Preprints
https://doi.org/10.5194/hess-2021-92
https://doi.org/10.5194/hess-2021-92

  16 Feb 2021

16 Feb 2021

Review status: this preprint is currently under review for the journal HESS.

Timing and magnitude of future annual runoff extremes in contrasting Alpine catchments in Austria

Sarah Hanus1,2, Markus Hrachowitz1, Harry Zekollari1,3, Gerrit Schoups1, Miren Vizcaino1, and Roland Kaitna4 Sarah Hanus et al.
  • 1Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, the Netherlands
  • 2Department of Geography, University of Zurich, Zurich, CH-8006, Switzerland
  • 3Laboratoire de Glaciologie, Université libre de Bruxelles, Brussels, Belgium
  • 4Institute of Mountain Risk Engineering. University of Natural Resources and Life Sciences, Vienna, Austria

Abstract. Hydrological regimes of alpine catchments are expected to be strongly affected by climate change mostly due to their dependence on snow and ice dynamics. While seasonal changes have been studied extensively, studies on changes in the timing and magnitude of annual extremes remain rare. This study investigates the effects of climate change on runoff patterns in six contrasting alpine catchments in Austria using a process-based semi-distributed hydrological model and projections from 14 regional climate and global climate model combinations for RCP 4.5 and RCP 8.5. The study catchments represent a spectrum of different hydrological regimes, from pluvial-nival to nivo-glacial, as well as distinct topographies and land forms, characterizing different elevation zones across the Eastern Alps to provide a comprehensive picture of future runoff changes. The climate projections are used to model river runoff in 2071–2100, which are then compared to the 1981–2010 reference period for all study catchments. Changes in timing and magnitude of annual maximum and minimum flows as well as in monthly runoff and snow melt are quantified and analyzed. Our results indicate a substantial shift to earlier occurrences in annual maximum flows by 9 to 31 days and an extension of the potential flood season by one to three months for high-elevation catchments. For low-elevation catchments, changes in timing of annual maximum flows are less pronounced. Magnitudes of annual maximum flows are likely to increase by 2–18 % under RCP 4.5, while no clear changes are projected for four catchments under RCP 8.5. The latter is caused by a pronounced increase in evaporation and decrease in snow melt contributions which offset increases in precipitation. Minimum annual runoff occur 13–31 days earlier in the winter months for high-elevation catchments, whereas for low-elevation catchments a shift from winter to autumn by about 15–100 days is projected. While all catchments show an increase in mean magnitude of minimum flows by 7–30 % under RCP 4.5, this is only the case for four catchments under RCP 8.5. Our results suggest a relationship between the elevation of catchments and changes in timing of annual maximum and minimum flows. For the magnitude of the extreme flows, a relationship is found between catchment elevation and annual minimum flows, whereas this relationship is lacking between elevation and annual maximum flow.

Sarah Hanus et al.

Status: open (until 13 Apr 2021)

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Sarah Hanus et al.

Data sets

Modelled runoff data for 14 climate models using RCP 4.5 & RCP 8.5 Sarah Hanus https://doi.org/10.5281/zenodo.4539986

Sarah Hanus et al.

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Short summary
This study investigates the effects of climate change on runoff patterns in six alpine catchments in Austria at the end of the 21st century. Our results indicate a substantial shift to earlier occurrences in annual maximum and minimum flows in high-elevation catchments. Magnitudes of annual extremes are projected to increase under a moderate emission scenario in all catchments. Changes are generally more pronounced for high-elevation catchments.