Characterizing ground- and surface-water resources in 

the Pawcatuck River Basin of southwestern Rhode Island and 

southeastern Connecticut requires an understanding of how 

precipitation enters, flows through, and leaves the aquifers 

and streams in the basin. Data to support this understanding 

include climatological, hydrogeologic, groundwater, pondlevel, streamflow, and water-use data. These data also 

are needed to develop and calibrate surface-water- and 

groundwater-flow models that characterize and simulate 

these flow processes. 

Climate

Climatological data were available for the Pawcatuck 

River Basin from several National Oceanic and Atmospheric 

Administration (NOAA) National Weather Service (NWS) 

stations in and near the basin and from two new stations 

established by USGS for the present study. Data included 

precipitation, air temperature, dew-point temperature, wind 

speed, and solar radiation (table 1–1). Long-term data were 

available from the NWS stations at Providence T.F. Green 

Airport in Warwick, R.I. (PROVID; hourly data) and at the 

University of Rhode Island in Kingston, R.I. (URI; hourly 

data since 1998). NWS weather stations at the Newport and 

Westerly Airports have collected data since the late 1990s. 

The PROVID and NEWPORT stations are about 10 miles 

(mi) to the northeast and about 11 mi to the east of the 

basin, respectively, and the WESTERLY station is in the 

southwestern part of the basin (fig. 1–1). The USGS stations 

at the Fisherville Brook Wildlife Refuge (FBWR) and the 

Narragansett Improvement Company (NIC) were established 

in the northeastern and central parts of the basin, respectively 

(fig. 1–1), to provide local climatological data for model 

calibration. Data from the FBWR station were available 

from November 22, 1999, through November 15, 2001, and 

October 1, 2002, through December 15, 2004. Data from the 

NIC station were available for the period December 15, 2002, 

through December 15, 2004.

Part 1. Water Resources in the Pawcatuck River Basin

By Gardner C. Bent, Andrew M. Waite, and Peter E. Church

Table 1–1. Types of climatological data collected at U.S. Geological Survey stations and compiled from National Oceanic and 

Atmospheric Administration National Weather Service (NOAA-NWS) stations in and near the Pawcatuck River Basin, southwestern 

Rhode Island and southeastern Connecticut, 2000–04.

[Locations shown in figure 1–1. USGS, U.S. Geological Survey; NWS, National Weather Service; IDLOC, identification attribute in the Watershed Data Management (WDM) database for the Hydrologic Simulation Program-FORTRAN (HSPF) model; FBWR, Fisherville Brook Wildlife Refuge; NIC, Narragansett 

Improvement Company; URI, University of Rhode Island; PROVID, Providence; Y, yes; N, no]

USGS station USGS station

NWS 

University of 

Rhode Island

NWS 

T.F. Green Airport

NWS 

Newport Airport

NWS 

Westerly Airport

IDLOCN FBWR NIC URI PROVID NEWPORT WESTERLY

Time step Hourly Hourly Hourly Hourly Hourly Hourly

Begin date 11/22/1999 12/4/2002 9/30/1998 1/1/1960 7/1/1996 7/28/1999

End date 12/31/2004 12/31/2004 12/31/2004 12/31/2004 12/31/2004 12/31/2004

Precipitation Y Y Y Y Y Y

Air temperature Y Y Y Y Y Y

Dew-point temperature Y Y Y Y Y Y

Wind speed Y Y Y Y Y Y

Solar radiation Y Y Y Y N N

Potential evapotranspiration computedY N N Y N N
12 Part 1. Water Resources in the Pawcatuck River Basin

Narragansett Improvement 

Company (NIC)

University of Rhode 

Island (URI)

Fisherville Brook 

Wildlife Refuge (FBWR)

Newport

Providence (PROVID)

Narragansett Improvement 

Company (NIC)

University of Rhode 

Island (URI)

Fisherville Brook 

Wildlife Refuge (FBWR)

Newport

Westerly

Providence (PROVID)

B L O C K I S L A N D S O U N D

L O N G I S L A N D S O U N D

A T L A N T I C O C E A N

N

A

R

R

A

G

A

N S E T T

B A Y

CONNECTICUT

RHODE ISLAND

MA

RI

0 3 6 MILES

0 3 6 KILOMETERS

EXPLANATION

Climatological station and name

State boundary

Pawcatuck Basin boundary

Newport

Beaver River

River

River

Wood

River

Chickasheen Brook

Pawcatuck

Pawcatuck

Tomaquag Brook

Queen River

Wood River

Ashaway River

ShunockRiver

Meadow Brook

Usquepaug River

Chipuxet River

Watchaug

Pond Chapman

Pond

Worden

Pond

Breakheart

Pond

Tucker

Pond Pasquiset

 Pond

71°50' 71°40' 71°30' 71°20'

41°40'

41°30'

41°20'

Base from U.S. Geological Survey digital data

North American Datum of 1983

Rhode Island state plane projection, 1:24,000

Figure 1–1. Location of climatological stations in and near the Pawcatuck River Basin, southwestern Rhode Island and 

southeastern Connecticut.
Geologic Setting 13

Mean annual precipitation was 46.45 in. at the PROVID 

station and 51.82 in. at the URI station for the 30-year period 

1971 through 2000 (National Oceanic and Atmospheric 

Administration, 2002a). Differences in total precipitation at 

the two stations may reflect local weather patterns given that 

mean annual precipitation ranged from 39.79 to 53.17 in. for 

the same period at six NWS stations (including the PROVID 

and URI stations) across the State. Mean monthly precipitation 

is fairly uniform throughout the year, with the mean monthly 

low of 3.17 in. at PROVID (3.31 in. at URI) in July and the 

high of 4.43 in. at PROVID (5.11 in. at URI) in March for 

the 30-year period. Snowfall generally occurs during the 

months of November through April, but on occasion has 

occurred in late October and early May (National Oceanic 

and Atmospheric Administration, 2002b). The 30-year mean 

annual snowfall at PROVID was 32.9 in., with 19.6 in. in the 

months of January and February together. The mean annual 

temperature was 51.1°F at the PROVID station (49.7°F at 

URI) with the mean monthly low of 28.7°F (28.6°F at URI) 

in January and the high of 73.3°F (70.7°F at URI) in July 

for the 30-year period (National Oceanic and Atmospheric 

Administration, 2002a). 

During the study period 2000–04, mean annual 

precipitation at the URI station was 52.08 in. (National 

Oceanic and Atmospheric Administration, 2007), which 

is very close to the long-term mean of 51.82 in/yr. March 

2001 was the wettest month, with 12.29 in. of precipitation, 

and October 2000 was the driest month, with 0.69 in. of 

precipitation (fig. 1–2A). A 13-month dry spell occurred from 

August 2001 through 2002 (fig. 1–2A) with only 38.93 in. 

of precipitation, which represented a deficit of about 17.3 in. 

based on the 1971–2000 normals. Mean annual snowfall was 

33.1 in. at the URI station during 2000–04; this value is very 

similar to the long-term mean of 32.9 in/yr at the PROVID 

station. Mean annual temperature at the URI station for 

2000–04 was 51.0°F, with January having the lowest mean 

temperature of 28.1°F and August having the highest mean 

temperature of 71.9°F. Monthly temperatures were similar to 

the 1971–2000 normals (fig. 1–2B).

Geologic Setting

The geology of the Pawcatuck River Basin is 

characterized by glacial deposits of variable thickness 

overlying crystalline bedrock. Stratified sand, gravel, silt, 

and clay (stratified glacial deposits), glacial till, and the 

Charlestown Moraine compose the glacial deposits 

(fig. I–2). Most of these materials are deposits from the last 

two continental ice sheets that covered New England during 

the middle and late Pleistocene. Most were laid down during 

the advance and retreat of the last (late Wisconsinan) ice 

sheet, which reached its maximum extent about 21,000 years 

ago and was retreating northward through southern Rhode 

Island by about 19,500 years ago (Stone and Borns, 1986; 

Boothroyd and others, 1998). Postglacial Holocene deposits, 

consisting of flood-plain alluvium along rivers and streams, 

organic peat, and muck (swamp deposits), are present in some 

areas. Bedrock beneath the basin is predominantly granite and 

granite gneiss of Late Proterozoic and Paleozoic age (Hermes 

and others, 1994). The bedrock surface is irregular and is 

characterized by preglacial, seaward-sloping, north-southtrending valleys (Masterson and others, 2007).

Glacial till was deposited directly by glacier ice and is 

characterized as an unsorted, unstratified, relatively compact 

mixture of sand, silt, and clay with variable amounts of 

stones, cobbles, and large boulders. Till blankets the bedrock 

surface in most places, and underlies most upland areas and 

extends beneath stratified glacial deposits in valleys. The 

thickness of the till layer is variable geographically, but is 

reported to average around 20 to 25 feet (ft) in the uplands 

and less than 10 ft beneath stratified glacial deposits (Johnston 

and Dickerman, 1985; Dickerman and others, 1990, 1997; 

Dickerman and Bell, 1993; Masterson and others, 2007). Local 

accumulations of till in drumlins and along some bedrock 

hills may reach thicknesses of 80 ft (Johnston and Dickerman, 

1985, Dickerman and others, 1990, 1997; Dickerman and Bell, 

1993). In upland areas where till is absent, bedrock is exposed 

at the land surface. 

The Charlestown Moraine is a WSW–ENE trending, 

hummocky linear ridge that forms the southern boundary or 

surface-water divide between the Pawcatuck River Basin and 

the South Coastal Basin (fig. I–2). The moraine represents 

a long-term recessional position of the retreating glacier 

(Schafer, 1965). The deposition of the moraine across the 

valleys of preglacial south-flowing rivers diverted drainage 

in the area and resulted in the southwesterly course of the 

present-day Pawcatuck River (Masterson and others, 2007). 

The moraine is a thick and complex mixture of sediments, 

including sandy ablation till and intermixed sands and gravel. 

The few lithologic logs available from the moraine indicate 

that the western part of the moraine consists of material that is 

more stratified and permeable than the material in the eastern 

part (Friesz, 2004). Masterson and others (2007) report that 

the glacial deposits are as much as 300 ft thick where the 

moraine crosses the deepest bedrock valleys.

The stratified glacial deposits are glaciofluvial and 

glaciolacustrine sands, gravel, silt, and clay. Stratified glacial 

deposits in valleys and lowlands cover about 35 percent of 

the basin (fig. I–2). The deposits were transported by meltwater streams that drained from the ice margin and commonly 

flowed directly or indirectly into glacial lakes (Dickerman and 

others, 1997). The deposits consist of multiple, sequentially 

deposited packages of proximal, coarse-grained (gravel, sand 

and gravel, and sand) sediments that grade into distal or lacustrine, fine-grained sediments (very fine sand, silt, and clay). 

These packages represent the systematic northward retreat of 

the ice sheet through the basin (Dickerman and others, 1997). 

Proximal deposits commonly consist of ice-marginal deltaic 

sequences. Lateral migration of depositional environments 

and collapse at the ice margin resulted in vertical gradations 

in grain size, such as sand and gravel overlying sand, or very 
14 Part 1. Water Resources in the Pawcatuck River Basin

*Data from National Oceanographic and Atmostpheric Administration, National Weather Service station at Univerisy of Rhode Island (NOAA-NWS at URI)

20

30

40

50

60

70

80

JAN.

2000

APR.

2000

JUL.

2000

OCT.

2000

JAN.

2001

APR.

2001

JUL.

2001

OCT.

2001

JAN.

2002

APR.

2002

JUL.

2002

OCT.

2002

JAN.

2003

APR.

2003

JUL.

2003

OCT.

2003

JAN.

2004

APR.

2004

JUL.

2004

OCT.

2004

MONTH AND YEAR

TEMPERA

TURE, IN DE

G

REES FAHRENHEI

T

2000–04 monthly mean temperature, NOAA-NWS at URI*

1971–2000 monthly temperature normals

B Temperature

0

1

2

3

4

5

6

7

8

9

10

11

12

13

PRECIPITATION, IN INCHES

2000–04 monthly precipitation, NOAA-NWS at URI*

1971–2000 monthly precipitation normals

A Precipitation

JAN.

2000

APR.

2000

JUL.

2000

OCT.

2000

JAN.

2001

APR.

2001

JUL.

2001

OCT.

2001

JAN.

2002

APR.

2002

JUL.

2002

OCT.

2002

JAN.

2003

APR.

2003

JUL.

2003

OCT.

2003

JAN.

2004

APR.

2004

JUL.

2004

OCT.

2004

Figure 1–2. Monthly (A) precipitation and (B) mean temperature at the National Oceanic and Atmospheric Administration 

National Weather Service (NOAA-NWS) University of Rhode Island (URI) climate station in the Pawcatuck River Basin, 

southwestern Rhode Island and southeastern Connecticut, 2000–04.
Groundwater 15

fine sand and silt overlying poorly sorted sand and gravel. The 

stratified glacial deposits range in thickness from a few feet 

at deposit margins to more than 100 ft, with typical ranges of 

about 60 to 80 ft; thicknesses are generally greatest along the 

axes of preglacial stream valleys (Dickerman and Ozbilgin, 

1985; Johnston and Dickerman, 1985; Dickerman and others, 

1990, 1997; Dickerman and Bell, 1993). 

Groundwater

Aquifers in the Pawcatuck River Basin typically are 

unconfined. Recharge occurs from precipitation in till and bedrock uplands and in areas of stratified glacial deposits; surface 

runoff from uplands also may recharge stratified glacial deposits at their upland boundaries. Groundwater generally flows 

from topographic highs in the uplands toward upland stream 

channels and the stratified glacial deposits in valleys and lowlands. The water table mimics topography; surface-water and 

groundwater divides typically coincide, especially in uplands. 

