Based on the daily precipitation data of 38 meteorological stations in the Huaihe River Basin from 1961 to 2020, the consecutive dry days (CDD) were selected. The variation characteristics of CDD and its response to 12 circulation index at different time scales were analyzed by using M-K trend test, principal component analysis, the lag correlation analysis and cross wavelet transform. The results indicate that the spatial distribution of CDD in Huaihe River Basin had obvious seasonal characteristics. It was high in the west and low in the east in summer, and high in the north and low in the south in spring, autumn and winter. In the past 60 years, the changes of CDD in different seasons were also different. The CDD increased in most stations and the basin tended to become dry in autumn, but the CDD decreased in all stations and drought slowed down in the basin in winter. The CDD with different time lags had good correlations with the WP, SOI and Nino4, and the strongest correlation with Nino4. The Nino4 had a significant strengthening effect on the CDD with a lag of 4 and 5 months, and a significant weakening effect on the CDD with a lag of 10 and 11 months. The significant influence of Nino4 on CDD was mainly concentrated in the resonance period of 10-15 months, and there was a significant negative correlation between Nino4 and CDD. The finding is prone to useful for drought prediction and water resources management in the future.

Analyzing the spatial and temporal characteristics of extreme precipitation and the response of wind speed before and after extreme precipitation are of great significance for extreme precipitation characterization, improving the understanding of the relationship between extreme precipitation and wind speed, as well as managing water-related disasters. This study defined event-based extreme precipitation by considering preceding and succeeding precipitation, and classified precipitation patterns into three types, i.e. early peak, later peak and bimodal types according to the locations of precipitation peak, after which the spatiotemporal distributions of extreme precipitation and its relationship with wind speed were analyzed. The results show that single-peak of extreme precipitation occurs more often than bimodal one, and the amount increases from northwest to southeast, with significant upward trend of extreme precipitation detected; Extreme daily precipitation threshold increases with higher wind speed over the southeast and northeast, contrary to the southwest; Moreover, wind speed tends to show anomalies before and after extreme daily precipitation, and it decreases when extreme daily precipitation occurs over the southwest; However, over other regions, it increases before extreme daily precipitation and decreases after then, reaching the peak at the extreme daily precipitation day.

In response to the complex mechanism of runoff yield and concentration, insufficient groundwater monitoring data, and low accuracy of runoff prediction in Karst areas, a similarity prediction method that integrates physical mechanisms and data-driven approaches has been proposed. The optimal combination prediction scheme has been established for different flow magnitudes, prediction factors, and preceding affected lag-time, which can achieve adaptive matching and intelligent switching of multiple modes under different water and rain conditions. It can generate interpretable runoff prediction results. This method is applied to the runoff prediction of Longtan Hydropower Station. The results indicate that this method improves the accuracy and effective prediction period of runoff in Karst areas, which has scientific significance and practical value for ensuring the scientific scheduling and safe operation of large power plants.

In order to quantitatively analyze the impact of upstream reservoirs and the operation of the Three Gorges Project on the hydrological rhythms of the lower reaches of the Yangtze River and lakes, M-K test, cumulative anomaly method, wavelet coherence spectrum method and other hydrological time series trend analysis methods with STL time series decomposition method were used to analyze the 49-year historical water level data of Sheshan Station at Lake Shijiu. The long-term change trend and law of hydrological rhythm of Lake Shijiu under the new relationship between Yangtze River and Lake Shuijiu were analyzed. The coherent relationship between hydrological rhythm changes and local meteorological factors were analyzed along with the ecological effects under the new river-lake relationship. Under the new river-lake relationship, the dry season is earlier and longer and the averaged water level is higher, the extreme low water level is more likely to occur, the variation is gentler, and it is difficult for high water level to happen. The extreme high water level in the flood season is lower and happens later, the averaged water level is lower, ends earlier, and the amplitude is gentler. The early dry season is beneficial to increase aquatic plant biomass, but the decrease of water level variation in dry season may cause biodiversity to decrease.

In order to study the water logging risk in lakeshore urban caused by the blocking drainage effect (BDE) of Poyang Lake, the "regulation and storage model" was used to elucidate the BDE of Poyang Lake on inner river drainage in Changnan District and to explore the impact of Poyang Lake on waterlogging risk of lakeshore urban. By defining the Index of Blocking Drainage (IBD) which quantifies the BDE, the main controlling factors that affect the IBD was explored and the response relationship between them was quantified. The results show that the main controlling factors affecting the IBD include rainfall intensity, water level of outer river, drainage capacity and storage space. There is an obvious quadric curve relationship between rainfall intensity and the IBD, and 11.67 mm/h is the inflection point of the curve. There is a four-quadrant risk diagram relationship between the IBD and the water level of outer river. The decrease frequency of the IBD increases with the increase of drainage capacity. The effect of reducing the IBD by improving the drainage capacity of Changnan District is obviously reduced when the rainfall intensity exceeds 11.67 mm/h. The IBD of the same rain intensity decreases gradually with the increase of storage space. The effect of reducing the IBD of Qingshanhu District by increasing the storage space is obviously reduced when the rainfall intensity exceeds 15.83 mm/h. The water logging risk in lakeshore urban caused by the DBE of Poyang Lake can be effectively reduced by appropriately improving the drainage capacity, reducing the proportion of impervious ground and increasing the adjustable storage space, but the ability to deal with extreme rainstorm events remains limited.

Aiming at the falling into locally optimal solution shortcomings of optimization algorithm and probability density method for inversion of river cross-sections in ungauged regions, this paper proposed a combination of Ensemble Kalman Filter (EnKF) method and particle swarm optimization algorithm (PSO). The PSO was used to initialize the missing section to form a trapezoidal initial section. Then the EnKF was used to correct the initial section, and the proposed method was verified by the ideal case. The results show that the R² and N_NSE of the model are higher than 0.99, and the relative mean square error is less than 0.04. Considering the observation errors in the engineering practice, the observation errors of 0.1%, 1%, 5% and 10% were selected to evaluate the hydrodynamic simulation errors of the missing section, the PSO initial section and the corrected section by the EnKF method. It is found that the errors are normally distributed with the selected errors, but the overall distribution is normal with different errors. But the EnKF method can maintain a high simulation accuracy with different observation errors, the R² is higher than 0.98, the relative mean square deviation (RMSD) is less than 0.06 m, and the N_NSE is higher than 0.98. Thus, the proposed method has a high feasibility.

