Abstract. Imaging geological layers beneath lakes, rivers, and shallow seawater
provides detailed information critical for hydrological modeling, 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 for a new, easily configurable
floating, transient electromagnetic instrument (FloaTEM) capable of imaging
the subsurface beneath both freshwater and saltwater. 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 freshwater 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 of
identifying and distinguishing clay and sand layers below the saline water column.
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.
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