In order to study the influence of climate change on rainfall extreme value distribution in main flood season, based on the daily rainfall data from 1960 to 2017 in Jiangxi Province, a variety of test methods were used to detect and test the abrupt change points. Genetic algorithm and Fisher's optimal segmentation method were used to stage the flood season before and after the climate abrupt change, and the extreme distribution of staged rainfall and design rainfall before and after the climate abrupt change were discussed. The results show that 1991 was the abrupt change year of precipitation in Jiangxi Province from 1960 to 2017, and it was necessary to pay more attention to the occurrence of extreme heavy rainfall in Guangchang and Poyang Lake regions. Genetic algorithm is suitable for the division and staging of flood season. After the abrupt climate change (1991-2017), the designed rainfall value in the main flood season of Jiangxi Province was greater than that before the abrupt climate change (1960-1990), and also greater than that in the whole period (1960-2017). When calculating the designed flood based on the designed rainfall, the influence of climate change on the designed rainfall value should be considered, and strengthen protection against floods.

The cluster forecasting model is a long-term forecasting physical model based on mathematical statistics. This method has been applied in the long-term forecast of the upper reaches of the Yangtze River. After years of practice, there is space for improvement in accuracy and efficiency of the model. This paper selected the upper reaches of the Yangtze River as the demonstration area for forecast, the monthly areal rainfall from June to August as the forecast object, and used the coincidence rate of anomaly symbol and the percentage of anomaly error as the test methods of the model. And then the construction process and improvement of the model were described. Finally, the improved model was used to forecast the monthly area rainfall in the upper reaches of the Yangtze River from June to August during 2020 to 2022. The prediction results show that the improved model has a great improvement in the anomaly sign agreement rate and the percentage of anomaly error, and it has been implemented easily, which has certain reference value.

Taking four small and medium-sized watersheds in the mountainous city (Chongqing) as the research objects, the application prospects of multi-source rainfall data in short-term hydrological forecasting were explored. The GPM-IMERG remote sensing precipitation data was introduced as the source of the satellite precipitation data, and the Mean Bias Correction (MBC) method, Linear Regression Model (LRM) and Geographically Weighted Regression (GWR) method were used to realize the fusion with the ground station measured data. A leave-one-out validation method was used to evaluate the accuracy of the fused precipitation data, and the SWAT model was applied to simulate the runoff of the selected basins using the precipitation data corrected by MBC, LRM, GWR, the original IMERG-early, and the measured data. The results show that the GWR was the best fused effect. The topography had great influence on the accuracy of the IMERG-early data and the fusion method. The accuracy of the fusion method was relatively high in low elevation regions, while in mountainous areas, the accuracy became low comparatively. The results showed a better agreement between the SWAT model and the measured runoff process using all kinds of precipitation data, in which the model using precipitation data corrected by GWR method was more accurate. Results can be referenced for hydrological forecast in similar small basins in the future.

A similar basin identification method was proposed to improve the reliability of similar basin identification for hydrological forecasting in ungauged basin. The method introduced the basin time-varying feature information and constructed a time-varying feature matrix (TVFM). A dimension reduction method for the TVFM was proposed to obtain the basin feature vector. The classical K-means clustering method was adopted to implement the identification of the similar basins. Seventeen natural catchments in Jiangxi Province were selected and the Xin'anjiang model was applied in this research. A series of studies were carried out which includes feature vector and feature matrix construction, similar basin identification, parameter transfer, and comparison & analysis of hydrological forecasting results. The following conclusions can be drawn. The proposed TVFM can achieve better forecasting results in ungauged basins. Compared with the traditional similar basin identification method based on time-invariant underlying surface information, the prediction accuracy is improved. The similar basin identification based on time-varying comprehensive features generates the best predictions, and the prediction accuracy based on time-varying meteorological features is better than that based only on time-invariant underlying surface features. Comparison with the single factor methods, the directional problem of the parameter transfer can be partially solved by the proposed comprehensive method. Unfortunately, the directional problem cannot be completely overcame until recently.

Vegetation is an important part of terrestrial ecosystem and is vulnerable to extreme climate events. It is of great significance to explore the spatio-temporal evolution and dynamic response relationship between extreme climate events and vegetation for scientific response to climate anomalies and prevention of natural disasters. Therefore, the RClimDex, trend analysis and detrended fluctuation analysis were used to analyze the spatio-temporal evolution of extreme climate and NDVI in the Huaihe River Basin from 1998 to 2019, and discuss their causes and future variation tendency as well as clarify the response of NDVI to extreme climate. The results demonstrate that the NDVI shows an increasing tendency with an increase of 0.002 5 a^-1 from 1998 to 2019. Among the extreme climate indices, warm temperature indices showed an increasing tendency, while the cold temperature indices and precipitation indices (except RX1day) showed a decreasing tendency. The distribution of NDVI in the Huaihe River Basin was closely related to the distribution of urbanization in the region. The NDVI has a lag response of about one month to extreme climate and will continue to rise. The annual variation of the NDVI is closely related to natural and human factors, and the intra-annual variation of the NDVI is mainly affected by the growth rhythm of crops in the cultivated land.

It was planned to carry out excavation and treatment of the deep trough in Maozhou Estuary for the construction of the new town, which occupied the -3 m deep trough. The Pearl River estuary physical model was used to carry out tide hydrodynamics modeling test and suspended load model test to simulate the siltation distribution of the deep trough after one year of implementation. The test results show that the hydrodynamic characteristics and flow pattern of the study area have changed and the average siltation near the Maozhou Estuary reaching 0.75 m is more serious than that in downstream with 0.53 m, the -3 m deep trough remains connected with the whole widening rate is 1.57% and the thalweg is distributed along the Shenzhen shoreline with the minimum elevation is -3.40 m. The section morphology shows that the siltation on the right side is more serious than the left side and the upstream is more serious than the downstream. The treatment scheme changed the riverbed, the river regime will be significantly adjusted in the short term, but the -3 m deep trough can be maintained. The scheme is generally feasible.

