After the operation of Lianghekou， Wudongde， and Baihetan Reservoirs in the upper Yangtze River， the inflow discharge and sediment of Three Gorges Reservoir （TGR） has significant changed. As a result， the current operation scheme of TGR can no longer meet the new demands. Based on rainfall data from the upper Yangtze River basin （1961-2022） and flow data from the Yichang Hydrological Station （1882-2022）， the flood season is divided by using several mathematical statistical methods. Furthermore， the temporal evolution patterns of Meiyu in the middle and lower reaches of the Yangtze River and the Autumn Rain in west China is analyzed， the TGR observed and restored inflow peak discharges and flood volumes are compared， and the necessity and feasibility of dynamically adjusting seasonal division and operational water levels are also discussed. The main flood season of the TGR is determined to be from June 21 to September 10 based on statistical analysis of rainfall and flow data series. The Meiyu is mainly occurred in late June and July， while the Autumn Rain begins in late August. Most reservoirs in the upper Yangtze River enter the refill period and TGR inflow peak discharges are reduced significantly. In summary， it is suggested to divide the TGR flood season into four periods： i.e.， drawdown period （May 1-June 20）， Meiyu flood period （June 21-July 31）， transition period （Aug. 1-Sept. 10）， and Autumn Rain refill period （Sept. 11-Oct. 31）. In practical operation scheduling， the phased transition points can be determined based on the forecasted dates of Meiyu onset and retreat. Following the Meiyu retreat， the flood control capacity reserved by the TGR may be gradually released， allowing a controlled rise in operational water levels. During the Autumn Rain period in West China， opportunities should be seized to initiate early impoundment. Dynamic control of operational water levels is implemented based on 1~5 day flood forecasting processes， balancing flood-drought mitigation and efficient water resource utilization. This integrated approach significantly enhances the comprehensive benefits of the Three Gorges Reservoir.

Revealing the intrinsic relationships between driving factors and water quality evolution within a river basin can support environmental authorities in implementing targeted water pollution control measures. However， existing studies predominantly conduct spatial analyses based on Euclidean distances from monitoring stations and often focus on either anthropogenic activities or climate change in isolation， lacking a comprehensive assessment of their combined effects. To address this gap， this study integrates multiple datasets from the Yangtze River Basin， including GDP distribution， population density， land use patterns， precipitation， temperature， flow discharge， and water quality monitoring data. Four distinct study zones were delineated based on flow accumulation length， Euclidean distance， county-level administrative boundaries， and city-level administrative boundaries. A comparative analysis was performed to examine how different spatial scales influence the correlations between various driving factors and water quality trends at key monitoring stations along the Yangtze mainstem， thereby identifying critical influencing zones. The results demonstrate that for permanganate index （COD_Mn）， ammonia nitrogen （NH₃-N）， and total phosphorus （TP）， the area within a flow accumulation length of 200 km constitutes the key influencing zone for Yangtze water quality. Moreover， three principal components were identified as the dominant drivers across all monitoring stations， collectively explaining an average of 86.7% of the total variance. Specifically， the first principal component includes GDP， population， per capita GDP， cropland area， and residential land area. The second principal component consists of precipitation， grassland area， water body area， and forestland area. The third principal component includes temperature and cross-sectional flow.

To mitigate the subjectivity of rust annotation and enhance annotation efficiency， this paper proposes a rust detection method based on a YOLOv8 cascaded architecture to rapidly implement deep learning-based corrosion detection for hydraulic engineering metal structures. To enhance accurate detection of rust target， the MobileViTv3 module is integrated into YOLOv8n， resulting in a modified model named YOLOv8-vit. Based on YOLOv8-vit， we further propose YOLOv8-vit-cls for rust grade learning and classification. This network leverages the pretrained parameters of YOLOv8-vit to efficiently learn features of different rust grades. Finally， a cascaded architecture combining YOLOv8-vit and YOLOv8-vit-cls is constructed to perform both rust detection and grade classification of hydraulic metal structures.

The Pinglu Canal construction involves extensive cutoff engineering， which creates semi-enclosed river segments with reduced flow velocity， thereby limiting hydrodynamic connectivity and adversely affecting wetland habitats and biodiversity. To optimize water exchange efficiency， this study employs three-dimensional numerical simulations to analyze the rectification scheme of gravel spur dikes in a representative cutoff section of the Pinglu Canal. Key parameters including water exchange time and spatial distribution of low-velocity zones are investigated to evaluate how channel narrowing rates and weir spacing affect water exchange efficiency. Further optimization is achieved through perforation strategies at dike roots and heads. Results demonstrate that under operating parameters of 175m dike spacing and 15% narrowing rate，the straightened section exhibits the shortest water exchange time and the smallest proportion of low-velocity zones at typical cross-sections. Water exchange time is reduced by 29.7% to 35.6% compared to pre-remediation conditions， with low-velocity zones in characteristic cross-sections decreasing to 11.3%、8.9% and 19.5%. Additionally， incorporating openings in the dike bodies further improved flow velocity distribution characteristics between dikes， with perforations at dike roots exhibiting superior performance in flow redistribution compared to head modifications. This research provides a scientifically validated approach for hydrodynamic optimization and ecological restoration in navigational channel engineering， offering practical solutions to mitigate environmental impacts of river regulation projects.

The establishment of a multi-field coupled model has become an important means of predicting the evolution of concrete properties， and the values of the parameters in the model have a great influence on the calculation results. Aiming at the problem of insufficient simulation accuracy due to the difficulty in determining parameters in the finite element simulation of early-age concrete， this paper proposes a multi-field coupled simulation method of concrete chemistry-heat-humidity （CTH） that integrates physical experiments and BP neural network parameter inversion. Firstly， an optimized chemical affinity function and a modified evaporable water equation are introduced to achieve an accurate simulation of the multi-stage evolution of relative humidity. subsequently， a parameter inversion method based on BP neural network is used to invert and optimize the key parameters of the CTH multi-field coupled model by combining physical experimental data， to construct a high-precision numerical model， which is then applied to the simulation calculations of concrete chunk casting. The training results of the BP neural network model of this method have good stability， and the predicted value of the humidity decline period fits the experimental data by more than 90%. The simulation results show that the constructed CTH multi-field coupling model can accurately simulate the spatial and temporal evolution of the temperature and humidity fields inside the concrete. This research result provides theoretical and methodological support for the parameter calibration and engineering prediction of multi-field coupled model for early-age concrete.

