Winter snow deficit was a harbinger of summer 2022 socio-hydrologic drought in the Po Basin, Italy

Snow in mountainous regions is a key water resource from local to continental scales. However, the link between increasingly frequent snow droughts and socio-hydrologic impacts from headwaters to lowlands is not fully understood. To untangle this relationship, here we combine snow and climate reanalyses with a range of data of terrestrial water storage, streamflow, and emergency water-use restrictions for the archetypal 2022 snow drought in the Po basin (Italy). We find that a persistent high-pressure ridge during winter 2021-2022 translated into a -88% anomaly in peak snow water equivalent, intraseasonal snowmelt, and earlier melt-out dates. Compounded by reduced summer precipitation and importantly increased temperatures, this snow deficit led to the lowest terrestrial water storage on record in summer 2022. Emergency water-use restrictions were concurrent with the peak in snowmelt deficit in early summer, rather than the peak in precipitation deficit in mid-winter. This study highlights the contribution of snowmelt deficit in driving the 2022 socio-hydrologic drought in the Po Basin.

Francesco Avanzi, Francesca Munerol, Massimo Milelli, Simone Gabellani, Christian Massari, Manuela Girotto, Edoardo Cremonese, Marta Galvagno, Giulia Bruno, Umberto Morra di Cella, Lauro Rossi, Marco Altamura, Luca Ferraris