The distribution and magnitude of earth pressure behind wall is the key basis for the design of assembled retaining wall. We investigated the displacement patterns and soil pressure distribution of retaining walls under loading conditions via designing and conducting field tests of a new type of assembled concrete retaining wall. Based on the field tests, we established the theoretical computational model of retaining wall with sloping and rough wall backs yet with no cohesive fill. In consideration of factors such as displacement pattern and magnitude, soil arching effect, and interlayer shear stress, we adopted the horizontal layer analysis method to derive an earth pressure formula for retaining wall rotating around the base (RB), defined as an RB displacement mode.Results indicate a sound overall performance of the retaining wall, rigidly rotating around the base. Under the RB mode, soils at the top of the wall reach the active limit state first, progressively followed by lower depths. Limit state will be reached when soil displacement Sc reaches 7 mm at any depth, corresponding to Sc=0.16%H(H is the wall height). The theoretical value closely matches test value, demonstrating the applicability of our derived formula in predicting the distribution and magnitude of earth pressure during the retaining wall’s rotation around the base. Furthermore, as the rotation intensifies, the concavity of the earth pressure distribution curve becomes more pronounced, and the height of the resultant soil pressure force point initially decreases and then recovers. A rotation angle η=0.007 rad is identified as the critical threshold for the retaining wall to reach its active limit state.
Ecological compensation is an economic means to improve, maintain and restore the ecosystem service function, and is also an important measure to implement the scientific outlook on development and promote the coordinated development among regions. In recent years, Hubei Province has made a lot of explorations in establishing a horizontal ecological compensation mechanism with prominent characteristics. This study comprehensively summarizes the construction and practice of basin ecological compensation system in Hubei Province, detailing its evolution, practical applications, and benefits. It also identifies current challenges and proposes solutions, including advancing inter-provincial basin ecological compensation, refining mechanisms for water source areas of the South-North Water Transfer Project, optimizing management coordination, securing funding, and developing robust assessment standards.
The unique geometric boundary characteristics of alluvial bends result in distinct water and sediment transport behaviors and bed evolution dynamics compared to other channel types. To simulate the natural evolution of riverbed scour and siltation in alluvial bends, we employed a natural modeling approach to replicate a representative bend channel in a laboratory flume to investigate the influence of varying water and sediment conditions on the formation and development of bends. The experiments reveal the following: 1) A longer cycle of incoming sediment with lower intensity results in a quicker attainment of dynamic equilibrium in the curved river channel, with a narrower stable channel width. 2) Throughout the formation and development of the bend, morphological changes in the channel are primarily dominated by the prevailing water and sediment conditions. 3) Specifically, within a certain range of variation, shorter cycles of sediment transport, reduced incoming flow rate, and higher sediment concentrations facilitate the development of a more pronounced curvature in the channel. 4) Conversely, higher flow rates causing scouring of shallow areas tend to shape the bend into a wider and shallower cross-section. The adjustments in channel curvature and cross-sectional morphology are predominantly driven by changes in water and sediment transport dynamics, highlighting their significant role in shaping channel morphology.
With the rapid development of the Yangtze River waterway construction, maintaining and managing the existing waterway regulation buildings has become an important task. Beach protection structures along the Yangtze River, despite their commonality, lack comprehensive research on their operational status in China. This study adopts an extension cloud theory that incorporates indicator fuzziness to establish an evaluation model for beach protection service status. Drawing from monitoring data, decades of maintenance experience and relevant specifications, we developed an evaluation index system. Utilizing a combined approach of order relationship and entropy weighting, we comprehensively determined index weights. Through model calculations, the service status level of beach protection can be accurately assessed. Application of the model to evaluate the service status of beach protection at Xinjiu Waterway in the midstream of the Yangtze River yielded consistent results with actual engineering conditions. Verification confirms the model’s accuracy in correctly identifying beach protection service status, guiding daily maintenance and promoting intelligent maintenance practices along the Yangtze River waterway.
