In order to clarify the effects of different tillage measures on the regulation of water, heat and salt under greenhouse cultivation, the effects of plastic film mulching and straw deep burying (J+M) on the dynamic changes of soil water, heat and salt under greenhouse cultivation are studied by greenhouse plot test method, with tillage (CK), plastic film mulching (M) and straw deep burying (J) as controls. The results show that the water content of J+M treatment is 8.96%, 5.45% and 14.32% higher than that of M, J and CK treatment, the soil temperature of J+M treatment was 3.35%, 5.21% and 8.32% higher than that of M, J and CK treatment, and the total salt content of J+M treatment is 24.44%, 19.65% and 26.64% lower than that of J, M and CK treatment. The research results can provide reference for the implementation of plastic film mulching and straw deep burial improvement measures in greenhouse planting in Ningxia.

Silage corn is the main target crop for grain reforming and planting structure adjustment in Hebei Province. In order to formulate reasonable water and fertilizer management measures and increase the yield of silage corn, the irrigation method and fertilization amount are selected as factors affecting the silage corn experiments. The irrigation method is set to two levels of border irrigation and furrow irrigation, and the amount of fertilizer is set at 4 levels, and the amount of fertilizer is between 300 and 750 kg/hm². Research indicates that compared with border irrigation, the plant height and fresh weight have increased by 2.2% and 3.6%, respectively, furrow irrigation is conducive to the growth and yield of silage corn. The amount of fertilizer applied has a significant effect on the growth and yield of silage corn. The growth status and yield of silage corn are the best when the fertilizer application rate is 600 kg/hm², compared with 750, 450 and 300 kg/hm² fertilization levels, plant height, leaf area index, chlorophyll and fresh weight have increased by 0.11% to 27.8%, 4.01% to 10.55%, 1.1% to 1.8% and 3.6% to 15.6%, respectively. The fresh weight yield of silage corn is between 69.09 and 81.4 t/hm². Correlation and regression analysis show that there is a significant positive correlation between fresh weight of silage corn and plant height and leaf area index，the treatment combination of furrow irrigation and fertilization of 600 kg/hm² contributes to plant height and leaf area growth, and therefore also contributes to higher yield of silage corn.

In order to meet the requirements of comprehensive reform of agricultural water price, taking Ganfu Plains Irrigation Area of Jiangxi Province as the research object. The water price of the state-owned project in Ganfu Plains Irrigation Area is 850.54 yuan/hm², and the water price of the final canal system in typical irrigation area is 849.53 yuan/hm², with a total of 1 700.07 yuan/hm². This paper analyzes the economic and psychological bearing capacity of agricultural water users in the irrigation area. Therefore, this paper recommends implementing two systems for agricultural terminal water price in irrigation area. 60% of the cost water price can be collected, which can be increased appropriately for high value-added crops, and the remaining 40% can be subsidized by the government. The water cost of the last canal system project is all borne by the government subsidy for the development of agricultural production.

In order to explore the adaptability of different numerical simulation models in the hilly area of central Sichuan and improve the ET₀ prediction accuracy under the condition of missing meteorological data. This study constructs four input combinations of different meteorological factors with the daily meteorological data from 7 representative stations from 1961 to 2016 and establishes numerical simulation models based on M5 regression tree (M5-RT), back propagation neural network optimized with double hidden layers (H-BPNN) and generalizes regression neural network of cross validation (CV-GRNN) optimization. At the same time, three empirical models (Jensen- Haise, Hargreaves-Li and Irmak-Allen models) with higher precision in the hilly area of central Sichuan are selected to compare with the numerical simulation models. Finally, this paper evaluates the ET₀ prediction accuracy of different models on a daily scale and evaluates the generalization ability of the three types of numerical simulation models in the hilly area of central Sichuan with portability analysis. The results are as follows: M5-RT2, CV-GRNN2 and H-BPNN2 models based on temperature, wind speed and extraterrestrial radiation have high precision, with their determination coefficients (R²) reaching 0.987, 0.967 and 0.988 respectively, and Nash-Sutcliffe efficiency coefficient (NSE) reaching 0.987 1, 0.937 4 and 0.988 8 respectively. The three models can fit the complicated nonlinear mapping relationship between ET₀ and meteorological parameters to a certain extent. The daily scale error analysis shows that M5-RT regression tree model is the best, H-BPNN model is the second, and CV-GRNN model is the worst, but the root-mean-square errors (RMSE) are less than 0.5 mm/d and the average relative errors (MRE) are less than 13.59% in all three models. The accuracy of the numerical simulation models is higher than that of the empirical models, among which, the M5-RT model input into combination 2 (extraterrestrial radiation, maximum/minimum temperature and wind speed), combination 3 (maximum/ minimum temperature and wind speed) and combination 4 (extraterrestrial radiation and wind speed) has wide adaptability in the simulated forecast of ET₀ with missing meteorological data. Portability analysis shows that the prediction accuracy of the numerical simulation models have decreased under the cross combination of training and prediction stations, among which, M5-RT model has the strongest generalization ability, its simulation output has the highest stability. The H-BPNN model and CV-GRNN model have a large truncation error when ET₀ is greater than 6 mm/d, the predicted value is generally small. At the same time, the slope of the trend line of the simulation result and the standard value of the CV-GRNN model is small, and the simulation value is small overall. The ET₀ prediction models based on M5 regression tree have high accuracy and stable simulation results, which can be recommended as a simplified model for predicting ET0 in the hilly area of central Sichuan.

