Using the daily meteorological dataset of basic meteorological elements of China National Surface Weather Station (V3.0) as a control, the reproducibility of the spatial and temporal distribution characteristics of hourly precipitation in North China during the warm season (June-September) by the China Hourly Merged Precipitation Analysis (CHMPA) and the CPC MORPHing technique (CMORPH) were compared and analyzed. The hourly precipitation and daily variation characteristics of the warm season in North China were further investigated. Results show that the spatial and temporal distribution of precipitation in CHMPA and CMORPH during 2008-2018 is basically consistent with the observation, the estimation of precipitation by CHMPA is generally smaller than the observation, while CMORPH is larger than the observation. The CHMPA data has high spatial resolution and little difference with the actual observation, which is more conducive to the diagnosis analysis of strong convective weather. The overall warm season hourly precipitation in North China is characterized by more precipitation in the southeast and less in the northwest, with normal rain mostly occurring in the plateau area and flash heavy rain mostly occurring in the transition area between the plateau and the plain and the plain area. The warm season precipitation in North China has obvious daily variation characteristics. The large value of precipitation center appears in the afternoon near the mountains, then gradually moves southeast and causes large precipitation in the western part of the North China Plain at night, and the precipitation center reaches the central part of the plain in the early morning of the next day. The precipitation gradually weakened in North China from early morning to noon the next day. The peak of precipitation and precipitation frequency occurs mostly from midday to late afternoon in the plateau area and from midnight to early morning in the plain area. The results provide a theoretical reference for precipitation research and forecast in North China.

To analyze the applicability of CMORPH merged hourly gridded precipitation product in Northern China, the statistical indicators between the observed grid precipitation and CMORPH merged gridded precipitation in temporal and spatial distribution of flood season from 2008 to 2012 were evaluated in the Yihe River Basin. Using the two precipitations as the input of HEC-HMS model, the feasibility of floods forecast of the CMORPH merged precipitation was evaluated. The results show that the CMORPH merged precipitation has a high correlation with the observed grid precipitation, and the flood simulation accuracy is comparable to the result of observed grid precipitation, and performing better in the simulations both runoff volume and flood peak. The satellite merged precipitation has good applicability in flood forecasting in the study area.

Rainfall observations derived from 76 ground rainfall gauges from January 1, 2018 to December 31, 2020 were used to evaluate the accuracy of IMERG Final Run (IMERG_FR) and IMERG Early Run (IMERG_ER) in IMERG (Integrated Multi-satellitE Retrievals for GPM) products over the small Sancha River basin in Guizhou Province. This study aimed to explore the precipitation detection capacity of IMERG_FR and IMERG_ER on different time scales. Metrics for assessment include correlation coefficient (C_CC), relative bias (R_RB), root-mean-squared error (R_RMSE), probability of detection (P_POD), false alarm ratio (F_FAR), critical success index (C_CSI). The performance of IMERG was assessed at different time scale with different precipitation thresholds. The results show that the IMERG_FR and IMERG_ER have a certain precipitation detection ability in the small basin on the whole, and it still needs to improve the accuracy of IMERG products in estimating precipitation intensity.

Flood prediction and design calculation in ungauged region are often restricted by data of rainfall and runoff. Based on the DEM data extraction of Horton geomorphologic parameters in Luoyang river basin, geomorphic units line of Luoyang river was calculated, and the basin confluence and the response relation between geomorphic parameters was established. The three layers of evaporation and saturation excess runoff were used to construct Xin’anjiang model based on geomorphic unit line. Luoyang river basin flood simulation was carried out by combination of genetic algorithm with objective optimization. Compared with Xin 'anjiang model, the results show that the Xin’anjiang model based on geomorphic unit line can obtain better simulation results, which can provide reliable technical support for hydrologic analysis and calculation of small and medium-sized rivers in ungauged region.

Naolihe National Nature Reserve is located in the hinterland of Heilongjiang Sanjiang Plain and is an important ecological function area in China. Based on remote sensing image data and hydrological data of the protected area, this paper inversed the vegetation coverage by pixel dichotomy, analyzed the spatial and temporal distribution characteristics of vegetation coverage in Naolihe Nature Reserve from 1984 to 2021, and studied the influence of precipitation and flooding frequency on vegetation coverage. Studies have shown that from 1984 to 2021, the low and middle vegetation coverage areas of Naolihe wetland first increased and then decreased, while the middle and high vegetation coverage areas showed the opposite trend. From the correlation coefficient between annual monthly precipitation and monthly vegetation coverage, the vegetation growth in Naolihe Nature Reserve is greatly affected by precipitation, which is positively correlated, and the response of vegetation coverage to precipitation is about one month behind. When the frequency of wetland flooding is between 0.45 and 0.50, the wetland vegetation grows well. The research can provide reference for Nalihe wetland ecological protection.

Analyzing the hydrological response of mining activities in the Loess Plateau will help to promote ecological protection and high-quality development in mining areas. This paper selected four typical small watersheds of Baima River, Songta River, Xinshui River and Zhouchuan River on the Loess Plateau, and conducted a study on the applicability of 8 base flow segmentation methods in the Loess Plateau. The difference of anomaly cumulative percentages (DACP) based on paired watersheds was employed to analyze the impact of mining disturbances on the base flow process in the basin. The results show that the Chapman-Maxwell filtering method and the Eckhardt filtering method have the best applicability in the typical small watersheds of the Loess Plateau, the segmented base flow is relatively stable, and the base flow hydrograph conforms to the precipitation and runoff mechanism and the water regression process of the watershed; The base flow of the four small watersheds showed significant downward trends from 1956 to 2012 as a whole; With the increase of mining disturbance intensity, the DACP index of base flow increased, and mining disturbance increased the base flow of the basin.

