A River Interrupted
Why Removing Defunct Dams is Critical for Restoring the Charles River.
The Charles River today reflects the long legacy of human intervention.
For over 400 years, the Charles River has been altered, controlled, and dammed to bend to the will of industry and development.
The consequences are numerous––today the river suffers impaired water quality, loss of habitat, impeded fish passage, invasive plant growth, contaminated sediment, and harmful cyanobacteria blooms, all of which are exacerbated by nineteen aging legacy dams that interrupt the flow of the Charles River on its eighty-mile journey from its source to the sea.
With climate change bringing more frequent and severe storm events, many of these functionless, crumbling mill dams are in dire need of costly repairs and are increasingly susceptible to failure, and some of the larger necessary dams that control flooding lack functional fish ladders. We are at a critical juncture, and the time is now to reimagine our relationship we’ve built with the river and remove unnecessary dams to restore a free-flowing, climate-resilient Charles for future generations.
Dispossession Through Dams
Watertown Dam was the first dam placed in the Charles River.
The Charles River flows through the traditional territory of the Massachusett, Nipmuc, and Wampanoag people and we humbly recognize Indigenous people as past, present, and future caretakers of the river and its watershed lands.
Before colonization, the Charles River flowed freely and Indigenous ancestors relied on its vibrant population of migratory fish, maintaining a productive fish weir just above the head-of-tide where the free-flowing Charles River met the Boston Harbor at what is now Watertown Square.
In 1632, Governor Winthrop granted colonists the right to build their own fish weir and prevented Indigenous people from using it , an act of systemic oppression to make room for the burgeoning settler population and industry.
In 1634, the fish weir was replaced with a stone dam, and a dam has remained in its place ever since.
Over its long history, various industries including grist mills, a sawmill, a cotton mill, a foundry, and even Bakers Chocolate Company were built around Watertown Dam and used it as a source of hydropower.
However, its construction had immediate consequences on the ecology of the Charles River and on the Indigenous communities who depended on it.
As the first major barrier between the wetland estuary of Boston Harbor and the majestic, meandering freshwater river, the dam stood in the way of migratory fish species that annually made their way to the ample lakes, ponds, and tributaries to spawn.
Dam Regulations Aim to Protect Fish Passage
Beginning in 1709, the first dam regulations were enacted to "prevent nuisances by hedges, wares, and other incumbrances obstructing the passage of fish in rivers."
In 1727, the law was strengthened with a penalty to fine dam owners for failing to provide ample fish passage.
In 1740, "An Act to Prevent the Destruction of Fish Called Alewives" was enacted to explicitly require dam owners to provide passage for river herring.
However, with the explosion of dams across New England and their role as the main economic engine for the Industrial Revolution, regulations to protect migratory fish species often went unenforced.
In 1783, despite Massachusetts law requiring dam owners to provide ample fish passage, colonists illegally raised Watertown Dam several feet to increase its power yield, completely blocking spring fish runs upstream to the Nipmuc people in Natick who relied on the annual migration for food, ecosystem benefits, and cultural survival.
Watertown Dam & Indigenous Food Sovereignty
And so began the long history of Indigenous resistance to dams on the Charles; Nipmuc ancestors residing in Natick actively petitioned the state legislature in opposition to the Watertown Dam , as it infringed on Indigenous rights to food sovereignty, stripping the community of vital resources, cultural ways of life, and free-flowing water.
However, the protest of Nipmuc ancestors was to no avail, and Watertown Dam was never lowered to restore migratory fish passage, resulting in the starvation, dispossession, and decline of the Natick Nipmuc community.
Today, the aging 180-foot long, 8-foot high concrete weir structure owned by the Department of Conservation and Recreation (DCR) remains an inert, useless barrier and a stark reminder of this legacy of dispossession. Its removal would be a first step towards healing––restoring Indigenous food sovereignty and acknowledging Indigenous leaders as the caretakers of the Charles River and its watershed lands.
As dam removals are explored across the watershed, the most significant benefit is the opportunity to acknowledge present-day Nipmuc and Massachusett leaders as the rightful stewards of the Charles River and its watershed and revive the migratory fish population. Kristen Wyman, Nipmuc leader and member of the Nipmuc Nation , shared the critical importance of reinstating migratory fish passage in a recent Charles River Dam Advisory Committee meeting .
