Quantifying the relative contributions of climate change and human activities to water and sediment variations is of great importance for regional resources and river basin management, which has become a hot topic in hydrology research. In this study, water discharge and sediment load in Xiangxi River basin of Three Gorges Reservoir area were investigated based on hydrometeorological time series since 1960s. The non-parametric Mann-Kendall (M-K) test was used to detect both the trends and abrupt changes in the time series. Double mass curve and sediment rating curve method were used to quantify and evaluate the climatic and anthropogenic effects on water discharge and sediment load. Results indicated that both water discharge and sediment load showed significant decreasing trends with annual decrement rate of –0.08 × 10⁸ and ‒1.011 × 10⁴ t/yr, respectively. The abrupt change points were observed in 1991 for water discharge and 1999 for sediment load by sequential M-K test and cumulative anomaly curve analysis. This study demonstrated that water discharge was mainly influenced by precipitation in 1990s while by human activities ever since 2000, and sediment load was predominantly influenced by human activities (relative contribution 86–98%, regardless of whether the effect is negative or positive). In this study, soil and water conservation as well as land use change were primarily responsible for water and sediment variations in Xiangxi river basin especially since 2000. Further studies need to be done to quantify the importance of a specific driving factor at multi-timescales.

Both vegetation coverage rates and arrangement patterns have important influences on erosion. Very little previous research focuses on the impacts of spatial vegetation distribution patterns on erosion. The slope-gully system was taken as the research object, which is composed of a 5.0 m long hillslope with a slope gradient of 20° and a 3.0 m long gully slope with a gradient of 50°. A series of scouring experiments with two inflow discharges (3.2 L min⁻¹, 5.2 L min⁻¹) was carried out. The effects of the flow discharges, spatial grass arrangement patterns (US, MS, and DS represent the presence of grass covering on up-hillslope, middle-hillslope, and down-hillslope, respectively) and grass coverage rates (0%, 30%, 50%, 70%, and 90%) on runoff and sediment were studied in this paper. The results indicated that either runoff or sediment yielding was significantly decreased with the grass coverage rates increasing and with the variation of grass arrangement patterns on a hillslope. While grass coverage had more effectiveness in controlling erosion compared with runoff reduction, and DS can control erosion more effectively than US and MS erosion controlling. For the gully slope, erosion significantly increased with the grass coverage rates increasing no matter how the grass arrangement patterns on the hillslope. Therefore, both different grass coverage and different grass arrangement patterns have an influence on erosion processes; any research that only takes care of the single factor mentioned above is not enough to reveal the effects of grass on erosion. In the process of erosion control in the Loess Plateau, taking effective measures both on the hillslope and gully slope will be effective methods of reducing soil erosion.

Rainfall erosivity is a key factor to predict soil erosion rate in universal soil loss equation (USLE) and revised USLE (RUSLE). Understanding rainfall erosivity characteristics, especially its spatial distribution and temporal trends, is essential for soil erosion risk assessment and soil conservation planning. In this study, the spatial-temporal variation of rainfall erosivity in the Three Gorges Reservoir Area (TGRA) of China during 1960–2010, at annual and seasonal scales, was explored based on daily rainfall data from 40 stations (26 meteorological stations and 14 hydrologic stations). The Mann–Kendall test and Co–kriging interpolation method were applied to detect the temporal trends and spatial patterns. The results showed that TGRA’s annual rainfall erosivity increased from west, south, and east to the north-central, ranging from 3647.0 to 10884.8 MJ·mm·ha⁻¹·h⁻¹ with an average value of 6108.1 MJ·mm·ha⁻¹·h⁻¹. The spatial distribution of summer and autumn rainfall erosivity was similar to the pattern of annual rainfall erosivity. Summer is the most erosive season among four seasons, accounting for 53% of the total annual rainfall erosivity, and winter is the least erosive season. July is the most erosive month with an average of 1327.3 MJ·mm·ha⁻¹·h⁻¹, and January is the least erosive month. Mean rainfall erosivity was 5969.2 MJ·mm·ha⁻¹·h⁻¹ during 1960–2010, with the lowest value of 3361.0 MJ·mm·ha⁻¹·h⁻¹ in 1966 and highest value of 8896.0 MJ·mm·ha⁻¹·h⁻¹ in 1982. Mann–Kendall test showed that the annual rainfall erosivity did not change significantly across TGRA. Seasonal rainfall erosivity showed a significant decrease in autumn and insignificant decrease in summer and winter. Monthly rainfall erosivity in TGRA showed insignificant increases from Jun to Jul and then underwent decreases from Aug to Nov. and from Dec to Feb and it rose again in Feb reaching a 0.01 level significance. The daily rainfall data of supplemental stations is very useful to interpolate rainfall erosivity map, which could help to find the credible maximum and minimum value of TGRA. In total, the findings could provide useful information both for soil erosion prediction, land management practices, and sediment control project of TGRA.

Understanding how soil microbial communities respond to water-level regulation is critical for predicting ecosystem functioning and water quality in reservoir drawdown zones, yet the mechanisms through which hydrological forcing reorganizes microbial structure and function remain unclear. Here, soil bacterial and fungal communities were investigated across four water-level zones in the Danjiangkou Reservoir, including the long-term submerged zone (LSZ), intermittently flooded zone (IFZ), seasonally drawdown zone (SDZ), and long-term exposed zone (LEZ). By integrating vegetation surveys, soil physicochemical analyses, high-throughput sequencing, and functional prediction, microbial community responses and their environmental controls were systematically assessed. Water level emerged as the dominant driver of soil environmental heterogeneity, characterized by coordinated shifts in soil texture (from sand- to silt-dominated), pH (from alkaline to weakly acidic), and nutrient availability (linear pattern of carbon and nitrogen). From the LSZ to the LEZ, bacterial functional profiles transitioned from anaerobic respiration-dominated pathways under persistent submergence toward aerobic chemoheterotrophic and cellulose-degrading functions with increasing exposure. In contrast, fungal functional strategies shifted from saprotrophic dominance toward symbiotic and pathogen-associated modes, closely tracking changes in vegetation cover and phosphorus availability. Co-occurrence network analyses revealed contrasting interaction patterns between kingdoms, with bacterial networks becoming increasingly competitive, whereas fungal networks become more cooperative toward higher water-level zones. Partial least squares path modeling further showed that bacterial functions were maintained through diversity-dependent buffering under hydrologically controlled soil conditions, whereas fungal functions were primarily regulated by vegetation-associated pathways. Collectively, these findings highlight distinct bacterial and fungal response strategies to water-level regulation and provide a mechanistic basis for ecosystem assessment and management in reservoir drawdown zones.