1
OPTIMISING THE USE OF WETLAND BENEFITS IN RIVER BASIN
MANAGEMENT:
A Case Study From The Murray-Darling Basin, Australia
Introduction
Characteristics Of The River Basin
Issues
Wetlands Within The Basin
Policy And Organisational Setup For Achieving Sustainable River Basin Management
Functions, Uses And Attributes Of The Barmah-Millewa Wetlands In Relation To River
Basin Management
The Integration Of Wetlands Into River Basin Management
Conclusion
Lessons Learned
Introduction
The Murray-Darling Basin covers an area in excess of one million km2, approximately one
seventh of the land area of Australia. The Basin is located in the south eastern section of the
continent. The majority of the area of the Basin consists of extensive plains. Almost threequarters of all water used for domestic, industrial and agricultural purposes in Australia comes
from the Basin (MDBMC, 1987a).
Land in the Basin is used for a variety of purposes, including urban settlements, irrigated and
dryland cropping, grazing of domestic stock, production forestry, and conservation of natural
areas in parks and reserves. Rainfall is extremely unreliable over much of the Basin; average
annual deviation from the mean rainfall, expressed as a percentage of the mean, ranges from
15% on the slopes of the Great Divide in Victoria to 30% in the Darling catchment (Tisdall,
1974).
The Murray and Darling Rivers have a total length of some 3,780 km, and comprise the fourth
longest river system in the world (MDBMC, 1987a). Runoff is very low, averaging 3% of
annual rainfall, and some 98% of the Basin exhibits drainage patterns typical of arid and semiarid environments, with frequently little contribution from surface runoff to overland flow. The
majority of runoff in the Basin is derived from the Great Dividing Range, on the southern and
eastern boundaries of the Basin.
ISSUES
The channel capacity of many of the rivers decreases as the rivers flow across the Basin. There
is significant spatial variation in discharge, reflecting the large extent of the Basin and the
consequent wide range of climatic conditions. The physical characteristics of the river systems
within the Basin have been extensively and significantly modified through a range of
interventions and the most significant are those associated with flow regulation.
To support the needs for water for both urban and agricultural developments, a number of water
storages have been constructed throughout the Basin. Three major reservoirs are located in the
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headwaters sections of the catchment, while diversion weirs and intermediate structures are
located along the length of the waterways.
The most significant feature of this river system is that most of the regulation of the rivers is
from reservoirs in the upper sections of the catchment. Thus it has little capacity to manage
flows once they are released from storage. This limits the flexibility of the system to provide
for the varying management needs of different components of the Basin, such as the need to
provide water for irrigation and for wetlands at different times of the year.
There is one large-scale diversion within the Basin. The so-called Snowy Mountains Scheme
permits diversion of water within and to the Basin. In addition to these significant
impoundments, there have been and continue to be numerous other interventions in the natural
flows of the rivers within the Basin. and other off-stream uses;
As a consequence, natural water flow regimes within the Basin have been extensively modified,
in terms of rate, variability, total volume and seasonality of flow. These changes have affected
both the watercourses themselves and those wetlands which are connected to the watercourses
at times of high flow. Sections of the Murray River now function as lakes rather than as parts of
a watercourse, due to the high level of interference with the natural. The biological impacts of
the alteration from a lotic to a lentic wetland are significant and, combined with the changes to
water quality and to the variability, rate, seasonality and volume of flow which have occurred,
have caused marked alterations to the natural habitats of the Basin.
The extent and impacts of these interventions vary markedly throughout the Basin. Along the
Murray, however, it is clear that the seasonality of flows has been reversed; the highest flows
now occur in the summer period, to meet the needs of irrigators. The lowest flows occur in the
winter and spring, when the storages refill. The impacts of these altered flows on wetlands along
the watercourses in the Basin have also been significant, and vary markedly depending on the
nature and extent of the alteration to the water regime.
Increased flexibility in delivery of irrigation water through proposed downstream structural
changes, perhaps through further off-river storage or more on-farm storage, will reduce the
pressure on existing water delivery infrastructure and provide greater ability to manage river
flows to meet wetlands and other ecological needs.
The environments within the Basin range from alpine to desert, and the vegetation varies
accordingly. Alterations to the water regimes of the Basin have resulted in significant indirect
impacts on the vegetation. As noted earlier, there has been significant alteration of the natural
water flow patterns within the Basin. That, combined with the effects of degraded water quality
primarily through increased salinity and nutrient levels, has impacted much of the remaining
natural vegetation surrounding wetlands and along the major water courses.
