中国岩溶

Applied research on integrated "Air-Ground-Cave" surveying of the World's Supercave, the Miao Chamber Cavern：A case study of the Ziyun Miao Chamber

ZHOU Wenlong, SONG Xiaoqing, LUO Ji, LI Huaibing, YANG Jiafang, ZHAO Shiqi, MO Guifen

, Available online , doi: 10.11932/karst2026y001

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As a world-class rare super cavern, the Ziyun Miao Chamber presents extraordinary challenges for traditional surveying techniques due to its vast spatial dimensions, intricate multi-level cave structures, and complex geological formations. To address the limitations of early exploration efforts, this study develops and implements an innovative integrated "air-ground-cave" surveying technology system. By synergizing advanced methodologies, including drone-based aerial photogrammetry, terrestrial laser scanning (TLS), and simultaneous localization and mapping (SLAM) technology, a comprehensive spatial data acquisition and multi-source data fusion framework was established. This system enabled, for the first time, high-precision, full-coverage 3D surveying and seamless registration of both surface karst landforms and multi-tiered underground cave networks within the Miao Chamber.The research outcomes, derived from technical summarization and extensive data analysis, yield the following key findings: (1) Data Correction and Spatial Referencing: Building upon the foundational 2014 Sino-British joint scientific survey, this study employed SLAM technology to rectify point cloud deviations from prior measurements of the Miao Chamber. By integrating real-time kinematic (RTK) positioning with the Qianxun Continuously Operating Reference Station (CORS) service, an absolute spatial reference framework was established for the entire cave system. This advancement not only enhances measurement accuracy but also provides reliable geo-spatial data for re-examining the developmental history and evolutionary mechanisms of the Miao Chamber. (2) Spatial Visualization and Geomorphological Analysis: Utilizing the fused and registered 3D spatial datasets, point cloud slicing analysis tools were applied to generate intuitive visualizations of the positional relationships between surface karst features and multi-level subterranean caves. These analyses reveal critical spatial correlations and composite geomorphological patterns, offering new insights into the formation processes of this world-class super cavern. The findings highlight the co-evolutionary dynamics between the Miao Chamber and the overlying karst landscape, driven by long-term hydrological and tectonic interactions. (3) Technological Advancements in Cave Surveying: The integrated "air-ground-cave" surveying approach effectively overcomes the constraints of traditional techniques in exploring giant cave systems. By combining aerial, terrestrial, and underground data acquisition methods, this system achieves highly accurate 3D reconstructions of surface topography and subterranean structures. The methodology not only enhances surveying accuarcy but also sets a benchmark for future explorations of similar large-scale karst environments. (4) Structural Controls and Hydrological Pathways: Geological investigations demonstrate that the development of the Miao Chamber is predominantly governed by four sets of hierarchically organized joints with varying orientations. Current structural assessments indicate that the cave system remains in a relatively stable state. Paleo-hydrological evidence suggests that ancient surface flows were divided into at least two distinct pathways (Zhongdong and Xiaochuandong). Modern surface runoff continues to recharge the underground system through karst conduits and fractures, sustaining the dynamic interplay between surface and subsurface processes. (5) Paradigm for Future Cave Exploration: The successful application of the integrated "air-ground-cave" surveying technology system in the Ziyun Miao Chamber establishes a pioneering framework for 3D spatial measurements of giant subterranean spaces and complex geological structures. This methodology not only enhances scientific understanding of karst systems but also provides a replicable model for global cave exploration, particularly in regions with similar geomorphological and hydrological conditions.In conclusion, this study advances the field of karst geomorphology by delivering a high-precision, multi-dimensional surveying solution for super caves. The findings contribute to a deeper comprehension of cave formation mechanisms, structural stability, and hydrological connectivity, while the developed techniques offer transformative potential for future research and exploration in subterranean environments worldwide.

Karst development characteristics and influencing factors in the Yangtze River- Pearl River Watershed in Huaxi, Guiyang

MA Jianfei, FU Changchang, ZHANG Chunchao, LI Xiangquan, GAO Ming, ZHANG Lei, WANG Zhenxing

, Available online , doi: 10.11932/karst2026y024

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The degree of karst development is a critical factor influencing geological hazard risks in karst terrains. Conducting detailed hydrogeological surveys to characterize karst features and their development intensity forms the essential basis for risk zonation and mitigation strategies related to geological disasters, engineering water inrush, mineral resource extraction, and foundation stability. In watershed areas, karst aquifers are generally considered to exhibit weak water abundance due to topographic and hydrogeological constraints, and are thus commonly classified as low-risk zones in geological safety assessments. However, investigations at a project site in the Huaxi District of Guiyang, located within the Yangtze River-Pearl River watershed divide, revealed locally well-developed karst features. To explain this anomaly and elucidate the controlling factors of karst development, this study integrated field surveys and high-density electrical resistivity tomography with multi-scale analyses of karst structures observed in drill cores. Techniques including optical image-based 3D modeling and computed tomography scanning were employed. The influencing factors were subsequently discussed based on the derived structural characteristics.Field survey results indicate that the study area is situated on a karst plateau, featuring landforms such as peak forest valleys and peak cluster depressions. High-density electrical resistivity tomography profiles identified two sets of karst development zones: a vertical karst development zone, extending downward below 1045 m elevation, and a sub-horizontal karst development zone, located between 1045 m and 1055 m elevation, which dips gently north-to-south across a 135 m profile length. A borehole drilled within the vertical development zone revealed dissolution features spanning seven orders of magnitude in size (10-⁶ to 10⁰ m). Macro-scale (10-¹ to 10⁰ m) karst features show vertical zonation, divisible into a karst cave zone, a fracture-dissolution zone, and a deep fracture zone. Meso-scale (10-³ to 10-¹ m) analysis highlights the heterogeneity of the karst medium, indicating enhanced development of dissolution pores at depths of 9-12 m, 20-25 m, 34-40 m, and 47-49 m. At the micro scale (10-⁶ to 10-³ m), with the increase of buried depth, the number of solution cracks decreases, the number of cracks increases, and the extension degree increases. The morphological characterization parameters such as void radius, throat length and throat radius show that the parameter characteristics of 69 m depth are significantly different from those of 9-68 m. Based on this, the difference between the characteristics of fractures and dissolved pores is distinguished, and the buried depth of karst development bottom boundary is determined to be 69 m.Topography and geological structure are identified as the primary controls on intense karst development in the study area. First, the relatively gentle terrain slope favors rainfall infiltration over rapid surface runoff. Second, groundwater within the 15-27 m depth range, controlled by the local discharge base level, remains relatively active, fostering the formation of the sub-horizontal karst zone. Third, the combined influence of mild topographic and hydraulic gradients prevents rapid groundwater runoff, allowing sufficient time for water-rock interaction. Fourth, structural fractures within a fault zone extend to greater depths, enhancing vertical permeability and facilitating karstification down to 69 m. In contrast, outside the fault zone, where a well-developed fracture-dissolution zone is absent, the lower boundary of karst development is only approximately 27 m.The innovation of this study lies in its integrated, multi-scale (macro-, meso-, micro-) and multi-dimensional (surface, borehole, core) characterization of karst structures using a suite of technical methods. This approach effectively reveals the patterns of karst development and explores its controlling factors across different scales. The findings provide methodological insights and technical support for engineering geology and geological hazard assessment in karst regions.

