from Wikipedia, the free encyclopedia
The catchment area of ​​the Oker from Harz to Müden and from Salzgitter to Helmstedt

The catchment area of ​​the Oker
from Harz to Müden and from Salzgitter to Helmstedt

Water code EN : 482
location Lower Saxony , Saxony-Anhalt
River system Weser
Drain over Aller  → Weser  → North Sea
source At Bruchberg in the Harz Mountains
51 ° 46 ′ 42 ″  N , 10 ° 29 ′ 29 ″  E
Source height 910  m above sea level NHN
muzzle For tired people in the Aller coordinates: 52 ° 31 '26 "  N , 10 ° 21' 39"  E 52 ° 31 '26 "  N , 10 ° 21' 39"  E
Mouth height 45  m above sea level NHN
Height difference 865 m
Bottom slope 6.7 ‰
length 128.3 km
Catchment area 1,822.13 km²
Discharge at level Gr. Schwülper
A Eo : 1734 km²
Location: 29.5 km above the mouth
NNQ (10/12/1959)
MNQ 1926/2014
MQ 1926/2014
Mq 1926/2014
MHQ 1926/2014
HHQ (02/11/1946)
1.51 m³ / s
3.31 m³ / s
11.5 m³ / s
6.6 l / (s km²)
72.6 m³ / s
217 m³ / s
Left tributaries Breeding , Warne
Right tributaries Radau , Ecker , Ilse , Altenau , Schunter
Flowing lakes Vienenburger See , Südsee , Ölpersee
Reservoirs flowed through Oker reservoir
Big cities Braunschweig
Medium-sized cities Goslar , Bad Harzburg , Wolfenbüttel
Small towns Altenau
Communities Schulenberg , Schladen-Werla , Börßum , Heiningen , Dorstadt , Ohrum , Schwülper , Wendeburg , Didderse , Hillerse , Leiferde , Meinersen
Residents in the catchment area 491,000 (Lower Saxony only)
Navigable in the Middle Ages north of Braunschweig, until the 18th century also south of Braunschweig
Water body NLWKN : 15035 (to the dam), 15002 (Harz foreland), 15001 (to Schunter), 15036 (to the mouth)
The Oker between the Okertalsperre and the village of Oker

The Oker between the Okertalsperre and the village of Oker

Oker at Schladen
This section of the Oker in downtown Wolfenbüttel is known as Little Venice
Raft on the Oker flood ditch in Braunschweig
The Schunter meets the Oker near Groß Schwülper
The Oker near Neubrück around 1654/1658, looking south, engraving by Matthäus Merian
Okeraue near Volkse south of Meinersen

The Oker [ ˈoːˌkɐ ] is a 128.3 km long left tributary of the Aller in Lower Saxony ( Germany ). It rises at the heights of the Harz Mountains and is one of the region's most abundant bodies of water because of its tributaries from the Brocken area.

It was mentioned for the first time in 747 as Ovacra in connection with the Oker crossing in Ohrum , making this place, together with Schöningen, the oldest mentioned in writing in Lower Saxony. Ohrum was also the scene of a mass baptism staged by Charlemagne . Other historical locations are the Kaiserpfalz Werla and the cities of Braunschweig and Wolfenbüttel .

South of Schladen , it also runs in several places on short stretches through the Saxony-Anhalt region. Part of their catchment area lies in this federal state, along with the Ilse and the Ecker .


Source and upper course

The Oker rises as the Große Oker at about 910  m above sea level. NHN Höhe in the Harz National Park in Hangmooren on the western slope of the Bruchberg , about one kilometer southwest of the Wolfswarte . About 2.5 km below the source, its Kerbtal is crossed by the Dammgraben , which diverts all the water of the Oker towards the west when the tide is low. One kilometer further north-west, the Große Oker reaches the urban area of Altenau , where it is now called Oker from the confluence of the Kleine Oker and also receives the Altenau with the cutting water , the Rotenbeek and the black water . The Okertalsperre just below Altenau is about 410  m above sea level. Other tributaries such as Kellwasser , Kalbe , Hune , Lange and Schalke flow here . The outflow from the dam usually reaches the underwater via the Romkerhalle hydropower plant about one kilometer below the dam. If necessary (excess water, operational disruptions), water is released through the bottom outlet at the foot of the dam; in the case of extremely rare flood events (about every 20 years) also via the flood relief system .

Below the reservoir, the Oker valley is cut to over 350 m deep into the surrounding Upper Harz hull areas . Here is the Brautstein-Osthang, the highest steep slope in the Harz with almost 350 m . Numerous cliffs such as B. the box cliffs . The river leaves the Harz at around 190  m above sea level and picks up the breeding from the left , which with the Gose drains the Goslar Rammelsberg area.

Steinfelder and Harz foreland

The Oker flows below the village of Oker in a north-easterly direction to Vienenburg through the Steinfeld , an area that is extraordinarily rich in groundwater and in which the river is separated from the gravel mining areas by dams . Between Harlingerode and Vienenburg, the Oker flows through the Okertal nature reserve south of Vienenburg . Passing the Vienenburger See the Oker follows the east Harlyberg where from Bad Harzburg coming wheel opens. At the end of Harly, it is overbuilt by Autobahn 36 . The Ecker from the Brocken flows into Wiedelah , unless it is run as an Eckergraben to the Steinfelder Mühle north of Schladen. The Oker bends to the north and is bordered on the left bank by the Oker Mountains. There it flows at about 110  m above sea level to Schladen, rich in meanders, through the Okertal nature reserve in Lower Saxony and Saxony-Anhalt. The river bed in these parts of the landscape, also known as stone fields , is gravelly and stony, the river is relatively wide and flat.

