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Master recession curves of 117 karstic springs from Middle and Upper Triassic carbonate aquifers in the Slovakian territory of the mountainous Western Carpathians were assembled from gauged discharge data. Identified slow-flow and fast-flow components were very diversely represented. Fast-flow components were missing in 47% of springs. In another 20% of springs, only fast-flow components were recognized, while slow-flow components were absent. Simultaneous discharge of both slow-flow and fast-flow components was found at 39 springs (33%). Known geology of recharge areas enabled examination of the impact that outcropping dolomites and/or limestones may pose to the discharge recession. It was found that dolomites in springsheds significantly affect slow-flow components, but do not influence the occurrence of the fast-flow ones. The purely fast-flow-driven recession was present both in limestone and dolomitic springsheds, but merely one fast-flow component was typical for the dolomitic ones. Two or three fast-flow components may appear in “purely limestone” springsheds. Recession coefficients of slow-flow components were within the interval of 0.0004–0.18 days−1 and those of fast-flow within 0.0017–0.31 days−1. The duration of the fast-flow components is mostly several days or several tens of days, while the theoretical duration of slow-flow may last for decades. Storage in matrix, fractures or conduits of the saturated zone cannot be separately estimated because, in discharged volumes, water from unsaturated and epikarst zones is included. Variable shapes of assembled master recession curves point to the important influence of unsaturated and epikarst zones on the discharge recessional patterns of karst springs.

The Baccatoio Stream basin (Apuan Alps) was subjected to numerous investigations linked to the presence of abandoned mines and related acid mine drainages. This study aims to achieve new insights into water circulation in carbonate aquifers feeding three of the major springs of the area (Moresco springs: VSMOA, VSMOS, VSMOG). VSMOA and VSMOS show evidences of hydraulic connection with Baccatoio stream, contaminated by acid mine drainages. The study focused on springs chemical and isotopic variations induced by a rainfall event. Some general conclusions can be drown: (i) the hydraulic connection between Baccatoio stream and VSMOA-VSMOS seems to be confirmed; (ii) during rainfall events, infiltrated rainwater seem to directly contribute to the perturbation of VSMOA-VSMOS; (iii) different flow fractions feeding VSMOA- VSMOS after rainfall pulse were quantified; (iv) VSMOG did not show any perturbation linked to the rainfall.

Thirty groundwater samples were collected from wells tapping Samalut fractured carbonate aquifer in the Eastern Desert fringes of the Nile Valley in Minia. The results show a wide variation of grou...

The geochemical evaluation of carbonate aquifers in Ngbo and environs has been executed to ascertain the major ion chemistry and quality of waters for domestic and drinking uses. Ten water samples were gathered from pit lakes, hand dug wells, boreholes and rivers. The collected samples were analysed for pH, EC, TDS, Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, SO42−, NO3− and PO42− in the laboratory using the standard methods. The results were compared with NDWQS and WHO standards. The physical parameters varied from pH (6.2–8.4), temp. (25.0–26.0 °C), electrical conductivity (4.9–102 µS/cm) and total dissolved solids (25.5–214.2 mg/l). The analysed results revealed the mean concentration of cations and anions in the following order: Ca2+ > Mg2+ > Na+ > K+ > Fe2+ and HCO3− > CO32− > SO42− > Cl−, respectively. Based on the standard limits, about 90% of the waters in the study area is suitable for domestic and drinking purposes. The Piper trilinear, Stiff and Durov diagrams showed that water samples from various locations fall into mixed CaCO32−+HCO3 type. Various ionic ratio plots show that water sources are from dissolution of minerals in the aquifer media. Geochemical parameters such as Cl−, Na+ and K+ show good interrelationship with positive factor loadings among the ions.

Viruses and bacteria which are characterized by finite lives in the subsurface are rapidly transported via fractures and cavities in fractured and karst aquifers. Here, we demonstrate how the coupling of a robust outcrop characterization and hydrogeophysical borehole testing is essential for prediction of contaminant velocities and hence wellhead protection areas. To show this, we use the dolostones of the Permian Magnesian Limestone aquifer in NE England, where we incorporated such information in a groundwater flow and particle tracking model. Within this aquifer, flow in relatively narrow (mechanical aperture of ~ 10−1–1 mm) fractures is coupled with that in pipe cavities (~ 0.20-m diameter) following normal faults. Karstic cavities and narrow fractures are hydraulically very different. Thus, the solutional features are represented within the model by a pipe network (which accounts for turbulence) embedded within an equivalent porous medium representing Darcian flowing fractures. Incorporation of fault conduits in a groundwater model shows that they strongly influence particle tracking results. Despite this, away from faulted areas, the effective flow porosity of the equivalent porous medium remains a crucial parameter. Here, we recommend as most appropriate a relatively low value of effective porosity (of 2.8 × 10−4) based on borehole hydrogeophysical testing. This contrasts with earlier studies using particle tracking analyses on analogous carbonate aquifers, which used much higher values of effective porosity, typically ~ 102 times higher than our value, resulting in highly non-conservative estimates of aquifer vulnerability. Low values of effective flow porosities yield modelled flow velocities ranging from ~ 100 up to ~ 500 m/day in un-faulted areas. However, the high fracturing density and presence of karstic cavities yield modelled flow velocities up to ~ 9000 m/day in fault zones. The combination of such flow velocities along particle traces results in 400-day particle traces up to 8-km length, implying the need for large well protection areas and high aquifer vulnerability to slowly degrading contaminants. Electronic supplementary material The online version of this article (10.1007/s11356-019-05525-z) contains supplementary material, which is available to authorized users.

The highest part of the Nera River basin (Central Italy) hosts significant water resources for drinking, hydroelectric, and aquaculture purposes. The river is fed by fractured large carbonate aquifers interconnected by Jurassic and Quaternary normal faults in an area characterized by high seismicity. The 30 October 2016, seismic sequence in Central Italy produced an abrupt increase in river discharge, which lasted for several months. The analysis of the recession curves well documented the processes occurring within the basal aquifer feeding the Nera River. In detail, a straight line has described the river discharge during the two years after the 2016 seismic sequence, indicating that a turbulent flow characterized the emptying process of the hydrogeological system. A permeability enhancement of the aquifer feeding the Nera River—due to cleaning of fractures and the co-seismic fracturing in the recharge area—coupled with an increase in groundwater flow velocity can explain this process. The most recent recession curves (2019 and 2020 periods) fit very well with the pre-seismic ones, indicating that after two years from the mainshock, the recession process recovered to the same pre-earthquake conditions (laminar flow). This behavior makes the hydrogeological system less vulnerable to prolonged droughts, the frequency and length of which are increasingly affecting the Apennine area of Central Italy.

