Flood forecasting is one of the important non-engineering measures for flood control and disaster reduction in the middle reaches of the Yellow River. In this study， a GRU-Transformer flood forecasting model is constructed by coupling gated recurrent units （GRU） with Transformer machine learning models， and rainfall-runoff simulations are conducted to predict flood events in typical sub-basins of the middle reaches of the Yellow River. The predictive results are compared and analyzed with those of the ANN（Artificial Neural Network） and WOA-GRU（Whale Optimization Algorithm Gate Recurrent Unit） neural network flood forecasting models， with a focus on exploring how to better apply the Transformer model to the field of flood forecasting in order to improve the accuracy of flood forecasting in the middle reaches of the Yellow River. The model is established by using historical observed flood data from 1990 to 2016 in the Gu County Reservoir Controlled Basin. The input data includes rainfall data measured at 24 stations and discharge data at the outlet cross-section， while the output data includes flood events under different lead times. The model is calibrated by using 39 flood cases and validated using 10 flood cases. The results of the study show that the GRU-Transformer model has good applicability in flood forecasting， exhibiting higher predictive accuracy in the 1~6 hour lead time flood forecasting， with NSE values of greater than 0.85 in both calibration and validation periods. Its predictive accuracy is better than the WOA-GRU and ANN models under the same lead time， but decreases to a certain extent with increasing lead times. The GRU-Transformer model is more stable and better at predicting flood peaks， showing excellent performance in predicting small flow flood processes and simulating the recession phase of floods. However， it tendes to underestimate flood peaks with longer lead times. Compared with the WOA-GRU and ANN models， the GRU-Transformer model has better robustness， and its predictive accuracy decreases slowly as lead times increases. Hence， the GRU-Transformer model can be used as one of the better flood forecasting methods， providing new forecasting methods and scientific decision-making basis for flood prevention and control in the river basin.

This paper evaluates the spatial equilibrium status of water resources in Yunnan Province from 2006 to 2022 and 2025 scientifically， and proposes a water resource spatial equilibrium evaluation model based on social network search （SNS） algorithm， mountaineering team optimization （MTBO） algorithm， bi-directional gated loop unit （BIGRU） optimization， and bi-directional long short-term memory （BILSTM） network optimization. First， 15 indicators are selected from three aspects of water resources support， water resources pressure and water resources regulation to build the evaluation index system and grade standard of water resources spatial balance， and the samples are generated by linear interpolation and random selection methods to build BiGRU and BiLSTM fitness function. Secondly， the principles of SNS and MTBO algorithms are briefly introduced. SNS-BIGRU， MTBO-BIGRU， SNS-BILSTM， and MTBO-BILSTM models are constructed by using SNS and MTBO to optimize the number of neurons in the hidden layer of BiGRU and BilSTM and the learning rate （hyperparameter）. The robustness of four models， including SNS-BIGRU， MTBO-BIGRU， SNS-BILSTM， and MTBO-BILSTM， is verified through different sample sizes and 10 consecutive runs. Finally， SNS-BIGRU， MTBO-BIGRU， SNS-BILSTM， and MTBO-BILSTM models are used to evaluate the spatial balance of water resources in Yunnan Province from 2006 to 2022 and 2025， and the evaluation results are compared with those of SNS-Support Vector Machine （SVM）， MTBO-SVM， and fuzzy comprehensive evaluation methods. The results show that： ① the models such as SNS-BIGRU have good recognition accuracy and robustness. SNS and MTBO can effectively optimize the hyper-parameter of BIGRU and BILSTM， and improve the prediction performance of BIGRU and BiLSTM. ② SNS-BIGRU and other four models evaluate the spatial balance of water resources in Yunnan Province from 2006 to 2011 as “unbalanced”， from 2012 to 2013 as “relatively unbalanced”， from 2014 to 2018 as “critical equilibrium”， from 2019 to 2022 as “relatively balanced”， and by 2025， it can basically reach the level of “balanced”. There is a 3-year difference in the evaluation results of the four models compared to SNS-SVM， MTBO-SVM， and fuzzy comprehensive evaluation methods. The model method constructed and proposed in this paper serve as a reference for the spatial balance evaluation of water resources.

Urban water resources planning and management is a key link to ensure sustainable urban development and satisfy the basic needs of residents. Short-term water demand forecasting is the basis of urban water resources planning and management. As temperature， precipitation and evaporation vary significantly with the seasons， they directly affect the peak of water consumption in different seasons. As a result， the traditional fixed time slot prediction based on time series algorithm cannot adapt to the change of time slot， so the prediction accuracy cannot be guaranteed. Aiming at the problem of low accuracy of fixed time slot prediction， this paper studies a dual-time scale urban short-term water demand prediction model based on 24 h time resolution in four seasons and 15 min time resolution in summer. This model uses Anomaly-Transformer model to detect outliers and calibrate outliers by piecewise curve fitting. Principal component analysis is used to analyze and extract the main components of urban short-term water demand factors. In the standard model analysis of AutoML， three models with the best effects are selected as the base learner of the stacking model combined with the long-term and short-term memory network （LSTM， long-term and short-term memory） and the neural prophet model （NP） after hyperparametric optimization of Optune framework predict the short-term water demand of the city on both time scales， and add the safety net mechanism to ensure the accuracy of the LSTM-NeuralProphet model. Compared with other models （LSTM model， Neural Prophet model， BP neural network model）， the average absolute error of LSTM-Neural Prophet model is reduced by 0.18%~1.96% on the data set with 24 h time resolution of four seasons. In the summer 15 min time resolution data set， the reduction is 0.45%~11.90%. The experimental results show that the LSTM-Neural Prophet model has a better fitting effect and higher prediction accuracy， and can accurately predict the urban water demand at both time scales， and can be applied to the short-term urban water demand prediction research.

Model parameter calibration is an important way to improve the simulation effect of hydrological models. In order to solve the problems of low initial population quality， prematurity and poor local search ability of traditional genetic algorithm， this paper proposes an improved adaptive genetic algorithm （IAGA） to optimize the parameters of Xin?anjiang model. The Ergodic characteristics of chaos variables are used to randomly generate the initial population and select the best， so as to improve the individual quality of the initial population. Aiming at the evolutionary process of crossover and mutation， this paper designs the discrete coefficient of population objective function to reflect the degree of population dispersion. By using this coefficient， the adaptive adjustment crossover and mutation probability operators are constructed to prevent premature convergence of genetic algorithm. Based on the ring crossover operator， the global search ability of the algorithm is improved. The adaptive non-uniform mutation operator is used to optimize the local search ability of the algorithm in real time and avoid falling into local optimum. The IAGA algorithm， traditional genetic algorithm （GA） and adaptive genetic algorithm （AGA） are applied to the parameter calibration of the Xin′anjiang model in the Qinhuai River Basin， and the performances are compared from the aspects of convergence， time-consuming， stability and effect. The results show that the IAGA algorithm has more excellent optimization ability， better convergence results， higher stability and accuracy. The flood simulation results are better than the GA algorithm and the AGA algorithm. During the calibration period and the verification period， the deterministic coefficients are higher than 0.85， and Nash-Sutcliffe efficiency coefficient are higher than 0.8， which generally meets the second-level standard of hydrological forecasting. The results show that it is feasible to improve the traditional genetic algorithm by using the above comprehensive means， and the improved IAGA algorithm has a good application prospect， which provides an effective way for the automatic calibration of Xin′anjiang model.

