[Objective] Developing an ecological security pattern plays a crucial role in ensuring regional ecological security, species survival, and information exchange, thereby providing strong support for sustainable development across natural, social, and economic dimensions. [Methods] The InVEST model was employed to simulate various ecosystem services in Beijing, and the simulation result were quantitatively analyzed. Additionally, Morphological Spatial Pattern Analysis(MSPA) analysis, the Minimum Cumulative Resistance(MCR) model, and circuit theory were integrated to develop an ecological security pattern for Beijing, providing a scientific basis for policy making. [Results] The result showed that high-value patches for water conservation, soil retention, carbon storage, water purification, and habitat quality covered areas of 1 984.59 km², 617.61 km², 8 041.22 km², 8 638.69 km², and 930.70 km², respectively, accounting for 12.09%, 3.76%, 49.00%, 52.64%, and 5.67% of the study area. These high-value patches were primarily located in the mountainous areas of western and northern Beijing. The ecological security pattern of Beijing was composed of 21 ecological sources, 46 ecological corridors, and 1 ecological pinch point. The total area of ecological sources covered 1 220.83 km², accounting for 7.45% of Beijing's total area, while the total length of ecological corridors extended to 1 003.78 km. [Conclusion] The ecological sources in Beijing are mainly distributed in the western and northern mountainous areas. Future efforts of ecological conservation are essential to further expand the area of ecological sources and enhance habitat quality.

[Objective] The coordination strategy between ecological operations of the Three Gorges Reservoir(TGR) to promote the natural spawning of the Four Major Chinese Carps and other comprehensive utilization demands has yet to be clearly defined. To clarify the constraints of ecological operations and propose coordination strategies between ecological operations and other comprehensive utilization demands, [Methods] past ecological operation experiments, operation regulations and operation practice of the TGR are summarized. Additionally, the impacts of conducting ecological operations during the concentrated falling stage and the flood stage on other comprehensive utilization demands have been quantitatively analyzed. [Results] The result show that, ecological operations during the per-flood falling stage will result in water abandonment at Gezhouba Dam in 47.3% of years and water level daily decrease of the TGR exceeding 1 m in 47.3% of the years. The risk of water abandonment at Gezhouba Dam and water level daily decrease of the TGR exceeding 1 meter will be significantly mitigated by raising the water level of the TGR on June 10th or lowering it on May 25th. Water demand of the ecological operations in mid-June and late June during flood stage can not be satisfied under the typical year of P=90%. [Conclusion] Conclusion can be drawn as follows: if ecological operations were conducted during the pre-flood falling stage, there would be no constraints on water quantity and no impact on flood control, water supply, and navigation. However, there would be risks associated with water abandonment at Gezhouba Dam and water level daily decrease of the TGR exceeding 1 m. Conducting ecological operation during flood stage is mainly subject to water constraints, while flood control risks remain manageable. Considering ecological operations, optimal operational rules for the TGR can be formulated as follows: in years with relatively abundant inflow forecasts, the reservoir level can be preemptively lowered the water level by May 25th. Conversely, the water level on June 10th can be further raised to 150.0 m in years with deficient inflow forecasts.

[Objective] The Taihu Lake Basin is a highly developed economic region in China and a typical area with prominent imbalance between supply and demand of water resources. The aim is to estimate the multi-year average surface water resources in the Taihu Lake Basin based on its geographical distribution, underlying surface types, and hydrometeorological conditions. [Methods] A zonal coupling modeling method was proposed, dividing the basin into the upstream hilly area and the middle-lower plain area. The Xin'anjiang three-source model and the runoff generation and concentration method based on underlying surface classification were used respectively to estimate the surface water resources from 1956 to 2020. The reliability of the result was verified through reservoir runoff simulation and a one-dimensional hydrodynamic model. [Results] The result showed that in the upstream hilly area, runoff simulation achieved an average coefficient of determination of 0.76, with relative errors controlled within ±7%. In the middle-lower plain area, water level simulation yielded an average coefficient of determination of 0.88, with better fitting performance in wet years. The model estimated the multi-year average surface water resources at 17.854 billion m³, which was 10.6% higher than the 16.15 billion m³ reported in the Second National Water Resources Survey and Assessment and 2.1% higher than the 17.481 billion m³ average in the water resources bulletins from 2006 to 2020. [Conclusion] The zonal coupling model demonstrates good applicability and reliability for estimating surface water resources in the Taihu Lake Basin. Differences between the model result and the “Second Survey” result primarily stem from the extended rainfall series, optimized runoff estimation method in the western lake area, and underlying surface changes. Future research should consider developing dynamic parameterization schemes to improve the model's estimation capabilities.

