In order to study the dynamics of the water resources system and to solve the problems existing in traditional TOPSIS evaluation of water resources carrying capacity， for example， when the evaluation values are close to the interval classification boundary，the grade differentiation is not high， thus it is difficult to form an objective and effective evaluation. In this paper， due to the advantage that D-S evidence theory can effectively reduce loss caused by data variability and fuse the results objectively and accurately， it is used to improve TOPSIS method for water resources carrying capacity evaluation. By fusing the distance between the indicator vectors in TOPSIS method and the positive and negative ideal solutions， the synthetic confidence of each grade of water resources carrying capacity is obtained， and the grade of water resources carrying capacity is judged based on the synthetic confidence value with greater differentiation. On this basis， the indicator increment is introduced to calculate the changes in the water resources carrying capacity over the years， and the time power vector is used to combine the changes over the years to analyze the trend of water resources carrying capacity. The results show that： the discriminations between the evaluation value and the interval boundary are improved from 0.000 3， 0.001 1 in 2018 and 2020 to 0.019 and 0.336 7 respectively by improved the TOPSIS. Meanwhile， the error between the predicted trend using the proposed trend analysis method and the actual result is 0.001 9 in 2020. Finally， it is predicted that the water resources carrying capacity will have a negative trend in 2021. The main impact indicators are annual precipitation and per capita water resources by the obstacle factor model. The suggestions are put forward to strengthen the construction of the ecological environment and optimize the rational allocation of water resources. The method in this paper has higher grade distinction， and the evaluation results are reasonable and objective， in line with the actual situation. And it can also make comprehensive use of the dynamic data of the past years so that it can accurately describe the changes in water resources carrying capacity， which can provide a scientific basis for the development and protection of water resources.

Considering that it is difficult to obtain the optimal operation scheme from the conventional reservoir operation diagram and that the stochastic optimal operation solution of cascade reservoirs causes “dimension disaster”， this paper takes Baishan and Fengman cascade reservoirs hydropower stations in the second Songhua River in northeast China as examples to analyze the actual runoff characteristics of cascade reservoirs， based on the characteristics that the natural runoff of cascade reservoirs in the same basin has strong correlation， a reduced-dimension Markov chain stochastic runoff description model is proposed to solve the dimension disaster problem of the stochastic optimal operation model of cascade reservoirs. At the same time， the description method of runoff forecast with and without time intervals is used to make the runoff description more practical. According to the proposed runoff description model， the maximum expected value of power generation during the operation period is used as the objective function of the optimal operation model， and the model recurrence equations under the conditions of no runoff forecast in the adjacent period， no runoff forecast in the adjacent period， no forecast in the current period and no forecast in the later period， no forecast in the current period and no forecast in the later period are studied. The optimal operation model of cascade reservoirs considering the combination of runoff forecast in the current period and no forecast in the later period is created for the first time. The method of combining the penalty coefficient and changing the guaranteed output constraint is used to solve the optimal decision scheme of the reservoir under various output guarantee rates. Under the same output guarantee rate， through a comparative analysis of the simulated optimal operation results of the historical runoff series of Baishan and Fengman cascade reservoirs， it can be seen that the optimal operation rules obtained in this paper obtain more power generation benefits than the conventional reservoir operation chart and the traditional stochastic optimal operation rules， and the model solving time is also several times more than that of the traditional method. It fully illustrates the effectiveness of the model and the superiority of the scheduling rules created in this paper.

The LMDI model for evaluation of water resources utilization efficiency in the Yangtze River Basin was established with 11 provinces in the Yangtze River Basin. It is used as a research object to identify the impact of labor scale effect， economic development level effect， technological progress effect， and water use scale on water use efficiency. And the STIRPAT model of water use efficiency is constructed to reveal the response relationship between water use efficiency and various influencing factors. According to the findings of the study， the labor scale effect of Qinghai， Tibet， Sichuan， Yunnan， Chongqing， Jiangxi， Anhui， and Shanghai has always played a positive role in promoting the growth of water resource utilization efficiency， and the effect of the economic development level of all the other provinces and cities has always played a role in promotion. The progress effect of technology and the scale effect of water consumption both have a negative inhibiting effect. The Yangtze River Basin is particularly sensitive to economic growth， technical advancement， and the size of water usage， yet economic development is a fundamental influencing element that encourages improved water resource utilization efficiency.

In the context of climate warming， the construction of reliable precipitation data is crucial for water resources management and soil erosion prevention and control. Spatial interpolation is an important way to obtain reliable precipitation data based on site observation data. To improve the accuracy of precipitation data in alpine mountainous watersheds with sparse hydro-meteorological stations， this paper uses runoff coefficient as an evaluation index to assesse the applicability of GLADS， GSMaP， and the reanalysis dataset CMFD in the Bahe River Basin. Then， considering the influence of elevation on the precipitation variations， an improved inverse distance weighting method based on elevation recurrence is proposed to analyze the spatial variations of precipitation at different elevations. The results show that the average annual precipitation simulated by GLADS， GSMaP and reanalysis data set CMFD precipitation data is underestimated to varying degrees， and their simulation accuracy is ranked as CMFD >GSMaP >GLADS， which is not capable of characterizing the variations of precipitation by elevation in the Bahe River Basin. There are few hydrological observation stations in the Bahe River Basin with limited representativeness， resulting in low accuracy of remote sensing data inversion. The precipitation data interpolated by the improved inverse distance weighting method effectively reproduced the spatial distribution of precipitation variation by elevation， which is significantly better than the traditional inverse distance weighting method. The simulation of precipitation showed that this method can well reflect the influence of elevation change on the spatial distribution of precipitation. The average precipitation in the Bahe River Basin calculated by the improved inverse distance weighting method was 1 522 mm with a runoff coefficient of 0.92， and the largest relative contribution rate of precipitation in areas with the elevation of 4 000~6 000 m was obviously higher than other areas， accounting for 89.5%， and that of precipitation below 4 000 m was 10.1%. This paper provides a new technical support for hydrological simulation and forecasting in alpine mountainous watersheds with scarce hydrological information.

Runoff prediction is helpful to the comprehensive and efficient allocation of water resources and flood control and disaster reduction operation in the basin. How to accurately carry out a short-term runoff prediction has always been the focus of hydrology and water resource research. Gaussian process regression （GPR） has been successfully applied in the long， medium and short-term hydrological process prediction research because of its generalization ability for complex nonlinear regression problems. The GPR regression analysis ability depends on not only the model parameters but also the kernel function. Therefore， this paper analyzes the effect of GPR prediction model under different kernel functions， and proposes a short-term runoff prediction model based on exponential kernel function. Through the multiple correlation coefficient analysis of the largest multiple correlation coefficient， and the shortest predictor period， and then the rational secondary， radial base， maton and exponential kernel function are chosen to establish different GPR short-term runoff prediction model， also joined the MLR， RT， SVM， BP model method prediction results as a comparison. Taking the short-term runoff prediction of Ji'an Hydrologic Station in the Ganjiang River Basin （the prediction step is 6 h， and the prediction period is 7 days） as an example， the relevant experimental results show that： ① There are obvious differences in the prediction results of GPR models using different kernel functions， and the prediction performance of different methods from good to bad is exponential GPR， rational quadratic GPR， RT， Marton GPR， Radial basis GPR， SVM， MLR， BP； ② The 4 evaluation indexes of the exponential GPR prediction model in 28 periods all performed best， DC and QR are close to 1 and 100% respectively， the forecast accuracy reaches grade A or above. In conclusion， this paper verifies the effectiveness and universality of the exponential kernel function GPR short-term runoff prediction model， and the model prediction accuracy meets the needs of practical engineering applications with practical application value.

