The origin and development processes of the urban water environment engineering are summarized. The presenting modes of functions and forms of the water engineering buildings are systematically analyzed, including functions comply with standards, forms follow culture, functions create forms, forms guide functions. From the perspective of new demands for urban development in the new period, the collision problems of common water engineering buildings between functions and forms are demonstrated. Finally, a dialectical unified design method is studied and proposed, including five aspects: the negation of negation of functions, the diversified interconversion of forms, the combination of time and space, the combination of overall and local parts, the combination of dynamic and static states. In conclusion, the research results could provide a good example and reference for the current water environment engineering.

In order to study the changes of phytoplankton community characteristics and its relationship with environmental factors before and after decommissioning of Pingshan Reservoir in autumn, four monitoring data in autumn of 2015-2018 are selected to analyze the changes of species and quantity of phytoplankton in composition. The relationship between phytoplankton community and environmental factors is studied by using Redundancy Analysis. The Margalef D index, Shannon-Wiener index H′ and Pielou index J of Pingshan Reservoir before and after dam demolition are studied and water quality is analyzed. The results show that before the decommissioning of the reservoir, Chlorophyta (42.25%) and Bacillariophyta (36.36%) are dominant, and the proportion of Cyanophyta is the largest (73.11%) in the four months of decommissioning (2016.09). In the autumn of 2017 and 2018, the proportion of diatom is 77.22% and 28.80%, respectively. The main environmental factors affecting phytoplankton community are TP, NH3-N, TSS and EC. The diversity of phytoplankton in Pingshan Reservoir is at a low level. After decommissioning, the Shannon-Wiener index and Margalef index of phytoplankton showed an upward trend. The ecosystem has gradually recovered.

It is of great significance for improving water quality and alleviating environmental problems of water conservancy projects to study the characteristics of stratified reservoirs and its influence on water environment. By reading and sorting out a large number of literatures at home and abroad, this paper reviews the causes, research methods, water quality response characteristics and the applications of current mitigation techniques of the stratified reservoirs. In addition, this paper analyzes the current research status and prospects the future developments.

Due to its wide pollution, large output, rapid growth and difficult collection, rural sewage in China has become a prominent problem in the comprehensive improvement of rural water environment. From the existing engineering examples, the urban centralized pipe network collection and processing model is not applicable to the relatively scattered rural reality. China has gradually shifted to the direction of “distributed treatment and local reuse” in the rural decentralized sewage treatment model. The source separation technology has the ecological connotation of resource and energy recycling, and will be a useful supplement to the rural dispersed domestic sewage treatment technology system. Through an analysis of the characteristics of rural domestic sewage, the principle and development history of source separation technology, the classification of source separation technology, and the short board of source separation technology, the application prospect of this technology in resource-oriented rural sewage treatment demand are discussed.

Non-point source pollution has a serious impact on water ecology and water environment. It is an important method to control the non-point source pollution in watershed to recognize and renovate the critical source area. Based on the phosphorus index model, a semi-quantitative non-point source pollution loss risk assessment model is proposed, with land use type as the source factor and distance from a river as the transfer factor, which identifies the key source areas of non-point source pollution in Taizhou by combining GIS spatial analysis technology. The results show that the risk of non-point source pollution loss in most areas of Taizhou was sorted into the category of “medium to high risk”. Low-risk areas were mainly concentrated in the northwest of Xinghua city and Tongnan area. The critical source areas of non-point source pollution output were distributed in cities, towns, villages and other areas with high human activity intensity and on both sides of major rivers. The critical source areas of non-point source pollution output need key governance and strictly control pollution output.

In terms of water supply, there are water environment problems such as lack of water resources and deterioration of water quality in northern rivers. According to the ratio of water resources from industry, agriculture and biological production, the water demand of agricultural and planting industry in northern areas accounts for more than 70% of the total water supply, and the pollution load is mainly non-point source pollution load. The guarantee of agricultural and sideline products in Beijing-Tianjin-Hebei Green Base Yanghe watershed as an example, based on the early stage of the Haihe River Basin ecological water requirement calculation methodology research results, selection of hydrology and water quality target method to calculate Yanghe River Zuowei, Xiangshuipu, Jimingyi and No. 8 Bridge’s four typical sections minimum ecological water demand, suitable and ideal, the calculation results show that: with the reference of Tennant Method, this calculation result is relatively reasonable. ① the minimum, appropriate and ideal ecological water demand calculated with COD index as the ecological target is 0.82, 1.64 and 248 million m3 respectively. ② the minimum, appropriate and ideal ecological water demand calculated with NH+4-N index as the ecological target is 0.83, 165 and 249 million m3 respectively. At the same time, considering the ecological water demand for agricultural irrigation in Yanghe River Basin comprehensively, CROPWAT model is used to calculate the crop water demand in the target region, and an appropriate amount of ecological demand for ensuring the crop irrigation in Yanghe River Basin is proposed, and the corresponding reservoir regulation and storage plan is formulated. As the largest reservoir in the main stream of Yanghe River, Youyi Reservoir needs to fill 0.006 million m3 water source downstream to meet the requirements of crop water demands.

