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Pawtuxet River Watershed

Map of Pawtuxet Watershed


The Pawtuxet River watershed, located in central-western Rhode Island, is the largest watershed in the state. The river flows generally from west to east. Its headwaters are in the hills of western Rhode Island. Its mouth is in historic Pawtuxet Village between the cities of Warwick and Cranston, the state's second and third largest cities. The watershed encompasses all or portions of the following communities: Coventry, Cranston, East Greenwich, Exeter, Foster, Glocester, Johnston, Providence, Scituate, Warwick, West Greenwich, and West Warwick.

The Pawtuxet River watershed comprises the Scituate Reservoir and its tributaries, the North Branch of the Pawtuxet, the Pocasset River, the Big River and its tributaries, the Flat River Reservoir and its tributaries. the South Branch of the Pawtuxet, and the main stem of the Pawtuxet. In total, the watershed contains 64 ponds, 93 brooks, 7 tributary rivers, and 18 dams.


The watershed is heavily influenced by the development patterns of the 19th and 20th centuries. With the second largest volume of water in Rhode Island and a substantial drop in elevation from its headwaters to Narragansett Bay, the Pawtuxet River watershed became a center of textile manufacturing plants. Numerous impoundments were created along the river and its tributaries, and along the banks were a series of mills and mill villages, many of which now have historical significance. In the late 19th century, this development was so intensive that an urban area emerged in the eastern Coventry-West Warwick area. Factories and villages both discharged their effluent and waste in the river, degrading water quality in the lower portions of the watershed.

As the city of Providence's population increased through the industrial era, public health became a major concern. It was decided that the northern and western portions of the Pawtuxet River watershed should be used as the source for the City's drinking water.

The Scituate Reservoir water system of the Providence Water Supply Board, completed in the 1920's, now provides drinking water to nearly two-thirds of the state's population. The Big River, a major tributary of the South Branch of the Pawtuxet, was recognized as another potential drinking water resource for the state, and land to construct a large surface water reservoir was acquired. The development of this project was dropped largely because of the loss of wetlands that would have resulted; the Big River Wildlife Management Area, however, remains available as a potential source of public water supply.

The Quidnick Reservoir Association controls the Flat River Reservoir system, as well as flows into the South Branch of the Pawtuxet River. The Pawtuxet River is also the receiving body for several wastewater treatment plant discharges. During the 1970s and 1980s, the treatment plants of Cranston, Warwick and West Warwick were upgraded to secondary treatment facilities, and most previous difficulties with their operation have been overcome. Notwithstanding these improvements, water quality on the main stem of the Pawtuxet is problematic, and an agreement was reached by the communities and the state to provide advanced wastewater treatment. The cost of these improvements is high, possibly in the vicinity of $100 million. In the past, industrial discharges were a major cause of water pollution; however, these sources have largely been eliminated through the decline of industry, the imposition of wastewater regulations, and connection to wastewater treatment facilities.

Through the second half of the 20th century, awareness has increased relative to water pollution from nonpoint sources. Threats occur especially from septic systems, runoff, road salt applications, and construction/development activities. The areas immediately south and west of Providence have been the direct path for post-World War II suburbanization. Interstate highways I-95 and I-295 traverse the watershed; and route RI-2, from the Pocasset River in Cranston through Warwick and West Warwick, has become a commercial center of development. The gains made in reducing point source pollution can be lost to nonpoint sources.

There is a high level of interest and potential for increasing recreational opportunities associated with the river way. The North Branch is swimmable between the Gainer Dam of the Scituate Reservoir and the village of Hope, but development in the area threatens water quality. The Flat River Reservoir system (which includes the Flat River Reservoir/Johnson's Pond, Quidnick Reservoir, and Stump Pond) is currently used for swimming, boating, and fishing.