Landslide susceptibility assessment of Yanhe County based on CF-SVM model

MO Si, JIANG Panhe

, Available online , doi: 10.11932/karst2026y025

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Yanhe County is situated within the transitional slope zone connecting the Guizhou Plateau, the Xiangxi Hilly Region, and the Sichuan Basin. The overall topography of the county exhibits a pattern of higher elevations in the northwest and southeast, with a lower central area. The landform is characterized by a distinct, narrow, and elongated belt that is wider in the south and tapers towards the north. This region features highly undulating terrain, intense geomorphological incision, complex geological structures, and consequently, a fragile geological environment. Under the combined influence of both endogenic and exogenic geological processes, the area exhibits a relatively high degree of landslide development, making geological disaster risks particularly prominent.To establish a scientifically sound and rational landslide susceptibility evaluation system, this study employed the Pearson correlation coefficient, Tolerance (TOL), and Variance Inflation Factor (VIF) to conduct correlation and multicollinearity analyses on candidate influencing factors. Through this process, nine key evaluation factors were ultimately selected: slope gradient, slope aspect, elevation, topographic relief, engineering rock group, distance to river system, distance to roads, distance to geological structures, and vegetation coverage. To address the issue of spatial bias inherent in the selection of non-landslide samples, negative samples were randomly distributed in areas outside predefined buffers surrounding known landslide points. This methodology effectively enhanced the spatial representativeness and overall rationality of the sample selection.Based on raster data units, and leveraging the respective strengths of different models, a combined approach was adopted. The Certainty Factor (CF) model offers advantages in quantitative analysis and indicator weight calculation, while the Support Vector Machine (SVM) model demonstrates excellent performance in handling non-linear relationships and complex pattern recognition. By integrating historical landslide distribution data, the nine selected evaluation factors, and the optimized non-landslide samples, a comprehensive training dataset suitable for the combined machine learning model was constructed. The study area was subsequently classified into four susceptibility grades—Low, Medium, High, and Very High—using the Natural Breaks classification method. The accuracy of the model predictions was determined based on the number of known landslide points falling within the Medium, High, and Very High susceptibility zones.The results revealed that the CF, SVM, and combined CF-SVM models successfully predicted 383, 389, and 392 landslide points, respectively. These figures account for 97.70%, 99.50%, and 99.74% of the total recorded landslides. The corresponding areal proportions designated as high-risk zones (encompassing High and Very High susceptibility classes) were 76.34%, 69.95%, and 60.96%, respectively. A key observation is that as the areal extent of the high-risk classification progressively decreased across the models, the concentration of landslide points within these zones significantly increased. This trend demonstrates a enhanced spatial aggregation of predicted hazard, indicating an improvement in the model's precision in pinpointing the most vulnerable areas.An analysis of the landslide susceptibility zoning results from the various models shows that the Very High and High susceptibility areas predominantly exhibit a belt-like distribution pattern. This pattern shows a significant spatial coupling relationship with the major surface water systems and geological structures. These high-risk zones are primarily concentrated in the mountainous areas near Heping Street, Ketian Town, and Xinjing Town, as well as the eastern sides of Heishui Town and Qitan Town. These regions are typically characterized by low mountain valley topography, well-developed geological structures, dense river networks, intensive transportation infrastructure, a high degree of urbanization, and frequent human activities—all factors contributing to the high frequency of landslide occurrences.In contrast, the Medium and Low susceptibility areas are mainly distributed in patchy and scattered patterns, though they are present in all townships. The Medium susceptibility zone generally forms a peripheral belt around the Very High and High susceptibility cores. These medium and low susceptibility areas are primarily located in mid-mountain valleys and high-altitude mountainous regions. Their geological environmental conditions are complex, but they feature lower population density, relatively scarce transportation facilities, lower levels of urbanization, and moderate to weak intensity of human engineering activities. While landslide hazards are still present in these areas, their developmental degree is relatively limited.The high-risk zones (combined High and Very High) identified by the CF-SVM model covered 90.3% of the historical landslide points. This distribution shows a high degree of consistency with the spatial pattern of actual recorded geological disaster hazards. Conversely, the proportion of disaster points located within the Low susceptibility area was merely 0.26%. This stark contrast further verifies the model's excellent discriminatory capability and predictive accuracy.The confusion matrix results for the three models indicate that the CF-SVM model performed the best, achieving a True Negative Rate of 91.45% and a True Positive Rate of 83.05%. The CF model, in comparison, demonstrated relatively weaker performance, with a True Negative Rate of 85.47% and a True Positive Rate of 68.64%. Overall, all models exhibited high classification performance in terms of both True Negative and True Positive Rates, reflecting their strong ability to discriminate unseen samples. However, when dealing with the complex and heterogeneous distribution of landslide and non-landslide samples, significant differences emerged between the models. Among them, the CF-SVM model demonstrated superior learning capability and produced the most effective classification results.The Receiver Operating Characteristic (ROC) curve analysis showed that the CF-SVM model achieved an Area Under the Curve (AUC) value of 0.889. This was significantly higher than the AUC values of the individually applied SVM model (0.871) and the CF model (0.790). This result indicates that the integrated CF-SVM model possesses a better goodness-of-fit and stronger generalization ability. It can more accurately delineate the spatial susceptibility characteristics of landslide geological disasters in Yanhe County. Therefore, this approach provides a scientific basis and reliable technical support for regional geological disaster risk assessment, monitoring and early warning systems, and prevention and control decision-making.

Spatial and temporal distribution characteristics of geological disasters and research on disaster−causing factors in Dali Prefecture

BI Yalong, CHEN An, JIANG Yuebin, YANG Yingdong, WEI Lei

, Available online , doi: 10.11932/karst2026y023

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T Dali Bai Autonomous Prefecture is located in the central-western part of Yunnan Province, spanning the four major river systems of the Jinsha River, Lancang River, Nujiang River, and Honghe River. Geologically situated at the junction of the Yangtze Craton and the Lanping-Simao Fold Belt, the region exhibits intense tectonic activity, well-developed faults, and complex lithology. Controlled by the Hengduan Mountains, the terrain slopes from northwest to southeast. The western region comprises the Yunling high-mountain gorge zone, exhibiting tectonic-eroded high-mountain topography. The eastern part features broad, gentle mountain basins dominated by tectonic-eroded medium-mountain and hilly landscapes. The central area is characterized by alluvial-lacustrine and fluvial-alluvial deposits. Under the combined influence of tectonics and geomorphology, geological hazards in this region exhibit diverse types, high frequency and intensity, significant spatial differentiation, and complex temporal variations.To systematically reveal the spatiotemporal distribution patterns and dominant factors of geological hazards in Dali Prefecture, this study established a three-dimensional analytical framework: “spatiotemporal pattern identification—quantification of evolutionary trends—analysis of hazard mechanisms.” Integrated methods including GIS spatial analysis (kernel density estimation and temporal overlay), Mann−Kendall trend tests, spatiotemporal hotspot evolution analysis, and the Maximum Entropy (MaxEnt) species distribution model were employed to quantitatively identify and analyze the spatiotemporal patterns, evolution, and triggering mechanisms of geological hazards.Results indicate: Landslides exhibit approximately 5-year periodic peaks, while debris flows follow roughly 10-year cycles. 98.6% of events occur between June and October, peaking in August, with disaster frequency significantly positively correlated with monthly precipitation. Spatially, a “dense north, sparse south” pattern emerged, with high-risk zones primarily clustered in Heqing, Yunlong, and Eryuan counties.Further analysis indicates that the spatiotemporal evolution of geological hazards in Dali Prefecture generally follows a “fluctuation-gradual change” pattern, with a potential trend inflection point around 2016. Spatial hotspots show an overall strengthening trend, migrating westward from Heqing to Eryuan and then to Yunlong. The MaxEnt model identifies topography and rainfall as primary controlling factors, with slope, elevation, annual precipitation, and distance from rivers as the four key contributing factors, collectively accounting for 63.8% of the total variation. Key thresholds for high-sensitivity zones are: a slope of about 10°; an elevation range of 1200—2000 m; an annual precipitation of 800—1600 mm; a proximity to rivers of less than 200 m; and an NDVI between 0.6 and 0.8. Fault zones, areas with weak rock formations, and high-mountain canyon regions constitute highly sensitive zones for geological hazards.These findings provide decision-making support for optimizing territorial spatial planning, developing geological hazard prevention strategies, and deploying emergency response resources in Dali Prefecture.

Study on the nonlinear response characteristics of conduit-fracture flow to rainfall in a karst small watershed

LUO Mengyao, WANG Fa, CHEN Hongsong, ZHANG Jun, LIAN Jinjiao

, Available online , doi: 10.11932/karst2026y003

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The intensification of global climate change has led to a widespread increase in both the frequency and magnitude of extreme precipitation events. This trend poses a serious threat to the karst regions of southwestern China, which are characterized by ecological fragility and hydrological complexity. Karst aquifers are highly developed with conduit and fracture networks that act as preferential flow paths during rainfall events. These pathways allow groundwater and surface water to rapidly converge into streams, substantially shortening runoff response times and amplifying flood peaks. As a result, the increasing occurrence of flood hazards has greatly complicated local water resources management and disaster mitigation efforts. However, the quantitative contributions of conduit flow and fracture flow to total runoff, as well as their activation mechanisms, remain poorly understood. This knowledge gap primarily arises from the concealed and highly heterogeneous nature of subsurface karst structures, which are difficult to characterize using conventional hydrological monitoring techniques. Consequently, existing hydrological models often underestimate peak discharges during extreme events in karst catchments.To address these challenges, we deployed a high-frequency electrical conductivity (EC) monitoring system with a 5-minute sampling interval at the outlet of a typical dolomite peak-cluster depression catchment in Huanjiang County, Guangxi Zhuang Autonomous Region, China. Such high temporal resolution is essential for tracking rapid hydrochemical dynamics during intense rainfall events. We applied a conductivity frequency distributions (CFDs) approach to decompose streamflow into different runoff components. This method is based on the principle that water flowing along different pathways-conduits, fractures, and matrix pores-exhibits distinct EC signatures due to differences in transport pathways and residence times. CFDs histograms were fitted using a mixture of multivariate normal distributions and decomposed into conduit flow (low EC, rapid transport), fracture flow (intermediate EC), and matrix flow (high EC, slow percolation). The proportional contributions of each component were then quantified. In addition, a boosted regression tree (BRT) model was used to assess the relative importance of 56 potential controlling factors and to identify the dominant rainfall characteristics regulating conduit and fracture flow contributions. Piecewise regression analysis (PRA) was further employed to construct nonlinear relationships between key rainfall variables and the contributions of conduit and fracture flow, allowing the identification of critical thresholds for flow activation and maximum runoff capacity.The results show that although conduit flow and fracture flow contribute only 4.1% and 6.6% to annual runoff, respectively, their importance increases dramatically during individual storm events. During extreme rainfall, the daily peak contribution of conduit flow reached up to 39.2%, while fracture flow peaked at 61.8%. The BRT model identified daily rainfall amount as the primary controlling factor, with relative importance exceeding 76% for both flow components. In contrast, antecedent soil moisture and other variables played a minor role, each contributing less than 10%. These findings confirm the strongly event-driven nature of rapid runoff generation in this karst system, characterized by short response times and weak hydrological memory. Single rainfall events act as the dominant trigger, with limited dependence on antecedent wetness. The PRA results revealed a clear sigmoidal (“S-shaped”) response of conduit and fracture flow contributions to increasing daily rainfall. Two distinct rainfall thresholds were identified for each flow component. The initial activation thresholds were 11 mm for fracture flow and 12 mm for conduit flow. The saturation thresholds were 32.5 mm and 49 mm, respectively. Below the activation threshold, the contributions of conduit and fracture flow to streamflow were negligible. Beyond the saturation threshold, their contributions stabilized and no longer increased with rainfall. This plateau indicates that the transport capacities of the subsurface networks had reached their maximum, constrained by physical structure and hydraulic conductivity. The higher saturation threshold of conduit flow suggests a greater storage and transmission capacity compared to fracture networks. Once saturation is reached, additional runoff must be generated through alternative mechanisms, such as matrix flow or surface runoff, reflecting a combined infiltration-excess and saturation-excess runoff generation process in karst systems.By integrating high-resolution EC monitoring with statistical modeling, this study quantitatively elucidates the threshold behavior of rapid flow in karst aquifers. It overcomes the limitations of traditional tracer experiments and recession curve analyses, which often fail to capture transient hydrological responses in highly heterogeneous environments. The identification of dual rainfall thresholds provides a robust scientific basis for improving the parameterization of rapid flow components in both conceptual and numerical hydrological models. Incorporating such threshold mechanisms and structural constraints is essential for enhancing flood forecasting and peak discharge prediction in karst regions.In summary, studies of karst hydrological processes must move beyond linear and continuous representations of rainfall−runoff relationships. This study quantitatively demonstrates the nonlinear dynamics and dual-threshold responses of conduit and fracture flow to rainfall, thereby advancing the mechanistic understanding of preferential flow in the karst critical zone. Future research should focus on testing the applicability of these thresholds across different lithologies, spatial scales, and climatic conditions. Such efforts will provide crucial support for sustainable water resources planning and flood risk management in karst regions.

