Why would they just now be drying up if that was all done with before 70AD?
I believe what you are referring to is called a drought. I wouldn't read too much into this, considering all the times the End-Times Alarmists have been wrong.
Recall Hal Lindsey's false prophesy of the 1970's, and how that turned out. He was on talk shows, news shows, you name it, plugging his book. When asked what would happen if his prediction was false, Lindsey said, "I'll be a bum."
LOL! He got that prophesy right, but that is the only one. His buddies have rehabilitated his image to the naive masses so he can still sell his books; but not to us old-timers.
Back to the Euphrates, I recommend against trying to take a book of prophecy literally, when they are loaded with figurative speech. For example:
"And I stood upon the sand of the sea, and saw a beast rise up out of the sea, having seven heads and ten horns, and upon his horns ten crowns, and upon his heads the name of blasphemy." (Rev 13:1)
If you take the other parts of the prophecy literally, shouldn't you also take that one literally? And how about this:
"And the second angel poured out his vial upon the sea; and it became as the blood of a dead man: and every living soul died in the sea." (Rev 16:3)
That doesn't mean they are not good imagery; only that generally a literal interpretation leads to false conclusions. If you read the history of the time, there are good explanations for all the events of the Revelation (well, most all, in my case.) Even "wars and rumors of wars" from the Olivet Discourse makes sense when you consider the Pax Romana period that began under Augustus was a long period of peace that lasted until a few years prior to the Jewish-Roman war that began about 66A.D. That kind of peace is unheard of in modern times.
For example, Chilton wrote on the Euphrates imagery:
"The image of the drying of the Euphrates for a conquering army is taken, in part, from a stratagem of Cyrus the Persian, who conquered Babylon by temporarily turning the Euphrates out of its course, enabling his army to march up the riverbed into the city, taking it by surprise.2] The more basic idea, of course, is the drying up of the Red Sea (Ex. 14:21-22) and the Jordan River (Josh. 3:9-17; 4:22-24) for the victorious people of God. Again there is the underlying note of tragic irony: Israel has become the new Babylon, an enemy of God that must now be conquered by a new Cyrus, as the true Covenant people are miraculously delivered and brought into their inheritance. As Barrington observes, the coming of the armies from the Euphrates “surely represents nothing but the return of Titus to besiege Jerusalem with further reinforcements”; 22 and it is certainly more than coincidental that thousands of these very troops actually did come from the Euphrates.23 [David Chilton, Days of Vengeance, "Judgement From The Sanctuary", p.407]
That last footnote was this:
"There followed him also three thousand drawn from those that guarded the river Euphrates;" [Flavius Josephus, Wars of the Jews, V.1.6]
Even the reference to the bloody sea in 16:3 above, has some historical significance:
"But some of them thought that to die by their own swords was lighter than by the sea, and so they killed themselves before they were drowned; although the greatest part of them were carried by the waves, and dashed to pieces against the abrupt parts of the rocks, insomuch that the sea was bloody a long way, and the maritime parts were full of dead bodies; for the Romans came upon those that were carried to the shore, and destroyed them; and the number of the bodies that were thus thrown out of the sea was four thousand and two hundred. The Romans also took the city without opposition, and utterly demolished it." [Flavius Josephus, Wars Of The Jews, III.9.3]
" … and the Romans leaped out of their vessels, and destroyed a great many more upon the land: one might then see the lake all bloody, and full of dead bodies, for not one of them escaped." [Flavius Josephus, Wars Of The Jews, III.10.9]
Philip