Between 1978 and 2011, the average water temperature of the Rhine has increased by 1 °C to 1.5 °C. The number of days per year with water temperatures above 22 °C is also increasing, as shown by the three Rhine monitoring stations Weil am Rhein on the German-Swiss border, Karlsruhe and Koblenz.
Climate change and further rising air temperatures will continue this development (see ICPR technical report no. 209). In addition, industry and energy production have permissions for thermal discharges.
Water related provisions limit thermal discharges from water uses. If water temperatures in the Rhine or its tributaries rise above 28 °C, no additional thermal discharges will normally be allowed.
The year 2018 can be described as an extreme year due to the combination of increased air temperatures and below-average precipitation. The low water was associated with high air and water temperatures in August 2018, which led to ecological impairments and restrictions, for example, in power plant operation (see ICPR technical report no. 263).