FOREST AREAS OF CATCHMENT BASINS 



(Impromptu, Address) 



BY 



H. M. WILSON 



United States Geological Survey 



I AM very much interested in one feature of the dis- 

 cussion that has been brought before you to-day, 

 and that is the relation of run-off from catchment 

 basins to the forested areas of those basins. There is 

 nothing new on this subject, however, which it seems 

 to me I can bring before you. I heartily concur in the 

 general opinion expressed by two of the speakers, 

 Messrs. Lippincott and Davis, upon the effect of forests 

 in regulating the discharge of streams and thus adding 

 to their usefulness as providers of water for irrigation 

 and upon the effect of this regulation in preventing 

 disastrous floods which, by eroding the surface of the 

 soil, carry vast amounts of sediment to the streams 

 below and destroy both them and the surfaces which 

 they erode. There are other features, however, of the 

 subject of forest influence on water supply which are 

 frequently noted in connection with the preservation 

 of forests, which it might be well for me to qualify. 

 We are familiar with the old-time claim of the effect 

 of forests in increasing the rainfall and all of the 

 foresters present who have looked into the subject, I 

 am sure, believe now that whereas it is possible that 

 forests may have some effect upon the amount of pre- 

 cipitation, there is as yet no definite information avail- 

 able from any source, either of experiment or investi- 

 gation, which goes to prove it. And that feature of the 

 subject of the effect of forests on water supply is one 

 which I think the Weather Bureau, or possibly the 



