The following summary is based on data from the 2023 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 2019 and 2015, the first year Environmental Services released the report cards, are included.
Water Quality Score: C
E. coli bacteria levels in the Fanno Creek watershed exceed state water quality standards. This bacteria may enter streams via sewer leaks and animal waste. High levels of total suspended solids stem from sediment from roads, development, and stream channel erosion. Pollutants that bind to sediment also contribute to poor water quality.
Improving stormwater management and decreasing impervious surfaces will improve scores and watershed health.
Scores for Water Quality Indicators
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 Indicator | 2023 Score | 2019 Score | 2015 Score |
|---|---|---|---|
| Ammonia-Nitrogen | 9.9 | 9.8 | 9.7 |
| Dissolved Copper | 4.4 | 4.9 | 4.8 |
| Dissolved Oxygen | 8.2 | 8.4 | 8.3 |
| E. coli | 1.3 | 2.7 | 3.3 |
| Temperature | 4.7 | 3.0 | 3.5 |
| Total Mercury | 1.2 | 1.7 | 2.6 |
| Total Phosphorus | 4.7 | 4.1 | 5.7 |
| Total Suspended Solids | 4.2 | 4.3 | 5.8 |
Habitat Score: B
Culverts in Fanno Creek limit migratory fish from accessing habitat. The lack of large wood in the stream and poor quality or non-existent vegetation cover in riparian zones lead to in-stream habitat deficiencies. Projects such as the Southwest 45th Avenue Culvert Replacement and the South Ash Creek Stream Enhancement contribute to improved fish passage and stream habitat. Find information on those projects.
Scores for Habitat Indicators
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.
| Habitat Indicator | 2023 Score | 2019 Score | 2015 Score |
|---|---|---|---|
| Bank Condition | 9.9 | 7.0 | 8.8 |
| Floodplain Condition | 6.5 | 7.0 | 7.0 |
| Large Wood | 2.0 | 2.0 | 2.4 |
| Riparian Integrity | 5.5 | 4.5 | 4.8 |
| Shallow Water Refugia | Not applicable | Not applicable | Not applicable |
| Stream Accessibility | 0.0 | 0.0 | 0.0 |
| Substrate Composition | 9.3 | 7.2 | 7.3 |
| Tree Canopy | 10 | 10 | 9.3 |
Hydrology Score: C
Stormwater runoff from impervious surfaces such as roads, roofs, and parking lots have negative impacts on many streams in the Fanno Creek watershed. It creates “flashy” hydrology during storm events that can lead to streambank instability and sediment deposition in streambeds. Stormwater management projects along SW Beaverton-Hillsdale Highway and SW Capitol Highway will lead to improvements in hydrologic conditions.
Scores for Hydrology Indicators
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 Indicator | 2023 Score | 2019 Score | 2015 Score |
|---|---|---|---|
| Effective Impervious Area | 4.3 | 4.3 | 4.2 |
| Stream Connectivity | 5.3 | 5.1 | 5.1 |
Fish and Wildlife Score: D-
Cutthroat trout are present in Fanno Creek, but total fish diversity and quantity are low. Culverts and other barriers exist, blocking fish passage. Aquatic insect counts are low due to water quality issues and “flashy” hydrology. To help support fish and wildlife in the watershed, we will create new green street projects, plant trees, and maintain riparian areas.
Scores for Fish and Wildlife Indicators
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.
| Fish and Wildlife Indicator | 2023 Score | 2019 Score | 2015 Score |
|---|---|---|---|
| Birds | 4.3 | 2.9 | 3.3 |
| Fish | 0.1 | 0.2 | 0.5 |
| Macroinvertebrates | 3.3 | 3.7 | 3.9 |
In Summary
Twenty-five years ago, water quality in Fanno Creek was rated as very poor. Since that time, we have been slowly and steadily improving. Watershed conditions will continue to improve if all local jurisdictions within the watershed continue to:
- Treat and manage stormwater.
- Plant trees and enhance riparian areas.
- Take advantage of opportunities to partner with private property owners to make improvements.
Read more about the Fanno Creek watershed.