Based on the daily precipitation data of 135 weather stations from the Yangtze river delta city during 1951-2017, spatio-temporal patterns of the extreme precipitation of the Yangtze river delta agglomeration were analyzed by the linear trend analysis, M-K trend test, wavelet cycle analysis and reverse distance weight interpolation methods. The extreme precipitation indexes were defined from the aspects of extreme precipitation amount, frequency, and intensity. The results show that except for a decrease in the continuous drought index of -0.11 d/a, the extreme precipitation indexes showed an increasing trend. The average period of change in extreme precipitation indicators was in the range of 15 a and 25 a, and the characteristic timescale was 40-50 a; The high-value area of the annual mean spatial distribution of maximum daily precipitation, maximum daily precipitation, continuous moisture index, strong rainfall, heavy rain days and annual rainy day precipitation presented in the southeast areas of the Yangtze River Delta urban agglomeration, which were distributed the opposite parts to the persistent drought index. However, the high-value areas of ordinary daily precipitation intensity were in the western part of the Yangtze River Delta urban agglomeration; The high-value areas of the changing trends of the spatial distribution and the maximum precipitation in the Yangtze River Delta urban agglomeration were all in Nanjing, Zhenjiang, Changzhou and Shanghai. The high-value areas of the spatial distribution change trend of ordinary daily precipitation intensity and annual rainy daily precipitation change trend were in Nanjing, Wuxi and Suzhou. The high-value areas of continuous moisture index, continuous drought index and heavy rain days were all in Hangzhou, Shaoxing and Wenzhou. The research findings can provide references for the prevention of rainstorm waterlogging disasters in the Yangtze River Delta Urban Agglomeration.

The medium and long-term runoff simulation can provide a scientific basis for the rational allocation of water resources, which is of great significance to the high-quality development of the basin. Based on the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) and singular spectrum analysis (SSA) two-stage decomposition strategy, the monthly runoff simulation model ICEEMDAN-SSA-WOA-LSTM was constructed by using the long short-term memory network model (LSTM) optimized by the whale optimization algorithm (WOA). It was applied to the simulation of monthly runoff in Stone River Reservoir and compared with the single decomposed ICEEMDAN-WOA-LSTM, SSA-WOA-LSTM and the undecomposed WOA-LSTM models. The results show that the ICEEMDAN-SSA-WOA-LSTM model has the best simulation effect, and the three evaluation indexes in the calibration period and validation period are better than other models, with the root mean square error of 1.278 m³/s, the average absolute error of 0.893 m³/s, and the Nash efficiency coefficient of 0.985 in the validation period. The two-stage decomposition strategy model can significantly improve the accuracy of monthly runoff simulation and can be used for year-round incoming runoff simulation.

Simulation and prediction of runoff under climate change and land use scenarios are of great significance for the study of water balance and water resources planning and management. Taking the Qingshui River Basin in Zhangjiakou City as the research area, the global climate model GFDL-ESM2M and CA-Markov model were used to analyze and predict the meteorological data and land use in the Qingshui River basin, and the SWAT hydrological model was constructed to quantify the changes of water balance factors in the basin in 2025 under the joint influence of climate change and land use. The results show that under the three GHG emission scenarios, the rainfall in Qingshui River Basin increased significantly in 2025, the maximum temperature and average temperature under the RCP2.6 emission scenario decreased compared with 2015; The maximum temperature and average temperature under the RCP4.5 and RCP8.5 emission scenario increased, and the minimum temperature under the three scenarios decreased. From 2015 to 2025, arable land, woodland, grassland, water area and construction land changed by -6.24 %, -0.86%, 6.32%, 0.20% and 0.59%, respectively. Compared with 2014-2015, the water balance distribution of the watershed changed in 2025, and the peak monthly runoff occurred from July to September. The average annual runoff under the three discharge scenarios were 4.40 m³/s, 5.84 m³/s and 9.94 m³/s, respectively.

In order to provide a suitable means for the tidal prediction of the Changjiang Estuary and its adjacent area and for the open boundary conditions of tidal flow numerical model of the Changjiang Estuary, accuracy of NAO.99Jb was evaluated. The feasibility of providing open boundary conditions for tidal flow numerical model of the Changjiang Estuary was studied. The results show that the NAO.99Jb model can accurately simulate the propagation of the tide outside the Changjiang Estuary and its adjacent area; The NAO.99Jb has good accuracy outside the Changjiang Estuary, but has lower accuracy inside the Changjiang Estuary; It is feasible for using the tidal level predicted by NAO.99Jb as the open boundary condition of the tidal flow numerical model of the Changjiang Estuary, and the accuracy is good, which can be further popularized and applied.

In order to address the limitations in forecasting the maximum scour depth of conventional river bends, this study amalgamated the methodologies of isolated forest (IF) and gene expression programming (GEP). An IF-GEP model for predicting the maximum scour depth of river bends was established. The validation results demonstrate that the IFGEP prediction model surpasses existing formulations in terms of its accuracy on the test set. Moreover, it exhibits enhanced predictive performance compared to the traditional GS-SVR and RF models. Application of the prediction model to various rivers yielded remarkably close results to the actual measured values, affirming its strong predictive capability and robust generalization performance.

The ultra-short-term reservoir water balance simulation of channel-type reservoirs is the key to the operation of the reservoir, but the results easily appear sawtooth oscillation. The calculation error is due to the fluctuation of the water level in front of the dam by extending the simulation time scale. Among the factors that cause the fluctuation of the water level in front of the dam, taking the load change as an example, the calculation error of water balance caused by the load change was corrected. An ultra-short-term water balance method for channel-type reservoirs was put forward based on one-dimensional hydrodynamics. The method established a one-dimensional hydrodynamic model of the river-reservoir area, and procured the accurate storage capacity by calculating the average water level instead of the water level in front of the dam, thereby eliminating the jagged error. The calculation results show that the simulation accuracy can be effectively improved after eliminating the influence of load changes. The ultra-short-term water balance method for channel-type reservoirs based on one-dimensional hydrodynamics can eliminate the sawtooth error and achieve high simulation accuracy.

