Snow-dominated watersheds are among the most sensitive environments to climate change. In Quebec, projections indicate that climate change will lead to reduced snow accumulation and more frequent winter rain events. This project aims to observe the hydrological dynamics of an extremely warm winter to better anticipate the impact of climate change on recharge and runoff.

To achieve this, historical data were analyzed for meteorological stations with long time series using both standard and original indexes to determine what made the winter of 2024 extreme in the study area. This analysis showed that two out of three stations recorded their lowest maximum snow depth since 1981. We also observed that that the number of precipitation events during winter were unusually frequent, and that maximum and minimum daily air temperature during winter were higher than average, with values between the 75th and the 100th percentiles of historical data at all the observed stations for both variables.

Local hydro-meteorological data was then examined at the basin scale to explore the interactions between these processes and their hydrological impacts. Findings suggest that the lack of snow led to a shorter frozen ground period and shallower frost depth, a higher annual recharge of the water table, and reduced runoff rates during winter (which was inferred from the watershed winter and spring outflow). As extreme winters are likely to become more frequent due to climate change, it is crucial to better understand the impact of unusual winters and develop methods to capture the nuances of their impact on hydrology.