DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 435 
question to be determined by an algebraic sum of “plus” and “minus” Mr. McMath. 
quantities, in which time is a variable factor. What was once easy 
is not difficult; what is now difficult will be more difficult later. 
4, Passing from the Ohio and Upper Mississippi water-sheds, it is 
a reasonable expectation that the floods from the Upper Missouri, 
Yellowstone, Platte, Kaw, Arkansas, Cimarron, Cottonwood, North 
and South Canadian, and Red Rivers will sooner or later be held in 
reserve for the benefit of the arid and semi-arid regions of the Middle 
West. The aggregate of flood decrease, not so much as to height as 
duration, is tremendous. This, in the writer’s opinion, is the chief 
hope for the Lower Mississippi for flood control, navigation, and 
security. 
5. A river from source to mouth is an indivisible unit, though it 
has many branches and serves many uses. 
The author’s treatment of the influence of forests on stream flow 
is weakened by his omission of the very great and almost universally 
present fact of ground storage. 
“The inclined-plane surface, practically impervious to water, with 
a layer of sand covering some small portion of it” with a uniform spray 
of water applied to the entire surface, has but little similarity to 
natural conditions. 
Some years ago the writer visited the head-waters of the Meramec 
River, Missouri. A heavy fall of wet snow, about 9 in. deep, had 
covered the country with practical uniformity. After two days of 
bright sun and warm wind the snow was all melted, and the streams 
were running full. 
The territory visited was near the junction of three streams, the 
drainage areas of which may be roughly estimated as being in the 
proportion of 1:3:4, with an aggregate area of about 2500 sq. miles, 
The smallest area has largely a clay subsoil of considerable depth, 
which is about as near an approach to an impervious surface as Nature 
makes; the underlying rock is sand and limestone. The slopes are 
moderately steep, largely cleared, and under cultivation. - Conditions 
are favorable to active soil wash. The outlet stream is extremely, 
turbid, the water being a dull brick-red in color, and the volume may 
be estimated at 150000000 gal. per 24 hours. Topographically, this 
stream should be the outlet for the second area as well as the first. 
It is known as the “Dry Fork of the Meramec,” and is well named, 
for normally it is dry. The first area has no springs fed by stored 
water, but, as the area bears crops, a part of the precipitation, say 
15%, must be absorbed. 
The middle area is largely a sandstone formation with a porous 
top soil. The valley has a stream bed for emergencies, but it is 
normally dry; the stream bed practically ends at a cavern in the hill- 
side. There is plenty of evidence in the shape of drift that water 