In order to realize the prediction of industrial water consumption and improve the prediction accuracy, a mixed strategy was introduced to optimize the sparrow search algorithm (SSA) for improving the global search ability. The improved sparrow search algorithm (ISSA) was used to optimize the parameters of support vector machine (SVM). A support vector machine model (ISSA-SVM) based on hybrid strategy and ISSA was established, and the prediction of industrial water consumption in Ningxia was taken as an example. The results show that the ISSA-SVM model has the characteristics of fast optimization speed and high precision, and it has good applicability and feasibility in industrial water consumption prediction.

The selection of a suitable, efficient and accurate numerical model for groundwater flow is an important basis for numerical simulation work. The analytical solution of water level of seepage calculations of fully penetrating well in a phreatic aquifer was compared with the numerical solution of water level of structured conventional model, structured encrypted model and two unstructured encrypted models to analyze the degree of fit and error. The results show that the accuracy of the numerical simulation of all four models is quite good, and the average absolute error is less than 0.1, R² is greater than 0.98. Compared with the structured traditional model, the accuracy of the structured encryption model is the best, the unstructured 4-level encryption model is the second and the 3-level encryption model is the worst; The accuracy of the unstructured four-level encryption model is slightly worse than that of the structured encryption model, but the number of mesh is reduced by 90%. It is a highly applicable, efficient and accurate numerical model for groundwater flow, which improves the computational efficiency and makes up for the poor applicability of multi-point encryption of the structured encryption model.

To scientifically evaluate the eutrophication degree of water bodies, based on the comparison and analysis of various eutrophication evaluation methods, convolutional neural network (CNN) was introduced to establish the convolutional-eutrophication (CNN-E) model. Based on the monthly-scale water quality and algae monitoring data of Honghu Lake from 2014 to 2019, the comprehensive nutrient index method, BP neural network method and CNN-E model were used to evaluate its eutrophication degree. The mean absolute error, root mean square error, coefficient of determination and Nash-Sutcliffe efficiency coefficient were used to evaluate the performance of the neural network model. The results show that Hong Lake was in a mild eutrophic state for a long time, and the eutrophication level was increasing. In terms of model performance, the four evaluation indexes of CNN-E model are better than BP neural network 0.166, 0.098, 0.078 and 0.087, respectively. The CNN-E model can provide technical support for the prevention and comprehensive management of eutrophication in lake water bodies.

A typical urban channelized (Urban) channel in Liangtan River, Chongqing, was reshaped into six types of channel by a numerical simulation tool named RiverBuilder. And then a two-dimensional hydrodynamic convection-diffusion model was constructed to study the effect of channel morphology reconfiguration on migration and diffusion index, such as water turn-over time (T_TOT), pollutant concentration curve (C_CC), pollutant reaching maximum time (M_MT) and pollutant arriving time (A_AT). The results show that the channel morphology reconfigured by changing the width (W_bf), depth (D_bf), and meandering (M_d) of the Urban channel can inhibit the migration and diffusion of pollutants to a certain extent, but the influencing effect is not as good as that of the composite channel based on the variable D_bf. Meanwhile, the near-natural (Natural) channel has the strongest anti-pollute capacity and inhibiting ability of pollutants diffusion, indicating it is more suitable for the self-purification process of pollutants. It is confirmed that the channel morphology based on disordered and complex changes in W_bf, D_bf, and M_d is closer to the Natural channel, which can provide good eco-hydraulic conditions for the improvement of river water quality.

In order to fully reflect the natural environmental conditions and effects formed and maintained by the river ecosystem, which is the basis of human life, after in-depth analysis of the river ecosystem service function, the calculation method of carbon fixation and other functions was optimized. Based on the functional value method, a scientific and reasonable river ecosystem service value (ESV) evaluation methods covering more comprehensive functions was proposed, and Nanhe River ESV in Liyang City was studied with an example. The total ESV of Nanhe River in 2019 is 1.242 billion yuan, with the value of regulation, support, supply and cultural functions accounting for 76.5%, 12.2%, 11.1% and 0.2% respectively, which can provide reference for natural resource asset accounting and ecological compensation standards.

In order to maximize the comprehensive benefits of cascade reservoirs in the lower reaches of the Jinsha River, it is necessary to study the application mode of joint flood control scheduling. Adopting the flood process in different areas with the incoming water from the Jinsha River and the Minjiang River as the mainstay, the flood regulation calculation, flood control analysis, flood control storage capacity utilization, and cascade power generation benefit calculation of the cascade reservoirs in the downstream of the Jinsha River were studied by using relevant mathematical analysis methods. The flood control distribution method of the cascade reservoirs in the lower reaches of the Jinsha River to meet the goal of flood prevention in the Chuanjiang River was studied. The research results show that on the premise of meeting the flood control requirements of the downstream Chuanjiang River, from the perspective of making full use of flood resources and increasing the overall power generation benefits of cascade power stations, in the distribution and dispatching of flood control, it is recommended that the order of flood control storage capacity utilization of cascade reservoirs downstream of the Jinsha River is as follows: Wudongde Reservoir, Xiluodu Reservoir, Baihetan Reservoir. The research results can provide references for rational and scientific flood control operation of cascade reservoirs in the lower reaches of the Jinsha River and similar basins.

