The Badoucun reservoir dam burst yesterday and its water had flooded Xintang village of Taojiang county, the Hunan provincial flood control and drought relief headquarters said.
Heavy rain since Tuesday had increased water levels, putting pressure on the dam.
The ensuing flood damaged 10 hectares of crops.
The local government has started the emergency response plan to repair the dam. The Badoucun reservoir was constructed in 1973.
It has been listed on the provincial reservoir reinforcement plan, as it was known to have safety risks, state-run Xinhua news agency repoRted.