Ecosystem water consumption (i.e. evapotranspiration, ET) is one of important components of the water cycle. The accurate estimation of ecosystem water consumption is crucial for the demand-determined supply and sustainable management of water resources in water scarce regions. In this study, the water consumption characteristics of the Daqing River Basin (DRB) in the North China Plain, where the Xiong'an New Area (XNA) is located, is investigated comprehensively using an ecohydrological model (i.e. WAVES) with balanced and coupled water-carbon-energy structure. The WAVES model is calibrated against the remotely sensed leaf area index and evapotranspiration data in three typical ecosystems of the DRB (i.e. farmland, grassland and woodland). Results show that the average annual water consumptions from 1982 to 2014 of farmland, grassland and woodland ecosystems in the DRB are 383.9, 424.5, and 439.6 mm. For different ET components, the soil evaporation and transpiration are roughly equal in farmland and grassland ecosystems, accounting for 40-50% of total water consumption, while that of the woodland is dominated by transpiration, accounting for about 70% of the total water consumption. This paper serves as a reference for the water and land resources management in the DRB and XNA with high-intensity human activities and over-utilized water resources.

In order to study the gravity erosion phenomenon of artificial loess slope, the finite difference software FLAC3D is used to redevelop the complex erosion terrain model, and the gravity erosion process on the slope is analyzed. The slope displacement field, stress field and plastic yield zone were analyzed. The results show that the three-dimensional model established by software can truly restore the topography of the erosion slope, and the simulation effect is good. By monitoring the displacement law of the point, the erosion is divided into three stages, and the erosion development stage of the lower part of the slope is earlier than the upper part of the slope. The erosion development is completed; the displacement of the slope is mainly sedimentation, and the stress concentration is caused by the increase in the slope. To a certain extent, the increase in the slope aggravates the occurrence of gravity erosion. By analyzing the stress of three consecutive rainfall slopes, it is found that the erosion terrain of the field is basically consistent with the distribution of the plastic zone in the equilibrium state of the previous model, indicating that FLAC3D can predict the development of the erosion terrain to a certain extent.

Sand loss caused by the damage of expansion joint is one of the main reasons for the void of protective face and the damage of dike body. To study on the sand loss characteristics of the seawall with damaged expansion joints, a seawall model with variable location and size of damaged expansion joints is designed, and a series of wave flume model test are carried out. The three-dimensional laser scanner is used to scan the model before and after the wave action, and the high-precision three-dimensional point cloud data is obtained. The effects of location, length and wave action time on sand loss and maximum scouring depth of seawall are studied quantitatively. In addition, the migration law of sand with different particle sizes under wave action is obtained by marking with different colors, and the mechanism of sand loss is preliminarily discussed. The results show that ① The sand scouring patterns of the seawall are U-shaped, and the more easily the sand is lost when the damaged zone is under the water surface. ② With the increase in the length of the damaged zone or wave action time, the sand loss becomes more obvious. The relationship between the length of the damaged zone and the amount of sand loss is linear, and the relationship between the maximum scouring depth and the length of the damaged zone is logarithmic. The relationship between the wave action time and the amount of sand loss and the maximum depth of sand erosion is logarithmic. ③ Positive pressure generated by wave climbing pushes sand particles away from the damage zone. The smaller the particle size, the easier the sand particles are pushed away. Negative pressure generated by wave fall brings sand particles out of the damaged zone. The smaller the particle size, the easier it is to be taken out.

In order to investigate the characteristics and evolution of phytoplankton community in lake-type drinking water sources in Suzhou, from July 2016 to June 2017, the sampling of 9 lakes in Suzhou was carried out in different seasons. Five representative drinking water sources of Yuyangshan, Puzhuang, Shanghu, Yangcheng and Kuilei Lake were selected for cluster analysis. A total of 186 species of 86 genera and 86 species of phytoplankton were detected in 5 drinking water sources. The number of species of chlorophyta was the highest, with 38 species and 87 species, followed by diatoms and cyanobacteria. The total algae density and biomass were Yangcheng Lake and alfalfa. There are many lakes, and the cyanobacteria and diatoms have a greater advantage. Based on the assessment of phytoplankton diversity index and comprehensive nutrient index, the water sources of Yuyangshan, Puzhuang and Shanghu are generally in a state of medium nutrition, and the water sources of Yangcheng Lake and Wuhu Lake are in a state of mild eutrophication. Pearson analysis showed that phytoplankton community was positively correlated with TN, TP, NH3-N and CODMn, and negatively correlated with DO, pH and SD. Phosphorus was the dominant factor affecting phytoplankton growth.

In order to reveal the structure characteristics of aquatic community in Jiuquwan Reservoir, this paper samples and analyzes phytoplankton and phytoplankton from top to bottom along the reservoir. At the same time, combined with water quality monitoring data, Pearson correlation coefficient analysis method is used to determine the correlation between water quality and aquatic community in different periods and locations. The results show that: ① From August 2016 to July 2018, 81 species of algae were collected from Jiuquwan Reservoir, of which cyanobacteria was the most abundant species; the average cell density of phytoplankton was 25.335×104 cells/L, and the average biomass was 109.11 mg/L, which was rich in species and quantity. ② There are 53 species of zooplankton in four categories, of which Rotifera is the most abundant, accounting for 54.72%; the average density of zooplankton in the whole river reaches is 91.00 ind./L, the average biomass is 1.16 mg/L, and the composition of the whole community is relatively simple. ③ The water quality was slightly polluted, in which the total nitrogen concentration was 2.33 times higher than the standard. The correlation analysis showed that the correlation between the biological density of Cyanophyta and pH value was the strongest, that between the biological density of Cyanophyta and DO value was the strongest, and that between protozoa, rotifers, cladocerans and copepods and pH, BOD5 and ammonia nitrogen were negatively correlated, and that between the biological density of Cyanophyta and DO and total nitrogen was positively correlated. The results can provide a scientific basis for the further operation planning of Jiuquwan Reservoir.

