The South African city of Cape Town will slash residents’ water allowance to 50 litres a day from next month amid fears that it could become the world’s first major city to run out of water.
Cape Town, a popular tourist destination, has been hit by its worst drought in a century.
Ms De Lille warned that the city risked reaching "Day Zero" on 21 April, when taps in homes could run dry.
"We can no longer ask people to stop wasting water.
We must force them," she said at a press conference.
Africa Live: More updates What is behind Cape Town’s water crisis?
Drought hits Cape Town’s economy A person uses about 15 litres per minute for a typical shower and the same amount when flushing a standard toilet, according to WaterWise, a South African water usage awareness campaign.
Cape Town had earlier banned car washing and filling up swimming pools as part of efforts to conserve water.
The Indian cricket team was also urged to take showers of no more than two minutes during its tour of the city earlier this month.
Much of southern Africa has been recovering from a drought caused by the El Nino weather phenomenon, following heavy summer rains.