catchment has reduced the mean
annual flow downstream of the dam from 113,000 ML/year naturally to 42,700
ML/year currently (data from this study). The dam also has the capacity to affect
major floods and medium flows, and whilst it has not had pronounced effects on low
flows in most months it has decreased winter and spring floods and high summer
flows (Mitchell 1996). Rocklands Reservoir also presents a barrier to the movement
of migratory fish species and localised movement of non-migratory species.
Furthermore, the mitigation of major floods may have implications for connectivity
between the main channel of the Glenelg River and its floodplain.
Mitchell et al. (1996) suggests that the altered flow regime in the mid to upper Glenelg
River may not have affected the spawning of endemic native fish in this region as the
spawning cycles of these species do not appear to be cued to flooding. Nevertheless,
flushes in late summer/early spring may be important for improving water quality after
low flow periods. This inturn may affect the recruitment success of native fish species
by influencing the survival of juvenile fish.
Primary impacts on the Glenelg River such as salinisation, erosion and sedimentation
are, to varying degrees, a result of extensive clearing of native vegetation for
agriculture (Mitchell 1996). Riparian vegetation is particularly important to in-stream
biota as it provides shading, food (terrestrial invertebrates) and shelter (leaf litter,
woody debris). Riparian vegetation also influences water chemistry through filtering
and buffering the in-stream environment from allocthanous sources of sediment,
chemicals and nutrients. In the Glenelg River catchment, clearing of vegetation has
resulted in gully and sheet erosion that delivers sediment to the upper river.
Moreover, removal of riparian vegetation in mid to lower reaches of the river has
resulted in bank instability and subsequent bank slumping which has contributed to
sedimentation and reduced capacity of the channel. These processes reduce instream
habitat complexity, an essential requirement for aquatic fauna in that it provides
different microhabitats for shelter, spawning, food production etc.
Primary factors resulting in a loss of habitat complexity are:
q sedimentation leading to the infilling of pools and smothering of coarse substrates,
woody debris and macrophytes
q
salinisation leading to stratification and subsequent deoxygenation of pool
habitats, also potentially the inhibition of aquatic macrophyte growth
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 16
q
river regulation leading to a reduction in the magnitude, frequency and duration of
high flows in winter and spring thus diminishing channel flushing (removal of
sediment from channel)
q
desnagging leading to a direct loss of woody substrates.
Many of these factors are interrelated and are affected by flow but not alone
attributable to the altered flow regime. For example, extensive sedimentation in the
Glenelg River (some reaches of stream have lost 80% of their former channel
capacity) has occurred as a result of vegetation clearing, introduction of rabbits and
erosion. Nevertheless, diminished flows over the winter/spring period result in a lack
of flushing of the river channel thus leaving sediment deposited in pools in the upper
and mid reaches of the Glenelg River
The loss of aquatic macrophytes, salinisation, sedimentation, smothering and removal
of snags and altered flow regimes have direct and indirect impacts on instream fauna
(macroinvertebrates, fish, reptiles and amphibians, and other vertebrates). Aquatic
vegetation and woody debris are an important component of habitat complexity in
deeper reaches of rivers (Walker et al. 1992) and are often correlated with
macroinvertebrate species (O’Connor 1991 in Mitchell et al 1996) and fish species
richness (Schlosser 1982). Decreases in the diversity and abundance of aquatic
macrophytes and the loss of snags lead to a loss of food source, spawning sites and
shelter for both aquatic macroinvertebrates and fish.
Salinisation as a result of native vegetation clearing and elevated groundwater levels is
a primary environmental issue in the Glenelg River (Mitchell 1996). Salinisation and
subsequent stratification occur in deep pools (>2 m) in the Glenelg River. In pools
over 3 m deep, stratification is stable, long-lived and reappears 1-2 months after
flushing (Mitchell 1996). Conductivity in the Glenelg River is highest during the low
flow period between January and March and shows a second increase in June-July
attributable to additional salt inputs from “first flush” events (Mitchell 1996).
Reduction in the magnitude of natural flows as a result of Rocklands Reservoir may
also contribute to salinisation of downstream sites. Saline groundwater intrusion
appears to be most pronounced above Fulham Bridge (Cameron and Jekabsons 1992,
McGuckin et al. 1991, Mitchell 1996) and results in stable stratification under low to
moderate flow conditions.
Salinisation may influence flora and fauna directly or indirectly through a variety of
complex mechanisms. For example, salinisation may affect organisms indirectly
through creating changes to habitat attributes (i.e. a direct effect on macrophytes
which are important as cover for some fish species) or trophic relationships between
species. Salinisation also leads to stratification and subsequent deoxygenation of the
water below the halocline, this in turn may preclude fish and macroinvertebrates from
important refuge habitats in pools. These indirect effects are complex and have been
summarised well by Mitchell (1996).
Direct effects of salinisation may result if salt tolerances of organisms are exceeded,
leading to lethal physiological effects. Similarly, increased levels of salt may have
sub-lethal effects on stream biota that may result in reduced growth rates, reduced
reproductive success and reduced health and vigour.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 17
While the following section considers each of the identified issues as separate
phenomena, they are in reality all interlinked. Moreover, their relative importance
changes with location within the catchment and through the year. Due to the
interaction between issues it is impossible to legitimately rank them relative to each
other. Hence, the order in which the issues are described is not one of relative
importance within the catchment.
In brief, the five key issues that confront the Glenelg River are as follows.
1. Sand slugs:
q
loss of channel form;
q
reduced substrate diversity; and
q
reduced instream habitat diversity.
2. Water quality:
q
salinisation;
q
stratification and subsequent deoxygenation of water column;
q
reduction in habitat availability for aquatic fauna; and
q
inhibition of aquatic macrophyte growth.
3. Flow regulation:
q
altered flood frequency, magnitude, duration;
q
changed flow seasonality; and
q
diminished channel flushing.
4. Channel condition:
q
bank erosion;
q
stock access;
q
riparian clearing; and
q
desnagging.
5. Current values of the Glenelg River:
q
riparian and instream flora present; and
q
aquatic fauna community.
6. Heritage river reach:
q
high environmental value; and
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 18
q
degraded riparian zone outside National Park.
3.2 Sand slugs
Sand accumulation in stream channels is a major stream management issue in the
Glenelg River catchment. Gully, sheet and rill erosion of granite portions of the
catchment have filled the Glenelg and its tributaries with about 6,000,000 m3 of sand
(Rutherfurd and Budahazy, 1996). Little sand is now coming from the catchment, so
the major source of sand to the Glenelg River is the lower reaches of tributary streams.
The tributaries introduce discrete slugs of sand to the main channel that often partially
dam the river, these slugs are commonly referred to as tributary junction plugs. As
these sand slugs move downstream they attenuate, gradually giving way to a
succession of small sluglettes. Rutherfurd and Budahazy (1996) estimate the sand
slugs are moving through the stream network at a slow rate, with only tens of
thousands of cubic metres being removed by bedload transport. The low transport rate
is due, in part, to regulation of the river from Rocklands Reservoir.
Rutherfurd and Budahazy estimate that there are 4 – 8 Mm3 of sand stored in the
Glenelg River and its tributaries. Channel storage estimates range from about 50,000
m3 /km in the Glenelg at Harrow, to an average of about 10 – 20,000 m3 /km elsewhere
in the system. The sand occupies a larger proportion of the cross-section in the
tributaries (up to 80%) than in the Glenelg River. Capacity loss (loss of channel
capacity) in the Glenelg River falls from about 60% between Harrow and Burkes
Bridge, to 20% at Casterton, and 10% at Dartmoor.
Most of the sand was deposited in the lower reaches of the streams very quickly after
the onset of channel extension through gullying. However, the original deep pools in
the Glenelg River, combined with regulation from Rocklands Reservoir, have limited
the movement of sand through the trunk stream. Of the sand already stored in the
main channel, only about two-thirds will be available for downstream transport.
About one-third will be more permanently stored in benches, pointbars or on the
floodplain. Rutherfurd and Budahazy cite several lines of evidence that suggest
bedload transport rates are in the order of 10-30,000 m3 /year.
The main source of sand for the main channel is now located in the lower few
kilometres of tributary streams. Importantly, in smaller tributaries, large volumes of
sand are stored in deep areas of the bed that have been abandoned by widening of the
channel. In Bryans Creek and Pigeon Ponds Creek, this bed storage has removed up
to half of the total volume of sand available for transport (Rutherfurd and Budahazy,
1996).
A major flood could move large volumes of sand, as occurred in the 1946 flood when
large volumes of sand were deposited in the channel and on the floodplain. However,
regulation has dramatically reduced the frequency of large floods, particularly close to
Rocklands Reservoir, and consequently the rate of sand transport (Ian Rutherfurd,
pers. comm.; Brizga et al., 2000). The sand is now moving through the stream
network in a complicated pattern, but it will take many decades for the sand to be
stabilised and removed.
The effect of the movement of sand into the Glenelg River and its tributaries is not
clear. Rainfall-runoff modelling suggests that filling half of the channel cross-section
with sand will have minimal impact on the size of flood peaks or their time-to-peak
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 19
because of the decreased roughness associated with sand sheets. In addition,
deposition on the floodplain has meant that in many reaches the rise in bed level has
been matched by an increase in bank height.
A complicating factor in managing sand in the Glenelg River is the form of channel
adjustment that takes place once the sand is removed from a reach. Both Rutherfurd
and Budahazy (1996) and Brizga et al. (2000) report examples of bed incision and
consequent bank erosion following sand extraction from the channel. Bed incision of
the main trunk can also lead to incision of the tributaries, particularly if those
tributaries are graded to the elevation of the sand surface.
The sediment influx has smothered the previous channel form and dramatically
simplified the geomorphological diversity of the channel by creating a sandy bed with
less deep holes. Loss of geomorphological diversity in turn restricts habitat
availability. Typically in rivers the greatest diversity of macroinvertebrates and fish
are found where there is an abundance of large woody debris (LWD), water plants or
cobbles and rocks. The effect of sand and silt is to fill crevices and bury potential
aquatic habitat. Where sand slugs do not totally bury LWD or completely smother
coarser substrates there is little evidence that species diversity or stream
environmental values are significantly reduced (Brizga et al., 2000).
Brizga et al. (2000) found that in fact there were very few areas where sand comprised
the only available habitat. While many pools may have partially filled with sand there
is still a remnant sequence of pools and shallow areas usually with some residual
LWD. However, the loss of deep holes in the river has removed sites of refuge for
platypus during periods of low flow. Furthermore, artificially reduced flows during
low flow periods may have implications for the movement of platypus between pools
and foraging behaviour, thus restricting platypus to regions of poor water quality.
Low flows and sediment deposition in the mid to upper Glenelg River have also been
found to promote excessive growth of Typha spp. and Phragmites australis in the river
channel (Mitchell et al. 1996). This consequently impedes flows and leads to further
sediment deposition and further reduction in habitat complexity.
The accumulation and slow movement of sand has led to a general decrease in habitat
availability and diversity. The provision of environmental flows will only go a small
way to moving the sand to alter this impact. There will not be a substantial increase in
habitat area in response to environmental flows, but there will be a relative increase in
the quality of habitat. Environmental flows will maximise the habitat available
considering the current levels of sand and habitat change in the river.
Overall the flow changes have resulted in reduced sediment transport through the
system which has had major implications for structural habitat change within the
channel. These structural habitat changes, in the form of sand slugs and isolation of
pools, have had significant resultant effects on other components of the ecosystem
such as water quality and community continuity.
3.3 Water quality
The analyses, described in Appendix C, indicate that the water quality in the Glenelg
River system is poor with respect to salinity. Salinity is particularly high in pools in
the reach of the Glenelg River between Rocklands Reservoir and Fulham Bridge
(Cameron and Jekabsons 1992, McGuckin et al. 1991, Mitchell et al. 1996). Although
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 20
turbidity and nutrients are generally not as high, historical levels have been, at times,
high enough to adversely impact the aquatic biota.
Salinisation is most likely to influence flora and fauna directly or indirectly through a
variety of complex mechanisms. For example, salinisation may affect organisms
indirectly through creating changes to habitat attributes (i.e. a direct effect on
macrophytes which are important as cover for some fish species) or trophic
relationships between species. Salinisation also leads to stratification and subsequent
deoxygenation of the water below the halocline, this in turn may preclude fish and
macroinvertebrates from important refuge habitats in pools. These indirect effects are
complex and have been summarised well by Mitchell et al. (1996).
Salinisation and subsequent stratification occur in deep pools (>2 m) in the Glenelg
River. In pools >3 m deep, stratification is stable, long-lived and reappears 1-2
months after flushing (Mitchell et al. 1996). Salinity in the Glenelg River is highest
during the low flow period between January and March and shows a second increase
in June-July attributable to additional salt inputs from “first flush” events from
tributary inflows (Mitchell et al. 1996). Reduction in the magnitude of natural flows
as a result of Rocklands Reservoir may also contribute to salinisation of downstream
sites.
There is currently an environmental flow allocation of 34,690 ML for sharing between
the Wimmera and Glenelg Catchments. Such flows have not been realised because of
drought conditions in recent years. This allocation is planned to increase with further
stages of pipelining of the Wimmera Mallee Water system. The current releases differ
from environmental flow recommendations as they are designed to sustain the
ecosystem, rather than return all or part of the natural flow regime. However, these
flows are not always delivered in their entirety. Deakin University is undertaking a
biological monitoring program in the Glenelg River to determine if the environmental
allocations have had a significant beneficial effect. Over the four seasons since
1994/95 when the monitoring began, there have effectively been two years when the
allocation was delivered to approximately 20-25% of allocated flows and two years
when it was 70-80% of recommended flows (B. Mitchell, pers. comm.).
The
reduction in flows delivered were due to periods of drought and subsequent water
limitations.
The Deakin University monitoring program has not reported yet but preliminary data
analysis suggests that when close to the 80% of the environmental allocation is
provided in a given year there is a positive response in water quality parameters,
particularly dissolved oxygen and salinity levels (B. Mitchell, pers. comm.). In years
when the proportion of environmental allocations has been closer to 25% of allocated
flows, there still remains a positive effect, although the improvement in water quality
is reduced. For example, even the relatively low environmental allocations delivered
in 1996/97 of 4,119 ML had a positive impact on water quality.
The work of Anderson and Morrison (1989) and Mitchell et al. (1996) suggest that
even if the environmental water was currently available, releasing large flushing flows
down the river could have substantial short term detrimental effects but in the long
term be beneficial. This short term detrimental effect would largely be due to the
mobilisation of highly saline water or water with low dissolved oxygen levels from the
existing deep pools. Sustained environmental flows would help to reduce salinity in
shallow water and the upper water column, however, saline water in deep pools should
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 21
not be managed using flushing (Mitchell et al. 1996). Mitchell et al. (1996)
recommend sustaining environmental flows in the summer-autumn period to
compensate for lost habitat with an additional provision for spring flows. The low
level sustaining flows would also help manage the water quality within the surface
water of the pools and the preliminary indications are that these flows are having a
beneficial effect on the surface water quality (B. Mitchell pers. comm.) In the long
term large flushing flows are important for managing the stream channel form and
movement of sediment. These flows would also act as important disturbances to the
biological community.
Direct effects of salinisation may result if salt tolerances of organisms are exceeded,
leading to lethal physiological effects. Similarly, increased levels of salt may have
sub-lethal effects on stream biota that may result in reduced growth rates, reduce
reproductive success and reduced health and vigour. For example, Mitchell et al.
(1996) suggest that the range of the Glenelg spiny crayfish, severely restricted by
habitat degradation in the Glenelg River basin, is also under threat from saline water.
Glenelg spiny crayfish moult frequently when small, but by 50 mm occipital length
moulting is restricted to once a year between January to May. At this time water
quality in the modified upper river is poor with elevated temperature and salinity, and
reduced oxygen levels. When a crayfish moults its ability to osmoregulate is reduced,
consequently high salinities may reduce growth or survival (Mitchell et al. 1996).
Mitchell et al. (1996) also noted that a conspicuous feature of macrophyte
communities was the absence of submerged aquatic macrophyte species in
downstream sites. It was suggested that salinities in pools at the downstream sites
might be sufficiently high to affect the growth of submerged macrophytes.
The salinity levels within the Glenelg River system may potentially affect a range of
biota. It is considered for example, that fish are a good indicator of the effect of
salinity on a river system because they are mobile and their occurrence may reflect the
health of a river reach (Ryan and Davies 1996). Some fish species found in the
Glenelg River, for example the Common Galaxias (Galaxias maculatus), are relatively
tolerant of salinity because of their migratory stages and may not be greatly affected
by current salinity levels (Pollard 1971). Other species found in the Glenelg River,
such as the River Blackfish (Gadopsis marmoratus), are relatively sensitive to saline
conditions, particularly in juvenile life stages (Ryan and Davies 1996). Salinity levels
found within the Glenelg River would also impact a range of invertebrate species,
resulting in a reduction in diversity and abundance (Hart 1982).
Consequently the impacts of salinity may be two-fold, direct effects on biotic health
and structural effects reducing useable habitat within the system.
3.4 Flow regulation
Rocklands Reservoir has diverted water from the upper Glenelg River catchment to
the Wimmera River system since 1953. Using the flow data for the Glenelg River,
developed in the current project, the average mean annual flow has reduced from
113,000 ML/year naturally to 42,700 ML/year currently.
These figures clearly
indicate that as a result of the diversion the natural flow regime of the Glenelg River
has been substantially altered and is missing several critical flow elements. Firstly,
the overall volumes of water are greatly reduced throughout the year and large
flushing flows are absent. These changes exacerbate sand slug formation, saline pools
and reduction in structural diversity. The mitigation of major floods also has
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 22
implications for connectivity between the main channel of the Glenelg River and its
floodplain.
As shown by the estimated natural and current flow duration curves presented in
Appendix A, streamflows upstream of Rocklands Reservoir have not changed
substantially. However, immediately below Rocklands Reservoir seasonality of flow
has been reversed by regulation. Immediately downstream of Rocklands Reservoir,
under natural conditions, median flows peak during August at 23,400 ML/month and
lowest flows occur during the summer months, particularly February. Current flows
are now less than natural flows for the majority of the year. Zero flows occur during
the months May to November, inclusive. Moreover, peak flows at this site occur
during December to February, inclusive. During June and July, zero flow prevails
100% of the time under current conditions. Between August and October, flow
exceeds 0 ML/month for less than 18% of the time under current conditions, while
under natural conditions, flow exceeded 700 ML/month.
The effect of regulation is obviously greatest immediately downstream of Rocklands
Reservoir, although effects continue a significant distance downstream. The reduction
in peak flows is highly significant all the way through to Casterton, downstream of the
confluence with the Wannon the impact of peak flows is still apparent (e.g. at
Dartmoor) although is relatively reduced. As discussed these peaks flows are
important for sand and sediment movement through the system. They also are
considered to be key trigger flows for a number of biological events such as fish
spawning and invertebrate recruitment.
Consequently, reduction in timing,
recurrence, duration and magnitude of peak flow events has a significant effect on
both the biological and physical processes in the river.
The natural periods of cease to flow that may have previously occurred have been
discussed previously. In addition the low flow conditions have also been significantly
altered. For example, between Rocklands outlet and Casterton the low flows over the
winter period are significantly reduced. This means that during winter the flow
between peak flow events is generally lower. This could reduce areas of spawning
habitat and general habitat diversity at key periods for the aquatic community.
The Glenelg River system is considered self regulatory by Southern Rural Water.
Southern Rural Water has not previously had a formal water restriction policy in place
due to flow rapidly dropping to zero as water levels begin to fall during the summer
months and water quality also declines. Ad hoc restrictions were imposed in the
summer of 1998/99, during which river flow of 10 ML/day was used as a trigger to
implement restrictions. Such restrictions were unnecessary due to the river rapidly
dropping to zero flow once it was below 10 ML/day and the water becoming too
saline for agricultural use. Therefore, the timing of bans coincided with conditions
that were unsuitable for pumping due to lack of water and high salt levels. Similarly,
restrictions were imposed on the Wannon last summer (1999/00) but due to the flow
dropping very quickly by mid January such restrictions were once again unnecessary.
Southern Rural Water also used 10 ML/day, an arbitrary figure, to impose restrictions
on the Crawford River and the Grange Burn (J Donovan, pers. comm.).
Rocklands Reservoir also presents a barrier to the movement of migratory fish species
and localised movement of non-migratory species. Although Mitchell et al. (1996)
suggest that the spawning cycles of endemic native fish do not appear to be linked
with flooding, altered flow regimes, in the Glenelg River, below Rocklands Reservoir,
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 23
may have adversely impacted fish communities through eliminating other flow related
cues. Flushes in late summer/early spring may be important for improving water
quality after low flow periods. This, in turn, may affect the recruitment success of
native fish species by influencing the survival of juvenile fish.
3.5 Channel condition
A number of reports discuss the degraded condition of the Glenelg River (e.g.
Rutherfurd and Budahazy 1996; Brizga et al. 2000; Erskine 1994). Each of these have
identified similar themes of degradation:
q catchment sheet and gully erosion;
q
sand slugs;
q
sand extraction;
q
macrophyte loss;
q
localised bed and bank erosion;
q
riparian degradation (including unmanaged stock access);
q
desnagging; and
q
river regulation.
Schreiber et al. (1998) also assessed the environmental aquatic habitat of the Glenelg
River based on bed composition, proportion of pools and riffles, bank vegetation,
degree of cover for fish and the extent of sedimentation or erosion. Their rating
ranged from moderate to very poor.
The loss of aquatic macrophytes, salinisation, sedimentation, smothering and removal
of snags and altered flow regimes have direct and indirect impacts on instream fauna
(macroinvertebrates, fish, reptiles and amphibians, and other vertebrates). Aquatic
vegetation and LWD are an important component of habitat complexity in deeper
reaches of rivers (Walker et al. 1992) and are often correlated with macroinvertebrate
species (O’Connor 1991 in Mitchell et al 1996) and fish species richness (Schlosser
1982).
Large woody debris plays a critical role in providing stable substrate and hydraulic
diversity in sand-bed streams, and is arguably even more important in sand-bed
streams than other types of streams (Brizga et al. 2000). There has been significant
desnagging within the Glenelg River system, specifically the reach in the Casterton
region. Decreases in the diversity and abundance of aquatic macrophytes and the loss
of LWD lead to a loss of food source, spawning sites and shelter for both aquatic
macroinvertebrates and fish. However, the available data on macroinvertebrate
populations in the river is equivocal. For example based on the macroinvertebrate the
communities present Glenelg River was assessed as good to excellent in both pools
and shallow habitats (OCE 1988). Whereas as part of the National River Health
Strategy the Glenelg River Catchment was described as highly degraded (Schreiber et
al. 1998). (See Appendix D for more detail).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 24
Riparian vegetation is particularly important to in-stream biota as it provides shading,
food (terrestrial invertebrates) and shelter (leaf litter, woody debris). Riparian
vegetation also influences water chemistry through filtering and buffering the instream environment from allocthanous sources of sediment, chemicals and nutrients.
In the Glenelg River catchment, clearing of vegetation has resulted in gully and sheet
erosion that delivers sediment to the upper river. Moreover, removal of riparian
vegetation in mid to lower reaches of the river has resulted in bank instability and
subsequent bank slumping which has contributed to sedimentation and reduced
capacity of the channel. Loss of riparian vegetation reduces shading for the stream
channel and has a consequent effect on water temperature also. These processes
reduce instream habitat complexity, an essential requirement for aquatic fauna in that
it provides different microhabitats for shelter, spawning, food production etc.
3.6 Current flora and fauna values of the Glenelg River
system
The native freshwater flora and fauna of the Glenelg River system represent a diverse
assemblage with many species of high conservation significance. This in turn is a key
issue for the system as it means that there are key species of recognised conservation
value many of which are under threat due to flow related changes within the Glenelg
River. There is a resultant increased potential for response by the ecosystem to
improvements in the flow regime as the system is not devoid of desirable species.
Consequently changes in the flow regime, or parts thereof, may be more likely to have
a beneficial ecosystem response.
Some examples of the flora and fauna of value include:
q
Eight fish species have conservation significance and of these, five species are
protected through their listing on the Victorian Flora and Fauna Guarantee Act
1988. Of these, four species are protected through their listing on the (ANZECC
2000) List of Threatened Australian Vertebrate Fauna.
q
There are 50 species of birds that have conservation significance either in Victoria
or nationally (DNRE 2000a, DNRE 2000b) and of the threatened species, 20 are
reliant directly upon the instream environment for their survival.
q
One species of threatened amphibian, the warty bell frog (Litoria raniformis), has
been recorded from the Glenelg catchment. The conservation status of this
species is vulnerable (DNRE 2000b).
q
There are two species of threatened reptile, the swamp skink (Egernia coventryi)
and tree goanna (Varanus varius), in the Glenelg catchment (DNRE 2000a). The
conservation status of the swamp skink is vulnerable that of the tree goanna is
data deficient (DNRE 2000b).
q
The platypus (Ornithorhynchus anatinus), although not of documented
conservation significance, have been recorded in the Glenelg River near
Casterton and Dartmoor and in the vicinity of Fulham Hole. The platypus is a
significant ‘icon species’ in Australian aquatic systems and considered of
considerable values by the community.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 25
q
There are 63 threatened flora species in the Glenelg River catchment, 15 of which
are dependant on the aquatic environment (DNRE, 2000; Dale Tonkinson DNRE
pers. comm., 2000).
In addition to the listed flora and fauna of the Glenelg River system there are
numerous other species of value to the region and community.
3.7 The heritage reach
The lower section of the Glenelg River, from Nelson on the coast to Dartmoor, is
designated a “Heritage River” under the Heritage Rivers Act 1992 (DNRE 1997) and
is listed as a Nationally Important Wetland by Environment Australia. The Heritage
River corridor covers an area of approximately 3020 Ha and is about 50 m wide for
most of its length. The lower section of the Heritage River flows through the Lower
Glenelg National Park. The Heritage River corridor provides an important habitat link
particularly between inland woodlands and the coast for species reliant on riparian
habitats. This habitat corridor is well protected within the National Park although
public land water frontages are degraded at Nelson, Donovan’s and below Dartmoor
(DNRE 1997).
There are several key values associated with the heritage river reach.
q Thirteen rare or threatened flora species are known to occur in the heritage river
corridor although many of these are only known from local knowledge (DNRE
1997). Rare Bog Gum and the Lime Fern are two examples. Additionally, the
leafy greenhood and the limestone spider-orchid are listed under the Flora and
Fauna Guarantee Act 1988.
q
Twenty three significant fauna species in the Heritage River Corridor. Of these
species 11 are listed in the Flora and Fauna Guarantee Act 1988.
q
A diverse fish fauna in both freshwater and estuarine sections, including five
significant fish species.
q
The lower Glenelg River karst area – an area of limestone between Keegan's Bend
and Nelson – is of state significance (LCC 1991). Extensive caves in the area
provide habitat for several significant species of bat.
q
The only Victorian estuary developed in dune calcarenite ridges (Bird 1977).
q
Remnant River Red Gum community south of Dartmoor (DNRE 1997).
q
Moleside Creek (tributary of the Glenelg River) contains numerous species of
fern.
q
Numerous recreational values – fishing, boating, camping, walking (DNRE 1997).
Key management directions have been proposed for the lower sections of the Glenelg
River that will maintain and enhance existing values (DNRE 1997). These include:
q restore habitat links along the River to the coast;
q
improve environmental water values of the river, particularly the estuary, and
develop trigger levels for opening of the river mouth;
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 26
q
undertake research and monitoring of significant fish species and environments,
monitor sand and silt effects on the River including the sand slug upstream the
Heritage River corridor (DNRE 1997).
Flow related threats to the lower Glenelg River might include the encroachment of the
upstream sand slug and the alteration of late summer/autumn and winter/spring flow
events. Rutherfurd and Budhazy (1996) suggest that the sand slug may not reach the
Heritage River for approximately 30-40 years. Nevertheless, the impacts of the sand
slug are likely to be similar to those that have occurred in the mid to upper reaches of
the Glenelg River (e.g. infilling of deep pools, smothering of substrates, etc)
ultimately leading to decreased habitat complexity. With regards to the alteration of
flows to the lower Glenelg River, this has not been quantified and hence it is difficult
to determine the potential biological impacts.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 27
4.
Methods
This project was completed concurrently with the Stressed Rivers Project that
developed a new method for the determination of environmental water requirements
for use within Victoria. The overall justification for the methodology and the detail of
the method is covered in a separate report. The overall methodology of this project
incorporated components as they were developed. The outline of the methodology is
shown in Figure 4-1.
Project
Inception
Data
Collation
Issues
Paper
EFTP
Fieldwork
Hydrology
Surveying
Hydraulic
Modeling
Analysis
Project
Group
Final
Report
n
Figure 4-1 Outline of the project methodology
The initial stage of the project involved a compilation of the set of issues relevant to
the catchment and production of two issues papers (Sinclair Knight Merz, 2001). The
subsequent stages of the project involved more detailed investigation at specific sites
determined to be representative of the key issues within the catchment. Descriptions
of the sites are included in subsequent sections, the sites were selected to represent a
range of hydrological, ecological and geomorphological features.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 28
The sites were assessed using a technical panel with relevant ecological and
geomorphological expertise. For this project the technical panel comprised Michael
Shirley (Project Manager and ecologist), Paul Close (Ecologist), Brenton Zampatti
(Ecologist), Tanya Wansbrough
(Geomorphologist) and Bruce Abernethy
(Geomorphologist).
At each site visited a series of standard descriptive tasks were undertaken. During this
stage, the locations of cross-sections at each site were identified for subsequent
surveying. Between six and nine cross sections were pegged at each site using a
single peg located on one bank. From this point the channel shape was surveyed
perpendicular to the flow. These cross sections were selected to be representative of
site features in areas of key habitats as identified across the relevant disciplines.
Following the pegging of all cross sections, each cross section was drawn and flow
bands identified. The cross sections were drawn to identify key features of ecological
or structural relevance within the section. These were then correlated to the surveyed
cross-sections to allow accurate determination of the ecological flow bands.
At each site a series of flow bands or flow components were identified that are
specific for that particular reach of the river. The flow bands are components of the
flow regime that are considered structurally or ecologically important for the
ecosystem. These bands were described hydrologically as well as the specific
ecosystem function that they fill.
All cross sections identified at the sites were surveyed for channel shape, using a total
station. The survey was conducted to indicate any significant changes in channel
shape, stream flows and habitat structure. All cross sections within a site were then
linked to each other to indicate the slope and meanders of the river at that site. Water
level was recorded at all sites to assist in validation of the hydraulic model.
A hydraulic model was prepared to develop a relationship between stream flow, and
water level and velocity for each site. The hydraulic analysis of the sites was
undertaken using the HEC-RAS software, which is designed to perform onedimensional steady state calculations for a full network of natural and constructed
channels or a single river reach. Separate hydraulic models were constructed for each
of the sites using the surveyed cross sections. These models were then validated over
a range of flows from minor to bankfull discharges.
Each model was then validated by undertaking a sensitivity analysis of the channel
roughness represented by Manning’s ‘n’ values and by adjusting the downstream
boundary condition. As there was little or no data available for calibration it will be
necessary to assign textbook Manning’s ‘n’ values for channel roughness.
Appropriate values were then selected based on photographs and the site visit.
Additionally, a sensitivity analysis was undertaken by adjusting Manning’s ‘n’.
Model outputs showed the variation in total depth for the range of Manning’s values
tested. The sensitivity of the model to the downstream condition was also assessed to
determine the impact on calculated results. The most appropriate downstream
boundary conditions were then determined by plotting each of the water surface
profiles and identifying the most realistic hydraulic gradient.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 29
A range of flows were routed through the model, these flows represented the full
range of flows up to bankfull.
A daily flow series was generated for each site through a separate project. At some
sites where there were no local gauges, flow data was transposed from existing gauge
data to provide the flow series for each site. A ‘natural’ and ‘current’ flow series was
determined where the natural flow series removed all known extractions under the
current landuse.
The hydrological assessment involved consideration of a range of hydrological
parameters to describe the flow regime, including:
q flow duration curves to examine the percentage of time that a flow of a given size
is exceeded;
q time series graphs to examine the sequence of flow events, particularly during
very dry or very wet conditions; and
q Get Spells analysis to describe flow spells (flow events over a defined threshold).
Key flow indicators were extracted from this information, such as mean and median
flow, and suitable high and low flow indices such as the flow exceeded 20% and 80%
of the time.
A series of fish surveys were conducted to assess the distribution of key fish species
through the catchment and the relationship with flow and groundwater flows. The
outcomes of these surveys have been incorporated into the recommendations
developed.
The analysis of the outputs and development of the recommendations was done by the
technical panel. The implications of changed flow regimes were examined based on
the specified flow bands for each site. Recommendations have been developed that
describe the entire flow regime, not solely a minimum flow over a defined period.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 30
5.
Site descriptions
Site 1 – Five Mile
Site 1 is located on the Glenelg River approximately 500 m downstream from the
confluence of the Five Mile Channel Outfall. This reach is characterised by a deep
pool upstream (>2 m deep), a glide/run section with a mid-channel island, mid-reach
and an anastomosing section downstream. The anastomosing reach is comprised of
two primary channels, one of which was flowing on our inspection, and the other
wetted with no flow. A number of secondary channels also dissect the floodplain.
Streambank sediments are mainly sandy loams whilst the streambed is dominated by
sands and silt.
The floodplain vegetation community is open grassy woodland with a Box
(Eucalyptus spp.) and River Red Gum (E. camaldulensis) overstorey and native/exotic
grass understorey which is generally in poor condition. Similarly, the riparian zone is
highly disturbed and comprises relatively sparse stands (~50% cover) of River Red
Gum with an understorey of native/exotic grasses with some native shrubs –
predominantly Tea-Tree (Leptospermum sp.) and Paperbark (Melaleuca sp.). Instream
vegetation is relatively diverse although restricted mostly to the margins of deep
pools. Aquatic vegetation includes Common Reed (Phragmites australis), Water
Ribbons (Triglochin sp.), Stonewort (Nitella sp.) and submerged grasses.
Instream habitat is reasonably diverse and includes aquatic vegetation (5%), large
woody debris (15%), organic debris (branch piles, leaves and bark 20%) and small
areas of undercut bank. Disturbances to the instream channel include stock access,
exotic fish (Gambusia and possibly Carp) and some siltation of instream habitats by
fine sediment.
n
Figure 5-1 Site photos from Five Mile Channel Outfall.
Site 2 – Pine Hut Hole
This site is characterised by a deep pool upstream (>2 m deep) and an anastomosing
reach downstream. The anastomosing reach comprises several channels that were
flowing on the day of our inspection and a number of other secondary channels that
were dry. The streambed and banks are comprised of fine sands and sandy loams.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 31
The floodplain is in relatively good condition and vegetated by an open grassy
woodland community with River Red Gum overstorey and native/exotic grass and
sedge understorey. There is also some eucalypt regeneration in the understorey. The
riparian zone exhibits similar floral characteristics with River Red Gum dominating
the overstorey. The understorey comprises native/exotic grasses, Common Reed,
Paperbark and Cumbungi.
Instream vegetation is relatively diverse. In the pool, aquatic vegetation is dominated
by stands of Common Reed, Spike Rush (Eleocharis sphacelata ), Cumbungi and
Tassled Sedge (Carex fascicularis). A diversity of aquatic plant species are also
established in open water areas in the anastomosing section of the reach downstream
of the pool. In this section, Common Reed, Cumbungi,Water Ribbons, Elodea
(Elodea sp.), Ribbon Weed (Vallisneria gigantea) and Pond Weed (Potamogeton sp.)
are wide spread and abundant.
