304 The Farm Woodlot 



When the surface of the earth is bare uncovered rock or 

 impervious soil, the rainfall runs off in unobstructed streams 

 as it falls. The result is a heavy flood, varying in strength 

 with the character of the country and the size of the drain- 

 age basin, for a short time, after the precipitation and then 

 a dry stream bed. This is true of the conditions existing 

 in a very large part of China and the Mediterranean coun- 

 tries, as well as in considerable areas of the United States. 



These conditions are not at all adapted to man's wants. 

 His business and even his life is dependent upon an even 

 supply of water in the rivers and springs, and this even 

 supply can best be secured by keeping the natural water- 

 sheds under forest. History and theory agree that this 

 will accomplish the purpose. Attempts have been made 

 in the United States to find two water-sheds, near together, 

 of practically the same area, one forested and one bare, — 

 to compare the run-off of the water in the two. It was 

 very difficult to find two water-sheds which exactly cor- 

 responded to the requirements, but sufficient data has 

 been secured to establish the following facts : 



The force of the falling raindrops is so broken by the 

 network of limbs and branches that the ground is not 

 beaten hard as is the case in the open. The soil remains 

 light and permeable; the organic litter from the trees 

 mingled with the surface soil helps to keep it so. The 

 water dripping lightly from the branches or sliding down 

 the trunks of the trees sinks readily into this permeable 

 soil, instead of running quickly over the surface as is the 

 case on rock or packed clay. Not until the soil has be- 

 come wet to the point of saturation does any moisture 

 run from it to the stream bed, which means that an 