The rapid development of urbanization has led to a large number of urban buildings and increased density. Dense buildings make the urban flood situation more complicated and bring rigorous challenges to urban flood simulation. The urban hydrological model is a key means of urban flood research. an urban pipe network and 2-D surface coupled model are constructed by flood analysis software Integrated Flood Modeling System（IFMS） in Liedechong watershed， Tianhe District， Guangzhou， and it is validated with experimental data. Then the high resolution digital surface model （DSM） is used to perform elevation interpolation on the grids with resolutions10， 20， 30 and 50 m， respectively. After the best grid resolution has been selected and buildings have been selected as the research object， the high resolution digital elevation model （DEM） and DSM are used to interpolate the grid elevation， and the situation of urban flood under dense buildings is explored by comparing the surface buildings depicted with DEM. The results show that when the grid resolution increases from 10 to 50 m， the inundation water depth become greater and the inundation range become wider， make the flood situation more serious. In the case of dense buildings， the proportion of inundation area increaseS from 15.46% decreases to 6.67%， and the maximum inundation water depth increases from 0.20 to 1.78 m. The conclusions are as follows： In the urban flood simulation research on buildings， the grid resolution should consider the actual building width， and the best simulation effect is when the grid resolution is 10 m； dense buildings reduce the inundation area and sped up concentration. The collected rainwater makes the drainage pipe network insufficient carrying capacity， resulting in overflows to form surface water and increase the depth of flood submerged water.Compared to interpolated with DEM， the use of DSM interpolated elevation can more truly reflect the current urban surface characteristics and improve simulation accuracy. The research conclusion can provide a scientific basis for urban construction and development.

In 2022， the Pearl River Basin underwent extensive， severe and protracted rainstorms and floods. This study investigates the causes of this event， compares it with historical floods， and exemplifies the patterns of rainstorms and floods in the Pearl River Basin. To this end this study first presents the meteorological context and precipitation events leading to the flood. It then examines the flooding process， flood composition， the impact of water conservancy projects and comparisons with past rainstorms and floods. The results reveal that cumulative rainfall in the Pearl River Basin from late May to early July in 2022 was 50% higher than a normal year， with the Beijiang and Hanjiang River Basins experiencing the highest levels since 1961. The Pearl River Basin endured two major floods and eight numbered floods due to persistent heavy rainfall， with the Beijiang River encountering the largest flood since 1915. Flood composition analysis using national flood forecasting system of China shows that the primary inflow for the Xijiang River originates from the Hongshui River， Liujiang River， Yujiang River and Guijiang Rivers， with different flood volume proportions for each flood. The Beijiang River’s primary flood comes from the Lianjiang River， followed by the interval flow， while the Hanjiang River’s main flood arises from the Meijiang and Ting Rivers. In comparison with the 2005 and 2008 rainstorms and floods， the 2022 rainstorm duration was longer and had more floods. Moreover， the flood magnitude of the Beijiang River in 2022 was a heavy flood， which was more severe than that in 2005 and 2008， while the flood magnitude of the Xijiang River was less severe. The coordinated operation of flood control projects in the basin achieved significant flood control benefits， during this flooding process， preventing the simultaneous occurrence of severe floods in the Xijiang and Beijiang Rivers， and effectively ensuring the flood control safety in crucial areas.

To realize efficient calculation of waterlogging risk in mountainous cities without pipe survey data， this paper takes a drainage subarea in Nan’an District of Chongqing City as the study area， and the panoramic static API function provided by Baidu Maps open platform is used to identify and locate the rainwater wells. The equivalent drainage method of rainwater wells is used to establish a storm flood model based on LISFLOOD-FP， and the ideal calculation case and historical rainfalls are used to verify the model， and the waterlogging characteristics such as the flood area， flood volume， and the distribution of waterlogging under different rainfall scenarios are simulated and analyzed in the study area. The results show that in the area without pipe survey data， the rainwater wells in the area can be effectively determined by using the panoramic static API function of Baidu Maps open platform. The growth of flood volume and flood area shows a synergistic effect， and the larger the return period， the greater the flood area and flood volume at the same time. The time when the growth rate of flood volume is the fastest is basically consistent with the time when the flood area reaches its peak， both of which lag behind the rain peak time. During the period of decreasing flood area， the flood volume is still increasing， indicating that steep slope sections may face high flood flow rates and have potential disaster risks for vulnerable groups. For mountainous cities with fluctuating terrain， bridge deck runoff may exacerbate local waterlogging levels and should be given attention. Based on the LISFLOOD-FP model， the full hydrodynamic surface runoff simulation is carried out by using the equivalent drainage method of rainwater wells and the direct rainfall method. Even when running on an ordinary personal computer， it still has high computational efficiency and can achieve efficient calculation of rainwater and flood in a large area and identification of waterlogging prone points. The proposed simulation calculation method can provide technical reference for efficient assessment of waterlogging risk in mountainous urban areas without pipe survey data， and also provide a reference for the use of the LISFLOOD-FP model in China.

Low agricultural water use efficiency and serious water pollution restrict the sustainable development of local agriculture in some water-receiving cities of the South-to-North Water Diversion Project’s Central Route. Therefore， it is important and urgent to improve the green efficiency of agricultural water resources in each water-receiving city. This paper uses the super-efficiency SBM model to measure the green efficiency of agricultural water in the area， and analyzes its spatial-temporal evolution law by using the panel data of 20 water-receiving cities from 2009 to 2020 and taking the grey water footprint as the undesired output. The Tobit model is used to identify the main influencing factors. The results show that：①From 2009 to 2020， the green efficiency of agricultural water in water-receiving area of the South-to-North Water Diversion Project’s Central Route was not high and showed a downward trend， mainly due to the low scale efficiency. Among them， the green efficiency in Beijing and in most cities in Hebei Province was relatively high， while Tianjin and most cities in Henan Province was low. ②The overall differences of agricultural water green efficiency in water-receiving area mainly resulted from the differences within the regions， especially within Henan Province， but the increasing inter-provincial differences promoted the overall differences to expand. ③ Cities with high or low green efficiency of agricultural water had a high probability of stable transfer， while cities with medium level had a large instability in transfer. Meanwhile， the spatial distribution of agricultural water efficiency had the phenomenon that the high-efficiency cities had a positive spillover effect on neighboring cities， while low-efficiency cities had a negative drag effect on neighboring cities in terms of water-saving technology and water resources management. ④Economic development level， agricultural degree， agricultural fixed capital， water-saving agriculture development level， water resources endowment， water supply structure were the main factors affecting the green efficiency of agricultural water. All water-receiving cities should adhere to the concept of green development and promote the intensive and economical use of agricultural water resources in the South-to-North Water Diversion Project’s Central Route.