The variation of inflow and outflow total phosphorus (TP) loads is a key factor that affects the state of eutrophication in Poyang Lake. Based on the monitoring data of water quality and quantity from 2009 to 2018, the inflow and outflow TP loads around Poyang Lake were calculated, the arithmetic mean and the weighted mean of annual TP concentrations were attained, and their spatio-temporal variations were analyzed. Moreover, the relations of inflow water volume and TP concentration versus inflow TP load were examined by using double accumulation curve method and regression analysis method to reveal the dominant factors for pollution loads. Findings revealed: (1) Compared to arithmetic mean, the weighted mean concentration of TP better reflects the spatio-temporal difference of water quality and volume around Poyang Lake. Annual inflow TP concentration in Raohe River stood at the highest (0.123 mg/L), followed by Xinjiang River (0.091 mg/L), Fuhe River(0.069 mg/L), Ganjiang River (0.063 mg/L), and Xiushui River (0.045 mg/L). (2) Annual inflow TP load totaled 98 514 t, lower than outflow (108 442 t), omitting inputs from waterfront, sediment release, and dry-wet subsidence. (3) Ganjiang River(45 208 t) and Raohe River (19 320 t) were top two contributors to the total inflow TP load among the five rivers, of which Ganjiang River alone accounted for 46%. (4) Significant correlations were found between monthly inflow TP load and inflow water quantity across different water zones, indicating that TP loads are largely influenced by inflow water volume.
A method to identify key factors contributing to water and soil erosion in mountainous railway projects is proposed. Initially, the disciplines prone to causing erosion are determined. Subsequently, the interactive relationship between railway projects and water and soil erosion is analyzed to identify essential elements and construct an indicator system. Furthermore, a multi-layer network model to identify key elements is developed using a complex network model combined with the entropy weighting method, IGAHP (Improved Group Analytic Hierarchy Process) method, and DWNodeRank algorithm. A specific mountainous railway project is examined as a case study. The key elements for mountainous railway project include residue disposal, embankment slope protection, and drainage ditch layout. Key elements for soil and water conservation performance include large-scale temporary soil disturbance and residue disposal.Factors influencing soil and water loss encompass hydrology, surface vegetation, and sedimentation. Emphasizing these key elements in water conservation measures and engineering design is crucial for effectively controlling soil and water erosion and enhancing the ecological environment in mountainous railway projects.
Wetlands possess some of the highest carbon densities among ecosystems. Understanding the dynamics and growth trends of wetland vegetation biomass is crucial for achieving the carbon peaking and carbon neutrality goals. Based on LandSat remote sensing images, we estimated the aboveground vegetation biomass in Poyang Lake wetland during spring and autumn between 2000 and 2020, and examined its development trend in different growing seasons and hotspot areas. The findings revealed that: 1) In recent two decades, aboveground vegetation biomass in spring ranged from 0.85×109 to 4.20×109 g, while in autumn from 0.68×109to 6.69×109 g. Spring biomass remained stable, whereas autumn biomass exhibited a consistent increase over time. 2) Hotspot areas for aboveground vegetation biomass in spring and autumn covered 754.15 km2 and 1 085.49 km2, respectively, representing 21.58% and 30.66% of the total wetland area. 3) Spring and autumn biomass showed a positive correlation with monthly mean temperature. The vegetation in Poyang Lake wetland serves as a robust carbon sink, aiding in the pursuit of carbon peaking and carbon neutrality.
To address the issue of soil erosion on sloping farmland with thin soils in the earth-rocky mountainous area of north China, we established standard runoff plots to investigate the comprehensive soil and water conservation effectiveness of stone-sill reverse-slope terraces. Our findings revealed a significant control effect on water and soil loss: runoff and sediment were reduced by 68.57% and 94.29%, respectively, compared to contour farming. Stone-sill reverse-slope terraces effectively increased soil moisture content and ensured a more uniform distribution of water across the slopes. The total soil moisture content increased by 7.78% compared to contour farming plots. Additionally, the stone-sill reverse-slope terraces markedly enhanced crop yields on sloping farmland; corn yields increased by 12.69% compared to contour farming. Our design and study of the stone-sill reverse-slope terrace contribute to the soil and water conservation methods for thin-soiled sloping farmland in north China’s earth-rocky mountainous areas.
