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The massive Grand Coulee Dam, on the Columbia River, is the largest concrete structure in the U.S., the largest hydroelectric facility in the U.S., and the sixth-largest hydroelectric facility in the world. It provides irrigation for up to 1.1 million acres of agricultural lands and the hydroelectric complex maintains a generating capacity of 6.8 million kilowatts. It also serves as the primary flood control for the Columbia River basin (with a capacity of 5.18 million acre-feet of water) and provides recreational opportunities on the 150-mile-long Franklin D. Roosevelt Lake.