Author(s)

F. Ali Swaid

Abstract

Electrical resistivity imaging has the capacity to map changes in soil water content and quality in the vadose zone. However, interpretation of the images is difficult because of the numerous variables that influence the measured resistivity. The dominant variables include porosity, degree of saturation, pore water salinity, clay content and clay type. There have been numerous models published that combine these variables in order to predict the bulk electrical conductivity of any mixture. All these equations need to be calibrated against controlled samples in order to determine parameters that account for geometrical effects and grain surface conduction. Recently, Glover et al. (Earth and Planetary Science Letters 2000) published an extension to Archie’s equation to account for the nonlinear behavior seen in the relationship between pore water salinity and soil/rock bulk conductivity. In this paper the Glover et al. model is extended to partial saturation conditions. The application of the new model in the evaluation of salinity and changes of soil moisture is possible wherever the required criteria are met. Furthermore, more, this relation can also be taken to estimate the changes in soil moisture caused by root uptake. Keywords: partial saturation, cation exchange capacity, saturation exponent, geometric factor, water conductivity, bulk conductivity.

Keywords

partial saturation, cation exchange capacity, saturation exponent,geometric factor, water conductivity, bulk conductivity