Seasonal shifts in drought characteristics and their drivers in Italian alpine catchments under climate change

Abstract. Drought is an increasingly important hazard in Alpine regions, where snow dynamics strongly influence river flow and support reservoir filling, irrigation, tourism, and ecosystem sustainability. Declining snow and warmer winters, which increase rainfall at the expense of snowfall, are shifting Alpine catchments toward lower-elevation hydrological regimes. This study examines shifts in drought seasonality and drivers in the Adige River basin under future climate conditions. Hydrological simulations for a reference period (1989–2018) and three future horizons (near 2020–2049, mid 2045–2074, and far 2070–2099) under climate scenarios are used to analyse drought drivers, timing, duration, severity, and intensity across catchments of different elevations. Results show that high-elevation catchments progressively shift from snowmelt- and glacier-driven droughts toward rainfall-deficit dominance. Drought peaks exhibit a bimodal pattern, occurring primarily in spring and summer, with summer peaks projected to shift earlier under future warming. Drought severity rises by more than 60% in winter and spring at high elevations, while duration remains stable. These findings highlight the need for adaptation strategies that account for both seasonal and driver-specific responses to sustain Alpine water systems.