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<br />002831 <br /> <br />- <br /> <br />- <br /> <br />RDATA (IPOW,12) = maximum storage capacity of Lake Powell. <br />RDATA (MEAD,12) = maximum storage capacity of Lake Mead. <br />SPCREQD (9) = flood control space required at the end of <br /> <br />September. Thirty percent of this space <br />requirement is assumed to be available in <br /> <br />reservoirs above Lake Powell. This assumption <br /> <br />was found to be generally consistent with <br /> <br />historical records. <br /> <br />3. Compute the annual surplus release from Lake Mead, if any. This <br />surplus release is a function of current storage levels, basin deple- <br />tions, and annual natural flow at Lee's Ferry for a selected probabil- <br />ity level. This probability term is the variable that changes from <br /> <br />one alternative strategy to the next. It is based on the assumption <br /> <br />that the frequency distribution pattern of natural flows at Lee's <br /> <br />Ferry is normal. This assumption has been verified by statistical <br />analysis of the historical data. A probability level of 0.80 will <br />cal~for using a natural flow at Lee's Ferry which is expected to be <br />exceeded 20 percent of the time. In an operational sense, this proba- <br /> <br />bility level is related to the probability of being at or below the <br />end of water year target storage levels for the combined storage of <br /> <br />Lakes Powell and Mead, without making annual releases below Hoover <br /> <br />Dam greater than 13,400,000 acre-feet. <br />\ j <br />~ 6"- <br />SRM = (PMS] - TRGT)(l + BANKST) + PFLO - USESUB - USESLB <br /> <br />where: <br /> <br />10 <br />