OCR Text |
Show SUMMARY This report presents the results of comprehensive investigations of water resources for formulation of framework plans to provide a broad guide to the best use, or combination of uses, of water resources to meet foreseeable short- and long-term needs. For flexibility in analysis and planning, the Upper Colorado River upstream from Lee Ferry, Arizona, has been divided into three subregions comprising the natural drainages of the Green River, Upper Main Stem, and San Juan- Colorado. Summaries of water resource data are also prepared for the states of Arizona, Colorado, New Mexico, Utah, and Wyoming. Water supply from precipitation averages about 95 million acre- feet a year. Annual precipitation varies from less than 6 inches in desert areas of the southwestern portion of the region to over 50 inches in the high elevation headwater areas in Colorado. A broad range of climatic and resulting streamflow conditions exist. Large variations in annual discharge occur also, from year to year due to variations in precipitation, and over periods of years due to long-term climatic trends. Average annual discharge of the Colorado River at Lee Ferry was 12,426,000 acre-feet for the 52-year period 1914-65, with extremes of 21,894,000 acre-feet in 1917 and 4,396,000 acre-feet in 1934. Average annual virgin flow at Lee Ferry, as unaffected by the activities of man, is estimated at 14.87 million acre-feet over the 52-year period 1914-65. Estimated average annual withdrawal and consumptive use of ground water is less than one percent of surface water use. A close relation exists in many areas between local ground and surface water resources. Water is used for irrigation, domestic-municipal-industrial purposes, livestock watering, hydroelectric and thermal electric power generation, mineral activity, fish and wildlife facilities, and recre- ation. Large amounts of water are also exported to adjoining regions for multiple-purpose uses. A total of 581 reservoirs with usable storage in excess of 29.7 million acre-feet had been constructed by 1965 to provide storage regulation for various water uses. Since 1965 over one million acre- feet of additional storage has been constructed or is under construc- tion. The largest part of the storage capacity has been constructed as part of the Colorado River Storage Project primarily to provide long-term regulatory storage. |