As an important part of rural energy, small hydropower plays an important role in driving rural economic development and promoting energy saving and emissions reduction. However, there is a lack of scientific guidance in the process of optimal operation of small hydropower stations in most areas. This paper takes the Mengdong River basin as an example to establish a cascade optimal operation model of small hydropower stations based on runoff simulation. The Xinanjiang (XAJ) model is combined with Manning's formula to establish a semi-distributed hydrological model for simulating the influence of reservoir operation on runoff. The successive approximation dynamic programming method is used to achieve optimal operation by considering the actual operating characteristics of small hydropower stations. The results demonstrate that the semi-distributed hydrological model has a good performance in the river basin. The changing pattern of simulated and measured runoff processes is basically consistent, and the Nash-Sutcliffe efficiency coefficient and coefficient of determination between the measured and simulated series are 0.86. The optimal operation model can reduce the spillage water effectively, which improves the utilization efficiency of water energy. Meanwhile, the optimal operation can match the actual intra-day features of small hydropower, indicating its feasibility in applications.

Under the situation of "abundant and dry electricity supply" in Sichuan Province, affected by complex market environment factors and intensified power supply competition, accurate prediction of power generation plan is the key to optimizing the power generation mode of hydropower in dry periods in the basin. This paper analyzed the power supply capacity of the main grid, new energy power, power regulation capacity of the national power grid, outsourcing power transmission capacity and power generation capacity of the provincial hydropower and thermal power, respectively, and established a forecasting method for the generation plan of the cascade hydropower stations in the Dadu River basin. The results show that the prediction accuracy of power supply in main grid is 91.8%, and the prediction accuracy of wind and solar power generation is 87.4%. The prediction accuracy of the medium and long-term overall power generation plan of the hydropower station belonging to Guoneng Dadu River Basin Hydropower Development Co., Ltd. is 90.5%. The model can effectively predict the electricity quantity of each power source and calculate the medium and long-term power generation plan of the cascade hydropower stations in the Dadu River basin, and intelligently generate the fluctuation process under different working conditions based on the prediction results, which provides technical support for the scientific dispatching and operation of the cascade hydropower stations.

The multi-energy complementary balance model used in the demonstration of the scale of pumped storage in the new power system only considers the high cost of deep peak shaving brought about by the minimum technical output of thermal power for coal-fired unit peak shaving, ignoring the economic issue of coordinated operation between coal-fired and pumped storage units. This paper proposed to use the economic output coefficient of thermal power and the minimum output coefficient of thermal power as discriminant indicators for coordinated operation of thermal power and pumped storage, and incorporate it into the original multi-energy complementary balance analysis model. From an economic perspective, the scale of pumped storage was predicted with the minimum total annual cost as goal. Taking a certain power grid as an example, the process of demonstrating the scale of pumped storage energy was illustrated, which provides reference for similar power grid development planning and early engineering design work.

Climate change and urbanization development have brought great challenges to reservoir flood control and disaster mitigation, and reservoir regulation is one of the important non-structural means for controlling floods. Therefore, this study applies the bibliometrics method and visualization analysis tools (CiteSpace and VOSviewer) to conduct a systematic quantitative analysis of the Chinese literature regarding the research topic of reservoir flood control regulation. The results indicate that the number of Chinese literature on reservoir flood control regulation can be divided into three periods in terms of the publication time, and the number of publications in different periods witnesses the development history of reservoir flood control regulation technology in China; The co-occurrence analysis of keywords provided the top 10 keywords in terms of frequency and centrality. The emergence analysis provided the development history of high popularity keywords since 2000. Cluster analysis classified keywords with significant correlation and displayed the relationship between different clusters; The analysis of authors, institutions, and literature sources can provide guidance for relevant researchers in the Chinese journal selection during the manuscript submission and the collaborator choices in Academia.

In order to solve the problem that the one-dimensional SWMM model is difficult to visually display the submerged depth and range of the study area, taking a residential area in Brighton as an example, the SWMM model coupled with the LISFLOOD-FP two-dimensional hydrodynamic model has a low impact on the residential area. The waterlogging situation before the development and renovation was analyzed and the inundation range and water depth map were made, and three different low-impact development (LID) schemes (single green roof scheme, single permeable pavement scheme, and combination scheme) were designed to transform the residential area. The results show that the inundation range is consistent with the actual waterlogging points, which shows that the two-dimensional coupling model has high reliability, and the three low-impact development schemes can effectively eliminate overflow nodes, reduce runoff peaks, and delay peak occurrence time and water receding time, which is of great significance to improve urban drainage and reconstruction technology.

In order to explore the solution to the risk of ponding and waterlogging in the sub-catchment area during sponge city design, SWMM modeling was used to study the peak runoff control characteristics of LID facilities and their combinations under different recurrence interval, as well as the peak runoff control laws of the incremental scale of volumetric LID facilities. The study shows that the peak runoff control effect of volumetric LID facilities is mainly achieved through peak time delay, while the peak runoff control effect of permeable LID facilities is mainly achieved through overall runoff reduction, and the peak runoff control effect of volumetric LID facilities is more significant; Only the combination of permeable LID facilities cannot significantly reduce peak runoff and delay peak time on a rainfall event with a recurrence interval of 5 years or more. When combined with volumetric LID facilities, it can achieve a peak runoff reduction rate of over 20% for rainfall with a recurrence interval of less than 10 years; When the scale of permeable LID facilities increases by 60% or more, the peak runoff reduction effect is more obvious for rainfall with a recurrence interval of 50 years or less; When its scale increases by 80% or more, it can basically ensure that the total runoff volume of post-development does not exceed which of pre-development with a recurrence interval of 50 years or less. The research results are aimed at exploring solutions to the risk of ponding and waterlogging in local areas, which provides theoretical reference for the design of peak runoff control in actual sponge city sub-catchments.

