Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Lower Columbia Rivers and Waterways
The Lower Columbia's main waters: the Columbia, Cowlitz and Willamette rivers, and Lacamas and Vancouver lakes.
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The idea
The Columbia River is the largest river in the Pacific Northwest. It starts in the Rocky Mountains of British Columbia, Canada, and forms most of the border between Washington and Oregon before it empties into the Pacific Ocean. Several smaller rivers in the region flow into it as tributaries.
The Willamette River flows north through Oregon and meets the Columbia at Portland, adding 12 to 15 percent of the Columbia's flow. The Cowlitz River in Washington drains a large area that includes the slopes of Mount Rainier, Mount Adams and Mount St. Helens. The Lewis River, another tributary, drains part of the Cascade Range north of the Columbia.
The region also has lakes. Vancouver Lake, just west of Vancouver, Washington, is very shallow, with an average depth of less than 3 feet. Lake River carries water from its north shore to the Columbia near Ridgefield. Lacamas Lake in Clark County is a popular spot for fishing and water skiing, but pollution from farm runoff has caused serious algae problems there. Where the Columbia meets the sea, the Columbia River Estuary is home to many plants and animals.
Check yourself
Question 1 of 2
Which river's tributaries drain the slopes of Mount Rainier, Mount Adams and Mount St. Helens?
Composition
what it's made of
- Columbia River — The largest river in the Pacific Northwest, flowing to the Pacific along the Washington-Oregon border.
- Willamette River — A major tributary from Oregon that supplies 12 to 15 percent of the Columbia's flow.
- Cowlitz River — A Washington tributary draining the slopes of Mount Rainier, Mount Adams and Mount St. Helens.
- Lakes — Vancouver Lake, just west of Vancouver, and Lacamas Lake in Clark County, Washington.
- Columbia River Estuary — Where the river meets the Pacific, on the Oregon-Washington border.
Connection
how it relates
Under Lower Columbia Region
Change
how and why it evolves
- Past
- In 1792 the American ship Columbia Rediviva became the first non-Indigenous vessel to enter the Columbia River, and the river later became a key route for fur traders and pioneers. In 1980 the eruption of Mount St. Helens sent mudflows down the Toutle River, a tributary of the Cowlitz.
- Now
- Locks, dredged shipping channels and dams now shape the rivers, and these changes have altered river environments through pollution and barriers to fish migration.
- Next
- Efforts to clean up polluted lakes and help fish get past dams will likely continue, though balancing shipping, power and wildlife will remain difficult.