U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1041

Prepared in cooperation with the 

Providence Water Supply Board and the

Rhode Island Department of Environmental Management

Streamflow, Water Quality, and Constituent 

Loads and Yields, Scituate Reservoir 

Drainage Area, Rhode Island, Water Year 2002
Cover. Photograph shows Ponaganset River at South Foster, Rhode Island. (Photograph by Kimberly Campo, U.S. Geological Survey)
Streamflow, Water Quality, and Constituent 

Loads and Yields, Scituate Reservoir 

Drainage Area, Rhode Island, 

Water Year 2002

By Robert F. Breault

Prepared in cooperation with the 

Providence Water Supply Board and the

Rhode Island Department of Environmental Management

Open-File Report 2009–1041

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Breault, R.F., 2009, Streamflow, water quality, and constituent loads and yields, Scituate Reservoir drainage area, 

Rhode Island, water year 2002: U.S. Geological Survey Open-File Report 2009–1041, 30 p., also available online at 

http://pubs.usgs.gov/ofr/2009/1041.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Streamflow Data Collection and Estimation..............................................................................................2

Water-Quality Data Collection and Analysis.............................................................................................7

Data Collected by the U.S. Geological Survey.................................................................................7

Data Collected by the Providence Water Supply Board................................................................7

Estimating Daily, Monthly, and Annual Loads and Yields........................................................................9

Streamflow......................................................................................................................................................9

Water Quality and Constituent Loads and Yields .....................................................................................9

Sodium and Chloride Loads and Yields Estimated from Specific-Conductance 

Monitoring Data.....................................................................................................................11

Physical and Chemical Properties and Daily Loads and Yields Estimated from 

Data Collected by the Providence Water Supply Board.................................................11

Physical and Chemical Properties..........................................................................................11

Constituent Concentrations and Daily Loads and Yields.....................................................15

Bacteria.......................................................................................................................................15

Chloride........................................................................................................................................15

Nutrients......................................................................................................................................15

References Cited..........................................................................................................................................20

Figures

1. Map showing locations of tributary-reservoir subbasins and streamflow-gaging 

and water-quality monitoring stations in the Scituate Reservoir drainage area, 

Rhode Island..................................................................................................................................3

2. Graph showing flow-duration curve for the U.S. Geological Survey continuous 

streamflow-gaging station on Ponaganset River at South Foster (station 01115187) 

for water year 2002 and streamflow measurements at the Ponaganset River 

gaging station on the dates when water-quality samples were collected at 

Dolly Cole Brook............................................................................................................................8

3. Graph showing measured daily mean streamflow for the U.S. Geological Survey 

continuous-record gaging station on the Ponaganset River at South Foster 

(station 01115187) in the Scituate Reservoir drainage area, Rhode Island, for 

October 1, 2001, through September 30, 2002, and mean daily streamflow for 

March 22, 1994, through July 13, 2008.....................................................................................10
iv

Tables

1. Providence Water Supply Board water-quality sampling stations, water-quality 

samples, and available streamflow and continuous monitoring stations by tributary 

reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, 

October 1, 2001, to September 30, 2002.....................................................................................4

2. Measured or estimated annual mean streamflows for tributary streams in the 

Scituate Reservoir drainage area, Rhode Island, October 1, 2001, through 

September 30, 2002.......................................................................................................................6

3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary 

reservoir subbasin, in the Scituate Reservoir drainage area, Rhode Island, 

October 1, 2001, through September 30, 2002 ........................................................................21

4. Monthly mean concentrations of chloride and sodium estimated from continuous 

measurements of specific conductance in the Scituate Reservoir drainage area, 

Rhode Island, October 1, 2001, through September 30, 2002...............................................12

5. Annual mean chloride and sodium concentrations, loads, and yields by sampling 

station in the Scituate Reservoir drainage area, Rhode Island, October 1, 2002, 

through September 30, 2003......................................................................................................13

6. Monthly estimated chloride and sodium loads by sampling station in the 

Scituate Reservoir drainage area, Rhode Island, October 1, 2001, through 

September 30, 2002.....................................................................................................................14

7. Median values for water-quality data collected at Providence Water stations by 

tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, 

October 1, 2001, through September 30, 2002 ........................................................................16

8. Median daily loads and yields of bacteria, chloride, nitrate, nitrite, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, 

Rhode Island, October 1, 2001, through September 30, 2002...............................................18
v

Conversion Factors

Multiply By To obtain

Area

square mile (mi2) 2.590 square kilometer (km2)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Mass

ton, short (2,000 lb) 907.2 kilogram (kg)

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or colony forming units per 100 milliliters (CFU/100mL).

Loads of chemical constituents in water are given in kilograms (or millions of colony forming 

units for bacteria) per day, month, or year, and yields are given in kilograms (or millions of 

colony forming units for bacteria) per day, month, or year per square mile.
Abstract

Streamflow and water-quality data were collected by the U.S. Geological Survey 

(USGS) or the Providence Water Supply Board, Rhode Island’s largest drinking-water 

supplier. Streamflow was measured or estimated by the USGS following standard methods at 

23 streamflow-gaging stations; 10 of these stations were also equipped with instrumentation 

capable of continuously monitoring specific conductance. Streamflow and concentrations of 

sodium and chloride estimated from records of specific conductance were used to calculate 

instantaneous (15-minute) loads of sodium and chloride during water year (WY) 2002 

(October 1, 2001 to September 30, 2002). Water-quality samples were also collected at 35 of 

37 sampling stations in the Scituate Reservoir drainage area by the Providence Water Supply 

Board during WY 2002 as part of a long-term sampling program. Water-quality data are 

summarized by using values of central tendency and are used, in combination with measured 

(or estimated) streamflows, to calculate loads and yields (loads per unit area) of selected waterquality constituents for WY 2002.

The largest tributary to the reservoir (the Ponaganset River, which was monitored by the 

USGS) contributed about 12.6 cubic feet per second (ft3/s) to the reservoir during WY 2002. 

For the same time period, annual mean1 streamflows measured (or estimated) for the other 

monitoring stations in this study ranged from about 0.14 to 8.1 ft3/s. Together, tributary streams 

(equipped with instrumentation capable of continuously monitoring specific conductance) 

transported about 534,000 kilograms (kg) of sodium and 851,000 kg of chloride to the Scituate 

Reservoir during WY 2002; sodium and chloride yields for the tributaries ranged from 2,900 to 

40,200 kilograms per square mile (kg/mi2) and from 4,200 to 68,200 kg/mi2, respectively.

At the stations where water-quality samples were collected by the Providence Water Supply 

Board, the median of the median chloride concentrations was 16.8 milligrams per liter (mg/L), 

median nitrate concentration was 0.02 mg/L as N, median nitrite concentration was 0.002 mg/L 

as N, median orthophosphate concentration was 0.03 mg/L as P, and median concentrations of 

total coliform and Escherichia coli (E. coli) bacteria were 22 and 14 colony forming units per 

100 milliliters (CFU/100 mL), respectively. The medians of the median daily loads (and yields) 

of chloride, nitrate, nitrite, orthophosphate and total coliform and E. coli bacteria were 21 kg/d 

(12 kg/d/mi2), 0.04 kg/d (0.014 kg/d/mi2), 0.005 kg/d (0.002 kg/d/mi2), 0.08 kg/d (0.035 kg/d/

mi2), and 370 million colony forming units per day (CFU×106/d) (120 CFU×106/d/ mi2) and 

300 CFU×106/d (75 CFU×106/d/mi2), respectively.

1

 The arithmetic mean of the individual daily mean discharges for the year noted or for the designated period. 

Streamflow, Water Quality, and Constituent 

Loads and Yields, Scituate Reservoir 

Drainage Area, Rhode Island, Water Year 2002

By Robert F. Breault
2 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

data collected by Providence Water at 35 sampling stations 

during WY 2002 also are presented, and these data were used 

to calculate loads and yields of selected water-quality constituents (table 1).

Streamflow Data Collection and 

Estimation

Streamflow and water-quality data were collected by 

the USGS or Providence Water. Streamflow was measured 

or estimated by the USGS at 23 streamflow-gaging stations. 

Measured and estimated streamflows are necessary to estimate 

water volume, water-quality constituent loads, and yields 

from tributary basins. At continuous-record streamflowgaging stations, stream stage is measured every 15 minutes. 

Streamflow is computed with a stage-discharge relation 

(or rating), which is developed on the basis of periodic 

manual measurements. Daily mean streamflow at a station is 

calculated by dividing the total volume of water that passes the 

station each day by 86,400, the number of seconds in a day. 

Periodic manual streamflow measurements at partial-record 

gaging stations are used with concurrent continuous-record 

measurements from stations in hydrologically similar drainage 

areas to estimate a continuous record at the partial-record site. 

Specifically, continuous streamflow records for the 21 partialrecord sites in the Scituate Reservoir drainage area were 

estimated by using the Maintenance of Variance Extension 

type 1 (MOVE.1) method, as described by Ries and Friesz 

(2000); data needed to estimate streamflows at partial-record 

sites were retrieved from the USGS National Water Inventory 

System (NWIS; http://waterdata.usgs.gov/nwis/) and 

formatted. Streamflows were estimated by MOVE.1 method 

by using a suite of USGS-developed computer programs 

(Granato, 2008). Errors for estimated streamflows are 

expressed as the upper and lower 90-percent confidence limits, 

as described by Tasker and Driver (1988) (table 2); there is a 

90-percent chance that streamflow is somewhere between the 

upper and lower 90-percent confidence limits.

Continuous-record streamflow-gaging stations were 

operated and maintained by the USGS during WY 2002 

on Peeptoad Brook (USGS station number 01115098 and 

Providence Water station number 16, in cooperation with 

RIDEM) and on the Ponaganset River (USGS station 

number 01115187 and Providence Water station number 35, 

in cooperation with Providence Water; fig. 1 and table 1). 

Streamflow data for these two gaging stations were collected 

at 15-minute intervals. Near-real-time data for the Ponaganset 

River were available on the World Wide Web (WWW), 

accessed through the NWIS Web Interface (NWIS Web; 

U.S. Geological Survey, 2006). Error associated with 

measured streamflows in Peeptoad Brook and Ponaganset 

River was generally within about 15 percent (Socolow and 

others, 2003); upper and lower 90-percent confidence limits 

calculated by methods described by the National Institute of 

Introduction

The Scituate Reservoir is the primary source of 

drinking water for more than 60 percent of the population 

of Rhode Island. It covers about 94 mi2 in parts of the towns 

of Cranston, Foster, Glocester, Johnston, and Scituate, R.I. 

(fig. 1). Information about the water quality of the reservoir 

and its tributary streams is important for management of the 

water supply and for the protection of human health. The 

Providence Water Supply Board (Providence Water), the 

agency responsible for the management and distribution of 

the Scituate Reservoir water supply, has been monitoring and 

assessing water quality in the reservoir and reservoir drainage 

area for more than 50 years.