Who would have ever thought, my ancestors, that I'd be speaking here a couple of hundred years later about the potential removal of one of those dams. I am encouraging us to think long-term about the possibility of that fish being revived because we do not give up that hope as Indigenous people, we will never give up that hope. We know that all things are possible.
—Kristen Wyman, Nipmuc leader and member of Natick Nipmuc Tribal Council, Charles River Dam Advisory Committee Meeting on November 9, 2021
Alewife and Blueback Herring swim beneath Watertown Dam (Madison Wolters)
Dams Impede Migratory Fish Passage
To dam a river is to reduce a free, wild, living thing to a dull, lifeless stream.
Before dams choked the Charles River, its vibrant river ecosystem was home to a thriving population of resident freshwater and migratory fish.
Each Spring, the Charles River historically welcomed hundreds of thousands of migratory fish from the depths of the ocean to the river’s numerous lakes, ponds, and tributaries to spawn. American Shad, Blueback Herring, Alewives, Rainbow Smelt, White Perch, Striped Bass, American Eel; diadromous fish species enjoyed ample, rich habitat with cool, flowing waters to begin their life.
From left, the diadromous fish of the Charles River; Alewife Herring, Rainbow Smelt, Blueback Herring, American Shad, and American Eel. (U.S. Fish & Wildlife)
Alewife and Blue Herring, two anadromous species that almost went extinct as a result of dams and industrial pollution, play important roles in the Charles River ecosystem.
Near Extinction of Migratory Fish
As dams were constructed on the Charles River, migratory fish lost a staggering two-thirds of their available habitat. The consequences were stark and swift.
By 1920, American Shad and Alewives, two of the most populous native migratory fish species, were declared extinct in the Charles River. The first Alewife fishery in Massachusetts to go extinct, the possibility of their return was deemed remote in a study from the Division of Fisheries & Game . Their sharp decline was attributed to industrial pollution and the significant obstruction of dams in the Charles River.
But, American Shad and Alewives did not go extinct, thanks to the considerable cleanup and restoration of the Charles River. But, today, these aging, functionless dams persist, obstructing the free passage of vital migratory fish species.
Today, nineteen dams dot the mainstem of the Charles River.
Working upstream from Boston Harbor; the New Charles River Dam, Watertown Dam, Bemis Dam, Bleachery Dam, Moody Street Dam, Newton Lower Falls Dam, Cordingly Dam, Metropolitan Circular Dam, Silk Mill Dam, Cochrane Dam, South Natick Dam, Sanford Mill Pond Dam, West Medway Dam, North Bellingham Dam, Box Pond Dam, Cedar Swamp Pond Dam, Storage Pond Dam, and Echo Lake Dam.
Before the Charles River was dammed to power industry, it historically welcomed millions of migratory fish to the ample lakes, ponds, and tributaries along its eighty-mile length.
When dams were first placed in the Charles River, migratory fish lost a staggering two-thirds of their available spawning habitat.
As they travel upstream from the locks of the Charles River Dam, migratory fish only experience free, unimpeded passage through the first ten miles of the Charles River.
American Shad (U.S. Fish & Wildlife Service)
American Shad Alosa sapidissima
American Shad are the most abundant anadromous fish in Eastern North America. With sleek, silver scales, and a row of black spots, they can grow to be two feet long and often travel in large schools.
American Shad return to the Charles River each Spring to spawn. Historically, American Shad have been found as far inland as Natick, and records indicate their presence in the numerous tributaries along the way including Beaver Brook and Hardy Pond in Waltham.
American Shad (U.S. Fish & Wildlife Service)
American Shad Alosa sapidissima
The American Shad were once plentiful in the Charles until the mid‐1800s. After 1850, the population sharply declined due to the obstruction of dams and the degradation of water quality. With improved water quality, CRWA and DMF have reintroduced American Shad in hopes of revitalizing the population.
However, studies have found that female American Shad are unable to pass the fishway at Watertown Dam, limiting their spawning habitat to the first ten miles of the Charles River.
