Le bilan thermique des étangs :reflexion épistémologique et application aux étangs limousins

摘要

The concept of heat budget of a lake, developed in the XIX~(th) Century, has undergone some of the most contrasting semantic changes in the history of limnology. Numerous derived meanings reveal a current understanding rather based on the algebraic sum of the energy flows at the air and water interface. This paradigm shift in epistemology leads to consider heat budget as a means, not as an end, and to take the parameter away from limnology for the benefit of climatology. The advantages of a potential return to the original sense (difference between maximum and minimum calorific contents in the water body) are discussed, to promote a geographical, integrative hydrologic systems approach. The Authors propose : (i) to apply this concept, originally created for lakes, to ponds with a smaller size, a temporary stratification and an ability to discharge the whole thermal content in the hydrographic network during emptying; (ii) to study the heat budget variations at all time scales including instantaneous ones; (iii) to work in the future with several thermal profiles. Our first results concerning ponds in the Limousin region show the merit of the return to the epistemological bases. Indeed, high values at the end of the summer come from the rhythms of water layer mixing by forced convection, that is from limnological processes and not directly from atmospheric energy flows.