THE SALINITY OF IRRIGATION WATER 



By Carl S. Scofield 

 United States Department of Agriculture 



[With 3 plates] 

 INTRODUCTION 



In the course of its development our irrigation agriculture has, in 

 some areas, utilized all of the available supplies of surface water. 

 Further progress calls for the use of underground water obtained by 

 pumping. In some situations, as in southern California and in Utah, 

 it has been found that some of the underground water is unsuited for 

 irrigation use because of the nature or quantity of its dissolved salts. 

 Furthermore, it has been found that some of the supplies of surface 

 water, such as the Rio Grande and the Colorado River, also contain 

 dissolved salts in quantities or of kinds that cause trouble after some 

 years of use on the same land. 



These experiences have appeared to warrant investigation of the 

 subject of the salinity of irrigation water in relation to the possibili- 

 ties and limitations of the further and more efficient utilization of 

 the water resources of our arid regions and also in relation to the 

 sustained productivity of our irrigated lands. The history of irri- 

 gation in other lands has shown that in some places irrigation agri- 

 culture has been carried on successfully for long periods, as in 

 Egypt, while in other places, as in Mesopotamia, it has failed to 

 survive. The direct causes of failure have been various. Salinity 

 of the water may have been only one of several reasons. But it is 

 fairly certain that in every one of the long-continued irrigated areas 

 the quality of the water has been excellent. 



THE SALINITY OF SOILS 



The phenomenon of soil salinity is one that is usually associated 

 with regions having an arid climate. The obvious reason for this 

 is that the water-soluble salts resulting from the weathering of rock 

 material into soil are leached away by the rains in a humid climate, 

 but remain in the soil under arid conditions. There are exceptions 



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