|Mouth||Long Island Sound|
|Length||45.5 miles (73.2 km)|
|Source elevation||~350 feet (107 m)|
|Avg. discharge||299 cubic feet/s (8.4 m³/s)|
|Basin area||165 square miles (427 km²)|
It rises in west central Connecticut from Dead Wood Swamp west of the city of New Britain. It flows roughly southward to Plainville, Southington, and Cheshire, west of the city of Meriden, through Wallingford and Yalesville, North Haven, and flows into New Haven Harbor, an inlet of Long Island Sound, east of downtown New Haven (Coordinates: ).
It has a total length of 45.5 miles (73.2 km) and a drainage area of approximately 165 square miles (430 km2). There are four dams, most of which are old remnants, that impede boat travel. The first dam is about 1/2 mile south of Plantsville, the second dam is at the southeast corner of Hanover Pond in South Meriden, the third dam is in northeast Yalesville, and the fourth dam is at the south end of Community Lake in Wallingford. Paddling is a frequent recreational activity along the Quinnipiac River, especially within the tidal marsh in North Haven. Additionally, the tidal variation extends approximately 14 miles (23 km) upriver from its mouth.
The name comes an Algonquian phrase for "long water land", and the name given to the river and the area around its mouth.
Throughout the 19th and 20th centuries, the river suffered from severe pollution problems because of the presence of heavy industry and population centers in its watershed. The Quinnipiac was the subject of the first ever pollution control measure in the state of Connecticut. In 1886, the state legislature passed a measure prohibiting the City of Meriden from discharging raw sewage into the river. In 1891, the act resulted in the building of state's first sewage treatment plant.
Nevertheless, by 1914, the State Board of Health reported that the major fish life had largely disappeared from its mouth. The pollution has been somewhat abated by the passage of the Connecticut Clean Water Act of 1967, and by the Water Pollution Control Act of 1972, which provided the legal authority to take measures to clean up the river's watershed. The measures included the construction of advanced waste management facilities for sewage and industrial waste. Levels of copper in the river have decreased 70% since the 1980s and are now comparable to other reference streams in Connecticut. Combined sewer overflows from the City of New Haven are still regarded as a major problem for the estuary.
- Tomlinson Bridge (U.S. Route 1)
- Pearl Harbor Memorial Bridge (Interstate 95)
- Ferry Street Bridge
- Grand Avenue Bridge
- I-91 Bridge (Interstate 91)
- Middletown Avenue Bridge
Bridges north of the Middletown Avenue bridge are relatively minor structures.
- U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed April 1, 2011
- State of Connecticut Department of Environmental Protection, A Total Maximum Daily Load Analysis for the Quinnipiac River Regional Basin, June 4, 2008