[Objective] Accurate landslide susceptibility results enable precise prevention and control of landslide hazards and risks. In landslide susceptibility evaluation, selection methods for different landslide negative samples represent a critical uncertainty factor that affects the prediction accuracy of landslide susceptibility. [Methods] Taking the mountainous area of the Minjiang River basin in Sichuan Province as the study area, data on 881 large landslides(>106 m³) were compiled through remote sensing imagery. Thirteen landslide evaluation factors including topography and geomorphology, basic geology, hydrogeology, geological environment, seismic parameters, and human activities were selected, and factor redundancy was examined through collinearity analysis. Subsequently, landslide negative samples were selected using random sampling across the study area, sampling in slope zones below 10°, sampling in areas outside 1 km buffer zones around landslides, Information Value(IV) method, Support Vector Machine(SVM) method, and semi-supervised method, with the same proportion as landslide positive samples. These negative samples were further coupled with the Random Forest(RF) to establish Random RF, Low-Slope RF, Buffer RF, IV-RF, SVM-RF, and Semi-Supervised RF models for landslide susceptibility zoning. Finally, the prediction accuracy of different sampling models for landslide negative samples was compared and evaluated using the mean Area Under the Curve(AUC) value derived from the Receiver Operating Characteristic(ROC) curve. [Results] The results showed that:(1) the high and extremely high landslide susceptibility zones obtained by different sampling methods for landslide negative samples were predominantly concentrated on both sides of the river valleys from Wolong to Yingxiu, Miansi to Gu'ergou, Heihu to Musu, and Diexi to Songpan.(2) The prediction accuracy of landslide susceptibility using different sampling methods for landslide negative samples ranked as follows: Semi-Supervised RF ($\overline{A U C}=0.971$)>SVM-RF($\overline{A U C}=0.954$)>IV-RF($\overline{A U C}=0.945$)>Buffer RF($\overline{A U C}=0.902$)>Low-Slope RF($\overline{A U C}=0.895$)>Random RF($\overline{A U C}=0.882$). (3) The selection of landslide negative samples in low-susceptibility areas significantly enhanced the prediction accuracy of susceptibility. Compared to Random RF model, the values of the Low-Slope RF, Buffer RF, IV-RF, SVM-RF, and Semi-Supervised RF models increased by 0.013, 0.02, 0.063, 0.072, and 0.089, respectively. [Conclusion] The Semi-Supervised RF model exhibits the smallest standard deviation(0.004) and the highest mean AUC value(0.971), demonstrating optimal stability and prediction capability. This indicates that the semi-supervised sampling method offers the best optimization for the model. These research findings provide references for selecting landslide negative samples and establishing models in landslide susceptibility prediction, while offering theoretical support for landslide risk assessment and disaster mitigation strategies in the upper Minjiang River Basin.

[Objective] The statistical survey on flood disasters is an important basis for regional disaster prevention, reduction and flood risk management under changing environmental conditions. The large language model(LLM) has shown potential in the field of hydraulic engineering. In order to utilize the capabilities of LLMs on semantic understanding and information extraction, the LLM-based method of statistical survey on flood disasters is proposed. All procedures of the statistical survey based on Internet data are completed by the LLM. [Methods] For the flood disasters on 21 July 2012 in Beijing(“7·21”), July 2023 in Beijing(“23·7”), on June 2022 in Pearl River Basin(“22·6”) and April 2024 in Southern China(“24·4”), the proposed LLM-based method is used to investigate the risk and loss. [Results] The accuracy of the statistical survey is the highest when the temperature of the LLM is 0 and decreases as the temperature increases. For the “7·21” flood disaster, the accuracy of the number of collapsed dwellings, the affected population and the direct economic losses is more than 90%. The proportion of no retrieved result of affected cropland area and peak discharge is more than 40%. For the “23·7” flood disaster, the accuracy is generally higher. The accuracy of the number of collapsed dwellings, the number of deaths and missing persons, the affected population, the affected cropland area and the peak discharge is more than 90%. For the “24·6” flood disaster in the Beijiang river basin, the accuracy of the maximum hourly precipitation, the average precipitation and the peak discharge is 83%, 61% and more than 90%. For the “22·4” flood disaster, the accuracy of the peak discharge at Shijiao station is 89%. the proportion of no retrieved result of the peak discharge at Feilaixia reservoir, the maximum hourly precipitation and the average precipitation exceeds 70%. [Conclusion] The LLM is suitable for the statistical survey of flood disasters and can provide data support for the management of flood and drought disasters.