The water conservancy industry is promoting digital twins in an unprecedented situation. The basis of smart water management is urgently needed to solve the problem that three-dimensional visualization of water conservancy projects cannot meet the requirements of professional visualization software. In this paper， a three-dimensional visualization platform for water conservancy is built based on technologies such as Cesium， Vue and Springboot. This platform has realized the key application technologies of thematic three-dimensional visualization such as multi-source data fusion， flood discharge and flood evolution， and laid a foundation for later digital twin visualization.

A multi-strategy fusion improved Golden Jackal Optimization Algorithm （MGJO） is proposed to address the shortcomings of the Golden Jackal Optimization Algorithm in solving complex or high-dimensional optimization problems， such as being prone to local optima， slow convergence speed， and low computational accuracy. Firstly， by introducing a chaotic mapping strategy to initialize the population instead of random parameters， the algorithm can generate initial solutions with good diversity in the search space and avoid the initial population distribution deviating from the optimal value. Secondly， a nonlinear dynamic inertia weight is proposed to make the search process more realistic， effectively balancing the algorithm′s global and local search capabilities. Finally， the position update strategy of Cauchy mutation is introduced to fully utilize the guiding role of the optimal individual to improve population diversity， effectively exploring unknown regions and avoiding the algorithm falling into local optima. In order to verify the optimization accuracy， convergence performance， and stability of the improved Golden Jackal Optimization Algorithm， eight benchmark test functions with different features are selected for experiments. The results show that among the 8 benchmark test functions， the improved Golden Jackal Optimization Algorithm has achieved optimal results in terms of mean， standard deviation， and optimal value. In addition， the results of Wilcoxon’s sign rank test indicate that the improved Golden Jackal Optimization Algorithm is significantly superior in statistics. Through practical applications， it shows that the Golden Jackal Optimization Algorithm based on multi-strategy fusion improvement can effectively estimate the parameters of the Muskingum Model， and the optimization effect is significantly better than the particle swarm optimization algorithm， the sine cosine optimization algorithm， and the Golden Jackal Optimization Algorithm. This further verifies the effectiveness of multi-strategy fusion improvement and the superiority of the improved algorithm in parameter optimization. This provides an effective new method for more accurate estimation of the parameters of the nonlinear Muskingum Model.

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.

In order to study the river regime evolution of the braided reach in Lower Yellow River after the operation of the Xiaolangdi Reservoir， the Landsat satellite remote sensing images of the braided reach in Lower Yellow River during the past 20 years from 2001 to 2020 are selected， and the edge extraction algorithm is used based on ARCGIS and ENVI software to extract water edge and correct the normalized differences. The water body index method （MNDWI） is used to extract the water body and analyze the characteristic indicators such as the water surface width of the river channel during the flood season， the position of the mainstream after the flood season， and the number of central banks after the flood season. The results show that： ①After the operation of Xiaolangdi Reservoir， after 20 years of dredging adjustment， the river conditions in the braided reach in Lower Yellow River have been significantly improved during the flood season， and the mainstream has basically returned.②There is no obvious change in the river shape of this reach， and the width of the water surface increases and decreases with the amount of water during the flood season， and generally widens year by year. However， the width of the water surface of the Jiahetan-Gaocun section is relatively stable due to the control of the river channel improvement project. ③Using the MNDWI method to intelligently extract the water body， it is found that the swing of the mainstream presents three rules： ①The position of the mainstream is basically unchanged. ②Mainstream position moves in the same direction. ③ Mainstream locations are migratory. ④The number of the mid-channel beaches is negatively correlated with the water volume， generally decreasing year by year from 2001 to 2007， reaching a minimum of 13 in 2007， increasing year by year from 2007 to 2015， reaching a maximum of 58 in 2015， and decreasing year by year from 2015 to 2020， and at the same time， the location of the river-shaped abrupt change in the channel will also change. The adjustment of river regime will change the effectiveness of the river improvement project， and will also affect the production and life of the people in the beach area. Therefore， it is necessary to strengthen the monitoring of the river regime in the wandering section of the Lower Yellow River and pay enough attention to the changes of the heart beach to enhance the understanding of the law of river situation adjustment and the evolution of the heart beach in the Lower Yellow River.

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.

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.

Irrigation is one of the types of land management that has the greatest impact on regional climate， and its impact has been increasing in recent decades. A large number of papers have demonstrated the cooling effect of irrigation， particularly in arid and semi-arid regions. However， the cooling effect in humid regions has been found to be not significant， and the investigation of the cooling effect pertaining to extreme high temperatures has received comparatively less attention.In this study， a sliding window search algorithm is used to investigate the impact of augmenting the proportion of irrigated areas on the occurrence of extreme high temperatures in the Yangtze River Basin based on a global gridded temperature dataset and a historical irrigation distribution dataset. To isolate the climatic effects of various factors in the observed data， the multiple linear regression techniques are employed. Furthermore， a control test is set up by using the WRF model of the coupled irrigation module to perform numerical simulations for verification.The results show that irrigation in the Yangtze River Basin has a cooling effect on extreme high temperatures， and the intensity of the cooling effect depends on the proportion of irrigated area， which becomes more obvious with the increase in irrigated area， but when the proportion of irrigated area exceeds the threshold （0.25~0.30）， the cooling effect gradually diminishes. Numerical simulation experiments verified the results of the analysis based on observed data， but the model would overestimate the cooling effect of irrigation to some extent. Meanwhile， it was found that irrigation could increase soil moisture and latent heat flux and decrease sensible heat flux and soil heat flux， and the cooling effect would be weakened as the proportion of irrigated area increased， the surface moisture increased and the albedo decreased. The results of this research can provide a theoretical basis for the scientific management of agricultural irrigation in the Yangtze River Basin， which is of great scientific significance.

