The researchers used information from the U.S. Geological Survey on the quality of groundwater across the country and looked specifically at salinity — how salty the water is. “We looked basin by basin at how that depth of fresh and brackish water changes across the United States,” says McIntosh.
The results were about half as much usable water as previous estimates. That means that deep groundwater reserves are not nearly as plentiful as we’d thought in some places.
That’s important because when shallow groundwater reserves become depleted or polluted, the strategy so far has been to drill deeper and deeper wells to keep the water flowing.
But we may not always be able to drill our way out of water shortages.https://therevelator.org/shrinking-groundwater/