PANAMA CITY, (Reuters) – The Panama Canal will extend restrictions on ships’ maximum depth, it said, and it has limited average crossings at one of the world’s busiest trade passages to just 32 ships a day as a prolonged drought continues.

The Panama Canal Authority (ACP) will maintain a depth limit of 44 feet, or 13.41 meters, for neo-Panamax container ships. In June, the authority put off further restrictions that would have brought depth limits up half a foot, meaning ships would have needed to lighten their loads to float higher.

During Panama’s rainy season, an average of 35-36 ships typically cross the canal each day, the authority has said. Each crossing uses some 51 million gallons of water.

About 3.5% of the world’s maritime trade passes through the 80-kilometer inter-oceanic waterway that connects the Atlantic and Pacific Oceans. The depth limit will remain at the current level as long as weather conditions do not drastically change, the ACP said in a statement.

“As part of a worldwide phenomenon, in the last six months, the Canal has experienced an extended dry season with high levels of evaporation, with a high probability of an El Nino condition before the end of this calendar year,” the canal authority said.

Panama typically sees heavy rains in July, and the canal authority called the current lack of precipitation “historically unprecedented.” Since the beginning of the year, the canal has rolled out water-efficiency measures while bracing itself for the long-term effects of climate change, it said.