Our Watershed

A watershed is like a great big bowl linking land, water and people.

Our Tualatin River watershed drains 712 square miles and ranges from densely populated areas of southwest Portland, Hillsboro, Tigard and Beaverton to agricultural areas near Scholls, Gaston, Banks, Mountaindale and North Plains to the forests of Oregon’s Coast Range, Tualatin Mountains and Chehalem Mountains. Most of the fast-growing urban population—over 600,000 residents—resides on 15 percent of the watershed’s area. Agricultural uses take up 35 percent, and 50 percent of the watershed is forest.


Floodplains & Models

Maps & Data

The Tualatin River

Water Resources Infrastructure

Investing in natural capital infrastructure for watershed health.

Tualatin Basin Water Supply and Flow Restoration

Clean Water Services, local cities and water providers are working to secure a long term water supply for municipal, industrial, agricultural and environmental needs. CWS staff partners with water resource managers to explore opportunities to improve watershed health and enhance stream flows. In addition to our timed releases with the Hagg Lake facility, we also work with farmers along Gales and McKay Creeks to enhance stream flows and support watershed health.

Regional Stream and Wetland Enhancements

We're working on a variety of projects, including aquatic habitat enhancement, riparian planting, wetland restoration and treatment facility upgrades across urban and rural areas of the Tualatin River Watershed.

  • Enhancing urban streams and wetlands is an investment that pays dividends in many ways.
  • Clean Water Services partners with the agricultural community to meet regulatory obligations and mutual goals for watershed health. Learn about Enhanced CREP and VEGBACC programs for rural landowners.

Energy and Resource Recovery

At our treatment facilities, we are working on feasibility and analysis of renewable energy opportunities to reduce operating and escalating energy costs. We are also exploring options for resource recovery and renewable energy production such as solar energy, heat recovery and options for biosolid use.

Strategic Watershed Assessment & Planning

Applying scientific knowledge and innovation to improve watershed health for community benefit.

Healthy Streams Plan (2005)

This plan provides strategic guidance to a variety of capital programs to protect, restore and manage watershed health. It was developed by Clean Water Services and local jurisdictions to identify ecological needs of the Tualatin Basin. Utilizing existing regulatory frameworks, incorporating community needs and providing value to Clean Water Services ratepayers are key elements of this watershed plan.

  • Since 2005, this plan has served as CWS' road map to community-based planting of native trees and shrubs, enhancing streams and wetlands, restoring flows, and retrofitting storm water outfalls and culverts.
  • We continue to refine the plan with updated information as needed and broaden the approaches to meet new challenges, though the framework and strategies remain consistent.
  • View the full Healthy Streams Plan (PDF, 35.6MB).

Ecosystem Markets are an emerging way to ensure that money being spent on the environment is put in the places that matter most for clean air, clean water and natural places to play. Clean Water Services works closely with the Willamette Partnership moving towards an integrated ecosystems market. Gales Creek pilot project includes riparian planting, salmon habitat improvement and wetland restoration.

Water Quality Credit Trading Annual Report (2021)

A watershed-based NPDES permit allows Clean Water Services to offset thermal loads from the Rock Creek, Durham and Forest Grove treatment facilities by implementing a water quality credit trading program for temperature. The 2021 Water Quality Credit Annual Report (PDF, 1.5MB) offers information on temperature-related activities during the period of January 1 through December 31, 2021.

Stream Stewardship

Restoring ecological function with sustained action.

Riparian Planting, Monitoring and Maintenance

Healthy riparian and wetland vegetation are central to Clean Water Services' strategy for improved water quality and aquatic habitat. Riparian planting with native plant communities stabilize vulnerable stream banks, filter pollution, shade waterways and provide essential wildlife habitat, among many other benefits.

  • The work doesn't end with planting native trees and shrubs. Most locations require active monitoring and maintenance to fully restore ecological functions of these sensitive habitats. Clean Water Services oversees a focused effort to maintain the gains and minimize emerging threats to our green infrastructure investments.
  • Non-native invasive plants and animals are an emerging threat to native species. CWS has multiple integrated programs especially targeted to prevent the spread of invasive plants that choke out native vegetation.
  • Clean Water Services works with many organizations, including the 4-county Cooperative Weed Management Area, and the Tualatin Watershed Weed Watchers group to combat the spread of invasive species in the Tualatin River Watershed. Report invasive species to the Oregon Invasive Species Hotline at 1.866.INVADER.
  • Revegetation (PDF, 212KB) is a multi-year process of restoring a native plant community to support clean water, resilient streams, and wildlife habitat. Clean Water Services works with partners across the region to enhance and sustain land along streams and wetlands to improve the health of our community, economy, and ecology. Revegetation activities and timelines vary based on the project area.
In Your Yard & Community

Building capacity in our community to sustain our natural capital investments.

Get Involved

Clean water and a healthy environment are good for us all! Discover what you can do to help protect water resources in your yard and neighborhood.

  • Tree for All is a community partnership of cities, nonprofits, farmers, volunteers and others who have joined hands (and shovels) to plant more than five million native trees and shrubs along the Tualatin River and its tributaries  to improve watershed health and habitat.
  • You can also get involved with one of our partners to make a difference in the local community.
  • Doing a community project or looking for resources for your own landscape? Visit our community resources section.

Q: What are PFAS and what are you doing about them?

A: Per- and Polyfluoroalkyl Substances (PFAS) are a family of more than 4,000 synthetic chemicals, including PFOA and PFOS, widely used since the 1940s in products that resist heat, oils, stains and water. While wastewater treatment facilities are not the source of PFAS, Clean Water Services (CWS) is working with national water quality experts to monitor research developments. We’re also collaborating with state industry expert Oregon Association of Clean Water Agencies to understand prevalence of PFAS in Oregon. Learn more in this PFAS fact sheet (PDF, 1.4MB).


Q: What do I do about beaver and/or nutria activity?

A: Nutria are an invasive, non-native species that we may have trapped if they are causing damage, while beavers are generally beneficial. Learn how to Report a Problem if wildlife is causing damage or read Oregon Department of Fish and Wildlife's Living with Wildlife document if there is no damage.


Q: What should I do in case of flooding?

A: Please refer to our Flood Facts page for information on flooding in the area.


Q: I live along a stream, should I do anything to protect water quality?

A: Yes! Please visit our webpage about stream-friendly yard care and read our Streamside Care Guide (PDF, 2.7MB).


Q: Whose responsibility is blackberry and brush in the stream or on its banks?

A: Property owners are responsible for removing unwanted vegetation. If you have a large area, HOA or neighbors who are interested in removing invasive vegetation as well, there are opportunities to work with volunteer organizations, use the Watershed Wagon & Tool Bank and to get native plants for replanting.


Q: Does Clean Water Services have information or recommendations on using herbicide near a stream?

A: Please refer to our Integrated Pest Management Plan (PDF, 2MB) document and our Herbicide Fact Sheet (PDF, 3MB).


Q: To whom do I report illegal dumping in a stream?

A: Please call Washington County Solid Waste at 503.846.8609.


Q: What is the Enhanced CREP & VEGBAC program?

A: Learn more about these programs for landowners from Tualatin Soil & Water Conservation District

The Tualatin River is the only river in Washington County.

The Tualatin River

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