Alewife Herring (U.S. Fish & Wildlife Service)
Alewife Herring Alosa pseudoharengus
Alewife herring are a key species in the Charles River ecosystem. With a silver back and blue-green undertones, these small, swift fish dart upstream to spawn before returning to the sea for most of their adult lives.
Alewife herring historically migrated inland, as they prefer slower, shallower portions of the river for spawning habitat. Alewife Herring have been found as far upstream as Natick, and records indicate their presence in the numerous tributaries along the way including Beaver Brook and Hardy Pond in Waltham.
Alewife Herring (U.S. Fish & Wildlife Service)
Alewife Herring Alosa pseudoharengus
Although Alewife range through the whole Northern Atlantic coast, their population is still in decline in the Charles River, and their passage is limited to downstream of the Metropolitan Circular Dam in Needham, which does not have a fish ladder.
Blueback Herring (U.S. Fish & Wildlife Service)
Blueback Herring Alosa aestivalis
Blueback Herring, like alewife herring, return from the sea each spring. With blue-green backs and silvery, metallic scales underneath, Blueback Herring are found across the Atlantic coast, but are a species of concern.
Blueback Herring are more adaptable in terms of spawning habitat, preferring cool, deep water. Historically, Blueback Herring have been found as far inland as Natick, and records indicate their presence in the numerous tributaries along the way including Beaver Brook and Hardy Pond in Waltham.
Blueback Herring (U.S. Fish & Wildlife Service)
Blueback Herring Alosa aestivalis
Like many anadromous fish, the Blueback herring is threatened by a rapid decline because of the construction of dams, and their passage in the Charles River is limited to downstream of the Metropolitan Circular Dam in Needham, which does not have a fish ladder.
Rainbow Smelt (U.S. Fish & Wildlife Service)
Rainbow Smelt Osmerus mordax
The Rainbow Smelt is the first diadromous fish to arrive in the Charles River in mid‐March. Small, slender, silver fish, Rainbow Smelt used to return to the Charles River by the millions each spring and were caught by the barrelful in the 1800s.
Historically, Rainbow Smelt migrated as far inland as Moody Street Dam in Waltham.
Rainbow Smelt (U.S. Fish & Wildlife Service)
Rainbow Smelt Osmerus mordax
Like other diadromous fish, although once common, their population has greatly decreased from historic standards. Currently, they are a popular prey fish for trout, bluefish, striped bass, and birds. Up to 72% of adult Rainbow Smelt die annually due to predation.
Currently, Rainbow Smelt can only migrate as far upstream as Watertown Dam, and their spawning habitat is constricted to the first ten miles of the Charles River.
Atlantic Salmon (U.S. Fish & Wildlife Service)
Atlantic Salmon Salmo salar
Atlantic Salmon, known as the king of fish, numbered in the hundreds of thousands in New England's coastal rivers, including the Charles River.
Historical records indicate Atlantic Salmon migrated as far inland as Wrentham, diverging from the main stem of the Charles River to the Mill River and Eagle Brook tributaries to spawn below present-day Lake Pearl.
Atlantic Salmon (U.S. Fish & Wildlife Service)
Atlantic Salmon Salmo salar
However, the legacy of dams, industrial pollution, and overfishing have caused the extinction of the wild Atlantic Salmon population in the Charles River.
Today, Atlantic Salmon are critically endangered, with under one thousand wild salmon returning to the Gulf of Maine each spring. Restoration of wild salmon populations in the Charles River is considered remote.
The fish ladder at Moody Street Dam in Waltham. (Julia Hopkins)
Migratory Fish Passage Today
Despite the presence of a fish ladder at Watertown Dam that promises aided passage for migratory species, in 2020, the MA Division of Marine Fisheries (DMF) released a report that confirmed the worst: female American shad and Rainbow Smelt are unable to pass Watertown Dam using the fishway, limiting their spawning habitat to the first ten miles of the eighty-mile length of the Charles River.
This is not surprising, as fish ladders are a mere band-aid and often fail in practice . Fish ladders only provide passage for certain fish species in certain flow conditions and add considerable stress to migration by causing fish to congregate beneath the dam, which increases the risk of predation and mass fish death.
