Ecologist Christina Gruber grew up by the Danube River. As a child, she often walked along the river with her parents and learned to swim there. There was a local saying: a child only truly learned to swim when they swam to the small island in the river.

Years ago, for the first time, people could walk to the island by stepping on the riverbed without getting into the water. Gruber felt that the familiar Danube River had seemingly "betrayed" her.

This summer, the river retreated even further. In the past, during low water levels, the World War II shipwrecks in the river would only show a small part; now, some of the wrecks are almost completely exposed. Islands, docks, and man-made facilities that had long been hidden underwater emerged one after another, leaving only a narrow strip of water in the river channel.

This scene is extremely powerful and cruel, and it visually shows how much water the Danube has lost," Gruber told The Paper (www.thepaper.cn). "Seeing the Danube like this makes me feel sad.

This change has also shaken Austrians' long-standing sense of water security. Austria, with its Alps, glaciers, snow cover and dense river network, rarely regarded drought as an urgent threat in the past. Today, this certainty is being broken.

The crisis is far from over in Austria. At present, Europe is gearing up for the fifth heatwave this summer, with high temperatures expected to spread from west to east. The maximum temperature in some parts of Spain may reach 43°C again, and then it will spread to Central and Eastern European countries such as Germany. Record-breaking high temperatures have triggered severe wildfires in many places, and the ongoing drought has caused the water levels of several important rivers to drop to historical lows. The Rhine, Danube, and multiple rivers in France, Italy, Germany, Hungary and Switzerland are in crisis, and shipping, agriculture, industry and power systems are all being affected.

As "once-in-a-century" events become frequent, Europe is facing not just an unusually hot summer, but a systemic crisis that impacts ecosystems, infrastructure, and energy systems.

European Rivers Cross the Drought Threshold

Low water levels on the Danube in summer are not uncommon, but Gruber believes this year's severity is unprecedented. If 2018 could be called a "drought", this year is a "severe drought".

Under normal circumstances, the upper reaches of the Danube River in Germany, Austria, Hungary and other regions have relatively sufficient water volume, while the flow slows down and the water volume decreases when it enters the southern and lower reaches. This year, almost all river sections are facing water shortage, with the lower reaches being particularly severely affected.

In Budapest, Hungary, the water level of the Danube once dropped to 41 centimeters, only 8 centimeters higher than the historical low recorded in 2018; in Romania, the level fell to the lowest point since 1996.

Low water quickly turned into economic losses. The Danube River is responsible for transporting grain, coal, fuel and industrial raw materials. The navigable water depth of some river sections is less than two meters, making it impossible for cargo barges to sail fully loaded, and a large amount of grain is stranded in silos. Losses caused by the suspension of tourist ferries, ship agroundings and voyage cancellations are also continuously increasing.

The Rhine is under even more severe pressure. Originating in the Swiss Alps, flowing through six countries and eventually emptying into the North Sea, this river stretches approximately 1,280 kilometers in length. It is one of Europe's most important economic arteries, transporting millions of tons of cargo each year.

On August 10, the Rhine's average flow at the Lobith monitoring station in the Netherlands dropped to 614 cubic meters per second, lower than the 620 cubic meters per second recorded in 1947, marking a new low since the official hydrological records began in 1880.

Notably, the low flow in 1947 occurred in November, but this record was broken earlier in the summer. Jan Verkade, a hydrometeorologist at the Dutch Water Board, pointed out that the reason behind this is the unusually warm spring this year, which caused the snow in the Swiss mountains to melt about three months earlier than usual. Subsequently, rainfall has been delayed, and the low flow may persist.

To avoid running aground, ships on the Rhine have been forced to reduce their load, leading to a rise in unit transportation costs. If the low water levels persist, the supply of coal, fuel and industrial raw materials may be disrupted, and even enterprises along the river may need to cut their output.