The Kaiserpfalz Werla lies on the left bank on a 20 m high land nose north of Schladen , where the Eckergraben flows from the right. At Börßum , the Ilse flowing through Hornburg joins it from the right at an altitude of 84  m and completes all tributaries coming from the Harz.

At Dorstadt , the Warne flows as the last left tributary into the Oker, which is now also rich in water in summer. The left bank forms the slopes of the Oder forest . In Ohrum , the place of the oldest mention, the Oker valley narrows and used to have a wide gravel bed between the branching arms, which is why this place was mentioned as the Oker crossing as early as the 8th century. Shortly before that, the Ilse flowed into the Oker near Hedwigsburg , now the rest arm Alte Ilse . The Ösel rises on the right bank of the river .


At Halchter , the Altenau brings the water masses from the area between Elm and Asse . In the Oker crossing in Wolfenbüttel , which has been developed into a residential town, numerous branches of the Oker are still visible or documented by information boards. From here it flows through the Loessboden of the Magdeburg Börde, with the slopes of the Thieder Lindenberg on the left and the Schieferberg on the right forming the valley. The Oker now clearly takes on the character of a meadow river, the river bed is no longer stony, but muddy. It meanders as far as Leiferde and old river loops can still be seen. In this section of the Thirty Years War at the height of Groß Stöckheim, the Schwedendamm was built to conquer Wolfenbüttel.


In the south of Braunschweig, the Oker was heavily regulated in the 1960s and is dammed by the Rüninger weir. Floods can escape into the South Seas specially created for this purpose at Melverode . The Eisenbütteler weir is the last water-technical building before the Braunschweig city center. In the Bürgerpark just before Braunschweig city center, the Oker is divided into the western and eastern flood ditches.

These around 6.5 km long flood ditches were dug in the 18th century to supplement the medieval fortification ditches in the course of the bastions. They are well contained on the slopes, a little above the old town. The natural course of the Oker through the center of the city had often led to flood damage and was largely covered up around 1900. It now runs underground to a limited extent in tubes and only reappears north of the Neustadt am Inselwall soft patch. The water level for the inner city area is regulated by the Petritor weir in the western and the Wenden weir in the eastern flood ditch.

Lower course

Below the Braunschweig city center, the Oker run to the Ölper See is heavily regulated. There, another structure on the site of the former Ölper Mühle controls the water level and thus the flood discharge into the lake. As far as Veltenhof and Watenbüttel , the character of the meandering meadow river and the Okeraue can be seen despite the interference from numerous traffic routes. The Okeraue is a protected nature reserve here as the Brunswick Okeraue . At Watenbüttel, the Oker runs through a culvert under the Mittelland Canal and flows through sandy soils ( asparagus cultivation ) to its mouth . Its catchment area is clearly delimited on the west side by the parallel flowing Erse / Aue ; from the mouth of the Aue-Oker Canal it no longer has any left tributaries.

The water-rich Schunter , which drains the entire northern Elm area as far as Helmstedt, flows out at Walle (Schwülper) . The right bank is formed by sand deposits from the Ice Age, such as the Galgenberg near Didderse , while the rainwater area of ​​the Braunschweig wastewater association extends on the left bank. To the north of Hillerse , extensive meadows, meanders and old river arms determine the character of the landscape.

On September 20, 1321, the “Princely Braunschweigisch-Lüneburgische Amtshaus” was first mentioned in a document as Castrum Bruckhe (today: Neubrück). For centuries it was a customs office located on the Oker between the Brunswick and Lüneburg parts of the country.

Up until the Middle Ages, the course of the Oker turned north-west near Meinersen and flowed into the Aller west of Wienhausen. Probably at the beginning of the 14th century - possibly in a flood bed - the bed of the Oker was artificially relocated from Meinersen directly to the north. The current confluence with the Aller is probably the third and last artificial structure from the 18th century.

Between Meinersen and Müden, the Sohlriethe is recorded on historical maps at the end of the 19th century as a regulated branch of the Oker to the west. It meandered in the area of ​​the Harsebruchs and was equipped with a sewer north of the Hünenberg . As a canal, it passed Flettmar in the west and met the Allerdeich south of Nienhof at an old Allerschleife. From there the canal led south of the Aller to the canal lock northwest of Langlingen , where the Wienhauser Mühlenkanal branches off. Today's remains of the Sohlriethe are not connected to the Oker and lead to the Flettmarschen drainage ditch , which begins west of Meinersen and flows into the Aller north of Flettmar. Another ditch called Neue Sohlriethe is mapped northwest of Flettmar , which flows south of Nienhof.

At Meinersen the Oker branches into a mill ditch and is regulated by a new weir. From there it's about eight meandering kilometers of the river to the Dieckhorst weir in Müden , where it joins the Aller and even represents the main river hydrologically . The Oker carries an average of 12.1 m³ / s of water here, while the average discharge of the Aller at this point is 8.2 m³ / s.

Catchment area and natural areas

The catchment area of ​​the Oker extends from the Südheide in the north to the Harz in the south and from Salzgitter in the west to Helmstedt in the east. The area is mainly in Lower Saxony, only the eastern catchment area of ​​the Ilse is in Saxony-Anhalt, that is 256 km² out of a total of 1,829 km². On the Lower Saxony side, 491,000 people live in the catchment area of ​​the Oker.

