Freshwater reserves were formed over the past hundreds of thousands of years when on average the sea level was much lower than it is today.

Flinders University reports that scientists have discovered enormous freshwater reserves beneath the oceans. They posit that these freshwater reserves offer new opportunities to put an end to an imminent global water crisis.

According to a study detailed in the journal Nature, scientists found that about 500,000 cubic km of low-salinity water are concealed beneath the seabed on continental shelves worldwide. Low-salinity water has been located off Australia, China, North America and South Africa.

“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,” posited lead author Vincent Post of the National Centre for Groundwater Research and Training and the School of the Environment at Flinders University in a statement. “Knowing about these reserves is great news because this volume of water could sustain some regions for decades.”

Prior to this research, groundwater scientists thought that low-salinity water under the seafloor only occurred under rare conditions. However, this study shows that freshwater aquifers beneath the oceans are more common than previously believed.

According to Post, the freshwater 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 extended 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,” Post noted.

As the ice caps began melting and the sea levels rose, the fresh and brackish aquifers were immune from salty seawater due to layers of clay and sediment that are located on top of them.

To access these aquifers, nations could build a platform out at sea and drill into the seabed or they could drill from the mainland close to the aquifers. According to Post, offshore drilling can be costly. Thus, the decision to drill should be carefully examined in terms of cost, sustainability and environmental impact.

“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,” Post said.

As nations attempt to take advantage of freshwater reserves, they should keep in mind that these aquifers can be easily contaminated if water extraction isn’t conducted in a careful manner. Boreholes, for instance, can impact the quality of the water. According to Post, freshwater reserves don’t replenish themselves. In other words, water from this newly discovered source should be used carefully.