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• COLORADO WATER SUPPLY CONDITIONS UPDATE OM THE OFFICE OF THE STATE ENGINEER; COIARADO DIVISION OF WATER RESOURCES January, — )OM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 i/II e( This month's SWSI values dropped from last month's values in all basins except the South Platte's. The South Platte SWSI indicates an above normal supply, the Yampa/White SWSI indicates a below normal supply, and the value in all remaining basins shows a near normal supply. The drop in SWSI values is most likely due to a statewide reduction in snowpack from the previous month. According to the Natural Resources Conservation Service the statewide snowpack averaged 81%of normal on January 1,with the Arkansas basin being the only basin with an above average amount at 135% of normal. The reason for the increase in the South Platte basin's SWSI is not known. Stream flow and reservoir storage conditions remain good throughout the state. The Surface Water Supply Index (SWSI) developed by this office and the U.S.D.A. Natural Resources Conservation Service is used as an indicator of mountain based water supply conditions in the major river basins of the state. It is based on snowpack,reservoir storage, and precipitation for the winter period (November through April). During the winter period snowpack is the primary component in all basins except the South Platte basin where reservoir storage is given the most weight. The following SWSI values were computed for each of the seven major basins for January 1, 1997 and reflect conditions during the month of December. January 1, 1998 Change From Change From Basin SWSI Value Previous Month Previous Year South Platte 3.0 +1.0 +0.4 Arkansas 0.8 -1.8 -2.1 Rio Grande -0.9 -1.0 -2.9 Gunnison -0.4 -1.6 -4.1 Colorado 0.1 -1.7 -3.2 Yampa/White -2.9 -2.3 -6.0 San Juan/Dolores -0.3 +0.4 -2.6 SCALE -4 -3 -2 -1 0 +i +2 +3 +4 Severe Moderate Near Normal Above Normal Abundant Drought Drought Supply Supply Supply 1