WATER SUPPLIES. 75 
to the flood plains. According to Homer Hamlin, a of the Reclama- 
tion Service, the acreage is distributed as follows: 
Irrigable land along Colorado River. 
Acres. 
( ottonwood Valley 5, 000 
Mohave Valley ' 50, 000 
Chemehuevis Valley 20, 000 
Great Colorado Valley 200, 000 
Yuma Valley 100, 000 
375, 000 
The ways and means of irrigating these lands have been investi- 
gated by the Reclamation Service, but except for the Yuma project, 
now under construction, no development has yet been undertaken. 
Outside of the flood plains no lands within the area described are 
sufficiently low to be irrigated from the river. The broad valleys 
and detrital plains occupying so large a part of the region, although 
admirably adapted to agriculture in other respects, are too high to 
be economically supplied with water from Colorado River b}^ any 
means known at the present time. In order to water the Hualpai or 
Detrital valleys it would be necessary to raise the water of the river 
about 2,000 feet, and the case is nearly as hopeless for the valleys 
farther south. 
Dam sites. — Several dam sites have been selected along Colorado 
River by the engineers of the Reclamation Service, and much has 
been done in the way of investigation as far north as the Cotton- 
wood Valley. Possible dam sites occur in Chocolate Canyon (fig. 
13), Aubrey Canyon, at Bulls Head in Pyramid Canyon (PL IX), 
and at Eagle Rock in the Cottonwood Valley (fig. 7). In none of 
these localities, however, has bed rock been found sufficiently near the 
surface to warrant the construction of masonry dams. In Chocolate 
Canyon borings reached the depth of 138 feet; in Aubrey Canyon, 
75 feet; in Pyramid Canyon, 100 feet. But in no case was the maxi- 
mum depth of the old gravel-filled channel reached. 
The canyons north of the Cottonwood Valley offer excellent oppor- 
tunities for the construction of dams, but little has been done further 
than the selection of certain favorable localities. Several have been 
selected by the Reclamation Service, and others by private compa- 
nies who contemplate using the water power in developing the min- 
eral resources of the region. The questions involved are mainly of 
an engineering nature, but it may be in place here to describe certain 
geologic conditions that are likely to affect development. 
In Recent time — the last epoch described under " Geologic his- 
tory" — the river has been filling its channel, at least in its lower 
" Personal communication. 
