Grand Coulee Dam is a concrete gravity dam on the Columbia River in the U.S. state of Washington, built to produce hydroelectric power and provide irrigation water. Constructed between 1933 and 1942, Grand Coulee originally had two powerhouses. The third powerhouse ("Nat"), completed in 1974 to increase energy production, makes Grand Coulee the largest power station in the United States by nameplate capacity at 6,809 MW. The proposal to build the dam was the focus of intense debate during the 1920s between two groups. One group wanted to irrigate the ancient Grand Coulee with a gravity canal while the other pursued a high dam and pumping scheme. The dam supporters won in 1933, but, although they fully intended otherwise, the initial proposal by the Bureau of Reclamation was for a "low dam" 290 feet (88 m) tall which would generate electricity without supporting irrigation. That year, the U.S. Bureau of Reclamation and a consortium of three companies called MWAK (Mason-Walsh-Atkinson Kier Company) began construction on a high dam, although they had received approval for a low dam. After visiting the construction site in August 1934, President Franklin Delano Roosevelt endorsed the "high dam" design, which at 550 ft (168 m) high would provide enough electricity to pump water into the Columbia basin for irrigation. Congress approved the high dam in 1935, and it was completed in 1942. The first waters overtopped Grand Coulee's spillway on June 1 of that year. Power from the dam fueled the growing industries of the Northwest United States during World War II. Between 1967 and 1974, the third powerplant was constructed. The decision to construct the additional facility was influenced by growing energy demand, regulated river flows stipulated in the Columbia River Treaty with Canada, and competition with the Soviet Union. Through a series of upgrades and the installation of pump-generators, the dam now supplies four power stations with an installed capacity of 6,809 MW. As the centerpiece of the Columbia Basin Project, the dam's reservoir supplies water for the irrigation of 671,000 acres (2,700 km2). The reservoir is called Franklin Delano Roosevelt Lake, named after the president who endorsed the dam's construction. Creation of the reservoir forced the relocation of over 3,000 people, including Native Americans whose lands were flooded. The dam was constructed without fish passage. The next one downstream, Chief Joseph Dam, which was built decades later, also does not have fish passage. This means no salmon reach the Grand Coulee Dam or much of the Colville Indian Reservation.
Background The Grand Coulee is an ancient river bed on the Columbia Plateau created during the Pliocene Epoch (Calabrian) by retreating glaciers and floods. Originally, geologists believed a glacier that diverted the Columbia River formed the Grand Coulee, but it was revealed in the mid-late 20th century that massive floods from Lake Missoula carved most of the gorge. The earliest known proposal to irrigate the Grand Coulee with the Columbia River dates to 1892, when the Coulee City News and The Spokesman Review reported on a scheme by a man named Laughlin McLean to construct a 1,000 ft (305 m) dam across the Columbia River, high enough that water would back up into the Grand Coulee. A dam that size would have its reservoir encroach into Canada, which would violate treaties. Soon after the Bureau of Reclamation was founded, it investigated a scheme for pumping water from the Columbia River to irrigate parts of central Washington. An attempt to raise funds for irrigation failed in 1914, as Washington voters rejected a bond measure.
… excerpt ends here. Continue reading the full article.