Wetlands of the Murray-Darling Basin
There are an estimated 30,000 wetlands in the Murray-Darling Basin (MDBC, 1994b),
encompassing a wide range of wetland types. In his study of wetlands on the Murray River
floodplain from the Hume Dam to the river mouth (a distance of 2,225 km), Pressey (1986)
identified more than 7,000 wetlands covering an area of approximately 2,200 km², in a total
study area of 10,000 km².
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In his assessment, Pressey used four hydrological categories, which were defined as shown in
Table 1. These data omit the details from the 600 wetlands located at or near the mouth of the
river.
TABLE 1
WETLANDS ALONG THE MURRAY RIVER - HYDROLOGICAL CATEGORIES
Hydrological Category
Number of
Percent of Wetland
Percent of
Wetlands
Wetlands Area (ha.) Area
1.
Wetland actually or
685
10.7
36 833
35.4
potentially connected to
the river at minimum
regulated flow or at pool
level.
2.
Wetland actually or
potentially connected to
the river above minimum
regulated flow but at or
below maximum regulated
flow.
3.
Wetland above maximum
regulated
flow, filled only by surplus flow.
4.
Total
Wetland above maximum
regulated flow and which
receives drainage, seepage
or effluent flow. Usually
receives surplus flow also.
740
11.5
23 950
23.0
4 434
68.9
31 647
30.4
574
8.9
11 600
11.2
6 433
100.0
104 030
100.0
The Barmah-Millewa forest is a seasonally flooded forest, dominated by river red gums
(Eucalyptus camaldulensis). The site contains a large number of permanent and temporary
wetlands, including swamps, lakes, grassland plains, and flooded forest. It is located on the
Murray River floodplain, and includes a section of floodplain along the Edward River. There are
a total of 3,300 ha of wetlands in the Barmah-Millewa forest; 90% of the wetlands are classified
as being connected or potentially connected to the river above the minimum regulated flow level
but at, or below, the maximum regulated flow level. The remaining 10% were classed as being
above the maximum regulated flow, being filled only by surplus flows. The flood retention
capacity of the Barmah section of the forest has been estimated to be some 321,000 ML (Dexter,
1970).
Average annual rainfall at Barmah is 396 mm, the majority of which is received in the winter
and spring, typically in low intensity events. Water quality monitoring in the Barmah-Millewa
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forest are limited to monitoring of dissolved oxygen, water temperature, electrical conductivity,
pH and turbidity. Water samples were also taken during spring flooding for analysis of
nutrients.
The hydrology of the Barmah section of the forest has been well-documented. The natural
pattern of flows in the Murray River involved high winter and spring volumes, as a consequence
of high winter and spring rainfall and of snowmelt in the Australian Alps, and lower flows over
the summer and autumn.
A detailed discussion of the major changes to the natural vegetation evident at Barmah is
provided. The authors hypothesised that changes to flood regimes which followed the
construction of the Hume Weir in 1934 have resulted in the decline of the grasslands. The
higher summer water levels ensured that some areas became swamps rather than seasonally
(winter/spring) flooded grasslands, and the vegetation consequently changed. Regulators
designed to restrict the entry of summer floods to selected areas were installed over the period
from 1939 to 1959, but these were only partially effective.
The Barmah-Millewa forest is of great significance for birds, particularly for waterbirds.
Barmah itself is a Ramsar site, and has previously supported large colonies of waterbirds. Even
though altered flooding regimes have reduced bird numbers somewhat, Barmah still remains
highly significant. Twenty seven species of freshwater fish occur in the Basin, of which 19 are
native. All would be expected to occur in the waters of the Barmah-Millewa forest.
At first glance, the extent of impact of human intervention appears to have been less on the
fauna than on the flora resources of the area. However, this may reflect the relative amounts of
data which have been collected, rather than real differences in severity of impact. It is clear that
increased grazing pressure following the introduction of domestic stock, coupled with the
arrival of rabbits into the forest, would have reduced feed available to herbivores significantly.
Further, the introduction of predators such as foxes and cats to the area would have resulted in
additional pressure on populations of native fauna.
There have been numerous direct and indirect human interventions in the Barmah-Millewa
forest e.g. intervention in the natural functioning of the site by aborigines include hunting and
fishing; collection of plant materials for food and fibre needs; harvesting of wood and bark for
fires, construction of dwellings and canoes, and other purposes; collection of honey and other
forest products; and periodic firing of the grasslands to alter the grazing patterns of native fauna.
As discussed in earlier sections, the natural flow regimes of the Murray River in the vicinity of
the forest have altered significantly due to human intervention. Attempts to moderate the
influence of these changes include the construction of levees and regulators. Levees serve to
protect the forest from unseasonal summer floods, but also restrict winter/spring floods from
reaching the protected parts of the forest. They are hence a less-favoured water management
tool than regulators, which enable more precise flow management.
