Heat waves are becoming more frequent and intense across the U.S., so perhaps this summer you took a dip in a river to cool off. However, according to new research it might not have been as refreshing as it once was.
Credit: Dillon Groves/Unsplash
A new study from Penn State found that heat waves are happening in rivers too, and they’re accelerating faster than and lasting nearly twice as long as the heat waves in the air. It’s a surprising finding, given that many rivers are fed by snowmelt and underground streams, but the team found that periods of abnormally high temperatures in rivers are becoming more common, more intense, and longer-lasting than they were 40 years ago. Lead author Li Li (李黎) wrote in The Conversation that the increased heat puts stress on aquatic ecosystems and can also raise the cost of treating drinking water.
The team collected river data at nearly 1,500 sites in the contiguous United States between 1980 and 2022. They found that temperatures rose above 59 °F (15 °C)—a threshold that can stress many species—at 82 percent of study areas for an average of 11.6 days per year. The places where the waters warmed the fastest were in the Northeast, the Rocky Mountains, and Appalachia.
The authors say climate change is driving river heat waves, as rising air temperatures affect water conditions. Changing precipitation patterns with global warming are shrinking winter snowpacks, leaving less meltwater to support river health. Low, slow-moving water warms more easily and holds less oxygen, creating dangerous conditions for aquatic life and increasing the chances of large-scale die-offs. The study adds that human activities, such as dams and agriculture, play a secondary role in shaping how and where rivers are most vulnerable to these impacts.
The study was published in the journal Proceedings of the National Academy of Sciences (PNAS).
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GET WET! 