Interesting about the water situation.
"If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans…..A civilization reading one of our messages could be billions of years ahead of us"
[Reminded me of Carolyn Palamas talking to Apollo in “Who mourns for Adonais?”]
Even if their technology only were, say, a thousand years ahead of ours, that could make them so unbeatably superior we might not be able to offer any effective resistance to them at all. And a thousand years is nothing on a cosmic timescale- not even a million years is.