1
2
1 Northern Territory Department of Natural Resources, Environment, the Arts and Sport
2 Environmental Research Institute of the Supervising Scientist
Low flows report series – June 2012

This paper is part of a series of works commissioned by the National Water Commission on key water issues. This work has been undertaken by the Northern Territory Government and the Environmental
Research Institute of the Supervising Scientist, via the Tropical Rivers and Coastal Knowledge research hub at Charles Darwin University, on behalf of the National Water Commission.
NATIONAL WATER COMMISSION — Low flows report series i

© Commonwealth of Australia 2012
This work is copyright.
Apart from any use as permitted under the Copyright Act 1968 , no part may be reproduced by any process without prior written permission from the Commonwealth.
Requests and enquiries concerning reproduction and rights should be addressed to the
Commonwealth Copyright Administration, Attorney General’s Department, National Circuit, Barton
ACT 2600 or posted at www.ag.gov.au/cca .
Online/print: ISBN: 978-1-921853-80-7
Published by the National Water Commission
95 Northbourne Avenue
Canberra ACT 2600
Tel: 02 6102 6000
Email: enquiries@nwc.gov.au
Date of publication: June 2012
An appropriate citation for this report is:
Dostine PL & Humphrey CL 2012, Macroinvertebrate responses to reduced baseflow in a stream in the monsoonal tropics of northern Australia, National Water Commission, Canberra
This paper is presented by the National Water Commission for the purpose of informing discussion and does not necessarily reflect the views or opinions of the Commission or the Northern Territory
Government.
NATIONAL WATER COMMISSION — Low flows report series ii

Executive summary ................................................................................................................... vi
Report context .......................................................................................................................... vii
1.
Introduction ...................................................................................................................... 1
2.
Methods ........................................................................................................................... 2
2.1.
Site description ..................................................................................................... 2
2.2.
Hydrological data .................................................................................................. 3
2.3.
Field sampling procedures ................................................................................... 3
2.4.
Laboratory processing of invertebrate samples ................................................... 4
2.5.
Data analysis ........................................................................................................ 4
2.6.
Multivariate data analysis ..................................................................................... 4
2.7.
Univariate data analysis ....................................................................................... 5
3.
Results ............................................................................................................................. 6
3.1.
Streamflow patterns ............................................................................................. 6
3.2.
Spatial and temporal patterns in water quality ..................................................... 7
3.3.
Macroinvertebrate community composition .......................................................... 7
3.4.
Multivariate analysis of community data .............................................................. 9
4.
Discussion ......................................................................................................................16
4.1.
Patterns in community composition....................................................................16
4.2.
Potential mechanisms for the switch between community states ......................16
Appendix 1: List of taxa with trophic groups, SIGNAL scores, and rheophily and thermophily scores ...................................................................................................................18
Appendix 2: Variation in six water quality parameters at sites 1, 5 and 8, 1987 –95 ...............20
References ...............................................................................................................................21
Other reports in this low flow series ................................................................................22
Table 1: Geographic location of macroinvertebrate sampling sites in the upper South
Alligator River. ..................................................................................................................... 3
Table 2: Number of sample quadrats per site per year ............................................................. 4
Table 3: Percent abundance of dominant orders of macroinvertebrates in pooled sample,
1987 –97. ............................................................................................................................. 8
Table 4: List of taxa contributing >1% of number of individuals in pooled sample, 1987 –
97. ....................................................................................................................................... 8
Table 5: Distribution of nine groups of site-year samples based on SIMPROF procedure. .... 10
Table 6: Top five characteristic insect families, in ascending order of influence in the classification (5 = most influential), as identified from CLUSTER and SIMPER analyses. ........................................................................................................................... 10
Table 7: Table of PERMANOVA results identifying spatial and temporal variation in macroinvertebrate community structure. .......................................................................... 11
Table 8: Table of PERMANOVA results identifying effect of the covariate instantaneous flow on spatial and temporal variation in macroinvertebrate community structure. .......... 12
Table 9: Results of SIMPER analysis showing taxa contributing to 50% of cumulative average dissimilarity between groups c and i . .................................................................. 12
Table 10: Results of SIMPER analysis showing taxa contributing to 50% of cumulative average dissimilarity between groups i and f . ................................................................... 12
Table 11: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data for years 1987 –97. ... 14
Table 12: Model parameters of preferred model of variation in taxa richness of stream macroinvertebrates. .......................................................................................................... 14
Table 13: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data from 1987 –92. .......... 15
Table 14: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data from 1993 –97. .......... 15
NATIONAL WATER COMMISSION — Low flows report series iii

Figure S1: Context of reports produced for the Low Flow Ecological Response and
Recovery Project. Each circle represents the location of individual case studies and the size of each circle represents the spatial extent of each case study .......................... vii
Figure 1: Macroinvertebrate sampling sites on the upper South Alligator River. ....................... 2
Figure 2: (a) and (b) Estimated daily flow (ML/day) at G8200052 (Gimbat) from
November 1990 to November 1991, and measurements of instantaneous flow at (c)
Gimbat and (d) El Sherana in August, September and October. ....................................... 6
Figure 3: Wet season (November to April) rainfall in Katherine, and 10-year average of wet season rainfall. ............................................................................................................. 7
Figure 4: Patterns of abundance of common taxa in relation to dry season flow volume,
1987 –97 (May–October, station G8200052). ..................................................................... 9
Figure 5: a) Compositional similarity of samples shown in MDS ordination space; b), c) and d) serial trajectory of sites 1, 5 and 8. ....................................................................... 11
Figure 6: a.) Principal coordinates analysis of sample data overlain by sample groups showing vectors for taxa with Pearson correlation coefficients >0.75; b.) principal coordinates analysis of sample data overlain by sample groups showing vectors for extrisic variables with Pearson correlation coefficients >0.5. ........................................... 13
Figure 7: Estimates of taxa richness (± 95% confidence limits) of macroinvertebrates,
1987 –97. ........................................................................................................................... 14
Figure 8: a.) Scatter-plot of taxa richness and instantaneous flow data, 1987 –92; b.) scatter-plot of taxa richness and instantaneous flow data, 1993 –97. ............................... 15
NATIONAL WATER COMMISSION — Low flows report series iv

