IRRIGATION KXl'KKIM KXTS IN IDAHO. 



37 



of waste from the fields, as well as the hardest one to overcome. 

 That large losses are experienced from this source is proved by the 

 fact that the ground water under almost all irrigated projects rises 

 rapidly, the rise being either a seasonal or a permanent one. Where 

 excellent underdrainage exists the water level usually recedes during 

 the winter or nonirrigation season, but drainage of some sort is 

 ultimately found necessary in at least a portion of most projects. 



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Fig. 10. — Variation in depth to water in wells in vicinity of Rigby, Idaho. 



A typical case of the annual rise of water caused by deep percolation 

 from porous irrigated land, there being excellent underdrainage 

 from the land in question, is shown by the accompanying curves 

 (fig. 10). These curves show the annual rise and fall of water in 13 

 wells in the vicinity of Rigby, Idaho, where there are 40,000 or 50,000 

 acres of porous irrigated land upon which large quantities of water 

 are applied. 



In order to demonstrate that a very large part ot the irrigation 

 water used in this locality was being lost by deep percolation, and to 



