[Objective] Precipitation events caused by Super Typhoon Doksuri in Fujian Province were simulated and evaluated based on the WRF model to provide a reference for typhoon precipitation simulation and forecasting in southeast coastal areas of China. [Methods] The next-generation mesoscale numerical weather prediction model WRF V4. 3(The Weather Research and Forecasting Model) was used to simulate the precipitation caused by Typhoon Doksuri in Fujian Province in 2023. Observations from 86 meteorological stations with hourly rainfall records were used to evaluate the model's performance. Six evaluation indices were used, including the correlation coefficient(R), root mean square error(RMSE), mean absolute error(MAE), equitable threat score(ETS), probability of detection(POD), and false alarm ratio(FAR). [Results] (1) The temporal and spatial evolution of precipitation during Typhoon Doksuri was effectively captured by the WRF model. Precipitation intensity increased gradually from July 27 to 29, 2023, with the heaviest rainfall concentrated in the northern and eastern coastal areas of Fujian Province.(2) Significant differences in model performance were observed in terms of R, RMSE, and MAE. The largest errors occurred in Putian City, while smaller errors were found in southwestern Fujian Province. The evaluation result of all six indices showed that the WRF model performed best in simulating daily precipitation compared to hourly, three-hourly, six-hourly, and twelve-hourly precipitation.(3) The R95p index indicated that the WRF model successfully captured the overall spatial distribution of extreme precipitation. However, extreme precipitation intensity was overestimated in certain coastal areas.(4) Despite accurately identifying the coastal regions of Fujian as being most affected, the WRF model failed to accurately simulate the spatial distribution and intensity of precipitation. The simulated precipitation centers showed discrepancies when compared with the observed centers. [Conclusion] Although the WRF model underestimated hourly precipitation, it successfully captured the temporal evolution and spatial distribution of rainfall caused by Typhoon Doksuri in Fujian Province. It reproduced the heavy rainfall centers in central Fujian Province, with daily precipitation peaks reaching up to 350 mm. This highlighted the severity of extreme rainfall caused by Typhoon Doksuri.

[Objective] Climate change will affect the frequency and intensity of floods and droughts. The impact of climate warming on the frequency and intensity of floods and droughts is empirically studied in the Poyang Lake Basin. [Methods] A flood and drought disaster intensity model is constructed, including the main disaster causing factors such as precipitation in the Poyang Lake Basin and the flow of the Yangtze River. This model is used to calculate the intensity of summer floods, spring and summer droughts in the Poyang Lake Basin from 1960 to 2022. By comparing the frequency and intensity of floods and droughts before and after climate change, the response of floods and droughts to climate change is obtained. [Results] After 1996, the climate has warmed in the Poyang Lake Basin, with precipitation and surface runoff decreasing by 1.9%~5.1% during the wet season and increasing by 1.1%~9.1% during the dry season. Climate warming will have a very limited impact on the frequency and intensity of summer floods and spring droughts, but will significantly increased the frequency and intensity of summer droughts, from 16% before warming to 28% after warming. [Conclusion] The solution result of the intensity model for flood and drought disasters in the Poyang Lake Basin are in line with the actual situation, and the time and intensity of flood and drought disasters are basically consistent with the recorded actual disaster situation. The model may have scientific value and the result are reliable. If statistical method well be used to determine the intensity classification of flood and drought disasters, it will promote the application and promotion of the model.

