Impact of seasonal snow on the recharge of a mountain karst aquifer under climate change: the Dévoluy case study (Southern Alps, France)

Abstract. Seasonal snow strongly influences groundwater recharge in mountain aquifers, yet its role in mid-altitude karst systems under climate warming remains poorly quantified. We investigated the Dévoluy karst aquifer (Southern French Alps) to assess how snow controls recharge and how spring discharge may respond to rising temperatures. Using the KarstMod platform, we developed a rainfall-snow-discharge model incorporating a degree-day snow routine to partition precipitation between rainfall and snow, and simulate the snowmelt. The model was calibrated and validated over four contrasting years (two low-snow, one high-snow, and one very high-snow year). Results show that accounting for snow processes is essential to reproduce the observed discharge dynamics, highlighting the dominant role of snow accumulation and melting in controlling both flow timing and magnitude in karst environments. We then tested the sensitivity of the karst spring discharge to temperature perturbations. Under +2 and +4 °C warming scenarios, simulated winter flows increase while snowmelt peaks occur earlier, resulting in earlier and more severe summer low-flow periods. August discharge decreases by 26 % to 42 %, respectively, compared to present conditions. These findings demonstrate the critical role of seasonal snow in regulating recharge in mid-altitude karst aquifers and highlight that ongoing warming will substantially reduce summer water availability in mountain regions.