In order to realize the sustainable utilization and maintain the healthy development of river and reservoir ecosystem, this paper applied energy value analysis to reservoir ecological operation for discussing the energy optimal operation of reservoir ecological service value. With the objective of maximizing the service energy of Manwan Reservoir and the constraints of ecological water demand and social economic water consumption, an optimal operation model of reservoir ecosystem service energy was established, and the ant colony algorithm was used to solve the model. The results show that the total service energy of Manwan Reservoir is 2.10×10²² sej in high flow year, 1.79×10²² sej in normal year, 1.58×10²² sej in dry year. Main service values are ecological regulation, water supply and ecological support, material production followed, cultural entertainment is the minimum. The results have practical value and important significance for maintaining the healthy development of the Lancang River basin, especially for the ecosystem of the Manwan Reservoir Region.

Taking the self- and cross-correlation of the multi-station streamflow series of the main and tributary of the basin as the starting point, a multi-site flood series simulation method based on the conditional resampling theory was proposed, and simulate the flood series of Pingshan, Cuntan and Yichang station on the main stream of Changjiang River. The simulation results were compared with the results of the multi-station seasonal autoregressive model (MSAR) for verification and analysis. The results show that compared with the traditional model, the proposed method can not only satisfy the basic statistical characteristics of the runoff series and the higher-order self- and cross-correlation structures of the series, but also further consider the historical extreme flood characteristic, and could generate multi-station simulated flood scenarios with different design frequency.

Ganjiang river trail channel is affected by both upstream water and the backwater effect of Poyang Lake during the flood season. The study of the water level changes has guiding significance for river flood control and shipping. Based on the measured data from 1990 to 2019 at the hydrological station in the Ganjiang river trail channel, this paper adopted the Mann-Kendall trend test and the Pettitt test to analyze the trend of the characteristic water level during the flood season (flood season and backwater of Poyang Lake season). The results show that the water level of the Ganjiang river trail channel had a significant downward trend. The interannual variation of the water level during the flood season was relatively uniform, while it showed a fluctuating shape during the backwater of Poyang Lake season. The mutation years were all around 2002. The main reason for the decline of the water level during the flood period is the erosion of the riverbed. The downward trend of the riverbed has slowed down significantly after 2013, so water level during the flood period stabilized after 2016. The water level during the backwater of Poyang Lake season is mainly affected by the erosion of the riverbed, and the change of the downstream water level will also have a certain impact.

In recent years, urban rainstorm disasters have occurred frequently in China. The community, as an important component of the city, is exposed to urban flooding. In view of the imperfection of the waterlogging prevention and control system, this paper briefly analyzes the characteristics and prevention methods of urban flooding, and summarizes the limitations of the current system. A waterlogging prevention system based on micro system, minor system and major system is constructed from a drainage perspective. The waterlogging prevention and control methods based on site elevation, terrain slope, and water-retaining measure is established. A design method system including design points, design process, design diagram, and key design parameters is formed, which provides reference for the planning and design of sponge communities in new era.

As a special structure connecting core wall and foundation of asphalt concrete rockfill dam, its stress state is very important to the stability of the dam. Taking the asphalt concrete core rockfill dam of Chongqing Miaotang under construction as an example, the maximum section of the dam was selected to establish a two-dimensional model for finite element calculation, and the stress distribution of the foundation under three different forms of unembedded bedrock, semi-embedded bedrock and fully embedded bedrock was discussed. The results show that there is a strong correlation between the embedment depth of the base in the bedrock and the tensile stress inside the base. During the period of water storage, the difference of tensile stress between different arrangement forms can reach up to 334%. Meanwhile, as the corridor was affected by the larger tensile stress inside the base during the period of water storage, it was easy to cause tensile damage. By changing the position of the corridor in the base, the tensile stress around the corridor can be reduced to avoid the damage of the corridor. After the location of the corridor is changed, the surrounding tensile stress can be reduced by up to 87% compared with the original.