This study is aimed at investigating the effect of controlled irrigation and drainage on rice growth, development and yield with biological carbon application. A pit experiment was conducted at the Lianshui Water Conservancy Test Station in 2016, and this paper set two water control modes: light drought control and drainage named W₁ and heavy drought control and drainage named W₂; without biochar treatment named B₀ and applied biochar treatment named B₁. This paper monitors and analyzes the growth index, lodging resistance of rice and the yield of rice. The study shows that the plant height of rice increases significantly because of the condition of biochar addition and controlled irrigation and drainage W₂. The application of biochar can shorten the length of rice internode, increase the thickness of stem wall and diameter of internode, and significantly improve the lodging resistance has decreased, and the lodging resistance of rice presents a declining trend due to the treatment of controlled irrigation and drainage W₂ Both water level control and biochar addition had significant effects on ear length and empty stem rate of rice, among which water level control had a more significant effect. Biochar addition alone and controlled irrigation and drainage W₂ both significantly increased rice yield, but the interaction between the two had no significant effect on yield, which means that the effect of controlled irrigation and drainage regulation on the enhanced yield of biochar is not obvious, and the related water-carbon coupling effect needs further study.

Under the influence of climate change and human activities, hydrologic series in many basins have shown mutative and inconsistency in recent years. In the meanwhile, the self-correlation of hydrologic series affects mutative identification. In order to study the variation characteristics of rainfall and runoff series in the Guanhe Reservoir Basin, based on the measured data of five rainfall station and two runoff stations within the basin for nearly 50 years, the Mann-Kendall rank test is used to test the trend, three approaches of Mann-Kendall, Pettitt and ordered aggregation are addressed to diagnose the mutation points, which are under two conditions: with or without the trend-free pre-whiting (TFPW) method, then the periodicities of these series are identified by Morlet wavelet further. The results show that the TFPW method could adjust the fake multi-mutation points after filtering out the correlation of series and to help determine the real points, which are verified by the periodic results from the Morlet wavelet method. The precipitation in the study area was mutated in 1978, while the runoff was mutuated in 1979. Precipitation is the main driver of the sudden change of runoff in the two stations, and the characteristic of these two runoff series have changed fundamentally around the abrupt change point. Compared with the Shizhandao Station, the annual runoff decline of Guanhe Station was more obvious, and unstable in periodicity and lower peak flow, not only impacted by climate change but human activities.

