Empty reservoirs, dry rivers, thirsty cities – and our water reserves are running out | Yasmin Siddiqi

Aquifers, the world's reserve water tank, are running dry. It's not easy, but we can work out how much groundwater is left, and how it's being used

We live on a parched planet. Farmers till arid pastureland and policymakers fret over empty reservoirs, dry rivers and thirsty cities. And that only scratches the surface - literally - of the world's water problem. Subterranean aquifers, the world's reserve water tank, are also running dry. The consequences could be dire, especially for water-stressed and fast-growing Asia.

These repositories of water located deep underground in permeable rock, soil or sand contain about 100 times the amount of water found on the Earth's surface in streams, lakes, rivers and wetlands. If you're in central Africa, South America or some parts of Europe, chances are you're standing a few hundred feet above one.