Wood-Pawcatuck Watershed

What is a watershed?

Watersheds come in all sizes and shapes. They ignore political boundaries. A watershed is the land area that drains to a common outlet like a lake, stream, river or bay. Often called a “basin,” you can think of a watershed as a large bathtub. The divides, or high points of a watershed, separate one watershed from another.

What is the Wood-Pawcatuck Watershed?

The Wood-Pawcatuck Watershed is located in southwestern Rhode Island and southeastern Connecticut. It is between the major metropolitan areas of New York and Boston. The watershed covers a land area of more than 300 square miles (194,000 acres). It includes all or sections of ten Rhode Island towns (Westerly, West Greenwich, Coventry, North Kingstown, Richmond, Hopkinton, Exeter, East Greenwich, Coventry, and Charlestown). Also included are four Connecticut towns (Voluntown, Stonington, Sterling, and North Stonington). Seven major rivers and their tributaries drain to the common outlet of the Pawcatuck River and Little Narragansett Bay. These rivers including the lakes, ponds, wetlands, and streams, serve as an important wildlife habitat, recreational resources, and water supplies for agricultural production. Significant groundwater resources underlie the watershed and remain the sole source of drinking water for people living within the watershed. The Wood-Pawcatuck Watershed is one of Southern New England’s “special places” and features several centuries of historical artifacts in a remarkably rural and unspoiled natural setting. It is rich in Native American sites, family-owned farms, small-scale mill villages, summer colonies and a picturesque downtown area (Westerly-Pawcatuck).

How was the Wood-Pawcatuck Watershed formed?

Glaciers formed this watershed approximately 16,000 to 17,000 years ago as the late Wisconsin continental ice sheet retreated from southern New England. As the glacier retreated from Block Island Sound, it deposited the 100-foot high Charlestown recessional moraine, a ridge of glacial sediment running alongside U.S. Route 1 on the south shore of Rhode Island. This ridge effectively blocked the southward flow of the rivers. Glacial lakes formed behind the moraine as the glacier retreated to the north. Melt water accumulated in the valleys. Drainage from these lakes was established to the west. This event created the ancestral Pawcatuck River. The current day Wood-Pawcatuck Watershed is characterized by low rolling hills, separated by relatively flat valleys. These geographical features were caused by erosion along pre-existing river valleys that produced a series of deep north-south bedrock valleys. Today, they are present beneath the cover of glacial deposits.

Worden Pond and the surrounding Great Swamp are the remnants of ancestral Lake Worden. They occupied a bedrock valley now filled with over 200 feet of sediment. Kettle ponds (Larkin Pond, Thirty-Acre Pond, Hundred Acre Pond, Yawgoo Pond and Sandy Pond) dot the landscape where blocks of ice, buried in the glacial outwash of sand and gravel, melted, leaving large depressions in the earth. Blockage of the bedrock valleys by the Charlestown moraine and the lack of significant topographical relief have created a relatively sluggish flow of water throughout the watershed. Now, rivers that might have drained southward flow instead to the west behind the moraine as tributaries to the Pawcatuck River. As a result, wetlands occur throughout the watershed. They are extensive at the southern end of some valley areas (Indian Cedar Swamp, Great Swamp, Chapman Swamp and Watchaug Pond). Preserving the watershed today represents a unique accommodation between the modern drainage system and the geologic features inherited from the last ice age. Together these forces have formed expanses of diverse, scenic and unspoiled habitats.

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