Modelling spatial and temporal variability of water temperature across six rivers in Western Canada

Abstract

Increasing river water temperature in response to the warming climate is concerning for water quality and ecosystem health of rivers. This study provides an assessment of the spatio-temporal variability of the ongoing and potential future river water temperature (Tw) change in western Canada. We use the air2stream model to reconstruct historical Tw dataset for 17 stations across six rivers, and employ the reconstructed Tw to analyze hydro-climatic controls, trends, and sensitivities in relation to air temperature (Ta) and discharge. Results provide insights on the contrasting summer (July and August) Tw responses. While Tw is primarily Ta controlled for the northern rivers, discharge exerts increasing influence that approaches Ta control for the southern rivers. Trends in Tw are increasing and spatially varied, with significant increases and occurrences above the critical 18 and 20°C thresholds for the southern Fraser and Similkameen Rivers. A sensitivity analysis indicated 0.5–1.5°C Tw increases for a 2.0°C Ta increase, and 0.2–0.6°C Tw increases for a 20% summer discharge decline. Overall, the results provide critical information for understanding the river ecosystem health, such as cold-water species habitat.