To analyze the impact of the construction of the Hengsha Dongtan (Phase 6-8) project on the Yangtze River Estuary, a two-dimensional tidal flow model was established using Delft3D, and tidal level and velocity calibration verification was conducted using existing hydrological data from 2008 and 2016. Based on the hydrological conditions in normal and flood years, the hydrological conditions, such as tidal volume, tidal level, and flow field in the main tributaries of the Yangtze River Estuary before and after the implementation of the Hengsha Dongtan Phase 6-8 Project were simulated. The results show that under two flow conditions, the construction of the Hengsha Dongtan Phase 6-8 project has a relatively small impact on the rising and falling tide flows of the main tributaries of the Yangtze River Estuary. The variation of high and low tide levels in the Yangtze River Estuary does not exceed 0.01 m, and the variation of high and low tide levels in the water area where the project is located does not exceed 0.02 m; The project has no significant adverse impact on the large-scale flow field structure of the Yangtze River Estuary. The rising tide velocity of the Beigang Waterway and Beigang Beisha Jiahong has decreased, with a maximum decrease of 0.03 m/s in Beigang Waterway and 0.02 m/s in Beigang Beisha Jiahong. The rising tide velocity of the Hengsha Channel and the North Channel of the Yangtze River Estuary has remained basically unchanged. Under the current riverbed terrain and engineering boundary conditions (all of the Hengsha East Beach project has been completed), there is a northwest southeast channel on the northeast side of the beach surface. The northern edge of the eighth phase project and the northern edge of the downstream sand body have a high ebb tide velocity, with a maximum velocity of 1.5 m/s or above, which is not conducive to the stability of the Hengsha East Beach regulation project.

In order to reduce the impact of bridge pier groups on the water flow at the intersection of the main rivers of Hangzhou Zhijiang New City, three shoreline optimization schemes were studied to improve the flow pattern based on a two-dimensional mathematical model. The optimal remediation plan was recommended based on multiple objectives such as water resistance ratio, land area, water area, bridge pier safety, and so on. The results show that the widening one side of the river channel to prevent bridge piers from being located in the main channel or changing the route to avoid bridge piers can effectively reduce the impact of bridge piers on the water level. The three optimization schemes have the same improvement effect on the backwater of the bridge piers. Scheme 2 and scheme 3 will affect the safety of bridge piers, with relatively small water area and large land acquisition area. Scheme 1 has little impact on the safety of bridge piers and is relatively easy to implement. Scheme 1 has high comprehensive advantages, and is recommended as the optimal option.

The scour of seawall toe is the one of the main factors for influencing structural stability of seawall estuary. The study of the scour characteristics at seawall toe under complex hydrodynamics and prediction method is of great significance for the seawall stability. Based on the field monthly measured topographic data since 2010, the time evolution of toe scour at Xijiangtang Seawall in Qiantang Estuary was discussed and the influence of flood was identified. The research results show that the seawall toe is eroded during flood, while there is silting during tide, and the critical flood discharge for scouring is about 5 000 m³/s. Based on the theory of sediment carrying capacity and riverbed deformation, a new scour prediction method is developed and the relative error is significantly improved within 20%.

Using GRACE gravity satellite data combined with GLDAS data inversion can obtain the change of groundwater reserves, which can monitor the change of groundwater reserves in the study area on a large scale, but the spatial resolution of the obtained data is only 0.25°, and it is difficult to be applied in the small scale. Based on the spatial relationship between GRACE terrestrial water storage and GLDAS shallow surface water storage and precipitation, NDVI, a downscaling method of groundwater storage change based on geographically weighted regression model (GWR model) was proposed, and the spatial resolution of groundwater storage was downscaled to 1 km. The results show that the GWR model downscaling method is successfully applied to the Haihe River Basin. The correlation coefficients between the groundwater storage data after downscaling and the measured groundwater level data at 46 verification points are all greater than 0.6, and the simulation results are reasonable and reliable. Furthermore, the temporal and spatial variation characteristics of groundwater storage in Haihe River Basin and Beijing Plain were analyzed by using the downscaling results. The results is highly consistent with the existing data, indicating that the downscaling method based on GWR model can effectively improve the spatial resolution of groundwater storage change data.

The study of groundwater chemical varieties has a positive indicator effect on the regulation and improvement of regional groundwater quality caused by infiltration in the Yellow River Irrigation Area. The field in-situ infiltration test was carried out to monitor and analyze the recharge water-groundwater during the recharge process of paddy field and dry field, and the groundwater chemical evolution law was revealed by AquaChem hydrochemical analysis and SPSS mathematical statistics. Under the condition of infiltration, the characteristics of groundwater chemical change show four evolution processes: "rapid change and active zone in the early stage, gradual transition zone in the middle stage, gentle and stable zone in the late stage, and potential recovery zone after stopping irrigation". It can be seen from the experiment that the groundwater is mainly affected by the physical mixing of recharge water, accompanied by the water-rock physical adsorption ion exchange, chemical dissolution and leaching, etc. especially, the amount of recharge water in paddy field was large, and the water quality of recharge determined the direction of groundwater chemical evolution. At the same time, the concentrations of Na⁺、Cl^- of groundwater chemical components showed a good linear change, and the correlation coefficient was above 0.93, and the concentrations of Ca²⁺、Mg²⁺ showed a certain linear correlation with SO₄^2-、HCO₃^-. After stopping irrigation, the evaporation and concentration of groundwater was strong, and the ions of groundwater showed an increasing trend. Especially for Na⁺、Cl^-, the drainage and precipitation are timely needed after the irrigation. The research shows that the water supply of groundwater not only enriched groundwater sources, but also improved groundwater quality.

