AZ vs. CA:24 California Exhibits, Vol. XXIV; Miscellaneous

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PROBLEMS OF IMPERIAL, VALLEY AND VICINITY^ stream and is also in an approximate alignment therewith, rises in northeastern Colorado and nas a length above its junction of about 450 miles. Its principal tributaries are Frazer, Blue, Eagle, Williams, and Roaring Forks, and the Gunnison River The Green is the longest branch, rises in the Wind River mountains of Wyoming, flows in a southerly "direction into Utah, and then turns eastward flowing into Colorado and back into Utah, and has a length of about 700 miles from its source to its mouth at the junction with the Grand. Its principal tributaries are Blacks Fork, Henrys Fork, Yampa River, Ashely Creek, Duchesne River, White River, Minnie Maud Creek, Price River, and San Rafael River. The length of the Colorado from the junction of the Green and the Grand to the Gulf of California is about 1,050 miles, thus making, with the continuation of the Green, 1,750 miles total length. Below the junction with the Green it flows southwesterly into Arizona across the northwest corner of that State, then turning south forms the boundary between Arizona on the east and Nevada,, California, and Mexico on the west, reaching the Gulf of California about 120 miles below Yuma. The drainage area of the Colorado River is 244,000 square miles, distributed as shown in the following table: Table No. 1.-Average discharges of principal tributaries. Green River..,................ Upper Colorado (Grand River) San Juan River................ Other areas except Gila........ Gila........................7.. Total.................... Percent of total ! Discharge in dis- j acre-feet, charge. 5,510,000 6,940,000 2,700,000 1,560,000 1,070,000 Square miles. 44,000 26,000 28,000 91,000 57,000 100 17,780,000 244,000 Percent of total area. Acre-feet per square mile. 125 267 104 16 19 loo! 70 The water supply from the various branches is also shown in this table and is by no means in proportion to the area drained, the discrepancy being due to the wide diversity of -climatic and topographic conditions. The rim of the basin whence the streams take their sources is composed largely of high mountain ranges. On the north and east the Wind River Mountains and the ranges of the Continental Divide are the highest and furnish the greatest water supply. This is especially true of the Rocky Mountains in north central Colorado, and for this reason the run-off from that region is far greater in proportion to area than tr^at of any other part of the basin. The lower third of the basin is composed mainly of hot, arid plains of low altitude, broken here and there by occasional short mountain groups or ranges reaching elevations of 3,000 to 6,000 feet. The central portion of the basin is a high plateau, through which the streams have cut narrow canyons, often of great depth. Every tributary through this region is in canyon, so that much of the central and upper1 part of the basin is traversed by deep gorges and is exceedingly rough. At its mouth the river has built up a great delta from the materials eroded in the canyons described and has by this means encroached upon the Gulf of California at its mouth, and finally cut off the upper end of this gulf entirely. The isolated portion, forming