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Hydrogeology Journal

, Volume 26, Issue 5, pp 1371–1385 | Cite as

Review: Characterization, evolution, and environmental issues of karst water systems in Northern China

  • Yongping Liang
  • Xubo Gao
  • Chunhong Zhao
  • Chunlei Tang
  • Haoyong Shen
  • Zhiheng Wang
  • Yanxin Wang
Paper
  • 155 Downloads

Abstract

In Northern China, karst systems in widely distributed carbonate rocks are one of the most important water supplies for local inhabitants. Constrained by the specific geological and geomorphological conditions, most karst water in this region is discharged as individual or groups of springs. This paper summarizes the characteristics, chemistry, and environmental quality of these karst systems in Northern China. Five structural models of karst water systems were identified based on the relationships between the karst geological strata and karst groundwater flow fields. These specific structural models may closely relate to the attendant environmental geological issues and consistent risks from pollution. Over the past 40 years, the karst water systems in Northern China have suffered from various environmental problems, including deteriorating water quality, the drying up of springs, a continuous decline in the level of karst water, and so on. Based on the field investigation and previous data, a preliminary summary is provided of the environmental problems related to the development and evolutionary trends of karst water in this region. The results highlight the significant challenges associated with karst water, and it is essential that all segments of society be made aware of the situation in order to demand change. In addition, the study provides a scientific basis for the management, protection, and sustainable utilization of karst water resources.

Keywords

Karst Characterization Structural models Environmental issues China 

Revue: Caractérisation, évolution, et questions environnementales des systèmes hydrogéologiques karstiques du Nord de la Chine

Résumé

Dans le Nord de la Chine, les systèmes karstiques qui se développent dans les roches carbonatées largement répandues constituent l’une des sources d’approvisionnement en eau plus importantes pour les habitants. Contrainte par les conditions spécifiques géologiques et géomorphologiques, la plupart des eaux karstiques émergent de sources individuelles ou de groupes de sources. Cet article résume les caractéristiques, la chimie et la qualité environnementale de ces systèmes karstiques du Nord de la Chine. Cinq modèles structuraux de systèmes hydrogéologiques karstiques ont été identifiés à partir des relations entre les couches géologiques karstiques et les domaines karstiques d’écoulements d’eaux souterraines. Ces modèles structuraux spécifiques peuvent être étroitement liés aux questions géologiques environnementales et aux risques cohérents de contamination. Au cours des 40 dernières années, les systèmes hydrogéologiques karstiques du Nord de la Chine ont souffert de différents problèmes environnementaux, y compris la dégradation de la qualité de l’eau, le tarissement des sources, une diminution continue de la charge hydraulique au sein des karsts, et ainsi de suite. Sur la base d’étude de terrain et de données antérieures, un résumé préliminaire concernant les problèmes environnementaux associés au développement et aux tendances évolutives de l’eau karstique dans cette région est. fourni. Les résultats mettent en évidence les défis significatifs associés à la qualité de l’eau karstique, et il est. essentiel que tous les segments de la société soient sensibilisés à la situation afin d’exiger un changement. En outre, l’étude fournit une base scientifique pour la gestion, la protection, et une utilization durable des ressources karstiques en eau.

Revisión: Caracterización, evolución y problemas ambientales de los sistemas de agua kárstica en el Norte de China

Resumen

En el norte de China, los sistemas kársticos, ampliamente distribuidos en rocas carbonatadas, son uno de los suministros de agua más importantes para los habitantes locales. Restringida por las condiciones geológicas y geomorfológicas específicas, la mayor parte del agua kárstica en esta región se descarga como manantiales individuales o en grupo. Este trabajo resume las características, la química y la calidad ambiental de estos sistemas kársticos en el norte de China. Se identificaron cinco modelos estructurales de sistemas de agua kárstica basados ​​en las relaciones entre los estratos geológicos y los campos de flujo de agua subterránea kárstica. Estos modelos estructurales específicos pueden relacionarse estrechamente con problemas geológicos ambientales y los riesgos constantes de la contaminación. En los últimos 40 años, los sistemas de agua kárstica en el norte de China han sufrido diversos problemas medioambientales, como el deterioro de la calidad del agua, el agotamiento de los manantiales, una disminución continua del nivel de agua kárstica, etc. Con base en la investigación de campo y los datos previos, se proporciona un resumen preliminar de los problemas ambientales relacionados con el desarrollo y las tendencias evolutivas del agua kárstica en esta región. Los resultados ponen de relieve los importantes desafíos asociados con el agua kárstica, y es esencial que todos los segmentos de la sociedad estén al tanto de la situación para poder exigir un cambio. Además, el estudio proporciona una base científica para la gestión, protección y utilización sostenible de los recursos hídricos kársticos.

