CHAPTER IV 

 FARMING UNDER IRRIGATION 



ABOUT 300,000,000 acres in the United States of other- 

 wise tillable land have been unproductive because of 

 lack of moisture. This area, which is approximately as 

 large as Iowa, Illinois, Indiana, Ohio, Missouri, Minnesota, 

 Wisconsin and Michigan, comprises what is known as the 

 arid and semi-arid region of the United States. The soil in 

 most cases contains abundant plant food and has been found 

 highly productive when the necessary amount of moisture 

 is supplied. Much of the arid West formerly called the 

 "Great American Desert" can be transformed into a veri- 

 table garden spot by proper irrigation and management. 



This territory extends from the Canadian boundary to 

 the Gulf of Mexico and includes large tracts of practically 

 all of the states in the West, such as Washington, Montana, 

 North Dakota, South Dakota, Idaho, Wyoming, Utah, 

 Colorado, Oregon, Nevada, California, New Mexico, Ari- 

 zona, Texas, Oklahoma, western Kansas and Nebraska, as 

 well as a part of Florida. 



1. Causes of Aridity 



There are three chief reasons why much of the 

 western dry territory is deprived of normal rainfall. The 

 first is that the Rocky Mountains rob the ocean breezes of 

 their moistures before they have reached the tillable lands. 

 The second is the altitude of a great portion of this terri- 

 tory; millions of acres are at an altitude which makes the 

 production of rain impossible. The third is the lack of 



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