[Objective] Under the background of rapid urbanization, the frequent occurrence of extreme weather events has led to the intensification of urban road flooding, which has led to vehicle instability, brake failure and other traffic safety problems that are becoming more and more prominent. The study of vehicle instability risk thresholds in flooded water is of great theoretical value and practical significance in the field of flood risk assessment and emergency management. [Methods] The friction coefficients of new and old wheels under different road conditions(dry, wet, and waterlogged) and different loads were investigated experimentally. Taking the Volkswagen Polo as the research object, the rotary bearing and three-axis attitude sensor were used to adjust the direction of the vehicle to meet the flow, and the mechanical sensors and data collector were used to measure the force of the water flow on the vehicle under different water depths and flow rates, so as to reveal the mechanism of the vehicle's destabilization. [Results] The results show that the coefficient of friction μ ranges from 0.320 to 0.898, the coefficient of friction of asphalt pavement with the same wheels is larger than that of cement pavement, and the condition of coefficient of friction under the same pavement condition is as follows: wet condition > dry condition > waterlogged condition, and the coefficient of friction of the new tires is generally larger than that of the old tires. For non-sealed vehicles, when the water depth is greater than 0.45 m, the buoyancy of the car gradually decreases until it sinks to the bottom, and under the same water depth conditions, the buoyancy shows a decreasing trend with the increase of flow velocity. The flow resistance F_D and transverse force F_T of the car increased with the increase of flow velocity and water depth, and the coefficient of flow resistance C_D of the car in different flow directions(0°~180°) ranged from 0.466 to 1.067, and the coefficient of transverse force C_T ranged from 0 to 0.407. [Conclusion] The car is most easily destabilized at 90° in the head-on direction and most difficult to destabilize at 0°. Adopting the bottom line thinking, the friction coefficient is taken as 0.320, and when the product of flow velocity and water depth hυ_min is greater than 0.81 m²·s^-1, the car slides and destabilizes. And fitted curves for the relationship between the critical flow rate threshold for instability and water depth for different headwater directions. The results of the study can provide key parameter support for the development of vehicle instability early warning system, and at the same time, provide scientific basis for the optimization of urban road drainage performance evaluation standard.

[Objective] Water conservancy plays a critical role in “dual carbon” strategy. Exploring the carbon reduction potential of water conservancy measures is essential for promoting the optimization of energy structure and achieving carbon neutrality. [Methods] Based on the LEAP model and combined with economic and social development policies, scenario analysis was adopted to establish the baseline, emission reduction, and enhanced emission reduction scenarios. By employing five emission reduction measures—increasing the proportion of hydroelectric power generation, expanding geothermal water utilization, enhancing blue carbon ecosystem carbon sinks, promoting water conservation in residential and industrial sectors—the study predicted and analyzed carbon emissions and the contribution of water conservancy measures to carbon reduction under each scenario in Hebei Province from 2025 to 2060. [Results] The result showed that under the baseline scenario, Hebei Province's total carbon emissions would reach 890.54 MtCO_2e by 2060, with no peak observed during this period. Under the emission reduction scenario, annual carbon emissions would decrease compared to the baseline, but the overall trend would remain the same. Under the enhanced emission reduction scenario, carbon emissions would peak at 837.12 MtCO_2e in 2030 and decrease to 831.46 MtCO_2e by 2060. The carbon reduction potential of water conservancy measures would reach 59.08 MtCO_2e, accounting for 6.63% of total carbon emissions. In terms of emission reduction contribution, increasing the proportion of hydroelectric power generation and expanding the use of geothermal resources were the most effective water conservancy measures, contributing nearly 90% of the total carbon reduction. Although the contributions of blue carbon ecosystem carbon sinks and water-saving measures were relatively small, they still played a positive role in emission reduction. [Conclusion] The result indicate that water conservancy measures have significant carbon reduction potential in achieving the “dual carbon” goals in Hebei Province. In the future, water conservancy measures should be further optimized, particularly by strengthening the development and utilization of hydroelectric power and geothermal resources, while also promoting blue carbon ecosystems and water-saving measures to maximize their role in carbon reduction. Additionally, the effective coordination of these measures in both time and space, through systematic and coordinated operations, is essential to achieve the expected emission reduction outcomes. This study provides reference for Hebei Province to fully leverage the carbon reduction role of the water conservancy sector and achieve the “dual carbon” goals as early as possible.

