↖Spruce Run Reservoir

Spruce Run Reservoir

The Spruce Run Reservoir is located in Hunterdon County, New Jersey and became operational in 1963. The 11 billion gallon on-stream water storage reservoir includes a 6,000 foot long earthen dam and two earthen dikes.
The Spruce Run Reservoir is an integral part of a water supply system that also consists of Round Valley Reservoir and the Delaware & Raritan Canal Transmission Complex. Together, they have the capability of delivering 241 million gallons of raw water per day to the water utilities that serve central New Jersey.
Photo Credit: Musconetcong Watershed Association

Round Valley Reservoir

The Round Valley Reservoir is located in Hunterdon County, New Jersey and became operational in 1965. The 55 billion gallon water storage reservoir was formed by construction of two dams and a dike closing off gaps in a natural horseshoe shaped valley.
Photo Credit: Musconetcong Watershed Association

Delaware & Raritan Canal

The Delaware and Raritan Canal was originally constructed in 1834 and operated as a barge canal until 1932. The Canal was taken over by the State of New Jersey from the Pennsylvania Railroad Company in 1934. During the 1950's the Canal was rehabilitated to serve as a public water supply transmission system. In 1974 the Canal was designated as a State Park and was also placed on the State and Federal Registry of Historic Sites.

Originally, the navigable Delaware and Raritan Canal consisted of 43 miles of main Canal between the Delaware River at Bordentown and the Raritan River at New Brunswick and 22 miles of feeder Canal between Bulls Island in Hunterdon County and the City of Trenton. The present Canal Water Supply Transmission Facility is 60 miles long with its Delaware River intake at Bulls Island in Hunterdon County and its outlet at the Raritan River in the City of New Brunswick.

About Reservoir Releases

The Authority is required to release enough water daily to maintain “minimum passing flow rates” in downstream areas of the Raritan Basin System. These minimum passing flows are required to be maintained while anticipating the volume of water that will be used by the downstream purveyors because minimum passing flows are measured at points upstream and downstream of the water treatment plant intakes. The minimum passing flow rates are set by the NJDEP and are designed to protect the availability and quality of water and the ecology of streams. Stream flow gauges, operated by the United States Geological Survey, are located throughout the downstream areas. Stream and rainfall gauges and the associated data can be accessed here.

The Authority maintains daily records of reservoir levels and releases, and that information can be accessed here. It is always the Authority’s goal to release as little as possible.

About the Raritan Basin Reservoirs

Both reservoirs were constructed by the State of New Jersey in the 1960s following a historic drought. The Authority was created in 1981 to operate the reservoirs and associated infrastructure as sources of raw drinking water. The Authority also operates the Delaware & Raritan(D&R) Canal and the Manasquan Reservoir. The Authority is a State Government Authority that is “in but not of” the New Jersey Department of Environmental Protection (NJDEP). The NJDEP Commissioner is the Chair of the Authority’s Board.

The Spruce Run Reservoir is an “on-stream” reservoir that holds up to 11 billion gallons of water. It is fed entirely by rain flowing through several streams including the Spruce Run and the Mulhockaway Creek. The watershed drainage area of the Spruce Run Reservoir is 41 square miles and encompasses parts of five municipalities. Water is released daily from the reservoir back into the Spruce Run, which enters the South Branch of the Raritan River in the Town of Clinton. The South Branch and the North Branch of the Raritan River converge in Branchburg Township (Somerset County), forming the Raritan River. Water purveyors withdraw and treat water from the Raritan River after its confluence with the Millstone River to provide to the public as drinking water.

The Round Valley Reservoir is an “off-stream pump storage” reservoir that holds up to 55 billion gallons of water. Because there are no streams feeding this reservoir it has a small natural drainage area of about five square miles and is fed almost entirely by manual transfer of water from the South Branch of the Raritan River. The Authority operates a pumping station in the Hamden section of Clinton Township to move water from the river into the reservoir via a large underground pipeline. The pumping station contains ten large pumps. How much water is pumped and when it is pumped is dependent on a number of factors, the most critical of which is the presence of sufficient flow in the South Branch of the Raritan River. Water is typically released from Round Valley by an underground pipeline that empties into the South Branch of the Rockaway Creek. The Rockaway Creek eventually empties into the North Branch of the Raritan River, which joins the South Branch to form the Raritan River in Branchburg Township (Somerset County). Water purveyors withdraw and treat water from the Raritan River after its confluence with the Millstone River to provide to the public as drinking water.

Both Spruce Run Reservoir and Round Valley Reservoir are designed for water supply purposes, but are also managed for recreational activities such as fishing, boating, hiking, and camping. The NJDEP Division of Fish and Wildlife manages the fishery at Round Valley Reservoir and the NJDEP State Park Service manages the other recreational aspects of both reservoirs.