Hangzhou Babao Drainage Pump Station with large drainage is the important hydraulic engineering of Expanded Hangjiahu Nanpai. The design drainage discharge is 200 m3/s, it is also the key project of the second channel connecting Beijing-Hangzhou Canal and Qiantang River. When the pump station is running, it influences the navigation flow condition and water-way erosion, because of the confluence of lock approach and the pump intakes. Based on the two-dimensional numerical model of the pump station and water-way near the pump, the velocity distribution near the pump intakes under different operating conditions is analyzed, and the operation scheme for the safety of water-way near the pump is proposed.

This research focuses on the influence of the Dam Gates on the connectivity of river basin (taking Fuhe River as an example), and analyzes the differences between the lateral and vertical connectivity indexes and the connectivity indexes of dendritic river networks so as to select the most reasonable evaluation indexes to study the aspects through which Dam Gate block and destroy the connectivity of river basin. In this paper, the dendritic connectivity index is used to evaluate the river basin and the influence of the number of dam gates, the geographical location and the capacity of the river on the connectivity is discussed. Finally, the feasibility of removing the dam gates with the priority of obstacles is explored, and the rationality of removing the dam with the priority is verified by comparing the random simulated removal of the dam gates with the simulated removal of the priority determined by analysis.

In order to quickly trace the sudden water pollution incident and obtain the emission location, emission and emission time of pollutants, this paper proposes a pollution source information inversion algorithm based on Bayesian and Markov Monte Carlo method. Based on the Bayesian-MCMC method, the likelihood function can be constructed based on the previously known information of the pollution source, and the posterior probability density function of the pollution source can be obtained, and then the traceability problem can be transformed into the sampling problem of the posterior probability density function. In the sampling method, the M-H sampling method and the Gibbs sampling method are selected, improved and compared. The results show that the method can trace the transient emission events of sudden point source more accurately, and the calculation result is close to the true value, which can effectively solve the traceability problem of instantaneous emissions of point source rim pollutants. And the improved M-H sampling method can effectively speed up the convergence speed in the iteration, so that the sampled value of the parameter to be inverted is closer to the target value.

Under rainwater and flood scenarios, which include the rainfall under different repetition period and the different lowest control water level of conditioning storage area, MIKE is used to simulate the drainage process of Qingshanhu drainage area (a zone in the central city of Nanchang). Based on the comparison of the statistical parameters such as the load of the pumping station, the water level and flow of the main control section, this paper analyzes the influence of the municipal drainage and urban drainage system under different rainwater and flood scenarios, and puts forward the joint scheduling strategy of the urban drainage system, which includes setting the time and threshold of water level under different rainfall conditions, establishing and improving the emergency operation rules of pumps, so as to effectively reduce the peak value of flood level, and maximize the existing functions of the waterlogging control system.

Based on the joint results of water quality and quantity of different water levels in urban rivers and lakes, this paper establishes a multi-objective evaluation index system including hydraulic conditions, water quality improvement and water transfer cost. The weight method is used to solve the problem. The urban rivers and lakes are at different water levels and water quality. The different ecological water transfer flow schemes in the state are compared, and the ecological water transfer flow of Qingshan Lake, Xianghu Lake, Aixi Lake and Meihu Lake in Nanchang City are optimized. The proportion of water storage in Nanchang City is reversed to obtain the annual ecological water transfer in different water levels and water quality conditions of urban rivers and lakes in Nanchang City, and the average number of ecological water transfers per year is 11.5 times.

The number of impeller blades is an important parameter in the design of multiphase pump and is closely related to the performance of the pump. In order to investigate the effect of blade numbers on the pressurization performance of the self-developed multiphase pump, the Geometry software is used to change impeller blades. Based on the standard k-ε turbulence model, the Fluent software is selected to simulate flow characteristics in a multiphase pump with the different impeller blades (Z= 3, 4, and 5) under the low flow rate condition. The effect of blade numbers on pressure distribution and pressurization performance is summarized. The results show that when the impeller blade is 4, the low-pressure region at the blade inlet is the smallest and the pressure variation is uniform. Meanwhile, the pressure pressurization on the medium is better. Therefore, it is found that when the impeller blade is 4, the pressurization performance of the pump is the best.

In order to study the effect of multistage pump clearance on cavitation performance at low specific speed, CFX numerical simulation software is applied to analyze the cavitation performance of model pumps with and without mouth ring clearance under different cavitation coefficients. Six clearance combination models are designed to analyze the influence of the clearance at different positions and its size on the cavitation performance of multistage pump. The results show that on the premise of decreasing cavitation coefficient, when cavitation is in the early and development stages, the existence of mouth ring clearance is beneficial to the cavitation performance of the impeller. When cavitation deteriorates, the clearance between the impeller and the ring reduces its cavitation performance. The larger the clearance of impeller ring, the better the cavitation performance of pump. The research findings lay a foundation for studying further the cavitation development in other working conditions and analyzing pressure pulsation, vibration and noise caused by cavitation.

