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Abstract Methods for calculating hydraulic conductivities of porous materials proposed by Marshall and by Millington and Quirk are similar except for the pore interaction term. This term was shown to be a constant for the Marshall method. Using a matching factor, equations for the two methods differ only by the exponent of the pore interaction term, being 0 for Marshall's method and 4/3 for Millington and Quirk's. Data for four porous materials, for which the hydraulic conductivities, pressure heads, and water contents were determined on the same sample, were used in a statistical procedure to obtain a best fit value for the exponent. For the four materials, an exponent of 1 adequately predicted the measured conductivities. With this exponent, hydraulic conductivities for a field soil were calculated from a laboratory‐determined pressure headwater content relation. Calculated and measured conductivities agreed to within the limits of error of measurement.
Ray D. Jackson (Wed,) studied this question.