The regulators which have been constructed in both the Barmah and Millewa sections of the
forest are used to control flooding in the forest, reducing the negative impacts of unseasonal
flooding and enhancing the benefit received from winter/spring flooding, through improved
flow management. Use of regulators is coordinated by the management agencies on both sides
of the Murray River, to ensure that optimal outcomes are achieved.
5
Policy and Organisational Setup for Achieving Sustainable River Basin Management
Organisational setup
The Murray-Darling Basin forms part of the territorial area of four States, covering threequarters of New South Wales, over half of Victoria, 7% of South Australia, 15% of
Queensland, and covers the whole of the Australian Capital Territory.
Co-ordination of the management and development of the resources of the Basin has been an
important issue for the various State and Commonwealth Governments since the 1860s. The
primary concerns initially related to navigation of the river system, followed by the need to
develop an agreement for sharing the water resources of the river system as irrigated
agriculture developed from the 1880s.
The River Murray Waters Agreement was signed in 1917, establishing the River Murray
Commission, with Commissioners from Victoria, New South Wales, South Australia and the
Commonwealth. This body was responsible for building, operation and management of water
storages, weirs and locks within the Murray River system, in order to regulate the river as a
basis for further development of agriculture and commerce in inland Australia. For the
following 60 years, the Commission was primarily responsible for development of increased
water storages, and the regulation of the river system to provide adequate water for
agriculture in the Basin. This period saw the construction of the major storages and weir
systems throughout the Basin.
Concerns developed about other resource management issues across the Basin from the
1960s, commencing with the salinity problems which were becoming very evident from that
time, and the role of the Commission was broadened in 1982 to include issues of water
quality, and subsequently a whole-of-catchment approach to natural resource management in
the Basin. This need for improved co-ordination of a wider range of issues resulted in the
formation of the Murray-Darling Basin Ministerial Council and the change of the River
Murray Commission into the current Murray-Darling Basin Commission, with a charter to
plan and co-ordinate natural resource management programmes throughout the whole Basin.
The Murray-Darling Basin Ministerial Council, established in 1985 under the MurrayDarling Basin Agreement, comprises Ministers of the various State Governments and the
Commonwealth Government responsible for water, land and the environment in the Basin,
and has included Queensland with the original three States since its agreement to join the
programme in 1991. The Ministerial Council sets policy and broad directions for planning
and management of the land, water and environmental resources of the Basin, with the
specific goals of maintaining and where possible improving water quality for all beneficial
uses, controlling and preventing land degradation and, where possible, rehabilitating land
resources to ensure their sustainable utilisation, and conserving the natural environment of the
Basin.
The executive arm of the Ministerial Council is the Murray-Darling Basin Commission, an
autonomous organisation with responsibilities to each of the participating Governments. Two
Commissioners are provided from each of these Governments, normally representing the
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relevant departments responsible for land, water and environment management for each of the
jurisdictions.
The Commission is responsible for providing administrative support and advice to the
Ministerial Council, managing distribution of River Murray waters to each of the States
according to the agreed sharing principles, and administers various approved strategies for
resource management within the Basin. Specific water responsibilities of the Commission
include regulation of the Murray River, water quality monitoring, co-ordination of river
management throughout the Basin and encouragement of practices to improve land use, water
quality and waste treatment.
The Commission also works with each of the governments and their relevant departments to
co-ordinate improved land and environmental management programmes within their areas of
responsibility, encouraging joint government actions and monitoring programmes within
individual States which may have an impact on other parts of the Basin.
Existing and proposed government policy statements
Since the establishment of the Murray-Darling Basin Ministerial Council and Commission, a
number of Basin-wide strategies have been developed and implemented, while others are in
the process of preparation. These strategies have been prepared to provide for co-ordinated
land, water and environmental protection and management, and are implemented after formal
agreement of the various constituent governments.
To date, the Murray-Darling Basin Ministerial Council has adopted the Salinity and Drainage
Strategy, the Natural Resources Management Strategy and the Algal Management Strategy,
while an Irrigation Management Strategy and a Wetlands Management Strategy are in the
process of finalisation. These strategies provide for co-ordinated management of resources
relevant to the long term well-being of the Basin, and are used to co-ordinate funding of
research, investigation and implementation projects and activities.
An audit of water use within the Murray-Darling Basin was commissioned by the Ministerial
Council in June 1993, to provide details on current water use in the Basin, documenting
trends and projecting those trends into the future to assess the impacts on existing
development within the Basin.
