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Time-lapse electrical resistivity imaging of solute transport in a karst conduit

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<mark>Journal publication date</mark>15/11/2015
<mark>Journal</mark>Hydrological Processes
Issue number23
Volume29
Number of pages9
Pages (from-to)4968-4976
Publication StatusPublished
Early online date26/08/15
<mark>Original language</mark>English

Abstract

The use of electrical resistivity surveys to locate karst conduits has shown mixed success. However, time-lapse electrical resistivity imaging combined with salt injection improves conduit detection and can yield valuable insight into solute transport behaviour. We present a proof of concept above a known karst conduit in the Kentucky Horse Park (Lexington, Kentucky). A salt tracer solution was injected into a karst window over a 45-min interval, and repeat resistivity surveys were collected every 20 min along a 125-m transect near a monitoring well approximately 750m downgradient from the injection site. In situ fluid conductivity measurements in the well peaked at approximately 25% of the initial value about 3 h after salt injection. Time-lapse electrical resistivity inversions show two broad zones at the approximate conduit depth where resistivity decreased and then recovered in general agreement with in situ measurements. Combined salt injection and electrical resistivity imaging are a promising tool for locating karst conduits. The method is also useful for gaining insight into conduit geometry and could be expanded to include multiple electrical resistivity transects.