NetWork
Characteristics Variation and Monitoring Optimization of Total Nitrogen Driven by Rainfall-Runoff
ZHENG Kaifeng;CUI Guotao;HAN Yuguo;DU Xinzhong;【Objective】To address the frequent agricultural non-point source pollution in the Baiyangdian Basin,there is an urgent need to elucidate the migration mechanisms of Total Nitrogen(TN) under rainfall-runoff conditions and to optimize monitoring strategies. 【 Methods 】 This study focuses on a typical agricultural watershed(Beihedian Station), with an urban watershed(Matou Station) serving as a comparative reference, and employs a Random Forest(RF) model coupled with the interpretable SHapley Additive ex Planations(SHAP)method. Using flow rate and readily observable conventional water quality indicators as inputs, we quantitatively analyzed TN response mechanisms and evaluated the impact of different monitoring frequencies on prediction accuracy. 【 Results 】(1) The RF model demonstrated good predictive performance at both sites(with Nash-Sutcliffe Efficiency, NSE = 0.981 and 0.972, respectively). On an annual scale, TN at the Beihedian station showed a synergistic association with electrical conductivity and water temperature, while water temperature was dominant at the Matou station, with both exhibiting distinct seasonal patterns.(2) During rainfall-runoff events, the agricultural area exhibited a runoff-dominated pattern, with a significant positive TN response lagging 48–72 hours after high-flow events. Short-term flow variations produced a mixed effect of scouring and dilution. The urban area displayed a significant shift in association characteristics where water temperature was no longer dominant, instead, TN concentration was positively correlated with electrical conductivity, while high flow primarily induced a dilution effect.(3) Monitoring frequency had a substantial impact on model performance. During rainfall-runoff periods, the accuracy of the daily-scale model decreased significantly compared to the hourly-scale model(NSE reduction > 42%), while the daily-scale model at the Matou station showed limited prediction performance(NSE < 0), whereas accuracy was similar during non-runoff periods(<1% difference). 【Conclusion】 The study elucidated the differentiated response mechanisms of TN under varying land-use types, highlighted the crucial role of high-frequency monitoring in capturing and predicting pollutant dynamics during key events, and provided a scientific foundation for advancing non-point source pollution control, real-time monitoring, and early warning systems.
Construction of a Multispectral Satellite-Based Retrieval Algorithm for Chlorophyll-a Concentration in Typical Lake Water Bodies of Henan Province
ZHANG Qiyue;QIU Shike;DU Jun;ZHU Chunhua;WANG Zheng;ZHANG Yingzhuo;WANG CHAO;DU Wencheng;DENG Yuhao;【Objective】Chlorophyll-a(Chl-a) concentration is a crucial parameter for assessing the degree of eutrophication and water quality status of water bodies. Due to the diverse types of lakes and reservoirs in Henan Province and the significant differences in their optical properties, retrieval models based on a single water body suffer from low accuracy and poor adaptability when applied regionally. Therefore, this study selects four representative reservoirs—Danjiangkou, Xiaolangdi, Luhun, and Baisha—from three major river basins within Henan Province, aiming to construct a robust and highly accurate remote sensing retrieval model for Chl-a concentration with strong regional adaptability.【Methods】This research integrates Sentinel-2 MSI and Landsat-8/9 OLI satellite data with field data from79 sampling points, including water surface spectra and measured Chl-a concentrations. Sensitive spectral bands were identified by applying first-order differentiation, normalization, and spectral equivalence analysis to the spectral data.Subsequently, various statistical models, including single-band, band ratio, and multi-band combination models, were developed. The optimal model was selected through accuracy comparison and systematically evaluated using the coefficient of determination(R2), Mean Relative Error(MRE), and Root Mean Square Error(RMSE).【Results】(1)The band ratio model utilizing the B4(Red) and B2(Blue) bands of Sentinel-2 MSI satellite data demonstrated the best performance, achieving a model R2 of 0.702 4. The Mean Relative Error(MRE) and Root Mean Square Error(RMSE)were 31.74% and 1.85 μg/L, respectively.(2)This model also showed good performance when applied to a long-term time-series analysis of Chl-a concentration in Luhun Reservoir.【Conclusion】The B4/B2 band ratio model based on Sentinel-2 MSI data developed in this study can effectively retrieve Chl-a concentrations in typical lakes and reservoirs of Henan Province. It exhibits good accuracy and regional adaptability, successfully addressing the limited transferability of single-water-body models. This model provides a reliable methodological basis for regional water quality monitoring and eutrophication management.