Below the Harz region of origin, the Harzrandmulde natural area joins to the north as a sub-area of ​​the North German lowlands , where the Oker forms the independent Okertal natural area (identifier 510.10). At the level of the Great Rift , which extends as a narrow band to the east , it leaves the Harz rim hollow and flows in the hill country of East Brunswick through the Börßum-Braunschweiger Okertal (sub-natural area 512.03). The Braunschweig – Wolfenbüttel area is assigned the code number 115 to the Braunschweig urban landscape by the Federal Agency for Nature Conservation .

To the north of Braunschweig, the Oker lowland divides the landscape into the Burgdorf-Peiner Geest to the west (code 623.0) and the East Brunswick lowland (code 624.0). It reaches the Allertal natural area (code 62702) near Meinersen.

River types

Almost half, or 48%, of the incoming waters from the type of the loess-lehmgeprägten lowland Bach . This type naturally occurs in the loess region between Braunschweig and Helmstedt. To the north of Braunschweig the sand- and clay-shaped lowland rivers predominate and make up a share of 23%. In the Harz and Harz foreland, the tributaries are mainly of the silicate low mountain stream type , while the Oker in the upper reaches is classified as a carbonate low mountain river .


Border river

Significant events along the Oker
year event
747 Ohrum's first mention
780 Historical mass baptism of the Saxons
by Charlemagne in Ohrum is documented.
First mention of Didderses
804 Halberstadt becomes a bishopric (western border is the Oker)
815 Hildesheim becomes a bishopric (eastern border is the Oker)
from 822 First mention of the pillow bridge
861 legendary foundation of Braunschweig by the Brunones
924/926 First mention of the Werla Palatinate
993-997 Construction of the Niederungsburg Mundburg (Mundborg)
by Bishop Bernward von Hildesheim at the confluence of
the Oker and Aller
1007 Steterburger annals mention numerous villages
along the Oker
1013 Kanonissenstift is founded in Heiningen
1031 Braunschweig is mentioned for the first time in a document
1090 First mention of the Scheverlingenburg near Walle (Schwülper)
1118 First mention of Wolfenbüttel
1151 First mention of Meinersen
1154 First mention of Schladen
1167 First mention of Dorstadt
1227 First mention of Altenau
14th century The plague brings mining to a standstill in the Harz Mountains,
the forests recover
1527 Barward Tafelmaker is building a
water supply with Oker water in Braunschweig .
1570 Juliusstau in the Harz Mountains to promote rafting
1627 Impoundment of the Oker by the Schwedendamm ,
to Wolfenbüttel take
1745 Extensive canal construction in the Oker catchment area
under Duke Karl I.
1807-1813 In the Napoleonic era, the Oker department was established
as part of the Kingdom of Westphalia.
1838 The first steam locomotive of
the first German State Railroad runs in the Okertal .
1956 Inauguration of the Okertalsperre
Memorial stone for the baptism of Saxony by Charlemagne in 780 in Ohrum

Already in the pre-Franconian period, the Oker was a tribal border between the Saxons ( Ostfalengau ) and Thuringians because of its high and irregular water supply . Ohrum is mentioned in the Franconian Annals as early as 747 as an Oker transition. It is assumed that a historical east-west Deitweg crossed the Oker here until the emergence of the cities of Braunschweig and Wolfenbüttel, which even in Ottonian times led via Schöningen to Magdeburg .

The Oker continued to form an important strategic border in the fight against the Hungarian invasions , so the Werla Palatinate was mentioned as early as 924 and from 968 onwards it became a regular meeting place for Otto the Great .

From the 9th century, the Oker formed the diocesan border between the dioceses of Halberstadt and Hildesheim . In the section from Ohrum to Börßum it also formed the eastern border of the Principality of Hildesheim opposite the Principality of Braunschweig-Wolfenbüttel and further south to Wiedelah opposite the Principality of Halberstadt, after its secularization the Electorate of Brandenburg .

After 1814 the Oker was the eastern border of the Kingdom of Hanover opposite the Duchy of Braunschweig and the Kingdom of Prussia . After 1866 it was the border between the Prussian provinces of Hanover and Saxony and north from Börßum to Ohrum between the province of Hanover in the west and the Duchy of Braunschweig in the east. From 1945 to 1990 the inner German border between the German Democratic Republic and the Federal Republic of Germany ran between Wiedelah and Schladen in the middle of the Okeraue.

Another special feature of the settlement area is the distribution of place names with the ending -büttel along the Oker. The southernmost ending in Germany can be found in the name of Wolfenbüttel . Apart from the places Eisenbüttel and Watenbüttel , which are located near Braunschweig on the Oker, all of the villages can be found in the Papenteich area in the triangle between Oker and Aller, with the Oker forming the western border. The area is also known colloquially as Büttelei .


Although the rafting is only documented in writing from the time of Duke Julius , it can be assumed that the wood from the Harz was transported by water as fuel and construction wood in the centuries before. Julius had the upper area of ​​the Oker vigorously expanded, so in 1570 a weir was built on the Radau around the level of Bündheim and later a tensioning point, to which the felled wood was brought and thrown into the river. When the weir was pulled, a great surge of water was generated that drove the wood down.

In 1576 the Kellwasser, a tributary of the Oker, was dammed near the Oker valley to transport wood down the Oker. In 1580, dams were built on the Ecker for the same purpose. The Ilse was no longer in the territorial area of ​​the Principality of Braunschweig-Wolfenbüttel .

