In order to analyze the Nitrogen pollution status and changes in the Yihe River Basin, a SWAT model was established, and the model was calibrated based on the monitoring data of Linyi Station. Its temporal and spatial distribution characteristics were analyzed and the key pollution sources were identified. The results show that the SWAT model has good applicability in the simulation research of runoff and pollution in the Yihe River Basin; The pollution is mainly concentrated in the flood season from July to September, and the ammonia nitrogen and total nitrogen load account for 73.34% and 81.58% of the whole year; The sub-basin in the southwest and close to the water system in the northeast are the main source area of pollution; The main sources of pollution in the basin are sewage discharge, agricultural fertilization and soil loss. Taking Nitrogen fertilizer reduction, returning farmland to forest and comprehensive management measures for the changes can effectively reduce the discharge of pollution load.

In order to solve the problem that the new hydraulic gate is difficult to manufacture experiment and debug in the real environment, the historical gate operation data was analyzed and transmitted based on the digital twin simulation platform. The designed gate was analyzed through numerical simulation, and the overall stress and deformation changes of the gate with different sub-gate opening degrees under hydrostatic pressure were analyzed. At the same time, the overall vibration frequency changes of the gate under the action of air and fluid-structure interaction were analyzed. The flow state of the fluid domain at the sub-gates with different opening degrees was simulated. The results show that with the increase of the opening of the sub-gate, the stress value of the gate varies from 58 MPa to 67.5 MPa, and the deformation change is not obvious; Compared with the natural vibration frequency of the gate in the air, the fluid-structure coupling effect will appropriate reduce the natural vibration frequency of the gate; Different sub-gate openings will affect the flow state of the fluid domain, and increasing the opening will reduce the water velocity. The results provide some references for its actual operation, maintenance and optimization of gate performance.

With many hydropower resources, Southwest China is a crucial area for current and future hydropower construction. However, most southwestern regions have deep overburden problems and high seismic intensity. The impact of these problems on the regular operation of high-face rockfill dams cannot be ignored. This paper established two-dimensional finite element models of 100 m, 200 m, and 300 m high-face rockfill dams on 100 m-deep overburden. Under the action of long-period ground motion and conventional ground motion, the elastic-plastic constitutive model was used to study the dynamic response characteristics of face rockfill dams with different heights on the same deep overburden. Compared with conventional ground motions, the results show that long-period ground motions significantly influence the acceleration of deep overburdened high-face rockfill dams. As the height of the dam body increases, the peak acceleration of the dynamic response of the dam body gradually decreases. Moreover, under the action of long-period ground motion, the higher the dam body is, the greater the displacement increment of the dam body in a short time. In this way, the resulting deformation is also more significant, which is not conducive to the seismic stability of the dam. Therefore, when building panel rockfill dams in areas with deep overburden and frequent long-period earthquakes, the effect of long-period ground shaking should be considered as a part of seismic stability evaluation.

The precipitation data with high quality and high spatial and temporal resolution is of great significance to the research of hydrology, meteorology and other fields. At present, remote sensing and reanalysis of precipitation data are widely used, but there are problems such as low resolution, high uncertainty of accuracy, etc. In this paper, a random forest precipitation fusion algorithm considering covariates is proposed to fuse seven sets of precipitation products, namely CMA, CN05, ERA5, GLDAS, TRMM, IMERG and PERSIANN. Three typical sub-basins of the Yangtze River basin (Jinsha River, Sanxiaqujian and Poyang Lake) are selected to test the effect of random forest fusion data (RFF). The results show that for the accuracy of precipitation products, the accuracy of random forest fusion data is improved compared with the original precipitation products. For the accuracy assessment of different precipitation events, with the increase of rainfall intensity, the T_TS score of each precipitation product shows a decreasing trend, and the T_TS score of RFF is better than the original precipitation product. Data fusion of precipitation products through random forest model considering covariates can improve the accuracy of precipitation data and the reliability of different precipitation events, which provides support for hydrological simulation.

