After the impoundment of the Three Gorges Reservoir， the braided river reaches downstream of the dam have undergone significant long-term scouring and silting adjustments under the condition of unsaturated sediment-laden flow. These changes have resulted in increased complexity in the diversion ratios of the main branch and tributary channels. It is extremely important to use different methods to assess the direction of scouring and silting adjustments in braided channels based on measured data， which provides support for effective flood control planning and the strategic layout of economic development. This paper takes the Tiebanzhou bifurcation section of the Middle Yangtze River in Wuhan as an example， using a combination of multiple methods including flow area change analysis， measured diversion ratio change analysis and river model experiment to assess the direction of scouring and silting adjustments after the operation of the Three Gorges Reservoir. Results show： ① All three methods yield consistent qualitative judgments regarding the scouring and silting adjustments in Tiebanzhou straight braided channel， specifically， the minor branch of the channel has generally undergone scouring development， with an increase in the flow area proportion and diversion ratio of the minor branch， while the diversion ratio of the main branch has decreased. ② The primary reasons contributing to the scouring development of the minor branch in Tiebanzhou straight braided channel are the sediment unsaturation in the minor branch exceeding that of the main branch and the leveling of the runoff process. ③ All three methods are effective in qualitatively assessing the direction of scour and silt in Tiebanzhou straight braided channel. Additionally， the river model experiment can offer valuable quantitative insights， particularly regarding changes in the diversion ratio at the same flow rate. Since the impoundment of the Three Gorges Reservoir， the diversion ratio in the minor branch has increased by 7.4% to 13.4% under different flow regimes， ranging from flood to low-flow conditions.

Compared with a single reservoir， successive breach disasters have a greater impact and more complex causative factors in cascade reservoirs. However， the numerical simulation of the successive breach process of the core wall dam in cascade reservoirs still faces significant difficulties. This article proposes a numerical simulation method for the cascading reservoir breach process： DLBreach is used to simulate the dam breach flood process， and a one-dimensional high-precision numerical simulation method of natural river hydrodynamics is used to simulate the dam breach flood evolution process. A numerical simulation program for successive breach process in cascade reservoirs is developed based on C# language. In terms of model connection， text interactive data is used to connect the dam breach model and flood routing model. Case studies have shown that the DLBreach model has a relative error of only 1.8% between the simulated flood peak of the Sheyuegou Reservoir dam breach and the measured value， with a peak time difference of only 1.2 minutes， indicating high simulation accuracy. In terms of dam breach flood evolution， the relative error between the method proposed in this paper and HEC-RAS （FVM） simulation of peak flow is only 1%. The process of flood evolution is similar. This indicates that the method is suitable for simulating the flood evolution of natural river channel breaches. The method described in this article has high calculation accuracy and efficiency， achieving rapid and high-precision numerical simulation of the successive breach of the core wall dam in cascade reservoirs. This method creates favorable conditions for rapid forecasting， early warning， and emergency response of sudden flood events and their consequences.

In order to explore the changes of water environment pollutant concentrations in the urban section of Qingjiang River in Changyang County， a water environment simulation study under three hydrological conditions （wet year， normal water year and dry year） was carried out based on the MIKE21 hydrodynamic water quality coupling model， and the single factor pollution index was used to evaluate the NH₃-N and TN indicators， and three pollutant discharge improvement measures were proposed for the non-standard scenarios. The results show that the water quality of the Qingjiang River urban section is characterized by a better pollutant content in wet years than in normal water years， while the water quality in dry years is the worst， and the NH₃-N and TN concentrations exceed the standard， which cannot be reduced by the self-purification capacity of the river section. However， by reducing the concentration of sewage at the outfall， the reduction of TN can reach up to 15%， and the reduction of NH₃-N can reach up to 20%. The results of this study are helpful to better understand the impact mechanism of sewage discharge on the water quality of Qingjiang River in Changyang County， and provide a reference for the prevention and improvement of pollution in the urban section of Qingjiang River.

With the increasing of the size of ship locks， it is difficult to find a reasonable balance between the high efficiency of filling and emptying system， the moored stability conditions of the ship and the project investment in the large-scale lock filling and emptying system. Based on a proposed large-scale ship lock， the effective scale of the lock chamber is 280 m×34 m×4.5 m（length×width×threshold water depth）， the overall physical model of 1∶30 of the hydraulic system of the lock filling and emptying system is established. A series of test studies are carried out focusing on the energy dissipation of the lock chamber， and the ship mooring force of different energy dissipation arrangement， valve opening mode and ship berthing position are measured and analyzed. At the same time， through a comprehensive analysis of the hydraulic and pressure characteristics of the filling and emptying system and the force characteristics of the ship in the lock chamber， an economic and reasonable type of water conveyance system is proposed. The results show that the energy dissipator directly affects the safety and stability of ships moored in the lock chamber. In order to take into account the high efficiency of water transfer， it is necessary to adopt a relatively complex energy dissipation structure of lock chamber for the ship lock with large plane scale. Under the recommended filling and emptying system layout scheme， the ship mooring force in the lock chamber， the hydraulic characteristics of the filling and emptying system and the pressure characteristics of the valve section all meet the specifications and design requirements， and there is a large surplus， which reserves operational space for future speed and efficiency improvement of the ship lock. The research ideas and results can be used as reference for similar projects.

In order to clarify the impact of flowing ice in water medium on flat steel gate， taking a sluice gate of a reservoir as an example， a three-dimensional coupling finite element model of ice-water-gate was established based on the fluid-solid coupling theory to analyze the energy process of ice impingement during the discharge of flat steel gate， and the stress distribution and energy transfer law of gate were obtained. The results showed that driven by kinetic energy， water and drifting ice acted together on the gate， and the gate absorbed a lot of energy during the collision. The highest absorbed energy accounted for 62.15% of the total energy of the system， absorbed by the main beam of the gate closest to the impact position of the ice accounted for 58.51% of the total energy of the gate， The energy distribution is concentrated near the impact area.

