Parts of the heavily-polluted river can reach a balmy high of 28 degrees during the summer, the study said. The warmest segment is between Mainz and Worms.
“The days when the water temperature exceeds 23 to 25 degrees have been increasing in the past few years,” the report said, which could have a major impact on marine life in the river, especially for the salmon population, which the government is trying to reintroduce to the river.
At least two degrees of the river's temperature rise is attributable to the number of coal and nuclear power plants along the Rhine, the report said. The plants draw in river water to cool the facilities and expel warm water. The report says the river has also warmed one degree due to climate change.
To preserve the river, BUND says planned coal power plants in Mainz and near Hanau should not be built. The report also singled out two French nuclear reactors in Alsace that lack cooling towers and have warmed canals that connect to the Rhine more than two degrees.
The organisation has also called for stricter European regulation of heat emissions into the river.