[Objective] The upper reaches of the Yangtze and Yellow Rivers, located in the eastern Qinghai-Xizang Plateau, serve as major water production and conservation areas. The study aims to analyze the impact of climate change on the probability of runoff abundance and depletion encounters in the water source and receiving regions of inter-basin water diversion projects in this area, thereby providing theoretical support for improving project planning, design, and operational efficiency. [Methods] A bivariate Copula function was employed to construct a runoff abundance and depletion encounter probability model, analyzing the characteristics of these probabilities in the upper reaches of the Yangtze and Yellow Rivers over the past 40 years. Distributed hydrological models and climate scenarios were used to predict changes in runoff abundance and depletion encounter probabilities by the mid-21st century and the end of the 21st century, as well as the response characteristics of diversion-favorable probabilities to climate change. [Results] During the historical period(1978—2020) in the study area, an overall increasing trend in annual runoff was observed. Significant fluctuations in runoff were recorded during the summer and autumn seasons(-3.29~11.78 m³·s^-1/a), reflecting distinct seasonal characteristics. The highest rate of increase in summer-autumn runoff was found in the Jinsha River Basin, which was generally higher than the runoff change trend in the Yellow River source region(-2.3~0.73 m³·s^-1/a), aligning with the requirements for water diversion. On an annual and flood season scale, the synchronous frequency of runoff abundance and depletion was generally higher than the asynchronous frequency, while on a non-flood season scale, it was lower. The probability of diversion-favorable conditions ranged from 68% to 75%, ensuring water supply feasibility. Future projections indicate that annual and flood season diversion-favorable probabilities will generally exceed historical values(3.53%~5.44%), whereas probabilities during the non-flood season under SSP245 and early SSP585 scenarios will fall below historical levels(-1.57%~0.91%). [Conclusion] Transitioning from SSP245 to SSP585 scenarios, the probability of asynchronous runoff abundance and depletion encounters is projected to increase, indicating that extreme climate conditions may lead to greater spatial differences in water resource distribution and more pronounced temporal-spatial variations. The average probability of diversion-favorable conditions is estimated to range from 71.2% to 73.2%, suggesting a high likelihood of compensatory water regulation. This finding is highly favorable for the implementation of the Western Route of the South-to-North Water Diversion Project, enabling compensatory water diversion during both flood and non-flood periods at different time stages.

[Objective] In the context of global climate change, climate variability has increased sharply, and extreme events have become more frequent, posing significant threats to people's lives, property, and the healthy development of the socio-economic system. During the 2021 Meiyu season in Anhui Province, the average rainfall was 317 mm, which was nearly 30% higher than the long-term average. To analyze the moisture transport field of heavy rainfall and reveal its development characteristics, [Methods]the Lagrangian Hybrid Single Particle Trajectory Model(HYSPLIT) was utilized to simulate the moisture transport trajectories during the rainfall event in the Dongpu and Dafangying reservoir basins of Hefei City in July 2021. [Results] The result indicate that the spatial distribution of rainfall was uneven, with an average rainfall of 306.6 mm. The highest rainfall was recorded at Liumiao Station(356.5 mm), while the lowest was at Shenyoufang Station(228.5 mm). The characteristics of moisture transport trajectories varied at different height levels. At 925 hPa, there were southeast paths from the Western Pacific, southwest paths from the Bay of Bengal, and southward paths from the South China Sea, with corresponding moisture contribution rates of 44.4%, 43.8%, and 11.8%, respectively. At 850 hPa, the paths from the Western Pacific and the Bay of Bengal accounted for 26.3% and 73.7%, respectively. At 700 hPa, the paths included the Western Pacific, southwest paths from the Indian Ocean, and westward paths from the Tibetan Plateau, with contributions of 17.1%, 77.9%, and 5.0%, respectively. As the initial height of the moisture trajectory simulation increased, the spatial distribution of the number of trajectories showed a pattern of more in the west and less in the east, and both temperature and specific humidity increased(decreased) during the transport process. [Conclusion] The moisture for the rainfall event in the Dongpu and Dafangying reservoir basins of Hefei City in July 2021 primarily originated from oceanic channels at different height levels, with significant contributions from the Western Pacific, the Bay of Bengal, and the Indian Ocean. At the 850 hPa level, a very strong moisture convergence zone was observed, providing ample moisture for localized heavy rainfall.

