Using geophysical surveys to test tracer-based storage estimates in headwater catchments

C. Soulsby, J. Bradford, J. Dick, J. P. McNamara, J. Geris, J. Lessels, M. Blumstock, D. Tetzlaff

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32 Citations (Scopus)
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Hydrogeophysical surveys were carried out in a 3.2 km2 Scottish catchment where previous isotope studies inferred significant groundwater storage that makes important contributions to streamflow. We used electrical resistivity tomography (ERT) to characterise the architecture of glacial drifts and make an approximation of catchment-scale storage. Four ERT lines (360-535 m in length) revealed extensive 5-10 m deep drift cover on steeper slopes, which extends up to 20-40 m in valley bottom areas. Assuming low clay fractions, we interpret variable resistivity as correlating with variations in porosity and water content. Using Archie's Law as a first approximation, we compute likely bounds for storage along the ERT transects. Areas of highest groundwater storage occur in valley bottom peat soils (up to 4 m deep) and underlying drift where up to 10,000 mm of precipitation equivalent may be stored. This is consistent with groundwater levels which indicate saturation to within 0.2 m of the surface. However, significant slow groundwater flow paths occur in the shallower drifts on steeper hillslopes, where point storage varies between ~1,000 mm–5,000 mm. These fluxes maintain saturated conditions in the valley bottom and are recharged from drift-free areas on the catchment interfluves. The surveys indicate that catchment scale storage is >2,000 mm which is consistent with tracer-based estimates. This article is protected by copyright. All rights reserved.
Original languageEnglish
Pages (from-to)4434-4445
Number of pages15
JournalHydrological Processes
Issue number23
Early online date15 Jun 2016
Publication statusPublished - 15 Nov 2016

Bibliographical note

The authors are grateful to Stian Bradford, Chris Gabrielli, and Julie Timms for practical and logistical assistance. The provision of transport by Iain Malcolm and Ross Glover of Marine Scotland Science was greatly appreciated. We also thank the European Research Council ERC (project GA 335910 VEWA) for funding through the VeWa project and the Leverhulme Trust for funding through PLATO (RPG-2014-016).


  • storage
  • groundwater
  • glacial drift deposits
  • tracers
  • electrical resistivity tomography


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