T?}KI.UK\(i: OF FOKKSTS ON NATURAL WaTKK-.SuI'PLY. \27 



thr authdi- has found the n?.sult of some observations recently pub- 

 lisheil by ^Ir. J. W. Touniey.* These are so striking that they are 

 i-eprodueed in full. He says that, as a result of a careful study of the 

 behaviour of the stream flow on several small catchment areas in the 

 Han Bernanhno Mountains, it has been found that the effect of forests 

 in decreasing the surface How on small catchment basins is enormous. 

 1)1 the following tables three well-timbered areas are compared with a 

 non-timbered one. 



Prkcipitation and Run-off during December, 1899. 



Area of Catch- Condition as 

 ment Basin. to Covei-. 



8(]. Miles. 



0-70 



105 



1-17 



•o3 



Forested 



Non-forested 



■D • -i. I Run-oft 



Frecipita- 



. • ^ per buuare 



tion. '^ ^r-i 

 Aide. 



Inches. 

 19 

 19 

 19 

 13 



Acre-feet. 



36 



73 



70 



312 



Run-off in Per- 

 ce)itage of Pre- 

 cipitation. 



Per cent. 



3 



<) 



6 



40 



At the beginning of the rain}' season, in early December, the soil 

 on all four of these basins was very dry as a result of the long dry 

 season. The accumulation of litter, duft', humus and soil on the 

 forest-covered catchment areas absorbed 95 per cent, of the unusually 

 large precipitation. On the non-forested ai-ea only 60 per cent, of 

 the pi-ecipitation was absorbed, although the rainfall was much less. 



Kainfall and Rux-off during January, February and March, 1900. 



Area of Catch- Condition as Precipita- ,, 



tion. I P^^: ^^»"^'"^ 



ment Basin. 



to Cover. 



>S«i. Miles. 



0-70 



105 



1-47 



•53 



Forested 



Non forested 



Inches. 

 24 

 24 

 24 

 16 



Bun-oft* 

 Mile. 



Acre-feet. 

 452 



428 

 557 

 828 



Run-oft' in Per- 

 centage of Pre- 

 cipita tioii. 



Per cent. 

 35 

 33 

 43 

 95 ' 



One striking feature of this table as compared with the previous 

 one is the uniformly large run-off as compared with the rainfall. This 

 clearly shows the enormous amount of water taken up by a dry soil, 

 cither forested or non-foi-ested, as compared with one nearly filled to 



* The Belntioii of Forests to Strmm Flon; Year Book, Department Agricul- 

 ture (I'.S.A.), 19M3.' 



