Transfert d'énergie thermique vers le fond d'un réservoir lacustre / Thermal energy transfer towards the bottom of water reservoirs (lakes)

Abstract

In water reservoirs (lakes) in the summer period, three layers can be observed: the epilimnion, metalimnion and hypolimnion. In summer an increase in the thickness of the epilimnion layer is observed together with a movement of the metalimnion towards the bottom and a significant increase in the temperature of the two layers. An increase in hypolimnion temperature is observed in autumn during the cooling of the surface layers of the water. The increase in temperature of the epilimnion and metalimnion in summer and the downward movement of the metalimnion has not been clearly explained. The movement of the metalimnion is connected with thermal energy transfer, but previous theories do not take into account the phenomenon observed. In this paper, a new theory of thermal energy transfer in water reservoirs is elaborated and subsequently checked by laboratory experiments. A physical model of the water reservoir was designed and constructed. During the investigations it was noted that thermal energy can be transferred towards the bottom of the reservoir due to the existence of anti-convectional currents, which appear with the water temperature inversion in the upper part of the water column. The results obtained in the laboratory were confirmed by measurements in the Solina Reservoir in Poland.