Usual conceptual models of karst hydrodynamics highlight the important role of unsaturated subsystems in recharge repartition. However, few of them have been compared with scarce suitable physically-based numerical models. Hybrid models that couple single continuum medium with discrete features promise an improved consideration of karst specificities. Here we evaluate their capability to properly reproduce interactions between a vertical conduit and the surrounding unsaturated matrix. We simulate the response of such a configuration to a single recharge event for various sets of parameters. We show the ability of hybrid models to reproduce the most significant behaviors described in the literature, i.e., transient storage and distribution of recharge, flow concentration towards conduits in the epikarst, and matrix-conduit exchanges varying in time and space. In addition to the explicit conduits, simulating variably saturated flows with the Richards equation and distinguishing the epikarst and the transmission zone are key elements to reproduce most processes. The contrasts between subsystems necessary to observe desired behaviors have been quantified. They are reinforced by the varying matrix saturation that causes realistic competition between matrix and explicit conduits. The study also highlights the need to deepen knowledge of the scaled medium properties we need to know to apply such models to actual cases.
20Geological and hydrological data collected at the Terrieu experimental site 21 north of Montpellier, in a confined carbonate aquifer indicates that both fracture 22 clusters and a major bedding plane form the main flow paths of this highly 23 heterogeneous karst aquifer. However, characterising the geometry and spatial 24 location of the main flow channels and estimating their flow properties remain 25 difficult. These challenges can be addressed by solving an inverse problem using the 26 available hydraulic head data recorded during a set of interference pumping tests.
27We first constructed a 2D equivalent porous medium model to represent the test analytical interpretations of pumping tests, were also added to the inversion models.
40In addition, the efficiency of the adopted inverse algorithm enables us to increase
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