When the Cleurie river valley was blocked by Würmian moraine in a double vallum 50 metres (160 ft) thick, the waters of the Hohneck massif stopped flowing towards le Tholy and accumulated upstream of the deposit, forming the lac de Gérardmer.

With no outlet to the west, the waters left the lake in the opposite direction to their historic one, via the Jamagne, which flows into the Vologne downstream of the hamlet of Kichompré.

The flow of the Jamagne was widely exploited during the 20th century for generating electricity as well as for powering sawmills which were set up on its banks.

Nonetheless, the path of the Phény stream accumulated with the lower part of the Jamagne amounts to a total length of 9 kilometres (6 mi).

The flow of the river has been regulated since the beginning of the 20th century by a system of valves located at the outlet of the lac de Gérardmer.