The 2016 season for Eurasian water chestnut (Trapa natans) removal was one of the most successful seasons yet! After a reduction in growth of 17% from the previous season, volunteer efforts in 2016 focused on clearing water chestnuts around Kingsbury Cove, E Island, Forest Grove Park, and the Charlesbank area.
Over 86,500 lbs of invasive mateial was removed by volunteers this year. The partnerships between CRWA, The Department of Conservation and Recreation, Charles River Canoe & Kayak, Boating in Boston, and the Citizen's Alliance for Noxious Weed Eradication led to a smooth and streamlined experience for our volunteers, who put in over 1,500 combined hours of their time to help restore the Charles.
Our sincerest "thank you" to all those who came out and made a difference! Your time and hard work are extremely appreciated, and our progress could not have been achieved without it. We hope to see you next year!
These invasive weeds grow prolifically throughout the Lakes District. The waterchestnut is an aquatic plant, with small green leaves growing in rosettes that float on the surface of the water. Each rosette can produce up to 20 large, spiked seeds that can survive up to 12 years. The seeds can then grow up to 20 new rosettes each.
As they reproduce, water chestnuts cause a myriad of issues for the ecosystems and waterways they inhabit.
Water chestnuts grow in abundance, partly because of excess levels of phosphorus, which is present in the water mainly as a result of stormwater runoff, bank erosion, and wastewater discharges. This nutrient acts as a fertilizer for water chestnut growth. When the weeds die, they can further increase the levels of nutrients present in the water, and they also hinder the photosynthesis process and lead to an explosion of bacteria. Bacteria use oxygen to decompose dead water chestnut plants, leading to hypoxia and anoxia, killing off fish, mullosks, and other species existing in the ecosystem. In addition, water chestnut growth disrupts natural current flow, which hinders downstream sediment deposition and nutrient transport. Water chestnut growth is also a nuisance to those who enjoy the river for recreational purposes, as it makes activities such as boating, fishing and paddling virtually inaccessible.
The water chestnut infestation is a symptom of high levels of phosphorus in the river. Growth can be eliminated through harvesting to reduce seed deposits and by preventing excess nutrients especially phosphorus from entering waterways. CRWA has developed several projects to help monitor and address water chestnut growth and nutrient overloading in the Charles River:
Water Chestnut Harvesting - In the Lakes District, the water chestnut issue is being addressed through awareness-building advocacy campaigns as well as through two different removal methods: mechanical harvesting and hand-pulling. Mechanical harvesters, partially funded through state grants, remove vast areas of plant coverage in deep water. The machines are unable to access weeds growing in shallow water, so hand pulling efforts are an essential aspect of CRWA's removal efforts. Through the Canoeing for Clean Water program, volunteers canoe through the Lakes District and remove water chestnuts by hand. CRWA hosts public and private volunteer group events throughout the summer months.
Water Quality Monitoring - CRWA manages a team of over 80 volunteers, or "citizen scientists, who monitor multiple sites along the Charles River and collect water samples, measure depth and temperature, and record river conditions. This data is used to identify problems in the river and trends in water quality, and to track the progress of efforts to clean up the Charles.
Blue Cities Initiative - CRWA designs and advocates for green infrastructure systems, like rain gardens and permeable pavement, to treat stormwater runoff naturally before it enters the Charles - all while enhancing neighborhoods and connecting existing open spaces.
Environmental Advocacy - Through reforming state water law, policy and practice, CRWA works to protect aquifers and maintain streamflow.