The hydrological and economic impacts of changing water allocations in political regions within the peri-urban South Creek catchment in Western Sydney II : scenarios

The aim in this paper is to assess the hydrological and economic impacts of deploying water in the political jurisdictions of the peri-urban South Creek catchment of Western Sydney. This catchment has been identified as the region in which the city of Sydney will grow into in the future, with a plan to move an extra one million people into the catchment in the next 25-30. years. In conjunction with this expansion, a plan exists to augment the existing water supply by treating waste water effluent, harvesting stormwater and improving irrigation efficiency, along with a strategy for saving water on farms. Water in this catchment is operated by and in the interests of society, where decisions on its allocation have a political perspective to them. However, the growth within this catchment and the water augmentation strategies are not split evenly amongst the political entities within this catchment, namely the Local Government Authorities. An integrated hydro-economic model segregated according to the political entities in the catchment is used in this study to address a range of water saving scenarios raised by stakeholders. The trade-offs inherent in all water allocation decisions on a regional basis are made transparent in this model and its political ramifications, defined as the impacts on different political regions, are identified. In analysing the measures designed to save water across the catchment, none resulted in a positive Net Present Value. Even just expanding the system to accommodate one million extra people resulted in significant economic losses. In addition, the impact of each measure in each political region was markedly different. The purpose of this study is to provide stakeholders in individual local government regions with evidence of the costs and impacts of rational decisions to change the management of water resources in South Creek catchment.