- Researchers say two-thirds of the global population — some four billion people, half of them in India or China — live under conditions of severe water scarcity at least one month out of the year.
- As many as half a billion people face severe water scarcity all year.
- The majority of water usage is for food, researchers say, so water scarcity primarily means decreasing or failing crop yields.
New research paints a sobering picture about the water crisis looming over our heads.
Previous studies have estimated anywhere from 1.7 and 3.1 billion people are already living with severe water shortages. But those studies underestimated the extent of water scarcity, according to researchers at the University of Twente in the Netherlands, who published their findings in the journal Science Advances last week.
The researchers say their results show that two-thirds of the global population — some four billion people, half of them in India or China — currently live under conditions of severe water scarcity at least one month out of the year.
As many as half a billion people face severe water scarcity all year, the University of Twente researchers found.
Prior studies that determined water scarcity was less widespread tended only to examine the issue at the level of very large spatial units, such as river basins, or only looked at water scarcity on an annual rather than on a monthly basis.
“Measuring at a basin scale and on an annual basis hides the water scarcity that manifests itself in particular places and specific parts of the year,” the authors of the Science Advances article wrote.
Previous studies also underestimated water scarcity by failing to account for the flow levels required to sustain ecosystems and livelihoods that depend on them. But “measuring the variability of water scarcity within the year helps to reveal what is actually experienced by people locally,” the researchers wrote.
“More than a billion people experience severe water scarcity ‘only’ 1 to 3 months per year, a fact that definitely affects the people involved but gets lost in annual water scarcity evaluations.”
The distinction the University of Twente researchers make is an important one. At the global level, statistically speaking, there is enough fresh water available to meet human demand on an annual basis. But fluctuating demand and availability throughout the year leads to water scarcity in several parts of the world during specific times, even if other parts of the world might never suffer from a shortage of water whatsoever.
“The essence of global water scarcity is the geographic and temporal mismatch between freshwater demand and availability, which can be measured in physical terms or in terms of social or economic implications based on adaptation capability,” according to the researchers.
“Various studies have assessed global water scarcity in physical terms at a high spatial resolution on a yearly time scale. Annual assessments of water scarcity, however, hide the variability within the year and underestimate the extent of water scarcity.”
“Most water is used for food,” Arjen Y. Hoekstra, Professor in Water Management at the University of Twente and lead author of the study, told Mongabay, “so water scarcity primarily translates to decreasing or failing crop yields.”
Just four percent of human fresh water consumption is for drinking, Hoekstra added, meaning water scarcity doesn’t primarily put that at risk — “although supplying drinking water to large population densities in relatively dry areas is problematic — think of Las Vegas, Beijing, Sao Paulo — the list is long. Water scarcity isn’t properly priced, so even the last drops are generally used for free.”
High water scarcity levels occur most in areas with high population density, such as the Greater London area, or where there is intensive use of irrigated agriculture, as in the High Plains of the United States, the researchers found. Some places, like India, eastern China, and the Nile delta, meet both criteria for susceptibility to high water scarcity.
Of course there are also parts of the world without dense populations or irrigated agriculture that have very low natural water availability, arid areas like the Sahara, Gobi, and Central Australia deserts. Water scarcity in the Arabian Desert is worse than in other deserts, Hoekstra and co-authors write in the study, because in addition to being an arid climate it also has a much denser population and more irrigation.
About 71 percent of the global population, 4.3 billion people, were found to be living under conditions of moderate to severe water scarcity at least 1 month of the year. 66 percent, or 4.0 billion people, live under severe water scarcity at least 1 month of the year.
While one billion people living in India and another 0.9 billion in China face severe water shortages during at least part of the year, there are also significant populations in Bangladesh (130 million), Mexico (90 million), Nigeria (110 million), Pakistan (120 million, of which 85 percent are in the Indus basin), and the United States (130 million, mostly in western and southern states) living under similar conditions.
The number of people found to be facing severe water scarcity at least four to six months per year was 1.8 to 2.9 billion.
Of the half-billion people who suffer severe water scarcity all year round, 27 million live in Egypt, 180 million in India, 20 million in Mexico, 73 million in Pakistan, 20 million in Saudi Arabia, and 18 million in Yemen. Large populations in Jordan, Libya, Morocco, Nigeria, Pakistan, and Somalia entirely lack reliable access to fresh water, as well.
The University of Twente researchers write that meeting humanity’s increasing demand for freshwater and protecting ecosystems at the same time “will be one of the most difficult and important challenges of this century,” especially in the context of a booming global population and climate change.
“Governments should put a cap on water footprints, per river basin and per month, to ensure that water consumption doesn’t exceed maximum sustainable levels,” Hoekstra told Mongabay.
“The absence of such caps gives room to the unbridled growth in water use. Caps will also function as an incentive to use water more efficiently. Companies should invest in their operations and supply chains to reduce water use, investors should include water sustainability into their investment decisions and consumers could reconsider their consumption pattern.”
- Mekonnen, M.M. & Arjen Y. Hoekstra, A.Y. (2016). Four billion people facing severe water scarcity. Science Advances 2(2). doi:10.1126/sciadv.1500323