The rescuers were trying to reinforce the two dams built about a week ago in anticipation of increasing silt-washing water in the Yellow River, according to Xinxiang Municipal Government in Henan.
The new round of silt-washing operations in Xiaolangdi Reservoir, the largest water conservation project on the Yellow River, began on June 16, aiming to flush silt from its lower reaches into the Bohai Sea.
The water in the Yellow River grew up rapidly and rushed directly to Zhangzhuang Village in Lizhuang Township in Fengqiu County. Local people built five temporary dams to protect the village.
Two of the dams broke down and about 200 meters of the river banks collapsed on Thursday.
The Yellow River has been plagued by increasingly more mud and sand and less water. Each year, the river bed grows higher due to silt deposits, slowing water flow in the lower reaches.
The Xiaolangdi Project, which is second only to the Three Gorges Project on the Yangtze in terms of workload, has pushed over 200 million tons of silt into the sea thanks to the past three rounds of silt-washing since 2002.
The 5,464-meter-long Yellow River originates on the Qinghai- Tibet Plateau, winds its way through eight provinces and autonomous regions, and empties into the Bohai Sea in north China.