Since 1993, the U.S. Geological Survey (USGS) has 

been cooperating with Providence Water and the Rhode Island 

Department of Environmental Management (RIDEM) to 

measure streamflow in tributaries to the Scituate Reservoir. 

Streamflow has been continuously measured at 2 streamflowgaging stations in the drainage area and has been periodically measured at 21 additional stations on tributaries in the 

drainage area. At these 21 partial-record stations, continuous 

streamflow records have been estimated by using methods 

developed by the USGS (Hirsch, 1982). More recently (since 

2000), the USGS also has been continuously measuring 

specific conductance at 10 monitoring stations. Equations that 

relate specific conductance to concentrations of sodium and 

chloride in streamwater also were developed as part of a previous USGS/Providence Water cooperative study (Nimiroski 

and Waldron, 2002). These equations, updated here and used 

together with measured (or estimated) streamflows, allow for 

nearly continuous estimation of sodium and chloride loads to 

the reservoir (Nimiroski and Waldron, 2002).

Currently (2008), Providence Water regularly collects water-quality samples from 37 tributary streams, either 

monthly or quarterly. Occasionally, samples are collected from 

other streams or stations as needed. Water-quality results are 

summarized by monitoring station and constituent or parameter in annual reports published by Providence Water. In addition, over the past 10 years, USGS reports have compiled and 

tabulated streamflow (measured or estimated by USGS) and 

water-quality data (collected by Providence Water; Breault and 

others, 2000; Nimiroski and others, 2008).

This report presents data on streamflow, water quality and 

loads and yields of selected constituents for water year2 (WY) 

2002 in the Scituate Reservoir drainage area. These data were 

collected as part of studies done by the USGS in cooperation 

with Providence Water and the RIDEM. A summary of measured and estimated streamflows is presented for the 2 continuous-record and 21 partial-record streamflow-gaging stations 

in the drainage area. Estimated monthly loads and annual 

loads (and yields) of sodium and chloride are presented for 

the 10 stations at which specific conductance is continuously 

monitored by the USGS. Summary statistics for water-quality 

2

 October 1, 2001 to September 30, 2002.
Streamflow Data Collection and Estimation 3

Figure 1. Locations of tributary-reservoir subbasins and streamflow-gaging and water-quality monitoring stations in the 

Scituate Reservoir drainage area, Rhode Island. 

NARRAGANSETT BAY

BLOCK ISLAND

SOUND

41o45'

71o

45' 71o30'

41o30'

42o

00'

0 10 MILES

0 10 KILOMETERS

RHODE ISLAND

STUDY

BASIN

Madison

Pond

Pine

Swamp

71O45'

71O

37'30"

41O

52'30"

41O

45'

Base from USGS Digital Data

State Plane Feet Zone 5176

1:24,000 Scale

GLOCESTER

SCITUATE

FOSTER

JOHNSTON

CRANSTON

Danielson Pike

116

6

14

101

12

3

28 29

8

9

12

5

4

6

33

1 2

32

31

13

22 21

34

19

20 16

14

15

17

18

23

27

25

26

24

10

11

7

30

35

36

Westconnaug 37

Reservoir

Ponaganset

Reservoir

Regulating 

Reservoir

Kimball

Reservoir

Barden

Reservoir

Moswansicut

Reservoir

Scituate 

Reservoir

0

0

1 2 3 4 5 MILES

1 2 3 4 5 KILOMETERS

Ponaganset Reservoir subbasins

Regulating Reservoir subbasins

Westconnaug Reservoir subbasins

EXPLANATION

Town boundary

Basin boundary

Subbasin boundary

Water-quality sampling

subbasin boundary

Barden Reservoir subbasins

Direct Runoff subbasins

Moswansicut Reservoir subbasins

Subbasins and reservoir areas

Unsampled area draining

 directly to Scituate 

 Reservoir 

STREAMFLOW OR WATER-QUALITY MONITORING 

STATIONS AND IDENTIFIER—black squares indicate 

measurements made by U.S. Geological Survey

Continuous

streamflow

Partial-record

streamflow 

Continuous

specific conductance

and temperature

Real-time monitoring

Primary roads, including 

arterial and collector roads
4 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 1. Providence Water Supply Board water-quality sampling stations, water-quality samples, and available streamflow and 

continuous monitoring stations by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2001, 

to September 30, 2002.—Continued

[PW, Providence Water; USGS, U.S. Geological Survey; mi2, square miles; QW, water quality; M, monthly; Q, quarterly; Y, yes; N, no; Na, sodium; Cl, chloride; --, none; Alternate station names in parentheses are historical names used for the same sampling location by Providence Water.]

PW 

station 

number

USGS 

station 

number

Station name

Drainage 

area 

(mi2)

Station 

active during study 

period

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Estimated 

streamflow calculated

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 5.01 Y M 12 Y Y

25 01115200 Shippee Brook 2.39 Y Q 4 N Y

26 01115185 Windsor Brook 4.22 Y Q 4 N Y

27 011151845 Unnamed Tributary to Ponaganset 

River (Unnamed Brook B, Unnamed 

Brook West of Windsor Brook)

0.10 Y Q 2 N N

28 01115265 Barden Reservoir (Hemlock Brook) 10.62 Y M 12 Y Y

29 01115271 Ponaganset River (Barden Stream) 33.02 N M -- N N

35 01115187 Ponaganset River 14.40 Y M 12 Y N

Direct Runoff subbasin

1 01115180 Brandy Brook 1.57 Y M 12 N Y

2 01115181 Unnamed Tributary #2 to Scituate 

Reservoir (Unnamed Brook North of 

Bullhead Brook)

0.15 Y Q 2 N N

3 01115280 Cork Brook 1.90 Y M 11 Y Y

4 01115400 Kent Brook (Betty Pond Stream) 0.86 Y M 11 N Y

5 01115184 Spruce Brook 1.23 Y Q 4 N Y

6 01115183 Quonapaug Brook 1.99 Y M 9 Y Y

7 01115297 Wilbur Hollow Brook 4.42 Y M 12 Y Y

8 01115276 Westconnaug Brook 

(Westconnaug Reservoir)

5.10 Y M 8 N Y

9 01115275 Bear Tree Brook 0.64 Y Q 4 Y Y

30 01115350 Unnamed Tributary #4 to Scituate 

Reservoir (Coventry Brook, 

Knight Brook)

0.74 Y Q 3 N N

31 01115177 Toad Pond 0.04 N Q -- N N

32 01115178 Unnamed Tributary #1 to Scituate 

Reservoir (Pine Swamp Brook)

0.40 Y Q 4 N Y

33 01115182 Unnamed Tributary #3 to Scituate 

Reservoir (Hall’s Estate Brook)

0.27 Y Q 3 N Y

36 -- Outflow from King Pond 0.77 Y Q 3 N N

37 -- Fire Tower Stream 0.15 Y Q 4 N N
Streamflow Data Collection and Estimation 5

Table 1. Providence Water Supply Board water-quality sampling stations, water-quality samples, and available streamflow and 

continuous monitoring stations by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2001, 

to September 30, 2002.—Continued

[PW, Providence Water; USGS, U.S. Geological Survey; mi2, square miles; QW, water quality; M, monthly; Q, quarterly; Y, yes; N, no; Na, sodium; Cl, chloride; --, none; Alternate station names in parentheses are historical names used for the same sampling location by Providence Water.]

PW 

station 

number

USGS 

station 

number

Station name

Drainage 

area 

(mi2)

Station 

active during study 

period

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Estimated 

streamflow calculated

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

3.20 Y M 7 Y Y

20 01115160 Unnamed Tributary #1 to Moswansicut 

Reservoir (Blanchard Brook)

1.21 Y M 8 N N

21 01115165 Unnamed Tributary #2 to 

Moswansicut Reservoir 

(Brook from Kimball Reservoir)

0.32 Y Q 3 N Y

22 01115167 Moswansicut Reservoir 

(Moswansicut Stream South)

0.22 Y M 7 N N

34 01115164 Kimball Stream 0.27 Y Q 3 N N

Ponaganset Reservoir subbasin

23 011151843 Ponaganset Reservoir 1.86 Y M 6 N N

Regulating Reservoir subbasin

13 01115176 Regulating Reservoir 22.17 Y M 9 N N

14 01115110 Huntinghouse Brook 6.24 Y M 12 Y Y

15 01115115 Regulating Reservoir (Rush Brook) 4.98 Y M 10 N Y

16 01115098 Peeptoad Brook (Harrisdale Brook) 4.92 Y M 11 Y N

17 01115119 Dexter Pond (Paine Pond) 0.13 Y Q 2 N N

18 01115120 Unnamed Tributary to Regulating 

Reservoir (Unnamed Brook A)

0.54 Y Q 3 N Y

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 1.37 Y M 8 N Y

11 01115273 Unnamed Tributary to Westconnaug 

Reservoir (Unnamed Brook south of 

Westconnaug Reservoir)

0.69 Y Q 3 N Y

12 011152745 Unnamed Tributary to Westconnaug 

Brook (Unnamed Brook north of 

Westconnaug Reservoir)

0.15 Y Q 1 N N

1

 Not all samples were analyzed for all water-quality properties or constituents.
6 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 2. Measured or estimated annual mean streamflows for tributary streams in the Scituate Reservoir drainage area, 

Rhode Island, October 1, 2001, through September 30, 2002.

[PW, Providence Water; USGS, U.S. Geological Survey; ft3/s, cubic feet per second; ft3/s/mi2, cubic feet per second per square mile]

PW 

station 

number

USGS 

station 

number

Station name

Annual mean 

streamflow 

(ft3/s)

Upper 

90-percent confidence limit 

(ft3/s)

Lower 

90-percent 

confidence limit 

(ft3/s)

Normalized 

annual mean 

streamflow 

(ft3/s/mi2)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 4.1 14.8 1.1 0.82

25 01115200 Shippee Brook 2.8 9.6 0.82 1.2

26 01115185 Windsor Brook 3.4 12.4 1.0 0.82

28 01115265 Barden Reservoir (Hemlock Brook) 8.1 21.1 3.1 0.76

35 01115187 Ponaganset River 12.6 11.0 14.1 0.87

Direct Runoff subbasin

1 01115180 Brandy Brook 1.7 4.1 0.74 1.1

3 01115280 Cork Brook 1.6 3.7 0.68 0.84

4 01115400 Kent Brook (Betty Pond Stream) 0.74 6.5 0.08 0.86

5 01115184 Spruce Brook 1.5 6.1 0.37 1.2

6 01115183 Quonapaug Brook 2.2 6.4 0.75 1.1

7 01115297 Wilbur Hollow Brook 4.5 18.5 1.1 1.0

8 01115276 Westconnaug Brook (Westconnaug 

Reservoir)

5.5 10.9 2.8 1.1

9 01115275 Bear Tree Brook 0.94 1.7 0.51 1.5

32 01115178 Unnamed Tributary #1 to Scituate 

Reservoir (Pine Swamp Brook)

0.33 0.59 0.18 0.83

33 01115182 Unnamed Tributary #3 to Scituate 

Reservoir (Hall’s Estate Brook)

0.28 0.73 0.11 1.1

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

3.3 14.0 0.79 1.0

21 01115165 Unnamed Tributary #2 to Moswansicut 

Reservoir (Blanchard Brook)

0.39 1.7 0.09 1.2

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 5.1 16.2 1.6 0.81

15 01115115 Regulating Reservoir (Rush Brook) 3.8 12.5 1.2 0.76

16 01115098 Peeptoad Brook (Harrisdale Brook) 5.1 4.5 5.7 1.0

18 01115120 Unnamed Tributary to Regulating Reservoir 0.14 0.35 0.06 0.27

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 1.6 5.1 0.51 1.2

11 01115273 Unnamed Tributary to Westconnaug 

Reservoir (Unnamed Brook south of 

Westconnaug Reservoir)

1.5 4.7 0.45 2.1
Water-Quality Data Collection and Analysis 7

Standards and Technology/SEmiconductor MAnufacturing 

TECHnology (NIST/SEMATECH e-Handbook of Statistical 

Methods, 2003) for Peeptoad Brook and Ponaganset River are 

shown in table 2.

