| Oker | |
|---|---|
 Confluence of the Oker and Aller near Müden | |
 | |
| Location | |
| Country | Germany |
| Physical characteristics | |
| Source | |
| • location | Harz Mountains |
| • coordinates | 51°46′42″N10°29′29″E / 51.77833°N 10.49139°E /51.77833; 10.49139 |
| • elevation | 900 metres (3,000 ft) |
| Mouth | |
• location | Aller |
• coordinates | 52°31′26″N10°21′39″E / 52.52389°N 10.36083°E /52.52389; 10.36083 |
| Length | 128.2 km (79.7 mi)[1] |
| Basin size | 1,822 km2 (703 sq mi)[1] |
| Basin features | |
| Progression | Aller→Weser→North Sea |
TheOker (pronounced[ˈoːkɐ]) is ariver inLower Saxony,Germany, that has historically formed an important political boundary. It is a left tributary of the RiverAller, 128 kilometres (80 mi) in length and runs in a generally northerly direction.
The river's name was recorded around 830 asObacra and, later, asOvokare undOvakara.[2] The origin of the name is derived from therootsov- and-akara meaning “upper” (cf.New High Germanober-) and “onward rushing” (rendered in German as “Vorwärtsdrängende”)[2] as distinct from its tributary, theEcker, whose name means only “onward rushing”.
The Oker rises at about 910 metres in theHarz National Park in a boggy area on theBruchberg in theHarz mountains ofcentral Germany. This early section is known as theGroße Oker ("Great Oker") and it is impounded belowAltenau by theOker Dam. From the dam wall to the former village ofOker, which is today part ofGoslar, the Oker is on certain occasions suitable forcanoeing. This section, often called the "Oker Valley" (Okertal), includes theRomkerhall Waterfall. Here theRomke stream drops about 64 metres (210 ft) in height over awaterfall laid out in 1863 into the Oker. Downstream in the river's fast-flowing waters, theVerlobungsinsel ("Betrothal Island") is to be found. Left and right of the Oker in this area are manycrags that are popular withclimbers.
In the Goslar vicinity of Oker the river is seriously polluted withheavy metals from theslag heaps as well asgroundwater andsurface runoff from the metalsmelters there.
From the village of Oker the River Oker flows away in a northeasterly direction toVienenburg, where it is joined from the south by theRadau and then from the southeast by theEcker. After these two confluences the river continues southeast past theHarly Forest, after which it bends north to flow throughSchladen andWolfenbüttel toBraunschweig. In south Braunschweig the Oker is dammed by the Eisenbüttel Weir. In theBürgerpark shortly before Braunschweig'sold town the Oker divides into the western and eastern bypass channels (Umflutgraben) which circumnavigate the historic city centre at a slightly higher level. These channels were laid in the 16th century as the external moats of the town's defences. The actual course of the Oker through the centre of the town was covered and, today, runs through pipes emerging again north of the old town. The water level in the city area is controlled by the St. Peter's Gate Weir (Petritorwehr) in the western and the "Wends Weir" (Wendenwehr) in the eastern ditch. Following the merger of the two channels northwest of the city centre the Oker runs north of the district ofWatenbüttel [de] in aculvert under theMittelland Canal before it is joined by theSchunter from the east near Groß Schwülper. It then flows down to its mouth into the RiverAller, which is located betweenGifhorn andCelle atMüden.
Since the early ninth century the middle Oker river has formed thediocesan boundary between thebishoprics of Halberstadt andHildesheim, established by EmperorCharlemagne and his sonLouis the Pious in theDuchy of Saxony. North of Schladen the royal palace (Königspfalz) ofWerla was established on the banks about 20 metres (66 ft) above the river bed. From the High Middle Ages the Oker between the villages ofOhrum andBörßum formed the eastern boundary of thePrince-Bishopric of Hildesheim with theDuchy of Brunswick-Wolfenbüttel, and further south to Wiedelah (today part ofVienenburg) with the Prince-Bishopric of Halberstadt, which became the PrussianPrincipality of Halberstadt following itssecularization in 1648.
The Bishopric of Halberstadt was likewisemediatised in 1803, and according to the Final Act of the 1815Vienna Congress, the Oker was the eastern border of theKingdom of Hanover with theDuchy of Brunswick and the PrussianProvince of Saxony. When theKingdom of Prussia annexed Hanover in 1866, it became the inner Prussian border between theprovinces of Hanover andSaxony as well as the border, north of Börßum to Ohrum between the Province of Hanover in the west and the Duchy of Brunswick in the east. From 1945 to 1990 theInner German border betweenEast andWest Germany ran down the centre of the Oker between Wiedelah and Schladen, today between the Germanstates ofSaxony-Anhalt andLower Saxony.
Since theExpo 2000 bridges over the Oker in Braunschweig and its surrounding area were artistically designed; after 2004 this was carried out as part of theOkerlicht project.
Left tributaries (from source to mouth):
| Right tributaries: |
| International | |
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| National | |
