Spatial difference analysis of the runoff evolution attribution in the Yellow River Basin

Attribution analysis of runoff evolution under changing environmental conditions is currently a hot yet challenging topic in hydrology research. In this study, the Budyko method was used to quantitatively identify the effects of climate conditions and the underlying surface such as topography, land use and vegetation cover on the runoff changes in the Yellow River Basin during 1961-2018, and to clarify the spatial differences in the sensitivity and attribution of the runoff evolution by dividing the entire basin into sub-basins. The results show that the runoff was more sensitive to the underlying surface and precipitation changes than to the potential evapo-ration. The sensitivity coefficients decreased from upstream to downstream and the aridity index increased. The contribution rates of the climatic and the underlying surface changes to the runoff changes were 10.3-36.8% and 62.9-88.7%, respectively, and the underlying surface changes were the dominant factor causing the decrease in the runoff. Climate change led to increased runoff in the upper reaches and decreased runoff in the middle and lower reaches; while the underlying surface changes led to decreased runoff throughout the entire basin, especially in the middle reaches of the Yellow River. The quantified spatial differences in the runoff evolution attribution can help improve regional water resource management and provide theoretical support for studying the water cycle evolution mechanism in the Yellow River Basin.