Instream habitat varies substantially between the pool and anastomosing sections of
the survey reach. The pool comprises mostly open water habitats (85% wetted area of
reach) with stands of aquatic vegetation and some large woody debris along the stream
margin. In the anastomosing section, aquatic vegetation (30%), large woody debris
(5%) and organic debris (leaves, branch pile and bark 10%) dominate the habitat
attributes. Disturbances to the instream channel include stock access and exotic fish
(Gambusia and possibly Carp).
n
Figure 5-2 Site photos from Pine Hut Hole.
Site 3 – Upstream of Harrow
This site was located upstream of the road crossing on private property (Dick Roberts)
upstream of Harrow township. The reach is characterised by a diversity of hydraulic
habitats including pool, run, riffle and glide. Adjacent hillslopes confine the channel,
with only narrow, discontinuous alluvial flats developed on the stream margins (<20
m wide). Deposits of coarse sand dominate the bed (75%) with small areas of gravel
(20%) and overlying silt (5%).
The riparian vegetation community is open woodland with River Red Gum overstorey,
with some Melaleuca and Casuarina species. The understorey consists of native
shrubs and a mixture of native and exotic grasses. There is a diversity of aquatic
vegetation present within the reach including Common Rush (Juncus usitatus), Water
Ribbons, Cumbungi (Typha sp.) and filamentous algae. Instream habitat is dominated
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 32
(55%) by emergent aquatic vegetation (Common Reed and Cumbungi) with small
areas of overhanging vegetation, coarse substrate and organic debris.
The most obvious instream disturbance was deposition of sand and smothering of
aquatic habitats. Channel constriction through partial revegetation of large sandbars
by Common Reed, Cumbungi and Paperbark is also evident and alters the natural
hydraulic characteristic of the reach. Tributaries and springs near the reach were
noticeably salty. Other instream disturbances included exotic fish (Gambusia) and
areas of bank instability (due to stock access) and rabbits.
n
Figure 5-3 Site photos from upstream of Harrow.
Site 4 – Burkes Bridge
Site 4 is located immediately upstream of Burkes Bridge on the Edenhope-Casterton
Road. The channel is confined by hillslopes on its right side. The floodplain (>500 m
wide) formed on the left side of the channel has some shallow secondary channels and
billabongs which were dry during the field inspection. The channel has been
extensively filled with sand that forms large point bars and braided channel
characteristics in some areas.
Floodplain and riparian vegetation communities are open woodland with an overstorey
of River Red Gum and an understorey of wattles (Acacia spp.), bracken and
native/exotic grasses and herbs. The riparian zone supports additional wetland species
including Common Reed, Common Rush and Tea-Tree. Instream vegetation is
generally sparse with the exception of the Common Reed, which forms dense stands
along the right hand stream margin. Only small areas of Common Rush and Ribbon
Weed were present within the reach.
The most obvious instream disturbance was deposition of sand and smothering of
aquatic habitats. Channel constriction through partial revegetation of large sand bars
by Common Reed and Common Rush is also evident and alters the natural hydraulic
characteristic of the reach. Tributaries and springs in the vicinity of the reach were
noticeably salty. Other instream disturbances included exotic fish (Gambusia), a road
crossing and weeds.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 33
n
Figure 5-4 Site photos from Burkes Bridge.
Site 5 – Roseneath
Site 5 was located approximately 200 m upstream of the bridge on Warrock Road at
Roseneath. This reach is characterised by riffle and pool hydraulics, active erosion of
the channel, unstable bed and banks (mass failures on outer banks) and a high load of
LWD. At the surveyed site, the channel bifurcates around a large vegetated island.
The channel is confined by hill slopes on its left side. A floodplain (>500 m wide)
exists on the right bank. Stream bank sediments are sandy loams whilst the streambed
is dominated by actively mobile sands.
The floodplain vegetation has been predominantly cleared and replaced with exotic
pasture grasses. The riparian zone exhibits similar floral characteristics. Isolated
River Red Gum woodland are present on both banks including some regeneration on
the left bank. Instream vegetation is sparse and includes Common Reed and Water
Ribbons.
Instream habitat is dominated by LWD (70% wetted area) with small areas of aquatic
vegetation, organic debris and rock habitat. The most obvious disturbances are stock
access, active erosion, sand accumulation and riparian clearing. Other instream
disturbances included exotic fish (Gambusia and possibly Carp) and weeds.
n
Figure 5-5 Site photos from Roseneath.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 34
Site 6 – Section Road
Site 6 is situated approximately 150 m downstream from Section Road in a reach of
the river that meanders across a broad floodplain. At this site, the instream habitat has
been totally smothered by sand, leaving a wide and shallow flowing reach. Stream
substrate is dominated by deposits of fine sand (75%), coarse sand (5%) and small
areas of gravel (20%).
The floodplain vegetation comprises predominantly cleared eucalypt woodland that
has been replaced with exotic pasture grasses. Similarly the riparian zone is highly
disturbed and comprises cleared eucalypt woodland although some regeneration is
occurring. Instream vegetation is in relatively poor condition and dominated by
emergent species such as Common Reed and Cumbungi. Instream cover is very
sparse and comprises only small amounts of aquatic vegetation (2%) and logs (2%).
The accumulation of sand has reduced structural habitat complexity. Other
disturbances are stock access and riparian zone degradation.
n
Figure 5-6 Site photos from Section Road.
Site 7 – Bahgallah Road
Site 7 is located approximately 150 m downstream of the Bahgallah Road bridge. The
stream is deeply incised (up to 10 m) with steep, unstable banks formed in sandy
loams. The channel is some 50 m wide with a flat bed of sand. On the day of our
inspection, low flow meandered within the channel bed.
The floodplain vegetation comprises only pasture grasses and generally is in poor
condition. The riparian zone is also disturbed and comprises remnant River Red Gum
woodland and an understorey of exotic grasses. Instream vegetation is in relatively
poor condition and comprises Water Ribbons, Common Reed and algae. Instream
habitat is dominated by algae (65%). Apart from the broad sand sheet that fills part of
the streambed, other instream disturbances include exotic fish (Gambusia), bank
instability (due to increasing height and steepness from bed degradation), a gauging
weir and a bridge.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 35
n
Figure 5-7 Site photos from Bahgallah Road.
Site 8 – Dartmoor
This site is located within a stream side reserve upstream of Greenham Road near
Dartmoor. The reach is characterised by a diversity of hydraulic habitats including
pool, run, riffle and glide. Streambanks are formed in silty loams whilst the streambed
is dominated by actively mobile sands.
The riparian zone comprises River Red Gum woodland with an understorey
dominated by exotic groundcover species. Regeneration of River Red Gum and
acacias is evident. Instream vegetation is in good condition and comprises
predominantly submerged species including Water Ribbons, filamentous algae and
Elodea. Instream habitat is reasonably diverse and includes aquatic vegetation (50%),
large woody debris (8%) and organic debris (branch piles, leaves and bark 2%).
Actively mobile sands have formed bars on the inside bends and benches on both
banks. Other disturbances include weed infestation, vehicle tracks and litter.
n
Figure 5-8 Site photos from Dartmoor.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 36
6.
Objectives
The objectives for this study are described in a structure that allows for specific detail
in each reach. The overarching objectives are the regional objectives, these are
relevant at a National, State and regional level. A series of strategies, Acts and
policies are listed that are relevant at each level. The environmental flow
recommendations have been developed and should be implemented within the context
set by these overall objectives. Where appropriate specific components may be
referenced in the supporting recommendations.
6.1 Policy and strategy objectives
National
q
Council of Australian Governments Water Reform Agenda
The Federal and State Governments in the Council of Australian Governments’
(COAG) Water Reform Agenda have recognised the need to reform the water resource
industry and provide water for the environment. The 1994 COAG agreement
recognises the environment as a legitimate water user and environmental water
requirements must be assessed and provided. This agreement is a key driver for
studies such as this current study.
State
q
q
q
q
q
State Environment Protection Policy (SEPP) Waters of Victoria objectives
(Government of Victoria, 1988);
River Health Strategy;
Stressed Rivers Program;
Flora and Fauna Guarantee Act; and
Water Act.
The Department of Natural Resources and Environment developed the Victorian
Water for the Environment Program, to provide water for the maintenance and
restoration of environmental values in rivers and wetlands. The program’s objective is
to increase environmental flows, whilst recognising existing entitlements.
The other State strategies and acts are aimed at overall environmental management.
Environmental flows are one tool that can work with the Flora and Fauna Guarantee
Act to help maintain threatened species or communities. SEpP and the River Health
Strategy are working to set targets and guidelines for environmental conditions in
Victorian waterways.
Regional
q
q
q
q
Glenelg Regional Catchment Strategy
Water Quality in the Glenelg Catchment
Glenelg Catchment Waterway Strategy
Glenelg Hopkins Native Vegetation Plan
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 37
There are a series of regional plans and strategies that are relevant to the
environmental flows study. The Regional Catchment Strategy recommends a series of
actions and works that are aimed at improving ecosystem health, although not limited
to the aquatic ecosystem. These actions generally in concept and action support the
philosophy and implementation of the environmental flow recommendations. Water
quality and specifically salinity is a key issues within the Glenelg River and although
there are impacts on the flow regime the key actions to deal with this is through the
Water Quality Strategy.
6.2 Catchment objectives
Catchment objectives have been developed that are relevant to the overall catchment,
detail from these objectives relevant to each reach is covered within the detailed reach
objectives.
1) Provide an adequate environmental flow regime throughout the year that includes:
q
q
q
q
periods of no flows but without extending their frequency or duration;
minimum environmental flows during low flow periods;
appropriate flushing flows to manage salinity and nutrient levels; and
large channel forming flows.
2) Maintain and restore longitudinal connectivity by:
q
q
ensuring farm dam development in upper catchment does not impact flow
levels and variability in downstream reaches; and
improving flow over/through existing weirs.
3) Maintain and improve (where possible) stream habitat condition to enhance:
q
q
q
channel morphology (including large woody debris);
riparian vegetation; and
instream vegetation.
4) Maintain and enhance self-sustaining populations of endemic native fish with
particular emphasis on threatened species.
5) Manage flows for 24 threatened flora species dependant on flows.
6) Ensure that links to other strategies are fostered to promote the benefits of
environmental flows (e.g. implementation of a nutrient management plan to assist
in reducing nutrient rich runoff).
6.3 Environmental objectives
Specific environmental objectives for flow limited assets are listed in Table 6.1. The
list of assets is derived from the identified assets of the Glenelg System in Appendix
D.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 38
n
Table 6-1: Environmental objectives for the Glenelg River
Environmental Objective
1a
Self sustaining populations of River
Blackfish
1b
1c
2a
Self sustaining populations of Mountain
Galaxias
2b
2c
Process
Objectives
Relevant Flow
Component
Habitat
Low
Timing of
Flow
Component
All year
Recruitment
Movement
Freshes
High
Winter/Spring
Winter/Spring
Habitat
Low
All year
Recruitment
Movement
Freshes
High
Winter/Spring
Winter/Spring
3
Self sustaining populations of Yarra
Pygmy Perch
Habitat
Low
All year
4a
Self sustaining populations of Southern
Pygmy Perch
Habitat
Low
All year
Recruitment
Freshes
Winter/Spring
Habitat
Low
All year
Recruitment
Freshes
Winter/Spring
Habitat
Low
All year
Recruitment
Freshes
Winter/Spring
4b
5a
Self sustaining populations of
Variegated Pygmy Perch
5b
6a
Self sustaining populations of Dwarf
Galaxias
6b
7
Sustainable River Swamp Wallabygrass
Maintenance
Bankfull flows
Spring
8
Sustainable River Red Gum community
Maintenance
Bankfull flows
Winter/srping
9
Maintain diversity in channel form
Habitat diversity
High
Winter/Spring
10
Maintenance of estuary ecosystem
Restoration of
natural flooding
events
High flows
Spring
11a
11b
11c
Maintain benthic community diversity
Disturbance
Habitat
Disturbance
Cease to Flow
Low
Freshes
Summer
Summer
Winter/spring
12a
Maintenance of water quality in pools
Mixing,
destratification
Mixing,
destratification
Low
Summer
Fresh
All year
12b
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 39
7.
Discussion
The magnitude, duration, frequency and timing of flows are key aspects of a natural
flow regime to maintain channel form and viable populations of freshwater biota.
Alteration of the natural flow regime of Australian rivers has been shown to interfere
with the biology and assemblage structures of aquatic flora and fauna (e.g. Gehrke et
al. 1995, 1999, Koehn et al. 1995, Walker et al. 1994) and alter natural geomorphic
processes such as erosion and sedimentation (e.g. Bird 1985, Erskine 1986, Benn and
Erskine 1994, Burston and Good 1996, Brooks and Brierley 1997, Prosser et al. in
press).
In the Glenelg River, the regulation of river flows through Rocklands Reservoir and
associated deterioration in water quality and the condition and diversity of instream
habitat due to excessive sedimentation are likely to have caused a decline in the health
of the riverine ecosystem. (SKM 2001a).
Using a multi-disciplinary approach and integrated information on the ecology,
hydrology, geomorphology and water quality within the study area we have
recommended a flow regime that aims to maintain and where possible restore the
environmental values of the Glenelg system. The recommended flow regime
incorporates key components of the natural flow regime that are necessary for
biological, geomorphological and physicochemical processes.
The key components of the natural flow regime and the magnitude, duration,
frequency and timing of these components have been derived from modelled natural
flow regimes.
These components are considered critical for biological,
geomorphological and physicochemical processes:
1) periods of cease to flow;
2) low flows;
3) freshes during periods of cease to flow/low flow;
4) freshes during spring;
5) flow variability;
6) medium/sustaining flows; and
7) High flow (channel forming).
These components are common for all defined reaches of the Glenelg River, although
the first component (periods of cease to flow) is unique to Reach 1 and 2. The
ecological, geomorphological and physicochemical significance of each of the
hydrological regime components is outlined below.
7.1 Seasonal timing of releases
The magnitude of an environmental flow is an important consideration when
developing recommendations, but of similar importance is the timing of such releases
on a seasonal scale. As biota frequently associate life stages, such as spawning in
freshwater fish, with changes in temperature and other parameters it is imperative that
environmental flows are provided at the appropriate time of the year to encourage
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 40
population growth. The recommendations have been presented based on season.
Summer is defined as the months of December to May, inclusive. Winter is the
months of July to October, inclusive. June and November are transition months.
7.2 Periods of cease to flow
The cessation of flow is a common natural occurrence in Australian rivers. During
these periods the river may contract to a series of isolated pools thus decreasing the
diversity and availability of aquatic habitats to instream biota. Furthermore biota in
these pools are likely to be subject to intensified predation and physicochemical
stresses (e.g. low dissolved oxygen concentrations).
Whilst these factors may be considered to have an immediate detrimental effect on
aquatic flora and fauna, they are important disturbance mechanisms that prevent the
system being dominated by any particular group of organisms. The duration and
frequency of cease to flow events have been substantially increased in the Glenelg
River downstream of Rocklands Reservoir. Consequently, it is recommended that a
reduction in cease to flow events occur to a frequency and duration similar to that
which would occur under natural conditions.
7.3 Baseflows
Whilst the Glenelg River may cease to flow (e.g. summer-autumn), under a natural
flow regime, the river would be subject to periods of low or base flow when not
ceasing to flow. The daily baseflow for each site is equal to the median flow that
would have occurred under natural conditions, during that period. These flows (as
specified in the recommendations) would inundate bars between pools thus providing
habitat for macroinvertebrates and small-bodied fish. The inundation of bars would
also provide important linkages between pools (refuge habitats) and may enable the
redistribution of mobile biota from areas of poor water quality or unfavourable biotic
interactions.
7.4 Freshes during periods of cease to flow/low flow
Cease to flow periods are a natural perturbation to the system, these impose a stress on
the ecosystem which helps support the maintenance of community diversity. A key
component of the flow regime linked to the cease to flow periods is the brief summer
freshes that result from flash summer rains. Summer freshes, those flows that exceed
the natural median daily flow, are important in ephemeral rivers for the maintenance
or improvement of water quality. These freshes provide a brief respite to the system
and are critical to the maintenance of the ecosystem.
Summer freshes are unlikely to cause mixing of the saline pools that characterise the
mid reaches of the Glenelg River. In the Wimmera River Anderson and Morison
(1989) suggest that flows in excess of 3,000 ML/d are required for the destratification
of large pools. Summer freshes have been suggested to prevent significant increases
in salinity in the Wimmera River that occurs at flows of less than 10-20 ML/d (SKM
1997). It follows that in the mid reaches of the Glenelg River where the saline pools
exist that the summer freshes are critical in ensuring that the salinity does not exceed
tolerable levels any further.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 41
7.5 Spring freshes
Spring freshes are an important ecological component of the Glenelg River system.
Seasonal high flows during spring may stimulate migration and/or spawning of native
fish species that inhabit the region. In addition, spring freshes make available inchannel habitats such as vegetated bars, benches and undercuts. These habitats may
be important for the colonisation of macroinvertebrates and as spawning sites and
refuges for native fish. High flows during spring may also mobilise fine organic
material that would otherwise smother instream habitats.
7.6 Flow variability
Maintaining natural variability in stream discharge over this period is important for
both ecological and geomorphological processes. Under natural conditions variations
in water surface level and associated wetting and drying regimes of stream banks are
important for the creation of channel forms (e.g. pools, riffles, bars, benches) and
habitat attributes (e.g. large woody debris transport and placement). However,
constant flows and water surface levels tend to accelerate the rate of scour at the bank
toe which, in turn, may lead to bank slumping. Furthermore, constant discharge over
this period (May to November) may be detrimental to life history strategies and
subsequent recruitment of native fish, macrophyte and macroinvertebrate species.
7.7 High flows
Bank-full flows represent disturbances that occur naturally in the Glenelg River
system. Although bank-full flows are unpredictable and episodic in the Glenelg River,
these flows provide lateral connectivity between in-channel and flood plain habitats.
Maintaining occasional inundation of the flood plain is ecologically important and is
known to provide significant carbon returns to the river after a period of significant
production (plants, algae, micro and macroinvertebrates and possibly fish).
Significant inputs of carbon to the river during floodplain inundation may be critical in
maintaining food webs in systems which experience periods of low and cease to flow
conditions (Davies et al. 2001).
High flow regimes including bank-full flows are also important geomorphologically in
shaping and maintaining river and anabranch channels and also in preserving the
condition and availability of instream habitats. For example, bank-full flows will
assist in the resuspension and distribution of sediments that would otherwise smother
important benthic habitats (large woody debris and leaf-packs).
High flows occur within the stream channel. Flows greater than these high flows
would spill outside the river channel and are known as overbank flows. Although
overbank flows occur naturally in many river systems, such flows will not be
recommended due to the extraction of water under the current level of water resource
development in the catchment being unlikely to impact on the frequency and duration
of these events. In addition, these overbank flows can not be regulated by existing
infrastructure as they occur outside of the stream channel, therefore there is no means
of managing a flow of such magnitude.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 42
8.
Recommendations
The recommendations for the Glenelg River have been developed to maximise the
environmental benefits of the water provided. In some cases a series of
recommendations allow for future increases in environmental flows as provisions for
the environment may increase. These recommendations have been developed with the
best available knowledge at the time of this project. Further developments and
collection of raw data will support the ongoing development and revision of this work.
The proposed environmental flow regime has been developed on a reach-by-reach
basis to maximise environmental health through the provision of favourable water
quality and aquatic habitat conditions. The timing and magnitude of environmental
flows is important for any benefit to be realised within an aquatic environment. The
timing of environmental flows may be described as months or seasons.
Recommendations are provided in two forms. The first are the direct flow based
recommendations. These recommendations are presented in a series of tables that
summarise the environmental flow regime. The determination of the frequency and
duration of the selected magnitude in these tables has been assisted by spells plots.
The data has been analysed using the program, GetSpells. GetSpells examines the
daily flow series and determines the number of times (events) that the flow was above
(or below, if selected) a given magnitude and the duration of each event (Figure 8-1).
The program then presents this information in a graphical form. The program
produces two graphs for each assessment; one showing the frequency of the events per
100 years and the second showing statistics on the duration of these events.
The second component of the recommendations is the supporting recommendations
that are not specifically flow regime components but directly support the efficacy of
the recommended flow regime.
It may not be possible to implement fully all of the recommendations presented in
each year, particularly during dry years. For example, 5 summer freshes may not be
provided within a given year, however such variation in the availability of water
would have occurred. Subsequently, the implementation of the recommendations
should account for dry and wet years. During dry years, at least low flows will be
provided, while during wet years low flows and freshes will be provided. It is
suggested that a 5 year period be used to measure the implementation of the
recommendations and the annual frequency be over that period.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 43
F requency Plot
90
D ickR
Frequency plot
indicates
the
number
of
times that such
a
threshold
occurs per 100
years e.g. 88
times per 100.
Frequency per 100 years
80
70
60
50
40
30
20
10
0
1
T hreshold (M L )
Percenti l e Pl ot
25% of events
have a duration of
10 .0%greater than this
20 .0%
point (12 days).
50 .0%
Spell duratio n (day s) belo w th reshold
D ick R
These
two
points
indicate the
duration that
50% of the
events occur
for, i.e. most
events occur
for 2 to 12
days.
14
12
80 .0%
90 .0%
10
This
point
indicates
the
median
(midpoint) duration of
events (3.5 days).
8
6
4
25% of events
have a duration of
less than this
point (2 days).
2
Natural
0
1
T hresho ld (M L ) Current
n
Figure 8-1 An example of the two graphs produced by GetSpells.
8.1 Flow Recommendations
8.1.1
Reach 1 – Rocklands Reservoir – Chetwynd River
The following section details the flow recommendations (Table 8-1) and rationale for
these recommendations developed for Reach 1 in the Glenelg River.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 44
n
Table 8-1 Flow Recommendations Reach 1 – Rocklands Reservoir to
Chetwynd River
River
Glenelg River
Compliance Point
Reach
Harrow
Rocklands – Chetwynd River
Gauge No.
Flow
238 210
Rationale
Season
Magnitude
Frequency
Duration
Objective
Evaluation
Summer
(Dec – May)
Minimum
11 ML/d
Annual
Dec – May
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
> 64 ML/d
5 annually
Minimum 6
days
12b
Self-sustaining
populations of small
bodied fish
Self-sustaining
populations of small
bodied fish
June
100 ML/day
Annual
June
Winter
(Jul-Oct)
Minimum
150 ML/d
> 1400 ML/d
Annual
July-Oct
3 annually
3 days
Spring
(Sept)
> 450 ML/d
2 annually
November
130 ML/day
Annual
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
8, 11c
Minimum Flow
Maintained
Occurrence of large flow
10 days
1b, 1c, 2b, 2c, 4b, 5b,
6b, 7,12b
Self-sustaining
populations of fish
(Mountain Galaxias,
River Blackfish,
Common Galaxias,
Spotted Galaxias)
Off-stream habitats
wetted
November
7, 8
Although the Glenelg River does cease to flow in this reach (Figure 8-3), it is an
annual event of very short duration (less than 1 week). Consequently a cease to flow
recommendation is not made, particularly in light of the saline groundwater inputs that
would cause a significant stress to the ecosystem in periods of no flow.
The existing minimum flow recommendation is for a passing flow of 11 ML/day at
Harrow (Mitchell et al. 1996). The new recommendation is to maintain the 11
ML/day as the minimum flow, as it links the key habitats through the reach (Figure
8-5). This minimum flow should
apply to the whole of the summer
period. The minimum flow is
important to keep water running
through the reach and reduce the
impact of the saline intrusions to
the
ecosystem.
This
recommendation is supported by
previous studies by Mitchell et al.
(1996).
A priority for implementation are
the summer freshes, these freshes
provide a critical respite from the
low summer flow and are
ecologically important. The flow
WC01432:R04_MJS_GLENELG_FINAL.DOC
n
Figure 8-2 Shallow habitats in Glenelg
River Reach 1.
Final
PAGE 45
of the fresh is often defined as the median (50%) flow for the period, in this case 64
ML/day is the recommended magnitude as it provides a greater flow through the
habitats (Figure 8-5). To maximise the ecological and water quality benefit of
summer freshes the median natural duration of 6 days is recommended as the
minimum duration (Figure 8-4). These freshes naturally occurred, on average, 5 times
annually. The recommendation is that 5 freshes be maintained on an annual basis.
This fresh will wet many of the areas on bars and reduce the saline pool stratification.
Ex ceedance F requency Plot
3
10
2
D i ck R
10
1
10
0
10
-1
10
0
10
20
30
40
50
60
70
80
90
100
T i m e Ex ceeded (%)
n
Figure 8-3 Natural flow duration Glenelg River Reach 1 (Dick Roberts)
(Summer: December – May inclusive).
550
S cenar io 1
450
400
350
300
250
200
150
100
S cenario 1
18
Spel l durati on (day s) above threshol d
500
F requency per 10 0 years
Percent ile Plot
F req uency Plo t
16
1 0.0%
2 5.0%
14
5 0.0%
7 5.0%
9 0.0%
12
10
8
6
4
2
50
0
0
64
T hresho l d (ML )
n
64
T h resho l d (ML )
Figure 8-4 Natural duration and frequency of flows above the recommended
fresh (64 ML/day) in the Glenelg River Reach 1.
Current research is suggesting that a translucent dam operational policy could provide
significant environmental benefits, returning flow variability to a system downstream.
The strategy releases a certain percentage of the flows entering a storage directly
downstream. Thus any variability in the inflows is reflected in the flows downstream
of the storage. The spring freshes recommendation is aiming to return the variability
around the high flows. It is suggested that in the long term a translucent dam
operation at Rocklands Reservoir may more effectively provide the required flow
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 46
components and variability. When current research is completed, and if it confirms
the efficacy of translucent dam operations for the environment, a similar operational
regime should be examined for Rocklands Reservoir. The outlet structures at
Rocklands Reservoir may need modification to implement a translucent dam policy.
In the interim a minimum winter flow and spring freshes are recommended. The
magnitude of the spring fresh is the median spring flow of 450 ML/day.
.06
127
Elevation (m)
126
125
124
123
122
0
10
20
30
40
50
60
70
Station (m)
n
Figure 8-5 Cross section showing 11 ML/day (filled area) and 64 ML/day
(solid line) in channel at Glenelg River Site Reach 1.
In winter the minimum flow of 150 ML/day is aimed to provide significant water
through the inchannel habitats. This flow provides a continuous flow through the
reach and will have several benefits. It will provide longitudinal connectivity for the
mobile species in the reach, such as the native fish species. In addition it will wet the
margins of the channel where the emergent vegetation is found and wet low lying bars
a key habitat.
A spring or winter fresh is important in this reach to provide the biological cues for the
freshwater fish community. These cues can induce spawning or movement. The
recommended magnitude is greater than 450 ML/day the median flow for this period.
This flow will also wet the bulk of the channel. Multiple events are recommended to
allow a biological response, 2
events annually meets the natural
frequency of these events (Figure
8-7). A minimum duration of 10
days is the median natural duration
and will allow an effective
biological response.
The sand accumulation in this reach
means
that
large
sediment
mobilising flows are a key feature
of the recommended flow regime.
The recommended winter high flow n Figure 8-6 Glenelg River Reach 1 –
of 1400 ML/day is between the planview with water level at 1400 ML/day.
20% and 30% natural flow and is a
significant annual flow event. The recommended flow (1400 ML/day) wets all major
habitats in the reach (Figure 8-6) and would induce significant sediment mobilisation.
Larger flows that inundate the complete channel including the mid channel bars would
be only when Rocklands Reservoir is spilling. To promote fine sediment movement
and inputs of fresh water to the pools the recommended frequency is 3 events
annually, this replicates the natural frequency of the events (Figure 8-7). Because the
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 47
responses are physical rather than biological, the duration of the events can be a
shorter 3 days.
June and November are the transitional months between the high and low flow
seasons. The recommended flows for these periods are the 80% flows for the relevant
month. The ramping up and ramping down of flow through these transitional months
should be a gradual change in flow.
Due to the current lack of a suitable compliance point for the flow recommendations,
it is recommended that the streamflow gauge at Harrow (238 210) be reactivated.
In dry years it may not be possible to implement fully all of the recommendations.
For example, there may not be sufficient water to implement the 5 summer freshes
within a given year. Naturally there would have been this variation. As such the
implementation of the recommendations should account for dry and wet years. It is
suggested that a 5 year period be used to measure the implementation of the
recommendations and the annual frequency be over that period.
Frequency Plot
Sp el l duratio n ( days) above threshol d
F requency per 1 00 years
250
200
150
100
50
Scen ar io 1
80
10.0 %
25. 0%
70
50. 0%
60
75. 0%
90.0 %
50
40
30
20
10
0
0
450
1400
T hr esho l d (ML )
n
Percent ile Plot
90
Scen ar io 1
300
450
1400
T hr esho l d (ML )
Figure 8-7 Natural duration and frequency of spells above the spring fresh
(450 ML/day) and winter high flow (1400 ML/day) thresholds (ML/day) in the
Glenelg River Reach 1.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 48
n
Table 8-2 Maximum water depth for each cross section at
recommended flow Reach 1 – Rocklands Reservoir to Chetwynd River
each
Cross
Section
Flow
ML/day
Minimum
Channel
Elevation
Water
Surface
Elevation (m)
Maximum
Depth (m)
Flow Area
(m 2)
Water
Surface
Width
1
1
1
1
1
11
23
150
450
1400
122.94
122.94
122.94
122.94
122.94
123.07
123.11
123.28
123.44
123.66
0.13
0.17
0.34
0.5
0.72
0.16
0.3
1.47
3.76
8.79
2.72
3.69
10.81
19.73
25.6
2
2
2
2
2
11
23
150
450
1400
122.73
122.73
122.73
122.73
122.73
123.14
123.21
123.48
123.71
124.06
0.41
0.48
0.75
0.98
1.33
1.66
2.54
7.7
15.28
29.61
9.95
13.97
25.35
35.94
44.9
3
3
3
3
3
11
23
150
450
1400
122.06
122.06
122.06
122.06
122.06
123.14
123.21
123.49
123.75
124.13
1.08
1.15
1.43
1.69
2.07
7.99
9.03
14.22
21.11
33.45
13.17
14.42
24.93
29.59
34.95
4
4
4
4
4
11
23
150
450
1400
121.47
121.47
121.47
121.47
121.47
123.14
123.22
123.5
123.75
124.15
1.67
1.75
2.03
2.28
2.68
12.42
14.55
24.17
34.33
51.74
26.78
28.68
37.96
41.54
46.69
5
5
5
5
5
11
23
150
450
1400
122.47
122.47
122.47
122.47
122.47
123.14
123.22
123.5
123.76
124.16
0.67
0.75
1.03
1.29
1.69
4.93
7.09
15.52
25.5
45.13
26.38
28.39
32.02
42.77
57.16
6
6
6
6
6
11
23
150
450
1400
121.36
121.36
121.36
121.36
121.36
123.14
123.22
123.5
123.76
124.17
1.78
1.86
2.14
2.4
2.81
28.18
30.13
37.95
46.62
63.04
24.43
25.45
30.33
35.56
45.63
For the purpose of monitoring. the maximum water depth was calculated for each
recommended daily flow at each cross section (Table 8-2). Following implementation
of specific flows it will be possible to validate the assumption of the recommendation
by checking the maximum water depth at each cross section within the site. The site
plan view and cross section profiles are provided to assist in the determination of the
maximum channel depth across each cross section (Figure 8-8).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 49
Cross Section: 1
54H 0562172
UTM 5885340
Cross Section: 2
132
132
130
130
128
128
126
126
124
124
122
122
120
120
0
10
20
30
40
50
60
Cross Section: 3
70
80
90
100
110
54H 0562245
UTM 5885339
0
10
20
30
40
50
60
Cross Section: 4
132
132
130
130
128
128
126
126
124
124
122
122
120
70
80
90
100
110
54H 0562281
UTM 5885313
120
0
10
20
30
40
50
60
Cross Section: 5
70
80
90
100 110
54H 0562294
UTM 5885280
0
10
20
30
40
50
60
Cross Section: 6
132
132
130
130
128
128
126
126
124
124
122
122
120
70
80
90
100
110
54H 0562317
UTM 5885246
120
0
n
54H 0562200
UTM 5885336
10
20
30
40
50
60
70
80
90
100
110
0
10
20
30
40
50
60
70
80
90
100
110
Figure 8-8 Cross Sections Site 3: Glenelg River upstream of Dick Roberts’
property, upstream of Harrow
For each flow recommendation for Reach 1, there are a series of risks associated with
not meeting the respective recommendation. Subsequently, these recommendations
have been prioritised based on the level of risk to the aquatic environment of not being
met (Table 8-3). The first priority for Reach 1 is the maintenance of a minimum
summer flow to maintain suitable conditions. If this flow is not met, water quality
would be compromised to the detriment of small bodied fish and the benthic
community. The flow recommendations with the lowest priority for implementation is
the winter high flow of 1400 ML/d. If this flow recommendation is not met, there is
likely to be a lack of diversity in channel form and subsequently aquatic habitat. In
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 50
addition, the lack of a flow of such magnitude would lead to a loss of benthic
community diversity and a build up of sand in the channel.
n
Table 8-3 Priority for implementation of flow recommendations for Reach 1,
indicating risk of not meeting respective recommendations.
Season
Magnitude
Priority
Risk if not met
Summer
(Dec – May)
Minimum
11 ML/d
A
Summer
(Dec – May)
Winter
>23 ML/d
C
Minimum
150 ML/d
>1400 ML/d
B
>450 ML/d
D
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish and the benthic
community
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish
Not mimicing natural flow variability as well as adverse water quality conditions
and limited availability of aquatic habitat
Lack of diversity in channel form and subsequently aquatic habitat. Also loss of
benthic community diversity and a build up of sand in the channel
Lack of recruitment of many fish species and a reduction in water quality
conditions to the detriment of aquatic species
(Jul – Oct)
Winter
(Jul – Oct)
Spring
E
(Sept)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 51
8.1.2
Reach 2 – Chetwynd River to Wannon River
The following section details the flow recommendations (Table 8-4) and the rationale
used in the development of those recommendations for Reach 2 of the Glenelg River.
n
Table 8-4 Reach 2 Chetwynd River to Wannon River
River
Glenelg River
Compliance Point
Reach
Roseneath
Chetwynd River – Wannon River
Gauge No.
Flow
238 211
Rationale
Season
Magnitude
Frequency
Duration
Objective
Evaluation
Summer
(Dec – May)
0 ML/d
3 annually
11a
Cease to flow occurs
Minimum
16 – 77 ML/d
Annual
Maximum 8
days
Dec – May
(excl. CTF)
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
> 77 ML/d
4 annually
7 – 15 days
12b
Self-sustaining
populations of small
bodied fish
Self-sustaining
populations of small
bodied fish
June
93 ML/d
Annual
June
1a, 2a, 3, 4a, 5a, 6a,
8a, 11a, 12b, 13a
Self-sustaining
populations of small
bodied fish
Winter
(July – Oct)
Minimum
385 ML/d
> 3600 ML/d
Annual
July – Oct
2 annually
Minimum 4
days
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
7, 8, 11c
Minimum Flow
Maintained
Occurrence of large flow
November
110 ML/d
Annual
November
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
Self-sustaining
populations of small
bodied fish
Spring
(Sept)
> 700 ML/ d
2 – 3 annually
5 days
1b, 1c, 2b, 2c, 4b, 5b,
6b, 12b
Self-sustaining
populations of fish
(Common Galaxias
Mountain Galaxias,
River Blackfish, Pygmy
Perch)
Off-stream habitats
wetted
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 52
Hydrological analysis indicates that cease to flow events would occur naturally within
Reach 2 approximately 30 % of the time during the identified summer period of
December to May, inclusive
(Figure 8-10). The events are
relatively short with a median
duration of 4 days and 75% of
events occurring for no longer
than 8 days, although the average
frequency is 3.5 times per year
(Figure 8-11). It is recommended
that these cease to flow events be
maintained to occur 3 times
annually and last no longer than 8
days. The occurrence of such
flow periods benefits the aquatic
ecosystem by providing an
environmental disturbance that n Figure 8-9 Cross section 3 at Site 5
(Roseneath) Reach 2 Glenelg River.
prevents the domination of an
area
by
a
particular
macroinvertebrate species, as many species would be reduced in their abundance and
distribution during the dry period. Species diversity would subsequently be increased
on rewetting of the channel. Extending the duration of these events risks impacts on
the ecosystem.
