Discover the Largest Dam in Rhode Island (And What Lives in the Waters Behind It)

Dams serve a variety of functions, including flood prevention, drinking water supply, hydroelectric power generation, and recreational activity. Some of the larger dams provide all four. Rhode Island, tiny as it is, does not need a Tennessee-Valley-Authority-sized operation or a Hoover Dam. Still, being the country’s second most densely populated state, it requires a stable drinking water supply. The largest dam in Rhode Island provides just that.

Initially called the Scituate Reservoir Dam, the Gainer Dam’s construction created the Scituate Reservoir. The city began planning and groundwork for the dam in 1913, construction started in 1921, and the reservoir was completely full by 1926. The purpose of the dam and reservoir was to supply drinking water to the citizens of Providence and other parts of Rhode Island.

Where Is the Gainer Memorial Dam Located on a Map?

The dam is about 14 miles from East Providence and is about a one-hour drive from Boston, MA. It is in Providence County near the town of Hope. Towns in its drainage area include Scituate, Foster, Glocester, Johnston, and Cranston.

The Largest Dam in Rhode Island: Design and Construction

Gainer Memorial Dam is a zoned embankment dam, meaning it consists of different layers, or “zones,” of material with varying levels of permeability. It stands approximately 100 feet (30 meters) high and has a total length of about 3,200 feet (975.36 meters). The reservoir contains approximately 39,000,000,000 gallons of water. The dam cost roughly $20 million to build, equating to about $300 million today.

The city of Providence took land for the project through the use of eminent domain. The construction of the dam displaced over 1,200 citizens and demolished six villages.

What Body of Water Does the Gainer Memorial Dam Control?

Gainer Memorial Dam controls the waters of the North Branch Pawtuxet River and its tributaries, the Moswansicut and Ponaganset Rivers, to create the Scituate Reservoir. This supplies drinking water to Providence and 60 percent of the state’s population. An aqueduct carries water from the reservoir to a water treatment facility, which then supplies water to the public.

Wildlife in the North Branch Pawtuxet River

Smallmouth and largemouth bass live in the reservoir, but fishing is prohibited by the city of Providence. In 2009, the town of Scituate looked into reintroducing shad, alewife, smelt, and sea-run brown trout to the reservoir.

After the construction of the dam, Providence planted over 7 million trees to help with water purification. This forested area now provides excellent habitat for much of the state’s wildlife, such as the North American black bear, white-tailed deer, fallow deer, eastern chipmunk, woodchuck, southern flying squirrel, beaver, muskrat, skunk, opossum, and raccoon. There are also salamanders, frogs, toads, and snakes.

What Would Happen If the Gainer Memorial Dam Ever Broke?

If the Gainer Memorial Dam were to fail, the most immediate impact would be flooding. Floodwaters would flow up to 20 miles downstream to the T.F. Green Airport. Due to its proximity to the city of Providence and the population density along the river downstream, a sudden failure would result in catastrophic property damage and loss of life.

The short to long-term impact of a dam failure would be the loss of drinking water to 60 percent of Rhode Island’s population. The Scituate Reservoir is the only water supply for most of the state.

Conclusion

Rhode Island has 235 dams spread throughout the state. Gainer Memorial Dam, owned by the city of Providence, is the largest of these at 100 feet tall and over 3,200 feet long.

The photo featured at the top of this post is © Morrow Long / flickr – License / Original