kooˈlē, 550 ft (168 m) high and 4,173 ft (1,272 m) long, on the Columbia River, N central Wash., NW of Spokane; built 1933–42 as a key unit in the Columbia basin project of the U.S. Bureau of Reclamation. Grand Coulee Dam, one of the world's largest concrete dams, is used for flood control, river navigation, irrigation, and power production that services the varied manufacturing in the area. The dam has the largest power-producing capacity (6,465 MW) in the United States. The dam impounds Franklin D. Roosevelt Lake, 130 sq mi (337 sq km), which extends to the Canadian border; it is one of the largest reservoirs in the United States. Power generated at the dam is used to pump water into Grand Coulee, a vertical-walled gorge, c.30 mi (48 km) long, carved by the Columbia River through the Columbia Plateau. The coulee, dammed at each end, is used as a reservoir (Banks Lake); it supplies water to more than 500,000 acres (202,343 hectares) on the plateau and acts as a backup against pump and power failures. Franklin D. Roosevelt Lake is part of Lake Roosevelt National Recreation Area. Located on the Pacific flyway, a chief north-south migratory route, the area has a great variety of waterfowl and land birds. Grand Coulee (1990 pop. 984) and Coulee Dam (1990 pop. 1,087) were founded by the U.S. government in 1935–36 as construction, operational, and housing bases for the dam.

See L. V. Downs, The Mightiest of Them All (rev. ed. 1993); P. C. Pitzer, Grand Coulee (1995).

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