Reciprocity theorems in geoelectric and geoelectromagnetic work

Parasnis, D.S.

doi:10.1016/0016-7142(88)90014-2

Cited by 46 publications

(34 citation statements)

References 2 publications

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“…A Syscal Pro electrical resistivity meter (Iris Instruments, Orleans, France) was used to measure apparent electrical resistivity, Ra over a dipole-dipole electrode configuration (see, for example, Binley 2015). These data were checked for reciprocity of measurements (Parasnis 1988) and then inverted to give a 2-D distribution of soil resistivity using the Occam's based R2 (version 2.7a) ERT inverse code (Binley 2013). The resistivity was converted to conductivity data (σ ERT ) and on each plot means were taken in the horizontal direction to give a 1-dimensional (1-D) electrical conductivity profile, which could be used to calibrate EMI data (Shanahan et al 2015) to make it consistent with resistivity profiles determined from ERT.…”

Section: Electrical Resistance Tomography (Ert)mentioning

confidence: 99%

Methods to estimate changes in soil water for phenotyping root activity in the field

et al. 2017

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Background and aims There is an urgent need to develop new high throughput approaches to phenotype roots in the field. Excavating roots to make direct measurements is labour intensive. An alternative to excavation is to measure soil drying profiles and to infer root activity. Methods We grew 23 lines of wheat in 2013, 2014 and 2015. In each year we estimated soil water profiles with electrical resistance tomography (ERT), electromagnetic inductance (EMI), penetrometer measurements and measurements of soil water content. We determined the relationships between the measured variable and soil water content and matric potential. Results We found that ERT and penetrometer measurements were closely related to soil matric potential and produced the best discrimination between wheat lines.We found genotypic differences in depth of water uptake in soil water profiles and in the extent of surface drying. Conclusions Penetrometer measurements can provide a reliable approach to comparing soil drying profiles by different wheat lines, and genotypic rankings are repeatable across years. EMI, which is more sensitive to soil water content than matric potential, and is less effective in drier soils than the penetrometer or ERT, nevertheless can be used to rapidly screen large populations for differences in root activity.

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Section: Electrical Resistance Tomography (Ert)mentioning

confidence: 99%

Methods to estimate changes in soil water for phenotyping root activity in the field

et al. 2017

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“…DD type surveys use dipole lengths (a-factor) of 1 to 3m and dipole separation (n-factor) of 1a to 10a, and involve reciprocal measurements. Exchanging current and potential electrodes should ideally deliver the 355 same results, as stated by the reciprocity theorem (Parasnis, 1988). Comparing forward and reciprocal measurements provides a robust method for estimating the data error and quality (LaBrecque et al, 1996b;Wilkinson et al, 2012).…”

Section: Ert Monitoring Installationmentioning

confidence: 99%

Imaging groundwater infiltration dynamics in karst vadose zone with long-term ERT monitoring

Watlet¹,

Kaufmann²,

Triantafyllou³

et al. 2017

Preprint

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Abstract. Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. Especially, temporarily saturated groundwater reservoirs hosted in the 15 vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonated rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of three years at the Rochefort Cave Laboratory (RCL) site in South Belgium highlight variable hydrodynamics in a karst vadose zone. These data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a 20 detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring/summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in 25 resistivity: (i) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (ii) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; (iii) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots 30 traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes.

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“…After this, equivalent reciprocal measurements were made with the current and potential bipoles interchanged (so that the potential differences are now measured beneath the current electrodes). The purpose of making reciprocal measurements is that, in the absence of systematic and random error, equivalent forward and reciprocal electrode configurations should yield the same resistivity value (Parasnis, 1988;Zhou and Dahlin, 2003). Any difference between the two gives a reliable indicator of the error in the measurement.…”

Section: Data Acquisitionmentioning

confidence: 99%

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

Wilkinson

Meldrum

Kuras

et al. 2010

Journal of Applied Geophysics

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A permanent geoelectrical subsurface imaging system has been installed at a contaminated land site to monitor changes in groundwater quality after the completion of a remediation programme. Since the resistivities of earth materials are sensitive to the presence of contaminants and their break-down products, 4-dimensional resistivity imaging can act as a surrogate monitoring technology for tracking and visualising changes in contaminant concentrations at much higher spatial and temporal resolution than manual intrusive investigations. The test site, a municipal car-park built on a former gas-works, had been polluted by a range of polycyclic aromatic hydrocarbons and dissolved phase contaminants. It was designated statutory contaminated land under Part IIA of the UK Environmental Protection Act due to the risk of polluting an underlying minor aquifer. Resistivity monitoring zones were established on the boundaries of the site by installing vertical electrode arrays in purpose-drilled boreholes. After a year of monitoring data had been collected, a tracer test was performed to investigate groundwater flow velocity and to demonstrate rapid volumetric monitoring of natural attenuation processes. A saline tracer was injected into the confined aquifer, and its motion and evolution were visualised directly in high-resolution tomographic images in near real-time. Breakthrough curves were calculated from independent resistivity measurements, and the estimated seepage velocities from the monitoring images and the breakthrough curves were found to be in good agreement with each other and with estimates based on the piezometric gradient and assumed material parameters.

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Reciprocity theorems in geoelectric and geoelectromagnetic work

Cited by 46 publications

References 2 publications

Methods to estimate changes in soil water for phenotyping root activity in the field

Methods to estimate changes in soil water for phenotyping root activity in the field

Imaging groundwater infiltration dynamics in karst vadose zone with long-term ERT monitoring

High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer

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