Explicit Solution to Green‐Ampt Equation for Nonuniform Soils

The solution for accumulated infiltration using the Green-Ampt equation requires an iterative solution. By using a power series approximtion to a logarithmic term, an equation has been developed to directly calculate the accumulated infiltration for nonuniform soils. A second equation developed primarily for computer models predicts the potential change in the depth of infiltration for discrete time steps. The expression is relatively simple and may be easily programmed for use in hydrologic models. The maximum error resulting from the power series approximation is 8% and will usually be much less. These solutions may be used by engineers and hydrologists to predict infiltration and runoff for vertically nonuniform soils without a time consuming iterative process.