Based on fractal geometry， the description of soil pore size distribution is established， and a suction model of unsaturated soil matrix considering the fractal characteristic of pores is proposed in combination with Young-Laplace theory. For the loess in Shaanxi region， the soil-water characteristic curves of different dry densities were collected， and the effects of dry density on pore distribution characteristics and matrix suction were analyzed. The results show that the loess pores have obvious fractal properties， which can be well described by the Menger Sponge fractal model. The pore fractal model parameter analysis shows that with the increase of dry density， the fractal dimension D increases approximately linearly， while the maximum aperture L decreases as a power function. Through function fitting， the characteristic relationship between loess pore size distribution and dry density is further established， and the suction capacity of loess matrix suction under different dry densities is quickly predicted.

Based on the knowledge and understanding of modernization of the physical irrigation district and digitalization of the analog irrigation district， this paper analyzes and summarizes the “five major functions” of the construction of modernized digital irrigation district including “Identification system of irrigation district”， “Stereoscopic Perception System”， “Precise Control System”， “Information Exchange System” and “Water Allocation System”. In order to meet the requirements of intelligent water projects and efficient operation and management of irrigation district， to efficiently simulate water flow in canal system， the generalized map of irrigation district with “joint flow process” as input and output is systematically sorted out， and the key application structure system of modernized digital irrigation district is studied and proposed. That is to build an interactive overall structure with “database” as the carrier， “mathematical model” as the support layer， “nine professional applications” as the interaction layer including “organization management”， “project management”， “security management”， “pumping station management”， “water saving and water supply management”， “economic management”， “information management” and “public services” on the basis of “one digital map of the irrigation district”. It is expected to effectively improve the safety， equity， reliability and flexibility of irrigation water supply services.

Researches on hydro-wind-solar hybrid energy systems have mostly focused on coordinated operation and enhancing the new energy consumption but often overlooked the potential impact on the water levels of reservoirs. In this paper， a long-term optimal operation model for hydro-wind-solar hybrid energy systems， nested with short-term energy curtailment， is established. Firstly， the curtailment loss function was fitted based on actual hydro-wind-solar output data simulating potential curtailment scenarios， which was incorporated into a long-term optimal operation simulation； Secondly， simulations of the reservoir dispatching operation process before and after the integration of wind and solar energy were conducted； Finally， the impacts of wind and solar energy consumption on the annual， sub-annual， and monthly operating water levels of the cascade reservoir group were analyzed. A case study was carried out using the hydro-wind-solar hybrid energy system from Longyangxia to Liujiaxia cascade reservoirs in the upper reaches of the Yellow River. The results show that： ① After wind and solar energy integration， the annual average output of the cascade reservoirs decreases by approximately 0.5% to enhance the consumption of wind and solar energy， increasing the wind-solar power in grid and total system output by approximately 2.2%. ② The wind and solar energy consumption leads to increased annual and monthly water level fluctuations in the cascade reservoir group. The end-of-year drawdown and annual average water level fluctuations ranges of Longyangxia and Liujiaxia reservoirs increase by 2.5%， 101.6%， 0.8% and 78.9%， respectively. Longyangxia experiences no change in monthly water level fluctuation， while Liujiaxia sees a reduction of 14.7% in the lower limit of monthly water levels. ③ In wet years， the wind and solar energy integration leads to a significant decrease in water levels of the cascade reservoirs. In normal years， Longyangxia reservoir experiences a slight decrease in water levels， while water level of Liujiaxia reservoir decreases in pre-flood spring and increases in post-flood autumn. In dry years， wind and solar energy consumption has almost no impact on reservoir water levels. These research findings hold significant practical implications for better understanding the complex relationship between wind and solar energy integration and reservoir operations and for optimizing the operational strategies of hydropower-wind-solar complementary systems.

Accurate groundwater modeling is essential for the scientific management and decision-making of groundwater resources， as it involves hydraulic conductivity， a key hydrogeological parameter. To fully understand and effectively utilize groundwater， we not only need to accurately estimate the spatial distribution of hydraulic conductivity but also need to quantify the uncertainty of the parameter to evaluate its credibility. In this study， parameter inversion and uncertainty analysis of hydraulic conductivity were investigated using the Bayesian Convolutional Neural Network （BCNN）. To test the validity of the method， a synthetic numerical experiment of a two-dimensional steady-state hydraulic tomography pumping test was conducted. The baseline model is a convolutional neural network with an encoder-decoder structure， which builds an inverse mapping that estimates the parameter field directly from the head fields obtained by spatial interpolation. Based on this deterministic model， we trained the Bayesian Convolutional Neural Network. The results show that the BCNN outperforms the deterministic model in accuracy under various training data sizes， with a more significant advantage when the data is scarce. By analyzing the test set samples， we observe that the models exhibit different levels of confidence for their estimates across different regions. A well-trained BCNN can faithfully capture the approximate pattern of the hydraulic conductivity distribution. Moreover， the BCNN also excels in estimating the more challenging multimodal non-Gaussian logarithmic hydraulic conductivity field compared to the generative model， which indicates the wide applicability of the BCNN under diverse geological media conditions. The use of Bayesian Convolutional Neural Networks enables accurate inversion of hydraulic conductivity and evaluating uncertainty， providing a solid basis for subsequent physical processes such as groundwater flow simulation.