Drought-flood abrupt alternation， a compound extreme climate phenomenon， has caused serious negative impacts on the ecological environment， agriculture production， and social economy. In order to deeply understand the regional characteristics and overall evolutionary patterns of drought-flood abrupt alternation events in summer in China， this study uses observational data and employs two indices， the Long-cycle Drought-Flood Abrupt Alternation Index （LDFAI） and the Short-cycle Drought-Flood Abrupt Alternation Index （SDFAI）， to identify the drought-flood abrupt alternation events in summer across the eight sub-regions in China. It further reveals the spatial and temporal distribution， trends and future persistence of the frequency and intensity of these events， and finally focuses on the characteristics of the short-cycle drought-flood events with different alternation timings and their influencing factors. The results show that： ① Drought-flood abrupt alternation events are primarily concentrated in eastern China， particularly in South China （SC）， Southwest China （SW）， Northeast China （NE）， and Eastern Northwest China （ENW）. The frequency of both long-cycle and short-cycle flood-to-drought events shows a significant increasing trend. Additionally， the future trends in the frequency and intensity of these events across all the sub-regions are consistent with those observed over the past 58 years. ② The short-cycle drought-flood abrupt alternation events with alternation timing between May and June generally exhibit higher intensity and show the characteristics of gradual enhancement. ③ The short-cycle drought-flood abrupt alternation events with different alternation timings primarily concentrate in the mid-latitude regions （20°N~40°N）. In particular， the alternation timing of drought-flood abrupt alternation events corresponded well to the advance of summer rain belt in eastern China. Meanwhile， the occurrence frequency of severe flood-to-drought events with different alternation timings remains relatively stable and consistently high. ④ Comparing to the earlier period （1961-1990）， influenced by the earlier onset of the South China Sea summer monsoon， the drought-to-flood abrupt alternation events with alternation timing between May and June （June and July） increased （decreased） in eastern China during the later period （1991-2018）. Similarly， flood-to-drought events with alternation timing between June and July （May and June， July and August） increased （decreased）.

In order to reveal the co-evolution mechanism of water-energy-food-ecology （WEFE） system security and economic resilience in the Beijing-Tianjin-Hebei urban agglomeration， this study used the panel data of 13 prefecture-level cities in the Beijing-Tianjin-Hebei region from 2007 to 2022 to construct a three-dimensional evaluation framework of pressure-state-response， and systematically analyzed the characteristics and influencing factors of regional coupling spatial network from 2007 to 2022 by comprehensively using the coupling coordination degree model， modified gravity model， social network analysis and secondary assignment procedure. By quantifying the nonlinear correlation between resource constraints and economic resilience， this paper aims to break the limitations of traditional single-factor research and propose a differentiated networked governance path， so as to provide theoretical support and decision-making basis for urban agglomerations to break through the path dependence of "resource consumption for growth" and realize sustainable development of ecological priority. The results show that from 2007 to 2022， the average coupling coordination degree of the WEFE system security and economic resilience in Beijing-Tianjin-Hebei increased from 0.38 to 0.48， but regional differences expanded significantly， and the spatial pattern evolved from a “core-periphery” fragmented structure to a “multipolar network” form. While the number and density of network associations are increasing， the correlation and stability still need to be optimized： Beijing and Tianjin form technology capital spillover through the “siphon-radiation” effect， and intermediary cities such as Shijiazhuang and Baoding play the role of “structural holes” to promote peripheral integration； Geographical proximity significantly strengthens network association， while population quality， government efficiency， technological innovation， openness level and climate risk differences have inhibiting effects on network formation. Based on this， this study proposes to promote the multi-directional circulation of elements by constructing a dynamic monitoring and three-level governance structure， implementing a core node feedback mechanism and reward fund to promote network collaboration， and establishing a cross-domain collaboration， talent sharing and climate adaptation mechanism， so as to realize the differentiated networked governance of the coupling of WEFE system security and economic resilience in Beijing-Tianjin-Hebei.

Reservoirs are critical infrastructure for watershed water resource management. The water storage and release processes of reservoirs directly influence the efficient utilization of water resources. Accurately monitoring changes in reservoir storage is of great significance for understanding operations of reservoirs and their impact on watershed water resources. Synthetic Aperture Radar （SAR） satellites and optical remote sensing satellites provide an effective means for accurately monitoring reservoir storage， due to wide coverage and high accuracy. However， the extraction of water bodies from SAR images is affected by the incidence angle effect. The reservoir storage results vary and the accuracy is reduced due to differences in water body extraction. Thus， this study focuses on the Maoergai and Qiaoqi Reservoirs in the Minjiang River Basin. A regression-based correction model was developed using Sentinel-2 optical imagery to reduce the impact of incidence angle effects on water surface area extraction from Sentinel-1 data. Then， an area-storage model was applied to fit reservoir storage based on area extraction results， using in-situ storage measurements. Finally， a consistency evaluation of the retrieval outcomes was performed. The results indicate that the combination of Sentinel-1 and Sentinel-2 data enhances observation frequency， improving the continuity of inundation area and storage observations， achieving continuous weekly monitoring. Orbital-specific correction reduces inter-orbital discrepancies， and improves the fitting accuracy of the area–storage capacity model. The fitted model accurately represents the relationship between water surface area and reservoir storage. Both reservoirs in the study area have a storage capacity exceeding 100 million cubic meters， consistent with the operational characteristics of multi-year regulation reservoirs. Both reservoirs released water earlier than usual in response to emerging drought conditions in the Yangtze River Basin during the 2022 flood season. This method provides reliable technical support for intelligent management based on remote sensing of reservoirs as well as the monitoring of unregulated reservoirs.

The conventional reservoir operation diagram， constrained by static regulation frameworks and linear assumptions， demonstrates limited capacity in characterizing dynamic coupling mechanisms and nonlinear constraints within cascade reservoir systems. To address this， based on the theory of system dynamics， this study built a simulation model for early flood-season storage scheduling in mega reservoirs. Taking six cascade reservoirs （Ludila， Guanyinyan， Wudongde， Baihetan， Xiluodu， and Xiangjiaba） in the middle and lower reaches of the Jinsha River as the case study， the dynamic coupling path among water level， reservoir capacity and flow rate was analyzed through system dynamics feedback loops and stock-flow architecture. The study coupled optimization scheduling techniques using LOOKUP functions and IF-THEN-ELSE conditional statements， which characterized nonlinear relationships including water-level-reservoir capacity curves and hydropower unit output constraints， achieving multi-objective dynamic simulation of coordinated reservoir impoundment operations. The Research results indicated that the system dynamics model could accurately depict the dynamic and nonlinear characteristics of the impoundment operations， and its simulation results were highly consistent with those of optimal operation schemes. Under various hydrological scenarios （wet， normal， dry， and extremely dry years）， the Nash-Sutcliffe Efficiency （NSE） values for the reservoir operation water levels exceed 0.99， and the NSE values for the reservoir discharge processes surpass 0.97. The mean absolute error （MAE） values for reservoir operation water levels have not exceeded 0.11 m， while the root mean square error （RMSE） values have not surpassed 0.28 m. For reservoir discharge simulations， the MAE values are below 54 m3/s， and the RMSE values are less than 171 m3/s. Compared with the conventional operation scheme， the system dynamics simulation scheme can increase the multi-year average hydropower output by 2.495 billion kWh/a （an improvement rate of 3.21%）， reduce the spilled water volume by 1.435 billion m3/a （an improvement rate of 15.61%）， and decrease the average computation time for the joint operation of mega reservoirs from 6 hours to 5 seconds. The results not only thoroughly demonstrate the accuracy and reliability of the simulation model， but also provide scientific and technical support for the joint operation of mega reservoirs.