Under global climate warming, frequent extreme dry and wet events threaten crop growth, highlighting the importance of studying their impact on agricultural production for regional food security and water resource management. In this study, the Normalized Difference Vegetation Index (NDVI) was employed to assess rice growth in Hubei Province. Meteorological data spanning 1990 to 2020 from 32 stations and the Standardized Precipitation Evapotranspiration Index (SPEI) were employed to analyze spatial and temporal changes in extreme dry and wet events. Based on the NDVI from 2000 to 2020, the rice growth and its response to extreme dry and wet events were scrutinized. Correlation coefficients were computed to investigate the possible impacts on rice growth. Findings indicate a decline in extreme drought frequency, with 7 events occurring in 1990-1999, 4 in 2000-2009, and only 2 in 2010-2020. Conversely, extreme wet events numbered 5 in 1990-1999, 2 in 2000-2009, and 5 in 2010-2020, expanding in spatial extent without significant frequency change. Notably, the NDVI during the crucial growth period (June-August) exhibited a significant increase (p=0.012), growing at a rate of 0.007 8 per year, indicating improved growth conditions. Extreme dry and wet events in general exerted negative impacts on rice growth, with the coefficient of correlation between NDVI and SPEI reaching 0.418 and -0.358, respectively. To mitigate the impact of extreme dry and wet events, enhancing meteorological monitoring during rice’s critical growth phases is recommended. This proactive measure aims to bolster resilience against droughts and floods, ensuring consistent and robust agricultural production.
A field experiment of water and fertilizer regulation was conducted at the Jiangxi Provincial Irrigation Experiment Center Station from 2020 to 2022 to investigate the impacts of water and fertilizer regulation on rice growth and water demands across varying hydrological conditions. The findings revealed that intermittent irrigation resulted in reduced irrigation (by 20.82%), drainage (by 3.93%), leakage (by 16.68%), and evapotranspiration (by 6.77%) compared to conventional irrigation methods during different hydrological years. Evapotranspiration during the late tillering and jointing-booting stages accounted for 40.2% of the total evapotranspiration throughout the growth period. Rice plant height, tiller number, leaf area index (LAI), and dry matter accumulation exhibited consistent dynamic changes across different hydrological years, all being greater under fertilization treatments compared to non-fertilized conditions, with fertilizer application notably affecting yield. However, in drought years, rice yield under intermittent irrigation was lower than that under submerged irrigation, and plant height, tiller number, LAI, dry matter accumulation, rice yield, and evapotranspiration were all restrained. Average irrigation amounts were higher in drought years compared to wet and normal years, while average drainage, leakage, and plant height were lower. Average evapotranspiration of paddy fields was lower in drought years compared to wet years but higher than in normal years, while tiller number, LAI, dry matter accumulation, and rice yield were lower in drought years compared to normal years but higher than in wet years.
The formation of thrust and drag forces and the fluid dynamics around juvenile fish bodies during burst-and-coast swimming were investigated by using Particle Image Velocimetry (PIV) to capture fluid pressure distribution around juvenile grass carp (Ctenopharyngodon idella). The forces generated by positive and negative fluid pressures were calculated, and the ratio of thrust and drag forces as well as the swimming efficiency were compared across the head, middle, and tail regions of the fish body. Results indicate that during the bursting, thrust force is primarily generated by negative fluid pressure, whereas during coasting, the forward swimming mainly relies on the thrust generated by positive fluid pressure. Throughout the burst-and-coast cycle, the tail region contributes significantly to thrust generation (48.81% of total thrust), exhibiting the highest average swimming efficiency (77.28%±16.87%). Conversely, the middle region of juvenile grass carp experiences the highest drag force (67.82% of total drag).
Particle motion was observed using high-speed imaging technology to investigate the fluid forces acting on particles in flowing water. The drag coefficient and lift coefficient were obtained by solving the mechanical equations for saltating spheres and natural sediments. Experimental results manifest that: 1) The average drag coefficient for particles with nonuniform velocity in flowing water, particles with nonuniform velocity in stilling water, and particles with uniform velocity in stilling water all decrease with the increase of Reynolds number. The difference between these coefficients diminishes when the particle-fluid relative velocity approaches the settling velocity. When the relative velocity equals the settling velocity, the coefficients are approximately equal. 2) Shape has a greater influence on lift coefficient than on drag coefficient; natural sediments exhibit larger average drag coefficient compared to spheres, whereas spheres demonstrate higher average lift coefficient than natural sediments. The equations for drag coefficient and lift coefficient of spheres and natural sediments are established, and the calculated values agree well with measured data.
To investigate the evolution of fractures in compacted loess under drying-wetting cycles, we conducted crack tests by varying the dry density and drying-wetting path using a self-developed device, and captured the surface crack patterns of soil samples.Furthermore, we quantitatively analyzed the soil cracks using PCAS software for morphological parameters and obtained strain fields via DIC (Digital Image Correlation) method. Our findings revealed three distinct stages in the development of compacted loess cracks with increasing drying-wetting cycles: initial slow growth, subsequent rapid expansion, and stabilization. Crack development intensity was influenced by both dry density and drying-wetting cycle paths. Higher dry densities hindered crack propagation, while larger amplitude of drying-wetting and lower moisture thresholds cultivated crack development. Additionally, the first principal strain along the crack’s central line exhibited a linear decrease with distance from the crack initiation point, indicating diminishing soil compression effects near the crack tip and adjacent blocks. These results provide insights into understanding crack evolution in compacted loess.
