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<br />. <br /> <br />, <br /> <br />Conclusions and Recommendations <br /> <br />1. A frequency analysis of the expected annual evaporation losses from <br /> <br />the conservation pool of the Chatfield Reservoir indicates that an <br /> <br /> <br />annual replacement water input of 3250 acre-feet would satisfy the <br /> <br /> <br />contract requirements at a high level of confidence. <br /> <br />2. Investigations revealed that water storage under the 1975 storage <br /> <br /> <br />right does not have sufficient reliability during dry years that would <br /> <br /> <br />justify its inclusion toward satisfying the requirements of the proposed <br /> <br /> <br />contract. <br /> <br />3. A frequency study indicates that the low runoff experienced during the <br /> <br /> <br />five consecutive years of 1953-57 has a return period of between 100 <br /> <br /> <br />and 500 years. Availability of reliable hydrologic data, with the low <br /> <br /> <br />frequency of this event, suggested a detailed operational analysis of <br /> <br /> <br />this drought period. <br /> <br />4. For purposes of the drought analysis the reservoir was assumed to be <br /> <br /> <br />constructed and operated under hypothesized input conditions. The <br /> <br /> <br />runoff conditions and the evaporation losses were those derived from <br /> <br /> <br />historic data. <br /> <br />Six case studies indicate that (a) with 3000 acre-feet annual replace- <br /> <br /> <br />ment, the contract requirements were never violated regardless of the <br /> <br /> <br />operation, and (b) imposing a strict operational policy could reduce <br /> <br />the annual replacement input to 2400 acre-feet without violating the <br /> <br /> <br />conditions of the contract. Hydrologic conditions prior to and immediately <br /> <br />following the period of analysis fully justify the assumptions made in <br /> <br /> <br />the operation study. <br /> <br /> <br />5. The District should consider the acquisition of water rights with a <br /> <br /> <br />transferrable dry-year yield of 2400 acre-feet. The unit price of this <br /> <br /> <br />water, including the costs of the transfer proceedings, may not exceed <br /> <br /> <br />$1200 per acre-foot. <br /> <br />6. In acquiring the needed replacement water, it is recommended that special <br />preference be given to reservoir water. <br /> <br />,.. 22 <br /> <br />M. W. BITTINGER AND ASSOCIATES, INC. <br />