From my understanding...... The hydro plant controls that whole area. First there has to be enough water for the lock to work, second if the hydro plant is going to run they push the water into it closing the apprpriate gates to achieve this, thirdly they have a deal with the park to keep the fossil beds dry as much as possible during June, July, August, and September to help them get people out to the park.
The energy cost in the Louisville area is 15% lower than it would be if that hydro plant was not there, but the majority of that electricity is shipped out of the area since it cannot be stored.