Prediction of unsaturated soil hydraulic conductivity with electrical conductivity

Abstract

Soil hydraulic conductivity (K) varies greatly with matric potential (h) and exhibits a high variability at the field scale. However, this key property for estimating water flux in soils is difficult to measure. In contrast, soil electrical conductivity (σ) is easier to measure and is influenced by the same parameters affecting K. We derive a simple relationship between σ and K(h) and test it against laboratory and literature data. Importantly, we show that parameters of this σ‐K(h) relationship can be completely determined with accessible measurements of saturated hydraulic conductivity, electrical conductivity of the soil solution, and clay content. This results in K(h) estimation with a RMSE ranging between 0.4 and 0.5 for log K, i.e., of the order of most experimental determinations of K. A further test of the σ‐K(h) relationship on the large UNSODA hydraulic database shows good agreement and the robustness of the relationship. Such a relation could be useful in the spatial monitoring of water fluxes at the field scale using electrical resistivity tomography if the σ(h) relationship can be obtained.

Electrical Conductivity of Partially Saturated Packings of Particles

“…Thus, in principle, there is no exact relation between k and σ . Despite this, σ is commonly used in geophysics and hydrology to predict k and the relative permeabilities (see, for example, Revil and Cathles 1999;Doussan and Ruy 2009;Niu et al 2015;Mawer et al 2015). For this reason, accurate prediction of σ has been a problem of great interest for a long time (see e.g., Knight 1991;Friedman 2005;Zhan et al 2010;Revil 2016), particularly under partially saturated conditions, for which various models have been proposed to predict σ .…”

Geoelectrical characterization of carbonate and silicate porous media in the presence of supercritical CO2–water flow

“…P c -S-K r functions) include their non-unique behaviour as the flow seems to vary with a number of parameters (Abidoye et al 2015). Factors found to contribute to the non-uniqueness of the P c -S-K r functions in two-phase flow systems in porous media have been reported to also affect the geoelectrical properties and saturation relationships in such systems (Doussan & Ruy 2009). For example, hysteresis is reported for P c -S relationships depending on phase distribution, saturation history ascribed to contact angle hysteresis, irreversible changes in pore-scale fluid distribution and the interfacial area .…”

A combined use of Archie and van Genuchten models for predicting hydraulic conductivity of unsaturated pyroclastic soils

“…Moreover, different electrical-hydraulic conductivity relationships have been derived, mostly for saturated media, by combining i) Kozeny-Carman type equations with the quadrature conductivity or ii) hydraulic conductivity expressions derived by percolation theory (applied to porous media) with the formation factor (Lesmes and Friedman, 2005;Slater, 2007). More recently, a relationship between electrical and hydraulic conductivity has been proposed by assuming that equations from percolation theory (Katz and Thompson, 1986;Thompson et al, 1987) also hold for unsaturated media (Doussan and Ruy, 2009).…”