Construction of a karst monitoring data aggregation system based on the Internet of Things

YANG Chen, BI Benteng

, Available online , doi: 10.11932/karst2026y011

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As a vital component of the Earth's Critical Zone, the karst critical zone exhibits highly sensitive hydrological, geochemical, and biological processes in response to environmental changes. Effective monitoring is therefore crucial for addressing key resource and environmental challenges in karst regions, including soil erosion, drought and flood disasters, and ecological conservation. However, existing monitoring stations, often constructed during different periods with varying observation indicators, suffer from incompatible equipment, transmission protocols, and data platforms. This significantly impedes data timeliness, unified management, and data sharing.To systematically resolve these issues, this paper designs and implements a standardized data convergence system based on Internet of Things (IoT) technology and cloud-native architecture. Firstly, at the device access layer, the system utilizes the MQTT protocol as its core while maintaining compatibility with standard protocols like ModBus. It also provides a flexible and extensible SDK, enabling efficient and cost-effective integration of both existing and new heterogeneous monitoring devices, thereby achieving unified access and management of multi-protocol equipment. Secondly, at the system architecture level, it employs advanced microservices design and containerization technology. Core functions are modularized through RESTful APIs, and services are containerized and automatically orchestrated using Docker and Kubernetes. This cloud-native architecture endows the system with high elasticity, scalability, and reliability, enabling self-healing, elastic scaling, and load balancing. This effectively supports the processing of massive concurrent data streams and accommodates future business growth. Regarding data storage, the system innovatively adopts a hybrid multi-type database architecture. It integrates Redis, Apache Doris, MongoDB, and MinIO to handle different scenario-scaching, real-time analysis, document storage, and object storage, respectively-ensuring highly efficient and stable data read/write operations. Furthermore, the system implements three data snapshot collection rules-immediate, change-based, and scheduled-and supports the import of historical data, guaranteeing the continuity and integrity of monitoring data. Security is embedded throughout the device end, transmission layer, and platform layer, with comprehensive data protection ensured through mechanisms such as pre-authorization, TLS encryption, and access control.The system concretely implements a three-tier application structure: a management console, a large monitoring screen, and a mobile APP. The management console handles device management, intelligent operational maintenance, and system configuration; the large screen provides a global data overview based on map visualization; the mobile terminal enables users to access device status and data anytime, anywhere. Application examples demonstrate that the system has been successfully deployed, integrating numerous monitoring stations from several national and provincial field observation and research stations, including those in Pingguo, Guangxi, and Guilin. It has accumulated over 2 million data entries, achieved a station data completeness rate of 99.94%, and operates stably. Performance tests indicate that the system maintains millisecond-level response times under simulated scenarios of millions of concurrent device connections and queries on massive historical datasets, demonstrating excellent processing capability and stability.In conclusion, this system effectively addresses the long-standing challenges of equipment heterogeneity and data silos in karst monitoring. It establishes a unified, efficient, and reliable data convergence and management platform, providing a solid data foundation for scientific research, ecological protection, and disaster early warning in karst areas. Future work will focus on the deep integration of artificial intelligence algorithms and professional models to further enhance the system's intelligence in data quality control, intelligent early warning, and analytical evaluation.

Study on pressure distribution characteristics of typical conduit-fracture medium in southwest karst area

YUE Zhisheng, QIN Xujian, QIN Jianwen

, Available online , doi: 10.11932/karst2026y022

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The southwest karst region of China is a unique area characterized by abundant groundwater resources and a fragile ecological environment. Its typical conduit-fracture dual aquifer system exhibits significant heterogeneity and anisotropy, which directly result in complex and variable groundwater recharge, flow, and discharge processes. These characteristics present numerous challenges to engineering activities such as regional groundwater development and utilization, mining, transportation, and foundation construction. When undertaking engineering projects in such areas, failure to accurately understand the flow dynamics and pressure distribution of groundwater within conduit-fracture media can lead to serious issues, including water inrush, mud outbursts, water resource wastage, groundwater contamination, and ecological damage.Therefore, systematically elucidating the hydraulic properties of these media is a critical prerequisite for addressing core hydrogeological problems in karst regions.This study focuses on the typical conduit-fracture medium aquifer in the southwestern karst region. Addressing the limitations of existing research—which primarily emphasizes macro-scale hydrological processes and lacks quantitative analysis of micro-scale pressure distribution and interpretation of water-conducting dominance relationships—this paper employs a combined approach of theoretical generalization and laboratory experiments. Complex factors influencing groundwater pressure distribution, such as fracture development angle, flow velocity within water-conducting channels, and groundwater supply mode, are systematically distilled into three adjustable key parameters: fracture aperture (three levels: 1 cm, 3 cm, 5 cm), flow rate (using pipe diameters of φ16 mm, φ21 mm, and φ26 mm combined with overflow heights of +3 cm, +5 cm, and +10 cm), and the angle between fracture and conduit (three levels: 60°, 70°, and 90°). An independently developed three-dimensional visual indoor test system is utilized, integrating four modules: water supply, fracture, conduit, and monitoring & data acquisition. This system offers precise parameter control and intuitive visualization of hydraulic phenomena. High-frequency, high-precision data on pressure and flow velocity within the conduit-fracture medium are collected using pressure sensors, paperless recorders, and flowmeters. Each experimental condition is repeated three times to ensure the reliability of the results.The experimental results demonstrate a significant "water wall" effect in the conduit-fracture medium: groundwater accumulating on the fracture surface forms a water-blocking "water wall" that effectively reduces flow velocity in both upstream and downstream conduits. The thickness of this "water wall" is positively correlated with the fracture aperture. When the fracture aperture increases from 1 cm to 5 cm, the pressure at the conduit mouth rises by approximately 3.1% compared to the baseline, accompanied by a more pronounced reduction in flow velocity. Based on differences in groundwater recharge sources, this paper innovatively introduces the concepts of "conduit dominance" and "fracture dominance. dominance refers to scenarios where water flow at the water gushing point or tracer receiving point primarily originates from the upstream conduit medium, with minimal contribution from the fracture medium. Conversely, fracture dominance describes cases where water flow mainly depends on recharge from the connected fracture medium. This classification offers a new theoretical framework for identifying groundwater recharge sources in karst areas. Additionally, the pressure distribution on the fracture surface exhibits a symmetrical "funnel" shape, with the funnel center aligned with the conduit mouth. A distinct influence radius exists around the conduit mouth, which first decreases and then increases as the fracture aperture grows (27 cm at 1 cm aperture, 24 cm at 3 cm, and expanding again at 5 cm). This influence radius is not significantly affected by changes in flow velocity. Quantitative analysis clarifies the relative importance of three factors affecting pressure distribution: fracture aperture > angle between conduit and fracture > flow rate. Specifically, the pressure at the conduit mouth when the angle is 90° is 4.4% lower than at 60°, and pressure decreases by approximately 1.9% as the flow rate increases from 228.3 mL/s to 874.0 mL/s.This study addresses the gap in systematic research on the micro-pressure distribution within conduit-fracture media in the southwest karst region. Its findings not only enhance the understanding of groundwater flow mechanisms but also provide valuable experimental data and theoretical support for engineering applications, including the identification of groundwater runoff channels, precise development and protection of groundwater resources, and the prevention and control of mine water inrush disasters in karst areas. This research holds significant practical importance for ensuring regional engineering safety and promoting sustainable ecological development.

