The world’s top 11 most water-challenged cities

The BBC world news desk has compiled a list of the top 11 cities most likely to run out of water — and they’re not where you might think.

Of the cities on the list, five have especially high populations, most of 20 million people or more; four suffer high levels of water pollution; and two have critical levels of leakage. Among the other challenges are drought, seawater intrusion, and water resource mismanagement.

1. Sao Paulo, Brazil

Why? High population of 21.7 million people; drought; water resource mismanagement.

2. Bangalore, India

Why? Rapid property development; high levels of pollution; antiquated infrastructure with 50 per cent leakage.

3. Beijing, China

Why? High population of 20 million people; low water availability; surface water pollution.

4. Cairo, Egypt

Why? High relative number of water pollution-related deaths; critical water shortages expected by 2025.

5. Jakarta, Indonesia

Why? Illegal well-drilling is draining aquifers; prone to flooding.

6. Moscow, Russia

Why? High levels of pollution; low water quality standards.

7. Istanbul, Turkey

Why? High population of 14 million people; low per-capita water availability; water scarcity possible by 2030.

8. Mexico City, Mexico

Why? High population of 21 million people; intermittent water supply; 40 per cent of water is imported; leakage at 40 per cent.

9. London, UK

Why? Low levels of rainfall; 80 per cent of supply from rivers Thames and Lea; supply problems expected by 2025.

10. Tokyo, Japan

Why? High population of 30 million people; rainfall is concentrated during four months of year and a dry season could lead to drought; 70 per cent of water comes from surface rivers, lakes and melted snow.

11. Miami, US

Why? Seawater intrusion to Biscayne Aquifer, the main source of water, continues; and sea levels are rising.