Transmissivity estimates can be obtained by different approaches, mainly analytical and empirical. The application of analytical methods requires checking non-linear well losses due to turbulence and vertical flow related to partial penetration. The empirical approach relates transmissivity values to specific capacity data measured in the same well. The interpretation of available pumping tests highlights porous media solutions’ applicability in most of the step-drawdown curves analyzed. Double or triple porosity approaches are more appropriate only for wells located close to fault systems. In this work, a new relationship to estimate transmissivity by specific capacity data in some Italian carbonate aquifers is proposed. The comparison with other relationships available in the literature for similar aquifers worldwide confirms the validity of a general equation for carbonate aquifers, helping the spatial characterization of aquifer transmissivity in scarce data regions. Nonetheless, the use of equations of the same kind with different coefficients allows good results on our set of data. Results can improve the knowledge of fractured–karst aquifers by also including data from Central Italy.

In arid and semi-arid lands like Iran water is scarce, and not all the wastewater can be treated. Hence, groundwater remains the primary and the principal source of water supply for human consumption. Therefore, this study attempted to spatially assess the groundwater potential in an aquifer in a semi-arid region of Iran using geographic information systems (GIS)-based statistical modeling. To this end, 75 agricultural wells across the Marvdasht Plain were sampled, and the water samples’ electrical conductivity (EC) was measured. To model the groundwater quality, multiple linear regression (MLR) and principal component regression (PCR) coupled with elven environmental parameters (soil-topographical parameters) were employed. The results showed that that soil EC (SEC) with Beta = 0.78 was selected as the most influential factor affecting groundwater EC (GEC). CaCO3 of soil samples and length-steepness (LS factor) were the second and third effective parameters. SEC with r = 0.89 and CaCO3 with r = 0.79 and LS factor with r = 0.69 were also characterized for PC1. According to performance criteria, the MLR model with R2 = 0.94, root mean square error (RMSE) = 450 µScm−1 and mean error (ME) = 125 µScm−1 provided better results in predicting the GEC. The GEC map indicated that 16% of the Marvdasht groundwater was not suitable for agriculture. It was concluded that GIS, combined with statistical methods, could predict groundwater quality in the semi-arid regions.

The carbonate aquifers are important freshwater resources in Israel. The chapter focuses on the geology and hydrology of the Western Mountain basin that is the most important carbonate aquifer. The high permeability together with the gentle gradient allows the stakeholder to shift the pumping from one part of the basin to another, by using the aquifer storage as an underground water carrier.

The systematically varying properties and generally coherent and predictable behavior of rare earth elements (REE) make them potential tracers for studying water/rock interaction and weathering processes. In this work, a compilation and analysis of REE data in mineral and thermal waters were performed, focusing on their content and distributions in different hydrogeological systems, to quantify the natural REE variability and to discuss the controlling factors of REE concentrations. Quantitative challenges presented by multiply censored data were addressed with nonparametric and multivariate statistical methods. Considering a regional character of the research the application of Q and R mode Hierarchical Cluster Analysis with spatial analysis was an important approach for meaningful interpretation of large data set. An efficient approach to analyze differences between obtained HCA groups (clusters) was using a plot of reference-normalized concentrations. The results showed that REE data along with anomalies of Ce and Eu and inter-element ratios were good indicators of the aquifer lithology (hydrogeological systems formed in granitoid and volcanic rocks of various age, two main types of hydrogeological basins, and carbonate aquifers). The important mechanisms controlling REE migration in water were hydrochemical conditions in aquifers. The significance of the applied statistical analyses was represented by defining specific hydrochemical fingerprints of identified hydrogeological systems with distinct geochemical characteristics where REE showed the necessity of understanding of complex geological and hydrogeological settings, geodynamic evolution, and hydrogeochemical processes in fluid flow systems.

This study offers a reinterpretation of archive aquifer tests, predominantly on the basis of recovery data, from an original datasheet of thermal water wells located in carbonate and sandstone aquifer units in the vicinity of Budapest, Hungary. The study compares the hydraulic conductivity (K) and specific storage (Ss) values derived in the first instance from an aquifer test evaluation. This included an initial application of the classical analytical Cooper and Jacob method. Subsequently, the visual two-zone (VTZ) numerical method was applied, then third, a more complex model, namely, WT software. It was found that the simple analytical solution is not able to represent the field conditions accurately, while in the course of the application of the VTZ model, it proved possible to alter the various hydraulic parameters within reasonable limits to fit the field data. In the case of the VTZ model, the researcher is required to calculate the accuracy of the fitted model separately, while with the WT model, this is automatic, the software seeks out the best fit. In addition to VTZ parameters, the WT model can efficiently incorporate data on up to 500 model layers, water level, and pressure. The optimization of the parameters may be achieved by automatic calibration, improving the accuracy of the numerical results. Recovery tests for 12 wells were numerically simulated to obtain values for vertical and horizontal hydraulic conductivity and specific storage for Triassic and Eocene fractured carbonate and the Upper-Miocene-Pliocene granular sandstone aquifer units. When an analytical solution is applied, only average values could be obtained. The conclusion reached was that the results of the analytical solution can be improved by the use of numerical methods. These methods are able to incorporate basic information on well design, aquifer material and the hydrogeological environment in the course of the evaluation. The revision of the archive recovery data using numerical methods may assist in the quest for better data for numerical flow and transport simulations without the need to perform new tests. In addition, the methods employed here can explain cases in which the original analytical interpretations proved unable to yield reliable data and predictions.

