The Otra is the largest

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

in the Sørlandet region of

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

. It begins in

Setesdalsheiene Setesdalsheiene () is the collective term for the mountains to the west and east of the Setesdalen valley in Agder county in Southern Norway. The river Otra flows through the valley between the mountains. This area is primarily located in the mu ...

mountains at the lake Breidvatnet in

Bykle Bykle is a municipality in Agder county, Norway. It is located in the traditional district of Setesdal. The administrative centre of the municipality is the village of Bykle. Other villages in Bykle municipality include Berdalen, Bjåen, Br ...

municipality in

Agder Agder is a county (''fylke'') and traditional region in the southern part of Norway. The county was established on 1 January 2020, when the old Vest-Agder and Aust-Agder counties were merged. Since the early 1900s, the term Sørlandet ("south ...

county, just south of the border with

Vinje Vinje is a Municipalities of Norway, municipality in Telemark in the Counties of Norway, county of Vestfold og Telemark in Norway. It is part of the Districts of Norway, traditional regions of Upper Telemark and Vest-Telemark. The administrative ...

municipality in

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 ...

county. The river then flows south through

Valle Valle may refer to: * Valle (surname) Geography *"Valle", the cultural and climatic zone of the dry subtropical Interandean Valles of the Andes of Peru, Bolivia, and northwest Argentina *University of Valle, a public university in Cali, Colombia ...

Bygland Bygland is a municipality in Agder county, Norway. It is located in the traditional district of Setesdal. The administrative centre of the municipality is the village of Bygland. Other villages in the municipality include Åraksbø, Austad, ...

Evje og Hornnes Evje og Hornnes is a municipality in Agder county, Norway. It is located in the traditional district of Setesdal. The administrative centre of the municipality is the village of Evje. Other villages in the municipality include Åneland, Dåsnes ...

Iveland Iveland is a municipality in Agder County, Norway. It is located in the traditional district of Setesdal. The administrative centre of the municipality is the village of Birketveit. Other villages in the municipality include Bakken, Skaiå, and ...

Vennesla Vennesla is a municipality in Agder county, Norway. It is located in the traditional district of Sørlandet. The administrative centre of the municipality is the village of Vennesla. Other villages in Vennesla include Grovane, Hægeland, Hom ...

, and

Kristiansand Kristiansand is a seaside resort city and municipality in Agder county, Norway. The city is the fifth-largest and the municipality the sixth-largest in Norway, with a population of around 112,000 as of January 2020, following the incorporati ...

municipalities. The river empties into the

Skagerrak The Skagerrak (, , ) is a strait running between the Jutland peninsula of Denmark, the southeast coast of Norway and the west coast of Sweden, connecting the North Sea and the Kattegat sea area through the Danish Straits to the Baltic Sea. T ...

in the center of the city of

on the southern coast of Norway. The Otra is long, making it Norway's eighth-longest river. There are many large lakes along the river including:

Åraksfjorden Åraksfjorden is a lake in the municipality of Bygland in Agder county, Norway. The lake is part of the Otra drainage basin. The northern part of the lake is fed directly by the river Otra. The southern part of the lake goes through a narrow ...

Byglandsfjorden Byglandsfjorden is a lake in Agder county, Norway. The lake lies on the river Otra, primarily in the municipality of Bygland, but the far southern tip of the lake extends into the neighboring municipality of Evje og Hornnes. The river flows o ...

Hartevatnet Hartevatnet or Hartevatn is a lake in the municipality of Bykle in Agder county, Norway. It is located along the river Otra, on the south side of the village of Hovden. The lake is a good fishing spot and contains many brown trout. The Norwegia ...

, and

Kilefjorden Kilefjorden is a lake on in Agder county, Norway. The lake is located on the border of the municipalities of Evje og Hornnes, Iveland, and Vennesla. The lake is part of the river Otra. The lake is located about west of the village of Birketve ...

. There are 12 hydroelectric power plants built along the river, which produce much of the electricity for the southern part of Norway. The

salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhy ...

do well in the Otra river because the water is not too

acidic In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...

. The

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...

rocks in the catchment area at the northern end of the

Setesdal Setesdal (; older name: Sætersdal) is a valley and a traditional district in Agder County in southern Norway. It consists of the municipalities of Bykle, Valle, Bygland, Iveland, and Evje og Hornnes. The Otra river flows through the ...

valley give the water a certain buffer capacity against

acidification Acidification may refer to: * Ocean acidification, decrease in the pH of the Earth's oceans * Freshwater acidification, atmospheric depositions and soil leaching of SOx and NOx * Soil acidification, buildup of hydrogen cations, which reduces the ...

References

External links

* Rivers of Agder Setesdal Geography of Kristiansand Vennesla Iveland Evje og Hornnes Bygland Valle, Norway Bykle Rivers of Norway {{Norway-river-stub