The rafting was only stopped in the 19th century after the railroad went to the Harz.


In the upper reaches to Braunschweig

In the upper Oker area, the mention of 1425 that the city of Braunschweig is allowed to break lime and stones in the Ösel (mountain) suggests that these materials were transported down the Oker by barges. In 1575 Duke Julius personally planned a branch canal from the Oker to Neindorf am Ösel and a loading station for the broken stones that were needed for the expansion of the residential city of Wolfenbüttel . From 1577 the operation of barges from the Ösel to the castle in Wolfenbüttel is documented, where they moored at fortifications with such illustrious names as "Wunderlicher Heinz" and "Wunderlicher Kurt".

For August 15, 1580, a princely pleasure trip on the Oker from Wolfenbüttel to the pleasure palace in Hedwigsburg , built in 1578, is described, for which the construction of a lock at Pillowbrück was necessary. In 1576, Duke Julius had the measures necessary to expand the Oker between Harzrand and Wolfenbüttel examined. For this purpose, the Oker would have had to be expanded extensively or even relocated and locks would have had to be rebuilt. So it remained in the area with rafting.

In Julius' time there were also plans to create a canal connection between the Oker and the Saale area via the Schiffgraben-West and Großer Graben . The aim was to get to Hamburg by water and bypass the customs duties in Celle and Bremen.

In the 18th century, it was Duke Karl I who massively promoted the making the Oker catchment area navigable and did so against major protests from the rural population. In 1745 he had over 1000 economically valuable willow trees felled along the Oker south of Wolfenbüttel in order to create a towpath. Two years later, the path between Wolfenbüttel and Braunschweig was "cleared", whereby, in addition to the willow trees , the farmers had to give up a number of flax rots - this time for compensation.

A pier was built in front of the southern city gates of Braunschweig in the Bruch area. At Stöckheim there was a port in which the crews of the ships were changed, the street name "Am Schiffhorn" still indicates this. 489 journeys are documented for 1753, most of which carried beer, bread and building materials. In particular, the beer was demonstrably "nibbled" by ship's crews, which is evident from court records.

Shipping on the Upper Oker was not economical in the long run due to the maintenance of the waterway and was stopped again in 1770.

In the lower reaches of the Aller

Boat on the Oker in Braunschweig near Bammelsburg (today about Inselwall), copper engraving from the Beck workshop in 1716
Confluence of the Oker (right) into the Aller bei Müden (Aller)

In the town charter of the Braunschweiger Weichbildes Hagen of 1227, reference is made to the right of free shipping for the Braunschweig merchants to Bremen, as evidenced by Heinrich the Lion . However, this right was only on paper, since the dukes from Braunschweig-Wolfenbüttel had no access to the northern Oker and the Aller due to the territorial division of the duchy . The city of Celle, on the other hand, had a shipping monopoly for the Aller and collected high customs duties , especially for the Braunschweiger Mumme transported this way . The time and extent to which the Okerschiffahrt was operated cannot be stated with the necessary certainty today.

This circumstance led permanently to disputes between the city of Braunschweig and the territorial lords as well as among the principalities. There were therefore always interesting plans for an alternative shipping route to the North Sea, such as the one described above for a connection to the Saale and the one from the Napoleonic era to build a canal to the Aller - an anticipation of the later Mittelland Canal .

In Meinersen, the construction of a new moated castle was completed under Ludolf von Hohnhorst in 1357. In terms of water technology, the construction of this system was only possible by artificially relocating the Oker course from Meinersen to Müden / Dieckhorst.


In the city of Braunschweig there were motorized excursions on the Oker until the 20th century: in the north of the city to the Ölper Mühle, in the south between the main station and Eisenbüttel (Heinrichshafen) and in the upper water between Eisenbüttel and the Großer Weghaus in Stöckheim .

Drinking water production

In the 16th century, the water supply in Braunschweig was expanded by Barward Tafelmaker . Pumping stations fed wooden pipes, dykes (pipes) , with oker water and thus supplied the connected houses. In the 19th century, Braunschweig investigated whether to pump water from wells in Steinfeld near Vienenburg to the city. This was rejected at that time and instead a waterworks was built near Rüningen , which drew from the groundwater area of ​​the Oker. As part of this, the drinking water clarification ponds of the Braunschweig kennel area and the pumping station in the Bürgerpark were created. In the second half of the 20th century, the water supply was switched to the Harz waterworks . In addition to the increasing demand for water, the better quality of the resin water ( water hardness ) also played a decisive role.

Misfortunes and witch trials

In 1765 people were drowned for the last time in the Oker near Meinersen. The drowned people were a poisoner named Maria Dorothea Hänen (Hoyers) from Alvesse , who is said to have deliberately murdered her husband in 1765. At the same time, her maid, Anna Ilse Gieselern, was found guilty of aiding and abetting.

In the local chronicle of Ohrum, several accidents on the Oker Bridge are also mentioned with fatal results, with some of the corpses of the residents not being allowed to be recovered because they had washed ashore across the border.


Water quality

The ore mining in the Rammelsberg , which has been going on for more than three millennia , the metal works there and the slag heaps in the Goslar district of Oker, the river and groundwater are polluted with heavy metals, arsenic and other pollutants. On the dumps, on numerous highly polluted soils and in the stone fields between Oker and Vienenburg, the carnation corridors adapted to heavy metals were detected as early as 1930 and are still present today. Due to the cyclical flooding and sedimentation, the floodplains on the left and right of the Oker up to the Aller are also contaminated with heavy metals. In pasture cattle malformations and bone brittleness occurred earlier, the so-called Okersteinfeld disease .

