In actual engineering projects， dynamic changes in the head difference between the upstream and downstream of embankment reservoirs （including amplitude changes and reciprocating fluctuations） exacerbate the risk of filter layer soil permeability instability. The particle transport mechanism requires further in-depth study. Using a self-developed large-scale permeameter， non-cohesive yellow sand was used as the base material and river pebbles as the filter material. Under the premise of keeping the composition of the filter and base materials unchanged， the effects of different pressure amplitudes and varying pressurization methods on the transport behavior of fine particles in the filter layer were investigated. The results indicate that as the amplitude of the head difference increases， seepage failure occurs in advance， and the anti-seepage capacity of the protected soil decreases. The critical hydraulic gradient and failure hydraulic gradient decrease， with their boundary becoming blurred， leading to a weakened anti-seepage capacity of the system. The larger the head difference， the lower the hydraulic gradient required for particle initiation and transport， making seepage failure more likely to occur. As the amplitude of the cyclic head difference increases， the system stability decreases， and particles are more likely to initiate and transport outside the filter layer. Even if no failure occurs under a steady head， a larger cyclic head amplitude may still induce instability and accelerate particle transport. The larger the amplitude， the shorter the seepage failure process， the more sudden the failure， and the greater the difficulty in prevention. Sudden rises or drops， or significant fluctuations in water level hinder the dissipation of water pressure， leading to the accumulation of excess pore water pressure， which weakens the effective stress of the soil and reduces system stability. Under the same head difference amplitude， cyclic head effects further weaken the anti-seepage capacity of the base-filter system， with the impact intensifying as the amplitude increases， thereby raising the risk of system instability.

The vertical distribution and spatial heterogeneity characteristics of soil moisture are key factors regulating slope hydrological processes， which profoundly influence slope hydrological response mechanisms by affecting rainfall infiltration and runoff formation processes. Taking loessial soil slopes as the research object， this study adopted the method of indoor simulated rainfall experiments to investigate the dynamic variation of soil moisture， vertical distribution characteristics， and their effects on sediment yield rate under rainfall conditions. Results showed that the response of soil moisture content to rainfall intensity followed a nonlinear growth pattern， with the response time significantly shortening as rainfall intensity increased. The dynamic variation of moisture content exhibited a typical "plateau-leap" stepwise growth pattern， which became more pronounced with increasing upstream slope length， and there exists a critical slope length. Vertically， soil moisture content decreased significantly with increasing soil depth， and the rate of decline diminished under higher rainfall intensities. The increase of upstream slope length notably enhanced moisture content in deeper soil layers. Analysis of Variance （ANOVA） revealed that rainfall intensity， moisture content， and slope length all had extremely significant effects on sediment yield rate （p<0.01）. The relationship between these three factors and sediment yield could be well characterized by a linear model （R ²=0.66）. This study can provide an important theoretical basis for optimizing soil and water conservation measures on slopes in the Loess Plateau region.

To systematically evaluate the characteristics of urban flooding risk under extreme rainfall conditions， this study focuses on the Economic Development Zone of Wuxi City and develops a coupled one- and two-dimensional urban inundation model based on the domestic IFMS hydrodynamic platform. Six long-duration （1 440 minutes） design storm scenarios with return periods ranging from 5 to 100 years were simulated to analyze the response of the drainage system and the evolution of surface flooding. The model combines one-dimensional river networks， drainage pipes， and two-dimensional surface overland flow modules， with a focus on quantitative assessments of key indicators such as node overflow， pipe surcharge， inundation depth and duration， and the spatial distribution of flood risk zones. Results show that， as the return period increases， the drainage system becomes more overloaded. Under the 100-year recurrence period scenario， 2 525 overflow nodes were identified， accounting for 45% of the system and indicating significant drainage bottlenecks. The total flooded area expanded rapidly from 2.29% in the 5-year event to 16.13% in the 100-year event， with maximum water depths also increasing considerably. Along major roads like Gonghu Avenue and Feng Road， inundation depths often exceeded 1.0m at return periods over 30 years， reaching a maximum of 1.52 m， which poses serious flooding risks to transportation and public safety. Spatially， high-risk zones mainly occurred in low-lying areas with limited drainage capacity， while low-risk zones expanded over impervious surfaces as rainfall intensity grew. Through high-resolution numerical simulations， this study uncovers the mechanisms and spatiotemporal patterns of urban flooding during extreme rainfall events. The findings offer quantitative evidence for assessing drainage capacity and provide valuable guidance for sponge city construction and flood control infrastructure optimization. These results are crucial for informing flood prevention strategies， improving urban water security， and supporting sustainable urban development.

This investigation focuses on the problem of local flow structure alterations around bridge piers induced by floating debris blockage. Taking a straight channel as a representative case， three-dimensional numerical flow simulations were employed to systematically explore the influences of skew angle， Froude number and water-blocking ratio on the hydrodynamic structure surrounding bridge piers. Detailed analyses were conducted on the longitudinal variation patterns of water level， spatial distribution characteristics of flow regimes， and vertical profile distributions of flow velocity. The result shows that along the centerline of the bridge opening， the water level undergoes a characteristic sequential longitudinal variation： "upstream rise – middle section drop – downstream recovery – stabilization". The relative value of the maximum water level difference exhibits a decreasing trend with increasing relative skew angle. Conversely， it demonstrates an increasing trend with both rising Froude number and increasing blockage ratio. Flow patterns around the piers undergo significant and complex changes. As the skew angle increases， the blocking effect exerted by the floating debris intensifies. This enhanced blockage leads to the expansion of the accelerated flow zone circumventing the piers and elevating the shear stress magnitudes on both lateral sides of the piers. Furthermore， the flow recovery distance downstream of the piers is prolonged， consequently forming a wider zone characterized by low flow velocities. The increase of Froude number induces a sharp rise in flow velocity within the accelerated zone around the piers， forms a high-velocity band behind the surface floating debris， and drastically reduce the low-velocity zone behind the upstream piers. Bed shear stress within the bridge opening area intensifies significantly， indicating a substantially heightened potential risk for local scour development on the riverbed. The presence of floating debris critically compresses the channel's effective flow cross-sectional area. This compression triggers the mutual overlap and interaction of the low-velocity zones downstream of adjacent piers and amplifies the heterogeneity and spatial variability of the flow patterns within the wake regions behind the piers. The near-surface backflow phenomenon observed at the center of the line connecting bridge piers is demonstrably sensitive to variations in skew angle， Froude number， and water-blockage ratio. Vertical flow velocity， however， exhibits relatively low sensitivity to changes in the skew angle. In contrast， as the Froude number and blockage ratio increase， vertical flow velocity undergoes marked and significant alterations. Critically， the zone of influence of the downflow currents extends deeper， reaching towards the channel bed. This extension substantially increases the potential for exacerbating bed scour processes in these deeper regions.

