An unsaturated soil water flow problem and its numerical simulation

A numerical model for the unsaturated flow equation with moisture content as prognostic variable is established in order to simulate liquid moisture flow in an unsaturated zone with homoge-neous soil, and different initial and boundary conditions. For an infiltration or evaporation prob-lem, its numerical solution by using a finite difference method is very sensitive to its upper bounda-ry condition and the related soil parameters, and using a traditional finite element method usually yields oscillatory non-physics profiles. However, we obtain a nonoscillatory solution and evade a non-physics solution for the problem by using the mass-lumped finite element method. This kind of boundary conditions is handled very well. Numerical simulations for certain soils show that the numerical scheme can be used in simulation of liquid moisture flow for infiltration, evaporation, re-distribution and their alternate appearances. It can be also applied to a high-resolution land surface model.