To investigate the impact of vegetation on the hydraulic characteristics of water flow in continuous curved rivers， this study uses the Reynolds Stress Model to simulate flow in a continuous bend with clusters of rigid vegetation. The results indicate that due to the centrifugal force and bend morphology， the flow forms a velocity distribution with high-velocity zones near the convex bank and low-velocity zones near the concave bank. The presence of vegetation inhibits the development of upstream high and low-velocity zones， promoting a more uniform velocity distribution. The vegetation on the concave bank expands the range of high and low-velocity zones， while the vegetation on the convex bank causes the positions of downstream high and low-velocity zones to switch， significantly impacting the flow field. Vegetation also affects the turbulent structure by reducing the velocity gradient， weakening overall turbulence intensity， and enhancing flow field stability. The impact of vegetation on turbulent kinetic energy is mainly observed at the top and downstream sections of the bend， leading to a more uniform distribution of turbulent kinetic energy. Additionally， vegetation influences water level changes upstream and downstream， increasing the longitudinal water surface slope and exacerbating lateral distortion， with a particularly significant impact on the convex bank water level.

Based on the monomer hydraulic model of the 1∶15 water diversion tunnel， five post-jump wave dissipation measures were studied to solve the problems of large post-jump waves and insufficient roof margin of long-distance open-flow tunnel in the connection pool of a large water diversion project under the condition of high Froude number flow. The results show that the single-layer pressure plate wave dissipation measure is difficult to adapt to projects with large operating head or flow amplitude； and the water resistance of the vertically flush and evenly arranged wave dissipation measure is obvious， and the head of the jump forward and the water level in the pool are relatively large. The wave dissipation beams measure with layered arrangement and appropriate staggering of each layer is adopted， and the effect in the open-flow tunnel is better. On this basis， the two-stage wave dissipation beams measure proposed reduces the maximum amplitude in the open-flow tunnel by about 66.7%， which meets the requirements of the long-distance open-flow water conveyance tunnel for the roof margin.

Well-type pumping station is a new type of pumping station layout， in which the pumps are arranged along the circumference of the top slab of the outer working wells. Compared with traditional pumping stations， the fluent conditions of the pump are more complex. Based on the SST k-ω turbulence model， numerical simulation was carried out， and combined with physical models， the flow pattern around the inlet of the pump with and without different vortex elimination measures. Furthermore， we selected appropriate vortex elimination measures was analyzed. The results show that under the condition of no vortex elimination measure， periodic top vortices will be generated near the inlet， and the asymmetry of water flow flanked the inlet is an important reason for the flow deviation. The four vortex elimination measures adopted can improve the flow state of varying degrees， among which the measure of setting a horizontal cover plate has the best improvement effect. The flow state near the bell mouth is uniform and the water inlet conditions are good.

To solve the problem that the acoustic signal used to detect the running state of the water supply pipeline is easily disturbed by noise， which leads to the low accuracy of leakage detection and leak location， a noise reduction algorithm for vibration acoustic signal was proposed， which combined variable mode decomposition （VMD） and Hilbert transform. Firstly， the leakage signal was decomposed into several intrinsic mode functions （IMF） by VMD， the number of decomposition layers was determined， and the IMF component was Hilbert transformed to obtain the marginal spectrum， and the noise was preliminarily screened through the characteristics of the marginal spectrum and the cross-correlation coefficient； Secondly， filter and cross-correlation coefficient were used to screen the secondary noise； Finally， the time delay of the denoised signal was estimated， and the leakage point position was calculated according to the positioning principle. To verify the performance of the algorithm， the cross-correlation algorithm， VMD correlation coefficient algorithm and the proposed algorithm were analyzed through experiments. The results show that compared with the other two algorithms， the proposed algorithm can effectively remove the noise in the leakage signal and reduce the positioning error.

To improve the data mining efficiency of dam safety monitoring database， an improved ECLAT association rule algorithm is introduced. The data mining techniques are used to analyze and process a large amount of dam safety monitoring data， and a vertical displacement prediction model for the dam crest is established. Firstly， the main influencing factors of the vertical displacement of the dam crest， including environmental temperature， water temperature in front of the dam， and water level in front of the dam， are selected. Then， the Eclat algorithm is used to mine the preprocessed basic data to screen out strong association rules that can be used for prediction. Finally， the lag of the vertical displacement of the dam crest in response to temperature changes is utilized to establish a dam crest displacement prediction model. The application of this model to a concrete arch dam has shown that the predicted results of the model have a certain degree of reliability.

In Xinzhou Shanxi region， with high mountains and deep valleys， gullies and ravines， the Yellow River diversion aqueduct adopts the form of high pier and large span to adapt to the terrain conditions， and its stability issues cannot be disregarded. Currently， most scholars conducting stability analysis of aqueducts adopt the consolidated boundary conditions at the base of piers， which exaggerates the soil's constraining effect on piles. To address this issue， this paper relies on the bridge-head aqueduct project and simulates the interaction between piles and soil using a three-spring boundary condition. It derives calculation formulas for the critical load of stability in both maximum cantilever state and trench formation state. Finally， numerical simulations are conducted to verify the correctness of the calculation formulas， providing a theoretical basis for disaster prevention and control of the Yellow River water diversion aqueduct.

