Intel Brief: Record low water levels in Rhine, Danube may disrupt aviation
- 4 days ago
- 7 min read
Updated: 3 days ago
Date: 06/08/2026
What happened?
Europe's two principal commercial waterways, the Rhine and the Danube, are simultaneously experiencing record or near-record low water levels, causing the third major European low-water shock since 2018 and significantly disrupting supply chains, energy generation and fuel distribution.
The Rhine's critical Kaub gauge fell as low as 21 centimetres overnight on 3–4 August, the lowest reading since records began in 1880 and below the previous minimum of 25 centimetres reached on 22 October 2018. It stood at approximately 19–20 centimetres on the morning of 6 August. Kaub is the principal reference point for navigation between the Amsterdam-Rotterdam-Antwerp refining and storage hub and industrial regions in southern Germany and Switzerland.
Conditions are expected to remain exceptionally low for weeks. Germany's Federal Institute of Hydrology forecasts Kaub generally between 18 and 22 centimetres through 9 August, with some forecasts pointing to a renewed drop towards 17 centimetres by 8 August.
Navigation has not formally stopped, but it has become marginal for many conventional barges. Vessels still able to operate are doing so at approximately 20% of normal capacity. Some loading and unloading points can no longer be reached, while only specialised shallow-draught vessels can operate reliably through the worst-affected sections.
Tanker-barge freight from Rotterdam to Karlsruhe rose to approximately €150–160 per tonne on 4 August, up from €45 at the end of June and above the €130–140 recorded in late July. Argus has described oil-product barge rates to several Rhine destinations as being at record highs.
On the Danube, the Budapest gauge was holding at approximately 19–20 centimetres on 6 August, continuing the modest recovery from approximately 10 centimetres on 3 August but still well below the previous all-time low of 33 centimetres recorded in 2018.
This modest rise prevented the complete shutdown of Hungary's Paks Nuclear Power Plant. Around 01:30 on 4 August, the plant came within millimetres of the threshold that would have forced its last operating turbine offline, but the river stopped falling and had risen by 1.5 centimetres by morning. As of 6 August, the final 240-megawatt turbine remains online, keeping the plant at just over 10% of capacity, with the river holding a few centimetres above the shutdown threshold. A cold front expected on 7 August could bring rainfall in Austria that raises upstream levels. But the shut-down units can only restart once levels remain sustainably above the required threshold.
Conditions are worse farther downstream. Danube flow entering Romania at Baziaș was approximately 1,500 cubic metres per second, well below the seasonal average, and is forecast to fall below the previous historical minimum by 10 August. Low levels are preventing barges from using several Romanian river ports and disrupting the movement of grain, fuel and other bulk cargo towards Constanța, a key export corridor for both Romanian and Ukrainian goods.
The rivers are also constraining electricity generation in Hungary, Romania and Serbia by reducing nuclear cooling capacity, hydropower output and fuel deliveries to thermal plants.
Analysis
Low water levels on the Rhine and Danube are no longer only disrupting inland shipping. Both rivers are vital transport corridors for fuels, agricultural products and industrial goods. With vessels carrying only a fraction of their normal loads, transport costs are rising sharply and more freight is being diverted to already constrained rail and road networks.
By early August, navigation through the Rhine’s Kaub bottleneck had become impractical for many conventional vessels. Shipping has not formally ceased because authorities do not impose a general closure at low water, but operators must decide whether individual passages remain safe and commercially viable. Loads must be divided among several vessels, shallow-draught barges command substantial premiums and some terminals have become inaccessible.
The volume of Rhine cargo moving to and from Rotterdam was already approximately 10% below normal by the end of July. Chemical tankers, oil-product barges and dry-bulk vessels are particularly exposed because they generally require greater draught than container barges. Rail and road transport provide partial alternatives, but spare capacity is limited and several companies are seeking the same substitutes simultaneously.
The increase in freight costs will be passed unevenly through supply chains. The first effects are likely to appear in fuels, chemicals and other products for which inland terminals depend heavily on Rhine deliveries. Food-price effects will take longer and will depend on the duration of the disruption, the availability of road and rail transport and whether producers can store grain rather than sell immediately. The original assertion that higher river freight costs would automatically produce an immediate increase in food prices was therefore too categorical.
The impact is already acute across interconnected electricity markets. As domestic power generation declines in Hungary, Romania and Serbia, demand for imported electricity is increasing during a heatwave that is simultaneously driving air-conditioning use higher. Low river levels are also restricting fuel movements, reducing the ability of governments and utilities to compensate for lost generation.
