A simple method for determining the evaporation from shallow lakes and ponds

This study examines the summertime evaporation from a shallow lake in the Hudson Bay lowlands evaluated by the energy budget (Bowen ratio) and equilibrium model approaches. Energy budget calculations reveal that on the average, 55% of the daily net radiation is utilized in the evaporative process over the lake. Half‐hourly and daily values of evaporation were approximated closely by the Priestley and Taylor (1972) model, where the ratio of actual to equilibrium evaporation equals 1.26. A simple model, expressed in terms of incoming solar radiation and screen height air temperature, is developed from the comparison of actual to equilibrium evaporation. Tests of the model at a different location indicate that the actual evaporation can be determined within 10% over periods of 2 weeks.