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Evaluation of karst hydrogeological conditions and reservoir leakage analysis in the basin of Yangquan River, Fengjie County, Chongqing City
WU Jian, MI Xiangli, LAN Meng
, Available online  , doi: 10.11932/karst2025y014
Abstract FullText HTML PDF(9190KB) icon18 icon0
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Southwest China constitutes the world's largest karst region with concentrated exposure and distribution of carbonate rocks.Within this area, Chongqing City is a pivotal component of the southwestern karst system, with karst landscapes covering approximately 30,000 km2, primarily concentrated in the northeastern and southeastern of Chongqing City. This region has experienced multiple phases of strong karstification, resulting in well-developed karst landforms such as solution caves, sinkholes, karst springs, and underground rivers. Abundant surface water and groundwater have triggered frequent karst geohazards, including reservoir leakage, water inrush in tunnels, and karst collapses. These events have seriously constrained the safety construction of hydraulic projects and local economic development.The Yangquan River basin in Fengjie County, Chongqing City covers an area of approximately 45.5 km2, with a total river length of about 14 km. The daily average river water level is 895.1 m, while the average annual flow is 0.686 m3∙s−1, corresponding to a average annual runoff of 21.63 million m3. The basin has a subtropical warm and humid monsoon climate, characterized by an average annual precipitation of 1163.1 mm, an average annual evaporation of 1267.8 mm, and an average annual temperature of 18.7 ℃. Limestone and dolomite strata are developed in the basin, with undeveloped and small-scale faults located on the slopes of both banks. In contrast, fold structures are extensively developed, generally trending parallel to the Yangquan River. The left bank of the Yangquan River exhibits multiple gullies controlled by lithology and NW-trending fold structures. The topographic divide is the Jinfeng Mountain with elevations ranging from 1800 m to 1900 m. The right bank constitutes an interstream block between the Yangquan River and the Taoyuan River, characterized by a topographic divide elevation of approximately 1450~1600 m. Therefore, the left and right banks of the Yangquan River have steep topography, forming a typical “V”-shaped longitudinal valley. Overall, the karst hydrogeological conditions are complex, and karst leakage has become a crucial issue in the construction of pumped storage power stations in this area.This paper evaluates the karst hydrogeological conditions of Yangquan River basin by using geological survey and mapping, hydrogeological field experiments, and karst water system analysis. Subsequently, the karst leakage type, karst leakage location, and karst leakage passage are systematically analyzed during the impoundment of the Yangquan River reservoir. Ultimately, the three-dimensional seepage filed of the Yangquan River under natural and impounding conditions are conducted by using MODFLOW software. The karst leakage rates are calculated and validated through numerical modelling and analytical formulas. The results show that in the Yangquan River basin, karst development is mainly concentrated in the high-purity zone of carbonate rocks, structural fracture development zone, and discharge base level, forming five concentrated zones that exhibit a northeast-trending banded distribution. The degree of karst development gradually decreases with the increase of depth, exhibiting significant elevation zoning characteristics. This results in a dual shell-core structure characterized by strong karst development on the surface and weak karst development internally. Moreover, the karst groundwater system in the Yangquan River is a typical type of karstic fissure-tube-underground river system in the anticline mountainous of Southwest China, which can be spatially divided into strong karst anticline zone, strong karst syncline zone, and moderate karst syncline zone. Based on the water balance theory, the karst groundwater system in the site is classified as a secondary hydrogeological unit, namely II-2 interstream block. The recharge, runoff, and discharge modes of karst groundwater in the basin are primarily characterized by rainfall infiltration and concentrated drainage through longitudinal-transverse conduit-fissure flow systems. Packer tests and groundwater tracer tests indicate that the left bank of the Yangquan River develops an interconnected karst conduit system, while the right bank exhibits a dual-media system composed of fissure networks and karst conduits. During the impoundment of the lower reservoir in the Yangquan River, pore leakage may occur at the dam foundation, while karstic tube leakage and karstic tube-fissure coupling leakage may develop on the both left and right banks; however, there will be no leakage in the lower adjacent valley. The analytical solutions for the pore leakage and karstic tube leakage are 9505.13 m3∙d−1 and 117979.20 m3∙d−1, respectively. As a comparison, the numerical result of karst leakage is approximately 12184.60 m3∙d−1, indicating that more efficient and reasonable numerical methods and anti-seepage control measures need to be adopted to address karst groundwater tube system on both banks to achieve the conditions for dam construction and reservoir formation. This study can provide some suggestions for hydraulic projects in Southwest China.
