A long drought in the southwestern United States, beginning in 1999 and often called a megadrought, now appears linked to human-caused climate change. The Colorado River, which supplies water to seven US states and Mexico, has seen lower flows because of rising temperatures and reduced winter snow as well as lower precipitation.
Researchers Jonathan Overpeck of the University of Michigan and Brad Udall of the Colorado Water Center at Colorado State University report that the recent precipitation drop is due in part to human emissions. They had considered natural variability, but new data and studies changed their view. Overpeck says long-term patterns now favor more dry winters than wet ones.
The updated graphs in this year's Colorado River Basin report reach two main conclusions: the downward precipitation trend is caused by people’s emissions and it is unlikely to reverse without action. They warn that reservoir storage has fallen over the past 26 years and the region is one dry winter away from severe and unprecedented water-use cuts.
Difficult words
- megadrought — very long and severe period without rain
- drought — long time with little or no rainfall
- precipitation — rain or snow that falls from the sky
- emissions — pollution or gases released by people
- variability — the natural changes in weather or climate
- reservoir — a lake or place that stores water
- unprecedented — never seen before or very new
- climate change — long-term shift in weather patterns on Earth
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What actions could local communities take to prepare for possible water-use cuts?
- What policies or changes could reduce emissions and help regional water supplies?
- How might a long drought affect farmers and people living in the affected states?
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