Global climate change has led to significant changes in hydrological cycle processes， resulting in an increased risk of hydrological droughts. Therefore， the study of hydrological drought changes under changing environments is of great significance for early warning of flood and drought and water resources management.Typical basins in north and south China （Xiangjiang river basin and Weihe river basin） are selected as the study areas.The period from 1982 to 2015 is selected as the base period （the historical period） and the period from 2030 to 2060 is selected as the future period. Five Global Climate Models （GCMs） provided by CMIP6 under the three scenarios of SSP126， SSP245 and SSP585 are selected to output the climate data for the future period.The Extreme Gradient Boost （XGBoost） is utilized to downscale the precipitation and temperature from GCMs to drive hydrological models to obtain streamflow in the future period， and then compare and analyze the evolution of hydrological drought characteristics in Xiangjiang river basin and Weihe river basin in different periods.The results indicate that， after downscaling by XGboost， the RMSE of simulated precipitation of Xiangjiang river basin and Weihe river basin are reduced by 57.6% and 51%， respectively， and the correlation coefficient with the measured values are improved by 20% and 32%， respectively. The RMSE of simulated temperature are reduced by 50.9% and 51%， and the correlation coefficients with the measured values are improved by 4.3% and 6.25%， respectively.The increase in precipitation in Xiangjiang river basin in the future period will increase the streamflow in this basin， thus alleviating hydrological drought， and the severity， duration， intensity and peak intensity of hydrological drought are reduced by 6.3%， 4.8%， 10.6%， and 6.5%， on average， compared with those in the historical period.In contrast to Xiangjiang basin， the increase in temperature and potential evapotranspiration decreases the streamflow in Weihe river basin.Therefore， Weihe river basin will face a greater risk of drought in the future period. Among the selected scenarios， the drought is the most severe under the SSP585 scenario. Compared with the historical period， the severity and duration of drought will be increased by 72.7% and 30.8%.

How to better assess the risk of urban rainstorm and waterlogging， and formulate corresponding drainage measures to make the city more resistant to waterlogging disasters， is an important practical problem that China needs to face and solve. Taking Dongsha Lake Basin as an example， this paper studies the urban waterlogging risk assessment method， constructs the waterlogging risk assessment index system of Dongsha Lake Basin from three aspects： the hazard of disaster factors， the sensitivity of disaster-prone environment， and the vulnerability of disaster-bearing bodies. The entropy weight method is used to assess the waterlogging risk level of Dongsha Lake Basin under two conditions of 20-year return period within the standard and 100-year return period beyond the standard. The results show that under the scenario of rainfall return period of 20 years， the entropy weight method calculates the low-risk area， sub low risk area， medium risk area， sub high risk area and high-risk area as 41.3%、31.4%、14.9%、9.9%、2.5%， respectively； Under the scenario of rainfall return period of 100 years， the entropy weight method calculated the low risk area， the sub low risk area， the medium risk area， the sub high risk area and the high risk area as 22.3%、23.1%、24.8%、17.4%、12.4%， respectively. The proportion of high risk and sub high risk levels in the study area calculated by entropy weight method increased from 12.4% in the 20-year return period to 29.8% in the 100 year return period， and the regional waterlogging risk showed a significant quantitative increasing trend. The entropy weight method takes into account the data information of the index itself， increases the weight of the sensitivity of the disaster-prone environment and the vulnerability of the disaster-bearing body， and can comprehensively reflect the objective importance of the risk index.

With the successive commissioning and operation of cascaded reservoirs in various river basins， conducting joint scheduling of reservoir groups can enhance the efficiency of flood resource utilization in the basin while ensuring flood control safety， thereby fully realizing the comprehensive benefits of the cascaded reservoirs. Typically， during the design phase， the flood control capacity of each cascade reservoir in a river basin is considered based on an individual reservoir's operation. In real-time scheduling， cascaded reservoirs often operate at or below the flood limit water level for extended periods， and the total storage capacity available for flood control is often much larger than the required reserved flood control storage capacity. Additionally， operating at lower water levels restricts the power generation output of hydropower stations， thereby hindering the full realization of the comprehensive benefits of the cascaded reservoirs. This study designs inflow scenarios for cascaded reservoirs in a basin and constructs a real-time joint scheduling model for the reservoirs. Joint simulation calculations are conducted based on flood control scheduling plans， and a calculation method for the equivalent utilization coefficient of reservoir capacity is proposed. This research is carried out in the Wujiang River Basin， exploring the equivalent utilization relationship between the adjustable storage capacity below the flood limit water level of the Goupitan Reservoir and the flood control capacities of the Silin and Shatuo reservoirs. The analysis results indicate that the composition of flood-prone areas is one of the influencing factors of the equivalent utilization relationship of reservoir capacities. The higher the upstream inflow proportion， the larger the equivalent utilization coefficient of the reservoir capacity. In practical scheduling， the equivalent utilization coefficient for the adjustable storage capacity below the flood limit water level of the Goupitan Reservoir in relation to the flood control capacities of the Silin and Shatuo reservoirs can be taken as 0.5. The results of this study can provide technical support for formulating flood season operation plans， preparing joint flood control scheduling schemes， and improving flood resource utilization efficiency， thereby ensuring flood control safety in river basins.

