Climate change and land-use policies exacerbate run-off reduction in a semi-arid inland river basin

• Runoff changes at multiple time scales. • Warming and drying trend of climate is the primary reason for the decline in runoff. • Policy measures are one of the important factors in affecting runoff. • Human activities mainly affect runoff during the snowmelt and irrigation periods. Semi-arid regions are characterized by scarce water resources and fragile ecosystems, making them highly sensitive to environmental changes. Assessing the impacts of climate change and human activity on hydrological processes in these areas is crucial for ecological conservation and social development. However, due to data limitations and the complex interactions between climate change and human activities, especially at seasonal scales, accurately quantifying their impacts on hydrological processes poses significant challenges. In the present study, the Budyko framework combined with the elasticity coefficient approach was adopted to assess the contribution of environmental changes to variations in annual and intra-annual runoff in the Xilin River Basin from 1963 to 2020. The results showed that annual runoff exhibited a significant declining trend at a rate of 0.05 mm/a (P < 0.05), with an abrupt change in 2001. The underlying surface characteristic parameters were the most sensitive factors affecting the changes in runoff; however, climate change was identified as the primary cause, accounting for 65.96 % of runoff reduction. Increased temperatures accelerated the melting of ice and snow, such that the highest runoff (36.24 % of the annual total) occurred during April. The impact of human activities on runoff varies across seasons, with the greatest impact observed during the snowmelt season, followed by the irrigation, rainy, and dry seasons, respectively. Based on our findings, we conclude that tailored land-use policies and science-based water management are required to mitigate the impacts of human activities on changes in runoff.