Australia-Wide Assessment of River Health: Western Australian Bioassessment Report (WA Final Report)
Monitoring River Health Initiative Technical Report Number 7
S.A. Halse, M.D. Scanlon and J.S. Cocking
- Department of Conservation and Land Management
Environment Australia, 2002
ISBN 0 642 54839 0 ISSN 1447-1280
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About the report
The First National Assessment of River Health (FNARH) comprised the second phase of the Monitoring River Health Initiative (MRHI), an Australia-wide program to develop a biomonitoring system for rivers based on macroinvertebrates. The biomonitoring system is called AusRivAS and measures river condition using a series of simple predictive models that compare the macroinvertebrate families occurring at a river site with those expected if the site were in good condition.
During the three years of FNARH fieldwork (1997-1999), the condition of 561 sites in all major rivers in Western Australia was assessed. Some further assessment work was done in 2000 and additional sites were evaluated during the first phase of the MRHI. In general terms, river condition is good in northern Australia, especially the northern Kimberley, although the Ord River catchment is noticeably degraded. Rivers in the Murchison-Gascoyne region are also mostly degraded. In the south-west of WA, rivers are mostly in poor condition with only the Shannon River, in a mostly forested catchment, being undisturbed. Rivers in coastal areas were degraded. The inland rivers of the Wheatbelt appeared to be only moderately impaired but this reflects some shortcomings of the AusRivAS models when assessing river condition in uniformly degraded regions. The reality is that Wheatbelt rivers are probably the most degraded in WA.
Results from AusRivAS confirmed that many catchment activities commonly regarded as inimical to river health are associated with changed macroinvertebrate community structure. These include activities causing erosion, nutrient and organic loads, loss of riparian vegetation and increased salinity. River regulation, channel modification and fire also deleteriously affect river condition but recreation did not appear to do so.
AusRivAS models are publicly available on the national AusRivAS website (http://ausrivas.canberra.edu.au). The website also contains a sampling manual that explains how to go about AusRivAS assessments in WA and what information must be collected. Access to the models is currently controlled by passwords that are obtainable from the University of Canberra via authorisation from the Department of Conservation and Land Management. This report, and the sampling manual, highlight that undertaking AusRivAS assessments requires biological expertise and suitable equipment. AusRivAS models are not an appropriate tool for widespread assessment of river condition by the community unless consultants are involved in the assessment process.
There are many potential applications of AusRivAS. Broad-scale assessment of river condition for State of the Environment reporting is one of the most obvious. Other uses include evaluation of the effects of local catchment management on river health, long-term monitoring of the condition of high-value river sites, environmental impact assessment and, possibly, compliance monitoring. The users of AusRivAS outputs are likely to range from individuals and community groups to Local Government and to the Commonwealth, who in conjunction with the State Government, funded the development of AusRivAS in WA. AusRivAS will work best with a State Government agency as sponsor to ensure that models are updated as environmental protection evolves and knowledge of WA rivers becomes more sophisticated. The agency could also provide training courses and assist first-time users of the system.
Major achievements and conclusions of the MRHI in WA include:
- Development of AusRivAS models for assessment of ecological condition of WA rivers;
- Assessment of river condition, using AusRivAS, at 685 sites throughout the State;
- Proposed bio-regionalisation scheme for aquatic invertebrates in WA;
- AusRivAS has the potential to measure the ecological effect of a wide range of catchment activities and processes; and can be used to increase understanding of river ecology as well as to monitor river health;
- AusRivAS models appeared to provide a more reliable measure of condition than chemical monitoring and some of the species-based metrics commonly used for assessment;
- AusRivAS outputs are easier to interpret and, in some cases at least, cheaper to obtain than broad-spectrum chemical monitoring;
- Aquatic macroinvertebrate family richness and ecological health are, within the bounds set by stream type, inter-related;
- Human-induced disturbances in rivers change the macroinvertebrate community structure and reduce the overall number of macroinvertebrate families present;
- Catchments in the northern Kimberley were mostly assessed as undisturbed and the region contains some of the least disturbed rivers in Australia.
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