Fractal dimension of drainage reflects the complexity of the river. The larger the fractal dimension, the more mature, the more complex and intense the water system is. Drainage networks of Siheshui Basin and the Hanjiang River Basin and Hanjiang's sub-basins are extracted based on 30 m and 90 m precision DEMs (Digital Elevation Models) by Arcgis. In order to avoid repetitive manual operation and improve computational efficiency, Arcgis' ModelBuilder and Microsoft's Excell are used to make the drainage networks extracted and the fractal dimension values analyze quantitative and automated. Potential drainage fractal dimension values in series confluence thresholds are calculated by box-counting method and compared with the fractal values of actual river networks. This paper analyzes the relationship between fractal dimension values with the resolution of DEMs, confluence thresholds, kinds of the river network diagrams and the drainage area. The results show that: ① The correlation index (R2) of drainage networks in Siheshui Basin are more than 0.98 and that of Hanjiang Basin are more than 0.97, showing that the study basins are homogeneous in scale-free range and have good fractal character respectively. ② Resolution of DEMs, such as 30 m and 90 m precision, have little effect on fractal value based on box-counting method without considering the accuracy of river network. ③ Fractal dimension values vary from the confluence thresholds of the drainage networks extracted from DEMs, and decrease sharply along with the increases in thresholds at the beginning, and then decrease gently to be value 1, but be more than 1. ④ The actual fractal dimension value of the river is unique and should be calculated based on real drainage networks. In another way, selecting the appropriate confluence threshold to make digital river network and the actual river network matches, the fractal dimension value of the digital river network can represent the actual dimension value of the real river to some extent. ⑤ When the drainage system is homogeneous, it has strong statistical self-similarity, so that the fractal dimension of the whole basin is similar to that of each sub-basin. Therefore, drainage fractal dimension values are not related to the basin area.

In the plain lake area where human activities are frequent, many polders designed for reclaiming land from lakes cannot be reflected by DEM, and water conservancy project will produce an effect on concentration. In this paper, the boundary of the polders of the Dongting Lake area are identified by the remote sensing satellite data of Google Earth to modify DEM and guide sub-basin delineation. The concentration module of SWAT model is replaced by the n-days average of natural runoff process. SWAT model can therefore be better used to simulate the uncontrolled zone of Dongting Lake. By using the modified DEM and the past n-day average outflow model, the interval runoff is simulated, and the result shows that the efficiency coefficient increases from 0.88 to 0.9 in calibration period, and from 0.85 to 0.88 in validation period. The proposed model is helpful for the application and research on the distributed hydrological model in the plain lake area.

Rainfall is the main input of hydrological model, so the density and uneven spatial distribution of observation stations are the main source of rainfall errors. Therefore, it is important for improving the accuracy of hydrological simulation to analyze the impact of rain gauge density and spatial distribution. In this study, the Xiangjiang River Basin with dense and evenly distributed rain gauge is selected as the study area. The influence of the density and the spatial distribution of rain gauge on hydrological simulation are analyzed by using Xin'anjiang Model. The result reveals that the improvement of rain gauge density can effectively reduce the estimation error of the model. The model performance is improved with the increase in the rain gauge density, but the simulation accuracy does not increase significantly when the rain gauge reaches a threshold. In addition, some combinations of rain gauge can get good simulation accuracy when rain gauge density is low. Therefore, increasing the number and optimizing the spatial distribution of rain gauge can improve the accuracy of hydrological simulation.

It is of great scientific significance to detect the breakpoint of hydrological series for understanding the trend of hydrological cycle and studying the impact of environmental changes on hydrological processes. By using the observed data from 1951 to 2015 at the Guantai hydrologic station of the Zhang River, the breakpoint of annual stream flow is detected by multiple methods including double-accumulation curve of precipitation and runoff methodology, orderly clustering breakpoint detection methodology, Mann-Kendall's test methodology and breakpoint detection methodology based on hydrological simulation. The results indicate that since 1951, there is a statistically significant decreasing trend in annual stream flow. In the 1950s and 1960s, the annual stream flow is higher, and it begins to decrease from the early 1970s, then after 1980s it is long period of dry. The breakpoint of annual stream flow happens from 1971 to 1978 is detected by different methodologies. Compared with the four methodologies, the breakpoint detected by the double-accumulation curve of precipitation and runoff reflects the moment when the relationship between precipitation and runoff changes significantly. The breakpoint detected by the orderly clustering breakpoint detection methodology reflects the clustering characteristics of stream flow series. The breakpoint detected by the Mann -Kendall's test methodology reflects the comprehensive abrupt changing characteristics of stream flow series. The breakpoint detected by the methodology based on hydrological simulation reflects the starting point of the impact of human activities on the relationship between precipitation and stream flow.

