Willamette River Mainstem Watershed Report Card

Information
Photo shows river with development and sea wall lining its banks
Find the latest water quality, habitat, and wildlife scores for the mainstem of the Willamette River based on data from the 2019 Watershed Health Index. The scores are a snapshot of the conditions in the mainstem of the river.

The following summary is based on data from the 2019 Watershed Health Index. The scores below are a snapshot of conditions across the entire watershed. Conditions can vary in smaller parts of the watershed.

The scores from 2015, the first year Environmental Services released the report cards, are included.

Water Quality Score: B

Water quality is much better today than in the past. It improved greatly after 2011 when the City finished the Big Pipe Project to control 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 most of the year.

But, water quality concerns remain for the river. Water that is too warm is bad news for migrating fish, and even small amounts of pollutants like copper can harm salmon. Portland is at the downstream end of the Willamette River and has little control over most water quality issues in the river. What we can do is improve water quality in Portland tributaries that flow to the river.

This report card does not include every pollutant that flows into the river. These scores are for water quality only—not pollutants in river sediment. The 10-mile section of the Willamette in Portland known as Portland Harbor is a federal Superfund site because the sediment contains PCBs, DDT, petroleum, and other pollutants.

Scores for Water Quality Indicators, 2019 and 2015

Graphic shows slider bars that represent data in table on water quality scores below.
Arrow shows 2019 score. Bar shows 2015 score.

Scores are on a scale of 0 to 10 with scores of 8 or higher meaning the indicator is properly functioning. A score of 3 or lower means the indicator is not functioning properly or provides little to no support for a healthy watershed. Find more information about the indicators and how to read the scores.

Water Quality Indicator2019 Score2015 Score
Ammonia-Nitrogen9.89.8
Dissolved Copper8.68.3
Dissolved Oxygen8.19.1
E. coli8.89.1
Temperature1.52.0
Total Mercury2.71.7
Total Phosphorus8.07.8
Total Suspended Solids6.96.0

Habitat Score: D+

Habitat scores are low for the Willamette River in Portland because of development. For generations, we have filled in the floodplain and hardened riverbanks with a seawall and riprap. The loss of off-channel habitat and impacts of urban development are hard to reverse, so restoring any habitat is significant. Projects like those at the confluences of Stephens and Tryon creeks or Oaks Bottom Wildlife Refuge restore habitat essential for supporting salmon recovery and wildlife.

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

The river also scores low for habitat because it lacks shallow areas where salmon, especially young salmon, can rest and feed.

Scores for Habitat Indicators, 2019 and 2015

Graphic shows slider bars that represent data in table on habitat scores below.
Arrow shows 2019 score. Bar shows 2015 score.

Scores are on a scale of 0 to 10 with scores of 8 or higher meaning the indicator is properly functioning. A score of 3 or lower means the indicator is not functioning properly or provides little to no support for a healthy watershed. Find more information about the indicators and how to read the scores.

Not applicable

Habitat Indicator2019 Score2015 Score
Bank Condition0.00.0
Floodplain Condition2.82.8
Large WoodNot applicableNot applicable
Riparian Integrity2.52.4
Shallow Water Refugia4.14.1
Stream Accessibility9.410.0
Substrate CompositionNot applicable
Tree Canopy5.03.0

Hydrology Score: C-

Portland is at the lower end of the Willamette River watershed. Our section of the river is affected by things out of our control, such as upstream dams, riverfront development in the floodplain, and agricultural runoff. Within Portland, parking lots, roofs, and streets prevent rain from soaking into the ground and recharging groundwater supplies. We have many projects completed and underway to capture rain, keep it out of the combined sewer system, and recharge groundwater. These projects also reduce basement sewer backups and reduce sewer overflows to the river.

Scores for Hydrology Indicators, 2019 and 2015

Graphic shows slider bars that represent data in table on hydrology scores below.
Arrow shows 2019 score. Bar shows 2015 score.

Scores are on a scale of 0 to 10 with scores of 8 or higher meaning the indicator is properly functioning. A score of 3 or lower means the indicator is not functioning properly or provides little to no support for a healthy watershed. Find more information about the indicators and how to read the scores.

Hydrology Indicator2019 Score2015 Score
Effective Impervious Area4.13.4
Stream ConnectivityNot applicableNot applicable

Fish and Wildlife Score: Under Development

We 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. Find more information about fish in Portland's rivers and streams.

In Summary

Many things that impact the Willamette River are out of the City’s control. Still, we can take action on important elements that can help improve overall conditions and support salmon recovery like increasing the riparian areas, planting trees, and creating off-channel habitat. In addition, restoration work in the river's many tributaries directly impact the mainstem.

Read more about the Willamette River watershed.