OCR Text |
Show FILLING OF UPPER BASIN STORAGE UNITS In order to accomplish an initial filling of Lake Powell to the water surface elevation at which the Glen Canyon Powerplant could be put in operation, releases of water from Lake Powell were curtailed during late 1964 and early 1965. This curtailment caused a draft of Lake Mead storage water to a point below its rated power head. Power generation at Glen Canyon Dam has since been maintained at reservoir levels slightly above minimum power head. With a favorable 1965 spring runoff, Lake Mead was restored to rated head (elevation 1122.8) in June 1965. Thereafter the level of Lake Mead has remained above rated head. The spring runoff of 1966 was extremely disappointing. It was possible only to achieve a maximum level at Lake Powell of elevation 3545.68 in June 1966, and a content of 9,536,000 acre-feet. Thereafter there was a draft on Lake Powell storage to maintain rated head at Lake Mead and power generation at Glen Canyon powerplant. By May 22, 1967 the water surface of Lake Powell had receded 43.5 feet to elevation 3502.23 and a content of 6,779,000 acre-feet. The spring runoff of 1967 was also disappointing, Lake Powell rising to only elevation 3532.85, content 8,645,000 acre-feet, on July 27, 1967, or 13 feet below the high point of the previous year. Lake Mead at the end of water year 1966-1967 contained 14,375,000 acre-feet* of available storage at elevation 1130.20. It should be noted that % million acre-feet were retained in Lake Mead in the 7.4 feet of depth above its rated head. The gates were closed at Blue Mesa reservoir on October 26, 1965, and commercial power generation commenced on September 13, 1967. The results of the filling procedures adopted by the Secretary of the Interior at Lake Powell, Flaming Gorge, Navajo and Blue Mesa Reservoirs in the Upper Colorado River Basin and at Lake Mead in the Lower Basin are illustrated in the graphs on the following pages. For reference purposes, the graph for Lake Mead has been extended back to 1935 when water was first stored behind Hoover Dam. * Based on April 1, 1967 Capacity Table revised according to Sedimentation Survey 1963-64. 29 |