Salmon Brook is one of the 6 major tributaries of the Merrimack River

Merrimack River

The Merrimack River is a river in the northeastern United States. It rises at the confluence of the Pemigewasset and Winnipesaukee rivers in Franklin, New Hampshire, flows southward into Massachusetts, and then flows northeast until it empties into the Atlantic Ocean at Newburyport...

 in northeastern Massachusetts

Massachusetts

The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Its watershed is 31 square miles (80.3 km²) and is one of the 14 subwatersheds of the Merrimack River. It passes through Groton

Groton, Massachusetts

Groton is a town located in northwestern Middlesex County, Massachusetts. The population was 10,646 at the 2010 census. It is home to two noted prep schools: Groton School, founded in 1884, and Lawrence Academy at Groton, founded in 1793. The historic town hosts the National Shepley Hill Horse...

, Dunstable

Dunstable, Massachusetts

Dunstable is a town in Middlesex County, Massachusetts, United States. The population was 3,179 at the 2010 census.-Etymology:Dunstable was named after its sister town Dunstable, UK....

, and Tyngsborough, Massachusetts

Tyngsborough, Massachusetts

Tyngsborough is a town located in the northwest section of Middlesex County, Massachusetts. Composed of of land and surface water, Tyngsborough borders the towns of Dunstable, Groton, Westford, Chelmsford, Dracut, and the City of Lowell, as well as the New Hampshire communities of Hudson,...

, and then through Nashua, New Hampshire

Nashua, New Hampshire

-Climate:-Demographics:As of the census of 2010, there were 86,494 people, 35,044 households, and 21,876 families residing in the city. The population density was 2,719.9 people per square mile . There were 37,168 housing units at an average density of 1,202.8 per square mile...

.

Route description

Salmon Brook begins at Martins Pond in Groton. It then flows approximately 17.5 miles (28.2 km) north-northeast to the Merrimack River. It runs through Lost Lake (Groton)

Lost Lake (Groton)

Lost Lake is a reservoir in Groton, Massachusetts, United States. It was formed from three lakes by the Salmon Brook. At its deepest in Knop's Pond, it is near 30 feet deep....

/ Knopps Pond, Whitney Pond, and Massapoag Ponds. All of these water bodies are dammed. The brook runs roughly parallel to the Nashua River

Nashua River

The Nashua River, long, is a tributary of the Merrimack River in Massachusetts and New Hampshire in the United States. It is formed in eastern Worcester County, Massachusetts, by junction of its north and south branches near Lancaster, and flows generally north-northeast past Groton to join the...

from Lost Lake to the brook's mouth in Nashua.