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<br />I. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />t <br />I <br />I <br /> <br />A. <br /> <br />CHAPTER IV <br /> <br />WATER SUPPLY AND WATER DEMAND <br /> <br />WATER SUPPLY <br /> <br />1. Water Sonrce <br /> <br />The power and irrigation water supply for the Orchard Mesa Irrigation District <br />is obtained from direct diversion of Colorado River flow. There are no <br />storage facilities on District lands; however, the District can call on storage <br />rights in Green Mountain reservoirs. River flow is derived principally from <br />snowmelt on the upper drainage west of the Continental divide of the Rocky <br />Mountains. Flows are highly seasonal, with maximums in late spring and low <br />flow occurring in winter. Upstream dams provide regulation of flow; <br />minimum flows are enhanced by the presence of the upstream Shoshone Power <br />Plant, a run-of-river plant with a senior water right. <br /> <br />2. River Flows and Diversion. <br /> <br />USGS has compiled 61 years of record (1934-1994) for the Colorado River at <br />the Cameo gauging station (5.9 miles above Grand Valley Diversion Dam). <br />Average daily flow is 3853 cfs ftom a drainage area of 8050 square miles. <br />Natural flows of the river are affected by upstream trans-mountain diversions, <br />storage, reservoirs, power development, and diversion for irrigation to 160,000 <br />acres. USGS flow data for the 61 years on record are given in Appendix F. <br /> <br />Extreme flows of record were a maximum of 39,300 cfs on May 26, 1984, <br />and a minimum flow of 700 cfs on December 29, 1939. The Corp of <br />Engineers has estimated the 100 year flood to be 50,000 cfs. The lowest 7- <br />day was 852 cfs in December 1939. Low flows typically occur in late fall <br />through early spring. The lowest flow year on record was 1977, when flows <br />averaged 1937 cfs, or 50% of normal. Table IV-A shows the 10 years of <br />lowest flow from 1934 to 1994; 3 of those years occurred from 1990-92, a <br />period of extreme drought in Western Colorado. <br /> <br />3. Major Diverters in the Grand Valley. <br /> <br />There are several irrigation systems which divert out of the Colorado River <br />above the Grand Valley. Table IV-B provides data on the two major <br />diversions from the river. <br /> <br />lV-I <br />