Hoover Dam
Staff posted on October 13, 2006 |
Hoover Dam

For millions of years, as the Colorado River followed its 1400-mile course from Colorado's Rocky Mountains to the Gulf of California, people, plants and animals have depended on its waters for sustenance.

Swollen by the melting snow that provides most of its water, the river frequently flooded low-lying lands along its route in the spring and early summer, destroying lives, crops, and property. In late summer and early fall, it often dried to a trickle, too low to divert. To protect the low-lying lands from flooding, and to assure a stable, year-round water supply, the river had to be harnessed.


Before the river could be harnessed, its waters had to be equitably divided among the seven states it serves. In 1922, a representative from each state and the federal government met for this purpose. The meetings resulted in the Colorado River Compact. Signed in November 1922, the Compact divided the Colorado River Basin into an upper and lower half, and gave half of the river's annual estimated flow to each basin. Division of each basin's apportionment was left to the states in that basin.

An Engineering Wonder

The Compact paved the way for the construction of storage dams and delivery facilities on the Colorado River, and, in 1928, Congress passed the Boulder Canyon Project Act, authorizing construction of Hoover Dam.

Hoover Dam was without precedent, the greatest dam of its day; it is still a world-renowned structure. Located in Black Canyon between Nevada and Arizona, the dam is a National Historic Landmark and a National Historic Civil Engineering Landmark. In 1994, the American Society of Civil Engineers named it one of America's Seven Modern Civil Engineering Wonders.

Construction of Hoover Dam began in 1931, and the last concrete was poured in 1935 - 2 years ahead of schedule. (President Franklin D. Roosevelt dedicated the dam on September 30, 1935.) The powerplant wings were completed in 1936, and the first generator began operation in October of that year. The 17th and final generator went into commercial operation in 1961. Hoover Dam's reservoir, Lake Mead, is America's largest man-made reservoir. Named for Reclamation Commissioner Dr. Elwood Mead, it can store 28.5 million acre-feet (9.2 trillion gallons!) of water, or nearly 2 years of the river's average annual flow. (An acre-foot of water would cover a football field to a depth of one foot.)

Hoover Dam is named for Herbert Hoover, the 31st President of the United States. (It has also been called Boulder Dam; the name Hoover Dam was permanently restored by Congress in 1947.) President Hoover strongly supported construction of a high concrete dam on the Colorado River to control its flows, provide irrigation water to nearby farmlands, and provide a dependable supply of water for southern California communities. He advocated that the Boulder Canyon Project be self-supporting, financed entirely through the sale of hydroelectric power generated at the dam, which it is today. Multipurpose Benefits

Hoover Dam's authorized purposes are: "flood control; improvement of navigation and regulation of the Colorado River; storage and delivery of Colorado River waters for reclamation of public lands and other beneficial uses exclusively within the United States; and hydroelectric power production." The water storage and river control Hoover and subsequent downstream dams and water delivery projects provide enables modern man to use the waters of the lower Colorado River for many purposes:

Irrigation of more than one million acres of land in the United States and nearly half a million acres in Mexico. These croplands, some of America's richest, grow a wide variety of fruits, vegetables, cotton, wheat, and hay throughout the year, generating millions of dollars for local economies.

Meeting the domestic water needs of more than 18 million people in homes and businesses in Las Vegas, Los Angeles, San Diego, Phoenix, Tucson, and other southwestern cities, towns and Indian communities in Arizona, Nevada, and California.

Hoover Powerplant

Generation of low-cost hydroelectric power for use in Nevada, Arizona, and California. Hoover Dam alone generates more than 4 billion kilowatt-hours a year - enough to serve 1.3 million people. From 1939 to 1949, Hoover Powerplant was the world's largest hydroelectric installation; with an installed capacity of 2.08 million kilowatts, it is still one of the country's largest.

Hoover Dam's $165 million cost has been repaid, with interest, to the Federal Treasury through the sale of its power. Hoover Dam energy is marketed by the Western Area Power Administration to 15 entities in Arizona, California, and Nevada under contracts which expire in 2017. Most of this power, 56 percent, goes to southern California users; Arizona contractors receive 19 percent, and Nevada users get 25 percent. The revenues from the sale of this power now pay for the dam's operation and maintenance. The power contractors also paid for the uprating of the powerplant's nameplate capacity from 1.3 million to over 2.0 million kilowatts.
Hoover Dam - Recreation Recreation, although a by-product, constitutes a major use of the lakes and controlled flows created by Hoover and other dams on the lower Colorado River today. Lake Mead is one of America's most popular recreation areas, with a 12-month season that attracts more than 9 million visitors each year for swimming, boating, skiing, and fishing. The lake and surrounding area are administered by the National Park Service as part of the Lake Mead National Recreation Area, which also includes Lake Mohave downstream from Hoover Dam.

Several wildlife refuges and backwaters have been constructed along the lower river to replace habitat lost with construction of the dams. River water is provided to these facilities, which create important habitat for native and introduced species. The river is also operated to the extent possible to protect native fish species and help them recover in population.

Physical Data

The Dam
Type: Arch gravity
Height: 726.4 feet (221.3 meters)
Crest length: 1244 feet (379.2 meters)
Crest width: 45 feet (13.7 meters)
Base width: 1660 feet (201.2 meters)
Volume of concrete: 4.25 million cubic yards (3.24 million cubic meters)

The Powerplant
Commercial generating units: 17
Station service units (to run dam and powerplant): 2
Nameplate capacity: 2080 megawatts (including station service)
Length (each wing): 650 feet (198 meters)
Width (each wing): 55 feet (16.8 meters)
Height (each wing): 75 feet (22.8 meters)

Lake Mead
Shoreline: 550 miles (885 kilometers)
Capacity: 28,537,000 acre-feet (35.2 million cubic meters)
Maximum depth: 500 feet (152 meters)
Surface Area: 157,900 acres (63,900 hectares)
Length when full: 110 miles (177 kilometers)
(All figures are for the reservoir at the top of conservation storage - elevation 1221.4 feet (372.28 meters))

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