Yawei Hu

Land-use transformation driven by large-scale water conservancy projects profoundly reshapes regional ecosystem structures and the supply capacity of ecosystem services, yet targeted quantitative assessments linking land-use evolution to ecosystem service values (ESV) in the Xiaolangdi Reservoir resettlement zone remain insufficient, restricting scientific ecological management and territorial spatial governance for reservoir-affected counties and districts. This study draws on the latest ecosystem service valuation theories proposed by domestic and international scholars and applies the value equivalence method to quantify variations in land-use pattern changes and ESV across nine resettlement counties and districts (including the Sanmenxia urban area) affected by the Xiaolangdi Reservoir relocation project. Data collected included historical records (1995–2020), digital elevation models (DEM, 30 m resolution), and land-use information. By applying value equivalence theory and analyzing land-use change impacts, the study calculated changes in ESV and conducted sensitivity analyses across different land types. The findings reveal significant impacts on surrounding counties following the reservoir’s completion. Data indicate that the expansion of water areas drove the total ESV to rise from US$3.3261 billion in 1995 to a peak of US$3.6557 billion in 2010, followed by a decline to US$3.6128 billion in 2020. The most pronounced changes occurred during the first five years post-reservoir filling (2000–2005), marked by elevated water sensitivity indices. This research clarifies the differentiated responses of ecosystem service functions to land-use changes across reservoir-affected counties, provides quantitative decision-making support for coordinated ecological restoration, cultivated land protection, and sustainable land management in the resettlement area of the Xiaolangdi Reservoir, and offers a replicable technical framework for ecosystem service valuation of large sediment-laden river reservoir regions worldwide.

Climate change and anthropogenic activities have substantially altered runoff generation and soil erosion processes. This study investigated the spatiotemporal patterns and influencing factors of the Potential Soil Erosion–Runoff Ratio (PERR), defined as the ratio of RUSLE-derived annual potential soil erosion amount to annual runoff volume, in the mountain–hill–plain transitional of Sanmenxia, China, from 1990 to 2015. Spatial statistical methods were integrated with comparative machine learning and SHAP-based interpretation. Among six candidate models, XGBoost achieved the best predictive performance, with R² values of 0.914 and 0.839 for the temporal and spatial holdout sets, respectively. PERR exhibited marked interannual fluctuations without a statistically significant monotonic trend, while the sequential Mann–Kendall test identified candidate temporal shifts around 1994–1995 and 2014. Spatially, persistent hot spots were concentrated in the southern mountainous and hilly regions, whereas persistent cold spots occurred mainly in the northern plains, revealing a clear geomorphic gradient. Slope, cropland cover, and elevation had the highest mean absolute SHAP values within the fitted model. A pronounced nonlinear transition in the modelled PERR response occurred near a slope of 17°, representing a model-derived and scale-dependent transition range rather than a universal physical threshold. These findings demonstrate the utility of explainable machine learning for identifying spatial heterogeneity and nonlinear controls in the runoff–potential erosion relationship and provide quantitative support for spatially targeted soil and water conservation.

Managed freshwater replenishment is a significant restoration method in the Yellow River Delta. However, their impacts on plankton communities, which are key bioindicators of aquatic ecosystem health and sensitive to the changes in the environment, remain poorly quantified. In this study, we conducted plankton surveys across wetlands subjected to freshwater restoration durations ranging from 5 to 22 years. We assessed shifts in phytoplankton and zooplankton community structure, biomass, diversity, and their relationships with environmental drivers. Results revealed distinct temporal dynamics: phytoplankton biomass and diversity followed a “U-shaped” trajectory (initial decline followed by recovery), while zooplankton biomass decreased but diversity increased with restoration duration. Canonical Correspondence Analysis (CCA) and Partial Least Squares Path Modeling (PLS-PM) identified salinity (Cl⁻, SO₄²⁻) and dissolved nitrate (NO₃⁻) as primary environmental controls for both groups. Cyanobacteria dominated phytoplankton biomass initially but declined with restoration age, while rotifers replaced copepods as the dominant zooplankton taxon over time. These findings demonstrate that freshwater restoration restructures plankton communities through salinity-mediated physiological constraints and altered nutrient availability, with implications for ecosystem function and adaptive management in anthropogenically influenced deltas.

In view of the energy dissipation design of the USBR Type III stilling basin, which is characterized by intense turbulent flow and complex flow patterns, a reliable mathematical model and calculation method is used to track and record the changes of flow parameters during fluid movement. The results of flow movement can be obtained, and the changes to the whole and local parameters of the flow field can be accurately simulated. Using the case of the discharge sluice stilling basin of the flood storage ecological treatment project of Jinchang Industrial Base in Gansu Province, this paper simulates the flow pattern through numerical calculation, thereby saving labor and material costs. The design cycle is also greatly shortened compared with the physical model test, and the technique has good repeatability, controllability, convenient optimization design, and provides technical support and quality assurance for complex energy dissipation problems.

