Geothermal drilling in an Alpine karst aquifer and its impact on downstream springs – A case study from Finkenberg, Tyrol, Austria

Abstract

Rafael Schäffer, Ingo Sass, Claus-Dieter Heldmann & Dirk Scheuvens: Geothermal drilling in an Alpine karst aquifer and its impact on downstream springs -A case study from Finkenberg, Tyrol, AustriaA 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 IzvlečekUDK 556.33:550.822(436.6) Rafael Schäffer, Ingo Sass, Claus-Dieter Heldmann & Dirk Scheuvens: 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 merj...

Water supply in times of climate change—Tracer tests to identify the catchment area of an Alpine karst spring, Tyrol, Austria

“…The study area is located on the northwestern edge of the Tauern Window, including several faults caused by nappe stacking. A more detailed description of the geological setting is given in Schäffer et al (2018). The Tuxbachquelle (TQ) is situated within the 4-kmlong and up to 60-m-deep gorge of the Tuxbach (Tux Creek) next to Finkenberg (Figure 1).…”

“…Simplified geological map of the project area, modified afterSchäffer et al (2018) andKogler (2018). Relief shading was taken from the Tyrolean Geographic Information System (2019).…”