A study by researchers at the University of Innsbruck shows that alpine watercourses are warming faster than expected – especially in the winter months. Long-term measurement data from the Tiroler Inn and the Großache were analyzed for the study. The ecologist Georg Niedrist warned of “wide-reaching impacts on riverine habitat”.
Niedrist had data for the last 45 years for the Inn and 25 years for the Großache. In Inn and Großache the water temperature increased by 0.24 and 0.44 degrees Celsius per decade, the annual maximum and minimum temperatures also increased strongly during the observation period and the warm periods became considerably longer.
“What is new is a general and significant warming of both water masses in the winter months. Winter temperatures are rising at least as fast as summer temperatures,” reports Niedrist.
The freezing point was no longer reached
The past decade in particular has seen a sharp rise in the lowest and highest water temperatures each year, which correlates with the rise in local air temperatures, it said. For example, the Inn’s five highest daily averages were all measured from 2013 to 2020 and the water temperature in the Inn has not reached freezing for several years – not even for a few hours.
“Particularly because of the newly identified winter warming of water bodies, we should assume that there will be drastic effects on the winter development of cold water organisms such as brown trout,” says the ecologist.
“Water temperature is crucial”
Niedrist emphasized the importance of the water temperature for life in the rivers: “The water temperature regulates the biological activity and the growth of aquatic organisms, it influences the physical and chemical properties of the water, for example the solubility of oxygen or minerals. , and rising water temperatures may allow alien species to migrate or also favor parasites.”
Moreover, through its influence on biological activity, water temperature would also regulate important ecosystem processes, such as the decomposition of organic matter and ultimately the self-cleansing capacity of the water bodies. The scientist now wants to investigate the consequences of the expected further warming.
Source: Krone
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