Streams and Watersheds

a stone arch bridge over a rocky wooden stream
The Hadlock Brook Bridge and stream in Acadia National Park. Photo: Emma Forthofer/Friends of Acadia

Running Waters

In additions to wetlands, marshes and swamps, and lakes and ponds, streams and watersheds round out Acadia's freshwater ecosystems. A "watershed" refers to the land area that directs precipitation, groundwater, seepage, and runoff down slope into a common location, such as a wetland, stream, or pond. Runoff can begin as rain on a mountain summit or come from underground sources like springs. Eventually, all water runs downhill and makes its way to the ocean. On Mount Desert Island (MDI) , where most of the park is located, this runoff heads in three directions - to Frenchman Bay to the east, to Blue Hill Bay to the west, and to Somes Sound in the center. These three large areas then have small streams and drainages that make up 12 watersheds on MDI. The Isle au Haut and Schoodic Peninsula portions of the park have few streams and lack defined sub-basins, except for small sub-basins located near Long Pond on the west shore of Isle au Haut.

Though most of these stream channels are small, ephemeral and unnamed, any hiker of Acadia's mountains knows that they are a primary feature of the park landscape. Small trail bridges and tickling streams dot the landscape and are a great place to pause and take in the sound. Amphibians and reptiles such as frogs, toads, and salamanders can often be found here as can a variety of freshwater plants. Depending on the size of the stream, brook trout and other fish call Acadia's streams home as well.

A Shared Future

Most park watersheds lie at least partially outside the park boundary. This means that, depending on the area, the preservation of Acadia's pristine waters is done in cooperation with state and local communities and with you, the visitor. The park owns the upland (upstream) portions of most watershed systems since most of the mountain summits on Mount Desert Island lie within the park boundary. But water flows in and out of the park boundary. Follow Leave No Trace principles while in the park and at home.

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    Last updated: February 26, 2022

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