Factors influencing calibration of a semi-distributed mixed runoff hydrological model: A study on nine small mountain catchments in China

Abstract

Study Region: Nine mountain catchments (5 in northern and 4 in southern China).Study Focus: Flash floods in small mountain catchments are some of the most frequent and most destructive natural disasters of China. Mixed runoff hydrological model is a popular method for flood warning and forecasting. However, the key factors affecting runoff components in hydrological model parameter calibration need to be further studied. In this study, four different overland flow routing techniques are implemented into a semi-distributed mixed runoff hydrological model system (MRHMS), which are the triangle unit hydrograph (TUH), geomorphological instantaneous unit hydrograph (GIUH), geomorphoclimatic instantaneous unit hydrograph (GcIUH) and kinematic wave (KW). MRHMS-KW is the previously developed spatiotemporally-mixed runoff (SKBY) model.New hydrological insights for the region: The study finds that sensitivity parameters of the MRHMS in northern and southern China are related to their main runoff components. Different parameter orders in automatic calibration of MRHMS result in different model performances, and the suggested parameter orders are consistent with the sensitivity of parameters in northern and southern China. Soil moisture and primary runoff components in northern and southern China differ significantly. Only MRHMS-GcIUH can achieve similar performance in northern and southern catchments. MRHMS-GcIUH therefore enhances our understanding of runoff formation mechanisms in the heterogeneous hydroclimatic landscape of China and is a promising tool for a nationwide flood prediction and flood warning system.