Abstract
Extensive in-depth research is required for the implementation of natural tracer approaches to hydrogeological investigation to be feasible in mountainous regions. This review considers the application of hydrochemical and biotic parameters in mountain regions over the past few decades with particular reference to the Austrian Alps, as an example for alpine-type mountain belts. A brief introduction to Austria’s hydrogeological arrangement is given to show the significance of fractured hard-rock aquifers for hydrogeological science as well as for water supply purposes. A literature search showed that research concerning fractured hard-rock aquifers in Austria is clearly underrepresented to date, especially when taking the abundance of this aquifer type and the significance of this topic into consideration. The application of abiotic natural tracers (hydrochemical and isotope parameters) is discussed generally and by means of examples from the Austrian Alps. The potential of biotic tracers (microbiota and meiofauna) is elucidated. It is shown that the meiofauna approach to investigating fractured aquifers has not yet been applied in the reviewed region, nor worldwide. Two examples of new approaches in mountainous fractured aquifers are introduced: (1) use of CO2 partial pressure and calcite saturation of spring water to reconstruct catchments and flow dynamics (abiotic approach), and, (2) consideration of hard-rock aquifers as habitats to reconstruct aquifer conditions (biotic approach).
Highlights
25% of the Earth’s total land area is mountainous (Meybeck et al 2001)
This review gives an overview of the state of the art in the use of natural tracers in alpine hard rock hydrogeology with a particular focus on the Austrian Alps region
The predominance of fractured hard rock aquifers arranged in folded and thrusted nappes of various lithology, elevation differences of several thousands of meters, the function as continental divide and shortcomings in hydrogeological methodology for this special environment are characteristic for alpine type mountain regions and make the European Alps a suitable representative for mountain hydrogeology
Summary
25% of the Earth’s total land area is mountainous (Meybeck et al 2001). This paper gives an overview of different types of fractured hard rock aquifers and their characteristics with the example of the Austrian Eastern Alps and some brief glances at studies in other mountain regions, and shows how hydrochemical and isotope data as well as biological data are currently used as hydrogeological indicators. Due to the share of carbonates in the sedimentary fill, the groundwater quality in the Molasse zone is characterised by the Ca–Mg–HCO3 water type (Kilchmann et al 2004), alkaline pH-values and, compared to other alpine hard rock environments, high electrical conductivity values (around 600 μS/ cm, Austrian Geological Survey 2004; Kralik et al 2005). The RFZ north of the Northern Calcareous Alps (NCA) is characterised by a hilly landscape with the highest elevations
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