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COLORADO WATER SUPPLY CONDITIONS UPDATE 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 June 2004 The lowest water supply index values were in the area from the northwest part of Colorado to the southeast and includes the Yampa-White Basin (-3.2), Colorado Basin (-1.8), and the Arkansas Basin (-2.4). Very low streamflows in these basins was the main factor for the low values. The other parts of the state show near normal index values for May. Reservoir storage is quite high in the Colorado Basin, San Juan - Dolores Basin, and Gunnison Basin, but storage is only a modest factor in the index calculation. Precipitation was very poor across all areas of the state in May. 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 stream flow, reservoir storage, and precipitation for the summer period (May through October). During the summer period, stream flow 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 June 1, 2004, and reflect the conditions during the month of May. June 1, 2004 Change From Change From Basin SWSI Value Previous Month Previous Year South Platte -0.2 -0.7 +0.7 Arkansas -2.4 -0.3 -0.4 Rio Grande +0.8 0.0 +3.1 Gunnison 0.0 -0.5 +0.4 Colorado -1.8 +0.3 -0.3 YampalWhite -3.2 -0.1 -4.0 San Juan/Dolores +0.7 -0.1 +2.0 Scale -4 -3 -2 -1 0 1 2 3 4 Severe Moderate Near Normal Above Normal Abundant Drought Drought Supply Supply Supply II:h