Evolution and driving mechanism of runoff in the Han River basin from 1980 to 2020 under changing environments

Recent studies in ecohydrology have focussed on the impact of climate and vegetation changes on runoff. To reveal the hydrological response mechanism under changing environments, this investigation explored the evolution and driving mechanism of Q (the mean annual runoff) in the Han River basin from 1980 to 2020 by combining the Budyko-Porporato-Guswa coupling model and the Soil and Water Assessment Tool (SWAT) model, with scenario analysis and statistical analysis. The results showed that (1) Q was 719.38 mm and showed a fluctuating trend from 1980 to 2020. The spatial distribution was characterised by the largest in the upper Mei River, the second in the Ting River, and the smallest in the lower Mei River and the upper-middle Han River. (2) Q increased with obvious spatial heterogeneity under the impact of climate change and the integrated impact of climate and vegetation changes. (3) Q had the strongest sensitivity to the change in E0, followed by P, and the weakest was vegetation. Q and E0 showed a strong correlation. (4) The principal driver for the change in Q was climate change, and the impact of P was greater than E0. The impact of vegetation variability was the smallest. This paper can serve as a reference for the research of hydrological response to changing environments and an academic foundation for the scheduling of water resources.