中国岩溶

Study on complexity of groundwater systems in the karst mining areas with abundant water on the Yunnan plateau

WANG Yu

2024, 43(6): 1223-1234. doi: 10.11932/karst20240601

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A mining area with abundant water usually refers to the mine with a pit water inflow greater than 10,000 m³·d⁻¹. In view of the unevenness of the water-richness of karst aquifers and the poor accuracy of predicting water inflow, the definition of a mining area with abundant water should not be confined to the specific values of water inflow. Instead, it should be defined mainly based on the conditions of high water-richness, abundant recharge and pipeline flow of aquifers. According to the standard of hydrogeological terminology, a hydrogeological unit is defined as a groundwater system characterized by uniform recharge boundaries and conditions of recharge, runoff, and discharge. The groundwater systems described in this paper belong to the same object and category. The Yunnan plateau refers to the western section of the Yunnan-Guizhou Plateau, and, in a broad sense, encompasses Yunnan Province, which covers an area of 39.4×10⁴ km². The karst contiguous areas on the Yunnan plateau are mainly located in the east area of 102°E and north of the Yuanjiang river in eastern Yunnan, and the northwest and the west from Baoshan to Cangyuan. These karst contiguous areas total 11.09×10⁴ km², corresponding to the upper Yangtze massif, South China massif, Sanjiang orogenic belt and Tengchong orogenic belt, with superior mineralization conditions and abundant mineral resources. Historically, minerals in karst areas are primarily exploited above the erosion base. The mountainous terrain typically facilitates natural drainage, which has led to a lack of emphasis on and research into the complexity of groundwater systems in mining areas. With the growing economic and social demands, the exploration areas and mining areas are continually expanded, and are increasingly extending to deeper areas. Some deposits with abundant water that were previously challenging in exploitation have been developed. This shift has transformed hydrogeological conditions, evolving from simple to complex or even extremely complex scenarios. As a result, the challenges associated with mine water control have intensified, and the requirements for exploration have correspondingly increased. Therefore, it is both necessary and urgent to study the complexity of groundwater systems in karst mining areas with abundant water, enhance the research level, and strengthen measures for exploration control.The complexity of a system encompasses the characteristics such as disorder, sudden change, detection errors, and inference errors, which arise from the pluralism, nonlinearity, and randomness of its constituent elements, organizational structures, influencing factors, and their interrelations and interactions with the environment. Based on existing research and exploration findings, the complexity of groundwater systems in karst mining areas with abundant water is mainly reflected in the intricate and variable characteristics of system boundary conditions, hydrogeological structures, properties of water-bearing media, and the effects of mining activities.In karst areas, the geological processes of mineralization and subsequent transformation are highly intense, and the geological conditions are exceedingly complex, no matter whether the deposits are endogenous, exogenous, or metamorphic. The complexity of boundary conditions of groundwater systems in karst mining areas with abundant water is mainly manifested in the irregularity of topographic watersheds, the multistage nature of erosion datum, the diversity and invisibility of genesis–tectonic types of geological boundary, and the variability of boundary hydrodynamic properties. The complexity of groundwater system structure is mainly manifested in the diversity and variability of karst aquifers, non-soluble rock aquifers (bodies), primary and secondary structural properties and their mutual relationship. The complexity of the properties of water-bearing media is mainly manifested in karst aquifers, which are not only strongly developed but also exhibit significant variability. This variability includes the direction, scale, density, and connectivity of karst caves, conduits and fissures. The characteristics of water richness, permeability, and hydraulic connections also display prominent anisotropy. The influence of mining engineering and mining activities on groundwater systems in mining areas is huge and far-reaching. In addition, the design of mine shafts, mining pits, and development engineering often requires real-time adjustments in response to changes in ore bodies and mining technical conditions during the mining process. The disturbances and impacts of mining engineering and activities on the water environment and groundwater systems are also difficult to predict accurately. These influences have increased the complexity of groundwater systems in mining areas to varying degrees.This paper systematically examines the complexity of groundwater systems in karst mining areas with abundant water. It provides a detail analysis of typical examples, along with a visual representation of the distinctive characteristics of these systems. This paper discusses the complexity of groundwater systems in mining areas with abundant water. It addresses the challenges encountered in hydrogeological exploration within mining areas. The discussion focuses on optimizing and adjusting the evaluation indices for the complexity of hydrogeological conditions as outlined in current specifications. Furthermore, it emphasizes the need for quantifying evaluation standards and establishing a reasonable assessment scale for the exploration control of complex hydrogeological conditions in mining areas. Besides, the paper offers recommendations for revising and improving the existing specifications.

Analysis of geological problems and difficulties in restoration and treatment of karst environment on the Yunnan plateau

ZHANG Hua, PENG Shuhui, WANG Yu, WANG Bo, GAO Yu, LI Qin

2024, 43(6): 1235-1247. doi: 10.11932/karst20240602

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The karst region of the Yunnan plateau is characterized by high altitudes, diverse landforms, variable meteorological and hydrological conditions, and strong internal and external dynamic geological processes. Additionally, the rapid increase in human activities and the detrimental effects of unsustainable development have resulted in many issues on karst environmental geology closely related to natural resources and the environment. The main issues are rocky desertification, waterlogging and drought, groundwater pollution, spring drainage, deterioration of wetland ecological environment, and karst geological disasters.According to the data on relevant remote sensing surveys, the total area of rocky desertification in Yunnan Province in 2020 reached 24,800 km², accounting for 26.41% of the karst area. Among them, the area of severe rocky desertification accounted for 69.46%, 20.72% for moderate rocky desertification, and 9.82% for mild rocky desertification. Rocky desertification is contiguously distributed in the karst mountainous areas of eastern and southeastern Yunnan, and in karst regions of western Yunnan, it is mostly distributed in sheets and bands. The severe rocky desertification area is mainly concentrated in the middle-height mountains, high-height mountains and valleys of the plateau karst. The distribution of waterlogging and drought in the karst region of the plateau shows obvious local characteristics. Drought disasters mainly occur in the mountainous and hilly areas with higher terrain, while waterlogging occurs more often in the valleys, basins and depressions among the mountains with lower terrain. There are 2,658,400 acres of arable land susceptible to waterlogging in karst regions of the Yunnan plateau. The degree of groundwater pollution varies greatly due to different types of groundwater, pollution protection properties and pollution sources. Generally, pore water is the most polluted with the lowest water quality. Medium to heavy pollution is mainly distributed in the middle of the basin, and the elements exceeding the permitted level mainly include nitrite, ammonia nitrogen, iron, manganese, etc. The heavily polluted areas include Kunming, Qujing, Kaiyuan, Mengzi, Gejiu and other places, mostly rated as serious or most serious pollution areas. The drainage of spring water in karst stone mountains typically results in a decline of regional groundwater levels. This decrease mainly occurs in basin areas, mining areas and the vicinity of engineering tunnel excavation, which is mainly caused by human engineering activities such as tunnel excavation, mine drainage and over-exploitation of groundwater. The wetland of the Yunnan plateau is mainly distributed in the lakeside. Due to the combined effects of ecological changes and human activities, the temporal and spatial distribution of water sources and the water cycle processes have been altered. The wetland area is shrinking, and its ecological service functions are increasingly degraded or even lost, resulting in a series of ecological and environmental geological problems. Karst geological disasters on the plateau primarily consist of karst collapses, which are mainly found in karst fault basins, trough valleys and platform areas. These collapses are mainly the result of external forces such as rainfall and earthquakes.Due to the fragility and complexity of the geological environment in karst regions of the plateau, addressing and managing various environmental geological issues is challenging, and the outcomes of restoration and control efforts are inconsistent. The main reasons can be summarized as the complex and changeable natural and social factors, resulting from issues related to the karst geological environment, the low carrying capacity of natural resources, the limited capacity of the geological environment, and the challenges in balancing survival, development and environmental protection. The economic and technical requirements for the restoration and treatment of karst environmental geological issues are increasingly demanding. Guided by the theories of hydrogeology, environmental geology and ecology, and based on a large number of detailed investigation data, this study systematically summarizes and analyzes the issues on karst environmental geology such as rocky desertification, waterlogging and drought, groundwater pollution, spring water drainage, deterioration of the wetland ecological environment, and karst geological disasters on the Yunnan plateau as well as the difficulties and causes of restoration and control of these disasters. The countermeasures and suggestions to address these issues have been put forward, which can provide the orientation and scientific basis for ecological protection and restoration.

