Canyon - 2nd Attempt

[RichTwo]

Pretty much it's the same as my previous.  I moved a few trees and added waves (maybe too much?) and whitecaps to the river - which increased render time 10X, even after removing reflective and luminous features.  I tried taming the waves by masking, but it seemed to have no effect.  Oh, well - here it is.

[Dune]

You don't really need transparency, which will decrease rendertime. For a really wild foaming river, you could even try just colors (greens, blues, whites for froth) and no-RT reflective shader, which would be superfast. Maybe in some calmer section (by mask; painted or PF) plug in a RT- reflective shader on a surface shader. You can even locally smooth the waves a bit by the smoothing function.

[René]

This looks promising. You already have a good point of view and a beautiful composition. The quiet river in your first attempt has a beautiful reflection and is a resting point in an image with a lot to see. I think a realistic wild river will require a lot of work, and if you don't do it right, it will ruin everything.
If you opted for a calm river, all you have to do is decide how big the waves should be in relation to the trees and you can concentrate on the rest of the image.

[Stormlord]

The point of view is good, but!!!
The waves on the surface does not really match reality. Make them a lot smaller and you will see, the result is more convincing!

But nevertheless a good start

STORMLORD

[bobbystahr]

This looks promising. You already have a good point of view and a beautiful composition. The quiet river in your first attempt has a beautiful reflection and is a resting point in an image with a lot to see. I think a realistic wild river will require a lot of work, and if you don't do it right, it will ruin everything.
If you opted for a calm river, all you have to do is decide how big the waves should be in relation to the trees and you can concentrate on the rest of the image.

I quite agree..liked the first one better as well...but good advice from René