Middle Rhine Gorge (Kaub)

The Middle Rhine Gorge is free-flowing — no locks, no dams, nothing holding the river up when rain stays away upstream. That's exactly what makes it beautiful, with castles and vineyard terraces lining the narrow turns between Rüdesheim and Koblenz, and exactly what makes it the reach cruise lines watch first. A dry spell over Switzerland and southern Germany shows up here before almost anywhere else on the river.

Kaub is the single gauge the whole industry uses as shorthand for Rhine conditions, because it's consistently the point where a shallow-water limit gets reached first. When it drops toward its low-water marks, lines start swapping ships for shallower-draft vessels or moving guests between two ships on either side of the shallow stretch by bus. A fast-rising Rhine can also pause sailing here for a shorter window, though that's a different kind of disruption from a sustained low-water stretch.

That's why, on the classic Rhine run between Amsterdam and Basel, this is the one stretch that shows up in trip reports and forum threads years after a low-water autumn — 2018 is still the year Rhine cruisers bring up first, and it's the reason this reach gets its own page rather than a line in a general Rhine summary.