Analysis of a new round of groundwater resource evaluation in Yunnan Province

GAO Yu, ZHANG Hua, WU Guihua, YANG Fan, KANG Xiaoli, ZHOU Junrong, WU Hongmei, LIU Haifeng

2024, 43(6): 1248-1260. doi: 10.11932/karst20240603

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Yunnan Province is located in the eastern region of the Qinghai-Tibet Plateau and the western area of the Yunnan-Guizhou Plateau. This province is characterized by mountainous plateau topography and is abundant in water resources. Groundwater resources hold great potential for development and utilization, but there is a critical issue regarding their uneven spatial distribution. Therefore, it is imperative to accurately investigate and evaluate the groundwater resources in Yunnan Province. Based on the systematic study of hydrogeological conditions in this province, its groundwater system is divided into 21 four-level basin systems and 41 five-level units for groundwater resource evaluation. In this paper, we systematically discuss the evaluation method and parameter determination for groundwater resources, and summarize and present the final evaluation results.In this evaluation, we utilized long-term rainfall data spanning from 2000 to 2020, along with the permeability coefficient and runoff modulus obtained from 1∶50,000 hydrogeological surveys conducted in Zhaotong, Yuanmou, Binchuan, Qujing, Yuxi, and other basins since 1960. Additionally, we incorporated data from the 1∶50,000 hydrogeological surveys of key karst areas in Yunnan, as well as the 1∶50,000 hydrogeological survey report of this province. We used the monitoring data from meteorological and hydrological stations to adjust the parameters of each evaluation zone in order to assess the groundwater resources in Yunnan Province. It is concluded that the average annual recharge of groundwater resources from 2000 to 2020 was 85.466 billion m³·a⁻¹. The average annual groundwater runoff resources was 62.916 billion m³·a⁻¹, accounting for 73.62% of the groundwater resource supply. Among them, the average annual groundwater resource supply in the Yangtze River Basin from 2000 to 2020 was 18.131 billion m³·a⁻¹, while the average annual groundwater runoff resources during the same period was 13.942 billion m³·a⁻¹. In contrast, the average annual groundwater resource supply in the river basins of Southwest China from 2000 to 2020 was 48.258 billion m³·a⁻¹, with average annual groundwater runoff resources amounting to 34.106 billion m³·a⁻¹. Besides, the average annual recharge of groundwater resources in the Pearl River Basin from 2000 to 2020 was 190.77 billion m³·a⁻¹, and the average annual groundwater runoff resources was 148.68 billion m³·a⁻¹. In the past 21 years, the groundwater resource supply in the Yangtze River Basin, the river basins of Southwest China, and the Pearl River Basin exhibited significant fluctuations, with the lowest supply occurring in 2011. The highest groundwater resource supply in the Yangtze River Basin was recorded in 2016. The Pearl River Basin experienced its peak supply in 2015, and the river basins of Southwest China had the highest supply in 2008. The data presented not only highlights the disparities in groundwater resources across various basins in Yunnan Province, but also serves as a crucial foundation for regional water resource management and planning. In terms of groundwater quality, the results from 223 water quality monitoring points in 2021 indicate that there were no Class I water samples detected; Class II water was found at 9 points, accounting for 4% of the total; Class III water was detected at 24 points, accounting for 10.76%; Class IV water was identified at 112 points, making up 50.22%; and Class V water was present at 78 points, which accounted for 34.98%. The types of contaminated groundwater primarily included pore water, which typically exhibited mild to moderate levels of pollution. In contrast, only a few areas were heavily polluted. Additionally, bedrock fissure water was present, but its degree of pollution was generally slight. Most of the pollutants were NH₄⁺, F⁻, Fe, Mn, volatile phenols, Hg, COD, etc. The analysis of the factors influencing the quality of Class IV and Class V groundwater indicated that the most significant contributor to water quality exceeding permitted levels was the visible matter, followed by volatile phenols and manganese. In addition to the sensory index, the most influential factor was volatile phenols, followed by manganese and ammonia nitrogen. The main areas of pollution were concentrated in economically developed and densely populated cities, such as Kunming, Qujing, Yuxi, Kaiyuan, Chuxiong, Dali, and other places.In summary, although the groundwater resources in Yunnan Province are abundant, the water quality problem cannot be ignored. In the future, the protection and management of groundwater resources should be strengthened, especially in the areas with rapid economic development. The sustainable utilization of groundwater resources should be ensured by implementing stricter environmental protection policies, strengthening the monitoring and control of pollution sources, promoting water-saving technologies, and raising public awareness of environmental protection.

Types and characteristics of vulnerable eco-geological environments on the Yunnan plateau and countermeasures for ecological restoration

LI Qin, WANG Yu, ZHANG Hua, CHAI Zhengjiao, XIONG Bo

2024, 43(6): 1261-1274. doi: 10.11932/karst20240604

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The geological background of the Yunnan plateau in the study area is complex, with significant uplift caused by the Himalayan orogeny, intense neotectonic movements, and pronounced variations in fault block elevation. The long-term shaping of internal and external dynamic geological processes has formed a modern ecological geological environment pattern with significant regional differences, diversity, and vulnerability. Therefore, the study of ecological vulnerability in high-altitude mountainous areas has always been an important issue facing the construction of ecological civilization in Yunnan Province. Currently, there are limited achievements in vulnerability research for specific regions within the province, and there is a lack of regional, comprehensive, and systematic research and analysis throughout the province. In order to improve the scientific compilation of national spatial planning and ecological restoration planning, as well as the feasibility and effectiveness of various restoration and governance projects, it is necessary to strengthen the investigation of ecological geological environment. Additionally, it is essential to enhance the identification and diagnosis of ecological problems, highlighting the importance of understanding these problems through the lens of nature principles, local conditions, and systematic restoration efforts.This article aims to systematically analyze the vulnerability characteristics of the ecological geological environment on the Yunnan plateau from the perspective of land and space protection and restoration in Yunnan Province. The manifestations of vulnerability are thoroughly analyzed, including geology, geomorphology, surface material composition, meteorological and hydrological characteristics, ecological patterns, etc. Based on the sensitivity of the ecological geological environment to external interference and limited self-recovery ability, four typical types of vulnerable ecological environments are identified: karst rocky mountains, plateau lakes, dry-hot valleys, and high-altitude mountainous areas. The karst rocky mountains experience severe soil erosion and water leakage, characterized by slow soil formation, limited growth, a scarcity of suitable tree species, simplistic communities, and a widespread shortage of surface water. The selection of ecological restoration models should be based on in-depth investigation and evaluation, as well as tailored plans. The plateau lakes exemplify a basin economy characterized by low carrying capacity for both resources and environment, and by both waterlogging and drought. Any adverse environmental effects resulted from ecological damage and pollution in the surrounding areas can be directly transmitted to plateau lakes through runoff, resulting in a focusing effect. The dry-hot valleys experience drought and water scarcity, with prominent water-heat contradictions. The ecological geological environment is vulnerable, and natural disasters occur frequently. There are intense soil erosion, soil degradation, and low productivity, leading to economic backwardness. Besides, agricultural, animal husbandry, and mining activities are extensive. In the high-altitude mountainous areas, the mountains are steep with intense erosion and denudation, resulting in thin and scattered soil layers. The biological conditions for plant growth are poor, and there is a strong trend towards desertification in the natural process. The ecological geological environment is vulnerable, with a high incidence of geological disasters. Human restoration is difficult and lacks sustainability.By analyzing and understanding the complex geological background, intense neotectonic movements, and the resulting vulnerability characteristics of the ecological geological environment, as well as addressing common problems and deficiencies in ecological restoration practices, we have proposed the following steps for the protection and restoration of plateau ecosystems. Firstly, we should conduct thorough research and investigation, adhering to natural and economic laws. We should carry out comprehensive and scientific research to identify the ecological geological environment and resource conditions, starting from the diversity of the ecological geological environment. We should also reveal the inherent connections and succession patterns of the ecosystem, accurately identify ecological problems, and enhance the specificity and effectiveness of ecological restoration. Secondly, we should plan the restoration in an integrated and coordinated manner and carry out the planning systematic, fully considering the differentiation of ecological geological environment. Taking the watersheds as units and considering the resources, environmental factors, and economic and social conditions of the restoration areas, we should implement comprehensive planning. This planning must align with the inherent connections among ecological elements and the principles governing material and energy transformation. Our goal is to ensure overall protection, integrated management, and systematic restoration. Thirdly, we must adhere to the principle of prioritizing protection while focusing on natural restoration. Given the vulnerability of the ecological geological environment, we should prioritize effective ecological protection by minimizing interference and destruction to vulnerable ecosystems, thereby avoiding situations that are difficult to remediate. Fourthly, we should enhance the overall coordination and guidance of national land space planning. Grounded in the principles and methods of earth system science, sustainable development theories, nature-based solutions, and relevant applied sciences, we must improve the evaluation of resources and environmental carrying capacity, as well as the suitability of national land space development within national spatial planning. This process involves thoroughly identifying the distribution and extent of ecologically vulnerable national land space, with the comprehensive consideration of factors such as precipitation distribution, vegetation cover, human interference, the significance of biodiversity conservation, and soil and water conservation to conduct resilience evaluation.Furthermore, this article proposes that while the analysis of ecological geological environment vulnerability primarily focuses on geological factors, vulnerability is closely related to human activities such as land development and utilization, climate change, and environmental pollution. Research on vulnerability should be an interdisciplinary collaboration to enhance its systematic nature and comprehensiveness. In future endeavors, the integration of ecology, geography, and geology can further broaden the content and indicators of research, thereby providing a scientific foundation for formulating more targeted policies.