The processes of rising water temperature， photosynthesis， and high dam discharge may all cause the problem of supersaturated dissolved gas， which can affect the biodiversity of fish in rivers and other water bodies. Aeration technology has been proven to significantly promote the release of supersaturated TDG， DO， and DN， and is an important method for mitigating the impact of supersaturated water bodies. This article conducted experiments on the release of supersaturated dissolved gas under different aeration rates and water depths using pinhole aeration discs and microporous aeration pipes， exploring the release laws of supersaturated dissolved gas. The experimental results show that the release processes of supersaturated TDG， DO， and DN under the action of microporous aeration conforms to the first-order dynamic equation. All supersaturated DO under experimental conditions can be released to an equilibrium state， while the release rate of supersaturated DN is slow and cannot reach an equilibrium state for a long time， showing k _DO>k _TDG>k _DN； The release coefficients of supersaturated TDG， DO， and DN increase with the increase of aeration volume， but decrease with the increase of aeration depth. The release effect of supersaturated TDG， DO， and DN using microporous aeration pipes is significantly better than that of pinhole aeration discs under the same aeration volume and aeration depth. A binary linear regression model was used to establish the release coefficient relationships of supersaturated TDG， DO， and DN under microporous aeration， which can effectively predict k _TDG with the correlation coefficient of 0.958. This study reveals the release characteristics of supersaturated dissolved gases under microporous aeration， providing certain reference value for aeration technology to mitigate the impact of supersaturated dissolved gases.

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.

Soil salinization and sodification is one of the key factors affecting the sustainable agricultural development in cold arid irrigated districts. Traditionally， the total soil salt contents were used as the indicator to evaluate the evolution trend of salinization and sodification， but little attention is paid to the change of ion composition. For a further study of the distribution and migration patterns of salt ions among various water in agricultural irrigation and drainage systems， this paper analyzes the distribution and change characteristics of salt and ions in different water in irrigation areas systematically based on the observation data of various water during the irrigation and drainage process. Research has shown that the composition of salt ions in waters in the irrigated districts is different obviously/ Irrigation water is dominated by Ca²⁺ and HCO₃ ^–， while groundwater and drainage are mainly Na⁺， Cl^– and SO₄ ^2–. The quality of irrigation water is relatively good， and it is generally HCO₃ ^–－Ca²⁺ type water. Groundwater shows weak alkalinity， and is generally of Cl^–·SO₄ ^2–－Na⁺ and Cl^–·SO₄ ^2–－Na⁺·Mg²⁺ type water. Drainage is mainly influenced by factors such as regional groundwater and irrigation recession， with Cl^–·SO₄ ^2–－Na⁺ and Cl^–·SO₄ ^2–－Na⁺·Mg²⁺ type.

In order to study the internal flow law of centrifugal pump during cavitation process and optimize its cavitation performance， this paper proposes an intelligent optimization method combining neural network and genetic algorithm on the basis of combining traditional optimization methods. Through the Plackett Burman experimental design， three optimization design variables are selected from 7 design parameters of the centrifugal pump， including impeller inlet and outlet diameter， inlet and outlet placement angle， number of blades， and blade wrap angle. The significance of the three optimized design variables’ impact on cavitation performance from large to small is ranked as follows：blade outlet width＞blade wrap angle ＞impeller inlet and outlet diameter. The Latin hypercube sampling method is used to extract 30 groups of design schemes， and the corresponding NPSH values are obtained by numerical simulation. The neural network model is established， and the optimal design variable combination and the optimal NPSH value are obtained by combining the genetic algorithm to optimize within the specified range. By taking the optimized parameters for numerical simulation calculation， the NPSH of the optimized centrifugal pump decreases by 43.1% under the same working conditions， indicating that the anti-cavitation performance of the optimized centrifugal pump was significantly improved.

