I am not sure if the ones in people's yards are the same found in all our major bodies of water, and our small creeks, too. I do know that crawdads can survive for a long amount of time out of water, so maybe it is not unreasonable to think they could travel far distances. However that would not explain how they could live without water in someone's yard, unless the tunnels under the cones they build go down to a water table of some sort. More info needed on this.