The precipitation data with high quality and high spatial and temporal resolution is of great significance to the research of hydrology, meteorology and other fields. At present, remote sensing and reanalysis of precipitation data are widely used, but there are problems such as low resolution, high uncertainty of accuracy, etc. In this paper, a random forest precipitation fusion algorithm considering covariates is proposed to fuse seven sets of precipitation products, namely CMA, CN05, ERA5, GLDAS, TRMM, IMERG and PERSIANN. Three typical sub-basins of the Yangtze River basin (Jinsha River, Sanxiaqujian and Poyang Lake) are selected to test the effect of random forest fusion data (RFF). The results show that for the accuracy of precipitation products, the accuracy of random forest fusion data is improved compared with the original precipitation products. For the accuracy assessment of different precipitation events, with the increase of rainfall intensity, the T_TS score of each precipitation product shows a decreasing trend, and the T_TS score of RFF is better than the original precipitation product. Data fusion of precipitation products through random forest model considering covariates can improve the accuracy of precipitation data and the reliability of different precipitation events, which provides support for hydrological simulation.

The Lhasa River Basin is a typical arid and semi-arid basin in the Qinghai-Tibet Plateau, where the ecosystem is extremely fragile. It is of great significance to study the spatio-temporal variation of vegetation index (NDVI) in response to the changes of meteorological factors, and to explore the adaptability of vegetation on the Qinghai-Tibet Plateau to the meteorological factors under the background of climate change. Based on the monthly NDVI, precipitation (P), and average temperature (T) time series dataset in the Lhasa River Basin from 1982 to 2017, using Pettitt, Mann-Kendall trend test and Pearson correlation analysis, this paper analyzed the spatio-temporal variation characteristics of growing period NDVI (G-NDVI) and meteorological factors, and identified responses patterns of G-NDVI to climate factors. The results show that the G-NDVI changed abruptly in 1997, and there was a trend shift from increasing to decreasing. The climate of the watershed changed from “wetting-colding” before the abrupt point to “drying-warming” after the abrupt point, and its effect on vegetation growth changed from promoting to inhibiting. There are two zones in the watershed where the responses patterns of G-NDVI to meteorological factors changed before and after the abrupt point. In the western permafrost areas, G-NDVI shows significant correlation with P and T in the second phase after 1997, i.e., emerging the “responding” function on meteorological factors variation. In the southern seasonal frozen zone, after the abrupt point, time lags of G-NDVI to P were elongated, and meanwhile the “responding” of G-NDVI to T has been triggered. The latency of NDVI response to P in the western permafrost region is longer than that in the southern seasonal frozen zone. In the second phase after 1997, the response area of NDVI to meteorological factors increased compared with that before the abrupt point, and the effect of meteorological factors on vegetation growth in the Lhasa River basin was enhanced.

Based on the monthly data of precipitation and average temperature from 36 reference meteorological stations in the six basins in Yunnan Province, 11 climate models published by CMIP6 were used to simulate and predict the change process of meteorological elements in six basins. Three model integration technologies were used to improve the simulation ability and evaluate the suitability of each model and integration method. The optimal method was chosen to predict the possible trend of climate change in six basins under the scenario of SSP2-4.5 in the future. The results showed that precipitation and temperature would increase gradually in the near, middle and long term in the six basins of Yunnan Province. Precipitation might increase significantly after 2060, and temperature might increase significantly after 2050.

The drought in the Fenhe River Basin has the characteristics of serious disaster and wide range of influence, which has a great blocking effect on the development of local society economy, so it is of great significance to accurately evaluate the drought situation in the basin. Based on Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Runoff Index (SRI), the data were grouped with Tyson polygons. A new comprehensive drought index Comprehensive Index (CI) was constructed by Caussian Copula function. Mann-Kendall trend test was used to test the trend of CI annual series, and the run-length theory was used to extract drought features. It is found that CI can respond well to both hydrological and meteorological droughts. The number of M-K trend series of CI sequence is -3.78. There is a trend towards drought in the upper reaches of the Fenhe River. The intensity of drought in 1970 is the smallest, which is 0.06. Four years from 2013 to 2016 appeared continuous drought, and the maximum intensity is 2.66.

In order to improve the accuracy of runoff prediction, based on the control variable method and the daily runoff data of Lanzhou hydrometric station from August 2001 to December 2019, the models of the LSTM, ARIMA, SVR and XGBoost were used to establish 12 model schemes, including single model, EMD decomposition and reconstruction, EMD decomposition and reconstruction after removing noise components, and evaluation indicators of the 12 schemes were compared. The results show that the EMD sequence decomposition and reconstruction technology and noise component elimination based on Hurst exponent are helpful to improve the prediction accuracy. Compared with the single model, the R_RMSE of the model constructed by the former decreased by 15.16% on average, and that of the latter decreased by 28.49% on average. Among the 12 schemes, EMD-SVR-ARIMA with noise components removed is the best model.

The change of channel storage capacity is an important content of river evolution analysis. In the past, the section method was mostly used for simplified calculation. However, in the complex river pattern with multistage branching or tributaries, the section method often needs to be dealt with separately, and the calculation efficiency is low. By introducing the water surface width ratio of the branching channel, optimizing the distribution of the calculated area of the section at the branching point, adding the section, estimating the storage capacity of the channel in the missing section near the tributary estuary, and using the topographic method to restore the section spacing under different water levels, the calculation model of the section method under the complex river pattern is improved. The comparison results show that the calculation accuracy of tank storage capacity is greatly improved by using the above method, which can provide a reference for batch calculation of tank storage capacity under various complex river types.