Groundwater levels and flow directions, especially in the sand 

and gravel deposits, are strongly influenced by the locations 

and elevations of streams, ponds, and wetlands that are the 

discharge points for the groundwater-flow system (Winter and 

others, 1998; Randall, 2001).

The geologic materials in the Pawcatuck River Basin 

differ substantially with respect to their hydraulic properties, 

which determine rates of groundwater flow and well yield. The 

primary porosity of crystalline bedrock is extremely low, and 

groundwater in bedrock flows through fractures and joints. 

Thus, bedrock permeabilitites are low except in some highly 

fractured zones, and supply wells in bedrock are usually small 

and low-yielding. The permeability of glacial till also is low, 

and it varies with till composition, structure, and process of 

deposition. Because of its low permeability and small saturated thickness, till is not a major aquifer, but it is an important component of the groundwater-flow system in the basin 

because it affects recharge to and discharge from underlying 

aquifers (Dickerman and others, 1997). Stratified glacial 

deposits with relatively high permeability and hydraulic conductivity form the major aquifers in the basin.

Detailed descriptions of the groundwater-flow systems 

in the Pawcatuck River Basin and its subbasins are in Allen 

and others (1963, 1966); Gonthier and others (1974); Johnston 

and Dickerman (1985); Dickerman and Ozbilgin (1985); 

Dickerman and others (1990); Dickerman and Bell (1993); 

Dickerman and others (1997); Friesz (2004); and Masterson 

and others (2007). These studies provide hydrogeologic 

information for the major glacial deposits in the basin and 

include geologic cross sections, water-table maps, saturatedthickness maps, transmissivity maps, aquifer tests, and other 

information. The present study did not develop new watertable, saturated-thickness, or transmissivity maps for the 

model areas or the entire basin.

Recharge

Groundwater recharge is the amount of precipitation 

that infiltrates through the land surface and reaches the water 

table. Generally, groundwater in the study area is recharged 

from October through April when evapotranspiration is low. 

From May through September, evapotranspiration generally 

exceeds precipitation, resulting in little to no groundwater 

recharge. During droughts, aquifers might not receive recharge 

for an extended time period. Annual recharge rates can vary 

substantially with annual precipitation. Groundwater recharge 

in the Pawcatuck River Basin was estimated from streamflow 

data by using the computer programs RECESS and RORA 

(Rutledge, 1998). These programs use the recession-curvedisplacement method to estimate groundwater recharge 

for each peak in streamflow during the period of record. 

Streamflow records from 1942 through 2004 (63 years) for 

three streamflow-gaging stations—the Pawcatuck River at 

Wood River Junction (01117500), Wood River at Hope Valley 

(01118000), and Pawcatuck River at Westerly (01118500)—

were used (fig. 1–3). The estimated average annual recharge 

rates of 25.9, 27.6, and 25.8 in/yr for the three stations, 

respectively, were similar. The recharge rates estimated from 

streamflow also were similar to recharge rates estimated as 

about 25 to 28 in/yr for sand and gravel deposits in southern 

Rhode Island in other studies (Dickerman and others, 1997; 

Barlow and Dickerman, 2001; Granato and others, 2003; 

Friesz, 2004; Zarriello and Bent, 2004; Masterson and others, 

2007). Therefore, on average, about 50 percent of the mean 

annual precipitation in the Pawcatuck River Basin (51.82 in/yr 

measured at the URI station) is lost through either evaporation 

or plant transpiration. These estimated RECESS and RORA 

recharge rates are basin-wide estimates that averaged different 

recharge rates for areas of stratified glacial deposits, glacial 

till, wetlands and ponds, and various land uses. 

Water Levels

Groundwater levels in the Pawcatuck River Basin are 

affected by many factors, including the amount of recharge; 

surficial geology in the area of the well; lithology at the well, 

particularly around the well screen; location of the well on a 

hilltop, hill slope, or in a valley; thickness of the unsaturated 

zone; and proximity of the well to surface-water bodies (such 

as a stream, pond, or wetland). Currently (2009), the USGS 

measures water levels in 19 wells (17 in Rhode Island and 2 in 

Connecticut) in the basin (table 1–2 and fig. 1–4). Four of the 

19 wells have continuous recorders and the remaining 15 wells 

are measured monthly between the 20th day and the last day 

of each month. During the study period (2000–04), water levels in 4 of the 15 monthly wells also were measured continuously from fall (October and November) 2002 through the end 

of 2004. Seven of the 8 continuously monitored wells during 

the study period were completed in sand and gravel deposits, 

and the other well (NSN–77) was completed in till deposits 

(fig. 1–5). Water levels in the monthly measured wells in sand 
16 Part 1. Water Resources in the Pawcatuck River Basin

Yawgoo

Pond

01118352

01118340

01118055

01118008

01118022

01117860

01117840

01117780

01117740

01117700

01117480

01117336

01118400

01118500

01118360

01118010

01117800

01117600

01117500

01117471

01117468

01118009

01118373

01118380

01118375

01118300

01118350

01118255

01118365

01117720

01117760

01117900

01117950

01118000

01118006

01117465

01117350

01117421

01117424

01117430

01117472

01117450

01117420

01117390

01117400 01117385

01117380

01117375

01117370

01117360

0111736701117365

011173545

01117354

01118355

01117750

01117355

01117368

01117410

01117500

01117450

01117472

Basin 

State 

EXPLANATION

Subbasin 

Continuous record

Partial record

Discontinued record

Boundaries Streamflow-gaging station, and number 

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Beaver River

River

River

Wood

River

Chickasheen Brook

Pawcatuck

Pawcatuck

Tomaquag

Brook

Queen

River

Wood River

Ashaway

River

Shunock River

Meadow

Brook

Usquepaug River

Chipuxet River

Watchaug Chapman Pond

Pond

Worden

Pond

Breakheart

Pond

Tucker

Pasquiset Pond

 Pond

RHODE ISLAND

CONNECTICUT

Base from U.S. Geological Survey digital data 

North American Datum of 1983

Rhode Island state plane projection, 1:24,000

Cedar

 Swamp

Brook

71o37' 30" 71o 71 30' o 71 45' o

52' 30"

42o

37'30"

41o

22'30"

41o

30'30"

Figure 1–3. Location of U.S. Geological Survey continuous streamflow-gaging stations and partial-record stations in the 

Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut.
Groundwater 17

Table 1–2. U.S. Geological Survey observation wells in which groundwater levels were measured in the Pawcatuck River Basin, 

southwestern Rhode Island and southeastern Connecticut, 2000–2004.

[Locations shown in figure 1–4. USGS, U.S. Geological Survey; no., number; NGVD 29, National Geodetic Vertical Datum of 1929]

USGS station no. Station name

Latitude 

(decimal 

degree)

Longitude 

(decimal 

degree)

Approximate 

altitude 

(feet above 

NGVD 29)

Aquifer material Measurement frequency

Rhode Island

412154071462901 WEW–522 41.3651 -71.7742 45 Sand and gravel Monthly 2000–fall 2002 and 

continuous fall 2002–2004.

412424071423601 CHW–587 41.4068 -71.7095 90 Till Monthly.

412434071422401 CHW–586 41.4095 -71.7062 125 Till Monthly.

412718071415201 RIW–785 41.4551 -71.6973 85 Sand and gravel Monthly 2000–fall 2002 and 

continuous fall 2002–2004.

412844071422802 RIW–600 41.4790 -71.7073 100 Sand and gravel Continuous.

412918071321001 SNW–6 41.4884 -71.5356 112 Sand and gravel Continuous.

412932071374302 RIW–417 41.4923 -71.6281 116 Sand and gravel Continuous.

412935071355701 SNW–1198 41.4932 -71.5987 112 Sand and gravel Monthly.

413126071455501 HOW–67 41.5240 -71.7648 335 Till Monthly.

413135071314201 EXW–278 41.5265 -71.5278 231 Till Monthly.

413252071323601 EXW–554 41.5479 -71.5428 155 Sand and gravel Monthly 2000–fall 2002 and 

continuous fall 2002–2004.

413358071433801 EXW–475 41.5662 -71.7267 143 Sand and gravel Continuous.

413400071363101 EXW–238 41.5668 -71.6081 334 Till Monthly.

413423071431901 EXW–6 41.5732 -71.7215 133 Sand and gravel Monthly.

413505071452801 EXW–158 41.5848 -71.7573 315 Till Monthly.

413645071332901 WGW–206 41.6126 -71.5576 374 Till Monthly.

413907071465001 WGW–181 41.6520 -71.7801 380 Sand and gravel Monthly.

Connecticut

412931071514201 NSN–77 41.4920 -71.8612 520 Till Monthly 2000–fall 2002 and 

continuous fall 2002–2004.

412746071510601 NSN–78 41.4964 -71.8506 325 Till Monthly.
18 Part 1. Water Resources in the Pawcatuck River Basin

71°50' 71°40' 71°30'

41°40'

41°30'

41°20' B L O C K I S L A N D

S O U N D

L O N G I S L A N D S O U N D

A T L A N T I C O C E A N

Hopkinton

Voluntown

Sterling Coventry

West Greenwich

East Greenwich

Richmond

South

Kingstown

North

Kingstown

Charlestown

Westerly Stonington

North Stonington

Exeter

Plainfield

Griswold Preston

Beaver River

Wood

River

Chickasheen Brook

Pawcatuck

Queen River

Wood River

Tomaquag Brook

Ashaway River

Shunock

River

Meadow

Brook

Usquepaug River

Chipuxet River

River

River

Pawcatuck

Meadow

Watchaug Pond Chapman Pond

Worden

Pond

Breakheart Pond

Tucker

Pond Pasquiset

 Pond

Cedar

 Swamp

Brook

NSN-78

NSN-77

EXW-6

EXW-238

WGW 181

WGW-206

EXW-158

EXW-475 EXW-554

EXW-278 HOW-67

SNW-1198

RIW-417

SNW-6

RIW-600

RIW-785

CHW-586

CHW-587

WEW-522 RHODE ISLAND

CONNECTICUT

EXW-554

EXPLANATION

Observation well 

and identifier

State 

Boundaries

Town 

Basin 

Base from U.S. Geological Survey digital data 

North American Datum of 1983

Rhode Island state plane projection, 1:24,000

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Figure 1–4. Location of U.S. Geological Survey groundwater observation wells in the Pawcatuck River Basin, southwestern 

Rhode Island and southeastern Connecticut.
Surface Water 19

and gravel deposits typically fluctuated only a few feet to 

7 ft (Socolow and others, 2001, 2002, 2003, 2004, 2005). 

Water levels in the continuously monitored wells in sand and 

gravel deposits fluctuated up to about 5 ft (fig. 1–5). Wells 

measured monthly in till deposits have more variable waterlevel fluctuations from a few feet up to 23 ft (Socolow and 

others, 2001, 2002, 2003, 2004, 2005). The water levels in the 

continuously monitored till-deposit well (NSN–77) fluctuated 

up to about 11 ft (fig. 1–5).

Surface Water

The Pawcatuck River originates at the outflow of Worden 

Pond in the southeastern part of the basin (fig. I–1). The drainage area at the outflow point is about 25.8 mi2

 and comprises 

the drainage areas of the Chipuxet River, which is the main 

tributary into Worden Pond, a few small brooks that flow 

into the pond, and the pond itself. The Pawcatuck River is a 

low-slope river, dropping only about 90 ft in altitude from its 

origin at Worden Pond to its outlet to the Atlantic Ocean; the 

entire drainage area of the river is 303 mi2. It generally flows 

east to west along the southern part of the basin. Several tributaries that flow from north to south include (from east to west) 

the Chipuxet River, Chickasheen Brook, Usquepaug-Queen 

River, Beaver River, Meadow Brook, Wood River, Tomaquag 

Brook, Ashaway River, and Shunock River (fig. I–1). Of the 

eight dams on the main stem of the Pawcatuck River, seven 

are less than or equal to 10 ft in height. The only dam higher 

than 10 ft is the Horseshoe Falls Dam in the village of 

Shannock in Richmond, R.I. Within the entire Pawcatuck 

River Basin in Rhode Island are about 100 dams on tributaries 

and the main stem of the river.

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

38

JAN.

2000

MAY.

2000

SEP.

2000

JAN.

2001

MAY.

2001

SEP.

2001

JAN.

2002

MAY.

2002

SEP.

2002

JAN.

2003

MAY.

2003

SEP.

2003

JAN.

2004

MAY.

2004

SEP.

2004

MONTH AND YEAR

GROUND-W

ATER LEVEL, IN FEET BELOW LAND SURFACE

WEW-522 (SG)

RIW-785 (SG)

RIW-600 (SG)

SNW-6 (SG)

RIW-417 (SG)

EXW-554 (SG)

EXW-475 (SG)

NSN-77 (T)

EXPLANATION

Figure 1–5. Groundwater levels in selected U.S. Geological Survey observation wells in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04 (SG, sand and gravel; T, till).
20 Part 1. Water Resources in the Pawcatuck River Basin

Streamflow

Streamflow data were collected at 18 of the 19 continuous streamflow-gaging stations and 38 of the 40 partial-record 

stations in the Pawcatuck River Basin during the study period 

(tables 1–3 and 1–4, fig. 1–3). One continuous streamflowgaging station and 2 partial-record stations were not operated 

and measured, respectively, during the study period. The 

streamflow data at 18 of the 19 continuous streamflow-gaging 

stations were needed to provide data for calibration of the 

precipitation-runoff and groundwater models and for the 

evaluation of their performance. The streamflow data from 35 

of the 40 partial-record stations provided supplemental information for evaluating the performance of the models across 

the respective areal extents of the models.