Joint flood control operation of reservoirs is an important technical measure to improve flood control safety of the river basin. During the flood control operation， water imbalance is usually caused by the flow travel time in the upper and lower reservoirs in a cascade reservoir system. It is of great significance to study the flow delay in that system and propose an effective measure for flood control operation. This study proposes a real-time flood control joint operation method to address the influence of water flow delays， applying information value maximization for cascade reservoirs under the condition of “weak coupling.” The excess water consumption mechanism is established from the lowest reservoir to the uppermost one. Based on this mechanism， a compensation operation model is established based on the maximum peak shaving principle， which minimizes peak flow on flood control cross-section， utilizing the hydrological and hydraulic compensation function in cascade reservoirs. This paper takes the northern tributary of the Beiliao River Basin of Jiangxi Province with three cascade reservoirs as a case study， whose results of the multi-scenario simulation show the following message. Considering the hydraulic engineering and flood characteristics of the area， during small and medium floods， the regulation function of each reservoir can be appropriately exploited to grasp the initiative of flood control. During large flood events， the flow should be pre-discharged to a lower water level to ensure that the reservoir group has sufficient flood control capacity. It can fully use the reservoir group’s flood control function in the basin and relieve downstream flood pressure to the greatest extent. After the operation mentioned above， the average ratio of cutting down flood peak of Luowan Reservoir is 20.63%， with a detention volume of 496 thousand cubic meters. The average ratio of cutting down flood peak of Hongping Reservoir is 30.09%， with a detention volume of 13.95 million cubic meters. The average ratio of cutting down flood peak of Xiaowan reservoir is 33.02%， with a detention volume of 5.97 million cubic meters. Peak flow at the flood control cross-section decreases by 48.83% on average compared to the peak flow of natural inflow. The peak reduction effect of the joint flood control operation of reservoirs is more significant than the original scheduling rules in the area.

The preservation and restoration of fish spawning grounds is a crucial objective in the ecological operation of reservoirs. The natural reproduction of fish is essential to the sustainability of fish populations and the provision of ecosystem services. The fluctuating backwater area， which is often overlooked， can serve as a potential habitat recovering area. This area is formed by the backwater effect caused by the reservoir’s operation， which creates a shallow and slow-flowing area that is suitable for fish spawning. The weighted usable area of fish is a measure of the habitat quality for fish， taking into account the flow velocity， water depth， and substrate composition. By combining the hydrodynamic model with fish habitat model， the weighted usable area of fish can be calculated for different flow and water level conditions. This study proposes a novel approach to establishing a ternary relationship between reservoir flow， water level， and the weighted usable area of fish， which can then be used to determine the target range for habitat recovery. The Zipingpu Reservoir in the upper reaches of the Minjiang River is chosen as the study site， and the spawning grounds of Schizothorax prenanti in the fluctuating backwater area are modeled. The weighted usable areas of fish are calculated for 182 combinations of flow and water level conditions， and a target range for habitat-recovering is determined to be 114~652 m³/s for the inflow and 817~844 m for the water level. This range can be used to adjust the reservoir water level and facilitate the recovery of spawning grounds in the fluctuating backwater area. The method is applicable to other reservoirs and fish species and provides a scientific basis for the ecological operation of reservoirs and the recovery of fish spawning grounds. The approach used in this study offers a fresh perspective for maximizing the ecological benefits of reservoirs by identifying previously overlooked areas for habitat recovery. And the ternary relationship established between reservoir flow， water level， and the weighted usable area of fish provides a valuable insight into the complex interactions between hydrodynamics and fish habitat. The research results provide scientific support for the functional restoration of fish spawning grounds and offer a new approach for ecological operation of reservoirs. This approach can be applied to other reservoirs to identify potential habitat recovering areas and establish target ranges for habitat recovery. This study highlights the importance of considering previously overlooked areas for habitat recovery and the value of integrating hydrodynamic models and fish habitat models to establish a ternary relationship between reservoir flow， water level， and the weighted usable area of fish. The findings of this study have important implications for the ecological operation of reservoirs and the preservation and restoration of fish spawning grounds.

In 2021， the Yellow River underwent the most serious autumn flood since the foundation of New China， during which the safety of flood control in the Lower Yellow River（LYR） was greatly threatened. It provides a rare opportunity to investigate how to make effective decisions on dealing with extreme floods， which is urgently needed for river management departments. The most dangerous reach of the LYR， the Kaifeng reach， is selected as the study object. Based on the measured flow data from the upstream hydrological stations and the topographic data of local reach， the characteristics of the 2021 autumn flood in the Kaifeng reach are analyzed. Then some successful practical experience about defending against the extreme flood， characterized by high flow， long duration and high water level， is summarized. Firstly， the “one center， two key points， three things that can’t happen， four measures to put in place， five transformations” basic principles of flood control were followed. Secondly， the flood defense mechanism of “leading of the party and government， emergency coordination， support of river administration bureau， departmental cooperation， group prevention and control” was adopted. Thirdly， four resettlement types of “self-owned housing， stay with relatives and friends， mutual help among residents， centralized resettlement” for the people who live on the floodplain of the Yellow River was sorted out. Fourthly，the defense measures of “plan before the river regime changes， prevention in the beginning of the danger， protection of key zones of river projects” were innovatively implemented. Lastly，the party branch played an important role. The above practical experience has proved to be effective， not only for the future flood control of the Yellow River， but it is also replicable and extendable， which is of great significance to flood safety management in other rivers.

High-precision water body interpretation of river channels is of great significance for a comprehensive and detailed understanding of changes in water resources， the scientific formulation of water resource protection strategies， and the rational planning and development of water resources. In this study， the main river channel in the lower reaches of Minjiang River is taken as the study area， the Landsat-8， Sentinel-2 and GF-6 satellite images are used as data sources to analyze and compare the water body identification performance of different spatial resolution remote sensing images in rivers identification in different morphological channels. The results show that remote sensing images with spatial resolutions of 2~30 m can effectively reflect the shape of the river. For the mountainous rivers with regular boundaries and seaward river with wide water surface， the remote sensing images with 2~30 m spatial resolution can obtain excellent interpretation results， which will not significantly affect the identification of water bodies in rivers. However， the spatial resolution of remote sensing images has a greater impact on the identification of water bodies in urban rivers with narrower widths， and the high spatial resolution remote sensing images are more conducive to identifying water bodies in urban rivers. And as the spatial resolution of remote sensing images decreases， the ability to characterize riverbank boundaries will gradually decreases， and the phenomena of water body leakage and misidentification will increase.