The inversion analysis of transient-rheological parameters of rockfill dam by using field monitoring data is very important to ensure the safety and stability of the dam. Aiming at the transient-rheological model of rockfill dam， the trained neural network in MATLAB is used to describe the mapping relationship between transient-rheological parameters and deformation， and the JAVA programming genetic algorithm is used to find the optimal transient-rheological parameters， so as to establish the intelligent inversion algorithm combination of transient-rheological parameters. Based on the hybrid programming of JAVA and MATLAB， the inversion of transient-rheological parameters is programmed， which has been applied and tested in a concrete face rockfill dam project of a hydropower station in Northwest China. The results show that the maximum relative error between the calculated settlement and the measured settlement based on the inversion parameters is 4.33 %. The time history curves of the two are in good agreement， and the deformation of the rockfill dam is within a reasonable range and tends to be stable. The research results meet the accuracy and engineering requirements， and can provide some reference for the inversion of transient-rheological parameters of rockfill dams.

To address the difficulty in accurately determining the seepage characteristics of wide-graded gravel soils in earth-rock dams， this paper conducts a micro-scale simulation of the soil skeleton-pore-fine-grained soil structure. A maximum single-particle pore aggregate void criterion is introduced， and a fractal model for soil seepage is proposed to calculate the permeability coefficient of the wide-graded gravel soil in the dam. The model's validity is verified through a comparison with experimental results. By analyzing the influencing factors， the paper studies the effects of porosity， gravel content， and particle irregularity on the permeability coefficient. The results show that porosity is the direct factor affecting the permeability coefficient， while increases in gravel content and particle irregularity influence the permeability coefficient by altering the porosity and uniformity of pore distribution. Based on an engineering case study， the findings demonstrate that the results of the fractal seepage model are aligned with the actual engineering conditions. The paper also provides suggestions for quality control in the construction of wide-graded gravel soil in earth-rock dams based on the research findings.

Laos is one of the important member countries of the “Belt and Road” construction， and the Nangong1 Hydropower Station is a key project of China-Laos clean energy strategic cooperation and development. In order to solve the problems of short construction period， shortage of personnel during the epidemic， the need for construction in high temperature seasons， and the difficulty in controlling the quality of spillway excavation materials used as dam materials for Nangong1 Hydropower Station， the construction process and crack prevention technology of the panel concrete were optimized through measures such as material selection， mix ratio experiments， and optimization of construction technology， ensuring the quality of concrete panels and the safety of dam operation. The main research results are as follows： during the construction process， the dam material effectively solves the problem of quality control in the construction of panel concrete during the high temperature season by controlling the compression of the side wall structure， concrete panels， and concrete pouring process， ensuring that the various performance indicators of the concrete panels of Nangong 1 hydropower station reach or even exceed the design standards and similar types of panels； We conducted relevant tests such as concrete shrinkage and cement hydration heat comparison， combined with the performance of concrete mixtures， concrete mechanics and other related test results， and selected the optimal concrete mix proportion that meets the design requirements to enhance the ability of panel concrete to adapt to deformation and reduce the occurrence of cracks in the panel. After testing， it was found that the panel of the Nangong 1 hydropower station′s rockfill dam is tightly combined with the squeezed side wall， and no cracks were found on the concrete panel. The quality is excellent， providing a guarantee for the stable and safe operation of the dam.

In order to explore the influencing factors of cracking damage of hydraulic asphalt concrete， finite element parameters were obtained through laboratory tests， and the cohesive force model CZM was used to numerically simulate the cracking process of asphalt concrete. A zero-thickness cohesive unit was inserted into the asphalt mortar and asphalt mortar-aggregate bonding surface， and the random distribution of aggregate was realized by program code. The influences of aggregate shape and spatial distribution， specimen size， initial crack length and aggregate content on the crack resistance of asphalt concrete were analyzed， and the whole process from crack germination and crack expansion to complete failure of asphalt concrete was simulated. The results show that cracks initially sprout at the bonding surface of asphalt mortar and aggregate， and then penetrate through the interface of asphalt mortar to complete the cracking. The larger the particle size and quantity of aggregate， the greater the probability and quantity of cracks. The more regular the aggregate shape and the more uniform the distribution， the stronger the material resistance to cracking； The spatial distribution of recipient aggregate with small specimen size is more obvious， and the mechanical properties are more sensitive. The greater the proportion of aggregate content， the more asphalt mortar-aggregate bonding surface， that is， the more weak areas， the weaker the ultimate bearing capacity of asphalt concrete.

As the weak part of seepage prevention of dam foundation， the torus structural joint of foundation gallery of high earth-rock dam on deep overburden is complicated in force and deformation， which is the key technical difficulty in the design of foundation gallery. Firstly， a three-dimensional finite element numerical model of the high rockfill dam on deep overburden was established. Secondly， the effects of different division positions of the circumferential structural joints on the stress and deformation of the anti-seepage system of the dam was compared， and the stress and deformation patterns at the joint location was revealed. Finally， some suggestions for the circumferential structural joints were proposed. The results showed that the different positions of the circumferential structural joints have little effect on the stress and deformation of the dam body and the asphalt concrete core wall as a whole， and have no effect on the maximum deformation of the dam foundation anti-seepage wall. Due to the end support effect， local tensile stresses near on the wall of the seepage wall on both sides of the foundation. When the depth of the foundation trench embedded in the bank slope rock increases， the longitudinal and vertical tensile stresses in the foundation trench at the embedded end increase significantly， while the axial and vertical compressive stresses change insignificantly. The compressive stresses in the three directions gradually decrease. The foundation trench should be embedded in the mountain body on both sides of the dam to a certain depth （usually not less than 2m）， and at least two W-shaped structural copper stopwater should be set in the circumferential structural joint. The elastic cushion layer should be installed between the dam foundation gallery and bedrock in the bank slope rock mass section.

