After the operation of Lianghekou， Wudongde， and Baihetan Reservoirs in the upper Yangtze River， the inflow discharge and sediment of Three Gorges Reservoir （TGR） has significant changed. As a result， the current operation scheme of TGR can no longer meet the new demands. Based on rainfall data from the upper Yangtze River basin （1961-2022） and flow data from the Yichang Hydrological Station （1882-2022）， the flood season is divided by using several mathematical statistical methods. Furthermore， the temporal evolution patterns of Meiyu in the middle and lower reaches of the Yangtze River and the Autumn Rain in west China is analyzed， the TGR observed and restored inflow peak discharges and flood volumes are compared， and the necessity and feasibility of dynamically adjusting seasonal division and operational water levels are also discussed. The main flood season of the TGR is determined to be from June 21 to September 10 based on statistical analysis of rainfall and flow data series. The Meiyu is mainly occurred in late June and July， while the Autumn Rain begins in late August. Most reservoirs in the upper Yangtze River enter the refill period and TGR inflow peak discharges are reduced significantly. In summary， it is suggested to divide the TGR flood season into four periods： i.e.， drawdown period （May 1-June 20）， Meiyu flood period （June 21-July 31）， transition period （Aug. 1-Sept. 10）， and Autumn Rain refill period （Sept. 11-Oct. 31）. In practical operation scheduling， the phased transition points can be determined based on the forecasted dates of Meiyu onset and retreat. Following the Meiyu retreat， the flood control capacity reserved by the TGR may be gradually released， allowing a controlled rise in operational water levels. During the Autumn Rain period in West China， opportunities should be seized to initiate early impoundment. Dynamic control of operational water levels is implemented based on 1~5 day flood forecasting processes， balancing flood-drought mitigation and efficient water resource utilization. This integrated approach significantly enhances the comprehensive benefits of the Three Gorges Reservoir.

The Northern Slope Economic Belt of Tianshan （NSEBT） is one of the core regions of the Silk Road Economic Belt， and its socio-economic development has long been limited by the shortage of water resources. Water resources carrying capacity is an important indicator of economic and social development space， and its quantitative research is of great significance to the sustainable development of regional socio-economic. This study proposes a method for evaluating water resources carrying capacity using water availability as a rigid constraint. This method can quantify the carrying capacity scales for population， economy， and cropland， as well as the overall carrying capacity status （severely overloaded， overloaded， critical， or not overloaded）. Using this method， we evaluated the water resources carrying capacity of the NSEBT from 1991 to 2020. Our results indicate that the sizes of population， economy， and cropland that can be supported by water resources all exhibited an increasing trend from 1991 to 2020. Specifically， during the three assessment periods （1991-2000， 2001-2010， 2011-2020）， the population carrying capacities are 7.06， 8.01 and 8.59 million respectively， the GDP carrying capacities are 46.9， 227.4 and 612.5 billion yuan， respectively， and the cropland carrying capacities are 19 251， 24 393 and 30 059 km²， respectively. Despite these increases， the whole region remained in an overloaded status， with significant variation across administrative regions. During 2011-2020，， Changji， Tacheng， and Kuitun were classified as severely overloaded status. Inter-decadal changes show that the water resources carrying state worsened in Changji， Tacheng， Bozhou and Kuitun， while it improved in Urumqi， Shihezi， Wujiaqu and Hami. The carrying state of the whole region shifted from a critical state in the 1990s and 2000s to an overloaded state in the 2010s. Given the severe situation of water resources carrying capacity in the NSEBT， we proposed a range of initiatives to enhance the carrying capacity of water resources， focusing on both increasing water supply and reducing water demand.

Against the backdrop of accelerating climate change and urbanization， extreme weather events are occurring with increasing frequency， and urban flooding issues are becoming increasingly severe. Simulating flood processes under various rainfall scenarios and analyzing the spatial distribution and evolution of flood risks have become key research focuses. Taking a typical area in Qiantang District， Hangzhou City as an example， this study employs the Mike Flood platform to couple the Mike Urban， Mike 11， and Mike 21 models， and validates the models using actual rainfall and water accumulation data. Six different rainfall scenarios with varying recurrence intervals were set based on the rainfall characteristics of the study area. Flood processes under each rainfall scenario were simulated， and potential flooding risks were analyzed from three processes： node overflow， pipeline convergence， and surface flooding. Flooding risk zones were delineated using two indicators： water depth and duration of flooding. The results indicate that the coupled model simulation results have an average error of 5.41% compared to measured values， accurately simulating real flooding conditions and demonstrating high applicability. Under high recurrence period rainfall scenarios， certain areas of the study region face severe risks of node overflow， pipeline pressure operation， and flood inundation. The drainage pipeline design standards in the study region are insufficient to cope with extreme rainfall scenarios. As the recurrence period increases， the number of overflow nodes， pipeline filling rate， maximum flood depth， and flood risk areas at all levels in the study area all show an increasing trend. Among these， roads and their adjacent areas， low-lying areas， multi-lane intersections， and areas near drainage outlets are high-risk zones， necessitating targeted disaster prevention measures. These findings can provide references for improving urban flood risk management work.

In order to improve the clarity of the visualisation of the dynamic simulation of flood evolution and to enhance the efficiency of disaster emergency response， this study proposes a flood extent visualisation method based on Unreal Engine 5 （UE5）. This method combines the shallow water equation （SWE） hydrodynamic model with virtual simulation technology to construct a three-dimensional terrain model using unstructured discrete grids and multi-source data， such as remote sensing images and terrain point clouds. It also uses Fluid Flux to calculate the fluid motion process and achieve high-precision flood visualisation. By defining spatial anchor points for data measurement， we can compare and analyse the simulated and measured flood inundation ranges. The results show that the ranges agree 98.14% of the time. In addition， this study uses C language and blueprint node hybrid programming based on the triangular dissection algorithm and vector fork multiplication principle to dynamically extract the inundation boundary. This allows the surface inundation area to be calculated in real time with a deviation rate of ≤1.86%. The findings show that the method can accurately represent flood propagation characteristics in complex terrain and show the trend of flood propagation along valleys. It provides decision makers with intuitive and accurate views of flood evolution. In terms of accurate simulation， the matching error between the simulated inundation area and the actual affected area is less than 2%， confirming the validity and reliability of the method. This study supports the interactive derivation of water flow paths in 3D scenes and updates the flood inundation area based on dynamic data. This provides strong visual decision support for planning flood evacuation routes and optimising flood control projects.

