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2018-03-01 - Article/Dans un journal avec peer-review - Anglais - 30 page(s)

Watlet Arnaud , Kaufmann Olivier , Triantafyllou Antoine, Poulain Amaël, Chambers Jonathan, Meldrum Philip, Wilkinson Paul, Hallet Vincent, Quinif Yves , Van Ruymbeke M., Van Camp Michel, "Imaging groundwater infiltration dynamics in karst vadose zone with long-term ERT monitoring" in Hydrology and Earth System Sciences, 22, 1563–1592, https://doi.org/10.5194/hess-22-1563-2018

  • Edition : European Geosciences Union, Katlenburg-Lindau (Germany)
  • Codes CREF : Sciences de l'ingénieur (DI2000), Environnement et pollution (DI3840), Hydrogéologie (DI1426)
  • Unités de recherche UMONS : Géologie fondamentale et appliquée (F401)
  • Instituts UMONS : Institut des Sciences et du Management des Risques (Risques)

Abstract(s) :

(Anglais) Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. Especially, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of three years at the Rochefort Cave Laboratory (RCL) site in South Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring/summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes.