Across the continents, around 13 million cubic kilometres of brackish and saline groundwater remain stored underground. This vast volume of so-called “unusable” groundwater exceeds the volume of fresh groundwater currently considered at risk (~10 million km³)—representing about 57% of all groundwater globally.

According to Thomas Schumann Capital (US), 2.4 billion people—nearly a third of the world’s population of 8 billion—live in water-scarce areas, with global freshwater demand projected to exceed supply by 2030.

As per the World Bank (2021), only 4.1% of Australia’s land is arable, compared to the global average of 14.92%.

However, Australia possesses significant underground water resources that remain largely underutilised.

The Australian Government Department of Climate Change, Energy, the Environment and Water (DCCEEW) states:

“The Great Artesian Basin (GAB) is one of the largest underground freshwater reserves in the world. It lies beneath parts of the Northern Territory, Queensland, South Australia, and New South Wales. The Basin spans almost 1.7 million square kilometres—over one-fifth of the Australian continent. It contains approximately 65 million gigalitres (GL) of groundwater, which is enough to fill Sydney Harbour 130,000 times.”

​Other important groundwater regions in Australia include the Perth Basin, Murray-Darling Basin, Canning Basin, Officer Basin, and Carnarvon Basin.

While GAB is largest artesian basin globally, other large aquifer systems include:

• Amazon Aquifer System (South America)
• Guarani Aquifer System (South America – Brasil, Paraguay, Uruguay, Argentina)
• Nubian Sandstone Aquifer System (North Africa – Libya, Egypt, Chad, Sudan)
• Ogallala Aquifer (United States – High Plains)