Mr. Willis, 
384 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
Baitey Wiuuts, Esq. (by letter).—Four propositions are stated by 
Colonel Chittenden, and his argument is devoted chiefly to proving 
that they are not true. The writer holds that they are essentially true, 
provided that the limiting conditions, such as modify any general 
case, are appropriately considered. These propositions will be con- 
sidered in order. 
“The commonly accepted opinion is that forests have a beneficial 
influence on stream flow: ; 
“(1) By storing the waters from rain and melting snow in the bed 
of humus that develops under forest cover, preventing their rapid rush 
to the streams and paying them out gradually afterward, thus acting 
as true reservoirs in equalizing the run-off.” 
Forests do have a beneficial effect, although their capacity for such 
effect is not unlimited; neither are they in every location the most 
effective means of regulation. It is important to distinguish between 
level or very gentle slopes and steeper slopes, particularly those of 
mountainous districts. On the level, a forest-covered area and a well- 
tilled field compare closely in their capacity to absorb rain, but the 
forest prevents from 20 to 40% of the rain from reaching the ground 
(according to density of foliage, kind of trees, intensity of storms, and 
other conditions), and it transpires a large amount of moisture. 
Consequently the bare level field nearby receives more rain, and con- 
tributes more to ground-water. It also evaporates less than the forest 
transpires, and consequently it retains more from the same rain than 
the adjoining forest. The statement quoted from Mr. Zon* is strictly 
correct, as is shown by the experiments cited by Ernst Ebermayer,t 
who sums up the ease as follows: 
“In view of the exact investigations which have been cited above 
and which extend through 30 years, it is no longer possible to main- 
tain the assumption so generally made, that forests increase the amount 
of ground-water, and constitute a storage reservoir for the supply of 
springs, at least not so far as plains are concerned. The draining 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 extended inconsiderately 
to uplands and mountains. 
“Although the influence of the woods upon soil, moisture, percola- 
tion, and ground-water, under like soil conditions, must be the same 
in mountains as it is in lowlands, and only moderate differences are 
likely to appear, nevertheless the forest on the mountain differs very 
‘decidedly from that on the plain in regard to water control, inasmuch 
* Page 251. 
+ Einfluss der Wilder auf die Bodenfeuchtigkeit, auf das Sick - 
wasser, und auf die Ergiebigkeit der Quellen, 1900, page”38. meeonnisese eutndas Somat 