In recent years， drastic changes in water-sediment regime of the lower Min River jeopardize channel stability and river health. To investigate recent flow dynamics in Min River's lower mainstream， coupled flood and tidal current simulations were performed using three distinct 2D hydrodynamic models specifically configured for the years 1997、2009 and 2020. Results indicate that： ① The water level of the study reach has dropped significantly in recent decades. During 1997-2009， the 50-year return period flood stage decreased by an average of 3.51 m. High and low water levels during spring tides in dry seasons declined by averages of 1.17 m and 2.85 m， respectively. From 2009 to 2020， the 50-year flood stage decreased by 1.23 m， while corresponding high and low water levels during dry-season spring tides decreased by 0.13 m and 0.82 m on average. ② In 1997， the tidal limit during dry-season spring tides remained below Huai’an Diversion， with the entire 50 km stretch downstream from Shuikou Dam being tidally unaffected. By 2009， the tidal limit advanced to approximately 14 km downstream of the Shuikou Dam site， with tidal influence commencing 5 km downstream of the dam. Tidal range increased progressively downstream， reaching a maximum of 2.78 m， while the maximum tidal prism at the Zhuqi section attained 27.25 million m3. By 2020， the entire reach experienced tidal influence， with the tidal limit positioned 5~6 km downstream of the Shuikou Dam site. The maximum tidal range increased to 3.20 m， and the Zhuqi section’s maximum tidal prism reached 42.48 million m3. ③ Flood discharge velocities were governed by riverbed morphology and water depth， exhibiting no consistent trend correlated with channel degradation or stage decline. Conversely， flood-tide velocities demonstrated an overall increase due to enhanced tidal dynamics. By 2020， peak flood-tide velocities persistently surpassed peak ebb-tide velocities throughout the river segment extending downstream from the point 22 km below Shuikou Dam. These findings document the hydrodynamic evolution within the study reach over recent decades， providing critical references for water resources planning， flood control strategies， river corridor conservation， and infrastructure development along the channel.

U-shaped channels are characterized by strong flow capacity， compact footprint， and superior seepage resistance. A flow measurement-control integrated device with an established discharge formula enables smart regulation. By combining a parabolic movable weir plate with a flat gate， this study designed a flat gate with parabolic slots for measurement and control. Through hydraulic tests， this study analyzed flow rates on different discharges， gate openings， and water levels to determine weir/office flow thresholds and critical submergence ratios， establishing the discharge formula with its coefficient. The research results show that under the condition of sluice hole outflow， the water flow in front of the sluice is stable. Due to the characteristic of the parabolic throat being narrower at the bottom and wider at the top， the rising trend of the water level in front of the sluice increases as the sluice opening decreases. The downstream water level increases as the flow rate increases. The relative opening under the critical state of sluice hole outflow and weir flow is close to 0.95， with a critical submergence ratio ranging from 0.53 to 0.73. The Froude number of the flow measuring section in front of the sluice is all less than 0.5， meeting the requirements for flow measurement. Based on the experimental data fitting， the discharge coefficients of this facility under the conditions of weir flow and sluice hole outflow are obtained. The established flow formula demonstrates high measurement accuracy， with errors less than 4.14%. The parabolic sluice groove flat gate has the functions of measurement and control and high flow measurement accuracy， which can provide a reference for the flow measurement and control facilities of the U-shaped channels in irrigation districts.

As a novel type of gate， centrally-pivoted sector gates are significantly different from those of traditional gates in water flow characteristics. In order to study the water flow characteristics of centrally-pivoted sector gates， numerical simulations were carried out based on the 60m span centrally-pivoted sector gate of the Wusong River Regulation Project. The study systematically analyzed the flow field structure of the water flow， the recirculation zone， variations in total flow energy， and energy dissipation rates under varying gate angles， upstream and downstream water depths. The results show that three recirculation zones are generated in the water flow passing through the gate； the height of the mainstream downstream of the gate is positively correlated with the relative downstream water depth， and negatively correlated with the relative upstream water depth. The maximum flow velocity on the gate surface initially increases and subsequently decreases as the gate angle decreases. When the gate angle is the same， the critical relative downstream water depth and the relative upstream water depth for the characteristic recirculation zone to enter the gate chamber are basically linearly positively correlated. The collision between the water flow and the bottom of the gate chamber and the vortex in the water flow under the gate are the main energy dissipation forms of the water flow passing through the gate. The energy dissipation rate is positively correlated with the gate angle and the relative upstream water depth， and negatively correlated with the relative downstream water depth.