[Objective] Global warming has accelerated the hydrological cycle in the regions, leading to an increase in the frequency and intensity of extreme precipitation events. Minjiang River Basin is an important basin in the southeast coast of China, so it is of great significance to study the spatiotemporal evolution of extreme precipitation for the prevention and control of flood disasters in the Minjiang River Basin. [Methods] Based on the daily precipitation data of 29 meteorological stations in the Minjiang River Basin, 9 extreme precipitation indices were selected. Applying the method of Mann-Kendall trend analysis, Sens' s slope estimation and Morlet wavelet analysis, the spatiotemporal evolution and periodic characteristics of extreme precipitation in the Minjiang River Basin were analyzed, and the influence of atmospheric circulation factors on extreme precipitation was further discussed. [Results] The result showed that during the period from 1962 to 2021, the total annual precipitation(PRCPTOT), maximum 1-day precipitation(Rx1day), maximum consecutive 5-day precipitation(Rx5day), extreme heavy precipitation(R99p), and the number of days with rainfall above heavy rain(R25mm) exhibited an insignificant upward trend. The upward trends of extreme precipitation(R95p), daily precipitation intensity(SDII), and the number of days above storm(R50mm) reached a significant level(P<0.05), with the growth rates reaching 20.48 mm/10 a, 0.22 mm·d^-1/10 a, and 0.28/10 a, respectively. The number of consecutive rainy days(CWD) showed an insignificant downward trend(-0.14 d/10 a). Indicators such as PRCPTOT, R25mm, and R50mm presented an increasing trend from the southeast coastal areas to the northwest mountainous areas. The low value areas of Rx1day, Rx5day, R95p, and R99p were mainly located in the central part of the basin, while the high value areas were concentrated in the northwest and southeast coastal areas. The high value areas of CWD were mainly distributed in the southwest of the basin. The SDII of all stations showed an upward trend, and 4 stations had a significant increase, mainly located in the northwest and southeast coastal areas of the basin. The extreme precipitation indices exhibited the periodic characteristics of two different time scales. The impacts of atmospheric circulation factors of EASMI, GMLOT, and Nino3.4 on extreme precipitation in the current year all reached a significant level(P<0.01). [Conclusion] The result indicated that in the past 60 years, the intensity and frequency of extreme precipitation in the Minjiang River Basin have exhibited an increasing trend, while the persistence of rainfall has decreased, and extreme precipitation has evolved from long-duration and low-intensity to short-duration and high-intensity. The high value areas of extreme precipitation are mainly located in the Wuyi Mountains in the northwest, the Jiuxian Mountain in the southern Daiyun Mountains, and the Changle city along the eastern coast. The extreme precipitation index has periodicities of two time scales, namely 6~8 years and 45~56 years. After 2000, the extreme precipitation in the basin oscillated more frequently at short period scales. The impacts of NAO, GMLOT, and Nino3.4 on extreme precipitation have a lag effect. The increase in global temperature is an important factor contributing to the increase of extreme precipitation and the decrease of continuous precipitation in the Minjiang River Basin.

[Objective] Flash flood disasters cause severe economic losses and casualties to human society, making the scientific identification and assessment of flash flood disaster risk an urgent issue to be addressed. The aim of the study is to improve the accuracy of flash flood risk prediction by coupling feature selection with the Random Forest algorithm, thereby providing a scientific basis for disaster early warning. [Methods] Seventeen feature factors associated with the occurrence of flash flood disasters were selected. A feature selection approach that integrated Classified Recursive Feature Elimination(RFE-class) with a Random Forest optimization algorithm was proposed to identify the optimal feature combination for flash flood risk simulation. [Results] The result showed that the optimal feature combination obtained using the RFE-class method significantly improved the predictive performance of the Random Forest model, achieving a Receiver Operating Characteristic(ROC) curve value of 94.7%, representing an approximately 5% improvement in accuracy compared to using the Random Forest algorithm alone. [Conclusion] In Fujian Province, the high-risk areas for flash flood disasters are primarily distributed in the Wuyi Mountains, Daiyun Mountains, and Daimao Mountain regions, covering an area of approximately 49 000 km² and affecting 27 million people.

[Objective] Accurate and rapid prediction of dynamic groundwater level changes is crucial for scientific groundwater management, yet long-term predictions influenced by multiple factors remain insufficiently researched. [Methods] To enhance the capability of long-term groundwater level forecasting, a multivariate long-term prediction model based on PatchTST(PatchTST-GWL) was developed. This model utilized cross-correlation functions to analyze the multivariate correlations and lag effects among factors like groundwater extraction, surface water recharge, rainfall, and lateral recharge. Long-term forecasts were conducted on groundwater levels in four typical shallow monitoring wells in the western suburbs of Beijing. The model performance and accuracy were assessed using the Nash-Sutcliffe Efficiency(NSE), Root Mean Square Error(RMSE), and Mean Absolute Error(MAE). The model's interpretability was also analyzed using the controlled variable method. [Results] The result showed that the prediction accuracy of the PatchTST-GWL model improves with the extension of the forecasting period. For 90 and 180 days forecasting periods, the NSE coefficients of groundwater level simulations exceeded 0.9 across all monitoring wells, with MAE, MSE, and RMSE reductions of 10% to 80% compared to commonly used deep learning models like Attention-Bi-LSTM and SVM. [Conclusion] The PatchTST-GWL model exhibits a significant advantage in the performance of long-term groundwater level predictions. By incorporating cross-correlation functions to calculate the lag effects of groundwater extraction, rainfall, surface water recharge, and lateral recharge changes on groundwater levels, the model significantly enhances prediction accuracy. Furthermore, the predictions align with the response patterns of various influencing factors, consistent with objective physical laws, demonstrating good interpretability. This model can accurately and swiftly predict groundwater levels, effectively supporting scientific assessments and rational utilization of groundwater resources.

