ESTIMATION OF GREEN-AMPT PARAMETERS FROM INFILTROMETER DATA

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Abstract
The Green-Ampt equation developed early in this century is regaining popularity in describing the infiltration of water into the soil as a function of time. The parameters defining the Green-Ampt equation have physical bases, and they can be determined from the physical properties of the soil. However, small variations in the Green-Ampt parameters may result in large deviations in the predicted values of the cumulative infiltration. In this report, I present a nonlinear least-squares scheme for estimation of the hydraulic conductivity, K, the product of available porosity, n, and the capillary pressure head, φt, which appear in the Green-Ampt equation. The method developed requires only infiltrometer data on cumulative infiltration measured at specified times. Four case studies investigated show that, in general, the method calculates the hydraulic conductivity lower and the capillary pressure head higher than do methods reported in literature. © Williams & Wilkins 1989. All Rights Reserved.