The effects of polyoxymethylene （POM） fiber geometric characteristics and fiber content （28 groups in total） on the mechanical properties and chloride ion resistance of self-compacting concrete （SCC） were analyzed. The electrical flux， current-time curve， chloride ion penetration depth and chloride ion diffusion coefficient were used as evaluation indexes of SCC's chloride ion penetration resistance. The research shows that the POM fiber content should not exceed 1.6 kg/m³ under the condition of keeping the mixture ratio of the reference group unchanged， and too high fiber content will lead to the decline of the overall performance of SCC. When the dosage of 6mm and 12 mm cylindrical POM fiber is about 1.6 kg/m³， the compressive strength and chloride ion permeability are the best， which is 3.6% higher than that of plain SCC at 28 d， and the chloride ion permeability changes from medium to low. The splitting tensile strength of SCC mixed with 12mm flat POM fiber and 6mm cylindrical POM fiber with the dosage of 1.6 kg/m³ is the highest， which is 14.52% higher than that of plain SCC at 28 d. Adding POM fiber can improve the mechanical properties and chloride ion penetration resistance of SCC. There is a good linear relationship between chloride diffusion coefficient and electric flux of SCC， and they are closely related to permeability and durability. The introduction of POM can improve the microstructure of SCC， optimize the internal pores， and improve the mechanical properties and chloride ion penetration resistance on the macro level. The research conclusion can provide references for the engineering application of POM fiber self-compacting concrete.

Excessive nitrogen（N） application to rice will increase field ammonia volatilization losses， aggravating resource waste and environmental risks. In order to investigate the effects of water-nitrogen coupling on ammonia volatilization and water-nitrogen use efficiency in paddy fields at higher N application rates in southern rice cropping areas and to explore suitable water-nitrogen management models for water conservation， emission reduction and fertilizer reduction in paddy fields， the present experiments conducted a field-located observational experiment with different water-nitrogen couplings. The experiment was set up with three water management： shallow wet irrigation W1 （conventional shallow wet irrigation + field leakage of 5mm/d）， controlled irrigation W2 （controlled irrigation + field leakage of 3mm/d）， and controlled irrigation W3 （controlled irrigation + field leakage of 5mm/d）； and two levels of nitrogen application： N1 （300 kg/hm²） and N2 （375 kg/hm²）， with its base fertilizer， the pure N ratio of tiller fertilizer and spike fertilizer being 4∶3∶3， with a total of 6 water-N treatments， to study the effects of different water-N coupling on ammonia volatilization and water-N use efficiency in paddy fields. The results showed that both N application and water management， as well as their interaction， significantly （P < 0.05） affected the ammonia volatilization loss rate in rice season. Under the same water management condition， increasing N fertilization would significantly increase the rate of rice season ammonia volatilization loss （1.54% to 9.83%）， and under the same N application level， controlled irrigation significantly reduced the rate of rice season ammonia volatilization loss （6.73% to 31.86%） compared with shallow wet irrigation. Ammonia volatilization losses ranged from 42.22% to 58.49% in the rice season for all treatments， among which the W1N2 treatment had the highest loss rate of 58.49%. The water use efficiency and nitrogen fertilizer bias productivity in this experiment ranged from 1.36 to 1.78 kg·m^-3 and 23.69 to 34.01 kg·kg^-1， respectively. Controlled irrigation was more effective in improving water and nitrogen use efficiency in paddy fields than shallow wet irrigation， and water use efficiency and nitrogen fertilizer bias productivity were higher in the W3N1 treatment， at 1.72 kg/m³ and 34.01 kg/kg， respectively. In a comprehensive comparison， the W3N1 treatment can effectively reduce ammonia volatilization loss in paddy fields and guarantee high rice yield， and at the same time improve water and nitrogen utilization efficiency， which has a better application value in field management.

In order to explore the improvement effect of sodium carboxymethyl cellulose （CMC） on remolded loess of channel cushion under the action of freeze-thaw cycle， based on determining the optimal dosage， permeability tests and triaxial shear tests were carried out on the CMC-modified and remodeled loess under different freeze-thaw cycles， and the changes of permeability and strength characteristics of the improved and remodeled loess under the action of freeze-thaw were compared and analyzed. The strengthening mechanism of CMC-improved loess was discussed from the microscopic point of view according to the scanning images of electron microscope. The results show that the optimal blending amount of CMC is 0.5%. The freeze-thaw cycle can increase the permeability coefficient of loess， decrease the failure strength， decrease the cohesion and internal friction angle， and the first freeze-thaw action has the most significant effect on the soil sample. The addition of CMC can significantly weaken the influence of freeze-thaw on loess， improve its permeability and strength， and make the permeability coefficient of improved loess significantly lower than that of remolded loess， while the failure strength， cohesion and internal friction angle are greater than that of remolded loess. The incorporation of CMC into loess can enhance the cementation between soil particles， increase the friction strength， stabilize the soil structure， and significantly improve the permeability， shear strength and freeze-thaw resistance of loess.

The three-dimensional reconstruction technology based on stereo vision effectively reduces the cost of image acquisition in non-destructive measurement of plant phenotype， but the computing power consumption is large. It is of great significance to carry out research on optimization of 3D reconstruction strategy to improve the extraction efficiency of plant phenotypic information. In this study， a multi-view imaging system using mobile phones as the means of image acquisition was constructed， and the image data of 30 pepper seedlings were obtained， and the three-dimensional point clouds of pepper seedlings were reconstructed under 2 160 different resolutions and different number of image combinations by combining the motion recovery structure and multi-view stereo （SFM-MVS） algorithm. Through the evaluation of the reconstruction speed， accuracy， stability and accuracy of plant phenotypic parameters （leaf length and leaf width）， the 3D point cloud reconstruction scheme of plants was optimized. The results showed that when the resolution was 480p and the number of images was greater than 45， the reconstruction success rate reached 80%， the average distance error between point clouds was less than 0.05 cm， and the R ² of the extracted phenotypic parameter value and the measured value was more than 0.96. At the same time， the average reconstruction time of a single plant under this scenario was 344 seconds， which was only 10% of the time taken by the reference scenario （resolution of 1 080 p and number of images of 120）. In summary， the resolution and number of images can be set to 480 p and 45， respectively， in the reconstruction of pepper seedlings， so as to optimize the phenotypic measurement efficiency. The results of this study can provide a technical reference for the rapid and non-destructive measurement of phenotypic parameters of pepper seedlings based on three-dimensional reconstruction.

