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Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys; implications for groundwater flow paths and the distribution of residence times

Jean-Christophe Comte, Ulrich S. Ofterdinger, A. Legchenko, J. Caulfield, R. Cassidy and J. A. Mezquita Gonzalez
Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys; implications for groundwater flow paths and the distribution of residence times (in Groundwater in fractured bedrock environments; managing catchment and subsurface resources, Ulrich S. Ofterdinger (editor), Alan M. MacDonald (editor), J. C. Comte (editor) and M. E. Young (editor))
Special Publication - Geological Society of London (May 2018) 479 (1): 35-58

Abstract

Groundwater pathways and residence times are controlled by aquifer flow and storage properties, which, in weathered/fractured hard rock aquifers, are characterized by high spatial heterogeneity. Building on earlier work in a metamorphic aquifer in NW Ireland, new clay mineralogy and analyses of geophysical data provided high spatial resolution constraints on the variations in aquifer properties. Groundwater storage values derived from magnetic resonance sounding and electrical resistivity tomography were found to largely vary laterally and with depth, by orders of magnitude. The subsequent implementation of hillslope, two-dimensional numerical groundwater models showed that incorporating heterogeneity from geophysical data in model parametrization led to the best fit to observations compared with a reference model based on borehole data alone. Model simulations further revealed that (1) strong spatial heterogeneity produces deeper, longer groundwater flow paths and higher age mixing, in agreement with the mixed sub-modern/modern ages (mostly <50 years) provided by independent tritium data, and (2) areas with extensive weathering/fracturing are correlated with seepage zones of older groundwater resulting from changes in the flow directions and are likely to act as drainage structures for younger groundwater on a catchment or regional scale. Implications for groundwater resilience to climate extremes and surface pollution are discussed together with recommendations for further research.


ISSN: 0305-8719
Coden: GSLSBW
Serial Title: Special Publication - Geological Society of London
Serial Volume: 479
Serial Issue: 1
Title: Catchment-scale heterogeneity of flow and storage properties in a weathered/fractured hard rock aquifer from resistivity and magnetic resonance surveys; implications for groundwater flow paths and the distribution of residence times
Title: Groundwater in fractured bedrock environments; managing catchment and subsurface resources
Author(s): Comte, Jean-ChristopheOfterdinger, Ulrich S.Legchenko, A.Caulfield, J.Cassidy, R.Mezquita Gonzalez, J. A.
Author(s): Ofterdinger, Ulrich S.editor
Author(s): MacDonald, Alan M.editor
Author(s): Comte, J. C.editor
Author(s): Young, M. E.editor
Affiliation: University of Aberdeen, School of Geosciences, Aberdeen, United Kingdom
Pages: 35-58
Published: 20180510
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 65
Accession Number: 2018-050998
Categories: Applied geophysicsHydrogeology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N54°28'00" - N55°22'60", W08°48'00" - W06°55'60"
Secondary Affiliation: Queen's University Belfast, GBR, United KingdomUniversite Joseph Fourier, FRA, FranceTrinity College Dublin, IRL, IrelandAgri-Food and Biosciences Institute, GBR, United Kingdom
Source Note: Online First
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201827
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