Pocket Guide: Columbia River Basin

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2005 Edition
document 2004-16

The Columbia River Basin is a region that includes parts of Washington, Oregon, Idaho, Montana, Wyoming, Utah, Nevada and British Columbia ? an area larger than France.
The river and its tributaries are the dominant water system in the Pacific Northwest.
The Columbia River is 1,214 miles long.
The Columbia River originates at Columbia Lake in British Columbia, and about 25 percent of the river flow comes from Canada.
The largest major tributary is the Snake River, which is 1,036 miles long.
The Columbia River is a snow-charged river that fluctuates seasonally in volume.
Average annual runoff at its mouth is about 198 million acre-feet.
The highest volumes are between April and September. The lowest volumes are from December to February.
From its source at 2,650 feet above sea level, the river falls an average of more than 2 feet per mile before reaching the ocean.
Humans have lived along the river for more than 10,000 years, with a large increase in population when the Euro-American settlers arrived in the 1800s.