Scientists discover huge freshwater reserves beneath the ocean

A new study published this month reveals that an estimated half a million cubic kilometres of low-salinity water are buried beneath the seabed on continental shelves around the world.

The water is located off the coast of Australia, North America, China and South Africa, reports Science Daily.

“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 lead author Dr Vincent Post of the National Centre for Groundwater Research and Training (NCGRT) and the School of the Environment at Flinders University.

Dr Post says that while scientists knew of freshwater under the sea floor, they thought it only occurred under rare and specific conditions.

“Fresh water 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,” Dr Post said.

These reserves were formed over the past hundreds of thousands of years when on average the sea level was much lower than it is today, and when the coastline was further out, Dr Post explains.

“So when it rained, the water would infiltrate into the ground and fill up the water table in areas that are nowadays under the sea.

“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,” he said.

Dr Post says that these aquifers (underground layers of water) are protected from seawater by the layers of clay and sediment that sit on top of them.

The aquifers are similar to the ones below land, which much of the world relies on for drinking water, and their salinity is low enough for them to be turned into portable water.

So how can we collect this hidden water source?

“There are two ways to access this water – build a platform out at sea and drill into the seabed, or drill from the mainland or islands close to the aquifers.”

But Dr Post also has cautions for the countries closest to the non-renewable freshwater deposits, saying that we should take care not to contaminate the seawater and subsequently the aquifers.

“We should use them carefully – once gone, they won’t be replenished until the sea level drops again, which is not likely to happen for a very long time.”