In order to comprehensively evaluate the water environment health status of Poyang Lake, a quantitative evaluation index system was established from three aspects of water quality, hydrology and aquatic organisms. The comprehensive weighting method combining analytic hierarchy process and coefficient of variation method was used to determine the comprehensive weights of indicators. The TOPSIS method was applied to construct the evaluation model, which determine the score of evaluation objects by combining the weights of indicators. The results show that there are seasonal changes in the water environment health status of Poyang Lake, and the two indicators of hydrology and aquatic organisms in summer are obviously better than other periods, so that water environment health grade is the highest and belongs to grade Ⅰ, with better coordination; The water environment health grade in autumn and winter is the worst and belongs to grade Ⅲ, among which hydrological condition is the main influencing indicator. This study can provide reference for water environment protection and construction of Poyang Lake.

Ground penetrating radar (GPR) has a broad application prospect in detecting the leakage area of water supply pipeline. In order to enhance the understanding of the response characteristics of GPR in the leakage area and improve the positioning accuracy of the leakage area, based on the finite difference time domain method, this paper simulated the response characteristics of ground penetrating radar for leakage at the bottom of metal pipes, and extracted the "three instantaneous" seismic attribution. The results show that the upper boundary signal of the leakage area is easy to be identified, and the internal signal has multiple reflections and oscillations. The reflection effect of the instantaneous amplitude attribution in the leakage area is similar to that of the original profile. The instantaneous phase attribution is obviously staggered, and the instantaneous frequency attribution is obviously attenuated. Instantaneous phase attribution and instantaneous frequency attribution can reflect the existence of leakage area and weak signal well, so the instantaneous phase attribution and instantaneous frequency attribution are preferred when analyzing the instantaneous attribution of leakage area. The research results can provide a reference for the interpretation of GPR pipeline leakage detection images and practical engineering applications.

In order to explore the calculation method of water demand of water-reduced river landscape under hydropower development, combined with the data of hydrology and social economy in the region, this paper compared the changes of landscape characteristics after water reduction in similar projects. Taking the water reduction channel caused by Danba Hydropower Station as an example, the landscape evaluation factors were chosen comprehensively. Considering human visual effects, the landscape water demand evaluation system was established. A calculation method for the landscape water demand of the water-reduced reaches caused by the construction of hydropower stations was proposed. Based on the hydraulic model, the landscape indicators of each river section were calculated according to the determined index system, and the water volume required for the wide valley section, canyon section and county river section to meet the landscape requirements of water-reduced river channels is 70.4 m³/s, 64.8 m³/s, 50.7 m³/s. The 70.4 m³/s is taken as the landscape water demand of the whole reach of the reduced water.

As an efficient, environmental and energy-saving transportation technology, the wheeled capsule transportation has promising application prospects. When the pipeline carriage was stationary in the pipe, it could be regarded as a crossing-cylinder structure. When water flowed around the structure, the vortices existed, which would cause energy loss. Therefore, the hydraulic characteristics at the downstream of the flow field around a pipeline car and the spatial vortices structure after the stabilized flow field were studied by numerical simulation, model test and theoretical analysis. The results show that the near-field areas of the downstream flow field of wheeled capsule with different diameters could be divided into the reflux zone and the jet zone. As the distance rose, the section-averaged velocity had a tendency of declining then rising in the near-field, and recovered the section-averaged velocity of pipe at the distance of the length of capsule. And in far-field, with the distance rose, the fluctuation of section-averaged velocity was gradually decreased, and the flow became stable. The eddy ring structures in the field were highly fractured, eddy structures were more on the side near the annular gap and less on the side near the pipe axis.

In order to overcome the difficult problem of establishing multi-factor and non-linear complex relationship of reservoir sand discharge and achieve its accurate prediction, four machine learning algorithms including XGBoost, KNN, SVR and RF were used to predict and analyze the sand content of reservoir outflow based on the series data of Wanjiazhai reservoir from 2002 to 2020, respectively. The results show that the use of machine learning algorithms can effectively realize the reservoir discharge prediction considering different influencing factors. The applicability of different machine learning algorithms in reservoir discharge prediction varies. In comparison, the highest coefficient of determination R² of the reservoir discharge prediction model based on RF algorithm is 0.9349, and the corresponding average absolute error and root mean square error are the smallest, which are 2.974 and 4.886, respectively. The prediction effect of the RF algorithm is better than the other three algorithms. The proposed method can provide a theoretical basis for accurate prediction of reservoir sand discharge and optimization of scheduling scheme.

