To explore temporal and spatial variations of extreme precipitation in the Rolling Hilly Region of Northeast China, a set of extreme precipitation evaluation indicators was established using the daily precipitation data from 79 meteorological stations covering the period from 1981 to 2015. The intensity, frequency and persistence of extreme precipitation were analyzed using various methods, including linear trend estimation, coefficient of variation, Mann-Kendall test, R/S analysis, and GIS spatial analysis. The results show that from 1981 to 2015, the overall extreme precipitation showed a weakening trend in the Rolling Hilly Region of Northeast China; R×1day, R×5day, R12D, R50D, and CRED decreased at rates of -0.5 mm/10a, -2.1 mm/10a, -0.2 d/10a, 0.02 d/10a and 0.03 d/10a, respectively. The inter-decade variation of the intensity index showed a state of "rise-fall-rise", and the annual change of frequency index and persistence index showed a "fall-rise" form, which increased by 12.5%-15% in the 2010s compared with the 2000s. The C_V value of frequency index R50D is 0.45, which fluctuates sharply, and the C_V value of other indices is less than 0.2, and the fluctuation range is small. R50D and CRED experienced abrupt changes in 1988 and 1990, respectively, and exhibited an increasing trend before the mutation points and a weakening trend after that. Extreme precipitation increased during the 1990s, weakened in most areas during the 2000s, and intensified in both frequency and intensity in the northern high-altitude areas of the Rolling Hilly Region of Northeast China in the 2010s, while it reduced in the Southern Regions. This study can provide a theoretical basis for formulating strategies to cope with extreme precipitation risks in the Rolling Hilly Region of Northeast China.

Studying the propagation of meteorological drought to hydrological drought is essential for meteorological information-based drought management and hydrological drought warning systems. Taking the Ganjiang River source basin as an example, this paper uses the basin's monthly meteorological and hydrological data for the past 60 years to study the propagation pattern of meteorological drought to hydrological drought, and explores the differences in drought propagation among sub-basins. The results show that the propagation of meteorological drought to hydrological drought has various ways, with a one-to-one correspondence; The drought events increase hazards after propagation from meteorology to hydrology; The Logistic model can better reflect the response relationship of hydrological drought characteristics to precipitation shortage conditions; The large reservoirs have a significant effect on the drought resistance of the basin.

Taking the section of Hunan in Xiangjiang River Basin (XRB) as an example, bases on the land use and evapotranspiration data in 2000, 2010 and 2020, this study discusses the characteristics of land use type, area change and mutual conversion in the XRB by using the methods of land use transfer matrix, integrated and single dynamic attitude model and GIS spatial analysis. The effects of land use type, area and conversion on evapotranspiration in the study area were revealed. The results show that the area, proportion and spatial pattern of land use types in the XRB have undergone great changes, especially the frequent conversion among land use types. However, in the past 20 years, the order of main land use areas in the XRB remained stable: forest > farmland > grassland > construction land > water area. The order of theoretical annual evapotranspiration based on land use type in the XRB is forest > grassland > farmland > construction land, which is different from the order of actual annual total evapotranspiration based on land use area: forest > farmland > grassland > construction land. Therefore, the land use type and land use area to evapotranspiration in the study area should be considered comprehensively. The conversion of different land use types in the XRB caused the change of evapotranspiration in different trends and degrees. The conversion between construction land and other land use types has a relatively large impact on evapotranspiration in the study area, while the conversion of other land use types has a small impact on regional evapotranspiration. The research results can provide scientific reference for land use planning and water resources management in the basin.

Aiming at the evolution of water resources in Qiandao Lake Basin under the condition of climate change, a WEP-L distributed hydrological model was established to simulate the water cycle process in the basin during 1960-2020. The Mann-Kendall non-parametric test method and Hurst index method were used to analyze the inter-annual variation and annual distribution characteristics of the total water resources in the basin. The temporal and spatial distribution and evolution trend of water resources in Qiandao Lake Basin were evaluated. The results indicate that The WEP-L model performs well in simulation the Qiandao Lake basin, and the Nash coefficient rate is above 0.83 in the calibration period and above 0.85 in the verification period; The water yield coefficient of the whole basin ranges from 0.436 to 0.630. The annual average total water resource is 122.5×10⁸m³, equivalent to 1 176.4 mm of water depth. The annual distribution process shows a unimodal structure, and the water depth of each sub-basin ranges from 742 mm to 1 266 mm, and the spatial distribution is higher in the west and lower in the east; The annual water resources series in the basin show an insignificant upward trend, and the Hurst index is 0.86, indicating a continuous upward trend. From the perspective of monthly water resources, January and February increased significantly, the other months were not significant changes.

In order to coordinate the balance between water resources supply and demand and promote the sustainable use of water resources in Wuhan City, this paper conducts a comprehensive evaluation and simulation of the water resources carrying capacity of Wuhan based on the improved TOPSIS method and system dynamics, and realizes a combination of static evaluation and dynamic prediction. The results show that the overall water resources carrying capacity of Wuhan City fluctuates and increases from 2010 to 2020, and the overall level is in a critical state; By simulating the development of Wuhan City from 2021 to 2035, the water resources carrying capacity of Wuhan City under the conventional development model has exceeded the limit and it is difficult to maintain the demand; The economic priority model sacrifices resources and environment for economic speed up, which shows the most serious water resources; The environment-friendly model can reduce water consumption and improve the ecological environment, but the economic development is also limited to a certain extent; The integrated development model, from the perspective of coordination and balance, can achieve resource conservation and environmental protection while satisfying the steady and rapid economic development, and obtain the maximum economic and ecological benefits with the minimum water consumption, achieving the harmonious development of human and nature.

Timely and accurate forecasting residential water consumption is critical to design and operational management of water supply systems. Long short-term memory (LSTM) is an effective data-driven prediction model for water consumption, but it usually relies on a large number of parameter settings. This paper proposed a multilayer long short-term memory neural network model (MLSTM), which was built on the LSTM model by superimposing a time distribution module. The results indicate that the MLSTM model has lower complexity and higher prediction accuracy than the LSTM model, especially for the prediction of peak water consumption with M_MAPE reduced by about 60%. Meanwhile, the MLSTM model is insignificantly affected by external environmental conditions (e.g., weather).