This report was completed with the support of the Tropical Rivers and Coastal Knowledge (TRaCK) research hub. TRaCK receives major funding for its research through the Australian Governm ent’s
Commonwealth Environment Research Facilities initiative, the Australian Government’s Raising
National Water Standards Program, Land and Water Australia, the Fisheries Research and
Development Corporation and the Queensland Government’s Smart State Innovation Fund.
The data analysed in this report were acquired by the Australian Government Department of
Sustainability, Environment, Water, Population and Communities (DSEWPaC) Supervising Scientist
Division (SSD) (1987 –1994) and from funding provided to the SSD from Environment Australia (now
DSEWPaC) through the Land and Water Resources Research and Development Corporation, as part of the National River Health Initiative (1995 –97).
NATIONAL WATER COMMISSION — Low flows report series v

For streams that flow year-round, knowledge of ecological responses to long-term variation in flow, particularly diminished late season flows, is required to manage water extraction practices.
This study examines the response of macroinvertebrate communities of riffle habitats of the upper reaches of the South Alligator River (Northern Territory) to variation in late dry season flows over 11 years that spanned declining, then increasing, baseflow phases. Sites within a 23 km stretch of the river were sampled in the late dry season (October) from 1987 to 1997.
Over the 11 years studied, marked changes in community structure occurred based predominantly on family-level analysis: initial dominant taxa including Leptophlebiidae and Baetidae declined in abundance, while Caenidae and Pyralidae increased in abundance. There were concurrent temporal changes in trophic organisation and taxa richness. Generalised linear modelling of the relationship between flow and taxa richness found no evidence of a flow effect on taxa richness during the declining phase (from 1987 to 1992) or the increasing phase (from 1993 to 1997). Despite a return to high-flow conditions in the latter part of the study there was only limited evidence of a return to macroinvertebrate communities that characterised the early higher-flow phase. Thus while a threshold response to declining flow was evident, responses beyond this were largely unrelated to flow and were unpredictable, particularly for previously dominant taxa.
NATIONAL WATER COMMISSION — Low flows report series vi

This report is part of a larger series of reports produced for the National Water Commission’s Low
Flow Ecological Response and Recovery Project (Figure S1). This report presents one of 11 hydroecological case studies. The purpose of the case studies is to test hypotheses that relate ecological process and function and biological traits to key hydrological measures that are affected by low flows.
A summary of the findings in this report and the other case studies are contained in Synthesis of case studies quantifying ecological responses to low flows (Marsh et al. 2012).
Guidance on ecological response and hydrological modelling for low-flow water planning
Low-flow hydrological classification of Australia
Review of literature quantifying ecological responses to low flows
Early warning, compliance and diagnostic monitoring of ecological responses to low flows
Synthesis of case studies quantifying ecological responses to low flows
Figure S1: Context of reports produced for the Low Flow Ecological Response and Recovery Project.
Each circle represents the location of individual case studies and the size of each circle represents the spatial extent of each case study
NATIONAL WATER COMMISSION — Low flows report series vii

Flow regime has a profound influence on the ecological processes and patterns in streams (Resh et al. 1988; Hart & Finelli 1999). Flow controls habitat availability and suitability, influences substrate composition and water chemistry, and the delivery of nutrients and food particles. Decreases in flow cause decreases in wetted area, water depth and water velocity, increases sedimentation and changes thermal regime and water chemistry (Dewson et al. 2007). Extreme low flows can alter habitat connectivity (Stanley et al. 1997) and lead to increased algal growth (Poff et al. 1990).
Knowledge of the effects of low-flow events comes from observational studies of drought (Boulton
2003), observations of paired streams with differing flow regimes (Miller & Golladay 1996), experimental streamflow diversions (Walters & Post 2011) and analysis of broadscale spatial (Brooks et al. 2011) and temporal (Humphrey et al. 2000) patterns in community composition. Reported effects vary depending on the temporal and spatial scale of the low-flow event. Manipulation of natural streamflow changed abundance, community composition and body-size distribution of aquatic insects
(Walters & Post 2011). Drying of intermittent riffles restricted the establishment of flow-dependent taxa (Miller & Golladay 1996).
For sections of stream ecosystems in northern Australia with permanent flow, there are few empirical studies of the impacts of low flows, and thus little basis for management of impact of modified flow regimes. We report here a study of the effects of long-term variation in the natural flow regime of a stream contained in an intact landscape in northern Australia. In the monsoonal tropics of northern
Australia, flow patterns are closely linked to predictable monsoonal rainfall. This results in high flows interspersed with flood pulses from November to April, followed by a period of steadily declining flows through the mostly rainless dry season months from May to October. While the absence of rainfall in the dry season means many streams cease to flow well before the onset of the next wet season, streamflow is maintained by seepage from groundwater and provides a stable and predictable habitat over the entire dry season.
The upper reaches of the South Alligator River (SAR) within Stage III of Kakadu National Park are spring-fed and provide permanent habitat for diverse fish and macroinvertebrate communities, as well as habitat for semi-aquatic reptile species including freshwater crocodile Crocodylus johnstoni and the pig-nosed turtle Carettochelys insculpta . Studies of the aquatic fauna in the upper SAR were initiated in 1987, in response to concerns about the effects of proposed mining activity at Coronation Hill.
Studies of macroinvertebrate communities of riffles sought to provide pre-mining baseline data and extension of this original baseline now provides a substantial long-term dataset to examine links between macroinvertebrate community structure and inter-annual variation in baseflow.
NATIONAL WATER COMMISSION — Low flows report series 1

Eight sites were sampled along a 23 km stretch of the upper SAR near Coronation Hill within Stage III of Kakadu National Park (Figure 1). Stage III of the national park was declared in June 1991 after a
Commonwealth decision that mining activity at Coronation Hill would not proceed. The SAR upstream of and near Coronation Hill is braided, though the river is confined to a single channel downstream of a point approximately 1 km below Coronation Hill. In these upper reaches, the river is perennial with flow minimal in the late dry season. The river is characterised by shallow riffles alternating with short to long (up to 1 km) pools of up to 3 m in depth. Pools are bordered mostly by dense growths of
Pandanus aquaticus shrubs, some Melaleuca and Syzygium spp. and, further downstream, stands of
Bambusa arnhemica . The substrates consist of sand in the pools, and sand, gravel, cobbles or root mats in riffle areas and on and under incised banks. There is generally an absence of aquatic macrophytes. Sites differed in characteristics such as shading by riparian vegetation and proximity to large pools or riffle beds upstream. Sites 1 to 5 were clustered within a distance of 6 km, with remaining sites separated by river distances of several kilometres (Figure 1, Table 1). While all eight sites have perennial flow in most years, flow diminishes downstream, and in low-flow years sites 7 and 8 approach cease-to-flow conditions. Further details of site characteristics are given in Dostine et al. (1992).
Figure 1: Macroinvertebrate sampling sites on the upper South Alligator River.
Source: ARRRI (1988)
NATIONAL WATER COMMISSION — Low flows report series 2

