300 



ELEMENTS OF GENERAL SCIENCE 



upon the fields when it is needed. In this way, with an 

 abundant supply of water and with constant sunshine, a 

 rapid and luxuriant growth of plants is made possible. 



FIG. 144. Irrigation in the United States 



The map shows the location of the more important government irrigation projects. 



There are in addition many other areas irrigated by government, private, and 



state enterprise. From map by the United States Reclamation Service 



It must not be forgotten that underground drainage is 

 advantageous for other purposes than the removal of sur- 

 plus water, though at times even irrigated farms need it for 