Three of the continuous streamflow-gaging stations 

in the Pawcatuck River Basin (table 1–3 and fig. 1–3) have 

been operated since the early 1940s as part of the USGS 

surface-water network for Rhode Island. The Pawcatuck 

River at Wood River Junction (01117500), Pawcatuck River 

at Westerly (01118500), and Wood River at Hope Valley 

(01118000) stations have been operated since from October 

1940, November 1940, and March 1941, respectively. Mean 

annual streamflow from the Pawcatuck River Basin was about 

577 ft3/s (1.96 ft3/s/mi2) from 1942 through 2004 on the basis 

of records for the Pawcatuck River at Westerly (01118500) 

station (table 1–5).

During the study period (2000–04), mean annual streamflow was about 571 ft3

/s (1.94 ft3/s/mi2) at the Pawcatuck 

River at Westerly (table 1–5). Streamflow across the basin was 

fairly uniform; streamflow at the Pawcatuck River at Wood 

River Junction (01117500) and Wood River at Hope Valley 

(01118000) stations averaged about 1.98 and 2.07 ft3/s/mi2, 

respectively, during the 2000–04 study period and about 1.96 

and 2.15 ft3/s/mi2 from 1942 through 2004. During the study 

period of 2000–04, average annual streamflow was close to the 

long-term average annual during the period 1942–2004. During the individual calendar years 2000, 2001, and 2004, annual 

streamflow was close to normal, but in calendar year 2002, the 

annual streamflow was about 30 to 32 percent below normal, 

and in calendar year 2003, annual streamflow was about 23 

to 26 percent above normal. From September 2001 through 

October 2002, monthly streamflows at all three stations were 

below the long-term (1942–2004) mean monthly streamflow, 

except for May and June 2002 (fig. 1–6A–C). This period of 

below-normal streamflow nearly coincided with the 13-month 

dry spell from August 2001 through 2002 in which precipitation was 17.3 in. below normal (fig. 1–2A). 

Continuous Stations

Nine of the 19 continuous streamflow-gaging stations are 

part of the USGS surface-water network for Rhode Island and 

Connecticut (long-term stations) and were operated during 

the entire study period (table 1–3 and fig. 1–3). Nine of the 

remaining 10 stations (short-term stations) were installed and 

operated for at least 2 years of the study period, generally 

during the period 2002–04. Streamflow data for these stations 

are published annually in the Massachusetts-Rhode Island 

Data Report (Socolow and others, 2001, 2002, 2003, 2004, 

2005) and all streamflow data are available online at 

http://waterdata.usgs.gov/ri/nwis/sw or http://waterdata.

usgs.gov/ct/nwis/sw through the USGS National Water 

Information System (NWIS). At the nine short-term stations 

operated for part of the study period, streamflow records (daily 

mean discharge) were estimated by use of record-extension 

techniques for the periods when the stations were not 

operating. Streamflow records for each of the nine short-term 

stations were related to concurrent daily mean streamflows 

for at least one nearby index station. The list of index stations 

used and the correlation coefficients describing the relations 

between the short-term stations and the index stations are 

listed in table 1–6. 
Surface Water 21

Table 1–3. U.S. Geological Survey continuous streamflow-gaging stations operated in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.[USGS station no.: Locations shown in figure 1–3. USGS, U.S. Geological Survey; no., number; mi2, square miles; IDLOCN, identification attribute in the Watershed Data Management (WDM) database for the Hydrologic Simulation Program-FORTRAN model; RCHRES, river or reservoir reach for the Hydrologic Simulation Program-FORTRAN model; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; St., Street; p, present; ft, feet; mi, miles; --, not applicable]

USGS 

station no. Station name

Latitude 

(decimal 

degree)

Longitude 

(decimal 

degree)

Drainage 

area 

(mi2)

Period of record Remarks Station IDLOCN Stream reach No. (RCHRES) Sub- basin IDLOCN

011173545 Queen River, 1,400 ft upstream 

Williams Reynolds Rd. at Exeter, RI

41.5658 -71.5475 3.69 2000–05 Occasional upstream withdrawals for irrigation at 

golf course from April through November.

QRPB 2 QUEN2

01117350 Chipuxet River, State Rte. 138 at 

West Kingston, RI

41.4823 -71.5512 9.99 1958–60, 1973–p Occasional upstream withdrawals for irrigation at 

turf farms from May through October and by supply wells year round.

CRWK 32 CHIP2

01117370 Queen River, Liberty Rd. at Liberty, RI 41.5390 -71.5687 19.1 1999–p QRLY 9 QUEN401117410 Usquepaug River, State Rte. 138 at 

Usquepaug, RI 

41.5026 -71.6078 32.8 1999–2005 Occasional upstream withdrawals for irrigation at 

turf farms from May through October.

URUS 19 QUEN6

01117420 Usquepaug River, State Rte. 2 near 

Usquepaug, RI

41.4768 -71.6048 36.1 1974–p Occasional upstream withdrawals for irrigation at 

turf farms and golf courses from April through November.

USQU 20 QUEN7

01117424 Chickasheen Brook, Liberty Lane at 

West Kingston, RI

41.4804 -71.5734 4.82 2002–05 Occasional upstream withdrawals for irrigation at 

turf farms from May through October.

CBLL 36 CHIC2

01117430 Pawcatuck River, State Rte. 2 at 

Kenyon, RI

41.4462 -71.6212 72.7 1958–60, 2002–05, 

2007–p

PRBC 37 PAWC2

01117468 Beaver River, State Rte. 138 near 

Usquepaug, RI

41.4926 -71.6281 8.87 1974–p BRUS 42 BEAV2

01117471 Beaver River, Shannock Hill Rd. near 

Shannock, RI

41.4643 -71.6278 11.2 2002–05 Occasional upstream withdrawals for irrigation at 

turf farms from May through October.

BRSH 43 BEAV3

01117472 Beaver River, 1 mi downstream 

Shannock Hill Rd. at Kenyon, RI

41.4523 -71.6281 11.7 1975–78 Not operated during the study period. Occasional 

upstream withdrawals for irrigation at turf farms from May through October.

-- -- --

01117500 Pawcatuck River, State Rte. 91 at 

Wood River Junction, RI

41.4451 -71.6809 100 1940–p Occasional upstream withdrawals for irrigation at 

turf farms from May through October.

PRWR 46 PAWC3

01117600 Meadow Brook, Pine Hill Rd. near 

Carolina, RI

41.4665 -71.6901 5.53 1965–74, 2002–05 MBCA 47 MEAD1

01117800 Wood River, State Rte. 165 near 

Arcadia, RI

41.5740 -71.7206 35.2 1964–81, 1983–p WRAR 53 WOOD2

01118000 Wood River, 0.2 mi upstream Interstate 95 

at Hope Valley, RI

41.4982 -71.7165 72.4 1941–p WRHV 63 WOOD5

01118010 Pawcatuck River, Burdickville Rd. at 

Burdickville, RI

41.4162 -71.7290 205 2002–05 PRBV 50 PAWC4

01118300 Pendleton Hill Brook, Grindstone Hill Rd. 

near Clarks Falls, CT

41.4748 -71.8342 4.02 1959–p PHBK 74 PEND1

01118360 Ashaway River, Laurel St. at Ashaway, RI 41.4234 -71.7917 28.6 2002–05 ASHA 77 ASHA101118400 Shunock River, State Rte. 49 near 

North Stonington, CT

41.4101 -71.8448 17.2 2002–05 SRNS 83 SHUN2

01118500 Pawcatuck River, 500 ft downstream 

Arch St. at Westerly, RI

41.3837 -71.8331 295 1940–p Upstream withdrawals by supply wells year 

round.

PRWS 84 PAWC9
22 Part 1. Water Resources in the Pawcatuck River Basin Table 1–4. U.S. Geological Survey partial-record stations measured in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued [USGS station no.: Locations shown in figure 1–3. USGS, U.S. Geological Survey; no., number; mi2, square miles; IDLOCN, identification attribute in the Watershed Data Management (WDM) database for the Hydrologic Simulation Program-FORTRAN model; RCHRES, river or reservoir reach for the Hydrologic Simulation Program-FORTRAN model; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable] USGS station no. Station name Latitude (decimal degree) Longitude (decimal degree) Drainage area (mi2) Period of record Number of mea- sure- ments Remarks Station IDLOCN Stream reach No. (RCHRES) Sub- basin IDLOCN 01117336 Chipuxet River, Yawgoo Valley Rd. near West Kingston, RI 41.5176 -71.5253 6.34 1959–60, 1972, 1980, 2002–04 19 Occasional upstream withdrawals for irrigation at turf farms from May through October. CRWK-p 31 CHIP1 01117354 Queen River, State Rte. 102 at Exeter, RI 41.5787 -71.5431 2.8 1993, 2000–04 29 QECC-p 1 QUEN1 01117355 Queen River, William Reynolds Rd. near Exeter, RI 41.5626 -71.5478 3.69 1959–60, 1988–93, 1999–2002 63 Occasional upstream withdrawals for irri- gation at golf course from April through November. QREX-p 3 QUEN3 01117360 Fisherville Brook, Liberty Church Rd. near Exeter, RI 41.5643 -71.5645 8.14 1959–60, 1988–93, 2000–04 65 FBEX-p 5 FISH2 01117365 Queens Fort Brook, Slocumville Rd. near Exeter, RI 41.5482 -71.5331 3.22 1988–91, 1996–97 46 Not measured during study period and not used in study. -- -- -- 01117367 Queens Fort Brook, intersection of Dawley Rd. and School Lands Rd. 

near Liberty, RI

41.5465 -71.5526 4.09 2000–03 29 Occasional upstream withdrawals for 

irrigation at turf farms from May through October.

QFBK-p 8 QUFB2

01117368 Queen River, Dawley Rd. near 

Liberty, RI

41.5487 -71.5603 18.4 1993, 2000–02 23 Not used in study. -- -- --

01117375 Unnamed Tributary to Queen River, 

Mail Rd. at Liberty, RI

41.5390 -71.5795 0.82 1988–91, 1999–2004 48 UTLY-p 11 TRIB1

01117380 Locke Brook, Mail Rd. at Liberty, RI 41.5373 -71.5876 4.37 1959–60, 1988–91, 

1993, 2000–04

61 LBLY-p 14 LOCK1

01117385 Rake Factory Brook, Glen Rock Rd. 

at Glen Rock, RI

41.5190 -71.5990 0.25 1988–91, 1999–2004 51 RFBK-p 16 RAKE

01117390 Glen Rock Brook, Glen Rock Rd. at 

Glen Rock, RI

41.5165 -71.6059 2.83 1988–91, 1993, 

2000–04

59 GRGR-p 18 GLEN1

01117400 Sherman Brook, Glen Rock Rd. at 

Glen Rock, RI

41.5179 -71.6045 1.04 1966–74, 1989–91, 

1993, 2000–04

58 Occasional upstream withdrawals for 

irrigation at vegetable farms from May through October.

SBGR-p 17 SHER1

01117421 Chickasheen Brook, State Rte. 2 at 

West Kingston, RI

41.4984 -71.5648 3.26 2002–04 14 Occasional upstream withdrawals for 

irrigation at turf farms from May through October.

CBLL-p 35 CHIC1

01117450 Pasquiset Brook, State Rte. 2 at 

Kenyon, RI

41.4440 -71.6270 6.32 1966–67, 1974, 

1976, 1980, 2002–04

20 PBWY-p 44 PASQ1

01117465 Beaver River, Hillsdale Rd. near 

Wyoming, RI

41.5257 -71.6392 5.53 1966–67, 1974, 

1976, 1991, 2002–04

22 BRWY-p 41 BEAV1

01117480 Taney Brook, Shannock Hill Rd. at 

Carolina, RI

41.4607 -71.6478 1.67 1966–67, 2002–04 18 TBCA-p 45 TANE1
Surface Water 23

Table 1–4. U.S. Geological Survey partial-record stations measured in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued[USGS station no.: Locations shown in figure 1–3. USGS, U.S. Geological Survey; no., number; mi2, square miles; IDLOCN, identification attribute in the Watershed Data Management (WDM) database for the Hydrologic Simulation Program-FORTRAN model; RCHRES, river or reservoir reach for the Hydrologic Simulation Program-FORTRAN model; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable]

USGS 

station 

no.

Station name

Latitude 

(decimal 

degree)

Longitude 

(decimal 

degree)

Drainage 

area 

(mi2)

Period of record

Number 

of measurements Remarks Station IDLOCN Stream reach No. (RCHRES) Sub- basin IDLOCN

01117700 Cedar Swamp Brook, Kings Factory 

Rd. at Wood River Junction, RI

41.4270 -71.6951 5.1 1966–67, 2002–04 18 CSBK-p 49 CEDA1

01117720 Wood River, Falls River Rd. at 

Escoheag, RI

41.6126 -71.7603 11.4 1966–67, 1991, 

2002–04

20 WREH-p 51 WOOD1

01117740 Kelley Brook, Falls River Rd. at 

Escoheag, RI

41.6123 -71.7531 4.2 1966–67, 1991, 

2002–04

20 KBEH-p 52 KELL1

01117750 Factory Brook, Plain Meetinghouse 

Rd. near Summit, RI

41.6332 -71.7223 1.31 1966, 2002–04 15 Not used in study. -- -- --

01117760 Flat River, Plain Rd. near Arcadia, RI 41.5957 -71.7201 8.38 1978, 1982, 2002–04 15 FRAR-p 54 FLAT101117780 Breakheart Brook, Frosty Hollow Rd. 

near Arcadia, RI

41.5879 -71.7095 6.68 1966–67, 1979, 

1982, 1991–92, 2002–04

22 BBAR-p 55 BREA1

01117840 Parris Brook, Blitzkrieg Trail near 

Arcadia, RI

41.5651 -71.7259 7.18 1966–67, 1979, 

1991, 2002–04

22 PBAR-p 56 PARR1

01117860 Roaring Brook, Arcadia Rd. at 

Arcadia, RI

41.5584 -71.6851 5.01 1966–67, 1991, 

2002–04

21 RBAR-p 58 ROAR1

01117900 Brushy Brook, Sawmill Rd. near 

Hope Valley, RI

41.5287 -71.7365 3.71 1966–67, 1977, 

1979, 1991, 2002–04

21 BBHV-p 60 BRUS1

01117950 Moscow Brook, Sawmill Rd. near 

Hope Valley, RI

41.5273 -71.7362 6.37 1966–67, 1977, 

1979, 1991, 2002–04

22 MBHV-p 61 MOSC1

01118006 Canonchet Brook, Woodville-Alton 

Rd. near Hope Valley, RI

41.4776 -71.7292 5.89 1977, 1979–80, 

1991, 2002–04

19 Occasional upstream withdrawals for irrigation at golf course from April through 

November.

