26 ELEMENTARY FORESTRY. 



and the rain fall of this section and that with the disappear- 

 ance of our forests will come a much more rigorous climate 

 and a decrease in rain fall. But the records of the weather- 

 bureau do not show that there is any connection between the 

 two or that there has been any apparent change in the general 

 climate or amount of rainfall due to the removal of our 

 forests. The flow of water in most of our rivers and in many 

 <cases the flow of water from springs and the height of the 

 water table in the land have been most seriously affected by 

 the removal of our forests and should be regarded as the 

 ways by which our water supply is to suffer most severely from 

 deforestation. ] 



DISPOSAL OF WATER SUPPLIES. 



"Given a certain amount of precipitation in rain or snow 

 over a certain area, the disposal of the water after it has 

 fallen, and the influence of the forest-cover on its disposal, 

 require our attention. For the sake of convenience we can 

 divide the elements which need consideration in this discus- 

 sion into elements of dissipation, elements of conservation, 

 elements of distribution. 



"The difference in effect between the first two classes of 

 elements will give us an idea of the amount of available water 

 supply or run off resulting from precipitation, while the third 

 class bears upon the methods of distributing the available 

 water supply. 



ELEMENTS OF DISSIPATION. 



* 'Elements of dissipation are those which diminish the 

 available water supplies; they are represented in the quantity 

 of water which is prevented by interception from reaching the 

 ground, in the quantity dissipated by evaporation, in the 

 quantity used by plants in their growth, and in that used by 

 transpiration during the process of growing. 



"Interception. The amount of rainfall and snow, which is 

 prevented by a forest from reaching the soil varies consider- 

 ably according to the nature of the precipitation and to the 

 kind of trees which form the forest as well as the density and 

 age of the growth. 



"A light drizzling rain of short duration may be almost 

 entirely intercepted by the foliage and at once returned to the 



