Rhine River

(3:15 p.m. EDT) -- Water levels on the most heavily trafficked European rivers are slowly returning to normal after drought conditions through July and August racked up dozens of river cruise cancellations and itinerary changes.

Difficult weather conditions have caused logistical problems for cruise lines attempting to navigate rivers both too shallow and too swollen throughout the 2015 season.

In addition to the disruption to cruises caused by low water this summer, a combination of heavy rainfall in the Alps and spring snowmelt in May waylaid ships from at least six river cruise lines, forcing the lines to put alternative measures into place in order to complete itineraries.

Thanks to some much-needed rain in mid-August, water levels are finally on the rise on Europe's largest rivers. No weather-related cancellations on the Rhine or Danube have been announced for more than a week. The Elbe, however, is lagging behind, and Viking River Cruises has continued to cancel sailings on the Elbe through August 22.

(For more, read How Wind and Water Could Affect Your River Cruise -- and What to Do About It)

Elbe River Most Affected

Why are some rivers still affected and not others? Water levels on major commercial shipping transit routes like the Rhine and Danube Rivers are more strictly managed and are able to recover more quickly. The Elbe, which runs through Germany and the Czech Republic, is more often subject to problems with fluctuating water levels.

AmaWaterways' Vice President Kristin Karst said that changing weather patterns in Central and Northern Europe have caused the line to scupper plans to expand to the Elbe River.

During a discussion regarding upcoming new-build ships and their deployment, on a christening cruise for the line's newest Danube-based ship AmaSerena, Karst said the Elbe -- of all Europe's rivers -- has been hardest hit by climate change.

For the river cruise lines that have decided to sail on the Elbe River, the impacts of fluctuating water levels have inspired some creative solutions.

Perhaps the best example is CroisiEurope's forthcoming 2016 launch of a uniquely designed ship called Elbe Princesse. The 80-passenger vessel is powered by two side-mounted paddlewheels and sports an ultra-shallow draft, allowing it to cruise year round -- even during the now common periods of low water. Elbe Princesse joins sister ship Loire Princesse, launched this year on the Loire River in France to counter similar problems with low water.

"With a changing climate and unpredictable weather, it is impossible to predict high or low water levels and their impact on river cruise operation," said Michel Grimm, Sales Director for CroisiEurope. "This is one of the reasons that CroisiEurope introduced its innovative paddlewheel ship on the Loire this year and will be introducing a similar ship on the Elbe next year. Thanks to these ships' shallow drafts and advanced paddlewheel technology, they are able to navigate low water -- something that vessels with regular propulsion and bigger drafts are unable to do."

Looking Ahead

Water levels in Europe right now are rising, to the relief of river cruise operators. A Viking representative told Cruise Critic that recent rainfall meant that life on the Rhine and Danube was returning to normal for river cruise lines and their passengers.

But continued rainfall is less than certain. The European Commission's latest long-range forecast predicts that drier-than-normal conditions will persist through September in Central and Northern Europe.

Whatever weather conditions may come, river cruise lines, which book trips well in advance, are looking toward a busy autumn and the ever-popular Christmas Markets season.

Their secret weapon against unpredictable weather and water levels? Ship swaps. For the larger lines sailing on the Rhine and Danube, sailing two ships from either end of an itinerary that meet in the middle allows them to bypass un-navigable stretches of river by simply moving passengers between ships.

For passengers planning a river cruise, it's important to note that not all river lines have a large enough fleet to allow for ship swaps. Depending on the line, a river cruise itinerary hit by high or low water can mean the trip essentially becomes a bus tour with nights spent on a grounded ship.

Cruise Critic member forums regularly run threads keeping tabs on where water levels are. To offset weather issues that might arise during a river cruise, most people recommend choosing your sail dates carefully and purchasing solid travel insurance with cancel-for-any-reason coverage, just in case the itinerary ends up radically changing.

--By Jamey Bergman, Editor