Billions of People Depend on Water From Shrinking Snowpacks – The New York Times

Snowpack in the Lesser Caucasus mountains of northeastern Turkey. The surrounding region depends on snowmelt as a water supply. Dario Martin-Benito

Snowpacks are a vital source of water for humans, but they may shrink in some regions as the climate warms. A new study estimates how changes in showfall will affect water supplies.

Justin S. Mankin, an earth scientist at Columbia University, and his colleagues analyzed 421 drainage basins in the Northern Hemisphere that depend on rainfall and snowmelt, and then combined the data with several different climate models.

They found that 97 basins, currently serving two billion people, depend heavily on snowmelt. The scientists calculated that the likelihood the basins would receive less snow in the coming century was 67 percent.

The most sensitive basins in the United States include those in Northern and Central California, and those of the Colorado and Rio Grande rivers. Internationally, the Atlas basin of Morocco and the Ebro-Duero basin, which feeds water to Portugal, Spain and southern France, are also particularly sensitive to change.

Dr. Mankin and his colleagues reported their findings in the journal Environmental Research Letters.

The study provides important information for city water managers as they make decisions about where to draw water from and how much to use. The loss of snow may also require cities and farmers to find more efficient irrigation methods, to recycle water and to grow fewer water-intensive crops.

“Water managers need to prepare themselves for the worst outcome,” Dr. Mankin said. The public can help mitigate threats to snowpacks by limiting contributions of greenhouse gas emissions, he added.

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