Development of a new method for efficiently calculating of evaporation from the phreatic aquifer in variably saturated flow modeling

In this paper, we proposed a new method that has been developed based on thesurface soil moisture content （SSMC） to more efficiently calculate the groundwaterevaporation in variably saturated flow modeling. In this method, the empirical formula tocalculate evaporation was modified and the value of the formula varies from zero to one as aclosed interval. In addition, the simulation code for calculating the groundwater evaporationbased on the SSMC method was incorporated into the EOS9 module of Tough2, a variablysaturated flow modeling code. Finally, two numerical tests and a case simulation wereconducted to verify the feasibility and accuracy of the SSMC method. Simulation resultsindicate that the SSMC method is capable of appropriately simulating the characteristics ofwater flow in vadose zone and the amount of evaporation with the variable water table. Andsuch results are in coincidence with the value calculated by the logistic function method, and fitwell with the measured data globally rather than locally.