Page 116


Page 116
Colorado River problem
Is Part Of,8
Full text
E. A. HILL ON THE COLORADO RIVER PROBLEM 421 enough actual stream-flow measurements, prior to 1902, to determine the continually changing gauge-discharge relation. As the river bed was steadily rising, calculations based on gauge heights would tend to give results lower than the actual discharge of the river. Fortunately, records covering many years of measured run-off will be available before the irrigable acreage will have expanded sufficiently to absorb the increase in supply which will come with regulation. In Table 11 the author shows a compilation and classification of the areas which may be served from the Colorado River. His conclusion that the water supply is obviously inadequate depends on the accuracy of the calculations as to the water supply, on the economic feasibility of agriculture on these lands, and on that use of water assumed as necessary. So much of the area included is less suited to agriculture than other large undeveloped sections in the United States and Mexico, that the writer, who is familiar with the entire area, cannot conceive of its complete development. In 1907, 190,000 acres were irrigated on all the projects of the U. S. Bureau of Reclamation; by 1921, the irrigated area had increased to only 1,250,000 acres, in spite of the fact that natural and economic conditions were favorable to rapid expansion. It has taken 20 years for less than 500,000 acres to be placed in cultivation in the Imperial Valley of California. When it is realized that these areas were the easiest and cheapest to develop, it should be obvious that a great many years must elapse before the irrigated area below the canyon will exceed 2,000,000 acres. Conservation of water by the reduction of the gross duty will more than offset any further increases in the irrigated area. The author has assumed that 4.2 to 4.5 acre-ft. of water will be consumed each year on every irrigable acre below the canyon. The actual consumption per gross acre of irrigable area in that part of the Imperial Valley served by the Imperial Irrigation District is shown in Table 34, summarized from the 1923 report of the Chief Engineer of that District. TABLE 34.—Water Delivery in Imperial Valley, 1923 Season. Division. Irrigable area, in acres. Water delivered to farms, in acre-feet. Acre-feet per gross acre. Calexico...................... Holtville........................ Imperial........................ Brawley, East.................. Brawley, West.................. Calipatria..................... 47,000 85,000 130,000 78,000 82,000 93,000 99,887 154,688 249,630 156,188 149,983 109,909 2.12 1.82 1.92 2.00 1.83 1.18 Total..................... 515,000 920,230 1.79 As about 80% of the irrigable area was actually cultivated in the Calexico Division, 70% in the Holtville, 70% in Imperial, 75% in Brawley, East, 70% in Brawley, West, and 45% in the Calipatria Division, the net duty for each acre actually cropped was approximately 2.7 acre-ft. The gross duty for each

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