In June 1994, the Ministerial Council agreed on a river flow policy for the basin, “to maintain
and, where appropriate, improve existing flow regimes in the waterways of the MurrayDarling Basin to protect and enhance the riverine environment”. (MDBC, 1995) This policy
was then incorporated into the ambit of the audit to ensure that it included an assessment of
the impact of current diversion levels on river health.
As a result of serious concerns outlined in the Water Audit report over increasing diversions
of water for agricultural use within the basin, and the adverse impacts these are having on
river health, the Ministerial Council decided in June 1995 to cap water diversions within the
Basin in order to prevent further deterioration of water quality and environmental values
within the Basin’s river systems. This cap on water use consists of an immediate moratorium
on further diversions, while the precise details of the long-term cap and its implementation
are established.
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Existing and proposed enactments
The Murray-Darling Basin Act 1993 became operative on 6 October 1993. This legislation
incorporates the revised Murray-Darling Basin Agreement 1992, which was signed by the
four contracting Governments
Existing and proposed NGO and people’s participation
The Ministerial Council, under the Agreement, established a 21-member Community
Advisory Committee to provide independent advice from the various communities across the
Basin on natural resource management programmes and issues. The members of this
Advisory Committee are drawn from representatives of regional and special interest groups
across the Basin, including catchment management groups, environment and conservation
groups, and other community organisations.
While this Advisory Committee is the primary formal avenue for advice and community input
to the programmes of the Council, there is also a strong commitment to wide involvement of
the community at all levels in project development and implementation across the Basin. The
Ministerial Council also encourages and supports the involvement of local and regional
community groups in evaluation of programme proposals, implementation of approved
projects, and advice on strategy development.
Under the Native Title Act 1993, a Native Title Claim has been initiated by representatives of
the Yorta Yorta aboriginal community covering a significant portion of the lands within the
central section of the Murray River floodplain. This claim embodies both the attitude of the
aboriginal people to this land, for which they have a strong feeling of traditional ownership,
and a belief by the Yorta Yorta and other aboriginal communities that they should have a
much stronger voice in management of land and other natural resources.
While there has been a definite intent on the part of various State and Commonwealth
governments to facilitate more active involvement of all communities, including those of
aboriginal origin, in land and water management issues, there is dissatisfaction on the part of
some of the aboriginal communities in relation to their ability to influence management of
resources for which they feel a strong sense of ownership.
FUNCTIONS, USES AND ATTRIBUTES OF THE BARMAH-MILLEWA
WETLANDS IN RELATION TO RIVER BASIN MANAGEMENT
The Barmah-Millewa forest exhibits many values which are of varying degrees of significance
in the management of the Murray-Darling Basin. The following section focuses on those which
make a significant contribution to improved Basin management.
Regulation of River Murray waters, particularly for agriculture had a substantial impact on
frequency and timing of floods within the floodplains and wetlands of the Murray River. The
wetlands of the Murray River and associated tributaries rely to a substantial extent on a
pattern of winter/spring flooding to provide the water for their survival, with a natural pattern
of extreme variability in flooding over periods of years.
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The Barmah Forest wetland system, under natural conditions, received significant flood
flows. Since regulation of the river system the extent and frequency of flooding has decrease
substantially. The season of flooding has been altered, with flooding occurring in the later
part of the season, and the earlier winter flows being most reduced. The most severe reduction
is in the small to mid-range floods; the incidence of major floods has not been markedly
altered, due to the limited capacity of upstream storages (Bren, undated).
In addition, the use of the Murray River for deliver y of irrigation water to downstream users
throughout the spring/summer/autumn irrigation period results in the river running at bankfull
capacity for that period. Any sudden decrease in demand for delivery of irrigation water, for
example as a result of rainfall in irrigated areas, will lead to a requirement for release of
surplus flows (termed ‘rain rejection flows’) into the forests, leading to unseasonal summer
flooding of forest wetlands.
Similarly, summer rainfall in upstream catchments, and particularly in the Ovens River,
which is largely unregulated, will result in excess flows down the river (termed ‘river
freshes’) and further unseasonal flooding of the wetlands. These are often combined with rain
rejection flows, and impact not only on ecological values, but may also impact on human
activities within the forests, including logging operations and recreation and tourism
activities.
When overbank flows occur, they initially commence through the natural effluents which
direct water from the river into creeks and wetlands throughout the forest, and then, as flows
increase, natural river levees are overtopped on a broadscale basis.
Major flood events cannot be effectively managed within the wetlands, as they quickly
overwhelm any structures or physical attempts to direct or manage flows. However, the minor
to moderate floods are the events most limited and affected by regulation within the overall
river system. The wetland-specific water management plans which have been developed to
date attempt to maximise the benefit of flows at these lower levels through the installation
and operation of internal and marginal structures such as regulators and through
modifications to channels.