In hydrological forecasting， the accurate identification and segmentation of independent flood events from continuous hydrological processes are crucial for ensuring parameter accuracy and improving flood forecast precision. Traditional manual methods for selecting flood events suffer from low efficiency and a lack of universal standards， leading to strong subjectivity in flood event extraction. This paper proposes a simple method for automatic identification of flood events from continuous flow process. The method fully considers the attributes and characteristics of flow data itself， and determines the flood peak and starting and ending points of flood events based on conditions such as flood peak flow threshold， start-stop flow threshold， rising slope threshold. The uniqueness of floods was ensured by rationality test， and the influences of peak flow threshold， start-stop flow threshold and rising slope threshold on flood segmentation were further analyzed. Taking the Muma River Basin as the study area， the proposed method and other flood segmentation methods were applied to segment the continuous flow process from 1980 to 1990. The impact of different flood segmentation methods on forecast accuracy was evaluated by employing the XAJ Model and the TOPMODEL for hydrological forecasting. Results indicate that the flood peak flow threshold controls the number of floods and the duration of floods， the start-stop flow threshold and rising slope threshold mainly affects the duration of floods， while the influence of the rising slope threshold being relatively limited. The proposed method can recognize the flood segmentation process in long series hydrological data based on the objective judgment criteria， and quickly split the flood segmentation of different flow processes with simple principle， high computational efficiency and high accuracy. Compared with other flood segmentation methods， it achieves more precise event segmentation， higher forecasting accuracy， and lower peak error， providing relatively accurate input data for flood forecasting research.

Studying the response of meteorological drought to seasonal heterogeneity of hydrological connectivity aids in understanding the evolution law of regional drought and provides new insight for optimal allocation of water resources and dynamic adjustment of agricultural water use in arid areas. Based on Sentinel-2 satellite remote sensing data， precipitation（P） data and potential evapotranspiration （PET） data from 2019 to 2023， this paper takes Shuozhou City， Shanxi Province， which has been affected by meteorological drought for a long time， as the research object. The hydrological connectivity comprehensive index method is used to quantify the surface hydrological connectivity （C）， and the meteorological drought level is divided by the Moisture Index （MI） to explore the response characteristics of meteorological drought to the seasonal heterogeneity of hydrological connectivity. The results show that： ① The water body area of Shuozhou City fluctuates significantly， reaching a peak of 93.12 km² in 2019， plummeting to 40.24 km² in 2020， and recovering to 67.76 km² in 2021 due to ecological engineering. The water distribution is scattered and the shortage of water resources is prominent. The composite water body area in winter is 4.9 times that in summer， and the seasonal difference is significant. ② The comprehensive index of surface hydrological connectivity in Shuozhou City from 2019 to 2023 is between 0.014 and 0.227， with an average value of 0.058， showing significant seasonal fluctuation characteristics. Affected by the increase of evapotranspiration in spring and summer， the C value from April to August is at the lowest level in the whole year （average 0.035）. The low temperature in winter inhibits evapotranspiration， which leads to the peak value of C value from November to January of the next year （average 0.099）. Evapotranspiration intensity is the core factor driving the seasonal heterogeneity of hydrological connectivity in Shuozhou City. ③ The response of meteorological drought to hydrological connectivity in Shuozhou City exhibits significant seasonal heterogeneity. In winter， hydrological connectivity was strongly negatively correlated with relative humidity index （r = -0.53）. In summer （r = -0.31） and autumn （r = -0.25）， it decreased in turn. In spring， there was no significant positive correlation （r = 0.16）. The risk of meteorological drought increased with the increase of surface hydrological connectivity. The results of this study provide a new idea for arid and semi-arid regions to use the seasonal heterogeneity of hydrological connectivity to cope with meteorological drought.

In recent years， river ecosystems have been facing challenges related to water scarcity and uneven flow regulation. Ecological flow is a crucial indicator for maintaining the ecological function of rivers. Therefore， ecological flow analysis is of great significance in maintaining the balance and stability of river ecosystems， protecting biodiversity， and providing various ecosystem services. This study conducted an ecological flow analysis for the Hailang River Basin based on the SWAT （Soil and Water Assessment Tool） model. We developed natural runoff and actual runoff models， analyzed the impact of land use changes on runoff， and calculated ecological flow thresholds using the Tennant method. The study also analyzed the temporal and spatial distribution characteristics of water volume in the basin， compared runoff differences under different hydrological years， and quantified the spatial pattern of ecological flow surplus. The results show that there are differences between natural runoff and actual runoff in terms of annual distribution and total volume. Specifically， during the flood season （May to September）， actual runoff is significantly lower than natural runoff， while changes in the non-flood season （October to April） are smaller. Actual runoff is influenced by human activities， causing the water resources in sub-basins 2， 12， 19， and 24 to be slightly lower than natural runoff. The land use change analysis revealed that simulated runoff for the Hailang River Basin in 2005 decreased by 4.25% compared to 2000， decreased by 1.56% in 2010 compared to 2005， and increased by 0.99% in 2015 compared to 2010. The ecological flow demand in the Hailang River Basin meets the "optimal" standard level according to the Tennant method. Ecological flow surplus analysis shows that water volume in the basin is unevenly distributed spatially. The study suggests that water resource scheduling strategies need to be optimized to address seasonal supply-demand imbalances， thereby providing a model integration analysis paradigm for ecological flow management in cold-region rivers.

