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| The map above shows the distribution of this modern groundwater around the globe. Dark blue shows where it is very quickly renewed. Light blue shows the older groundwater, which is mostly stagnant and non-renewable. |
The total amount of groundwater on the planet, held in rock and soil below our feet, is estimated to be 23 million cubic km. If this volume is hard to visualize, imagine the Earth's entire land surface covered in a layer some 180m deep.
The new calculation comes from a Canadian-led team led by study leader Tom Gleeson from the University of Victoria and is published in the journal Nature Geoscience.
To quantify just how much water is stored in the top 2km of the Earth's surface, Dr Gleeson's team had to combine large data sets with an element of modelling. They included information on the permeability of rocks and soil, on their porosity, and all that is known about water table gradients, which tell you about inputs from precipitation.
Gleeson et al. “The global volume and distribution of modern groundwater”
Gleeson et al. “The global volume and distribution of modern groundwater”