The executive mayor of Cape Town has warned citizens and prospective visitors that the city is “very likely” to run out of water in April. After two years of drought which saw rain at about one-third of normal levels, reservoirs supplying the city are running dry. Calls to limit individual consumption to 87 litres per day have, say the authorities, been ignored by three-fifths of the people living in greater Cape Town - which has 3.7 million people.

The mayor, Patricia de Lille, said: “It is quite unbelievable that a majority of people do not seem to care and are sending all of us headlong towards Day Zero.” That is the date on which the city runs dry. It was initially set at 21 April, but has since been moved forward to 12 April.

“Day Zero is the day that almost all of the taps in the city will be turned off and we will have to queue for water,” says the city council.

For tourists as well as locals, coping with the water shortage is becoming a daily struggle. Water pressure has been reduced to limit consumption and water leaks, and cuts in the supply are becoming more common.

Alistair Coy, a British visitor to Cape Town, tweeted footage of one of the reservoirs supplying the city. He called the crisis an “impending disaster in one of the world’s greatest cities”, and predicted Day Zero will arrive in March.

“Four million citizens will be expected to collect 25 litres per person from one of 200 collection points,” he said. “A true nightmare scenario is developing before our very eyes.”

Jamie Bowden, a long-stay UK visitor to the city, told The Independent: “The water crisis is the only topic of conversation. Arriving passengers at Cape Town airport are met with a huge banner on the drive out of the airport imploring visitors to shower for just two minutes.

“The tourism infrastructure is working – hotels, bars and restaurants are doing a roaring trade as always. But many of them have now turned off the water in the public loos and have put jars of hand sanitisers on the sinks instead.

“Tourists should be sensitive that this is a real crisis and they can play their part by acting like responsible Capetonians by conserving water.”

A statement from South African Tourism said: “To counter the short-term effects of the drought, the city has put in place a number of initiatives to increase the supply of water and make provision for water shortages for locals and visitors.

“There will be water for tourists’ essential daily needs including access to drinking water and for personal hygiene. At present, tourists will be able to shower and maintain daily hygiene. Some swimming pools at hotels have been converted to salt (ocean) water.”

Dealing with the drought has been made more complicated because the Western Cape province, in which Cape Town is located, is governed by the Democratic Alliance — which opposes the national government, the ANC.

Four new desalination plants are under construction in and around Cape Town, but three are running behind schedule and none is likely to be ready by “Day Zero”. Desalination ships are also being prepared.

Meanwhile a black market in drinking water is taking shape, according to Mr Bowden: ”I went to a warehouse that stocks large plastic water containers and the place is just being stripped every day. New supplies are coming by lorry every day from Johannesburg and they are gone in a couple of hours.

A spring used by a brewery in the Newlands area of the city has become a popular place for citizens - and organised gangs - to get additional water.

“It’s clear that the guys turning up in vans full of 25-litre containers are not doing it for their ‘personal use’,” said Mr Bowden.

“For enterprising gangs this is South Africa’s bitcoin. They know the value of stored fresh drinking water will soar in coming weeks and getting thousands of litres of it now for free is likely to be extremely profitable.”