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Zusammenfassung:
Limited information exists on the linkages between snowmelt and summer low flow generation in cold region rivers. This study examined the influence of snowpack conditions on low flow during the warm season for a sample of 260 snow-affected pristine river basins in North America. Correlations between summer low flow magnitude and antecedent winter and summer hydroclimate variables showed that the maximum winter snow water equivalent (SWE) influenced summer low flow, with a decreasing influence of SWE throughout summer and significant inter-basin heterogeneity. The sensitivity of low flow to both SWE and summer rainfall was assessed using multivariate hierarchical models which include the effects of catchment attributes. Expectedly, the rainfall accumulated between the snowmelt onset and the low flow period was the dominant control on low flow volumes, but snow storage also had a significant influence. The sensitivity of low flows to SWE was stronger towards higher elevations and weaker in more forested catchments. While snow accumulation and melt are known to be a prime flood generation mechanism in several cold regions, our results also show that snowmelt is an important contributor to low flow discharge in summer via subsurface and groundwater flows. Future depletion of snowpacks in response to climate change could thus exacerbate hydrological droughts in regions with limited summer rainfall.
