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Cape Town had to dry out on April 12, 2018, leaving its 3.7 million inhabitants without running water.
The "zero day" was narrowly avoided by drastic cuts in municipal water consumption and last-minute transfers from the agricultural sector. But the process was painful and unfair, causing much controversy.
The city has managed to push back "Day Zero", but does that mean that Cape Town's water system is resilient?
We do not think so.
This may well suggest problems beyond Cape Town. Cities in the northern hemisphere, including Canada, are well into another summer season that has already brought record heat, drought and flooding with increased flow.
Water crises are not just about scarcity
Water scarcity crises are most often the result of mismanagement rather than an absolute decline in the physical water supply.
In Cape Town, below-average rainfall tipped the scales towards a "crisis," but the situation was compounded by slow and inadequate governance responses. Putting aside the debates about the responsibility to act and when, in our opinion, the most important problem was the persistence of obsolete ways of thinking about "uncertainty" in the system of action. ;water.
As the drought worsened in 2016, Cape Town water managers remained confident in the system's ability to withstand drought. Engineers and senior managers felt Cape Town's water system was ideally placed to deal with a severe drought, in part because of the much vaunted success of their current water demand management strategies. .
They were not totally wrong: demand management has reduced overall daily consumption by 50% since 2016. So what went wrong?
Limits of Demand Management
Water management was not well equipped to cope with the increasing uncertainty of rainfall patterns – a major challenge for cities around the world. Researchers at the University of Cape Town have recently argued that conventional models long used to forecast supply and demand underestimate the probability of water system failure.
Second, Cape Town's water supply system experienced a disaster in part because demand management seemed to have reached its limits. From the end of last year, the city imposed a water consumption limit of 87 liters per person per day. This ceiling then decreased to 50 liters per person per day.
Despite these efforts, Cape Town has never been able to reduce demand beyond the target of 500 million liters per day needed for the system to run until the next rainy season.
The mayor accused residents of the city of wasting water, but his reprimanding rhetoric should not be seen as a sign that citizens were non-compliant. The continued reduction of water goals was an indefensible long-term management strategy.
Buffers are the Key to Water Resilience
In the end, "Day Zero" was avoided primarily by relying on unexpected buffers, including temporary agricultural transfers and the private installation of water systems and boreholes in the richest areas of the city. The former has increased water supply and the latter has reduced the demand of the municipal system. However, these buffers are unlikely to be available next year, as water allocations for the agricultural sector will not be renewed and there is uncertainty about the long – term sustainability of removals. underground water.
For more than a decade, there has been leveling demand, reduced leakage and applied pressure management and water restrictions. This made the Cape water system very efficient and therefore less resilient because there were fewer reserves to tap during periods of unusual scarcity.
The UN Water 2015 report found that most cities are not very resistant to water hazards. As water managers continue to wait for climate change patterns to become more certain or more specific, they delay action, cripple decision makers.
If we really want our cities to resist water, we need to change collectively on water supply and demand. This will require technological and institutional innovations, as well as behavioral changes, to create new, more flexible buffers – for example, through water recycling, green infrastructure and other innovative measures.
Although Cape Town has avoided a disaster this year, it does not make it water resistant. Despite the arrival of the rainy season, Cape Town is still likely to face Day Zero at some point in the future.
Chances are the city is not alone.
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