NepRWA’s water quality reports help us identify pollution and advocate for cleanup.
Since 1995, NepRWA has monitored water quality across the Neponset River Watershed through our Community Water Monitoring Network (CWMN) — a volunteer-based program approved by the Environmental Protection Agency.
CWMN volunteers take water samples at various sites throughout the Neponset River Watershed, from May through October. Training and supplies are provided by NepRWA staff. Learn more.
View Detailed Reports
NepRWA’s annual report cards summarize water quality throughout the Neponset River Watershed, including bacteria levels, recreation safety, and key environmental challenges.
Based on multi-year monitoring by NepRWA science staff and volunteers from our Community Water Monitoring Network (CWMN), the grades provide a snapshot of how safe swimming and boating are while highlighting areas needing attention.
Explore past report cards to see trends, improvements, and ongoing challenges across the Watershed.
Each year, NepRWA’s science team analyzes water samples collected by volunteers through our Community Water Monitoring Network (CWMN).
The data gives us a clear picture of the health of the Neponset River, helping us track water quality, identify trends, and better understand changes in the River over time.
NepRWA’s Environmental Science Fellows share the findings with the public each year through our annual State of the Neponset River presentation.
The presentation is both an educational event and an opportunity to recognize and thank the CWMN volunteers whose time and commitment make this work possible.
Presentations in PDF Format.
Several Neponset Stormwater Partnership (NSP) communities conduct regular water testing with the help of volunteers in one or more of their watersheds. In other areas, water quality data may be collected by nonprofit groups or the Massachusetts Department of Environmental Protection (MassDEP).
The data helps assess the health of the Neponset River and tributaries for both wildlife and recreational use — and is used to locate pollution sources for follow-up sampling.
2025 — coming soon!
Learn more about the Neponset Stormwater Partnership (NSP)
E. coli
The concentration of E. coli bacteria is used to assess a waterbody’s safety for “contact recreation” through activities such as swimming, fishing, boating, and wading.
The presence of E. coli is evidence of fecal contamination and is an indicator of the likely presence of other, more dangerous pathogens associated with human and animal waste.
The most common sources of E. coli include improper disposal of pet waste in streets, lawns, and catch basins. Additional common sources include sewer or septic system malfunctions and discharges of organic wastes from household or commercial garbage.
Wildlife waste also contains E. coli; however, elevated concentrations from wildlife are typically associated with human activities, such as feeding ducks.
Management interventions to reduce E. coli loads can include:
- Education on pet waste disposal
- Proper management of solid waste
- Frequent cleaning of catch basins
- Filtration stormwater best management practices (BMPs) to reduce the runoff that reaches a water body
- Rapid identification and repair of sewage leaks and spills.
Phosphorus
Phosphorus is a required plant nutrient that is often the “limiting nutrient” in freshwater ecosystems.
This means that the concentration of available phosphorus in a freshwater body typically controls the rate of aquatic plant growth, as the other required nutrients are usually present at proportionately higher levels.
Excess phosphorus creates excess biomass, especially algae, in a process called eutrophication.
When the excess plants and algae die, the process of decomposition consumes dissolved oxygen, and in extreme cases, dissolved oxygen levels get too low to support aquatic animals such as fish.
Other impacts of eutrophication include unattractive and smelly algal blooms and the destruction of underwater plant communities through reduced light penetration.
Elevated phosphorus concentrations can cause harmful algal blooms (HABs), such as cyanobacteria that produce toxins harmful to people.
Interestingly, phosphorus can also accumulate on these surfaces from atmospheric deposition. Illegal dumping of organic matter, such as leaves, in or near waterways or catch basins is a common problem.
Phosphorus sources can include wet (from rain) or dry (from sprinklers) weather runoff from parking lots, streets/gutters, and lawns.
These surfaces contain phosphorus from fertilizers, organic matter (leaves, grass clippings), soil, garbage, and pet waste.
Poorly maintained septic systems, illicit discharges of sewage, and naturally occurring dead aquatic plant materials are additional sources.
pH
The pH of a waterbody is a measure of how much free hydrogen ion (H+) is present in the water—a lot of free hydrogen ions leads to acidity (low pH) and low amounts of free hydrogen ions lead to more basic conditions (high pH).
Water that is too acidic or too basic can be toxic to aquatic life. The pH is influenced by bedrock characteristics, groundwater seepage, acid rain, or heavy loading of tannin-rich leaves/needles.
Dissolved Oxygen
Adequate concentrations of dissolved oxygen (DO) are necessary to support fish, amphibians, mollusks, aquatic insects, and other invertebrate species. Many environmental drivers impact the DO levels in a water body.
For example, cooler water temperatures sustain higher levels of DO, which is why there is often a seasonal trend in DO concentration: low levels in the warm months and higher levels in the colder months.
Rapid mixing and turbulence (such as riffles or step pools) also result in high levels of DO due to atmospheric mixing.
Alternatively, large amounts of decaying organic matter consume dissolved oxygen as microorganisms degrade the organic matter, and lower levels of DO result.
Excessive phosphorus that causes eutrophic conditions is also closely associated with low dissolved oxygen levels because it drives plant growth and subsequent decomposition.
In thermally stratified lakes, oxygen-deficient conditions can occur in the deeper portions of the water where there is no atmospheric mixing and no photosynthesis (the two sources of DO in aquatic systems).
In the summer, ponds and lakes typically have warmer surface waters and thus lower surface DO concentrations.
Management interventions that can increase DO levels include increasing riparian shading to maintain lower water temperatures, removing obsolete dams, reducing excessive water diversions, and reducing decaying organic matter through the reduction of phosphorus runoff and other drivers of eutrophication.
While NepRWA monitors water quality in local streams and ponds, the collected data primarily captures trends over time rather than daily fluctuations. For the most up-to-date information on water quality in your town, check with your local board of health or town website.