Maintaining ecological flow in a river is an important initiative to coordinate water resources development and utilization with river ecological protection. Most of the existing ecological flow calculation methods are limited by insufficient ecological data, difficult ecological modeling. In this paper, a Bayesian hierarchical model based on phytoplankton biomass was established to investigate the hydrological-ecological response relationship. The relationship between phytoplankton biomass and flow and water temperature in pre-flood, flood and post-flood periods was analyzed by taking the Shaying River as a case study. The results show that the Bayesian hierarchical model can identify the complex hydrological-ecological response relationship, and the advantage of hierarchical analysis improves the availability of short series data; The probability of biomass-flow covariate parameter β greater than 0 in pre-flood is 0.683, and the probability of less than 0 in flood is 0.577, and the guarantee of flow in the river channel in pre-flood and the control of discharge in flood have positive effects on phytoplankton biomass; Under the ecological flow conditions that meet the design requirements, the predicted maximum and minimum biomass improvements occur in river section 7 (+32.05% before flood, + 871.80% during flood, and +81.79% after flood) and river section 3 (+3.91% before flood, +1.16% during flood, and +2.89% after flood), respectively.

Factors such as climate change have increased the spatial-temporal distribution heterogeneity of rainfall, it is thus important to study the response of hydrograph to the influence of the spatial heterogeneity of rainfall, which is of great importance to provide guidance to the hydrologic simulation of the flooding under conditions that the rainfall of the mainstream and tributary streams have different occurrence frequencies. The watershed above Linyi station of the Yihe River in Shandong Province was selected as an example. The watershed hydrological model was established using the Xinanjiang model. Hourly rainfall data from June to September from 1980 to 2020 were used for frequency analysis to obtain the design storms with different return periods in the Yihe river basin with a duration of 72 h. The flood process at Linyi station was analyzed by considering combined design scenarios of design storms with different return periods. Simulations were run using the established hydrologic model to obtain the response of flood process to the spatial heterogeneity of rainfall. The results show that the spatial distribution of rainfall has a significant impact on peak flows, with rainfall in areas close to the basin outlet being the determining factor for peak flood flows, and that smaller amounts of rainfall can produce larger peak flows in scenarios with high spatial heterogeneity of rainfall. The results can provide reference for the flood forecasting of downstream cross-sections under conditions that the mainstream and tributary floods have different occurrence frequencies due to spatial heterogeneity of rainfall.

Taking double-discharge building in branching stream of Baiyang Lake as an example, the relationship between water level and discharge capacity of only spillway gate and overflow weir was determined by model test, and then the mutual influence between them was determined by numerical simulation. The method of combined model test and numerical simulation to determine the diversion ratio and discharge capacity were explored. Through this method, the diversion ratio of the spillway gate and the overflow weir and the water level under the gate and weir were obtained. Compared with the design value, the difference is very small within 6%. The results show that the discharge capacity of the spillway gate and overflow weir mainly meet the requirements.

Concrete faced rockfill dam is widely used and rapidly developed in water conservancy and hydropower construction in China. This paper optimized the design method of concrete face dam based on BIM technology, realizing the dynamic comparison and selection of toe slab alignment by visual comparison and selection, achieving dynamic calculation of structural stress by structural parametric design and dynamic decision of dam excavation and filling through module-drawing-chart correlation measurement. As the result of dynamic design method, the model was applied to engineering digitization. Then the method was applied to the design of Gaopingqiao Reservoir face dam. Through the development of BIM plug-in, visual programming and customized intelligent cross section, it has played a role in improving the quality and efficiency of toe slab alignment, BIM-FEM joint analysis and zoning quantity calculation. In addition, the lightweight delivery of the model results supports the "intelligent application of Gaopingqiao digital reservoir" and gives full play to the value of the whole life cycle of BIM.

In order to understand the mechanism of crack formation in the RCC gravity dam body during operation, this paper takes the Shimantan reservoir dam as the research object, adopts a method of using the ESEL command in APDL language and the rotation of local coordinate system to complete the random aggregate delivery, and constructs a three-dimensional macro-micro finite element model of the No. 9 non-overflow dam section of the Shimantan dam. The simulation results of aggregate placement show that the method can quickly generate three-dimensional spherical and polyhedral aggregates, greatly improving the efficiency of aggregate generation. The results calculated by the macro-micro model are more consistent with the actual crack distribution of the dam, and the impact of the rapid rise in summer temperature and rapid drop in winter temperature on the cracking of concrete dams during operation cannot be ignored.

Accurate inversion of dam mechanical parameters based on dam monitoring data is crucial to ensure the safe and stable operation of the dam. This paper presented an arch dam parameter inversion model based on radial basis function (RBF) network and Artificial Gorilla Troops Optimizer (GTO). Firstly, the RBF surrogate model was used to replace the finite element model to discuss the relationship between the material parameters and the displacement response of the monitoring point. The sampling data of the RBF surrogate model was generated by the efficient Latin hypercube sampling technology. Secondly, the GTO intelligent optimization algorithm was adopted to minimize the objective function of material parameter identification. The analysis results of engineering examples show that the RBF-GTO model can achieve high-precision parameter inversion analysis of concrete super-high arch dams while reducing the calculation cost.

The arch dam deformation monitoring model is the most commonly used method for arch dam health monitoring. Aiming at the deformation monitoring problem of extra-high arch dams, this paper proposes an intelligent optimization support vector machine deformation monitoring model for concrete extra-high arch dams. Particle swarm optimization (PSO) was used to optimize the penalty factor, kernel function parameters of the support vector machine (SVM), and tolerate bias. The deformation monitoring model of concrete extra-high arch dam based on PSO-SVM was established, and the influence of aging factors on the model performance was analyzed. Engineering examples show that the PSO-SVM deformation monitoring model of concrete extra-high arch dam has good prediction accuracy and generalization ability, which is suitable for deformation monitoring of extra-high arch dam.

The noise and nonlinear characteristics in the deformation sequence of concrete dam seriously affect the accuracy of dam deformation prediction. In this paper, ensemble empirical modal decomposition (EEMD) was used to decompose the horizontal displacement signal of the dam to mine the effective deformation information. The singular spectrum analysis (SSA) was used to extract features from the high-frequency eigenmodal components (IMF) obtained from the decomposition to reduce the loss of effective information. Considering the complex stochastic and non-linear mapping relationship between effector and environmental variables, extreme gradient boosting (XGBoost) was used to model the prediction of the noise-reduced data. Considering the significant influence of XGBoost hyperparameters on the prediction performance of the model, the Northern Goshawk algorithm (NGO) with better global search capability was introduced to perform parameter search, and an NGO-XGBoost-based dam displacement prediction model was constructed. The calculation results show that the EEMD-SSA can effectively remove the noise from the dam displacement monitoring information, and the dam deformation prediction model based on NGO-XGBoost can significantly improve the prediction accuracy.

