Optimal sequencing of water supply options at the regional scale incorporating sustainability, uncertainty and robustness

Abstract

Planning sustainable urban water supplies requires the use of a long-term planning horizon and multiple criteria for assessment, all of which have inherent uncertainties and difficulties. This paper presents the application of an optimization framework incorporating a post-optimization robustness assessment to the case study of the southern Adelaide water supply system to determine its effectiveness. Various water supply alternatives (i.e. reservoirs, desalination plant, rainwater tank, and water reuse schemes) are considered. Additionally, a 90 year planning horizon and two competing sustainability objectives, including the minimization of economic cost and greenhouse gas emissions, are adopted. In order to determined the robustness of the optimal solutions in the face of a variety of potential future conditions, the sensitivity of the costs and greenhouse gas emissions of the optimal supply sequences is assessed under a range of water supply, population growth and climate change scenarios. The results obtained indicate that there are significant trade-offs between average cost and GHG emissions, but that these trade-offs are relatively robust in terms of GHG emissions under a range of future scenarios. However, there was significant variation in the robustness of the economic costs of the solutions.