Low water levels on the Rhine, Germany's main shipping artery, will affect output over the coming month from major coal-fired power stations, one east of Frankfurt and another in the northern Ruhr area, notes on the website of power bourse EEX showed on Thursday.
The Staudinger 5 plant has 510 megawatts of capacity and is operated by Uniper (UN01.DE) and situated on the Main, a major Rhine tributary.
Its output may be irregular until Sept 7 "due to a limitation of coal volumes on site" caused by the low level of the Rhine, according to the document on EEX's transparency site.
Another document posted late on Thursday morning said the 1,100 MW Datteln 4 plant may also see irregular output to Sept 7 due to water levels.
Germany last month agreed to reactivate its coal-fired power plants or extend their lifespans in response to its worst energy crisis in generations, triggered by dwindling supplies of Russian gas.
But shallow river levels following a hot, dry summer mean that barges taking coal feed stock to generating plants can only sail with partial loads. Similar conditions caused a fall in output at power stations and hit profitability at chemical manufacturing plants in 2018.
A reference Rhine waterline level at Kaub , where vessels need about 1.5 metres of clearance to sail fully loaded, fell to only 55 centimetres on Thursday.
A heat wave this week has also boosted transport prices on the river as fewer vessels can travel on it and pass through choke points, tightening transport space.
Low water likewise affects power prices as well as other commodities such as mineral oil products and grains.
Warming rivers in recent weeks have also curtailed French supplies of cooling water to nuclear plants, contributing to tightness in the European power system and driving up spot electricity prices