Table 1: Geographic location of macroinvertebrate sampling sites in the upper South Alligator River.
Data from Dostine et al. (1992)
Site
4
5
6
7
1
2
3
8
Elevation (AHD) (m)
86
83
82
80
78
70
66
60
Distance from site 1
(km)
0
2.35
3.14
4.73
6.25
12.25
16.2
22.85
Catchment area
(km 2 )
316
377
377
377
377
764
1,251
1,368
Flow data (ML/day) were available for two Northern Territory Government gauging stations in the study reach: gauging station G8200052 located immediately upstream of the Gimbat causeway near
Coronation Hill and just downstream of sampling site 3, and gauge station G8200045 located near El
Sherana just downstream of site 7. The catchment area at station G8200052 is approximately 377 km 2 and at station G8200045 is approximately 1250 km 2 . For the purposes of this study, the flow records for sites 3 and 7 corresponded with the data arising from gauging stations G820052 and
G8200045 respectively. Streamflow was measured by Northern Territory Government hydrologists at
G8200052 on 274 occasions from 1958 to 2007, including 53 occasions during the late dry season months of August, September and October. Streamflow was measured at G8200045 on 74 occasions from 1985 to 2003, including 18 occasions during the late dry season months of August, September and October. Streamflow was also measured on five occasions in October at several sampling sites by Supervising Scientist Division staff. Despite some anomalies in the flow record in some years, these data, together with the daily streamflow estimates at G8200052 and G8200045, were used to infill (by regression) flow estimates at the time of sampling for the remaining six sampling sites using the relationship between flow and river distance in each year. Estimates of dry season flow volume
(May to October) were calculated using data from station G8200052.
Benthic macroinvertebrate samples were collected from the riffles in substrate dominated by ‘small pebbles ’ (16–32 mm size class). This riffle substrate provided a suitable and common habitat among sites for routine study. On each sampling occasion and at each site, four samples were collected using a Surber sampler. Benthic samples were scooped from within a 25 cm metal quadrat into a 500
µm mesh net. Invertebrates and associated organic material were separated from coarse inorganic material by elutriation. All invertebrates and fine organic material retained on a 500 µm sieve were collected and preserved with 70 per cent ethanol for later laboratory processing. Samples were collected in various months over the entire study period but for this assessment samples from the late dry season month of October are used, when flow is most stable and predictable. From 1987 to 1995 samples were collected from eight sites, and from 1996 to 1997 samples were collected from sites 1,
5 and 8 only. Ten samples were lost or desiccated before processing, leaving a total of 302 replicate quadrat samples (Table 2).
NATIONAL WATER COMMISSION — Low flows report series 3

Year
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
All years
Table 2: Number of sample quadrats per site per year
Site
5
4
4
4
4
4
4
4
4
4
3
4
4
-
-
4
4
4
4
4
4
4
4
2
3
-
-
4
4
4
4
4
4
4
4
4
2
-
-
4
4
4
4
4
4
4
4
4
1
4
4
4
4
4
4
4
4
4
4
2
42 36 36 34 43
6
-
-
4
4
4
4
4
4
4
4
1
7
-
-
4
4
4
4
4
4
4
4
3
33 35
8
4
4
4
4
4
4
4
4
4
4
3
43 302
Total
32
32
32
12
12
32
32
32
32
31
23
At each site and on each sampling occasion, a number of water quality variables were measured.
Measurements were made in situ in the early morning (usually before 0900) one or two days after the benthic samples were collected. Surface water temperature (0.1 m depth) was read using a calibrated mercury thermometer, with conductivity measured to the n earest 1 µS/cm with an Activon model 301 conductivity meter, and dissolved oxygen measured with a Hach model 16046 dissolved oxygen meter. At each site, water samples were collected for later laboratory analysis of a suite of physicochemical variables. Water quality data are not available for 1996 or 1997.
Invertebrate specimens were hand-picked from detritus placed in a petri dish under a Wild M3, M8 or
MZ8 microscope. Identifications were conducted to family level using regional taxonomic keys.
Abundance data arising from each of the four replicate samples for each taxon at each site and on each sampling occasion were tallied to calculate percentage of total number of individuals in the pooled sample, from 1987 to 1997. The mean number of individuals per replicate by year was calculated for the most numerous taxa. These data are presented graphically, together with estimates of the dry season (May to October) flow volume measured at Gimbat gauge station (G8200052).
Multivariate analyses were conducted using the software program PRIMER version 6.1.13 with the
PERMANOVA add-on version 1.0.3 (Clarke & Gorley 2006; Anderson et al. 2008). Abundance data for each macroinvertebrate taxon were averaged within sites for each year to give 78 site samples.
Data were transformed using log( x +1) before analysis. This is a moderate data transformation to give additional weight to species of intermediate abundance (Clarke & Warwick 1994). The Bray-Curtis dissimilarity measure was used to calculate the similarity of compositional structure among sites.
Discrete groups in the site data were identified using SIMPROF in the CLUSTER classification
NATIONAL WATER COMMISSION — Low flows report series 4

