An evaluation of the benefits of source control measures at the regional scale

Source control measures include rainwater tanks, infiltration trenches, grassed swales, detention basins and constructed wetlands that can be used in housing allotments and subdivisions. A methodology for evaluating the regional economic benefits due to implementation of source control measures is presented and illustrated for two case studies in the Lower Hunter and Central Coast regions of New South Wales, Australia. It is demonstrated that use of rainwater tanks to supplement mains water supply for toilet, hot water and outdoor uses can very significantly reduce demand on mains water supply. Reductions in regional water demand will enable deferment of water supply headworks augmentation, while reductions in peak mains water demand will extend the life of water supply distribution infrastructure. In addition, substantial reduction of stormwater discharge from allotments can be realised. For the Lower Hunter region with an urban population of about 450,000 it is shown that construction of new water supply headworks infrastructure can be delayed by up to 34 years. Compared with the traditional provision of mains water and stormwater disposal, the use of rainwater tanks along with other source control measures can produce present worth savings to the Lower Hunter region conservatively estimated to be up to $67 million. Similar results were found for the Central Coast region.