Continued land development around the world has accelerated the construction of impervious surfaces, thereby changing the hydrological cycle of the natural environment itself, resulting in frequent urban waterlogging disasters. Due to its own limitations, the old city not only cannot reasonably utilize rainwater resources, resulting in a waste of rainwater resources, but also is often in the predicament of flooding every time when it rains. Taking the Nandajie area of the old city of Xifeng District in Qingyan City, Gansu Province as an example, the construction effect of different LID measures in each return period was simulated through SWMM modeling. The best LID measures suitable for the study area were selected. The results show that the reduction effect of the combined measures is the best, the reduction rates of the total runoff and the peak runoff are over 68.71% and 68.90%, respectively, the peak time is delayed between 10-15 minutes, and the reduction rate of the overload of the pipe network decreases with the increase of rainfall return period. The research results provide reference for optimization of LID measures in the old urban areas of Northwest China.

Analyzing the spatial and temporal distribution characteristics of flash flood disasters is crucial for flood control and prevention. Taking Guangdong Province as an example, this study first compiled historical data on flash flood disasters in Guangdong Province from 2017 to 2021. Using methods such as standard deviation ellipse and kernel density, the spatial and temporal characteristics were analyzed, and the complex interaction relationships of triggering factors were explored. The results show that there were a total of 79 flash flood disasters, mainly concentrated in May and June, with uneven temporal distribution. The spatial distribution pattern of flash flood disasters exhibited a "dispersed east and west, concentrated north and south" pattern, with the northern cities of Heyuan, Shaoguan, and Meizhou being high-risk areas for flash flood disasters. Short-duration heavy rainfall was the main driving factor for flash flood disasters, with significant influences from topography, vegetation cover, and land use. The findings of this study can provide reference for flash flood disaster prevention and control in Guangdong Province.

The study of water-sediment processes and dam-land-erosion mechanisms under warping-dam-break conditions is of great significance for the construction and later management of warping dams in the Loess Plateau. Based on the literature research and field investigation, this paper identified the main causes of dam-land-erosion under warpingdam-break conditions, including the nature of the dam soil, the formation characteristics of the dam and the check dam break mode. It proposed that the process of dam erosions and gully erosions after warping dam failures was as follows: “warping dam failure → retrogressive erosion → scouring and undercutting → collapse of gully walls → mixed flow of water and sand”. Taking the ^#2 main dam in Macaoli of Lishi District in Lvliang City, Shanxi Province as an example, the numerical calculation results indicate that the water-sand process under the condition of warping dam failures was significantly changed by the siltation of the reservoir areas, and the dam lands have the role of shaving peaks and sinking sands.

Reasonable data mining and accurate prediction and analysis of concrete dam deformation monitoring data are the key means to ensure the safe and long-term operation of the dam. Due to the impact of environmental variables such as temperature and water level, the dam deformation time series has periodic, nonlinear and other change characteristics. Existing intelligent algorithms can not capture the nonlinear relationship of sequences well, A concrete dam deformation prediction model based on EEMD-AEFA-LSTM model was proposed. Ensemble empirical mode decomposition was used to effectively decompose the deformation time series. The long short-term memory network model optimized by the artificial electric field algorithm was used to predict the decomposition components and reconstruct the prediction results. The deformation monitoring data of EX16 and EX24 measuring points of a concrete dam were selected for prediction research. The results show that the prediction accuracy of the EEMD-AEFA-LSTM model is significantly higher than that of the AEFA-LSTM model, PSO-LSTM model, and GA-LSTM model. The average absolute error, mean square error, and root mean square error of the prediction results are the minimum values, providing a new way for accurate prediction of concrete dam deformation.

In view of the fact that traditional neural network models can hardly make full use of the topological relationship of the backward forward information of dam deformation monitoring time series data, while the bidirectional long short-term memory (BiLSTM) can effectively learn the backward forward information, a combined dam deformation prediction model BES-BiLSTM was proposed based on bald eagle search algorithm optimized bidirectional long short-term memory neural network. Firstly, the bald eagle search algorithm was used to optimize parameters of the model. Secondly, the bidirectional learning feature of BiLSTM was used to train the model to enhance the correlation between the data. Then, the settlement value of a concrete dam hydropower station was taken as example 1 for dam deformation prediction based on the BES-BiLSTM model. Another concrete dam horizontal displacement value was taken as example 2 to verify the model performance. Finally, the prediction results of the BES-BiLSTM model were studied in comparison with those of the traditional long and short term memory neural network (LSTM) model and the BiLSTM model. The results show that the BES-BiLSTM model has stronger fitting and prediction capabilities than the single traditional LSTM and BiLSTM models, which can be used for deformation prediction of concrete dams and slopes.

For side channel spillways, although the adjustment section can be arranged on the downstream side to smooth the water flow, it is difficult to completely avoid the interference of the transverse axis spiral flow on the water flow pattern of the chute. Through numerical simulation, the impacts of the curved circulation in the turning section of the chute on the spiral flow on the lateral axis of the side trough were studied. The results show that when the direction of the circulation and the spiral flow are the same (the turning angle is 14.505°), the streamline in the bend rolls obliquely from the concave bank to the convex bank, the superposition of the flow velocity is obvious, and the circulation intensity intensifies. The lateral flow velocity of the outlet section of the curve reaches 3.29 m/s, and the height difference of the outlet water surface has reached 1.140 m (low left and high right); When the circulation flow of channel bend and spiral flow are in opposite directions (the turning angle is -5°); The water flow in the bend turns from both sides to the axis and then flows downstream, and the circulation phenomenon almost disappears; The lateral flow velocity at the outlet section of the bend decreases to -0.19 m/s, and the height difference of the outlet water surface decreases to -0.467 m (high left and low right). That is, the turbulence of the spiral flow in the upstream groove can be improved by providing a curved path in the chute.

