- A general infiltration model is derived using a systems approach. The models of Horton, Kostiakov, Overton, Green and Ampt, and Philip are some of the example models that are shown as special cases of the general model. An equivalence between the Green-Ampt model and the Philip two-term model is shown. The general model also provides a solution for the Holtan model expressing infiltration as a function of time. This solution of the Holtan model has not been reported in the literature. A first-order analysis is performed to quantify the uncertainty involved with the generalized model. The general infiltration model contains five parameters. Two of the parameters are physically based and can therefore be estimated from the knowledge of soil properties, antecedent soil moisture conditions, and infiltration measurements; the remaining three can be determined using the least squares method. The model is verified using ten observed infiltration data sets. Agreement between observed and computed infiltration is quite good. ASCE.