Flow and sediment are the driving force and material basis for shaping the riverbed. The process of flow and sediment changed by the operation of Three Gorges Reservoir leads to severe riverbed adjustment downstream of the dam. This paper selects the straight-braided channel-Bailuoji as typical which locates in the middle reaches of the Yangtze River, and analyzes the channel development characteristics from perspectives of channel storage capacity, beach-trough scouring and silting and branch channel diversion capacity variation after the impoundment of the Three Gorges Reservoir. Combined with the change in the duration of floods above the channel forming discharge, the impact of the flow process change on the development of the Bailuoji Reach is quantitatively calculated. The results show that in recent years, the channel storage capacity of the Bailuoji reach has increased and scouring mainly locates in the low-flow channel. The right branch is the main branch and the diversion ratio has increased under the low-discharge. The flow and sediment conditions after the impoundment of the Three Gorges Reservoir can maintain the development of the main branch of the Bailuoji reach. Compared with the flow process without reservoir regulation and storage, the duration of high flow above the channel forming discharge is relatively shortened under the current dispatching mode, the total amount of erosion in the Bailuoji reach is relatively small and the diversion ratio of the right branch is slightly reduced. The research results can provide reference for middle-small flood dispatch of Three Gorges Reservoir.

In order to understand the impact of vegetation groups on the hydraulic characteristics of natural meandering river, this paper designed two kinds of layout forms in which the cluster layout simulated the natural cluster vegetation group, and the uniform layout simulated the artificial regular planting vegetation group. Through the flume experiment, the impact of different layout forms of vegetation on the distribution of flow field, hydrodynamic axis, turbulent kinetic energy and transverse circulation structure in continuous bends was explored. The results show that the flow field in the bend appears obvious velocity partition in which the high velocity area is close to the convex bank, and the low velocity area is attached to the concave bank. Vegetation layout makes the distribution range of high and low flow rate areas have the opposite change rule: the high flow rate area increases, while the low flow rate area decreases. Under the action of the bend, the hydrodynamic axis 'gradually swings to the convex bank on the upstream side of the bend top, close to the convex bank near the bend top and swings to the concave bank on the downstream side of the bend top, completing a cycle of motion changes. Vegetation layout makes it swing to the middle of the flume and the deviation degree of cluster layout is greater than that of uniform layout. Under the action of the bend, the distribution of turbulent kinetic energy of water flow is small on both sides and large in the middle. On the whole, the layout of vegetation increases the turbulent kinetic energy on the downstream side of the bent top, and the impact of cluster layout is greater than the uniform. The vegetation layout changes the circulation structure of the section, which is manifested by the swing of the vortex core position and the change of the distribution range.

Aiming at the impact of large-scale ecological water replenishment (four times of ecological water replenishment in Beijing section of Yongding River) on the long-term cut-off river, a MIKE 11 hydrodynamic model was established. The variation characteristics of runoff and infiltration capacity before and after water replenishment were quantitatively evaluated by scenario simulation analysis. The results show that the inflow runoff sequence of Guanting Reservoir can be divided into three stages: natural stage, human weak interference stage and human strong interference stage. During the three ecological replenishment periods from 2019 to 2020, the flow of the main section of the Beijing section of Yongding River is much larger than the ecological flow of human strong interference stage. In the autumn of 2021, the loss of permeability coefficient and leakage of ecological water supplement was the lowest, indicating that the leakage of Yongding River was significantly reduced through three consecutive years of large-scale ecological water supplement. Taking the ecological replenishment in autumn of 2021 as an example, the fitting functions of channel storage and replenishment flow, submerged area and replenishment flow, submerged area and channel storage, permeability coefficient and replenishment flow were established, which can provide some guidance for the development of ecological replenishment in Yongding River. The results of this study can effectively guide the optimization and formulation of ecological water supplement scheme in the Beijing section of the Yongding River, and provide reference for the comprehensive management of the Yongding River Basin and the exploration of ecological restoration of long-term river courses in North China.

As an essential influencing factor of permissible pollution bearing capacity, hydrological condition was changed significantly due to hydropower cascade development. According to the water functional division and water quality control target in Panzhihua reach of Jinsha River, the variation of dynamic permissible pollution bearing capacity (COD, NH3-N) with hydropower cascade development were calculated depending on 2-D hydrodynamic and water quality models. Furthermore, response relationship between permissible pollution bearing capacity and hydrological factors was established to evaluate the effect of hydropower cascade. The results show that the dynamic permissible pollution bearing capacity of COD and NH3-N decreased by 5.2%-27.8% and 3.8%-41.2%, respectively, and its decreased range was found to be more evident in dry season. The variation trend of permissible pollution bearing capacity and near-bank discharge was similar for different conditions. Simple coefficients between the variation of near-bank discharge and permissible pollution bearing capacity were calculated. However, a significant correlation was found with permissible pollution bearing capacity of NH3-N only.

Based on the understanding of the concept of happiness river, taking 6 rivers with moderate river scale in Qiqihar Areas as an example, the TOPSIS evaluation model is constructed by combining the proportional scale AHP and AEM to carry out the evaluation on the happiness river, whose goal was divided into 5 guiding layers and 20 indicator layers. The evaluation results show that the overall happiness of the rivers in Qiqihar Areas is grade Ⅲ, which the happiness of Yalu River is grade Ⅳ, the happiness of Alen River, Nuomin River, Yin River and Runjin River is grade Ⅲ, and the happiness of Chaoer River is grade Ⅱ. In addition, the common problems of poor evaluation grade in the results were analyzed and the treatment suggestions were put forward.

The nonlinear equation was established for the incipient motion of sediment under constant flow, including Reynolds number, Hiltz number and sediment erosion intensity. Based on cusp catastrophe theory, this experimental process focused on the main factors affecting incipient motion of sediment and bottom riverbed scouring, and considerd different flow intensity conditions. The Reynolds number of sand particles from other experiments was used in the nonlinear equation of this study to verify the influence of Reynolds number. The theoretical value calculated by this formula has a strong consistency with the test value, after comparing the results and data. Therefore, this nonlinear equation can basically meet the requirements for predicting the scouring intensity of fine sediment.

To determine the appropriate ecological flow for small watershed assessment, taking Qingshui River in Pearl River Basin as an example, the monthly ecological flow was calculated by using six hydrological methods such as Tennant method, Texas method and frequency curve method. Furthermore, combined with hydrological rhythm and ecological flow guarantee rate, the advantages and disadvantages of the six methods were compared and analyzed in the dry and flood periods, and the most suitable ecological flow calculation method for small watershed was obtained to determine the ecological flow. The results show that the ecological flow of Hongqi Reservoir section is between 0.12-1.52 m³/s, and the ecological flow of Puzhehei section is between 0.30-4.95 m³/s. The fitting coefficients of hydrological rhythm are 0.993 and 0.998, respectively. The ecological flow guarantee rate is at a good level, and the ecological flow selection result is reasonable. The results can provide a reference for similar national small watersheds to select appropriate calculation method to determine the ecological flow.

