Sensitivity of river flow regime to snow water storage variability across mid˗latitude region in Eastern Europe

Seasonal snow cover has important implications for water cycles, freshwater ecosystems, and human activities. Despite a number of global studies on the relationship between snow water storage features and streamflow variability, such interdependences remain largely under-exploited, particularly in lowland areas. An open question remains: how are snow metrics and streamflow signatures interconnected over a broad range of variability? Focusing on the mid-latitude region of the Eastern European Lowlands, this study quantitatively explains (1) how cold-season thermal features and snow water storage (SWS) have been changing over recent decades and (2) how these shifts impact spring snowmelt, streamflow features, and baseflow. Here, a 60-year (19612020) snow water equivalent dataset and hydrometeorological observations are used to conceptualize the linkages between a selected set of paired indicators. The streamflow sensitivity to the snow water storage is examined using the elasticity approach. An advance is made by defining the design of the SWS and then deriving synthetic snow and streamflow patterns. The results show that SWS of 9076 mm is accompanied by a snowmelt rate of 4.1 mm/d, causing a streamflow raising rate of 0.1 mm/d and a peak flow of 2.4 mm/d. Conversely, lower SWS of 2062 mm and a snowmelt rate of 0.7 mm/d cause a lower streamflow raising rate of 0.02 mm/d and a peak flow of 0.9 mm/d. Moreover, with reduced SWS, the share of the spring baseflow increases from 47 % to 66 %. These findings advance our understanding of how changing SWS transforms nival river regimes. The vulnerability of a nival river regime to climate change is identified, which might facilitate comparisons across different river basins and regions.