Groundwater-flow characterization in a multilayered karst aquifer on the edge of a sedimentary basin in western France

Toulon Springs, located in western France, provides the opportunity to study relationships between two multilayered karst aquifers. Hydrograph and chemograph analysis coupled with principal component analysis (PCA) are used to evaluate groundwater-flow origins on the northern edge of a sedimentary basin. Natural hydrodynamic responses (baseflow recession analysis, auto-cross correlation function) show an important volume of water located in a saturated zone of the Toulon karst system. Significant contrasts in water quality as a function of the hydrological regime (flood, recession, and baseflow regime) and comparison with shallow and deep water show the participation of a deep aquifer supporting the flow of Toulon Springs.