Charles River turns yellow, sparks questions

By Martin Finucane

Boston Globe, December 28, 2010

The Charles River took on an unusual hue during the major nor'easter that hammered the state on Sunday and Monday, but environmental officials said there was nothing wrong.

The natural color of the Charles is a yellow-brown color due to tannins from organic matter that seep into the slow-moving river, according to Julie Wood, a watershed scientist at the Charles River Watershed Association.

Wood said that the river may appear yellow now as a result of the fierce winds of the snowstorm that churned up the water, mixing the yellow-brown water with ice and snow, and then refreezing. What might have made the color more striking, Wood said, was the contrast to the pristine white snow on the banks and the fact that the river was not frozen solid.

"A lot of times when we get heavy snow, the river is already frozen so you just get the white blanket over the river," said Wood. "That wasn’t the case this time; there’s areas that it looks like thawed and refroze."

Catherine Williams, a spokeswoman for the Massachusetts Department of Environmental Protection, which took samples and performed tests on the river on Monday, said the yellow-brown color of the river was a completely normal phenomenon.

"It's actually a natural occurrence," Williams said Monday. "Some of the storm water runoff has seeped out onto the ice. That combination of organic matter is what gives it the yellow-brownish color."

She added that test results were typical for the river.

"The pH was normal. There was no odor and no sheen," Williams said.

The river may appear bluish on a sunny day when the sky and the sun are reflected in the water, but Wood noted that a clear cup of the water from the river, would have a tea-like tinge, year-round. If the source of the yellow color were a spill of some kind, there would be a plume. Instead, the yellowish color is evenly distributed along the river.

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