The flood control function of urban water network is an important guarantee for urban social and economic development. Modern cities are faced with the problem of water resources shortage, and their flood control demands should be combined with water resources utilization to improve the efficiency of rain-flood resources utilization. Gucheng Lake is the most important water source in Gaochun District, Nanjing City. Without the control of gate and pumping station, it is vulnerable to flood in the year of abundant water. The level of Gucheng Lake can be controlled within 13 meters (flood control standard with 50-year return period) through the control of gate and pumping station. Meanwhile, rain-flood resources utilization through water networks can increase the annual water supply by about 44 million m³ under the premise of ensuring flood control safety. It is suggested that the research on the utilization of rain and flood resources should be strengthened in the future urban construction, and the flood control and water resources utilization benefits should be taken into account.

The floodplain is one of the most important components in fluvial system. It provides a wide range of ecological functions and benefits such as natural moderation of floods, water quality maintenance and natural habitats supply. Taking Lingshan River, Zhejiang Province as a typical mountain river, we propose the definition of Index of edge sinuosity (I_e) on the basis of field surveys to quantify the floodplain edge concave morphology. The floodplain edge morphology grades can be divided into ‘Low sinuosity’ (I_e≤2), ‘Medium sinuosity’ (2≤I_e<4), ‘High sinuosity’ (I_e≥4) based on I_e. Four field surveys are carried out in the Lingshan River downstream with 18 floodplains. A hydrodynamic 2-D, depth averaged advection-dispersion transport numerical model based on Mike 21 is set up to explore the solute transport in the water area near floodplain. Both field surveys and numerical simulation results show that the river water quality risk increases significantly with the increase in I_e level (P<0.01). The numerical simulation results further show that the appropriate reduction of High sinuosity, can effectively reduce the river water quality risk. Considering the need to maintain ecosystem diversity. However, it is not advisable to reduce to the 'low sinuosity' morphology. The spatial and temporal distribution of solute transport under different edge morphological conditions obtained in this paper can provide an important reference for floodplain protection and restoration.

To solve the problem of water resources allocation in complex river basins and ecological operation of reservoirs, taking the Shaying River Basin (SRB) with numerous floodgates and dams as an example, based on the ecological base flow of the key sections, a water allocation model with the objective of 'Ensure instream ecological water demand and prioritize domestic water use' was developed. The model took the actual water consumption of consumers in 2017 as the water demand level of the base year, optimized the allocation scheme of water resources in SRB by applying large-scale linear programming methods under the conditions of wet, normal, dry and extremely dry years. The reservoir ecological operation control line, operation rules and the water resource allocation scheme were obtained after the statistical analysis of calculation results, verified with 85% water supply conditions in dry years. By comparing the conventional operation results, the ecological operation can make full use of the spatial and temporal distribution of the adjustable water quantity and the operation capacity of floodgates and dams. It can also improve the guarantee rate of ecological water use in key sections of SRB. This study provides technical support and decisionmaking support for the comprehensive management of water resources in SRB.

Most of modern cities face the problem of pollution-induced water shortage. Almost all river systems in urban cities are of bad water quality because of excessive discharge of pollutants and low efficiency of water connection. The construction of connection among river systems in cities is one of the most important measures to handle the problems of uneven allocation of water resources and poor water quality. This article chooses Gucheng lake, Shuibiqiao river, Shigu river, Guanxi river in Gaochun district, Nanjing city as research subjects. Constructed coupled one dimension and two dimensions hydraulic and advection-diffusion model. Chose COD and NH₃-N as water quality indexes. Simulated spatial-temporal change of water quality indexes under different water utilization scenarios. And then evaluated effect of water improvement under the construction of connection among river systems. The study shows that connection between river systems and scientifically regulation can significantly improve water quality in river systems.

The Guide proposes using Test Algorithm and Model Simulation Method to decompose the rigid index, Annual Total Runoff Control Rate in Sponge City Special Planning, However, because the Guide is still in the trial stage when there is no answer for how to use the Model Simulation Method in index decomposition, and there are less Hydrological and Hydraulic Simulation Researches with SWMM as a typical representative. This method is used as a starting point for study. Therefore, this research in virtue of SWMM model explores a universally suitable index decomposition approach, through three stages as present situation assessment, the rigid index decomposition and instructive index decomposition to complete the decomposition of Annual Total Runoff Control Index, and cases are used to present elaboration on case assignment method, hopefully providing some reference for the compiling work of Sponge City Special Planning in the future.

