The Coginchaug River in Connecticut, with a watershed of 39 square miles (100 km2) including forests, pastures, farmland, industrial, and commercial areas, is the predominant tributary of the Mattabesset River. 15.5 miles (24.9 km) long,[1] it flows mostly north from Myer Huber Pond in Guilford, Connecticut (about 1.2 miles (1.9 km) by road south of the Durham line, and about 400 feet (120 m) west of Route 77)[2] into Durham and then Middlefield, meeting the Mattabesset in Middletown,[3] about 0.8 miles (1.3 km) upstream[4] of the Connecticut River. The name "Coginchaug" comes from a local Native American name for the Durham area, and it was the original name for the town. It has been said to mean "The Great Swamp", and is a reference to the meadows found in the central part of town.
In 2006, the Coginchaug was among Connecticut 85 waterways cited as of "lower quality", in view of elevated levels of bacteria, including E. coli. Efforts are currently under way by the Natural Resources Conservation Service of the United States Department of Agriculture to recommend practices to reduce the bacteria introduced into the river from untreated sewage, sanitary sewer overflow, agricultural runoff, leaking septic tanks, etc.[3]
The river has become a popular canoeing route (and in 2006 it was considered safe for canoeing, even though not for in-water activities like swimming). Flowing from Myer Huber Pond, it has low volume through difficult swamps continuing over 3 miles (5 km), which are likely to be impassable except soon after heavy rain. The main paddling route starts at Route 147 and continues downstream, north, through additional slow-moving waters and a swamp. There are many portages, including those at six dams and at Wadsworth Falls, the only major waterfall. Class II whitewater is possible before it flows into the tidal marsh of the Mattabesset River.