综述:中国北方岩溶水系统特征描述、演化和环境问题

摘要

中国北方广泛分布的碳酸盐岩中的岩溶系统是当地居民最重要的供水水源之一。受特殊的地质和地貌条件约束,这个地区大多数岩溶水以单个泉或泉群的形式排泄。本文概述了中国北方这些岩溶系统的特征、化学成分和环境质量。根据岩溶水系统和岩溶地下水水流场之间的相互关系,确定了岩溶水系统五种构造模型。这些特殊的构造模型可与伴随的环境地质问题和污染产生的一贯风险密切相关。在过去的40年,中国北方的岩溶水系统遭遇各种各样的环境问题,包括水质下降、泉干涸、岩溶水水位持续下降等等。 在野外调查和先前的资料基础上,概述了本地区与岩溶水开发和演化趋势相关的环境问题。结果强调了与岩溶水相关的重要挑战,最重要的是,使全社会各部门意识到目前的形势,以便采取改进措施。另外,研究成果为岩溶水资源的管理、保护和可持续利用提供了科学依据。

Revisão: Caracterização, evolução e questões ambientais dos sistemas hídricos cársticos no Norte da China

Resumo

No norte da China, os sistemas cársticos em rochas carbonáticas amplamente distribuídas são um dos mais importantes suprimentos de água para os habitantes locais. Forçada pelas condições geológicas e geomorfológicas específicas, a maioria das águas cársticas nesta região é descarregada individualmente ou em grupos de nascentes. Este artigo resume as características, a química e a qualidade ambiental desses sistemas cársticos no norte da China. Cinco modelos estruturais de sistemas hídricos cársticos foram identificados com base nas relações entre os estratos geológicos cársticos e os campos de fluxo de águas subterrâneas cársticas. Estes modelos estruturais específicos podem estar intimamente relacionados com as questões geológicas ambientais associadas e os riscos consistentes da poluição. Nos últimos 40 anos, os sistemas hídricos cársticos no norte da China sofreram com vários problemas ambientais, incluindo a deterioração da qualidade da água, o secamento de nascentes, um declínio contínuo no nível de água cárstica e assim por diante. Com base na investigação de campo e em dados anteriores, é apresentado um resumo preliminar dos problemas ambientais relacionados ao desenvolvimento e às tendências evolutivas da água cárstica nessa região. Os resultados destacam os desafios significativos associados à água cársica, e é essencial que todos os segmentos da sociedade sejam conscientizados da situação a fim de exigir mudanças. Além disso, o estudo fornece uma base científica para a gestão, proteção e utilização sustentável dos recursos hídricos cársticos.

Introduction

The main purpose of this paper is to provide a scientific basis for the management, protection and rational utilization of karst water resources. Over the past 20 years, researchers in academic circles have become increasingly concerned about environmental problems associated with karst water resources. More than 25% of people around the world reside in areas in which karst groundwater is used as a drinking water source. Karst water is the focus of important ongoing research in the field of hydrogeology, and was selected as the theme of the International Association of Hydrogeologists (IAH) Congress held in Paris (1975) for the first time. Because of the fragility of the environment in karst areas and the openness of the associated groundwater systems, karst areas are extremely sensitive to human activity. Since the mid-twentieth century, along with population growth and the accelerating pace of construction globally, the load imposed on karst areas has also increased, thereby causing serious problems in the karst water environment. In the middle and last parts of the last century, there was a significant amount of research internationally into the scientific management and protection of karst spring-water resources in karst development regions, such as Texas and Florida in the USA, and in Europe (Civita 2008; Escolero et al. 2002; Maramathas 2006; Plagnes and Bakalowicz 2002; Plagnes and Bakalowicz 2001; Xanke et al. 2017; Zwahlen 2004). It is globally recognized that the protection of karst springs is extremely important in order to conserve the natural state of karst environments and to maintain the water balance. In Europe and North America, karst resource development has been predominantly focused on spring water use instead of the use of water from wells. For this reason, the problem of reduced flows of karst springs is much less prevalent in these regions compared to the northern part of China; thus, karst water research in Europe and North America is focused on the prevention and control of pollution and the protection of the water environment. In contrast, studies of karst water in Northern China in the period from the 1950s to the 1970s were primarily focused on ground investigations, water source exploration, and mine water discharge. The first study of karst and karst water in Northern China was conducted in 1981, and did not involve the secondary environmental geological problems of karst water. In the 1980s, research began to focus on karst groundwater in large-scale water exploration, evaluation and development stages, spring-flow attenuation and the associated pathways of karst groundwater flow, karst groundwater pollution, ground subsidence, and karst-related geological and environmental problems. At the second congress on “Study on karst and karst water in Northern China” held in Ji’nan, Shandong Province (1991), the problems of karst-environment geology and disaster geology were the focus of an important discussion. Spurred by the increasing number of hydrogeological problems in karst environments, researchers continued to produce relevant reports and to participate in a variety of related discussions (Han et al. 1993). Water problems at some well-known springs, such as Baotu Spring (Ji’nan, Shandong), Jinci Spring (Taiyuan, Shanxi), and Baiquan Spring (Huixian, Henan), have attracted attention from all sectors of society. In terms of protection and management, various measures, including limiting water extraction, pressurized mining (mining coal without water drainage), water-resource supplementation, and water conservation, have been adopted. At the same time, a series of national and local regulations on the protection of karst water resources have been enacted (Jin et al. 2001; Hu 1999).