In order to make up for the shortcomings of the single Gini coefficient method in the evaluation of spatial equilibrium of water resources, it needs to systematically evaluate the matching relationship between water resources and social development. Selecting arable land area, population size, industrial and agricultural output value and gross product in Xinjiang as the indicators, which affects the carrying capacity of water resources, combination of correlation number method and Lorenz curves was used to quantitatively analyze the equilibrium between regional and sub-regional water resources and indicators. Five element subtractive set of potentials was adopted to identify the development of equilibrium of sub-regional water resources. The results show that the overall water balance in Xinjiang has been rising and then falling during 2011-2018, and is uneven from year to year. The analysis of the indicators shows that the water balance fluctuates between uneven and uneven. The analysis of the sub-regional water balance and trends shows that most areas are in an uneven and inverse state, and exacerbates the unevenness of water resources and identifies the targets for water balance regulation, which points out the direction for reasonable improvement of the balance of water resources.

Scientific evaluation of flood resource utilization potential is an important prerequisite for carrying out flood resource utilization in the basin and alleviating the contradiction between supply and demand of water resources. To evaluate the potential of flood resource utilization in different sections of the Xizhijiang River Basin, the SWAT model was constructed to simulate the natural runoff process of Xizhijiang River Basin, and the flood resources of the basin were quantified by combining the limit analysis theory. The potential of flood resources utilization in the upper, middle and lower reaches of the basin was evaluated, and the feasibility of flood resources utilization in Xizhijiang River Basin was discussed based on the water quality conditions. The results show that the SWAT model has good applicability in runoff simulation of Xizhijiang River Basin; The inter-annual distribution of flood resources is uneven, and there are great differences in inter-annual flood resources utilization potentiality. The utilization condition of flood resources in the lower reaches is better than that in the upper reaches, while the utilization rate of flood resources in the lower reaches is lower. The average annual current and theoretical utilization potential of flood resources in the lower reaches are 3.48×10⁸m³ and 7.97×10⁸m³, respectively. The water quality indexes of the main stream of Xizhijiang River Basin are not lower than the class Ⅲ standard, and the utilization of flood resources in Xizhijiang River is feasible. This study can provide support for the optimal allocation of flood resources in Xizhijiang River Basin, and it has an important reference value for achievement of high quality development of the basin.

In order to analyze the Nitrogen pollution status and changes in the Yihe River Basin, a SWAT model was established, and the model was calibrated based on the monitoring data of Linyi Station. Its temporal and spatial distribution characteristics were analyzed and the key pollution sources were identified. The results show that the SWAT model has good applicability in the simulation research of runoff and pollution in the Yihe River Basin; The pollution is mainly concentrated in the flood season from July to September, and the ammonia nitrogen and total nitrogen load account for 73.34% and 81.58% of the whole year; The sub-basin in the southwest and close to the water system in the northeast are the main source area of pollution; The main sources of pollution in the basin are sewage discharge, agricultural fertilization and soil loss. Taking Nitrogen fertilizer reduction, returning farmland to forest and comprehensive management measures for the changes can effectively reduce the discharge of pollution load.

Support Vector Machine (SVM) has advantages in small sample simulation prediction, but there is subjectivity in the selection of penalty factor C and kernel function parameter γ in SVM. Therefore, the Harris Hawks Optimization (HHO) algorithm was used to optimize C and γ in the SVM. And then the HHO-SVM mode was established to predict water quality in the Xiyuan tunnel section of Lake Dianchi Caohai. The results show that the prediction accuracy of the water quality prediction model based on HHO-SVM is higher than that of the SVM based on genetic algorithm (GASVM) and the SVM based on whale optimization algorithm (WOA-SVM). It is proved that the HHO is feasible to optimize the parameters in SVM, and HHO-SVM can be used in water quality prediction.

Aiming at the problem that the traditional water quality prediction method is difficult to capture the spatial and temporal characteristics of the sample, this paper proposes to establish a CNN-EA-ConvLSTM based water quality prediction model. The convolutional neural network (CNN) was used to reduce the dimensionality of the data and extract the sample features. Then the hidden information among samples was explored by the external attention mechanism. The convolutional long and short-term memory network (ConvLSTM) was further used to capture the spatial characteristics of the data. To achieve optimal results of the model, a genetic algorithm was used to optimize the parameters of the model. The water quality test data of Qinghai Province was used as a sample to simulate and validate the model. The results show that the mean absolute error (M_MAE) of the model is 0.063, the root mean square error (R_RMSE) is 0.012, and the mean absolute percentage error is 2.6%, which are respectively reduced by 18% and 24%, 14% and 25%, 16% and 21% compared with the CNN-EA model and CNN-LSTM model. Therefore, the model can effectively obtain the spatial and temporal characteristics of water quality, attenuate the influence of different samples, and achieve the ideal prediction effect.

In the case that hydrological data only include rainfall station data and measured water level data of river monitoring section, it is always a major challenge to improve the accuracy of flood forecasting in small and medium-sized basins. In this paper, flood automatic coding was realized according to data characteristics, and historical floods were classified by using decision tree model, thus the candidate flood groups and eliminated flood groups were obtained and the calculation efficiency was improved. On this basis, a flood forecasting model was established based on the similarity measurement of spatio-temporal hydrological data. Taking the hydrological data of Dafenshui Basin in Jiangxi Province as an example, a case analysis of hydrological data was carried out, and four floods were randomly selected for verification. The results show that the qualification rate of flood peak water level is 100%, and the qualification rate of flood peak time is 75%, the accuracy is high, which has important theoretical value and practical significance in hydrological data research.

