This needs to change.
Between 2015 and 2017 South Africa’s South Western Cape region experienced three of its lowest rainfall years on record.
And many water resource planners are taking climate change into account when upgrading existing or designing new water supply systems.
But has this changing global climate already altered the risk of droughts like the one Cape Town just experienced?
Using a range of modelling approaches, we first estimated the frequency and intensity of three-year rainfall amounts over the South Western Cape in a world without human-induced warming of the climate.
This means that the key assumption of a stable climate, which underpins the design of the water supply system, has been undermined by climate change, at least for the South Western Cape region.
Our analysis shows that what has been predicted to happen in Southern Africa under changing climate in the future is already happening, with more dry periods today than, say, 20 or 50 years ago.
In addition to assessing current risk, our analysis also showed that with a further doubling of global warming over today from 1.0 to 2.0 degrees – likely to happen sometime in the next 50 years – there is a further threefold increase in risk of severe drought.
This means that droughts which the current water resource system is designed to survive will occur much more frequently.
Climate change projections are often taken into account when designing future water supply systems and other infrastructure.