Aiming at the problems of difficulty in determining the optimal parameters and low accuracy of the deep learning method in dam prediction, the sparrow search algorithm (SSA) was improved, and the parameters of the gated recurrent unit (GRU) were optimized by the improved sparrow search algorithm (ISSA). Then a dam deformation prediction model based on the ISSA-GRU was constructed, and this model was applied to the deformation prediction of the Longyangxia Dam of Qinghai Section in the upper reaches of the Yellow River. The results show that the dam deformation prediction model based on ISSA-GRU has higher prediction accuracy and stability, which can be used as a reference for dam deformation prediction.

In order to explore the impact of river level and total rainfall duration on the drainage performance of rainwater pipe network, an integrated SWMM generalized model of pipe network and river in a certain industrial park was constructed. Based on the rainfall events with a return period of 5 years and the total rainfall duration of 2 h and 24 h, the drainage conditions of rainwater pipe network and river in industrial parks with different initial river levels were simulated and analyzed. The results show that when the initial river level is low and the outlet is free outflow, river level has little impact on the drainage performance of the rainwater pipe network. When the outlet is submerged, with the increase of the initial river level, the proportion of overloaded pipelines and overflow nodes in the drainage system increases, the overload time and overflow time are prolonged, the peak flow of outlets and pipeline nodes decreases, and the peak flow of node which is closer to outlet decreases more sharply. Based on the same rainfall return period and the initial river level, compared with the short duration rainfall, the proportion of overloaded pipelines and overflow nodes in the long-duration rainfall is larger, the overload time and overflow time are longer, and the peak flow of outlets and pipeline nodes decreases greatly. When designing the storm water drainage system with river-pipe network, it is advisable to check the drainage performance of storm water drainage system for 24 h rainfall and different river levels.

In order to study the distribution of the annular gap flow field during the bend start of the pipeline vehicle under different loading conditions. Numerical simulation combined with physical model test verification was used to study the annular gap flow field during the horizontal bend start of duct trucks with different loads. The results show that the increase of load does not change the overall distribution of the gap flow field velocity, but only changes the magnitude of the gap flow field velocity; Under different loading conditions, the axial flow velocity of the gap flow field of the pipe vehicle in the horizontal bend has the law of increasing and then decreasing from the inner wall of the pipe to the outer wall of the pipe vehicle. The circumferential flow velocity is more uniformly distributed at the section of the pipe vehicle gap inflow port and the section in the vehicle, but the opposite distribution of flow velocity on both sides of the sealing cover appears at the section of the gap flow outlet. The radial flow velocity is more uniformly distributed as far away from the support body and the seal cover, and the flow velocity increases significantly at the support body in the slit flow outlet section of the pipeline vehicle. This study explains the reasons for the formation of annular gap flow field distribution law and obtains the flow velocity distribution law of the gap flow field when the pipe vehicle is started at the bend with different loads. While improving and enriching the theory of annular gap flow, it provides theoretical basis for the application of hydraulic conveying in cartridge loading pipeline.

The proposed Longweizhou junction is a low-head hydro-junction project that focuses on navigation, flood control, water resources, and protection of the aquatic ecological environment. There are two continuous bends upstream and downstream of the dam site, and the straight section where the dam site is located is also short, so the river boundary conditions are not conducive to smooth flood discharge after the project. To demonstrate and optimize the general layout of the proposed hydro-junction, an integrated hydraulic-physical model with a scale of 1∶80 was adopted. On the basis of hydrodynamic similarity verification, a detailed experimental study was conducted on the discharge capacity of the hydro-junction, revealing the characteristics of flow velocity distribution and flow distribution in the original design scheme under typical flood conditions, clarifying the shortcomings of the original scheme and corresponding optimization ideas, putting forward the measure of cutting the side beach to improve discharge capacity. The optimized scheme test verified that the discharge capacity could meet the design requirements. The research results may serve as reference for the design of this project and other similar projects.

For underflow energy dissipation, the arrangement of the grille shortens the length of the stilling pool and makes it easier to adapt to changes in terrain conditions. The two-phase flow of water and gas in the round-bore Γ-shaped grille type stilling pool was numerically simulated by the aeration model in FLOW-3D. The results show that the concentration of longitudinal bottoming gas decreased (31.3% →8.0%) along the way, and decreased significantly at the grid position, the minimum number of holes in front of the grid (^#6 section) was 5.6, the number of holes near the grid was about 9.0, and the number of holes behind the grid was much greater than 9.0. The bubble size near the bottom of the grid front axis increases along the course (0.9 mm→8.1 mm), and the bubble size of the near bottom plate after the grid decreases along the way (1.6 mm decreases to close to 0 mm). It can be considered that the bubbles with smaller diameters in large flow velocity areas play a major role in aeration corrosion reduction, which has obvious protective effect on the solid boundary of concrete, and the structure of the stilling pool including the grid is not easy to occur cavitation erosion damage.

Considering the lack of research on the ventilation characteristics of open flow spillway tunnels under high flow velocity conditions, based on a 50 m/s high-speed jet test device, this paper investigated the effects of flow velocity, ventilation tunnel area, and relative height of spillway tunnels on the ventilation volume and wind speed distribution in ventilation tunnels. By analyzing 44 sets of prototype observation data and 28 sets of experimental data, an empirical formula for calculating ventilation at high flow rates was proposed. The results show that the measured value of ventilation is 2.1-9.6 times of the standard value when the water flow velocity is 18.0-37.2 m/s. As the area of the ventilation tunnel increases, the rate of increase in ventilation volume gradually decreases, and the distribution of wind speed inside the ventilation tunnel is related to the area of the ventilation tunnel. The ventilation volume first increases and then decreases with the increase of the height of the spillway tunnel, and the change in the relative height of the spillway does not change the wind speed distribution characteristics. The calculated ventilation value by the improved formula is relatively close to the actual measurement value, with 3/4 of the data within the 20% error line range. Research results can provide guidance for engineering practice.