Water-Quality Data Collection and 

Analysis

Water-quality data were collected by the USGS or 

Providence Water. Concentrations of sodium and chloride 

were estimated (by USGS) from continuous records of specific 

conductance from 10 of the 23 streamflow-gaging stations. 

Water-quality samples were collected monthly or quarterly at 

35 of 37 sampling stations in the Scituate Reservoir drainage area by Providence Water during WY 2002, as part of a 

long-term sampling program. Daily loads of chloride, bacteria, nitrate, nitrite, and orthophosphate were calculated at 

23 monitoring stations where streamflow data were collected 

by the USGS and water-quality samples were collected by 

Providence Water. Yields were calculated by dividing load by 

drainage area.

Data Collected by the U.S. Geological Survey

Water quality was monitored in a periodic water-quality 

sampling program that included measurements by automatic 

specific-conductance probes. The USGS collected and analyzed the specific conductance data. Specific conductance was 

measured by the USGS at 15-minute intervals at the 10 monitoring stations, including the 2 continuous streamflow-gaging 

stations and 8 partial-record sites (fig. 1). Measurements were 

made by using an instream probe and standard USGS methods 

for continuous streamwater-quality monitoring (Wagner and 

others, 2006). Specific conductance data for the 10 monitoring 

stations were published in the USGS Annual Data Report for 

WY 2002 (Socolow and others, 2003).

Concentrations of sodium and chloride were estimated 

from continuous measurements of specific conductance 

by using equations that were developed by the USGS to 

relate specific conductance to concentrations of sodium and 

chloride (equations 1 and 2). These regression equations were 

developed by the MOVE.1 method (also known as the line of 

organic correlation; Helsel and Hirsch, 2002) on the basis of 

concurrent measurements of specific conductance along with 

sodium and chloride concentrations measured in water-quality 

samples collected from tributary streams in the Scituate 

Reservoir drainage area (Marcus Waldron, U.S. Geological 

Survey, unpublished data, 2008):

C Spc Na = ⋅ 1.2828 + 0.05063 and (1)

 C Spc Cl = ⋅ 1.1794 + 0.05240, (2)

where

CNa is the sodium concentration, in milligrams 

per liter;

CCl is the chloride concentration, in milligrams 

per liter; and

Spc is the specific conductance, in microseimens 

per centimeter.

MOVE.1 was chosen for regression analysis to maintain 

variance (Hirsch and Gilroy, 1984). Some missing values of 

specific conductance were estimated. In these cases, seasonal 

(July to October; November to June) averages were used for 

estimated values of specific conductance. 

Data Collected by the Providence Water 

Supply Board

Water-quality samples were collected at 35 of 37 monitoring stations by Providence Water. Sampling was monthly 

at 18 monitoring stations and quarterly at another 17 stations 

(table 1) during WY 2002. Water-quality samples were not 

collected during specific weather conditions; rather, a strictly 

periodic water-quality sampling schedule was followed so 

that water-quality samples would be representative of various 

weather conditions. However, sometimes samples could not be 

collected because streams at the sampling stations were dry or 

frozen. When possible, water-quality samples were collected 

by dipping the sample bottle into the stream at the center of 

flow (Richard Blodgett, Providence Water Supply Board, 

written commun., 2005). Samples were transported on ice to 

the water-quality laboratory of Providence Water at the P.J. 

Holton Water Purification Plant in Scituate, R.I. Water-quality 

properties and constituent concentrations were measured by 

using unfiltered water samples. These water-quality properties 

included pH, temperature, acidity, alkalinity, color, turbidity, 

and concentrations of chloride, nitrite, nitrate, orthophosphate, 

and (Escherichia coli (E. coli) and total coliform). More information on sample-collection, analytical, and quality-control 

procedures can be found in the Providence Water Quality 

Assurance Program Manual (Providence Water Supply Board 

Water Quality Laboratory, 2003).

Providence Water collected samples during a wide 

range of flow conditions. The daily mean flow-duration curve 

for the Ponaganset River at South Foster (USGS station 

number 01115187) for WY 2002 is shown in figure 2. The 

curve represents the percentage of time that each flow was 

exceeded at this station. The flows at this station on days 

when water-quality samples were collected at a representative 

station (Dolly Cole Brook, fig. 2) are represented by the 

plotted points superimposed on the curve. Samples were 

collected at flow durations ranging from the 1st percentile 

to the 90th percentile; this range indicates that water-quality 

samples collected in WY 2002 represent a wide range of flow 

conditions during that water year.
8 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

0.001 0.01 1 10 40 70 95 99.5 99.999

1,000

100

10

1

0.1

0.01

STREAMFLOW, IN CUBIC FEET PER SECOND

PERCENTAGE OF TIME STREAMFLOW WAS EQUALED OR EXCEEDED

Water-quality sample collected at Dolly Cole Brook

Figure 2. Flow-duration curve for the U.S. Geological Survey continuous streamflow-gaging station on Ponaganset River at 

South Foster (station 01115187) for water year 2002 and streamflow measurements at the Ponaganset River gaging station on 

the dates when water-quality samples were collected at Dolly Cole Brook (shown as points). 
Water Quality and Constituent Loads and Yields 9

mean streamflow in Peeptoad Brook during WY 2002 was 

5.1 ft3/s (Socolow and others, 2003). 

The 10-year periods of record at these two streamflowgaging stations are shorter than time periods typically used to 

represent long-term average conditions. However, comparison 

with a nearby station having a period of record from 

WY 1940–2006 (Quinsigamond River at North Grafton, 

Mass., USGS station number 01110000) indicates that the 

distribution of streamflows regionally during the study period 

with respect to the long-term average flow at that station 

(41.3 ft3/s; wdr.water.usgs.gov/) was similar to the distribution 

at Ponaganset River and Peeptoad Brook; the annual mean 

flow in WY 2002 was considerably lower than average 

(17.4 ft3/s; Socolow and others, 2003). Annual mean streamflows estimated for partial-record monitoring stations are 

given in table 2. Estimated annual mean streamflows at partial 

record stations ranged from 0.14 to 8.1 ft3/s. Annual mean 

streamflows normalized by drainage area ranged from 

0.27 to 2.1 ft3/s/mi2 (table 2).

Water Quality and Constituent Loads 

and Yields

Water-quality conditions in the Scituate Reservoir drainage area are described by summary statistics for water-quality 

properties and constituent concentrations and estimated 

constituent loads and yields. Loads and yields characterize the rates at which masses of constituents are transferred 

to the reservoir by tributary streams. In the case of loads, 

streams with higher flows tend to have higher loads because 

the greater volume of water carries more of the constituent 

to the reservoir per unit time. Yields represent the constituent 

load per unit drainage area and are calculated by dividing the 

load estimated for a monitoring station by the drainage area 

to the station. Yields are useful for comparison among sites of 

different drainage-area sizes because the effects of basin size 

and, therefore, total streamflow volume are attenuated. Yields 

are useful for examining potential differences among basin 

properties that may contribute to reservoir quality.

Summary statistics include means and medians. For some 

purposes, median values are more appropriate because they 

are less likely to be affected by high or low concentrations 

(or outliers). Medians are especially important to use for 

summarizing a relatively limited number of values. In contrast, 

continuously monitored streamflow and sodium and chloride 

loads (estimated from measurements of specific conductance), 

which include a large number of values, are better summarized 

in terms of means because a large data set is more resistant 

to the effects of outliers. Mean values also are particularly 

appropriate for characterizing loads because outlier values, 

which typically represent large flows, are important to include 

when representing the delivery of constituent masses to 

receiving waters.

Estimating Daily, Monthly, and Annual 

Loads and Yields

Daily (table 1), monthly, and annual sodium and 

chloride loads in kilograms were estimated for all sampling 

sites for which streamflow (periodic or continuous) and 

continuous specific-conductance data were available during 

WY 2002. Daily sodium and chloride loads were estimated 

by multiplying daily (flow-weighted) concentrations of 

sodium and chloride in milligrams per liter by daily discharge 

(in liters per day) and added by month or water year. Daily 

flow-weighted concentrations of sodium and chloride were 

calculated by multiplying instantaneous flows by concurrent 

concentrations of sodium and chloride (estimated from 

measurements of specific conductance) for each day and 

dividing by the total flow for that day.

Daily loads of water-quality constituents (in samples 

collected by Providence Water) were calculated for all 

sampling dates during WY 2002 (table 3, at back of report) 

for which periodic or continuous streamflow data were 

available (table 1). These loads were calculated by multiplying 

constituent concentrations in milligrams per liter or colony 

forming units (CFU) per 100 milliliters in single samples 

multiplied by the daily discharge (in liters per day) for the 

day on which each sample was collected. The flows, which in 

most cases were estimates, were assumed to be representative 

of the flow at the time of the sample collection. Loads in 

kilograms (or millions of CFUs for bacteria) per day and 

yields in kilograms (or millions of CFUs for bacteria) per day 

per square mile were calculated for chloride, bacteria, nitrate, 

nitrite, and orthophosphate from this water-quality data. 

Censored data (or concentrations reported as less than method 

detection limits) were replaced with one-half the method 

detection limit.

Streamflow

Monitoring streamflow is necessary to measure the 

volume of water and estimate constituent loads to the Scituate 

Reservoir. The Ponaganset River is the largest monitored 

tributary to the Scituate Reservoir. Mean streamflow at the 

gaging station on the Ponaganset River (USGS station number 

01115187) for the entire time period of its operation (mean 

of the daily mean streamflows for the period of record, 

WY 1994–2006) was 28.3 ft3/s (wdr.waterdata.usgs.gov/). 

During WY 2002, annual mean streamflow was 12.6 ft3/s 

(fig. 3; Socolow and others, 2003). Mean streamflow in 

Peeptoad Brook (01115098), the other continuous streamflowgaging station in the Scituate Reservoir drainage area 

(USGS station number 01115098), for its period of record 

(WY 1994–2006) was 10.5 ft3/s (wdr.water.usgs.gov/). Annual 
10 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT.

