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<br />. <br /> <br />. <br /> <br />. <br /> <br />OOD3tl4 <br /> <br />tions as described in Part X of this report. Since releases from Jackson Gulch <br /> <br />Reservoir for supplemental irrigation were relatively minor during February <br /> <br /> <br />through June, the irrigation depletion on a month-by-month basis could be more <br /> <br /> <br />accurately calculated during this period. Historic diversions to storage in Jackson <br /> <br /> <br />Gulch Reservoir constituted a depletion to the Mancos River. It was estimated <br /> <br /> <br />that diversions for stock water or irrigation in February and March resulted <br /> <br /> <br />in a 50 percent depletion to the Mancos River during this period, with most <br /> <br /> <br />of the depletion associated with replenishment of soil moisture and the lagged <br /> <br /> <br />effects of groundwater returns. hTigation diversions during April and May were <br /> <br /> <br />estimated to result in a 90 percent depletion, while diversions in June were <br /> <br /> <br />estimated to result in a 70 percent depletion. Although a 60 percent irrigation <br /> <br /> <br />efficiency for the entire irrigation season is assumed, a higher depletion rate <br /> <br /> <br />of 90 percent is estimated for April and May because of soil moisture replenish- <br /> <br /> <br />ment and the delayed effect of groundwater returns. Table Z is a summary <br /> <br /> <br />of the estimated depletion to the Mancos River associated with diversions in <br /> <br /> <br />February through June. It is estimated that depletions during this period, includ- <br /> <br /> <br />ing diversions for storage at Jackson Gulch Reservoir, averaged about 16,000 <br /> <br /> <br />acre-feet per year during the 1951 through 1980 study period. <br /> <br />-18- <br /> <br />-11. <br />