The change of hydrological situation and the operation scheduling of the downstream of the hub make the water level at the inlet and outlet of the fish channel change at all time, and the fish channel is running improperly. The insufficient inlet water depth will cause water drop and hinder the backtracking of fish. The integrated model was used to analyze the hydraulic characteristics under different water level combinations at the inlet and outlet of the fishing channel. The results show that the hydrodynamic changes of the fish tunnel tank chamber are mainly concentrated in the pool chamber near the inlet, and the greater the influence is closer to the downstream. When the inlet water level decreases, the water drops at the inlet and it is difficult for fish to trace; When the inlet water level rises, the inlet velocity slows down rapidly. In view of the design inlet flow velocity is 0.60 m/s-1.00 m/s, the maximum drop between the outlet of the fish channel and the inlet water depth is recommended to be controlled at 1.00 m. At the same time, appropriate water replenishment measures should be taken according to the water depth of the inlet to form effective lure flow rate at the inlet, and there is a good linear relationship between the supplementary water flow and the inlet water depth.

Under the condition of low flow ratio, the flow structure of the inlet area of tributaries is very complicated. Based on physical model test and PIV particle image velocimetry technology, the average velocity distribution and three-dimensional velocity spatial distribution of open channel tributaries under different intersection conditions were observed, and the variation law of the flow field of tributaries was analyzed. The results show that when the confluence is relatively small, the surface water of the tributaries will have reverse reflux phenomenon to varying degrees due to the top supporting effect of the main stream water, while the bottom water flows downstream to the main stream, and there is a relatively obvious oblique mixing interface. With the increase of the confluence ratio, the influence of the main stream on the flow structure of the left bank of the tributary decreases gradually. When the intersection angle is 30° and 90°, the water flow structure near the right bank section is most affected by the water top support of the main flow. When the intersection angle is 150°, the tributaries are basically in reverse reflux state, and the maximum reflux velocity area is formed at the intersection. The results can provide theoretical support for the study of frequent bloom caused by nutrient enrichment in tributaries of reservoir area.

The groundwater level in the deep foundation pit project close to the river shows a dynamic characteristic of long-term low water level but high water level during flood season. Foundation pit dewatering leads to the complexity of the seepage field in the surrounding stratum environment, destruction of enclosure structures, accidents include piping and instability at the bottom of the pit. Therefore, this paper simulated the excavation-precipitation process of deep foundation pit project based on the HS-Small constitutive model, analyzed the sensitivity of precipitation influencing factors (precipitation depth, mode, rate and water stop curtain) to the surrounding environment deformation and their relationship. Compared the analysis results with the measured results, it can be found that the settlement of the top of the foundation pit, the soil outside the pit and the surrounding buildings gradually increases, and the dewatering has a more obvious influence on the deformation during the excavation and dewatering of the foundation pit; Fractional precipitation can effectively reduce the settlement deformation of surrounding buildings and ground surface; It is recommended that the dewatering depth of foundation pit should be controlled within 0.5-2.0 m below the bottom plate; The precipitation rate has a relatively small impact on the total settlement of the surrounding environment, but has a great impact on the settlement rate. When the precipitation rate reaches the optimal value, it is beneficial to the stability control of the foundation pit. The embedded depth of water-proof curtain in this project is more than 30 m, which has no obvious effect on controlling the settlement of surrounding buildings. The research results can provide reference for the dewatering design and construction of similar deep foundation pit projects closed to the river.

To ensure the structural safety of the double row steel sheet pile cofferdam and control its water use area, the single-factor sensitivity analysis method was carried out to study the impact of various items on the deformation of cofferdam, and the PLAXIS software was used to implement the 2D and 3D finite element calculation. The results show that the elevation and tension of tie rod, and the specification of steel sheet pile have little impact on the deformation of cofferdam in soil; Compared with the width of the cofferdam itself, the deformation of cofferdam is more affected by the width of inner foot, so the width of the inner foot should be increased as much as possible; The depth of the outer sheet pile has no obvious impact on the deformation of the cofferdam, so that it can be reduced appropriately, and the depth of the inner sheet pile can be increased; The effect of the transverse structure on controlling the deformation of the cofferdam is not obvious, and other measures can be taken to strengthen the connection between the inner and outer sheet pile. The research ideas and calculation results can provide reference for structural design optimization of steel cofferdam in similar projects.

In order to study whether the original design flow can be met after the lining scheme of sections of a long distance non-pressure diversion tunnel is changed, the flow capacity of typical sections of the tunnel was analyzed by model test and theoretical calculation. There are 4 tunnel diameters and 2 roughness in the typical section of the tunnel. In order to meet the conditions of similar resistance, different materials were compared and tested, and the roughness was determined. Through testing and analyzing the flow capacity and flow characteristics at three operating conditions, it is concluded that the flow can be safely passed under operating condition 1, and the clearance margin of some tunnel sections under operating condition 2 is insufficient, with the minimum margin of 14.39%. Most tunnel sections under operating condition 3 do not meet the safety flow. Comparing the test and theoretical calculation, the results of the two are relatively close, and the test value is relatively safe, which can provide a theoretical basis for the construction and operation of the project.

Rock wall crane beam is a common bearing structure in underground powerhouse. Because it is directly supported on the surrounding rock, the stability of the rock crane beam is greatly affected by the geological conditions of the surrounding rock. Taking the rock wall crane beam of phase Ⅱ underground powerhouse of Fengning pumped storage power as an example, the distribution law of rock wall crane beam anchor stress and surrounding rock deformation were explained by analyzing the rock mass structural plane characteristics, the rock mass alteration effect as well as the in-situ observation data of the rock wall crane beam. Furthermore, the correlations between the bolt stress of the crane beam and the deformation of surrounding rock, the geological conditions as well as the construction process were deeply analyzed. The reasons for the large bolt stresses and the large deformations of surrounding rock of the crane beam were then explained, and the influence mechanism of rock mass structural plane and rock mass alteration on the stability of the crane beam was finally revealed. This research can provide technical support for the structural design, the construction organization and the safety demonstration of the rock wall crane beam, thus has practical engineering significance.