[Objective] Analysis of the evolution of regional water consumption structure and identification of its driving factors has important practical significance for formulating comprehensive water resource utilization plans. [Methods] Taking Ordos City as an example, the information entropy and center of gravity migration model were applied to analyze the characteristics of regional water consumption structure changes, and the logarithmic mean divisia index(LMDI) decomposition model was adopted to identify the main driving factors of local water consumption structure evolution. [Results] The result showed that:(1) the central urban area and Jungar Banner were dominated by domestic and industrial water consumption, respectively, while agricultural water consumption accounted for a larger proportion in other banners and districts. The center of gravity of total and agricultural water consumption was located in Hangjin Banner, while centers of gravity of industrial, domestic, and ecological water consumption have shifted to Ejin Horo Banner in recent years.(2) From 2007 to 2023, the water consumption structure of Ordos City remained generally stable, with the equilibrium degree decreasing from the central urban area outward. The water consumption structure in the central urban area showed strong stability, while the regions dominated by agricultural water consumption exhibited weaker equilibrium.(3) Socioeconomic development, technological progress, and ecological environment were the main driving factors of the water consumption structure of Ordos City. Among them, disposable income of urban permanent residents, gross industrial product, water consumption per 10 000 yuan of GDP, and per capita green area were the key drivers. [Conclusion] Rapid urbanization and industrial restructuring have driven the evolution of the urban water consumption structure. Therefore, promoting urbanization development, optimizing industrial structure, implementing deep water-saving and control measures, and enhancing ecological protection and restoration are effective strategies to achieve a balanced water consumption structure in Ordos City.

[Objective] The “Basing Four Aspects on Water Resources” principle, as a concrete embodiment of the sixteen-character water governance concept, aims to investigate future trends in water resources carrying capacity in water-scarce regions and formulate targeted policies and plans for intervention and regulation. This is a key issue in contemporary planning and management of water resources. [Methods] A system dynamics model was established to explore the spatiotemporal evolution of water resources carrying capacity in Tai'an City. On this basis, the water resources carrying capacity model of “Basing Four Aspects on Water Resources” was introduced to analyze the carrying capacity of urban areas, land, population, and industry before and after the implementation of the Eastern Route Phase II project of the South-to-North Water Diversion Project. [Results] The result showed that by 2035, Tai'an's total population would exceed its capacity by 920 000 people, the urban built-up area would exceed its capacity by 7267hm², the irrigated cultivated area would exceed its capacity by 628 000 mu, and the industrial added value would exceed its capacity by 41 900 hm². [Conclusion] The result indicate thatfuture development will be primarily constrained by industrial growth. Since 2017, the water resources carrying capacity index of Tai'an City has shown a continuous worsening trend, facing the risk of water resource overload. The spatial differences in water resources carrying capacity across different districts and counties are significant. Although the implementation of the South-to-North Water Diversion East Route Phase II project can improve the water resources carrying capacity of Tai'an to some extent, it cannot fundamentally resolve the issue of water resource overload. Without considering water use priorities, the rapid growth of industrial water use in Tai'an may reduce water availability for other sectors, leading to varying degrees of overload in urban areas, land, population, and industry. These findings can provide a reference for developing future planning and management policies of water resources in Tai'an City.

