Constraining 3-D electrical resistance tomography with GPR reflection data for improved aquifer characterization

Doetsch, Joseph; Linde, Niklas; Pessognelli, Mirco; Green, Alan G.; Günther, Thomas

doi:10.1016/j.jappgeo.2011.04.008

Cited by 104 publications

(85 citation statements)

References 37 publications

(58 reference statements)

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“…However, such a constraint is often not coherent with the geology. Thus, many alternatives have been developed in static imaging, such as blocky inversion (Farquharson and Oldenburg, 1998), structural inversion (Kaipio et al, 1999;Doetsch et al, 2012a), minimum support (MS) and gradient support functionals (Portnaguine and Zhdanov, 1999;Blaschek et al, 2008), or other prior information incorporation methods (Caterina et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

2016

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Hydrogeophysics has become a major field of research in the past two decades, and time-lapse electrical resistivity tomography (ERT) is one of the most popular techniques to monitor passive and active processes in shallow subsurface reservoirs. Time-lapse inversion schemes have been developed to refine inversion results, but they mostly still rely on a spatial regularization procedure based on the standard smoothness constraint. We have applied a covariance-based regularization operator to the time-lapse ERT inverse problem. We first evaluated the method for surface and crosshole ERT with two synthetic cases and compared the results with the smoothness-constrained inversion (SCI). These tests showed that the covariance-constrained inversion (CCI) better images the target in terms of shape and amplitude. Although more important in low-sensitivity zones, we have observed improvements everywhere in the tomograms. Those synthetic examples also show that an error made in the range or in the type of the variogram model had a limited impact on the resulting image, which still remained better than SCI. We then applied the method to cross-borehole ERT field data from a heat-tracing experiment, in which the comparison with direct measurements showed a strong improvement of the breakthrough curves retrieved from ERT. This method could be extended to the time dimension, which would allow the use of CCI in 4D inversion schemes.

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Section: Introductionmentioning

confidence: 99%

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

2016

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“…Bakker and van der Meer, 2003;Smith and Jol, 1992;Trafford, 2009;Ulriksen, 1982). The integration of electrical and electromagnetic geophysical techniques as complementary tools for unconsolidated sediment characterisation has been widely explored during the last decade in fields such as: describing peatland areas (Comas et al, 2004;Kittredge et al, 2008;Slater and Reeve, 2002); 3D visualisation of active faults (Vanneste et al, 2008); mapping river terrace deposits (Hirsch et al, 2008); characterising shallow aquifers (Doetsch et al, 2011;Turesson, 2006); recognising groundwater flow through glacial sediments (McClymont et al, 2011); and investigating the influence of glacial sediments on the development of peatlands (Comas et al, 2011). However, the combination of these techniques as unconsolidated sediment mapping tools has not been explored in Ireland.…”

Section: Introductionmentioning

confidence: 99%

Electrical resistivity and Ground Penetrating Radar for the characterisation of the internal architecture of Quaternary sediments in the Midlands of Ireland

Pellicer

Gibson

2011

Journal of Applied Geophysics

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a b s t r a c t a r t i c l e i n f oGeophysical techniques Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) supported by traditional field methods are used for the geological mapping, description and interpretation of Quaternary unconsolidated sediments in a site located in the Midlands of Ireland. The site comprises a broad range of glacial and postglacial sediments (diamicton, esker sand and gravel, glaciolacustrine sand, glaciolacustrine silt/clay and peat). Preliminary fieldwork comprising, geomorphological mapping, lithostratigraphic analysis of exposures and borehole drilling and laboratory testing encompassing particle size distribution analysis were carried out to broadly characterise the geology of the study area. These data aided locating the geophysical profiles and supported the geophysical data interpretation. Five GPR radargrams were collected and permitted depicting the subsurface internal architecture within low conductivity unconsolidated sediments and aided to the classification and characterisation of sedimentological and deformational structures. Four ERT profiles allowed the depth to bedrock to be determined and lithological classification of the sediments. The use of these geophysical techniques in combination with geotechnical and geological data allowed (i) the determination of the lithological composition and detailed internal architecture of the subsurface, (ii) the characterisation and description of the geology of the site and (iii) understanding the depositional processes acting in the area during ice withdrawal. Diamicton and esker gravels were deposited subglacially by an ice sheet withdrawing westwards; glaciolacustrine sediments located along the south margin of the esker ridge were laid down in an ice marginal environment as a subaqueous fan composed of silt, sand and gravel, and as distal deposits composed of silt and clay in the lower ground area between the fan and the esker ridge. Peat developed during postglacial times and was partially cut away by anthropogenic action at a later stage.

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“…The experimental set-up using wrapped optical fibers to monitor high-resolution temperature profiles is based on the study of Vogt et al (2010b). In contrast to the latter, we use the high vertical resolution of the wrapped optical fibers not for vertical flow but for vertical variations of lateral flow, which may be considered typical in pre-alpine riparian zones (Huggenberger et al, 1998) and have already been hypothesized for the test site at River Thur (Doetsch et al, 2012). Such variations are caused by spatial variability of hydraulic properties in riparian sediments.…”

Section: Discussionmentioning

confidence: 99%

Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution

Vogt

Schirmer

Cirpka³

2012

Hydrol. Earth Syst. Sci.

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Abstract. River-water infiltration is of high relevance for hyporheic and riparian groundwater ecology as well as for drinking water supply by river-bank filtration. Heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. However, quantifying flow patterns and velocities is impeded by spatial and temporal variations of exchange fluxes, insufficient sensors spacing during field investigations, or simplifying assumptions for analysis or modeling such as uniform flow. The objective of this study is to investigate lateral shallow groundwater flow upon river-water infiltration at the shoreline of the riverbed and in the adjacent riparian zone of the River Thur in northeast Switzerland. Here we have applied distributed temperature sensing (DTS) along optical fibers wrapped around tubes to measure high-resolution vertical temperature profiles of the unsaturated zone and shallow riparian groundwater. Diurnal temperature oscillations were tracked in the subsurface and analyzed by means of dynamic harmonic regression to extract amplitudes and phase angles. Subsequent calculations of amplitude attenuation and time shift relative to the river signal show in detail vertical and temporal variations of heat transport in shallow riparian groundwater. In addition, we apply a numerical two-dimensional heat transport model for the unsaturated zone and shallow groundwater to obtain a better understanding of the observed heat transport processes in shallow riparian groundwater and to estimate the groundwater flow velocity. Our results show that the observed riparian groundwater temperature distribution cannot be described by uniform flow, but rather by horizontal groundwater flow velocities varying over depth. In addition, heat transfer of diurnal temperature oscillations from the losing river through shallow groundwater is influenced by thermal exchange with the unsaturated zone. Neglecting the influence of the unsaturated zone would cause biased interpretation and underestimation of groundwater flow velocities. The combination of high resolution field data and modeling shows the complex hydraulic and thermal processes occurring in shallow riparian groundwater close to losing river sections as well as potential errors sources for interpreting diurnal temperature oscillations in such environments.

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Constraining 3-D electrical resistance tomography with GPR reflection data for improved aquifer characterization

Cited by 104 publications

References 37 publications

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

Covariance-constrained difference inversion of time-lapse electrical resistivity tomography data

Electrical resistivity and Ground Penetrating Radar for the characterisation of the internal architecture of Quaternary sediments in the Midlands of Ireland

Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution

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