Forests and Water-Supply. 



Owing to the importance of the water-supply question in the 

 State, we have given long and careful study to the effect of 

 forests upon the run-off of the streams. As a result, we have 

 reached the following conclusions, resting upon reasons and data 

 which we give later on : 



1. Forests have no important effect upon the total evaporation 

 from the stream catchment, consequently the total run-off from 

 forested catchments is not greater than from deforested or culti- 

 vated catchments. 



2. The springs are better sustained in forested country, the 

 rain-fall being absorbed more readily by the humus'and soil of 

 the forest, and the flow of water over the surface to the stream 

 channels being obstructed by roots and other inequalities, con- 

 sequently forest streams have a more equable flow and are not 

 subject to such long periods of extreme low water. 



3. Floods are less frequent on forested streams, owing partly 

 to the above causes and also to the slow melting of snow and 

 ice accumulating in the winter season, but forested streams are 

 nevertheless subject to occasional high freshets. 



4. Forest streams carry less mud and silt in suspension. The 

 most desirable conditions for water-supply are found when about 

 three-fourths of the catchments, including the slopes and higher 

 ground, is covered with forests, while the remainder, near the 

 stream lines, is in grass. 



In those respects in which the above findings differ from 

 popular opinion they have been verified with great care. Such 

 opinion is largely to the effect that forests decrease evaporation, 

 and that consequently deforestation is responsible for the drying- 

 up of streams. That popular impressions are not always a safe 

 guide is evidenced by the fact that it is commonly alleged in 

 this State that the streams are falling off because of the cutting- 

 off of forests ; but the facts, ascertained with much care, are that 



(i37) 



