Eidselva lies in Nome municipality in Telemark. It rises in Flåvatn, and runs into Norsjø in Ulefoss. The river is part of Skiensvassdraget, and an important part of the Telemark Canal. On the stretch from Ulefoss to Flåvatn there are five sluices (14 sluicegates), with a total rise of around 57 meter. In the river, there are four hydroelecric power stations: Eidsfoss, Vrangfoss, Ulefoss and Aall-Ulefoss.