1997-2002 PhD thesis University of Karlsruhe 2002-2010 Senior Lecturer University of Neuchatel 2010-2011 Prof. for Hydrogeology and Geothermics, TUM Munich Since 2011 Prof. for Hydrogeology, KIT Karlsruhe
Abstract: Karstified aquifers are a major source of water in global terms. Most standard textbooks on hydrogeology make little mention of the peculiarities of karst groundwater systems in terms of their behaviour and in terms of the methods most appropriate to investigating them. The aim of this book is to give an account of those methods that are particularly appropriate for use in karst terrains. These include groups of methods (for example hydraulic investigations, hydrochemistry, geophysics, isotopic investigations and modelling) that are basic to all hydrogeological studies, but the emphasis placed on particular aspects of these groups of methods is often different in karst areas. Others such as speleological investigations, â the direct exploration of aquifers â are rarely if ever appropriate to non-karst areas but are a major significance in karst, whilst water tracing methods are a fundamental tool for karst investigations but less widespread in conventional hydrogeology. The various chapters are written by experts in the particular methods and are usually multi-authored, including hydrogeologists with experience of differing karst environments to provide a balanced view of the methods described. The final chapter discusses the application of groups of method to solve particular problems or to investigate particular karst aquifers.
This is the first book devoted to describing methods of groundwater investigation appropriate to karst systems and is intended to be of use to practising hydrogeologists with no special training in karst-oriented methods and scientists working in the fields of karst groundwater exploitation, protection and research.
Abstract: The Swiss Water Protection Ordinance not only defines microbiological and chemical water quality standards but also ecological goals for groundwater. The ordinance demands that biocenoses in groundwater should be in a ânatural state adapted to the habitatâ and âcharacteristic of groundwater that is not or only slightly pollutedâ. This was the starting point for the present study.
The study briefly presents some basic knowledge in microbiology, microbial ecology and hydrogeology. On this basis and by means of numerous examples from the literature, the study then discusses the present state of knowledge on the structure and activity of microbial biocenoses in groundwater and aquifers. Microbiological communities essentially consist of bacteria, archebacteria, protozoans, and a variety of microscopically small invertebrates. The aquifer ecosystem is characterised by a total absence of light, and often a shortage in organic carbon and nutrients, i.e. oligotrophic conditions. Consequently, the microorganisms are less numerous than in nutrient-rich systems; they are often very small and in a state of reduced activity. Under these conditions, even smallest energy gradients and nutrient resources are exploited. The geochemical heterogeneity of the aquifer is reflected in the heterogeneous distribution of the microbial communities. Some groundwater ecosystems also show strong temporal variations.
A variety of methods can be used to characterise microbial communities. Sampling of groundwater and the aquifer material require specially adapted techniques. A large proportion of microorganisms in groundwater are viable but non-culturable cells. Classical cultivation techniques thus provide an incomplete picture of the microbial communities. Modern methods using molecular microbiological techniques allow the non-cultivable microorganisms to be detected and the microbial communities to be characterised by means of a genetic fingerprint. Different methods are available to detect the activity of the microorganisms, thus permitting their ecological function to be further investigated.
The study finally discusses if and how it is possible to define and prove the natural state of the biocenoses that is demanded by the Water Protection Ordinance, and shows the advantages and limits of this new ecological approach to groundwater protection.
Abstract: About two hydrological years of continuous data of discharge, temperature, electrical conductivity and pH have been recorded at the Glarey spring in the Tsanfleuron glaciated karst area in the Swiss Alps, in order to understand how glaciated karst aquifer systems respond hydrochemically to diurnal and seasonal recharge variations, and how calcite dissolution by glacial meltwater contributes to the atmospheric CO2 sink. A thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of CO2 partial pressures and calcite saturation indexes. The results show diurnal and seasonal hydrochemical variations controlled chiefly by air temperature, the latter influencing karst aquifer recharge by ice and snowmelt. Karst process-related atmospheric CO2 sinks were more than 4-times higher in the melting season than those in the freezing season. This finding has implication for understanding the atmospheric CO2 sink in glaciated carbonate rock terrains: The carbon sink will increase with increasing runoff caused by global warming, i.e. carbonate weathering provides a negative feedback for anthropogenic CO2 release. However, this is a transient regulation effect that is most efficient when glacial meltwater production is highest, which in turn depends on the future climatic evolution.
Notes: Special Issue prepared by the IAH Karst Commission
Abstract: Aquifers provide water, nutrients and energy with various patterns for many aquatic and terrestrial ecosystems. Groundwater-dependent ecosystems (GDEs) are increasingly recognized for their ecological and socio-economic values. The current knowledge of the processes governing the ecohydrological functioning of inland GDEs is reviewed, in order to assess the key drivers constraining their viability. These processes occur both at the watershed and emergence scale. Recharge patterns, geomorphology, internal geometry and geochemistry of aquifers control water availability and nutritive status of groundwater. The interface structure between the groundwater system and the biocenoses may modify the groundwater features by physicochemical or biological processes, for which biocenoses need to adapt. Four major types of aquifer-GDE interface have been described: springs, surface waters, peatlands and terrestrial ecosystems. The ecological roles of groundwater are conditioned by morphological characteristics for spring GDEs, by the hyporheic zone structure for surface waters, by the organic soil structure and volume for peatland GDEs, and by water-table fluctuation and surface floods in terrestrial GDEs. Based on these considerations, an ecohydrological classification system for GDEs is proposed and applied to Central and Western-Central Europe, as a basis for modeling approaches for GDEs and as a tool for groundwater and landscape management.
Abstract: The Munich Gravel Plain has been studied under various aspects, but there has been no detailed hydrogeological underground model of the entire city area. As a result of the âurban heat-islandâ effect, groundwater temperatures reach 18 °C and locally exceed 20 °C. Therefore, this aquifer is suitable for systematic and large-scale near-surface geothermal energy exploitation. The goal of this study was to establish the first detailed hydrogeological underground model of the city of Munich, as a basis for an estimation of the geothermal potential. A database of more than 20.000 borings was available, of which 730 were selected, interpreted and processed. As a result, 26 east-west cross sections were constructed, showing the geometry and structure of the aquifer and the position of the free groundwater table during low, average and high-water conditions. Based on these profiles and basic hydraulic considerations, a groundwater flow rate of about 3 m3/s has been calculated. Results of this study indicate a high potential for thermal groundwater use and corresponding reductions of heating oil consumption and CO2 emissions. At the same time, thermal rehabilitation of the overheated urban groundwater could be achieved. The quantification of this geothermal potential and the space-time optimisation of thermal groundwater use for heating and cooling require, as next steps, a detailed analysis of groundwater temperatures and numerical groundwater flow and heat transport modelling.
Abstract: Clastic sedimentary rocks are generally considered non-karstifiable and thus less vulnerable to pathogen contamination than karst aquifers. However, dissolution phenomena have been observed in clastic carbonate conglomerates of the Subalpine Molasse zone of the northern Alps and other regions of Europe, indicating karstification and high vulnerability, which is currently not considered for source protection zoning. Therefore, a research program was established at the Hochgrat site (Austria/Germany), as a demonstration that karst-like characteristics, flow behavior and high vulnerability to microbial contamination are possible in this type of aquifer. The study included geomorphologic mapping, comparative multi-tracer tests with fluorescent dyes and bacteria-sized fluorescent microspheres, and analyses of fecal indicator bacteria (FIB) in spring waters during different seasons. Results demonstrate that (i) flow velocities in carbonate conglomerates are similar as in typical karst aquifers, often exceeding 100 m/h; (ii) microbial contaminants are rapidly transported towards springs; and (iii) the magnitude and seasonal pattern of FIB variability depends on the land use in the spring catchment and its altitude. Different ground water protection strategies than currently applied are consequently required in regions formed by karstified carbonatic clastic rocks, taking into account their high degree of heterogeneity and vulnerability.
