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<br /> <br />1981 <br />1982 <br />1983 <br />1984 <br />1985 <br /> <br />3,660,600 <br /> <br />3,732,800 <br /> <br />3,533,700 <br /> <br />3,432,100 <br /> <br />3,716,500 <br /> <br /> <br />5.0 <br /> <br />DEPLETION ANALYSIS <br /> <br />5.1 BACKGROUND <br /> <br />Daily snowmelt inflow hydrographs for Glen Canyon (Lake Powell) and <br />Hoover Dam (Lake Mead) were calculated, along with the intervening <br />inflow between Glen Canyon and Hoover Dams. The 100-year undepleted <br />base snowmelt flood inflow into Hoover Dam has an annual volume of <br />26,656,000 acre-feet. This inflow hydrograph was separated into <br />hydrographs for each major upstream reservoir to accommodate the <br />modeling requirements for operation of the upstream facilities. <br /> <br />5.2 1985-LEVEL DEPLETIONS ABOVE GLEN CANYON <br /> <br />The 100-year base snowmelt floods are undepleted, unregulated <br />natural flows. The depletions for the Colorado River basin above <br />Glen Canyon Dam (Lake Powell) were obtained from the Upper Colorado <br />Region of the Bureau of Reclamation. The preliminary data, which <br />were used in this study and have since been revised, were used in <br />developing the Colorado River System Consumptive Uses and Losses <br />Report, 1981-1985. Annual depletions for the years 1981 through <br />1985 were as shown in table 5.1. <br /> <br />Table 5.1 - Annual depletions above Glen Canyon Dam <br /> <br />Year <br /> <br />Depletion <br />(acre-feet) <br /> <br />Total <br />Average <br /> <br />18,075,700 <br />3,615,100 <br /> <br />The 1985-level depletions represent present water resource <br />development conditions in the basin. The 1985-level depletion above <br />Glen Canyon, which is estimated as the 1981-1985 average annual <br />depletion, is 3,615,100 acre-feet. The monthly distribution <br />percentages were estimated by examining a typical irrigated area in <br />the basin (e.g., the Grand Junction area). Data from the irrigation <br />seasons of 1981, 1982, and 1983 were analyzed. The agricultural <br /> <br />61 <br />