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• <br /> COLORADO <br /> WATER SUPPLY CONDITIONS UPDATE <br /> FROM THE OFFICE of THE STATE ENGINEER: DIVISION OF WATER RESOURCES October, 1990 <br /> ROOM 818.1313 SHERMAN ST.,DENVER.CO 80203; (303)-866-3581 <br /> Statewide precipitation was significantly above normal for the month of September. Precipitation averaged 168% <br /> of normal with a high of 264% of normal in the Rio Grande basin and a low of 110% of normal in the Yampa/White <br /> basin. These precipitation amounts are in contrast to the August conditions when statewide precipitation was 84% of <br /> normal. As is common in Colorado, precipitation varied considerably. Substantial rainfall was recorded at Wolf Creek Pass, <br /> Durango, and Saguache with 6.3 inches, 5.1 inches, and 2.9 inches respectively. Abnormally dry conditions were <br /> experienced at Rabbit Ears Pass and Cedaredge with 1.1 inches and 0.7 inches of precipitation for the month respectively. <br /> Cumulative precipitation for the 1990 Water Year (October, 1989 through September, 1990) was 25% above normal for <br /> the central South Platte basin area and 25% below normal for the extreme northwest and west-central sectors of the state. <br /> In other areas of the state cumulative precipitation was near normal. <br /> Although reservoir storage has been drawn down considerably in the last 12 months, statewide it still remains <br /> normal to above normal when compared to historic reservoir storage levels. Storage levels are below normal in the Rio <br /> Grande, Gunnison and Colorado basins. Relative storage rpmair" highest in the Arkansas basin. The consumption of <br /> reservoir carry-over storage this year will impact conditions next year if the 1991 runoff is below normal and as a result <br /> storage cannot be replaced, The greatest impacts would be on recreational uses of water. Streamfiow at key index gaging <br /> stations approached twenty year lows in the Arkansas, Gunnison and Yampa/White basins. Even with significantly above <br /> normal precipitation for the month, streamflow remained low in these basins due to low soil moisture levels. Soil moisture <br /> deficiency remains at high levels in the west-central and northwest sectors of the state. <br /> The Surface Water Supply Index (SWSI) developed by this office is used as an indicator of water supply conditions <br /> in the state. It is based on reservoir storage, streamflow and precipitation for the summer period (May 1 through <br /> December 1). Weight factors are applied to each of the measured hydrologic factors in computing the SWSI values. <br /> During the summer period, streamflow is the primary component in each basin except the South Platte where reservoir <br /> storage is the primary component. The following SWSI values were computed for each of the seven basins on October <br /> 1, 1990. <br /> October 1 Change from <br /> Basin SWSI Value September 1, 1990 <br /> South Platte +2.1 0.0 <br /> Arkansas -0.1 -0.6 <br /> Rio Grande 0.0 +0.4 <br /> Gunnison -1.9 +0.7 <br /> Colorado -0.6 +1.3 <br /> Yampa/White -2,7 +0.8 <br /> San Juan/Dolores +0.3 +1.0 <br /> SCALE <br /> -4 -3 -2 -1 0 +1 +2 +3 +4 <br /> Severe Moderate Near Normal Above Normal Abundant <br /> Drought Drought Supply Supply Supply <br /> 1 <br />