The aim of this paper is to describe the drought events in the Zhanghe upstream comprehensively. Firstly, monthly precipitation data were selected to calculate standardized precipitation index. And then, both drought duration and drought severity were identified according to runoff theory. Finally, Copula function was adopted to establish joint distribution between drought duration and drought severity to explore the spatial and temporal distribution of drought characteristics. The results show that the highest frequent drought events in the Zhanghe upstream from 2001 to 2020 is 3 months drought, and the drought severity ranges from 2.24 to 4.92; There is a strong positive correlation between drought duration and drought severity, and Frank Copula function is the most optimal joint distribution function of them; The joint return period of drought characteristics ranges from 18.56-23.94 years, and the northwest and southeast parts of the Zhanghe upstream basin are the two key drought risk areas; The co-occurrence return period of drought characteristics ranges from 22.25-31.94 years, and the northwest, northeast and southeast parts of the Zhanghe upstream basin are the three key drought risk areas. Consequently, it can be obtained that the joint distribution can analyze drought events comprehensively, and thus provide scientific guidance for thorough evaluation of drought.

In view of the relatively serious drought in the Feiyun River basin in recent years, the inability to effectively utilize the regulating capacity of the counter-regulating reservoir, and the inability to effectively guarantee the timeliness and scientificity of the operation, which affect the water supply safety of nearly 6 million people in Wenzhou, the anti-drought operation model and data center of the Feiyun River basin are established. The real-time data of rainfall, water level, water supply flow and ecological flow of multiple reservoirs in the basin are quoted. The meteorological data including 1 h, 3 h, 6 h short-term and imminent grid forecast data, and 1 d, 3 d, 7 d, 15 d, 30 d, 90 d and other long-term rainfall forecast data are introduced. Combined with water and soil moisture in the basin, reservoir and basin evaporation, support vector regression (SVR) calculation method is used to develop a distributed digital twinning business system based on SPARK components, which realizes early warning of available water supply, drought-resistant water level early warning, drought-resistant days early warning and ecological flow early warning, increases the use of the anti-regulation storage capacity of 2.8 million cubic meters and the reserve storage capacity of 2.93 million cubic meters. Thus, it provides data basis and technical support for the drought-resistant decision-making, scientific scheduling and "four pre-" realization in the Feiyun River basin.

Based on the agricultural drought-affected rate of 13 major grain producing provinces in China from 1980 to 2019 and the daily rainfall data, the climate-caucusing loss intensity (CCLI) were extracted using H-P filtering, and its responses to dry-days indices (DDI) and large-scale atmospheric-ocean indices (LAOI) were explored. The correlation analysis between CCLI of each province and DDI in different months indicated that summer drought had the higher contribution to the disaster situation, especially the total number of dry days in July was identified as the primary drought-causing factors (PDCF) in 10 provinces. The PDCF in Henan, Jiangsu, Hubei, Inner Mongolia, Jilin, and Liaoning all showed a significant strengthening trends, indicating the intensification of drought risk in the key month of summer; The fluctuation of PDCF in each province had a main cycle of 2-3 years; At the time-lag of 0-12 months, circulation signals such as North Atlantic Oscillation, Pacific Warm Pool, and Arctic Oscillation had the significant impacts on the drought situation. This study can provide scientific basis for regional drought monitoring and early warning.

In order to solve the problem that the current existing precipitation trend analysis methods cannot simultaneously detect precipitation trends in low and high value areas, this article introduces innovative trend analysis (ITA) and combines it with traditional trend analysis methods for analysis. Taking the station data of Yili River basin from 1961 to 2020 as an example, the ITA and Mann-Kendall (MK) series, Theil Sen and other seven methods are compared and analyzed. The results show that the annual precipitation of stations in Yili River basin, except Huocheng Station, Yining County Station and Zhaosu Station, increases significantly in other stations in high value areas, which is the same as the trend of annual extreme precipitation; The extreme precipitation intensity in the low and median areas of other stations shows an increasing trend, while the high value areas show a decreasing trend, and the overall trend is increasing; The ITA can reflect the range of rainfall changes and detect the trend changes of rainfall in low, medium, and high value areas. Therefore, the combination of ITA and traditional trend method to conduct trend analysis on the overall rainfall and rainfall in high and low regions simultaneously will help to more comprehensively analyze the precipitation change law of Yili River basin.

Due to the existence of snow, melting snow and frozen soil, the hydrological cycle in cold regions has its particularity. In order to probe into the hydrological law of small watershed in cold region and simulate the process of runoff formation, the hydrological data of Yongcuihe River basin from 1994 to 2015 were selected as the research area. The SWAT model for runoff simulation in cold region was constructed, and the applicability of DEM with different resolution, as well as three kinds of meteorological data, CMADS data set and CFSR data set, in Yongcuihe River basin was analyzed. The results show that the SWAT model can simulate the runoff process of Yongcuihe River. DEM resolution has a great impact on the extraction of watershed features, but has no obvious effect on runoff simulation. The applicability of different meteorological data has significant difference, the simulation effect of measured meteorological data is the best, the simulation effect of CMADS data set is better, and the simulation effect of CFSR data set is worse, which provides a reference for further study of small watershed in cold region.

In order to improve the accuracy and reliability of runoff prediction, the advantages of EMD in dealing with non-stationary time series are introduced, and a BP neural network prediction model based improved adaptive noise complete set empirical mode decomposition (ICEEMDAN) and whale algorithm (WOA) optimization is established. Taking the inflow runoff prediction of Jinpen Reservoir in Heihe, Shaanxi Province as an example, a simulation model based on multiple intelligent optimization algorithms is established to predict the inflow runoff of the reservoir. At the same time, historical data of different time series, such as precipitation and runoff, are selected as input factors to compare the prediction ability and results of BP, WOA-BP, ICEEMDAN-BP and ICEEMDAN-WOA-BP models under the same input factor conditions. The results show that as far as the input sequence is concerned, the prediction effect of the model with precipitation as the input factor is better than that of the model with runoff as the input factor; For different algorithms, ICEEMDAN-WOA-BP model has good stability, Nash coefficient can reach 80%-90%, and the prediction accuracy is higher. The proposed ICEEMDAN-WOA-BP model can provide technical support for river runoff prediction, reservoir hydrological prediction and watershed water resources management.

