EXTENSION OF THE HEASLET-ALKSNE TECHNIQUE TO ARBITRARY SOIL-WATER DIFFUSIVITIES

The Heaslet-Alksne technique solved the nonlinear diffusion equation by expansion around the wetting front for power taw diffusivities. Essentially the same technique has been applied when a well-defined wetting front exists at a finite distance. In this paper, the method is extended for an arbitrary diffusivity and to the case when there is no well-defined wetting front at a finite distance. Two illustrations for exponential and power law diffusivities show the excellent accuracy of the method.