The Oradell Reservoir was formed by the Oradell Reservoir Dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 placed on the Hackensack River

Hackensack River

The Hackensack River is a river, approximately 45 miles long, in the U.S. states of New York and New Jersey, emptying into Newark Bay, a back chamber of New York Harbor. The watershed of the river includes part of the suburban area outside New York City just west of the lower Hudson River,...

 in Bergen County, New Jersey

Bergen County, New Jersey

Bergen County is the most populous county of the state of New Jersey, United States. As of the 2010 United States Census, its population was 905,116. The county is part of the New York City Metropolitan Area. Its county seat is Hackensack...

, completed in 1923. The Oradell Reservoir Dam is located in Oradell

Oradell, New Jersey

Oradell is a borough in Bergen County, New Jersey, United States. At the 2010 United States Census, the borough population was 7,978. The borough's territory includes a dam on the Hackensack River that forms the Oradell Reservoir...

, but the reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 also straddles the borders of Haworth

Haworth, New Jersey

Haworth is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough population was 3,382.Haworth was formed by an Act of the New Jersey Legislature on February 24, 1904, from portions of both Dumont and Harrington Townships.-Geography:Haworth is...

, Emerson

Emerson, New Jersey

Emerson is a borough in Bergen County, New Jersey, United States, a suburb in the New York metropolitan area. As of the 2010 United States Census, the borough population was 7,401....

, Closter

Closter, New Jersey

Closter is a Borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough population was 8,373. After the turn of the century, Closter changed from being sprawling estates and farms into a middle and upper middle class suburban town...

 and Harrington Park

Harrington Park, New Jersey

Harrington Park is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough population was 4,664....

.

The reservoir is fed by the Pascack Brook

Pascack Brook

The Pascack Brook is a tributary of the Hackensack River in Bergen County, New Jersey in the United States. It forms a region known as the Pascack Valley. The brook is dammed to form the Woodcliff Lake Reservoir in the town of Woodcliff Lake...

 and Dwars Kill

Dwars Kill

The Dwars Kill is a tributary of the Hackensack River in Bergen County, New Jersey, in the United States...

 in addition to the Hackensack River.

Upstream from the Oradell Reservoir are three other reservoirs: Woodcliff Lake Reservoir

Woodcliff Lake Reservoir

Woodcliff Lake is the name of a reservoir in Woodcliff Lake and portions of Hillsdale and Park Ridge, in Bergen County, New Jersey. It was created circa 1903 by damming the Pascack Brook and is also fed by the Bear Brook which joins the Pascack at the reservoir...

 and Lake Tappan

Lake Tappan

Lake Tappan is a reservoir that was formed by the Tappan Dam placed on the Hackensack River in 1967. It straddles the border between River Vale and Old Tappan, New Jersey...

 also in Bergen County and DeForest Lake in Rockland County, New York

Rockland County, New York

Rockland County is a suburban county 15 miles to the northwest of Manhattan and part of the New York City Metropolitan Area, in the U.S. state of New York. It is the southernmost county in New York west of the Hudson River, and the smallest county in New York outside of New York City. The...

.

Construction on the Oradell Reservoir began in 1901 by the dredging of a mill pond. The mill pond dam was replaced in 1911 by a low timber-crib dam that increased reservoir storage. In 1921 a 22 feet (6.7 m) high concrete Oradell Reservoir Dam was built to expand reservoir storage even more.

The Oradell Reservoir and its tributaries are protected with Category 1 water purity status in New Jersey.

The reservoir is managed by United Water New Jersey, a unit of United Water

United Water

United Water Resources, founded as Hackensack Water Company in 1869, has grown into one of the United States's largest water services companies. It is headquartered in Harrington Park, New Jersey. The company owns and operates water and wastewater utilities and also has contracts to operate...

, a private utility. It provides drinking water for an estimated 750,000 residents of Bergen and Hudson

Hudson County, New Jersey

Hudson County is the smallest county in New Jersey and one of the most densely populated in United States. It takes its name from the Hudson River, which creates part of its eastern border. Part of the New York metropolitan area, its county seat and largest city is Jersey City.- Municipalities...

counties.