The reservoir's role in regulating runoff from the watershed influences the pattern of hydrological response of the upstream and downstream of the natural watershed. Traditional hydrological models constructed on the basis of the hydrological cycle of natural watersheds often fail to consider the influence of reservoir factors on runoff， leading to a decrease in simulation accuracy. Therefore， coupling the reservoir module in the hydrological model to simulate the storage and discharge process of the reservoir on the incoming flow is the key to improve the accuracy of the hydrological simulation of the basin under the effect of reservoir regulation. However， existing studies on reservoir outflow simulation modelling are scarce and generally of low accuracy. This study is based on the simulation model of outflow from the Target Capacity Curve （TCC）， to improve the theory of “water abandonment and inflow are positively proportional to a certain extent”： taking into account the effects of the reservoir operation cycle， the pre-dam level and the target capacity， it is proposed that the reservoir will make different abandonment decisions for different levels of incoming water. Based on this assumption， a TCC model with improved abandonment algorithm was constructed and applied to four large and medium-sized reservoirs upstream of Guilin City， and a control model was set up for comparison. The results show that： ① the improved TCC model improves the simulation of reservoir outflow and water level to different degrees compared with the pre-improvement model， and the improved model performs better； ② the comparison of the multi-year average operating level of each reservoir reveals that the improved TCC model better reflects the cyclical operation law of the reservoir， indicating that the new water abandonment strategy is reasonable and effective.

In order to better solve the contradiction between water resources and socio-economic development， and to realise the sustainable use of water resources， it is of great siginificance to carry out historical assessment and future projection of water resource carrying capacity. Taking the Tarim River Basin， the largest inland river basin in China， as the research object， we constructed a system dynamics model of water resources carrying capacity， verified the accuracy of the model by using historical data. At the same time， combined the shared socio-economic paths and future precipitation data， the dual impacts of human activities and climate change was considered. Based on the Cooperative Gaming Combined Weights-VIKOR comprehensive evaluation method， we conducted a comprehensive evaluation of the water resources carrying capacity of the Tarim River Basin for the historical period （2002-2021） and the future period （2025-2050）. The results show that the relative errors between the simulated data of the system dynamics model and actual data for each variable are within ±10%， indicating good simulation performance. The water resources carrying capacity of each state in the Tarim River Basin showed a general upward trend in the historical period， with the best in Bayingolin Mongolian Autonomous Prefecture and Kizilsu Kirgiz Autonomous Prefecture， the worst in Aksu and Kashgar， and a more obvious upward trend in Hotan. The results of the future prediction show that the water resources carrying capacity of all the states under the SSP1 path is generally increasing， and by 2050， Bayingolin Mongolian Autonomous Prefecture， Kizilsu Kirgiz Autonomous Prefecture and Hotan areas will all have suitable carrying capacity. Under the SSP2 path， except for Kashgar， which shows a trend of decreasing and then increasing， the other prefectures and cities show a slowly fluctuating upward trend. The water resources carrying capacity of some areas decreases under the SSP3 and SSP5 paths， of which Hotan and Aksu areas under the SSP5 path decreases significantly. By 2050， Hotan will be mildly overloaded and Aksu will be overloaded. This study is conducive to promoting the rational allocation and effective use of water resources， and is of great significance for ensuring regional water security， ecological security and sustainable economic and social development.

With the intensification of global climate change， extreme weather events are becoming increasingly frequent， posing significant challenges to socio-economic and ecological systems. The three northeastern provinces of China， a region particularly sensitive to climate change， have experienced compound dry-hot events（CDHEs） that severely impact local agriculture， society， and the economy. To systematically assess the characteristics and evolution of summer compound dry-hot events in this region， this study constructed the Standardized Temperature-Precipitation Index （STPI） using the Copula joint probability method， based on observational data from 82 meteorological stations covering the period 1961-2020.The reliability and applicability of the STPI in describing compound dry-hot conditions were validated through historical compound dry-hot events and the hit rate verification method. Using run theory， the study identified the duration and intensity of compound dry-hot events， analyzed their spatiotemporal distribution patterns， and explored the respective roles of temperature and precipitation using Theil-Sen median trend analysis and the Mann-Kendall test. Results revealed a general increase in the severity of compound dry-hot events over time. Although the STPI exhibited a slow decreasing trend on an interannual scale， its value was generally above -2.0， indicating a continuous rise in event severity across the study area. The frequency of compound dry-hot events ranged from 28.4% to 40.3%， showing significant spatial heterogeneity in the distribution of moderate， severe， and extreme events. Most stations in the region displayed a non-significant decreasing trend in SPI （Standardized Precipitation Index） and a significant increasing trend in STI （Standardized Temperature Index）. This suggests that rising temperatures are the primary driver of increasing severity in compound dry-hot events. Additionally， the 1990s marked a critical turning point， after which the frequency， intensity， and spatial extent of compound dry-hot events significantly intensified. This study provides valuable insights and a scientific foundation for climate adaptation strategies and risk management in the region.

With the intensification of global climate change and the deepening impact of human activities， the proportion of losses caused by mountain flood disasters in overall flood disasters has significantly increased. Among these， small watershed flash floods have become a key focus in disaster prevention and mitigation efforts due to their sudden onset and rapid disaster formation characteristics. Flood analysis and assessment serve as crucial non-engineering measures for mountain flood disaster prevention， where the design flood hydrograph constitutes a vital component that directly determines the timeliness of disaster warnings and the scientific validity of emergency plans. However， constrained by challenges such as sparse hydrological monitoring stations and insufficient baseline data in mountainous regions， verifying the rationality of design flood hydrographs in ungauged areas has become an urgent technical challenge. To evaluate the reliability of design flood hydrographs in mountain flood analysis and assessment， this study employed the Xin'anjiang （XAJ） model and MISDc model. Utilizing both measured data and flood disaster investigation assessment results， we conducted separate validations of design flood hydrographs. Taking the Guanshan River Basin as the study area， hydrological model parameters were calibrated using measured data and flood investigation assessment results respectively. Subsequent validation was performed through flood hydrograph simulations. The results demonstrate that when substituting measured parameters with design parameters for model simulation： the relative error of the simulated flood peak and the relative error of the flood volume of the XAJ model showed increases of 25.72% and 10.33% respectively， while the MISDc model exhibited increases of 40.59% and 31.34% in corresponding errors. The Xin'anjiang model outperformed the MISDc model in simulation accuracy. Although parameters calibrated from measured data showed superior performance compared to those derived from design assessment results， the latter still proved applicable for flood process simulation. These findings provide valuable references for mountain flood analysis and calculation in regions lacking long-term measured hydrological data.