Serbia’s largest hydropower plant, Djerdap 1, is operating at approximately 20% of capacity. Low water has also disrupted cooling systems at the coal-fired Kostolac plants, reducing thermal generation. Serbia is consequently losing output from two major sources of electricity while its ability to import fuel by river has also fallen sharply. The government is opening part of the NIS refinery system to other domestic suppliers while seeking to preserve state reserves for a more severe emergency.
Hungary’s Paks Nuclear Power Plant, which normally generates nearly half of the country’s electricity, is operating at just over 10% of capacity and may remain at that level for several weeks. Companies and households have reduced peak electricity demand following government appeals, while freight rail operations have been suspended during parts of the evening peak to reduce pressure on the grid.
Romania has shut one of the two reactors at Cernavodă, which normally provides approximately one-fifth of national electricity. Authorities carried out controlled explosions on 3 August to remove a rock outcrop and redirect additional water towards the cooling channel for the remaining reactor. Romania has declared a nationwide state of alert for August, but its ability to replace lost production through imports is constrained by limited cross-border transmission capacity.
As several countries seek additional electricity at the same time, regional markets become more vulnerable to price increases and supply shortages during peak summer demand. The consequences are mutually reinforcing: low water reduces domestic generation, increases electricity-import dependence, restricts fuel transport and makes alternative logistics more expensive.
Aviation
Aviation is already being affected through higher fuel and distribution costs, so the immediate risk over the coming weeks from the dry rivers is an even tighter logistics chain.
With the Kaub gauge expected to remain below the 77-centimetre low-water reference level through at least 18 August and likely beyond, barge deliveries of refined products from the Amsterdam-Rotterdam-Antwerp hub into southern Germany and Switzerland will remain severely restricted.
Tanker-barge freight from Rotterdam to Karlsruhe has already reached approximately €150–160 per tonne, above the peak of around €118 recorded during the 2022 low-water episode. Higher transport costs will feed directly into delivered jet-fuel prices, while suppliers will rely more heavily on pipelines, terminal inventories, road tankers and rail deliveries.
Frankfurt and Zurich airports are relatively resilient because both are connected to NATO’s Central Europe Pipeline System, while Frankfurt also receives fuel through the Rhein-Main pipeline network.
So while restricted Rhine deliveries do not automatically cause an airport shortage, pipeline capacity is finite and must also be supplied from refineries and coastal storage. Prolonged low water will therefore reduce flexibility across the wider fuel-distribution system, particularly as road and rail alternatives are already under pressure from other displaced freight.
The most likely operational effects during August are higher fuel costs, increased use of airport and supplier inventories, and greater tankering by airlines. Aircraft may carry additional fuel from less-constrained airports, reducing the amount they need to uplift at destinations exposed to Rhine disruption. This protects schedules but increases aircraft weight, fuel consumption and operating costs. Airlines may also adjust refuelling contracts and reduce discretionary uplift at more expensive or less reliable locations.
The 2018 drought demonstrated the potential scale of the cost shock. The estimated cost of transporting fuel from Rotterdam to Basel rose from approximately US$5 per barrel in July to more than US$35 by late October, tightening petroleum supplies across southern Germany and Switzerland. However, the disruption developed later in the year. In 2026, Kaub has fallen below the 2018 record in early August, when aviation demand, industrial cooling requirements and agricultural transport are all elevated.
The 2022 episode provides an even clearer precedent for aviation. When Kaub fell to approximately 32 centimetres, Lufthansa stopped moving its own jet fuel to Frankfurt by barge, although limited commercial deliveries continued. Frankfurt avoided a physical shortage because its pipeline connections were operating at full capacity. Zurich was more exposed and Switzerland released aviation fuel from strategic reserves after normal barge deliveries were disrupted.
Current conditions are therefore more severe than in 2022 in terms of river level and freight cost, but the likely transmission mechanism remains similar.
Disruptions are expected to worsen farther downstream. Danube flow entering Romania at Baziaș was approximately 1,500 cubic metres per second in early August and is forecast to decline to 1,350 cubic metres per second by 10 August. This would be below the previous historical minimum of 1,400 cubic metres per second and barely one-third of the August average of 3,900 cubic metres per second.
Low Danube levels are preventing barges from using several Romanian river ports and disrupting the movement of grain during the harvest season. In Hungary, Serbia and Romania, barges and tankers are operating at approximately 30–40% of cargo capacity. Serbia received only 25% of its targeted monthly fuel imports in July as a result.
The rivers are also constraining electricity generation in Hungary, Romania and Serbia by reducing nuclear cooling water, hydropower output and cooling capacity at thermal power plants. Short-term improvement at Budapest will not resolve the wider energy and transport disruption, particularly as flows continue to decline across the lower Danube.