After the operation of the Three Gorges Project, the process of water and sediment in the lower reaches of the reservoir changed greatly and led to the adjustment of the evolution law of the curved channel, which may have adverse effects on the stability of the river and the safety of flood control. Based on the measured data, the evolution law of the typical bends in the lower reaches of the reservoir and its main causes were analyzed. The results show that after the operation of the Three Gorges Project, the typical bends in the lower reaches of the reservoir all appear "cutting beaches", and the main reason is that the sediments enter each river reaches. The amount of sand, especially fine-grained sand, has been greatly reduced. The main reasons for the "skipping bends" in most of the bends in the Lower Jingjiang are that the variation coefficient of the monthly average runoff process is large and the bending radius of the bends itself is small. With the successive operation of cascade reservoirs in the main and tributaries of the upper reaches of the Yangtze River, it is expected that the variation coefficient of the monthly average runoff process in the lower reaches of the reservoir will continue to increase, which may lead to the occurrence of bends with relatively small bending radius that do not currently have "skipping bends".

Since total organic carbon (TOC) is not a routine hydrological monitoring data, the monitoring frequency is much lower than that of flow data and it often has missing values, which makes it difficult to evaluate TOC flux. This study proposes an improved computational model based on functional data analysis (FDA) for the evaluation of riverine TOC fluxes. First, the discrete data set is functionalized, and all the indicators are transformed into s function curves in the same evaluation time domain. And then the TOC flux of the evaluation section during the study period is calculated by Riemann integral. The results of the TOC evaluation at the Zhutuo station on the Yangtze River show that, The average value of the annual TOC flux at Zhutuo Station from 2018 to 2020 is 702 000 t; The intra-annual distribution of TOC fluxes is extremely uneven, with a high concentration in the flood season, especially in summer; The annual average value of TOC flux during the flood season (June to September) is 438 200 t, equivalent to 62.43% of the total; The annual average TOC flux in summer is 349 000 t, equivalent to 49.72% of the total; While the annual average value of TOC flux during the dry season (October to May) is 263 700 t, equivalent to 37.57% of the total; The annual average TOC flux in winter is 71 300 t, equivalent to 10.15% of the total; Compared with the traditional method, the improved TOC flux model is also able to deal with missing values and inconsistencies in multi-indicator monitoring sequences more effectively, and to accurately assess the course of TOC fluxes over different seasons and periods of abundance and depletion.

The paper aims to comprehensively grasp the carrying capacity of water and soil resources in Ningxia, and promotes the coordinated development of water and soil resources in arid and semi-arid areas. An evaluation index system was constructed based on DPSIR model. The CRITIC-entropy weight-TOPSIS was applied to evaluate the carrying capacity of water and soil resources in Ningxia from 2012 to 2019. The obstacle degree model and R/S method were used to explore the influencing factors and predict the future trend. The results showed that from 2012 to 2019, the carrying capacity of water and soil resources in the whole Ningxia region shows an upward trend, but the overall situation is basically overloaded. The carrying capacity in Guyuan City is greatest in the Ningxia region. Based on the obstacle analysis, the driving force subsystem has the strongest restriction on the carrying capacity of water and soil resources in Ningxia. Economic density, natural population growth rate, per capita GDP, grain output per unit of arable land and per capita water resources are the main factors affecting the water and soil resources carrying capacity in Ningxia. According to the R/S method, in the future, the water and soil resources carrying capacity in Ningxia will show an upward trend. Guyuan and Zhongwei have a significant upward trend, while other cities have a weak upward trend.

Water footprint evaluation is of guiding significance for the rational development of regional water resources. The input-output method was used to account for the water footprint of Hubei Province from 2007 to 2017, and the driving factors of water footprint changes were analyzed using the structural decomposition model. The results show that the virtual water content in Hubei Province decreased significantly, and water use efficiency improved from 2007 to 2017. The total water footprint showed a trend of rising and then falling, with a net increase of 19.9%, and the main growth sectors were construction and services. Technology level and economic scale were the main factors inhibiting and promoting the increase of water footprint, respectively. However, their effects on water footprint changes gradually weakened, and both showed a reduction effect. From 2007 to 2017, the sectoral linkages changed from positive to negative driving force, and the inhibitory effect on water footprint was revealed, which shows that optimizing the industrial production process helps carry out water conservation. The impact of driving factor on different sectors showed heterogeneity. The adjustment of industrial structure inhibited the increase of water footprint in high water-consuming sectors such as agriculture while promoting the increase in construction and services. In the future, the industry scale and residential demand in sectors producing high-value-added products will grow, such as services, and water-saving technology development should be shifted to these sectors promptly.

Reservoir operation rules, as an important tool to guide reservoir operation, are not only the decision-making reference in the reservoir planning and design period, but also one of the key technologies affecting the comprehensive benefits of the reservoir in the operation and management period. Therefore, based on the historical operation data of reservoirs in the upper reaches of the Yangtze River, the number of periods, early water level, inflow, outflow and current inflow were selected as the influence factors to form the input factor set combined with the reservoir operation principle and operation characteristics. Comprehensively considering the characteristics of operation data and the principle of decision tree, the end of period water level was determined as the model output and then the corresponding simulated water level evaluation index was proposed based on the reservoir regulation capacity. The correlation coefficient and mutual information were used as the correlation evaluation index of model input factors, and the tree Parzen evaluator was introduced to optimize the number of input factors and algorithm super parameters. Finally, the reservoir operation rule extraction model based on decision tree and its integrated model was established and the reservoir operation rule integrating historical operation process and expert experience was formed. The experimental results show that the decision tree and its integrated model have strong ability and applicability in the extraction and application of reservoir operation rules.

