Tinnsjå (also known as ''Tinnsjø'' or ''Tinnsjøen''; ) is one of the largest

lakes A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

measuring about . At a depth of it is the third deepest lake in Norway and Europe. Tinnsjå is located in the municipalities of

Tinn Tinn is a municipality in Telemark county, Norway. It is located in the traditional districts of Aust-Telemark and Upper Telemark. The administrative centre of the municipality is the town of Rjukan. Some of the villages in Tinn include Atr� ...

and

Notodden is a municipality in Telemark county, Norway. It is located in the traditional district of Aust-Telemark. The administrative centre of the municipality is the town of Notodden. Other population centres include the villages of Bolkesjø, G ...

Telemark Telemark () is a Counties of Norway, county and a current electoral district in Norway. Telemark borders the counties of Vestfold, Buskerud, Vestland, Rogaland and Agder. In 2020, Telemark merged with the county of Vestfold to form the county o ...

county. At its source in the west, the

Måna The Måna or Måne is a river in Tinn Municipality in Telemark county, Norway. The river flows from the lake Møsvatn through the Vestfjorddalen valley and the town of Rjukan to the large lake Tinnsjå near the village of Miland. It is part of t ...

river flows out of the lake

Møsvatn Møsvatn or Møsvann is a lake in Vinje Municipality in Telemark county, Norway. It is the tenth-largest lake in Norway with a surface area of and a volume of . The lake lies just east of the Hardangervidda National Park, in Skien watershed ...

and past the town of

Rjukan Rjukan () is a List of towns and cities in Norway, town in Tinn Municipality in Telemark county, Norway. The town is also the administrative centre of Tinn Municipality. The town is located in the Vestfjorddalen valley, between the lakes Møsvatn ...

into Tinnsjå. From the north, the river Mår flows from the lakes Mår, Gøystavatn, and

Kalhovdfjorden Kalhovdfjorden is a lake in Tinn Municipality in Telemark county, Norway. The lake lies about to the north of the town of Rjukan and about east of the Hardangervidda National Park. The lake is part of the Skien watershed. The river Mår is the ...

into Tinnsjå. Tinnsjå is part of the

Skien watershed The Skien watershed is the third largest watershed of Norway after those of the Glomma and the Drammen rivers. The catchment area is , and the maximum length is . The Skien watershed includes rivers which feed Lake Norsjø above Skien; * Vinje ...

, and it drains via the

Tinnelva Tinnelva (also known as Tinne or Tinnåa) is a river in Notodden Municipality in Telemark county, Norway. The long river flows between two lakes: Tinnsjå and Heddalsvatnet. The river begins at the village of Tinnoset draining from the lake Tin ...

river in the south, down to the lake Heddalsvatn. At the north end of the lake lie the villages of

Atrå Atrå is a village in Tinn Municipality in Telemark county, Norway. The village is located at the northwestern end of the large lake Tinnsjå, about to the west of the village of Tinn Austbygd and about to the north of the village of Miland. ...

and Austbygdi. The village of

Miland Miland is a village in Tinn Municipality in Telemark county, Norway. The village is located in the Vestfjorddalen valley, near the western shore of the large lake Tinnsjå, about east of the town of Rjukan, about south of the village of Atrå ...

lies on the western shore of the lake. The village of Hovin lies up on a hill overlooking the eastern shore of the lake and the village of

Rudsgrendi Rudsgrendi or Rugsgrend is a village in Notodden Municipality in Telemark county, Norway. The village is located on the western shore of the large lake Tinnsjå, halfway between the village of Gransherad and the town of Rjukan. On the opposite si ...

lies on the western shore. There is a small

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

at the south end of the lake which regulates the surface elevation of the lake and the village of

Tinnoset Tinnoset is a village in Notodden Municipality in Telemark county, Norway. The village is located at the southernmost end of the large lake Tinnsjå, where the river Tinnelva begins flowing south out of the lake. It is about south of the villa ...

is located at this end of the lake. The village of

Gransherad Gransherad is a List of former municipalities of Norway, former municipality in Telemark county, Norway. The municipality existed from 1860 until its dissolution in 1964. The area is now part of Notodden Municipality (in Telemark) and Kongsberg ...

lies about south of this dam.

History

In 1944, during the German occupation of Norway, the

ferry A ferry is a boat or ship that transports passengers, and occasionally vehicles and cargo, across a body of water. A small passenger ferry with multiple stops, like those in Venice, Italy, is sometimes referred to as a water taxi or water bus ...

SF ''Hydro'' was sunk in Tinnsjå by the Norwegian resistance. The Germans were using the ferry to transport a large quantity of

heavy water Heavy water (deuterium oxide, , ) is a form of water (molecule), water in which hydrogen atoms are all deuterium ( or D, also known as ''heavy hydrogen'') rather than the common hydrogen-1 isotope (, also called ''protium'') that makes up most o ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, where it was to be used for

nuclear weapons research Nuclear weapons design are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: # Pure fission weapons are the simplest, least technically de ...

. The heavy water had been produced at

Vemork Vemork is a hydroelectric power plant outside the town of Rjukan in Tinn Municipality in Telemark county, Norway. The plant was built by Norsk Hydro and opened in 1911, its main purpose being to fix nitrogen for the production of fertilizer. ...

, a factory located in

. The wreck of the ferry was discovered in 1993. In 2004, it was investigated and filmed for an episode of

NOVA A nova ( novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months. All observed novae involve white ...

; heavy water samples were recovered and

deuterium Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...

isotopic enrichment Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. The use of the nuclides produced is varied. The largest variety is used in research (e.g. in chemistry where atoms of "marker" n ...

was confirmed. In 2004, a film crew shooting footage for a new documentary on the heavy water sabotage became aware of an unusual fish, swimming near the lake bottom at a depth of . Two specimens of the previously unknown fish were captured in April 2005. Analysis revealed the fish to be closely related to

Arctic char The Arctic char or Arctic charr (''Salvelinus alpinus'') is a cold-water fish in the family Salmonidae, native to alpine lakes, as well as Arctic and subarctic coastal waters in the Holarctic realm, Holarctic. Distribution and habitat It Spaw ...

. The light-colored, translucent fish is up to long and lacks a

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ (anatomy), organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift ...

References

{{use dmy dates, date=August 2023 Tinn Notodden Lakes of Telemark

History

See also

References