Cease to flow events should not be implemented until there is further improvement in
water quality, specifically salinity throughout the reach. In the current catchment
conditions, saline inputs into the river lead to saline pool formation in this reach of the
Glenelg River. A cease to flow period under these conditions could significantly
exacerbate this issue and result in impacts to the aquatic ecosystem. Consequently, in
the interim it is not recommended to implement the cease to flow period until the
impacts of saline pool formation has been reduced by catchment actions.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 53
3
D ai l y F l ow (M L /day )
10
2
10
1
10
0
10
-1
10
0
10
20
30
40
50
60
70
80
90
100
T i m e E xceeded (% )
n
Figure 8-10 Flow duration Glenelg River Reach 2 at Site 5 (Roseneath)
(Summer December – May inclusive).
Percent il e Pl ot
Freq uency Pl ot
400
25
350
10.0 %
25 .0%
20
50 .0%
75 .0%
90.0 %
15
10
Frequen cy per 10 0 years
Spel l d urati on ( days) bel ow thresho ld
S cenar io 1
300
250
200
150
100
5
50
0
0
1
16
T hre sh ol d (ML )
n
1
16
T hre sh ol d (ML )
Figure 8-11 Spell analysis Glenelg River Reach 2 at Site 5 (Roseneath),
spells less than threshold (1 ML/day, 16 ML/day) (Summer: December – May
inclusive).
In summer the recommended minimum flow is 16 ML/day, this provides a minimum
level of connectivity through the habitats in the reach (Figure 8-12). It is also the
equivalent flow to the minimum flow recommendation in Reach 1, accounting for
inflows over the distance between the two compliance points. Cross section 3 is a low
flow control and at the minimum flow of 16 ML/day there would be approximately
0.08m of water passing over this point. This water depth presents a potential risk, but
the sandy nature of the Glenelg River at this location would suggest that such a
discharge would maintain flow through the large woody debris (LWD), roots and sand
in this cross section (Figure 8-9). The maintenance of a connecting flow within this
reach would assist in maintaining a water quality within the pools over summer. This
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 54
flow would mix the water in these pools to the benefit of temperature, dissolved
oxygen and salinity.
Glenelg
Plan: Site 5 - roseneath
TS3
.06
55.0
54.5
Elevation (m)
54.0
53.5
53.0
52.5
52.0
51.5
51.0
0
20
40
60
80
Station (m)
n
Figure 8-12 Cross section 3 Site 5 (Roseneath) Glenelg River Reach 2,
showing water level at recommended summer minimum flow 16 ML/day.
The summer fresh for Reach 2 is greater than the median summer flow of 77 ML/day
(Table 8-5). The recommendation for the summer fresh is for it to last at least 7 days
on average 4 times annually. This recommendation means that the freshes will exceed
the duration of 75% of the natural events (Figure 8-13). These short, but frequent,
summer freshes will act to mix pools and minimise the risk of saline pool formation to
the benefit of aquatic dependent species.
n
Table 8-5 Flow percentiles Glenelg River Reach 2 (Summer: December-May
inclusive).
Site
BurkesB
Roseneath
Section Rd
10%
335.6
356
434.5
20%
193.6
199.1
243
30%
137
138.8
169.4
40%
105.6
103.4
126.2
50%
86.5
77.2
94.3
60%
70.5
55.5
67.8
Percenti le Pl ot
450
Sce nar io 1
400
80
1 0.0 %
25. 0%
70
50. 0%
75. 0%
9 0.0 %
60
50
40
30
Freq uen cy p er 1 00 y ears
Spell dur ation (days) abov e threshold
80%
14.5
15.8
19.3
Frequenc y Pl ot
90
350
300
250
200
150
20
100
10
50
0
0
16
77
T hr eshold ( ML )
n
70%
55.4
29.4
35.9
16
77
T hr esh old ( ML )
Figure 8-13 Spell analysis Glenelg River Reach 2 at Site 5 (Roseneath),
spells greater than threshold (16 ML/day, 77 ML/day) (Summer: December –
May inclusive).
The winter minimum flow is aimed at maintaining a flow over a range of habitats
throughout the site. The recommended minimum is 385 ML/day, which is between
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 55
90%
4.2
0.1
0.1
the 70% and 80% flow for the winter period naturally (Table 8-6). Similar to the
minimum flow recommendation during the summer period, the winter minimum flow
is aimed at improving water quality conditions, including diluting salinity in pools, to
the benefit of aquatic dependent species.
n
Table 8-6 Flow percentiles Glenelg River Reach 2 (Winter: July-October
inclusive).
Site
BurkesB
Roseneath
SectionRd
10%
3210.8
4153.2
5068.4
20%
2075.6
2510.7
3063.9
30%
1472.2
1647.5
2010.5
40%
1122.4
1204.6
1470.1
50%
837.1
926.6
1130.7
60%
652.3
653.3
797.3
70%
490.0
477.8
583.1
80%
345.6
348.8
425.7
The accumulation of sand within this reach of the Glenelg River has smothered the
aquatic habitat, hence large sediment mobilising flows are a key recommended feature
of the flow regime. During winter the recommended large flows can be utilised to
displace this sand deposit. To prevent the accumulation of further sand downstream, it
is also recommended that sand extraction be conducted in addition to the large flows
to remove, rather than shift, the problem. The recommended flow is that in excess of
3600 ML/day for a minimum of 4 days twice annually (Figure 8-14). The relatively
short duration annual event will be able to provide the large disturbance required.
Percen t il e Pl ot
Freq uen cy Pl ot
300
Scena rio 1
80
10. 0%
25 .0%
70
50 .0%
75 .0%
90. 0%
60
50
40
30
250
Freq uen cy p er 10 0 y ears
Spell du ration (d ays) abo ve th resho ld
90
200
150
100
20
50
10
0
0
707
3653
T hr esho ld ( ML )
n
707
3653
T hr esho ld ( ML )
Figure 8-14 Spell analysis Glenelg River Reach 2 at Site 5 (Roseneath),
spells greater than threshold (707 ML/day, 8653 ML/day) (Winter: July October inclusive).
Many aquatic biota utilise increases in flow to induce certain stages of their lifecycle.
Many fish species utilise these increases in flow to induce spawning, and such flows
permit the access to previously inaccessible habitats. The proposed spring freshes
would be utilised by many fish species in the Glenelg River to gain access to suitable
sites for spawning. The recommended spring fresh is greater than 700 ML/day for a
minimum of 5 days, 2 – 3 time annually. Although 75% of the events would have
occurred for at least 4 days (Figure 8-14), 5 days is a suggested minimum as this has
been agreed as the minimum duration for an event to have ecological significance.
June and November are the transitional months between the high and low flow
seasons. The recommended flows for these periods are the 80% flows for the relevant
month. The recommendation for June is 83 ML/day, and 110 ML/day in November.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 56
90%
221.8
209.1
255.1
The ramping up and ramping down of flow through these transitional months should
be a gradual change in flow.
The most appropriate location for gauging the compliance with the recommended
environmental flows is Warrock Road at Roseneath. A gauge is not currently
established at this site but it is recommended that such a gauge be established in the
near future. Until this gauge is created it is recommended that gauge 238 211 at
Dergholm be utilised in the interim.
n
Table 8-7 Maximum water depth for each cross section at
recommended flow Reach 2 – Rocklands Reservoir to Chetwynd River.
Cross
Section
Flow
ML/day
1
1
1
1
1
each
Water
Surface
Elevation (m)
51.5
51.69
52.22
52.03
53.28
Water Depth
(m)
Flow Area
(m 2)
16
77
700
385
3600
Minimum
Channel
Elevation
51
51
51
51
51
0.5
0.69
1.22
1.03
2.28
1.74
3.74
10.87
7.99
30.75
Water
Surface
Width (m)
8.55
11.47
15.1
13.92
25.54
2
2
2
2
2
16
77
700
385
3600
51.24
51.24
51.24
51.24
51.24
51.46
51.6
52.1
51.88
53.2
0.22
0.36
0.86
0.64
1.96
0.59
2
13.85
7.65
49.75
6.22
13.72
29.05
25.74
36.7
3
3
3
3
3
16
77
700
385
3600
51.17
51.17
51.17
51.17
51.17
51.25
51.36
52.03
51.71
53.18
0.08
0.19
0.86
0.54
2.01
0.24
0.78
9.12
3.73
45.89
4.14
5.98
18.83
12.42
41.49
4
4
4
4
4
16
77
700
385
3600
50.19
50.19
50.19
50.19
50.19
50.86
51.1
51.94
51.62
53.1
0.67
0.91
1.75
1.43
2.91
2.46
4.29
15.33
9.47
50.5
7.42
8.08
20.27
14.97
38.67
5
5
5
5
5
16
77
700
385
3600
49.41
49.41
49.41
49.41
49.41
50.86
51.1
51.94
51.62
53.09
1.45
1.69
2.53
2.21
3.68
14.89
18.79
37.56
28.72
84.93
15.85
16.85
30.71
23.19
52.08
6
6
6
6
6
16
77
700
385
3600
50.57
50.57
50.57
50.57
50.57
50.86
51.09
51.9
51.59
53.02
0.29
0.52
1.33
1.02
2.45
0.64
1.95
9.15
5.95
38.91
4.4
6.58
11.23
9.44
36.02
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 57
n
Figure 8-15 Plan View Site 5: Glenelg River at Roseneath, Reach 2.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 58
Cross Section: 1
54H 0523995
UTM 5856182
Cross Section: 2
56
56
55
55
54
54
53
53
52
52
51
51
50
54H 0524013
UTM 5856164
50
49
0
10
20
30
40
50
60
Cross Section: 3
70
80
90
100
110
49
0
54H 0523999
UTM 5856163
10
20
30
40
50
60
Cross Section: 4
56
56
55
55
54
54
53
70
80
90
100
110
54H 0524027
UTM 5856160
53
52
52
51
51
50
50
49
0
10
20
30
40
50
60
Cross Section: 5
70
80
90
100
110
0
54H 0524039
UTM 5856081
10
20
30
40
50
60
Cross Section: 6
56
56
55
55
54
54
53
53
52
70
80
90
100
110
54H 0524071
UTM 5856101
52
51
51
50
50
49
0
n
49
10
20
30
40
50
60
70
80
90
100
110
49
0
10
20
30
40
50
60
70
80
90
100
110
Figure 8-16 Cross Sections Site 5: Glenelg River at Roseneath.
For each flow recommendation for Reach 2, there are a series of risks associated with
not meeting the respective recommendation. Subsequently, these recommendations
have been prioritised based on the level of risk to the aquatic environment of not being
met (Table 8-8), which do not necessarily correspond to the relative increases in flow
magnitude. The first priority for Reach 2 is the maintenance of a minimum summer
flow to maintain suitable conditions. If this flow is not met, water quality would be
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 59
compromised to the detriment of small bodied fish and the benthic community. The
flow recommendations with the lowest priority for implementation is the winter high
flow of 3600 ML/d. If this flow recommendation is not met, there is likely to be a lack
of diversity in channel form and subsequently aquatic habitat. In addition, the lack of a
flow of such magnitude would lead to a loss of benthic community diversity and a
build up of sand in the channel.
n
Table 8-8 Priority for implementation of flow recommendations for Reach 2,
indicating risk of not meeting respective recommendations.
Season
Magnitude
Priority
Summer
(Dec – May)
Summer
(Dec – May)
0 ML/d
E
Loss of benthic community diversity
Minimum
16-77 ML/d
A
>77 ML/d
C
Minimum
385 ML/d
>3600 ML/d
B
>700 ML/d
D
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish and the benthic
community
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish
Not mimicing natural flow variability as well as adverse water quality conditions
and limited availability of aquatic habitat
Lack of diversity in channel form and subsequently aquatic habitat. Also loss of
benthic community diversity and a build up of sand in the channel
Lack of recruitment of many fish species and a reduction in water quality
conditions to the detriment of aquatic species
Summer
(Dec – May)
Winter
(Jul – Oct)
Winter
(Jul – Oct)
Spring
F
(Sept)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Risk if not met
Final
PAGE 60
8.1.3
Reach 3 – Wannon River to Tidal Extent
The following section details the flow recommendations (Table 8-9) and the rationale
used in the development of those recommendations for Reach 3 of the Glenelg River.
n
Table 8-9 Reach 3 – Wannon River to Tidal Extent
River
Glenelg River
Compliance Point
Reach
Dartmoor
Wannon River – Tidal Extent
Gauge No.
Flow
238206
Rationale
Season
Magnitude
Frequency
Duration
Objective
Evaluation
Summer
(Dec – May)
Minimum
83 ML/d
Annual
Dec – May
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
> 216 ML/d
4 annually
Minimum
5 days
12b
Self-sustaining
populations of small
bodied fish
Self-sustaining
populations of small
bodied fish
June
180 ML/d
Annual
June
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
Self-sustaining
populations of small
bodied fish
Winter
(July – Oct)
Minimum
629 ML/d
Annual
July – Oct
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
Minimum Flow
Maintained
November
130 ML/d
Annual
November
1a, 2a, 3, 4a, 5a, 6a,
11b, 12a
Self-sustaining
populations of small
bodied fish
Spring
(Sept)
> 2200 ML/d
2 – 3 annually
Minimum 5
days
1b, 1c, 2b, 2c, 4b, 5b,
6b, 7,11c, 12b
Self-sustaining
populations of fish
(Common Galaxias,
Australian Smelt)
Recommendations in this reach could be divided into two components. A cease to
flow is a relevant feature of the flow regime near Sandford, whereas it is not near
Dartmoor (Figure 8-17; Figure 8-18). The difference in the flow regime is likely to be
a result of the different positions in the catchment, with the region near Sandford
being a losing greater water than it gains. Losses occur for a variety of reasons in
rivers including evaporation, seepage into ground water and the occurrence of
subterranean flow that will resurface further downstream.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 61
4
10
Dail y Flow (ML /day)
3
10
Dartmoor
2
10
Sandford
1
10
0
10
-1
10
0
10
20
30
40
50
60
70
80
90
100
T im e Ex ceeded (% )
n
Figure 8-17 Flow duration Glenelg River Reach 3 at Site 7 – Sandford
(Red/Solid) and Site 8 – Dartmoor (dotted) (Summer December – May
inclusive).
Percent i le Plot
Freq uency Pl ot
8
350
7
6
1 0.0%
2 5.0 %
5 0.0 %
5
7 5.0 %
9 0.0%
4
3
300
250
200
150
2
100
1
50
0
n
Freq uency per 1 00 y ears
Spel l dur ati on ( days) b el o w th resho ld
Sce nar io 1
0
1
1
Th resh ol d (M L )
Th resh ol d (M L )
Figure 8-18 Spell analysis Glenelg River Reach 3 at Site 7 (Sandford), spells
less than threshold (1 ML/day) (Summer: December – May inclusive).
The recommended minimum summer flow of 83 ML/day through Reach 3 is aimed to
provided longitudinal habitat connectivity through the reach. The river is a wide
U-shaped channel in this lower reach and the minimum flow is needed to be
significantly higher that that in upstream reaches to provide this connectivity to benefit
water quality and subsequently aquatic species (Figure 8-19; Figure 8-23).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 62
n
Figure 8-19 Glenelg River Reach 3, Site 8 (Dartrmoor) – indicating wide
channel and abundance of woody debris.
The summer and spring freshes are the key components of the flow regime that should
be implemented as a priority in this reach. The summer freshes, flows greater than
216 ML/day (Table 8-10), naturally occurred on average 4 times per year (Figure
8-20). The recommendation has been to mimic this frequency with a duration for a
minimum of 5 days. Naturally 75% of the events lasted for 7 days minimum, but 5
days is considered a minimum duration for events to be ecologically relevant and it
was considered more important to maintain the annual frequency. These freshes will
improve water quality conditions, particularly temperature, dissolved oxygen and
salinity, to the benefit of aquatic biota.
n
Table 8-10 Flow percentiles Glenelg River Reach 3 (Summer: December-May
inclusive).
Site
Sandford
Dartmoor
10%
642.5
864.9
20%
363.6
493.4
30%
246.5
343.1
40%
189.5
269.7
50%
149.8
215.5
Perc enti le Pl ot
Scen ar io 1
70%
72.6
119
80%
45.2
82.9
Frequency Plot
400
40
10 .0 %
2 5. 0%
35
5 0. 0%
7 5. 0%
90 .0 %
30
25
20
15
350
300
250
200
150
100
10
50
5
0
0
n
450
Frequency per 100 y ears
Spell dur at ion (day s) abov e threshold
45
60%
115.8
158.6
216
216
T hr eshold ( ML )
Threshold (M L)
Figure 8-20 Spell analysis Glenelg River Reach 3 at Site 8 (Dartmoor), spells
greater than threshold (21 ML/day) (Summer: December – May inclusive).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 63
90%
10.9
54.7
The minimum winter flow is recommended to be 629 ML/day. This flow is aimed at
providing connectivity through the major habitats in the system, subsequently wetting
a large portion of the stream channel (Table 8-12). The minimum winter flow acts as
a base from which larger flows such as the high flows or freshes develop. The
abundance of large woody debris in this reach will be inundated under such flow and
lead to increased submersed habitat complexity.
The spring freshes are targeted to act as biological cues for the biota that occur in
Reach 3. These freshes would have occurred naturally on average 2.5 times annually
(Figure 8-21), the recommendation is for the average to be between 2 – 3 times
annually. Naturally 75% of the events would have lasted for 5 days, and the
recommendation is for this to be the minimum duration of the freshes.
Frequ en cy Pl ot
Percent i le Plo t
Scen ari o 1
250
70
10 .0%
2 5.0 %
60
5 0.0 %
7 5.0 %
90 .0%
50
40
30
20
200
150
100
50
10
0
n
Fre qu en c y p er 1 0 0 y e ars
Spe ll d ur atio n (d ay s) ab ov e thr esh o ld
80
0
2200
2200
Th resh old (M L )
T hr esho ld ( ML )
Figure 8-21 Spell analysis Glenelg River Reach 3 at Site 8 (Dartmoor), spells
greater than threshold (2200 ML/day) (Winter: July – October inclusive).
The high flow recommendations of greater than 2200 ML/day will have a key benefit
for the freshwater section of this reach providing a significant disturbance and
sediment mobilisation. In addition, there are substantial benefits to the estuarine
section of the Heritage Reach of the river from the high flows. One of the key threats
to the tidal reach is the lack of flushing because of the reduced flows in the river. The
high winter flow event will increase the large flushing flows through the tidal reach.
The implementation of this recommendation is not a high priority, relative to the
minimum flows and freshes. It is likely that large events will be beyond the control of
extractions and regulating structures and occur on a more natural frequency.
n
Table 8-11 Flow percentiles Glenelg River Reach 3 (Winter: July-October
inclusive).
Site
Sandford
Dartmoor
10%
8693.0
11946.4
20%
5290.1
7238.0
WC01432:R04_MJS_GLENELG_FINAL.DOC
30%
3472.4
4743.7
40%
2577.3
3493.8
50%
1984.6
2681.3
60%
1440.0
2047.1
70%
1042.7
1476.0
80%
711.1
926.8
Final
PAGE 64
90%
417.1
531.9
n
Table 8-12 Maximum water depth for each cross section at each
recommended flow Reach 3 – Wannon River to Tidal Extent.
Cross
Section
Flow
ML/day
Water
Surface
Elevation (m)
0.76
0.95
2.15
1.34
Water Depth
(m)
Flow Area
(m 2)
83
216
2200
629
Minimum
Channel
Elevation
-0.45
-0.45
-0.45
-0.45
1.21
1.4
2.6
1.79
6.96
8.7
27.27
13.44
Water
Surface
Width (m)
9
10.05
21.05
13.98
1
1
1
1
2
2
2
2
83
216
2200
629
-0.25
-0.25
-0.25
-0.25
0.76
0.94
2.12
1.32
1.01
1.19
2.37
1.57
6.83
9.34
31.55
15.77
12.94
15.03
21.45
18.14
3
3
3
3
83
216
2200
629
0.5
0.5
0.5
0.5
0.67
0.77
2
1.2
0.17
0.27
1.5
0.7
0.95
2.11
27.3
9.7
9.04
15.07
24.04
19.67
4
4
4
4
83
216
2200
629
-0.86
-0.86
-0.86
-0.86
0.54
0.76
1.9
1.15
1.4
1.62
2.76
2.01
12.25
15.27
36.25
21.48
13.26
14.46
21.44
17.5
5
5
5
5
83
216
2200
629
0.03
0.03
0.03
0.03
0.53
0.74
1.86
1.13
0.5
0.71
1.83
1.1
2.14
5.12
28.88
12.73
8.63
18.07
23.35
20.56
6
6
6
6
83
216
2200
629
-0.05
-0.05
-0.05
-0.05
0.41
0.62
1.78
1.04
0.46
0.67
1.83
1.09
2.99
5.72
31.57
12.45
11.49
13.78
30.19
19.36
Glenelg
Plan: Site 8 - dartmoor
Legend
WS PF 3
Ground
Bank Sta
n
Figure 8-22 Plan View Site 8: Glenelg River at Dartmoor, Reach 3.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 65
Cross Section: 1
54H 0525093
UTM 5802697
Cross Section: 2
10
10
8
8
6
6
4
4
2
2
0
0
20
40
60
80
100
-2
0
0
20
40
60
80
100
-2
Cross Section: 3
54H 0525073
UTM 5802641
Cross Section: 4
10
10
8
8
6
6
4
4
2
2
0
0.0
20.0
40.0
60.0
80.0
100.0
-2
54H 0525041
UTM 5802614
0
0.0
20.0
40.0
60.0
80.0
100.0
-2
Cross Section: 5
54H 0525020
UTM 5802620
Cross Section: 6
10
10
8
8
6
6
4
4
2
2
0
0.0
20.0
40.0
60.0
80.0
-2
n
54H 0525092
UTM 5802692
100.0
54H 0524979
UTM 5802562
0
0.0
20.0
40.0
60.0
80.0
100.0
-2
Figure 8-23 Cross Sections Site 8: Glenelg River at Dartmoor.
For each flow recommendation for Reach 3, there are a series of risks associated with
not meeting the respective recommendation. Subsequently, these recommendations
have been prioritised based on the level of risk to the aquatic environment of not being
met (Table 8-13), which do not necessarily correspond to the relative increases in flow
magnitude. The first priority for Reach 3 is the maintenance of a minimum summer
flow to maintain suitable conditions. If this flow is not met, water quality would be
compromised to the detriment of small bodied fish and the benthic community. The
flow recommendations with the lowest priority for implementation is the winter high
flow of 2200 ML/d. If this flow recommendation is not met, there is likely to be a lack
of diversity in channel form and subsequently aquatic habitat. In addition, the lack of a
flow of such magnitude would lead to a loss of benthic community diversity and a
build up of sand in the channel.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 66
n
Table 8-13 Priority for implementation of flow recommendations for Reach 3,
indicating risk of not meeting respective recommendations.
Season
Magnitude
Priority
Risk if not met
Summer
(Dec – May)
Minimum
83 ML/d
A
Summer
(Dec – May)
Winter
>216 ML/d
C
Minimum
629 ML/d
B
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish and the benthic
community
Adverse water quality conditions and low availability of aquatic habitat that
may lead to deleterious effects on small bodied fish
Not mimicing natural flow variability as well as adverse water quality conditions
and limited availability of aquatic habitat
>2200 ML/d
D
(Jul – Oct)
Winter
(Jul – Oct)
Lack of recruitment of many fish species and a reduction in water quality
conditions to the detriment of aquatic species. Also lack of diversity in channel
form and subsequently aquatic habitat. Also loss of benthic community
diversity and a build up of sand in the channel
8.2 Supporting recommendations
While site-specific flow bands are in themselves important, our recommendations also
consider longitudinal and lateral connectivity issues and tributary inflows. We
recognise that not all flow peaks were naturally conveyed down the length of the
channel, so not all freshes recommended in upper sections are included in the lower
reaches. Hence, our recommendations for lower reaches allow for travel times and
attenuation of flows as water is moved downstream through the system.
The additional water introduced to the system from the various confluences is a major
factor in our recommendations and affects the timing and magnitude of any of the
flow components in downstream reaches.
The value of managing summer flows in the river is limited if the peaks in flow caused
by freshes are taken off along the way and not allowed to flow through the system to
lower reaches. These flows are vital to ease the summer stress that the low-flow
condition imposes on the instream ecosystem. Even small flows can freshen up pools
and provide some opportunity for movement into other habitats that are possibly less
stressed or less utilised by competitors.
Lateral connectivity issues are also complicated in the Glenelg River. Although there
are real management issues associated with recommending higher flows, connectivity
with a degraded riparian zone may be of limited ecological value. Two main issues
require attention throughout the catchment: better management of stock access
(through fencing) to the stream margins and better weed management throughout the
riparian zone.
Lateral connectivity also relates to connectivity to the local groundwater. In the case
of the Glenelg River, water quality in the mid reaches is adversely affected by saline
groundwater returns. Catchment management of irrigation techniques and vegetation
cover often quite remote to the stream will be required to manage groundwater
interception.
Finally, we cannot recommend strongly enough, the need for ongoing monitoring of
the implementation of our recommendations. There is no easily prescribed recipe for
returning natural values to impacted streams and our recommendations must be
carefully scrutinised and adapted, as appropriate. Streams are dynamic parts of the
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 67
landscape that demand equally dynamic management. All recommendations listed
here rely on the information available at the time of writing. This information will
change and should be monitored to allow an adaptive management regime of the
system into the future.
In summary the series of key supporting recommendations include:
1) Monitor the implementation of the recommendations and adapt where
appropriate
There is a range of monitoring components that should be considered, including:
q
As the summer and spring freshes are implemented, physical monitoring of key
water quality parameters (dissolved oxygen, temperature and electrical
conductivity) should be monitoring on a regular frequency at stages downstream.
For example, ongoing monitoring in Reach 2 to assess changes in saline pools
formation, the impact of cease to flow events and freshes is critical.
q
Recruitment of key fish species is a suggested indicator for several flow
components this requires ongoing monitoring to understand what the limiting
factors for recruitment are in the system.
q
Within the Glenelg River, sand accumulation and its effect on channel structure
and habitat diversity are key issues. Large flows have been recommended that
should mobilise sediments through the system. The efficacy of the large flows
recommended should be monitored to determine if sand is moving and where it is
accumulating. This could be used to target sand extraction activities.
q
To validate the assumptions used in the development of the recommendations,
depth monitoring at the cross-sections should occur during implementation of the
flow components to check the assumptions and accuracy of the flow benefits.
The tables have been provided that specify the maximum depth of water for each
cross section at recommended flows.
q
An integrated monitoring program to assess the changes and benefits of the
environmental flow releases should be designed and implemented as soon as
possible. This program should integrate water quality and biological indicators
through the system and build on the work by Brad Mitchell and Deakin
University.
2) Monitor the impact of future extractions within the catchment
Currently there are relatively small levels of extractions from the Glenelg River,
excluding Rocklands and Moora Moora Reservoirs. Any further extractions through
pumping or farm dams should be closely monitored.
3) Examine the removal of fish barriers
The highest priority fish barrier has already been removed from the Glenelg River, the
remaining identified barriers are the series of fixed crest weirs near Balmoral. These
barriers should be removed when appropriate in line with the state fishway strategy
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 68
(DNRE 1999). In addition, the feasibility of improving the movement of fish beyond
Rocklands Reservoir.
4) Fencing and stock control of stream length
This is an ongoing program as part of the waterway planning process. To manage bed
and bank structure with flows, external influences such as stock access require control.
5) Weed control
This action is also supported by the catchment plan and waterway plans. Weed
management will enhance the benefits as a result of the implementation of
environmental flows.
6) Manage inputs of saline water into the lower reaches
This is a key catchment action that will remove the requirement of large flushing
flows to ameliorate saline pool effects. Until these actions have been undertaken,
recommendations into summer cease to flow would not be implemented.
7) Examine impact of cold water releases downstream of Rocklands Reservoir
This is a key study that is beyond the scope of the current study but would build upon
the current results. Rocklands Reservoir is deep enough and has a bottom release
outlet to consequently be a substantial source of cold water effects in the mid reaches
of the Glenelg River. Cold water released from Rocklands Reservoir may have a
significant effect on the community structure or reproductive capacity of the
populations, reducing potential benefits of the environmental flow releases for this
reach. A study should examine the potential impacts of the Rocklands Reservoir
releases and determine if they would limit the environmental flow benefits in the
system.
8) Examine potential sand extraction sites
As discussed in previous strategies sand extraction is likely to be the only method of
removing significant amounts of sand from the Glenelg River. High flows will move
sand down this system, but this is just likely to transfer the problem. The best option
would be to extract sand directly from several sites to increase the efficacy of the high
flows recommended.
9) Areas of bank stabilisation
The stabilisation of stream banks is important to reduce erosion and hence encourage
the establishment of native fringing vegetation and reduce input of sediment into the
river. Unstable banks can also lead to lateral expansion of the river channel that result
in the reduction of the velocity of flows down the system as the same volume of water
is spread over a larger area. Bank stabilisation practices linked with fencing of the
riparian zone can encourage the regrowth of vegetation, hence improving water
quality and instream habitat.
10) Install/Reactivate Gauges for Compliance Points
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 69
Environmental flow recommendations have been developed to be gauged at particular
compliance points throughout the system, specifically streamflow gauging sites.
However, in the Glenelg River, these streamflow gauges are not at the most
appropriate site or the collection of records has ceased. It is therefore recommended
that the gauge at Harrow (238 210) be reactivated in order to gauge compliance in
Reach 1. In addition, due to the lack of a suitable compliance point toward the lower
end of Reach 2, it is recommended that a gauge be established at Warrock Road at
Roseneath. Until this gauge is established, the gauge on the Glenelg River at
Dergholm (238 211) should be utilised.
11) Reintroduce snags in areas of mid reaches where desnagging has occurred
Extensive desnagging has occurred in certain areas of the mid reach of the Glenelg
River. Habitat is a key factor in community maintenance and large woody debris
(snags) has been identified as a key habitat type in the aquatic ecosystem. Habitat
improvement through resnagging will assist in maximising the benefits of flow regime
improvements.
12) Investigate limitation of outlet capacities
The current capacity and operation of releases from outlets into the Glenelg River may
limit the ability to provide adequate environmental flows into the main stem of the
river. Releases from Rocklands Reservoir are currently capped at 35 ML/d due to
greater flows resulting in flooding at Fraser’s Swamp. Secondly, releases from both
the 5 Mile and 12 Mile outlet channels are limited to 20 ML/d due to the clogging up
of carp screens with debris at flows in excess of this magnitude. These carp screens
have been set in place to limit the distribution of this species throughout the system
and require substantial labour to clean the screens of debris. In addition, as the screens
clog up, the volume of water being released at the outlets is reduced as less water
passes through the screens.
The valve capacity at Rocklands Reservoir is 600 ML/day, the volume of water that is
released to the river can be further reduced depending on the demand for water
through the Toolondo channel. Consequently there are issues as to how some of the
large flows (e.g. > 1400 ML/day) may be released in the current infrastructure.
Therefore to utilise these outlet points to provide environmental flows in the most
efficient and reliable way will require further investigation.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 70
9.
References
ANZECC (2000). ANZECC List of Threatened Vertebrate Fauna. The Australian
and New Zealand Environment Conservation Council, Canberra.
Bird, E.C.F. (1977). Sites of special scientific interest in the Victorian coastal region.
A report on geological and geomorphological aspects prepared for the Town
and Country Planning Board.
Bird, J.F. (1985). Review of channel changes along creeks in the northern part of the
Latrobe River basin, Gippsland, Victoria, Australia.
Zeitschrift für
Geomorphologie Supplement Band, 55: 97-111.
Brizga, S.O., N.M. Craigie, P. Condina and Lawson and Treloar Pty Ltd (2000).
Development of operational guidelines for sand management sites on the
Glenelg River: Feasibility study. Final report to the Glenelg Hopkins
Catchment Management Authority.
Brooks, A.P. and G.J. Brierley, (1997). Geomorphic responses of the lower Bega
River to catchment disturbance, 1851-1926. Geomorphology, 18: 291-304.
Burston, J. and M. Good, (1996). The impact of European settlement on erosion and
sedimentation in the Inman River catchment, South Australia. In I.D.
Rutherfurd and M. Walker (eds.), Stream Management ’96, Proceedings of the
First National Conference on Stream Management in Australia, Merrijig.
Cooperative Research Centre for Catchment Hydrology, Melbourne: 259-64.
Cameron, M. and Jekabsons, M. (1992). Salinity in the Glenelg and Wannon Rivers,
Victoria. Department of Conservation and Natural Resources, Victoria,
Davidson, N., Jeffery, G., and Wagg, C. (1994). The Environmental Condition of
Streams in the Glenelg Basin. Department of Conservation and Natural
Resources and National landcare Program, Victoria,
Dixon, P.R., Wagg, C., and Amirtharajah, M. (1998). Aspects of Environmental
Conditions in the Glenelg-Hopkins Region with Particular Reference to Salinity
and Nutrients in Rivers, Wetlands and Remnant Vegetation. Department of
Natural Resources and Environment,
DNRE (1997). Heritage rivers and natural catchment areas. Draft management plans
Volume 1 - Western Victoria. Department of Natural Resources and
Environment, East Melbourne.
DNRE (1997a). Victoria's Environmental Flow Program. Department of Natural
Resources and Environment.
DNRE (1999). State Fishway Program - an inventory of fishways and potential
barriers to fish movement and migration in Victoria. Department of Natural
Resources and Environment, Waterways Unit.
DNRE (2000a). Atlas of Victorian Wildlife. Arthur Rylah Institute - Department of
Natural Resources and Environment, Heidelberg.
DNRE (2000b). Threatened vertebrate fauna in Victoria - 2000. Department of
Natural Resources and Environment, East Melbourne.
DNRE (2000c). Victorian Aquatic Fauna Database. Arthur Rylah Institute Department of Natural Resources and Environment, Heidelberg.
DWR (1989). Water Victoria: a Resource Handbook. Victorian Government Printing
Office, Melbourne.
EPA (1999). The health of streams in the Glenelg catchment. River Health Bulletin.
Environment Protection Authority, Victoria.
Erskine, W.D. (1994). River response to accelerated soil erosion in the Glenelg River
catchment. Australian Journal of Soil and Water Conservation 7: 39-47.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 71
Godoy, W. (1996). The Effects of Rocklands Reservoir on the Glenelg River.
Department of Natural Resources and Environment - Water Bureau, July 1996.
GRCLPB (1997). Glenelg Regional Catchment Strategy. Glenelg Regional
Catchment and Land Protection Board, May 1997.
