Panama Canal officials will restrict the size of ships that can pass through the waterway for the first time since 1998 as a drought brought about by El Niño causes water levels to fall.

Beginning Sept. 8, the maximum draft for ships traversing the canal will fall to 39 feet from the usual 39.5 feet, a limit that could be reduced again to 38.5 feet on Sept. 16, officials said in a statement. The change would affect 18.5% of ships using the canal, officials said.

Supply chain experts said the new restrictions could force shipping lines traveling from Asia to the U.S. East and Gulf Coasts via the canal to leave some cargo behind in order to reduce their draft.

top logistics news Get the latest logistics and supply chain news and analysis via an email newsletter. Sign up here. Smaller customers that don’t have well-established relationships with ocean carriers could see their shipments held back, said Joel Sutherland, director of the Supply Chain Management Institute at the University of San Diego’s business school. Even a small amount of delayed cargo can have a far-reaching impact, he added. For example, manufacturing companies waiting on key components could be forced to shut down temporarily. “Everything backs up,” Mr. Sutherland said. “You could have some stock-outs, you could have some promises that aren’t met.” Panama Canal officials attributed the drought conditions to this year’s El Niño, a periodic warming of ocean waters in the Pacific Ocean that affects global weather patterns. In a statement, port officials said any further restrictions would be announced at least four weeks ahead of time to allow for planning. And if rainfall levels return, the draft restrictions could be lifted.

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