Clackamas River Basin future stream habitat suitability
Stream temperatures and salmon habitat amid climate change scenarios
This resource is meant to aid understanding of future climate effects on water temperatures and habitat suitability for salmonids in the Clackamas River Basin.
While maps and other information available through this site may be used in planning river restoration and species conservation projects, these resources are also meant to appeal to anyone broadly interested in the topic and looking to become more involved in these efforts.
Objectives & background
Portland State University's Department of Geography, Clackamas River Basin Council, and Oregon Department of Fish and Wildlife are working with agencies and interested individuals across the basin to:
- Use geostatistical modeling to predict future stream temperatures under future warming scenarios.
- Integrate the results of this model with salmonid habitat and species' thermal tolerances to identify priority areas for stream habitat restoration under a warming climate.
- Provide a clearinghouse for all stream temperature data collected in the Clackamas River Basin.
Other than the presence of water itself, stream temperature is arguably the most important indicator of aquatic ecosystem health. Temperature drives biochemical processes and sets the geographic distributions of cold-water dependent species, including salmon.
Heat-stressed salmon with visible injury due to fungal infection (image: Columbia Riverkeeper)
Above certain temperature thresholds, salmon suffer from increased metabolic stress, reduced growth and reproductive success, and increased susceptibility to disease. These species have cultural importance to native tribes, as well as broad economic and recreational value.
As annual snowpack decreases with rising air temperatures, mountain streams will become warmer during the summer months. Figure adapted from Washington State Governor’s Salmon Recovery Office
Air temperature, exposure to sunlight, streamflow, and channel topography all play significant roles in controlling stream temperature. In the Pacific Northwest, climate change is affecting the thermal regimes of rivers due to increasing air temperature trends and changes in the timing and amounts of precipitation.
Study area
Located in northwest Oregon, the Clackamas River flows 83 miles from its headwaters to its confluence with the Willamette River near Oregon City, draining more than 940 square miles.
The basin includes a mix of land cover types ranging from forested and undeveloped in the upper basin to urbanized in the lower basin. The basin provides drinking water to over 300,000 residents, while also providing critical habitat for several culturally significant and federally protected runs of salmon.
To see where you are relative to the Clackamas Basin, click on the crosshair icon on the right side of the map
The purple lines show the known distribution of Chinook salmon (Oncorhynchus tshawytscha) in the Clackamas River basin, according to the Oregon Department of Fish and Wildlife.
Chinook salmon (image: Bureau of Land Management)
This map shows the known species distribution of winter steelhead (Oncorhynchus mykiss) across the basin. Another cold-water dependent species.
Steelhead salmon (image: Greg Shields)
This map shows coho salmon (Oncorhynchus kisutch) distribution within the basin.
Coho salmon (image: Wikipedia Commons)
Distribution of bull trout (Salvelinus confluentus), a recently reintroduced species to the Upper Clackamas River.
Bull trout (image: Joel Sartore)
In 2020 and 2021, historic wildfires collectively burned across 23 percent of the basin, reducing canopy shade in previously forested areas.
And in 2021, a historic heat dome event occurred in Oregon, which brought several streams up to record temperatures, many of which exceeded lethal thresholds for salmon.
Stream temperatures collected along Delph Creek, a tributary to the Clackamas, in 2021.
When looking back at August daily mean maximum air temperatures in the basin over the past 30 years, we can observe a trend of an approximately 0.07 degree increase each year.
Data collection and analysis
Stream temperature data collected in the basin between 1991 - 2023 was compiled. Each data point was assigned the annual maximum of the 7-day average of daily maximum stream temperatures at the site (Max7DADM, °C). This rolling average is a common regulatory metric for stream temperature and helps assess impacts to cold water species.
A number of watershed conditions related to stream temperature were also derived.
Representative Concentration Pathway (RCP) scenarios are climate projections developed by the Intergovernmental Panel on Climate Change (IPCC) and used in climate research to describe different greenhouse gas concentration trajectories. Each RCP scenario represents a different level of warming compared to pre-industrial levels.
For making future stream temperature predictions, we include projected future air temperatures. Use the slider to compare present-day summer (June, July, August) air temperatures on the left to the IPCC's low-emissions (RCP 4.5) scenario for 2050 temperatures on the right.
Now use the slider to compare the historic air temperatures to the IPCC's high-emissions (RCP 8.5) 2080 scenario's projected temperatures
For our analysis, we use a geostatistical model which draws upon spatial patterns in our data based on in-stream distances, flow accumulation and flow direction. Watershed variables are also included.
Stream sampling locations are incorporated into a virtual landscape network. Reach contributing areas are assigned for each stream, with the numerous predictor variables summarized for each.
A standardized approach is used to select the optimum set of watershed variables required for our analysis, which include streamflow, topography, underlying geology, land cover, and air temperature.
Using this model, stream temperature predictions are generated across the entire basin for each year, 1991-2023.
Modeled scenarios
Using the results of the annual models, we can derive annual trend for stream temperature. We next model future stream temperatures using air temperatures from IPCC low and high emissions models for the mid-century and end-of-century time periods.