[Objective] The surface nuclear magnetic resonance(SNMR) method for groundwater exploration is a highly promising technique with exceptional detection performance. Traditionally, SNMR operates using a co-located transmitter-receiver coil to excite and receive signals for groundwater detection. The objective is to diversify SNMR operational modes and enhance the accuracy of groundwater detection using SNMR method. [Methods] A simulation analysis was conducted on the signal characteristics of the SNMR transverse gradient coil device in groundwater detection, followed by field experiments in the river beach area along the Han River in Tianmen to validate the result. [Results] The response signal of the transverse gradient coil device showed an approximate positive correlation with water content and aquifer thickness, and a negative correlation with aquifer depth. The difference analysis of the transverse gradient coil signals revealed that the occurrence of zero values in the signal difference, as well as the pulse moment magnitude corresponding to the signal peak, can qualitatively indicate the aquifer depth. Additionally, combining the gradient signal difference with the original coil signal for joint inversion can significantly improve the inversion accuracy of the SNMR method. [Conclusion] The findings demonstrate that utilizing the SNMR transverse gradient coil device is an effective approach to improving the accuracy of groundwater detection.

[Objective] Geomembrane defects represent a potential influencing factor causing dam breaches. However, there is no consensus yet on how to accurately simulate geomembrane defects in finite element calculations and on the influence of geomembrane defects on dam breach. [Methods] To refine simulation method for geomembrane defects, the finite element software was used to investigate different defect simulation approaches and the breach effects caused by them. Simulation calculations were carried out for three conditions: intact geomembrane, geomembrane with actual defects, and geomembrane with equivalent defects. The simulations analyzed seepage, stability states, and dam breach effects under different breach depths. [Results] The result showed that geomembrane defects significantly elevated the seepage line within dam bodies while reducing the safety factors of the downstream slope. A 10 cm geomembrane defect required the permeability coefficient to be increased by 10⁸ times for equivalent simulation. In addition, large-area geomembrane defects could induce the formation of dam breaches, and different breach depths result ed in different degrees of downstream hazard. When the breach depth reached 9.0 m, 15.0 m, and 21.5 m, respectively, the flow reached about 300 m, 300 m, and 350 m from the dam toe, respectively. The maximum water pressure corresponding to these three breach depths reached 297.8 kPa, 315.3 kPa, and 351.38 kPa, respectively, while the maximum breach flow velocities reached 21.3 m/s, 20.7 m/s, and 20.3 m/s, respectively. The discharge rates at breach locations were 2.628×10³ m³/s, 6.240×10³ m³/s, and 12.040×10³ m³/s, respectively. [Conclusion] The refined equivalent permeability coefficient for geomembrane defect simulations demonstrates enhanced accuracy in characterizing the actual condition of geomembrane defects. Furthermore, the findings on the influence of breach depth under conditions of geomembrane defects on dam breach dynamics can underscore the necessity of geomembrane protection during construction.

[Objective] Vortex issues in hydraulic engineering cannot be ignored, as they reduce the discharge capacity of the hub, deteriorate the flow pattern, increase head loss, and pose risks to the safe operation of structures. To mitigate the potential risks of vortices in side intake structures and to propose a reasonable vortex suppression scheme, [Methods]vortex suppression characteristics and mechanisms of single-layer and double-layer vortex suppression beams were investigated through physical model experiments, focusing on side intake structures and air-entraining vortices. [Results] The result showed that the vortex suppression beams mainly reduce the tangential velocity V_θ and radial velocity V_r in the vortex region. This reduction weakens the circulation on the water surface in front of the intake, ultimately leading to the elimination of air-entraining vortices. For single-layer vortex suppression beams, reducing the relative spacing∑Δ l/l or increasing the installation height h_e/D enhances the vortex suppression effect. Compared to the scheme without vortex suppression beams(∑Δ l/l=1.000), when ∑Δ l/l=0.357, the intensity of the lower vortex is reduced by about 80.0%. Compared to the scheme where the beam is installed at the top of the intake(h_e/D=0.00), when h_e/D=0.40, the vortex intensity is reduced by about 78.8%. For double-layer vortex suppression beams, when using both transverse and longitudinal beams and ∑Δ L/L_z being reduced from 0.710 to 0.310, the vortex intensity is reduced by about 70.0%. The cross-arranged configuration achieves the best vortex dissipation effect compared to the V-shaped and stepped vertical configurations. [Conclusion] The spacing, installation height, and arrangement of vortex suppression beams significantly impact their suppression characteristics. A deeper understanding of vortex suppression laws is gained, providing a reference for future solutions to vortex problems in side intake structures.

