For four years, Europe's energy security debate has focused on one question: how to reduce dependence on Russian gas without undermining competitiveness. The shift has been substantial. According to the European Commission, Russian pipeline gas and LNG fell from 45% of total EU gas imports in 2021 to 12% in 2025;
in volume terms, from 152 billion cubic metres to 36 billion cubic metres. Europe has materially reduced a geopolitical concentration risk. The summer of 2026 is showing that another constraint is becoming harder to ignore.
That constraint is water. Record low river levels and repeated heatwaves are affecting several parts of the energy system at once; nuclear cooling, hydropower, inland freight and, indirectly, gas storage. The significance is not that Europe is short of generation capacity in aggregate. It is that assets expected to provide resilience can become exposed to the same physical variable at the same time.
The scale is measurable. Across a corridor covering Austria, Italy, Romania, Serbia, Hungary, Slovakia and France, hydroelectric output between April and July 2026 was approximately 13 TWh below the 2019 to 2025 average for the same months; a shortfall of roughly one fifth, based on ENTSO-E transparency data.
Romania: an entire nuclear fleet offline
Romania is the clearest example. Cernavoda's two reactors, with combined capacity of around 1,400 MW, normally provide about one fifth of the country's electricity. Unit 1 was disconnected from the national grid on 28 July; by 13 August both units were offline as record low Danube levels made continued operation untenable.
The mitigation effort is instructive in itself. The energy ministry used explosives to remove a submerged rock obstruction, dredged the riverbed and sank four rock-filled barges to redirect flow toward the plant's intake, reporting that this raised water levels around Unit 2 by four centimetres and bought roughly nine additional days of operation. The river fell below the operating threshold regardless. Engineering responses to hydrological deficit have limits, and those limits arrive quickly.
The government declared a state of alert in the energy sector on 31 July for the month of August, prepared staged reductions for large industrial consumers during evening peak hours, and saw carmakers Dacia and Ford pause domestic production until 19 August to relieve the deficit. A hydrological event became a manufacturing shutdown within three weeks, with no interruption to gas supply and no blackout.
Hungary: concentration risk, and the value of a narrow margin
Hungary faced the same problem at a more concentrated scale. Paks normally supplies close to half of national electricity from four units totalling 2,000 MW.
The degradation was progressive. Units 1, 3 and 4 were shut down in stages from late July, while Unit 2 operated at 50% of capacity for eleven days; grid output fell to 240 MW, around 12% of normal. A full shutdown was announced and then averted. From 10 August, as the Danube rose 19 centimetres above its low point, a phased restart began and output recovered to roughly 500 MW, approximately a quarter of capacity. On 13 August the government announced construction of a riverbed sill at Dunaszentbenedek to sustain water levels at the intake.
Two points follow. First, the plant avoided a total halt by a margin of centimetres, not by design redundancy. Second, Hungary has built an industrial strategy around automotive, battery and electronics investment; sectors that require stable electricity, tightly coordinated supply chains and high asset utilisation. The transmission path runs from river level to power availability, from power availability to plant utilisation, and from plant utilisation into supply chains spanning Germany, Austria, Slovakia and Czechia.
France: thermal limits as a regional price mechanism
France illustrates a different mechanism. High river temperatures, rather than insufficient water alone, force EDF to limit output in order to comply with environmental discharge rules protecting aquatic ecosystems.
On 14 August, heat-related curtailments were expected to reach 9.4 GW at peak across nine reactors, roughly 15% of fleet capacity, with six reactors fully offline. Combined with scheduled maintenance, technical issues and fuel saving, some 27.7 GW of nuclear capacity was expected to be unavailable; the lowest French nuclear availability since August 2023. France relies on nuclear for approximately 70% of annual electricity production.
The effects do not stop at national borders. France remains a net exporter, but when nuclear availability falls, neighbouring systems replace part of that supply with more expensive generation. Gas and coal plants move up the merit order and prices rise. The French day-ahead contract reached €154.5/MWh, the highest since late June. More gas is consumed at precisely the moment Europe is attempting to rebuild inventories for winter.
The financial consequence is already visible on the balance sheet. EDF expects 2026 EBITDA to decline by around 10% against 2025, in an environment it attributes to lower market prices and heatwaves; successive heat episodes reduced flows on the Rhone and the Garonne and depleted reservoirs, eroding the group's highest-margin flexible generation.
Italy and Austria: how a summer drought consumes winter security
Italy makes the connection to gas particularly visible. Terna data show hydroelectric generation down 38.5% year on year in May and 19.3% across the first five months of 2026, against a 2025 that had already fallen 21.2% from the 2024 record; June was down 24%, and the sector association has indicated steeper declines through July and August as reservoir reserves were exhausted.