Regarding the impact of the construction of the Guotan Hub of the Tanghe Navigation Project on the flood control safety of the river channel, the design flood of Guotan Hub was calculated through measured flood data of hydrological stations and linear interpolation method. According to the measured cross sections and thalwegs over the years, the river channel scouring and silting evolution and evolution trend prediction were analyzed. The water surface profile of a river was calculated using the energy equation of a constant non-uniform gradient flow equation. The second-order RungeKutta method of a two-dimensional model was used to simulate the impact of construction projects on the flow field during river flood discharge. The results indicate that the Guotan Hub of the Tanghe Navigation Project has a relatively small impact on river flooding so that solved the technical problem of flood impact assessment for Guotan Shipping Hub, which provided reference for relevant departments.

Aiming at the problem of campus waterlogging in Hefei City, this paper constructs a 1D-2D coupled model based on Mike Flood. Firstly, GIS was used to obtain the distribution information of the five types of land surface in the study area by analyzing satellite images, and to automatically divide the catchment areas. Secondly, combined with the measured elevations by using the RTK device, the 3 m×3 m high-precision DEM data of the study area were obtained. A 1D pipeline model and a 2D surface model in the study area were constructed using Mike Urban and Mike 21 respectively, and the two models were coupled on Mike Flood. At the same time, a flowmeter, a liquid level meter and a rain gauge were installed in the campus. The model was calibrated by two measured rainfall events according to R² and E_NSE. Finally, the Chicago rainfall pattern was used to design rainfall scenarios for the 5, 10, 30 and 50 years of recurrence periods, and the severity, inundation range and inundation depth of nodes and pipelines in different rainfall processes were simulated. The simulation results show that main causes for the waterlogging in the campus are due to unreasonable sub-catchment designs, which resulted in limited absorption of rain peak runoff and serious overload of the pipe network.

In view of the frequent occurrence and serious loss of urban waterlogging disasters in recent years, this paper focuses on the current situation of engineering of waterlogging drainage, and takes Lu'an City, Anhui Province, which experienced waterlogging disasters in 2016 and 2020 as the research object. Considering the connection relationship between drainage network and drainage channel systematically, the study analyzes and determines the engineering weakness that cause urban waterlogging from the aspects of the standard of drainage network corresponding to the location of water logging points, the relationship between ground elevation and the design water level of the corresponding receiving rainwater river, the drainage capacity of the river, and the operation conditions of the drainage pumping station, based on the tracking of rainwater discharge process of pipe network-inland river-outland river. The results show that the elevation of water logging point in the old urban area of Lu'an City has the condition of flowing into the river by gravity, and the drainage channel and drainage pumping station can meet the drainage requirements. The main engineering reason for the occurrence of waterlogging is that most drainage network have low standards and can not drain rainwater into the river in time. On this basis, it is further considered that the implementation of the drainage network rectification in the old urban area is difficult and long cycle. In order to minimize the risk of waterlogging before rectification, it is proposed to reduce the operation water level of the drainage pumping station at the estuary of the outland river, so as to improve the ability of urban drainage and disaster reduction.

In order to study the impact of the dam break of the Huiling tailings pond in Guangxi on the downstream region, a three-dimensional model of the tailings pond region conforming to the actual terrain was established with the help of GOCAD and Rhino software. In addition, PFC3D discrete element simulation software was used to simulate the state of dam break when the tailings pond runs to the final accumulation elevation +490 m, and the possible submerged range of tailings discharge and the area affected by tailings debris flow were analyzed. The results show that the evolution rate of tailings debris flow increases rapidly to the maximum value in a short time after dam break, and then decreases gradually. The farther away from the dam site, the faster the reduction of tailings debris flow evolution rate is. When the evolution time of dam break is 1 100 s, the furthest evolution distance of tailings is 1 215 m at the foot of tailings dam, the maximum width of the drainage body is 853 m, and the maximum depth is about 30 m. In the process, many sensitive points are submerged. The research provides decision-making information for early warning, personnel evacuation and flood relief of tailings pond accident.

In view of the case that the high wave wall changes from inclined to vertical near the dam slope and crest, numerical simulation and physical model tests were used to mutually verify the calculation of wave run-up. The working conditions of different wave elements and water depth in front of the dam were analyzed to study the impact of high wave walls on wave run-up in the reservoir. The results show that when the same wave factor is applied to different reservoir depths, the wave run-up shows an inverted parabolic trend with the reservoir depth; The maximum wave run-up occurs at the intersection of the vertical section of the wave wall and the slope section; When the water depth in front of the wall is higher than the intersection of the vertical section and the slope section, the wave run-up calculated by the standard method is larger compared with the results of mathematical and physical models. The finding can provide a reference for the refined design of the top elevation of high wave walls considering the impact of wave run-up in the design of earth-rockfill dam.

In order to study the response relationship between sediment discharge ratio (SDR) and influencing factors under actual water and sediment conditions, based on the measured water and sediment data of the Three Gorges Reservoir (TGR) from 2003 to 2018, this paper discussed the response relationship between SDR and various influencing factors on the basis of analyzing the characteristics of water and sediment from the reservoir, and established the formula of SDR in the main flood season. The results show that the correlation between SDR and single factor is not obvious, indicating that the SDR is affected by multiple factors. From the perspective of reservoir operation and regulation, the SDR is negatively related to the flood detention time, and the sediment discharge efficiency should be improved by shortening the flood detention time; From the perspective of incoming water and sediment, the greater the amount of sediment entering the reservoir, the greater the sediment discharge ratio of fine sediment is; Coarse sediment, on the contrary, is characterized by more coming and less discharging. In the main flood season, the relationship between the SDR and the proposed expression is good. This study can provide reference for the operation of TGR.

In the construction of hydropower projects under the same dam site, the height of water-retaining structures is a key index affected by many factors. In this paper, the responses of three design dam height schemes of a water-retaining structure under static and dynamic superposition conditions were analyzed. The results show that although the dead weight and reservoir water pressure of the arch dam increase with the increase of the dam height, the ground motion response of the arch dam does not all increase with the increase of the dam height. In this calculation case, the beam compressive stress and arch compressive stress on the upstream surface of the arch dam increase with the increase of the dam height, the beam compressive stress on the downstream surface decreases with the increase of the dam height, and the arch compressive stress first decreases and then increases with the increase of the dam height, the forward displacement and openness first increase and then decrease with the increase of the dam height. The research results can provide a reference for the design of water-retaining structures.