In order to comprehensively evaluate the degree of satisfaction of ecological flow in rivers, an evaluation system was constructed based on the daily average flow, monthly average flow, and the lowest monthly flow data of the Kushui River in Ningxia from 2017 to 2019, including indicators such as flow changes, flow satisfaction at different levels, ecological water demand guarantee, and monthly average ecological water demand suitability, to assess the health status of the Kushui River. The results showed that the minimum runoff of the Guojiaqiao hydrological station in the Kushui River during the dry season was relatively small, with a large gap compared to the annual average daily flow, but the degree of ecological flow guarantee was high, reflecting the seasonal and uneven distribution characteristics of the Kushui River. It is recommended to strengthen the research on the dispatching of water storage reservoirs, rationally allocate water, and gradually improve and improve the sustainable guarantee degree of ecological flow in the Kushui River.

Understanding the patterns of greenhouse gas emissions and the changes in pollution load in terrestrial freshwater systems is crucial for accurately assessing the global carbon cycle and overall greenhouse gas emissions. However, current research often focuses on wetlands and rivers, with few studies on agricultural drainage ditches, which are an important part of the agricultural ecosystem. Investigating the greenhouse gas emission patterns and pollution load changes in agricultural drainage ditches can help accurately assess the greenhouse effect of agricultural systems and improve fertilization measures in farmlands. This study explored the effects of nitrogen input and aeration on the pollution load and greenhouse gas emission processes in paddy field drainage ditches. The results showed that aeration significantly reduced the concentration of ammonium nitrogen (NH₄⁺) in the water, decreased the emissions of nitrous oxide (N₂O) and methane (CH₄), and slightly increased the emission of carbon dioxide (CO₂), resulting in an overall reduction of the global warming potential (GWP) by 34.02%. Nitrogen input significantly increased the concentration of ammonium nitrogen in the water, slightly reduced the emissions of N₂O and CH₄, and increased the CO₂ emissions by 46.60%, thereby increasing the GWP by 15.24%. The drainage ditches reduced the pollution load in both the water and sediment, with the overall GWP downstream being 9.34% lower than upstream.

This paper assesses the sustainability impacts in the middle and lower reaches of the Yellow River in China after the Xiaolangdi Dam was constructed. Based on land use data interpreted from Landsat remote sensing images, covering the time period from 2000 to 2020 at 5-year intervals, this research uses a land dynamic attitude index and comprehensive index of land use degree to reveal the degree of land use type change in the study area and analyze the relationship between land use and social economy. The results show that urban and rural construction land is the land use type with the largest annual change rate, and the increase is most obvious from 2005 to 2010, growing by nearly 900 km². The six types of land use in the research area changed sharply from 2000 to 2010, with grassland and unused land showing the most significant change. On the whole, the dynamic attitude of comprehensive land use tends to be stable. The comprehensive index analysis of land use degree indicates that the study area has developed in the direction of urban settlement. Population and GDP are the main driving factors affecting the constant change in land use types in this region, in which population growth and rapid economic development are the main factors leading to the decline of grassland area, and are also the main driving factors for the expansion of construction land. The research results provide a scientific basis for sustainable land use and development in the middle and lower reaches of the Yellow River Basin.

The removal of nitrogen from water is a consequence of the synergistic action of plant uptake, sediment sorption, and microbial decomposition. However, there is a lack of long-term experimental studies on the effects of each component in the process of nitrogen removal. In this study, we investigated the effect of sediment, plants, and microorganisms on nitrogen removal by setting up three systems: water–sterilized sediment, water–sediment, and water–sediment–plant. The nitrogen removal effect followed the following rank order of effectiveness: the “water–sediment–plant” system > the “water–sediment” system > the “water–sterilized sediment” system. The ditch sediment had a strong enrichment effect for nitrogen. In addition, the migration rate of nitrogen in the sediment with different depths was different. The ammonia-nitrogen migration rate in the sediment showed an increasing trend with time and depth. The nitrate-nitrogen migration process in the sediment showed a trend of enrichment toward the middle layer (15.0–25.0 cm). Aquatic plants and microorganisms can promote the removal of nitrogen in water, with the average purification rates of 13.92% and 19.92%, respectively.

Human activities input a large amount of carbon and nitrogen nutrients into water, resulting in inland freshwater becoming an important source of greenhouse gas (GHG) emissions. Agricultural drainage ditches are the main transport route of non-point source pollution. Understanding the rules for how greenhouse gas emissions from drainage ditches impact the environment can help to accurately estimate the greenhouse effect of agricultural systems. However, current research mainly focuses on the effect of different measures on the migration and transformation process of pollutants in drainage ditches. The process of greenhouse gas emissions when the non-point source of pollution is transported by drainage ditches is still unclear. In this study, the influence of aeration on the pollution load and GHG emission process of a drainage ditch in a paddy field was explored. The following conclusions were drawn: Aeration reduced the content of nitrate nitrogen in the water but had no significant effect on the content of ammonium nitrogen and it reduced the chemical oxygen demand (COD) of water by 24.9%. Aeration increased the potential of hydrogen (PH), dissolved oxygen (DO) and oxidation–reduction potential (ORP) of water and reduced the total organic carbon content, microbial carbon content and soluble carbon content of the soil in the sediment. Aeration reduced the N₂O and CH₄ emission fluxes and increased the CO₂ emission fluxes in the drainage ditch, but it reduced the greenhouse effect generated by the drainage ditch by 33.7%. This study shows that aeration can reduce both the pollution load and the greenhouse gas emission flux in drainage ditches.