Decoupling the effects of climate, topography, land use, revegetation, and dam construction on streamflow, sediment, total nitrogen and phosphorus in the Yangtze River Basin

Evaluating changes in streamflow, sediment, and nutrient fluxes, as well as quantifying their influencing factors, is crucial for regional water resource protection. While the relationships between major influencing factors and these indicators have been widely studied, the quantitative contributions of the separate and interactive effects of these influencing factors have not been fully explored. This study quantitatively evaluated the changing characteristics of streamflow, sediment discharge, total nitrogen (TN) and total phosphorus (TP), as well as the separate and interactive effects of various major influencing factors such as—rainfall, temperature, evapotranspiration (ET), revegetation, dam construction, and land use change—by applying the GeoDetector method to account for their spatial heterogeneity and contributions. Our findings reveal that the influence of these factors has gradually intensified over time, with dam construction and land use change emerging as the most significant contributors to changes in sediment discharge and TN, respectively. Notably, the interactive effects between dam capacity and vegetation cover on streamflow and sediment discharge was twice as strong as their separate impacts, highlighting the effectiveness of integrating dam construction with reforestation to control erosion and sediment transport. Similarly, the interaction of dam capacity and land use change had a 1.5 times greater impact on TN and TP than their separate effects, indicating that reducing fertilizer application at the source and in the meantime implementing direct interception measures are more effective ways to control water pollution. These findings provide a solid foundation for policymakers to develop integrated water management strategies targeting multiple factors simultaneously, that address both water quantity and quality concerns in the Yangtze River Basin and similar regions.