The wetland systems of the Murray River floodplain are used to a limited degree as a water
supply for domestic and local irrigation supply for adjoining landholders.
Apart from irrigation, the other major focus of management of Murray-Darling Basin waters
is the requirement to provide for an adequate supply of water, in terms of both quantity and
quality, for the city of Adelaide, with a population of approximately 1 million. All of the
rivers of the Basin tend to become increasingly saline and turbid as they flow westward, with
the result that water quality becomes a major concern. These increases in salinity and
turbidity are largely due to natural causes such as groundwater inflows, catchment inputs and
evaporation. Catchment degradation has assisted in acceleration of these trends.
As all major tributaries enter the Murray River above the water offtakes for Adelaide,
integrated management of waters is essential across the Basin, especially as the quality and
quantity of water reaching the Murray from some of these tributaries may be highly variable.
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Pollutants enter the Murray River, its tributaries, and its associated wetlands, from a variety
of agricultural and urban sources. The principal point sources of waste water disposal to the
river system consist of urban stormwater, irrigation drainage, which is the largest source of
input to the rivers, and sewage treatment plant effluent (Shafron et al., 1990). Nutrients also
enter the river system from diffuse sources, comprising runoff from non-irrigated pasture,
croplands and forest lands across the catchment.
Urban stormwater runoff is a significant point source of pollution along the river system,
contributing nutrients, oils, heavy metals, and micro-organisms, particularly in the first rains
after summer. Irrigation drainage introduces and sewage treatment plant effluent also
contribute to pollution.
Within the Murray-Darling Basin, the Murray River remains the only avenue of disposal of
farm drainage water, where this water cannot be utilised as an on-farm resource. Agricultural
drainage has two major impacts on the waterways, wetlands and riparian zones of the MurrayDarling Basin: through deposition of nutrients in increasing quantities into the rivers and
streams, and disposal of salt to the same waterways.
The Salinity and Drainage Strategy (MDBMC, 1988) and the Algal Management Strategy
(MDBMC, 1994) have both been developed to address specific land management problems,
but the two strategies conflict to some extent. While drainage is encouraged, within
management limits, to reduce salinity and waterlogging, off-farm drainage is also
discouraged, in attempts to reduce the amount of nutrients reaching the waterways of the
Basin.
Salinity is regarded as the principal environmental issue across the Basin as a whole, affecting
the long-term and immediate future of the Basin. Saline flows reach the Murray River and its
major tributaries as a result both of natural inflows to the river system and through disposal of
agricultural drainage water from surface and sub-surface drainage, particularly from irrigated
sections of the Basin.
The Murray-Darling Basin Salinity and Drainage Strategy (MDBMC, 1988) provides for a
coordinated programme to ensure that disposal of saline drainage to the Murray River is
managed to minimise impacts on downstream users, and, in particular, on the supply of water
to Adelaide. Under this strategy, each State which requires disposal of saline drainage to the
Murray may only discharge an agreed total amount of salt through release of saline drainage
water at times when the river flow rates reach pre-determined levels.
Salinity has been identified as the greatest long-term environmental threat to the land, waters
and ecology of the Murray-Darling Basin. As salinity levels in wetlands increase, alterations
occur to vegetation, fauna and soils, with different flora and fauna species having different
responses to and tolerances of salinity. Nutrients from both organic and inorganic sources,
which are of considerable concern across the Basin, contribute to outbreaks of blue-green
algae, which are a human health concern, impact on agricultural productivity, and affect the
abundance and species composition of the zooplankton. Excessive nutrients also promote
eutrophication and can result in fish kills within rivers, and lead to substantial modifications
of wetland vegetation (Barmuta, 1989).
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Deposition of sediments within the forests and wetlands reduces problems associated with
deposition further downstream within the river channels, but excessive sedimentation also
causes changes in water flow patterns within the wetlands where deposition occurs. This may
impact on individual wetlands or specific sections of them, leading to changes in water
regimes and associated vegetation and fauna.
The Barmah-Millewa forest is an important recreational destination for visitors from southern
New South Wales and northern Victoria. Visitors come primarily from within a 200 km radius.
Principal recreational activities are swimming, boating (motorised and other), fishing, bird
watching, bushwalking, hunting, horse riding and camping.
The forests of the wetlands and river floodplains, whether private land or public land, have
long been utilised by the farming community as a resource for grazing of sheep and cattle.
Management of wetlands and floodplains on public lands in the Basin generally now only
allows for grazing by cattle, as the more intensive grazing habit of sheep was considered to
have unacceptable impacts on forest grasses and other flora, including tree regeneration.