Notes: Theme Issue on "Pathogens and Fecal Indicators in Ground Water" (Guest Editor: Larry McKay)
Abstract: Anomalous behaviour of specific electrical conductivity (SEC) was observed at a karst spring in Slovenia during 26 high-flow events in an 18-month monitoring period. A conceptual model explaining this anomalous SEC variability is presented and reproduced by numerical modelling, and the practical relevance for source protection zoning is discussed. After storm rainfall, discharge increases rapidly, which is typical for karst springs. SEC displays a first maximum during the rising limb of the spring hydrograph, followed by a minimum indicating the arrival of freshly infiltrated water, often confirmed by increased levels of total organic carbon (TOC). The anomalous behaviour starts after this SEC minimum, when SEC rises again and remains elevated during the entire high-flow period, typically 20â40 μS/cm above the baseflow value. This is explained by variable catchment boundaries: When the water level in the aquifer rises, the catchment expands, incorporating zones of groundwater with higher SEC, caused by higher unsaturated zone thickness and subtle lithologic changes. This conceptual model has been checked by numerical investigations. A generalised finite difference model including high-conductivity cells representing the conduit network (âdiscrete-continuum approachâ) was set up to simulate the observed behaviour of the karst system. The model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and SEC during high-flow periods. The observed behaviour is relevant for groundwater source protection zoning, which requires reliable delineation of catchment areas. Anomalous behaviour of SEC can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions.
Abstract: Groundwater in sufficient amounts and of suitable quality is essential for potable water supplies, crop irrigation and healthy habitats for plant and animal biocenoses. The groundwater resource is currently under severe pressure from land use and pollution and there is evidence of dramatic changes in aquifer resources in Europe and elsewhere, despite numerous policy measures on sustainable use and protection of groundwater. Little is known about how such changes affect groundwater dependent ecosystems (GDEs), which include various aquatic and terrestrial ecosystems above ground and inside the aquifer. Future management must take this uncertainty into account. This paper focuses on multiple aspects of groundwater science, policy and sustainable management. Examples of current management methods and practices are presented for selected aquifers in Europe and an assessment is made of the effectiveness of existing policies such as the European Water Framework Directive and the Habitat Directive in practice and of how groundwaters and GDEs are managed in various conditions. The paper highlights a number of issues that should be considered in an integrated and holistic approach to future management of groundwater and its dependent ecosystems.
Abstract: The Folded Molasse zone of the Northern Alps consists of clastic sedimentary rocks that are usually not considered to be karstifiable. However, large areas within this zone are composed of carbonatic conglomerates. Numerous karst landforms have recently been discovered but are not recorded on official maps and in the literature. Therefore, a research programme was initiated at the Hochgrat site (Austria/ Germany) that included geomorphological mapping and characterisation of the karst phenomena. Both fracture-controlled and hydrodynamically-controlled karren were observed on conglomerate outcrops. The predominant karst landforms, dolines, are typically circular, funnel shaped, most often 2 to 9 m in diameter, 1 to 6 m deep, and frequently act as swallow holes. Poljes that are atypically small (~1 ha) occur in either glacial cirques or syncline depressions, are flat floored and lined with sediment and soil, and drain underground via swallow holes. Short caves, springs with marked discharge variations and estavelles are further evidence for karst development. Karstic landforms are widespread in carbonatic conglomerate terrains, but their dimensions are smaller than in typical limestone karst. The practical implications of these findings are also briefly mentioned in this paper.
Abstract: Groundwater dependent ecosystems (GDEs) include valuable ecosystems such as springs, wetlands, rivers, lakes and lagoons. The protection of these systems and services they provide is highlighted by international agreements, i.e. Ramsar convention on wetlands, and regional legislation, i.e. the European Water Framework Directive. Groundwater provides water, nutrients and a relatively stable temperature. However, the role of groundwater in surface ecosystems is not fully understood. The ecosystem can depend on groundwater directly or indirectly, and the reliance can be continuous, seasonal or occasional. This has implications for the vulnerability of ecosystems, as some may be easily affected by external pressure. Conceptual models and quantitative assessments of how groundwater interacts with the environment are needed. GDEs are also threatened by different land use activities and climate change. Hence, we need to understand how GDEs are affected by changes in groundwater quantity and quality, as severe groundwater changes have been observed in many regions. This study examines key aspects of GDEs (hydrogeology, geochemistry and biodiversity) in order to improve conceptual understanding of the role of groundwater in such ecosystems. The status and baseline of different types of GDEs are discussed, with particular emphasis on past evidence of environmental change and potential thresholds and threats in GDEs in various parts of Europe with different land use, climate and geology.
Abstract: Lithostratigraphy and geologic structures are major controls on groundwater flow in alpine karst systems. Understanding these factors is important for the delimitation of drinking water protection zones. The Winterstaude mountain chain, western Austria, belongs to the Helvetic nappes and consists of Cretaceous sedimentary rocks, including two karstifiable formations: Ãrfla and Schrattenkalk Limestone (lower and upper karst aquifer), separated by 60 m of marl. Strata are folded and cut by faults with displacements of 40â70 m. Folded carbonate rocks continue below the alluvial valley floor so that the karst system can be subdivided in shallow and deep phreatic zones. This area is suitable for studying the combined influence of folds and faults on groundwater flow in a double-aquifer system. A multi-tracer test with seven injections aimed at characterising hydraulic connections and linear flow velocities. Results show that (i) plunging synclines form the main drainage pathways in the upper karst aquifer, with maximum linear velocities of 91 m/h, while anticlines act as water divides; (ii) recharge into the lower aquifer, which forms the central ridge of the mountain chain, contributes to springs discharging from the upper aquifer near the foot of the mountain (local flow systems); (iii) the two aquifers are hydraulically connected, presumably via faults, because their displacements are in the same order of magnitude as the thickness of the intervening marl; (iv) flow in the upper aquifer continues below the valley floor toward the river, with maximum velocities of 22 m/h (intermediate flow system).
Notes: Published in a special issue of Acta Carsologica prepared by the Karst Commission of the International Association of Hydrogeologists (IAH)
Abstract: Alpine glaciers store large amounts of freshwater contributing to groundwater recharge during warmer periods, but the interactions between glaciers and aquifers have rarely been investigated in detail. The Tsanfleuron-Sanetsch area, Switzerland, is an ideal test site to study glacier-aquifer interactions. It consists of a rapidly retreating glacier (2.8 km2) overlying a karst aquifer drained by a spring (mean discharge 600â700 L/s) used for drinking water supply and irrigation. The geometry and structure of the glacier were assessed by means of geophysical surveys, using radiomagnetotellurics (RMT). The estimated ice volume is 1.0 x 10E+8 m3 (0.92 x 10E+8 m3 water equivalent), but the glacier currently loses 1.5 m ice thickness per year. Field observations, flow measurements and tracer tests allowed characterisation of glacier drainage and aquifer recharge. Three recharge pathways have been identified: 1) The main glacial stream sinks into the aquifer via swallow holes 3 km downstream of the glacier mouth; 2) Numerous small meltwater streams sink underground shortly below the glacier front; 3) Subglacial meltwaters and supraglacial streams sink into the glacier via moulins and contribute to aquifer recharge through fractures and swallow holes underneath the glacier. Recharge and spring discharge display strong diurnal and seasonal variability, with a general high-flow period during snow and glacier melt from spring to autumn. Preliminary predictions of the future availability of spring water after disappearance of the glacier suggest that the discharge may decrease by 20â30 %. Nearly all of this loss will occur in summer and autumn, presumably resulting in temporary water shortage.
