China began a routine "health check" on the Gezhouba Dam, the first water control project on the Yangtze River, on Wednesday.
This is the third such check since the project commenced operation in 1981, local authorities said.
The checks, expected to last for 16 months, will cover all the water retaining and discharging structures around the dam and the reservoir, ship locks, banks and other facilities, said a statement issued on Wednesday by the Three Gorges Navigation Administration.
Further, an expert panel will make an appraisal report after all the checks are finished, said the statement.
The Gezhouba Dam, about 38 kilometers from neighboring Three Gorges Dam on its upper reaches, is located in Yichang City in central China's Hubei province.
The facility has undergone two routine safety checks in the past 30 years; the first was conducted in the 1990s and the second in 2005.