THE EFFECT OF THE FOREST UPON WATERS 



165 



region had been reforested with spruce 

 for forty years. "One of them." he 

 wrote, "that gave no water during the 

 summer, never dries up now, and issues 

 seventy meters higher on the slope than 

 did the former spring. x\t Bois-le- 

 Francois, parish of Villers-devant- 

 Orval, after clearing away an old cop- 

 pice forest, tw^o springs disappeared. 

 The place where the water issued can 

 be seen yet, and the little channel that 

 it followed down the slope." 



At the International Congress of 

 Silviculture, which was held at Paris 

 on the occasion of the exposition of 

 1900, Mr. Grebe^ forester councilor at 

 Eisenach (Alsace), cited numerous ex- 

 amples of springs that had dried away 

 or of diminutions in stream-flow noticed 

 after deforestation in central Ger- 

 many ; he told, also, of cases where 

 springs reappeared after reforestation 

 had taken place. Another German for- 

 ester, M. B. A. Bargmann, told of the 

 disappearance of two springs in the 

 valley on Saint Amarin (Alsace), aftev 

 clearings had been made above them. 



At the same congress. Mr. Servier, a 

 landholder at Lamure-sur-Azergues 

 (Rhone) gave several interesting facts. 

 The region in which he lives having 

 been until late years almost completely 

 deforested, he noticed that wherever a 

 cluster of trees remained, their presence 

 was coincident with the existence of a 

 spring. On the western outskirts of a 

 coppice wood a spring exists ; the flow 

 of this spring diminished continually 

 when the coppice had been cut ; it be- 

 came normal when the coppice had shot 

 up again. 



Observations made at the German 

 forestry stations show that of 100 milli- 

 meters of rain water falling upon for- 

 ested territory, ten and one-half milli- 

 meters evaporate ; twenty are arrested 

 by the crowns of the trees, twenty-five 

 are retained by the forest floor. Forty- 

 four and one-half, then, reach the up- 

 per layers of the soil. On open ground, 

 evaporation consumes sixty-eight and 

 three-tenths millimeters. Only thirty- 

 one and seven-tenths millimeters, then, 

 penetrate the soil. If the quantity of 



rain was the same in the forest and out- 

 side, the presence of the forest would 

 augment, then, by twelve and one-half 

 per cent^ or about one-eighth, the pro- 

 portion of water absorbed by the 

 ground. 



Without doubt, it is very difficult to 

 prove incontestably the influence of for- 

 estation or deforestation upon a par- 

 ticular spring, as it is impossible to ex- 

 actly determine the area that feeds the 

 spring. Nevertheless, the observations 

 that have just been cited, and to which 

 many others could be added, justify us 

 in arriving at conclusions favorable to 

 forest influence. 



The facts verified by Mr. Fautrat in 

 the forest of Halatte (Oise), by Messrs. 

 Mathieu, Bartet, and de Drouin de Bou- 

 ville in the forest of Haye (Meurthe- 

 et-Moselle), from 1867 to 1898, estab- 

 lish beyond a doubt that more rain falls 

 over forest areas than over open coun- 

 try (twenty-three per cent, on an av- 

 erage) ; this increase of rainfall is not, 

 moreover, counterbalanced by the re- 

 tention of a part by the foliage of the 

 trees. The diminution of evaporation 

 and of surface off-flow resulting from 

 the presence of the forest contribute 

 equally to favor the nourishment of 

 subterranean sheets of water, which 

 give birth to springs. We can say. 

 then, with Mr. Hiiffel that "the forest 

 is the mother of rivers, as our fathers 

 declared," and that "the work of mod- 

 ern science has only confirmed the re- 

 lationship, recognized at all times and 

 universally, which binds the spring to 

 the tree that shades it." 



Mr. Hiiffel has. moreover, described 

 in his Economic Forcsticre the experi- 

 ments carried on since 1900 in the val- 

 ley of the Emmenthal, by the Swiss 

 central station of forestry research, in 

 order to compare the flow of two water 

 courses, one issuing from a basin con- 

 taining only eighteen per cent of forest 

 area, the other from a basin covered 

 with forest over ninety-one per cent of 

 its area. The learned professor has 

 just announced that the verifications 

 made up to the present have estab- 

 lished : 



