4 THE FORESTS OF THE UNITED STATES: THEIR USE. 
more water than will the harder and relatively less porous soil of 
the open. A forest soil when saturated will hold more than half its 
dry weight in water, or over 6 inches of water for every foot of soil. 
This, as well as the breaking up of forest soil by the roots of trees 
.and undergrowth, makes it more effective than any other cover for 
the intake of water into that vast underground reservoir from which 
all streams and springs are fed. 
When the forest is cleared from a mountain watershed the blanket 
formed by the decaying leaves, branches, and fallen trees is burned 
up, dried by the sun, or carried off by wind and water. This is 
inevitably followed by increase in the frequency and duration of 
floods. This fact is known to every man who has had an opportunity 
to observe it. To those who have not had this opportunity the story 
is told by actual record of stream flow upon rivers for a period during 
which the mountain forests on their watersheds were rapidly denuded. 
These are such as the Ohio, Monongahela, Allegheny, Cumberland, 
Alabama, Savannah, Wateree, Congaree, and Muskingum. 
That surface conditions affect stream flow is shown by the record 
of streams whose naturally treeless watersheds by cultivation have 
been made more retentive of water. The principal watershed of the 
Red River lies in the prairie country of western Texas and Okla- 
homa. With slightly decreased rainfall this stream shows during 
the last sixteen years a marked decrease in the frequency and dura- 
tion of floods and of low water. During this period much of its 
watershed has been cultivated, groves have been planted, and fires 
checked, resulting in a larger capacity for the absorption and storage 
of water. 
That forests hold soil and that hillsides denuded of forest do not 
hold their soil is to be seen in any mountain region in the United 
States. One small stream has been found by actual measurement to 
deposit silt in one year equal to 14 tons per acre of its watershed. 
For the whole United States the loss of soil each year is from one to 
two thousand million tons. At the lowest estimate the total quantity 
of silt carried by our streams would cover 1 foot deep a surface of 
more than 900 square miles. The larger part of it is deposited in the 
lower courses of our streams and in our harbors, a menace to naviga- 
tion and to present developed water powers, and a handicap to their 
development. 
The National Forests in the Rocky Mountain and Pacific coast 
States afford summer ranges to over 12 per cent of the cattle and 21 
per cent of the sheep in the States in which they he. If this live 
stock were not fed in the forests during the summer months it would 
be without natural forage during the winter.’ For the East, the num- 
[Cir. 171] 
