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?
Chennai, the sixth largest city in India, has between six to ten million residents and reached Day Zero in 2019. As they came closer to Day Zero, there were restrictions on water supply to houses, which meant that people had to take buckets and queue up for water collection. They had to purchase water from private vendors at very high costs.
It had a big impact on local businesses and hospitals (to provide vital healthcare services, you need access to water). Once again, the city was saved by rain, but it was a very serious situation affecting mental health and wellbeing, the economics of the city, but also the social fabric of Chennai.
What does it take for this to happen?
As human beings, we have overexploited environmental resources on our planet. In places where we rely on groundwater, we keep on pumping and extracting it out, and this happens over a period of years.
Chennai, for example, had about a thousand small lakes, wetlands and bodies of water which provided water, but in the last 30 years or so, with urbanisation, that number has reduced to 200. This is a process that has been a few decades in the making, but we’re seeing an increase due to climate change as we have drier summers – and that’s not helping us build up reserves of water.
How close is the UK to Day zero?
We’ve had droughts over the last few summers, including a hosepipe ban for gardens and discussions about restrictions on car washing and how we use water in the garden. It’s not hit drinking water yet, but the Environment Agency’s national framework for water resources has identified a water scarcity crisis as a huge risk. It has said that we need to act now.
So we need to boost our water resources: we need to reduce leakage, we need to reduce demand and we need this action plan to build resilience in the water supply. Otherwise, we do run a risk of running out of water in England.
People may be surprised by this because it rains a lot in England, but the amount of rain is actually not enough – and I think we’re all noticing that our summers are getting drier.
What are the solutions and innovations that could help us tackle this issue?
There are a few things we can do. Addressing leakages in the water infrastructure system is part of it (in the UK about 20 per cent of water is lost through leaks). Then we have water meters, which enable households to look at how much water they’re using to see if they can change their behaviour.
Rainwater harvesting, if done at a neighbourhood or community scale, has huge potential – along with nature-based solutions.
For example, sustainable urban drainage systems (SUDS) involve opening up drains in cities to collect rainfall, allow it to percolate into the ground and recharge groundwater. Landscaping is also a good option: planting trees is not only good for carbon emissions, but also helps to reduce the flow of rains and enables more water to be absorbed into the ground.
Desalination [of seawater] is often seen as a solution, but the salty brine this produces causes havoc to our environment as it builds up deposits of salt in our oceans and damages marine ecosystems.
What role does personal water consumption play?
Behaviour change is a big part of this. We have a high water footprint, which includes actual and virtual water consumption. For example, we need 15,000 litres of water to produce a kilogram of beef, and 90-150l for a pint of beer.
We need to look at our consumption patterns, because in a city at the scale of London, every little bit will matter.
The UK’s average water footprint is between 120-150l a day, which is high. If we benchmark ourselves against water-scarce regions, such as Jordan, that’s double. Jordan is down to 50-70l, depending on seasons. But we aren’t the highest. In the US, the water consumption per person is double the UK’s. This is not a sustainable model.
On this planet, it feels like we have a lot of water, but the proportion of water that we can really use is about one per cent.
About our expert, Prof Priti Parikh
Priti Parikh is a professor of infrastructure engineering and international development at University College London. She is also the research chair at The Bartlett School of Sustainable Construction. Her research investigates water infrastructure for resource-constrained settings such as slums and rural communities in Africa and Asia.
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