A river flowed out of Eden to water the garden, and there it divided and became four rivers.
Genesis 2:10

The following verses talk about rivers in the Middle East. The descriptions are like the Tigris, Euphrates, Nile, and a mysterious river called Pishon, but these rivers don't have a common source today, which means logically means they never did. Obviously, they aren't really the same rivers that we know. They are four completely different rivers that existed in the general area of Mesopotamia before the Flood. People after the flood re-used names, much as Americans re-used European placenames.