328 



GENERAL SCIENCE 



gation system to supply water when the needed rain does 

 not come. Gardeners near cities use the city water and 

 sprinkling hose to supply extra water. 



The United States Reclamation Service under the 

 Department of the Interior has reclaimed large sections 

 of the desert land of the West by building dams in streams 

 to hold the water so that it can be diverted from its 



AN IRRIGATION CANAL IN ARIZONA 



natural course to fertile fields where large crops are now 

 being grown. The farmers pay from $30 to $60 per acre 

 for their "water right." 



The Roosevelt dam in Salt River, Arizona, is 280 feet 

 high and 1080 feet long. It forms a lake of 25.5 square 

 miles and will irrigate 190,000 acres of land. The Sho- 

 shone dam, Wyoming, is 328 feet high, 108 feet thick 

 at the bottom, and only 200 feet long at the top. This 

 is the highest dam in the world. The reservoir created 

 by it has an area of 6,600 acres and a capacity of 456,000 

 acre feet; that is, it will hold enough water to cover 456,- 

 ooo acres one foot in depth. Twelve miles below this 