Due to the uncertainty of runoff, there are certain risks when formulating hydropower station power generation plans. In this paper, the concept of spectral risk measurement in economics was introduced in reservoir dispatch to quantify risk, and a benefit-risk equilibrium optimization model was established, which can reflect the attitude of decision makers to risk through different risk aversion coefficients and confidence values according to the actual situation of the power station. Taking the Three Gorges Power Station as an example, the results show that compared with the traditional model of maximum power generation benefit, the proposed benefit-risk equilibrium optimization model can effectively reduce the risk caused by the uncertainty of inflow in hydropower stations under the condition that the loss of power generation income is extremely small.

The reservoir flood control operation problem has the characteristics of multi-stage, nonlinear and multiple complex constraints. The research of solution method will help to improve the effect of flood control optimal operation. Differential evolution algorithm (DE) has a good effect in the application of reservoir optimal operation, but it is prone to premature convergence and fall into local optimum due to the random search strategy. In order to balance the global and local search ability of DE, this paper proposed an improved differential evolution algorithm SDE, which is used to improve the search ability by considering the differential mutation strategy of fitness ranking and to improve the development ability by random selection mechanism. The related numerical experiments verified that the SDE convergence is significantly better than that of the DE, GA, PSO, and ACOR. The results of case study show that the SDE is better than POA and DE in terms of the feasible solution, calculation time, accuracy, convergence stability and speed. The average flood-peak rate of the SDE is 0.17%-4.26% higher than the POA, and is 0.13%-1.26% higher than the DE.

The Gaoxin District and Jinshui District were selected as the representatives of the new and old urban areas of Zhengzhou to explore the evaluation indexes that affect the risk of rainstorm waterlogging in cities and the importance of each index, and a risk index evaluation system covering natural and social factors was established. The importance of each evaluation index in new and old urban areas was determined by using random forest model. The results show that for both new and old urban areas, the sensitivity of disaster-inducing environment is the most important first-level indicator. Among them, imperviousness and pipe density are the most important tertiary indicators for surface and subsurface disaster-preventing environments, respectively. The risk of disaster-causing factors is the least important for Jinshui District and Gaoxin District, and the importance of rainfall is much greater than that of rain type. The difference between the old and new urban areas is mainly reflected in the stability of disaster-bearing body, whose importance is 0.23 and 0.09 for Jinshui District and Gaoxin District. The conclusion can provide some reference for the prevention and control of rainstorm waterlogging disaster in Zhengzhou.

Aiming at the problem of urban waterlogging caused by heavy rainstorms in coastal cities, this paper takes Fuzhou City as an example and constructs a fined coupling model of urban one-dimensional drainage network and two-dimensional land surface hydrodynamics based on Infoworks ICM. The model was applied to the analysis of rainstorm waterlogging in Gutian Road area of Fuzhou during Typhoon "Lubi" in August 2021, which verified the high simulation accuracy of the model. Based on this model, the rainstorm waterlogging process in Gutian area under different recurrence periods was analyzed, and two "sponge" reconstruction schemes were proposed. It is found that increasing the pipe diameter is more conducive to improving the waterlogging situation in the study area. The study can be used to accurately calculate the process of urban underground drainage and land area water in Fuzhou City, which provide technical support for the real-time decision of flood control and drainage in coastal cities.

To further promote the construction of sponge cities, system dynamics and Morris, EFAST sensitivity analysis methods were used to analyze the regional differences in the benefits of sponge facilities in residential areas. The research conclusions are as follows: The comprehensive incremental cost benefit and economic, environmental, and incremental social benefits of Shenzhen, Beijing, Lanzhou sponge facilities in operation for 20 years accounted for 1 504.5 (69%, 23%, 8%), 352.4 (54%, 28%, 18%), and 2.0 (27%, 53%, 20%) ten thousand yuan, respectively. The sensitivity of the comprehensive benefit parameters of sponge facilities from high to low is sorted as average annual precipitation, rainwater recovery rate, economic loss caused by water shortage, etc. Among them, the rainfall and rainfall characteristics limit the benefit value of Beijing and Lanzhou. The low of water use in Lanzhou also affects the benefit value.

Influenced by terrain and construction costs, the water flow of the flood drainage ditch outside the surrounding wall of the construction project in hilly regions should be minimized as much as possible. However, the capacity of existing or planned small reservoir in the low-lying areas of mountain flood gully outside the walls of construction projects is usually small and difficult to expand, which cannot meet the normal requirements of reservoir flood control. Aiming at this kind of engineering technical problems, this paper proposes a technical scheme with the construction of a small empty reservoir for flood prevention and drainage in construction projects. Compared with the normal reservoir flood regulating system, the storage capacity in this system can be greatly reduced, and the downstream flow reduction requirements can be met. The function and design points of the empty storage capacity peak cutting and flood regulating system are elaborated in detail combined with the actual engineering cases, which aim to provide important technical support and experience for the flood prevention and drainage project of small watershed in mountain and hilly regions.

Under the background of global climate change, river flood risk assessment is of great significance to disaster prevention and mitigation in river basins. By analyzing the spatiotemporal change characteristics of floods in the Nanliu River Basin from 1960 to 2021, a flood risk assessment index system was established for flood risk assessment. The results show that the interannual variation of flood disaster in Nanliu River shows a fluctuating upward trend; 1993 was a big catastrophe year of flood disaster change; On the whole, the upstream basin, the middle river valley and the downstream estuary plain are the flood prone areas, and the flood risk shows a distribution pattern of high in the southeast and low in the northwest, which is consistent with the characteristics of historical flood data. The results can provide scientific basis for the comprehensive management of Nanliu River Basin.

