FOREST COYER IX PROTECTING RESERVOIRS 6 
The loss in investment, however, through the silting up of a storage 
reservoir on a head stream is trivial when compared with the actual 
loss to the region of the reservoir site ; for when the storage capacity 
of a reservoir has once been destroyed the site can not be replaced. 
For this reason, it is of paramount importance that, wherever it is 
possible, the permanence of the reservoir be assured through adequate 
protection of the stream basins. 
Just as the public is demanding that hydroelectric developments 
shall not be made piecemeal, but that they shall be so coordinated as 
to obtain the full and complete use of power possibilities, so it will 
require that the catchment area shall be protected from erosion as 
thoroughly as the physical conditions justify. This restriction would 
not apply to clams constructed largely to secure fall and not to pro- 
vide storage, but only to such reservoirs as are located at or near 
headwaters and designed to provide storage, which will modify the 
regimen of the river, affecting its power possibilities and possibly 
its use for navigation, and tending to lessen floods. 
It is believed that the same public conscience which now demands 
that the earning value of forest lands shall not be destroyed will also 
soon require the protection of reservoir basins, in the same manner 
perhaps as sanitation is now often provided for. Hydroelectric 
engineers and investors in water-power securities, as well as indus- 
tries using hydroelectric power, should all be vitally interested in 
obtaining such protection to basins employed for water storage. 
INFLUENCE OF FOREST PROTECTION ON SILTING 
Excessive erosion in the forested parts of the United States is 
largely the result of unnatural conditions, and on many head streams 
it can be prevented or greatly reduced. Notwithstanding the fact 
that there are many reservoirs which have become so silted up that 
only the channel of the stream remains, this is not the natural condi- 
tion for most streams the sources of which are within well-wooded 
regions; it is a condition produced very largely and often entirely 
through exposure of the naked soil — the removal of the protective 
cover of forest and of forest litter and humus. (PL 3, figs. 1 and 2.) 
Though a number of reservoirs have silted flush except for the 
stream channel, these are chiefly on the smaller streams or where 
the solid burden contains a large proportion of coarse material. The 
reservoirs on larger streams where most of the material being trans- 
ported consists of finer silt more easily held in suspension do not 
seem in all cases to silt flush, or they do so very slowly. There is a 
relatively rapid silting on the upper portions of the reservoirs. The 
silting then proceeds less rapidly until a stage is reached at which the 
rate of silting is materially reduced, either because eddies and con- 
vective currents hold matter in suspension or because velocity 
during floods scours the silt above a certain level. There are local 
features in nearly every reservoir which control the rate and the 
ultimate extent of deposit. 
A matter for serious consideration also is the control which should 
be exercised by the States in preventing an increase in the solid 
burdens of streams in cases where such an increase would jeopard 
valuable power sites. In certain States large sums of money are 
spent by the Federal Government for channel dredging or for the, 