Characteristics and prospective evaluation of natural mineral water resources in the Erhai lake basin

WANG Bo, ZHAO Li, CHEN Xiaomei, ZHU Guangyi, ZHANG Gaoyin

2024, 43(6): 1275-1286. doi: 10.11932/karst20240605

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The Erhai lake basin is an area with a beautiful ecological environment and important cultural and economic value in Southwestern China; therefore, in-depth studies on mineral water resources in this region hold far-reaching significance in ecology, environment, economy and society. This study is based on the project of the investigation of hydrogeological elements of typical wetland environment in the Erhai lake basin, located in northwest Yunnan. It systematically summarizes, organizes, and analyzes various factors, including landforms, stratigraphy and lithology, geological structure, climate, and water quality, based on extensive investigations and sampling tests. By examining the characteristics of mineral water resources, this study elucidates their water quality, quantity, and distribution patterns. Through a long-term evaluation, it forecasts the development potential and sustainable utilization prospects of these mineral water resources, thereby providing robust support for ecological protection, sustainable water resource utilization, economic development, and social stability in the Erhai lake basin. The mineral water resources in the basin encompass drinking mineral water containing both metasilicic acid and trace elements, and therapeutic mineral water. These resources are primarily distributed in a belt-like pattern across the western part of the basin, exhibiting higher abundance in the northwest and lower abundance in the southeast. They are more prevalent in mountainous areas and less so in the basin. These mineral water resources are typically located in regions with well-developed faults and folds, frequent variations in stratigraphic lithology, and a widespread presence of magmatic rocks. In terms of water quality characteristics, mineral water typically contains a high concentration of metasilicic acid. In areas with carbonate rocks, drinking mineral water often contains trace elements such as Sr and Zn. Conversely, in basalt regions, mineral water rich in metasilicic acid is more common. For therapeutic mineral water, both the concentration necessary for medical efficacy and the concentration required for classification as mineral water must meet or exceed three specific criteria. Based on the differences in the primary controlling factors of formation conditions—such as geological structure, topography, aquifer burial and distribution, and groundwater runoff circulation—the mineral water in the basin can be categorized into two types of genesis: fault-zone convection type and subsurface dissolution-filtration type. The fault-zone convection type constitutes 42% of the total and is characterized by deeper circulation, pressurization, higher water temperatures, and more stable dynamics. This type often yields high-quality therapeutic mineral water. In contrast, the subsurface dissolution-filtration type accounts for 58% and primarily produces drinking mineral water rich in metasilicic acid. This type is associated with simpler hydrogeological conditions, exhibiting characteristics such as shallower circulation depth, shorter cycles, and unstable dynamics. The Erhai lake basin is abundant in mineral water resources, which are currently underexploited, indicating significant potential for further development. Conducting research and analysis on the characteristics of these mineral water resources, performing long-term evaluations, and scientifically formulating protection and development strategies can help forecast the development potential and sustainable utilization prospects of mineral water resources. These efforts will contribute to the rational planning of the water resources development, help prevent over-exploitation, and ensure sustainable use. Furthermore, they will play a crucial role in maintaining the ecological balance of the basin, protecting biodiversity, and promoting the coordinated development of the regional economy and the environment.

Study on the variation characteristics of backwater levels of the Pijiazhai karst spring in Luxi county, Yunnan

ZHOU Cuiqiong, CHAI Jinlong, ZHANG Gui, WANG Yu, HE Raosheng, WANG Jin, LI Jihong

2024, 43(6): 1287-1294. doi: 10.11932/karst20240606

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The Pijiazhai karst spring is located at the edge of the upstream Luxi basin, where the terrain shifts from steep to gentle slopes. The spring's recharge area covers 115 km², where the recharge runoff area is the white water karst trough valley in the upper reaches of the basin and the peak-cluster depression area at the edge of the basin. There are more springs in the white water karst trough valley but the dynamic is unstable. The main aquifer formations in the spring are dolomite and limestone of the Triassic Gejiu Formation. Although karst development is strong, it is uneven, leading to significant variability in hydraulic properties. Besides precipitation recharge, leakage from the Baishuitang reservoir is a crucial source of recharge. The hydraulic gradient, from the Baishuitang reservoir to the spring outlet, ranges from 1.43% to 1.62%, with groundwater flow velocities between 144.82 and 176.45 m·h⁻¹. The spring discharge varies from 1,072 to 1,957 L·s⁻¹ and remains relatively stable. By means of drilling, geophysical exploration and backwater test, the water levels of the Pijiazhai karst spring are studied. A total of 16 boreholes were drilled near the spring outlet, with depths ranging from 15.1 to 45.1 meters, and the maximum rise in backwater level reached 0.66 meter.Results indicate that, despite the intense karst development near the Pijiazhai karst spring, the distribution of this development is spatially uneven. Horizontally, the analysis of joint fissures reveals four major karst development zones composed of densely distributed caves and solution fissures. Additionally, at varying depths, these dense zones of caves and solution fissures are also present vertically. To the north of the spring outlet, karst development is intense but uneven, predominantly featuring solution fissures and caves, with some caves diameters reaching 4.7 meters. Downstream of the spring, karst development is relatively weaker and more uniform, primarily consisting of solution fissures, with fewer and smaller caves, the largest being 0.6 meters in diameter. At the eastern side of the spring outlet, a significant karst development zone is dominated by solution fissures, which generally exceed 70 meters in thickness, and are widely distributed. Overall, at the area near the spring outlet, a complex and interconnected network of fissures and conduits have been developed. The Pijiazhai karst spring exhibits a certain degree of pressure resistance. Prior to the backwater at the spring outlet, the water levels in 15 nearby observation boreholes, with the exception of the upstream Borehole zk1, are consistently 0.3 to 3.0 meters lower than the water levels at the spring outlet. After backwater, the water levels at the spring outlet remains elevated compared to the levels in the other observation boreholes. The increase in water levels around the spring outlet during the backwater process, as well as the response time and distance, do not exhibit a direct relationship; rather, they are influenced by the development and connectivity of the karst system, demonstrating significant anisotropy. Notably, the spring outlet experiences the most substantial rise in water levels, while the northern upstream area shows a relatively larger increase. In contrast, the southern downstream area exhibits a rapid decline in the amplitude of the rise, and the eastern region experiences a smaller and slower increase. Upstream of the spring outlet, the aquifer structure is mainly characterized by fissure-conduit systems, which show substantial and rapid water level rises during backwater. This often results in a 2–3 hours of groundwater "surge" phenomenon, initially marked by a rapid rise to a peak, and then a brief decline, followed by a gradual rise to a stable level, forming a "double-peak" pattern. Downstream, the aquifer structure is primarily a fissure network, leading to smaller and slower rises of water levels during backwater, typically showing a more uniform "linear" rise, with occasional short-term anomalies of water level decrease before rising. When the backwater height at the spring outlet maintains within a specific range, short-term fluctuations in groundwater levels may cause the spring water to become turbid; however, this does not result in a significant decrease in discharge. Engineering practice confirms that a rise of 4.4 meters in spring head does not lead to a noticeable reduction in discharge.

Study on the characteristics of interannual dynamic variations in groundwater levels in the Dianchi lake basin

ZHOU Junrong, ZHANG Hua, KANG Xiaoli, GAO Yu, HE Raosheng, WU Hongmei, LI Qin

2024, 43(6): 1295-1304. doi: 10.11932/karst20240607

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Between 1980 and 2020, with the continuous development of the social economy and the expansion of urban areas, the urban underground engineering in the Dianchi lake basin, also known as the Kunming basin, became increasingly dense. Industrial water consumption increased, and the government strengthened its management of groundwater resources, resulting in variations in groundwater levels. The demand for water resources continued to increase, but the problem of water pollution remained severe. Under the premise that some surface water bodies and pore water have been polluted by human activities, deep well drilling became a common way to extract groundwater at that time. However, with the increasing number of deep wells, the overall groundwater levels of the entire basin were affected, and problems such as the drying up of spring water, falling funnels, and ground collapses occurred in succession. This study is based on the statistical analysis of water level monitoring data collected from existing monitoring wells in the 1980s, 2006, and 2020. With statistical and comparative methods, ArcGIS was used to create contour maps of groundwater levels and maps of water level variations in the Kunming basin over various periods. Based on the principles of hydrogeology, environmental geology, and groundwater system analysis, this study identified the main natural and human influencing factors, effects of controlling groundwater resources and environment, and the existing challenges. It analyzed and summarized the variations in water levels in the Kunming basin over the past 40 years. Additionally, this study outlined the reasons for these water level fluctuations and the potential problems of environmental geology that may arise as a result.Analyses indicate that groundwater levels in the Kunming basin have shown an overall upward trend over the past 40 years. From the 1960s to the 1980s, fluctuations in groundwater levels in the Kunming basin were not significant, although the overall situation indicated a decline. Besides, and the extraction of groundwater and its rate of increase were relatively modest. From the 1980s to 2006, the groundwater levels in the Kunming basin showed a downward trend, especially in the areas of Dounan flower market in Chenggong district, as well as Paomashan and Jinma temple in Guandu district, where the water levels experienced a notable decrease. From 2006 to 2020, overall groundwater levels showed an upward trend, with significant increases observed in the area of Cuihu and the area of Majie printing and dyeing factory in Xishan district, which was classified as a zone of strong upward trends. However, most areas were characterized as the zones where the water levels experienced slight rises, including the area of Dounan flower market in Chenggong district, as well as the areas of Paomashan and Jinma temple in Guandu district. In these areas, the groundwater levels were relatively stable, with a fluctuation of about +1 m in 2020 compared to 2006. The water levels observed in the area of heavy machinery factory in Panlong district indicated a significantly downward trend. After the large-scale closure of underground water wells from 2008 to 2009, the groundwater levels in most areas of the basin showed a significant upward trend after 2009, while in some areas, due to large industrial water consumption and other reasons, the water levels still showed a downward trend.At present, the changes in the low water level center of the basin are closely related to human activities. With the development of the social economy, the changes in the low water level center are no longer only biased towards excessive exploitation of industrial, agricultural, and domestic water. The construction of a large number of civil defense projects and underground transportation projects in the urban area requires a large amount of drainage in the early stages of construction, resulting in a decrease in the surrounding groundwater levels. The decrease in groundwater levels causes changes in hydrodynamic conditions, accelerating the circulation and alternation between surface water, pore water, and bedrock water, leading to the continuous concentration of nearby sewage in the funnel area and promoting groundwater pollution. The overall decline in the water level of the aquifer may also lead to the lateral replenishment of groundwater by polluted rivers, resulting in contamination of the aquifer. For example, the Mayuan river, the Liangjia river, the Xibian river, the Panlong river, and the Jinzhi river collect industrial wastewater and domestic sewage from the west and east of the city. The decline in groundwater levels on both sides of the river will cause groundwater pollution. Today, the groundwater flow field in the Kunming basin has become a natural and artificial compound flow field. The water level dynamics under the influence of meteorological cycles are significantly affected by human factors. The change and amplitude of water level rise and fall are synchronized with the increase and decrease of groundwater mining output, excavation and drainage of underground space, etc. The projects of cross-flow diversion and water diversion have alleviated the decline of groundwater levels to a certain extent. With the popularization of knowledge related to groundwater, the government and the people gradually understand the environmental geological problems that excessive exploitation of groundwater resources may bring, and hence taking corresponding corrective measures.

