Runoff changes and influencing factors in the Nyang River Basin in Xizang

This study aims to construct a large-scale hydrological Variable Infiltration Capacity (VIC) model based on temperature and precipitation at high altitudes, while elucidating the applicability of the model for hydrological simulation and analyzing the factors affecting runoff volume. Runoff volume and runoff depth were simulated using the VIC model and its performance was evaluated. Meanwhile, the factors affecting runoff volume were analyzed using Spearman correlation. The following model sensitivity parameters were obtained based on the China Natural Runoff Grid Point Dataset (CNRD v1.0): The variable infiltration curve parameter was 0.3, the Dsmax fraction where non-linear baseflow begins was 0.02, the maximum baseflow velocity was 15 mm/d, the maximum soil moisture where non-linear baseflow occurred was 0.7, the second soil moisture layer thickness was 0.3, and the thickness of the third soil moisture layer was 1.5. The surface runoff values in the Nyang River basin were similar in the first and fourth quarters (1.05–2.27 mm and 2.38–4.77 mm, respectively), and the surface runoff values were similar in the second and third quarters when the surface runoff was greater (23.46–52.20 mm and 60.59–85.63 mm, respectively). Watershed area, temperature, and precipitation significantly influenced the amount of runoff from the Nyang River. The applicability of the model to the Nyang River basin was confirmed using two different rate models. In some areas, precipitation and temperature did not have a dominating influence on runoff. Although the VIC model has significant advantages in runoff simulation, it requires a wealth of meteorological, soil, and hydrological data that may be difficult to obtain in some areas.