Explicit infiltration equations based on the Green–Ampt model

Abstract

The Green–Ampt infiltration equations are based on physical parameters of the soil that can be either measured or calculated reasonably easily. However, neither the infiltration rate equation nor the cumulative depth of infiltration equation is in a form that can be used easily in hydrologic modeling, as both equations are in an implicit form when time is the independent variable. Therefore iterative procedures must be used to find either the infiltration rate or cumulative depth at a specific time.Explicit infiltration equations have been developed, based on the Green–Ampt infiltration model. These equations describe the infiltration rate and the cumulative depth of infiltration with a maximum deviation from the Green–Ampt equations of 2.5% for any time. The derived equations have been put in dimensionless form by choosing appropriate length and time scales. Approximate values for the length and time scales for 11 different soil textures, ranging from sand to clay, are given. Key words: infiltration, Green–Ampt explicit equations, hydrology, hydrologic models, surface irrigation, surface irrigation models.