The role of porous matrix in water flow regulation within a karst unsaturated zone: an integrated hydrogeophysical approach

Carrière, Simon D.; Chalikakis, Konstantinos; Danquigny, Charles; Davi, Hendrik; Mazzilli, Naomi; Ollivier, Chloé; Emblanch, Christophe

The role of porous matrix in water flow regulation within a karst unsaturated zone: an integrated hydrogeophysical approach | Le rôle de la matrice poreuse dans la régulation des flux d'eau dans la zone non saturée du karst: une approche hydrogéophysique intégrée El papel de la matriz porosa en la regulación del flujo de agua dentro de la zona no saturada en un karst: un enfoque hidrogeofísico integrado 岩溶非饱和带内多孔基体在水流调解中的作用:一种综合的水文地球物理方法 O papel da matriz porosa na regulação do fluxo de água dentro da uma zona não saturada cárstica: uma abordagem hidrogeofísica integrada

2016

Some portions of the porous rock matrix in the karst unsaturated zone (UZ) can contain large volumes of water and play a major role in water flow regulation. The essential results are presented of a local-scale study conducted in 2011 and 2012 above the Low Noise Underground Laboratory (LSBB – Laboratoire Souterrain à Bas Bruit) at Rustrel, southeastern France. Previous research revealed the geological structure and water-related features of the study site and illustrated the feasibility of specific hydrogeophysical measurements. In this study, the focus is on hydrodynamics at the seasonal and event timescales. Magnetic resonance sounding (MRS) measured a high water content (more than 10 %) in a large volume of rock. This large volume of water cannot be stored in fractures and conduits within the UZ. MRS was also used to measure the seasonal variation of water stored in the karst UZ. A process-based model was developed to simulate the effect of vegetation on groundwater recharge dynamics. In addition, electrical resistivity tomography (ERT) monitoring was used to assess preferential water pathways during a rain event. This study demonstrates the major influence of water flow within the porous rock matrix on the UZ hydrogeological functioning at both the local (LSBB) and regional (Fontaine de Vaucluse) scales. By taking into account the role of the porous matrix in water flow regulation, these findings may significantly improve karst groundwater hydrodynamic modelling, exploitation, and sustainable management.

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