I think there is a third tailwater in Va. Its Back Creek in Bath Co. I've never fished it.
I know most of the tailwaters that I fish up here (around Louisville) are more for flood control. So I mainly use USGS stream data and try to guess if its worth my while to travel.
Besides Cumberland, I fish Brookville up in Indiana. The USGS site for it is http://waterdata.usgs.gov/in/nwis/uv?site_no=03276000. 3' and below for stream flow is the best.