626 JOURNAL OF FORESTRY 



mountain streams and therefore provides a scientific basis for deter- 

 mining for any given condition the effect of forest vegetation or lack 

 of it upon the behavior of the stream. 



Of the two Swiss watersheds seh^cted for the experiment, one is 

 known as Sperbelgraben. It comprises 137 acres and is wholly for- 

 ested. The other is known as Rappengraben. Its area is 172 acres 

 and it is only about one-third forested. Sperbelgraben lies within the 

 watershed of the Kurzeneigrabens and Rappengraben within the 

 watershed of the Hornbach, both of which flow into the great Emme, 

 and the experiment is known as the Emmental Experiment. 



Of the two watersheds selected by the Forest Service in the Rocky 

 Mountains one is 223 acres and the other is 212 acres, somewhat larger 

 than the Swiss watersheds. The comparison between the forested and 

 poorly forested watersheds in Switzerland was begun at once. In our 

 experiment the two watersheds had originally about the same forest 

 cover. The observations upon the behavior of the streams in the two 

 watersheds were continued for nearly i) years without any change in the 

 cover. Last summer one of the watersheds was denuded and from 

 now on observations will be conducted on the streams of which one 

 rises in a forested watershed and the other in a completely denuded 

 watershed except for a fringe of trees left along the stream. 



The mountain range of Hinterarni, which in the peak Farnli reaches 

 an elevation of 4,135 feet above sea level, Hes between the two Swiss 

 watersheds. The distance between the two watersheds where they are 

 nearest together is 2.4 kilometers in an air line. Both valleys trend 

 northeast to southwest. The small tributaries which enter the main 

 iStream on the left have in Sperbelgraben a north to northwest ex- 

 posure, on the right a south to southeast exposure. 



The altitude of our watersheds in the Rocky Mountains is much 

 higher. One of the watersheds has an altitude of from 9,375 to 

 11,360 feet, while the other lies between an elevation of 9,240 and 

 10,940 feet. Both streams in the Rocky Mountain watersheds have 

 an easterly bearing flowing out of the mountains on to the broad bot- 

 tom of the Rio Grande where, except at the highest st^ge, they dis- 

 appear into the loose soil of the river bottom. With regard to ex- 

 posure and geological structure, the two watersheds in Switzerland, 

 just as our own watersheds, bear a close resemblance to each other. 

 The rock is the same in the two Swiss experiment stations and is only 

 slightly permeable. No losses of water through its disappearance in 

 deep-lying clefts were discovered. 