In the urban area of ​​Braunschweig, soil investigations were carried out, according to which the soil had to be replaced in 2012 on the Stöckheim football field, which is located in the Okeraue. When evaluating the inner-city Okerlauf Bosselgraben as a possible canoe route for children, the sediment was examined in 2008 and classified as hazardous waste . The values ​​for arsenic were 380 mg / kg of tested dry matter, the test value according to the Federal Soil Protection Act is 125 mg / kg for leisure facilities. High concentrations of cadmium, copper and zinc have also been detected in the sludge.

With regard to the fish toxicity of the substances produced during smelting, vitriols in particular are named by the anglers, which led to the extinction of the salmon in the Oker.

For the year 2000, the biological water quality of the Oker (without tributaries) is classified by the NLWKN between II and III (“critically polluted”). A problem for the Oker itself are the inputs from agriculture, which come from fertilizers and pesticides. In particular in the loess and clay regions, this occurs together with eroded soil particles. The proportion of arable land in the entire Oker catchment area is 57.7%.

Direct discharges from so-called point sources such as sewage treatment plants, sugar factories and industrial plants still lead to local deterioration of the analyzed values ​​in some tributaries, but do not pollute the Oker as much as in the 1950s. The cooling water withdrawal of the Braunschweig central heating power station does not pose a direct burden on the biology, but the approved inlet temperature of 28 ° C in connection with the barrage in front of the Ölper Weir is assessed as critical, at least for the resettlement of the Atlantic salmon.

Structural quality

Oker weir in Oker
Fish pass at the Eisenbütteler weir with canoe pass - with drained headwater

Since the European Water Framework Directive was published , not only the biological and chemical quality of flowing water has been assessed, but also its structural condition. Here, morphological deviations from a natural course such as dams, canals and bank reinforcements are taken into account. Further criteria are the design of the edge area, the shading of the water with natural vegetation and the presence of dead wood. The scale ranges from I to VII, with the water sections with the best I rating normally ensuring optimal living conditions for flora and fauna. The Oker is graded VI in sections. In the area of ​​dams in particular, it is classified as a Heavily Modified Waterbody .

In this regard, the Oker does poorly in the upper reaches, as the dam, the power plant and the equalization basin mean that the Oker is almost completely built up and only runs in its natural river bed in exceptional cases. The previously strong fluctuations in water volume due to snowmelt and rain events are now almost completely buffered by the dam, which also means that natural changes and flooding in the lowlands do not occur. At the Vienenburger gravel ponds there are a number of bottom falls in quick succession. These prevent the natural transport of gravel and other debris and prevent migratory fish from climbing.

In the further course of the Oker, historical barriers partially determine the image of the river. This includes the mills and bridges as well as the flood ditches in the cities. Since the 1960s, numerous regulations with bottom falls and weirs have been added. The Okerlachs 2000 project, which is run jointly by the state of Lower Saxony , municipal institutions and fishing clubs in the Aller-Oker-Salmon community, is intended to remedy this situation . In this context, the main aim is to make the Oker more permeable for migratory fish such as salmon and sea trout. Bottom drops at weirs are made passable by fish ladders. As of 2010, only the Braunschweiger Petri weir forms the last barrier, which is planned to be converted.

Bank fortifications made of stones, which are mainly to be found in the urban ditches of Wolfenbüttel and Braunschweig, further impair the natural flora and fauna.

Renaturation measures that could restore a near-natural, meandering water flow and sufficient flood plains have only been initiated in individual sections of the tributaries of the Oker. The Schunter with the Beberbach and other streams are an example . A catalog of measures exists for the urban area of ​​Braunschweig, which indicates a great need for action with the dams and for possible renaturation in the southern urban area.

Nature reserves

Substantial parts of the river course are under nature protection and are part of EU bird sanctuaries or FFH regions .

In the Vorharz these are the areas between Oker and Schladen that are only interrupted by roads or paths

An almost continuous band of protected areas extends from the north of the Braunschweig urban area to the Dieckhorster weir shortly before the confluence with the Aller:


Rothemühle near Groß Schwülper - information board
Rothemühle with building from 1587, weir system and building with modern electricity generation

Watermills have been documented throughout the Okerlauf since the 12th century . The oldest has been the mill in Eisenbüttel since 1180 , at whose location there is still a weir system for regulating the water level in the city of Braunschweig. Numerous mills in the monasteries of the Vorharz and in the cities of Wolfenbüttel and Braunschweig are no longer recognizable today, but there are still some that are either still in use today or at whose location the energy of the water is converted into electrical energy.

In the Okertal, the Romkerhalle hydropower plant has been generating an annual electrical output of 12.5 million kWh from the water dammed up in the Oker reservoir since 1956.

In the monastery estate Wöltingerode , which was notarized in 1174, the former mill building has been used as a salmon information center since 2011. The Mühlenbach is branched off from the ponds of the Steinfelder in the upper reaches of the Oker, leads through the cloister wall at an artificially high level and flows back into the Oker at Harly. On the site of the project is under Okerlachs 2000 salmon spawning fertilized and into the Oker drained in the hope that these salmon later the Oker wander back up and set up spawning grounds.