It is of great significance for the long-term planning and allocation of Nanjing water resources to analyze the current situation of Nanjing water consumption, make reasonable prediction of Nanjing water consumption and master the future water demand. The analysis of water consumption in Nanjing from 2009 to 2019 showed that industrial and agricultural water consumption accounted for a large proportion of total water consumption in Nanjing, which played a crucial role in the change of total water consumption. The combined model of grey GM(1,1) model and Elman neural network was used to forecast the water consumption of all districts and the total water consumption of Nanjing. The results show that the grey Elman neural network model has a good prediction effect on the total water consumption of Nanjing City from 2009 to 2019. The relative errors of the forecasts were all less than 3.5%, and the average relative errors of the predicted results over the years were 1.55%; The relative error of the forecast results is less than 8.5% in the forecast of the water consumption of all districts in Nanjing in 2019. The model used in this paper can accurately predict the water consumption of Nanjing, which is of great significance to effectively control the regional water consumption and realize the principle of "four water and four determinations".

In response to the problems of low accuracy and poor reliability of water consumption prediction due to the strong randomness and non-stationary state exhibited by the water consumption signal, this paper proposed a hybrid water consumption prediction model based on improved EEMD-WOA-SRU. Firstly, the LSTM prediction method was used to suppress the endpoint effect of the EEMD to obtain the improved intrinsic mode functions (IMF). Then the whale optimization algorithm (WOA) was used to optimize the simple recurrent unit (SRU) and predicted each component. Finally, the final prediction results were obtained by accumulation. The experimental results show that the decomposition error of the EEMD is reduced by 0.94% on average; Compared with the SRU, the average absolute error of EEMD-WOASRU model prediction is reduced by 45.42%, the root mean square error is reduced by 50.43%, and the reliability is improved by 52.38%. It can provide a basis for water resources decision making.

The current regional water supply and power generation structure is not able to achieve sustainable development in the long term. It is worth exploring whether the production, trade and the corresponding water footprint of the power sector in the Beijing-Tianjin-Hebei (BTH) region can meet the long-term development needs of the region after the dual-carbon goals is proposed. Therefore, this study constructed a dynamic multiregional computable general equilibrium model to simulate the changes in the production and trade of the power sector and its water footprint in the BTH region caused by the carbon reduction policy. Four carbon reduction scenarios were designed in the model to explore the impacts of policies such as carbon tax, investment and renewable energy subsidies. The results show that the carbon tax policy has the most significant water saving effect on power generation; The carbon reduction policy significantly increases the inter-regional flow of virtual water in the power trade; The complete water footprint of the power sector under various scenarios does not change much (less than 15%), in which the water footprint of the power sector in Beijing has the highest sensitivity to the carbon reduction policy. Therefore, the focus of water conservation in the power sector under the dual-carbon target should be on the trade chain, optimizing the trade structure and reducing interregional virtual water flows.

The identification of key influencing factors and their critical values for the prevention and control of water bloom in lakes is of great significance. Taking Wuhan South Lake as the study area, based on hydrological, water quality and meteorological monitoring data, Pearson Correlation Analysis, Gray Correlation Analysis and Principal Component Analysis were used to screen and identify key environmental factors with high correlation with chlorophyll a concentration, and the critical values of key environmental impact factors were analyzed by the Receiver Operating Characteristic (ROC) curve method. The results show that the COD_Mn, total phosphorus, total nitrogen, water temperature and air temperature had strong correlations with chlorophyll a concentration and were the key factors for water bloom outbreak, with the critical values of 6.25 mg/L, 0.146 mg/L, 0.725 mg/L, 27.05 ℃ and 22.35 ℃, respectively. It was found that the accuracy of the ROC curve method for solving the critical values of COD_Mn, total phosphorus, total nitrogen and other environmental factors with small daily variation was better than that of environmental factors with large daily variation such as air temperature and water temperature, and the ROC curve method has a greater advantage in determining the critical values of nutrient concentrations for water blooms in lakes.

The health of the water cycle is a key factor in high-quality regional development. The prediction of water cycle health state is of great significance to the coordinated development of regional water resources system, economic and social system and ecological environment system. Taking Zhengzhou City as a typical research area, this study constructed a DPSIR model for urban water cycle health evaluation, and analyzed the evolution process of water cycle health status in Zhengzhou from 2010 to 2020 by using entropy weight fuzzy comprehensive evaluation method. The system dynamics model and entropy weight fuzzy comprehensive evaluation method were used to predict the health status of water cycle in Zhengzhou from 2021 to 2030 under five types of comprehensive coordination type, economic development type and water resources optimization type. The results show that the health status of water cycle in Zhengzhou has been developing well in the past decade, and the indicators of per capita GDP, urbanization rate and intelligent water resources management have reached the "healthy" state. Under the five prediction scenarios, the urban water cycle reaches the state of "subhealth" or above, and under the comprehensive coordination scenario that takes into account economic development, ecological protection and water resources optimization, the water cycle health status of Zhengzhou reaches the state of " health", and this scheme is the optimal scheme. The results can provide theoretical basis and technical support for ecological protection and high quality development in Zhengzhou City.

In order to understand the water quality of Wuliangsu Lake, an inversion method of total suspended matter concentration based on M-GA-BP was proposed. Using Sentinel-2 remote sensing satellite images as the data source and considering the spatial and temporal characteristics existing in the study area, the monthly data was considered as a feature for the inversion of TSM concentration. The GA-BP model was built by optimizing the weights and thresholds of the BP neural network using genetic algorithm (GA), and comparing with the traditional BP neural network model. The results show that the introduction of the monthly feature model effectively reduces the model complexity and improves the model inversion accuracy, among which the M-GA-BP model has the highest inversion accuracy with the coefficients of determination of 0.916 and 0.903 for the training and test sets, respectively, and the root mean square errors of 0.049 μg/L and 0.057 μg/L for the training and test sets, respectively. The study can provide a new idea for the inversion of TSM concentration in the Wuliangsu Lake.

