Heddalsvatnet ( en, Lake Heddal) is a lake in the municipalities

Notodden Notodden () is a List of towns and cities in Norway, city and List of municipalities of Norway, municipality in Vestfold og Telemark Counties of Norway, county, Norway. It is part of the Districts of Norway, traditional region of Øst-Telemark. ...

and

Sauherad Sauherad is a former municipality in Telemark county, Norway. It is part of the traditional region of Midt-Telemark. The administrative centre of the municipality is the village of Akkerhaugen. The municipality borders Kongsberg, Skien, Nome, ...

Vestfold og Telemark Vestfold og Telemark (; ) is a county under disestablishment in Norway. The county is the southernmost one of Eastern Norway and consists of two distinct and separate traditional regions: the former counties of Telemark and (most of) Vestfold. T ...

, Norway. The main influx comes from the rivers

Tinnelva Tinnelva is a river in Notodden, Vestfold og Telemark, Norway. It flows from Lake Tinn to Heddalsvatnet. The waterfalls Årlifossene, Grønvollfoss, Svelgfoss and Tinnfoss are exploited, and the hydroelectric power stations have a combined installe ...

and

Heddøla Heddøla is a river in the municipalities Hjartdal and Notodden in Vestfold og Telemark, Norway. It starts from the junction of Hjartdøla and Skogsåa in Sauland, and flows through the valley Heddal Heddal is a village and parish in Notodden ...

. The lake covers an area of 11.9 km² or 13.2 km² according to NVE. The catchment basin covers a total area of 5380,5 km². The southern part of the lake is called Bråfjorden and is separated from the northern part by Nautsundet strait crossed county road 360 bridge. The railway line to Notodden (the

Bratsberg Line The Bratsberg Line ( no, Bratsbergbanen) is a railway line between Eidanger and Notodden in Vestfold og Telemark county, Norway. It opened in 1917, connecting the Tinnos Line, the Sørland Line and the Vestfold Line; allowing Norsk Hydro to tran ...

) runs along the eastern shore. The lake 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 is connected to the ocean by the

Telemark Canal The Telemark Canal connects the towns Skien and Dalen in southern Norway by linking several long lakes in the Skien watershed through a series of 18 locks. It originally consisted of two canals. The Norsjø–Skien Canal, with locks in Skien a ...

. Heddalsvatnet is only 16 meters above sea level and only two locks at

Skien Skien () is a city and municipality in Vestfold og Telemark county in Norway. In modern times it is regarded as part of the traditional region of Grenland, although historically it belonged to Grenmar/Skiensfjorden, while Grenland referred the Norsj ...

were needed to allow ships to sail on the lake. The canal opened in 1861 and made Notodden into Norway's largest fresh water port. In the late 1800s seafaring vessels were constructed at the shores of Heddalsvatnet.

History

After the ice age the ocean was about 150 meter higher in this area. The ocean stretched like a

fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Germany, Greenland, the Faroe Islands, Ice ...

passed Heddalsvatnet all the way to

Hjartdal Hjartdal is a municipality in Telemark in the county of Vestfold og Telemark in Norway. It is part of the traditional regions of Upper Telemark and Øst-Telemark. The administrative centre of the municipality is the village of Sauland. The munic ...

. The first humans in central Telemark presumably travelled by boat deep inland along the fjords that are now gone.

Post-glacial rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound a ...

eventually separated Heddalsvatnet from the ocean and turned it into a freshwater lake. The water in the lake gradually became

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

around the

Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...

, according to archaeologist Pål Nymoen. In

neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...

times Heddalsvatnet was still a saltwater fjord connected to the ocean, and was separated from the ocean around 1500 BC.Mikkelsen, Egil (1989). ''Fra jeger til bonde: utviklingen av jordbrukssamfunn i Telemark i steinalder og bronsealder.'' Oslo: Universitetets oldsaksamling. .

References

{{reflist Lakes of Vestfold og Telemark Notodden