Origin and dynamics of spring flows during flood events inferred from innovative tracers

Abstract : Understanding the dynamics of flow and recharge processes is crucial information for managing water resources. However, this is challenging in heterogeneous systems, e.g. karst, due to the strong spatial variability in flow pathways. In addition, the evolution of mixing at the event-scale is rarely characterized with sufficient details to constrain or validate hydrodynamic models. The objectives of this study were to (1) identify event-scale variations in contributions from different flow pathways to a karst spring, and (2) better constrain the response of spring dynamics to the spatio-temporal variability of flood events. The study focuses on the main spring (Lez spring) of a Mediterranean karst aquifer near Montpellier (SE France), which is subject to intense autumn rainfall events. We used innovations in (1) the continuous and high frequency monitoring of tracers (delta18O, delta2H, and natural fluorescence+ humic and proteic-like compounds), and (2) the types of tracers monitored (natural and anthropogenic dissolved gases, radon and radium isotopes, 3D-fluorescence and total organic carbon). Three rainfall events highlighted distinct spring chemical responses. The first event was characterized by a contribution of deep groundwater flow (low CFC contents, low (228Ra 226Ra) ratios and low organic carbon concentrations) resulting from a piston flow effect due to heavy rainfalls at the basin margins. The second event showed a proteic peak associated with a sharp decline in DO concentrations and an anomalous peak in delta18O. The third event was characterized by a dilution effect by subsurface waters (CFC contamination, high turbidity and radon peak) due to high local rainfall. The simultaneous monitoring of these tracers during multiple rainfall events provides an innovative approach in spring dynamics analysis, and improves our understanding of a complex hydrogeological system. The Lez spring supplies drinking water for Montpellier, therefore understanding the variability of water origins and potential contamination pathways during intense storm events is essential.
Type de document :
Communication dans un congrès
Liste complète des métadonnées

https://hal.umontpellier.fr/hal-02122794
Contributeur : Pascale Roussel <>
Soumis le : mardi 7 mai 2019 - 15:19:57
Dernière modification le : mardi 28 mai 2019 - 13:48:10

Identifiants

  • HAL Id : hal-02122794, version 1

Citation

Véronique de Montety, Sarah Tweed, Arnold Molina Porras, Jean Luc Seidel, Christelle Batiot-Guilhe, et al.. Origin and dynamics of spring flows during flood events inferred from innovative tracers. 43rd IAH International Congress “Groundwater and society : 60 years of IAH”, Sep 2016, Montpellier, France. ⟨hal-02122794⟩

Partager

Métriques

Consultations de la notice

27