The operational regulation of newly constructed upstream reservoirs induces structural changes in the inflow formation mechanisms of downstream reservoirs due to artificial flow regulation. Conventional hydrological models， predominantly designed for characterizing natural rainfall-runoff processes， are inadequate for addressing runoff prediction requirements under dual natural-human regulated drivers. Focusing on the Jiangya Reservoir in the Lou River Basin， this study proposes a runoff prediction framework that integrates data-driven modeling and interpretability analysis. A CatBoost-based inflow prediction model is developed， combined with parameter sensitivity analysis and SHAP （Shapley Additive Explanations） interpretability methods， to unravel the impact mechanisms of upstream reservoir operation on the inflow of the downstream. The results demonstrate that： ① The CatBoost model outperforms comparison models in predicting Jiangya Reservoir inflows， with a 6.3%~15.8% improvement in the Nash-Sutcliffe Efficiency （NSE） coefficient and a 19%~33% enhancement in prediction stability （measured by the Bias-Variance metric， BV）. These quantitative advancements verify its superior capability in modeling complex hydrological correlations through the symmetrical tree structure， ordered target statistics， and ordered boosting mechanism. ② Parameter sensitivity analysis optimizes the inflow prediction model by identifying the optimal combination of CatBoost hyperparameters. This process reveals the mechanisms by which the learning rate， number of iterations， tree depth， and regularization constraints affect the model， while also validating parameter synergy effects and strategies for enhancing model robustness. ③ SHAP interpretability analysis quantitatively verifies the model's decision logic while revealing operational thresholds governing the transition between natural precipitation-dominated and artificial regulation-dominated inflow generation modes. This study validates the applicability of the CatBoost model for runoff prediction under dual natural-anthropogenic drivers， and the proposed parameter optimization framework and interpretability methodology provide technical references for inflow forecasting in cascade reservoir systems.

To mitigate the subjectivity of rust annotation and enhance annotation efficiency， this paper proposes a rust detection method based on a YOLOv8 cascaded architecture to rapidly implement deep learning-based corrosion detection for hydraulic engineering metal structures. To enhance accurate detection of rust target， the MobileViTv3 module is integrated into YOLOv8n， resulting in a modified model named YOLOv8-vit. Based on YOLOv8-vit， we further propose YOLOv8-vit-cls for rust grade learning and classification. This network leverages the pretrained parameters of YOLOv8-vit to efficiently learn features of different rust grades. Finally， a cascaded architecture combining YOLOv8-vit and YOLOv8-vit-cls is constructed to perform both rust detection and grade classification of hydraulic metal structures.

Air bulging （also known as “whale” or “hippo”） and even failure frequently occur in large-area geomembrane seepage control projects. However， since the issue emerged with relatively short history alongside geomembrane applications， current case studies remain scarce and lack systematic investigation. This study employs literature review， categorical analysis， and statistical methods to collect， organize， and analyze 30 cases of geomembrane bulging deformation and failure. Based on three hierarchical criteria： installation position （basal， slope， and floating/cover geomembranes）， occurrence stage （field testing， construction， initial impoundment， and operational phases）， and project type （water storage， liquid containment， and solid/slurry waste facilities）， a comprehensive classification system was formed and case database was established for geomembrane bulging deformation and failure issues. According to the case database， base-installed geomembranes accounted for the highest proportion （80.0%） of air bulging cases. Most issues arose during the operational phase （66.7%）， followed by initial impoundment （23.3%）. Cases were reported in surface water storage （43.3%）， liquid containment （33.3%）， and solid waste/slurry storage （23.3%） facilities. Construction/environmental factors （63.3%）， trapped air beneath geomembranes （30.0%）， groundwater rise （23.3%）， geomembrane leakage （13.3%） and newly generated gas/liquid （13.3%） were the primary causes of air bulging. Their main consequences included bulging or rupture of geomembrane （96.7%） and leakage （30.0%） while venting/drainage pathways （16.7%） and overburden weight （13.3%） were the primary countermeasures. The case survey and database will provide a robust empirical foundation for air bulging research， effectively supporting subsequent studies and problem-solving efforts.

Vegetation slope protection is often susceptible to surface slumping caused by rainfall erosion during its initial stages. Tthe biological polymer guar gum， with its excellent gelling properties， can reduce the soil permeability coefficient， thereby inhibiting water infiltration and mitigating rainfall damage to slope surfaces. Through the vertical infiltration model test of soil column under simulated continuous rainfall conditions， the volumetric water content and pore water pressure were measured at different depths of the soil column to explore the influence of different guar gum dosages on the infiltration law. The Philip infiltration model and Horton infiltration formula were used to fit the infiltration rate and cumulative infiltration amount of the improved soil with different dosages. The results show that： ① the volumetric water content and pore water pressure under all working conditions decrease with the increase of depth. ② Compared with the plain soil， with the increase of guar gum dosage， the volumetric water content and pore water pressure at the depth of 25.5 cm decrease significantly， by 6.5%~20.6% and 4.3%~26% respectively. ③ With the increase of guar gum dosage， the infiltration rate decreases by 34.4%~64%， and the cumulative infiltration amount is reduced by 1.76%~24.5%. ④ The fitting determination coefficient （R2） of the Horton formula for the infiltration rate and cumulative infiltration amount is significantly higher than that of the Philip formula， and its root mean square error （RMSE） statistical index shows better performance， indicating that the Horton infiltration formula has better adaptability in describing water infiltration in the one-dimensional soil column infiltration test of guar gum improved sand under rainfall conditions.

