Let me see if I can remember. I started with a stroke width of 5.0 and ended with a stroke width of 1.0. For example if you can find the Village of Oldroot, (It's just north of the Ethereal Coast). When I redrew that river that is just to the west of Oldroot using the 03 circle pencil and adjusted the paths so the new river would follow the route of the old and then applied the Tapered Stroke Path from the edit menu I was getting a river that was all the same width, from the Kunguzun Mountains down to the Ethereal Coast.

I have to redrawn all my rivers and lake again(no biggie) because I merged them all together and applied a G Blur to them. So I can't get them back to a normal straight line. I tried to erase parts like Ramah suggested but I can't do it that way with my damn hand shake. I end up erasing way to much of the line.