Wetting front pressure head in the infiltration model of Green and Ampt

A theoretical expression relating the wetting front pressure head in the infiltration model of Green and Ampt (1911) to soil characteristics is derived. This expression is identical to that previously suggested by Bouwer (1964) on the basis of an analogy with horizontal flow. It differs from a more complete expression recently proposed by Morel‐Seytoux and Khanji (1974) in that the effect of air mobility is neglected, the need for determining the functional relationship between the relative permeability of air and water saturation thus being avoided.