What is "uldalsana"

Uldalsåna is a lake in the municipalities of Birkenes and Froland in Aust-Agder county, Norway. It is part of the Tovdalselva river drainage basin. On the southeastern end of the lake, there is a hydroelectric dam which releases water into the waterfall, Hanefoss, on its way down to the Herefossfjorden near the village of Herefoss.