Day-Zero: An Introduction to the Cape Town Water Crisis (Part 1)

In 2018, Cape Town almost became the world’s first city to run out of water. Three consecutive dry winters (2015–2017) prompted a literal countdown to a so-called ‘Day Zero’. A day where city managers would be forced to cut off water supplies and the reservoirs would run dry. It was an incredibly close call, figure 1 shows how close reservoir levels were to running out.  Thankfully, the crisis was averted due to strict rationing and fortunately timed rainfall. Concerningly,  however, more recent research from Stanford University, suggests that in a warming world,  Cape Town’s ‘Day Zero’ drought won’t be an anomaly (Pascale et al. 2020). Instead, drought events could become common in semi-arid and arid regions, especially in southwestern South Africa, which has already been highlighted as highly vulnerable by the IPCC (2007). Therefore, to minimise risks from current climate change variability we must learn from the experiences of Cape Town. Over the next two blogs, I will reflect on what caused the drought and the lessons we can take to improve water resilience in other big African cities. 

Figure 1. An almost empty Theewaterskloof Dam in May 2017 and regional reservoir levels. Adapted from: (Muller, 2018)

Was Global Warming to Blame? 

 

As with any catastrophe, there has been considerable effort to understand what caused the drought and whether the region might face a repeat anytime soon (e.g Pascale et al. 2020; Otto et al. 2018; Muller, 2018). However, when it comes to these end-of-the-world type scenarios it seems that climate change is always to blame and that's exactly what city authorities used as a scapegoat. They weren't wrong and historical observations and climate models support their case. 

First, let's take a historical perspective (Figure 2 below). Rainfall in the region has been decreasing by an estimated 17mm per decade (Wolski, 2018). Although it is barely statistically significant (P-Value: 0.11), it could perhaps reflect the way in which anthropogenic climate change is affecting wider climate mechanisms. For example, linking these trends to findings from the fifth IPCC assessment report suggests that the increased aridity is as a result of stronger El Niño patterns, the poleward expansion of the Hadley Cell, and the southward shift of the Southern Hemisphere Jet Stream. Furthermore, Richman et al. (2018) found that although long-lasting droughts have occurred previously (1920s, 1970s and early 2000’s), the 2015-2017 drought was unique as it was the lowest rainfall in over a century and the first occasion where rainfall totals were less than the 10th percentile. Climate change is clearly resulting in prolonged dry spells and more variability. 

Figure 2. The trend in rainfall in the WCWSS region over the last 84 years. Source:(Wolski, 2018)

Future projections also suggest that climate change was to blame. Using climate simulations, researchers from Stanford found that the likelihood of the Cape Town drought occurring was made 5 to 6 times more likely as a result of climate change. The model also projected that under the most extreme projections of greenhouse gas emissions the city would be 80% more likely to experience another 'Day Zero' drought by the end of the century. These findings were also substantiated by other climate models, which showed that the risk of drought increased threefold because of global warming (Otto et al. 2018). Moreover, Cape Town is experiencing a greater number of drier periods than 50 years ago. Therefore, it is possible what has been predicted to happen over Cape Town is already happening and water resource systems will increasingly be stressed. It seems clear, then, that as a result of climate change the frequency of droughts will increase and that more projections should be made for thorough water risk management.

Final Thoughts.

Following the narrow escape from the ‘Day Zero’ scenario, the link between drought and climate change has become increasingly clear. The research above suggests that meteorological droughts within the region are likely to be more frequent within the future because of global warming. However, I believe that meteorological drought does not necessarily have to translate into what was experienced in Cape Town. Climate change adds to the uncertainties. However, I think it is important to examine whether extreme shortages are often exacerbated by poor management. In the next part of this blog series, I explore why climate change shouldn’t take the whole blame and explore whether political factors and poor planning were behind the urban water shortage.