In Northern China, there are 68.5 × 104 km2 of carbonate rocks, including exposed areas of 7.78 × 104 km2, covered areas of 8.74 × 104 km2, and deep burial areas of 51.95 × 104 km2 (Liang and Han 2013). When combined, these regions yield a total of 108.8 × 108 m3/year of karst water resources (Hou et al. 2008; Water Resources Department of Shanxi Province, Institute of Karst Geology (CAGS), Water Resources Management Committee of Shanxi Province 2008; Zhang and Li 2004). Karst systems in Northern China have become an important source of water due to their enhancement of the carbonate aquifer resources, stable groundwater flow, and good water quality. Currently, karst groundwater sources supply drinking water to more than 30 large cities, 100 county-level cities, and numerous towns in the karst mountain areas in Northern China. In addition, these sources also supply more than 70% of the required water to large state-owned coal mines, cooling water for dozens of large-scale thermal power plants, and irrigation water for thousands of acres of farmland in Northern China (Liang and Han 2013).

In the Northern China region, a total of 119 karst systems have been delineated (Fig. 1) with their own characteristic recharge, runoff, storage, and discharge flows (Liang 2010), most of which are part of a massive karst artesian water system. Springs are the most common natural discharge method for karst groundwater systems. Of the karst springs recorded in the region, 170 have a flow higher than 0.1 m3/s, of which 41 have a natural flow higher than 1.0 m3/s.
Fig. 1

The location and structural models of karst water systems in Northern China

Northern China has both arid and semi-arid climatic zones with an annual precipitation of approximately 200–700 mm. However, the available water supply in this region is not sufficient to meet the ever-increasing demand for water resources. The past 40 years of reform and expansion, the global effects of climate change (Guo et al. 2005; Wang et al. 2012), increased development of karst systems for water supply, and human activities such as coal mining, have caused dramatic changes to the input-output structure of the karst water systems in this region. In the past few decades, a third of the previously identified large karst springs have disappeared, the flow from 80% of the remaining springs has been significantly reduced, the regional karst groundwater level has declined at a rate of 1–2 m/year from the end of the twentieth century to the beginning of this century, and the quality of karst water has continuously deteriorated. This has resulted in the removal of hanging pumps in wells, and there has been a reduction in the value of tourism to springs and a loss of ecological function in many areas (Shang et al. 2016; Zhu et al. 2015). Other potential environment problems that have arisen include: dewatering and a decrease in the storage function of karst aquifers, land subsidence caused by reduced recharge of Quaternary aquifers by karst aquifers, karst collapse, accelerated seawater intrusion in coastal areas, siphoning of water resources between different karst aquifers, and the pollution or quality degradation of karst water.

By defining the system boundaries of hydrogeological properties using previously acquired data, the karst groundwater systems in Northern China were divided into 119 units and five structural system models: (1) the unidirectional incline bedding type system, (2) the unidirectional incline inverse type system, (3) the strata type system, (4) the syncline-basin type system, and (5) the fault block type and other types. These modeled systems were derived from the overlay relationships between the karst water system’s geological structure and the groundwater flow field. The problems and development trends of the karst water environment in Northern China are systematically summarized here, and the causes of karst water environmental problems in Northern China are analyzed. A nonlinear equation that relates river leakage and water volume in the carbonate area has been established.

Characteristics of karst water systems in Northern China

General characteristics of karst water systems in Northern China

The karst water systems in Northern China have been characterized as large-scale multiple water resources with complex exchanges between different water bodies and high vulnerability to environmental and water quality degradation. Karst systems often coexist with coal strata.

The average area of the 119 karst systems is 1,453.2 km2, with the largest being 13,383 km2. Among these, two are larger than 10,000 km2, four are 5,000–10,000 km2, 44 have areas of 1,000–5,000 km2, 64 are 100–1,000 km2, and five have areas less than 100 km2.

Karst water systems are generally composed of several components of the water cycle (Zang et al. 2015; Ma et al. 2009), including atmospheric precipitation, surface water, groundwater in loose sediments (Wang et al. 2001), clastic fissure groundwater, and karst water, and there is often a direct or indirect water exchange between these different components.

Coal seam water and karst water often coexist. Coal-bearing strata are present in 83 of the total 119 karst water systems in Northern China. The Cambrian–Ordovician carbonate formation, which is the most important karst aquifer in Northern China, was deposited with Carboniferous–Permian coal-bearing strata. The vertical distance between the coal strata and nearest karst aquifer is generally 20–60 m. A direct or indirect hydraulic connection is typical between the coal strata and the karst aquifers below, which is defined as a ‘coal–karst water coexistence system’ because of the widely distributed structural fractures, karst collapse pillars, and fractures formed during coal mining activity. The quantity and quality of karst water may be significantly impacted by coal mining activity even after the closure of coal mines (Zhang et al. 2016; Qiao et al. 2011), which is an indicator of the fragile environmental conditions in karst areas.

