Just when you thought it was safe to get back in the pandemic-snarled water, Europe is having another cataclysmic summer. This time, it's not pandemic red tape, but what looks set to be the continent's worst drought in history. Around 63% of the land across the EU and UK had either drought warnings or alerts, according to the EU's European Drought Observatory last week -- and that figure was issued before the UK declared a drought in eight out of 14 areas. New alerts are pouring in every day.

While the landscape is tinder-dry, water levels are plummeting. Rivers and lakes are drying up -- and as well that having devastating effects on trade and industry, it's also hitting a sector that was already on its knees thanks to the pandemic: tourism. Worse, experts say that this is a worrying sign of things to come.

Drama on the Rhine

The 766-mile Rhine is one of Europe's most important trade routes, with container ships plying their way around its looping bends.

It's also a classic cruise itinerary. But now some of those waterway dreams seem set to run aground.

On Saturday, the water level at the German town of Kaub -- a critical juncture -- slipped to just 36 centimeters, or 14 inches, according to official figures. That's devastatingly low -- at 40 centimeters, commercial shipping becomes unprofitable.

None of this is news, says Clare Weeden, principal lecturer in tourism and marketing at the University of Brighton.

“Anybody who operates river cruise boats would have had an understanding of this because of the way the climate has changed in the last 20 years,” she says, adding that low levels on the Rhine and Danube have seen incidents of passengers being bussed from one destination to another for the past five or six years. But while the cruise companies may have foreseen this, clients haven't.

“River cruising is becoming much more popular, particularly for active people,” she says.

“You dock early, spend all day enjoying a city, then go back to the boat at the end of the day and sail on. It's much quieter [than mass cruising]. But drought and climate change has coincided with the increase in river cruising.”

But she warns that, with the climate crisis, Europe's traditional river cruising is “definitely going to suffer” and predicts “the industry is likely to reset as a result.”

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Helen Prochilo of cruise specialist Promal Vacations calls European river cruising “the hottest thing we are selling this year.”

A little too hot: Although none of her clients have been affected yet, she says that among her fellow agents, one had a client's cruise canceled this week, and another had their itinerary adjusted. River cruise alterations tend to be very last-minute, because they depend on water levels and rain.

Prochilo says that many river cruise boats are specifically built with flatter hulls to deal with low water levels. If in difficulty, those with swimming pools on board can empty them. Railings, furniture and even the captain's bridge are designed to be lowered, while passing under bridges in high water, adds Rob Clabbers, president of Q Cruise + Travel, a Virtuoso member agency in Chicago.

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Not that that prevents problems. In 2017, Prochilo booked a Rhine sailing herself with Emerald, only to find “very low levels” of water.

“The ship emptied the pool to lighten the load and we could actually feel the ship tapping the bottom of the river,” she says.

“We never saw the captain after the first night. He stayed on the bridge to ensure the ship was carefully handled.”

Others weren't so lucky. Prochilo says that they floated past another cruise line offloading their passengers onto buses.

“The ship builds and experience of the captains is very important when the weather is like this,” she says. And she's not taking any chances -- watching the water levels drop on the Rhine over the past month has made her advice would-be bookers to wait till next year.

“I'm also advising them to cruise earlier in the season as the river levels don't seem to be a problem if traveling in May or June versus July or August,” she says.

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For those who've already booked, she makes regular calls to the river cruise lines checking the conditions.

Those conditions are pretty devastating -- levels are “exceptionally low” in some areas, German officials told CNN on Friday.

In fact, Weeden believes that Rhine cruises “will be a thing of the past” before too long.

So what will happen this year? CLIA, which represents cruise operators, says:

“River cruise operators ... are monitoring the situation and responding appropriately in liaison with the relevant authorities.

“The safety of guests and crew will be central to any decisions relating to itineraries. Where any changes are planned, operators are working hard to minimize any disruption.”

River cruise specialist Riviera Travel said in a statement: "We have seen minimal disruption so far as we have put measures in place, such as ship swaps and minor itinerary changes, to ensure guests can still make the most of their cruises.” A ship might leave a destination a couple of hours early, for example.

Viking Cruises' website states that “low water levels will affect select river itineraries.” Impacted travelers will be contacted by the cruise line.

To mitigate issues, Viking runs sister ships sailing the same itinerary, but in opposite directions. If there's a problem on one side of the river, guests can transfer to the other ship.

Clobbers say that “many lines” do this. “If low (or high) water prevents passage at a certain point, the line simply moves the downstream sailing passengers (and their luggage) to the upstream ship and vice versa. The ships turn back to their point of origin with their 'new' passengers who simply continue their journey without too much interruption.”

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And if all else fails, they use the boat as a hotel, and bus travelers to their destinations each day. It may not be as romantic, but it's effective.

“The distances traveled by river cruise are not very long, so sometimes passengers will even get to see more as buses travel faster,” says Clabbers, from personal experience.

“On a Uniworld cruise a few years ago, high water kept the ship in Vienna for three days, and the company did a fantastic job in setting up additional tours that showed us sights that were not included in our original schedule.”

Got a Rhine cruise booked for this year? Don't cancel, he says -- you may be penalized. Just try to go with the flow. But if you haven't yet booked, and want to travel this year, he suggests looking at alternatives like the Seine or the Douro.

No river unscathed

Not that they're much better. The picture is bleak for all Europe's rivers.

In France, some parts of the famous Loire River have dried up almost completely. Some canals have also been closed. “I think canals are a no-go,” says Weeden, about the future.

