Abstract: Studying the impact of future climate change on hydrological processes in the water source areas holds immense significance for the water transfer planning, development, and utilization of the Western Route of the South-to-North Water Diversion Project. We employ predictions from 12 General Circulation Models (GCMs) under four combination scenarios of Shared Socioeconomic Pathways-Representative Concentration Pathways (SSPs-RCPs) to drive the DTVGM model in the purpose of examining how climate change influences streamflow in the three major water source areas of the Western Route Project throughout the 21st century. The findings reveal increasing trends in the annual average temperature, precipitation, and streamflow of the Yalong River basin, Jinsha River basin, and Dadu River basin from 2021 to 2100 under SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios when compared to the base period. Moreover, such increment rises as radiative forcing intensifies, and the changes relative to the base period progressively amplify over time. Specifically, the Jinsha River exhibits greater interannual and decadal variability in streamflow, manifesting a more conspicuous response to climate change compared to the Yalong River and Dadu River. Predictions indicate an upward trend in monthly average streamflow in future, although variations across months are noticeable. In comparison to the base period, variations in streamflow in dry periods are minimal, while increases in wet periods are more substantial. Through correlation analysis of streamflow with temperature, and precipitation, we found that streamflow is more sensitive to precipitation, with an evident impact of precipitation on streamflow. The impact of temperature on streamflow intensifies with the rise of radiative force. The findings offer valuable insights for adapting to climate change and integrated water resource management in the water source areas of the Western Route Project of the South-to-North Water Diversion Project.

Key words: climate change, streamflow change, DTVGM model, CMIP6, water source areas of the Western Route Project