Focusing on the "dual carbon" strategy and the recycling of waste resources， avoiding traditional breakwaters made of cement， rocks or concrete， fully utilizing the advantages of anti scouring， anti buffering performance of waste tires as well as good bending resistance of bamboo poles， a new type of ecological breakwater structure is proposed， which is light in texture， low in engineering cost， and easy to construct and dismantle， using bamboo poles as the main reinforcement to fix and stack waste tires. It is referred to as the "permeable breakwater composed of bamboo poles and waste tire strings". In order to obtain a new type of permeable breakwater structure with good wave dissipation， weak flow， and shore protection performance， a water flow erosion model test was conducted to consider the effects of waste tire opening ratio， opening direction， symmetry of front and rear holes， arrangement of permeable breakwater， and water depth. The variation laws of soil pressure， pore water pressure， and wave reduction coefficient before and after the permeable breakwater were analyzed under different working conditions. The inclination angle before and after the permeable breakwater scouring and the amount of mud and sand loss of the embankment were compared under different working conditions. The wave dissipation， current weakening， and shore protection performance under each working condition were analyzed， and compared with the amount of mud and sand loss without a breakwater. According to the physical experiment scale， it is found that when the median particle size of sandy coast in the actual engineering is 0.375~0.75 mm and the water depth is 3.5m， the "permeable breakwater composed of bamboo poles and tire strings" with a tire opening rate of 30% has the best anti current and revetment protection performance； When the direction of the waste tire opening on the permeable breakwater is consistent with the direction of water flow， this new type of permeable breakwater is more suitable for flow dissipation and shore protection； When the front and rear holes of the waste tire of the permeable breakwater are asymmetric， the new type of permeable breakwater has better flow dissipation performance； When the spacing between rows of the permeable breakwater is equal to the diameter of the waste tire of the new permeable breakwater， the new type of permeable breakwater has better flow dissipation performance； When the permeable breakwater is arranged in two rows， the comprehensive benefits of this new type of permeable breakwater project are the highest.

In-depth analysis of deformation monitoring data of hydraulic concrete structures is one of the most important means to assess their real-time operational state. However， due to the complex environmental conditions under which these structures typically operate， nonlinear coupling relationships often exist among deformation monitoring points， making direct quantification challenging. To address this issue， an adaptive X-means clustering algorithm is first employed to group multiple deformation monitoring points of a given hydraulic concrete structure. Then， based on stochastic analysis theory， the synergistic relationships among various monitoring points within strongly correlated groups are extracted. The statistical characteristics of these correlations are incorporated into the traditional set of deformation-influencing factors. Using the measured values of one point within a correlated group as the input variable， a multi-kernel least squares support vector regression （MK-LSSVR） model is applied to capture the nonlinear relationships between input and output variables. This approach establishes a deformation monitoring model for hydraulic concrete structures， and its effectiveness in improving monitoring accuracy is validated through relevant evaluation metrics.

Tunnel Boring Machines （TBMs） have extremely strict limitations on geological conditions， and a reasonable and accurate assessment of rock mass excavatability is crucial for safe and efficient TBM excavation. Based on the on-site measured data of TBM construction tunnels in the Quxi urban and rural water supply project in Tianshui， a comprehensive rock machine energy interaction exploitability index SE _TBM was integrated. The statistical characteristics of TBM excavation parameters under different rock mass categories were analyzed， and prediction formulas for penetration P， cutterhead thrust TF， and excavation speed PR were established using SE _TBM as the index. Furthermore， the TBM exploitability level was divided into 5 levels based on the BIRCH clustering method， and recommended values for TBM excavation parameters under different rock mass levels were obtained. The research results indicate that SE _TBM effectively eliminates the impact of variations in TBM driving parameters and machine technical specifications， serving as a new indicator for accurately assessing rock mass excavability. Compared to traditional classification methods， the rock excavability classification based on the BIRCH clustering method proves to be more accurate and scientific. Additionally， the recommended driving parameters for small-diameter TBMs under different excavability levels are proposed， which can guide practical construction.

Reservoir dam risk standard and risk acceptability determination are important bases for risk management. This paper comprehensively considers three aspects including standard rigor， risk probability accuracy and risk level difference， and explores the risk acceptability determination based on existing risk standards. Firstly， risk standards at home and abroad are compared to explore the strictness of our standards. Secondly， the application of the reliability method in calculating the risk probability is investigated. Then， the difference between risk level and acceptability are discussed. Finally， the feasibility and applicability of this paper are verified by combining with the risk assessment process of a certain gravity dam. The results show that the gravity dam has a reliability index β=4.42， an annualized probability of failure F=2.5×10^-8， and a loss of life N=535.The risk level under Chinese standard is classified as "risk that should be reduced as far as possible"， while it is an “acceptable risk” under foreign standards， which indicates the strictness of Chinese standard. The risk level is general risk， which combined with the acceptability determination indicates that the risk level of the gravity dam is within the tolerable range， and it is necessary to strengthen the risk monitoring and take appropriate safety measures to reduce the risk. The research content of this paper can provide reference for the risk management of reservoir dams in China.

The operational status of culverts beneath dams significantly affects the functioning of reservoirs. The presence of overburden layers increases the uncertainty of culvert performance， making it essential to study their structural safety in this context. Using the overburden drilling and reservoir design data， a finite element simulation was employed to analyze the stress and deformation distribution of the culvert structure under varying overburden thicknesses. Results demonstrate that as the overburden thickness increases， the maximum settlement of the dam body and the culvert shift upstream， creating an inverted slope in the culvert. The compressive stress in the culvert increases， while the tensile stress decreases. The slope ratio of the culvert and the deformation of the culvert joints both increase. Shear deformation in the high plasticity clay zone remains relatively unchanged across different overburden thicknesses. The settlement deformation difference of the culvert before and after cushion layer replacement decreases with increasing overburden thickness. This study indicates that within a certain range， an increase in overburden thickness can adversely affect the water conveyance performance of culverts beneath dams and elevate the risk of seepage. This thickness range is correlated with the properties of the overburden soil， potentially reaching several hundred meters. It is recommended to thoroughly consider the impact of thick overburden on culverts during the design phase， particularly by analyzing and controlling the maximum displacement of culverts under various operating conditions. Additionally， measures such as reinforcing joint structures should be implemented.