Aquatic floating vegetation usually can be found in natural rivers，and it decreases the discharge capacity of rivers. Furthermore， it changes the flow structure and causes the flow status more complicated. To explore the characteristics of flow under the action of floating vegetation group， rigid floating vegetation is simulated by using cylindrical glass rods with a diameter of 0.01m， particle image velocimeter （PIV） and wireless ultrasonic water level measuring system are used to measure water level and flow velocity. Water flow characteristics affected by the vegetation root into water， vegetation layout and vegetation density on are investigated by using experimental tests in a laboratory flume. Experimental results show that the floating vegetation group has a great effect on the flow structure in the channel. After the float vegetation group is set in the cannel， the maximum flow velocity occurs at the center between the vegetation roots and the flume bed. The maximum turbulent kinetic energy appears near the vegetation roots and the channel bed， while the minimum turbulent kinetic energy appears near the center between the vegetation roots and the channel bed. The length of the floating vegetation in the water affects the water level distribution in the channel. Both the water level and water surface slope along the way at the upstream of the vegetation area grow with the increase in the length of the vegetation in the water. Furthermore， vegetation layout affects the transverse distribution of the flow velocity at the downstream of the vegetation area. The same side layout of the floating vegetation groups in the flume causes the phenomenon “strengthening effect” for flow velocity at the downstream of the vegetation area， i.e. the flow velocity at the downstream of the vegetation area becomes greater. Similarly， the staggered layout of the floating vegetation groups in the flume causes the phenomenon of “weaning effect” for flow velocity at the downstream of the vegetation area， i.e. the flow velocity on the downstream sides becomes smaller. The strongest turbulent kinetic energy occurs at the boundary between vegetated area and non-vegetated area. In addition， the vegetation density also affects the flow velocity and turbulence intensity distributions. With the increase in vegetation density， the variation amplitude of the flow velocity in the vegetation area grows， while the turbulence intensity decreases. Under the floating vegetation groups， the flow velocity grows with the increase in vegetation density， and above the floating vegetation groups’ root， the flow velocity decreases with the increase in vegetation density. In the vegetation area， the flow velocity shows an S-shaped distribution along vertical direction.

To study the key water quality indexes affecting the water quality of the basin， this paper selects Yihe River as the research area. The annual water quality monitoring data and laboratory sampling data of the Yihe River from 2006 to 2019 are used to evaluate and model the river water quality by using the water quality index method. Water quality index （WQI） can transform a large number of complex water quality data into a single index. This single index can reflect the overall state of water quality， so the water quality index is often used to evaluate water quality at present. A total of 10 water quality indexes including total phosphorus （TP）， pH， water temperature （WT）， dissolved oxygen （DO）， nitrate nitrogen （NO₃-N）， 5-day biochemical oxygen demand （BOD₅）， fluoride （F^-）， chemical oxygen demand （COD）， sulfate （SO₄ ^2-）， and ammonia nitrogen （NH₃-N） are analyzed. Based on the multiple linear regression analysis， the key water quality index evaluation model WQI_min of the Yihe River is established. The indexes involved in the evaluation of the Yihe River water quality are reduced. The results of this paper are as follows. When the water quality index is not weighted， the fitting degree and prediction accuracy of the four-index water quality assessment model and the six-index water quality assessment model do not reach the highest； when the water quality index is weighted， the fitting degree and prediction accuracy of the four-index water quality assessment model and the six-index water quality assessment model do not reach the highest， too. Neither of these two simplified index models is the optimal critical water quality evaluation model in this study. Through model training and testing， the weighted five-index model \mathrm{W} \mathrm{Q} {\mathrm{I}}_{\mathrm{m}\mathrm{i}\mathrm{n}+\mathrm{W}\mathrm{T}}^{\mathrm{w}} has good water quality evaluation performance， R ²=0.972，MSE=0.51，PE=2.07%，P<0.05， and is the optimal key water quality index model in this study. The \mathrm{W} \mathrm{Q} {\mathrm{I}}_{\mathrm{m}\mathrm{i}\mathrm{n}+\mathrm{W}\mathrm{T}}^{\mathrm{w}} model is a weighted five-index water quality evaluation model， including five water quality indexes： NH₃-N， BOD₅， DO， SO₄ ^2-， and WT， which shows a significant positive correlation with the WQI model （P<0.001）. The weighted five-index model not only maintains the accuracy of water quality evaluation， but also effectively reduces the cost of water quality index detection， improves the efficiency of water resources evaluation， and can effectively replace the WQI model for water quality evaluation in the basin. In addition， the artificial neural network model is developed based on the same sample data， which can be effectively applied to the evaluation and prediction of water quality in the Yihe River. On the one hand， the artificial neural network model can provide a reference for the future change trend of water quality in the Yihe River. On the other hand， the artificial neural network model can provide a new technical way for the intelligent simulation of water environment.

Evaluating the connectivity of river and lake systems is important for implementing the regional water network connectivity strategy， improving the regional water resources coordination， deployment and carrying capacity， and restoring and improving the water ecological environment. In this study， river and lake systems in the Jianghan Plain are taken as the object， and the improved graph theory method considering the barrier effect of gates and dams and the hierarchical analysis method based on multidimensional connectivity mechanism are adopted. The current situation and factors influencing the connectivity of river and lake systems are analyzed and evaluated in terms of network structure and connectivity function.The results show that： ①The structural connectivity of the water network in the study area is 0.717 2， which is in the “good” level， but the spatial distribution is uneven， with higher connectivity in the west and east， lower connectivity in the middle， and higher connectivity in the Tongshun River area than in the Four Lakes area； ②The functional connectivity of the water network in the study area is 0.688 5， which is in the “good” level. Mainly affected by the number of regional irrigation and drainage gates， the high degree of control and the long closing time， local areas such as the Four Lakes Main Canal， the Tongshun River and Hong Lake have poor water flow and low connectivity； ⑤The results of structural and functional connectivity evaluation are basically consistent， and reliable and applicable are the evaluation methods， which can provide some reference for the adjustment of water network engineering system and ecological river-lake connectivity system construction in Jianghan Plains.

When the tributary discharge in the reservoir channel is small， the water and pollutants from the tributary are retained in the tributary confluence due to the obstructing effect of the main stream， and in serious cases， it is easy to burst large areas of algal bloom in tributaries. In this paper， the hydraulic characteristics of tributary confluence under weak mixing conditions are investigated by using numerical simulations combined with flume experiments. The RNG k-ε turbulent model is used to close the control equations， and a three-dimensional numerical simulation model of the open channel intersection flow is established， and the simulation results such as vertical flow velocity distribution and velocity vector diagram are in great agreement with the open channel flume experiments data. Based on the numerical simulation results of 4 different convergence ratios and 3 different junction angles conditions， the flow structure partitioning of the tributary confluence under weak mixing conditions is proposed， and the effects of different junction angles and convergence ratios on the key hydraulic characteristics of the tributary confluence are analyzed. The study found that， under the weak mixing conditions， the right bank of the tributary confluence generates backflow to form a backwater zone， and the water of the left bank is squeezed to form an acceleration zone， and the peak backflow velocity occurs near the right bank wall； the length of the backwater zone under different junction angle conditions is 150°>30°>90°， and the length of the backwater zone gradually decreases with the increase in the convergence ratio until the backwater zone disappears； and the distance between the maximum width of the backwater zone and the confluence is inversely proportional to the convergence ratio； both the high turbulent kinetic energy region size and value at the tributary confluence are inversely proportional to the convergence ratio and positively proportional to the junction angle， and the influence of the junction angle on the turbulent kinetic energy is greater than that of the convergence ratio.

