Evaporation from Lakes

Lakes are an important part of the hydrological cycle, but quantifying the evaporation rates from them is not a trivial task. The amount of radiant energy captured by a lake is generally the dominant control on the annual evaporation rate. At shorter time periods, the major factors affecting lake evaporation are: the albedo, the heat-storage term of the energy budget, and the atmospheric diffusion processes. The albedo is a function of the solar elevation angle and the proportion of downward diffuse radiation, and can be predicted from empirical relationships. The heat-storage term can decouple the evaporation rates from the net radiation, but can be estimated simply in the case of well-mixed water. However, in the situation where the lake becomes thermally stratified, more complex, hydrodynamic models are required. The three commonly used methods of estimating lake evaporation are: mass transfer, energy balance, and combination equations. There are strengths and limitations to each of these methods. Keywords: lake; evaporation; open water; available energy; heat storage