CBHV-p 64 CANO1

01118008 Wood River Tributary, WoodvilleAlton Rd. at Alton, RI 41.4376 -71.7231 2.05 1977, 2002–04 15 CHAL-p 66 COON101118009 Wood River, State Rte. 91 near 

Alton, RI

41.4362 -71.7209 85.7 1977, 1979–81, 

1991, 2002–04

18 Occasional upstream withdrawals for 

irrigation at turf farms from May through October.

WRAL-p 65 WOOD6

01118022 Perry-Healy Brook, Klondike Rd. 

near Bradford, RI

41.3745 -71.7159 2.36 2002–04 13 PHBB-p 67 PERR1

01118055 Tomaquag Brook, State Rte. 216 at 

Bradford, RI

41.4111 -71.7642 6.67 1991, 2002–04 16 TBBF-p 70 TOMA1

01118255 Green Fall River, Putker Rd. at 

Laurel Glen, CT

41.4723 -71.8162 7.42 1963–67, 2002–04 24 GRLG-p 73 GREE1

01118340 Wyassup Brook, State Rte. 216 at 

Clarks Falls, CT

41.4547 -71.8267 11.5 2002–04 14 WBCF-p 75 WYAS1
24 Part 1. Water Resources in the Pawcatuck River Basin Table 1

–4. U.S. Geological Survey partial-record stations measured in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued

[USGS station no.: Locations shown in figure 1–3. USGS, U.S. Geological Survey; no., number; mi2, square miles; IDLOCN, identification attribute in the Watershed Data Management (WDM) database for the Hydrologic Simulation Program-FORTRAN model; RCHRES, river or reservoir reach for the Hydrologic Simulation Program-FORTRAN model; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable]

USGS 

station 

no.

Station name

Latitude 

(decimal 

degree)

Longitude 

(decimal 

degree)

Drainage 

area 

(mi2

)

Period of record

Number 

of measurements Remarks Station IDLOCN Stream reach No. (RCHRES) Sub- basin IDLOCN

01118350 Green Fall River, State Rte. 216 at 

Clarks Falls, CT

41.4548 -71.8140 19.8 1961–73 25 Not measured during study period and not 

used in study.

-- -- --

01118352 Glade Brook, Pine Woods Rd. near 

Laurel Glen, CT

41.4682 -71.8081 1.92 1965–67, 2002–04 18 GBLG-p 76 GLAD1

01118355 Parmenter Brook, Extension 184 near 

Hopkinton, RI

41.4476 -71.7903 2.54 1966–67, 2002–04 17 PBHK-p 78 PARM1

01118365 Lewis Pond Outlet, Boom Bridge Rd. 

near Potter Hill, RI

41.4204 -71.8217 1.59 1966–67, 2002–04 18 LPPH-p 79 LWPD1

01118373 Shunock River, Main St. at 

North Stonington, CT

41.4409 -71.8823 7.79 1965, 2002–04 15 SRPH-p 81 SHUN1

01118375 Assekonk Brook, Jeremy Hill Rd. 

near North Stonington, CT

41.4387 -71.9104 1.63 1963–65, 2002–04 26 -- -- --

01118380 Assekonk Brook, State Rte. 2 at 

North Stonington, CT

41.4387 -71.8842 4.54 1963–65, 2002–04 22 ABNS-p 82 ASSE1
Surface Water 25

Table 1–5. Streamflow and estimated baseflow for selected U.S. Geological Survey streamflow-gaging stations in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04 and 1942–2004.[Locations shown in figure 1–5. ft3/s, cubic feet per second; RI, Rhode Island]

Streamflow

(ft3/s)

Estimated baseflow

(ft3/s)1 Estimated percentage of baseflow to streamflow

Period

Pawcatuck River 

at Wood River 

Junction, RI 

(01117500)

Wood River at 

Hope Valley, RI 

(01118000)

Pawcatuck 

River at 

Westerly, RI 

(01118500)

Pawcatuck River 

at Wood River 

Junction, RI 

(01117500)

Wood River at 

Hope Valley, RI 

(01118000)

Pawcatuck 

River at 

Westerly, RI 

(01118500)

Pawcatuck River 

at Wood River 

Junction, RI 

(01117500)

Wood River at 

Hope Valley, RI 

(01118000)

Pawcatuck 

River at 

Westerly, RI 

(01118500)

2000 201 145 570 176 122 481 87.5 84.1 84.42001 209 165 595 184 137 506 88.4 83.0 85.02002 135 103 397 118 87 330 87.3 84.6 83.12003 247 185 721 221 157 615 89.5 84.5 85.32004 199 151 573 176 129 488 88.6 85.2 85.3

Study period

Mean 2000–04 198 150 571 175 126 484 88.4 84.2 84.8

Long-term period

Mean 1942–2004 196 156 577 176 132 501 89.9 85.0 86.8Minimum 1942–2004 99 85 296 89 74 258 89.4 86.8 87.4Maximum 1942–2004 322 254 914 287 204 789 89.3 80.3 86.3

1 Baseflow estimated using the computer program PART (Rutledge, 1998).
26 Part 1. Water Resources in the Pawcatuck River Basin

C 01118500 Pawcatuck River at Westerly, RI

10

100

1,000

10,000

JAN.

2000

APR.

2000

JUL.

2000

OCT.

2000

JAN.

2001

APR.

2001

JUL.

2001

OCT.

2001

JAN.

2002

APR.

2002

JUL.

2002

OCT.

2002

JAN.

2003

APR.

2003

JUL.

2003

OCT.

2003

JAN.

2004

APR.

2004

JUL.

2004

OCT.

2004

Jan. 2000–Dec. 2004

1971–2000

1942–2004

M

O

N

THLY

MEA

N STREA

MFLO

W, IN CU

BIC FEET PER SECO

ND

MONTH AND YEAR

A 01117500 Pawcatuck River at Wood River Junction, RI

10

100

1,000

10,000

Jan. 2000–Dec. 2004

1971–2000

1942–2004

100

1,000

10,000

B 01118000 Wood River at Hope Valley, RI

10

Jan. 2000–Dec. 2004

1971–2000

1942–2004

Figure 1–6. Mean monthly 

streamflows for selected longterm U.S. Geological Survey 

streamflow-gaging stations in 

the Pawcatuck River Basin, 

southwestern Rhode Island 

and southeastern Connecticut.
Surface Water 27

Table 1–6. Relation of U.S. Geological Survey short-term streamflow-gaging stations and partial-record stations to nearby long-term index streamflow-gaging stations used to estimate streamflow records in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued[USGS station no.: Locations shown in figure 1–3 and described in table 1–3 for streamflow-gaging stations and in table 1–4 for partial-record stations. USGS, U.S. Geological Survey; no., number; ft, feet; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable]

USGS 

station no. Station name

Number of 

measurements 

used in 

relation 

to index 

gages

Correlation coefficient

Long-term index streamflow-gaging stations1

Queen River 

at Liberty Rd. 

at Liberty, RI 

(01117370)

Usquepaug 

River near 

Usquepaug, RI 

(01117420)

Beaver 

River near 

Usquepaug, RI 

(01117468)

Pawcatuck 

River at 

Wood 

River Junction, RI 

(01117500)

Wood 

River near 

Arcadia, RI 

(01117800)

Wood 

River at 

Hope 

Valley, RI 

(01118000)

Pendleton 

Hill Brook 

near Clarks 

Falls, CT 

(01118300)

Remarks

Short-term streamflow-gaging stations2

011173545 Queen River 1,400 ft upstream 

Williams Reynolds Rd. at Exeter, RI

-- -- -- -- -- -- -- -- No analysis was done.

01117410 Usquepaug River at Rte. 138 at 

Usquepaug, RI 

1,605 -- 0.99 -- -- -- -- --

01117424 Chickasheen Brook at West Kingston, RI 731 0.92 -- 0.94 -- -- -- --01117430 Pawcatuck River at Rte. 2 at Kenyon, RI 1,752 -- -- -- 0.98 -- 0.92 --01117471 Beaver River at Shannock Hill Rd. near 

Shannock, RI 

731 -- -- 0.98 -- -- -- --

01117600 Meadow Brook near Carolina, RI 791 0.93 -- 0.96 -- -- -- 0.9101118010 Pawcatuck River at Burdickville, RI 787 -- -- -- 0.99 0.97 0.98 --01118360 Ashaway River at Ashaway, RI 777 -- -- 0.91 -- 0.94 -- --01118400 Shunock River at North Stonington, CT 731 -- -- 0.92 -- 0.95 -- --

Partial-record stations

01117336 Chipuxet River, Yawgoo Valley Rd. near 

West Kingston, RI

15 -- -- 0.90 -- 0.88 -- 0.88

01117354 Queen River, State Rte. 102 at Exeter, RI 27 -- -- 0.96 -- 0.96 -- 0.8601117355 Queen River, William Reynolds Rd. near 

Exeter, RI

-- -- -- -- -- -- -- -- No analysis was done.

01117360 Fisherville Brook, Liberty Church Rd. near 

Exeter, RI

61 -- -- 0.98 -- 0.95 -- 0.91

01117365 Queens Fort Brook, Slocumville Rd. near 

Exeter, RI

12 -- -- 0.94 -- 0.94 -- 0.97 Correlation was based on arithmetic 

relation (streamflows were not transformed to logarithmic units).

01117367 Queens Fort Brook, intersection of 

Dawley Rd. and School Lands Rd. near Liberty, RI

27 -- -- 0.95 -- 0.91 -- 0.87

01117368 Queen River, Dawley Rd. near Liberty, RI -- -- -- -- -- -- -- -- No analysis was done.01117375 Unnamed Tributary to Queen River, 

Mail Rd. at Liberty, RI

40 -- -- 0.97 -- 0.95 -- 0.96 Correlation was based on arithmetic 

relation (streamflows were not transformed to logarithmic units).
28 Part 1. Water Resources in the Pawcatuck River Basin Table 1–6. Relation of U.S. Geological Survey short-term streamflow-gaging stations and partial-record stations to nearby long-term index streamflow-gaging stations used to estimate streamflow records in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued [USGS station no.: Locations shown in figure 1–3 and described in table 1–3 for streamflow-gaging stations and in table 1–4 for partial-record stations. USGS, U.S. Geological Survey; no., number; ft, feet; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable] USGS station no. Station name Number of measure- ments used in relation to index gages Correlation coefficient Long-term index streamflow-gaging stations1 Queen River at Liberty Rd. at Liberty, RI (01117370) Usque- paug River near Usque- paug, RI (01117420) Beaver River near Usque- paug, RI (01117468) Pawcatuck River at Wood River Junc- tion, RI (01117500) Wood River near Arcadia, RI (01117800) Wood River at Hope Valley, RI (01118000) Pendleton Hill Brook near Clarks Falls, CT (01118300) Remarks Partial-record stations—Continued 01117380 Locke Brook, Mail Rd. at Liberty, RI 56 -- -- 0.97 -- 0.97 -- 0.93 01117385 Rake Factory Brook, Glen Rock Rd. at Glen Rock, RI 47 -- -- 0.92 -- 0.95 -- 0.97 Correlation was based on arithmetic relation (streamflows were not transformed to logarithmic units). 01117390 Glen Rock Brook, Glen Rock Rd. at Glen Rock, RI 58 -- -- 0.96 -- 0.94 -- 0.95 01117400 Sherman Brook, Glen Rock Rd. at Glen Rock, RI 53 -- -- 0.94 -- 0.93 -- 0.95

01117421 Chickasheen Brook, State Rte. 2 at 

West Kingston, RI

12 -- -- 0.91 -- 0.89 -- 0.84

01117450 Pasquiset Brook, State Rte. 2 at 

Kenyon, RI

15 -- -- 0.92 -- 0.90 -- 0.89

01117465 Beaver River, Hillsdale Rd. near 

Wyoming, RI

16 -- -- 0.94 -- 0.96 -- 0.97

01117480 Taney Brook, Shannock Hill Rd. at 

Carolina, RI

14 -- -- 0.94 -- 0.92 -- 0.90

01117700 Cedar Swamp Brook, Kings Factory Rd. at 

Wood River Junction, RI

13 -- -- 0.95 -- 0.93 -- 0.94

01117720 Wood River, Falls River Rd. at 

Escoheag, RI

15 -- -- 0.87 -- 0.95 -- 0.98

01117740 Kelley Brook, Falls River Rd. at 

Escoheag, RI

15 -- -- 0.88 -- 0.95 -- 0.94

01117750 Factory Brook, Plain Meetinghouse Rd. 

near Summit, RI

14 -- -- 0.92 -- 0.93 -- 0.96

01117760 Flat River, Plain Rd. near Arcadia, RI 14 -- -- 0.97 -- 0.97 -- 0.9001117780 Breakheart Brook, Frosty Hollow Rd. near 

