Runoff simulation and analysis of water source in the high-altitude and cold region of the Shaliu River Basin

The Shaliu river basin, a small basin in a high-altitude cold region. An improved SWAT model was used to simulate monthly runoff from 1960 to 2022. The snowmelt module was improved using a dual-factor method of temperature and radiation, and the surface runoff module was optimized under the condition of permafrost presence. The period from 1960 to 1964 was used as the model warm-up period, 1965–2000 as the calibration period, and 2001–2022 as the validation period. The study quantified the contributions of different components of the basin to runoff, analyzed the changes in blue and green water, and assessed the contributions of meteorological factors to runoff changes. The study identified CN2, GW_DELAY, SOL_BD, and ESCO as the key parameters affecting annual runoff changes. The improved SWAT model showed better performance in simulating runoff, especially during snowmelt and permafrost periods, with improved R² 0.686 to 0.702), reduced PBIAS (by 4.8 %), and increased NSE (by 0.041) in the calibration period. The snowmelt contribution rate was 6.5 %, peaking in spring, The contribution of snowmelt is decreasing with time and the contribution of baseflow is increasing on time scales. Blue water increased significantly annually, green water decreased slightly, and the green water coefficient decreased. The highest values were observed in August. Spatially, green water was higher in the middle and lower at both ends, blue water was higher upstream, and the green water coefficient was lower upstream. At the basin scale, green water was more abundant than blue water. Precipitation, temperature, and relative humidity were the main factors affecting runoff changes. This study offers a theoretical basis for water resource management in cold-region watersheds. • The improved model has seen a certain degree of enhancement in the simulation. • Precipitation, snowmelt, and groundwater contribute to the runoff by 53.81 %, 8.63 %, and 37.56 %, respectively. • Green water resources were found to be much higher than blue water resources at the basin scale. • The changes in precipitation, average temperature, and relative humidity were identified as the most significant climatic factors affecting the runoff variation in the Shaliu River Basin.