1.5 billion people will depend on water from mountains

Date:
July 7, 2020
Source:
University of Zurich
Summary:
Global water consumption has increased almost fourfold in the past
100 years, and many regions can only meet their water demand thanks
to essential contributions from mountain regions. In 30 years,
almost a quarter of the world's lowland population will strongly
depend on runoff from the mountains. Only sustainable development
can ensure the important function of mountain areas as Earth's
''water towers''.



FULL STORY ========================================================================== Global water consumption has increased almost fourfold in the past
100 years, and many regions can only meet their water demand thanks to essential contributions from mountain regions. In 30 years, almost a
quarter of the world's lowland population will strongly depend on runoff
from the mountains.

Only sustainable development can ensure the important function of mountain areas as Earth's "water towers."

========================================================================== Water is a key resource for the 21st century, and many lowland regions
all over the world depend on water resources originating in mountain
regions, not least when it comes to irrigating agricultural land. A study
led by the University of Zurich has now quantified this dependence for
the first time by comparing water supply and consumption in the world's
lowland areas with runoff contributions from the mountains. Based on a high-resolution global model, the study provides detailed information
on the dependence on mountain water resources around the globe. The comprehensive analyses were carried out using a regular grid and then
compared for every river catchment area of at least 10,000 km2. This
allowed for highly differentiated insights into regional characteristics
and differences.

Increasing dependence despite declining per-capita consumption "Until
now, research has focused mainly on river basins that originate in High Mountain Asia," says Daniel Viviroli from the Department of Geography
at the University of Zurich, first author of the study. "But in many
other regions, irrigated agriculture is heavily dependent on water from mountainous areas, such as in the Middle East and North Africa, as well
as parts of North America, South America and Australia." This dependence
has increased strongly since the 1960s -- despite more efficient water use
and thus declining per-capita water consumption. Whereas only 7 percent
of the lowland population used to be strongly dependent on contributions
from mountain areas at that time, this figure is projected to rise to
24 percent by mid-21st century. This corresponds to about 1.5 billion
people in lowland areas. Particular focus is on catchment areas such as
those of the Ganges-Brahmaputra-Meghna, Yangtze and Indus rivers in Asia,
the Nile and Niger in Africa, the Euphrates and Tigris in the Middle East
as well as the Colorado River in North America. For their analyses, the researchers assumed a middle-of-the-road scenario in terms of population
growth as well as technological, economic and social development.

Functioning ecosystems and climate protection "Ensuring the function
of mountains as 'water towers' should be a major concern of the world's
lowland populations," says Viviroli. Sustainable development of mountain regions is therefore essential, for example by preventing agricultural
overuse and ensuring the functioning of ecosystems, the researchers
say. In addition, climate action is of paramount importance: Due to the
rising temperatures, meltwater peaks from snow-covered mountain regions sometimes already occur several weeks earlier and are thus not as useful
for summer agriculture. Adjustments in water management will be necessary,
and possibly also new infrastructure such as dams and water transfers.

"However, technical solutions go hand in hand with major ecological
damage, and some rivers, such as the Indus, have little potential for expansion," says Viviroli. For the future, it will be crucial that
lowland and mountain regions work closely together despite political,
cultural, social and economic differences.


========================================================================== Story Source: Materials provided by University_of_Zurich. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Daniel Viviroli, Matti Kummu, Michel Meybeck, Marko Kallio,
Yoshihide
Wada. Increasing dependence of lowland populations on
mountain water resources. Nature Sustainability, 2020; DOI:
10.1038/s41893-020-0559-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200707113333.htm

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