Scientists in Australia have reported the discovery of huge freshwater reserves preserved in aquifers under the world's oceans. The water has remained shielded from seawater thanks to the accumulation of a protective layer of sediment and clay. And it’s not a local phenomenon. Such reserves are to be found under continental shelves off Australia, China, North America and South Africa.

The discovery was made by researchers at the National Centre for Groundwater Research and Training (NCGRT) and the School of the Environment at Flinders University. The scientists estimate there is around half a million cubic kilometers of what they describe as “low salinity” water, which means it could be processed into fresh, potable water economically.

The reserves formed when ocean levels were lower and rainwater made its way into the ground in land areas that were not covered until the ice caps melted 20,000 years ago, causing sea levels to rise.

"The volume of this water resource is a hundred times greater than the amount we’ve extracted from the Earth’s sub-surface in the past century since 1900," says study lead author Dr. Vincent Post. "Our research shows that fresh and brackish aquifers below the seabed are actually quite a common phenomenon."

To access these non-renewable water reserves, it would be necessary to drill into the seabed from man-made, offshore platforms or from the mainland or nearby islands. Despite the high costs involved, the water would require less energy to desalinate than it does to desalinate sea water, although a careful assessment of the economics, sustainability and environmental impact of the exploration of such water reserves would be necessary.

Post added that humanity needs to be careful not to contaminate these aquifers while drilling for oil or disposing of carbon dioxide as suggested in some carbon capture and storage proposals.

Water scarcity is set to be one of the biggest environmental challenges of the 21st century, with global warming, deforestation, overpopulation, industrial demand, irrigation and several other factors taking a huge toll on the planet’s water reserves. According to UN-Water, in 2011 some 768 million people lacked access to suitable sources of drinking water. Seawater desalination plants are becoming a more widely-used source of drinkable water, but the process is generally costly and extremely energy-intensive.

The team's research is described in a paper published in the December 5th issue of Nature.

Source: Flinders University