Abstract: BackgroundTo quantitatively analyze the impact of land use change on runoff in the Yuanjiang River Basin, this study aims to examine the evolution of hydrological response units (HRUs) under dynamic land use conditions. It further investigates how these changes influence the hydrological response characteristics of surface runoff.MethodsUsing observed runoff, meteorological, and land use data from 2003 to 2022, this study constructed five phases of the SWAT distributed hydrological model to conduct simulation analyses.Results1)The SWAT model demonstrates strong applicability in the Yuanjiang River Basin. 2)Over the past two decades, the basin’s land use structure has undergone significant changes, primarily characterized by the mutual conversion between cropland and forest land, the continuous expansion of built-up areas, and notable fluctuations in the areas of water bodies, grasslands, and unused land. 3)Correspondingly, the total number of hydrological response units (HRUs) has increased, indicating a growing degree of land fragmentation. Urbanization has been identified as the main driving factor behind the rise in urban HRUs. 4)In addition, the reduction of grassland and the expansion of construction land have both contributed to an increase in surface runoff, while the restoration of forest land has played a mitigating role in this trend.ConclusionThis finding confirms the combined influence of human activities and ecological restoration measures on the watershed’s hydrological cycle. It provides a scientific basis for understanding the hydrological response mechanisms under the interaction between humans and the natural environment.