Formation and evolution of the karst pastoral landscape in Puzhehei

REN Shichuan, YANG Xiaoyan, CHAI Zhengjiao, TIAN Wenrui, YANG Fan

2024, 43(6): 1305-1316. doi: 10.11932/karst20240608

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Traditional karstology examines karst geomorphic landscapes as geological processes occurring at the interface of lithosphere and hydrosphere. It concludes with a discussion on how factors such as structure, stratigraphy, hydrology, climatic conditions and neotectonic movements influence karst development. The emergence of theories in Earth system science has opened up new avenues for the advancement of karstology.Based on a substantial collection of geological relics, this study examines the formation process of the karst ecological pastoral landscape in Puzhehei from the perspective of Earth system science. It is posited that this evolution occurred gradually over hundreds of millions of years. From the Devonian period to the end of the Triassic period, a set of strata dominated by carbonate rocks with shallow marine and platform facies were deposited, which established a favorable lithospheric foundation for the karst development in the study area. The Indosinian movement and Yanshan movement from the Jurassic to the Cretaceous laid an important structural and topographic foundation for the study area. The period from the Paleogene to the present marks the formation of the karst ecological pastoral landscape in Puzhehei, which can be further divided into four stages. In the first act of the Himalayan movement, the northwest fault of the study area was reactivated, forming a topography characterized by high elevations in the south and low elevations in the north, as well as high terrain on the eastern and western sides and a low area in the center. This represents the initial stage of karst development. In the second act of the Himalayan movement, the northern plate of the Yangqi fault rose, creating a low-lying center around Luoshuidong lake. This led to the formation of fault depression lake basin in Puzhehei, marking an important stage in karst development. In the third act of the Himalayan movement, the uplift of the northern panel of the Yangqi fault intensified, leading to the gradual disappearance of surface water outlets. Consequently, the lake surface rapidly expanded southward, reaching the vicinity of Qiubei county. During this process, triangular fault basins were fully formed, and karst was further developed. Since the Late Pleistocene, the uplift of the crust and the headward erosion of the Beimen river have created a new water outlet in the surrounding area. Consequently, the lake water rapidly drained, resulting in the formation of a karst landscape. Since the Holocene, under the influence and transformation of human activities, today's pastoral landscape has come into being.According to the evolutionary process, this study preliminarily predicts the changing trends of landscape and lake water quality, and proposes several protective suggestions. First, conducting a survey on resource carrying capacity and standardizing tourism management. Second, strengthening infrastructure development and improving the sewage system. Third, establishing a scientific monitoring system for regular tracking and monitoring. Fourth, enhancing public awareness of environmental protection through effective science communication.

Characteristics of the underground hot water circulation system western Yunnan Yingjiang basin and resources development potential

ZHANG Hua, HE Raosheng, KANG Xiaobo, YANG Yingbin, LI Qin, GAO Yu, ZHOU Junrong, CHAI Jinlong

2024, 43(6): 1317-1326. doi: 10.11932/karst20240609

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The geothermal energy of the Yingjiang basin is located within Yingjiang–Longchuan high-temperature hot water belt, which is part of Gaoligongshan–Tengchong sub-area of high-temperature hot water region of western Yunnan. The study area belongs to the southern extension of Gaoligong mountain, where the terrain gradually descends from the northeast to the southwest, resulting in an overall spatial pattern characterized by valleys and ridges. Basins, mountains, and rivers in the area are controlled by structure, showing a NE-SW trend. In addition, the Yingjiang basin is a fault basin formed by geological structure. Its geomorphology are divided into five categories: fault accumulations, low hills of lake terraces, shallow cutting gentle slopes of low or middle-height mountains, medium cutting steep slopes of middle-height mountains, and karst middle-height mountains. The Yingjiang basin is located in the eastern margin of the collision zone between the Indian Plate and the Eurasian Plate. Due to the active crustal movement for a long time, the geological structure in this area is complicated, the rock fold is broken and the stratum is missing. The outcrop strata are mainly composed of Lower Proterozoic Gaoligongshan Group (Pt₁GL.), Devonian Guanguan Formation (D₁g), Permian Bangdu Formation (P₁b), Neogene Mangbang Formation (N₂m) and alluvial and pluvial strata of the Quaternary (Q). The Yingjiang basin is rich in geothermal resources with a total of 38 geothermal points, and the geothermal outcrops can primarily be classified into 3 types: hot springs, hot wells, and open wells. However, the investigations and studies on geothermal resources are not sufficient, and especially the source of geothermal resources recharge, and the amount and potential of geothermal resources need to be illuminated. In this study, the geothermal geological structures, geothermal structures, boundaries, sources and pathways of geothermal recharge of the study area have been analyzed and studied through field investigations, basic geological analyses, mathematical models, and equations of atmospheric precipitation lines in China. Geothermal resources have been calculated by the method of heat release for hot springs and the summary of spring flow.According to the research findings, the cover layer in the study area is composed of multiple cycles from the coarse to the fine, arranged from bottom to top. The sedimentary environment is dominated by fluvial facies and lakefront facies, with a total thickness of 100–2,000 m, and some of them are more than 2,400 m, providing an environment for geothermal heat storage and preservation. The heat storage structure is belt-shaped, and its conditions are controlled by principle faults and concealed faults. The main layers for heat storage are composed of magmatic rocks, metamorphic rocks, granitic sand conglomerate, fine sandstone, magmatic rocks and metamorphic rocks of Neogene Manbang Formation, which provide the necessary conditions for the exposure of hot springs. At present, the highest temperature is shown in the borehole drilled by Dimete Company in the geothermal anomaly area of Lianhua mountain. The temperature in the borehole reaches 155 ℃. The layers of heat storage are composed of magmatic rocks, metamorphic rocks, granitic sand conglomerate and fine sandstone of Neogene Manangba Formation. The Yingjiang basin is characterized by strong neotectonic movements, structural development, and heat flow activities in the depth, which suggests that magma pocket is the source of heat energy in this area. Combined with the terrain conditions around the basin, it is considered that groundwater is recharged by the deep circulation of atmospheric precipitation infiltration in the mountainous areas around the basin, with the recharge distance of 2.0–9.9 km, and the recharge depth of 1.6–3.0 km. Groundwater permeates to the deep crust along the primary fissures and late tectonic fracture zones of weathered granite and metamorphic rocks, and then moves upward after being heated by deep heat sources to form geothermal fluids, which are stored in the pores, fractured aquifers and fracture zones at the bottom and edge of the basin, and are exposed to form hot springs and geothermal springs at the parts where geomorphologic features and structures are favorable. According to the principles of geology, structure, temperature and concentration of geothermal resources, four evaluation units are divided. They are the unit of geothermal resources at medium-high temperature (I) in Lianhua mountain of the Yingjiang river in the northwest of the basin, the unit of warm water resources at low temperature (II) in the Yingjiang river in the northeast of the basin, the unit of warm water resources at low temperature (III) in Taiping–south slope in the middle of the basin, and the unit of warm water resources at low temperature (IV) in Nongmu–Manyun of Yingjiang in the south of the basin. Based on the existing parameters, it is estimated that the heat stored by geothermal fluids in the study area is 484.63×10⁶ MJ, and the recoverable amount of geothermal fluids is 3.178 million m³·a⁻¹. The study on geothermal genesis and the characteristics of circulation system of hot water in the Yingjiang basin has improved the research of deep geothermal resources in the Yingjiang basin and western Yunnan, providing resource guarantee for the exploration, development and utilization of geothermal resources, and providing the basis for the local government to confirm the registration and management of geothermal resources.

Characteristics of groundwater system and assessment of groundwater vulnerability of the Tengchong volcano group in western Yunnan

WANG Yangyang, HUANG Shengdong, PAN Dong, HUANG Guiren, WANG Yu, CHANG He, PU Yue

