Cape Town’s wet winter is much drier than usual and city officials are pleading with residents to help build up the city’s water reserves.
Reporting on the dire state of affairs, news agency GroundUp discussed a number of the city’s projects to conserve water.
The article highlighted that “65% of [city] water goes to formal residential customers. Half of that is used for non-essential purposes – filling pools, watering gardens, washing cars and so forth.”
Stats came from mayoral committee member
To get the source of the statement, Africa Check spoke to the article’s author, Lilly Wimberly. Wimberly told us the data was provided by councillor Xanthea Limberg’s office.
Limberg is the city’s mayoral committee member for informal settlements, water and waste services, and energy. She gave Africa Check a breakdown of the city’s water consumption patterns by category for the financial years 2015/16 and 2016/17.
At last count, the city was using 610 million litres of water per day.
The city’s water consumption data shows that residential units (69.9%) used the majority of supplied water. The bulk of this residential consumption was in formal settlements (64.5%), while informal settlements accounted for 3.6% of the consumption.
But how is this water use determined? Limberg explained to Africa Check that “the city has at least one meter [for] all formal developed stands and we have accurate information on the land use and land zoning of each stand therefore we are able to determine consumption levels per land use category”.
Africa Check spoke to Prof Heinz Jacobs, a director at Stellenbosch University’s Institute for Water and Environmental Engineering. He pointed us to a study he co-authored on the water saving achieved following water restrictions the City of Cape Town implemented in 2004.
The study compared individual water meter readings from the City of Cape Town’s treasury system. Readings before water restrictions (1 October 2003 to 1 April 2004) and during water restrictions (1 October 2004 to 1 April 2005) were collected.
The researchers grouped their findings into four land use categories, namely residential (single standing dwellings), industrial, commercial and institutional, “other” (including group housing, flats and farmland) and “unknown”.
The study found that water use in the residential category accounted for 55.1% of total water use during the 2003/2004 period and 54.2% of total water use during the 2004/2005 period. (Note: Water use fell by approximately 14% following the restrictions.)
Because of this, Jacobs notes that the 65% figure the City of Cape Town provides is “plausible because we did not include flats in our sample set… [the city] lists “flats and complexes” as 9.2% and 9.5% of the total, so give or take a few minor errors I will believe the 65% without arguing about it”.
What exactly does the city consider as non-essential water use?
“We regard outdoor water use as non-essential and we are allowing essential water use only for bathing, eating and drinking,” Limberg told Africa Check. “The quantities of water required for outdoor purposes are on the whole much greater than quantities necessary for indoor functions.”
We asked how the city measured the use of water within a residential setting. Limberg noted that the city had conducted “various engineering research analyses and site studies to determine typical patterns of household water consumption in order to be able to collate such a breakdown”.
“We also make use of other national and international research to get guideline figures,” Limberg added.
Africa Check asked for access to the research mentioned, but the city hasn’t supplied it yet.
Jacobs told Africa Check that, on average, an individual will use between 100 litres to 250 litres of water per day. “Most people will use 120 litres [per day] as a realistic low consumption for a house connection,” he said.
With 69.9% of supplied water going to formal and informal residential units – or about 426.4 million litres per day – this would mean that the 4,004,793 people living in the Cape Town metropolitan municipality consume, on average, 106.5 litres per person per day.
“These numbers are very low, and one could argue that there is very little room for ‘non-essential use’ in these current numbers,” Jacobs told Africa Check.
Dr Kirsty Carden, the urban water management theme leader at the University of Cape Town’s Future Water Institute agreed that while the average is arguably low, the exact “percentage of water used for outdoor purposes is open to interpretation. . . [it] is often quoted as being on average (per year), half of the total residential demand”.
“Bear in mind though that there is virtually no outdoor demand in winter in Cape Town, when it is raining and garden irrigation is minimized and swimming pools do not need topping up. Similarly, during water restrictions – as in our current situation – it can be assumed that all potable water consumption is for indoor purposes.”
In a previous fact-check, we highlighted that few studies have been conducted in South Africa to measure water end-use as they are expensive to run. One study, though, found that 32 respondents surveyed via the internet – who were “likely to be the higher income users” – estimated using 37.6% of their total water consumption on watering their gardens.
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