Lost, A Desert River and its Native Fishes - Sierra Club

Fig. 28. Photograph of Boulder Dam, 5119A. Courtesy of
the Bureau of Reclamation, Boulder City, Nevada.
Hoover Dam impounds Lake Mead, which extends
115 miles upstream into the Grand Canyon. It has 550
miles of shoreline and is a maximum width of 8 miles. The
reservoir is the largest by volume in North America and is
capable of holding nearly 28 maf of water. The lake‘s surface
area is roughly 162,700 acres with a maximum depth
of 550 feet.
Parker Dam
Parker Dam is located 15 miles upstream of Parker,
Arizona, and forms Lake Havasu. The Municipal Water
District (MWD) of southern California advanced funding
to the Federal government for construction of Parker Dam.
Excavation began in 1934, and construction was finished
in 1938 (Fig. 29). The powerhouse was completed in 1942.
Fig. 29. Parker Dam. Courtesy of the Bureau of
Reclamation, Boulder City, Nevada.
MUELLER AND MARSH 27
The concrete arched dam is roughly 860 feet in length
and one of the deepest based dams built. It has a hydraulic
height of only 75 feet, but the structure is 320 feet tall.
Lake Havasu backs up roughly 35 miles into the
Topock Gorge. The reservoir has a maximum capacity of
648,000 acre-feet and a surface area of 20,400 acres. Maximum
depth is 70 feet. The reservoir serves as a diversion
basin where water is pumped from MWD facilities for
southern California and from the Lake Havasu Pumping
Plant for the Central Arizona Project. These two pumping
facilities remove approximately 2.6 maf or more than a
third of the rivers‘ average flow.
Imperial Dam
Imperial Dam and Desilting Works are located 18 miles
upstream of Yuma, Arizona. The project was authorized
by Congress in 1928 as part of the Boulder Canyon Project.
Construction started in 1936 and was completed in 1938
(Fig. 30). Imperial Dam is short, having a hydraulic height
of only 23 feet, but the structure is 3,475 feet in length. It
provides the head needed to divert water to the All-
American Canal located in California.
The Desilting Works consist of three basins laid off
at a 60° angle from the intake channel. The basins are
divided in half and measure approximately 270 x 780 feet
each. Water velocity slows to less than 0.25 feet per second,
thus allowing silt to settle. A series of rotating scrapers
pushes the sediment into a sludge collection system
that flushes sediment out of collection pipes. The system
is designed to remove 70,000 tons of sediment per day.
Construction of the All-American Canal began in 1934.
It started delivering water to the Imperial Valley in 1940.
The delivery system was expanded with the construction
of the Coachella Canal. The Coachella Valley branches
Fig. 30. Imperial Dam, P212-3000-3890-1A. Courtesy of
the Bureau of Reclamation, Boulder City, Nevada.