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<br />002865 <br /> <br />. <br /> <br />. <br /> <br />d. Estimated future depletions ln the upper basin, <br />including the effects of recurrence of critical <br />periods of water supply; <br />e. The "Report of the Committee on Probabilities and <br />Test Studies to the Task Force on Operating <br />Criteria for the Colorado River," dated October 30, <br />1969, and such additional studies as the Secretary <br />deems necessary; <br />f. 'The necessity to assure that upper basin <br />consumptive uses not be impaired because of failure <br />to store sufficient water to assure deliveries <br />under Section 602(a)(1) and (2) of P.L. 90-537. <br /> <br />In evaluating compliance of the CRSS/CRSM 602(a) storage <br />computation with the above criteria the following <br />corresponding observations are made tor each item: a) The <br />historic streamflows utilized are the natural flows <br />developed by Reclamation. The natural flow data base is an <br />improvement over the "virgin flow" computations as described <br />in tne systems overview and previous reviews. However, the <br />natural flows are only reliable on an annual basis. <br />Significant work remains in order for the natural flow data <br />base to accurately simulate the monthly hydrograph <br />distributions. The hydrology data base will be further <br />analyzed in a subsequent memorandum. <br /> <br />b) Only the the "most critical period of record" is <br />determined and utilized in CRSS/CRSM. The critical period <br />was determined as briefly described on page 37 of the <br />systems overview. As indicated the critical period is <br />dependent on the level of depletions assumed. Thus, <br />periodic adjustment of this factor is important. <br /> <br />c) The probability of water supply is limited to the <br />critical period of record only in actual computation of <br />602(a) storage in CRSS/CRSM. However, Lake Powell storage <br />is checked against 602(a) required storage at the 90 <br />percentile normal probability natural flow level in the <br />surplus strategy. The lower basin position on probabilities <br />is expressed in the attached March 15, 1982 letter from <br />Myron Holburt and the lower basin states to Clifford I. <br />Barrett. ,The surplus-storage strategy will also be <br />discussed in a subsequent memorandum. <br /> <br />d) Estimated future depletions are considered as indicated <br />by the attached table. <br /> <br />e) The 1969 report of the Committee on probabilities was <br />investigated further in a Bureau of Reclamation study done <br />in June, 1978. The present criteria consider the critical <br />factors identified in these studies. <br /> <br />-3- <br />