Soil salinization is one of the key factors affecting the sustainable development of agriculture in the Hetao Irrigation District. Accurate prediction of soil salinization and sodification trend is an important means to formulate scientific prevention and control measures. Traditional studies usually use the total amount of soil salinity in the root zone as an indicator to evaluate the evolution trend of salinization， while rarely paying attention to changes in ion composition. Due to the different physical and chemical behaviors and migration capacities of different salt ions， soil salts not only changes in total amount， but also change in composition of salt ions under the influence of external forces such as irrigation leaching， evaporation， freezing and thawing. To conduct in-depth research on the distribution and transport patterns of salt ions in different land use types， this paper selects a typical area in the Yichang Irrigation Area of Inner Mongolia's Hetao Irrigation District as the research area. From 2017 to 2019， observations were conducted on the distribution processes of various ions， analyzing the dynamic processes of water， salt， and ions， as well as the characteristics of ion differentiation.The soil moisture content increases with depth due to water infiltration and water-holding capacity， while variability showes an inverse trend， decreasing with soil depth. The electrical conductivity （EC） profile of abandoned cultivated land decreases with depth， with surface accumulation being the main feature of overall salt distribution. The distribution of salt ions in soils of different land types is primarily characterized by highly differentiated Na⁺， Cl^-， and SO₄ ^2- ions. The HCO₃ ^- content is also significant but is relatively uniformly distributed in the soil profile. The contents of Ca²⁺ and Mg²⁺ are noticeably lower， especially in wasteland where both their composition and proportion are minimal. The mobility differentiation of various salt ions is evident. The migration degree and rate of cations are in the order of Na⁺ > Mg²⁺ > Ca²⁺， which correlates with ion migration rates through soil layers. Among anions， Cl^- shows the strongest differentiation， while HCO^3- exhibits weaker differentiation.

The Jinsha River serves as the main stem of the upper Yangtze River， contributing approximately 50% to the total runoff discharge and 60% to the total sediment load in the upper Yangtze River Basin. Its extensive tributary network and complex sediment sources render its hydrological dynamics highly complex. In recent years， the operation of key cascade reservoirs has significantly altered flow and sediment transport characteristics， necessitating an in-depth analysis of these changes. In this study， hydrological data （1977-2020） from the Xiangjiaba（Pingshan） Hydrological Station in the lower reaches of the Jinsha River were used to investigate sediment transport dynamics during flood events before and after the impoundment of the Xiangjiaba Reservoir and Xiluodu Reservoir. Flood events were extracted from the time series data， and analytical methods， including Mann?Kendall （M?K） analysis， sediment rating curve analysis， and hysteresis pattern analysis methods， were systematically applied. The key findings indicated that a 99% reduction in sediment load occurred during the postimpoundment period， which was primarily attributable to reservoir sediment trapping. The discharge?sediment concentration relationship exhibited fundamental regime shifts. The original robust power-law relationship between water discharge and sediment load was disrupted after reservoir operation. Under moderate and high discharge levels （10 000~13 000 m3/s）， the sediment transport capacity was no longer governed primarily by hydrodynamic forces but was instead constrained by sediment supply limitations. However， this flow range remained the dominant sediment transport range. The sediment rating curves significantly flattened （the coefficient decreased by 87%）， reflecting reservoir-induced flood peak attenuation and changes in the discharge?sediment relationship. Asynchrony analysis of flood events revealed that under natural conditions， sediment source depletion during flood events led to insufficient subsequent supply， causing sand peaks to exhibit predominantly leading asynchrony. After reservoir operation， a notable change in asynchrony characteristics between flood and concentration peaks occurred， with the sediment peak lag pattern becoming dominant， driven by a substantial weakening of hydrodynamic conditions due to elevated reservoir water levels. This study elucidated the mechanistic shifts in water?sediment transport in the lower Jinsha River， thereby providing theoretical foundations for the formulation of reservoir sediment management strategies.

Branching channels are common in nature. After the construction of the upstream reservoir hub， the downstream clear water scouring causes the riverbed armoring of the branching channel to become normal. Therefore， it is of great significance to study the laws related to the riverbed armoring of the branching channel under the action of clear water. Through the flume test， it is found that in the dynamic process of the damage and formation of the armoring layer in the branching river bed caused by clear water scouring， the bed-load transport rate presents a fluctuating change of first increasing and then decreasing. And with the increase of flow， the peak value of the transport rate increases， the occurrence time is advanced， and the formation time of the armoring layer is shortened. The armoring degree of the main branch is higher than that of the branch， and the increase of discharge intensifies the damage of armoring layer， resulting in the overall increase of sediment diameter and the reduction of particle size distribution. In addition， the erosion and deposition of riverbed topography are significant. The main branch erodes violently and the branch deposits， and there is a dynamic balance between the flow and the riverbed topography.

Aiming at the freezing and thawing damage observed in dispersive soil canal slopes with high groundwater levels in seasonal frozen regions， we systematically investigated the frost-heave and thawing deformation characteristics of dispersive soils under varying initial conditions of temperature， moisture， and stress. The results indicated that： ① During the freezing process， as the temperature decreased， the freezing front of the dispersive soil advanced downward， and moisture within the soil migrated toward the freezing front， leading to ice formation. Ice layers and lenses were primarily distributed within the 1/2 to 2/3 depth range of the maximum frozen depth. ② The pore water pressure within the soil exhibited distinct periodic fluctuations in response to temperature changes， accompanied by a significant hysteresis effect. ③ Under identical conditions， as the dry density increased， the frost heave rate increased， the thaw settlement rate decreased， and the cumulative freeze-thaw deformation was reduced. ④ External water supply significantly influenced the frost heave process. Under conditions with external water supply， the frost heave rate of dispersive soil was 3 to 4 times higher than that without external water supply. ⑤ After three freeze-thaw cycles， greater overburden pressure resulted in a lower frost heave rate and a higher thaw settlement rate， indicating that overburden pressure effectively suppressed frost heave deformation. Based on the research findings， it is recommended that the anti-frost design of dispersive soil channel slopes in seasonal frozen regions should prioritize the impact of external water supply. Comprehensive measures， including thermal insulation， soil replacement， drainage， dry density control， and optimization of protective structure thickness， should be adopted to enhance frost resistance.

