Local Melting of Ice Cover by Thermal Side Effluent

Abstract

In northern rivers, reaches of open water in the ice cover may exist throughout the winter season. Some of these reaches are the result of a tributary effluent of higher temperature or of fast‐moving water that alter the thermal and hydrodynamic conditions of ice‐cover progression. The temperature distribution downstream of the point of effluent discharge is controlled by the hydrodynamic characteristics of the stream and the meteorological conditions prevailing at the site. This paper deals with the development and the testing of an analytical approach concerned with the suppression of ice cover from the point of effluent discharge up to the ultimate advancing of its fronts. The the‐oretical formulation is based on a quasi‐one‐dimensional approach; however, it allows for special consideration of the nonlinear variation in the stream geometry and adjustment for a partial mixing assumption. The formulation of the upstream ice‐edge location is developed based on the 0 °C isotherm. The up‐stream and the downstream ice edges are investigated for the unsteady uniform flow and for the steady nonuniform flow. Conditions for the nonsuppression of the ice cover are also obtained based on the relative positions of the upstream and downstream ice edges. Comparison with field data suggests a good agreement with the formulation incorporating the thermal velocity effluent.