World Facts

The 10 Longest Rivers in New Hampshire

The Connecticut River is the longest river in the state of New Hampshire.

There are about 17,000 miles of rivers and streams all packed into the tiny state of New Hampshire. They are all connected to the five major watersheds which are the Connecticut, Androscoggin, Merrimack, Piscataqua, and Saco Rivers. The following are the longest rivers in the state.

The 10 Longest Rivers in New Hampshire

Connecticut River - 407 Miles

The Connecticut River is the longest in New Hampshire and the entire New England regions of the U.S. It flows for 406 miles across the states of Connecticut, Massachusetts, Vermont, and New Hampshire. The river originates from the Connecticut Lakes along the border with Canada and discharges at the Long Island Sound. Its drainage basin is approximately 11,260 square miles and extends across five American states and the Canadian province of Quebec. The 19,600 cubic feet discharged by the river accounts for 70% of the freshwater discharged at the Long Island Sound.

Androscoggin River - 178 Miles

The Androscoggin River flows for 164 miles from the Umbagog Lake in New Hampshire and discharges into the Merrymeeting Bay in Maine. It is the second longest river in New Hampshire. The river has a drainage basin of 3,530 square miles. The course of the Androscoggin cuts across the town of Milan, Errol, and Gorham, and the cities of Berlin in New Hampshire. The textile industries polluted the river heavily to the point that it was used as a reference when formulating the Clean Water Act. However, rehabilitation efforts have seen the river bounce back although the level of Mercury is still higher than the recommended.

Saco River - 136 Miles

The Saco River flows for 136 miles from Saco Lake in the White Mountains of New Hampshire to the Gulf of Maine. The river has a drainage basin of 1,700 square miles of farmlands and forest. The Saco is an essential source of water for half a million people across the two states. The river’s path in Maine has been altered severely by canals and dams used for irrigation and hydroelectric power. The banks of the Saco attracts thousands of tourists during the summer especially in locations with waterfalls and rapids.

Merrimack River - 117 Miles

The Merrimack River flows for 117 miles across New Hampshire and Massachusetts. The river originates from the confluence of the Winnipesaukee and Pemigewasset rivers in New Hampshire and drains into the Atlantic Ocean at Newburyport. The river has seven major tributaries and flows across three cities in New Hampshire and four in Massachusetts. The Merrimack has a drainage basin of 5,010 square miles and discharges an average of 7,562 cu ft/s.

Threats to the rivers of New Hampshire.

The construction of dams, reservoirs, and channels are the major threat to the rivers of New Hampshire. There are several dams and reservoirs used for power generation, household and commercial use, and irrigation that prevent rivers from reaching their destination. The destruction of drainage basins by human activities lead to the drying up of rivers. The rivers flowing across cities and towns also have pollution to deal with as commercial and household wastes find their way downstream.


The 10 Longest Rivers in New Hampshire

RankRiverLength (miles)Length (km)
1Connecticut River 407655
2Androscoggin River 178286
3Saco River136219
4Merrimack River 117188
5Contoocook River71114
6Pemigewasset River65105
7Ashuelot River64103
8Ammonoosuc River 5589
9Lamprey River5080
10Magalloway River 4776

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