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• 23 • <br />tion difficulty and not an isoh~~etal limitation on reclamation potential, <br />and assuming that reclamation is considered as site-specific with other <br />limiting factors near the 250 mm precipitation limit, several disturbing <br />questions still arise from the Academy simplifications. <br />The National Academy Precipitation Question <br />Assuming that the precipitation limit is intended as merely an index <br />of potential reclamation difficulties, one still needs to analyze the reliability <br />of precipitation information and adequacy of that value to truly reflect re- <br />clamation potentials for the high northern plains. Fewer than half the years <br />achieve mean annual precipitation in this region, and about 30 percent of the <br />annual amount is never absorbed at the ground surface to become effective soil <br />moisture due to sublimation of snow, interception of growing season precipita- <br />tion, and runoff from thunderstorms (Trelease et al. 1970, 30 percent falls <br />as snow of which 70-80 percent sublimates and 20-25 percent of the growing <br />season precipitation is intercepted or runs off). Eighty to eighty-five per- <br />cent of the area of stripable coal reserves as outlined by the National Academy <br />20 cm <br />in Montana and Wyoming lie within a precipitation zone between the(8-inch)and 41 an <br />(16-inch)mean annual precipitation isohyets of the National Atlas. A preliminary <br />review of precipitation station data suggests that the range of values for <br />