An unsaturated soil water flow problem and its numerical simulation

A numerical model for the unsaturated flow equation with moisture content a s prognostic variable is established in order to simulate liquid moisture f low in an unsaturated zone with homogeneous soil, and different initial and boundary conditions. For an infiltration or evaporation problem, its numer ical solution by using a finite difference method is very sensitive to its upper boundary condition and the related soil parameters, and using a tradi tional finite element method usually yields oscillatory non-physics profile s. However, we obtain a nonoscillatory solution and evade a non-physics sol ution 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 the ir alternate appearances. It can be also applied to a high-resolution land surface model.