A new anti-seepage structure between the asphalt concrete slab and geomembrane is proposed, which eliminates the concrete connecting plate and adopts backfilling elastomeric epoxy mortar into drilling holes. The mechanical and impervious properties, as well as anchoring parameters of the connecting joints in the anchorage area, are experimentally studied. It is found that the torsional and anti-pulling performance of the proposed anchoring approach is reliable. The suggested double-channel anchoring approach is more compatible with the large deformation of the geomembrane under a pressure of 0.4MPa. According to the results, optimal drilling parameters are proposed, which have the features of good porosity, reliable impermeability and less impact on the asphalt slab, providing a reference for engineering design.

The Wangyu River is an important watercourse connecting the Yangtze River and Taihu Lake. Relevant hydrological data shows that the pumping opportunity can account for 25.9% of the total drainage period from the Wangyu River to the Yangtze River, which indicates that the pumping station plays a crucial role in the drainage period of Taihu Basin. The current design lift (2.5 m) of the pumping station is higher than the actual operating lift, and the running time of the pumping station exceeding 20% of the installed designed capacity accounts for 65.9% of the total operation time. According to the design specifications of the pumping station and relevant local standards, combined with the analysis of the hydrological data, it is recommended to adjust the design lift of the pump station to 1.78 m in the subsequent upgrading of the pumping station. The optimized design lift is more compatible with the actual operating environment of the pumping station, and it also reduces the operating costs of the pumping station such as power consumption, and prolongs the service life of equipment, which is of great significance for the overall benefits of the Wangyu River Hydro-junction.

In view of the frequent occurrence and serious loss of urban waterlogging disasters in recent years, this paper focuses on the current situation of engineering of waterlogging drainage, and takes Lu'an City, Anhui Province, which experienced waterlogging disasters in 2016 and 2020 as the research object. Considering the connection relationship between drainage network and drainage channel systematically, the study analyzes and determines the engineering weakness that cause urban waterlogging from the aspects of the standard of drainage network corresponding to the location of water logging points, the relationship between ground elevation and the design water level of the corresponding receiving rainwater river, the drainage capacity of the river, and the operation conditions of the drainage pumping station, based on the tracking of rainwater discharge process of pipe network-inland river-outland river. The results show that the elevation of water logging point in the old urban area of Lu'an City has the condition of flowing into the river by gravity, and the drainage channel and drainage pumping station can meet the drainage requirements. The main engineering reason for the occurrence of waterlogging is that most drainage network have low standards and can not drain rainwater into the river in time. On this basis, it is further considered that the implementation of the drainage network rectification in the old urban area is difficult and long cycle. In order to minimize the risk of waterlogging before rectification, it is proposed to reduce the operation water level of the drainage pumping station at the estuary of the outland river, so as to improve the ability of urban drainage and disaster reduction.

In order to ensure the service performance of underwater concrete structures, it is urgent to carry out the detections and quantitative analyses of underwater concrete structure defects. Aiming at the common failure forms of underwater concrete structures such as collapse and indentation in practical projects, model plates with different shapes and sizes of indentations were designed and made. Using the side scan sonar carried by the unmanned ship, the defect model plates were scanned at a constant speed in a test pool. The acoustic characteristics of the defect areas were summarized by extracting the echo intensity waveforms of different shaped defects along the transverse sections. Image segmentation, mathematical morphology processing, and edge feature extraction were carried out on the original sonar image of different sizes of defects to obtain clear and complete contours of the defect areas. Through the interpretation of the longitudinal length of the defect areas, the quantitative analyses of underwater concrete defects were realized, and the identification error ratios were within 10%. It provides a new method for detecting the defects of underwater concrete structures.

To improve the accuracy of areal mean rainfall data and solve the problems of instability of least square estimation in runoff error correction based on dynamic system response curve, ridge estimation of rainfall error based on differential response was introduced based on least square ridge estimation. The calculation of the Xin’anjiang model was generalized a system. The method was applied in flood forecast error correction in Jianyang basin with 37 historical floods chosen as test samples. The results indicate that the ridge estimation of rainfall error based on differential response has obvious correction effects in Jianyang basin, which can improve the accuracy and stability of flood forecasting.

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.