The excavation of the foundation, the process of dam construction and the water level variation in foundation have significant effects on the displacement of the foundation and structure of a sluice dam on deep overburden. A finite element simulation method for the coupling of seepage and deformation during the whole process of the dam construction and operation was proposed to treat the foundation of a dam in Jinsha River. The results show that the foundation settlement caused by the dead weight of the filled concrete body of about 1 m height can be offset by 3 m height groundwater level rising in the foundation during the sluice construction. The change of groundwater level has a significant impact on the displacement increment of sluice dam during the construction period. The coupling simulation of seepage and deformation of the sluice dam in the whole construction and operation process was realized, which has supported the engineering design of the dam foundation treatment.

In order to study the surge wave characteristics of pumped storage power station with upstream and downstream surge chambers under small fluctuations, the mathematical model of small fluctuations in a pumped storage power station with this type of arrangement was derived based on the state-space method. The time-domain process of surge wave in the upstream and downstream surge chambers was solved by numerical simulation. The frequency-domain process of surge wave in the upstream and downstream surge chambers was obtained by the fast Fourier transform (FFT). Without considering the hydraulic coupling between the speed regulating system and the surge chamber system, the transfer function between the pressure pipeline flow and the water level of the surge chamber was established to obtain the amplitude-frequency characteristics of the surge chamber systems. The results show that the input signal frequency corresponding to the maximum amplitude of the surge wave in the upstream and downstream surge chambers is similar to the natural frequency of the surge chamber system, and the surge wave oscillation frequency in the surge chamber corresponds to the tail wave oscillation frequency of the unit speed. The surge wave characteristics of the surge chamber are closely related to the area of the surge chamber and the head loss coefficient of the water delivery tunnel. Increasing the area of two surge chambers can reduce the frequency and amplitude of surge wave in the upstream and downstream surge chambers, and enhance the stability of the system. The variation of head loss coefficient of the tunnel has no impact on the oscillation frequency of surge wave in the upstream and downstream surge chambers, but has a great impact on surge wave amplitude in the upstream and downstream surge chambers. The larger the head loss coefficient is, the smaller surge amplitude is, the system stability is better.

In view of the short water hammer control distance of a single air valve in long-distance and low lift water delivery projects, which can not effectively suppress the vacuum in the pipe, a new water hammer control scheme of combined protection of air-valve surge tank and air valve was proposed. Taking a practical project as an example, a comparative analysis of the hydraulic transient process was carried out for the air valve protection and the combined protection scheme of air-valve surge tank and air valve. The results show that the water column separation occurs in the main pipe when the air valve is used for protection, and a large impact water hammer is caused by the rapid exhaust. The combined protection scheme of air-valve surge tank and air valve can not only effectively suppress the vacuum in the main pipe, but also effectively alleviate the impact water hammer caused by exhaust. It is an economic and effective water hammer protection scheme, and can provide a reference for the water hammer protection of other long-distance and low-lift water delivery projects.

In order to alleviate the waste of resources caused by the leakage of urban water supply networks, taking predictive classification as the basic idea, the monitoring data after wavelet noise reduction processing was used in the prediction model of PSO seeking least squares support vector machine algorithm, and the prediction model was trained and evaluated, then combined with the model prediction error distribution law, the estimation method of threshold value and leakage volume was introduced for leakage detection. The results show that the average error between the model prediction and the actual water volume is low, the stability is high, and the combination of the prediction-threshold classification method can detect sudden leakage in a timely manner and estimate the leakage volume relatively accurately.

Aiming at the leakage problem of urban water supply network, the traditional leakage location model is solved by single objective optimization method. Its objective function is composed of the weighted sum of optimization objectives. Improper value of weight factor will degrade the model positioning result. This paper proposed a multi-objective optimization model for leakage location of water supply network based on NSGA-Ⅱ. In this model, the number of leakage point and diffuser coefficient were taken as decision variables, and the minimum error between the actual monitoring value and the simulation value of pressure and flow monitoring point was taken as the optimization objective, and NSGA-Ⅱ algorithm was used to find the optimal solution. In order to verify the effectiveness of the model, it was applied to the actual water supply network in a residential area. Considering the common fault conditions in the actual operation of the pipe network, the leakage accidents of single node and two nodes were respectively simulated and located. Compared with the two widely used leak location models, the results show that the multi-objective optimization model based on NSGA-Ⅱ can accurately and stably locate the nearby area where the actual leak occurs.