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  • Staff file photo by Don Himsel

    Two years ago, the Nashua River just upstream from Mine Falls dam was covered with water chestnuts. This photo shows John Fisher and Kathy Nelson on the Nashua River Thursday, July 21, 2011.
  • Staff photo by Don Himsel

    Facebook- Don Himsel at The Telegraph

    John Fisher holds water chestnut pulled from the Nashua River Thursday, July 21, 2011.
  • File photo by Don Himsel

    Two volunteers, John Fisher and Kath Nelson collect invasive water chestnuts on the Nashua River on July 21, 2011.
  • Staff photo by Don Himsel

    Facebook- Don Himsel at The Telegraph

    John Fisher and Kath Nelson pull water chestnut while paddling on the Nashua River Thursday, July 21, 2011.
  • Staff file photo by Don Himsel

    John Fisher and Kath Nelson paddle on the Nashua River in Nashua on July 21, 2011.
  • Staff photo by Don Himsel

    Facebook- Don Himsel at The Telegraph

    Water Chestnut growing on the Nashua River
  • File photo by Don Himsel

    Part of an estimated 35 acres of water chestnut bloom on the Nashua River in this photo from Thursday, July 21, 2011.
  • Staff photo by Don Himsel

    Facebook- Don Himsel at The Telegraph

    John Fisher and Kath Nelson paddle on the Nashua River Thursday, July 21, 2011.Staff photo by Don Himsel

    Facebook- Don Himsel at The Telegraph

Monday, August 1, 2011

Could the Nashua River turn into Water Chestnut Way?

David Brooks

A river is forever, right? Not if one of the most prolific weeds in the world has anything to do with it.

“Every year the Nashua River gets smaller and smaller, as the (water chestnuts) keep encroaching. If we don’t do something about the problem, we’re going to lose the river.”

That’s the dire prediction of John Fisher, a retired Navy submarine commander who lives on the bank of the Nashua River, roughly across from Nashua High North. In the five years since he and his wife, Catherine, bought their house they have watched the thick mats made by the floating invasive weed spread to the point that they now cover about 35 acres of waterway, upriver from the Mine Falls Dam.

“This wasn’t here at all when we bought the house,” he said on a recent canoe trip, gesturing at one of the two huge floating mats. The mats are acres and acres of intertwined plants so thick that they’re impossible to drive a boat through. They’re so thick, in fact, that they pose a danger to swimmers, who can get badly tangled in the long, tough stems that anchor floating pads to the river bottom. They choke out almost all the other river life.

(Incidentally, these water chestnuts, Latin name Trapa natans, have no relation to the crunchy plant of the same name used in Chinese food, Latin name Eleocharis dulcis.)

I first came face-to-face with water chestnuts, so to speak, a week prior, when my wife and I joined a dozen volunteers gathered by the Nashua River Watershed Association in Pepperell, Mass., near the headwaters of the Nashua River. That end of the river has had a huge water chestnut problem for years, with 50 acres of winding coves are covered by mats of weeds.

We spent a pleasant (although wet and muddy) four hours, paddling around in our kayaks, pulling up the floating plants and piling them into old plastic clothes baskets. These baskets were gathered up occasionally by volunteer boaters, who took them to a field alongside the river, where they are used as compost by a local farmer.

We didn’t even try to tackle the mats but hunted down stray plants that had snuck into covers and among weeds, trying to uproot them before they could create new mats.

The mats have too much biomass for individuals to handle. The association rented a mechanical harvester for two years to rip up water chestnuts and collected roughly 1,500 tons – yes, tons! – of material in two years, although a lot of that weight was water that drained away.

“The harvester is like a floating combine, like you see in the Midwest,” said Kathryn Nelson of the watershed association. “It’s a big machine.”

Nashua is going to see one of these harvesters, probably next month, churning through the river in an attempt to chop back water chestnuts.

A roughly $170,000, four-year plan is being developed by the city to tackle the weeds. A lot of work will need to be done beyond hiring the harvester.

A place along the river has to be found to dump hundreds of tons of water-soaked weeds, and then somebody – the Department of Public Works, presumably – will have to haul them to a place where they can compost over time. If you’re a farmer who wants a lot of compost, check with the city.

After the harvesting, the Nashua River Watershed Association will hold a volunteer chestnut-pull, to try and snag the plants that were in water too shallow, or too full of stumps and logs, for the harvester to reach.

The harvester will have to return for several more years to make a difference. The association found such repetition necessary in Pepperell, where the harvester came two years in a row before money ran out. Water chestnuts are pretty much back where they were before.

“You need to do this for at least four years,” said Nelson.

Volunteer pulls are also important to find the stragglers.

“This isn’t a one-time event, a ‘feel good, go out and pull it and then you’re done’ sort of thing,” Nelson said. “You’ve got to keep at it.”

Fisher agreed. “We’re not going to eradicate water chestnut, but we can control it.”

It’s easy to get discouraged about invasive species. The Nashua River is the only location in New Hampshire with water chestnut but it’s also one of plenty of water bodies clogged with Eurasia milfoil, which is even harder to get rid of, and fanwort.

And that’s not even counting weeds on land. I bet the river banks are full of Japanese knotwood (that bamboo-ish plant) or black swallow-wort (which is trying to take over my home) or other “noxious” invasive weeds, to use the official classification.

These aquatic and land invasive weeds are all species brought here from afar, usually Eurasia, that explode in population because they lack predators and have some trait which out-competes local plants. Water chestnuts have barbed seed pods that can be carried in the feathers of water birds, and also can stab swimmers’ bare feet, and can stay viable for years. Fisher isn’t discouraged, though, because he single-handedly cleared out an entire cove next to his property that was clogged with weeds.

“It is 100 percent clear, and they haven’t come back,” he said. “I am very encouraged that this thing is controllable.”

So the Nashua River can remain part of the landscape. It’s just going to take a lot of work.

Granite Geek appears Mondays in the Telegraph, and online at www.granitegeek.org. David Brooks can be reached at 594-5831 or dbrooks@nashuatelegraph.com.