Local Watershed Groups Announce 2024 Water Quality Report Card Grades for Boston’s Urban Rivers (Press Release)
FOR IMMEDIATE RELEASE: JUNE 17, 2025
Boston, MA – On Tuesday, June 17, 2025, watershed associations representing the Charles, Mystic, and Neponset watersheds announced the latest Water Quality Report Card grades for the rivers that flow into Boston Harbor.
Partners, local leaders, and community members from across the region gathered at the Francis D. Martini Memorial Shell Park in Hyde Park, along the Neponset River, to celebrate ongoing efforts to measure and improve water quality, and to spotlight the challenges our rivers still face.
This announcement highlighted trends in recreational water quality, the growing impacts of climate change, and the vital role of partnerships between various levels of government and community organizations in protecting local waterways.
Since 2020, these watershed groups have assigned letter grades (A+ to F) to river segments based on how often water quality meets state bacteria standards for safe boating and swimming over the past three years. While all three rivers show continued improvement due to better stormwater management over the last few decades, all three still have lingering issues due to urban runoff, extreme weather, and aging sewer infrastructure. In particular, water bodies surrounded by paved or impervious surfaces experience worse water quality due to pet waste and other runoff entering waterways unfiltered.
“The 2025 3 Rivers Report Card makes clear that our watersheds thrive with strong partnerships at all levels,” said U.S. Senator Edward J. Markey. “As the saying goes, when it rains, it pours, and the climate crisis is only making extreme weather more frequent and more severe, threatening water quality. Now more than ever, we must invest in our communities to provide safe and clean places for folks to swim, play, gather, cool off, and rest. I will continue fighting to bring Massachusetts the resources and support it needs to ensure we protect our beautiful rivers for decades to come.”
WHAT GOES INTO A GRADE
Water quality standards are set at the state and federal levels. The US Environmental Protection Agency (EPA) establishes water discharge permitting requirements in Massachusetts and funds grants for dealing with nonpoint source pollution. Meanwhile, the Massachusetts Department of Environmental Protection (MassDEP) tracks pollution sources, identifies impaired water resources, develops cleanup plans, and supports cities and towns in upgrading their infrastructure. Cities, towns, and private landowners build and operate sewer and stormdrain systems that handle sewage and polluted rain runoff.
The Charles, Mystic, and Neponset River Watershed Associations monitor water quality at more than 50 rivers, ponds, lakes, and estuaries. Grades are based on a three-year rolling average and factor in rainy versus dry weather to better reflect long-term trends and the impact of stormwater runoff. More than 150 trained volunteers collect and process samples every month. Samples are then analyzed by the Massachusetts Water Resources Authority (MWRA) laboratory at Deer Island, and the results are shared with the state through MassDEP’s external data submission program. This work has led to impairment listings and the development of remediation plans between the state and local municipalities.
This year marks the 30th anniversary of both the Charles River’s Volunteer Monthly Monitoring (VMM) program and Neponset’s Community Water Monitoring Network (CWMN).
“VMM provides a consistent and impactful volunteer opportunity for my students, allowing them to contribute meaningfully to their community and develop a deeper connection to their local environment,” said Christina Gasbarro, Head Teacher at Woodside Montessori Academy. “CWMN samplers expand our reach, allowing us to assess the entire watershed despite limited resources and staff,” says Paul Hanbury, Environmental Fellow at the Neponset River Watershed Association.
Because the report cards focus solely on bacterial contamination, they primarily address recreational safety for boating and swimming. For a full picture of river health, a myriad of additional factors also need to be considered, like nutrient pollution, biodiversity of aquatic life, river flow, temperature, other contaminants, and more. Highlights of the report cards for each river can be found below.
CLIMATE CHANGE AND WATER QUALITY
The 2024 grades reflect a year marked by both heavy rain and a prolonged drought, which has only recently ended for most of the state. Intense storms can overwhelm sewer systems causing overflows into waterways and even homes. The Charles and Mystic still suffer from combined sewer overflows (CSOs)—a 19th-century design flaw that sends untreated sewage into rivers during heavy rains. While many cities have worked hard to reduce CSO events, they remain a serious health risk, especially in environmental justice communities. The Neponset has challenges with sewer underdrains, another type of older sewer infrastructure, and all three rivers still have some areas where cross connections between sewers and storm drains allow sewage to escape to the rivers.
However, the largest remaining source of pollution occurs when storms wash pollutants off streets and parking lots and into storm drains that then carry pollution into nearby water bodies. Polluted stormwater picks up everything, including pet waste, trash, oil, and fertilizer, and brings it to the rivers.