Hart, B.T. (1982). Water quality: formulation of criteria. In: O'Loughlin, E.M. and
Cullen, P. (Eds) Predictions in Water quality. Australian Academy of Science,
Canberra, pp 11-26.
Ingeme, Y. (1996). Glenelg River Catchment Environmental Flows Technical Report
- Draft Report. Department of Natural Resources and Environment, July 1996.
Koehn, J. D. and O'Connor, C., W.G. (1990). Biological information for the
management of native freshwater fish in Victoria. Government Printer,
Melbourne.
LCC (1991). Glenelg River - Victorian heritage river. Rivers and streams special
investigation - final recommendations. Report extract. Land Conservation
Council, Victoria.
McGuckin, J.T., Anderson, J.R., and Gasior, R.J. (1991). Salt Affected Rivers in
Victoria. Arthur Rylah Institute for Environmental Research, July 1991.
Mitchell, B., Rutherfurd, I., Constable, A., Stagnitti, F., and Merrick, C. (1996). An
Ecological and Environmental Flow Study of the Glenelg River from Casterton
to Rocklands Reservoir. Aquatic Resource Utilisation and Management
Research Group, Deakin University, Warrnambool. August 1996.
Mitchell, P. (1990). The Environmental Condition of Victorian Streams. Department
of Water Resources, Victoria.
OCE (1988). State of the environment report 1988. Victoria's inland waters. Office
of the Commissioner for the Environment, Victoria.
Pollard, D.A. (1971). The biology of a landlocked form of the normally catadromous
salmoniform fish Galaxias maculatus (Jenyns). I. life cycle and origin.
Australian Journal of Marine and Freshwater Research 22: 91-123.
Prosser, I.P., I.D. Rutherfurd, J.M. Olley, W.J. Young and P.J. Wallbrink, in press.
Patterns and processes of erosion and sediment transport in Australian rivers.
Marine and Freshwater Research.
Rutherfurd, I.D. and Budahazy, M. (1996). A Sand Management Strategy for the
Glenelg River and its Tributaries, Western Victoria. Report to the Department
of Natural Resources and Environment, Victoria and Southern Rural Water.
Cooperative Research Centre for Catchment Hydrology, Report 96/9,
Melbourne. Melbourne. December, 1996.
Ryan, T. and Davies, P. (1996). Environmental effects of salinity and nutrients from
salt disposal: approaches to the development of management criteria. Flora and
Fauna Technical Report 137.
Department of Natural Resources and
Environment.
SKM (2001a). Glenelg River Environmental Flow Study. Issues Paper. Report to the
Glenelg Hopkins Catchment Management Authority. Sinclair Knight Merz.
SKM (2001b). Glenelg River Natural Flow Estimation. Report to the Department of
Natural Resources and Environment. Sinclair Knight Merz.
Schlosser, I.J. (1982). Fish community structure and function along two habitat
gradients in a headwater stream. Ecological Monographs 52: 395-414.
Schreiber, E.S.G., Wagg, C., Metzeling, L., and Perriss, S. (1998). Assessing stream
health in the Glenelg catchment - using macroinvertebrates. Department of
natural Resources and Environment and Environment Protection Authority,
Sherwood, J., Magilton, C. and Rouse, A. (1998). The Glenelg River: Nutrient and
Estuarine Hydrodynamics. Deakin University, Warrnambool. July 1998.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 72
Wagg, C. (1997). A Summary of the Water Quality in the Glenelg Catchment.
Department of Natural Resources and Environment,
Walker, K.F., Thoms, M.C., and Sheldon, F. (1992). Effect of weirs on the littoral
environment of the River Murray, South Australia. Pages 270-293 in Boon, P.
J., Calow, P. A., and Petts, G. E., eds. River Conservation and Management.
Wiley, Chichester.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 73
Environmental Flow Study of the
Glenelg River System
PART B
Issues Paper
Final
April 2001
This document was completed in Stage 1 of the project. It was approved
by the Glenelg Hopkins CMA and formed the basis for Stage 2 of the
project.
590 Orrong Road
Armadale
VIC 3143
COPYRIGHT: The concepts and information contained in
this document are the property of Sinclair Knight Merz Pty.
Ltd. Use or copying of this document in whole or in part
without the written permission of the Sinclair Knight Merz
constitutes an infringement of copyright.
Contents
1. Introduction...............................................................................................1
1.1
Project scope ......................................................................................1
2. Catchment description...........................................................................2
2.1
2.2
2.3
2.4
Physiography ......................................................................................2
Landuse ..............................................................................................6
Hydrology ............................................................................................7
Water quality .....................................................................................10
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.5
2.6
Salinity.................................................................................... 10
Dissolved oxygen..................................................................... 11
Nutrients ................................................................................. 11
pH........................................................................................... 11
Turbidity.................................................................................. 11
Biota ..................................................................................................12
Summary...........................................................................................14
3. Key issues .............................................................................................. 16
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Potential environmental issues ........................................................16
Sand slugs ........................................................................................19
Water quality .....................................................................................20
Regulation .........................................................................................22
Channel condition .............................................................................24
Current flora and fauna values of the Glenelg River system ...........25
The heritage reach............................................................................26
4. Methods................................................................................................... 28
5. Site descriptions................................................................................... 31
6. Objectives ............................................................................................... 37
6.1
6.2
6.3
Policy and strategy objectives ..........................................................37
Catchment objectives .......................................................................38
Environmental objectives..................................................................38
7. Discussion.............................................................................................. 40
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Seasonal timing of releases .............................................................40
Periods of cease to flow ...................................................................41
Baseflows .........................................................................................41
Freshes during periods of cease to flow/low flow ............................41
Spring freshes...................................................................................42
Flow variability...................................................................................42
High flows .........................................................................................42
8. Recommendations ............................................................................... 43
8.1
Flow Recommendations ...................................................................44
8.1.1
8.1.2
8.1.3
8.2
Reach 1 – Rocklands Reservoir – Chetwynd River..................... 44
Reach 2 – Chetwynd River to Wannon River ............................. 52
Reach 3 – Wannon River to Tidal Extent ................................... 61
Supporting recommendations ..........................................................67
9. References ............................................................................................. 71
1. Introduction...............................................................................................1
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE i
1.1
1.2
Project scope ......................................................................................1
Report structure..................................................................................2
2. Catchment description...........................................................................3
2.1
2.2
2.3
2.4
Physiography ......................................................................................3
Landuse ..............................................................................................3
Hydrology ............................................................................................7
Water quality .....................................................................................10
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.5
2.6
Salinity.................................................................................... 10
Dissolved oxygen..................................................................... 11
Nutrients ................................................................................. 11
pH........................................................................................... 11
Turbidity.................................................................................. 12
Biota ..................................................................................................12
Summary...........................................................................................14
3. Key issues .............................................................................................. 16
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Potential environmental issues ........................................................16
Sand slugs ........................................................................................19
Water quality .....................................................................................20
Regulation .........................................................................................22
Channel condition .............................................................................23
Current flora and fauna values of the Glenelg River system ...........24
The heritage reach............................................................................25
4. Environmental objectives................................................................... 27
Preliminary umbrella objectives ..................Error! Bookmark not defined.
4.2 Preliminary specific objectives .........................................................27
5. Outcomes................................................................................................ 28
5.1
Assessment framework....................................................................28
5.1.1
5.1.2
5.1.3
5.2
Technical panel........................................................................ 28
Study reaches ......................................................................... 28
Use of existing data and information.......................................... 30
Reporting...........................................................................................30
6. References ............................................................................................. 31
Appendix A
A.1
A.2
A.3
A.4
A.5
A.6
A.7
Appendix B
B.1
B.2
B.3
B.4
B.5
B.6
Hydrology.......................................................................... 34
Streamflows......................................................................................34
Licensed water use...........................................................................36
System operation..............................................................................37
Summary...........................................................................................38
Flow plots ..........................................................................................39
Flow duration curves.........................................................................42
Rocklands Reservoir Discharge.......................................................54
Geomorphology............................................................... 55
Introduction .......................................................................................55
Stream network.................................................................................55
Hydrology ..........................................................................................56
Landuse ............................................................................................56
Sand slugs ........................................................................................57
Summary...........................................................................................58
Appendix C
Water quality..................................................................... 59
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE ii
C.1
C.2
C.3
C.4
C.5
C.6
C.7
Salinity...............................................................................................60
Nutrients ............................................................................................61
pH......................................................................................................62
Dissolved oxygen..............................................................................63
Turbidity.............................................................................................63
Summary...........................................................................................64
Water quality plots indicating guideline values ................................65
Appendix D
D.1
D.2
D.2.1
D.2.2
D.2.3
D.3
D.4
D.5
D.6
D.7
Biota
77
Condition of instream and riparian habitat........................................77
Fish, decapod crustacea and molluscs............................................77
Fish ........................................................................................ 77
Decapod Crustacea ................................................................. 82
Macroinvertebrates .................................................................. 82
Birds ..................................................................................................83
Amphibians and reptiles ...................................................................83
Other vertebrates ..............................................................................84
Instream and riparian flora................................................................85
The Glenelg Heritage River and Lower Glenelg National Park. ......86
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE iii
Document History and Status
Issue
Rev.
Issued To
Qty
Date
Reviewed
Approved
1
Draft
1
15/02/01
Brenton Zampatti (ARI)
Michael Shirley
2
Draft
1
23/02/01
Draft
1
2705/01
Melanie Tranter
(GHCMA)
John Martin (WMW)
Glenelg Project Group
Michael Shirley
3
Melanie Tranter
(GHCMA)
Melanie Tranter
(GHCMA)
Glenelg Project Group
Alex Marshall (GHCMA)
4
Final
Alex Marshall (GHCMA)
1
7/06/01
Alex Marshall (GHCMA)
Michael Shirley
Printed:
Last Saved:
File Name:
7 May, 2003
15 October, 2002
Project Manager:
Name of Organisation:
Name of Project:
Name of Document:
Document Version:
Project Number:
Michael Shirley
Glenelg Hopkins Catchment Management Authority
Wimmera, Avoca and Glenelg Environmental Flows
Glenelg River issues paper
Final
WC01432
I:\WCMS\Wc01432\500_Analysis_Reporting\Reporting\Released
Reports\Revised\R04_Mjs_Glenelg_Final.Doc
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE iv
Michael Shirley
1.
Introduction
Reducing or altering streamflows can have dramatic impacts on the health of riverine ecosystems with
subsequent implications for other water users. Flow is the governing influence in rivers, controlling
many aspects of the physical environment and significantly affecting the biota of a riverine system. It
is, therefore, essential that adequate water be provided for the purpose of protecting the physical and
ecological processes and features of rivers.
The need to reform the water resource industry and provide water for the environment has been
recognised by both Federal and State Governments in the Council of Australian Governments’
(COAG) Water Reform Agenda (ARMCANZ, 1995). Under the 1994 COAG agreement, the
environment is recognised as a legitimate water user and environmental water requirements must be
assessed and provided. The National Principles for the Provision of Water for Ecosystems define
environmental water requirements as:
…the water regimes needed to sustain the ecological values of aquatic ecosystems at a low level of
risk (ARMCANZ and ANZECC 1996).
Given that some systems are over-allocated and unable to provide fully for environmental water
requirements, negotiation between stakeholders can lead to the establishment of flows for the purpose
of environmental protection. Such flows are defined in this report as environmental water provisions,
meaning:
…that part of environmental flow requirements that can be met (ARMCANZ and ANZECC 1996).
The Department of Natural Resources and Environment has developed the Victorian Water for the
Environment Program to implement measures in place to provide water to meet environmental needs.
The shared objective of this program to increase environmental flows is to maintain and, where
possible, restore the environmental values of rivers and wetlands, whilst recognising existing
entitlements. The program includes a two-stage process for providing water for the environment:
13) protecting and enhancing environmental flows through water entitlement agreements; and
14) rehabilitating stressed river systems (DNRE 1997a).
1.1 Project scope
The Glenelg River was identified as the highest priority river for restoration as part of the Victorian
Stressed Rivers Programs. The current study was consequently developed to address the key flow
related issues in the Glenelg River system, specifically the environmental water requirements of the
surface water systems of the Glenelg River catchment.
The aim of this project is to provide a scientific basis for the implementation of environmental flow
provisions for water dependent ecosystems of the Glenelg River. The project requires a multidisciplinary approach, with a need to integrate information from ecology, hydrology, geomorphology,
and water quality.
The project defines a clear scientific process for the determination of environmental water
requirements and strategies to implement and test the efficacy of the environmental water provisions
that are implemented. The project will include:
q investigation of existing information on key flow related issues;
q
definition of multi-disciplinary objectives and targets;
q
use of a sound scientific method to define the environmental water needs;
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 1
q
develop recommendations for monitoring to support and measure the implementation of
environmental water provisions.
The project will be conducted in two stages. In Stage 1, the current environmental status of the
catchment will be examined. This includes examination of the current system operation, aquatic
ecology, hydrology, geomorphology and water quality conditions. Information will also be sought on
current and future threats to the ecological and biodiversity values of the catchment, as related to water
management. The current management arrangements and the implications of these for the Glenelg
River and water dependant ecosystems will also be determined. This stage also aims to clarify
specific objectives and required project outcomes. Some ground-truthing of the information gathered
through Stage 1 will underpin the selection of key areas, study reaches and issues for further targeted
investigation. This information will enable the selection of the most appropriate method for the
determination of environmental water requirements, and the refinement of the detailed work plan for
subsequent stages of the project. This report is the output of Stage 1.
Recommendations for the environmental water requirements of the Glenelg River are developed in
Stage 2. This is discussed in more detail in Section 5 of this report.
1.2 Report structure
As part of Stage 1, a series of preliminary Issues Papers were produced to review available
information on the environmental status of the catchment according to discipline categories including
ecology, hydrology, geomorphology and water quality. Information in the preliminary Issues Papers
was verified via comments from the Project Group, discussion with Brad Mitchell of Deakin
University, Project Steering Committee and during a field inspection of the catchment in September
2000 by Bruce Abernethy and Paul Close.
The project is now at the completion of Stage 1 and the preliminary Issues Papers (see appendices)
together with information obtained during a field inspection by the team have been used to produce
this Integrated Issues Paper. This paper identifies and reviews the available background information
on the values and issues in the catchment and river system, assesses critical knowledge gaps and
considers key issues for consideration in developing an approach to determining the environmental
water requirements of the Glenelg River.
This document reports on an audit of available information, undertaken to identify the ecological,
hydrological and geomorphological values and flow related issues in the Glenelg River catchment.
Section 2 describes the Glenelg River catchment in terms of its geomorphology, landuse, hydrology,
water quality and biota. Section 3 provides an overview of the key issues that are apparent in the
catchment and comment on how they relate to environmental water management. Section 4 identifies
flow-related environmental objectives for the Glenelg River while Section 5 provides a framework for
further work required to determine the river’s environmental water requirements. Detailed issues
papers are appended at the end of the document.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 2
2.
Catchment description
The study area specified for this report is the main channel of the Glenelg River. No tributaries are
included in the study area.
2.1 Physiography
The Glenelg River rises in the Grampians and flows to the Southern Ocean (Figure 2-1 Glenelg River
catchment.). On leaving the Grampians the river flows along the northern and then the western edge
of the Dundas Tablelands, between Rocklands Reservoir and Casterton. Near Casterton the Wannon
River joins the Glenelg River and from there the Glenelg River meanders across broad coastal plains
towards Dartmoor. Below Dartmoor the river follows a generally southerly course becoming
increasingly incised in limestone (Erskine 1994). At the confluence of Moleside Creek the river turns
WNW and runs parallel to the coast, eventually looping into South Australia before entering the sea at
Nelson.
The catchment is approximately 120 km wide and 100 km from north to south, covering a total area of
1,266,030 ha (Department of Water Resources Victoria 1989). The topography of the catchment
varies substantially from the rugged escarpments of the Grampians in the northeast to the coastal
plains in the southwest. The Victoria and Serra Ranges of the Grampians drain into both the Glenelg
and the Wannon Rivers; the former drains the north and west of the catchment and the latter the east
and south. The central portion of the catchment is composed of the deeply dissected Dundas and
Merino tablelands. Towards the southeast the tablelands drop down to the flat basal plains around
Hamilton. Near Nelson there is an estuarine lagoon at the mouth of the Glenelg River and a line of
calcareous sand dunes fringes the coastline. During low flow conditions salt water penetrates
upstream beyond the boundary of the Lower Glenelg National Park. At over 70 km, the Glenelg
estuary is one of the State’s longest (Sherwood et al. 1998b).
In 1986, the Department of Water Resources conducted a survey of the environmental condition of
Victorian streams. Within the Glenelg River catchment the condition or health of 58 sites located on
both the Glenelg River and its tributaries was described using both biological and physical assessment
criteria (Mitchell 1990). In general, approximately 45% of the Glenelg River and 70% of tributaries
within the catchment were described as poor to very poor environmental condition. In 1994 seven of
the original 58 sites were resurveyed. While some sites had improved as a result of exclusion of stock
from riparian zones, stream condition was still described as generally poor (Davidson et al. 1994).
Davidson et al. (1994) suggested that flow regulation, sedimentation, salinisation and extensive snag
removal were the main factors leading to poor channel condition. Our field observations support those
of Mitchell et al. (1996) that the riparian vegetation is continuous to discontinuous along both banks of
the river but is generally restricted to the bankface and the immediate bank verge (Figure 25, Figure
26). The lower section in the Lower Glenelg National Park is in good condition with excellent bank
and verge vegetation (Figure 29). The banks are generally stable with only isolated examples of bank
erosion (Figure 42). In some locations, bank instability is associated with stock traffic.
The main issue associated with physical condition of the Glenelg River is the high sand load that
occupies a large proportion of the channel (Figure 43). The sediment has created a sandy bed with and
reduced the occurrence of deep holes (>2m) in sections of the river. Areas of sediment build-up are
most obvious are around Casterton and Harrow.
2.2 Landuse
The Department of Water Resources Victoria (1989) reports that European settlement of the Glenelg
catchment began in 1837. The merino wool industry was established quickly and today wool is still
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 3
Glenelg Hopkins Catchment Management Authority
n
Figure 39: Glenelg River catchment.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 4
n
n Figure 25: Glenelg River at Fulham Hole Streamside Reserve (note typical
riparian vegetation,
understorey).
consisting
of
patchy
overstorey
and
little
or
no
n Figure 26: Glenelg River at Dartmoor.
the main product of the region with prime lamb production also important. The beef industry is well
established and a small amount of dairying occurs in the catchment. Since 1837, two-thirds of the
catchment has been cleared for pasture to graze sheep and cattle and today only two main forested
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 5
areas remain. The northeast of the catchment is forested and includes the Grampians National Park, as
well as State Forest where a small amount of hardwood is logged. In the west there is a mixture of
native hardwood forests (the Glenelg National Park) and intensive softwood plantations (Department
of Water Resources Victoria 1989). Hamilton is the major urban centre within the catchment, located
in the southeast.
n Figure 42: Glenelg River at Wannon River confluence (note erosion of left bank).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 6
n
n Figure 43: Sand slug in the Glenelg River downstream of Chetwynd River
confluence.
2.3 Hydrology
Rainfall varies seasonally and spatially within the catchment. While winter months are wetter
throughout the catchment, there is a gradual decline in mean annual rainfall from the coast near
Nelson (approximately 750 mm) to the centre of the catchment (approximately 550 mm). In the
northeast of the catchment, in the vicinity of the Grampians, annual rainfall increases with elevation to
more than 900 mm on the Victoria Range. Rainfall is relatively reliable along the coast and in the
higher parts of the Grampians (Department of Water Resources Victoria, 1989).
Reflecting rainfall distribution, flows are strongly seasonal with 70% of average annual flow in the
Glenelg River above the Wannon River junction occurring in the three months August to October. At
Dartmoor (Station 238206), the residual mean annual flow of the Glenelg River, post Rocklands
Reservoir construction, is 639,000 ML. Although only 1.5 % of that total occurs in the months
January to March, there are reliable base flows rarely falling below 30 ML per day during this period
(Department of Water Resources Victoria 1989).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 7
n
n
Figure 29: Lower Glenelg River.
There are three notable water storages within the Glenelg River basin. These are Konong Wootong
Reservoir, Moora Moora Reservoir, and Rocklands Reservoir. Konong Wootong is a small reservoir
constructed on Den Hills Creek, a tributary of the Wannon River, to supply the townships of Casterton
and Coleraine. The capacity of this storage is 1,920 ML and diverts approximately 852 ML/year out
of the system (Ingeme 1996). Moora Moora Reservoir is located in the upper reaches of the Glenelg
River. The reservoir is a small, offstream storage with a capacity of only 6,300 ML (Department of
Water Resources Victoria 1989). Lake Bellfield diverts water from the upper Wannon River.
Rocklands Reservoir is the largest storage in the catchment with a total capacity of 348,000 ML. The
primary purpose of the storage is to provide domestic and stock supply to the Wimmera Mallee Water
channel system (Godoy 1996).
Rocklands Reservoir has a significant impact on the seasonal flow pattern downstream of the
reservoir, although the impact decreases with distance from the dam. Rocklands has a storage
capacity about three times its average annual inflow and has spilled once every four years on average
since construction. Downstream of Chetwynd River, flows are continuous due to natural inflow from
the catchment adding to the river flows and current releases from the reservoir do not appear to exert
an influence below Casterton (Mitchell et al. 1996). Recent observations in December 2000 have
shown that this section of the Glenelg River did cease to flow (M. Tranter pers. comm.)
The Glenelg River, under natural conditions, commonly ceased to flow at Balmoral over the three
months February to April, sometimes for months longer (Godoy 1996). The deep pools through the
river would have allowed the key biota to persist during the cease to flow periods. However, the cease
to flow does not occur within the current flow regime, which is a summer autumn flow release. Under
low flow conditions transit times for releases from Rocklands Reservoir are approximately 7 days to
Balmoral, 14 days to Fulham Bridge and 21 days to Harrow. According to Mitchell et al. (1996) a 2025 ML/day release at Rocklands delivers 10 ML/day at Fulham Bridge and 2 ML/day at Harrow.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 8
The total licensed volume for water extraction from the main channel of the Glenelg River is 68.2
ML/year which is a very small proportion of licensed water entitlement in the Glenelg River system
(Table 6-1). All licences on the Glenelg River extract upstream of the Wannon River confluence (J
Donovan, pers. comm.). An additional 878.6 ML/year is licensed for extraction from the remainder of
the catchment. Of the 68.2 ML/year available for extraction from the Glenelg River, 66 ML/year is
extracted through two irrigation licences. These licences are generally used sometime between
September and February, although the specific timing of such use is dependent on the crops being
irrigated. The remaining 2.2 ML/year is a dairy licence, which is used throughout the year for dairy
washing and stock watering.
Further information on the licensed entitlement within the Glenelg River system is presented in
Appendix A. The licensed volume is distinct from the total volume that is actually extracted each year
due to a number of factors including the availability of flow and water quality.
The Rocklands Outlet channel passes from Rocklands Reservoir in the Glenelg River Basin to
Toolondo Reservoir in the Wimmera Catchment. Water is also lost from the Glenelg River due to
evaporation at Fraser’s Swamp and water being held up by the tributary junction plugs that are present
in the stream. To reduce losses along the river to Fulham Bridge, Wimmera Mallee Water can release
water from the 5 and 12 Mile channel outfalls, although this is generally only done when there are
concurrent transfers to Toolondo Reservoir. There is some leakage from the Rocklands Outlet channel
that reaches the Glenelg River and helps offset some of the losses in this reach.
A compensation flow from Rocklands Reservoir down the Glenelg River is currently fixed at 3,300
ML/year. This was previously a sliding scale between 2,500 ML and 3,700 ML/year, but at the request
of the Glenelg Hopkins CMA, a new formula has been developed being the average of the historic
releases, (3,300 ML/year)(Table 2-1)(R Leeson, pers. comm.). Wimmera Mallee Water is required to
maintain a reserve volume in Rocklands to guarantee this compensation flow. The compensation
flows, released in summer and autumn, are aimed to maintain a target flow of 5-10 ML/d at Fulham
Bridge and 1-2 ML/day at Harrow. Commencement of compensation flows is timed to take advantage
of the wet river channel and thus prevent the flow from ceasing altogether (Godoy 1996) and the
releases to the river are based on the flow measured at Fulham Bridge (Gauge 238224). The
compensation flows are generally released between mid November to late April, depending on the
weather.
n
Table 2-1 Summary of environmental flow releases for the Glenelg River (Source Wimmera
Mallee Water)
Season
1996-97
1997-98
1998-99
1999-2000
Compensation Flow
ML
3,700
3,210
3,300
3,300
WC01432:R04_MJS_GLENELG_FINAL.DOC
Environmental Flow
ML
4,119
6,167
5,736
1,994
Total Release
ML
7,819
9,377
9,036
5,294
Final
PAGE 9
2.4 Water quality
The key parameters that influence ecological processes and water use are salinity, nutrients (TN and
TP), pH, dissolved oxygen (DO), and turbidity. For example, low levels of dissolved oxygen can
restrict aerobic respiration resulting in stress to or mortality of aquatic biota. Similarly, high nutrient
levels can result in algal blooms that make the water unsuitable for consumption.
The VWQMN Annual Report presents attainment values (with the set guideline) for each water
quality parameter. Attainment is the frequency (% occurrence) that a particular water quality
parameter falls within developed guidelines for a specific site. Attainment values are described as
either high (> 95%), moderate (90-95%) or low (< 90%) (AWT 1999).
Water quality data has been assessed for this project at five sites along the river system:
q
Glenelg River at Big Cord (238231), upstream of Rocklands Reservoir;
q
Glenelg River at Fulham Bridge (238224), about 20km downstream of Rocklands Reservoir;
q
Wannon River at Henty (238228), about 15km upstream of the confluence with the Glenelg River;
q
Glenelg River at Sandford (238202), immediately downstream of the Wannon River confluence;
and,
q
Glenelg River at Dartmoor (238206).
Data from these sites for the years 1990 to 1999, inclusive, are plotted in Appendix C and summarised
in Table 6-2 (Appendix C).
2.4.1
Salinity
Salinity varies along the length of the Glenelg River, with the structure of the channel and
groundwater intrusions characterising different reaches and the resultant impact of salinity. Salinity is
probably the key impacting water quality parameter in the Glenelg River system, that is directly
impacted by the flow regime.
The section of the Glenelg River between Rocklands Reservoir and Fulham Bridge was characterised
by Sherwood et al. (1998a) as shallow sections (<3 m deep) interspersed with deep elongated pools
(>8.5 m deep). This section of the river has been identified as a major source of salt. Salinity
increases with distance downstream from Rocklands Reservoir through this reach (Sherwood et al.
1998a).
McGuckin et al. (1991) also documented salinity in the 15 km section downstream of Rocklands
Reservoir. They found surface and bottom salinities were between 3,500 µS/cm and 7000 µS/cm with
surface salinities approximately 2000 µS/cm less than that at the bottom. Further downstream,
conductivity declined to approximately 2000 µS/cm with the exception of Fulham Bridge, where
bottom conductivity was 10,380 µS/cm. In the reach between Casterton and Dartmoor, McGuckin et
al. (1991) found no significant difference in surface and bottom salinities.
Deoxygenation also prevailed in the section of the river between Rocklands Reservoir and Fulham
Bridge with the lowest concentrations of dissolved oxygen coinciding with high bottom conductivities
(McGuckin et al. 1991). Adverse temperature was also closely associated with saline pools in this
reach. The persistence of such conditions greatly affects the amount of suitable available habitat for
aquatic organisms. If the deeper areas of the pool habitats are highly deoxygenated it may cause a
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 10
significant reduction in useable habitat, and also reduce access to the benthos which is a significant
source of food and resources. Although stratification and deoxygenation would have occurred
naturally in pools, particularly in low flow events, the current reduced flow conditions exacerbate this
effect.
At times of low flow, saline groundwater is a major source of salt (Glenelg Regional Catchment
Strategy, 1997). At higher flows, fresh surface water masks the effect of groundwater (Sherwood et
al. 1998a). A decrease in salinity that occurs between Myaring Bridge to Dartmoor, approximately 20
km downstream, is likely to be due to dilution that results from inflow of less saline surface or
groundwater.
2.4.2
Dissolved oxygen
Severe deoxygenation has been found throughout the length of the Glenelg River (McGuckin et al.
1991). McGuckin et al. found that deoxygenation was closely associated with the presence of saline
pools in the reach from Rocklands Reservoir to Fulham Bridge with each pool registering a bottom
dissolved oxygen concentration of less than 10% saturation. Sites between Casterton and Dartmoor
were only slightly better than upstream with values ranging between 10-40% saturation. McGuckin et
al. suggested that the temperature gradient in this section of the river was most likely associated with
the depth of the pool and was the governing factor controlling DO at conductivities less than 500
µS/cm.
Although low dissolved oxygen does not appear to be of concern at the VWQMN sampling sites,
isolated locations do exhibit low DO concentrations. Of particular concern is the significant reduction
in DO at depth in the deep pools along the Glenelg River, especially in the reach from Rocklands
Reservoir to Fulham Bridge. Low levels of DO also occur at depth in the estuarine section of the
river.
2.4.3
Nutrients
Nutrient enrichment of the waterways within the catchment has also been recognised as a significant
issue. To date there have been no blue green algal blooms reported in the Glenelg River although
eutrophication of the farm dams and lakes has been recorded (Dixon et al. 1998). Blooms have,
however been recorded in Rocklands Reservoir in 1991 and the Casterton Sewage Treatment Ponds in
1995 (GRCLPB 1997).
Sources of nutrients within the Glenelg River are varied. For example, contrary to the norm, active
erosion in the subcatchment of Sandford contributes to total nitrogen (TN) loads but no total
phosphorus (TP). Nitrogen may be from decaying organic material and animal wastes. Until 1996/97,
the Casterton Wastewater Treatment Plant was contributing an unknown load of nutrients to the river,
which would be having a major impact. This practice of discharging has now ceased (Wagg 1997).
Septic tank effluent at Dartmoor may also contribute to nitrogen concentrations in the river (Sherwood
et al. 1998a). At Dartmoor, TKN associated with organic material is also positively related to flow,
similarly for TP, which is attached to sediments (Wagg 1997).
Although TP rarely exceeds the guideline values (see Appendix C) in the Glenelg River, values of TN
progressively exceed guideline values with distance downstream. The occurrence of high nitrogen
values can potentially lead to the growth of algal blooms.
2.4.4
pH
With few exceptions, monitored values of pH within the catchment over the past decade have been
within guidelines. Median pH values have only been outside the two guidelines at Big Cord where
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 11
water was slightly acidic. This indicates that pH is not an issue in terms of water quality in the
Glenelg River below Rocklands Reservoir.
2.4.5
Turbidity
Median turbidity values have been recorded as excellent for the past 10 years at all sites presented.
The 90th percentile values for turbidity at Henty, Dartmoor and Sandford have frequently indicated
degraded conditions that correlate with periods of high flow during winter (Department of Water
Resources Victoria 1989). Turbidity at Fulham Bridge has been shown to correlate positively with
discharge at flows greater than 10 ML/day (Mitchell et al. 1996). Turbidity is not of concern in the
Glenelg River system as the high winter turbidity levels are not prolonged and return to acceptable
levels.
2.5 Biota
The native freshwater fauna of the Glenelg River system represent a diverse assemblage with high
conservation significance. As shown in Table 3 (Appendix D), twenty species of native freshwater
fish and 26 estuarine species have been recorded from the Glenelg River system (DNRE 2000c).
Eight species have conservation significance and of these, five are protected through their listing on
the Victorian Flora and Fauna Guarantee Act 1988. Four species are protected through their listing
on the List of Threatened Australian Vertebrate Fauna (ANZECC 2000). Of the 20 species of native
freshwater fish, seven are known to migrate between freshwater and estuarine/marine habitats at some
stage in their life cycle (Koehn and O’Connor 1990).
Seven species of decapod crustacea and at least three species of bivalve mollusc have also been
recorded (Table 3, Appendix D). Of these, the Glenelg freshwater mussel (Hyridella glenelgensis)
and the western swamp cray (Gramastacus insolitus) are suspected of being rare, with restricted
distributions and low abundances (Tarmo Raadik pers. comm.). Consequently, these species may in
the near future be rated as highly threatened fauna in Victoria.
The EPA (1999) recorded a total of 86 families of macroinvertebrates from a total of 61 survey sites
throughout the Glenelg River catchment (Table 4, Appendix D). Mitchell et al. (1996) and EPA
(1999) report a dominance of insects (such as beetles, mayflies and true bugs) in the macroinvertebrate
community, as is commonly the case in fresh waters. Based on the macroinvertebrate communities
present, the health of sites in the Glenelg River was assessed as good to excellent in both pools and
shallow habitats based on ratings presented in OCE (1988). Increased community complexity and
abundance of macroinvertebrates was reported at sites with macrophytes and organic debris (Mitchell
et al.1996).
There have been 271 species of bird recorded in the Glenelg River of which 50 species have
conservation significance either in Victoria or nationally (DNRE 2000a, DNRE 2000b). Of the
threatened species, 20 are reliant directly upon the instream environment for their survival (Table 5,
Appendix D).
The warty bell frog (Litoria raniformis), has been recorded in the Glenelg catchment and is listed as
vulnerable by DNRE (2000b). Two species of threatened reptile, the swamp skink (Egernia coventryi)
and tree goanna (Varanus varius), have been recorded from the Glenelg catchment (DNRE 2000a).
Although the tree goanna does not directly depend on the riparian environment, such areas often
provide the only remaining habitat. It should be noted that the latest recorded sightings of these
species date from the early 1980’s.
Other vertebrates present in the catchment and known to depend directly on the instream environment
for food and shelter include the platypus (Ornithorhynchus anatinus) and water rat (Hydromys
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 12
chrysogaster). Platypus have been recorded in the Glenelg River near Casterton and Dartmoor and in
the vicinity of Fulham Hole. The species has also been recorded in the Wannon River near Coleraine
and Hamilton, Mackinnon Creek and Grange Burn (unpublished database Australian Platypus
Conservancy; Melanie Tranter pers. comm.). There is no documented distribution information for the
water rat.
Of the 63 threatened flora species that occur in the Glenelg River catchment (Table 6, Appendix D),
15 of them rely directly on the instream environment or temporary inundation for their survival
(DNRE, 2000; Dale Tonkinson pers. comm.). Thirty species of aquatic and semi-terrestrial
macrophyte have been recorded in the mid to upper reaches of the Glenelg River (Mitchell 1996).
Species richness within sites ranged from 7-11. Emergent aquatic macrophyte species were dominant
and represent between 67 and 100% of species present at sites surveyed.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 13
2.6 Summary
The following table provides a summary of the issues on a reach by reach basis.
Reach
Headwaters to backwater
of Rocklands Reservoir
Rocklands Reservoir to
Chetwynd River
Geomorphology
q
q
Sediment
buildup
around Harrow
q
Regulation of Rocklands
Reservoir is inpart
responsible for the low
transport rate
q
Chetwynd River to
Wannon River
q
60% loss of capacity
due to sand slugs at
Harrow and Burkes
Bridge
q
Sediment
buildup
around Casterton
q
20% loss of capacity
due to sand slugs at
Casterton
q
q
q
Low flows and sediment deposition in
mid to upper reaches of Glenelg have
been shown to promote excessive
growth of Typha spp. and Phragmites
australis
Rocklands Dam significantly impedes
upstream movement of migratory fish
species.