In order to study the adjustment characteristics and response of the important shoals in the bar area of the Yangtze River estuary under the influence of sediment discharge decreasing and human activities, this article took the Hengsha shoal, the Jiuduansha shoal and the eastern Nanhui beach as examples. The measured hydrological and topographic data were used to investigate the morphological adjustment of the shoals and the response to changed environment. The results show that in recent years, the two-dimensional geomorphology of the shoals were shrank in the bar area of the Yangtze River estuary, and the tail of the shoals stop progradation in general. The Hengsha shoal and Jiuduansha shoal had different degrees of tidal creeks development; Empirical relationships were developed between the areas of the Hengsha shoal and the previous seven-year average fluvial erosion intensity during flood seasons. This relationship can be used to reflect the change tendency of shoal’s area with the altered flow and sediment regime; The estuarine regulation project can restrain some part of the shoal’s erosion, which was caused by the variation of the flow and sediment conditions. However, the estuarine regulation project may have a slow and long-term cumulative impact on the surrounding regions.

Aiming at the problem that the evaluation and prediction of water resources carrying capacity involves multi-factor comprehensive indicators, particle swarm optimization algorithm was used to optimize the training parameter penalty factor C and kernel parameter σ in the support vector machine model, and a water resources carrying capacity prediction model was established based on PSO-SVM. According to the index grade standard, the training set data was constructed to evaluate the water resources carrying capacity of Heilongjiang Province in 2017. The results show that the water resources carrying capacity index of Heilongjiang Province in 2017 is between 0.423 4 and 0.709 2. The water resources carrying capacity in some areas is at level II, the carrying capacity is weak, and there is still much room for improvement.

In order to analyze the influencing factors and their correlations of water use efficiency, incorporate all independent variables and overcome multicollinearity, the partial least squares method was used to study the correlation factors of water use efficiency in 2019 in China. The results show that the partial least square method can describe the correlation between variables effectively. Factors that are highly correlated with water consumption per ten thousand Yuan of GDP are natural conditions, social development level, GDP proportion of added value of primary industry, and the proportion of labor force in the water industry. The overall economic water use efficiency is high in the eastern region and low in the western region. Factors that are highly correlated with actual irrigation water consumption per mu of cultivated land are natural conditions and GDP proportion of added value of primary and secondary industries. Agricultural water use efficiency is high in the central region and low in the western region. Factors highly correlated with the water consumption per ten thousand Yuan of industrial added value are natural conditions, sewage treatment rate, urbanization rate and the capital proportion of water industry. Industrial water efficiency is high in the eastern region and low in the central region. Factors highly correlated with per capita public water consumption are per capita water resources, annual precipitation, sewage treatment rate, per capita GDP and GDP proportion of added value of primary and secondary industries. There is little correlation between regional factors and public water use efficiency. The research results can provide reference for the optimal management and rational utilization of water resources.

The tidal river network area has the characteristics of criss-crossed water systems and developed cities. High intensity land use and development leads to serious hydrological pollution and degradation of ecological environment functions of urban landscape lakes. Taking the typical urban landscape lake in the river network area - Baiyun Lake in Guangzhou as the research object, this paper constructed a two-dimensional hydrodynamic and water quality coupling model to study its eco-environmental water demand and its water supplement schemes. The results show that the two-dimensional hydrodynamic and water quality coupling model in the river network area based on Mike21 can effectively simulate the temporal and spatial evolution law of water quality in urban landscape lakes, and the relative errors between the simulated values and the measured values are less than 0.20, Nash efficiency coefficients are greater than 0.75. By jointly using Baiyun Lake sluice and pump hydraulic engineering to dispatch and replenish water, the assurance rates of eco-environmental water demand of Baiyun Lake and its connected rivers are basically 100%, the contents of TN and TP meet the fourth class water quality. The research results can provide reference for ecological and environmental governance of urban landscape lake of polluted river network.

The ecological security of rivers is not only closely related to the physical, chemical and biological integrity of the river itself, but also affected by the natural, economic and social conditions of the regions through which it flows. Based on the "driving force-pressur-state-function-response" (DPSFR) framework and matter-element extension model, a river ecological security evaluation system was constructed. Taking Hongru River as an example, it was divided into 10 evaluation units according to the spatial differences such as physical geography and water conservancy projects, and the river ecological security evaluation and spatial differentiation characteristics research were carried out. The results show that the ecological safety level of the Hongru River in 2017 was in a critical safety state, and there was a tendency to develop to an unsafe level. Its spatial differentiation characteristics were that the upstream was better than the downstream, and the tributaries were better than the mainstream, especially in the functional and response layers. Among the indicators, total phosphorus, per capita comprehensive water consumption, river longitudinal connectivity, and water quality assessment cross-section compliance rate are the main factors affecting the spatial distribution of ecological security differences in Hongru River. The response is a criterion layer that is significantly related to the spatial differentiation of the ecological security of the Hongru River.

As a key point in early-warning of river system health, alert source verification is an important basis for eliminating hidden trouble and maintaining the river system health. Based on the analysis of the alarm source factors affecting the health status of Dongjiang river system, the alarm source index system was constructed, and the alert sources verification model of Dongjiang river system health was established by the partial least squares regression (PLSR) method. This model was used to verify main alarm source factors for affecting the health status of the Dongjiang river system (2015-2019), and the influence trend and degree of different alarm source factor on the health status of Dongjiang river system were analyzed. The results show that annual rainfall is the most direct and significant positive effect factor on the health status of Dongjiang River system. In addition, factors such as ecological water use, social development and river management level in this basin also play a promoting role. However, the flood disaster, sewage discharge, water for production and living, non-eco-friendly water conservancy facilities in this basin, and inter-basin water transfer have obvious negative effects on the health of Dongjiang river system.

Taking 16 cities and prefectures in Hubei Province as the research object, from the perspective of unexpected output, DEA-SBM model was used to calculate the water environment governance efficiency from 2014 to 2018. Combined with GIS spatial analysis method, the temporal and spatial variation characteristics of urban water environment governance efficiency were explored, and the influencing factors of urban water environment governance efficiency were analyzed by multiple linear regression model. The results show that the efficiency of urban water environmental governance in Hubei Province has rising trend, but there is a difference in time-order changes in water environmental governance between different cities; The efficiency of urban water environment treatment in Hubei Province shows a spatial distribution trend of low in the central region and high in the eastern and western regions; The level of infrastructure and environmental regulation have a significant positive impact on urban water environmental governance, and urbanization level has a significant negative impact on water environmental governance efficiency.