Aiming at the shortcomings that traditional water weirs cannot measure the sand content of runoff and the traditional measurement methods are not accurate, it is difficult to realize online measurement in the field of dam water weirs. By analyzing the negative correlation between the sand content of the water flow of the water weir and the gray value of the image, sand volume measurement technology was proposed to automatically measure the sand content of the water flow of the weir. The test results show that the deviation between the detection result of sand content and the actual value is low, and it is a convenient, efficient and real-time determination method. The research results have certain reference value for dam seepage monitoring.

Based on the finite element method, this paper numerically analyzes the stress behavior and its adverse effects when diaphragm of dam foundation axis shifts downstream during operation, and proposes remedial measures and reference critical values. The results show that when the axis does not shift, diaphragm of dam foundation is only subjected to bending moment and produces local tensile stress, but its influence is not obvious. When the axis is shifted downstream and the offset is less than 30 cm, diaphragm of dam foundation is subjected to the combined action of pressure and bending moment, resulting in stress concentration and adverse effects. In the case of no other processing, when the axis does not shift and the offset is less than 15 cm, it can be temporarily not processed; If the axis offset to the downstream is more than 15 cm and not more than 27 cm (measured maximum offset), in the subsequent construction, the concrete base needs to be widened downstream at least 20 cm, which can reduce the tensile stress extreme of diaphragm of dam foundation and weaken the stress concentration, so as to improve the stress behavior of diaphragm of dam foundation. The finite element simulation provides a reference for the safety evaluation and treatment measures when diaphragm of dam foundation is eccentric.

The Duncan-Zhang model is not able to reflect the influence of the mid-major stress on the strength and deformation of the rockfill body in the finite element calculations of the panel rockfill dam. The Duncan-Zhang E-B model and its optimization model for the panel rockfill dam has been developed by the secondary development of ANSYS based APDL language. The Duncan-Zhang E-B model and its optimization model were used to calculate the three-dimensional finite element static force of a panel rockfill dam in Yunnan Province. The results show that the settlement of the dam body was reduced, the horizontal displacement was reduced, and the stress change was small. The strain results obtained from the optimization model are closer to the actual data. The optimizaion Duncan-Zhang E-B model considering the medium principal stress can better reflect the stress-deformation characteristics of the panel rockfill dam.

With the development of urbanization in China, secondary water supply has become a key part of urban water supply, but the utilization efficiency of water resources is low. This paper proposes the Demand Side Management (DSM) model based on the user's perspective. Starting from the user's Demand Side Management, the low water tank in the secondary water supply system at the end of the pipe network is taken as the research object. Using adaptive FCM clustering analysis and grey relational analysis, the paper analyzes the characteristics of user water use in different types of small areas, excavates the potential of regulation and storage and studies the peak-shifting scheme, and determines the appropriate peak-shifting scheme, so as to achieve good peak-shifting by demand-side management.

With the acceleration of urbanization in China, the demand for water resources is increasing, and the leakage of the water supply pipe network has caused waste of water resources. Therefore, leakage control is imminent. The first is to accurately calculate the leakage of the pipe network, but the current methods have certain deficiencies. Based on the Kalman filter, this paper establishes an analysis model of pipeline network leakage, and uses the empirical formula of node leakage, standard Kalman filter (SKF) and innovation adaptive Kalman filter (IAKF) to calculate the leakage of the pipeline network, respectively. Taking the actual pipe network project as an example, the EPANET simulation was carried out, and the calculation results were compared. The results show that using both filtering algorithms is more accurate than the nodal leakage formula, and the result of the IAKF algorithm is better than that of the SKF algorithm. This provides a theoretical basis for accelerating the research on leakage control technology and implementing scientific and effective leakage control methods, which has certain significance for urban water saving and sustainable development.

The effect of luring fish is one of the key factors affecting fish passing efficiency in the entrance area of fish-passing facilities. Proposed a new optimization idea of side-channel drop-flow to lure fish. The upstream water was replenished to the area outside the fishway entrance as drop-flow. With the help of auxiliary facilities such as cantilever plate, the attractive flow was formed in the horizontal orientation. Take the fishway project of Shaping I Hydropower Station as example, a large scale physical model was established to demonstrate and optimize the scheme, and the flow pattern near the entrance of the fish-passing facility were analyzed, and the possibility of attracting fish was discussed. The experimental results show that the one-dop scheme is favorable for attracting the migratory fish in the horizontal orientation, with the flow velocity of 0.3-0.5 m/s, and the information of flow pattern is rich in the entrance area, which is suitable for fish aggregation.

In order to improve the aerated concentration of the stepped energy dissipator, mitigate the damage of cavitation and cavitation erosion, and improve the energy dissipation rate, the stepped energy dissipator with segmented piers was proposed. The influence of the arrangement of the front pier and the reverse pier of the energy dissipator on the hydraulic characteristics of the stepped energy dissipator with segmented piers was studied by numerical simulation. The results show that the stepped energy dissipators with segmented piers generate hydraulic jump near the energy dissipators in the flat and straight section of the terrace. The arrangement of the main pier has better effect of hydraulic jump aeration, higher concentration of aeration along the way, and better effect of cavitation erosion mitigation; The flow velocity along each stage increases gradually, and the arrangement of the main pier has lower flow velocity and better energy dissipation effect; A large range of positive pressure is formed on the upstream area and the upstream area of the energy dissipation pier, and negative pressure is generated on the top and back surface of the energy dissipation pier. The arrangement of the positive pier has a high blocking effect on the water flow, and the arrangement of the reverse pier has a large negative pressure; Under each flow condition, the energy dissipation rate of the two arrangement forms is higher, and the energy dissipation rate of the positive pier arrangement form is higher when the flow is larger, which has better energy dissipation effect. The arrangement of the main pier has better effect in reducing the cavitation damage of the step and improving the energy dissipation rate, which can provide a reference for the structural design of the stepped energy dissipator with segmented piers.