Structural models of karst water systems in Northern China

The geological structure in Northern China is characterized by fault block structures, and the corresponding macroscopic structures include the North China Plain, Fenwei Graben, Ordos Basin, Qinshui Syncline, and the fault–folded belts of the and Mountains. Structural models of karst water systems are constrained by both the regional structure and the karst-water-drainage-datum plane, which is itself dictated by the geomorphology. The structural models of the 119 karst water systems can be divided into five categories (Fig. 1), depending on the direction of the overall karst groundwater flow and the tendencies and overlay relationship of the carbonate aquifers. A summary of the features of the karst water systems and their structural models is provided in Table 1.
Table 1

Summary of the features of the five different models of karst water systems

Feature

Unidirectional incline bedding type

Unidirectional incline inverse type

Strata type

Syncline-basin type

Fault block and other types

Occurrence of karst aquifers

Flat monoclinic

Flat monoclinic

Steep monoclinic

Rift basin or syncline configuration

Fault block

The relationship of karst aquifer tendency and karst water flow direction

Consistent

Opposite

Parallel to Strata strike

Flow to the center of the basin or the axis of the syncline

Undetermined

Shape of the flow field

Fan

Fan

Rectangle

Concentric circles

Undetermined

Springs discharge

The erosion and overflow spring

The erosion and overflow spring

The erosion and overflow spring

The erosion and overflow spring

Undetermined

Distribution of discharge points

Aggregated

Scattered

Agminated

Scattered

Undetermined

Position of coal-bearing strata

Downstream of the system

Upstream of the system

Side of the system

Middle of the system

Undetermined

Recharge sources

Precipitation

Precipitation, river leakage

Precipitation

Precipitation

Precipitation

Hydrodynamic areas

Recharge - runoff - discharge - pressure hysteresis

Recharge - runoff - confluence - discharge

Recharge - runoff - discharge - pressure hysteresis

Recharge - runoff - discharge

Coal mine water inrush

Serious

General (several)

Medium

Serious

Average area (km2)

1,521.89

2,594.97

713.79

1,197.99

1,017.66

Number of systems (total 119)

49

19

17

20

14

Unidirectional incline bedding type system

This type of system refers to the monoclinic structure in a wing of the relief anticline (Fig. 2a). The overall tendency of this formation is consistent with the flow direction of karst groundwater. The main recharge source of karst groundwater in this structure is precipitation in the carbonate-rock outcrop areas. Springs are the main method of discharge of the karst groundwater, and appear in the locations where karst water is blocked by an impermeable resistant roof layer. The springs are typically ascension springs and tend to cluster. Depending on the hydrodynamic characteristics, this karst system can be divided into several subareas: recharge areas, runoff areas, discharge areas, and artesian areas. A total of 49 karst systems consistent with this system are primarily distributed in the west of Lvliang Mountains, in front of Taihang Mountain, west of Henan province, and in the Central-South region of Shandong province, and these systems have an average area of 1,521.89 km2.
Fig. 2

Schematic of the structural model of the karst-groundwater-circulation system: a unidirectional incline bedding type, b unidirectional incline inverse type

Unidirectional incline inverse type system

This system also includes a monoclinic structure in a wing of the relief anticline (Fig. 2b); however, the overall flow direction of the karst groundwater is opposite to the karst formation tendency. The rainfall infiltration in the outcrop areas of the karst system and leakage of overland runoff produced in the clastic areas are the main sources of karst groundwater recharge. The karst groundwater is primarily discharged as springs, which arise from the impermeable roof layer. The springs are descending springs and spatially scattered. This type of karst system can be divided into three subareas: recharge areas, runoff areas, and discharge areas, based on the hydrodynamic characteristics. Nineteen of these systems, with an average area of 2,594.97 km2, are primarily distributed west of the Tai-hang Mountains and north-west of the Fenwei Graben.

Strata type system

This type is a variant of the former models, and is composed of a wing of tight folds in which the karst groundwater may flow across the fold axis. The overall flow direction of the karst groundwater is consistent with the strike direction of the carbonate aquifers. Precipitation is the single source of recharge in the system and karst groundwater is discharged in the plunging part of the folds. A total of 17 karst systems of this type are mainly distributed in areas with strong deformation such as the ancient spine belt along the west ridge of the Ordos Basin, the Yanshan area, and the Huainan area, with an average area of 713.79 km2, which is smaller than that of the previous types.

Syncline-basin type system

This type of system is composed of a relatively complete system of small rift basins or syncline configurations (Fig. 3) in which the surface water and groundwater both flow to and from the center of the basin. In general, karst groundwater is scatter discharged into rivers in the central basin or along the synclinal axis, and there may be a complex recharge/discharge relationship between the karst groundwater, pore water, and surface water. Karst water is sensitive to pollution from agricultural fertilizers. There is a total of 20 syncline-basin type karst water systems in the Northern China, with an average area of 1,197.99 km2, and these systems are primarily distributed in the contiguous area of the Taihang and Yanshan Mountains, Yanshan piedmont, and Taizi River basin, with a small amount in the mountainous areas in the central region of Shandong Province.
Fig. 3

Simplified hydrogeological profile of the karst Laiyuan basin

Fault block type and other types

Karst aquifers consist of a number of fault blocks and other structures in the karst water system, and the recharge and discharge of the karst water depends on the characteristics. There are a total of 14 such systems, with an average area of 1,017.66 km2.

Karst water chemistry in Northern China

The chemical makeup of the karst groundwater may vary across different regions because of differences in regional geology, climate, hydrodynamic conditions, and human activities (Wu and Wang 2014). Based on the chemical composition of 894 karst water samples taken since 1980, the maximum value of total dissolved solids (TDS) was found to be 9,010 mg/L, which is 65 times higher than the minimum value, 133.8 mg/L. Regionally, the highest values of pH, TDS, total hardness (HB), SO42−, Cl, F, K+, and Na+ are normally present in karst water from the western margin areas of the Ordos Basin, which reflects the impact of local geological conditions on the karst water chemistry in the area. The average temperature of karst water is over 20 °C in the Fenwei graben and western part of Henan Province, which indicates the groundwater temperature is affected by the active modern tectonic movements there.