[Objective] Designing rainfall patterns serves as a crucial component in calculating design floods for ungauged basins, significantly influencing peak flow rates and temporal distribution of design floods. Given the impacts of climate change, existing rainfall patterns may alter, necessitating the extension of hydrology data to further investigate these changes. [Methods] This study adopts the Mann-Kendall trend test and fuzzy clustering soft partition method, selecting 12 rainfall stations within four typical watersheds in Guangdong Province, focusing on their annual maximum 24-hour and 72-hour rainfall processes. Based on an index system, a fuzzy equivalence matrix is constructed, and the design rainfall patterns under different durations are derived using fuzzy clustering. [Results] The results indicate that annual maximum 24-hour and 72-hour rainfall in the Dongguan River Basin exhibits an increasing trend, with Baimang meteorological station showing the highest rate of change at 0.96 mm/a for annual maximum 24-hour rainfall. Conversely, a decreasing trend is observed in the Rongjiang North River Basin, with Fukou meteorological station experiencing a rate of change of-1.25 mm/a for annual maximum 72-hour rainfall. Furthermore, the design rainfall patterns in all typical basins exhibit composite peak characteristics, with no significant difference in the proportion of the main rain peak in total rainfall. The primary difference lies in the temporal distribution of rainfall. [Conclusion] Compared with the design rainfall patterns outlined in the “Rainstorm Runoff Calculation Chart Manual of Guangdong Province”, the control period of the main peak was shifted. This research not only provides valuable references for design flood calculations in typical watersheds but also offers insights into the study of rainstorm patterns in ungauged regions.

[Objective] Improving the accuracy of groundwater level time series prediction is of great significance for scientifically predicting the change trends of groundwater levels and ensuring the rational development and utilization of groundwater resources. The aim is to improve the accuracy of groundwater level time series prediction and address the issues of large computational scale and high complexity in data decomposition-based combination time series prediction models. [Methods] A WPT-decomposed IWO/FPA/TGA/SFO/CPA/DO/IVYA/AO/MGO/LEA-RELM prediction model was proposed, combining Regularized Extreme Learning Machine(RELM) with ten “plant” optimization algorithms, including Wavelet Packet Decomposition(WPT), Invasive Weed Optimization(IWO), Flower Pollination Algorithm(FPA), Tree Growth Algorithm(TGA), Sunflower Optimization(SFO), Carnivorous Plant Algorithm(CPA), Dandelion Optimization(DO), Ivy Algorithm(IVYA), Artemisinin Optimization(AO), Moss Growth Optimization(MGO), and Lotus Effect Optimization Algorithm(LEA). This model was validated using groundwater level time series prediction examples from six locations in Yunnan Province, including Xicheng, Nanzhuang, Lin'an, Wenlan, Zhelinzhai, and Botanical Garden. First, the example's groundwater level time series were decomposed into trend and fluctuation components using one-level WPT. Based on these components, a RELM hyperparameter optimization objective function for the example was established. Then, the ten “plant” algorithms were used to optimize the objective function to determine the best hyperparameters. Finally, the optimal hyperparameters were used to establish IWO/FPA/TGA/SFO/CPA/DO/IVYA/AO/MGO/LEA-RELM models to predict and reconstruct the trend and fluctuation components of the example's groundwater level time series. [Results] The result showed that IVYA, CPA, and FPA outperformed IWO, AO, SFO, DO in optimization performance, and significantly outperformed LEA, MGO, and TGA. The IVYA-RELM, CPA-RELM, and FPA-RELM models achieved a MEAn absolute percentage error(MAPE) of 0.003 0% to 0.000 4%, a MEA absolute error(MAE) of 0.038 9 m to 0.006 3 m, and a coefficient of determination(DC) of 0.997 7 to 0.999 8, which outperformed other comparison models and demonstrated excellent prediction performance. [Conclusion] The result indicate that the optimization performance of the ten “plant” algorithms is highly consistent with the fitting and prediction accuracy rankings of the ten combined models. Overall, the stronger the optimization ability of the algorithms, the higher the fitting and prediction accuracy, and the better the performance of the combined models. The WPT decomposition, with fewer components and strong regularity, is a simple and efficient decomposition method.