Water Quality
q
Hydrology
q
q
Salinity increases with distance
downstream from this reach
q
70% of annual flow occurs Aug to
Oct to Wannon
q
For a distance 15km downstream of
Rocklands salinity varies greatly
between the surface and bottom of the
river.
q
Significant impact on streamflows
caused by Rocklands and spills
only once every four years
q
q
Very low Dissolved oxygen and
temperature is associated with saline
pools for the above distance
Glenelg R used to dry at
Balmoral Feb to Apr under
natural conditions but current
conditions do not lead to drying
q
Water lost due to evaporation at
Fraser’s Swamp
q
There is a significant reduction in
peak flows, due to Rocklands
Reservoir, down to Casterton
A large proportion of high and moderate
value with only one sub-reach requiring
rehabilitation*
q
Platypus recorded near Casterton
q
Erosion in the Sandford subcatchment
contributes to increased nitrogen loads
q
70% of annual flow occurs Aug to
Oct to Wannon
q
Variegated pygmy perch endemic to
Glenelg catchment and found in reach
between Harrow and Strathdownie
q
Deoxygenated pools present
q
Continuous streamflow due to
natural inflows
q
There is a significant reduction in
peak flows, due to Rocklands
Reservoir, down to Casterton
q
WC01432:R04_MJS_GLENELG_FINAL.DOC
Flora and Fauna
Low flows and sediment deposition in
mid to upper reaches of Glenelg have
been shown to promote excessive
growth of Typha spp. and Phragmites
australis
A large proportion of this reach is
comprised of moderate value subreaches with a similar number but
smaller length of high value subreaches. Two small sub-reaches
requiring rehabilitation occur in this
region*
Final
PAGE 14
Reach
Wannon River to tidal
extent
Tidal extent to river mouth
q
Geomorphology
10% loss of capacity
due to sand slugs at
Dartmoor
q
WC01432:R04_MJS_GLENELG_FINAL.DOC
q
Flora and Fauna
Lower Glenelg National Park in good
condition with excellent bank and verge
vegetation
q
Platypus recorded near Dartmoor
q
This reach contains a larger proportion of
high value than moderate value subreaches. There are not any sub-reaches
requiring rehabilitation in this reach*
q
q
Water Quality
High nitrogen due to septic inflows
q
Deoxygenated pools present
q
Final
q
q
PAGE 15
Hydrology
No licences for extraction in this
reach
No licences for extraction in this
reach
n
Table 3-1: Threatened aquatic and semi-terrestrial flora
present in the Glenelg River, and associated seasonally
inundated wetlands.
Scientific Name
Agrostis aemula var. setifolia
Agrostis avenacea var. perennis
Agrostis billardierei var. filifolia
Amphibromus fluitans
Baumea laxa
Dianella callicarpa
Eucalyptus kitsoniana
Euphrasia scabra
Lobelia beaugleholei
Microtis orbicularis
Pneumatopteris pennigera
Pterostylis tenuissima
Senecio psilocarpus
Thelymitra epipactoides
Utricularia violacea
Common Name
Gilgai blown-grass
Wetland blown-grass
Gilgai blown-grass
River swamp wallaby-grass
Lax twig-sedge
Swamp flax-lily
Bog gum
Rough eyebright
Showy lobelia
Dark mignonette-orchid
Lime fern
Swamp greenhood)
Swamp Fireweed
Metallic sun-orchid
Violet bladderwort
Status 1
v
k
v
V, k
r
r
R, r
K, e
R, r
v
e
V, v
V, v
E, e
r
1
Abbreviations denote conservation status following (Gullan
1990). Upper-case refers to categories in Australia and lowercase to Victoria. E,e, endangered; V,v, vulnerable; R,r, rare; K,k,
uncertain.
3.
Key issues
In common with other river basins around Australia, the hydrology of the Glenelg River catchment has
undergone substantial change in the past 200 years. Extensive clearing of native vegetation for
agriculture has resulted in a number of primary impacts on the Glenelg River such as salinisation,
erosion and sedimentation. These modifications to the channel system have been further exacerbated
as a result of system regulation by Rocklands Reservoir and water harvesting.
3.1 Potential environmental issues
Rocklands Reservoir in the upper Glenelg River catchment has reduced the mean annual flow
downstream of the dam from 113,000 ML/year naturally to 42,700 ML/year currently (data from this
study). The dam also has the capacity to affect major floods and medium flows, and whilst it has not
had pronounced effects on low flows in most months it has decreased winter and spring floods and
high summer flows (Mitchell 1996). Rocklands Reservoir also presents a barrier to the movement of
migratory fish species and localised movement of non-migratory species. Furthermore, the mitigation
of major floods may have implications for connectivity between the main channel of the Glenelg River
and its floodplain.
Mitchell et al. (1996) suggests that the altered flow regime in the mid to upper Glenelg River may not
have affected the spawning of endemic native fish in this region as the spawning cycles of these
species do not appear to be cued to flooding. Nevertheless, flushes in late summer/early spring may
be important for improving water quality after low flow periods. This inturn may affect the
recruitment success of native fish species by influencing the survival of juvenile fish.
Primary impacts on the Glenelg River such as salinisation, erosion and sedimentation are, to varying
degrees, a result of extensive clearing of native vegetation for agriculture (Mitchell 1996). Riparian
vegetation is particularly important to in-stream biota as it provides shading, food (terrestrial
invertebrates) and shelter (leaf litter, woody debris). Riparian vegetation also influences water
chemistry through filtering and buffering the in-stream environment from allocthanous sources of
sediment, chemicals and nutrients. In the Glenelg River catchment, clearing of vegetation has resulted
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 16
in sheet erosion that delivers sediment to the upper river. Moreover, removal of riparian vegetation in
mid to lower reaches of the river has resulted in bank instability and subsequent bank slumping which
has contributed to sedimentation and reduced capacity of the channel. These processes reduce
instream habitat complexity, an essential requirement for aquatic fauna in that it provides different
microhabitats for shelter, spawning, food production etc.
Primary factors resulting in a loss of habitat complexity are:
q sedimentation leading to the infilling of pools and smothering of coarse substrates, woody debris
and macrophytes
q
salinisation leading to stratification and subsequent deoxygenation of pool habitats, also
potentially the inhibition of aquatic macrophyte growth
q
river regulation leading to a reduction in the magnitude, frequency and duration of high flows in
winter and spring thus diminishing channel flushing (removal of sediment from channel).
q
desnagging leading to a direct loss of woody substrates
Many of these factors are interrelated and are affected by flow but not alone attributable to the altered
flow regime. For example, extensive sedimentation in the Glenelg River (some reaches of stream
have lost 80% of their former channel capacity) has occurred as a result of vegetation clearing and
erosion. Nevertheless, diminished flows over the winter/spring period result in a lack of flushing of
the river channel thus leaving sediment deposited in pools in the upper and mid reaches of the Glenelg
River
The loss of aquatic macrophytes, salinisation, sedimentation, smothering and removal of snags and
altered flow regimes have direct and indirect impacts on instream fauna (macroinvertebrates, fish,
reptiles and amphibians, and other vertebrates). Aquatic vegetation and woody debris are an important
component of habitat complexity in deeper reaches of rivers (Walker et al. 1992) and are often
correlated with macroinvertebrate species (O’Connor 1991 in Mitchell et al 1996) and fish species
richness (Schlosser 1982). Decreases in the diversity and abundance of aquatic macrophytes and the
loss of snags lead to a loss of food source, spawning sites and shelter for both aquatic
macroinvertebrates and fish.
Salinisation as a result of native vegetation clearing and elevated groundwater levels is a primary
environmental issue in the Glenelg River (Mitchell 1996). Salinisation and subsequent stratification
occur in deep pools (>2 m) in the Glenelg River. In pools over 3 m deep, stratification is stable, longlived and reappears 1-2 months after flushing (Mitchell 1996). Conductivity in the Glenelg River is
highest during the low flow period between January and March and shows a second increase in JuneJuly attributable to additional salt inputs from “first flush” events (Mitchell 1996). Reduction in the
magnitude of natural flows as a result of Rocklands Reservoir may also contribute to salinisation of
downstream sites. Saline groundwater intrusion appears to be most pronounced above Fulham Bridge
(Cameron and Jekabsons 1992, McGuckin et al. 1991, Mitchell 1996) and results in stable
stratification under low to moderate flow conditions.
Salinisation may influence flora and fauna directly or indirectly through a variety of complex
mechanisms. For example, salinisation may affect organisms indirectly through creating changes to
habitat attributes (i.e. a direct effect on macrophytes which are important as cover for some fish
species) or trophic relationships between species. Salinisation also leads to stratification and
subsequent deoxygenation of the water below the halocline, this in turn may preclude fish and
macroinvertebrates from important refuge habitats in pools. These indirect effects are complex and
have been summarised well by Mitchell (1996).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 17
Direct effects of salinisation may result if salt tolerances of organisms are exceeded, leading to lethal
physiological effects. Similarly, increase levels of salt may have sub-lethal effects on stream biota
that may result in reduced growth rates, reduce reproductive success and reduced health and vigour.
While the following section considers each of the identified issues as separate phenomena, they are in
reality all interlinked. Moreover, their relative importance changes with location within the catchment
and though the year. Due to the interaction between issues it is impossible to legitimately rank them
relative to each other. Hence, the order in which the issues are described is not one of relative
importance within the catchment.
In brief, the five key issues that confront the Glenelg River are as follows.
7. Sand slugs:
– loss of channel form;
– reduced substrate diversity; and
– reduced instream habitat diversity.
8. Water quality:
– salinisation;
– stratification and subsequent deoxygenation of water column;
– reduction in habitat availability for aquatic fauna; and
– inhibition of aquatic macrophyte growth.
9. Flow regulation:
– altered flood frequency, magnitude, duration;
– changed flow seasonality; and
– diminished channel flushing.
10. Channel condition:
– bank erosion;
– stock access;
– riparian clearing; and
– desnagging.
11. Current values of the Glenelg River:
– riparian and instream flora present; and
– aquatic fauna community.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 18
12. Heritage river reach:
– high environmental value; and
– degraded riparian zone outside National Park.
3.2 Sand slugs
Sand accumulation in stream channels is a major stream management issue in the Glenelg River
catchment. Sheet, rill and gully erosion of granite portions of the catchment have filled the Glenelg
and its tributaries with about 6,000,000 m3 of sand (Rutherfurd and Budahazy, 1996). Little sand is
now coming from the catchment, so the major source of sand to the Glenelg River is the lower reaches
of tributary streams. The tributaries introduce discrete slugs of sand to main channel that often
partially dam the river, these slugs are commonly referred to as tributary junction plugs. As these sand
slugs move downstream they attenuate, gradually giving way to a succession of small sluglettes.
Rutherfurd and Budahazy (1996) estimate the sand slugs are moving through the stream network at a
slow rate, with only tens of thousands of cubic metres being removed by bedload transport. The low
transport rate is due, in part, to regulation of the river from Rocklands Reservoir.
Rutherfurd and Budahazy estimate that there are 4 – 8 Mm3 of sand stored in the Glenelg River and its
tributaries. Channel storage estimates range from about 50,000 m3 /km in the Glenelg at Harrow, to an
average of about 10 – 20,000 m3 /km elsewhere in the system. The sand occupies a larger proportion
of the cross-section in the tributaries (up to 80%) than in the Glenelg River. Capacity loss (loss of
channel capacity) in the Glenelg River falls from about 60% between Harrow and Burkes Bridge, to
20% at Casterton, and 10% at Dartmoor.
Most of the sand was deposited in the lower reaches of the streams very quickly after the onset of
channel extension through gullying. However, the original deep pools in the Glenelg River, combined
with regulation from Rocklands Reservoir, have limited the movement of sand through the trunk
stream. Of the sand already stored in the main channel, only about two-thirds will be available for
downstream transport. About one-third will be more permanently stored in benches, pointbars or on
the floodplain. Rutherfurd and Budahazy cite several lines of evidence that suggest bedload transport
rates are in the order of 10-30,000 m3 /year.
The main source of sand for the main channel is now located in the lower few kilometres of tributary
streams. Importantly, in smaller tributaries, large volumes of sand are stored in deep areas of the bed
that have been abandoned by widening of the channel. In Bryans Creek and Pigeon Ponds Creek, this
bed storage has removed up to half of the total volume of sand available for transport (Rutherfurd and
Budahazy, 1996).
A major flood could move large volumes of sand, as occurred in the 1946 flood when large volumes
of sand were deposited in the channel and on the floodplain. However, regulation has dramatically
reduced the frequency of large floods, particularly close to Rocklands Reservoir, and consequently the
rate of sand transport (Ian Rutherfurd, pers. comm.; Brizga et al., 2000). The sand is now moving
through the stream network in a complicated pattern, but it will take many decades for the sand to be
stabilised and removed.
The effect of the movement of sand into the Glenelg River and its tributaries is not clear. Rainfallrunoff modelling suggests that filling half of the channel cross-section with sand will have minimal
impact on the size of flood peaks or their time-to-peak because of the decreased roughness associated
with sand sheets. In addition, deposition on the floodplain has meant that in many reaches the rise in
bed level has been matched by an increase in bank height.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 19
A complicating factor in managing sand in the Glenelg River is the form of channel adjustment that
takes place once the sand is removed from a reach. Both Rutherfurd and Budahazy (1996) and Brizga
et al. (2000) report examples of bed incision and consequent bank erosion following sand extraction
from the channel. Bed incision of the main trunk can also lead to incision of the tributaries,
particularly if those tributaries are graded to the elevation of the sand surface.
The sediment influx has smothered the previous channel form and dramatically simplified the
geomorphological diversity of the channel by creating a sandy bed with less deep holes. Loss of
geomorphological diversity in turn restricts habitat availability. Typically in rivers the greatest
diversity of macroinvertebrates and fish are found where there is an abundance of large woody debris
(LWD), water plants or cobbles and rocks. The effect of sand and silt is to fill crevices and bury
potential aquatic habitat. Where sand slugs do not totally bury LWD or completely smother coarser
substrates there is little evidence that species diversity or stream environmental values are significantly
reduced (Brizga et al., 2000).
Brizga et al. found that in fact there were very few areas where sand comprised the only available
habitat. While many pools may have partially filled with sand there is still a remnant sequence of
pools and shallow areas usually with some residual LWD. However, the loss of deep holes in the river
has removed sites of refuge for platypus during periods of low flow. Furthermore, artificially reduced
flows during low flow periods may have implications for the movement of platypus between pools and
foraging behaviour, thus restricting platypus to regions of poor water quality. Low flows and
sediment deposition in the mid to upper Glenelg River have also been found to promote excessive
growth of Typha spp. and Phragmites australis in the river channel (Mitchell et al. 1996). This
consequently impedes flows and leads to further sediment deposition and further reduction in habitat
complexity.
Overall the flow changes have resulted in reduced sediment transport through the system which has
had major implications for structural habitat change within the channel. These structural habitat
changes, in the form of sand slugs and isolation of pools, have had significant resultant effects on
other components of the ecosystem such as water quality and community continuity.
3.3 Water quality
The analyses, described in Appendix C, indicate that the water quality in the Glenelg River system is
poor with respect to salinity. Salinity is particularly high in pools in the reach of the Glenelg River
between Rocklands Reservoir and Fulham Bridge (Cameron and Jekabsons 1992, McGuckin et al.
1991, Mitchell et al. 1996). Although turbidity and nutrients are generally not as high, historical
levels have been, at times, high enough to adversely impact the aquatic biota.
Salinisation is most likely to influence flora and fauna directly or indirectly through a variety of
complex mechanisms. For example, salinisation may affect organisms indirectly through creating
changes to habitat attributes (i.e. a direct effect on macrophytes which are important as cover for some
fish species) or trophic relationships between species. Salinisation also leads to stratification and
subsequent deoxygenation of the water below the halocline, this in turn may preclude fish and
macroinvertebrates from important refuge habitats in pools. These indirect effects are complex and
have been summarised well by Mitchell et al. (1996).
Salinisation and subsequent stratification occur in deep pools (>2 m) in the Glenelg River. In pools >3
m deep, stratification is stable, long-lived and reappears 1-2 months after flushing (Mitchell et al.
1996). Salinity in the Glenelg River is highest during the low flow period between January and March
and shows a second increase in June-July attributable to additional salt inputs from “first flush” events
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 20
from tributary inflows (Mitchell et al. 1996). Reduction in the magnitude of natural flows as a result
of Rocklands Reservoir may also contribute to salinisation of downstream sites.
There is currently an flow allocation for the Glenelg River of 13,360 ML annually, although this is
planned to increase with further stages of pipelining of the Wimmera Mallee Water system. The
current releases differ from environmental flow recommendations as they are designed to sustain the
ecosystem, rather than return all or part of the natural flow regime. However, these flows are not
always delivered in their entirety. Deakin University is undertaking a biological monitoring program
in the Glenelg River to determine if the environmental allocations have had a significant beneficial
effect. Over the four seasons since 1994/95 when the monitoring began, there have effectively been
two years when the allocation was delivered to approximately 20-25% of allocated flows and two
years when it was 70-80% of recommended flows (B. Mitchell, pers. comm.). The reduction in flows
delivered were due to periods of drought and subsequent water limitations.
The Deakin University monitoring program has not reported yet but preliminary data analysis suggests
that when close to the 80% of the environmental allocation is provided in a given year there is a
positive response in water quality parameters, particularly dissolved oxygen and salinity levels (B.
Mitchell, pers. comm.). In years when the proportion of environmental allocations has been closer to
25% of allocated flows, there still remains a positive effect, although the improvement in water quality
is reduced. For example, even the relatively low environmental allocations delivered in 1996/97 of
4,119 ML had a positive impact on water quality.
The work of Anderson and Morrison (1989) and Mitchell et al. (1996) suggest that even if the
environmental water was currently available, releasing large flushing flows down the river could have
substantial short term detrimental effects but in the long term be beneficial. This short term
detrimental effect would largely be due to the mobilisation of highly saline water or water with low
dissolved oxygen levels from the existing deep pools. Sustained environmental flows would help to
reduce salinity in shallow water and the upper water column, however, saline water in deep pools
should not be managed using flushing (Mitchell et al. 1996). Mitchell et al. (1996) recommend
sustaining environmental flows in the summer-autumn period to compensate for lost habitat with an
additional provision for spring flows. The low level sustaining flows would also help manage the
water quality within the surface water of the pools and the preliminary indications are that these flows
are having a beneficial effect on the surface water quality (B. Mitchell pers. comm.) In the long term
large flushing flows are important for managing the stream channel form and movement of sediment.
These flows would also act as important disturbances to the biological community.
Direct effects of salinisation may result if salt tolerances of organisms are exceeded, leading to lethal
physiological effects. Similarly, increased levels of salt may have sub-lethal effects on stream biota
that may result in reduced growth rates, reduce reproductive success and reduced health and vigour.
For example, Mitchell et al. (1996) suggest that the range of the Glenelg spiny crayfish, severely
restricted by habitat degradation in the Glenelg River basin, is also under threat from saline water.
Glenelg spiny crayfish moult frequently when small, but by 50 mm occipital length moulting is
restricted to once a year between January to May. At this time water quality in the modified upper
river is poor with elevated temperature and salinity, and reduced oxygen levels. When a crayfish
moults its ability to osmoregulate is reduced, consequently high salinities may reduce growth or
survival (Mitchell et al. 1996). Mitchell et al. (1996) also noted that a conspicuous feature of
macrophyte communities was the absence of submerged aquatic macrophyte species in downstream
sites. It was suggested that salinities in pools at the downstream sites might be sufficiently high to
affect the growth of submerged macrophytes.
The salinity levels within the Glenelg River system may potentially affect a range of biota. It is
considered for example, that fish are a good indicator of the effect of salinity on a river system
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 21
because they are mobile and their occurrence may reflect the health of a river reach (Ryan and Davies
1996). Some fish species found in the Glenelg River, for example the Common Galaxias (Galaxias
maculatus), are relatively tolerant of salinity because of their migratory stages and may not be greatly
affected by current salinity levels (Pollard 1971). Other species found in the Glenelg River, such as
the River Blackfish (Gadopsis marmoratus), are relatively sensitive to saline conditions, particularly
in juvenile life stages (Ryan and Davies 1996). Salinity levels found within the Glenelg River would
also impact a range of invertebrate species, resulting in a reduction in diversity and abundance (Hart
1982).
Consequently the impacts of salinity may be two-fold, direct effects on biotic health and structural
effects reducing useable habitat within the system.
3.4 Regulation
Rocklands Reservoir has diverted water from the upper Glenelg River catchment to the Wimmera
River system since 1953. The diversion has reduced the mean annual flow downstream of the dam
from 113,000 ML/year naturally to 42,700 ML/year currently (data from this study). Alternate
calculations have suggested that the mean annual natural flow downstream of Rocklands Reservoir,
for the period 1990-99, were 103,000 ML and current annual flow was 19,000 ML (J. Martin pers
comm.). Both of these figures clearly indicate that as a result of the diversion the natural flow regime
of the Glenelg River has been substantially altered and is missing several critical flow elements.
Firstly, the overall volumes of water are greatly reduced throughout the year and large flushing flows
are absent. These changes exacerbate sand slug formation, saline pools and reduction in structural
diversity. The mitigation of major floods also has implications for connectivity between the main
channel of the Glenelg River and its floodplain.
As shown by the estimated natural and current flow duration curves presented in Appendix A,
streamflows upstream of Rocklands Reservoir have not changed substantially. However, immediately
below Rocklands Reservoir seasonality of flow has been reversed by regulation. Immediately
downstream of Rocklands Reservoir, under natural conditions, median flows peak during August at
23,400 ML/month and lowest flows occur during the summer months, particularly February. Current
flows are now less than natural flows for the majority of the year. Zero flows occur during the months
May to November, inclusive. Moreover, peak flows at this site occur during December to February,
inclusive. During June and July, zero flow prevails 100% of the time under current conditions.
Between August and October, flow exceeds 0 ML/month for less than 18% of the time under current
conditions, while under natural conditions, flow exceeded 700 ML/month under natural conditions.
The effect of regulation is obviously greatest immediately downstream of Rocklands Reservoir,
although effects continue a significant distance downstream. The reduction in peak flows is highly
significant all the way through to Casterton, downstream of the confluence with the Wannon the
impact of peak flows is still apparent (e.g. at Dartmour) although is relatively reduced. As discussed
these peaks flows are important for sand and sediment movement through the system. They also are
considered to be key trigger flows for a number of biological events such as fish spawning and
invertebrate recruitment. Consequently, reduction in timing, recurrence, duration and magnitude of
peak flow events has a significant effect on both the biological and physical processes in the river.
The natural periods of cease to flow that may have previously occurred have been discussed
previously. In addition the low flow conditions have also been significantly altered. For example,
between Rocklands outlet and Casterton the low flows over the winter period are significantly
reduced. This means that during winter the flow between peak flow events is generally lower. This
could reduce areas of spawning habitat and general habitat diversity at key periods for the aquatic
community.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 22
The Glenelg River system is considered self regulatory by Southern Rural Water. Southern Rural
Water has not previously had a formal water restriction policy in place due to flow rapidly dropping to
zero as water levels begin to fall during the summer months and water quality also declines. Ad hoc
restrictions were imposed in the summer of 1998/99, during which river flow of 10 ML/day was used
as a trigger to implement restrictions. Such restrictions were unnecessary due to the river rapidly
dropping to zero flow once it was below 10 ML/day and the water becoming too saline for agricultural
use. Therefore, the timing of bans coincided with conditions that were unsuitable for pumping due to
lack of water and high salt levels. Similarly, restrictions were imposed on the Wannon last summer
(1999/00) but due to the flow dropping very quickly by mid January such restrictions were once again
unnecessary. Southern Rural Water also used 10 ML/day, an arbitrary figure, to impose restrictions on
the Crawford River and the Grange burn Creek (J Donovan, pers. comm.).
Rocklands Reservoir also presents a barrier to the movement of migratory fish species and localised
movement of non-migratory species. Although Mitchell et al. (1996) suggest that the spawning cycles
of endemic native fish do not appear to be linked with flooding, altered flow regimes, in the Glenelg
River, below Rocklands Reservoir, may have adversely impacted fish communities through
eliminating other flow related cues. Flushes in late summer/early spring may be important for
improving water quality after low flow periods. This, in turn, may affect the recruitment success of
native fish species by influencing the survival of juvenile fish.
3.5 Channel condition
A number of reports discuss the degraded condition of the Glenelg River (e.g. Rutherfurd and
Budahazy; Brizga et al. 2000; Erskine ). Each of these have identified similar themes of degradation:
q catchment sheet and gully erosion;
q sand slugs;
q sand extraction;
q macrophyte loss;
q localised bed and bank erosion;
q riparian degradation (including unmanaged stock access);
q desnagging; and
q river regulation.
Schreiber et al. (1998) also assessed the environmental aquatic habitat of the Glenelg River based on
bed composition, proportion of pools and riffles, bank vegetation, degree of cover for fish and the
extent of sedimentation or erosion. Their rating ranged from moderate to very poor.
The loss of aquatic macrophytes, salinisation, sedimentation, smothering and removal of snags and
altered flow regimes have direct and indirect impacts on instream fauna (macroinvertebrates, fish,
reptiles and amphibians, and other vertebrates). Aquatic vegetation and LWD are an important
component of habitat complexity in deeper reaches of rivers (Walker et al. 1992) and are often
correlated with macroinvertebrate species (O’Connor 1991 in Mitchell et al 1996) and fish species
richness (Schlosser 1982).
Large woody debris plays a critical role in providing stable substrate and hydraulic diversity in sandbed streams, and is arguably even more important in sand bed streams than other types of streams
(Brizga et al. 2000). There has been significant desnagging within the Glenelg River system,
particulalry in the reach in the Casterton region. Decreases in the diversity and abundance of aquatic
macrophytes and the loss of LWD lead to a loss of food source, spawning sites and shelter for both
aquatic macroinvertebrates and fish. However, the available data on macroinvertebrate populations in
the river is equivocal. For example the heath of the Glenelg River was assessed as good to excellent in
both pools and shallow habitats based on the macroinvertebrate communities present (OCE 1988).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 23
Whereas as part of the National River Health Strategy the Glenelg River Catchment was described as
highly degraded (Schreiber et al. 1998). (See Appendix D for more detail).
Riparian vegetation is particularly important to in-stream biota as it provides shading, food (terrestrial
invertebrates) and shelter (leaf litter, woody debris). Riparian vegetation also influences water
chemistry through filtering and buffering the in-stream environment from allocthanous sources of
sediment, chemicals and nutrients. In the Glenelg River catchment, clearing of vegetation has resulted
in sheet erosion that delivers sediment to the upper river. Moreover, removal of riparian vegetation in
mid to lower reaches of the river has resulted in bank instability and subsequent bank slumping which
has contributed to sedimentation and reduced capacity of the channel. Loss of riparian vegetation
reduces shading for the stream channel and has a consequent affect on water temperature also. These
processes reduce instream habitat complexity, an essential requirement for aquatic fauna in that it
provides different microhabitats for shelter, spawning, food production etc.
3.6 Current flora and fauna values of the Glenelg River system
The native freshwater flora and fauna of the Glenelg River system represent a diverse assemblage with
many species of high conservation significance. This in turn is a key issue for the system as it means
that there are key species of recognised conservation value many of which are under threat due to flow
related changes within the Glenelg River. There is a resultant increased potential for response by the
ecosystem to improvements in the flow regime as the system is not devoid of desirable species.
Consequently changes in the flow regime, or parts thereof, may be more likely to have a beneficial
ecosystem response.
Some examples of the flora and fauna of value include:
q
Eight fish species have conservation significance and of these, five species are protected through
their listing on the Victorian Flora and Fauna Guarantee Act 1988. Of these, four species are
protected through their listing on the (ANZECC 2000) List of Threatened Australian Vertebrate
Fauna.
q
There are 50 species of birds that have conservation significance either in Victoria or nationally
(DNRE 2000a, DNRE 2000b) and of the threatened species, 20 are reliant directly upon the
instream environment for their survival.
q
One species of threatened amphibian, the warty bell frog (Litoria raniformis), has been recorded
from the Glenelg catchment. The conservation status of this species is vulnerable (DNRE 2000b).
q
There are two species of threatened reptile, the swamp skink (Egernia coventryi) and tree goanna
(Varanus varius), in the Glenelg catchment (DNRE 2000a). The conservation status of the
swamp skink is vulnerable that of the tree goanna is data deficient (DNRE 2000b).
q
The platypus (Ornithorhynchus anatinus), although not of documented conservation significance,
have been recorded in the Glenelg River near Casterton and Dartmoor and in the vicinity of
Fulham Hole. The platypus is a significant ‘icon species’ in Australian aquatic systems and
considered of considerable values by the community.
q
There are 63 threatened flora species in the Glenelg River catchment, 15 of which are dependant
on the aquatic environment [DNRE, 2000; Dale Tonkinson DNRE pers. comm., 2000).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 24
In addition to the listed flora and fauna of the Glenelg River system there are numerous other species
of value to the region and community.
3.7 The heritage reach
The lower section of the Glenelg River, from Nelson on the coast to Dartmoor, is designated a
“Heritage River” under the Heritage Rivers ACT 1992 (DNRE 1997) and is listed as a Nationally
Important Wetland by Environment Australia. The Heritage River corridor covers an area of
approximately 3020 Ha and is about 50 m wide for most of its length. The lower section of the
Heritage River flows through the Lower Glenelg National Park. The Heritage River corridor provides
an important habitat link particularly between inland woodlands and the coast for species reliant on
riparian habitats. This habitat corridor is well protected within the National park although public land
water frontages are degraded at Nelson, Donovan’s and below Dartmoor (DNRE 1997).
There are several key values associated with the heritage river reach.
q Thirteen rare or threatened flora species are known to occur in the heritage river corridor although
many of these are only known from local knowledge (DNRE 1997). Rare Bog Gum and the
Lime Fern are two examples. Additionally, the leafy greenhood and the limestone spider-orchid
are listed under the Flora and Fauna Guarantee Act 1988.
q
Twenty three significant fauna species in the Heritage River Corridor. Of these species 11 are
listed in the Flora and Fauna Guarantee Act 1988.
q
A diverse fish fauna in both freshwater and estuarine sections, including five significant fish
species.
q
The lower Glenelg River karst area – an area of limestone between Keegan's Bend and Nelson – is
of state significance (LCC 1991). Extensive caves in the area provide habitat for several
significant species of bat.
q
The only Victorian estuary developed in dune calcarenite ridges (Bird 1977).
q
Remnant River Red Gum community south of Dartmoor (DNRE 1997).
q
Moleside Creek (tributary of the Glenelg River) contains numerous species of fern.
q
Numerous recreational values – fishing, boating, camping, walking (DNRE 1997).
Key management directions have been proposed for the lower sections of the Glenelg River that will
maintain and enhance existing values (DNRE 1997). These include:
q restore habitat links along the River to the coast;
q
improve environmental water values of the river, particularly the estuary, and develop trigger
levels for opening of the river mouth;
q
undertake research and monitoring of significant fish species and environments, monitor sand and
silt effects on the River including the sand slug upstream the heritage River corridor (DNRE
1997).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 25
Flow related threats to the lower Glenelg River might include the encroachment of the upstream sand
slug and the alteration of late summer/autumn and winter/spring flow events. Rutherfurd and Budhazy
(1996) suggest that the sand slug may not reach the Heritage River for approximately 30-40 years.
Nevertheless, the impacts of the sand slug are likely to be similar to those that have occurred in the
mid to upper reaches of the Glenelg River (e.g. infilling of deep pools, smothering of substrates, etc)
ultimately leading to decreased habitat complexity. With regards to the alteration of flows to the
lower Glenelg River, this has not been quantified and hence it is difficult to determine the potential
biological impacts.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 26
4.
Environmental objectives
4.1 Preliminary umbrella objectives
1) Maintain/improve water quality in accordance with SEPP Waters of Victoria objectives
(Government of Victoria, 1988).
This section outlines the
preliminary environmental 2) Achieve an assured and adequate quality of water resource and
objectives that have been a balanced and fair distribution between human and environmental
developed for the Glenelg uses (see Glenelg Regional Catchment Strategy: GRCLPB, 1997).
River system. Two types of
environmental objectives are
4.2 Preliminary specific objectives
proposed:
umbrella
objectives (reflect state and 7) Provide an adequate environmental flow regime throughout the
regional objectives) and year that includes:
specific objectives (focus on q periods of no flows but without extending their frequency or
environmental
water duration;
q
minimum environmental flows during low flow periods;
q
appropriate flushing flows to manage salinity and nutrient levels; and
q
flows of a sufficient magnitude to facilitate geomorphological processes.
8) Maintain and restore longitudinal connectivity by:
q minimising changes in flow regime (from natural) due to regulation at Rocklands Reservoir;
q improving flow over/through existing weirs; and
q providing natural flood regime along entire stream length.
9) Maintain and improve (where possible) stream habitat condition by providing flows to enhance:
q channel morphology;
q appropriate water quality;
q riparian vegetation; and
q instream vegetation.
10) Maintain self-sustaining populations of endemic native fish with particular emphasis on threatened
species.
11) Ensure that links to other strategies (e.g. Wagg, 1997) are fostered to promote the benefits of
environmental flows.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 27
5.
Outcomes
The previous sections have described the catchment, identified issues that are related to environmental
water management and set out preliminary environmental management objectives. Following is a
summary of further work that is required to assess the environmental flow requirements of the Glenelg
River. The methodology that we have adopted is detailed in the state-wide methodology developed as
part of the Stressed rivers project for the Wimmera, Avoca and Glenelg Rivers. The full state-wide
methodology will not be repeated in detail here but in brief the key steps include:
q field assessment of a number of field sites that typify relatively homogenous reaches;
q
hydraulic modelling to relate channel morphology to streamflow;
q
identification of critical flow components along with discussion of the ecological and
geomorphological roles of these components; and
q
modelling flow components for different management scenarios to understand how the wetted
area of the channel changes as critical flow components change under different management
scenarios.
5.1 Assessment framework
Information collected throughout the project, including agreement on critical flow components, will be
used to finalise objectives. Recommendations will be then developed to meet each objective. The key
basis for the recommendations will be an assessment of the differences between management
scenarios within a number of study reaches by the technical panel.
5.1.1
Technical panel
Fieldwork will be conducted at each of the sites by technical panel. The composition of the panel is
not set at this stage but should include personnel experienced in:
q hydrology;
q
aquatic ecology; and
q
geomorphology.
These disciplines will be combined across key project personnel as appropriate.
5.1.2
Study reaches
In order to meet the environmental objectives of the Glenelg River, data for appropriate water resource
management reaches are required. To this end the river has been divided into five distinct reaches.
Within each reach, potential field sites have been identified where environmental value can be
measured or gauged by technical panel. The reaches and sites have been selected on the basis of
catchment issues and a number of practical criteria. Selection criteria include the proximity of sites to
flow gauges, features of site that are typical of the wider reach (e.g. channel morphology and
topography) and site access. Links with Deakin University studies in the catchment have been
maintained by choosing common sites, where possible. Study reaches and field sites that meet these
criteria are listed below. It should be noted that field sites may change with field inspection.
1) Headwaters to backwater of Rocklands Reservoir
The upper reach is distinguished from the lower reaches on the basis of its relief, drainage density,
adjacent landuse (predominantly National Park) and its lack of regulation.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 28
There was no field assessment undertaken in this reach as environmental flows were not a key
issue in the reach.