In response to the current problems in water quality prediction models， such as the complexity of the data itself， noise interference in signal processing， and insufficient decomposition depth， which make it difficult for a single decomposition to fully capture the nonlinear features of the signal， this paper proposes a water quality prediction model based on secondary decomposition. This innovative method firstly uses the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise （CEEMDAN） to decompose the raw data. Then， Variational Mode Decomposition （VMD） is adopted to perform a secondary decomposition of the Intrinsic Mode Function （IMF） with the highest entropy value. Finally， the processed time series are put into the TCN-light GBM multi-feature prediction model. At the same time， the Sparrow Search Algorithm （SSA） is used to optimize the prediction model. By taking the water quality of Yufu River in Shandong Province as an example， the Root Mean Square Error （RMSE） of this model is 0.105 3， the Mean Absolute Error （MAE） is 0.081 5， and the coefficient of determination （R ²） is 0.947 1.The predictive metrics of the model are compared with those from popular contemporary deep learning and neural network algorithms， such as the Gated Recurrent Unit （GRU）， Long Short-Term Memory （LSTM）， Light Gradient Boosting Machine （Light GBM）， and Temporal Convolutional Networks （TCN）， among others. The results show that， in terms of R ²， the model achieved improvements of 53.04%， 70.41%， 66.07%， and 65.20% respectively. In terms of RMSE， the model represented reductions of 62.76%， 65.50%， 64.93%， and 64.80% respectively. And in terms of MAE， the model witnessed decreases of 62.76%， 66.24%， 63.80%， and 65.24% respectively. Therefore， it is evident that the model based on CEEMDAN-VMD-TCN-light GBM exhibits superior predictive performance， which can reduce the fluctuation of water quality sequences more effectively and improve the ability to capture nonlinear features of signals.

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 view of the fact that the multi-stage pump type intermediate guide vane designed according to the pump working condition cannot meet the runner’s requirements for flow circulation when used in hydraulic turbine devices， the influence of key structural parameters of pump type equal diameter positive and negative guide vanes on water head loss， efficiency and working head of hydraulic turbine devices is studied by combining the hydraulic turbine design theory and CFD numerical simulation. The results show that appropriately increasing the diameter of the inlet edge of the reverse guide vane， chamfering the edge of the baffle， and chamfering the inner and outer walls of the inter-stage guide vane inlet can reduce the head loss of the inter-stage guide vane and improve the working efficiency of the hydraulic turbine； the shape and number of guide vanes have a significant impact on their outlet water flow velocity circulation； increasing the wrap angle or increasing the number of blades can enhance the forcing effect of the guide vanes on water flow， increase the outlet water circulation， but increase the head loss of the guide vanes. This paper can provide a reference for the design of the same diameter forward and backward guide vanes used in hydraulic turbines.

To meet the requirements of developing high head and huge capacity hydropower plants， this paper proposes a new Pelton turbine that joints three runners by one vertical shaft to have a rated head of 1 000 m and a single unit capacity close to 800 MW. The design concept of increasing capacity by increasing the number of runners and the structural components of the new turbine-generator unit are explained， the theoretical design parameters of the runner are calculated and presented， the performance characteristics and the flow patterns in runner and casing are predicted and optimized by CFD simulation. The results show that the rated operating efficiency of the turbine can reach 87%， and the operating characteristic curves are smooth for different heads and outputs， the water splashing interference in the casing is an important factor affecting the efficiency of the turbine. By optimizing the layout of the runners and nozzles in the casing to suppress the splashing interference， the efficiency level， torque oscillation， and operation stability of the Pelton turbine can be improved. This preliminary attempt has demonstrated the feasibility of the concept and also found the importance of optimizing the water splashing in the casing， which has reference values for further researches.

Preferential flow during on-farm irrigation management can reduce water and fertilizer use efficiency and exacerbate the risk of groundwater contamination. Based on potassium iodide-starch dye tracing experiment， this paper analyzes the soil water distribution characteristics under surface irrigation DM， micro-sprinkler irrigation WP1 （20 mm/h）， irrigation WP2 （40 mm/h） treatments， verifies the validity of dual-permeability model based on principle of water volume balance， and uses four levels of antecedent water content （ 0.20， 0.25， 0.30， 0.35 cm³/cm³） with five levels of irrigation intensity （12.0， 24.0， 36.0， 48.0， 60.0 mm/h） in a rotating combination design for application analysis. The results show that water infiltrated in the form of uniform matrix flow in WP1 and WP2 treatments as a whole； the soil profile staining area under DM treatment can be clearly divided into substrate flow area （0~6.9 cm） and preferential flow area （>6.9 cm） in the vertical direction. In addition， the matrix flow depth and irrigation uniformity under DM treatment are significantly （P<0.05） smaller than those under WP1 and WP2 treatments， while their the fraction of preferential flow and wetting front curvature are highly significantly larger （P<0.01） than those under WP1 and WP2 treatments， which indicates that surface irrigation can activate more preferential flow paths， increase the degree of preferential flow development and spatial heterogeneity， and reduce irrigation quality. The dual-permeability model based on principle of water volume balance can effectively predict the trends of matrix flow depth and soil profile staining area ratio under different irrigation intensities （R ²≥0.927 6， NSE≥0.884 4， RSR≤0.023 0）， and the simulation results of the rotational combination design of antecedent volumetric water content and irrigation intensity show that increasing irrigation intensity or decreasing antecedent water content will increase the degree of preferential flow and reduce irrigation quality. Therefore， this paper recommend using “high-frequency， low-flow” irrigation mode in irrigation management to reduce the reduction of water and fertilizer use efficiency due to priority flow. The research results can provide a theoretical basis for irrigation decision， and the experimental data can provide important data support for the optimization and validation of the preferential flow model.

