How to get your rivers in the right place

[Trismegistus]

The definition of "endorheic" is that the basin is closed, not that is part of that list. So it's not "by definition". If an outlet formed from the Caspian to the Black Sea, the Caspian would cease to be endorheic. As you point out a little later, the Saint Lawrence drains the Great Lakes into the Atlantic, so the Great Lakes watershed is not endorheic. Lake Baikal also has an outlet in the Angara River, a tributary of the Yenisei River, which flows into the Arctic Ocean.

I didn't know that about Lake Baikal. Thanks for pointing that out. I should have caught myself with the obviously inconsistent statement about the Great Lakes. I've been looking at fractals lately and river systems are sort of like that, especially as you look at them in closer and closer detail.