So Len Testa and Jim Hill were talking about Pandora on the Disney Dish and they mentioned how some of the waterfalls were projected, so that they would look more real for the forced perspective. They fall at a slower rate than a small stream of water would, to make them appear farther away. They said the projections were even visible during the day.
I knew that couldn't be right. No way those waterfalls were projections. So on my second trip I zoomed in my video camera... And what did I see? They're wheels!
They're physical wheels with a water texture carved into them rotating with only a small section visible from the front. There's some netting placed at the bottom to make it look like mist below it. It's a convincing effect, but once you see it up close you'll never be able to un-see it.