The ferry mill on the east bank of the Oker near Ohrum has been documented since 1318 , and it still exists today and belongs to Hedwigsburg . The mill was temporarily owned by the city of Braunschweig in the 15th century and is now operated as the Hedwigsburger Okermühle by a large biscuit manufacturer in Lower Saxony. The drive energy is taken from the power grid.

In Wolfenbüttel , the original Damm Mill was demolished in 1990, but the Schünemannsche Mühle, also known as the New Mill , has been preserved as a building. The building now serves as a guest house for the Federal Academy for Cultural Education , which is entered above the rushing fall of the Oker.

In Rüningen , a mill is mentioned as early as 1312 in the degeding book of the city of Braunschweig, making it the oldest manufacturing company in Lower Saxony. Here, too, the drive energy was switched to steam in the 19th century and later to electricity. As in the Hedwigsburger Okermühle, mainly grain is ground for commercial use.

In the Braunschweig city ​​area, of the original six mills, only the Neustadtmühle building has been preserved, which has been used as the municipal youth facility Mühle since 1957 . The historical bridge over the Neustadtmühlengraben and the weir system can still be seen in front of the building.

At the former Ölper mill , historical weir systems and today's Ölper weir testify to the earlier existence of one of the largest mills on the Oker.

In Rothemühle , the complete water mill, which has been attested since 1348, has been preserved and can be visited from time to time. The system was supplemented by a fish pass. Although it is no longer in operation as a producing mill, it has been generating annual energy of 120,000 kWh since 1993, which is sufficient to supply around 50 households.

In Meinersen , the mill has been documented since 1551 and is part of the historic town center and the fish farms in the Oker catchment area. A Kaplan turbine has been generating electricity here since 1994.

At the end of the Oker in Dieckhorst, in addition to a historic barrage for the Oker, there is a hydropower plant for generating electricity with an output of 223 kW and thus an average annual output of 1,414,556 kWh.

Today's meaning

water sports

Paddlers on the last section of the whitewater trail

Between the outlet of the Romkerhalle hydropower plant and the compensation basin of the Okertalsperre, located about 1200 m below, the river reaches whitewater quality for a few hours a day due to the discontinuous operation of the peak current power plant and is then a popular training route for canoeing .

From Dorstadt the Oker is so rich in water even in summer that it is used by canoeists and paddlers from here to the mouth. Rowing and canoeing clubs have settled along the Oker, and the Braunschweig “Rowing Club Normannia” (founded in 1910) can look back on over a hundred years of tradition.

Sailing is possible in the Braunschweig South Sea , where the "Braunschweiger Seglerverein" operates a water sports center.

In the Braunschweig city area, several boat rental stations along the Eastern Umflutgraben and in the Bürgerpark are open in the summer months .

Cultural place

Since the Expo 2000 , bridges over the Oker and its surroundings have been artistically designed within Braunschweig, after 2004 as part of the Okerlicht project .

On the Oker there are regular raft trips with readings. Sometimes there are also jazz concerts on the river and events as part of the Braunschweiger Kulturnacht.


The Oker and especially its adjacent lakes and backwaters have been popular fishing grounds for several years. Fishing clubs have leased a number of water and bank areas and are actively involved in the renaturation of the Oker and its tributaries (Okerlachs 2000 project).


Engagement island with engagement bridge in the Okertal near Romkerhalle

There are numerous opportunities for hiking or cycling along the entire course of the Oker. The European long-distance hiking trail E6 leads along the Oker and the Oker reservoir in the Harz Mountains , which meets the European long-distance hiking trail E11 west of the Goslar district of Oker and crosses the Oker for the last time outside the Harz in Wolfenbüttel. At the Harzer Dammgraben , which among other things connects the Kleine Oker with the Große Oker , there is stamp number 149 Kleine Oker of the Harz hiking pin near a refuge . The Braunschweig green spaces offer plenty of space for those looking for relaxation and dining facilities right on the shore. The adjacent districts maintain a well-marked network of cycle paths. The Weser-Harz-Heide-Radfernweg leads directly through the Oker lowlands.


Along the Oker there are a multitude of historical places such as monasteries and castles that can still be visited today:

  • The Wöltingerode monastery is freely accessible and houses the salmon information center.
  • The remains of the wall of the Harliburg can be reached in Harly .
  • The Palatinate Werla is an archaeological park, in which excavations can be seen and agriculture of the Middle Ages is practiced.
  • The Heiningen and Dorstadt monasteries are privately owned and can only be viewed to a limited extent from the outside.
  • The place of the baptism of Saxony is documented in Ohrum.
  • Wolfenbüttel and Braunschweig each offer a wide range of sights.
  • The Scheverlingenburg in Walle is documented locally.
  • Meinersen offers an ensemble of old mansions at the Oker crossing. A nature trail documents the times of intensive river use and today's measures to reintroduce salmon.
  • Hillerse has been offering an observation platform on the Okeraue between Hillerse and Volkse since autumn 2015 with the interactive information board Der Oker-Altarm about native and immigrant species.