With many hydropower resources, Southwest China is a crucial area for current and future hydropower construction. However, most southwestern regions have deep overburden problems and high seismic intensity. The impact of these problems on the regular operation of high-face rockfill dams cannot be ignored. This paper established two-dimensional finite element models of 100 m, 200 m, and 300 m high-face rockfill dams on 100 m-deep overburden. Under the action of long-period ground motion and conventional ground motion, the elastic-plastic constitutive model was used to study the dynamic response characteristics of face rockfill dams with different heights on the same deep overburden. Compared with conventional ground motions, the results show that long-period ground motions significantly influence the acceleration of deep overburdened high-face rockfill dams. As the height of the dam body increases, the peak acceleration of the dynamic response of the dam body gradually decreases. Moreover, under the action of long-period ground motion, the higher the dam body is, the greater the displacement increment of the dam body in a short time. In this way, the resulting deformation is also more significant, which is not conducive to the seismic stability of the dam. Therefore, when building panel rockfill dams in areas with deep overburden and frequent long-period earthquakes, the effect of long-period ground shaking should be considered as a part of seismic stability evaluation.

A new anti-seepage structure between the asphalt concrete slab and geomembrane is proposed, which eliminates the concrete connecting plate and adopts backfilling elastomeric epoxy mortar into drilling holes. The mechanical and impervious properties, as well as anchoring parameters of the connecting joints in the anchorage area, are experimentally studied. It is found that the torsional and anti-pulling performance of the proposed anchoring approach is reliable. The suggested double-channel anchoring approach is more compatible with the large deformation of the geomembrane under a pressure of 0.4MPa. According to the results, optimal drilling parameters are proposed, which have the features of good porosity, reliable impermeability and less impact on the asphalt slab, providing a reference for engineering design.

The common deformation and failure mechanism of retaining wall at foot of earth-rock dam is mainly caused by insufficient bearing capacity of foundation, uneven settlement of foundation, temperature effect or insufficient anti-sliding stability. For a certain project, the retaining wall deformation characteristics are not consistent with the above causes after the drainage of the embankment foot of the earth-rock dam is changed to the retaining wall. The deformation is only visible at the expansion joints of the retaining wall, and the expansion joints are open, closed or misplaced. Through calculation and analysis, it is found that the expansion joint deformation is caused by the retaining wall horizontal displacement caused by the consolidation settlement of the dam, and the size of the deformation is related to the horizontal displacement difference between adjacent retaining walls. The larger the displacement difference is, the more serious the deformation is. At the same time, the horizontal displacement of retaining wall is related to the height of dam section, hydrogeologic conditions of dam foundation. Based on this, it is proposed that after the prism drainage of the downstream earth-rock dam is changed into gravity retaining wall, in addition to the design and calculation according to the standard requirements, the horizontal displacement difference between retaining walls should also be calculated, and the damage of retaining wall displacement and poor drainage to the downstream drainage system of the dam body should be considered. The research results have a good reference value for the correct analysis of deformation mechanism and anti-slip design of retaining wall at dam foot.

Affected by global climate change and human activities, extreme weather events such as drought and rainfall have led to landslides and other disasters in the reservoir dam. At the same time, the impact of evaporation and rainfall on the seepage and stability of the dam slope has not been considered in the design specifications for roller compacted earth-rockfill dams. Taking an earth-rockfill dam as the research object, a finite element calculation model was established to study the impacts of evaporation, rainfall and reservoir water level changes on the pore water pressure, saturation line and safety factor of anti-sliding stability of the earth-rockfill dam. And the cause mechanism of landslide was analyzed in combination with geological exploration and monitoring data. The results show that evaporation and rainfall have a great impact on the pore water pressure of the soil within 0~2 m of the downstream dam slope. The difference between the measured water level of the piezometer and the saturation line calculated by the finite element method is less than 0.4 m. At the initial stage, evaporation improves the stability of the dam slope, but evaporation causes the surface fill of the dam body to shrink and crack continuously, providing a channel for rainfall infiltration. With the increase of the number of rainfall and evaporation cycles and the rising of the reservoir water level, the cracks continue to increase, and the local stagnant areas near the bottom of the cracks are interconnected to form a saturation zone, which leads to the instability and damage of the shallow dam slope downstream of the dam. The research results provide a scientific basis for improving the design specifications of earth-rockfill dams and the early warning of reservoir dam landslides.

The measured deformation data contain rich temporal and spatial information and evolution laws of dam deformation. To study the co-integration relationship of the aging deformation of extra-high arch dams, wavelet decomposition was firstly used to obtain the aging component of the dam displacement. Considering the weak spatial integrity of extra-high arch dams, the FCM clustering algorithm was utilized to realize the regionalization of aging deformation. With the help of the idea of regional linearization, the spatial nonlinear co-integration relationship of the whole dam aging deformation was transformed into several approximate linear co-integration relationships within different regions. The zonal co-integration model was established to describe the development law of time-varying co-integration in different regions of the dam. The co-integration development monitoring and early warning of multi-measuring points aging deformation were realized by co-integration residual.

The Wangyu River is an important watercourse connecting the Yangtze River and Taihu Lake. Relevant hydrological data shows that the pumping opportunity can account for 25.9% of the total drainage period from the Wangyu River to the Yangtze River, which indicates that the pumping station plays a crucial role in the drainage period of Taihu Basin. The current design lift (2.5 m) of the pumping station is higher than the actual operating lift, and the running time of the pumping station exceeding 20% of the installed designed capacity accounts for 65.9% of the total operation time. According to the design specifications of the pumping station and relevant local standards, combined with the analysis of the hydrological data, it is recommended to adjust the design lift of the pump station to 1.78 m in the subsequent upgrading of the pumping station. The optimized design lift is more compatible with the actual operating environment of the pumping station, and it also reduces the operating costs of the pumping station such as power consumption, and prolongs the service life of equipment, which is of great significance for the overall benefits of the Wangyu River Hydro-junction.

