| The evaporation rate of water surface (expressed with E0) is contained in the common empirical models of groundwater evaporation, which can be replaced by the evaporation rate of soil surface at groundwater depth of zero. Measured data of groundwater evaporation rate, evaporation rate of soil surface at groundwater depth of zero and evaporation rate of water surface were used to made a discussion on the selection of E0 value in Averiyanov equation, Ye equation and Lei equation, so as to improve the accuracy of calculation. Meanwhile, the groundwater vaporation rate was compared under the two conditions in which E0 was the evaporation rate of water surface and the evaporation rate of soil surface at groundwater depth of zero, respectively. The results turned to be that, in the light of clay loam in Xinjiang, some calculation error would be caused if the evaporation rate of soil surface at groundwater depth of zero were used instead of the evaporation rate of water surface as for the above three equations. So it was suggested that the evaporation rate of water surface be used as E0, and an exponential function relationship between η and groundwater table was obtained. The study results may provide references for the selection of E0 in the empirical models of phreatic evaporation, and offer a new method for calculating the parameter η in Lei equation. |