Taking 16 cities and prefectures in Hubei Province as the research object, from the perspective of unexpected output, DEA-SBM model was used to calculate the water environment governance efficiency from 2014 to 2018. Combined with GIS spatial analysis method, the temporal and spatial variation characteristics of urban water environment governance efficiency were explored, and the influencing factors of urban water environment governance efficiency were analyzed by multiple linear regression model. The results show that the efficiency of urban water environmental governance in Hubei Province has rising trend, but there is a difference in time-order changes in water environmental governance between different cities; The efficiency of urban water environment treatment in Hubei Province shows a spatial distribution trend of low in the central region and high in the eastern and western regions; The level of infrastructure and environmental regulation have a significant positive impact on urban water environmental governance, and urbanization level has a significant negative impact on water environmental governance efficiency.

In order to study the correlation and distribution characteristics of arsenic (As 75) and other trace elements in the water of plateau rivers, the trace elements in the water of Yalong River in July 2021 (wet season) and November 2021 (dry season), an important tributary of the Yarlung Zangbo River, were investigated and analyzed. Based on correlation analysis, cluster analysis and principal component analysis, the relationships among arsenic 75 (As 75), boron 11 (B 11), iron (Fe 57), strontium 88 (Sr 88), tin 118 (Sn 118), lithium 7 (Li 7), vanadium 51 (V 51), cobalt 59 (Co 59), nickel 60 (Ni 60), copper 63 (Cu 63), zinc 66 (Zn 66), selenium 82 (Se 82), molybdenum 98 (Mo 98) and lead 208 (Pb 208) in water were explored. The results show that there are significant differences among the elements in wet season and dry season, which can be divided into three categories: The elements with stable contents in wet season and dry season (Ni 60, Co 59, Cu 63, Li 7, Zn 66); The elements with obvious seasonal variation (Sr 88, V 51, Mo 98, Li 7, Se 82, As 75, B 11, Pb 208); Elements less associated with other elements (Sn 118). In addition, most of the trace elements in the Yalong River Basin are related to Ni 60, Co 59, Cu 63, Li 7 and Zn 66. The study can provide scientific basis for understanding the changes of water environment in the basin and subsequent environmental protection.

In order to explore the spatiotemporal characteristics of water quality and its correlation with land use type in the middle and lower reaches of the Chanba River, sampling and monitoring were conducted in April (wet period), August (flow period) and December (dry period) of 2019 based on seventeen sampling sites. The spatial-temporal characteristics of water quality and the identification of main pollution factors were analyzed by employing multivariate statistical, and the relationship between the land use type and water quality indexes was studied by the method of Spearman analysis. The results show that water quality had spatial and temporal characteristics in the middle and lower reaches of Chanba River in 2019. In terms of time, the concentration values of NH₃-N, TP and COD_Mn were maximum in flow period; The order of TP and COD_Mn was sorted as flow period > wet period > dry period. Spatially, the concentrations of NH3-N, TP and COD_Mn basically increased from the middle reaches to the lower reaches. Influenced by human activities along the river, the water quality was mainly polluted by nutrient and organic matter in the middle and lower reaches of Chanba river. Construction land had a positive correlation with pollutants and played a "source" role, while forest had a negative correlation with pollutants and played a "sink" role. The results can provide reference for water environmental management in Chanba River Basin.

To determine the key water quality indicators for influencing the Weihe River tributaries of Chanhe, Bahe, Fenghe and Zaohe Rivers and the minimum water quality index (W_WQImin) is of great significance for simplifying water quality evaluation. The research set up a total of 30 sampling points in the 4 rivers and collected water quality samples in April, August, and December 2019, respectively. Fifteen water quality indicators were analyzed by laboratory experiment and mathematical statistics. It was found that the content of DO in Fenghe River was obviously highest, and the contents of EC and nitrite in Zaohe River and the Bahe River reach after the convergence of Chanhe River were higher than other rivers. In addition, based on 15 water quality indicators, the water quality index (W_WQI) was calculated to evaluate the temporal and spatial changes of water quality of the 4 rivers. This study shows that the water quality indices were generally above the medium level (W_WQI≥51) in all four rivers, and the water quality of the Fenghe River was better among the four rivers. On time scale, the water quality in the spring of 2019 was better than the other two periods. Besides, stepwise multiple linear regression analysis and empirical method were used to determine the appropriate minimum water quality index (W_WQImin), which contains DO, ammonia nitrogen, COD_Mn, turbidity, nitrate nitrogen, $\mathrm{SO}_{4}^{2-}$, and EC. Compared with the W_WQI based on 15 water quality indicators, the relative error (P_PE) is only 4.78%, the linear correlation coefficient R² reaches 0.95, and the root mean square error (R_RMSE) is only 3.99. Finally, the spatial and temporal distribution of W_WQI and the appropriate W_WQImin in the 4 rivers are consistent. Therefore, it can be considered that the selected appropriate W_WQImin can be replaced of WQI, which is more efficient for time-saving, low-cost and high-efficiency water quality evaluation in the basin near the Chanhe, Bahe, Fenghe and Zaohe Rivers.

