Europe's Drought Corridor Cuts Hydro Output by a Fifth and Trims Danube Nuclear as Rivers Hit Multi-Year Lows

A drought stretching from the Rhine delta to the lower Danube cut hydropower output across seven European countries by about one fifth between April and July 2026, according to an analysis of river flow, generation and price data published by pv magazine on 10 August. Nuclear plants on the Danube also reduced output as river flows fell to their lowest levels in seven years, while wholesale power prices rose steadily through the summer. The analysis, by consultancy WSP, compared 2026 with the 2019 to 2025 average using Copernicus river discharge modelling and generation data from the ENTSO-E Transparency Platform.

Modelled discharge of the Rhine at Lobith, where it enters the Netherlands, averaged 81% of its 2019 to 2025 norm in April, 66% in May, 58% in June and 37% in July. In France, the Garonne at Tonneins averaged 5% of its normal July flow, the Loire at Saumur 13% and the Rhône at Beaucaire 41%. The seven corridor systems, Austria, Italy, Romania, Serbia, Hungary, Slovakia and France, produced roughly 13 TWh less hydropower between April and July than the 2019 to 2025 average, a shortfall of about one fifth.

By mid-July, Italian and Romanian reservoir storage was closer to the 2015 to 2025 minimum than the median, while Spanish reservoirs were near the top of their historical range. At Cernavoda in Romania, output fell to about 15 GWh a day over the last three days of July, against a July norm near 29 GWh. French nuclear output, by contrast, ran 10% to 15% above its 2019 to 2025 norm in every month from April to July, despite heat-related curtailments at individual plants such as Golfech on the Garonne.

Italy replaced 3.6 TWh of lost hydro, compared with 2025, with 4.1 TWh of additional gas-fired generation and 1.1 TWh of new solar. Solar output grew year on year in every corridor market reporting to ENTSO-E, from 0.3 TWh in Hungary to 1.1 TWh in Italy, and by 5.4 TWh in Spain.