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<br />-32- <br /> <br />I <br />I <br />I <br />I <br />I <br />1 <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />o <br />~ <br />(Jt <br />0')' <br /> <br />1,071,540 ha-m/yr. In comparison, data published by the <br />U.S. Department of the Interior (USDI, BR, 1979a) indicate <br />an actual observed average flow of 1.27 x 106 ha-m.at Lee's <br /> <br />Perry for the period of 1941-1978. <br /> <br /> <br />The difference between virgin and observed flows should <br /> <br /> <br />ideally represent the consumptive use in the Upper Basin. <br /> <br />Estimates of consumptive use and water availability vary <br /> <br />widely. The USDI (1974) estimated the present depletion to <br />be about 4,562 x 105 ha-m/yr, and using different assump- <br />tions, the Westwide Study (USDI, BR, 1975b) estimated the <br /> <br />5 <br />1975 total consumptive use to be about 3,946 x 10 ha-m/yr. <br />The USDI estimated that an average of 7.15 x 105 ha-m of <br /> <br />water is the total available water supply in the Basin, <br /> <br />leaving about 260,000 ha-m for future development. <br /> <br />The most obvious conclusion which can be derived from <br /> <br />the above data is that there is little water for new develop- <br />ment without conflicting with present use. The USDI (1974) <br />calculated that 1.85 x 105 to 2.28 x 105 ha-m/yr of addi- <br /> <br />tional water would be consumed for nonenergy uses by the <br /> <br />year 2000. Plotkin et al. (1979) presented data which <br />indicates that just energy development consumption by the <br />year 2000 could be between 74,000 and 136,000 ha-m/yr. <br />The WPRS developed the "1976-Modified Base (1)" which <br />states that 1,158,030 ha-m/yr water with a concentration of <br />1,100 mg/l at Imperial Dam depicts conditions expected by <br />1900 (USDI, BR, 1979a). This "base" includes existing <br /> <br />observed conditions in 1976 plus effects of projects under <br />