Dilatancy is an important mechanical issue in the study on strength and deformation of coarse granular materials. It is governed by microscopic factors such as particle arrangement and inter-particle pressure, and hence is affected by macroscopic variables including relative density and stress state. In this article, research progresses in the dilatancy of coarse granular materials under complex stress conditions are reviewed from the aspects of mechanical properties, strength criteria, critical state, and dilatancy behavior. Future trends in research are outlined as follows: 1) Laboratory investigation via large-scale true triaxial tests and theoretical analysis on the dilatancy of coarse granular material would drive advancements in constitutive modeling. 2) Study on the stress-deformation facilitates the dilatancy equations under conventional triaxial condition developing into that under complex stress condition, thereby unifying strength and deformation issues. 3) Coupling stress state and void ratio with state parameters offers a systematic approach to assessing the compactness state of soils and their dilatancy behavior, potentially reducing the reliance on multiple material parameters. The integration of state parameters and stress paths indicates a more scientific and systematic approach in the research on the mechanical properties of coarse granular materials.
Hydraulic fracturing easily occurs in rock masses under high-pressure packer tests, involving dual water conduction via pores and cracks. This interaction between the seepage and stress fields results in spatial-temporal variations in rock mass permeability parameters. For accurate permeability parameter inversion during high-pressure packer tests, it is recommended to consider the change in permeability coefficient before and after fracture occurrence under hydro-mechanical coupling of dual media. A hydro-mechanical coupling numerical model is employed to simulate high-pressure packer tests, and parameter inversion is conducted using on-site test data to calculate limestone permeability across different pressure stages. Key findings include: before hydraulic fracturing, as injection pressure increases, permeability and pore water pressure sees distinct boundaries among different pressure stages, with inverted permeability closely aligning with specified formula values. After hydraulic fracturing, rock mass permeability increases by about 2 times, accompanied by sharp declines in matrix pore medium permeability and flow rates.
The strength of root-soil complex is significantly influenced by the morphology and spatial distribution of the root system. However, current studies have been limited to shear tests of root-soil complexes containing herbaceous roots and conventional indoor direct-shear tests. To investigate the impacts of root morphology and spatial distribution of perennial shrubs on root reinforcement, shearing experiments were conducted on in situ root-soil complex using a large-scale direct-shear apparatus (diameter 400 mm). The root morphological parameters (root area ratio RAR, root length density, root bulk density, and root surface area density), dilatancy and shear strength of the root-soil complex were measured. The distribution characteristics of root system along soil depth, the dilatancy of root-soil complex, and the correlation between root morphological parameters and shear strength were examined. Findings indicate that the root system exacerbates the dilatancy of the root-soil complex. Among the four evaluated root morphological parameters, RAR and root surface area density contribute the most to the shear strength. While Wu’s model effectively reflects the enhancement effect of root system on soil strength, it occasionally overestimates or underestimates the strength. The findings in the present research is conducive to promoting the application of root system in soil reinforcement.
The study of hydraulic characteristics in unsaturated soils is crucial for analyzing seepage and deformation of loess during engineering activities. This research focuses on loess from the southern suburbs of Xi’an City. The filter paper method and saturated salt solution method were employed to measure soil-water characteristic curves under three dry density conditions with varying degrees of wetness. The Childs & Collis-George model was used to predict unsaturated permeability coefficient, examining the impacts of dry density and wetting/drying cycles on these characteristics. Results indicate that unsaturated permeability coefficient increased with volumetric moisture content and decreased with matric suction, dropping significantly by 4-5 orders of magnitude within the 0-5 MPa range. Due to bottleneck effects and moisture-reduction-induced shrinkage, the variation in permeability coefficient during wetting stages was smaller compared to drying stages. Furthermore, with dry density increasing from 1.719 g/cm3 to 1.834 g/cm3, permeability coefficient decreased by two orders of magnitude. The unsaturated permeability coefficient of compacted loess varied by a factor of up to 3-4 between wetting and drying phases.