Conversely, free-flowing rivers pass all fish.
Blue Herons and Herring Gulls take advantage of migratory fish gathering below Watertown Dam as they struggle to pass upstream. (Julia Hopkins, Brooks Mathewson)
Historic fish kill near Perkins School for the Blind in Watertown in June 1964. (CRWA Archives)
Climate Change and Migratory Fish
Today, migratory fish populations remain in sharp decline and the climate crisis brings additional threats of extreme heat, drought, and sea-level rise. The migratory fish that still return to the Charles River face warmer waters with lower streamflow, which constrict spawning habitats even further and can cause catastrophic fish kills. And, as sea levels rise and saltwater intrudes further inland, the critical freshwater spawning habitat that many species require is restricted at a time when they need it most.
A Chance to Restore Fish Passage
Removing Watertown Dam and subsequent upstream barriers to fish migration has the potential to welcome migratory fish populations back to an additional forty miles of the Charles River ecosystem, restoring life to our river, supporting fish populations, and healing historic wrongs.
The falls of Watertown Dam seen through the trees on the riverbank. (Julia Hopkins)
Dams Destroy the Charles River Ecosystem
When you think of a river, you probably imagine a bubbling, free-flowing stream buffered by plants, trees, and wildlife, not a polluted pool of stagnant water.
The violent intervention of damming a free-flowing river completely transforms the natural hydrology of a river and alters the river ecosystem; creating consequences for water quality, aquatic life, public health, and climate resilience.
The ecosystem impacts of dams are two-fold.
Upstream, the slow-flowing water trapped in the impoundment above the dam faces rising temperatures, rapid evaporation, the accumulation of sediments and excess nutrients, and disastrously low dissolved oxygen levels; all of which contribute to rampant invasive species growth, severe cyanobacteria blooms, and biodiversity and habitat loss, and in extreme conditions, the death of all aquatic life.
Downstream of the dam, fast rushing water erodes the river bottom and starves it of necessary sediment, creating a lifeless, empty streambed unsuitable for benthic macroinvertebrates and native plants that provide habitat for migratory fish to spawn.
What results is an uninhabitable river for wildlife and people, and these conditions will only be exacerbated by climate change.
A permanent warning for the presence of harmful Cyanobacteria bloom in the Charles River near Watertown Dam. (Julia Hopkins)
Harmful Algal Blooms
In 2020, extreme heat and prolonged drought triggered the longest cyanobacteria bloom in the history of the Charles River, which persisted for a staggering twelve weeks in the Lower Basin.
Dams increase the likelihood of prolonged cyanobacteria blooms. In the warm, stagnant water in the impoundment above the dam, temperatures rise and excess nutrients from stormwater pollution collect, creating the perfect conditions for cyanobacteria to rapidly reproduce and explode into a bloom.
Cyanobacteria blooms pose a significant hazard to humans and wildlife. Exposure to cyanobacteria can cause headaches, nausea, vomiting, diarrhea, liver damage, severe neurological damage, and the death of pets. These blooms will only become more common and severe as the climate warms, threatening the ecosystem and public health.
The effects of dams on the Charles River ecosystem are numerous; invasive species growth, harmful cyanobacteria blooms, low dissolved oxygen, sediment accumulation, and fish kills.
An Opportunity to Change the Course
Removing Watertown Dam would transform the Charles River ecosystem, restoring a clean, healthy, free-flowing river with improved water quality, natural riffles, healthy benthic habitat, improved biodiversity, and a restored streambank with native plants.
By removing this functionless barrier and allowing nature to take its course, the Charles River has the opportunity to again be a welcome place for people, plants, and wildlife.
VIDEO: Voice of Beth Lambert, Director of the Massachusetts Division of Ecological Restoration (DER).
The amazing thing about dams is that when you remove the dam, you are immediately removing the impacts that dam was causing, and you immediately restore river health. And so many river scientists say that one of the best things you can do for a river is to remove the dams that are on it.
—Beth Lambert, Director of the Massachusetts Division of Ecological Restoration (DER), during The Dam Removal Movement hosted on December 6, 2021 .