In order to study the correlation and distribution characteristics of arsenic (As 75) and other trace elements in the water of plateau rivers, the trace elements in the water of Yalong River in July 2021 (wet season) and November 2021 (dry season), an important tributary of the Yarlung Zangbo River, were investigated and analyzed. Based on correlation analysis, cluster analysis and principal component analysis, the relationships among arsenic 75 (As 75), boron 11 (B 11), iron (Fe 57), strontium 88 (Sr 88), tin 118 (Sn 118), lithium 7 (Li 7), vanadium 51 (V 51), cobalt 59 (Co 59), nickel 60 (Ni 60), copper 63 (Cu 63), zinc 66 (Zn 66), selenium 82 (Se 82), molybdenum 98 (Mo 98) and lead 208 (Pb 208) in water were explored. The results show that there are significant differences among the elements in wet season and dry season, which can be divided into three categories: The elements with stable contents in wet season and dry season (Ni 60, Co 59, Cu 63, Li 7, Zn 66); The elements with obvious seasonal variation (Sr 88, V 51, Mo 98, Li 7, Se 82, As 75, B 11, Pb 208); Elements less associated with other elements (Sn 118). In addition, most of the trace elements in the Yalong River Basin are related to Ni 60, Co 59, Cu 63, Li 7 and Zn 66. The study can provide scientific basis for understanding the changes of water environment in the basin and subsequent environmental protection.

In order to explore the spatiotemporal characteristics of water quality and its correlation with land use type in the middle and lower reaches of the Chanba River, sampling and monitoring were conducted in April (wet period), August (flow period) and December (dry period) of 2019 based on seventeen sampling sites. The spatial-temporal characteristics of water quality and the identification of main pollution factors were analyzed by employing multivariate statistical, and the relationship between the land use type and water quality indexes was studied by the method of Spearman analysis. The results show that water quality had spatial and temporal characteristics in the middle and lower reaches of Chanba River in 2019. In terms of time, the concentration values of NH₃-N, TP and COD_Mn were maximum in flow period; The order of TP and COD_Mn was sorted as flow period > wet period > dry period. Spatially, the concentrations of NH3-N, TP and COD_Mn basically increased from the middle reaches to the lower reaches. Influenced by human activities along the river, the water quality was mainly polluted by nutrient and organic matter in the middle and lower reaches of Chanba river. Construction land had a positive correlation with pollutants and played a "source" role, while forest had a negative correlation with pollutants and played a "sink" role. The results can provide reference for water environmental management in Chanba River Basin.

To determine the key water quality indicators for influencing the Weihe River tributaries of Chanhe, Bahe, Fenghe and Zaohe Rivers and the minimum water quality index (W_WQImin) is of great significance for simplifying water quality evaluation. The research set up a total of 30 sampling points in the 4 rivers and collected water quality samples in April, August, and December 2019, respectively. Fifteen water quality indicators were analyzed by laboratory experiment and mathematical statistics. It was found that the content of DO in Fenghe River was obviously highest, and the contents of EC and nitrite in Zaohe River and the Bahe River reach after the convergence of Chanhe River were higher than other rivers. In addition, based on 15 water quality indicators, the water quality index (W_WQI) was calculated to evaluate the temporal and spatial changes of water quality of the 4 rivers. This study shows that the water quality indices were generally above the medium level (W_WQI≥51) in all four rivers, and the water quality of the Fenghe River was better among the four rivers. On time scale, the water quality in the spring of 2019 was better than the other two periods. Besides, stepwise multiple linear regression analysis and empirical method were used to determine the appropriate minimum water quality index (W_WQImin), which contains DO, ammonia nitrogen, COD_Mn, turbidity, nitrate nitrogen, $\mathrm{SO}_{4}^{2-}$, and EC. Compared with the W_WQI based on 15 water quality indicators, the relative error (P_PE) is only 4.78%, the linear correlation coefficient R² reaches 0.95, and the root mean square error (R_RMSE) is only 3.99. Finally, the spatial and temporal distribution of W_WQI and the appropriate W_WQImin in the 4 rivers are consistent. Therefore, it can be considered that the selected appropriate W_WQImin can be replaced of WQI, which is more efficient for time-saving, low-cost and high-efficiency water quality evaluation in the basin near the Chanhe, Bahe, Fenghe and Zaohe Rivers.

Under the influence of climate change and land use/land cover (LULC) change, the combined influence of multiple factors has significantly increased the difficulty of probable maximum flood (PMF) estimation. A PMF estimation framework was proposed, integrating post-processing of climate model results, probable maximum precipitation (PMP) estimation and future LULC change setting under climate change scenarios, impact analysis of base flow/antecedent rainfall, and similarity-based PMP spatio-temporal distribution. This new framwork was applied to the Upper Nujiang River Basin. The results show that the uncertainty of base flow/antecedent rainfall and PMP spatio-temporal distribution are important factors affecting PMF for basins, and the dual-drive of climate change and LULC change has a greater impact on PMF, and the amplitude of change increases with the degree of change.

Plain river network, especially near the airport area, has complex hydrological structure, and the flood control and drainage are very important. Taking the Hangzhou International Airport as an example, one-dimensional hydrodynamic model of the river network was built based on MIKE11. The current situation of drainage was analyzed through different startup conditions of the existing drainage pumping station, and the optimization and promotion plan was proposed. The result indicates that the overall drainage capacity of the West Work Area of Hangzhou Airport cannot meet the standard of “once in 20 years”, which needs to be optimized for drainage. Under comprehensive consideration, it is recommended to use strong drainage instead of regulation and storage, and adopt the drainage idea of "mainly strong drainage, combined with regulation and storage" to form an overall drainage pattern of "backbone river channel + strong drainage pumping station".