Dams are important structures that provide various benefits， such as hydroelectric power generation， irrigation， and flood control. However， dam failures can lead to catastrophic consequences， causing significant economic and human losses. Therefore， predicting the potential impact of a dam break is crucial for ensuring the safety of people and property downstream. The width of the breach is a critical factor in estimating the flooded area downstream of an earth-rock dam during a dam break. Traditional empirical formulas developed by the Scientific Research Institute of the Ministry of Railways and the Yellow River Water Conservancy Commission are used to estimate the width of the breach， taking into account the storage capacity， length， and height of the dam. However， these formulas have been found to have significant errors when compared to actual breach widths observed in dam break cases at home and abroad. To improve the accuracy of these formulas， this paper uses an allometric model to fit the data from seven dam break cases， resulting in an optimization formula for calculating the width of the breach. The new formula takes into account the length， height， and storage capacity of the dam， as well as the degree of compaction of the soil in the dam body. The optimized formula has been found to have a maximum error of only 4.5% when compared to actual breach widths， indicating that it is more accurate than the traditional empirical formulas. The optimization formula proposed in this study provides a more accurate method for estimating the width of the breach in earth-rock dam breaks， and can be used to improve the accuracy of calculations for maximum flow rate. The results of this study can also have significant implications for dam safety engineering， as well as for the development of effective emergency response plans in the event of a dam break. In addition， the DBFL-IWHR model is used to simulate the downstream flood evolution and compared with the traditional empirical formula. The DBFL-IWHR model is a two-dimensional hydrodynamic model that takes into account the complex interactions between the water flow and the topography of the river channel. The results show that the maximum flow rate calculated by the traditional formula is lower than that of the DBFL-IWHR model， and that the arrival time of the maximum flow rate in the downstream section is delayed compared to that of the DBFL-IWHR model. This highlights the importance of using accurate models in predicting the potential impact of dam breaks on downstream areas. In conclusion， the optimization formula proposed in this study provides a more accurate method for estimating the width of the breach in earth-rock dam breaks， and can be used to improve the accuracy of calculations for maximum flow rate. Furthermore， the use of accurate hydrodynamic models， such as the DBFL-IWHR model， is recommended for simulating the downstream flood evolution and predicting the potential impact of dam breaks. These findings may have significant implications for dam safety engineering， emergency response planning， and the protection of people and property downstream of earth-rock dams.

In the 1990s， the discipline of eco-hydrology was gradually derived. Eco-hydrology mainly studies the coupling mechanism and development law of ecological process and hydrological process. In recent years， water resources shortage， uneven spatial and temporal distribution of water resources， water waste， water pollution and other problems are prominent. It has become an urgent need for the rational allocation of water resources to master the distribution law of water resources with temporal and spatial changes， formulate ecological protection strategies suitable for sustainable development of local ecological environment， and establish watershed management and control mode and water resources development strategy based on water resources carrying capacity. To achieve the above requirements and objectives， eco-hydrological regionalization is the basis， and the objective of eco-hydrological regionalization is to provide a minimum management unit for analysis and evaluation under different ecological systems and hydrological characteristics. Eco-hydrological regionalization is mainly used to study the regional differentiation of eco-hydrological phenomena and reveal the regional distribution law of eco-hydrological phenomena. This paper focuses on the development of ecological regionalization， hydrological regionalization and eco-hydrological regionalization， the construction of ecohydrological regionalization index system， and the methods of eco-hydrological regionalization. The problems existing in the current research are discussed： foreign researches mainly focus on ecological regionalization or hydrological regionalization， but the regionalization considering the coupling relationship between ecology and hydrology is scarce. Although domestic researches on eco-hydrological regionalization have been carried out， they focus on traditional methods such as principal component analysis and clustering method， fixed time period analysis and large and medium spatial scale research. The future research direction and development trend are put forward： optimizing the evaluation index system， integrating multi-source data， improving the accuracy of regionalization method and monitoring the dynamic change of regionalization.

In order to dynamically analyze the impact of future land use change on the non-point source pollution load in the watershed，this study couples the PLUS land use prediction model with the SWAT non-point source pollution load model，so as to reveal the distribution of non-point source pollution in the watershed under different land use change scenarios．By taking the Dongjiang Lake Basin as the research area，this paper simulates and predicts the temporal and spatial evolution of non-point source pollution under different land use patterns in the historical series of the study area and in the following 2035 by building the SWAT non-point source pollution model and the PLUS land use model．The results show that the SWAT model has good applicability to the Dongjiang Lake Basin．The Nash–Sutcliffe efficiency index of the river runoff in regular and verification periods are 0.80 and 0.71. Meanwhile，the ammonia nitrogen and total phosphorus rates are higher than 0.5 in both periods．The temporal and spatial evolution characteristics，as well as changing trends，of non-point source pollution in the Dongjiang Lake Basin are studied by using long series simulation results．Non-point source pollution in the Dongjiang Lake Basin is affected by natural processes such as precipitation and runoff and land use patterns. From a time perspective，the pollution output load is concentrated during the high-water period with heavy precipitation. The inter-regional change reveals a trend of non-point source pollution first increasing and then decreasing； from the perspective of spatial scale，higher loads of ammonia nitrogen and total phosphorus are concentrated in the northwestern and central sub-basins with larger runoff and scattered farmland. The impact of different types of land use on non-point source pollution is studied in conjunction with the distribution pattern of land use and non-point source pollution．The contribution degree of total phosphorus load is cultivated land > construction land > grassland > forest land >unused. The land use pattern in 2035 is set by using the PLUS land use model under the historical trend scenario and territorial spatial planning， and the simulation and analysis of the response to non-point source pollution are completed on this basis．Under two different land use pattern scenarios，the territorial spatial planning scenario reduces ammonia nitrogen by 2.12 t and total phosphorus by 54.6 t compared with the historical trend scenario．The former scenario is more beneficial to control the non-point source pollution loads in the Dongjiang Lake Basin．The increase in pollution load is caused by the pollution of farmland， the rapid expansion of construction land and the reduction of forest land，and the restricted conversion of forest land and cultivated land plays an important role in reducing the pollution load of the watershed．

Ponds are essential elements of both natural landscapes and urban environments， serving as green infrastructures and playing a vital role in contemporary water conservation planning. They provide a wide range of ecosystem services that contribute to the overall health and sustainability of the environment. These services include flood regulation， nutrient retention， mitigation of the urban heat island effect， as well as supporting fish production and aquaculture. Evaluating the significance of ponds by examining their characteristics， determining their priority level for governance and protection， and proposing utilization strategies based on their importance levels are crucial steps in understanding and optimizing their ecological service functions. These efforts form the foundation for effective governance and protection of ponds and ensure their continued contribution to the land ecosystem’s service function and overall effectiveness. By analyzing the land use status of Liaocheng City， an assessment is conducted to understand the characteristics and spatial distribution of pits and ponds. Subsequently， an evaluation index system is developed to determine the importance of these pits and ponds in the region. This comprehensive analysis provides valuable insights into the significance of these water bodies and their role in the local ecosystem. It is found that the distance from the main rivers/lakes and reservoirs is conducive to the migration of Amphibian. The number and area of ponds around cultivated land are much larger than other types of land use. The number of ponds in each district and county decreases according to cultivated land， forest land， rural residential land， and urban residential land. The density of pits and ponds is 3~10 /km²， and the main gathering centers are in the northeast of Dongchangfu District， the middle of Dong’e County and the northeast of Gaotang County.The density and importance of ponds show a trend of high in the north and low in the south， and high in the east and low in the west. To make the most of ponds with high importance scores， this paper recommends strategically utilizing them based on their specific morphology and spatial distribution. This may involve implementing measures such as maintaining their natural features， protecting the surrounding vegetation， and ensuring proper water management practices. On the other hand， for ponds with low importance scores， an ecological reclamation approach can be pursued in conjunction with local land comprehensive improvement plans. By implementing these strategies， Liaocheng City can effectively utilize and protect its pit and pond resources. This will contribute to the preservation of the land ecosystem’s service functions and enhance the overall ecological well-being of the region.