To study the trend of runoff evolution under the influence of climate change and human activities, the Qinhuai River Basin was taken as the research area based on the hydrometeorological data of representative stations. Firstly, the Mann-Kendall method was used to study the variation trend of hydrometeorological elements in the basin. Secondly, the abrupt change points of the runoff series were discussed by orderly cluster method and double cumulative curve method. Thirdly, the key factors affecting runoff were screened from numerous hydrometeorological factors, and the Wavelet Analysis-BP neural network coupling model was established to predict the runoff. Finally, attribution analysis method was used to identify contribution of climate change and human activities to the runoff variation. The results show that the rainfall of the Xinhe river sluice presents a downward trend, while the Wudingmen sluice and the whole basin show an upward trend, but none of the trends were significant. The runoff of the basin shows an upward trend, and the increase trend of Xinhe river sluice is not significant, both the Wudingmen sluice and the whole basin increase trend pass the test of 0.01 confidence level, and the annual evaporation tends to decrease. There is a great consistency between the Wudingmen sluice and the whole basin in the variation trend of rainfall, runoff, and the time of abrupt change point. The contribution rates of human activities and climate change to runoff increase were 73.92% and 26.08%, respectively, the human activities were an important factor that led to the runoff variation. The conclusion provides a scientific basis for flood and drought prevention and water resources planning in this basin.

Rainfall will affect the characteristics of slope flow field. Due to the continuous flow of fluid, the surface runoff and slope seepage usually exist a coupling linkage phenomenon. The surface runoff is described by the N-S equation, while the Darcy’s law is used to describe the seepage in the slope. The analytical solutions of velocity distribution, pressure and discharge as well as the semi-analytical solution of runoff surface line are derived by the separation of variables method under the velocity slipping boundary condition at the interface between runoff and soil. In addition, the explicit Runge-Kutta method is adopted to solve the water depth, velocity and discharge values at different locations. The results show that the steeper the slope is, the faster the fluid movement and the shallower the water depth is. The greater the rainfall intensity is, the deeper the overall water depth is. The flow velocity at the slope surface is not equal to 0. The closer to the downstream, the larger the proportion of runoff flow discharge is. The study can provide reference for the research of the slope flow field characteristics.

To study on water replenishment effect of ecological gate in the Tarim River Basin, the MODFLOW was used to establish the numerical simulation of the two-dimensional flow movement of the groundwater profile in the Wusiman section, and to analyze the evolution process of the groundwater flow field in 4 years. On this basis, the two schemes with or without ecological sluice were predicted and compared. The results show that in the fifth year under the two prediction schemes, compared with the single main river channel, the buried depth area less than 8 m in the study area increased by 6.62% by using the ecological sluice water conveyance scheme. The ecological gates restored the groundwater level far away from the ecological area of the main river channel, and the groundwater level on the north side of the section increased by 2-3 m on average. Compared with the single main channel water conveyance, the phreatic evaporation consumed by the increment of groundwater storage per cubic meter was reduced by 24.6%. The ecological sluice solves the problem that the groundwater level is difficult to recover in the ecological area far away from the main river channel under the traditional water conveyance mode, and creates conditions for the restoration of the river network ecosystem formed by multiple branches in the middle reaches and the safety belt of biodiversity along the main stream.

The unsteady inflow process changes the hydrodynamic characteristics of the compound open channel and then determines the processes of material transfer and energy transfer in the floodplain and main channel. In order to study the influence of different unsteady inflow processes on the hydrodynamic characteristics of the compound open channel, indoor flume experiments were carried out to analyze the influence of different unsteady inflow processes on the water level, flow instability, and discharge per unit width process of the compound open channel, taking into account three factors: discharge amplitude, unsteady period, and rising duration. The results show that with the increase of discharge amplitude, the slope of wave peak growth of water level is greater than that of wave valley, and the wave height increases linearly. The discharge process of the unit width of the channel is deformed over time, and there is an obvious slow change process in the descending process of the main channel and the rising process of the floodplain. With the increase of the unsteady period, the wave peak of the water level increases, the wave valley decreases, and the wave height also increases linearly. The phenomenon of deformation of the unit width discharge of the channel over time disappears. The water level peaks and valleys change synchronously with the hydrologic skewness. When the hydrologic skewness (ratio of fluctuation water duration) is greater than 1, the rising process of the unit width discharge of the floodplain and main channel will also have an obvious slow change stage.

The Guangxi coastal of Beibu Gulf has abundant water resources, but the inter-annual distribution is uneven under the influence of El Niño/La Niña events. The Nanliu River is the largest river located in the costal of Beibu Gulf, Guangxi. Based on SWAT model, the characteristics of blue water, green water flow, and green water storage in typical El Niño/La Niña years in the river basin were quantitatively analyzed. The results show that from 1971 to 2015, the annual average blue water, green water flow, and green water storage in the river basin was 835.0 mm/year, 929.0 mm/year, and 114.0 mm/year, respectively. In the typical El Niño years (1997)/La Niña years (2007), the blue water, green water flow and green water storage in the river basin are 145.7%/51.6%, 92.4%/96.9% and 115.5%/78.3% of the multi-year average, respectively. The El Niño/La Niña event caused a significant increase/decrease in precipitation in the river basin, which mainly affected the amount of blue water. Due to humid climate in the basin, the amount of green water flow was mainly affected by solar radiation and wind speed. The research can provide an important reference for the rational and efficient utilization of water resources and the high-quality development of the region.