At present, most leakage location methods rely on the hydraulic model of the pipe network. However, when the accuracy of the hydraulic model cannot meet certain requirements, or when the model cannot be established due to the lack of basic data, the model-based method will fail. For this purpose, the study of the leakage location of the water supply network was carried out on the basis of pressure monitoring data. Based on the modeling theory of graph theory, the interpolation method for estimating the node pressure of pipe network was obtained. The leakage position was estimated by analyzing the residual of the pressure monitoring value of each node and the measured value after the leakage occurs. With the help of Bayesian theorem, time-series reasoning was carried out on the positioning results, and the node with the largest probability in a certain period of time was regarded as the location where leakage occurs. By using the case of L Town, the state of pipe network was simulated when single point leakage occured, and the feasibility and location performance of the leakage location method were verified.

When the source-based reduction facilities cannot be carried out during the construction of sponge city, the stormwater control measures (SCM) are usually set up at the terminal drainage outlets to achieve the goal of runoff control and pollutant reduction. Because there is usually large drop between the drainage outlet and the waterfront zone in mountain city, resulting in a high flow rate of water from the drainage outlets, it is easy to cause strong hydraulic erosion to the SCM and may adversely affect their normal operation. Based on the falling-sill dissipation facility installed according to the high drop topographic features of drainage outlets in Chongqing urban, the numerical model with FULENT software was constructed to simulate the hydraulic process of different energy dissipation configurations in this study. The results show that the solid-baffle typed falling-sill dissipation facility has out-performance energy dissipation, and the energy dissipation rate was as high as 90%, and the outlet velocity of the end of facilities was irrelevant to the inlet flow, while only related to single drop height. The higher the single drop height, the water flow was susceptible to form a hydraulic vortex in the backwater area of falling-sill under the influence of potential energy, which can lead the greatest extent of turbulence kinetic energy dissipation, and finally result in a gradual decrease of the maximum pressure of water flow in the horizontal direction to achieve the targeted hydraulic energy dissipation.

To study the diversion risk of pumped storage power station construction under extreme rainfall, based on the idea of system risk analysis, the Copula-Monte Carlo method for diversion risk prediction was proposed by considering the correlation between upper and lower reservoir inflow. Joint distribution of the upper reservoir extreme rainfall and the lower reservoir flood volume was constructed to simulate the construction flood process caused by extreme rainfall. According to the characteristics of the upper and lower reservoirs diversion engineering, the risk model of the diversion system in the pumped storage power station was established to simulate the risk rate by considering hydrological and hydraulic uncertainty. Finally, a pumped storage power station under construction in southwest China was taken as an example, the results show Gumbel-Copula joint distribution fits the construction flood well in extreme rainfall cases, the diversion system risk rate is higher and more realistic when considering the correlation. It provides a reference for pumped storage power station construction diversion scheme selection and flood standard design under extreme rainfall.

The three-dimensional seepage analysis and control of underground plants and complex tunnels are related to the long-term seepage safety of underground spaces, which is one of the key technical issues facing the construction of pumped storage power stations by abandoned coal mines. Considering the reinforcement schemes for different surrounding rocks of the lower reservoir, the spatial location of the upper reservoir, the main powerhouse and the coal mine extraction area, a refined three-dimensional finite element model for seepage analysis of complex underground space in Longdong coal mine was established. Three-dimensional seepage field analysis was carried out for typical working conditions during the construction and operation periods. Important design parameters such as external water pressure and seepage volume of the underground tunnels during the construction and operation periods were obtained. Refined simulation of the numerous drainage holes in pumped storage power stations was implemented. By calculations of the seepage field under various unfavourable conditions, the optimal spacing of the drainage holes was determined. The research results are of great significance in the evaluation of seepage safety and the design of underground roadway protection schemes for the construction of pumped storage power stations by abandoned coal mines.

In order to study the shear resistance of the inclined section of steel fiber reinforced concrete beams with BFRP bars, this paper takes the steel fiber reinforced concrete beams with BFRP bars as the research object, and carries out the shear capacity tests of 9 steel fiber reinforced concrete beams with BFRP bars. The effects of failure mode, shear span ratio, BFRP reinforcement ratio, steel fiber volume fraction, and steel fiber range on the shear resistance of steel fiber reinforced concrete beams with BFRP bars are analyzed. The results show that the failure mode of steel fiber reinforced concrete beams reinforced with BFRP is mainly shear failure; The shear capacity of the inclined section decreases with the increase of shear span ratio, and increases with the increase of fiber content and BFRP reinforcement ratio; Setting steel fiber within the shear span of the support can better improve the shear resistance of the inclined section of the concrete beam with BFRP reinforcement. Finally, the formula for calculating the shear capacity of steel fiber reinforced concrete beams with BFRP bars is obtained by fitting test data, and the calculated results of the formula are consistent with the experimental results. The research enriches the design theory of inclined section of FRP reinforced concrete composite structure, and has reference value for the application of FRP reinforced steel fiber concrete composite structure in practical projects.

The shear performance of heterogeneous concrete is very important. In this paper, the parallel bonding model of particle discrete element was used to simulate the direct shear test process of concrete to reveal the shear characteristic and failure mechanism of concrete. The impacts of meso parameters, such as contact modulus, contact stiffness ratio, particle friction coefficient, tensile strength, ratio of cohesive strength to tensile strength, and contact friction angle, on the results of concrete direct shear test results were studied by controlling the variable parameters. The shear deformation resistance of specimen has a significant linear relationship with the contact elastic modulus. The contact stiffness ratio has little impact on the shear test results. Particle friction coefficient, contact tensile strength, ratio between cohesion strength and tensile strength, and contact friction angle have a significant effect on the shear strength parameters. Contact tensile strength, ratio between cohesion strength and tensile strength, and contact friction angle could affact the curve form after peak of shear stress vs. horizontal displacement. This paper provided a reference for particle discrete element simulation of direct shear test of concrete specimens.