Based on the RNG Κ-ε double-equation turbulence model and the VOF two-phase flow model, the flow regime, flow velocity, pressure, energy dissipation, cavitation and sediment transport characteristics of the double volute chamber vortex shaft were studied using model test and numerical simulation. The results were in good agreement with the experimental values. The vortex chamber was more thoroughly dosed with gas through an aerator device, which reduced the possibility of cavitation erosion. The measured energy dissipation rate exceeded 75%, indicating a good energy dissipation effect. The sediment siltation existed at the bottom of the shaft for various particle sizes at various flow rates, reducing the depth of the stilling well. At low flow operation, the siltation might reached up to 72% of the stilling well’s depth. However, the sediment was cleared away after a big flood and the silt height was lowered to 1.6% of the well depth, enabling the cyclone shaft to have a sufficient water cushion for energy dissipation that would not interfere with its regular functioning. Control the size of the barrage in actual projects to prevent congestion caused by large particles of sediment entering the floodway. In actuality, the operating mode can be altered to control the stilling well’s silting height, ensuring that it has sufficient rich water cushion depth to match the cyclone shaft's design and regular operation requirements.

In view of the serious cavitation erosion and local cracks of water turbine runner after the capacity expansion and transformation of four runners in Shangyoujiang hydropower station in 1998, JF3057 turbine runner with excellent hydraulic performance was developed through numerical analysis and optimization design in 2017 for the innovation of unit ^#2 of the power station. The measured results of the prototype turbine after innovation show that the new runner has greater output and higher efficiency, and the vibration and the shaft runout are normal, but strong noise and metal roar within a certain load range exist in the turbine. In 2018, the strong noise and metal roar were basically eliminated after the blade outlet edge modification. After 5-year operation test and periodic inspections of the runner, the cavitation phenomenon of the new runner has been greatly improved, and the transformation of No. 2 turbine has been successful.

In view of the problem that hydraulic concrete buildings in cold regions are vulnerable to early freezing injury during pouring construction and may affect the later healthy service, in order to study the strength damage law of early frozen concrete and optimize its ratio, Box-Behnken (RSM-BBD) response surface method was used to optimize the experimental design. The RSM response surface model was established by taking water binder ratio, fly ash content and air entraining agent content as variables. A GA-BPNN strength prediction model was constructed to predict the strength of early-frozen concrete accurately. Compared with the RSM model, the results show that the GA-BPNN has more accurate prediction performance and can optimize proportion design more efficiently. The goodness of fit R² and average relative error e_MRE by the GA-BPNN strength prediction model are 0.998 5 and 2.13%, respectively. The relative error between the predicted value of the optimal strength ratio and the experimental value is about 1%. The application of GA-BPNN strength prediction model can realize the efficient optimization of concrete freezing strength and its ratio.

In order to study the mechanical properties and damage mechanism of recycled brick concrete, the shape of recycled aggregate was regarded as a random concave convex polygon. Recycled brick concrete was regarded as seven-phase heterogeneous composite materials such as waste brick aggregate, waste concrete aggregate, new and old mortar, waste brick-new mortar, aggregate-old mortar, new and old mortar. Based on the ABAQUS development program of PYTHON, the numerical model of recycled concrete with different aggregate rate and different brick quantity was established. The meso-mechanical properties of recycled concrete containing brick with 45% coarse aggregate content were analyzed. The damage and failure patterns of recycled concrete containing bricks under load were studied. The results show that the algorithm is efficient in modeling, and can establish the mesoscopic model of recycled concrete containing bricks with different aggregate rates and different brick quantities, which can meet certain engineering requirements; The peak stress and elastic modulus of recycled brick concrete gradually decrease with the increase of brick quantity, while the peak strain increases with the increase of brick quantity; The damage and failure patterns of concrete with different brick quantities are basically the same.

The contradiction between the supply and demand of water resources becomes increasingly acute, so it is particularly important to optimize the allocation and efficiently utilize the limited water resources in the region. Water resources allocation in Hengshui city was taken as a case study. The demand of optimal allocation of Hengshui city water resources was considered comprehensively. The multi-objective optimal allocation of water resources model was established by taking the social benefit, economic benefit and ecological benefit as the objective function. The scheme of optimal allocation of water resources based on MOEA/D algorithm was given, and comparison experiments between the proposed scheme and the scheme based on NSGA-Ⅲ algorithm was done. The experimental results show that proposed scheme is superior to the scheme reported by literature, which can provide relevant support for the rational allocation of water resources in Hengshui city.