COLOGNE — Low water levels on the Rhine forced barge operators to cut cargo loads on Thursday, disrupting shipments of coal, chemicals and grain along one of Europe's busiest inland waterways. Shipping and logistics firms reported the bottleneck raised costs for industrial users reliant on the route.

The Rhine carries fuels, minerals, chemicals and agricultural goods between the ports of Rotterdam and southern Germany. The German Federal Waterways and Shipping Administration reported that gauge readings at Kaub, west of Frankfurt, had dropped to levels that make full loading uneconomical for many vessels.

Barges were sailing partly empty to avoid running aground, pushing freight rates higher. Chemical group BASF, whose Ludwigshafen site depends heavily on Rhine transport, has previously warned that sustained low water can constrain production and force reliance on rail and road alternatives.

The disruption revived memories of 2018 and 2022, when droughts sharply reduced Rhine navigability and reduced output across German manufacturing. Economists at the Kiel Institute for the World Economy noted that prolonged low-water episodes can measurably dent industrial activity in Europe's largest economy.

The German Weather Service forecast little significant rainfall in the Rhine catchment area in the coming days. Utilities and commodity traders said they were preparing contingency plans should the dry spell persist into late August.