procedure. Non-metric multi-dimensional scaling (MDS) was used to display structural similarities, and the distribution of site-groups identified by SIMPROF. The serial trajectory of three sites with 11 years of data (sites 1, 5 and 8) was displayed on MDS ordinations to examine temporal trends in community structure. PERMANOVA was used to conduct a two-factor multivariate analysis of variance of differences in community structure among years and sites for data from sites 1, 5 and 8 from 1987 to
1997. In this analysis Years was a random factor and Sites was a fixed factor. The analysis was repeated using the covariate instantaneous flow. The PRIMER procedure SIMPER was used to identify those taxa discriminating between groups identified by SIMPROF.
Principal coordinates analysis (PCO) was used to display the structural similarity of samples and to display vectors associated with transformed taxa abundance and values for extrinsic variables.
Extrinsic vectors included instantaneous flow at each site, taxa richness, total abundance, mean
SIGNAL (biotic index) grade and percentage abundance by feeding group. Mean SIGNAL scores were calculated using published values (Chessman 2003); taxa without grades were not used in calculations. Most taxa were assigned to one of five feeding groups (collector-gatherer, collectorfilterer, herbivore, predator and shredder) although this classification masks the variability in feeding behaviours that can occur within individual families. For example, the common and ubiquitous dipteran family Chironomidae includes taxa that are predominantly predaceous (many Tanypodinae), herbivorous (many Orthocladiinae) or wood-boring (Chironominae genus Stenochironomus ). Taxa were also assigned biological trait values for rheophily and thermophily, using values derived by
Chessman (2009). A note of caution is placed on analysis of data using SIGNAL, functional feeding group and trait scores or values in that these are assumed similar for northern wet-dry tropical taxa, even though they have been derived for taxa usually from temperate locations in Australia. For taxa, only vectors with Pearson correlation coefficients >0.75 are shown and for extrinsic variables, only vectors with Pearson correlation coefficients >0.5 are shown. In addition, a dummy variable was created for a vector (Period) representing years 1987 to 1992 (-1) and years 1993 to 1997 (+1), based on results of multivariate classification.
The effects of Year, Site and Flow (instantaneous flow in cumecs) on taxa richness at the quadrat scale were modelled by generalised linear modelling using the R software package (R Development
Core Team 2008), and using data from sites 1, 5 and 8 from 1987 to 1997. Counts of taxa present in each quadrat were modelled using Poisson errors and the log link function. Kullback-Leibler (K-L) information was used to assign relative strengths of evidence to different competing models. The
Akaike Information Criterion, corrected for small sample size (AICc) (Burnham & Anderson 2002), was used as an objective means of model selection. The approach identifies the most parsimonious model or models from a set of candidate models given maximised log likelihood of the fitted model. AIC differences (ΔAICc) were taken as the relative level of empirical support for each model. Values between 0 –2 provide substantial support, 4–7 considerably less and >10 essentially none (Burnham &
Anderson 2002). Given AIC differences for each model, the relative likelihood of a set of candidate models was calculated using Akaike weights ( w i
) (Burnham & Anderson 2002). The weight of any particular model depends on the entire set of candidate models, and varies from 0 (i.e. no support) to
1 (complete support). A given w i is considered as the weight of evidence in favour of model i being the actual K-L best model of that set of models. In the tables of model results, k is the number of model parameters and pcdev is explained model deviance. Three sets of models were analysed using data from 1987 to 1997, from 1987 to 1992, and from 1993 to 1997.
NATIONAL WATER COMMISSION — Low flows report series 5

Flow is highly seasonal, and the flow year is typically divided into wet season months of high and variable flows from November to April, and dry season months with steady declining flows from May to October (Figure 2). Measurements of instantaneous flow from August to October by the Northern
Territory Government and Supervising Scientist Division show marked inter-annual variation. For the discharge record (from 1958), base-level streamflow peaked in the mid 1970s, declined to a minimum in the early 1990s and increased thereafter (Figure 2). This pattern is also evident in estimates of dry season flow volume (Figure 4), and matches the long-term patterns of variation in regional rainfall.
Wet season rainfall (November to April) at Katherine exhibits decadal-scale variation and periodicity
(Figure 3). a.) Daily flow Nov 1990
–Nov 1991 b.) Log daily flow Nov 1990
–Nov 1991 c.) Instantaneous flow Aug
–Oct, Gimbat d.) Instantaneous flow Aug
–Oct, El Sherana
Figure 2: (a) and (b) Estimated daily flow (ML/day) at G8200052 (Gimbat) from November 1990 to
November 1991, and measurements of instantaneous flow at (c) Gimbat and (d) El Sherana in
August, September and October.
Blue shading Northern Territory Government gauge measurements; red shading Supervising Science Division gauge measurements
NATIONAL WATER COMMISSION — Low flows report series 6

Figure 3: Wet season (November to April) rainfall in Katherine, and 10-year average of wet season rainfall.
Inter-annual trends in six water quality parameters measured from three sites (1, 5 and 8) in October from 1987 to 1995 are shown in Appendix 2. Electrical conductivity (EC) did not fluctuate markedly
(mean 119 µS/cm, range 104–136). Alkalinity was also relatively invariable but demonstrated a slight increase over time. EC and alkalinity were both slightly higher at the downstream site. Water temperature and dissolved oxygen (DO) fluctuated among years: temperature was higher at site 8 relative to upstream sites 1 and 5, while DO levels were lower at site 8 relative to upstream sites.
Turbidity and total organic carbon also fluctuated across the years and showed an increasing downstream trend. Total organic carbon peaked at all three sites in 1992, coincident with the period of lowest streamflows. The generally higher EC, alkalinity, turbidity and water temperature values but lower DO values, with increasing distance downstream, correspond with increasingly lower flows in
October measured in the same downstream direction. These are expected changes in water quality associated with decline in flow.
Fifty-eight taxa (mostly family level) and 254,636 individuals were identified in 302 quadrat samples collected from 1987 to 1997. Samples were dominated by the immature stages of aquatic insects.
Non-insects contributed only 1.8 per cent of the total number of individuals counted and 14 of 58 taxa.
The insect orders Diptera, Ephemeroptera and Coleoptera each comprised more than a quarter of all individuals (Table 3). Only 11 taxa contributed >1 per cent of the total number of individuals, with numerically-dominant families including elmid Coleoptera (26.9%), chironomid Diptera (25.3%) and leptophlebiid Ephemeroptera (16.7%) (Table 4). From species-level identifications performed from
1987 to 1991, Elmidae comprised principally larvae and adults of several species of the genus
Austrolimnius and Chironomidae comprised principally several species of tanytarsine Chironominae, especially the genera Rheotanytarsus and Tanytarsus . Leptophlebiidae consisted almost exclusively of two species belonging to the genera Austrophlebioides and Manggabora (Dostine et al. 1992).
NATIONAL WATER COMMISSION — Low flows report series 7

