Columbia

River in western North America; length over 2,005 km/1,245 mi. It rises in Columbia Lake on the western slope of the Rocky Mountains in British Columbia, Canada, 130 km/81 mi north of the USA border. It flows through Washington State along the northern border of Oregon, until it reaches the Pacific below Astoria; its estuary is about 55 km/34 mi long and from 5-11 km/3-7 mi wide, and its mouth is the only deep-water harbour between San Francisco and Cape Flattery.

The Columbia River was harnessed for irrigation and power by the Grand Coulee and other major dams, as part of the Columbia Basin Project. The river with its tributaries possesses one-third of the entire hydroelectricity potential of the USA. Although it was once famous for its salmon fishing, the catch here is now much reduced as a result of pollution and dam construction; it was listed in 1994 as being in danger of ecological collapse, along with its main tributary, the Snake River. It was listed as an endangered river for most of the 1990s, and salmon stocks were estimated to be under one tenth of their usual size, despite hatchery programmes.

The mouth of the Columbia River was reached by Robert Gray in 1792; the explorer David Thompson followed it from its source to its mouth in 1811. The Columbia and its tributaries drain a huge basin of approximately 668,215 sq km/258,000 sq mi, including most of Idaho, Washington, and Oregon, and parts of Montana, Wyoming, Nevada, and Utah. Since 1964 its flow has been the subject of a treaty between the USA and Canada, the two countries combining to promote a development programme of flood control, water storage, and hydroelectricity generation.