Europe's rivers run dry as drought forces hard choices on water use

The Rhine and the Danube, the two arteries that bind Europe's industrial heartland to the Black Sea, are running at levels not seen in modern records. The consequences are no longer theoretical. In Romania, the last working reactor at the Cernavoda nuclear plant went offline on Thursday because the Danube has fallen too low to supply cooling water. The plant's two reactors normally provide around 20 percent of the country's electricity. In Hungary, output at the Paks nuclear plant, also cooled by the Danube, has dropped sharply; authorities have dumped roughly 145,000 cubic metres of rock into the riverbed to build a sill that raises water at the cooling intake.

Further west, the Rhine's decline is choking Germany's chemical and steel sectors. Covestro, one of the world's largest polymer producers, has told customers it cannot guarantee deliveries because barges cannot carry full loads through the shallow stretches near Kaub, a notorious bottleneck between Mainz and St Goar. Fuel, grain and chemical shipments are backing up or moving by rail and road at significantly higher cost. The European Environment Agency has documented a clear trend: river discharge across much of the continent has been declining for decades, and the frequency of extreme low-flow events is rising.

The engineering fix: deepening the Rhine's navigational channel

The disruption has revived a project that has sat on the statute books for nearly a decade. A plan to deepen the navigational channel on the Middle Rhine between Mainz and St Goar was written into German federal law in 2016. The work targets the Kaub passage, where the river narrows and low water repeatedly halts freight. Industry associations argue that repeated droughts make the investment overdue. They see a deeper channel as a pragmatic defence of supply chains: if barges can operate with less water, the economic damage from each dry spell is reduced.

The logic is seductive in its simplicity. Dig the river deeper, keep the barges moving, protect the industrial model that depends on cheap waterborne transport. But the hydrologists who study the river system say the logic is flawed. Thibault Datry, research director at the French National Research Institute for Agriculture, Food and Environment (Inrae), puts it bluntly: "You don't create water by digging out rivers." His argument rests on the hydraulic connection between a river and the aquifer beneath it. Lowering the riverbed increases the gradient that draws groundwater into the channel, pulling down the water table across the surrounding landscape.

Why hydrologists warn against digging deeper

The cascade of effects Datry describes is not speculative. When groundwater levels fall, drinking-water catchments yield less, irrigation becomes harder or more expensive, and wetlands and floodplain meadows dry out. "If groundwater levels fall, you reduce water in drinking water catchments, water available for industry and water in meadows or agricultural fields," he said. "There will be a cascade of negative effects on many other uses." The term he uses for this kind of response is maladaptation: an intervention that solves the immediate symptom while worsening the underlying condition. Even a deeper channel will eventually run dry if the catchment receives less recharge. "At some point there won't be enough water left, even for the river that has been dug out."

There is also the ecological cost. Riverbed sediment is not inert filler; it is habitat. "When you remove sediment from the bottom of a river, you remove the habitat of all the river's inhabitants," Datry explained. The Rhine and Danube are already heavily modified. Further engineering risks locking in a simplified, less resilient ecosystem that cannot buffer the very extremes climate change is delivering.

Nature-based solutions: wetlands as sponges

Datry's alternative is to work with the landscape's own storage capacity. For centuries, European land management prioritised moving water off the land as fast as possible, drainage ditches, straightened channels, levees that cut rivers off from their floodplains. As drought becomes more frequent, the challenge is the reverse: slowing water down, letting it soak into soils, and holding it in wetlands and reconnected floodplains. "Nature stores water in wetlands, which are nothing more than enormous sponges," he said. "It's the best way of storing and slowing water."

Restoring floodplains and reopening former river bends to the main channel can recharge aquifers, reduce peak flood flows, and maintain baseflow during dry periods. The sixth assessment report of the Intergovernmental Panel on Climate Change assessed the effectiveness of such nature-based solutions and found they can contribute significantly to adaptation when implemented at scale. But many of Europe's wetlands are degraded or lost entirely. The European Commission's Water Framework Directive and the newer Nature Restoration Regulation set targets for restoration, yet implementation across member states remains uneven.

Reducing evaporation is the other half of the equation. "Planting trees, creating shade, maintaining forests along waterways or restoring them are all part of the solution," Datry said. Riparian vegetation lowers water temperature, cuts evaporative loss, and stabilises banks. These measures are not quick fixes; they take years to mature. But they address the water balance at its source rather than chasing the symptom downstream.

The growing competition for a shrinking resource

Behind the technical debate lies a political one. Less water is reaching some river basins, and precipitation patterns are shifting. The result is intensifying competition between households, agriculture, industry, inland navigation and energy production. Each sector has legitimate claims. Nuclear plants need cooling water to generate low-carbon electricity. Chemical plants need feedstock transport to keep factories running. Farmers need irrigation to maintain yields. Cities need drinking water. The current framework allocates water through a patchwork of national permits and historical rights that were not designed for systemic scarcity.

Datry argues that the only durable solution is negotiated allocation. "There is no other solution than to bring all users around a table, present them with scientific facts and decide together what we want," he said. "It isn't logical for one use of water to take precedence over all others, and it wouldn't be socially accepted. We have to share a limited and very precious resource in a sustainable, fair and lasting way." That conversation has barely started in most basins. The Rhine Commission and the International Commission for the Protection of the Danube River provide forums for cooperation, but their mandates focus on water quality and flood protection, not quantity allocation during drought.

What the data shows about Europe's water stress

Eurostat figures for inland waterway transport show a clear correlation between low-water years and freight volumes. In 2018, a severe drought year, goods transported on the Rhine fell by more than 10 percent compared with the previous year, while rail and road freight rose sharply. The German Federal Institute of Hydrology (BfG) reports that the number of days with water levels below the critical 78 centimetre mark at Kaub has increased from an average of 20 days per year in the 1990s to over 60 days in the past decade. The trend is not linear; it is stepped, with each extreme summer resetting the baseline.

The energy sector faces a parallel squeeze. The International Energy Agency has warned that thermal power plants, nuclear, coal, gas, are increasingly vulnerable to cooling-water shortages. In France, EDF has repeatedly cut nuclear output during heatwaves because river temperatures exceeded regulatory limits for discharge. The Cernavoda shutdown is the first time a European reactor has been taken offline entirely due to low river levels, a precedent that regulators and grid operators will be watching closely.