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<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 />Safe yield estimate <br /> <br /> <br />The underflow from the Hay Gulch alluvium into the South Platte Valley <br /> <br /> <br />alluvium is estimated to be about 3000 acre feet per year. Since the <br /> <br /> <br />water table is over 20 feet below the surface throughout most of the basin, <br /> <br /> <br />the natural discharge from evapotranspiration is minor. <br /> <br />With wells placed in the deepest part of the alluvium near the lower <br />end of the basin, 40 to 50 percent of the natural underflow may be inter- <br />cepted and consumptively used. T"lUS, the safe yield of the Hay Gulch <br />aquifer is estimated to be 1200 to 1500 acre feet per year. <br /> <br />Dependability of quality <br /> <br />Because no major pollution or contamination sources exist in the Hay <br /> <br /> <br />Gulch watershed, the possibilities of maintaining the existing ground- <br /> <br /> <br />water quality are good. Further, if the ground water is developed for a <br /> <br /> <br />public supply by a water district, state laws can help to prevent others <br /> <br /> <br />from contaminating that supply. <br /> <br />Lost Creek Alluvium <br /> <br />The Lost Creek drainage area is the largest of the three under con- <br /> <br /> <br />sideration in this study. Lost Creek heads in T4S in northern Arapahoe <br /> <br /> <br />County some 40 miles from the South Platte Riv~r. It joins the South <br /> <br /> <br />Platte Valley in T4N near Dearfield. The lower portion of the basin is <br /> <br /> <br />shown in Figure 1. <br /> <br /> <br />The Lost Creek alluvial aquifer has been utilized as an irrigation <br /> <br /> <br />water supply for many years, therefore a fair amount of information is <br /> <br /> <br />available. Because of this, no additional test drilling was conducted on <br /> <br /> <br />behalf of the Morgan County Quality Water Association. <br /> <br /> <br />General geology and hydrology <br /> <br /> <br />The Lost Creek alluvium is underlain by bedrock consisting of the <br /> <br /> <br />Upper Cretaceous Pierre shale, Fox Hills sandstone and Laramie formations. <br /> <br /> <br />In the southern portion of the area the Denver and Arapahoe formations <br /> <br /> <br />of Tertiary to Upper Cretaceous Age underlie the alluvium. The alluvial <br /> <br /> <br />deposits in the ancient channels of the bedrock are rather extensive and <br /> <br />permeable. Dune deposits overlie a portion of the alluvium. <br /> <br />- 20 - <br /> <br />M. W, BITTINGER AND ASSOCIATES, INC. <br />