The $2 billion desalination plant at Kurnell was predicted to be a "white elephant" during fierce debate over the project, which was announced 14 years ago.
NSW was in the grip of drought when Bob Carr announced the project in 2005 during a visit to Dubai, a few weeks before he stepped down as premier.
A short time later, Kurnell was announced as the preferred site, leading to protests from residents and environmental groups.
Objections included potential environmental damage to Kurnell and the Botany Bay seabed, across which a pipeline would be laid.
Residents feared damage and disruption of the pipes to be laid through the streets of Kurnell.
A Newspoll, released in December 2005, found seven out of ten Sydney residents were opposed to building the desalination plant.
They believed the Government should instead invest in water reuse and recycling initiatives.
The poll was commissioned by an alliance of councils, environment groups, scientists, and engineering experts, known as SCUD (Sydney Community United against Desalination)).
In 2006, a parliamentary inquiry concluded the likelihood of Sydney ever needing a desalination plant was small.
The head of a government-appointed team which assessed Sydney's water needs in 2006 said the plant was likely to be needed very infrequently.
''It would never have been needed in all the droughts in the last century,'' said Professor Stuart White, director of the Institute for Sustainable Futures at UTS.
''This makes it a 'stranded asset', which is economic language for 'white elephant'.''
So strong was the opposition, the new premier Morris Iemma put the project on hold, saying the government had "got the message"' that people wanted a focus on recycling and other water saving measures.
However, he was adamant the government would retain the site and complete the pilot tests at a total cost of $120 million in case dam levels fell to a crisis point of 30 per cent.
Less than a year later, with dam levels continuing to fall, Mr Iemma announced that if Labor was returned at the March, 2007, election, he would sign the contract.
"It is time to get on with it,"' he said.
Mr Iemma shrugged off earlier assurances that the ''trigger'' for building the plant would be dam levels falling to 30 per cent capacity.
Dam levels were at 34 per cent, but Mr Iemma said that with no sign of the long drought ending, the government had to act.
He said desalination plants were being built in other cities in Australia and overseas, and competition for materials and expertise could lead to cost and construction time blowouts.
Labor had a resounding win at the 2007 election.
Opposition Leader Peter Debnam's alternative plan to mix recycled sewage effluent to Sydney's catchments was rejected by voters.
The first desalinated drinking water flowed in February 2010, and the plant ran continuously for two years to prove plant capacity and reliability before it was placed in mothballs.
In 2015, the plant was living up to predictions it would be a "white elephant" when Sydney dam levels rose above 90 per cent.
In January 2019, the desalination plant was switched on following an extended dry spell which saw water levels drop to 60 percent capacity.
Seven months later, the state government announced it had begun "preliminary planning" to expand the plant as Sydney dam levels continued to drop at record pace.
The plant is producing 250 million litres of water a day at present, but was constructed in such a way that capacity can be scaled up to 500 million litres per day.