Pulsating artery of life
Contrary to the Lech and Tagliamento, the Isel is also a glacial river. It has its source at the Umbalkees glacier, high up in the wilderness of the Hohe Tauern National Park. From the glacier, it rushes as a pulsating artery of life of Osttirol down to its estuary into the Drau in Lienz. It thus links the expanse of alpine seclusion with the cultivated landscape in the valley basin.
With its tributaries, it forms a giant original waterway system. Its tributaries are also largely untouched, a guarantee for the purest water quality. A rarity in the landscape shaped intensely by people. The Isel is therefore the longest still free-flowing and therefore ecologically functional glacial river of the entire Alps.
Fluctuating water flow
Glacial rivers are different: their water flow fluctuates significantly depending on the time of day or the season, depending on the meltwater inflow from the glaciers in the catchment area. The water flow of glacial rivers in the summer months is determined by the glacial melt and displays a typical daily pattern: on a cool morning, a lot less water flows than in the evening, because the glacier melts less strongly. In the early afternoon, the incidence of sunshine on the glacier is the greatest, the ice melts away. In the case of the Isel, the meltwater reaches the valleys in the early evening and arrives during the night at the estuary of the Isel in Lienz.
In such as dynamic riverbed, floodwaters can flow around gravel masses and thereby create everchanging new islands, gravel bars and shore areas. This creates constantly new habitats that are then resettled. Specialists call this: pioneer sites. These are the condition for a series of rare flora and fauna, which have adapted to the constant change and need it for their continued existence.
The rare plant tamarisk
The German tamarisk (Myricaria germanica) is such a plant, the only one of its genre to exist in Central Europe. In the past, it was widespread by our rivers – every older botany book is witness to this. Today it is a rarity. As it needs a lot of light, but willow and alder trees easily overgrow it, it can only survive for the duration where new sand and gravel banks keep being created through the shifting activity of rivers.
Nature reserve as a flora-fauna habitat
The tamarisk is an unmistakable indication of the undisturbed dynamics and ecological functionality of a river. For these reasons, the Isel has been designated a nature reserve according to the Flora-Fauna-Habitat Directive of the EU. The tamarisks can be found especially in the lower Isel valley. Please appreciate the tamarisks from a respectful distance and do not step onto the gravel banks because of nesting birds!