Emergency crews have started to drain floodwaters at a township beside Dongting Lake in Hunan province after a dike breach was sealed off on Monday night.

The National Flood Control and Drought Relief Headquarters and the Ministry of Emergency Management have dispatched a first batch of 397 rescue workers and 47 pieces of equipment from provinces including Hubei, Fujian and Sichuan to support the drainage efforts in the inundated Tuanzhou township.

Firefighters from the city of Yueyang arrived at the dike at 7 am on Tuesday to start pumping.

The breach occurred in Tuanzhou on Friday afternoon when water began flowing through channels in the dike and expanded to a 226-meter gap after failed salvage attempts.

An area of 47.6 square kilometers — 92.5 percent of the township — has been flooded. There have been no reports of casualties.

About 210 million cubic meters of floodwater needs to be pumped out, according to local authorities.

Yao Wei, a director at the State-owned Changjiang Institute of Survey, Planning, Design and Research Corporation, said he expected it would take about 17 days for the water to be pumped out.

If the water is discharged too soon, it might have an impact on the safety of the embankment dividing Tuanzhou from nearby Qiannan township, so the water level should drop less than 30 centimeters a day, he told China Central Television.

More leaks have been reported in the embankment, so authorities have started to build a third embankment.

They have mapped out plans for a "third-line of defense" and construction has started with seven different teams, according to Zeng Qiming, director of Hunan's flood and drought disaster prevention affairs center.

Min Heyuan, 65, a villager in Qiannan, patrols the embankment from 6 pm to morning.

"It is the responsibility of us local people to go and check the embankment, which protects our safety, houses and properties," he said.