Exerting huge economic and social benefits, the construction and operation of water conservancy projects have an impact on the ecological environment of upstream and downstream reaches. However, it is also an effective way to regulate and improve the ecological environment by rationally optimizing the water storage and release process of the reservoir and carrying out targeted ecological management of the reservoir. From the perspective of ecological flow constraints, through data investigation and analysis, the appropriate flow ranges of the Yangtze River main stream conducive to the natural reproduction of the four major Chinese carps, Chinese sturgeon and the control of estuary salt tide intrusion were determined. Then, the optimal scheduling model of the Three Gorges Reservoir was established considering the downstream ecological flow constraints. Multi-objective reservoir ecological dispatching model is emphasized. The results show that the ecological flow of the lower reaches of the Three Gorges Reservoir was basically guaranteed during the wet season from May to September, but the ecological water shortage was prone to occur in different degrees in other seasons, especially in the dry years. For the optimal scheduling, the power generation and the monthly maximum ecological water shortage rate showed a positive relationship, indicating that the two scheduling objectives could not reach the optimum simultaneously. The power generation of the optimal scheduling in a typical dry year was between 80.2 billion and 83.5 billion kW·h, and the monthly maximum ecological water shortage rate was between 24% and 48%. The optimal scheme obtained by multi-objective dispatching can basically coordinate the ecological and power generation needs. On the basis of the downstream ecological flow needs, the power generation benefits increases by 4.07% compared to the design scheme.

In view of the fact that the reservoirs of medium and small hydropower stations usually operate at a lower level during the flood season because of the smaller regulating reservoir capacity, short decision time for flood regulation, maximum head of the unit and inundation limitation of the upstream reservoir area, etc., the flood resource utilization benefit is not fully utilized during the flood season regardless of the magnitude of the flood. The multi-objective risk analysis model for flood operation and scheduling of medium and small hydropower reservoirs is established with the objective of maximizing the power generation benefit and minimizing the flood risk, and the solution method for the optimal flood level is given when the forecasted incoming flood flow is in different ranges. The results show that when the reservoir faces different levels of floods, the optimal operation level can be obtained by coordinating the benefits and risks to increase the power generation benefits during small floods and reduce the flood losses during large floods, which provides a reference for the flood operation and scheduling of medium and small hydropower reservoirs under changing environment.

Limited by hydrometeorological data, flood forecasting in ungauged basins still faces challenges. Parameter regionalization is a common method to solve this problem. The machine learning model has the characteristics of simple modeling and convenient use compared with the traditional flood forecasting model. Taking the West Plain of Nansihu Lake in Shandong Province as the research area, referencing the idea of hydrological regional synthesis, this paper synthesizes the data of 40 floods in 8 watersheds from 2010 to 2021, and builds a regionalized flood forecasting model based on Long Short-Term Memory (LSTM). The results show that the regionalized flood forecasting model can simulate the actual flood process well, the relative error of flood peak in both the training set and the testing set are less than 10%, and the Nash-Sutcliffe efficiency coefficients are all greater than 0.9; In the 15 h forecast period, the regionalized flood forecasting model has higher forecasting accuracy, and when the forecast period is more than 15 h, the forecast accuracy of the model decreases.

An accurate hydrological model with strong adaptability is crucial for predicting floods and preventing disasters. The antecedent soil moisture and rain intensity factors are considered to improve the SCS-CN runoff generation model. Then the new SCS-CN hydrological model is developed by adding the watershed concentration module. From the perspectives of different climate zones and magnitude floods, the new model is applied in four basins to flow simulation, which include semiarid basins of Hancun and Macun, and humid basins of Shenglihe and Gongcheng. The results demonstrate that new SCS-CN hydrological model has good applicability in both semi-arid and humid basins, with better performance in semi-arid basins. Generally, the model shows better accuracy in simulating floods of different magnitudes, especially for small and medium floods.

From the objectives, variables and relations of the time-varying linear confluence model, it can be seen that the model has some constraints such as static parameters and the inability to consider the influence of interval runoff, and there are significant defects in the application of flood prediction. Therefore, the time-varying linear confluence model is improved by combining the chaotic mapping with the rich model to solve the diversity and adding the influence operator to replace the interval runoff. Using the measured runoff data of Maoergai Hydropower Station in the Heishui River basin for many years, and taking the forecast process, flood volume, flood peak and peak time as the evaluation index, the application analysis of the improved time-varying linear confluence model is carried out. The results show that the overall prediction qualification rate of the improved model is increased by 9.13%, and the certainty coefficient is increased by 0.25, which expands the reliability and practicability of the application of the time-varying linear confluence model.

In order to enhance the real-time flood forecasting accuracy in the Linyi River Basin, a TOPKAPI grid model was developed based on the underlying surface characteristics of the Linyi River Basin. The TOPKAPI model simulation results were corrected at different lead times using BP neural networks and LSTM models. Furthermore, a stacking approach was applied, employing the Transformer model as a secondary learning tool to refine the corrections made by BP and LSTM. The results indicate that after real-time correction with the BP and LSTM models, the improvement of the simulation accuracy of the TOPKAPI model is obvious, with better correction results for shorter lead times. Following the stacking method for secondary learning, the correction results is the best, effectively enhancing the flood forecasting accuracy in the Linyi River Basin.

The regulation and storage capacity of a river channel plays an important role in the safety of drainage in polder areas. In order to study the factors related to the actual effective regulation and storage capacity of a river channel in polder areas, this paper adopts the unsteady flow model and the water balance method to calculate the regulation and storage capacity of a single river channel. The calculation results of the two methods show that the main influencing factors of the regulation and storage capacity of a river channel are the water depth corresponding to the starting regulation level, the roughness of the river channel, the length of the river channel and the cross-section morphology, etc. For the backbone drainage channel with large discharge, the actual effective regulation and storage capacity is the storage capacity from above the water surface line corresponding to the designed discharge to the maximum water level. The research results have certain reference value for the planning and design of drainage in polder areas.

