Following an intense heat wave in June and severe wildfires in southern France and Spain, Europe's summer of climate-fueled crises continues with rivers across the continent running low.

Parts of the vital Rhine, Danube and Po rivers have fallen to historically low levels, threatening freight transport, the wider economy, and agriculture, with farmers warning of increased prices due to poor harvests amid the drought. 

Along the Danube, cargo and cruise ships can no longer pass in some places. In Hungary, Romania and Croatia, sunken ships and cars have reemerged as riverbeds dry out. 

In German cities, including Cologne and Düsseldorf, people can now walk across parts of the Rhine where strong currents normally flow. River levels could fall even more dramatically in the coming days.

The water crisis is being intensified by global warming driven by the burning of coal, oil and gas. Low water levels are also taking a growing toll on ecosystems — and could eventually drive up the cost of clean drinking water. 

The impact on nature 

Parched fields, millions of hectares of lost harvests and exposed riverbeds are among the most obvious consequences of the drought. But underwater ecosystems are suffering too.

As water levels fall, rivers become warmer and contain less dissolved oxygen, increasing the risk of fish die-offs, explained Jeanette Völker, a scientist with Germany's federal environment agency, the UBA. 

"Especially along the Rhine, you can see how the gravel banks are drying up. These are habitats for mussels and invertebrates, which in turn serve as food for fish. This puts enormous stress on these ecosystems. Mussels cannot move away quickly enough and die off," Völker told DW.

Drought, intense sunshine, and high nutrient loads from agricultural fertilizers also encourage algal blooms harmful to fish.

These effects were seen in 2022 on the Oder River in eastern Germany. High temperatures, low water levels and elevated salinity allowed a toxic invasive algae to spread. Around 1,000 metric tons of fish died along parts of the German-Polish border river.

Experts do not expect a repeat of the Oder disaster on the Rhine this summer because oxygen levels remain sufficiently high. But the danger to the wider freshwater ecosystem remains.

What dwindling rivers mean for drinking water costs 

The Rhine and the Danube are fed by numerous tributaries that are also running low. These tributaries are crucial because their lush, reed-filled banks act as natural filters, allowing water to slowly pass through layers of soil that help remove pollutants before water reaches underground wells. 

"Much of our drinking water is what's known as 'riverbank filtration,'" said Hagen Koch, a researcher specializing in climate adaptation and resilience at Germany's Potsdam Institute for Climate Impact Research.

In other words, Germany's drinking water comes from those wells. But drought is weakening this process. Pollutant concentrations are increasing because roughly the same volume of wastewater — largely from industry and sewage works — is discharged into rivers even as water levels fall. 

"If the ecosystem is damaged — that is, the animals and plants that contribute to water purification — this results in significant additional costs. Additional treatment is needed to supply clean drinking water to millions of people," Koch told DW. 

German industry groups estimate water supply costs could rise by up to 30% as a result of climate change. By 2035, additional investments of up to €14 billion could be needed for improved water treatment systems, as well as deeper mains and upgraded reservoirs designed to keep water temperatures low and limit microbial growth.

The situation has drawn attention to a broader debate over water use. While households pay for the water they consume, several industries — including mining and agriculture — are exempt from water abstraction fees in many German states.

To conserve water, authorities in some German cities are currently severely restricting withdrawal from streams and rivers by private individuals. In Cologne, residents who violate the ban face fines of up to €50,000 ($58,000). 

Low water levels hitting the economy 

Low water levels in Germany's rivers are already taking a significant toll on the economy. Some vessels are carrying just a fifth of their usual cargo, delaying production and driving up prices. Germany's steel, chemical and petroleum industries have been hit particularly hard.

Energy supplies are also under pressure. Hungarian Prime Minister Peter Magyar has urged households and businesses to conserve electricity. He warned the country could face an unprecedented energy crisis after low water levels in the Danube forced the shutdown of the Paks nuclear power plant. 

Romania blasts rocks as Europe searches for solutions 

Politicians are exploring emergency measures in response to the situation. In Romania, the military blasted apart a rock formation in a branch of the Danube to secure the cooling water supply for the Cernavoda nuclear power plant and avoid a shutdown.

Germany's transport minister brought together representatives from industry, ports and inland shipping on August 6 to consider short- and long-term solutions to the crisis. One proposal under discussion was deepening parts of the Rhine's navigation channel so shipping can continue despite low water levels.

Critics warn that further dredging and deepening of shipping channels would accelerate water runoff, lower groundwater levels, and cause floodplains to dry out more quickly, ultimately do little to solve the problem in the long-term.  

Instead, they're calling for the expanded use of low-water vessels, as well as a shift from freight transport to rail. Koch supports the development of ships with shallower drafts, but notes such changes require significant time and investment.

For Jeanette Völker, the solution lies in restoring parts of Europe's heavily modified rivers. Reconnecting floodplains, protecting wetlands and restoring peatlands would help landscapes retain more water and improve resilience during future droughts.

Reservoirs and dams may also play a role where they are environmentally acceptable. But experts warn adaptation alone will not be enough. Without climate protection and a rapid reduction in greenhouse gas emissions, any investments are little more than a drop in a fast-flowing river.  

 This article orginally appeared in German and was translated by Josh Axelrod.