The content of HCO3 is high in Xuhuai area, Huainan area, and the west part of Henan province, which can be attributed to the relatively hot and humid climate that is favorable for producing bicarbonate in karst groundwater. The nitrogen content is generally high in the eastern region of Northern China due to the dense population and heavy pollution from agricultural activities. In the Piper diagram in Fig. 4, the groundwater samples collected from the eastern areas of the Lvliang Mountains are primarily located at the top left side of the diamond while the karst water samples from the areas in the west of the Lvliang Mountains are found scattered in the diamond. The water chemistry types of west surrounding areas of the Lvliang Mountains are complex and varied, and the content of easily soluble ions, such as K+ and Na+, is high. This is mainly due to the low rainfall in the local area, which causes the low degree of mineralization transport from the ground surface layers to the groundwater. This area is largely covered by a thick layer of loess, containing a variety of mineral components that have a fairly rich supply of soluble material. The hydrochemical samples from the eastern areas of the Lvliang Mountains are located on the left side of the Piper plot. This is mainly because these areas of carbonate rock aquifer generally contain gypsum strata. The groundwater dissolves the gypsum, causing a higher sulfate content in groundwater. Due to different gypsum content in different regions, the sulfur content is different, which leads to a larger change in the HCO3 content in the groundwater.
Fig. 4

Piper diagrams of karst water in Northern China

Environmental concerns in the karst water system

Over the past 40 years, as the natural conditions of the karst water system have changed and human activities have intensified, particularly in mining and related industries, the input–output relationships in the karst spring water system have undergone fundamental changes. In addition, a series of karst water/environmental problems have arisen such as the drying up of karst springs, decline of the karst water level, etc. (Allen et al. 2004; Brouyère et al. 2004; Chen et al. 2004; Guo et al. 2005; Ma et al. 2004).

Reduction in karst water resources

The main reasons for the attenuation of karst water flow in the north are as follows: (1) global climate change, increasing temperature, increasing evaporation, and decreasing rainfall have attenuated the available recharge supply (Ma et al. 2004; Wu and Wang 2014; Hao et al. 2009a, b; Jia et al. 2017); (2) the decreasing quantity of river water and the interception of surface water has caused decreasing surface runoff and decreasing karst water leakage; (3) the increasingly large-scale exploitation of karst groundwater has reduced the flow of spring water, and is the most direct reason for the decline of the water level of the region; (4) the depressurization of karst water due to mining and karst water inrush have also contributed to decreasing the flow of karst spring water; (5) in recent years, large-scale construction to support roads and towns has reduced the area available for infiltration and recharge of karst water, and has also contributed to a reduction in the karst water resources.

Drying up of karst springs

Records show that over 30% (46) of the karst springs in Northern China are in the process of drying up, or dried up in the past 40 years. Six of the 36 large springs (spring flow greater than 0.12 m3/s) in Shandong Province ceased to flow in the early 1980s (Hao et al. 2009a, b) and only 16 springs remain. Information pertaining to these springs is listed in Table 2.
Table 2

Springs that have dried up, are close to drying up, or intermittently cease flowing located in Northern China

Administrative area

Springs

Beijing

Yuquashan Spring,Shangqingshui Springa, Mapao Springb, Wanfutang Spring (Qincheng Spring, Jiulong Spring)

Tianjin

Gongleting Spring

Hebei province

Hailongdong Springb, Xingtai Bai Spring, Shigu Spring, Yigu Spring, Pantaoyu Spring, (Bailongdong Spring, Dahuo Spring in Xingtai city)

Henan province

Jiulishan Spring, Huixianbai Spring, Zhenzhu Springb, Chaohua Spring, Baishuzui Spring, Sanli Spring, Miaoshui Springb, LongJian Spring, Shiyangguan Spring, Miaogou Spring

Inner Mongolia

Lasen Spring, North Spring of Ecker Spring a

Shandong province

Baotu Springb, Mingshui Springb, Laolongwang Springb, Yangzhuang Spring, Yuanyuan Spring, Shili Spring, Xichangwang Springa, Guoniang Spring, Fengshui Spring, Bai Spring, Liangcheng Spring, Jing Spring, Hulutao Spring, Lu Spring, Loude Spring, Linyi Spring, (Zaozhuang Spring), Liangcheng Spring, Longkou Spring, Tai’anjiuxiang Spring, Weihetou Spring, Dong Spring)

Shanxi province

Jinci Spring, Lancong Spring, Gudui Spring, Xinan Springc, Niangziguan Springc,Guozhuang Springa, Hongshan Spring, (Xiakou Spring Haitou Spring, Nanliang Spring, Wulong Spring, Xingdao Spring, Donggubi Spring, Xuanquanshi Spring, Zhike Spring, Taipei Spring, Wucheng Spring), Shengtou Springb

Shannxi province

Longyanshi Spring, Zhougongmiao Spring, Shen Spring, Yuanjiapo Springc (Yongshougong Spring)

Gansu province

(Pingliang Warm Spring)