Quotes on the Oker

“The ocher winds in graceful curves through a large meadow. Here the little river likes to follow the guiding hand of art; he willingly made a broader stream or divided himself into more turns (...). "

- Hirschfeld (1785) in Theory of Garden Art

“The Oker, a wide river four fathoms deep, coming from the Harz, flows past Braunschweig and Wolfenbüttel. Insignificant, but very useful. "

- Stendhal (1808)

“The name of the place is borrowed from the river of the same name. Already from the 12th to the 15th century you can find the designation: the Nebelhütten, Galmhütten u. a. at the Oker. "

- Schucht (1888)

Origin and meaning of the name

The name of the river is documented as Ovacra (747), Obacra (748), Ovacrus (775), Obacrus (780) etc., 994 as Ovaccara and 1128 as Ovakara . Since the latter form is used in documents drawn up in the Oker region, it is believed that this is the most accurately preserved form. The origin of the name is interpreted from the syllables ov- and -akara as “upper” and “forward-pushing”, in contrast to the “forward-pushing” tributary Ecker .


Backwaters of the Oker in the Harz
Left Right muzzle source
Ditch crosses at Bruchberg (Upper Harz Water Management)
Little oker Altenau Bruchberg
Altenau Altenau Bruchberg
Rotenbeek Altenau Sparrowhawk shark
Black water Altenau Polstertal
Kellwasser Okertalsperre Tendon head
Long Okertalsperre East of Clausthal
Schalke Okertalsperre Schalke (Harz)
Giant stream Okertalsperre Altetalskopf
Great Bramke Okertalsperre Big head
Calf Okertalsperre Tendon head
Big hune Okertalsperre East of the Okertalsperre
Romke Romkerhalle Taternbruch
Romke Romkerhalle Tube dance
Sülpke Romkerhalle Eichenberg
Gloomy valley water Waldhaus / Oker Eichenberg / Gloomy Valley
Backwaters of the Oker north of the Harz
Left Right muzzle source
Röseckenbach Oker (Goslar) Göttingerode / Hessental
Breeding Oker (Goslar) Goslar / Wintertal
Hurlebach Vienenburg lake Harlingerode / Langenberg
Racket Vienenburg Near the peat house
Ecker Reunion Eckersprung / Brocken
Ohebach Lengde Harly
Weddebach Schladen Grauhof
Eckergraben Steinfelder Mill Branch of the Ecker near Wiedelah
Ilse / Kanalilse Exchange rate Heinrichshöhe / Brocken
Warn Dorstadt Döhrenberg near SZ-Bad
Altenau Halchter / Wolfenbüttel Eitzum / Schöppenstedt
Brückenbach Groß Stöckheim / Wolfenbüttel Leinde / Oderwald
Thiedebach Leiferde / Braunschweig SZ-Thiede
Fuhse Canal South Pacific (Braunschweig) Devil's jump at BS-Broitzem
Springbach Melverode / Braunschweig Jump at Mascherode
Schölke Ölper / Braunschweig Jödebrunnen
Aue-Oker Canal Hülperode / Schwülper Aue near Wendeburg
Schunter Walle / Schwülper Räbke am Elm
Bickgraben Big muggy Vordorf
Frankenmoorgraben Neubrück Adenbüttel
Slope I Neubrück
Rolfsbüttelerbach Rolfsbüttel Rolfsbüttel
Danningmoorgraben Hillerse
Slope II Hillerse
Bockerholzgraben Volkse
Slope III Volkse / Seehausen
Slope IV Seershausen
Derivation Mühlengraben Seershausen
Meinersengraben Meinersen
Okerwiesengraben Seershausen
Temple moat Meinersen
Junction of the Müdener Kanal Müden-Diekhorst


  • Wilhelm Appelt and Theodor Müller: Water arts and waterworks of the city of Braunschweig . In: Braunschweiger Werkstücke , Vol. 33, Braunschweig 1964.
  • Wilhelm Bornstedt : Chronicle of Stöckheim . Braunschweig 1967.
  • Jürgen Hodemacher : From the source to the mouth: The Oker . Elm-Verlag, Cremlingen 1992, ISBN 3-927060-07-0 .
  • Theodor Müller: Shipping and rafting in the river area of ​​the Oker . In: Braunschweiger Werkstücke , vol. 39. Braunschweig 1968.
  • Arnold Peters: History of shipping on the Aller, Leine and Oker until 1618 . Research on the history of Lower Saxony, ed. from the Historical Association for Lower Saxony , Vol. 4, Issue 6. Hanover 1913.
  • NLWK operations center south (ed.) : Water quality report Oker 2002 . NLWK series of publications, Vol. 4, Braunschweig 2002.

