The Three-Parameter Infiltration Equation

A new infiltration equation is obtained by introducing a new parameter, in addition to the usual sorptivity and conductivity at saturation. This third parameter can be related to the conductivity of the soil. In particular, if this parameter is equal to zero, then the infiltration equation reduces to the well-known Green and Ampt equation. Comparison with accurate simulations carried out earlier for a sand and clay indicates that sorptivity, conductivity at saturation, and this additional parameter are sufficient to describe cumulative infiltration accurately. Finally, the two examples discussed in detail suggest that this parameter is not very sensitive to soil structure, i.e., it has about the same value for the clay and the sand. Hence, in practice, use of the new law may require a sorptivity and conductivity determination only, i.e., two rather than three parameters. Finally, this new law has about the same precision as existing laws that require knowledge of up to six parameters.