Within the hierarchical decision structure of reservoir pre-impoundment operations， the parameter equifinality of hydropower generation leads to non-uniqueness of optimal solutions， i.e.， the “ill-posedness” of solving reservoir operation optimization problems. Under such circumstances， the realization of operation benefits is affected by whether the reservoir operator selects the refill plan in favor of flood safety， implying that not only competitive relationship but also cooperative potential exists between flood control and water conservation. In light of this， a cooperation incentive （CI） model based on the lower-level satisfaction is developed to provide a mechanism to promote the water conservation department’s cooperation with the flood control department and enhance the reservoir operation benefit. Based on the framework of ill-posed bilevel programming， regarding the actual decision characteristics， the model described the nonlinear correlation between the cooperation willingness and the expected benefit of the water conservation department given certain flood control rule， so that the probability of selecting the refill plan in favor of flood safety can be derived. The CI model is solved by using multi-swarm evolutionary particle swarm optimization algorithms. Quantitative indicators are proposed to evaluate the Pareto efficiency loss and overall goal achievement of the reservoir operation optimization under cooperation. In the Three Gorges Reservoir pre-impoundment case study， the results are compared with those of the optimistic， pessimistic， and partial cooperation models. Results show that the CI mechanism motivates the benefit concession of the flood control department to increase hydropower generation and encourage the water conservation department’s choice in favor of flood safety. Further， the efficiency loss in operation decisions due to competitive gaming process can be more prominently reduced. Findings also indicate that nonlinear satisfaction-expected benefit relationship can better describe the practical decision making in reservoir operation.

Dam deformation is the visual representation of the state of a dam under the influence of internal and external loads during its operation. Building a high-precision deformation prediction model is of significant importance for dam safety monitoring and operational assessment. Existing dam displacement models have long training times， and their prediction accuracy and generalization capabilities are often suboptimal， making them unsuitable for accurate short- to medium-term displacement predictions. This paper coupled Long Short-Term Memory （LSTM） with the Transformer framework and introduced an improved Invasive Particle Swarm Optimization （IPSO） algorithm for optimization to create the IPSO-LSTM-Transformer （ILT） dam deformation prediction model. Using data from measurement point 11-1 on the vertical axis of the Jinshuitan arch dam as an example， this paper analyzed and predicted deformation time series data from 6，150 data sets. The research results demonstrate that the model's prediction accuracy decreases to a certain extent as the prediction horizon increases， but it maintains good predictive capabilities within a prediction step of 10. Compared to traditional Particle Swarm Optimization algorithms， the ILT model significantly improves the model's optimization precision and convergence speed. When compared to the single-step and multi-step prediction results of RNN， LSTM， and IPSO-Transformer neural network models， the ILT model exhibits higher accuracy and better stability， even when trained with limited data. The research findings provide new technical means for the precise short-to-medium-term prediction of dam displacement during operation.

Subsurface infiltrating irrigation is a kind of underground micro-irrigation method. The irrigation water is diverted to the soil at a certain depth under the ground through the buried pipe for subsurface infiltrating irrigation，and then the soil capillary action is used to achieve direct water supply to the root zone of crops. This irrigation method is essentially the same as the irrigation process of “Subsurface Drip Irrigation”. Subsurface infiltrating irrigation can effectively improve soil environmental quality and facilitate crop growth， and it is a highly efficient and water-saving irrigation technology with broad development prospects. It is of great significance to research on subsurface drip irrigation for promoting the development of efficient water-saving agriculture. In this paper， the relevant research progress and existing problems are reviewed from the aspects of soil water transport rule， irrigation technology parameters， irrigation system， influence and regulation of infiltration irrigation pipe clogging etc.， and the future research directions are proposed，which may be referred to by scholars in the field of water-saving irrigation research. It is concluded from this review that， compared with the production practice of subsurface infiltrating irrigation， the research on its mechanism is relatively lagging behind， which limits the deep popularization and application of this technology. The main manifestations are as follows： the law of soil water transport under subsurface infiltration irrigation is not clear enough， clogging is still the limiting factor that hinders the application and development of subsurface infiltration irrigation technology， the optimization design of subsurface infiltration irrigation water distribution system needs further research. This paper suggests carrying out a numerical simulation analysis of water infiltration under different irrigation conditions in the future， selecting the appropriate treatment level， studying the main factors affecting the effect of infiltration irrigation， and seeking the optimal combination of irrigation technology parameters. Research on crop irrigation system under the condition of subsurface infiltration irrigation is carried out to form a set of reasonable and perfect irrigation system and test method. Further research should be carried out on the rule of subsurface infiltration irrigation pipe outflow， clogging mechanism and the effective control threshold of key parameters of irrigation water quality when entering the subsurface infiltration irrigation system.

In recent years， extreme weather events have shown multiple and strong occurrences， and extreme hydrological events such as possible maximum floods triggered by extreme weather have posed serious threats to reservoir safety， while the use of conventional flood control scheduling protocols for reservoirs may fail in the face of their threats. Therefore， it is especially important to optimize the regular scheduling protocols of reservoirs and to form emergency scheduling for extreme situations. To address the problem， this paper focuses on the Zipingpu Reservoir， an incomplete regulated reservoir located in the upper reaches of the Min River as the research object， establishes a one-dimensional hydrodynamic model of the river section in the reservoir area based on HEC-RAS， following the “spatial-temporal trade-off” scheduling approach， the optimization principle of “advance pre-release combined with increased release” is adopted， and carries out a study on the scheduling mode of the reservoir in the face of possible maximum floods and the optimization of the scheduling timing with the goal of ensuring the safety of the reservoir and minimizing the downstream risk. It is found that when facing the maximum possible flood with the total influent flow rate of 8 times the reservoir flood control capacity， a reasonable dynamic allocation of the reservoir flood control capacity can be achieved through the combined mode of flood discharge and the joint optimization of the scheduling start and end times， developing an emergency scheduling protocol for the reservoir to cope with the potential maximum flood events. It realizes the reasonable dynamic distribution of reservoir flood control capacity with flood history， and wins more time for reservoirs to complete the flood release task. The optimized scheduling method avoids the hidden danger of conventional scheduling failure， the peak water level in front of the dam during the flooding period is lowered by 18.4 m compared to the original scheduling method， ensure that the water level in the reservoir is always in the safe range； the change of water surface line in the reservoir area is controlled within 14.7 m， which is 55.6% lower compared with the original dispatch， and the overall water level change in the reservoir area is more stable； and the peak reduction rate under the optimized scheme reaches 74%， which minimizes the threat of flooding to the downstream. On this basis， through a further analysis of the definition of reservoir flood control potential， it reveals the reasons for the obvious differences in the flood control effect of reservoirs under the two scheduling methods， and provides new ideas and references for reservoirs to carry out emergency scheduling in the face of extreme floods.

