Aaron River Reservoir sits on the eastern edge of Wompatuck State Park, accessible off Beechwood Street in Cohasset, and it doesn’t get nearly the attention of the bike trails or the main entrance off Union Street in Hingham. That’s part of what makes it worth the drive.
I got there mid-afternoon on a weekday and had most of the shoreline to myself. The reservoir is a working water supply — a backup source for Cohasset — and a water quality monitoring station stands at the edge of the riprap shore. The 900-foot-wide dam was built between 1976 and 1978, and on a calm afternoon the water behind it barely moves.
Below the Spillway
What I didn’t expect was the wildlife. On the way up the hill, there’s a fish ladder beside the fence — and below the spillway, the stream opens up into a different world. Tadpoles clustered in the shallows over submerged granite, a painted turtle was cruising just under the surface near a patch of yellow pond lilies, and a garter snake was moving through the leaf litter at the edge of the trail close enough that I could have stepped on it.
Spring was doing its thing: the birches were leafed out, the shrubs along the water were backlit yellow-green in the afternoon light.
About Wompatuck State Park
Wompatuck State Park covers roughly 3,500 acres across Hingham, Cohasset, Scituate, and Norwell. Much of the land was the Hingham Naval Ammunition Annex through World War II and the Korean War, which explains some of the old infrastructure still scattered through the woods. The park takes its name from Chief Josiah Wompatuck of the Massachusett people.
Below the dam, the Aaron River continues northeast through Cohasset, joining Brass Kettle Brook before eventually reaching Cohasset Harbor. The reservoir loop isn’t a well-marked hike so much as a wander — trails along the water, a walk across the top of the dam, and if you time it right, the last two hours of light hitting the pines from the west.
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