Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
4.3.5 Water temperature
Key messages
• Water temperatures in major European rivers have increased by 1–3 °C over the last century. Several time series show
increasing lake and river temperatures all over Europe since the early 1900s.
• Lake and river surface water temperatures are projected to increase further with projected increases in air temperature.
• Increased water temperature can result in marked changes in species composition and functioning of aquatic ecosystems.
Relevance
Water temperature is one of the parameters that
determine the overall health of aquatic ecosystems.
Most aquatic organisms have a specific range of
temperatures that they can tolerate, which determines
their spatial distribution. Changes in temperature also
determine ice cover periods, thermal stratification of
lakes, nutrient availability and the duration of growing
seasons that in turn affect species composition and
food web structures (e.g. Moss et al., 2009; Markovic
et al., 2014).
Past trends
The surface water temperatures of major rivers in
Europe have increased by 1–3 °C over the last century
(Figure 4.14). For example, the average temperature
in the Rhine near Basel, Switzerland, has risen by
more than 2 °C since the 1960s (FOEN, 2015). The
temperature of the downstream part of the Rhine
increased by nearly 3 °C between 1910 and 2013.
A similar increase of 2.4 °C has been observed in the
Meuse. Two-thirds of the increase of the downstream
part of the Rhine is attributed to the increased use of
Figure 4.14
Observed trends in water temperature of large European rivers and lakes
Degrees celcius (°C)
25
20
15
10
5
0
1900 1920 1940 1960 1980 2000
Rhine, Lobith
Meuse, Eijsden
Lake Võrtsjärv, Estonia
Danube, Vienna
Lake Saimaa, Finland
Note:
This figure shows the annual average water temperature in the Rhine and the Meuse (1911–2013), the Danube (1901–1998) and Lake
Võrtsjärv (1947–2014), and the average water temperature in August in Lake Saimaa, Finland (1924–2014).
Source: Rhine and Meuse (CBS et al., 2014); Danube (Hohensinner, 2006, personal communication); Lake Saimaa (Johanne Korhonen, 2015,
personal communication); Lake Võrtsjärv (Peeter Nõges, 2015, personal communication).
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