THE THREAT OF DAY ZERO

Queues at public water taps could become normal. What can we do to avoid them?

- Prithi Parikh

Last month saw the hottest start to June on record, the arrival of increasingly normal hosepipe bans and water infrastructure targeted in the Russia-Ukraine war. As things heat up, aquifers shrivel – and London’s 90-day-supply of water means the city is never far from having its taps run dry. That’s Day Zero: a benchmark that several cities around the world have come alarmingly close to – or, in some cases, already reached – in the last decade. We spoke to Priti Parikh, professor of infrastructure engineering and international development at University College London, about the looming threat of Day Zero and how household tricks and national innovations offer promising solutions.

WHAT IS DAY ZERO?

Day Zero is the countdown to when a city or location runs out of water. The term was coined initially in South Africa, in Cape Town, where there was a water crisis in 2018. The city, which had four million people, was at risk of being left without water – and this led to a series of campaigns and restrictions on water use. In January 2018, for example, Cape Town declared water restrictions of 87 litres (l) per person per day, and later decreased it to 50l per day. The actual Day Zero was estimated to happen in April or May – there were complicated calculations around the exact date because the city is dependent on water from six dams. But luckily it rained and Day Zero didn’t happen. It’s quite striking that a city of four million residents was left at the mercy of rains.

WHAT WOULD DAY ZERO LOOK LIKE?