6 Places Where Melting Snow Means Less Drinking Water — National Geographic

Here’s a report from Brian Clark Howard writing for National Geographic. Here’s an excerpt:

Climate scientists have a pretty good idea what is going to happen to much of the Earth’s snow as the planet warms over the next century: It’s going to melt. But the melting will occur at different rates in different places, which has major implications for the 2 billion people who rely on snowmelt for water.

What’s more, over the next few decades, some areas are likely to see increased snow and rainfall as climate changes in complicated ways.

“Such confounding factors complicate how water managers will be able to respond to climate change,” says Justin Mankin, a climate scientist at Columbia University’s Earth Institute.

In order to help water providers better forecast their supply, Mankin led a team of scientists in a new study published Thursday in the journal Environmental Research Letters. Climate models were used to predict changes in rainfall and snowpack across basins in the northern hemisphere that supply water to large numbers of people. These areas include much of the American West, the Middle East, Central Asia, and southern Europe.

The scientists concluded that overall there is a 67 percent risk of less water available from snowpack by 2060. But over the next few decades, some regions face more risk than others.

In some areas precipitation could actually increase. That’s because a warmer atmosphere can hold more moisture. Yet “the extent that people have the capacity to capture and use that water is a different matter,” says Mankin.

Snow’s Holding Power

Traditionally, when precipitation falls as rain only some of it can be captured in aquifers, lakes, and manmade reservoirs. When the moisture falls as snow, it often sticks to mountains for long periods of time, where it melts slowly, trickling down as a nearly steady water supply. (Read more about this process.)

“In the future, water managers are going to have to adjust to a decrease in the amount of water available from snowpack,” says Mankin. Strategies could include building more reservoirs, either above or below ground, tougher water conservation measures, desalination, deeper wells, or other plans…

The Colorado River Basin

Home to 11 million people, the Colorado River system fared only somewhat better in the analysis, with a decline in snowpack in 74 percent of the tests.

“Our water supply is not going to look the same in the future,” says Mankin. “We’re going to have to get innovative about what management practices really make sense.” (Read more about the embattled Colorado River.)

Rio Grande Basin

The Rio Grande Basin that straddles Mexico and the U.S. is home to 16 million people. Like the Central Valley, in 95 percent of the trials run through the climate models, the snowmelt runoff fell short of demand by mid-century.

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