History of Slack Reservoir

The history of Slack Reservoir began during the Industrial Revolution.  After Samuel Slater built his mill utilizing the water of the Blackstone River to power his mill, Daniel Lyman decided to build a mill in what is known as the Woonasquatucket River Valley in 1809.  Five additional cotton mills were built between 1812 and 1813.  Over the next several decades more mills began to spring up along the Woonasquatucket River putting a tremendous drain on the water level in the river.  Waterpower was essential to running the large textile mills along the Woonasquatucket River.  While the water was generally plentiful during the spring, fall, and winter, summer droughts sometimes left the mills without the natural resource necessary to keep the factories running.  In order to keep the mills open during the dry months of the year, the mill owners formed a company to build reservoirs upstream to hold water in reserve so that dams could be opened when water became scarce to power their mills downstream. 

The Tenth Census for the United States (1880) described the Woonasquatucket River as a small stream but essential to the mill owners for power.  The census listed the various reservoirs controlled by the Woonasquatucket Reservoir Company in 1880.  The Waterman Reservoir, just west of Slack's covering 318 acres when full, with a depth of 9 feet which all could be drawn off if necessary.  The Waterman Reservoir was built some 50 years before the 1880 census around 1830.  The "Slack" Reservoir, built in 1823, covers 153 acres and has a depth of about ten feet.  The "Slack" Reservoir was controlled by the Bernon Manufacturing Company in 1880.  The Sprague Reservoir was controlled by private parties at the time of the census and was said to cover 95 acres and be about 9-10 feet in depth.  The Hawkins Reservoir, which was about 95 acres and on a tributary was also controlled by private parties.  Finally, the Georgiaville Reservoir or "Pond of the Georgiaville Mills" covered 130 acres and consistently drawn down several feet.  According to the census, there were 12 mills along the Woonasquatucket.  The reservoirs could provide up to 3 months of waterpower for the mills. 

The forming of a company to build reservoirs was an innovation in manufacturing.  The General Assembly, in January, 1824, issued a charter to the Woonasquatucket River Co., among whom were Messrs. Zachariah Allen, Philip Allen, Samuel G. Arnold, Thomas Thompson, and Samuel Nightingale.  The object of this corporation was the construction of reservoirs along the line of the above-mentioned river, and its several branches, in which should be collected the water from the spring rains, to be held as a supply to aid the running of the factories during the dry season.  This was the first charter granted in Rhode Island to a company for this express purpose.  The gentlemen comprising this company united their capital, and commenced operations at or near the village of Greenville, and constructed what is known as Slack Reservoir.

This is probably the first work of the kind ever completed by a corporation chartered for this purpose.  In 1827, the Sprague lower reservoir was completed.  The Waterman Reservoir was constructed in 1838, and, still later, or in 1853, the Stillwater Reservoir was built.  These reservoirs cover an average area of five hundred and sixty-six acres.  The following table will be of interest, as showing the date of construction, average area covered, average depth, and the number of days each of these water repositories was able to power the mills.




Two early Greenville residents whose families joined through marriage provided the names for two of the Woonasquatucket River Companies Reservoirs.  In the early 1700s Mr. Waterman built a grist mill and owned a large tract of land in Greenville.  When Mr. Waterman died, his daughter Mercy inherited the property.  Mercy was married to Joseph Slack.  Mercy died when she was 83 years old and the property passed some years later to Mr. Welcome Aldrich.

Today, Slack Reservoir is owned and operated by the Slack Reservoir Association, a non-profit, volunteer organization dedicated to the preservation and conservation of this beautiful watershed.  Perhaps the biggest challenge overcome by this organization was the complete restoration and rebuilding of the Slack Reservoir Dam, which, after over 170 years of service, had deteriorated to the point of being unsafe.  Rather than see the dam fall apart, threatening the life and vitality of the reservoir, the Association banded together, raising well over a half-million dollars, and putting in countless hours of work to make the dam stable and safe for the generations to come.