In urban areas, rain that falls on roads, roofs, pavements and other hard surfaces is usually swept across these surfaces as runoff. As runoff flows across these hard surfaces it generally picks up pollutants such as heavy metals, oils, nutrients and litter. Stormwater caries these pollutants to local waterways such as rivers and creeks before making its way into the ocean. This water is known as stormwater and represents a major threat to river health. As stormwater is rarely filtered or treated, pollutants such as heavy metals, oils, pesticides and other chemicals can enter our aquatic ecosystems. This can harm wildlife and degrade local waterways. Developing a Science-driven stormwater education program for the Werribee River will prioritise catchment strategies moving forward.
Even when it is not raining, human activities can impact waterway health. Dry-weather flows from activities such as machinery wash-downs, inappropriate disposal of waste into stormwater drains and car washing are important sources of pollution. While dry-weather flows carry much lower volumes of water than rain events, they often have very high pollutant concentrations. This is especially true in areas associated with industrial and mechanical processing and manufacturing industries.
This Science-driven stormwater education program aims to improve the health of Port Phillip Bay by identifying the major sources of stormwater pollution in the Werribee catchment. Identifying priority pollution sources, this program will increase local environmental awareness of stormwater pollution issues. Allowing local government, EPA, Melbourne Water and the community to prioritise pollution issues and better target stormwater education program is the focus of this project. Collaboration between stakeholders is critical to improve the condition of our urban waterways. The collection of baseline stormwater pollution profiles and sediment and biological quality information will also form the basis for evaluating long term success of the program.
Interim Results from Phase 1:
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 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, which services a significant area of industrial catchment south of the Werribee township. A more details survey of this catchment is currently in progress. Other drains with consistently heavy pollution generally had significant areas of industrial (Skeleton Ck drain at Old Geelong Rd) or commercial (Heaths Rd drain) catchment.
Apart from the Skeleton Creek at Princess Freeway, the SIGNAL scores from the biological monitoring carried out at sites along the Creek were lower than the recommended SEPP guideline. Again, this substantiates the findings of the stormwater pollution profiling, which found heavy pollution in industrial and commercial parts of Skeleton Creek.