This paper investigates the effect of the fixed-point pulse strike of droplets on the sputtering erosion of non-uniform sand by simulating raindrop sputtering tests. The experiments are conducted on four kinds of non-uniform sand with median particle size （1， 2， 3， 3.7 mm） at four different slopes （0°， 15°， 25°， 35°） with 3.65 mm diameter pulsed droplets. By comparing the sputtering erosion process and the sputtering pit type， this paper has drawn the following conclusions： The effect of the pulsed droplets on the non-uniform sand slope surface is more obvious than that of the single droplet， and the droplets produce a certain “superposition effect” when striking continuously. The change of the slope of the underlying surface and the median particle size also has a significant impact on the sputtering erosion process and the sputtering pit type. The initial strike of droplets makes the particles unstable. With the continuous strike of droplets， the central particles are compacted to form a collapse， and the surrounding particles leap around under the action of side pressure and the impulse of droplet strike， and coarse particles are formed around the collapse to form loose deposits， and the coarsening of the underlying surface develops into a sputtering pit. As the slope increases， the stability of the slope surface deteriorates， the diameter of the pit opening of the sputtering pit becomes larger， the upper wall becomes steeper， the lower wall becomes slower， and the accumulation of particles at the lower pit lip increases， making it easier to destabilize and collapse. At the same time， the larger the median particle size， the stronger the shading effect on the fine sand， the greater the energy loss of droplets， the less energy used to destroy the original structure of the underlying surface， the more difficult it is to form sputtering pits.

Flash flood disaster is one of the natural disasters that have a significant impact on human beings， causing enormous damage to the national economy and people’s lives and properties. Conducting a risk assessment of flash floods is an effective way to defend against them， and an accurate assessment of flash flood risk can provide strong technical support for flash flood prevention and decision-making. A study is conducted on the western region of Nanyang City based on 415 historical flash flood disaster points， and 12 risk indicators such as elevation， slope， mean annual rainfall， and mean annual maximum 3-hour rainfall are selected to construct a LightGBM flash flood risk assessment model. Additionally， random forest （RF） and extreme gradient boosting （XGBoost） methods are combined， and the accuracy and precision of the models are compared by using five main evaluation indicators. The model with the best performance is used to create a flash flood risk map for the study area， and a multi-scale flash flood risk assessment map is generated based on this. The distribution characteristics of flash flood disasters in the western region of Nanyang City are explored， and the causes of flash flood are analyzed. The results show that： ① The LightGBM model performs the best with an accuracy of 0.915 7. The RF model performs poorly with an accuracy of 0.846 2； ② slope， elevation， and mean annual precipitation are the main risk indicators affecting flash floods in the study area； ③ The flash flood risk assessment results for the study area are consistent with the actual occurrence of flash floods. The high-risk and extremely high-risk areas account for 21% of the total area and are mainly distributed near mountains， the lowest areas around rivers， and regions with high agricultural productivity. LightGBM is an effective method for assessing flash flood risks and can provide guidance for flash flood prevention and management planning in Nanyang City.

Bottom mud is an important source of release of ecological endogenous pollution of reservoirs. In order to comprehensively understand the content of heavy metals in the bottom mud of major reservoirs in Huangdao District， Shandong Province and its potential ecological hazards. In this paper， samples of 10 reservoirs， including Dijiahe Reservoir in Huangdao District， tested 10 heavy metal contents such as Hg， Cd， Pb， Cr， Cu， Zn， Ni， Fe， Mn and As in the sludge， analyzed the content and source of each element， and analyzed the degree of sediment pollution and potential Ecological risks are evaluated， and possible sources of heavy metals are analyzed. The results show that the Hg content of Xizhai Reservoir exceeds the standard requirements， the Cd content of Huagou Reservoir exceeds the standard requirements， and the content of the rest of heavy metals does not exceed the standard requirements. The degree of heavy metal pollution in the bottom mud of Huangdao Reservoir is from strong to weak： Hg>Cd>Zn>Pb≥Cu≥As>Ni≥Cr， and Hg and Cd are the most important heavy metal pollution elements. The potential ecological hazards of heavy metals are from strong to weak： Hg>Cd>As>Pb>Cu>Cr>Ni>Zn. Hg and Cd are potential ecological hazard elements. Huagou Reservoir， Geely River Channel， Xizhai Reservoir and Dijiahe Reservoir， especially Xizhai Reservoir， have a serious degree of pollution. The main factors of reservoir pollution are mainly man-made factors， and the main sources are industrial sewage and domestic water discharge.

To determine which DEM data are more suitable for river network extraction in mountainous river basins， this paper selects mountainous river basins in the upper reaches of Yangtze River and Pearl River， including the Liqiu River Basin， the Zagunao River Basin， the Heshui River Basin， the Gantangjiang River Basin， and the Lijiang River Basin above the Darongjiang River Hydrological Station， and uses ALOS 12.5 m DEM， ASTER 30 m GDEM and SRTM 90 m DEM as the base data. The extraction of the river network in the study area is based on Arcpy， and the extraction results are corrected and evaluated by the river network ensemble difference and Arc Hydro Tools to explore the influence of the selection of the optimal catchment area threshold and topographic features on the extraction of the digital river network in mountainous watersheds. The results show that： ① ALOS DEM with 12.5 m resolution has the smallest river network ensemble difference， which can reflect the degree of water system development in the mountainous watersheds more realistically， and the river network ensemble differences of ALOS DEM in the Liqiu River Basin， the Zagunao River Basin， the Heshui River Basin， the Gantangjiang River Basin and the Lijiang River Basin above the Darongjiang River Hydrological Station are 0.380%， 0.275%， 0.312%， 1.374% and 0.873%. ② By correcting the DEM data with Arc Hydro Tools， the river network ensemble differences of the three DEMs are reduced， which can significantly improve the extraction accuracy of the river network， and the extraction effect of ALOS DEM before and after correction is optimal and applicable to different river basins. The SRTM 90 m DEM is still better than the ASTER 30 m GDEM in the upper Li River Basin and the Li River Basin after correction， while the accuracy of the ASTER 30 m GDEM is higher in the Zaguzhong River Basin， the Heshui River Basin and the Gantang River Basin after correction； ③ the coefficient of determination of the SRTM DEM is 0.930 2 in the upper Li River （the Li River basin above the Da Sol River Hydrological Station）， and the coefficient of determination of the ALOS DEM in the Zaguzhong River Basin is 0.985 4. The coefficient of determination for the rest of the conditions is more than 0.99， which indicates that the correlation is good. Based on the mean-variable point analysis method to determine the best catchment area threshold for the study area， the best catchment area threshold is 20 000 for ALOS DEM and 500 for ASTER GDEM and SRTM DEM； ④ The large undulating hills are favorable for river network extraction， and the DEM correction converts some watersheds into large undulating hills favorable for river network extraction， and the ALOS DEM has the best extraction effect. Therefore， the modified ALOS DEM extracts the watershed water system with the best effect， and the results can provide some reference for the extraction of water system in mountainous watersheds.