Notes: Published in a special issue of Acta Carsologica prepared by the Karst Commission of the International Association of Hydrogeologists (IAH)
Abstract: Mobile particles play crucial roles for contaminant transport in karst aquifers, but few studies have investigated the relationships between sediment dynamics and contaminants. This is partly due to the difficulty in monitoring suspended particles: Turbidity is easy to measure but does not deliver detailed information on the size and type of particles; mineralogical laboratory analyses are laborious and not suitable for continuous monitoring. A portable particle counter was used for the study presented here. The instrument delivers time-series of particle-size distribution (PSD), i.e. the number and diameter of suspended particles, grouped into different size-classes ranging from 0.9 to 139 µm. The test site is a karst system near the city of Yverdon-les-Bains, Switzerland. A swallow hole draining agricultural land is connected to two karst springs, 4.8 and 6.3 km away, which are occasionally contaminated by faecal bacteria at highly variable levels. Turbidity alone turned out not to be a reliable indicator for microbial contamination. To obtain more insight into bacteria and particle transport towards the springs, a comprehensive research program was carried out, including tracer tests and monitoring of PSD, turbidity, total organic carbon (TOC), faecal bacteria (E. coli) and various hydrologic and physicochemical parameters. Results show that there are two types of turbidity: A primary turbidity signal occurs shortly after rainfall during the rising limb of the hydrograph; a secondary signal typically occurs during spring flow recession. The first signal is explained by remobilization of conduit sediments due to a hydraulic pressure pulse (autochthonous or pulse-through turbidity). The second peak indicates the arrival of water from the swallow hole, often together with TOC and faecal bacteria (allochthonous or flow-through turbidity). PSD analyses revealed that autochthonous turbidity is composed of a broad mixture of fine and large particles, while allochthonous turbidity predominantly consists of very fine particles. This is explained by sedimentation of larger particles between the swallow hole and the springs. During allochthonous turbidity periods, very good correlation between the finest particles (0.9â1.5 micro-m) and E. coli was found (R2 = 0.93). The relative increase of fine particles can consequently be used as an "early-warning parameter" for microbial contamination of karst spring water. Further applicability and limitations of this approach are also discussed.
Abstract: The current knowledge on thermal water resources in carbonate rock aquifers is presented in this review, which also discusses geochemical processes creating reservoir porosity and different types of utilisations of these resources, such as thermal baths, geothermal energy and CO2 sequestration. Carbonate aquifers probably constitute the most important thermal water resources outside of volcanic areas. Several processes contribute to the creation of porosity, summarised under the term hypogenic (or hypogene) speleogenesis, including retrograde calcite solubility, mixing corrosion induced by cross-formational flow, and dissolution by geogenic acids from deep sources. Thermal and mineral waters from karst aquifers supply spas all over the world, such as the famous bath in Budapest, Hungary. Geothermal installations use these resources for electricity production, district heating or other purposes, with low CO2 emissions and land consumption, for example Germanyâs largest geothermal power plant at Unterhaching near Munich. Regional fault and fracture zones are often the most productive zones, but sometimes difficult to locate, resulting in a relatively high exploration uncertainty. Geothermal installations in deep carbonate rocks could also be used for CO2 sequestration. Carbonate dissolution would neutralise this gas and thereby increase reservoir porosity. The feasibility and limitations of this technique should be further investigated.
Notes: This article belongs to a series of "Reviews in Karst Hydrogeology" promoted by the IAH Karst Commission (www.iah.org/karst) with the goal to collect and evaluate current knowledge in different fields of karst hydrogeology and make it available to the scientific community.
Abstract: The impact of a railway tunnel on groundwater and surface waters in the Northern Apennines (Italy) was demonstrated and characterised by multi-tracer tests and hydrological observations. The 15-km-long Firenzuola tunnel crosses turbidite marls and sandstones previously not considered as aquifers. During the drilling, water inrushes occurred at fracture zones, and the tunnel still continues to drain the aquifer. The water table dropped below the level of the valleys, and gaining streams transformed into losing streams or ran completely dry, as did many springs, causing severe damage to the aquatic fauna and other elements of the ecosystem. Two multitracer tests, each using uranine and sulforhodamine G, were carried out in two impacted catchments in order to confirm and quantify the streamâaquiferâtunnel interrelations. The results proved connection between losing streams and numerous water inlets in the tunnel, with maximum linear distances of 1.4 km and velocities up to 135 m/d. Several of the demonstrated flowpaths pass under previous groundwater divides (mountain ridges), proving that the tunnel has completely modified the regional flow system. Water balance estimations demonstrate that the observed water losses cannot be explained by climate change but can largely be attributed to the tunnel drainage.
Abstract: Four methods of groundwater vulnerability mapping have been applied in a Slovene karst catchment and validated by tracer tests. The test site is characterised by high water table fluctuations, manifested in intermittent
lakes and variable drainage divides. A first multi-tracer test (two injections) allowed subdivision of the catchment
into zones of different degrees of contribution (âinner zoneâ and âouter zoneâ). For vulnerability mapping, only methods that consider the specific nature of karst aquifers such as heterogeneity and duality of infiltration processes, were selected: EPIK, PI, the âSimplified Methodâ and the âSlovene Approachâ. For validation, a second multi-tracer test (four injections) was carried out. The time of first detection and the normalised recovery were used as validation criteria. The results suggest that EPIK and the Simplified Method sometimes overestimate vulnerability, while PI and the Slovene Approach tend to deliver more realistic results, at least during low-flow conditions. The Slovene Approach gives the clearest guidance on how to deal with hydrologic variability, for example by assigning lower vulnerability to occasionally active sinking surface waters than to permanent ones. As a conclusion, commonly accepted validation techniques are needed and should be applied by default to evaluate different vulnerability mapping methods and the resulting maps.
Abstract: Recharge and contamination of karst aquifers often occurs via the unsaturated zone, but the functioning of this zone has not yet been fully understood. Therefore, irrigation and tracer experiments, along with monitoring of rainfall events, were used to examine water percolation and the transport of solutes, particles and fecal bacteria between the land surface and a water outlet into a shallow cave. Monitored parameters included discharge, electrical conductivity, temperature, organic carbon, turbidity, particle-size distribution (PSD), fecal indicator bacteria, chloride, bromide and uranine. Percolation following rainfall or irrigation can be subdivided into a lag phase (no response at the outlet), a piston-flow phase (release of epikarst storage water by pressure transfer) and a mixed-flow phase (increasing contribution of freshly infiltrated water), starting between 20 min and a few hours after the start of recharge event. Concerning particle and bacteria transport, results demonstrate that (i) a first turbidity signal occurs during increasing discharge due to remobilization of particles from fractures (pulse-through turbidity); (ii) a second turbidity signal is caused by direct particle transfer from the soil (flow-through turbidity), often accompanied by high levels of fecal indicator bacteria, up to 17,000 E. coli/100 mL; (iii) PSD allows differentiation between the two types of turbidity. A relative increase of fine particles (0.9 â 1.5 micro-m) coincides with microbial contamination. These findings help to quantify water storage and percolation in the epikarst and to better understand contaminant transport and attenuation. The use of PSD as âearly-warning parameterâ for microbial contamination in karst waters is confirmed.
