A METHOD FOR DETERMINING THE EFFECTS OF 

 FORESTS UPON RUN-OFF IN THE ROCKIES. 



R. D. Garver. 



In the determination of this most important question,* 

 the effects of forests upon run-off and water supply, there 

 seems but one general plan, i.e., the comparison of two areas 

 similar in every respect except forest cover. In the selection 

 of the two areas to be compared and the inauguration of the 

 plan of procedure to bring about comparison it seems very 

 important that the following points be carefully considered. 



The experiment should be represented by areas which 

 are component parts of the mountain region in which the study 

 is to be made and should represent typical average conditions. 

 In order to choose areas that will meet the above requirements 

 the following considerations are offered: the areas chosen for 

 study should include both sides of a valley and take in (1) 

 the entire altitudinal range from the perpetual snow line to 

 the arid zone occupied by the Yellow Pine type or, (2) they 

 should lie at middle altitude in the zone between 9,000 feet 

 and 11,000 feet. The latter seems the most desirable because of 

 the ease in selection and the greater simplicity of the areas 

 involved. Another important factor in favor of this alter- 

 native is the condition found in the Englemann Spruce type 

 and the area above timber-line where the soil is always moist 

 and in consequence continually feeds and perpetuates stream- 

 flow, while areas lying at low elevations furnish little ground 

 waiter and streams dependent upon such supplies may become 

 dry regardless of forest cover or other conditions influenced 

 by slope or aspect. 



To be representative of the Rockies the slopes of the 

 watersheds should be steep but not precipitous. The general 

 direction is an important factor and upon further consideration 

 it appears that a watershed with a northerly or southerly as- 



*Contralablatt fur Das Gesammte Forstwesen, January, 1907. Silvical Re- 

 port, Dist. 2, 1909. 



