Hydraulic and geochemical impact of occasional saltwater intrusions through a submarine spring in a karst and thermal aquifer (Balaruc peninsula near Montpellier, France)

• DOI: 10.5194/hess-24-5655-2020
• Publication Date: 2020-11-27T06:09:28Z
• Authors: Marie-Amélie Pétré; Bernard Ladouche; Jean-Luc Seidel; Romain Hemelsdaël; Véronique de Montety; Christelle Batiot...; Claudine Lamotte
• Keywords: Saltwater intrusion; Peninsula; Submarine groundwater discharge

Abstract. Submarine springs are a common discharge feature of the karst aquifers along Mediterranean coast. In some instances, occasional and localized saltwater intrusions can occur through submarine spring negatively impact quality groundwater resource. The hydraulic geochemical behaviour discharging into Thau Lagoon just offshore Balaruc peninsula near Montpellier, France, has been characterized to determine impacts such phenomena better understand dynamics regional aquifer improve its management. This work is based on both historical new hydrogeological data, illustrating six intrusion events (from 1967 2014) in area (southern France). Hydraulic perturbation propagated instantly within Balaruc-les-Bains reaches distance about 5 km upgradient 9 d. Comparison heads during seawater 2010 2014 indicates an aggravation phenomenon with increase head variations. contrast, isotopic tracers (87Sr∕86Sr, D/H, 18O∕16O) rare earth elements (REEs) demonstrate that these inversac only observed at local scale but still perceptible several years after event. For example, thermal wells had not recovered their initial state 20 40 months last two (2010 2014, respectively), suggesting legacy this complex system. By adjacent deep compartment located south study affected by distinctly different hydrodynamic behaviour. Overall, constitutes key step understanding karstic will support management