Sensitivity of Streamflow Response in the Snow-Dominated Sierra Nevada Watershed Using Projected CMIP5 Data

Abstract

The American River basin, a snow-dominated alpine watershed in Northern California, was simulated using the Soil and Water Assessment Tool (SWAT) model to evaluate change in future streamflow characteristics in response to potential climate change. Seven global climate model (GCM) outputs from Phase Five of the Coupled Model Intercomparison Project (CMIP5) were used to generate 5-year (215–264) future climate scenarios. GCM outputs predict an increase in winter precipitation in the watershed and the maximum and minimum daily temperatures to rise by more than 1°C in the fall and spring. Compared to the baseline scenario (1964–214), the results showed that increased winter air temperature reduced the amount of snowfall, which eventually decreased the basin average snowmelt runoff by more than 7%. With the increase in winter rainfall, the mean annual streamflow in the basin increases by 6.7%, but peak streamflow shifts from mid-March to early February. Winter flood frequency as well as summer extreme low flow frequency are projected to increase. Therefore, future challenges in the watershed will be to balance the seasonal effects of climate change.