If Watertown Dam were to fail in extreme weather, it could cause extensive flooding in downstream communities. (Julia Hopkins)
Climate Change Brings Dam Failure & Catastrophic Flooding
Dams may put communities at increased risk of flooding, especially with the more intense storms we are seeing from a changing climate.
Before the Charles River was dammed, culverted, and controlled for power and development, the river meandered through dense forest and resilient wetlands on its eighty-mile journey from Hopkinton to the tidal estuary that interfaced with Boston Harbor. In the event of heavy rainfall, the wetland ecosystems and mature trees of the Charles River ecosystem were ready; easily accommodating and storing floodwaters until the river could naturally recover.
Today, numerous dams dot the Charles River and impervious surfaces jut up to the river's edge. When the rain falls, it flows directly into the Charles River untreated. The naturally fluctuating river shoreline is transformed into an inert, rigid barrier, significantly reducing the river’s ability to adapt to changing water levels.
Historic images from the March 2010 storm show Watertown Dam completely submerged beneath the floodwaters. (CRWA Archives)
Dams Threaten Climate Resilience
In the northeastern United States, precipitation during heavy rain events has increased by more than 70% since 1950. What does this mean for our highly urbanized watershed? More flooding.
In fact, as climate change brings more frequent and intense heavy rainfall events , dams reduce the ability of the Charles River to accommodate these floodwaters, instead flooding homes, roads, and infrastructure.
The greatest example of this came in the historic storm event of March 2010, when a Nor-easter brought extreme, prolonged heavy rain to the region and completely submerged Watertown Dam and its surrounding areas. With nowhere to go, all of the water from the highly urbanized areas of Watertown, Waltham, Newton, and Brighton ended up in the Charles River, flooding nearby Pleasant Street.
Floodwaters completely inundated the Charles River Greenway by Watertown Dam in March 2010.
The DCR’s Office of Dam Safety (ODS) classifies the Watertown Dam as a Small Size, Significant Hazard Potential (Class II) structure. This map shows areas that will be impacted if Watertown Dam were to fail in extreme weather. (CDR Maguire)
High Hazard Potential Dams
It comes as no surprise that aging dams were constructed for the weather of the past, and climate change is bringing added stresses to these historic structures, making them more susceptible to failure in extreme weather.
Some dams are more dangerous than others. The DCR Office of Dam Safety (ODS) rates dams as high, significant, and low hazard potential based on the consequences of dam failure. High Hazard Potential (Class I) dams, like Moody Street Dam in Waltham, are extremely likely to cause loss of life and significant damage to property and critical facilities in the event of dam failure.
Watertown Dam is rated as a Significant (Class II) Hazard Potential by the DCR Office of Dam Safety (ODS), and in fair condition, but if it were to fail during a severe storm, flooding may put downstream areas in Newton and Brighton "at risk of loss of life, damage to property and critical infrastructure, and large-scale economic disruption" according to the Watertown Dam Removal Feasibility Study .
The Massachusetts Office of Dam Safety (ODS) classifies many dams within the Charles River watershed as High Hazard and Significant Hazard Dams dams, colored in red and orange respectively. On the mainstem of the Charles River, Moody Street Dam, South Natick Dam, and Echo Lake Dam are classified as High Hazard Potential Dams by the Office of Dam Safety (ODS).
The Promise of Restoring Climate Resilience
Removing Watertown Dam has the opportunity to increase climate resilience for future extreme weather events, and protect downstream areas from future flooding.
Dam removal could lower 100-year flood elevations by at least six feet upriver of the dam up to half a mile upstream, increasing flood resilience of the Charles River significantly by increasing its ability to store floodwaters. Watertown Dam is a run-of-river dam, meaning no change in flooding is anticipated downstream of dam when it is removed. And, dam removal offers the chance to remediate contaminated sediment from the legacy of industrial pollution.
In anticipation of increased precipitation and stronger storms of climate change, these interventions are especially critical to protect Watertown and downstream communities.