We can now spatially assess the amount of stream temperature change across the entire Clackamas River Basin relative to the modeled historic mean Max7DADM °C.
Use the slider to compare the present-day stream temperatures on the left to predicted low emissions scenario for mid-century on the right.
Use the slider again to compare the historic temperature predictions to those under the low emissions scenario for end-of-century. You can see that the change is more prominent in some areas than others.
Now observe the changes under the high emissions scenario for mid-century. Much of the same pattern emerges, although the changes are more drastic for this time period than under the low emissions scenario.
Now explore the changes in stream temperature under the high emissions end-of-century scenario. It is apparent that nearly all of the waters within the coldest category have disappeared, and considerable warming has occurred along some of the main tributaries in the upper basin, as well as most stream reaches in the lower basin.
We are also interested in where warming will occur the most relative to the entire basin. To do this, we can observe the degree of change of Max7DADM °C relative to the historic mean, which is mapped under the low emissions mid-century scenario.
Click the icon on the lower left of the map to view its legend.
Now look at the high emissions mid-century scenario. Much more relative warming has occurred across the entire basin relative to the low emissions scenario.
Under the end-of-century low emissions scenario, it is apparent that more relative warming has occurred across the lower basin than in the upper basin. This is a result of several factors, including cold groundwater contributions, increased shade, and steeper topography, despite air temperatures rising faster in the upper basin under future scenarios.
Under the end-of-century high emissions scenario, we see a considerable jump in stream temperature warming relative to the historic mean. Under this scenario, no stream reach within the basin is unaffected by the dramatic rise in air temperatures under climate change.
Salmon thermal tolerances are based on performance curves under a range of temperatures. This curve models the relationship between stream temperature and biological performance, with maximum performance within optimal thermal ranges and decreasing as temperatures approach sub-lethal levels.
Figure adapted from Kara Anlauf-Dunn
With this information, the quality of thermal habitat can be mapped across the watershed under current and future conditions.
The species range map shows thermal suitability for Chinook, coho, and steelhead. Use the swipe tool to compare thermal suitability for the present day versus late century under a high emissions climate change scenario.
Map by Kara Anlauf-Dunn
Finally, stream flow and channel topography are used to model streams' physical habitat within each species' range. Intrinsic potential habitat scores are based on empirical relationships between stream attributes and juvenile fish use, with values greater than 0.8 considered having high intrinsic potential (HIP).
This map displays only the HIP for Chinook salmon, along with thermal suitability for the species on a scale of 0-1. This suitability was modeled for the 2045-2075 time period under a low emissions climate change scenario.
Using these physical and thermal habitat parameters, we can map suitability across all future climate change scenarios.
Explore the data
Action & more resources
Forecasts of thermal suitability at locations of high intrinsic habitat value provide a powerful tool for better-informed decision making by land and resource managers.
By leveraging this data, practitioners can more accurately plan restoration activities and prioritize areas for intervention that will have the greatest long-term impact.
We encourage the use of this information to guide efforts in restoring and conserving critical habitats, ensuring their resilience in the face of climate change.
In the lower basin, riparian shading can mitigate rising temperatures along tributaries to the river. Explore the map on this page to find out which riparian areas are in the most need of increased tree cover within lower basin as of 2024. Open the Legend icon in the lower left corner of the map to view the various land cover classifications. (Data retrieved from landfire.gov)
We also encourage you to take what you've learned from this site and advocate for stream habitat restoration with public officials and decision-makers.
Let them know the importance of prioritizing restoration activities like streamside tree planting and the restoration of important structures like log jams, side channels and gravel bars can help further ensure that these areas will provide suitable habitats for salmon as air temperatures rise.
Other ways you can contribute to the cause of habitat conservation and stream restoration:
- Visit the Clackamas River Basin Council to learn about volunteer opportunities and how you can support local efforts.
- Trout Unlimited and American Rivers are just a few of the many other organizations focused on protecting cold-water fisheries and their habitats that we encourage you to connect with.
Photos of the North Fork Eagle Creek Restoration Project by Dave Bugni
Additional resources:
Clackamas stream temperature monitoring project page
Scales of Connectivity within Stream Temperature Networks of the Clackamas River Basin, Oregon, in the Annals of the American Association of Geographers
Portland State University Water as an Integrated System and Environment (WISE) Research Group
Oregon Department of Fish and Wildlife (ODFW): Oregon Fish Habitat Distribution Data
Acknowledgements
This webpage was created with ArcGIS StoryMaps, a digital storytelling tool, by Michael Krochta.
Please provide feedback by following this link or contact mkrochta@pdx.edu.
This project was funded by the Clackamas River Basin Council, Clackamas River Water Providers, Oregon Department of Fish and Wildlife's Oregon Conservation & Recreation Fund.
Special thanks to Kara Anlauf-Dunn, Dave Bugni, and Heejun Chang for their valuable contributions and feedback on this project. Thank you also to our project partners for their contributions of equipment, data, and expertise:
