Cities are running out of water - can engineers save the day?

Think of a major city suffering from a water crisis and you’ll probably imagine somewhere dry and hot - Dubai, Cairo, or maybe Madrid. In fact, none of these even makes the top 20 most water-stressed cities, according to US charity the Nature Conservancy. Tokyo tops the list, but rainy London is ranked 15th. As it stands, water use in the British capital is at capacity, and the city is set to experience shortages of supply by 2025.
Londoners are not alone. 70% of the world’s population lives in places that suffer water stress at least once a year. The European Commission defines water stress as occurring when the demand for water exceeds the available amount during a certain period, or when poor quality restricts its use. And, with the world’s population forecast to reach 10bn by 2050, the situation looks set to worsen.