Qiang Yan

As the core water source area of the Middle Route of the South-to-North Water Diversion Project, the Danjiangkou Reservoir Area plays a critical role in regional ecological security and water resource security. Its land use transitions and associated ecosystem service dynamics are examined. Based on land use, ecological sensitivity, and ecosystem service value data from 2000 to 2020, this study employed the FLUS model to simulate four scenarios—natural development, cropland protection, ecological protection, and ecological–cropland synergy—for 2050, systematically revealing the characteristics of land use transition, the coupled evolution of ecological sensitivity and ecosystem service value, and the trade-off mechanisms between ecological security and food security under multiple scenarios. The results show that: (1) From 2000 to 2020, land use in the reservoir area exhibited an ecological transition characterized by “two expansions and three contractions”: forestland and water bodies increased by 764.16 km² and 324.36 km², respectively, while cropland and grassland decreased by 664.33 km² and 547.08 km², the comprehensive index of land use degree declined by approximately 1.0%, indicating continuously weakening development intensity. (2) The overall hierarchical structure of ecological sensitivity improved, with the area of highly sensitive zones decreasing from 5201.60 km² to 3729.91 km²; however, the concentration risk of highly sensitive forestland and the unexpected increase in extremely sensitive cropland persisted. (3) Total ecosystem service value increased from CNY 51.92 billion to CNY 58.35 billion (+12.38%), with hydrological regulation contributing 79.83% of the total increment; regulating services remained the core functional type. Sensitivity analysis indicated that the coefficient of sensitivity (CS) values were below 1, confirming the robustness of the findings. (4) Multi-scenario simulations revealed a rigid ecological–food security trade-off: under natural development, ESV increased by 15.44% but cropland loss reached 1033.29 km²; under cropland protection, ESV decreased by 1.50%, the only scenario with negative ecological outcomes; under ecological protection, ESV increased by 16.59% but with the most severe cropland loss (−1072.98 km²); under ecological–cropland synergy, water bodies expanded the most substantially (+562.75 km²) while cropland loss was the most severe (−1118.19 km²), indicating that the synergy goal was not achieved, as gains in regulating services came at the cost of further provisioning services losses. The study confirms the positive effects of ecological land use transition in the reservoir area, while also highlighting the intensifying conflict between ecological protection and food security against the backdrop of ecological improvement.

The ecological consequences of hydraulic engineering on riverine environments have intensified the need for scientifically grounded ecological flow regimes. To ensure habitat suitability during critical fish spawning periods, this study developed habitat preference curves by correlating physiological parameters with key hydro-environmental drivers. A habitat suitability index (HSI) model was established using fuzzy logic, integrated with a genetic algorithm (GA) to simultaneously optimize fuzzy membership functions and inference rules. This model was applied to simulate the relationship between the weighted usable area (WUA) and discharge for various fish egg types in the reach downstream of the Fengman Dam, ultimately facilitating the determination of an optimized ecological pulse flow hydrograph. The results reveal distinct hydro-environmental preference variations among species. Specifically, drifting eggs require specific hatching cycles supported by higher flow magnitudes and velocities. Conversely, adhesive eggs experience a significant reduction in suitable habitat area under high-flow and high-velocity conditions. These findings suggest that reservoir water resource allocation must be tailored to the life-history requirements of target species to maximize spawning success. This study provides a robust scientific framework for eco-friendly reservoir scheduling and the conservation of regulated river ecosystems.

Natural gas hydrate (NGH hereafter), commonly known as combustible ice ((CH₄)n·mH₂O), is an abundant non-conventional clean energy resource. It is mainly located in permafrost areas and submarine sediment layers at depths of 0–200 m and 300~3000 m underwater. Submarine NGH accounts for about 97%. Its commercial mining may be a solution to mankind’s future energy problems, as well as the beginning of a series of geological risks. These risks can be divided into two categories: natural geological hazards and secondary geological accidents. Based on the viewpoints of Earth system science researchers, this paper discusses the main potential geo-hazards of submarine NGH mining: stratum subsidence, seafloor landslides, the greenhouse effect, sand piping, well blowout, and wellbore instability. To minimize the potential catastrophic impacts on the Earth’s ecosystem or mechanical accidents, corresponding technical precautions and policy suggestions have been put forward. Hopefully, this paper will provide a useful reference for the commercial mining of NGH.

Workover operations significantly impact the service life and gas production capacity of coalbed methane (CBM) wells and are crucial for optimizing resource exploitation. To investigate workover operations’ impact on coal seam reservoirs, the authors designed a series of experiments and obtained the following results: (1) The workover operation induced a phase transition in the solid-liquid composition produced by the CBM well, indicating changes in the coal reservoir’s internal structure. (2) During the stable production stage before and after the workover, the proportion of Na⁺, Cl⁻, Ca²⁺, and Total Dissolved Solids (TDS) in the water samples showed a downward trend as a whole, while the HCO₃⁻; after the workover, the Na⁺, Cl⁻, Ca²⁺, and TDS all increased suddenly, while the HCO₃⁻ decreased. (3) While inorganic minerals predominated in the precipitation material during the stable production stage pre-workover, their proportion decreased post-workover, with a noticeable shift in their qualitative composition. (4) It is an indisputable fact that workover operations cause physical and chemical damage to coal seam reservoirs. During workover operation, how to avoid damage and conduct benign reconstruction to the reservoir will be the direction of our future efforts. The experimental results provide valuable insights that can guide the optimization of CBM workover operations and inform the strategic planning of subsequent drainage activities.

