Abstract: Quantitative assessment of the impact of underlying surface changes on water balance components is of great significance for revealing the attribution of runoff changes in the source region of the Yellow River (SRYR). This study simulates the relationship between precipitation and runoff under underlying surface changes, using a variable infiltration capacity (VIC) model considering dynamic land use/cover change (LUCC) and leaf area index (LAI) change. The results show this model improves the simulations of the SRYR hydrological process through considering the dynamic evolution of the underlying surface, achieving a relative error reduction of 8.8% - 12.9%. From 2001 to 2018, the combined effects of LAI and LUCC led to an average annual increase of 15% in plant transpiration, while the runoffs at Maqu and Tangnaihai were decreased by 7.17% and 9.19%, respectively. The impact of LAI on runoff was more significant than that of LUCC. The average annual contributions of LAI to these two runoffs were -4.80% and 4.48%, respectively, while those of LUCC were 0.16% and -3.15%. The study explains the changes in underlying surfaces are the cause of insignificant changes in runoff under increasing precipitation in SRYR, and deepens our understanding of the hydrological responses to climate change and ecological protection.

Key words: variable infiltration capacity model, land cover, leaf area index, source region of the Yellow River, runoff simulation