Table 3: Percent abundance of dominant orders of macroinvertebrates in pooled sample, 1987 –97.
Order
% abundance
Diptera 31.5
Ephemeroptera 28.5
Coleoptera
Trichoptera
27.0
7.8
Lepidoptera
Odonata
Hemiptera
Total insects
2.9
0.4
0.1
98.2
Table 4: List of taxa contributing >1% of number of individuals in pooled sample, 1987 –97.
Family Order % abundance
Elmidae
Chironomidae
Leptophlebiidae
Caenidae
Baetidae
Coleoptera
Diptera
26.9
25.3
Ephemeroptera 16.7
Ephemeroptera 8.0
Ephemeroptera 3.8
Pyralidae
Hydroptilidae
Hydropsychidae
Lepidoptera
Trichoptera
Trichoptera
Ceratopogonidae Diptera
Simuliidae Diptera
Philopotamidae Trichoptera
2.9
2.6
2.4
2.1
1.9
1.3
Individual taxa demonstrated different patterns of abundance from 1987 to 1997 (Figure 4). Three patterns are evident in the data: (i) some taxa have a threshold response to low flow and decline suddenly but don’t bounce back with a return to higher-flow conditions (e.g. leptophlebiids and baetids); (ii) conversely, some taxa increased dramatically at that threshold but stayed there, despite increases in flow (e.g. caenids and pyralids); and (iii) others are more closely correlated with flow either positively (e.g. hydropsychids) or inversely (e.g. chironomids, elmids and ceratopogonids).
These results suggest taxa-specific responses to long-term variation in flow, but the following caveats need to be borne in mind. Abundance data are based on the average per quadrat across all sites and consequently mask variation among individual sites. Similarly, variation in flow among sites is masked and as noted, in low-flow years there is a linear downstream decline in flow. Mean quadrat abundance and taxa richness also varied among years, with high mean abundance tending to occur during lowflow years, and taxa richness tending to decline from 1991.
NATIONAL WATER COMMISSION — Low flows report series 8

a.) Abundance b.) Richness c.) Leptophlebiidae d.) Baetidae e.) Caenidae f.) Pyralidae g.) Chironomidae h.) Elmidae i.) Hydroptilidae j.) Ceratopogonidae k.) Hydropsychidae l.) Simuliidae
Figure 4: Patterns of abundance of common taxa in relation to dry season flow volume, 1987 –97
(May –October, station G8200052).
The SIMPROF procedure classified 78 year-site samples into nine discrete groups, comprising a large group (group c ) of 32 samples mostly from sites 1 to 5 in the years before 1993, and several smaller groups (Table 5). Group c was replaced by groups d , i and f in years from 1993. Groups form discrete clusters in MDS ordination space (Figure 5). The shift in community structure among classification groups and according to key insect families influencing the classification is shown in
Table 6.
NATIONAL WATER COMMISSION — Low flows report series 9

Table 5: Distribution of nine groups of site-year samples based on SIMPROF procedure.
Site
Year 1 2 3 4 5 6 7 8 f f g g f b e g g g h i i i
-
- c c b e g i
-
- d d d c e d e d e d g d d e c e c c c c
-
-
I
F
F c c c c c c
-
- i i a c c c c c c i i f
-
- c c c c c c i f d d f c c c c c c
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
Table 6: Top five characteristic insect families, in ascending order of influence in the classification (5 = most influential), as identified from CLUSTER and SIMPER analyses.
Group
Taxa c B e d g i f
Leptophlebiidae
Elmidae
Baetidae
Chironomidae
Hydropsychidae
Philopotamidae
Ceratopogonidae
Caenidae
Pyralidae
Hydroptilidae
Tabanidae
No. of samples 32
5
4
3
2
1
5
3
4
2
2
1
2
7
4
5
1
3
5
4
2
3
1
10
4
5
1
3
2
7
5
3
2
4
1
10
5
4
1
3
2
8
Supporting the data presented in Table 4, the trajectories of sites 1, 5 and 8 in MDS ordination space differed (Figure 5). Site 1 fluctuated within group c community type for six years from 1987 to 1992, then shifted to groups d , f and i from 1993 to 1997, with little evidence of return to the previous group c state. Site 5 similiarly fluctuated, mostly within group c for six years from 1987 to 1992, and thereafter within three separate groups d , g and e , but with some evidence of return to the previous group c state. Communities at site 8 were variable through time. Downstream sites switched to other community states before upstream sites.
NATIONAL WATER COMMISSION — Low flows report series 10

a) b) Site 1
2D Stress: 0.15
2D Stress: 0.15
h i b c b c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c e a e e e g d e e e d d f f d f d f d f g g d i f f d f d d i g g g g i i i i i i i h i b c b c c c c c c c c c c c c c c c c c c c c c c c c c c c c c e a e e e g d e e e d d f f f d d f f d g g d i f f d f d d i g g g g i i i i i i i c) Site 5
2D Stress: 0.15
d) Site 8
2D Stress: 0.15
h h i i b a c b c c c c c c c c c c c c c c c c c c c c c c c c c c c c c c e e e e g d e e e d d f f f d d f d f g g d i f f d f d d i i i i i i i i b a c b c c c c c c c c c c c c c c c c c c c c c c c c c c c c c e e e e g d e e e d d f f f d f d f d g g d i f f d f d d i g g g g i i i i i i i g g g g
Figure 5: a) Compositional similarity of samples shown in MDS ordination space; b), c) and d) serial trajectory of sites 1, 5 and 8.
These results are strengthened by a formal test of the differences among years and sites using
PERMANOVA (Table 7). The interaction between Year and Site is highly significant (P<0.0001), reflecting the idiosyncratic nature of community trajectories at individual sites.
Table 7: Table of PERMANOVA results identifying spatial and temporal variation in macroinvertebrate community structure.
Source df SS MS Pseudo-F P(perm)
Year
Site
10
2
34203 3420.3
14341 7170.4
15.764
4.7066
0.0001
0.0002
Year x Site
Residual
20
95
30148 1507.4
20611 216.96
6.9477 0.0001
Total 127 99303
Including the covariate instantaneous flow in this PERMANOVA analysis found no effect of Flow on community structure, and significant interactions between Flow and Year, and Year and Site (Table
8).
NATIONAL WATER COMMISSION — Low flows report series 11