The uneven distribution of hydrological monitoring networks has resulted in a lack of long-term available streamflow monitoring data in most watersheds worldwide. However， traditional hydrological models and single machine learning models have poor simulation accuracy and generalization capability when simulating runoff in data-scarce watersheds. This study proposes a SWAT-LSTM-Transformer （SLT） coupled modeling framework that integrates physical mechanisms with data-driven approaches， implementing cross-basin knowledge transfer through transfer learning and innovatively introducing a rainfall-based peak flow identification correction method to enhance daily runoff simulation performance in data-scarce watersheds. Using the Hanjiang River Basin （a data-rich basin） as the source domain， a multi-feature input set was constructed， which includes seven hydrological variables simulated by SWAT （actual evapotranspiration， infiltration， surface runoff， etc.） and five meteorological factors （rainfall， temperature， etc.）. The SLT model demonstrated excellent simulation performance in both training and testing periods， with Nash-Sutcliffe efficiency （NSE） coefficients reaching 0.96 and 0.95， respectively. To address the streamflow data scarcity in the target domain of the Wusha River Basin（a data-scarce basin）， a cross-basin transfer learning strategy was designed： based on hydrological similarity analysis， the parameters of the pre-trained SLT model from the Hanjiang River Basin were transferred to the Wusha River Basin's SLT model， incorporating rainfall-based peak flow identification correction for runoff simulation at the Wanli station. Results show that the SLT model performed well in streamflow simulation at the Wanli station， achieving NSE values of 0.86 and 0.73 for the training and testing periods， respectively. Soil infiltration， rainfall， surface runoff， and soil moisture content significantly influenced the SLT model’s simulation performance. The established SWAT-LSTM-Transformer coupled model provides a viable approach for runoff simulation in data-scarce watersheds.

The tidal level in tidal river sections is influenced by multiple factors， including river hydrodynamics， astronomical tides， and meteorological conditions， with complex physical mechanisms that make precise forecasting challenging. This study develops a tidal level forecasting model on integration of mechanism-based and data-driven approaches. The Non-Stationary Harmonic Analysis Model （NS_TIDE） analyzes the seasonal and periodic characteristics of tidal level changes， accounting for the underlying mechanisms. This model provides a baseline for tidal level forecasting， ensuring the rationality of the predicted tidal level trends. The data-driven model， DRSN-LSTM， is constructed using Deep Residual Shrinkage Networks （DRSN） and Long Short-Term Memory Networks （LSTM）. It captures the impacts of multiple influencing factors on tidal levels and generates amplitude values for tidal changes. An Adaptive Genetic Algorithm （AGA） is employed to couple and optimize the forecasting results of the NS_TIDE and DRSN-LSTM models. The proposed model was applied to the entrance of the Qinhuai New River in the Yangtze River basin. By comparing the forecasting performance of NS_TIDE， DRSN-LSTM， and the coupled model under different forecast periods， the results demonstrate that the coupled model not only adheres to the physical laws governing tidal level changes but also simulates the effects of multiple influencing factors on tidal amplitude. For a 24-hour forecast period， the Root Mean Square Error （RMSE） for hourly forecasts in non-flood and flood seasons were 0.15 m and 0.18 m， respectively. During typhoon events， the average accuracy rate for forecasts with errors within ±0.30 m exceeded 80%. The coupled model exhibits high accuracy and practicality， ensuring the scientific validity and precision of hydraulic engineering operations in tidal rivers.

To achieve efficient resource utilization of construction waste residue （CWR） and address the issue of effluent pH reduction during the nitrogen removal process in a pyrite-enhanced bioretention system， a bioretention system was constructed using a composite medium composed of CWR and pyrite. This study investigated the impacts of varying dosing of CWR and different compositing approaches for the mixture medium on pollutant removal efficiency by bioretention system. Moreover， an optimal strategy for composite media was determined by analyzing microbial community composition and evaluating by-products control effects. The results demonstrated that the addition of 40% （V/V） CWR into the traditional medium resulted in an enhancement of 8.70% and 9.69% in the removal rates of NH₄ ⁺-N and TP， respectively. Nevertheless， due to alkaline leaching stress， there was a decrease of 5.27% in COD removal rate and emergence of NO₂ ^--N accumulation phenomenon. The integration of media significantly mitigated the alkaline stress effect caused by CWR， leveraged the strong adsorption capacity of CWR for nitrogen and phosphorus， and enhanced denitrification through the use of pyrite as an electron donor for autotrophic denitrification. Consequently， this strategy not only increased the α-diversity of the microbial community but also elevated the relative abundance of nitrifying genera （e.g.， Nitrospira） and denitrifying genera （e.g.， Denitratisoma and Bacilli）， while simultaneously inhibiting the growth of Thiobacillus and Thauera. As a result， the system's pollution removal efficiency was significantly improved， effectively addressing the issue of NO₂ ^--N accumulation in the effluent and achieving better control over effluent pH、TFe and SO₄ ^2- byproducts. Particularly， incorporating 40% （V/V） CWR in the planting layer along with 20% （V/V） in the submerged layer of bioretention system achieved superior decontamination performance with respective removal rates for COD、TP、NH₄ ⁺-N、NO₃ ^--N and TN being 84.49%、96.94%、91.83%、87.11% and 82.13% respectively. Additionally， all concentration levels for by-products remained below permissible limits.

Aerodynamic resistance represents the mass transport capacity of atmospheric turbulence in water-heat exchange， and its accuracy is important for modelling and estimation of land surface water-heat exchange. However， due to the absence of data of atmospheric stability， the existing studies usually estimate aerodynamic resistance based on the neutral stratification hypothesis， which would result in considerable uncertainties. Therefore， based on data at 187 global stations and the Monin-Obukhov similarity theory， Penman-Monteith equation， Thom model and nonlinear regression methods， this study constructed an aerodynamic resistance estimation model， which considers the effects of atmospheric stability and vegetation characteristics， and investigated the ecohydrological implications of the aerodynamic resistance estimation model based on comparing the estimated potential evapotranspiration using different aerodynamic resistance estimations. Results showed that： ① the mean equivalent aerodynamic resistance at the 187 flux stations was 44.6±24.6 s/m， while those estimated using the traditional method was 125.1±22.7 s/m， which considerably overestimated aerodynamic resistance； ② the land surface factors including canopy height（h_c ）， Leaf Area Index（LAI）， Normalized Difference Vegetation Index（NDVI） and Enhanced Vegetation Index（EVI） could express most of the variabilities in the aerodynamic resistance coefficient （R ²=0.81）， based on which the estimated mean aerodynamic resistance at the 187 stations was 57.8±51.9 s/m， which is significantly improved compared with the traditional method； ③ the potential evapotranspiration （PET） based on traditional aerodynamic resistance methods considerably underestimated PET （y=0.55 x）， while those based on the aerodynamic resistance coefficient model were very close to the truth （y=1.15 x）， especially in land surfaces with high canopy heights， such as deciduous broad-leaved forests， evergreen broad-leaved forests， and mixed forests，where the traditional method overestimated PET dramatically. These findings would be valuable for evaluating the interactions among land surface and atmosphere and for estimating water-heat exchange.

