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COLORADO <br /> WATER SUPPLY CONDITIONS UPDATE <br /> GROM THE OFFICE OF THE STATE ENGINEER; COLORADO DIVISION OF WATER RESOURCES July 1996 <br /> IM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 <br /> June stream flows in the southern mountains were extremely low. The Rio Grande, Conejos,Animas, La Plata, and <br /> Navajo stream flow totals were all in single digit percentiles for June, meaning the flows were lower than are expected to <br /> occur 10% of the time. These conditions are a result of last winter's very low snowpack in the southern mountains. The <br /> SWSI values in the Rio Grande and San Juan/Dolores basins are a reflection of these very low stream flows. The southern <br /> tributaries in the Arkansas basin are also running very low, but the SWSI value in that basin is supported by good flows on <br /> the Arkansas mainstem. The San Juan/Dolores basin is the only basin having a lower than average reservoir storage total. <br /> The stream flow situation,and SWSI values,improve as one looks northward. This is due to the improved snowpack <br /> those mountains received,and because the weather has allowed the runoff to occur in a relatively steady manner. The runoff <br /> did not have a sharp peak, which helped to eliminate flood problems. A more gradual runoff helps most irrigators as it <br /> allows greater use of the river water farther into the summer irrigation season. <br /> The Surface Water Supply Index (SWSI) developed by this office and the U.S.D.A. Natural Resources Conservation <br /> Service is used as an indicator of mountain based water supply conditions in the major river basins of the state. It is based <br /> on stream flow, reservoir storage, and precipitation for the summer period (May through October). During the summer <br /> period stream flow is the primary component in all basins except the South Platte basin where reservoir storage is given the <br /> most weight. The following SWSI values were computed for each of the seven major basins for July 1, 1996 and reflect <br /> conditions during the month of June. <br /> July 1, 1996 Change From Change From <br /> Basin SWSI Value Previous Month Previous Year <br /> South Platte +3.2 +0.3 -0.7 <br /> Arkansas +2.8 -0.7 -1.6 <br /> Rio Grande -2.8 -2.7 -5.5 <br /> Gunnison +0.9 -1.9 -2.9 <br /> Colorado +1.8 -1.5 -0.9 <br /> Yampa/White +1.0 -1.8 -1.9 <br /> San Juan/Dolores -2.8 -3.0 -5.7 <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 />