[Objective] The safe and stable operation of pumped storage units and the avoidance of shafting resonance are essential for pumped storage power stations to effectively meet the regulation demands of new-type power systems. [Methods] Different structural units were selected to study the modal characteristics of the unit shafting in the pumped storage power stations. Based on the finite element method, six rotational speed conditions of 400.0~3 000.0 r/min were selected to conduct a comparative analysis of the sixth-order excitation frequencies and vibration modes of three structural units: independent turbine runner, turbine runner-shaft, and turbine runner-shaft-generator rotor. [Results] The result showed that for different structural units, the natural frequencies and vibration modes of the components were different, though identical vibration modes could occur under different structures. The independent turbine runner structure had the highest sixth-order natural frequency, with no critical speed observed. The runner-shaft-rotor structure had the lowest sixth-order natural frequency, with critical speeds occurring in the first two modes. In the modal analysis of the rotating components of the pump turbine, critical speeds were observed at the 1st and 2nd modes, with speeds of 1 387.1 r/min and 2 164 r/min, respectively. However, when only the runner and shaft components of the pump turbine were considered, the critical speed was observed only at the 1st mode, with a speed identical to the 2nd mode critical speed of the runner-shaft-generator rotor, which was 2 164.0 r/min. The corresponding vibration mode and natural frequency were identical. No critical speed was observed when considering only the runner components of pump turbine. [Conclusion] Therefore, in the modal analysis of the rotating components of the pump turbine, considering the generator rotor and shaft components can more accurately identify the critical speeds of the rotating components and predict the resonance frequencies and vibration modes, which is beneficial for avoiding resonance in the unit. The research findings provide a theoretical basis and engineering support for the design of shafting structure in pumped storage units.

[Objective] To apply the cross-modal retrieval mechanisms to scenarios such as personnel security, facility protection, and equipment status monitoring in hydropower video surveillance systems, a multi-modal data mapping between texts and images is developed to enable flexible semantic content search through textual descriptions. [Methods] In order to address issues of the slow inference speed of single-stream models and the lack of modal fusion in dual-stream models in existing cross-modal method, a multi-level denoising multimodal fusion technology was proposed. Based on a dual-stream pre-trained model, this technology integrated masked language modeling with fine-grained cross-modal semantic alignment. A “noise addition followed by denoising” task was designed at multiple levels of the neural network to promote fine-grained interactions between texts and images. [Results] Through extensive experiments, it was validated that under different settings, compared with the fine-tuned CLIP baseline model, the R@1 recall rates for image and text retrieval tasks were increased by 4.1% and 2.7%, respectively, on the Flickr30K dataset. On the MS-COCO dataset, the recall rates were increased by 4.3% and 3.2%, respectively. In a self-collected dataset of hydropower system surveillance scenarios, retrieval tests for personnel in dam areas, equipment operating status, and instrument anomalies were conducted, achieving satisfactory result. [Conclusion] Experiments verify the advantages of the multi-level denoising algorithm in cross-modal semantic retrieval tasks and prove its applicability in hydropower plant surveillance video scenarios.

[Objective] The storage capacity curve of a reservoir plays an important role in flood prevention and disaster mitigation. To address issues of limited data sources and the selection of calculation models for reconstructing reservoir storage capacity curves. [Methods] First, a remote sensing water area inversion method for reservoir storage capacity calculation was used to assess the rationality of the original storage capacity curve, providing a basis for analyzing storage variations. Then, based on the characteristics of the multi-source data, the differences between the contour volume method and the DEM method in volume calculation were analyzed, and a hybrid model for calculating storage capacity was established. [Results] Taking the Wujiazhuang Reservoir in Pingyi County, Linyi City, Shandong Province, as a case study, the storage variations calculated using the multi-source data hybrid model showed a reduction of 163 600 m³ in dead storage, a reduction of 145 100 m³ in active storage, and a reduction of 270 500 m³ in total storage. An in-depth analysis of the reasons for the storage reduction was conducted, considering the topography, time-series remote sensing images, and engineering development in the reservoir area. The reliability of this method in calculating storage capacity was verified. [Conclusion] The findings show that the hybrid multi-source data curve reconstruction method overcomes the challenge of discrepancies between surface and sub-surface data, addresses the limitations of traditional method in handling complex topography, and provides a valuable calculation paradigm. It effectively improves the accuracy and efficiency of storage capacity curve reconstruction, provides a scientific basis for flood prevention and disaster mitigation in reservoirs, and enhances the efficiency and safety of reservoir management.

