Surface water

The North and South River basins covers about 105 mi2 of eastern Massachusetts. Many wetlands and small lakes and ponds exist throughout the basins. Many wetland areas, especially south of the North River, are used to cultivate cranberries. There are a total of 57 lakes and ponds, 30 of which cover at least 10 acres. The largest lake is Oldham Pond in Pembroke, which is 235 acres.

The North and South Rivers flow into an estuary, which extends about 13 mi upstream along the North River and about 8 mi upstream along the South River, and is bordered by tidal marshes for many miles above its mouth at Massachusetts Bay. The tidal reaches of streams in the basins contain a mixture of fresh and salt water. The freshwater portion of the North River in the upper part of the basin is called the Indian Head River. Stream gradients are low throughout the basins. For example, a tributary of the South River, Furnace Brook, drops about 2.5 ft/mi over a distance of almost 3 river mi.