Ningxia

Gun Spring (not in Northern China)

Jiangsu province

Sanguanmiao Spring

aSpring flow has stopped

bSpring flow intermittently stops

cPart of spring flow stops

Springs of non-key drainage are shown in parentheses

Attenuation of karst springs flow

In the past 40 years, 80% of the large karst springs have suffered from dramatic and continuous flow attenuation in Northern China. Figure 5 shows the recorded flow of the 15 largest karst springs in Shanxi Province only (Liang 2013). The total discharge of springs decreased from 73 m3/s (the average value between 1956 and 1979) to 46 m3/s (1980–2008), and was 34.84 m3/s for 2008, which is less than 50% of the earlier flow.
Fig. 5

Variation in the total flow (Q) of the fifteen largest karst springs in Shanxi Province

Decline of the karst water level

The decline of the karst water level has been accompanied by the attenuation of karst springs. From the 1980s to the beginning of this century, the karst water level has shown a general declining trend at an annual rate of 1–2 m. Figure 6 shows the dynamic variation of the karst water level in several specific cases.
Fig. 6

Variation of the karst water level (H) in selected karst systems (in Northern China) at: a Luqiao, b Lancun, c Liujiakou, and d Yuquanshan

As one of the biggest karst systems in Northern China, the Niangziguan karst spring system, showed a decline in the karst groundwater level of about 20 m from 1982 to 2004. The area of the depression cone where the water level is less than 410 m has expanded from 383 to 681 km2 in 2004 (Fig. 7) and to 747.9 km2 in 2015.
Fig. 7

Contour map of the groundwater level (m above sea level) in the Niangziguan karst water system, Shanxi province, in 1982 and 2015

Prior to the 1980s in the Heilongdong karst water system in Hebei province, artificial discharge and a small amount of coal mining drainage caused several small-scale depression cones in the water supply and mine drainage areas. At this point, the karst water continued to flow in its natural pattern (Fig. 8). After the 1980s, the karst water table declined gradually due to decreasing rainfall and increased artificial extraction. By the early 1990s, the Heilongdong springs frequently stopped flowing due to the over exploitation of karst water. Since then, the natural groundwater flow pattern gradually evolved into a pattern controlled by both natural and artificial factors. The water level in the water supply source area (the Yangtoupu) has been lower than that of the Heilongdong spring, which is the main discharge site of regional karst water.
Fig. 8

The flow field (a 1975; b 2007) of the Heilongdong karst water system, Hebei province (according to the First Hydrogeological Exploration Team, CNACG)

In this century, the Chinese government has vigorously promoted the construction of environmentally friendly structures. Once a series of such measures was completed, the karst groundwater level was restored to more or less its former level in certain areas, such as at Jinan, Taiyuan, Shanxi, Hebei Xingtai, Beijing, and other places.

Karst water quality

Karst water contamination

As a large open system, the karst water system has a positive energy and exchanges mass with other system, which provides ample opportunity for pollution to enter the karst groundwater. The factors controlling karst groundwater quality may also be complicated by the effects of large-scale development, wide catchment areas, and multiple sources of water recharge.

As mentioned previously, in many parts of Northern China, the karst water system is typically a water–coal coexistence system in which the coal bed is located above the karst water. The waste gas and water produced by coal mining, power plant, and agricultural activities infiltrate the karst groundwater, thereby causing the gradual degradation of the karst water quality (Zhang et al. 2016; Gao et al. 2010, 2011).

An assessment of the karst water quality was conducted using a fuzzy mathematics method and a comprehensive evaluation of a dataset containing 857 historical samples and 115 representative samples (collected from the discharge areas in the year of 2009); see Table 3. The results show that over 58% of the karst water can be classified as I and II level water (high quality), while 20–26.38% of the karst water can be classified as level IV and V water quality, which is substandard. As shown in the table, the concentrations of TDS, total hardness (HB), SO42−, Cl, F, total nitrate, Fe, and volatile phenols in karst water are higher than the national drinking water standards of China. This situation reflects two sides of a coin. One side is that the overall quality of karst water is good in Northern China, while on the other hand, this good quality karst water is suffering serious pollution problems. Frequent monitoring of the water chemistry indicates that karst water quality continues to decline.
Table 3

Summary of karst groundwater quality

Groundwater quality level

Samples from the discharge areas of karst systems in Northern China (n = 115)

Samples from all the karst areas in Northern China (n = 857)

No. of samples

Percentage (%)

No. of samples

Percentage (%)

Level I

13

11.30

156

18.20

Level II

56

48.7

259

30.22

Level III

24

20.87

217

25.32

Level IV

11

9.57

65

7.59

Level V

11

9.57

160

18.67

Degradation of karst water quality

Figure 9 illustrates the variation of major chemicals in three major karst springs in Northern China. The concentrations of all the chemicals show an increasing trend, which indicates worsening water quality in these springs. Therefore, the local government of Yangquan city must take action to ensure the safety of the water supply because the concentration of SO42− and total hardness in the karst water has exceeded the standard for drinking water in China.
Fig. 9

Concentrations of major chemicals in three representative karst springs in Northern China. a Niangziguan Spring in Yangquan City, Shanxi Province; b Baotu Spring in Jinan City, Shandong Province (Xing 2006); c Jiulishan Spring in Xuzhou City, Jiangsu Province

The contamination of karst water can be partially explained by the decline of the regional karst water level, which is referred to as “extraction pollution.” It is known that the chemical composition of karst water is closely related to the groundwater flow field in a karst area with a relatively stable physical structure. Theoretically, the concentrations of chemical components such as the TDS in groundwater generally increase as the depth increases in the vertical direction. This point is proven by the chemical composition of karst water samples at different depths in some karst areas.

