172 CONTROL OF EROSION ON RANGE AND PASTURE 



knows how thoroughly this ground cover protects the soil and 

 retards or stores the water. The force of the falling rain and 

 the downward pull exerted by gravity after the water reaches 

 the ground are to a certain extent overcome by the vegetation 

 and the litter on the surface. When the fallen rain finally reaches 

 the soil, a part of the water is soaked up by nature's " sponge," 

 a humus layer so rich in organic matter that it will hold several 

 times its own weight in water. The water so held is liberated 

 gradually, and the streams into which this clear, pure water 

 drains vary but little in their flow the season through. Such 

 streams furnish the best water supply for our most valuable 

 irrigated lands. 



Every drop of rain that falls on more or less exposed soil, 

 on the other hand, has the power of removing soil particles, and 

 with them the soluble salts essential to plant growth. If the 

 vegetative cover on a drainage area has been largely destroyed, 

 the washing off of the surface soil may remove far more decom- 

 posed vegetable matter and soluble plant food in a single season 

 — indeed during one violent storm — than would be deposited 

 by the decay of the vegetation in many years. More than this, 

 the resulting erosion, with its rush of water and debris, frequently 

 ruins the lands where the debris is deposited; and often roads, 

 trails, power plants, and other improvements are destroyed. 

 In many localities the loss of property from this source has been 

 appalling. 



Damage by Erosion. — The farmer-stockman who lives in 

 the more arid parts of the far West probably realizes more 

 keenly than those who enjoy an abundance of rainfall that 

 prosperity depends largely upon an adequate water supply for 

 the production of good crops. Water, ample water, and always 

 more water is the real necessity of the West — the essential 

 factor in making the lands pay a reasonable dividend. It is 

 an interesting fact that the prosperity enjoyed from irrigated 

 lands in the West is often directly traceable to the condition of 

 the enormous drainage areas, or watersheds, of the National 

 Forests. The intimate relation that exists between the National 

 Forests and a sustained streamflow for irrigation in the West is 



