"If Capetonians don't cut water use even more, the next step to avert dry taps could be putting treated waste water back into the system and an expensive desalination plant, which would push water prices up by at least 50%," Mayor Patricia de Lille said on Tuesday.
With the dams that feed the city at 33% capacity, De Lille plans to ask for Cape Town to be declared a disaster area.
The reduced consumption target of 700 million litres a day still seems out of reach, with the latest figure at 837 million litres, thanks to around 20 000 excessive water users.
"We have 121 days left of usable water in our dams," said De Lille at a briefing to drive home the city's water crisis.
De Lille plans to write to Western Cape Environment MEC Anton Bredell, asking for the city to be declared a disaster area, so that it can institute emergency measures.
These would include treating waste water even further to put it in the potable system, drawing water from the Table Mountain Group Aquifer and the Cape Flats Aquifer, and in the long term, an ambitious R15bn desalination project with Eskom that would cost R1.2bn in operating expenditure.
"Please help us. We are in this together and we are going to suffer together," she said.
De Lille warned that the dams could soon be below 10% full and, if that happened, they would have to provide water intermittently, even though this would create problems such as air pockets in the water pipes.
The City was already reducing pressure from the Faure reservoir. It would also intensify the current 3B restrictions for summer and autumn, which means all garden watering will be stopped, and water use exemptions will be withdrawn.
"We are in a crisis," said De Lille.