Water use efficiency includes any measure that reduces the amount of water used per unit of any given activity, consistent with the maintenance or enhancement of water quality.
Water use efficiency is closely related to, and in several cases overlaps, other basic concepts of current environmental resource management. The best established of these related concepts, perhaps, is water conservation. The latter term has received many definitions in the past, but perhaps the definition used by Baumann et al. (1979) is most useful here, namely, that water conservation is any socially beneficial reduction in water use or water loss. Put in this manner, water use efficiency is of central importance to conservation. At the same time, the conservation definition suggests that efficiency measures should, in addition to reducing water use per unit of activity, make sense economically and socially.
The importance of efficiency in water use clearly varies across regions and nations, as well as through time. Geographically, for instance, water availability will condition the manner in which use patterns develop. Other things being equal, arid and semi-arid regions require a greater efficiency of water use than humid ones. But simple geographical patterns mask several equally important factors. Economic conditions will often lead to greater or lesser water use efficiency. Many regions in the world have been assisted in their development through public financing of water development. While the benefits or costs of such projects in efficiency terms is often debatable, the main point here is that economic factors can influence water use efficiency. Further, in some cases, where water developments have supported new settlements in dry areas, industrial processes and technologies that use water more efficiently than elsewhere may develop. An example would be the development of recirculation technologies or process changes. Social conditions may also be important in examining the efficient use of water resources. The literature reveals many areas where public education has led to conservation and better use of available water supplies.
