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 245 kilometres (152 mi) long, making it Norway's eighth-longest river.

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

The calcareous rocks in the catchment area at the northern end of the Setesdal valley give the water a certain buffer capacity against acidification.