Jean-Christophe Maréchal

Hydrogeologist - Fractured and karst aquifers

Fontaine de Nimes karst system (France)


Multi-tracer investigations and modelling revealed the structure and preferential flow paths of the Fontaine de Nîmes karst system. The research demonstrated how groundwater storage can initially attenuate rainfall-runoff, but how aquifer saturation and rapid conduit flow can subsequently amplify flash-flood response. These findings led to a hydrogeological forecasting approach for karst floods.


🆔

Location: the city of Nimes, Occitanie region, France

Elevation: 55 - 120 m a.s.l.

Geology: Cretaceous limestone

Aquifer type: karst aquifer

Scientific question: " What is the role of groundwater during floods "

The Fontaine de Nimes system is part of  SNO Karst and the OZCAR research infrastructure

Location map

Interview with France 3 reporters at the Mazauric Cave (Fontaine-de-Nîmes) monitoring station

Key findings

  • Karst catchment and groundwater flow: hydrogeological investigations and multi-tracer experiments defined the structure and recharge area of the Fontaine de Nîmes system and identified preferential underground flow paths.
  • Groundwater contribution to flash floods: the 2005 events showed that the karst system can rapidly transmit newly infiltrated rainfall to the spring. After an initial rainfall event saturates the aquifer, its remaining storage capacity decreases, increasing runoff and flood response during a subsequent storm.
  • Karst as both buffer and flood amplifier: the aquifer can initially store and attenuate part of the rainfall, but once highly saturated, rapid conduit flow and limited storage can contribute to very rapid flooding.
  • Hydrogeological modelling for flood forecasting: a conceptual and numerical model of the karst response to rainfall was developed and used to create a practical forecasting approach for karst flash floods in Nîmes.

Hydrogeological model

Picture gallery

Scientific collaborations

  • BRGM team: N. Dörfliger, B. Ladouche, V. Bailly-Comte, JB. Charlier, P. Fleury, N. Courtois
  • Associations spéléologique Nîmoise (ASN) team: G. Jouanen
  • SNO Karst network

Related publications

Quantifying water origin of a Mediterranean urban karst aquifer using storm event typology and high-frequency physicochemical signatures


Jean-Baptiste Charlier, Vincent Bailly-Comte, Bernard Ladouche, Jean-Christophe Maréchal

Hydrogeology Journal, 2026 Oct


Comprehensive dataset of continuously monitored hydrodynamic and physico-chemical parameters in various karst systems, France


Guillaume Cinkus, Raphaël Bondu, Mohammed Aliouache, Hervé Jourde, Naomi Mazzilli, Bruno Arfib, Vincent Bailly-Comte, Christelle Batiot-Guilhe, Hélène Celle, Célestine Delbart, Matthieu Fournier, David Labat, Nicolas Peyraube, Marc Steinmann, Danièle Valdès-Lao, Cécile Baudement, Sandra Béranger, Stéphane Binet, Anne Boetsch, Pascal Brunet, Simon Damien Carrière, Konstantinos Chalikakis, Jean-Baptiste Charlier, Yohann Cousquer, Christian Défarge, Joshua Ducasse, Christophe Emblanch, Juliette Fabre, Perrine Fleury, Thibaut Garin, Julien Huon, Abderrahim Jardani, Anne Johannet, Johan Jouves, Nevila Jozja, Lucile Justy, Bernard Ladouche, Thierry Lamarque, Roland Lastennet, Véronique Léonardi, Olivier Lobry, Guillaume Lorette, Christophe Loup, Pierre Marchand, Louis Manière, Jean-Christophe Maréchal, Lucie Martin, Rémi Muller, Nicolas Massei, Fabien Naessens, Chloé Ollivier, Anne Probst, Jean-Luc Seidel, Leïla Serene, Vianney Sivelle, Alexandre Zappelli

Scientific Data, vol. 13, Nature Publishing Group, 2026 Jun, p. 1531


SNO KARST : A French Network of Observatories for the Multidisciplinary Study of Critical Zone Processes in Karst Watersheds and Aquifers


H. Jourde, N. Massei, N. Mazzilli, S. Binet, C. Batiot-Guilhe, D. Labat, M. Steinmann, V. Bailly-Comte, J.L. Seidel, B. Arfib, J.B. Charlier, V. Guinot, A. Jardani, M. Fournier, M. Aliouache, M. Babic, C. Bertrand, P. Brunet, J.F. Boyer, J.P. Bricquet, T. Camboulive, S.D. Carrière, H. Celle-Jeanton, K. Chalikakis, N. Chen, C. Cholet, V. Clauzon, L. Dal Soglio, C. Danquigny, C. Défargue, S. Denimal, C. Emblanch, F. Hernandez, M. Gillon, A. Gutierrez, L. Hidalgo Sanchez, M. Hery, N. Houillon, A. Johannet, J. Jouves, N. Jozja, B. Ladouche, V. Leonardi, G. Lorette, C. Loup, P. Marchand, V. de Montety, R. Muller, C. Ollivier, V. Sivelle, R. Lastennet, N. Lecoq, Jean-Christophe Maréchal, L. Perotin, J. Perrin, M.A. Petre, N. Peyraube, S. Pistre, V. Plagnes, A. Probst, J.L. Probst, R. Simler, V. Stefani, D. Valdes-Lao, S. Viseur, X. Wang

Vadose Zone Journal, vol. 17, Soil Science Society of America, 2018, p. 180094


Karst flash-flood forecasting in the city of Nimes (southern France)


Perrine Fleury, Jean-Christophe Maréchal, Bernard Ladouche

Engineering Geology, vol. 164, 2013 Sep, pp. 26--35


Karst flash flooding in a Mediterranean karst, the example of Fontaine de Nimes


Jean-Christophe Maréchal, Bernard Ladouche, Nathalie Dorfliger

Engineering Geology, vol. 99, 2008, pp. 138--146