In order to explore the influence of the staggered impeller on the pressure fluctuation characteristics of the double entry two-stage double suction centrifugal pump， this paper uses the method of combining experiment and numerical simulation to carry out a research on the same pump with symmetrical impeller and staggered impeller as the contrast scheme， and quantifies the pressure pulsation characteristics of the suction chamber， inter-stage flow channel and volute under three typical working conditions of 0.6Q， 1.0Q and 1.2Q. The results show that： ① in terms of external characteristics， the head and efficiency of the pump with staggered impeller are higher than those with symmetrical impeller at all working conditions， and they can be 2% and 3% higher than those at 1.0Q working condition. ② In terms of pressure pulsation characteristics， for the suction chamber， the influence of staggered impellers on pressure pulsation is small at all working conditions， and the difference of dominant frequency amplitude is less than 2%. For the inter-stage flow channel， the staggered impeller can restrain the pressure fluctuation at all working conditions. For example， the dominant frequency amplitude at the tongue of the inter-stage flow channel can be reduced by 13.5% compared with that of the symmetrical impeller. For the volute， the staggered impeller can improve the pressure fluctuation under all working conditions. For example， the dominant frequency amplitude at the tongue of the volute can be reduced by 31.9% at most. This finding can provide a reference for the application of staggered impeller in double inlet two-stage double suction centrifugal pump.

Climate change and human activities are important causes of runoff changes in watersheds. The Budyko hydrothermal coupled equilibrium equation is a common tool for runoff change analysis， because it takes into account certain physical causes on the one hand， and the parameters of the equation are simple on the other hand， so it has been widely used in runoff change attribution for a long time. However， the current research and application of Budyko’s formula for time-varying forms still need to be strengthened. Therefore， this paper first analyzes the trend and abrupt change of annual runoff in the study area by Mann-Kendall test and abrupt change test， and then constructs the time-varying Budyko formula based on the principle of hydrothermal coupling equilibrium， including linear， quadratic polynomial and physical mechanism， and uses Nash efficiency coefficient as the evaluation index to verify the most suitable. Finally， the contribution of precipitation， potential evapotranspiration and human activities to the runoff change is calculated， and the attribution analysis of the runoff change in the Liudong River basin is carried out. The results of this study show that the runoff of the river basin has been decreasing in recent years with the impact of climate change， with a significant change in 1997. A comparison of the sensitivity of precipitation， potential evapotranspiration and human activities to runoff show that the decrease in precipitation is the dominant factor in the decrease in runoff， with a contribution of 49%. Meanwhile， with the development of human economy and society and the construction of large water conservancy facilities， the influence of human activities on runoff changes in the basin is gradually emerging， with a contribution rate of about 26%.

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.

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.

With the guide vane of the pump-turbine as the main research object， the guide vane opening of 11， 33 and 41 mm is selected to analyze the influence of different guide vane airfoils on runaway characteristics of pump-turbine， so as to provide methods and theoretical guidance for the design and optimization of guide vane airfoil of pump-turbine. The results show that the improved guide vane airfoil has a better improvement effect on the "S" characteristics of the unit under three kinds of guide vane openings. After the improvement of the guide vane airfoil， the internal flow state of the unit is improved on runaway characteristics. The velocity streamlines in the guide vane and runner area are evenly distributed， and the concentrated distribution area of vortex core is reduced. After the improvement of guide vane airfoil， the relative value of pressure pulsation amplitude of monitoring points in vaneless area at different openings decreases in different degrees， and the velocity pulsation curve is gentle and the velocity peak value is smaller than before the improvement. The concentrated distribution area of vortex core in the draft tube of the improved guide vane airfoil is reduced， and the unit can operate in a relatively stable state.

In recent years，the water level in Poyang Lake has repeatedly reached a record low in dry seasons，which has led to increasingly prominent economic and social development and ecological and environmental protection issues. In order to identify the law of water level changes of Poyang Lake and quantify the degree of contribution of different influencing factors on the changes in the water level of Poyang Lake， this paper uses Mann-Kendall test and polynomial regression analysis methods to quantitatively analyze the change trend of water level of Poyang Lake and its causes. In this paper， Xingzi Station and Hukou Station are taken as the water level and flow representative stations of Poyang Lake respectively， and Jiujiang Station is taken as the representative station of the mainstream of the middle and lower reaches of the Yangtze River. First， the long-term observed data of the Yangtze River Basin and Poyang Lake from 1981 to 2021 are selected for case studies. The main influencing factors of the water level changes of Xingzi Station on the Poyang Lake are identified by correlation analysis. The trend characteristics of the water level of Poyang Lake are analyzed by the Mann-Kendall test method. Finally， the degree of contribution to the changes in the water level of Poyang Lake during the dry season is quantified based on the water volume relationship. The results show that the changes in Poyang Lake′s water level from the perspective of water volume are mainly affected by the total water volume of Jiujiang Station and Hukou Station. In 1981 before the Three Gorges Reservoir was built， the lowest water level of Poyang Lake had shown a significant downward trend. After the reservoir was built， the lowest water level of Poyang Lake in the normal storage period rose by 0.44 m compared with the initial storage period， indicating that the water supply regulation of the Three Gorges Reservoir in the dry season alleviated the downward trend of the water level of Poyang Lake in the dry season to some extent. Impoundment of the Three Gorges Project is not a key factor affecting the decrease in water level in the dry season of Poyang Lake， with a contribution of 35.4%， but is mainly affected by the comprehensive factors such as decreased water and cutting under the river bed， with a contribution of 64.6%. In addition， the water supplement of the Three Gorges Reservoir has a positive effect on the increase in water level of Poyang Lake in the dry season， with a contribution of 20%， and the contribution of factors such as the cutting of the riverbed and the reduction of other incoming water is -120%. The study can provide scientific basis and guidance for formulating countermeasures for low and dry water levels of Poyang Lake in the dry season and improving water resources and water environment carrying capacity of the lake area.

In recent years， uncommonly severe droughts have attacked many places in Guangdong Province， with long duration， wide impact and serious consequences， which is contrary to people’s general understanding of the water-rich areas in the south. In order to find out the causes， influencing factors and characteristics of drought in Guangdong Province， and effectively identify the weaknesses in drought disaster prevention and control， taking the typical drought-prone counties in Guangdong Province-Chaonan District in eastern Guangdong and Xuwen County in western Guangdong Province as examples， based on the natural disaster risk theory， this paper establishes a drought disaster risk assessment zoning model， which couples the three elements of hazard， vulnerability and defense， and the evaluation index system and calculation method of comprehensive risk index are put forward. The index weight is determined by analytic hierarchy process. The natural breakpoint method is used to scientifically divide the regionalization， and the risk matrix method is introduced to aggregate the drought risk and drought defense and disaster reduction ability to represent the level of drought disaster prevention and control， and the risk influencing factors and risk levels of drought disaster are qualitatively and quantitatively evaluated. The results show that， under the main influence of less natural rainfall and large demand for economic and social water， the comprehensive risk of drought disaster in Chaonan increase from west to east， most towns and streets have moderate drought risks， while the whole area of Xuwen has medium-high and above drought risks， the comprehensive risk of drought disaster in western and central areas is high. If the water supply engineering capacity， river system density and drought-defense investment level are not high， it can be determined that most towns and streets in Chaonan are medium prevention areas， and most towns and villages in Xuwen are key prevention areas. The rationality of the results is verified by typical historical drought events， and some measures and suggestions are put forward for the weaknesses of drought defense in drought-prone counties. The research results can provide technical support for improving the drought-defense and disaster reduction system in typical drought-prone counties in Guangdong Province.