In view of the local large deformation, collapse and erosion of silty mudstone entrance section of Daliangshan Highway #2 tunnel, through the field monitoring, indoor swelling test of surrounding rock and 3D modeling analysis, the mechanism of large deformation of initial support was studied. The impact of factors including rainwater, secondary deformation of surrounding rock and silt bias on the large deformation was discussed. The remediation plan was put forward. The results show that the surface clay rock above the tunnel is swelling rock, and the silty mudstone is non-expansive rock, and the tunnel deformation has little affected by the expansion of the surrounding rock. Affected by continuous rainfall, the change in the settlement of the vault is the most obvious, and the settlement increased by 150 mm compared with the pre-rainfall. The theoretical value of horizontal pressure on the deep buried side of the tunnel is 1.73 times that of the shallow side, and the tunnel structure is subjected to obvious bias load. The comprehensive treatment scheme of strengthening temporary support + advanced support of large pipe shed + grouting reinforcement of double-layer small conduit + addition of anti-slip piles at the junction of light and dark at the top of the cave + two rows of pipe piles on the left side of the left hole and two rows of pipe piles in the middle of the left and right holes of the hole section of the hole was adopted, and the deformation of the tunnel was reduced by 87%, and the large deformation of the initial support is effectively controlled.

Based on the instability criterion proposed by the cusp catastrophe theory, the whole surrounding rock was judged, and the relevant tunnel excavation model was established by using the finite element software MIDAS GTS NX, and the changes in surrounding rock stress, displacement and maximum vibration velocity peak in the tunnel-fault system under the conditions of groundwater seepage and blasting were studied by taking No. 2 tunnel project of Daliangshan in Lexi Highway of Sichuan Province for an example. The results show that the comprehensive stiffness ratio of the surrounding rock k<1 and the bifurcation set equation Δ<0 are found by the calculation of the instability criterion, both of which indicate that the surrounding rock has the risk of instability. Under the seepage condition, the maximum principal stress of the fault surrounding rock is 27.71 MPa, and the displacement settlement of the vault is 307.83 mm. Compared with the non-fault area, the stress increases by about 20.64%, and the displacement increases by 105.21%. Influenced by blasting factors, the maximum vertical peak vibration velocity at the fault area is about 13 times that of the common surrounding rock, it is up to 162.97 cm/s. It can be seen that the existence of a fault will have an amplification effect on the dynamic response of surrounding rock. Both theoretical calculation and numerical simulation results show that the F3 fracture of the Daliangshan Tunnel has the risk of instability, and corresponding preventive measures should be taken in advance during construction.

The characteristics and distribution of in-situ stress field have an important influence on the stability and engineering design of the surrounding rock of underground power house. According to the deep surface drilling hole and engineering geological conditions of the underground power house of a pumped storage power station, a three-dimensional numerical analysis model was established, and the inversion reconstruction of the initial in-situ stress field was realized through multiple linear regression analysis. The results show that the maximum horizontal principal stress measured in deep holes is 6.7-17.6 MPa. The magnitude and direction of the inversion model are in good agreement with the measured value, and the horizontal stress in the underground workshop area is dominant, and the maximum horizontal principal stress is 16.2-17.4 MPa. The maximum principal stress azimuth of the stress field in the plant area is less than 30°, and the stress distribution and azimuth angle meet the design requirements. The research results provide a reference for similar large-scale underground projects.

Currently, the researchers have not yet conducted a detailed analysis of the anchor block stability and there exist shortcomings in the discriminatory formula for the slip length. On the basis of the existing computational formulas, the axial force formula for the pipeline was optimized considering expansion joints, and the axial force formula was proposed for downstream elbow pipe without considering the expansion joints. Furthermore, by analyzing axial thrust on pipelines in the context of considering or not considering the expansion joints and comparing the concrete amount of the anchor block under all conditions, the anchor block of the buried steel pipe was found to have the minimum amount of concrete used in the context of not considering the expansion joints and under certain condition, which can provide a reference for future research and design work.

Anti-seepage wall is an important anti-seepage structure in cofferdam, which plays an active role in improving the distribution of seepage field and the stability of cofferdam. This paper presents an optimization method of cutoff wall structure based on artificial fish optimization algorithm. Taking a cofferdam project as an example, the calculation model of cofferdam was established based on finite element analysis, and the wall thickness and rock depth of cutoff wall were taken as the variables to be optimized. Finally, the safety factor of cofferdam under the condition of constant water level and sudden drop of water level was obtained through seepage and stress coupling analysis. Compared with the traditional artificial fish swarm algorithm, the results show that the optimized method based on the improved artificial fish swarm algorithm has faster convergence speed and convergence accuracy, and the optimized anti-seepage wall structure can achieve the balance between the anti-seepage effect and the economy. The pore water pressure behind the cutoff wall decreased significantly, and the safety factors of the cofferdam under the conditions of constant water level and falling water level (falling rates are v=0.5 m/d, 1.0 m/d and 2.0 m/d, respectively) were 1.489, 1.410, 1.376 and 1.321, which met the safety requirements, reflecting the feasibility and rationality of the proposed method. The research results can provide reference for the design and construction of cofferdam.

In response to the inadequacies of traditional earthen and reinforced concrete flood walls that create barriers between urban areas and waterfront regions, which no longer meet the public's demands, the introduction of aluminum alloy flood walls in the Moon Bay flood control renovation project has been proposed. A transformation plan that combines modular flood walls with ecological embankments has been implemented. The post-renovation project has demonstrated excellent operational effectiveness, eliminating the oppressive feel of conventional flood defenses within the urban space. Furthermore, it seamlessly extends the urban landscape space to the water's edge, creating a unified and continuous landscape interface. This approach ensures flood safety while fostering a waterfront landscape with distinctive regional characteristics.

