Can I call you Galph?
Take a look at what RobA has done here. One problem you can run in to with rivers is that, in the real world, they don't really display the fact that they're moving until they're interrupted. As a result, you'll need objects to create turbulence downstream themselves that would show how the water moves. Longer "tails" to your objects suggests a faster flow, while more vibrant/brighter suggests more power in the water, causing it to churn up more at those places.
Wynn has some amazing water effects here on a city map. In the river, although he hasn't added the bridges yet, he's already drawn in the turbulence created by their supports. You get the impression that the longer turbulence tails have faster water in them (or at least I do). In the bay at the mouth of the river, he's also beautifully rendered effluent patterns spreading out, which mitigates the change from flowing to mostly stationary water. You typically only see those types of patterns generated at rivermouths with relatively high organic matter in them that empty into bodies with strong tidal forces. I haven't the foggiest idea why you see that, it's just what I've noticed looking at Google Earth images over the years. Maybe an actual geologist or cartographer could shed some light on that. My point being that I wouldn't try to replicate that second effect in your lake, as I don't think it would actually occur, given the size of it. That island is a great place for a turbulence tail though, and you could always add a few more rocks into the river to give it some character and churn it up a bit.
There's a good show of short-length high turbulence here by Wannabehero. You may want to add small versions of that in your mountain streams. Since they come very directly out of the mountains, rather than winding down through them, there must be some very steep changes in grade, and probably even a few waterfalls. Don't be afraid to widen them into pools and narrow them into rapids either. I'm not too sure of the scale of this map, but I think that adding more fine details to your shorelines would give you opportunities to show off the motion of your rivers, and create interesting places along the route. Not sure if this is for a story, a game, or just for fun, but characters will be involved at all, they'll be drawn to landmarks, and you may see your story unfolding as a result of the map, rather than the other way around.