In levee engineering， the presence of highly permeable sandy gravel strata in the foundation often leads to seepage and piping risks， seriously compromising the long-term stability and safety of the structure. Currently， cement filling grouting is widely used in practice to enhance the seepage resistance and overall strength of such strata. However， due to the loose structure， high porosity， and complex seepage paths of sandy gravel layers， traditional grouting techniques often result in uneven grout diffusion and unsatisfactory reinforcement. The layout of grouting sequences particularly influences the grout diffusion behavior， yet systematic design and control methods remain lacking. Therefore， this study focuses on the mechanism of grout diffusion during sequential grouting in sandy gravel formations and the influence of hole arrangement. Field tests were conducted， systematically monitoring key parameters such as grouting pressure， grout flow rate， and pore water pressure. The impact of different grouting sequences and hole patterns on the diffusion path and range was thoroughly analyzed. The results demonstrate that the “curtain effect” formed by the preceding grout holes significantly obstructs the diffusion of grout from subsequent holes， leading to a reduced diffusion radius and diminished grouting effectiveness. To address this issue， a "three-sequence staggered diamond layout" grouting technique suitable for sandy gravel strata is proposed. By implementing a sequential construction strategy of "corner holes first， intermediate holes follow， and corner holes seal edges，" this method effectively mitigates the blocking effect of prior grouting on subsequent grout spread， ensuring uniform diffusion and effective filling， thereby significantly improving the overall anti-seepage performance. Field application results show that after implementing this technique， the shear wave velocity in the grouted zone increased by 13.1%， and the permeability coefficient decreased from the order of 10^-3 cm/s to 10^-5 cm/s， indicating a remarkable enhancement in seepage resistance. This research not only elucidates the mechanism of how grouting hole sequences affect grout diffusion behavior but also provides theoretical support and practical guidance for the anti-seepage reinforcement of sandy gravel strata through grouting， offering valuable insights for seepage control under similar geological conditions.

In order to solve the problem of time-dependent deformation caused by the coupling of unloading damage and stress relaxation during the excavation of deep rock mass， the Triassic redbed mudstone in Badong， Hubei Province was taken as the research object in this study. The unloading damage was simulated by the constant axial pressure unloading confining pressure test， and the graded stress relaxation test was combined to reveal the deterioration law of the macro-fine mechanics and structural characteristics of the mudstone under the action of unloading damage-stress relaxation sequence. The results show that with the increase of the degree of unloading damage （D?）， the residual stress ratio of mudstone decreases nonlinearly by 23%~59%， and the dominant role in the rapid relaxation stage is enhanced， and the stress drop is dominated by the rapid relaxation mode when the degree of unloading damage is D?≥28.80%. Based on the SEM images and numerical software， the mesofractal dimension calculated shows that the unloading damage increases the pore fractal dimension by 10%~25%， and further increases by 8%~15% after stress relaxation， revealing the synergistic deterioration mechanism of unloading damage and stress relaxation. The unloading damage-relaxation coupling constitutive model of quaternary Maxwell is constructed based on the generalized Maxwell model， and the fitting error of the model is reduced by 35%~52% compared with the traditional model， and the unloading damage-relaxation coupling effect is accurately characterized. The research results provide a theoretical basis for the long-term stability assessment and support design threshold setting of deep rock mass engineering， and make up for the limitations of the traditional rheological theory of ignorant damage accumulation.

The East Extension Project of the Dalu Line utilizes split-type plane arc gates， As a relatively new gate design， this kind of gate has the characteristics of low head， large span， operation in the horizontal plane， and limited application in China. In this study， the split-type planar arc gate in the East Extension Project of the Dalu Line was taken as the research object. The static and modal characteristics of the gate under dangerous conditions were analyzed by constructing finite element model using ANSYS software. Furthermore， the flow characteristics of the discharge flow under the gate were deeply discussed. In order to study the flow characteristics of the sluice gate under different opening conditions， the flow field in the river channel was analyzed by using Fluent， and the results were compared with the flow data in the physical model test. This study provides a basis for the optimal design of the gate， and can provide a reference for the design and structural analysis of the split-type planar arc gate of similar projects.

This paper proposes a polygonal finite element method （FEM） for the numerical simulation of steady-state and transient seepage problems by introducing Wachspress polygonal interpolation shape functions. The proposed method is capable of handling seepage issues in arbitrary non-convex polygonal elements. Through secondary development of user-defined elements （UEL） in the commercial finite element software ABAQUS， the element-level stiffness and mass matrices for polygonal elements are formulated， enabling robust analysis under both steady and transient seepage conditions. The accuracy and convergence of the proposed approach are validated using benchmark problems， including steady-state and transient seepage through dam foundations. A seepage example involving a rectangular plate further demonstrates the method’s capability to conform to complex geometric boundaries. Numerical results indicate that the polygonal FEM exhibits superior convergence characteristics compared to conventional FEM. For equivalent mesh densities， polygonal elements achieve higher computational accuracy. Additionally， local mesh refinement within polygonal discretizations significantly improves solution accuracy in regions of interest. The polygonal FEM enables automatic conformity to intricate geometries without manual meshing， while ensuring numerical stability， accuracy， and convergence.

Soil-rock interface （SRI） is widely distributed in nature and engineering constructions. The shear mechanical properties of SRI are crucial to the safety of engineering. The properties depended not only on the mechanical characteristics of soil matrix or rock blocks， but also on the geometrical feature of interfaces between soils and rocks. In this paper， the interaction mechanism of SRI， interface digitization method， macroscopic mechanical parameters of soil and boundary conditions of numerical direct shear test are studied， and the macroscopic mechanical properties of SRI are analyzed based on the research results. According to the numercial results， quantitative characterization model of the maximum shear strength， roughness and normal stress of the SRI are established. The results show that the shear strength of SRI increases with the increase of normal stress， which shows a nearly linear relationship. The larger the roughness of the interface， the larger the shear strength is， and the relationship is approximately linear. Soil strength has little effect on shear strength of SRI. The research results can provide reference for strength prediction of SRI in engineering practice.

Synchronous acquisition of transient flow fields on fishway surfaces and fish swimming trajectories typically relies on single-lens systems， which suffer from limitations such as restricted observation ranges and low sampling frequencies. These constraints make it challenging to achieve transient measurements of full-scale （prototype） fishway surface flow fields. Taking uniform flow in a flume as an example， this paper synchronously captured high-resolution image sequences of the flume surface flow field from dual perspectives. By employing a feature matching algorithm and an adaptive weighted fusion method， a seamless stitching technique for multi-source images was developed. Furthermore， a comprehensive workflow was established， encompassing image stitching， data processing， and flow field reconstruction. Measurement results demonstrate that the proposed approach significantly extends the effective coverage area of flow field observations， successfully and efficiently extracting and stitching transient surface flow fields in the flume. The developed system and method exhibit excellent scalability， providing a simple yet practical measurement apparatus and technique for future synchronous acquisition of high-frequency transient flow fields and fish swimming trajectories in fishways. Furthermore， this apparatus and method can be readily extended to measure high-frequency transient surface flow fields in other types of fluid flows.