Hydrogeochemistry and Carbon Cycling in the Lijiang River Basin during the Dry Season: Coupling Control of Geological Background and Biological Processes

LU Ruting, HUANG Fen, HU Xiaonong, ZHANG Tao, Hou Yuxia, HUANG Weiyi

, Available online , doi: 10.11932/karst2026y012

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To systematically elucidate the intricate carbon cycling processes and identify their primary controlling factors within karst river systems during the hydrologically stable dry season, this empirical study selected the Lijiang River Basin as a representative research domain. We established a monitoring network comprising four distinct cross-sections characterized by a progressively increasing spatial proportion of karst geomorphology: a non-karst area (HJ_n), a karst contact area (CT_min), a half karst area (JC_mid), and a typical karst area (XL_max). Routine monthly hydrochemical sampling was initially conducted during the dry season. Furthermore, to explicitly prevent rainfall-induced surface runoff from masking the metabolic activity signals of aquatic organisms, a specific environmental window was deliberately targeted. A continuous, completely rainless period from November 12 to 24, 2024, was selected, ensuring the absolute absence of precipitation for both the two weeks preceding the monitoring and during the sampling phase itself. Utilizing this optimal temporal window, high-frequency continuous diel monitoring was executed across the four cross-sections at strictly two-hour intervals over a consecutive 48-hour span. We systematically analyzed a comprehensive suite of variables, including general hydrochemical parameters (specifically water temperature, dissolved oxygen, electrical conductivity, and total dissolved solids), major cations and anions, dissolved inorganic carbon (DIC), and its stable carbon isotopic composition (δ¹³C_DIC). Additionally, the calcite saturation index (SIc), the partial pressure of carbon dioxide (P_CO2) and Net Ecosystem Productivity (NEP) were calculated to thoroughly explore the coupled controlling effects of the underlying geological background and aquatic biological processes.The comprehensive results demonstrate three major findings: (1) Based on the projection of hydrochemical data onto a Piper trilinear diagram, the dominant dissolved cation across all evaluated river cross-sections is exclusively calcium (Ca²⁺), while the dominant dissolved anion is universally bicarbonate (${\rm{HCO}}_3^{-}$). Other constituent ions account for comparatively marginal proportions; consequently, the fundamental hydrochemical facies characterizing all four monitoring sites are uniformly classified as a typical HCO₃-Ca water type. Concurrently, the ionic composition of the water bodies is overwhelmingly governed by natural rock weathering mechanisms. Specifically, the overarching hydrochemistry of the studied watershed is jointly controlled by the concurrent weathering and dissolution processes of both silicate and carbonate rocks. Moreover, the aqueous concentrations of Ca²⁺, ${\rm{HCO}}_3^{-}$, magnesium ions (Mg²⁺), and the aggregate metric of Total Dissolved Solids (TDS) systematically increased in direct conjunction with the expanding areal proportion of karst landscapes. The specific solute concentrations documented in the non-karst cross-section were significantly and consistently lower than those recorded in the karst cross-sections, definitively constituting a well-defined spatial pattern of aquatic hydrochemistry. (2) The vast majority of evaluated parameters exhibited exceptionally strong diel variation patterns. In the karst areas, intense photosynthetic activities executed by aquatic biological communities during the daytime generated profound geochemical shifts, resulting in significant increases in dissolved oxygen (DO), pH, and SIc. Simultaneously, this process caused a precipitous decline in the aqueous concentrations of ${\rm{HCO}}_3^{-}$, Ca²⁺ and P_CO2, while inducing a pronounced positive shift in the δ¹³C_DIC signature. Conversely, during the nighttime hours, biological respiration became the dominant metabolic process, dictating completely inverse geochemical trajectories: DO, pH, and SIc decreased, whereas the concentrations of ${\rm{HCO}}_3^{-}$, Ca²⁺ and P_CO2 rebounded substantially, accompanied by a distinct negative shift in the δ¹³C_DIC values. In stark contrast, the amplitude of diel variations in the non-karst area (HJ_n) was notably smaller than that observed in the karst regions. Although parameters such as DO, pH, and δ¹³C_DIC in the non-karst area also exhibited corresponding diurnal fluctuations in response to aquatic biological metabolism, the underlying drivers were fundamentally inconsistent with the dry-season karst areas, where variations were primarily governed by robust aquatic photosynthesis. Instead, the dynamics in the non-karst area were simultaneously constrained by physical degassing processes typical of the dry season, the strict limitation imposed on photosynthesis due to an insufficient supply of inorganic carbon sources, and the characteristically low geochemical buffering capacity of mountainous headwater streams. Under these compounding conditions, the observed diel variations were far less pronounced. (3) The quantitative results derived from the NEP calculations revealed that the cross-sections located within the karst areas consistently functioned as autotrophic ecosystems throughout the monitoring period, definitively indicated by positive NEP values (NEP > 0). This robust autotrophy signifies that biological carbon fixation operates as an exceptionally active carbon sink process within karst regions. In direct contrast, the non-karst area persistently exhibited a heterotrophic state characterized by negative NEP values (NEP < 0), effectively acting as a net carbon source. This spatial dichotomy effectively substantiates the "fertilization effect" exerted by naturally high concentrations of ${\rm{HCO}}_3^{-}$on the photosynthetic capabilities of aquatic organisms in karst areas. Essentially, the karst geological background directly enhances the operational efficiency of the biological carbon pump by consistently providing an abundant supply of inorganic carbon sources, although this process is also dynamically modulated by the local spatial richness of aquatic biological communities. In summary, this empirical investigation profoundly elucidates the coupled mechanistic framework governing the carbon cycle in karst rivers: the underlying geological background fundamentally dictates the capacity for carbon source supply, whereas dynamic biological metabolic processes directly drive the ultimate transformation of that carbon.

Vulnerability assessment of karst water in cloud floating city based on PLEIK-V model

WU Chengye, WANG Xiaoming, YANG Dongsheng, HUANG Junlong

, Available online , doi: 10.11932/karst2026y019

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This study addresses the critical issue of the dynamic nature deficiency inherent in existing models for assessing the vulnerability of karst groundwater systems. Karst aquifers are particularly susceptible to contamination due to their unique hydrogeological characteristics, such as rapid recharge, high flow velocities, and limited natural attenuation capacity. Traditional assessment methods often fail to capture the temporal and spatial variability of these systems, leading to inaccurate vulnerability evaluations. To bridge this research gap, the city of Yunfu in Guangdong Province, China, was selected as a representative study area due to its typical karst hydrogeological features and the widespread development of karst landforms. Yunfu's geological setting, characterized by soluble carbonate rocks and complex aquifer systems, provides an ideal natural laboratory for testing and refining vulnerability assessment methodologies.Based on an in-depth analysis of the regional geological background, hydrogeological conditions, and anthropogenic influences, this study employs Geographic Information System (GIS) technology to develop a novel assessment framework—the PLEIK-V system. This model integrates six key indicators to systematically evaluate the vulnerability of karst groundwater: the protective cap (P), which refers to the overlying layers that shield the aquifer from surface contaminants; land type (L), encompassing land use and land cover patterns that influence contaminant loading; the intensity of surface karst zone development (E), which affects direct recharge and pollutant transport; recharge intensity (I), representing the amount and rate of water infiltrating the aquifer; the degree of karst network development (K), reflecting the internal drainage and storage characteristics; and the average annual rate of decline in groundwater level (V), a dynamic indicator that captures the stress and recovery potential of the groundwater system. By incorporating this dynamic component, the PLEIK-V model addresses a significant limitation of conventional static assessment tools.The study demonstrates that the PLEIK-V model exhibits robust applicability in the field of karst water vulnerability assessment. The empirical analysis reveals that the vulnerability of karst groundwater in Yunfu presents a distinct "three-class" spatial pattern. Specifically, approximately 24.1% of the study area is classified as low vulnerability, 51.5% as medium vulnerability, and 24.4% as high vulnerability. This zoning reflects the heterogeneous nature of the karst aquifer system and the varying degrees of exposure to contamination risks. High vulnerability areas are typically associated with thin protective covers, intense karst development, and significant groundwater level fluctuations, making them particularly prone to pollution from surface sources.To validate the scientificity and reliability of the PLEIK-V assessment model, a correlation analysis was conducted between the vulnerability index and two key groundwater quality parameters: overall groundwater quality types and nitrate concentrations. Nitrate is a common indicator of anthropogenic contamination from agricultural and urban activities. The results show a significant positive correlation, with a correlation coefficient of 0.892 and a coefficient of determination (R²) of 0.797. This strong statistical relationship confirms that areas identified as highly vulnerable indeed exhibit poorer water quality and higher nitrate levels, thereby substantiating the predictive capability of the model.Based on the vulnerability assessment results and considering the distinctive characteristics of special geological units within the karst system, the vulnerability zoning of karst groundwater in Yunfu has been further optimized. This refined zoning provides a more nuanced understanding of the spatial distribution of contamination risks, accounting for local geological anomalies and hydrogeological complexities. The outcomes of this study offer a valuable environmental hydrogeological basis for the prevention and control of urban karst groundwater pollution. By identifying priority areas for protection and guiding land use planning, the PLEIK-V model can support sustainable groundwater management and inform policy decisions aimed at safeguarding water resources in karst regions. Future research could focus on integrating additional dynamic factors, such as climate change impacts and long-term monitoring data, to further enhance the model's predictive accuracy and applicability in diverse karst environments worldwide.