Grazing of wetland forests has been identified as potentially having a detrimental impact on
ecological values. Undesirable impacts of grazing identified include trampling of river and
wetland banks, broad-scale pugging of wetland soils, excessive selective grazing of wetland
vegetation, reduction of regeneration, and addition of nutrients to waters and wetlands (Bacon
et al., 1992).
Urban and agricultural development across the Murray-Darling Basin has resulted in
extensive clearing of native vegetation throughout much of the catchment and extensive
drainage of wetlands in much of the broad floodplain of the main rivers and their tributaries.
Consideration is given to the relationships which may exist between the contribution of
particular wetland benefits to river basin management, and the maintenance of naturally
functioning river basin and wetland systems with all their normally accruing benefits and
costs. These benefits have the potential to contribute to management of the Murray-Darling
Basin.
The consequences of using those wetland benefits are examined, and the processes used to
manage any potential impacts of the use of the wetland in Basin management are outlined.
The discussion focusses on the impact of the use of wetland benefits on other wetland values,
and does not encompass fully the impacts of wetland benefit use on river basin values. This is
partly as a consequence of the relative paucity of information regarding many of the basin
values, and hence an inability to specify adequately the level of impact of use of wetland
values on those values.
Floodplain wetlands play an important role in flood mitigation along the rivers of the MurrayDarling Basin. While much of the broad floodplain has been cleared, drained and developed
for agriculture, the immediate floodplain remains generally forested and provides a significant
temporary storage of water during flood times.
These flood flows provide the essential recharge of water to the wetlands along the river
during winter and spring. It has been estimated that the Barmah-Millewa forests retain
11
approximately 10% of the water entering the forests during the years of minor to moderate
flooding, although a much lower proportion of major flood flows is retained.
Upstream storages have reduced the number and extent of flood flows along the river, with
the result that the forests now play a lesser role in flood mitigation overall, and especially as a
result of the reduction in the minor to moderate floods.
Wetlands along the Murray River floodplain are often identified by farmers of adjoining land
as a source of water for minor irrigation and for domestic and stock water supply uses, with
pumping systems established on many permanent or semi-permanent water bodies. Within
the Barmah-Millewa forest there are no major withdrawals of water from wetlands for these
purposes.
Extraction and use of water is controlled by a licensing system administered by the relevant
State Water Authority within overall quantity limits established for each Authority. Licences
for extraction of water from wetlands will only be issued after consultation with and
agreement from the State land management authority responsible for each State’s section of
the forest. Considerations in any licensing proposal will give a high priority to an assessment
of the impact on ecological values, especially in view of the significance of these wetlands on
a State, national and international basis.
Impacts of benefit use
Within the Murray-Darling Basin, the Murray River remains the only avenue for disposal of
excess farm drainage water. Active programmes for drainage and disposal of excess water
from irrigated farms exist across the Basin, and these are increasing steadily in efforts to
retain or improve agricultural productivity by reducing waterlogging, pumping of
groundwater to control rising water tables, and disposal of excess irrigation water.
Natural and artificial wetlands play an important role in removing nutrients and toxicants
from rivers and waste water within the Basin. Conversely, nutrients, salt and other pollutants
in inflowing water may also cause significant degradation of natural wetlands if delivered in
sufficient quantities and frequency.
While it is clear that natural wetlands play an essential routine role in maintenance of water
quality in the Murray-Darling Basin, there are no data on the level of improvement of Basin
water quality which may be attributed to individual wetlands.
With regard to the pollution of wetlands from inflowing waters, plans are being developed to
avoid significant detrimental impacts of the increasing amounts of water-borne pollutants on
wetlands across the Basin (MDBMC, 1994). The proposed actions include reduction in offfarm and urban drainage quantities, carefully managed timing of drainage releases to the
rivers to coincide with periods of high flows in the rivers, as well as improved management
of catchment land at the source of these problems.
Sediment Reduction
Siltation is known to be occurring in upper reaches of the Darling River and others, as a result
of changed land management practices. There has been record of increased sediment
12
deposition in wetlands along the river floodplains. Trapping of sediment by the floodplain
wetlands reduces the impact of silt within the river channels, however, deposition of
sediments within the wetlands modifies water flow patterns, and may accelerate degradation
of the wetlands such as accelerated vegetation modification.
With the wetland providing a trap for a significant proportion of the sediment carried within
the river system, the accelerated input of sediment through land degradation within the
catchment remains a serious concern.
Impact management processes
The land management issues have been identified in each of the sub-catchments of the Basin
(MDBC 1987), and the Natural Resources Management Strategy has been developed to
provide a framework for a co-ordinated approach to reducing soil loss and soil movement in
the rivers. Improved land management in catchments throughout the Basin is being promoted
through a variety of community-based programmes, involving Total Catchment Management
groups and Landcare groups, with coordination and support being provided by the MurrayDarling Basin Commission programmes and by the various State Government authorities
with responsibility for these programmes.
