It seems almost inevitable. The river cruise season gets underway and then either high or low water levels due to heavy rains or lack thereof cause some disruptions. And this season is no exception.

Since the start of the month, river cruise lines have been dealing with higher than normal water levels on Europe’s Rhine, Danube, Rhone and Seine rivers, which forced several river cruise lines to alter some of their itineraries.

The challenge is that there is no telling when or how severely these highs and lows will happen. But river cruise passengers should perhaps be made aware of the possibility and of the ways in which high or low water levels could impact their trip, because as we have seen year in and year out, some disruptions, however minor, almost always occur at some point in the season.

“So far, it doesn’t seem to have deterred clients from river cruising but if these dramatic rain or drought weather patterns continue with more and more sailings affected, it may start to have an impact in the future,” said Linda Dinsmore, a river and small ship specialist who runs the website The River Cruise Lady.

Dinsmore admitted that she doesn’t talk to clients about water levels before they take a river cruise, and that so far clients haven’t been asking about water levels, “so I think it’s a situation that you hope doesn’t happen.”

That said, she had clients that ran into some issues last week on the Rhine River, where they were driven further up the river to board their ship due to the higher waters, an adjustment that “was not too disruptive,” she noted.

When water levels are higher than normal, river cruise vessels can’t squeeze under the low bridges they need to bypass to complete their sailings, and when water levels are low they can’t sail through shallower waters where there isn’t enough clearance for the ships’ drafts. So, each river cruise line undertakes a variety of contingency plans when this happens, including (but not limited to) busing passengers to ports and destinations they can’t reach by ship, having them stay in a hotel for an extra night or two if the ship cannot get to them, or having passengers swap ships, which entails boarding another ship on the other side of an impassable bridge or stretch of water, a strategy Viking River Cruises employed for this most recent water rise.

Viking said on its website that it has contacted guests whose cruises need to be adjusted due to this month’s higher water levels, including those on the May 13 Passage to Eastern Europe cruise aboard Viking Lif, which is now taking place on sister ship, Viking Aegir; and those on the May 13 Grand European Tour aboard Viking Aegir, which is now taking place on sister ship, Viking Lif. (Viking said it does not anticipate any further itinerary changes beyond these sailings.)

While this season’s disruptions are nowhere near the mayhem caused by the historic floods in Europe two years back, they serve as a reminder that river cruising, despite all its potential and success, still has some notable vulnerabilities. And while river cruise companies have grown very accustomed to working around water-level issues, for customers the required itinerary changes can still serve as a disappointment if they weren’t made aware of the possibility in advance.“The mainstream cruise lines are getting better at handling these conditions and it’s not something that occurs too often or for too long when it does,” said Pete Larson, owner of River Cruise Guru. But, he added, “I always advise my clients about fluctuating river levels and how it could affect their cruise … Many new river cruisers come from the ocean cruise market where this isn’t something they may have experienced or thought about.”