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<br />I Plan of Operation <br />I Water Year 1975 <br /> <br />The projected operation of each of the reservoirs in the <br />Colorado River Basin during water year 1975 for average <br />runoff conditions is described in the following paragraphs. <br />Charts 1 through 9 show hydrographs of the projected <br />monthly outflow from the reservoirs and the projected <br />end-of-month elevation and active storage in the reservoirs <br />for average and three other assumptions of 1975 modified <br />runoff from the Basin. The four assumptions are: <br />(I) AVERAGE based on the 1906-68 record of runoff, <br />(2) UPPER QUARTILE based on flows exceeded 25 percent <br />of the time during 1906-68, (3) LOWER QUARTILE based <br />on flows exceeded 75 percent of the time during 1906-68, <br />and (4) MOST ADVERSE based on the lowest year of <br />record which occurred in 1934. <br /> <br />The projected releases from Lake Powell are 8.23 <br />million acre-feet for the Most Adverse and Lower Quartile <br />assumed runoff conditions. Average and Upper Quartile <br />assumed runoff conditions would cause a splitting of storage <br />condition between Lake Mead and Lake Powell and releases <br />from Lake Powell would be 8.7 and 9.9 million acre-feet, <br />respectively. The Average and Upper Quartile release to Lake <br />Mead would cause the reservoir to rise 4 feet and 13 feet <br />higher at the end of the current year than the level reached <br />by the Most Adverse and Lower Quartile conditions. The <br />projected operations of Lake Mohave and Lake Havasu are <br />the same under all four of the runoff assumptions. <br /> <br />Upper Basin Reservoirs <br /> <br />Fontenelle <br /> <br />It is planned to lower the level of the reservoir. through <br />the fall and winter months until a water surface elevation <br />of about 6,480 feet is reached, then from the lasLoLMarch <br />through April to hold releases at about 1,400 ft3/s to <br />encourage wild geese to nest back away from the river. With <br />average runoff during the spring months, Fontenelle <br />Reservoir will fill by the end of June. After the spring runoff <br />the reservoir level will be controlled by adjusting the releases <br />through the powerplant to slowly reduce the elevation to <br />6,504 feet by the end of the summer of 1975. (Chart I) <br /> <br />29 <br />