Grand Coulee Dam is a hydroelectric gravity dam on the Columbia River in the U.S. state of Washington. In the United States, it is the largest electric power producing facility and the largest concrete structure. It is the fifth largest producer of hydroelectricity in the world.
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The Grand Coulee Dam is almost a mile long at 5223 feet (1586 m). The spillway is 1,650 feet (503 m) wide. At 550 feet (168 m), it is taller than the Great Pyramid of Giza. Its hydraulic height of 380 feet (115 m) is more than twice that of Niagara Falls. After hydroelectric power, the dam's main goal is irrigation of a vast dry area in the center of Washington state. A water distribution network was built using the adjacent coulee to hold the main reservoir now known as Banks Lake. Water is pumped up 280 feet (85 m) from Lake Roosevelt to Banks Lake using twelve 14-foot-wide pipes. Pumped-storage hydroelectricity capability was incorporated into the final six pumps. During low-demand periods, water is pumped into Banks Lake, to be used later during high-demand periods. Water flow is reversed, powering generators as it falls back into Lake Roosevelt. This function is used regularly when irrigation water demand is low and electricity demand is high.