Shifting Snowmelt Regime in a High-Latitude Asian Basin: Insights from the Songhua River Basin

The Songhua River Basin (SRB) in Northeast China is a high-latitude basin experiencing significant snow cover changes under global warming. This study quantified spatiotemporal changes in snowmelt in the SRB (1961–2020). A specific focus was placed on the changes at event scale, including frequency, magnitude and duration, that have been underexplored in previous work. Correlations between snowmelt and key driving factors were assessed to identify the dominant controls governing the melt process. A significant elevation-dependent decreasing trend in annual snowmelt was found over the decades, with the decrease most pronounced at lower elevations. Relative to the baseline period (1961–1990), the snowmelt dates during 1991–2020 advanced, with the 25%, 50%, and 75% cumulative levels occurring 9, 6, and 2 days earlier, respectively. Seasonally, snowmelt increased significantly in early spring (February to March) but decreased notably in late spring (April to May). Snowmelt events exhibited reduced frequency, total volume, peak value, and mean rate, along with fewer extreme events. The strongest correlation across snowmelt event types was found with mean snow depth for complete depletion and with accumulated sunshine duration for incomplete depletion, while Rain-on-Snow Melt events were most closely associated with sunshine and temperature. This study can provide a crucial reference for sustainable water management and spring agricultural irrigation in the SRB.