The City of Cape Town on Wednesday approved Level 4 water restrictions, which limits residents to 100 l of water per person per day.
It also bans all use of municipal water for outside and non-essential use. The restrictions come into effect from Thursday.
Mayor Patricia de Lille warned that she had asked council to support further restrictions, 4B, that can be implemented in the next 60 days.
This level would be more closely aligned with a 500-million litre per day goal, and be based on daily demand and supply, with no more public pools and spray pools, and water purely for drinking, cooking and washing.
Currently, the city uses about 666-million litres of water a day.
"We really are hoping that if the worst comes to the worst, the city will bring in - truck in water. We will make sure that the modular desalination plant comes on as soon as possible," she told reporters.
"The best still is for people to save water."
Every citizen had to decide how to "budget" their 100 l.
This meant not showering for longer than two minutes, not flushing the toilet more than three to five times a day, and using grey water wherever possible.
"We need a new relationship with water. The days of plentiful water supply in Cape Town are over," said De Lille.
"We need to embrace the fact that water scarcity is the new normal and all our future planning must accept that we are living in a drought stricken area."
Resilience was one of the key principles included in the Integrated Development Plan for 2017 - 2022, passed by the council on Tuesday.
Bottled water scams
The mayor said various small-scale augmentation schemes were being put into place, including drawing water from the Table Mountain Group aquifer and the Cape Flats aquifer, and small-scale desalination at Koeberg.
A water resilience task team, made up of city officials, would be established under the city's new Chief Resilience Officer.
A water resilience advisory committee would also be formed to give advice to the mayor, task team and mayoral committee.
"This committee will include a variety of stakeholders and experts, ranging from academics to members of communities."
De Lille said they had not yet asked for help from provincial and national officials.
She would set up a meeting with Water and Sanitation Minister Nomvula Mokonyane to "discuss exactly what role national can play".
Officials emphasised that there was nothing wrong with the quality of water coming out of the city's taps and that it was perfectly safe to drink.
People were warned about scams that encouraged them to buy bottled water.
De Lille thanked the city's inhabitants for all they had done so far to save water.