Flow around twin cylinders and bridge pier scouring are widespread problems in practical hydraulic engineering and river fluid dynamics， often leading to reduced structural stability and fatigue damage. In this paper， a numerical simulation and flow mechanism analysis of the flow around juxtaposed twin cylinders（Re=3 900） with equal diameter in a three-dimensional curved channel is carried out using the LES method. First， the N-S equations for incompressible fluid motion are given， and the sublattice scale model of Smagorinsky-Lilly， which is commonly used in the LES method， is introduced. Second， the grid-independence is verified and discussed for the computational grid of 3D flow field simulation. Third， numerical predictions of the flow field around the juxtaposed twin cylinders（Re=3900） in both straight and curved channels are conducted， with design parameters including different center-to-center spacing ratios L/D， different tangential heights z， and different placing angles α in the curved channel The numerical results show that， with the increase of L/D， the cylindrical trailing edge in both straight and curved channels gradually develops from a single wide wake with vortex mixing to a separated wake， and the juxtaposed double-cylindrical flow field with different placing angles also shows similar characteristics. The distributions of the flow field characteristics at the same tangential height z section are basically the same for different L/D and cylinder placement angles. Different from the case of straight channel， the drag time curves of different placement angles are significantly different and the amplitude increases. Meanwhile， with the increase of L/D and placement angle， the flow field in the curved channel shows the flow characteristics of high velocity inside and low velocity outside， and the secondary flow is significant. This leads to the gathering of strong vortex structures in the inside of the curved channel， and the increase of the distribution area of fragmented vortex structures in the exit channel. These phenomena indicate that the placement angle of the cylindrical columns， high curvature of curved channel and centrifugal effect can cause significant changes in the flow field characteristics. In summary， the study of parallel cylindrical flow in curved channel carried out in this paper can provide data reference for the physical problems such as double cylindrical flow and bridge abutment scour which are widely encountered in water conservancy projects.

Aiming at the cavitation problem at discharge orifice with high head， the hydraulic characteristics of sudden lateral enlargement and bottom drop are investigated based on the length ratio of 1∶50 hydraulic model test. And the numerical simulation uses Fluent software to study the hydraulic characteristic laws under different water body parameters. The calculation uses the VOF multiphase flow model， the RNG k-ε turbulence model， and the PISO velocity-pressure coupling equation. The calculated flow rate， water surface line， flow velocity， and time-averaged pressure distribution have a maximum error of less than 10% compared to the measured values from the test， which meets the engineering accuracy requirements. Further study found that as the gate opening decreases and the outlet narrow slit becomes wider， the sidewall constraints on water flow decrease， longitudinal stretching is weakened， and the cavity length， net cavity length， and net cavity height all increase. At high water levels， the growth trend of cavity hydrodynamic metrics exceeds that at low water levels. Assuming all other conditions are equal， cavity backwater exhibits greater sensitivity to slot contraction ratio changes than jet impact points. As the sidewall gradually deflects from symmetric to unilateral contraction， the location of the longest jet fallout point remains constant and the position is gradually deflected from the center to the non-contracting side. Adopting the method of increasing the width of slit and the slope of bottom can better solve the problem of cavity backwater. The results of the study help to understand the three-dimensional hydraulic characteristics of aeration facilities of the discharge orifice adopting slit-type flip bucket， which can provide a reference for the sizing of similar projects.

Non-submerged attracting groynes have been widely used in regulation works of natural rivers due to their excellent capabilities in guiding flow， preventing bank erosion， and maintaining channel stability. However， existing research has mainly focused on single spur dikes or deflecting groynes， with insufficient investigation into the flow characteristics around undercut weir clusters under different structural configurations. In this study， a three-dimensional numerical simulation of flow around spur dike groups was carried out based on the open-source computational fluid dynamics （CFD） platform OpenFOAM， adopting the realizable k-ε turbulence model to solve the Reynolds-averaged Navier–Stokes equations. The accuracy and applicability of the model were verified by comparing its results with published physical flume experiment data. With reference to actual design parameters from the Lower Yellow River's spur dike projects， this study systematically explored the influence of deflection angle and longitudinal spacing on the mean flow field and turbulence characteristics surrounding the groynes. The results show that： ① As the angle increases， the maximum value of negative flow velocity in the return zone between dikes would decrease by 75.5%， and the maximum value of turbulent kinetic energy would decrease by 0.6 times， with the maximum value of bed shear stress decreasing by 83.1%. The maximum value of negative flow velocity in the return zone behind dikes would increase by 13.8%， and the maximum value of turbulent kinetic energy would increase by 3.23 times， with the maximum value of bed shear stress increasing by 95.6%. ② With the increase of spacing， the maximum value of negative flow velocity in the return zone between dikes would increase by 4.3 times， the maximum value of turbulent kinetic energy would increase by 20.6 times， and the maximum value of bed shear stress in the return zone between dikes would increase by 36.3%. The maximum value of negative flow velocity in the return zone behind dikes would decrease by 26.7%， the maximum value of turbulent kinetic energy would decrease by 81.5%， and the maximum value of bed shear stress in the return zone behind dikes would decrease by 26.9%. These findings reveal the influence patterns of different design parameters on the flow characteristics around non-submerged attracting groynes. The flow behavior observed in this study aligns well with scouring trends reported under mobile-bed conditions in previous research. The insights obtained provide valuable reference for optimizing the spatial arrangement and structural design of spur dike groups in practical river regulation projects.