Arcadia, RI

17 -- -- 0.95 -- 0.97 -- 0.93

01117840 Parris Brook, Blitzkrieg Trail near 

Arcadia, RI

17 -- -- 0.92 -- 0.96 -- 0.98

01117860 Roaring Brook, Arcadia Rd. at Arcadia, RI 16 -- -- 0.92 -- 0.94 -- 0.9101117900 Brushy Brook, Sawmill Rd. near 

Hope Valley, RI

17 -- -- 0.93 -- 0.97 -- 0.98
Surface Water 29

Table 1–6. Relation of U.S. Geological Survey short-term streamflow-gaging stations and partial-record stations to nearby long-term index streamflow-gaging stations used to estimate streamflow records in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.—Continued[USGS station no.: Locations shown in figure 1–3 and described in table 1–3 for streamflow-gaging stations and in table 1–4 for partial-record stations. USGS, U.S. Geological Survey; no., number; ft, feet; RI, Rhode Island; CT, Connecticut; Rte., Route; Rd., Road; --, not applicable]

USGS 

station no. Station name

Number of 

measurements 

used in 

relation 

to index 

gages

Correlation coefficient

Long-term index streamflow-gaging stations1

Queen River 

at Liberty Rd. 

at Liberty, RI 

(01117370)

Usquepaug 

River near 

Usquepaug, RI 

(01117420)

Beaver 

River near 

Usquepaug, RI 

(01117468)

Pawcatuck 

River at 

Wood 

River Junction, RI 

(01117500)

Wood 

River near 

Arcadia, RI 

(01117800)

Wood 

River at 

Hope 

Valley, RI 

(01118000)

Pendleton 

Hill Brook 

near Clarks 

Falls, CT 

(01118300)

Remarks

Partial-record stations—Continued

01117950 Moscow Brook, Sawmill Rd. near 

Hope Valley, RI

18 -- -- 0.92 -- 0.96 -- 0.96

01118006 Canonchet Brook, Woodville-Alton Rd. 

near Hope Valley, RI

19 -- -- 0.99 -- 0.97 -- 0.91

01118008 Wood River Tributary, Woodville-Alton 

Rd. at Alton, RI

15 -- -- 0.99 -- 0.98 -- 0.91

01118009 Wood River, State Rte. 91 near Alton, RI 18 -- -- -- 0.96 0.96 0.99 --01118022 Perry-Healy Brook, Klondike Rd. near 

Bradford, RI

12 -- -- 0.98 -- 0.96 -- 0.96

01118055 Tomaquag Brook, State Rte. 216 at 

Bradford, RI

16 -- -- 0.97 -- 0.96 -- 0.94

01118255 Green Fall River, Putker Rd. at 

Laurel Glen, CT

11 -- -- 0.96 -- 0.97 -- 0.99

01118340 Wyassup Brook, State Rte. 216 at 

Clarks Falls, CT

14 -- -- 0.97 -- 0.97 -- 0.96

01118350 Green Fall River, State Rte. 216 at 

Clarks Falls, CT

-- -- -- -- -- -- -- -- No analysis was done.

01118352 Glade Brook, Pine Woods Rd. near 

Laurel Glen, CT

14 -- -- 0.96 -- 0.96 -- 0.98 Correlation was based on arithmetic 

relation (streamflows were not transformed to logarithmic units).

01118355 Parmenter Brook, Extension 184 near 

Hopkinton, RI

14 -- -- 0.95 -- 0.95 -- 0.99

01118365 Lewis Pond Outlet, Boom Bridge Rd. near 

Potter Hill, RI

14 -- -- 0.96 -- 0.96 -- 0.92

01118373 Shunock River, Main St. at North 

Stonington, CT

14 -- -- 0.97 -- 0.97 -- 0.93

01118375 Assekonk Brook, Jeremy Hill Rd. near 

North Stonington, CT

13 -- -- 0.95 -- 0.99 -- 0.99 Correlation was based on arithmetic 

relation (streamflows were not transformed to logarithmic units).

01118380 Assekonk Brook, State Rte. 2 at North 

Stonington, CT

14 -- -- 0.92 -- 0.93 -- 0.99

1 Long-term index streamflow-gaging stations are generally naturally flowing sites that are part of the long-term network of streamflow-gaging stations in Rhode Island and Connecticut.2 Short-term streamflow-gaging stations were installed and operated during part of the study.
30 Part 1. Water Resources in the Pawcatuck River Basin

Partial-Record Stations

To augment the data from the continuous streamflowgaging stations, miscellaneous streamflow data were collected 

at 40 partial-record stations (table 1–4 and fig. 1–3), mostly 

located on tributary streams to the major rivers within the 

Pawcatuck River Basin. Periodic streamflow measurements 

made at these stations, generally during base-flow conditions 

(about 2 to 5 days after a precipitation event), were mainly 

correlated with concurrent daily mean discharges representing natural-flow conditions at three nearby long-term index 

stations—Beaver River at Usquepaug (01117468), Wood 

River near Arcadia (01117800), and Pendleton Hill Brook 

near Clarks Falls, Conn. (01118300)—to obtain a continuous 

discharge record (table 1–6). Streamflows at each partialrecord station were measured 11 to 61 times during this study 

and in past studies. Streamflow measurements at partial-record 

stations are published in the Annual Water Resources Data 

Reports for Massachusetts and Rhode Island (Socolow and 

others, 2001, 2002, 2003, 2004, 2005) for the water years 

(October 1 to September 30) in which the measurements were 

made. The number of correlated streamflow measurements 

depended on the availability of concurrent streamflow records 

at the index station (table 1–6). For example, the Beaver River 

at Usquepaug (0117468) station did not begin operation until 

December 1974, so streamflow measurements made prior 

to 1974 at partial-record stations were not included in this 

analysis. Correlations were generally made for a wide range of 

discharges (low flows through at least medium flows) at each 

partial-record station.

A mathematical procedure developed by Hirsch (1982) 

known as Maintenance of Variance Extension (MOVE.1) 

was applied to logarithms of the measured streamflow at each 

partial-record station and the same-day daily mean discharge 

at the index stations. Scatter plots indicated which relations 

between the log-transformed measured streamflow at each 

partial-record station and the same-day log-transformed daily 

mean discharges at each of the index stations were linear. Estimated daily mean discharges for water years 2000–04 were 

computed for each partial-record station from the streamflow 

records for the selected index stations (based on a linear relation, a high correlation coefficient, and general drainage-area 

size) (table 1–6) by the MOVE.1 procedure. The final daily 

mean discharge at each partial-record station for water years 

2000–04 was then computed by a weighted average of the 

mean daily discharges for each index station. Each indexstation discharge was weighted on the basis of the mean 

square error between the computed discharge and the measured discharge at the partial-record station.

The retransformation of the computed logs of discharges 

into arithmetic units for each equation can create a bias. 

This bias was evaluated by Duan’s smearing method (Duan, 

1983); however, a bias-correction factor was not applied to the 

retransformed log discharges because the overall bias among 

index stations was generally small (less than a few percent). 

The accuracy of this record-extension technique is 

determined by the goodness-of-fit between the instantaneous 

discharge measurements at the partial-record station and 

the same-day daily mean discharge records at continuous 

streamflow-gaging stations, the accuracy of the instantaneous 

discharge measurements, the accuracy of the continuousdischarge record, and the range of the flows measured at 

the partial-record station. Because each of these factors can 

introduce error, the extrapolated records for the partial-record 

stations are considered estimates. Because most measurements 

at the partial-record stations were made during low to moderate flows, the estimates of daily discharge during high flows 

could be poor.

Baseflow

Baseflow (groundwater discharge) is that part of streamflow that discharges from an aquifer to the stream channel 

upstream from the measuring point. Groundwater discharges 

to streams and is typically the principal component of streamflow 3 to 7 days after a peak in streamflow caused by periods 

of precipitation or snowmelt. During most years, groundwater levels and baseflow decrease during the growing season. 

Annual baseflow can vary significantly with annual precipitation and long-term variations in groundwater storage.

Baseflow was estimated from streamflow by the computer program PART (Rutledge, 1998), which uses an automated hydrograph-separation technique. Mean annual baseflow from the Pawcatuck River Basin is estimated to be about 

501 ft3/s (about 87 percent of mean annual streamflow) on 

the basis of analysis of streamflow records for the Pawcatuck 

River at Westerly (01118500) station from 1942 through 2004 

(table 1–5). Baseflow also was estimated for the Pawcatuck 

River at Wood River Junction (01117500) and the Wood River 

at Hope Valley (01118000) stations. The long-term mean 

annual baseflows for these two stations were about 176 and 

132 ft3/s (about 90 and 85 percent of the respective mean 

annual streamflows) for 1942–2004. During the study period 

(2000–04), mean annual baseflows for the stations Pawcatuck 

River at Wood River Junction, Wood River at Hope Valley, 

and Pawcatuck River at Westerly were 175, 126, and 484 ft3/s 

(about 88, 84, and 85 percent of the respective mean annual 

streamflows during 2000–04); these values are fairly close to 

the long-term means for 1942–2004. During 2002, however, 

baseflows were about 32 to 34 percent lower than the longterm means, and in 2003, baseflows were 19 to 26 percent 

higher than the long-term means.
Water Withdrawals 31

Ponds and Wetlands

Numerous ponds throughout the Pawcatuck River Basin 

make up about 2.7 percent of the area in the basin (fig. I–3). 

During the period 2003–04, water levels were measured 1 to 

2 times per month at 22 of the larger ponds across the basin 

(table 1–7 and fig. 1–7). Water-level measurements were made 

during 2000–02 for one pond (Glen Rock Reservoir). Water 

levels for ponds in the basin generally fluctuated about 0.3 to 

2.1 ft during the 1.5 years of miscellaneous measurements. 

Several of the ponds were affected by water withdrawals for 

irrigation and other regulations, specifically Yawgoo Mill 

Pond, Hundred Acre Pond, Thirty Acre Pond, Barber Pond, 

and Glen Rock Reservoir (table 1–7 and fig. 1–7). Water levels 

in these ponds could be affected by these regulations, especially during the summer (June through August) and early fall 

(September and October). Additionally, several unidentified 

ponds may be affected by lowering of water levels in the fall 

to kill weeds over the winter and then refilling of the pond in 

the spring. 

Wetlands make up a significant portion of the Pawcatuck 

River Basin. Nonforested wetlands occupy about 2.3 percent 

and forested wetlands about 12.5 percent of the basin. 

Wetlands are mainly in the southern part of the basin along 

the Pawcatuck River, with extensive areas upstream of the 

Pawcatuck River at Kenyon (station 01117430) to Worden 

Pond; around the north side of Worden Pond at the mouths of 

the Chipuxet River, Chickasheen Brook, and the Usquepaug 

River; and around Cedar Swamp Brook (south side of the 

Pawcatuck River in Charlestown), Watchaug Pond, and 

Chapman Pond (figs. I–3 and 1–7). 

Water Withdrawals

Municipal groundwater withdrawals and irrigation were 

the primary water uses in the basin during the study period 

(2000–04). Municipal withdrawals averaged 7.18 Mgal/d 

during the study period. Irrigation in the basin is mainly for 

turf farms (4.40 mi2) and golf courses (0.76 mi2); irrigation for 

vegetable farms (0.41 mi2) and tree nurseries (0.005 mi2) was 

minor. Estimated agricultural (turf, vegetables, and tree nurseries) and golf course irrigation withdrawals totaled 8.44 and 

0.88 Mgal/d, respectively, on an average day of irrigation in 

the basin during the study period. Unlike domestic water use, 

irrigation can vary widely from day to day, season to season, 

and among farms. Irrigation water use may be estimated from 

climatic factors, but estimation may also be complicated by 

limited data from turf farms and golf courses. It was estimated 

that agricultural irrigation withdrawals occurred on average 

about 68 days per year from May 1 through October 30, and 

golf course irrigation occurred on average about 140 days per 

year from April 16 through November 15 during the study 

period. If measured withdrawal data were available, they were 

incorporated into the HSPF and MODFLOW models for calibration. Irrigation withdrawals were estimated for unmetered 

sites and unmetered periods from 1960 through 2004. The 

irrigation data were estimated by using logistic regression to 

predict the probability of irrigation on a specific day, an average 24-hr rate of irrigation, and an average rate per unit area 

on the basis of data collected during 2000–04 (see below).

Municipal Withdrawals

During the study period, five major water suppliers in 

the basin operated a total of 16 wells (fig. 1–8). The five water 

suppliers’ total average withdrawals for 2000–04 were about 

7.18 Mgal/d (table 1–8). Wild and Nimiroski (2004) reported 

a total average withdrawal rate for these same suppliers of 

about 6.77 Mgal/d for 1995–99; this value is about 6 percent 

lower than the value during the study period. During the study 

period, municipal withdrawals did not vary much from year to 

year (table 1–8), but during all years, withdrawals were generally greater during May through September and especially 

during July and August (fig. 1–9). These higher withdrawals 

during the summer months may be a result of outdoor water 

use and increases in summer population for communities 

near the ocean. This pattern of greater municipal withdrawals during the summer months than during the rest of the year 

was also documented in Rhode Island by Granato and Barlow 

(2005, p. 32). The only major supplier whose summer withdrawals decreased was the WSCB Well #1; this well supplied 

a school, and the majority of students were not at the school 

during most of May through August.