The construction of deep excavations inevitably disturbs surrounding strata, particularly causing excessive surface settlement which can significantly threaten nearby buildings. It is essential to study surface settlement in excavations. To enhance current research on characterizing functions and indicators for surface settlement, we employ the skewed distribution function to describe surface settlement, and propose a set of indicator system applicable to excavations by scrutinizing the characterizing indicators of the settlement curves. On this basis, we put forward a skewed distribution function for predicting surface settlement. The applicability and effectiveness of the skewed distribution function as well as the indicator system and the prediction function in describing excavation-induced surface settlement are validated through analyzing two practical engineering projects. Findings demonstrate the rationality of the skewed distribution function in describing excavation-induced surface settlement. The characterizing indicator system, with explicit and implicit indicators at its core, takes into consideration the settlement curve envelope area, the maximum surface settlement and its location. Regression and prediction using the skewed distribution function demonstrate a close alignment between predicted settlement curves and actual data, confirming the function's rationality and applicability for describing surface settlement in excavations.
To enhance the erosion resistance of cement-solidified soil and facilitate its application in underwater structural protection, an investigation was conducted into the erosion resistance of cement-solidified soil through the addition of cement and a liquid curing agent to sand and clay. Erosion resistance tests were performed using the erosion function apparatus (EFA). The curing mechanisms was analyzed and the impact of curing agent and curing duration on the erosion resistance of cement-solidified soil was examined. The findings indicated that the strength of cement-solidified soil increased with longer curing times, with clay reaching its rapid strength development stage earlier than sand. Curing agent notably augmented the critical shear stress of the soil and significantly reduced erosion rates, thereby enhancing erosion resistance. Moreover, the rate of increase in critical shear stress gradually diminished with longer curing times until reaching a critical maximum value. Based on the observed variations in critical shear stress, a predictive model for the critical shear stress of cement-solidified soil was proposed. Experimental data comparisons validated the efficacy of the model in predicting critical shear stress variations with curing time.
A unique square-bottom pedestal has been adopted in the non-overflow sections of a gravity dam in southwest China. Given the region’s susceptibility to severe earthquakes, the influence of the pedestal on the failure mode and the ultimate seismic resistance capacity of the gravity dam is investigated. An acoustic-solid-coupled damage simulation method is proposed with the acoustic element simulating the reservoir water and the elasto-plastic damage model reflecting the nonlinear characteristics of concrete.The feasibility of this method in predicting structural failure modes is verified by analyzing the Koyna gravity dam under the Koyna earthquake. Comparative analyses between the pedestal section and conventional section reveal similar failure areas in the upstream slope, dam heel, and downstream face. Specific impacts of the pedestal include: new failure zones in the pedestal section; effective reduction of depth and area of the failure zone at dam heel; and generation of two development paths in the downstream failure area of pedestal section. According to the criteria of failure area breakthrough, the ultimate ground motion peak acceleration is 0.50-0.55g for conventional section and 0.55-0.60g for the pedestal section. In conclusion, the bottom pedestal enhances the ultimate seismic resistance capacity of the non-overflow dam section.
River simulation technology plays a crucial role in watershed digital twin. However, current precise modelling of physical rivers to virtual watershed faces several deficiencies. To address such deficiencies, a 3D hydrodynamic model was developed in this study based on terrain measurements, remote sensing images,hydrological data, and water surface line calculated by hydrological model. The UE5 engine and Fluid Flux plug-in rendering was employed in the model. Blueprints were reconstructed and compiled, data assets were trained and coordinate system disparities were reconciled to finally achieve high fidelity simulation of the water flow of Hudu River. Calibration results indicate that the present model accurately reflects real-world conditions with small errors. The simulation model depicts the water flow dynamics during different periods, the relative height difference between water level and embankment, the artificial flood diversion blasting, and underwater scenarios. Parameter adjustments enable comparative analysis of different scenarios, offering visualization support for flood control decision-making.