Paddy fields and final ditches are important sources of non-point source pollution in farmland， and the water quality of ditches is a direct factor affecting non-point source pollution in paddy fields. This study selected agricultural land situated in a typical low-hilly rice cultivation zone located in the Jiangning District of Nanjing City， Jiangsu Province. Throughout the 2022-2023 rice cultivation phase， both field surface water and ditch water samples were collected systematically to analyze the changing patterns in ditch water quality over time. The single factor evaluation method and comprehensive water quality identification index method were used to comprehensively analyze the ditch water quality. The findings of the study revealed a reverse pattern in Total Phosphorus （TP） and Chemical Oxygen Demand （COD） levels in ditch water throughout the entire rice cultivation period. Furthermore， the levels of Total Nitrogen （TN） and Ammonia Nitrogen （NH₃-N） in field water exhibited a dual-phase fluctuation pattern， in contrast to the concentrations of TN and NH₃-N in ditch water， which demonstrated varied trends. Notably， during the tillering and jointing growth phases of rice， the levels of various water quality indicators in ditch water were significantly elevated， thus posing a considerable risk of water pollution. Results from the single-factor water quality assessments indicated that， in 2022 and 2023， the proportion of field surface water quality exceeding Class IV water quality standardswas 83.9% and 88.0%， respectively， and the proportion of terminal ditch water quality evaluation exceeding Class IV was 89.7% and 76.9%. With respect to the comprehensive identification indices for surface water， values ranged from 3.410 5 to 5.141 5 in 2022 and from 4.720 4 to 6.242 4 in 2023. For ditch water， the indices ranged from 3.210 5 to 4.730 5 and from 4.110 4 to 5.731 4， predominantly falling within Class III to Class V on the water quality scale. An analytical comparison of the two water quality assessment methods indicated that the single-factor method is more proficient in identifying the primary pollution indices in ditch water across various growth phases and time intervals. Conversely， the comprehensive method is better suited for conducting in-depth evaluations and nuanced segmentation of ditch water quality. This study meticulously addressed the management of water quality of rice fields and their associated drainage ditches. The findings derived from this research provide fundamental information essential for the rational development of efficient rice field drainage systems and provide a scientific basis for the precise prevention and control of rice field non-point source pollution.

In order to investigate the effect of composite microbial bacteria on the improvement of saline soil， through the indoor soil column simulation test， after sampling saline soil in the diversion irrigation area of Ningxia， the composite microbial bacteria consisting of Bacillus sphaericus and Bacillus cereus developed by the group were treated in accordance with five different ratios， and the treated soil was subjected to a soil column test and potting of anemones test， which comparatively analyzed the changes in water stability， water content， nutrients and salinity and the effect on the growth of anemones in the soil before and after treatment. The water stability， water content， nutrients and salinity of the soil before and after treatment were compared and analyzed， as well as the effects on the growth of anemones. Composite microbial bacteria can significantly improve the soil water stability agglomerate content， the highest increase in water stability agglomerate content after treatment compared with the control group by 82%； composite microbial bacteria can improve the water retention performance of the soil， the soil water content after treatment were higher than that of the control group， with a maximum increase of up to 25.32%； composite microbial bacteria can effectively improve the soil water supply and water-holding capacity， compared with the control group， the soil of the treatment groups in the different absorption The water holding capacity of the soil can be improved， and the composite microbial fungus can effectively reduce soil salinity by up to 57%； it can also increase the nutrients of the soil， and the total nitrogen， quick-acting phosphorus， nitrate nitrogen and ammoniacal nitrogen in the soil of each treatment group have increased by 72.32%， 68.64%， 79.27% and 73.49%， respectively； the composite microbial fungus can effectively promote the growth of the crop， and the treated soil can be compared with that of control after planting sunflower， regardless of the stem thickness of the oil sunflower， and the soil can be compared with that of control. Comparing with the control group， both the stem thickness and leaf area of oil sunflower were improved to a certain extent. The application of appropriate amount of compound microbial fungi in salinized soil in the irrigation area of Ningxia Diversion Yellow Irrigation District has significant effect on soil improvement. The research results can provide scientific theoretical basis and technical support for the improvement of salinized soil in Ningxia Huanghuang Irrigation Area.

To better understand the evolution of heatwaves characteristics at global scale， this study introduced a temperature threshold based on the Excess Heat Factor （EHF） index， and analyzed the characteristics of the heatwave occurrence， frequency， duration and average cumulative intensity. The increases in four heatwave characteristics in 20 IPCC regions were compared. In addition， differences in heatwaves based on four global temperature datasets， ERA5， MERRA2， JRA55 and NCEP/NCAR， were evaluated. The results show that during 2002-2021， the number， frequency and duration of extreme heatwave events are larger in Europe， northern and southern Africa， southern North America， eastern South America and eastern Australia， while the higher cumulative intensity are concentrated in the mid-latitude regions. The heatwave trend has increased significantly since the 21st century， among which the growth trend of extreme heatwave days is greater than the cumulative intensity. Western Asia， Southern Europe and the Mediterranean region have not only experienced more frequent heatwaves， but also greater cumulative intensity. The four reanalysis datasets show differences in the number， frequency and duration of heatwaves， but have a high consistency in the average cumulative intensity. These findings are helpful to better understand the evolution of global extreme heatwaves， providing scientific basis for mitigating the adverse effects of extreme events and enhancing regional adaptation to climate change.

