Termites build nest systems within embankments,damaging the integrity of the soil structure,which is one of the main causes of major engineering accidents such as piping and landslides,seriously threatening the safe operation of China's water conservancy projects.According to statistics,the direct economic losses caused by termite damage in China exceed 2.5 billion yuan annually.Moreover,with climate warming of the climate and the northward shift of the rain belt,the activity range of termites continues to expand,affecting 18 provinces including Jiangsu,Zhejiang,Anhui,and Henan.The prevention and control of termite infestation in embankments is urgent.Ground-penetrating radar technology,with its rapid,non-destructive,and high-resolution imaging capabilities,demonstrates significant advantages in detecting termite nests and has become an important research direction in this field.However,this technology still faces many challenges in practical applications.This paper systematically explains the technical principles of ground-penetrating radar for detecting termite nests,introduces the core detection method of reflection and the basis for equipment selection,and analyzes the structural characteristics(including the main nest,secondary nests,and tunnel network)and geophysical properties(conductivity,dielectric properties,density differences)of termite nests,clarifying their physical property basis for detection.Based on this,the paper comprehensively reviews the research and application progress from four aspects:detection influence mechanisms,data processing and analysis,integrated geophysical exploration techniques,and intelligent detection systems.In terms of detection influence mechanisms,existing studies have revealed the constraining relationship between antenna frequency and detection depth,clarified the rule that high water content leads to intensified signal attenuation,and summarized the differences in signal characteristics between nests and tree roots,cavities,etc.However,understanding of the combined effects of multiple factors remains insufficient,and the fidelity of numerical simulations is limited.In terms of data processing and analysis,techniques such as singular value decomposition have been applied for signal denoising,and indicators such as reflection coefficient and peak frequency can be used for nest identification,but the clata processing still relies on experience and lacks dedicated algorithms and a multi-parameter joint discrimination system.In terms of integrated geophysical exploration technology,the joint application of ground-penetrating radar and the high-density resistivity method has been preliminarily implemented,effectively reducing the misjudgment rates,but standardized technical procedures are still lacking.In terms of intelligent detection systems,deep learning algorithms have achieved classification and recognition of nests and interference objects,but the model generalization remains limited,and the recognition accuracy for deep and small-sized nests needs improvement.In response to the above technical bottlenecks,this paper proposes the following five future research directions and corresponding solutions:first,promote coordinated innovation in detection equipment and methods,develop a composite antennas integrating low-frequency penetration and high-frequency resolution,and enhance detection capability for medium-and shallow-depth nests;second,deepen the research on environmental coupling mechanisms,use CT scanning and 3D printing technologies to construct a high-fidelity physical models of nests,and establish a quantitative relationship between nest parameters and radar spectral characteristics;third,improve data processing and multi-parameter analysis capability by extracting multi-dimensional features such as amplitude,phase and frequency,and establish a dedicated discrimination system for termite nests;fourth,advance integrated geophysical exploration technologies by establishing a three-level detection system"general survey-detailed survey-precise survey",and formulating data fusion and interpretation standards;fifth,develop end-to-end intelligent detection systems by integrating deep learning from data acquisition to risk assessment to achieve automation and intelligence.The coordinated advancement of above research directions is expected to overcome existing technical bottlenecks and provide a theoretical basis and technical reference for achieving precise and efficient detection of termite nests.