Analysis of Navigation Conditions and Flood Simulation Study for the Zhoukou-Jieshou Section of the Shaying River
MAO Jikang;LIU Mingxiao;YANG Chao;ZHANG Tong;DAI Hongfei;BIAN Jiang;【Objective】Inland waterway transportation offers low environmental pollution and transportation costs,while interconnected water systems enable access to rivers and seas, presenting promising development prospects. For plain rivers with significant seasonal flow variations, navigability is influenced by hydrological sediment and river engineering. It is essential to investigate factors constraining inland waterway safety and the impact of river floods to enhance navigational capacity and flood control safety.【Methods】The lower reaches of the Shaying River from Zhoukou to Jieshou were selected as a representative study area. Employing a combined approach of vessel-based surveys, riverbed evolution analysis, and numerical sediment transport modeling, this study analyzed the navigational constraints within the section and investigated the impacts of floods and sediment transport on shipping operations.【 Results 】 This section of the river features a meandering course and numerous bridges spanning the waterway.Following river channel improvements and regulation by a Class 2 lock, it currently meets the requirements for a ClassⅢ navigation channel; however, the navigation channels upstream and downstream of bridges located in sharp bends still need to be widened, and the water depth in the transition sections is slightly insufficient. The river embankments meet the design standards for a 20-year flood event, but there are 22 high-risk sections during a 50-year flood event;During the flood season, the clearance under urban bridges allows passage only for 50–100-ton vessels, while other sections of the river can accommodate 1,000-ton vessels; cross-currents exceeding 2.3 m/s in bends have a certain impact on vessel navigation. Simulated flood-induced riverbed scouring and deposition varies by less than 0.35 m, with scouring being the predominant process.【Conclusion】The studied river section meets navigation requirements, but local sections require channel improvements. Concave harbor basins should address backwater siltation, and high floodwater levels may compromise levee safety and bridge navigation conditions. These findings provide technical support for navigation planning and construction in the Shaying River and similar sections, advancing the development of high-grade waterways in the Shaying River and modern water networks in Henan Province.
Research on Propagation Thresholds from Meteorological Drought to Agricultural Drought in the Huaibei Plain
LI Yihao;JU Qin;LIN Hui;JIN Junliang;LIU Cuishan;SHU Zhangkang;LIU Yanli;【Objective】To analyze the propagation law and critical threshold characteristics of meteorological drought to agricultural drought in Huaibei Plain, and provide scientific reference and theoretical support for regional agricultural drought early warning and food security.【Methods】Taking Huaibei plain, an important commodity grain production base in China, as the research area, the standardized precipitation evapotranspiration index(SPEI) and standardized soil moisture index(SSMI) were selected as the identification indicators of meteorological drought and agricultural drought, respectively. The run theory was used to identify the meteorological drought and agricultural drought events from 1976 to 2022, and the propagation threshold from meteorological drought to agricultural drought was quantified based on Copula function.【Results 】（1）The transmission time of meteorological drought to agricultural drought varies greatly in different seasons. The transmission time of drought in spring(2 months) and winter(1.67 months) is shorter, and the transmission time of drought in summer(4.67 months) and autumn(4 months)is longer.(2)The frequency of meteorological drought events is higher than that of agricultural drought, and the duration and intensity of meteorological drought are lower than that of agricultural drought events.(3)The threshold of drought transmission from meteorological drought to agricultural drought increases with the increase of drought grade. The threshold of drought transmission at different sites is different, and the threshold of drought transmission in the middle and north of Huaibei Plain is higher.【Conclusion】The Huaibei Plain is dominated by mild and moderate drought, and the transmission time from meteorological drought to agricultural drought is 2 months. In the future, we can focus on how to comprehensively describe the coupling effect of natural characteristics of agricultural drought and human activities, further improve the characterization and research system of agricultural drought, and provide important data support for the improvement of drought monitoring and early warning system, agricultural disaster prevention and mitigation planning and food security in Huaibei Plain.
