Assessment of groundwater recharge processes through karst vadose zone by cave percolation monitoring |
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| Authors: | Amaël Poulain Arnaud Watlet Olivier Kaufmann Michel Van Camp Hervé Jourde Naomi Mazzilli Gaëtan Rochez Romain Deleu Yves Quinif Vincent Hallet |
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| Institution: | 1. University of Namur—Rue de Bruxelles, Namur, Belgium;2. University of Mons—Rue de Houdain, Mons, Belgium;3. Royal Observatory of Belgium—Avenue Circulaire, Uccle, Belgium;4. Hydrosciences Montpellier—Avenue Professeur Emile Jeanbreau, Montpellier, France;5. Université d'Avignon et des Pays de Vaucluse, UMR 1114 EMMAH—Rue Baruch de Spinoza, Avignon, France |
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| Abstract: | Recharge processes of karst aquifers are difficult to assess given their strong heterogeneity and the poorly known effect of vadose zone on infiltration. However, recharge assessment is crucial for the evaluation of groundwater resources. Moreover, the vulnerability of karst aquifers depends on vadose zone behaviour because it is the place where most contamination takes place. In this work, an in situ experimental approach was performed to identify and quantify flow and storage processes occurring in karst vadose zone. Cave percolation monitoring and dye tracing were used to investigate unsaturated zone hydrological processes. Two flow components (diffuse and quick) were identified and, respectively, account for 66% and 34% of the recharge. Quickflow was found to be the result of bypass phenomenon in vadose zone related to water saturation. We identify the role of epikarst as a shunting area, most of the storage in the vadose zone occurring via the diffuse flow component in low permeability zones. Relationship between rainfall intensity and transit velocity was demonstrated, with 5 times higher velocities for the quick recharge mode than the diffuse mode. Modelling approach with KarstMod software allowed to simulate the hybrid recharge through vadose zone and shows promising chances to properly assess the recharge processes in karst aquifer based on simple physical models. |
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| Keywords: | cave monitoring dye tracing epikarst groundwater recharge karst aquifer stalactite drip vadose zone |
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