The Enns, a southern tributary of the Danube and the main river of north-western Styria is – with its length of 254 km – a typical torrent of the north part of the Eastern Alps, with the fifth largest catchment area of Austria (6080 km2).
Lifeline, waterway and ecosystem
The Enns has its source in the Radstädter Tauern mountains in Salzburg, flows into a partially marshy longitudinal valley, which was formed during the Ice Age, at the border between the northern Limestone Alps and the Central Alps right through to the Palten estuary. It reaches Styria at the Mandling pass and cuts through the limestone massif Ennstal Alps, forming the narrow, 15-km-long Gesaeuse valley between Admont and Hieflau.
The Enns then turns northwards and, after being joined by the Laußabach stream, flows on Upper Austrian territory. North of Steyr it forms the border between Upper Austria and Lower Austria. Here it reaches the foothills of the Alps (hence the old names "Oesterreich ob der Enns" - i.e. above the Enns, and "Oesterreich unter der Enns" - i.e. below the Enns) and flows into the Danube at Mauthausen.
The main towns and villages in the Ennstal: Radstadt in Salzburg; Schladming, Gröbming, Liezen, Selzthal and Admont in Styria; Großraming, Ternberg, Garsten, Steyr and Enns in Upper Austria. Running through the upper Ennstal valley is an important transit road from Germany to Slovenia.
Regulation began in the mid 19th century on the approx. 70-km-long stretch between Weißenbach near Haus and the Gesäuse valley, in order to gain effective agricultural and forestry surfaces by draining the valley floor. As early as 1939, the course of the river was shortened by 19 km.
At the flow measuring post of Enns-ortskai, the average flow rate amounts to 201 m3/second.
Hydropower plants on the Enns
In the lower Ennstal valley, Ennskraftwerke AG (Ennskraft – 50% owned by VERBUND) constructed 10 run-of-river power plants (Schönau, Weyer, Großraming, Losenstein, Ternberg, Rosenau, Garsten-St. Ulrich, Staning, Mühlrading and St. Pantaleon).
The total generation from these 10 power plants, with hydro peaking, amounted to 1.8 billion kilowatts in 1998.