The Washington Post reports: Alarming new research has found that 4 billion people around the globe — including close to 2 billion in India and China — live in conditions of extreme water scarcity at least one month during the year. Half a billion, meanwhile, experience it throughout the entire year.

The new study, by Mesfin Mekonnen and Arjen Hoekstra of the University of Twente in the Netherlands, uses a high resolution global model to examine the availability of “blue water” — both surface and underground freshwater — in comparison with the demand for it from agriculture, industry and human household needs. The model — which zoomed in on areas as small as 60 kilometers by 60 kilometers in size at the equator — also took into account climatic factors, ecological ones (how much water is needed to sustain a river ecosystem or lake) and other causes of depletion such simple evaporation.

“We find that 4 billion people live in areas that experience severe water scarcity at least part of the year, which is more than previously thought, based on those earlier studies done on an annual basis,” says Hoekstra, who published the work in Science Advances Friday. “You have to look really month by month, in order to get the scarcity.” [Continue reading…]