3 Rivers

Protected & Clean

Flowing Free

For all to Enjoy

Wild & Scenic

WATERSHED ORGANIZATION
FOR THE SUDBURY ASSABET & CONCORD RIVERS

Our Vision

A watershed with resilient streams and rivers that provide healthy wildlife habitat, water supplies, beauty, education, and recreational opportunities for all. OARS is the voice of the rivers, and is an effective, innovative, and inclusive science-based non-profit organization.

The Rivers

The quiet beauty of the Sudbury, Assabet, and Concord (SuAsCo) rivers in eastern Massachusetts provides an antidote to our modern lives. They form the 399-square mile SuAsCo watershed. The rivers flow north through mill towns and farms, small cities and suburbs, to pass through the Merrimack River in the City of Lowell. Sections were federally designated as Wild and Scenic Rivers in 1999 for their outstanding recreation, ecology, scenic, and historic resources and place in American literature.

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Recognizing Indigenous Stewardship

We would like to honor all the ancestral stewards of this land including the Massachusett, Nipmuc, and Pawtucket Nations. We endeavor to be responsible stewards of their traditional and contemporary territories. We recognize their invaluable efforts by continuing the conservation legacy they started as caretakers of our watershed.

 

The name Assabet is likely from a Nipmuc word for the area’s marshes. The confluence of the Assabet and Sudbury rivers is named Musketaquid, where the waters flow through the grasses.

Diversity and Belonging

OARS is committed to the ongoing work of promoting diversity, equity, inclusion, and belonging within our organization so that all may enjoy and benefit from these rivers.

Enjoy and help our rivers!

River Maps

Recreational guides for Sudbury, Assabet, and Concord rivers are available as a series of single-river maps and as an interactive online map.

RIVER MAPS

Events!

Upcoming events. Explore our opportunities and get involved!

SEE WHAT’S HAPPENING

Dam Removal

Our watershed has over 160 dams. Many are old mill dams in disrepair and result in aquatic weed growth, flooding, warmer water, and degraded wildlife habitat. Learn more about our efforts to let our rivers run clean and free.

DAM REMOVAL

Water Quality Monitoring

Read our latest findings on water pollution and work to build climate resilience.

UNDERSTANDING OUR RIVERS’ HEALTH

Report & Pull Water Chestnut

Help us manage invasive water chestnut by using our reporting app to share where you have seen or pulled water chestnuts.

HELP COMBAT INVASIVES

RIVER REPORT CARD

How healthy are your Sudbury, Assabet, and Concord rivers?

READ OUR REPORT CARD
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OARS Events Spotlight

 

Click Logo above for River RAT Community Paddle Schedule

Upcoming Events

Events Calendar

River RATs Kayaking Trip—Maynard September

September 18 - September 18, 2025

WHEN WHERE Thursday, September 18, 5:30–7:30 PM Ice House Landing Assabet River Rail Trail, Maynard, MA 01754   Join us and paddle the scenic Assabet River! If you’re interested in …

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PARTNER EVENT—Nature Journaling

September 20 - September 20, 2025

  Join The Nature Connection in welcoming the Fall Equinox with a mindful nature journaling workshop!   Nature journaling is a way to record your observations, questions, and experiences of …

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River RATs Canoeing Trip—Framingham September

September 25 - September 25, 2025

WHEN WHERE Thursday, September 25, 5:30–7:30 PM Kellogg Park Kellogg Street, Framingham, MA 01710   Join us and paddle the scenic Assabet River! If you’re interested in river recreation, environmental …

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Stow Cleanup—Assabet River

September 27 - September 27, 2025

      When: Saturday, September 27th, from 10:00 AM to 12:00 PM Where: 139 White Pond Road, Stow, MA   Host: OARS & Bill Werner from Stow Conservation Trust …

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Hopkinton Cleanup—Sudbury River

September 27 - September 27, 2025

        When: Saturday, September 27th, from 9:00 AM to 11:00 PM Where: 10 River Road, Southborough, MA   Host: Scout Troop 4, Hopkinton DPW, and OARS   …

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Bedford & Carlisle Cleanup

September 27 - September 27, 2025

            When: Saturday, September 27th, from 9:00 AM to 12:00 PM Where: Bedford Boat Ramp, 285–305 Carlisle Road, Bedford, MA   Host: Carlise Conservation Foundation …

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Concord Cleanup—Assabet River & Nashoba Brook

September 27 - September 27, 2025

        When: Saturday, September 27th, from 10:00 AM to 12:00 PM Where: Parking lot next to the Bruce Freeman Rail Trail behind train station: 50 Beharrell Street, …

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Framingham Cleanup—Sudbury River

September 27 - September 27, 2025

      When: Saturday, September 27th, from 10:00 AM to 12:00 PM Where: Kellogg Park Canoe Launch, 5 Kellogg Street, Framingham, MA 01742   Host: Framingham Resident   Cleanup …

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Maynard Cleanup—Assabet River

September 27 - September 27, 2025

          When: Saturday, September 27th, from 10:00 AM to 12:00 PM Where: 305 Old High Street, Acton, MA   Host: OARS, Sarah Measures, and Abby Barrett …

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Assabet River Tire Cleanup

September 27 - September 27, 2025

    When: Saturday, September 27th, from 10:00 AM to 2:00 PM Where: Assabet River, 3 sections between Acton Canoe Launch and Egg Rock   Host: OARS   Cleanup type: …

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News & Alerts

River Log

Concord River Water Chestnut Pull Extracted Tons of Invasives

July 23, 2025

by Jonathan DeKock | June 25, 2025 | The Bedford Citizen   An estimated 32,000 invasive water chestnut plants (Trapa natans) were pulled from the Concord River along the Carlisle …

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PRESS RELEASE: Collaborative Action for a Cleaner, Healthier Sudbury River

July 15, 2025

by Sarah Kwan, Director of Communications and Development, OARS | July 15, 2025   FOR IMMEDIATE RELEASE   OARS 3 Rivers, the watershed organization for the Sudbury, Assabet, and Concord …

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Maynard man takes OARS summerlong paddling challenge to the next level

June 25, 2025

by Peter Currier | June 25, 2025 | The Lowell Sun   Chester ‘Ozzy’ Osborne paddles 86 miles on local river in under 48 hours     When Chester “Ozzy” …

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A 48 Hour 86 Mile River Paddling Challenge Set to Dock in Bedford on June 22

June 11, 2025

by Mary Stewart | June 11, 2025 | The Bedford Citizen   In late June, paddler Chester “Ozzy” Osborne will embark on a challenge to paddle all 86 navigable miles …

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Three ‘enduring’ rivers inspire Fowler art exhibit

June 11, 2025

by Laurie O’Neill | June 11, 2025 | The Concord Bridge   A river runs through it. Or rather, three rivers do.   They are the Concord, Sudbury, and Assabet, …

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Maynard MA man will cover 86 miles in 48 hours by canoe. Why he’s doing it

June 10, 2025

by Ruth Thompson | June 10, 2025 | MetroWest Daily News   Every year, Chester “Ozzy” Osborne takes on a paddle or bike trip that really tests his endurance. Two years ago, for …

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Fast Facts for 2024

>295

water samples were collected to monitor our river health and provide data for informed decision-making

~106K

water chestnut rosettes were hand-pulled by the OARS community

~1700

members of the community joined OARS (and growing)

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In memory of Marty Moran of Hudson

Board member, steadfast volunteer, and lover of rivers. We are deeply grateful for all you have done for OARS. Your legacy gift, along with the generous support of the Sudbury Foundation, made the creation of this website possible.