Pond water is an important part of urban water body. To reveal the temporal variation characteristics of pond water quality under the background of urbanization. A pond in the Lunan Campus of Yangzhou University is chosen as the study area. Observations on the water quality parameters such as blue-green algae content (Phyco), water temperature (WT), dissolved oxygen (DO), pH and electrical conductivity (EC) is carried out in the period from July 2018 to June 2019 (1 year). An analysis of the water quality parameters is carried out by using the methods of coefficient of variation method, single factor water quality index method and multiple linear regression method. The results indicate that WT seasonally changes; pH varies from 7.74 to 9.98 that the water is alkaline during the research period; DO changes randomly, no obvious discipline; the order of the variability and weight of each water quality parameter is WT>DO>EC>pH; the single factor water quality index of DO shows that the water quality category is mostly III which accounts for 84% of the research period. An analysis of the multiple linear regression method shows that DO is positively correlated with WT and pH, negatively correlated with Phyco, the effect of Phyco and pH on DO is more significant than that of WT.

One of the factors affecting the determination of the coefficient of permeability of remolded fine-grained soil is the preparation of soil samples. Variable head permeability test and mercury injection test of remolded silty clay in the plain reservoir in North China are conducted to seek the changes of permeability and pore of building materials for hydraulic structures caused by initial water head and consolidation time. The effect of consolidation on the permeability coefficient of silty clay is significant. The permeability of 8 hours of consolidation time is 3.8 times that of 24 hours. The initial water head also has an effect on the permeability of the remolded silty clay, but it does not exceed 2 times. The shorter the consolidation time, the larger the permeability coefficient and the rate of change under the influence of the water head. For remodeling silty clay, it is appropriate to consolidate for at least 10 hours with a starting water head of 100 cm. Consolidation causes large pores(>40 μm) reduced to small pores(<10 μm), the pores in the soil tend to be uniform. The pore content of 10~40 μm plays a decisive role in permeability, the permeability increases with its increase. The conclusions are useful for the determination of the coefficient of permeability for remolded fine-grained soil and the application of permeability in engineering.

In order to endow the traditional concrete retaining wall with mature technology, safety and reliability, and wide application with ecological characteristics, the vertical wall surface is slowed down and retreated appropriately, poured into a stepped shape, and a low wall is arranged on the edge of the stepped to form an ecological groove, fill with planting soil, and suitable landscape plants are cultivated. Combined with the application of plant ecological retaining wall in the treatment of Chazi River, the design of retaining wall is optimized. The comprehensive slope ratio of the wall surface on the water side is 1∶0.8, the clear width of ecological trough is 0.65~0.85 m, the depth of trough is 0.4 m, the thickness of trough wall is 0.15 m, and the distance between adjacent troughs is 1.0 mm. At the same time, the back of the wall is adjusted to be tilted upward, the slope ratio is 1∶0.25, and the toe of the wall is equipped with gabion foot guards to prevent scour. The ecological retaining wall is used in river course management, which is durable, can form ecological beauty, and is also beneficial for unfortunate people who fall into the water to climb ashore and save themselves.

The cofferdam is a temporary water retaining structure for the construction of water resources and hydropower projects，the construction scheme of which has an important impact on the construction progress. Yongning Water Conservancy Project adopts the method of multistage diversion. The 1st stage temporary earth-rock cofferdam is a difficult point for the construction due to its characteristics, such as tight schedule, deep water depth, relating to multiple zones and multiple materials and so on. In order to deeply study the construction scheme of the cofferdam, the simulation model of the cofferdam construction transport system is established with the cyclic operation network, and the program is written as C#. Firstly, three kinds of construction schemes are put forward according to the above characteristics and the optimum construction scheme is obtained on the basis of the simulation results. Secondly, the number of loading devices and emptying points is optimized and the optimum scheme for equipment configuration is obtained. Finally, the optimum scheme is visualized with BIM. The research results provide a basis for the better construction of the cofferdam and can provide references for the similar projects.

Considering that the deep sliding problem of gravity dam along the rock bed's weak structural surface belongs to the typical local displacement non-continuous contact problem, and the traditional algorithms have limitations on solving this kind of problem, this paper uses the iterative method of partitioned finite elements and interface boundary elements to carry on the deep sliding stability analysis of a certain gravity dam. Given that the iterative method needs to know the possible contact surfaces in advance, the FEM strength reduction method is firstly used to search the possible deep sliding surface, and then nodal pairs are generated on the sliding surface. The iterative method of partitioned finite elements and interface boundary elements combined with strength reduction method is applied to calculate the safety factor by defining the states of all nodal pairs at the failure states. Meanwhile, the result of the proposed method is compared with that of the traditional FEM strength reduction method. It shows that this method can simulate the mechanical behavior well of discontinuous structural surface with high computational efficiency, and can effectively avoid the subjectivity in determining safety factors with the FEM strength reduction method.

