UBC Theses and Dissertations
A spatio-temporal stream temperature model for the southern Coast Mountains of British Columbia Collins, Sierra
Stream temperature is an important water quality parameter, particularly as it influences thermal habitat suitability for a range of species. Despite stream temperature having such a vital role, stream temperature monitoring networks are sparse in many parts of the world, with few long-term records available. Empirical models are useful for estimating stream temperatures where no or limited data exist. Previous research shows that snow dynamics strongly influence stream thermal regimes in mountainous regions, yet few studies to date have incorporated the role of snowmelt in empirical stream temperature models, and no studies to date have used catchment snow cover from MODIS products as a predictor. The objective of this research was to explore the usefulness of fractional snow cover as a predictor of stream temperature in a spatio-temporal empirical model. The study focused on the southern Coast Mountains of British Columbia, where stream temperature data have been monitored for 124 sites, with records spanning one to four years between 2016-2022. Daily air temperatures were estimated for the locations using ECMWF Reanalysis v5 (ERA5). Daily time series of fractional snow cover in catchment areas were extracted from the MODIS snow cover product. Mean fractional snow cover for June of each year was calculated and used as a predictor in models for the following July to October to represent the thermal memory of snow cover. Exploratory analyses and application of fixed-effects models at individual sites supported the use of daily snow cover fraction as a predictor for April to June and mean June snow cover for the following months. Monthly spatio-temporal models that included additional catchment characteristics such as catchment area, relief, distance to coast, fractional lake cover, and fractional glacier cover were fit to the full dataset. Cross-validation suggested that the models performed well, with an overall RMSE of 1.28 °C, and monthly RMSE values ranging from 0.80-1.54 °C. This research supports advances in stream temperature modelling, which contributes to a better understanding of changing thermal regimes and thus aquatic habitat suitability.
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