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<br />18 <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />roughly five feet of water). When applied to the estimated <br />acreage in playas in the High Plains region, this repre- <br />sents a potential water evaporation (Ew) loss of up to 3.5 <br />million acre-feet per year. <br /> <br />The capability to capture and use for productive agricul- <br />tural purposes even 50 percent of that avail abl e surface <br />water supply would represent a significant reduction in the <br />present rate of ground water withdrawal from the Ogallala <br />on an annual basis. <br /> <br />It is generally the case that the soil characteri st i cs <br />underlying most playas is so impermeable that very minor <br />quantities of playa water ever reach the aquifer from deep <br />percolation. Some water is taken up by native vegetation <br />and phreatophytes that characterize the frequently flooded <br />areas of most playas. Such waters are then transpired into <br />the atmosphere with much the same nonproductive effect as <br />the Ew loss. The vegetation does provide some feed and <br />cover for wildlife, helps prevent more serious wind erosion <br />during dry periods from blowing soils, may provide some <br />minor benefit as livestock pasturage and other insignifi- <br />cant benefi ts. <br /> <br />Modification of playas to concentrate the runoff waters <br />into smaller, deeper pools, thus reducing surface evapo- <br />rative losses and providing an improved area for pumping, <br />is bei ng carri ed out on a modest scale. An addit i ona 1 <br />benefit is real ized in reducing both the areal extent <br />and duration of inundation during periods of water <br />accumulation. It is conceivable that with significant <br />modification, as much as 40 to 60 percent of the acreage <br />in playa lakes in cultivated areas could be used more <br />