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A complete water analysis typically contains at least 65 chemical and physical parameters. This variety of parameters complicates temporal or spatial comparisons of different water samples. Hence, special hydrogeological diagrams, such as the Schoeller diagram, were developed to facilitate the evaluation and interpretation of analytical results of multiple samples. In conventional Schoeller diagrams, the concentrations of calcium, magnesium, sodium, chloride, sulfate, and bicarbonate/carbonate are plotted as points on logarithmic scales. Points of one analysis are connected to form characteristic signatures of each sample. Occasionally, resulting parallel signatures indicate a similar water genesis. Here, we present standardized Schoeller diagrams and introduce a practical Matlab tool for this purpose. Standardization means that the different logarithmic axes are shifted towards each other so that the signature of a selected sample becomes a horizontal line. This procedure greatly facilitates comparisons of water samples to the chosen standard and increases the informative value of the diagrams. However, manual implementations of standardizations are arduous and time-consuming, as a single calculation of the relocation of each axis is necessary. In addition, the calculations must be repeated if another sample is chosen as the standard. We developed a Matlab tool that allows the fast generation of standardized Schoeller diagrams with many options and implements user-specific preferences with just one command. Probably the most useful feature is that users can choose which parameters are displayed, opening up new areas of application for Schoeller diagrams.

Climate change and glacial retreat are changing the runoff behavior of Alpine springs and streams. For example, in the extremely dry and hot summer of 2018, many springs used for drinking water supply lost up to 50 percent of their average discharge; a few springs have even run dry. In order to ensure drinking water supply in the future, springs featuring large and constantly sufficient discharge rates will have to be identified and tapped. A case study was undertaken at the Tuxbachquelle because catchment area and temporal variation of physicochemical and hydrochemical properties were previously unknown. Tracer tests with uranine proved a hydraulic connection between this karst spring and a stream a few kilometers uphill. At low runoff, uranine needed about 4½ hours from the sink to the spring, whereas at high runoff more than four days was required. It became evident that discharge, electrical conductivity, temperature, and turbidity of the Tuxbachquelle respond within a few hours to precipitation events. The water quality and an examination of the water balance resulted in a significantly larger catchment area. It is assumed that widely karstified calcite marble subterraneously drains a considerable part of the Tuxertal (Tux Valley), including some active rock glaciers.

In the Tuxertal (Tux Valley, Austria), like in other Alpine regions, drinking water supply is predominantly organised privately or in cooperatives from nearby springs. Currently used springs may become unsuitable in future due to increasingly strict legal limits and changes in the water balance caused by climate change. In this study, the Tuxbach catchment area (135 km 2 ) is examined by a reference-date measurement. Within 11 days, 153 springs and creeks were sampled to evaluate their appropriateness. All results of critical parameters for the drinking water supply are summarized and displayed in a hydrochemical map. Locally the groundwater composition differs due to various changes of petrographic units. Analysis results are statistically evaluated and characteristic values derived from six rock types. It becomes evident that apart from ammonium and arsenic, legal limits are mostly met. Low discharge rates present the major challenge for drinking water supply in future.

Europe’s highest thermal springs are located at 1500 m asl in Hintertux, Tyrol. Only 30% of the springs with temperatures up to 22.5 °C are utilized. Future exploration and exploitation will require quantifying their resource potential and development of a conceptual hydrogeological model. A detailed and comprehensible explanation of the thermal anomaly has not yet been formulated. Methods including a combination of natural tracers, geochemical indicators and stable isotopes (δ¹⁸O, δD, δ³⁴S) have been used for identifying their genesis and their associated aquifers. Hydrogeological and hydrochemical investigations have been conducted from 2011–2018, evaluating groundwater from 14 surrounding springs and two tunnels. This study shows that the thermal water originates mainly from rock glaciers and meteoric waters from the Grierkar, entering swallow holes of the Hochstegen formation at the Grieralm. The thermal anomaly is caused by a groundwater component (20–40%) from footwall gneisses, probably connected to the marble aquifer by the Tux shear zones.

