THE FOREST IX RELATION TO MAN 



551 



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The practical bearing of these facts is not hard to understand. 

 Every year, as the snows on the hills begin to melt, the water 

 rushes down the hillsides in the deforested regions, causing the 

 streams to overflow their banks and the torrents to tear down 

 and destroy everything in their path. The annual damage done 

 by floods in this country 

 is estimated to be equal 

 to one hundred million 

 dollars. This does not in- 

 clude the destruction of 

 human life that is often 

 involved in the floods. 



Streams depending upon 

 deforested areas for their 

 water will be too full in 

 the spring and will run 

 too low in the summer. 

 Water used for agricul- 

 tural purposes must be 

 had in abundance through- 

 out the summer, and the 

 destruction of forests in 

 one region has often re- 

 sulted in the ruin of agri- 

 culture and the migration 

 of peoples in a distant 

 valley. Navigation on the 

 larger streams is influ- 

 enced by the forest in two 



ways : the steady flow of water is maintained by a proper con- 

 dition of the forest, and the filling up of the stream by soil is at 

 the same time prevented. 



395. Water power. As our industries expand we are pressed 

 to find sources of energy for driving our machines. The con- 

 sumption of coal has increased so rapidly that the exhaustion of 

 the earth's supply is threatened. Water power seems to be the 



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Covered Bare 



April 2-9 



Covered Bare 

 AprU 14-17 



Covered Bare 

 April 22-24 



Fig. 



224. 



The relation of the forest to 

 water flow 



In experiments made by government agents a 

 comparison of a covered area with one devoid 

 of trees showed ( i ) that in a given period the 

 covered area accumulated more snow than the 

 bare area (this is shown by the relative heights 

 of the two columns in each pair), and (2) that 

 in a given period the bare area lost more water 

 than the covered area ( this is shown by the rela- 

 tive heights of the shaded portions in each pair) 