1,000

100

10

1

0.1

STREAMFLOW, IN CUBIC FEET PER SECOND

2000 2002

Figure 3. Measured daily mean streamflow for the U.S. Geological Survey continuous-record gaging station on the 

Ponaganset River at South Foster (station 01115187) in the Scituate Reservoir drainage area, Rhode Island, for 

October 1, 2001, through September 30, 2002 (solid line), and mean daily streamflow for March 22, 1994, through July 13, 2008 

(dotted line).
Water Quality and Constituent Loads and Yields 11

Sodium and Chloride Loads and Yields 

Estimated from Specific-Conductance 

Monitoring Data

Sodium and chloride are constituents of special concern in the Scituate Reservoir drainage area; they are major 

constituents of road salt used for deicing, and several major 

roadways cross the drainage basin. State Routes 12 and 14 

cut across the main body of the reservoir, and State Route 116 

parallels the eastern limb (fig. 1). A recent study by the USGS, 

in cooperation with Providence Water, indicated that tributary 

streams in basins with state-maintained roads have substantially higher concentrations of sodium and chloride, presumably because of deicing activities (Nimiroski and Waldron, 

2002). In addition, sodium is a constituent of potential concern 

for human health; some persons on restrictive diets need to 

limit their intake of sodium.

Estimated monthly mean3 sodium concentrations in 

tributary streams of the Scituate Reservoir drainage area 

ranged from 2.0 to 65.2 mg/L, and estimated monthly 

mean chloride concentrations ranged from 2.7 to 120 mg/L. 

The highest monthly mean concentrations of sodium and 

chloride were measured at station 6 (Quonapaug Brook) in 

April 2002 (65.2 and 120 mg/L, respectively) (table 4). The 

highest annual mean4 concentrations of sodium and chloride 

were measured at station 9 (Bear Tree Brook) at 30.6 and 

51.9 mg/L, respectively (table 5). These high values are not 

surprising, because the waters that pass this station contain 

sodium and chloride from a formerly uncovered salt storage 

pile (Nimiroski and Waldron, 2002). 

The Scituate Reservoir received about 534,000 kg (about 

587 tons) of sodium and 851,000 kg (about 938 tons) of chloride from tributary streams—equipped with instrumentation 

capable of continuously monitoring specific conductance—

during WY 2002. The highest sodium and chloride loads in 

WY 2002—111,000 and 184,000 kg, respectively—were 

measured at the Peeptoad Brook (Harrisdale Brook) station 

(Providence Water Station Number 16) (table 5). Monthly 

sodium and chloride loads were highest at all stations in 

March and May, with two exceptions (table 6). Monthly 

sodium and chloride loads were highest in April at the 

Quonapaug Brook Station and in June at the Bear Tree Brook 

station, respectively. The totals of the March and May loads 

of sodium and chloride accounted for about 44 percent of 

the annual load for each constituent, on average. The highest 

3

 Monthly mean concentrations were calculated by dividing the total 

monthly load by the total discharge for the month.

4

 Annual mean concentrations were calculated by dividing the total annual 

load by the total discharge for the year.

annual sodium and chloride yields were 40,200 and 

68,200 kg/mi2, respectively, and were measured at Bear Tree 

Brook (station 9; table 5).

Uncertainties associated with measuring streamflow and 

specific conductance and with sodium and chloride sample 

collection, preservation, and analysis produce uncertainties 

in load and yield estimates. The load and yield estimates 

presented in the text and tables are estimated to be the most 

likely values for loads and yields of sodium and chloride 

coming from tributary streams or their drainage basins. It 

may be best to discuss loads and yields in terms of a range 

within which the true values lies; however, the most probable 

values of loads and yields are presented for ease of discussion 

and presentation. The range within which the true values lie 

depends on the uncertainties in individual measurements of 

streamflow and concentration, which are difficult to quantify 

with available information. It is commonly assumed that the 

uncertainties associated with estimating streamflow affect 

load and yield calculations more than the error associated with 

measuring specific conductance and (or) chemical analysis. 

The most probable values of loads and yields presented in the 

tables and text are sufficient for planning-level analysis of 

water quality in tributary streams and their drainage basins.

Physical and Chemical Properties and Daily 

Loads and Yields Estimated from Data Collected 

by the Providence Water Supply Board

Physical and Chemical Properties

Physical and chemical properties including pH, turbidity, alkalinity, specific conductance, and color were routinely 

measured to characterize water quality in each basin (table 7). 

Specifically, pH is a measure of the acidity of the water; color 

can be an indirect measure of the amount of organic carbon 

dissolved in the water column; turbidity is an indirect measure 

of suspended particles; and alkalinity is a measure of the acidneutralizing capacity of water.

The median pH in tributary streams in the Scituate 

Reservoir drainage area ranged from 5.2 to 6.7; the median 

of the medians among all stations was 6.2. Median values of 

color ranged from 8.0 to 133 platinum cobalt units (PCU); 

the median among all stations was 32 PCU. Median values of 

turbidity ranged from 0.3 to 1.9 nephelometric turbidity units 

(NTU); the median among all stations was 0.7 NTU. Median 

alkalinity values in tributary streams were low, ranging from 

1.9 to 14.5 mg/L as CaCO3; the median among all stations was 

5.6 mg/L as CaCO3 (table 7).
12 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 4. Monthly mean concentrations of chloride and sodium estimated from continuous measurements of specific conductance in 

the Scituate Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.

[PW, Providence Water; USGS, U.S. Geological Survey; No., number; Cl, chloride; Na, sodium; mg/L, milligrams per liter; the average root mean square error 

of the regression estimates for sodium and chloride are 1.2 and 0.06, respectively; monthly mean concentrations were calculated by dividing the monthly load 

by the total discharge for the month]

PW 

station 

No.

USGS 

station 

No.

Station name

OCT NOV DEC JAN FEB MAR

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 18.8 12.1 19.1 12.2 19.8 12.7 18.8 12.1 19.3 12.4 20.4 13.1

28 01115265 Barden Reservoir 

(Hemlock Brook)

22.4 14.2 23.4 14.8 19.5 12.5 14.3 9.4 15.3 10.0 14.2 9.4

35 01115187 Ponaganset River 15.4 10.0 15.4 10.1 16.1 10.4 14.7 9.5 14.0 9.2 13.1 8.6

Direct Runoff subbasin

3 01115280 Cork Brook 28.1 17.5 29.6 18.3 30.5 18.9 25.8 16.2 25.0 15.7 23.9 15.1

6 01115183 Quonapaug Brook 53.3 31.5 40.1 24.2 36.1 22.0 32.2 19.8 31.1 19.2 24.9 15.6

7 01115297 Wilbur Hollow Brook 14.0 9.2 12.5 8.3 11.9 7.9 10.2 6.9 9.8 6.6 8.8 6.0

9 01115275 Bear Tree Brook 72.5 41.8 69.0 39.9 60.6 35.4 53.0 31.3 49.3 29.3 38.6 23.4

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, 

Moswansicut Pond)

24.7 15.4 28.6 17.8 29.0 18.0 33.2 20.4 34.4 21.1 39.5 23.6

Regulating Reservoir

14 01115110 Huntinghouse Brook 5.5 3.9 2.7 2.0 3.4 2.5 3.2 2.4 3.2 2.4 3.8 2.7

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

28.1 17.5 27.7 17.3 31.3 19.3 44.9 26.9 44.2 26.5 42.9 25.8

Scituate Reservoir basin

Average 28.3 17.3 26.8 16.5 25.8 16.0 25.0 15.5 24.6 15.2 23.0 14.3

PW 

station 

No.

USGS 

station 

No.

Station name

APR MAY JUN JUL AUG SEP

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 23.0 14.5 20.8 13.3 20.4 13.0 20.9 13.3 21.3 13.5 29.3 18.2

28 01115265 Barden Reservoir 

(Hemlock Brook)

15.5 10.1 12.4 8.3 13.5 8.9 21.0 13.4 21.6 13.7 29.7 18.4

35 01115187 Ponaganset River 12.7 8.3 13.4 9.4 15.7 10.2 15.4 10.3 22.8 12.3 19.3 11.1

Direct Runoff subbasin

3 01115280 Cork Brook 21.2 13.5 18.7 12.0 16.8 10.9 18.6 12.0 28.4 17.6 35.1 21.4

6 01115183 Quonapaug Brook 120 65.2 26.8 16.6 25.3 15.8 45.7 27.4 51.8 30.6 74.7 42.8

7 01115297 Wilbur Hollow Brook 10.6 7.2 9.4 6.4 12.1 8.1 11.3 7.5 16.0 10.4 24.0 15.1

9 01115275 Bear Tree Brook 38.7 23.5 35.4 21.6 68.0 39.4 80.2 45.8 100 57.7 85.0 48.3

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, 

Moswansicut Pond)

28.4 17.7 28.6 17.8 29.0 18.0 31.6 19.5 30.2 18.7 30.3 18.8

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 3.0 2.3 9.1 6.2 10.6 7.1 14.5 9.5 14.9 9.8 17.3 11.2

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

42.8 25.8 38.8 23.5 36.2 22.1 27.5 17.0 20.3 12.9 18.2 11.7

Scituate Reservoir basin

Average 31.9 18.8 21.3 13.5 24.8 15.4 28.7 17.6 33.0 19.7 36.3 21.7
Water Quality and Constituent Loads and Yields 13

Table 5. Annual mean chloride and sodium concentrations, loads, and yields by sampling station in the Scituate Reservoir drainage 

area, Rhode Island, October 1, 2002, through September 30, 2003.

[PW, Providence Water; USGS, U.S. Geological Survey; No., number; Cl, chloride; Na, sodium; mg/L, milligrams per liter; kg/yr, kilograms per year; 

kg/yr/mi2, kilograms per year per square mile; annual mean concentrations were calculated by dividing the annual load by the total discharge for the year.]

PW 

station 

No.

USGS 

station 

No.

Station name

Concentration Load Yield

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(kg/yr)

Na 

(kg/yr)

Cl 

(kg/yr/mi2)

Na 

(kg/yr/mi2)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 20.8 13.3 76,200 48,600 15,200 9,700

28 01115265 Barden Reservoir (Hemlock Brook) 14.4 9.5 104,000 68,500 9,900 6,500

35 01115187 Ponaganset River 14.1 9.3 158,000 104,000 11,000 7,200

Direct Runoff subbasin

3 01115280 Cork Brook 21.8 13.8 31,000 19,700 16,300 10,400

6 01115183 Quonapaug Brook 46.1 26.5 90,800 52,100 45,400 26,100

7 01115297 Wilbur Hollow Brook 10.0 6.8 40,500 27,300 9,200 6,200

9 01115275 Bear Tree Brook 51.9 30.6 43,700 25,700 68,200 40,200

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir, 

(Moswansicut Stream North, 

Moswansicut Pond)

32.2 19.7 95,600 58,600 29,900 18,300

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 5.7 4.0 25,800 18,000 4,200 2,900

16 01115098 Peeptoad Brook (Harrisdale Brook) 40.5 24.5 184,000 111,000 37,600 22,700

Scituate Reservoir basin

Average Total Average

25.8 15.8 851,000 534,000 24,700 15,000
14 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 6. Monthly estimated chloride and sodium loads by sampling station in the Scituate Reservoir drainage area, Rhode Island, 

October 1, 2001, through September 30, 2002.

