Benefits of Grand Coulee Dam


Grand Coulee Dam first generated electricity in 1941. It fueled the American war machine in the Pacific Northwest during World War II. Other advantages were gained too.

Construction of Grand Coulee Dam on the Columbia River in Washington State was completed in 1941. The dam began generating power in 1941 and 1942. Benefits of the dam were seen right away.

On December 7, 1941, the Japanese attacked America at Pearl Harbor, Hawaii. As a result, America entered World War II on the side of the Allies. Grand Coulee Dam came on line just in time to power aluminum plants at Longview and Vancouver, Washington. The dam also powered the Boeing plants in Seattle and shipyards at Vancouver and Portland, Oregon. When the government began building the top secret plutonium manufacturing plants at Richland, Washington, in 1943, the dam provided critical electrical power to that project too. Twelve new generators were installed in the dam from 1948-51 to handle the post-war electrical shortages.

Another benefit of the dam was flood control. It hadn’t been used as such during the war years. However, there was a severe flood in 1948, which flooded every low lying town on the Columbia and its tributaries. Officials allowed formation of a large reservoir behind the dam that contained 1 million acre feet. This reservoir became known was Lake Roosevelt and it stretches 150 miles to the Canadian border.

Now that the electrical generators, power plants, and utilities lines were installed, it was time to focus on the original plan, which was to bring irrigation to this arid part of the state. On August 31, 1945, various irrigation districts signed a contract with the U.S. Bureau of Reclamation (USBR) to build a massive irrigation system.

In January 1946 construction began on the main canals. Dams were built at both ends of the Grand Coulee formation to receive water pumped from behind the dam. By 1951, water began to fill Banks Lake. In January 1947, construction began on O’Sullivan Dam. The dam was over 3 miles long. The dam created the Potholes reservoir, another key component of the irrigation system. Pinto Dam was built at the base of Billy Clapp lake to form another reservoir. These three main reservoirs are linked together by a system of canals, syphons, and tunnels, creating a network of irrigation lines that ultimately provided water to over 500,000 acres.

Irrigation created an unanticipated problem when canals leaked and the water table rose. The soil was very shallow in some areas and bedrock caused runoff. Roads were washed out and basements were flooded. Excess runoff flooded homes and threatened sewer system, the city pool, and beach at Soap Lake. By 1961, 700 miles of wasteways and thousands of wells were built by the USBR to combat the problem.

One advantage of the runoff was that small lakes formed throughout the area. The Washington State Department of Fish and Wildlife planted fish in the various lakes. Three state parks were created around lakes near Coulee City. In 1955, 32,000 acres were set aside as the Columbia National Wildlife Refuge. The refuge is used extensively by resident and migrating birds. Sandhill cranes feed in the area during their spring and fall migration.

From its beginnings, Grand Coulee Dam has been a tourist attraction. People came by the carloads to watch its construction. A visitor center was later added at the site of a popular restaurant. In 1957, a free laser light show was added. Installation of the equipment cost $150,000. The laser light show was broadcast against the face of the dam during summer evenings to encourage people to stay overnight.


  1. “Grand Coulee: Harnessing a Dream,” Paul C. Pitzer, Washington State University Press, Pullman, Washington, 1994.