2) Rocklands Reservoir to Chetwynd River
This reach is very affected by regulation and salinisation. Two sites will be used to characterise
the reach:
q
Site 1
Downstream 5 mile outlet
q
Site 2
Pine Hut Hole – upstream Gauge 238224
Site 3
Upstream Harrow at Dick’s Place off Greens Lane
q
3) Chetwynd River to Wannon River
The effects of regulation are diminished below the Chetwynd River confluence and the Chetwynd
River remains one of the largest sources of sand to the Glenelg River. Two sites will be
investigated to characterise this reach;
q
Site 4
Burkes Bridge – downstream Chetwynd River
q
q
Site 5
Roseneath – upstream of bridge
Site 6
Section Rd – downstream of bridge (Downstream Wando River)
4) Wannon River to tidal extent
The Wannon River is the largest tributary of the Glenelg River, draining almost half the
catchment. The Wannon River is also the watercourse most affected by abstractions for irrigation,
other than the diversion at Rocklands Reservoir. Unregulated flows entering this reach distinguish
it from its upstream counterparts. Hence this reach is of key importance in characterising the
environmental flows of the Glenelg River. Two sites will be investigated by the technical panel:
q
Site 7
Gauge 238202
q
Site 8
Gauge 238206
5) Tidal extent to river mouth
Heritage river reach. Although not particularly affected by abstractions, this reach is of high
environmental value and consequently is of importance to this study. One site with adequate
access will be chosen in the field. A detailed flow assessment at this site will not be undertaken,
although a brief site inspection will be conducted.
Information collected at each site will include stream channel measurements and records of key
features and issues as outlined in the state-wide methodology. This information will form the basis of
a simple 1-D hydraulic model. The panel will also take photographs and video footage of each site.
The aim of collecting this information is to allow the panel to understand and visualise how
streamflow fluctuations affect instream habitat and ecosystem condition. A team member will
undertake two subsequent visits to the field sites in order to provide an assessment of stream condition
at different streamflows. This will involve the completion of a sub-set of the field sheets completed by
the Technical Panel on the first trip and taking 180 degree photographs and videos of each site for
latter analysis by the Technical Panel.
It should be noted that field sites may vary at the discretion of the technical panel. Sites might need to
be altered due to flow-data availability, site access, channel modifications, etc.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 29
5.1.3
Use of existing data and information
As referred to in this document, the existing data and literature on the Glenelg River are adequate to
describe the environmental condition of the catchment. We propose to critically review the
applicability of this information to the current assessment of environmental water requirements. In
addition, Dr Brad Mitchell has offered to make available unpublished data sets on water quality,
macroinvertebrates and fish habitat (e.g. mapping of snags) for analysis and evaluation as part of
Phase 2 of this environmental flow study. The critical review and evaluation of existing data and
information is a key step in developing recommendations as part of Phase 2.
5.2 Reporting
Following finalisation of the state-wide methodology, fieldwork, consultation and further study, the
technical panel will report its final recommendations for environmental objectives and for strategies to
attain those objectives. Catchment issues that affect the flow regime of the Glenelg River will be
addressed in the final report. Nevertheless, it is worth being clear here on the type and scope of those
recommendations.
The final report will detail all strategies and works, directly related to environmental water allocations,
required for the main trunk of the Glenelg River to attain the environmental objectives. It is expected
that recommendations will include:
q environmental flow recommendations for the Glenelg River, including a range of flow
requirements at different times of the year and/or maximum extraction rates;
q
indication of the impact of the current water resource development within the catchment on
instream habitat, specific species and broader ecological processes;
q
comment on the expected impact of additional water resource development for the agreed
scenarios used as part of the hydraulic modelling;
q
appropriate monitoring program; and
q
suggestions for further work to fill knowledge gaps.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 30
6.
References
Andrews, A.P. (1996). Family Bovichtidae. Congolli. Pages 198-199 in McDowall, R. M., ed.
Freshwater fishes of south-eastern Australia. Reed Books, Chatswood.
ANZECC (1992). Australian Water Quality Guidelines for Fresh and Marine Waters. A report for the
National Water Quality Management Strategy. ANZECC, Canberra.
ANZECC (2000). ANZECC List of Threatened Vertebrate Fauna. The Australian and New Zealand
Environment Conservation Council, Canberra.
ARMCANZ and ANZECC (1996). National Principles for the Provision of Water for Ecosystems.
ARMCANZ and ANZECC, Sydney.
Beumer, J.P. (1996). Family Anguillidae. Freshwater eels. Pages 39-43 in McDowall, R. M., ed.
Freshwater fishes of south-eastern Australia. Reed Books, Chatswood.
Bird, E.C.F. (1977). Sites of special scientific interest in the Victorian coastal region. A report on
geological and geomorphological aspects prepared for the Town and Country Planning Board.
Brizga, S.O., N.M. Craigie, P. Condina and Lawson and Treloar Pty Ltd (2000). Development of
operational guidelines for sand management sites on the Glenelg River: Feasibility study. Final
report to the Glenelg Hopkins Catchment Management Authority.
Cameron, M. and Jekabsons, M. (1992). Salinity in the Glenelg and Wannon Rivers, Victoria.
Department of Conservation and Natural Resources, Victoria,
Chessman, B.C. (1995). Rapid assessment of rivers using macroinvertebrates: A procedure based on
habitat-specific sampling, family level identification and a biotic index. Australian Journal of
Ecology 20: 122-129.
Davidson, N., Jeffery, G., and Wagg, C. (1994). The Environmental Condition of Streams in the
Glenelg Basin. Department of Conservation and Natural Resources and National landcare
Program, Victoria,
DCNR (1993). Action Statement No. 42 Variegated (Ewen's Pygmy Perch) Nannoperca variegata .
Department of Conservation and Natural Resources, East Melbourne.
DWR (1989). Water Victoria: a Resource Handbook. Victorian Government Printing Office,
Melbourne.
Dixon, P.R., Wagg, C., and Amirtharajah, M. (1998). Aspects of Environmental Conditions in the
Glenelg-Hopkins Region with Particular Reference to Salinity and Nutrients in Rivers,
Wetlands and Remnant Vegetation. Department of Natural Resources and Environment,
DNRE (1997). Heritage rivers and natural catchment areas. Draft management plans Volume 1 Western Victoria. Department of Natural Resources and Environment, East Melbourne.
DNRE (1997a). Victoria's Environmental Flow Program. Department of Natural Resources and
Environment.
DNRE (2000a). Atlas of Victorian Wildlife. Arthur Rylah Institute - Department of Natural
Resources and Environment, Heidelberg.
DNRE (2000b). Threatened vertebrate fauna in Victoria - 2000. Department of Natural Resources
and Environment, East Melbourne.
DNRE (2000c). Victorian Aquatic Fauna Database. Arthur Rylah Institute - Department of Natural
Resources and Environment, Heidelberg.
Doeg, T. . a. K., J.D. (1994). Effects of draining and desilting a small weir on downstream fish and
macroinvertebrates. Regulated Rivers: Research and Management 9: 263-277.
EPA (1999). The health of streams in the Glenelg catchment. River Health Bulletin. Environment
Protection Authority, Victoria.
Erskine, W.D. (1994). River response to accelerated soil erosion in the Glenelg River catchment.
Australian Journal of Soil and Water Conservation 7: 39-47.
Godoy, W. (1996). The Effects of Rocklands Reservoir on the Glenelg River. Department of Natural
Resources and Environment - Water Bureau, July 1996.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 31
GRCLPB (1997). Glenelg Regional Catchment Strategy. Glenelg Regional Catchment and Land
Protection Board, May 1997.
Gullan, P.K., Cheal, D.C. and Walsh, N.G. (1990). Rare or threatened plants in Victoria. Department
of Conservation and Environment, East Melbourne.
Harris, J. H. a. R., S.J. (1996). Family Percichthyidae. Australian freshwater cods and basses. Pages
150-163 in McDowall, R. M., ed. Freshwater fishes of south-eastern Australia. Reed Books,
Chatswood.
HArt, B.T. (1982). Water quality: formulation of criteria. In: O'Loughlin, E.M. and Cullen, P. (Eds)
Predictions in Water quality. Australian Academy of Science, Canberra, pp 11-26.
Humphries, P. (1986). Observations on the ecology of Galaxiella pusilla (Mack) (Salmoniformes:
Galaxiidae) in Diamond Creek, Victoria. Proceedings of the Royal Society of Victoria 98: 133137.
Ingeme, Y. (1996). Glenelg River Catchment Environmental Flows Technical Report - Draft Report.
Department of Natural Resources and Environment, July 1996.
Koehn, J. D. a. O. C., W.G. (1990). Biological information for the management of native freshwater
fish in Victoria . Government Printer, Melbourne.
Koster, W.M. (1997). A study of the interactions between the dwarf galaxias, southern pigmy perch
and eastern gambusia. Pages 88. School of Ecology and Environment. Deakin University,
Melbourne.
Kuiter, R.H., Humphries, P.A. and Arthington, A.H. (1996). Family Nannopercidae. Pygmy perches.
Pages 168-175 in McDowall, R. M., ed. Freshwater fishes of south-eastern Australia . Reed
Books, Chatswood.
Larson, H. K. a. H., D.F. (1996). Family Gobiidae, subfamilies Eleotrinidae and Butinae. Gudgeons.
Pages 200-219 in McDowall, R. M., ed. Freshwater fishes of south-eastern Australia. Reed
Books, Chatswood.
LCC (1991). Glenelg River - Victorian heritage river. Rivers and streams special investigation - final
recommendations. Report extract. Land Conservation Council, Victoria.
McDowall, R.M. (1996a). Family Retropinnidae. Southern smelts. Pages 92-95 in McDowall, R. M.,
ed. Freshwater fishes of south-eastern Australia. Reed Books, Chatswood.
McDowall, R.M. a. F., W. (1996b). Family Galaxiidae. Galaxiids. Pages 52-77 in McDowall, R. M.,
ed. Freshwater fishes of south-eastern Australia. Reed Books, Chatswood.
McDowall, R. M. a. F., W. (1996c). Family Prototroctidae. Southern graylings. Pages 96-98 in
McDowall, R. M., ed. Freshwater fishes of south-eastern Australia . Reed Books, Chatswood.
McGuckin, J.T., Anderson, J.R., and Gasior, R.J. (1991). Salt Affected Rivers in Victoria. Arthur
Rylah Institute for Environmental Research, July 1991.
Mitchell, B., Rutherfurd, I., Constable, A., Stagnitti, F., and Merrick, C. (1996). An Ecological and
Environmental Flow Study of the Glenelg River from Casterton to Rocklands Reservoir.
Aquatic Resource Utilisation and Management Research Group, Deakin University,
Warrnambool. August 1996.
Mitchell, B., Rutherfurd, I., Constable, A., Stagnitti, F., and Merrick, C. (1996). An Ecological and
Environmental Flow Study of the Glenelg River from Casterton to Rocklands Reservoir.
Aquatic Resource Utilisation and Management Research Group, Deakin University,
Warrnambool.
Mitchell, P. (1990). The Environmental Condition of Victorian Streams. Department of Water
Resources, Victoria.
OCE (1988). State of the environment report 1988. Victoria's inland waters. Office of the
Commissioner for the Environment, Victoria.
O'Connor, W.G. a. K., J.D. (1998). Spawning of the broad-finned galaxias, Galaxias brevipinnis
Gunther (Pisces: Galaxiidae) in coastal streams of southeastern Australia. Ecology of
Freshwater Fish 7: 95-100.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 32
Pollard, D.A. (1971). The biology of a landlocked form of the normally catadromous salmoniform fish
Galaxias maculatus (Jenyns). I. life cycle and origin. Australian Journal of Marine and
Freshwater Research 22: 91-123.
Rutherfurd, I.D. and Budahazy, M. (1996). A Sand Management Strategy for the Glenelg River and
its Tributaries, Western Victoria. Report to the Department of Natural Resources and
Environment, Victoria and Southern Rural Water. Cooperative Research Centre for Catchment
Hydrology, Report 96/9, Melbourne. Melbourne. December, 1996.
Ryan, T. and Davies, P. (1996). Environmental effects of salinity and nutrients from salt disposal:
approaches to the development of management criteria. Flora and Fauna Technical Report 137.
Department of Natural Resources and Environment.
SAC (1991a). Final recommendation on a nomination for listing. Edelia obscura (Klunzinger, 1972) Yarra Pygmy Perch. Nomination No. 125. Flora and Fauna Guarantee - Scientific Advisory
Committee, Victoria.
SAC (1991b). Final recommendation on a nomination for listing. Galaxiella pusilla (Mack, 1936) Dwarf Galaxias. Nomination No. 141. Flora and Fauna Guarantee - Scientific Advisory
Committee, Victoria.
SAC (1991c). Final recommendation on a nomination for listing. Prototroctes maraena (Gunther,
1864) - Australian Grayling. Nomination No. 3. Flora and Fauna Guarantee - Scientific
Advisory Committee, Victoria.
SKM (2001). Glenelg River Natural Flow Estimation. Report to the Department of Natural Resources
and Environment. Sinclair Knight Merz.
Schlosser, I.J. (1982). Fish community structure and function along two habitat gradients in a
headwater stream. Ecological Monographs 52: 395-414.
Schreiber, E.S.G., Wagg, C., Metzeling, L., and Perriss, S. (1998). Assessing stream health in the
Glenelg catchment - using macroinvertebrates. Department of natural Resources and
Environment and Environment Protection Authority,
Sherwood, J., Magilton, C. and Rouse, A. (1998a). The Glenelg River: Nutrient and Estuarine
Hydrodynamics. Deakin University, Warrnambool. July 1998.
Sherwood, J., Magilton, C. and Rouse, A. (1998b). The Glenelg River: Nutrients and Estuarine
Hydrodynamics. Department of Natural Resources and Environment, Hamilton. July.
VWQMN (1999). Victorian Water Quality Monitoring Network Database, AWT Victoria.
Wagg, C. (1997). A Summary of the Water Quality in the Glenelg Catchment. Department of Natural
Resources and Environment,
Walker, K.F., Thoms, M.C., and Sheldon, F. (1992). Effect of weirs on the littoral environment of the
River Murray, South Australia. Pages 270-293 in Boon, P. J., Calow, P. A., and Petts, G. E.,
eds. River Conservation and Management. Wiley, Chichester.
Zeidler, W. and Adams, M. (1990). Revision of the Australian crustacean genus of freshwater
crayfish Gramastacus Riek (Decapoda: Parastacidae). Invertebrate Taxonomy 3: 913-924.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 33
Appendix A
Hydrology
Hydrology is an integral component to the development of environmental flows. It is important to
understand where and when water is being diverted as well as the volumes of diversion so that it can
be identified what source, if any, may supply water back to the environment.
This chapter outlines the demands that are placed on the system by water extraction as well as the
operation of the Glenelg River system downstream from Rocklands Reservoir. The patterns of
streamflows are also compared between natural flow (no extraction) and the current level of demand at
six geographically distinct locations within the project area. A resource allocation model (REALM)
was constructed to quantify flows under natural and contemporary conditions.
Natural flows were calculated by adding rural and urban water demands to gauged flow data. All
catchment storages were accounted for during the process. Natural flows generated in this manner do
not reflect potential changes to flows as a result of landuse changes. Only those licensed private
diverters on the Wannon River were considered in the generation of natural flows. Private diversions
from the Glenelg River and its other tributaries are small relative to its flows and as such were
assumed to be negligible. Current conditions were assumed to be equal to the 1993/94 level of
development and were generated using REALM (SKM 2001b).
A.1 Streamflows
Rainfall varies seasonally and spatially within the catchment. Although winter months are wetter
throughout the catchment, there is a gradual decline in mean annual rainfall from the coast near
Nelson (approximately 750 mm) to the centre of the catchment (approximately 550 mm). In the
northeast of the catchment, in the vicinity of the Grampians, annual rainfall increases with elevation to
more than 900 mm on the Victoria Range. Rainfall is relatively reliable along the coast and in the
higher parts of the Grampians (Department of Water Resources Victoria 1989).
Reflecting rainfall distribution, flows are strongly seasonal with 70% of average annual flow in the
Glenelg River above the Wannon River junction occurring in the three months August to October. At
Dartmoor (Station No. 238 206), the residual mean annual flow of the Glenelg River is 639,000 ML.
Although only 1.5 % of that total occurs in the months January to March, there are reliable base flows
rarely falling below 30 ML per day during this period (Department of Water Resources Victoria
1989).
The Glenelg River, under natural conditions, commonly dried up at Balmoral over the three months
February to April, sometimes for months longer. Flows at Balmoral are now highly regulated by
Rocklands Reservoir. Rocklands has a storage capacity about three times its average annual inflow.
Since construction Rocklands Reservoir has spilled 14 times, approximately every four years on
average. However, current releases from Rocklands Reservoir do not appear to exert an influence
below Casterton due to the size of these releases 20-25 ML/day (Mitchell et al. 1996).
Under low flow conditions transit times for releases from Rocklands are approximately 7 days to
Balmoral, 14 days to Fulham Bridge and 21 days to Harrow. According to Mitchell (1996) a
continuous 20-25 ML/day release from Rocklands Reservoir delivers 10 ML/day at Fulham Bridge
and 2 ML/day at Harrow.
Streamflows within the Glenelg River exhibit the greatest alteration due to development at Rocklands
Reservoir, as exhibited by the variation between pre-regulation flows (natural flows) and flows under
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 34
the current level of development (current flows). Flows are least affected by development upstream of
Rocklands Reservoir.
Streamflows (frequency, duration and magnitude) upstream of Rocklands Reservoir are similar under
natural and current conditions for the majority of the year (April to November inclusive) (Figure A.5).
The most significant difference in current and natural flows is most distinct during January and
February. During February, 10 ML/month is exceeded 95% of the time under natural conditions,
while under current conditions this flow is only exceeded 73% of the time. Under current conditions,
there is no flow at this site for 20% of the time during February.
Streamflows are significantly altered from natural immediately downstream of Rocklands Reservoir.
At this site under natural conditions, median flows peak during August at 23 400 ML/month (Figure
A.4). Lowest flows occur during the summer months, particularly February. The current flow pattern
is the inverse of that that occurs under natural conditions reflecting discharge from the reservoir
(Figure A.7). Current flows are less than natural flows during all months of the year. Zero flows
occur during the months May to November, inclusive. Peak flows at this site occur during December
to February, inclusive, under current conditions. During June and July zero flow prevails 100% of the
time under current conditions (Figure A.5). Between August and October, flow exceeds 0 ML/month
for less than 18% of the time under current conditions, while under natural conditions, flow exceeded
600 ML/month 100% of the time.
At Fulham Bridge, about 20 km downstream of Rocklands Reservoir, the current level of development
results in much lower flows, although the pattern of flows is similar (Figure A.5). Flows peak during
August under both current and natural conditions (approximately 9,000 and 31,000 ML/month
respectively). The breadth of the peak is however much broader under natural conditions. Streamflow
begins to peak during April and declines during December under natural conditions, while under
current conditions, streamflow begins to peak during June and decline during November. The summer
low flows are considerably lower under current conditions than would naturally occur.
Further downstream, at Casterton the pattern of streamflows is similar to that at Fulham Bridge but
with considerably higher flows under both natural and current conditions. The peak median flows
under both current and natural conditions occur during August, however flow under natural conditions
is approximately 65 000 ML/month while under current conditions flow is approximately 44 000
ML/month (Figure A.4). The summer flows that occur under natural conditions are also higher than
those that occur under current conditions.
The Wannon River at the Glenelg River confluence has similar streamflows under both natural and
current conditions. Natural flows exhibit a peak of flow during August of 45 600 ML/month while
that under current conditions peaks during 44 400 ML/month (Figure A.4). The similarity in flows
may be due to the number of sleeper licences on this reach. Only 61% of the total licensed
entitlements are currently active.
Natural and current streamflows at Dartmoor are also similar with a slight reduction in streamflows
under the current conditions. Natural flows at Dartmoor exceed current flows for all months of the
year (Figure A.5). The peak in streamflow at this site occurs during August at this site under both
natural (155 000 ML/month) and current conditions (132 500 ML/month). The breadth of this peak is
also similar, beginning during May and declining up until December. Similar to the Wannon River
site, low flows under natural conditions are higher.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 35
n
Table 6-1: Licensed private diversions from the Glenelg River system (figures are ML/day,
those in parenthesise indicate number of licences).
Stream
Irrigation
66
(2)
-
Dairy
2.2
(1)
2.2
(1)
2.2
(1)
-
Winter Fill
-
Total
68.2
Glenelg River
(3)
2.2
Glenelg River Trib
(1)
2.2
Corea Ck
(1)
50
50
Crawford River
(1)
(1)
587.8
4.4
232
824.2
Wannon River1
(8)
(2)
(4)
(14)
703.8
11
232
946.8
Total
(11)
(5)
(4)
(20)
1
Data for the main channel of the Wannon River and its tributaries are pooled under the Wannon River.
A.2 Licensed water use
A large proportion of the water used within the Glenelg River Basin is obtained from groundwater.
This volume is equal to 2/3 of the total water used (Department of Water Resources Victoria 1989).
Information on the licensed entitlement within the Glenelg River system is presented, which is distinct
from the total volume that is actually extracted each year due to a number of factors including the
availability of flow and water quality.
The total licensed volume for water extraction from the main channel of the Glenelg River is 68.2
ML/year which is a very small proportion of the total licensed water entitlement in the Glenelg River
system. An additional 878.6 ML/year is licensed for extraction from the remainder of the Glenelg
River System. The majority of extractions in the system are through irrigation licences held on the
Wannon River and its tributaries. A total annual entitlement of 824.2 ML is held on the Wannon
River, of which 587.8 ML is licensed for extraction through 8 licences (Table 6-1).
Licences to divert water from within the Glenelg River system have been granted for the purposes of
irrigation, dairy and winter dam-fill. Licences for irrigation in the Glenelg River system are generally
used sometime between September and February, although the specific timing of such use is
dependent on the crops being irrigated. The dairy licences are used throughout the year for the
purposes of washing the dairy and watering stock. The winter fill licences are used to fill both
onstream and offstream storages during winter.
All licences on the Glenelg River extract upstream of the Wannon River confluence (J Donovan, pers.
comm.). Of the 68.2 ML/year available for extraction from the Glenelg River proper, 66 ML/year is
available for extraction through two irrigation licences. The remaining 2.2 ML/year is a dairy licence.
Two additional dairy licences are held on tributaries of the Glenelg River, other than the Wannon
River. The largest volume licence that is not held on the Wannon River or one of its tributaries is a
licence for 50 ML/year for an instream storage on Crawford River, which enters the Glenelg River
near Dartmoor. The largest winter fill licence for the whole catchment is held on Muddy Creek, a
tributary of the Wannon River, for 150 ML/year.
The Glenelg River system is self regulatory. Southern Rural Water has not previously had a formal
water restriction policy in place due to flow rapidly dropping to zero as water levels begin to fall
during the summer months and water quality also declines. Ad hoc restrictions were imposed last
summer (1998/99), during which river flow of 10 ML/day was used as a trigger to implement
restrictions. Such restrictions were unnecessary due to the river rapidly dropping to zero flow once it
was below 10 ML/day and the water becoming too saline. Therefore, bans were being imposed when
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 36
conditions were unsuitable for pumping due to lack of water and high salt levels. Similarly,
restrictions were imposed on the Wannon last summer (1999/00) but due to the flow dropping very
quickly over a short period of time, and then to no flow by mid January such restrictions were once
again unnecessary. Southern Rural Water also used 10 ML/day, an arbitrary figure, to impose
restrictions on the Crawford River and the Grange burn Creek.
A.3 System operation
Three major water storages exist within the Glenelg River Basin. These are Konong Wootong
Reservoir, Moora Moora Reservoir and Rocklands Reservoir. Konong Wootong is a small reservoir
constructed on Den Hills Creek, a tributary of the Wannon River, to supply the townships of Casterton
and Coleraine. The capacity of this storage is 1920 ML and diverts approximately 852 ML/year out of
the system (Ingeme 1996). Moora Moora Reservoir is a small, offstream storage with a capacity of
only 6,300 ML located in the upper reaches of the Glenelg River (Department of Water Resources
Victoria 1989). This storage does not remain full over the summer period as much of the flow is used
to supply part of the summer domestic and stock demand to the Wimmera River system.
Rocklands Reservoir is the largest storage in the Wimmera Mallee Water Supply System. It was
completed in 1953 and has a total capacity of 348, 000 ML. The primary purpose of this storage is to
provide domestic and stock supply to the Wimmera Basin (Godoy 1996). Approximately 85% of the
water from the upper Glenelg River is diverted out of the system from Rocklands Reservoir. This
amounts to 76 000ML/year of diversion out of the basin into the Wimmera-Mallee Domestic and
Stock Supply System (Cameron and Jekabsons 1992). Water is diverted via the Moora Channel to
Distribution Heads in the Wimmera River catchment.
Rocklands Reservoir has a significant impact on the seasonal flow pattern downstream of the reservoir
between the dam wall and the confluence of the Chetwynd River. The impact decreases with distance
from the storage. Downstream of Chetwynd River flows are generally continuous due to natural
inflow from the catchment adding to the river flows, this section of river was observed to cease to flow
in December 2000 (M. Tranter pers. comm.). The Glenelg River dries upstream of the confluence
each year (Godoy 1996).
A compensation flow from Rocklands Reservoir down the Glenelg River is fixed at 3300 ML/year.
This was previously a sliding scale between 2500 ML and 3700 ML/year, but at the request of the
Glenelg Hopkins CMA, a new formula has been developed being the average of the historic releases,
i.e. 3300 ML/year (R Leeson, pers. comm.). Wimmera Mallee Water is required to maintain a reserve
volume in Rocklands to guarantee this compensation flow. This compensation flow is subject to
restrictions during times of drought. The compensation flows aimed to maintain a target flow of 10-11
ML/day at Fulham Bridge, and consequently 1-2 ML/day at Harrow at all times.
Commencement of compensation flows is timed to take advantage of the wet river channel and thus
prevent the flow from ceasing altogether (Godoy 1996). Releases to the river are based on the flow at
Fulham's Bridge (238224). Compensation flows are timed to maintain a minimum flow of 15 ML/day
at Fulham’s Bridge (R Leeson, pers. comm.). The compensation flows are generally released between
mid November to late April and are in the order of 15-25 ML/day, weather dependent. There is,
however, leakage from the Rocklands-Toolondo channel back into the river, as such the releases are
reduced to account for this gain (Godoy 1996).
The Rocklands Outlet channel passes from Rocklands Reservoir over the Great Dividing Range to
Toolondo Reservoir in the Wimmera Catchment. Water is also lost from the Glenelg River due to
evaporation at Fraser's Swamp and water being held up by the sand slugs that are present in the
stream. To compensate for the losses along the river to Fulham's Bridge, Wimmera Mallee Water
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 37
release water from the 5 and 12 Mile channel outfalls i.e. outfalls on the Rocklands Outlet channel
located 5 or 12 channel miles from the reservoir. These outfalls have been used to:
q reduce the time taken for flows to reach the “lower” part of the River if flows at Fulham bridge
have suddenly dropped;
q
avoid capacity problems in the “upper” reaches of the river during times of high environmental
flow releases; and
q
avoid the high losses that seem to occur in the Rocklands – Fulham Bridge reach (R Leeson, pers.
comm.).
Wimmera Mallee Water has found that flows in the order of 50 ML/d are larger than the river
channel’s capacity in some areas upstream of Balmoral. In particular, on Trevor Wood’s property
some adjoining minor flood lines also carry water during this period, which significantly limits access
to the property.
A.4 Summary
The current level of development along the Glenelg River has resulted in streamflows frequently being
considerably lower than that which would have occurred under natural conditions. The greatest
impact along the Glenelg River is caused by the presence and management of Rocklands Reservoir in
the upper reaches of the river. Rocklands Reservoir has drastically reduced the frequency of large
flows that under natural conditions occurred during late winter and into September. Compensation
flows are released from Rocklands Reservoir between November and April, and are approximately of
15-25 ML/day, weather dependent. During the remainder of the year, flows immediately downstream
of the storage are zero. To account for losses from the Glenelg River between Rocklands Reservoir
and Fulham Bridge, water is released into the Glenelg River from the 5 and 12 Mile channel outfalls.
This is done to ensure the flows achieve the desired target at Fulham Bridge. Although, this is
generally only done when transfers are being made to Toolondo Reservoir.
Progressively downstream, flow increases due to runoff, groundwater and flow from tributaries.
Licensed demand on the Wannon River is having little effect on the streamflows of this river near the
confluence of the Glenelg River.
The majority of private diversion licences to extract water from the Glenelg River catchment are held
on the Wannon River, of which the licences are primarily not used (sleeper licences). Water use along
the Glenelg River has its greatest impact on peak flow periods, reducing the magnitude of such flows.
A formal restriction policy is not developed for the Glenelg River but restrictions are generally
imposed during low flow periods as during such times flows rapidly drop to zero and prevailing water
quality renders the water unsuitable for use.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 38
A.5 Flow plots
Glenelg River upstream of Rocklands - Current Flow
40000
40000
35000
35000
30000
30000
25000
80th Percentile
20000
Median
20th Percentile
15000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Glenelg River upstream of Rocklands - Natural Flow
25000
80th Percentile
20000
20th Percentile
15000
10000
10000
5000
5000
0
Median
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River at Rocklands Outlet-Current Flow
40000
40000
35000
35000
30000
30000
25000
80th Percentile
20000
Median
20th Percentile
15000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Glenelg River at Rocklands Outlet-Natural Flow
Apr
25000
80th Percentile
20000
20th Percentile
15000
10000
10000
5000
5000
0
Median
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Final
PAGE 39
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River at Fulhams Bridge-Current Flow
60000
50000
50000
40000
80th Percentile
30000
Median
20th Percentile
20000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Glenelg River at Fulhams Bridge-Natural Flow
60000
10000
40000
80th Percentile
30000
Median
20th Percentile
20000
10000
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River at Casterton-Current Flow
120000
120000
110000
110000
100000
100000
90000
90000
80000
70000
80th Percentile
60000
Median
20th Percentile
50000
40000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Glenelg River at Casterton- Natural Flow
May
80000
70000
80th Percentile
60000
20th Percentile
40000
30000
30000
20000
20000
10000
10000
0
Median
50000
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Final
PAGE 40
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Wannon at Glenelg River - Current Flow
100000
90000
90000
80000
80000
70000
70000
60000
80th Percentile
50000
Median
20th Percentile
40000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Wannon at Glenelg River - Natural Flow
100000
60000
80th Percentile
50000
20th Percentile
40000
30000
30000
20000
20000
10000
10000
0
Median
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River at Dartmoor - Current Flow
260000
260000
240000
240000
220000
220000
200000
200000
180000
180000
160000
20th Percentile
140000
Median
120000
80th Percentile
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
Glenelg River at Dartmoor - Natural Flow
May
160000
Median
120000
80th Percentile
100000
80000
80000
60000
60000
40000
40000
20000
20000
0
20th Percentile
140000
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
June
July
Aug
Sep
Oct
Nov
Dec
Jan
Final
PAGE 41
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
A.6 Flow duration curves
Flow duration curve for Glenelg River upstream of Rocklands
-JANUARY-
Flow duration curve for Glenelg River upstream of Rocklands
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River upstream of Rocklands
-MARCH-
Flow duration curve for Glenelg River upstream of Rocklands
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River upstream of Rocklands
-MAY-
Flow duration curve for Glenelg River upstream of Rocklands
-JUNE-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 42
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River upstream of Rocklands
-JULY-
Flow duration curve for Glenelg River upstream of Rocklands
-AUGUST-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River upstream of Rocklands
-SEPTEMBER-
Flow duration curve for Glenelg River upstream of Rocklands
-OCTOBER100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River upstream of Rocklands
-NOVEMBER-
Flow duration curve for Glenelg River upstream of Rocklands
-DECEMBER-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 43
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River at Rocklands Outlet
-JANUARY-
Flow duration curve for Glenelg River at Rocklands Outlet
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Rocklands Outlet
-MARCH-
Flow duration curve for Glenelg River at Rocklands Outlet
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Rocklands Outlet
-MAY-
Flow duration curve for Glenelg River at Rocklands Outlet
-JUNE-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 44
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River at Rocklands Outlet
-JULY-
Flow duration curve for Glenelg River at Rocklands Outlet
-AUGUST-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Rocklands Outlet
-SEPTEMBER-
Flow duration curve for Glenelg River at Rocklands Outlet
-OCTOBER100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Rocklands Outlet
-NOVEMBER-
Flow duration curve for Glenelg River at Rocklands Outlet
-DECEMBER-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 45
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River at Fulhams Bridge
-JANUARY-
Flow duration curve for Glenelg River at Fulhams Bridge
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Fulhams Bridge
-MARCH-
Flow duration curve for Glenelg River at Fulhams Bridge
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Fulhams Bridge
-MAY-
Flow duration curve for Glenelg River at Fulhams Bridge
-JUNE-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 46
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River at Fulhams Bridge
-JULY-
Flow duration curve for Glenelg River at Fulhams Bridge
-AUGUST-
100000
1000000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
10000
1000
100
10000
1000
100
10
Proportion of time exceeded (%)
97
85
74
62
50
38
26
15
3
1
97
85
74
62
50
38
26
15
1
3
10
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Fulhams Bridge
-SEPTEMBER-
Flow duration curve for Glenelg River at Fulhams Bridge
-OCTOBER-
100000
1000000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
10000
1000
100
10000
1000
100
10
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Fulhams Bridge
-NOVEMBER-
Flow duration curve for Glenelg River at Fulhams Bridge
-DECEMBER100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 47
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
3
1
97
85
74
62
50
38
26
15
1
3
10
Flow duration curve for Glenelg River at Casterton
-JANUARY-
Flow duration curve for Glenelg River at Casterton
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Casterton
-MARCH-
Flow duration curve for Glenelg River at Casterton
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Casterton
-MAY-
Flow duration curve for Glenelg River at Casterton
-JUNE-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 48
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Glenelg River at Casterton
-JULY-
Flow duration curve for Glenelg River at Casterton
-AUGUST-
1000000
1000000
Est. natural flow
Current Conditions
10000
1000
100
10000
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Casterton
-SEPTEMBER-
97
85
74
Flow duration curve for Glenelg River at Casterton
-OCTOBER1000000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
100000
10000
1000
100
1000
100
Proportion of time exceeded (%)
97
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
10000
3
Monthly Flow (ML/month)
62
Proportion of time exceeded (%)
1000000
1
50
38
26
15
3
1
97
85
74
62
50
38
26
15
10
3
10
1
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
100000
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Casterton
-NOVEMBER-
Flow duration curve for Glenelg River at Casterton
-DECEMBER-
1000000
100000
Est. natural flow
Current Conditions
100000
Est. natural flow
Current Conditions
Monthly Flow (ML/month)
Monthly Flow (ML/month)
10000
10000
1000
100
1000
100
10
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 49
97
85
74
62
50
38
26
15
1
3
97
85
74
62
50
38
26
15
1
3
10
Flow duration curve for Wannon River at Glenelg River
-JANUARY-
Flow duration curve for Wannon River at Glenelg River
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Wannon River at Glenelg River
-MARCH-
Flow duration curve for Wannon River at Glenelg River
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
100
Proportion of time exceeded (%)
97
Proportion of time exceeded (%)
Flow duration curve for Wannon River at Glenelg River
-MAY-
Flow duration curve for Wannon River at Glenelg River
-JUNE-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 50
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
10000
1
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Flow duration curve for Wannon River at Glenelg River
-JULY-
Flow duration curve for Wannon River at Glenelg River
-AUGUST-
1000000
1000000
Est. natural flow
Current Conditions
10000
1000
100
10000
1000
100
Proportion of time exceeded (%)
Flow duration curve for Wannon River at Glenelg River
-SEPTEMBER-
Est. natural flow
Current Conditions
Monthly Flow (ML/month)
1000
100
10000
1000
100
Proportion of time exceeded (%)
97
85
74
62
50
38
26
15
3
1
97
85
74
62
50
38
26
15
10
3
10
Proportion of time exceeded (%)
Flow duration curve for Wannon River at Glenelg River
-NOVEMBER-
Flow duration curve for Wannon River at Glenelg River
-DECEMBER-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 51
97
85
74
62
50
38
26
1
15
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
97
Est. natural flow
Current Conditions
100000
10000
1
85
74
Flow duration curve for Wannon River at Glenelg River
-OCTOBER1000000
100000
Monthly Flow (ML/month)
62
Proportion of time exceeded (%)
1000000
1
50
38
26
15
3
1
97
85
74
62
50
38
26
15
10
3
10
1
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
100000
Flow duration curve for Glenelg River at Dartmoor
-JANUARY-
Flow duration curve for Glenelg River at Dartmoor
-FEBRUARY-
100000
100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Dartmoor
-MARCH-
Flow duration curve for Glenelg River at Dartmoor
-APRIL100000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
10000
Monthly Flow (ML/month)
10000
1000
100
100
Proportion of time exceeded (%)
97
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
1000
3
Monthly Flow (ML/month)
97
Proportion of time exceeded (%)
100000
1
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
1
100
10
3
10
1000
3
Monthly Flow (ML/month)
10000
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Dartmoor
-MAY-
Flow duration curve for Glenelg River at Dartmoor
-JUNE-
100000
1000000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
10000
1000
100
10000
1000
100
10
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 52
97
85
74
62
50
38
26
15
1
3
97
85
74
62
50
38
26
15
1
3
10
Flow duration curve for Glenelg River at Dartmoor
-JULY-
Flow duration curve for Glenelg River at Dartmoor
-AUGUST-
1000000
1000000
Est. natural flow
Current Conditions
10000
1000
100
10000
1000
100
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Dartmoor
-SEPTEMBER-
97
85
74
Flow duration curve for Glenelg River at Dartmoor
-OCTOBER1000000
Est. natural flow
Current Conditions
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
100000
10000
1000
100
1000
100
Proportion of time exceeded (%)
97
85
74
62
50
38
26
15
1
97
85
74
62
50
38
26
15
10
3
10
10000
3
Monthly Flow (ML/month)
62
Proportion of time exceeded (%)
1000000
1
50
38
26
15
3
1
97
85
74
62
50
38
26
15
10
3
10
1
Est. natural flow
Current Conditions
100000
Monthly Flow (ML/month)
Monthly Flow (ML/month)
100000
Proportion of time exceeded (%)
Flow duration curve for Glenelg River at Dartmoor
-NOVEMBER-
Flow duration curve for Glenelg River at Dartmoor
-DECEMBER-
1000000
100000
Est. natural flow
Current Conditions
100000
Est. natural flow
Current Conditions
Monthly Flow (ML/month)
Monthly Flow (ML/month)
10000
10000
1000
100
1000
100
10
Proportion of time exceeded (%)
WC01432:R04_MJS_GLENELG_FINAL.DOC
Proportion of time exceeded (%)
Final
PAGE 53
97
85
74
62
50
38
26
15
1
3
97
85
74
62
50
38
26
15
1
3
10
A.7 Rocklands Reservoir discharge
Discharge from Rocklands Reservoir for past 10 years
4000
Mean Discharge (ML/month)
3500
3000
2500
Median
2000
20th percentile
80th percentile
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 54
Appendix B
Geomorphology
B.1 Introduction
Sand accumulation in stream channels is a major stream management issue in the
Glenelg River catchment. Sheet, rill and gully erosion of granite portions of the
catchment have filled the Glenelg and its tributaries with about 6,000,000 m3 of sand
(Rutherfurd and Budahazy, 1996). Little sand is now coming from the catchment, so
the major source of sand to the Glenelg River is the lower reaches of tributary streams.
