CAPE TOWN, Jan. 18 (Xinhua) -- The drought-stricken city of Cape Town in South Africa warned on Thursday that the chance of reaching Day Zero when water supply is cut off "is now very likely".

The chance of reaching Day Zero on April 21 is now very likely, the city said in an emergency notice to the citizens.

April 21 is the day when dams supplying water to the city would run dry, the city's taps would be switched off and water would have to be collected from designated points.

The city will be announcing everyone's local collection points from next week so that communities can begin preparing for that eventuality, according to the notice.

"The time to act for everyone's sake is now. So if we reduce the demand enough now, we can still get our water delivered to our houses and not have to queue daily for our allocation.

"We will also be making detailed Day Zero contingency plans available soon to answer all questions that residents and businesses might have," the statement said.

The city imposed Level Six water restrictions on January 1 amid predictions that Cape Town might become the first metropolis in the world to run out of water.

The city, hit by the worst drought in history since 2015, had urged the public to use no more than 87 liters of municipal drinking water per person per day.

But in Thursday's notice, the city urges its residents to use 50 liters per person per day for the next 150 days, after which the city will reassess the situation.

The new restrictions will come into effect on February 1.

The City Council will on Friday be voting on the punitive tariff that will charge residents exponentially higher rates for water usage above 6,000 liters per month.

As the second-most populous urban area in South Africa after Johannesburg, Cape Town is the capital of the Western Cape province and the seat of South Africa's Parliament, with a population of nearly four million.

In 2014, the city was named the best place in the world to visit by both the New York Times and the British Daily Telegraph.