Conductivity is an important parameter to measure water quality. High-frequency monitoring of water conductivity plays an important role in water quality management. Due to the complexity of field conditions, equipment failure often leads to data loss. In order to improve the high-frequency monitoring data, machine learning model was used to predict the conductivity content in water body based on the meteorological and physical indexes obtained from high-frequency monitoring. The results show that the random forest regression model has the best prediction effect, with its determination coefficient R² reaching 0.996, root mean square error (R_RMSE) 1.31 μS/cm, and mean relative error (M MRE) 0.38%. The pH value contributed the most and was the dominant factor affecting the conductivity. The results are conducive to optimizing the field high-frequency monitoring system platform, improving the high-frequency monitoring data, which provides scientific basis for water quality management.

In order to analyze the influence of Poyang Lake Water Control Project on wetland vegetation habitat, MIKE21 was used to establish two-dimensional hydrodynamic model of Poyang Lake. Through the scenario of the typical years, the changes of water level and wetland vegetation growth habitat area in the main lake area and wetland nature reserve after the operation of the water conservancy project were simulated. The simulation results show that the operation of the Hydraulic Project has a great influence on the water level in the north of Songmen Mountain, and the influence degree gradually decreases from north to south. The operation of the hub has a great influence on the most suitable area and suitable habitat area of wetland vegetation in different hydrological years. The vegetation habitat surface varies greatly. After the operation of the hub, the dry year increases by 43.8 %, the normal year increases by 24.6 %, and the wet year is only 16.4 %. In October and November, the suitable habitat area can reach more than 2,000 km², accounting for about 2/3 of the total lake area, indicating that wetland vegetation will provide Siberian cranes with rich food sources and make them better survive and reproduce in wetlands. The simulation results reveal the influence of the Hydraulic Project on the change law of lake water level and wetland vegetation habitat interval under the current scheduling scheme, which can provide a theoretical reference for engineering construction and dispatching operation and maintenance.

Danjiangkou Dam is a control project for the development and protection of the Hanjiang River basin, and is also a water source project for the Middle Route Project of the South-to-North Water Transfer Project. The dam operation safety is the support and guarantee of the national strategy. After the dam heightening, the operating water head will increase, and there may be cavitation, and the downstream scour pit will move upward during the flood discharge process. In order to master the mechanical characteristics of flood discharge after heightening the dam and evaluate the safety of flood discharge structures, the parameters such as bottom flow velocity, dynamic water pressure, flow cavitation noise, and scouring under the dam are mainly observed by means of field hydraulic prototype observation, and the results of previous studies are analyzed. The observation parameters under the design water level are within the safe range. Aiming at the problem that the water tongue of the surface hole impacts the middle wall, the opening order of the flood discharge orifice is optimized. The causes of the scour holes in the flow channel and side wall after the flood season are analyzed and the treatment suggestions are put forward. The problems found and treatment measures can provide reference for similar projects.

To explore the temporal and spatial distribution and attribution of mountain torrent disaster risk in Sichuan Province, the spatial distribution difference and high-risk areas of mountain torrent risk during 1990-2020 were studied by AHP and cluster analysis methods, and the changing characteristic and driving reason were investigated. The results show that the risk of mountain torrent disasters increased from the west to the east in Sichuan Province. High-risk areas mostly existed in areas with dense river networks and high exposure and vulnerability, such as Meishan, Zigong, Neijiang, Ziyang, Suining, Guangan and Nanchong. From 1990 to 2020, the risk of mountain torrents showed an increasing trend in Sichuan Province. The proportion of areas with high and above risk increased from 17% to 34%. Increased risk levels were concentrated in central Sichuan, and most of them were from moderately high and relatively high risk transformed into high risk. In the past 30 years, the risk of mountain torrents has shown a downward trend in Sichuan Province, while the greater GDP and population density had changed vulnerability and disaster prevention capacity, leading to increasing risk level of mountain torrents in local areas. The results can provide theoretical guidance and practical support for forecast and early warn in flood disaster and disaster prevention and mitigation in Sichuan Province.

With the increase of economic development and the frequency and intensity of flood disasters, post-disaster emergency management requires rapid understanding of disaster losses. This paper firstly constructed an index system from five aspects including disaster-causing factors, disaster-bearing bodies, disaster-pregnant environment, emergency response capacity and disaster situation, and verified its rationality based on generalized gray correlation analysis. Secondly, Gaussian process regression model was introduced to pre-evaluate and simulate the economic losses of flood disasters. Finally, the method was applied to evaluate the direct economic losses of flood disasters in Beijing-Tianjin-Hebei urban agglomeration from 2010 to 2020. The results show that the generalized gray correlation analysis-Gaussian process regression model has the best fitting accuracy when comparing the simple Gaussian process regression with the neural network assessment model.

The risk of water flow compensation caused by the additional discharge of leading hydropower station has increased the difficulty of multi entity cascade hydropower optimal operation, and the backwater jacking effect of downstream hydropower stations has further increased the complexity of the model. Therefore, non-linear modeling is carried out for the flow compensation process of leading hydropower station, and the risk of flow compensation in the compensation period and the recharge period is quantified. At the same time, the impact of backwater jacking effect of downstream hydropower stations on the tail water level of leading hydropower station is considered, and then a scheduling model with the goal of maximizing the joint operation revenue of cascade hydropower stations is constructed. The analysis of the example shows that the method can more reasonably distribute the benefits between the upstream and downstream hydropower stations in the cascade basin, coordinate the conflicts of interests among the multi entity cascade hydropower stations, and improve the activity of the hydropower stations at all levels in participating in the market scheduling.

In recent years, it is urgent to solve the interest allotment problem of multi-energy joint delivery alliance considering the impact of carbon peaking and carbon neutrality goals. Based on the traditional Shapley value method and considering the fairness of contribution, four indicators of resource input, risk allocation, carbon policy impact, and contribution degree were introduced to build an improved MCGC-Shapley based the cloud center method. Taking Sichuan Province as an example, benefit distribution was calculated by quantifying the comprehensive contribution of each party. Compared with the traditional Shapley value allocation strategy, the example analysis shows that the improved MCGC-Shapley benefit allocation method can better achieve the matching between the interests of the main body and the comprehensive contribution, improve the investment enthusiasm, and play a positive role to promote all-win of power generation enterprises and power grid enterprises.

