Merrimack (Upper) River Watershed Assessment Study

The Merrimack River is formed by the confluence of the Pemigewasset and Winnipesaukee Rivers in Franklin, New Hampshire. The river flows southward for approximately 78 miles in New Hampshire before crossing the New Hampshire/Massachusetts border and flowing in a northeasterly direction for approximately another 50 miles before discharging to the Atlantic Ocean at Newburyport, Massachusetts.  The final 22 miles of the river, downstream of Haverhill, Massachusetts, are tidally influenced.

The watershed study was designed to develop a comprehensive understanding of the existing water quality conditions of the river, the pollution sources impairing designated uses along the river, and the water quality benefits of different water quality management scenarios. The overall goal of the study is to develop a comprehensive watershed assessment to guide water quality related investments in the basin.

The Non-Federal sponsor for study that focused on the Upper Merrimack River watershed was the New Hampshire Department of Environmental Services in partnership with multiple New Hampshire communities.  The Southern New Hampshire Planning Commission assisted with stakeholder engagement.

The Environmental Protection Agency, Massachusetts Department of Environmental Protection, New Hampshire Department of Environmental Services, U.S. Geological Survey have provided technical assistance to the U.S. Army Corps of Engineers New England District for this study.  This study is authorized by Section 729 of Water Resources Development Act (WRDA) of 1986 entitled “Study of Water Resources Needs of River Basins and Regions” as amended.

The study area for the Upper Merrimack and Pemigewasset River Study is the mainstem Pemigewasset (54 miles) and the Merrimack River in New Hampshire (66 miles).  Six dams are included in the study area:

  • Ayers Island Dam in Bristol/New Hampton
  • Franklin Falls Dam in Franklin
  • Eastman Falls Dam in Franklin
  • Garvins Falls Dam in Concord/Bow
  • Hooksett Dam in Hooksett
  • Amoskeag Dam in Manchester

Franklin Falls Dam is owned and operated by USACE and is used primarily for flood control purposes while the other dams are owned and operated by Public Service Company of New Hampshire and are used for hydroelectric power generation.

The study included sampling and analysis of water quality and river flows and development of a watershed/river computer simulation model.  The three major components of the model are: watershed runoff and loading, hydraulic routing, and water quality simulation.  

Available reports are provided under the Menu bar on this website.  The USACE is preparing a Draft Watershed Assessment Report that will be available for public review in fall 2019.

For more information, please contact the Project Manager, by email.

Updated: June 14, 2019

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