Mr. Labelle. 
440 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
that other factors, like rainfall, its distribution, and the condition of 
the ground-water, may mask the effect of forests, and that a thorough 
analysis of these other factors is necessary before the real effect of 
deforestation becomes apparent. 
It is believed that Mr. Leighton, in his remarks on the Tennessee 
River, has gone to the heart of the whole question, and that rainfall 
has to be considered in conjunction with deforestation. The writer 
also believes that the condition of the ground-water is the governing 
factor in low stages. This question has already been taken up by the 
Forestry Bureau, and diagrams have been made for a number of 
streams. Jf these diagrams show that neither the rainfall nor the 
condition of the ground-water can account for changes in the run-off, 
the theory of forests and stream flow will be materially strengthened. 
It is to be hoped that these diagrams, or, at least, the results obtained 
from them, will soon be published, and that they will be for a great 
variety of rivers in different parts of the country, including rivers 
having water-sheds which have suffered little or no deforestation. It 
is much to be desired, however, that this work be done by disinterested 
parties. The question of obtaining correctly the total daily or monthly 
rainfall in a water-shed from a few widely scattered stations is no 
easy task; it is strongly dependent on the judgment and experience of 
the computer, and, obviously, he should be free from preconceived 
ideas. 
Mr. Pinchot has mentioned the importance of forest cover as in- 
creasing ground-water storage and the consequent increasing of low- 
water stages. It is believed that there are other factors of much 
greater importance than forest cover in the creation and conservation 
of ground-water. A comparison of the minimum run-off of that part 
of the Susquehanna water-shed above Harrisburg with the minimum 
run-off of the Octoraro Creek, a tributary of the Susquehanna, 
draining a water-shed of 217 sq. miles near tide-water, devoid of 
forests and under a high state of cultivation, while the country above 
Harrisburg is only partly deforested, gives the following results: 
Susquehanna River 
above Harrisburg. Octoraro Basin. 
Minimum run-off Minimum run-off 
Year. per square mile. per square mile. 
1897 0.19 sec-ft. 0.63 sec-ft. 
1898 O21. & 0.83“ 
1899 0) Es eas 0.80 “ “ 
The factors favoring the Octoraro Basin, which is in the alluvial 
plain at the head of Chesapeake Bay, are porosity of ground and flat 
slopes, while the water-shed above Harrisburg is in the hills and the 
ground has less retentivity. Even if the forests above Harrisburg 
had remained intact, it is difficult to conceive that low-water run-off 