2024, 43(6): 1327-1340. doi: 10.11932/karst20240610

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The Tengchong volcanic group encompasses a vast area and exhibits a diverse range of eruption types. It is one of the youngest volcanic areas in China. Studying the characteristics of its groundwater system is the basis for analysis and evaluation of pollution mechanisms. Ma'anshan exhibits typical genetic and morphological characteristics in the Tengchong volcanic group. The volcanic cones and craters of Ma'anshan are relatively complete. Because the lava flows exhibit no weathered layers, Ma'anshan retains the geomorphological characteristics of the volcanos with the most recent eruption. It is dated at the Late Pleistocene or Holocene. The boundary of the groundwater system is relatively clear. Starting with the geological structure and hydrogeological characteristics of Ma'anshan area, this paper summarized the boundary characteristics of groundwater system, aquifer system characteristics, aquifer flow characteristics, and characteristics of groundwater recharge and drainage in the study area. The single factor analysis was conducted to evaluate 39 groups of water samples collected. Combined with on-site investigations, pollution sources, pollution mechanisms were explored and the groundwater vulnerability of the study area was evaluated through DRASTIC model.The results show as follows. (1) The Ma'anshan area is located in the groundwater system of Bapaidaquan, bounded by the Shitoushan underground watershed at the northeast, by the groundwater barrier on the right bank of the Nandi river at the southeast, and by the recharge boundary of the Minglang river valley at the west. The Ma'anshan area constitutes an inter-river landmass composed of the Minglang river, the Nandi river, and north-east oriented catchment valley, and mainly receives infiltration and recharge from granite fissure water, weathered fissure water and fissure water from fractured structural zones. (2) Under the strong tectonic movement and volcanic eruption, the groundwater system exhibits a complex structure and changeable hydrodynamic properties. The water-collecting chambers formed by pumice aggregates, breccia, and volcanic bomb fragments in the volcanic lava accumulation, and the lava fissures connected between them, are evenly distributed in space. Each water collecting chamber is also hydraulically connected under the communication of fractures or pores. Showing obvious characteristics with layered structures, the aquifers of the mountains in the study area are all exposed in the alluvial and pluvial layers underlying the volcanic accumulations, which supports the multi-layer interactive structural characteristics of water from lava pores and from alluvial and pluvial layers. (3) Groundwater in the study area forms pipe-type runoff along faults and continuous lava channels, and forms strands of runoff in the loose accumulations along lava fissures, volcanic bombs and volcanic breccia of varying sizes and in macropores of alluvial and pluvial gravel layers. Then, runoff converges in the lava fissure zone on the gentle slope of the mountain on the east side of the Minglang river valley and in the ancient river channel at the valley edge, and is finally discharged into the Bapai spring. (4) Areas where the water quality exceeds permitted levels are mainly distributed in industrial parks, solid waste landfills and agricultural living areas. In industrial parks, the water quality exceeds permitted levels mainly due to excessive heavy metal elements. In solid waste landfills and agricultural living areas, water contains excessive pH values. According to the characteristics of pollution sources, structure and water-containing media, aquifer anti-fouling performance, and conversion process between surface water and groundwater, there are two main types of groundwater pollution mechanisms in the study area: trans-flow infiltration and direct infiltration. (5) The proportions of low-vulnerability areas, medium-vulnerability areas, and high-vulnerability areas in the study area are 3.6%, 42.1%, and 54.3% respectively. The high-vulnerability areas are mainly distributed in the lower reaches of the Minglang river, Ganzhezhai–Hehua–Bapai and other areas with more water resources. The depth of the groundwater level in this area is small, and the water-bearing medium is uneven. The recharge of groundwater can be directly infiltrated through pipes and trough fissures. The adsorption effect of volcanic ash and alluvial mud filled or accumulated in the air-bearing zone is approximate to be missing. Because industrial enterprises are also concentrated here, the background values of heavy metals and harmful metals in groundwater are high. Aquifers are highly sensitive to pollutants or human activities, and are, therefore, highly vulnerable. The water samples with relatively poor water quality of Class III and Class IV are mostly distributed in the areas with medium-and-high-vulnerability, indicating that the results of groundwater vulnerability assessment are basically reliable.

Response of carbonate weathering and dissolution processes in the Kunming basin to changes in atmospheric CO₂ concentration over the past 40 years

YANG Xiaoyan, REN Shichuan, TIAN Wenrui, MA Nengwei, SONG Zenghong, LI Guorui, ZHANG Gaoyin

2024, 43(6): 1341-1349. doi: 10.11932/karst20240611

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The carbon cycle of the Earth's system coexists with global climate change. Carbon circulates in different forms between different reservoirs, with carbonate rocks actively participating in the global carbon cycling through karst processes. The recovered CO₂ accounts for about one-third of the "missing sink", making it an important link between the atmosphere and the sink of CO₂. Currently, the dynamic studies on the karst carbon cycling are mainly focused on short time scales such as daily, monthly, seasonal, and annual dynamics, as well as the effects of precipitation. These studies suggest that karst processes are extremely sensitive to environmental changes and are basically synchronized with various climate changes (such as precipitation and temperature) and biological activities, with no significant lag observed. The long-term dynamic changes and responses to climate change are mainly based on carbon isotope records in stalagmites. These records indicate that the changes in carbon content within stalagmites lag behind alterations in atmospheric CO₂ concentration by 16 years. Although the IPCC's AR5 and AR6 reports acknowledge the important role of karst carbon sink in sequestering atmospheric CO₂, they classify the carbon sink associated with carbonate rock weathering (karst action) as a long-term carbon sink with a time scale of 10³–10⁴ years. Furthermore, this process has not been incorporated into the global carbon budget. There is considerable controversy surrounding the timescale of karst carbon sink. Consequently, the long-term dynamics of carbonate weathering, carbon sink, and their responses to climate change necessitate further in-depth research.The outcropping area of carbonate rocks in the karst area of Southwest China covers 540,000 km², encompassing three major geomorphic units of the country. This area represents the largest contiguous distribution of exposed carbonate rocks in the world. It benefits from favorable water and heat conditions, along with intense karst processes, which contribute to significant carbon sink effects. The Kunming basin is a water-collecting karst graben basin, with a catchment area of 2,924.5 km². The outcropping area of carbonate rock layers accounts for about 32% of the total basin area. Karst water in the basin is characterized by abundant amount, concentrated storage, and good water quality. Meanwhile, Kunming, as the capital city of Yunnan Province, has a developed socio-economy. Groundwater monitoring in the area began early and has resulted in a substantial accumulation of foundational data. However, research on karst carbon sink remains relatively underdeveloped. Based on the long-term observation data of karst springs in the Kunming basin, this paper analyzes and calculates the changes in atmospheric CO₂ concentration, climate indicators (temperature and precipitation), and data on spring water quality. The response of carbonate weathering to fluctuations in atmospheric CO₂ concentration and climate change over the past 40 years, along with its carbon sink effect and contribution to CO₂ emission reduction is preliminarily evaluated. The results show that the CO₂ consumption rate by carbonate weathering is positively correlated with atmospheric CO₂ concentration, exhibiting a lag time of about 20 years, and the rate of change is basically the same. The variations in carbon sink intensity are mainly controlled by changes in precipitation, with no obvious lag time, while also being affected by changes in atmospheric CO₂ concentration, with a lag of 20 years. The research findings indicate that the increase in atmospheric CO₂ concentration will enhance the dissolution of carbonate rocks, allowing more CO₂ to be sequestrated from the atmosphere. This process plays an important role in mitigating global warming. These findings are significant for accurately evaluating the intensity of karst carbon sink, incorporating karst carbon sink into global carbon accounting, addressing the "missing sink" problem, and promoting the achievement of the "dual carbon" goals.

Study on distribution law of geological disasters in karst mountainous area of east Yunnan

ZHANG Jie, ZHANG Weifeng, WEI Lei, DAI Xusheng, ZHANG Wenjun

2024, 43(6): 1350-1361. doi: 10.11932/karst20240612

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Based on a comprehensive and detailed investigation, coupled with a risk assessment of geological disasters at a scale of 1∶50,000 in the study area, this paper focuses on the unique characteristics of high mountain valleys and karst rock mountains prevalent within the region. Through a combination of data statistics and qualitative analysis, the distribution patterns and laws of geological disasters in the study area are meticulously elaborated in terms of landform, slope structure type, geological structure, geological engineering, and rock formation.The findings are listed as followings: (1) The terrain in northeast Yunnan is characterized by significant relief, with deep river valleys predominantly located along the plateau edges and valley slopes. Consequently, the distribution of geological disasters gradually diminishes from north to south, with a mean density of 8.62 per 100 km². The northern alpine valleys and valley slope areas exhibit the most developed geological disasters, which are approximately 2 to 3 times more numerous than those in the central plateau basin. (2) Geological disasters are more prevalent in the geomorphic units dominated by the edges of plateaus and slopes of river valleys, with a total of 3,161 occurrences, which accounts for 29.67% of all recorded disasters. The geological disasters are not developed in the plateau areas of central and east Yunnan, where the plateau morphology is relatively intact and the terrain is gentle, with only 87 occurrences, accounting for 0.82% of the total disasters. (3) The geological disasters in the study area are mainly distributed in sections with slopes of 10°–30°, totaling of 7,028 occurrences, which account for 66.62% of all geological disasters. In contrast, the sections with slopes greater than 40° exhibit the fewest geological disasters, with only 797 occurrences, representing 7.55% of the total. Additionally, geological disasters in the study area are primarily concentrated in slope sections with orientations of 90°–135°, 225°–270°, and 270°–315°, totaling 4,249 occurrences, which account for 39.88% of the overall. These disasters generally extend from north to south and west, demonstrating a correlation with the northeast-to-south and north structural patterns. (4) Geological disasters predominantly occur at the intersections of fault zones or in regions where the orientation of the primary faults changes. These disasters tend to be distributed in a linear or belt-like patterns. When faults remain continuously active, signs of multiple disasters events become apparent. The distribution of geological disasters correlates with structural features, including the orientation of faults, and the dip direction of slopes. Geological disasters are arranged in an imbricated pattern on both sides of the main controlling faults. In the case of strike-slip reverse faults, the distribution of geological disasters exhibits a notable "upper plate effect". Particularly, under seismic activities, the frequency of geological disasters on the upper plate is significantly greater than that on the lower plate. (5) In the study area, geological disasters are most prevalent in dip-slope formations that contain weak interlayers of mudstone and shale, with a total 2,995 occurrences, accounting for 31.94% of all recorded disasters. In contrast, slopes formations with orthogonal structures lack natural medium interfaces, which hinders the formation of continuous structural sliding surfaces. Consequently, geological disasters are less common in these areas, with only 901 occurrences, representing 9.61% of the total number of disasters. (6) The carbonate group containing weak interlayers is more susceptible to the development of joint fissures under tectonic forces. Surface water and groundwater can easily infiltrate these joint fissures, leading to the hydration and softening of the interlayers. Over time, this process may evolve into a slip zone for rock falls or landsides, resulting in a disaster-prone structural formation characterized by being solid and heavy on top, and soft and light below. This rock group is where geological disasters are most prevalent in the study area. The findings from this study can provide a geological foundation for comprehensive prevention and control of geological disasters, as well as a foundation for land use planning and regulation in the study area.