Manually planning concrete gravity dam pouring scheme is time consuming, lower efficiency and complex. It is also difficult to make adjustment and to visualize the process. An automatic BIM-based pouring scheme planning system is proposed. The system associates the pouring information with the BIM model directly, and is capable to do the pouring-related parameters calculation, pouring constraints customization, dam blocks scheduling, Gantt charts drawing, dam timeframe display, pouring process visualization. Finally, this paper uses the Zhuxi Dam as an example to verify the efficiency and intuitiveness of the system, which provides a reference for research on the development of similar systems.

The geological conditions of a certain reservoir area and dam site are complex, with multiple penetrating faults. In order to analyze the seepage situation in the reservoir area and the dam body, the finite element method was used to conduct three-dimensional numerical simulation of the seepage field in the dam and reservoir area. Based on the actual operating conditions, parameter inversion was conducted, and the anti-seepage safety of the dam was analyzed and evaluated based on the distribution of water head and the calculation results of seepage flow. The results indicate that the change of permeability coefficient of faults in the reservoir area has the most significant impact on the seepage flow rate of the left bank and dam section, and the left bank seepage is more severe. The seepage line of the dam body is relatively high, and there are cracks in the upstream anti-seepage panel, causing jet flow in the high water level dam body. There is a lot of accumulated water in the corridor, and the comprehensive anti-seepage and drainage system facilities of the dam are not perfect. The overall seepage flow in the dam site area is too large, especially in the thin watershed on the left bank, where leakage is more severe. There are serious problems with dam foundation leakage and seepage around the dam, and it should be treated.

The total leakage amount behind a certain reservoir dam reaches 16.7 L/s, with the seepage points being the drainage body at the dam foot and the low culvert, but the anti-seepage body inside the dam is weak to slightly permeable and tightly cemented. The image recognition results reveal that the dam body outside the low culvert pipe has formed a penetrating leakage channel. This article selects the centerline of the dam body and the cross-section of the culvert pipe position as example. Based on measured data such as the physical parameters of the rock and soil of the dam body and the leakage amount behind the dam, AutoBank modeling was used to calculate and modify the stability of the dam, while simulating the stability of the reinforced dam. The results show that the water inside the low culvert pipe comes from the water seepage outside the pipe wall, and the leakage points are generally concentrated in the pile number K0+058~0+131.5, mainly in the form of rain or jet, while other sections are in the form of drip or no seepage. The dam body within 2.9 m outside the culvert pipe has formed a penetrating leakage channel, which is the main cause of drainage and culvert pipe leakage. The central section of the dam is in a state of seepage and anti-sliding stability under the conditions of 176.50 m water level, normal water storage level, and check flood level. The cross-section of the dam culvert pipe location undergoes seepage failure under various working conditions, and the calculated total leakage is in good agreement with the on-site measured value; Except for the anti-sliding instability of the upstream dam slope under the condition of sudden water level drop, the dam slopes under all other conditions are stable. After reinforcement, the dam is in seepage and anti-sliding stability under all working conditions.

With the increase of the service life of the dam, inversion analysis of dam mechanical parameters based on the prototype monitoring data is necessary. At present, the dam inversion analysis model is still mainly based on the dam displacement monitoring data, which can only reflect the dam displacement law at the macroscopic level, while the change law of the strain field and stress field of the dam is ignored from the mesoscopic perspective. Therefore, a high arch dam mechanical parameter inversion model based on WOA-BPNN and MOEA/D was proposed, which consider both the dam displacement monitoring data and the dam strain monitoring data. The mechanical parameter inversion analysis of the arch dam was carried by the dam’s displacement data and strain data. The results show that the inversion parameter is more accurate and reasonable.

Dam displacement can directly affect the quality and operation safety of the dam. To find out the prediction model of the dam displacement, the temporal convolutional neural network model was used to predict the dam displacement. Three bionic algorithms of the sparrow search algorithm (SSA), the gray wolf algorithm (GWO) and the bat algorithm (BA) were improved by genetic algorithm, and three optimization algorithms including MSSA, MGWO and MBA were obtained. Taking root mean square error, determination coefficient, mean absolute error, efficiency coefficient and GPI index as precision index system, three combined weighted models including D-MSSA-TCN, D-MGWO-TCN and DMBA-TCN were constructed based on the deep belief network model (DBN). The results show that the MSSA algorithm had the highest operating efficiency and accuracy among all the algorithms. The accuracy of the three combined models was significantly higher than the rest of the models. The D-MSSA-TCN model had the highest accuracy among all models and can be recommended for estimating dam displacement.

Cross building is inevitable in water diversion projects, and the structural state of cross buildings is crucial to the safe operation of the project. Based on a water transfer project in Henan Province, a three-dimensional finite element model of cross-crossing of water pipeline structures in the inverted siphon and water transfer project of the South-North Water Transfer Central Project was established by taking into account the coupling effect between soil-water-structure in the process of water transfer and diversion. The structural state effect of cross building under each simulation operating condition was analyzed by considering the periods of unconstructed structure, completion, normal operating. The results show that the cross-crossing building has impact on the existing building, especially for the large change of structural state in cross part. The maximum tensile stress in the inverted siphon structure increases from 0.54 MPa to 0.97 MPa, and the maximum settlement increases from -1.38 mm to -1.90 mm; The tensile stress in the aqueduct increases from 1.03 MPa to 1.34 MPa, and the maximum settlement increases from -3.78 mm to -4.07 mm. The stress value and settlement amount can meet the engineering requirements. Moreover, with the increase of the buried depth of the two supports of the water pipeline, the less the impact on inverted siphon is. The research results can provide reference for the analysis of similar projects.

