Very nice render! Color/veggie scheme of the ground is very good too. Only thing I'd do is decrease the wetness of the stones to a certain altitude, just above water level. As the water is not really rough, it's a bit too wet.
You could take out the displacement of the foam in the little waterfall, that would probably render faster. Or take out the transparency of that small area, but that needs additional masking and a reflective shader.
Rough water in center can be done by reducing the water mask again, and using as mask for extra displacement.
