[Objective] Accurately estimating the friction velocity within the backwater region of deposit body is crucial for deriving hydraulic parameters and predicting river scour and deposition. While classical friction velocity methods (e.g., the logarithmic velocity method) are well-established for uniform flows, their applicability and the associated velocity-turbulence parameter characteristics in backwater regions with non-uniform deposits remain systematically underexplored in current research. [Methods] We conducted a series of flume experiments, employing three distinct flow rates to simulate conditions ranging from low to heavy rainfall during the rainy season. A plexiglass deposit model, characterized by a 45° slope and a channel width contraction ratio of 0.5, was utilized. Three-dimensional velocities and water levels were measured at 19 cross-sections using an Acoustic Doppler Velocimeter (ADV) to systematically analyze the hydraulic characteristics of the deposit-induced backwater region. Four classical methods-the Single-point Reynolds Stress Method, Three-dimensional Turbulent Kinetic Energy Method, Vertical Turbulent Kinetic Energy Method, and Logarithmic Velocity Method were selected to estimate friction velocity, and their relationships with backwater characteristics were investigated. The Karman constant (k) and integration constant (A) were fitted based on the measured velocity distributions. Additionally, empirical coefficients D and λ were derived from turbulence intensity measurements to elucidate their influencing factors. [Results] The key findings of this study are as follows: (1) The Three-dimensional Turbulent Kinetic Energy Method and the Single-point Reynolds Stress Method proved most effective in characterizing bed friction under the influence of deposits, yielding the smallest relative deviations for the estimated mean friction velocities. Furthermore, a significant monotonic negative correlation was observed between friction velocity and the backwater parameter (h/h0). (2) While the vertical velocity profiles within the backwater region still adhered to a logarithmic distribution, the mean Karman constant (k) fitted across the entire water depth was lower than the conventionally recommended value of 0.4. Consequently, the integration constant (A) is proposed to be revised to 7.5-9.5 to better align with engineering requirements. (3) The empirical coefficient D for turbulence intensity was found to be jointly influenced by both flow rate and the friction velocity model, exhibiting a stable mean ratio of Du∶Dv∶Dw=1.41∶1.00∶0.40. In contrast, λ was solely driven by flow rate. The observed decaying trend of vertical, longitudinal, and transverse turbulence intensities with increasing water depth further corroborated the reliability of the friction velocity estimations. [Conclusion] This research successfully identified the optimal method for estimating friction velocity in backwater regions characterized by non-uniform deposits and refined the empirical values of velocity-turbulence parameters. The findings offer crucial experimental evidence for advanced hydraulic modeling, flood control engineering design, and river management strategies in mountainous river sections affected by deposits. Furthermore, this study holds significant implications for river restoration efforts following earthquake-induced secondary geological hazards.
[Objective] Traditional evaporation models are limited in floating ball coverage scenarios by complex parameterization, reliance on sensible heat flux data, and cumbersome aerodynamic calculations. This study aims to develop a highly accurate evaporation prediction formula with simplified parameters, adaptable to varying coverage ratios, to provide a reference for water resource quantification. [Method] Based on the Priestley-Taylor model, a modified model was developed by introducing correction term g(m) to address evaporation prediction under floating ball coverage. By analyzing the relationship between coverage ratio and latent heat flux, exponential (for high-temperature seasons) and linear (for transition seasons) correction forms were determined. Robust regression was employed to minimize the impact of outliers. The optimal model was selected through model comparison and cross-validation. [Result] (1) The response relationship between latent heat flux and floating ball coverage ratio exhibited significant monthly variations. At high-temperatures during high-radiation season (June-August), the exponential correction yielded the best fit (R2≥0.985), whereas the linear correction performed better during the transition seasons (March-May and September-October) (R2≥0.986). (2) The exponential model demonstrated superior adaptability and predictive advantages for floating ball evaporation. Over the entire experimental period, it achieved a Willmott’s index of agreement (D) of 0.986, a Nash-Sutcliffe efficiency (NSE) of 0.947, a root mean square error (RMSE) of 0.54 mm/d, and a mean absolute error (MAE) of 0.43 mm/d, with strong parameter stability and no systematic bias. (3) The model also showed good adaptability during external validation under high-coverage conditions (NSE=0.734, D=0.890). [Conclusion] The proposed modified model establishes a unified prediction framework based on basic meteorological parameters for varying floating ball coverage ratios. It enables precise estimation of evaporation processes across different coverage levels, providing an efficient and practical computational method for water resource management in arid regions.
[Objectives] This study aims to quantify the respective contributions of suspended load and bed load to reservoir sedimentation over different operational periods, and to evaluate the impacts of upstream bed load supply rate, grain size distribution, and intra-annual distribution on reservoir sedimentation. The findings are intended to provide scientific support for the design, long-term operation, and numerical modeling of reservoir projects, especially in data-scarce mountainous regions. [Methods] The study takes the Tianzishan Reservoir in Hunan Province, China, as a case study. A one-dimensional water-sediment mathematical model, “HELIU-2” developed by the Changjiang River Scientific Research Institute (CRSRI), is employed to simulate reservoir sedimentation over a 300-year operational period. The model is set up using measured cross-sectional profiles along the entire reservoir reach (12.23 km, 31 sections), sediment gradation data from the dam site, and hydrological data at the dam site, with key empirical parameters adopted from established practices. Scenarios are designed to assess the influences of upstream bed load supply, bed load gradation, and intra-annual distribution of bed load supply. [Results] During the early operational period (first 10 years), bed load primarily deposits near the reservoir inlet (10 229-12 230 m from the dam), while suspended load dominates overall reservoir sedimentation, accounting for 89.78%-91.04% of total deposition over different operational years. In the near-dam reach (0-3 534 m from the dam), the proportion of bed load deposition increases gradually with operation time, reaching 40.98% at 300 years. In the inlet reach, bed load deposition reaches 100% after 100 years. In contrast, in the middle reaches (e.g., 5 884-7 110 m from the dam), the bed load deposition proportion declines after an initial increase, eventually disappearing as bed load migrates further downstream. Among the three factors examined—upstream bed load supply rate, bed load gradation, and intra-annual distribution of bed load supply—the supply rate has the greatest impact on reservoir sedimentation. A higher bed load supply rate leads to higher along-channel bed elevation and a steeper riverbed slope near the dam. The effect is more pronounced in reaches with initially milder bed slopes, where sediment deposition is more sensitive to changes in bed load supply. The influence of bed load supply rate becomes increasingly significant with longer operation time.In contrast, bed load gradation has a limited effect: coarser bed load gradation results in slightly higher bed elevation in the near-dam reach, but the overall impact on the longitudinal sedimentation profile is small. Similarly, the intra-annual distribution of bed load supply (flood-season-only versus year-round) shows negligible influence on both the sedimentation profile and bed slope. [Conclusions] (1) In the early stage of reservoir operation, bed load mainly deposits near the reservoir inlet, while suspended load dominates sedimentation in the reservoir area. As operation time increases, the proportion of bed load deposition in the near-dam reach gradually rises and reaches 100% in the inlet reach after 100 years. In the middle reaches, the proportion of bed load deposition first increases and then decreases.(2) The upstream bed load supply rate has a greater impact on reservoir sedimentation than bed load gradation and intra-annual distribution. A higher bed load supply rate leads to higher along-channel bed elevation and a steeper riverbed slope near the dam, with the effect being more pronounced in reaches of milder initial bed slope. This influence becomes increasingly significant with longer operation time. (3) Coarser bed load gradation results in slightly higher bed elevation in the near-dam reach, but its overall impact on the sedimentation profile is limited. The intra-annual distribution of bed load supply also shows negligible influence. For reservoirs with moderate sedimentation, neither factor is a controlling element.
