Freshwater Reserves Discovered Under Ocean Floor in Aquifers

Freshwater reserves discovered in aquifers beneath oceans

According to a recent press release from Flinders University, scientists have now discovered sizable freshwater reserves underneath the seabed on the continental shelves around the world. It is estimated that a staggering 500,000 cubic kilometers of low-salinity water exists off the coast of North America, Australia, China and South Africa, potentially yielding vast water supplies that could delay – what researchers believe to be – a “… looming global water crisis.”

A New Source of Freshwater

Dr Vincent Post of the NCGRT and School of the Environment at Flinders University
Dr Vincent Post of the NCGRT and School of the Environment at Flinders University.

The study was published in the Dec. 5 issue of the journal Nature. Dr. Vincent Post served as the lead author on the project, a researcher at the National Centre for Groundwater Research and Training (NCGRT) and the School of the Environment at Flinders University.

Post explains the volume of this water source to be approximately 100 times greater than the volume extracted from Earth’s subsurface, since the beginning of the 1900s. Understanding more about these freshwater reserves could prove essential, as Post suggests they could serve as important resources for sustaining entire cities, for decades to come.

The Australian researchers were already fully aware that supplies of freshwater were situated beneath the seafloor, but were under the illusion that they were infrequent and only formed under special conditions. On the contrary, the team’s research demonstrated that fresh and brackish aquifers – representing underground layers of water-infused, permeable material – were relatively commonplace.

Glacial and interglacial aquifers
Geology and the key groundwater flow, and transportation of the dissolved salts, beneath the continental shelf during glacial and interglacial periods.

These reserves developed earlier on in Earth’s history, over the course of thousands of years, when the average sea level height was much lower. Post explains, historically, what happened when these regions were subjected to rainfall:

“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.”

He goes on to explain that this phenomenon took place all over the world, when the coastline was much further out than it is today. However, once the ice caps began melting around 20,000 years ago, these regions were covered by the ocean. The contents of the aquifers were safeguarded by the many layers of clay and sediments that had formed over their surface.

The salinity of these water sources is sufficiently low enough for them to be transformed into drinkable water.

Many land areas across Earth possess underlying aquifers, often based at vast depths. These sources of freshwater are becoming rapidly depleted, and have been excessively pumped in a number of regions. The tendency to abuse particular aquifers has sometimes led to non-potable water being drawn into these useful freshwater reserves, through hydraulically connected water bodies.

Aquifers an Advantageous Source of Potable Water

In terms of accessing these water sources, Post outlines two possible methods; construct drilling platforms at sea, where the water can be accessed after breaching the seabed, or drill from the mainland close to aquifers. These drilling techniques present their own problems, including environmental and economic costs. However, Post suggests that these disadvantages should be evaluated against those encountered when acquiring potable water from desalination methods, or in erecting new dams.

Salt water can undergo desalination to eliminate salts and minerals, thereby generating freshwater for human consumption. Unfortunately, desalination requires costly infrastructure and maintenance, as well as a large expenditure of energy to facilitate the process. Another drawback lies in the need to dispose of the concentrated salt byproduct.

Meanwhile, dams are extremely costly to build and culminate in the destruction of the local environment. They have also been known to disrupt the natural water table levels, leading to the accumulation of destructive salts and minerals in certain regions.

Since freshwater from aquifers under the seabed are much less salty, converting it into drinkable water requires a lower energy demand, relative to desalination techniques. Alternative water sources are also desperately needed, since, according to the United Nations, around half of the planet’s populations will remain under water stress by 2030. Post elaborates on this evident water strain and the implications of the research team’s new discovery:

“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.”

The team outlines the need for caution in using these invaluable, non-renewable resources, however. They are prone to contamination when organizations drill boreholes for oil and gas exploration.

By James Fenner

Nature Journal

Flinders University

European Environment Agency

Science Daily

Science Recorder

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