Green–Ampt infiltration model

Summary

The Green–Ampt model describes the infiltration of water from a ponded surface into a uniform soil as a sharp wetting front moving downward. Above the front the soil is saturated, and below it the soil keeps its initial dryness. W. Heber Green and G. A. Ampt proposed it in 1911. Applying Darcy's law to the saturated zone gives an ordinary differential equation for the cumulative infiltration, with a closed-form solution in implicit form. It is a physically based model with few parameters, used in hydrology to split rainfall into infiltration and runoff.