Web links

Commons : Oker  - collection of images, videos and audio files

References and comments

  1. a b State Office for Geoinformation and Land Surveying Lower Saxony: Top 50 - Topographic Map 1: 50,000 Lower Saxony / Bremen , as of 2000.
  2. a b Braunschweig District Government / NLWK: Inventory for the implementation of the EC Water Framework Directive, surface waters, Oker processing area , draft of November 22, 2004, Table 1: Mention and description of the main flowing waters. Source http://www.wasserblick.net/servlet/is/17842/ , accessed on October 2, 2012.
  3. NLWKN : Area directory for the Lower Saxony Hydrographic Map , as of 2010, p. 51, accessed on August 19, 2013, from Umwelt.niedersachsen.de (PDF; 599.8 kB)
  4. ^ German Hydrological Yearbook Weser-Ems 2014. Lower Saxony State Agency for Water Management, Coastal Protection and Nature Conservation, p. 178, accessed on October 4, 2017 (PDF, German, 8805 kB).
  5. NLWKN water body data sheets in the web links section
  6. a b Appel, Wilhelm; Müller, Theodor: Water arts and waterworks of the city of Braunschweig , in Braunschweiger Werkstücke, Vol. 33, Waisenhaus-Verlag, Braunschweig 1964.
  7. W. Christoph Seiler: The Aller - A river changes its course: The historical course of the Aller between Müden and Celle , Celle 2002, ISBN 3-9805636-4-2 .
  8. Kurhannoversche Landesaufnahme 1781, sheet 112 Gifhorn.
  9. Historical maps, accessed on March 23, 2013, navigator.geolife.de
  10. The figures are composed of the level values Groß Schwülper (Oker) and Brenneckenbrück (Aller) and the calculated values ​​for the missing (in both cases) around 5% of the catchment area. The averaged discharge of both rivers was used as a basis for the remaining area .
  11. a b c Braunschweig District Government / NLWKN : Inventory of the implementation of the EU Water Framework Directive, Oker processing area , Braunschweig, November 22, 2004, accessed on February 1, 2010, on wasserblick.net
  12. ^ Theodor Müller: Geographische Landesaufnahme: The natural space units on sheet 87 Braunschweig. Federal Institute for Regional Studies, Bad Godesberg 1962. →  Online map (PDF; 4.8 MB)
  13. The Federal Agency for Nature Conservation (BfN) assigns the reference number 51002 to the Okertal natural area
  14. a b c d Riefenstein, Elisabeth: Chronik Ohrum 747–1997 , Wolfenbüttel 1997.
  15. Dietrich Schmidtsdorff: "Ransom money for the Vikings was minted on the Mundburg", in: Geldgeschichtliche Nachrichten, September 2005, p. 167 ff.
  16. ^ Theodor Müller: Shipping and rafting in the river area of ​​the Oker . In: Braunschweiger Werkstücke , Vol. 39, Braunschweig 1968, pp. 70 ff.
  17. Rolf Ahlers: On the size of the ships on Aller, Oker and Schunter in the Middle Ages. Braunschweigische Heimat (102) 2016, issue 2, pp. 20–24.
  18. Henning Steinführer: Brief History of the Hanseatic City of Braunschweig, Braunschweig 2017.
  19. Peter Przybilla: Die Edelherren von Meinersen , Hannover 2007, ISBN 978-3-7752-6036-7 .
  20. Matthias Blazek: The last execution by drowning in the Kingdom of Hanover , in Der "Sachsenspiegel" Part 2 (from 2006) , on matthias-blazek.eu
  21. Friedhardt Knolle (inter alia): Heavy metal vegetation, mining and metallurgy in the western Harz Geopark - an ecotoxicological excursion , Braunschweiger Naturkundliche Schriften, Vol. 10, Issue 1, August 30, 2011, pp. 1-44, ISSN  0174-3384 , accessed on October 5, 2015, at geobotanik.uni-goettingen.de (PDF; 6.81 MB)
  22. Oppermann, Brandes: Die Uferflora der Oker , Braunschweig Botanical Institute and Botanical Garden, Geobotany and Biology of Higher Plants Working Group, 1993, published on September 15, 2009, on digibib.tu-bs.de
  23. Christian Braun: Rehabilitation and hydraulic engineering redesign of the Bosselgraben in Braunschweig as a canoe route for children , study draft at the Leichtweiss Institute for Hydraulic Engineering at the Technical University of Braunschweig, July 2009.
  24. Aller-Oker-Salmon Community ( Memento from March 7, 2014 in the Internet Archive ), in project activities at the Oker , accessed on March 10, 2013
  25. NLWKN: Karte_12b_Gewaesserguete_2000_041222.pdf , accessed on February 1, 2010, on wasserblik.net
  26. a b ALAND (commissioned by the city of Braunschweig): Concept of measures according to the WFD for the water body Oker in Braunschweig , Hanover, March 2012.
  27. City of Braunschweig: Planning approval "Conversion of the Petriwehr" , with appendices, from October 27, 2009, accessed on October 2, 2012, on braunschweig.de
  28. Water with energy - electricity from hydropower ( Memento from October 29, 2013 in the Internet Archive ), brochure by Harzwasserwerke GmbH, p. 15 (PDF; 9.63 MB)
  29. Salmon Infocenter at Klostergut Wöltingerode , accessed on March 10, 2013, at lachs-infocenter.de
  30. Hedwigsburger Okermühle , accessed March 9, 2013, okermuehle.de
  31. Bundesverband Deutscher Wasserkraftwerke (BDW): Information board Wassermühle Rothemühle , as of May 17, 2012
  32. Harzer Wanderadel: stamp point 149 / Kleine Oker , on harzer-wandernadel.de
  33. Heinz-Joachim Tute, Marcus Köhler, Wolf-Dieter Schuegraf (ed.): Garden art in Braunschweig. From the princely gardens of the Baroque to the public park of the Wilhelminian era . City Library, Braunschweig 1989, ISBN 3-87884-037-3 ( Braunschweiger Werkstücke. 76 / Series A. Publications from the City Archives and the City Library . Vol. 26), p. 93
  34. Renate Guddas: The city of Braunschweig in literary evidence , Braunschweig 1979, p. 19
  35. ^ Heinrich Schucht: Chronicle and local history of the Hüttenortes Oker, Harzburg, Stolle 1888, p. 8.
  36. See Hans Krahe : About some names of waters with the st suffix , in: BNF 10 (1959), pp. 1–17 (p. 8).
  37. Herbert Blume : Oker, Schunter, Wabe , in: Braunschweigisches Jahrbuch für Landesgeschichte, Vol. 86, Braunschweig 2005, pp. 14 ff.