Characterization of karst systems using SI_c-Pco₂ method coupled with PCA and frequency distribution analysis. Application to karst systems in the Vaucluse county (Southeastern France)

Estimating vulnerability of a karst system to pollution is a major current issue. However, to assess vulnerability, an understanding of the karst system functioning is necessary. The aim of this paper was to characterize the degree of karst network development used by flows (i.e. karst system functioning) to have a better knowledge on the resource and its vulnerability to any possible contamination. This characterization can be done with an analysis of water chemistry emerging from a system. Carbon dioxide partial pressure (Pco₂) and saturation index with respect to calcite (SI_c) are two significant parameters that can be used to study water chemistry of karst systems through calcium-carbonate equilibriums. These enable the implementation of the SI_c–Pco₂ method. In this article, a methodology is proposed based on the SI_c–Pco₂ method coupled with frequency distribution analysis and principal components analysis (PCA). This study considers three karst systems with a developed saturated zone and one epikarst spring, located near the Fontaine de Vaucluse spring (Southeast France). Results show that different water types and flowing conditions in the karst system are identified. From this acquired information, karst network development can be estimated. Finally, results can aid in the vulnerability assessment of karst systems.