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.