Inland Waters Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7
Introduction (continued)
Condition of inland waters
Our knowledge of the condition of inland waters and their catchments has increased considerably over the past five years due to programs such as the National Land and Water Resources Audit (NLWRA) (see http://www.nlwra.gov.au/ ), the Natural Heritage Trust's National River Health Program, and State of the Environment Reporting. National core indicators have been developed to provide a common reporting and assessment system (ANZECC 2000). Although there are still significant gaps in our knowledge (especially in the condition of aquatic ecosystems, flora and fauna), there is sufficient information to assess:
- the condition of inland waters and their catchments
- the relationship between condition and pressure
- trends in condition and predicted future trends in condition.
Some indicators of the condition of the inland waters are focused on human uses, while others measure the condition of aquatic ecosystems. Both uses are related to environmental values set out under the National Water Quality Management Strategy. The two important indicators of condition for human uses are:
- the sustainability of water extraction - unsustainable use of inland waters can lead to degradation of the environment and water resources
- quality of surface waters and groundwaters - poor quality surface and groundwaters can result in waters being unsuitable for their intended use (i.e. loss of resource) or increased treatment costs.
To ensure that our inland waters can provide for human requirements into the future, their aquatic ecosystems and biological functions must also be protected. Ultimately, the cumulative pressures discussed previously are reflected in the condition of aquatic ecosystems. The concept of ecosystem 'health' is a measure of condition and can be assessed by measuring different components of ecosystems such as the type and abundance of flora and fauna (e.g. waterbirds or riparian vegetation) or habitats (e.g. wetland communities). The current working definition of river health is:
The ability of the aquatic ecosystem to support and maintain key ecological processes and a community of organisms with a species composition, diversity, and functional organisation as comparable as possible to that of undisturbed habitats within the region (Schofield & Davies 1996).
Information on the distribution and population trends for animals such as waterbirds, frogs, platypus, freshwater crayfish and fish are presented in Aquatic ecosystems later in this report. However, the data is geographically patchy and a national assessment of aquatic ecosystem 'health' based on this information is difficult. This data is also complicated by the fact that these animals vary naturally in their distribution across Australia and it is difficult to use the data to compare between different climatic regions and types of inland waters.
The AusRivAS monitoring program aims to overcome some of the difficulties in assessing the health of aquatic ecosystems by using a group of animals that are a part of every inland aquatic ecosystem, namely aquatic macroinvertebrates. Aquatic macroinvertebrates are a diverse group of animals that include a range of insect, crustacean and molluscan groups such as snails, water boatmen, dragonflies, stoneflies, mayflies and aquatic worms. They are widespread, easy to sample, relatively immobile, and most importantly, their composition reflects the historical impact of environmental changes on the stream ecosystem for up to several months before sampling. They therefore provide an 'integrated' indicator of human impact on the stream ecosystem. All states and territories have undertaken a recent assessment of their waterways using the AusRivAS methodology and the results of the assessment are presented in Aquatic ecosystems.
Other important indicators of aquatic ecosystem 'health' include:
- geomorphology (physical and chemical condition), diatoms, benthic community metabolism, riparian vegetation, and fish. These are all agreed indicators of river health under the National River Health Program and are being progressively incorporated into the Australian River Assessment Scheme
- the condition and extent of important habitats such as riparian vegetation, wetlands and unmodified rivers and streams. As well as supporting a diverse and sometimes unique range of aquatic plants and animals, these habitats play an important role in maintaining good water quality and providing structural stability to soils
- water quality - whether it is of sufficient quality for the protection of aquatic ecosystems.