The water industry in Australia and international is involved in a period of significant change. The conventional roles of water and wastewater utilities are being redefined with the objectives of resource conservation and sustainable development added to existing responsibilities. Least cost planning (LCP) has emerged as the way forward for water utilities in regions where water conservation has become an objective or where ongoing supply expansion is constrained. It involves techniques for the design and evaluation of demand management programs and aims to compare demand- and supply-side options on an equivalent basis. The approach is based on the key ideas that: demand is for the services water provides rather than the actual volume supplied; and that a drop of water saved is equal to a drop supplied. This paper contends that LCP has much to offer the water sector beyond demand management. It is an approach that has potential for options assessment across the water cycle and can aid planning towards more sustainable outcomes within the sector. The paper concludes that LCP concepts and techniques will have worth in addressing the challenges of sustainable development for both urban water systems and catchment managemen