[Objective] The water-air coupling and its simulation method have long been recognized as a scientific challenge in the hydraulics of long-distance pressurized water conveyance pipelines. Comparing the performance of different water-air two-phase flow models in simulating the water-air coupling is essential for investigating the evolution and migration process of trapped air mass in long-distance pressurized water pipelines. [Methods] Three water-air two-phase flow models, VOF, CLSVOF, and CFD-PBM, were used to simulate transient flow scenarios of water flow impacting trapped air mass at pipeline dead end. A comparative analysis was conducted based on the transient pressure variations and morphological variations of the air mass. [Results] The result showed that the error range for the maximum pressure at the first peak simulated by the three models was 0.78 m to 1.45 m, and the error range for the minimum pressure at the first trough was-0.55 m to-0.03 m, both within acceptable error ranges in transient pressure simulation. The CLSVOF model outperformed both VOF and CFD-PBM models in simulating the fragmentation and coalescence of air mass, making it more suitable for analyzing the migration of trapped air mass in long-distance pipelines. [Conclusion] The result indicate that the CLSVOF model successfully simulates the migration process of trapped air mass under the impact of water flow in long-distance pipelines. A significant velocity difference between the trapped air mass and the water flow is observed. Under the drag force of the water flow, the air mass migrates downstream in the form of slug flow. The correctness of the simulation result is verified through flow pattern diagrams, demonstrating the applicability of the CLSVOF model in simulating the migration and evolution of trapped air mass in long-distance water conveyance pipelines.

[Objective] After the reservoir operation of the downstream cascade reservoirs of the Jinsha River, the water temperature structure of the reservoir area and the water temperature variation in the downstream river channel were significantly impacted. The study of the spatiotemporal distribution characteristics of water temperature in the reservoir area and the effects of stratified water intake with stoplog gates is crucial for the protection of the river's ecological environment. [Methods] Taking Xiluodu Reservoir as an example, the Delft3D model was employed to simulate the three-dimensional water temperature distribution in the reservoir area, and the effect of stratified water intake by stoplog gates on downstream discharged water temperature increase was predicted. [Results] The result indicated that the water temperature at Xiluodu Reservoir exhibited seasonal stratification, with significant stratification in spring and summer, and almost no stratification in autumn and winter. Installing stoplog gates in front of the power station intake could increase the temperature of the downstream discharged water, but the improvement was limited. Single-layer stoplog gates could increase the temperature by 0.10 to 0.30 ℃, and double-layer stoplog gates could increase it by 0.10 to 0.40 ℃. However, the improvement gradually weakened over time. The arrangement of stoplog gates also had an impact on the downstream water temperature. Installing stoplog gates at only some of the water intakes did not significantly enhance the overall temperature of the downstream discharged water. [Conclusion] The water temperature structure of Xiluodu Reservoir is stratified. When the water temperature stratification is pronounced, the overall downstream discharged water temperature can be improved by placing stoplog gates on both the left and right banks. Simulating and predicting the water temperature stratification pattern of the reservoir and effectively assessing the influence of stratified water intake with stoplog gates can provide a reference for optimizing the implementation plan for ecological scheduling at Xiluodu Reservoir.

[Objective] In order to understand the community structure of macrobenthos in Houxia River basin and evaluate the ecological health status of river water scientifically. [Methods] Through analyzing the community structure characteristics of macrobenthos in Houxia River Basin, building B-IBI health evaluation index system and correlation analysis of water environmental factors, 18 candidate parameters in 4 categories, including community richness, pollution capacity, functional feeding group and biodiversity index, were screened. After distribution range analysis, discrimination ability analysis and correlation analysis, Five core indexes, including total taxa, sensitive taxa and pollution tolerance taxa, were selected for evaluation. The ratio method was used to unify the dimensions, and the evaluation criteria were established with reference to 25% quantile of loci. [Results] The result showed as follows:(1) The benthos belonging to 3 phyla, 4 classes and 35 families were detected in Houxihe River basin, and arthropods were the dominant group in the basin. Shannon-wiener diversity index, Margalef species richness index and Pielou species evenness in wet season were higher than those in normal season. In terms of spatial distribution, three indices were relatively higher in the upper reaches of the river and the inlet of the reservoir.(2) The health status of river monitoring sites in Houxia River basin was generally better than that in wet season in terms of time distribution; In terms of spatial distribution, the health status of the middle and lower reaches of the river is generally poor, while the health status of the upper reaches is generally good. [Conclusion] The assessment criteria of river B-IBI health in Houxia River basin are as follows: B-IBI> 3.92 is healthy, 2.94 < B-IBI≤3.92 is sub-healthy, 1.96 < B-IBI≤2.94 is general, 0.98 < B-IBI≤1.96 is poor, and B-IBI ≤0.98 is extremely poor. The B-IBI index has a strong correlation with water environmental factors, in which the positive correlation with dissolved oxygen is extremely significant, and the negative correlation with chemical oxygen demand is extremely significant. In this study, the selection of reference points is reasonable, the construction of B-IBI evaluation index system is highly applicable to the river health status of Houxia River basin, and the research result can provide scientific basis and theoretical reference for the restoration and protection of water ecosystem in Houxia River basin and the evaluation method of mountain river health.

