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Improving the understanding and conceptualization of regional groundwater flow patterns in fractured rocks with self-potential data
Robert, Tanguy; Molron, Justine; De Schepper, Guillaume et al.
2018IAH 2018
 

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Keywords :
Self-potential; Geophysics; Fractures
Abstract :
[en] This collection of geophysical case studies demonstrates the positive impact of self-potential (SP) data on the understanding and conceptualization of groundwater flow patterns in fractured rocks of Wallonia, Belgium. We first identify the SP signature of a preferential groundwater flow path in Cambrian fractured quartzite as a negative anomaly of 15 mV in the raw SP signal. This result allowed the delineation of hydraulically-active fractured rocks as well as the refinement of groundwater flow conceptual models with zones of higher hydraulic conductivities. We then demonstrate that the apparent electrokinetic coupling coefficient C_w that links SP and hydraulic gradients is often positive for Carboniferous limestone (although its exact value is site dependent) while it is often presented as negative in the literature (mostly focusing on silicates). With this result in mind, we illustrate several methodologies to quickly and almost inexpensively investigate Carboniferous limestone valleys/synclines qualitatively and quantitatively such as SP mapping and profiling. These allowed us to demonstrate the presence of two perpendicular hydraulic gradients in such typical synclines. In a monitoring mode, SP profiling can follow the increase (and then the decrease) of the hydraulic gradient during high (low) groundwater level periods, offering an interesting potentiality to densely monitor complex hydrogeological systems. Combined with classical piezometric heads measured in wells, SP profiling (or mapping) can become quantitative once C_w is correctly estimated, allowing either the reconstruction of a smooth piezometric profile (or map) or the amplitude of hydraulic gradients along different directions, as proven by our data which were able to image the drawdown in an aquifer submitted to dewatering in a limestone quarry. This work also shows promising perspectives by considering SP measurements as hard data for groundwater flow modeling.
Disciplines :
Geological, petroleum & mining engineering
Author, co-author :
Robert, Tanguy ;  Université de Liège - ULiège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement
Molron, Justine;  Aquale SPRL > Department of R&D
De Schepper, Guillaume;  Aquale SPRL > Department of R&D
Gaule, David;  Aquale SPRL
Bolly, Pierre-Yves;  Aquale SPRL
Nguyen, Frédéric ;  Université de Liège - ULiège > Département ArGEnCo > Géophysique appliquée
Language :
English
Title :
Improving the understanding and conceptualization of regional groundwater flow patterns in fractured rocks with self-potential data
Publication date :
11 September 2018
Event name :
IAH 2018
Event organizer :
Korean Chapter of the International Association of Hydrogeologists
Event place :
Daejeon, South Korea
Event date :
du 10 septembre 2018 au 14 septembre 2018
Audience :
International
References of the abstract :
FP-100 - T7.1 Groundwater in karst and fractured rock aquifer
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 19 September 2018

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