Simulation System for the Prediction of Water Flow and Solute Transport in Partially Saturated Soils

摘要

A numerical scheme of Richards' equation in its bidimensional form is presented. The finite difference scheme is obtained using the integral interpolation method. Integrals are evaluted considering weight factors in the extremes, so the resulting scheme is a Crank Nicholson type. The scheme is applied to a rectangular mesh with variable steps in space and time, so that, the mathematical model is transformed in a nonlinear equation system, solved applying a Picard iterative technique. van Genuchten relationships are used to represent the hydrodynamic properties of soil (hydraulic conductivity k ( PSI ), storage capacity of soil s( PSI ) and matric potential ( PSI ). This are empirical relations adjusted with experimental data. Beside this, the advection- dispersion equation for conservative solute transport were discrettized using the same technique. The resulting model were compared with an analytical solution that considers an isotropic, homogeneous media with permanent unidirectional flux.