The Three Gorges Reservoir has started to discharge water, to be prepared for the coming flood season of China's longest waterway, the Yangtze River.

The reservoir is planned to discharge 2.7 billion cubic meters of water before June 10, when the water level is expected to drop to 144.5 meters, a fall of six meters from the previous level, said an engineer with the Three Gorges Project Development Corporation on Thursday.

The water level marked 148.1 meters at 7 p.m. Thursday, said Yuan Jie, the engineer in charge of the discharge work.

"As the flood season approaches, it is necessary for us to make preparations beforehand," said Yuan.

Water in some tributaries of the Yangtze in the upper-reach areas of the reservoir has been reported to be flowing more slowly than before since the water level of the reservoir rose to 156 meters in October last year, adding to the risks of flooding "if we don't take measures now," said Yuan.

The local marine affairs department has asked vessels on the Yangtze River to pay attention to the changes of the river's waterlevel to avoid accidents.

Located where the Yangtze River's upper and middle reaches meet, the mammoth Three Gorges Project is said to be capable of holding back major floods on the country's longest river.

Its reservoir is capable of holding 22.15 billion cubic meters of water when it attains a normal water level of 175 meters, according to the corporation.

Launched in 1993, construction of the gigantic concrete structure of the Three Gorges dam was completed in May last year.

The water level in the reservoir will eventually reach 175 meters in 2009, when the Three Gorges project is finally completed.