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This practical training guidebook makes an important contribution to karst hydrogeology. It presents supporting material for academic courses worldwide that include this and similar topics. It is an excellent sourcebook for students and other attendees of the International Karst School: Characterization and Engineering of Karst Aquifers, which opened in Trebinje, Bosnia & Herzegovina in 2014 and which will be organized every year in early summer.

As opposed to more theoretical works, this is a catalog of possible engineering interventions in karst and their implications. Although the majority of readers will be professionals with geology/hydrogeology backgrounds, the language is not purely technical making it accessible to a wider audience. This means that the methodology, case studies and experiences presented will also benefit water managers working in karst environments.

Inhaltsverzeichnis

Frontmatter

Characterization of Karst Aquifer

Frontmatter

Chapter 1. Historical Overview on Karst Research

Early civilizations recognized the importance of springwaters generally and of karstic springs in particular. Due to the unique nature of karst, man in karst or limestone terrains perhaps understood this importance better than man in other terrains. In fact, the earliest hydrologic concepts of the hydrologic cycle, water source, occurrence, and quality were developed in relation to karst environments. Among others, Chinese, Arabs, Greeks, and Romans contributed to this early knowledge. It was in the karst aquifers in the high mountains of Greece that the first theories of the origin of springwater were born. Aqueducts as architectural master works were developed and designed by the Romans to enable the long-distance transportation of high-quality waters. At the zenith of the Roman Empire, several aqueducts delivered the incredible amount of around 13 m3/s of water supply mainly tapped at karstic springs to the center of Rome. Xu Xiake (1587–1641) was one of the very important figures of that time traveling and exploring the caves in China. A new scientific discipline, karstology, was born in the second half of the nineteenth century. The Frenchman Edouard Martel is considered the “father of speleology,” but it is the Serbian scientist Jovan Cvijić who, due to his doctoral thesis “Das Karstphänomen” and later works, is often called the “father of karst geomorphology and hydrology.” His research provided systematic treatment of karrens, dolines, karst rivers, karst valleys, poljes, and other types of karst phenomena. During the latter part of the twentieth century, a flood of analyses and information from field surveys and laboratory works resulted in different, sometimes contradictory theories on many aspects of karst hydrogeology.
James W. LaMoreaux, Zoran Stevanović

Chapter 2. Karst Environment and Phenomena

Karstified rocks of different lithology cover more than 10 % of the continental surface of our planet. But in many places worldwide, where there is karst, there are also limited natural resources including absence of surface waters. The karst environment is therefore not always friendly, and various kinds of intervention are sometimes needed to adapt the ambience to human needs. In this chapter, classification of karstic rocks, karstification forces and mechanisms, and types of karstic terrains are discussed. Special attention is given to terminology and explanation of the main karstic features. To avoid the present trend whereby relatively simple things can sometimes become very complicated in order to suggest something very new, innovative, and if possible extraordinary, the explanations of main karstic features and phenomena are simple and shown in many photographs from all over the world, with links to the main literature sources provided. In each of the five distinguished basic regional types of karst (geosynclinal carbonate karst, platform carbonate karst, tropical karst, hypogenic and evaporitic karst, and glacial karst), typical karstic features and processes are presented and explained. The chapter aims to demonstrate how specific the karst environment is and the problems its inhabitants and ecosystems face. Understanding of these basic facts should facilitate understanding of later chapters in this guidebook.
Zoran Stevanović

Chapter 3. Characterization of Karst Aquifer

Proper knowledge of an aquifer system is prerequisite for its utilization, protection from pollution, and sustainable development. The sections of this chapter provide an overview of main aspects, which must be surveyed and recognized for proper characterization of a karstic aquifer: aquifer geometry and elements, permeability and storativity, flow types and pattern, aquifer recharge, aquifer discharge, quality of karst groundwater. Based on rich literature (82 listed references) and its evaluation sometimes including contradictory theories and approaches, main principles of karst aquifer hydrodynamics and karstic groundwater flow and storage are explained. Numerous classifications are also given. They consider aquifer properties such as porosity and permeability, types of recharge, flow, and discharge regime. Different factors that influence aquifer properties are also specified and their roles explained. Limitation of application of the Darcy hydraulic law in heterogenous and anisotropic aquifer such as karstic is also discussed and illustrated with a few examples. Special attention has been paid to the role of epikarst, the depth to the karstification base, and effective storativity of the aquifers which influence the natural aquifer discharge regime and enable or diminish opportunities for engineering interventions to regulate this regime.The broad classification of karstic springs provided is based on ten different criteria and includes 41 spring types. Some of the world’s largest springs such as Fontaine de Vaucluse or Kaiserbrunn are used to illustrate different discharge mechanisms of the springs or their importance for potable water supply. Although mostly theoretical, this chapter contains 19 boxes with practical examples and exercises for the trainees. The large number of illustrations, in total 58 photographs and sketches, helps to familiarize readers with various aspects of karst aquifer behavior and its quantitative and qualitative components.
Zoran Stevanović

