Nidelva (Agder)

Nidelva
Nidelva near Blakstad in Froland
Location of the river
Nidelva (Agder) (Norway)
Location
CountryNorway
CountiesAgder, Telemark
MunicipalitiesGrimstad, Arendal, Froland, Åmli, Nissedal
Physical characteristics
SourceConfluence of Nisserelva and Fyresdalsåna rivers
  locationHaugsjåsund, Nissedal, Telemark
  coordinates58°56′26″N 8°30′04″E / 58.9406°N 08.5011°E / 58.9406; 08.5011
  elevation160 metres (520 ft)
MouthSkaggerak
  location
Arendal, Agder
  coordinates
58°26′06″N 8°42′49″E / 58.4349°N 08.7137°E / 58.4349; 08.7137
  elevation
0 metres (0 ft)
Length221.7 km (137.8 mi)
Basin size4,011 km2 (1,549 sq mi)
Discharge 
  locationRykene, Arendal
  average114.4 m3/s (4,040 cu ft/s)
Basin features
River systemArendalvassdraget
Tributaries 
  leftKarlsåna, Katteråsåna
  rightBlekevja, Gjøv, Sigridneskilen, Songeelva, Trevann, Rore
WaterbodiesNelaug
WaterfallsKastefossen

Nidelva is the main river in the Arendal drainage basin in Agder county, Norway. The 221.7-kilometre (137.8 mi) long river begins at the confluence of two rivers: Nisserelva and Fyreselv. The confluence is located by the village of Haugsjåsund in Nissedal municipality in southern Telemark county. The river flows south into the Skagerrak at the city of Arendal. The watershed covers 4,011 square kilometres (1,549 sq mi) and has an average waterflow of 114.4 cubic metres per second (4,040 cu ft/s) at Rykene near the mouth. The highest waterflow ever recorded on the river was 1,200 cubic metres per second (42,000 cu ft/s) in the autumn of 1987.