"One theory is the water disappeared through cracks in the lake bottom into underground fissures. But experts do not know why the cracks would have appeared because there have been no earthquakes reported in the area recently, Romero said." From the article

Tell you what: I'd be expecting an earthquake.

How to remove a lake: In dead of winter, cut the surface into manageable blocks, load on trucks and transport to where you want the lake to be. Unload.

Repeat.