LONDON: Groundwater, the unseen source of life for two billion people, is diminishing almost everywhere in the world, according to a study published on Thursday by the UN Environment Programme.

So much water has been pumped from beneath Mexico City that buildings have in some places sunk two metres. The water table under the high plains in the American Midwest has fallen on average by three metres a decade and up to 30 metres in some places. So much has been extracted from southern Florida that the aquifers are at risk of flooding by sea water.

Paradoxically, some cities in the Arabian Gulf have become waterlogged because of leaking pipes from coastal desalination plants.

Twelve cities of more than 10 million people — including Bangkok, Shanghai, London and Calcutta — rely on underground water reserves.

“Some two billion people and as much as 40 per cent of agriculture is at least partly reliant on these hidden stores,” said Klaus Toepfer, executive director of UNEP. “Groundwater also supplements river flows, springs and wetlands vital for rural and urban communities and wildlife. Most of the world’s liquid freshwaters are found not in rivers and lakes, but below ground.” The world population has more than doubled in the past 60 years; water is used heavily by both industry and agriculture.

The report, published to mark World Environment Day, warns that in rural India, 50 per cent of irrigation water and 80 per cent of drinking water comes from underground, through three million hand-pumped wells.

Around 96 per cent of Saudi Arabia’s water and 69 per cent of Bangladesh’s comes from below ground. There are 1,300 boreholes tapping water below Dhaka, the Bangladeshi capital, and in some areas the water table has fallen by 40 metres.

Some 450m people in 29 countries live with chronic water shortages. One person in six cannot rely on safe drinking water.

More than 2bn people have no adequate sanitation. Water-borne diseases kill a child every eight seconds, and are behind 80 per cent of all illness and death in the developing world.—Dawn/The Guardian News Service.