The Watersheds of Southeastern Massachusetts

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Southeastern Massachusetts, SEMA, is the region south of Boston, West of Cape Cod Bay, East of Providence and North of Buzzards Bay. Historically the region was largely defined as the tribal lands or the Wampanoag Native American nation. SEMA includes 500 miles of major rivers and streams that have long been a core part of the culture in each community, offering historically important venues for commerce, fisheries (both inland and coastal), hydro power for grist mills, and boatbuilding trades. Today, Southeastern Massachusetts has multiple watersheds (boundaries in black in map) that are complex networks of wetlands, streams, and rivers and sometimes tidelands that are home to many critical environmental resources, including globally rare species, coastal plain ponds, pine barrens, free-flowing undimmed rivers, the state’s second-larges sole source aquifer, and the largest freshwater swamp in Southern New England (Hobomock swamp). Groundwater resources include the Canoe River aquifer and the Plymouty Carver aquifer and the ground water/surface water interactions are critical to sustaining the aquatic habitats of our watersheds.

What is a Watershed?

A watershed is the land area that drains to a common body of water such as a lake, river, or ocean. Everyone,-whether we live on a farm, in a city, or on the coast-live is a watershed and we all have an impact on its health. They are our ecological address and are important to our sense of place. Some watersheds are small and drain a few acres and some are expansive estuaries where rivers meet the sea (the black lines on the map below are watershed boundaries). Watersheds supply drinking water, provide recreation and sustain life.

There are thirteen watershed Associations working to protect and restore our aquatic habitats of our watersheds. They are working to ensure that future growth is sustainable to our natural assets so that they will be here for future generations. Click on the names for contact information.

Download the South Coastal Watershed Action Plan for more information: Southcoastal.zip 27 MB

Threats to Our Watersheds

By 2020, there will be likely over 200,000 new residents in the region. Between 1960 and 1990 SEMA grew by more that 10,000 people per year (a growth rate of 40 percent). As a result land in Southeastern Massachusetts is being consumed at a rate two and one-half times the rate of state population growth. Between 1951 and 1985, one third of agricultural and open land was converted to urbanized land uses. Agricultural and open land declined from over 150,000 acres to 100,000 acres. In the same period, urbanized land use more than doubled. By the year 2020, without changes in current development patterns, the percentage of land in Southeastern Massachusetts that is developed is liable to increase by an additional 20 percent. This has profound implications for our watersheds.

Impaired Water Quality:

As land is lost to development, impervious surface increase which caused multiple problems for our watersheds. Aquifers are no longer recharged as rainfall is channeled as run-off into stormwater systems that deposit water (now laden with road-side pollutants) into waterways far from the “home” watershed. The number of waterways impacted by pollutants is increasing each year and the leading cause of contamination is run-off from highways, farms, golf courses, lawns and other areas. Run-off carries pathogens from failed septic that make water unsafe for recreational use, and nutrients that cause algal blooms and growth of invasive plants.

For example, Furnace pond located in Pembroke is deteriorating rapidly due to eutrophication and sedimentation. The pond experiences extensive algae blooms, odors, weed overgrowth, invasive species of weeds, low dissolved oxygen (causing fish kills), and is losing depth (in some places the pond is 5 feet deep. The condition of Furnace Pond impacts not only Silver Lake (the pond is a water supply for Brockton), but may also soon spread to include Herring Brook, and eventually the North River.

Reduced Water Flow:

By 2020, there will be likely over 200,000 new residents in the region. Between 1960 and 1990 SEMA grew by more that 10,000 people per year (a growth rate of 40 percent). An addition of 10,000 new residents per year requires an addition 3,500 housing units, and consumes 710,000 gallons of water per day. The increase in paved surfaces, demand for drinking water, increased stormwater and wastewater discharge carries water away from its watershed and prevents the watershed’s aquifer from recharging. As a result, rivers cannot sustain a diversity of aquatic life and in some areas are running dry (Upper Jones River right). Unmanaged competition for limited water supplies could forestall economic development where it is desired and severely degrade the natural resources that are dependent on adequate pond depths and stream flows including the region’s herring and shad as well as the unique coastal plain pond species.

Loss of Aquatic Habitat:

Large scale development has meant the loss of vegetated buffers and inadequate erosion control. Related sediment and turbidity has impacted anadromous fish spawning habitat, eel grass communities, and the overall natural functioning of ponds and wetlands. As impervious surfaces increase, water polluted by road and surface contaminates is rapidly absorbed by surface waters instead of naturally filtered and reabsorbed to recharge groundwater aquifers. In addition, over 600 dams fragment river habitat, isolate fish populations, diminish biological diversity, prevent coastal fish from spawning their historical breeding grounds, and alter stream flow and prevent sediment from flowing downstream to feed marshes that mitigate for flooding.

Threats to Endangered Species

The region of southeastern Massachusetts provide a viable habitat for a rich diversity of flora and fauna, including many rare and endangered species. Twenty percent of coastal Southeastern Massachusetts acreage is designated as Biocore habitat by the Natural Heritage and Endangered Species Program. These areas are considered the most viable for sustaining a diversity of naturally occurring species. Plymouth with its many acres of Pine Barrens and coastal plain ponds is a hot spot of biological diversity, and is one of 5 areas in the state that has over 100 rare plants and animal records in the National Heritage Endangered Species Program database. These animals and plants are especially susceptible to water level changes and loss of habitat.