Austria is experiencing a comparable squeeze. Verbund reported a first-half run-of-river hydro coefficient of 0.68, some 32 percentage points below the long-term average, with total hydropower generation down 9.8% to 11,191 GWh. At the Greifenstein plant upstream of Vienna, Danube flow was running at approximately 700 cubic metres per second against a normal summer level of around 2,000.
The buffer that is already thin
This matters because Europe's gas cushion entered the summer weaker than usual. EU storage stood just under 58% full in early August; the lowest for the time of year in records going back to 2011, and 12 percentage points behind the previous year. The mandatory fill target has been relaxed from 90% by November to 80% by December.
The cause is not primarily the drought, and this distinction matters for anyone modelling the winter. Injection stalled because the global LNG market tightened sharply following conflict in the Middle East, which halted tanker traffic through the Strait of Hormuz, disrupted Qatari supply and left Asian buyers outbidding Europe for spot cargoes. The drought is therefore loading onto a buffer that was already impaired. Every additional unit of gas burned to compensate for lost hydro or nuclear output is gas that cannot be stored for winter.
Germany: the Rhine as a profit and loss variable
Germany shows how the same drought moves directly into manufacturing economics. The Rhine is not simply a river; it is part of Europe's industrial infrastructure.
Extremely low water has reduced cargo capacity, increased freight costs and constrained shipments of chemicals, coal, fuels, minerals and agricultural products. Covestro has declared force majeure for polyether polyols produced at its Dormagen site, where propylene oxide can only be delivered by ship; the company has stated that shifting volumes to road and rail could not fully offset the loss of transport capacity. More than 30% of Covestro's finished materials and 75% of its raw materials in Europe move on the waterway. Evonik has reported disruption at its Marl chemical park. Salzgitter has shifted coal movements from barge to rail between Rotterdam and its HKM division. BASF has declared force majeure on various surfactants produced at European sites because of raw material shortages, while stating that it is considerably better prepared than during the 2018 low-water event.
Substitution capacity is thinner than commonly assumed. A single 1,500-tonne barge is equivalent to roughly 60 trucks, and the German construction industry federation has indicated that certain high-volume construction materials can require as many as 150 trucks to replace one barge; road and rail lack the surge capacity to absorb that shift at scale.
The distinction matters for risk assessment. Germany does not require an electricity shortage for drought to damage industrial output. The Rhine transmits the shock directly into unit economics, working capital and delivery reliability.
The industrial implication
The most probable consequence is not widespread blackouts; it is a sustained deterioration in the economics of European manufacturing.
Chemicals face higher power and gas costs at the same time as freight rates and working capital requirements rise, and many sites depend on the same rivers for process cooling. Steel and metals face expensive energy alongside constrained raw material logistics. Automotive and battery manufacturing are vulnerable through tightly synchronised supply chains and high utilisation requirements, as the Romanian production pauses demonstrated. Glass, ceramics, paper, cement and fertilisers are exposed because continuous processes are costly to stop and restart, so volatility translates into lower utilisation, deferred investment and, over time, relocation of capacity.
The strategic question is changing
Europe has made real progress in reducing its dependence on Russian energy; that should not be confused with eliminating energy security risk. The system now relies more heavily on LNG, storage, interconnectors, renewables and flexible generation. In normal conditions, diversification strengthens resilience. During a severe regional drought coinciding with a constrained LNG market, several of those buffers are called upon simultaneously.
Energy security can therefore no longer be assessed only through installed capacity, fuel contracts and storage volumes. Utilities need to reconsider cooling technologies, reservoir management and the hydrological assumptions embedded in long-term investment models. Governments need to treat inland waterways and cross-border transmission as critical energy infrastructure. Manufacturers need to incorporate water stress into site selection, energy procurement, inventory policy and logistics design.
There is a disclosure dimension as well. Under IFRS S2 and the corresponding ESRS requirements, entities are expected to disclose material physical climate risks, the resilience of their strategy under different scenarios and the anticipated financial effects; water is addressed separately under ESRS E3, and the EU Taxonomy's climate adaptation criteria require asset-level physical risk assessment. The recurring weakness in practice is that water is presented as a site-level operational matter rather than as a correlated, system-level exposure spanning generation, logistics, process cooling and market price formation. A scenario analysis that treats reactor cooling, barge draught and hydro inflows as independent variables will systematically understate tail risk.
The next European energy shock may not start with a supplier closing a pipeline. It may start when a river can no longer perform the energy, cooling and logistics functions that the industrial system was built around. Water is moving from the sustainability agenda into the core economics of European energy security and manufacturing competitiveness.
(K. Burak Oguz, August 14, 2026)