Analysis of 12 years’ groundwater level data (2007–2019) from a well in a carbonate aquifer in northern China reveals that the groundwater response to earthquakes may be dependent on frequency. While the coseismic permeability increased during the 2008 M7.9 Wenchuan earthquake and eventually recovered to pre-seismic values (similar to that reported in previous studies), the observed increase following the 2011 M9.0 Tohoku earthquake in the same well showed no such recovery. Analysis of the seismograms of the two earthquakes near the well shows that the dominant frequency of the Rayleigh waves was lower in the Tohoku earthquake by a factor of five, compared with that during the Wenchuan earthquake. We hypothesize that Rayleigh waves with lower frequency are more efficient in clearing clogs from larger fractures in carbonate aquifers, or the clogging in larger fractures in the given azimuth are more easily to be cleared to the seismic wave following the Tohoku earthquake, and that the cleared large fractures are difficult to recover with post-seismic groundwater processes.

Position, width and fragmentation level of fracture zones and position, sig-nificance and characteristic distance of fractures were aimed to determine in a carbonate aquifer. These are fundamental parameters, e.g. in hydrogeological modelling of aquifers, due to their role in subsurface water movements. The description of small scale fracture systems is however a challenging task. In the test area (Kadarta, Bakony Mts, Hungary), two methods proved to be applicable to get reasonable information about the fractures: Electrical Resistivity Tomography (ERT) and Pricking-Probe (PriP). PriP is a simple mechanical tool which has been successfully applied in archaeological investigations. ERT results demonstrated its applicability in this small scale fracture study. PriP proved to be a good verification tool both for fracture zone mapping and detecting fractures, but in certain areas, it produced different results than the ERT. The applicability of this method has therefore to be tested yet, although its problems most probably origin from human activity which reorganises the near-surface debris distribution. In the test site, both methods displayed fracture zones including a very characteristic one and a number of individual fractures and determined their characteristic distance and significance. Both methods prove to be able to produce hydrogeologically important parameters even individually, but their simultaneous application is recommended to decrease the possible discrepancies.

This work addresses the detection of aquifers and the delineation of subsurface structures predominant in the basement rocks and their relations with these aquifers at the Bahariya Oasis, Western Desert, Egypt, and the relationship between the subsurface structures and the aquifers. In this respect, land geomagnetic and geoelectric-reconnaissance surveys were carried out over the oasis. Additionally, wells and bore-hole logs were used to verify the results and to explore the distributions of the subsurface reservoirs and the geological sequences. The results illustrate that the main groundwater aquifers in the fractured limestone ranges from 40 m to 90 m in depth and in the saturated Nubian sandstone from 800 m to 1200 m in depth. The thickness of the Carbonate reservoir varies from 90 m to 160 m. The Nubian sandstone formation that unconformably overlies the basement rocks has a thickness of approximately 250 m. In general, the depth to the basement rocks ranges from 1.2 km and 2.9 km in certain local areas according to the magnetic data. The structure trend analyses show that the dominant tectonic trends are northeastward and northwestward. These structures play an important role in controlling the aquifer depths and most probably supply water from the deeper Nubian aquifer to the shallower Carbonate aquifer.

It is generally considered that karst aquifers have distinctly different properties from other bedrock aquifers. A search of the literature found five definitions that have been proposed to differentiate karst aquifers from non-karstic aquifers. The five definitions are based upon the presence of solution channel networks, hydraulic conductivities >10−6 m/s, karst landscapes, channels with turbulent flow, and caves. The percentage of unconfined carbonate aquifers that would classify as ‘karst’ ranges from 50%.

Determination of recharge from precipitation and its distribution in karst areas is of great importance in water budget calculations. Several multi-parameter weighting-rating methods have been proposed to determine the recharge into karst aquifers; one of the most precise methods used in this field is the KARSTLOP. It is always necessary that the weight of recharge estimation method becomes calibrated by new techniques due to the diversity conditions of each area. Therefore, in this study, the analytical hierarchy process (AHP) technique has been used as a powerful decision-helping subjective tool. Using this method, the weights of the original KARSTLOP method were modified and improved based on the comments from water experts in the area. The mean annual recharge in the study area was 27.5% and 34.5% for the KARSTLOP-AHO and KARSTLOP methods, respectively. The results of KARSTLOP–AHP method are in accordance with the discharge of selected springs in the study area and budget reports.

A multi-species, multi-stable-isotope approach (δ15NNO3, δ18ONO3, δ34SSO4, δ18OSO4, δ18OH2O and δ2HH2O) was used together with environmental tracers (Ar, Ne, CFC-11 and CFC-12) and geochemical modelling to characterize sources and processes controlling concentrations of NO3− and SO42- in groundwater of the carbonate aquifer Gliwice (southern Poland). The study area represents a strongly transformed environment with a range of human activities i.a. Agriculture, urbanization and industry. The δ15NNO3 and δ18ONO3 indicated that most samples contained NO3− of mixed sources: artificial fertilizers, municipal and industrial sewage, while very good correlation between NO3− and CFC-12 suggested that nitrate originated primarily from residential and industrial sewage. Conversely, isotopic composition of sulphate in groundwater suggested agriculture as well as oxidation of sulphides as dominant. The conclusion was supported by the comparison of CFCs and sulphate concentrations which revealed no relevant correlation. Geochemical modelling confirmed the presence of sulphate reduction in areas where isotopic analyses were not possible due to undetectable sulphate. Thus, the integrated application of stable isotopes, environmental tracers, groundwater chemistry and geochemical modelling shows a complex origin of groundwater pollution in the study area as well as variety of geochemical processes controlling chemistry of groundwater in a triple-porosity aquifer influenced by different types of human activity.

This research was focused on the analyses of the hydrochemical behaviour of long-lived natural radionuclides (210Po, 210Pb, 234,238U, 230,232Th, 226,228Ra) in groundwaters from Spanish aquifers with different geological characteristics and the evaluation of the dose by ingestion of these waters. The study was performed by the gross alpha-beta, alpha spectrometry and physicochemical analysis of a set of bottled drinking waters. Radionuclide activities in the investigated aquifers were highly variable. High concentration of 210Pb is associated with granitic bedrock and reducing conditions. On the other hand, the highest 238,234U concentrations were found in carbonate aquifers. Activities of 226Ra are largely controlled by ion exchange reactions due to the presence of relatively high concentration of chloride. Several waters exceeded the parametric value for gross alpha mainly due to 234U, 226Ra and/or 210Pb concentrations. Moreover, the content of 226Ra and 210Pb in the water contributed mainly to the indicative dose.

