Cape Town Droughts 2015-17: The Result of Climate Change?

For the last two weeks, we have explored the adverse impacts that climate change can have on rural water supplies in Africa and the ways socio-economic factors such as population growth and low funds can exacerbate these conditions. For the next topic of this blog, we are going to look at the extent to which climate change is to blame for the Cape Town droughts of 2015-17 (Figure 1). This was arguably one of the most extreme urban water shortages that has taken place over the 21^st century and we will see how the interaction between human and climatic stressors are again vital to understanding people’s poor access to water resources. 

Figure 1. The once submerged area of the Theewaterskloof Dam near Cape Town that became dry during the peak of the droughts in January 2018 (The World 2018).

Droughts have occurred regularly in Southwestern South Africa (SSA) over the last century, but the impacts of the 2015-17 droughts in Cape Town were particularly severe (Wolski 2018). As the video below shows, during the peak of the droughts in 2017, the municipal government imposed strict water restrictions in the city which resulted in household water rationing and greater social inequities relating to water privatisation. These restrictions were largely to avoid “Day Zero”, a shorthand term for the day when major dams supplying Cape Town’s water would get so low that water supplies would have to be turned off (National Geographic 2018). Day Zero is significant because It would have marked the first time the water supplies in a major city would have essentially run out (Booysen et al. 2019). Although Day Zero never materialised, it doesn’t stop us wondering how Cape Town got to where it did. Why did the city almost run out of water and what can be done to improve the city’s water resilience in the future?

Some argue that Cape Town water crises was inevitable as it was largely down to the severity of the droughts during those years. For example, Richman and Leslie (2018) suggest that the Cape Town droughts during 2015-17 were particularly intense as it was the first time when rainfall levels in the region were less than the 10^th percentile for three consecutive years (Figure 2). In fact, the study shows that previous droughts were normally caused by precipitation less than the 10^th percentile for just a single year making the prolonged rainfall deficit of the 2015-17 droughts a rather exceptional event (Figure 2). 

Figure 2. The cool season precipitation in Cape Town with the dashed lines representing the quantiles and ‘D’ representing droughts (Adapted from Richman and Leslie 2018).

The reason for the intensity of the Cape Town droughts in 2015-17 could be attributed to global warming. For example, there appears to be an increase in the severity of droughts after 1993 as the percentile of cool season precipitation for the recorded droughts gets smaller (Figure 2) (Richman and Leslie 2018). What’s more, the average temperature over Cape Town has gradually risen over the last 100 years, with the 2015-17 droughts coinciding with the highest temperatures on record (Morishima and Akasaka 2010; Richman and Leslie 2018) (Figure 3). This supports the Niang et al.'s (2014) prediction that climate change is expected to cause SSA such as Cape Town to become drier, intensifying the frequency of prolonged drought events. This suggests that climate change likely played an important role in reducing Cape Town’s water availability that may have contributed to the 2015-17 water crisis. 

Figure 3. The average cool season temperature in Cape Town with the dashed lines representing the quantiles (Richman and Leslie 2018).

Overall, there is strong evidence that climate change is to blame for the water shortages experienced in Cape Town during 2015-17. Furthermore, given that extreme droughts are likely to increase in SSA, will the threat of Day Zero continue to loom over the city (IPCC 2014)? As we will explore in the next post, climate change is not the only threat to water resources in the Cape Town. In fact, there are numerous social-economic and political factors that could also determine future access to water.