Hidden beneath the depths of the world’s oceans are large pockets of mostly fresh water that could serve as replacement water sources for the many land-based aquifers that are on the verge of drying up, a new study suggests. Discovered off the coasts of Australia, China, North America and South Africa, these massive underwater aquifers contain such high amounts of freshwater, say Australian researchers, that water shortages could become a thing of the past.
It is estimated that roughly half a million cubic kilometers of low-salinity water are just waiting to be tapped underneath various sections of ocean seabed, a volume that the researchers who discovered the water say is many times greater than the overall volume extracted from land-based aquifers throughout the past 100-or-so years. Assuming this water can be successfully extracted and transported, they say it could provide sustenance to the nations of the world for many years to come.
“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 Dr. Vincent Post from the National Centre for Groundwater Research and Training and the Flinders University School of the Environment. “Knowing about these reserves is great news because this volume of water could sustain some regions for decades.”
Published in the international scientific journal Nature, Dr. Post and his colleagues’ research confirms that there is far more freshwater buried inside the earth than previously believed. Instead of being a rare occurrence, these ocean-based aquifers are actually quite common, typically forming on continental shelves near coastlines.
“Our research shows that fresh and brackish aquifers below the seabed are actually quite a common phenomenon,” adds Dr. Post. “Many aquifers were — and are still — protected from seawater by layers of clay and sediment that sit on top of them.”
Because they are non-renewable, ocean aquifers need to be utilized sustainably
Believed to have formed during a previous age when sea level was much lower and coastlines were further out, underground ocean aquifers are only rare in the sense that they are non-renewable. In other words, once all the freshwater is extracted from them, there is no feasible way for new freshwater to take its place.
“[W]hen it rained, the water would infiltrate into the ground and fill up the water table in areas that are nowadays under the sea,” explains Dr. Post. “It happened all around the world, and when the sea level rose… these areas were covered by the ocean.”
In order to access this previously unknown source of freshwater, Dr. Post says platforms would have to be constructed out at sea in order to drill into the seabed. Either this or drilling would have to take place on the mainland or nearby islands and pipes run to the source of the water. In either case, care will need to be taken to protect these natural resources from becoming contaminated or destroyed.
“Sometimes boreholes are drilled into the aquifers for oil and gas exploration or production, or aquifers are targeted for carbon dioxide disposal,” says Dr. Post. “These activities can threaten the quality of the water. We should use [the aquifers] 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.”
You can read an abstract of the new study at Nature.com:
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