The problem of waterlogging in old city has become the focus of natural disaster research. Taking Fenghuang District of Nanchang City as an example, the MIKE FLOOD model was established to analyze the risk and causes of waterlogging. Based on the above results, the SWMM model was used to conduct the research on LID layout and optimization. Analytic hierarchy process was used to evaluate its comprehensive benefits, and the optimal cost-benefit scheme was finally obtained. According to the study, the rainfall return period is 5 years, there are 16 waterlogging points, and the risk level of waterlogging in some areas has reached level Ⅳ. It can be seen that the urban waterlogging prevention and control research is urgent. LID combination facilities have a good effect on alleviating waterlogging. The scheme of 22.5% rainwater garden +7.5% pervious pavement is the best. This conclusion can provide technical reference for the following low impact development and construction of sponge cities and the proportion selection of facilities.

In view of the uncertain factors of natural inflow and electricity price during participating in bilateral transactions at different time scales for cascade hydropower plants, there are problems of market share determination, water resources utilization and profit risk since electricity allocated irrationally. Therefore, this paper presented a risk-based optimal combination model of medium- and long-term contract electricity for cascade hydropower stations. To realize the goal of the minimum profit risk under a given confidence, the monthly inflow process was randomly generated by annual inflow data. Three electricity price functions were fitted by different proportions of hydropower stations in the market. The combination of power output and contract electricity of cascade hydropower plants were solved by the loop-Iteration method of hybrid progressive optimization with successive approximation method. The model was demonstrated using the hydropower plants in the southwest region. The results show that proposed model can determine the declaration strategy between monthly and annual bilateral contract electricity, and reduce the profit risk. It can provide reliable basis for bilateral transactions at different time scales of cascade hydropower plants.

In order to optimize the dispatching mode of Luntan hydropower plant, the process of socio-economic and ecological water demand in the downstream were analyzed. Considering the downstream water demand, the monthly generation dispatching function were extracted from the results of optimal generation dispatching by use of stepwise regression method. The results show that the dispatching of Luntan reservoir plays a great role in the downstream water demand process. The main period of water replenishment is from July to the following February, which directly changes the process of power generation diversion flow of Luntan hydropower plant. The NSE coefficients of the generation dispatching function of Luntan hydropower plant based on multiple linear regression model and BP neural network are greater than 0.90 in most months. Considering the advantages of simple structure and convenient implementation, the generation dispatching function based on multiple linear regression model is selected for Luntan hydropower plant. Compared with the results of actual dispatching and dispatching diagram of Luntan hydropower plant, the generation capacity of the dispatching function is increased by 338.4×10⁴ kW·h/month and 183.8×10⁴ kW·h/month from March 2017 to February 2019, respectively. As a result, the water level of Luntan Reservoir can be significantly increased by use of the dispatching function. The research can provide a support for the generation optimal dispatching process of Luntan hydropower plant, and provide a useful reference for many other hydropower plants to improve the practical way of the generation dispatching.

A large area of tensile stress in the middle and lower part of the upstream of a stone-masonry arch dam exceeds the standard and needs to be strengthened. Based on two local reinforcement schemes of a masonry dam, the contact element was used to simulate the joint characteristics of the new and old dam bodies, and the stress and deformation characteristics of the joint surface under five standard working conditions were analyzed. The results show that after reinforcement, the opening and loading characteristics of the joints of the two schemes are similar, and the side pier of the rib pier scheme has asymmetrical opening and loading phenomenon. Under the condition of high water level, the reinforced structure mainly supports the load at the upper part, and the stress at the lower part is small and may open. Under the condition of low water level, the stress level of the joint surface is low and the reinforced structure does not bear the load. Under the condition of temperature drop after reinforcement, the masonry dam body rotates and deforms with the upper part of the reinforced structure as the fulcrum, and the joint surface will open in a large area under the condition of low water level. Under the condition of temperature rise, the dam body shifts upstream when the water level is low, resulting in a symmetrical and smooth parabolic clearance distribution on the horizontal direction.

In order to evaluate the quality of "stepped" concrete cut-off wall of Hejiagou reservoir dam, the ground penetrating radar was used to detect the whole cut-off wall, and the cross-hole ultrasonic method was used to detect the " steps" of the concrete cut-off wall. The detection shows that the overall quality of the cut-off wall is good. Core drilling and water pressure test were carried out in the areas where there may be abnormalities, and the quality of the cut-off wall was comprehensively evaluated in combination with the monitoring data of the osmometer in front of and behind the cutoff wall. The results show that no major quality defects are found on the cutoff wall, local abnormalities exist, and the overall working performance is normal. This comprehensive geophysical detection method can effectively reflect the actual quality of the "stepped" cutoff wall, and the comprehensive utilization of relevant technologies can provide reference for similar projects.

Dewatering in deep well would lead to the decline of groundwater level and reduce the strength and stability of the soil, which affects the construction safety of the diversion tunnel. In order to study the influence of deep well dewatering on the seepage field of the tunnel during the construction period, a three-dimensional seepage finite element model of Chuanqin tunnel of Xixiayuan water control project and irrigation area project was established. The construction plan of the tunnel and the change of Qinhe water level were considered to analyze the seepage characteristics of the tunnel under the conditions of deep well dewatering and without dewatering. The results show that the dewatering of the deep wells affects the tunnel excavation, changes the potential distribution characteristics of the seepage field around the deep well, forms a falling funnel on the infiltration surface. The water level contour is in a backwater ring near the deep wells. Compared with the deep well without dewatering, the maximum seepage gradient and unit width seepage flow of deep well dewatering are increased by 18.6 times and 3.3 times, respectively, and the seepage stability of soil layer under all working conditions meets the requirements. The research results can provide a basis for the design and construction of similar water diversion projects.