The water flow disorder, shock, spray splashing out of the side wall and incomplete water jump are often caused by insufficient discharge energy dissipation in the pool. In order to solve this problem, the influence law of the layout of T-shaped pier and its parameter variation on the hydraulic characteristics in the ballast tank was studied by using the model test method and numerical simulation. The results show that the energy dissipation rate increases with the increase of the length of T-shaped pier legs; The water depth increases with the installation of the impingement baffle, and the efficiency increases, and the energy dissipation rate decreases with the increase of the impingement baffle; The flow state of the water in the stilling pool is stable after the double-row T-shaped piers are arranged, and the energy dissipation increases first and then decreases with the increase of the distance between the front and back. According to the simulation results, a reasonable scheme is recommended and verified by model test. The results show that the energy dissipation rate of the recommended scheme reaches 76.06%, which increases by 12.51%. The flow state is stable and meets the engineering requirements.

The ZM Fishway is the rare vertical slot fishway with high altitude and the long length at the domestic and foreign. The effect of fishway is particularly vital for the gene exchange and population reproduction of the upstream and downstream fish. To investigate the effectiveness of the fishway, we monitored the species, quantity and environmental factors of fish by trap and video observation method from March to July in 2021. In total, 9 species of 143 680 fish belonging to 2 orders, 4 families and 7 genera were captured. The species and quantity of fish passing through were mainly Schizothorax oconnori, Schizothorax macropogon and Racoma waltoni, which were the main objects of fishway designed. The number and species of fish showed obvious seasonal and circadian rhythms. The number and species of fish in May and June were significantly higher than those in other months, and the number of fish during the day was significantly higher than that at night. The canonical correspondence analysis (CCA) results of fishway environmental factors show that the main environmental factors affecting the effect of fishway were the water stage and water temperature. The research results could provide reference data for the optimization and effective operation of the ZM fishway, and it was of great significance to the protection of fishery resources in the middle and lower reaches of the Brahmaputra River.

In order to investigate the impact of typical ecological revetment fish-nest brick on the hydrodynamic characteristics of straight water conveyance channels, a 3-D numerical model (LES) incorporating fish-nest brick was developed using large-eddy simulation technology. Periodic boundaries were employed in the longitudinal direction to allow for the repeated development of water flow within the computational domain. The reliability of the numerical model was extensively validated through experimental data from flume tests. Subsequently, the LES model was used to simulate the hydrodynamic characteristics of channels containing fish-nest brick. The results indicate that the fish-nest brick divide the channel into a high-speed main flow region and a low-speed fish-nest cavity. The time-averaged flow velocity in the main flow region is approximately 1.8 times the cross-sectional average flow velocity (U₀), and a continuous distribution of vortices exists throughout the entire water depth range. Conversely, the time-averaged flow velocity and turbulence within the fish-nest cavity are at relatively low levels, making it suitable for fish habitat and the hatching of adhesive eggs. The mixing layer at the mouth of the fish-nest cavity exhibits relatively strong vortex structures, which significantly enhances turbulence intensity and services as the primary driving force for momentum exchange between the interior and exterior of the fish-nest cavity.

In order to investigate the influence of the vegetation in beach and river bottom on the water flow characteristics at different time periods, under the condition of changing the vegetation diameter (6-10 mm) only, the numerical simulation was used to study the variation of vertical velocity distribution, contoured velocity, water level and intensity of turbulence along the way at different vegetation diameter. The results show that the vertical velocity distribution shows an "S" distribution in the vegetation zone and a "J" distribution outside the vegetation zone; In general, the larger the diameter is, the lower the overall velocity is, the more obvious the upstream congestion of the water level is, and the larger the water surface slope ratio is; The turbulence intensity is proportional to the vegetation diameter; The turbulence intensity of water flowing through the vegetation is greater than that of the vegetation channel when the vegetation diameter is the same.

Geotechnical engineering generally involves three-dimensional steady seepage problem with free surface. Traditional numerical methods for solving free surface are based on the assumption of continuum, and the pore flow is averaged over the whole area containing solid particles. In fact, water flow can only occur along the pores of porous media. Based on the equivalent principle of head and flow, the equivalent seepage velocity, continuity equation and boundary conditions of the pipe network model were derived by simplifying the pore structure of porous media into a three-dimensional orthogonal pipe network. Based on the local coordinate system, continuous penalty Heaviside function and variational principle, a three-dimensional steady seepage analysis method with free surface was established for equivalent pipe network model. Thus, the three-dimensional seepage problem was simplified to a one-dimensional form, which greatly reduces the difficulty of solving the three-dimensional steady seepage problem with free surface. The effectiveness of the equivalent pipe network model was verified by the three-dimensional free surface seepage analysis of homogeneous right-angle trapezoidal dam. The three-dimensional steady seepage analysis of the left abutment slope of Kajiwa Hydropower Station was carried out. By comparing with the variational inequality method, the equivalent pipe network model can well reflect the seepage field characteristics of the left abutment slope of Kajiwa Hydropower Station, and has strong applicability and high computational efficiency for the seepage problem of 3D complex engineering.

During the excavation of the construction adit, the Jiangmen Neutrino Underground Laboratory revealed three long and water rich cracks, and high-pressure jet water gushing appeared in local water exploration holes, which may have adverse effects on the stability of the surrounding rock of the tunnel. The influence of L1, L2, L3 on the deformation of surrounding rock of the experimental hall under different water pressures of the excavation face was systematically analyzed by using the discrete element method. The results show that the influence of water rich long cracks on the overall stability of the arch surrounding rock is small. The arch surrounding rock at L1 and L2 is not sensitive to the change of the drainage conditions of the excavation face. With the increase of the water pressure of the excavation face, the deformation of L3 arch shoulder increases sharply and the trend is not convergent. L2 has little effect on the deformation of the lower pool, and the shallow surrounding rock near L1 and L3 is obviously unloaded. Based on comprehensive analysis, 0.5 MPa is recommended as the control standard for shallow surrounding rock drainage at the excavation face of this project.

