The Möhne Reservoir, or Moehne Reservoir, is an artificial

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

North Rhine-Westphalia North Rhine-Westphalia (german: Nordrhein-Westfalen, ; li, Noordrien-Wesfale ; nds, Noordrhien-Westfalen; ksh, Noodrhing-Wäßßfaale), commonly shortened to NRW (), is a States of Germany, state (''Land'') in Western Germany. With more tha ...

, some 45 km east of

Dortmund Dortmund (; Westphalian nds, Düörpm ; la, Tremonia) is the third-largest city in North Rhine-Westphalia after Cologne and Düsseldorf, and the eighth-largest city of Germany, with a population of 588,250 inhabitants as of 2021. It is the la ...

, Germany. The lake is formed by the damming of two rivers,

Möhne The Möhne () is a river in North Rhine-Westphalia, Germany. It is a right tributary of the Ruhr. The Möhne passes the towns of Brilon, Rüthen and Warstein. There is a large artificial lake near the mouth of the river, the Möhne Reservoir, use ...

and Heve, and with its four basins stores as much as 135 million cubic metres of water.

History

Construction and inauguration

In 1904, calculations about the future demand for water for people and industry in the growing Ruhr-area determined that the existing storage volume of 32.4 million m³ in dams of the Ruhr river system needed tripling. Thus, on 28 November 1904, the general assembly of the ''Ruhrtalsperreverein'' decided to construct additional dams. During 1908 to 1913 they built the Möhnetalsperre at a cost of 23.5 million marks. When opened, the dam was the largest dam in Europe. 140 homesteads with 700 people had to move. It was built to help control floods, regulate water levels on the

Ruhr The Ruhr ( ; german: Ruhrgebiet , also ''Ruhrpott'' ), also referred to as the Ruhr area, sometimes Ruhr district, Ruhr region, or Ruhr valley, is a polycentric urban area in North Rhine-Westphalia, Germany. With a population density of 2,800/km ...

river downstream, and generate

hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, converting the Pot ...

. Today, the lake is also a tourist attraction. Mohne Dam Breached

Second World War

The dam () was breached by

RAF The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

Lancaster Bombers ( "The Dambusters") during

Operation Chastise Operation Chastise or commonly known as the Dambusters Raid was an attack on German dams carried out on the night of 16/17 May 1943 by 617 Squadron RAF Bomber Command, later called the Dam Busters, using special "bouncing bombs" developed by ...

on the night of 16–17 May 1943, together with the

Edersee The Edersee, also known as the Ederstausee, is an reservoir in Waldeck-Frankenberg, Hesse, Germany with of storage space. It has the 2nd largest area (behind the Forggensee), and the 3rd largest volume (behind the Bleilochstausee and Rurstause ...

dam in northern

Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a States of Germany, state in Germany. Its capital city is Wiesbaden, and the largest urban area is Frankfurt. Two other major histor ...

Bouncing bomb A bouncing bomb is a bomb designed to bounce to a target across water in a calculated manner to avoid obstacles such as torpedo nets, and to allow both the bomb's speed on arrival at the target and the timing of its detonation to be pre-deter ...

s had been constructed which were able to skip over the protective nets that hung in the water. A huge hole of 77 m by 22 m was blown into the dam. The resulting huge floodwave killed at least 1,579 people,Article of Landschaftsverband Westfalen-Lippe
1,026 of them foreign forced labourers held in camps downriver. The small city of

Neheim-Hüsten Arnsberg (; wep, Arensperg) is a town in the Hochsauerland county, in the German state of North Rhine-Westphalia. It is the location of the Regierungsbezirk Arnsberg administration and one of the three local administration offices of the Hochs ...

was particularly hard-hit with over 800 victims, among them at least 526 victims in a camp for Russian women held for forced labour. Kanzelbruecke01

Though the

Organisation Todt Organisation Todt (OT; ) was a civil and military engineering organisation in Nazi Germany from 1933 to 1945, named for its founder, Fritz Todt, an engineer and senior Nazi. The organisation was responsible for a huge range of engineering projec ...

quickly repaired the dams through the labor of 7,000 men taken from the construction of the

Atlantic Wall The Atlantic Wall (german: link=no, Atlantikwall) was an extensive system of coastal defences and fortifications built by Nazi Germany between 1942 and 1944 along the coast of continental Europe and Scandinavia as a defence against an anticip ...