The optimal regulation of multi-energy complementary systems helps to take advantages of different power sources. The growing installed capacity of wind and photovoltaic power has brought about the problems of clean energy consumption and grid peak shaving. A bi-level optimal scheduling model of wind， photovoltaic（PV）， hydropower， thermal power and energy storage is proposed to solve the problems. Firstly， considering that there are many variables and constraints involved in the optimal scheduling of multi-energy complementary， the model is processed hierarchically based on the output characteristics and complementary relationship of multiple energy sources， to reduce the complexity of model solving. Then， according to the demand of source-load coordination， clean energy consumption and power generation economy， the model is divided into the upper-level model of Wind-PV-Hydro-Storage joint optimal scheduling and the lower-level model of thermal power unit optimal scheduling. The optimization objectives of upper-level model are the minimum net load variance and the maximum clean energy generation， and the optimization objective of lower-level model is the minimum operation cost of thermal power units. The net load curve achieved by the upper-level model is used as the constraint of the lower-level model. Finally， taking the IEEE30-bus system as an example， the CPLEX solver of MATLAB platform is used to calculate three pre-defined scheduling scenarios. The results show that the anti-peak regulation of wind power and photovoltaic output will expand the peak-valley difference and variance of net load， increase the pressure of peak shavingand reserve of thermal power， and increase the power generation cost and unit loss. The participation of hydropower in multi-energy complementary systems has a significant improvement on the net load fluctuation of the power grid， which can effectively reduce the peaking pressure of the power system. Energy storage can reduce the conflict between smoothing net load fluctuation and improving clean energy generation to a certain extent. The optimal scheduling model proposed can effectively reduce the fluctuation of source and load， promote the consumption of clean energy and reduce the operation cost of the system， which contribute to the low-carbon and safe operation goals of the grid.

Evapotranspiration is a key factor in hydrological and energy cycles， and its spatio-temporal evolution is influenced by various complex factors such as watershed climate， energy， and underlying surface. The influencing factors of evapotranspiration in different climate regions have spatio-temporal differences and different sensitivity characteristics. Studying the spatio-temporal changes in evapotranspiration is beneficial for revealing the response characteristics of hydrological cycles in complex environments， further deepening people’s understanding of water balance in watersheds， and providing theoretical reference for the rational planning and utilization of water resources in watersheds. Based on the SWH dual source evapotranspiration model， the evapotranspiration and its components of the Poyang Lake Basin from 2001 to 2017 are simulated. On the basis of multi-temporal and spatial scale validation， the spatial-temporal evolution characteristics of the total evapotranspiration （ET）， soil evaporation （Es）， plant transpiration （Ec） and evaporation ratio （Es/ET） of the basin are analyzed. Based on the SOBOL sensitivity analysis method， the sensitive influencing factors and actual change causes of the evapotranspiration components of the basin are explored. The results show that the correlation coefficients between the simulated and measured values of the SWH model at the 8-day scale are 0.92 and 0.89 at the station and watershed， respectively， indicating good simulation results. At the 0.05 significance level， the annual ET in the Poyang Lake Basin does not decrease significantly at the rate of 1.0 mm/a， Es decreases significantly at the rate of 2.6 mm/a， Ec does not increase significantly at the rate of 1.7 mm/a， and Es/ET decreases significantly at the rate of 0.28%/a. The spatial distribution characteristics of Es/ET in the basin are high in the middle and low around， with Es/ET in winter>spring>autumn>summer. Except for summer， Es/ET shows a significant downward trend， mainly concentrated in the southern plain of the lake area and the Xinjiang River basin， accounting for 33.86% of the total basin area. Temperature and wind speed are the main sensitive factors affecting changes in ET and Es in the watershed， followed by precipitation and net radiation. Es is also more sensitive to NDVI. The main sensitive factor for Ec and Es/ET at both annual and seasonal scales is the NDVI， and the significant increase in NDVI is the main reason for the changes in Ec and Es/ET in the watershed.

Riverbed roughness is an important aspect of river dynamics research， and its quantitative measurement has always been challenging. In this experiment， regardless of the macroscopic undulation of the riverbed， we laid the initial bed surface in a straight channel with non-uniform natural sand and thickened it by gradually increasing the flow rate of water. Laser scanning technology was used to obtain high-resolution bed elevation data after each bed roughening. Statistical theory and variogram function were used to investigate the surface roughness characteristics of riverbeds with varying degrees of coarseness， and to deepen the understanding of their statistical characteristics. The study's main finding is that artificially laid non-uniform sand presents an elevation frequency distribution that approximates a normal distribution. On the contrary， the frequency distribution of the stable rough bed surface formed by the continuous cumulative erosion of different flow intensities shows a slight positive deviation trend. The study found evidence that the increase of flow intensity leads strictly to an associated elevation standard deviation increase. This finding indicates that elevation standard deviation can be used as a reliable indicator to measure the characteristics of riverbed roughness in future studies. The study revealed that the kurtosis of the bed elevation data precisely decreased monotonically with the flow intensity， and that skewness and kurtosis showed a monotonic trend， indicating that they can be used to measure bed roughness. Additionally， the study found that the flow forming the bed surface is anisotropic， and as flow intensity increases， the rough layer breaks and becomes rougher again. This leads to an increase in the base value of the two-dimensional bed elevation variogram. Therefore， the study suggests that the base value of the two-dimensional variogram could serve as another reliable index for evaluating bed surface roughness. In addition， due to the influence of water flow， although the change trend of the characteristic parameters of the average variogram along the flow direction， vertical flow direction and radial profile elevation is consistent， the average variogram base value and golden point value of the transverse section are slightly larger than those of the transverse and longitudinal sections. Conversely， in the radial section， the abutment value and nugget value are considerably smaller than the values in transverse and longitudinal sections. In conclusion， this study enhances our understanding of the characteristics of bed roughness and provides crucial insights into statistical expressions for quantifying it.

