Upper Passaic River

Streams of the Great Swamp Watershed:
Upper Passaic River

The Passaic River is the westernmost of Great Swamp’s five feeder streams.

The Passaic River is the westernmost of Great Swamp’s five feeder streams, originating in the southeastern portions of Mendham Township, Mendham Borough, and Bernardsville Borough (See Passaic River map). Flowing from these three municipalities and either through or alongside Harding Township, Bernards Township, and Long Hill Township, the Passaic River passes through more Great Swamp communities than any of the five other streams. By the time it exits Great Swamp via the Millington Gorge, the Passaic has been joined by these five streams, together forming the great Passaic River, a 90-mile waterway that traverses 45 municipalities and provides drinking water for more than 2 million people before emptying into Newark Bay.

Map of Upper Passaic subwatershedTributary stems of the upper Passaic arise in all six watershed towns through which it passes, but two primary stems arise in the Mendhams and Bernardsville Borough and a third arises in Bernards Township. The northernmost stem in the Mendhams flows from Mendham High School and then through a mix of residential properties and lands protected by the municipality or through conservation easement. After emptying into Leddel’s Pond it flows alongside Morris County’s Lewis Morris Park and then through the Morris Area Girl Scouts Camp, after which it flows through a section of the Morristown National Historical Park and then the New Jersey Audubon Society’s Scherman-Hoffman Sanctuaries. At this point the tributary is joined by the Passaic’s second major tributary, which arises in Bernardsville Borough and flows almost due east. Together the two tributaries then leave the protection of Scherman-Hoffman, traverse Routes 202 and I-287, and flow through residential sections in Bernards and Harding Townships into Osborne Pond and then into the Basking Ridge Golf Club. The third tributary joins the main stem inside the Golf Club, and the three flow as one between the Great Swamp National Wildlife Refuge to the east and Somerset County’s Lord Stirling Park to the west. It also serves as the physical border between Morris and Somerset counties.

Rain gauge

One of two rain gauges (the other is located on Black Brook) that feeds rainfall data to the monitoring station every 15 minutes.

The importance of protecting the upper reaches of the Passaic River from non-point source pollutants associated with urban and suburban development cannot be overstated. Because it originates in a relatively undeveloped portion of the watershed, the upper reaches of the Passaic are pristine by almost any measure. The June 2002 Great Swamp Watershed Water Quality Monitoring Report shows that the Passaic scores higher than any other Great Swamp stream, meeting or exceeding every baseflow and stormflow standard set by the state. However, despite these apparently noteworthy findings, macroinvertebrate sampling below Route I-287 yields decidedly poorer results, with Benthic Index of Biological Integrity Sampling between 1999 and 2001 placing water quality in the “poor” to “very poor” range. This may be due to the fact that the Passaic Stream Monitoring station is just below the Osborne Pond impoundment, where water temperatures are elevated above normal and pH rises during the day.

Upper Passaic River on April 16, 2007, after the Nor’easter

Osborn Pond on the Passaic River

Osborn Pond

Outfall from Osborn Pond on the Passaic River

Outfall from Osborn Pond

Passaic River, looking downstream

Looking downstream

Staff gauge on the Passaic River

Staff gauge



Monitoring Results on the Upper Passaic, Interim Report (through May 2012)
Black Brook
Great Brook
Loantaka Brook
Primrose Brook