Started a YnAMP TSL Huge(?) Earth map [ ont recall the exact name, but it is the ~120x60(?) one, without warnings about being too big to load] . Chose Elizabeth I/England. Game started properly right next to Thames, just N of Cliffs of Dover.

While I was spending the turn thinking where to settle, Cardiff plopped almost next to me. Decided to reroll city-states and restarted game.

Blam. No more Thames.

Okay, I figured maybe rivers are randomly placed too.

But by now it is Late Medieva era, I've got Caravels and explored most of Earth.

There are ZERO rivers anywhere.

Seems like a bug?