Seepage safety of river cofferdam foundations is a critical control factor for the construction and renovation of barrage projects. This study investigates the dewatering scheme optimization for the cofferdam foundation pit in the Sukkur Barrage Rehabilitation Project， Pakistan， by combining analytical solutions with three-dimensional seepage numerical simulations. Through comparative analysis of different well layouts， depth variations， and geological parameters， an optimal dewatering scheme is proposed by balancing economic feasibility with seepage safety requirements. The results demonstrate that： ① increasing well depth can reduce the required number of wells， but it will also lead to a significant increase in the total pumping volume when meeting the drawdown requirement； ② a linear positive correlation exists between permeability coefficient and pumping volume； and ③ the cofferdam section perpendicular to the barrage direction， due to insufficient cutoff measures， tends to form a seepage weak zone， necessitating additional safety measures such as standby wells. The findings provide both theoretical guidance and practical references for seepage control design in similar barrage rehabilitation projects.

In order to study the influence of fracture inclination angle on the mechanical properties and macroscopic and microscopic failure mechanisms of rocks， this article first conducted uniaxial compression tests on fractured limestone samples with different inclination angles to study their macroscopic mechanical failure characteristics. Then， a corresponding numerical calculation model was constructed using a particle flow platform to reveal the micro crack propagation law of fractured limestone with different inclination angles. The results showed that as the inclination angle of the crack increased， the peak strength of the crack specimen showed a "V"-shaped trend of first decreasing and then increasing， while the elastic modulus showed a linear change. The minimum peak strength was observed at a crack inclination angle of 15°， which decreased by 57.3% compared to the intact specimen. During the loading process， the number of cracks shows a trend of first increasing， then decreasing and increasing again with the increase of the inclination Angle. The mesoscopic crack occurrence events are classified into three stages： the dormant period， the active period and the surging period， and the cumulative crack occurrence curves respectively show a gentle trend， an upward trend and a steep trend. Mesoscopic cracks first originate from the tip of the prefabricated crack and gradually extend and penetrate towards both ends. When the inclination Angle is less than 45°， the crack propagation direction is at an acute angle to the crack direction. When the inclination angle is less than 45°， the crack propagation direction forms an acute angle with the fracture direction. When the fracture inclination angle is greater than 45°， the angle between the mesoscopic crack propagation penetration direction and the fracture inclination angle direction is close to 90°.

In view of the difficulty of deformation prediction due to the complex operating environment， random load and strong nonlinearity of the bank slope of the library， Kernel Extreme Learning Machine （KELM） is proposed to model the monitoring data and hybrid kernel function is introduced to enhance the model mapping ability. In order to solve the problem that the mapping ability of the Hybrid Kernel Extreme Learning Machine （HKELM） is affected by hyperparameters， a combined prediction model named CPO-HKELM is constructed by applying the Crested Porcupine Optimizer （CPO） to optimize the nuclear parameters and penalty factors of HKELM. Taking the landslide of a certain reservoir bank as the research object， the H04 monitoring data of the landslide was modeled. In order to verify the feasibility and superiority of the proposed model， CPO-KELM， CPO-ELM and CPO-BP models were introduced for comparative analysis. The results show that the prediction accuracy of the proposed CPO-HKELM is obviously higher than the other two models， and the error is smaller， which has a good application prospect in landslide displacement prediction.

In the field of layered water intake of water conservancy projects， existing water intake facilities have drawbacks such as difficulty in accessing surface water， high operation frequency and difficulty in inspection and maintenance， which restrict the efficiency and quality of water intake. In view of this， this paper innovatively proposes a new type of pontoon-stoplog combined layered water intake gate structure with stepless adjustment function， excellent surface water extraction effect， and can greatly reduce the number of stoplog operations. In this study， the layered water intake gate of Zaodu Reservoir project was taken as the research object， the overall layout scheme of the layered water intake was proposed， the operation principle of the pontoon-stoplog combined gate was analyzed， and the design and calculation of the stoplog and the pontoon structure were carried out. The finite element analysis method is used to systematically analyze the strength and stiffness of the pontoon structure， and the possibility of coupling vibration is studied through modal analysis and comparison with the fluctuation frequency of water flow pressure. The results show that the strength and stiffness of the pontoon structure meet the design requirements， and the possibility of flow-induced vibration is low， which proves the safety and reliability of the structure. The research results can be widely used in the layered water intake of large and medium-sized reservoir irrigation and water intake， and can also be used for the layered water intake of power station water intake， which can provide reference for similar layered water intake projects， and has good social and economic benefits.

The reasonable selection of kernel functions and kernel function parameters is of great significance for improving the performance of Twin Support Vector Regression （TWSVR）. To improve the prediction accuracy of monthly runoff time series and compare and verify the effectiveness of TWSVR with different kernel function mappings， Wavelet Packet Transform（WPT）， 18 kernel functions（such as linear kernel function）， Superb Fairy-wren Optimization Algorithm （SFOA）， and TWSVR were used to propose the WPT-SFOA-TWSVR model with 18 kernel function mappings. Five common kernel function mappings of WPT-SFOA-SVR models were constructed for comparative analysis. A total of 23 models were validated through monthly runoff prediction examples at the Dishui， Nandong， Mengda， and Nankanghe hydrological stations in Yunnan Province. Firstly， WPT is used to decompose and process the monthly runoff time-series data of the instance， dividing it into a training set and a validation set. Then， SFOA is applied to optimize the TWSVR/SVR hyperparameters of different kernel function mappings. Finally， using the optimal hyperparameters， a WPT-SFOA-TWSVR/SVR model with different kernel function mappings was established to train， predict， and reconstruct each component of monthly runoff for the four instances. The results show that： ① The WPT-SFOA-TWSVR model based on linear kernel function， Gaussian kernel function， polynomial kernel function， wavelet kernel function， Sigmoid kernel function， and neural kernel function mapping has the smallest prediction error and the best performance. The WPT-SFOA-TWSVR model based on ANOVA kernel function， Bessel kernel function， logarithmic kernel function， multiple quadratic kernel function， and power-law kernel function mapping follows closely. The WPT-SFOA-TWSVR model based on T-Student kernel function， Cauchy kernel function， and rational quadratic kernel function mapping has relatively larger prediction errors； The WPT-SFOA-TWSVR model based on Laplace kernel function， Fourier kernel function， chi square kernel function， and spherical kernel function mapping has the largest prediction error. ② Under the same WPT decomposition and SFOA optimization conditions， the TWSVR model performs significantly better than SVR. ③ Optimizing TWSVR hyperparameters using SFOA can significantly improve model performance and computational efficiency. ④ The WPT-SFOA-TWSVR model with different kernel function mappings has good universality， providing reference and inspiration for the selection and optimization of TWSVR kernel functions.