The flood discharge tunnel of large pumped storage power stations will be subject to high speed water flow, sand transport erosion and external water pressure during operation period, and the tunnel may suffer from local damage such as lining cracking, spalling and falling blocks, which will have a negative impact on its long-term use. Taking the flood discharge and sand drainage tunnel of the Fengning Pumped Storage Power Station as the research object, this paper firstly carried out robot-based real-time video, high-definition image and multi-parameter gas collection to realize the inspection of nearly 2 km cavern section. The defects of the tunnel were classified into structural and functional defects and graded. Then, the stability of the tunnel envelope was initially evaluated by combining the monitoring data within the tunnel for the past 6 years. Finally, numerical analysis methods were used to analyze and evaluate the forces on the tunnel envelope and lining structure under different operating conditions. The results show that the flood discharge and sand drainage tunnel has good service performance in the current state. The results of the study are of reference value for the operation and maintenance management of existing power stations and for the inspection of similar tunnels.

In view of the problem of rapid durability deterioration and the service reliability reduction of concrete structure caused by saline ions erosion and freeze-thaw coupling in cold and drought irrigation area in northwest China, based on the rapid indoor freeze-thaw test, mechanical property change of clean water, 3%NaCl solution, 5%Na₂SO₄ solution was studied in the process of freeze-thaw. The freeze-thaw damage model was established to analyze the damage degree of relative dynamic elastic modulus of concrete block for three kinds of freeze-thaw mediums. The Weibull life prediction model was used to predict the life of test specimen. The results show that the mass loss, compressive strength and dynamic elastic modulus of the concrete mass damage sizes are 3%NaCl> 5%Na₂SO₄ > clean water; According to Weibull life prediction model, the fitting parameters b and C were obtained, and the correlation coefficient R₂ is above 0.9; The prediction results of model life are consistent with the mechanical performance test results at different operating conditions; The mass loss, compressive strength and dynamic elastic modulus life prediction of concrete under three freeze-thaw mediums are clear water> 5% Na₂SO₄>₃% NaCl. It can be seen that in the environment of freezing-melting and thawing erosion, $\text{SO}^{2-}_4$ erosion degree is greater than Cl^- erosion, and the clean water erosion degree is minimal. The research results can provide a theoretical basis for the mechanical performance characteristics research and later maintenance of concrete in cold and drought irrigation areas.

In order to study the viscoelastic properties of hydraulic asphalt concrete, bending creep tests under different temperatures and stress conditions were carried out. The Burgers model was used as a constitution model for the viscoelastic mechanical behavior of hydraulic asphalt concrete, and a nonlinear fitting of the test data was carried out by the most rapid descent iteration method to obtain the fitting curves and Burgers model parameters under different test conditions. By analyzing the variation law of the parameters, the function equation of the parameters with temperature and stress was established by using Origin polynomial fitting function. The creep behavior of hydraulic asphalt concrete was predicted. The test results show that the Burgers model optimized by the most rapid descent method can better fit the test curve, and the fitted correlation coefficients are all greater than 0.996, especially in the isokinetic creep stage, the fitted curve is closest to the test curve; Under the condition of constant stress, the parameters of the Burgers model decrease with the increase of temperature; Under the condition of constant temperature, the parameters E₁ and E₂ increase with increasing stress, and the parameters η₁ and η₂ decrease with increasing stress.

The selection of instability criterion is particularly important when the finite element strength reduction method is used to analyze slope stability, but a consensus has not yet been reached. Based on ABAQUS finite element software, the method of total displacement mode combined with cusp catastrophe theory was proposed to judge the safety coefficient of slope. For a classical slope case, the safety coefficient was calculated by using calculation non-convergence, abrupt change of displacement of characteristic point, plastic zone penetration and abrupt change of total displacement mode as the instability criterion, and compared with Spencer method. The results show that the new criterion has a clear meaning, is less subject to human interference, has a wide range of application, and has certain advantages over the traditional three criteria.

Aiming at the Dakuaitian landslide in the Three Gorges reservoir area, which appeared cracks in July 2021 and intensified deformation in August, causing serious safety hazards to local villagers and infrastructure, 9-view Sentinel-1A uplift SAR image data from March 2021 to August 2021 were used as data sources to obtain the time-series deformation characteristics of the landslide in this time period by using SBAS-InSAR technology, and compared with the concurrent GNSS monitoring and geological exploration data. The results show that the deformation of the middle and rear part of the landslide is obvious and is in the state of creeping deformation; The signs of landslide deformation are in good agreement with the InSAR results, which verifies the effectiveness of SBAS-InSAR technology in landslide monitoring; The accumulated rainfall in the previous period and the short-time intense rainfall are the main factors that induce the current deformation of Dakuaitian landslide. This study shows that the SBAS-InSAR technology has a broader application prospect in the field of geological disaster monitoring and early warning in the Three Gorges reservoir area, and provides a reference for similar reservoir area landslide deformation monitoring and early warning.

The practice of ecological governance and reforestation was carried out by taking Pianyanzi fluctuation zone as the object, proposed the stone cage anti wall technology, stone cage plate slope protection technology, ecological bag slope protection technology, which provides the necessary soil matrix for plant growth and prevents the soil from being soaked by reservoir water and erosion. On this basis, more than a dozen species of water-resistant plants were screened, and different plant species were configured in different elevation areas. After a long period of inundation in one hydrological year, the overall survival rate of trees and shrubs was 54.9% and 35%, respectively. Among them, Taxodium ascendens Brongn, Ascendens mucronatum, Betula nigra, Myricaria laxiflora, and Salix variegata had better submergence tolerance and higher survival rates, which were 84%, 74.2%, 88.3%, 97%, and 95%. They could withstand long-term overtop submergence, and the effect of reforestation in the water-level zone was obvious.

