The Treene is a river, hydrologically and nominally long, in the north of Schleswig-Holstein, Germany. It is a right-bank tributary of the River Eider. It starts in northern Angeln, southeast of Flensburg, and flows mainly south-south-west before joining the Eider near Friedrichstadt. The upper course is called Bondenau. Its source is situated in the ground of Mohrkirch. The name 'Treene' begins at the Tresssee lake near Großsolt in the district of Schleswig-Flensburg. After about it reaches the town of Friedrichstadt. There it is released through valves into the estuary of the Eider, above the Eider Barrage. It is the most important tributary of Eider river. Since the construction of Kiel Canal, it is even stronger than Eider river itself.
Details
The Bondenau, as the main headstream of the Treene, rises east of the Tressee on the peninsula of Angeln, bounded by the Flensburger Förde and the Schlei. So the Treene is an unusual case of a river that rises on a peninsula in the Baltic Sea, but flows into the North Sea. The length of Bondenau is. Half a kilometer before the Treßsee, it is joined by a stream named Kielstau or Kielsau, by some people considered another headstream of Treene river. Between the Treßsee and Tüdal, there is a natural reserve covering an area of called Obere Treenelandschaft that extends along the river. Especially the lower part is a retreat area for migratory birds. The middling section between Langstedt and Treia developed to be a popular canoe district, the lower section can be used by pleasure crafts as well. In Schwabstedt, there is a public swimming site in the river.
History
From antiquity to High Middle Ages, the strip of dry land between Treene wetlands and Schlei had the function of an isthmus. Here the Danevirke secured the south border of Denmark, which at that time was marked by the Eider, more than further south. And the route Eider - Treene - Rheider Au - Schlei served as a shipping route between the North Sea and Baltic Sea. Whether thereby boats were pulled between Selker Noor and the Rheider Au on primitive rollers over the 20 m high land ridges, or whether the Kograben, 1 to 2 km south of and parallel to the walls of Danevirke, also served as a shipping canal, has not yet finally been clarified.
