Merrimack watershed map
The main branch of the greater Merrimack River is formed in central New Hampshire by the confluence of the Pemigewasset and Winnipesaukee Rivers. It is the fourth largest watershed in New England.

The river flows south through central New Hampshire for 78 miles and into Massachusetts. Once in Massachusetts, it continues generally southeast for about 6 miles before turning to the northeast, near the City of Lowell, Massachusetts. From here, the Merrimack flows its remaining 44 miles to the City of Newburyport where it empties into the Atlantic Ocean. The Merrimack River Watershed has a total drainage area of 5,010 square miles, with 24 percent, or 1,200 square miles, in Massachusetts. It includes all or part of 24 Massachusetts municipalities.

Watershed Priorities

  • Improve the protection of present and future water supply within the watershed by working to develop a water budget model
  • Improve water quality through bio-monitoring of local waterways, stream team participation, and interagency cooperation on water quality issues such as control of combined sewer overflows
  • Continue work on flow issues previously identified within the Merrimack River, as well as develop a flood mitigation plan for the Spickett River, one of the main tributaries to the Merrimack River
  • Promote growth management within the watershed
  • Continue to improve access to the river and the acquisition of open space

Watershed Success

Scenic view of river
A major water study to better understand water flow/supply dynamics stemming from human uses and/or consumption of waters from the watershed from Manchester, NH to the Newburyport, MA portion of the mainstem river has been completed.

Critically low water flows have occurred during recent extended dry weather periods. This has affected habitat quality all along the river. Future follow-up projects will look at developing and implementing better water conservation practices, as well as other incentives to reduce unneeded consumption demands in communities throughout the watershed.

Watershed Publications

Watershed Links

Merrimack Valley Planning Commission
Merrimack River Watershed Council




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