- London could run out of water sooner than you think
- Water simulators can help shed light on the future of the city’s water
- A multi-pronged strategy will be needed to relieve a water-stressed London
In early 2018, Cape Town was approaching “Day Zero”—the day when the citizens’ taps would run dry following a three-year drought. Day Zero in Cape Town was avoided thanks to water use restrictions, cutting water to agriculture and pumping in extra water. However, unless decisive actions are taken, it is only a matter of time before a new water crisis comes. This is true for Cape Town, and for many other cities around the world, including London.
While we think of London as a rainy city, it actually receives less rainfall per year than Rome, Istanbul and Sydney. Given London’s population, it’s only a matter of time before the city runs into a major water scarcity crisis like Cape Town. The UK’s Environment Agency recently said that within 25 years London could run out of water.
To prevent London from becoming the next Cape Town, water engineers develop and apply mathematical models to identify potential risks to water supplies and solutions to mitigate them. These models are particularly powerful because of their capacity to test and explore shocks and scenarios that have never happened, by subjecting a simulator of a water supply system to those conditions. Like a flight simulator tells a pilot how a plane reacts to turbulence and her/his maneuvers, the water simulator tells water engineers how water supply security changes under different shocks, such as prolonged drought under climate change.
Simulators of London’s water systems show that if no action is taken, London is indeed set to experience more frequent and severe water shortages in the future. This is mainly down to population growth, but climate change complicates things further as it will mean more frequent and intense droughts.
Through these simulators, water engineers can also help identify solutions to prevent London from running out of water. Water simulators show that aggressive demand management to reduce consumption and losses in the distribution system (called leakage) is a priority to be implemented immediately. But reducing leaks from London’s old water pipes is not an easy task and will not be enough on its own.
Instead, engineers have been thinking about innovative ways to augment supplies. These include building new reservoirs, transferring water from other parts of the country or recycling wastewater. How should London choose between these different alternatives? The city needs something that’s not too expensive, that keeps residents happy with the price, taste and appearance of the water, while also reducing the risk of the taps running dry. Finally, water supplies need to be shared with ecosystems, so any solution needs to take into account the needs of the environment.
Deciding which action to pursue is particularly challenging, because the future will be significantly different from anything imagined when water supply systems were first built. Population growth and climate change mean that water engineers can no longer assume that past observations of water availability and demand are representative for the future.
To address this challenge, engineers focus on designs and strategies that combine robustness—through measures that work well under many possible climate futures—as well as flexibility to ensure we retain the capacity to adjust course and overcome hazards that might materialize. In the case of London, this means planning for an innovative wastewater reuse facility in North London while also bringing-in additional water via the Oxford Canal. And this approach has been used to help plan water resources not just in London, but across England and around the world. A nation-scale water simulator helped the National Infrastructure Commission understand and quantify the costs and effectiveness of strategies for coping in the most extreme drought conditions. In Australia, complex water system simulators underpin the country’s water markets and in East Africa they are being used to test alternative scenarios for cooperative water management of the Nile basin.