[PW, Providence Water; USGS, U.S. Geological Survey; No., number; Cl, chloride; Na, sodium; kg, kilogram]

PW 

station 

No.

USGS 

station 

No.

Station name

OCT NOV DEC JAN FEB MAR

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 190 120 280 180 930 600 3,400 2,200 8,000 5,100 19,300 12,300

28 01115265 Barden Reservoir 

(Hemlock Brook)

760 480 1,100 700 2,500 1,600 6,000 3,900 13,100 8,600 25,400 16,700

35 01115187 Ponaganset River 1,700 1,100 3,100 2,000 6,800 4,400 12,300 8,100 14,900 9,800 26,600 17,700

Direct Runoff subbasin

3 01115280 Cork Brook 150 96 230 140 690 420 2,000 1,300 4,200 2,600 8,600 5,400

6 01115183 Quonapaug Brook 620 370 640 380 1,400 880 3,900 2,400 7,400 4,600 11,700 7,400

7 01115297 Wilbur Hollow Brook 290 190 360 240 900 600 2,400 1,600 4,700 3,200 8,700 5,900

9 01115275 Bear Tree Brook 2,000 1,100 2,100 1,200 2,800 1,600 3,900 2,300 4,800 2,900 5,400 3,300

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

570 350 860 540 2,000 1,300 6,500 4,000 12,500 7,600 27,200 16,300

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 48 34 36 27 160 120 660 490 1,600 1,200 4,500 3,300

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

990 620 1,300 800 3,400 2,100 13,400 8,000 24,600 14,800 45,200 27,200

Scituate Reservoir basin

Total 7,300 4,500 10,000 6,200 21,600 13,600 54,500 34,300 95,700 60,300 183,000 115,000

PW 

station 

No.

USGS 

station 

No.

Station name

APR MAY JUN JUL AUG SEP

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 16,200 10,300 19,800 12,600 7,200 4,600 570 360 160 100 190 120

28 01115265 Barden Reservoir 

(Hemlock Brook)

21,200 13,800 21,700 14,400 9,800 6,400 1,700 1,100 540 340 650 410

35 01115187 Ponaganset River 22,400 14,900 39,000 25,500 26,200 17,100 2,500 1,600 550 350 2,000 1,300

Direct Runoff subbasin

3 01115280 Cork Brook 5,800 3,700 6,600 4,200 2,400 1,500 250 160 110 71 120 75

6 01115183 Quonapaug Brook 45,500 24,100 12,400 7,700 5,100 3,200 1,200 700 440 260 580 330

7 01115297 Wilbur Hollow Brook 8,100 5,400 9,000 6,100 4,900 3,300 540 360 250 160 330 210

9 01115275 Bear Tree Brook 4,700 2,900 4,700 2,900 6,100 3,500 3,100 1,700 2,300 1,300 1,800 1,000

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

15,500 9,600 19,100 11,800 8,900 5,500 1,500 920 510 320 470 290

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 2,700 2,000 11,200 7,600 4,500 3,000 370 240 95 63 92 59

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

35,800 21,500 39,700 24,000 17,100 10,400 2,000 1,200 530 340 430 280

Scituate Reservoir basin

Total 178,000 108,000 183,000 117,000 92,000 58,500 13,600 8,400 5,500 3,300 6,700 4,100
Water Quality and Constituent Loads and Yields 15

Constituent Concentrations and Daily Loads 

and Yields

Fecal indicator bacteria, chloride, and nutrients like 

phosphorus and nitrogen are commonly detected in natural 

water; at elevated concentrations, these constituents can render 

water unfit for the intended use. Fecal indicator bacteria, 

which are found in the intestines of warm-blooded animals, 

may indicate impairment from sewage contamination or 

from livestock or wildlife that defecate in or near the stream 

margin. Chloride originates in tributary streamwater from 

precipitation, weathering, or human activities like waste 

disposal and road deicing. Sources of nutrients in tributary 

streamwater include atmospheric deposition, leaching of 

naturally occurring organic material, discharge of groundwater 

that is enriched in nutrients from septic-system leachate, 

and runoff contaminated with fertilizer or animal waste. The 

ultimate intended use of water in the tributary streams is 

ultimately drinking water, which must meet specific waterquality standards. For this reason, Providence Water and the 

USGS closely monitor concentrations of these constituents in 

tributary streams. Median concentrations, loads, and yields of 

water-quality constituents are given in tables 7 and 8.

Bacteria

Median concentrations of total coliform and E. coli bacteria were above the detection limit (3 CFU/100 mL) at nearly 

all sites (table 7). Total coliform bacteria concentrations were 

in most cases equal to or greater than E. coli concentrations 

(as expected because total coliform is more inclusive); the 

median concentrations among all sites in the drainage basin 

were equal to 22 CFU/100 mL for total coliform bacteria and 

14 CFU/100 mL for E. coli bacteria. Median concentrations 

of total coliform and E. coli bacteria were greatest (1,205 

and 551 CFU/100 mL) at the Unnamed Tributary #2 to 

Scituate Reservoir (Providence Water Station 2) (table 7). 

Concentrations of fecal indicator bacteria in some cases were 

lowest at monitoring stations immediately downstream of 

subbasin reservoirs, such as station 23 at the outlet of the 

Ponaganset Reservoir.

Median daily loads and yields of total coliform and 

E. coli bacteria varied over three orders of magnitude; the 

highest median daily yield was at station 6 (Quonapaug 

Brook) in the Direct Runoff subbasin (table 8). Although relatively high for monitoring stations in the Scituate Reservoir 

subbasin, median daily bacteria yields at this station are low 

compared to yields of indicator bacteria in sewage-contaminated streamwater or streamwater influenced by stormwater 

runoff in an urban environment (Breault and others, 2002). 

The median of the median daily loads for both types of bacteria for the entire Scituate Reservoir drainage area ranged from 

4 to 7,740 CFU×106/day and 16 to 3,870 CFU×106/day/mi2

for yields of total coliform, from 4 to 4,590 CFU×106/day for 

loads of E. coli, and from about 12 to 2,300 CFU×106/day/mi2

for yields of E. coli (table 8).

Chloride

The highest median chloride concentration (60.4 mg/L) 

was measured in the Direct Runoff Subbasin at the Bear Tree 

Brook station (9) (table 7); this value compares well to the 

annual mean chloride concentration (51.9 mg/L) estimated 

from continuously monitored specific conductance at this 

station (table 5). Median daily chloride loads and yields varied 

among monitoring stations in the drainage area (table 8), but 

yields at most stations were within a factor of 2 of the median 

for the overall drainage area of about 12 kg/d/mi2, with a few 

exceptions (Bear Tree Brook (9), Moswansicut Reservoir (19), 

Unnamed Tributary #2 to Moswansicut Reservoir (21), and 

Westconnaug Brook (10)). Of these, samples measured at the 

Moswansicut Reservoir station (19) had the largest median 

daily chloride load (220 kg/d), whereas the largest median 

daily chloride yield was determined for Bear Tree Brook 

station (190 kg/d/mi2); this yield compares well with the 

annual mean chloride yield (68,200 kg/yr/mi2 (table 5) or about 

190 kg/d/mi2) measured at that station by using continuously 

measured specific-conductance records.

Nutrients

Median concentrations of nitrite and nitrate (table 7) 

were 0.002 and 0.02 mg/L as N, respectively. Relatively 

high concentrations of nitrite in Spruce Brook (5) at the 

Direct Runoff subbasin (0.035 mg/L as N) and nitrate at 

some monitoring sites, such as Moswansicut Reservoir (22) 

in the Moswansicut Reservoir subbasin (0.25 mg/L as N) 

and Unnamed Tributary #2 to Scituate Reservoir (2) in the 

Direct Runoff subbasin (0.225 mg/L as N), may be affected 

by nitrogen-enriched runoff or groundwater (Nimiroski and 

others, 2008). The median concentration of orthophosphate 

for the entire study area (table 7) was 0.03 mg/L as P. The 

maximum median concentration of orthophosphate (0.13 mg/L 

as P) was measured at Unnamed Tributary to Ponaganset 

River (27). Nutrient loadings from the Ponaganset River (35) 

into the Scituate Reservoir—nitrate (0.195 kg/d), nitrite 

(0.195 kg/d), and orthophosphate (0.325 kg/d)—were 

among the largest of all the sampled stations. Median daily 

nitrate loads for WY 2002 were larger at only two stations, 

Westconnaug Brook (8; 0.250 kg/d) and Bear Tree Brook 

(9; 0.315 kg/d). The largest median daily nutrient yield for 

nitrate (0.492 kg/d/mi2) was determined for Bear Tree Brook 

(9); at Spruce Brook (5) for nitrite (0.029 kg/d/mi2); and at 

Unnamed Tributary #2 to Moswansicut Reservoir (21) for 

orthophosphate (0.125 kg/d/mi2) (table 8). 
16 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 7. Median values for water-quality data collected at Providence Water stations by tributary reservoir subbasin in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; PCU, platinum cobalt units; 

NTU, nephelometric turbidity units; CFU/100mL, colony forming units per 100 milliliters; E. coli., Escherichia coli; mg/L, milligrams per liter; CaCO3, calcium 

carbonate; N, nitrate; P, phosphorus; <, less than; --, no data]

PW 

station 

No.

