Vise karst system and Thau lagoon (France)
Mechanisms controlling flow reversal at a submarine karst spring
Key findings
- Flow reversal at a submarine karst spring: long-term monitoring provided the first complete observation of an inversac, showing that the Vise can switch abruptly from freshwater discharge to saltwater inflow into the karst aquifer.
- Hydraulic control of the inversac: the reversal is controlled by the hydraulic gradient between the karst aquifer and Thau Lagoon, taking into account the density difference between freshwater and saline water.
- Tipping points and hysteresis: the system has two distinct thresholds: one for the onset of saltwater intrusion and a substantially higher one for recovery. Saltwater filling of the vertical karst conduit creates strong hysteresis, explaining why inversacs can persist for months.
- Modelling and monitoring for water-resource management: combining continuous underwater monitoring, hydrogeological observations and modelling has provided a mechanistic understanding of the inversac and the basis for anticipating and mitigating saltwater intrusion into the Thau karst aquifer.
Jean-Christophe Maréchal, Bernard Ladouche, Claudine Lamotte, Benoit Dewandel, Vivien Hakoun, Pierre Perrochet
Communications Earth \& Environment, vol. 6, 2025 Aug, p. 697
Bernard Ladouche, Jean-Christophe Maréchal, Claudine Lamotte, Vincent Durand, Vincent Bailly-Comte, Vivien Hakoun
Data in Brief, vol. 50, 2023 Oct