Thallium is among the most toxic elements to humans. Environmental regulations of the European Community adopted by Italy pose a maximum concentration level for Tl in groundwater of 2 μg/L. However, at present drinkable water must not abide any concentration threshold for thallium and this element is not routinely monitored. In the past-mining area nearby the Valdicastello Carducci village (northern Tuscany, Italy), characterized by Tl-bearing ores, water from a spring that has been tapped for human consumption contains thallium in the range 4.3–27.8 μg/L. The challenge of this study is to highlight the mechanisms leading to Tl contamination in groundwater, by crossing hydrochemical and O-H isotopic data with hydrogeological information. We propose that the Tl-contamination in the spring results from a binary mixing that occurs within a karst system involving an uncontaminated Ca-HCO3 water (mainly interacting with limestone) and a component originated by the interaction of acid drainages (generated by the weathering of Tl-bearing mineral phases in the area) with dolomitic host rocks. In this process, most of the potentially toxic elements released during the weathering are scavenged by the carbonate neutralization of the acid plume due to adsorption onto the iron and manganese oxyhydroxides that formed during pH changes. Nevertheless, the aquifer has little or no attenuation capacity for thallium. Moreover, O-H isotopic data and hydrogeological constraints are compatible with a spring feeding mechanism related to a piston displacement effect.

This study focuses on three springs located within the Baccatoio Stream basin (Southern Apuan Alps) that are fed by a carbonate aquifer system. This area is characterized by intense mineralization, mostly formed of barite-pyrite-iron oxides, which was mined until the early 90s. The springs were investigated with a multidisciplinary approach based on hydrogeological, chemical and stable isotopetechniques. Groundwater hydrochemistry, aquifer hydrodynamic conditions and springs-stream relations were preliminarily studied. The achieved results suggest the existence of two different groundwater flow systems: the first one shallower feeding two of the three springs (VSMOA and VSMOS), and the second one deeper feeding the third one (VSMOG). In addition, the results seem to point out the presence of a connection between the Baccatoio Stream and the springs VSMOA and VSMOS.

Florida’s karst constitutes some of Earth’s largest expanses of geologically young carbonate sedimentary deposits (shelly sediments, limestone and dolostone) with bare and covered karst. Because of the large population of Florida and the dependence of that population on carbonate aquifers, the karst of Florida is has been extensively investigated. This book synthesizes our knowledge about Florida karst, beginning with why Florida karst differs from older, telogenetic karst elsewhere in North America and the world.

We performed continuous recordings (May 2015 – January 2017) of hydraulic pressure and electrical conductivity of groundwater in the 190 m-long horizontal S13 borehole drilled next to the deep underground laboratories of Gran Sasso (LNGS-INFN), located in the core of the Gran Sasso carbonate aquifer (central Italy) at a distance of about 39 km south-eastward from the 24 August 2016 Amatrice earthquake (6.0 Mw) epicenter. Using a 3-channel, 24-bit ADC we achieved a sampling rate of groundwater physical properties up to 50 Hz for each channel. We focused on the analysis of data recorded before, during and after the Amatrice earthquake, describing and discussing in detail the evidence for significant hydraulic pressure and electrical conductivity anomalies recorded before the main shock. We identified unambiguous signals in the hydraulic pressure data starting on 19 August, i.e. five days before the 24 August mainshock. A more careful analysis allowed us to detect the inception of a weak change up to 40 days before the Amatrice earthquake and a significant variation in the electrical conductivity data about 60 days before. The data revealed highly dynamic aquifer behaviour associated with the uprising of geogas probably related to the preparation stage of the Amatrice earthquake.

On the selected cases, Gotalovec in the area of Pannonian basin and Baska in the Dinaridic karst area, that are representing a common hydrogeological model in both regions of Croatia, CSAMT data together with data of other geophysical methods (electrical resistivity tomography , electrical sounding and seismic reflection) enabled the definition of a reliable prognostic geological model. The model consists of carbonate aquifer which underlies an impermeable thick package of clastic deposits. There are great variations of the dolomitic aquifer depths in the Gotalovec area due to strong tectonic activity, while in the Baska area depth changes are caused by the layer folding. The CSAMT method provides the most complete data on lithological and structural relationships in cases of hydrogeological targets deeper than 100 m. Based on the presented models we can conclude that the CSAMT method can provide greater exploration depth than electrical resistivity tomography (ERT) and can be considered as a fundamental geophysical method for exploration of buried carbonate aquifers, deeper than 100 m. But, the CSAMT research may demonstrate its advantages only in the case of very dense layout of CSAMT stations (25–50 m), due to the greater sensitivity to noise in relation to resistivity methods. Interpretation of CSAMT data is more complex in relation to resistivity methods, and a forward modelling method sometimes gives better results than an inversion due to possibility of the use of additional data acquired by other geophysical methods (ERT, electrical sounding and seismic reflection). At greater depths, the resolution of all electrical methods including the CSAMT method is significantly reduced, and seismic reflection can be very useful to resolve deeper lithological interfaces.

Application of sulfate isotope studies and geochemical modeling in determining processes affecting groundwater chemistry in the Gliwice-£abedy well-field area. A b s t r a c t. In order to determine geochemical processes affecting chemical composition of groundwater in the Gliwice-Łabedy well-field area two research methods were applied. Chemical analysis allowed us to assess the quality of groundwater in the Triassic karst-fractured-porous aquifer of the southwestern part of the major groundwater basin no. 330. The chemical composition of groundwater is distinguished by spatial heterogeneity highlighted by higher mineralization and concentrations of individual ions in the western area. In addition, all samples collected in 2016 were analyzed for the 34 S and 18 O to identify sources of sulfates in the waters examined. The study revealed a different origin of these ions depending on location of the wells sampled. The results of chemical analysis and archival data allowed for application of geochemical modeling in identification of processes taking part in groundwater chemistry evolution. Simulations of processes controlling water chemistry within the Triassic aquifer were conducted using The Geochemist’s Workbench 10.0.6. The examined processes encompassed dissolution of minerals forming the carbonate aquifer and Miocene evaporates overlying the Triassic aquifer as well as mixing of groundwater and surface water.