Disaster-causing process of steep columnar karst mountain collapse induced by mine mining -Taking Guizhou Yiziyan Collapse as an Example

DENG Zhinan, YANG Liang, JIANG Xingyuan, WU Di, YANG Yi, WANG Changhui

, Available online , doi: 10.11932/karst2026y020

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To reveal the collapse disaster mechanism of steep columnar karst mountains under mining disturbance, this study taking a typical“hard-top, soft-bottom; steep-top, gentle-bottom” collapse body at Yiziyan, Jinsha County, Guizhou Province as the research object, systematically analyzes the entire deformation and failure process of the slope under multiple mining activities. It is based on field geological surveys and laboratory rock mechanics tests, conducting bottom friction physical simulation experiments, combined with PhotoInfor digital imaging system for quantitative monitoring of slope deformation and displacement. The results indicate that slope deformation caused by mining disturbance presents a four evolution stages pattern. During the initial unloading and joint development phase, unloading rebound occurs in the roof above the goaf, forming joint zones and collapse bands. The displacement areas shows a crescent-shaped distribution and has a relatively minimal impact on the slope surface. At the overburden overall subsidence and slope surface response stage, the overall collapse of roof causes significant subsidence of the surface slope, the deformation of overburden continues to intensify and extends to the slope crest area. In the fissure expansion and stress redistribution stage, mining induces secondary roof unloading rebound, causing the joint zones and collapse bands to develop further upward, promoting this reactivates and widens existing dissolution fissures at the slope crest. During shear failure and overturning collapse stage, the compressive shear stresses at the bottom of the rock mass is highly concentrated to form a continuous shear failure plane. The slope surface experiences intense compressive shear failure, with rear-edge tensile fractures progressively worsening. Ultimately, the steep inclined columnar unstable rock masses collapses toward the open face. The evolution of the shear strain field indicates that the maximum shear strain during mining process gradually increases from an initial value of 1.2 to 1.7. The stress concentration zone expands from within the collapse zone to the vicinity of the slope top fractures and the vertically overlapping regions of multiple mining voids. This study has confirmed that progressive deformation and stress redistribution of the overburden caused by multiple mining activities are the key mechanisms controlling the instability of columnar rock masses. The bottom friction combined with digital image measurement technology can effectively reveal the four-stage evolution pattern-“initial unloading- overburden overall subsidence - fissure expansion -shear overturning”-under mining influence, clarifying the deformation characteristics and mechanical response mechanisms at each stage.

Utilization of inorganic carbon by aquatic plants and its regulation on water-air interface CO₂ exchange in karst surface aquatic systems

ZHANG Xinyao, XIAO Qiong, CHEN Fajia, SUN Pingan, GUO Yongli, ZHANG Ning, LI Jianhong, LIU Yifei, ZHOU Tiantong, TIAN Huanjie, Matej Blatnik, YUAN Daoxian

, Available online , doi: 10.11932/karst2026y010

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Geological carbon sinks have gained increasing attention as a critical component of the missing carbon sinks. In karst regions, the weathering of carbonate minerals converts atmospheric CO₂ into dissolved ${\rm{HCO}}_3^{-}$, which is then transported via rivers to the ocean, ultimately forming a stable carbon sink. Recent studies have shown that aquatic plants in karst regions have considerable carbon sink potential. Through photosynthesis, these plants absorb dissolved inorganic carbon (DIC), thereby contributing to organic carbon sinks. Approximately 28.6% of global CO₂ is assimilated via photosynthesis by aquatic organisms within the hydrological cycle. Aquatic plants regulate the carbonate equilibrium in aquatic environments during photosynthesis and respiration, leading to periodic fluctuations in water chemistry and ion concentrations. Studies indicate that aquatic plants in karst underground rivers utilize DIC most efficiently during the summer and exhibit diurnal variation patterns. Although previous research has highlighted the carbon sink potential of terrestrial and aquatic plants in karst regions, detailed monitoring of the carbon sink processes in aquatic plants within karst surface waters and quantitative studies on the biological carbon pump effect remain limited.This study aims to address this research gap by focusing on two common aquatic plants in karst regions, Ceratophyllum and Potamogeton and conducting high resolution monitoring at an aquatic biological experimental site. The objective is to elucidate the regulatory mechanisms of karst aquatic systems in the carbon cycle from a biogeochemical perspective. First, data on water temperature (T), electrical conductivity (Ec), pH, dissolved oxygen (DO), and partial pressure of carbon dioxide (pCO₂) in the water were screened and processed in suit. Simultaneously, net primary productivity (NPP), CO₂ exchange flux at the water−air interface (FCO₂), and inorganic carbon flux at the cross−section (F) were systematically quantified, with corresponding charts generated for visual analysis. Second, evaluate the seasonal and diurnal variations in karst surface aquatic systems based on these indicators and analyze their underlying causes. Finally, systematically analyze the differences in seasonal NPP dynamics across aquatic systems driven by precipitation, exploring the biological carbon pump mechanisms and seasonal variations through which different aquatic plants enhance the carbon sink functions of karst water bodies via dual mechanisms.The conclusions are as follows: aquatic plants play a crucial role in regulating carbon cycling processes and carbon sink intensity, as demonstrated by studies conducted at the aquatic biological experimental site supplied by the karst river in Liuzhou, Guangxi (characterized by a typical HCO₃−Ca²⁺ type). Seasonal and diurnal dynamics were observed at all locations (SK01—SK04): concentrations of pCO₂, EC, and ${\rm{HCO}}_3^{-}$ followed seasonal patterns, with higher values in autumn and winter, and lower values in spring and summer. Stronger circadian cycles were observed in SK03 and SK04, with higher daytime pH and DO, lower night−time pH, and a more pronounced “daytime decrease, night−time increase” pattern for pCO₂, Ec, and ${\rm{HCO}}_3^{-}$. Three synergistic processes enable aquatic plants to enhance aquatic carbon sink: (1) NPP to directly fix organic carbon, with annual carbon sink increments of 0.08 kg·C and 0.17 kg·C in aquatic systems SK03 and SK04, respectively, compared to SK02; (2) Reducing gaseous inorganic carbon loss by inhibiting aquatic CO₂ degassing; (3) Enhancing the stability of dissolved inorganic carbon and promoting ${\rm{HCO}}_3^{-}$ precipitation to increase inorganic carbon sink. Compared to the blank pond (SK02), the Ceratophyllum pond (SK03) and the Potamogeton pond (SK04) achieved net carbon sink increments of 19.61 kg·C and 6.01 kg·C in 2023, respectively. The ${\rm{HCO}}_3^{-}$ carbon fixation rates were 1.46 kg C·m⁻²·y⁻¹ and 0.45 kg C·m⁻²·y⁻¹, respectively. The fundamental carbon sink mechanism of “promoting fixation and suppressing release” comprises these three pathways. Different aquatic plants exhibit distinct carbon fixation patterns: Ceratophyllum, through its “photosynthesis-calcification coupling”mechanism, enhances NPP while efficiently driving inorganic carbon precipitation and strongly suppressing CO₂ emissions. Potamogeton's carbon fixation relies more on rhizosphere metabolic activity, exhibiting relatively weaker overall carbon sink capacity and emission regulation intensity.The above analysis indicates that the metabolic processes of aquatic plants in karst water significantly influence the carbon cycle. Future research should delve into the carbon sink capacity and mechanisms of different aquatic plants under varying environmental conditions, as well as their impact on long−term changes in the carbon cycle. Additionally, studies should focus on the interactions between aquatic plants and other ecological factors in karst water to further elucidate how biogeochemical processes affect carbon sink effects. This study analyzed aquatic plant carbon sink solely within the karst river of a typical karst peak cluster depression area in southwest China. The findings may exhibit regional limitations, and the research depth has certain constraints. The discovery that aquatic plants can simultaneously achieve “enhanced sink” and “emission reduction” in karst water, yielding dual environmental benefits, not only highlights the pivotal role of photosynthetic carbon sink by aquatic plants in karst carbon sink research, but also provides a robust theoretical basis for artificial carbon sink enhancement.

Study on seepage leakage evaluation model of pumped storage power station in karst area

FAN Zhujun, LIU Zhiwei, WANG Jiyang, ZHANG Yong, HUANG Qibo, LI Tengfang

, Available online , doi: 10.11932/karst2026y008

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So far, there is still no good method to quantitatively predict and evaluate the seepage volume of karst reservoirs.The reason is that the factors influencing the leakage of karst reservoirs are numerous and very complex, such as being affected by the lithology of the strata, the degree of structural development, the type of groundwater, the development of karst, hydrodynamic conditions, and anti-seepage treatment measures, etc. Most of these factors are not completely quantitative, and even random and ambiguous, making it difficult to describe them with deterministic models .On the other hand, the various factors influencing leakage have complex cross-effects and dynamic effects of mutual influence and mutual restraint. There exist complex nonlinear relationships among these factors, which are far beyond the description of a single (group of) simple algebraic equation.Machine learning algorithms have the characteristics of high accuracy and stability in simulating complex groundwater runoff and assessing reservoir seepage, which have attracted the interest of many researchers in recent years.Machine learning algorithms are a type of algorithm that can automatically analyze and obtain patterns from data and use these patterns to predict unknown data. They can automatically select the features with the highest correlation to evaluation events and solve problems such as noise, missing values, and outliers in the data, thereby improving the quality and integrity of the data.It has obvious advantages in reducing the time required for data processing. Compared with other classic statistical methods, its ability to identify nonlinear patterns of input and output is more reliable.Since most of the factors influencing reservoir leakage are qualitative and interact with each other, there is a certain correlation. Therefore, machine learning algorithms can be adopted to study the intrinsic connection and regularity between these qualitative influencing factors and the seepage of karst reservoirs, establish mathematical models, achieve the transformation from qualitative variables to quantitative evaluation, and conduct quantitative evaluation of the seepage volume of karst reservoirs.In this study, a model for predicting the leakage of karst reservoirs based on random forest (RF), artificial neural network (ANN), and vector machine (SVM) was innovatively constructed. By comparing and analyzing the results, it was found that all three models could achieve good prediction results. In this regard, the random forest model exhibited the best prediction performance: its simulated values were highly consistent with the measured values during the training and validation phases, accurately the dynamic change law of the leakage volume. The model has high prediction accuracy and good stability, and can be used as the preferred prediction model for the evaluation of reservoir leakage in karst areas. Four indicators, namely rock mass permeability, fault development degree, seepage channel morphology and hydrodynamic conditions, were selected as the main influencing factors of reservoir seepage. This research result provides new technical means and support for the risk assessment of leakage in pumped storage power stations.

