There are no real groups. TU used to have some pull but lost all credibility many moons ago. It pretty much has to be done on an individual basis. Call, send letters, call, call, and call some more. Every year there is a meeting which is open to the public and both TVA and TWRA are there and the whole focus of the meeting is the coldwater tailwaters.
AS soon as I know the date I will be happy to post. It is the best forum for voicing an opinion and they do listen and do care what we think, or at least they used to.