FORESTS, RESERVOIRS, AND STREAM FLOW 289 
problem of developing storage on such sites is beset with difficulties 
of many kinds that greatly increase the cost. 
In 1897 the writer made a careful study of this question of flood 
control by means of reservoirs in connection with an official investi- 
gation of the advisability of building reservoirs in the arid regions. 
His view of the difficulties in the way of any general application of 
such a system is quite fully stated in his report,* and the following 
extracts are directly in point: 
“Tt is the enst, not the physical difficulties, which stands in the way. 
It may be stated that as a general rule a sufficient amount of storage 
can be artificially created in the valley of any stream to rob its floods 
of their destructive character; but it is equally true that the benefits 
to be gained will not ordinarily justify the cost. The reason for this 
is plain. Floods are only occasional calamities at worst. Probably on 
the majority of streams destructive floods do not occur, on the average, 
oftener than once in five years. Every reservoir built for the purpose 
of flood protection alone would mean the dedication of so much land 
to a condition of permanent overflow in order that three or four 
times as much might be redeemed from occasional overflow. One 
acre permanently inundated to rescue three or four acres from inun- 
dation of a few weeks once in three or four years, and this at a great 
cost, could not be considered a wise proceeding, no matter how prac- 
ticable it might be from engineering considerations alone. The enst, 
coupled with the loss of so much land to industrial uses, would be far 
greater than that of levees or other methods of flood protection. 
* * * The construction of reservoirs for flood protection is not, 
therefore, to be expected, except where the reservoirs are to serve 
some other purpose as well.” 
The above conclusions are still as applicable as they were when 
written. The subject has been given renewed prominence quite recently 
in connection with the Ohio River floods, but, before considering this 
particular application, attention will be given to certain reservoir 
systems that have been proposed elsewhere, and particularly to one 
already built and put in operation by the Government and which will 
be referred to frequently in the following pages. This is the system 
at the head-waters of the Mississippi—the largest artificial reservoir 
system in the world. 
The project of converting the more important of the numerous 
lakes around the sources of the Mississippi and its tributaries into 
*House Doc., No. 141, 55th Cong., 2d Sess., p. 46. 
