The City of Cape Town has expressed sceptism about a study which suggests that the fear associated with Day Zero was the single most successful intervention in its campaign to get residents to slash water consumption.
The University of Stellenbosch and University of Cape Town study, published in the journal Water Research, found that the fear of Day Zero - the day when the City said Cape Town's taps could run dry - was more successful than imposing water restrictions.
Deputy Mayor Ian Neilson said in response that he found it difficult to believe that any one factor had overwhelmed the others.
"Many factors affected people's behaviour toward water during the drought. It is also necessary to note that the reduction in water consumption was not only due to changed behaviour. Other factors, such as pressure reduction also had a large impact on water usage," Neilson said on Wednesday.
But he "noted" that the City's communication campaigns had been recognised by the researchers as a very necessary part of the strategy to cut water consumption.
Neilson said the City's overall management of the "unprecedented water crisis" had been internationally recognised, adding that water restrictions with increased tariffs played a vital role.
The researchers, led by Professor Thinus Booysen from the Department of Electrical and Electronic Engineering at the University of Stellenbosch, used data from a sample of middle to high-income consumers who had smart water meters, combined with billing information.
The study said Cape Town had become "notorious" in the international media in 2017 as a major city about to run out of municipal water.
"The prospect of dry taps was dramatically named 'Day Zero' by the City," researchers wrote.
From November 2016 to February 2018, the City of Cape Town had incrementally imposed six levels of water restrictions, from Level 3 to Level 6B, in an attempt to curb usage.
But the study's findings suggest that "users responded more strongly to the threat of waterless taps than to the implemented levels of water restrictions".
In September 2017, when the City introduced Level 5 water restrictions, these had the perverse effect of resulting in an increase in water consumption.
Booysen, with co-authors Martine Visser from UCT's School of Economics and Ronelle Burger from the Department of Economics at the University of Stellenbosch, suggest this was possibly the result of confusing messages contained in the Level 5 restrictions.
On October 4, the City of Cape Town released its Critical Water Shortages Disaster Plan.
This included information that there was only 27% of usable water left in the dams, and that Cape Town was expected to run out of water by March 2018.
The City spelled out the three phases of the disaster plan: phase two said water collection points would be set up for residents to collect water in containers, and the army and police would be deployed to ensure there was general safety in the city.
Phase 3 was that the system would collapse.
"The most dramatic change in behaviour appears to have been instigated by a media storm and consequent user panic after the release of the City's Critical Water Shortages Disaster Plan in October 2017," the study said.
The drop in water consumption was seen in the second and third week of October.
The study also analysed mainstream media and social media reactions to the government announcements.
After the release of the disaster plan, there had been an "outpouring of alarmist and distrustful articles in the media, voicing threats of dams less than a third full at the end of the rainy season, disease and death, and accusing the City of mismanagement and bad planning and non-viable augmentation schemes".
A graph shows the sudden effect of water usage plummeting for three weeks after the "media surge".
On October 25, after the "negative press and panic", the Western Cape premier and the national minister of water and sanitation issued separate statements "in an apparent attempt to calm the situation", and said Cape Town would probably not run out of water.
Although the most dramatic changes in water consumption behaviour appeared to have been instigated by the "media storm and consequent user panic" after the release of the City's disaster plan, the statements from the premier and minister, contradicting the City, "eroded some of this gain".
There was a further drop in water consumption after the stringent Level 6B water restrictions started on February 1. Water usage increased slightly after February 22, when it was announced that Day Zero had been postponed to July.
"The biggest response was observed, not when the restrictions or tariff increases were imposed, but in response to a three-phased disaster plan that warned of disastrous outcomes," the study said.
The results suggest that Capetonians responded more strongly to the threat of waterless taps than to the levels of water restrictions.
The researchers say their study points to a "remarkable success on the side of citizens to drastically revise their consumption patterns over a relatively short period of time".
"Moreover, our research seems to indicate that, while inciting some level of fear-mongering may have been a risky strategy for the municipality to undertake, it may have been the single most successful intervention in effecting profound behavioural change amongst citizens," the study found.