The installation of groynes along the riverbanks is a widely adopted practice in stream corridor restoration projects， aiming to create backflow zones （also known as dead-water zones） that can effectively enhance the river geomorphological diversity.The presence of low-velocity circulation pattern in dead-water zones can promote sediment deposition and nutrient accumulation， thus creating a conductive environment for the growth of aquatic plants. Simultaneously， it can also influence material transport and diffusion processes within rivers， which holds immense importance to river ecosystems.The mean residence time relationship for the dead-water zone with emergent vegetation is investigated here by using a combination of dimensional analysis and genetic algorithm. For vegetated dead-water zones， the factors influencing the mean residence time can be classified into three categories： the hydraulic characteristics of the mixing layer， the morphology features of side-cavities， and the drag effect caused by vegetation. Firstly， the parameter 1+C_Dad_c， which represents the obstructive impact of vegetation， is introduced via π theorem with reference to previous work. It should be noted that in the absence of vegetation， i.e.， 1+C_Dad_c =1， the material exchange activities are not affected by the canopy factor 1+C_Dad_c . However， in the presence of vegetation， the equation 1+C_Dad_c >1 suggests an influence on exchange processes. Secondly， other dominant factors， including the mainstream Froude number Fr which reflects the inlet flow intensity， as well as the three-dimensional shape factor （Wd_c ）^0.5/L and the width-to-length ratioW/L，which reflect the morphological features of cavities， are identified through a comprehensive analysis and comparison. Then， the aforementioned four factors are used as independent variables to construct a general predictive model for the mean residence time in the vegetated cavity， i.e.， a product model of power functions incorporating these four factors. Finally， based on 85 groups of data gathered from previous studies， the genetic program Eureqa is employed to train this general model， and subsequently， a mean residence time relationship is developed for vegetated dead-water zones. The evaluation on the coefficient of determination R ² and the mean absolute error MAE demonstrates that the present formula possesses good predictive ability， and the analysis of the value ranges of each factor reveals that this formula exhibits a broad range of applicability. In addition， based on a comparative analysis of the impact of the four factors on the model results， the cavity aspect ratioW/L is considered as a critical parameter that significantly influences water residence characteristics in dead-water zones and should be duly taken into account when relevant engineering designs are conducted.

Based on BP neural network and higher-order moment method， combined with measured data， a time-varying reliability analysis method for the bending resistance of reinforced concrete aqueduct side walls is proposed. In order to evaluate the bending time-varying reliability of aqueduct side walls under the influence of steel corrosion， this paper considers the effective cross-sectional area loss effect of steel bars in concrete structures， and derives the bending time-varying performance function under the limit state of bearing capacity of the aqueduct side wall. Then， combined with the measured data of steel corrosion and the principle of BP neural network， the prediction model of steel corrosion rate is designed， and the calculation formula of effective cross-sectional area of steel bars in concrete structures is established through the hemispherical pitting model. On this basis， the point estimation and high-order moment reliability theory is introduced to develop the time-varying reliability analysis method of aqueduct structure， and finally the proposed method is applied to the bending time-varying reliability analysis of the side wall of an actual aqueduct. The results show that compared with the previous eight practical empirical models， the prediction model of BP neural network built in this paper can predict the corrosion rate of rebar in concrete structures more accurately， comprehensively， easily and quickly. By comparing with Monte Carlo simulation method， the time-varying reliability index of this method is efficient and accurate， which can provide an effective way for the evaluation and prediction of time-varying reliability of aqueducts.

