Swiss rivers on track to overheat by the end of the century

Date:
February 25, 2022
Source:
Ecole Polytechnique Fe'de'rale de Lausanne
Summary:
According to a new study, if we take immediate measures to reduce
CO2 emissions, we could limit the rise in the temperature of Swiss
rivers to 1DEGC between now and 2090 without drastically affecting
their discharge.



FULL STORY ========================================================================== "People tend to think that water is an unlimited resource in Switzerland,"
says Adrien Michel, who recently completed his PhD in environmental
science and engineering at EPFL. "But by the end of this century, we
may well have to choose between using our rivers to water our crops and
damming them up in order to produce electricity." Michel carried out his doctoral work at the Laboratory of Cryospheric Sciences (CRYOS) within
EPFL's School of Architecture, Civil and Environmental Engineering. After completing a retrospective study on the impact of global warming on
Swiss rivers, Michel has now published a forward-looking study on the
same topic in the journal Hydrology and Earth System Sciences.


========================================================================== Three scenarios Michel's research lays out three possible scenarios
that depend on whether greenhouse gas emissions are low, moderate or
high. In the most extreme scenario, in which we take no action, river temperatures in the summer can be expected to increase by 5.5DEGC in
Alpine regions and by 4DEGC in Swiss Plateau catchments. At the same time, average river discharge could decrease by 30% in the mountains and 25%
in lowland areas. Conversely, if CO2 emissions are reduced in line with
the Paris Climate Accord, both Alpine and Swiss Plateau rivers would only
be 1DEGC warmer at the end of the century, and discharge would decrease
by 5% in mountain catchments while remaining nearly unchanged in the
lowlands. In the low-emission scenario, nearly half of all remaining
glaciers would be preserved, with retreat leveling off around 2050,
whereas in the high-emission scenario they would all but disappear.

Pushing the extremes The study also showed that winter and summer extremes
will be greater in Plateau regions under all three scenarios. In the
winter, increased precipitation will bring about higher discharge. In the summer, more sporadic precipitation along with higher evaporation rates
caused by rising temperatures will lead to a decrease in discharge. Michel relied on climate projections from MeteoSwiss and glacier melt data from
ETH Zurich to model snow and discharge levels and river temperatures.

"We'll surely be able to grow oranges in this part of the world,"
says Michel.

"But what about the rest of biodiversity?" This study is naturally
based on how things stand today, while much about the end of the century remains unknown.

What will happen to the agricultural and energy sectors? And to river
flora and fauna, since rising temperatures hinder reproduction and
increase the risk of disease in fish? How will we ensure adequate
electricity production if discharge decreases drastically? And if
Switzerland decides to build new nuclear power or other industrial
plants, how will we keep them cool? The need to act now Rather than
tackling questions about the future, Michel is calling for action
now: "Our study of river discharge and temperatures shows, for one,
that the impact of global warming is inevitable, and that we must
begin making changes today, through energy and agriculture policies,
for example. It's also showing us that we can still save a part of our environmental heritage -- but only if we act swiftly and aggressively." ========================================================================== Story Source: Materials provided by
Ecole_Polytechnique_Fe'de'rale_de_Lausanne. Original written by Sandrine Perroud. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Adrien Michel, Bettina Schaefli, Nander Wever, Harry Zekollari,
Michael
Lehning, Hendrik Huwald. Future water temperature of rivers in
Switzerland under climate change investigated with physics-based
models.

Hydrology and Earth System Sciences, 2022; 26 (4): 1063 DOI:
10.5194/ hess-26-1063-2022 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220225100216.htm

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