Charles River watershed map
The Charles River is 80 miles in length - the longest river with its entire length in Massachusetts. The Charles River Watershed has a drainage area of approximately 308 square miles and encompasses all or part of 35 municipalities.

It is generally divided into three distinct regions: the rural upper basin, the suburban lakes or middle region, and the urban lower basin. In the area surrounding its headwaters, located at Echo Lake in Hopkinton along the Interstate 495 belt, the watershed contains several of the fastest growing communities in the state. The watershed supports a population of just under 900,000 people, nearly one-sixth of the state's total population.

The Charles River, referred to by early Native American tribes as "Quinobequin," meaning winding river, also represents one of the area's primary sources of recreation and includes some of the most heavily utilized waterways in the country. The Lower Charles River Basin and the extensive park system along its banks host the highest number of boaters and recreational visitors of any other urban river system in the country.

The watershed also contains over 8,000 acres of protected wetlands, referred to as Natural Valley Storage areas, which play a critical role in flood protection and provide various habitats for the numerous plant and animal species that contribute to the state's wealth of biodiversity. The Charles River and its tributaries are home to many species of resident fish and provide important breeding habitat for anadromous fish (ones that live much of their lives in saltwater, but swim up freshwater streams to spawn). Currently, most migrating fish enter the river through the locks in the Charles River Dam and use a series of fish ladders to navigate dams upstream of the Lower Basin.

Watershed Priorities

  • Fall foliage on Charles River
    Work to eliminate point-source pollution by reducing combined sewer overflows and illicit discharges in the watershed
  • Improve surface water quality and replenish natural groundwater aquifers by reducing urban stormwater runoff and promoting stormwater infiltration
  • Enhance natural habitats and fish passage along the river
  • Support municipalities in developing regional approaches to managing water resources and planning for growth and development
  • Improve access to the river and adjacent lands for human recreational purposes, increase citizen awareness of the watershed as an ecological resource base, and foster informed watershed stewardship

Watershed Success

As part of EPA's Clean Charles 2005 Initiative to make the Charles fishable and swimmable by Earth Day 2005, pollution remediation is occurring and the ecology of the river restored. The Charles River has become substantially cleaner over the past year, receiving a grade "B" for the last three years. The river was clean enough for boating 88 percent of the time overall (100 percent of the time in dry weather), and met swimming standards 33 percent of the time overall (78 percent of the time in dry weather). Note that only one dry weather sampling day occurred during last year's sampling season.

Watershed Publications

strolling along Charles River

Watershed Links

Charles River Watershed Association
Charles River Conservancy
Center for Watershed Protection
Charles River Natural Valley Storage Area (U.S. Army Corps of Engineers)


This information is provided by the Executive Office of Energy and Environmental Affairs, Office of Water Policy