, the impact of the raid on German industry in the

valley and on the civil population was significant. According to

Albert Speer Berthold Konrad Hermann Albert Speer (; ; 19 March 1905 – 1 September 1981) was a German architect who served as the Minister of Armaments and War Production in Nazi Germany during most of World War II. A close ally of Adolf Hitler, he ...

, "the power plant at the foot of the shattered dam looked as if it had been erased, along with its heavy turbines." "Industry was brought to a standstill", due to the "electrical installations being soaked and muddied." Three other reservoirs were still intact, though the largest, the

Sorpe Dam The Sorpe Dam (german: Sorpetalsperre) is a dam on the Sorpe river, near the small town of Sundern in the district of Hochsauerland in North Rhine-Westphalia, Germany. Together with the Biggesee, the Möhne Reservoir, and the Verse reservoir ...

, had a hole above the water line. Another destroyed dam, the

Edersee Dam The Edersee Dam is a hydroelectric dam spanning the Eder river in northern Hesse, Germany. Constructed between 1908 and 1914, it lies near the small town of Waldeck at the northern edge of the Kellerwald. Breached by Allied bombs during Worl ...

, "had nothing to do with the supply of water to the Ruhr." The Mohne Dam was repaired by 23 September 1943, in time to collect water needed for the following summer, when the British failed to follow up with additional raids to hamper reconstruction.

Nature and environment

Lake Möhne is designated as a European bird sanctuary "Möhne Lake" in the EU's Natura 2000 system of protected areas. Lake Heve and the Heve arm in the south of Lake Möhne as well as the inlet of the Möhne into the lake are designated as the Hevearm and Hevesee nature reserve. The Heve forebay and adjacent areas have also been registered as an FFH site.

Importance for bird protection

Lake Möhne is an important resting place in North Rhine-Westphalia with four to six thousand waterfowl. The important resting birds are, with percentages for the years 2001 to 2006, the

tufted duck The tufted duck or tufted pochard (''Aythya fuligula'') is a small diving duck with a population of close to one million birds, found in northern Eurasia. The scientific name is derived from Ancient Greek '' aithuia'', an unidentified seabird ment ...

with 31 percent, the

mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

with 24 percent, the

coot Coots are medium-sized water birds that are members of the rail family, Rallidae. They constitute the genus ''Fulica'', the name being the Latin term for "coot". Coots have predominantly black plumage, and—unlike many rails—they are usually ...

with 22 percent, the

great crested grebe The great crested grebe (''Podiceps cristatus'') is a member of the grebe family of water birds noted for its elaborate mating display. Taxonomy The great crested grebe was formally described by the Swedish naturalist Carl Linnaeus in 1758 in t ...

with 9 percent, the

pochard Pochard is a common name used for several species of diving ducks: *Four species in the genus ''Aythya'': ** Common pochard, ''Aythya ferina'' ** Baer's pochard, ''Aythya baeri'' ** Ferruginous pochard, ''Aythya nyroca'' ** Madagascar pochard, '' ...

with 5 percent and other species with 9 percent. An important reason for greater resting occurrences of diving ducks and coots is the presence of the migratory mussel in the lake. The

zebra mussel The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally introduced to numerous other areas and has become an invasive species in ma ...

forms mussel beds on the stony lake bottom with several thousand animals per square meter. At the inflows of the Möhne and the smaller streams into the lake there are occurrences of

kingfisher Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly colored birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species found in the tropical regions of Africa, Asia, and Oceania, ...

grey wagtail The grey wagtail (''Motacilla cinerea'') is a member of the wagtail family, Motacillidae, measuring around 18–19 cm overall length. The species looks somewhat similar to the yellow wagtail but has the yellow on its underside restricted t ...

and

dipper Dippers are members of the genus ''Cinclus'' in the bird family Cinclidae, so-called because of their bobbing or dipping movements. They are unique among passerines for their ability to dive and swim underwater. Taxonomy The genus ''Cinclus'' ...

. However, their actual breeding sites are not directly at the lake, but at the tributaries. On the shore of the lake breed mallard, tufted duck,

moorhen Moorhens—sometimes called marsh hens—are medium-sized water birds that are members of the rail family (Rallidae). Most species are placed in the genus ''Gallinula'', Latin for "little hen". They are close relatives of coots. They are of ...