Existing water resource system simulation and scheduling models fall short in meeting the demands of"forward and reverse pre-rehearsal"in water resource allocation and management.These demands entail multi-element simulation and forecasting,integrated with the flexible and efficient optimization of complex regulation rules.To address these challenges,this study first reviews the pre-rehearsal requirements for basin-level water resource management.On this basis,it proposes a novel approach that divides the water resource system into core units by twinning key nodes.The study outlines system generalization principles and unit modeling methodologies,and introduces a comprehensive simulation model for basin water resources.This model simulates the dynamic interactions of various elements—available water,inflow,demand,usage,and shortage—across multiple scheduling schemes,capturing the full lifecycle of water resource dynamics within the basin.Further,based on this simulation model,the study develops a method for constructing optimization-based scheduling models adaptable to diverse scheduling goals,thereby providing a framework for efficiently deriving optimal operational rules.The proposed methods are implemented on the digital twin platform developed for the Huanglei River Basin(Shandong Peninsula,China).Validation is carried out through two key case studies:Retrospective Analysis of a Typical Drought Year(2015):The model accurately reproduced historical drought conditions,validating its capability for historical scenario reconstruction("reverse pre-rehearsal").Dynamic Assessment of a Real-time Water Shortage Event(May 2023):The platform dynamically evaluated a live water shortage scenario,demonstrating its utility for real-time awareness and forecasting("forward pre-rehearsal").The findings confirm that the proposed approach enables:Full-process simulation of multi-element water dynamics throughout the basin;highly efficient optimization of scheduling rules for key infrastructure—including surface reservoirs,sluices/dams,and water diversion works—under various goals.Significance and Support Capabilities:The integrated modeling framework offers robust computational support for pre-rehearsal functions in three key domains:(1)Identifying Issues under Routine Schemes:Facilitates early detection and diagnosis during evaluations of conventional scheduling plans.(2)Pre-rehearsing Decision Impacts during Consultations:Supports assessment of anticipated impacts prior to implementing decisions during coordination meetings.(3)Deriving Optimized Schemes for Specific Targets:Enables generation of scientifically grounded,optimized scheduling strategies for defined management goals(e.g.,maximizing supply reliability,minimizing shortages,or preserving ecological flows).In sum,this research delivers a robust,adaptable modeling foundation essential for enhancing the precision and effectiveness of water resource pre-rehearsal within digital twin-based basin management systems.
The intake and drainage system of cooling water is a key component of coastal power plant projects.In recent years,as China's nuclear power development has steadily expanded and shifted toward offshore islands,increasingly complex wave conditions in open sea areas have made wave forces a primary factor affecting the safety of drainage structures.The steel cap-type variable cross-section drainage riser structure is a commonly employed configuration in the drainage engineering of coastal power projects.In this study,a three-dimensional(3D)wave physical model test was conducted to simultaneously measure the inline force,transverse force,and uplift force acting on the steel cap-type variable cross-section drainage riser.The temporal variation of the forces on the variable cross-section drainage riser was analyzed,the effects of water discharge and submergence depth on the forces were examined,and calculation methods for the inline and transverse forces of the variable cross-section drainage riser were developed.The 3D wave physical model test was performed in the wave basin of Nanjing Hydraulic Research Institute,which has dimensions of 50.0 m in length,17.5 m in width,and 1.2 m in depth.Wave-absorbing slopes or plates were installed around the basin to reduce wave reflection.The results of the 3D wave physical model test indicate that under the combined action of waves and water discharge,the forces on the drainage riser display periodic variations,with the force variation period corresponding to the wave period and accompanied by high-frequency fluctuations.These high-frequency fluctuations may be attributed to the turbulent state of the discharged water inside the pipe and the pulsating behavior of water particle motion.By comparing the peak values of the uplift force,inline force,and transverse force on the drainage riser structure,it is found that the uplift force is the largest,followed by the inline force,while the transverse force is slightly smaller than the inline force.The influence of the transverse force on the drainage riser structure cannot be ignored and must be highlighted in future engineering design.Regarding the timing of the peak values of the uplift force,inline force,and transverse force on the steel cap-type variable cross-section drainage riser structure,the peaks of the inline force and transverse force occur simultaneously,indicating no phase difference between them.However,the peak of the uplift force does not coincide with that of the inline force or transverse force,showing a phase difference of approximately π/2 between the uplift force and the inline or transverse forces.Water discharge has almost no effect on the phase relationship among the inline force,transverse force,and uplift force.Water discharge significantly amplifies the uplift force,with an increase ranging from 25%to 75%.The uplift force under the combined action of waves and water discharge exceeds the linear superposition of the force due to waves alone and the force due to water discharge alone.In contrast,water discharge has no significant amplifying effect on the inline force and transverse force of the drainage riser.The relative submergence depth is a key parameter affecting the forces on the drainage riser.The relative maximum inline force and transverse force occur at a relative submergence depth of zero,while the relative maximum uplift force occurs at a relative submergence depth of 0.013.For small-scale variable cross-section drainage riser structures,the Morison equation can be applied for segmented calculation.However,for the force calculation of the perforated structure,a void ratio reduction coefficient should be introduced.By incorporating this coefficient,the wave force on the perforated structure can be calculated with a maximum error of less than 4%.The wave force calculation method for variable cross-section perforated drainage riser structures proposed in this study can serve as a reference and validation for future similar engineering designs and numerical simulations.
