The watershed of the Delaware River drains an area of 14,119 square miles (36,570 km2) and encompasses 42 counties and 838 municipalities in five U.S. states, New York, New Jersey, Pennsylvania, Maryland, and Delaware.[1]: p.9 This total area constitutes approximately 0.4% of the land mass in the United States.[1]: p.9 The Delaware River rises in the Catskill MountainsinUpstate New York, flowing southward for 419 miles (674 km) into Delaware Bay where its waters enter the Atlantic Ocean near Cape May in New Jersey and Cape Henlopen in Delaware. There are 216 tributary streams and creeks, comprising an estimated 14,057 miles of streams and creeks, in the watershed.[1]: p.11, 25
The waters of the Delaware River's basin are used to sustain "fishing, transportation, power, cooling, recreation, and other industrial and residential purposes."[1]: p.9 While the watershed is home to 4.17 million people according to the 2000 U.S. census, these bodies of water provide drinking water to 17 million people, roughly 10% of the population of the United States.[1]: p.vi, 9 It is the 33rd largest river in the United States in terms of flow, but the nation's most heavily used rivers in daily volume of tonnage.[1]: p.11 The average annual flow rate of the Delaware is 11,700 cubic feet per second at Trenton, New Jersey.[1]: p.9
Tributaries are arranged generally north to south from the source of the river to its mouth, its confluence with the Delaware River, tributaries within that rivers' watershed are mentioned in notes.
Delaware Bay is a major estuary outlet of the Delaware River on the Northeast seaboard of the United States whose fresh water mixes for many miles with the waters of the Atlantic Ocean. The bay, as an estuary, forms a transitional zone between the river environment provided by the Delaware River and maritime environment of the Atlantic Ocean that is subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. Delaware Bay covers 782 square miles (2,030 km2) in area.[2] The bay is bordered by the State of New Jersey and the State of Delaware. The bay's outermost boundary separating it from the Atlantic are two capes: Cape Henlopen and Cape May.