Bidding is the main way for a hydraulic engineering contractor to obtain a project, and the level of the bid price directly affects whether the contractor can obtain its construction right. Before bidding, predicting the distribution of the bid price of the proposed hydraulic engineering can optimize the formulation of its own quotation. A global optimization Bayesian-MCMC algorithm was used to predict the Beta distribution parameters. Bidding behavior of contractor was simulated by numeric analysis. The algorithm does not need to consider the conjugate of the prior distribution and likelihood function in Bayesian estimation. The numerical simulation results show that the Bayesian-MCMC algorithm requires less data for simulation and has better prediction effect than the traditional moment estimation method.

Aiming at the nonlinearity and non-stationary of vibration signals of hydropower units and the timeliness of prediction, this paper proposed a vibration prediction model of hydropower units based on VMD-CIMFs-TCN. Firstly, the VMD algorithm was used to decompose the vibration signal to obtain the IMFs component with the minimum signal distortion, which realizes the accurate decomposition of the vibration signal. Secondly, by calculating the power spectrum entropy and the permutation entropy of each IMF component, the aggregation of the IMF components was realized to reduce the computational load of the prediction model. Finally, the TCN network was used to realize the accurate prediction of CIMFs, and the final vibration signal prediction results were obtained by adding them. The analysis shows that this method shortens the time required for prediction on the premise of ensuring the prediction accuracy, and meets the timeliness of the prediction model.

The influence of inlet blade setting angle valued in a large range was studied on the performance of residual energy recovery turbine. Firstly, the theoretical predicted model was established between the inlet setting angle and optimal unit speed, and the numerical simulation model was determined based on the characteristics of residual energy recovery turbine. Then, three runners with different inlet setting angle were gave for the residual energy recovery turbine in water distribution networks, and numerical simulations were carried out with the same conditions of flow rate, head and rotate speed. The flow field and performance of the runner were compared. The results show that the optimal unit speed of residual energy recovery turbine was negatively correlated with the inlet setting angle. The range of best numerical predicted efficiency is between 92.72% and 93.60% while the inlet setting angle is between 30° and 70°. The inlet setting angle and optimal efficiency was hardly correlated. However, the range with high efficiency was corresponded to a larger unit speed with the decrease of inlet setting angle. It is feasible for residual energy recovery turbine to increase working range by changing inlet setting angle. The conclusions could provide a reference for the design of residual energy recovery turbine.

The movable guide vane of domestic large hydropower units in early stage was mostly made by sand casting, which had the characteristics of large abnormal shape parts and they were located in the water wheel room of the units with narrow space. At present, the nondestructive testing of the area where the movable guide vane is hided in the shaft sleeve of large hydropower unit in service is generally carried out after the movable guide vane is lifted out during the unit overhaul period. This paper attempts to test it though phased array testing technology, modeling simulation and simulated test block test. This method is successfully applied in actual detection. Finally, the problem that coarse crystal, long sound path and abnormal shape of casting movable guide vane have serious attenuation, loss of sound energy, and difficulty in receiving defect echo is solved. The feasibility of nondestructive detection on the hided area of casting movable guide vane in completely assembling state of large hydropower units in service is verified.

To analyze the causes of turbine segmented shutdown device miloperation for a hydropower station in Central Asia, the structure of mechanical hydraulic control system of governor and its principle were described, and oil line of mechanical hydraulic control system was analyzed. It found that after the operation of the emergency pressure distribution valve, the pressure oil velocity in pipe was too fast, so the pressure of the control chamber of the segment closing device was reduced and the hydro-generator speed was too high because of the long closing time of the servomotor. The oil intake port of the control pressure oil of the stage closing device can be moved from the main pressure oil supply pipe of the emergency pressure distribution valve to the energy storage tank of the governor system. The feasibility of the scheme was verified by test.

In order to accurately grasp the actual operation of the governor of hydropower units, this paper proposed a multi-dimensional verification method of the governor operation data of hydropower units based on correlation analysis. The multi-dimensional correlation verification architecture was constructed to process the multi-dimensional operation data of the unit governor. The correlation analysis method was used to calculate the correlation degree between the multi-dimensional operation data change sequences, and the anomaly identification of the multi-dimensional operation data was completed by judging the range of the correlation degree. Based on the characteristics of the identified abnormal data, abnormal data reconstruction was completed from three dimensions of single point, multi-point and continuous abnormal data respectively to achieve multi-dimensional verification of governor operation data of hydropower units. The experiment shows that the method can effectively identify the abnormal data, reconstruct the missing data, reduce the abnormal rate of data through verification, and improve the availability of the governor operation data of hydropower units.

In order to shorten the start-up time of the hydroelectric generating set and improve the stability of the generating set 's start-up process and non-loading, a start-up optimization strategy of hydropower unit based on improved grey wolf search coupling cuckoo algorithm was proposed. This fitness function weighs the two index values of the unit ' s start-up frequency ITAE index and the unit 's start-up time and standardizes them. Two penalty functions of unit frequency overshoot and unit frequency steady-state error are introduced to effectively improve the start-up performance evaluation index of the hydroelectric generating set. An improved grey wolf search coupled cuckoo algorithm (IGWSCSA) based on good point set theory to improve the initial population is proposed to optimize the start-up parameters of the generating set. Based on the simulation experiment of the refined model of the speed control system, the optimal parameters are obtained to shorten the start-up adjustment time of the generating set, and the overshoot is reduced from 0.235 to 0.004, which greatly optimizes the start-up speed and frequency fluctuation of the hydroelectric generating set.

When the magnetoelectric velocity sensor is used to test the vibration of the top cover, distortion is easy to occur due to the inherent characteristics of the sensor and the test conditions, and the data can not truly and effectively reflect the operation state of the water turbine top cover. The correlation among excitation force, vibration and strain was clarified through vibration theoretical analysis and stress calculation of top cover structure. Using finite element structural analysis to determine the weak position of the rigidity and strength of the top cover, the dynamic strain value based on this position was proposed as an indicator parameter for evaluating the operation status of the hydraulic turbine top cover. Based on the vibration value and dynamic strain value in the stable operation area, a mapping relationship between strain and vibration was established to solve the problem of inaccurate vibration measurement of the top cover. Taking a power plant unit as an example, the feasibility of the proposed method was verified.