Groundwater management authorities usually use groundwater budget calculations to evaluate the sustainability of withdrawals for different purposes. The groundwater budget calculation does not always provide reliable information, and it must often be supported by further aquifer monitoring in the case of hydraulic connections between neighboring aquifers. The Riardo Plain aquifer is a strategic drinking resource for more than 100,000 people, water storage for 60 km2 of irrigated land, and the source of a mineral water bottling plant. Over a long period, the comparison between the direct recharge and the estimated natural outflow and withdrawals highlights a severe water deficit of approximately 40% of the total groundwater outflow. A groundwater budget deficit should be a clue to the aquifer depletion, but the results of long-term water level monitoring allowed the observation of the good condition of this aquifer. In fact, in the Riardo Plain, the calculated deficit is not comparable to the aquifer monitoring data acquired in the same period (1992–2014). The small oscillations of the groundwater level and the almost stable streambed spring discharge allows the presumption of an additional aquifer recharge source. The confined carbonate aquifer locally mixes with the above volcanic aquifer, providing an externally stable recharge that reduces the effects of the local rainfall variability. The combined approach of the groundwater budget results and long-term aquifer monitoring (spring discharge and/or hydraulic head oscillation) provides information about significant external groundwater exchanges, even if unidentified by field measurements, and supports the stakeholders in groundwater resource management.

As karst aquifers are often characterised by non-linear behaviour, ascertaining the turning points in their hydraulic regime may provide essential information on the functioning of the aquifer. These characteristics also apply to the Silurian-Ordovician aquifer system, composed of diverse carbonate rocks, in Estonia. The aquifer system is an important source of drinking water in northern Estonia. It also comprises the Nabala- Rakvere aquifer, a locally important groundwater resource that underlies the Tuhala karst area famous for an intermittently overflowing karst spring known as the Witch's Well. The water rich in humic substances of the Tuhala River recharges the Tuhala karst system, which is drained by two spring groups. In order to develop measures for the sustainable management of the aquifer in the future, the aim of this study was to enhance understanding of the hydraulic behaviour and hydrodynamic properties of the Tuhala karst system. From October 2014 to December 2016 an extensive field campaign was carried out comprising the observation of 22 surface- and groundwater monitoring points for water level and physico-chemical parameters and the performance of four quantitative tracer tests. The data obtained were evaluated in accordance with the input� output water level relation curves and a conceptual model of the system was set up. The results show that a strong hydraulic link exists, primarily through well-developed conduits between the recharge and discharge area of the karst system. Depending on the hydrological conditions, groundwater flow direc tions vary and maximum linear flow velocities range between \~225 and 800 m/h. A threshold-controlled throughput capacity and interaction with the adjacent aquifer cause imbalances between the input and output discharges of the karst system. Tracer tests coupled with surface and groundwater level relation curve analysis allowed the specification of flow threshold conditions for the Witch's Well spring group and the overflow threshold for the Witch's Well, among other key hydrological events. The hydraulic regime of the karst system was divided into three stages, each with differing threshold controls and hydrodynamic characteristics. Key words: karst system, shallow carbonate aquifer, monitoring, tracer test, water level relation curve, threshold, overflow.  Dolo\vanje mejnih vrednosti tristopenjskega hidravlji\vnega obna\vanja pokritega plitvega karbonatnega vodonosnika (Tuhalski kras, severna Estonija) Kra\vki vodonosniki se pogosto obna\vajo nelinearno, zato lahko z ugotavljanjem mejnih vrednosti v hidravli\vnem re\vimu zagotovimo bistvene informacije o delovanju vodonosnika. To velja tudi za silurijsko-ordovicijski vodonosni sistem v Estoniji, ki ga sestavljajo razli\vne karbonatne kamnine in je pomemben vir pitne vode na severu dr\vave. Vklju\vuje tudi vodonosnik Nabala- Rakvere, ki je lokalno pomemben vodni vir. Na tem obmo\vju se nahaja Tuhalski kras, ki je znan po ob\vasno bruhajo\vem kra\vkem izviru Witch's Well (\varovni\vin vodnjak). Tuhalski vodonosnik napaja reka Tuhala, bogata z huminskimi snovmi, prazni pa se skozi dve skupini izvirov. Da bi v prihodnje razvili ukrepe za trajnostno upravljanje vodonosnika, je bil namen te raziskave izbolj\vati razumevanje hidravli\vnega obna\vanja in hidrodinami\vnih lastnosti kra\vkega sistema. Od oktobra 2014 do decembra 2016 smo opravili obse\vno terensko delo, ki je obsegalo spremljanje vodostajev in fizikalno-kemijskih parametrov v 23 povr\vinskih in podzemnih to\vkah ter izvedbo \vtirih kvantitativnih sledilnih poskusov. Pridobljene podatke smo ovrednotili na podlagi krivulje odvisnosti vhodnih in izhodnih vodnih nivojev. Vzpostavili smo konceptualni model sistema. Rezultati ka\vejo na obstoj mo\vne hidravli\vne povezave predvsem z dobro razvitimi kanali med obmo\vji napajanja in praznjenja kra\vkega sistema. Odvisno od hidrolo\vkih razmer se spreminjajo smeri in hitrosti toka podzemne vode, ki zna\vajo od \~225 do 800 m/h. Kapaciteta prepustnosti, ki jo uravnavajo dolo\vene mejne vrednosti, in posledi\vne in terakcije s sosednjimi vodonosniki povzro\vajo neravnovesja med vhodnimi in izhodnimi preto\vnimi vrednostmi kra\vkega sistema. Zdru\vevanje rezultatov sledilnih poskusov z analizo krivulje odvisnosti povr\vinskih in podzemnih vodostajev nam je omogo\vilo, da smo dolo\vili mejne preto\vne vrednosti izvira Witch's Well in druge klju\vne hidrolo\vke dogodke. Hidravli\vni re\vim kra\vkega sistema smo razdelili na tri faze, od katerih ima vsaka dolo\vene mejne vrednosti in hidrodinami\vne lastnosti. Klju\vne besede: kra\vki sistem, plitvi karbonatni vodonosnik, monitoring, sledilni poskus, krivulja odvisnosti vodnih nivojev, prag, preliv.