USGS 

station No. Station name pH 

(units)

Color 

(PCU)

Turbidity 

(NTU)

Total 

coliform 

bacteria 

(CFU/

100mL)

E. coli

(CFU/

100mL)

Alkalinity 

(mg/L as 

CaCO3)

Chloride 

(mg/L)

Nitrite 

(mg/L 

as N)

Nitrate 

(mg/L 

as N)

Orthophosphate 

(mg/L 

as P)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 6.2 44 0.9 5 5 4.2 19.1 0.002 0.015 0.02

25 01115200 Shippee Brook 6.1 27 0.5 8 8 4.4 8.7 0.001 0.025 0.03

26 01115185 Windsor Brook 6.2 33 0.4 12 12 4.2 19.8 0.001 0.015 0.04

27 011151845 Unnamed Tributary to Ponaganset 

River (Unnamed Brook B, 

Unnamed Brook West of 

Windsor Brook)

5.5 21 0.4 5 5 3.0 7.4 0.001 0.150 0.13

28 01115265 Barden Reservoir (Hemlock 

Brook)

5.8 70 0.7 23 23 4.4 20.4 0.002 <0.001 0.03

29 01115271 Ponaganset River (Barden Stream) -- -- -- -- -- -- -- -- -- --

35 01115187 Ponaganset River 6.3 30 0.6 9 23 5.1 15.9 0.015 0.015 0.03

Direct Runoff subbasin

1 01115180 Brandy Brook 6.6 55 1.5 23 23 9.4 10.1 0.003 0.045 0.04

2 01115181 Unnamed Tributary #2 to Scituate 

Reservoir (Unnamed Brook 

North of Bullhead Brook)

5.9 9 0.6 1,205 551 4.5 -- 0.001 0.225 0.08

3 01115280 Cork Brook 6.3 18 0.3 22 12 5.2 25.9 0.001 0.040 0.05

4 01115400 Kent Brook (Betty Pond Stream) 6.6 27 0.8 14 4 6.7 4.0 0.002 0.010 0.01

5 01115184 Spruce Brook 6.1 54 0.5 12 3 5.5 9.5 0.035 0.035 0.06

6 01115183 Quonapaug Brook 6.4 90 1.9 113 57 9.9 31.4 0.003 0.020 0.03

7 01115297 Wilbur Hollow Brook 6.3 133 1.2 14 19 7.1 9.0 0.004 <0.001 0.03

8 01115276 Westconnaug Brook (Westconnaug 

Reservoir)

6.1 12 0.4 <3 <3 3.1 9.1 0.001 0.020 0.02

9 01115275 Bear Tree Brook 6.5 32 0.4 23 23 7.6 60.4 0.001 0.160 0.04

30 01115350 Unnamed Tributary #4 to Scituate 

Reservoir (Coventry Brook, 

Knight Brook)

6.1 27 0.5 23 23 5.7 23.2 0.001 0.010 0.05

31 01115177 Toad Pond -- -- -- -- -- -- -- -- -- --

32 01115178 Unnamed Tributary #1 to Scituate 

Reservoir (Pine Swamp Brook)

6.6 68 0.9 75 23 8.6 6.7 0.002 0.050 0.03

33 01115182 Unnamed Tributary #3 to Scituate 

Reservoir (Hall’s Estate Brook)

6.2 18 0.3 23 3 6.3 9.0 0.002 0.040 0.04

36 -- Outflow from King Pond 6.4 22 0.3 12 -- 4.5 2.5 0.001 0.030 0.04

37 -- Fire Tower Stream 6.3 20 0.3 23 -- 4.8 3.0 0.001 0.025 0.05
Water Quality and Constituent Loads and Yields 17

Table 7. Median values for water-quality data collected at Providence Water stations by tributary reservoir subbasin in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; PCU, platinum cobalt units; 

NTU, nephelometric turbidity units; CFU/100mL, colony forming units per 100 milliliters; E. coli., Escherichia coli; mg/L, milligrams per liter; CaCO3, calcium 

carbonate; N, nitrate; P, phosphorus; <, less than; --, no data]

PW 

station 

No.

USGS 

station No. Station name pH 

(units)

Color 

(PCU)

Turbidity 

(NTU)

Total 

coliform 

bacteria 

(CFU/

100mL)

E. coli

(CFU/

100mL)

Alkalinity 

(mg/L as 

CaCO3)

Chloride 

(mg/L)

Nitrite 

(mg/L 

as N)

Nitrate 

(mg/L 

as N)

Orthophosphate 

(mg/L 

as P)

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, 

Moswansicut Pond)

6.7 15 1.6 7 16 9.1 26.5 0.002 0.020 0.03

20 01115160 Unnamed Tributary #1 to 

Moswansicut Reservoir 

(Blanchard Brook)

5.8 120 1.2 23 23 4.7 36.0 0.003 0.005 0.04

21 01115165 Unnamed Tributary #2 to 

Moswansicut Reservoir (Brook 

from Kimball Reservoir)

6.5 85 1.4 23 23 13.7 31.2 0.003 0.100 0.02

22 01115167 Moswansicut Reservoir 

(Moswansicut Stream South)

6.5 45 1.9 460 460 14.5 38.4 0.006 0.250 0.03

34 01115164 Kimball Stream 6.2 62 1.1 43 -- 14.5 28.6 0.003 0.001 0.01

Ponaganset Reservoir subbasin

23 011151843 Ponaganset Reservoir 5.4 8 0.6 <3 <3 1.9 9.9 0.001 0.060 0.02

Regulating Reservoir subbasin

13 01115176 Regulating Reservoir 6.6 17 0.6 <3 <3 8.8 26.0 0.001 0.010 0.01

14 01115110 Huntinghouse Brook 6.3 35 0.8 39 23 7.3 7.3 0.002 0.020 0.03

15 01115115 Regulating Reservoir 

(Rush Brook)

6.5 61 0.9 23 23 10.5 23.6 0.002 0.010 0.04

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

6.6 28 1.0 23 23 11.2 25.5 0.002 0.020 0.02

17 01115119 Dexter Pond (Paine Pond) 5.8 78 0.7 <3 <3 5.6 19.7 0.002 0.005 0.03

18 01115120 Unnamed Tributary to Regulating 

Reservoir (Unnamed Brook A)

6.2 50 0.5 121 4 7.8 10.0 0.001 0.030 0.04

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 5.2 23 0.3 4 4 2.0 17.6 0.001 0.015 0.02

11 01115273 Unnamed Tributary to 

Westconnaug Reservoir 

(Unnamed Brook South of 

Westconnaug Reservoir)

5.5 90 0.7 <3 <3 3.8 0.67 0.003 0.010 0.03

12 011152745 Unnamed Tributary to Westconnaug Brook (Unnamed Brook 

north of Westconnaug reservoir)

6.0 18 0.9 4 4 4.1 9.1 0.001 0.010 0.01

Scituate Reservoir basin

Median 6.2 32 0.7 22 14 5.6 16.8 0.002 0.020 0.03
18 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island Table 8. Median daily loads and yields of bacteria, chloride, nitrate, nitrite, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued [Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; CFU×106/d, millions of colony forming units per day; CFU×106/mi2, millions of colony forming units per square mile; E. coli, Escherichia coli; kg/d, kilograms per day; kg/d/mi2, kilograms per day per square mile] PW station No. USGS station No. Station name Total coliform bacteria E. coli Chloride Nitrate (as N) Nitrite (as N) Orthophosphate (as P) (CFU×106/d) (CFU×106/mi2

) (CFU×106/d) (CFU×106/mi2

) (kg/d) (kg/d/mi2

) (kg/d) (kg/d/mi2

) (kg/d) (kg/d/mi2

) (kg/d) (kg/d/mi2

)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 210 41 210 41 21 4.2 0.015 0.003 0.002 0.0004 0.015 0.003

25 01115200 Shippee Brook 41 17 41 17 19 7.8 0.050 0.021 0.002 0.001 0.035 0.01526 01115185 Windsor Brook 110 27 110 27 51 12 0.025 0.006 0.003 0.001 0.085 0.02028 01115265 Barden Reservoir 1,160 110 770 73 196 18 0.020 0.002 0.025 0.002 0.135 0.01335 01115187 Ponaganset River 1,730 120 1,280 89 168 12 0.195 0.014 0.195 0.014 0.325 0.023

Direct Runoff subbasin

1 01115180 Brandy Brook 1,260 790 990 620 29 18 0.115 0.072 0.007 0.004 0.110 0.0693 01115280 Cork Brook 140 76 130 67 11 5.7 0.060 0.032 0.001 0.0004 0.020 0.0114 01115400 Kent Brook 79 92 28 33 2 2.1 0.002 0.002 0.001 0.001 0.003 0.0045 01115184 Spruce Brook 68 56 68 56 14 11 0.035 0.029 0.035 0.029 0.105 0.0886 01115183 Quonapaug Brook 7,740 3,870 4,590 2,300 47 23 0.020 0.010 0.010 0.005 0.070 0.0357 01115297 Wilbur Hollow Brook 440 99 330 75 16 3.6 0.005 0.001 0.008 0.002 0.065 0.0158 01115276 Westconnaug Brook 300 58 300 58 130 25 0.250 0.049 0.010 0.002 0.225 0.0449 01115275 Bear Tree Brook 200 320 200 320 120 190 0.315 0.492 0.002 0.003 0.080 0.125

32 01115178 Unnamed Tributary #1 

to Scituate Reservoir (Pine Swamp Brook)

830 2,060 250 630 6.3 16 0.052 0.129 0.001 0.003 0.020 0.050

33 01115182 Unnamed Tributary #3 

to Scituate Reservoir (Hall’s Estate Brook)

4 16 4 16 2.6 9.8 0.030 0.111 0.001 0.002 0.010 0.037

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

370 120 950 300 220 68 0.040 0.013 0.020 0.006 0.170 0.053

21 01115165 Unnamed Tributary #2 

to Moswansicut Reservoir (Brook from Kimball Reservoir)

480 1,510 480 1,510 43 136 0.130 0.406 0.004 0.013 0.040 0.125
Water Quality and Constituent Loads and Yields 19

Table 8. Median daily loads and yields of bacteria, chloride, nitrate, nitrite, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; CFU×106/d, millions of colony forming units per day; CFU×106/mi2, 

millions of colony forming units per square mile; E. coli, Escherichia coli; kg/d, kilograms per day; kg/d/mi2, kilograms per day per square mile]

PW 

station 

No.

USGS 

station No. Station name

Total coliform bacteria E. coli Chloride Nitrate (as N) Nitrite (as N) Orthophosphate (as P)

(CFU×106/d) (CFU×106/mi2) (CFU×106/d) (CFU×106/mi2) (kg/d) (kg/d/mi2) (kg/d) (kg/d/mi2) (kg/d) (kg/d/mi2) (kg/d) (kg/d/mi2)

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 3,190 510 920 150 15 2.4 0.085 0.014 0.005 0.001 0.130 0.021

15 01115115 Regulating Reservoir 

(Rush Brook)

1,090 220 810 160 21 4.1 0.035 0.007 0.009 0.002 0.190 0.038

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

1,350 280 490 100 68 14 0.040 0.008 0.010 0.002 0.105 0.021

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

1,060 1,960 6 12 7.1 13 0.001 0.001 0.0004 0.001 0.010 0.019

Wesconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 340 240 340 240 91 65 0.040 0.029 0.008 0.005 0.090 0.064

11 01115273 Unnamed Tributary to 

Westconnaug Reservoir (Unnamed Brook South of Westconnaug Reservoir)

30 44 30 44 3.0 4.3 0.002 0.003 0.004 0.006 0.060 0.087

Scituate Reservoir basin

Median 370 120 300 75 21 12 0.040 0.014 0.005 0.002 0.080 0.035
20 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Nimiroski, M.T., DeSimone, L.A., and Waldron, M.C., 2008, 

Water-quality conditions and constituent loads, 1996–2002, 

and water-quality trends, 1983–2002, in the Scituate Reservoir drainage area, Rhode Island: U.S. Geological Survey 

Scientific Investigations Report 2008–5060, 55 p.