The Sixth Coupled Model Comparison Program （CMIP6） data is often employed to evaluate potential global-scale changes in climate variables. However， it is less efficacious in projecting changes at the regional level. The Ili River Basin in Xinjiang Uygur Autonomous Region of China （IRBC）， characterized by significant elevation variation and complex terrain， gives rise to considerable discrepancies in data analyses based on limited number of meteorological stations. Consequently， reliable meteorological data are essential for climatic and hydrological research. This study develops CMIP6 data into a new multi-model ensemble dataset by four approaches： reliability ensemble average （REA）， convolutional neural network （CNN）， random forest （RF）， and Bayesian model average （BMA）. Additionally， we employed performance indicators such as the Taylor Diagram， Taylor Skill Score （TSS）， and Kling-Gupta Efficiency （KGE） to identify the method with the best simulation effect on precipitation and temperature in the study area. The results demonstrate that the BMA dataset exhibits the most effective simulation of precipitation patterns across a range of extreme precipitation indices. In calibration period（1961-1999）， the annual total precipitation when daily wet day amount 95th percentile （R95PTOT） is the highest. In the validation period（2000-2014）， BMA's rank sum ratio （RSR） is 1.1， ranking first， indicating that its comprehensive simulation effect is the best. The KGE results of annual maximum consecutive 1-day （Rx1day） and 5 day precipitation （Rx5day）， and R95PTOT are 0.032， 0.39 and 0.52， respectively， which are all higher than the values obtained from other datasets. In the average temperature simulation， the RF dataset performed the best. The standardization deviation （SD）， the center root mean square error （CRMSE）， the correlation coefficient （r） and TSS in the calibration period are 1.005， 0.088， 0.996 and 0.49， respectively. These values represent the most favorable outcomes compared to other datasets. Similarly， the RF also outperformed others during the validation period， with a RSR value of 1.18. The findings of this study assess the efficacy of various approaches in simulating meteorological data within the study area. This can provide a usable method for the analysis of meteorological data in future scenarios and provide a scientific foundation for the management of meteorological disasters and water resources in the IRBC.

Combined supporting structures consisting of steel set and shotcrete are widely used in underground tunnels when the geological conditions are poor. However， there exist many difficulties in conducting nonlinear finite element analyses for the steel set due to its small size and dense arrangement. Therefore， according to the mechanical properties of the steel set， a four-node isoparametric element model of the steel set structure was proposed， and its mechanical action was simulated by stiffness superposition. Based on the Mises yield criterion and the secondary plastic flow model， an elastoplastic constitutive model was established to simulate the yielding and hardening behavior of steel set. The elastic damage constitutive model was used to simulate the damage softening behavior of concrete， and finally， a nonlinear numerical simulation method for the combined supporting structure of steel set and concrete was formed， which is verified to be reasonable by a planar circular tunnel example. This method was used to investigate the force characteristics of the combined supporting structure， and the results show that： when the surrounding rock pressure is small， the concrete is in an elastic state so it has a high bearing capacity and is the main bearing structure； when the surrounding rock pressure is large， the concrete undergoes compression damage， and the excess stress is transferred to the steel set， resulting in a significant increase in the stress of the steel set， and the steel set evolves into the main bearing structure； reducing the spacing between steel sets can to some extent reduce the steel set’s stress， slow down the development of concrete damage， and enhance the supporting effect of the combined supporting structure.

Global climate change has led to significant changes in hydrological cycle processes， resulting in an increased risk of hydrological droughts. Therefore， the study of hydrological drought changes under changing environments is of great significance for early warning of flood and drought and water resources management.Typical basins in north and south China （Xiangjiang river basin and Weihe river basin） are selected as the study areas.The period from 1982 to 2015 is selected as the base period （the historical period） and the period from 2030 to 2060 is selected as the future period. Five Global Climate Models （GCMs） provided by CMIP6 under the three scenarios of SSP126， SSP245 and SSP585 are selected to output the climate data for the future period.The Extreme Gradient Boost （XGBoost） is utilized to downscale the precipitation and temperature from GCMs to drive hydrological models to obtain streamflow in the future period， and then compare and analyze the evolution of hydrological drought characteristics in Xiangjiang river basin and Weihe river basin in different periods.The results indicate that， after downscaling by XGboost， the RMSE of simulated precipitation of Xiangjiang river basin and Weihe river basin are reduced by 57.6% and 51%， respectively， and the correlation coefficient with the measured values are improved by 20% and 32%， respectively. The RMSE of simulated temperature are reduced by 50.9% and 51%， and the correlation coefficients with the measured values are improved by 4.3% and 6.25%， respectively.The increase in precipitation in Xiangjiang river basin in the future period will increase the streamflow in this basin， thus alleviating hydrological drought， and the severity， duration， intensity and peak intensity of hydrological drought are reduced by 6.3%， 4.8%， 10.6%， and 6.5%， on average， compared with those in the historical period.In contrast to Xiangjiang basin， the increase in temperature and potential evapotranspiration decreases the streamflow in Weihe river basin.Therefore， Weihe river basin will face a greater risk of drought in the future period. Among the selected scenarios， the drought is the most severe under the SSP585 scenario. Compared with the historical period， the severity and duration of drought will be increased by 72.7% and 30.8%.

In deep buried water diversion tunnels， there are limited measures for preventing and controlling rock burst risks of TBM construction. Once an extremely strong rock burst occurs， the TBM machinery will be buried. Therefore， it is of great significance to study rock burst risk prevention and control measures suitable for TBM excavation. This paper proposes a method of using drilling and blasting pilot tunnels for stress release in the construction of deep buried water diversion tunnels. The stress adjustment process induced by drilling and blasting pilot tunnel excavation and full section excavation methods （single drilling and blasting or TBM method） was compared. The evolution law of strain energy near the TBM excavation face induced by pilot tunnel excavation was analyzed. The results show that the excavation of pilot tunnel reduces the degree of strain energy accumulation near the TBM excavation face， and the peak accumulation position of strain energy is far away from the tunnel surface， which will make the TBM excavation face in the stress release area and reduce the risk of rock burst. Finally， the strain energy release effect of drilling and blasting pilot tunnel excavation is verified based on case study.

The high energy efficiency of hydraulic machinery has always been the direction pursued by many scholars. Centrifugal pump is a kind of widely used hydraulic machinery， and its efficiency is generally between 70% and 80%. The method of optimizing centrifugal pump and improving its efficiency is worth discussing. In this paper， a vertical single-stage single-suction volute centrifugal pump is used to calculate and analyze the simulated fluid. Based on RNG turbulence model， the fluid simulation calculation of centrifugal pump under seven different flow inlet conditions of 0.5Q_d ~1.3Q_d was carried out， and the hydraulic performance of centrifugal pump under large and small flow conditions was obtained. The main performance was low efficiency and high head under low flow conditions. The opposite was true for large large flow conditions， with high efficiency and low head. After that， the impeller of centrifugal pump was optimized by Bezier spline curve， which mainly shows the change of bending degree of edge profile of blade inlet. Five schemes including the initial model were established. The simulation numerical calculation of different schemes was carried out under rated working conditions， and the changes of efficiency and head with the bending of blade inlet edge profile were analyzed. The difference of blade pressure， velocity vector and outlet pipe flow pattern under different schemes was compared. Finally， the optimal scheme was obtained， with the efficiency slightly increased to 91.2% and the head became closer to the design head.

