Sponsor
This research was supported by the National Science Foundation under grant no. 2244551 through Portland State University's Research Experiences for Undergraduates (REU) program. We extend our gratitude to the anonymous reviewers whose thoughtful feedback significantly improved this manuscript. We also thank the agencies and contributors involved in the coordinated stream temperature data collection efforts that made this study possible. Figure 1 and the graphical abstract were created in BioRender (Milburn, S. (2026). BioRender. BioRender.com).
Published In
Hydrological Processes
Document Type
Article
Publication Date
10-1-2026
Subjects
Thermal Sensitivity -- Cascades River Basin
Abstract
Increasing stream temperatures resulting from climate change and consequent detrimental impacts on temperature‐dependent aquatic species have signalled the need to better understand how different streams respond to changes in air temperature. This research generates a new assessment of thermal sensitivity in the Clackamas River Basin, Oregon, USA by analysing how underlying geology, climate, hydrology and land cover explain spatial variation in stream thermal sensitivity. Multiple linear regression analysis using spatially explicit landscape predictors across 72 sites identified upstream High Cascades geology, elevation, baseflow index, total upstream area and upstream shrubland area as the most significant and stable predictors determining thermal sensitivity. Spatial stream network and random forest models further validated and clarified spatial influences on stream temperature and each improved performance relative to multiple linear regression. Predictors derived at the total upstream area scale were most consistently associated with thermal sensitivity when compared to local reach contributing area or 100‐m wide buffer area scales. Streams underlain by High Cascades geology, with higher baseflow and greater upstream area were substantially less sensitive to air‐temperature changes ( β = −0.27 to −0.61). Meanwhile, higher elevation ( β = −0.51 to −0.59) and lower shrubland cover ( β = 0.19 to 0.30) were associated with lower thermal sensitivity. Variation in predictors retained among models appears to reflect different indicators of shared underlying processes. Furthermore, this study confirms that these predictors are statistically robust drivers of stream thermal sensitivity via regularized regression techniques. Analysing why streams are more or less climate‐resilient can inform management and restoration efforts and protect cold‐water habitats.
Rights
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium,provided the original work is properly cited.© 2026 The Author(s). Hydrological Processes published by John Wiley & Sons Ltd.
Locate the Document
DOI
10.1002/hyp.70745
Persistent Identifier
https://archives.pdx.edu/ds/psu/45314
Publisher
Wiley
Citation Details
Milburn, S., Krochta, M., & Chang, H. (2026). What Controls the Spatial Variation in Thermal Sensitivity in a Cascades River Basin During an Extreme Heat Year? Hydrological Processes, 40(10). Portico.
Description
This research was supported by the National Science Foundation under grant no. 2244551 through Portland State University's Research Experiences for Undergraduates (REU) program.