IRRIGATION AND HYDRO-ELECTRIC DEVELOPMENTS 

 dred thousand acres of land have been brought 

 under cultivation in an almost rainless region, the 

 mean annual rainfall being only three to five inches. 

 The irrigation canal which has here transformed 

 the desert into a highly productive region, now 

 under intense cultivation, has its head in the south- 

 eastern corner of California. A concrete structure 

 controls the flow into the canal. A few hundred 

 yards below, the canal enters Mexico, but re-enters 

 California forty miles farther west. The capacity 

 of the canal is several thousand cubic feet per 

 second. The region irrigated is nearly all below 

 sea level, the lowest point being about 280 feet 

 below the sea. In 1905 and 1906, as the result of 

 open unprotected cuts from the river to the canal 

 and unusual high waters, the river changed its 

 course, cut a new channel, and discharged its en- 

 tire flow for a time across the Imperial country 

 into the Salton basin, where the water accumulated 

 to a depth of about eighty feet. The turning of 

 the river back into its original channel at a time 

 when its flow was about 20,000 cubic feet per 

 second, and with works that rested upon an un- 

 stable sand and silt foundation, was a notable feat, 

 for which the engineer in charge, Mr. H. T. Cory, 

 and the Southern Pacific Company, which financed 

 the enterprise, deserve particular credit. 



UNITED STATES RECLAMATION SERVICE IRRIGATION 

 PROJECTS: Salt River Valley Project. In the Salt 

 River Valley, Arizona, near Phoenix, the disastrous 

 shortage of water in the irrigation canals, due to 

 the irregular water supply from an unregulated 

 river, has been relieved by the construction of a 

 great masonry dam, sixty miles up stream, which 

 has converted the Tonto Basin into a great reser- 

 voir which holds back the entire flow of ordinary 

 freshets and makes the water, under natural con- 

 ditions wasted, available for use as needed. This 

 Roosevelt Dam was constructed by the United 

 States at a cost of about $3,000,000, under the co- 

 operation authorized by the United States Reclama- 

 tion Act, which permits the Secretary of the In- 

 terior to undertake such works with the under- 

 standing that their cost, without interest, will be 

 repaid in the course of twenty years. 



Phoenix, population in 1910 was 11,134. 



Sources of water: Salt and Verde rivers, and 

 wells. 



Reservoir: Roosevelt on the Salt River at the 

 Tonto Basin has an area, when full, of 16,320 acres. 

 Its capacity is 1,284,000 acre feet. The Roosevelt 

 Dam has "been constructed of rubble concrete 

 masonry. It is arched, has a crest length of 1125 



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