[Objective] Water level variations in tidal river reaches are highly complex and influenced by both upstream runoff and downstream tides. Accurate prediction of these variations is crucial for flood control, disaster reduction and ecological security. Taking the Nanjing Hydrological Experimental Station in the tidal reach of the Yangtze River as a case study, this paper aims to develop a model that can capture the nonlinear, dynamic and complex fluctuation characteristics of water levels and achieve real-time prediction. [Methods] A hybrid CNN-LSTM-KAN model is proposed, which combines a Convolutional Neural Network (CNN), a Long Short-Term Memory (LSTM) network, and a Kolmogorov-Arnold Network (KAN). First, the CNN is used to extract spatial features from the water level sequence. Then, the LSTM captures the dynamic temporal dependencies of water level changes. Finally, KAN is introduced to further enhance the model’s ability to represent nonlinear and dynamic characteristics. [Results] The hybrid model shows strong real-time prediction performance on the measured data from the Nanjing station. It outperforms conventional deep learning methods such as optimized LSTM and CNN-LSTM in terms of prediction accuracy, peak capture capability and robustness to input data. On the test set, the model achieves a root mean square error (RMSE) of 0.065 4 m, a mean absolute error (MAE) of 0.042 9 m, a mean absolute percentage error (MAPE) of 0.023 5, and a Nash-Sutcliffe efficiency coefficient (NSE) of 0.995 1. [Conclusions] The proposed CNN-LSTM-KAN hybrid model has a simple structure and is easy to implement. It provides strong technical support for flood and drought disaster prevention and sustainable socio-economic development in the tidal reaches of the lower Yangtze River.
[Objective] Current research on groundwater reserves in China primarily focuses on northern regions. Key challenges remain regarding the relationship between groundwater reserves and routine-emergency water supply, the construction of reserve systems, and the principles for reserve utilization. Focusing on the middle reaches of the Yangtze River—a region with favorable groundwater reserve conditions, dense urban distribution, and insufficient urban water supply security under extreme conditions—this study explores the connotation, hierarchical framework, and utilization strategies of groundwater reserves. The aim is to mitigate extreme water scarcity threats and enhance urban water supply security. [Method] Groundwater reserve volume was defined as the volume of groundwater stored to address water supply security threats in routine systems caused by extreme droughts or emergencies. The risks of extreme droughts and sudden pollution events, urban water supply security capacity, and groundwater occurrence and utilization in the middle reaches of the Yangtze River were analyzed. On this basis, a hierarchical groundwater reserve framework (HWUSR) was innovatively constructed based on five dimensions: crisis level of urban water supply security (How), urban scale (Where), reserve purpose (Use), reserve area scale (Scale), and groundwater renewability (Renewability). [Results] (1) Extreme droughts occur frequently in the middle reaches of the Yangtze River, severely threatening urban water supply systems that rely primarily on surface water. The region possesses massive groundwater storage, which can resolve the insufficient water supply security capacity for critical towns during extreme water scarcity events. (2) Groundwater reserves in important towns with abundant groundwater and low exploitation rates should follow a hierarchical approach. Priority should be given to megacities with dense populations and developed industries, as well as pilot zones with strong economic foundations, high population density, primary reliance on surface water, and inadequate emergency supply capacity. Domestic water needs for urban residents should be prioritized over industrial demands. Shallow aquifers with good water quality, high extractability, and strong renewability should be prioritized for reserves. (3) The utilization of groundwater reserves should adhere to the principles of confirmed necessity, dedicated use, shallow-deep complementarity, appropriate utilization, post-use recovery, and dynamic early warning. (4) Strategic reserve utilization must clarify responsibilities, implementation entities, timing, plans, and evaluations of effectiveness and environmental impacts. Following the principle of “whoever utilizes compensates, whoever benefits restores”, compensation and restoration measures must be implemented post-utilization. [Conclusion] These findings provide an important reference for the formulation and implementation of the groundwater reserve system and the construction of reserve demonstration projects in the Yangtze River Basin.