In order to explore the cavitation characteristics and change rules of centrifugal pump，the vibration signals of centrifugal pump under different cavitation degree are measured based on the cavitation test platform of centrifugal pump. Furthermore，the time-frequency analysis technology of smoothed pseudo Wigner-Ville Distribution is introduced，and the frequency-domain characteristics of vibration under various working conditions are obtained by using SPWVD transformation，the cavitation characteristics of centrifugal pump are studied. The test results show that the NPSH value is 10.920 m under rated conditions，and there is no cavitation phenomenon under this condition. However，with the NPSH value decreasing gradually，the cavitation phenomenon occurs in the centrifugal pump. The cavitation phenomenon is most obvious when the cavitation number is 5.643，and the frequency is stable near 190 Hz. In addition，with the increase in cavitation degree，the vibration frequency is decreasing and increasing，but it is stable in the range of 160 to 200 Hz.

Considering the axial flow pump operating characteristic curve, the least squares method and the neural network method are used to fit accuracy analysis, and the points on the four curves of 2°, 0°, -4°, -6° are used as the training sample set, 4°. A point on the two curves of -2° is used as a test sample set. The research shows that the mean square error of predicted values by the neural network in the range of values (-2° line) and outside the range of values (4° line) are 0.004 and 0.007, respectively, which is much higher than the least squares fitting result; least squares method. The fit data only within the range of values (-2° line) is relatively accurate.

The plain reservoir in the arid area causes the groundwater level of farmland behind the dam to rise, which intensifies the degree of soil salinization. It is convenient to take effective measures to control the groundwater level, and then to control the occurrence of soil salinization. Therefore, in this paper, the test monitoring and numerical modeling is used to simulate the law of water and salt movement of farmland soil behind the dam by using hydrus software. The results show that the change of water level of the reservoir affects the change of groundwater level in the downstream farmland. The higher the water level of the reservoir, the greater the water level difference between the upstream and downstream, the greater the seepage flow, the increase in groundwater supply, and the faster the water level rises. The soil groundwater level is positively related to the water content. The higher the groundwater level is, the higher the water content is. The water content of soil is negatively related to the salt content. With the increase in evaporation, the speed of water evaporation is accelerated, the water content is gradually reduced, the salt in the water is left in the soil, the speed of surface salt accumulation is increased, so the salt content is increased. The shallower the soil depth is, the more obvious the change is. Therefore, the change of groundwater level has a greater impact on water and salt dynamics, which is the internal cause of salinization. The evaporation of meteorological factors is the original driving force of water and salt transport and the external cause of soil salinization. Through reasonable measures to effectively control the groundwater level, we can reduce or prevent the secondary salinization of the soil behind the dam.

In order to study the spatial distribution characteristics of soil salinization in Ogan-Kucha river oasis, the spatial distribution characteristics of soil salt in the study area were analyzed by calculating the half-variation function and fitting the theoretical model based on the soil data sampled from the field survey and the ordinary kriging interpolation in the statistical analysis method. Taking the equivalent salt ions of SO2-4、Cl-、HCO-3、CO2-3、Mg2+、Na+、Ca2+、K+ in soil as explanatory variables,, soil salinity, electrical conductivity, absorption ratio, and PH as response variables, the paper carried out Redundancy Analysis (RDA) on soil layer, and analyzed the correspondence between explanatory variables and response variables. Finally, Moran scatter map and LISA cluster map were used to explore the spatial autocorrelation characteristics of soil salt content in the study area. The results show that with the increase of soil depth, the salt content of the study area decreases gradually, and it presents a trend from heavy salinization to non-salinization. The salt content in the eastern part of the soil is higher than that in the western part of the soil. The analysis of soil salt ion showed that it was the main ion in the cation and the main ion in the anion. The regions with high soil salt content and those with low soil salt content showed polar agglomeration.

For the serious landslide of farmland drainage ditches in Yellow River Irrigation District in Ningxia, the authors use soilbags to protect the ditch slope, and evaluates the effect of slope stabilization. This paper introduces the general layout of the monitoring devices of proctecting the agro-ditch with soilbags in the high-standard farmland construction project of Dong Fanghong Village, Shaogang Town, Qing Tongxia Irrigation District, Ningxia. Then the data in 2018 are analyzed and discussed. On this basis, the soil pressure, pore water pressure, internal displacement of the slope and other factors are used to evaluate the stability of the agro-ditch by the set pair analysis method under the mode of soilbags protecting slope. The effect of soilbags is compared with that of the grass-soil-pile. The results show that the effect of soilbags is excellent. It is also feasible to apply the set pair analysis method to evaluate the stability of agro-ditch.

