Outside the Berm had a great post recently with Pre-Fantasmic shots of the drained Rivers of America. Here are some pictures circa February 1992. Fantasmic contruction was in full-swing.
In the picture above (enlarged) the pieces of metal tubing are gas lines for the fire effect. Sometimes the black lifts didn't raise. Either one of the side projectors or lifts could go out but the show would be cancelled if the center lift didn't work.
On the left side, near Fowler's Harbor, a black bag tube blocks the river. This bladder functioned as a dam to allow the backside of the river to be filled
After the river was filled the water screen lifts wouldn't always go down all the way so they were marked off with floating barrels or boxes. Keel boats, rafts, and canoes could then safely avoid getting beached. Anybody have pictures of those markers?