Nonmunicipal Withdrawals

Thirteen minor nonmunicipal suppliers were reported in 

the basin in 1999 by Wild and Nimiroski (2004, p. 10, 22); 

these wells withdrew an average of about 0.1 Mgal/d and 

serviced only about 60 to 200 people each. These minor nonmunicipal suppliers withdraw water from wells registered with 

the Rhode Island Department of Environmental Management 

(RIDEM) as serving 25 or more people for a minimum of 60 

days. Wild and Nimiroski (2004) estimated that self-supply 

withdrawals for domestic, commercial, industrial, and agricultural use averaged about 2.3, 0.2, 0.5, and 1.4 Mgal/d during 

1995–99 in the Pawcatuck River Basin.
32 Part 1. Water Resources in the Pawcatuck River Basin Table 1

–7. U.S. Geological Survey pond-level stations in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.

[USGS station no.: Locations shown in figure 1–7. USGS, U.S. Geological Survey; no., number; NAVD 88, North American Vertical Datum 1988; RI, Rhode Island; CT, Connecticut; URI, University of Rhode Island]

USGS station no. Station name

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Period of record

Number 

of measurements

Water level (feet above NAVD 88)

Remarks Average Me- dian Mini- mum Maxi- mum Range

412254071414701 Watchaug Pond, Burlingame State Park, 

Charlestown, RI

41.3817 -71.6965 04/2003–09/2004 27 36.84 36.83 36.31 37.41 1.10

412258071471901 Chapman Pond, at Moose Lodge, 

State Route 91, Westerly, RI

41.3828 -71.7887 04/2003–09/2004 26 30.24 30.20 29.75 31.07 1.32

412520071325009 Tucker Pond, off a gravel road, 

South Kingstown, RI

41.4221 -71.5472 04/2003–09/2004 26 92.97 92.96 92.58 93.29 0.71

412537071374401 Pasquiset Pond, Old Coach Road, 

Charlestown, RI

41.4269 -71.6290 04/2003–09/2004 26 87.39 87.38 87.14 87.64 0.50

412548071340401 Worden Pond, Wordens Pond Road, 

South Kingstown, RI

41.4299 -71.5677 04/2003–09/2004 26 89.38 89.52 88.08 89.98 1.90

412616071432101 Alton Pond, State Route 91, 

Hopkinton, RI

41.4378 -71.7225 04/2003–09/2004 30 48.55 48.49 48.27 48.96 0.69

412617071412701 Meadow Brook Pond, State Route 91, 

Richmond, RI

41.4382 -71.6909 04/2003–09/2004 28 53.57 53.59 52.94 53.82 0.88

412718071493001 Spaulding Pond, State Route 216, 

North Stonington, CT

41.4550 -71.8250 04/2003–09/2004 26 80.19 80.13 79.91 80.67 0.76

412817071333101 Larkin Pond, at Camp Hoffman, 

South Kingstown, RI

41.4713 -71.5586 04/2003–09/2004 26 93.41 93.37 93.14 93.73 0.59

412928071323901 Thirty Acre Pond, Thirty Acre Pond 

Road, South Kingstown, RI

41.4912 -71.5441 04/2003–09/2004 26 94.83 94.91 93.61 95.70 2.09 Occasional withdrawals for irrigation at 

turf farms from May through October and manipulation of pond levels.

412943071323801 Hundred Acre Pond, East Hundred Acre 

Pond Road, South Kingstown, RI

41.4952 -71.5438 04/2003–09/2004 26 95.82 95.90 94.88 96.48 1.60 Occasional withdrawals for irrigation at 

turf farms from May through October and manipulation of pond levels.

413010071425901 Pond on Wood River, Mechanic Street, 

Hopkinton, RI

41.5028 -71.7163 04/2003–09/2004 27 76.10 76.06 75.72 76.58 0.86

413015071334801 Barber Pond, Barber Pond Road, South 

Kingstown, RI

41.5042 -71.5634 04/2003–09/2004 26 114.79 114.73 114.28 115.37 1.09 Occasional withdrawals for irrigation at 

turf farms from May through October.

413016071363001 Glen Rock Reservoir, Kenyon Corn 

Meal Company, South Kingstown, RI

41.5045 -71.6085 03/2000–12/2002 

and 05/2003–09/2004

83 111.35 111.30 110.67 112.64 1.97 Occasional withdrawals for irrigation at 

turf farms from May through October.

413030071425701 Locustville Pond, Locustville Rd., 

Hopkinton, RI

41.5084 -71.7159 04/2003–09/2004 27 93.74 93.70 93.56 93.98 0.42

413056071421001 Wyoming Pond, Arcadia Road, 

Richmond, RI

41.5154 -71.7027 04/2003–09/2004 27 96.83 96.80 96.61 97.10 0.49

413057071342301 Yawgoo Pond, at Camp Miskiania, 

Exeter, RI

41.5159 -71.5732 04/2003–09/2004 26 118.88 118.90 118.31 119.63 1.32

413130071310901 Yawgoo Mill Pond, at dock near pump 

house, Exeter, RI

41.5249 -71.5193 05/2003–09/2004 30 119.84 119.90 118.77 120.08 1.31 Occasional withdrawals for irrigation at 

turf farms from May through October.

413224071311901 The Reservoir, Canonicus Camp, 

Exeter, RI

41.5401 -71.5221 05/2003–09/2004 26 133.86 133.85 133.67 134.23 0.56

413544071421201 Breakheart Pond, Plain Road, Exeter, RI 41.5955 -71.7034 05/2003–09/2004 27 234.27 234.28 233.91 234.47 0.56413703071431301 Eisenhower Lake, on URI dock, 

West Greenwich, RI

41.6174 -71.7202 04/2003–09/2004 26 206.50 206.51 206.40 206.69 0.29

413735071465601 Hazard Pond, Hazard Road, 

West Greenwich, RI

41.6265 -71.7821 04/2003–09/2004 25 326.56 326.57 325.80 327.29 1.49
Water Withdrawals 33

Cedar

 Swamp

Brook

71°50' 71°40' 71°30'

41°40'

41°30'

41°20' B L O C K I S L A N D

S O U N D

L O N G I S L A N D S O U N D

A T L A N T I C O C E A N

Hopkinton

Griswold Voluntown

Sterling Coventry

West Greenwich

East Greenwich

Richmond

South

Kingstown

North

Kingstown

Charlestown

Westerly

Stonington

North Stonington

Exeter

Plainfield

Preston

Beaver River

River

River

Wood

River

Chickasheen Brook

Pawcatuck

Pawcatuck

Queen River

Wood River

Tomaquag Brook

Ashaway River

Shunock

River

Meadow Brook

Usquepaug River

Chipuxet River

RHODE ISLAND

CONNECTICUT

Spaulding Pond

Hazard Pond

Eisenhower Lake

Breakheart

Pond

The Reservoir

Yawgoo Mill Pond

Wyoming Pond Yawgoo Pond 

Locustville Pond

Glen Rock 

Reservoir

Pond on Wood River Barber Pond

Thirty Acre Pond

Hundred Acre Pond

Larkin Pond

Meadow Brook Pond

Alton Pond

Worden Pasquiset Pond Pond Tucker

Pond

Chapman Pond

Watchaug 

Pond 

Hazard Pond

EXPLANATION

Pond-level station

 and name

State 

Town 

Basin 

Boundaries

Base from U.S. Geological Survey digital data 

North American Datum of 1983

Rhode Island state plane projection, 1:24,000

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Figure 1–7. Location of U.S. Geological Survey pond-level stations in the Pawcatuck River Basin, southwestern Rhode 

Island and southeastern Connecticut.
34 Part 1. Water Resources in the Pawcatuck River Basin

Cedar

 Swamp

Brook

71°50' 71°40' 71°30'

41°40'

41°30'

41°20' B L O C K I S L A N D

S O U N D

L O N G I S L A N D S O U N D

A T L A N T I C O C E A N

Hopkinton

Voluntown

Sterling Coventry

West Greenwich

East Greenwich

Richmond

South

Kingstown

North

Kingstown

Charlestown

Westerly

Stonington

North Stonington

Exeter

Griswold

Plainfield

Preston

Beaver River

River

River

Wood

River

Chickasheen Brook

Pawcatuck

Pawcatuck

Queen River

Wood River

Tomaquag Brook

Ashaway River

Shunock

River

Meadow Brook

Usquepaug River

Chipuxet River

RHODE ISLAND

CONNECTICUT

WSP-2

WSW-1

WSP-2

WSP-3

WSP-1

WSP-6

WSP-5

WSP-4

WSCB-1

WSCA-1

WSCA-2

WSCB-1

WSCA-1

WSCA-2

WSM-6

WSM-1

WSM-2

WSM-5

WSM-4

WSM-3

Wastewater-treatment 

 facility (WWTF) discharge

Westerly WWTF 

discharge

Stonington WWTF 

discharge 

South Kingstown 

Regional WWTF 

discharge

Narragansett-Scarborough 

WWTF discharge

EXPLANATION

State 

Town 

Basin 

Water-supply well 

 and identifier

Boundaries

Base from U.S. Geological Survey digital data 

North American Datum of 1983

Rhode Island state plane projection, 1:24,000

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Figure 1–8. Location of major water-supply wells and wastewater treatment facilities in the Pawcatuck River Basin, 

southwestern Rhode Island and southeastern Connecticut.
Water Withdrawals 35

Table 1–8. Water withdrawals for major water suppliers in the Pawcatuck River Basin, southwestern Rhode Island and 

southeastern Connecticut, 2000–04.

[Locations shown in figure 1–8. Mgal/d, million gallons per day; Jan., January; Sept., September; Dec., December]

Well

Average withdrawals

(Mgal/d)

Average withdrawals

(Mgal/d)

2000 2001 2002 2003 2004 Jan. 2000–Sept. 2004 Jan. 2000–Dec. 2004 

(study period)

WSCA

Well #1 0.168 0.149 0.092 0.191 0.095 0.139 0.139

Well #2 0.219 0.252 0.312 0.198 0.192 0.241 0.235

Subtotal 0.387 0.401 0.404 0.389 0.286 0.380 0.374

WSCB

Well #1 0.457 0.432 0.404 0.410 0.428 0.424 0.426

WSM

Well #1 0.044 0.085 0.058 0.056 0.060 0.064 0.061

Well #2 0.344 0.353 0.347 0.346 0.377 0.358 0.354

Well #3 0.057 0.096 0.067 0.065 0.069 0.075 0.071

Well #4 0.450 0.458 0.421 0.431 0.507 0.451 0.453

Well #5 0.759 0.830 0.886 0.969 0.966 0.882 0.882

Well #6 1.084 1.063 1.082 1.191 1.167 1.121 1.118

Subtotal 2.739 2.885 2.860 3.059 3.147 2.950 2.938

WSW

Well #1 0.052 0.056 0.063 0.057 0.053 0.057 0.056

WSP

Well #1 0.807 0.882 0.764 0.788 0.629 0.781 0.774

Well #2 1.168 1.300 1.456 1.219 1.379 1.310 1.304

Well #3 0.433 0.502 0.475 0.520 0.460 0.479 0.478

Well #4 0.198 0.138 0.217 0.185 0.212 0.192 0.190

Well #5 0.316 0.369 0.285 0.225 0.273 0.299 0.293

Well #6 0.346 0.427 0.365 0.303 0.309 0.356 0.350

Subtotal 3.267 3.617 3.561 3.240 3.263 3.417 3.390

TOTAL 6.902 7.391 7.292 7.156 7.177 7.228 7.184
36 Part 1. Water Resources in the Pawcatuck River Basin

B Monthly percentage water withdrawal patterns for major suppliers in the Pawcatuck River Basin, southwestern Rhode Island 

and southeastern Connecticut, 2000–04.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

JAN.

2000

APR.

2000

JUL.

2000

OCT.

2000

JAN.

2001

APR.

2001

JUL.

2001

OCT.

2001

JAN.

2002

APR.

2002

JUL.

2002

OCT.

2002

JAN.

2003

APR.

2003

JUL.

2003

OCT.

2003

JAN.

2004

APR.

2004

JUL.

2004

OCT.

2004

MONTH AND YEAR

MONTHLY PERCENTAGE OF TOTAL WATER

WITHDRA

WALS FROM 2000–04 BY SUPPLIER

WSCA

WSW

WSCB

WSM

WSP

A Monthly rate water withdrawal patterns for major suppliers in the Pawcatuck River Basin, southwestern Rhode Island 

and southeastern Connecticut, 2000–04.

1

10

100

1,000

TOTAL WATER WITHDRA

WALS RATE, IN MILLION GALLONS

WSCA

WSW

WSCB

WSM

WSP

Figure 1–9. Monthly water withdrawal patterns for major suppliers in the Pawcatuck River Basin, southwestern 

Rhode Island and southeastern Connecticut, 2000–04.
Water Withdrawals 37

Agricultural Withdrawals

The Pawcatuck River Basin is estimated from GIS data 

layers (1995) and aerial photographs (2002) to include about 

4.82 mi2 (3,082 acres) of irrigated agricultural land (turf farms, 

vegetable farms, and tree nurseries). Turf farms are estimated 

to account for about 4.40 mi2 (2,815 acres) of the irrigated 

agricultural land in the basin. Withdrawals from streams or 

instream ponds are the sources of irrigation water for about 

3.31 mi2 (2,115 acres) of the turf farms; about 1.09 mi2

(700 acres) are irrigated from wells or ponds not directly connected to streams. Vegetable farms were estimated to account 

for about 0.41 mi2 (264 acres) of the irrigated agricultural 

land in the basin. Nearly all the vegetable farms, about 

0.35 mi2 (227 acres), were irrigated from water withdrawals on 

streams or instream ponds, and only about 0.06 mi2 (37 acres) 

was irrigated from wells or ponds not directly connected to 

streams. Tree nurseries were estimated to account for about 

0.005 mi2 (3.0 acres) of the irrigated agricultural land, and all 

were irrigated from instream ponds.