Nimiroski, M.T., and Waldron, M.C., 2002, Sources of sodium 

and chloride in the Scituate Reservoir drainage basin, 

Rhode Island: U.S. Geological Survey Water-Resources 

Investigations Report 02–4149, 16 p.

Providence Water Supply Board Water Quality Laboratory, 

2003, Quality Assurance Program Manual: Providence 

Water Supply Board, variously paged. 

Ries, K.G., III, and Friesz, P.J., 2000, Methods for 

estimating low-flow statistics for Massachusetts streams: 

U.S. Geological Survey Water-Resources Investigations 

Report 00–4136, 81 p.

Socolow, R.S., Girouard, G.G., and Ramsbey, L.R., 2003, 

Water resources data for Massachusetts and Rhode Island, 

2002: U.S. Geological Survey Water-Data Report MA-RI02-1, 340 p.

Tasker, G.D., and Driver, N.E., 1988, Nationwide regression models for predicting urban runoff water quality at 

unmonitored sites: Water Resources Bulletin, v. 24, no. 5, 

p. 1090–1101.

U.S. Geological Survey, 2006, National Water Information 

System, accessed November 17, 2008, at http://waterdata.

usgs.gov/nwis

Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, 

B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record computation, and data reporting: U.S. Geological Survey Techniques and Methods 1–D3, 51 p., 8 attachments, accessed 

April 10, 2006, at http://pubs.water.usgs.gov/tm1d3

References Cited

Breault, R.F., Sorenson, J.R., and Weiskel, P.K., 2002, Streamflow, water quality, and contaminant loads in the lower 

Charles River watershed, Massachusetts, 1999–2000: 

U.S. Geological Survey Water-Resources Investigations 

Report 02–4137, 131 p.

Breault, R.F., Waldron, M.C., Barlow, L.K., and Dickerman, 

D.C., 2000, Water-quality conditions in relation to drainage 

basin characteristics in the Scituate Reservoir basin, Rhode 

Island, 1982–95: U.S. Geological Survey Water-Resources 

Investigations Report 00–4086, 46 p.

Granato, G.E., 2008, Computer programs for obtaining and 

analyzing daily-mean streamflow data from the U.S. Geological Survey National Water Information System Web 

Site: U.S. Geological Survey Open-File Report 2008–1362, 

CD-ROM. 

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: New York, Elsevier, Studies in Environmental Science 49, 522 p.

Hirsch, R.M., 1982, A comparison of four streamflow record 

extension techniques: Water Resources Research, v. 18, 

no. 4, p. 1081–1088.

Hirsch, R.M., and Gilroy, E.J., 1984, Methods of fitting a 

straight line to data—Examples in water resources: Water 

Resources Bulletin, v. 20, no. 5, p. 705–711.

National Institute of Standards and Technology/SEmiconductor MAnufacturing TECHnology, 2003, NIST/SEMATECH 

e-Handbook of Statistical Methods, accessed April 15, 

2008, at http://www.itl.nist.gov/div898/handbook/.
Table 3 21

Table 3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary reservoir subbasin, in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; ft3/s, cubic feet per 

second; CFU×106/d, millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; --, no data]

PW 

station 

No.

USGS 

station 

No.

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total 

coliform 

bacteria

(CFU×106/d)

E. coli

(CFU×106/d)

Chloride

(kg/d)

Nitrate

(kg/d 

as N)

Nitrite

(kg/d 

as N)

Orthophosphate

(kg/d as P)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 10/5/2001 0.13 140 140 6.1 0.0032 0.0006 0.0064

11/2/2001 0.14 5 5 7.2 0.0100 0.0007 0.0034

12/7/2001 0.27 10 10 15 0.0100 0.0007 0.0100

1/3/2002 0.37 14 14 20 0.0091 0.0018 0.0100

2/1/2002 5.6 210 210 248 0.2700 0.0200 0.2700

3/1/2002 5.7 210 210 286 0.1300 0.0200 0.1300

4/5/2002 11.0 400 400 498 0.2600 0.0200 0.2600

5/16/2002 13.0 2,860 2,860 595 0.6300 -- 0.3100

6/7/2002 26.0 47,700 47,700 1,070 0.6300 0.1200 1.9

7/5/2002 0.47 260 260 22 0.0006 0.0034 0.0200

8/2/2002 0.26 590 590 6.6 0.0100 0.0019 0.0032

9/6/2002 0.08 86 18 3.9 0.0200 0.0002 0.0040

25 01115200 Shippee Brook 10/19/2001 0.03 13 13 0.70 0.0009 0.0001 0.0100

1/18/2002 1.3 48 48 37 0.0900 0.0032 0.0600

4/19/2002 3.2 120 120 75 0.1500 0.0078 0.2300

7/19/2002 0.06 35 35 1.0 0.0100 0.0002 0.0045

26 01115185 Windsor Brook 10/19/2001 0.07 43 43 4.0 0.0019 0.0002 0.0400

1/18/2002 1.9 70 70 98 0.0400 0.0046 0.1300

4/19/2002 4.3 160 160 195 0.2100 0.0100 0.2100

7/19/2002 0.12 700 700 3.6 0.0100 0.0006 0.0100

28 01115265 Barden Reservoir 10/9/2001 0.41 90 40 24 0.0005 0.0030 0.0300

11/13/2001 0.57 1,300 600 39 0.0007 0.0028 0.0400

12/11/2001 1.1 1,160 1,160 67 0.0200 0.0054 0.0800

1/15/2002 8.9 5,010 5,010 335 0.2100 0.0400 0.6500

2/12/2002 18.0 10,100 10,100 784 0.4400 0.0400 0.4400

3/12/2002 18.0 660 660 744 0.0200 0.0400 1.3

4/9/2002 16.0 590 3,520 2,350 0.0300 18 0.1900

5/14/2002 103 108,000 108,000 4,790 0.1200 1.0 7.6

6/11/2002 9.9 -- -- 324 0.0100 0.0700 0.9600

7/9/2002 0.95 2,160 70 46 0.0012 0.0100 0.0600

8/13/2002 0.21 770 770 11 0.0200 0.0010 0.0051

9/10/2002 0.18 100 18 9.8 0.0088 0.0004 0.0044

35 01115187 Ponaganset River 10/5/2001 1.4 310 790 55 0.0300 0.0300 0.1700

11/2/2001 1.8 400 1,890 73 0.0022 0.0022 0.0800

12/7/2001 2.5 92 1,280 106 0.1200 0.1200 0.1200

1/3/2002 3.8 840 -- 214 0.2700 0.2700 0.1800

2/1/2002 17.0 1,660 -- 620 2.1 2.1 1.2

3/1/2002 14.0 510 -- 541 0.0100 0.0100 0.3400

4/5/2002 28.0 2,740 -- 973 1.4 1.4 0.6800

5/16/2002 47.0 10,300 -- 1,670 1.1 1.1 3.4

6/7/2002 127 1,430,000 -- 3,570 3.1 3.1 9.3

7/5/2002 3.2 1,800 -- 121 0.3100 0.3100 0.3100

8/2/2002 0.65 17,500 -- 29 0.0600 0.0600 0.0079

9/6/2002 1.1 2,500 -- 44 0.0200 0.0200 0.7800
22 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary reservoir subbasin, in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; ft3/s, cubic feet per 

second; CFU×106/d, millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; --, no data]

PW 

station 

No.

USGS 

station 

No.

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total 

coliform 

bacteria

(CFU×106/d)

E. coli

(CFU×106/d)

Chloride

(kg/d)

Nitrate

(kg/d 

as N)

Nitrite

(kg/d 

as N)

Orthophosphate

(kg/d as P)

Direct Runoff subbasin

1 01115180 Brandy Brook 10/2/2001 0.42 2,470 240 10 0.0700 0.0021 0.0400

11/6/2001 0.42 41 15 11 0.0400 0.0005 0.0300

12/19/2001 1.2 1,260 1,260 30 0.2600 0.0059 0.2000

1/8/2002 1.1 110 110 29 0.2100 0.0081 0.0500

2/5/2002 2.5 240 240 62 0.5500 0.0100 0.2400

3/5/2002 4.5 990 990 101 0.1100 0.0300 0.2200

4/3/2002 4.9 2,760 2,760 87 0.3500 0.0300 0.7100

5/6/2002 3.3 6,050 6,050 62 0.1600 0.0200 0.1600

6/4/2002 1.7 -- -- 30 0.1200 0.0100 0.1600

7/30/2002 0.62 3,640 3,640 17 0.0700 0.0030 0.0600

8/6/2002 0.40 230 230 9.1 0.0100 0.0010 0.0300

9/3/2002 0.37 4,160 2,170 9.7 0.0800 0.0018 0.0200

3 01115280 Cork Brook 10/4/2001 0.08 43 30 3.9 0.0200 0.0002 0.0100

11/1/2001 0.07 16 7 5.0 0.0035 0.0002 0.0100

12/6/2001 0.14 -- -- 11 0.0100 0.0007 0.0200

2/7/2002 1.5 55 55 105 0.6900 0.0073 0.0100

3/7/2002 3.5 130 130 222 1.3 0.0086 0.0800

4/4/2002 5.1 2,870 2,870 331 0.0062 0.0100 0.9900

5/17/2002 4.3 160 160 226 0.2100 0.0100 0.3100

6/6/2002 3.1 34,900 34,900 133 0.2200 0.0100 0.3700

7/29/2002 0.23 130 51 11 0.0900 0.0006 0.0700

8/1/2002 0.14 3,770 3,770 6.8 0.0600 0.0003 0.0100

9/5/2002 0.05 320 130 4.2 0.0054 0.0001 0.0013

4 01115400 Kent Brook 10/2/2001 0.01 88 1 0.10 0.0004 0.00004 0.0002

12/19/2001 0.14 -- -- 1.3 0.0200 0.0007 0.0034

1/8/2002 0.12 4 4 1.8 0.0029 0.0012 0.0029

2/5/2002 0.70 26 26 6.0 0.0009 0.0034 0.0086

3/5/2002 2.5 240 240 20 0.1200 0.0061 0.0300

4/3/2002 3.1 110 110 30 0.1500 0.0100 0.5300

5/6/2002 1.3 730 730 13 0.0016 0.0095 0.0600

6/4/2002 0.32 31 31 3.3 0.0078 0.0008 0.0100

7/30/2002 0.03 210 210 0.40 0.0009 0.0002 0.0018

8/6/2002 0.01 8 8 0.10 0.00002 0.00003 0.0002

9/3/2002 0.01 70 1 0.10 0.0003 0.00003 0.0001

5 01115184 Spruce Brook 10/16/2001 0.08 46 8 5.6 0.0100 0.0100 0.0100

1/31/2002 1.7 62 62 65 0.5400 0.5400 0.3300

4/16/2002 2.8 100 100 22 0.0600 0.0600 0.2000

7/16/2002 0.13 73 73 0.90 0.0002 0.0002 0.0064

6 01115183 Quonapaug Brook 10/2/2001 0.22 12,900 5,920 17 0.0200 0.0011 0.0200

11/6/2001 0.22 810 59 17 0.0003 0.0011 0.0200

12/19/2001 0.96 -- -- 75 0.0012 0.0094 0.0700

3/5/2002 6.7 12,300 12,300 344 0.9800 0.0400 0.6500

4/3/2002 7.7 4,330 1,700 345 0.3700 0.0500 0.5600

5/6/2002 5.8 3,260 3,260 57 0.2800 0.0400 0.4200

6/4/2002 1.7 3,120 1,620 9.6 0.0021 0.0100 0.3300

7/30/2002 0.39 22,900 22,900 47 0.0095 0.0048 0.0200

9/3/2002 0.19 11,200 11,200 18 0.0600 0.0014 0.0100
Table 3 23

Table 3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary reservoir subbasin, in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; ft3/s, cubic feet per 

second; CFU×106/d, millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; --, no data]

PW 

station 

No.