In order to investigate the dynamic stress characteristics of runner and distributor of pump-turbine， this paper establishes the solid domain models of stay vanes， guide vanes and runner， and carries out the FSI-based computation of runner and distributor. The calculation results show that the stress concentration at the “T” junction between the runner blade and crown is related to the vortex development state at the runner inlet； the dynamic and static interference between runner and guide vanes is the main source of pressure pulsation in the vaneless zone， where the main frequency is the blade passing frequency； the dynamic stress of guide vanes and runner is generally high because the pump-turbine is easily involved in the unstable area while working under smaller GVO （guide vanes opening） or low head conditions. The dynamic stress of guide vanes is greater than that of the runner owing to its constraint guidance effect on water flow， and increased flow rate is beneficial to reducing the dynamic stress of the runner. So for the purpose of improving the dynamic stress of runner， the measures could be taken， such as changing the distance between the guide vanes tail and runner inlet， i.e. changing the width of vaneless zone， or adjusting the unit operation area， i.e. avoiding working in low road or small opening conditions for long.

In our present stage， agricultural water right trading is dispersed and the scale is smaller， and the market activity of agricultural water right trading is not in full swing. With the contradiction between supply and demand of water resources becoming increasingly tense， agriculture has necessity to stimulate the decisive role of market in water resources allocation， and further create greater trading space for agricultural water rights. Agricultural water rights involve multi-level management systems， but few studies have analyzed the factors affecting the development of agricultural water rights trading from different dimensions in detail， so it is impossible to systematically promote the development of agricultural water rights trading. Therefore， this paper divides the key factors affecting the development of agricultural water rights trading into three dimensions： macro social economy， middle market players and their mutual relations， and micro trading elements. A qualitative analysis is made of the substantive attributes of each factor index in different dimensions and its impact on the development of agricultural water rights trading， and the macro-support for the development of agricultural water rights trading is found. This paper clarifies the development ideas of agricultural water rights trading market， and then focus on the role of micro-trading elements in the process of water rights trading. From three dimensions， it puts forward suggestions on how to strengthen the agricultural water rights trading policy and promote the construction of rural water system connectivity in multiple ways， clarify the role positioning of government and enterprises， and encourage the synchronous transfer of agricultural water rights trading and land to activate the agricultural water rights trading market so as to improve the agricultural water rights trading market to provide the construction foundation and ideas.

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.

To address the insufficient consideration on water level safety requirements at flood control stations in conventional reservoir flood control operation， this study proposes an optimal flood control operation method for reservoir group coupled with water level calculation at basin flood control stations. First， the station water level characteristics are analyzed through the multi-site water level and flow relationship to identify the key factors affecting the water level. The input features for water level calculation are screened according to the correlation between the influencing factors and the water level. The multi-layer feed-forward back propagation neural network （BP neural network） is introduced to fit the complex non-linear relationship between the input features and the observed water level， to realize the accurate calculation of water level at the station. Then， the safety margin index is proposed to quantify the station water level safety. With the objective of maximizing the overall safety margin of the downstream flood control stations， the optimal flood control operation model for cascade reservoirs， coupled with BP neural network， is constructed. Finally， a hybrid optimization algorithm （DPSA-POA-PSO） is developed to solve the model by combining the advantages of the Dynamic Programming Successive Approximation （DPSA）， Progressive Optimization Algorithm （POA） and Particle Swarm Optimization （PSO）. The results show that the water level calculation accuracy of the BP neural network is significantly improved by considering the station water level characteristics， and the flood level fitting deviation for typical floods is limited within 0.05m. Compared with the DPSA and PSO algorithms， the downstream overall safety margin from the hybrid optimization algorithm is improved by 0.88% and 2.58% in the joint operation of three cascade reservoirs， and is improved by 0.85% and 1.87% in the joint operation of five cascade reservoirs. Meanwhile， the derived operation schemes satisfies all the guaranteed water level requirements， which provides reliable support for improving the basin flood control safety.

The purpose of this paper is to study the effect of the subsurface drainpipe with triangular section and pipeless wall on inhibiting water flow around the cross section in unsaturated soil. In this study， the water drainage tests are carried out by using the subsurface drainpipe with triangular section （symbol T1） in indoor soil tank， as well as the subsurface drainpipe with circular section （symbol CK） done as a control test， both kinds of drainpipes are pipeless wall. The MATLAB system is utilized to simulate the process of soil water flowing around pipe section. The experimental results show that the soil water content at the bottom of the drainpipe T1 treatment is less than that of CK treatment， and the soil salt content at the bottom of the drainpipe T1 treatment is more than that of CK treatment， indicating that the inhibitory effect of T1 treatment on soil water flow around drainpipe cross section is better than that of CK treatment. The beginning time of soil water discharging from the outlet of T1 treatment is 3.89 h earlier than that of CK treatment， and there is no significant difference between the two treatments in drainage and salt discharge（p>0.05）. The simulation results reveal the characteristics of the drainage of this kind of subsurface drainpipe in unsaturated soil， which proves theoretically that the water content under the T1 treatment is lower than that of the CK treatment， and T1 treatment has a better inhibitory effect on the flow detour around drainpipe cross section. In unsaturated soil， the subsurface drainpipe with triangular section and pipeless wall can effectively inhibit soil water flow around the cross section than the circular section subsurface drainpipe， which is conducive to the drainage for this king of subsurface drainpipe in unsaturated soil.