Abstract: No abstract. Introduction: Geothermal energy can be used for heating, electric power generation and other applications. The confidence of the public in this technology is currently compromised by several bad examples where inappropriate implementation of geothermal installations has caused avoidable damage. A dramatic but instructive case is presented here. This article is a plea both for the reasonable use of geothermal energy and for more geologic and hydrogeologic competence and education in geothermics. Connoisseurs of classical German literature know the historic town of Staufen (7,800 inhabitants) as the town of Doctor Faust, immortalised by the eponymous drama written by Johann Wolfgang von Goethe (1749-1832). The town is currently suffering severe damage that began immediately following geothermal drillings in the city centre...
Abstract: The relationships between stratigraphic and tectonic setting, recharge processes and underground
drainage of the glacierised karst aquifer system âTsanfleuron-Sanetschâ in the Swiss Alps have been studied by
means of various methods, particularly tracer tests (19 injections). The area belongs to the Helvetic nappes and
consists of Jurassic to Palaeogene sedimentary rocks. Strata are folded and form a regional anticlinorium.
Cretaceous Urgonian limestone constitutes the main karst aquifer, overlain by a retreating glacier in its upper part. Polished limestone surfaces are exposed between the glacier front and the end moraine of 1855/1860 (Little Ice Age); typical alpine karrenfields can be observed further below. Results show that (1) large parts of the area are drained by the Glarey spring, which is used as a drinking water source, while marginal parts belong to the catchments of other springs; (2) groundwater flow towards the Glarey spring occurs in the main aquifer, parallel to stratification, while flow towards another spring crosses the entire stratigraphic sequence, consisting of about 800m of marl and limestone, along deep faults that were probably enlarged by mass movements; (3) the variability of glacial meltwater production influences the shape of the tracer breakthrough curves and, consequently, flow and transport in the aquifer.
Abstract: The structure, diversity and dynamics of microbial communities from a swallow hole draining agricultural land and two connected karst springs (Switzerland) were studied using molecular microbiological methods and related to hydrological and physicochemical parameters. Storm responses and an annual hydrological cycle were monitored to determine the short- and long-term variability, respectively, of bacterial communities. Statistical analysis of bacterial genetic fingerprints (16S rDNA PCR-DGGE) of spring water samples revealed several clusters that corresponded well with different levels of the allochthonous swallow hole contribution. Microbial communities in spring water samples highly affected by the swallow hole showed low similarities among them, reflecting the high temporal variability of the bacterial communities infiltrating at the swallow hole. Conversely, high similarities among samples with low allochthonous contribution provided evidence for a stable autochthonous endokarst microbial community. Three spring samples, representative for low, medium and high swallow hole contribution, were analysed by cloning/sequencing in order to identify the major bacterial groups in the communities. The autochthonous endokarst microbial community was mainly characterized of δ-Proteobacteria, Acidobacteria and Nitrospira species. A high percentage of unknown sequences suggested further that many karst aquifer bacteria are still undiscovered. Finally, the potential use of groundwater biomonitoring using microbial communities is discussed.
Abstract: This paper discusses the roles of sediments and particles/colloids for contaminant attenuation and transport in karst groundwater and presents experimental results concerning the relations between particles and microbial contamination in a karst system in Switzerland. The test site consists of a swallow hole draining agricultural land, connected to two springs, one of which is used for water supply. A portable particle counter was used to obtain detailed time-series of Particle-Size Distribution (PSD) in spring water, along with continuous monitoring of turbidity, total organic carbon (TOC) and other parameters, and analyses of faecal bacteria (E. coli). Two types of turbidity were observed at the springs following intense rainfall: A primary signal occurred during increasing discharge and is explained by remobilisation of intrakarstic sediments due to a hydraulic pulse (autochthonous or pulse-through turbidity). A secondary turbidity is typically observed after several days and indicates the arrival of water from the swallow hole (allochthonous or flow-through turbidity), often associated with high levels of TOC, nitrate and E. coli. PSD analyses allowed further differentiation: The primary turbidity consists of a mixture of different particles sizes, while the secondary signal predominantly consists of very fine particles, because larger particles are removed by sedimentation between the swallow hole and the springs. There is good correlation between E. coli and 0.9â1.5 micro-m flow-through particles. A relative increase of very fine particles can thus be used as an "early-warning system" for microbial contamination. PSD monitoring could also help to study other problems in karst environments, not only water contamination, but also soil erosion.
Abstract: No Abstract. Introduction: Every hydrogeologist dealing with tracer tests is aware of the textbook of Werner Käss (born 1924 in Stuttgart, Germany) on Tracing Technique in Geohydrology, which was first published in German (Käss 1992), then translated into English (Käss 1998) and finally published as a second German edition (Käss 2004). There is probably no other hydrogeologic discipline where a single book has such unrivalled status as a unique standard reference, gathering all available knowledge. (...)
Abstract: Hydrogeologists and speleologists all over the world recognise William B. White (born 1934, USA) and Elizabeth L. White (born 1936, USA) for their achievements in the fields of karst hydrogeology and cave research, and have learned a great deal from their books, papers and lectures. It is also thanks to the Whites that many aspects of the specific hydrogeological characteristics of carbonate aquifers, such as turbulent flow in caves and conduits, are generally acknowledged today. Amazingly, both of them earned their merits in other subject areas and dedicated only a portion of their time to karst hydrogeology. However, cave and karst research is the topic on which they worked as a couple, at least partly, and their karst-related work is not only driven by scientific interest but also by personal interest and passion.
During a workshop that took place at the Southwest University of China in Chongqing in October 2007, the authors had the opportunity to talk with the Whites about their life and research. A transcript of the complete interview is available (as Electronic supplementary material) and the interview itself can be seen on the Hydrogeologist Time Capsule website. This profile focuses on the scientific contributions of William and Elizabeth White to karst hydrogeology.
Abstract: The origin and distribution of microbial contamination in Lake Genevaâs most polluted bay were assessed using faecal indicator bacteria (FIB). The lake is used as drinking water, for recreation and fishing. During 1 year, water samples were taken at 23 points in the bay and three contamination sources: a wastewater treatment plant (WWTP), a river and a storm water outlet. Analyses included Escherichia coli, enterococci (ENT), total coliforms (TC), and heterotrophic plate counts (HPC). E. coli input flux rates from the WWTP can reach 2.5 Ã 10^10 CFU/s; those from the river are one to three orders of magnitude lower. Different pathogenic Salmonella serotypes were identified in water from these sources. FIB levels in the bay are highly variable. Results demonstrate that (1) the WWTP outlet at 30 m depth impacts near-surface water quality during holomixis in winter; (2) when the lake is stratified, the effluent water is generally trapped below the thermocline; (3) during major floods, upwelling across the thermocline may occur; (4) the river permanently contributes to contamination, mainly near the river mouth and during floods, when the storm water outlet contributes additionally; (5) the lowest FIB levels in the nearsurface water occur during low-flow periods in the bathing season.
