Columbia

Columbia, major river of western North America, rising in Columbia Lake, just west of the main range of the Rocky Mountains, in south-eastern British Columbia. The river was formerly known as the Oregon River. The Columbia River is about 2,005 km (1,245 mi) long. It initially flows north-west, through a long, narrow valley called the Rocky Mountain Trench, and then turns sharply south, skirting the Selkirk Mountains and passing through Upper Arrow Lake and Lower Arrow Lake. It next receives the Kootenay (spelled Kootenai in the United States) and Pend Oreille rivers before entering the US state of Washington, where it first flows south and then traverses a great arc, known as the Big Bend. After receiving the Snake River, the Columbia turns west and forms much of the boundary between the states of Washington and Oregon before emptying into the Pacific Ocean through a broad estuary. The river flows through several spectacular canyons and deep valleys. About one-third of its course is in Canada. The Columbia and its tributaries together drain a vast basin of about 673,400 sq km (260,000 sq mi).

Large ocean-going ships can navigate the lower Columbia River as far as Vancouver, Washington; and, with the aid of locks, smaller marine vessels can reach the Dalles, Oregon, about 300 km (186 mi) upstream. Barges and other shallow-draft boats can navigate a further 220 km (137 mi).

The Columbia River has immense hydroelectric potential, and since the 1930s several large power projects have been built on it. The largest of these, the Grand Coulee Dam, in central Washington, is the key unit of the Columbia Basin Project, a federal undertaking also designed to irrigate up to 485,623 hectares (1.2 million acres) of semi-arid land. Other important power projects on the Columbia include Bonneville, the Dalles, John Day, McNary, Priest Rapids, Rocky Reach, and Chief Joseph dams, in the United States, and Mica Dam, in Canada. Most of these dams are also used for flood control and for irrigation.

The American explorer Robert Gray explored the mouth of the Columbia River in 1792, naming it after his ship. The Lewis and Clark expedition explored the lower Columbia from 1805 to 1806, and David Thompson, a Canadian surveyor and explorer, followed the river from its source to its mouth in 1811, and it subsequently became a central artery of the fur trade. The Columbia once had great numbers of salmon and supported a large canning industry; however, the fish stock was severely depleted in the 20th century as a result of dam construction and pollution, including radioactive contamination. In an effort to protect the salmon from extinction, the Northwest Power Planning Council in 1994 approved a plan to rebuild salmon stock by increasing the water flow through the dams and by developing habitat protection standards.