APPENDIX A 



THE FOREST AND SPRINGS 



(By PIuffel) 



Springs and Their Origin. — Before approaching the difficult and controversial 

 question of the influence of forests on the maintenance of springs/ it is necessary to 

 define exactly what is meant by a "spring," and what is the origin of springs. 



" A spring," says Littre " is the water which issues from the ground at the origin of a 

 stream." 



Nowada\'s everyone admits that springs are fed by the percolation of water into 

 the earth derived from the atmosphere. It has been calculated = that the total flow 

 of water into the ocean of the principal rivers of the globe represents only about three- 

 sevenths of the water which fafls into their basins, derived from atmospheric sources. 

 There is therefore sufficient rainwater alone to feed the water courses, without its 

 being necessary to seek for other sources of supply, as Descartes has done. 



Percolation, or infiltration, is the slow penetration through fissures and through 

 interstices in the soU, of water derived from rain, from the melting of snows, from the 

 condensation of atmospheric vapors on the surface of vegetation, and on the super- 

 ficial parts of the soil. 



These waters, after penetrating into the soil, accumulate in certain parts and form 

 what is called subterranean sheets of water. 



In fact the deeper the water penetrates the less subject does it become to evaporation, 

 and finally it reaches a point where it has passed beyond the region of drainage, and 

 that tapped by the roots of plants. It is thus, generally speaking, that subterranean 

 sheets of water are formed below this region, which, at any point where there is a de- 

 pression in the soil at their level, come out as springs.^ 



The level of the subterranean sheet of water in permeable soils is more or less deep, 

 according to whether there have been recent rainfalls or not and whether these have 

 been abundant or scanty. Evaporation prevents it from establishing itself habitually 

 at the surface of the soil; the effect of drainage, and the suction'of plant roots will equally 

 prevent the entire saturation of a more or less substantial stratum of soil, or one more 

 or less deeply situated, according to the nature of the flora. Thus it will be found that 

 under a forest, the stratum of soil dried by roots is appreciably deeper than that below 

 a piece of ground under cultivation. 



Other things being equal, the level of "phreatic" ^ waters will be all the lower: if 

 the soil is more permeable; if the rains have been less abundant or less recent; if evapora- 

 tion has been greater; if the stratum drained by the roots of plants is deeper. 



1 Translated (literally) from ficonomie Forestiere, G. Huffel, Vol. I, pp. 83-124, 

 Chapter III, "The Forest and Springs." 



^Elisee Reclus, "La Terre." 



'See the "Traite de Geologic" of M. de Lapparent, 4th edition 1900, Vol. I, p. 195 

 and following pages. 



■* Daubrce ("Les Eaux Souterraines." Vol. I, p. 19) has introduced this term to 

 designate the sheet of subterranean water the nearest to the surface, because this is 

 the one which feeds the wells. 



361 



