Our Watershed
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Why watersheds matter:
We all live in a watershed.
If you live, work, or play in Washington County, then you’re part of the Tualatin River watershed! The Tualatin River is the only river in the county, and an important resource for drinking water, irrigation, fish and wildlife habitat, and recreation.
We all live in a watershed, and we all play an important role in keeping our watershed healthy.
Elements of a Watershed
A watershed is a drainage basin – an area of land where all water that falls onto or runs under it drains to the same place. The boundaries of a watershed are defined by the shape of the land (mountain peaks, slopes, valleys). Think about it like a bathtub – the sloped edges direct all the water within the tub to drain at one spot.
Every part of a watershed is connected and plays an important role in supplying people, wildlife, and plants with clean, fresh water.
Mainstem
The primary waterway in a watershed is the mainstem. In the Tualatin River watershed, the Tualatin River is of course the mainstem.
Tributaries
The many creeks and streams that flow into larger waterways are called tributaries. Major tributaries of the Tualatin River include Scoggins Creek, Gales Creek, Dairy Creek, Rock Creek, and Fanno Creek.
Headwaters
A river’s source is called the headwaters. The headwaters of the Tualatin River are nestled in a forested area of the Coast Mountain Range. After dropping down from the steep mountain range, the Tualatin River meanders lazily from west to east across the valley floor.
Watershed divide
The watershed boundary is where all of the water falling on one side of the boundary will flow into one watershed, while water on the other side of the boundary will flow into a neighboring watershed.
Surface water
In a watershed, water will follow the path of least resistance as it runs downhill. Surface water makes its way through the basin by moving over land and into streams, lakes, wetlands, and rivers.
GroundwaterGroundwater Water held underground in the soil or in crevices of rock.
Water that soaks into the land moves slowly underground through spaces between soil and rock, gradually seeping back into waterways.
Riparian area
These areas are directly adjacent to flowing streams, creeks, or rivers and provide a link between land and water habitats.
Confluence
This is the point where two waterways join together. Where the Tualatin River flows into the Willamette River (near West Linn) is the confluence of these two rivers.
Fun fact about confluences
When you’re looking at waterways on a map, you can tell which way the water is flowing by looking at which direction the “v” of a confluence points. The confluence of the Tualatin River and Willamette River points to the north, indicating that the water flows north, through Portland, before joining the Columbia River.
Fun facts about the Tualatin River watershed:
- What's in a name?
The name “Tualatin” is derived from the name given to the river by the Atfalati, a tribe of Kalapuya Native Americans who made their home in the Tualatin Valley. The name translates to “lazy” or “sluggish,” which describes the slow, meandering nature of the river.
- Miles and miles
The Tualatin River is almost 90 miles long and is fed by over 900 miles of tributary streams. It drains over 700 square miles of land.
- How flat is it?
Most of the watershed is very flat! While the Tualatin River begins at about 2,000 feet above sea level, it drops almost 1,800 feet within the first 15 miles as it winds its way down the Coast Mountain Range! For the remaining 70 miles of its journey, the river descends less than 200 feet. There are parts of the river that are so flat that they might not look like they’re flowing at all!
- It has wetlands
The Tualatin River watershed contains many natural wetlands. Several large wetland preserves along the river provide important habitat for local and migratory birds, fish, and other aquatic wildlife. You can experience these wetland habitats by visiting the Jackson Bottom Wetlands Preserve or Tualatin River National Wildlife Refuge.
Why is conservation important on a watershed scale?
A watershed approach to conservation recognizes the connectedness of natural systems – because activities that happen in one part of the watershed affect the health of areas downstream.
Many conservation organizations set goals and plan restoration projects around the location, influences, and effects they will have within a watershed. As individuals and communities, any improvements we make to water quality, soil health, and wildlife habitat will benefit the watershed as a whole.
We All Live in a Watershed