Parameter estimation of the Green and Ampt Infiltration Equation

Infiltrometer data are utilized to test a fitting procedure for the Green and Ampt infiltration equation parameters. The spatial variation of the estimated parameters is averaged to give lumped parameter values for watershed modeling. An appropriate scale for parameter averaging is discussed, which transforms parameter values to normal deviates. A sensitivity analysis for the equation parameters is performed for both infiltration estimates and runoff hydrograph volume and peak rates. The capillary pressure parameter shows least sensitivity; however, variation in the fillable porosity and effective conductivity parameters has a major influence on infiltration and runoff amounts and rates.