Parlange, J.-Y.Hogarth, W. L.Parlange, M. B.Haverkamp, R.Barry, D. A.Ross, P. J.Steenhuis, T. S.2005-12-092005-12-09199810.1023/A:1006508721609https://infoscience.epfl.ch/handle/20.500.14299/221075A general approximation for the solution of the one- dimensional nonlinear diffusion equation is presented. It applies to arbitrary soil properties and boundary conditions. The approximation becomes more accurate when the soil-water diffusivity approaches a delta function, yet the result is still very accurate for constant diffusivity suggesting that the present formulation is a reliable one. Three examples are given where the method is applied, for a constant water content at the surface, when a saturated zone exists and for a time-dependent surface flux.Nonlinear diffusionAnalytic solutionsExact solutionsApproximationsSimilaritySoilWaterInfiltration equationFirst integralsSorptivitySoilsFlowPorous mediatext::journal::journal article::research article