It may be the same river but the river is not the "same" for the river is ever flowing, the banks are ever eroding and the river once was not and in the future will not be again.
Well, as long as it is the same river, then, even if the river is not the "same" what Heraclitus said was false. As Wittgenstein said, we should not confuse the notions of identical with same. Necessarily, X is self-identical, even if X changes. This is true for all X. By the way, that something ceases to exist, or that something begins to exist, is not a change in that something. "What a change in Bill, he vanished!". "What a change in Bill, he was born!".
Yes, I know, word games. That is, trying to say clearly what is true, rather than saying nothing idiotically.