River runoff in Switzerland in a changing climate – changes in moderate extremes and their seasonality

Muelchi, Regula; Rössler, Ole; Schwanbeck, Jan; Weingartner, Rolf; Martius, Olivia (2021). River runoff in Switzerland in a changing climate – changes in moderate extremes and their seasonality. Hydrology and earth system sciences, 25(6), pp. 3577-3594. European Geosciences Union EGU 10.5194/hess-25-3577-2021

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Future changes in river runoff will impact many sectors such as agriculture, energy production, or ecosystems. Here, we study changes in the seasonality, frequency, and magnitude of moderate low and high flows and their time of emergence. The time of emergence indicates the timing of significant changes in the flow magnitudes. Daily runoff is simulated for 93 Swiss catchments for the period 1981–2099 under Representative Concentration Pathway 8.5 with 20 climate model chains from the most recent transient Swiss Climate Change Scenarios.

In the present climate, annual low flows typically occur in the summer half-year in lower-lying catchments (<1500 m a.s.l.) and in the winter half-year in Alpine catchments (>1500 m a.s.l.). By the end of the 21st century, annual low flows are projected to occur in late summer and early autumn in most catchments. This indicates that decreasing precipitation and increasing evapotranspiration in summer and autumn exceed the water contributions from other processes such as snowmelt and glacier melt. In lower-lying catchments, the frequency of annual low flows increases, but their magnitude decreases and becomes more severe. In Alpine catchments, annual low flows occur less often and their magnitude increases. The magnitude of seasonal low flows is projected to decrease in the summer half-year in most catchments and to increase in the winter half-year in Alpine catchments. Early time of emergence is found for annual low flows in Alpine catchments in the 21st century due to early changes in low flows in the winter half-year. In lower-lying catchments, significant changes in low flows emerge later in the century.

Annual high flows occur today in lower-lying catchments in the winter half-year and in Alpine catchments in the summer half-year. Climate change will change this seasonality mainly in Alpine catchments with a shift towards earlier seasonality in summer due to the reduced contribution of snowmelt and glacier melt in summer. Annual high flows tend to occur more frequent, and their magnitude increases in most catchments except some Alpine catchments. The magnitude of seasonal high flows in most catchments is projected to increase in the winter half-year and to decrease in the summer half-year. However, the climate model agreement on the sign of change in moderate high flows is weak.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography > Unit Impact
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography > Physical Geography

UniBE Contributor:

Mülchi, Regula Isabelle; Weingartner, Rolf and Romppainen-Martius, Olivia

Subjects:

900 History > 910 Geography & travel
500 Science > 550 Earth sciences & geology

ISSN:

1027-5606

Publisher:

European Geosciences Union EGU

Funders:

[70] Bundesamt fur Umwelt (BAFU)

Projects:

[245] Mobiliar Lab für Naturrisiken Official URL

Language:

English

Submitter:

Yannick Barton

Date Deposited:

06 Aug 2021 14:08

Last Modified:

06 Aug 2021 14:08

Publisher DOI:

10.5194/hess-25-3577-2021

BORIS DOI:

10.48350/157850

URI:

https://boris.unibe.ch/id/eprint/157850

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