CogKnoSys

Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.

Physical

Columbia River Estuary

The Columbia River Estuary is the stretch where the Columbia River meets the Pacific, on the Oregon–Washington border, and river water mixes with the sea.

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The idea

The Columbia River Estuary lies on the border between Oregon and Washington, where the Columbia reaches the Pacific Coast. An estuary is a partly enclosed body of water along a coast where fresh river water meets and mixes with salty seawater. This blend of fresh and salt water is called brackish water. In an estuary, the rising tide pushes salty water upstream, and the falling tide lets it drain back out. The Columbia's estuary is defined as reaching inland as far as Bonneville Dam, the furthest point where tides still change the river level enough to be recorded.

The estuary sits in a valley that was cut into old marine sediments and volcanic rocks. It receives large volumes of water from the Cascade Range to its east, where the mountains trap rain and snow. Sediments laid down since the ice ages have filled the valley, and they keep shaping the estuary.

The estuary is an extremely biodiverse system. At some stage of their lives, over 70 species of fish and hundreds of species of birds use it, along with many reptiles, mammals and amphibians. The Chinook people, who lived along a large stretch of its northern shore, are its traditional owners and first people.

Check yourself

Question 1 of 3

How far inland is the Columbia River Estuary defined to reach?

Pick one. The first pick counts.

Composition

what it's made of

  • Cape Disappointment — The northern point at the river's mouth, named by fur trader John Meares in 1788.
  • River bar — The shallow entrance from the ocean, where rough breakers once kept ships from crossing.
  • Tidal reach — The long upstream stretch where tides still raise and lower the water, as far inland as Bonneville Dam.
  • Marshes and wetlands — Shoreline habitats that shelter fish and birds, many of them lost to diking, dredging and jetties.

Connection

how it relates

Under Lower Columbia Rivers and Waterways

Cause and effect

  1. Biodiversitystrength 70 of 100

    The estuary supports great biodiversity, hosting over 70 species of fish and hundreds of bird species.

  2. Habitatsstrength 60 of 100

    The estuary provides a varied environment that many species rely on for habitat.

In place

  1. Bonneville Damstrength 70 of 100

    The estuary is defined as reaching inland as far as Bonneville Dam.

Related

  1. Chinookan Peoplesstrength 60 of 100

    The Chinook people are the traditional owners and first people of the estuary.

Change

how and why it evolves

Past
In 1792 the American merchant sea captain Robert Gray sailed across the bar into the estuary and named the river the Columbia. John Meares had come close in 1788, but his ship could not get through the rough breakers at the bar. Over its history, jetty building, diking and dredging destroyed more than half of the estuary's wetlands, and over 70% of that loss came from diking and filling.
Now
Conservation groups such as the Lower Columbia Estuary Partnership and the Columbia River Estuary Study Taskforce have worked for decades to restore marshes and watch over the estuary's health.
Next
Restoration work will likely keep reconnecting lost marshes so that fish, birds and other wildlife can use them again.

Knowledge you can walk. Read the idea, then step up, across or down.

Columbia River Estuary

The Columbia River Estuary is the stretch where the Columbia River meets the Pacific, on the Oregon–Washington border, and river water mixes with the sea.

Learn, discuss, create, buy or invest

The idea

The Columbia River Estuary lies on the border between Oregon and Washington, where the Columbia reaches the Pacific Coast. An estuary is a partly enclosed body of water along a coast where fresh river water meets and mixes with salty seawater. This blend of fresh and salt water is called brackish water. In an estuary, the rising tide pushes salty water upstream, and the falling tide lets it drain back out. The Columbia's estuary is defined as reaching inland as far as Bonneville Dam, the furthest point where tides still change the river level enough to be recorded.

The estuary sits in a valley that was cut into old marine sediments and volcanic rocks. It receives large volumes of water from the Cascade Range to its east, where the mountains trap rain and snow. Sediments laid down since the ice ages have filled the valley, and they keep shaping the estuary.

The estuary is an extremely biodiverse system. At some stage of their lives, over 70 species of fish and hundreds of species of birds use it, along with many reptiles, mammals and amphibians. The Chinook people, who lived along a large stretch of its northern shore, are its traditional owners and first people.

Check yourself

3 quick questions, instant feedback.