Undersea freshwater supplies could help stave off global water crisis

A massive supply of freshwater has been discovered beneath the sea floor on continental shelves around the world, a finding that could provide a new solution to a looming global water crisis according to a report published last week.

“Knowing about these reserves is great news because this volume of water could sustain some regions for decades,” lead author Dr. Vincent Post said according to a release. Post is a researcher for Australia's National Centre for Groundwater Research and Training (NCGRT) and a lecturer at the School of Environment at Flinders University in Australia.

“Freshwater on our planet is increasingly under stress and strain so the discovery of significant new stores off the coast is very exciting. It means that more options can be considered to help reduce the impact of droughts and continental water shortages.”

Water scarcity affects almost half of the world’s population, and scientists predict that by 2030 47 percent of the population will be living in areas of high water stress, according to U.N. Water, an inter-agency of the United Nations that supports states in water-related efforts.

According to U.N. Water, humans are also over-consuming natural resources, including water, at an unsustainable rate. About 3.5 Earths would be needed to supply water to a global population consuming at the rates of the average European or North American.

The Flinders University study, published Dec. 5 in the international scientific journal Nature, said there is an estimated half million cubic kilometers (nearly 120,000 cubic miles) of low-salinity water buried under the seabed.

The water could be used to supplement water supplies of coastal cities in Australia, China, North America, and South Africa.

“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,” Post said, adding that while scientists knew freshwater could be found under the sea floor, they believed it was rare.

Now, Post said their research shows that “fresh and brackish aquifers below the seabed are actually quite a common phenomenon.”

Undersea water reserves were formed over hundreds of thousands of years when the sea level was much lower than it is today, and the coastlines were further out. When it rained, the water would seep into the ground and fill up the water table in areas that are underwater today.

“It happened all around the world, and when the sea level rose when ice caps started melting some 20,000 years ago, these areas were covered by the ocean,” Post said.

“Many aquifers were — and are still — protected from seawater by layers of clay and sediment that sit on top of them.”

The undersea aquifers contain what is called "low-salinity" water, which is much less salty than seawater and can be converted to drinking water with less energy than seawater desalination — the process of converting salt water to drinking water.

Desalination would most likely be the process used to make the water drinkable.

"Although the water is relatively fresh compared to seawater, none of it is drinkable," Ward Sanford, a United States Geological Survey hydrologist, told Al Jazeera in an email.

But desalination, which is already heavily used in arid countries like Israel and Qatar, may not be the best way to handle converting the newly discovered low-salinity water for drinking. Critics say desalination is too costly, could kill marine life, pollute water and that it is too energy intensive.

Sanford said the economics may be the biggest hindrance to using desalination to convert the undersea aquifers.

"The big question is: is it economical? Mostly the answer is no at this point, but engineering studies are underway to see just what the cost would be," Sanford said.