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

Abstract

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.

Hydrochemistry of the Tuxertal, NW Tauern Window, Austria: water use and drinking water supply in an alpine environment

“…Bauer et al, 2016). Karstified zones have a permeability in the range of 1.2 • 10 −1 to 1.6 • 10 −4 m/s (Lehr & Sass, 2014;Schäffer et al, 2020a). Other rocks offer orders of magnitude lower formation permeability from 10 −6 to 10 −9 m/s.…”

“…The Hochstegen Formation is the only major aquifer in the Tuxertal and drains large parts of the southern valley slope subterraneously (Sass et al, 2016a). Two supposed effluents are the karst springs Tuxbachquelle and Goldbründl nearby Finkenberg, with a discharge of up to 1.5 m³/s (Schäffer et al, 2020a). Apparently, the karstification is not distributed randomly, but strikes SW-NE, following the direction of several thrust faults shown in Figure 1 (cf.…”

“…Various quaternary deposits are present in the Tuxertal, mainly valley fills, slope debris, alluvial fans, rock falls, landslides and moraines. The most prominent ones are the landslides between Finkenberg and Lanersbach (Kossendey, 1992), glacial deposits below the Tuxer Ferner (Zasadni, 2007) and several rock glaciers between Höllenstein and Grinbergspitze (Kogler, 2018;Krainer & Ribis, 2012;Schäffer et al, 2020a).…”

“…Pröbstl et al (2009) state that in the Tuxertal (Tux Valley), glacier area reduced from 20.6 km² to 7.1 km² between 1850 and 2004 (confer data for the whole Zillertal in Lambrecht and Kuhn (2007) and Fischer et al (2015)). In the Tuxertal, glacier area was 5.2 km² in 2016 (Schäffer et al, 2020a) and has decreased significantly since then. Active and inactive/fossil rock glaciers present an area of 2.2 and 9.1 km², respectively (Krainer & Ribis, 2012).…”