The drought is also spreading to land and groundwater. Data from France's meteorological department shows that July 2026 was the hottest July on record in the country and the third driest, with the rainfall deficit reaching nearly 70%. As of August 1st, 63% of France's groundwater levels were below normal, and nearly 70% of the country had implemented water restrictions.

England and Wales have experienced the worst drought in July since records began in 1836. Europe's water crisis has spread from river channels to groundwater, agriculture, food, transportation and industrial supply chains.

In Austria, some residents have had to deepen their wells. Rivers cannot provide enough water for the surrounding land, and the floodplains, which originally could absorb floods and recharge groundwater, are isolated from the main river channels, leading to a continuous decline in groundwater levels.

Gruber noticed that the grass leaves in the garden used to be covered with dew every early morning in the past, but now they are still dry. "This means that what the local area has lost is not only precipitation, but also the original humidity in the air and on the surface.

Insufficient winter snow and rain, below-average spring precipitation, coupled with the early arrival of an early summer heatwave, have left both natural and man-made water storage systems unreplenished. As a result, Austria's forests and soils have become extremely dry.

Meteorologist Guido Cioni pointed out that Austria is experiencing an extreme heatwave this year, with the country's highest temperature continuously setting a new record and reaching 41.2 degrees Celsius within two days. Among the top 20 highest temperature readings in the country's history, 17 occurred consecutively over several days in 2026.

Fish Trapped, River Ecosystems Accelerated to Imbalance

Ecosystems bear the brunt of low water levels and high temperatures first. Some streams connected to the Danube River are gradually drying up, and Gruber and his colleagues catch stranded fish every day and move them to areas with more water. They also keep receiving calls from the public reporting that fish have died due to dried-up riverbeds.

Rising water temperatures further exacerbate the crisis. In the past, the water temperature of the Danube River in Austria was relatively low, but now it is warming earlier and earlier, disrupting the cycles of fish spawning, foraging and migration. Fish may spawn prematurely, but at this time aquatic vegetation and food sources have not yet formed, and suitable spawning grounds are also very limited.

Gruber said that for some fish species, a rise in water temperature of approximately 0.5 degrees Celsius could alter their living environment. When the water temperature in certain river sections reaches about 26 degrees Celsius and remains high for an extended period, the fish may die. High temperatures will accelerate the fish's metabolism, increasing their food requirements, while at the same time reducing dissolved oxygen in the water and stimulating algae reproduction, ultimately leading to an imbalance in the ecosystem.

Climate change is happening too fast for river ecosystems to keep up," she said.

For a long time, hydropower stations and other river projects have also cut off fish migration routes and altered their habitats. Along the Danube River in Austria, professional fishing is now difficult to sustain, and according to Gruber, there may be only one or two professional fishermen or fishing families left there.

The disappearance of fishermen not only means the decline of a livelihood and culture but also deprives the river of a set of "early warning systems". Fishermen who have lived by the river for a long time are often the first to detect pollution, fish abnormalities and water quality changes, while scientists usually can only conduct investigations after the fact.

The Danube's significance to Europe is far more than just a waterway. It transports goods, provides food, connects cities, and also carries culture and history," Gruber said. Cities like Vienna developed along the river, and the historical "Danubian Monarchies" were even directly named after it. What the Danube has lost is not only water and shipping capacity but also the economic and cultural foundation that Europe has relied on for hundreds of years.

From Hydropower Reduction to "Blowing Up Rivers to Protect Power

The low water levels in the rivers have also hit the Achilles' heel of Europe's energy system.

Austria has been developing hydropower on a large scale since the 1960s. In the past, this was regarded as a successful low-carbon energy path; today, the river water that sustains hydropower is dwindling. Preliminary information shows that Austria's hydropower generation in the first quarter of this year may be about 30% lower than the normal level.

When the water level is too low, the water turbines struggle to operate normally. To prevent the downstream river section from drying up further, hydropower stations must also increase the discharge flow to protect the aquatic ecosystem. This means the contradiction between power generation and maintaining the basic water volume of the river has become increasingly prominent.