[Objective] This study aims to quantitatively assess the contributions of individual meteorological factors to hydrological drought evolution in the Yuanjiang River Basin, a typical humid region in the middle reaches of the Yangtze River, and to reveal the climatic mechanisms. [Methods] We integrated historical hydrometeorological observations (1975-2022) with future climate projections (2026-2050) derived from five CMIP6 global climate models (GCMs) under three Shared Socioeconomic Pathways (SSP126, SSP245, and SSP370). To ensure regional accuracy, the future meteorological projections were bias-corrected using the quantile delta mapping method. Subsequently, we developed and validated a monthly streamflow prediction model across six hydrological stations utilizing the XGBoost algorithm. This model incorporated a comprehensive set of predictors, including meteorological variables (precipitation, relative humidity, radiation, and temperature) and human activity indicators (reservoir operation and land use changes). To ensure the interpretability of the machine learning model, the SHAP (SHapley Additive exPlanations) framework was employed to quantify the marginal contributions and unravel the directional influences of each driving factor on streamflow variations. Finally, the validated XGBoost model was driven by the bias-corrected future data to project long-term streamflow dynamics. Based on these projections, hydrological drought events were characterized using the standardized runoff index (SRI) at 3- and 6-month scales, with key drought features (frequency, duration, severity, and intensity) systematically extracted via the run theory. [Results] From 1975 to 2022, the XGBoost model demonstrated excellent performance, achieving average Nash-Sutcliffe efficiency (NSE) values of approximately 0.90 for calibration and 0.80 for validation. SHAP analysis revealed precipitation as the dominant driver of streamflow variability, accounting for 69.8% of the total explained variance, followed by relative humidity (11.9%). Furthermore, analysis of the daily-to-monthly aggregation methods showed that the monthly mean contributed 58.2% of the variance, whereas metrics capturing intra-monthly fluctuations and extreme distributions (std, p90, and p10) cumulatively contributed 41.8%. Specifically, standard deviation (20.8%) and the 90th percentile (14.4%) had high explanatory weights, highlighting the critical importance of intra-monthly meteorological variability. Historically, hydrological droughts exhibited distinct spatiotemporal heterogeneity, with more frequent occurrences in winter and spring and greater frequency and severity at upstream stations (e.g., Taoyi). Under future climate scenarios (2026-2050), precipitation was projected to follow a “drier dry season and wetter wet season” pattern, with reductions of approximately 25 mm from September to November and increases of up to 50 mm from April to August. Concurrently, relative humidity was projected to decline throughout the year, with pronounced decreases of 0.05-0.10 during the dry season. Consequently, hydrological droughts were expected to worsen, with projected increases in frequency (0.04-0.06), duration (0.2-0.4 months), and intensity (0.05). A significant structural shift in drought categories was also anticipated: moderate drought frequency increased markedly (0.04-0.08), while severe drought frequency generally declined, dropping by approximately 0.06 at Taoyi Station. This structural transition from “long-duration, high-intensity” to “high-frequency, moderate-intensity” droughts in the future was driven by seasonal moisture dynamics. Sharp declines in precipitation and relative humidity in June acted as the trigger for drought onset (with the combined SHAP negative contribution reaching approximately -230 m3/s), followed by continuous moisture deficits from July to October that drove the progression into moderate drought. However, steady moisture increases from November to May created a significant compensation effect, interrupting the deep accumulation of streamflow deficits and preventing the evolution into severe droughts. These findings highlighted that future drought mitigation in the Yuanjiang River Basin should prioritize managing seasonal consecutive droughts and the cumulative impacts of moderate droughts. [Conclusion] Precipitation and relative humidity are the dominant meteorological factors controlling hydrological drought in the Yuanjiang Basin. The XGBoost-SHAP framework effectively quantifies their individual contributions and reveals that the seasonal coupling between precipitation reduction and enhanced evapotranspiration due to declining relative humidity is the primary mechanism driving future drought intensification. Future hydrological drought across the basin is projected to intensify, characterized by increased frequency, prolonged duration, and a structural shift toward more frequent moderate drought events. Machine-learning interpretability approach provides a valuable and robust supplement to traditional physical models for understanding and projecting climate change impacts on hydrological drought. This integrated analytical framework offers scientific support for adaptive water resource management and drought mitigation strategies in the Yuanjiang River Basin and similar humid regions facing escalating drought risks under climate change.
[Objective] There are significant differences between source reservoirs and receiving reservoirs in arid regions of Northwest China in terms of spatial distribution and functional positioning. Traditional single-level operation models are difficult to achieve the global optimal allocation of water resources. To improve the scientific basis of reservoir operation and the efficiency of intensive water resources utilization, this study constructs a joint operation model for reservoir groups based on bi-level optimization. [Methods] A bi-level optimization model was established for the joint operation of reservoir groups, and the particle swarm optimization (PSO) algorithm was used to solve the model. The upper-level model takes the source reservoir as the operation core and aims to minimize water transfer deviation and evaporation-seepage losses. The lower-level model takes the receiving reservoirs as the regulation objects and aims to minimize water shortage in irrigation districts. Hydrological methods were used to quantitatively evaluate ecological flow, which was incorporated into the operation model as a rigid constraint. [Results] The variation trends of water transfer amount and water diversion amount were consistent, and the ratio between them remained within the range of 0.87-1.07. The multi-year monthly average evaporation-seepage loss decreased from 413.14×104 m3 before optimization to 348.46×104 m3 after optimization, with a reduction of 15.66%. The water supply reliability of each sub-irrigation district reached 87.33%-95.63%. [Conclusions] The proposed reservoir group joint operation model based on bi-level optimization can coordinate the relationship between source reservoir regulation and receiving reservoir water demand, reduce evaporation-seepage losses, and improve irrigation water supply reliability under ecological flow constraints. The research results can provide a reference for the joint operation of reservoir groups in similar regions.
[Objective] The Bishan-Tongliang Line is an east-west municipal express railway in the suburbs of Chongqing， aimed at promoting rapid development in the western Chongqing area. During the construction of the Yunwu Mountain Tunnel—a critical control project—a sudden water inrush occurred in the adit. This study aims to accurately identify the causes of the water inrush， providing a scientific basis and technical support for waterproofing measures during construction and the identification of water inrush sources in similar tunnel projects. [Method] Taking the water inrush in this tunnel as a case study， potential water-conducting channels were analyzed based on a comprehensive review of regional engineering geology， hydrogeological characteristics， and the features of the adit water inrush. Through laboratory and field tests， as well as physical and chemical analysis methods， the differences and correlations between water samples from regional aquifer channels and the inrush water were investigated to achieve accurate and efficient identification of the water inrush source. [Result] The regional groundwater primarily consists of red bed fissure water， detrital rock pore-fissure water， and carbonate karst water. Potential sources of the adit water inrush include surface water leakage， bedrock fissure water， water accumulated in mined-out coal areas， water inrush from water-conducting faults， and karst water. Through a comprehensive multi-factor analysis combining field investigations， physical methods， and chemical methods， it was identified that the water inrush originated from confined fissure water in sandstone strata interbedded within impermeable shale， supplemented by reservoir water recharged through water-conducting faults. [Conclusion] This study provides a universal methodology for identifying water inrush sources in tunnel engineering under complex geological conditions. This approach involves predicting potential water inrush factors by integrating regional engineering and hydrogeological characteristics， followed by systematic investigation and comparative analysis of each factor using field surveys， physical methods， and chemical methods to accurately and effectively identify the source of tunnel water inrush.
