The Delaware Estuary formed after flooding of the coastal plain by the Delaware River after the last ice age. The Estuary is a “drowned” river valley, or a valley previously at sea level that has become submerged.
The Delaware Estuary is a tidally dominated system, where the tidal flow is 300 times the freshwater flow. The tide ranges in height, on average, from 4.25 ft at the confluence with the Atlantic Ocean to 8.25 ft at the head of tide in Trenton, NJ. The Delaware Estuary is about 133 miles long. The salinity distribution in the Estuary is caused by the interaction of the tidal flow from the Atlantic Ocean and the freshwater flows from the main-stem Delaware River and its tributaries. Salinity is a controlling factor for the ecology of the Estuary.
The salinity distribution affects the aquatic and wetland habitats that exist, and the species that can live in these habitats. The greatest changes in salinity exist in the transition zone between the Delaware River and the Atlantic Ocean.
(where the water comes from)
60% Delaware River
10% Schuylkill River
30% Chesapeake Bay, Delaware Canal, tributaries, and non-point sources