In this paper, the annual variation of reference crop evapotranspiration ET0 in the Three Gorges Reservoir area is analyzed by means of M-K method, and the path analysis method is used to explore the evapotranspiration of reference crops in different reference factors before and after the first 135 m water storage of the Three Gorges Project. The results show that during the period from 1961 to 2014, the annual average ET0 in the Three Gorges reservoir area showed a downward trend, among them, the period from 1961 to 2002 was a decline trend, and the performance was a rise trend from 2003 to 2014. Before the first 135 m impoundment of the Three Gorges Project, the meteorological factors affecting the annual average reference crop evapotranspiration ET0 in the reservoir area were different. After 2003, the annual average ET0 in the reservoir area was mainly affected by the annual average temperature.

In order to explore the hydraulic characteristics of stone plastic mixed media filter under the condition of clear water, Physical model tests were carried out on three different media: stone - plastic mixture, quartz sand and PVC.The experiment results show that: The water head loss of the mixed stone and plastic media is about 20% less than that of the original quartz sand, Compared with PVC plastic medium increased by about 18%; The structural coefficient of head loss is that the quartz sand medium is larger than the mixed stone plastic medium than the PVC plastic medium. The expansion rate and rising thickness of the filter material in backwash are proportional to the flow rate. The initial expansion velocity of each filter material is different. The largest is the mixed medium of stone and plastic, followed by quartz sand, and finally the PVC plastic medium; After backwashing, the corresponding expansion of different filter materials occurred, PVC plastic media is serious, followed by quartz sand, and finally the mixed stone plastic media; The backwash flow rate of PVC plastic media, quartz sand media and stone-plastic mixed media is controlled within 0.036~0.064, 0.042~0.084 and 0.045~0.077 m/s respectively, exceeding the upper limit of flow rate will lead to reverse blockage. Through comparative analysis of the test, it can be seen that the stone plastic mixed media filter can effectively reduce the head loss. The use of some PVC plastic medium is added to relatively extend the service life of the medium. After backwashing, the filter material expands less, the inner structure of the filter layer is more stable, and the filtration effect will be better. Combined with the advantages of quartz sand and PVC plastic media, it is beneficial to explore better hydraulic properties of multilayer composite media.

Hubei Province is a traditional agricultural province and an important grain production base in central China. As a typical multi-water source irrigation area in Hubei Province, the water supply for agricultural production and residential life in irrigated area is provided through the joint dispatching of reservoir, pump station ponds and weirs. Through the review of the development history of the Dabeiwan Irrigation Area, this paper analyzes the current situation and problems in engineering construction, water management and institutional management of the Dabeiwan Irrigation Area. Based on the current situation and challenges, construction of modernized and high-standard irrigated areas, reform of water price and market management, reform of institutional management of irrigated area, exploration of new form of water conservancy organization, etc. are proposed.

Based on the historical annual precipitation data from 1900 to 2009, it conducts hydrological frequency curve fitting researches on seven typical regions of China, by using P-Ⅲ distribution, LN(3P) distribution, GEV distribution, Logistic distribution, Burr distribution, Weibull distribution and so on. The results of K-S and A-D test show that Weibull distribution is poorly applicable in China. Burr distribution is extremely unstable, while it is well fit in some specific areas. Logistic distribution is general, the fitting effects of western regions are better than the east. P-Ⅲ distribution and LN(3P) distribution are equivalent, but the stability of P-Ⅲ distribution is weaker than LN(3P) distribution. The overall performance of GEV distribution is the best and the stability is stronger, which is better than P-Ⅲ distribution recommended by the specification. The research results can provide some scientific guidance for the selection of hydrological frequency line types in various regions of China in the future.

Hydrological phenomena caused by different surface cover conditions have great variability. Previous studies on hydrological phenomena mainly used empirical methods, and generalization was not reasonable. In this study, HEC- HMS distributed hydrological model is used to generalize the 30 meter precision digital elevation model of Beizhangdian watershed under ARCGIS platform, which is divided into 11 sub-basin. Remote sensing interprets the changes of surface cover types in the basin in 2002, 2007 and 2017. The influence of different surface cover conditions on the formation of flood in the basin is discussed quantitatively. The results show that the runoff depth and flood peak are reduced by 16% and 11% respectively when forest land increases by 11%, cultivated land decreases by 16% and grassland increases by 47%. Under the conditions of 52% increase in grassland, 35% decrease in cultivated land and 9% increase in forest land, the runoff depth and flood peak are reduced by 9% and 6% respectively. The research findings serve as a basis for flood prediction of similar underlying surface types.

It is difficult to guarantee the natural flood discharge while the river form has been greatly improved. Under this background, Qingshui River Basin in Chongli District, Zhangjiakou City, Hebei Province, is selected as a typical area of flood discharge basin in the mountainous areas of North China to carry out investigation and experiment, and the hydrological model is used to explore whether natural flood discharge in artificial lining river could be guaranteed and play a certain economic effect. The results show that the artificial lining channel can give full play to the social and economic benefits without affecting the natural function of the river to a certain extent after being supplemented by appropriate engineering measures such as energy dissipation barrier, which is a desirable river course reconstruction measure.

Based on the rainfall data of Yinchuan City from 1968 to 2018, the trend and abrupt change of rainfall in recent 51 years are analyzed by 5-year sliding smoothing curve and Mann-Kendall method. Using wavelet analysis to analyze the variation of precipitation in Yinchuan City in different time scales, we can see that the precipitation in Yinchuan City has a small upward trend in the past 51 years. The rainfall in Yinchuan City has a small upward trend in the past 51 years. The climate tilt rate is 3.11mm/10a. After the Mann-Kendall trend analysis, the rising change has passed the 90% confidence test. The mutation analysis shows that in 1975, in 1979 and in 2015, there was a sudden change in rainfall in Yinchuan City. Through wavelet analysis, it can be seen that there are four distinct periods of precipitation change in Yinchuan City in the past 51 years. At the same time, there are different rainfall change cycles in different seasons, and the summer rainfall cycle changes are close to the whole year.

