How was this amazing video done?

Not real. That’s how.

One of the commenters said, “Very nice use of forced perspective optical illusion and cleverly hiding the pump. Congrats!”

The water sure looks CG, to me. I could be wrong.

I dunno how he did it for sure, and he is definitely clever.

What I do know: the left-middle support (right-most leg of the left square) isn’t real, if that helps.

This may help too: 3D computer-rendering of the waterfall

Watch how the man’s shadow falls on the apparatus when he walks past it. It should fall uniformly, but it’s actually fragmented across different parts of the waterfall at different times. This (plus the fact that it’s impossible to begin with) suggests it’s an optical illusion.

After watching the special features on the LOTR discs showing how they played tricks with perspective and camera angles and cleverly cut pieces of furniture to make it look as if huge Gandalf and tiny Frodo were sitting at the same table eating together, when actually Frodo was some distance behind and all the edges just matched up perfectly, I think the comment quoted by @Nullo must have it.

Thanks for all of the great answers so far. It seems like most people are saying that there is a real structure being arranged using forced perspective. I have to agree with @ANef_is_Enuf‘s comment that the water looks generated, but there might be some other possibilities. What if the structure was actually taken in multiple shots and then digitally stitched together? In other words, maybe there are simply 3 wooden platforms and only one was used for each take, and then they were all knitted together in post-production?

I also agree that the shadows are the key to figuring it out.

Another 3D rendering, although it doesn’t really explain the water pushing the wheel

This one is neat, but same problem as first, and less likely since wood doesn’t really bend that way, but still. (The clip starts slow and ends fast).

Here’s yet another I found, this time of a store-bought plastic model, although whoever made this video had way too much fun with the effects (jump to the 2:15 mark to skip most of them) and made it way too long .
Here the fall and the wheel line up, but the rest of the water doesn’t.
(And here’s a less annoying picture of that in an article)

Here’s a piece of what someone said on a site:
“If you look closely at the water on the floor closest to the camera you can see that the entire base of the waterfall is not in contact with the ground, which aids in the slope of the first wooden channel.”

All of the ideas sound good to me—hidden pumps, CG, stitched-together takes. But so far as I can tell, the secret has not been leaked on the internet… which is another incredible feat, I think.

And I guess it’s good… I don’t want to be told the answer, I’d just sure like to know it.

Geez this is driving me crazy—thanks so much @gorillapaws ahaha ; )

It’s an illusion.
Simply look at the shadow the waterfall casts versus the shadow that the person moving casts.

http://www.boingboing.net/2011/02/18/is-this-how-the-esch.html

I went to visit one of my favorite websites today and saw this had been posted. It reminded me of your question. Here it is!

@podwarp—that’s really close, I think it’s probably something along those lines, but it’s not exact: the wooden pole just below point A is wrong in the diagram. Or, I should say different not wrong… with a bit of tweaking that area it’ll probably look the same.
Like, maybe partial pieces on that part, and then a thinner support behind that’s hidden?

Whoever made that drawing diagram is really clever, too. Great find!