As a core economic province in China， Zhejiang is confronted with severe challenges regarding its Water Resources Carrying Capacity （WRCC） due to economic growth， population agglomeration， and accelerated urbanization. The spatio-temporal dynamics of WRCC exert a crucial impact on regional sustainable development. This study aims to reveal the evolutionary patterns， spatial differentiation characteristics， and core influencing factors of WRCC in Zhejiang Province from 2016 to 2023， so as to provide support for water resources management strategies. The research integrates multi-dimensional methods： based on panel data of 11 prefecture-level cities， an evaluation system comprising 17 indicators across 4 subsystems （water resources， society， economy， and ecology） is constructed； a coupled model of improved Analytic Hierarchy Process （AHP） and anti-entropy weight method is employed to determine indicator weights； the improved TOPSIS method is used to calculate the WRCC index； the Theil index is applied to decompose regional differences； the coupling coordination model is adopted to analyze the interaction and coordination degree among subsystems； and the obstacle degree model is utilized to diagnose restrictive factors. The results indicate that ecological water consumption and surface water supply are the core contributing factors. Temporally， the provincial WRCC increased by 44.09%， showing a trend of "rising-peaking-falling"， peaking in 2021， and falling back in 2023 but still exceeding the 2016 level. Spatially， there is significant heterogeneity： regions with ecological advantages such as Zhoushan and Lishui perform the best， while economic core areas like Hangzhou and Ningbo show weaker performance due to high population density and intense industrial water use. The Theil index reveals that regional differences mainly originate from intra-regional disparities， with the ecological subsystem exhibiting the most prominent differences. The subsystems demonstrate a high coupling degree but insufficient coordination； after 2021， the water resources subsystem became the main limiting factor. The obstacle degree model shows that rainfall fluctuations and population density growth are the core pressure sources， and the insufficient efficiency of water resources allocation and lagging water-saving technologies exacerbate the contradictions. In conclusion， this study clarifies the spatio-temporal evolution mechanism and restrictive factors of WRCC， and suggests improving carrying capacity by optimizing water resources allocation， popularizing water-saving technologies， and guiding population and industrial layout， thus providing a basis for coordinated sustainable development.

Similarity measurement is a key factor for finding similar samples and affecting the accuracy of similarity-based runoff forecasting models. This study proposes a comprehensive “quantity-shape” similarity measurement index-optimal similarity coefficient， analyzes the advantages of this method compared to the “quantitative” similarity and “shape” similarity measurement index in selecting historical similar samples， and evaluates the accuracy of runoff prediction models based on different similarity measurement indices. By combing a rolling forecasting method that uses real-time updated prediction information， runoff forecasting within the 10 day forecast period is achieved. The model is applied to the daily runoff forecasting of the Danba section of the Dadu River throughout the year. The results show that compared with the “quantity” similarity and “shape” similarity measurement index， the sample values and variation trends found by the optimal similarity coefficient are the most similar to the target sample. The average relative error of the forecast results for a 1-day lead time is 3.18%， which is reduced by 0.18% and 0.74% respectively compared to the “quantity” similarity and “shape” similarity measurement index. This advantage is more prominent during the flood season due to the large fluctuations in rainfall and runoff. The average relative error of the forecast results for a 1-day lead time in flood season is 3.73%， which is reduced by 0.31% and 0.83% respectively compared to the “quantity” similarity and “shape” similarity measurement index. In addition， the model significantly improves the flood forecasting accuracy at the Danba section， with the average relative error of the flood peak forecast under a 1-day forecast period not exceeding 8% and the lowest being 0.99%. In the 10-day rolling runoff prediction， the average relative errors of the forecast results for the 3-day， 7-day and 10-day forecast periods are 6.72%， 10.18% and 12.79%， respectively， and the forecast performance is good in terms of flood peak and peak occurrence time. This study validates the advantages of the “quantity-shape” similarity measurement index in improving forecast accuracy， providing a scientific basis for optimizing the similarity runoff forecasting model.

Under the dual pressures of climate change and intensive human activities， groundwater systems in this basin have experienced continuous decline， with an increasing frequency and intensity of droughts. This highlights the urgent need to establish reliable monitoring and identification methods. In this study， the Tarim River Basin was selected as the research area， and a standardized Groundwater Drought Index （GGDI） was constructed using GRACE gravity satellite inversion data from 2002 to 2024， integrated with multi-source remote sensing products such as GLDAS and JRC. The spatiotemporal evolution characteristics of groundwater drought processes were analyzed comprehensively at annual， seasonal， and spatial scales and migration patterns in typical years and typical regions were identified. The results indicate that extreme drought events occurred in 2008、2011、2015、2020 and 2022， with minimum GGDI values falling below-2. In particular， Bayingolin Mongolian Autonomous Prefecture and Kashgar experienced droughts lasting longer than 12 months， while in the mid- and lower-reach oasis belt the number of drought months exceeded 8 months. The basin-wide annual minimum GGDI reached -1.76 in 2022， marking the most severe year during the study period. At the seasonal scale， winter droughts averaged around -1.1， spring recovery was limited， summer conditions improved significantly with an average GGDI of +0.7 due to precipitation and snowmelt recharge， whereas autumn droughts intensified again， reflecting the contradiction between recharge and over-extraction. Spatially， the drought center exhibited a southward migration trend： from the northern margin of the middle reaches during 2002-2010， to the downstream oasis during 2011-2015， and stabilizing in the Luntai–Yuli region after 2016. Validation against in-situ groundwater level data yielded a Pearson correlation coefficient of 0.83 （R2=0.69）， confirming the monitoring reliability of GGDI. Based on these findings， the study identifies high-risk drought zones， proposes extraction-limiting policy recommendations， and emphasizes the establishment of multi-scale monitoring and early-warning mechanisms. These results provide both theoretical insights and technical support for groundwater management and water resource regulation in arid regions.