Cracking with different degrees appears in some high core wall rock-fill dams built on deep overburden layer in China, which threatens the long-term safety and stability of dams and has attracted widespread attention. Based on the cracking mechanism of rock-fill dams, coupling relationship between the cracking modes and the monitoring characterization is investigated. Take a high core wall rock-fill dam with cracking in dam crest as an example, the spatial, temporal distribution and the failure characteristics of deformation are studied by using the geological radar, high density electrical method and actual monitoring data. The results show that the stress of soil exceeds its tensile strength or shear strength, which is the fundamental cause of cracking in dam crest. The direct reason is the non-uniform settlement of dam crest, and it is influenced mainly by the water loads, wetting deformation, storage velocity and material characteristics.

In recent years, catenary channel has been widely used. There is no analytical solution to the transcendental equation for the calculation of critical depth and normal depth of catenary linear section. Firstly, the uniform flow and critical flow equations of the catenary linear section are derived by introducing appropriate dimensionless parameters in combination with the geometric characteristics of the catenary linear section, the hydraulic elements, and the basic equations of uniform flow and critical flow. After mathematical transformation, the Newtonian iterative formulae of normal and critical water depths of catenary linear section are obtained, and the initial value calculation formulas of them are obtained by using the optimization fitting principle, and the direct calculation formulas of normal and critical water depths are obtained after an iteration. Finally, the error analysis and comparison of the formula show that within the scope of engineering application, the maximum absolute relative error of the direct calculation formula of normal water depth and critical water depth is 5.33×10^-5% and 5.05×10^-5%, respectively. After the second iteration, the accuracy can be improved by 10⁸ times and 10⁶ times, respectively.

The main factors affecting the flow state and the length of the water pool in the forward water intake are the sizes of the diffusion angle of the forward water intake pool at the pumping station. The inlet flow state, flow rate distribution and siltation pattern of the front pool under different conditions and different conditions observed. At the inlet diffusion angles of 20°, 25°, 30°, and 35°of the former pool, the results show that the flow rate of the mainstream zone increase with the increase in the diffusion angle. The siltation thickness on both sides of the front pool is greater than that in the middle, and the greater the sediment content, the greater the siltation thickness of the front pool. The same water and sand conditions, running the same time, diffusion angle hours, large amount of silt. The distribution of the diffusion angle of 25°and 30°in the front pool of the pump station is more reasonable, and the combined performance of water flow and silting is better.

Taking small Irrigation Pumping Station as an example and comparing the advantages and disadvantages of four different schemes of submersible pumping stations, a pipeline-rail integrated cable-stayed submersible pump is designed. Compared with other schemes, it has the following advantages: less investment, shorter construction period, more convenient in management and maintenance of pumping station, and a solution to the problem of siltation in pumping stations. After four years of operation, the pumping station is in good condition. The pipeline-rail integrated cable-stayed submersible pump has been gradually applied in river intake projects and has a wide application prospect.

The pumping station can be used for field water distribution and urban water transfer. Multistage pumping stations are mostly built in the Loess Plateau. Because of the uneven distribution of water use in each region, the complexity of water delivery system and operation management, multistage pumping stations need to be optimized. This paper takes a multistage pumping station as the research object. When the pump station is in normal operation (flow rate is 6.1 m³/s), particle swarm optimization algorithm is used to optimize the pump station. Compared with the actual operation, the water level of pumping stations at all levels is slightly adjusted. At this flow rate, the water level can achieve a relatively good cooperation. It can save 1.66% energy per unit time. About 980 000 kWh of electricity can be saved in one year. After optimization, the energy consumption of multistage pumping station is reduced. On the basis of improving operation efficiency and reducing energy consumption as much as possible, it can operate in a safe and economic situation.

