An evaluation of simplified field methods used for estimating soil hydraulic conductivity

Abstract

Hydraulic properties of three soils from the western Cape and two from the eastern Cape were studied. Water content (θ) data, obtained during drainage of field plots were used to estimate soil hydraulic conductivity [K(θ)] using five methods based on Richards' equation for one-dimensional water flow in soil, with various simplifying assumptions. Values of steady state hydraulic conductivity (K ₀) varied between 3,7 mm h⁻¹ for the least permeable horizon of a Hutton soil, to 446,8 mm h⁻¹ for the well-drained horizon of a Clovelly sand. For all soil types and at all depths, values of K(θ) calculated using the Flux method were higher, and values of K(θ) obtained with the Lax-W method were lower than values produced using the θ, Lax-θ and CGA methods. The assumption of unit hydraulic gradient used in the estimation of K(θ) is briefly discussed.