Water temperature increases in the river Rhine in response to climate change

The present study analyzes climate change effects on the water temperature of the Rhine, one of the largest rivers in Central Europe. Simulation calculations were performed based on a range of climate and river flow projections for the near (2021-2050) and for the far future (2071-2100) compared to a reference period (1961-1990). Changes in mean annual water temperature in the near future range between +0.6 and +1.4 A degrees C and between +1.9 and +2.2 A degrees C in the far future (average of nine stations). Monthly mean values of the far future change in a more differentiated way by +0.4 to +1.3 A degrees C in spring and +2.7 to +3.4 A degrees C in late summer. The length of periods of high water temperature, expressed as successive days with water temperatures over 27 A degrees C, increases by a factor of four until 2100. These prolonged durations of periods with unusually high water temperatures may provoke changes in the food web and in the rates of biological processes in the Rhine.