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<br /> <br /> <br /> <br />eRB <br />2-13-63 <br /> <br />.' <br /> <br />Estimates of Average Annual Depletions in the Upper Colorado <br />River Basin and Related Data <br />1910 - 2000 <br /> <br />r..n <br />(,,;I <br />..,J <br /> <br />Attached are two sets of tabulations: (1) "Estimated Annual <br />Upper Basin Depletions Other Than Initial ~illing of CRSP Reservoirs" <br />dated 2/1/63; and (2) Upper Basin Compact Allocations and Estimated <br />Depletions in the Upper Colorado River Basin by States" dated 1/28/63. <br /> <br />The tables dated 2/1/63 are based on the most r8cent and <br />reliable data available and show estimates of future depletions in <br />the Upper Basin assuming average runoff conditions. The estimates <br />indicate the Upper Basin depletions will reach 3.0 million acre-feet <br />next year, 4.0 million acre-feet in 1973, and 5.0 million acre-feet <br />in 1982. <br /> <br />The data are useful for estimatin: the amount and timing of <br />water available for beneficial consumptive use in California under <br />different legal assumptions. F'or example, the potential impact of <br />the proposed Rifkind decree in Arizona v. California is o~ particular <br />interest at this time. ihe estimated lon~-time average dependable, <br />undepleted flow at Lee ~erry is 14.0 million acre-feet a year, of <br />~hich 2.5 million is needed for net mainstream losses below Lee ferry <br />and the ~~exican i;'atET Treaty, leaving 11.5 million for Upper Basin <br />depletion and Lower Basin mainstream use. <br /> <br />The attached tables and chart show the estimated Upper Basin <br />depletions by 1982 will reach about 5.0 million acre-feet a year. <br />The remaining mainstream water supply at that ti~e of 6.5 million <br />would be avai12ble for use in the LOher Basin, of which rtifkindwould <br />allocate California 6nly 3.8 million (44/75 of 6.5). Such an amount <br />would be 1.2 million less than California's measured diversions less <br />mea sure,',. returns in each of the last two years anC: would provi,ie no <br />water for the Colorado River Aqueduct under the Beven-Party Agreement. <br />It is emphasized that all oi thes8 figures are based on average long- <br />time runoff conditions. It is a reas5nable assumption oVlin~ fo the <br />massive storace capacity 01 Lakes Pmlell and Lead vJhich will iron out <br />annual varie.tions in runoff over extended time periods. <br /> <br />The 1/28/63 tables shO\, the estimated depletion for existing <br />and authorized projects lor each of four states in the Upper Basin. <br />Shown also is a percentage compa~ison with the state allocations in <br />the Upper Colorado River Compact. The tabulations show th~t existing <br />and authorized depletions in. Colorado and New !vlcxico are ahec:d by 3/4 <br />and 2-1/4 percent, respectively, of the Compact percenta .es anJ those <br />in Utah and Wyoming are lagging behind by 1/2 and 2-1/2 percent, res- <br />pectively. 'l'he tables seerel!;ate projects into four general classifi- <br />cations (1) existing and authorized, (2) pending, (3) under active <br />investigation (feasibility stage) and (4) other active proposals <br />(reconnai ssahce star:e investigat ions or equi val ent). 'rhe est illJated <br />aggregate annual depletion for the four states for all four classifi- <br />cations is 6.7$ million acre-feet. <br />