With the continuous construction of large-scale water transfer projects, the role of cascade pump stations is becoming more and more important. In order to improve the operation efficiency of cascade pump stations and reduce energy consumption, it is necessary to study the optimal operation of cascade pumping stations. Firstly, this paper describes an optimal operation model of cascade pumping stations and an optimal model of daily operating electricity tariffs based on decomposition-coordination approach. Secondly, taking the cascade pumping stations of Wohushan Reservoir at Yufu River in Jinan City for the South-to-North Water Diversion Project as an example, the local sensitivity analysis of the model is carried out by using the modified Morris Screening Method. The results show that for the optimization model of energy consumption, the energy consumption, unit flow rate and head energy consumption increase based on the increasing in instantaneous flow rate and behind water level as well as decrease in the forebay water level. The paramtric sensitivity is ranked as instantaneous flow rate > forebay water level > behind water level. For the model of daily operating electricity tariffs, its paramtric sensitivity is ranked as daily water regulation > minimum flow rate during peak period > maximum flow rate during trough period. At the same time, under the condition that not exceeding the unit's carrying capacity and meeting with various operating conditions, the smaller the minimum flow rate during the peak period, the larger the maximum flow rate during the trough period, the relatively smaller the daily operating electricity tariffs is. This paper innovatively explores the characteristics of the actual operation of the cascade pumping stations, and then quantitatively identifies the sensitive parameters, which can provide reference and guidance for the optimization research on the cascade pumping stations.

In order to study the influence of the effective flow area ratio between the inlet and outlet of the space guide vane blade and the change law of its cross-section area on the performance of submersible well pump, nine possible configurations have been considered by changing the area ratio while keeping all the other parameters unchanged. Based on the area ratio guide vane model with optimal efficiency, four kinds of guide vanes are designed, including linear, convex up, concave down and S-shaped. The CFD numerical simulation method is used to calculate the internal flow field. And the simulation results are in good agreement with the experiment results, the errors of head and efficiency under design conditions are less than 3%. By analyzing the characteristics of submersible pump, the variation law of guide vane cross-section area has a significant effect on pump efficiency under design condition, efficiency increased by about 4%. But it has a weak influence on the head, the maximum head difference is only 0.7m. The results of the internal flow field distribution in the guide vane passages of different schemes show that the concave down area change law can effectively improve the flow state of fluid in the guide vane and reduce the energy loss. The law of area change of concave down is better than linear, S-shaped and convex up, but how to find the optimal law of area change still needs to be further explored in the future.

In order to analyze the influence of impeller diameter on the pressure pulsation characteristics of the double volute centrifugal pump, the SST k-ω turbulence model and SIMPLEC algorithm are used to calculate the double volute centrifugal pump under different impeller diameters.Compared the experiment results of the external characteristic parameters with the calculated results. The research shows that the external characteristic parameters of the centrifugal pump are equi-gradient with the change of the diameter, and the calculated values are basically consistent with the experiment values. Under the low flow rates, the pressure pulsation amplitude is higher than other flow rates. The impeller diameter change will change the blade curvature, and the pulsation superposition phenomenon will occur due to the rotor-stator interaction and the jet-wake, thereby generating a high amplitude pulsation at a frequency doubling of the blade passing frequency (3f_BPF or 4f_BPF). The flow mixing phenomenon is most pronounced in the tongue region, and except for D′₂/D₂= 1 (model 3), the pressure pulsation peak at the tongue position appears at the blade passing frequency. In the model selected in this paper, the pulsation amplitude at the peak of the pressure pulsation at other monitoring points except the monitoring area of the tongue area gradually increases with the increase in the diameter of the impeller, and the highest amplitude fluctuation reaches 23.8%. The jet-wake and rotor-stator interaction under the impeller diameter change have an important influence on the internal pressure pulsation characteristics of the centrifugal pump.

Three-girder reinforced bifurcation with flat floor combines the characteristics of crescent-rib and three-girder reinforced bifurcation, the entire bifurcation has the same elevation at the bottom, which is helpful to solve the problems of pipeline system drainage during maintenance, but its structure is complex and there is no reliable structural mechanics calculation method. When the bifurcation design scheme is optimized or changed, the finite element software needs to be used for repeated modeling and calculation, with tedious process and heavy workload. In this paper, through the secondary development of CATIA, the computer-aided design system is designed to carry out the shape design and finite element analysis of the three-girder reinforced bifurcation with flat floor, which can effectively improve the design efficiency and accuracy. This program is divided into two modules of symmetry and Y-type according to the arrangement of the bifurcation, including both the shape design, three-dimensional modeling, mesh division, data conversion and other functions. Designing the underground three-girder reinforced bifurcation with flat floor combined with bearing of surrounding rock by this program, the calculation results can be more reasonable, the size of shell and reinforced beam can be further optimized, and the application prospect is very broad.

