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Nashua;40.0;http://forecast.weather.gov/images/wtf/small/nskc.png;2014-11-26 05:01:19
Monday, September 16, 2013

Dissolved oxygen is a sign of the region’s healthier rivers

Since water molecules are one-third oxygen, you wouldn’t think a shortage of oxygen would ever be an issue in rivers.

But it can be an issue, which is why the annual volunteer-led sampling of the Merrimack and Souhegan rivers examines not just levels of E. coli bacteria but also of dissolved oxygen. ...

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Since water molecules are one-third oxygen, you wouldn’t think a shortage of oxygen would ever be an issue in rivers.

But it can be an issue, which is why the annual volunteer-led sampling of the Merrimack and Souhegan rivers examines not just levels of E. coli bacteria but also of dissolved oxygen.

“We’re always looking for something that we can test that will give us a measure of the health of the river,” said George May, of Merrimack, who as a director of the Souhegan Watershed Association has been the driving force behind the water-sampling work for almost two decades.

“We look at E. coli – that gives us the level of pollution, but that affects human beings for the most part. We’re looking for (measuring) the health of the river for the organisms in the river, and the one test that works best for that is dissolved oxygen.”

The key word is “dissolved,” meaning, May said, “oxygen that’s introduced into the water as opposed to already being in the water.”

“Fish, plants, insects, use the oxygen that’s introduced ... by rainfall, water splashing over rocks, any place that (the river) gets aerated,” May said.

Happily, May said, measurements of dissolved oxygen in parts per million, have improved over the years just like measurements of E. coli, as the two rivers have become cleaner due to changes in industry practices, improvements in local sewage systems, and various regulations about constructions near river banks.

“This year it has been particularly good, probably because we’ve had a lot of rain,” May said.

Ironically, he noted, heavy rains can be bad for bacteria counts, washing various pollutants such as fertilizer and animal waste – or, if sewer systems are overwhelmed, human waste – into the rivers, causing E. coli to multiply.

May and others with the Souhegan Watershed Association, a volunteer group, started taking water samples in local rivers 17 years ago. Water is collected at two dozen spots biweekly and taken to local wastewater treatment plants, where labs test it.

The work provides one measure of river health, but May noted that it has another purpose: Public awareness.

“We getting people thinking about the rivers,” he said. “Most people aren’t out on the rivers; they don’t have canoes. They drive over the river but maybe this makes them pay a little more attention.”

“That’s the kind of education that I’m really interested in,” he said.

Results from the testing are put on a Google map hosted by The Telegraph’s website, at: www.nashua
telegraph.com/special
reports/rivertestresults/
?key=RiverTest
.

David Brooks can be reached at 594-6531 or dbrooks@nashua
telegraph.com. Also, follow Brooks on Twitter (@GraniteGeek).