Higher water levels than a year ago bode well for Europe's hydro plants

By Forrest Crellin and Nora Buli

PARIS/OSLO (Reuters) - Water levels in Europe as heatwave season gets underway have improved from last year when low rainfall caused curbs to hydropower output, with most countries' reservoir levels either above or nearer the seasonal average than in 2022.

In 2022, low water levels in reservoirs and rivers exacerbated the wider European energy crisis as hydropower output and cooling water usage at French nuclear plants had to be curbed.

"The hydropower situation across the continent is mainly strongly improved since last year, when the second and third quarter were very dry with several hot spells," Eylert Ellefsen, senior analyst and hydrologist at EQ-Montel, said.

In France, reservoirs are 10% above last year's levels and 28% above the five-year average, while run-of-river generation is 33% above last year but 13% below the seasonal average, ICIS data showed.

Run-of-river hydroelectric plants typically have little or no water storage and are therefore susceptible to seasonal river flows, with fewer options to control production volumes.

Temperatures in France this month have been near 40-year highs, and outlooks for July are close to the high levels recorded last year. Hot spells during the summer are expected, but more rainfall would reduce the drought effect compared to last year, EQ-Montel data showed.

High temperatures could see a repeat of last year's issues at nuclear plants, which use river water to cool down reactors and then discharge it back at a slightly higher temperature. If the water gets too warm, production must be curtailed.

The Bugey nuclear plant on the Rhone river and the Golfech plant on the Garonne river, which account for roughly 10% of total French nuclear capacity, are currently most at risk, according to Refinitiv analyst Stefan Soderberg.

However, a higher flow rate and a slightly better soil situation in the upper Rhone has reduced the overall risk of cooling problems compared with last year, he added.

A nuclear supply shortfall in southern France would be less critical than last year given a better supply picture overall, allowing France to remain a net power exporter through the summer months, Refinitiv analyst Nathalie Gerl said.

Supply in neighbouring countries has also improved, and British and German power imports could cover a potential shortfall, Gerl added.

There is a severe drought in Spain however and dry and sunny conditions are expected to persist in southern Europe, with slightly above-normal precipitation from mid-July, ICIS analyst Ellie Chambers said.

The Nordics have also seen drier weather than normal in recent months, said Olav Botnen at Volt Power Analytics. "We expect Norway and Sweden to perform with somewhat lower reservoir levels than normal over this summer season," he added.

But compared to last year southern Norway, which holds some of the biggest water reserves and is a key power export hub to Europe, had significantly reduced its deficit, analysts agreed.

"Hydropower is still attractive to the continental power markets, and extensive exports will persist from the Nordics in general and (southern Norway price zone) NO2 specifically," said Paal Svendsen, an analyst at consultancy Nena.

(This story has been refiled to correct the spelling of Garonne river in paragraph 8)

(Reporting by Forrest Crellin and Nora Buli; editing by Nina Chestney and Jan Harvey)