Heat flux dynamics at the water-sediment interface is considered in the article. Features of heat transfer in a small lake during the freeze-up period are discussed. Estimates The heat flux was estimated for different winter months and different depth areas of the lake using temperature gradient measurements in the near-bottom layer of small lake Vendyurskoe in the winters of 1995-1999. Regression equations to calculate the heat flux as a function of time, depth and near-bottom temperature were obtained. Analysis of continuous temperature measurement data for the winter 2007–2008 in the central part of the lake with high spatial (2–5 cm in near-bottom layers and 0.5–1 m in the water column) and temporal (1-min step) resolution allowed analyzing the change in the heat content of the water column during the winter. A circuit of heat transfer in a small lake which, along with the sediment-to-water and water-to-ice heat fluxes, includes heat transfer along the slopes from shallow to deep–water areas is suggested. It was found that during the first two months under ice prevalent heat transfer is along the slope to the profundal zone, so that it is gradually filled with denser warm water. Vertical heat transport in the water column begins to dominate in January-March, when the heat flux from sediment to water and its transfer along the slope drop severalfold.