Relatively high concentrations of dissolved bio-Barium and bio-silica in groundwater in Paleocene–Eocene carbonate aquifers caused by the Paleocene–Eocene thermal maximum are proposed as tracers for delineating zones of leakage into adjacent aquifers. In fresh, oxidized and not thermal groundwater (within a narrow range of temperatures) these tracers can be considered as conservative. In addition, certain trace elements (U, Mo, Se and Tl) of phosphates widespread in Senonian carbonate strata are suggested to serve as tracers of water originating from these sediments. The locally increased concentrations of these trace elements in groundwater of a carbonate aquifer underlying the Senonian strata were also proposed as tracers of water leakage from above. The proposed tracers of water in Eocene and Senonian strata have been used for delineating zones of local leakage into the underlying Turonian aquifer in the Yarkon-Taninim basin (YTB) of Israel. Results of geochemical survey of 208 wells in the Turonian aquifer of the YTB were used for Pearson’s correlation and Principal Component Analysis (PCA) for detection of interconnection zones. PCA revealed 4 factors explaining up to 86% of variance in groundwater chemistry in the Turonian carbonate aquifer. Two factors, first – with high loadings of Ba and SiO 2 , and second – with high loadings of U, Mo, Se and Tl, were interpreted to be related to local groundwater leakage from Eocene strata into the Turonian aquifer, fast and slow, respectively. Mapping of these two factors enabled delineation of areas where local inflow of water from the Eocene aquitard exists.

Characterizing the quality and radioactivity of groundwater is vital as it represents valuable resource in arid regions. Here we present radioactivity level in groundwater collected from wells in a region along the border between Sultanate of Oman and United Arab Emirates (UAE). The aquifers are alluvium deposits (silt, sand and gravel) and the measured groundwater radioac- tivity (including 232 Th, 238 U, 235 U, 226 Ra, 222 Rn, gross-a and gross-b) indicates values below the WHO permissible limits for drinking water. The results also show large dif- ference in radioactivity fingerprints, in particular for 226 Ra and 222 Rn within the investigated aquifers. The data further indicate lower radioactivity in groundwater of the alluviums compared to the carbonate aquifers in the region. This feature makes the alluvium aquifers valuable reservoirs that should be carefully exploited as a source of groundwater. As this is the first investigation on the radioactivity of groundwater in alluvial aquifers in the region, it suggests that other alluvial deposits, particularly those inland and far from the marine water intrusion or seepage from carbonate rocks would have low radioactivity fingerprints.

The adequate management of small aquifers located in structurally complex areas requires detailed geological and hydrogeological knowledge of the system. The analysis may include features related to the aquifers´ 3D geometry, their lateral connection with other aquifers, their hydraulic parameters, and their storage and recovery capacities during dry periods. To accomplish such a study is complex, and it involves even more uncertainties in the case of karst aquifers due to their special features. In this paper we present a multidisciplinary hydrogeological approach to explore a carbonate aquifer of southern Spain subjected to intensive exploitation. The study allowed us to redefine its geometry and its limits through the acquisition of geological and geophysical (gravity) data. New hydrodynamic, hydrogeochemical and isotopic information led to a new conceptual model and the definition of guidelines for a more efficient management., Unidad de Granada, Instituto Geológico y Minero de España, España, Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas, España, Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada, España

The exploitation of groundwater resources must always keep in account the geology and hydrogeological settings of the catchment basin for the sustainability of withdrawals, in order not to overexploit the aquifer. Especially, in the case of mineral water extraction, even more attention should be paid to understand what are the water-rock-gases interaction mechanisms, which allow obtaining a specific water chemistry. The case of Ferrarelle mineral water (western sector of Riardo Plain, Caserta) is particularly complex. Through the acquisition of a great amount of former geological and hydrogeological data and by new hydrogeological surveys, it has been possible to distinguish the aquifer levels, distinguishing four circulations over the Roccamonfina Volcano and in the Riardo Plain. The presence of volcanic and volcaniclastic deposits deriving from the Roccamonfina Volcano which cover a highlytectonized carbonate bedrock, allows the formation of two aquifers in hydraulic continuity. This mixing between the two aquifers allows, with the ascent of deep CO2 through faults in the carbonate bedrock, the formation of the typical chemical composition of the mineral water Ferrarelle. In the eastern sector of the plain, it is possible to distinguish the volcanic aquifer from the carbonate one, probably due to the presence of low permeability deposits.

V povprecju obisce jamo Nerja ve~ kot 500.000 ljudi letno. Od leta 1993 je v jami instalirana mreža monitoringa, ki vsako uro meri stevilne parametre, da bi ugotovili vplive obiskovalcev na podzemno okolje. Od 1991 izvrsujejo hidrokemicne meritve vode v curkih v jami in pri naravnih iztokih iz karbonatnega vodonosnika. Zvezna merjenja fizikalno kemijskih parametrov prenikajoce vode, dnevni odtok, kakor tudi temperatura in relativna vlažnost zraka, koncentracija CO2 in temperatura skale kažejo clovekov vpliv. Glavne spremembe okoljskih parametrov so naslednje: 1. zracna temperatura zraste za 0,2 °C na vsakih 1000 obiskovalcev na dan; 2. relativni porast relativne zracne vlage med 2 in 3 %, ki v poletnih dneh doseže nasicenost; 3. koncentracija CO2 v zraku narase do vrednosti med 500 in 700 ppm v obdobju manjsega obiska in za desetkratno izhodiscno vrednost ob casu velikega obiska (2.800 ppm); 4. temperatura skale narase med 0,02 °C do 0,15 °C na dan in 5. PCO2 prenikajo~e vode izkazuje spremembe, narascajoce med velikim obiskom in padajoci indeks nasicenosti karbonatnih mineralov. The Nerja Cave receives on average more than 500,000 visitors per year. In order to know the possible impact in the underground environment by human visits, a monitoring network was installed since 1993, to control hourly several parameters. Also, since 1991 a hydrochemical control has been carried out in the drip water points of the cave and in the natural discharge points of the carbonate aquifer. This continuous record of physical-chemical parameters of drip water, its daily outflow, as well as temperature and relative humidity in the air, CO 2 concentration and rock temperature shows the human influence. The main changes in environmental parameters are the following: 1. cave air temperature rises 0.2 °C by 1000 visitors/day; 2. a daily increase between 2 and 3 % in relative air humidity, reaching saturation on summer days; 3. CO 2 concentration in air increases up to values between 500 and 700 ppm during low visitability periods and 10 times the background value during high visitability periods (2.800 ppm); 4. temperature of the rock rises between 0.02 °C and 0.15 °C/day, and (5) PCO 2 of drip water also presents variations, increasing during the big influx of visits and decreasing the saturation index of carbonated minerals.

