Empirical modelling of lake water‐temperature relationships: a comparison of approaches

Summary 1. As a result of the role that temperature plays in many aquatic processes, good predictive models of annual maximum near‐surface lake water temperature across large spatial scales are needed, particularly given concerns regarding climate change. Comparisons of suitable modelling approaches are required to determine their relative merit and suitability for providing good predictions of current conditions. We developed models predicting annual maximum near‐surface lake water temperatures for lakes across Canada using four statistical approaches: multiple regression, regression tree, artificial neural networks and Bayesian multiple regression. 2. Annual maximum near‐surface (from 0 to 2 m) lake water‐temperature data were obtained for more than 13 000 lakes and were matched to geographic, climatic, lake morphology, physical habitat and water chemistry data. We modelled 2348 lakes and three subsets thereof encompassing different spatial scales and predictor variables to identify the relative importance of these variables at predicting lake temperature. 3. Although artificial neural networks were marginally better for three of the four data sets, multiple regression was considered to provide the best solution based on the combination of model performance and computational complexity. Climatic variables and date of sampling were the most important variables for predicting water temperature in our models. 4. Lake morphology did not play a substantial role in predicting lake temperature across any of the spatial scales. Maximum near‐surface temperatures for Canadian lakes appeared to be dominated by large‐scale climatic and geographic patterns, rather than lake‐specific variables, such as lake morphology and water chemistry.