Streamflow and Snow Contribution to the Boulder Creek Watershed under Climate Change (Climate Perturbations?)

Hydrological processes in mountainous watersheds control downstream processes, such as ecosystem interactions and groundwater recharge. The impact of climate change on the water cycle in mountainous regionsparticularly on snow and ice-is non-linear and requires more detailed research to help quantifying uncertainties in projections related to climate forcing. In this study, the VIC model is applied to the 270 km2 Boulder Creek Watershed at Orodell, Colorado, to simulate streamflow amount under a meteorological drought condition, and changes in snow water equivalent. The model parameters were first adjusted using current climatic forcings and streamflow measurements. The Nash-Sutcliffe efficiency (NSE) for streamflow from 2006 to 2010 is 0.77, rootmean-square-error (RMSE) is 0.45, and percent bias is 0.1%, which are within acceptable range. Sensitivity analyses show that the effect of 1℃ increase in temperature is the same as 5% ~7% decrease in precipitation on streamflow. With an increased temperature, the timing of peak flow will appear early. Under the condition of decreased precipitation or increased temperature, values of daily streamflow, runoff efficiency, and snow water equivalent will decrease. Understanding the response of streamflow to precipitation and temperature perturbations is significant in regulating water supply, and maintaining water balance in the mountainous areas under future climate change.   (KEYWORDS:  Boulder Creek, climate change, Variable Infiltration Model,)