Nice MOC and the waterfall technique works well. I like the solid white bits representing the broken water, but can't help but think they are a little small, given the hight of the falls. But overall the scene makes a very pleasing impression. Best of luck in the comp! :)
I think Deus has a very good point about the water at the base of the falls. A little blue paper underneath might have done wonders. It is nit-picky though, and I'm sure you'll be onto round 2 with this quality build. Best of luck!