Sensitivity and uncertainty analysis of the Variable Infiltration Capacity model in the upstream of Heihe River basin

Abstract. The increasing water problems and eco-environmental issues of Heihe River basin have attracted widespread attention. In this research, the VIC (Variable Infiltration Capacity) model was selected to simulate the water cycle of the upstream in Heihe River basin. The GLUE (Generalized Likelihood Uncertainty Estimation) method was used to study the sensitivity of the model parameters and the uncertainty of model outputs. The results showed that the Nash-Sutcliffe efficient coefficient was 0.62 in the calibration period and 0.64 in the validation period. Of the seven elected parameters, Dm (maximum baseflow that can occur from the third soil layer), Ws (fraction of the maximum soil moisture of the third soil layer where non-linear baseflow occurs), and d1 (soil depth of the first soil layer), were very sensitive, especially d1. Observed discharges were almost in the range of the 95% predicted confidence range.