Almost half a million people have been evacuated from the flood basin of China's Huai River, swollen to its highest level in over half a century, with their misery compounded by a plague of rats blamed on a scarcity of snakes and owls.
Most of the evacuees are villagers from the dirt-poor eastern province of Anhui with the rest from Henan to the northwest and Jiangsu to the east.
"The three provincial authorities have mobilised 511,000 people to patrol the Huai embankments and issue emergency warnings," Xinhua news agency quoted the State Flood Control and Drought Relief Headquarters as saying.
Thirteen huge sluices at Wangjiaba, a key hydrological station on the river after it flows out of Henan into Anhui, were opened on Tuesday to divert waters to adjacent the Mengwa buffer zone, home to 150,000 people.
They were closed again on Thursday as the river level receded below the danger zone, the central government said on its Web site.
The Huai originates in Henan and runs east between the Yellow River and the Yangtze River, cutting through Henan, Anhui and Jiangsu before entering the Yangtze at the vast Hongze Lake.
The pressure on the embankments along both banks of the river has been mounting, threatening key cities and railway lines on the middle and lower reaches.
Authorities diverted water to another five buffer zones on Wednesday where residents were evacuated to temporary shelters on high ground.
Water remained above danger levels and cities and towns still suffered serious street flooding, but no casualties have been reported along the Huai so far, state media said.
Floods and landslides in other parts of Anhui have killed at least 26.
Tens of millions of residents across southwestern, central and eastern China are grappling with the threat or aftermath of floods that have killed at least 131 people in the past two weeks.
China is also trying to deal with 2 billion flood-displaced rats in the central province of Hunan alone which have destroyed 1.6 million ha (6,200 sq miles) of crops.
Experts blame the plague partly on the shortage of owls and snakes, both popular in traditional Chinese medicine, with snake a favourite winter dish in the south.
"A snake can eat as many as 400 rats a year and an owl 1,500," state media reported. "Snakes in the region have been caught and exported to Guangdong in recent years and have ended up on the dining table. It has become a lucrative business and depleted the number of snakes...
"Owls have suffered the same fate."
China's flood season is notoriously deadly. At least 360 people have died in floods and related disasters across the country this summer and more than 4 million hectares (15,440 sq miles) of crops had been destroyed.
This year, it has been compounded by heavy rainstorms and deadly lightning in the central, southern and coastal regions. Two people were killed and 18,000 evacuated when heavy rains and hailstorms hit the coastal province of Shandong on Wednesday, the Xinhua news agency said.
Chinese President Hu Jintao and Premier Wen Jiabao urged local governments on Wednesday to improve weather monitoring, give priority to people's safety and relocate people in flood-hit areas.