To improve the large-scale wall separation and backflow area existing in the forebay of a certain continuous single-sided large diffusion angle pumping station， a combined method of physical model test and numerical simulation was adopted to analyze the flow pattern of the forebay at the designed water level of the pumping station. The uniformity of the axial velocity distribution was used as the evaluation index to explore the optimization effect of different rectification measures. The research shows that without rectification measures， a large-scale backflow area appears on the diffusion side of the forebay， and the flow velocity distribution at the entrances of No.1 and No.2 channels is uneven and the flow velocity is relatively high. The rectification measure of staggered arrangement of "oblique guide piers + oblique angle guide piers" in the slope section of the forebay can effectively eliminate the backflow area in the forebay. When the angle of the guide piers is 30°， the optimization effect is the best. This scheme increases the uniformity of the axial velocity distribution at the inlet sections of the channels by 5.33%、19.47%、13.44%、5.17%、0.68% and 1.78% respectively， and reduces the hydraulic loss by 0.281 m， ensuring the safe operation of the pumping station. The research results can provide a reference for the improvement of the flow pattern in similar pumping station forebays.

This paper focuses on a giant mixed-flow hydro turbine as the research object and employs Computational Fluid Dynamics （CFD） methods to numerically simulate the flow field characteristics， pressure pulsations， and cavitation phenomena during the turbine's startup process. The multi-dimensional data characteristics of the internal flow field of the giant Francis turbine in the startup process were obtained. The results indicate that under low-load conditions， runner passage vortices and the tailrace swirling flow are the main causes of pressure pulsations， while the cavitation phenomena at the runner outlet are closely related to the evolution of vortices. Additionally， the non-uniform flow distribution within the spiral casing， pressure gradients on the runner blade surfaces， and the recirculation zone in the draft tube can also affect the turbine's performance. This study reveals the complex hydraulic characteristics inside the hydro turbine and provides a theoretical reference for optimizing turbine design and improving operational stability.

To explore the influence of inlet pipes on the flow and erosion characteristics of Pelton turbine injector， two different inlet pipe schemes and six schemes with different numbers of guide vanes were designed. CFD technology was applied to calculate the hydraulic erosion of the injector under rated conditions， and the influence of inlet pipes and guide vanes on the flow and erosion characteristics of Pelton turbine injector was analyzed. The results show that the internal vortex structure of Pelton turbine injector is mainly composed of the Dean vortex generated by elbow inlet pipes and the attached vortex and stretching vortex generated by the guide vanes. The deformation of the jet liquid surface of the injector is mainly affected by the Dean vortex. The erosion distribution of Pelton turbine injector is mainly concentrated in the nozzle throat area， the downstream needle throat area of the guide vane， and the needle tip. Its erosion characteristics are jointly affected by the form of the inlet pipe and the guide vane. When the number of guide vanes in the elbow inlet pipe of the injector is not more than 5， the erosion of the spray needle in the injector is mainly affected by the Dean vortex generated by the elbow inlet pipe. Conversely， the erosion of the spray needle in the injector is mainly affected by the stretching vortex generated by the guide vanes.

A RANS-DEM coupling approach was employed to perform a comprehensive numerical simulation of the internal flow characteristics and particle dynamics within an annular jet pump operating under solid–liquid two-phase flow conditions. The Archard wear model was further incorporated to quantitatively evaluate the wear evolution of the flow-passage components. The study primarily investigated the influence of particle density on pump performance parameters—including hydraulic efficiency， pressure ratio， and specific energy consumption per unit particle mass—as well as on particle motion behavior， collision characteristics and their spatial distribution， and wall wear morphology. The results reveal that as particle density increases， both the pressure ratio and hydraulic efficiency of the pump exhibit a decreasing trend， while the specific transport energy consumption rises significantly. The time for particles to reach the throat and diffuser for the first time is slightly delayed， whereas the overall time for particles to pass through the pump decreases. The acceleration period of the particles shortens， leading to a slightly higher steady-state velocity. The total number of collisions increases and their collision occurrence time advances marginally； however， the proportion of direct particle–particle collisions relative to all collision events decreases progressively. In addition， the suction and discharge sections display more concentrated and pronounced localized wear spots， and the overall wall wear intensity increases with increasing particle density.

The water hammer phenomenon， induced by fluctuations in water pressure within pressurized pipelines， can significantly affect the entire water transmission system. Accurate prediction of this phenomenon hinges on determining the water hammer wave velocity， which is influenced by various factors such as pipeline characteristics， fluid properties， and the presence and state of gas in practical engineering. Among these factors， the existence and state of gas play a particularly critical role in affecting wave velocity. This paper develops a model for uniformly distributed bubbles using the second-order finite volume method based on the Godunov scheme， integrated with the pressure equilibrium equation and the gas state equation. This approach enables real-time calculation and control of the water hammer wave velocity. Numerical simulations are conducted to compare the model's results with experimental data， thereby validating the influence of the Courant number on the model's stability and accuracy. Additionally， the simulations provide a deeper analysis of the mechanism by which gas affects wave velocity in gas-liquid two-phase flow. The findings indicate that， compared to traditional transient process calculation methods with fixed wave velocities， the proposed model more accurately simulates the dynamic behavior of gas-liquid two-phase flow in pressurized pipelines. The adoption of a second-order numerical scheme effectively mitigates numerical dissipation caused by variations in wave velocity. Furthermore， the presence of gas in pressurized pipeline systems significantly reduces the intensity of the water hammer effect.

