S7 Ep45: Cape Town's day zero: How data rebuilt a city's water resilience

By 2018 the reservoirs supplying Cape Town were down to 20% of capacity. If they reached 13.5%, the city would need to shut down parts of the water network and send residents to collection points to fetch water. That was known as Day Zero, and the rain came just in time to avoid it.

Hugh Cole (City of Cape Town) joined the city government in the middle of the crisis, and has subsequently driven the use of data for many aspects of city planning, not just for water. Cape Town now runs its own household survey, works with a private sector partner to measure net migration, and randomises the rollout of water meters so it can find out how they change behaviour. It also runs trials on its electricity subsidy to check whether the money reaches the households it is meant to reach.

Cole tells Tim Phillips how the Day Zero near miss changed how the city's leadership uses evidence, and how other cities can follow the same path.

The research behind this episode:

Abajian, Alexander C., Cassandra Cole, Kelsey Jack, Kyle C. Meng, and Martine Visser. 2025. "Dodging Day Zero: Drought, Adaptation, and Inequality in Cape Town." NBER Working Paper 33468.

Cole, Hugh, Kelsey Jack, Derek Strong, and Brendan Maughan-Brown. 2020. "City of Cape Town, South Africa: Aligning Internal Data Capabilities with External Research Partnerships." In Handbook on Using Administrative Data for Research and Evidence-based Policy, edited by Shawn Cole, Iqbal Dhaliwal, Anja Sautmann, and Lars Vilhuber. Cambridge, MA: Abdul Latif Jameel Poverty Action Lab.

To cite this episode:

Phillips, Tim, and Hugh Cole. 2026. "Cape Town's day zero: How data rebuilt a city's water resilience." VoxDev Talks (podcast).

About the guest

Hugh Cole is Director of Policy and Strategy and Chief Data Officer at the City of Cape Town, where his department covers strategic policy, strategic planning, research and economic analysis. He is a Visiting Senior Fellow at the School of Public Policy at the London School of Economics. Before joining the city in 2017 he was Director of Country Programmes at the International Growth Centre, running teams in 14 countries across sub-Saharan Africa and South Asia.

Research cited in this episode

Day Zero. The term began in the media as the day Cape Town's taps would run dry, then settled on something more specific. It became the day dam levels would hit 13.5%, at which point the city planned to shut down parts of the reticulation network and open water collection points, sequenced so that the most vulnerable communities were affected last.