The Treene near Wohlde
The Treene (Danish: Trenen) is a river, 73 km (45 mi) long, in the north of Schleswig-Holstein. It is a right-bank tributary of the Eider River. It starts in northern Angeln, southeast of Flensburg, and flows mainly south-south-west before joining the Eider near Friedrichstadt.
The Treene begins at the Tresssee lake near Großsolt in the district of Schleswig-Flensburg and flows for about 73 km, passing the town of Friedrichstadt (in Nordfriesland district) to a point 25 km above the Eider Barrage where it discharges into the Eider as its most important tributary. The Bondenau, which is the most important inlet to the Tressee, is the main headstream of the Treene, and rises 15 km east of the Tressee near Sörup on the Angeln peninsula, 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 then flows into the North Sea. Between the Treßsee and Tüdal, there is a nature reserve covering an area of 20 square kilometres (7.7 sq mi) called Ober Treenelandschaft that runs along the river.
The middle section between Oeversee and Langstedt and Treia developed to the popular paddle district; further river downward the Eider Treene concern valley forms an ecologically valuable retreat area for migratory birds ("stork village" Bergenhusen). In Schwabstedt a river public swimming pool exists; off there the Treene can be driven on muendungswaerts also with sport boats.
In early historical time the strip of dry country between Treene (Niederung) and Schlei had the function of an isthmus. Here the Danewerk secured the south border of Denmark, which at that time was more than 20 km further south running to the Eider. And the route Eider - Treene - Rheider Au (tributary of the Treene) - Schlei served as a shipping route between the North Sea and Baltic Sea (see also Haithabu). Whether thereby boats were pulled between the Schleibucht Selker Noor and the Rheider Au 16 km on primitive rollers over the 20 m high land ridges (usual opinion), or whether the Kograben, 1 to 2 km south of and parallel to the Danewerk, served as the ship canal, is not yet finally clarified.
- Gerd Quedenbaum: Vorflut. Der Eiderverband, ein Beitrag zur Geschichte des Deich- und Entwässerungswesens in der mittleren Eiderregion. Eider-Verlag, Düsseldorf 2000
- Gerd Quedenbaum: Sorge und Treene. Eider-Verlag, Düsseldorf 1984