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Huge freshwater reserves discovered under the sea

Singapore : As the search for water continues across celestial bodies, scientists in Australia have discovered huge reserves of freshwater under the sea. The find, and subsequent extraction of water from under the sea bed, could help stave off future water scarcities in several regions.

The scientists discovered that an estimated half a million cubic kilometres of low-salinity water are buried beneath the seabed on continental shelves, located off Australia, China, North America and South Africa.

For now, the discovery is of immense importance as it gives hope to a world struggling with dwindling water supplies that major sources of water are available in the future, ready to be tapped as technological advancements permit efficient and inexpensive extraction for use in coastal cities close by.

The discovery was published as a study in international scientific journal Nature last week.

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

"Knowing about these reserves is great news because this volume of water could sustain some regions for decades".

According to Post, groundwater scientists knew of freshwater under the seafloor, but thought it only occurred under rare and special conditions. “Our research shows that fresh and brackish aquifers below the seabed are actually quite a common phenomenon,” he 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. “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. Many aquifers were – and are still – protected from seawater by layers of clay and sediment that sit on top of them", Post said.

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 potable water.

“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", Post added.

While countries may now have new reserves of freshwater offshore, the team of scientists -- Jacobus Groen, Henk Kooi, Mark Person, Shemin Ge and W Mike Edmunds -- warned that they will need to take care in how they manage the seabed: “For example, where low-salinity groundwater below the sea is likely to exist, we should take care to not contaminate it".

Post also warned that these water reserves are non-renewable: “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.”

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