Four Billion People Face Severe Water Scarcity

Two-thirds of the planet’s population, or 4 billion people, lives at least one month per year with water scarcity, according to the most detailed water scarcity assessment to date.

Previous studies — which estimated between 1.7 billion and 3.1 billion in water-scarce areas — were too broad for an accurate depiction of the problem, the study claims. Those assessments looked at annual averages over whole watersheds and did not account for ecosystem needs.

The study from researchers at the University of Twente, in the Netherlands, looked more closely. They used monthly averages of water availability, analyzed water supply and consumption at a scale that included municipal, industrial, and agriculture data, and apportioned water to maintain ecosystem health.

The researchers defined water scarcity as consuming more fresh groundwater and surface water than is available, after subtracting upstream use and water required for ecosystems, estimated at 60 percent to 80 percent of natural runoff.

Under these conditions many more people than previously thought live with water scarcity at least one month per year.