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<br />River Regulation <br /> <br /> <br />Check gates. <br /> <br />Water levels in nearly all of the major <br />reservoirs in the Colorado River basin <br />reached the same high levels as in water <br />year 1983. Early runoff forecasts in 1984 <br />indicated an abnormally high flood potential <br />which triggered reservoir drawdowns <br />sufficient to accommodate the anticipated <br />runoff volume. Consequently. maximum <br />releases from mainstem reservoirs during <br />the runoff were much less than in water <br />year 1983 even though the 1984 runoff was <br />higher in both volume and peak. The <br />nctural virgin runoff reaching the streams <br />of the Colorado River drainage system <br />above Glen Canyon Dam during water year <br />1984 was estimated- at- about. 24.5 million- - <br />acre.feet. Of this amount, approximately <br />3.8 million acre-feet were consumptively <br />used within the Upper Colorado River Basin <br />States. <br /> <br />Adjustments in storage in Upper Basin <br />reservoirs resulted in on actual inflow to <br />lake Powell of 21.2 million acre-feet during <br />water year 1984. The annual release from <br />lake Powell, based on measurements at <br />the gaging station at lees Ferry, Arizona, <br />wos 21.1 million acre-feet. For the l-year <br />and 10.year periods ending September 30, <br />1984. 21.098.000 acre.feet and 108.796.000 <br />acre-feet, respectively, passed the compact <br />point at lee Ferry. <br /> <br />22 <br /> <br />The projected water year 1985 release from <br />lake Powell, based on reasonable minimum <br />runoff conditions is lO,700,OCO acre-feet. <br />The projected release for the reasonable <br />maximum runoff condition is 18,100,OCO <br />acre-feet. When combined with tf1e <br />average annual flow of the Pari a River, this <br />would result in an Upper Basin delivery <br />ranging from 113.1 to 117.5 million acre- <br />feet for the 10-year period ending <br />September 30, 1985. <br /> <br />Daily releases are made from the storage <br />reservoirs in the Lower Basin to meet the <br />incoming orders of the water user <br />. agencies. - When possible, all. water -passes <br />through the powerplant units. The daily <br />releases are regulated on an f10urly basis <br />to meet as nearly os possible the power <br />loads of the electric power customers. <br />Minimum daily flow objectives are provided <br />in the river to maintain fishery f1abitat. <br /> <br />The combination of high runoff conditions <br />and river regulation below Hoover Dam <br />resulted in a total delivery to Mexico of <br />approximately 15,160,000 acre-feet in <br />excess of the scheduled treaty quantity <br />(1,700,000 acre-feet) during water year <br />1984. Of that amount, 137,500 acre-feet of <br />drainage waters were bypassed to the Gulf <br />of California via the Santa Clara Slough. <br /> <br /> <br />Equipmont usod 10 clean canal$. <br /> <br />This bypass channel was constructed <br />pursuant to provisions of Minute No. 242 of <br />tf1e International Boundary and Water <br />Commission. <br /> <br />The current most probable water supply <br />condition operation plan yields slightly in <br />excess of 6.0 maf of vacant storage space <br />as of January 1, 1985, or a little more than <br />the 5.6 maf that was available on January <br />1, 1984, but less than the 6.6 maf that was <br />available January 1, 1983. With only 6 maf <br />of vacant storage space on January 1, it is <br />virtually assured that at least a 19,000 cfs <br />flood control release is required at Hoover <br />Dam-under-the -flood-control regulations. <br />