cape town

Why Day Zero Couldn't Happen!

See the amended version on The Conversation

When dealing with a complex crisis such as the Cape Town water situation, it is important to understand how proposed interventions would achieve the intended goals by using systems thinking. The world has zoomed its focus to Cape Town as the city faces an impending threat of “Day Zero” – albeit with shifting dates. Day Zero represents the point at which the municipality turns of water distribution system for much of the city except strategic and vulnerable areas. The big question is whether the measures in place to manage Day Zero on a day-to-day basis are robust or even feasible. The city has broadcast a disaster management strategy which includes establishing 200 water distribution points across the city, at which citizens can collect their 25 litre daily water allocation. This thought piece utilised system dynamics – a modelling approach - to simulate water collection in this manner over the course of a day (24 hours). Key assumptions were made: the population of Cape Town is estimated at 4 million people – 700 000 people who live in strategic areas or informal settlements will not have their taps turned off – 800 000 people within proximity of informal settlements will potentially source water there; 2 500 000 people will be required to collect water at designated water points; 200 distribution points are planned; an average of 50 taps per distribution site; water distributed is 25 litres per person – individuals are able to collect up to 100 litres a day to cover four day of consumption or share with other members of their household - this model assumes that the whole population must receive their allocation, but does not specify the hoarding or sharing behaviours which enable this; initial water pressure is assumed at a level which allows outflow of 10 litres per minute, which implies it requires 2.5 minutes to fill 25 litres or service one person; a waiting delay of half a minute (30 seconds) from changing between containers and people is assumed; equal distribution of people per water distribution point is assumed.

Insights and possible reactions
With the above assumptions, it would require 12.5 hours to provide water to the entire population per day, which can be cumbersome! Possible reactions to deal with the Day Zero water supply approach, illustrated in Figure 1, include: (i) doubling the number of distribution points (grey), which would require increasing the distribution points from 200 to 400, which will enable serving the population within 5 hours; (ii) changing water pressure to between 20 – 30 litres per minute (yellow), based on the population requiring to be serviced, which enables servicing the population within 8 hours; (iii) increasing the number of taps per distribution point to 75 or 100 per distribution point (blues), which would make it possible to service the population within 9 hours and 7 hours respectively. A combined scenario of 75 taps per site and increasing water pressure to 20 – 30 litres per minute, while maintaining the 200 sites (green), shows that the population are serviced much faster but within 6 hours. This appears more practical scenario, than doubling distribution points, with only one hour less time (5 hours) in servicing the population, in comparison with the combined scenario.

Figure 1_Population Serviced per Distribution Point Scenarios
Figure 1: Population Serviced per Distribution Point Scenarios

Socio-political dynamics of water crisis

Water crisis is a socio-political issue, and the insights discussed above could function perfectly as technical solutions. However, socio-political realities would quickly undermine these imagined, technical, plausible scenarios. For instance, how can the city ensure that people are taking the allocated amount of water? How would military order at a distribution point look in practice? What is the extent of conflict arising at the water points due to long queues and unmanaged behaviours, and how does this compromise the ability to service the people at a distribution point? To what extent can the water crisis contribute to some sort of social cohesion, given that water does not discriminate against anyone? How can water remain in the commons when those with means are able to develop private sources?

The aggregate impact of socio-political dynamics deviates from the well-organised technical solutions proposed above. They can be represented as random shocks, referred as ‘disruption noise’. This could dramatically increase the time required to service each person, implying that less people are serviced per hour (see Figure 2). It also means that, it will require 25 hours to service the population per distribution point, illustrated in Figure 3.

Figure 2_Average Population Serviced per hour due to Disruption Noise
Figure 2: Average Population Serviced per hour due to Disruption Noise
Figure 3_Comparison of Population Serviced per Distribution in Base and Disruption Noise Scenarios
Figure 3: Comparison of Population Serviced per Distribution in Base and Disruption Noise Scenarios

A key insight of the scenarios suggests that should Day Zero occur, the best technical intervention with less time required to service the population, would be doubling the number of distribution points to 400. However, a combined scenario of increasing number of taps per distribution point and increasing water pressure, while keeping the distribution points at 200, would be more practical. Further, the reality of conflict and water collection delays would increase the amount of time needed to service the whole population. These delays are unpredictable and incalculable and are the greatest indication for why Day Zero cannot be allowed to happen. The disaster management plan is unfeasible and would struggle to service people timeously while managing conflict.

