The Columbia 

The Columbia River is the USA's fourth largest river by volume. At its mouth, the Columbia's average annual flow is about 265,000 cubic feet per second--or roughly 160 million acre-feet of water. Its headwaters are in Canada, and it flows 1,243 miles to where it empties into the Pacific at Astoria. The Willamette joins the Columbia about 105 miles upstream from Astoria.