A SIMPLE METHOD FOR DETERMINING UNSATURATED CONDUCTIVITY FROM MOISTURE RETENTION DATA

The unsaturated hydraulic conductivity function for soil can be calculated directly from a moisture retention function and a single measurement of hydraulic conductivity at some water content. If the moisture retention function can be represented by ψ = ψc (θ/θa)−b, where ψc is the air entry water potential, θ, is the saturated water content, and b is an emperically determined constant, then the hydraulic conductivity is given by k = ks (θ/θs)2b+3, where ks is the saturated hydraulic conductivity. Agreement of k calculated using this procedure with experimentally determined conductivities for five soil samples was found to be at least as good as with other calculation procedures.