History of Dams in New England

From the mid-1600s to the late 1800s, New England had a large number of gristmills for grinding grain, sawmills for sawing lumber, and fulling mills for making cloth (Eves 2019). These mills are small dams that still impede natural flowing waters. The majority of these dams occurred in small order streams that likely aren’t being used for milling, today. However, we still need dams to harvest their power for electricity, reserve freshwater for drinking and recreation, and control floodwaters. 

In the United States, the majority of dams are over 50 years old and have reached their designated lifespan (due to climate change or design life cycle) (Scinto 2019). In New England, 127 dams have been removed from 1990-2013; as a result, around 3% of New England’s river network was reconnected to its natural flow regime (Magilligan 2016).  CT contains over 4000 dams which makes it one of the many states that need dam repair or removal; 12 of these dams are of high hazard risk and need to be repaired or removed (Scinto 2019).

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Dam Effects on Flowing Waters

Many dams are long past their life expectancy, yet they still slow down surface waters, increase stream temperatures, and build up legacy sediments throughout river networks. New England watersheds are not connected well because dams impede the flow of surface waters causing longer water residence times. Dams are a difficult barrier for native brook trout and salmon species as they seek spawning habitat. Dams also increase surface water temperatures due to longer water residence times further compounding aquatic species seeking thermal refugia from cold tributaries.