Remote sensing interpretation and application of geological environment conditions in early identification of potential geo-hazards: A case study of Huaping county

YANG Yanfang, JU Hejian, CHENG Yang, WANG Yong, YAN Shuhao, WANG Shanshan, LI Qin

2024, 43(6): 1362-1375. doi: 10.11932/karst20240613

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Huaping county is located in the mountains bordering the Yunnan–Guizhou Plateau and the Qinghai–Xizang Plateau, where geo-hazards occur frequently. In order to understand the background of disaster generation and the laws of their occurrence, as well as to enhance the accuracy of early identification of potential geo-hazards and reduce the likelihood of disasters, this study has developed a county-level system for remote sensing interpretation of the geological environment. This system is designed for the early identification of potential geo-hazards, based on practical work and existing norms and standards. Additionally, this study has established a set of full-element interpretation signs for geological environment conditions in Huaping county by utilizing Beijing-2 High-Resolution Optical Remote Sensing Images, thereby completing the remote sensing interpretation of the geological environment in Huaping county. Based on the interpretation results of the geological environment in this county, this study examines the potential landslide hazards in Bade village, Huaping county, as a case study. It demonstrates how remote sensing interpretation of the geological environment facilitates the early identification and risk assessment of potential geo-hazards occurring in a single geographic unit. The overall findings of this study are as follows:(1) The remote sensing interpretation system of county-level geological conditions, based on potential geo-hazards, can be summarized and classified into seven categories: topography and geomorphology, geological structure, stratum lithology, hydrogeology, land use, human activities, and adverse geological phenomena.(2) With the use of seven categories of geological environment elements, the process of interpreting and assessing potential disasters in a single geographic unit can be summarized as the following steps. First, the characteristics of surface deformation, and indicators of topography and geomorphology were analyzed to determine the activity and the topographic associated with the occurrence of potential geo-hazards. Second, based on the four kinds of indicators of geological structure, stratum lithology, hydrogeological conditions, and adverse geological phenomena, hidden dangers in the disaster environment were assessed. Third, with the use of two indicators of human activities and land use, the type of the hidden bearing body and the associated hazards were evaluated. Finally, the risk level of the hidden danger was evaluated based on the activity and the potential harm involved. It is important to note that this assessment was conducted indoors, and the final risk level must be verified in the field.(3) Conducting a full-element optical remote sensing interpretation of geological environment can rapidly and accurately assess the disaster-bearing conditions of specific geo-hazards in a single geographical unit such as the potential landslides in Badu village, Huaping county. This approach can significantly enhance the accuracy of early identification of potential geo-hazards and holds significant importance for identifying such geo-hazards in the mountainous areas of Southwest China. It is recommended to implement a thorough remote sensing interpretation.

Research on early warning for meteorological risks of rainfall-induced landslide hazards in typical areas of southwest Yunnan

WEI Lei, MEI Hongbo, ZHAO Peng, YANG Yingdong, LUO Zeyang, LIU Bowen

2024, 43(6): 1376-1385. doi: 10.11932/karst20240614

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The area of Longyang district–Mangshi section is located in the middle and lower reaches of the Nujiang river and the Daying river. The landform in this area is dominated by medium mountains, wide valleys, and basins. This area is characterized by a southern subtropical monsoon climate and a southern subtropical mountain monsoon climate. The overall structural features within the area are composed of a series of near north-south faults, and their derived secondary transverse tensile faults as well as tight folds. Lithology is mainly composed of metamorphic rock strata in the Proterozoic Gaoligong mountains, strata from the Paleozoic to the Mesozoic, and clay, fragments, gravel from the Quaternary. The study area is typically concentrated and developed with rainfall-induced landslides, and geological disasters mainly include collapses, landslides, debris flows and ground subsidence. Among these disasters, there are 1,175 landslide events, with rainfall-induced landslides accounting for over 95%. This type of disaster is the most significant in the study area. Water systems are intensively distributed in this area, with large depths of river valleys, and a pronounced variation in terrain. Landslide hazards are mainly distributed along valleys on both sides of rivers. Based on the assessment of vulnerability and the analysis of rainfall thresholds, an early warning model for rainfall-induced landslide risks has been established. This model can effectively support early warnings for regional landslide risks.The study area is located in the section of Longyang district–Mangshi section in southwest Yunnan Province, which is prone to frequent landslide hazards. This study employed Pearson correlation coefficient to analyze the relationships among various evaluation factors. A total of 13 evaluation factors, including elevation, slope and slope direction, were selected, and grid units measuring 100 m×100 m were divided. The random forest model was employed to evaluate the vulnerability of landslide hazards and the area under curve (AUC) was utilized to verify the accuracy of the model. Then, by analyzing the coupling relationship between landslides and rainfall, the early effective rainfall intensity (EI) was calculated. The EI and rainfall duration (D) were used as the horizontal and vertical coordinates respectively, to create a double-logarithmic coordinate system. This system illustrated the scatter distribution of the probability of landslide occurrence time and allowed for the fitting of the EI-D threshold curve according to the classification standards for landslide warning grades. Subsequently, a rainfall threshold model was created. Finally, the susceptibility classification region and the EI-D rainfall threshold were superimposed and combined to establish early warning levels for meteorological risks of rainfall-induced landslides based on the EI-D rainfall threshold.Research findings indicate that the AUC value of the training results for the random forest model is 0.84. This suggests that the model selection is appropriate and that the susceptibility evaluation results are reliable. An EI-D rainfall threshold model has been developed, and four EI-D rainfall threshold curves have been fitted. In conjunction with the evaluation results of the vulnerability of the study area, a dynamic evaluation model for landslide risks based on the EI-D rainfall threshold has been established. This model can serve as a reference for early warning evaluations of meteorological risks in the study area.

A study on multiple-model evaluation of landslide susceptibility

HUANG Cheng, DENG Yunlong, YAN Xiangsheng, ZHOU Xincheng

2024, 43(6): 1386-1397. doi: 10.11932/karst20240615

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Landslides are one of the most common geological disasters in China, characterized by sudden occurrence and uncertainty. The evaluation of landslide susceptibility is a complex process. Conventional methods mainly use static factors, making it difficult to achieve dynamic assessment of landslide susceptibility. With the ongoing advancement of science and technology, interferometric synthetic aperture radar (InSAR) has been successively applied to the study of geological disasters. This technology is characterized by its all-weather capability, continuous operation, and extensive coverage, allowing for real-time monitoring of the Earth's surface under varying environmental conditions. InSAR enables a comprehensive understanding of the movement of the surface rocks and soil masses associated with landslide geological disasters. It effectively captures the dynamic deformation characteristics of landslides in the vertical direction, thereby enhancing the identification and dynamic monitoring of surface deformation and improving the accuracy of evaluating landslide susceptibility. In this study, the surface deformation representative factor has been introduced into the conventional evaluation of geological disaster susceptibility. This addition improves the reliability of the evaluation of landslide susceptibility and enhances the overall accuracy.This study focused on Shuangjiang county as the research area. It utilizes evaluation index factors such as Digital Elevation Model (DEM), slope gradients, aspects, curvatures, stratigraphic lithology, faults, land use, annual average rainfall, roads, and rivers. The representative factor of InSAR surface deformation was comprehensively considered to evaluate landslide susceptibility. Through an extensive analysis of InSAR deformation, a dataset of landslides was established, identifying a total of 116 landslide geological disasters. Among them, 56 landslide areas exhibited deformation, with some slopes showing significant signs of deformation. The information quantity, certainty factor, and frequency ratio models were employed to evaluate the susceptibility of areas to landslides. The accuracy of the generated landslide susceptibility was evaluated with the use of the landslide density ratio, curve of Receiver Operating Characteristic (ROC), and the Area Under the Curve (AUC). In this study, 70% of the landslide events were randomly selected for spatial modeling training, while the remaining 30% were used for model verification. The segment set statistical tool in ArcGIS software was utilized to conduct the mutual independence test on the evaluation factors. Research findings indicate that all the correlation coefficients are less than 0.3, suggesting that the evaluation factors are independent of one another. According to the natural paragraph point method in Geographic Information System (GIS), the susceptibility can be categorized into five intervals: low susceptibility area, relatively low susceptibility area, medium susceptibility area, relatively high susceptibility area, and high susceptibility area. The high landslide susceptibility areas are mainly distributed in the northern part of Shuangjiang county; the low landslide susceptibility areas are mainly concentrated in its northwestern part. In the relatively high susceptibility area and the high susceptibility area, the raster of the inspection samples accounts for 88.69% of the total landslide inspection raster. The experimental results show that the Certainty Factor (CF) model exhibits a relatively high landslide density ratio in both the high susceptibility area and the relatively high susceptibility area, with ratios of 7.77 and 1.10, respectively. Additionally, the model demonstrates the highest accuracy and AUC values, which are 0.822 and 0.879, respectively. The accuracy of Frequency Ratio (FR) model is followed by CF model, and that of Information Quantity (I) model is the lowest. The landslide susceptibility map generated by the CF model provides a more accurate evaluation of slope instability in Shuangjiang county. Therefore, deriving the surface deformation factor based on InSAR technology and the CF model for evaluating landslide susceptibility yields the highest accuracy.

