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Show APPENDIX XII XII-55 area extends from the Continental Divide in New Mexico to the river's mouth near Yuma, Ariz. Elevations in the basin range from nearly 12,000 feet in the eastern mountains to about 150 feet at the mouth. The selected outflow point for the basin is at Painted Rock Dam, a flood control structure located about 20 miles west of Gila Bend, Ariz. The drainage area above Painted Rock Dam is about 50,900 square miles, of which 5,600 square miles are in New Mexico and 1,100 square miles in Mexico. The dam was constructed to protect agricultural and urban developments downstream. Major conservation storage reservoirs in the basin include the San Carlos Reservoir on the Gila River; Lake Pleasant on the Agua Fria River; and the six reservoirs of the Salt River Project. Total usable capacity of these reservoirs is about 3,180,000 acre-feet. Nearly 75 percent of the population of the Lower Colorado River system lives in the Gila River Basin; most of these reside in the metropolitan Phoenix and Tucson areas. Industry and recreation play a large part in the economy. About two-thirds of the agricultural development in the Lower Colorado River system is located in the Gila River Basin. This development is concentrated in the central area of Maricopa, Pinal, and Pima Counties and is supported to a large degree by a long-term overdraft of the ground water resources. Nearly all of the surface water resources in the basin have been developed for decades. Except for the infrequent major flood event, such as occurred in 1973, inflows to the Colorado River mainstream are negligible. Releases through Painted Rock Dam in water year 1973 totaled 412,700 acre-feet although only slightly more than 100,000 acre-feet reached the Colorado River. Construction of the Central Arizona Project is in progress. This project, which would divert Colorado River water at Lake Havasu to central Arizona, is intended to reduce ground-water pumpage and partially arrest the large annual increases in the depths to ground water. Remaining area in Arizona, Nevada, and Utah: Outside of the Colorado River mainstream and flood plain and the selected tributaries, development for the most part is limited by the availability of water and the rugged terrain. In the Boulder City-Las Vegas Valley area there has been a significant increase in the municipal and industrial demand for water. Construction which would complete the Southern Nevada Water Project is scheduled to begin in 1977. Completion of the project would allow Nevada to essentially use its complete entitlement from the Colorado River. Most of the irrigated lands in this area are located in the lower reach of the Virgin River and Las Vegas Vajley in Nevada, on Kanab Creek in Arizona and Utah, and the lower portions of the Gila and Bill Williams Rivers in Arizona. North Las Vegas, Las Vegas, Henderson,'and Boulder City in Nevada, and Kingman and Williams in Arizona are the leading cities. Terminology The Colorado River is not only one of the most highly controlled rivers in the world, but is also one of the most institutionally encompassed. A multitude of legal documents, known collectively as the "Law of the River," affect and sometimes dictate its management and operation. Major documents include: Colorado River Compact-1922 Boulder Canyon Project Act-1928 California Limitation Act-1929 California Seven Party Agreement-1931 Mexican Water Treaty-1944 Upper Colorado River Compact-1948 Colorado River Storage Project Act-1956 United States Supreme Court Decree in Arizona v. California-1964 Colorado River Basin Project Act-1968 Minute 242 of the International Boundary and Water Commission, United States and Mexico-1973 Colorado River Basin Salinity Control Act-1974 The Colorado River system is defined in the Colorado River Compact of 1922 as ". . . that portion of the Colorado River and its tributaries within the United States," whereas |
