New approximate analytical technique to solve Richards equation for arbitrary surface boundary conditions

Abstract

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