It's said that while a person can survive without food for weeks,
without water they would perish in a handful of days. But a new report
on water scarcity, just published
on PloS ONE, shows that 2.7 billion people endure the meagerest of
water rations for a month or more, in some of the world's
heavily-stressed water basins. That can seriously affect health, food
harvests and even economic growth, say the authors, whose paper takes a
fresh look at uncovering water scarcity.
"Freshwater is a scarce resource; its annual availability is limited
and demand is growing," said lead author Arjen Hoekstra, from the
University of Twente. "There are many places in the world where serious
water depletion takes place: rivers running dry and dropping lake and
groundwater levels." But the water stress resulting from scarcity has
not always been properly picked up in the past.
Digging deeper to find the dry spots
When maps of water use and water supply are compared, it's been
common to look at totals for the whole of the year. That can be
misleading, because the amount rainfall zips up and down so much, from
season-to-season. Which is why the research team behind this report - Global Monthly Water Scarcity
- dug a little deeper, to look at how water flows varied from month to
month. They also tried to peg how much monthly water local ecosystems
needed to function properly.
The results, from over 400 river basins across the globe, present a
stark snapshot of water's unequal spread. For those living in two
hundred of the river basins looked at - that's nearly 3 billion people -
water shortages were severe for at least one month in the year. Some
areas were being particularly hard-hit. Much of the Indus river valley,
home to 200 million people, suffers severe water shortages for 8 months
out of 12. And in Australia, the Murray-Darling river system is close to
running dry for half the year, causing severe stress to the area's
ecosystems.
Farmers sucking harder on scarce resource
The most intense users of water are to be found in cities, but it is
irrigated agriculture that sucks most greedily on the sparse water
resource, explained report author Brian Richter. "Cities use more water
than crops on a per-area basis, but it's important to note that
irrigated agriculture occupies four times as much land as cities do. We
need to help farmers implement state-of-the-science irrigation methods
and improve the productivity of rain-fed farms as soon as possible. We
are going to have to produce more food with less water."
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