The mechanical effect of plant roots on soil is an important factor in improving the erosion resistance of slopes, and the relevant research on the impact resistance of plant roots under water flow at home and abroad is in a blank spot. In this paper, the common soil and water conservation plants tall fescue and dogtooth roots were selected as the research objects, and the jet erosion test was carried out on the slope of the plant model, and the erosion failure mechanism of the root slope of different species of plants was compared. The main conclusions are as follows: the variation law of the average erosion depth ΔD_AE of high fescue slope, dogtooth root slope and plain soil slope under different working conditions is similar and consistent, and it increases exponentially as a function with the increase of erosion flow velocity and linear function with the increase of erosion angle. The average erosion depth under various working conditions was generally as follows: high fescue< dog tooth root< plain soil; The average erosion depth of high fescue at each flow rate decreased slightly ΔD_AE slightly greater than that of dog tooth root. When the scouring angle was fixed, the ΔD_AE of each angle was the largest when the flow rate was 1.6 m/s, and the flow rate was higher than 1.6 m/s, and gradually decreased. When the erosion flow rate is constant, there is a decreasing tendency ΔD_AE increase with the increase of the scouring angle.

In order to explore the energy evolution law of rock failure process in the excavation process of diversion tunnel, this paper selects magnetite ore and carries out conventional triaxial and triaxial pre-peak constant axial pressure unloading confining pressure tests. The results show that in the conventional triaxial test, the rock is dominated by elastic strain energy storage and dissipative strain energy consumption before the peak stress, and the elastic strain energy release and dissipative strain energy consumption after the peak stress. With the increase of confining pressure, pre-peak shear fracture energy is higher than post-peak shear fracture energy. In the unloading confining pressure test, the dissipated strain energy increases exponentially. The faster the unloading rate, the shorter the unloading period is, and the higher the rate of energy increment per unit time between the unloading point and the drop point. Based on the M-C criterion of rockburst dynamics, the loss of rock cohesion and the dissipated strain energy of rock under unloading path, the damage variable in the process of rock unloading is defined, and the damage degree of rock deformation and failure is revealed from the perspective of energy.

The diversion tunnel plug is a key project for the safety of water conservancy and hydropower projects. Wedge-shaped plugs are widely used in engineering. There are many calculation methods for columnar plug, but not so much for the wedge-shaped plug. Based on the design scheme of the diversion tunnel plug in Karot power station, this paper carried out the theoretical and numerical simulation analysis. Through the force analysis of the wedge, the calculation method of the hydraulic pressure bearing capacity of the wedge-shaped plug was proposed. The comparative analysis of wedge and columnar plug safety was carried out by three-dimensional elastoplastic numerical simulation. The result shows that the maximum deformation under the calibration water level of the wedge-shaped plug was 0.8 mm, and its overload safety factor was 1.08 times that of the columnar plug. By comparing the numerical simulation with the formula calculation results, the rationality and accuracy of the calculation method for the bearing capacity of the wedge-shaped plug were verified. The research results have important guiding value for the design of wedge-shaped block.

The Xiongan storage reservoir is a pumped storage reservoir, an important water source project supporting the construction and development of the Xiongan new area, and a key supporting project to ensure the safety of water supply in the new area, with high requirements for project seepage prevention. The F₁₇₃ fault, which is the largest fault in the reservoir basin, runs through the NE-SW direction, and forms low passes on the NE side and the SW side of the reservoir basin, and there is local dissolution along the fault. The lithology and structural sealing conditions of the reservoir are poor. In order to control the seepage of the reservoir, curtain grouting was used to prevent seepage around the reservoir. In order to explore a suitable implementation method for curtain grouting of Xiongan storage reservoir, it is necessary to determine the anti-seepage treatment measures, grouting construction method and construction technology of the F₁₇₃ fault through grouting test research. The results indicate that the permeability meets the anti-seepage standards and the fatigue resistance is improved.

Research and exploration on intelligent grouting technology has been conducted in some hydro-power stations in recent years. Intelligent grouting equipment has been invented and intelligent control strategies for conventional geological conditions have been developed. However, the existing technology lacks the intelligent control strategies for pressure sensitive and weak stratum, and is not suitable for grouting construction under complex geological conditions. Relying on the Xiong'an regulation and storage reservoir project and based on the empirical research method, this paper has carried out researches on new intelligent strategies for weak strata such as lift sensitive and split sensitive. The field test results show that the intelligent grouting technology meets the needs of field construction, in which the water pressure and grouting construction process can be intelligently completed, and the lifting and splitting situation can be handled. The research is conducive to ensuring the quality of grouting projects and improving the level of intelligent construction.