Under the condition of many years of operation， the existing water conservancy projects are faced with problems such as structure aging and operation condition change， which cannot meet the safe operation under the design conditions， causing the problem of cooperative scheduling between the existing water conservancy projects and the new projects. In order to solve the problem of cooperative flood control and dispatch of new and old water conservancy projects， this paper collects historical flood data， and uses Pearson-Ⅲ distribution and normal distribution to fit the peak flow distribution respectively. Monte Carlo method is used to randomly select the pseudo-random numbers， which are more than the current design standard， and then uses the peak-ratio amplification method to design the 15 d flood process. The characteristic flows of the new and old projects are combined to form different operating conditions， and the risk of collaborative flood control under various working conditions are calculated. This paper takes the pre-post aqueduct （the old aqueduct） in Ganfu Plains of Jiangxi Province and its extension project， inverts siphon （the new aqueduct） ， as the research objects. After the characteristics of the projects have been analyzed， the characteristic flows of the projects are presented as the minimum operating flow under the current safety control and the design flow of the old aqueduct， and the design flow and increased flow of the new aqueduct. The results show that the flood risk calculation results based on the P-Ⅲ distribution are about 40% higher than that of the normal distribution， indicating that the flood peak distribution using P-Ⅲ distribution can simulate more adverse flood conditions. When the P-III distribution is used to fit the flood peak discharge， the risk rate of the old aqueduct is 23% when the new aqueduct is operated according to the design standard， while the risk rate of the new aqueduct is 8% when the old aqueduct is operated according to the design standard. It indicates that the risk of old aqueduct is higher when aqueducts work together to control floods.

Our country’s water-saving contract projects are still in the promotion stage at present， and they face many uncertain risks. Under this background， the risk assessment of water-saving contract projects has very important theoretical and practical significance. The literature analysis method is used to determine the potential risks in the whole life cycle of water-saving contract projects， and the multi-connection number set is used to evaluate the risk of water-saving contract projects in the whole life cycle. The following conclusions are drawn： our country’s water-saving contract projects. The overall risk level of the project is low， so it is very suitable for promotion， but there are also some potential high-risk factors. When the risk of water-saving contract projects is controlled， it is necessary to focus on controlling risks with high risk levels， such as： information risk， financing risk and customer At the same time， it is necessary to strengthen the control of risks with an upward trend in risk levels， such as market competition risks and inflation risks. Finally， this paper puts forward corresponding policy recommendations for these risks.

The operation of urban water supply network has an important impact on social and economic development and people’s production and life. To ensure the safe and stable operation of urban water supply network， it is necessary to study methods to reduce the failure rate of the network. In the design of urban pipe network， it is necessary to consider not only the economic indicators such as the total cost of the pipe network， but also the reliability indicators such as the failure rate of the pipe network. With the increase in the total cost， the failure rate shows a downward trend. On the contrary， with the reduction of the total cost， the failure rate shows an upward trend. Obviously， total costs and failure rates are a pair of conflicting objectives. This paper adopts the decomposition-based multi-objective evolutionary algorithm （MOEA/D） to deal with the multi-objective optimization problem. MOEA/D can obtain a set of mutually non-dominated solutions in one run， which is called Pareto solution. To balance the diversity and convergence of the Pareto solutions， this paper proposes an adaptive MOEA/D algorithm with two-stage strategy and niche guidance strategy， named MOEA/D-TPN. In the MOEA/D-TPN， the evolution process is divided into two stages. In the first stage， the algorithm uses the ideal point z ^* as the reference point， and in the second stage， the algorithm uses the peak point z ^nad as the reference point， so it can better solve the multi-objective optimization problems with convex or concave shapes. At the same time， the algorithm designs a niche guidance strategy to select different mating individuals， so as to enhance the diversity of the final obtained approximate Pareto front. The performance of the proposed MOEA/D-TPN algorithm is verified by six benchmark testing problems and urban water supply network optimization problems. The simulation results show that MOEA/D-TPN algorithm can deal with complex multi-objective optimization problems， and the obtained solutions can balance the total cost and failure rate， providing a feasible reference scheme for the engineering design of urban water supply network.

With the rapid development of economy， the demand of water resources in Hebei Plains is increasing rapidly， the groundwater is over-exploited and the cost of water for agriculture is increasing rapidly， which has a great negative impact on the economic development and ecological construction， it is imperative to save and use water efficiently. Water-saving policy is one of the effective strategies with low costs and direct effects. In this paper， through an in-depth and systematic study of the“Collect then Refund” water-saving policy in the actual implementation of the various problems， from the internal causes of system design， through the establishment of price increases， price increases and water-saving effect model， this paper estimates costs and benefits， studies the optimized countermeasures， and puts forward a new water-saving management mode of“One levy， one guarantee”， which is effective， fair， universal and operable， and can promote the optimal allocation of water resources， it provides theoretical basis and experience for the reform of agricultural water price in China， especially for the comprehensive management of groundwater over-extraction area.

To clarify the influence of freeze-thaw process on the thermal conductivity of insulation materials， the changes of water absorption and thermal conductivity of polystyrene （XPS） are obtained by rapid freeze-thaw experiment. Combined with the porous structure characteristics of insulation materials， the thermal conductivity model of three-phase materials is constructed， and the volume fraction correction parameter is introduced to improve the prediction accuracy of the proposed model. Finally， the reliability of the proposed model is verified. The results show that after 200 freeze-thaw cycles， the water content of the XPS increases about 4.55% and the thermal conductivity of the XPS increases by about 43%. By adjusting the two fitting parameters， the maximum relative error between the predicted thermal conductivity and the measured value is less than 5%. The long-term thermal insulation properties of XPS board are influenced by freeze-thaw cycles， so it is of great significance to improve its freeze-thaw resistance. Besides， it is recommended to raise the safety factor of thermal insulation performance to cope with the problems caused by the increase in thermal conductivity of materials.

In order to investigate the quantitative characteristics of priority infiltration under different land use types， this paper takes garden land， cultivated land and forest land of terraced fields in the southwest karst region as research objects， and carries out staining infiltration tests by means of a table-mounted ring infiltrator and bright blue to quantitatively classify the priority flow and matrix flow of different land use types on terraced fields， and conducts a comparative study on their infiltration rates and cumulative infiltration amounts. The results show that： ① matrix flow is the main part of soil infiltration in the terraces in this area. ② During the whole infiltration process， the infiltration rates of priority flow in both garden land and cultivated land are greater than those in forest land， and when stable infiltration is reached， the infiltration rates of priority flow in cultivated land and garden land are 1.87 and 1.80 times higher than those in forest land， respectively， and the cumulative infiltration number is 1.2 or 1.3 times higher than those in forest land. ③ In terms of staining infiltration depth， the preferential flow movement depth of arable land can reach 32.1 cm， which is significantly greater than that of garden land （25.5 cm） and forest land （15.7 cm）， that is， compared with forest land， garden land and arable land have better pore development and the preferential flow phenomenon is more obvious. ④ The soil texture of different land uses significantly affects the priority inflow rate and the magnitude of infiltration.

