Lakes are highly susceptible to eutrophication due to their long-term closed or semi-closed status and poor hydrodynamic conditions. This paper constructed a hydrodynamic-convective diffusion model with MIKE21 software by considering the influence of rainfall on the spatial and temporal distribution of TN concentration in the Yilong Lake. The model simulated the hydrodynamic conditions under different inlet opening and closing conditions and different flow diversion schemes. The improvement of TN concentration based on the flow velocity distribution of the lake flow field was discussed. The results show that the hydrodynamic conditions and the water quality of the lake can be effectively improved by setting up water diversion inlets and increasing water diversion flow. The overall effect of diverting water from the Chenghe alone is better than diverting water from the Chenghe and Longgang River together. Under the scheme of separate diversion from the Chenghe, when the water diversion flow was double, the overall flow rate of the lake was increased by 44.04% and the TN concentration decreased by 52.78%, with the best effect of hydrodynamic optimization and water quality improvement, but the efficiency of water quality improvement per unit of water recharge is reduced. This research could provide some references for similar projects.

In order to explore the evolution of rainfall at multiple time scales, this paper takes the Changtan Reservoir in Jiaojiang River Basin as an example and classifies independent rainfall events based on rainfall data from 1960 to 2019. The evolution of rainfall event elements is discussed from four perspectives of rainfall event scale, seasonal scale, changes in annual trends and interannual decadal change. The results show that the extreme rainfall events has strong rainfall and long rainfall duration; The rainfall duration of typhoon rainy season is shorter and the rainfall intensity is greater than that of the plum rainy season, and the variation of rainfall distribution is greater; The annual trends of rainfall event elements are similar between the two stations during the plum rainy season, but the annual trends of rainfall duration and rainfall intensity are significantly different between the two stations during the typhoon rainy season; The rainfall events of the two stations in the plum rainy season have a good response to El Nino events, while the annual rainfall of El Nino/PDO- in the typhoon rainy season is abnormally small, which is prone to drought. El Nino/PDO+ annual rainfall is abnormally high and is prone to appear flood disaster.

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.

Affected by the changes of East Asian monsoon and human activities, the hydrological processes in the southeast coastal area have been changed, and the rational development and utilization of regional water resources are facing challenges. Taking Feiyunjiang as an example, the variable parameter Budyko equation based on the moving average treatment was constructed to analyze the runoff change in the basin, and the future runoff change trend was predicted qualitatively combined with the CMIP5 model. The results show that the time-varying Budyko model is much better than the constant parameter Budyko model in the simulation of annual runoff. The hydrometeorological elements in Feiyunjiang Basin showed an upward trend after eliminating the influence of cycle. The contribution rate of climate to runoff variation in the Feiyunjiang Basin reached 85.56%, and showed a downward trend. Compared with before 2000, the contribution rate of the underlying surface to runoff change increased by 6% from 2000 to 2020. At the same time, the influence intensity of climate on runoff change changed sharply. The influence of the underlying surface on runoff reduction was weakened. In addition, under the RCP4.5 scenario, the runoff in the Feiyunjiang Basin will show a decreasing trend in the future. The research results can provide theoretical support for regional water resources planning.

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.

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.

In order to study the damage behavior of fiber reinforced concrete at high temperature, the acoustic characteristics of hybrid fiber reinforced concrete (PVA fiber and basalt fiber) at different temperatures were tested, and the mechanism was explained from the microscopic level by combining the results of the SEM. The results show that with the rising of temperature, the degree of ultrasonic waveform distortion is more significant, and the attenuation of waveform amplitude is gradually intensified; The incorporation of fiber or the increase of temperature will reduce the amplitude of the dominant frequency of the waveform and increase the energy dissipation caused by the ultrasonic penetration of the specimen. At high temperature, after PVA fiber is melted, a large number of pores remain and gradually form connecting pores, which promote the release of pore steam pressure and alleviate high-temperature damage, while basalt fiber continues to play a bridging effect to inhibit the continuous development of high-temperature cracks.

To accurately evaluate the comprehensive utility tunnel under river shield tunnel construction safety, reduce the safety accidents in the construction process, based on the method of risk breakdown structure (RBS), risk evaluation index system of four first-level indicators was constructed including engineering geological risk and comprehensive utility tunnel itself risk, environment risk, construction risk management. Based on the linear combination of interval number analytic hierarchy process (AHP) and indicator correlation method (CRITIC), the comprehensive weight was determined. Based on matter element theory, the weighted average relation degree was calculated to determine the final evaluation result. This method was applied to the comprehensive pipe corridor project of Yueyang Avenue sewage treatment at the Wangjia River section. Monte Carlo method was used to analyze the sensitivity of 15 basic indexes based on matter-element theory. The research results show that the construction project of Yueyang Avenue sewage treatment comprehensive pipe corridor at Wangjia River section is medium-risk, which is consistent with the actual situation. The sensitivity analysis shows that the surrounding rock strength and the buried depth of tunnel are more sensitive. The research results can provide a basis for the safety control decision and measure making of the project.

Based on the runoff duration data of the basin in the past 50 years, the spatial-temporal evolution and ecological effects of hydrological variation in the Zuli River basin in arid and semi-arid region were studied by using cumulative anomaly analysis, M-K nonparametric mutation test, and runoff ecological index analysis with flow duration curve. The results show that since 1970, the surface runoff of the study basin was strongly affected by climate, and its runoff appeared sudden change in 1995. After studying the variation of runoff in the basin, the surface runoff decreased significantly, and the runoff in flood season and annual runoff decreased 36.9 million m³ and 32.12 million m³, respectively. After runoff variation, the ecological deficit in the study basin was obvious, and the annual proportion of runoff ecological indexes in non-flood season increased.

With the continuous development of the city, influenced by climate change and human activities, the runoff of urban water system has changed greatly. In order to further research the runoff trend and its main influencing factors brought by urbanization, the application of the comparison of slope change ratio in hydrological change analysis was further innovated, and the contribution rate of underlying surface to runoff change was separated from human activities. Taking Zhengzhou city as an example, combined with Mann-Kendall test method, the contribution rate of climate change factors, underlying surface factors and other human activities to runoff change was calculated. The results indicate that the measured runoff flow showed an upward trend from 1980 to 2019, and a sudden change occurred in 2008. In the impact analysis of runoff, the change of underlying surface and other human activities are the main influencing factors, and their contribution rates are 69.76% and 56.19%. According to the analysis of the main influencing factors, the main reasons are as follows: The hardening of the underlying surface increases runoff yield and flow concentration, and the population increases and the emissions increase.