Recreation and Tourism
As noted briefly in Table 11 above, the use of a wetland to provide recreational and tourism
opportunities may result in some impacts on other functions, uses and attributes of both the
wetland itself and the wider Basin.
In the case of the Barmah-Millewa forest, impacts on the wetland resulting from recreational
and ecotourism use include all of the impacts specified in Table 11. The more significant
impacts are those which involve the potential interference of recreationists with uses such as
flood mitigation and forestry and agricultural production.
Impact Management Processes
Forest Resources
Forest resource use and water-related benefits
The benefits of the forest which are directly and positively related to the volume of water
moving through or held in the forest including water quality amelioration and sediment
reduction as provided by the Barmah-Millewa forest have not been quantified
Forest resource use and sediment reduction
Aside from the diminished capacity of the wetland to manage large volumes of water, where
such flows would diminish access to logging areas, there is no direct management link or
tradeoff process between the use of the forest resources and the impacts of such use on the
sediment reduction capacity of the wetland.
Logging contribute to sediment load in waters exiting the wetland. However, in the Barmah
section of the forest logging is conducted under the provisions of the Victorian Code of Forest
Practice, which provides, inter alia, for the protection of highly erodible sites such as water
13
course margins. The restrictions on logging practice obtained in the Code, coupled with the
exclusion of large areas of the forest from logging (as detailed in Section 2) and controls on
the volume of timber which may be harvested in any one year, assist in the minimisation of
the downstream impacts of logging on water quality.
Forest resource use and flora and fauna resources
The protection of flora and fauna resources in the Barmah section of the forest is
accomplished through a hierarchy of measures. The management plan for the Barmah section
provides for the restriction of timber harvesting to specified areas, and provides specific
protection for areas of potentially high conservation value. In addition, the selection of coupes
to be subject to logging in any year is subject to detailed assessment and documented in a
Wood Utilisation Plan.
The controls noted above, including the zoning of logging away from areas of high
conservation value, assist in the reduction of the impacts of logging on fauna habitats within
Barmah.
Flora and Fauna Resources
The most significant interactions between the use of flora and fauna resources, and the other
various wetland values in the Barmah-Millewa forest are those which involve a relatively
high level of modification of the natural systems operating in the forest. These are briefly
discussed below.
Impact management processes
Flora and fauna resources and flood mitigation
The requirements for conservation of viable flora and fauna communities in the BarmahMillewa forest limit the capacity of the wetland to be used for year-round flood mitigation. As
noted earlier, there have been substantial changes to the vegetation of the forest since the
commencement of large-scale regulation of the Murray River, and the consequent alterations
to flow regimes.
Agriculture
Some of the impacts of wetland agriculture on other wetland values are impacts of cattle
grazing. Within the Barmah-Millewa forests, cattle grazing is an important component of
local farming activities. However, grazing of wetlands is also considered by many to be an
activity which can cause significant degradation to ecological values, through selective
grazing of wetlands vegetation, reduction in plant regeneration, damage to stream banks,
compaction of soils and introduction of weed species to wetlands and forests.
A number of studies of cattle grazing impacts have been carried out to determine the extent of
impacts and identify possible modifications to grazing regimes, and cattle numbers and
movements are managed and monitored within the forests.
THE INTEGRATION OF WETLANDS INTO RIVER BASIN MANAGEMENT
14
The use of wetland benefits to enhance river basin management should ideally involve
optimisation of the use of those wetlands. Wetlands should be managed in such a manner as
to maximise net social benefit, whilst ensuring that their capacity to yield the full complement
of functions, uses and attributes is maintained.
The use of the Barmah-Millewa forest to provide benefits for management of the MurrayDarling Basin and, specifically, the Murray River, is complex. It involves a series of
frequently uncoordinated tradeoffs between the benefits and costs of wetland use for river
basin management purposes. Many of these tradeoffs are not recognised either formally or
otherwise. Those tradeoffs and conflicts which are explicitly recognised and assessed are
examined in a variety of fora, often by different agencies.
However, it is clear that wetlands such as the Barmah-Millewa forest can provide significant
levels of benefits to river basin management, involving a number of functions, uses and
attributes of the wetlands. A number of these have been examined for the Barmah-Millewa
forest in the preceding material.
The Barmah-Millewa forest has been subject to a degree of research and management effort,
and a level of public interest, uncommon for other wetlands along the Murray River. This
reflects in part the appreciation of the biophysical and aesthetic characteristics of the forest.
The forest represents, therefore, an isolated and special situation with regard to knowledge of
the potential for, and impacts of, its use in river basin management.