Under the influence of climate change, the water area of Poyang Lake exhibits seasonal fluctuations. To elucidate these changes comprehensively, we propose a water information extraction approach that integrates multi-temporal radar images and optical data. Leveraging Sentinel-1A radar images and Sentinel-2 optical images as our research datasets, we initiated a sequence of data preprocessing steps on the remote sensing image set. Employing the Sentinel-1 dual polarized water index (SDWI) and the improved normalized differential water index (MNDWI), we delineated the lake’s boundary and computed its water area using radar and optical data. The precision, timing, and change detection of our water extraction results were evaluated meticulously. Analyzing the lake area’s change trends aims to furnish scientific insights for disaster management and Poyang Lake’s conservation. Our findings revealed that: 1)The water bodies of Poyang Lake extracted from radar and optical remote sensing data were mostly congruent. Radar image extraction outperformed optical image extraction when delineating farmlands, small water bodies, and cloud-covered areas, suggesting radar images’ superiority in capturing comprehensive water information. 2)The average water area of Poyang Lake during normal, wet, and dry seasons is 3 686.49, 4 077.73, and 2 612.81 km2, respectively, with the wet season’s water volume being 1.56 times that of the dry season. 3)Time-series water extraction results from radar images exhibited strong consistency with water level variation data from Xingzi Station, Duchang Station, Hukou Station, and Kangshan Station, yielding Pearson correlation coefficients of 0.89, 0.87, 0.90, and 0.81, respectively.
The new-generation information technology confronts several challenges in its application to smart water conservancy, particularly in the depth of application and in water conservancy business models. This paper explores key technologies such as baseplate database and intelligent simulation models, applying these innovations to meet the practical needs of the Digital Twin Jiangya and Zaoshi project. We first examined the use of a three-dimensional monitoring system for constructing high-precision baseplate database, employing techniques such as satellite remote sensing and unmanned aerial vehicle (UAV) oblique photogrammetry. Next, we investigated digital water conservancy models for flood evolution and engineering safety through virtual simulations. Finally, we expounded the application of these key technologies in the Jiangya and Zaoshi project, demonstrating that the developed digital twin water conservancy model and platform effectively support intelligent management and decision-making.
In the context of global climate change, the Changjiang River basin has suffered from multiple severe high temperatures and drought disasters. Drought resistance management in the basin is faced with such bottleneck problems as low efficiency of drought monitoring and warning, inadequate accuracy of drought prediction and early-warning, and insufficient ability to deduce drought plans. To address these issues, digital transformation has become exigent. In line with the comprehensive requirements of smart water conservancy and digital twin technology, a digital twin platform for drought prevention has been constructed by utilizing WebGL and GIS to meet the operational management requirements of drought resistance and disaster mitigation in the Changjiang River Basin, aligning with the demands of the “forecast, early warning, preview, and contingency planning” principles. Key technologies have been developed, including remote sensing drought monitoring and evaluation, dynamic loading of drought-specific models, early-warning of water levels exceeding drought limit, and visualization of drought reduction plans. Consequently, the business application covering the full chain of “forecast, early warning, preview, and contingency planning” has been achieved. This has effectively improved the intelligent and refined level of drought resistance management in the Changjiang River Basin, providing technical support for drought prevention and disaster reduction in the basin.
Addressing the challenge that existing visualization methods struggle to dynamically present the deduction process of three-dimensional(3D) water quality, this study explores an integration strategy combining water quality calculation results with digital twin scenarios. We propose a 3D water quality deduction and simulation method to achieve intuitive, precise, smooth, and dynamic presentations of 3D water quality deduction process within digital twin environments. We applied the model to simulate the standard-exceeding total phosphorus in the Danjiangkou Reservoir in autumn 2021 as a case study, and integrated the simulation results into the digital twin environment to simulate the transfer and diffusion of organic pollutants. Application outcomes demonstrate that compared to traditional two-dimensional displays, our proposed method offers more intuitive and richer information content as well as dynamic representation of hierarchical water quality indicators within digital twin scenarios.
The digital twin technology has been developing rapidly in the water resources field. This paper outlines how hydrodynamic models underpin the digital twin of water resources, and proposes the requirements for advancing hydrodynamic models and suggests corresponding model solutions. Key techniques for enhancing the capabilities of typical models in digital twins of water resources, such as 1D free surface and/or pressurized hydrodynamic models, are introduced. Techniques for improving the computational efficiency of 2D hydrodynamic models in large areas with high resolution are also described. Specifically, the mathematical challenges, key techniques and applications of recently developed models inclusive of coupled hydrodynamics and sediment transport models for the breaching processes of dams and dikes as well as hydrodynamic models for flash floods aiming at optimizing early warning systems are expounded. Finally, directions for further development of hydrodynamic models are proposed, including the need for higher-dimensional models and coupled models involving different dimensions, models for multi-phase processes, further investigation into evaluation and real-time modification techniques for hydrodynamic modeling, development of integrated models combining physically-based and data-driven approaches, and the establishment of mutual connections and feedback models for virtual modeling and physical reality control.