Chapter 4. Overview of Methods Applied in Karst Hydrogeology

Because of their heterogeneity and specific hydraulic structure, karst aquifers require adapted investigation methods. Based on a conceptual model of karst aquifers, this chapter outlines the “karst hydrogeology toolbox”, consisting of geological, geophysical and speleological methods, hydrologic and hydraulic techniques, the use of natural tracers, such as isotopes and hydrochemical parameters, as well as the application of artificial tracer tests. Geologic and geophysical methods are useful to define the external boundaries and internal geometry and properties of karst systems. Speleological investigations make it possible to obtain direct insights into the drainage structure of conduit networks. Hydrological and hydrologic methods are used to establish water balances and to determine aquifer parameters and hydraulic boundary conditions. Hydrochemical and microbiological techniques are used to characterize water quality and contamination problems. Because of the extreme variability of karst water sources, continuous on-line monitoring techniques are generally preferred. Natural tracers help to identify the origin, movement and mixing of water and to characterize water-rock interactions. Artificial tracers, such as fluorescent dyes, are the most powerful tool to confirm underground connections, to delineate spring catchments, to quantify flow velocities and to obtain relevant contaminant transport parameters. The fields of application, as well as the required adaptations and the limitations of these methods are discussed and illustrated by means of several application examples and case studies.
Nico Goldscheider

Engineering Aspects of Control and Protection of Karst Aquifer

Frontmatter

Chapter 5. Surface Waters and Groundwater in Karst

In karst terrains, groundwater and surface water constitute a single dynamic system. In this chapter the following aspects of the interaction between the surface water and groundwater are discussed: (1) catchment in karst; (2) karst aquifer; (3) karst spring; (4) karst ponor; (5) karst open streamflow (sinking, losing and underground streams); (6) piezometers. Surface water and groundwater in karst terrains are hydraulically connected through numerous karst forms which facilitate and govern the exchange of water between the surface and subsurface. Due to this fact determination of karst catchment area and boundaries is a difficult and complex task, which very often remains unsolved. The specific characteristic of karst aquifer is existence of solution and erosion generation and permanently enlarged karst voids of different dimensions. Circulation of groundwater in karst aquifers is quite different from water circulation in other non-karstic type aquifers. In karst aquifers water is being collected in networks of interconnected cracks, caverns, and channels. Because of very special and complex underground and surface karst forms, which control surface water and groundwater behavior there are very different cases of karst springs. Karst springs can be perennial (permanent) or intermittent (temporary, ephemeral, or seasonal). The piezometer boreholes represent an exceptionally important source of information of a wide range, necessary for all types of investigations related to the regime of water circulation in karst.
Ognjen Bonacci

Chapter 6. Budget and General Assessment of Karst Groundwater Resources

Groundwater budgeting as a process of definition or estimation of different input (recharge) and output (discharge) components is an important step in the process of utilization of karst aquifers. Following the general water budget equation, each of the involved input/output parameters is discussed and explained in this chapter. Some of these parameters, such as precipitation, runoff, spring discharge, or artificial withdrawal, can be easily determined, but others could only be estimated by some specific surveying methods or simply approximated, such as surface water infiltration, evapotranspiration, or subsurface aquifer drainage. For the former, some of the common instruments or methods are shown, while empirical formulae or helpful methods such as simultaneous river flow measurements, groundwater table observations, and base flow separation of hydrographs are identified as supportive to perceive “problematic” budget components. Water budget analysis and knowledge of budget elements is the best way to determine groundwater reserves. The classification of the reserves and suggested methods for their calculation is discussed. Here, attention is also paid to aquifer geometry and the specificity of the “breathing” catchment (changeable in time) as an important element for estimation of aquifer size and volume of stored waters.The table which can be used for a rough assessment of groundwater reserves and five case studies with solved practical problems are useful training tools and are also included in this chapter.
Zoran Stevanović

