US Army Corps of Engineers
New England District

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New Hampshire River Basins

There are 19 principal river basins that lie entirely or partially in New England. Five river basins lie in New Hampshire to include the Connecticut, Merrimack, Androscoggin, Saco and Piscataqua. Three of these basins (the Connecticut, Merrimack and Piscataqua) have Corps' flood risk management projects within their drainage areas.

Merrimack River Basin
The Merrimack River Basin extends from the rugged White Mountain region of northern New Hampshire to southeastern Massachusetts. It has a maximum length of 134 miles and a maximum width of 68 miles.

The basin’s 5,010 square miles make it the fourth largest river basin in New England. About 3,810 square miles (76 percent) lie in New Hampshire, and 1,200 square miles (24 percent) lie in Massachusetts. The Merrimack River Basin covers parts of every county (except Coos) in New Hampshire, including all of Hillsborough County, most of Merrimack County, the northwestern half of Belknap County, and the western half of Rockingham County.

Connecticut River Basin
The Connecticut River Basin, one of the largest river basins in New England, stretches from southern Quebec to Long Island Sound, off the Connecticut coast. It has a total length of 280 miles and a maximum width of 60 miles.

Of the 11,250 square miles in the basin, 1,436 square miles, or about 13 percent, lie in Connecticut; 3,928 square miles, or 35 percent lie in Vermont; 3,406 square miles, or about 27 percent l in New Hampshire; and 2,726 square miles, or 24 percent, lie in Massachusetts. About 114 square miles (one percent) are located in Quebec. In New Hampshire, the Connecticut River Basin occupies the western halves of Coos and Grafton counties, most of Sullivan and Cheshire counties, and the western fringes of Merrimack and Hillsborough counties.

Piscataqua River Basin
Although it lies mostly in southeastern New Hampshire, a portion of the Piscataqua River Basin lies at the southern tip of Maine. Of the basin’s total area of 1,022 square miles, 776 square miles (76 percent) lie in New Hampshire and 246 square miles (24 percent) lie in Maine. The Piscataqua River and its largest tributary, the Salmon Falls River, form the boundary between New Hampshire and Maine.

The Piscataqua River Basin has a maximum length of 48 miles and a maximum width of 35 miles. In New Hampshire, it occupies the southeastern corner of Carroll County, most of Strafford County, and the northern two-thirds of Rockingham County.

Saco River Basin
The Saco River Basin stretches from eastern New Hampshire into southern Maine. It covers an area of 1,697 square miles, of which 870 square miles (51 percent) lie in New Hampshire and 827 square miles (49 percent) in Maine. The basin has a length of nearly 75 miles and a maximum width of 44 miles.

In New Hampshire, the basin occupies nearly all of Carroll County, the northeastern section of Grafton County, and small sections of southeastern Coos County.

Androscoggin River Basin
The Androscoggin River Basin, which lies partly in western Maine and partly in northeastern New Hampshire, begins at the Canadian border and stretches to the Atlantic Ocean. It has a maximum length of 110 miles and a maximum width of 65 miles.

The basin consists of 3,450 square miles, with 2,730 square miles (79 percent) lying in Maine and 720 square miles (19 percent) in New Hampshire. In New Hampshire, the Androscoggin River Basin covers nearly half of Coos County.


- Updated: 12 June 2015