In order to explore the causes of urban waterlogging, taking Guangzhou as an example, a drainage model was established based on SWMM. A waterlogging cause analysis method based on real-time monitoring data was proposed. Combining with the real-time monitoring data, the water-collecting capacity of water-logging points, the flow capacity of pipeline and the runoff generated by rainstorm were calculated. At the same time, the corresponding waterlogging measures were given according to different waterlogging causes. The results show that 75% of waterlogging cases involved insufficient surface drainage capacity, 57.7% of waterlogging cases involved watercourse top support, and 44.2% of waterlogging cases involved excessive rainfall intensity and insufficient pipe drainage capacity.

Aiming at the shortcomings of slow convergence and easily falling into the local minimum in the learning process for the traditional BP neural network, particle swarm algorithm with fast convergence speed and strong global optimization ability was introduced so as to establish the PSO-BP model. Taking the seepage monitoring data of an earth and rockfill dam as an example, the seepage was predicted. Compared with the prediction model, the BP model and the traditional statistical regression model, the results show that the PSO-BP model has a higher goodness-of-fit and convergence.

Conventional dam displacement monitoring methods are often associated with large errors and low efficiency. Manual monitoring methods cannot provide continuous real-time monitoring, while automated monitoring methods, such as total station robot and GNSS, are affected by weather and have limited accuracy for vertical displacement. To overcome these shortcomings, this study proposes a new intelligent monitoring method for dam displacement based on machine vision. The method utilizes the internet of things and intelligent disaster recognition algorithm to convert picture data into deformation data, enabling ultra-high precision non-contact real-time measurement of the dam. The monitoring system was tested at Lianghui Reservoir, the results demonstrate that the operation of monitoring system is stable, and the horizontal and vertical monitoring accuracy are both 1.5 mm. The proposed method has the potential to be widely applied in other water conservancy projects for surface displacement monitoring.

The phased trend recognition of deformation monitoring sequences for dams can deepen the understanding of the evolution laws of deformation monitoring sequences at different time scales, which is of great significance for the safe operation and management of dams. The heuristic segmentation algorithm (BG algorithm) is adopted to identify the mutation points of deformation monitoring sequences for dams, which can effectively avoid the interference of mutation points in trend recognition. On this basis, the segmented sub-sequences are trend identified using an improved ITA method, which can retain the internal correlation of the sequences and has good applicability. The engineering case analysis shows that the proposed method can effectively identify the mutation points in the deformation monitoring sequences for dams, divide the monitoring sequences into sub-sequences with stable trends, and identify the changing trends of each sub-sequence.

In order to study the characteristics of the hydraulic transition process of accidental pump stoppage before and after the pipeline optimization of pumping station water delivery system, based on the actual project, Bentley Hammer software was used to establish a mathematical model of the pumping station water delivery system with two pumps in parallel units to study the effects of the most unfavorable water hammer parameters such as water hammer pressure and unit speed before and after the pipeline optimization under different two-stage valve shutdown schemes. The results show that the maximum water hammer pressure decreased by 3.76%-8.85%, the minimum water hammer pressure increased by 4.89%-8.85%, and the maximum reversal speed increased by 1.47%-81.35% after pipeline optimization; The fast shutdown time had a significant effect on the most unfavorable water hammer parameters, and the most unfavorable water hammer parameters of the pumping station water delivery system all occurred before than before the optimization after pipeline optimization. It shows that the pipeline optimization effectively improved the water hammer characteristics and the safety of the pumping station water delivery system.

For the pump-stopping water hammer prevention of the floating pumping station water-conveying system, in addition to ensuring the safety of the pump unit and the pipeline, the impact of the water hammer pressure on the movable rocker pipe and the floating boat should be considered to ensure the stability of the floating boat. The numerical simulation of the pump-stopping transient of a floating pumping station water-conveying system under large range variable water source level was conducted. The results show that the lowest inlet water level is the most unfavorable condition for water hammer prevention. Under the condition that the pump outlet valve refuses to close, if the unit’s reverse speed exceeds the standard and the maximum reverse flow is reached within 3 s after the pump-stopping. The axial-flow check valve is recommended for the pump outlet valve considering the valve driving capacity requirements, the unit reverse speed and water hammer pressure. In the water hammer protection scheme of "pump outlet axial-flow check valve + air chamber on shore + intermediate check valve + hammer-prevention air valve", the axial-flow check valve ensures that the pump unit does not reverse, the air chamber and air valve reduce the maximum water hammer pressure and improve the negative pressure condition in the pipeline, and the intermediate check valve reduces the pressure oscillation amplitude and oscillation time in the pump outlet and rocker pipe. Therefore, the water hammer prevention problem in the floating pumping station water-conveying system is effectively solved.

The friction factor of pipeline is a key parameter in the design calculation, operation scheduling optimization and fault diagnosis of water supply system. In order to determine this parameter accurately, an intelligent back-analysis method of pipe section friction factor based on dynamic search fireworks algorithm (dynFWA) coupled with hydraulic calculation model of pipe network was proposed. The partial derivative relationship between node water pressure and friction factor was taken as the node sensitivity. In the improved genetic algorithm, the maximum sum of node maximum sensitivity was taken as the goal to optimize the layout of monitoring points. Based on the optimized water pressure monitoring value at the monitoring point, the dynFWA algorithm was used to inverse the friction factor of each pipe section with the objective of minimizing the average double error between the water pressure monitoring value and the calculated value. In order to verify the inversion performance of dynFWA algorithm, the inversion of friction factor by dynFWA algorithm and particle swarm optimization (PSO) algorithm were compared. The results show that the maximum relative errors of the inverse value of the friction factor are 17.7% and 0.7% before and after the optimization of the monitoring points, which proves the necessity of the monitoring point selection and the superiority of the improved genetic algorithm for the monitoring point selection. Under the condition that the water pressure at the monitoring node is added to noise, the relative errors of the friction factor inversion results based on the dynFWA algorithm and the PSO algorithm are 9.67% and 14.33% respectively, and the maximum relative errors between the actual water pressure value and the simulated water pressure value at the monitoring point are 0.358% and 0.655%, which proves that the dynFWA algorithm has higher accuracy in the parameter inversion problem compared with the PSO algorithm.