In order to ensure the service performance of underwater concrete structures, it is urgent to carry out the detections and quantitative analyses of underwater concrete structure defects. Aiming at the common failure forms of underwater concrete structures such as collapse and indentation in practical projects, model plates with different shapes and sizes of indentations were designed and made. Using the side scan sonar carried by the unmanned ship, the defect model plates were scanned at a constant speed in a test pool. The acoustic characteristics of the defect areas were summarized by extracting the echo intensity waveforms of different shaped defects along the transverse sections. Image segmentation, mathematical morphology processing, and edge feature extraction were carried out on the original sonar image of different sizes of defects to obtain clear and complete contours of the defect areas. Through the interpretation of the longitudinal length of the defect areas, the quantitative analyses of underwater concrete defects were realized, and the identification error ratios were within 10%. It provides a new method for detecting the defects of underwater concrete structures.

In order to explore the microcrack initiation, propagation and damage evolution of rock samples with different crack types (opening and closed), inclination and crack length, based on PFC2D, the fractured rock sample model was constructed and the uniaxial compression numerical tests were carried out. The initial crack and failure characteristics of rock sample under different crack obliquity and type were explained from the perspective of mesoscopics. The damage analysis of rock samples was carried out from the perspective of energy. The results are as follows. With the increase of crack inclination angle, the peak strength of the open type is positively correlated, while that of the closed type decreases first and then increases. The elastic modulus is consistent with the change of peak strength. When 30°≤α≤60°, the microcrack initiation characteristics of the two kinds of fractured rock samples are consistent. When 60°≤α≤90°, the failure paths of the two rock samples are similar. The damage variable and correction coefficient were defined based on the energy of cementation failure, and the evolution model was established. The rationality of the model was verified from the perspectives of fracture type, inclination angle and length. The research results can provide a theoretical basis for further understanding the damage evolution process of fractured rock mass after loading.

Based on elasto-viscoplastic theory of Perzyna and strain energy theory and 3D yield criterion considering the effect of intermediate principal stress, a mesoscopic coupled elasto-viscoplastic-damage model is developed in order to explore the intermediate principal stress effect on the time-dependent behavior of deep hard rock in excavation damage zone. The model is implemented in a software for engineering rockmass fracturing process (CASRock). By comparing modeling results with experimental results, the model and the code are validated. Furthermore, the time-dependent behaviour of ^#1 laboratory of CJPL-II project is simulated, and the time-dependent fracture process of hard rock in excavation damage zones under different intermediate principal stresses are investigated. The results show that the time-dependent fracture behavior of hard rock exhibits an obvious interval effect of intermediate principal stress. It is found that the interval effect of the intermediate principal stress is affected by time through the isochronous curve clusters of the total viscoplastic strain and the intermediate principal stress. Finally, the existence of the excavation damage zone can promote the development of time-dependent fracture of its internal surrounding rock, thereby expanding the scope of the plastic zone.

Landslides induced by typhoon rainstorm has the characteristics of abruptness and difficulty in the investigation. Taking the Shanzao landslide that occurred during the typhoon "Lekima" as an example, based on 24 landscape data of Railway Sentinel-1 from Sept. 12, 2017, to Aug. 9, 2019, this paper analyzed the sequential cumulative deformation of landslides in this period by SBAS-InSAR technology and further analyzed the regularity of surface deformation of landslide mass with meteorological data. The results show that the deformation before the occurrence of Shanzao landslide is mainly divided into three stages: creep stage of landslide mass, deformation of front edge of landslide mass increases significantly and gradually expands toward the middle of the slope mass, and accelerated deformation stage of the rear edge of landslide mass. The vertical deformation rate and accumulated deformation data of InSAR monitoring points on the landslide mass show that the deformation rate and accumulated deformation in the front and middle of slope are small, and it mainly focus on the rear edge of the landslide, with the maximum deformation rate and accumulated settlement of 40 mm/a and 320 mm respectively. The landslide is a push-over landslide. The research results provide a new idea and method for the early identification, monitoring and early warning of landslides, and have a certain reference value for the prevention and control of landslide disasters.

In order to effectively grasp the reactivation mechanism and deformation law of the old landslide, this paper takes the bedding old landslide in a metamorphic rock area as the engineering background and combines the deformation monitoring results to carry out the existing deformation law analysis and deformation prediction research. The result of the case analysis shows that the deformation characteristics of the resurrection body of the old landslide are significant, especially the deformation in the middle of the resurrection body. Through the deformation prediction, it is concluded that the cumulative deformation of the resurrection body will still increase, and its stability will tend to weaken. Among them, the deformation in the middle position has no trend of convergence, that is, the increase rate will also tend to increase, and its stability will weaken more, so it is very important to carry out its prevention and control.

To accurately obtain the health performance level of a pumped storage unit (PSU), a health performance tendency prediction method based on convolution neural network-long short-term memory neural network (CNN-LSTM) is proposed. Firstly, a unit health state model based on Gaussian process regression was constructed to effectively characterize the operating characteristics of the PSU. Then, an index that can quantify the health performance of the PSU was proposed. Finally, by integrating the good local feature extraction ability of the CNN and the advantage of the LSTM in time series prediction, a prediction model based on CNN-LSTM was proposed. The experiments were conducted using monitoring data from a pumped storage station in China. The results show that the proposed method can betterly predict the future evolution of the PSU's health performance.

In order to realize the safe monitoring of the operation status of hydroelectric units and solve the problem of automated watch keeping, based on speech recognition technology, the normal status model of measurement points based on the operation monitoring information of generating units was established to implement abnormality detection. Firstly, the experimental data of the bearings of Western Reserve University were used to verify the correctness of the selected modeling method of deep convolutional neural network (CNN) and Gaussian mixture model (GMM). Secondly, a total of forty-two measurement points were arranged for the turbine set, and ten sensitive measurement points were selected for position classification based on the rise rate of RMS before and after overspeed. Then some data were selected as training data to get CNN model and unit sound features. The GMM model was obtained by further training. Finally, the scoring results of the test data were used to determine the machine operation status, i.e., the degree of deviation from the normal status was determined to achieve abnormal status detection. The experimental scheme was confirmed by manual annotation, thus verifying the feasibility of the method, which realizes the design of sound-based abnormality detection algorithm for hydropower units.

