214 GUIDEBOOK OF THE WESTERN UNITED STATES 
of eastern Arizona, where there is a moderately large rainfall and much 
snow. Its volume varies considerably from year to year; in 1914 the 
flow into the reservoir was 629,500 acre-feet, and in 1915 it was 
1,440,100 acre-feet (U.S. Bur. Reclamation). Tonto Creek drains an 
extensive district north of the reservoir but has a much smaller flow 
than the Salt River. The reservoir when full is 15 miles long and 
from 2 to 4 miles wide and provides water for the irrigation of the 
Mesa-Phoenix region, 70 to 80 miles west of the dam. 
This project was one of the early ones of the United States Bureau 
of Reclamation. At the time the work was begun in 1903 the region 
was inaccessible, so that roads had to be built, a cement mill erected, 
and a plant constructed for development of power from a canal taken 
out of the Salt River 19 miles above the dam site. Much of the work 
_ was done by Apache Indians. (See pl. 29, A.) The dam was com- 
pleted in 1911 and dedicated by ex-President Theodore Roosevelt on 
oy 7? 
Ye 
“ i 
Horizontal scale 
o ' 
L lL 
Vertical scale 
500 1000 Feet 
FicuRE 56.—Section through Sierra Ancha, 15 miles northeast of Roosevelt, Ariz; d, Dripping 
Spring quartzite; b, Barnes conglomerate; p, Pioneer shale; s, Scanlan conglomerate 
March 18 of that year. According to the United States Bureau of 
Reclamation it is 1,125 feet long and 280 feet high (to the roadway), 
with great spillways, in all requiring about 340,000 cubic yards of 
masonry. The power plant develops as much as 10,000 kilowatts, 
which is transmitted to the Phoenix region on three wires carrying 
20 per cent to this capacity and treble the electric power. These 
features completely control the Salt River, which formerly wasted 
flood waters that caused devastation in the lower country. From 
° dams water is let out as needed, and the supply is sufficient for 
about $10,000,000. 