Chapter 7. Evaluating Discharge Regimes of Karst Aquifer

Karst springs are typical for abrupt changes of discharge immediately following recharge events. Monitored discharges of springs are used to determine quantitative variability over the period of time, showing their reliability as dependable water sources. Karst aquifers also exhibit (at least) dual ground-water flow regimes, that is, fast (conduit-dominated) flow and slow (diffuse) flow. This is something that can be observed in nature as the fast change of water amount outflowing from the groundwater source, or described by rapidly responding hydrographs, recording water levels or discharges. Selection of proper investigative techniques characterizing discharge regime properties of a karst aquifer is therefore important in order to identify possible theoretical background models describing this behaviour. On this basis, we can also find a particular method of hydrograph separation into flow components linked to the fast-flow regime, slow-flow regime, or intermediate regimes as well. With this point in mind, several quantitative methods that might be particularly useful in hydrograph analysis of water outlets from the karst aquifer system are briefly discussed here.
Peter Malík

Chapter 8. Vulnerability to Contamination of Karst Aquifers

The karst aquifers are especially vulnerable to pollution due to their hydrological behavior derived from karstification. The vulnerability mapping is one of the most applied tools to protect them. There is a wide range of methodologies for vulnerability mapping that have been developed for karst aquifer, to consider the specific characteristics of karst into the vulnerability assessment, such as EPIK, PI, COP, Slovene Approach and PaPRIKa, among others. The vulnerability map can help the water stakeholder for decision-making and to promote a land-use management compatible with the water protection. So the maps should have reliable accuracy. Many works highlight that the maps of groundwater contamination vulnerability obtained from different methods differ significantly, although they were all obtained by methods developed for karst aquifers or they are obtained from the same source of information and applied by the same person. So, the validation is an essential element of any contamination vulnerability assessment. The current challenge of researchers is to obtain versatile and easy methods to test and validate vulnerability maps.
Ana I. Marín, Bartolomé Andreo

Chapter 9. Physical Modeling of Karst Environment

It is very difficult to define hydrogeological parameters in an anisotropic media and in carbonate matrix. Even after the employment of many different methods, it is a problem to define hydrogeological parameters. Still, in the past few years, a whole new branch of karst investigations has become widely used in the earth sciences and generally can be recognized as 3D modeling of karst aquifers and karst conduits. Modeling of karst environment generally combines state-of-the-art solids and parameter modeling with advanced survey technologies to produce decision support tools that are vastly superior to standard groundwater flow models. This kind of modeling visually conveys the real morphology and hydrogeology data of a conduit system in as much detail as was recorded by the geological, hydrogeological, speleological, cave diving, and other habitual survey methods. The main focus in this chapter is on 3D reconstruction and modeling of karst physical interior as a new approach in karst hydrogeology. Powerful tools such as ArcGIS and other software for three-dimensional modeling enable fast quantitative analysis and reconstruction of karstic conduits from the surface (sinkholes, pits, dolines, ponors) to the discharge zone (karstic springs) in 3D environment.
Saša Milanović

Chapter 10. Mathematical Modeling of Karst Aquifers

The chapter presents an overview of numerical modeling techniques for equivalent porous media (EPM) and conduit flow formulations, including a case study illustrating the value of conduit presentation. The authors provide an overview of basic numerical modeling concepts, including layering and the assignment of boundary conditions. The limitations of using classical MODFLOW EPM for karst aquifers are discussed, and alternative approaches such as the Conduit Flow Process (CFP) are introduced. Different implementations of the CFP are described, including discrete pipe networks and high-conductivity turbulent–laminar layers. While acknowledging the difficulties of numeric modeling of karst systems, the authors present justification for the use of new tools such as the CFP. This includes the ability to simulate sinks, turbulent and laminar flow processes, and two-way water exchange between porous media and conduits. More generally, the authors explain why and how numeric modeling adds value to water resources and site remediation projects of all kinds. The case study compares the results of EPM and CFP numerical modeling approaches for a karstic site in the southeast USA.
Alex Mikszewski, Neven Kresic

