The calibration of frequency-domain electromagnetic induction meters and their possible use in recharge studies

Abstract

Published models of soil conductivity are used to develop a calibration for frequency-domain electromagnetic induction meters. The calibration is portable, requiring only a knowledge of certain soil properties. One critical soil property is the impedance factor, a function of the soil water content. We select an impedance factor from the literature which, when incorporated in the calibration, provides the best fit to measured apparent electrical conductivity. The calibration derived is used to test the ability of frequency-domain electromagnetic induction meters to estimate groundwater recharge rates in a semi-arid area of South Australia. Two analytical models relating total (or cumulative) recharge to soil solute profiles are used to derive theoretical relationships between electrical conductivity and total recharge. These modelled relationships provide a good fit to field data, suggesting that electromagnetic techniques have value in recharge studies.