Catchment threshold is a key element that affects the extraction of digital river network based on DEM. Theoretically， there exists an optimal catchment threshold corresponding to the best digital river network. In order to improve the accuracy of determining the optimal catchment threshold and extract a more accurate river network， this paper proposes an improved river network density method based on the principle of the river network density method. The Jinsha River Basin， Daqing River Basin and Yishu-Si River Basin were used as the study areas， and ASTER GDEMV3 （30 m）， SRTM DEM （90 m） and GEBCODEM （450 m） were used as the data sources to analyse the universality of the method， the effect of the improvement， and the effect of the catchment thresholds on the extraction of the river network. The results show that： ① the catchment threshold is inversely related to the river network density as a power function， and the larger the catchment threshold， the smaller the river network density. ② Under the same catchment threshold， the results of river network extraction from DEM data with different resolutions are different， and with the increase of catchment threshold， the difference of river network is bigger. ③ The resolution of DEM data affects the river network extraction results. The lower the resolution， the larger the optimal catchment threshold and the lower the accuracy of river network extraction. When the accuracy of DEM data is too low， the river network extraction results of plain basins and hilly basins are seriously distorted， and it is not possible to extract the more realistic river network data. ④ When the parameter B=0 of the improved river network density method， the extraction effect is optimal under different terrain basin conditions and different resolution data. ⑤ The optimal threshold value obtained by the river network density method is often too large， and the improved river network density method is better than the river network density method in extracting the river network under different topographic watershed conditions and different resolution data； and the improved river network density method has the best effect on the mountainous watersheds and low-resolution DEM data. This study can provide an important reference for the efficient extraction of digital river network and the digital construction of water conservancy.

Marine pile foundations are subjected to wave loads and ocean current forces over extended periods. This results in various hydrodynamic phenomena， including downdiving currents， horseshoe-shaped vortices， and wake vortices， which develop around the pile foundation. These interactions can lead to varying degrees of local erosion of the soil surrounding the pile as they interact with nearby soil particles. Such erosion poses significant risks to the safety and stability of the marine pile foundation throughout its entire lifecycle. Therefore， it is essential to investigate the local scouring mechanisms around the pile to propose more effective erosion protection measures. To address the issue of local erosion in marine pile foundations， a fluid dynamics model was validated through three-dimensional cylindrical flow simulations conducted under various bed roughness conditions. The simulation results show that the simulation results of the three-dimensional cylinder flow field are basically consistent with the measured water velocity distribution in the test， indicating that the fluid dynamics model accurately calculates the three-dimensional flow field around the pile. The computational fluid dynamics （CFD） software Fluent and discrete element software EDEM were employed to develop a CFD-DEM numerical model for local erosion. This model was used to investigate the influence of sediment particle size， density， angle of repose， and cohesion on local erosion. The findings reveal that these factors significantly affect scouring depth， equilibrium time， scouring pit range， and morphology. Notably， increases in sediment particle size and density result in a marked reduction in the drag force acting on sediment particles. Conversely， an increase in sediment cohesion substantially enhances both the normal viscous contact force and the tangential collision contact force between sediment particles， leading to a continuous decrease in scouring depth. The angle of repose of the sediment has minimal impact on the force and movement mechanisms， scouring depth， and equilibrium time of the particles， although it does influence the morphology and slope angle of the scouring pit. These research conclusions provide valuable theoretical guidance for understanding sediment erosion in pile foundations.

To investigate the appropriate energy dissipation structures for the inlet of a regulating pool， the Volume of Fluid （VOF） model was employed to simulate the non-pressurized flow from the tailrace of a cascade hydropower station to the front end of the regulating pool. The simulations were based on the Realizable k-ε turbulence model and the PISO algorithm for computational analysis. Under the premise of ensuring grid division followed the same principles and maintained consistent orders of magnitude， a comparison was conducted between multi-stage drop dissipation， stepped dissipation， and bucket-type energy dissipation. The focus was on key hydraulic characteristics such as energy dissipation efficiency， flow velocity， and water-air mixing state under the same boundary conditions and operational scenarios. The computational results revealed that， under the same water head and unit width discharge conditions， multi-stage drop dissipation exhibited a lower maximum flow velocity within the flow field compared to stepped dissipation and bucket-type energy dissipation. This indicated that the scouring effect of the regional water flow on the energy dissipation structures themselves would be relatively weakened. Simultaneously， multi-stage drop dissipation induced smaller water surface fluctuations within the regulating pool， which was beneficial for maintaining a stable operational state. The comprehensive energy dissipation efficiencies achieved by the three types of energy dissipation structures were as follows： bucket-type energy dissipation at 37.00%， stepped dissipation at 62.26%， and multi-stage drop dissipation at 89.93%. By combining the analysis of flow field characteristics， it was evident that the adoption of multi-stage drop dissipation not only facilitated the stability of the water level within the regulating pool but also significantly enhanced the durability of the energy dissipation structures at its inlet. This， in turn， provided a robust guaranty for the stable operation of the entire water conveyance and power generation system. After a comprehensive comparison， it was concluded that multi-stage drop dissipation was a suitable energy dissipation method for the inlet of the regulating pool. The research findings offered valuable insights and could serve as a reference for subsequent engineering design and construction.