Chapter 11. Tapping of Karst Groundwater

The tapping of karstic groundwater flow as an “invisible” resource can be done in two ways: directly at springs’ discharge points and within the aquifer catchment by artificial intakes such as wells, galleries, or other similar structures. Although many spring intakes are not engineering masterpieces and were constructed by local semiskilled inhabitants, to ensure technically proper and environmentally friendly tapping of springwater, many steps in design, construction work, and utilization as well as in springwater protection from pollution should be taken. These steps are further discussed and optimal order in their implementation proposed. The design of the tapping structure of springs depends mostly on the discharge mechanism, and through several examples, optimal solutions for tapping ascending or gravity flows are shown. How to calculate spring box volume or why and where to locate additional sediment boxes within a tapping chamber are also presented. The list of activities and general specification of construction works at the spring site may be used not only for training purposes but also as a reminder in engineering practice. The issue of drilling the wells was discussed from several points of view: feasibility, determination of drilling site, and well design. The last includes selection and optimization of drilling method, the depth of the well, drilling diameter, casing/grouting, well development, and pumping. Six drilling technologies are briefly explained, and their advantages and disadvantages for use in karstic rocks are also discussed. Additionally, as an important fact for the well’s productivity, emphasis is given to the selection of the types of screens for wells, including open-hole option. Along with the explained and proposed procedures of development and pumping of the well, some important technical questions such as how to optimize yield, select, and install a pump and protect the well head are also emphasized.
Zoran Stevanović

Chapter 12. Monitoring of Karst Groundwater

Monitoring of groundwater in karst aquifer (quantitative and qualitative characteristics) is of great importance for its abstraction and its long-term and safe use, particularly for the purposes of water supply. In order to obtain relevant information about the functioning of karst aquifer it is necessary to implement a series of actions and measures (monitoring) to track the quantity and quality of groundwater. Consideration of the capacity and chemical composition of groundwater, as well as the establishment of a system of monitoring, is the first step in this process. The establishment of a monitoring network involves the definition of a number of observation points, observation frequency, and the quantitative and qualitative parameters needed for further analyses. Monitoring of karst groundwater provides data that give us a basic outline of the groundwater and the ability to define recommendations and measures for its use or for the improvement of its protection. Reliable monitoring of groundwater quality and quantity in any terrain is difficult, but in karst terrains it is especially hard. The main points and types of groundwater monitoring in karst terrains are shown in this chapter.
Saša Milanović, Ljiljana Vasić

Chapter 13. Catalog of Engineering Works in Karst and Their Effects

Due to an increased demand, in past century, for drinking water, land reclamation, energy, and urbanization, many engineering projects have been developed in karst regions all over the world. However, as a consequence of complex and unique geological nature, the road to final success was often paved with failures in spite of the best engineering approach was applied. Problems and failures in karst are connected with any kind of human activities, particularly with dams, reservoirs, tunnels, roads, and mines. Dam sites and reservoirs with leakage (sometime unacceptable high), tunnels and mines with disastrous water burst, huge cavern along tunnel routes, and catastrophic collapse in urbanized areas were common consequences of karst nature but also as a consequence of inadequate knowledge of karst geology. Article contains catalog of more than 150 dams and reservoirs in karst including short engineering review of selected examples from different karst regions. Catalog contains examples of successful, partially successful and unsuccessful corrective engineering works. Particular hazardous environment for engineering works, very soluble karstified evaporates, as well as, engineering problems with construction of underground dams and tunnels in karst are represented with selected examples. At the last section are listed the most effective investigation approaches and engineering methods for prevention and remediation.
Petar Milanović