Groundwater resources are an important part of water resources. In recent years， the influence of climate change on groundwater has gained increasing significance. This study establishes a numerical model for groundwater based on precipitation， groundwater depth， and borehole data specific to the study area， while considering its hydrogeological characteristics. Future rainfall data from CMIP6 is processed using statistical downscaling methods to obtain projected rainfall data for the study area. Further deviation correction is performed using both linear shrinkage and quantile mapping techniques. The rainfall input model with superior correction effectiveness is selected to predict the response of groundwater levels under different climate scenarios （SSP126， SSP245， SSP585）， thereby providing a scientific basis for sustainable development and utilization of groundwater resources in this region. The findings reveal that there are certain discrepancies in the original downscaled rainfall data from CMIP6； however， employing a linear reduction method yields good agreement with measured data within the research area. Compared to the average annual rainfall observed in this region， all three models project an increase： 7.7% under SSP126 model， 1.2% under SSP245 model， and 6.9% under SSP585 model. Utilizing the established MODFLOW modeling techniques enables us to predict future groundwater levels across various climate scenarios （SSP126， SSP245， SSP585）， revealing similar trends for changes in groundwater levels within each scenario. From a spatial point of view， higher predicted groundwater levels are observed in northeastern regions while lower levels prevail in southwestern areas throughout all three climate models considered here. From a temporal point of view （from 2022 to 2075）， significant upward trends are evident for changes in groundwater level within northwestern and northeastern regions； conversely downward trends occur within southeastern regions along with slight increases noted for southern areas as well as localized substantial increases found within western regions.

The tidal river section of the lower reaches of the Yangtze River is jointly affected by the upstream water and the ocean tide， which made the flood prevention situation of the river section complex and severe. Therefore， identifying the encounter risk of runoff and tide of the lower reaches of the Yangtze River is of practical significance for regional flood prevention. This study takes the downstream section of the Yangtze River as the study area， and uses the maximum flow from Datong hydrological station and the highest tidal level from Nanjing， Zhenjiang and Jiangyin Tide station as the data basis to explore the probability distribution of flood and tide encounter along the lower reaches of the Yangtze River. We construct the joint distribution of the largest traffic of the Datong Hydrological Station with the largest annual flow of Nanjing Tide Station， Zhenjiang Tide Station， and Jiangyin Tide Station through the COPULA function. Comparing the fitness of Gumbel Copula， Clayton Copula and Frank Copula， we finally chose Clayton Copula to establish the joint distribution of flood and tide combination in the lower reaches of the Yangtze River. The co-occurrence risk rate， conditional risk rate， and combined risk rate of each site are analyzed to further explore the laws of various risks. By comparing the risks of the upstream and downstream floods， it is found that the emergence of the highest tide level of each tide station is affected by the largest flow of the annual flow of Datong Station. The greater the annual maximum flow of Datong station， the greater the possibility of exceeding a certain high tide level at each downstream tidal station. Moreover， it is found that the closer the station is to the estuary， the less it is affected by the maximum flow of the upstream Datong station， that is， the less it is affected by the upstream flood， so the probability of encountering extreme flood and tide combination events is lower. The results show that the risk and protection of extreme flood and tide combination events should be considered in flood control in the lower reaches of the Yangtze River. Different stations are subject to different flood and tide risks， and different regions should formulate corresponding risk analysis and prevention measures for different risks.

In recent years， urban flooding events have occurred frequently， causing significant losses to the lives and property of urban residents. Traditional monitoring methods are limited by high installation and maintenance costs of equipment， as well as low labor efficiency. Additionally， traditional convolutional neural networks are unable to distinguish between video images from surveillance facilities with different resolutions， making it difficult to comprehensively and efficiently respond to flooding disasters. Therefore， this study innovatively proposes an urban flooding monitoring method based on HRNetV2. This method fully exploits the advantages of the HRNet model， which has demonstrated superior performance in applications such as object detection， image classification， and human pose estimation. It can share convolutional weights while operating in parallel on multiple convolutional branches with different resolutions， reducing the number of model parameters and computations， and improving model training efficiency. In this study， a dataset composed of urban flooding images collected by monitoring equipment and social sources was used for training. Two key evaluation indicators， accuracy and complexity， were adopted to comprehensively compare the training results of HRNetV2 with four mainstream models： Unet， PSPNet， ResUnet， and DeeplabV3+. The experimental results demonstrate that HRNetV2 exhibits exceptional performance in floodwater image recognition. Its Intersection over Union （IOU）， accuracy， recall rate， and F1 score reached 92.19%， 96.90%， 95.76%， and 95.83% respectively， significantly outperforming the other four comparison models. Meanwhile， HRNetV2 also performs excellently in terms of complexity， with a significant reduction in computational complexity compared to other models， making it more suitable for practical monitoring scenarios. This research not only provides a novel technical means for urban flooding monitoring， enabling more accurate and efficient monitoring of urban flooding situations， but also offers valuable references for urban planning， disaster management， and other related fields.