Precipitation data of river basins in northwest region of Qinghai are collected to analyze the temporal and spatial distribution rules of precipitation in this region from 1956 to 2016.The results show that: ① Precipitation concentration and precipitation from May to September shows a slight upward trend and tended to be uneven, while the concentration period shows a slight downward trend, showing an ahead trend. ② The annual precipitation shows a significant increase trend, and the precipitation time series has a long-range correlation, which is predicted to maintain the trend of continuous increase; the abrupt change of precipitation around 2001. The periodic fluctuations of five time scales control the variation characteristics of annual precipitation in the whole time domain, of which 31a is the main period. ③Precipitation in the region is extremely uneven in the plane distribution, the eastern and southern mountainous areas are decreasing to the northwest basin, the vertical difference of precipitation is obvious and shows some regularity. ④ In space, the annual average precipitation shows a progressive trend from the high value of the surrounding mountain area to the low value center of Qaidam Basin, and the low value area shrinks.

In view of the characteristics of monthly runoff series which contain complex frequency information, in order to improve the prediction accuracy, the data of monthly runoff series from 1958 to 2000 at Shangjingyou Station, Fenhe Reservoir Station, Zhaishang Station and Lancun Station are analyzed and predicted. This paper proposes a combined model of Variational Mode Decomposition (VMD) and Least-Square Support Vector Machines (LSSVM) (VMD-LSSVM), compared with single LSSVM model, the Empirical Mode Decomposition with LSSVM(EMD-LSSVM) model and the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise with LSSVM (CEEMDAN-LSSVM) model. Nash efficiency coefficient (NS), root mean square error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) are used. The results show that the combined model has better prediction accuracy than single LSSVM model, among which VMD-LSSVM model has the highest accuracy. MAE, MAPE, RMSE of that are 50%~75%, 40%~70%, 40%~70% less than CEEMDAN-LSSVM, 70%~80%, 60%~85%, 50%~80% less than EMD-LSSVM and 80%~90%, 75%~90%, 50%~90% less than LSSVM respectively. Therefore, VMD-LSSVM model can be applied to multi-frequency monthly runoff prediction and can achieve higher accuracy.

In order to improve the accuracy of hydrological forecast, this paper proposes a support vector machine (SVM) monthly runoff prediction model optimized by Mittag-Leffler, Pareto, and Cauchy improved cuckoo search algorithms (MLCS, PCS, CCS). Six typical test functions are selected to simulate and verify the MLCS, PCS and CCS algorithms, and compared with the simulation results of the basic cuckoo search algorithm (CS). MLCS, PCS, CCS, and CS algorithms are used to optimize the key parameters of the SVM, and MLCS-SVM, PCS-SVM, CCS-SVM, and CS-SVM models were established to study the monthly runoff during the dry season at the Gulaohe Station in Yunnan Province. And the data for the next 13 years are used to train and predict each model. The results show that MLCS, PCS and CCS algorithms have better optimization capabilities than standard CS algorithms, and have better optimization accuracy and global search capabilities. The average relative errors of the MLCS-SVM, PCS-SVM, and CCS-SVM models for the monthly runoff forecast of the examples from January to March are between 4.89%~4.94%, 6.87%~7.07%, and 6.87%~7.09%, respectively. The model has improved by 34.5%, 8.30%, and 23.6%, respectively, and has better prediction accuracy and generalization ability. It shows that MLCS, PCS, and CCS algorithms can effectively optimize SVM related parameters. Models and methods can provide references for the hydrological forecasting and other related forecasting studies.

Based on the daily average flow data of Chutoulang Hydrologic Station from 1971 to 2016, the RVA is applied to comprehensively evaluate the impact of Sanzuodian Reservoir on river runoff hydrological situation. Due to the correlation among many hydrological indicators, the PCA method selects the three most relevant hydrological indicators among the 33 indicators, monthly flows for June, the 30day minimum average flow rate and zero-flow days. After the establishment of Sanzuodian Reservoir, monthly flows for June decreased by 68%, the hydrologic change degree was 41%, the 30-Day minimum average flow rate decreased by 88.48%, the hydrologic change degree was 48%, zero-flow days increased by 3191%, and the hydrologic change degree was 62%. As a result, the downstream flow rate showed a gradual decrease trend and the hydrologic regime of river is moderately changed by human activities.

