Hydrological simulation and runoff components analysis in the high cold alpine region: case study in the upper reaches of the Parlung Zangbo watershed of the Yarlung Zangbo River basin

Runoff components in high cold alpine region were investigated in the Parlung Zangbo basin．The multi-objective calibration methods such as monthly flow, remote sensing snow area data and measured glacier runoff data were used to calibrate model instead of only using streamflow data．Both hydrological simulation and runoff analysis were carried out based on SPHY (Spatial Processes in Hydrology) hydrological model, to improve overall simulation quality．Nash–Sutcliffe coefficient of efficiency in calibration and validation periods were found to be 0.95 and 0.94, respectively．The model had a good applicability．Rainfall runoff, snow runoff, glacier runoff and base flow were the sources of runoff, accounting for 10%, 25%, 45% and 20% of the total, respectively．Glacier melt water and snow melt water were the most important sources．On a monthly scale, glacier runoff accounted for the largest proportion from July to August, snowmelt runoff accounted for the largest proportion from April to June, and rainfall runoff accounted for the smallest proportion．Glacier runoff accounted for the highest proportion, which could provide more water resources to ensure social and economic development in the short term. In the long term, glacier runoff would gradually decrease, resulting in water shortage．Therefore, the local government needs to improve strategies to deal with potential risks of runoff changes．