After the reduction in hydropower output, Austria may need to import more electricity, including both renewable energy and possibly power generated from fossil fuels. Although wind power and solar energy in the eastern region can provide some supplementary supply, the longer the low water level persists, the greater the pressure on electricity prices and supply will be.

Nuclear power is also highly dependent on river water. Roger Spautz, the head of Greenpeace France and Luxembourg's nuclear energy projects, said that some riverfront nuclear power plants in France, Hungary, Switzerland and Romania have either shut down or reduced power due to excessively low water levels or high water temperatures.

About 65% to 68% of France's electricity comes from nuclear power. According to data from Électricité de France (EDF), as of August 10, 2026, the reduction in nuclear power output caused by high temperatures had reached 15.2% of the nuclear installed capacity, the highest level this year and also the highest since the relevant data was first released in 2015.

Nuclear power plants face two constraints: water volume and water temperature. When the water level is too low, the power plants may not be able to obtain sufficient cooling water; when the river water is overheated, discharging the cooling water will further raise the water temperature, threatening the aquatic ecosystem, so the power plants must reduce their output or shut down.

In addition, transboundary rivers are also subject to agreements between countries. Spoetz took France's Chooz Nuclear Power Plant as an example. Located on the Meuse River, the plant needs to shut down when the river level drops below a certain threshold to avoid continuing water intake that would affect shipping on the Belgian side.

The situation in the Danube River basin is even more tense. Hungary's only nuclear power plant, Paks I, supplies more than 40% of the country's electricity. During the period of extremely low water levels, the river once approached the minimum standard for the normal operation of cooling water intake pumps, forcing the power plant to reduce its output. Hungarian authorities have stated that the nuclear power plant is "only a few millimeters away" from a complete shutdown.

Eszter Mátyás, the head of Greenpeace's Natural Gas Project for Central and Eastern Europe, told The Paper that to maintain the operation of the power grid, hundreds of large industrial enterprises in Hungary have voluntarily reduced energy consumption during the evening peak power consumption period, and local governments, enterprises and residents have also been called on to save electricity.

In Romania, Unit 1 of the Cernavodă Nuclear Power Plant was once shut down, and Unit 2 was also approaching the standard for forced shutdown. To ensure that the reactor obtained cooling water, Romania declared a state of emergency and deployed military personnel to conduct controlled underwater blasting on the rocks of the Danube riverbed. Meanwhile, barges filled with stones were sunk to direct more riverwater to the water intake of the nuclear power plant.

Water shortages also affect coal-fired power plants. Power plants such as Kostolac in Serbia face both insufficient cooling water and difficulties in obtaining coal by barge because rivers have lost navigability. The Iron Gate Hydroelectric Power Plant, located on the border of Romania and Serbia, is also affected; in Slovakia, seven out of the eight turbines of the country's largest hydroelectric power plant were once shut down.

In Mátyás's view, this crisis shattered the traditional perception that nuclear and thermal power could provide stable "base-load electricity" unaffected by weather. Thermal power facilities require both sufficient water and water with a sufficiently low temperature. During severe heatwaves, falling water levels and rising water temperatures often occur simultaneously, while electricity demand for air conditioning drives up power consumption.

Solar played an unexpected "savior" role in this crisis. When temperatures in Hungary exceeded 40°C and air conditioning consumption surged at noon, photovoltaic facilities supplied a large amount of electricity; in Romania, solar energy could meet up to 70% of the midday electricity demand during certain periods.

But Mátyás emphasized that solar energy alone is still not enough to support the entire system. Hungary has insufficient energy storage capacity, and the development of onshore wind power has long been restricted. The output of photovoltaic power drops rapidly after sunset, while nuclear and hydropower plants affected by drought struggle to fill the gap, making the period from evening to night the highest-risk time. In contrast, Bulgaria, which has vigorously developed battery energy storage in recent years, has shown the potential to shift solar energy from daytime to nighttime use.