Since the flow of dike breaches is very complicated, understanding its hydraulic characteristics is the basis of plugging and repairing it. So based on the characteristic values of typical breaches determined by cluster analysis, the hydraulic model of the breaches is established, and the observation test of both the flow fields and flow patterns of the breaches and the basic hydraulic factors is conducted. The Velocity Distribution Measuring System (VDMS) is used to collect the surface velocity fields of river channels, breach gates and flood areas, and then the flow fields and flow patterns of the breaches is analyzed. The test shows that the flow velocity at the breach gaps is the highest and the velocity rate is generally within 4.81~5.80 m/s, and there is a wide range of eddy current phenomenon on both sides downstream of the breaches and velocity is generally within 0.64~0.92 m/s. Not only are the change rules of water level ~ flow and water level ~ flow velocity in the upper and lower reaches of the breach complementary, but also the non-dimensional waterhead of the breaches is related to the single width flow power and the equivalent water depth. In conclusion, the research results deepen the understanding of the hydraulic characteristics of the breaches, and provide technical parameters for the study of plugging and repairing breaches.

The main driving force that affects the structure and function of river ecosystem is the change of hydrological situation. In order to study the change of hydrological situation in the Xiangjiang River Basin and select the daily flow data of the Xiangtan hydrological station (1959-2016 years), the flow characteristics are analyzed by Mann-Kendall method, cumulative anomaly method and sliding T test, analysis of hydrological indexes before and after the abrupt change of hydrological situation, and the water resources change range method (IHA-RVA) and the water text change degree method are used to evaluate the degree of hydrological change in Xiangjiang River basin. The results show that the average annual flow in Xiangjiang River basin is increasing, the growth trend is not obvious, the year of the sudden change in hydrological regime was 1991. By analyzing the hydrological indexes of Xiangjiang River basin before and after the hydrological mutation, the overall hydrological variability of Xiangjiang River was 36%, its degree of hydrological change has just reached moderate change, among them, the average annual minimum flow occurrence time is most affected, the change was 100%.

To improve the safety management level of small reservoir in water sector, based on the safety engineering short plank and insufficient supervision of small reservoirs, according to related regulations and normative documents, from the point of view of improving weak links and strengthening supervision, the typical process for improving safety management of small reservoir, methods, main contents and details of each link are given. Combined with small reservoir supervision, relevant suggestions are put forward in this paper, which provides a reference for realizing the precise safety management of small reservoirs in water sectors.

Taking the design process of the inlet of the flood-discharging tunnel of the Chemabi Reservoir Project as an example, this paper studies the feasibility of the arrangement of the pressure vertical inlet in the case of low head, and analyses the model test and verification of the inlet and vortex of multiple sets of different body types. By establishing a reasonable test model, the flow state, discharge capacity and pressure distribution along the vertical inlet of each scheme are analyzed. Thus, a structural arrangement scheme can be obtained which can effectively control the vertical vortex of the water inlet, the flow stability with lower engineering costs and easier construction process. The research process can serves as a reference for the design of the body type and the vortex-reducing device for the low-headed pressure vertical inlet of other projects.

The three-way pipe is widely used in various industries. In view of the problems of large local head loss coefficient ζ and poor internal flow characteristics of the existing three-way pipe, a new type of three-way pipe runner structure is developed to reveal the resistance of the new tee pipe. The relationship between flow characteristics and related structural parameters is used to obtain a reasonable internal flow passage design scheme for the new tee. Based on SolidWorks2016 and CFD software, this paper numerically calculates the normal 120° equal-diameter tee of DN32, verifies the reliability of the simulation, and optimizes the internal flow channel structure parameters of the new tee. The results show that: ① Both ζ01 and ζ02 at the inlet and at the two exits decrease first and then increase with the obesity coefficient λ and the maximum width B, and the change trend curves of both and λ exhibit a quadratic function change. ζ01, ζ02 corresponds to λ=4.270 6, B=42.22 mm. ② The split loss coefficient ratio β with both B and λ is flat at both ends, and the trend of intermediate variation changes. ③The new three-way pipe is not symmetric about the symmetry plane velocity distribution, and the low-speed zone will be biased to the lower left of the center of gravity of the tee. As the Reynolds number increases, the low-speed zone becomes smaller and smaller. The distribution of the obesity coefficient λ is smooth and uniform within the range of (4.15, 4.91].

The reserved rock ridge cofferdam for the intake of circulating water of middle yellow projection has the characteristics of complex surrounding environment, closed to the construction and building and reinforced with steel piles in the previous procedure. In order to solve those difficulties, a one-time overall blasting demolition scheme is adopted, which is composed of damping hole, pre-splitting hole blasting and primary hole blasting, unit consumption and charging in sections, controlling the quantity of single period charges, the non-electric detonator and delayed millisecond initiation. In this paper, the blasting parameters of damping hole, pre-splitting hole blasting and primary hole blasting are designed. The degree of blasting residue is controlled and predicted according to the requirement of ≤ 50 cm. The protected object safety control under blasting vibration is checked by controlling the maximum single period charge, and the corresponding protective measures are proposed. The blasting effect is good, rock ridge is broken evenly, no flying stone is found, and no damage is done to the surrounding buildings.

Due to the large specific drop of river and high sediment content in flood season, the design of sluice in mountainous area usually adopts apron energy dissipator to connect with the downstream river. Based on the physical model test of a hydropower station, this paper makes a comparative study of the two connecting forms of the anti-arc apron and the straight slope apron. By comparing the flow pattern, flow field distribution and downstream riverbed scour, the results show that the anti-arc apron is obviously superior to the straight slope apron in terms of flow pattern and downstream riverbed scour. Specifically to eliminate the left-side reflow of the apron. The maximum scouring depth is reduced by 38%. However, at the downstream low water level, the shore flow velocity of the two banks is larger than that of the straight slope apron, with the average increase of 12.5% on the right bank. Considering comprehensively, if the mountains on both sides are relatively complete, better engineering results can be obtained by adopting anti-arc apron.

