Calibrating the Dynamic Reservoir Simulation Model (DYRESM) and filling required data gaps for one‐dimensional thermal profile predictions in a boreal lake

Abstract

One‐dimensional vertical heat transfer and mixing models, such as the Dynamic Reservoir Simulation Model (DYRESM), have seldom been applied to lakes in the boreal region even though this region houses the majority of global freshwater lakes. In order to employ DYRESM to predict the thermal structure of a boreal lake located near Sudbury, Ontario, Canada, we overcame two methodological challenges. First, we developed models to predict the vertical light extinction coefficient (Kd) from dissolved organic carbon (DOC) concentrations and hydraulic retention time. We also developed models to predict stream temperatures from local meteorology, and to predict the discharge of lake inflows and the lake outflow from runoff per unit area at gauged streams nearby. We then re‐calibrated several DYRESM parameters which had been tested previously primarily in the Southern Hemisphere, and explored the sensitivity of the re‐calibrated model to all of the remaining uncalibrated inputs implicated in heating and mixing processes. The mean difference between values predicted with the re‐calibrated model and field measurements (± 1 standard deviation), 1.09 m (± 0.89 m) for thermocline depth and 1.98°C (± 1.58°C) for bottom water temperature, was relatively small compared with other North American studies, and likely due to the model rather than our parameterization. Our calibration of DYRESM for Clearwater Lake, and supplementary models, provide a demonstration for and guidance to those wishing to simulate changes in thermal regimes of boreal lakes in response to climate change or other broad‐scale environmental stressors of importance both to local fisheries and freshwater resource management.