China’s premier said flood control efforts are at a “crucial stage” as the death toll jumped by more than a dozen on Saturday and more torrential rains are expected through Sunday night.

Water levels on the upper parts of China’s largest river, the Yangtze, are at their highest since 1987, the state—run Xinhua News Agency reported.

Chinese Premier Wen Jiabao has ordered officials to prepare for “more serious floods and disasters,” Xinhua reported.

Mr. Wen was touring flood damage in the central province of Hubei, where the rising waters have put pressure on the world’s largest hydroelectric project, the Three Gorges Dam. China Central Television on Saturday evening showed Mr. Wen wading through floodwaters in rubber boots.

The government says the latest flooding this year has left more than 270 people dead since July 1.

Another 13 died early Saturday in a landslide caused by heavy rains in Pingliang city, a provincial official in Gansu told The Associated Press. He would not give his name, as is common with Chinese officials.

The Ministry of Water Resources around noon Saturday warned that the water level at the dam will rise again soon and may exceed the record high reached on Friday.

Mr. Wen ordered officials to control the dam and other key anti—flood projects.

China’s national weather centre has forecast more torrential rains for the region through 8 p.m. on Sunday.

Hubei flood control officials told The Associated Press that the water level at the dam was 55 feet, or 17 meters, from its maximum capacity of 573 feet (175 meters) as of 8 a.m. on Saturday.

An official with the Hubei flood control headquarters said there was no need to take special precautions because the top of the dam is 606 feet (185 meters) high.

“There’s no need to worry about it in the future. It will be safe,” the official said.

China has for years promoted the Three Gorges Dam as the best way to end centuries of floods along the Yangtze basin and dismissed complaints about the enormous environmental impact of the $23 billion reservoir that has displaced more than 1.4 million people.

Mr. Wen said the dam has played an important role in flood prevention along the Yangtze, Xinhua reported.

More than 1,000 people have died or disappeared in severe flooding in China so far this year, the highest death toll since 1998.

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