The widespread construction of hydropower projects worldwide represents a double-edged sword,providing essential energy while simultaneously causing profound ecological disturbances by erecting impassable barriers that severely fragment riverine habitats.This fragmentation critically disrupts the longitudinal connectivity required by numerous rheophilic fish species to complete their essential life-cycle migrations—such as movements to and from spawning,feeding,and overwintering grounds—inevitably leading to the decline of native riverine fish populations.To mitigate these adverse ecological impacts,the installation of fish passage facilities has become an indispensable component of modern dam design and river restoration strategies.Among these engineering solutions,the fishway(or fish ladder)is particularly prevalent,owing to its relatively simple structure,lower construction cost,and ease of maintenance,making it a primary tool for restoring connectivity.Despite their widespread use and apparent necessity,fishways suffer from a critical deficiency:the lack of rigorous,quantitative assessment of their actual ecological effectiveness.The success of a fishway is seldom measured by the number of fish that successfully pass the barrier,making it difficult to distinguish a functional facility from a mere structural appendage.This difficulty in achieving quantitative evaluation is multifaceted,arising from the substantial variability in fish community structures across different rivers,the markedly diverse migratory behaviors and swimming capabilities of target species,the broad spectrum of existing fishway structural designs(e.g.,vertical-slot and pool-and-weir types),and the highly dynamic hydraulic conditions governed by fluctuating hydropower operational regimes.Consequently,making meaningful cross-system comparisons of passage efficiency remains exceptionally challenging,firmly establishing the development of robust,standardized,and quantifiable metrics as a priority for future ecological engineering research.To address this pressing need and enhance the effectiveness of existing infrastructure,this comprehensive study conducted a detailed investigation into the hydraulic characteristics and attraction efficiency of the Jiacha fishway during its peak migratory season.The research employed a rigorous methodology,beginning with intensive fishery surveys conducted both within the fishway structure and in the immediately downstream river reach.This effort successfully characterized the local fish community,unequivocally identifying the three dominant species of Schizothorax—namely the Schizothorax waltoni,Schizothorax oconnori,and Schizothorax macropogon—as the primary migratory targets.Collectively,these three species accounted for approximately 78.9%of the total fish encountered,underscoring their critical ecological and conservation significance.Building upon this biological foundation,the research proceeded to the critical hydraulic analysis.By synthesizing physiological data on the species'swimming performance—including both prolonged and burst speeds—the suitable flow velocity range permitting successful and non-exhausting upstream movement within the fishway was theoretically determined to be 0.2 to 1.9 m/s.This range is essential for guiding operational limits.Furthermore,to fully characterize the flow dynamics,a detailed two-dimensional(2D)hydrodynamic model was developed specifically for the complex geometry of the fishway's entrance pool and initial channel segment.This model was then employed to perform numerical simulations of the flow field across a comprehensive matrix of operating scenarios,encompassing varied fishway discharge rates in combination with different downstream river water levels(tailwater depths).The key findings from the simulations provided actionable insights for adaptive management.The research conclusively established that downstream river water level is the most influential factor controlling flow velocity at the fishway entrance.Notably,the simulations indicated that during periods of significantly low river levels,the maximum velocity generated at the narrow vertical slot of the entrance often exceeds the burst swimming capacity of the target Schizothorax species.This condition creates an overpowering velocity barrier,or an"impassable jet,"effectively preventing or severely deterring fish from successfully detecting and entering the facility.Based on these findings,the study proposes a refined,adaptive operational strategy essential for optimizing the fishway's performance.To manage this velocity barrier effectively,the operational recommendation is clear:during periods of low downstream water level,the fishway discharge must be systematically reduced.This measure is intended to directly control the water head drop(energy dissipation)at the entrance,thereby ensuring that the resulting flow velocities remain safely within the ecologically determined optimal range of 0.2 to 1.9 m/s.By implementing this dynamic operational adjustment,the Jiacha fishway can substantially minimize hydraulic interference with the natural migratory behavior of the fish.In conclusion,this research not only provides a concrete,scientifically supported optimization plan for the Jiacha fishway—significantly enhancing its ecological effectiveness—but also establishes a robust,quantitative methodology that can be readily transferred and applied to the assessment and adaptive management of fish passage facilities across diverse river systems worldwide.
