Hydrological response to future changes in climate and land use/land cover in the Hanjiang River Basin

Climate and land use/land cover (LULC) changes significantly affect Hanjiang River Basin (HRB) hydrology, making it more unpredictable with global warming. Using a patch-generating land-use simulation model, we projected LULC from 2030 to 2100 and applied the VIC model to assess hydrological responses. Then, we quantified the contributions of climate and LULC changes to streamflow at Danjiangkou (DJK) and the basin outlet (OUT), as well as to the water yield in the HRB in four periods: 2021–2040, 2041–2060, 2061–2080, and 2081–2100. The results showed that: (1) the escalating trend of air temperature and precipitation will become more remarkable under the high emissions scenario; (2) the considerable LULC changes include grassland conversion to forests, primarily upstream, and cropland conversion to urban lands, mainly in the middle and downstream areas; (3) under the SSP245 scenario, climate change will decrease streamflow at DJK and OUT by ‒0.67 m3/s and ‒1.21 m3/s, respectively, with annual water yield varying ‒1.26 ~ 2.00 mm/a. Under the SSP585 scenario, the streamflow in DJK and OUT will rise by 1.67 m3/s and 1.62 m3/s, with annual water yield ranging from ‒1.06 to 2.89 mm/a; (4) under SSP245, climate change dominates streamflow variability, and in SSP585, it remains the key driver except for 2041–2060. Moreover, LULC changes also play a decisive role in the water yield of a certain area, and their impact on the basin hydrology cannot be ignored. This work provides a guide for watershed management decision-making, especially carbon emission policies and land-use planning, to enable the better allocation of water resources and addressing water supply risks in the future.