The phenomenon of mixed free-surface-pressure flow exists in the process of water level variation in the lower reservoir (roadway group) of mine-type pumped storage power station, which directly affects the operation stability of the system and the hydraulic safety of the roadway group. Based on 3D numerical simulation technology of hydraulic system, considering the three controlling cases including lower reservoir water filling, load rejection and pumping power failure, the characteristics of the transition process of water flow in roadway group and the evolution law of related hydraulic parameters were analyzed, and its influence on the hydraulic safety of roadway group was evaluated. The research shows that there is no obvious unfavorable flow pattern in the initial water filling process of the lower reservoir (roadway group); For load rejection with dead water level of the lower reservoir, the water level of the regulating pool decreases by less than 0.4 m, and for pumping power failure with the normal water level of the lower reservoir, the water level of the regulating pool increases by less than 10.0 m; The roadway group can enter and exhaust normally during the transition process, and the hydraulic transitions in the roadway section is smooth including the possible free-surface-pressure flow; The regulating pool and the ventilation channel meet the requirements of hydraulic optimization to ensure the hydraulic safety of the roadway group.

Based on the spillway tunnel of Kangsu Reservoir Project, the RNG turbulence model and VOF model in FLOW 3D software was used to study the flow characteristics of the spillway tunnel. The flow velocity and relative energy dissipation rate under different conditions of the original design scheme was analyzed, and compared with the model test. The reliability of the numerical simulation was verified. In view of the problems in the original design scheme, such as the water-wing in the upstream transition section of the spillway tunnel, the far drive hydraulic jump in the stilling basin, and the downstream gully flow not returning to the channel, the modified scheme was proposed. The results show that the modified scheme can effectively reduce the water wing phenomenon, and can effectively reduce the downstream gully flow velocity and the riverbed scouring by adding multi-level energy dissipation, which can provide a reference for the design.

With the completion of a large number of major water conservancy projects with the characteristics of "high water head, large flow, and complex geological conditions", the environmental problems caused by flood discharge atomization have become increasingly prominent, and it is urgent to carry out research on mitigation technology of flood discharge atomization. The types of flip bucket have a direct impact on flood discharge atomization. Based on the methods of physical model test and numerical simulation calculation, the influence of flip bucket types on flood discharge atomization is studied. The results show that: under the same test conditions, the distribution of the nappe wind velocity of the continuous bucket is symmetrical along the two sides of the downstream axis, showing a unimodal distribution; and the distribution of the nappe wind velocity of the contraction bucket and the expansion bucket is approximately symmetrical bimodal distribution. The distribution of flood discharge rainfall is closely related to the type of the flip bucket. Compared with the continuous bucket, the number of the splashed water droplets of contraction bucket and expansion bucket is greatly increased. In the actual project, the purpose of reducing the influence of flood discharge atomization can be achieved by reasonably optimizing the types of flip bucket.

On the non-uniform sand river bed, the armor layer at the bottom of the bridge pier local scour pit will affect the maximum local scour depth of the bridge pier. Through a flume model experiment, the sediment gradation, relative coarseness, and non-uniformity of the armor layer at the bottom of the local scour pit on the bridge pier were studied. The results indicate that the median particle size of the sediment in the armor layer at the bottom of the local scour pit on the bridge pier increases with the increase of the local scour depth on the bridge pier, and its relative coarsening degree increases with the increase of the Froude number, while the degree of non-uniformity decreases with the increase of the Froude number. A formula for calculating sediment particle grading in the armor layer at the bottom of the local scour pit on the bridge pier has been proposed. The applicability and reliability of the proposed formula is verifies by the measured data.

In order to study the dynamic response of pipe-piercing dike under seismic load, taking a dike-crossing project in Guangdong Province as the research object, considering the interaction between pipeline and soil, a three-dimensional numerical simulation model of pipeline-dike was established. The simulation of foundation boundary spring-damper was realized through secondary development. The results show that under the action of 0.1g seismic acceleration, the vertical displacement of the dike increases with the increase of the height of the dike and decreases along the axis of the dike. The maximum displacement at the top of the pipeline is greater than that at the left and right ends. The stress distribution law of the pipeline is consistent with displacement, and the maximum stress of the pipeline is proportional to the thickness of the soil cover layer. The Mises stress at each point of the midpoint section of the pipeline through the dike is the largest, and the seismic capacity of the middle section of the dike is relatively weak. The stress and displacement near the midpoint section of the pipeline in the dike should be monitored in the seismic design of the subsequent dike project. This study has important practical significance to ensure the safe and stable operation of the dike-crossing project.

A study was performed on the stress characteristics of the urban emergency flood-control box—a new equipment made of polymer material. The finite element analysis method was used to study the stress, strain and deformation characteristics of the flood control box under different water retaining heights. The results show that the stress concentration area of the box is mainly appeared at the water retaining surface and the two sides; With the increase of the water retaining height, the difference of water level between inside and outside of box as well as the maximum stress and the deformation are gradually smaller. Compared with the ABS, LLDPE, HDPE and PP materials, the deformation of the flood control box with ABS material is relatively smaller under the same conditions. An optimization study was carried out on the scheme of the flood-control box. And the stress, strain and deformation of the optimization scheme under the same conditions are greatly improved. The maximum stress decreases from 16.09 MPa in the original form to 7.31 MPa in the optimized form, and the maximum deformation decreases from 0.78 cm to 0.13 cm. The mechanical characteristics of the box structure are obviously improved.