[Objective] To address the stability issues of rock ridges during the blasting demolition of the large cofferdam for the unit expansion project at Wuqiangxi Hydropower Station， this study proposes an optimized blasting scheme， aiming to prevent the sliding instability of the remaining thin rock ridge after layered blasting under the influence of fracture seepage. [Method] A discrete fracture seepage-stress coupling model was employed to evaluate the excavation sequence， slope height-to-width ratios， and seepage stability of the downstream slope of the rock ridge. The stability of the rock ridge under various blasting schemes and slope height-to-width ratios was analyzed considering fracture seepage. By integrating safety factors and failure slip modes， the optimal blasting sequence and a reasonable downstream slope height-to-width ratio were determined， providing precursor information on potential failure modes of bedded rock masses under seepage conditions. [Result] （1） Based on the engineering characteristics and blasting challenges， a demolition design for the intake cofferdam was formulated： blasting the outer earth-rock cofferdam during the dry season， thinning the inner side of the cofferdam， removing the top concrete cofferdam， and blasting the remaining rock ridge in a single pass. This scheme prevents the instability of the remaining thin bedded rock ridge under fracture seepage while minimizing risks to existing structures. （2） At slope height-to-width ratios of 1∶0， 1∶0.3， and 1∶0.5， the failure mode was global， with failure boundaries comprising a composite slip surface of the concrete-rock interface， weak interlayers， and bedding planes. At ratios of 1∶0.7， 1∶0.9， 1∶1.1， and 1∶1.3， the failure mode transitioned to local bedding slip instability. As the ratio increased， the tensile failure boundary at the trailing edge moved further from the toe of the excavated slope， and the thickness of the unstable rock layer decreased， indicating an evolution toward shallow bedding slip failure. [Conclusion] Considering both the safety factor and the failure slip mode， a slope height-to-width ratio of 1∶0.7 was determined to be optimal for the downstream slope excavation， as the safety factor exceeded 1 and the failure mode transitioned from global to local. The proposed scheme effectively controls the deformation and instability risks of the reserved thin-walled rock ridge. These findings provide valuable references for the demolition of large cofferdams and the stability evaluation of rock ridges under fracture seepage conditions.
[Objective]Since the operation of Xiaolangdi reservoir in 1999,continuous erosion has happened in the lower Yellow River.As of 2023,the accumulated erosion volume of Tie-Li reach(from Tiexie station to Lijin sta-tion)in the lower Yellow River has reached 2.2 billion m3.However,the erosion efficiency gradually decreases from 13.6 kg/m3 to 6.3 kg/m3.It is important to realize the temporal and spatial accumulation variation law of con-tinuous erosion in the lower Yellow River in order to estimate the erosion potential.[Methods]Through collecting the annual erosion volume data from 2001 to 2024 for different sub-reaches,the temporal and spatial accumulation variation law of continuous erosion in the lower Yellow River is analyzed.Based on the river spatial non-equilibrium sediment transport theory,and combined with the temporal delayed response model of sediment transport capacity adjustment during the processes of erosion and sedimentation of river bed,a temporal and spatial accumulation vari-ation model of continuous erosion volume is proposed,and then is used to simulate the temporal and spatial accu-mulation variation of continuous erosion in the lower Yellow River and predict the future erosion potential.The mod-el parameter φ is calibrated based on the measured spatial accumulation erosion data of 2017,the model parameters K(0)and β is determined based on the measured temporal accumulation erosion data from 2001 to 2017 of the Hua-Li reach.These calibrated parameters are used to simulate the temporal and spatial accumulation erosion from 2018 to 2024 of the different sub-reaches for model validation and the performance is evaluated using the certainty coeffi-cient and the Nash-Sutcliffe efficiency coefficient.[Results]Data analysis results show that the temporal and spa-tial accumulation variation law of continuous erosion in the lower Yellow River shows a set of different growth curves,and the growth rates present a first fast and then slow down change trend,finally gradually tending towards 0.The simulation results of the temporal and spatial accumulation erosion volume show that the simulated and meas-ured values are in good agreement,the values of the certainty coefficient and the Nash-Sutcliffe efficiency coeffi-cient are 0.98 and 0.99.The sediment transport capacity coefficient K decreased to 0.005 4 kg·s/m6 by 2024.The continuous erosion in the lower Yellow River is approaching equilibrium.If further erosion is desired,it is necessary to optimize the water and sediment combination conditions.If the average discharge increases by half to 1 191 m3/s and the sediment concentration decreases by half to 1.98 kg/m3,the erosion potential can increase to 860 million m3.[Conclusion]The high model precision illustrates the rationality of the proposed temporal and spatial accumu-lation variation model of continuous erosion volume.As a macro accumulation model,the proposed model in this paper is not suitable to simulate different annual erosion volumes of different sub-reaches of the lower Yellow River and the spatial accumulation variation law.But after long term self-adjustment,its macro temporal and spatial accu-mulation variation law conforms to the model proposed in this paper reflecting the macro fluvial process tend towards equilibrium.In the future,from a micro perspective of the different independent year,how to finely simulate the annual erosion volume of different sub-reach and the complex spatial accumulation variation law in the lower Yellow River is still to be further studied.