Setting a panel outside the soilbags-constructed retaining wall may affect the behavior of the wall. Therefore, a full-scale test of the soilbags-constructed retaining wall with fixed panels and with unfixed panels were conducted to explore the influence of the panel on the deformation mode and lateral earth pressure of the wall. The results show the walls with fixed and unfixed panels deformed laterally in a cantilever-like manner, but the lateral earth pressure acting in the fixed-panel wall is greater than that in the unfixed-panel wall. A calculation formula for calculating the earth pressure acting on the soilbags-constructed retaining wall under limited displacement was established based on the linear elastic constitution theory, and then it was used to analyze the relationship between the lateral earth pressures and lateral strain. It is found that distribution of the lateral earth pressure of the soilbags-constructed retaining wall with unfixed panel is close to the calculated active earth pressure as a result of the poor deformation constraint of the unfixed-panel, which indicates that the flexible characteristics of the soilbags-constructed retaining wall can be fully utilized by the wall with unfixed panel, so as to effectively reduce the earth pressure behind the wall.

Early and timely defect detection is essential to ensure the safe operation of hydraulic concrete structures. The deep learning-based computer vision method does not require complex manual feature engineering, and can automatically determine the category of structural defects in remote images, overcoming the shortcomings of traditional manual vision that are labor-intensive, subjective and prone to errors. Inspired by this, this paper proposes a deep learning-based defect detection method, which introduces attention mechanism into the ResNeXt50 network to adaptively recalibrate the channel-level feature responses, so that the model can pay more attention to the defect information in the image and enhance the feature extraction ability. Test results show that the proposed method can achieve an F1 score of 88.0%, and realize a good classification effect for common concrete defects.

The geometric characteristics of landslide are closely related to the rainfall infiltration process, which is the key internal factor to control the stability of rainfall-induced landslides. There are many rainfall-induced landslides in the Three Gorges Reservoir area, and it is of great significance to deeply reveal the body shape characteristics of rainfall-induced landslides (landslide whose stability is sensitive to rainfall in hydraulic engineering are generally referred to as rainfall-induced landslides) for the identification and prevention of landslide disasters in the reservoir area. In this paper, the data of 275 rainfall-type sedimentary landslides in the Three Gorges Reservoir area were collected, and their body shape characteristics were statistically analyzed. The rainfall-type landslides in the area are narrow and long, thin in thickness and gentle in slope. Combined with the numerical simulation of the rainfall infiltration process of typical landslides, it is found that the landslides of this type have a larger rain-receiving area and infiltrated rainwater is more likely to infiltrate the sliding bed, which makes the effect of rainfall more significant, and is not conducive to the stability of the slope under rainfall conditions.

Baishuihe landslide is a typical representative of bedding landslide in the Three Gorges reservoir area. However, the research on its formation evolution process and deformation characteristics after water storage is not deep. On the basis of field geological investigation and the latest survey data and GPS monitoring data, this paper makes a detailed study on the rock and soil structure of Baishuihe landslide and its deformation characteristics after impounding. The results show that the evolution process of Baishuihe landslide has gone through the early stage of landslide, the rock landslide and the accumulation landslide. At present, Baishuihe landslide is in the accumulation landslide stage; Baishuihe accumulation landslide is the product of vertical superposition of landslide accumulation bodies caused by the destruction of the second-stage rock landslide, and there is a clay layer in the middle. Corresponding to the water level of 135 m and 156-175 m, the deformation of Baishuihe landslide can be divided into two stages. The deformation characteristics of Baishuihe landslide are gently inclined steps and steeply inclined steps. The research results provide the corresponding decision-making suggestions for the treatment of Baishui River landslide, and also provide the direction for the later treatment of geological disasters with similar structural characteristics.

In order to explore the feasibility of using waste concrete to dispose expansive soil and make it as roadbed filler, the waste concrete and expansive soil were mixed evenly according to the ratio of 96 : 4, 92 : 8, 88 : 12, 84 : 16, 80 : 20 and 76 : 24. The boundary moisture content, linear shrinkage rate, expansion force and compaction tests were carried out. The influence of curing time was considered in unconfined strength and CBR tests to explore the improvement effect of the selected materials. The experimental results show that the liquid limit and plastic index decrease first and then increase with the increase of waste concrete content, and the minimum value appears when the content is 12 %, while the plastic limit increases slowly. The linear shrinkage rate increases first and then decreases with the increase of dosage, and the linear shrinkage rate is the smallest when the dosage is 12 %. The expansion force under different curing periods decreases slowly with the incorporation of concrete. When the dosage is 12 %, the dry density of the treated expansive soil is greater than that of the plain soil, and the optimum moisture content is less than that of the plain soil. Considering various factors, 12 % is determined as the best dosage. Under this dosage, the unconfined compressive strength of the mixed soil can reach the peak value, and the bearing capacity of the treated soil is about 5 times that of the plain soil. The treated expansive soil can be used as roadbed filler.

Aiming at the nonlinear problem of regret value when regret theory is used to solve multi-attribute group decision making problems in hydraulic engineering, a multi-attribute group decision making method combined with grey correlation analysis method is proposed. Firstly, the regret theory was used to obtain the decision maker's perceived utility for each option and determine the regret decision matrix. Secondly, according to the nonlinear problem between regret values, the weight of attributes and the comprehensive regret value of each scheme were calculated by grey correlation analysis, and then the best scheme was obtained according to the ranking of the comprehensive regret value. Finally, the feasibility of the method was verified by case analysis. The results show that this method can solve the nonlinear characteristics and weight problems in regret theory, and make decision-making more reasonable when considering psychological factors.

Considering the importance of reasonably setting water prices for water transfer projects in promoting the healthy operation and sustainable development of the projects, taking water resources allocation project around Beibu Gulf as an example, this paper put forward a new idea to calculate the water price. Firstly, the influencing factors of the project water price were identified through sensitivity analysis. And then through in-depth consideration of the value of each factor and its time change process, the calculated water price is low before and high after, which is realistic and easy to bear as well as conducive to the connection between the water transfer price and the current water price in the receiving area. The results show that the design parameters of water price scheme are reasonable and the calculation results are feasible. This study can provide a certain reference for the water receiving area government in the cost accounting and water price formulation of this project.

