Water levels on the Rhine River are subject to seasonal weather patterns. If the river is too high, vessels can't fit under bridges or go through locks. High water levels are usually caused by snow melting in the Alps and heavy rains in the spring and early summer.
On the flipside, droughts and extreme heat waves -- which have both become more common in Western Europe over the last three decades -- causes the water level of the Rhine river to drop. When Rhine water levels are extremely low, ships can't sail because they could run aground.
It's generally more common for water levels on the Rhine to be low, rather than high. This is most likely to happen during the hottest and driest time of year, from late July through August and sometimes onwards. In 2022, for example, Europe had one of its driest years and summers on record. Germany's drought that year severely impacted Rhine water levels, causing shipping disruptions and even some cruises to be rerouted over land at parts.
The shallowest part of the Rhine is the scenic UNESCO-listed Middle Rhine Valley. There is a water level measuring station at Kaub that constantly monitors water levels on this stretch of the river. That also means this part of the Rhine is more vulnerable when water levels increase or decrease.
River cruise ships have very shallow draughts, which generally enable them to sail even when water levels are low or when there is a drought. In fact, river ships can often continue cruising the Rhine even when heavy commercial barges have to stop. All river cruise lines monitor water levels on Rhine river cruises and have plans in place to make modifications to itineraries if needed.
River cruise lines can handle extreme Rhine water levels in a number of ways. In some cases, coach buses will cover the ground between destinations and to each port's excursions if the river is impassable. But you'll have to keep in mind that you'll spend more time on the bus getting from point A to point B, as distances by road between ports are generally longer than distances on the river. If these distances become too great, the line might organize overnight stays in hotels along the way.
Larger lines like Viking operate numerous ships on the Rhine, meaning that passengers might sail one part of the itinerary on one vessel and then be transferred -- with luggage -- to exactly the same cabin on another ship for the rest of their trip.
The worst case scenario is that Rhine water levels cause your cruise to be canceled, but this is rare. In those cases, lines will contact passengers to explain the situation and often provide the opportunity to rebook the cruise at no extra cost. However, it should be remembered that water levels are unpredictable and can change quickly, so communication might be close to the departure date.
If you're booked on an upcoming Rhine river cruise, there's a useful Rhine River water levels thread on Cruise Critic's forums that monitors and reports on water levels on the Rhine. Bookmark it so that you have it ready, as it's regularly updated with data and intel. You can also check out other helpful sites such as
Rhine Forecast, which report on Rhine River water levels by months of the year.
Updated April 21, 2023