The Rockaway River Watershed has a drainage area of 133 square miles. The main flowing water body within the watershed is the Rockaway River, which is approximately 40 miles in length.
The Rockaway River runs from springs in a Sparta Mountain meadow in Sussex County to its confluence with the Passaic River in East Hanover. The river flows south towards the Berkshire Valley, then through Jefferson Township, Roxbury Township, Wharton Borough, and Rockaway Township. The Morris Canal joins the Rockaway River. The river then goes through the areas of Dover Town, Rockaway Borough, and Denville Township. The course continues through Boonton Township and Boonton Town where the river is dammed to form the Boonton Reservoir (Jersey City Reservoir). The Rockaway River continues flowing through Parsippany and Montville Townships and continues to its confluence with the Passaic River in East Hanover.