With the development of industrialization and urbanization， untreated domestic sewage， industrial sewage and pollutants of surface runoff in the rainy season are discharged into the river system， leading to the serious urban water pollution. Due to the complexity and variability of the sources of urban polluted water bodies and environmental conditions， the current river restoration focuses on the rapid recovery of water quality， but does not fundamentally clarify the source of pollution， and does not consider the restoration of river water ecosystem damage. It leads to the fact that urban river is characterized with poor ability of self-purification and imperfect biodiversity， meanwhile， it is difficult to maintain and continuously improve water quality. This paper systematically illustrates the development process and inherent science of the concept of near naturalization restoration and urban sponge city. Both of them have separate characteristics， the concept and measures of which have commonality with the urban river restoration. The ecological restoration under the guidance of near-naturalization concept is beneficial to restore the hydrological continuity of river channels， to reshape the meandering and winding landscape of rivers， to increase the biodiversity index， making full use of their original ecological functions and values. Whereas， the concept of sponge city can effectively reduce surface runoff， purify， accumulate， utilize rainwater and alleviate the discharge of pollutants into river or water bodies. They also contribute to the mitigation of flooding risk and improvement of river dredging and drainage functions. In addition， this paper summarizes the near-naturalized and sponge city part from the project carried out in Fuyang City， Anhui Province. Through the combination technology of “source control， pollution interception， dredging， water diversion and management”， ecological restoration makes the near naturalization and sponge city integrated， which also emphasizes the construction of food chain system and greening management in the river channels. The two concepts focus on the restoration of self-purification capacity of the river and the reconstruction of ecosystem integrity， emphasize the treatment and reuse of rainwater resources， achieving the harmonious development of urban ecological restoration and landscape. Finally， to ensure the sound cycle and sustainable development of urban water ecosystem， the paper develops the direction of urban river restoration under the concept of near naturalization and sponge city intersection based on the current advanced environmental remediation and administration of domestic and foreign countries. It mainly includes two aspects： one is that the river restoration should be implemented in combination with the over-all planning of urban areas， making the river channel construction as an organic component of urban landscape； the other one is to gradually establish the evaluation indicators and standard for urban river restoration， including the traditional water quality indicators and those indicators related to the biological habitat and biodiversity.

Since 1956， the Dongting lake basin has experienced a historical process from shrinkage to development. To investigate the reason behind its evolution during each historical stage and predict its evolution trend， we work out this study based on data of water-sediment discharge， lake-basin water surface area and lake capacity during 1956-2019， in which contribution ratios of sedimentation， lake basin subsidence， reclamation and sand mining on lake-capacity variation are identified using the variable separation method. Results show that the lake-basin water surface area decreased by 1 247.59 km² during 1956-2019， in which the shrinkage of the east lake basin was the most severe， and reclamation within the lake basin was the major driving factor during 1956-1980， whereas the lake-basin water surface area became stable after 1980. Both sediment input and output continuously declined before the impoundment of the Three Gorges Dam （1956-2002）， with a rough sedimentation ratio of 70% in the lake. However， sediment input experienced a remarkable reduction after the impoundment （2003-2019）， with the sedimentation ratio falling to 14%. There was an offset effect among lake-basin subsidence， sand mining and sedimentation when they altered the lake capacity. At present， the lake basin is still in a slow tectonic subsidence， with an average rate of 3 mm/a. As sand minning proceeds， the lake shrinkage slows down. Before 1980， the lake capacity decreased， with contribution ratios of reclamation， sedimentation and tectonic subsidence were -92.7%， -13.2% and 5.9%. However， after 1980， the lake capacity witnessed a shift from declination during 1981-2002 to augment during 2003-2019 and a net declination， with contribution ratios of sedimentation and tectonic subsidence were -107.6% and 7.6% during 1981-2002 and those of sedimentation， tectonic subsidence and sand mining were -11%， 24.8% and 86.2% during 2003-2019. Considering the higher rate of tectonic subsidence than sedimentation after the impoundment of the Three Gorges Dam and the dominance of sand mining in the lake capacity change， the Dongting lake will continuously develop as the new sand mining planning （2023-2027） implements.

Controlling the outlet flow rate at the lower boundary of a river can alter the flow rate and direction of the water body， leading to an improvement in the water quality of the river， the improvement effect is related to the scale of diversion and drainage， the layout of the outlet， etc. Scientific and rational allocation of water resources is the core of sustainable water resources use. This paper presents a case study of the river network area of Jiangbei Zhenhai Plains， Ningbo， for example， and selects the simulation period from October 1 to November 1， 2022， NH₃-N as an indicator for the main pollutant， construction of a one dimensional non-constant flow dynamics MIKE11 water quality and water quantity coupling model， taking into account the outflow capacity of the outflow pump station and maintains the minimum water consumption in the basin. The study sets up 28 outflow scenarios with outflow flow rates of 9，18，24 and 36 m³/s through the combination of three outflow opening and closing arrangements. This study aims to simulate the impact of boundary outlet flows on water velocity in various scenarios using a coupled water quality and water quantity model， and analysis of water quality change characteristics. The results show that： ①The higher the outlet flow of the basin， the more significant the increase in the flow velocity of the watershed， comprehensive hydrodynamic and water quality factors， the outflow of 18m³/s can better improve the hydrodynamic conditions and water quality of the river. However， if the flow rate increases to 24 or 36 m³/s and only one or two outlets are opened， the river has the risk of overflow. Therefore， opening more outlets is recommended to ensure flood safety； ② the optimal solution after simulation makes the average flow rate of the basin reach 0.056 m/s， the average concentration of NH₃-N decreases to 1.660 mg/L， the water quality improvement rate reaches 17.0%， the water quality condition of the river can be improved from poor V to IV or V water standard， the results provide a reference basis for improving the hydrodynamic water quality of the river.

This paper analyzed the pre-stressing mechanism of the steel wire and the damage process of the pipeline， and proposes a method of PCCP wire broken warning and alarm threshold assessment based on mechanical simulation analysis. The PCCP finite element model was established by ABAQUS program， and the complete construction process including laying bedding， installing pipelines， backfilling in steps was simulated， and the stress state of pipeline prestressing steel wires， steel cylinders and pipe core concrete was calculated under nearly 100 working conditions with different depths of burial and different design working pressures. It was proposed to take the maximum permissible number of broken wires of the pipe core concrete cracked under the action of water hammer as the early warning threshold for the bursting of the pipeline， and the maximum permissible number of broken wires in the limit state of the buried bearing capacity of the pipeline as the alarm threshold for pipe bursting， and analyzed the relationship between the PCCP wire broken warning and the alarm threshold under different working pressures and burial depths.

As an important non-engineering measure， the optimal operation of reservoir flood control can reduce the loss caused by flood disasters with little investment and plays a key role in flood control and disaster reduction. In this paper， considering the safety of the reservoirs themselves and the safety of the downstream flood control section， a multi-objective optimal model for real-time flood control operation of reservoirs is established with the objective function of minimizing the maximum flow of the downstream flood control section and minimizing the maximum water level of each reservoir. Based on the “filter operator”， an improved multi-objective Lichtenberg algorithm （MOLA） is proposed， which is used to solve the multi-objective model， and the real-time flood control operation schemes of the reservoirs are obtained， to enhance the practicability of operation solutions. Finally， a comprehensive screening method based on hierarchical clustering and the physical meaning of Pareto front is proposed to screen the scheduling schemes on the Pareto front and select limited ones for the scheduler， to increase the focus of decision-making. Taking the Shiguanhe flood control system of the Huaihe River Basin as an example， this paper applies the multi-objective optimal model for real-time flood control operation of reservoirs. The result shows that the proposed model based on the improved multi-objective Lichtenberg algorithm has high computational efficiency and strong applicability. The gradient analysis method is used to quantitatively analyze the mutual feedback relationship between the maximum water level of Nianyushan Reservoir， the maximum water level of Meishan Reservoir， and the maximum flow of Jiangjiaji flood control section. The results show that the water level change of Meishan Reservoir has a more significant impact on the flow of Jiangjiaji section， and the Meishan Reservoir is a priority in flood risk control of Shiguanhe River Basin. The research results can provide decision-making support for real-time flood control operation of reservoirs.

