{{short description|River in Agder, Norway}} {{For|the Royal Norwegian Navy minesweepers named after the river|HNoMS Otra}} {{Infobox river |name = Otra |name_native = |name_native_lang = |name_other = <big>Torridalselva<ref name="name2">{{Cite web |title=Informasjon om stadnamn |url=https://stadnamn.kartverket.no/fakta/648125 |access-date=2026-05-08 |website=Norgeskart |publisher=Kartverket |language=no}}</ref></big><br />Otri<ref name="name" /> |etymology = |image = Otra-Kristiansand.jpg |image_size = |image_caption = View of the river Otra running through the city of Kristiansand, where it is also called Torridalselva or Torridalselven |mapframe = yes |mapframe-zoom = 6 |mapframe-caption = Interactive map of the river (the gap in the middle is the large lake Byglandsfjorden) |subdivision_type1 = Country |subdivision_name1 = Norway |subdivision_type2 = County |subdivision_name2 = Agder |subdivision_type3 = Municipalities |subdivision_name3 = Bykle, Valle, Bygland, Evje og Hornnes, Iveland, Vennesla, Kristiansand <!-----------BASIN-----------> |source1_location = Setesdalsheiene, Bykle Municipality, Norway |source1_coordinates = {{coord|59.6284|07.4321|region:NO}} |source1_elevation = {{convert|896|m}} |mouth_location = Skagerrak, Kristiansand Municipality, Norway |mouth_coordinates = {{coord|58.1434|08.0134|display=inline,title}} |mouth_elevation = {{convert|0|m}} |river_system = Otra |basin_size = {{convert|3752|km2|sqmi|abbr=on}} <!-----------PHYSICAL CHARACTERISTICS-----------> |length = {{convert|245|km|mi|abbr=on}} |width_min = |width_avg = |width_max = |depth_min = |depth_avg = |depth_max = |discharge1_location = |discharge1_min = |discharge1_avg = {{convert|150|m3/s|abbr=on}} |discharge1_max = <!-----------FEATURES-----------> |tributaries_left = |tributaries_right = |waterbodies = |waterfalls = |bridges = |ports = }}
The '''Otra'''<ref name="name">{{Cite web |title=Informasjon om stadnamn |url=https://stadnamn.kartverket.no/fakta/28 |access-date=2026-05-08 |website=Norgeskart |publisher=Kartverket |language=no}}</ref> is the largest river in the Sørlandet region of Norway. It begins in Setesdalsheiene mountains at the lake Breidvatnet in Bykle Municipality in Agder county, just south of the border with Vinje Municipality in Telemark county. The river then flows south through Bykle, Valle, Bygland, Evje og Hornnes, Iveland, Vennesla, and Kristiansand municipalities. The river empties into the Skagerrak in the center of the city of Kristiansand on the southern coast of Norway.
The Otra is {{convert|245|km}} long, making it Norway's eighth-longest river. There are many large lakes along the river including: Åraksfjorden, Byglandsfjorden, Hartevatn, and Kilefjorden. There are 12 hydroelectric power plants built along the river, which produce much of the electricity for the southern part of Norway.<ref name="snl">{{Cite SNL|Otra|Otra|2026-05-08|Heggstad|Ragnar|2024-11-26|editor2-first=Geir|editor2-last=Thorsnæs|editor3-first=Jo Halvard|editor3-last=Halleraker}}</ref>
The salmon do well in the Otra river because the water is not too acidic. The calcareous rocks in the catchment area at the northern end of the Setesdal valley give the water a certain buffer capacity against acidification.<ref>{{Cite web |title=Mindre forurensning og mer laks i Otra |url=http://www.dirnat.no/content/500034188/Mindre-forurensning-og-mer-laks-i-Otra |url-status=dead |archive-url=https://web.archive.org/web/20200409175721/http://www.dirnat.no/content/500034188/Mindre-forurensning-og-mer-laks-i-Otra |archive-date=2020-04-09 |access-date=2012-02-10 |publisher=Dirna.no |language=no}}</ref>
==References== {{reflist}}
==External links== *{{commons category-inline|Otra}}
{{use dmy dates|date=May 2026}} {{authority control}}
Category:Rivers of Agder Category:Setesdal Category:Geography of Kristiansand Category:Vennesla Category:Iveland Category:Evje og Hornnes Category:Bygland Category:Valle, Norway Category:Bykle Category:Rivers of Norway