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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 />has been estimated by others to have a 150-year recurrence interval and is the <br />driest year recorded in the Yampa Basin. <br /> <br />The DOW storage allocation is used to provide a minumum reservoir pool. Its <br />purpose is to provide water for maintaining a fishery and to support <br />water-based recreation opportunities such as boating, fishing, water skiing, <br />and picnicking. <br /> <br />The reservoir operations simulation was conducted for the water years from <br />1953 through 1985. If Elkhead Lake is enlarged by at least 2,400 acre-feet, <br />the reservoir would provide a safe yield of 2,300 acre-feet annually. Total <br />reservoi r storage woul d fl uctuate between about 12,600 acre-feet and 16,180 <br />acre-feet during the normal and Viet years in the study period. During the <br />1977 drought, reservoir storage could be expected to drop to around 5,400 <br />acre-feet during the SUlrmer, as Colorado-Ute and Craig used the storage. The <br />full storage level would be o~tained dJring the next spring runoff. <br /> <br />Elkhead Lake was operated to maintain an instream flow below the dam of 5 cfs <br />throughout the year. Flows were al so bypassed to account for downstream <br />senior rights as outlined in Section 3.0. These rights were assumed diverted <br />duri ng the i rri gati on season at a maximum rate of 82 cfs. Evaporati on rates <br />were determined from National Oceanic and Atmospheric Administration Technical <br />Reports IJo. 33 and 34, and averaged 40 inches annually. Total reservoi r <br />evaporati on was shared among storage owners. For the cri ti ca 1 dry peri ods <br />this sharing of evaporative losses is important. <br /> <br />The year by year summary of the reservoir operations is shown on Table IV.5. <br />The detailed monthly operation study is included in the Appendix. The <br />reservoi r si zi ng study i ndi cated that 2400 acre-feet of storage is needed to <br />provide 2,300 acre-feet of firm municipal yield. Basically, the evaluation <br />i ndi cates the reservoi r refi 11 s every year, and no carryover storage capac i ty <br />is needed. At an average use rate of 130 gpcd, this method of operation would <br />supply water to an additional 15,800 people. <br /> <br />- 28 - <br />