In recent years, part of water conveyance buildings of the main canal of the middle route of the South-to-North Water Diversion project have high water level and abnormal flow pattern, which lead to the risk of reduced water conveyance capacity. Therefore, it is urgent to assess the head loss. However, there are no monitoring stations inside the buildings, the project operation has not reached the designed scale, and the monitoring data lacks verification. The monitoring data of water level and discharge of the main canal during the large water delivery period in 2022 were collected, and the third-party hydraulic prototype measurement was carried out, and the monitoring data was reviewed and corrected. A calculation method of head loss was put forward using comprehensive head loss coefficient. The head loss of 143 out of 158 water transport structures in the main canal was calculated under enlarged flow. The results show that there is surplus in the distribution of head in the main canal. The total surplus head of the whole line is 3.05 m, among which the surplus in the section south to the Yellow River, the section between the Yellow River and the Zhang River, the section north to the Zhang River are 0.48 m, 1.06 m and 1.51 m respectively, accounting for 4%, 13% and 12% of the allocated head, respectively. The head loss of 40 water conveyance buildings exceeded the assigned value, among which were 31 inverted siphon, 4 aqueduct, 4 culvert and 1 tunnel.

When there is a leakage point in the water supply pipe network, it is not easy to be detected due to its concealment, and the long-term leakage accumulation will not only cause waste of water resources, but also lead to the problem of poor production and marketing of water supply. The frequency domain analysis was introduced into the water supply industry, and a node pressure of water supply pipe network based on FFT was proposed. Firstly, the specific method is called EPANET by writing a program to optimize the operation simulation of water supply pipe network, and then solve the optimal pump and valve scheduling scheme back into the simulated leakage point working condition. With the help of Fourier transform to convert the time-varying node pressure into an amplitude signal, the pipeline node pressure was analyzed from the perspective of the frequency domain. Therefore, the length range between the leakage point and the starting node of the pipeline was judged. Through verification and compared with the previous pressure based analysis of the leakage point, the proposed method can judge whether the pipeline is normal operation and the location range of the leakage point from the perspective of frequency domain.

The problem of standard disconnection often exists in the two-level drainage mode of plain river network cities in China. As a result, when heavy rainfall occurs, the hydraulic characteristics and drainage capacity of pipe network system are affected by both rainfall intensity and water level of drainage water, making it difficult for waterlogging to discharge out. Therefore, taking the municipal drainage system and water drainage system of Suzhou Industrial Park as an example, the multi-scenario flood process simulation based on SWMM was carried out, and the analysis showed that when the river water level was between 1.70 m and 2.30 m, the main reason for the water accumulation in the study area was the insufficient capacity of the current pipe network system itself, and the river water level aggravated the water accumulation. When the water level exceeded 2.30 m and keep rising, the drainage capacity of the pipe network system decreased sharply, and the river level gradually became the main factor restricting the flow capacity of the pipeline and aggravating the degree of water accumulation. It is suggested that the maximum water level for river drainage control in the study area should be around 2.30-2.32 m. This conclusion can provide reference for urban river level regulation to improve urban drainage and waterlogging capacity.

In order to alleviate the water shortage in the development of oil and gas resources, horizontal wells are often used to exploit groundwater resources, but there is little analysis on the factors affecting the water intake of horizontal wells. Therefore, the numerical model is used to simulate the horizontal well mining mode and explore the influence of horizontal well layout direction, burial depth, pipe length and well pipe permeability on the water intake effect. The results show that considering the water intake efficiency and construction difficulty, the optimal horizontal well layout direction should be laid along the incoming water direction, and the location should be located in the upper layer of Luohe Formation as far as possible. The recommended pipe length and well pipe permeability are 800 m-1 000 m and 0.15, respectively, and the corresponding production volume is 1 368 m³/d-2 389 m³/d. The research results have important guiding significance for alleviating the shortage of water resources in the development of oil and gas resources in the eastern region of Longdong and formulating reasonable development strategies of water resources.

Fenghuangjing new station belongs to the front inflow pump station with large diffusion angle. Large scale off-wall reflux is easy to occur at the bank walls on both sides of the forebay, which can not provide good inlet conditions and endanger the safe and stable operation of the pump station. Forebay at river diversion side of Fenghuangjing new station was taken as the research object. Based on the CFD numerical simulation software, the improvement effect of trapezoidal sill position and height on the flow pattern in the forebay of the front inflow pump station with large diffusion angle was studied. And the numerical simulation results were verified by physical model tests. The results show that when the trapezoidal sill is located at 10 m from the entrance of the forebay and the height of the sill is 1.2 m, the inflow conditions of Fenghuangjing new station can be better improved. The research results can provide technical support and reference for this project and the similar projects.

In order to solve the problem of instability of the bottom plate and pressure damage of the suspended grid due to the excessive time-average pressure in the suspended grid stilling basin, numerical simulation was used to study the water level difference and pressure field in four different arrangements of the suspended grille under the design and calibration flow. Two optimization schemes of the combined toe pier-suspended grille and circularized suspended grille were proposed on the basis of the scheme 4 with better water stabilization effect. The results show that the combined toe pier-hanging grille optimisation scheme can reduce the time-average pressure at the bottom plate by 63% and 50% compared to scheme 4 at the design and calibration flow rates, effectively reducing the difference in the time-average pressure Δp₂ between the upper surface C and the lower surface D of the grille in the basin. The rounded grille optimisation scheme can make the total pressure distribution at the grille more uniform and avoid local damage to the grille. Therefore, it is recommended to choose a combined auxiliary energy dissipation method of toe pier-suspended grille for high flow stilling basin with pressure requirements.