A borehole heat exchanger array was installed in an Alpine karst aquifer for the first time in Europe. It is composed of nine 400 m deep boreholes in the dolomitic marble of the Hochstegen Formation. New approaches were developed for this unprecedented application and potential risks were checked throughout the sinking of the initial exploratory wellbore. As Finkenberg is located in a tourist area, drilling operations had to be executed within only a few weeks. Several springs downstream from the drilling site are sources of drinking water and tap water supply. Given that the degree and distribution of the Hochstegen Formation karstification was unknown, a spring monitoring program was mandatory in order to obtain drilling permission from public authorities. A practicable and affordable spring monitoring program including several physical and chemical parameters was developed and implemented to document the potential impact of the drilling activities on the spring water. A temporary and locally limited impact of the drilling works on groundwater quality was detected by turbidity measurements. This paper reports the implementation of geothermal drilling in a karst aquifer with a focus on karstification as well as planning, implementation and the results of the spring monitoring program. Such a program can be recommended for comparable projects or questions, adapting the characteristic parameters to be collected and the measurement intervals in consultation with the relevant authorities. It might also increase the chances of gaining approval for geothermal projects in karst and could enhance public acceptance.Key words: Pneumatic down hole hammer drilling, Borehole heat exchanger, Groundwater monitoring, Turbidity, Hochstegen Formation.Geotermalno vrtanje v alpskem kraškem vodonosniku in njegov vpliv na dolvodne izvire - študija primera Finkenberg, Tirolska, AvstrijaV alpskem kraškem vodonosniku je bilo prvič v Evropi vzpostavljeno polje geosond. Vključuje devet 400 m globokih vrtin, izvrtanih v dolomitnem marmorju Hochstegenove formacije. Razvili smo nove pristope za to aplikacijo brez primere in potrdili morebitna tveganja v času potopitve prvotne raziskovalne vrtine. Ker je študijsko območje Finkenberg na turističnem območju, je bilo treba opraviti vrtanje v samo nekaj tednih. Več izvirov od mesta vrtanja so viri oskrbe s pitno vodo. Glede na to, da stopnja in porazdelitev zakraselosti Hochstegenove formacije nista bili znani, je bilo treba za pridobitev dovoljenja za vrtanje nujno opazovati izvire. Da bi dokumentirali vpliv vrtanja na izvirsko vodo, je bilo pri spremljanju izvirov treba upoštevati več fizikalnih in kemijskih parametrov. Zaznali smo občasen in lokalno omejen vpliv vrtanja na kakovost podzemne vode. V prispevku smo predstavili izvajanje geotermalnega vrtanja v kraškem vodonosniku s poudarkom na identifikaciji zakraselosti ter načrtovanju ter na izvedbi in spremljanju kakovosti voda na izviru. Tak program se lahko uporabi pri primerljivih projektih ali iskanju odgovorov na podobna vprašanja s prilagojenim programom opazovanih parametrov in intervalov merjenja. Prav tako bi lahko povečal možnosti za pridobitev soglasja za geotermalne projekte na krasu in povečal ozaveščenost javnosti.Ključne besede: vrtanje s pnevmatskim kladivom, geosonda, spremljanje podzemne vode, motnost, Hochstegenova formacija. A borehole heat exchanger array was installed in an Alpinekarst aquifer for the first time in Europe. It is composed of nine400 m deep boreholes in the dolomitic marble of the HochstegenFormation. New approaches were developed for thisunprecedented application and potential risks were checkedthroughout the sinking of the initial exploratory wellbore. AsFinkenberg is located in a tourist area, drilling operations hadto be executed within only a few weeks. Several springs downstreamfrom the drilling site are sources of drinking water andtap water supply. Given that the degree and distribution of theHochstegen Formation karstification was unknown, a springmonitoring program was mandatory in order to obtain drillingpermission from public authorities. A practicable and affordablespring monitoring program including several physical andchemical parameters was developed and implemented to documentthe potential impact of the drilling activities on the springwater. A temporary and locally limited impact of the drillingworks on groundwater quality was detected by turbidity measurements.This paper reports the implementation of geothermaldrilling in a karst aquifer with a focus on karstification aswell as planning, implementation and the results of the springmonitoring program. Such a program can be recommended forcomparable projects or questions, adapting the characteristic

As renewable energy, geothermal can contribute substantially to the energy transition. To generate electricity or to harvest heat, high-saline fluids are tapped by wells of a few kilometres and extracted from hydrothermal reservoirs. After the heat exchanger units have been passed by, these fluids are reinjected into the reservoir. Due to the pressure and temperature differences between the subsurface and the surface, as well as the cooling of the fluids in the power plant, unwanted chemical reactions can occur within the reservoir, in the borehole, and within the power plant itself. This can reduce the permeability of the reservoir as well as the output of the geothermal power plant. This study aims to simulate real subsurface reactions using batch and leaching experiments with sandstone or sandstone powder as solid phase, and deionised water or natural brine as liquid phase. It is demonstrated that fluid composition changes after only a few days. In particular, calcite, aragonite, clay minerals, and zinc phases precipitate from the natural brine. In contrast, in particular minerals containing potassium, arsenic, barium, and silica are dissolved. Due to the experimental set-up, these mineral reactions mainly took place on the surface of the samples, which is why no substantial changes in petrophysical properties could be observed. However, it is assumed that the observed reactions on the reservoir scale have a relevant influence on parameters such as permeability.