The safe and economic support of pressure tunnel under the condition of high head and low crustal stress has always been a difficult design problem in water conservancy and hydropower projects. Based on the diversion and power generation pressure tunnel of Coca Codo Sinclair hydropower station in Ecuador, the combined support type of steel lining and reinforced concrete permeable lining was adopted within the framework of the Norwegian guidelines. The coupling theoretical model of steel lining and reinforced concrete permeable lining considering the influence of crustal stress was constructed to determine the starting point of steel lining. Based on the three-dimensional seepage field analysis, the optimal grouting depth and pressure of reinforced concrete permeable lining of high-pressure tunnel were determined. The analysis of monitoring data during operation shows that the selection of various indexes of the combined support of the pressure tunnel is appropriate. This study effectively solves the problem of safe and economic support of high head and low crustal stress tunnel, and ensures the safety and stability of pressure tunnel structure.

The local open channels play a certain role in regulating and storing water, but the water flow in the junction section with open channel variation and pressure is relatively complex, which may cause adverse water flow phenomena such as air intake, whirlpool and surges. In order to study the hydraulic pattern of the connecting section between the open channel and the pressurized tunnel, based on the water conveyance tunnel of Wenzhou Oujiang water diversion project, a 30:1 large scale normal local hydraulic model was built according to the gravity similarity criterion. The hydraulic pattern, water surface line distribution, velocity distribution and wave characteristics under different conditions were observed through hydraulic model tests. The flow trend, depth, velocity and wave characteristic parameters under different working conditions were obtained. The research results show that the flow in the open channel and the pressurized junction section through the gradual transition is in good shape, and there is no air intake, backflow and surge, which provides support for the safe operation of the project.

In order to analyze the dynamic response law of geotechnical slope, support and cavity structure under strong earthquake, taking a cavity section project in northwest China as an example, this paper firstly proposed a comprehensive management plan and then analyzed the management effect by combining field monitoring and FLAC^3D numerical simulation. Finally, the effect of support structure and cavern chamber on the dynamic response of rocky soil slope was analyzed under strong seismic load, and some suggestions for seismic protection of cavern section were discussed. The results show that after the treatment, the stability coefficient increases from 1.140 to 1.473, an increase of 29.2%; The imposition of the support structure effectively reduces the acceleration and displacement of the slope and cave roof axis; The presence of the cave chamber has a greater impact on the cave axis compared with the impact of the slope dynamic amplification effect; By analyzing the acceleration of the slope and the tunnel axis vault lining, the maddle is very important for the slope seismic resistance. It is suggested that the seismic protection length of the project should take the range of 3.4 and 4.8 times the diameter of the cave.

To analyze the impact of unsteady state friction and tube wall viscoelastic on leakage, based on the energy conservation theory of the transient flow in a closed pipeline, the leakage numerical model for the hydraulic transient pipeline was constructed considering the dynamic term in the unstable friction and the elastic viscosity effect of the pipe wall. The transient flow reverse analysis method (ITA) was improved. As a case study, Xujiaya Reservoir Irrigation District in Shandong Province was selected to carry out field experiments. The leakage process was assumed to be quasi-normal distribution. Based on the field water flow transient test data, pipeline leakage location and leakage amount were simulated. The simulated error was calculated by the ITA method. When a single point leakage occurs in the experimental pipeline, the average location error of the simulated leakage is 1.44%, and the maximum error is 6.89%, the average area error of the simulated leakage hole is 3.85%, and the maximum error is 14.77%. When multipoint leakage occurs in the experimental pipeline, the average error of the simulated leakage location is 1.31% and the maximum error is 3.91%; the average area error of the simulated leakage hole is 1.74% and the maximum error is 4.35%. The study results could provide theoretical and technical support for the leakage detection of water pipelines.

In order to study the hydraulic characteristics of staggered stepped energy dissipaters with different slopes, the flow pattern, flow field, pressure field and energy dissipation characteristics of staggered stepped and rectangular stepped energy dissipaters with slope of 1:2.0 and 1:2.5 under different flow rates were compared and studied by using the method of numerical simulation and model test. The results show that with the increase of the slope of the staggered step dissipator, the three-dimensional vortex scale formed at the step groove increases, the water flow is violent and the water depth is large. The absolute value of the vertical pressure of the step is larger, and the range of negative pressure zone increases. The horizontal pressure distribution of the step under the two slopes is similar, and the closer the step is, the smaller the pressure is. The energy dissipation rate of stepped energy dissipaters with a slope of 1:2.0 is larger. The energy dissipation rate of energy dissipaters with the same slope has a nonlinear relationship with the flow rate. The larger the flow rate is, the slower the energy dissipation rate changes. The staggered stepped energy dissipater is more fully aerated and has higher energy dissipation rate than the rectangular stepped spillway. The conclusions can provide a theoretical basis for the structural optimization of staggered stepped energy dissipater.

In order to obtain a more accurate calculation model of punching shear capacity of FRP reinforced two-way concrete slab, taking the FRP reinforced two-way concrete slab as the research object, using the research methods of literature review, data statistics, model analysis and regression calculation, and with the help of the commonly used calculation model of punching shear capacity of FRP reinforced two-way concrete slab, based on the collected punching test data of 98 FRP reinforced two-way concrete slabs, the inversion method of critical punching section coefficient of two-way slabs was used to establish a new calculation model of punching bearing capacity of FRP reinforced two-way concrete slabs. The model has high accuracy in predicting the punching bearing capacity of FRP reinforced concrete structures under concentrated load. The predicted results are in good agreement with the experimental database. The model has guiding significance for the design of punching shear capacity of FRP reinforced two-way concrete slab, which provides an important reference for further improving the accuracy of punching shear capacity calculation model of FRP reinforced two-way concrete slab in the future.