Genesis analysis of karst groundwater inrush and prediction of its water inflow in the Huxitai Tunnel
SHAO Changjie, WANG Lei, LIU Huidong, CUI Yongxing, LIU Wei
, Available online  , doi: 10.11932/karst20250303
Abstract FullText HTML PDF(4153KB) icon14 icon2
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Tunnel water inrush is one of the primary threats to tunnel construction safety, not only posing risks during the construction but also creating long-term hidden dangers for the post-construction operation and maintenance. This issue is particularly severe in karst tunnels, where dense karst fractures and conduit networks will lead to rapid water inrush responses to precipitation. Extreme rainfall events can trigger the instantaneous and massive water influxes, making tunnel water inrush in karst regions especially serious. Therefore, it is critical to elucidate the formation mechanisms of tunnel water inrush and to predict water influxes during extreme rainfall conditions in order to address water inrush challenges and ensure safety of tunnel construction in karst regions.The Huxitai Tunnel is examined here as a case study. This tunnel is a critical component of Linjian Expressway, located in the subtropical humid zone of Eastern China, characterized by abundant preciptation and complex geological conditions.The tunnel tranverses through the Carboniferous Huanglong Formation (C2h) and the Chuanshan Formation (C2c) limestones, which features well-developed karst conduits, abundant water, and high permeability. These features result in significant water inrush problems, increased construction challenges, and heightened safety risks. Since the beginning of tunnel construction, water inrush events in varying degrees have occurred in the limestone sections of the tunnel.To investigate the causes of water inrush in the Huxitai Tunnel under karst geological conditions and to estimate its influxes, this study conducted detailed field investigations and in-situ tests to analyze the hydrogeological conditions of the water inrush sections and to determine the groundwater flow systems. Based on the hydrogeochemical characteristics and hydrogen-oxygen isotopes of groundwater, the study analyzed the pathways of karst groundwater flow and the mechanisms of water inrush. It also estimated the contributions of different water sources to the tunnel water inrush by employing the isotopic end-member mixing model. Using precipitation infiltration methods and groundwater dynamics principles, the study calculated groundwater recharge rates and the proportion of tunnel water inrush relative to total recharge, while predicting the maximum water influx in the tunnel during extreme rainfall events. The findings include:(1) According to the pathways of groundwater flow, the tunnel region is divided into three groundwater flow systems: the Caoyuanxi groundwater flow system, the Fenshuijiang karst groundwater flow system, and the Dakengxi–Chaipingli groundwater flow system. The karst water inrush section (K65+100-K65+360) lies within the Fenshuijiang karst groundwater flow system, which consists of the Huanglong Formation and the Chuanshan Formation limestone characterized by intensive karst development, abundant water influx, and high risks.(2) Karst groundwater in the tunnel area is primarily recharged by precipitation, which infiltrates through sinkholes and karst conduits. The hydrochemical characteristics of tunnel water inrush are similar to those of underground river discharge, dominated by carbonate rock dissolution, reflecting a mixture of karst water and sandstone water. Karst water vertically infiltrating from the Huanglong Formation and the Chuanshan Formation limestone accounts for 70% to 79% of tunnel water inrush, with 21% to 30% contributed by lateral sandstone water.(3) During the runoff process, the recharge of groundwater from atmospheric precipitation amounts to 19,324.89 m3·d−1, of which 48.29% is discharged through the tunnel.Under non-extreme rainfall conditions, the predicted water influx into the Huxitai Tunnel is 10,684.89 m³/d; however, during extreme rainfall events, the maximum predicted water influx can reach up to 79,364.13 m3·d−1.To sum up, these results provide a quantitative decision-making basis for the prevention and control of water inrush in the Huxitai Tunnel, and also serve as valuable references for similar studies on water inrush of karst tunnel.
