Background Soil and water loss is serious in the sediment source area of the upper reaches of the Yanhe River. Climate change and human activities are important driving forces affecting the temporal and spatial changes of hydrological processes in the basin. The study of hydrological process and attribution analysis under the influence of climate change and human activities is of great significance for understanding the law of hydrological evolution and formulating soil erosion control plan. It is particularly important for the high-quality development of the basin, the planning and management of soil and water conservation, and the protection of the Yellow River.

Methods Taking Xichuan River Basin in the loess hilly and gully region of northern Shaanxi province as an example, data from hydrological stations and meteorological data shared by websites were collected. M-K test, cumulative anomaly method, coefficient of variation and runoff extreme value ratio were used to analyze the variation trend and evolution characteristics of rainfall, sediment transport and runoff in recent 50 years. The dominant factors driving runoff change in the basin were identified based on Budyko hypothesis, and quantitative attribution research.

Results According to the M-K trend test, the change rate of precipitation in the basin is -0.085 4 mm/a, the test statistic(Z) value is -0.026, and the overall change is not obvious. The Z values of sediment transport and runoff were -3.35 and -2.38, respectively, and the inter-annual variation showed a significant downward trend. The spring flood occurs in March, and the flood season is concentrated in July-September, accounting for more than 50% of the annual runoff. Sediment discharge of decadal swings (the largest coefficient of variation (C_v) value of 0.40-1.18), runoff times (C_v value of 0.21-0.43), the rainfall fluctuation minimum (C_v value of 0.18-0.23). The mutation year was determined according to M-K mutation test and cumulative anomaly curve, and the study period was divided into two periods, 1971-1996 as the base period and 1997-2019 as the change period. Runoff changes are most sensitive to rainfall factors, and human activities are the main reason for the decrease of runoff. Underlying surface change contributed the most, accounting for 69.15%, rainfall contributed 21.99%, and potential evapotranspiration contributed 8.86%.

Conclusions Due to the influence of human activities, the variation of runoff in the Xichuan River Basin in a long time scale shows obvious non-uniformity and trend. In order to minimize soil erosion and reduce the amount of silt entering the Yellow River, relevant organizations have carried out a lot of soil and water conservation work in the region. By emphasizing the process of ecological reclamation and land use structure transformation, we make the assessment of land use/cover change and its hydrological response as the key points of soil and water loss management, and we will strive for comprehensive response part in the future.