The tributaries introduce discrete slugs of sand to main channel that often partially
dam the river. As these sand ‘slugs’ move downstream they attenuate, gradually
giving way to a succession of small ‘sluglettes’. Rutherfurd and Budahazy (1996)
estimate the sand slugs are moving through the stream network at a slow rate, with
only tens of thousands of cubic metres being removed by bedload transport. The low
transport rate is due, in part, to regulation of the river from Rocklands Reservoir.
Near Dartmoor the river has well vegetated banks but is affected by sediment input
(Figure 26). The sediment has created a sandy bed with few deep holes. Sites where
sediment build-up is most obvious are around Casterton and Harrow. The lower
section in the Lower Glenelg National Park is in good condition with excellent bank
and verge vegetation (Figure 29).
B.2 Stream network
The Glenelg River rises in the Grampians and flows to the Southern Ocean. On
leaving the Grampians, between Rocklands Reservoir and Casterton, the river flows
along the northern and then the western edge of the Dundas Tablelands. Near
Casterton the Wannon River joins the Glenelg River and from here the Glenelg River
meanders across the broader coastal plains towards Dartmoor. Below Dartmoor the
river follows a generally southerly course becoming increasingly incised in limestone
(Erskine, 1994). At the confluence of Moleside Creek the river turns WNW and runs
parallel to the coast, eventually looping into South Australia before entering the sea at
Nelson.
The catchment boundary follows the state border quite closely in the west but swings
eastwards at to abut the Wimmera region in the north. The boundary swings towards
the south at the Grampians then winds its way in a southwesterly direction back to the
coast. The catchment is approximately 120 km wide and 100 km from north to south,
covering a total area of 1,266,030 ha (Department of Water Resources Victoria, 1989).
The topography of the catchment varies substantially from the coastal plains in the
southwest to the rugged escarpments of the Grampians in the northeast. The Victoria
and Serra Ranges of the Grampians drain into both the Glenelg and the Wannon
Rivers; the former of which ultimately drains the north and west of the catchment and
the latter the east and south. The cental portion of the catchment is composed of the
deeply dissected Dundas and Merino tablelands. Towards the southeast the tablelands
drop down to the flat basal plains around Hamilton. Near Nelson there is an estuarine
lagoon at the mouth of the Glenelg River and a line of calcereous sand dunes fringes
the coastline. During low flow conditions salt water penetrates upstream beyond the
boundary of the Lower Glenelg National Park. At over 70 km, the Glenelg estuary
one of the State’s longest (Sherwood et al. 1998).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 55
Mitchell (1990) reported that the river down to about Dartmoor is generally in poor to
moderate condition. Riparian vegetation is continuous to discontinuous along both
banks of the river but is generally restricted to the bank crest fringe (Sherwood et al.
1998). Near Dartmoor the river has well vegetated banks but is affected by sediment
input. The sediment has created a sandy bed with few deep holes. Sites where
sediment build-up is most obvious are around Casterton and Harrow. The lower
section in the Lower Glenelg National Park is in good condition with excellent bank
and verge vegetation.
In their more complete description of the Glenelg River channel, Rutherfurd and
Budahazy (1996) divide the river into four reaches:
3) Rocklands to Fulham Bridge (30 km);
4) Fulham Bridge to Killara Bridge (120km);
5) Killara Bridge to Dartmoor (30 km); and
6) the estuarine section (65 km).
B.3 Hydrology
Rainfall varies seasonally and spatially within the catchment. While winter months
are wetter throughout the catchment, there is a gradual decline in mean annual rainfall
from the coast near Nelson (approximately 750 mm) to the centre of the catchment
(approximately 550 mm). In the northeast of the catchment, in the vicinity of the
Grampians, annual rainfall increases with elevation to more than 900 mm on the
Victoria Range. Rainfall is relatively reliable along the coast and in the higher parts of
the Grampians (Department of Water Resources Victoria, 1989).
Reflecting rainfall distribution, flows are strongly seasonal with 70% of average
annual flow in the Glenelg River above the Wannon River junction occurring in the
three months August to October. At Dartmoor (Station No. 238 206), the residual
mean annual flow of the Glenelg River is 639,000 ML. Although only 1.5 % of that
total occurs in the months January to March, there are reliable base flows rarely falling
below 30 ML per day.
The Glenelg River, under natural conditions, commonly dried up at Balmoral over the
three months February to April, sometimes for months longer. Flows at Balmoral are
now highly regulated by Rocklands Reservoir. Rocklands has a storage capacity
about three times its average annual inflow and very rarely spills. However, releases
from Rocklands Reservoir do not appear to exert an influence below Casterton
(Mitchell et al. 1996). Under low flow conditions transit times for releases from
Rocklands are approximately 7 days to Balmoral, 14 days to Fulham Bridge and 21
days to Harrow. According to Mitchell et al. (1996) a 20-25 ML/day release at
Rocklands delivers 10 ML/day at Fulham Bridge and 2 ML/day at Harrow.
B.4 Landuse
The Department of Water Resources Victoria (1989) reports that European settlement
of the Glenelg catchment began in 1837. The merino wool industry was established
quickly and today wool is still the main product of the region with prime lamb
production also important. The beef industry is well established and dairying has been
steadily declining. Since 1837, two-thirds of the catchment has been cleared for
pasture to graze sheep and cattle and today only two main forested areas remain. The
northeast of the catchment is forested and includes the Grampians National Park, as
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 56
well as State Forest where hardwood is logged. In the west there is a mixture of native
hardwood forests (the Glenelg National Park) and intensive softwood plantations
(Department of Water Resources Victoria, 1989).
Hamilton is the major urban centre within the catchment, located in the southeast.
B.5 Sand slugs
The following discussion of sediment transport/storage in the Glenelg River is drawn
from Rutherfurd and Budahazy (1996).
Before European settlement, the upper Glenelg River and its tributaries were
characterised by pools separated by densely vegetated reaches. Below Harrow,
vegetated reaches were less common but there were still deep pools. Since the 1850s,
gullying and sheet erosion of granite portions of the catchment have filled long
reaches of the Glenelg and its tributaries with sand. The sand is moving through the
stream network in a complicated pattern, but it will take many decades for the sand to
be stabilised and removed (Rutherfurd and Budahazy 1996).
Rutherfurd and Budahazy estimate that there are between 4 and 8 million cubic metres
of sand stored in the Glenelg River and its tributaries. Channel storage estimates
range from about 50,000 m3 /km in the Glenelg at Harrow, to an average of about 1020,000 m3 /km elsewhere in the system. The sand occupies a larger proportion of the
cross-section in the tributaries (up to 80%) than in the Glenelg River. Capacity loss in
the Glenelg River falls from about 60% between Harrow and Burkes Bridge, to 20%
at Casterton, and 10% at Dartmoor.
Most of the sand was deposited in the lower reaches of the streams very quickly after
the onset of channel extension through gullying. The 1946 flood was particularly
effective at moving the sediment through the system. However, the original deep
pools in the Glenelg River, combined with regulation from Rocklands Reservoir, have
limited the movement of sand through the trunk stream. As a result, sand in the
Glenelg River is stored in discrete slugs originating from several tributary streams:
Mathers, Deep, and Pigeon Ponds Creeks, Chetwynd, Wando, and Wannon Rivers.
There is no doubt that the major period of catchment and gully erosion has passed in
the Glenelg River catchment, and that soil conservation activities have contributed to a
reduced erosion rate. However, the sand slugs in the lower tributaries are still on their
rising limb, or close to their peaks. Sand located in the lower few kilometres of
tributary streams are now the major store of sand in the catchment. There are no large
reserves of sand moving through stream networks towards the Glenelg River (with the
possible exception of the Chetwynd River).
Of the sand already stored in the main channel, only about two-thirds will be available
for downstream transport. About one-third will be more permanently stored in
benches, pointbars or on the floodplain. Importantly, in smaller tributaries, large
volumes of sand are stored in deep areas of the bed that have been abandoned by
widening of the channel. In Bryans Creek and Pigeon Ponds Creek, this bed storage
has removed up to half of the total volume of sand available for transport.
The effect of the movement of sand into the Glenelg River and its tributaries is not
clear. Rainfall-runoff modelling suggests that filling half of the channel cross-section
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 57
with sand will have minimal impact on the size of flood peaks or their time-to-peak
because of the decreased roughness associated with sand sheets. In addition,
deposition on the floodplain has meant that in many reaches the rise in bed level has
been matched by an increase in bank height.
The available evidence suggests that the present distribution of sand in the Glenelg
catchment was in place by the 1940s and has changed very little over the past half
century. Discrete sand slugs below the Wannon River junction have remained in the
same position since 1947. Contrary to earlier estimates of huge bedload transport
rates in the Glenelg River, (hundreds of thousands of tonnes per year), several lines of
evidence suggest that bedload transport rates are in the order of 10-30,000 m3 /year.
The major tributaries transport less than 5000 m3 /year.
A major flood could move large volumes of sand. This certainly occurred in the 1946
flood when large volumes of sand were deposited in the channel and on the floodplain.
However, regulation has dramatically reduced the frequency of large floods (I.
Rutherfurd, pers. comm.), and so the rate of sand transport.
Sand slugs buffer channel morphology from hydrological changes in the catchment.
Hydrology has changed because of catchment clearing, and because gully
development has increased the efficiency of the drainage network. As sand moves
through a stream reach, the channel is exposed to the changed hydrological conditions
of the catchment, and typically adjusts to the new flow regime by incising. Such
incision also leads to incision of the tributaries, particularly if those tributaries are
graded to the elevation of the sand surface.
Moreover, removal of the sand that fills some channels in the Glenelg catchment to
one-third or half of their depth has implications for bank stability. This sand has
supported the bank and reduced the incidence of bank failure. The movement of sand
out of a reach and any subsequent incision of the bed can heighten the banks and cause
the onset of slumping.
B.6 Summary
Sand accumulation in stream channels is the major stream management issue in the
Glenelg River catchment. The sediment influx has smothered the previous channel
form and dramatically simplified the geomorphological diversity of the channel by
creating a sandy bed with few deep holes. The sand is moving through the stream
network in a complicated pattern, but it will take many decades for the sand to be
stabilised and removed. The available evidence suggests that the present distribution
of sand in the Glenelg catchment was in place by the middle of last century and has
changed very little over the intervening 50 years. However, a large flood could rework and transport large volumes of sand as occurred during the 1946 flood. The
effect of regulation has limited the magnitude and frequency of floods downstream
from Rocklands Reservoir.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 58
Appendix C
Water quality
Water Quality can be characterised by a large variety of parameters, many of which
are important to the ecological condition of a waterway. Key parameters for the
monitoring of water quality include salinity, DO, nutrients, pH and turbidity. These
parameters are important as they influence ecological processes and water use. For
example, low levels of dissolved oxygen can restrict aerobic respiration resulting in
stress to or mortality of aquatic biota. Similarly, high turbidity levels can restrict the
use of water for irrigation through reducing the efficiency of irrigation pumps and
high nutrient levels can result in algal blooms that make the water unsuitable for
consumption.
Numerous sites have been established throughout the Glenelg catchment for the
purposes of water quality monitoring. Ten sites are still active along the Glenelg
River and its tributaries and of these 5 have been selected for the analysis of water
quality along the river system. These are (progressing downstream):
q
Glenelg River at Big Cord (238 231), upstream of Rocklands Reservoir;
q
Glenelg River at Fulham Bridge (238 224), about 20km downstream of Rocklands
Reservoir;
q
Wannon River at Henty (238 228), about 15km upstream of the confluence with
the Glenelg River;
q
Glenelg River at Sandford (238 202), immediately downstream of the Wannon
River confluence; and,
q
Glenelg River at Dartmoor (238 206).
All data presented in this document has been sourced from the Victorian Water
Quality Monitoring Network (VWQMN). Three sets of data have been discussed.
Firstly, the results presented in the VWQMN Annual Report, 1998 (AWT 1999) are
presented as these indicate the compliance of each parameter with selected guidelines.
To supplement this, percentiles have been calculated on the past 10 full years of data
(1990-1999), therefore where data is presented for the previous 3 years or 10 years
this is prior to and including 1999 (VWQMN 1999). Thirdly, monthly percentile plots
showing seasonal variation of selected parameters is also presented. All values are
discussed in relation to the guidelines set out in the VWQMN Annual Report (AWT
1999).
The VWQMN Annual Report presents attainment values (with the set guideline) for
each water quality parameter. Attainment is the frequency (% occurrence) that a
particular water quality parameter falls within developed guidelines for a specific site.
For example, if pH was to have an attainment of 20%, this indicates that 20% of the
total number of values for a specified time period were within the guidelines specified.
Attainment values are described as either high (> 95%), moderate (90-95%) or low (<
90%) (AWT 1999).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 59
C.1 Salinity
Salinity or electrical conductivity (EC) is a measure of the salt content of the water.
High EC can threaten the survival of native flora and fauna as well as affect the use of
the water for drinking and irrigation. Aquatic biota are adapted to tolerate a certain
salinity range. Conditions outside this tolerable range can create stressful conditions
that may lead to reduced biodiversity and biomass through the exclusion of species or
even mortality. There are a number of factors that may contribute to high EC values,
however if EC is already moderate, evaporation can increase the EC by removing a
large proportion of water while leaving the dissolved salts behind. The guideline
value for EC varies depending on the use of the water, however for the protection of
the aquatic environment, EC values should not exceed 1500 µS/cm for any period of
the year. Attainment of the electrical conductivity during 1998 with the ANZECC
guidelines decreased with distance downstream. Attainment at Big Cord was 100%
and 33% attainment was achieved at Fulham Bridge, while the remaining two sites on
the Glenelg River and that on the Wannon River achieved 0% attainment, indicating
that at no time was a record collected that was less than 1500 µS/cm (AWT 1999).
This increase in salinity with distance downstream was consistent with findings by
Mitchell (1990).
Median EC values for the past 10 years increase with distance downstream, peaking at
Sandford and then decrease slightly at Dartmoor. Median and 90th percentile values at
Big Cord have always been recorded within the ANZECC guideline for the past 10
years. In contrast the median values have exceeded the guideline value at all sites
during all but one year at Fulham Bridge. During 1993 EC was 1300 µS/cm at
Fulham Bridge. Salinity varies little at Big Cord, while that for the other four sites
varies greatly throughout the year. Salinity in the Wannon River at Henty and at both
Sandford peaks during March when flushing flows are lowest. The peak in salinity at
Dartmoor is greatest during May. The lowest median and greatest variation in
salinities, as shown by the variation between the 10th and 90th percentiles, occurs when
flows are lowest, between September and October. In contrast, salinity at Fulham
Bridge exhibits an inverse pattern that possibly coincides with high volume releases
from Rocklands Reservoir. Discharge from Rocklands Reservoir is greatest during
February-March and lowest during August (Figure C.7). Salinity peaks during
September and is lowest during May. There has not been any long term change in
electrical conductivity for the past 20 years at any site (Mitchell 1990).
Salinity varies along the length of the Glenelg River, with saline pools present at
specific locations. A major source of salt in the Glenelg River is saline groundwater
(Glenelg Regional Catchment Strategy, 1997).
Under low flow conditions,
groundwater plays an important role in determining salinity along the entire river
length. At higher flows, surface water dilutes the effect of groundwater on salinity
(Sherwood et al. 1998a). A decrease in salinity that occurs between Myaring Bridge
to Dartmoor, approximately 20km downstream, is likely to be due to dilution that
results from inflow of less saline surface or groundwater.
The section of the Glenelg River between Rocklands Reservoir and Fulham Bridge is
characterised by shallow sections of less than 3 m deep interspersed with deep
elongated pools up to 8.5 m in depth (Sherwood et al. 1998a). This section of the
river has been identified as a major source of salt with salinity increasing with
increasing distance downstream from Rocklands Reservoir (Sherwood et al. 1998a).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 60
A long-lived saline pool is present just upstream of Fulham Bridge. The water depth,
conductivity and dissolved oxygen profile showed little change between September
1990 to March 1991. The bottom 3 metres of the pool had conductivity levels
exceeding 10000 µS/cm with associated low dissolved oxygen. The surface 2-2.5 m
showed variation in temperature but with little change in the underlying water
(McGuckin et al. 1991).
In the 15km section downstream of Rocklands Reservoir, surface and bottom salinities
were between 3500 µS/cm and 7000 µS/cm with surface salinities approximately 2000
µS/cm less than that at the bottom. Further downstream, conductivity declined to
approximately 2000 µS/cm with the exception of Fulham Bridge, where bottom
conductivity was 10380 µS/cm. In the reach between Casterton and Dartmoor, a 1991
survey revealed no significant difference in surface and bottom salinities (McGuckin
et al. 1991).
Deoxygenation also prevailed in the section of the river between Rocklands Reservoir
and Fulham Bridge with lowest concentrations of dissolved oxygen coinciding with
high bottom conductivities (McGuckin et al. 1991).
The high salinity in the Glenelg River is of particular concern in the upper reaches of
the river near Fulham Bridge. The presence of saline pools is also closely associated
with adverse temperature and dissolved oxygen conditions. The persistence of such
conditions greatly affects the amount of suitable available habitat for aquatic
organisms.
C.2 Nutrients
High values of nitrogen and or phosphorus produces nutrient enrichment, increasing
plant and animal biomass, benefiting certain species and potentially altering species
diversity and abundance in affected systems. Eutrophication may result if nutrient
levels get sufficiently high and other conditions are favourable. Under eutrophic
conditions, waters can become anoxic, and turbidity becomes high, potentially leading
to algal blooms and fish kills (OCFE 1988). The attainment of total nitrogen in the
Glenelg River (TN) records with the ANZECC guideline of <0.75 mg/L (ANZECC
1992) decreased with distance downstream during 1998. The lowest attainment in the
Glenelg River was at Dartmoor (25%), while the lowest attainment of 8% was
recorded on the Wannon River at Henty. Attainment at Big Cord during 1998 was
92%. Attainment with the EPA guideline of 1.0 mg/L was similar with decreasing
attainment with distance downstream on the Glenelg River and the lowest attainment
of 50% recorded at Henty. Percentile values at Big Cord, however did not exceed the
guideline during any of the past 10 years. A general increase in median TN values
was also exhibited with distance downstream. Median TN at Henty and Sandford was
within the ANZECC guideline value on two occasions only in the past 10 years and
four times at Dartmoor. Median TN values only exceeded the EPA guideline during
1990-92, at Dartmoor. Annual fluctuation of total nitrogen varies greatly between
sites (Appendix C). Similar to salinity, total nitrogen varies little at Big Cord.
Variation in total nitrogen values is also minor at Fulham Bridge although values are
consistently greater. The greatest variation in TN occurs at the Henty, Sandford and
Dartmoor. Total Nitrogen peaks during July but remains high until October, while at
Sandford and Dartmoor the peak is exhibited during September. The peak in TN
values is possibly correlated with high runoff.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 61
Attainment with the ANZECC guideline for total phosphorus (TP) of <0.1 mg/L
during 1998 was 100% at all sites presented , while attainment with the EPA guideline
of 0.035 mg/L decreased with distance downstream and was lowest at Henty (50%).
(AWT 1999). Similar to TN, there is a general increase in median TP with distance
downstream. Median TP values have consistently been within the ANZECC guideline
at all sites over the past 10 years. While exceedance of the EPA guideline was most
frequent at Sandford. The 90th percentile values for TP have exceeded the ANZECC
guideline value during three years at Henty and Dartmoor and four years at Sandford.
As has been shown with the above parameters in the Glenelg River, seasonal variation
in TP is similar at Henty, Sandford and Dartmoor (Appendix C). At Big Cord and
Fulham Bridge median TP remains low for much of the year. In contrast, median TP
peaks during September at Sandford and Dartmoor, and during August at Henty. The
peaks in TP possibly correlate to patterns of runoff.
Nutrient enrichment of the waterways has been recognised as a significant issue. To
date there have been no blue green algal blooms reported in the Glenelg River
although eutrophication of farm dams and lakes has been recorded (Dixon et al. 1998).
Blooms have, however been recorded in Rocklands Reservoir (1991) and the
Casterton Sewage Treatment Ponds (1995) (GRCLPB 1997).
Sources of nutrients within the Glenelg River are varied. Active erosion in the
subcatchment of Sandford contributes to nitrogen loads but not phosphorus. Nitrogen
may be from decaying organic material and animal wastes. Until 1996/97, the
Casterton Wastewater Treatment Plant was contributing an unknown load of nutrients
to the river, which would be having a major impact. This practice has now ceased
(Wagg 1997). Septic tank effluent at Dartmoor may also contribute to nitrogen
concentrations in the river (Sherwood et al. 1998a). At Dartmoor, TKN associated
with organic material is also positively related to flow, similarly for TP, which is
attached to sediments (Wagg 1997).
Although TP rarely exceeds the guideline values in the Glenelg River, values of TN
progressively exceed guideline values with distance downstream. The occurrence of
high nitrogen values can potentially lead to the growth of algal blooms and
development of anoxic conditions.
C.3 pH
The acidity of a waterway is measured by its pH. Reduced pH values are associated
with more acidic conditions in a river. The chemical properties of water can be altered
by the pH. Spawning failure and diminished hatching success for fish has been
associated with pH values less than 6.0 (ANZECC 1992). Macroinvertebrate
communities generally have reduced numbers, fewer species and altered species
composition at lower pH values. The SEPP Waters of Victoria (1988) guidelines for
pH are 6.0 to 9.0. During 1998 there was 100% attainment with the SEPP guidelines
for pH at the four of the five sites presented. Glenelg River at Big Cord had an
attainment of only 33% during this period. Attainment with the ANZECC guideline
of 6.5-9.0 was only 17% at Big Cord but 100% at the remaining sites (AWT 1999).
Median pH values have only been outside the two guidelines at Big Cord where water
was slightly acidic. During the past 10 years, 10th and 90th percentile pH values have
consistently been within the ANZECC guideline at the four sites downstream from
Rocklands Reservoir. At Big Cord, pH values demonstrate slightly acidic conditions
with median values being greater than or equal 6.0 during only 4 of the past 10 years.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 62
This indicates that pH is not an issue in terms of water quality in the Glenelg River
below Rocklands Reservoir.
C.4 Dissolved oxygen
There are a variety of natural and human activities that contribute to reduced
concentrations of dissolved oxygen (DO) including pollutants and bacterial activity in
enriched sediments (OCFE 1988). Low DO can also be expected in slow moving or
still waters. Low DO concentrations can be harmful to aquatic biota, as it is required
for aerobic respiration. The SEPP Waters of Victoria guideline for DO is a
concentration that exceeds 5 mg/L for general surface waters. Attainment of 100%
was achieved at all sites during 1998 (AWT 1999). With the exception of Fulham
Bridge during 1993, all 10th percentile values of DO have been greater than this
guideline value for the past 10 years. Median DO values vary throughout the year
generally peaking in the middle of the year (Appendix C). The earliest peak in median
DO occurs during May at Big Bend while at the other four sites this parameter peaks
between June and July, Sandford does however have an additional spike during
March. The lowest peaks in median DO have been exhibited at Big Cord and Fulham
Bridge. The peak in DO prior to the high flow period of September to October may be
as a result of water temperature. During periods of low water temperature the water
holds oxygen better, therefore although mixing is not at its maximum during this
period, the potential for the water to hold oxygen is at its optimum.
Severe deoxygenation has been found throughout the length of the Glenelg River.
Severe deoxygenation is closely associated with the presence of saline pools and has
been recorded in the reach from Rocklands Reservoir to Fulham Bridge with each
pool registering a bottom dissolved oxygen concentration of less than 10% saturation.
Sites between Casterton and Dartmoor were only slightly better during a 1991 survey
with values ranging between 10-40% saturation (McGuckin et al. 1991). It is
suggested that the temperature gradients in this section of the river are most likely
associated with the depth of the pool and are the governing factor controlling DO at
conductivities less than 500 µS/cm. Conversely, pools between Casterton and
Dartmoor had no significant difference in surface and bottom salinity (McGuckin et
al. 1991).
Although low dissolved oxygen does not appear to be of concern at the VWQMN
sampling sites, isolated locations do exhibit low DO concentrations. Of particular
concern is the significant reduction in DO in the deep pools along the Glenelg River,
especially in the reach from Rocklands Reservoir to Fulham Bridge.
C.5 Turbidity
Increased turbidity limits the penetration of light through the water in the river thereby
reducing the growth of aquatic flora and impeding the feeding of visual predators,
such as some fish species. There are not any SEPP or ANZECC guidelines for
turbidity but those from the Office of the Commissioner for the Environment (1988)
indicate a range of guideline values that vary depending on the area. Degraded, in a
mountain area, relates to a turbidity value of >12.5 NTU, >22.5 NTU a valley and on a
plain >30.0 NTU, values less than these indicate better water quality with respect to
turbidity. Median turbidity values have been recorded as excellent for the past 10
years at all sites presented. The 90th percentile values for turbidity at Henty, Dartmoor
and Sandford have frequently been recorded greater than 30.0 NTU indicating
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 63
degraded conditions that correlates with periods of high flow (winter) and hence
runoff (Department of Water Resources Victoria 1989). Turbidity at Fulham Bridge
has been shown to correlate positively with discharge at flows greater than 10 ML/day
(Mitchell et al. 1996). Turbidity is not a of concern in the Glenelg River system as the
winter high turbidities return to acceptable levels.
C.6 Summary
This analysis indicates that water quality in the Glenelg River system is poor with
respect to electrical conductivity. Electrical conductivity is particularly high in pools
in the reach of the Glenelg River between Rocklands Reservoir and Fulham Bridge.
Although turbidity and nutrients are generally not high, historical levels have been
shown to get high and hence may impact on the aquatic biota. Low concentrations of
dissolved oxygen is not of concern at a river wide scale but decreases in DO in the
saline pools is a factor that may inhibit the occurrence of some species in the areas of
the river where they persist. The concentrations of some parameters are closely
related to river flow. Clear patterns in nutrients and salinity can be observed during
high flow periods
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 64
C.7 Water quality plots indicating guideline values
Glenelg River @ Big Cord (238231) - Salinity
6500
6000
5500
5000
4500
4000
Median
3500
10th Percentile
3000
90th Percentile
2500
2000
Guideline
1500 µS/cm
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Big Cord (238231) - Total Nitrogen
2.5
2
1.5
Median
10th Percentile
90th Percentile
EPA
1
ANZECC
0.5
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 65
Glenelg River @ Big Cord (238231) - Total Phosphorus
0.18
0.16
0.14
0.12
ANZECC
0.1
Median
10th Percentile
90th Percentile
0.08
0.06
0.04
EPA
0.02
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Big Cord (238231) - Dissolved Oxygen
14
12
10
8
Median
10th Percentile
90th Percentile
6
Guideline
5 mg/L
4
2
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 66
Glenelg River @ Fulhams Bridge (238224) - Salinity
6500
6000
5500
5000
4500
4000
Median
3500
10th Percentile
3000
90th Percentile
2500
2000
Guideline
1500 µS/cm
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Fulhams Bridge (238224) - Total Nitrogen
2.5
2
1.5
Median
10th Percentile
90th Percentile
EPA
1
ANZECC
0.5
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 67
Glenelg River @ Fulhams Bridge (238224) - Total Phosphorus
0.18
0.16
0.14
0.12
ANZECC
0.1
Median
10th Percentile
90th Percentile
0.08
0.06
0.04
EPA
0.02
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Fulhams Bridge (238224) - Dissolved Oxygen
14
12
10
8
Median
10th Percentile
90th Percentile
6
Guideline
5 mg/L
4
2
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 68
Wannon River @ Henty (238228) - Salinity
6500
6000
5500
5000
4500
4000
Median
3500
10th Percentile
3000
90th Percentile
2500
2000
Guideline
1500 µS/cm
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Wannon River @ Henty (238228) - Total Nitrogen
2.5
2
1.5
mg/L
Median
10th Percentile
90th Percentile
EPA
1
ANZECC
0.5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 69
Wannon River @ Henty (238228) - Total Phosphorus
0.18
0.16
0.14
0.12
ANZECC
0.1
Median
10th Percentile
90th Percentile
0.08
0.06
0.04
EPA
0.02
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Wannon River @ Henty (238228) - Dissolved Oxygen
14
12
10
8
Median
10th Percentile
90th Percentile
6
Guideline
5 mg/L
4
2
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 70
Glenelg River @ Sandford (238202) - Salinity
6500
6000
5500
5000
4500
EC Units
4000
Median
3500
10th Percentile
3000
90th Percentile
2500
2000
Guideline
1500 µS/cm
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Glenelg River @ Sandford (238202) - Total Nitrogen
2.5
2
1.5
mg/L
Median
10th Percentile
90th Percentile
EPA
1
ANZECC
0.5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 71
Glenelg River @ Sandford (238202) - Total Phosphorus
0.18
0.16
0.14
0.12
ANZECC
0.1
Median
10th Percentile
90th Percentile
0.08
0.06
0.04
EPA
0.02
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Sandford (238202) - Dissolved Oxygen
14
12
10
8
Median
10th Percentile
90th Percentile
6
Guideline
5 mg/L
4
2
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 72
Glenelg River @ Dartmoor (238206) - Salinity
6500
6000
5500
5000
4500
EC Units
4000
Median
3500
10th Percentile
3000
90th Percentile
2500
2000
Guideline
1500 µS/cm
1500
1000
500
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Glenelg River @ Dartmoor (238206) - Total Nitrogen
2.5
2
1.5
mg/L
Median
10th Percentile
90th Percentile
EPA
1
ANZECC
0.5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 73
Glenelg River @ Dartmoor (238206) - Total Phosphorus
0.18
0.16
0.14
0.12
ANZECC
0.1
Median
10th Percentile
90th Percentile
0.08
0.06
0.04
EPA
0.02
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Glenelg River @ Dartmoor (238206) - Dissolved Oxygen
14
12
10
8
Median
10th Percentile
90th Percentile
6
Guideline
5 mg/L
4
2
0
Jan
Feb
Mar
Apr
May
WC01432:R04_MJS_GLENELG_FINAL.DOC
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Final
PAGE 74
n
Table 6-2: Basic statistics for water quality parameters for the year
1999, collected, progressively downstream, in the Glenelg River
catchment as part of the Victorian Water Quality Monitoring Network
(Rivers and Streams).
a) Glenelg River at Big Cord (238231).
