A precipitation shift from snow towards rain leads to a decrease in streamflow

In a warming climate, precipitation is less likely to occur as snowfall1,2. A shift from a snow- towards a rain-dominated regime is currently assumed not to influence the mean streamflow significantly 1,3-5. Contradicting the current paradigm, we argue that mean streamflow is likely to reduce for catchments that experience significant reductions in the fraction of precipitation falling as snow. With more than one-sixth of the Earths population depending on meltwater for their water supply3 and ecosystems that can be sensitive to streamflow alterations6, the socio-economic consequences of a reduction in streamflowcan be substantial. By applying the Budykowater balance framework 7 to catchments located throughout the contiguous United Stateswedemonstrate that a higher fraction of precipitation falling as snow is associated with higher mean streamflow, compared to catchments with marginal or no snowfall. Furthermore,we showthat the fraction of each years precipitation falling as snowfall has a significant influence on the annual streamflowwithin individual catchments.This study is limited to introducing these observations; process-based understanding at the catchment scale is not yet provided. Given the importance of streamflow for society, further studies are required to respond to the consequences of a temperature-induced precipitation shift from snow to rain. © 2014 Macmillan Publishers Limited. All rights reserved.