Tension is mounting at a natural spring in Cape Town that is popular with residents forced to contend with water restrictions due to severe drought, the city council said.

A fight broke out and one person was arrested by police earlier in the week in long queues at the Newland spring, southeast of the city centre, and local residents have complained of traffic gridlock.

Residents will be expected to abide by a 50 litre-a-day personal consumption limit from tomorrow in an effort to avert the so-called "Day Zero" scenario which would see taps shut off across the city.

"Day Zero" is currently forecast for 16 April.

Householders and traders would be forced to queue at 200 water collection points to collect a daily allocation of 25 litres per person - less than a two-minute shower.

The Newland spring has attracted hundreds of residents keen to supplement their current 87-litre quota.

"A physical conflict broke out and a person was arrested by the South African Police Service," said city security chief, councillor Jean-Pierre Smith in a statement.

"Congestion and noise from cars and persons visiting the site at all hours of the day and night is causing many complaints."

Residents will only be able to collect 25 litres per visit to the spring and officials will be posted to the site 24-hours a day to keep order in the queue.

Current dam levels fell last week to 26.3%, with the last 10% difficult to use, according to the Cape Town government.

But only about 55% of residents stuck to last week's limit of 87 litres a day.

A typical shower uses 15 litres per minute while a standard toilet consumes 15 litres per flush, according to WaterWise, a South African water usage awareness campaign.