[Objective] Current research on multi-objective optimization scheduling primarily focuses on interannual and intra-annual ecological flow variations in medium-and large-scale reservoir groups and hydropower stations, while research on monthly ecological flow constraints for cascade small hydropower stations in mountainous rivers remains limited. [Methods] Three cascade small hydropower stations(Liangkou Dam, Qingnian, and Shengli) in the Liuxi River Basin were selected as the research objects. A multi-objective optimization model for cascade hydropower stations was established based on monthly ecological flow constraints. The model aimed to maximize power generation and minimize ecological water shortages and spillages, and was solved using the non-dominated sorting genetic algorithm(NSGA-Ⅱ). Optimization scheduling schemes were selected using the Knee Point method and compared with a fixed ecological flow scheme based on the Tennant method(10%~80% standard). [Results] The result showed that the annual power generation under the optimized monthly scheduling scheme increased by 13% compared to the Tennant method scheme, while ecological water shortages and spillages were reduced by 12%. The power generation of the three stations increased by 26%, 32%, and 26.7%, respectively. The increase in the upper limit of ecological flow constraints significantly reduced ecological water shortages during high-load operations, achieving simultaneous optimization of power generation and ecological benefits. [Conclusion] The findings provide a scientific basis and technical support for the multi-objective optimization scheduling and management of cascade small hydropower stations in mountainous rivers, enhancing both ecological and economic benefits.

[Objective] To investigate the impact of stratified dewatering in a foundation pit under extreme rainfall conditions on the stability of the foundation pits retaining structures and the adjacent road embankment, [Methods]a three-dimensional finite element analysis model was constructed based on the deep foundation pit project of the Yancheng Railway Passenger Hub. The accuracy of the model was validated using field measurement data. By systematically analyzing the variation patterns of lateral displacement of the retaining structures, axial force of the concrete supports, and settlement of the adjacent road embankment during the stratified dewatering and excavation processes, the influence of stratified dewatering and extreme rainfall conditions on the lateral displacement of the retaining structures and the settlement of the adjacent road embankment was revealed. [Results] The results show that, under stratified dewatering conditions, the maximum lateral displacement of the retaining walls increased by approximately 7% to 45%, and the maximum bending moment increased by about 5% to 13% compared to the scenario without considering stratified dewatering. During the excavation process, the surface settlement of the road embankment without considering stratified dewatering was significantly smaller than that with stratified dewatering. When the rainfall condition increased from heavy rain(28.15 mm/d) to heavy downpour(100.80 mm/d), the lateral displacement of the retaining structures increased by about 40%. When the rainfall condition increased from heavy rain(50.00 mm/d) to heavy downpour(100.80 mm/d), the maximum horizontal displacements at the toe and shoulder of the road embankment slope increased by about 35% and 142%, respectively. Under extreme rainfall conditions(100.80 mm/d), as the embedment depth of the wall increased, the reduction in the maximum lateral displacement of the wall decreased from 13% to 6%, and the maximum horizontal displacements in various regions of the road embankment slope showed a gradually decreasing trend. As the horizontal distance of the internal supports decreased, the large lateral displacement of the wall reduced by about 9%, and the maximum displacement of the road embankment slope decreased by about 11%. [Conclusion] Stratified dewatering in foundation pits under extreme rainfall conditions has a significant impact on the stability of the retaining structures and the adjacent road embankment. It is recommended to appropriately increase the embedment depth of the retaining structures or reduce the horizontal spacing of the internal supports during deep foundation pit construction, especially during the rainy season, to achieve better control over the stability of the retaining structures and adjacent buildings.

