The Oradell Reservoir is a reservoir formed by the Oradell Dam on the Hackensack River in Bergen County, New Jersey, United States. The Oradell Reservoir Dam is located primarily in the borough of Oradell, but the reservoir also extends across the borders of the nearby boroughs of Haworth, Emerson, Closter, and Harrington Park. The reservoir is fe…The Oradell Reservoir is a reservoir formed by the Oradell Dam on the Hackensack River in Bergen County, New Jersey, United States. The Oradell Reservoir Dam is located primarily in the borough of Oradell, but the reservoir also extends across the borders of the nearby boroughs of Haworth, Emerson, Closter, and Harrington Park. The reservoir is fed by the Upper Hackensack River, the Pascack Brook and Dwars Kill. The reservoir feeds the Lower Hackensack River via the Oradell Dam. Upstream from the Oradell Reservoir are three other reservoirs: Woodcliff Lake Reservoir, also in Bergen County; Lake DeForest in Rockland County in New York; and Lake Tappan, traversing the borders of Bergen and Rockland counties across the state line. The Oradell Dam was constructed to supply potable water to northern New Jersey and has essentially separated the Hackensack River into two distinct components: the upper river and the lower river.