Scituate Reservoir

Scituate Reservoir
shoreline in early autumn
Location	Scituate, Providence County, Rhode Island, United States
Coordinates	41°45′N 71°35′W / 41.750°N 71.583°W / 41.750; -71.583Coordinates: 41°45′N 71°35′W / 41.750°N 71.583°W / 41.750; -71.583
Type	Reservoir
Primary inflows	North Branch Pawtuxet River Moswansicut River Ponaganset River
Primary outflows	North Branch Pawtuxet River
Catchment area	94 sq mi (240 km2)
Basin countries	United States
Max. length	7 mi (11 km)
Max. width	2.5 mi (4.0 km)
Surface area	5.3 sq mi (14 km2)
Average depth	32 ft (9.8 m)
Max. depth	87 ft (27 m)
Water volume	39×10^9 US gal (150,000,000 m3).
Shore length1	66 mi (106 km)
1 Shore length is not a well-defined measure.

The Scituate Reservoir is the largest inland body of water in the state of Rhode Island. It has an aggregate capacity of 39 billion US gallons (150,000,000 m³) and a surface area of 5.3 square miles (13.7 km²). It and its six tributary reservoirs—which make up a total surface area of 7.2 square miles (18.6 km²)—supply drinking water to more than 60 percent of the state population, including Providence.

The surrounding drainage basin that provides water to the reservoir system covers an area of about 94 square miles (243.5 km²), which includes most of the town of Scituate and parts of Foster, Glocester, Johnston, and Cranston. The Scituate Reservoir is operated by Providence Water Supply Board.

The reservoir is formed by an earth-filled dam spanning the North Branch Pawtuxet River, about 3200 feet (975 m) long by 100 feet (30 m) high. An aqueduct from the dam carries water to a nearby treatment plant, which filters the water. Two major aqueducts carry the water from the plant into the distribution system. The original 90-inch (2,300 mm) aqueduct is 4.5 miles (7.2 km) long and ends at the siphon chamber in Cranston, where it splits into a series of smaller and smaller conduits that supply the water delivery system. The other 78- and 102-inch (2,600 mm) aqueduct is 9.5 miles (15.3 km) long and was built in the 1970s to supplement the original aqueduct. 75% of distribution is by gravity and 25% by pumping. The system consists of 870 miles (1400 km) of water mains.

Providence's original public water supply came from the Pawtuxet River at Pettaconsett in Cranston. The plan was approved in 1869 and the first service pipe opened on December 1, 1871. By 1910, with Providence's heavy industry growing and the supply system being expanded to surrounding communities, people realized that the flow from Pettaconsett would soon fall short of the rising demands. For some years, extremely dry weather caused water consumption to exceed the natural flow of the river, and water had to be supplied by small reservoirs owned by mill companies further upstream.