[Objective] Currently, research on the overall scale of the Momoge Wetland remains limited, especially the lack of consideration of the variations in ecological water demand across different periods within a year. To address this, an estimation framework for the wetland ecological water demand indicator system, consisting of five indicators, is developed for Momoge Wetland. [Methods] Based on the established ecological water demand indicator system, the ecological function method was employed to estimate the ecological water demand of Momoge Wetland across three levels and for three time periods. Moreover, the Grey Model(GM) was utilized to predict the wetland area under various hydrological scenarios of water abundance and water scarcity, thereby determining the water replenishment schemes in response to wetland changes of Momoge Wetland. [Results] The result showed that the maximum, suitable, and minimum ecological water demands of Momoge Wetland were 24.14×10⁸ m³, 16.65×10⁸ m³, and 10.88×10⁸ m³, respectively. The water demands for the overwintering period, breeding period, and flood season were 1.92×10⁸ m³, 5.39×10⁸ m³, and 8.73×10⁸ m³, respectively. Based on the predicted wetland area under different scenarios of water abundance and scarcity, the required water replenishment volumes for Momoge Wetland under the four scenarios — dry-dry-dry, dry-dry-normal, dry-normal-dry, and normal-normal-normal — were 0.70×10⁸ m³, 0.49×10⁸ m³, 0.68×10⁸ m³, and 0.36×10⁸ m³, respectively. [Conclusion] In years of water scarcity, existing water replenishment projects fail to meet the water storage requirements of the Momoge Wetland, highlighting the urgent need to implement multi-source water replenishment method to enhance water replenishment efficiency. The calculation result of this study can inform annual and within-year water replenishment schemes and multi-source water regulation for the Momoge Wetland, thereby improving the efficiency of regional water resource utilization and ensuring the stability of the wetland ecosystem.

[Objective] Xiangjiaba hydropower station is an important peak-shaving power source for China's west-east power transmission. In order to fully tap the peak shaving capacity of Xiangjiaba hydropower Station and clarify the influence of various factors, [Methods] firstly, a hydropower operation model and a unsteady flow hydrodynamic model are constructed to simulate the reservoir regulation process and the water level process of the downstream river section of the dam under XiangjiaBa peak shaving scenarios, respectively. Then, the mapping relationship of maximum hourly variation amplitude of water level between downstream sections and tail water is used to calculate the amplitude threshold of the tail water level. Finally, according to the operation constraints and amplitude threshold of the tail water level, the peak shaving capacity calculation model is constructed to evaluate the peaking shaving capacity of Xiangjiaba hydropower station under different combinations of typical load curve during dry season and flood season, different levels of inflow and reservoir water level. [Results] The results show that the hydropower operation model can simulate the hydropower station output well, and the unsteady flow hydrodynamic model can simulate the change process of water level downstream of Xiangjiaba dam well. There is a significant linear positive correlation for maximum hourly variation amplitude of water level between downstream sections and tail water. According to the relationship between the two, the threshold of maximum hourly variation of the tail water level is set as 1.3 m/h. The peak shaving capacity of hydropower stations that take into account the downstream navigation demand can be solved by the peak shaving capacity calculation model established by additionally considering the threshold of maximum hourly variation of the tail water level. [Conclusion] The maximum peak shaving amplitude of Xiangjiaba hydropower station in dry season and flood season is 1.4~1.5 million kW and 2.4 million kW, respectively. The maximum peak amplitude is dependent on base load and independent on peak regulation modes of single and double peaks. Study of influencing factors of peak shaving capacity indicates that when the initial reservoir water level is low, a small inflow and a large inflow will respectively cause the reservoir water level and the daily increase in reservoir water level to exceed the limit. The limit daily decrease in reservoir water level and the upper limit of reservoir water level during the dry season have no effect on peak shaving. But the upper limit of reservoir water level will restrict the peak shaving operation of hydropower station during flood season when the upper limit of reservoir water level is ≤ 378 m, the inflow is large, and the reservoir water level is close to the upper limit.When the hydropower station can operate with peak regulation, the peak regulation capacity of increases with the initial water level of the reservoir under the same inflow, and remains unchanged after reaching the maximum value. The downstream navigation severely restricts the peak shaving capacity of Xiangjiaba hydropower stations during the dry season, but has no effect during the flood season. The research result can provide guiding and reference significance for the quantification method of peak shaving capacity of hydropower stations and peak shaving operation of Xiangjiaba hydropower station.

