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GOM Watershed

What is the Gulf of Maine Watershed?

First, what is a watershed? A watershed is the area of land that collects all the water from rainfall and snowmelt. This includes water that has seeped through soil to form groundwater and channels it to a single point, or outlet. Water flows downhill due to gravity, so boundaries of watersheds are formed by high points, like hills or ridges.

Watersheds vary in size, with small watersheds nested inside larger ones, creating larger and larger water networks. Each watershed is defined by where all the flow comes together – into a stream, river, or estuary all the way to the ocean.

Image from , Slide 10

All land is in a watershed, whether it be forested, farmland, or neighborhoods and cities. What happens on land is connected to waterbodies within the watershed and downstream in the next. For this reason, the way the land is used is important to maintaining water quality throughout the network.

The Gulf of Maine watershed is quite large, containing 27 major river watersheds from Nova Scotia to Cape Cod, and covering 69,115 square miles. The watershed has a wealth of streams, smaller rivers, lakes, and wetlands. Many headwater streams flow from mountains of the Appalachian Mountain Chain, which form the western boundary. Except for southern portions in Massachusetts and New Hampshire, the watershed is largely forested. (Benoy et al., 2016)

A major river in the GOM watershed that is familiar to many GOMI members is the Merrimack River. The Merrimack enters the GOM at Newburyport, however, its headwaters are over 150 miles away in the White Mountains. One of the smaller headwater watersheds is Hubbard Brook. This watershed itself contains many even smaller watersheds, some of which are part of the Hubbard Brook Experimental Forest, outlined and numbered 1-9 in the top left figure below. The Hubbard Brook watershed is nested within the Pemigewasset River watershed, which in turn is nested within the Merrimack River watershed.

Maps from:


Use this visualization tool created by Sam Lerner to follow a drop of water on its journey from Hubbard Brook all the way to the Gulf of Maine and see all the different landscapes that the water passes through!


For more information about watersheds, see:


“This animation covers the basics on what a watershed is. It also discusses how scientists use precipitation data to predict how much water will flow into streams and rivers in your watershed.”

CoCoRAHS (Community Collaborative Rain Hail and Snow Network)

NOAA and NSF and Colorado State sponsored

What is a Watershed Illustration, animated

“The key thing to know about watersheds is that water does in fact all flow downhill, and that when all the “hills” in a certain area send water (or at least try to, only to be stopped by dry soil, lakes, swimming pools, or puddles) to the same place, that area makes up a watershed.”


San Jacinto River Authority


“The video, targeting middle and high school students, discusses the function of a watershed and how human actions affect the health of a watershed and the quality of water within it.” Lessons

Southwest Florida Water ManagementDistrict

What is a Watershed

City of Griffin, Georgia

Fundamentals of Watershed Hydrology

Pamela J. Edwards1, Karl W.J. Williard2, and Jon E. Schoonover

Universities Council on Water Resources

Journal of Contemporary Water Res earch and Education

Issue 154, pages 3-20, April 2015

Abstract: This is a primer about hydrology, the science of water. Watersheds are the basic land unit for water resource management and their delineation, importance, and variation are explained and illustrated. The hydrologic cycle and its components (precipitation, evaporation, transpiration, soil water, groundwater, and streamflow) which collectively provide a foundation for how landscapes and water interact are discussed at length. Important hydrologic concepts and methods are described in detail but primarily within the context of forested watersheds since most of the nation’s fresh water originates from forest lands. The contents of this paper are designed to provide fundamental hydrologic principles to both citizens and policy makers, with the intention of helping to guide informed watershed management activities.


Jane Tucker

Jane grew up on the coast of North Carolina, and holds a B.S. and M.S. in Marine Sciences from UNC-Chapel Hill. Now living on the Massachusetts coast, she works at the Marine Biological Laboratory’s Ecosystems Center in Woods Hole. She is part of a team of scientists that studiesthe ecology and biogeochemistry ofthe marshes,estuaries, and watersheds inthe Plum Island EcosystemsLongTerm Ecological Research program and at other coastal sites. Her dry-land interests include gardening and dressage.

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