Application of the Vic Model to Predict Streamflow in the Como Creek Watershed, Colorado Front Range

Monday, 15 December 2014
Qinghuan Zhang, University of Colorado at Boulder, Boulder, CO, United States, Mark W Williams, Univ Colorado, Boulder, CO, United States and Rory M Cowie, INSTAAR, Boulder, CO, United States
Mountains are water towers that provide water security to many billions of people. An outstanding question is how climate change may affect surface-groundwater interactions in snow and ice-covered catchments. To address this question, we applied the Variable Infiltration Capacity (VIC) model to the seasonally snow-covered Como Creek watershed to simulate discharge. The results for the years 2005-2008 show that the simulated discharge approximated the measured data in 2008, while the other years have been underestimated. As for the year 2008, sensitivity analysis shows that the correctly simulated discharge depends greatly on soil depth2, depth3 and Ws. For example, a 1% increase in soil depth2, depth3 or Ws leads to 1.3%, 0.8% and 1.3% increases in the Nash-Sutcliffe efficiency (Er). When depth2 and depth3 increased at the same time, Er increased higher than merely depth2 or depth3. The VIC results suggest that 85% of discharge is from groundwater in this snow-covered catchment. End-member mixing analysis using isotopic and geochemical tracers in 2010 showed that groundwater is the main water source for discharge, suggesting that the VIC modeling results are reasonable. The calibration of the VIC model serves as the basis for future projections in discharge after perturbations such as climate change and increases in the magnitude and timing of wildfires.