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I I I I" I I I I I I I I I I I I I I I n ". <; (( ') 1, uti.;;,. J -I.).. called playas, which range in size from a few acres to several hundred acres in the case of a few very large. pl ayas. It is estimated that there are more than 37 thousand playas scattered unevenly throughout much of the High Plains area south of the Platte River system. The heaviest concentrations of playas is in the southern High Plains region, with over 19 thousand located in the Texas High Plains alone. Abo~t two-thirds of these occur in non- cultivated areas and many could be managed for supplemental water supplies. A survey of playa incidence and use in Texas shows about 19,240 lakes with a total acreage of some 339,685 acres. This results in an average size for all Texas playas of 17.65 acres, although the average size varies on a county to county basis from a low of about 5 acres (Cochran and Gray Counties) to a high average of over 70 acres (Potter County). Applying this average playa size to the entire High Plains region, the 37 thousand playas would encompass over 653 thousand acres, or more than a thousand square miles of potential water storage capacity. Estimates of annual water runoff into the playa lakes range from a low of 1.5 million acre-feet to a high of as much as 8 million acre-feet in favorable years. Although the inci- dence of reuse of playa waters for irrigation, either by pumping directly from the lakes with portable or temporary facilities, or more permanent modifications and installa- tions, has increased significantly in recent years, it is still estimated that as much as 80-90 percent of playa water is simply lost to evaporation. The average annual rate of evaporation from free water sur- faces in the High Plains region is over 60" per year (or 17