Under the influence of climate change and land use/land cover (LULC) change, the combined influence of multiple factors has significantly increased the difficulty of probable maximum flood (PMF) estimation. A PMF estimation framework was proposed, integrating post-processing of climate model results, probable maximum precipitation (PMP) estimation and future LULC change setting under climate change scenarios, impact analysis of base flow/antecedent rainfall, and similarity-based PMP spatio-temporal distribution. This new framwork was applied to the Upper Nujiang River Basin. The results show that the uncertainty of base flow/antecedent rainfall and PMP spatio-temporal distribution are important factors affecting PMF for basins, and the dual-drive of climate change and LULC change has a greater impact on PMF, and the amplitude of change increases with the degree of change.

Plain river network, especially near the airport area, has complex hydrological structure, and the flood control and drainage are very important. Taking the Hangzhou International Airport as an example, one-dimensional hydrodynamic model of the river network was built based on MIKE11. The current situation of drainage was analyzed through different startup conditions of the existing drainage pumping station, and the optimization and promotion plan was proposed. The result indicates that the overall drainage capacity of the West Work Area of Hangzhou Airport cannot meet the standard of “once in 20 years”, which needs to be optimized for drainage. Under comprehensive consideration, it is recommended to use strong drainage instead of regulation and storage, and adopt the drainage idea of "mainly strong drainage, combined with regulation and storage" to form an overall drainage pattern of "backbone river channel + strong drainage pumping station".

The problem of waterlogging in old city has become the focus of natural disaster research. Taking Fenghuang District of Nanchang City as an example, the MIKE FLOOD model was established to analyze the risk and causes of waterlogging. Based on the above results, the SWMM model was used to conduct the research on LID layout and optimization. Analytic hierarchy process was used to evaluate its comprehensive benefits, and the optimal cost-benefit scheme was finally obtained. According to the study, the rainfall return period is 5 years, there are 16 waterlogging points, and the risk level of waterlogging in some areas has reached level Ⅳ. It can be seen that the urban waterlogging prevention and control research is urgent. LID combination facilities have a good effect on alleviating waterlogging. The scheme of 22.5% rainwater garden +7.5% pervious pavement is the best. This conclusion can provide technical reference for the following low impact development and construction of sponge cities and the proportion selection of facilities.

In view of the uncertain factors of natural inflow and electricity price during participating in bilateral transactions at different time scales for cascade hydropower plants, there are problems of market share determination, water resources utilization and profit risk since electricity allocated irrationally. Therefore, this paper presented a risk-based optimal combination model of medium- and long-term contract electricity for cascade hydropower stations. To realize the goal of the minimum profit risk under a given confidence, the monthly inflow process was randomly generated by annual inflow data. Three electricity price functions were fitted by different proportions of hydropower stations in the market. The combination of power output and contract electricity of cascade hydropower plants were solved by the loop-Iteration method of hybrid progressive optimization with successive approximation method. The model was demonstrated using the hydropower plants in the southwest region. The results show that proposed model can determine the declaration strategy between monthly and annual bilateral contract electricity, and reduce the profit risk. It can provide reliable basis for bilateral transactions at different time scales of cascade hydropower plants.

In order to optimize the dispatching mode of Luntan hydropower plant, the process of socio-economic and ecological water demand in the downstream were analyzed. Considering the downstream water demand, the monthly generation dispatching function were extracted from the results of optimal generation dispatching by use of stepwise regression method. The results show that the dispatching of Luntan reservoir plays a great role in the downstream water demand process. The main period of water replenishment is from July to the following February, which directly changes the process of power generation diversion flow of Luntan hydropower plant. The NSE coefficients of the generation dispatching function of Luntan hydropower plant based on multiple linear regression model and BP neural network are greater than 0.90 in most months. Considering the advantages of simple structure and convenient implementation, the generation dispatching function based on multiple linear regression model is selected for Luntan hydropower plant. Compared with the results of actual dispatching and dispatching diagram of Luntan hydropower plant, the generation capacity of the dispatching function is increased by 338.4×10⁴ kW·h/month and 183.8×10⁴ kW·h/month from March 2017 to February 2019, respectively. As a result, the water level of Luntan Reservoir can be significantly increased by use of the dispatching function. The research can provide a support for the generation optimal dispatching process of Luntan hydropower plant, and provide a useful reference for many other hydropower plants to improve the practical way of the generation dispatching.

A large area of tensile stress in the middle and lower part of the upstream of a stone-masonry arch dam exceeds the standard and needs to be strengthened. Based on two local reinforcement schemes of a masonry dam, the contact element was used to simulate the joint characteristics of the new and old dam bodies, and the stress and deformation characteristics of the joint surface under five standard working conditions were analyzed. The results show that after reinforcement, the opening and loading characteristics of the joints of the two schemes are similar, and the side pier of the rib pier scheme has asymmetrical opening and loading phenomenon. Under the condition of high water level, the reinforced structure mainly supports the load at the upper part, and the stress at the lower part is small and may open. Under the condition of low water level, the stress level of the joint surface is low and the reinforced structure does not bear the load. Under the condition of temperature drop after reinforcement, the masonry dam body rotates and deforms with the upper part of the reinforced structure as the fulcrum, and the joint surface will open in a large area under the condition of low water level. Under the condition of temperature rise, the dam body shifts upstream when the water level is low, resulting in a symmetrical and smooth parabolic clearance distribution on the horizontal direction.