Assessment of future eco-hydrological regime and uncertainty under climate changes over an alpine region

The source region of the Yellow River Basin (SYRB) is an alpine region sensitive to climate changes. As global climate change intensifies, it is essential to explore the future hydrological regime alteration and its ecological effects on the basin to provide evidence for water resources management and ecological restoration in the area. This study offers a framework for assessing the future multi-dimensional hydrological regime alteration and its ecological effects. Selected from Global Climate Models (GCMs) that performed well in the Sixth Coupled Model Intercomparison Project (CMIP6), the VIC model was forced by the GCMs after downscaling and bias-correction. Then the hydrological regime alteration and potential ecological effects in the region under SSP126, SSP245, SSP585 future scenarios were systematically assessed by the IHA-RVA system, and the contribution of different uncertainty sources was quantified through the two-way ANOVA. The results indicated that: (1) The temperature and precipitation will increase in the future under all scenarios, while the runoff tends to show a downward trend. By 2015-2100, the flow under SSP126, SSP245 and SSP585 scenarios may vary from-44.7 to 13.0 %,-48.7 to 2.43 %,-53.7 to 4.0 %, respectively, when compared to the reference period (1961-1990). (2) Moderate alterations with RVA = 33 % will be observed in the hydrological regime in the basin under SSP245 and SSP585 scenarios, and low alterations with RVA = 26.7 % under the SSP126 scenario. The spring discharge of the basin will decrease significantly, and the annual extreme flow is projected to decrease, but the frequency of drought and flood events will tend to increase. (3) There are multiple sources of uncertainty in predicting the future hydrological regime in the SYRB. The uncertainty due to the climate model is the dominant factor, fol-lowed by the interaction between emission scenarios and the climate model, and the average contribution to uncertainty of them is 69.5 % and 20.8 % respectively. The uncertainty of emission scenarios is mainly reflected in winter flow, while the climate model mainly affects the summer flow and annual maximum flow, and the uncertainty of interaction between them varies in different periods.