A shared responsibility to become water cognisant

Water crisis in the city of Cape Town is a shared responsibility which faces a ‘tragedy of Commons’ systems archetype. What this means is that individuals may act in self-interest (such as water hoarding or wasteful water activities) at the expense of society. The availability of water resource, which may prevent the occurrence of Day Zero, is dependent on everyone acting in water-conscious manners, and being cognisant of how day-to-day activities, contribute to water efficiency and water availability for all.

Cape Town has for a long time, focused and relied, on water demand management measures, with limited interventions on the supply side management. Lessons from the Cape Town water crisis for other cities include better planning by focusing on the root cause of problems and not their symptoms, identifying high leverage intervention points, and understanding how best to affect these interventions. We hope the efforts to record how the many actors in Cape Town have contributed to water demand reduction as well as supply augmentation, will be used when future interventions are needed.

The Cape Town water crisis has been a result of the patterns and trends that systemic structures generated. Further, the variety and diversity of our understanding of how the system works, means that various actors in society (e.g. households, government, business, and academics) perceived and interpreted the systemic structures differently, and therefore acted differently.

This is a lesson that the City should take on: by more actively understanding, characterising, measuring, and communicating its dynamic metabolic patterns, which include not only water, but also energy, food, and wastes. There are many groups in the city that can improve the sourcing, utilisation and efficiency of the resource systems on which the city relies. After all, you cannot manage what you cannot measure.


the memory of water

This poem was presented by Paul at the Joint Conference of the International Society of Industrial Ecology and International Symposium of Sustainable Systems and Technology, hosted in Chicago from June 25-29 2017.

the memory of water
(or: cape town’s linear, unsustainable water metabolism and the lack of anticipatory planning which led to crisis)

August 2014

rain falls on the slopes of the berg river catchment
drops coalesce into streams
that meet the theewaterskloof dam
steady. waiting. evaporating

a pump pumps
(with lightning tamed from broken atoms 50 kilometres away)
with grav assist
water moves through harsh environs
of chlorine and lyme.

in darkness enters the city and
split and split and split again
till bright light opens it upon
hands and dishes – in toilet bowls – from showerheads
sprayed across flowering plants and gleaming mercs
from running taps down muddy roads past informal homes
in boilers and engines and cooling contraptions
reshaped and shifted. evapotranspirated

condensed. absorbed -
the lucky become clouds
free float and fly
or sink underground
to feed green crop
or recharge the aquifer.

while the rest, suds and all
reenter the pipes
darkens conveys through solids extraction
anerobic and aerobic trauma
and absorbed by salty surrounds of ocean water
where nutrients bloom
and biodiversity

ecoli wash past blue flag beaches
touching bathing tourists
city patrons who come to cape town
for natures beauty
and may not feel
the memory of water.

March 2017

No rain has fallen on the slopes of the theewaterskloof
and the city –
surprised by events it predicted in 20 oh 6
– calls for all:
reduce your use

so highway signs count down to the
end of water
ignored by urbanites who imagine
water comes only from taps
120 days left
no thought of the panic elicited
when a disgruntled public
see only
20 days left
so the signs much change
pipe pressure is dropped
and government states plainly its policy:
lets pray for precipitation

meanwhile the gardens die
cars lie conscientiously dirty
while the city’s gone from
green to beige
and blame is passed
from citizens to city
from rich to poor
to fire helicopters dumping dam water on an intense fire season
(predicted in 20 oh 6)

June 2016

no rain has fallen on the slopes of the theewaterskloof
though drizzles tickle eyes of
longing capetonians
looking for rain
a perhaps psychological balm to signal the end
of crisis
hopefully not ending the
3 daily toilet flush – the 2 minute shower – the limited laundry
all part of the 100 litre goal per person.
too bad drizzle isn’t drinkable

when the rain arrives
the waves arise
a storm of note
floods the city but
the dam levels rise

this crisis will last
reduce your use
says the mayor
unveils a new planned portfolio
on sustainable views
of how the city will change
and so ensues
that resource efficiency is finally
on the agenda

August 2030

rain falls on the slopes of the theewaterskloof
flows through pipes to the city
meeting water that’s
with the system it moves through
supports. hydrates

now toilet wash holds value
fueling gardens (indigenous)
and busses (electric)
no highway signs needed
as society’s conceded:
reduce your use – we’re water scarce!

our water adventures in circular fashion
now city’s caught-on
that’s a good pattern
expanding its works
water treatment reverts
to send back grey black blue
for an extra purpose

and throughout the system
pipes are lined with messages to keep
the crisis of cape town
in the memory of water