Comprehensive Evaluation and Restoration Management of Ecological Issues in Historical Abandoned Mines in Plateau Mountain Areas: A Case Study of Qujing City, Yunnan
WANG Bo, ZHAO Li, GUO Yun, CHEN Xiaomei, SONG Zenghong
, Available online  , doi: 10.11932/karst2025y016
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Due to the early extensive development, the geomorphic landscape, land resources and forest vegetation have been seriously damaged, coupled with the fragile ecological environment in the plateau and mountain areas, the ecological problems of the abandoned mines left over from history have seriously affected the regional natural ecosystem and human settlements, restricting economic and social development. In recent years, China has continued to promote the ecological restoration of mines, and the quality of the ecological environment has been significantly improved, but some abandoned mines have unclear restoration goals, improper management measures and poor restoration results due to inadequate investigation and inadequate comprehensive evaluation of ecological problems.This article selects Qujing City, a typical area in the eastern plateau mountainous region, as the research subject. It systematically analyzes the geological environmental issues caused by historical abandoned mines in the area, as well as the ecological and environmental conditions of the areas where these abandoned mines are located. A comprehensive evaluation of the ecological issues of historical abandoned mines within the region is conducted.The ecological issues of the mining areas in the study zone have been classified into different levels. The assessment results indicate that the area with severe (Level I) and moderately severe (Level II) ecological problems in the abandoned mines covers a total of 999.01 hectares, accounting for 90.18% of the total area. Among these, the areas with severe ecological problems (Level I) are mainly located in the Shizong, Luoping, and Fuyuan counties along the Nanpan River basin, whereas the areas with moderately severe ecological problems (Level II) are primarily found in the Shizong county and Fuyuan county along the Nanpan River basin, as well as in the Xuanwei city along the Beipan River basin.Based on the comprehensive assessment results of the ecological issues of historical abandoned mines in the study area, combined with the territorial spatial planning, the Nanpanjiang River Basin, which is the most prominent and typical in terms of problems, is taken as a priority. At the same time, considering the natural geographical pattern, and focusing on the protection of the ecological barriers at the source of the Pearl River and the upper reaches of the Yangtze River, as well as the key ecological issues of soil erosion and rocky desertification, the study area is divided into four restoration zones (the Nanpanjiang River Basin water conservation and rocky desertification prevention and control restoration area at the source of the Pearl River, the Beipanjiang River Basin water conservation restoration area in the upper reaches of the Pearl River, the Xiaojiang River Basin soil and water conservation restoration area in the upper reaches of the Yangtze River, and the Niu Lanjiang River Basin biodiversity conservation restoration area in the upper reaches of the Yangtze River).For the severely ecological problem areas classified as Type I, the main strategy is to carry out ecological restoration, expand the scale of forests and grasslands, and enhance the overall function and value of the ecosystem; for areas classified as Type II and Type III where ecological issues are relatively concentrated but not as severe, the emphasis is on ensuring that development and ecological protection can proceed in a coordinated manner while meeting land use needs. By dividing the regions according to the severity of ecological problems, more precise targeted ecological restoration measures are proposed, providing reference and lessons for the ecological .
