3D crosshole ERT for aquifer characterization and monitoring of infiltrating river water

The hydrogeological properties and responses of a productive aquifer in northeastern Switzerland are investigated. For this purpose, 3D crosshole electrical resistivity tomography (ERT) is used to define the main lithological structures within the aquifer (through static inversion) and to monitor the water infiltration from an adjacent river. During precipitation events and subsequent river flooding, the river water resistivity increases. As a consequence, the electrical characteristics of the infiltrating water can be used as a natural tracer to delineate preferential flow paths and flow velocities. The focus is primarily on the experiment installation, data collection strategy, and the structural characterization of the site and a brief overview of the ERT monitoring results. The monitoring system comprises 18 boreholes each equipped with 10 electrodes straddling the entire thickness of the gravel aquifer. A multichannel resistivity system programmed to cycle through various four-point electrode configurations of the 180 electrodes in a rolling sequence allows for the measurement of approximately 15,500 apparent resistivity values every 7 h on a continuous basis. The 3D static ERT inversion of data acquired under stable hydrological conditions provides a base model for future time-lapse inversion studies and the means to investigate the resolving capability of our acquisition scheme. In particular, it enables definition of the main lithological structures within the aquifer. The final ERT static model delineates a relatively high-resistivity, low-porosity, intermediate-depth layer throughout the investigated aquifer volume that is consistent with results from well logging and seismic and radar tomography models. The next step will be to define and implement an appropriate time-lapse ERT inversion scheme using the river water as a natural tracer. The main challenge will be to separate the superposed time-varying effects of water table height, temperature, and salinity variations associated with the infiltrating water.

[1]  T. Günther,et al.  Three‐dimensional modelling and inversion of dc resistivity data incorporating topography – II. Inversion , 2006 .

[2]  Andrew Binley,et al.  Electrical resistivity imaging of conductive plume dilution in fractured rock , 2007 .

[3]  W. Barrash,et al.  Hierarchical geostatistics and multifacies systems: Boise Hydrogeophysical Research Site, Boise, Idaho , 2002 .

[4]  S. Gorelick,et al.  Saline tracer visualized with three‐dimensional electrical resistivity tomography: Field‐scale spatial moment analysis , 2005 .

[5]  Sarah E. Kruse,et al.  Sinkhole structure imaging in covered Karst terrain , 2006 .

[6]  H. Maurer,et al.  Advances in three-dimensional geoelectric forward solver techniques , 2009 .

[7]  James J. Butler,et al.  Direct‐Push Electrical Conductivity Logging for High‐Resolution Hydrostratigraphic Characterization , 2003 .

[8]  A. Binley,et al.  Snowmelt infiltration: monitoring temporal and spatial variability using time-lapse electrical resistivity , 2004 .

[9]  Niklas Linde,et al.  The borehole-fluid effect in electrical resistivity imaging , 2010 .

[10]  Sam Johansson,et al.  Embankment dam seepage evaluation from resistivity monitoring data , 2009 .

[11]  W. Timms,et al.  Hydrogeological investigation of mud-mound springs developed over a weathered basalt aquifer on the Liverpool Plains, New South Wales, Australia , 2003 .

[12]  Clifton C. Casey,et al.  Geophysical Monitoring of a Field‐Scale Biostimulation Pilot Project , 2006, Ground water.

[13]  A. Binley,et al.  Cross-hole electrical imaging of a controlled saline tracer injection , 2000 .

[14]  J. Chambers,et al.  High-resolution Electrical Resistivity Tomography monitoring of a tracer test in a confined aquifer , 2010 .

[15]  A. Flores-Orozco,et al.  Temperature‐calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps) , 2010 .

[16]  L. Cathles,et al.  Electrical conductivity in shaly sands with geophysical applications , 1998 .

[17]  Samuel Diem,et al.  Räumliche Charakterisierung der hydraulischen Leitfähigkeit in alluvialen Schotter-Grundwasserleitern: Ein Methodenvergleich , 2010 .

[18]  C. Hauck.  Frozen ground monitoring using DC resistivity tomography , 2002 .

[19]  Jan Vanderborght,et al.  Imaging and characterization of solute transport during two tracer tests in a shallow aquifer using electrical resistivity tomography and multilevel groundwater samplers , 2010 .

[20]  J. Gisbert,et al.  Automated monitoring of coastal aquifers with electrical resistivity tomography , 2009 .

