Actually, there is a better way to gauge the Upper Gauley release. The Gauge at Belva is below the takeout for the Lower Gauley and therefore several hours behind the Dam, but is still a pretty good indicator of what's going on. Subtract the flow of the meadow and you have the water on the Gauley. Since they're at summer pool with a decreasing flow coming into the lake, they will likely maintain a fairly steady slowly decreasing release.
The Belva gauge shows 1040 CFS right now and the Meadow gauge shows 277. The difference is 763. There are other tribs, like Peter's Creek, but they usually aren't of significant import unless there's a lot of rain and then the release from the dam is usually high anyway.
http://waterdata.usgs.gov/usa/nwis/uv?03192000
I've run the Upper down to 200 and it's still a great day on the water. At 700+ you should have a fantastic time. Run Iron Ring multiple times, it's too easy to carry up and do again and it's one of the best rapids at this water level.
The diversion tunnel that makes the New River Dries dry holds 10,000 CFS, so whenever the New is over 10,000 there is water in the Dries. 5 feet on the new is 10,000, 5.5 feet makes a bony run on the Dries, but 6.5 or 7 feet translates to 4,000-6000 on the Dries and makes for a great run with some fantastic surfing waves and more gradient than the New River Gorge.
Have fun, the Gauley will be a hoot this weekend.
Hanley