Evaluation and Generalization of 13 Mass-transfer Equations for Determining Free Water Evaporation

Thirteen equations based on the mass-transfer method for determining free water evaporation were expressed in seven generalized equations. These seven equations were then compared with pan evaporation at four climatological stations in north-western Ontario, Canada. The comparisons were based on monthly evaporation. Equations were compared by calibrating them on the entire data sets as well as by calibrating on part of the data and then verifying them on the remainder of the data. The results of comparison showed that all equations were in reasonable agreement with observed evaporation, and that the e€ect of wind velocity on monthly evaporation was marginal. However, when an equation with parameters obtained at one site was applied to compute evaporation at another site, the computed evaporation was not in good agreement with observed values. # 1997 by John Wiley & Sons, Ltd. Hydrological Processes, vol. 11, 311±323 (1997). (No. of Figures: 6 No. of Tables: 3 No. of Refs: 39)