Both the demand for agricultural irrigation and the level of water-saving technology in water-scarce regions have met food demand with technological progress and economic growth. There are differences in irrigation water demand drivers in regions with different levels of irrigated agricultural development. However, the relationship between related drivers in response to regional irrigation water demand is not fully understood. This study quantified the driving influence of six indicators, including technological progress, planting structure, water conservation management, economic development, planting scale, and consumption intensity, on agricultural irrigation water demand in JC (Jinchang) and WW (Wuwei), two cities in the Shiyang River Basin, from 2011 to 2020. The results shows that economic development is the main driver of the increase in irrigation water demand, with 29% and 43% driving contributions in JC and WW, respectively. Consumption intensity contributes the most to the decrease in irrigation water demand, with 31% and 23% of driving contribution in JC and WW, respectively. Cropping size has a greater positive drive on irrigation water demand in non-agricultural areas relative to agricultural areas. Planting structure has a more pronounced negative drive on irrigation water demand in agricultural areas relative to non-agricultural areas. In particular, relative to irrigated areas, the proportion of water-saving irrigated areas to the sown areas has a greater impact on changes in irrigation water demand, with a significant rebound effect when it exceeds 80%, so that blindly expanding water-saving irrigated areas will drive an increase in irrigation water demand. The results of this study can provide useful suggestions for agricultural water management in water-scarce areas with different levels of water-saving irrigation development, and realize the sustainable development of agriculture in water-scarce areas.

The medium and long-term demand prediction for water resources is critical to the country’s macro-allocation of water resources and the formulation of a long-term regional economic development strategy. However, the official prediction report of China’s water resources was created ten years ago, and its results are far from accurate in practice making it difficult to direct China’s water resource planning in the coming ten years. By introducing the demand forecasting method for the first time, this study built a mathematical prediction model that integrates “data constraint + mathematical prediction + actuarial prediction”. The conclusions are as follows: (1) The new method developed in this research is more accurate than previous prediction methods and has a higher degree of matching with actual data. Despite the problem of trend extrapolation, this model can accurately understand the long-term trend. However, the amount of data must be calculated. (2) China’s consumption of total water, agricultural water, industrial water, domestic water, and ecological water will predict to be 552.9 billion m³, 319.1 billion m³, 95.7 billion m³, 95.5 billion m³ and 42.6 billion m³ in 2030, respectively, as well as 504.7 billion m³, 281.1 billion m³, 61.4 billion m³, 101.4 billion m³, and 60.8 billion m³ in 2050, respectively, indicating obvious structural changes. (3) China’s industrial structure evolves frequently; therefore, water resource forecasting must account for changes in industrial structure as well as geographical variances. In North China, agricultural water demand will fall, but ecological water investment will rise. The planning and distribution of the nation’s water resources will significantly be influenced theoretically and practically by the development of this methodology study. This method is universal and can be used for long-term prediction of future water demand in other countries.

Research on the enrichment mechanism of lithium in coal can increase its economic value. We applied a series of techniques such as X-ray diffraction and ICP-MS to analyze the coal samples collected in the Bijie area and studied the enrichment mechanism of lithium in coal based on the theory of mineralogy and sedimentology. The results show that (1) the highest abundance of lithium in coal is 222 μg/g, the lowest 33.2 μg/g, and the average 87.05 μg/g. Among them, the abundance of lithium in coal samples from Xinhua coalfield and Wenjiaba coalfield reached 136 and 222 μg/g, respectively, which reached the minimum industrial grade (120 μg/g). (2) Lithium in coal was positively correlated not only with ash (0.46) and clay minerals (0.41) but also with total organic matter (0.38) and volatile matter (0.58) in coal, indicating that lithium in coal in the Bijie area has both inorganic and organic origins. (3) The ratio of TiO₂/Al₂O₃, a geochemical index, shows that the maximum ratio is 0.37, and the average is 0.09, indicating that the metal elements are a product of volcanic eruption, and the paleogeographic environment also shows that igneous rocks are exposed in the western provenance area of this study area. (4) The enrichment of lithium in coal is not closely related to the pure marine environment but is closely related to the marine-land transitional environment. In the past, there was a lack of relevant research on lithium in coal in the Bijie area, and the proposal of organic and inorganic coupling causes is of great significance for the development and utilization of lithium in coal.

Shale gas, with its lower carbon content and pollution potential, is the most promising natural gas resource in China. When modeling the shale gas supply in a specific gas field, it is of paramount importance to determine the gas supply under economic considerations. Two common calculation methods are used in China for this purpose: Method 1 (M1) is the breakeven analysis, where the gas supply is based on the relationship between costs and revenues, while Method 2 (M2) is the Geologic Resource Supply-Demand Model, where the supply relies on demand and price scenarios. No comparisons has been made between these two methods. In this study, the Fuling shale gas field in the Sichuan Basin was chosen as a study case to forecast the shale gas supply using these two different methods. A sensitivity analysis was performed to discuss the influencing factors of each method and error measures were used to compare the different shale gas supply values calculated by each method. The results shows that M1 is more sensitive to initial production, while M2 is more sensitive to gas price. In addition, M2 is more feasible for its simplicity and accuracy at high price scenarios and M1 is considered to be reliable for low price scenarios with profit. This study can provide a quick and comprehensive assessment method for the shale gas supply in China.