Months of drought have left water levels on Germany's Rhine river at a record low, exposing a World War II bomb and forcing ship operators to halt services to prevent vessels from running aground.
The water level on the Rhine on Friday reached just 77 centimetres (30 inches), 4 cm below a previous record low of 81 cm recorded in 2003, Cologne's waterworks authorities said.
Although rainfall is expected next week, forecasters said it would not suffice to bring up water levels in Germany's most important waterway and a key shipping route for the Netherlands and France.
Freight ships have had to reduce the volume of cargo carried in the shallow waters.
Passenger liners plying Cologne and Mainz have been halted since Monday because of the low water level, operator KD said.
Meanwhile the dried out riverbed has exposed all kinds of objects, including a 50-kilo World War II bomb that would have to be defused in the coming days.
Ahead of the operation, water traffic around the site in Cologne has been halted.
Germany, like much of Europe, has enjoyed a prolonged period of warm and sunny weather.
But farmers have long complained that the persistent drought was wreaking havoc on crops, with annual production expected to be down by a fifth.
Fourteen of Germany's 16 states have applied to benefit from a federal aid
programme for farmers.