Make a layer and use the brushes to paint white and a secondary color for depth and add some mist by adding another layer and changing the brush and the opacity. If you want to post the image or send it to me @: retrocity@renderosity.com i'll do it and build a step-by-step. The approach is the same regardless if you use Bryce, Vue, or any other 3D render package. I've found you get the most believable waterfalls if you do them by hand in PS.