Revealing the intrinsic relationships between driving factors and water quality evolution within a river basin can support environmental authorities in implementing targeted water pollution control measures. However， existing studies predominantly conduct spatial analyses based on Euclidean distances from monitoring stations and often focus on either anthropogenic activities or climate change in isolation， lacking a comprehensive assessment of their combined effects. To address this gap， this study integrates multiple datasets from the Yangtze River Basin， including GDP distribution， population density， land use patterns， precipitation， temperature， flow discharge， and water quality monitoring data. Four distinct study zones were delineated based on flow accumulation length， Euclidean distance， county-level administrative boundaries， and city-level administrative boundaries. A comparative analysis was performed to examine how different spatial scales influence the correlations between various driving factors and water quality trends at key monitoring stations along the Yangtze mainstem， thereby identifying critical influencing zones. The results demonstrate that for permanganate index （COD_Mn）， ammonia nitrogen （NH₃-N）， and total phosphorus （TP）， the area within a flow accumulation length of 200 km constitutes the key influencing zone for Yangtze water quality. Moreover， three principal components were identified as the dominant drivers across all monitoring stations， collectively explaining an average of 86.7% of the total variance. Specifically， the first principal component includes GDP， population， per capita GDP， cropland area， and residential land area. The second principal component consists of precipitation， grassland area， water body area， and forestland area. The third principal component includes temperature and cross-sectional flow.

To optimize scheduling strategies for combined sewer outfalls that meet the dual requirements of urban drainage safety and water pollution reduction， determining balanced scheduling rules is key to upgrading intelligent water management technology. This study selected the combined sewer system outlets in the Outer Qinhuai River， Nanjing， as the research subject. Taking the Outer Qinhuai River combined sewer system in Nanjing， China， as a case study， a Storm Water Management Model （SWMM） was developed to simulate urban hydrological and hydraulic processes， including surface runoff， pipe flow dynamics， storage node responses， and pollutant transport during typical rainfall events. Based on this， a dispatch rule balancing urban flood safety and maximizing sewage interception efficiency was proposed， incorporating critical rainfall control indicators as dispatch thresholds， along with its model application. Actual dispatch results showed that， at the R05 outfall， full gate opening is required when the water level reaches 6.30?m. Similarly， at the R07/08 outfall， the same measure is required when the water level reaches 5.68m. When water levels reach 6.10m and 5.48m respectively， a single stormwater gate should be opened. The deviations between the optimized hydraulic thresholds and the predicted critical rainfall depths were within 9.33% and 4.17%. Based on this scheduling rule， seven simulation scenarios were designed under different recurrence intervals for safety and pollution control. The rainfall errors between the gate opening thresholds at R05 and R07/08 discharge points and the theoretical critical rainfall levels were all within safe tolerances. Additionally， the water quality simulations indicated substantial improvements in pollutant reduction， with total nitrogen （TN）， total phosphorus （TP）， and chemical oxygen demand （COD） removal efficiencies increasing by 26.4%， 19.8%， and 33.0%， respectively， compared to uncontrolled scenarios. This demonstrates that the balanced scheduling rule can simultaneously meet water safety and water quality requirements.

Phosphogypsum has become one of the industrial solid wastes that urgently needs to be solved due to its large production and potential pollution. Phosphorus （P） and fluoride （F） in phosphogypsum are the main pollutants， which are easily leached into surface water and soil with rainwater， posing serious environmental hazards. Steel slag is a solid waste generated during the steel-making process and is also a common industrial solid waste with good adsorption performance. This study uses steel slag as an adsorbent to remove soluble P and F from phosphogypsum leachate， achieving the goal of “treating waste with waste”， with both environmental and economic benefits. At pH=2， steel slag dosage of 10 g/L， and reaction time of 18 hours， the P removal rate was close to 100%， and F removal was 75.04%. Correspondingly， the P and F adsorption capacity was 8.84 mg/g and 3.52 mg/g， respectively， which was higher than many other common adsorbents. The removal rates of P and F increased with the increase of steel slag dosage. The removal rate of P and F was 97% and 73%， respectively， in the presence of 10 g/L steel slag. The initial pH had an insignificant effect on P adsorption by steel slag， achieving nearly 100% P removal in all cases. However， for the adsorption of F， the initial pH exhibited significant impact. The removal rate of F showed a continuous decrease as the pH increase. When the initial pH was 2， the removal of P and F was 96.58% and 88.37%， respectively. Steel slag has excellent anti-interference ability， which was not affected by coexisting ions， but maintaining a good adsorption effect on P and F. The coexisting SO?2^-， Cl^-， and NO?^- posed insignificant impact on the adsorption of P by steel slag， while they had a certain promoting effect on F adsorption. The adsorption of P by steel slag better conforms to the first-order kinetic model （R ²=0.886 95）， and the adsorption of F better conforms to the second-order kinetic model （R ²=0.999 6）. The acidic phosphogypsum leachate leads to the dissolution of calcium salts in steel slag， which results in Ca²⁺ release and precipitation with P and F. Under alkaline conditions， the removal mechanism of P is the formation of calcium phosphate with lower solubility. Steel slag can reach adsorption equilibrium for both P and F in a short time. Solution pH and competition between F and P for the adsorption sites on the surface of steel slag are the main factors affecting the adsorption rate. The results of this study indicate that steel slag is an effective material for adsorbing P and F， demonstrating potential application value.

This study aims to design a novel dual-cavitation nozzle and evaluate its effectiveness in removing Limnoperna fortunei， with the goal of optimizing the application of cavitation jet technology in water treatment. To address the limitations of traditional physical removal methods， such as low efficiency and significant environmental impact， this study explores a highly efficient and environmentally friendly removal technology. The research team developed a computational model of the dual-cavitation nozzle and conducted numerical simulations using Fluent software. The simulations focused on analyzing the effects of varying the annular spacing between the inner and outer nozzles， the inlet pressure of the outer nozzle， and the axial outlet spacing on the cavitation region and flow field characteristics. Experimental settings specifically included： variations in annular spacing between inner and outer nozzles， adjustments to outer nozzle pressure ranging from 0.1 MPa to 0.6 MPa， and systematic investigation of axial outlet spacing. By setting different target distances and jet angles， the influence of these parameters on the removal efficiency of Limnoperna fortunei was further investigated. The results show that increasing the annular spacing significantly expands the cavitation region. However， excessive spacing reduces flow velocity and cavitation intensity. The optimal conditions for cavitation were achieved at an inlet pressure of 0.2 MPa and an axial outlet spacing of 2 mm. Under these conditions， a target distance of 30 mm and a jet angle of 60° produced the highest impact force and removal efficiency， achieving a removal rate of up to 66.67% when the Limnoperna fortunei attachment was thin. However， removal efficiency declined significantly with increasing attachment thickness， particularly when attachment layers reached three or more， revealing a negative correlation between removal efficiency and attachment quantity and thickness. This study confirms the effectiveness of the dual-cavitation nozzle in removing Limnoperna fortunei and provides a theoretical foundation for optimizing nozzle design. The findings emphasize the importance of selecting appropriate nozzle parameters and jet angles to enhance cleaning efficiency. By optimizing nozzle structure and parameter configurations， the removal efficiency of Limnoperna fortunei can be significantly improved while minimizing environmental impact. This novel nozzle design and its application demonstrate the significant potential of cavitation jet technology in water treatment， offering a valuable solution for hydraulic engineering and aquaculture industries.

