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C". ..... 00 - c water for irrigation and power produc- tion. causes the lake's level to fluctuate annually. From about February to June each year, the lake gradually lowers as water is released to meet downstream commitments. Between June and February. water released from Glen Canyon Dam upstream coupled with lowered downstream demands allows the lake's level to be gradually raised again. Because of this ability to adjust releases to changing conditions, and because the lower river's channels and levees arc maintained, the homes and highly productive farmlands in the low, flat valleys of sOllthern California and southwestern Arizona are less likely to . be flooded. However. flood control does not mean flood prevention. The Flood of 1983 Each winter and spring, forecasts of snowmelt runoff are ulxtated monthly to assist in preparing reservoirs for the fonhcoming runoff In January 1983, the predicted runoff for the Colorado River was 112 percent of normal-not unusual- ly high. The forecast dropped slightly in February. In the spring, forecasts rose, but predictions were still for only a moderately high runoff. Then a series of unpredictcd weather patterns altered forecasts dramatically. Late snows, cooler-than-norma] weather in the early spring, an extremely wann weather trend in late spring, and substan- tial rains, caused a sudden and unforeseen magnitude of runoff. The snowmelt runoff for April through July was about 210 percellt of normal. Reservoirs in the Upper Colorado Basin began to fill. Regulations require that on January 1st each year, at least 5.35 million acre-fect (mat) of flood control space be availahle in Lake Mead and upstream reservoirs. On that date in 1983,6.5 maf werc available. But record /lows soon raced down the river. Bureau of Reclamation engineers increased releases from all Colorado River dams. 30 Water rushing over the Nevada spillway at peak capacity of 13,944 cubic feet per second and 4-1/2 feet above spillway gates, July 1983 By late June, it was apparent Lake Mead would soon reach the top of the spillway gates. and that the sight of water flowing into the Hoover Dam' spillways-not seen since the spillways were tested in 1941 - was a certainty. Finally, in the late hours of the even- ing of July 2, water began to slide across the top of the spillway gates. Within days, over 4 feet {)f water ,poured into the foaming basins and into the spillway tunnels-falling at over 100 miles per hour. The reservoir system peaked at 1225.83 feet on July 24. On September 6, the lake level receded below 1221.4 feet and the spill ceased on September 6. The peak passed, but higher than normal 110ws continued through the Colorado River Basin the remainder of the year. Although the Colorado River reservoir system did function in 1983 as it was designed, flooding caused a great deal of hardship for people located in the flood- way and for businesses located near the river or adjacent to Lakes Mead and Powell. At the same time, the 1983 flood illustrated how effective Reclama- tion's system of dams and reservoirs can be, not only to store precious water in n0I111al times, but to cut peaks from in~ evitable floods. No More Drought Hoover Dam also provides an ade- quate and reliable water supply for downstream agricultural users. The irrigated lands of the Southwest provide fresh vegetables and fruits for the entire Nation year-round. An ade- quate and dependable supply of irrigation water, rich soils, and warm climate in the valleys of the lower Colorado River