Groundwater — not ice sheets — is the largest source of water on land and most of it is ancient

Source: Groundwater — not ice sheets — is the largest source of water on land and most of it is ancient

Groundwater is used for irrigation and drinking water, but those wells are rarely more than one kilometre deep. A huge volume of salty water exists as much as 10 kilometres below the Earth’s surface. (Shutterstock)

January 19, 2022 5.18pm GMT

Authors

1. Grant FergusonProfessor, Department of Civil, Geological and Environmental Engineering and School of Environment and Sustainability, University of Saskatchewan
2. Jennifer C. McIntoshProfessor, Department of Hydrology and Atmospheric Sciences, University of Arizona

Outside of the world’s oceans, groundwater is one of the largest stores of water on Earth. While it might appear that the planet is covered in vast lakes and river systems, they make up only 0.01 per cent of the Earth’s water. In fact, we now know there is 100 times as much groundwater on this planet as there is freshwater on its surface.

Groundwater is the water contained beneath the Earth’s surface. It’s stored in the tiny cracks found within rock and the spaces between soil particles. It can extend deep into the subsurface, at least as much as 10 kilometres.

As groundwater researchers, we’re interested in how governments and industries might use these extensive groundwater reservoirs, such as for storing liquid waste and carbon dioxide. But groundwater may also have environmental functions that have not yet been revealed — this body of water remains hidden, with very few windows available for us to explore it.

One of Earth’s largest stores of water

While scientists have known for at least five decades that groundwater makes up a large fraction of the world’s water, estimated volumes of groundwater had focused on the upper two kilometres of the Earth’s crust.