Southeast Queensland will get a new desalination plant and the existing Gold Coast facility will be expanded under a new water security plan.
Premier Annastacia Palaszczuk told parliament on Tuesday the new desalination plant would be delivered by 2035 after cabinet endorsed the 30-year water strategy.
There are also plans to expand the Gold Coast's desalination plant by 2033.
"A detailed business case for the new desalination plant will be completed for budget consideration in 2025," Ms Palaszczuk said.
"The precise location of the desalination plant is yet to be determined and will be reliant on the business case."
Ms Palaszczuk said the water security plan was completed with Seqwater, Queensland's bulk water supply authority, and focused specifically on desalination to bolster the state's water supply in the face of climate change and natural disasters.
The government has also committed to constructing a new water treatment plant by 2033 and connecting Wyaralong Dam in the Scenic Rim region to the main Seqwater grid.
Ms Palaszczuk said connecting Wyaralong to the grid was the first step before expanding the Tugun desalination plant on the Gold Coast.
"Our priority next year in our budget will be these two key measures," the premier said.
She said Kawana, on the Sunshine Coast, had been earmarked as a possible location for the new facility while Water Minister Glenn Butcher told reporters early estimates put the cost at between $4 billion and $8 billion.
He said Queensland's grid must be prepared for booming population growth combined with climate challenges, and the Sunshine Coast was a logical choice for the new plant.
"It's a 30-year plan that considers population growth, projected rainfall and climate change to determine what new water infrastructure is needed and when we will need it," Mr Butcher told parliament.
"Part of the detailed business case that they will put be forward from Seqwater will identify how big it needs to be at that particular time, how much water will they be using out of it, and certainly the location as well."
Mr Butcher said modelling showed the proposed new desalination plant wasn't required until the mid-2030s but the government was keen to begin planning early.
