IRRIGATION EXPERIMENTS IN IDAHO. one 
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 of the irrigation 
water used in this locality was being lost by deep percolation, and to 
