I took the coordinates shown on that earlier post, dropped them into Google Earth and then used the historical imagery selection to push it back to 2005. It appears to be a quarry and you can actually see some earth moving equipment down in the hole, water only at the far end.
If it was being dug out as recent as 2005 and perhaps later, I think what we are likely seeing is just water. I can't imagine how a fish population could have populated it unless it was stocked heavily.
Hmm? You know how they use huge quantities of water for fracking? I wonder if it is being used as a reservoir for water for such purposes.
Still a cool looking place!
Brad
