Nashua River in Harvard MA - photo by Kristopher Kvenvold

Invasive Water Chestnuts Discovered in Oxbow National Wildlife Refuge

Nashua River Watershed Association (NRWA) staff members have discovered and removed patches of invasive water chestnuts in the Oxbow National Wildlife Refuge reach of the Nashua River. The aquatic invasive plant, while present in the Pepperell, MA and Nashua, NH reaches of the Nashua River, has not previously been found near the Oxbow NWR. The annual plant (not the same as the water chestnut in Asian foods), grows at an alarming rate to take over vast areas of slow-moving rivers, lakes, and ponds in just a few years.

Martha Morgan, NRWA’s Water Programs Director, stated that “it’s disheartening to know the plants exist in a part of the river where we haven’t seen them before, but the good news is they can be removed easily by hand. The key is to get them out as soon as they are found.”

Water chestnuts are known to exist in two other areas of the Nashua River. The 80+ acres of water chestnuts in the Pepperell Pond impoundment of the Nashua River need to be controlled by mechanical harvesting or other means. The City of Nashua paid for mechanical harvesting of a 14-acre infestation in Nashua, and that, combined with extensive volunteer efforts, has reduced the population of water chestnuts there to scattered plants removable by just hand-pulling efforts.

The NRWA asks boaters to please remove any water chestnut plants they see, and dispose of them away from the water. Every plant removed prevents the development of potentially hundreds of plants the next year.  Learn more about water chestnuts and what they look like.   

In addition to scouting for invasive plants, NRWA is monitoring bacteria levels at three sites on the Nashua River and a tributary in Harvard on a weekly basis in July and August. “We have been pleased to see bacteria levels stay within state standards for swimming or boating for these sites with the exception of times when it rained hard the day of monitoring, or the previous day,” Morgan said.  “The weekly monitoring gives us a much better picture of how clean the water is during the summer months and how heavy rainfall can wash pollutants into the water.”  View data from July and August monitoring.

“Our weekly monitoring in Harvard was conducted by our interns, Brianna Harte from Harvard and Anthony Sisti from Pepperell.  Both were looking to gain experience in the environmental field,” says Kathryn Nelson, Water Monitoring Coordinator. “After orientation and training, they have been collecting samples and data as well as running the bacteria tests each week. This has given them practical hands on experience while helping the project tremendously.”  

This monitoring for aquatic invasive plants and bacteria levels in Harvard and the Oxbow National Wildlife Refuge, together with public outreach, is part of NRWA’s “Protecting Our Waterways: Aquatic Invasive Surveys and Bacterial Testing in Harvard and the Oxbow National Wildlife Refuge” project that is funded in part by a grant from the Foundation for MetroWest.

Established in 1995, the Foundation for MetroWest is the only community foundation serving the 33 cities and towns in the MetroWest region, connecting the philanthropic interests of donors with demonstrated need in the areas of Family Support, Arts & Culture, Environment and Youth Development. The Foundation has granted over $9 million to charitable organizations and currently stewards more than $15 million in charitable assets for current needs and future impact. Learn more about the Foundation for MetroWest. 

For more information about water chestnuts or this project, please contact Martha Morgan at (978) 448-0299, or email This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it..