Chesapeake Bay streams warming, study finds

Turning up the heat: Scientists find streams warming that flow into the Chesapeake Bay.

Most streams in the Chesapeake Bay region are warming, an air-driven increase that could have significant impacts on the ailing estuary, a new study says.

Evaluating 51 years' of data across most of the six-state bay watershed, scientists with the U.S. Geological Survey found water temperatures increased 2.52 degrees Fahrenheit between 1960 and 2010, while air temperatures went up 1.98 degrees over the same time.

Their research was published in the journal Climate Change.

Even small increases in water temperature can affect water quality and the animals that rely on the bay's streams, said Karen Rice, USGS research hydrologist and lead author of the study. 

Warming water could aggravate the effects of the nutrient pollution that's plagued the bay for decades, she noted. It also might lead to shifts in plant and animal abundance in the region.

Stream temperatures could be affected by loss of tree cover, Rice said. Researchers looked at land use changes over the time period, but neither that nor anything else — other than rising air temperatures — could account for the overall increase in water temperatures, she said.

Rice said the warming signal was strong across the region, even in the northern portion, where increasing stream flows might have been expected to dampen any rise in water temperatures.

"What was really surprising to us," she said, "was that in the northern part of the study area, even though water flow was increasing, we still found increases in temperature."

Earlier analysis by others has found rising water temperatures in the bay itself. Rice said the USGS team found temperatures rising faster in streams and rivers than in the bay mainstem.

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