Rhine water levels hit their lowest level of the year Wednesday as warm temperatures across Europe continued, German Federal Waterways data showed.

The water level measured 2.44 meters at eight key locations along the river, the lowest seen all year, according to the data.

They fell below the 4-meter mark on July 10 and continued to drop afterwards. On August 15, they dropped below 3 meters.

In Germany's Koblenz, water levels were just 1.18 meters Wednesday.

Traders said continued low water levels had forced them to underload refined product barges, limiting the flow of oil from the Amsterdam-Rotterdam-Antwerp hub up the river.

"We've had to take 650 tons less than originally anticipated on my barge loading in early September...we've come to an agreement with the company selling us the products," said one diesel trader.

The Rhine is used to transport refined products from the ARA refining hub to the demand centers of Germany, France, Switzerland and Eastern Europe.