The restart of Sydney's desalination plant is proceeding faster than expected, helping to slow the drawdown of the city's reservoirs amid the ongoing drought.

The $2.3 billion plant, which resumed operations in January, has been supplying water to Sydney's network for about six weeks. Production is now between 300 and 400 million litres per week.

Cordeaux Dam is about 40 per cent full, while Sydney's reservoirs are now below 55 per cent capacity - and falling. Credit:NIck Moir

"In line with our operating licence, [the plant] has until September to reach its maximum capacity of producing 250 million litres per day of water - or about 15 per cent of Sydney’s drinking water requirements," Keith Davies, the facility's chief executive, said.

“However, we expect to reach full capacity by August, which is also ahead of schedule."