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1 ~ COLORADO WATER SUPPLY CONDITIONS UPDATE MARCH 2003 FROM THE OFFICE OF THE STATE ENGINEER: COLORADO DIVISION OF WATER RESOURCES ROOM 818,1313 SHERMAN ST., DENVER, CO 80203 303-866-3581; www.water.state.co.us A wetter February boosted the SWSI and snowpack values over most of the state. The March 1 statewide snowpack is 83% of average. The Colorado River basin has the highest value at 93% of average, and the Rio Grande basin has the lowest at 73% of average. The SWSI values are negative, but not in the sever drought category that covered the state through most of 2002. However, water users should take care in viewing this index because although the index (and current snowpack) are higher than last year, spring and summer stream flows are still anticipated to be well below average because the runoff will have to build from the current low winter base flows, and dry soil and low ground water levels will take up some snow melt before it reaches the streams. The three eastern slope index stream flow gages shown in this report had lower flows this February than they did in February 2002, the western slope index stream gages had about the same flows. Total reservoir storage in Colorado is at about one-half of normal. Reservoirs are storing what they can during the winter, but low winter flows mean less water is being stored than in a normal year. The Surface Water Supply Index (SWSI) developed by this office and the U.S.DA 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 March 1, 2003, and reflect the conditions during the month of February. Basin South Platte Arkansas Rio Grande Gunnison Colorado Yampa/White San Juan/Dolores March 1, 2003 SWSI Value -2.6 -2.3 -1.0 -1.4 -1.0 -1.8 -1.4 -4 Severe Drought -3 -1 -2 Moderate Drought Change From Previous Month +0.4 -0.3 +1.0 +0.5 +0.8 +0.3 +0.9 Scale o Near Normal Supply 1 Change From Previous Year -0.6 +0.2 +2.1 +1.3 +1.8 +1.4 +1.7 2 Above Normal Supply 3 4 Abundant Supply