The recharge sources of karst water, both before and after the karst groundwater level drops, were analyzed using analytical methods. From this, it can be concluded that a decreasing regional water level will cause karst water pollution. This is because the spring elevations are fixed, which means that the declining karst water level can cause a reduction in the hydraulic gradient in the karst system. Therefore, on the one hand, the groundwater circulation rate slows down and the time for karst water–rock interaction is prolonged, while on the other hand, this causes an increase in the proportion of deep “high concentration” karst water in the total flow of the karst springs.

Environmental geological disasters and other issues

As discussed previously, the quality and quantity of karst water have changed significantly in the past 40 years. This phenomenon is an important indicator of the problems currently faced by the karst system, which include the fact that the karst-water-circulation system, i.e., the recharge and discharge, are out of balance and the overall environmental quality has declined. The dramatic changes in the karst system have caused a series of environmental geological disasters and other negative effects.

Water supply

The normal water supply has been affected by corrosion of the extraction wells, a declining regional karst water level, and groundwater pollution.

Reduced tourism value and ecological function

Many of the karst spring sites are famous scenic spots, due to their murmuring springs, shaded trees on the mountains, and ancient temples. However, some of these springs, which have nurtured the people for thousands of years and represent ancient civilizations, have already disappeared, or will do so in the next few decades. At that point, the sites will have lost all their appeal (Lu et al. 2006).

Triggering of geological disasters

The decline of the karst water level in some areas has caused a large number of karst structures to collapse (Shao et al. 2017). At this time, there are a total of 114 areas where the karst has collapsed, and 5,879 karst collapse pits have been reported in Northern China (He et al. 2004, 2005). Among these, 72 of the 114 areas and 1,583 of the 5,879 pits appeared in modern times, the principal cause of which is the over-pumping of karst water. Over exploration of karst water has caused collapses in 59 areas with the appearance of 1,243 pits, which accounts for >78% of the total number of collapses in modern times. Karst collapses have occurred in the Dauejia and Fuzhouwan water supply area.

Transfer of water resources between different karst systems

A decline in the karst water table may also result in the movement of groundwater along with the boundary of the karst system, which further leads to the transfer of water resources and changes in the catchment area (Chu et al. 2017; He et al. 2009). By way of example, there are three karst systems (Niangziguan, Xin’an, and Sangu) located west of the Taihang Mountains, located from north to south; these karst systems are divided by the groundwater watershed and the karst system boundaries are movable. The decline of the karst water table may cause the movement of karst system boundaries. The groundwater discharge datum in the Xin’an karst water system—615 m above sea level (asl)—is 200 m or more above that of the northern Niangziguan karst system (360 m asl) and the southern Sangu karst system (342 m asl). With the large amount of mining, the groundwater level in Niangziguan karst system and Sangu karst system has declined. This has caused the karst water of Xin’an karst system to recharge Niangziguan karst system and Sangu karst system, resulting in a decline in the water level in the Xin’an karst system. Thus, after a 20-year decline in the karst water table, the south and north boundaries of the Xin’an karst water system are restricted to 20 km.

Seawater intrusion

Over-exploitation of karst water led to seawater intrusion in the Lushun and Daliang areas in the mid-1960s, and the seawater intrusion area later expanded from 4.2 to 178.5 km2 in 1981 and 288.6 km2 in 1986. At the beginning of this century, the size of the seawater invasion area was 486 km2 with an invasion distance of 8.6 km from the seaside (Sheng et al. 1996). At the same time, the average content of chloride in the karst water was 593 mg/L with the highest value up to 7,900 mg/L. The water supply capacity of one of the karst wells, Daweijia, was severely threated due to the seawater intrusion.

Other potential environmental geological problems

Other geological problems are reported by Arfib and Ganoulis 2004; Zhao et al. 2016; Xu et al. 2016, 2018. Northern China is an important production base for energy. Coal production accounts for over two-thirds of the national energy output (Wu 2003). Karst-water bursts and karst-water drainage from karst aquifers that lie beneath the coal strata, managed to reduce water pressure during coal mining, have caused a shortage of water for agriculture, etc. In many places, the karst water in aquifers becomes contaminated due to recharge from poor quality mine drainage. It should be noted that after many years of large-scale coal mining activity, underground cavities have been formed with a total volume of tens of billions of m3 and have increased in volume at a rate of 10 × 108 m3/year in Northern China. In the future, once the coal resources have been depleted and the coal mines are closed, as the result of poor regulation there will be a large number of abandoned mines filled with polluted wastewater. In consideration of the possibly huge volume of abandoned mine wastewater, this will become a most dangerous large-scale source of pollution and will require a fast response to maintain the quality of the karst groundwater.