The disordered flow state in inverted siphons poses significant challenges to their flow capacity and structural safety. For large-flow water conveyance channels， it is crucial to study and implement effective measures to optimize and improve the flow state of inverted siphons. This not only enhances their flow capacity but also ensures the long-term safety and reliability of the engineering structures. In this study， we focus on the Kuhe Inverted Siphon of the Middle Route of the South-to-North Water Diversion Project as a representative case. First， we employed a three-dimensional numerical simulation to accurately reproduce the current flow conditions within the inverted siphon and analyze the root causes of the current flow patterns such as “Kármán vortex street” Combined with the prototype observation data， the accuracy of the numerical simulation was verified. Next， through the detailed comparative analysis of multiple flow state optimization schemes at the outlet of the inverted siphon， the engineering measures for optimizing the flow pattern of the inverted siphon are determined， and the turbulent flow pattern of the inverted siphon is solved. The results of this comparative study helped us to determine the most suitable engineering measures for optimizing the flow state of the inverted siphon. Among the various optimization measures， the installation of flow-guiding piers at the outlet of the inverted siphon was found to be particularly effective. The length of these piers was a critical parameter， and our analysis indicated that a pier length of approximately 4 to 5 times the pier width yielded the best results in terms of flow stabilization and efficiency enhancement. This solution not only resolves the existing flow state issues but also provides a valuable reference for the design and subsequent operation management of similar inverted siphon projects.

Trapezoidal broad-crested weirs， as a type of low weir， are widely used in sluice gates for flood control projects in plain areas. However， large-scale river engineering models incorporating such sluice structures are often constrained by spatial dimensions， necessitating the use of distorted models with different horizontal and vertical scale ratios. Existing studies have demonstrated that in distorted models of trapezoidal broad-crested weirs， variations in the distortion ratio （i.e.， the ratio of the horizontal scale to the vertical scale） can significantly alter hydraulic similarity. This discrepancy leads to deviations in flow characteristics—particularly discharge capacity—compared to prototype conditions. To quantitatively investigate the impact of distortion ratio on the flow behavior of trapezoidal broad-crested weirs and provide a theoretical foundation for designing and correcting distorted physical models in river engineering， this study systematically examines the influence of different distortion ratios on weir flow characteristics through integrated physical model experiments and theoretical analysis. The research further elucidates the physical mechanisms underlying distortion-induced effects， including deviations in the discharge coefficient， alterations in water surface profiles， and variations in flow velocity distributions. The experimental results indicate that the area most significantly affected by the distortion ratio on the water surface profile is located on the downstream side of the weir. At the same cross-section， the flow velocity differences between models with different distortion ratios and the normal model are negligible. Under the same discharge， trapezoidal broad-crested weirs with different distortion ratios exhibit a transition from a parabolic distribution at low Reynolds numbers to a logarithmic distribution at high Reynolds numbers. The discharge capacity shows a proportional relationship with the model distortion ratio. A relational expression between the distortion ratio and the discharge coefficient for distorted models under free-flow conditions was established. Comparisons between calculated and experimental values demonstrate errors within ±5%， indicating a good fit.

Sediment deposition is a significant problem that should not be ignored in the process of operating deep-water ports in shallow water area on muddy coasts. Based on historical topographic data and human activity survey results， this study analyzed the historical erosion and deposition evolution of the muddy coasts in southern Zhejiang Province， and explored the impact of constructing guide embankments and excavating navigation channels on sediment movement. In physical model experiments， the sediment deposition patterns on the muddy coasts after human activities were reproduced. In addition， a comparative analysis was conducted on the hydrodynamic features and sediment deposition change characteristics after the implementation of guide embankments of different lengths. By using empirical theoretical formulas， this study identified the corresponding relationship between the length of guide embankments and the total amount of sediment deposition， and proposed a method for determining the optimal length of guide embankments. It is found that prior to human activities， the seabed of the muddy coasts in southern Zhejiang was basically in a balanced state between erosion and deposition. After the implementation of guide embankments， the closer the channel is to the port area， the greater the sediment deposition， with an average thickness of approximately 0.08 m for the monthly sediment deposition in the first year. Then after the excavation of navigation channels， the closer the channel is to the shallow water area， the greater the sediment deposition， with the monthly sediment deposition thickness ranging from 0.1 to 0.3 m. The physical model experiment can effectively reproduce and predict the range and magnitude of sediment deposition influenced by human activities. The length of guide embankments and their sediment reduction effect are related to the planar distribution of sediment concentration. If the planar distribution varies slightly， the sediment reduction effect would increase first and then decrease with the extending length of guide embankments. If the sediment concentration varies significantly with water depth， the longer the guide embankment， the better the sediment reduction effect. Furthermore， when the sedimentation amplitude at the mouth of harbors formed by guide embankments is close to that of channels， the length of guide embankments would become the optimal. If this length is too long or too short， the total sedimentation amount in the channels would increase. In the process of actual design and implementation， the final length of a guide embankment should be determined by comprehensively considering the engineering cost， environmental impact and other factors.

