German inland waterway operators are sounding the alarm due to the persistently low water levels on the Rhine, which are threatening to divide the river into two navigable regions.
At the Kaub gauge - which is crucial for shipping and the economy in western Germany - a single-digit reading is expected for the first time this week, Jens Schwanen, managing director of the Federal Association of German Inland Waterway Transport (BDB), told the Rheinische Post newspaper on Monday.
The gauge is on the Middle Rhine section of Germany's longest river between Koblenz and Mainz.
With water levels this low in the region, commercial shipping will no longer be able to transport goods, he warned. The same applies to day-trip and cruise services, he added.
"In principle, the Rhine is therefore no longer navigable throughout its length and is thus divided into two parts," said Schwanen.
In the north, shipping can continue between the Dutch border and Cologne on the Rhine and through the western German canal system.
Further south, there is shipping traffic on the tributaries Neckar, Moselle and Main, as well as on the Main-Danube Canal.
The low water levels have been putting a strain on the German economy for weeks now.
When water levels are low, ships can carry less cargo, which drives up transport costs and puts pressure on supply chains.
Several German states have suspended laws banning hauling services on Sundays and public holidays in an effort to relieve the pressure.