Excerpt from "What's the Dam Story" which aired on The Chronicle in August 2021. (WCVB-TV Channel 5 Boston)
If Hurricane Sandy had hit Boston during a high tide, we would have looked like Katrina. We've just been lucky. And to quote Sen. Ed Markey, luck is not a climate resilience strategy. But that is what we've been relying on.
— Emily Norton, Executive Director of Charles River Watershed Association
Rendering of the restored Charles River after removal of Watertown Dam shows a free-flowing river with natural riffles and a restored stream bank of native plants. (SLR)
A River Restored
We have the opportunity of a lifetime to remove aging, derelict dams, and restore a natural, free-flowing Charles River.
Removal of Watertown Dam offers the possibility to begin to right past wrongs against Indigenous peoples, heal our relationship with nature, and restore the Charles River.
Renderings present the vision for a climate-resilient Charles River after the removal of Watertown Dam. (Milone & Macbroom)
The Watertown Dam Removal Feasibility Study
In June 2021, the Massachusetts Division of Ecological Restoration (DER) released the final draft of the Watertown Dam Removal Feasibility Study . The report confirms that removing Watertown Dam is indeed feasible, and we believe it is advisable, as the aging dam impedes migratory fish passage, degrades the river ecosystem, and is susceptible to failure in extreme weather.
The Vision for Dam Removal
Did you know there are more than 3,000 dams in Massachusetts? Across the state, over sixty useless mill dams have been removed from our rivers, and many more are under consideration.
Removal of defunct mill dams improves public safety, makes economic sense, and restores riverine habitat. In practice, dam removal is hard to picture. But when a dam is removed, rivers are free to be rivers. With the help of streambank restoration, native plantings, and removal of contaminated sediment, nature quickly takes its course; and rivers again become beautiful, wild, scenic places.
In 2017, Old Mill Dam in Bellingham was removed from the main stem of the Charles River. Just a season later, the restored streambank came back to life.
Although some may see dams as beautiful structures sometimes reminiscent of waterfalls, there is nothing more beautiful than a free-flowing river.
—Robert Kearns, Climate Resilience Specialist of Charles River Watershed Association
Sunrise over the Charles River. (Julia Hopkins)
Join the Movement for Dam Removal
We are building momentum to remove these failing, defunct mill dams to restore fish passage and heal the river ecosystem for the entire eighty miles of the Charles River, starting with Watertown Dam.
With the completion of the Watertown Dam Removal Feasibility Study by the Massachusetts Division of Ecological Restoration (DER), we have the scientific backing and tangible proof to move the Department of Conservation and Recreation (DCR) and the state of Massachusetts to act.
CRWA is leading long-term advocacy and education efforts to educate the public on the benefits of dam removal and empower residents like you to be well-versed river advocates. It is our intention to work upstream, creating a grassroots movement for river restoration in each of our communities. And where dam removal isn’t the right option, we’re advocating for fish ladders to ensure migratory fish can follow the flow.
From public education events, to press interviews, to meeting with state and local leaders, to producing education materials, and more; we are working to change the course of our river and achieve our vision for a free-flowing, restored, climate-resilient Charles for future generations.
Clockwise, from left: CRWA leads an educational site-walk at Watertown Dam in October 2021, Executive Director Emily Norton and Robert Kearns meet with Watertown Town Councilor Carolyn Bays at Watertown Public Library, Climate Resilience Specialist Robert Kearns is interviewed by Watertown Weekly News, and CRWA participates in the latest episode of A Watershed Moment produced by Pierce Press and Arlington Communitiy Media Initiative.
Ways to Take Action
We need your support to remove this aging, defunct mill dam and restore a clean, free-flowing, resilient Charles River for future generations.
Stay In-the-Know
Sign up for the latest news, updates, and action alerts about the dam removal movement in Watertown from CRWA by joining our email list.
Share Your Story
Submit a written testimony in support of the immediate removal of DCR's Watertown Dam. We need your voice to push state and local leaders to act on dam removal.
Support Our Work
Did you know we rely on individual donations from river lovers like you for over sixty percent of our budget? Your contribution goes directly towards helping CRWA achieve its mission of protecting, restoring, and enhancing the Charles River and its watershed through science, advocacy and the law.