238231
EC
TN
TP
pH
DO
Turbidity
Statistic
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
1990
115
101
139
0.202
0.202
0.251
0.002
0.002
0.002
6.3
5.7
6.8
9.1
8.3
10.9
2.3
1.6
3.3
1991
105
98
110
0.202
0.052
0.208
0.002
0.002
0.006
5.5
5.1
7.2
9.6
8.1
10.7
1.8
1.3
3.1
1992
100
92
119
0.252
0.102
0.302
0.004
0.002
0.011
5.2
4.9
5.8
8.7
7.4
10.5
2.4
1.5
5.3
1993
110
99
139
0.302
0.112
0.302
0.004
0.002
0.009
5.8
5.0
6.1
8.4
7.6
9.7
3.1
1.6
5.7
1994
105
95
119
0.202
0.112
0.292
0.003
0.002
0.010
6.5
5.7
7.1
9.5
8.7
10.6
2.2
1.6
4.8
1995
100
93
147
0.204
0.102
0.327
0.009
0.002
0.011
6.0
5.4
6.7
9.2
8.5
9.7
2.2
1.6
3.7
1996
105
100
120
0.203
0.102
0.261
0.010
0.002
0.027
6.9
5.6
7.6
9.0
7.9
10.2
2.0
1.5
3.8
1997
98
91
110
0.192
0.103
0.312
0.008
0.002
0.012
5.8
5.6
6.6
8.9
8.2
10.9
2.2
1.2
3.4
1998
97
87
109
0.226
0.183
0.371
0.007
0.002
0.012
5.6
5.1
6.5
9.1
7.4
10.0
2.0
1.4
2.8
1999
105
86
149
0.259
0.183
0.393
0.012
0.005
0.018
5.6
5.0
6.4
9.3
8.1
9.8
1.6
1.2
2.6
1992
1700
637
3160
7.2
6.7
7.8
8.0
6.1
9.0
2.3
1.0
19.4
1993
1300
612
2920
0.757
0.714
0.799
0.018
0.017
0.018
6.9
6.4
7.2
7.9
3.7
9.5
3.1
2.0
10.9
1994
2350
1220
4500
0.704
0.403
1.186
0.012
0.009
0.021
7.0
6.6
7.4
8.0
6.1
9.7
2.6
1.6
4.0
1995
2950
1730
3290
0.882
0.803
1.398
0.016
0.015
0.023
7.1
6.7
7.6
7.7
6.5
9.0
2.3
1.5
7.5
1996
1600
973
3830
0.807
0.536
1.469
0.024
0.014
0.059
7.0
6.9
7.4
8.0
5.6
8.8
2.1
1.3
27.9
1997
2000
1110
3390
0.588
0.506
0.843
0.017
0.007
0.026
7.4
7.0
7.7
8.3
6.2
9.7
1.8
1.3
2.3
1998
1900
964
3430
0.653
0.516
0.802
0.014
0.011
0.023
7.1
6.8
7.4
7.9
6.5
10.0
2.2
1.4
2.8
1999
2600
1300
4400
0.563
0.520
0.741
0.015
0.012
0.019
7.1
6.9
7.3
8.6
7.1
9.7
1.4
0.7
1.7
1992
3200
658
5360
1.085
0.614
1.930
0.058
0.011
0.158
7.9
7.4
8.0
8.4
7.4
11.1
16.0
1993
2850
1460
4690
0.967
0.671
1.558
0.036
0.012
0.078
7.8
7.4
8.0
9.6
7.8
10.4
11.4
1994
4500
3730
5090
0.710
0.605
1.014
0.020
0.013
0.062
7.8
7.0
8.1
9.7
8.5
11.2
5.6
1995
3600
917
5760
0.920
0.849
1.924
0.028
0.018
0.136
7.8
7.2
8.2
9.3
7.4
10.7
8.0
1996
4400
923
5280
1.026
0.626
1.901
0.034
0.020
0.120
8.0
7.3
8.4
8.7
7.7
11.4
7.6
1997
4650
4210
5290
0.781
0.654
0.951
0.022
0.013
0.054
8.2
8.0
8.2
9.4
8.6
11.1
3.2
1998
4850
3230
5700
0.986
0.859
1.392
0.035
0.022
0.084
8.0
7.9
8.2
9.3
8.2
10.7
4.5
1999
4950
4400
5300
0.860
0.574
1.008
0.030
0.022
0.056
8.1
7.6
8.3
9.9
8.0
11.2
3.2
b) Glenelg River at Fulham Bridge (238224)
238224
EC
TN
TP
pH
DO
Turbidity
Statistic
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
1990
-
1991
2450
1330
3100
7.4
7.2
7.7
7.1
5.7
8.6
1.9
0.8
12.9
c) Wannon River at Henty (238228)
238228
EC
TN
TP
pH
DO
Turbidity
Statistic
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
1990
4300
2220
5400
0.930
0.845
1.738
0.041
0.023
0.083
8.0
6.8
8.2
9.3
8.5
11.0
4.2
WC01432:R04_MJS_GLENELG_FINAL.DOC
1991
4200
1490
5090
0.731
0.611
2.089
0.021
0.010
0.073
8.0
7.5
8.3
9.8
8.3
10.9
6.9
Final
PAGE 75
238228
Statistic
10th Percentile
90th Percentile
1990
2.5
42.0
1991
2.7
37.0
1992
2.4
54.2
1993
2.7
32.7
1994
2.2
15.2
1995
2.4
50.7
1996
1.3
56.9
1997
1.9
13.2
1998
2.9
17.3
1999
1.7
6.0
1993
2450
928
4570
0.873
0.560
1.345
0.036
0.026
0.102
7.9
7.4
8.3
10.2
7.8
11.6
9.2
2.0
40.0
1994
4400
3600
4700
0.690
0.512
1.089
0.032
0.016
0.067
8.0
7.3
8.5
11.1
9.2
11.6
2.6
2.1
14.0
1995
3850
927
6310
0.958
0.772
2.259
0.053
0.026
0.136
7.8
7.0
8.4
9.7
7.7
11.7
4.4
2.2
52.3
1996
4200
977
5550
0.808
0.582
2.181
0.050
0.019
0.145
7.9
7.2
8.2
9.3
7.5
10.6
5.4
1.6
52.0
1997
4050
3710
4390
0.652
0.574
0.875
0.022
0.009
0.053
8.0
7.9
8.3
9.9
7.7
11.9
2.9
1.6
16.7
1998
4050
3150
4980
0.763
0.666
1.159
0.036
0.026
0.063
8.0
7.8
8.1
9.8
8.9
11.1
2.9
2.3
13.6
1999
4500
3900
5090
0.650
0.529
0.899
0.024
0.016
0.042
8.1
7.6
8.2
9.9
8.8
10.9
2.7
1.6
6.4
1993
1950
1250
3180
0.900
0.711
1.646
0.024
0.010
0.106
7.7
7.2
7.8
8.8
7.7
10.4
9.5
1.9
49.7
1994
3000
2420
3690
0.735
0.634
0.978
0.013
0.009
0.028
7.6
7.0
8.0
9.6
8.0
10.9
2.8
1.5
15.1
1995
2500
1760
4020
0.995
0.682
1.658
0.022
0.010
0.087
7.7
7.4
7.9
9.4
8.2
10.1
2.4
1.7
42.8
1996
2750
904
3980
0.960
0.668
2.399
0.028
0.013
0.156
7.3
6.4
8.0
8.7
8.3
9.8
2.7
1.2
75.6
1997
3350
2700
3790
0.725
0.642
0.879
0.020
0.008
0.030
7.8
7.7
7.9
8.9
6.5
11.2
1.8
1.2
3.4
1998
2900
2600
3660
0.882
0.700
1.351
0.021
0.008
0.069
7.6
7.0
8.0
9.4
8.0
10.0
2.2
1.6
20.7
1999
3550
3020
3890
0.710
0.590
0.866
0.025
0.015
0.045
7.6
7.4
7.9
8.8
6.4
10.1
1.2
0.7
2.1
d) Glenelg River at Sandford (238 202).
238202
EC
TN
TP
pH
DO
Turbidity
Statistic
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
1990
3950
2310
4700
0.889
0.595
1.648
0.036
0.021
0.089
7.9
6.8
8.2
10.4
8.7
11.5
5.2
1.7
38.5
1991
4000
1610
5080
0.706
0.555
1.784
0.030
0.018
0.066
8.2
7.6
8.5
10.3
8.3
14.3
4.5
2.0
49.6
1992
2300
628
5500
0.900
0.615
1.765
0.049
0.029
0.137
8.1
7.4
8.3
10.8
7.8
11.6
5.6
1.9
58.0
e) Glenelg River at Dartmoor (238 206).
238206
EC
TN
TP
pH
DO
Turbidity
Statistic
Median
10th Percentile
th
90 Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
Median
10th Percentile
90th Percentile
1990
2550
1810
3690
1.010
0.642
1.560
0.026
0.014
0.106
7.7
6.4
7.9
8.9
7.4
10.4
1.9
1.3
53.3
WC01432:R04_MJS_GLENELG_FINAL.DOC
1991
2800
1320
3670
1.005
0.599
1.605
0.023
0.009
0.092
7.8
7.6
8.0
9.5
8.2
10.6
2.9
1.5
33.1
1992
2950
687
3670
1.115
0.659
1.494
0.039
0.010
0.095
7.7
7.5
7.9
8.1
7.2
11.0
16.1
1.5
47.2
Final
PAGE 76
Appendix D
Biota
D.1 Condition of instream and riparian habitat
The lower reaches of the Glenelg River are classified as a “Heritage River” and lie
within the Lower Glenelg National Park. As a consequence of being in the National
Park, riparian and instream habitats relatively intact. Upstream of the National Park,
however, the Glenelg River catchment has been extensively cleared for dryland
agriculture. Mitchell et al. (1996) indicates that despite extensive clearing for
agriculture in the mid to upper reaches of the river, riparian vegetation shows
continuous or discontinuous cover on both banks. Nevertheless, riparian vegetation is
restricted to the banktop fringe and is influenced by adjacent landuse.
In 1986, the Department of Water Resources conducted a survey of the environmental
condition of Victorian streams. Within the Glenelg River catchment the condition or
health of 58 sites located on both the Glenelg River and its tributaries was described
using both biological and physical assessment criteria (Mitchell 1990). In general,
approximately 45% of the Glenelg River and 70% of tributaries within the catchment
were described as poor to very poor environmental condition. In 1994 seven of the
original 58 sites were resurveyed. While some sites had improved as a result of
exclusion of stock from riparian zones, stream condition was still described as
generally poor (Davidson et al. 1994). Davidson et al. (1994) suggested that flow
regulation, sedimentation, salinisation and extensive snag removal were the main
factors resulting in 55% of the total stream length in the Glenelg catchment being
classified as being in very poor condition.
D.2 Fish, decapod crustacea and molluscs
The native freshwater fauna (fish, decapod crustacea and bivalve mollusc) of the
Glenelg River system represent a diverse assemblage with high conservation
significance. Twenty species of native freshwater fish and 26 species of estuarine
species have been recorded from the Glenelg River system (DNRE 2000c) (Table
6-3). Eight species have conservation significance and of these, five species are
protected through their listing on the Victorian Flora and Fauna Guarantee Act 1988.
Of these, four species are protected through their listing on the (ANZECC 2000) List
of Threatened Australian Vertebrate Fauna. Of the twenty species of native
freshwater fish, seven are known to migrate between freshwater and estuarine/marine
habitats at some stage in their life cycle (Koehn 1990, O'Connor 1998) (Table 6-3).
Seven species of decapod crustacea and at least three species of bivalve mollusc have
also been recorded (Table 6-3). Of these, the Glenelg freshwater mussel (Hyridella
glenelgensis) and the western swamp cray (Gramastacus insolitus) are suspected of
being rare, with restricted distributions and low abundances (Tarmo Raadik pers
comm). Consequently, these species may in the near future be rated as highly
threatened fauna in Victoria (Tarmo Raadik pers comm).
D.2.1
Fish
The distribution of native freshwater fish recorded from the Glenelg River system is
discussed below. Flow and habitat related issues that may be impacting on the fish
fauna of the Glenelg River are discussed in section 6.7.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 77
Dwarf galaxias have been recorded in the upper Glenelg River upstream of Balmoral
to the headwaters, including Rocklands Reservoir and its tributaries (DNRE 2000c).
This species has also been recorded near Dartmoor in Scott Creek, a tributary of the
lower Glenelg River and from the upper Crawford River, upper Wannon River and
various other tributaries and wetlands (DNRE 2000c). The Glenelg River basin
contains some of the best dwarf galaxias populations in Victoria (Tarmo Raadik pers
comm). Dwarf galaxias are classified as lower risk-near threatened (DNRE 2000b)
and vulnerable (ANZECC 2000), and protected through their listing on the Victorian
Flora and Fauna Guarantee Act 1988. Dwarf galaxias typically inhabit swamps and
billabongs and occasionally streams (Humphries 1986, Koster 1997, McDowall
1996b). The species is considered prone to threats including habitat degradation
caused by swamp drainage (SAC 1991b).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 78
n
Table 6-3: Conservation status of fish, decapod crustacea and bivalve mollusc species recorded
in the Glenelg River Catchment.
Scientific Name
Common Name
Native Migratory
Anguilla australis
Short-finned eel
Galaxias truttaceus
Spotted galaxias
Galaxias maculatus
Common galaxias
Geotria australis
Pouched lamprey
Mordacia mordax
Short-headed lamprey
Prototroctes maraena
Australian grayling
Pseudaphritis urvilli
Tupong
Native Non-Migratory
Edelia obscura
Yarra pygmy perch
Gadopsis marmoratus
River blackfish upper
upper Wannon
Wannon form
Gadopsis marmoratus
River blackfish
Galaxias olidus lower
Mountain galaxias
Glenelg
(lower Glenelg form)
Galaxias olidus
Mountain galaxias
Galaxiella pusilla
Dwarf galaxias
Hypseleotris klunzingeri
Western carp gudgeon
Macquaria ambigua
Golden perch
Macquaria australasica
Macquarie perch
Nannoperca australis
Southern pygmy perch
Nannoperca variegata
Variegated pygmy
Perch
Philypnodon grandiceps
Flat-headed gudgeon
Retropinna semoni
Australian smelt
Freshwater Exotic
Carassius auratus
Goldfish
Gambusia holbrooki
Eastern gambusia
Oncorhynchus mykiss
Rainbow trout
Oncorhynchus
Chinook salmon
tshawytscha
Salmo trutta
Brown trout
Tinca tinca
Tench
Perca fluviatilis
Redfin
Decapod crustacea
Cherax destructor
Yabby
Euastacus bispinosis
Glenelg spiny cray
Geocherax falcata
Western cray
Gramastacus insolitus
Western swamp cray
Paratya australiensis
Freshwater shrimp
Engaeus lyelli
Upland burrowing cray
Engaeus strictifrons
Portland burrowing
Cray
Status
C
C
C
C
C
V, L, v
LN, L, v
D
C
D
C
LN, L, v
C
V,
End, L
C
V, L, v
C
C
Common
Common
Common
Common
Common
Common
Common
Scientific Name
Common Name
Native Estuarine
Atherinasoma
Small-mouthed
microstoma
hardyhead
Acanthopagrus butcheri
Black bream
Afurcagobius tamarensis Tamar river goby
Aldrichetta forsteri
Yellow-eye mullet
Ammotretis rostratus
Longsnouted flounder
Arenigobius bifrenatus
Bridled goby
Argyrosomus
Mulloway
hololepidotus
Arripis georgianus
Tommy rough
Arripis truttaceus
West. Aust. salmon
Chelidonichthyes kumu
Red Gurnard
Dactylophora nigricans
Dusky morwong
Engraulis australis
Australian anchovy
Girella tricuspidata
Luderick
Hyporhampus
Southern sea garfish
melanochir
Macquaria colonorum
Estuary perch
Mugil cephalus
Sea mullet
Nemadactylus douglasii
Blue morwong
Nesogobius hinsbyi
Orange spotted goby
Platycephalus bassensis Sand flathead
Pomatomus saltatrix
Tailor
Pseudogobius olorum
Swan river goby
Rhomboselea taparina
Greenback flounder
Ruboralaga
Red rock cod
ergastulorum
Sillaginodes punctata
King George whiting
Tasmanogobius lasti
Lagoon goby
Tetractenos glaber
Smooth toadfish
Hyridella glenelgensis
Velesunio ambiguus
Corbicula australis
Bivalve mollusca
Glenelg freshwater
mussel
Freshwater mussel
Pea mussel
1
Status 1
Rare2
Common
Common
Abbreviations denote conservation status as; LN, lower risk-near threatened; C, common; End, endangered; V,
vulnerable D, data deficient (DNRE 2000b); L, listed; E, endangered; N, nominated (Flora and Fauna Guarantee
Act); v, vulnerable (ANZECC 2000)
2
suspected to be endangered (Tarmo Raadik pers comm)
Variegated pygmy perch are endemic to the Glenelg River system and have been
recorded in the mid reaches of the Glenelg River between Harrow to Strathdownie
(DNRE 2000c). This species has also been recorded in the lower Crawford, Stokes
and Wannon rivers, Grange Burn and various tributaries. Little is known about the
species distribution upstream of Harrow. The species typically inhabits flowing water,
and is associated with dense aquatic vegetation and substrates of gravel, cobble or
boulder in the absence of silt (Koehn 1990, Kuiter 1996). Variegated pygmy perch are
classified as vulnerable (ANZECC 2000, DNRE 2000b) and protected through their
listing on the Victorian Flora and Fauna Guarantee Act 1988. The species is
considered prone to threats including habitat degradation caused by stock access,
alteration to temperature regimes and sediment input to streams (DCNR 1993).
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 79
Yarra pygmy perch have been recorded in the Glenelg River from Balmoral to
Casterton (DNRE 2000c). The species is widespread with the Glenelg River
catchment having been recorded in the Crawford River, Wannon River and tributaries,
and various wetlands. It is likely that the Glenelg River catchment supports some of
the best Yarra pygmy perch population in Victoria (Tarmo Raadik pers comm). The
species typically inhabits flowing water and well-vegetated streams (Koehn 1990,
Kuiter 1996). Yarra pygmy perch are classified as lower risk-near threatened (DNRE
2000b) and vulnerable (ANZECC 2000), and protected through their listing on the
Victorian Flora and Fauna Guarantee Act 1988. The species is considered prone to
threats including habitat modification, in particular the removal of riparian and
instream vegetation (SAC 1991a).
Golden perch and Macquarie perch are not indigenous to the Glenelg catchment.
Nevertheless, both species are of conservation significance. The conservation status
of golden perch in Victoria is described as vulnerable (DNRE 2000b). Similarly,
Macquarie perch are considered endangered in Victoria (DNRE 2000b) and are
protected through their listing on the Victorian Flora and Fauna Guarantee Act 1988.
Golden perch have been recorded from Ess Lagoon off the Glenelg River, Wannon
River near Wannon Falls and Hamilton Lake (DNRE 2000c). The species typically
inhabits slow-flowing rivers and floodplain lakes (Harris 1996) and has undergone a
decline in number across its range, potentially due to habitat degradation, construction
of dams and weirs and alteration of the natural hydrology (flow and temperature
regimes) (Harris 1996). Macquarie perch have been recorded from Ess Lagoon and
the Wannon River between Wannon Falls and Nigretta Falls (DNRE 2000c). This
species typically inhabits riverine and lake habitats (Harris 1996) and has undergone a
decline in number across its range, potentially due to siltation of stream beds,
construction of dams and weirs and alteration of the natural hydrology (flow and
temperature regimes) (Koehn 1990).
Australian grayling was recorded in the Glenelg River in 1896, however no recent
records exist (DNRE 2000c). Australian grayling are classified as vulnerable
(ANZECC 2000, DNRE 2000b) and protected through their listing on the Victorian
Flora and Fauna Guarantee Act 1988. The species typically inhabits streams with a
moderate flow and gravel substrate (McDowall 1996c). Australian grayling has
become extinct in a major part of its range attributable to the construction of dams and
weirs restricting migration, and the alteration of natural stream flow and temperature
regimes (SAC 1991c).
River blackfish have been recorded throughout most of the Glenelg River and
tributary streams (DNRE 2000c). River blackfish populations in the upper Wannon
River are spatially isolated from other Victorian populations and as such may be
genetically distinct and of conservation significance. This particular population has
been recognised and its conservation status classified as "data deficient" (DNRE
2000b). River blackfish inhabit a variety of stream types, preferably with abundant
cover such as snags and vegetation (Koehn 1990). The species is considered
susceptible to increased sediment loads in streams and degradation of natural riparian
vegetation (Doeg 1994).
Mountain galaxias have been recorded in the Glenelg River between Harrow and
Rocklands Reservoir and most tributary streams throughout the catchment (DNRE
2000c). Mountain galaxias populations in the lower Glenelg River are spatially
isolated from other Victorian populations and as such may be genetically distinct and
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 80
of conservation significance. This particular population has been recognised and its
conservation status classified as "data deficient" (DNRE 2000b). Mountain galaxias
typically inhabits small streams at higher elevations where water temperatures remain
cool in summer (McDowall 1996b).
Southern pygmy perch have been recorded in the Glenelg River between Balmoral
and Chetwynd most other parts of the catchment in tributary streams and wetlands
(DNRE 2000c). Southern pygmy perch typically inhabit small, slow flowing streams
and wetlands with abundant aquatic vegetation (Kuiter 1996).
Common galaxias have been recorded throughout most of the Glenelg River and
tributary streams (DNRE 2000c). This species typically inhabits slow flowing or still
waters (Koehn 1990). A land-locked population of this species is present in
Rocklands Reservoir (Tarmo Raadik pers comm).
Australian smelt have been recorded in the mid reaches of the Glenelg River near
Dergholm and Casterton as well as from the river mouth (DNRE 2000c). This species
has also been recorded in the Wando, Stokes and Wannon rivers and various
tributaries. Australian smelt typically inhabit slow flowing or still waters (McDowall
1996a).
Short-finned eel have been recorded in the Glenelg River near Balmoral, Chetwynd
and Casterton, and from the river mouth (DNRE 2000c). This species has also been
recorded in the Crawford and Wannon rivers and Grange Burn. Short-finned eel
occupy a variety of habitats including rivers, creeks and wetlands (Beumer 1996).
Tupong have been recorded in the Glenelg River from Harrow downstream to the
river mouth (DNRE 2000c). This species has also been recorded in the Wando,
Wannon and Crawford rivers and tributaries. Tupong typically inhabit the beds of
slow flowing streams, and often remain partly buried among rocks and logs (Andrews
1996).
Flat-headed gudgeon have been recorded in the Glenelg River from Balmoral
downstream to the river mouth (DNRE 2000c). This species has also been recorded in
Rocklands Reservoir, the Wannon and Crawford rivers and various tributary streams.
Flat-headed gudgeon typically inhabit slow flowing or still waters, usually amongst
weed or mud bottoms (Larson 1996).
Spotted galaxias have been recorded from a number of tributaries of the lower
Glenelg River (DNRE 2000c). This species typically inhabits the lower reaches of
streams, occupying pool habitats amongst logs, boulders or overhanging banks
(McDowall 1996b).
Western carp gudgeon have only been recorded in the Wannon River and its
tributaries, there are no records for the Glenelg River (DNRE 2000c). This species
typically inhabits slow flowing streams amongst aquatic vegetation (Koehn 1990) and
may have been introduced into the Glenelg River catchment via stockings of other
native fish species (e.g. golden perch).
Short-headed lamprey has been recorded in the Glenelg River near Harrow and
Chetwynd (DNRE 2000c). This species has also been recorded in the lower Wannon,
Stokes and Crawford rivers and Moleside Creek.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 81
Pouched lamprey are only known from the Glenelg River near Casterton (1888) and
from an unspecified location in 1928. No recent records exist (DNRE 2000c).
Pouched lamprey are a cryptic species that are rarely caught throughout their range in
Victoria (Tarmo Raadik pers comm).
D.2.2
Decapod Crustacea
Distribution information for decapod crustaceans in the Glenelg River catchment is
limited. Available records primarily represent by-catch of netting and electrofishing
surveys conducted for fish species. Nevertheless, some information is available on the
distribution of Glenelg spiny crayfish (Euastacus bispinosus).
In Victoria, Glenelg spiny crayfish are restricted to the Glenelg River basin. Mitchell
et al. (1996) suggest that they may once have been distributed throughout the basin
but their range may now be restricted by habitat degradation. The distribution of the
species is now associated with large areas of remnant bush and may be particularly
reliant on intact riparian vegetation (Mitchell et al. 1996). Crayfish are also likely to
require deep pools as drought refuges and abundant woody debris for cover. Siltation,
flow regulation, desnagging and riparian vegetation clearing in the Glenelg River
basin have led to the loss of important habitat attributes, particularly in the mid to
upper catchment.
Salinisation may have also had an impact on Glenelg spiny crayfish. Crayfish moult
frequently when small, but by 50 mm OCL moulting is restricted to once a year
between January to May. At this time water quality in the modified upper river is
poor with elevated temperature and salinity, and reduced oxygen levels. When a
crayfish moults its ability to osmoregulate is reduced, consequently high salinities may
reduce growth or survival (Mitchell 1996).
Western swamp cray in the Glenelg River basin are restricted in distribution and have
only been collected in low abundances (Zeidler and Adams 1990). The species is
most often associated with wetlands, permanent swamps, creeks and drains.
D.2.3
Macroinvertebrates
(EPA 1999) recorded a total of 86 families of macroinvertebrates from a total of 61
survey sites throughout the Glenelg River catchment (Table 6-4). Studies by (Mitchell
1996) and (EPA 1999) report a dominance of insects (such as beetles, mayflies and
true bugs) in the macroinvertebrate community, as is commonly the case in fresh
waters (EPA 1999). Based on the macroinvertebrate communities present, the health
of sites in the Glenelg River were assessed as good to excellent in both pools and
shallow habitats based on ratings presented on OCE (1988). Increased community
complexity and abundance of macroinvertebrates was reported at sites with
macrophytes and organic debris (Mitchell 1996).
In contrast, a study undertaken as part of the National River Health Strategy
(Schreiber et al. 1998) the Glenelg River Catchment was described as highly
degraded, based on several measures of stream health including the assessment of instream habitats and macroinvertebrate populations. One particular analysis of water
health (Chessman 1995), which uses macroinvertebrate populations and the relative
pollution sensitivities of individual taxa, identified the possible presence of mild to
moderate pollution at most of the sites sampled. Only four sites were described as
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 82
n
Table
6-4:
Macroinvertebrate
communities in the mid to upper
Glenelg River (Mitchell 1996).
Group
Crustacea
Mollusca
Insecta
Annelida
Hemiptera
Trichoptera
Diptera
Hymenoptera
Ephemeroptera
Coleoptera
Odonata
Lepidoptera
Mecoptera
Oligochaeta
Hirudinea
Arachnida
Platyhelminthes
% of taxa
8
9
12
11
10
6
2
19
4
4
1
2
3
9
1
having clean water quality status (Schreiber et al. 1998). Conflicting results, however,
were obtained using AUSRIVAS, another tool for assessing the condition of streams.
AUSRIVAS is a biotic index that relates the macroinvertebrate taxa occurring at
individual sites to species that are expected to occur at those sites. The list of
expected taxa is based on the macroinvertebrate populations present at reference sites
located in pristine reaches of stream. Of 53 sites used in the AUSRIVAS model, 26
sites had the expected macroinvertebrate fauna and were therefore described as good
condition (Schreiber et al. 1998). However due to reference sites being non-pristine
these results were confounded and might be misleading. Signal scores for these 26
sites however showed the macroinvertebrate fauna at 20 sites was reasonably tolerant
and therefore indicated that mild to moderate pollution may exist. Twenty-six sites
had AUSRIVAS scores that indicated mild disturbance. A further five sites had
AUSRIVAS scores indicating moderate to severe impact on water and/or habitat
condition
In general, most sites in the Glenelg River Catchment are considered to have poor or
very poor aquatic habitats. SIGNAL scores indicate mild or moderate pollution at
most sites. The degraded condition of Glenelg River catchment reflects the high level
of erosion and clearing that has occurred. Sites considered to have good habitat
quality and water quality were located in or near National Parks.
D.3 Birds
There have been 271 species of bird recorded in the Glenelg River of which 50 species
have conservation significance either in Victoria or nationally (DNRE 2000a, DNRE
2000b). Of the threatened species, 20 are reliant directly upon the instream
environment for their survival (Table 6-5). No information, however, is available on
the impacts of altered flow regimes on these species.
D.4 Amphibians and reptiles
One species of threatened amphibian, the warty bell frog (Litoria raniformis), has
been recorded from the Glenelg catchment from near Balmoral in 1963, Dartmoor in
1972, Dergholm in 1979, and from Rocklands Reservoir in 1981. Nevertheless, no
recent records exist (DNRE 2000a). The conservation status of this species is
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 83
vulnerable (DNRE 2000b). Two species of threatened reptile, the swamp skink
(Egernia coventryi) and tree goanna (Varanus varius), have been recorded from the
Glenelg catchment (DNRE 2000a). Only two records of the swamp skink exist in the
catchment, namely, near Nelson (1980) and the Crawford River (1988). No recent
records exist and the conservation status of this species is vulnerable (DNRE 2000b).
Only one record of the tree goanna exists in the catchment (Rocklands Reservoir 1981) and its conservation status is data deficient (DNRE 2000b). Although the tree
goanna does not directly depend on the riparian environment, such areas often provide
the only remaining habitat.
D.5 Other vertebrates
Other vertebrates present in the catchment and known to depend directly on the
instream environment for food and shelter include the platypus (Ornithorhynchus
anatinus) and water rat (Hydromys chrysogaster) (DNRE 2000a). Platypus have
been recorded in the Glenelg River near Casterton and Dartmoor and in the vicinity of
Fulham Hole. The species has also been recorded in the Wannon River near
Coleraine and Hamilton, Mackinnon Creek and Grange Burn (unpublished database
Australian Platypus Conservancy; Melanie Tranter pers comm). There is no
documented distribution information for the water rat.
The effect of altered flow regimes on these species is undocumented. Nevertheless, it
may be assumed that deep holes would provide refuge areas during periods of low
flow. Consequently, sedimentation and salinisation may restrict the availability of this
important habitat. Further more, artificially reduced flows during low flow periods
may lead to a direct loss of habitat (through a lack of water depth) and the potential
loss of runs between pools. This may have implications for the movement of platypus
between pools and foraging behaviour, thus restricting platypus to regions of poor
water quality.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 84
D.6 Instream and riparian flora
Of the 63 threatened flora species that occur in the Glenelg River catchment, 15 of
them rely directly on the instream environment or temporary inundation of off channel
areas for their survival (DNRE, 2000; Dale Tonkinson DNRE pers. comm., 2000)
(Table 6-5). Gilgai Blown-grass. (Agrostis aemula var setifolia), wetland blowngrass (Agrostis avenacea var. perennis) and Gilgai blown-grass (Agrostis billardierei
var. filifolia) all occur in seasonally wet areas. River swamp wallaby-grass
(Amphibromus fluitans), lax twig-sedge (Baumea laxa), swamp flax-lily (Dianella
callicarpa), showy lobelia (Lobelia beaugleholei), violet bladderwort (Utricularia
violacea) and swamp fireweed (Senecio psilocarpus) all occur in swampy and
waterlogged soils. Bog gum (Eucalyptus kitsoniana) and dark mignonette-orchid
(Microtis orbicularis) occur in coastal swamps, metallic sun-orchid (Thelymitra
epipactoides) occurs in heathy swamps and swamp greenhood (Pterostylis tenuissima)
occurs in tea-tree swamps. Lime fern (Pneumatopteris pennigera) is a riparian species
that grows on limestone and rough eyebright (Euphrasia scabra) is a riparian species
that has become extinct in the area except for one locality at Wandovale (Dale
n
1
Table 6-5: Threatened birds dependent on
instream and wetland habitats of the Glenelg River.
Scientific Name
Anas rhynchotis
Ardea alba
Aythya australis
Biziura lobata
Botaurus poiciloptilus
Burhinus grallarius
Cereopsis novaehollandiae
Chlidonias hybridus
Egretta garzetta
Grus rubicunda
Haliaeetus leucogaster
Ixobrychus minutus
Numenius madagascariensis
Nycticorax caledonicus
Oxyura australis
Phalacrocorax varius
Platalea regia
Porzana pusilla
Rallus pectoralis
Sterna caspia
Stictonetta naevosa
Common Name
Australasian shoveler
Great egret
Hardhead
Musk duck
Australasian bittern
Bush stone-curlew
Cape barren goose
Whiskered tern
Little egret
Brolga
White-bellied sea eagle
Australasian bittern
Eastern curlew
Nankeen night heron
Blue-billed duck
Pied cormorant
Royal spoonbill
Baillon’s crake
Lewin’s rail
Caspian tern
Freckled duck
Status 1
V
E, L
V
V
E, N
E, L
V
LN
CE, L
V, L
E, L
E, N
LN
V
V, N
V
V
V, N
E, N
V
E, L
Abbreviations denote conservation status as E,
endangered; V, vulnerable; LN, lower risk-near
threatened; D, data deficient (DNRE 2000b); L, listed; N,
nominated (Victorian Flora and Fauna Guarantee Act
1988).
Tonkinson, DNRE, pers. comm., 2000).
Thirty species of aquatic and semi-terrestrial macrophyte have been recorded in the
mid to upper reaches of the Glenelg River (Mitchell 1996). Species richness within
sites ranged from 7-11. Emergent aquatic macrophyte species were dominant and
represent between 67 and 100% of species present at sites surveyed.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 85
Low flows and sediment deposition in the mid to upper Glenelg River have been
found to be facilitating the excessive growth of Typha and Phragmites australis in the
river channel (Mitchell 1996). This consequently impedes flows and leads to further
sediment deposition and reduction in habitat complexity.
Mitchell et al. (1996) also noted that a conspicuous feature of macrophyte
communities was the absence of submerged aquatic macrophyte species in
downstream sites. It was suggested that salinities in pools at the downstream sites
may be sufficiently high to affect the growth of submerged macrophytes.
D.7 The Glenelg Heritage River and Lower Glenelg National
Park.
The lower section of the Glenelg River, from Nelson on the coast to Dartmoor, is
designated a “Heritage River” under the Heritage Rivers ACT 1992 (DNRE 1997).
The Heritage River corridor covers an area of approximately 3020 Ha and is about 50
m wide for most of its length. The lower section of the Heritage River flows through
the Lower Glenelg National Park. The Heritage River corridor provides an important
habitat link particularly between inland woodlands and the coast for species reliant on
riparian habitats. This habitat corridor is well protected within the National park
although public land water frontages are degraded at Nelson and below Dartmoor
(DNRE 1997).
There are several key values associated with the heritage section of the lower Glenelg
River. These include;
q 13 rare or threatened flora species are known to occur in the Heritage River
corridor although many of these are only known from local knowledge (DNRE
1997). Rare Bog Gum, The Lime Fern are two examples. Two species are listed
under the Flora and Fauna Guarantee Act 1988 (FFG): the leafy greenhood and
the limestone spider-orchid.
q
23 significant fauna species in the Heritage River Corridor. A further five
significant fish species. Of these species 11 are listed in the FFG ACT 1988
(DNRE 1997).
q
the Lower Glenelg karst area – an area of limestone between Keegan's Bend and
Nelson which is of state significance (LCC 1991),
q
rare and threatened fauna (see section 6.2-6.6),
q
remnant River Red Gum community south of Dartmoor (DNRE 1997),
q
Moleside Creek ( a tributary of the Glenelg River) contains numerous species of
fern,
q
a diverse fish fauna in both freshwater and estuarine sections,
q
high landscape values including extensive caves that provide habitat for several
significant species of bat and the Glenelg River estuary which represents the only
estuary in Victoria developed in a framework of dune calcarenite ridges (Bird
1977),
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 86
q
numerous recreational values – fishing, boating, camping, walking (DNRE 1997).
Key management directions have been proposed for the lower sections of the Glenelg
River that will maintain and enhance existing values. These include;
q restore habitat links along the River to the coast,
q
improve environmental water values of the River, particularly the estuary, and
develop trigger levels for opening of the river mouth,
q
undertake research and monitoring of significant fish species and environments,
monitor sand and silt effects on the River including the sand slug upstream the
heritage River corridor (DNRE 1997).
Flow related threats to the lower Glenelg River might include the encroachment of the
upstream sand slug and the alteration of late summer/autumn and winter/spring flow
events. Rutherfurd and Budhazy (1996) suggest that the sand slug may not reach the
Heritage River for approximately 30-40 years. Nevertheless, the impacts of the sand
slug are likely to be similar to those that have occurred in the mid to upper reaches of
the Glenelg River (e.g. infilling of deep pools, smothering of substrates, etc)
ultimately leading to decreased habitat complexity. With regards to the alteration of
flows to the lower Glenelg River, this has not been quantified and hence it is difficult
to determine the potential biological impacts.
WC01432:R04_MJS_GLENELG_FINAL.DOC
Final
PAGE 87