[Objective]This study aims to reveal the seasonal concentration characteristics and spatial differentia-tion patterns of precipitation in Tianjin from 1980 to 2023 by quantifying long-term seasonal trends,characterizing the spatial patterns of Precipitation Concentration Degree(PCD)and Precipitation Concentration Period(PCP),and establishing a bivariate risk assessment method based on PCD-PCP joint return periods using Copula functions.The innovation lies in the first application of Copula-based PCD-PCP coupled analysis to the hydrometeorological field of Tianjin,providing support for extreme flood prevention.[Methods]Daily precipitation data from 13 mete-orological stations in Tianjin during 1980-2023 were employed.The Mann-Kendall trend test and Sen's slope esti-mator were used to detect monotonic trends in seasonal and annual precipitation.The vector-based PCD and PCP indices were calculated to quantify precipitation concentration uniformity and peak timing.Inverse distance weigh-ting(IDW)was applied to visualize spatial patterns.The distribution characteristics of PCD-PCP under specific scenarios were analyzed based on copula joint distribution.[Results]Seasonal precipitation in Tianjin is highly un-even.Summer dominates with a mean of 383.6 mnm(70.1％of annual total),while winter precipitation is extremely low(11.5 mum)but shows the highest interannual variability(extreme value ratio:180.50).Summer precipitation exhibits a significant increasing trend,which may elevate the risk of extreme precipitation events,whereas the in-creased variability of autumn precipitation could prolong the urban waterlogging risk window.Spatially,annual pre-cipitation exhibits a stable"higher in the north and lower in the south"pattern across the 1980s-2010s.The spatial pattern of PCD shows limited variability,with values predominantly ranging from 0.68 to 0.73.A high-value zone is identified in the Binhai New Area(PCD ≈ 0.73),reflecting strong precipitation concentration within a short annual window,whereas lower values in Jizhou and Wuqing suggest a more even precipitation regime.In contrast,PCP ex-hibits a west-east gradient,increasing from approximately 201 in the west to 207 in the east(mid-to-late July),in-dicating spatial asynchrony in precipitation concentration timing.Temporally,PCD shows substantial interannual fluctuations(0.50-0.85),yet its long-term trend remains stable,as evidenced by decadal means ranging from 0.69 to 0.71.PCP also exhibits notable interannual variability(180-220)but demonstrates a significant decadal delay,progressing from 198.5 in the 1980s to 203.7 in the 2010s,a trend intrinsically linked to the phenomenon of sum-mer rainfall shifting to autumn in the Beijing-Tianjin-Hebei region.The copula-based analysis reveals a non-inde-pendent relationship between PCD and PCP,whereby higher PCD values tend to coincide with PCP falling within the annual peak precipitation period.The 50-year precipitation event corresponds to the combination of high PCD and a specific PCP,indicating that this extreme scenario arises from the simultaneous deviation of both variables from their normal states.Under this scenario,PCD is significantly above the multi-year average,and PCP falls within the main summer flood season.This concurrence of high precipitation concentration and flood season timing will substantially elevate the risk of urban waterlogging and basin flooding.Therefore,responding to extreme precip-itation events requires attention not only to increases in total precipitation but also to high temporal concentration and its coincidence with the main flood season.[Conclusion]This study systematically quantifies the seasonal con-centration characteristics and spatial differentiation of precipitation across Tianjin.Summer dominates both the total amount and long-term trends.PCD is spatially homogeneous but interannually variable,whereas PCP shows a clear west-east gradient.Under the 50-year precipitation event,Tianjin faces credible extreme flood hazards.Future work should incorporate climate model projections to assess non-stationarity in the PCD-PCP dependence structure under warming scenarios.
[Objective]The intrinsic mechanisms underlying the spatiotemporal heterogeneity of nutrient removal efficiency and the regulatory role of aquatic plant rhizosphere effects in micro-scale surface flow constructed wet-lands(SFCWs)remain unclear.This study aims to address the following issues:(1)Elucidate the spatiotemporal distribution patterns of nitrogen(N)and phosphorus(P)removal efficiency;(2)Reveal the correlation mecha-nisms among microbial community structure,metabolic potential,and N/P removal;and(3)Evaluate the effects of the plant rhizosphere and three typical plant species on microbial community structure and N/P metabolic poten-tial,providing a basis for the design and maintenance of micro-scale SFCWs.[Method]Using a specific wetland as a case study,water quality monitoring and high-throughput microbial sequencing were employed to systematically analyze the spatiotemporal characteristics of N/P removal and their microbial driving mechanisms.The regulatory mechanisms of substrate types and plant rhizospheres on microbial community composition and metabolic potential were also clarified.[Results](1)The ammonia nitrogen removal rate remained stable(89.3％-95.8％),while the total nitrogen removal rate exhibited seasonal variation:summer(75.6％)＞autumn(64.9％)＞spring(54.3％)＞winter(21.9％).This process was closely related to the succession of functional bacterial communities and changes in metabolic potential.N-cycling functional bacteria,including Kosakonia,Bacillus,Noviherbaspiril-lum,Ellin6067,and Anaeromyxobacter,were significantly enriched in spring and summer,resulting in significantly higher N metabolic potential compared to autumn and winter.(2)The total phosphorus removal rate,co-regulated by microbial action and adsorption/sedimentation,showed seasonal variation(summer 74.9％＞spring 65.6％＞autumn 59.8％＞winter 46.7％).Microbial influence on seasonal fluctuations was evidenced by the significant en-richment of P-cycling functional bacteria,such as Massilia,Bacillus,Saccharimonadales,and Gemmatimonas,in spring and summer,with P metabolic potential significantly higher than in autumn and winter.(3)Spatially,N/P metabolic potential demonstrated stability.Although substrate types(gravel,non-rhizosphere soil,and rhizosphere soil)significantly altered bacterial community composition,no significant differences in N/P metabolic potential were observed among substrates.This provides empirical evidence for the weakened rhizosphere boundary effect and the maintenance of metabolic homeostasis via functional redundancy at specific scales in micro-scale wetlands.[Conclusion]In space-constrained SFCWs with low pollution loads,water temperature dominates the biochemical reaction rates of N/P transformation.Alkaline pH and an appropriate increase in total nitrogen concentration syner-gistically promote P removal.Microbial community distribution is influenced by nutrient substrates and environmen-tal factors.Based on these findings,the following optimization strategies are proposed:(1)Install a pre-treatment unit for total phosphorus at the inlet to mitigate the risk of endogenous release caused by substrate saturation;(2)Utilize aquatic plant root systems to promote the enrichment and spread of denitrifying bacteria,while reducing the reliance on precise plant species configuration;(3)Based on the succession characteristics of functional bacteria,apply targeted inoculation of highly efficient microbial agents for N/P removal;and(4)Maintain stable system op-eration through water temperature regulation,pH optimization,and nutrient load management.
