I like the red water too. I think it sets the map into a certain style that I really like. Unfortunately, I agree, the rivers look transparent. And because they are over the top of forests, it makes the river look like it is hovering above the tree line. That is unfortunate because I love the rest of this map. Since I don't really know how to use photoshop or gimp I have no suggestions for you on how to change it. Maybe you could re-draw the area of the forests where the river goes so there is a canopy split that reveals the rivers?

I know that is an awful lot of work so it probably isn't feasable.

Anyway, I'm really looking forward to watching this one become a completed map.