Abstract: This article presents an introduction to the fundamentals of tracing techniques and their application in cave and karst environments, illustrated by case studies from the Mammoth Cave, USA, and a small experimental site in Switzerland. The properties and limitations of the most important artificial tracers are discussed, and the available methods of tracer injection, sampling, online monitoring and laboratory analysis are presented. Fully quantitative tracer experiments result in continuous or discrete concentration-time data series, i.e. breakthrough curves, and concomitant discharge data, which make it possible to obtain detailed information about groundwater flow and contaminant transport. Within the frame of speleological investigations, tracer tests can help to resolve the active and often inaccessible part of cave and conduit networks and to obtain indications about the geometry and volume of the conduits. For hydrogeological studies, caves can in turn be used as natural experimental and monitoring sites inside the unsaturated or saturated zone of karst aquifer systems.
Abstract: In 1998 and 1999, two multi-tracer experiments were conducted in the artesian karst aquifer of the mineral springs of Stuttgart, Germany. The breakthrough curves (BTCs) monitored at the springs showed very long tails or developed plateau-like concentration levels for more than 200 days. Initially, this observation was qualitatively explained by exchange between cavities with stagnant water and the active conduits. Since then, a new analytical solution for tracer transport in karst aquifers has become available, the âtwo-region non-equilibrium modelâ (2RNE), which assumes the presence of mobile and immobile fluid regions, and mass transfer between these two regions. The experiments were thus revisited, and it was possible to provide a more quantitative explanation of the observed behaviour. The new model simulated all BTCs very well, thus confirming the earlier qualitative explanation. The prolonged BTCs can be attributed to intermediate storage in cavities containing quasi-immobile groundwater, and slow release into active fractures and conduits. The results also demonstrate that karst aquifers are not always fast-flushing systems, but contaminants can sometimes remain in immobile fluid regions for long periods.
Abstract: Solute and colloid transport in karst aquifers under low and high flows was investigated by tracer tests using fluorescent dyes (uranine) and microspheres of the size of pathogenic bacteria (1 µm) and Cryptosporidium cysts (5 μm), which were injected into a cave stream and sampled at a spring 2.5 km away. The two types of microspheres were analyzed using an epifluorescence microscope or a novel fluorescence-particle counter, respectively. Uranine breakthrough curves (BTCs) were regular-shaped and recovery approached 100 %. Microsphere recoveries ranged between 27 and 75 %. During low flow, the 1-μm spheres displayed an irregular BTC preceding the uranine peak. Only very few 5-μm spheres were recovered. During high flow, the 1-μm-spheres BTC was regular and more similar to the uranine curve. BTCs were modeled analytically with CXTFIT using a conventional advection dispersion model (ADM) and a two-region non-equilibrium model (2RNE). The results show that (i) colloids travel at higher velocities than solutes during low flow; (ii) colloids and solutes travel at similar velocities during high flow; (iii) higher maximum concentrations occur during high flow; (iv) the 2RNE achieves a better fit of the tails, while the ADM is more robust, as it requires less parameters.
Abstract: A tracer experiment with uranine in a gravel aquifer aimed to assess the risk of a drinking water well near Pratteln, Switzerland, resulting from a contaminated site 760 m further upgradient. The experiment revealed a maximum linear flow velocity of 127 m/d and a mass recovery of 0.93 %. The tracer was also detected at two intermediate monitoring wells. This paper discusses the causes of this high flow velocity. Three different analytical models allowed simulation of the breakthrough curves and determination of transport parameters. A two-dimensional numerical model (FEFLOW) with simplified geometry provided a hydrogeologically consistent and probable explanation of all results. The aquifer is most likely relatively homogeneous, the steep hydraulic gradient (6 â°) and high conductivity (3 x 10E-2 m/s) cause high flow velocities, and most of the tracer passed northeast of the wells. Recently conducted small scale pumping tests largely confirmed this conceptual model. These findings should be considered for future protection measures.
Abstract: The world is very concerned about the huge environmental problems in China. Yuan Daoxian (born in 1933) is one of the leading scientists working on the investigation and resolution of these problems, with a particular focus on the karst regions of southwest China, which are home to more than 100 million people. Soil erosion and rock desertification affect an estimated 100,000 km2, but groundwater contamination and local or temporal water shortages are also key problems to be addressed. Yuan Daoxian is arguably the most experienced karst and hydrogeology researcher in China; he is a great teacher to the younger generation, and a great communicator who has opened Chinese karst and environmental research to the world.
During a workshop that took place at the Southwest University of China in Chongqing, October 2007, the authors had the opportunity to talk with Yuan Daoxian about his life and his research. The transcript of the interview is available as Electronic Supplementary Material and the interview itself can be seen on the Hydrogeologist Time Capsule website. This profile highlights several stations of his life and summarises his main scientific achievements, which can only be fully appreciated in relation to the recent history of China and the present environmental problems in this emerging economic power.
Notes: Transcript of Interview available as Electronic Supplementary Material
Abstract: Multi-tracer tests with three types of marine bacteriophages (H4/4, H6/1, and H40/1), together with various limnological methods, including physicochemical depth profiling, surface drifters, deep current measurements, and fecal indicator bacteria analyses, have been applied to characterize water circulation and pathogen transport in the Bay of Vidy (Lake Geneva, Switzerland). The experimental program was carried out twice, first in November 2005, when the lake was stratified, and a second time during holomixis in February 2006. The bacteriophages were injected at three points at different depths, where contaminated waters enter the lake, including the outlet pipe of a wastewater treatment plant, a river, and a stormwater outlet. Thereafter, water samples were collected in the lake at 2 m depth during a 48 h sampling campaign. The results demonstrate that (i) contaminated river water spreads rapidly in the bay; (ii) a well-developed thermocline is highly effective in preventing contamination from the depth to rise up to the surface; (iii) rapid vertical mixing and pathogen transport occur under thermally homogeneous conditions; and (iv) repeated multi-tracer tests with bacteriophages are a powerful technique to assess water circulation and contaminant transport in lakes where high dilution occurs.
Abstract: A variety of geological, hydrochemical and isotopic techniques were applied to explain the origin of exceptionally high radon levels in the St.Placidus spring near the city of Disentis in the Swiss Alps, where an average of 650 Bq/L 222Rn was measured. 222Rn is a radioactive noble gas with a half-life of 4 days, which results from the disintegration of radium (226Ra). The high radon levels can neither be explained by generally increased radium content in the fractured aquifer rock (orthogneiss), nor by the radium concentration in the spring water. It was possible to show that there must be a productive radium reservoir inside the aquifer but very near to the spring. This reservoir mainly consists of iron and manganese oxides and hydroxides, which precipitate in a zone where reduced, iron-rich groundwaters mix occasionally with oxygen-rich, freshly infiltrated rainwater or meltwater. The iron, as well as the reduced and slightly acid conditions, can be attributed to pyrite oxidation in the recharge area of the spring. Radium cations strongly adsorb and accumulate on such deposits, and generate radon, which is then quickly transported to the spring with the flowing groundwater.
Abstract: On the basis of work accomplished by the European COST Action 620, a comprehensive approach to groundwater vulnerability and contamination risk assessment is proposed, taking into account the special characteristics of Slovene karst aquifer systems. The Slovene Approach is consistent with national environmental legislation and enables comparison across European countries. The method integrates temporal hydrological variability in the concept of groundwater vulnerability and offers a new possibility to combine surface and groundwater source and resource protection, which required the development
of a new K factor (karst groundwater flow within the saturated zone). The risk analysis considers intrinsic vulnerability, contamination hazards and the importance of the source or resource. It has been first applied to the Podstenjšek springs catchment in southwestern Slovenia and validated by means of two multi-tracer tests with a total of six injection points. The resulting vulnerability, hazard and risk maps are plausible, and the validation confirmed the vulnerability assessment at the representative sites that were selected for tracer injection. The maps provide improved source protection zones and make it possible to identify land mismanagement and to propose better practices for future planning.