[Objective]In typical plain tidal river networks at the Yangtze River Delta front,dense waterways and frequent navigation significantly impact levee safety through channel operations and bed scour.Focusing on two typi-cal levee structural types along the Huangpu River and its main tributaries,this study investigates the scour re-sponse under the coupling of structural dimensions and scour depth.The findings aim to provide a scientific basis for accurately identifying high-risk bank sections,optimizing bank protection structures,and enhancing the targeted management of levee engineering in tidal navigable rivers.[Methods]To examine the scour resistance sensitivity and its variation of levee structures in tidal navigable rivers,the theoretical scour depth was calculated based on the actual operating conditions of a navigable tributary in the upper Huangpu River.Using these calculated values as a reference,finite element models were developed to analyze the displacement responses of gravity-type and pile-foun-ded levees under coupled conditions of varying structural dimensions and scour depths.This approach allowed for the determination of the scour resistance sensitivity and evolutionary trends for different levee structural types.[Results]The scour resistance sensitivity of gravity-type levees is primarily influenced by the base slab width and embedment depth.When the base slab width is＜4 m or the embedment depth is＜2 m,a toe scour 0.5-1.0 m trig-gers a sharp increase in the displacement rate at the wall top.Conversely,when the base slab width exceeds 5 m or the embedment depth exceeds 2 m,further increasing the dimensions yields significantly diminishing returns in scour resistance.The scour resistance sensitivity of pile-founded levees is mainly governed by the pile length.When the pile length is＜15 m,the displacement growth rate accelerates markedly once the scour depth 1.0-1.5 m.Beyond a pile length of 15 m,the effectiveness of increasing pile length to enhance scour resistance weakens.[Conclusion](1)The sensitivity of different structural types to toe scour must be fully considered during the selec-tion and sizing of levee structures in tidal navigable rivers.Under the given typical boundary conditions,the scour resistance sensitivity increases with the base slab width,embedment depth,and pile length.However,beyond cer-tain thresholds,the marginal gain in sensitivity decreases,making it economically inefficient to further improve scour resistance solely by enlarging structural dimensions.Instead,altering the structural type or controlling the scour depth is recommended to enhance levee safety.(2)For the design of gravity-type levees,it is advisable to maintain a base slab width of ≥4 m and an embedment depth of ≥3 m.If the anticipated scour depth exceeds 1 m,gravity-type structures are not recommended.For existing gravity levees,the impact of scour should be mitigated through strengthened vessel traffic management and the installation of protective structures.(3)For the design of pile-founded levees,the pile length should be controlled at ≥15 m.When the anticipated scour depth reaches 1 m,measures such as enhanced vessel traffic management and protective structures should be implemented to reduce scour impacts.The proposed structural dimensions and structural adaptability under varying scour conditions provide a scientific basis for the design and management of levees in tidal navigable rivers.
With the increasing internationalization of geotechnical engineering projects in China and the growth of international engineering cooperation， the demand for referencing and applying foreign technical standards in engineering practice is growing. As a widely used in-situ testing method， the technical requirements and application of plate load test （PLT） results vary across different standard systems. To facilitate international engineering practice and standard alignment， this paper provides a comparative analysis of the similarities and differences between current domestic and foreign PLT standards from three aspects： standard systems， testing methods， and data interpretation. The analysis reveals the following：（1） In terms of standard systems， foreign standards typically focus on specific fields by proposing mandatory provisions and technical requirements， featuring a relatively concise structure. （2） Regarding testing methods， foreign standards are primarily principle-based and guidance-oriented， imposing higher requirements on engineers to conduct tests based on actual field conditions. （3） In data interpretation， domestic standards usually determine the allowable bearing capacity directly from the load-settlement curve. In contrast， foreign standards derive the allowable bearing capacity by back-calculating strength parameters under specific conditions and applying ultimate bearing capacity theories. This study provides a valuable reference for conducting PLTs and analyzing results under foreign standard frameworks.
[Objective] This study aims to analyze the spatiotemporal distribution and probabilistic characteristics of multi-level meteorological droughts at the seasonal scale in Guangxi， China， with a focus on seasonal continuous drought events. The study quantitatively analyzes drought frequency trends， identifies the optimal probability distribution function for seasonal precipitation， and assesses the joint probability of consecutive seasonal droughts with the goal of providing more scientific basis for drought risk management in Guangxi. [Methods] Using daily precipitation data from 18 meteorological stations （1960-2020）， we calculated the Standardized Precipitation Index （SPI） for four seasonal scales and classified drought thresholds into four levels （mild， moderate， severe， and extreme）. The GAMLSS （Generalized Additive Models for Location， Scale and Shape） model compared six probability distributions （Gamma， Normal， Lognormal， Gumbel， Weibull， and Logistic） to fit precipitation sequences， and the Gamma function was selected as the optimal model based on the AIC （Akaike Information Criterion）. Five Copula functions （Clayton， Frank， Gaussian， Gumbel， and t-Copula） were used to construct the joint distribution of continuous seasonal drought， and the optimal Copula function was determined using the squared Euclidean distance （OSL）. Spatial interpolation techniques were applied to visualize regional drought probabilities. [Results] The SPI in spring showed a decreasing trend （-0.005 8/a）， indicating an increase in drought frequency， while the SPI in summer （0.007 6/a）， autumn （0.002 1/a）， and winter （0.015 3/a） showed an increasing trend， indicating a decrease in drought frequency. Based on the fitting results of the GAMLSS model using six probability distribution functions for the seasonal precipitation series in Guangxi， the gamma function appeared most frequently in the optimal and suboptimal distributions， indicating that the gamma function can effectively describe the characteristics of precipitation changes. The seasonal frequencies of different drought levels at various stations show that mild droughts （30%-48%） are more common in summer， while moderate droughts （20%-37%）， severe droughts （10%-27%）， and extreme droughts （5%-17%） are more likely to occur in autumn. The gamma distribution performs exceptionally well， with the difference between theoretical and empirical frequencies not exceeding 11%. Different regions in Guangxi exhibit significant differences in consecutive drought characteristics. Among the four consecutive seasons of spring-summer， summer-autumn， autumn-winter， and winter-spring， the probability of consecutive droughts， moderate droughts， severe droughts， and extreme droughts is higher and more widespread during the winter-spring season. The probability range for consecutive winter-spring droughts is 13.1%-20.9%， primarily distributed in the southern coastal areas of Guangxi， central Guangxi， and northeastern Guangxi， with the highest probability of drought occurring in the northwestern part of Wuzhou City. Regions with a higher probability of severe consecutive droughts are distributed in Liuzhou， Laibin， Qinzhou， and Baise. Regions with a higher probability of severe and extreme consecutive droughts are distributed in Liuzhou， Laibin， Qinzhou， and Baise， among which Liuzhou has the highest probability of severe and extreme consecutive droughts during the spring-summer season， with probabilities of 7.1% and 3.9%， respectively. [Conclusions] The study revealed differences in seasonal drought trends in Guangxi， with spring becoming increasingly dry， while other seasons exhibit a trend toward greater moisture. The robustness of the gamma function in precipitation modeling highlights its practicality in drought frequency analysis. Crucially， the Copula-based joint probability analysis identified winter and spring as the most susceptible periods for consecutive droughts， particularly in regions dominated by karst topography. These findings provide scientific basis for adaptive drought management strategies， emphasizing the need to prioritize addressing composite drought risks in regional water resource planning.