In addition to bacterial contamination, phosphorus pollution is a serious concern in all three watersheds. Phosphorus is a necessary plant nutrient, but in excessive amounts it contributes to algae and aquatic plant overgrowth. It fuels cyanobacteria blooms, which are dangerous to people and pets and can shut down beaches and recreation areas. The Charles and Mystic Rivers and Sprague Pond, and Lake Massapoag in the Neponset Watershed all experienced cyanobacteria blooms last year.
The threat of excess phosphorus has already led to the entire Charles and Mystic watersheds, and portions of the Neponset, being listed as “impaired” for phosphorus and established criteria for their towns and cities to control the amount of phosphorus entering waterbodies within their borders. The EPA is in the process of developing a new permit for private parcels that contain large areas of pavement and other impervious surface coverage. If adopted, the draft Commercial, Industrial, and Institutional General Permit is expected to assist municipalities by also requiring large private developments to reduce the amount of phosphorus they discharge. Municipalities are already required to reduce their phosphorus pollution, but more pollutants discharge from private property than municipal property.
Despite these improvements in policy and infrastructure, increasingly intensive rainfall, warmer water temperatures, and reduced streamflow due to more frequent drought have worsened the problem of phosphorus pollution and its impacts.
“As climate change brings more extreme weather, such as droughts and intense rains, we need to do our best to conserve more pristine water resources from development where we can and implement nature-based solutions to safeguard and improve water quality today and into the future,” said Marielena Lima, River Science Program Manager at Charles River Watershed Association.
A SHARED COMMITMENT TO HEALTHY RIVERS
Rivers, lakes, and streams connect communities across the Boston area, linking dozens of cities and towns. Clean water supports public health, outdoor recreation, climate resilience, and biodiversity. The Charles, Mystic, and Neponset Watershed Associations are united in their commitment to vibrant, accessible waterways for all.
The Neponset River flows north from Foxborough, the Charles River reaches southwest to Franklin and Milford, and the Mystic River stretches northwest to Reading and Wilmington. All ultimately drain into Boston Harbor.
Improving water quality protects public health and ecosystems — especially for vulnerable populations — and supports investment in waterfront spaces where people swim, paddle, sail, walk, bike, and gather.
INDIVIDUAL RIVER HIGHLIGHTS:
CHARLES RIVER WATERSHED
In the Charles River, grades ranged from A’s in the upper and lower middle watersheds, B’s in the headwaters and Lower Basin, and a C+ in the Muddy River, following trends observed across recent years. More urbanized, paved areas consistently see lower grades due to stormwater pollution while greener, more forested areas of the watershed are safe for swimming on most days.
Progress has largely stalled in the Upper and Middle watersheds, while the more urban parts of the Charles show improvements in water quality over time. Drought, heat, and increased precipitation from climate change make low water levels, toxic cyanobacteria blooms, combined-sewer overflows, and stormwater pollution more frequent, inhibiting safe recreation. In Summer 2024, the Charles River Lower Basin experienced a cyanobacteria bloom that lasted for 19 days. In both 2022 and 2024, severe drought caused several sections of the Charles River to run very low, with observed water levels under half a foot in Medway, Medfield, and Wellesley. Additionally, in the past two years – due to 95 inches of precipitation – 63 known CSO events discharged more than 100 million gallons of sewage into the Charles.
Three areas saw grades improve slightly –– the Lower Basin increased from a B- in 2023 to a B in 2024, and similar trends are seen in the Upper Middle Watershed and the Muddy River tributary. This improvement is a result of two drought years, which resulted in less stormwater runoff pollution, contributing to a slightly higher grade. The recent improvement in the Muddy River may be due to several years of restoration work, as well as improved watershed maintenance practices by local municipalities. However, Muddy River grades have fluctuated between a C+ and D- since 2004, which is significantly lower than the main stem of the Charles. A C+ grade still indicates highly degraded conditions, being safe for swimming only about 45% of the time. The Upper Watershed, Stop River tributary in Medfield, and Lower Middle Watershed maintained the same grades as last year.
“These grades make it clear: progress has hit a wall. That’s unacceptable — and the public shouldn’t accept it either. The Clean Water Act set a goal of fishable, swimmable rivers by 1983. The EPA’s Clean Charles Initiative aimed for a swimmable Charles by 2005. Those commitments haven’t been met. Cities and towns need to cut back on polluted stormwater runoff, and Cambridge, Boston, Somerville, and the MWRA must stop releasing sewage into the river. A swimmable Charles River is absolutely within reach — but we need the public’s help to put real pressure on decision-makers to invest in the solutions,” said Emily Norton, Executive Director of the Charles River Watershed Association.