This drought raises a more complex question than "nuclear energy or renewable energy": as extreme climates become increasingly normalized, any energy system that is overly concentrated or relies on a single resource or single facility may reveal new vulnerabilities.

Faced with the crisis, the current response measures of European governments and energy enterprises are still relatively limited, mainly including reducing the power or shutting down nuclear power plants, temporarily relaxing cooling water discharge standards, encouraging enterprises and residents to save electricity, and altering river courses through engineering means. However, Spoats and Magash warned that these measures can only provide temporary relief, and may also push up water temperature, damage river beds and fish migration routes, failing to solve the high dependence of energy facilities on water resources. The two believe that Europe should reduce its reliance on centralized, water-intensive power generation facilities, accelerate the development of wind power, solar energy and large-scale energy storage, and improve the power grid, demand response and cross-border interconnection. Otherwise, continuing to expand the construction of thermal power generation projects such as nuclear power along the increasingly warming river banks may exacerbate long-term climate and financial risks.

Climate Change Reduces Recharge, River Engineering Accelerates Water Loss

Gruber believes that the fundamental cause of the worsening drought in Europe is climate change. The Danube and Rhine rivers are highly dependent on glaciers and snowpack in the Alpine region. In the past, these natural water storage systems slowly released melted water across different seasons, providing a steady supply to the rivers.

Today, rising winter temperatures have reduced snowfall, caused snow to melt earlier, and led to continuous glacial retreat. During unusually warm springs, the snow that should have been reserved for summer melts months in advance, leaving rivers without water supply when the weather is hottest and water demand is highest.

In the past, the Danube River basin usually experienced a summer rise in August, when the high-altitude snow in the Alps melted. Nowadays, snowmelt often occurs as early as June. The water does not disappear entirely; instead, it flows away just when it is really needed.

At the same time, the long-term transformation of rivers by humans has further amplified the risk of drought.

Gruber said that natural rivers include not only the main channel, but also floodplains, wetlands, tributaries and side branches. These areas can absorb water during floods, maintain soil moisture and recharge groundwater during droughts, as well as filter pollutants and lower the surrounding temperature.

However, as agriculture, industry and residential areas continue to occupy land along rivers, people have used levees to isolate floodplains and straightened meandering river channels. The rivers have lost the space for lateral expansion and water storage, and rainfall and snowmelt can only flow rapidly downstream along the narrow main channels. Although the projects seem to have tamed the rivers, they have also weakened the watershed's ability to retain water.

To maintain shipping, some areas continue to deepen waterways. Although this practice can temporarily ensure the passage of ships, it may cause the riverbed to cut further and weaken the connection between the river, floodplains and groundwater.

Gruber argues that what Europe needs to change is not just its energy structure, but also the way rivers and land are governed. Countries should restore more natural river sections, rebuild tributaries and side branches, widen river channels and restore their meandering forms, and return part of the floodplains to rivers. Land planning also needs to be adjusted accordingly, allowing some farmland to act as water storage during floods while providing compensation to affected farmers.

This approach is completely different from the past governance logic of "keeping water out of the land". Faced with the new climate of alternating floods and droughts, people need to let water re-enter the land, stay in the landscape and recharge groundwater.

Gruber still remembers the scene from his childhood when he swam to an island in the Danube River. Back then, the river was both a challenge and an existence he never doubted. Today, people can walk to the island across the exposed riverbed; shipwrecks, docks and stones emerge under the scorching sun. Trapped fish are moved one by one, while cargo ships, hydropower stations and nuclear power plants all wait for the river's return.

When "once-in-a-century" events repeat themselves time and again and "historical lows" are constantly being broken, it becomes hard for people to regard each extreme weather event as a coincidence. The receding Danube River is like a warning spread out across the European continent. The sunlight illuminates not only sunken ships and parched riverbeds but also reveals the long-standing exploitation and dependence of modern society on rivers.

What people need to do is no longer just wait.

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