Based on the temperature load on the wall slab of a large aqueduct when the temperature suddenly drops, the temperature self-confinement stress of the upper surface of the concrete slab was tested and analyzed. The temperature difference between upper and lower surfaces of concrete slabs at different cooling rates and the self-constrained principal stress of concrete slab surface temperature at 1 h at a cooling rate of 10 ℃/h were measured. The accuracy of finite element modeling was verified by comparing the numerical value of concrete transient temperature stress simulated by finite element method with the experimental test data. On this basis, the influence of cooling rate on transient temperature and stress field of aqueduct was analyzed. The impact of different insulation materials on surface temperature and stress field of aqueduct was discussed. The results show that the temperature tensile stress on the aqueduct surface will increase at a faster rate with the increase of the ambient temperature decreasing rate. Compared with the external surface temperature stress of the aqueduct without insulation measures, the tensile stress of the external surface temperature of the U-shaped aqueduct was reduced by 83%, 80% and 68%, respectively, when the polyurethane, polystyrene board and vitrified microbeads with 2mm thickness were adopted. Considering the cost and construction technology, vitrified microbead insulation materials are more suitable as thermal insulation materials on the outer surface of aqueducts.

During construction and operation, it is inevitable to have such engineering problems as cutoff wall defects. It is very important to accurately and systematically analyze the influence of defects in anti-seepage wall on seepage and deformation of cofferdam. The finite element model of an anti-seepage wall cofferdam project was established. By using the fluid-solid coupling analysis method, the material parameters of anti-seepage wall element in the finite element model were changed one by one to simulate different defects of anti-seepage wall. The influence of defect location of anti-seepage wall on saturation line, velocity vector field and deformation field of cofferdam was studied. The results show that the bottom defects of the anti-seepage wall have little influence on the saturation line, velocity vector field and deformation field of the cofferdam. With the upward movement of the anti-seepage wall defects, saturation line, pore water pressure and deformation value of the cofferdam behind the anti-seepage wall increase continuously, and the velocity of the cofferdam increases firstly and then tends to be stable. The research results can provide reference for the design and construction of anti-seepage wall and stability analysis of cofferdam.

Flexible Mattress is the main beach guarding structure in the middle and lower reaches of the Yangtze River. The water flow scouring is likely to cause the deformation of the flexible mattress, affecting the guarding effect. Aiming at its deformation monitoring difficulties, this paper explores the feasibility of using optical fiber sensing to monitor the deformation of the flexible mattress through the indoor experiment. The results of the study show that at the initial stage of tensile deformation (less than 20 mm), the measured strain value deviates less from the actual value. When the tensile length is greater than 20 mm, the error rate of each measurement point is exponentially increasing, and the fixing effect of the optical fiber cable and the flexible mattress at the fixed point determines the monitoring accuracy of tensile deformation. The positioning accuracy of optical fiber sensing to measure bending deformation is 3 times fixed-points interval. For the concentrated stress areas (such as the edge of scour pits), positive strain is mainly generated. Optical fiber sensing has the feasibility of monitoring the tensile deformation of flexible beach protection structures. When applying this technology, it is necessary to consider the coupling of the sensing fiber and the deformation of the flexible structure, the destruction of sinking the mattress and the complexity of the construction process. The results can be reference for the research and development of monitoring and assessment technology of the in-service condition of the flexible mattress.

In view of the influence of the analysis method of geosynthetics axial tensile test results on the authenticity of mechanical properties, the mechanical properties of PVC geomembrane and HDPE geomembrane materials were studied respectively, and the relationship curves of the two materials under different analysis methods were obtained. Then the error of material tensile index under the two analysis methods was compared. The results indicate that the experimental curves obtained by the true stress-strain analysis method considering thickness changes can more accurately reflect the tensile deformation process of materials. When the materials are different, the modulus errors of the materials under the two analysis methods are also completely different. However, the variation law of the true stress-strain curve is more consistent compared to standard methods for processing, which can more accurately evaluate the material's ability to adapt to load deformation.

In order to study the mechanical characteristics such as fracture mode, crack propagation characteristics, and strength characteristics of intersecting multi-fractured rock masses in uniaxial compression tests, the particle flow program was used to simulate the mechanical characteristics of intersecting multi-fractured rock masses in uniaxial compression tests. The impact of the angle between intersecting cracks on the strength characteristics, failure mode, microcrack development and evolution law of multi-fractured samples during uniaxial compression was analyzed. The experimental results show that the failure strength of the cross multi-crack specimen exhibits a slow bottom "U" shaped characteristic with the increase of crack angle; The failure mode of intersecting multi-crack specimens is mainly tensile shear failure, with some specimens exhibiting shear failure; The failure process of intersecting multi-crack specimens first involves the generation and intersection of cracks between the tips inside the cracks, followed by the generation of cracks at the outer tips of the cracks and their transmission parallel to the loading direction to both ends of the rock mass, ultimately leading to macroscopic failure of the rock mass. The results of this study contribute to the understanding of the mechanical mechanism of cross fissured rock masses in compression failure, and are a supplement to the research on the mechanical properties of cross fissured rock masses.

To improve the added value utilization rate of reservoir sediment in the field of construction materials, the reservoir sediment was used as auxiliary cementitious material to prepare pervious concrete. The results show that with the increase of reservoir sediment content, the compressive strength of the specimens will decrease, and the permeability will increase. With the extension of mechanical activation time, the compressive strength of the specimen increases and the permeability decreases. When the water cement ratio is 0.3, the mechanical activation time is 45 min, the 28 d compressive strength of the prepared pervious concrete can reach 21.44 MPa, and the permeation coefficient is 0.56 mm/s. The results of this study can provide reference for the resource utilization of reservoir sediment in the field of building materials.

