Notes
Academic journal article by M. Th. van Genuchten (USDA Salinity Laboratory, Riverside, CA) published in Soil Science Society of America Journal, Vol. 44, 1980, pp. 892-898. Derives closed-form analytical expressions for predicting relative hydraulic conductivity of unsaturated soils using a new soil-water retention curve equation based on Mualem’s (1976) model. Introduces the van Genuchten equation (θ = θ_r + (θ_s – θ_r)/[1+(αh)^n]^m) with independent parameters α, n, m, θ_s, and θ_r. Compares results with Burdine theory, Brooks and Corey (1964), Millington-Quirk method, and observed hydraulic conductivity data for five soils. Filed as Exhibit AR020939 in PCHB third-runway EIS administrative record.