The effect occurs faster than expected – and especially in the winter months. Long-term measurement data from the Tyrolean rivers Inn and Großache were analyzed for the study.
A study by researchers from the University of Innsbruck shows that alpine watercourses are getting warmer faster than expected – especially in the winter months. Long-term measurement data from the Tyrolean Inn and the Großache were analyzed for the study, the university announced in a broadcast on Wednesday. The ecologist Georg Niedrist warned of “far-reaching consequences for the river habitat”.
Niedrist had data from the last 45 years for the Inn and 25 years for the Großache. In Inn and Großache, the water temperature rose by 0.24 and 0.44 degrees Celsius per decade, the annual maximum and minimum temperatures also increased significantly during the observation period and the warm periods became significantly longer. “What is new is a general and significant warming of both bodies of water in the winter months. The winter temperatures are rising at least as quickly as those in the summer,” reported Niedrist.
Temperature rise has been particularly strong over the past ten years
The past decade in particular has shown a sharp increase in the lowest and highest water temperatures per year, which correlates with the increase in local air temperatures, it said. For example, the five highest daily mean values of the Inn were all measured in the period from 2013 to 2020 and for several years the water temperature in the Inn has not reached the freezing point – not even for a few hours. “Especially due to the newly identified warming of water bodies in winter, we must assume that there will be drastic effects on the winter development of cold-water organisms such as brown trout,” says the ecologist.
Expert: “Water temperature regulates biological activity”
Niedrist emphasized the importance of the water temperature for life in the rivers: “The water temperature regulates the biological activity and the growth of water-bound organisms, it influences the physical and chemical properties of the water, for example the solubility of oxygen or minerals, and increasing Water temperatures allow alien species to migrate or also favor parasites”. In addition, through its influence on biological activity, the water temperature would also regulate important ecosystem processes such as the decomposition of organic material and ultimately also the self-purification power of the water bodies. The scientist now wants to investigate the consequences of the expected further warming.