, coot,

mute swan The mute swan (''Cygnus olor'') is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Eurosiberia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, home ...

greylag goose The greylag goose or graylag goose (''Anser anser'') is a species of large goose in the waterfowl family Anatidae and the type species of the genus ''Anser''. It has mottled and barred grey and white plumage and an orange beak and pink legs. A ...

Canada goose The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...

Egyptian goose The Egyptian goose (''Alopochen aegyptiaca'') is a member of the duck, goose, and swan family Anatidae. It is native to Africa south of the Sahara and the Nile Valley. Egyptian geese were considered sacred by the Ancient Egyptians, and appeared ...

and great crested grebe. The great crested grebe has its largest breeding population in Westphalia here, with about fifty breeding pairs on the lake. The

grey heron The grey heron (''Ardea cinerea'') is a long-legged wading bird of the heron family, Ardeidae, native throughout temperate Europe and Asia and also parts of Africa. It is resident in much of its range, but some populations from the more northern ...

has a breeding colony on the Westenberg in Wamel with 15 to 30 occupied nests. The

cormorant Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...

has so far made only unsuccessful breeding attempts, probably due to human disturbance. The

red-necked grebe The red-necked grebe (''Podiceps grisegena'') is a migratory aquatic bird found in the temperate regions of the northern hemisphere. Its wintering habitat is largely restricted to calm waters just beyond the waves around ocean coasts, although ...

has also bred unsuccessfully at the lake several times since 2002. The

little grebe The little grebe (''Tachybaptus ruficollis''), also known as dabchick, is a member of the grebe family of water birds. The genus name is from Ancient Greek ''takhus'' "fast" and ''bapto'' "to sink under". The specific ''ruficollis'' is from Latin ...

, on the other hand, has had single successful broods in the past. A special feature was the year-round occurrence of the

common eider The common eider (pronounced ) (''Somateria mollissima''), also called St. Cuthbert's duck or Cuddy's duck, is a large ( in body length) sea-duck that is distributed over the northern coasts of Europe, North America and eastern Siberia. It bree ...

, a sea duck, from September 2001 to December 2006. In July 2006, the first breeding record for North Rhine-Westphalia was found here: a female with three half-grown young. When the water level rose sharply in December 2006, the eiders could no longer reach the zebra mussel beds and left the lake. Other sea ducks also appear more frequently during the winter season.

Fish stock at Möhne Reservoir

Thirteen species of fish were found in the lake during sample fisheries conducted by the Ruhr Association. The largest stocks come from

perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Percif ...

with 53 percent,

ruffe The Eurasian ruffe (''Gymnocephalus cernua''), also known as ruffe or pope, is a freshwater fish found in temperate regions of Europe and northern Asia. It has been introduced into the Great Lakes of North America, reportedly with unfortuna ...

with 20.3 percent and

roach Roach may refer to: Animals * Cockroach, various insect species of the order Blattodea * Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae ** ''Rutilus'' or roaches, a genus of fishes * California roach ...

with 13.9 percent. In addition, whitefish,

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

pike Pike, Pikes or The Pike may refer to: Fish * Blue pike or blue walleye, an extinct color morph of the yellow walleye ''Sander vitreus'' * Ctenoluciidae, the "pike characins", some species of which are commonly known as pikes * ''Esox'', genus of ...

zander The zander (''Sander lucioperca''), sander or pikeperch, is a species of ray-finned fish from the family Percidae, which includes the perches, ruffes and darters. It is found in freshwater and brackish habitats in western Eurasia. It is a popul ...

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

bream Bream ( ) are species of freshwater and marine fish belonging to a variety of genera including ''Abramis'' (e.g., ''A. brama'', the common bream), ''Acanthopagrus'', '' Argyrops'', ''Blicca'', '' Brama'', ''Chilotilapia'', '' Etelis'', ''Lepo ...

carp Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

tench The tench or doctor fish (''Tinca tinca'') is a fresh- and brackish-water fish of the order Cypriniformes found throughout Eurasia from Western Europe including the British Isles east into Asia as far as the Ob and Yenisei Rivers. It is also ...

and chub are also found. Lake trout and eel occur only because of artificial stocking and do not reproduce naturally. The

muskrat The muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitat ...

is also present.

References

{{DEFAULTSORT:Mohne Reservoir Reservoirs in North Rhine-Westphalia Dams in North Rhine-Westphalia Lakes of North Rhine-Westphalia Dams completed in 1913 1913 establishments in Germany RMohne Dam failures in Europe