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Originally Posted by
GrumpyDiver
I heard two different local reasons; and can't confirm either.
One is that it has rained more and the lakes drainage through fissures (it is surrounded by mountains) can't keep up influx of water.
The other theory is that the lake itself sits on top of a magma bed and periodic volcanic activitiy pushes the lake bed up and raises the water. Other than the lake itself, there that three other volcanos here; it appears to be dormant, the second one has not errupted in about 80,000 years and the third one is considered to be active, with the last eruption in the 1850s.