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Replacement Water Supply <br /> WMI is the owner or leaseholder of senior water rights which were historically used <br /> to irrigate crops on the Challenger property now being mined for sand and gravel. It is these <br /> rights which will be used in a temporary substitute supply plan to replace the depletions <br /> attributable to the water uses at the mining operation. <br /> Adjudication Awaprtetion Decreed Total WI <br /> f Meer Dote Dete - — - <br /> e — <br /> Hill wd ermh Ditch 5.28-1883 6.30-19" 27.0 128 20 <br /> The 20 shares of the Hill and Brush Ditch under lease to WMI were historically used <br /> for the irrigation of about 61.5 acres on wbat is now the Challenger Pit mining area (See <br /> Figure B-2). Using aerial photographs taken in July 1969 and in September 1989,it has been <br /> determined that about 12.5 acres out of the 61.5 acres (20%) have been removed from <br /> $ production due to the mining activities. <br /> The net potential evapotranspiration (Et) of pasture grass, corn and alfalfa was <br /> estimated using the modified Blaney-Criddle formula with crop coefficients published in StS. <br /> Technical Manual No.21 and using climatic data from the Fort Collins weather station. The <br /> average annual consumptive use of irrigation water, weighted for a historical crop rotation <br /> of corn (33%), alfalfa (33%) and pasture grass (33%), is estimated to be 1-58 acre-feet per <br /> r <br /> acre. <br /> The historic consumptive use of irrigation water attributable to the use of the 20 <br /> shares of the Hill and Brush Ditch on the Challenger parcel was determined using a simplified <br /> water budget analysis comparing the available diversions with the potential crop requirement <br /> In this analysis, the following assumptions were made: <br /> • Diversions based on 20 shares out of 128 outstanding shares (15.6%). <br /> • Ditch loss = 20% of headgate diversions. <br /> 3 <br />