Often, information on spatial water use efficiencies in a whole-of-the-catchment context does not exist or does not feed into the water policy process to guide investments. Significant gains in water use efficiency are achievable but the water savings are often assumed rather than identified systematically. This paper used a whole-of-the-catchment water accounting framework to identify the main pathways to enhance water use efficiency, taking the Murrumbidgee catchment in the Murray–Darling Basin in Australia as an example. The results show that large amounts of water remain unaccounted for in the river system account; the true water losses occur in the nearfarm and onfarm zones, most of which can be saved cost effectively. The catchment water accounting procedure thus offers a useful framework for bringing unaccounted/lost water flows into human and environmental uses, for enhancing water use efficiency, for targeting investments to the water system components with the largest potential gains in efficiency, and for garnering private sector investments to realize true water savings. The pro-investment technical and institutional, as well as governance and policy, interventions to revamp private sector participation in water infrastructure are articulated.
Keywords: Irrigation infrastructure, Murrumbidgee River, Public–private, investments, Water accounting, Water use efficiency, Whole-of-the-catchment