During each year, an estimated 40 to 50 percent of the 

turf-farm area is kept fallow (Vicky Drew, U.S. Department 

of Agriculture, Natural Resources Conservation Service, 

oral commun., 2005). Most turf farms irrigate the remaining 

active areas of turf. Irrigation-withdrawal data were collected 

by direct measurement at 11 turf-farm sites, at 2 of which 

groundwater was withdrawn and at 9 of which surface water 

was withdrawn from the basin (table 1–9). At two turf farms, 

irrigation-withdrawal data from two measured withdrawal 

points had to be combined into one data set, because the 

areas irrigated by withdrawal at the two points could not be 

determined individually. As a result of the two combined sites, 

data were available only for 9 separate turf-farm sites in the 

basin. Data were collected for either three or five irrigation 

seasons (May through October) during 2000–04. These 

withdrawals were measured continuously and totaled hourly 

by an impeller flowmeter installed between the pump and the 

irrigation nozzles. 

The turf farms where irrigation data were collected 

covered a total area of about 2.08 mi2 (1,329 acres) or about 

47 percent of the turf-farm land in the basin. The total area of 

turf farms where irrigation data were collected includes the 

areas that were fallow during part of the study, because the 

fallow areas were changed during the year and from year to 

year. When they were irrigated, the metered turf farms applied 

an average of 3,399 gal/d/acre (table 1–9). On an average 

day, withdrawal rates at the turf farms tended to increase 

from about 0800 hours and continue to about 1300 hours, 

after which withdrawal rates decreased steadily through the 

remainder of the day (fig. 1–10). A wide range of withdrawal 

rates per unit area was measured among the turf farms over the 

average 24-hour period. Site AUQ8A was generally operated 

differently than the other turf farms; withdrawals increased 

during the early evening hours, remained steady through the 

early morning hours, and then decreased during the day 

(fig. 1–10). This unusual pattern may be a result of the fact 

that an electric pump was used to withdraw groundwater at 

this site, probably because electric pumps are quieter than the 

diesel engine pumps used at most other sites. Operation of 

the electric pump during the nighttime also may be preferred 

because of lower electricity rates. The nine turf-farm sites 

averaged about 31 days of irrigation during the May-throughOctober irrigation seasons for 2000–04, but the number of 

days of irrigation varied among sites and years from 0 days 

(one farm in 2003) to 75 days (one farm in 2001) per year. The 

number of days of irrigation in any season was likely dependent on climatic factors, such as precipitation and temperature, 

and on other factors, such as soil moisture, grass type, and 

planned harvest time. During some years, turf farms left fields 

fallow; during summer 2003, when conditions were wetter, a 

few turf farms did not irrigate at all.

Golf-Course Withdrawals

Eleven golf courses are currently (2009 ) in the 

Pawcatuck River Basin, of which 10 are completely in the 

basin and 1 is partially in the basin. The total in-basin area of 

greens and fairways for the 11 golf courses was about 

0.89 mi2 (572 acres). All 11 golf courses irrigate their greens, 

and 9 of the 11 golf courses irrigate their fairways, for a total 

of 0.76 mi2 (487 acres) of irrigated area. Withdrawals for 

irrigation at the golf courses come from surface-water (streams 

or instream ponds) or groundwater sources; groundwater 

withdrawals may be directly from wells or from ponds that 

have been filled with water from wells.

The two golf courses in the basin where irrigation 

data were collected covered a total area of about 0.19 mi2

(124 acres), or about 25 percent of the irrigated golf-course 

area in the basin. Irrigation data were collected at one course 

that used direct stream withdrawals (GUQ2A and GUQ2B) 

and at another course that filled a pond from groundwater 

withdrawals (GMB2A) (table 1–9). Groundwater-withdrawal 

data were also collected at a third golf course (GP2A), of 

which only a few fairways and green were in the basin. 

Average withdrawals at the three metered golf courses were 

1,756 gal/d/acre during the irrigation period of April 16 

through November 15 for the 4 years of the study (table 1–9). 

Water-withdrawal rates per unit area for all three golf courses 

were similar. Although the withdrawal rates per unit area for 

these three metered golf courses were similar, they may not 

represent the general withdrawal rates or patterns at the other 

golf courses in the basin. 

On an average day, metered withdrawal rates at the two 

golf courses dependent on groundwater sources (GMB2A and 

GP2A) were generally at their highest from about 2200 hours 

until about 0600 hours and at their lowest from about 0700 

hours through about 2100 hours (fig. 1–11). The golf course 

dependent on surface-water sources (GUQ2A and GUQ2B—

two metered withdrawal sites at the same course) had a 

distinctly different average daily water-withdrawal rate than 

the two courses dependent on groundwater sources; the highest withdrawal rates occurred from 0400 through 0900 hours. 
38 Part 1. Water Resources in the Pawcatuck River Basin Table 1–9. Summary of irrigation withdrawals for metered turf farms and golf courses in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04. [USGS, U.S. Geological Survey; gal, gallons; SW, surface water; GW, groundwater; yr, year; ac, acre; d, day; ft, feet; °, degrees; ′, minutes; ′′, seconds] Turf farms USGS station name With- drawal type Irrigated area (acres) Pe- riod of record Remarks Number of days of measured water with- drawals during period of record Average num- ber of days of measured wa- ter withdrawals per year Total measured withdrawals during period of record (gal) Average measured withdrawals (gal/yr) Average measured withdrawals per unit area (gal/yr/ac) Average measured withdrawals (gal/d) Average measured withdrawals per unit area (gal/d/ac) AC1A and AC1B SW 504.80 2002–04 Two withdrawal points metered, but withdrawals combined into one system because individual irrigated acres were unknown. 129 43 87,515,611 29,171,870 57,789 678,416 1,344 AUQ10A SW 83.52 2000–04 165 33 48,541,025 9,708,205 116,238 294,362 3,525 AUQ10B SW 48.31 2000–04 81 16 7,438,463 1,487,693 30,795 91,833 1,901 AUQ10C SW 47.50 2000–04 73 15 10,885,400 2,177,080 45,833 149,115 3,139 AP1A and AW2A SW 351.86 2000–04 Several days of missing data in 2001 and 2002. Two withdrawal points metered, but with- drawals combined into one system because individual irrigated acres were unknown. 318 64 230,073,537 46,014,707 130,776 725,191 2,061 AUQ8A GW 95.22 2002–04 112 37 31,091,912 10,363,971 108,842 272,736 2,864

AC5A GW 61.89 2002–04 102 34 27,410,730 9,136,910 147,631 268,733 4,342AB4A SW 33.82 2002–04 48 16 9,825,879 3,275,293 96,845 204,706 6,053AW1A SW 101.80 2002–04 Several days of missing data in 2004. 57 19 31,121,926 10,373,975 101,905 545,999 5,364

All metered 

turf farms Total 1,328.72 Average -- 31 -- 13,523,300 92,962 359,010 3,399

Golf courses

GUQ2A and 

GUQ2B

SW 62.30 2000–04 Two withdrawal points metered, but withdrawals 

combined into one system because individual irrigated acres were unknown.

374 75 39,912,585 7,982,517 128,130 106,718 1,713

GP2A GW 64.19 2002–04 Only partially (a few fairways and greens) in the 

basin.

389 130 42,310,384 14,103,461 219,714 108,740 1,694

GMB2A GW 62.02 2002–04 Several days of missing data in 2002 and 2004. 397 132 45,364,524 15,121,508 243,817 115,358 1,860

All metered 

golf courses Total 188.51 Average -- 105 -- 12,402,495 197,220 110,272 1,756

GUQ1A SW 71.50 2000–04 Estimated withdrawals based on streamflow 

fluctuations at USGS station 011173545 about 3,300 ft downstream of withdrawal point. No streamflow data recorded during irrigation period of April through mid-July 2002.

323 65 28,592,045 5,718,409 79,978 88,520 1,238
Water Withdrawals 39

The different patterns for the groundwater and surface-water 

withdrawals may be a result of the fact that the electric pumps 

at the groundwater-withdrawal sites were outfitted with timers. 

Nighttime pumping may be preferred for the groundwater 

withdrawal golf courses because of lower electricity rates. The 

surface-water site is dependent on diesel-engine pumps that 

can be loud and have to be turned on manually. Golf courses 

were irrigated 62 days (one course in 2004) to 208 days (one 

course in 2002) per year during 2000–04.

At a fourth golf course (GUQ1A), surface-water withdrawals were estimated by linear interpolation between abrupt 

drops and rises in the observed streamflow hydrograph for a 

USGS station about 3,300 ft downstream of the withdrawal 

point. The difference between the interpolated and observed 

hydrograph during these periods was assumed to represent 

withdrawals. The estimated average water withdrawal at this 

site, 1,238 gallons per day per acre (gal/d/acre), was about 

29 percent lower than the average water withdrawal measured at the other three golf courses (1,756 gal/d/acre) during 

either 2000–04 or 2002–04 (table 1–9). This difference in 

average water withdrawals per day per acre may be a result 

of the estimation method used, which did not include time 

periods during which abrupt drops and rises in the hydrograph 

were not noticeable. During these periods, which may have 

coincided with the irrigation of greens only, withdrawals 

may have been low enough not to have noticeably affected 

the hydrograph at the downstream USGS streamflow-gaging 

station. Additionally, from April 16 through July 16, 2002, the 

downstream USGS streamflow-gaging station was not operating. During this period, water withdrawals likely would have 

occurred, because at the other surface-water-withdrawal golf 

course (GUQ2A and GUQ2B—two metered withdrawal sites 

at the same course), 39 days of withdrawals were measured 

from May 7 through July 16, 2002. Even though water withdrawals could be estimated for the period of April 16 through 

July 16, 2002 at site GUQ1A, withdrawals were estimated for 

323 other days during 2000–04 (table 1–9). This number of 

days of surface-water withdrawals compared well with the 337 

days of measured surface-water withdrawals at golf course site 

GUQ2A and GUQ2B for the same time period excluding April 

16 through July 16, 2002. 

Groundwater-withdrawal data measured at golf-course 

site GP2A averaged a little more than 247,000 gallons per 

year per acre (gal/yr/acre) for the period 1994–2004 

(table 1–10). This 11-year average water-withdrawal rate 

compares reasonably well to the average groundwaterwithdrawal rates per year per acre for the two groundwater 

sites (GMB2A and GP2A) during 2002–04 (table 1–9). During 

the 11 years, yearly groundwater withdrawals rates per year 

per acre ranged from 39 percent less to 36 percent more than 

the 11-year-average withdrawal rate. This wide range of yearly 

groundwater withdrawals likely is the result of climatic factors 

during each of the years (table 1–10).

0

100

200

300

400

500

600

700

HOUR

IRRIG

ATION-WITHDRAWAL RATE, IN G

ALLONS PER DAY PER ACRE

AC1A and AC1B (surface water)

AC5A (ground water)

AUQ8A (ground water)

AB4A (surface water)

AUQ10A (surface water)

AUQ10B (surface water)

AUQ10C (surface water)

AW1A (surface water)

AP1A and AW2A (surface water)

Average

Metered turf farms

000001000200030004000500060007000800090010001100120013001400150016001700180019002000210022002300

Figure 1–10. Average 24-hour irrigation-withdrawal rates for metered turf farms in the Pawcatuck River Basin, 

southwestern Rhode Island and southeastern Connecticut, 2000–04.
40 Part 1. Water Resources in the Pawcatuck River Basin

0

100

200

300

400

500

600

700

HOUR

IRRIGATION-WITHDRAWAL RATE, IN GALLONS PER DAY PER ACRE

GMB2A (ground water)

Metered golf courses

GP2A (ground water)

GUQ2A and GUQ2B (surface water)

Average (GMB2A AND GP2A) (ground water)

000001000200030004000500060007000800090010001100120013001400150016001700180019002000210022002300

Table 1–10. Annual groundwater withdrawals at golf course GP2A partially located in the Pawcatuck River Basin, southwestern 

Rhode Island and southeastern Connecticut, 1994–2004.

[NOAA-NWS, National Oceanic and Atmospheric Administration National Weather Service; URI, University of Rhode Island; gal, gallons; yr, year; 

ac, acres; yd, yards; in., inches; --, not applicable; /, per]

Year

Total groundwater 

withdrawals 

(gal/yr)

Groundwater 

withdrawals 

(gal/yr/ac)

Groundwater 

withdrawals 

(gal/yr/yd)

Rank of yearly 

groundwater 

withdrawals from 

highest to lowest

Total precipitation 

from April 16 through 

November 15 at the 

NOAA-NWS-URI station 

(in.)

Rank of yearly 

precipitation from 

lowest to highest

1994 21,583,000 336,236 3,473 2 18.94 1

1995 15,577,000 242,670 2,507 7 27.09 5

1996 9,640,000 150,179 1,551 11 34.82 10

1997 14,164,000 220,657 2,279 8 27.61 6

1998 16,874,000 262,876 2,715 5 36.33 11

1999 17,851,000 278,096 2,873 3 26.59 3

2000 11,419,000 177,894 1,838 10 34.27 8

2001 21,618,000 336,781 3,479 1 24.76 2

2002 17,471,000 272,176 2,812 4 31.04 7

2003 12,158,707 189,417 1,957 9 34.47 9

2004 16,141,046 251,457 2,598 6 26.90 4

Minimum 9,640,000 150,179 1,551 -- 18.94 --

Maximum 21,618,000 336,781 3,479 -- 36.33 --

Average 15,863,341 247,131 2,553 -- 29.35 --

Median 16,141,046 251,457 2,598 -- 27.61 --

Figure 1–11. Average 24-hour irrigation-withdrawal rates for metered golf courses in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04.
Water Withdrawals 41

Predicting Turf-Farm and Golf-Course Irrigation

Logistic-regression equations were developed to predict 

the probability of irrigation on a specific day at turf farms and 

golf courses from 1960 through 2004, so water withdrawal 

estimates were available for long-term model analyses. Separate equations were developed for turf farms (includes vegetable farms and tree nurseries), golf courses with surface-water 

withdrawals, and golf courses with groundwater withdrawals. 