Hydrochemical Drivers and Enhanced Chemical Weathering Mechanisms of a Subtropical Karst River under Anthropogenic Influences: A Case Study of the Wengjiang River Basin

WANG Song, LIU Fan, HOU Tao, ZHOU Zhenzhao, LI Ming, WANG Zibo, CHEN Jianqing, GUO Fang

, Available online , doi: 10.11932/karst2025y031

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This study systematically investigates the hydrogeochemical characteristics and chemical weathering processes within the Wengjiang River Basin, a primary tributary of the Beijiang River in the Pearl River system, under the combined influences of human activities and lithology. The research aims to elucidate the controlling mechanisms of ion sources and hydrochemical characteristics across wet and dry seasons, with a particular focus on the role of anthropogenic disturbances. This work provides a comprehensive analysis of the hydrogeochemical dynamics in a subtropical karst basin under monsoon climate conditions by integrating hydrochemical, isotopic, and ion ratio diagrams.The Wengjiang River Basin exhibits significant seasonal hydrological variability due to the dominant subtropical monsoon climate. During the wet season, river water is primarily recharged by precipitation, which has more depleted isotopic signatures, resulting in rapid hydrological responses dominated by quickflow pathways. In contrast, dry season baseflow is mainly sustained by groundwater that has undergone substantial evaporative fractionation, as clearly indicated by lower d-excess values. This shift leads to distinct evaporative concentration effects in hydrochemical compositions during the dry season. Moreover, water regulation through reservoir operations and agricultural irrigation further reduces flow velocity and attenuates water circulation during low-flow periods. Lithology is identified as the primary factor controlling the spatial distribution of hydrochemical characteristics. Carbonate weathering dominates the ionic composition of the river water, with Ca-HCO₃ being the predominant water type. In areas where silicate rocks are distributed, the total dissolved solids (TDS) content is significantly lower, and the chemical composition is more influenced by precipitation inputs. Carbonate rock weathering remains the dominant source of major ions throughout the year, but anthropogenic contributions become substantially more prominent during the dry season.A key finding of this study is the quantification of the impact of anthoropegenic activities on chemical weathering rates. The calculated total chemical weathering rate for the Wengjiang Basin is 78.7 t·km⁻²·a⁻¹. Notably, the involvement of sulfuric acid enhances the carbonate weathering rate by approximately 19.8%. This underscores the role of anthropogenic factors as a significant geochemical agent that intensifies weathering processes. Anthropogenic activities, particularly mining operations that introduce exogenous acids, alter natural weathering pathways and modify ionic ratios, especially during the dry season when natural hydrological buffering capacity is reduced. The research demonstrates that the hydrogeochemical response in the Wengjiang Basin is a result of the synergistic interaction between natural lithological background, seasonal hydrological variations, and intensive anthropogenic activities. The study highlights that anthropogenic impacts can modify geochemical cycles and weathering mechanisms in vulnerable karst systems.In conclusion, this work provides a systematic analysis of the hydrochemical drivers and ionic sources in the Wengjiang Basin from three perspectives: lithological control, hydrological seasonality, and anthropogenic interference. The findings offer valuable scientific insights for water environmental protection and sustainable development in highly human-impacted basins. Furthermore, this study contributes to a deeper understanding of geochemical cycles in subtropical monsoonal basins with complex geological backgrounds, highlighting the necessity of incorporating anthropogenic influences into future hydrogeochemical models and management strategies.

Hydrochemical Characteristics and Control Factors of Surface Water and Groundwater in a Typical Coal Mining Area of Southwestern Hunan

XU Zhen, ZHEN Jie, DAI Liangliang, LI Teng

, Available online , doi: 10.11932/karst2026y006

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The southwestern Hunan region is a significant coal resource accumulation zone in China. Within its coal mining areas, carbonate rocks and coal-bearing clastic rock strata are distributed in an interbedded manner, resulting in complex geological structures. Hydrogeochemical processes are jointly influenced by mining activities and karstification. This study focuses on a typical small watershed in southwestern Hunan, with a total area of approximately 20.51 km². The landform is predominantly characterized by dissolution-tectonic features of low mountains and wide valleys, and denudation-tectonic features of clastic rock hills and valleys. The regional strata are primarily composed of the Quaternary System of the Cenozoic Erathem and the Carboniferous System of the Upper Paleozoic Erathem. Groundwater types mainly include pore water in loose rocks, fissure-karst water in carbonate rocks, and pore-fissure water in clastic rocks. To systematically reveal the hydrochemical characteristics and dominant controlling factors of surface water and groundwater in this typical coal mining area of southwestern Hunan, 16 surface water and 13 groundwater samples (including 4 mine water samples) were collected. A comprehensive multi-indicator analysis was conducted using mathematical statistical analysis, Piper trilinear diagrams, Gibbs diagrams, and ion ratio methods to investigate the hydrochemical composition, spatial distribution patterns, and formation mechanisms of various water bodies in the region.The results indicate that both surface water and groundwater in the study area are generally weakly alkaline, with pH values ranging from 7.06 to 8.33 and TDS values between 236 and 884 mg·L⁻¹. Groundwater is minimally affected by mine water, with its hydrochemical types predominantly being HCO₃·SO₄-Ca, followed by HCO₃-Ca. For surface water, the major hydrochemical indicators (${\rm{SO}}_4^{2-}$, Ca²⁺, Mn, TDS, and toxic metals) exhibited the spatial distribution pattern: Shiqiao Creek (North Branch) > Shiyan Creek (Downstream) > Shijing Creek (South Branch). In contrast, the trends for pH and ${\rm{HCO}}_3^{-}$ concentration were the opposite. The North Branch (Shiqiao Creek), influenced by mine water input, has a SO₄-Ca hydrochemical type. The South Branch (Shijing Creek), less affected by mining activities, is primarily of the HCO₃·SO₄-Ca type. After their confluence, the main stream of Shiyan Creek generally exhibits a SO₄-Ca hydrochemical type.Gibbs diagrams show that most samples from the study area plot within the rock weathering dominance field, indicating that the chemical composition of the water bodies is primarily controlled by mineral dissolution within the aquifers, with relatively weaker influences from evaporation concentration and atmospheric precipitation. However, most mine water samples deviate from the model's distribution range, and their spatial heterogeneity may originate from geochemical disturbances caused by historical coal mining activities. The end-member diagram illustrating the relative contributions of rock weathering and dissolution shows that regional water samples are concentrated towards the carbonate rock end-member, with some samples trending towards the silicate rock end-member. Ion ratio analysis indicates that Ca²⁺, Mg²⁺, and ${\rm{HCO}}_3^{-}$ are mainly derived from the dissolution of carbonate minerals. ${\rm{SO}}_4^{2-}$ primarily originates from the dissolution of gypsum interbeds within the Zimenqiao Formation limestone and the oxidation of pyrite in the coal-bearing strata. Cl⁻ and ${\rm{NO}}_3^{-}$ are mainly attributed to inputs from human activities such as domestic sewage and agricultural fertilization. Mine water samples exhibit significantly higher concentrations of Fe and Mn and are locally acidic, indicating that historical mining disturbances have enhanced sulfide oxidation, creating an acidic environment that promotes the dissolution and migration of metallic elements. In surface water, the concentrations of ions like ${\rm{SO}}_4^{2-}$, Ca²⁺, and TDS show a positive correlation with the intensity of mine water input, reflecting the significant impact of mining activities on surface water chemistry.Principal Component Analysis results reveal that groundwater chemical composition is primarily controlled by three factors: PC1, with a variance contribution of 39.65%, reflects the dominant role of carbonate rock dissolution on regional groundwater chemistry; PC2, with a variance contribution of 36.08%, represents the influence of Cl⁻ and Na⁺ inputs from human activities; PC3, with a variance contribution of 11.35%, signifies the effect of gypsum dissolution. Surface water chemistry is mainly governed by three factors: PC1, with a variance contribution of 54.28%, characterizes the dual influence of gypsum dissolution and coal seam sulfide oxidation on surface water chemistry; PC2, with a variance contribution of 24.69%, embodies the coupled effects of silicate weathering from the Carboniferous Ceshui Formation and anthropogenic NaCl input; PC3, with a variance contribution of 11.80%, reflects ${\rm{NO}}_3^{-}$ input from agricultural fertilization.Integrating the multi-indicator analysis results, rock weathering/dissolution and human activities are identified as the two main factors controlling the hydrochemical evolution in the study area. Specifically, carbonate rock dissolution governs the variations of Ca²⁺, Mg²⁺, and ${\rm{HCO}}_3^{-}$; sulfide oxidation and gypsum dissolution control ${\rm{SO}}_4^{2-}$ enrichment; and human activities primarily influence the distribution of Cl⁻ and ${\rm{NO}}_3^{-}$. This study systematically reveals the hydrochemical characteristics and formation mechanisms of surface water and groundwater in a typical coal mining area of southwestern Hunan, clarifying the hydrochemical relationships and spatial distribution patterns within the "surface water-groundwater-mine water" ternary system. The results demonstrate that the coupled effects of carbonate rock weathering/dissolution and sulfide oxidation from coal-bearing strata jointly determine the chemical evolution of regional water bodies, while human activities have intensified ion migration in localized areas. The comprehensive multi-indicator analytical methodology proposed in this study can provide a scientific basis and methodological reference for identifying hydrochemical characteristics, preventing and controlling pollution, and protecting regional water resources in karst coal mining areas.

