Study Says U.S. Waterways Are Warming
By SINDYA N. BHANOO
Chris Ramirez for The New York Times
Many streams and rivers in the United States are getting warmer, with the greatest increases in urbanized areas, according to research to be published in an upcoming edition of the journal Frontiers of the Ecology and the Environment.
Twenty major streams and rivers, including the Colorado, Potomac, Delaware and Hudson Rivers, are warming at statistically significant rates, the study found.
Increases in water temperature were often directly correlated to increases in air temperature and high levels of urbanization, said Sujay Kaushal, the paper’s lead author and a professor at University of Maryland’s Center for Environmental Science.
“We found the most rapid rates of increase in urban areas — this may be related to ‘urban heat island effects,’ from buildings, parking lots and pavements,” he said.
The researchers compiled all the historical data they could find, which in some cases included 50 to 90 years of water measurements. The vast majority of data was from the last 10 years. They found that the annual mean water temperature increase is between 0.02 to 0.14 degrees per year.
The river with the most rapid rate of increase was the Delaware near Chester, Pa., a densely populated area near Philadelphia.
Such increases could decrease aquatic biodiversity and trigger the growth of invasive species like algae. They could also impact water toxicity levels.
Although previous studies have looked at warming freshwater in countries like France and Switzerland, this is the first major analysis of streams and rivers in the United States.
“We need to pay attention to it and also think about mitigation and adaption strategies while we have this chance in terms of greening,” Dr. Kaushal said.
Those strategies might include planting trees to shade streams and cool urban areas. Increasing wastewater recycling and thereby reducing withdrawal of water from rivers and streams will also help keep temperatures down, the paper reports.
Of course, the most critical strategy, Mr. Kaushal said, is one that politicians and scientists are struggling to grapple with: reducing greenhouse gas emissions.
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