Why Climate Change Brings Both More and Less Water

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Among the more perplexing bits of climate change research are the predictions for both more droughts and more floods. How could that be? Well, when I was reporting the recently published story on the Colorado River, geoscientist Bradley Udall, director of the University of Colorado's Western Water Assessment, had one of the best explanations for this area of climate change impacts.

The atmosphere, Udall told me, is like a sponge hanging over our heads. You heat it up and it holds a lot more water vapor. That's why droughts become more common. But all that water won't sit in the atmosphere indefinitely, so when you wring out the sponge, more water comes out and you get more intense rainfalls and floods.

Those changes to the water cycle won't have the same effect everywhere, Udall says. In the United States, the Northeast and Midwest will get more flooding while the Southwest will get less rainfall. And the timing of the water cycle will change, too. "In cases where we have snow pack, you’re going to see earlier runoff and lower flows later in the year," Udall says.

And there are plenty of unknowns to make the situation even more confusing. For example, surface water quality and groundwater will both be affected by climate change, but scientists aren't yet sure in what ways. And then there's the question of how all those changes to the water cycle will affect the living plants and creatures in these ecosystems.

Udall and other geoscientists have been working with people in the water management community to try to prepare for all of these coming changes. Until recently, water management has focused on looking at past records of water availability and water use to predict what to do to make sure that we all have clean water readily available. But these records of the past are becoming less and less valuable, Udall says, because of climate change. Water managers are "scratching their heads and pulling out their hair trying to figure out what replaces all these engineering practices based on the past," Udall says. "And no one knows really."

It's a reminder that no matter how advanced we may be as a society, we're still dreadfully dependent on simple things like water and the great sponge that sits above us in the atmosphere.

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