Abstract: Continuous monitoring of particle-size distribution (PSD), total organic carbon (TOC), turbidity, discharge and physicochemical parameters, together with analyses of fecal indicator bacteria, particularly E. coli, made it possible to better understand the processes governing pathogen transport in karst groundwater and to establish PSD as indicator for possible microbial contamination of drinking water from karst springs. In the study area near Yverdon-les-Bains, Switzerland, tracer tests proved connection between a sinking stream draining agricultural land and several springs, 4.8â6.3 km away. Tracing and monitoring results demonstrate that (i) suspended particles (turbidity) in the spring water either originate from remobilization of sediments inside the aquifer (autochthonous) or from the sinking stream and land surface (allochthonous); (ii) allochthonous turbidity coincides with increased E. coli and TOC levels; (iii) PSD makes it possible to distinguish the two types of turbidity; (iv) a relative increase of finer particles (0.9â10 micro-m) indicates allochthonous turbidity and thus possible fecal contamination. The method permits to optimize water treatment and identify periods when the spring water must be rejected. Findings from other test sites confirm the feasibility of this approach.
Abstract: A simplified methodology for mapping groundwater vulnerability and contamination risk is proposed, and the first application of the methodology, in a mountainous tropical karst area, is presented. The test site is the Tam Duong area, one of the poorest and remotest regions in northern Vietnam. The methodology requires a minimum of input data, which makes it particularly useful for developing countries. Vulnerability is assessed on the basis of two factors, which take into account the duality of recharge processes in karst aquifer systems: the overlying layers (O) and the concentration of flow (C). The risk map is obtained by putting together the vulnerability map and a simplified hazard assessment. The resulting maps provide a basis for groundwater protection zoning and land-use planning. Tracer tests and microbiological data confirmed the vulnerability and risk assessment in the test site.
Abstract: The current knowledge of microbial biocenoses (communities) in pristine aquifers is presented in a review, which also discusses their relevance for questions of groundwater protection. Aquifers are heterogeneous on all scales and structured in a variety of habitats. The void spaces in many aquifers are small. The biocenoses are thus predominantly composed of microorganisms and, often, microinvertebrates. Larger voids and macroorganisms occur in karst cavities. Due to the absence of light, the biocenoses depend on chemical energy resources, which are, however, scarce in non-contaminated groundwater. The microorganisms thus show small cell sizes, low population densities and reduced activity; they developed specific strategies to survive oligotrophic conditions. The review also discusses the impact of contamination on the biocenoses, and the potential use of the biocenoses or specific organisms as indicators for groundwater quality, and the limits of this approach. Bacteria are either planktonic or attached to aquifer material, which requires both fluid and solid phase sampling. Most groundwater bacteria are viable but non-culturable. Consequently, cultivation techniques give an incomplete picture of the biocenoses, while methods from molecular microbiology provide genetic fingerprints of the entire community. Different analytical methods are available to count microorganisms, identify species, characterise microbial diversity, and measure activity.
Abstract: The dynamics of organic carbon (OC), turbidity, faecal indicator bacteria and physicochemical parameters was studied in a karst system near Yverdon, Switzerland. Online measurements and sampling were done at a swallow hole draining an agricultural surface (the input), and two groups of springs (the outputs) that often show bacterial contamination. A fluorescent tracer that was injected into the swallow hole during low-flow conditions first arrived at the springs 10â12 days after injection; the total recovery rate was 29%. Previous tracer tests during high-flow conditions gave shorter travel times. After a major rainfall event, a primary turbidity peak was observed at the springs. It coincides with the rising limb of the hydrograph, indicating remobilisation of autochthonous particles from the aquifer. A secondary turbidity peak occurs several days later, suggesting the arrival of allochthonous particles from the swallow hole. Wider peaks of OC and bacteria were observed simultaneously. Applying methods from molecular microbiology (PCR-DGGE) allowed characterisation of the bacterial communities at the swallow hole and the springs. The results demonstrate that the swallow hole is an important source of groundwater contamination, while its contribution to aquifer recharge is insignificant. OC appears to be a better indicator for bacterial contamination than turbidity.
Abstract: The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.
Abstract: In the region of Scuol-Tarasp in the Lower Engadine Valley in the Eastern Swiss Alps, there are a variety of phenomena related to a geogenetic CO2 production, including carbogaseous mineral springs, previously active coldwater geysers and dry gas exhalations from the ground via mofettes. Previous isotopic studies revealed that the CO2 originates from the metamorphic decomposition of carbonate rocks in the crust. This paper presents an inventory of the springs, geysers and mofettes, and proposes a conceptual model on the regional gas and water circulation. Based on hydrochemical criteria, it was possible to identify six main groups of spring waters, three of which are carbogaseous mineral springs. Most of the carbogaseous springs and gas exhalations are bound to the Bündnerschiefer fractured aquifer. The different water types originate from mixing of groundwater and highly mineralised carbogaseous fluids from depth. Near-surface degassing of CO2 from the fluid phase creates the dry gas exhalations. CO2 and radon measurements in 178 soil boreholes suggest that the gas exhalations occur at a limited number of point-like anomalies, and there is no evidence for regionally important diffuse CO2 discharges from the ground.
Abstract: The European COST action 620 proposed a comprehensive approach to karst groundwater protection, comprising methods of intrinsic and specific vulnerability mapping, validation of vulnerability maps, hazard and risk mapping. This paper presents the first application of all components of this Pan-European Approach to the Sierra de LÃbar, a karst hydrogeology system in Andalusia, Spain. The intrinsic vulnerability maps take into account the hydrogeological characteristics of the area but are independent from specific contaminant properties. Two specific vulnerability maps were prepared for faecal coliforms and BTEX. These maps take into account the specific properties of these two groups of contaminants and their interaction with the karst hydrogeological system. The vulnerability assessment was validated by means of tracing tests, hydrological, hydrochemical and isotope methods. The hazard map shows the localization of potential contamination sources resulting from human activities, and evaluates those according to their dangerousness. The risk of groundwater contamination depends on the hazards and the vulnerability of the aquifer system. The risk map for the Sierra de LÃbar was thus created by overlaying the hazard and vulnerability maps.
Abstract: Groundwater from karst aquifers is an important drinking water resource, which is, however, particularly vulnerable to contamination. Karst aquifers consequently need special protection. This paper discusses the concept of groundwater vulnerability mapping and the special characteristics of karst aquifers that are relevant in this context. On this basis, a new method of groundwater vulnerability mapping is proposed-the PI method. It can be applied for all types of aquifers, but provides special tools for karst. Vulnerability is assessed as the product of two factors: protective cover (P) and infiltration conditions (I). The method was first applied and compared with two other methods (EPIK and the German method) in a test site in the Swabian Alb, Germany. The results obtained with the different methods are discussed and an outlook on the role of vulnerability maps within an overall groundwater protections scheme is given.