In the multi-energy complementary power generation system， the wind-photovoltaic output is unstable and discontinuous， which makes the hydropower units in the system need to change the working condition frequently， which brings challenges to the economy， safety and stability of hydropower station operation. When the unit vibration avoidance strategy is considered in the load distribution of the hydropower plant， the decision variables of the ordinary particle swarm optimization model will become a complex matrix with high dimensionality， mutual coupling and discontinuity. The convergence result of the particle velocity updating process in the model is greatly reduced due to the reduced suitability of the process. In this paper， a bidirectional updating multi-objective particle swarm model is proposed innovatively. Based on the day-ahead hour-level scheduling mode and vibration avoidance strategy of the unit， two objectives of the unit combined crossing number and the sum of the optimal working conditions of the unit throughout the day are optimized. The results show that compared with the ordinary particle swarm optimization algorithm， the calculation speed of the optimization model is improved by 14.7%， and the convergence accuracy range is improved by 4% to 6% on average， which can provide a new theoretical support for the optimization operation of hydropower station with both economy and safety stability.

The tidal level fluctuations in the estuarine area trigger fluctuations in the water level of the coastal diving layer， exhibiting a non-synchronous fluctuation pattern with the tidal level. This phenomenon has a profound impact on the stability of the bank slope. The varying water levels disrupt the equilibrium and increase the risk of slope instability， posing significant challenges to the structural integrity and long-term stability of the slope. During the ebb tide stage， the groundwater table within the interior of the bank slope tends to be higher than the tidal level. Consequently， this leads to a greater water holding capacity in the saturated area and creates conditions that are more susceptible to inducing bank slope collapse and instability. The higher water levels during this stage increase the potential for instability， posing a significant risk to the structural integrity and stability of the bank slope. In order to address the specific challenges of complex estuaries， this paper presents SUBS， a bank collapse warning model. SUBS is developed by improving the BSTEM （Bank Stability and Toe Erosion Model） and coupling it with SUTRA （Saturated-Unsaturated Transport）， a groundwater model that incorporates unsaturated flow movement. By combining these advancements， SUBS provides a comprehensive and accurate framework for predicting bank collapse events in intricate estuarine environments， contributing to improved bank collapse risk assessment. The research findings show that the fluctuation of groundwater caused by the fluctuation of tidal level in estuarine area has quite a strong hysteretic property. The Factor of Safety of the bank slope and the most dangerous failure surface will change periodically with the tide. And the Factor of Safety will increase during the rising tide， reflecting improved stability. Conversely， during the ebb tide， the Factor of Safety decreases due to the lag in groundwater drainage. Especially during the ebb stage of the spring tide， the water level plummets rapidly， significantly heightening the risk of bank slope collapse. Additionally， the presence of seepage faces on the bank slope further increases the vulnerability to instability. By comparing the stability of homogeneous and composite bank slopes， the results strongly indicate that soil cohesion plays a significant role in determining the stability of the slope. This finding underscores the importance of considering the cohesive properties of the soil when bank slope stability is assessed. The stability of the bank slope is significantly enhanced in the composite structure， where clay is present on the upper part and sand on the lower part. This configuration outperforms the bank slope composed of homogeneous sand with low cohesion. The presence of clay provides increased cohesion， resulting in improved resistance to slope failure and greater overall stability of the composite bank slope. In this context， more attention should be paid to the influence of groundwater level fluctuation. This paper expands the application scope of the traditional BSTEM model by coupling a groundwater model and considering real-time fluctuations in groundwater levels. It introduces a new research method for predicting the slope stability in estuarine areas， thereby enhancing our understanding and analysis of slope behavior in these complex environments.

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.

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.

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.

