Water levels on the Rhine in Germany remain too low in most of the river for cargo vessels to sail fully loaded despite recent rain, commodity traders said on Friday.

Rain over the past few days helped stabilize the river at low levels but was not enough to bring a substantial improvement, traders said.

Dry weather in June meant the river became too shallow for vessels to sail fully loaded and ship operators imposed surcharges on freight rates to compensate for vessels sailing partly empty, increasing costs for cargo owners.

The Rhine is still too shallow for normal sailings at the chokepoint of Kaub and northern areas around Cologne and Duisburg.

Some vessels, depending on type, are only sailing 50% full in northern regions, they said. This means freight has to be divided among more vessels, increasing costs for cargo owners.

Some rain is forecast over the weekend in south German river catchment areas which could help stabilize water levels, traders said.

The Rhine is an important shipping route for commodities such as grains, minerals, ores, coal and oil products, including heating oil. German companies faced supply bottlenecks and production problems last summer after a drought and heatwave led to unusually low water levels on the Rhine. (Reporting by Michael Hogan; Editing by Sonali Paul)