Laserfiche WebLink
<br />elJ0157 <br /> <br />. <br /> <br />. <br /> <br />Efficiency criteria as applied to water use has not incorporated <br /> <br /> <br />quality considerations, Yet quality is a key element today in water <br /> <br /> <br />management. Referring again to the diagram of single and sequential uses, <br /> <br /> <br />if the first withdrawal contains water having 100 ppm of dissolved solids, <br /> <br /> <br />and if the output is evapotranspiration through growing crops, the dis- <br /> <br /> <br />solved solids must be carried out of the first individual system by the <br /> <br /> <br />water identified as "waste," Thus the concentration of dissolved solids <br /> <br /> <br />in the supply to the second individual user will be 200 ppm unless salt <br /> <br /> <br />accumulation is allowed in the first system. Each sequential user will <br /> <br /> <br />receive a water supply of lesser quality compared to the preceding user. <br /> <br />The quality factor is not normally reflected in efficiency terms, yet it <br /> <br />has significant economic impacts. <br /> <br /> <br />In a limited sense the economic efficiency of a specific water use <br /> <br /> <br />is reflected by the ratio of dollar output per unit of water input. In <br /> <br /> <br />the case of irrigation, the yield of agricultural product per acre-foot <br /> <br />of water withdrawn from supply would represent the economic efficiency <br /> <br /> <br />relative to water uSe. In this connotation the most efficient use would <br /> <br /> <br />be that which adds the greatest value to the general economy, <br /> <br /> <br />Institutional and legal circumstances have an important influence <br /> <br /> <br />on how well a given water supply can be made to accommodate all legitimate <br /> <br /> <br />uses. If these elements are flexible and up-to-date, they can facilitate <br /> <br /> <br />improvement in efficiencies of water use, If not, they can be a serious <br /> <br /> <br />deterrent to improvements even though technical and managerial options <br /> <br />may be available. <br /> <br />. <br /> <br />iii <br />