Numerical modelling of the thermal bar and its ecological consequences in a river-dominated lake

Predictions from the first realistic model of the hydrodynamics of the riverine thermal bar in a medium-size lake are presented. Important features of field observations from Kamloops Lake, British Columbia are successfully reproduced, but the model adopts a generalised section, which is regarded as being representative of many other lakes. A study of the model sensitivity to various aspects of its formulation is also presented, particularly emphasising the important influence of Coriolis forcing on the thermal bar circulation. Plankton population dynamics within the thermal bar flow field is then studied by means of two ecological models of differing complexity. Differences between the predictions of the two models are explained with reference to intermediate simulations, and it is found that the simple ecosystem formulation used in previous work may give misleading results. The flow and stability conditions of the riverine thermal bar have a profound influence on ecosystem development, and support greater phytoplankton growth than in thermal bars resulting purely from radiative effects.