USGS 

station 

No.

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total 

coliform 

bacteria

(CFU×106/d)

E. coli

(CFU×106/d)

Chloride

(kg/d)

Nitrate

(kg/d 

as N)

Nitrite

(kg/d 

as N)

Orthophosphate

(kg/d as P)

Direct Runoff subbasin—Continued

7 01115297 Wilbur Hollow Brook 10/4/2001 0.32 590 590 6.7 0.0004 0.0031 0.0800

11/1/2001 0.27 10 10 7.4 0.0003 0.0026 0.0300

12/6/2001 0.52 290 290 13 0.0200 0.0051 0.0300

1/2/2002 0.73 27 27 17 0.0009 0.0071 0.0500

2/7/2002 4.4 160 160 83 0.0054 0.0300 0.0500

3/7/2002 9.8 360 360 230 0.0100 0.0400 0.7100

4/4/2002 14.0 510 14,700 2,530 0.0600 27 0.1700

5/17/2002 12.0 1,170 1,170 161 0.0100 0.0800 0.5800

6/6/2002 8.8 9,260 9,260 77 0.0100 0.0800 0.6400

7/29/2002 0.81 4,750 300 15 0.0010 0.0079 0.3300

8/1/2002 0.50 780 780 9.4 0.0006 0.0006 0.0100

9/5/2002 0.21 120 120 6.1 0.0051 0.0015 0.0200

8 01115276 Westconnaug Brook 11/9/2001 3.1 110 110 64 0.1500 0.0076 0.0700

12/20/2001 4.6 -- -- 95 0.3300 0.0100 0.3300

2/8/2002 6.8 250 250 143 0.1600 0.0100 0.0800

3/8/2002 8.5 310 310 202 0.4100 0.0200 0.2000

4/12/2002 8.2 300 300 321 0.0200 12 0.4000

5/10/2002 8.0 290 290 188 0.3900 0.0100 2.0

6/14/2002 6.8 -- -- 108 0.1600 0.0100 0.1600

7/12/2002 3.5 340 340 86 0.2500 0.0043 0.2500

9 01115275 Bear Tree Brook 10/16/2001 0.36 200 200 60 0.1700 0.0009 0.1000

1/31/2002 1.3 -- -- 167 0.7300 0.0032 0.0600

4/16/2002 1.6 59 59 189 0.4600 0.0039 0.1100

7/16/2002 0.44 1,000 1,000 80 0.0200 0.0011 0.0400

32 01115178 Unnamed Tributary #1 

to Scituate Reservoir 

(Pine Swamp Brook)

10/18/2001 0.06 -- -- 0.01 0.0033 0.0003 0.0100

1/30/2002 0.45 830 250 12 0.1900 0.0022 0.0300

4/18/2002 0.55 54 54 16 0.1000 0.0027 0.0400

7/18/2002 0.08 910 910 0.50 0.0020 0.0004 0.0020

33 01115182 Unnamed Tributary #3 

to Scituate Reservoir 

(Hall’s Estate Brook)

10/24/2001 0.00 3 1 0.10 0.0001 0.00001 0.0004

1/23/2002 0.12 4 4 2.6 0.0400 0.0006 0.0100

4/24/2002 0.31 170 23 6.7 0.0300 0.0008 0.0100

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut 

Stream North, Moswansicut Pond)

10/11/2001 0.28 160 160 18 0.0100 0.0007 0.0300

11/8/2001 0.42 11,300 4,730 28 0.0400 0.0041 0.1700

2/14/2002 5.0 180 5,260 183 0.0300 9.3 0.3600

3/14/2002 7.2 1,580 260 468 1.2 0.0300 0.5200

4/11/2002 6.3 230 1,390 293 0.0300 15 0.9200

5/9/2002 5.3 520 520 362 0.7700 0.0200 0.1200

6/13/2002 3.5 -- -- 217 0.1700 0.0086 0.0400
24 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island

Table 3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary reservoir subbasin, in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; ft3/s, cubic feet per 

second; CFU×106/d, millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; --, no data]

PW 

station 

No.

USGS 

station 

No.

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total 

coliform 

bacteria

(CFU×106/d)

E. coli

(CFU×106/d)

Chloride

(kg/d)

Nitrate

(kg/d 

as N)

Nitrite

(kg/d 

as N)

Orthophosphate

(kg/d as P)

Moswansicut Reservoir subbasin—Continued

21 01115165 Unnamed Tributary #2 

to Moswansicut Reservoir (Brook from 

Kimball Reservoir)

1/25/2002 0.57 21 21 43 0.1300 0.0042 0.0800

4/26/2002 0.86 480 480 68 0.2100 0.0042 0.0400

7/26/2002 0.11 3,290 1,540 6.0 0.0027 0.0007 0.0027

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 10/1/2001 0.20 1,170 1,170 3.4 0.0098 0.0005 0.0100

11/5/2001 0.16 90 6 0.02 0.0002 0.0008 0.0200

12/3/2001 0.28 290 290 4.8 0.0100 0.0003 0.1300

1/7/2002 1.2 680 680 26 0.2600 0.0088 0.0500

2/4/2002 6.6 650 650 145 0.6400 0.0100 0.4800

3/4/2002 37.0 8,150 20,800 824 1.8 0.1800 1.8

4/1/2002 43.0 41,000 1,580 957 2.1 0.2100 7.4

5/6/2002 9.4 3,450 8,970 156 0.6800 0.0400 0.2200

6/3/2002 3.3 3,470 1,210 61 0.1600 0.0081 0.4800

7/1/2002 0.87 3,190 320 0.40 0.0011 0.0021 0.0600

8/5/2002 0.21 12,300 120 2.8 0.0100 0.0015 0.0100

9/16/2002 0.12 -- 7,040 2.5 0.0100 0.0009 --

15 01115115 Regulating Reservoir 

(Rush Brook)

10/1/2001 0.18 1,060 1,060 16 0.0002 0.0004 0.0100

11/5/2001 0.14 5 5 16 0.0034 0.0003 0.0200

12/3/2001 0.24 9 9 22 0.0059 0.0003 0.0100

1/7/2002 1.0 560 560 7.6 0.1400 0.0073 0.0400

2/4/2002 5.1 1,120 1,120 397 0.6200 0.0200 0.3700

3/4/2002 27.0 15,200 15,200 1,510 2.6 0.1300 0.6600

4/1/2002 31.0 32,600 32,600 1,600 1.5 0.2200 12

5/6/2002 7.2 4,050 530 426 0.0088 0.0300 0.7000

6/3/2002 2.6 2,480 2,480 20 0.0600 0.0100 0.3100

7/1/2002 0.72 410 410 15 0.0100 0.0053 0.0700

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

10/1/2001 0.69 390 25 41 0.0100 0.0034 0.1600

11/5/2001 0.59 330 330 34 0.0200 0.0014 0.0100

12/3/2001 0.87 490 490 52 0.0400 0.0011 0.0400

1/7/2002 2.4 1,350 1,350 219 0.3500 0.0100 0.0500

2/4/2002 7.8 290 290 727 1.9 0.0300 0.3800

3/4/2002 26.0 47,700 14,600 2,230 3.8 0.1200 3.2

4/1/2002 29.0 170,000 16,300 2,450 2.8 0.0700 0.3500

5/6/2002 10.0 5,630 980 739 0.0100 0.0400 0.4800

6/3/2002 4.8 1,060 1,060 68 0.1100 0.0200 --

7/1/2002 1.9 11,200 330 35 0.0400 0.0100 0.0200

8/5/2002 0.71 4,170 400 44 0.0100 0.0017 0.0087

18 01115120 Unnamed Tributary to 

Regulating Reservoir 

(Unnamed Brook A)

1/25/2002 0.17 6 6 18 0.0100 0.0004 0.0100

4/26/2002 0.36 2,110 2,110 7.1 0.0004 0.0026 0.0400

7/26/2002 0.01 -- 1 0.20 0.0006 0.0000 0.0006
Table 3 25

Table 3. Daily loads of bacteria, chloride, nitrate, nitrite, and orthophosphate, by tributary reservoir subbasin, in the Scituate 

Reservoir drainage area, Rhode Island, October 1, 2001, through September 30, 2002.—Continued

[Water-quality data are from samples collected and analyzed by Providence Water (PW); USGS, U.S. Geological Survey; No., number; ft3/s, cubic feet per 

second; CFU×106/d, millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; --, no data]

PW 

station 

No.

USGS 

station 

No.

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total 

coliform 

bacteria

(CFU×106/d)

E. coli

(CFU×106/d)

Chloride

(kg/d)

Nitrate

(kg/d 

as N)

Nitrite

(kg/d 

as N)

Orthophosphate

(kg/d as P)

Wesconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 12/11/2001 0.17 96 96 5.9 0.0042 0.0004 0.0083

1/15/2002 1.7 170 170 71 0.2400 0.0042 0.0400

2/12/2002 3.5 340 340 173 0.1700 0.0086 0.0800

3/12/2002 3.5 3,680 3,680 132 0.1700 0.0086 0.1700

4/9/2002 3.1 300 300 89 0.0038 0.0076 0.7500

5/14/2002 24.0 880 2,350 1,350 0.0500 17 180

6/11/2002 1.9 21,400 11,200 93 0.0400 0.0093 0.0900

7/9/2002 0.15 -- -- 6.7 0.0073 0.0002 --

11 01115273 Unnamed Tributary 

to Westconnaug 

Reservoir 

(Unnamed Brook 

South of Westconnaug Reservoir)

10/23/2001 0.03 1 1 0.04 0.0008 0.0003 0.0047

1/22/2002 0.83 30 30 3.0 0.0600 0.0041 0.0600

4/23/2002 1.9 2,000 70 3.1 0.0023 0.0100 0.0900
Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Office of the Deputy Director

U.S. Geological Survey

Rhode Island Subdistrict Office

42 Albion Road, Suite 107

Lincoln, RI 02865

rbreault@usgs.gov

or visit our Web site at:

http://ri.water.usgs.gov
Breault—Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, Water Year 2002—Open-File Report 2009–1041

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