Many rivers and estuaries in Western Australia have seen a decline in water quality, due to the changes in the way land is used and managed in catchments. Runoff from urban, industrial and agricultural land often carries excessive nutrients to downstream waterways – a process known as eutrophication.
Symptoms of eutrophication include excessive algal growth and the proliferation of harmful cyano-bacteria, low oxygen concentrations, fish kills, loss of biodiversity, and offensive odours. The more populated South West and areas with extensive artificial drainage tend to be where declines in water quality are most prevalent.
Supporting community values
Water quality improvement plans summarise the condition of an estuary or river and document strategies to improve water quality and support the community values of that system. The plans require extensive consultation, coordination and action among key state government agencies, local government authorities, industry representative bodies and the community.
The plans must always have a view to the community values – the specific characteristics or uses of the environment that are important for a healthy ecosystem or support public benefit, welfare, safety or wellbeing. The community values are often grouped by the categories of aquatic ecosystems, fisheries, recreation and aesthetics and cultural and spiritual.
How plans are developed
Water quality improvement plans are informed by long-term monitoring programs of water quality and ecological health that identify problem ‘hotspots’ and support a consolidated understanding of the baseline water quality. Numerical catchment models help identify and quantify nutrient sources in the catchment based on its physical and hydrological characterises, land uses and management practices.
Best management practices are identified through extensive consultation with community, landholders, industry and relevant agencies such as Department and Agriculture and Food. Catchment models run combinations of management practices to predict their effect on water quality and help us determine the most efficient way to meet management goals.
Water quality improvement plans have been developed for the Hardy Inlet (with a focus on the Scott River), Vasse Wonnerup, Leschenault and the Swan-Canning estuarine systems in the south-west.
