20 USE OF THE NATIONAL FORESTS. 



TO KEEP THE WATER FLOW STEADY. 



It should be clearly understood that in regions of 

 heavy rainfall — for example, on the Pacific slopes in 

 Washington, Oregon, northern California, and Alaska — 

 National Forests are not made for the purpose of regu- 

 lating the water flow for irrigation. In these localities 

 there is plenty of water to spare. The Forests here are 

 created and maintained to protect the timber and keep 

 it in the people's hands for their own present and future 

 use and to prevent the water from running off suddenly 

 in destructive floods. 



In other parts of the West, however, in all the great 

 arid regions of the Rockies and the eastern Pacific slopes, 

 one of the most vital reasons for making and maintain- 

 ing the National Forests is to save every drop of water 

 and to make it do the most effective work. 



No one has yet proved that forests increase the rain- 

 fall to any great extent. What they do, and this no 

 one of experience disputes, is to nurse and conserve the 

 rain and snow after they have fallen. Water runs down 

 a barren, hard surface with a rush, all at once. It runs 

 down a spongy, soft surface much more slowly, little by 

 little. A very large part of the rain and snow of the 

 arid regions falls upon the great mountain ranges. If 

 these were bare of soil and vegetation, the waters would 

 rush down to the valleys below in floods. But the for- 

 est cover — the trees, brush, grass, weeds, and vegetable 

 litter — acts like a big sponge. It soaks up the v/ater, 

 checks it from rushing down all at once, and brings 

 about an even flow during the whole season. 



In irrigation it is very important to have an even flow 

 throughout the growing season, especially toward the 



