2 BULLETIN 1430, U. S. DEPARTMENT OF AGRICULTURE 
M. O. Leighton, of the United States Geological Survey, that with 
a minimum of 36,000,000 horsepower without storage -there might 
with storage "eventually be established a total power installation 
of at least 200,000,000 horsepower and probably much more." 
The minimum water-power resource of the eight southern Appala- 
chian States, without storage, is placed by the United States Geolo- 
gical Survey at 3,340,000 horsepower. If storage of storm water is 
employed, this minimum can be increased, at a conservative estimate, 
to 5,678,000 horsepower. This increase is based upon the figures of 
the Geological Survey of Tennessee 2 indicating the possible increase 
in that State. Plans which have been worked out for the develop- 
ment of water power in Tennessee show that the power could be in- 
creased by storage 70 per cent above the minimum dry-season flow. 
Since the Tennessee River, on which these figures are based, is a 
large stream, its tributaries having their sources in six other States, 
it can reasonably be assumed that the water-power resources of the 
Appalachian and Piedmont regions as a whole might be increased 
in the same proportion. 
A vast power plan which has been outlined by Harold C. Fiske for 
the full development of the Tennessee River calls for the construction 
of about 100 dams on the river above Knoxville. It is estimated that 
under this development there might be produced about 4,000,000 
horsepower on the river at and above Muscle Shoals. The economic 
feasibility of this plan would depend largely upon the possibility of 
procuring at low prices much of the land which would be submerged 
by the reservoirs, many of which would be vast lakes. 
This proposed plan may never be entirely consummated. In any 
event, if the enormous resource of this river at and above Muscle 
Shoals is to be adequately developed, it must be through a series of 
storage reservoirs, the ultimate value of which will depend upon the 
maintenance of storage capacity through reducing siltage. 
NECESSITY OF PERMANENCY OF POWER RESERVOIRS 
The value of a storage reservoir depends largely upon its life, 
that is, upon the permanency of its storage capacity. The rate at 
which erosion of soil is taking place on the basin of the supplying 
stream is the all-important factor in determining the period of 
service, or the number of years which will elapse before the soil re- 
moved by heavy rains from the lands on its catchment areas will 
fill the reservoir. 3 (PI. 2, figs. 1 and 2.) 
Many engineers, accepting siltage in certain regions as a natural 
condition, customarily determine the life of a reservoir and ascer- 
tain whether the earnings will provide for the amortization of its 
costs. There are regions, as will be pointed out, where methods for 
the control or reduction in silting are impossible or impracticable. 
2 Switzer, J. A. the water powers of Tennessee. Tenn. State Geol. Survey Bull. 
17, 137 pp., illus., 1914. 
3 In most cases it is not possible to remove economically the silt deposited above the 
dam. To do so would often mean merely passing it to a reservoir lower down on the 
stream. It is suggested that the proposed Boulder Canyon Reservoir on the Colorado 
River be flushed, after draining it, once in about 10 years by means of a reservoir located 
above it and employed only for this purpose. It is doubtful, however, if this can actu- 
ally be done since the river at present carries its full load of silt and the load could not 
be materially increased by flushing. There are likewise mechanical difficulties. But if 
such a system could ever be employed it might also be used most advantageously on the 
streams of middle and western Texas with their high silt burden. 
