Energy budget evaporation from Williams Lake: A closed lake in north central Minnesota

Abstract

Evaporation from Williams Lake, computed by the energy budget method for the five open‐water seasons of 1982–1986, varied from a maximum seasonal rate of 0.282 cm/d in 1983 to a minimum seasonal rate of 0.219 cm/d in 1982. The pattern of monthly values of evaporation is not consistent from year to year. The normally expected pattern of low evaporation values in May, followed by increasing values in June to maximum values in July is true for only 3 of the 5 years. Comparison of annual evaporation calculated by the energy budget and mass transfer methods indicates that energy budget values varied from 13% greater to 11% less than mass transfer values. Furthermore, there is no seasonal bias in the pattern. Large differences exist in the magnitude of energy fluxes to and from Williams Lake. By far the greatest energy fluxes, having magnitudes of hundreds of watts per square meter, are incoming solar radiation, incoming atmospheric radiation, and outgoing long‐wave radiation emitted by the lake water. The least energy fluxes are related to advection, which generally have magnitudes less than 5 W m−2.