[Objective] Conducting quantitative analysis of water conservancy investment and financing policies can provide crucial references for the formulation and improvement of subsequent related policies, accelerating high-quality water conservancy development. [Methods] Content analysis and text mining techniques were comprehensively applied to organize and analyze the water conservancy investment and financing policies in the Yangtze River Delta region, and an evaluation index system was established. The Policy Modeling Consistency(PMC) index model was applied to conduct quantitative analysis of eight policies from four provinces(municipalities) in the Yangtze River Delta, and improvement pathways were proposed accordingly. [Results] The result indicate that:(1) the overall policy design was relatively reasonable, with all eight selected policies rated as excellent and none classified as perfect, acceptable, or poor.(2) The water conservancy investment and financing policies in provinces(municipalities) showed notable strengths in policy targets, policy nature, and policy evaluation. However, there were certain shortcomings in policy instruments and policy incentives that required urgent improvement. [Conclusion] Through quantitative study on water conservancy investment and financing policies in the Yangtze River Delta region, important references can be provided for the formulation and improvement of relevant policies in different regions of China.

[Objective] Rockslide disaster caused by slope instability of reverse gently inclined layered jointed fragmentation rock mass structure is one of the common types of mountain disasters. It is of practical significance to explore the process of instability and failure for disaster prevention and control. Taking the ‘8.28 Pusa collapse' in Guizhou as the research object, the deformation history and rock mass structure characteristics of Pusa rockslide were analyzed. [Methods] Using the topographic mapping data, a three-dimensional geological model was constructed, and the block size of the rockslide accumulation body was counted by the Particles(Pores) and Cracks Analysis System(PCAS). Four different block sizes of 0.5 m, 2.0 m, 3.5 m and 5 m were set to invert the rockfall movement process of the Pusa rockslide. [Results] The research shows that:(1)The block size of the rockslide accumulation block ladder in Pusa is mostly concentrated between 1~2 m;(2)Under different block size conditions, the maximum velocity, maximum energy, maximum distance and maximum height of the broken block reach 74.55 m/s, 2.3×104 kJ, 667 m and 107 m respectively, and the particle size has different degrees of influence on the motion characteristics of rockfall.(3)The velocity of the third zone changes abruptly at the step of the accumulation zone, and the velocity decreases rapidly from 30 m/s to about 20 m/s. [Conclusion] Block size affects rockfall movement; The movement mode of rockfall in the process of migration is “free fall—rolling(collision/impact bounce)—rolling(collision/sliding friction)”; Micro-topography affects rockfall movement. The research ideas and method of this paper can be used for the risk of other landslide disasters.

