The final cost of the Belmont desalination plant is yet to be finalised, the NSW Budget Estimates hearings has been told.
In response to a question about the project's funding envelop, Hunter Water's chief investment officer Darren Cleary said the final cost would be dependant on the Department of Planning's conditions of consent.
An Environmental Impact Statement was submitted late last year after a period of public exhibition.
Hunter Water is hoping to receive approval for the project in the middle of this year.
"It [the cost] will be finalised after the EIS because some of the conditions of consent may affect the cost," Mr Cleary told the hearing.
The government has previously estimated the project would cost about $100 million.
The desalination plant, which is part of Hunter Water's drought response package, will be switched on if overall storages drop to 15 per cent.
Construction is due to start when storages drop to between 35 and 40 per cent.
When fully operational it would produce 15 million litres of water a day or 10 per cent of the region's water needs.
Mr Cleary emphasised to the hearing that project's progress was dependent on storage levels.
"At the moment we are at 64 per cent, if we get back to average rainfall then we get back above 70 per cent the planning consent will be put on hold and we will only activate it should storage levels fall again," he said.
"I have taken advice from Hunter Water. We are in a firm situation, this dam (Grahamstown) is nearly at 60 per cent," she said on February 13.
"We expect that when all of the inflows come in we might get around 65 per cent. There are some good weather patterns developing."
A desalination plant at Walsh Point in Newcastle Harbour, a new dam, and increased water recycling are also under consideration.