This study presents an experimental study on the noise characteristics of cavitation in a waterjet pump. Noise signals were acquired at both the inlet and outlet of the pump during continuous pressure drop， covering various cavitation stages， while the evolution of cavitation morphology was simultaneously captured. Based on frequency domain analysis， the noise signals were divided into four frequency bands： 0~5， 5~15， 15~25 and 25~60 kHz. The overall sound pressure level （SPL） in each band was calculated to characterize its variation across different cavitation phases. The results show that the SPL above 15 kHz increases sharply at cavitation inception， exhibiting significantly higher sensitivity than those in lower frequency bands. When sheet cavitation appears and the cavitation regime transitions from cloud cavitation to a coexistence of cloud and sheet cavitation， the SPL in high-frequency bands shifts from an increasing to a decreasing trend. This characteristic is consistently observed at both inlet and outlet of the pump， independent of hydrophone positioning. These findings indicate that the SPL in frequency bands above 15 kHz can serve as an effective indicator for identifying cavitation states in waterjet pumps， enabling not only the detection of cavitation occurrence but also the differentiation of cavitation types. This work offers a potential technical approach for cavitation monitoring and diagnosis in hydraulic machinery.

In order to improve the cavitation performance of centrifugal pumps， an impeller model with ridged structure arranged at the leading edge of centrifugal pump blades was proposed. Hydraulic performance experiments and cavitation performance experiments of the original model were carried out， and the transient cavitation of the original model and the ridge-structured model was numerically simulated. The external characteristic curve and cavitation performance curve， as well as the changes in the volume of cavitation， flow field structure， absolute pressure distribution， vorticity field and turbulent kinetic energy in the impeller channel were compared and analyzed. The results show that the ridge-structured model has little influence on the external characteristics of the original model， and the numerical simulation results are in good agreement with the experimental data. The volume of vacuoles is significantly lower than that of the original model. The ridge-structured model effectively optimizes the flow field structure， reduces part of the backflow and lateral jet， and increases the local pressure at the leading edge of the impeller inlet， thereby inhibiting the occurrence of cavitation. The ridged structure reduces the generation of vortices inside the impeller， makes the flow more stable， reduces the turbulence intensity in the impeller， reduces the energy dissipation， and improves the cavitation performance of the centrifugal pump.

To investigate the influence of radial clearance backflow on the flow characteristics of a full-flow pump unit in the Saddle Zone， this study adopted a combined method of numerical simulation and model test. The radial clearance backflow was controlled by changing the width of radial clearance， and a comparative analysis was conducted on the characteristics of the saddle region of full tubular pump units under the radial clearance widths of 1、2 and 4 mm. The results indicate that as the clearance width increases， the critical flow rate for the pump unit entering the Saddle Zone operation shifts toward higher values. The enlarged clearance exacerbates the axial velocity decline in the rim region at the impeller inlet， disrupts the inflow pattern， and leads to gradual expansion of the recirculation zone. These flow characteristics compress the high-pressure zone in the impeller chamber， resulting in expanded flow separation vortices and increased vortex density， ultimately causing the pump unit to enter the Saddle Zone prematurely. The pressure pulsation at the impeller inlet is dominated by a frequency of three times the rotational frequency， and reducing the clearance width increases the pulsation amplitude. Smaller clearance widths reduce the radial resultant force of the impeller but intensify transient non-steady fluctuations in both axial and radial forces. This study provides insights into the mechanism of premature Saddle Zone occurrence， broadens the efficient operating range of full-flow pump units， and offers theoretical guidance for improving operational stability in the Saddle Zone.

Under the new power system， hydroelectric generators are faced with frequent peak shaving and frequency regulation tasks， and the temperature rise problem of large-scale hydroelectric units is becoming increasingly serious. Existing research lacks specific changes in the ventilation and temperature field of generators under full operating conditions for large units， and lacks experience to guide the operation of existing large units. This paper studies the ventilation and temperature field of the hydraulic generator on the left bank of a large hydropower station under different operating conditions during start-up and shutdown. It analyzes the changes in the ventilation system air volume caused by variable speeds and the influence of different operating conditions on the temperature of each heat-generating component of the generator， and masters the temperature change trends of each heat-generating component under different operating conditions. The research results of this paper have important practical engineering significance. Based on the calculation results of this paper， the power station can safely switch between different operating conditions， thereby improving the operation and maintenance level of the power station.

This study explores the regional differences and dynamic evolution of the high-quality development of rural water conservancy and hydropower， aiming to provide theoretical basis and empirical support for promoting the high-quality development of rural water conservancy and hydropower in China. Based on the perspective of the new development concept， we constructed an evaluation index system for high-quality development of rural water conservancy and hydropower， and analyzed the regional differences and dynamic evolution of high-quality development of rural water conservancy and hydropower in China from 2011 to 2022 by using the longitudinal and transversal pull-out grade method， Dagum Gini coefficient， and kernel density estimation method. The results show that： ① The level of high-quality development of rural water conservancy and hydropower has been continuously improving， driven primarily by open development and coordinated development， while constrained by shared development， innovative development， and green development. Spatially， the pattern shows that the eastern region leads， the western region is in the middle， and the central region is relatively lagging behind. ② The overall regional disparity in the high-quality development of rural water conservancy and hydropower has gradually narrowed， with the main difference arising from inter-regional disparities. Among these， the East-Central region disparity is the primary source of inter-regional differences， while intra-regional differences in the central region are the primary source of intra-regional disparities. ③ The overall level of high-quality development of rural water conservancy and hydropower in China continues to rise， with the eastern region showing a high degree of concentration， the central region showing fluctuations before tending toward balance， and the western region exhibiting a trend of differentiation. To promote the high-quality development of rural water conservancy and hydropower and reduce regional disparities， it is necessary to optimize resource allocation， promote shared， innovative， and green development of rural water conservancy and hydropower； strengthen policy support to facilitate balanced regional development of rural water conservancy and hydropower； and further drive precise management and resource optimization in the central region.