Steel fiber reinforced concrete has been widely used in engineering practice due to its superior mechanical properties. However， unlike other fibers， steel fibers are susceptible to corrosion in corrosive environments. This paper systematically reviews the research progress and key findings on the corrosion of steel fiber concrete at home and abroad， including the corrosion mechanism， as well as the effects of corrosion on the mechanical and durability properties of concrete. Previous studies have shown that the corrosion resistance of steel fibers is influenced by several main factors， such as the water-cement ratio， fiber type， concrete cracks， and the erosion environment. Besides， steel fibers corrode only within approximately 5 mm of the surface layer in uncracked concrete. The strength of the steel fibers gradually decreases as corrosion advances， while the corrosion products play dominant roles in the filling and compression of pores at different stages. These processes affect the bonding performance between the steel fibers and the cement matrix， thereby altering the mechanical properties of the concrete. Consequently， the mechanical properties of the concrete are closely related to the corrosion degree of steel fibers. Most existing studies have not considered the impact of the corrosion degree on the strength of steel fiber concrete， and the quantitative relationship between the corrosion degree of steel fibers and the degradation of concrete mechanical property has not been established. Finally， this paper discusses the challenges in steel fiber corrosion research and suggests future research trend.

Developing a realistic and feasible water allocation solution is the key to resolving water competition conflicts of the trans-administrative rivers under water scarcity. The demand ratio method has been widely used in water management practice due to its simple calculation principle， transparent water distribution ratio， and easily operational solution. However， this method only considers regional water demand as the sole influencing factor for water allocation， without paying attention to the influence of other characteristic factors， and may result in a certain degree of one-sidedness in the allocation results. In response to the limitations of the demand ratio allocation method in resolving water allocation conflicts of the trans-administrative rivers， this study proposed a water allocation index system considering principles such as water contribution， social equity， respect for current situation， water use efficiency， and ecological environment sustainability. And an asymmetric demand proportion model for inter-administrative river water allocation was proposed by combining the information entropy-CRITIC method and bankruptcy game theory. Subsequently， taking the Hanjiang River Basin of Hubei Province as the practical case， it conducted study on trans-administrative river water allocation under two supply and demand scenarios using the basic data including distributable water volume， water demand， average annual runoff， water user population size， current water consumption， GDP， ecological environment flow， and sewage discharge as model inputs. The results showed that compared with the demand ratio allocation method， because the proposed model comprehensively considered the differences in water contribution， water use population， water demand， water use efficiency， and ecological environment among agents， the water allocation satisfactions of Shiyan and Xiangyang cities with higher water demand and larger weight coefficients both increased by 2.39% in dry year， while that of Suizhou and Qianjiang cities with lower water demand and smaller weight coefficients decreased by 47.25% and 33.54%， respectively； In the extremely dry year， the water allocation satisfaction obtained by Shiyan and Xiangyang cities raised by 32.09% and 23.10% respectively， whereas Suizhou and Qianjiang cities decreased by 46.71% and 40.94% respectively. The proposed model can highlight the differences in various influencing factors of the agents in water allocation， and ensure that the principle of individual rationality is not undermined. It has high application value in solving water allocation conflicts of the trans-administrative rivers.

Accurate water quantity estimation is the foundation for the rational development and utilization of water resources in a watershed. It is mainly based on the main stream runoff data and uses the fitting line method for hydrological frequency analysis. To ensure the accuracy and rationality of the calculation of the design value of available water supply， it is generally necessary to consider different distribution curves and fitting line rules. At the same time， to consider the differences in water demand in different regions， the regional composition of available water supply cannot be ignored. This article establishes a watershed available water supply calculation model based on genetic algorithm and Copula function. The model selects three different distribution lines， namely Gamma， P-III， and log normal， with two parameters. Based on the minimum sum of squares of relative deviations criterion and the minimum root mean square error criterion， the genetic algorithm is used to optimize and solve the optimal distribution line of water supply for each tributary in the watershed. Based on this， a joint distribution function of available water supply for downstream design sections of the watershed is constructed using GH Copula function， which can reflect the regional composition of water supply while calculating available water supply. The model is applied to the Liuxi River Basin， to obtain the optimal distribution lines of each tributary under different scenarios， and to calculate the range of available water supply for the downstream control section of the Liuxi River Basin under different assurance rates. In the optimization and fitting results of water volume in various tributaries of the watershed， the optimization and fitting based on the minimum sum of squared deviations criterion has a good fitting effect on the low water points of the sample， while the optimization and fitting based on the minimum root mean square error criterion has a good fitting effect on the overall sample data. Based on this result， using GH Copula function to construct a joint distribution function for the available water supply of the watershed design section to solve the available water supply of the watershed can better reflect its regional composition and has higher accuracy than traditional available water supply estimation methods.

The Simulation of daily water and nitrogen output processes during the snowmelt runoff generation period in seasonal freeze-thaw zones remains challenging due to influences from processes such as snowmelt and soil freeze-thaw. In this study， we took the Heidingzi River basin in Changchun City， Jilin Province， a typical seasonal freeze-thaw zone， as an example. Calibration and validation of the Soil and Water Assessment Tool （SWAT） model were conducted using daily monitoring data of water and nitrogen at the basin outlet during the freeze-thaw period from 2014 to 2016. The applicability of the SWAT model in simulating daily runoff and daily nitrogen loads during the thawing period was explored. The results indicated that within the SWAT model， the parameters CN₂， CNFROZ， SNOCOVMX （for daily runoff） and CN₂， SDNCO， CNFROZ （for daily nitrate nitrogen output） were the three most influential parameters. The SWAT model performed well in simulating daily runoff， with Nash-Sutcliffe Efficiency （NSE）， coefficient of determination （R2） and relative error （Re） values of 0.75、0.78 and -12.76% during the calibration period， and 0.54、0.51 and 5.65% during the validation period， respectively. The primary reasons for the decline in accuracy were that the SWAT model did not consider the lag effect of snowpack on runoff generation and the snowmelt-refreezing process. Additionally， parameters adjusted for accurate simulation of the snowmelt runoff process during the soil thawing period often led to overestimation of runoff and underestimation of baseflow during non-freeze-thaw periods. Due to biases in runoff simulation and inadequate representation of the impact of freeze-thaw processes on nitrogen transformation within the model， the SWAT model exhibited relatively low accuracy in simulating daily nitrate nitrogen loads， with NSE， R2 and Re values of -0.19、0.44 and 2.7% during the calibration period， and 0.60、0.26 and -13.79% during the validation period， respectively. This study validated the applicability of the SWAT model in seasonal freeze-thaw zones and revealed its limitations， providing a scientific basis for model optimization and application.

In this paper， the study collected and calculated the water level difference between upstream and downstream of the annual peak of more than 40 typical ship locks in China， and obtained the uncertainty parameters and coefficients of variation of hydrostatic pressure. Based on the statistical parameters of resistance under the current code， the modified-JC method was used to calibrate and calculate the reliability index for different components of all levels of the mitre gate， and a method for determining the five partial factors in the ultimate limit state design formula was proposed. The research methodology and theoretical framework can be used as a reference for the research on the structural reliability of similar hydraulic steel gates， provide methodological guidance for the revision of specifications， and help to promote the updating and improvement of specifications.