Urban form refers to the spatial structure that describes the composition， environment， and various activities of a city， including the geometric shape of urban land， various functions within the city， and the spatial pattern of buildings. To explore the impact of different building patterns on rainfall and flood processes in cities， 12 regions were selected in Zhengzhou city based on different building patterns， and urban waterlogging models were constructed for 12 different urban building patterns. Based on the designed rainfall data， waterlogging processes were simulated for four different recurrence periods （10、20、50 and 100 years）. By analyzing the changes in the inflow rate of drainage outlets and the characteristic values of waterlogging under different building patterns and impermeable area percentages of rainfall scenarios， the influence of urban building patterns on the process of rainfall and flooding was explored. The results indicate that： ①The peak flow rate of emission outlets shows certain differences in the distribution of building patterns in different cities， with significant differences in rectangular and circular patterns， and relatively small differences in fan-shaped patterns. ②As the impermeability rate increases， the flow rate of the drainage outlet during the water withdrawal stage also increases； Under the same impermeability rate， there are differences in the rain and flood processes of different urban building patterns， which are more pronounced in the circular pattern. ③In the numerical simulation scenario of this study， the distribution of different urban building patterns has a certain impact on the runoff characteristic values， mainly manifested as a relatively small impact of different urban building pattern distributions on the runoff coefficient， and a more significant impact on the peak runoff and peak appearance time. The research results reveal the relationship between spatial layout and rain and flood management in urban architectural design， and systematically discuss the impact of different architectural patterns on rainfall runoff， providing scientific references for the optimization of urban architectural patterns and the study of the formation mechanism of rainwater processes.

In this study， a water cycle simulation model based on system dynamics was established in Baifuhe River basin of Guizhou Province. After calibration and verification， the model can quantitatively describe the relationship of water volume conversion （δ _max=3.35%， R² =0.74， RMSE = 0.006， MAB = 0.0056， NSE = 0.67）. The model can be well applied to： ① Water balance analysis and verification， such as watershed water balance test， vegetation water absorption transpiration system water balance calculation， soil water cycle simulation， surface water flow analysis. ② Rapid calculation of regional water volume data， model input of rainfall data and ET ₀ data， which can facilitate the quick calculation of economic and social water consumption， soil underwater infiltration， vegetation water absorption， surface evaporation and vegetation transpiration. The total water consumption in Baifuhe River basin is 133.44 million m3， the ground evaporation is 441.98 million m3， the vegetation transpiration is 1 127.33 million m3， and the surface water runoff is 692.82 million m3. ③ In-depth analysis of water use proportion and influencing factors in each link. For example，the results of the regional evapotranspiration of reference crops show the maximum ET ₀， while the actual evapotranspiration ETa is smallest. During the rapid vegetation growth period， the potential evaporation ETp may be greater than ET ₀； the actual evapotranspiration of Baifuhe River basin in 2020 is 71.84%， indicating that the total land evapotranspiration is returned to the atmosphere through vegetation transpiration， and vegetation transpiration plays a leading role in the total evapotranspiration. In addition， the results of the analysis and discussion of the influencing factors of evapotranspiration showed that vegetation transpiration， water absorption from the second soil layer by vegetation， and minimum temperature were the most important factors affecting steapotranspiration. The correlation coefficient were 0.929， 9.916 and 0.824， respectively， all of which were significant at the 0.01 level. The model established in this study can provide a reference for the calculation and analysis of the regional water cycle.

Based on the precipitation， runoff and sediment transport data of three typical hydrological stations （Lanzhou， Longmen and Lijin） in the upper， middle and lower reaches of the Yellow River Basin from 2002 to 2022， the characteristics of water-sediment change and its driving factors were analyzed by the Mann-Kendall trend test， Pettitt mutation test， water-sediment relationship curve and double accumulation curve， and the contribution rates of climate change and human activities to the changes of runoff and sediment discharge were calculated. The results show that the runoff of Lanzhou （flood season and non-flood season） and Lijin （non-flood season） has a significant increasing trend and the change rates are 483， 247 and 337 million m³/a， respectively； the sediment transport of Longmen has a significant decreasing trend and the change rate is -1.280 1 million t/a in the non-flood season. The abrupt change points of precipitation， runoff and sediment transport at each hydrological station are different to some extent. For example， the abrupt change points of sediment transport at Lanzhou， Longmen and Lijin during the flood season are 2008， 2009 and 2018， respectively. The water-sediment relationship fitting of Lanzhou （non-flood season） and Lijin （flood season and non-flood season） is relatively good， Longmen （flood season） and Lijin （non-flood season） have the largest sediment transport capacity under the action of runoff erosion， and Lanzhou （non-flood season） and Lijin （flood season） have the strongest erosion capacity. In the non-flood season， the contribution rates of human activities to Longmen （runoff） and Lijin （sediment transport） are relatively large， at 94.69% and 94.50%， respectively， and the contribution rates of precipitation to Lanzhou and Longmen are relatively large， at 99.54% and 99.03%， respectively. The research results can provide a scientific basis for the rational control of water and sediment and the high-quality sustainable development of ecological environment in the upper， middle and lower reaches of the Yellow River basin.

Heilongjiang Province is the main distribution area of high-latitude permafrost in China. Under the trend of climate warming， the degradation of permafrost is serious， and the hydrological， ecological and environmental problems caused by it have become the focus of attention of related scientific research. Based on the air temperature and surface temperature data from 34 meteorological stations in Heilongjiang Province from 1971 to 2019， the temporal and spatial variations of mean annual air temperature， mean annual surface temperature， freeze-thaw index， the characteristics of permafrost distribution and its influencing factors were investigated by using the freeze-thaw index and surface freezing number models， combined with the trend fitting and the localized thin-disk smooth spline function interpolation method. The results show that the range of multi-year mean air and surface temperature changes in Heilongjiang Province is -8.64~5.60 ℃ and -6.52~7.58 ℃， respectively， with a banded spatial distribution with latitude and altitude， and the interannual warming rates of mean annual air and surface temperatures tend to be consistent with each other， which are 0.34 and 0.33 °C/10 a， respectively. From 1971 to 2019， the air freezing index and surface freezing index decreased at the rate of -5.07¹ and -5.04 ℃·d/a， respectively， and the air thawing index and surface thawing index increased at the rate of 7.63 and 11.89 ℃·d/a. The spatial distribution of the air/surface freeze-thaw index all showed latitudinal trends， but in the northern mountainous areas the effect of elevation was greater than latitude. Permafrost is mainly distributed in the Greater and Lesser Khingan Mountains in the north， and sporadically distributed in the central mountainous areas. The southern boundary of permafrost shifted northward by about 2° from 1970 to 2010s， and the total area of permafrost shrunk from 11.1×10⁴ km² in the 1970s to 6.53×10⁴ km² in the 2010s， and the distribution of permafrost is most highly correlated with the air temperature， the surface temperature and air freezing index， and its spatial distribution is strongly correlated with latitude and altitude. The results of the study are of great significance for analyzing the trend of high-latitude multi-year permafrost degradation in Heilongjiang Province and the entire Northeast China， and can also provide references for the development of natural cold resources， ecological protection and engineering construction in permafrost areas.

