How do we stop a “day zero” of running out of water? Cape Town was one of the first cities facing this problem. How did it escape — and can it do it again?
Day Zero is reached when Cape Town’s dam levels fall below 13,5% (Climate Portal, 2022). During the severe drought of 2015-2018, dam levels were under 21%, and taps were on the verge of going dry (memeburn, 2018). Farmers helped by giving their water to the city. The government added restrictions to water use, increased water tariffs for heavy water users, and reconfigured its pressure management system — saving around 10% of supply (Global Resilience Institute, Bloomberg, 2019). The return of rain also helped, but these actions and results may not be easy for the next drought hitting Cape Town or another city.
So which measures should always be taken to avoid a day zero? The answer may be by trying to change the water usage habits of citizens. How did Cape Town change this successfully? They started by making things such as filling pools, water gardens, washing cars, or other non-essential uses illegal (National Geographic, 2018). Restaurants asked people to minimize toilet flushing with the slogan “if it’s yellow, let it mellow” (World Economic Forum, 2019). But maybe the most important measures were the social controls that the city implemented. This started with weekly updates of the dam levels to create awareness of water scarcity and digital boards on highways that counted down to Day Zero. In 2018, the city published a city-wide water map showing household level water usage, which helped people hold each other accountable (Bloomberg, 2019). An online community shared tips for saving water.
Do social norms work in long term? Demand is increasing again because social measures only worked when the drought was severe. When supplies returned, so did demand. It is necessary to “destroy” demand if the city wants to avoid a future day zero, by encouraging people to permanently reduce their demand for water.
Bottom Line: Cape Town implemented restrictions to avoid Day Zero once; if it wants to avoid a future day zero, then it needs to destroy demand.
* Please help my Water Scarcity students by commenting on unclear analysis, alternative perspectives, better data sources, or maybe just saying something nice 🙂