While China’s economy has progressed exceedingly rapidly， its adverse impact on the environment has been overlooked， thus resulting in numerous issues related to environmental contamination， including water resources pollution. The submersible pusher， due to its diminutive size， facile installation process， and excellent maintenance qualities， is capable of being installed within treatment pools of limited volumetric capacity. By enabling enhanced processing efficiency within each pool， this approach facilitates system-wide efficiency without being subject to the limitations of a singular step’s efficiency. During the procedure of wastewater treatment， the submersible mixer plays a paramount role as one of the essential core components. Its performance and function bear a significant impact on the ultimate quality of the entire sewage treatment process. Hence， the subaqueous propeller has emerged as a crucial apparatus that facilitates the process of amalgamating and propelling fluid within sewage treatment facilities. An integration of experimentation and computational fluid dynamics （CFD） numerical simulation is employed to investigate the various performance indicators， including thrust， power， and thrust-to-power ratio of a submersible thruster operating at a rotating speed of 980 r/min and having a diameter of 400 mm. Additionally， a three-dimensional geometric model is established， followed by the conduction of structured mesh delineation and mesh-independence analysis in order to ensure accurate simulation results. Finally， non-stationary calculations are conducted on the submersible thruster using the aforementioned methodology. Through numerical calculations， it is determined that the submersible mixer equipped with the deflector generated a thrust of 759.33 N， consumed 888.29 W of power， and yielded a thrust to power ratio of 0.85 N/W. Conversely， the submersible mixer without the deflector produced a thrust of 1 003.39 N， utilized 1 144.72 W of power， and resulted in a thrust to power ratio of 0.88 N/W. The present study examines the impact of a deflector on a submersible thruster’s thrust， power， and thrust-to-power ratio. Results indicate that the inclusion of a deflector reduces the aforementioned variables by 24.3%， 22.4%， and 2.4%， respectively， as compared to a submersible thruster lacking a deflector. Through the experiment， it is determined that the submersible mixer equipped with the deflector generated a thrust of 740 N， consumed 903 W of power， and yields a thrust to power ratio of 0.82 N/W. Conversely， the submersible mixer without the deflector produces a thrust of 977 N， utilized 1 164 W of power， and results in a thrust to power ratio of 0.84 N/W. The thrust， power， and thrust-to-power ratio of a submersible thruster with a deflector are reduced by 24.3%， 22.4%， and 2.4%， respectively， for a submersible thruster without a deflector. The discrepancy observed in the comparison of the simulated and experimental measurements of thrust， power， and thrust-to-power ratio falls under 5%， hence confirming the reliability of the experimental results and effectively attesting the precision of numerical simulation. The application of a deflector to the thruster has a positive impact on the thruster's effective propulsive distance. Specifically， when compared to the situation in which a deflector is not applied， the effective propulsive distance increases by 4.8%， 28.4%， and 30.8% at velocities of 0.3， 0.4， and 0.6 m/s， respectively.

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.

In order to explore the influence of jet pipe structure on the flow field of annular jet pump， three-dimensional numerical simulation of annular jet pump under right-angle turn and arc turn was carried out， and the straight section of annular nozzle outlet was calculated and analyzed. The results show that the flow field is unevenly distributed around the nozzle， throat and diffuser in the jet pipe with right-angle turn. The annular nozzle forms a uniform jet in the jet pipe with arc turn， which is conducive to the uniform and symmetrical mixing and energy transfer between the primary flow and the secondary flow， so that the pressure ratio and efficiency are improved under each flow ratio. The performance of the annular jet pump can be improved by setting （0.5~1） times the outlet width of the straight section at annular nozzle outlet， and the efficiency can increase by 1% at the middle and low flow ratio. At the same time， the straight section helps to stabilize the pressure at the nozzle outlet and to reduce the range of the recirculation area near the inlet of the throat and the extent of the pressure drop. The research findings serve as a support for the analysis of the overall flow field of annular jet pump and the design of jet pipe structure.

Through the complex function method， an analytical method for solving the circular hydraulic tunnel with double lining is proposed. The established model is based on the interaction between the surrounding rock and the primary lining， the primary lining and the secondary lining （full contact）， taking internal water pressure and the support delay into account. Based on the preset boundary conditions， the equations for solving the coefficients of the relevant analytic functions can be established， and then the obtained analytical function can be used， the stress components of any point in the surrounding rock， the primary lining and the secondary lining can be solved. By comparing the numerical solution， it is found that the analytical method proposed is correct and effective. At last， the parameters are analyzed from three aspects of controlling the water pressure in the hydraulic tunnel， exchanging the elastic modulus of linings and controlling the thickness of linings， and the factors and results affecting the stress distribution of lining are discussed. The load transfer mechanism and law of the double-lined hydraulic tunnel are revealed， which provides a theoretical basis for the preliminary design and construction of the lining protection project.

