Fresh groundwater is less abundant in the US than previously thought, with some regions having reserves that extend less than 300 m deep, an analysis has shown.
In the south-west US, fresh groundwater extends to more than 1000 metres below ground, whereas in certain regions of the east, and in the semi-arid High Plains of the central US, fresh supplies range to just tens of metres deep, potentially threatening future agriculture, the analysis shows.
On average, the transition from freshwater to deeper brackish water occurs at about 550 metres, but according to Grant Ferguson of the University of Saskatchewan in Canada, that is still far less than the 1000–2000 m typically assumed. […]
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