In order to study the influence of mineral admixture on steam-cured concrete under freeze-thaw environment, CT technology was used to scan the steam-cured concrete after freeze-thaw cycle, and the sectional images were obtained. The three-dimensional reconstruction of steam-cured concrete was carried out by Fiji and Avizo software, and the pore structure characteristics of the samples were obtained. The results show that the compressive strength of steam-cured concrete decreases with the increase of freeze-thaw times, and the deterioration of pore structure is the main reason for the decrease of compressive strength; The mechanical properties and pore structure characteristics of steam-cured concrete mixed with mineral powder and fly ash are better than those of ordinary steam-cured concrete under the same freeze-thaw conditions. The mineral powder and fly ash have a certain effect on improving the pore structure of steam-cured concrete.

To study the evolution law of member properties of hydraulic concrete materials under the coupling effect of freeze thaw cycles and salt erosion, early frozen specimens with different air-entraining agent admixtures (0, 0.005%, 0.01%) were selected and placed in a composite solution with a mass fraction of 3.5% sodium chloride +5% sodium sulfate for freeze-thaw cycle tests. Based on nuclear magnetic resonance (NMR)-fractal theory, the coupling relationship between the fractal dimension of the concrete pore volume and the damage degree of the specimens was constructed. The results show that the addition of air-entraining agents in concrete materials in appropriate amounts can effectively improve the mechanical properties such as elastic modulus and compressive strength of the members under the effect of salt freezing, and can improve the pore structure and frost resistance. The fractal dimension of concrete pore volume tested by nuclear magnetic resonance gradually decreases with the increase of freeze-thaw cycles, which indicates that the addition of air-entraining agent can change the internal pore structure of concrete in the initial state, and the effect is more obvious with the increase of air-entraining agent mixture. The correlation model between fractal dimension of pore volume and compressive strength was established by combining fractal theory, and the best functional relationship between fractal dimension D_MAX and compressive strength was found to be approximately exponential function. The regression coefficients R² is greater than 0.85, and the fitting effect is ideal, which provides a reference for durability assessment of concrete structures.

Analysis of rock fracture seepage plays an important role in evaluation of rock engineering safety. The three-dimensional coordinate points of the rock fracture surface were scanned by a three-dimensional structure optical scanner and visually reconstructed. Parameters such as joint roughness coefficient JRC and topography statistics were used to quantitatively describe the roughness and undulation characteristics of rock fractures. Through experimental research, it is found that when the seepage pressure gradient increases, the seepage in rock fractures will change from linear seepage to non-linear seepage, and the Forchheimer formula can better fit this process. The threshold and Reynolds number of the critical Darcy flow were obtained by introducing he nonlinear factor E. The relative loss of momentum-Euler number was introduced to study the law of fluid energy evolution in the process of fracture seepage. It is found that the Euler number shows a trend that first drops rapidly and then gradually stabilizes. The result has certain guiding significance for actual engineering.

To explore the microseismic evolution characteristics of instability failure of surrounding rock of deep buried tunnel, biaxial compression tests of granite were carried out under different intermediate principal stresses (σ₂). The microseismic monitoring system and high-definition camera were used to monitor and record the failure of granite in real time. The evolution characteristics of microseismic b value and dominant frequency of rock failure process under different σ₂ conditions were analyzed, and the index of microseismic energy release (MSER) was proposed to describe the degree of rock failure. The results show that with the increase of σ₂, the cumulative microseismic energy release, the maximum value of lgN/b and the ratio of low frequency signal before rock failure, and the microseismic energy release rate at rock failure time all increase, while the minimum value of b value before rock failure decreases. In addition, the microseismic precursor of rock instability lists as follows: b value drops to less than 0.8; lgN/b rises to more than 3; High amplitude and low frequency signal appears. The precursors of rock slabbing are high amplitude low frequency signals accompanied by a small number of high amplitude high frequency signals, while the precursors of rockburst failure are that b value drops to less than 0.5, and lgN/b rises to more than 5, and high amplitude signal only appears in the low frequency band.

To solve the disadvantage of high cost and low efficiency in the traditional three-way crack detection methods, a three-dimensional crack change detection method based on binocular vision was proposed. Three-dimensional equivalent model of crack change was established, and the calculation of crack changes was equivalent to the calculation of changes between targets. Three-dimensional reconstruction of cracks was carried out through feature point code matching, spatial coordinate system transformation, three-dimensional coordinate calculation, and the three-dimensional situation of the fracture change was obtained. To verify the accuracy of the method, a unidirectional displacement test was carried out. The results show that the maximum measurement error of the opening and dislocation of the crack is within 0.2 mm, and the maximum measurement absolute error of settlement of the crack is within 0.3 mm, which meets the requirements for crack detection in technical specification for earth-rockfill dam safety monitoring.

The internal defects of rock mass have a significant effect on its mechanical properties and damage and fracture. The influence of fissure angles and bridge lengths on rock mechanical properties and failure was analyzed by uniaxial compression test and DIC technique. The research findings are as follows: The peak stress and elastic modulus of the samples have an obvious change trend with the change of the fissure angle. Compared with the length of the rock bridge, the fissure angle has a more significant effect on the mechanical properties of the rock. With the increase of fissure angle, the number of surface cracks, main failure cracks and surface spalling decreases, while the area of falling blocks increases obviously. However, with the increase of bridge length, the characteristics of crack propagation and spalling are basically the same. In the process of crack propagation, the connection of rock bridge is related to the fissure angle and the length of rock bridge. In the low fissure angle, the failure mode of rock samples is dominated by tensile failure cracks; With the increase of the fissure angle, the performance is as follows: the tension damage crack to shear damage crack transformation to form a mixed tensile shear damage mode; At the same time, with the increase of bridge length, the more difficult the rock bridge is to penetrate, and the local crack expansion failure changes from tensile-shear crack to tensile crack.

