After doing the various water fill textures last week, it occurred to us that we needed a good river bed fill texture to put under the water. Here it is in light and dark versions.
The graphic shows how you can create a couple of water layers with less transparency on each as you get toward the middle. Feather effects help soften the transitions. This is a quickie. For really good results, I'd do about twice as many water layers with more transparency on the shoreline and none at all in the middle.
The fill patterns are released under the Open Game License 1.0a.