Melting Snow Means Less Drinking Water

All basins will likely have less water from snowpack as the planet warms. But some regions will be in worse shape than others, a new report says 

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. (Learn how scientists measure snowpack.)

The team did not attempt to consider rising human population or migrations, which may increase water needs. They assumed that demand would remain constant, which is unlikely given recent trends. The study also did not take into account the ecological needs of the basins to support fish and other wildlife.

Source: National Geographic

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