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—_c COLORADO WATER SUPPLY CONDITIONS UPDATE )M THE OFFICE OF THE STATE ENGINEER; COLORADO DIVISION OF WATER RESOURCES March 1997 3M 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 The SWSI indicator and snowpack figures continued to hold well above average through February. Statewide the snowpack is 142%of average as reported by the Natural Resources Conservation Service. The Gunnison River basin has the highest snowpack at 154% of average, and the South Platte River basin has the lowest at 134% of average. As the snowpack continues to hold above normal through late winter prospects increase for an above average runoff. Spring weather significantly affects the duration and peak flow rates of the runoff. Temperature affects the rate of snow melt, wind affects rate of melt and the amount of runoff vs. evaporation, and rainfall directly adds to stream flow and can increse the rate of snow melt. 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 snow pack,reservoir storage,and precipitation for the winter period(November through April). During the winter period snow pack 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 March 1, 1997 and reflect conditions during the month of February. March 1, 1997 Change From Change From Basin SWSI Value Previous Month Previous Year South Platte 3.2 +0.2 -0.6 Arkansas 3.3 0.0 +4.9 Rio Grande 3.5 +0.4 +6.2 Gunnison 3.9 +0.1 +2.2 Colorado 3.5 +0.2 +1.6 Yampa/White 3.8 -0.1 +1.1 San Juan/Dolores 3.5 +0.1 +6.2 SCALE -4 -3 -2 -1 0 +1 +2 +3 +4 Severe Moderate Near Normal Above Normal Abundant Drought Drought Supply Supply Supply 1