Drop-flow vertical shaft spillway tunnel is widely used in pumped storage power stations. However， there are no relevant design guidelines and specifications for the diameter design of the circular overflow weir at its inlet. The influence of the weir crest diameter on the flow patterns and hydraulic characteristics of the overflow weir needs to be further studied. In this study， a drop-flow shaft spillway tunnel was taken as an example. Firstly， the different flow patterns of the overflow weir with the variation of the head were revealed by model tests. Then， a three-dimensional CFD numerical simulation method was applied to study the flow patterns and hydraulic characteristics of the overflow weir when the weir crest diameter was 2、 2.5 and 3 times the vertical shaft diameter， respectively. It is shown that the flow patterns of the circular overflow weir can be classified into the free weir flow， obstructed weir flow， submerged weir flow， and orifice flow as the water head increases， while the flow coefficient decreases in sequence. Under the weir flow state， the six water tongues of the overflow weir converge and freely fall at the center of the vertical shaft， forming an inverted triangular air-inlet channel at the tail of the isolation pier. As the intersection degree of water tongue increases， a low velocity zone is formed at the intersection center， and the flow state changes from free weir flow to obstructed weir flow. Once the weir flow is submerged， the flow state transforms into submerged weir flow， and the range of low velocity zone at the intersection center increases. When the water level under the overflow weir is higher than the elevation of the overflow weir crest， the water flow completely submerges the shaft mouth， and the water flow enters the vertical shaft under the pressure of the submerged head， and then the flow pattern changes to orifice flow. The position of the water tongue intersection lowers as the diameter of the weir crest increases， and the flow patterns can undergo a transition from orifice flow to submerged weir flow and obstructed weir flow， resulting in increases in discharge capacity. However， increasing the diameter of the weir crest can reduce the negative pressure on the overflow weir surface in free weir flow conditions， and the overflow capacity is slightly reduced. The finding of this paper can provide a reference basis for the design of an overflow weir of the drop-flow shaft spillway.

Reservoir inflow estimation is a key issue in flood forecasting and control. Influenced by the dynamic storage capacity and observation errors of water level， the inflow calculated by the traditional water balance method tends to fluctuate sharply in a jagged shape and is prone to negative values at small time scales， which needs to be post-processed with the help of a smoothing algorithm. To address the above problems， this paper proposes an ensemble Kalman filtering method coupled with hydrodynamics based on the assumption of flow continuity. Firstly， the inflow is taken as a model parameter， and the inflow set is generated at the next moment based on the assumption of flow continuity. Then multiple instances of hydrodynamic model are constructed and run to get the simulated water level set under different inflow conditions. Finally， based on multiple measured water level data， the ensemble Kalman filter method is applied to update the generated inflow set， and the average value of the set of flow is taken as the target flow， and the above steps are repeated. Smooth reservoir inflow backcasting is achieved by rolling forward filtering. Taking the Three Gorges Reservoir as an example， the flood processes in July 2020 and October 2022 are selected for the study， and the results show that： ① The method is able to significantly reduce the fluctuation of the reservoir inflow estimation while meeting the timeliness requirements， and the improvement of the smoothing degree is 0.56 compared with the eight-segment method； ② The method is closer to the artificial smoothing results and the eight-segment results in the low flow， and the difference is larger in the peak flow； ③ The water bias indicator shows that all methods overestimate the inflow， with the filtering method overestimating by 7%， the eight-segment method overestimating by 6%， and the manual smoothing method overestimating by 8%. The reservoir inflow estimation method proposed in this paper can provide technical support for flood forecasting and dispatching.

The residual accumulation of agricultural plastic films in soil significantly influences soil hydraulic properties and the processes of soil water and salt transport. Studying the hysteresis of soil water characteristic curves is crucial for accurately characterizing soil hydraulic properties under wetting-drying cycles. This study employs the tensiometer method to assess the effects of residual film content， residual film size， and soil shrinkage on the sorption and desorption curves， as well as the hysteresis degree in sandy loam under wetting-drying cycles. The aim is to explore the mechanisms by which residual films impact soil water characteristic curves and their hysteresis. Results indicate that residual films decrease soil water retention capacity by occupying soil pores and due to their hydrophobic properties. With increased residual film content， both the desorption and absorption curves shift downward. The influence of film size on the water retention curve is negligible due to the random deformation of residual films within the soil. Additionally， because residual films have lower shrinkage properties than the soil， they mitigate soil shrinkage， with a reduction in the net volumetric shrinkage rate of 0.51% for every 100 kg/hm2 increase in residual film content， showing a significant linear relationship. A significant negative linear correlation was found between residual film content and the average total hysteresis， indicating that residual films reduce the irregularity of soil pore structure and the differences in contact angles between the solid-liquid interfaces during drying and wetting. Furthermore， residual films inhibit soil shrinkage， minimizing structural differences between wetting and drying cycles， and thus indirectly reduce hysteresis. The combined effects of the residual films and their impact on soil shrinkage collaboratively suppress the hysteresis in soil water retention curves. This study is of great significance for advancing the understanding of factors and mechanisms affecting hysteresis in soil water characteristic curves and provides a basis for accurately evaluating the dynamics of soil water and salt transport in areas contaminated with residual films.

The mesh filter assumes a critical role in eliminating impurities from the water within the drip irrigation system， precluding the clogging of droppers and ensuring the stable and efficient operation of the system. To further explore the filter performance， this study designates the mesh filter， which is the most prevalently employed in the drip irrigation system， as the research object and undertakes filtration clogging tests in accordance with three factors exerting the most substantial influence on the filter operation in actual irrigation， namely the flow rate， the mesh number， and the concentration. The durations of the filter stage （T1） and the filter cake stage （T2）， along with the ratio of the effective filtration time under different mesh numbers， flow rates， and sediment concentrations， are inspected. Based on the outcomes of the all-factor test， the impact of each factor on the total filtration time and the ratio of the effective filtration time was appraised by employing the range analysis method. The results show that the increase in sediment concentration and flow rate both led to a shortening of the duration of the T1 and T2 stages， indicating that the greater the concentration and the greater the flow rate， the faster the filter clogging process. With the increase of mesh number， the duration of T1 and T2 increases but the effective filtration time ratio decreases. The range analysis discloses that the mesh number， the sediment concentration， and the inlet flow have significant repercussions on the total filtration time and the ratio of the effective filtration time. Among them， the influence of the inlet flow rate， the sediment concentration， and the filter aperture on the total filtration time of the mesh filter is in the descending order of the filter mesh number， the sediment concentration， and the inlet flow. Their influence on the ratio of the effective filtration time of the mesh filter is in the descending order of the inlet flow， the filter mesh number， and the sediment concentration. The results of this study not only facilitate the assessment of the filter performance under diverse working conditions but also furnish an essential theoretical foundation for the selection of filter operating conditions. This holds considerable significance for augmenting the filtration efficiency and the service life of the filter.