Pointed to the hydraulic safety issues of the switching operation of parallel water supply pipelines， combined with engineering characteristics， a simplified idea is proposed that the water pump section is approximately a flow source， and the high-level water tank is regarded as a finite volume head end water tank. Corresponding boundary conditions are established， and the characteristic line algorithm is used to calculate and analyze the hydraulic transition process. Research shows that the switching of working conditions in parallel water supply pipelines is closely related to the flow rate， and relying solely on controlling the opening and closing speed of butterfly valves is difficult to achieve good water hammer protection effect. It is recommended to switch the working conditions under low flow rates： when switching from double-pipe operation to single-pipe operation， the pump station needs to be reduced to 2 units； with single pipe operation switching， the pump station needs to be adjusted to 1 variable frequency operation， and the flow rate should be controlled at 10 m³/s；when switching from single-pipe operation to double-pipe operation， it should be ensured that the pump station initially operates below 2 units.

Aiming at the disadvantages of complex construction process， high cost and long construction period of water-filled pressure-maintaining volute， a new embedding technology of ultra-thin cushion （1 mm class） volute is proposed in this paper. Combined with the specific conditions of a pumped storage power station， an axismetrical model of the inlet section of volute is established， and the force transmission characteristics of thin cushion volute and water-filled volute are systematically compared. The feasibility of substituting water-filled volute is studied. The results show that when thin cushion volute is used in pumped storage power station， the radial deformation of steel volute can be very close to that of water-filled volute， and the stress distribution law， load ratio and reinforcement amount of outer concrete are basically the same， which can also reduce the water pressure transfer in the volute and reduce the stress and reinforcement of outer concrete. In order to make the thin cushion scheme better replace the water-filling and pressure retaining scheme， it is suggested that the thickness of the thin cushion layer should be gradually reduced with the diameter of the volute section （1.0~0.5 mm）， and the cushion covering angle should be as large as possible in the meridian section of the volute.

The Baihetan Hydropower Station is China's second largest hydropower facility. The left bank features complex geological conditions and extensive underground caverns， which have exhibited seepage in the powerhouse area after reservoir impoundment. This seepage significantly influences the deformation and stability of the surrounding rock. This study investigates the stability of the surrounding rock of the underground caverns on the left bank during the reservoir filling process， employing a combination of onsite monitoring data and numerical simulations to analyze the mechanism of how rising reservoir water levels affect the deformation of the surrounding rock. Monitoring data were used to analyze characteristics of the seepage field， such as the underground water free surface， seepage pressure， and leakage quantity， thereby revealing patterns in the deformation and stress trends of the powerhouse surrounding rock. Based on the theory of steady-state seepage， the Finite Element Method was used to simulate the left bank seepage field at reservoir levels of 640、775 and 816 m. Furthermore， the Finite Difference numerical simulation software FLAC3D was utilized to study the impact of groundwater seepage on the deformation of the surrounding rock. The comparison between numerical simulations and monitoring results shows a consistent deformation pattern. The findings indicate that during the reservoir impoundment， the deformation of the surrounding rock of the Baihetan left bank powerhouse is positively correlated with the reservoir water level， with rock deformation increasing as the water level rises. The maximum displacement of the upstream rock bench reached 8.27 mm. The rise in reservoir water level led to changes in the seepage field within the powerhouse area， particularly in regions with developed geological structures. These changes in the seepage field during the impoundment period are the primary cause of deformation in the underground powerhouse surrounding rock. Overall， the stability of the surrounding rock of the left bank underground powerhouse during the impoundment period is satisfactory. Stability can be further enhanced by either extending the length of the C₂ seepage-cutoff tunnel or increasing the drain-hole in the exposed area of fault zone C₂ to mitigate the impact of C₂ seepage on the stability of the surrounding rock.

As China continues to promote the green and low-carbon transformation of energy， grid peak shaving plays a crucial role in supporting the large-scale and high-proportion development of new energy sources. At present， the medium- and long-term scheduling objective of cascade hydropower stations is gradually shifting from maximizing power generation towards peak shaving， aiming to alleviate issues such as unstable residual loads and frequent start-ups of thermal power units. However， the competitive and synergistic relationship between power generation and peak shaving objectives in medium- and long-term scheduling is not yet clear. To address this， this study compares a peak shaving model with the objective of minimizing mean square error of residual load and a power generation model with the objective of maximizing power generation. An empirical study is conducted at the Gutianxi Cascade Hydropower Station in Fujian Province. The results indicate that： ① There is a competitive relationship between peak shaving and the maximum power generation objectives. The peak shaving model shows more advantages as it can improve the stability of the mean square error of residual load while minimizing the loss of power generation compared to the power generation model； ② The relationship between inflow and the mean square error as well as power generation is inversely proportional. The larger the inflow， the steeper the slope， indicating a more significant advantage for the peak shaving model. This research provides a reference for selecting objective functions for medium- and long-term scheduling models of cascade hydropower stations， thereby further enhancing their peak shaving capabilities.