An Analytical Solution to Soil Steady-State Evaporation

Evaporation from soil and other porous media constitutes a significant source of waterloss affecting global water balance and energy exchange between land andatmosphere. The presence of a shallow water table can lead to sustained water loss thatis dependent on porous media hydraulic properties and water table depth among otherfactors. In this paper, an exact analytical solution to steady-state evaporation fromporous media is developed using the Brooks-Corey hydraulic conductivity model. Thesolution is presented in terms of a set of infinite series. An advantage of this solutioncompared to previous derivations is that the infinite series can be very closelyapproximated using a closed-form solution (i.e., excluding integrals or series). Thenovel solution shows excellent agreement with the exact solution for a broad range ofsoil texture from sand to clay. The applicability of the solution to predict the locationof the drying front was also verified using experimental data taken from the literature.The solution may be used for directly modeling steady-state evaporation or for inversedetermination of the Brooks-Corey hydraulic parameters.

Keywords:

Steady-state evaporation , water table , film region , Brooks-Corey