Optimal sequencing of water supply options at the regional scale incorporating alternative water supply sources and multiple objectives

In recent years, the sequencing of water supply projects has become increasingly complex, as a result of the need to consider alternative water sources and additional objectives. In order to address this problem, two sequencing approaches are presented in this paper to assist in identifying the optimal sequence of water supply projects. The methods are applied to a case study based on the southern Adelaide water supply system, South Australia, over a 40-year planning horizon. Desalination plants, rainwater and stormwater sources are considered in addition to existing surface water sources. The objectives used include the present value of cost and greenhouse gas (GHG) emissions and optimal sequences are obtained for a range of demand and discount rate scenarios. The results demonstrate that there are noticeable tradeoffs between costs and GHG emissions when favouring different objectives, but that the impacts of uncertain demands and discount rates are potentially more significant.