In the UK, the source of the Thames has moved five miles downriver for the first time in history.

And of course there's the Danube. The situation on Europe's other prime tourism river is looking blue, too. Emergency dredging is currently taking place on the lower river, in Serbia, Romania and Bulgaria.

Although there are “no problems” on the Austrian stretch, authorities told CNN on Friday, the situation in Hungary -- perhaps the most famous part of the Danube -- is more concerning.

The drought is already devastating for trade -- an average 1,600-tonne vessel can now only navigate the river without any cargo, according to the Hungary Tourist Board. So far, the situation for tourist boats is holding out. The Mahart Passnave Passenger Shipping Ltd., which runs river cruises, is still operating all the way along the Danube, although some stations are closed north of Budapest. Between Szentendre and Visegràd, around 15 miles north of the capital, the river takes a major loop. “Some stations [there] have been closed for about a month, as ships cannot moor due to the low water level,” says a representative of the Hungary Tourist Board.

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But not all companies are managing to navigate the river -- and not all of those are having as good an experience of bussing as Clabbers did.

“I had travelers whose ship couldn't make it to Budapest -- they had to board their ship in Komarno” -- about an hour away in Slovakia -- says tour guide Julia Kravianszky.

“Travelers flew to Budapest, from where they were taken to Komarno by bus, and they were bussed back to Budapest the next day for their city tour, only to return to the ship by bus after the tour.”

Things are already looking different in Budapest, perhaps the most beautiful city along the river.

“The Danube is visibly lower at the moment, it's been really low for two or three weeks now,” says Kravianszky.

“Margaret Island looks bigger, because all the rocks at the bottom of the river are visible now. Some parts of the old Margaret Bridge destroyed in World War II are visible now, too.”

But don't cancel your trip just yet. The river still “looks large and majestic -- it doesn't really give the image of a dried-up river,” she says. For now, it's the locals who can tell the difference.

'If it's like this next year, I'll retire'

And then there's Italy, where the Po River is at historic lows, and has close to disappeared in places. It's disastrous news for the entire country -- and has also put an end to tourism on parts of the river this summer.

For the past 20 years, Stefano Barborini has rented boats and taken visitors out on his stretch of the Po, near Parma. This year, he hasn't been able to manage even a single outing.

“I've been on the Po for 40 years, and this has never happened before,” he says. “We've had droughts before, but this low -- never. There's been erosion of the bottom so the river has actually got deeper. Usually it's navigable year-round.”

This year, he says, “It started very early -- there was no rain and everything dried up.”

His small boats usually dart all over the river, and up close to the beaches, to see things -- Barborini usually points out medieval remains, and has found things like buffalo bones and even mammoth teeth, he says, while out on excursions.

He normally rents boats to fishermen but, he asks, “Where would they go to fish?” Anyone using a boat in the Po needs to be extremely experienced right now -- even professional fishermen are not able to navigate, he says.

Barborini has 30-odd excursions lined up for September. By then, he hopes that the water levels will be higher. Even then, it could be difficult to load and unload passengers, as they'll have to navigate steep walks on and off the boat.

“If it's the same next year, I'll retire,” he says.

Dried-up lakes

It's not just rivers. Italy's largest lake, Garda, is nearing its lowest ever levels, adding a stretch of land around the peninsula of Sirmione, which famously ends with some impressive Roman ruins -- or did, until now.

And parts of Lake Tisza, Hungary's largest artificial lake, are no longer accessible by boat, according to Kravianszky. “In Abadki [a popular rental spot] the water level is 50 centimeters [20 inches] lower than the minimum required,” she says.

“They stopped renting out boats, and many owners were forced to remove their boats from the water. The Tisza lake cross-swimming event scheduled for the 13th of August was canceled.”

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Tisza borders the Hortobágy National Park, a landscape of plains and wetlands that has UNESCO World Heritage status. Animals have been brought here to graze for around 2,000 years.

“It's one of [Hungary's] defining characteristics... it's heartbreaking to see how it slowly dries up, how the birds have started avoiding the area or nesting less around the National Park,” says Kravianszky.

From drought to flash floods

The other side of drought is flash flooding -- something that has hit the US in the past few weeks, with Yellowstone suffering a once-in-500-years incident in June, and two people being killed in Las Vegas this week.

Barborini says that he's worried for the Po this fall. “Two years ago the water levels were high in January and February, because when the snow fell on the Alps it immediately warmed and came down in levels that weren't normal,” he says.

“The climate has changed a lot in the past five or six years.”

An uncertain future

“Travel has a front row seat as climate change unfolds in the destinations we visit and, if this becomes a standard summer, it will massively impact our industry. Unless urgent action is taken on climate change, the reality is that extreme weather is going to have an impact on the destinations and communities we visit.”

That's the opinion of Susanne Etti, environmental impact manager at Intrepid Travel, who calls this summer “a wake-up call for the entire sector.” She's not alone.

“The places where we can ski have shrunk -- the same will be true for river cruising in 20 years. There won't even be (environmentally damaging) snow cannons to help out,” says Justin Francis, CEO of Responsible Travel.

Weeden thinks that as Rhine tourism dries up, river cruising companies will look elsewhere. “Ships are mobile; companies are not loyal to destinations. They will move and find new areas for river cruises beyond the traditional European ones,” she says. They'll also look beyond rivers. Market leader Viking, she says has been “heavily investing in ocean cruising these past few years.”

This year, she says, has shown us that “climate change isn't just about heat, but also about water.

“As the weather becomes more unpredictable, I think there's going to be some kind of reset.” (CNN)

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