Here are my flow impressions(note: this is for the actual flow in the river. sometimes you might have to subtract 2500 if the generators are running).

1000 minimum
2500 medium
4000 medium high
6000+ is high

2500 is a great stable level. At higher flows there are some epic spots and scary rapids/holes. It wasn't nearly as good at 1200. Class 2-3 with some bumpy spots.

It should be running for the next while. Its great at the current level.