Shipping companies are preparing for the worst as the level of the Rhine is close to the critical level

Shipping companies prepared to halt freight traffic on the Rhine as water levels in Germany’s largest river approached a critical low point on Saturday.

A continuing drought affecting much of Europe has lowered rivers such as the Rhine, preventing large ships laden with heavy loads from passing key waypoints and forcing them to use smaller vessels or split cargo into several expeditions.

At a bottleneck near the town of Kaub on the Middle Rhine, an official gauge measured the water level at 37 centimeters (14.6 inches) on Saturday.

Large heavy ships cannot pass if the level drops below 40 cm (15.7 in).

A container ship passes Pfalzgrafenstein Castle in the middle of the Rhine in Kaub (Michael Probst/AP)

While the depth of the shipping lane at Kaub was still around 150cm (59in), experts say passage becomes difficult even for light or specially adapted freighters if water levels fall below 35 cm (14 inches) to the gauge mark.

A reading below 30 cm (11.8 inches) is considered impassable.

Maritime authorities predict that point could be reached early next week, although it is unclear whether water levels will reach the record high of 25cm measured at the Kaub gauge in October 2018.

Logistics company Contargo said on Friday it was preparing to halt shipping on the Upper and Middle Rhine for safety reasons and planned to transfer some of its cargo to trucks.

A transport ship passes the Rheinturm (Rhine Tower) in Düsseldorf, Germany (Christoph Reichwein/dpa/AP)

However, road and rail freight capacity is limited.

Businesses along the Rhine that rely on ships to receive raw materials and deliver finished goods are expected to face delays and shortages.

Coal-fired power plants and petrol stations could also experience supply shortages, if navigation on the Rhine is interrupted.

Meteorologists are predicting rain in the coming days, although it is unclear whether that would be enough to prevent water levels on the Rhine from dropping to a point that affects navigation.

In Italy, authorities have allowed more water from Lake Garda to flow into local parched rivers like the Po that farmers use to irrigate crops.

Combined with Italy’s worst drought in decades, the country’s largest lake is approaching its lowest water level on record.