In view of the realistic background of the increasing scale of water distribution ring pipes in impulse turbine units domestically， this paper relies on the actual project of the world's first 500 MW impulse turbine unit. Based on the ANSYS platform， it realizes the simulation of the entire process of the distribution pipe filled with pressurized water using the embedment method， and investigates the contact force transmission behavior and structural mechanical response characteristics between the distribution pipe and the concrete. The results show that， under the action of the pressure-retaining head， the section of the distribution pipe expands， and the plane expands as a whole. The overall contraction after the pressure is removed leads to a small initial pressure-retaining gap on the inner side of the section and a larger one on the outer side， presenting obvious non-uniform distribution characteristics. During the operational period， water temperature significantly influences the contact status between the distribution pipe and concrete， as well as the ratio of internal pressure to external pressure. A certain range of dehollowing zone exists on the inner side of the distribution pipe during the operational season with low water temperature. In the high water temperature season， the concrete bearing ratio increases， the tensile stress level increases accordingly， and there is a possibility of developing penetrating cracks in the weak parts of the concrete on the inner side and the top plate of the machine wells. There is no abnormal stress concentration phenomenon in the distribution pipe itself under the water-filled and pressure-retaining burying method， which indicates that the burying method is basically suitable for giant distributor structure.

Addressing the complex 3D flow mechanisms of flooding accidents in the underground powerhouses of giant hydropower stations， this paper constructs a three-dimensional （3D） CFD simulation model based on an actual hydropower station project， combining the Volume of Fluid （VOF） multiphase flow model and the k-ε turbulence model to systematically simulate the water flow evolution under extreme flooding conditions. The study reveals the common hydrodynamic mechanisms driven by high-pressure flood flows： the initial inflow intensity dominates the flooding rate， the channel structural complexity significantly attenuates flow energy through diversion effects， and the status of the drainage system directly affects the flooding process. Quantitative analysis indicates that insufficient flow capacity of vertical channels and backwater rise at abrupt cross-sectional area changes in channels are critical factors leading to rapid inundation. The research extracts a four-dimensional common mechanism of "high-pressure flood flow—spatial diversion—layered inundation—differential pressure submersion，" providing theoretical support for improving hydropower station waterproofing design codes and formulating emergency plans， which is of significant engineering value for enhancing flood safety in underground cavern groups.

The excessive dynamic response of plate-beam-column structural systems in underground powerhouses of pumped storage plants under hydraulic pulsation loads is a critical issue in the vibration-resistant design of powerhouse structures. A three-dimensional finite element model is developed based on the structural configuration of an underground powerhouse in a pumped storage power station. The primary focus is on calculating and analyzing the vibration response of key structural components， including the floor slabs， columns， and staircases， under hydraulic pulsation， and proposes optimization measures for components with excessive vibrations. Through computational analysis of hydraulic pulsation responses under different optimization schemes， this study proposes mitigation strategies for beam-column-slab structures in industrial plants. The results demonstrate that： For columns exhibiting high vibration amplitude in their mid-sections， adding horizontal beams with cross-sectional dimensions identical to those of the columns yields a significantly superior vibration reduction effect compared to merely adjusting the column cross-sectional size. Furthermore， the incorporation of horizontal beams effectively mitigates the vibration response of staircases. By increasing the thickness of staircases or adding a 0.5 m-thick wall at the locations of maximum vibration response， the vibration of staircases can be effectively reduced. Among these measures， adjusting the staircase thickness to 0.35 m proves to be the most effective in optimizing vibration performance.

In the context of the "dual carbon" goals， enhancing the regulation capacity of hydropower is crucial for optimizing energy structure and facilitating the absorption of renewable energy. Reservoir storage is a key indicator of adjustable power generation capacity； however， existing studies predominantly focus on single models or watershed optimization， with insufficient research on the comparative analysis of storage time-series characteristics across different basins and the adaptability of models to different runoff replenishment types. To reveal the adaptability patterns of different basin storage trend analysis models， this study employed the SARIMA and HWES models to conduct a comparative analysis of the storage time-series characteristics from 2015 to 2023 for typical seasonal regulation reservoirs in three representative basins： Yalong River （snowmelt-dominated）， Dadu River （precipitation-snowmelt mixed）， and Min River （precipitation-dominated）. The study also forecasted storage data for 2024 to validate the models' adaptability. The results showed that model adaptability is significantly influenced by the replenishment type of the basin. The SARIMA model proved more suitable for basins with long-term stable trends， such as the snowmelt-dominated Yalong River， where its prediction error during the wet season was 12.4% lower than that of the HWES model. On the other hand， the HWES model better suited basins with frequent short-term fluctuations， such as the precipitation-dominated Dadu and Min rivers， where its prediction error was as low as 0.84% during the wet season of the Dadu River， and remained under 10% throughout the year for the Min River. The study concluded that the differences in model adaptability for storage trend prediction are mainly influenced by the replenishment type and scheduling characteristics of the basin. These findings provide clear model selection strategies for different replenishment-type basins and offer direct theoretical support for differentiated scheduling in multi-energy complementary systems， contributing to the enhanced regulation capacity of hydropower in the new energy system.