Early freezing of concrete is common in the construction of water conservancy projects in northern China. Early freezing damage induces the deterioration of mechanical properties of concrete structures, which seriously affects the safety, stability and service life of engineering structures. Through laboratory uniaxial compression test and CT scan test, the influence law of freezing time and freezing temperature on the mechanical properties of concrete was analyzed, the three-dimensional pore structure of concrete at different freezing time was reconstructed, the pore distribution and pore structure characteristic parameters of concrete at different freezing time were studied, and the correlation analysis between mechanical properties and pore structure of early frozen concrete was carried out. The results show that with the delay of freezing time, the porosity of concrete test blocks increases first and then decreases, the average pore surface area decreases first and then increases, the average pore diameter increases with the trend of quadratic parabola, and the average pore shape factor increases first and decreases then increases and decreases. The correlation between the average pore surface area and the compressive strength and elastic modulus of early frozen concrete is the best. It is suggested that the average pore surface area should be preferred to construct the mesoscopic damage index of early frozen concrete. Relevant research results provide support for revealing the macro and micro damage mechanism of early frozen concrete.

In order to explore the impact of moisture change on the pore structure of reshaped loess, different times of humidification-dehumidification cycle tests were carried out for remodeled loess with different dry densities, and the pore structure inside the soil under different cycles was tested by nuclear magnetic resonance technology. The results show that the NMR T₂ pattern of reshaped loess presents a bimodal structure, that is, the sample contains two pore structures; The dry and wet cycles have an impact on the change of the pore structure of the loess, and the pore structure shows different laws under different times of dry and wet cycles. Finally, based on the quantitative parameters extracted from the T₂ pattern, the permeability of reshaped loess under different cycles were calculated by SDR permeability model, and the permeability mechanism of loess was explained from the microscopic aspect.

In order to deal with the serious problem of siltation in the main channel of the Yellow River Diversion Irrigation Area in Zuncun Village, Shanxi Province, a field water and sediment test was carried out on the main channel. The distribution law of suspended sediment in the channel, the relationship between channel flow and sediment deposition, and the sediment carrying capacity of the channel flow were explored by using the vertical suspension index and the planning solution method, so that it could express the sediment carrying capacity of the flow within a certain range. The critical suspended flow corresponding to the channel particle size was put forward. It was beneficial to prevent siltation by adjusting the flow according to the working conditions and particle size. The sediment carrying capacity formula was optimized. The conclusions are as follows: When the diversion flow is 4.46-24.52 m³/s, the sediment content in the channel is between 0.9-4.0 kg/m³, and the sediment content is positively correlated with the flow velocity. The channel flow can be properly adjusted to more than 39.6 m³/s to effectively suspend the sediment with large particle size. The correlation between the optimized sediment carrying capacity formula and the measured value of the main channel sediment reaches 0.828, which indicates that this formula can reflect the current sediment concentration to a high degree, and provide support for the design and analysis of the balance of channel erosion and deposition in the later stage.

In order to improve the prediction accuracy of vibration signals of hydropower units, a prediction method based on variational mode decomposition (VMD), sample entropy (SE) reconstruction and particle swarm optimization (PSO) optimization of bi-directional gated circulation unit (BIGRU) was proposed. In the VMD-SE-PSO-BIGRU model, firstly, the vibration signal was decomposed into several subsequences by VMD, and the subsequences were reconstructed by SE. The trend, oscillation and noise components of the vibration signal were obtained. Then, parameter optimized BIGRU prediction models were established for the reconstructed components. Finally, the prediction results of each component were superimposed to achieve vibration prediction. Compared with other models, example analysis shows that the prediction error of the model is smaller and the prediction accuracy is higher, which can effectively predict the vibration signals of hydropower units.

To effectively judge the vibrational stationary state of hydropower units, the whirling characteristics of the rotor vibration and the evaluation method of stability of shaft vibration were studied. The theoretical expression of instantaneous whirling velocity was derived, and the characteristic parameters of whirling velocity were analyzed. A holographic whirling velocity analysis method for shaft vibration was proposed. The whirling characteristics indicators and vibration stability evaluation index of shaft vibration were established. Finally, the theory of this paper was applied to the shaft vibration data analysis of Zhejiang Xianju pumped storage power station. The key characteristic indicators of vibration were extracted and the shafting stationary was evaluated. The results show that the established characteristic indicators have good performance in evaluating the stationary of shaft vibration, and have broad application prospects for the monitoring and performance evaluation of actual hydropower units.

The health status assessment of hydraulic turbines is a necessary task for achieving health management of hydraulic turbines, and is a key step in achieving condition based maintenance of hydraulic turbines. Considering the uncertainty and fuzziness of the obtained representation information of the health status of hydraulic turbines, a combination of qualitative and quantitative indicator systems was constructed. The health status of hydraulic turbines was defined as 5 states and transformed into cloud droplets using language scale functions. The evaluation of the health status of hydraulic turbines was achieved through cloud distance. The effectiveness of the health status evaluation model was verified using a certain type of hydraulic turbine as an example, which provides a solid foundation for equipment health management of hydraulic turbine.

At present, the issue on the influence of mixed arrangement of variable and constant speed units on the load rejection transition process under the complex water delivery system with multi-units sharing multi-tunnels is scarce. Based on the transient flow theory of one-dimensional pipeline, this paper established the mathematic model of hydraulic transition process of variable-constant speed pumped storage units that four units share two tunnels in the diversion system and one tunnel in the tailrace system by using the characteristic method, and discussed the influence of the mixed arrangement of variable and constant speed units on regulation guarantee parameters under the load rejection condition by combining with practical engineering examples. The results show that regulation guarantee parameters during the load rejection transition process under the layout of two variable speed units sharing one diversion hole are safer than those under the layout of variable speed units sharing different diversion holes in the region with higher power generation efficiency.

With the transformation of the southwest power grid with a high proportion of hydropower into an UHV AC-DC network structure, ultra-low frequency oscillations have occurred in the power grid. According to the characteristics of the hydropower unit governor, a small disturbance model of the hydropower unit was established. The impact of various parameters of the hydropower unit governor on the system stability in primary frequency modulation was discussed by using the eigenvalue analysis method, and the power mode and the opening mode were compared. Finally, the impact of the opening mode and the power mode with AGC was studied. The results show that the parameter adjustable range of the opening mode is larger than that of the power mode, but it is more easily affected by AGC. This study lays a foundation for further research on suppression methods of ultra-low frequency oscillations.