The Qinghai-Tibet Plateau,a region highly sensitive to global climate change,hosts the headwaters of the Yangtze River.The dynamics of its cryosphere,particularly snow cover,are critical to regional water resources and ecological security.Given the observed high variability of snow cover under climate warming,a quantitative analysis of its response mechanisms to temperature and precipitation anomalies at the sub-basin scale'is essential for accurate hydrological projections.To better reveal the spatial heterogeneity and climate-driven mechanisms of snow cover change in the source area of the Yangtze River,the region was divided into four sub-regions based on sub-basins:Tuotuo River,Dangqu,Chumar River,and other sub-regions,and the variation characteristics of snow cover indices in each sub-region and their relationships with climatic factors were explored.Based on snow cover,temperature,and precipitation data from 1980 to 2020,the spatiotemporal variation characteristics of snow cover in sub-regions were analyzed,using the Mann-Kendall test to detect monotonic trends and the ESMD method to identify nonlinear and non-stationary oscillations in the time series.The relationship between snow cover and climatic factors was analyzed using the partial correlation method to isolate the individual influence of temperature and precipitation by controlling for the other.To move beyond traditional statistical correlations and explore the physical mechanisms,the XGBoost-SHAP model was employed,leveraging its strong predictive performance and the SHAP framework's interpretability to reveal nonlinear thresholds and interaction effects.The results showed that snow cover changes exhibited significant spatial heterogeneity:during the snow accumulation period in the source area of the Yangtze River,average snow depth and snow water equivalent showed an increasing trend in southeastern and high-altitude peripheral areas,while other areas showed a decreasing trend.Snow depth and snow water equivalent increased in high-altitude areas of the Tuotuo River,the margins of Dangqu,the northwest of the Chumar River,and small southeastern parts of other regions,while most other areas generally decreased,and snow cover extent was mostly declining.This spatial pattern can be attributed to the fact that high-altitude and southeastern peripheral regions,with persistently lower temperatures,are less susceptible to warming-induced melt,allowing potential precipitation increases to dominate snow accumulation trends,whereas lower-lying and central areas are more vulnerable to temperature-driven ablation.Correlation analysis showed that snow cover changes in the four sub-regions were not consistent with changes in precipitation and temperature,overall,snow cover was positively correlated with precipitation;snow depth and snow water equivalent were negatively correlated with air temperature in the Tuotuo River and Dangqu,while a few areas in the northwest of the Chumar River and southeastern parts of other regions showed positive correlations,and most other regions showed negative correlations;snow cover extent was mostly negatively correlated with temperature,indicating spatial differences in the impact of climate warming and humidification on snow cover in cold regions.The XGBoost-SHAP model shows that historical precipitation conditions have a greater effect on current snow depth than instantaneous precipitation.Precipitation in low-temperature ranges contributes positively to snow cover,but as temperature rises,this positive contribution gradually weakens until it disappears,with SHAP values approaching 0 when the temperature is at-15℃to-10℃.Thereafter,the interaction between temperature and precipitation leads to snow reduction,and even increased precipitation cannot further increase snow.When the temperature is at-5℃to 0℃,snow change reaches another critical point,beyond which further temperature increases no longer significantly intensify snow reduction.The stronger influence of historical precipitation indicates that snow has a"memory effect",whereby prolonged wet or dry conditions affect subsequent accumulation or melting.The nonlinear relationship between temperature and snow characterizes phase change processes more accurately than linear assumptions,helping to improve traditional hydrological models,enhance snow prediction accuracy,and better assess the impacts of climate change on the cryosphere.
