A numerical model for preferential solute movement in structured soils

Abstract

A model for preferential flow for the vadose zone is presented. In the model, a piecewise linear approximation of the hydraulic conductivity as a function of water content is used to identify the flow paths (or pore groups) in which water moves at distinct velocities. By choosing the linear approximations in such a way that the velocity in a pore group is an integer multiple of the velocity of the adjoining pore group, a simple numeric procedure can be formulated for simulating solute movement. The character of the solute exchange among the pore groups may be altered as demanded by the nature of the system being modeled. If complete mixing among the pore groups is specified, the model is reduced to the convective-dispersive equation. If no mixing is specified, it behaves as a pore bundle model.