In hydro-generator units, the thrust bearing oil tank has the largest volume and the internal structure is relatively more complex. Therefore, there are many oil mists in the oil tank, and there are often internal and external oil spills, which have a great impact on the safe and stable operation of the unit. Based on the basic theory of computational fluid dynamics, the calculation model of thrust bearing in a power station was established, and the number of pressure oil blade was changed. The ICEM was used to mesh the three-dimensional model, and Fluent was used to calculate. The CFD-POST was used to analyze the oil mist related parameters of thrust bearing oil tank. The results show that in the design of hydro-generator units, the number of pressure oil blade can be appropriately increased, so as to increase the temperature difference between the upper and lower blades, reduce the oil temperature below the blade and increase the pressure, so as to better inhibit the occurrence of internal oil rejection and effectively prevent the diffusion of oil mist due to low pressure.

The shaft system of hydropower unit has a significant impact on the stability of the unit. The degradation assessment of the shaft system can visually reflect the operating condition of the unit. This paper presents a method for assessing the degradation of the unit’s shaft system using instantaneous orbit feature image and conditional adversarial generative network (CGAN). Firstly, the vertical signals of each bearing were constructed as a complex signal, and the multivariate complex variational mode decomposition (MCVMD) method was used to process the signal and extract the instantaneous orbit features to construct the instantaneous orbit feature images. CGAN was used to construct the health model. The health model can fit the distribution of feature images in different operating conditions in healthy state and thus output health feature images. The healthy indicator was constructed using the differences between real and healthy images. The genetic algorithm was used to optimize the weights of multiple bearings in order to reduce the volatility of the comprehensive degradation curve in the healthy zone. The proposed method was tested on the unit's shaft system data and its validity has been proved.

To study the internal flow characteristics of bulb tubular turbine with different blade opening structures under large medium and small flow conditions, and to make theoretical support for the optimization of the flow passage components structure and the coordinated relationship, the research indexes were taken as three-dimensional streamline distribution, central meridian plane streamline distribution and central meridian plane pressure distribution. The results indicated that the maximum flow velocity existed at the runner of the bulb tubular turbine in the flow pattern analysis, and the flow pattern was chaotic, which was the focus of efficiency optimization. The reason of vortex in the draft tube was analyzed, and it could be optimized by reducing the dead water area. The internal pressure showed an overall decline tendency from the inlet channel to the draft tube. The pressure value at the runner discharge cone was the smallest. The pressure in the draft tube gradually increased along the flow direction, and the highest pressure value was 82 464.15 Pa when the flow rate reached 124.92 m³/s. The calculation results can provide a reference basis for the modification and optimization of the bulb tubular turbine.

Prediction of the vibration trend of hydropower units is an important measure to ensure the normal operation of the unit. However, due to the complexity and non-stationarity of the vibration signal of the unit, accurate prediction becomes a difficult problem. To this end, this paper proposes a combined trend prediction model based on adaptive variational modal decomposition and temporal convolutional network (TCN). Firstly, the Whale Swarm Algorithm (WOA) was used to optimize the parameters of Variational Mode Decomposition (VMD) to avoid the drawbacks of blindly selecting parameters, and to achieve adaptive decomposition of vibration signals. And then each decomposed component signal was normalized to establish TCN for trend prediction. Finally the original vibration signal prediction was obtained by superimposing the results. The proposed model was demonstrated and tested with the actual operation data of a domestic power station. The results show that the proposed model has high prediction accuracy and can be used in engineering practice.

The escape of oil mist from bearing oil groove of power station will not only pollute the environment of power station, but also bring safety hazard to electrical equipment. Combined with the actual situation of hydropower station, the installation of oil mist absorption device can help to discharge excess oil mist from oil tank and effectively avoid the pollution problem of oil mist in power station. In order to investigate the variation of oil mist distribution, velocity, pressure at measuring points and discharge amount of oil mist in the oil tank, numerical simulation calculation of thrust bearing oil tank with negative pressure oil mist pipe was carried out. It is found that after complete oil mist discharged, most of the oil mist can be effectively discharged; The overall change of the amount of oil mist at the outlet follows the law of rising first and then falling. Under the suction pressure of -500 Pa, the maximum discharge amount of oil mist could reach 0.008 23 kg/s. After the oil mist is discharged, the pressure drop at the oil tank upper region reaches 96.07%, and the reduction of the pressure difference can effectively prevent the oil mist from escaping to the cover plate, the wind tunnel, the rotor and so on. The research can provide some theoretical help for the oil mist discharge process of oil tank so as to better formulate the oil mist control strategy.

The emergency shutdown device of the hydro-generator governor should not only meet the requirements of "power loss action" in the 25 anti-accident measures, but also avoid the hidden danger of unplanned outage of the unit caused by the electromagnetic valve coil of the device being charged for a long time and easy to burn. This paper introduces three generations of technical improvement of the emergency shutdown device of hydro-generator governor of a large hydropower station, from double electromagnet two-position solenoid valve, single electromagnet spring return two-position solenoid valve to double solenoid valve and linkage valve, expounds their working principle and compares their respective advantages and disadvantages. It is proved that the emergency stop device of hydro-generator governor based on double solenoid valve and linkage valve is a practical and reliable emergency stop control optimization scheme of speed regulating system, which has great popularization value in hydropower plants.

