The wetlands that surround the lake spread over an area of 0.63 km, and are enclosed into an ancient shoreline. The origin of this larger open water lake remains unclear. If the lake level has remained stable, then the reduction in lake size is solely due to the conversion of these open waters into wetlands. Alternatively, lake shrinking might reflect a slight lowering of the average lake level, possibly due to a more efficient drainage at the lake outlet. In any case, it cannot be excluded that the lake level reverts in the future to its ancient stand, flooding areas that have now been filled and urbanized. Besides, the outlet drains to a cave that might get partially of completely obstructed by debris following large storms. Water ponding upstream of the cave could result in an increase in the lake level of  4,0 ± 0,3 m before surface overflow is achieved near the cave.