The fairness of water use is one of the key factors to be considered in the balanced allocation of water resources. Aiming at the problem that the fairness of water use in the basin is not considered enough in the different industries， an evaluation method based on multi-factor Gini coefficient in different industries is proposed. The Gini coefficient between industry water consumption and industry scale is used to represent industry water fairness. The comprehensive Gini coefficient of water use in the basin is calculated based on the proportion of water consumption in each industry to represent the fairness of water use in the basin. Taking the Yellow River Basin as an example， this paper calculates the Gini coefficient and analyzes the variation of the fairness of water use of different industries in nine provinces of the Yellow River Basin from 1980 to 2020. Take 1995 and 2005 before and after the integrated water regulation of the Yellow River as examples， the impact of integrated water regulation on the fairness of water use in the basin was compared and analyzed. The results show that over the past 40 years， the fairness of water use in domestic， industry， urban public， and agriculture were “highly fair”， “relatively fair”， from “highly fair” to “relatively fair”， and from “relatively fair” to “highly fair”， respectively. The proportion of agricultural water use exceeds 70%， and the Gini coefficient of watershed water use is mainly affected by agricultural water use， the comprehensive Gini coefficient of economic and social water use in the basin is 0.16~0.25 from 1980 to 2020， which is in a downward trend， indicating that the fairness of economic and social water use in the basin has gradually improved， changing from “relatively fairness” to “highly fairness”. The fairness of water use for domestic and agriculture is gradually improved， and the fairness of public water use in industry， especially in urban areas， has decreased significantly. This is mainly because the differences in water use quotas for domestic and agriculture between 9 provinces in the basin have decreased， while the differences in water use quotas for the tertiary industry have increased. The integrated water regulation of the Yellow River has effectively controlled the total water use in the basin， promoted the improvement of agricultural water use efficiency and the reduction of water quota differences between provinces， and improved the fairness of agricultural water use and water use in the entire basin.

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.

Research on the cross-domain flow pattern of agricultural virtual water can reveal the deeper relationship between trade and regional water shortage， which is of great significance for ensuring food security， optimizing water resources allocation， and promoting high-quality regional development. As the largest urban agglomerations in China， the Yangtze River Delta has frequent internal resource flows and close agricultural trade with other domestic regions. But it also faces risks such as water shortage. Taking the Yangtze River Delta as an example， this paper constructs the input-output model of water resources expansion to calculate the agricultural virtual water flow momentum， and combined with the virtual water balance state and water resources pressure state， the influence of the virtual water flow relationship driven by agricultural products trade in domestic urban agglomeration is explored. The results show that： from the state of regional water resources， the pressure state of water resources in the Yangtze River Delta is relatively high， and the water use contradiction is prominent. The state of virtual water balance is highly dependent on the inflow of virtual water from outside the region. From the perspective of time， since the new normal of economy， the Yangtze River Delta has always shown a state of net agricultural virtual water input， with the input of virtual water resources on the whole showing an upward trend， while the self-sufficiency rate of virtual water shows a downward trend and then an upward trend. Before and after the structural reform of agricultural supply side， the flow structure of agricultural virtual water in the Yangtze River Delta has changed， and Jiangsu Province has replaced Anhui Province as the most important source of virtual water in Shanghai. From the spatial dimension， the virtual water flow in the Yangtze River Delta presents a chain structure of “Anhui-Jiangsu-Zhejiang-Shanghai”. The Yangtze River Delta and the rest of the country show a virtual water flow feature of “one-way flow in the north and two-way interaction in the south”. Finally， based on the perspective of virtual water strategy implementation， relevant policy suggestions are put forward from the perspectives of guiding the orderly flow of resource elements within the region， perfecting the value realization mechanism of ecological products and improving the inter-regional trade structure， so as to provide references for adjusting and optimizing the regional agricultural production and trade pattern and promoting the construction of urban agglomeration in harmony between people and water.

In view of the problems of high energy consumption， poor ecological restoration and rational utilization of waste concrete in the practical application of acid mine wastewater treatment methods.Based on the water purification characteristics of pervious concrete， waste concrete， cement and other materials are used to develop water purification reclaimed aggregate pervious concrete （ZSCR）， combined with diatomite and swelling. The performance and practical application prospect of different ZSCR were studied by modifying the clay and red mud. The recycled aggregate and ore were analyzed by XRD， SEM and other testing methods，Effect of material admixture on its water purification performance. The results show that： compared with ordinary pervious concrete， recycled aggregate has less influence on the water purification performance of pervious concrete.The water purification performance of ZSCR was obviously enhanced after the modification of the admixture. The addition of diatomite and other materials improved the pore structure of the specimen and produced a lot in the gel layer.The unhydrated mineral phase gel particles enhanced the adsorption performance of ZSCR to heavy metal pollutants. When the hydraulic retention time is 12 h and the red mud content is 30%， the red mud reclaimed aggregate pervious concrete can effectively intercept heavy metal ions in surface water of mining area， it can be used as reaction medium in water ecological restoration technology such as constructed wetland and biological filter to treat acid mine wastewater.

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 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.

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.

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.

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 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.