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The Westport River Watershed
westport watershed map.jpg

The Westport River Watershed encompasses parts of Westport, Dartmouth, Fall River, and Freetown in Massachusetts, and Tiverton and Little Compton in Rhode Island.  Eighty-five percent of the watershed’s landmass drains into the two branches, East and West, of the Westport River. 

The river is comprised of two major drowned river estuaries that are connected to Buzzards Bay tidal waters by a single inlet.  The Westport River is one of the Commonwealth’s greatest coastal assets in both habitat quality and scenic beauty.  Nutrient loading and pathogen contamination are major water quality concerns, particularly in the upper reaches of the 35 mile shoreline.

WRWA’s goal is to keep people informed about topics regarding the health of the Westport River and its watershed. Many of these topics are interrelated and complex, yet addressing them is valuable in order to raise awareness and understanding of the concerns facing the Westport River and its environment.


Pollution in the Westport River

Heathy rivers are clean, swimmable, and fishable… and flow freely to the sea. If we all work together, we can keep the Westport River – and all local waters – healthy for generations to come. Currently, the most dominant problem affecting the Westport River is pollution, most significantly from nitrogen and pathogens (fecal waste). Both branches of the river, along with numerous tributaries, are considered impaired waters by the Massachusetts Department of Environmental Protection (Mass DEP) due to the high existing levels of bacteria and nitrogen. Mass DEP is responsible under Massachusetts General Law (MGL) Chapter 21 for monitoring the waters of the Commonwealth, identifying those waters that are impaired, and developing a plan to bring them back into compliance with the Massachusetts Surface Water Quality Standards. The list of impaired waters, better known as the “303d list,” identifies river, lake, and coastal waters and the reasons for impairment. Once a waterbody is identified as impaired, Mass DEP is required by the Federal Clean Water Act to essentially develop a “pollution budget” designed to restore the health of the impaired waterbody. The process of developing this budget, generally referred to as a Total Maximum Daily Load (TMDL), includes identifying the causes (types of pollutant) and source(s) (where the pollutants come from) of the pollutant from direct discharges (point sources) and indirect discharges (non-point sources), determining the maximum amount of the pollutant that can be discharged to a specific water body to meet water quality standards, and developing a plan to meet that goal.

Bacteria and Pathogens

Bacteria are a big water quality problem in our nation’s waters. Not all bacteria are harmful (yogurt contains live bacteria cultures!), but the presence of some indicator bacteria is a clue that other germs and viruses that can make you sick might be in the water too.

  • Generally speaking, the order of risk of infection to humans is: infection to humans is: human > domestic human > domestic animal > wild animal animal > wild animal feces.

  • Many pathogens are host-specific: ( specific: (e.g., Salmonella Salmonella typhi, Shigella Shigella, Vibrio cholerae, cholerae, Entamoeba, many viruses).

  • Many more recorded disease outbreaks due Many more recorded disease outbreaks due to domestic animals than indigenous animals. to domestic animals than indigenous animals.

  • But, the amount of difference in risk is But, the amount of difference in risk is unknown. unknown. (e.g., birds are carriers of Salmonella, Campylobacter, and other human pathogens.)

Where do the bacteria come from?

Total rainfall, salinity, temperature, and tide are the most important involved in determining the fecal coliform count in the river. Rainfall is responsible for washing fecal coliform into the river. The amount of rainfall directly affects the amount of fecal coliform in the river. During periods of drought, fecal coliform counts in the river tend to drop significantly. When there is prolonged or large amounts of rain, the effect on fecal coliform is two-fold. First the increase in rainfall simply adds more fecal coliform to the river. Second, the rain decreases the salinity in the estuary, making it more favorable for bacterial growth. Temperature affects fecal coliform growth only when it is extremely cold. In January and February, bacterial growth is inhibited as a result of the cold water temperatures. In the months of May through December, temperature does not seem to play a role in limiting or fostering bacterial growth. During this period the amount of rainfall is the most important factor.



What is nitrogen and why should we be concerned?
Nitrogen is an essential element for life.  It is naturally cycled through the land, water, and air.  Most plants and soil organisms use nitrogen in the form of nitrate. 

But, nitrogen turns into a pollutant when it becomes overabundant in the environment.  The nitrate in fertilizers that we add to lawns, gardens, and farms that is not taken up and used by plants or microbes, leaches from the soil and finds its way into surface and ground water.  Nitrogen pollution also flows into our waters from inadequate septic systems, waterfowl and other animal waste sources, and stormwater runoff from paved surfaces. Nitrogen emitted into the air by cars, trucks, electric utilities, and industry is deposited on land or directly into water bodies.

What’s at stake?
In the Westport River, increased nitrogen causes algae to grow rapidly. Too much algae can damages the river. It decreases the amount of light transmitted through the water.  Too little light puts stress on the river’s eelgrass beds, eventually killing them.

Eelgrass creates critical nursery habitats for fish and shellfish. Too much algae also decrease the amount of oxygen in the water.   In severe cases, oxygen levels can become so low that fish kills occur. Shellfish are smothered when algae overgrowth sinks to the river bottom. 

A big word for a big problem: eutrophication!

When nitrogen pollution causes poor water clarity, loss of habitat, and low oxygen levels, it’s called EUTROPHICATION. Upgrading waste water treatment and protecting forests and wetlands are the best defense against eutrophication because they filter out and consume nitrogen before it has a chance to reach the river. 


What’s being done locally to control nutrients in the watershed?

  • The Board of Health now requires nitrogen reducing septic systems for all new construction since January of 2022.

  • The Board of Health has also required the upgrade of all cesspools to Title 5 compliant status by February 2026.

  • The Town offers 1% loans to low and moderate income homebuyers to install nitrogen reducing septic systems.

  • An updated Targeted Integrated Water Management Plan has been prepared for the East Branch to bring it into EPA compliance.

  • The Westport Land Conservation Trust has been very active in protecting environmentally sensitive properties from development to reduce future nitrogen loading. 

  • The sewer plan for Route 6 and nearby neighborhoods in densely populated North Westport is advancing to the final design phase, and a project manager has been hired. 

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