Risk Assessment of Geological Hazard Based On GIS and Information Modeling Methods
XIE Siqin, LUAN Song, ZHOU Dahai
, Available online  , doi: 10.11932/karst2025y013
Abstract FullText HTML PDF(3826KB) icon32 icon3
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Over the years, geological hazard such as collapses landslide, dangerous rock, and karst collapse have occurred frequently in Guangxi, with a wide distribution area, long impact time, a large number of people affected, and heavy economic losses. It has practical guidance significance to provide basic scientific for disaster prevention and reduction work in the area, and to carry out early prediction and evaluation of geological hazard risk.The risk of geological hazard refers to the possibility of a specific scale and type of geological hazard occurring within a certain area and time period under the influence of certain triggering factors.The early prediction and evaluation of geological hazard risk is currently a major challenge in disaster prevention and reduction. There are many influencing factors and evaluation methods for risk assessment of geological hazard. This article takes Xiangzhou County in Guangxi Province as an example, and selects the information model method based on the investigation of the main control geological conditions for potential hazards. Based on the overlay analysis function of ArcGIS on spatial data, according to the characteristics of geological hazard development and potential hazards in the work area, 8 evaluation indicators are selected, including landform type, geological structure, engineering geological rock group and terrain slope, karst development degree, slope structure, vegetation coverage, and human engineering activities. The engineering geological rock group and terrain slope are taken as the main control factors, and other factors are used as secondary factors for overlay zoning. After using the natural breakpoint method in statistics to reclassify the prone zoning, an evaluation grid measured by the value of information is generated to evaluate the susceptibility of geological hazards. The susceptibility of geological hazards in Xiangzhou County is divided into four levels, including low susceptibility, medium susceptibility, high susceptibility, and extremely high susceptibility. Among them, extremely high and high susceptibility are mainly distributed in river terraces, peak forests and valleys where the underground karst areas is strong development, and in the rocky mountain areas, and areas with strong human engineering activities. Medium and low susceptibility are mainly distributed in hilly and low mountain hilly terrain areas. On the basis of susceptibility assessment, according to the meteorological characteristics of the study area, the maximum 24-hour rainfall at each return period of rainfall stations in Xiangzhou County and surrounding areas was collected. The Kriging method in AcrGIS was used to generate contour maps of rainfall once in10 years, once in 20 years, once in 50 years, and once in 100 years. The geological hazard susceptibility assessment map and contour maps of different rainfall conditions were normalized, and spatial superposition analysis was carried out to generate geological hazard risk assessment maps under different rainfall return periods measured by the value of information. The probability was divided into extremely high risk, high risk, medium risk, and low risk using the natural breakpoint method, and the geological hazard risk assessment under different rainfall conditions return periods was obtained. The evaluation results indicate that the larger the recurrence period of rainfall conditions, the larger the distribution area of high and extremely high risk geological hazards, and the impact of rainfall on geological hazards is significant. The areas with extremely high geological hazard risk in Xiangzhou County are mainly distributed in the central part near the Sicun Town, where is the river terrace landform units, and the sand gravel clay double-layer structure soil rock formation areas, the eastern Dale Town to Baizhang Town and the western Maping Town, where is the peak forest valley landform units, and the thick to blocky strong rock melted hard limestone and dolomite rock formation areas; The high-risk areas are mainly distributed in the hilly and river terrace landform units, including the northeast of Yunjiang Town, Sicun Town to Dale and Baizhang Township, as well as the west of Maping Town; The remaining areas are mainly classified as medium to low risk areas, with hills and low mountain hills being the main geomorphic units.This article scientifically evaluates the geological hazard risk in Xiangzhou County, Guangxi, highlighting the key points and adapting measures to local conditions, dividing different geological hazard risk levels, and clarifying the geological hazard risk zoning under different rainfall conditions, to provides a certain reference basis for geological hazard warning and forecasting, and improves the technical support system for geological hazard identification, zoning, and control in the research area. At the same time, its evaluation results can serve as the basis for national spatial planning, guiding population and economy to gather in low-risk areas in an orderly manner.