Table 8: Table of PERMANOVA results identifying effect of the covariate instantaneous flow on spatial and temporal variation in macroinvertebrate community structure.
Source df SS MS Pseudo-F P(perm)
Flow
Year
Site
1
10
2
2436
33602
13194
2436.4
3360.2
6596.8
0.870
15.487
6.018
0.5637
0.0001
0.0005
Flow x Year
Flow x Site
Year x Site
Residual
10
2
7
95
19463
2458
7539
20611
1946.3
1229.1
1076.9
217.0
8.971
1.125
4.964
0.0001
0.3673
0.0001
Total 127 99303
Patterns in the abundance of taxa between groups were further explored using the results of SIMPER analysis. Tables 9 and 10 show taxa contributing to 50 per cent of the cumulative average dissimilarity between groups c and i , and groups i and f respectively. Discriminating taxa between groups c and i include the flow-dependent taxa Leptophlebiidae, Baetidae, Hydropsychidae and
Simuliidae (all with greater abundances in group c samples) (see also Table 6). Discriminating taxa between groups i and f include the flow-dependent taxa Hydropsychidae, Baetidae, Philopotamidae and Simuliidae (all with greater abundances in group f ). This suggests a partial return to community types present during high-flow conditions but with the absence of Leptophlebiidae.
Table 9: Results of SIMPER analysis showing taxa contributing to 50% of cumulative average dissimilarity between groups c and i .
Group c Group i
Family Av.Abund Av.Abund Av.Diss Diss/SD Contrib% Cum.%
Leptophlebiidae 5.51 0.1 7.22 8.95 14.85 14.85
Baetidae
Caenidae
3.99
1.21
Hydropsychidae 2.94
Tipulidae 2.15
Simuliidae 2.31
0.36
4.64
0.37
0.2
0.67
4.87
4.59
3.39
2.61
2.36
4.05
2.59
2.59
3.36
1.57
10.02
9.44
6.97
5.36
4.86
24.87
34.3
41.28
46.64
51.5
Table 10: Results of SIMPER analysis showing taxa contributing to 50% of cumulative average dissimilarity between groups i and f .
Group i Group f
Family
Hydropsychidae 0.37
Baetidae 0.36
Philopotamidae
Caenidae
0.38
4.64
Simuliidae
Pyralidae
Hydroptilidae
Hydracarina
0.67
1.98
1.31
0.84
Av.Abund Av.Abund Av.Diss Diss/SD Contrib% Cum.%
2.73
2.41
2.24
4.22
1.94
2.97
2.26
1.42
3.23
2.82
2.55
2.02
1.98
1.9
1.65
1.49
2.61
2.87
2.86
1.57
1.58
1.53
1.59
1.32
9.52
8.32
7.52
5.95
5.84
5.61
4.88
4.39
9.52
17.84
25.36
31.3
37.14
42.75
47.63
52.02
NATIONAL WATER COMMISSION — Low flows report series 12

Principal coordinates analysis (PCO) yielded results with a strong resemblance to non-metric MDS.
The first two axes of the PCO accounted for 54.4 per cent of the variation. Taxa with Pearson correlation coefficients >0.75 include Leptophlebiidae, Tipulidae, Baetidae, Hydropsychidae,
Hydroptilidae, Chironomidae and Caenidae. Vectors for Leptophlebiidae, Tipulidae, Baetidae and
Caenidae were strongly aligned with the first PCO axis. Nine of the 12 extrinsic variables had vectors with Pearson correlation coefficients >0.5. The vector ‘Period’ was strongly aligned with the first PCO axis, as were, to a lesser extent, vectors for ‘%shredder’, ‘%collector-filterer’, and ‘SIGNAL’ and mean thermophily grade (Figure 6). Variables with vectors with Pearson correlation coefficients <0.5 include
‘%predator’ and mean rheophily grade and Flow.
Axis 1 of the PCO accounts for most of the variation and distinguishes the flow-dependent taxa abundant pre-1993 (Leptophlebiidae, Tipulidae and Baetidae) from those post-1992, best exemplified by Caenidae. The extrinsic factors that best characterise these taxa separations are: for flowdependent taxa %shredders, %collector-filterers and SIGNAL (i.e. taxa indicative of high water quality); and for the post-1992 period, taxa more tolerant of warm-water conditions with higher thermophily grades. Separation on axis 2 is strongly associated with hydroptilids and chironomids, characteristic of the post-1992 classification groups d and g . Each extrinsic factor is consistent with the change in feeding opportunity and water quality tolerance as baseflow in the SAR changed from high to lower flows at about the threshold 1993 period. a.)
40 b.)
40
20
0
-20
Lep Tip
Baetidae c c c c c b c c c c c c c c c c c c c b c c c c c c c c a e e e e
Hydropsychidae i h i i i i i i i i d g i e e f g f f d d f f f f f d d d g g g g d d g d
Caenidae
Chironomidae
Hydroptilidae
20
0
-20
%shred c c c c
%coll_filt b c c c c c c c c c c c c c c c b c c c c c c c c a e e e e richness i h
%coll_gath i i i i i i therm i i d g i e e g g f f d d f f f f f d d d
%herb g g d d d g period abund
-40 -40
-40 -20 0
PCO1 (39.1% of total variation)
20 40 -40 -20 0
PCO1 (39.1% of total variation)
20 40
Figure 6: a) Principal coordinates analysis of sample data overlain by sample groups showing vectors for taxa with Pearson correlation coefficients >0.75; b) principal coordinates analysis of sample data overlain by sample groups showing vectors for extrisic variables with Pearson correlation coefficients
>0.5.
(Lep = Leptophlebiidae, Tip = Tipulidae)
Generalised linear modelling of the effect of Year, Site and Flow on variation in taxa richness indicated a strong effect of Year. The preferred model explained 41.4 per cent of the deviance (Table
11). Taxa richness varied through time, declining in 1992 and 1996; 1996 had significantly less taxa than 1987 (Table 12, Figure 7). Modelled estimates accord with year-averaged data in Figure 4b, indicating generally higher richness from 1987 to 1991 and lower richness from 1992 to 1997. As both high and low river flows characterised the latter period, it is unsurprising that flow alone accounted for only a small amount of the explained deviance.
NATIONAL WATER COMMISSION — Low flows report series 13

