I'd say creating a Color Math ->Multiply node would do the trick. Plug the output of that color math node into the reflection input of the root node, plug the output of the Reflection node into one of the Color Math inputs. You'd have to make a node setup that somehow determines the distance to the bottom. I haven't the foggiest idea how to do that. The P (position) node only works on the current object, which is the water plane. You could paint a depth map of your river/lake in a 2D program. White for highest, black for lowest, greyscale in between. Then you could make an image_map node containing the depth map, plug the output into a Color_Ramp node, choose four different colors for the depth effects, and plug the output into the other input of the ColorMath_Multiply node. Just thinking aloud. I don't know if it'll work.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

My gallery   My freestuff