Europe's major rivers hit record-low summer flows, disrupting shipping, nuclear cooling and hydropower
Copernicus, the EU's Earth observation programme, reported that Europe's summer of 2026 was its third-warmest on record and that western Europe's was the warmest, with 12 major rivers including the Rhine, Danube and Po recording their lowest summer flows since records began in 1992. According to Copernicus, the low flows caused major disruption to cargo transport and to nuclear reactor cooling, and cut hydropower output. The International Transport Forum reported that Rhine barges sailed at around 15% of normal loads in August, and that Hungary's Paks nuclear plant had to scale back when the Danube could not supply enough cooling water.
Bottom line — Copernicus says the 2026 low flows show a close link between climate change and energy security, though it has not yet run an attribution study.
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Copernicus said 52% of the continent was exposed to at least 'very strong' heat stress by the end of the season, corresponding to feels-like temperatures of 38°C or more.
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Copernicus reported western Europe's summer average at 21.7°C, 2.5°C above the 1991–2020 average and above the previous record set in 2003.
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According to the International Transport Forum, Danube barge-carrying capacity fell to around 30% of its usual level, and inland waterway freight rates at times doubled.
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The ITF cited a 2018 study finding that a similar Rhine low-flow episode cut German GDP by up to 0.4%, and warned similar effects could follow this year.
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Austria's hydropower generation fell to 51% of its usual output and Switzerland's to 26%, according to the OSCE study cited by El País.
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Samantha Burgess of ECMWF said the dataset starts in 1992, which she said makes it harder to firmly establish a long-term climate link.
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Hungary's Paks plant supplies over 40% of the country's electricity, according to El País.
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Deutsche Welle reported that German industry groups estimate water supply costs could rise by up to 30% because of climate change, and that up to €14 billion (€14 billion) in extra investment could be needed by 2035.
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DW quoted the UBA's Jeanette Völker warning that low water and warm temperatures raise the risk of fish die-offs, and that mussel habitats on exposed gravel banks are being lost.
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The Hess study projected that flow intermittence will intensify across six European river networks in Spain, France, Croatia, Hungary, Czechia and Finland, with the most severe scenarios showing some reaches moving from perennial to intermittent flow.
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DW reported that Hungary's Prime Minister Peter Magyar urged households and businesses to conserve electricity, and that the Romanian military blasted rock in a Danube branch to protect cooling water for the Cernavoda plant.