As of 2023 [update] , the U.S. state of Washington has 1,242 dams that are able to impound 10 acre-feet or more of water and are regulated by the Washington State Department of Ecology (DOE). These include dams that produce hydroelectricity and create reservoirs for irrigation, drinking water, or recreational uses. According to the DOE, approximately 52 percent of dams in the state are privately-owned, while 31 percent are owned by local governments. [1]
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Approximately 87 percent of dams in Washington are earth fill dams, with the second most-common type being concrete gravity dams (6%). Only 113 dams in the state are taller than 50 feet (15 m). King County has 123 dams—the most of any county in the state. [1] The majority of dams were built between 1960 and 1999. [1] Proposals to remove underused dams and restore fish habitats emerged in the early 21st century with support from the state's Native American tribes; the first major dam removal was the Condit Dam near White Salmon in 2011, which was followed by two dams on the Elwha River near Port Angeles. As of 2024 [update] , 39 dams in Washington have been removed. [2]
The largest dam in Washington, in terms of structural volume, reservoir capacity, and electricity production, is the Grand Coulee Dam on the Columbia River. It is the largest power station in the United States with a nameplate capacity of 6,809 megawatts and one of the largest concrete structures in the world. [3] The tallest dam is Mossyrock Dam on the Cowlitz River in Lewis County, at 606 feet (185 m). [4] The longest dam is O'Sullivan Dam on Crab Creek, at 19,000 feet (5,800 m); it is among the longest earth fill dams in the United States. [5]