Genetic mechanism of karst water revealed by hydrochemistry and isotopes in Pingliang, Gansu province
ZHANG Chengwen, ZHENG Haofan, HE Jianbo, LIU Zilong, MAO Xumei
, Available online  , doi: 10.11932/karst2025y015
Abstract FullText HTML PDF(2581KB) icon24 icon1
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Karst water is one of the significant water resources in the Pingliang region. Investigating the formation mechanism of karst water is crucial for the sustainable utilization of karst water resources, the protection of water sources, and the formulation of environmental protection measures in the area. It provides a scientific basis and theoretical support for promoting the sustainable development of regional water resources and the health of the water environment. The hydrochemical composition of karst water can reveal the processes of recharge, runoff, and discharge, while isotopic tracing methods help indicate the scope and dynamic changes of the karst water system. To uncover the genetic mechanism of karst water in Pingliang City, we comprehensively analyzed the hydrochemical characteristics and sources of karst water in Pingliang City using methods such as Piper trilinear diagrams, mathematical approaches, and ion ratio coefficients. The research results indicate that the groundwater in the region can be mainly divided into two types: HCO3-Ca and HCO3·SO4-Na, with Ca2+ and Na+ as the primary cations and ${\rm{HCO}}_3^{-}$ as the primary anion. The pH value ranges from 6.72 to 6.9, exhibiting weakly alkaline hydrochemical characteristics overall. The total dissolved solids (TDS) value of groundwater ranges from 158.01 mg·L−1 to 1519.40 mg·L−1. Spearman correlation analysis shows that the hydrochemistry of karst water in the study area is primarily controlled by the dissolution of minerals such as dolomite and evaporites. TDS is highly positively correlated with the contents of Na+, Mg2+, Cl−, ${\rm{SO}}_4^{2-}$, and ${\rm{HCO}}_3^{-}$. Additionally, the content of Mg2+ is significantly positively correlated with the contents of the main anions Cl−, ${\rm{SO}}_4^{2-}$, and ${\rm{HCO}}_3^{-}$ (r > 0.7, p < 0.01), and the content of Na+ also has a significant positive correlation with the contents of Cl− and ${\rm{SO}}_4^{2-}$ (r > 0.98, p < 0.01). In the analysis of ion proportional coefficients, the hydrochemical characteristics of karst water in Pingliang City are mainly influenced by rock weathering. Na+ not only originates from the dissolution of rock salt but may also come from the dissolution of sulfate or silicate minerals; Mg2+ is derived from the combined action of calcite and dolomite; Ca2+ is produced not only from the dissolution of dolomite but also from the dissolution of calcite and dolomite. During the rock weathering process, dolomite, calcite, and evaporites dominate the hydrochemical formation of Pingliang karst water. Gibbs diagram combined with mineral saturation index analysis further confirms that the dissolution of evaporites, carbonates, and silicate minerals is the natural source of hydrochemical components in Pingliang City. Ca2+, Mg2+, and ${\rm{HCO}}_3^{-}$ in the karst groundwater of Pingliang City mainly originate from the combined dissolution of calcite and dolomite. Hydrogeological conditions and hydrogen-oxygen isotope results show that δD values range from -75.45‰ to -64.80‰, with an average of -69.20‰; while δ18O values range from -11.26‰ to -9.16‰, with an average of -10.07‰, indicating that all groundwater is recharged by atmospheric precipitation infiltration. Based on the identification of the karst water genetic model, it is determined that there are two genetic modes of karst water in the Pingliang area. Mode 1: Atmospheric precipitation infiltrates through the overlying Quaternary loess layer, continuously dissolving sulfate minerals in the loess, and enters the limestone confined aquifer through karst fissures formed by faults, eventually emerging as springs at the interface between the loess and limestone aquifer. In this mode, the chemical type of karst water is mainly HCO3·SO4-Na. Mode 2: Atmospheric precipitation infiltrates through the overlying Quaternary sandstone layer, continuously dissolving carbonate minerals in the sandstone layer, and enters the limestone confined aquifer through karst fissures formed by faults, eventually emerging as springs at the interface between the sandstone and limestone aquifer. In this mode, the chemical type of karst water is mainly HCO3-Ca. Although both modes receive atmospheric precipitation recharge from the front of the mountain and enter the aquifer through karst fissures through the overlying strata, the differences in the overlying strata lead to different hydrochemical characteristics. This indicates that the mineral dissolution in the overlying strata is the main factor in the formation of the hydrochemical composition of Pingliang karst water.
, Available online  
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