Integrated surface geophysical approach to locate a karst conduit: a case study from Royal Spring Basin, Kentucky, USA

Abstract

Groundwater flow in karst terrains is difficult to map because it can be concentrated through conduits that do not necessarily coincide with the surface features. We applied electrical resistivity (ER) and self-potential (SP) techniques at three sites to locate an inferred trunk conduit feeding a major spring in the Inner Bluegrass region of Kentucky (USA). Royal Spring is the primary water supply for the city of Georgetown; the upper part of its basin coincides with the Cane Run watershed. ER profiles (972 m total length) were measured using a dipole–dipole electrode configuration with 2- to 3-m spacing. SP measurements were taken along those ER lines and an additional test profile (230 m) using one stationary reference electrode and another roving electrode at a fixed interval. The SP technique has been used by many researchers to detect the electro kinetic potential generated by groundwater flow. The low resistivity of water in the conduit, as compared to the high background resistivity of limestone bedrock, was the ER exploration target. A negative SP anomaly corresponded to a low ER anomaly for most of the profiles, but a few are not comparable. Although SP data collected over multiple days along the test profile differed significantly, they showed similar trends. Field drift in SP data was found to be highly sensitive to temperature changes during the time of measurement. Although the overall trends of the final SP profiles for different dates were similar, the SP magnitudes varied with the amount of precipitation and the average soil temperature. The low-resistivity anomalies in the 2D inverted sections and corresponding negative SP anomalies at two sites (Berea Road and Kentucky Horse Park) encountered water-filled conduits, although mudfilled voids encountered during drilling at University of Kentucky Agricultural Research Farm sites suggest that these may be tributary conduits rather than the trunk conduit.

Characterization of groundwater and surface water mixing in a semiconfined karst aquifer using time‐lapse electrical resistivity tomography

“…Early studies used electrical resistivity tomography to determine resistivity anomalies in karstic regions [ Smith and Randazzo , ; Denahan and Smith , ]. Hydrogeophysics has more recently been used to determine locations of sinkholes [ van Schoor , ; Jardani et al ., ] and both air‐filled and water‐filled subsurface voids [ Smith and Randazzo , ; Vouillamoz et al ., ; Legchenko et al ., ; Tripathi , ; Zhu et al ., ; Vadillo et al ., ] or to optimize the position of wells in karstic aquifers [ Robert et al ., ]. Currently, electromagnetic methods, gravity, and ground penetrating radar are considered the most suitable methods for detecting karst conduits and other large cavities [ Thomas and Roth , ; Chalikakis et al ., ] although some studies have used geodesy [ Longuevergne et al ., ; Grillo et al ., ; Tenze et al ., ] or electrical resistivity tomography to determine locations of subsurface conduits [ Smith and Randazzo , ; Denahan and Smith , ; Guérin and Benderitter , ; Gautam et al ., ; Vouillamoz et al ., ; Guérin et al ., ; Tripathi , ; Zhu et al ., ; Meyerhoff et al ., ; Vadillo et al ., ].…”

Quantitative analysis of self-potential anomalies: Review of case studies from various SP applications

“…Other SP application is revealing some dangerous environmental phenomena (karst cavities, faults, rockslides) (e.g., Ogilvi and Bogoslovsky, 1979;Corwin, 1990Corwin, , 1996Quarto and Schiavone, 1996;Gurk and Bosch, 2001;Vichabian and Morgan, 2002;Lapenna et al, 2003;Jardani et al, 2006aJardani et al, , 2006bEppelbaum, 2007;Jardani et al, 2007;Rozycki et al, 2007;Gibert and Sailhac, 2008;Srigutomo et al, 2010;Tripathi and Frayar, 2016;Chen et al, 2018;Gusev et al, 2018;Oliveti and Cardarelli, 2019).…”

Identification of Karstification Zoning and Aquifer Channels in Karst Basin at Sendang Biru Beach, Malang-Indonesia: A Case Study

“…In this regard, geophysical surveys have a significant role in identifying and displaying geological structures near the surface, such as karst voids, faults, aquifer structures (type, depth, groundwater level), and geological structures [7]. However, according to Tripathi & Fryar [8], characterizing the aquifer flow in the karst plain is difficult to map because it can be concentrated through the conduit, and it does not always match the appearance on the surface. Therefore, several methods such as ERT, IP, and SP have good correlations for different purposes.…”

“…On the other hand, several studies use geophysical methods to characterize karst landscapes. Among them, identifying the voids and morphology of karst landscapes and karst water circulation in karst structures [3,[8][9][10], SP and ERT methods of karst aquifer exploration [5,11,12], as well as IP methods for the use of detection features. doline cover debris [13][14][15][16].…”

“…Another method is a combination of Ground Penetrating Radar (GPR) and ERT to study karst structures [21], a combination of geoelectrical localization and electromagnetic geohydrology [22]. In addition, several researchers have carried out geophysical approaches such as the application of geophysical and hydro-chemical methods to protect karst aquifers [23], integrated geophysical approaches for localization of karst channels [8], and hydro-geophysical characterization of karst aquifers [24]. However, what is interesting is the use of ERT, IP, and SP methods which gives good results.…”