The Columbia River Basin is the most hydroelectrically developed river system in the world. More than 400 dams — 11 run-of-the-river dams on the mainstem — and hundreds of major and modest structures on tributaries block river flows and tap a large portion of the estimated Columbia’s generating capacity: more than 21 million kilowatts. Rock Island Dam on the middle river was the first major hydropower producer on the Columbia. Completed in 1932, Rock Island Dam is small compared to the behemoths — Bonneville and Grand Coulee — that the federal government completed respectively in 1938 and 1941. The last dams built on the Columbia came on line during the 1960s and 1970s. In 1973, Canada completed the last of the mainstem dams, Mica Dam on the upper river. The dams created large reservoirs that provide water for vast irrigation systems on the Columbia Plateau, and with the completion of four dams on the lower Snake River during the 1970s the engineers strung together a series of slackwater lakes that allowed barges to navigate more than 465 miles from the Pacific to the inland port of Lewiston, Idaho. The hydroelectric projects connect the entire region through a network of interties and relay stations into a powergrid system. A treaty with Canada in 1964 and creation of the NW-SW Intertie with California made the network inter-regional and international.
Dams on the Columbia have contributed significantly to steep declines in historically strong fish runs. Between the 1860s and 1960s, commercial fisheries annually harvested millions of pounds of anadromous fish, especially five species of salmonids. The largest catch came from the estuary and lower river, where fishers use gillnets. On the middle river, native fishers used dipnets, hooks, and setnets. Since the 1950s, the combined consequences of dams, increased ocean fishing, deterioration of stream and river habitats, and changing river conditions have made the Columbia less and less habitable for anadromous fish. Ever since the early 1970s, the fish catch has dramatically declined, with hatchery-raised species making up more than 80 percent of commercially caught salmon in the river. In 1992, the government listed the native Snake River Sockeye salmon as an endangered species, and in 1998 Willamette steelhead joined the list of endangered fish.
— Dr. William Lang, Director of the Center for Columbia River History
Dams have transformed the look and operation of the Columbia River. While dams have long existed on the river and its tributaries (in the form of fish weirs that spanned the river and early power and navigation structures), the federal dams of the 1930s through the 1970s transformed the wild, living river into a system of lakes. The transformation has wrought unexpected and, in some cases, unintended consequences while many have considered some changes the price of progress. Read about some of the mainstem dams in the following pages.
