Green and Ampt infiltration model extended beyond rain duration

A simple method requiring only hand calculations is presented in this study that enables the use of the Green and Ampt infiltration model beyond the rain duration. The method takes into account that the runoff and infiltration processes continue for some period of time after the rain stops. Both the ground surface and subsurface characteristics are considered. A conjunctive overland flow‐infiltration mathematical model is employed for this purpose. A kinematic‐wave approach is used to model the overland flow, and the Green and Ampt equations are employed to calculate the infiltration rates. The governing equations are expressed and solved in terms of dimensionless parameters to enable the generalization of the results based on the principle of hydrologic similarity. A four‐point finite difference scheme is used to solve the governing equations. The results are presented in chart form. An example application of the proposed method is included.