Cape Town’s household water consumption figures don’t add up

15 February 2018

Since 2017 I've disputed the City of Cape Town’s claims, unquestioningly repeated by media, politicians and others that allegedly, over 60% - in fact, 63% - of households are not saving water and must be forced to with punitive measures.

Note this figure has remained constant despite residents drastically reducing consumption from a year ago.

Their numbers just don’t add up. I believe their flawed analysis has been used to demonise householders and shift blame and attention away from the city's poor management of the disaster. In a News24 Q&A Deputy Mayor Ian Neilson said of the 60%:

"This is based on the billing information of account holders. It looks at what should be paid if one is within the limits, and then identifies the account holders who are over that and who have not applied for quota increases."

Incidentally, the city never says how many businesses, etc are not saving water.  Are residents the only ones responsible for conserving?

They've extrapolated account holders – I assume householders only and not business, industry, government, etc – to the city's 3.7 million people including informal settlement and backyard dwellers and tenants who don't receive accounts and arrived at an assumption 60% of residents, i.e., 2.2 million, are not saving water. I don't think that’s credible.

My view is supported by the statement "some 200 000 households are using more than 10 500 litres per month (more than 350 litres per day)". 200 000 is 18% of the city's 1.1 million households, not 60%.

Well, which is it – over 60% or 18%?  I think they’re conflating two datasets or misinterpreting one or the other and arriving at conflicting figures, both of which they use in public information.

Looking at it another way, of the city’s almost 4 million people, 1 million live in informal settlements and use only 4.5% of city water (this excludes backyard dwellers). Let’s assume informal settlement residents don’t get municipal accounts. So the city does not have billing and therefore consumption data for 1 million people (the 60% is based on billing information). They’re basing total, city-wide household consumption on the formal residential population only, i.e., 2.7 million. If so, 60% of that is 1.6 million who allegedly are using too much water, or 44% of the total population.

Or are they including informal settlements among residents they say are not saving water? But we know they can’t be because they’re using billing data and informal settlements residents are not billed. The qualitative information they’ve shared in press releases is confusing and contradictory and mathematically, methodologically and factually suspect. What is the true situation?

In a Daily Maverick article this week Jason Norwood-Young analysed consumption data extracted from data on Cape Town’s Open Portal Data and finds the city’s “60% figure could be the result of rounding error”. (His previous article contested the 60%, and said the crisis is not residents’ fault.)

“If we look at the actual number of households up to and including 10 kilolitres of water a month, we find that the overwhelming majority – 505 766 – are compliant. That leaves just 12% using 11kl and up. Without more granular data it is difficult to gauge the true figure accurately, but the data indicates that 60% is an inflated claim. The true number is somewhere between 60% and 12%, and would be closer to 12%.”

Another factor is the city is basing household consumption on an assumed, average number of people per household. In his response to Daily Maverick’s findings Neilson said, “The city assumed 3.2 people per household, which would set the target per household per month as 8 352 litres, not 10 000 litres. This then provided a relationship which we tracked, on the assumption that at 500 megalitres per day of demand, 100% of Capetonians would be using 87 litres of water”.

That’s a lot of assuming. The average household figure is incorrect because it includes informal householders not on the city's billing system and doesn't factor multi- and extended families – more than four people – on one property. The fact is they don't know how many people are in a household. For example, half the households on my street have more than four people on the property, including two multi-families.

My household has five people and numerous cats, dogs and wild birds, which also need water. Three months ago our billed water use was 12kl for 33 days but individually (including animals) we used 73l per person per day, less than the then limit of 87l. We're doing all we can to save water. We are conservation-minded and reused grey water and bucket washed long before it was fashionable or necessary. And we didn’t tweet vainglorious pictures of our feet in a bucket of water. Until restrictions prohibited it, our extravagance was the garden, which now must take care of itself but is still doing reasonably well in the circumstances. We can’t do much more.

Therefore, I get irritated with the self-righteous born again water warriors including media, celebrity and political darlings who preach to the converted about what they are doing to save water, which most people are doing anyway. I ask: What were you doing before this?

Which leads me to the question: Is it fair and just a household of more than four people (3.2 to be exact) will be penalised and named and shamed and collectively must do more to save water than a smaller household? The city said households may now apply for quota increases but this is a recent thing that dates after they claimed over 60% of people are not saving. How many households have applied for the exemption? We shall not.

Another problem is meter readings are taken from 20- to 30-odd day periods.  Our account two months ago was for 25 days (9.5kl). When the city performs its calculations of the "billing information", do they reduce it to a 30-day monthly baseline or, as I think, read the raw accounting data dump without qualification so it includes meter readings taken anywhere from 20 to above 30 days? This is the kind of small 0.5kl increment Norwood-Young spoke of that pushes a household into punitive territory of “overuse”.  Obviously, water accounts for periods over 30 days will show higher consumption than 30 days or less and thus be above monthly limits and be among the "over 60%" households.

You see, to breakdown, refine and analyse bulk information for 1.1 million households as I've described takes a lot of work, which I don't think they’re doing. Two years ago when I requested Neilson and city for accounting information for the Cape Town Stadium I was told the information, which ordinarily is extracted from their accounting system, "simply does not exist" and had to be specially compiled.

Compare Norwood-Young’s, who is not a water expert and lacked accurate billing data, detailed and credible analysis of publically available information to former hydrologist and city finance member Neilson’s generalisations on which they are actually making policy.

Therefore, to allege 60% of the city’s population of almost 4 million people are not saving water when most are probably doing everything they can is disinformation, miscalculation and/or misinterpretation of the data.

For a city with a sophisticated multi-million rand accounting system and scores of accountants, engineers and quantity surveyors, guessing is unacceptable, incompetent and unprofessional. It’s more so during an unprecedented crisis where residents are being blamed for almost everything, named and shamed, punitively fined and where the city tacitly encourages people to spy on neighbours using the water map and report their alleged overuse, leading to civil tension.

Any confidence they know what they’re doing was demolished when Neilson, who responded to Norwood-Young’s questions with assumptions, recently was unable to answer a single question about Day Zero.

Accidental or deliberate, their guessing is negligent and in this tense situation, highly irresponsible. This is another instance of their bungling of the disaster – a “monumental failure of vision and planning” – from the outset. Their mantra the majority of households are to blame, which they, their agents and supporters, and with a very few exceptions, the media, have unquestioningly repeated, is part of the mischievous narrative vilifying residents that Premier Helen Zille recently posited suggesting civil “anarchy” and “World War 2” and “9/11”-type scenarios if and when the taps run dry.

But even at this late stage they can and ought to do better rather than rely on the finger-pointing tropes they believed worked for them so far.

I sent a previous version of this article, before and excluding Daily Maverick’s findings posted this week, to Ian Neilson and mayco member for water Xanthea Limberg for comment. There was no response.