To improve the state detection effect of large supercritical generator rotor set, the RSO (Cyclic Periodic Electrical Impulse) detection method of large supercritical generator rotor set based on time difference calculation is designed. According to the principle of RSO detection method, the characteristics of time difference pulse signal are extracted. The detection model of coil short circuit is constructed according to the time difference characteristics of signal. Wavelet transform is used to denoise the time difference signal. Fix the rotor position and winding parameters are fixed to determine the fault position of the rotor set. Thus, the RSO detection of the rotor set of large supercritical generator unit is realized. The experimental results show that the difference between the detection results of the power spectrum amplitude of the initial rotor position, the rotor position at startup, the normal broken bar and the broken bar fault is small, which verifies the effectiveness of the proposed method.

In order to solve the problem that the new hydraulic gate is difficult to manufacture experiment and debug in the real environment, the historical gate operation data was analyzed and transmitted based on the digital twin simulation platform. The designed gate was analyzed through numerical simulation, and the overall stress and deformation changes of the gate with different sub-gate opening degrees under hydrostatic pressure were analyzed. At the same time, the overall vibration frequency changes of the gate under the action of air and fluid-structure interaction were analyzed. The flow state of the fluid domain at the sub-gates with different opening degrees was simulated. The results show that with the increase of the opening of the sub-gate, the stress value of the gate varies from 58 MPa to 67.5 MPa, and the deformation change is not obvious; Compared with the natural vibration frequency of the gate in the air, the fluid-structure coupling effect will appropriate reduce the natural vibration frequency of the gate; Different sub-gate openings will affect the flow state of the fluid domain, and increasing the opening will reduce the water velocity. The results provide some references for its actual operation, maintenance and optimization of gate performance.

In view of the serious problem of scouring under the sluice gate of the Tidal River, taking the Shanghai area as an example, from the perspective of operation and maintenance management, the scouring mechanism under the sluice and the optimization method of operation and maintenance management were explored. Through the flow state analysis and hydraulic jump formula derivation, the variation law among the water level, the critical water depth of the outer river and Froude number in front of hydraulic jump was revealed. The water level solution formula suitable for the operation and maintenance management of the tidal estuary gate was proposed. The results show that the water level of the outer river fluctuates greatly because the tidal estuary sluice is affected by tidal action; When the water level of the outer river is lower than the critical water depth, it should be prohibited to open the gate; When the Froude number in front of the hydraulic jump section of the outer river level is between 4.5 and 9.0, the drainage of the gate can be effectively exerted, and the erosion under the gate can be effectively reduced. The results can provide a reference for the operation and maintenance management of similar tidal estuarine gates.

To decrease the costs associated with wave energy conversion and improve the performance of wave energy converters (WECs), a multi-float WEC that also serves as a breakwater is proposed, and its hydrodynamic performance is explored through physical model tests. The control variable method was used to investigate the free water surface, the dynamic response of the floats, and the energy conversion of the device under different PTO damping loads and wave conditions. These tests allowed for an analysis of the wave energy capture, as well as the device’s ability to prevent and dissipate waves. The test results show that the device functions well as a breakwater, with an average transmittance of 0.48 under typical test conditions, meaning that less than a quarter of the wave energy is transmitted to the rear of the device. Moreover, the device can effectively convert wave energy, with K_e exceeding 20% within the range of 0.64≤kh≤1.39 under suitable PTO loads.

For the transmission line distributed traveling wave fault ranging system, this paper proposes a distributed fault location matrix algorithm of transmission lines based on traveling wave time difference information. The algorithm uses the principle of double-ended traveling wave ranging to construct the lower triangular fault location matrix by combining the monitoring node data two by two. The nature of matrix rank was used to select the fault point area and calculate the fault location distance simultaneously. The matrix zeroing algorithm was set to accelerate the find of matrix rank. The distance correction algorithm was set to improve the accuracy of positioning results. The applicability and reliability of the distributed traveling wave fault location matrix algorithm for transmission lines were verified by modeling and simulation with PSCAD and MATLAB software. The necessity of the corrected zeroing algorithm and the significant improvement of the distance correction algorithm on the fault location accuracy were demonstrated by comparison during the operation.

The low voltage winding interturn insulation fault of dry-type transformer is not easy to find directly through the appearance of the phenomenon, and is difficult to real-time monitoring, seriously affecting the safe and stable operation of power systems. In view of the lack of fault detection methods due to insufficient research on the electromagnetic characteristics of single-turn interturn short-circuit faults in low-voltage windings of dry-type transformers, and the difficulty in setting interturn short-circuit faults in practical projects, finite element simulation software was used to establish a field-circuit coupling model which is consistent with the actual dry-type transformer, and the accuracy of the model was verified under rated operating conditions. On this basis, the variation rules of electromagnetic parameters of short-circuit turns at different positions were explored when interturn short-circuit faults occur in low-voltage windings. The distribution of electromagnetic force on short-circuit turns when interturn short-circuit faults occur in windings at different positions was simulated. The results show that when the interturn short circuit occurs at different positions of the winding, the maximum magnetic density appears in the outermost short-circuit turn; the outermost short-circuit turn is subjected to the largest radial force, and the innermost short-circuit turn is subjected to the largest axial force. Therefore, it provides a theoretical basis for on-line monitoring and protection technology of dry-type transformer interturn insulation, which is conducive to the research and implementation of measures to improve short-circuit resistance.

New energy grid connection is easy to cause voltage fluctuation, frequency oscillation and other problems. For this, the paper adopts a frequency division control strategy of hybrid energy storage unit, which based on the storage of photovoltaic grid-connected system as the research subject, thus improving the dynamic stability of DC bus voltage, and proposes an improved virtual synchronous generator. According to the characteristics of flexible adjustment of inertia parameters, the virtual inertia and parameters are adjusted adaptively to suppress the frequency and power oscillation caused by the disturbance. Finally, a simulation model of photovoltaic storage grid-connection is established. It verifies that the proposed strategy can not only stabilize the DC bus voltage and supplement the power deficiency under different operating conditions. At the same time, it can slow down the sudden change of the system frequency and reduce the overshoot, showing good grid-connected performance.