The very diverse types of ground-water behavior in carbonate terrains can be classified by relating the flow type to a particular hydrogeologic environment each exhibiting a characteristic cave morphology. The ground water may move by diffuse flow, by retarded flow, or by free flow. Diffuse flow occurs in less soluble rocks such as extremely shaley limestones or crystalline dolomites. Integrated conduits are rare. Caves tend to be small, irregular, and often little more than solutionally widened joints. Retarded flows occur in artesian environments and in situations where unfavorable stratigraphy forces ground water to be confined to relatively thin beds. Network cave patterns are characteristic since hydrodynamic forces are damped by the external controls. Solution occurs along many available joints. Free flowing aquifers are those in which solution has developed a subsurface drainage system logically regarded as an underground extension of surface streams. These streams may have fully developed surface tributaries as well as recharge from sinkholes and general infiltration. Characteristic cave patterns are those of integrated conduit systems which are often truncated into linear, angulate, and branchwork caves. Free Flow aquifers may be further subdivided into Open aquifers lying beneath karst plains and Capped aquifers in which significant parts of the drainage net lie beneath an insoluble cap rock. Other geologic factors such as structure, detailed lithology, relief, and locations of major streams, control the details of cave morphology and orientation of the drainage network.

This study applies gray relation analysis method to make an estimate of the range that influenced by Tongluoshan tunnel construction on groundwater environment, using hydrochemical data of groundwater sampled from tunnel and wells as well as springs. Results calculated reveal that the gray relation grades varies from 0.48 to 0.89 with an average of 0.63 to 0.76, implying that the inflow from tunnel is closely related to the groundwater system which recharges the wells and springs. And an area about 3.5 square kilometers consists of rangeⅠand rangeⅡ, distributing mainly in the carbonate aquifer field around tunnel is inferred as the zone that might be influenced by Tongluoshan tunnel construction. So the wells and springs in these ranges may disappear if a good link existing between the tunnel and aquifers that recharges the wells and springs.

Summary From analysis of the hydrodynamic and hydrochemical responses of karst springs, it is possible to know the behaviour of the aquifers they drain. This manuscript aims to contribute to the characterization of infiltration process, and to determine the relative importance of the saturated zone and of the unsaturated zone in the hydrogeological functioning of carbonate aquifers, using natural hydrochemical tracers. Thus, chemical components together with temperature and electrical conductivity (both punctual and continuous records) have been monitored in three springs which drain Alta Cadena carbonate aquifer, Southern Spain. An evaluation of the percentage of the electrical conductivity frequency peaks determined for each of the three springs is linked to the chemical parameters that comprise the conductivity signal. One of these springs responds rapidly to precipitation (conduit flow system), due to the existence of a high degree of karstification in the unsaturated zone and in the saturated zone, both of which play a similar role in the functioning of the spring. Another spring responds to precipitation with small increases in water flow, somewhat lagged, because the aquifer has a low degree of karstification, even in the unsaturated zone, which seems to influence its functioning more strongly than does the saturated zone. The third spring drains a sector of the aquifer with a moderately developed degree of karstification, one that is intermediate between the other two, in which both the unsaturated zone and the saturated zone participate in the functioning of the spring, but with the latter zone having a stronger influence. These three springs show different hydrogeological functioning although they are in similar geological and climatic contexts, which show the heterogeneity of karst media and the importance of an adequate investigation for groundwater management and protection in karst areas.

This article presents results of hydrogeological and hydrogeochemical research conducted at south hills, Ivanščica Mountain, situated in the northwestern part of the Republic of Croatia. Research was carried out in the summer 2013, between July and September. Hydrogeological mapping was undertaken on approximately 20 km2 (at a scale of 1:25000), with water samples taken from 10 springs. Rocks and deposits were classified into three hydrogeological units with respect to permeability. Two main aquifers were identified – the Triassic carbonate aquifer and the Badenian carbonate aquifer. The overall capacity of 41 registered springs (permanent and periodic) was estimated. According to their basic chemical composition, water from springs belong to Ca-HCO3 (calcium-hydrogen carbonate), CaMg-HCO3 (calcium magnesium-hydrogen carbonate) and to MgCa-HCO3 (magnesium calcium-hydrogen carbonate) types.

Geochemical processes occurring at the seawater/freshwater interface were studied for the aquifer feeding the Santa Cesarea thermal springs, located along the coastal sector of the Salento peninsula (southern Italy). In this coastal area, seawater is moving into the freshwater carbonate aquifer, pushing so inland beneath the freshwater and creating so an extremely active geochemical environment. In the transition zone, the interaction between the freshwater/saltwater and the aquifer rocks could affect the geochemical composition of the groundwater itself, modifying it even profoundly, as discussed in the paper. The geochemical processes occurring at a seawater/freshwater interface are also described together with the chemical composition of Santa Cesarea thermal springs.

Hydrogeological and geophysical investigations demonstrated the existence of an epikarstic zone in a carbonate aquifer of Southern Italy, about 10 m thick. Nevertheless, the hydrogeological behaviour of the epikarst is different from that schematized by several authors. In the test site, the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium. Because of the high fracture density and good interconnection of openings within the underlying limestone, the percolation is diffuse also below the epikarstic zone, as well as the groundwater flow. The ‘funnelling’ effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer.

