Quonochontaug Pond is the deepest and most saline of the salt ponds. It is connected directly to the sea by a breachway that was stabilized with rock jetties by the US Army Corps of Engineers in the 1950s. And, as in the other ponds, sand eroding from the ocean side of the barrier beach is transported through the breachway into the pond where it settles and creates expanding shoals. In contrast to the other ponds, however, much of “Quonnie’s” western barrier beach remains in a protected, undeveloped state even though it is privately owned.

The town boundary between Westerly and Charlestown cuts through the middle of the pond. Water quality in past years has been very good because the pond is relatively deep, well flushed by the tides, and development has been limited. Quonnie is the least intensely developed of any of the ponds. Most of the development is residential and much of it is occupied only seasonally. Like all of the ponds, Quonnie is an important nursery for winter flounder, young striped bass, blue fish, and tautog. Bay scallops fluctuate in abundance from year to year, but in a good year, they are often found in this salt pond.

In the past few years, development pressures have increased dramatically, even though the watershed area is relatively small and a large portion of it is comprised of wet, red maple swamps. Much of the available remaining land is being subdivided into building lots.