The effects of waterlogging stress on cotton vary significantly across different growth stages. The waterlogging stress day index （SDI） is a reasonable indicator for evaluating the overall impact of waterlogging over the entire growing period on crop yields， but it is still in the research stage and lacking practical application for cotton plants in China. To this end， this study took a five-year continuous cotton waterlogging experiments covering multiple growth stages conducted in Jingzhou， Hubei Province as the test database， and integrated cotton waterlogging data from another three published experiments which were performed in other regions. This study proposed three methods to calculate the key parameter of SDI model （Normalized Crop Susceptibility， NCS）， and finally established and compared various SDI models under different situations. The results indicate that in most cases， the fitting effect of the SDI is better than that of the regression model without considering the growth stage effect. In addition， using the ‘heavy waterlogging method’ to determine NCS can best characterize the differences among growth stages， while the usage of ‘averaging method’ yielded the poorest performance of the SDI models. The SDI model performs better when the cotton growth period is divided into four stages rather than three stages. The NCS values of cotton seedling， budding， flowering and boll-opening stages can be conveniently set as 0.2， 0.3， 0.4， and 0.1. In addition， the recommended form of cotton waterlogging SDI method was determined as follows： relative cotton yield=-0.232 55 SDI+1（p<0.001）. This study can provide valuable guidance for cotton field drainage scheduling as well as waterlogging disaster reduction in China， especially under the context of increasing climate change.

To further alleviate the shortage of freshwater resources in the comprehensive management of saline-alkali land， this study investigates the effects of combined irrigation with canal water， ditch water， shallow well water， and deep well water on alfalfa cultivation in saline-alkali land. Five treatments were set up： single shallow well water irrigation （T1）， combined irrigation with canal water and ditch water at a ratio of 2∶1 （T2）， combined irrigation with canal water and shallow well water （14 m deep） at a ratio of 2∶1 （T3）， combined irrigation with canal water and deep well water （200 m deep） at a ratio of 2∶1 （T4）， and single Yellow River water irrigation （CK）. The response relationships between different treatments and indicators such as alfalfa growth indices， soil salt content， crop yield， and water use efficiency were analyzed， and the entropy weight-TOPSIS model was used to evaluate and screen the optimal combined irrigation mode. The results showed that： the combined use of multiple water sources was beneficial to the growth of alfalfa， and the growth indices of the first alfalfa cutting performed best among the three cuttings. Shallow well water substitution for supplementary irrigation was suitable for the second and third cuttings， which was beneficial to stem thickness growth and could increase the number of alfalfa branches. When the groundwater depth was below 0.5 m， the soil salt content after the experiment in each treatment increased to different degrees compared with that before the experiment. Frequent small-scale combined irrigation with multiple water sources was beneficial to improving alfalfa yield， irrigation water use efficiency （IWUE） of hay， and water use efficiency （WUE）. Treatment T3 performed the best， with a yield 12.56% higher than that of CK， and IWUE and WUE of hay increased by 12.56% and 14.73% respectively compared with CK. The entropy weight-TOPSIS comprehensive evaluation recommended the T3 irrigation mode， that is， when the rainfall was 135 mm， 375 m3/hm2 of canal water was irrigated at the early flowering stage of the first cutting， 225 m3/hm2 of shallow well water was irrigated at the budding stage of the second cutting， 225 m3/hm2 of canal water was irrigated at the branching stage of the third cutting， and 105 m3/hm2 of shallow well water was irrigated at the budding stage， with a yield of 28.01 t/hm2 and a water use efficiency of 6.24 kg/m3.

Rural water supply systems are highly vulnerable to prolonged droughts， which can trigger significant water supply risks. However， quantitative assessments of such risks remain lacking， limiting early-warning and preventive measures. Based on the principles of water supply–demand balance and the characteristics of rural water supply systems， this study develops， for the first time， Rural Supply Drought Index （RSDI） and applies it to a case study in Chongqing， China. The results show that under drought durations of 10~60 days， the RSDI across districts and counties in Chongqing ranges from 0 to 0.23， with southeastern Chongqing exhibiting the highest drought-related supply risk. Under a 60-day drought scenario， the average RSDI for this region reaches 0.16. Among different water source types， spring water shows the strongest positive correlation with RSDI， with the correlation coefficient increasing from 0.18 to 0.46 as drought duration lengthens， indicating that areas relying primarily on spring water are more prone to supply risks. In addition， small-scale systems serving approximately 100 people exhibit a positive correlation with RSDI， reflecting their limited capacity to withstand drought-induced supply stress. This study provides a scientific basis for quantitatively assessing rural water supply risks under varying drought conditions.

To improve nitrogen use efficiency in rice fields and reduce agricultural non-point source pollution， five experimental fields were selected in this study， where a combination of slow-release fertilizer and conventional fast-release fertilizer were applied. The field experiments set up treatment groups including traditional flooding irrigation， shallow-wet-dry irrigation， intermittent irrigation， alternate wetting and drying irrigation， and a blank control group. The distribution characteristics of NH₄ ⁺-N and NO₃ ^--N concentrations in the soil profile from surface water to 30 cm below the soil surface were compared and analyzed. The research results showed that shallow-wet-dry irrigation， intermittent irrigation， and alternate wetting and drying irrigation modes were all more beneficial for nitrogen utilization and reduced leaching losses compared to traditional irrigation. Slow-release fertilizer was well-matched with shallow-wet-dry irrigation， resulting in more uniform nitrogen concentration distribution. And higher nitrogen concentrations were maintained with conventional fast-release fertilizer combined with alternate wetting and drying irrigation. While slow-release fertilizer showed gradual and sustained nitrogen release， which was conducive to enrichment for root zone， fast-release fertilizer released quickly and was prone to leaching， and therefore the application of slow-release fertilizer was superior to fast-release fertilizer. The research findings are of important theoretical and practical reference for optimizing agricultural irrigation modes， improving fertilizer use efficiency and reducing agricultural non-point source pollution.