Precipitation is one of the most important driving factors in hydrological processes， and its data source and accuracy are key factors affecting the accuracy of flood forecasting. Affected by many factors such as the imperfect water and rain condition monitoring system and the small range of the basin， the accuracy of the measurement of precipitation data in the small and medium -sized basin is high， but the distribution is uneven， which will affect the simulation results of hydrological models. In order to improve the accuracy of flood forecasting in the watershed， this study combines the measurement data with satellite product precipitation data by constructing a CNN-LSTM neural network model， and combines the HEC-HMS model to carry out the flood simulation Taking the catchment area above the Jinpen Reservoir in the Heihe River Basin in Shaanxi as an example， the application effect and applicability of satellite-ground fusion precipitation in the flood simulation are discussed. The results show that ① The HEC-HMS model with the site precipitation data as the input has good applicability in the research area， and can achieve Class B accuracy in both the rate period and verification period. ② The correlation coefficients between the two types of IMERG satellite products and measured precipitation are low， which are generally higher than the actual value， and the error is large. After CNN-LSTM data fusion， it is close to the measured precipitation data， and the fusion effect of the IMERG-Early product is better. ③ The HEC-HMS model after fusion of satellite products has a simulation pass rate of 80% for the 10 floods， with an average definitive coefficient of 0.856 9， and the average absolute value of the absolute value of the flood peak is 0.8h， reaching Class A accuracy. ④ The certainty coefficient of the flood simulation results of satellite-ground fusion precipitation increases， and the absolute value of the average flood peak time difference is reduced； the simulation effect of the flood peak flow decreases and is significantly smaller. The results show that integrating the actual measurement precipitation data and appropriate satellite precipitation product data in small and medium -sized basin can improve the accuracy of flood forecast models to a certain extent.

In natural river channels， aquatic vegetation typically grows in the areas near the riverbanks， which in turn affects the stability of the riverbank and the discharge capacity of the river channel. During the growth of vegetation， the inundation degree （ratio of water depth to vegetation height， H/hv） will change with the change of vegetation height or water level， which will affect the flow characteristics.By constructing a three-dimensional numerical model of an open channel with submerged vegetation groups distributed along the river bank， the Large Eddy Simulation （LES） method was used to study the average flow field and turbulent structure around the vegetation group under four submergence levels （4.0、3.0、2.0 and 1.5）. The results indicate that， when submerged vegetation is distributed on one side of the open channel， the maximum cross-sectional velocity deviates from the channel center， appearing on the non-vegetation area， and gradually approaches the water surface as the submergence ratio decreases. The presence of submerged vegetation generates a mixing layer in the vertical direction， intensifying flow turbulence. High turbulent kinetic energy regions are distributed along the interface between the vegetation and non-vegetation area as well as at the vertical interface between the submerged vegetation and the upper water layer. As the submergence ratio decreases， the size of the horizontal shear layer vortices increases. When the submergence level is 1.5， the horizontal shear layer vortex can extend into the non-vegetated area. At the same time， the intensity of the secondary flow in the cross-section strengthens， and the turbulence within the entire flow field becomes more intense.

Intelligent grouting technology plays a critical role in hydraulic engineering and foundation reinforcement. Currently， grouting pressure and unit grouting rate are primarily adjusted manually， leading to low grouting precision and frequent overpressure incidents. This study designs an intelligent grouting pressure control system， integrating a pressure regulation platform， intelligent control unit， and upper-level master control center. The system is capable of controlling pressure and processing real-time data， ensuring the stability and safety of the grouting process. The system's hardware includes key components such as a grouting pump， diverter valve， inflow meter， pressure gauge， outflow meter， and electric control valve. By integrating a PLC with the electric control valve， real-time adjustments to the return pressure are made， ensuring stable and precise pressure control. A data acquisition and pressure stability control logic program for the grouting process are developed， and an integral sliding mode controller is applied for pressure regulation. The controller's performance under dynamic and disturbance conditions is verified， demonstrating its ability to respond quickly to pressure changes and adapt to different grouting requirements. This enhances the automation and intelligence of the grouting operation. This provides a solid foundation for the widespread application of intelligent grouting technology and offers significant potential for future use. This work presents a comprehensive design of an intelligent grouting system， explores the effects of various pressure control algorithms， and confirms the system's performance in real-world applications. The research results show that the intelligent grouting system operates stably and has precise pressure control， which provides a solid foundation for the widespread application of intelligent grouting technology and has broad application prospects.

Revealing the coupling coordination relationship between water resources utilization and high-quality economic development in the Yellow River Basin is very important for improving the macroeconomic regulation of natural resources and economy society， as well as promoting regional sustainable development. Taking cities along the Yellow River in Henan as the research object， an index system of high-quality economic development and water resources utilization was established in this study. Based on the panel data of Henan Province from 2012 to 2022， the comprehensive empowerment-TOPSIS method， which combines entropy weight method and coefficient of variation method， is used to measure the water resources utilization and high-quality economic development level；Combined with the coupling coordination degree model and the relative development degree model， the coupling coordination development trend and interaction mechanism of the two are analyzed. The results show that： ① During the study period， the water resources utilization efficiency of the cities along the Yellow River in Henan fluctuated and increased. The water resources utilization efficiency of Zhengzhou city was the highest， and the water resources utilization effect of Xinxiang city was the worst； ② The overall economic quality development index of cities along the Yellow River in Henan has been continuously improved， with Zhengzhou having the highest economic quality development index and Puyang having the lowest economic quality development level； ③ The cities along the Yellow River in Henan Province as a whole showed the characteristics of high quality economic development synchronized with water resource utilization， but there were obvious differences among cities； ④ The coupling coordination degree between water resources use efficiency and high-quality economic development in cities along the Yellow River in Henan Province is on the rise， but the level is still low. In terms of time series， it has undergone the evolution process of forced coordination - primary coordination， and the spatial distribution pattern is south of the Yellow River > north of the Yellow River， and the coupling coordination evolution process of each city is different. It is necessary to combine the characteristics of cities， pay attention to energy conservation and environmental protection， improve water-saving measures in agriculture and industry， and strengthen scientific and technological innovation capabilities， so as to improve the coupling and coordination of water resources utilization and high-quality economic development.