Regulating and Protecting Karst Aquifer—Case Studies

Frontmatter

Chapter 14. Managing Karst Aquifers—Conceptualizations, Solutions, Impacts

This is an introductory chapter to the third chapter of the guidebook in which three major groups of problems and experiences obtained from practical engineering works dealing with karst are included: 1. Watering—Effective utilization of karstic water resources for drinking water supply and other purposes;  2. Dewatering—Mitigation of karst inflow in mining, urban areas, dams or other construction works;  and 3. Protecting – Prevention of pollution and remediation of karst water quality. The chapter provides an overview recommended as a common engineering approach to the definition of problems, the required conceptualization of and research into aquifers, possible solutions and alternatives, and finally optimization, implementation and assessment of any environmental impact this engineering work may have. The sections Problem definition and research procedure and Kinds of hydrogeological surveys (Reconnaissance survey; Basic survey; Detail survey; Monitoring) aim to help less experienced researchers organize their scientific and engineering works and evaluate circumstances and conditions for successful project results. The largest part is dedicated to the section Environmental implications of the engineering works in karst. Living in a time when almost every technical solution should conform to environmental conditions requires from engineers the exclusive application of sustainable and environmentally friendly solutions. Several case studies are also included in this part. They consider proposals on how to utilize unconfined, confined and littoral karst aquifers as well as how to organize dewatering of mines and prevent leakage from open water reservoirs. The content of the Environmental impact assessment study, dealing with limitations in groundwater extractions and indicators. which should be closely monitored to assess impact on environment, is also put forth. Some of these indicators may also help in assessment of pressures on groundwater quantity and quality.
Zoran Stevanović

Chapter 15. Karst Groundwater Availability and Sustainable Development

The hydraulic behavior of karst aquifers under several hydrologic conditions is described. Different parts of a spring hydrograph have been associated with hydrodynamics of karst aquifers, starting from a strong recharge event up to a long-term flow recession condition. As karst aquifers are characterized by a complex conduit network developing in a fractured carbonate rocks, an exchange of water between conduit and matrix/fractures generally occurs. Under strong recharge conditions, concentrated infiltration favors an increase in the hydraulic head in the conduit network, and a rapid pressure pulse is forced through the phreatic conduits giving a hydrographic peak at the spring. Later, after the end of recharge processes, the karst conduit network drains the saturated zone of the aquifer, and water table decreases. After prolonged rainfall deficit, a meteorological drought can induce a groundwater drought, and the water table falls to a minimum height; this hydrologic condition highlights the hydraulic behavior of karst aquifers under droughts. Statistical analyses could forecast a groundwater drought using rainfall data series, and provide a useful tool for water management. An example for karst aquifers of Picentini Mountains (Southern Italy) has been described, where spring discharge time series are available for several decades. Besides, the exceptional spring discharge increase after 1980 Irpinia earthquake is also described. The underground flow through karstic aquifer depends on the size, shape, nature, filling, and interconnection of cavities and voids. The transformation of rainfall into karst spring discharge can be very rapid, or the process can be rather slow and long lasting, due to the storage potential and retardation capacity of the underground voids. Autocorrelation and cross-correlation analyses can be very useful tools for evaluation of discharge regime and forecast of karstic aquifer behavior under different circumstances. In addition to these analysis, this section provides a theoretical base of a linear multiple regression model used for karst spring discharge simulations based on daily values, as well as examples based on autoregressive models (AR), cross-regressive models (CR), and most often used hybrid models (ARCR). The theoretical basis of transformation functions which is used for simulation of daily values of karst spring discharges was explained in detail. For the purposes of assessing partially (insufficiently) gauged karst springs, developed model presented in