Stormwater harvesting: Assessing operational system performance

Recently, it has become apparent that stormwater harvesting has the potential to play a significant role in the sustainable management of water resources. However, it has been recognised that uncertainties concerning the operational performance of existing stormwater harvesting systems and also the lack of appropriate design standards are barriers to the widespread adoption and utilisation of stormwater harvesting. In this study, we gathered design and operational information regarding three stormwater harvesting systems located in Melbourne, as well as undertaking water quality and quantity monitoring. It was found that the design objectives of each system were developed in order to meet a range of environmental, social and economic outcomes, and while most of these objectives were met, some were rather qualitative and so were difficult to assess. The design of each harvesting system did not represent what was built and this is likely to be limiting operational performance. The ongoing drought has severely impacted on the volume of stormwater harvested from the two smaller systems, however, recent winter/spring rainfall has increased the volume of stormwater in storage. In comparison, the larger system has been able to provide significant amounts of stormwater during the very dry summer of 2007 and throughout the year. Preliminary water quality monitoring indicated that systems featuring WSUD devices are able to improve the water quality (in terms of TSS, TN and TP) of stormwater. Importantly, it appears that systems that do not have disinfection will more frequently have E. coli levels that exceed 10 orgs/100 mL.