Scientists find vast new freshwater sources under the sea

Untapped reserves of fresh groundwater – up to 0.5 million km3 – are buried beneath continental shelves around the world, according to new findings published in the international scientific journal Nature,

The research was led by Vincent Post (Flinders University, Australia) and co-authored by Mike Edmunds (Oxford), Jacobus Groen and Henk Kooi (Amsterdam), Mark Person (New Mexico), and Shemin Ge (Colorado).

These reserves were formed during the glacial periods over thousands of years when on average the sea level was much lower than it is today, and when the coastline was further out, rainwater would infiltrate into the ground and fill up the water table in areas that are nowadays under the sea. When the sea level rose due to the melting ice caps some 9000 years ago these areas were covered by the ocean. Many aquifers were – and are still – protected from seawater by overlying layers of clay and sediment.

This is good news since this water is accessible to many of the world’s burgeoning coastal cities suffering from water stress. But, it should be stressed, these waters are non-renewable and would need to be ‘mined’. Yet, the reserves are estimated at 100 times the amount we have already extracted from the earth’s subsurface.

In Europe freshwater has been found at and beyond the English Channel and North Sea coasts of the UK and the Netherlands, areas that were exposed as land masses for much of the past 80 000 years. Other areas with considerable offshore reserves include North America, China, Indonesia, Australia and South Africa.

There are two ways to access this water – through platforms out at sea or by drilling from the mainland or islands close to the aquifers. While offshore drilling can be very costly, this method should be assessed and considered in terms of cost, sustainability and environmental impact against other water sources such as desalination, or even building large new dams on land.

But while nations may now have new reserves of freshwater offshore, they will need to take care to not contaminate it. Boreholes drilled into the aquifers for oil and gas exploration or production, or targeted for carbon dioxide disposal can threaten the quality of the water.

The study “Offshore fresh groundwater reserves as a global phenomenon” by Vincent E.A. Post, Jacobus Groen, Henk Kooi, Mark Person, Shemin Ge and W. Mike Edmunds is published in the latest issue of Nature.

Reference

Post, V.E.A., Groen, J., Kooi, H., Person, M., Ge, S. and Edmunds, W.M. (2013) Offshore fresh groundwater reserves as a global phenomenonNature, 504: 71-78

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