Based on the standard k-epsilon liquid turbulence model, Eulerian method is used to simulate the two-phase flow of water and sand in concrete volute of turbine. The simulation conditions contain two factors with three levels each. The first factor is the sand content, which is set at 0.5%, 1% and 1.5%. The second factor is particle diameter, which is set at 0.05mm, 0.1mm and 0.5mm.The results show that the pressure increases with the increase in sand content. Under the condition of the same sand content, the increase in diameter will lead to the increase in the volume fraction of sand in the volute. Under the condition of the same diameter, the volume fraction of the sand increases in the volute with the increase in the sand content at the inlet of the volute.

When the Francis turbine is operated under deviating from the optimal working condition, there will be a rotating vortex in the runner blade, which affects the efficient and stable operation of the turbine. In order to investigate the flow characteristics of the inter-blade vortices at Low-Specific-Speed Francis turbines under small opening conditions. The Navier-Stokes equation and the Sparlart-Almaras equation turbulence model are used to simulate the three-dimensional full-flow steady flow of a Low-Specific-Speed Francis turbines at small opening conditions at different rotational speeds. The results show that under the condition of small opening degree, there are inter-blade vortices with different distribution positions and different shapes and sizes in the two rotation conditions, with the increase in the rotational speed, the vortex structure tends to be unstable, and the flow state of the internal flow field becomes disordered, and the hydraulic efficiency of the turbines decreases. The flow characteristics of the inter-blade vortices are closely related to the rotational speed of the runner.

Sichuan Province is an important ecological barrier in the upper reaches of the Yangtze River, and its ecological environment is fragile. The compilation of “Three Lines and One List” in Sichuan Province is extremely important for dealing with the relationship between the protection of ecological barriers in the upper reaches of the Yangtze River and the development of the Yangtze River Economic Belt. Sichuan Province is rich in water resources and has many small hydropower developments. With the improvement of ecological environment protection requirements, the ecological environment problems caused by the disorderly and excessive development of small hydropower have gradually become prominent. In order to effectively maintain the river ecosystem health of the Yangtze River Economy Belt and promote the compilation of “Three Lines and One List” in Sichuan Province, it is urgent to carry out research on the requirements of small hydropower management and control. This study intends to establish the withdrawal criteria of small hydropower from the perspective of watershed, and puts forward the requirements of management and control of small hydropower. It will provide technical support for the state to control small hydropower, the government to manage small hydropower and promote the compilation of “Three Lines and One List”. It will also provide a theoretical basis for the exploration of the green development of small hydropower.

One of the main reasons for frequent regulation of the main distribution in the hydraulic servo system is that the middle position of the main distribution gas is not set accurately and the temperature drift effect occurs. Technicians are conducting an in-depth theoretical research on the hydraulic servo system of governor, putting forward the static balance theory and the principle of correcting the deviation in the main distribution gas, exploring the method of the middle adaptive control in the main distribution gas, and realizing the automatic diagnosis and wisdom of the middle automatic control in the main distribution gas through the development of the software for the adaptive control function of the electric control system of governor. It can rectify the deviation function and verify its function effect through a real machine test. It perfectly solves the problem of frequent adjustment of governor system main distribution caused by unsettled middle position in the main distribution gas of hydraulic servo system or temperature drift, and ensures the safe and stable operation of units and power grids.

The development of rural hydropower resources plays an important role in promoting local economic development, but there are still some problems of safe production and operation management.In pilot plant safety production standardization, 90 rural hydropower station in jiangxi province as an example, this paper introduces the pilot hydropower station in jiangxi province evaluation method, from the safety production target and input, staffing, and responsibility, hidden perils in production facilities and operation safety, management and emergency rescue, incident reporting and investigation and handling of six statistical review elements common problems, and mainly from the installed capacity, rating situation of rural hydropower station in jiangxi province and the overall situation around the city are analyzed, and discussed the causes of common problems and corresponding measures are put forward.The research results can provide reference for promoting scientific and orderly development of rural hydropower resources.