What happens when the water runs out?

Day Zero: Cape Town - South Africa

In 2017 the city of Cape Town in South Africa was close to “Day Zero”. What does that mean? A town of 3.7 million residents. No tap-water, strict rations and long queues in front of water collection points. But Cape Town managed to avoid the actual Day Zero by cutting the water usage by more than half.

An interesting aspect of managing water sustainably is the Water-Energy-Food (WEF) nexus. It describes the interactions between food, energy, and water resources and the systems by which these resources are produced, refined, distributed, and consumed. The water management gets complicated by the temporal variation in rainfall which is caused by climate change. The supply of water and the demand for water and energy are both affected by climate and weather. Energy, water and food are all deeply intertwined: while food production requires water and energy, energy production requires water (e.g. for hydroelectric generation and for cooling generators), and the water supply requires energy for treatment or delivery.

WEF-Nexus (Source)

But what caused the immense water scarcity in Cape Town that almost led to Day Zero? It is different factors that came together to lead to that event in the end. South Africa is largely dependent on rainfall, at the same time the levels of rainfall get more and more unpredictable, unevenly distributed and less due to the global warming. Cape Town draws most of its water from six large dams: the Theewaterskloof, Voëlvlei, Berg River, Wemmershoek, and the Steenbras Upper and Lower dams. There are eight more, much smaller dams responsible for the water supply, but their water capacity contribute only a 0.4% percent to the total capacity of 900 billion liters. It had been three years with very poor rainfall when the reservoirs were almost depleted in 2018. While this is the main reason for the water crisis in Cape town, a growing urban population and poor planning and mismanagement of the Western Cape Water Supply System (WCWSS) who own and manage the three largest dams. Cape Town’s residents also have a relatively high per capita water consumption, so that already weakened water resources are shrinking even faster.

The figure below shows some numbers underlining the reasons for water scarcity in South Africa. One example: South Africa’s average annual rainfall is way lower that the world’s average annual rainfall and evaporation is more than 3 times the rainfall.

South Africa's water resources by numbers (Source)

Another contributing factor (again strongly connected to the Water-Energy-Food-Nexus) is agricultural irrigation, especially for the wine regions bordering Cape Town. In the Western Cape Region, it usually starts with the planting season in early October, and peaks in January and February. It drops to nearly zero during the winter rainy season, which begins at the end of April. While the City of Cape Town consumes more than half from the Western Cape water supply system, the wine regions have over 90,000 hectares of irrigated land and consume the majority of the remaining water. Other urban areas in Western Cape Province consume less than 7% of the water.

Most aspects of the WEF nexus can be found in the example of Cape Town, but this blogpost continues focusing on the aspect of water. The WEF nexus is mainly used to design management strategies and explain interrelationships between various aspects. So, when Day Zero came closer, Cape Town had to decide on strategies to prevent that: reducing the high demand was a key priority. Residents of the city were instructed to shower less, flush their toilets less and recycle home-used water. At the most extreme times, people could only use a maximum of 50 litres a day. The city also restricted on what the water was used for. Washing your car or filling a swimming pool was prohibited. There are voices that claim that there is inequality between the rich and the poor in Cape Town and that the rich have been able to keep their water privileges during this time. Nevertheless, the city averted the worst of the water crisis by changing its habits and incoming rainfall. In 2019, the dams were over 80% full again, but researchers from Stanford University and the National Oceanic and Atmospheric Administration (NOAA) concluded that human-caused climate change made the “Day Zero” drought in southwestern South Africa five to six times more likely.

For that reason, I’d like to address water scarcity and food production in relation to the climate change in my next blogpost!