In order to solve the upstream demand of small fish with weak swimming ability in the vertical slot fishway, an anti-flow cylinder is added to the migration channel between the long and short baffles. Hydro 3D open source code and LES-based numerical simulation technology are used to simulate the flow field in the vertical slot fishway before and after the anti-flow cylinder is added. According to the streamline distribution in the time-averaged flow field, the results show that the area of the vortex area in the pool is reduced after adding the blocking cylinder, which solves the problem of lack of sense of direction in the process of fish upstream in the traditional vertical slot fishway. The turbulent kinetic energy in the pool increases by 20%, which raised the energy dissipation of the water flow and reduced the energy consumption during the fish upstream process. The increase of vorticity around the long and short baffles and the blocking cylinder may have an adverse effect on the stability of the fish during swimming. However, according to the vortex structure, the vortex diameter behind the blocking cylinder is less than 76% of the body length of the small fish, so it has little impact on the stability of the fish during swimming. In summary, the setting of a flow blocking cylinder in the vertical slit fishway can improve the success rate of small fish upstream.

River bank collapse is very common in natural rivers and plays an important role in the evolution of river channels. In order to quantitatively study the influence of river bank soil properties and bank slope inclination on river bank stability, the BSTEM model for calculating river bank stability and bank toe erosion was adopted, and six typical river bank materials were selected to study the stability of homogeneous river banks under six bank slope inclination angles. Under the condition of ignoring the water table, the collapse modes of non-cohesive bank slope and cohesive bank slope are different. For non-cohesive bank, the dominant factor affecting bank stability is the effective internal friction angle. The larger the effective internal friction angle is, the more stable the bank is. For cohesive bank, the dominant factor affecting the stability of the cohesive bank is effective cohesion. The greater the effective cohesion is, the more stable the bank is. When the effective cohesion difference is the same, the smaller the absolute value of the effective internal friction angle difference is, the more the safety factor increases. The increase of bank slope inclination reduces river bank stability and the safety factor. The larger the effective internal friction angle of the non-cohesive bank is, the more sensitive the safety factor to the change of bank slope inclination is. For cohesive banks, the greater the effective cohesion is, the more sensitive the safety factor to the change of bank slope inclination is.

Water and sediment conditions are complicated in waters affected by the interaction of flood and tide. Therefore, the bend regulation in these waters is more difficult and its effect is more uncertain than that of ordinary rivers. This paper aims at the above problems by taking the treatment project of Wenjiayan bend as an example, which lies in Qiantang estuary. This treatment project consisted of the riprap protection at concave bank and retreating dike at the opposite bank combine with the shoal-cutting measure. Based on the observed hydrology and topography data for years, the variation of flow conditions, deep channel distribution, scouring elevation and siltation velocity before and after the project was analyzed. The results show that the bend effect is greatly weakened and flow conditions are improved after the treatment. Meanwhile, the deep channel in the bend reach moves from the foot of the dike to middle. These results can provide reference for measures to similar sharp-bend treatment. Meanwhile, the balance section area after the project implementation was predicted through the methods of river correlation coefficient method and section average statistics. The dredging conditions of the reach were determined, which can provide guidance to operation and maintenance for the subsequent project.

The flow field characteristics of vortex setting chamber (VSC) play a decisive role in its water and sediment separation performance. In order to clarify the influence of the inclination angle of the curved deflector on the flow field characteristics of VSC, the large eddy simulation and VOF method are used to study the three-dimensional flow field characteristics of the VSC when the inclination angles of the curved deflector are 5°, 10° and 15° respectively, and the flow field characteristics of the VSC with the plane deflector under the same inlet flow rate are compared. The results show that the use of curved cantilever deflector will increase the eddy current intensity in the VSC chamber and reduce the range of low velocity zone. The increase of the inclination angle can improve the stability of the air vortex, increase the strength and size of the air vortex, which is beneficial to the separation of water and sediment. The radial velocity in the cone area increases with the increase of the inclination angle, and basically points to the center of the VSC, which is conducive to the rapid transport of sediment to the bottom hole of the sediment discharge. The velocity of the overflow flow on the surface of the curved deflector is greater than that on the surface of the plane deflector, and the flow velocity on the deflector is the largest when the inclination angle is 15°.

There are some problems in construction, such as inaccurate material parameters and unclear influence of shield operation parameters on ground settlement. Based on a water-rich sand layer shield construction diversion tunnel, an orthogonal experiment is designed by setting the index of ground surface settlement, and a three-dimensional numerical simulation is used to analyze sensitivity of different material’s parameter. Mechanical parameters of materials are inverted according to the observed settlement. The subsidence lines under different excavation pressures, different synchronous grouting pressures and different speeds of the shield are calculated. The result shows that the surface subsidence is most sensitive to the change of internal friction angle of sand layer. Increasing the internal friction angle of the sand layer and the elastic modulus of the lining will reduce the settlement. The speed of the shield has a great influence on the subsidence. Increasing the speed of the shield, the maximum settlement of the surface settlement curve will increase, and the width of the "settlement tank" will also increase. The maximum settlement and the width of "settlement tank" decrease with the increase of excavation chamber pressure or synchronous grouting pressure.

In view of the lack of research on the creep characteristics of hydraulic concrete in water from mesoscale scale, a meso-finite element model of concrete specimen of "aggregate-mortar-transition layer" was established. Based on the test data of tensile and compressive creep in water, the method of "orthogonal design-neural network-meso-finite element calculation" was adopted to implement the inversion analysis of the tensile and compressive specific creep of hydraulic concrete specimens at mesoscale. Finally, the relationship between tensile and compressive specific creep of hydraulic concrete and mortar was compared. The results show that the variation law of tension creep degree of hydraulic concrete in water is similar to that in sealed. The creep degree of mortar water is 2.4 times of hydraulic concrete water under conditions of tensile and compressive creep.

In order to understand the influence of thermodynamic coupling factors on the damage characteristics of hydraulic engineering concrete materials within 100 ℃, the temperature of concrete specimens is applied and stabilized by self-designed temperature control device, and non-destructive monitoring acoustic emission technology (AE) is used to monitor the uniaxial compression of concrete under different temperature environments. The AE ringing count and amplitude change during concrete failure at five different temperatures are explored, and the constitutive model of concrete damage under thermodynamic coupling is established according to the relationship between ringing count and stress. The results of the cumulative ringing count and amplitude show that the higher the temperature, the higher the number of damage events, the more severe the degree of damage, respectively, the cumulative ringing count increases by 5.25 times at 100 °C compared with 20 °C, and the amplitude can be increased by 20-40 dB in the late loading stage compared with the previous stage. The established damage constitutive model shows that the increase of temperature will increase the degree of damage of concrete, which provides a theoretical reference for understanding the influence of thermodynamic coupling on the damage of concrete materials.

