Three great rivers flow north to south in New England. One is our Connecticut River. The others are the Hudson River, most often thought of as the river that flows past New York City, and the Merrimack River that drains central New Hampshire and flows through Concord.
The source of the Connecticut River is Fourth Connecticut Lake in Pittsburgh, NH at the Canadian border. It begins its seaward journey at an elevation of 2,660 feet above sea level some 410 miles from Long Island Sound where it enters the Sound at Old Saybrook, CT. Of course, estimating the length of a major river is a human conceit since a river is as long as it wants to be. The average river discharge at Thompsonville, CT is 17,100 cubic feet per second. This is where the river ceases to be tidal, 40 miles from Long Island Sound.

The Hudson River with its 13,440 square mile watershed is only slightly larger than the Connecticut’s 11,200 sq. mi. watershed. They both have a distinct north to south flow and both are tidal at their lower reaches as they enter salt water. The Hudson watershed is home to 3.9 million people while the Connecticut’s total population is 2.3 million. The Hudson River figure does include the New York City boroughs of Manhattan (1.4 million) and the Bronx (1.3 million). The river is tidal all the way up river to Troy, NY some 132 miles from the Atlantic Ocean indicating the flatness of the river.
The Hudson River rises up out of the Lake Tear of the Clouds in the Adirondack Mountains in central New York at an elevation of 4,590 feet where it begins its southward flow of some 315 miles to Lower New York Bay just down river from Manhattan where the river is discharging an average of 21,900 cubic feet per second. Its final “tributary” is the East River, a salt water tidal cut created by the glaciers 11,000 years ago that connects the Hudson River with Long Island Sound.

The Merrimack River for most of its 117-mile length flows north to south with the total watershed of the river alone approximately 4,700 square miles. Those 117 miles though are not the entire watershed, more on this shortly. The river flows south until it reaches Lowell, MA where it take a sharp swing to the northeast following the contour of the lands as laid down by the same glaciers that created the East River 11,000 years ago. When it joins the Gulf of Maine at Newburyport, MA, its flow is on average 7,565 cubic feet per second. The lower 22 miles of river are tidal.

Totaling the full watershed for the Merrimack River requires that you add in the watersheds for the Pemigewasset River starting in the Pemigewasset wilderness at 1,930 feet in elevation and the Winnipesaukee River at 504 feet in elevation that join at Franklin, NH forming the Merrimack River. When you add these 75 miles of river length and 1,500 square miles of watershed, the total length is 192 miles with a total watershed of 6,250 square miles. That total does not include the tributaries to and full acreage of glaciered Lake Winnipesauke that is some 21 miles in length, 9 wide, and 71 square miles in size.
Measuring the environmental health of the three rivers is complex. Each has its unique features and values as well as various water quality problems. One measure of the health of each river is their returns of anadromous fish, especially the American shad.
After two decades of decline, shad returns rebounded in the Connecticut in 2016 to 416,350. Since 1992 when a record 720,000 fish returned, the number of returning fish has been in a steady decline. 2016 is the first year since 1992 that the river has not had a five-degree artificial increase in the temperature of the entire river flow caused by the Entergy thermal discharge at Vernon that affects the river some 50 downriver miles all the way to Holyoke.
The Merrimack shad returns were 86,857 in 2015. This is a significant increase over historic levels of returning shad; in fact, 2015 is the highest number of returning fish since records began in 1983.
It is clear that shad are not faring well in the Hudson River. The NY Department of Environmental Conservation does not publish information on shad returns; they do measure the abundance of young of the year shad. Unfortunately as of 2013, the count was so low they simply could not measure the numbers of fish. Shad face what many call a thermal and impingement barrier at Indian Point where one nuclear and two fossil fuel power plants suck huge amounts of water from the river and discharge heated water back to the river.
Topography and the action of the last great glacier period have given New England and New York three great north to south flowing rivers. Get out and experience all of them.
David Deen is River Steward for the Connecticut River Watershed Council. CRWC has been a protector of the Connecticut River for more than 60 years.