As an important underground structure in water transfer projects， the inverted siphon structure is easily affected by earthquake and geological conditions， and the inverted siphon structure with shallow buried depth is more likely to affect the structural stability due to soil vibration. In this paper， the inverted siphon structure of a project will be selected as the research object， and the three-dimensional finite element dynamic response analysis will be carried out by using Newmark Time History Analysis Method to study the seismic response law of the inverted siphon under the geological type of medium soft soil. The results show that the peak acceleration response is about 1.4 times more than the maximum input acceleration， but it changes little along the height of the inverted siphon section. The x-direction displacement of each characteristic point of the horizontal section is greater than that of the inlet transition section. Staggered damage is apt to occur at the interface between the two pipe sections， and the maximum settlement is 13.6 mm， which is within the safety range. Under the Ⅶ degree earthquake， the maximum third principal stress is 3.23 MPa， which is less than the standard value of compressive strength of C20 concrete. The maximum first principal stress of inverted siphon structure is 1.48 MPa， which is equivalent to the tensile strength value and is prone to damage. The integral structure of inverted siphon under VII degree earthquake is in a safe state.

The deep anti-sliding stability calculation of the structure should be carried out in the case of unexpected joints， fissures and weak structural planes in the foundation of the gate dam. There is a head difference between the upstream and downstream of the structure. The concrete is usually considered as an impermeable material. The foundation bears most of the head loss， and its seepage effect cannot be ignored. In this paper， the seepage field force is divided into seepage volume force and buoyancy force. And based on the strength reduction method of finite element method， the deep anti-sliding stability of the gate dam under seepage is studied with the body force of seepage. The results show that the foundation curtain grouting can effectively cut off the seepage and significantly improve the deep anti-sliding stability of the gate dam structure. And in terms of the safety factor， consider the seepage volume force alone>consider the buoyancy force alone>consider the seepage volume force and buoyancy force at the same time. The buoyancy force plays a leading role， but the role of the seepage volume force cannot be ignored.

To explore the response characteristics of soil water infiltration and water-salt migration to the cotton straw-sand interlayer， this paper uses the indoor soil column experiment to study the effects of the cotton straw interlayer mixed with different ratios of sand on soil infiltration and water-salt migration. The mass ratios are 0， 50%， 75%， 85%， 90%， 95%， and 100%， expressed in terms of T0， T50， T75， T85， T90， T95， and T100， respectively. The results are as follows. ① Cotton straw-sand interlayer blocks the infiltration of water and prolonged the infiltration time， with T0 and T95 is listed as the top two.T50， T75， T85， T90 and T100 infiltration time is short， and the difference is not obvious. ② The cotton straw-sand interlayer has no effect on the cumulative infiltration amount and the advancing law of the wetting front above the interlayer， but has a significant impact on the lower layer. The infiltration time of T0 is the longest， followed by T95. ③ With respect of correlation between the cumulative infiltration amount and time， the Kostiakov model is fitted well to CK. In terms of the cotton straw-sand interlayer treatments， the Kostiakov model is fitted well within the range of 30 cm above； the linear model is well described below 30 cm. ④ After infiltration， the upper layer is desalinated， and the salt in the bottom is accumulated. The water content in the upper layer of T0 and T95 is the highest. Two days after infiltration， the salinity in the middle part of the soil layer moves down to a certain extent， with the largest decline in T0 and T95. In order to prevent soil salinization and improve water use efficiency， it is recommended to promote the application of cotton straw interlayer and the cotton straw interlayer with 95 aeolian sand in arid regions of Xinjiang， which is based on the infiltration characteristics indicators such as wetting front and cumulative infiltration amount， as well as the law of water and salt migration and redistribution.

In order to explore the distribution characteristics of sand and gravel coverage on coastal saline-alkali soil water and salt， this paper adopts laboratory experiments to study the effects of sand and gravel coverage （0， 25%， 50%， 75%， 100%） on soil water， salt and evaporation. influence of characteristics. The results show that sand covering can effectively retain soil moisture and reduce the salinity content of soil surface， the effect of preserving moisture and salt inhibition increases with the increase in sand coverage. During the test period， the soil surface water content in the sand-covered treatment increased by 58.57%~232.71% compared with CK， the profile water content increased by 82.41%~220.91% compared with the CK treatment， and the surface soil salinity content decreased by 22.72%~46.04% compared with CK. Compared with CK， the salinity content decreased by 7.15%~11.76%. Sand and gravel coverage can effectively inhibit the accumulation of soil surface and improve the spatial distribution uniformity of salinity in the soil profile； during the test period， the soil evaporation intensity in the sand-covered treatment decreased by 15.51%~48.82% compared with the CK treatment， the effect of sand and gravel mulching on soil evaporation intensity was stronger in the early stage of evaporation than in the later stage of evaporation.

To improve the scientificity and normalization of structural linear analysis of plane steel gate via ANSYS software， some problems are deeply discussed from grid division and leakage hole simplification on the basis of the intake emergency gate of a hydropower station. The results show that： ① the element type shell281 is preferred for spatial thin-walled structures， such as plane steel gates， due to its higher accuracy of stress； ② the size of the mesh has little effect on the deflection， but a reasonable mesh size can make the finite element calculation results of stress independent of the mesh size and reduce the calculation amount； ③ compared with free partition， mapping partition will provide higher grid quality， but it also brings in a large amount of work without obviously improving of calculation accuracy of stress and deflection； ④ leakage hole can be simplified and ignored in establishing the plane steel gate model if the ratio between hole diameter and beam height of plane steel gate is less than or equal to 0.15 and vice versa.

One parametric design method is suggested for the convenience of blade design operation and shape control， which is firstly used in the design process of hydraulic energy recovery turbine. Firstly， the theoretical models of parametric design is established based on the derivation of meridional streamline integral equations， meanwhile the flow chart and calculation table are offered. Then the characteristics of hydraulic energy recovery turbine are analyzed. Moreover， the process of parametric design is carried out for a case of hydraulic energy recovery in water distribution network. Finally， the flow field and performance are studied by numerical simulation. The curves of wrap angle and setting angle are obtained in the process of parametric design， after that the velocity moment at blade outlet was changed by control of wrap angle distribution. The flow field is uniformly and maximum numerical predicted efficiency has reached 93.6%. Moreover the feasible of hydraulic energy recovery turbine is verified by test and the operating efficiency has reached 88.3%. The conclusions can provide guidance in the design process of hydraulic energy recovery turbine.

