NEW APPROXIMATE ANALYTICAL TECHNIQUE TO SOLVE RICHARDS EQUATION FOR ARBITRARY SURFACE BOUNDARY-CONDITIONS

A general approximation for the solution to the one-dimensional Richar ds equation is presented. It applies to arbitrary soil properties and boundary conditions but only uniform initial conditions at current sta ge. The result is very accurate (within 2%) when the diffusivity is co nstant, suggesting that the present general formulation is reliable, s ince the approximation becomes increasingly accurate as the soil-water diffusivity approaches a delta function.