Reflection and enlightenment on monitoring and early warning of debris flows in Eryuan: A case study of the "9.13" large-scale freshet-induced debris flow of the Tiejia river

TANG Pei, ZHU Chuanbing, JIANG Yuebin, ZHOU Cuiqiong, LI Xiaomei, ZHANG Lingze, XIAO Huazong, ZHANG Wenjun

2024, 43(6): 1398-1407. doi: 10.11932/karst20240616

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Eryuan county is located in the northern part of Dali Bai Autonomous Prefecture, Yunnan Province. It borders Heqing county and Binchuan county to the east, Dali City and Yangbi county to the south, Yunlong county to the west, and Jianchuan county to the north. The maximum straight-line distance from east to west is about 80 km, and the maximum straight-line distance from north to south is about 68 km. The circumference of the county is about 340 km. Eryuan county is located at the collision zone between the Indian Plate and the Eurasian Plate, and is strongly influenced by the Himalayan orogeny. Since the Miocene, the plateau has experienced substantial uplift, accompanied by vigorous neotectonic movements. Earthquakes are common in this area due to its complex and varied geological and topographical conditions. The terrain is characterized by significant cutting, with high mountains and deep valleys. Additionally, this area has well-developed water systems, and geological disasters occur frequently in this area. It is a high-risk area for geological disasters in Yunnan Province. Since 2012, casualties resulting from geological disasters in Eryuan have primarily been attributed to rainstorm-induced gully-type debris flows. This type of debris flow disaster in the Tiejia river basin is characterized by sudden heavy rainfall occurring in the early morning, leading to large-scale events at a high level of risk. This area also serves as a site for projects of monitoring and early warning geological disasters. It represents a typical case for studies on gully-type debris flow disasters throughout the entire county.Based on the characteristics of gully-type debris flows in the Tiejia river basin, and in accordance with the Technical Specification for Geological Disasters Monitoring and Early Warning by Combination of Professional and Masses Methods and the Technical Guidelines for Monitoring and Early Warning of Geological Hazards in Yunnan Province (Trial), in this study, we employed rainfall stations and mud water levels as main monitoring sites and data, video monitoring stations as auxiliary monitoring sites, and warning broadcasting stations as sites for on-site warning techniques. We analyzed the background and movement characteristics of debris flow disasters in the Eryuan gully. Additionally, we selected a warning model based on the similarities in geological environment and the differences in disaster conditions between the gullies of the Lanlin river and of the Heilong river. Because the main gully of the Lanlin river is shorter than that of the Heilong river, has a smaller drainage area, and features a flatter gully, we adopted a single-parameter warning model to ensure response time. Besides, the development of the main gully of the Heilong river is more tortuous and complex, and it covers a larger watershed area; therefore, we adopted a multi-parameter warning model to reduce the false alarming rate. Based on the analysis of the early warning results of the two gullies of debris flows, and the selection and layout of monitoring and early warning equipment for rainstorm-induced debris flows, we illuminated the setting of model thresholds, and summarized the experience and enlightenment of monitoring and early warning debris flows in Eryuan.The gully debris flows triggered by sudden heavy rainfall are often large in scale, possess strong destructive power, have a brief duration of occurrence, and threaten numerous objects. This presents a key challenge in the prevention of geological disasters in Eryuan county. In the work of monitoring and early warning, we should focus on the monitoring of the strong rainfall that triggers debris flows upstream and the flood flows that causes disasters in the middle and downstream areas of the debris flows. In the work of early warning response, we should identify the main threat after the disaster, and ensure that the deployed warning equipment and warning information are transmitted in a timely manner. We should comprehensively set warning thresholds and models, based on the characteristics of disasters. We should also prioritize the resettlement of evacuees and its regulation. Even if we have implemented projects of controlling debris flows, it is likely to occur debris flows under the influence of extremely heavy rainfall, especially the rainstorm-induced gully-type debris flows taking place in the Tiejia river. Projects of monitoring and early warning can still serve as an effective supplementary measure for engineering management after disaster treatment, so as to enhance the capabilities of comprehensive prevention and control of debris flows.

Measures for the protection and utilization of geo-environment during the urbanization in Yunnan

ZHANG Weifeng, ZHANG Jie, DING Zhongkai, KANG Xiaobo, ZHANG Ruxiang

2024, 43(6): 1408-1421. doi: 10.11932/karst20240617

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Yunnan, a province with a vast territory, is located in the southwest of China. It serves as a convergence zone for the Eurasian Plate, India Ocean Plate, and Pacific Plate. The western part of Yunnan belongs to Tethys–Himalaya orogenic belt, which exhibits strong crustal activities, while its eastern part falls into the stable or semi-stable platform and portions of the Pacific Plate. Yunnan subordinates both the Qinghai–Xizang Plateau and the Yunnan–Guizhou Plateau in terms of geomorphology. It is one of the youngest, most active and continuously rising plateaus, and also an area characterized by rare grand canyons. In this area, strong tectonic movements and frequent magmatic activities have formed many geomorphologic landscapes such as plateau lakes, stone forest landforms, volcano vestiges, Sanjiang gorge in the northwest of Yunnan, and hot springs in Tengchong. However, the geological conditions in Yunnan are generally complex and highly fragile.Since China's reform and opening-up over the past 40 years, Yunnan's economy has achieved great progress, and its urbanization has developed rapidly. However, while enjoying various convenience brought about by economy development, people from different ethnic groups in Yunnan are also facing a range of geo-environmental issues. These include declining water levels, drying water sources, rising snow lines, and other geological disasters. Therefore, finding ways to reduce or prevent the occurrence of geo-environment problems and to protect geo-environment during urbanization has become an important issue.This study uses a comprehensive research and analysis methodology. The entire area is categorized into six major water system basins, serving as the first-level protection unit, plateau-lake basins as the second-level protection unit, and key geological relics as the third-level protection unit. Additionally, the area can be divided into development, protection, and utilization zones, each with clearly defined protection goals and levels corresponding to each unit within the zone. In this study, we have put forward measures for the protection and utilization of geo-environment during the urbanization in Yunnan. We will strengthen research on the coordinated development model of urbanization and geological environment, and focus on areas with fragile geological environment. The key areas of geological environment vulnerability and sensitivity in Yunnan Province are divided into three major regions: the geological environment vulnerability zone on the southeastern edge of the Qinghai–Xizang Plateau in northwest Yunnan, the geological environment vulnerability zone in the dry-hot valley of the Jinsha river in northeast Yunnan, and the geological environment vulnerability zone between Ailao mountain and Wuliang mountain in southern Yunnan.In order to protect and utilize geo-environment, it is essential to enhance comprehensive dynamic monitoring of the geo-environment in urban areas within the area. This includes setting reference values for dynamic monitoring indicators and accurately capturing the changes in geo-environmental elements over time. We should promptly initiate the comprehensive protection and management of the geo-environment. Through human intervention, we can select appropriate engineering and non-engineering measures to restore the capacity and ensure the sustainable utilization of the geo-environment. The development of urban areas should be grounded in the characteristics of the geo-environment and aligned with the advantages of geographical resources. Additionally, effective national spatial planning should be implemented. Most towns can be typically constructed in basins and river valleys, where the terrain is more expansive, while a smaller number can be constructed on slopes of mountainous areas. This mountainous terrain will create a magnificent landscape that harmonious blends nature and culture. According to the terrain and landform conditions, cities and towns can be categorized into four types: mountain basin, mountain slope, valley basin, and valley slope. This classification aims to facilitate the development of aesthetically pleasing urban areas. In the future, research will focus on geo-environmental issues, including key points, hotspots, and challenges. The scientific understanding of how human activities impact the geo-environment, the implementation of coordinated development between urbanization and the geo-environment, and the enhancement of comprehensive three-dimensional protection and governance of the geo-environment are crucial for the advancement of urbanization and the effective protection of geo-environment. The mechanism behind the formation of geo-environmental problems should be studied in order to prevent geo-environment from exacerbation or occurrence. Studies should be conducted to promote sustainable development that balances urbanization with the geo-environment and to propose effective countermeasures for addressing geo-environmental problems.

Study on ecological restoration countermeasures of abandoned mines in Yunnan Province

