TRAVELING FRONT APPROXIMATIONS FOR INFILTRATION INTO STRATIFIED SOILS

Two approximations are developed for infiltration into a stratified soil profile. Both satisfy the initial conditions, give the correct water content at a given depth for large time, obey mass conservation and give the correct rate of advance for large time. The first is referred to as the 'square front' solution and is analogous to Green-Ampt theory in that the profile is either wet or dry without a transition zone. The second solution is based on a homogeneous analog for which Philip's solution for a profile at large time is invoked. Examples are given for surface boundary conditions both as a specified head and as a flux density.