NEPONSET RIVER WATERSHED
For the Neponset River watershed, overall grades were similar to previous years, with “A” or “B” grades for the mainstem and most ponds, where the vast majority of people actively recreate. This year saw slight improvements over last year, likely a combination of both progress in stormwater treatment and a decrease in rainy weather contributing to bacteria runoff. Willett and Turner Ponds in Walpole and Sprague Pond in Boston remain the top-scoring sites, almost always remaining safe for swimming and boating from a bacteria perspective.
However, issues remain for the tributaries draining from some of the most urbanized areas in the watershed. Three segments earned “D” or “F” grades, marking them unsafe for recreational use most of the time: Unquity Brook in Milton, Traphole Brook in Walpole and Norwood, and Meadow Brook in Norwood. All face similar problems with high bacteria concentrations in both dry and wet weather conditions. These low scores reflect the excessive amount of pollution carried by runoff from streets and paved areas, as well as potential problems with aging sewer infrastructure. Other tributaries, such as Mill Brook in Westwood and Spring Brook in Walpole, have more natural land use, which helps filter pollutants before they reach the brooks.
“The gradual improvement of the Neponset River and its tributaries is very gratifying to see,” says Sean McCanty, River Restoration Director for the Neponset River Watershed Association. “It’s a testament to the power of collaboration between the state and federal governments, who set stormwater standards; municipal partners who implement improvements like green infrastructure and conduct illicit discharge detection; and non-profits like NepRWA who monitor water quality and assist our towns with education and technical assistance on stormwater issues.”
MYSTIC RIVER WATERSHED
In the Mystic River watershed, water quality grades have remained consistent with previous years, with little change, ranging from A to F. The Mystic Lakes and the main stem of the Mystic River boast A’s and B’s, reflecting conditions that meet boating public health standards more than 90% of the time. Many smaller tributaries score worse.
Upper Mystic Lake continues to score the highest in the watershed for water quality with an A grade. Featuring the only free state beach in the watershed, Upper Mystic Lake is a popular swimming, boating, and recreational destination for people from across the Mystic region and beyond. Its shores are packed with visitors over the summer. And yet, despite its strong overall grade, the beach still closes temporarily due to bacterial contamination, particularly after heavy rain.
Originating in Reading and Woburn, the Aberjona River was among the Mystic’s major tributaries to receive a C grade. Like many urban streams, it is channelized (straightened) and often runs through underground culverts before emerging in Winchester town center. Each spring, the Aberjona is a key element in a major wildlife migration: tens of thousands of river herring use the Aberjona River as far upstream as Horn Pond, where they spawn before returning to the ocean. Despite its relatively suburban location, it too suffers from bacterial pollution, which flows into Upper Mystic Lake, contributing to beach closures.
Smaller tributaries have even lower grades. The Alewife Brook, for example, received a D+. It suffers from persistent sewage pollution and regularly receives the highest volume of untreated combined sewer overflows (CSOs) in Greater Boston. The Alewife Brook alone received 19 million gallons of CSO discharge – 3 days worth of dry weather flow – a mix of rainwater and completely untreated raw sewage. The area around it remains a popular commuter and recreational destination with a linear park, boardwalk, and neighborhood bird gardens. It flows through residential neighborhoods in Somerville, Medford, and East Arlington and, despite its low grade, remains a cherished local resource, with many local residents mobilized to improve its conditions.
“We now have 25+ years of data thanks to the hard work of our many water quality monitors,” says Jennifer Delgado, Watershed Field Scientist at the Mystic River Watershed Association (MyRWA). “They not only contribute knowledge that guides policy and education work in the watershed, but also bring a spirit that makes our work more joyful. Without these dedicated volunteers, the Mystic River Watershed Association would not be where it is now.”
“We’re really proud to be able to contribute to public knowledge about water quality conditions in our cities and towns,” says Andy Hrycyna, Water Quality Program Manager at MyRWA. “But we don’t publish data for the sake of publishing data. We all go to this effort because these waterbodies are important – recreationally and ecologically. We think of this report card as an annual call for more attention – and more investment – in these resources.”
Patrick Herron, Executive Director of MyRWA, adds, “We know the sources of the pollution measured in these report cards – all the ways that sewage can work its way into the stormwater system. We know that the pollution is worse when it rains. We know that climate change is going to increase the frequency and intensity of storms. All roads to cleaner water lead through investments in infrastructure, and we hope that our report card can help make the public case that we should increase local spending on stormwater infrastructure for the sake of our rivers, streams, and lakes.”