Plant roots can directly enhance the tensile strength of the soil through mechanical reinforcement， effectively suppressing nearby soil cracking. This study establishes a numerical model that describes the process of three-dimensional soil shrinkage cracking influenced by roots， based on a three-dimensional soil cracking model and incorporating a non-stationary random field characterized by trend and random fluctuation components. The model introduces a three-dimensional root density distribution function and represents the reinforcing effect of roots on the soil within the non-stationary random field using an exponential function relationship between critical strain and root density. Minkowski density （including area density， length density， and Euler number density） is utilized to quantify crack patterns. The model parameters are calibrated and validated by field experimental results， with an evaluation of the model's accuracy. The determination coefficients of the Minkowski densities of experimental and simulated crack images， as well as the relative frequency of crack depths， range from 0.769 7 to 0.998 3， while the root mean square error varies from 0.005 to 0.083 and deviations range from 0.014 8 to 0.081 0. The consistency index exceeds 0.961 7， indicating that the newly constructed model can effectively simulate the three-dimensional soil shrinkage cracks influenced by root systems. In addition， the distribution of soil surface cracks decreases as the lateral distribution radius of the three-dimensional radial distribution density function （RDDF） of roots increases， while the relative frequency of crack depth is more significantly influenced by the polar radius. The research findings are significant for understanding soil structure changes under drought conditions.

In order to improve the management of water diversion and transfer in Xiaokaihe Irrigation District and to minimize leakage losses during diversion， an optimization model of water diversion for reservoir groups in the irrigation district is established in this paper， with minimizing leakage loss and water diversion in the main canal and at the same time reducing the frequency of water diversion and transfer throughout the year as the main objective. A genetic algorithm is employed to solve the model， providing an optimized scheme for the year-round process of water diversion and transfer from reservoir groups in the irrigation district. Taking the 2022-2023 reservoir water diversion and transfer operations in the Xiaokaihe Irrigation District as a case study， the results demonstrate that the water diversion and transfer scheme developed through the reservoir groups optimization model for the irrigation district can reduce seepage losses by up to 812 600 m3 in a single diversion process， achieving a 4.25% reduction in the loss rate. Annually， leakage losses could be reduced by 3 138 400 m3， a 2.35% decrease in loss rate， along with a reduction of three diversion events per year， thereby significantly minimizing leakage losses and enhancing water diversion management in the irrigation district. The reservoir groups diversion optimization model developed in this study provides a scientific basis for irrigation districts to formulate water diversion and transfer plans， guiding irrigation districts in scientific and reasonable water distribution and centralised and unified scheduling.

The wind-photovoltaic-hydro complementary energy is an effective strategy to enhance the consumption of renewable energy. In the context of short-term operational scheduling， the multi-energy complementary dispatch of cascade reservoir systems necessitates the coordination of power generation and load balancing across various reservoirs and diverse renewable energy sources. Furthermore， the scheduling process must consider the time delay associated with water flow through the cascade reservoirs， resulting in a lag effect on power discharge during the scheduling period. This scenario presents a multi-objective optimization challenge， requiring a balance between the benefits of power generation both within and outside the scheduling period， as well as the benefits of peak-shaving during the scheduling period. This study develops a short-term multi-objective optimization model for the wind-photovoltaic-hydro complementary energy in cascade reservoir systems. The model generates a Pareto-optimal set of solutions， encompassing power generation benefits， peak-shaving benefits， and potential power outside the scheduling period. Additionally， it investigates the conflicting and synergistic relationships among these multiple objectives and quantitatively assesses the comprehensive benefits of complementary dispatch through comparative analysis. Using the cascade hydropower station group in the Yuanshui River Basin as a case study， model simulations for typical dry and wet seasons yield the following key findings： ① There exists a conflict between long-term and short-term scheduling benefits. As the energy storage capacity and lagged power within the cascade reservoirs increase， the power generation benefits within the scheduling period diminish. ② A trade-off exists between power generation and peak-shaving objectives， with this trade-off becoming less significant as the potential power decreases. ③ Hydro power compensation for wind and photovoltaic generation effectively enhances the total system output， with additional generation during the dry and wet periods amounting to 8.08 million and 5.2 million kWh， respectively. In peak-shaving mode， the maximum residual load is reduced by 880，000 and 60，000 kW during the dry and wet seasons， respectively. The multi-objective optimization scheduling model for wind-photovoltaic-hydro complementary energy in cascade reservoirs provides valuable insights for advancing the integration and consumption of renewable energy.

Pipe cooling is one of the most commonly used temperature control measures in the construction of mass concrete. With the continuous development of hydropower engineering in China， water engineering projects are facing increasingly complex environments and stricter construction schedule requirements. Rapidly formulating reasonable pipe cooling temperature control measures based on real-time changes in meteorological conditions and continuously optimized construction schedules has become a critical technical challenge that needs to be addressed. To this end， this paper proposes a transfer learning-based surrogate-assisted optimization method （TLSAO） for the initial stage of pipe cooling in concrete dams， aiming to improve efficiency and reduce optimization costs. First， an artificial neural network is used to capture the nonlinear relationship between the computed temperature field of the prior block and its input parameters， and the trained model is then transferred to the target domain of the dam block to establish a transfer learning-based surrogate model （TLANN）， thereby reducing the required number of samples. Subsequently， a dual-objective optimization model is constructed with maximum temperature and cooling cost as the objectives， and the NSGA-II algorithm is used to optimize pipe cooling schemes for the dam block. To improve the accuracy and reliability of numerical simulation results， thermal parameters are calibrated dynamically through model updates based on accumulating monitoring data， gradually enhancing calibration precision and improving optimization reliability. This method achieves optimization within a short time， completing optimization for a single dam in just 41 hours， which is more than twice as efficient as traditional ANN-based optimization assistance. The proposed method provides strong support for the automation， intelligence， and precision of temperature control in concrete dams.