In order to realize the reverse power generation operation of large-scale low-lift vertical axial flow pump, using electronic frequency conversion technology instead of mechanical frequency conversion technology, the high voltage four-quadrant frequency converter was applied to Huaiyin second station reverse frequency conversion power generation, and the grid-connected scheme and variable frequency control strategy were analyzed. At the same time, the on-site transformation was carried out to realize the stepless speed regulation of the pump power generation operation. The pump unit can be automatically tracked according to the operating conditions of optimal generating speed to achieve the maximum generating power and maximize the benefit.

A new type of MBC impellerr with a guide vane slot structure was proposed to improve the energy capture and wave reduction efficiency of Savonius-type (S-type) impeller. A multi-objective optimization algorithm combined BP neural network, NSGA-Ⅱ, numerical simulation and experimental test was used to optimize five parameters of the MBC impeller including overlap ratio, gap ratio, internal and external arc angle, internal arc radius, and guide vane size. The performance of the optimal MBC impeller was compared with that of the S-type and MB-type impellers. The results show that the prediction error of the relevant performance values is less than 10% compared to the actual values, verifying the good performance of the established prediction model. The obtained optimal parameters are: overlap ratio of 0.136, gap ratio of 0.003, internal and external arc angle of 5.23°, internal arc radius of 41.42 mm, and guide vane size of 2.83 mm. Compared with the traditional S-type impeller, the optimal MBC impeller has increased energy capture efficiency by 35.8% and wave reduction efficiency by 11%.

Pressure fluctuation in the flow field around a tidal current turbine is one of the key factors affecting the safe and stable operation of the turbine. To evaluate the effects of the duct and the duct-to-rotor clearance ratio δ on the pressure fluctuation characteristics of the tidal current turbine, three-dimensional transient CFD methods and slip-grid techniques were used to perform three-dimensional numerical simulations of the bare turbine and the ducted turbine with the blade tip clearance of δ=0.02D and δ=0.06D, respectively, under the optimal operating conditions (T_TSR=4). By analyzing the unsteady flow phenomenon of the flow field around the turbine, the pressure pulsation and frequency-domain vibration characteristics of the turbine under three different working conditions were obtained. The results show that the pressure fluctuation amplitude of the turbine is basically increasing from the root to the tip of the blade; The addition of a duct can effectively reduce the pressure fluctuation amplitude of the turbine; δ has less impact on the pressure fluctuation coefficient of the turbine and more impact on the vibration characteristics in the frequency domain of the pressure fluctuation; The main frequency of the pressure fluctuation of the turbine is mainly concentrated near the leaf frequency of the corresponding operating conditions. In addition, it is also found that the pressure fluctuation of turbine blade suction surface is stronger than the pressure surface, and the addition of duct can effectively reduce this fluctuation.

The design of culverts in hydraulic engineering involves many common and repetitive tasks. In order to achieve the parametric application of BIM design in culvert engineering, this study has carried out the research on the parametric modelling method of culvert engineering based on Revit platform, and developed a parametric modelling system for culvert through secondary development of Revit according to the relevant technical specifications. By inputting specified parameters, the system can complete the model building, calculation, and drawing, which greatly improves the efficiency of culvert engineering design. The research results achieve a high standard of engineering parametric design, which can provide technical reference for BIM parametric design of similar projects.

Aiming at the problem that the background harmonic voltage fluctuation and the abnormal harmonic measurement samples significantly affect the accuracy of harmonic impedance estimation, a method for calculating utility harmonic impedance based on generalized jackknife least square estimation and data screening is proposed. According to the principle that the assumption of the fluctuation method and least squares regression are the same, the measurement period when the background harmonic voltage fluctuation is stable is selected for the regression calculation, which can restrain the influence of background harmonic voltage fluctuation on impedance estimation. According to the jackknife principle, the harmonic measurement data is resampled, and the generalized least square method is combined to effectively suppress the adverse effects of abnormal measurement data on the regression. The accuracy and practicability of the proposed method are verified by simulation and actual measured data test.

Photovoltaic power generation is affected by the chaotic characteristics of meteorology, and its stochastic, volatile and intermittent characteristics affect the operation of power systems seriously. Aiming at the problem of large dimension of original PV power generation data and the vulnerability of power generation to weather conditions, a data processing method based on Principal Component Analysis (PCA) and BRICH clustering was proposed to reduce the dimensionality of model input variables and facilitate statistical modeling. Secondly, a Copula-Monte Carlo-based probabilistic PV power probabilistic prediction model was constructed to calculate the probabilistic interval prediction of PV power output given the future point prediction values. The model was evaluated based on interval coverage and average width of prediction interval. Finally, the summer data of the actual photovoltaic power station were taken as an example for verification analysis. The results show that the Copula-Monte Carlo method can intuitively show the fluctuation range and expected value of photovoltaic power generation, and is superior to other power prediction models.

Based on the ground radiation observation data of Hubei Huashi photovoltaic power station from April to September in 2022, the forecast accuracy of the ground radiation products of Wind Energy and Solar Energy Forecasting System of China Meteorological Administration (CMA-WSP) was evaluated. Overall, the correlation coefficient between ground solar radiation and observation in the next 5 days predicted by CMA-WSP is between 0.85 and 0.91, and the forecast effect on the first day is the best. With the increase of forecast time, the forecast accuracy gradually decreases. From the perspective of month-by-month effect, the CMA-WSP has the best effect on ground radiation forecasting in August and September, and the forecast accuracy rate in May and June is relatively low. In terms of daily changes, the CMAWSP has a relatively poor forecasting effect on ground radiation at 10:00~16:00, and is better in other periods. The prediction of ground radiation by CMA-WSP has strong seasonality. The forecast results of different times in spring are quite different, and are relatively stable in summer. The forecast effect in autumn is the most stable, and the correlation coefficient between the prediction results and observation can reach 0.92. In general, the CMA-WSP has a good effect on the ground radiation forecasting in Hubei Province, which can provide good support for the short-term forecasting of photovoltaic resources in Hubei Province.