Residents of Cape Town's Philippi, Khayelitsha and Mitchell's Plain might think they are imagining things at the sight of a helicopter carrying what looks like a giant steering wheel over their properties this week.

According to Cape Town Mayor Patricia De Lille, this is actually a low flying helicopter carrying a device used to confirm the underground aquifers and water flows in the area that could provide much-needed water for the drought-stricken city.

"We ask residents and farmers not to be surprised when they see these field workers or helicopter operations in their areas," said De Lille.

"As far we possible, we’ll also try not to conduct the surveys on private land."

The survey is to confirm where the highest volume of water can be abstracted from the aquifers and ground water flow as the city moves to avoid "Day Zero" - the day the taps could run dry.

This could happen by May 13, 2018, according to the city's calculations, and disaster management teams are already working on setting up water points around the city in case it comes to that.

In the meantime, the city has introduced severe water restrictions to preserve the water supplies on hand, and is working on establishing desalination plants and aquifer extraction sites until the drought breaks.

The plans are also to shock proof the city for any future droughts and water shortages. No danger to residents

The helicopters will fly about 60 to 70m above ground using underslung measuring equipment called an electromagnetic loop flying around 30 to 40m above ground.

"The method being used for the survey will not pose any danger to residents," said De Lille of the airborne geophysical surveys.

She said the survey of the Atlantis Aquifer north of the city is finished, and this week contractors will focus on the Cape Flats Aquifer, specifically Philippi, Mitchells Plain and Khayelitsha.

De Lille said refurbishment of boreholes and other infrastructure at the Atlantis-Silwerstroom Aquifer has already increased production by an additional five million litres of water per day, and by July 2018 it should be bringing an extra 25 million litres of water a day.

The Cape Flats Aquifer is also expected to bring an extra 25 million litres of water per day from June 2018.

The City is also drilling abstraction boreholes in the Steenbras Catchment area.

The yield from the other areas of the Table Mountain Group aquifers such as the Helderberg, South Peninsula and Wemmershoek is expected to bring approximately 50 to 60 million litres per day.