In order to study the impacts of aggregate size and fiber length on the mechanical properties of basalt fiber concrete, three aggregate sizes and basalt fiber lengths have been taken into account, and 108 concrete test blocks (including 72 cubic test blocks and 36 prism test blocks) have been designed and made. Furthermore, axial compression test, splitting tensile test as well as bending test have been carried out to analyze each parameter influence on compression strength, splitting tensile strength and bending strength. On the basis of random fiber script, ABAQUS finite element modeling analysis is carried out, and the corresponding strength calculation has been proposed. The results show that with the increase of aggregate size, the mechanical properties of matrix concrete are improved. While with the adding of basalt fibers, the concrete mechanical properties rise higher than aggregate size increase. The concrete mechanical properties present good performance when 30mm aggregate size mixes with 18 mm and 24 mm basalt fibers. The result of designed random fiber script in ABAQUS finite element modeling matches with the experiment well, and the calculation method considering two-parameter influence of aggregate size and basalt fiber length has good applicability.

Aiming at analyzing the mechanism of slope failure and evolution propagation induced by typhoon and rainstorm, a numerical simulation of the safety state of a slope was carried out based on the measured rainfall data during various typhoons in Fujian Province of China. For the slope before instability, Monte Carlo method was used to calculate the real-time failure probability and reliability index and reveal the transient change characteristics of the seepage field and plastic zone of the slope. For the slope after instability, Herschel-Bulkley-Papanastasiou (HBP) model was used to describe the rheological characteristics of the slope using the SPH method. The propagation process of landslides was analyzed in terms of velocity and accumulation characteristics. The results show that the rainfall is the key factor to induce slope instability. When the slope failure occurs, the sliding speed of the leading edge can reach 15 m/s. This study provides a reference for the early warning and disaster prevention and mitigation of slope engineering under extreme conditions.

The resistivity method can reflect the soil physical index and structural properties, and it has the characteristics of high efficiency, convenience and non-destructive. In this study, the resistivity characteristics and the resistivity model of laterite had been analyzed using the pore water, water content and porosity as the key factors. A correction formula of contact resistance was proposed considering the influence of electrode area, and the resistivity prediction model of laterite had been established by introducing the structural factors to reflect the influence of pore water on the resistivity of laterite. The results show that the proposed contact resistivity correction formula can effectively reduce the test error, the laterite resistivity and structure factors decrease with the increasing water content and porosity with a power function relationship. The correlation of influencing factors of laterite resistivity is sorted as: pore water>water content>porosity. The resistivity prediction model of laterite was constructed with the variables of contact resistance, pore water, water content and porosity, which has high fitting accuracy. Thus, it can provide a reference for evaluating the physical indicators and structural properties of laterite.

In view of the issue of the traditional questionnaire survey method with high human and time costs, a set of resettlement survey system based on B/S framework and cloud platform was designed on the basis of the analysis of the business needs of the survey of post resettlement support monitoring and evaluation of large and medium-sized reservoirs in Ningxia. The system implements the import, update, deletion of historical data, as well as the addition, modification, query, statistical analysis, and other functions of sample information through two subsystems: the household survey of mobile terminal and the data management of PC terminal, and was applied to survey work examples. Compared with the traditional survey method used before, the application results indicate that it has increased the average number of daily survey samples by about 1.5 times, saved 78% of the labor and time costs required for the collation and filing of survey data, and greatly reduced the repeated printing and output of paper survey forms, and to effectively avoided the less of paper data.

Aiming at the shortcomings of hydropower unit vibration signal denoising using ensemble empirical mode decomposition (EEMD), a denoising algorithm based on an improved fruit fly optimization algorithm (RFOA) for optimizing the EEMD noise IMF component threshold was proposed. Firstly, the noise signal was decomposed using the EEMD algorithm to obtain the IMF components, and then the correlation coefficient method was used to determine the noise signal and the effective signal. Then, the RFOA was used to determine the noise signal IMF component threshold. Finally, the sample entropy of the obtained IMF components was used as a feature vector input of the GRNN algorithm for vibration mode recognition. Compared with the wavelet threshold method and the EEMD-GA method, the results show that the proposed algorithm has the highest signal-to-noise ratio and the best denoising effect.

The distribution of measured operating data of hydraulic turbines is non-structural and uneven density. The moving least squares method was used to fit the measured operating parameters to obtain the spatial characteristic surface of the water turbine, which can reflect the local characteristics of data surface and avoid the distortion caused by the differences of data distribution density. The Riyadh criteria was used to perform preliminary data filtering. The support radius was adaptively determined by local fitting across different ranges of discrete sample points. The robust moving least square surface reconstruction model was established combined with the Mahalanobis distance denoising method. Compared with the least squares method, the example calculation results show that the moving least squares method fits the operating characteristics of hydraulic turbines with higher accuracy and supplements the local data effectively. The result can reflect the operating characteristics of hydraulic turbines authenticity, which provides a reference for correcting the operating characteristic curve given by the turbine manufacturer.

The premise of non-conformity traceability and correction of run-off is that there is an accurate and reliable long series measured flow sequence as the calibration reference. For watersheds without long series of measured flow data, the accuracy of calculated flow can be verified through short-term and typical test data to obtain a calibration benchmark. In this study, the accuracy of NHQ curves and discharge curves of Pubugou Reservoir was analyzed and verified based on the ultrasonic flow, combined with the analysis of the level-flow relationship under stable and sudden change working conditions. The research results have proven the accuracy of the outflow calculation of Pubugou reservoir, which provided basic support for tracing and correcting the non-uniformity of cascade runoff.

In response to the evident phenomena of flow separation and backflow, low efficiency, and increased cavitation in the tailrace conduit of the Deneng Xiangjiang Hydropower Station after expansion, computational fluid dynamics (CFD) analysis was employed. Two methods, namely, modifying the shape of the tailrace conduit or replacing the runner, were proposed to improve the flow pattern within the tailrace conduit. Research has demonstrated the effectiveness of both methods, which can provide reference for similar projects.

