The lake is surrounded by mountain ranges, and is fed by three tributaries, all located in the northern end.

The lake was formed by a tectonic earthquake with the magnitude of a 6.8 on the Richter scale that hit the southern portion of the island of Negros, and caused landslides in the southern ends of both the Balanan and Nasig-id ranges in Siaton.

The fallen rocks and soil dammed the Balanan River that flowed between these mountain ranges forming a 25-hectare (62-acre) "humerus" bone-formed lake oriented along the Northwest-Southeast line.

This proposal was endorsed by the Department of Environment and Natural Resources, Region 7, in January 1987.

The dam, called Sampong (meaning "to close"), blocked the flow of Balanan River, turning it into a lake.