The three separate equations for predicting water withdrawals were needed because of differences in the number of days 

of withdrawals per year (table 1–9), withdrawal rates per day 

per acre (table 1–9), and 24-hour irrigation patterns at the nine 

turf farms (fig. 1–10) and three golf courses (fig. 1–11). The 

approach of developing separate equations for turf farms and 

golf courses with surface-water and groundwater withdrawals differed from that of a previous study for the UsquepaugQueen River Basin (Zarriello and Bent, 2004), because the 

additional data collected in this study revealed different and 

more detailed patterns.

The equations were developed from irrigation-withdrawal 

data measured during 2000–04 or 2002–04 and antecedent 

precipitation and potential evapotranspiration rates that served 

as potential explanatory variables for these time periods. The 

rates were determined from climatic data collected at the 

FBWR station. The equations were developed with the stepwise-logistic regression procedure in SAS (SAS Institute, Inc., 

1989, 1995). Explanatory climatic variables tested included 

total rainfall and potential evapotranspiration rates during 

the previous 2, 5, 10, 15, and 20 days. Correlated explanatory variables were not used during the stepwise-regression 

analysis because colinearity between independent variables 

can result in erroneous results (Helsel and Hirsch, 1992). 

Explanatory variables for sequences of data collected during 

closely overlapping time intervals—for example, rainfall in 

the previous 2 days and in the previous 5 days—tended to be 

correlated and were not used together in the analysis. Other 

climatic variables were dropped from the stepwise regression 

or only marginally added to the goodness-of-fit as indicated 

by the chi-squared values and Akaike Information Criterion 

(AIC) values.

Irrigation withdrawals at turf farms were made only from 

May 1 through October 31 in any year; for this reason, data 

from November 1 through April 30 were omitted from the 

analysis. Irrigation data were available for three turf-farm sites 

for 2000–04 and for eight other turf-farm sites for 2002–04. 

Several days of data were missing for the three turf-farm sites 

for which data were collected in 2000 and 2001. Turf-farm 

irrigation occurred on 373 of the 920 days used in the analysis 

during the 5-year period (table 1–11). Irrigation at turf farms 

differed with respect to the number of days of withdrawals and 

the amount withdrawn in any one year. The logistic-regression 

analysis determined that the best equation for estimating the 

probability of turf-farm irrigation on any day from May 1 

through October 31 (P) was based on total potential evapotranspiration during the previous 5 days (PET5) and total 

precipitation during the previous 2 days (PREC2) and the 

previous 20 days (PREC20). The probability (P) of irrigation 

occurring on a specific day at turf farms is given by

P

PET PREC PREC = (exp (-2. . 1149 + 5 1917 ( 5 0 ) − .7777( 2 0 ) − .5877( 20)

1

)

+ (exp (-2. . 1149 + 5 1917 (PET 5 0 ) − .7777(PREC2 0 ) − .5877(PREC20)) (1)

Results of the analysis of maximum likelihood estimates for 

equation (1) are presented in table 1–11.

Irrigation withdrawals at golf courses were made only 

from April 16 through November 15 in any year; for this 

reason, data from November 16 through April 15 were omitted 

from the analysis. Irrigation data were available for one golf 

course with surface-water withdrawals for 2000–04 and for 

two golf courses with groundwater withdrawals for 2002–04. 

Separate logistic-regression equations for estimating the 

probability of irrigation on any day were developed for golf 

courses with surface-water withdrawals and golf courses with 

groundwater withdrawals. Two separate equations were developed because the golf course with surface-water withdrawals irrigated on only 374 of the 1,075 days between April 16 

and November 15 during the 5-year period, whereas the golf 

courses with groundwater withdrawals irrigated on 472 of 

568 days during 2002–04.

For golf courses irrigated with surface-water withdrawals, the logistic-regression analysis determined that the best 

equation for estimating the probability of irrigation on any 

day from April 16 through November 15 (P) was based on 

total potential evapotranspiration during the previous 5 days 

(PET5) and total precipitation during the previous 5 days 

(PREC5) and the previous 20 days (PREC20). The probability 

(P) of irrigation occurring on a specific day at golf courses 

with surface-water withdrawals is given by

P

PET PREC PREC = (exp (-2. . 1590 + 4 3063( 5 1 ) − .4975( 5 0 ) − .1506( 20)

1

)

+ (exp (-2. . 1590 + 4 3063(PET 5 1 ) − .4975(PREC5 0 ) − .1506(PREC20)) (2)

Results of the analysis of maximum likelihood estimates for 

equation (2) are presented in table 1–11.

For golf courses irrigated with groundwater withdrawals, the logistic-regression analysis determined that the best 

equation for estimating the probability of irrigation on any 

day from April 16 through November 15 (P) was based on 

total potential evapotranspiration during the previous 20 days 

(PET20) and total precipitation during the previous 5 days 

(PREC5). The probability (P) of irrigation occurring on a 

specific day at golf courses with groundwater withdrawals is 

given by

P

PET PREC = + −

+ +

(exp (- . . ( ) . ( )

exp - . .

0 9898 1 9531 20 0 6466 5

1 0 9898 1

)

( ( 9531(PET 20) − 0.6466(PREC5)) (3)

Results of the analysis of maximum likelihood estimates for 

equation (3) are presented in table 1–11.
42 Part 1. Water Resources in the Pawcatuck River Basin Table 1–11. Summary statistics for logistic-regression analyses of the equations for estimating the probability of irrigation on a specific day at a (A) turf farm, (B) golf course with surface-water withdrawals, and (C) golf course with groundwater withdrawals in the Pawcatuck River Basin, southwestern Rhode Island and southeastern Connecticut, 2000–04. [Helsel and Hirsch, 1992, p. 393–402; SAS Institute, Inc., 1995; PET-[x], [x]-day potential evapotranspiration; PREC-[x], [x]-day precipitation; AIC, Akaike Information Criterion; C, rank correlation coef- ficient of predicted probabilities and observed responses; <, actual value is less than value shown] (A) Turf-farm irrigation - equation 1 (B) Golf-course irrigation with surface-water withdrawals - equation 2 (C) Golf-course irrigation with ground- water withdrawals - equation 3 Intercept PET5 PREC2 PREC20 Intercept PET5 PREC5 PREC20 Intercept PET20 PREC5 Analysis of maximum likelihood estimates: Degrees of freedom 1 1 1 1 1 1 1 1 1 1 1 Estimate -2.1149 5.1917 -0.7777 -0.5877 -2.159 4.3063 -1.4975 -0.1506 -0.9898 1.9531 -0.6466 Standard error 0.2678 0.3958 0.2818 0.0634 0.2355 0.3237 0.1972 0.0544 0.3135 0.2166 0.1696 Chi-square 62.3687 172.0721 7.6188 86.0436 84.0518 177.0236 57.6486 7.6612 9.9695 81.3048 14.539 p-value <0.0001 <0.0001 0.0058 <0.0001 <0.0001 <0.0001 <0.0001 0.0056 0.0016 <0.0001 0.0001 Likelihood ratio: Number of data points (total number of days) 920 1,075 568 Number of days with irrigation 373 374 472 Number of days with no irrigation 547 701 96 AIC 841.092 956.162 343.168

C 0.861 0.861 0.886-2 Log likelihood 833.092 948.162 337.168Chi-square 409.1914 441.0414 178.9394Degrees of freedom 3 3 2p-value <0.0001 <0.0001 <0.0001

Score:

Chi-square 333.9262 344.9402 139.8057Degrees of freedom 3 3 2p-value <0.0001 <0.0001 <0.0001
Wastewater Discharge and Return Flow 43

Equation 1 for turf farms and equations 2 and 3 for golf 

courses yield the probability of irrigation on a specific day at 

turf farms for May 1 through October 31 and at golf courses 

for April 16 through November 15 as a value between 0 and 

1.0; the closer the value is to 1.0, the greater the likelihood 

of irrigation. For turf farms, a probability of 0.40 provided 

the best cutoff value for estimating observed irrigation: if the 

estimated probability of turf-farm irrigation on a day is equal 

to or greater than 0.40, then irrigation was assumed to have 

occurred, but if the probability is less than 0.40, then irrigation was assumed not to have occurred. At the 40-percent 

probability, the equation correctly estimated turf-farm irrigation about 78 percent of the time and balanced the sensitivity1

and specificity2 of the equation more closely than at the other 

probabilities (appendix 1, table A1–1). For golf courses with 

surface-water withdrawals, a probability of 0.36 provided 

the best cutoff value for estimating observed irrigation. At 

the 36-percent probability, the equation correctly estimated 

golf-course surface-water irrigation about 79 percent of the 

time and balanced the sensitivity and specificity of the equation more closely than at the other probabilities (appendix 1, 

table A1–2). For golf courses with groundwater withdrawals, a 

probability of 0.80 provided the best cutoff value for estimating observed irrigation. At the 80-percent probability, the 

equation correctly estimated golf-course groundwater irrigation about 80 percent of the time and balanced the sensitivity 

and specificity of the equation more closely than at the other 

probabilities (appendix 1, table A1–3).

Each of the individual logistic-regression equations 

was used to estimate the specific days of irrigation for turf 

farms, surface-water-supplied golf courses, and groundwatersupplied golf courses. The turf-farm equation was used 

to estimate the specific dates of irrigation for unmetered 

withdrawal sites (29 turf farms, 8 vegetable farms, and 1 tree 

nursery). The groundwater-supplied golf-course equation 

was used to estimate the specific days of irrigation for six 

unmetered groundwater golf courses, with a total of nine 

different withdrawal sites. The surface-water-supplied golfcourse equation was used to estimate the specific days of 

irrigation for one unmetered surface-water golf course, and 

the specific days of irrigation at golf course GUQ1A from 

April 16 through July 16, 2002, when no streamflow data 

were available for the downstream streamflow-gaging station. 

After the specific days of irrigation were estimated for the 

study period (2000–04) by each equation, the appropriate 

average hourly water-withdrawal rate per acre was multiplied 

by the number of acres to be irrigated to estimate the hourly 

withdrawal rate for each unmetered site. 

1

 Sensitivity: The ratio of correctly classified events (days of irrigation) to 

the total number of events (days of irrigation).

2

 Specificity: The ratio of correctly classified nonevents (days of no irrigation) to the total number of nonevents (days of no irrigation).

Water-withdrawal data were also estimated for all turf 

farms, vegetable farms, tree nurseries, and golf courses 

using the appropriate logistic regression equations in the 

Pawcatuck River Basin for the period of 1960–99, so that 

water-withdrawal estimates were available for model analyses 

during 1960–2004. It was assumed that the irrigation rate, 

irrigated acres, type of withdrawal (surface- or groundwater), 

and locations of withdrawals for the period of 1960–99 

were the same as those used 2000–04 because metered 

water use data were not available during the earlier period. 

To estimate the water withdrawals during this period using 

the logistic-regression equations, precipitation and potential 

evapotranspiration data from the PROVID climate station 

were adjusted by the differences between data from the 

FBWR and PROVID climate stations for the 2000–04 study 

period, because climatic data were not available for FBWR 

for 1960–99. During 2000–04, daily precipitation and 

potential evapotranspiration data at the FBWR climate station 

were 9.9 percent higher and 8.5 percent lower, respectively, 

than at the PROVID climate station. Thus, PROVID daily 

precipitation data were multiplied by 1.099 and PROVID 

daily potential evapotranspiration data were multiplied by 

0.915 to adjust for climatic conditions in the Pawcatuck River 

Basin. The adjusted antecedent-precipitation and potentialevapotranspiration explanatory variables were then used in 

the appropriate logistic-regression equations to estimate the 

days of irrigation for 1960–99. On the basis of the appropriate 

hourly water withdrawal rate per acre and the acreage of 

each turf farm, vegetable farm, tree nursery, and golf course, 

the hourly withdrawal rate for each withdrawal point was 

estimated during the irrigation seasons for the period of 

1960–99.

Wastewater Discharge and Return Flow

The withdrawals of most major and minor production 

wells are returned to the basin through onsite septic systems. 

Withdrawals from domestic self-supply wells are also mostly 

returned to the basin through onsite septic systems. Wild and 

Nimiroski (2004, p. 40) reported 11 Rhode Island National 

Pollutant Discharge Elimination System (NPDES) sites 

discharging an average return flow of about 1.7 Mgal/d in the 

Pawcatuck River Basin during 1995–99. Wild and Nimiroski 

(2004, p. 42) also reported average return flows of about 

2.8 Mgal/d from two wastewater-treatment facilities in 

the southwestern part of the basin during 1995–99 

(fig. 1–8). The wastewater from these two facilities discharges 

near the mouth of the Pawcatuck River below the Pawcatuck 

River at Westerly (01118500) streamflow-gaging station. 

The wastewater-treatment facility in the southeastern part of 

the basin, which services parts of one town and a university, 

discharges return flow into the Atlantic Ocean.
THIS PAGE INTENTIONALLY LEFT BLANK