Vast areas of the northern hemisphere that are home to nearly two billion people face dangerous water shortages due to shrinking snowpacks, according to a new study released Thursday.
Less snowfall and earlier melting over the next century, coupled with the current trajectory of greenhouse gas emissions, means that people living in nearly a hundred watershed basins worldwide which rely on melting snow for water supply face a 67 percent chance of decline by 2060. That figure remains true even if present demand does not increase.
“Snow is important because it forms its own reservoir,” said lead author Justin Mankin of Columbia University. “But the consequences of reduced snowpack are not the same for all places—it is also a function of where and when people demand water. Water managers in a lot of places may need to prepare for a world where the snow reservoir no longer exists.”
The most at-risk basins lie in the American West and South, southern Europe, the Middle East, and central Asia, according to the report, published in Environmental Research Letters.
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Using two sets of climate models, the team of U.S. and European researchers predicted future changes in snow and rain runoffs. For basins in the Duero-Adour in northern Portugal and Spain, the Central Apennines in Italy, and the Rio Grande in Texas and Mexico, which are dependent on snow, the findings showed water declines even in best-case scenarios.
But even basins that meet their water demand through rainfall are at risk.
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