How large is the Columbia River?
Columbia River Basin? The Columbia River flows south from its source in British Columbia, Canada to the Pacific Ocean. This passage runs 1,214 miles and flows through two countries and three states, Washington, Oregon and Idaho. It is the fourth largest watershed in the United States, receiving waters from seven states and one province. The largest tributary is the Snake River. The Columbia River has the second largest volume of flow of any river in the United States. Second to the Mississippi River.
