WSP10089

• File Number: 8220.200.05.A
• Description: Hoover Dam/Lake Mead/Boulder Canyon Project
• Basin: Colorado Mainstem
• Date: 1/1/1950
• Title: The Story of Hoover Dam: Conservation Bulletin No. 9
• Water Supply Pro - Doc Type: Publication

Uncontrolled and unregulated the Colorado had little value. The yearly
spring run.off followed by rainless months made any large irrigation or power
development uncertain and unprofitable without control measures. Nor,
was the undependable silt-laden flow of the river suitable for city water
supplies. Also, further development in the area was infeasible; for already
more land had been reclaimed for irrigation than could be sustained by
depending on the natural flow of the river.
Dammed and under control all of these problems would be alleviated.
And there were many possible damsites along the course of the Colorado.
Thc area tributary to the Colorado is, by nature, roughly divided into an
upper and a lower basin. The dividing line falls at Lee Ferry, Arizona, a
few miles south of the Arizona.Utah boundary.
As defined in the Colorado River Compact, the upper basin includes those
parts of the States of Arizona, Colorado, Nev..- Mexico, Utah, and Wyoming
within and from which waters naturally drain into the Colorado River system
above Lee Ferry, and also all purts of those States located without the drainage
area of the Colorado River system which are novo{ or shall hereafter be bene-
ficially served by waters diverted from the system above Lee Ferry; and the
lower basin includes those parts of the States of Arizona, California, Nevada,
New Mexico, and Utah within and from which waters naturally drain into
the Colorado River system below Lee Ferry, and also all parts of those States
located without the drainage area of the Colorado River system which are
now or shall hereafter be beneficially served by waters diverted from the
system below Lee Ferry.
The two basins are about equal in area and are separated by the "canyon
region"-a 400.mile bottleneck through which the Colorado has battered its
way for countless eons of time. The gorges begin at Lee Ferry and end
with Black Canyon.
A comprehensive plan of development required detailed data from hath
npper and lower basins. Bureau of Reclamation engineers investigated a
total of 70 dam and reservoir sites along the entire course of the river.
The most suitable sites in the upper basin were: the Flaming Gorge site
on the Green River in northern Utah, with a potential reservoir capacity of
4,000,000 acre.feet; the Juniper site on the Yampa River in Colorado, with
1,500,000 acre-feet; and Dewey site on the Colorado in eastern Utah, with
2,370,000 acre.feet.
All of the above sites were objectionable for several reasons. In the first
place, neither site offered sufficient storage capacity for adequate.river regula-
tion. Another disadvantage was the distance from where regulation was
most needed. Furthermore, hundreds of miles separated these sites from the
irrigable fields of Arizona and California. Again. there were too many
tributaries below these sites which might cause destructive floods.
In the lower basin two excellent sites were found-Boulder Canyon and
Black Canyon. Each offered potential reservoir capacity of over 30,000,000
acre-feet, but each site posed engineering problems of stupendous proportions.

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After having compared data from the two basins the engineers favored
the lower basin sites. The Bureau of Reclamation intensified invesligations
there by making geologic and topographic surveys, starting in 1919. These
investigations revealed Black Canyon to be fayored over Boulder Canyon in
several respect3. The depth to bedrock was less, the geologic structure was
better, and a dam of smaller dimensions would give the same reservoir
capacity. From 1920 to 1923 men actually lived in Black Canyon, diamond
drilling and testing the rock; for the rock had to offer an unquestionably
.sound foundation. It was to support the highest dam that the world had
ever seen.
The proposed dam would be so high that its reservoir could store the
entire flow of the Colorado River-including all average floods-for two
whole years. Furthermore, it would be located below the large tributaries
and would thus control them. It would create a po'wer head within trans-
mission distance of the power markets of southern California. And, it
would be in the midst of a heavily mineralized region in Nevada and Arizona
where lo\,'.cost power could be a boon to strategic metal production.

Looking up$tream through Black Canyon toward Boulder dam site
l)efore construction activities were begun.