[Objective] The urban agglomeration in the middle reaches of Yangtze River Basin is a key region in the “Rise of Central China” strategy. Dense population and high-level industrialization have led to severe contradictions between water supply and demand. By calculating the connection values of regional water resources carrying capacity （WRCC）， this research aims to provide scientific references and empirical support for optimizing regional water resource allocation， promoting sustainable socioeconomic development， and informing policy practices for high-quality water conservancy development within the Yangtze River Economic Belt. [Methods] Based on multi-year statistical data from Hubei， Hunan， and Jiangxi provinces， we applied the fuzzy analytic hierarchy process （FAHP） to calculate indicator weights， set pair analysis （SPA） to evaluate the WRCC by quantifying the connection numbers between the system and carrying grades， and the standard deviational ellipse （SDE） method to analyze the spatial distribution pattern and evolution trajectory of WRCC. [Results] （1） The WRCC of the urban agglomeration in the middle reaches of Yangtze River were increasing， with the average connection number increasing by 0.20； （2） Water allocation and pollution control have been optimized， with connection numbers for water use per GDP unit and urban sewage treatment rate increasing by more than 0.70； （3） Northern cities exhibit lower WRCC， and the SDE centroid has shifted from the east to the northwest， indicating improved spatial balance in WRCC. [Conclusions] Although the WRCC of the study region has been continuously improving， there are still spatial differences. It is necessary to strengthen water resources regulation and control capabilities in the high-consumption industrial areas and high-population density areas in the northern part of the urban agglomeration. The findings provide scientific evidence and decision-making support for water resource optimization and regional coordinated management in the middle Yangtze River region.
[Objective] In 2024， the Xin’anjiang Reservoir experienced the largest inflow flood since its construction due to persistent and intense rainfall during the Meiyu season. The return periods of the maximum 5-day and 7-day inflow volumes both reached the 50-year level. This study conducts a post-event assessment based on the actual forecasting and operation process. [Methods] Multi-source and multi-model quantitative precipitation forecasts were assimilated to analyze the rainfall intensity characteristics of typical historical floods. Representative forecast rainfall time series were optimized under unfavorable， moderate， and favorable conditions with phased temporal distribution， extending forecast lead time while reducing rainfall uncertainty. The Xin’anjiang three-component runoff generation framework was applied to construct a basin-wide flood forecasting model， coupled with reservoir operation rules to form an integrated forecasting-operation modeling scheme. Hourly rolling forecasts were performed based on real-time rainfall and operational information. Considering multiple objectives such as controlling maximum reservoir level， ensuring downstream safety discharge， and managing flood-peak staggering with the mainstream， iterative forward-and-reverse scenario simulations generated 215 forecast scenarios， providing precise support for ten rounds of gate operation decisions. [Results] A comparative assessment of the two major floods in 2024 and 2020 shows that although the 2024 event involved larger rainfall and greater inflow volume， the forecasting was more refined， the regulation was earlier and more proactive， and the peak staggering with the Lan River was more precise. This demonstrates that the integrated forecasting-operation model can effectively support multi-objective risk control， achieving the systemic goal of “zero major disaster and zero casualty”. [Conclusion] The full-process summary highlights that dynamic and accurate forecasting is the key to scientific operation， comparative scenario analysis supports refined decision-making， and the principle of “early action， rapid response， and incremental adjustment” is more conducive to basin-wide flood risk reduction.
[Objective] This study comprehensively investigated the applicability， failure mechanisms， and adaptability characteristics of different bank protection structures to provide theoretical basis and technical support for structural optimization， engineering design， and the development of new ecological revetment technologies under complex river conditions in the middle reaches of Yangtze River. [Methods] Typical bank collapse cases and operational data from engineering practices in the middle reaches of the Yangtze River were collected and analyzed. Representative revetment structures， including riprap， articulated concrete mattresses， gabions， geotextile sand pillows， pebble mattresses， precast concrete blocks， Reno mattresses， geogrid stone mattresses， and vegetative revetments， were systematically investigated. Their mechanical properties， protection mechanisms， failure modes， and improvement measures were summarized by integrating previous physical experiments， numerical simulations， field observations， and engineering applications. A comprehensive evaluation framework accounting for ecological， hydrological and sediment conditions and riverbed evolution processes was established. [Results] Riprap revetment remains the most widely used protection type in the middle reaches of the Yangtze River， while ecological concrete， Reno mattresses， and gabions have been increasingly adopted， reflecting a shift from conventional engineering protection to environmentally oriented designs. Revetment stability is jointly influenced by hydrodynamic conditions， water level fluctuations， riverbed deformation， bank material properties， structural parameters， and construction quality， among which flow scouring is the dominant factor responsible for structural failures. After bank protection works are implemented， channel deformation tends to shift from lateral migration to vertical erosion， resulting in deep-channel encroachment and severe toe scour. Consequently， failures usually initiate from underwater toe protection. Different revetment structures exhibit distinct characteristics. Traditional structures such as riprap and dry masonry show favorable economic performance but relatively poor ecological adaptability， whereas vegetative revetments provide the highest ecological benefits but insufficient resistance to strong hydraulic disturbances. Articulated concrete mattresses， gabions， and Reno mattresses exhibit balanced flexibility and integrity. Geogrid stone mattresses possess strong hydraulic adaptability but relatively high construction and maintenance costs. Comprehensive evaluation demonstrates that ecological concrete revetments perform well in hydraulic， ecological， and economic aspects and exhibit obvious advantages in overall adaptability. [Conclusions] The adaptability of bank protection engineering in the middle reaches of the Yangtze River is characterized by the coupling effects of multiple factors， and structural stability depends not only on the properties of the revetment itself but also on river regime evolution， hydrological conditions， and maintenance practices. For reaches subjected to severe scouring and strong flow attacks， rigid-flexible combined structures with high erosion resistance should be preferentially adopted， whereas ecological revetments with good permeability and environmental compatibility are more suitable for relatively stable reaches. Compared with traditional structures， new ecological revetments integrating structural stability and ecological functions exhibit better comprehensive adaptability， among which ecological concrete shows great development potential. The proposed multi-dimensional evaluation framework enables a systematic comparison of different revetment types and provides a new analytical approach for revetment optimization and bank collapse prevention. Future studies should strengthen the integration of bank protection engineering with river regime prediction and intelligent monitoring technologies to improve the long-term adaptability of revetment systems under continuously changing hydrological and sediment conditions.
