Hoover Dam
,
dam
in Black Canyon on the
Colorado River
, at the
Arizona
-
Nevada
border, U.S. Constructed between 1930 and 1936, it is the highest
concrete
arch-
gravity dam
in the
United States
. It impounds
Lake Mead
, which extends for 115 miles (185 km) upstream and is one of the largest artificial lakes in the world. The
dam
is used for flood and silt control,
hydroelectric power
, agricultural
irrigation
, and domestic
water supply
. It is also a major sightseeing destination, with some seven million visitors a year, almost one million of whom go on tours through the dam.
Hoover Dam is 726 feet (221 metres) high and 1,244 feet (379 metres) long at the crest. It contains 4,400,000 cubic yards (3,360,000 cubic metres) of concrete. Four reinforced-concrete intake towers located above the dam divert water from the reservoir into huge steel pipes called
penstocks. The water, after falling some 500 feet (150 metres) through the pipes to a
hydroelectric power
plant in the base of the dam, turns 17 Francis-type vertical hydraulic
turbines
, which rotate a series of
electric generators
that have a total power
capacity
of 2,080 megawatts. Nearly half of the generated
electric power
goes to the Metropolitan Water District of Southern California, the city of
Los Angeles
, and other destinations in southern California; the rest goes to Nevada and Arizona. The dam, power plant, and reservoir are owned and managed by the U.S. Department of the Interior’s Bureau of Reclamation.
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Which Is Taller? Quiz
Hoover Dam is named in honour of
Herbert Hoover
, the U.S.
president
during whose administration (1929?33) construction began on the dam and whose work as commerce secretary in the 1920s secured agreements necessary for the project to proceed. Erected during the
Great Depression
, the dam was a major endeavour that employed thousands of workers; around 100 fatalities occurred during its construction. Although legislation passed by
Congress
in 1931 officially named the dam for Hoover, officials in the succeeding administrations of
Franklin D. Roosevelt
and
Harry S. Truman
referred to it as Boulder Dam, its name during the planning stages before construction. In 1947 Truman signed a congressional resolution restoring the structure’s formal name to official use.
From the time of the dam’s construction, a federal highway
traversed
the dam’s crest, serving both visitors to the dam and travelers between Nevada and Arizona. As the dam and surrounding Lake Mead recreation area rose in popularity, traffic increased; traffic problems became especially severe under the security restrictions imposed after the
attacks of September 11, 2001
. Construction began in January 2005 on a long-planned
Hoover Dam Bypass Project, and in October 2010 a concrete
arch bridge
with a 1,060-foot (322-metre) span?the longest in
North America
for that type of bridge?opened for through traffic within view of Hoover Dam. The old road along the crest is reserved for use by visitors to the dam.