Coral sand is an important material for island and reef engineering construction. Its physical and mechanical properties in different marine environments directly affect the design, construction and long-term operation of island and reef structures. In order to study the shear mechanical properties of coral sand under the influence of temperature and salinity, the triaxial drainage shear tests of coral sand in the South China Sea were carried out at different temperatures and salinity by using the self-developed temperature controlled pile-soil interface triaxial tester. The results show that similar to ISO standard sand, the shear stress-strain curves of coral sand have peaks, presenting its characteristics of strain softening; The shear strength of coral sand is not significantly affected by temperature, but it is sensitive to salinity. Compared with fresh water environment, the peak shear strength of coral sand in salt water environment decreases by 2.5%-8.5%, and the lower of confining pressure, the greater of decrease range; Salinity has a deterioration effect on the cohesion of coral sand, and its reduction range is about 30%, but the effect on the internal friction angle of coral sand is not obvious.

Taking Shiping large irrigation area in Yunnan Province as an example, this paper studied the economic value of irrigation water and analyzed the influencing factors of crops in the irrigation area through the benefit sharing coefficient method and residual value method. It is found that the economic value of irrigation water for cash crops and fruits is higher than that for food crops. At the same time, it is recommended to use the benefit sharing coefficient method to calculate the benefits in irrigation district planning. The results of this study can guide similar irrigation district planning and help the construction of high standard modern irrigation districts.

The large pulses superimposed on the upper guide swing time-domain waveform measured by the eddy current displacement sensor of a generator-motor in a certain pumped storage station which affects the accuracy of the post-data processing. The data measured were analyzed in detail, and a three-dimensional finite element simulation model was established for calculation and verification. It is concluded that the fixed mode of the magnetic pole lead of the generator-motor on the upper end shaft is the main cause of large pulse. The temporary measures and completely improvement measures to ensure the accuracy of data were proposed, which are he pulse data elimination method and the sensor replacement method, respectively. It can provide the reference for the accurate measurement of the upper guide swing of a generator-motor with the same type of shaft-through mode.

The phenomenon of oil spilling and oil spilling in the lubricating oil system of the water guide bearing occurs frequently during the operation of the pumped-storage unit, which significantly affects the safety and stability of the unit and the operating environment of the power station. With the help of CFD numerical simulation technology and VOF multiphase flow simulation method, the dynamic characteristics of water guide bearing lubricating oil system in the multi-oil level working condition under the pumping mode of the pumped-storage unit were explored. The research results show that under the low oil level condition, the system flow cycle is formed faster, the flow state is stable and the oil level is low during the transition process, so the oil rejection phenomenon is milder, but too low oil level may lead to unfavorable control of oil temperature; Under the condition of high oil level, the phenomenon of oil spillage in the early stage of the flow mostly occurs near the side of the Pitot tube of the rotating oil basin, and it mostly occurs on the other side of the Pitot tube in the later stage of the flow. Compared with the traditional method of increasing the diameter of the Pitot tube, the method of optimizing the outer wall of the Pitot tube is more effective in suppressing the phenomenon of oil spillage. The results provide a theoretical basis for exploring the causes of the oil spill phenomenon in the water guide bearing lubricating oil system of the pumped-storage unit and the optimization of the oil slinger.

Malfunctions resulting from rub-impact between moving and stationary parts of bulb tubular unit will jeopardize the safety and stability of hydropower units. Aiming at the bulb tubular unit shaft rubbing system, a coupled bending-torsional rotor-runner system with faulty oil receiver under multi-vibration source and corresponding differential equation were established. The Floquet theory was applied to investigate the stability of periodic solution. The results reveal that when faulty oil receiver is taken into account, the system dynamic feature alters dramatically, which aggravates the possibility of system instability and alternates frequency transition between steady and non-steady state. This fault aggravates the unsteady vibration characteristics of different rotating parts, especially for the runner structure response trend, which needs to be paid enough attention. The results can provide useful references for safe operation and stability analysis of bulb tubular units.

In order to analyze the flow characteristics of the plane S-type axial extension tubular pump unit, the software CFX was used to conduct three-dimensional full channel numerical simulation, and the energy gradient theory was used to analyze the flow characteristics of pump unit under different working conditions. The results show that under different flow conditions, the water flow in the inlet passage of the plane S-type axial extension tubular pump is very smooth, and the overall difference is small. The flow pattern in the outlet channel is quite different, and the smaller the flow rate is, the worse the flow pattern in the outlet channel is. The pressure pulsation at the same position in the plane S-type axial extension tubular pump unit is the largest under low flow conditions. The difference of energy gradient in the outlet channel is the largest under the condition of small flow, which indicates that a large energy loss will occur in the outlet channel under this condition. When designing the outlet passage of the plane S-type axial extension tubular pump unit, the length of the smooth section of the outlet passage should be increased as much as possible to ensure the uniform distribution of energy gradient. The research results can provide theoretical guidance for better understanding of the plane S-type axial extension pump device and optimization design.

To ensure the safe and stable operation of large radial gate in service, taking the hydraulic radial gate of Gezhouba Project as an example, the finite element analysis software was used to analyze the static strength and modal to obtain the maximum stress concentration point and deformation of the gate under the design head condition. The vibration intensity of the gate was judged according to the natural frequency, vibration model and maximum deformation displacement. The results show that the deviation between the total design water pressure of the gate and the theoretical calculation is 4.7%, which is located in the 5% error control range. The overall maximum stress of the radial gate is 373.86 MPa and the deformation is 12.938 mm, meeting the design requirements of the specification. The bottom of the panel exists local stress concentration, the overall vibration deformation of the gate is less than 0.508 mm, and the vibration intensity is small. Only low-order frequencies appear in the high-energy region of the pulsating pressure of the water flow, and the possibility of resonance is small.

The space angles of inclined supporting arm of large radial gate are easily confused and mistaken, and its small errors may cause large structural errors, which will affect the manufacturing, installation and safe operation of the radial gate. Therefore, this paper defined, distinguished and calculated several key space angles of the radial gate inclined supporting arm. Taking an actual project radial gate as an example, the influence extent of each key angle of the inclined supporting arm on the manufacturing and installation accuracy of the gate was analyzed. Furthermore, this paper put forward several measures to improve the manufacturing and installation accuracy, which can be used as a reference for the subsequent design, manufacturing and installation of radial gate with inclined supporting arm.

