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• <br /> COLORADO <br /> WATER SUPPLY CONDITIONS UPDATE <br /> PROM THE OFFICE OP THE STATE ENGINEER; DIVISION OP WATER RESOURCES February, 1991 <br /> ROOM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 <br /> JOHN R.KALISZEWSKI;EDITOR <br /> THINK SNOW! Eighty percent of Colorado's annual streamflow comes from snowpack runoff. The Soil Conservation <br /> Service reports that the statewide snowpack on February 1, 1991 was only 77% of avenge. However, it is 127%of last year's <br /> snowpack for that date. Snowpack development is highest in the Rio Grande basin with 102%of average and lowest in the <br /> South Platte basin with 63% of average. Typically, 50% of the seasonal snowpack is received by February 1. Statewide <br /> precipitation was 82% of average for the month of January with a high of 107% of average in the Gunnison basin and a <br /> low of 63%of average in the Arkansas basin. Statewide precipitation totals for the water year (beginning October 1, 1990) <br /> are 104% of normal. The statewide reservoir storage is 113% of average with a high of 141% of average in the San <br /> Juan/Dolores basin and a low of 84% of average in the Rio Grande basin. Streamflow statewide was below normal for the <br /> month of January due to abnormally cold temperatures resulting in low snowpack runoff. <br /> The National Weather Service forecasts warmer and drier than average conditions for Colorado through April 1, 1991. <br /> While at this time last year the driest conditions were in the south and southwest sections of the state, this year the trend <br /> has reversed. The best prospects for near normal water conditions are in the Arkansas, Rio Grande, and San Juan/Dolores <br /> basins while the central and northern basins are currently forecast to have less than 70% of normal runoff. The National <br /> Weather Service also advises that Colorado is a difficult region to develop long-range forecasts due to geographic diversity <br /> and a variety of weather patterns that impact Colorado conditions. <br /> Southern California is now in the fifth year of a drought and is growing increasingly dependent on excess flows in <br /> the Colorado River that Colorado is entitled to,but is currently not using. Northern California reservoirs are at a lower level <br /> than they were in 1977,the worst drought year in California history. The streamflow forecasts are extremely low. The Sierra <br /> Nevada snowpack is less than 25%of average. The Governor of California announced a suspension of all of its agricultural <br /> deliveries and disclosed that Federal water deliveries would be cut by two-thirds. He further stated that mandatory rationing, <br /> 0 as strict as 300 gallons per day per household is probably inevitable. <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, snowpack, and precipitation for the winter period (December 1 through May <br /> 1). Weight factors are applied to each of the measured hydrologic factors in computing the SWSI values for each basin. <br /> During the winter period,snowpack is the primary component in each basin except the South Platte where reservoir storage <br /> is the primary component. The following SWSI values were computed for each of the seven basins on February 1, 1991. <br /> February 1, 1991 Change from <br /> Basin SWSI Value Previous Month <br /> South Platte -0.6 0.0 <br /> Arkansas -0.9 -1.1 <br /> Rio Grande +0.9 -0.6 <br /> Gunnison -0.2 -0.4 <br /> Colorado -1.6 -1.3 <br /> Yampa/White -1.1 -1.2 <br /> San Juan/Dolores -0.3 -0.5 <br /> SCALE <br /> -4 -3 -2 -1 0 +1 +2 +3 +4 <br /> Severe Moderate Near Normal Above Normal Abundant <br /> Drought Drought Supply Supply Supply <br /> NOTE: The +2.6 SWSI value listed for the Arkansas basin in the January report was incorrect. It should have been +0.2. <br /> 1 <br />