No Abstract Keywords: Turbulent flow, Aquifer, Tracer tests, Spring discharge, Hydraulic conductivity

The study area, Odukpani is underlain by cretaceous sediments of the Calabar Flank. The main aquifers are fractured black shales that are inter-bedded with calcareous sandstones. The aquifers range from confined to unconfined. Water samples were taken from boreholes and shallow hand dug wells for chemical characterization with standard laboratory techniques. Results from the chemical analysis show that the waters are mostly alkaline with the exception of two mildly acidic samples. They depicted low electrical conductivity values and a total dissolved solids range from 13.1 to 341 mg/l which indicate fresh water. Cations levels occur in the order, Ca2+ ˃ Na+ ˃ Mg2+ ˃ K+ ˃ Fe2+ while anions occur as the following order, HCO3− ˃ SO42− ˃ Cl− ˃ CO3− ˃ NO3−. Piper trilinear and stiff plots show that Ca2+ – Na+ – HCO3− is dominant water type. The waters are supersaturated with respect to calcite in five of the samples. The rest have calcite under-saturation. Areas of calcite super-saturations are likely undergoing precipitation of carbonate minerals in the aquifer matrices. Precipitation and dissolution of carbonate minerals within the aquifers are likely contributing to the modification of flow characteristics of the aquifer. Comparison of the water chemistry with standards set by regulatory bodies indicates that the waters are of good quality.

Limestone aquifers provide the main drinking water resources of southern Italy. Due to cattle grazing and/or manure spreading, these aquifers are often characterized by microbial contamination of groundwater. The aim of this paper is to summarize the results obtained during a 10-year research carried out in experimental field sites in southern Italy, analyzing (1) the influence of the topsoil of pyroclastic origin on the migration of microbial cells from the ground towards the groundwater, and then on the groundwater vulnerability, (2) the influence of the rainfall regime on the breakthrough at the springs, (3) the reliability of thermotolerant coliforms and fecal enterococci as bacterial indicators of microbial contamination, and (4) the effectiveness of microorganisms as natural tracers for some hydrogeological purposes. The results obtained showed that fecal enterococci are a more reliable indicator than thermotolerant coliforms for detecting contamination and that the entity and distribution over time of microbial contamination of fecal origin are influenced by several factors, such as precipitation regime, thermal regime and existence and thickness of the topsoil of pyroclastic origin. Moreover, the migration of a significant amount of bacterial cells through the topsoil and the underlying carbonate rocks allows the utilization of microorganisms as effective natural tracers, to be coupled with other classic tracers to study the recharge and the flow processes. In a broader perspective, these results can be used to optimize the investigations in other hydrogeological scenarios, with emphasis on those where different water types coexist and interact in same aquifer systems.

The feasibility of using a subsurface intake system for a seawater reverse osmosis (SWRO) water treatment plant is based on the site-specific hydrogeologic conditions which control the type of intake design that can be used and the capacity of the intake. Planning for future development of subsurface intake systems requires a careful analysis of the shoreline and shallow offshore area. Example regions, the Red Sea coast of Saudi Arabia and the shoreline of Florida (USA), were investigated to develop general feasibility criteria for possible development of SWRO intake systems. Within the Red Sea, it was found that various well intake systems could be feasible for low-capacity SWRO facilities and high capacity intake systems would be limited to seabed gallery intakes. Coastal Florida had more subsurface intake options available, including wells, beach galleries, and seabed galleries which could be used based on the required capacity and the specific site conditions. The presence of high transmissivity carbonate aquifers containing seawater in Florida would allow medium capacity SWRO systems to use conventional vertical wells. High capacity systems could be developed using beach gallery systems in many locations. The methods developed for shoreline and nearshore evaluation contained herein could be applied to any coastal region of the world for subsurface intake evaluation.

Summary Zona Citricola is an important area for Mexico due to its citriculture activity. Situated in a sub-humid to humid climate adjacent to the Sierra Madre Oriental, this valley hosts an aquifer system that represents sequences of shales, marls, conglomerates, and alluvial deposits. Groundwater flows from mountainous recharge areas to the basin-fill deposits and provides base flows to supply drinking water to the adjacent metropolitan area of Monterrey. Recent studies examining the groundwater quality of the study area urge the mitigation of groundwater pollution. The objective of this study was to characterize the physical and chemical properties of the groundwater and to assess the processes controlling the groundwater’s chemistry. Correlation was used to identify associations among various geochemical constituents. Factor analysis was applied to identify the water’s chemical characteristics that were responsible for generating most of the variability within the dataset. Hierarchical cluster analysis was employed in combination with a post-hoc analysis of variance to partition the water samples into hydrochemical water groups: recharge waters (Ca–HCO 3 ), transition zone waters (Ca–HCO 3 –SO 4 to Ca–SO 4 –HCO 3 ) and discharge waters (Ca–SO 4 ). Inverse geochemical models of these groups were developed and constrained using PHREEQC to elucidate the chemical reactions controlling the water’s chemistry between an initial (recharge) and final water. The primary reactions contributing to salinity were the following: (1) water–rock interactions, including the weathering of evaporitic rocks and dedolomitization; (2) dissolution of soil gas carbon dioxide; and (3) input from animal/human wastewater and manure in combination with by denitrification processes. Contributions from silicate weathering to salinity ranged from less important to insignificant. The findings suggest that it may not be cost-effective to regulate manure application to mitigate groundwater pollution.

The aim of the present study is to characterize the distribution of the 238U decay series radionuclides, focusing on uranium, radium, in the cold, lukewarm and thermal karst waters in the Bukk region. This is a novel approach to characterize fluids and understand their mixing in regional discharge zones of carbonate aquifers. Based on the measurements, simple flow system, without mixing, is supposed, and the elevated radium content might be connected to hydrocarbon reservoir fluids. The results may support the improvement of protection strategies of springs and wells involved in water supply.

A methodological procedure is proposed for evaluating the groundwater reserves in carbonate aquifers. It is applied to the Solana-Onteniente-Volcadores aquifer (Alicante, SE Spain), subjected to groundwater mining exploitation. The large amount of geological and geophysical information available (361 km2 of geological mapping, 84 lithological columns of boreholes, 47 km of seismic reflection profiles, 68 vertical electrical soundings [VES], 22 MT soundings and 1,600 gravity measurements) was integrated using two different 3D geological modelling codes: 3D Geomodeller and GOCAD. In addition, a petrophysical study of the rock matrix was accomplished with 39 rock samples, aiming to determine their storage capacity and calculate the total groundwater reserves. Information provided by the 3D model stands as a great advance in our hydrogeological knowledge of the region.