Influence of Near-Fault Ground Motion Characteristics on the Dynamic Response of a Twin-Pylon Cable-Stayed Bridge
LI Yue;LI Mingshuo;ZHANG Changyong;WU Xinlan;LI Chong;【Objective】 The unique structural system of cable-stayed bridges leads to complex dynamic responses under seismic actions. Near-fault ground motions, characterized by prominent long-period pulses and significant permanent displacement effects, can induce considerably adverse effects on such flexible structures. To investigate the influence of nearfault ground motion characteristics on the dynamic response of a double-pylon cable-stayed bridge, a finite element model was established in SAP2000 based on a long-span bridge case study. 【Methods】 The nonlinear time history analysis method was employed to systematically examine the effects of ground motion duration, fault-crossing angle, and permanent fault displacement on the internal forces at the pier and tower bases and the displacement at the pier top. 【Results】(1) Ground motion duration significantly influences the seismic response. An increase in duration from 8.5 s to 26.3 s led to maximum increases in the pier base bending moments and shear forces of 287.5% and 266.6%, respectively.(2) The faultcrossing angle has a notable impact on the main tower displacement and pier base internal forces. The longitudinal responses minimize at 90° and peak at 0° and 180°, whereas the transverse responses exhibit an opposite, symmetric distribution pattern about the 90° axis.(3) The relative displacement between the pier and girder generally shows a progressively increasing trend with larger permanent fault displacements. 【Conclusion】 The seismic design of cable-stayed bridges crossing fault zones should involve strengthening the piers and towers for longitudinal shear or transverse bending capacity based on the specific fault-crossing angle. Furthermore, prioritizing seismic isolation devices such as Friction Pendulum Bearings to accommodate permanent fault displacements is essential for systematically enhancing the seismic resilience of the bridges.
Study on Seepage Characteristics of Soil Media under Oil Pollution Conditions
ZHAO Guizhang;ZHOU Jiangtao;SUOKui;ZHANG Chunyan;ANJie;JIAJia;【Objective】The seepage characteristics of soil media serve as the fundamental basis for risk management in petroleum-contaminated sites and groundwater pollution prevention. However, the impact mechanisms of petroleum contamination on permeability properties of various porous media remain unclear, with insufficient systematic quantitative analysis of influencing factors. To address this, this study conducted permeability tests using silty clay and three different particle-size quartz sands under varying oil saturation conditions. The research aims to elucidate the influence patterns of oil contamination on permeability coefficients across media types, quantify the effects of medium composition, particle size distribution, and oil content on seepage characteristics, and provide scientific evidence for pollution site remediation and engineering seepage prevention design.【Methods】Using a variable head soil permeability apparatus, the permeability performance of silty clay and three types of quartz sand with different particle sizes was tested under a gradient of 2.5% to 12.5% volumetric oil content. Parallel experiments were conducted to strictly control measurement accuracy, and linear regression analysis was employed to quantify the impact mechanisms of medium type and oil content on permeability characteristics.【Results】The permeability coefficient of sand is significantly influenced by factors such as soil particle gradation, dry density, porosity, particle size, and mineral composition. Petroleum contamination can lead to substantial changes in permeability coefficients. As the medium particle size decreases, the inhibitory effect of oil contamination on permeability performance becomes markedly stronger. When the oil content reaches 2.5%, the permeability coefficient of silty clay decreases by 40.05% compared to oil-free conditions.Among three types of quartz sand ranked by particle size from smallest to largest, the permeability coefficient reductions are 26.62%,12.24%, and 1.54%, respectively. This difference primarily stems from the tendency of fine-grained media pore structures to be easily blocked by oil contaminants. Linear regression analysis was employed to quantify the impact of medium type and oil content on permeability characteristics.【Conclusion】The study reveals the impact patterns of oil contamination on permeability characteristics across different media, providing critical empirical evidence for understanding oil migration mechanisms in underground environments. These findings can be directly applied to practical fields such as contaminated site risk assessment, groundwater pollution prevention and control, and geotechnical engineering seepage prevention design.