[Purpose] Rainfall infiltration has a great influence on the stability analysis of slopes, and the Green-Ampt model is commonly used in the analysis of rainfall infiltration problems, but some of its assumption conditions are quite different from the actual situation. In order to get more realistic calculation result, [Methods] made some improvements on the basis of the Green-Ampt model: under the condition of stable rainfall intensity, based on the stratification assumption, the wetted area is divided into a saturated zone, transition zone and initial zone, and at the same time, the slope seepage effect of the saturated zone of the finite-length side slope is considered, and the assumption that the rainfall in the early stage of infiltration completely seeps into the soil body is made by taking the chalky soil as an example. The two stages of infiltration(rainfall intensity control stage, and soil infiltration capacity control stage) are analysed separately, and the infiltration coefficient is corrected to obtain the infiltration depth change rule curve with time, which is called the PSGA model. Improved PSGA infiltration model for slope stability analysis, here consider rainfall infiltration area are above the water table, and respectively selected wetting front, saturated zone-unsaturated zone interface as a dangerous sliding surface for calculation, take the smaller value to the slope safety coefficient with infiltration time. Finally, the PSGA model was used to analyse the rainfall infiltration and stability of the Zhangjiawan landslide. [Results] The result show that: from the error analysis, it can be seen that the calculation result of the PSGA model are more accurate compared with the GA, SGA, and MSGA models; according to the slope stability analysis: the GA model reaches the critical safety coefficient at the earliest time(2.71 h), followed by the PSGA model(4.74 h), and lastly, the PSGA model(6.27 h); the stability analysis of Zhangjiawan landslide: compared with the SGA model, the PSGA model is more accurate than the SGA model, the PSGA model is more accurate than the SGA model, and the stability analysis is more accurate than the SGA model. SGA model, and PSGA model calculation result are closer to the actual situation. [Conclusion] The result show that: the calculation accuracy of the PSGA model is higher and more in line with the actual situation; the critical destabilisation time obtained by the PSGA infiltration model is longer than that of the traditional GA infiltration model and shorter than that of the SGA infiltration model; the seepage effect of the saturated zone of the slope has a greater influence on the depth of the wetting front when the length of the slope is smaller; and the analysis of Zhangjiawan landslide by PSGA model verifies the reasonableness of this model.

[Objective] The solidification effect of cement and lime on Zn²⁺ contaminated red clay was investigated. [Methods] Taking Guilin red clay as the research object, the effects of different cement and lime contents on the strength characteristics, conductive behavior, heavy metal migration law, and microstructure of contaminated soil were systematically studied through unconfined compressive strength test, conductivity test, soil column leaching test, and microscopic analysis. [Results] The results show that increased curing agent content significantly enhances the curing effect, and the optimum proportion is 6% of cement and 6% of lime. The curing treatment significantly improves the unconfined compressive strength of Zn²⁺ contaminated red clay, and the resistivity is negatively correlated with stress-strain. The soil column leaching test showed that Zn²⁺ gradually migrated downward under the action of rainwater, resulting in pollution of the lower soil layer. The leaching concentration increased with the increase in rainwater volume. The microstructure analysis showed that the immobilization of Zn²⁺ was mainly due to the C-S-H gel and Ca(OH)₂ generated by the hydration reaction of cement and lime. These products filled the soil pores and formed stable compounds with Zn²⁺, effectively inhibiting heavy metal migration. [Concluion] Cement and lime can effectively immobilize Zn²⁺ and inhibit ion migration. The recommended cement 6%+lime 6% ratio is applied in the remediation project of heavy metal-contaminated red clay in Guilin. The research result provide micro-mechanism support and process parameter optimization for the treatment of heavy metal-contaminated soil.

[Objective] The livelihood issues of reservoir resettlers arising from the construction of water conservancy and hydropower projects have become an important global challenge. Researching the key factors and driving pathways of livelihood transformation helps formulate precise and targeted policies and promote the realization of common prosperity for reservoir resettlers. [Methods] Based on the social-ecological systems theory, an empirical analysis was conducted on survey data collected from 1 092 reservoir resettlers using a multivariate ordinal Logistic regression model and fuzzy-set qualitative comparative analysis. [Results] (1) Among the samples, only 17.6 % of the resettlers had diversified livelihoods, and industrial development was the key influencing factor.(2) At the 1% significance level, policy frameworks, governance capacity, industrial development, production conditions, resource endowments, and the natural environment were all found to have significant positive effects on livelihood transformation, with regression coefficients of 1.573, 2.558, 3.822, 2.854, 0.613, and 2.043, respectively.(3) The necessity analysis result of each condition variable were below the critical threshold of 0.90, indicating that the effectiveness of livelihood transformation depended on the dynamic alignment of social, economic, and ecological systems. A single factor could not independently drive transformation, and the configuration pathways for livelihood transformation among reservoir resettlers could be divided into four types: governance-production integration, eco-economic synergy, social-production synergy and policy governance. [Conclusion] The findings empirically confirm the important role of social-ecological systems in the livelihood transformation of reservoir resettlers. Optimizing the combination of key elements is an effective pathway to achieve positive transformation outcomes. Based on this, in the process of achieving common prosperity for reservoir resettlers, it is recommended to strengthen support for livelihood transformation, adhere to tailored and targeted assistance, and match regional resource endowments with the needs of reservoir resettlers.