Streamflow response to snow regime shift associated with climate variability in four mountain watersheds in the US Great Basin.

• Streamflow is correlated more strongly with snowfall than with rainfall. • Warming has caused peak flow to occur earlier. • The effects of snowmelt on streamflow is subject to rainfall regulation on soil moisture condition. • Spring rainfall and snowmelt play a dominant role in spring and summer flow generation. • The mechanisms for flow generation in autumn and winter are complex and vary across space. Mountain watersheds serve as important water sources for socioeconomic activities in semiarid and arid regions. This study examined the streamflow response to snow regime shifts associated with climate variability in the US Great Basin. To this end, the coupled hydro-ecological simulation system (CHESS), a process-based and distributed model, was applied to four mountain watersheds in the US Great Basin. Historical weather records for the period of 1961–1990 were used to spin-up model simulations so that the soil water and vegetation reached the equilibrium state under long-term climate conditions; the period of 1991–2015 was selected as the study period. The model evaluation suggested that CHESS was able to simulate major hydrological processes in the four mountain watersheds. In addition, it was found that annual streamflow was more strongly correlated with snowfall than with rainfall during 1991–2015 and increased by 0.62–0.76 mm as snowfall increased by 1 mm in the study regions. Recent regional warming advanced the timing of the peak flow and shifts in the snow regime also affected the intra-annual pattern of the soil moisture content. Seasonally, spring rainfall and snowmelt were dominant factors in generating spring streamflow and summer baseflow. The mechanisms for flow generation were more complex and more variable in the four watersheds in autumn and winter than in spring and summer. On an annual basis, shifts in snowmelt resulting from climate variability accounted for more than 60% of the variability in the annual streamflow, surpassing the contribution of rainfall in the four watersheds. Overall, our results suggest that shifts in the snow regime due to climate variability have important implications for the intra-annual distribution and availability of water resources in semiarid and arid regions of the US Great Basin. [ABSTRACT FROM AUTHOR]