[21]  Roelof Versteeg,et al.  Improved hydrogeophysical characterization and monitoring through parallel modeling and inversion of time-domain resistivity andinduced-polarization data , 2010 .

[22]  Andrew Binley,et al.  Electrical resistance tomography : theory and practice. , 2005 .

[23]  A. Binley,et al.  Improved hydrogeophysical characterization using joint inversion of cross‐hole electrical resistance and ground‐penetrating radar traveltime data , 2006 .

[24]  D. Hyndman,et al.  Subsurface imaging of vegetation, climate, and root‐zone moisture interactions , 2008 .

[25]  Andrew Binley,et al.  Electrical resistivity imaging of the architecture of substream sediments , 2008 .

[26]  L. Slater,et al.  Resistivity and induced polarization monitoring of salt transport under natural hydraulic gradients , 2000 .

[27]  Laurence R. Bentley,et al.  Time‐lapse electrical resistivity monitoring of salt‐affected soil and groundwater , 2009 .

[28]  J. Chambers,et al.  Mineshaft imaging using surface and crosshole 3D electrical resistivity tomography: A case history from the East Pennine Coalfield, UK , 2007 .

[29]  Venkat Lakshmi,et al.  Advancing process‐based watershed hydrological research using near‐surface geophysics: a vision for, and review of, electrical and magnetic geophysical methods , 2008 .

[30]  S. Greenhalgh,et al.  Zonation for 3D aquifer characterization based on joint inversions of multimethod crosshole geophysical data , 2010 .

[31]  E. Sudicky,et al.  A view toward the future of subsurface characterization: CAT scanning groundwater basins , 2008 .

[32]  L. Tosi,et al.  Monitoring the saltwater intrusion by time lapse electrical resistivity tomography: The Chioggia test site (Venice Lagoon, Italy) , 2009 .

[33]  T. Günther.  Inversion methods and resolution analysis for the 2D/3D reconstruction of resistivity structures from DC measurements , 2004 .

[34]  L. Toran,et al.  Stream Bottom Resistivity Tomography to Map Ground Water Discharge , 2008, Ground water.

[35]  Andrew Binley,et al.  Electrical resistance tomography. , 2000 .

[36]  S. Friedel,et al.  Characterization of a coastal aquifer using seismic and geoelectric borehole methods , 2009 .

[37]  W. Daily,et al.  Cross-borehole resistivity tomography , 1991 .

[38]  Andrew Binley,et al.  Synthetic and field-based electrical imaging of a zerovalent iron barrier: Implications for monitoring long-term barrier performance , 2006 .

[39]  K. Singha,et al.  Imaging hyporheic zone solute transport using electrical resistivity , 2009 .

[40]  Abelardo Ramirez,et al.  Electrical resistance tomography during in-situ trichloroethylene remediation at the Savannah River Site , 1995 .

[41]  Alberto Villa,et al.  An experiment of non‐invasive characterization of the vadose zone via water injection and cross‐hole time‐lapse geophysical monitoring , 2007 .

[42]  James P. McNamara,et al.  Application of time-lapse ERT imaging to watershed characterization , 2008 .

[43]  Douglas LaBrecque,et al.  Monitoring an underground steam injection process using electrical resistance tomography , 1993 .

[44]  Markus Hofer,et al.  Analyzing Bank Filtration by Deconvoluting Time Series of Electric Conductivity , 2007, Ground water.

[45]  Zhou Bing,et al.  Cross‐hole resistivity tomography using different electrode configurations , 2000 .

[46]  Andrew Binley,et al.  ERT monitoring of environmental remediation processes , 1996 .

[47]  A. Binley,et al.  Vadose zone flow model parameterisation using cross-borehole radar and resistivity imaging , 2001 .

[48]  A. Binley,et al.  A saline trace test monitored via time-lapse surface electrical resistivity tomography. , 2006 .

[49]  H. Vereecken,et al.  Imaging and characterisation of subsurface solute transport using electrical resistivity tomography (ERT) and equivalent transport models , 2002 .

[50]  W. Daily,et al.  The effects of noise on Occam's inversion of resistivity tomography data , 1996 .

[51]  J. Pritchard,et al.  Monitoring hydraulic processes with automated time-lapse electrical resistivity tomography (ALERT) , 2009 .