Simulation of Urban Waterlogging Risk Based on Measured and Design Hyetographs
GUO Qingyuan;HOU Jingming;YANG Xiaochun;DU Mengmeng;WANG Tian;LI Donglai;【Objective】To improve the accuracy and applicability of urban waterlogging simulation under climate change, this study investigates the impacts of different rainfall scenarios on surface inundation and urban waterlogging risk.【Methods】A typical urban district in Xi'an was selected as the study area. A rainfall-runoff model was developed based on the GAST-SWMM coupled model to simulate and compare the spatial distribution of inundation, variations in water depth, and differences in risk levels under observed and design hyetographs.【Results】(1) The coupled model showed good reliability in simulating urban hydrodynamic processes, with Nash–Sutcliffe efficiency(NSE) values greater than 0.79 for outlet discharge simulations, providing a sound basis for subsequent waterlogging analysis under both observed and design rainfall events.(2) Under comparable total rainfall amounts,design rainfall produced substantially greater inundation extent, water depth, and high-risk waterlogging area than observed rainfall, and thus more effectively reflected the potential stress imposed by extreme storm events on the drainage system; waterlogging occurrence was influenced by multiple factors.(3) Total event rainfall was not the sole determinant of waterlogging severity. Instead, the severity depended strongly on the temporal distribution of rainfall,such as peak intensity and single-or double-peak patterns, while high-risk hotspots were mainly concentrated in local low-lying areas or zones with insufficient drainage capacity. 【 Conclusion 】 Although design hyetographs are effective for identifying high-risk conditions, they may involve a degree of standard redundancy; observed rainfall better captures actual system responses but is limited in representativeness. Future urban drainage planning and engineering design should therefore optimize the application of design rainfall by accounting for local climatic characteristics and drainage subarea conditions.
Pore Pressure Dissipation in Saturated Soil of Dam Foundation under Dynamic Compaction
ZHOU Fengming;WANG Hongyu;LI Quanling;WANG Shuonan;WANG Zhongfu;【Objective】 The response and dissipation of excess pore water pressure in dam foundation soil induced by dynamic compaction affect the evaluation of reinforcement. Addressing the limitations of existing one-dimensional consolidation theories, this paper proposes a dynamic compaction consolidation model that considers two-dimensional seepage characteristics. 【Methods】 A finite difference grid is constructed by setting virtual boundary nodes, a dynamic coupling algorithm for contact stress is introduced to characterize dynamic compaction. 【Results】 The two-dimensional model effectively captures the accelerating effect of horizontal seepage on pore pressure dissipation. The horizontal influence zone is approximately four times the tamper radius and the vertical influence range is greater than the horizontal zone. Both tamper weight and radius influence the duration of the dynamic compaction cycle and the peak excess pore pressure, while drop height only affects the peak value. 【Conclusion】 The proposed method effectively simulates the distribution and dissipation of excess pore pressure under two-dimensional conditions and reveals the influence of tamper parameters on reinforcement. It is recommended to determining tamper weight and radius first to control the action cycle,then adjusting drop height to regulate reinforcement intensity. This study provides a theoretical basis for optimizing dynamic compaction construction parameters.
