A filtering method to correct time-lapse 3D ERT data and improve imaging of natural aquifer dynamics

Simple item page
dc.contributor.authorCoscia, I.
dc.contributor.authorLinde, N.
dc.contributor.authorGreenhalgh, S.
dc.contributor.authorGunther, T.
dc.contributor.authorGreen, A.
dc.date.issued2012
dc.description.abstractWe have developed a processing methodology that allows crosshole ERT (electrical resistivity tomography) monitoring data to be used to derive temporal fluctuations of groundwater electrical resistivity and thereby characterize the dynamics of groundwater in a gravel aquifer as it is infiltrated by river water. Temporal variations of the raw ERT apparent-resistivity data were mainly sensitive to the resistivity (salinity), temperature and height of the groundwater, with the relative contributions of these effects depending on the time and the electrode configuration. To resolve the changes in groundwater resistivity, we first expressed fluctuations of temperature-detrended apparent-resistivity data as linear superpositions of (i) time series of river-water-resistivity variations convolved with suitable filter functions and (ii) linear and quadratic representations of river-water-height variations multiplied by appropriate sensitivity factors; river-water height was determined to be a reliable proxy for groundwater height. Individual filter functions and sensitivity factors were obtained for each electrode configuration via deconvolution using a one month calibration period and then the predicted contributions related to changes in water height were removed prior to inversion of the temperature-detrended apparent-resistivity data. Applications of the filter functions and sensitivity factors accurately predicted the apparent-resistivity variations (the correlation coefficient was 0.98). Furthermore, the filtered ERT monitoring data and resultant time-lapse resistivity models correlated closely with independently measured groundwater electrical resistivity monitoring data and only weakly with the groundwater-height fluctuations. The inversion results based on the filtered ERT data also showed significantly less inversion artefacts than the raw data inversions. We observed resistivity increases of up to 10% and the arrival time peaks in the time-lapse resistivity models matched those in the groundwater resistivity monitoring data. © 2012 Elsevier B.V..
dc.description.statementofresponsibilityIlaria Coscia, Niklas Linde, Stewart Greenhalgh, Thomas Günther, Alan Green
dc.identifier.citationJournal of Applied Geophysics, 2012; 80:12-24
dc.identifier.doi10.1016/j.jappgeo.2011.12.015
dc.identifier.issn0926-9851
dc.identifier.issn1879-1859
dc.identifier.urihttp://hdl.handle.net/2440/72636
dc.language.isoen
dc.publisherElsevier Science BV
dc.rightsCopyright © 2012 Elsevier B.V. All rights reserved.
dc.source.urihttps://doi.org/10.1016/j.jappgeo.2011.12.015
dc.subjectHydrogeophysics
dc.subjectTime-lapse inversion
dc.subjectElectrical resistivity tomography
dc.subjectRiver–groundwater interaction
dc.titleA filtering method to correct time-lapse 3D ERT data and improve imaging of natural aquifer dynamics
dc.typeJournal article
pubs.publication-statusPublished

Files

Collections

Physics publications