this section can be used for extending recorded discharge time series, for computing the real evapotranspiration, catchment size, and dynamic storage volume of the karst aquifer. The estimation of the groundwater potential for exploitation is of utmost importance, particularly during the planning or in the initial stages of the regulatory system development. This section examines two different concepts of the possible implementation of regulatory systems: first one, based on water “borrowing” from natural storage—static reserves—and second one is based on the increase in the dynamic groundwater storage by the construction of underground reservoir. By simulating different scenarios of groundwater exploitation, along with knowledge of hydrogeological behavior, a realistic basis for future optimal control of karst outflow regime can be created. This implies the analyses of storage changes in karst water reservoirs under natural conditions, and calculation of the future potential exploitation. The applied concept is based on the karst groundwater budget, which provides valuable information on storage changes in the karst aquifer, enables further predictions of the optimal exploitation rate, and facilitates karst groundwater management. Several examples are use to illustrate model performances and outputs. In hydrogeological and engineering geological surveys of karst interior, the only research methods that allow direct observation, investigation, and exact geological mapping of channels and caverns are speleology and cave diving. Data collected during speleological and cave diving exploration significantly contribute to the reconstruction of the evolution of karst processes, which is very important in assessing the depth of karstification which is in turn important for tapping of deep siphonal springs for water supply, as well as for other hydrotechnical structures in karst. Section 15.4 is an overview of four phases of speleological and cave diving explorations, from planning through exploration to the final data analysis. The examples of research given in this chapter are only a part of the experiences that point to significant development of karstic channels in karst areas. Speleodiving and speleology research in defining the position and functioning of karstic aquifer have contributed significantly to solving water supply problems, and to the implementation of hydrotechnical and other structures in karst. Although karst aquifers are one of the main water sources for drinking water supply worldwide, it is well known that they are at the same time one of the most problematic resources. Due to the unstable flow and great variation of the discharge of the karstic springs, during recession (lean) periods, the local population often suffers from water shortage. If aquifer is well karstified and has adequate storage in its deeper parts, it is often possible, just as it is in the case of open water reservoirs, to regulate and manage minimal flow by various engineering interventions. Such an option provides opportunities to satisfy water demands not only of direct consumers but of ecosystems as well by ensuring ecological flow downstream. In this section, possible engineering solutions to regulate groundwater flow in karst and physical, ecological, and economical implications of such interventions are discussed. The three prerequisites for implementation of an engineering regulation project which should be fulfilled are as follows: Regulation is physically possible; regulation is environmentally sound and friendly; and regulation is economically feasible and sustainable. Each of them is explained, and guidance for a realistic evaluation is provided. Several case studies facilitate understanding of the regulation opportunities and threats as well as identify some helpful surveying methods used in water practice. The two main groups of engineering regulation for controlling karstic groundwater are discussed in detail: (1) regulation of discharge zone and (2) regulations, i.e., interventions in the wider catchment area. The former can be achieved by spring overpumping, drilling the wells or other supplementary intakes, constructing a subsurface (underground) dam, or by artificial recharge. The riverbed regulation, directing groundwater to other more promising catchment areas, closing or regulating ponors (swallow holes), and building impermeable barriers are some of the measures which can be applied in the wider catchment to maintain seasonal flow. A few successfully implemented projects of aquifer discharge control and lessons learned in management of groundwater reserves are also presented in this section.
Francesco Fiorillo, Vesna Ristić Vakanjac, Igor Jemcov, Saša Milanović, Zoran Stevanović