As a unit hydrograph method widely used in engineering practice， the synthetic unit hydrograph of Guangdong is obtained from the analysis and synthesis of rain and flood data before 1983， which reflects the production-confluence relationship before urbanization in Guangdong Province. However， there are few studies on the evaluation and modification of its applicability in urbanized areas. Taking Jingtian Watershed of Shenzhen City， Guangdong Province as an example， based on the rainstorm and flood records of Jingtian Hydrology Station from 2011 to 2019， this paper evaluates the applicability of the comprehensive unit line in Guangdong Province by using evaluation indexes such as Nash efficiency coefficient， identification index and correlation coefficient， and conducts a sensitivity analysis of important parameters by Spearman rank correlation coefficient method. Based on Latin hypercube sampling method and constrained least square method， the comprehensive unit line method of Guangdong Province is modified. The results show that the Jingtian Basin has experienced rapid urban expansion since the 1980s， and the proportion of impervious surface has exceeded 90%. The comprehensive unit line method in Guangdong Province has obvious shortcomings in describing the storm-flood process in this basin. The two schemes proposed in this paper can improve the simulation effect of the model by determining important parameters and modifying the unit line. Among them， the cross-validation parameter optimization method based on grid search and the unit line correction method based on constrained least square method proposed for small samples show a good simulation performance， and the indexes such as Nash efficiency coefficient， identification index and correlation coefficient are significantly improved， which better reflects the characteristics of production and convergence in Jingtian Basin. Compared with the recommended unit line of the integrated unit line method in Guangdong Province， the modified unit hydrograph method shows the characteristics of larger peak discharge， earlier peak time and smaller total duration， which is more in line with the law of production and confluence of urbanization.

It is one of the most effective ways to reduce pipe network leakage by controlling pipe network pressure. Traditionally， the pressure reducing valve is only applicable to the pressure management of local pipe network. In this paper， the method of real-time regulation of the pressure reducing valve and the water supply pump station is used to manage the pipe network pressure. Based on the systematic analysis of the response relationship and characteristics between the leakage amount and the node pressure， a hydraulic model of pipe network leakage is established.Taking the water supply network in CYN District of a city in North China as an example， genetic algorithm （GA）， particle swarm optimization （PSO） and whale optimization algorithm （WOA） are used to solve the case， and then the operation effects of these three algorithms are compared and analyzed. The results show that the whale optimization algorithm has better performance for solving the leakage model.

Agriculture is an important part of the global ecosystem carbon cycle， which is greatly affected by drought. Therefore， understanding the impact of drought on the carbon sink intensity of agro-ecosystems helps to figure out the change regular of agro-ecosystem carbon cycle and provide a theoretical basis for realizing the control of carbon emissions. In this paper， the net ecosystem exchange （NEE） of winter wheat-summer maize rotation system in North China Plains is simulated by vegetation photosynthesis and respiration model （VPRM）， and Drought Severity Index （DSI） is calculated based on evapotranspiration and normalized vegetation index to evaluate the agricultural drought intensity. The spatiotemporal response of NEE to agricultural drought is also assessed by using geographic detectors and de-trended analysis. The results show that the agricultural drought intensity in the northern part of North China Plains is more than that in the southern part of North China Plains during the growth period of winter wheat， and the agricultural drought intensity gradually decreases with the development of winter wheat. During the growth period of summer maize， North China Plains enters the rainy season and is generally wet. The carbon sequestration capacity of cropland ecosystem decreases with the increase in agricultural drought intensity， and the sensitivity of NEE of cropland ecosystem to agricultural drought is greater in the middle growth stage of winter wheat/summer maize than in the early and late growth stages. The spatial variability of agricultural drought has the largest explanatory power for NEE of winter wheat in March （q=0.681）. The explanatory power for NEE of summer maize is the highest in August （q=0.792）. With the increase in agricultural drought intensity， wheat and maize fields change from strong carbon sink to weak carbon sink if grain carbon content is not considered， and finally change to carbon source if grain carbon content is considered.

In order to simulate the operating status of the irrigation networks with pipe conveyance under different working conditions， this paper presents a numerical simulation model based on the mass conservation law and energy conservation law of constant flow. In this model， the equations of hydraulic state are established respectively to indicate the irrigation networks with pipe conveyance by using the bisection method to solve the equations respectively， the simulation results include the actual working points of the main nodes of the pipelines and the outlets， and the actual flow rate， head， power and efficiency of pumps. The case analysis shows that the model converges rapidly under the condition of each rotational irrigation schemes， the simulation results provide an important basis for water management of the system and the optimization of the engineering designs， which reflects a good practical application value.

Due to climate change and human activities， the runoff characteristics of the upper Yangtze River have changed significantly in recent years， bringing many challenges to the development and utilization of water resources in the upper Yangtze River Basin and the functions of national strategic freshwater resource reservoirs such as the Three Gorges and the upstream reservoir group. Attribution analysis of runoff changes is of great importance to the development and utilization of water resources in the basin. Based on the observed runoff data from 1951 to 2013， statistical methods such as Mann-Kendall test， Spearman test and Pettitt test are used to diagnose the variation patterns of the Three Gorges inflow runoff. Based on the meteorological and land use data of the same period， the causes of the variation of the Three Gorges inflow runoff are further quantitatively analyzed by using the climate elasticity method， the water-energy balance equation and the SWAT. The results show that： ① the inflow runoff of the Three Gorges was significantly changed around 1993， before 1993 the runoff was relatively natural and less affected by climate change and human activities， and after 1993 the runoff changed and was more affected. ② During the study period， the inflow runoff from the Three Gorges decreased significantly， at a rate of 8.8 mm/10 a. Large-scale human activities in the upper Yangtze River were the main cause of the decrease in inflow runoff into the Three Gorges， while the decrease in precipitation and the increase in temperature were important causes. ③ The attribution results of the climate elasticity approach are consistent with the SWAT-based method， while the water-energy balance approach underestimates the impact of human activities on runoff. ④ SWAT takes into account the spatial and temporal changes in land use， can better describe the causes of runoff changes than the traditional “two-stage” method. These results are important to guiding the comprehensive utilization of water resources in the Three Gorges Reservoir and the rational development of water resources in the upper Yangtze River.

Wheat drip irrigation technology is the main project of high-standard farmland construction in North China， and it is also an important technical means to deal with the shortage of water resources in the region and ensure national food security. Based on the latest research progresses of drip irrigation technology on wheat at home and abroad and the research results of our group for many years， this paper elaborates the influences of drip irrigation factors such as drip flow， dripping element spacing， drip belt laying distance on soil water distribution， the ways of drip irrigation scheduling on wheat， and the effects of drip irrigation on wheat water consumption characteristics， dry matter accumulations， yield compositions and so on. At the same time， the development trends of wheat drip irrigation in the future are put forward： smart irrigation decision-making and water-fertilizer integration technology that integrates multiple factors such as meteorology， soil and crops， It is hoped these contents would provide theoretical and technical support for accelerating the application and popularization of drip irrigation technology in the main wheat-producing areas in China..