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r _ <br /> COLORADO <br /> WATER SUPPLY CONDITIONS UPDATE <br /> FROM THE OFFICE OF THE STATE ENGINEER; DIVISION OF WATER RESOURCES June, 1991 <br /> ROOM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 <br /> JOHN R.KALISZEWSKI;EDITOR <br /> The Colorado snowpack was significantly diminished by spring-like weather conditions during the month of May. <br /> Low elevation snowpack is totally depleted leaving snowpack remaining only at high elevations on north and east facing <br /> drainages. Streamflow forecasts have been downgraded throughout the state. Reservoir storage remains above average. <br /> Soil moisture conditions are generally much improved over last year's conditions. Water shortages are likely to occur by late <br /> summer in those areas of the state with less than adequate storage. <br /> The statewide snowpack decreased from 93% of average on May 1 to only 43% of average on June 1. The North <br /> Platte basin reported the highest snowpack in the state at 95%of average. The lowest snowpack totals are in the San Juan, <br /> Animas, and Dolores basins at 29%of average. Statewide precipitation for the month of May was 85%of average ranging <br /> from a low of 54%of average in the San Juan/Dolores/Animas basin to 131%of average in the Arkansas basin. Water year <br /> totals are near normal across the state with the Rio Grande basin at 122%of average and the South Platte basin the lowest <br /> at 84% of average. The statewide reservoir storage was 110% of average on June 1, which is 109% of last year's June 1 <br /> amount. The Gunnison basin continues to have the highest storage rate at 144% of average while the Colorado basin has <br /> the lowest storage rate at 89%of average. Stateside storage is currently 53%of capacity(approximately 9 million acre-feet). <br /> Streamfow forecasts range from 70%-90%of average for most of the state. Less than 70% of average flows are forecast for <br /> the Little Snake, North Platte, and Lower Gunnison drainages. <br /> The National Weather Service forecasts above average precipitation in Colorado for the June 1-September 1 period. <br /> Going into 1991, 25%of the contiguous U.S.was experiencing drought conditions while 10%of the U.S.was experiencing <br /> extremely wet conditions. Little has occurred during the first half of 1991 to change these statistics. During the severe <br /> drought of the 1930's, 1950's, 1977, and 1988, approximately 50%of the U.S. experienced drought conditions. Storage in <br /> Lake Powell is 14,600,000 acre-feet. This is 3,100,000 acre-feet less than one year ago. Storage in California is now 65% <br /> of average while storage in Nevada is only 16% of average. Conditions in New Mexico are much better where storage is at <br /> 212%of average. <br /> The Surface Water Supply Index (SWSI) developed by this office is used as an indicator of water supply conditions <br /> in the state. It is based on reservoir storage, streamflow, and precipitation for the summer period (May 1st through <br /> November 30). Weight factors are applied to each of the measured hydrologic factors in computing the SWSI values for each <br /> basin. During the summer period, streamflow is the primary component in each basin except the South Platte where <br /> reservoir storage is the primary component. The following SWSI values were computed for each of the seven basins on June <br /> 1, 1991 and 1990: <br /> June 1, 1991 June 1, 1990 <br /> Basin SWSI Value SWSI Value <br /> South Platte +0.7 +0.3 <br /> Arkansas +0.2 -0.7 <br /> Rio Grande +1.7 -1.7 <br /> Gunnison +1.1 -1.4 <br /> Colorado -0.5 -2.5 <br /> Yampa/White -2.4 -3.8 <br /> San Juan/Dolores +0.4 -2.1 <br /> SCALE-4 -3 -2 -1 0 +1 +2 +3 +4 <br /> Severe Moderate Near Normal Above Normal Abundant <br /> Drought Drought Supply Supply Supply <br /> 1 <br />