Chapter 16. Prevent Leakage and Mixture of Karst Groundwater

Choosing optimal dam sites is a very complicated task due to the nature of karst and the insecurity of water storage often resulting in leakage from reservoirs. An appropriate project concept prior to exploration can significantly reduce the risks of water losses or at least minimize them to acceptable levels, while the absence or reduction of exploratory works can increase them. Many analyses show that once the reservoir is filled up, groundwater flow currently oriented toward the future reservoir would saturate the upper part of the karstified rocks, reactivate currently unsaturated (fossilized conduits) pathways, and form a reverse discharge outside of the reservoir area. The geological, hydrogeological, speleological, and other special investigation procedures should be permanent activities during the design stage, during the construction of the dam site and filling of the reservoir, as well as during exploitation. Having a good map, database, models, and geological, hydrogeological, and other 2D and 3D layers increases the chances of choosing a successful dam site and minimizes the possibilities of further leakage from reservoirs below the dam site and through the reservoir and dam site embankment. This chapter summarizes the necessary procedures for the acquisition of some of the basic information for choosing an optimal dam site and preventing leakage from reservoirs in karst formations through chosen characteristic examples. Several case studies involving mineral ore extraction and mine drainage in a karst aquifer environment are presented in this section. Mining operations often entail extremely high rates of groundwater inflow, which is a threat to safe mining. Insufficient knowledge about the hydrogeological setting and a lack of preventative drainage often lead to sudden inrushes. In the past, this has caused rapid mine flooding, material losses, and even human casualties. In the case of evaporite karst, ground subsidence resulting from rather fast dissolution of evaporite rocks is a special problem. The practical experience discussed in the section shows that various measures are undertaken to drain mining operations (including drainage wells on the ground surface, underground dewatering boreholes, drainage galleries, drainage shafts, and the like), as well as that grouting of karst conduits and caverns has not always been effective. The quality of karst groundwater, before it enters the zone of mining operations, is generally good. However, after the groundwater comes into contact with ore deposits, this quality frequently deteriorates. Numerous examples show that karst groundwater, when abstracted before it reaches mining operations, can be used for drinking water supply, irrigation water supply, and other similar purposes. The majority of karst terrains are characterized by a high degree of heterogeneity. The results obtained by applying methods for the assessment of local karstification (e.g., borehole tests) often cannot be reliable to extrapolate to a wider area. The use of remote sensing provides the opportunity to assess the spatial distribution of karstification in the subregional scale. Analysis of satellite and aerial images allows the identification of geomorphological and tectonic forms that may indicate the highly karstified zones. From the factors that indicate the karstification, and which can be mapped by remote sensing, two factors are selected: surface karstification (K sf) and density of faults (T f). By overlapping maps of these two factors using geographical information systems (GIS) techniques, the final map expressed through a KARST (karstification assessed by remote sensing techniques) index is obtained. For the first time, the mapping approach has been applied to the catchment area of Karuč springs (Montenegro). By surveying the catchment area after the preparation of the map of the KARST index, it was noted that the assessed degree of karstification by using remote sensing mainly matches to the field assessment of shallow karstification. The application of this approach provides an image of the spatial distribution of karstification, even for areas that are inaccessible for direct field research. The obtained map can be used as a basis for solving some of engineering problems in karst that are related to the regulation of water, extraction of groundwater, and protection of karst aquifers from contamination. The mixture of fresh groundwater and surface water is a frequent problem in karst, and most problematic for the sustainable use of fresh groundwater. This is mostly a result of a high permeability and low attenuation capacity of karst aquifers, particularly those formed in open (unconfined) structures. The problem becomes more complicated when karst aquifer is in contact with seawater and tapping coastal aquifers and distinguishing fresh from seawaters is regularly a very difficult task. For this purpose, the Phoenicians constructed special intake structures and still today, many attempts to address this problem are made and similar devices constructed. The regions in which a large number of submarine springs exist are the Mediterranean basin, Florida, the Caribbean basin, the Black Sea, the Persian Gulf, and the Pacific islands. The section includes an explanation of the classical Ghyben-Herzberg formula, which defines the relationship and interface between fresh and salty water, but also states that its application, as in the case of Darcy law, should be used with caution in the case of karst aquifers. Several chosen case studies from different locations (Yucatan Mexico, Libya, France, and Montenegro) provide an overview of problematic and very difficult management of littoral karstic aquifers. It is often the case that even implementation of sophisticated engineering works and controlled pumping of fresh groundwater cannot completely diminish salt water intrusion.
Saša Milanović, Veselin Dragišić, Milan M. Radulović, Zoran Stevanović

