Laserfiche WebLink
<br />o <br /> <br />000155 <br /> <br />. <br /> <br />PRE F ACE <br /> <br />EFFICIENCY OF WATER USE--AN OVERVIEW <br />By Norman A. Evans <br /> <br />Water-use efficiency is used to describe how well the resource is <br /> <br /> <br />conserved or utilized. Higher efficiencies in particular uses are assumed <br /> <br /> <br />to have the effect of releasing unneeded resources for use by others. <br /> <br /> <br />The purpose of this study is to examine that question as it applies to <br /> <br /> <br />water in the South Platte River Basin. <br /> <br />. <br /> <br />Efficiency is evaluated by dividing the quantity of output from some <br /> <br /> <br />given system by the quantity of input. A high efficiency implies that <br /> <br /> <br />there is little waste involved in the system, In the case of water systems, <br /> <br /> <br />if a high proportion of the water withdrawn from supply for a particular <br /> <br />use is utilized in that use, the efficiency is said to be high. Although <br /> <br /> <br />this concept is useful, its indiscriminate use can be deceiving. <br /> <br /> <br />For example, a high proportion of waste through deep percolation and <br /> <br /> <br />surface runoff from an irrigated farm would result in a low irrigation <br /> <br /> <br />water-use efficiency, This waste may be a real one to the individual farm, <br /> <br /> <br />but the water is still contained within a larger hydrologic system of <br /> <br /> <br />which the farm is merely a part. The water is not lost to the larger <br /> <br /> <br />system; it is merely routed differently through the system. High seepage <br /> <br /> <br />losses in conveyance or through deep percolation and surface runoff are <br /> <br /> <br />not critical in terms of reducing the total water supply for a basin. <br /> <br /> <br />It is true that its rerouting affects water distribution with time through <br /> <br /> <br />the basin; this may be a benefit. There may be a loss of quality, however. <br /> <br /> <br />Extrapolation of efficiencies from a single user to regional or basin- <br /> <br /> <br />wide efficiency would give misleading indications of new water supplies <br /> <br /> <br />that could be available through adoption of efficiency measures. This is <br /> <br /> <br />because one user's waste may be another user's supply. <br /> <br />. <br /> <br />The following diagram compares the efficiency concept applied to a <br /> <br /> <br />single use for that of a larger system where several single uses are tied <br /> <br /> <br />tcgether in sequence, as i.s the case in a river basin. It is quite evident <br /> <br />i <br />