If a drawdown were completed, it would take a very long time for the silt to dry out. When the muck/silt gets to dry out, it compacts itself. This would buy some time, but inevitably our impoundment would continue to fill with silt. In the long run, such compacted silt would be more difficult to remove by hydraulic dredging, which is the most efficient dredging method.
Winter drawdowns would also radically shorten the boating season. Drawdowns would have to begin early enough for aquatic amphibians and reptiles to burrow into the bottom for hibernation, without later being exposed to subfreezing temperatures. The duck-hunting community would not like drawdowns either.