Credit: Jim Lukach

In the Great Swamp Watershed, five streams — the Upper Passaic River, Black Brook, Great Brook, Loantaka Brook, and Primrose Brook — all flow into Great Swamp and exit as the Passaic River via Millington Gorge.

Five tributaries or feeder streams convey water from where it falls on higher elevations of the watershed (850 feet above sea level at its highest point) down to the much lower elevations of the Great Swamp National Wildlife Refuge (around 220 feet above sea level). Once in the swamp, four of the five streams merge and then join with the Passaic River and exit the watershed at the Millington Gorge.