Geez. Hoover dam is not exploded and there were no DUMBs built under Lake Mead when that dam was built in 1932 and there has certainly been no one under it surreptitiously drilling holes, as there are always people diving boats around and looking at every inch of the water and shore. Do the people who come up with this stuff have any idea of how big a hole that would have to be, how much manpower, how big and obvious the drilling rig? That the water displaced would have to find an equal area to occupy, so these fancied DUMBs would be as big as Lake Mead? Where is the rock pile developed by this excavation? What happened to critical thinking around here? Human mismanagement ruined bigger bodies of water, e.g. the Aral Sea. Look it up, it was the fourth largest inland body of water in the world. My vote is overused and underfed by runoff. The only way there is a hole draining it is if some ancient volcanic void happens to be at a lower elevation and a crack developed.