The low Froude number flow has insufficient energy dissipation in the down-dug type stilling pool. Generally, the addition of a stilling sill at the tail sill of the stilling pool to form a comprehensive stilling pool, thereby increasing the energy dissipation rate in the stilling pool. Aiming at the influence of the shape of the stilling sill of the integrated stilling pool on the energy dissipation rate of the stilling pool of the new water conservancy project, numerical calculations of different forms of stilling sills are performed based on Flow3D. The body shape design type of the stilling pool is a new type of energy dissipation tail sill. This toothed shape sill has an important effect on increasing the energy dissipation rate of the still pool.

At the early stage of the development of hydropower station, most stations built in China did not have special facilities for ecological discharge due to some historical reasons. The rehabilitation of these hydropower stations is the call of our times and an essential way to maintain the sustainable development of small hydropower. Based on the experience of rehabilitation of the small hydropower stations in Zhejiang Province and Fujian Province, this paper introduces some common biological discharge facilities, and analyzes their applicable range and effects. In addition, some typical cases will be shown as reference for the rehabilitation of old hydropower stations.

Based on the hydraulic model experiments, the flow characteristics after the three dimensional convex and concave aerators with curved boundary set on the base plate of the rectangle flume are investigated and are compared with the conventional straight aerator set on the same flume. The results show that the aerated flow characteristics downstream and flow patterns downstreamthe of three kind aerators have obvious differences. The cavity length of the conventional straight aerator is the longest among the three kind aerators. The convex and concave aerators are not good for increasing the cavity length. For the three kind of tested aerators, the depth of back water in the cavity after the aerator increases with the increase of the flow discharge. But the convex aerator is good at reducing the backwater in the cavity after the aerator, especially in big flow discharge. The air concentration in the flow area near the surfaces of the base plate and the side walls of the flume after the aerator decreases rapidly along the flow route for all tested aerators, but the distribution of the air concentration in the flow is different for each aerator, which leads to their own different length of protective segments. For the protective segment length of the base plate of the tested flume, it is the longest for the conventional straight aerator and the shortest for the convex aerator. But for the protective segment length of the side walls of the tested flume, it is the longest for the concave aerator. It shows that the concave aerator maybe good at for protecting side walls of spillway from cavitation erosion in the projects. The research results can provide useful theoretical and experimental evidences for better use of aeration facilities.

The diagonal-flow pump turbine is widely used. The flow inside the spiral casing and fixed guide vane is one of the important factors that affect the efficiency of the pump turbine. CAD-CFD modern design technology were used to design the pump turbine with superior performance, According to the basic theory of water flow, the design method of flow into runner is adopted, and combined with reverse flow thinking to optimize the design of the spiral casing. According to the streamline principle, the fixed guide vane is modified. The numerical simulation results show that the cross section area of the optimized spiral casing is reduced, and the tip nose is more streamlined. The modified guide vane has better symmetry and the velocity can flow out axisymmetrically. The optimized flow parts can effectively reduce the internal interference phenomenon, and reduce the vibration of the unit.

Pump load rejection is one of the key check working points for the guarantee calculation of pump storage unit. In this paper, phenomenon of reversal rotation of pump storage unit was introduced and factors related to it are discussed. For a specified pumped storage power plant, numerical model of water passing system and the unit are established, and the validity of the model is verified by measured data. Trends of control parameters are drawn from the numerical model for one-step guide vane closing principle. The research indicates that once pump load rejection happens, parameters in time domain has overlapping trends for different guide vane principle in initial stage; the reversal rotation speed and torque become larger with the guide vane closing time extending; water levels of surge tanks and gate shaft are unaffected by guide vane closing time; maximum pressure at spiral case inlet and minimum pressure at draft cone tube reaches optimum values at different guide vane closing time; that whether the reversal rotation occurs or not depends on the guide vane closing time; the minimum guide vane closing time is determined by the pressure oscillation in the spiral case inlet and intrinsic characteristic of oil pressure system of speed governor; the maximum guide vane closing time is determined by the reversal speed and main shaft torque. On the reversal speed and torque under the rated values, there is optimum guide vane closing time to ensure the parameters in guarantee calculation balanced.

With the continuous increase in single unit capacity of hydropower station and the giant size of powerhouse, the structural vibration problem of the hydropower house has become increasingly prominent. It is an important means to solve the problem to fully grasp and control the structural vibration of the hydropower house through limited monitoring data. In this paper, an improved bat algorithm (IBA) with inertia weight and tangent random exploration mechanism is proposed, and the expanded parameters of radial basis function neural network (RBF) is optimized by this algorithm. An IBA-RBF model for predicting the vibration response of hydropower house structure is established. Based on the monitoring data of unit vibration and tailrace fluctuation, the proposed model is compared with the Relevant Vector Machine (RVM) model in the circumferential direction. The results show that the average relative error between the predicted and actual values of the IBA-RBF model is within 6%, which is 2% lower than the average relative error of correlation vector machine model. Meanwhile, it provides a new method for the prediction of vibration response of hydropower house.