Water and soil resources are the basic elements of “Production-Living-Ecological Space”. The particularity of water and soil resources in Inner Mongolia Autonomous Region makes the optimization of “Production-Living-Ecological Space” face major challenges. Based on the perspective of “Production-Living-Ecological Space” and PSR model， an evaluation index system of water and soil resources carrying capacity in Inner Mongolia Autonomous Region was constructed. The entropy weight-TOPSIS evaluation model was used to study the spatial-temporal evolution and influencing factors of water and soil resources carrying capacity in Inner Mongolia Autonomous Region from 2013 to 2022. The coupling coordination degree model was used to analyze the coupling coordination degree of “Production-Living-Ecological Space” for the water and soil resources carrying capacity. The results show that： ① The carrying capacity of water and soil resources in each league and city of Inner Mongolia Autonomous Region showed a fluctuating upward trend， and it was mainly at three levels： lower carrying capacity， general carrying capacity and higher carrying capacity， and there is no low carrying capacity level and high carrying capacity level. ② During the study period， the carrying capacity of water and soil resources in each city and league can be divided into two stages： In the first stage （2013-2017）， the carrying capacity of water and soil resources in each city and league showed a slow and fluctuating upward trend， which was mainly at a lower carrying capacity and general carrying capacity level， and the evaluation value of carrying capacity was mainly concentrated in 0.3~0.6； In the second stage （2018-2022）， the carrying capacity of water and soil resources in each city and league showed a steady and upward trend， which was mainly in the general carrying capacity and higher carrying capacity level， and the evaluation value of carrying capacity was mainly concentrated in 0.4~0.7， which has been improved to a certain extent compared with the first stage. ③ The coupling coordination degree of “Production-Living-Ecological Space” for the water and soil resources carrying capacity in Inner Mongolia Autonomous Region generally shows an upward trend. The change trend of the coupling coordination degree of “Production-Living-Ecological Space” was basically consistent with the spatial-temporal evolution trend of water and soil resources carrying capacity in each city and league， which is the result of a steady improvement in the coordination between production， living and ecological space. The research results can provide reference for the sustainable planning， utilization and management of water and soil resources as well as the optimization of “Production-Living-Ecological Space” pattern in Inner Mongolia Autonomous Region.

Based on the upper reservoir face rockfill dam of a pumped storage power station， the analysis methods and safety control standards of the ultimate seismic capacity of the concrete-face rockfill dam （CFRD） are expounded from the aspects of permanent deformation of the dam body， seismic stability of the dam slope， tensile fracture resistance of dam body and seismic safety of face slab. The seismic wave overload method is used to calculate the three-dimensional seismic response of the dam under different peak accelerations， and the ultimate seismic capacity of the CFRD is quantitatively analyzed based on the indexes such as the seismic subsidence rate at the top of the dam， the cumulative duration when the minimum safety factor of the slope is less than 1.0， the cumulative slip， the deformation gradient of the dam after the earthquake and the stress of the face slab. Through in-depth and comprehensive analysis， the following conclusions can be drawn： the dam has strong seismic resistance， and its ultimate seismic resistance is between 0.55~0.60 g. The calculation and analysis results provide reference for scientific evaluation of seismic safety of CFRD and reasonable formulation of seismic reinforcement measures.

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.

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.

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.

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.

The carbon sequestration and oxygen release function of wetlands plays an important role in regional atmospheric regulation and is one of the important ecosystem service functions of wetlands. To quantify the carbon sequestration and oxygen release capacity of the Yellow River Delta wetland ecosystem and analyze its driving mechanism， this paper used the CASA model to calculate the net primary productivity（NPP） of the Yellow River Delta Wetland from 2005 to 2020， and converted it into carbon sequestration and oxygen release through the photosynthesis equation， and used the geographical detector and contribution index to identify the main driving factors and contributions of the evolution of carbon sequestration and oxygen release function. The results showed that the multi-year average net primary productivity of the Yellow River Delta wetland from 2005 to 2020 was 321.5 g/m²， with a total of 907.9 Gg C/a， with an overall decreasing trend in NPP from 2005 to 2020； the multi-year average of carbon sequestration and oxygen release were 309.3 and 836.4 g/m²， respectively. The overall trend of carbon sequestration and oxygen release is decreasing. In terms of spatial distribution， the spatial distribution characteristics of oxygen sequestration were consistent with those of NPP， and the high value areas were mainly concentrated in forest land， followed by grassland and cropland； the results of the Geodetector indicated that the land use type and NDVI are the main controlling factors for the spatial distribution of carbon sequestration and oxygen release in the Yellow River Delta wetland； the analysis results of the contribution index show that forest， grassland， and cropland have positive contributions to carbon sequestration and oxygen release， while land use types such as aquaculture ponds， salt pans， and construction land have negative contributions to carbon sequestration and oxygen release， the contribution indices of culture ponds， salt pans and construction land showed an increasing trend from 2005 to 2020， indicating that the negative impacts of human activities such as the development of urbanization and reclamation culture on the carbon sequestration and oxygen release functions of the Yellow River Delta wetland have been gradually strengthened. The study results can provide the scientific basis for the stability and sustainable healthy development of the Yellow River Delta wetland ecosystem.

In order to investigate the mechanical mechanisms of compression failure in cohesive soil under varying initial moisture conditions and unveil the microscale mechanical effects of water on the macroscopic deformation properties， advanced particle flow software PFC^3d was employed in conjunction with indoor triaxial compression test results. The results show： the DEM simulation results established can effectively reflect the mechanical performance of soil under varying initial moisture content conditions； The peak strength， tangent modulus， cohesion and internal friction angle of the soil exhibit a decreasing trend with the moisture content increases； As the vertical strain increases， larger displacements occur at the specimen's ends， with smaller displacements in the central region. This leads to the formation of a shear zone in the central area， characterized by initial shear contraction followed by shear dilation of the soil. Upon applying confining pressure， the anisotropy of the particle contact normal is initially small. However， as the soil reaches its peak state， the contact normal of the particle system exhibits strong anisotropy； During the shear process， the development of microcracks in the specimen undergoes stages of zero development， rapid development， and slow development， with shear cracks dominating the process；In the model， shearing converts a significant portion of boundary energy into elastic strain energy and a smaller portion into damping energy. This study offers a novel approach to understand the compressive deformation and failure behavior of soil under varying initial moisture content.

In order to investigate the effect of air-entraining agent dosage on the capillary water absorption saturation of unsaturated hydraulic concrete， the capillary water absorption test of unsaturated hydraulic concrete with different air-entraining agent dosage （mass fractions of 0?， 2.50?， 3.75?， 5.00?， 6.25?， respectively） was carried out in a low-temperature environment， by using infiltration absorption and horizontal absorption methods. Then the effect of air-entraining agent dosage on concrete porosity， compressive strength， and capillary water absorption saturation was studied. And finally a prediction model for the capillary water absorption saturation of unsaturated hydraulic concrete coupled with different depths of water absorption and different air-entraining agent contents was established. The results show that： with the increase of air-entraining agent dosage， the porosity of hydraulic concrete increases linearly， the compressive strength decreases slightly with an upward convex curve， and the saturation degree decreases gradually. The saturation degree and water absorption depth were exponentially related. The saturation degree of concrete and air-entraining agent admixture of the infiltration absorption and horizontal absorption methods were linearly and quadratically related， respectively. Then a prediction model of capillary water absorption saturation of unsaturated air-entraining hydraulic concrete was established based on the separation of variables model. And the analysis shows that the new model can better predict the distribution law of capillary water absorption saturation of unsaturated hydraulic concrete under the joint action of different water absorption depths and different air-entraining agent mixing amounts.