Dry-wet cycle effect is an important factor affecting slope stability in red mudstone reservoir area. Triaxial consolidation undrained shear experiments, CT scans and high precision scanning electron microscopy experiments were carried out to investigate the mechanical and fracture evolution characteristics of in situ weathered mudstones during dry and wet cycles. The results show that the stress-strain relationship of red-bed mudstone presents strain softening characteristics at low confining pressures and strain hardening characteristics at high confining pressures. The shear strength parameters of red-bed mudstone decrease gradually during the dry-wet cycle. The volume content of cracks decreases exponentially with the increase of the time of dry-wet cycles, and has a negative linear correlation with cohesion function. The microstructure of mudstone gradually breaks down in the process of dry-wet cycles, leading to the connectivity of cracks and the attenuation of mechanical properties.

To prompt grouting construction quality management of Wuyue Pumped Storage Power Station, combining with exposed geological conditions after excavation, designed grouting parameters, this paper conducts grouting test, and determines the grouting process parameters. The introduction of intelligent grouting system can reduce labor intensity of workers and the labor cost, and improve the traceability of quality work, save the construction period. The introduction of third-party testing units brings advanced technology and management experience, and improves the credibility of testing results. Using the results of water pressure test and comparative analysis of wave velocities of different types of rock masses can evaluate the grouting quality. The evaluation results are mutually verified, which improves the persuasiveness of the grouting effect. The grouting project has achieved satisfactory results for all parties involved in the construction, and this grouting construction process management experience can be a reference for similar projects.

In view of the complex and changeable construction site and high difficulty in construction of water conservancy safety, the risk assessment of all hazard sources is the premise of safety control of a project. The traditional LEC method has the defects of large influence of subjective factors and unclear weight of each hazard source. Based on the introduction of expert credibility, the background differences between risk evaluation subjects were converted to quantitative analysis, and the subjective impairments was modified. This paper combined fuzzy comprehensive evaluation method with traditional LEC method to establish the risk evaluation index system. By calculating every index weight factor with the modified risk values in LEC method, the risk assessment was converted from qualitative to quantitative by membership degree matrix and the defection of imprecise weight factor in LEC method was solved. Finally, a verification of Xinmeng River shows that the objectivity of risk assessment of hazard sources has been improved significantly through the modified method, which provides scientific basis for the risk hierarchical control of water conservancy safety.

The study of classified water price can provide scientific basis for the rational formulation of agricultural water price, which is of great significance for guaranteeing the benign operation of irrigated areas and promoting the high quality development of regional agriculture. Taking grain and oil crops as the research object, two evaluation indexes of irrigation benefit apportionment coefficient and irrigation water output were selected to define the irrigation benefit apportionment coefficient by emergy theory. The agricultural water price share evaluation system of different crops was constructed based on entropy weight method, and the irrigation classified water price evaluation model was established and applied in Baojixia irrigation district of Xianyang City. The results show that the share coefficient of irrigation benefit was 0.42, the share of agricultural water price of grain and oil crops was 0.37, and that of cash crops was 0.63. For agricultural water supply at full cost, the agricultural water price of grain and oil crops was 0.485 yuan/m³, and that of cash crops was 0.827 yuan/m³. As for the water price of agricultural water supply operation cost, the agricultural water price of grain and oil crops was 0.377 yuan/m³, and that of cash crops was 0.641 yuan/m³.

At present, the TV card model of PSD-PBA platform used in power system stability calculation cannot reflect the difference of units under multiple water heads, which is specifically reflected its dynamic response speed and anti-regulation accuracy. Based on the TV card model, an improved scheme is proposed. The water head-opening-power characteristics and power T_w characteristics of the model are obtained by program processing with the early operation data of the hydropower station, and then added to the improved model successively. The results show that the dynamic characteristics of the TV card model do not have the conditions for multi-parameter identification under the power mode primary frequency modulation. Moreover, the accuracy of anti-regulation under different loads is poor. The response characteristics of the improved model accord with the operation law of the real machine and can accommodate the difference of multiple water heads of the unit.

At present, most variable-speed pumped-storage units use converters (AC excitation) to control power. There is a problem of reverse speed overshoot caused by rapid power changes, and the traditional governors are difficult to ensure good control effects, which affects the operating efficiency of variable-speed units. In order to study the control of the speed regulation system under the active power regulation of the variable speed unit, the speed regulation system of the variable speed pumped storage unit with adaptive backstepping sliding mode control (ABSMC) was proposed. Firstly, a mathematical model of the variable-speed pumped-storage unit speed control system including the optimal speed module was established. Secondly, taking the electromagnetic power as the system disturbance, an adaptive backstepping sliding mode controller for the variable-speed pumped-storage unit speed control system was designed and its stability was analyzed. Finally, a simulation test platform for the speed regulation system of the variable speed pumped storage unit was built, and the dynamic response simulation analysis of the speed of the variable speed pumped storage unit was carried out under the given power of the power generation condition. Compared with the sliding mode controller (SMC) and PID controller, the results show that the reverse overshoot of the controlled unit speed by the ABSMC is small, the adjustment time is short, and the effect of tracking the optimal speed is ideal. The effectiveness of the designed controller was verified.