There is in general a paucity of data for other wetlands which may provide benefits to basin
management. However, extrapolation from the Barmah-Millewa example can provide
significant insight into the key factors for the successful integration of wetlands into river
basin management.
The optimisation of use of wetland benefits in river basin management requires a number of
factors including:
Recognition of wetland functions, uses and attributes
Wetlands provide a suite of benefits to the Barmah-Millewa forest. These benefits may be
classified as either functions, uses or attributes. The accurate identification of all wetland
values (or functions, uses and attributes) is an essential precursor to the optimisation of their
use
Determination and quantification of river basin management requirements for wetland
services
Those wetland values specified in the preceding stage which may contribute to the
management of the river basin must be clearly understood and specified.
Identification and quantification of any impacts of river basin management requirements on
wetland values
The impacts of the use of the specified level of wetland values on other wetland values must
be identified and specified. In the example developed above, the use of the wetland to
mitigate floods in the basin may reduce the potential for forestry and for recreation within the
wetland. Similarly, the increased frequency and duration of floods may increase the
15
production of pest species such as feral pigs and increase the distribution and/or production of
particular weed species.
Optimisation of the use of the wetland functions, uses and attributes
Optimisation of the use of wetland values may involve examination of the outcomes of uses
from a number of viewpoints. Analysis of the allocation of wetland resources to particular
uses may require comparison of outcomes over time; between geographic areas; between
different social/community groups; and at varying scales.
Optimal allocation of wetland resources requires, inter alia the determination of criteria for
the weighting and aggregation of the outcomes of the use of wetland values in river basin
management; and the existence of the necessary legal and institutional frameworks within
which to perform the tradeoffs which are identified as required to achieve optimisation.
Conceptually, the basis for an ideal optimisation process can be expressed as follows.
Index (A) =  [(Outcome;) (Probability;) (Weighting;)]
Index (A) = the outcome of the use of Wetland Benefit A at a specified level and time
n
=
the number of wetland values affected
Outcome; = the change in Wetland Value; as a consequence of the use of A as specified
Probability;= the probability of Outcome:
Weighting; = the weighting ascribed to Outcome;
Under ideal circumstances, alternative allocations of wetland resources would be compared
using such a conceptual basis. Where the outcomes of the use of wetland benefits can be
valued, a cost-benefit analysis can be conducted, in order to enable aggregation of otherwise
disparate outcomes. More commonly, outcomes cannot be or are not fully valued, for a range
of technical and financial reasons.
Consequently, the processes most usually employed in attempts to ensure optimal use of
wetland resources are based on a mix of social, political, economic and bureaucratic
interactions, supported by varying amounts of technical data.
CONCLUSION
The various governments, working through the Murray-Darling Basin Ministerial Council
and Commission, have made substantial progress in developing a Basin-wide approach to
tackling land and water management problems. The co-ordination achieved in dealing with
these issues comes from a shared concern over the extent and expansion of a number of major
problems, including land and water salinisation, nutrient impacts on waterways, inefficiencies
in water use, and degradation of the natural environment.
However, there is still a long way to go to achieve broad community understanding and
ownership of all of these issues, and much remains to be done in integrating programmes to
solve these problems. Each strategies has been developed independently, and although there
has been substantial community consultation in the process, each strategy has still focussed
largely on its primary concern, without looking broadly enough to ensure that there is a
blending of objectives. While this has mostly been due to a lack of understanding of the wider
issues as each strategy is developed, there is still a strong pressure for specific objectives to
16
be achieved quickly to satisfy organisational and political needs. Greater efficiencies in
reaching long term stability of environmental processes may now be achieved by reviewing
these to define areas of duplication, overlap and conflict.
While there have been major gains in management of the Barmah-Millewa wetlands, with
strong community interest and a shared commitment to work to restore the ecological balance
of the wetlands as far as possible, this level of input is yet to be expanded to similar wetlands
along the rivers. There is still no clear approach to developing an integrated approach to
provision of water for environmental values for wetlands along the Murray River, and the
wider community still tends to view each wetland as a separate entity, without recognising the
very high level of significance of the wetland network as a whole.
Decisions on the use of wetland values are made in a fragmentary, uncoordinated manner,
with little explicit consideration given to the optimisation of the uses of benefits. The
potential contributions of wetland benefits to river basin management are frequently
unrealised, and the costs of those contributions are rarely recognised. The guidelines
presented above are intended to provide an outline of the mechanisms by which this situation
could be avoided, and the use of wetland values optimised. The decision-making process
employed in determining the use of the values of the Barmah-Millewa forest provides a
partial illustration of the use of this ideal process.
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FURTHER READING
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