CAI Baoxin, LI Qin, KONG Zhigang, YANG Xiaoyan, LI Yanqing, SONG Zenghong

2024, 43(6): 1422-1429. doi: 10.11932/karst20240618

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Ecological restoration of abandoned mines is an important step in practicing ecological civilization and is of great significance in maintaining ecological security in Southwest China. Yunnan Province is abundant in mineral resources and is often referred to as the "Kingdom of Non-ferrous Metals" and the "Province for Phosphorus Chemical Industry". Mining is one of the pillar industries in Yunnan, making significant contributions to the socio-economic development of Yunnan and the rest of China. However, the ecological and environmental issues carried over from mining activities of the past are prominent. The abandoned mines have, to some extent, hindered local socio-economic development; however, they also represent a natural resource that can be re-exploited. Mining activities in the past have excavated and occupied land resources, changed the original topography, destroyed forest and grassland vegetation, disrupted the connectivity of ecological corridors, caused damage or degradation to ecosystems, diminished water conservation functions, and aggravated rocky desertification and soil erosion. There are numerous abandoned mines in Yunnan Province, which are widely distributed and predominantly small in scale. These sites are burdened by significant debt, face complex ecological issues carried over from the past, and possess inadequate natural recovery capacity, resulting in a challenging remediation task. In recent years, there has been a focus on key watersheds and important ecological areas. This focus aligns with the overarching principles of respecting and adapting to nature, following the laws of natural ecosystem succession, prioritizing natural recovery while supplementing it with engineering solutions, and ensuring that all actions are suitable, technically feasible, and financially viable. As a result, ecological restoration methods and measures have been selected based on scientific criteria. Near-natural solutions have been implemented to fully embody the principles of comprehensive management and systematic restoration. These approaches have actively and systematically promoted the ecological restoration of abandoned mines, resulting in positive outcomes. However, the extensive number of abandoned mines and the funding shortfall for restoration efforts have resulted in a critical ecological restoration situation. Currently, over 100,000 acres of abandoned mines in Yunnan Province urgently require ecological restoration, posing significant challenges to the livelihoods and daily lives of local villagers.The diversity of Yunnan's climate presents varying requirements and challenges for environmental protection and ecological restoration. The northwestern cold climate zone of Yunnan experiences long winters with no summers and only short spring and autumn seasons, resulting in slow vegetation growth and significant challenges for ecological restoration. In contrast, the eastern and central temperate climate zones of Yunnan have indistinct seasons, characterized by moderate average annual temperatures and precipitation, which facilitate the recovery and growth of vegetation. The southern and southwestern tropical and subtropical climate zones of Yunnan are abundant in precipitation and biodiversity, creating favorable conditions for vegetation restoration and the protection of biodiversity. Dry and hot river valley regions of the Jinsha river and Yuanjiang river experience a scorching climate characterized by drought and limited rainfall. This results in an imbalance between water and heat, as well as low soil organic matter and nutrient content. Ecological restoration efforts in these areas should prioritize soil and water conservation, along with the protection of water sources.Based on the current situation of ecological and environment damage caused by abandoned mines in Yunnan Province, this paper analyzes the ecological problems of mines. Drawing on the experience gained in the ecological restoration of abandoned mines, it constructs restoration modes such as "natural restoration, ecological carbon sink, transformation and utilization, and ecological restoration+". Fully considering factors such as the natural geography of mining areas, the pattern of ecological restoration, incentive policies, and the requirements of controlling national land space use, it discusses countermeasures and suggestions for the ecological restoration of abandoned mines, focusing on aspects such as restoration direction, engineering measures, and investment mechanisms. The aim is to provide technical support and innovative ideas for the ecological restoration of abandoned mines in the context of the new paradigm of "mountains, rivers, forests, farmlands, lakes, and grasslands as a community of life". In the next step of promoting the restoration of abandoned mines, it is necessary to redefine the concept of ecological restoration of mines. This involves accurately understanding the relationship between natural and artificial restoration. It is crucial to adhere to the principles of ensuring safety, restoring ecological balance, and considering the landscape. Additionally, it is important to scientifically select appropriate models for mine ecological restoration and engineering measures based on the potential value of abandoned land resources, while also complying with regulations of controlling national land space use. Taking into account the current situation of social and economic development in mining areas, as well as factors such as micro-landforms, surrounding vegetation, traffic conditions, and water and soil quality, the ecological restoration of mines has been carried out, and the restoration direction has been determined with careful consideration. Through policy incentives and the strategic allocation of financial funds, we will encourage social capital to engage in the ecological restoration of abandoned mines. Our goal is to revitalize these sites, and establish a new model of self-sustaining and self-cycling ecological restoration of abandoned mines.

Features and genesis analysis of geological relics of karst landforms in the Laoshan area of Malipo, Yunnan Province

PAN Tianwang, SHI Wenqiang, LI Chengzhan, CHEN Weihai, TANG Liangliang, WU Hongmei

2024, 43(6): 1430-1444. doi: 10.11932/karst20240619

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The Laoshan area in Malipo, Yunnan Province is located in the transitional zone from the karst plateau in southeastern Yunnan to the Red River Delta Plain in Northern Vietnam, where the gorge-type karst landform is typically developed, forming a rich and diverse set of geological relics of karst landforms. These relics play an important connecting role and are typical representatives in the evolution process of karst landforms in Southwest China and Southeast Asia. Since 2013, the development of the scenic area named "Heroic Laoshan Sacred Land" has prominently featured nature sightseeing tours centered around geological relics of karst landforms. Surveys have found 47 typical geological relics in this area, characterized by cave groups, canyon groups, waterfall groups, peak-cluster depressions, and peak-cluster valleys. However, the existing data indicates that this area primarily focuses on the investigation and research of mineral resources, and structural and rock unit systems. In contrast, there is a significant gap in understanding the unique geological relic characteristics and composition of subtropical canyon-type karst landforms, as well as their spatial distribution, and evolutionary causes, which are critical issues. This lack of understanding has affected high-quality development and reasonable protection, and there is an urgent need for further research and discussion. Therefore, based on the investigation of karst landform geological relics, it is essential to enhance studies on the characteristics and genesis analysis of geological relics in the study area. These studies are of practical significance for revealing the formation and evolutionary mechanisms of the typical areas developed with karst landforms that transition from the karst plateau in southeastern Yunnan to the plains of the Northern Vietnamese Delta. Additionally, these studies will contribute to the economic development of border area tourism and the prosperity of the border area and its inhabitants.This article analyzes the distribution and developmental characteristics of geological relics of karst landforms in the study area, examines the causes of their formation, and, based on previous research findings, discusses the formation and evolutionary mechanisms of typical canyon karst landforms in Yunnan. The results show as follows, (1) The study area boasts a rich variety of geological relics of karst landform, including surface karst landforms, subsurfaces karst landforms, transitional karst landforms and hydrological landforms. Surface karst landforms include peak clusters, depressions, karst gorges, clints, grikes and karstic traces. Subsurface karst landforms consist of karst caves, underground rivers, and various depositional forms. The transitional karst landforms from surface to subsurface are represented by small-scale karst collapse doline groups that are locally exposed. Hydrological landforms include karst waterfalls and karst springs. (2) The study area is characterized by gorge-type karst landforms, with developed karst caves that exhibit stratification. The types of caves and depositional forms at different levels are similar, with low-altitude caves being a distinctive feature. They can be divided into five levels: >1,750 m, 1,200–1,600 m, 600–1,000 m, 200–500 m, and <150 m. The main types of caves are dry caves, water-out caves, water-in caves, and their mixed types. In the karst dry caves, there is a significant amount of collapse debris of original rock or sandy silt blocking the cave passages, and secondary chemical sediments are generally underdeveloped. There are few large cave halls in the caves, and medium to large-scale caves represented by Qingliang cave and Mangun cave are characterized by different traces and different periods of structures overlapping and interacting with each other and by double-layered development. Several caves with convenient transportation show clear signs of human activities, but the most remain in their pristine states. (3) The Wenshan-Malipo NW-trending left-lateral strike-slip fault zone significantly influences the formation and evolution of geological relics of karst landforms. The geological relics of karst landforms are mainly distributed in a northwest to southeast strip along the karst gorge of the Nanwen river. The multi-stage uplift of neotectonic movements also has significantly impacted the formation of karst landforms. The continuous deposition, stable stratification, and extensive distribution of Cambrian, Devonian, and Permian carbonate formations, characterized by significant depositional thickness in the study area create optimal material conditions for the formation and development of geological relics. These factors also control the regional distribution of these relics. At the same time, the study area is located in the subtropical monsoon climate zone, south of the Tropic of Cancer, where the unique climate and hydrological conditions have a significant impact on the formation of karst landforms. The abundant atmospheric precipitation provides ample water sources for the karstification process in this area. (4) Based on previous research findings and comparison of regional elevations, landform morphologies, individual morphological characteristics of karst landforms in the study area, as well as the conditions for the formation of different landform combinations, the genesis and evolutionary process of geological relics of karst landforms in the study area since the Late Mesozoic can be preliminarily divided into two stages: the formation of the tectonic basin during the Yanshan Period and the crustal differential uplift during the Himalayan Period.

Research on water conservation in karst graben basin from the perspective of ecological restoration of territory space: A case study of the Erhai lake basin

YANG Fengji, HE Xiang, CHEN Chaowen, WANG Jinman, ZHOU Zhiping, ZHANG Hua, LIU Biao

2024, 43(6): 1445-1458. doi: 10.11932/karst20240620

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The Erhai lake basin is an important ecological area outlined in the "14^th Five-Year Plan" and the Master Plan on Major Projects for the Conservation and Restoration of National Key Ecosystems (2021–2035). The water conservation function in the Erhai lake basin plays a crucial role in maintaining the balance of water resources and ecology. To formulate effective protection and restoration strategies, methods such as ANUSPLIN meteorological interpolation, regional hydrogeological assessment, and InVEST water yield calculation have been employed to evaluate and predict the water yield and water conservation function of the Erhai lake basin.The research conclusions are as follows, (1) Through hydrological and geological assessments, it is confirmed that the Erhai basin constitutes a relatively complete hydrogeological unit. Influenced by climate change and land use, there was a 3.6% increase in water yield in 2022 compared to 2006, alongside a 1.65% decrease in water conservation. The areas with high water conservation rates are mainly located in the Cangshan mountain and northern mountainous regions, with an average water conservation rate exceeding 10%. In contrast, the areas with low water conservation rates are primarily found in the garben basin region, where the average water conservation rate is only 2.89%. (2) The prediction results indicate that, due to the decrease of precipitation, both the natural inertia development scenario and the ecological protection and restoration scenario will experience a decline in water source conservation. However, the reduction in water conservation under the ecological restoration scenario is significantly lower than that under the natural inertia development scenario, and the water conservation rate in ecological restoration has increased. There is a risk of local degradation in the natural inertia development scenario, while the ecological protection and restoration scenario can enhance the water conservation capacity through measures, and reduce the risk of degradation. (3)The spatial and temporal distribution of water conservation in the Erhai lake basin is closely related to natural factors such as climate and land use structure. In response to the degradation of water conservation function in the Erhai lake basin, existing sub-projects were studied and evaluated.Special attention was given to the northern Cangshan range and southeastern mountainous area, where measures such as ecological status assessment, and engineering water supplement were proposed to enhance water conservation, maintain ecosystem stability, and promote sustainable development.

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2024 Vol. 43, No. 6

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Current Issue 2024 Vol. 43, No. 6

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Submission Guide

Current Issue
2024 Vol. 43, No. 6