The waters of Babylon: The drying up of the Euphrates

I have listened to debates between Preterists and Millenialists. One of the good points the Millenialists would bring up was when did the River Euphrates ever dry up? Since Revelation states:

the sixth angel emptied his bowl on the great river Euphrates. Its water was dried up to prepare the way for the kings of the East. -Revelation 16:12

The only thing Preterists said was a lot of the language about land and places did not happen literally, then they'd point to where the gospel says make way for the Lord, lowering mountains, filling valleys etc, then state its not literal, since St John the Baptist did not physically do those things.

I thought it was a valid point, but weak, and not enough to really be convincing. Then, today I read Revelation 17 where it says:
"The waters that you saw where the harlot lives represent large numbers of peoples, nations, and tongues."-Revelation 17:16

If you think about it, consider what St John is saying. Its a metaphor based where the land of Babylon was, its modern day Iraq.  One of the rivers goes through Babylon is......the river Euphrates! So Revelation 16 when it speaks of the drying up of the Euphrates River, it probably has something to do with people (perhaps dying?). The exact reading I have no figured out, but this seems the best way to deal with the text. This makes me wonder, do the people that DEBATE the book of Revelation's interpretation ACTUALLY read the Book? I've seen a number of people talk about the candle sticks of Revelation 2, no one seems to know what they are, but Revelation 1 tells you EXACTLY what they represent:

 the seven lampstands are the seven churches.--Revelation 1:20