New study claims 4 billion people face severe water scarcity for at least part of the year.
When the World Economic Forum, a Swiss non-profit dedicated to "improving the state of the world," released its annual Global Risks Report last year it cited "water crises" as the number one global risk in terms of impact. This is significant because for the past 8 years, the number one global risk in terms of impact had been financial in nature (either asset price collapse, fiscal crises, or major systemic financial failure), but 2015 was the first year that saw a climate related issue top the list of risks.
Citing "water crises" as the number one global risk ahead of "rapid and massive spread of infectious diseases" and "weapons of mass destruction" certainly speaks volumes about the magnitude of the problem, but figuring out a way to reliably quantify the extent of the crisis remained elusive at the time of the WEF's report. Yet as a new study published Friday in Science Advances details, researchers from the Twente Water Center at the University of Twente in the Netherlands found a more accurate way to quantify the extent of the global water scarcity problem.
According to the results of the Twente study, the water scarcity crisis is significantly worse than previously assumed.
As the study's co-authors Mesfin Mekonnen and Arjen Hoekstra show in the report, approximately two-thirds of the world's population (or about 4 billion people) live under conditions of "severe water scarcity" for at least one month out of the year, with 1.8 to 2.9 billion people facing severe water scarcity for four to six months of the year. Even more concerning, the study found that about half a billion people live under conditions of severe water scarcity all year around.
"The finding that 4.0 billion people, two-thirds of the world population, experience severe water scarcity, during at least part of the year, implies that the situation is worse than suggested by previous studies, which give estimates between 1.7 and 3.1 billion," Mekonnen and Hoekstra wrote in their report.
According to the duo, this large discrepancy in reporting the extent of the water crisis was the result of shoddy methodology in previous studies. These studies underestimated water scarcity because they would assess the problem at very large spatial units (such as entire river basins), on an annual rather than a monthly basis, and without accounting for the water flows required to remain in a river to sustain flow-dependent ecosystems.
As the team notes, by measuring at such a large spatial scale and only on an annual basis, previous reports inadvertently hide water scarcity in particular places and during specific times of the year because a few months of water severe water scarcity in one locale will average out with other less scarce months. By measuring on a monthly basis, the team revealed the water scarcity actually experienced by people locally.
"More than a billion people experience severe water scarcity "only" 1 to 3 months per year," Mekonnen and Hoekstra write. "That definitely affects the people involved but gets lost in annual water scarcity evaluations."
To rectify the errors of previous studies, the authors scaled significantly down the spatial scale, measuring local water scarcity using a grid with a resolution of 30 x 30 arcminutes (one arcminute being equal to 1/60 of one degree). What they found was that high water scarcity levels prevail in areas with either high population density (such as the Greater London area) or the presence of a lot of irrigated agriculture (such as the High Plains in the United States), or areas with both of these factors (such as India and eastern China). Obviously there are also high water scarcity levels in areas without dense populations, but which have very low natural water availability (such as the Gobi, Sahara, or Central Australian deserts). According to the authors, water scarcity in the Arabian Desert is particularly acute because of the lack of natural water availability coupled with higher population density.
The team also cites the overconsumption of water as an important variable, particularly when this water consumption is countercyclical (i.e., water consumption is highest when water availability is lowest). The overconsumption of water (relative to its availability) has something of a cascading affect, insofar as it results in decreased river flows and declining lake and groundwater levels. The team cites the Colorado River and China's Yellow River as the unfortunate results of this effect, where the rivers are nearly depleted before they reach the end of their course. As the team notes, the direct victims of the overconsumption of water resources are those that are doing the overconsumption, as they increasingly suffer from water shortages during droughts which result in reduced harvest and "threaten the livelihoods of whole communities."
Mekonnen and Hoekstra hope their study will lay the groundwork for more comprehensive analysis of our global water crisis in the future.
"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," they wrote. "Proper water scarcity assessment, at the necessary detail, will facilitate governments, companies, and investors to develop adequate response strategies."