Although thallium is a widespread and highly toxic element, it is rarely investigated in environmental chemistry due to its typically low concentrations in water. Consequently, little is known about the occurrence of thallium in groundwater and its origin. Here we show that high thallium concentrations of 5 up to 99 µg/l occur in Hesse exclusively in Na-Cl-waters and are locally clustered within the Taunus Border Zone. These variable concentrations seem to result from different thallium sources, varying mixing ratios of brine components, and varying degrees of thallium incorporation in hydrothermal minerals. We present evidence for a thallium origin from Zechstein (Permian) and Oligocene evaporites. A third possible source are basement brines from the Rhenish Massif. As the evaporite deposits are located tens of kilometers away from thallium-bearing wells, high thallium concentrations appear to be a good indicator of deep and regionally circulating brines.

The thermal springs alongside Wadi Araba, Dead Sea and Jordan valley, Jordan, were investigated and sampled in a comprehensive field study of 2 weeks. Conventional physicochemical properties were measured in situ; dissolved solids and isotopic composition were analyzed. Two main spring locations on the east side of the Dead Sea were mapped. It became evident, that the hottest springs are among the closest to prominent faults; some springs are controlled by gas lift. Jordan’s hot springs are described by means of a broad hydrochemical and physicochemical data set and several figures are presented. Based on their hydrochemistry, the thermal springs are classified into four thermal provinces. Water genesis is discussed. Several geothermometers are applied to estimate reservoir temperatures. Observed discharge rate, water temperature and isotopic composition are compared with data from the literature. Although discharge and water temperature are reported to be constant over the last decades, groundwater overexploitation led to a shift of the isotopic composition, what is documented for the first time in Jordan. Thus, the effect of groundwater mining on Jordan’s hot springs can be stated as a fact.

In the unlined Tuxbach water transfer tunnel, running between Hintertux (1,500 m asl) and the Schlegeis Reservoir (Austria), a local geothermal anomaly with temperatures up to 14.6 °C exists. These temperatures are around 3 °C higher than expected, considering the tunnel’s shallow depth, together with its surrounding alpine environment and regional heat flow. This is especially noticeable because the temperatures have remained stable since the tunnel’s construction in 1969, although the tunnel is generally cooling the surrounding rock massive. The objective of this investigation is to explain the origin of the anomaly with hydrogeological methods and to evaluate the hydrogeological properties of the gneisses exposed in the tunnel. The anomaly is caused by the high hydraulic conductivity (~2.5∙10−5 m s−1) within a narrow shear-zone core, part of the Tux Shear Zones in the Ahorn Gneiss Core. The zone triggers fast groundwater transport over 1.5 km from both sides towards the tunnel. One reason is that the morphology provides thicker overburden with growing distance from the tunnel and therefore higher temperatures on the same horizontal level in the directions of the fault plane. The second explanation is that the narrowness of the shear zone permits effective heat transfer similar to a heat exchanger. No hydrothermal water share is recognizable; instead, mainly cold glacial melt water and snow contribute to the section of the anomaly and all other runouts of the tunnel. Factually based results show the disproportionately high contribution of snow and glaciers to the groundwater recharge in this alpine hard-rock aquifer.

Anomalous high temperatures, salt contents and carbon dioxide concentrations were detected in shallow groundwater in the famous Art Deco ensemble, Sprudelhof. A carbon dioxide lifted thermal brine is discharged by ancient wells down to 180 m deep. Since 1856, the well installation had been operated without any changes and a low level of maintenance. During the last centuries, however, numerous anthropogenic interventions in the Sprudelhof’s underground led to changes of the natural brine system, as well as mixing, dilution and expansion processes in the near-surface aquifers. Recently, the thermal brine has been escaping from the well bore by uncontrolled means, contaminating the shallow underground. Corrosion of the casings has allowed the natural mixing system to reactivate. A groundwater monitoring network containing Duo-wells, allows independent samplings of the liquid and gaseous phases. Coinciding brine-groundwater mixing ratios were calculated for the two uppermost aquifers, as well as a gradient for increasing electric conductivities with depth.