As the most basic precipitation collection equipment in the field of hydrometeorology, the tipping bucket rain gauge has the characteristics of practicality and good stability, but there are some deficiencies in the research on the tipping characteristics and mechanism of the tipping bucket rain gauge and the causes of the mechanical error of the tipping bucket rain gauge. In this study, the mechanism of the tipping process of tipping bucket rain gauge was explored by means of combination of numerical simulation and indoor experiment with high-speed camera. The results show that during the turnover process, the time from start to stop is about 0.35-0.40 s, the time t₁ from start to level is relatively high, about 80%-85%, and the time t₂ from level to stop is only about 0.05 s, and there is a slight rebound after the turnover touches the adjusting nut. During t₁ period, water will be continuously injected into the tipping bucket, which is the fundamental reason for the change of additional water volume and mechanical error of rain gauge with rain intensity. The tipping bucket will pour out the water in a very short time (about 0.4 s), and because the tipping bucket will cause slight rebound when touching the stop bolt, it will cause the "double peak" phenomenon of the tipping flow of the rain gauge tipping bucket when pouring out the water, and it will increase with the small installation inclination of the tipping bucket on the left and right. The research results can provide basic theoretical support for the improvement of tipping bucket rain gauge in the future.

In the hydraulic transition calculation of long-distance water transmission pipeline, the intake and exhaust coefficient of air valve is mostly constant. In order to explore the influence of the intake and exhaust coefficient of water hammer air valve on the change of pipeline pressure, the DN100 water hammer air valve was simulated by FLUENT software to obtain the mass flow at -9 kPa -11 kPa, and the dynamic intake and exhaust coefficient curves with different pressure differences were established. Taking Xishan primary water lift pump station as an example, dynamic value and fixed value were adopted for air valve inlet and exhaust coefficient respectively (mean value 0.55) to calculate and compare the transition process. The numerical simulation results show that the improved dynamic inlet and exhaust coefficient of the air valve has little impact on the negative pressure of the pipeline and great impact on the positive pressure. The improved dynamic inlet and exhaust coefficient effectively reduces the pressure fluctuation in the pipeline. In the actual operation of the pump station, it is necessary to pay attention to the positive pressure change of the pipeline, and strengthen protection. The calculation of water hammer prevention should be based on the measured data of air valve inlet and exhaust. The research results can provide some references for the hydraulic transition calculation of air valve in the operation of pump station.

Aiming at the inability to accurately locate the fault of the transmission line in hydropower station, an improved double-end location algorithm independent of wave velocity was derived from the actual propagation theory of traveling waves. Using the unique advantages of variational mode decomposition (VMD) which can adaptively decompose fault current traveling wave signals, and the Teager energy operator (TEO) which can quickly track the energy change of signals and has less computation, a traveling wave positioning model for 220 kV transmission lines based on VMD-TEO was established. The model does not need to consider wave velocity correction and double terminal time synchronization. The simulation results of PSCAD show that the maximum error percentage of the improved double-end fault location model is 0.239%, which is superior to other location algorithms. The reliability and superiority of the proposed method were verified.

In practical engineering, there are few samples of arrester failures, and it is difficult for intelligent algorithms such as neural networks to make accurate judgments. To this end, a fault diagnosis method of arrester based on Bayesian network was proposed. Firstly, the principal component analysis was used to extract 21 characteristic parameters that affect the operation of arrester. And then the extracted characteristic parameters was chosen to establish two-layer information architecture defect diagnosis model. The classification probability of different categories was calculated according to the existing real-time data. If the first classification result indicated that the arrester is abnormal, new detection evidence was added for the second diagnosis. Finally, 6 arresters under the same voltage level in a certain area were selected to analyze and verify the validity and correctness of the proposed method.

A CVMD-GRU-DenseNet model for short-term load forecasting based on a decomposition-prediction-reconstruction framework is proposed to aim at the nonlinear and multi-period characteristics of power load time series. In the decomposition stage, the optimal decomposition number of VMD is determined according to the correlation entropy between subsequences to improve the decomposition quality. In the prediction stage, the input features are selected according to the characteristics of each sub-sequence. The GRU neural network and the DenseNet model are employed to forecast the regular low-frequency and highly random high-frequency components, respectively. Finally, the prediction results for each element are reconstructed into a load prediction curve. The short-term load forecasting results of four seasons for a city in Hubei Province show that the proposed method can effectively improve forecasting accuracy and has strong generalization ability.

Aiming at the topology optimization of large-scale offshore wind power collection system, an improved partheno genetic algorithm was proposed. The calculation model of the present value of the life cycle cost of the power collection system was established. Taking the minimum of the sum of present value as the goal, the population generation mode meeting the current carrying capacity constraints of the submarine cable and the elimination coefficient related to the number of crossing points were designed to avoid the submarine cable crossing. The topology of the power collection system with 35 kV and 66 kV voltage levels was optimized and compared. The example results show that the total cost of the improved partheno genetic algorithm can be reduced by 14.2% compared with the traditional algorithm; Compared with 35 kV, 66 kV voltage level has better comprehensive benefits, which can provide reference for the planning and design of large-scale offshore wind farm power collection system.

In order to improve the prediction accuracy of ultra short-term wind power, a combined wind power prediction model based on IEWT-FE-BO-LSTM was proposed. Firstly, an improved empirical wavelet decomposition (IEWT) was used to decompose the historical wind power data. The Fuzzy Entropy (FE) algorithm was introduced to calculate the complexity of each decomposed submodel and reconstruct the submodel. For each recostructed component, a prediction model based on long short term neural network (LSTM) was established. Bayesian optimization algorithm (BO) was used for hyper parameters to solve the problem of poor training results caused by manual parameter adjustment. The example analysis based on historical wind farm data shows that the IEWT-FE-BO-LSTM model has high prediction accuracy and efficiency for ultra short-term wind power.