Flip a light switch in Las Vegas or Los Angeles, and there is a chance that some of that power was generated at Hoover Dam, the Depression-era behemoth on the Nevada-Arizona line that, at one time, was the largest hydroelectric producer in the world.
Even today, the plant has a capacity of 2,080 megawatts, enough to meet the needs of 1.3 million people. To understand the generation process, which combines technology with the brute force of rushing water, look first not at the 726-foot dam, but right behind it, at the four intake towers in Lake Mead.
Intake Towers and Pipes
The lake's surface obscures the towers' true size. The towers, built into the sides of the original canyon, are each 395 feet high, or about as tall as a 30-story building. Combined, the towers are capable of taking in 118,000 cubic feet of water per second, of which 32,000 cubic feet per second is used for power generation. The water is diverted to the generating plant through 30-foot diameter penstocks, or pipes, which are in concrete-lined tunnels.
Turbines and Generators
The generating plant is a U-shaped structure with 10 acres of floor space located at the base of the dam. Inside are 17 turbines--nine on the Arizona side and eight on the Nevada side--plus two small units used to create power for the plant itself. The force of the water spins the turbines, which, in turn, spin magnets past stationary coils of copper wire. The act of spinning the magnets past the copper coils creates the electricity--a principle discovered by British scientist Michael Faraday in 1831.
The U.S. Bureau of Reclamation, which operates the dam, says the largest share of the power (28.5 percent) goes to the Metropolitan Water District of Southern California, followed by the state of Nevada (23.4 percent), the state of Arizona (19 percent), the city of Los Angeles (15.4 percent) and the Southern California Edison Co. (5.5 percent). Other recipients include Anaheim, Azusa, Banning, Burbank, Colton, Glendale, Pasadena, Riverside and Vernon, all in California, and Boulder City, in Nevada.