Heavy rain has hindered efforts by workers to repair reservoirs and place sandbags along breached riverbanks as the death toll from China's worst flooding in a decade climbed above 1,000.
Thousands of workers rushed to repair 51 small reservoirs that suffered damage and to fortify riverbanks along the Songhua River after floods triggered by torrential rain pounded north-eastern Jilin province, the official Xinhua News Agency reported.
Flooding overwhelmed major roads after some portions of the Songhua reached water levels twice as high as normal.
The death toll rose to 1,072 people, with 619 still missing, and the floods have caused tens of billions of pounds in damage across 28 provinces and regions, Xinhua said.
Premier Wen Jiabao visited the flood-hit town of Yongji county in Jilin this week, urging local officials to increase efforts to repair reservoir damage and prevent further flooding.
Shu Qingpeng, deputy director of the State Flood Control and Drought Relief Headquarters, said record rains had left thousands of reservoirs in a dangerous condition and affected most major rivers.
"Although the level of the Three Gorges (dam) continues to fall ... the country is still in a critical period of flood prevention, so we need better forecasts and early warning systems," Mr Shu said.
He warned of the potential for landslides and flash floods caused by severe flooding to continue around the Songliao Basin in northern China and along the Yangtze River as the rainy season continues, with more storms expected in the north east, south west and east.
There has been flooding all over China this year. About 875,000 homes have been destroyed, 9.61 million people evacuated, and 22 million acres of crops ruined, according to the state flood control office.