In order to improve the control performance of hydro-turbine speed control system containing surge tanks, this paper proposes a control parameter optimization method based on the improved whale optimization algorithm (IWOA). Firstly, the mathematical model of the turbine speed control system with surge tanks was established. The turbine inlet head-flow transfer function containing the dynamics of surge tanks was established by using the continuity equation and pipe transfer function. And then the turbine speed control system model with surge tanks was formed together with the turbine speed control model. The time integral value of the speed deviation of the turbine in this system was used as the fitness value in the optimization process, and IWOA was used to perform optimization of the PID controller parameters of the study object with the objective of minimizing this fitness. The results show that the IWOA algorithm has the advantages of fast convergence speed and high accuracy, and the optimized PID controller provides better regulation and robustness to various types of disturbances.

In view of the problem that the comprehensive output coefficient of power station deviates from the actual situation in varying degrees with the accumulation of operation time, the change of operating conditions, unit wear, the comprehensive output coefficient was calibrated according to the average comprehensive output coefficient and the piecewise fitting coefficient. The piecewise fitting method was further divided into piecewise fitting according to the water head and piecewise fitting considering the water head and power generation flow in terms of the dispatching characteristics. The results were verified by precision evaluation. Combined with the historical operation process of Hongjiadu Hydropower Station, a case study was carried out. The results show that compared with the actual results, the relative error of the average coefficient method is 2.64%, that of the piecewise fitting method according to the head is 2.52%, and that of the piecewise fitting method considering the head and flow is 0.59%. The piecewise fitting method is closer to the actual production process than the average comprehensive output coefficient method, and the piecewise fitting method considering the head and power flow is the most accurate.

Dispatching operation of hydropower station is in face of the large capacity and large units, unit control new scheduling features such as irregular more limits and more complicated operation requirements. To aim at power station safe, stable and economic operation, a model of economic operation inside the station was established to realize optimal load distribution of hydropower station units under various operation conditions. The optimal output range of each unit under different head was analyzed. The optimal load distribution rule of the power station was studied, and the economic operation model of the station was established. Based on the economic operation model of the station, the optimal load distribution table was designed. The optimal load distribution result table of the power station under different loads, different heads, and different unit commitment was proposed to guide the real-time economic scheduling of the power station. Taking Hongjiadu station as an example, the results show that the model can reasonably arrange the start-stop sequence and number of units according to the real-time load instruction, and give real-time start-stop suggestions of units. It can obtain the optimal load distribution combination of the proposed unit under various working conditions, reduce the monthly average water consumption rate by 0.18%, reduce the adverse working conditions such as frequent start-stop and frequent crossing of the vibration zone by 9.5%, ensure the efficiency of the unit operation, and improve the economic benefits of the power station.

In order to understand whether the power frequency electric field level generated by the UHV AC power transmission and transformation project meets the relevant requirements, this paper uses the EFA-300 power frequency field strength meter to conduct the cross-section of the substation and transmission line of the Ximeng-Shengli 1 000 kV AC power transmission and transformation project, and evaluate the uncertainty of the measurement results. The results show that the maximum measured value of the substation boundary is (3.65±0.18) kV/m, k=2, which is lower than the electric field limit of the substation boundary, 4 kV/m; the maximum measured value of the line cross-section is (5.41±0.28) kV/m, k=2, which is lower than the electric field limit below the overhead transmission line, 10 kV/m, which meets the requirements of relevant national standards. It is found that the error of the field strength meter has a great influence. The uncertainty of the power frequency electric field measurement can be reduced by improving the calibration accuracy of the power frequency field strength meter. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China-Research on Power Frequency Electric Field Calibration Technology (GYW1720200201).

The power imbalance between DC side and AC side of single-phase grid-connected photovoltaic inverter leads to double frequency power pulsation on DC side. The additional active power decoupling circuit can effectively suppress the secondary ripple, but due to the additional components, the system efficiency of single-phase inverter will be reduced. Aiming at the above problems, this paper proposes a control strategy based on Buck converter that can reduce the power loss of decoupling circuit. By calculating the power loss of the decoupling circuit and analyzing the working constraints, the relationship between the power loss and the average voltage of the decoupling capacitor was obtained, and then a control strategy to directly control the average voltage of the decoupling capacitor was proposed. Simulation results show that the proposed control strategy can effectively suppress the DC side voltage ripple and reduce the power loss of the decoupled circuit.

Aiming at the problem that the convective heat transfer coefficient depends on experience in the calculation process of arrester temperature rise, a method of determining convective heat transfer coefficient was proposed. The temperature field distribution inside the arrester was studied. The influences of pollution, wind speed and sunshine on the temperature rise of the arrester at different damp degree and different damp positions were analyzed. The results show that under different influencing factors, the convective heat transfer coefficient of the arrester ranges from 5 to 31, 27 to 35 and 19 to 34 W/(m²·℃), respectively. The pollution location will affect the temperature rise distribution of MOA surface, and the greater the degree of moisture, the more significant the impact on temperature rise. With the increase of wind speed, the temperature on the valve plate decreases slightly. However, the surface temperature decreases greatly. The influence of sunshine on the temperature rise of lightning arrester is obviously increased, but it is smaller than that of pollution and wind speed.

In the high proportion hydropower market, it is of great practical significance to establish a reasonable day-ahead quotation strategy for hydropower plants to ensure the effective participation of hydropower in the market. Firstly, the uncertainty of the clearing price of the system on the operation day was considering. Based on the identification of historical similar days, Gaussian process regression was used to establish the probability prediction method of the day-ahead clearing price. Furthermore, considering the revenue preference and risk aversion psychology of decision makers, and taking the maximum expectation of the hydropower plant's own power sales revenue as the goal, the day-ahead piecewise capacity optimization bidding method for cascade hydropower stations was constructed. Finally, the feasibility and effectiveness of the proposed method were verified by the simulation analysis of the day-ahead piewise capacity declaration of the actual cascade hydropower stations.