Abstract: This paper summarises seven years of hydrogeological research in the alpine karst system Hochifen-Gottesacker (Germany/Austria). Geologically, the site belongs to the Helvetic nappes and consists of Cretaceous sedimentary rocks. The Schrattenkalk limestone forms a relatively thin karst aquifer above or between thick marl aquicludes, forcing groundwater to flow parallel to the strata. The limestone is intensively cut by faults and fractures favouring karstification. The fault offsets are relatively small, so that their influence on the large-scale groundwater flow paths is limited. The site is thus ideal to study the influence of fold structures on the drainage pattern. Multi-tracer tests with a total of 16 injections demonstrated that troughs of plunging synclines form the main underground flow paths, while crests of anticlines act as local groundwater divides in the higher karst zones where the base of the aquifer is above the level of the surrounding valleys. In an adjacent valley that receives inflow from several synclines, tracer tests confirmed a major underground drainage system running across the folds. An axial culmination in the area is part of the continental water divide Rhine-Danube; an axial depression acts as a zone of confluence.
Abstract: Chlorinated solvents have been detected at low concentrations in some of the mineral and medicinal springs (spas) of Stuttgart since 1984. These springs discharge from a confined karst aquifer. In order to investigate both the properties of the aquifer and the mechanisms of contaminant trans port, two multi-tracer tests were carried out in 1998 and 1999. Both fluorescent tracers (naphthionate, eosin, pyranine) and particle tracers (clubmoss spores, microspheres) were used. All available wells and springs were sampled for at least 12 months. In these experiments naphthionate produced the best results. Maximum flow velocities were established to be within the range of 53 and 230 m/day. The breakthrough curves demonstrated a heterogeneous aquifer. The results identified flow to the springs from the west and south-west. It was possible to prove an assumed boundary between the northern zone of low mineralised water and the southern zone of highly mineralised water.
Abstract: In order to achieve some consistency in the establishment of groundwater intrinsic vulnerability maps in Europe. a new, approach is proposed by Working Group 1 of the European COST Action 620 on "Vulnerability mapping for the protection of carbonate (karst) aquifers". A general procedure is offered which provides consistency while allowing the required flexibility for application to a continent and under conditions of varying geology, scale, information availability, time, and resources. The proposed methodology is designed to be clearly more physically based than the existing vulnerability-mapping techniques. It takes the specificity of the karstic environments into account without necessarily excluding the applicability to other geological conditions. Combined "core factors" for overlying layers and for concentration of flow, account for the relative protection of groundwater from contamination while taking into account any bypass of the overlying layers. A precipitation factor is distinguished for describing: characteristics of the input of water to the system. Differentiation is made between groundwater resource intrinsic vulnerability Mapping and Source intrinsic vulnerability mapping. For the latter, a factor describing the karst network development is relevant. This short technical note describes a first stop in the work program of Working Group 1 of the COST Action 620. Future steps are now in progress to quantify the approach and to apply it in various European pilot areas.
Abstract: Mass movements alter the internal structure of rock units and thereby often change their hydraulic characteristics. In the present case a rockfall mass in an alpine karst area of Austria (Schwarzwasser valley, Vorarlberg) was hydrogeologically studied using discharge measurements, hydrochemical analysis and tracer tests.
The groundwater in the rockfall mass is mainly recharged by sinking streams and discharged by two resurgences and by subterranean seepage to the underlying karst aquifer. The rockfall mass itself is subdivided by an internal hydraulic barrier that can only be breached during strong flood events. The hydrogeological behaviour of the mass is characterized by very high flow velocities along discrete flow paths, and by a low storage capacity. These characteristics which are more typical at a karstic rather than a porous aquifer are interpreted as the result of post-rockfall internal washing processes.
Abstract: Coarse-grained conglomerates, which predominantly consist of carbonate components in a carbonate matrix, make up significant parts of the Folded Molasse zone (also referred to as Sub-Alpine Molasse) in Southwest Bavaria and Western Austria, at the northern margin of the Alps. Although these rocks are predisposed to karstification, due to their mineralogical composition, there are no recorded karst features in the official geological descriptions of the area. However, a large variety of karst landforms can be observed in the field on areas made of carbonate conglomerates.
Within the framework of this study, the relation between geomorphological karst landforms and geological structure was mapped and analysed systematically in a selected test site. The presence of an underground karst drainage network was checked for and its hydrogeological properties were investigated by means of a combined tracer test. Besides karrenfields and hundreds of dolines, two closed depressions with a flat floor were observed. These small poljes drain underground via swallow holes. It was possible to prove that most of these landforms were predominantly formed by karst processes, while mass movements, erosion and glacial processes are less significant. The presence of swallow holes, estavelles and springs with high discharge variations indicate the presence of an underground drainage network with strong hydraulic reactions on hydrologic events. A combined tracer test was undertaken during a storm event, the results of this test gave groundwater flow velocities of up to 286 m/h, flow paths of up to 7.7 km length were observed.
The results of this study proves that the test site is karstic in terms of both its geomorphology and hydrogeology. As many areas in the Folded Molasse zone of the Northern Alps show similar lithological characteristics, karstification should be expected there as well. However, apart from some areas in Switzerland, karstification has to date gone unrecorded. As karst groundwaters are particularly vulnerable to contamination from surface activities, they require special protection. The karstification of carbonate conglomerates should consequently be investigated in more detail and has to be considered for the delineation of groundwater protection zones.
Abstract: A comparative tracer test between a swallow hole and two karst springs 1.0 and 2.2 km away using 10 different tracer substances made it possible to compare the transport behaviour of these tracers in karst aquifer. The tracers include 4 different fluorescent dyes (uranine, naphthionate, pyranine, sulforhodamine B), 3 salts or ionic tracers (lithium, strontium, bromide) and 3 types of particulate tracers (red and green 1-micrometer spheres, and fluorescent-dyed inactivated Escherichia coli). Four of these tracer substances disappeared completely. The loss of pyranine can be explained by microbial degradation; the particulate tracers were probably lost by filtration and/or adsorption. The other six tracers arrived at the karst springs, but at different recoveries, 5 % for sulforhodamine B, 14 to 16 % for uranine, lithium and strontium, 20 % for naphthionate and 33 % for bromide.
Abstract: The PI method is a GIS-based approach to mapping the vulnerability of groundwater to contamination with special consideration of karst aquifers. Vulnerability is classified on the basis of the product of two factors: The P factor indicates the effectiveness of the protective cover as a function of the thickness and hydraulic properties of all the strata between the ground surface and the groundwater table: the soil, the subsoil, the non-karstic bedrock, and the unsaturated zone of the karstic bedrock. It is calculated using a slightly modified version of a method proposed by Hölting et al. (1995). The I factor (infiltration conditions) indicates the degree to which the protective cover is bypassed by surface and near-surface flow, especially if it occurs within the catchment area of a sinking stream. It takes into account the properties of the soil, land use and vegetation, the slope, and above all, the locations of karst features that allow surface water to rapidly enter the groundwater, for example via swallow holes.
Abstract: A groundwater vulnerability map was prepared for the Son La karst area, Vietnam, using an approach developed by the European COST action 620 on âvulnerability and risk mapping for the protection of carbonate (karst) areasâ. It was necessary to adapt this approach to the local hydrogeological, climatic and economic conditions. The modified (simplified) method is proposed for vulnerability mapping in other Vietnamese karst areas.
Abstract: Carbonate terrains comprise one third of the land area of Europe. Karst aquifers hold important groundwater resources supplying up to 50% of drinking water in some countries. The European COST Action 620 (Cooperation in Science and Technology), including delegates from 16 countries, worked from 1997 to 2002 to develop an approach to vulnerability and risk mapping, which takes into consideration the particular characteristics of carbonate (karst) aquifers, but which can, however, also be used for other aquifer types. The project was given impetus by the European Water Framework Directive, which is intended to provide a common framework for water resource policy and management.
