Hydrogeochemical assessment and vulnerability analysis of mountain springs in a karstic water system in northeastern Italy

Mountain springs are essential freshwater resources for both communities and ecosystems, but they are increasingly threatened by climate variability and human pressure. This study investigates the vulnerability and recharge dynamics of two springs (LAR and CAN) in the Cansiglio Massif karst system (NE Italy). The novelty of this work lies in applying an integrated hydrogeological, hydrogeochemical, isotopic, and vulnerability-based framework to two springs in the foothills of a main karst system, showing how multiple complementary techniques can support the definition of recharge areas and protection zones even for small sources that remain essential for local water-supply management. Monitoring (September 2018 to September 2021) shows that recharge likely originates from the Mt. Pizzoc area and follows structurally and topographically controlled pathways toward the springs. Results reveal a dual recharge regime: rapid infiltration through fractured and karstified carbonates and coarse slope deposits, and slower, laterally redistributed flow where marly-silty-clayey layers hinder vertical percolation. A simplified water budget constrained the minimum and net recharge areas, while isotope-elevation relationships estimated mean recharge elevations of about 732–879 m a.s.l. for LAR and 617–767 m a.s.l. for CAN. Hydrological patterns and vulnerability indicators show that CAN responds much faster and is far more vulnerable (VESPA V = 14–38.7; MDHT 1–4 days) than LAR (VESPA V = 0.36–0.77; MDHT 9–22 days). By combining multiple approaches, this integrated framework offers practical support for identifying protection priorities, especially in shallow and highly responsive mountain spring catchments.