Efficient Numerical Method for Infiltration in Unsaturated Soil

A finite difference method for solving Richards' Equation in one dimension is presented, and the calculated results agree well with the observed data. The method is an implicit iterative scheme with a hyperbolic sine transform for the matrio potential.The infiltration in a range of soils for sand, silt loam and clay can be simulated in a few seconds on a personal computer with errors of only a few percent in the amount of soilwater. The beaviour of infiltration in unsaturated soil is divided into three phases: before ponding time, after ponding time and recession.