[Objective] In order to realize that dredged sand from the Yangtze River can be used in construction of hydraulic structures near estuary, [Methods]proportion of dredged sand to the mass of fine aggregate was defined as the Content. 5 kinds of concrete trabecular specimens with different Content were designed, and the specimens were placed in 4 different salt environments(composed of NaCl and Na_2SO₄ solution) for full immersion erosion. Non-standard three-point bending tests were carried out on the specimens with erosion time of 30 d, 60 d and 90 d and those without erosion. The mechanical properties were studied and the crack development was monitored by acoustic emission(AE) technology. [Results] The results show:(1) Crack resistance of concrete gradually decreases with increase of the dosage. For every 12.5% increase, the peak breaking load decreases by about 5%. When the dosage is greater than or equal to 37.5%, the peak breaking load drops by more than 30%.(2) The higher ion concentration is, the more obvious erosion effect is, and addition of Cl~- can alleviate the erosion process of SO₄^2-.(3) The analysis of AF-RA values shows that tensile cracks are the main cracks in early stage, and the proportion of shear cracks increases gradually with the process of crack expansion. The proportion of shear cracks is the smallest when the content is 12.5%, and the fracture development is the best. The higher the ion concentration, the larger the proportion of shear fractures, the more incomplete the fracture development. The research result provide experimental basis for the application of dredged sand concrete in water conservancy and water transportation engineering under salt environment. [Conclusion] The addition of dredged sand and the erosion of salt environment have obvious deterioration effect on the mechanical properties of concrete. The accumulate counts of AE showed three stages, reflecting fracture characteristics and verifying boundary effect.

[Objective] According to the actual service environment of the face slab of rockfill dam in northern China, the failure of carbonation durability under freeze-thaw conditions is the main problem leading to the deterioration of the durability of face slab concrete in cold areas. In order to explore the influence law and mechanism of freeze-thaw cycles on carbonation durability of face slab concrete, [Methods]the rapid freeze-thaw test, accelerated carbonation test, scanning electron microscope and nuclear magnetic resonance analysis technology were used to conduct freeze-thaw cycles on concrete specimens for 0, 50, 100, 150 and 200 times, and then accelerate carbonation for 0, 7, 14 and 28 days. By testing the macro indexes of concrete such as carbonation depth, relative dynamic elastic modulus, ultrasonic wave velocity, splitting tensile strength and compressive strength, and micro indexes such as porosity and pore size distribution, the influence of freeze-thaw cycle and carbonation on the micro-pore structure and durability of concrete is analyzed. [Results] The results show that the carbonation depth of concrete after carbonation is greater than that under the condition of freeze-thaw damage. Carbonization improves the relative dynamic elastic modulus, ultrasonic wave velocity, splitting tensile strength and compressive strength of concrete face slab. After 200 freeze-thaw cycles, the most probable pore size of carbonization for 28 days decreased from 59.35 nm to 41.94 nm, a decrease of 29.33%. [Conclusion] The damage caused by freeze-thaw cycle to concrete reduces the carbonation resistance of concrete; Carbonization reaction reduces the porosity and the most probable pore size of face slab concrete, and alleviates the damage to concrete caused by freeze-thaw cycle. Controlling the pore content in the range of concrete internal pore diameter d>1 000 nm and increasing the pore content in the range of 10 nm≤d<100 nm can improve the carbonation resistance of face slab concrete under freezing and thawing conditions.

[Objective] As an important supporting platform for marine resources development, it is of great significance to prepare coral concrete in the construction of the island reef project. In order to solve problems such as low coral concrete strength, high brittleness, durability and poor and pronounced problems, the coral concrete needs to be modified to increase to meet the high-level building structure and even explosion-proof seismic fields. [Methods] Based on literature surveys, the research progress of coral aggregate characteristics, coral concrete performance, modified enhancement technology, durability and high-strength and high-performance coral concrete development research progress. [Results] The result showed that the strength of the aggregate aggregate, the high pore rate, and the high concentration of the sea salt restricted the development of coral concrete performance; except for the ingredients itself, the cohesive materials, external agents, fibrous products, etc. in the design of the than the design of the than the design of the corals The performance of concrete has an important impact. [Conclusion] Gel condensate materials, external agents, optimized coordination ratio, use of acid solution or organic solution to treat aggregate, incorporate fiber and other technical method can effectively improve coral concrete performance; exposure time and mineral component can improve the anti-osmotic anti-penetration of coral concrete Capability; carbonization is related to the environment, not all mineral components are conducive to improving the resistance of carbon; considering the type of cement and mineral components that are conducive to improving the anti-sulfate performance of concrete; Low pressure stirring or ground polymer can prepare high-strength/high-performance coral concrete. Research findings also explores the advantages and disadvantages and effects of different modified enhanced technologies, and looks forward to the field of high-strength/high-performance coral concrete materials and structural research on cutting-edge at front, which can provide a reference for subsequent research directions.