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COLORADO <br /> q <br /> WATER SUPPLY CONDITIONS UPDATE <br /> FROM THE OFFICE OF THE STATE ENGINEER; COLORADO DIVISION OF WATER RESOURCES December, 1998 <br /> ROOM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 <br /> December 1 marks a change in SWSI values from the summer stream flow component to the winter snowpack <br /> component. Low early snowpack in the northern mountains dropped the SWSI values in the northern basins. For instance, <br /> the negative SWSI values in the South Platte and Yampa/While river basins are a result of 70% and 68% of average <br /> snowpack in each basin, respectively. In contrast, the San Juan/Dolores and Rio Grande basins have the state's highest <br /> relative snowpack at 163%and 159%of average,respectively,and also have the highest SWSI values. December 1 snowpack <br /> values are the earliest readings of the winter, and contain only a fraction of the snowpack that will accumulate over the <br /> winter. They are most likely not indicative of the winter's snowpack contributions to next year's water supply as significant <br /> changes will occur before next spring. Both stream flow and reservoir storage remain adequate statewide. <br /> The Surface Water Supply Index (SWSI) developed by this office and the U.S.D.A. Natural Resources Conservation <br /> Service is used as an indicator of mountain based water supply conditions in the major river basins of the state. It is based <br /> on snowpack,reservoir storage,and precipitation for the winter period (November through April). During the winter period <br /> snowpack is the primary component in all basins except the South Platte basin where reservoir storage is given the most <br /> weight. The following SWSI values were computed for each of the seven major basins for December 1, 1998 and reflect <br /> conditions during the month of November. <br /> December 1, 1998 Change From Change From <br /> Basin SWSI Value Previous Month Previous Year <br /> South Platte -2.2 -5.0 -4.2 <br /> Arkansas 0.4 -1.4 -2.2 <br /> Rio Grande 3.0 +1.8 +2.9 <br /> Gunnison 1.1 +0.6 -0.1 <br /> Colorado 0.2 -1.7 +1.6 <br /> Yampa/White -1.8 -4.6 -1.2 <br /> San Juan/Dolores 2.8 +2.3 +3.5 <br /> SCALE <br /> -4 -3 -2 -1 b +1 +2 +3 +4 <br /> Severe Moderate Near Normal Above Normal Abundant <br /> Drought Drought Supply Supply Supply <br /> 1 <br />