The multi-type flexible resources of “Hydropower-PV-Charging-Storage” introduce random volatility risk， and also form a flexible resource adjustment pool with many points， wide area and large volume， but there is a lack of method to quantify the adjustable ability of the multi-coupled system of “Hydropower-PV-Charging-Storage”. Therefore， this paper proposes a day-ahead two-stage optimal scheduling strategy for the system with electric vehicles and a quantitative method of regulating ability， which can effectively take into account the safe and stable operation of the power grid， reduce the operating cost of the system， promote the consumption of new energy and provide richer and more efficient adjustment capabilities. Firstly， Monte Carlo sampling is used to simulate the charging demand and grid-connected time of electric vehicles. Secondly， a two-stage optimal scheduling model is established with the goal of minimum net load fluctuation and minimum total operating cost to optimize the charging and discharging strategy of electric vehicles and the output of each unit in the distribution network. Then， considering the coordinated regulation ability of thermal power， hydropower， photovoltaic， energy storage and electric vehicles， a feasible domain calculation method of system flexibility resources is proposed based on improved adaptive constraint generation algorithm combining iterative linear programming. The regulation ability and flexibility of the proposed scheduling strategy is evaluated by the volume， surface area ratio and roundness of the feasible domain. Finally， taking the IEEE 33-node system as an example， we conduct simulation analysis on the optimization results of electric vehicles under three different charging modes：unordered charging， ordered unidirectional charging， and ordered bidirectional charging. The results show that the optimization model can not only better realize the consumption of renewable energy and stabilize the fluctuation of load， but also maximize the comprehensive income of various resources. It provides strong decision support for power grid operators， helps to optimize resource scheduling， and improves the stability and cleanliness of power grid.

The generator floor is the most concentrated place for the operation personnel and equipment of the hydropower plant， and it is also the relatively weak part of the vibration resistance of the power plant structure， which is crucial for the long-term stable operation of the hydropower station. In this paper， an actual model of generator floor and turbine roof is established， and the dynamic response under the pulsating pressure in the volute and draft pipe passage and the unit vibration load is numerically analyzed and compared with the dynamic response of the generator floor structure under the traditional simulation. The results show that the decoration layer of the generator floor has little effect on the vibration response of the floor structure， and the anti-vibration analysis of the plant can be calculated using the model without decoration layer （just considering its quality）. The real modeling of the steel structure of the roof and considering the action mode of the pulsating pressure in the roof area can make the calculation results of the dynamic response of the plant structure more accurate than the traditional model and more close to the measured response data of the plant vibration. Therefore， in order to improve the accuracy of numerical calculation results， it is suggested that when conducting numerical analysis of the dynamic response of the plant，it is necessary to include the roof structure for overall simulation.

In deep buried water diversion tunnels， there are limited measures for preventing and controlling rock burst risks of TBM construction. Once an extremely strong rock burst occurs， the TBM machinery will be buried. Therefore， it is of great significance to study rock burst risk prevention and control measures suitable for TBM excavation. This paper proposes a method of using drilling and blasting pilot tunnels for stress release in the construction of deep buried water diversion tunnels. The stress adjustment process induced by drilling and blasting pilot tunnel excavation and full section excavation methods （single drilling and blasting or TBM method） was compared. The evolution law of strain energy near the TBM excavation face induced by pilot tunnel excavation was analyzed. The results show that the excavation of pilot tunnel reduces the degree of strain energy accumulation near the TBM excavation face， and the peak accumulation position of strain energy is far away from the tunnel surface， which will make the TBM excavation face in the stress release area and reduce the risk of rock burst. Finally， the strain energy release effect of drilling and blasting pilot tunnel excavation is verified based on case study.

The traditional added mass method （referred to as the traditional method） couples the additional fluid mass per unit area to the nodes of the fluid-solid coupling interface in the form of particles according to the hydrodynamic pressure Westergaard formula. In view of the error caused by the traditional method with multiple equivalences and the complexity of the model during the creation of mass particles， an optimization method based on parameterization of material density（referred to as the optimization method） is proposed. In this paper， the wet modes solved by the traditional method and the optimization method are compared and analyzed for the cantilever beam model， the four-sided simply supported plate model and the engineering model. The results show that for the same simple model， the results obtained by the two methods are basically consistent with the theoretical solution， which shows the correctness and high accuracy of the optimization method. In addition， when analyzing computationally intensive models， the processing time of the optimization method is much shorter than that of the traditional method， which becomes more prominent with the increasing number of nodes.

The protection of diversion tunnel floor concrete has long troubled the safe， efficient and high-quality construction of the project. The construction method of “lining while excavating， floor first and top arch later” will cause the floor concrete to be crushed by heavy vehicles， causing quality problems. Therefore， for the protection of the floor concrete during the parallel operation of tunnel excavation and concrete lining， the protective layer laying methods under the working conditions of water-free and watered were proposed. Using the ABAQUS numerical simulation software， the stress and deformation characteristics of the floor concrete were analyzed， and the influence law of the heavy vehicle's mass change on the protective effect of the floor was determined. Two protective technologies of the floor concrete， namely “composite geomembrane + fine sand + hole slag” and “geotextile + concrete + hole slag”， were formed， and a set of concrete finished product protection system was established. The effective control of the construction quality of the floor concrete under the synchronous operation of tunnel excavation support and secondary lining is realized. Field application results show that the proposed technology reduced the deformation of concrete and effectively solved the problem of protecting floor concrete， greatly reduced the cost of quality defect rectification， accelerated the construction progress on the premise of ensuring quality， and provided theoretical and technical guidance for the protection of the tunnel floor concrete from rolling damage.

