I floated the Holston three days last week with clients. The water temperature was 65 degrees when we started early in the morning and reached 70 degrees by about 1 o'clock with a noticeable drop in fish activity.
Waterwolf is right about water temps changing very rapidly on the Holston. The river has warmed 5 degrees in less than 10 days. While 70 degrees will probably not kill trout on it's own, stress at 70 degrees can. Especially if care is not taken in landing and releasing fish. Let the water warm another 5 or 6 degrees and the fish are in real trouble.
The temps did stay cooler for a longer period of time this year but when Cherokee lake is out of cold water that is it. It happens every year..at least every year I have fished it ( since they started stocking trout). It doesn't make much difference what section you are in when the lake temperature reaches a certain point no cold water gets released. We normally stop fishing the river when that happens, yes ,you can still catch fish but a higher number of those released will not survive.
There is no private water on the Holston river. It is a public fishery. Hope this helps. Good fishing to everyone.