Stream Temperature Patterns in British Columbia, Canada, Based on Routine Spot Measurements

Abstract

Spot stream temperatures recorded by Water Survey of Canada technicians during visits to gauging stations in British Columbia were used to characterize stream temperature patterns. A general linear modelling approach was used to relate the median water temperatures for each month to a set of variables describing catchment and climatic characteristics. Models were fitted for stations with drainage areas greater than 100 km2 to avoid possible regional bias, because most of the stations with areas less than 100 km2 were located south of 52°N. The final predictor variables varied by month and, for July and August, included normal monthly maximum air temperature, normal annual precipitation, mean catchment elevation, logarithm of drainage area, percent glacier cover, percent lake cover, and whether or not the flow regime is regulated. The models explained up to 79% of the variance in water temperature, with standard errors of the estimate ranging from 0.7°C in January to 1.6°C in August. Values of the coefficients for the predictor variables and their seasonal variations were consistent with the physical processes governing stream temperature. These models suggest that catchment characteristics leave an imprint on stream temperature, even for large catchments, and need to be accounted for in efforts to model regional variations in stream temperature.