Flood events are major drivers of soil erosion and sediment yield on the Loess Plateau, where extensive ecological restoration has been implemented. This study investigates runoff–sediment dynamics by analyzing 215 flood events recorded in the Chabagou watershed (1959–2022), with a focus on changes under intensifying restoration efforts. Using long-term hydrological and rainfall data, we applied cluster and discriminant analyses to classify flood events based on sediment hysteresis loops and evaluated variations across three management periods (1959–1979, 1980–1999, and 2000–2022), characterized by progressive increases in check dam construction and vegetation recovery. The results show that the floods characterized by short duration, low peak flow, and low sediment concentration were predominant, accounting for 77.7% of the recorded 215 events. A clear decreasing trend was observed, with average sediment yield and peak discharge declining by approximately 68% and 52%, respectively. Anticlockwise hysteresis loops were most common (45.6%), followed by complex (27.9%) and figure-of-eight loops (23.7%). The proportion of figure-of-eight loops increased notably from 17% to 39%, indicating reduced sediment connectivity due to large-scale ecological restoration. Extreme rainfall events consistently produced complex hysteresis patterns, influenced mainly by rainfall intensity but increasingly modulated by human interventions. These results highlight adaptive watershed management strategies that target figure-of-eight and complex flood events to mitigate erosion and flood risks.

A large number of radionuclides, produced by nuclear accidents or nuclear waste, may cause radioactive contamination in the agricultural and aquatic ecosystems. Under these circumstances, it is necessary to optimize the remediation of agricultural areas polluted by radionuclides using innovative monitoring and prediction techniques. To mitigate radioactive contamination in farmland soil and effectively protect groundwater, some measures should be taken against on field investigation, laboratory experiment and model prediction. In this study, the HYDRUS-1D model was used to simulate the vertical migration of 137Cs and 60Co in farmland soil in northern China calibrating by the soil lysimeter experiment, and the scenario simulations of 137Cs and 60Co migration were conducted under different radioactive levels. Results showed that the order of sensitivity in saturated water content (θs), residual water content(θr), saturated hydraulic conductivity(Ks) and distribution coefficient (Kd) applied in HYDRUS 1D model was Kd > θs > θr >Ks. The simulated concentrations ​​of 137Cs and 60Co in Brown soil and Aeolian sandy soil on day 175 and 355 were significantly positively correlated with the measured values​​ (r>0.90, p<0.01). The verification results showed that the predictive values on the 577th day were also significant positive correlated with the measured values ​​(r>0.90, p<0.01). The RMSE, CRM and NRMSE calculating by simulated and measured values ​​of 137Cs and 60Co in soil were very small, indicating that HYDRUS 1D can be used to simulate the migration of radionuclides in farmland soil. Scenarios simulation results revealed that radionuclides were concentrated in the surface layer within 5 cm, but the migration depth has exceed 10 cm soil depth, and even reaches up to 23.5 cm depth at high concentration level. The surface soil should be cleaned timely to protect groundwater with high level from radioactive contamination and further study should be done about horizontal transport and numerical simulation.

Riverine dissolved matter reflects geochemical genesis information, which is vital to understand and manage the water environment in a basin. The Ganjing River located in the hinterland of the Three Gorges Reservoir was systematically investigated to analyze the composition and spatial variation of riverine ions, probe the source and influencing factors, and assess the chemical weathering rates and CO₂ consumption. The results showed that the total dissolved solid value (473.31 ± 154.87 mg/L) with the type of “HCO₃⁻–Ca²⁺” was higher than that of the global rivers’ average. The hydrochemical parameters were relatively stable in the lower reservoir area of the Ganjing River, which was largely influenced by the backwater of Three Gorges Reservoir. The carbonate weathering source contributed 69.63% of TDS (Total dissolved solids), which generally dominated the hydrochemical characteristics. The contribution rates of atmospheric rainfall were relatively low and stable in the basin, with an average of 4.01 ± 1.28%. The average contribution rate of anthropogenic activities was 12.05% in the basin and even up to 27.80% in the lower reservoir area of the Ganjing River, which illustrated that the impoundment of Three Gorges Reservoir had brought great challenges to the water environment in the reservoir bay. The empirical power functions were tentatively proposed to eliminate the dilution effect caused by runoff discharge on the basis of previous studies. Accordingly, the rock weathering rate was calculated as 23.54 t/km² in the Ganjing River Basin, which consumed atmospheric CO₂ with a flux of 6.88 × 10⁵ mol/y/km². These results highlight the geochemical information of tributaries in the hinterland of the Three Gorges Reservoir, have significant implications for understanding the impact of impoundment, and provide data support for the integrated management of water resources in the Ganjing River Basin.