Spatial and Temporal Variability in Stream Thermal Regime Drivers for Three River Networks During the Summer Growing...

Area of Science:

• Environmental Science
• Ecology
• Hydrology

Background:

• Increasing water temperatures due to climate change negatively impact cold-water aquatic organisms.
• Habitat and population declines are observed in cold-water dependent species.
• Understanding stream thermal regimes is crucial for effective ecological restoration.

Purpose of the Study:

• To develop a modeling process for identifying statistical relationships between stream temperature drivers and landscape, climate, and management covariates.
• To analyze spatial and temporal variations in stream temperatures within and among river basins.
• To identify potential restoration actions based on the relative importance of identified drivers.

Main Methods:

• A statistical modeling process was developed to link stream temperature drivers with relevant covariates.
• The model was tested across three study areas in the Pacific Northwest, USA, during the growing season (May, August, September).
• Covariate importance was assessed using relative importance metrics.

Main Results:

• Physical landscape (elevation, catchment area, main channel slope) and climate (mean monthly air temperature, discharge) covariates were most important.
• Management covariates, including groundwater use and riparian shade, also showed high relative importance.
• The influence of slope shifted from local reach slope in May to regional main channel slope later in the growing season.

Conclusions:

• The developed modeling process effectively identified both regionally consistent and locally specific drivers of stream temperature.
• Management-related factors were significant, indicating potential for targeted restoration actions.
• Findings facilitate restoration planning at ecologically relevant scales for cold-water aquatic ecosystems.