The size of the energy exchange surface of a body of water, like Lake Servières, is an essential element in its cooling and freezing. The larger it is in relation to the global volume of water, the faster the transfer of energy between the atmosphere and the water. This phenomenon also explains the difference in sensitivity to freezing of the different zones of the lake. The edges of a lake, shallower than its center, receive the same quantity of energy per unit of surface despite a lower volume of water to cool. Subject to the same climatic conditions, the edges, therefore, freeze first and have a higher rate of ice.