WATER CIRCULATION AND ITS CONTROL 



419 



so far as plains are concerned. The drain- 

 ing effect of the forest is, on the contrary, 

 so great that a much greater supply of water 

 gathers in the depths beneath a treeless 

 plain than beneath dense woods, provided 

 that the underground conditions be the same 

 in both cases. It follows that under these 

 conditions the discharge of springs is not 

 increased, but lessened, by woods. Decided 

 emphasis must, however, be laid upon the 

 fact that these conclusions hold primarily 

 only for the plains, and are not to be ex- 

 tended inconsiderately to uplands and moun- 

 tains. Although the influence of the woods 

 upon soil, moisture, percolation, and ground 

 water under like conditions must be the 

 same in mountains as it is in lowlands, and 

 only moderate differences are likely to ap- 

 pear, nevertheless the forest on the moun- 

 tain differs very decidedly from that on the 

 plain in regard to water control, inasmuch 

 as in mountain regions, in consequence of 

 the surface run-off of rain and snow water 

 from the slopes, a factor is introduced 

 through which wooded mountain slopes re- 

 ceive a much larger amount of water than 

 bare, unwooded watersheds. 



Forests in relation to erosion. — The 

 emphasis which Ebermayer lays upon 

 the loss through run-off from bare 

 slopes is in no sense exaggerated. The 

 detrimental character of this loss in re- 

 lation to storage of water for all the 

 activities of civilized communities, in- 

 cluding navigation, cannot be exag- 

 gerated. Its effects have already been 

 described in speaking of flood run-off, 

 but we may here recur to the injury 

 which it does, particularly with refer- 

 ence of the erosion of soil. If it were 

 conceivable that we could adjust our 

 activities to the loss of one-half of the 

 available water through flood run-off 

 it would still be inconceivable that we 

 could permit the accompanying loss of 

 the soil. Without soil the earth be- 

 comes a desert and without soil man 

 must cease to exist. 



This consideration is of prime im- 

 portance everywhere, but it assumes 

 overshadowing importance beyond any 

 other in mountain regions of large rain- 

 fall. The Appalachian Mountains con- 

 stitute such an area of great extent and 

 of very marked character, and they oc- 

 cupy a very critical position in the cen- 

 ter of the richest half of our country. 

 Concerning the effect of uncontrolled 

 run-off from this region we have, un- 

 fortunatelv, abundant evidence, the em- 



phatic testimony of ruined and aban- 

 doned lands. 



Summing up the observations of the 

 thoroughly qualified and unbiased ob- 

 server, L. C. Glenn, we are able to 

 show what relation the destruction of 

 the forest bears to run-off in the water- 

 sheds of the southern Appalachians. 



Forty-six creeks and small rivers, 

 whose watersheds may be described as 

 timbered rather than cleared, are 

 known, according to observation and 

 local repute, in times of flood to rise 

 gradually, to continue high for several 

 days, and to subside slowly. They car- 

 ry but little sediment and they main- 

 tain a good volume of water during dry 

 seasons. 



Thirty-eight creeks and small rivers 

 in the same watersheds, whose slopes 

 may be described as cleared rather than 

 timbered, are known, according to ob- 

 servation and local repute, in times of 

 flood to rise rapidly to extreme flood 

 height, to carry excessive quantities of 

 mud. sand, and gravel, and to fall 

 quickly. In dry seasons they are very 

 low, and the range from lowest to high- 

 est stages has increased and inflicted 

 much damage in very recent years. 



Two other classes of conditions may 

 be recognized in Professor Glenn's de- 

 scriptions : The one of valleys still 

 timbered, but which are being damaged 

 by beginning of logging and particular- 

 ly by erosion of logging chutes ; the 

 other, of watersheds that are largely 

 cleared but grassed, and which the 

 grass protects from erosion, though not 

 in the same degree from rapid run-off. 



Such evidence as this, collected by a 

 qualified and impartial observer with 

 reference to individual watersheds, 

 establishes for the region in question, 

 comprising the mountains of North 

 Carolina, Tennessee, and Georgia, the 

 fact "that forests do exert a beneficial 

 influence on stream flow by storing the 

 waters from rain, preventing their rapid 

 rush to the streams, and paying them 

 out graduallv afterward, thus acting as 

 true reservoirs in equalizing the run- 

 off." 



These detailed observations sustain the 

 general facts which every mountaineer 