With the large amount of wind power， photovoltaic and other renewable energy have fed in， the power grid structure is becoming increasingly complex. In this context， hydropower units will often operate under variable conditions as required， and the operating environment will become harsh. Its traditional PID control strategy is obviously difficult to achieve optimal control under various complex conditions. Therefore， the generalized predictive control （GPC） is applied to hydropower units and its parameters are optimized based on gravity search algorithm （GSA） to realize the adaptive predictive control of hydropower units based on GSA-GPC. The simulation results show that， compared with the traditional PID controller， the designed adaptive predictive controller based on GSA-GPC has excellent regulation performance under different working conditions， and realizes the optimal control of hydropower units under multiple working conditions.

To analyze the dynamic characteristics of the hydropower plant and solve the position of the stiffness center， based on the traditional calculation method of the stiffness center， the method of obtaining the flexibility coefficient in the calculation formula is changed， and the calculation method of the stiffness center of the hydropower plant is revised. By taking the powerhouse of a hydropower station as the calculation model， this paper carries out the rigid-flexible coupling simulation analysis by using the finite element software ANSYS， and the stiffness center of the structure is obtained. In addition， the factors affecting the accuracy of the calculation results are analyzed when ANSYS is used to solve the stiffness center. The results show that the revised stiffness center calculation method combined with ANSYS software can solve the stiffness center of complex structure， the solution speed and accuracy are also higher than the traditional calculation method. However， in the solution process， the uneven refinement of the grid will cause the lateral stiffness of the calculation model to change unevenly， which has a certain influence on the accuracy of the numerical calculation results of the stiffness center.

Variable speed operation can greatly improve the operation efficiency and regulation performance on hydropower unit. It is an effective way to solve the low operation efficiency and poor regulation quality on small hydropower unit. This paper discusses the variable speed operation schemes and control strategies for small hydropower units. The suitable system mathematical model and control strategy model are built for small hydropower units. The variable speed unit dynamic process of different control strategies is compared by simulation. The results show that， small hydropower unit is more suitable for using variable speed scheme based on full power converter and synchronous generator， at the same time， the control system control strategy suitable for the grid side converter control inverter DC bus voltage and reactive power output， the machine side converter control active power， the governor control speed of unit. The power anti-regulation phenomenon does not appear in simulation. And the active power stability time can be achieved in 0.9 seconds. The results of this paper can provide reference for the efficient development of small hydropower resources.

A state feedback sliding mode fault-tolerant control strategy based on linear matrix inequalities is proposed for the regulation system of hydropower units considering control uncertainties and disturbances. Firstly， a mathematical model of the regulation system of hydropower unit is established and the control law is designed with the model. Then， the sliding mode fault-tolerant control design is implemented based on the equivalent control principle of linear matrix inequality to improve the control performance and the reliability of the regulation system. In addition， the stability of the controller is analyzed based on the linear matrix inequality theory and Lyapunov stability criteria. The simulation results show that the sliding mode fault-tolerant control method can achieve better control effects for the regulation system of hydropower units with introduced control uncertainties and disturbances.

In order to further effectively detect and analyze the defects of the diversion tunnel， this paper uses a robot equipped with a three-dimensional laser scanner to carry out the apparent inspection of the lining in the tunnel emptying state. It introduces the operation flow of 3D laser scanning in tunnel inspection， and analyzes the defect statistics and distribution law based on the inspection data. The results show that the three-dimensional laser scanning technology can effectively reflect the apparent cracks of the tunnel， which shows the reliability of the hidden danger detection of the diversion tunnel. The defects of diversion tunnel include cracks and leakage， which are mainly distributed in the upper and lower sections. From the tunnel section， the defects are mainly distributed at the top of the tunnel. Compared with other defects， the crack is the main defect type of the headrace tunnel， so more attention should be paid to the crack propagation at the top of the headrace tunnel during the later project operation and safety inspection.

With the increase in the service life of masonry hydraulic culvert， the existing culvert structure needs to be quickly and accurately detected and evaluated. The detection method based on digital image can significantly improve the detection efficiency， but the application of this method is faced with many challenges due to the poor lighting conditions and narrow space in the detection of hydraulic culvert diseases. In view of the above problems， a hydraulic culvert disease detection model based on YOLOv5 network is established. Through the target detection of the collected culvert images and optimization of the recognition results， the rapid identification of hydraulic culvert diseases is realized. Mosaic data enhancement， multi-scale training and Adam optimizer are used to optimize and analyze the performance of the model to improve the reconstruction effect of the model. The application results of field examples show that the YOLOv5 network can quickly and efficiently identify hydraulic culvert diseases. This method can overcome the appearance interference characteristics of hydraulic culvert， and its recognition accuracy is consistent with the actual situation. It can accurately identify the disease grade of hydraulic culvert， and has a broad application prospect.

To improve the safe and stable operation of pumped storage units， this paper analyzes their operational status， obtains the health condition of unit equipment， and accurately predicts their future development trend. It proposes a trend prediction model that integrates variational mode decomposition （VMD） and attention mechanism （AM） into a bidirectional long short-term memory network （BiLSTM）. Firstly， a healthy state model of the unit is established by using the Bagging algorithm， which considers the influence of factors such as active power， working head， guide vane opening， and speed. Secondly， based on the healthy state model， the degradation trend sequence of the unit is calculated， and the VMD algorithm is used to decompose the trend sequence into multiple smooth and stable modal components. Finally， a BiLSTM network and attention mechanism model is established for each modal component to predict the trend， and the predicted results of each component are superimposed to obtain the final trend prediction result of the unit. Simulation results show that the proposed method can accurately express the degradation trend of the unit and effectively improve the prediction accuracy of the degradation trend.

In view of the large amount of calculation of the traditional benefit allocation method in the joint operation of cascade multi-agent hydropower stations， and the influence of the depth of marketization on hydropower， a benefit allocation method for joint operation of cascade hydropower stations under market economy is put forward. Firstly， the inflow into the reservoir during joint dispatching is calculated by using the “reduction method”， and the maximum power generation benefit model of cascade hydropower stations under the market economy is solved by improving the electricity generation-electricity price function to fit the market electricity price. Then the information entropy method is used to quantify the complex benefit relationship between cascade power stations under the market economy as the benefit sharing ratio represented by the benefit contribution of each power station， and the competitiveness index method is used to transform the power station characteristic parameters into the benefit sharing ratio represented by the power station competitiveness. The linear weighting method is used to share the benefits of cascade joint dispatching. Finally， the evaluation of satisfaction and the tendency analysis of allocation strategy are used to evaluate the allocation results. The results of Wujiang cascade examples are as follows： compared with objective weight combination allocation method and loss proportion method based on Shapley Value Method， this method is compared with objective weight combination allocation method and loss proportion method for benefit allocation of three power stations and six power stations. The maximum value and the average variance of the allocation strategy tend to be smaller， and the variance of the satisfaction of each subject is the smallest， which shows that the result of benefit allocation is more fair and reasonable. The benefit sharing of three power stations and six power stations requires only four and seven pieces of benefit information respectively， indicating that the calculation efficiency is higher. The allocation results show that this research method can effectively solve the benefit allocation problem of multi-agent cascade hydropower stations with less benefit information， and has some reference significance for realizing the joint optimal dispatching of multi-agent cascade hydropower stations under the market background.