In order to solve the frequency safety problem caused by the large-scale access of renewable energy, adjustable-speed pumped storage unit (ASPSU) was involved in frequency regulation of new power system. Firstly, the AGC frequency regulation stability of ASPSU was analyzed through the root locus method. Then, the evaluation scheme of unit power command response performance was designed to measure the rapidity and accuracy of output of ASPSU. And on this basis, the active power dynamic optimization allocation strategy based on the rate of change of frequency (ROCOF) was proposed. The new energy disturbance was simulated in the LFC model of a two-area interconnected power system to verify the effectiveness of proposed strategy. The results show that the proposed active power dynamic optimization allocation strategy can give full play to the frequency regulation advantage of ASPSU, effectively prevent frequency exceedance and maintain the frequency stability of power system.

In order to explore the cause of the flow pattern problem in the forebay of the pumping station at the diversion operating condition in Taihuzhuangyuan in Changzhou City, and find the corresponding solution, the three-dimensional turbulent numerical simulation method was used to calculate the inlet flow pattern after the prototype of the lock station and the addition of the diversion pier. By analyzing the flow uniformity and weighted average angle of the inlet section in each case, it can be concluded that the flow pattern of the forepbay is mainly caused by the large diffusion angle. The longer a single diversion pier is added to the forebay, the better the rectification effect will be. Compared with the single pier, the combined pier can weaken the recirculation region more and improve the inlet flow pattern. The research results can provide reference for engineering practice.

Aiming at the problem of sluice flow, based on the smooth particle hydrodynamics method (SPH), the boundary treatment method was improved, and the main parameters of repulsion force were re-calibrated, which can avoid non-physical oscillation with n₁=4 and n₂=2. At the same time, the comparison and selection of water replenishment modes were carried out, and it was clear that the bottom hole water replenishment mode with 3 m elevation difference in the optimal water replenishment mode can reduce the net outflow of particles from the upstream water body. On this basis, the numerical model of the flow through the gate impacting the stilling pool downstream was established, and the process of the flow from the sluice to the stilling pool was simulated. The results show that at the initial time, the maximum pressure at the bottom of the upstream water is 127.4 kPa; At the 7th second, the average velocity at the right end of the stilling pool is 7.07 m/s, at the 19th second, the average velocity at the right end of the stilling pool decreases to 1.4 m/s. Thus, the SPH method can accurately simulate the changes of flow velocity, pressure and flow pattern in the discharge process.

The weir-gate structure has larger discharge capacity. To accurately and efficiently check the discharge of weir-gate, three intelligent algorithms including BP neural network, SVM and GRNN were used to predict the discharge coefficient of cylindrical weir-gate. The correlation analysis and variation law between dimensionless parameters and discharge coefficient were discussed. The results show that the GRNN and the BP can accurately predict the discharge coefficient of the cylindrical weir-gate. The determination coefficient of the BP in the test stage is 0.997, the root mean square error is 0.009, the average absolute percentage is 0.801 %, and the Nash efficiency coefficient is 0.997, which is superior to the GRNN, and it can be used as an efficient and high-precision prediction model for the discharge coefficient of the weir-gate. There is a stronger correlation between the ratio of gate opening to cylinder diameter (a/D), the ratio of weir head to cylinder diameter (H_w/D) and C_d. The C_d increased with the increase of upstream Froude number (Fr) and H_w/D, and the greater the a/D is, the greater the increase of C_d is. The search results provide theoretical reference and technical support for the popularization and application of cylindrical weir gate in practical engineering.

In order to response the request of hydraulic digital twin, this paper studied how it implement in long linear engine hydraulic project so that the manage system can show any position and any changes of the project. The data linkage inquiry method in both two and three dimension and the shortest distance algorithm innovatively were proposed based on BIM, GIS and geological profile graph. It is implemented through data fusion, data structure design, software design etc., which can make digital scene and geological profile graph's view move and inquire together. The user can immediately acquire mileage, geological conditions, design section, construction and operating state through moving and pre-clicking the cursor. It's proved in a certain water diversion project that the project manager can inquire and acquire real-time project information immediately by using this method without inspect the whole engineering. This method lays the foundation of real-time data inquiry, engineering safety intelligent analysis and production operation management, which implement engineering digital twin to some extent.

To solve the problem of low recognition accuracy caused by insufficient power data feature mining, this paper proposed a novel power data identification method based on multi-domain feature analysis and feature selection. Firstly, aiming at the shortcomings of existing power data feature extraction methods, a feature extraction method based on empirical mode decomposition (EMD) and Hilbert transform (EMD-Hilbert) was proposed, and the power features and V-I trajectory features of power data were quantified. Secondly, based on random forest and generalized sequence backward selection search strategy, the optimal feature subset was obtained. The random forest was employed to build a recognition model for the power data. Finally, the experimental results verified the effectiveness and identification accuracy of the proposed method. The results show that the proposed method can utilize the complementarity of different features to overcome the problem of low accuracy by single feature, and further improve the model recognition performance through feature selection.

Considering the wide frequency range, strong nonlinearity, and multimodal characteristics of "double high" power systems, an adaptive identification method for broadband oscillation modes was proposed. Firstly, an adaptive threshold filtering technique was applied to the spectrum of the Blackman-Harris windowed signal to extract the dominant components. Then the three-spectrum line interpolation FFT and the ZoomFFT were used to adaptively analyze the signals after using main-lobe interference criterion of modes with close frequencies. Finally, the proposed method was tested by using 20-mode example signals and a measurement signal of a power system model. The results demonstrate that the method can accurately identify the parameters of complex broadband oscillation modes, adapt to various oscillation scenarios, and meet the signal characteristics of "double high" power systems, thus confirming its applicability and feasibility.