Estimating evaporation: A comparison between Penman, Idso-Jackson, and zero-flux methods

Abstract

A field evaporation-drainage study was conducted to compare three methods of predicting evaporative losses from a bare soil. Two of the methods (modified Penman combination and Idso-Jackson) are dependent only on measurements of atmospheric parameters whereas the third method (plane of zero flux) is dependent only on measurements of soil parameters. A Captina soil profile was wet up and allowed to dry by evaporation and drainage. For the initial two days after infiltration ceased all three methods predicted similar evaporative losses. Differences between the three methods occurred when the soil moisture content at the soil surface controlled the evaporation rates. Under the three drying conditions the three methods behaved somewhat differently in the prediction of the amounts of water evaporated from the soil surface. Lower losses by evaporation were predicted by the Idso-Jackson and zero-flux methods. In the case of the Idso-Jackson method this result was attributed to the influence of clouds on albedo, the impact of wind and the importance of albedo in the predictive equation. For the zero-flux method the decrease in evaporation was due to lower soil water contents and matrix potentials near the surface which resulted in lower transport rates of water to the surface. © 1984.