Power producers in Germany’s Rhine region are warning of lower output as low water levels delay deliveries of coal.

Germany is battling with decreased river levels and competition for barges on its key waterways amid a drought that threatens the ability of coal plants to stock up ahead of winter. The reduced shipments come as the government revives some dormant coal stations as a way to avoid burning natural gas, which is in short supply as Russia squeezes flows to Europe.

Plants operated by utilities EnBW AG and Trianel GmbH issued notices saying they are experiencing supply issues, with Trianel’s Lunen station facing a cut in generation over the weekend. EnBW said its Heilbronn plant on the Neckar river, a tributary of the Rhine, is “affected” but didn’t provide further details, according to a filing on the European Energy Exchange website.

A Trianel spokesman said the low levels are limiting the amount of coal barges can carry. “This is the normal business these days,” they said by phone. “This situation will only change when it rains more.” 

Trianel, whose Lunen power station has a 750-megawatt capacity, gets its coal via Rotterdam, but also tries to book trucks to transport the fuel. 

EnBW, which currently has large stocks of coal, said its plants along the Rhine and Neckar rivers are also served by rail. “But even for rail deliveries, the situation is tense for all train transport services,” a spokesperson said, adding that the utility was seeking the best use of the limited resources.

The water level at Kaub, a key point on the Rhine, is at 87 centimeters (34 inches), an increase of 7 centimeters from Thursday and more than double the depth in mid-August. The level is not the actual depth of the river, but rather a measure used to calculate navigability for vessels.

European coal futures for next year rose 2.2% on Friday to trade as high as $320/ton, more than triple the price at the start of the year.