The accurate estimation of sediment flux in naturally confluent rivers remains challenging. In this study, we developed a momentum‐sediment model (MSM) that considers the complex structure of confluent rivers to estimate sediment flux. Trend analyses of annual runoff and sediment flux from 1956 to 2022 were conducted at four hydrological stations in the upper reaches of the Yangtze River Basin: Pingshan, Zhutuo, Cuntan, and Yichang. Runoff change was insignificant, whereas the sediment flux decreased significantly at all four stations. The entire time series was divided into five periods: a reference period (P1: 1956–1984) and four changing periods (P2: 1985–1993; P3: 1994–2002; P4: 2003–2012; and P5: 2013–2022). The hydrological time series of the reference period served as the calibration period for constructing the momentum‐sediment models for Zhutuo, Cuntan, and Yichang stations. The MSM expressions were validated in the four changing periods. The momentum‐sediment models for period P1 at Zhutuo and Cuntan stations could be directly applied in periods P2–P5. The MSM for the Yichang station was improved by incorporating the trapping efficiency of the Three Gorges Reservoir. The simulation results of the MSM for sediment flux outperformed the sediment rating curves and linear relationship, particularly for maximum measured values. The applicability of the MSM was validated in the Jialing River, which is characterized by a small basin area, and the Yellow River, which is known for its scarce water and rich sediments. This confirmed that the MSM was insensitive to watershed scale and hydrological conditions.

As an important soil and water conservation engineering measure, check dams have been constructed on a large scale in the Loess Plateau of China. However, their effects on runoff and sediment processes in the basin are still unclear. In this study, the hydrodynamic processes of the Wangmaogou watershed located in the Loess Plateau were simulated, and the influence of check dams on the flood and erosion dynamic processes in this watershed were also evaluated. The results showed that the check dams obviously reduced the flood peak and flood volume and mitigated the flood process. After the dam system was completed, the flood peak and flood volume were reduced by 65.34% and 58.67%, respectively. The erosion dynamic distribution of the main channel in the small watershed was changed to different extents by the different dam type combinations, and the erosion dynamic parameters of the channel decreased most after the dam system was completed, when the velocity and runoff shear stress of the outlet section were reduced by 10.69% and 31.08%, respectively. Additionally, the benefits of sediment reduction were most obvious after the check dam system was completed, with the sediment discharge in the watershed being reduced by 83.92%. The results of this study would provide specific implications for construction and management of check dams in the Loess plateau.

As the “roof of the world”, the Tibetan Plateau (TP) is a unique geographical unit on Earth. In recent years, vegetation has gradually become a key factor reflecting the ecosystem since it is sensitive to ecological changes especially in arid and semi-arid areas. Based on the normalized difference vegetation index (NDVI) dataset of TP from 2000 to 2015, this study analyzed the characteristics of vegetation variation and the correlation between vegetation change and climatic factors at different time scales, based on a Mann–Kendall trend analyses, the Hurst exponent, and the Pettitt change-point test. The results showed that the vegetation fractional coverage (VFC) generally increased in the past 16 years, with 60.3% of the TP experiencing an increase, of which significant (p < 0.05) increases accounted for 28.79% and were mainly distributed in the north of the TP. Temperature had the largest response with the VFC on the seasonal scale. During the growing season, the correlation between precipitation and sunshine duration with VFC was high (p < 0.05). The change-points of the VFC were mainly distributed in the north of the TP during 2007–2009. Slope and elevation had an impact on the VFC; the areas with large vegetation change are mainly distributed in slopes <20° and elevation of 3000–5000 m. For elevation above 3000–4000 m, the response of the VFC to precipitation and temperature was the strongest. This study provided important information for ecological environment protection and ecosystem degradation on the Tibetan Plateau.