4 BULLETIN 1430, U. S. DEPARTMENT OF AGRICULTURE 
purchase of woodland for the protection of stream flow, yet many 
States have taken no measures to check or control stream pollution. 
Enormous quantities of earth from mines, from washing kaolin, or 
from other sources are deposited in streams without protest. Thou- 
sands of acres of land too steep for permanent profitable cultivation 
are cleared, only to be abandoned, the subsequent erosion adding to 
the streams tons of silt, much of which is deposited, destroying 
reservoir space and increasing the cost of power or filling navigable 
channels. Later these deposits are removed at the expense of the 
general public, when a careful exercise by the State of its police 
power would have maintained the land in some form of permanent 
productivity, would have avoided much of the wasted effort in clear- 
ing it, and would have prevented the needless expenditure of public 
funds in the removal of silt beds from stream channels. 
The western streams from Colorado and middle California north- 
ward which have their sources in the forested mountains are largely 
clear, or of prevailingly low turpidity, until they enter the treeless 
plains. Those which have their sources in ancl flow through the 
wooded regions of the Northeast are likewise clear. The headwaters 
of the Appalachian and southeastern Piedmont Rivers are clear and 
carry little silt burden so long as their watersheds are protected from 
erosion. Tallulah River in northeastern Georgia, on which are 
located tw T o large storage reservoirs, is a typical stream of this kind. 
One of these reservoirs was recently emptied after 10 years of serv- 
ice, and when it was examined only a trace of sedimentation was 
found. There are, however, a few small clearings on the catchment 
area of this river. If such of these clearings as are hilly or have a 
rolling surface had not been cultivated, it is probable that even 
this trace of sedimentation would have been less. The North 
Fork of Swananoa River, from which the city of Asheville, 
N. C, obtains its supply of domestic water, has a very broken sur- 
face but is entirely forested. During very prolonged and heavy 
rains there is considerable turpidity, chiefly from leaching of vege- 
table matter, which is eliminated in a settling basin; at other times 
there is none. This small river is one of the head streams of the 
Tennessee River. The influence of the forest on soils subject to 
erosion is indicated by the difference between such head streams 
with forested basins and the Tennessee River in its lower reaches 
where it draws from similar soils unprotected by forest cover. So 
great is the silt burden of the main Tennessee River 4 that the pool 
above the dam at Hales Bar is reported 5 by the engineer in charge 
to have silted up in many places to the surface of the water, only the 
channel for the flow of the river remaining open. 
Whether forests exercise any beneficial influence upon stream flow 
is beyond the scope of this bulletin. Certain hydrographers claim 
that they do not. 6 If the advocates of the protective values of for- 
4 Prom data furnished by Herman Stabler, of the U. S. Geological Survey, it is com- 
puted that the Tennessee River, with a basin of 85,000 square miles, yearly transports 
nearly 11,000,000 tons of earth. 
5 Matthes, Gerard H. Tennessee river and tributaries, north Carolina, Tennessee, 
Alabama, and Kentucky, appendix a. U. S. Congress, 67th, 2d sess., House Doc. 319, 
p. 110. 1922. 
6 It is the opinion of D. W. Mead that forests exert practically no influence upon stream 
flow in Wisconsin, and F. E. Frothingham has recently made the same statement regard- 
ing forest cover in relation to the streams of New England. Frothinham. F. E. for- 
estry, hydro-electric development, and conservation. N. Y. Forestry, 9 : 18—19. 1923. 
But Charles L. Potter, president, Mississippi River Commission, is inclined to the view, 