The integration of hydro， wind and solar power has been proven to be an effective method for enhancing the utilization of renewable energy. Traditional flexible operation interval models for hydro-wind-solar complementary systems often neglect local minimum width， leading to operation interval that may not adequately adapt to emergencies. Therefore， this study proposes a flexible operation interval derive method， which takes local minimum width into account. First， the local minimum width metric for interval is introduced， and a multi-objective model is developed considering the minimum width， the minimum power generation as well as width of the interval. Second， a two-layer nested solution framework is employed， with the upper layer using the NSGA-II algorithm and the lower layer using the discrete differential dynamic programming （DDDP） algorithm to improve calculation efficiency. Finally， the effectiveness of the flexible operation interval was validated through random simulations， and the performance of the interval operation considering the local minimum width was analyzed in comparison with traditional flexible interval derivation method. Results for case study of a certain hydro-wind-solar complementary system indicate the flexible operation interval considering local minimum width exhibit reduced fluctuations in lower bounds. Additionally， power generation simulations validate operation interval considering local minimum width are more effective in mitigating potential risks during emergencies， with power generation loss amounting to only 0.65% of the total power generation. The proposed interval operation method significantly enhances the ability of hydro-wind-solar complementary systems to handle emergencies.

In remote areas where clean resources are abundant but regulatory resources are scarce， constructing hybrid pumped storage power plants and forming virtual power plants （VPP） by aggregating wind and water enables unified dispatch participation in electricity markets， thereby enhancing the profitability of clean energy. Based on this， we propose a two-layer optimization model for cooperative game day bidding among multiple virtual power plants， considering hydro coupling. The outer layer optimizes market clearing results based on the bidding information of each participant with the aim of maximizing social welfare. The inner layer， which comprises the multi-VPP alliance， optimizes the alliance's bidding strategy based on market clearing results to enhance market revenue by addressing the uncertainty of wind power and the hydraulic coupling characteristics of the watersheds. Furthermore， to ensure fairness in revenue distribution among the VPPs， we propose a Shapley value allocation that takes hydraulic coupling into account. The Karush-Kuhn-Tucker （KKT） method is adopted to solve the transformation of the two-layer model. The example results validate the effectiveness and efficiency of the proposed model， promoting the active participation of clean energy sources in the electricity market in remote areas.

For hydropower units with open channel tailrace systems， there is currently no effective frequency-domain model for open channels， which hinders the ability to conduct frequency-domain stability analyses. In this study， a frequency-domain model for open channels is derived based on the global matrix method， and small-disturbance stability analysis is carried out for a hydropower unit with a single-penstock， single-turbine configuration including an open channel. The results indicate that， in the absence of a tailrace surge chamber， an increase in open channel length negatively affects system stability. The area of the stability region decreases by 0.466 as the open channel length increases from 100 m to 500 m. Conversely， when a tailrace surge chamber is present， the stability region of the system initially decreases and then increases with the extension of the open channel， which is closely related to the system's natural frequency. Regardless of whether a tailrace surge chamber is used， an increase in the initial water depth of the open channel generally enhances system stability， although its impact on the stability region remains limited. The area of the stability region increases by 0.130 as the initial depth of the open channel increasing from 12 m to 18 m， whereas with the surge chamber installed， the area only increases by 0.258.

Accurate short-term forecasts of residual loads are of great significance for the stable operation of the power grid and the integration of renewable energy. To improve short-term forecast accuracy of residual loads， this study proposes a hybrid forecasting model by integrating daily normalization method， Complete Ensemble Empirical Mode Decomposition with Adaptive Noise（CEEMDAN） and Long Short-Term Memory（LSTM） neural network. The Hunan provincial power grid was selected as case study. Firstly， the residual load series were extracted using the daily 24-point loads， new energy output， and output power both inside and outside Hunan Province from 2020 to 2023， and normalized on a daily basis. Then， CEEMDAN was used to decompose the normalized sequence into multiple intrinsic mode functions （IMFs）， and an independent LSTM model was established to predict each IMF and daily maximum value series. Finally， the aggregation operation was utilized to create the results of residual load forecasts. The results indicate that the daily normalization-based model outperforms traditional global normalization models across multiple evaluation metrics for a 24-hour forecast period. The daily normalized CEEMDAN-LSTM model has the best performance. The R² value of the daily normalized CEEMDAN-LSTM model is 0.83 in the testing stage， which is 45.6%， 9.2% and 5.0% higher than those of LSTM， EMD-LSTM and CEEMDAN-LSTM models， respectively. The Mean Absolute Error（MAE） and Root Mean Square Error（RMSE） values of the daily normalized CEEMDAN-LSTM model are 1209 MW and 1604 MW， respectively， which are 18.3% and 9.0% lower than those of the basic CEEMDAN-LSTM model. The proposed hybrid forecasting model can significantly improve the short-term forecasting accuracy of residual loads， providing technical support for stable operation of power grid and the absorption of new energy.

With the large-scale integration of new energy sources in China， leveraging the peak regulation capacity of hydropower to implement hydro-wind-solar complementary operation has emerged as a critical approach to ensure secure and stable grid operation after new energy integration. However， enhancing peak regulation capacity often compromises the economic benefits of hydropower. To balance the trade-off between hydropower peak regulation capability and the economic efficiency of the hydro-wind-solar complementary system， this study proposes a short-term optimal scheduling model for the hybrid system， aiming to minimize the variance of the remaining load process and maximize the stored energy at the end of the dispatch period. The model is solved using the NSGA-II algorithm， followed by the TOPSIS method to evaluate and select the recommended decision-making scheme. Case studies based on the cascade hydropower stations in the lower reaches of the Yalong River， considering three typical days （high-flow， average-flow， and low-flow periods）， reveal that： ① a distinct competitive relationship exists between hydropower peak regulation capacity and the economic efficiency of the complementary system； ② the selected scheme effectively balances both peak regulation and energy storage objectives， satisfying multi-objective requirements during dispatch. The results validate the model's effectiveness and provide valuable insights for coordinating hydropower peak regulation capabilities with the economic performance of hydro-wind-solar complementary systems.