A few years ago somebody found a muscle that was on the endangered species list. The colony is located somewhere between the tail waters and before Barren and Nolin feed into the river. Since finding the almost extinct muscle the corp of engineers have been working with the Nature Conservatory Project. They wait for approval from them as to when to discharge water. If flood conditions exist they release water. If under normal conditions they wait until the water temperature is at a certain point then they release water. From what I was told the young/newly hatched muscles will have a higher mortality rate if the water is above a certain temperature.
For the last 4-5 years it has been anywhere from early to late November when the draw down has started. I found out the information a couple of years ago when I was at the office at the dam buying a parking permit. I asked why the drawdown did not start on Oct. 15 like it has been for many years. That is when I was told the information about the rare muscle and how it affects the drawdown. This is also the same reason they no longer draw the lake down 11ft. They now only draw it down 7ft. A call to the office at the dam may give you an idea as to when it will start.