CNR Hydro Output Down 30% on Rhone as Drought Squeezes French Power System from Two Sides
France's largest Rhone hydropower producer has run 25-30% below normal since June, compounding nuclear outages that cut the country's generation buffer through peak summer demand.
France's largest hydropower operator on the Rhone reported on Thursday (2026-08-20) that its output has run 25-30% below normal since June, a sustained shortfall caused by early snowmelt followed by a heatwave-linked drought that cut the river flows its turbines depend on. Pierre-Jean Grangette, CNR's executive director for energy optimisation and commercialisation, gave the figures to Montel.5
By the end of July, CNR had generated 7.5 TWh from its 3 GW of Rhone capacity. In a normal year the company would have been tracking well ahead of that pace. Grangette told Montel that wetter weather expected in October and November could lift full-year output to 12.5-13 TWh, just below the 13.2 TWh CNR produced in 2025. That projection depends on precipitation arriving on schedule and restoring river flows before the winter demand period.5
The depleted Rhone has pressed on two parts of France's power system simultaneously. Low flows constrain CNR's hydro turbines. The same shallow, warm water limits the nuclear plants sited along the river bank, because they cannot discharge cooling water at the rate needed for sustained full-power operation. EDF curtailed about 1.9 GW of nuclear capacity, around 3% of its fleet, on Thursday (2026-07-02) despite cooler air temperatures, with its 1.3 GW St Alban 2 unit running 115 MW below capacity due to environmental restrictions tied to Rhone water temperatures, Montel reported.1
The sharpest episode came on Monday (2026-07-13). A prolonged heatwave that week forced EDF to remove 6.4 GW of nuclear generation from service, a cut equivalent to 14% of France's total power demand that morning, according to Oilprice.com. Nuclear ordinarily accounts for roughly 70% of France's electricity mix. Still, RTE data showed France remained a net exporter that day, with more than 10 GW flowing to neighboring countries despite the scale of the outages.2
But that export cushion has been absorbing concurrent pressure since June, not just during acute heatwave spikes. CNR's output deficit has run across a period when normal hydro generation would typically provide stable baseload backing for the system. Swiss alpine hydro capacity, which influences cross-border power flows across the region, was also reported to face continued strain from drought, Montel noted on August 7 (2026-08-07).5,4
EDF said on July 31 (2026-07-31) that the drought would have a "limited" impact on French hydro output. CNR's reported 25-30% deficit, sustained across June and July, sits at a distance from that characterisation. The two assessments may cover different asset bases or periods; available data does not allow direct reconciliation.3,5
ICE Endex TTF front-month held at €65.83/MWh at 08:15 UTC on Monday (2026-08-24). Whether that price incorporates any specific CNR shortfall, as opposed to broader storage and supply dynamics, cannot be determined from available data. France has been managing its grid through a summer of concurrent hydro and nuclear stress on a system whose generation surplus typically depends on both running near capacity.5
Grangette's full-year projection of 12.5-13 TWh already sits below CNR's 2025 output, and it assumes autumn rain patterns hold. If precipitation through September and October fails to restore Rhone flows to seasonal norms, that figure slips further, and the buffer France relies on to sustain its winter export position erodes with it. Rhone flow gauges through September are the first hard data on whether even the lower bound of that range is achievable.5