Application of integrated geophysical exploration methods in target area selection for geothermal field in Xianxian County

REN Xiaoqing, GAO Xiaorong, XU Yong, LIU Jian, WANG Hao, SUN Caixia, LU Xingchen, ZHENG Ruosi, SONG Xianlong, CHENChong

, Available online , doi: 10.11932/karst2026y002

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Xianxian County is recognized as "the largest geothermal enrichment area in North China," boasting abundant medium- and low-temperature geothermal resources. To address the insufficient understanding of deep geothermal resource distribution and heat-controlling structure development in the southeastern block of Xianxian County, and to support the large-scale development of bedrock fracture-type thermal reservoirs, this study employed an integrated geophysical exploration approach combining the Magnetotelluric (MT) method and microtremor survey. It conducted exploration and interpretation of stratigraphic, fault, and thermal reservoir characteristics in the study area, with the reliability of results verified using drilling data.The study area is situated in the northern part of the Xianxian Uplift, Cangxian Uplift, Bohai Bay Basin. Within the depth of 4000 m, the strata from top to bottom include the Cenozoic, Mesozoic, Paleozoic, and Middle-Upper Proterozoic Erathems. For fieldwork, 5 MT profiles (total length: 28.67 km; measurement points: 60) were deployed. A V8 electrical instrument recorded orthogonal electromagnetic field components, and electrical structures were derived via multi-method inversion (1D Bostick, 2D RRI, 2D Occam). For microtremor surveys, 1 profile (length: 8.54 km; measurement points: 19) was laid out. An EPS-D10 broadband seismograph extracted Rayleigh wave dispersion curves to invert the underground shear wave velocity structure, and the two methods constrained each other to reduce geophysical non-uniqueness.Results show: (1) 6 secondary faults and fractured zones were identified, mainly distributed in the northwest of the study area. Well-developed fractures around fault zones provide channels for geothermal fluid migration, serving as key drilling targets. (2) Burial depths of the top/bottom boundaries of major strata were clarified: Quaternary System (Cenozoic) bottom boundary: 415−471 m; Neogene System bottom boundary: 980−1420 m; Wumishan Formation (Jixian System, Middle-Upper Proterozoic) top boundary: 980−1430 m. Strata exhibit a "deeper burial in the northwest, shallower in the southeast" pattern. (3) Geothermal gradient laws were revealed: the highest heating rate occurs in the Cenozoic and Mesozoic (Cenozoic geothermal gradient: 3.5−4.0 ℃/100 m); after entering the Middle-Upper Proterozoic basement, the heating rate slows down (bedrock geothermal gradient: 1−1.5 ℃/100 m); the temperature in the middle of the Wumishan Formation thermal reservoir is 70−80 ℃, decreasing gradually from northwest to southeast. (4) Suitable and relatively suitable geothermal mining areas were delineated. Karst-fracture thermal reservoirs of the Jixian System (Middle-Upper Proterozoic) are distributed throughout the area, with thermal reservoir thickness: 500−600 m, water inflow: 57−140.19 m³/h, and specific water inflow: 0.266−8.67 m³/(h·m).Verification via Exploration-Production Well 1 in southeastern Xianxian County (well depth: 2508 m; water temperature: 70 ℃; water inflow: 100 m³/h) shows high consistency between geophysically interpreted stratigraphic sequences/burial depths and actual drilling data. This study confirms that the combined application of MT and microtremor methods effectively characterizes geothermal geological structures, providing technical support for the scientific development of Xianxian's geothermal resources and the achievement of regional "dual carbon" goals.

Hydrochemical and Isotopic Characteristics of the Yepu River Basin in Southern Tibet: A Preliminary Investigation

REN Kun, WANG Yan, LIU Haiyong, WANG Yu, WU Huaying, ZENG Jie, PENG Cong, PAN Xiaodong, LAN Ganjiang, TANG Weiwei, JIANG Dansi

, Available online , doi: 10.11932/karst2026y004

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The Tibetan Plateau, known as the "Asian Water Tower," plays a critical role in regional water resource sustainability. This study focuses on the water cycle processes and hydrogeochemical mechanisms in the Yepuqu Basin, southern Tibet, through systematic sampling of spring water, river water, snowmelt, and rainwater (21 samples collected in June2023). By integrating hydrochemical analysis, hydrogen-oxygen isotope tracers (δD, δ¹⁸O), and deuterium excess (d-excess) parameters, the research investigates water cycle pathways, solute sources, and rock weathering dynamics. Key findings include: (1) Water chemistry predominantly follows the Ca-HCO₃ type (88%), with Ca-HCO₃·SO₄ as a secondary classification (12%). Isotopic runoff separation reveals distinct recharge patterns: spring water derives 84% from snowmelt and 16% from rainfall, while river water combines 68% from snowmelt/groundwater and 32% from rainfall. Downstream analysis shows a gradual decrease in snowmelt and groundwater contributions along the river course. (2) Solutes originate primarily from atmospheric deposition, carbonate weathering, and silicate dissolution. Rainwater contributes 7.6% of total cations and 4.2% of ${\rm{SO}}_4^{2-}$ in springs, compared to 6.7% and 2.5% in rivers. Notably, sulfuric acid weathering dominates cationic contributions, accounting for 53% in springs and 52% in rivers—surpassing carbonate weathering inputs. This phenomenon is attributed to sulfide oxidation in coal-bearing strata, which generates substantial acidity within the basin. (3) Springs exhibit highly variable d-excess values (7.5‰−22.4‰) indicating isolated hydrogeological units with diverse recharge pathways. In contrast, river waters display clustered d-excess signatures (11.2‰−12.7‰), reflecting stable recharge sources. The downstream decline in river d-excess values suggests increasing groundwater contributions along the flow path. This study pioneers the quantification of sulfide oxidation as the dominant driver of rock weathering in Tibetan Plateau basins. The d-excess parameter is demonstrated to be a robust indicator for identifying aquifer structures and water-rock interactions. These findings advance the understanding of cryospheric hydrogeochemical processes and provide a scientific foundation for sustainable water resource management in high-altitude regions. The integration of multi-isotope tracers with hydrochemical proxies establishes a replicable framework for diagnosing water cycle dynamics in complex alpine environments. The methodology resolves critical uncertainties in distinguishing atmospheric, cryospheric, and lithospheric contributions to riverine systems. By elucidating the coupling mechanisms between sulfide-rich strata weathering and water quality evolution, this work highlights the vulnerability of Tibetan water resources to geological and climatic perturbations. The dominance of sulfuric acid weathering underscores the need to reassess carbon sink calculations in high-altitude basins, traditionally attributed to carbonate dissolution. This research enhances predictive models of water resource responses to glacier retreat and permafrost degradation, offering actionable insights for policymakers engaged in transboundary water governance across the Third Pole region.

