Capetonians are using about 40 million litres less water a day than they are allowed to, even though the water crisis ended nearly five months ago.
Experts say this could indicate a sea change in consumers' understanding of the value of water.
It could also be that the fear of Day Zero, when taps were predicted to run dry last April, is still fresh in people's minds.
Christine Colvin, senior manager of WWF's freshwater programme, said WWF had done a small survey among office staff and had found that most people were still sticking to their water-saving behaviour – and that most people were doing so out of fear of a Day Zero scenario happening again.
"One question in the survey was about why they saved water and we gave them various options such as 'because it is the right thing to do' and 'because of peer pressure' and so on, but the reason most people gave is that they changed out of fear.
"My sense is that we learn from previous harsh lessons. What will be interesting to monitor is how long the behaviour changes last, whether they are permanent or not."
It is a year this month since Cape Town was forced to cut water use to just 50 litres a person a day in the face of Day Zero.
Day Zero was averted because farmers gave Cape Town some of their water allocation, and because of good early winter rains.
The strict regime of a total of 450 million litres a day for the City lasted from February until the end of September last year.
At the start of October, when dam levels had risen but dams were not filled to capacity after a below-average total winter rainfall, the water restrictions were eased to allow 500 million litres a day.
These restrictions were eased even further at the start of December to 650 million litres of water a day.
However, in the 12 weeks since then, water consumption has stayed well below 650 million litres a day.
Karoo still in the grip of drought
From December to mid-January, consumption ranged from 540 to 595 million litres a day. So despite the heat of summer, consumers used 55 million to 110 million litres less than they were allowed to use.
Consumption crossed the 600 million litres a day mark only on January 21, when it rose to 604 million litres a day. Since then, the weekly consumption has been 602, 614, 633 and 610 million litres a day over the past five weeks.
The Cape Town supply dam level was 56% of storage capacity on Monday, a drop from 57.4% this time last week, but well above the 24.5% it was this time last year.
The average level of all dams in the Western Cape is 43.5%, compared to 22.5% last year during the same period.
Anton Bredell, MEC for local government, environmental affairs and development planning, said on Monday the Karoo region was still in the grip of drought as the recent thundershowers had been very localised and hadn't fallen in the catchment area, so very little of the rain had run into the storage dams.
Bredell was concerned about the slow progress the Department of Water and Sanitation was making on raising the Clanwilliam Dam wall.