Table 11: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data for years 1987 –97.
Model Log likelihood k AICc
ΔAICc w i pcdev
Year
Year + Flow
Year + Site
Year + Flow +
Site
Flow
Null model
Site
-325.35
-325.34
-324.62
-324.49
-342.82
-343.95
-343.37
3
2
4
1
2
1
3
1
4
1
5
677.41
679.88
680.95
683.27
691.84
691.99
695.06
0.00
2.47
3.54
5.86
14.43
14.58
17.65
0.660
0.192
0.112
0.035
0.000
0.000
0.000
41.4
41.4
43.0
43.3
2.5
0.0
1.3
Table 12: Model parameters of preferred model of variation in taxa richness of stream macroinvertebrates.
Model variable
Constant
YEAR88
YEAR89
YEAR90
YEAR91
YEAR92
YEAR93
YEAR94
YEAR95
YEAR96
YEAR97
Estimate
2.895
-0.019
0.041
0.023
0.145
-0.180
-0.072
0.023
-0.062
-0.383
-0.181
Std error
0.068
0.096
0.095
0.095
0.095
0.109
0.098
0.095
0.098
0.107
0.101 z value
42.65
-0.19
0.43
0.24
1.53
-1.64
-0.73
0.24
-0.63
-3.59
-1.80
Pr(>|z|)
< 2e-16
0.8470
0.6690
0.8114
0.1250
0.1006
0.4638
0.8114
0.5264
0.0003
0.0715
Sig.
Ns
Ns
***
Ns
***
Ns
Ns
Ns
Ns
Ns
Ns
Figure 7: Estimates of taxa richness (± 95% confidence limits) of macroinvertebrates, 1987–97.
NATIONAL WATER COMMISSION — Low flows report series 14

From 1987 to 1992, there was no effect of Flow with the null model being the preferred model (Table
13) and from 1993 to 1997 the preferred model included Year (Table 14). Despite a consistent decline in flow from 1987 to 1992 followed by a corresponding increase in flow from 1993 to 1997, there was little evidence of related changes in taxa richness (Figure 8). The maximum mean taxa richness was recorded at site 8 in 1989 (23.2) and the minimum mean taxa richness was recorded at site 8 in 1992
(10.7).
Overall, taxa richness resembled the pattern in abundances of the flow-dependent mayfly families,
Leptophlebiidae and Baetidae, in demonstrating high values to a threshold point in decline in base river flow, thereafter remaining lower and not returning to previous high values despite a return to high-flow values.
Table 13: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data from 1987 –92.
Model Log likelihood k AICc
ΔAICc w i pcdev
Null model
Year
Flow
Site
Year + Flow
Year + Flow + Site
Year + Site
-182.96
-178.13
-182.96
-182.34
-178.05
-175.90
-177.38
2
7
3
4
8
10
9
370.11
372.12
372.30
373.32
374.54
375.66
375.86
0.00
2.01
2.19
3.21
4.43
5.55
5.75
0.470
0.172
0.157
0.094
0.051
0.029
0.027
0.0
22.0
0.0
2.8
22.4
32.2
25.4
Table 14: Results of generalised linear modelling of variation in taxa richness of stream macroinvertebrates with variables Site, Year and Flow using data from 1993 –97.
Model Log likelihood k AICc ΔAICc w i pcdev
Year
Year + Flow
Year + Site
Year + Flow + Site
Null model
Flow
Site
-147.22
-147.20
-146.96
-146.94
-155.87
-155.25
-155.61 a.) Taxa richness vs flow, 1987
–1992
6
7
8
9
2
3
4
308.03
310.56
312.74
315.48
315.95
316.93
319.95
0.00
2.53
4.71
7.45
7.92
8.90
11.91
0.697
0.197
0.066
0.017
0.013
0.008
0.002
48.3
48.4
49.8
49.9
0.0
3.5
1.5 b.) Taxa richness vs flow, 1993
–1997
Figure 8: a.) Scatter-plot of taxa richness and instantaneous flow data, 1987 –92; b.) scatter-plot of taxa richness and instantaneous flow data, 1993 –97.
NATIONAL WATER COMMISSION — Low flows report series 15

Macroinvertebrate assemblages in riffle habitats in the upper SAR underwent a marked shift in composition during the 11-year study. Assemblages dominated by leptophlebiid ( Manggabora and
Austrophlebioides ) and baetid ( Platybaetis ) mayflies, and filter-feeding hydropyschid
( Cheumatopsyche ) and philopotamid ( Chimarra ) caddisflies were replaced by assemblages dominated by Caenidae ( Tasmanocaenis ), Elmidae ( Austrolimnius ) and Chironomidae. These taxa reflect changes from a high-flow to a low-flow community state respectively. The community shift did not occur simultaneously at all sites but was a gradual process evident as early as 1988 at downstream sites. The switch between the two community states was associated with the gradual decline in late dry season river flow from 1987 to 1993 which culminated in low-flow assemblages present at all sites by 1993. The response to declining flows appeared to be asymmetric and not predictably reversible, with only limited evidence of a return to a high-flow community state despite a return to higher streamflow years. The nature and duration of this possible lag and potential to return to a previous high-flow state are unknown because sampling ceased from 1997.
The loss or general decline in taxa typically assigned as flow-dependent associated with decreases in base streamflow is not unexpected. There may be many direct and indirect reasons for these declines, and as the role of flow is confounded by simultaneous variation in water quality as well as habitat availability and suitability, cause and effect are difficult to separate. Some more common explanations for loss or general declines in flow-dependant taxa may apply to SAR communities and these include: i) Reduced water velocities (per se)
Net-spinning caddisfly larvae (e.g. Hydropsychidae) rely on flow to capture food items suspended in the water column. Insufficient flow velocities will disrupt this feeding mechanism. For mayflies and some caddisflies (which as adults are generally regarded as poor dispersers) recruitment in some situations (e.g. relatively isolated riffle zones) may rely heavily on downstream drift of aquatic immature stages. Low-flow conditions may impede these colonisation opportunities. Indeed, with very significant reductions in population abundances of mayfly and some caddisfly taxa that occurred in the SAR from 1992 to 1993, poor adult dispersion may explain the very low rates of return of these taxa to the river, even after a return to higher-flow conditions. ii) Exceedence of physiological tolerances of water-quality-sensitive taxa
Flowing waters are typically associated with particular water quality conditions, including relatively high DO concentrations and low turbidity and water temperature, to which many flow-dependent taxa are adapted. However, there were no marked temporal trends in water quality data in the upper SAR, apart from the anomalously high concentrations of total organic carbon observed in 1992. Upland flow-dependant taxa are typically associated with good water quality and biotic indices such as
SIGNAL often reflect this observation in their scores. Whether the significant difference in mean
SIGNAL grades observed between high-flow and low-flow community states in this study indicates subtle declines in overall water quality with reduced flow is not known.
An aspect of water quality that may become increasingly evident with decreasing water flows in
Australian streams is potential toxicity associated with riparian leaf-fall accumulations. High
NATIONAL WATER COMMISSION — Low flows report series 16

