Characterising the hydrogeological dynamic of the inertial multi-layered Moulineaux karst system in Dordogne, France, through a multi-method hydrogeological approach

The Moulineaux karst system, located in the Aquitaine Basin in Dordogne, southwestern France, is an inertial multi-layered karst system. Its vauclusian spring provides drinking water to over 50,000 inhabitants in the Périgueux area. This study aims to improve understanding of the hydrodynamic and hydrochemical functioning of the system using a multidisciplinary approach combining continuous monitoring, hydrochemical analyses, and artificial tracer tests. Between 2023 and 2025, 94 samples were collected at the main spring and 209 samples at secondary springs and outlets. Major ions, silica, pesticides, organic carbon and microbiological parameter (coliforms) were analysed, together with high-frequency monitoring of discharge and physico-chemical parameters. Recession analysis, correlation methods and principal component analysis (PCA) were applied to characterize flow dynamics, storage processes and system responses. Results reveal an inertial karst system characterized by long-term storage and dominant delayed flow, with recession coefficients indicative of slow drainage. Correlation analyses highlight variable lag times and a significant system memory, while tracer tests identify the coexistence of rapid flow pathways and diffuse infiltration. The unsaturated zone acts as an overlying cover with an ambivalent role, providing both protection and localized vulnerability to contamination. These findings support a conceptual model of a multi-layered karst system with strongly inertial hydrodynamic and hydrochemical behaviour, offering new insights for the sustainable management of groundwater resources. • A conceptual model developed of the Moulineaux high-inertia karst system. • The unsaturated zone delays pollutant transport and modulates water flow. • Artificial tracers evaluate rapid flow through the inertial karst system. • A robust framework for characterizing recharge in high-inertia karst systems.