11 Jan 2021

11 Jan 2021

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

Moderate runoff extremes in Swiss rivers and their seasonal occurrence in a changing climate

Regula Muelchi1, Ole Rössler1,a, Jan Schwanbeck1, Rolf Weingartner1,2, and Olivia Martius1,2 Regula Muelchi et al.
  • 1Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Switzerland
  • 2Mobiliar Lab for Natural Risks, University of Bern, Switzerland
  • anow at: German Federal Institute of Hydrology (BfG), Germany

Abstract. Future changes in runoff impact many sectors such as agriculture, energy production, or ecosystems. Therefore, assessments of runoff characteristics under climate change are crucial for decision-makers and water management planners. We study changes in moderate runoff extremes, i.e. low and high flows that occur once every year or season in today's climate. Daily runoff is simulated for 93 Swiss catchments for the period 1981–2099 under the Representative Concentration Pathway 8.5 using 20 downscaled regional climate models from the newest transient Swiss climate change scenarios.

The magnitude of moderate annual low flows is projected to decrease in lower lying catchments and to increase in Alpine catchments. Seasonal low flows in summer are projected to decrease and seasonal low flows in winter to increase. Moderate annual high flows are projected to slightly increase in most catchments but to decrease in high Alpine catchments. However, the climate model agreement on the sign of change in moderate high flows is not robust. The projected decrease in Alpine catchments contradicts results for extreme high flows from previous studies. This difference may be due to different indicators used (moderate extremes vs. extremes). The time of emergence indicates the timing of significant changes in the flow magnitudes. For low flows the time of emergence is early in 21st century in high Alpine catchments due to early changes in winter low flows. In lower lying catchments, significant changes in low flows emerge later in the century. For moderate high flows, only few catchments indicate a significant change.

Shifts in the seasonality of moderate low flows due to climate change are found in many catchments. By end of the 21st century, low flows are projected to occur in late summer and early autumn in most catchments indicating that the lack of precipitation in summer and autumn exceeds the contributions from other processes such as snow and glacier melt contributions. For moderate high flows, changes in seasonality are found in Alpine catchments with a shift towards earlier occurrence in summer due to a reduced contribution of snow and glacier melt in summer. In the projections, low flows occur more frequently in lower lying catchments and less frequently in Alpine catchments. For high flows the frequency increases slightly in most catchments, but models often disagree on the sign of change. Changes in the annual co-occurrence of moderate low and high flows are mainly due to changes in the frequency of low flows that increases in lower lying catchments and decreases in Alpine catchments.

Regula Muelchi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2020-667', Anonymous Referee #1, 28 Jan 2021
    • AC1: 'Reply on RC1', Regula Mülchi, 14 Apr 2021
  • RC2: 'Comment on hess-2020-667', Anonymous Referee #2, 18 Mar 2021
    • AC2: 'Reply on RC2', Regula Mülchi, 14 Apr 2021

Regula Muelchi et al.

Data sets

Hydro-CH2018-Runoff ensemble Muelchi, Regula, Schwanbeck, Jan, Rössler, Ole, Weingartner, Rolf, and Martius, Olivia

Regula Muelchi et al.


Total article views: 447 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
329 106 12 447 8 4
  • HTML: 329
  • PDF: 106
  • XML: 12
  • Total: 447
  • BibTeX: 8
  • EndNote: 4
Views and downloads (calculated since 11 Jan 2021)
Cumulative views and downloads (calculated since 11 Jan 2021)

Viewed (geographical distribution)

Total article views: 368 (including HTML, PDF, and XML) Thereof 361 with geography defined and 7 with unknown origin.
Country # Views %
  • 1
Latest update: 19 Apr 2021