[Objective] The northern Guangxi region is a typical karst rocky desertification area in China， where ecological restoration faces severe challenges. Current applied research on bryophyte-based ecological restoration mainly focuses on the Loess Plateau and the karst areas of Guizhou Province. However， studies focusing on the karst area of northern Guangxi Province—characterized by unique eco-geographical conditions （subtropical monsoon climate， favorable hydrothermal conditions， and limestone-dominated bedrock） and severe rocky desertification—remain relatively limited. In particular， research on the environmental adaptability of bryophytes and their functions and effectiveness in localized restoration practices is relatively scarce. [Methods] This study was conducted in the experimental area of Pingfeng Mountain in Qixing District， Guilin City. Three bryophyte species—Barbula unguiculata， Bryum paradoxum， and Hyophila involuta—were selected as the research objects. Through water-holding capacity test （for drought adaptation）， high-temperature resistance test （for surface high temperature adaptation）， acid and alkali resistance test （for soil and acid rain adaptation）， and erosion resistance test （for soil and water conservation assessment）， their environmental adaptability and ecological restoration potential were quantitatively evaluated. [Results] （1） All three bryophyte species exhibited significant water-holding capacity， with H. involuta showing the highest water-holding rate （581.71%）. This capacity enabled this species of bryophytes to effectively store water in the rocky desertification areas of northern Guangxi， contributing to improved soil moisture conditions. However， its high-temperature resistance was weak. After treatment at 60 ℃， some tissues turned black and necrotic. （2） B. unguiculata and B. paradoxum had water-holding rates of 408.88% and 389.82%， respectively， and demonstrated stronger resistance to high temperature， acid and alkali， and erosion， indicating better adaptability to the high-temperature and arid conditions of the rocky desertification areas in northern Guangxi. Among them， B. paradoxum achieved a plant density of 102 plants/cm2 at pH=6， and its crust thickness （2.54 mm） and dry weight （0.311 g/cm2） were significantly higher than those under other treatments. （3） All three bryophyte species exhibited a certain degree of tolerance to different pH conditions. B. paradoxum showed the best growth performance in weakly acidic environments， indicating its good adaptability to acidic soil. （4） Bryophytes effectively reduced soil erosion， especially on steep slopes. B. unguiculata and B. paradoxum exhibited better erosion resistance than H. involuta， making them suitable for rocky desertification areas with large slope gradients to reduce soil loss. At a slope gradient of 30°， the soil erosion amounts of B. unguiculata and B. paradoxum （71.1 g， 67.2 g） decreased by more than 62% compared with bare soil （187.8 g）. [Conclusion] Considering the high water-holding capacity， strong environmental tolerance， and excellent erosion resistance of B. unguiculata and B. paradoxum， they are suitable for rocky desertification areas with large slope gradients to reduce soil loss and hold great potential for ecological restoration in the rocky desertification areas of northern Guangxi. They can not only improve soil moisture conditions but also effectively reduce soil erosion and enhance ecosystem stability， making them suitable as pioneer plants for ecological restoration in rocky desertification areas.
[Objective]This study aims to clarify the laws of sediment deposition and the distribution characteristics of pollutants in the Yangtze River Basin.To fill the research gap regarding the spatio-temporal evolution of flocs and their driving factors along the mainstream from the Three Gorges Reservoir(TGR)Area to the Yangtze River estu-ary,this research systematically explores the variation rules of flocs and identifies their key influencing factors,so as to provide theoretical and practical support for sediment regulation and pollutant research in the basin.[Methods]Combining published literature and in-situ field measurement data of sediment flocculation collected from the TGR Area to the Yangtze River estuary,this paper conducts a comprehensive analysis on the spatio-tempo-ral variation characteristics of sediment flocs.Field observations and statistical analyses are adopted to quantify the particle size,effective density and settling velocity of flocs in different river sections,different seasons and different water depths.Meanwhile,the correlations between floc properties and hydrodynamic conditions,sediment concentra-tion,salinity and organic matter are further discussed to determine the dominant factors affecting floc formation and development.[Results]Obvious flocculation of fine-grained sediment was observed throughout the reach from the TGR Area to the Yangtze River estuary.The floc particle size ranged from 22.0 μm to 58.0 μm in the TGR Area,25.4 μm to 101.4 μm in the middle and lower mainstream of the Yangtze River,and 32.6 μm to 179.0 μm in the Yangtze River estuary.During the flood season,the floc particle size first decreased and then increased along the river from the TGR Area to the estuary.In the dry season,the average floc particle size at each monitoring station from Chenglingji to Datong in the middle and lower mainstream was larger than that in the estuary.Vertical distribu-tion of floc size varied across regions:at Hankou and Hukou stations,floc particle size gradually increased from the water surface to the bottom layer.There was no significant difference in the effective density of flocs among different regions in the flood season.In the dry season,the effective density of flocs in the estuary was notably higher than that in the middle and lower mainstream.In terms of settling velocity,the ranges were 0.13～0.61 mm/s for the TGR Area,0.30～0.68 mm/s for the middle and lower mainstream,and 0.46～2.32 mm/s for the estuary.At Xuli-ujing station,the settling velocity of flocs presented an upward trend from the surface layer to the bottom layer.Weak hydrodynamic conditions,fine primary sediment particles and high sediment concentration were conducive to the formation and growth of flocs along the entire study reach.Salinity exerted a prominent promoting effect on sedi-ment flocculation in the estuary area,while organic matter was a vital factor that intensified flocculation in partial sections of the middle and lower mainstream.[Conclusions]This study quantitatively reveals the spatio-temporal distribution patterns and vertical stratification features of floc particle size,effective density and settling velocity a-long the Yangtze River from the TGR to the estuary,and clarifies the differentiated controlling mechanisms of multi-ple environmental factors on flocculation in different river segments.The findings improve the basic theoretical sys-tem of cohesive sediment movement in large river basins.Practically,the research results offer important references for the prevention and control of waterway,lake and reservoir sedimentation in the Yangtze River Basin,as well as the investigation on distribution,migration and transformation of pollutants.Furthermore,the differentiated influ-ence rules of hydrodynamic force,salinity and organic matter summarized in this paper can provide a new research perspective for follow-up studies on river sediment dynamics and pollutant migration in similar large river systems.
