OCR Text |
Show APPENDIX XII XII-53 Juan River are the Navajo, Los Pinos, Animas, and La Plata Rivers. The other main tributaries in the basin are the Dirty Devil, Escalante, and Paria Rivers which drain a portion of the eastern slope of the Wasatch Plateau in Utah. The reporting area includes about 38,600 square miles in portions of Utah, New Mexico, Arizona, and Colorado. The largest towns are Durango and Cortez in Colorado; Monticello and Blanding in Utah; and Farmington in New Mexico. Page, near Glen Canyon Dam, is the only community of significant size in Arizona. Most of the remaining Arizona portion is in the Navajo Indian Reservation. Mining and agriculture form the economic base for the San Juan-Colorado reporting area. The agricultural development is similar to that of the Upper Main Stem with most of the cropland devoted to livestock feeds but with production of diversified market crops on lands with favorable air drainage. The main market crops are fruit, vegetables, and dry beans. Oil, natural gas, and coal are the most important minerals produced. Thermal electric power production is increasingly important to the economy of the area. Irrigation accounts for the largest use of water, nearly 80 percent of the total basin use. About 240,000 acres of land are irrigated in an average year. LOWER COLORADO RIVER Mainstream below Lee Ferry, Arizona-California-Nevada: The Colorado River has a length of over 700 miles and a drainage area of 132,300 square miles within the Lower Colorado River system in the United States. From Lee Ferry to the headwaters of Lake Mead, the river flows through the spectacular canyons of northern Arizona, including the Grand Canyon. At Lake Mead, diversions are made to the rapidly expanding North Las Vegas-Las Vegas-Henderson-Boulder City area for municipal and industrial purposes. Below Lake Mead, the river courses through broad alluvial valleys interspersed with mountain chains. Lakes Mohave and Havasu provide flood control and regulatory storage below Lake Mead. In addition, Lake Havasu provides a forebay for pumped export to the Metropolitan Water District of Southern California and Lake Mohave reregulates Hoover Dam releases for power production and for deliveries to Mexico. Lesser structures downstream include Head-gate Rock, Palo Verde, Senator Wash, Imperial, and Laguna Dams. Laguna and Senator Wash Dams provide reregulation capacity while the others are used principally for diversion. Diversions below Lake Mead for agriculture, municipal and industrial, power, export, and other purposes are of the magnitude of 9 to 9.5 million acre-feet annually. A considerable portion of these diversions is satisfied from upstream return flows. Yuma and Lake Havasu City in Arizona, and Needles and Blythe in California are the major cities along the mainstream below Lake Mead. Current irrigated land adjacent to the mainstream is estimated to be about 351,000 acres. There has been a significant annual increase in the diversions for municipal and industrial purposes, particularly to Nevada. Little Colorado River, Arizona-New Mexico: The Little Colorado River drainage area occupies a large part of northern Arizona and a portion of west-central New Mexico. It rises on the north slopes of the White Mountains about 20 miles above Springerville, Ariz.; has a mainstream length of about 356 miles; and joins the Colorado River on the east boundary of Grand Canyon National Park about 78 miles downstream from Glen Canyon Dam. A series of saline springs near the mouth produce an estimated 160,000 acre-feet of water annually. The Geological Survey gaging station near Cameron is located in the Navajo Indian Reservation about 45 miles upstream from the mouth. Streamflow is uh-dependable and erratic, subject to flash floods of considerable magnitude. During the period 1971-75, water year outflow at the gaging station near Cameron varied from the floodflow of 815,900 acre-feet in 1973 to 28,300 acre-feet in 1974. Only a minor development of the ground water has occurred because of low yields and poor quality. Excessive erosion and sediment deposition plague |