| OCR Text |
Show XII-60 UPDATING THE HOOVER DAM DOCUMENTS mates for local areas. The 1975 population of the Lower Colorado River system is estimated at about 2.6 million and increasing at an annual rate of nearly 5 percent. A large portion of the population resides within Maricopa and Pima Counties in Arizona, and in Clark County, Nev. Net water use rates for domestic, urban, and rural uses in the various reporting areas were derived from available studies in the metropolitan areas, State Water Plan reports, and appropriate appendices of the Comprehensive Framework Study, Lower Colorado Region. Mineral Resources: Arizona leads the Nation in the production of copper, producing more than half of the supply. Following in copper production are Utah, New Mexico, Montana, and Nevada. Most of the copper production, however, in Utah, New Mexico, and Nevada is produced outside of the Lower Colorado River system. The net water use for the production of copper represents about 90 percent of the total water use for the production of minerals within the Lower Colorado River system. The net water use for copper and other mineral production, composed principally of the byproducts and coproducts of copper production (gold, silver, molybdenum, lead, zinc) sand and gravel, lime, coal, stone, pumice, and cement, was estimated from available production data and nominal water use rates. A large part of the information used to estimate current water uses by the mineral industry comes from the Bureau of Mines. This information includes preliminary figures of annual gross value and quantities of mineral production by State. Basic data available from the Bureau of Mines include published figures of gross value of mineral production in relation to amount of water consumed and is expressed as gallons consumed per dollar of production. Figures are available for many mineral types mined and produced in Arizona and Nevada. A continued updating of unit price for each mineral in relation to quantity produced is maintained to arrive at current consumptive use figures based on current gallons consumed per dollar of production figures. Electric Power: The net use of water for the production of thermal electric energy from the tributaries of the Lower Colorado River system was estimated from diversions to pow-erplants and from information contained in State water plan reports. Fish and Wildlife: The many multipurpose lakes, stockponds, and impoundments in the tributaries are used extensively for fishing and recreation activities, as well as for preservation of wildlife. Water consumption in the form of evaporation from these facilities has been included as lake evaporation in this report. There is little information concerning the remaining water consumption for fish and wildlife purposes which may occur at fish hatcheries, marshes, and on croplands administered by the United States or various State Fish and Wildlife Agencies. These remaining uses are believed to be relatively small in the tributary areas and have not been included in this report. Recreation: At many of the lakes, reservoirs, and impoundments, recreation may be one of the important functions or purposes. Other minor water uses for recreation purposes have not been included herein. Exports: The relatively minor exports of tributary water outside the Lower Colorado-River system are measured by the Geological Survey or water-using organizations. Similarly, most of the exports between tributaries or reporting areas are measured. Water used to transport coal from the Black Mesa (Arizona) to the Mohave Steam Plant (Nevada) is estimated from records of coal burned at the plant. Adequacy of Data The adequacy of data is judged on the basis for which it is to be used. Methods of estimating consumptive use are normally established by theoretical or indirect approaches. A formula may be dependent on a number of variables. The relationship and achievable accuracy of each variable must be weighed carefully with the results to justify any significant upgrading of data with respect to accuracy and adequacy. To a degree, this report makes use of the 1965 development year estimates of consumptive use prepared for the Upper and Lower 14 |
