Groundwater circulation and mixing inferred from age dating with dissolved gas tracers in a complex Mediterranean karstic and thermal aquifer (Thau lagoon area, Montpellier, France)
| Autor: | Véronique de Montety, Laurie Lemaitre, Bernard Ladouche, Vincent Bailly-Comte, Laïna Pérotin, Marina Hery, Christelle Guilhe-Batiot, Marie-Amélie Pétré, Jean-Luc Seidel |
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| Přispěvatelé: | Hydrosciences Montpellier (HSM), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Université de Montpellier (UM), Laboratoire d'Ecologie Microbienne - UMR 5557 (LEM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Ecole Nationale Vétérinaire de Lyon (ENVL)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre de Géosciences (GEOSCIENCES), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université Montpellier 2 - Sciences et Techniques (UM2) |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | 22nd EGU General Assembly 22nd EGU General Assembly, May 2020, Online, Austria HAL |
| Popis: | Groundwater in coastal area is a strategic but fragile resource since it undergoes high anthropogenic pressure that can lead to saltwater intrusion. Therefore the use of coastal groundwater needs a thorough understanding of the groundwater flow and mixing to assure a suitable management of the resource.The coastal and thermal karstic hydrosystem of the Thau basin (South of France) shows a good example of the pressure that can undergoes coastal groundwater as it is a strategic resource for drinking water, spa activities as well as shellfish aquaculture. In this aquifer, groundwater originates from 3 different naturally sources with contrasted mean residence time (MRT): 1) cold and young karstic water, 2) warm and mineralized thermal waters with long MRT, and 3) marine waters (Thau lagoon and/or seawater). In this context, age dating tracers can be valuable tools for the characterization of the groundwater flow circulations, the estimation of their residence time but also of the mixing which can affect the thermal system.We used dissolved gases (CFCs and SF6) and 3H age dating tracers to characterize the young end-member, as these tracers are particularly suitable for identifying and quantifying water mixing of different ages (Newman et al., 2010). Strategic locations representative of each component of the system (surficial and deep karst, springs and thermal boreholes) were sampled during different hydrogeological contexts (high flow/base flow).The first results show that as expected, in general, the thermal component has a very low level of dissolved gas indicating long MRT and few mixing whereas karstic springs show high contents of dissolved gas. However, some thermal wells show important and variable gas content indicating mixing with the karstic component and rapid circulation in some parts of the system. These data will contribute to determine the groundwater transfer model(s) in the Thau system and to estimate the contribution of the current karst water to the Balaruc thermal system. These results will in turn, be used within the framework of the “Dem’Eaux Thau project” to develop tools for groundwater resources management allowing decision-makers to take on the challenges of this region. |
| Databáze: | OpenAIRE |
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