Mandalselva

Mandalselva, Mandalsåni, or Marna (English: Mandal River, Mǫrn) is a river in Agder county in Norway. The river has its origins in the mountains between Ose in Setesdal and the Upper Sirdal valley. The river flows south to its mouth at the North Sea at the town of Mandal. The river is 115 km long and flows through the municipalities Åseral, Lyngdal, and Lindesnes. The largest tributaries are Monn, Logna, Skjerka, Kosåna, Logåna, and Røyselandsbekken. Skjerka, Monn and Logna all flow into the lake Øre in Åseral which is considered the beginning of the main Mandalselva river. The river passes through the villages of Kylland, Bjelland, Laudal, Heddeland, Øyslebø, and Krossen.

Hydropower development
Hydropower development of the river on a larger scale started in 1930. At present there are six power plants along the river and its upper tributaries: Logna, Smeland, Skjerka, Håverstad, Bjelland, and Laudal.

The drainage basin covers an area of 1800 km2. The mean flow of water in the river is 85 m3/s. During flooding periods in the spring and autumn, water flow can be far greater. The highest stream flow in recent times were measured in October 1987, when it passed about 970 m3/s at Kjølemoen in Holum.

Salmon and trout
The original salmon stocks are extinct as a result of acid rain, but extensive liming has led to a better environment in the river, and a new salmon stocks are established. It was caught 8785 kg of salmon and sea trout in Mandalselva in 2015.