Legacy pumping tests revisited with their complete recovery records: a bounded marsh aquifer, an unidentified late water supply and conditional detectability of inter-aquifer exchange (southern Marais Poitevin, France)

This study re-examines four historical pumping tests conducted in the southern Marais Poitevin (western France) using previously published field data and newly reconstructed recovery records. Derivative analysis, comparative hydrodynamic modelling, Bayesian uncertainty assessment and numerical simulations are used to reassess aquifer properties and hydraulic interactions. The results reveal that the previously reported transmissivity of the Quaternary aquifer was underestimated, identify a nearby no-flow boundary, and show that the source of late-time water supply remains unresolved. Recovery analysis provides local hydraulic conductivity estimates for the confined Upper Oxfordian limestone, while numerical simulations establish conditional detection limits for inter-aquifer leakage. The study also reassesses historical Porchet infiltration measurements and clarifies the limitations of earlier hydrogeological interpretations.