Water gushed down the Leslie Harrison Dam spillway on Tuesday after dam operators opened one of the four giant gates for the first time since December.
Dam operator Mick O'Hanlon deftly raised the massive gate 75mm before 1cubic metre of water a second rushed out into the creek, which is west of Capalaba Regional Park.
Mr O'Hanlon, who lives at Capalaba and has worked at the dam for 41 years, was able to raise the gate electronically from an office overlooking the spillway.
The gates will be opened for two months to drain the dam from 75 per cent or 18,000 megalitres to about 50 per cent or 13,500 megalitres.
Over that time, it is estimated more than 86 megalitres (86 million litres) will wash out of the 24,000 megalitre dam every day.
Seqwater operations coordinator Craig Duncan assured residents east of the catchment there would be no flooding as the water would be slowly released.
The dam is being drained so engineers and Seqwater can check, and if necessary repair, the dam walls.
Local residents were told at the beginning of the year plans to introduce non-motorised water sports on the dam would be shelved until after the investigations, which could take up to five years.
