Summer temperatures and reduced rainfall have seen water levels fall further on the Rhine, at some places just 38 centimeters (15 inches) from the river bed, according to a German research institution.
Water levels will continue to fall until the beginning of next week, according to the Institute for Hydrology.
The levels are affecting private and industrial traffic on the river.
Bastian Klein from the Institute told German news agency, dpa, that next week the level could slip to 30 centimeters and disrupt barge traffic.
The Rhine is crucial to German industry. Heavy barges carry coal and diesel from port to industry and refineries.
But because of low water levels, barges are being loaded at one-quarter to one-half capacity, to keep them higher in the water.
That means three to four barges are now required to move the amount of goods that would normally fit on a single barge.
Media reports said shipping costs have gone up nearly five times.
By Salman Ahmed in Berlin
Anadolu Agency
energy@aa.com.tr