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

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 750 m 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. Copyright © 2015 John Wiley & Sons, Ltd.

Electrical resistivity imaging of hydrologic flow through surface coal mine valley fills with comparison to other landforms

“…Boundary layers exist in undisturbed landscapes but are heightened in highly heterogeneous mined landscapes such as those investigated in this study. Note that in our tomograms, the red areas are all adjacent and proportional to blue areas rather than occurring on their own, corroborating that they are artifacts of the inversion process rather than real increases in resistivity, consistent with prior studies (Sawyer et al, ). This adjacency indicates the contrast between a layer that has increased in EC due to increase in moisture content and an adjacent layer that has not experienced such increase.…”

“…ERI improves upon traditional hydrologic approaches because errors induced by the earth meter and inversion process are less than those induced via interpolation between point measurements (Crook et al, 2008). The hydrologic interpretation used here has been shown as viable by previous studies (Menichino et al, 2014;Rugh & Burbey, 2008;Sawyer et al, 2015;Travelletti et al, 2012).…”

“…Only increases and decreases in EC (blue and yellow-red, respectively) are shown (Figures 7 and 8). We only considered areas in these tomograms with increases in EC of >10% to be sufficiently significant for hydrologic interpretation similar to other studies (Menichino et al, 2014;Sawyer et al, 2015;Ward, Gooseff, & Singha, 2010b). Assuming no change in subsurface geologic structure during a given rainfall experiment, an increase in water saturation is the only way to induce a change in EC response (Travelletti et al, 2012), which appears as an increase in EC (teal and blue areas).…”

“…Previous noncoal applications include open pits (Ramalho, Carvalho, Barbosa, & Monteiro Santos, 2009), tailings impoundments and dams (Buselli & Lu, 2001;Grangeia, Ávila, Matias, & Ferreira de Silva, 2011;Martín-Crespo, Martín-Velázquez, Gómez-Ortiz, Ignacio-San José, & Lillo-Ramos, 2010), and a capped waste rock repository (Wangerud, Versteeg, Heath, Markiewicz, & Richardson, 2006). ERI has also imaged polymetallic mine spoil structure (Anterrieu, Chouteau, & Aubertin, 2010) and Karst conduits (Sawyer, Zhu, Currens, Atcher, & Binley, 2015). Nevertheless, no previous study has been done on a valley fill of any sort, and none have visualized preferential stormwater flow.…”

Characterization of karst structures using quasi-3D electrical resistivity tomography

“…Electrical resistivity tomography (ERT) (e.g., Gunther et al 2006;Binley 2015) is widely used in groundwater investigations and is recognized as an effective technique for revealing karst aquifer structure (e.g., Al-Fares et al 2002;Chalikakis et al 2011;Margiotta et al 2012Margiotta et al , 2016Metwaly and Al Fouzan 2013;Kaufmann and Deceuster 2014). Furthermore, time-lapse ERT imaging has been successfully used to assess groundwater pathways in karstic environments (e.g., Sawyer et al 2015;Watlet et al 2018).…”