Table 4 and Fig. 1 summarize the environmental geology issues in different karst zones. As described in the preceding, the environmental problems affecting the quality and quantity of karst water are complex and diverse in Northern China. The deterioration of water quality has a great impact on local industrial and agricultural production, and on the lives of habitants. In addition, this directly threatens the development of the national economy, the sustainable utilization of water resources, and presents a great threat to drinking water safety.
Table 4

Summary of the major environmental geology issues in different karst zones of Northern China

Partitions

No. of karst systems

Major environmental geology issues

Western edge of Ordos Basin (A)a

13

Original pollution, spring water flow attenuation, drying (3)a, in some areas a serious over-mining, mine water inrush (1)

West side of Lvliang Mountains (B)

3

Spring flow attenuation, potential mine water inrush

Fenwei Rift Valley (C)

20

Water pollution, spring flow attenuation or drying (7), regional water level decline, along the piedmont fault zone mine water inrush (4)

Border area of Taihang - Yanshan Mountains (D)

5

Agricultural pollution, urban pollution (high nitrogen content in water), mine water inrush

West part of Taihang Mountains (E)

6

Water pollution, spring water flow attenuation, potential mine water inrush (1), the system resource capture (underground watershed movement)

East part of Taihang Mountains (F)

10

Mine water inrush (9), spring water flow intermittent or intermittent drying (6), water pollution

West part of Henan province (G)

11

Mine water inrush (6), spring dry (7)

Yanshan-Liaoxi area (H)

12

Mine water inrush (2), karst collapse (2), ground fissures or ground subsidence (2)

Central and south area of Shandong province (I)

31

Spring attenuation or flow stops (16), mine water inrush (9), water pollution, karst collapse (8), ground fissure (2)

Xuzhou and Huizhou area (J)

2

Spring dry (1), water level drop, karst collapse (1), groundwater pollution

Taizihe area (K)

2

Water pollution, karst collapse (2), mine water inrush (1)

Lushun and Dalian area (L)

1

Water level decline, seawater intrusion, karst water pollution, karst collapse (1)

aLettering refers to Fig. 1

bThe number in parentheses (number) refers to the number of incidents

Conclusions

Karst water is the most important source of water for local habitants in Northern China. Constrained by the specific geological and geomorphological conditions, karst water systems are characterized as having relatively independent water circulation, with springs as the major sources of discharge. These karst systems are large and include multiple components, complicated water exchanges, and water and coal coexistence, and are extremely environmentally sensitive.

Depending on the superimposition of the kart water flow direction and formation tendencies, karst water systems in Northern China can be classified as one of five structural models. Karst water systems with different structural models may have different patterns of water recharge, runoff, discharge, hydrodynamic subareas, risk degree, and type of environmental geological problems.

At the large-scale (regional) level, the climatic and geochemical background plays a controlling role in the chemical composition and hydrochemistry of the karst water. Karst water has a higher ion concentration in the arid areas in northwestern China; for example, the content of K+ and Na+ is five times higher in the karst water in the west arid areas of the Lvliang Mountains than that in the eastern region of the Lvliang Mountains. The sulfate content is generally higher in the karst water in the central area of Northern China due to the naturally deposited gypsum in the middle Ordovician carbonate aquifers. Finally, the karst water in the south-central areas of Northern China has the highest HCO3 concentration of all, which is caused by the hot and humid climatic conditions in that region.

Over the past 40 years in Northern China, increased development of karst water resources and human activities such as coal mining, have caused dramatic changes in the input–output structure of the karst water system along with a series of environmental geology issues. Over the course of these years, a third of the large karst springs have disappeared, and more than 80% of the remaining springs have experienced reduced flow. In addition, the regional karst groundwater level has declined at a rate of one to 2 m/year, and the karst water quality has continuously deteriorated. This has resulted in a reduction in the value of tourism to the springs, the loss of ecological function, land subsidence, and seawater intrusion in the coastal areas. Another potential threat to karst water is the polluted “old acid mine wastewater” found in many abandoned coal mines, which has the potential to significantly affect the water supply in Northern China. In view of this, the Chinese government has made significant investments in ecological restoration in certain areas, on which some progress has been made in recent years.

In view of the environmental geological problems caused by the utilization of karst water in Northern China, research work on the karst springs and karst water systems needs to be further strengthened, especially with respect to karst springs with landscape and ecological value and those with complex flow. Research work and policies should address the management of karst water resources, control the exploitation of karst groundwater, and increase the amount of recharge. Research should also aim at addressing the water-coal relationship in karst water systems, with focus on studying the formation and evolution mechanisms of goaf water and its remediation.

Notes

Acknowledgements

The authors thank Dr. Felix Mwiathi Njagi for his help in reviewing the English. The authors are thankful to the reviewers and editors for their comments and suggestions.

Funding Information

This study was financially supported by the National Natural Science Foundation of China (NSFC grant no. 41672253) and the China Geological Survey Project (no. DD20160242).

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Yongping Liang
    • 1
  • Xubo Gao
    • 2
  • Chunhong Zhao
    • 1
  • Chunlei Tang
    • 1
  • Haoyong Shen
    • 1
  • Zhiheng Wang
    • 1
  • Yanxin Wang
    • 2
  1. 1.Institute of Karst GeologyChinese Academy of Geological SciencesGuilinChina
  2. 2.China University of GeosciencesWuhanChina

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