I know the Track between Nurnberg and Passau ,
The Problem is the Track Around around the city and before a certain lock,
the goverment wants to make an extra lock but the greenies ( political party) makes protest.
You never can say in front about waterlevels, captains can sail with a couple of inches water on the ship. I know rivercruise companies decide in the last minutes to sail or to stop the track.
Captains and Cruise companies do everything that is possible to continue the trip.
I worked on a ship with a indoor-swimmingpool, if we know we had low water, one or two hours before we reached the track with low level we emptied the 50 tons of swimwater into the river to continue the track. Result , we had a couple of inches under the ship, we could heard the sand grinding to the ships bottum , sometimes we hit the ground. Nothing worried about this, it is all sand and no stones.
So they can never tell you some days before about the waterlevels
If the water raises a couple of inches during the night the ships will start and will cruise directly.
Again experienced captains and cruise companys do everything to continue the track, even it depence on a couple of inches. A local shower can make the difference.
It is not like a hurricane , you can see that on the satelite and so on. You can tell them what way the are going.