Scientists from Flinders University in Australia have discovered huge reserves of freshwater buried beneath the seabed on continental shelves located off Australia, China, North America and South America. Estimated at half a million cubic kilometres, the finding provides new opportunities to stave off a looming global water crisis. Barbara Barkhausen reports from Sydney.
Scientists have discovered huge reserves of freshwater beneath the oceans kilometres out to sea, providing new opportunities to stave off a looming global water crisis. Around 500,000 cubic kilometres of low-salinity water are buried beneath the seabed on continental shelves located off Australia, China, North America and South America. The discovery, which was published in the scientific journal Nature, could sustain some regions for decades.
Prevent a global water crisis?
“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, a hydrologist from Flinders University in Adelaide, Australia. The reserves could help reduce the impact of droughts and continental water shortages.
According to UN-Water, the water agency of the United Nations, water scarcity already affects every continent on the planet and impacts more than 40 per cent of the world’s population in their daily lives. Irrigation and meat production are especially responsible for devouring vast amounts of water. By 2030, the percentage of people suffering from acute water shortage is expected to rise to 47 per cent.
Not as rare as once thought
Dr. Post says that groundwater scientists knew of freshwater under the seafloor, but though 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 says.
The 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.” When the ice caps started melting some 20,000 years ago and sea levels rose, these areas were covered by the ocean.
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, Dr. Post says.
Offshore drilling for water
The water can be accessed in two ways: Build a platform out at sea and drill into the seabed, or drill from the mainland or islands close to the aquifers. While offshore drilling can be very costly, Dr. Post says this source of freshwater should be assessed and considered in terms of cost, sustainability and environmental impact against other water sources such as desalination.
Dr. Post warns that these water reserves are non-renewable and they must be used very carefully. Once they are gone, they won’t be replenished. Countries will also have to be careful 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”. This could happen if boreholes are drilled into the aquifers for oil and gas exploration or production, or if aquifers are targeted for carbon dioxide disposal. Both activities could threaten the quality of water.
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