312 



GENERAL SCIENCE 



United States receives insufficient rainfall to produce 

 yearly crops without irrigation. In some parts of this 

 area occasional crops may be produced by dry farming, 

 but this means that only a small fraction of what the land 

 is capable of producing with adequate rainfall will be 

 produced. The land along a stream is always more fertile 

 than the land farther away from the stream. In some 



U. S. Reclamation Service. 

 FIG. 268. Salt River Project, Arizona. The Desert Before Reclamation. 



regions it has been possible to divert part of the water of 

 streams through canals and ditches so that a much larger 

 area is watered. This is called irrigation. 



In the western part .of the United States, especially in 

 the region west of the Rocky Mountains, the United States 

 Reclamation Service and a number of private organiza- 

 tions are maintaining a number of irrigation systems 

 (Figures 268, 269). The engineering problems involved 



