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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Willamette (Mainstem) Report Card

Willamette River This is a summary of conditions in the Willamette River Watershed based on data from the 2015 Watershed Health Index. The scores are a snapshot of conditions across the entire watershed. Conditions can vary in smaller parts of the watershed.

This report card covers the mainstem area of the Willamette River through Portland, as well as a portion of Portland’s land area that does not first drain to another local watershed, such as Johnson Creek or the Willamette’s tributary streams in the southwest and northwest hills.

 Link to introduction page on the watershed report cards


Learn more about the Willamette Watershed
Program and Projects

Willamette River (Mainstem) Hydrology Score: D

Portland is at the lower end of the Willamette River watershed, so things like upstream dams, riverfront development in the floodplain, and agricultural runoff affect our section of the river but are out of the city’s control.

In Portland, parking lots, roofs and streets prevent rain from soaking into the ground and recharging groundwater supplies. Projects like Tabor to the River are improving stormwater management and allowing more stormwater to soak in. They also reduce basement sewer backups and help control sewer overflows to the river.

Willamette River (Mainstem)
Hydrology Average Score

Hydrology score: 3.4


What is this?
Effective impervious area
Effective impervious area: 3.4
What is this?
Stream connectivity
Not applicable

Willamette River (Mainstem) Water Quality Score: BUntil Portland activated the Columbia Boulevard Wastewater Treatment Plant in 1952, all of the city’s untreated sewage flowed directly to the Willamette River and Columbia Slough. Water quality is much better today, especially since 2011 when the city finished controlling combined sewer overflows caused by rain storms.

Because of these sewer improvements, E. coli bacteria levels are low and the river is safe for recreation for most of the year. From 2012 through 2014, E. coli exceeded healthy levels in only five of 335 samples collected at swimming beaches. Nitrogen-ammonia scores are also good in the Willamette and other Portland watersheds. However, water quality concerns remain for the river. For example, river temperature is a problem. Water that is too warm is bad news for migrating fish, and even small amounts of pollutants like copper can harm salmon. Note that this report card does not include every pollutant that flows into the river, like pesticides, personal care products and pharmaceuticals.

Portland is at the downstream end of the Willamette River and has little control over most water quality issues in the river. Much of the work to improve water quality in Portland focuses on our local streams that have significant water quality challenges and regulations. Portland’s streams all flow to the Willamette, so improving water quality in those tributaries protects water quality in the river.

These scores are for water quality only, not pollutants in river sediment. The ten-mile section of the Willamette in Portland known as Portland Harbor is a federal Superfund site because the sediment is contaminated with PCBs, DDT, petroleum and other pollutants.

Willamette River (Mainstem)
Water Quality Average Score

Water quality score: 6.7


What is this? Ammonia-nitrogen Ammonia-nitrogen: 9.8
What is this?
Dissolved copper
Dissolved copper: 8.3
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Dissolved oxygen
Dissolved oxygen: 9.1
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E. coli
E. coli: 9.1
What is this? Temperature Temperature: 2.0
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Total mercury
Total mercury: 1.7
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Total phosphorus
Total phosphorus: 7.8
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Total suspended solids
Total suspended solids: 6.0

Willamette River (Mainstem) Habitat Score: C-

Habitat scores are low for the Willamette River in Portland because of generations of development along the river, filling in the floodplain and hardening banks with a seawall and riprap. The loss of off-channel habitat and impacts of urban development are hard to reverse. That’s why restoring the habitat that we can, such as at the Stephens Creek Confluence and the Tryon Creek Confluence, is important for supporting fish and wildlife. Protecting and improving good quality habitat at Oaks Bottom Wildlife Refuge and Powers Marine Park are also important.

The tree canopy score is low because of development and lack of trees in the Central City and industrial areas. Recent tree planting projects have focused on the Central Eastside and Northwest Industrial area. Where there is not room for large trees, ecoroofs are a good way to add habitat and manage stormwater.

The Willamette River through Portland is accessible to migratory fish, but it lacks shallow areas where salmon can rest and feed.

Willamette River (Mainstem)
Habitat Average Score

Johnson Creek Habitat score: 4.2


What is this? Bank condition (hardening) Bank condition:  0
What is this? Floodplain condition Floodplain condition: 2.8 2.8
What is this? Large wood Not applicable  
What is this? Riparian integrity Riparian integrity: 2.4
 What is this? Shallow water refugia Shallow water refugia: 4.1 4.1
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Stream accessibility  Stream accessibility: 10 10
What is this? Substrate composition Not applicable  
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Tree canopy
Tree canopy: 3.0

Willamette River (Mainstem) Fish and Wildlife Score: Under developmentWe are still developing these scores for the mainstem Willamette because analyzing the data for a large river is different than for smaller streams. The Willamette has many native fish and wildlife species. Fifteen species of salmon and steelhead trout found in Portland are federally listed as threatened under the Endangered Species Act. For more information about fish, birds and other wildlife in Portland, visit the Environmental Services Science, Fish and Wildlife Division.

Willamette River (Mainstem)
Fish and Wildlife Average Score

Under development

What is this? Birds Under development  
What is this?
Under development
What is this?
Not applicable

For more information about what we measure and where these scores come from, visit the About Watershed Report Cards page.

See some of what Environmental Services is doing for healthy rivers and streams on the Explore Portland’s Watersheds map.