Comparison of infiltration equations and their field validation by rainfall simulation

Infiltration is a complex process with many factors contributing to the rate. Different approximate equations for infiltration differ in the parameters they require and predict different infiltration rate curves.;Five equations including those of Kostiakov, Horton, Holtan, Philip and Green-Ampt were compared to determine which one most accurately predicted measured infiltration rates from rainfall simulation events at two different locations. Parameters were developed from measured infiltration data and laboratory analyses of soil samples.;The Green-Ampt, Holtan and Philip equations with respective root mean squared errors of 0.15, 0.17, and 0.19 cmh-1, provided the first, second and third best estimates of infiltration rates, for observed infiltration data at the University of Maryland's Research and Education Center in Upper Marlboro, Maryland. An atypical infiltration curve was observed for the Poplar Hill site on the Eastern Shore of Maryland for which infiltration rate was constant and equal to rainfall rate.