Drinking water is supplied to Melbourne from both open and protected catchments. The open catchment in the mid-Yarra region supports agricultural and recreation activities as well as some urban development. Water from open catchments is fully treated and tested before supply to customers, so it meets the same quality requirements as water from protected catchments, although there is an increased likelihood of agri-chemicals being present in low amounts in the raw water. We explored how catchment management techniques could be used to mitigate impacts of agri-chemicals on the drinking water supply, with an added benefit of reducing impacts to local waterways.
We used a source-pathway-receptor model to understand how agri-chemicals are transported in the catchment and developed a profile for potential treatment options using attributes which could be located spatially across the catchment. From this a spatial mapping tool was developed to explore treatment options.
We were able to identify locations within the catchment with suitable attributes for treatment options including sediment traps, buffer strips, swales and wetlands. By creating a spatial tool with search functions, we were able to interrogate the data to find locations were a certain agri-chemical could be treated, multiple treatment options could be deployed or other benefits realised.
Management of water quality issues is shifting from a reactive to proactive mindset however it can be difficult to know where to target management actions for diffuse pollution. Our approach can be applied to other pollution types or catchments, e.g. treatment of stormwater in urban catchments.