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MISC. PUBLICATION 9 0, U. S. DEPT. OF AGRICULTURE 



from November 1 to May 1. During this period, at that elevation, 

 the temperature does not rise high enough for much of the snow to 

 melt, and most of it is stored on the ground under the timber and in 

 big drifts in the open. When warmer temperatures come in the 

 spring, the accumulated snow melts rapidly. Most of it disappears 

 within from four to six weeks, although where deeply drifted and 

 well packed some snow may remain late into the summer. It is 

 in the spring that most of the high water occurs in streams and that 

 the ground water supply is replenished. Observations have shown 

 that under some conditions up to 95 per cent of the annual surface 

 run-off in the high mountains comes from snow and only 5 per cent 

 from rain. 



When water falls in the form of rain or snow it is removed from 

 the place where it falls in a number of ways. Some of the water is 



Figure 44. — Snow scene in the mountains east of Ephraim. Utah. Snow which 

 accumulates to great depths during the winter is the principal source of the 

 water supply for irrigation, domestic use, and hydroelectric power 



intercepted by the leaves and branches of trees and other plants, 

 evaporates, and is returned to the air ; some evaporates from the sur- 

 face of the ground directly into the air ; and some sinks into the soil. 

 If the rain is heavy enough, or in the case of snow if it is melting 

 fast enough, part of the water runs off on the surface of the ground 

 and finds its way directly into streams and lakes. One or more of 

 several things may happen to that which sinks into the ground. 

 A part is held in the soil by capillary action and may evaporate 

 from the soil directly into the air and be lost. Another part is 

 taken from the soil by growing plants and is returned to the air 

 through the leaves of the plants by the process of transpiration. 

 If more moisture is absorbed by the soil than can be held by capil- 

 lary action, it finds its way down between the soil particles and 

 broken rock to impervious rock strata below, which it follows under- 

 ground. Most of this eventually reappears in springs to feed 



