536 Bulletin 95 



there is no good dam site for a storage reservoir between Boulder 

 Canyon and Yuma. 



THE THREE GREAT PROBLEMS 



Three objects are sought in the development of the Colorado River. 

 They are : — 



1. Storage for flood protection; 



2. Storage to provide more water for the latter half of the 

 irrigation season and for dry years ; and, 



3. Hydro-electric power. 



The flood protection is the main incent-ive which is spurring many 

 agencies to action. The people of the Imperial Valley, for 16 years, 

 have been fighting a defensive battle against the Colorado, sometimes 

 gaining, sometimes losing, but in the main losing. They cannot hold out 

 for many more years. At least once every year, in June, and sometimes 

 at other seasons, the river threatens to change its course from the Gulf 

 of California to the Imperial Valley, as it did in 1905. The only protec- 

 tion at present is the system of levees, called respectively the first, 

 second, and third lines of defense. Frequently the floods break through 

 the first and second lines and reach the third line. Each year the river, 

 through silt deposition, builds up that part of the alluvial fan In front 

 o-f the levees, in some years as much as four feet, and each year the 

 levees must be raised an equal amount. Over one-quarter of a million 

 dollars is expended each year by the farmers of the Imperial Valley 

 in this work. The limit will be reached soon. Levees forty or fifty 

 feet high cannot be maintained. 



The Yuma Valley, also, is protected by levees, but the danger 

 there does not increase. Arizona hopes to develop another great irri- 

 gated valley farther upstream at Parker, but much of the Parker Valley 

 is now subject to overflow and must be protected by an expensive sys- 

 tem of levees unless adequate regulation of the floodwaters is provided 

 by storage reservoirs. Regulation of the Green and the Grand will solve 

 the problem in large measure, but tributaries below the junction must 

 he given consideration. On one occasion a flood of 150,000 second- 

 feet measured at Bluff, Utah, was contributed by the San Juan, and 

 the Gila River floods likewise are a menace with which to reckon. 



As for storage to equalize the supply for irrigation, the situation 

 is more critical than is commonly known. Despite the great excess of 