The approach comprises methods of intrinsic and specific vulnerability mapping, hazard and risk mapping, and validation. Vulnerability maps can be produced both for resource and source protection. The proposed method is based on an origin-pathway-target model. The origin is the point of release of a potential contaminant, mostly the land surface. The target may be the groundwater table (resource) or a spring/well (source). The pathway comprises all compartments between the origin and the target. Intrinsic vulnerability only takes into account the hydrogeological properties of the system, while specific vulnerability additionally considers the specific interactions with particular contaminants. Hazards are defined as potential sources of groundwater contamination resulting from human activities, and overlaying vulnerability and hazard maps creates risk maps. Different techniques to validating vulnerability maps are proposed, comprising tracer tests, hydrograph and chemograph analyses, and modelling. The new approach was successfully tested in 11 European test sites.
Abstract: The drinking water for the city of Nürnberg in South Germany is partly extracted from the Upper Jurassic karst aquifer of the Franconian Alb. A groundwater resource vulnerability map using the PI method was created as a basis for land-use planning and protection zoning in the catchment of the drinking water sources. The thickness and properties of the protective layers overlying the karst aquifer (P factor) are crucial for vulnerability assessment. However, this factor is difficult to determine in the area of study: The Franconian Alb is a palaeo tower karst landscape, which formed in the Lower Cretaceous, was covered with sediments in the Upper Cretaceous and has been re-exposed to erosion since the early Tertiary. The thickness of the sediments overlying the karst surface is consequently highly variable, ranging between zero and 150 m, and difficult to predict using simple interpolation techniques. Thus, a GIS supported multiple regression approach was applied, using data from boreholes and geoelectrical soundings. The statistical evaluation of the available spatial data identified five variables, which were used to estimate the thickness of layers overlaying the karst aquifer. It was possible to create a digital elevation model of the palaeo tower karst landscape by subtracting the determined sediment thickness from the elevation of the present landscape.
Abstract: Coarse-grained conglomerates, which predominantly consist of carbonate components in a carbonate matrix, make up significant parts of the Sub-Alpine Molasse zone at the northern margin of the Alps. Although these rocks are predisposed to karstification, due to their mineralogical composition, the karst development was often overlooked in the past and not taken into account sufficiently in groundwater protection zoning. Within the framework of the two studies synthesised in this paper, the karst development in carbonate conglomerates (and sandstones) and the consequences for groundwater protection were investigated in two test sites in the Austro-German and Swiss Alps. The relation between geological structure and karst landforms was analysed. Besides karren and dolines, closed depressions (small poljes) with a flat floor were observed. Estavelles and springs with high discharge rates and variations indicate the presence of an underground drainage network with fast reactions to hydrologic events. Tracer tests gave groundwater flow velocities up to 286 m/h and flow path horizontal distances up to 7.7 km. A new method of groundwater vulnerability mapping was developed for highly heterogeneous fissured aquifers. This DISCO method takes into account discontinuities like fractures. It was applied in the Swiss test site; the resulting map served as a basis for the delineation of source protection zones.
Abstract: Vulnerability maps are tools for land-use planning and protection zoning. However, different methods produce different results that are usually not validated and can consequently be contested. In the catchment of a karst spring in the Swiss Jura Mountains, a vulnerability map (EPIK) was validated with tracer tests. Seven tracers were injected on the land surface and in a swallow hole in order to simulate the impact of hazards. The concentration and the recovery rate were found to be suitable for the validation while the transit time is less significant. The advantages and limitations of this validation technique are discussed.
Abstract: The UV fluorescent dye Naphthionate is often used for groundwater tracing due to its favourable properties. As it is invisible in the water it was selected as a tracer for an experiment in the karstic catchment of the mineral springs of Stuttgart (Germany) where any risk of colouring had to be avoided. Irregular breakthrough curves indicated the decay of Naphthionate. It was possible to demonstrate that the decay does not occur in the aquifer but in the sampling bottles. Laboratory experiments proved that the decay is due to microbiological activity and favoured by room temperature while the light has no significant influence.
Abstract: Groundwater from karst aquifers is among the most important drinking water resource for humanity. About one quarter of the global population is supplied by karst waters. In some alpine countries, karst water con-tributes 50 % to the total drinking water supply and some cities in the alpine region are almost totally dependent on karst waters. At the same time, karst aquifers are particularly vulnerable to contamination. Con-taminants can easily enter the underground and are transported rapidly over large distances in the aquifer. Processes of contaminant retarda-tion and attenuation often do not work effectively in karst systems. Therefore, karst groundwater needs special protection. A detailed knowledge of the hydrogeology of karst systems is the precondition for the development of sustainable protection schemes. Any kind of gen-eralisation is problematic and each karst system has to be investigated individually. This is particularly important for alpine karst systems which comprise a large variety of geologic, hydrologic, climatic and topog-raphic settings.
Within the framework of this thesis, the hydrogeology of three karst systems in the Northern Alps was investigated by means of geological and hydrogeological methods, above all tracer tests. The Hochifen-Gottesacker and the Winterstaude area are formed by relatively thin (about 100 m) karstified limestone formations which are under- and locally overlain by impervious marl. The strata are folded. Tracer tests proved that the underground drainage pattern is controlled by the strati-fication and, consequently, by the fold pattern: Synclines form the main flow paths, anticlines from local watersheds. Unlike that, the Alpspitze area is made of very thick (about 1000 m) limestone without interstrati-fied impervious layers. Tracer tests proved flow paths which are largely independent of the stratification and the folds, but controlled by the base level conditions and fault tectonics.
The hydrogeological understanding of a karst system and particularly the delineation of the catchments of the karst springs is the precondi-tion for the delineation of groundwater protection zones. However, karst areas are often very large and it is thus impossible to demand maxi-mum protection for the entire system as the resulting land-use restric-tions would not be acceptable in many cases. It is consequently essen-tial to protect at least those areas which are especially vulnerable to contamination. This leads to the concept of groundwater vulnerability mapping which aims at a compromise between groundwater protection on the one hand and land-use on the other hand. The basics of the concept of vulnerability mapping and a critical discussion of the existing methods is presented. Most of the methods are not applicable or lead to inconsistent results if they are applied to alpine karst systems.
Thus, a new method of groundwater vulnerability mapping with special consideration of karst aquifers was developed in co-operation with the European COST Action 620 on âvulnerability and risk mapping for the protection of carbonate (karst) aquifersâ. This so-called PI method classifies vulnerability on the basis of the product of two factors: The P factor indicates the protective function of the layers above the ground-water surface and the I factor (infiltration conditions) indicates the de-gree to which the protective cover is bypassed by lateral surface and subsurface flow which enters the aquifer at another place, e.g. via a swallow hole.
The PI method was tested and compared with other methods for the first time in the Engen area, a karst landscape in the Swabian Alb (SW Germany). Later on, the method was applied in the two alpine test sites Hochifen-Gottesacker and Winterstaude. The vulnerability map for the Winterstaude area will be used for source protection zoning for the community of Bezau.
Vulnerability maps were found to be a useful tool if the limitations of the concepts are clarified. Vulnerability maps should be made for a well defined purpose and should not be a stand-alone element but an inte-grated part of an overall groundwater protection scheme.