Chapter 17. Hazards in Karst and Managing Water Resources Quality

Karst is an extremely fragile natural environment. The geological, morphological, hydrological, and hydrogeological features of karst determine an overall high vulnerability to a number of potentially dangerous events. The delicate equilibrium of karst ecosystems can be dramatically and irreversibly changed, as a consequence of both natural and anthropogenic impacts. This contribution examines the main peculiarity of karst and discusses the main natural and anthropogenic hazards affecting karst. Sinkholes, mass movements, floods, and loss of karst landscape are dealt with and discussed also by means of description of some case studies. Actions to mitigate the hazard in karst are also treated, highlighting the necessity to protect karst, an environment that needs specific regulations to be properly safeguarded. In particular, the Karst Disturbance Index, to evaluate the degree of disturbance done by man to the natural karst, is discussed. Groundwater contamination is by the World Health Organization listed among the world’s severest problems. Globally, water resources are limited and under pressure from urbanization and climate change. Among available drinking water resources, groundwater from karst aquifers is progressively becoming more valuable for potable, irrigation, and other agricultural and industrial use due to its abundance (high flow rate springs up to some tens of m3/s) and relatively high quality of water. However, its efficient use and protection poses a great challenge to urban karstology due to the very high susceptibility to contamination. The concept of groundwater vulnerability and contamination risk assessment is presented as an alternative approach for source protection zoning and land-use planning in karst. Specifically, vulnerability assessment has in some countries already been adopted by some national water-related policies as it confirmed to be a practical tool for protection zoning. It offers balance between groundwater protection and economic interests. The resulting maps are useful for planners and developers dealing with the protection and management of karst groundwater. However, caution needs to be taken when selecting the appropriate method for vulnerability assessment and when interpreting the results. Karst groundwater protection mostly relies on the implementation of sanitary protection zones where different restrictions apply. A review of the relevant legislation of several European countries showed that the groundwater travel time is the most frequent criterion for the delineation of sanitary protection zones, where the horizontal travel time to the groundwater source is generally considered. As a result, some countries increasingly use groundwater vulnerability maps to define sanitary protection zones and to implement more stringent measures where groundwater is vulnerable. A step further in the optimization of the sanitary protection zone delineation approach is to include the travel time through the vadose zone and to take into account surface water flow to the ponor. The total travel time (ttot) is calculated to obtain the travel time from any point in the catchment area to the tapping structure. For the ponor catchment area, ttot is the sum of the surface water travel time to the ponor (ts) and the travel time from the ponor to the tapping structure, based on dye-tracing tests. For any point outside the catchment area of the ponor, the total travel time is the sum of the vertical (t v) and horizontal (t h) groundwater travel times. Apart from test results obtained using natural and artificial dye tracers, the vertical travel time can be estimated based on vulnerability assessment, while the horizontal time can be assessed by analyzing spring hydrographs. The vulnerability map produced on the basis of total travel time calculations can easily be converted into a map of sanitary protection zones, depending on national legislation. The Remediation of Groundwater in Karst section describes aggressive technologies currently being applied to remediate karst aquifers, including in situ thermal treatment, in situ chemical oxidation, in situ bioremediation, and pump and treat. The fundamentals of each technology are discussed, including design principles, failure mechanisms, and amenable contaminants. The authors first provide an overview of trends in the groundwater remediation industry, which is followed by thought-provoking discussion on the politics of remediation in karst. Special attention is given to the technical challenges presented by karst, such as conduit flow and dissolution features, which may make remediation impracticable. On the technical side, this chapter includes a demonstration of modeling tools to assist with remedial evaluation and design. For example, the authors illustrate the use of VS2DTI for heat transport modeling in thermal remediation design, and the conduit flow process (CFP) for pump and treat design. Each example illustrates the need to incorporate conduit geometry and flow in the remedial analysis, as the use of equivalent porous media (EPM) techniques would lead to poor remedial performance. The hydrogeology of the thick karstified carbonate regions is challenging not only theoretically but also from a practical point of view. In these systems different types of groundwater flow are operating on distinct timescales associated with different types of permeability. Practical and scientific concerns related to karst hydrogeology are often on a regional scale such as sustainable water management, contamination of aquifers, and geothermal utilization. It is key issue to understand the regional and hydraulically connected nature of carbonate systems and to find appropriate solution for these particular problems. The importance of the gravity-driven flow concept is that it helps to understand the common genesis of thermal flow. The paper presents a deduced generalized flow pattern for deep carbonate regions which can provide a basis for finding similarities between thermal springs connected to continental carbonates. The understanding of the scale effect is highlighted to resolve practical problems. An important consequence of the hydraulic continuity and relatively higher hydraulic diffusivity of karst is that the effects of natural or artificial stresses on the groundwater level can propagate greater distances and depths than in siliciclastic sedimentary basins. The Transdanubian Range, Hungary can give an “in situ example” for the operation of hydraulic continuity based on a “long-term pumping test.” The fact of hydraulic continuity operating on a different scale can be used also during the planning of geothermal doublet systems and in the necessity of the use of heat content of effluent lukewarm and thermal springs and wastewater of spas in discharge zones of thermal water. Inadequate management of transboundary aquifers can lead to various groundwater quality (changes in groundwater flow, levels, volumes) and quantity (dissolved substances) problems. These problems are more difficult to prevent, mitigate, and solve in an international context than in the case of national aquifers. International cooperation is necessary to ensure an appropriate assessment, monitoring, and management of transboundary groundwater resources. International agreements are made to prevent potential conflicts and to improve the overall benefit from groundwater. In practice, agreements, to be made and respected, require a sufficient knowledge on the resource, its current state, and the trends. This is often a challenge for invisible groundwater and especially in a complex hydrogeological environment like karst. Aquifers in karst are very vulnerable as well, asking for an additional attention of national and international water authorities. This chapter describes DIKTAS, a case study of transboundary aquifers in the Dinaric karst region; it addresses motivation for international water cooperation, methodological approach, achieved results, and current efforts.
Mario Parise, Nataša Ravbar, Vladimir Živanović, Alex Mikszewski, Neven Kresic, Judit Mádl-Szőnyi, Neno Kukurić

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