One of the most effective ways to reduce the ecological impact of stormwater pollution on waterway biota is to prevent pollution in the first place. The aim of this project was to reduce threats to the health of Melbourne’s Port Phillip Bay, by determining sources and impacts of pollution in the Werribee catchment. Identifying priority sources of pollution can help local government, EPA, Melbourne Water, and the community better target education and enforcement campaigns.
River sediment quality surveys, passive sampling and macroinvertebrate monitoring were conducted across fifteen major catchments. Sediments were analysed for persistent contaminants commonly found in Melbourne stormwater, including heavy metals (arsenic, cadmium, copper, chromium, nickel, lead, zinc) and oils (as total petroleum hydrocarbons or TPH). Contaminant concentrations were compared with the Victoria’s State Environmental Protection Policy Waters (SEPP) and National Sediment Quality Guidelines and classified as either low, medium or high risk. Stormwater pollution profiles were developed using passive samplers to collect a time-integrated assessment of pollution from a defined catchment.
Volunteers conducted quarterly biological monitoring at 13 sites across the Werribee River catchment to complement the passive sampling and sediment surveys. Using the same sampling protocol as the citizen science program Waterwatch, macroinvertebrates were collected from a variety of habitats at each site along a 10 m transect for 10 minutes. Once samples had been collected, they were placed in trays and macroinvertebrates were ‘live picked’. A SIGNAL score was calculated for each site.
The most polluted waterways were immediately downstream of the urban catchment around Werribee township and the surrounding suburbs. In contrast, the upper and lower reaches of the Werribee River had much lower levels of pollution. The most polluted area of the Werribee River corresponded with the most polluted stormwater outfall at the Maltby Bypass drain. To reduce pollution, a stormwater education program was delivered to the types of businesses in the vicinity, that was likely to be contributing to the levels seen.
Involving environmental groups in waterway health and assessment can provide an important link between waterway managers and the local community.