Preprints
https://doi.org/10.5194/hess-2021-540
https://doi.org/10.5194/hess-2021-540

  08 Dec 2021

08 Dec 2021

Review status: this preprint is currently under review for the journal HESS.

Technical note: Efficient imaging of hydrological units below lakes and fjords with a floating, transient electromagnetic system (FloaTEM)

Pradip Kumar Maurya1, Frederik Ersted Christensen1, M. Andy Kass1, Jesper Bjergsted Pedersen1, Rasmus Rumph Frederiksen1, Nikolaj Foged1, Anders Vest Christiansen1, and Esben Auken2,a Pradip Kumar Maurya et al.
  • 1Department of Geoscience, HydroGeophysics Group Aarhus University, C.F. Møllers Alle, 4, Aarhus C, Denmark
  • 2The Geological Survey of Denmark and Greenland (GEUS) Oester Voldgade 10 1350 Copenhagen K Denmark
  • aformerly at: Department of Geoscience, HydroGeophysics Group Aarhus University, C.F. Møllers Alle, 4, Aarhus C, Denmark

Abstract. Imagining geological layers beneath lakes, rivers, and shallow seawater provides detailed information critical for hydrological modelling, geologic studies, contaminant mapping, and more. However, significant engineering and interpretation challenges have limited the applications, preventing widespread adoption in aquatic environments. We have developed a towed transient electromagnetic (tTEM) system to a new, easily configurable floating, transient electromagnetic instrument (FloaTEM) capable of imaging the subsurface beneath both fresh and saltwater water bodies. Based on the terrestrial tTEM instrument, the FloaTEM system utilizes a similar philosophy of a lightweight towed transmitter with a trailing, offset receiver, pulled by a small boat. The FloaTEM system is tailored to the specific fresh or saltwater application as necessary, allowing investigations down to 100 m in freshwater environments, and up to 20 m on saline waters. Through synthetic analysis we show how the depth of investigation of the FloaTEM system greatly depends on the resistivity and thickness of the water column. The system has been successfully deployed in Denmark for a variety of hydrologic investigations, improving the ability to understand and model processes beneath water bodies. We present two freshwater applications and a saltwater application. Imaging results reveal significant heterogeneities in the sediment types below the freshwater lakes. The saline water example demonstrates that the system is capable to identify and distinguish clay and sand layers below the saline water column.

Pradip Kumar Maurya et al.

Status: open (until 18 Feb 2022)

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Pradip Kumar Maurya et al.

Pradip Kumar Maurya et al.

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Short summary
In this paper, we present an application of electromagnetic method to image the subsurface below the rivers, lake, or any surface water body. The scanning of the subsurface is carried out by sailing an electromagnetic sensor called FloaTEM. Imaging results shows 3D distribution of different sediment types below the freshwater lakes. In case of saline water system is capable to identify probable location of ground water discharge into seawater.