The primary frequency modulation function of the hydropower unit plays an increasingly important role in maintaining the safe and stable operation of the power grid, and it is necessary to ensure that the units integrated into the power grid have good primary frequency modulation performance. The influence of various dead zone nonlinear factors in the hydraulic turbine adjustment system on the dynamic performance of primary frequency modulation cannot be ignored. The nonlinearity of the dead zone in all links of the adjustment system is comprehensively analyzed. Based on the established high-precision primary frequency modulation model of hydropower units, the influence of frequency dead zone, openness dead zone, power dead zone and dead zone of the follow-up system on the performance of the primary frequency modulation response performance of large and small frequency difference is explored, and it is emphasized that the next frequency modulation inaction of small disturbances may be related to the dead zone of the follow-up system, which provides important theoretical guidance for the improvement and optimization of the primary frequency modulation function of the hydropower unit.

The load rejection process is one of the most dangerous transients in pumped storage hydropower plants. The current design criteria of plant guarantee that the lowest pressure in draft-tube inlet is higher than the saturation pressure during transients, but there is still local cavitation inside the pump-turbines. The one-dimensional pipeline and three-dimensional pump-turbine coupled computational fluid dynamics simulation method was used to simulate the simultaneous load rejection process in a pumped-storage hydropower plant. The results show that a spiral cavitation cavity is in the center of the draft-tube inlet, and five wedge-shaped cavitation cavities are in the outlets of runner channels. The collapse of the spiral cavitation cavity in the draft-tube leads to instantaneous pulse impacts on the pressure and runner forces. There is no obvious impact when the wedge cavities collapse.

In the hydraulic model test of the CB hydroelectric station in Jinsha River, occasional penetrating vortexes were observed in front of the sluice gate. In order to eliminate the vortex, this paper improved a vertical eddy-eliminating barries and proposed a new horizontal eddy-eliminating barries. The flow field in front of the sluice gate, vortex scale, and vortex generation frequency of the new horizontal eddy-eliminating barries were measured and analyzed for its vortex elimination effect. The results show that the proposed horizontal eddy-eliminating barries has better vortex elimination effect than the previous vertical eddy-eliminating barries, and it is a low-cost and efficient vortex elimination facility for sluice gate.

In order to address the limitations of the existing vibration trend prediction model for hydroelectric units, a vibration trend prediction method for hydroelectric units based on optimal variational mode decomposition (OVMD), time-varying filter empirical mode decomposition (TVFEMD), hunter-prey optimization algorithm (HPO), and extreme learning machine (ELM) is proposed. This method first applies OVMD to adaptively decompose the original vibration signal of the hydroelectric unit, and then further employs TVFEMD to perform a secondary decomposition of the residuals obtained from the first decomposition. Subsequently, vibration trend prediction models HPO-ELM are established for each subsequence. The final predicted vibration signal is obtained by aggregating and reconstructing the prediction results of all the sub-sequences. The research results demonstrate that this method outperforms traditional methods in terms of prediction accuracy for the vibration trend of hydroelectric units, and it has good engineering application value.

After the Deneng Xiangjiang Hydropower Station replaced the 4-blade runner with a 5-blade runner, the unit started experiencing severe vibrations, which eventually led to coupling vibrations in the powerhouse structure and posed significant safety hazards. This paper explores the vibration source and employs Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) methods for analysis. Finally, modal verification through actual measurements validates the relevant conclusions. The study reveals that the resonance is caused by the multiple frequency relationship between the runner blade rotational frequency and the natural frequencies of the powerhouse structure. The research on the vibration issue at this power station hold great practical value.

In the condition monitoring of pumped storage units, vibration velocity signal is often integrated into the displacement signal, and then calculate characteristic values for unit evaluation. Taking the horizontal vibration velocity signal of upper bracket of a case unit under stable working condition as an example, the method of integrating velocity signal into displacement signal and the setting of filter parameters are studied. Furthermore, vibration signal in transient working condition is adopted for verification. The results indicate that a high-pass filter shall be used when the vibration velocity signal is integrated into the displacement signal under stable conditions, and the cut-off frequency of the high-pass filter can be set as per 0.2 times of the rotational frequency. Under transient conditions, there is a risk of over estimating unit vibration when using unfiltered displacement signals integrated from velocity signals to calculate characteristic values for unit safety assessment.

Aiming at the two failure modes of hydraulic steel gates, the relative deformation failure under the normal service state and the bending shear composite strength failure under the limit state of bearing capacity, the corresponding failure probability analysis models were established respectively. The influence of different parameter distribution types on the failure probability of two failure modes of outcrop steel gates and deep-hole steel gates in hydraulic steel gates was explored through Monte Carlo simulations. The results show that under the same failure mode, when the coefficient of variation of the variable itself remains unchanged, the failure probabilities obtained by different distribution types are relatively close. Compared with the outcrop gate, the deep-hole gate has a higher failure probability and is more prone to instability. But the type of parameter distribution has little influence on the failure probability of deep-hole gate and has great influence on the outcrop gate. When the random variables of each parameter follow the logarithmic normal distribution, it will have a relatively maximum failure probability. It is easy to overestimate the reliability of hydraulic steel gates by considering only the normal distribution.

In respect to the network security situation and attacks of new types, the needs of trusted computing of applications in SCADA for pumped storage power station was analyzed. Based on the trusted hardware platform and operating system, a system structure of trusted applications in SCADA was proposed, and the key techniques such as trusted distributed services and trusted behavior analysis were discussed. The results show that the proposed design realizes the trusted applications in SCADA, and provides active defense mechanism for SCADA, and adapts to the development of prospective SCADA applications for pumped storage power station.

After a blackout occurs resulting from an extreme disaster, the active distribution network with distributed generation and energy storage equipment can perform service restoration by island partition and network reconfiguration. To solve the service restoration problem for the active distribution network with uncertain wind power output, this paper proposes a two-stage service restoration model based on robust stochastic optimization. In the first stage, the event-wise ambiguity set of wind power output is constructed based on the historical data and the model which minimizes the outage cost is solved by the robust stochastic optimization method. In the second stage, the energy storage and controllable loads in the distribution network are used to track the wind power output, so as to optimize the scheduling during the fault recovery of the distribution network, which minimizes the outage cost and the total power loss. Finally, the superiority of the proposed the model and strategy is verified by the simulations of a modified IEEE 33-bus distribution system case.