The deicing effect of wind turbine blades was tested and analyzed based on the air-thermal method. The thermal conductivity efficiency of the paving structure and the influence of blower speed (or frequency) on the deicing efficiency were mainly considered. Firstly, the blade structure and layering structure were introduced, and the thermal conductivity was estimated by measuring the thickness of the layering structure. According to the ice-covered position of the blade in winter, the rationality of the thermal conductivity distribution of the blade during air-thermal deicing was verified. After that, the field blade deicing test was carried out by changing the speed (or frequency) of the blower. The test results reveal the root cause of the unbalanced deicing phenomenon in the process of wind turbine blade deicing by air thermal deicing system. It shows that the higher the speed (or frequency) of the blower is, the better the deicing equilibrium of the blade surface and the more significant the deicing effect are under the premise of ensuring the temperature stability of the outlet of the ventilation pipe. In addition, with the use of larger blower frequency, the internal circulation of the blade was enhanced, and the reasonable setting of the internal circulation structure of the blade can effectively improve the de-icing efficiency and reduce the de-icing consumption time.

For water supply systems with high-lift, the pump-stopping water hammer caused by the power failure is usually greater than the direct water hammer caused by the check valve closing. Based on the Joukovsky equation and the pressure drop law behind the pump, the influence of the check valve closing law on the pressure along the pipeline was studied, and the theoretical value of the optimal closing time (i.e., T_g=T_d) was obtained when a pump trip occurred. The theoretical value was verified by numerical simulation through a practical project. The results show that for high-lift water supply projects, the theoretical closing time of the check valve can minimize the pressure drop along the pipeline when the pump trip occurred.

The water intake mode of pumping station under the condition of large variable water level of water source has great impact on the reliability of water intake, project cost and safety of water intake building, so the reasonable evaluation of different water intake mode is one of the key problems in engineering design. In this paper, a two-level evaluation index system consisting of 3 quantitative indicators and 14 qualitative indicators was constructed. The analytic hierarchy process (AHP), entropy weight method and least square method were used to assign the combination of subjective and objective weights. The method of membership degree and fuzzy comprehensive evaluation was used to evaluate and rank different water intake schemes, and an engineering example was analyzed. The results show that the proposed index system is comprehensive, the weighting method is reasonable, and the evaluation method can better reflect the uncertainty of the scheme selection. The practical engineering example verified the feasibility of the evaluation method.

The fan-shaped central revolving gate is a new type of gate with a significantly different flow pattern from the traditional gate. In order to study the hydrodynamic pressure characteristics of the fan-shaped central revolving gate, model experiment was conducted on the different opening coefficients of the gate based on the 60 m span gate of Wusongjiang regulation project and its energy dissipation design conditions, and the time-average pressure, average fluctuation amplitude, pulsation intensity and spectral characteristics under different opening coefficients were analyzed. The results show that the time-average pressure of the gate blade is positive pressure at each opening coefficient, and the overall pulsating pressure amplitude is relatively stable. The pulsating pressure of each measuring point is close to normal distribution under different opening coefficients. The pulsation intensity changes with the change of the opening and measuring point position. With the increase of the opening coefficient, the pulsation intensity presents a trend distribution of decreasing first and then increasing, and the pulsation intensity belongs to the low-frequency pulsation. The change of the measuring point position in the width direction will affect the pulsation intensity of the measuring point, and the center line pulsation intensity can be used instead of the whole gate pulsation intensity.

The high penetration of distributed renewable energy aggravates the power fluctuation and uncertainty of distribution network. In this paper, a two-stage optimal operation strategy of distribution network based on multi-objective reduction and multi-step reconfiguration was proposed. In the day-ahead stage, multiple operational flexibility index models of voltage deviation, power loss, total operating cost, net load peak-valley difference and net load coefficient were constructed. On the basis of the model, a multi-flexibility index dimension reduction method based on target correlation was proposed, which aims to balance the relationship between various indicators, reduce the number of targets and improve computational efficiency. In the intraday phase, a distribution network reconfiguration method based on multi-step switch sequence exchange was proposed by cooperatively controlling the sectionalizing switches and tie switches, which fully exploits the available flexibility resources of the system. Finally, the simulation of arithmetic cases based on the IEEE-33 node system, the IEEE-84 node system, the IEEE-119 node system and the IEEE-136 node system were carried out, and the results show the effectiveness of the proposed two-stage distribution network flexibility enhancement strategy.

The calculation of maximum power supply capacity is an important issue in optimal operation of UHV complex large power grid. With the large-scale access of high-proportion renewable energy to the power grid, the problem of power and energy balance is becoming more and more prominent. Considering the stability spinning constraint, coupling section constraint and unit regulation capacity constraint, the calculation problem of maximum power supply capacity presents high-dimensional characteristics, which is difficult to model and solve. According to the limitation of transmission section and the characteristics of partition operation of UHV complex large power grid, an optimal dispatching model of maximum power supply capacity of UHV complex large power grid considering section coupling control was established. Then, the Simplex method (SM), Interior Point method (IP), Simulated Annealing (SA), Beluga Whale Optimization (BWO) and Artificial bee colony algorithm (ABC) were applied to solve the model respectively, and the maximum power supply capacity of the large power grid in the next 15 minutes was calculated. The coordinated optimization scheme of various types of power supply and reserve was proposed. Finally, a regional power grid was taken as an example to verify the model and the solution method. The simulation results show that because of the large scale of the power system and the complex coupling relationship between the sections, the heuristic intelligent optimization algorithm has a long running time, slow convergence speed and low search accuracy. The interior point method converges rapidly, has strong robustness, is insensitive to the selection of initial values, has better stability and computational efficiency, which can provide effective and practical support for power supply and power balance of complex UHV power.

Under the background of building a new-type power systems, the hydro-thermal-wind-solar-storage system with a high proportion of new energy has become the main research object of power system planning. It is necessary to perform high-frequency iterative calculations on the long-term supply-demand balance of the hydro-thermal-wind-solarstorage system to achieve quantitative analysis of sensitive boundaries, which puts forward higher requirements for the calculation efficiency of the analysis method. Considering the working characteristics of various power sources and the output probability characteristics of new energy sources, this paper proposed a heuristic unit commitment algorithm based on operating rules, which realizes the daily determination of the unit start-up mode throughout the year, and further constructed a supply-demand balance model. Finally, a case study based on a regional power grid example proved that the proposed model and method were feasible and effective, which provides reference for analyzing long-term supply-demand balance of the hydro-thermal-wind-solar-storage system.