concentrations of leaf leachates can be toxic to aquatic invertebrates (Canhoto & Laranjeira 2007) and, in Australia, Melaleuca leaves in particular (common along the SAR) are known to produce toxic tannins or other compounds that can suppress important ecosystem functions (e.g. Bailey et al.
2003). In northern Australia leaves of the common riparian tree, Barringtonia acutangula , are also known to have ichthyocidal properties (Bishop & Forbes 1991). Accumulations of leaf-fall, in general, can also lead to surface water deoxygenation. iii) Changes to habitat
Reduced water flow may lead to conditions that increase sedimentation rates and rates of bio-film
(including epi-benthic algae) and macroalgae development. These deposits may lead to clogging of gills or other interference to the feeding mechanisms of particular flow-dependant taxa. Leaf-fall accumulations may also lead to physical smothering of stream substrates.
Apart from these commonly-invoked mechanisms that may explain changes in community composition associated with changes in streamflow conditions, other landscape-level changes may also be invoked for upper SAR communities. Thus: iv) Long-term changes associated with catchment management
It is possible that trends in macroinvertebrate composition are partly related to changes in catchment management practices. Incorporation of the upper SAR catchment into Stage III of Kakadu National
Park in 1991 was followed by a program of feral buffalo eradication. Buffalo used the riparian corridor for shade, watered at the stream edge and used shallow riffles for crossing points. Buffalo control coincided with an improvement in water quality (e.g. decreased turbidity), though their impact on the stream fauna is unknown. Since buffalo removal coincided generally with the loss of or general decline in flow-dependant taxa, any link would suggest buffalo-related disturbance sustained these taxa. Rather, flow and its direct and indirect effects appear far more likely and parsimonious explanations for the observed stream community changes.
One of this study’s more interesting results is the observation that the high-flow (1987–92) communities were observed to be relatively homogenous (evident, for example, in ordination space) and diverse, but post-disturbance communities exhibited greater variability in composition. It may be that some flow-dependant taxa (such as leptophlebiid mayfly nymphs) play a key role in structuring benthic communities by controlling periphyton biomass or the settlement of tube-dwelling organisms and their loss from the system, by whatever mechanism, leads to substantial and persistent changes in community structure.
Another observation associated with the loss of leptophlebiid and baetid mayfly nymphs was the replacement in similar abundances by caenid mayfly nymphs (Figure 4). It is unknown whether this represents in-filling of a vacant niche (ecological release) and/or simply an increase in habitat and water quality conditions that favoured Caenidae.
Empirical data on the consequences of rare (in time) but periodic phenomena are usually not readily available, given the requirement for a sustained effort to collect long-term data. Unambiguous interpretation of the processes underlying structural patterns requires a parallel experimental approach to tease apart several competing hypotheses. This study suggests an increase in the frequency and intensity of low-flow events in these wet-dry tropical systems may have significant consequences for stream biodiversity. These results are important for river health management in the context of proposed agricultural developments that could potentially lead to reduced streamflow. The information arising from this study could contribute to a better understanding of the relationship between reduced flow and ecological response in wet-dry tropical streams. These investigations are currently underway for the adjacent Daly River under the TRaCK (Tropical Rivers and Coastal
Knowledge) research hub (F. Pantus, Griffith University, pers. comm.).
NATIONAL WATER COMMISSION — Low flows report series 17

Trophic group codes 1=collector-gatherer, 2=collector-filterer, 3=herbivore, 4=predator, 5=shredder
Taxa
Ancylidae
Baetidae
Caenidae
Calamoceratidae
Ceratopogonidae
Chironomidae
Collembola
Corbiculidae
Corduliidae
Corixidae
Culicidae
Dytiscidae
Ecnomidae
Elmidae
Empididae
Gerridae
Gomphidae
Gyrinidae
Helicopsychidae
Hirudinea
Hydracarina
Hydraenidae
Hydridae
Hydrophilidae
Hydropsychidae
Hydroptilidae
Hyriidae
Leptoceridae
Leptophlebiidae
Libellulidae
Limnichidae
Mesostigmata
Mesoveliidae
Microsporidae
Naucoridae
Nematoda
Nemertea
Trophic group
2
3
4
4
4
4
4
4
1
4
3
1
1
4
4
3
5
4
1
1
1
4
5
6
3
2
2
6
8
4
4
2
3
4
8
1
5
4
5
1
2
4
7
1
4
5
2
SIGNAL score
4
5
4
7
4
Rheophily
2.65
1.02
0.74
2.75
0.18
1.26
1.81
1.28
0.36
0.28
0.39
2.02
1.29
0.99
0.88
0.79
1.03
Thermophily
0.95
1.00
1.00
0.91
1.05
1.06
0.89
0.95
1.03
1.05
1.04
0.98
0.99
1.03
0.98
1.02
1.00
NATIONAL WATER COMMISSION — Low flows report series 18

Taxa
Trophic group
Nepidae
Neuroptera
Notonectidae
Oligochaeta
Oribatida
Ostracoda
Palaemonidae
Philopotamidae 2
Platyhelminthes
Pleidae
Polycentropodidae 4
Psychodidae 2
3 Pyralidae
Sciomyzidae
Scirtidae
2 Simuliidae
Stratiomyidae
Tabanidae
Tipulidae
4
4
4
5
Veliidae
Zygoptera
4
4
6
5
2
3
5
3
2
7
3
3
4
8
SIGNAL score
3
6
1
2
Rheophily
3.39
0.88
1.51
2.34
2.14
0.38
Thermophily
0.94
0.91
1.09
0.95
0.92
1.00
NATIONAL WATER COMMISSION — Low flows report series 19

Blue line = site 1; red line = site 5; green line = site 8 a) Electrical conductivity b) Alkalinity c) Water temperature d) Dissolved oxygen f) Total organic carbon e) Turbidity
NATIONAL WATER COMMISSION — Low flows report series 20

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NATIONAL WATER COMMISSION — Low flows report series 21

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NATIONAL WATER COMMISSION — Low flows report series 22

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NATIONAL WATER COMMISSION — Low flows report series 23