In 1987, the Pawtuxet River Authority (created in part to develop recreational opportunities on the North and South Branches and the main stem of the river) drafted a plan for "a series of river walks, canoe access sites, and significant natural areas along the Pawtuxet River." Progress toward full implementation of this plan has been incremental, impeded by a lack of funds.

The purposes of the classifications for the Pawtuxet River are, first, to protect current values and uses within the watershed, especially in the Big River, Scituate, and Flat River Reservoirs and the North Branch to Hope areas; and second, to foster the goal of making the River a major recreational resource in the intensively suburbanized central portion of the state.


The main stem of the Pawtuxet River is listed as impaired by low dissolved oxygen and nutrients. The upper reaches of the river supply drinking water and meet fishable standards. Several ponds in the lower watershed (Roger Williams Park Ponds, Mashapaug Pond, and Spectacle Pond) are listed as impaired by low oxygen, excess algal growth, and phosphorus.

RI DEM has addressed the main stem impairment by issuing discharge permits that constitute a control action equivalent to a TMDL. Three WWTFs discharge to the Pawtuxet River. Together these plants constitute the majority of nutrient loading to the river. All the plants now have total nitrogen limits of 8 mg/l, including not more than 2 mg/l of ammonia nitrogen. Phosphorus is limited to 1 mg/l. The West Warwick plant is due to complete construction of upgrades to meet these permit limits in July, 2005. The Warwick plant improvements should be completed by September, 2004. The Cranston plant is currently achieving the ammonia limit and additional upgrades for phosphorus and nitrogen should be completed in 2007. These projects are on the

CWFA PPL or have been supported in the past. Sewers and interceptors for Coventry, West Warwick, and West Greenwich are also on the CWFA PPL. Johnston has established a municipal onsite treatment system management plan and three other communities (Scituate, Foster and Coventry) are considering such plans. Other communities in the Pawtuxet watershed are largely sewered. Stormwater management actions in 5 areas of the watershed (all state responsibility) are also included on DEM's TMDL implementation list. Eleven of the twenty largest outfalls identified by RI DOT (by mass of pollutants discharged) discharge to the Pawtuxet River. RI DOT's I-95 Stormdrain Retrofit Project has prioritized work in the Pawtuxet watershed - with the five largest outfalls targeted for construction of retrofit BMPs.


The Pawtuxet River Authority monitors water quality in the Pawtuxet River Watershed. The monitoring program is divided into three categories: rivers and streams, lakes and ponds, and wetlands and land use. River and stream monitoring is principally conducted with Cranston Water Pollution Control Facility.

Sub-basins exit points are monitored monthly for pH, DO, temperature and nutrients. Lake and pond monitoring is mainly conducted with URI Watershed Watch. 18+ water bodies are monitored biweekly for clarity, temperature, algal biomass, dissolved oxygen and salinity. They are also monitored tri-seasonally for pH and alkalinity, total and dissolved phosphorus, total nitrate and ammonium content, bacterial content, and chloride.

Fish Restoration

In February 2006, The CRMC awarded $50,000 to the Pawtuxet River Authority for its Pawtuxet River Anadromous Fish Restoration project, which would restore a self-sustaining run of river herring an American shad to the river. Currently, fish passage is obstructed by the Pawtuxet Falls Dam at the river's mouth. Restoring the fish run would open up 7.5 miles of spawning habitat above the dam on the main stem of the River and Pocasset River.

Organizations & Links

Pawtuxet River Authority and Watershed Council

The R.I. General Assembly created the Pawtuxet River Authority in 1972. For 30 years, the PRA has worked to reverse the damage done by 150 years of industrial development. The PRA has cleaned hundreds of tons of debris from the Pawtuxet, built river access and trails, obtained funds to upgrade sewage treatment plants, and worked to preserve open space.

Currently, the PRA is engaged in a major project to restore migratory shad and herring to the Pawtuxet River system. Volunteers are always needed!

Robert Nero
Pawtuxet River Authority & Watershed Council
618 Main St., Coventry, RI 02816

Informational Links