Spatiotemporal Variation of Vegetation in the Shaying River Basin and Its Response to Meteorological Factors
GAO Xin;YAN Hui;LI Jingzhong;ZHANG Pengfei;XU Shuna;【Objective】This study aims to analyze vegetation changes and their responses to meteorological factors in the Shaying River Basin, and explore the spatial differentiation laws of regional vegetation coupling with hydrothermal conditions, so as to provide a theoretical basis for vegetation restoration and protection as well as scientific agricultural management in the basin. 【Methods】Based on satellite remote sensing NDVI products, meteorological and land use raster data, harmonic regression and correlation analysis methods were adopted to analyze the spatio-temporal variation characteristics of vegetation in the Shaying River Basin at different scales from 2000 to 2024, and to study the differences in multi-scale responses of basin vegetation to meteorological factors during the growing season and the time lag effect. 【Results】(1) The Shaying River Basin is dominated by crop vegetation, supplemented by shallow hills and mountain vegetation, with a pattern of high in the southwest and central-eastern regions and low in the northwest.(2) Compared with the univariate linear regression method, the harmonic regression method can effectively improve the pass rate of the significance test for trend estimation.(3) The correlation between basin vegetation and temperature is dominated by short-term behavior, supplemented by long-term trend, while the correlation with precipitation is dominated only by short-term behavior.(4) The time lag of watershed vegetation in response to meteorological factors exhibits significant spatial heterogeneity. The time lag for temperature across the entire region ranges from 0 to 1 month. For precipitation, mountainous and hilly areas show a time lag of 0 to 2 months, the central plains have a time lag of 0 to 1 month, and the eastern plains show no time lag. 【Conclusion】In the Shaying River Basin, the vegetation coverage of agricultural and forestry land has increased significantly, and the growth trend is consistent with the rise in temperature. The real-time and lagged responses of vegetation to meteorological factors are closely related to factors such as the basin's topography and geomorphology, agricultural management measures, and vegetation type composition. In the future, field observations will be further combined with multi-source remote sensing data to deeply explore the internal mechanisms of different vegetation types responding to meteorological factors, so as to provide more scientific decision-making basis for precise restoration of the basin ecosystem, sustainable agricultural development and climate change adaptation.
Research Progress on Multi-Source Monitoring Technology and Artificial Intelligence Algorithms for Landslides
AN Ning;ZHANG Zhixun;LI Zhengfa;HUANG Minghao;WANG Zhihao;HOU Rui;【Objective】This study aims to investigate key technologies and methodologies in landslide monitoring and prediction, analyze the efficiency and accuracy of various algorithms in landslide monitoring scenarios, and enhance the identification accuracy and early warning efficiency of landslide disasters, thereby providing a scientific basis for constructing intelligent and systematic landslide disaster prevention and control systems.【Methods】Through literature review, this study comparatively analyzed the application characteristics of surface monitoring technologies including fiber optic sensing technology, microtremor detection technology, Global Navigation Satellite System(GNSS), and Interferometric Synthetic Aperture Radar(InSAR). Meanwhile, the synergistic mechanisms of multi-source heterogeneous monitoring technologies were explored, and the practical value of intelligent algorithms in landslide monitoring was analyzed.【Results】(1) individual landslide monitoring technologies each have distinct advantages and limitations, with issues such as monitoring blind spots or environmental interference;(2) multi-source heterogeneous monitoring technologies can integrate multi-dimensional data from space, air, and ground platforms, compensating for the deficiencies of single technologies and enhancing monitoring comprehensiveness;(3) intelligent algorithms can automatically extract data features and strengthen nonlinear modeling capabilities, effectively improving landslide deformation prediction and disaster identification accuracy, while their integration with multi-source monitoring data can further optimize early warning performance. 【 Conclusion 】 The development of multi-source monitoring technology has driven the transformation of landslide monitoring from traditional point-based to multi-dimensional, continuous and intelligent. This paper clarifies the core value and application limitations of landslide monitoring methods, and clarifies the development direction of multi-technology collaborative integration. In the future, it can be combined with factors such as extreme weather and geological environment evolution to deepen the integrated application of intelligent algorithms and multi-source data, providing technical references and practical guidance for the precise monitoring, early warning and scientific prevention and control of landslide disasters.