OCR Text |
Show FILLING OF UPPER BASIN STORAGE UNITS Having acquired a minimum operating pool (6,124,000 acre-ft at elevation 3,490 ft) the Glen Canyon powerplant was tested and placed in operation on September 4, 1964. Thereafter Lake Powell was held close to minimum operating level. Releases of water at Glen Canyon Dam for power generation were not sufficient to satisfy Hoover power demands. Storage water was drawn from Lake Mead causing it to be lowered to elevation 1,088 ft in April 1965. This level was five feet above the minimum (elevation 1,083 ft) promulgated in the May 11, 1964 criteria revision by the Secretary of the Interior. The spring of 1965 provided favorable runoff. All Lake Powell water inflows in excess of releases through the turbines were bypassed at Glen Canyon Dam to restore power generating head at Hoover Dam. Rated power head at elevation 1,123 ft (14,500,000 acre-ft) at Lake Mead was achieved on June 23, 1965. Favorable runoff permitted Lake Mead to be maintained at near rated head for the remainder of the 1965 water year. Inflows in excess of those required for Glen Canyon power demands were retained in Lake Powell. On August 10, 1965 Lake Powell achieved a level of 3,533.9 ft (8,715,000 acre ft), maximum for water year 1964-65. It then receded slightly due to power generating demands. At the end of the 1965 water year the level at Lake Powell was at elevation 3530.1 ft (8,463,000 acre-ft) and Lake Mead elevation was 1,124.8 ft (14,709,000 acre-ft). The results of the filling procedures adopted by the Secretary of the Interior on Navajo and Flaming Gorge Reservoirs and Lake Powell in the Upper Colorado River Basin and on 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. From August, 1954 through May, 1957 Lake Mead was drawn below rated head to levels below those experienced during the recent thirteen months while accumulating water in Upper Basin Storage Units. 27 |