South Africa's drought-stricken city of Cape Town has pushed back its estimate for "Day Zero," when residents will have to start queueing for water, to May 11 from April 16, authorities said on Monday, citing a decline in agricultural water usage.

"Capetonians must continue reducing consumption if we are to avoid Day Zero," Cape Town's executive deputy major, Alderman Ian Neilson, was quoted as saying.

Neilson added: "All Capetonians must therefore continue to use no more than 50 litres per person per day to help stretch our dwindling supplies."