Scientists in Australia have identified vast meteoric groundwater reserves (VMGRs) of freshwater below the ocean floor, a discovery that could provide much-needed relief to those who lack access to drinking water.

The report, titled "Offshore fresh groundwater reserves as a global phenomenon," was published as a review in Nature last week. Lead author Vincent Post said that the existence of freshwater beneath the seabed had been previously established, but that the prevalence of such reserves was an unexpected and exciting find: 

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

Image courtesy of Nature

Post explains that the reserves were formed over hundreds of thousands of years, when rainwater was captured below layers of sediment and clay as ice caps began to melt and sea levels rose. Post and his team found 500,000 cubic km of freshwater stored across continental shelves off the coasts of Australia, China, South Africa and North America. In the U.S., VMGRs were found off Florida, Nantucket, and New Jersey. According to the authors, the water can be reached through offshore or mainland drilling, but would have to be accessed with care. Post elaborated, "Sometimes boreholes are drilled into the aquifers for oil and gas exploration or production, or aquifers are targeted for carbon dioxide disposal. These activities can threaten the quality of the water."

Water experts warned earlier this year that most people will be afflicted by water shortage within the next two decades. Professor Charles Vörösmarty told the Guardian that the threat is caused by our careless treatment of water as an infinite resource. "These are self-inflicted wounds," he noted, a sentiment echoed by Post, who said of the reserves"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."