The first thing that caught my eye in this picture was the waterfalls and then the rainbow. Nice capture. There's a few things that I think think would have made this image better. First, there is no real sense of perspective here, it's just not very obvious. The blurring of the water works wonderfully with waterfalls but here the highlights are too blown. Perhaps a shorter shutter speed would have worked better. The colors look muted, a little bit of saturation would make this a much more appealing photo. This image has to potential, it just has to be tweaked a little.
If you have any questions or comments about this critique, please feel free to PM me.
You'd have to find Ron to see the perspective. He's at the top of the falls on the left hand side. In finding Ron, the size and magnitude of the falls will be realized. That's the perspective!