exlude waterbody from Directional Light

[rLiebert]

Hi,

is there a way to exclude waterbody from the directional light source. My directional light is set pretty low and from the back to have a nightly backligt atmosphere situation. But my Water (a river) is just almost flat bright with this. I added extra lights to give it nice reflections, but as soon as I turn on directional light its too much. Lightchannels doesnt work in this case.?

Thank you

[rLiebert]

Here is what I mean: I don`t want my river to be affected (or much less) by the direct light