The distribution mode of fault creep dislocation has a significant impact on the design of the structures crossing active fault. However， there is currently no unified understanding of the distribution pattern of fault creep deformation at home and abroad， and there is no research on the influence of various common deformation distribution patterns on the penstock crossing active fault. In this paper， the finite element method is used to establish a finite element model of a shallow buried steel-lined reinforced concrete penstock crossing active fault， and the structural responses of the penstock under four types of fault creep dislocation distribution modes： linear， convex， concave and S-shaped were compared and analyzed. The results indicated that the distribution mode of fault creep dislocation had little effect on the displacement and stress distribution law of the steel-lined reinforced concrete penstock， but had a more obvious impact on the deformation of expansion joints and the axial stress of reinforced concrete around the steel liner. Under all the dislocation distribution modes， the expansion joint could play an important role in reducing the pipe stress and protecting the pipeline structures. The responses of the penstock were larger under the S-shaped distribution mode， and the responses were minimal under the concave distribution mode. The calculation results of the linear distribution mode were closest to those of the S-shaped distribution mode， and the linear distribution mode was easier to implement in the calculation. When the distribution of fault creep and displacement is unclear， it is recommended to prioritize the S-shaped and linear distribution modes in the study of pipeline structures crossing fault.

The construction of water conveyance tunnels in the loess tableland area inevitably encounters the problem of underpassing rivers. Existing theoretical calculations for minimum overburden thickness only consider a single or several factors， ignoring the superimposed effects of all potential factors， and there are few studies on the minimum overburden thickness of shield tunnels passing under rivers in loess areas. This paper proposes a theoretical calculation formula for the minimum overburden thickness that comprehensively considers the friction between segment bolts， grouting pressure， surrounding rock and soil friction resistance， and uneven ground stress. A system for determining the minimum overburden thickness consisting of engineering analogy， theoretical calculation， and finite element numerical analysis was established. Taking the risk removal and reinforcement renovation project of the canal along the margin of loess tableland in Baojixia Irrigation Area as an example， the effectiveness and applicability of this method were verified. The research results indicate that the calculation results of the minimum overburden thickness considering the superimposed effects of favorable and unfavorable factors are more reasonable， and the minimum safe overburden thickness for crossing the Jinling River section is about 8 m.

In order to effectively achieve information transmission of long-distance tunnel monitoring equipment， avoid installing microcontroller units （MCUs） inside the tunnel， which may cause abnormal damage to the equipment， prolong its service life， improve equipment utilization， and facilitate the investigation and tracking of equipment data abnormalities， as well as equipment operation and maintenance， a communication link construction method for installing MCU inside and outside the tunnel is proposed. Fiber optic channels are configured based on factors such as the installation position， wavelength， and number of gratings of each section instrument. Instruments in the same channel are connected in series to the main fiber optic link， and then MCU is introduced into the outside and inside of the tunnel. This method does not require power supply to the equipment inside the tunnel， and fully utilizes the number of interfaces of each device， improving the utilization rate of the equipment. In addition， the indoor environment provides a better operating environment for MCU installation， extending the service life of the equipment. This method has been applied in a 172 key national project and achieved good monitoring results， providing reference for the construction of fiber Bragg grating technology in long-distance tunnel engineering monitoring communication links.

Addressing the challenges of identifying damages in hydraulic radial gates， particularly the low accuracy in recognizing minor damages， a damage identification method based on Gramian Angular Fields （GAF） transformation and Two-Stream Multi-Channel Convolutional Neural Network （TM-CNN） was proposed. In this method， one-dimensional vibration signals collected under various damage states were transformed into two-dimensional images using GAF transformation. These images were then used to train the TM-CNN to establish a mapping between vibration signals and damage states， enabling damage identification. Experimental results on gate damage revealed that the proposed method achieved recognition accuracies of 98.04% and 99.88% in single-point and multi-point damage scenarios， respectively. Additionally， it exhibited strong capability in identifying minor damage， with average AUC values of 0.9996 and 1 for 5% damage severity in single-point and multi-point experiments， respectively. These results confirm that the proposed deep learning-based method for classifying vibration signals is applicable for gate damage identification and holds significant value for the health monitoring of hydraulic gates.

This study aims to explore the coupling mechanism of main risk factors in high slope construction and reduce the occurrence of construction safety accidents. Firstly， based on the reports of high slope construction accidents and theoretical methods such as the 4M system， a risk index system that includes four categories： personnel， materials， environment， and management is constructed. Secondly， the coupling mechanism is analyzed by combining the trajectory intersection theory， the N-K model is used to calculate the coupling degree， and a simulation model of human pipe coupling system dynamics （SD） is constructed. Finally， simulation analysis is conducted on the evolution trend of risk factor coupling level with progress and the sensitivity of risk factor coupling level to changes in coupling degree based on actual engineering cases. The results indicate that as the risk factors involved in coupling increase， the level of risk coupling and the probability of accidents also increase. The coupling between personnel factors and management factors is a key focus of prevention and control. In addition， by strengthening the control of personnel and management risk factors such as weak safety awareness and unqualified personnel during construction， the coupling level of safety risks in high slope construction can be effectively reduced.