Goodness, if you took this shot handheld at 1/5 and with a 310mm lens, it's a miracle that it isn't just a blur! You would need to shoot at at least 1/250 or 1/500 to prevent camera shake with a lens that long! Anyway, I think this is a very successful shot, and I like it very much.

A very serene shot, OB. I assumed you'd manipulated these colours in Photoshop, but perhaps from your question you didn't?

Water in a river often takes on different colours if there are differences in depth, or currents, or turbulence. Sometimes water of different temperatures is mixing as well. In this case I suspect that the water in the foreground, which is clearly flowing less turbulently, is also reflecting the sky colour more as a result. It's hard to know when you can't see what other factors might be at play.