Application of 3D sonar seepage detection technology in deep mining engineering

HUANG Hailong, LU Jiayan, JIANG Fan, YANG Pengshuai

, Available online , doi: 10.11932/karst2025y023

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In regions characterized by extensive karst landform development, the extraction of deep mineral resources faces significant challenges in preventing and controlling water hazards. Hydrogeological parameters, which are essential for understanding groundwater movement patterns and assessing water hazard risks, critically influence the effectiveness of prevention measures in mining areas. Inaccurate acquisition of these parameters can easily lead to disasters such as water inrushes and sudden water surges during mining operations. These events not only jeopardize the safety of underground personnel but also pose risks to equipment, disrupt mining progress, result in substantial economic losses, and cause ecological damage.Currently, traditional methods for obtaining hydrogeological parameters on-site primarily include pumping tests, water injection tests, and water pressure tests. These methods, which rely on direct interaction with groundwater systems, can accurately determine key parameters of aquifers and have long been regarded as essential in the field of hydrogeological research. However, they are often associated with tedious on-site testing and high costs in practical applications. Furthermore, the process—from experimental design and on-site implementation to stable data collection and final analysis—can take several months or even years. This lengthy timeline significantly lags behind the demands of mining area development and construction, making it challenging to address the urgent need for dynamic water hazard prevention and control. Geophysical methods have become a widely utilized approach for obtaining hydrogeological parameters in the industry due to their distinct advantages. Unlike traditional experimental methods, geophysical techniques do not require large-scale destruction of geological formations, significantly reduce operational costs, and facilitate the preliminary exploration of extensive areas within a short timeframe, thereby enhancing efficiency. However, as detection depth increases, deep strata are influenced by various factors, including complex geological structures, the degree of rock weathering, and the chemical composition of groundwater. Consequently, the signal experiences significant attenuation and distortion during propagation, leading to a marked decline in detection accuracy. This challenge is particularly pronounced for deep karst aquifers, where intricate cave and fissure systems complicate the interpretation of geophysical signals, making it difficult to accurately represent the true hydrogeological parameters. This complexity poses potential risks for water hazard prevention and control in deep mining areas. In response to various technological challenges, 3D sonar seepage detection technology has emerged as an innovative method for obtaining hydrogeological parameters of deep karst aquifers. 3D sonar seepage detection technology effectively mitigates the issue of reduced detection accuracy with depth. Whether dealing with shallow weathered fissure aquifers or deep karst conduit systems extending hundreds or even thousands of meters, high-precision parameter determination is achievable. Additionally, its high-resolution imaging capability can visually represent the three-dimensional motion state of water flow within the borehole, providing a powerful tool for a deeper understanding of groundwater seepage dynamics.Based on this background, this study focuses on the Panlong Lead-Zinc Mine's deep mining area in Guangxi. Situated in the western region of Guangxi, which is characterized by intense karst development, the mine features a vigorous subsurface karst system that poses significant water hazard threats during deep mining operations. This study employs 3D sonar seepage detection technology, strategically deploying monitoring boreholes on both the eastern and western sides of the mining area to achieve a comprehensive and detailed characterization of groundwater seepage within the boreholes. Through prolonged and high-frequency data acquisition, a substantial volume of accurate seepage parameters—including seepage velocity, direction, flow rate, and permeability coefficient—was obtained. Building upon this data foundation, the spatial distribution patterns of these parameters were analyzed in depth to investigate the differences in groundwater seepage across various depths and regions. This analysis aims to reveal the water-conducting characteristics and karst development features of the aquifers on the eastern and western flanks of the mining area, thereby providing robust data support and a theoretical basis for the scientific formulation of water hazard prevention and control strategies for deep mining operations in the region. The research results indicate that sonar seepage detection technology can accurately evaluate the variation characteristics of parameters such as seepage velocity, seepage direction, permeability coefficient, and seepage flow rate with depth in deeply buried karst aquifers. It can also accurately predict the presence of groundwater runoff channels in the eastern part of the mining area at elevations between -25m and -78m, as well as below -85m at the water 22. Additionally, it can identify groundwater runoff channels in the western part of the mining area at elevations below -90m at the SK4. The total proven seepage flow in the mining area is 6,494.31m³/d, which represents only one-third of the daily drainage in the region. Groundwater seepage flow on the eastern and western sides of the mining area accounts for 58% and 42% of the total seepage flow, respectively. The sonar seepage detection technology is limited by the arrangement of measurement hole positions. Utilizing key measurement holes (holes revealing the main runoff channels) for detection significantly enhances the accuracy of predicting water inflow in mining areas.

Hydrochemical evolution of karst groundwater under the mining influence in Beiya Mine, Northwest Yunnan Province

HE Xiang, YANG Chao, DONG Xuelan, GUO Xiaojiao, YANG Haifeng, LI Jiahuai, YANG Fengji

, Available online , doi: 10.11932/karst2025y026

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The Beiya gold mine in Yunnan Province, which is a karst water-filled mine, is a typical skarn-porphyry type deposits in China. Its groundwater has been unbalanced for a long time caused by mining activities, which has affected or damaged the aquifer to varying degrees, resulting in constant change of groundwater dynamic field and chemical field, and forming a typical human activities influenced groundwater system. In order to reveal the impact of mining activities on chemical evolution of groundwater and the water sources change of mine pit filling, this paper analyze the water chemical evolution under long-term mining, and the implication of conventional components of the karst groundwater chemistry in Beiya mining area to the water filling sources change in mine pit, by Piper three-line graph and ion combination ratio methods and according to water chemical data of different mining stages. Research shows that: (1) Influenced by mining activities, the overall concentrations of TDS, Na⁺, ${\rm{SO}}_4^{2-}$, and ${\rm{NO}}_3^{-}$ increased, and the concentrations of Na⁺ and ${\rm{SO}}_4^{2-}$ increased significantly in deep mining. The water chemical type evolves from calcium-carbonate water to calcium sulfate and sodium sulfate water, while the karst spring water chemistry is less affected by mining activities. (2) Obvious mixing occurred in mine pit water. It was initially determined that the shallow groundwater was HCO₃-Ca·Mg water or HCO₃-Mg·Ca water, while the groundwater in the structural zone and deep layers was SO₄-Na·Ca water or HCO₃-Na water. The karst water in the contact zone between limestone and porphyritic rock belongs to HCO₃·SO₄-Na and HCO₃-Na water. The water gushing point at 1,614m on the southwest side and 1,564m on the southeast side of the mining pit have similar hydrochemical types, belonging to HCO₃-Ca·Mg water or HCO₃-Mg·Ca water, which have a close hydraulic connection, and from the same water source. (3) The karst water chemistry in the study area is mainly controlled by carbonate water-rock reaction. Ca²⁺, Mg²⁺ and ${\rm{HCO}}_3^{-}$ in groundwater and surface water are mainly from the dissolution of carbonates. Na⁺ in the shallow part come from weathering and dissolution of porphyry, while in the deep part mainly come from dissolution of sodium-containing feldspar sandstone and underground low-temperature hot water. ${\rm{SO}}_4^{2-}$ is mainly affected by mining activities and originates from the oxidation of metal sulfides. ${\rm{NO}}_3^{-}$ in the shallow quaternary pore water is mainly affected by agricultural production and mining blasting operations. (4) The karst water chemistry is controlled by mining activities, mixing and water-rock interaction. Mining activities are the main influencing factor to the water chemical changes in the karst water system. Accompanied by gradual mining activities, the sealing degree of the aquifer is damaged, and the alternating rate of groundwater increases, which will affect the occurrence degree of water-rock interaction. It is suggested that optimized mining plans is necessary to enhance the comprehensive utilization rate of water resources, and establish and improve the monitoring system for surface water and groundwater to protect the water environment in karst areas.

Transformation Characteristics and Monitoring-Evaluation Methods of Atmospheric Water, Surface Water, and Groundwater in Southern Karst Regions

WANG Yu

, Available online , doi: 10.11932/karst2026y005

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New demands in natural resource management, ecological environment protection, and integrated water resource investigation and assessment have driven research on the transformation characteristics and monitoring-evaluation methods of the "three waters" (atmospheric water, surface water, and groundwater) in the karst areas of southern China. The research trends are mainly manifested in four aspects: (1) Focus on the conditions of complex underlying surfaces and heterogeneous media, and combine regional geographical and climatic factors to deepen the exploration of regional-scale "three waters" transformation conditions; (2) Strengthen hydrogeological surveys, experiments, and monitoring of the spatial structure, hydrodynamic properties, and transformation processes of transformation boundaries, so as to clarify the mechanisms and laws of "three waters" transformation at the boundaries; 3) Conduct comprehensive multi-scale and multi-factor studies to reveal transformation patterns and their interrelationships, take into account regional and ecosystem differences, and construct more targeted and universal models; (4) Develop automated and intelligent monitoring equipment, enhance data analysis, and improve cross-departmental data sharing mechanisms.Guided by the theory of systems science, and based on the principles of hydrology, hydraulics, hydrogeology, groundwater dynamics, as well as the technologies and methods for water resource investigation and assessment, this paper sorts out the research trends of "three waters" transformation monitoring, analyzes the "three waters" transformation characteristics of different watershed types, and summarizes the monitoring contents, station layout, and evaluation principles and methods through the collection, collation, and comprehensive study of literature. It forms a systematic review to provide references for the practice of integrated water resource investigation and assessment and related research.Watershed geomorphology, as the dominant factor controlling the direction, path, and speed of water flow, directly affects the "three waters" transformation process and determines its basic characteristics. Therefore, the classification of watershed geomorphic forms is a prerequisite for the analysis of "three waters" transformation characteristics. Combined with the results of regional hydrogeological surveys, the main types of watershed geomorphic forms in the karst areas of southern China can be summarized into three categories: deeply incised canyon watersheds, shallowly incised wide-valley watersheds, and intermontane basin watersheds.The key interfaces for "three waters" transformation in the karst areas of southern China are complex and diverse, mainly including: the surface underlying surface and vadose zone, which are the initial interfaces for precipitation transformation; springs, spring groups, or diffuse discharge zones where aquifers (zones) are exposed; The groundwater-surface water interaction zone beneath and on both sides of surface water bodies such as gullies, riverbeds, lakes, and wetlands; and sinking stream inlets and underground river outlets unique to karst areas. Different from the planar geometric interfaces in the distribution areas of layered porous aquifers in alluvial plains, these interfaces have more complex forms.The monitoring layout for "three waters" transformation shall follow the principles of full-process monitoring, key point enhancement, and systematic correlation. Specifically, it is necessary to arrange monitoring stations throughout the process from the runoff generation area, recharge area, runoff area to the discharge and confluence area; densify monitoring points at the key interfaces of "three waters" transformation and areas affected by human activities; and construct a complete spatio-temporal dynamic monitoring system for "three waters" transformation through synchronous multi-factor monitoring at stations. Meanwhile, the monitoring layout shall take into account the differences in "three waters" transformation characteristics of different watershed types: for deeply incised canyon watersheds, monitoring of the rapid transformation process under gully control shall be strengthened based on the characteristics of vertical gradients and linear confluence; for shallowly incised wide-valley watersheds, monitoring of the double-layer runoff process with interwoven surface and groundwater shall be enhanced in combination with the characteristics of the karst diversion network system; for intermontane basin watersheds, aiming at the characteristics of layered structure and clear zoning, monitoring shall focus on the transformation processes of edge input, internal alternation, and basin bottom output.The monitoring and evaluation methods for "three waters" transformation are characterized by the combination of traditional and modern methods, and the promotion and application of modern new technologies and methods show a strong momentum. Since all types of methods have limitations as well as advantages and disadvantages, different methods need to be used in combination in practice to make up for the defects of a single method through mutual inspection and verification.

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