Prepared in cooperation with the Providence Water Supply Board

Streamflow, Water Quality, and Constituent Loads and 

Yields, Scituate Reservoir Drainage Area, Rhode Island, 

Water Year 2011

Open-File Report 2013–1127 

Version 1.1, July 2014

U.S. Department of the Interior

U.S. Geological Survey
Cover. Photograph shows Hemlock Brook.
Streamflow, Water Quality, and Constituent 

Loads and Yields, Scituate Reservoir 

Drainage Area, Rhode Island, Water 

Year 2011

By Kirk P. Smith 

Prepared in cooperation with the Providence Water Supply Board

Open-File Report 2013–1127

Version 1.1, July 2014

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia

First release: 2013

Revised: July 2014 (ver. 1.1)

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Smith, K.P., 2014, Streamflow, water quality, and constituent loads and yields, Scituate Reservoir drainage area, 

Rhode Island, water year 2011 (ver. 1.1, July 2014): U.S. Geological Survey Open-File Report 2013–1127, 32 p., 

http://pubs.usgs.gov/of/2013/1127/.
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........................................................................8

Streamflow....................................................................................................................................................10

Water Quality and Constituent Loads and Yields ...................................................................................10

Sodium and Chloride Loads and Yields Estimated from Specific-Conductance 

Monitoring Data.....................................................................................................................10

Physical and Chemical Properties and Daily Loads and Yields Estimated from Data

Collected by the Providence Water Supply Board..........................................................14

Physical and Chemical Properties..........................................................................................14

Constituent Concentrations and Daily Loads and Yields.....................................................14

Bacteria.......................................................................................................................................22

Chloride........................................................................................................................................22

Nutrients......................................................................................................................................22

References Cited..........................................................................................................................................23

Figures

1. Map showing locations of tributary-reservoir subbasins and streamgage 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

streamgage on Quonapaug Brook at North Scituate (01115183) for water year 2011

and streamflow measurements at this streamgage on the dates (represented by

points) when water-quality samples were collected ............................................................9

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

continuous-record streamgage on the Ponaganset River at South Foster (01115187)

in the Scituate Reservoir drainage area, Rhode Island, for October 1, 2010, through

September 30, 2011, and mean daily streamflow for October 1, 1994, through

September 30, 2010.....................................................................................................................11

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, 2010, to September 30, 2011 ....................................................................................................4

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

Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through

September 30, 2011.......................................................................................................................6
iv

3. Regression equation coefficients used to estimate concentrations of chloride

and sodium from values of specific conductance for each U.S. Geological Survey

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

2010, through September 30, 2011..............................................................................................8

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

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

October 1, 2010, through September 30, 2011 ........................................................................24

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

measurements of specific conductance in the Scituate Reservoir drainage area,

Rhode Island, October 1, 2010, through September 30, 2011...............................................12

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

station in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010,

through September 30, 2011......................................................................................................15

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

Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011 ..16

8. Median values for water-quality data collected at Providence Water Supply Board

stations, by tributary reservoir subbasin in the Scituate Reservoir drainage area

Rhode Island, October 1, 2010, through September 30, 2011...............................................18

9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and

orthophosphate by tributary reservoir subbasin, in the Scituate Reservoir drainage

area Rhode Island, October 1, 2010, through September 30, 2011 .....................................20

 Conversion Factors and Datum

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)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).

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 either in grams or kilograms (or millions 

of colony forming units for bacteria) per day, month, or year, and yields are given in grams 

or kilograms (or millions of colony forming units for bacteria) per day, month, or year per 

square mile.
v

Abbreviations

CFU colony forming units

E. coli Escherichia coli

MOVE.1 Maintenance of Variance Extension type 1

NWIS National Water Inventory System

NTU nephelometric turbidity units

PCU platinum cobalt units

PWSB Providence Water Supply Board

RIDEM Rhode Island Department of Environmental Management

USGS U.S. Geological Survey

WY water year
vi

This page has been left blank intentionally.
Streamflow, Water Quality, and Constituent 

Loads and Yields, Scituate Reservoir 

Drainage Area, Rhode Island, Water Year 2011

By Kirk P. Smith

Abstract

Streamflow and concentrations of sodium and chloride estimated from records of specific 

conductance were used to calculate loads of sodium and chloride during water year (WY) 2011 

(October 1, 2010, to September 30, 2011), for tributaries to the Scituate Reservoir, Rhode Island. 

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

(USGS) or the Providence Water Supply Board (PWSB). Streamflow was measured or estimated 

by the USGS following standard methods at 23 streamgages; 14 of these streamgages were also 

equipped with instrumentation capable of continuously monitoring water level, specific conductance, 

and water temperature. Water-quality samples also were collected at 37 sampling stations by the 

PWSB and at 14 continuous-record streamgages by the USGS during WY 2011 as part of a longterm sampling program; all stations were in the Scituate Reservoir drainage area. Water-quality data 

collected by PWSB 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 water-quality constituents for WY 2011.

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

USGS) contributed a mean streamflow of about 37 cubic feet per second (ft3/s) to the reservoir 

during WY 2011. For the same time period, annual mean1 streamflows measured (or estimated) 

for the other monitoring stations in this study ranged from about 0.5 to about 21ft3/s. Together, 

tributaries (equipped with instrumentation capable of continuously monitoring specific conductance) 

transported about 1,600,000 kg (kilograms) of sodium and 2,600,000 kg of chloride to the Scituate 

Reservoir during WY 2011; sodium and chloride yields for the tributaries ranged from 9,800 to 

53,000 kilograms per square mile (kg/mi2) and from 15,000 to 90,000 kg/mi2, respectively.

At the stations where water-quality samples were collected by the PWSB, the median 

of the median chloride concentrations was 20.0 milligrams per liter (mg/L), median nitrite 

concentration was 0.002 mg/L as nitrogen (N), median nitrate concentration was 0.01 mg/L as N, 

median orthophosphate concentration was 0.07 mg/L as phosphorus, and median concentrations 

of total coliform and Escherichia coli (E. coli) bacteria were 33 and 23 colony forming units 

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

yields) of chloride, nitrite, nitrate, orthophosphate, and total coliform and E. coli bacteria were 

230 kilograms per day (kg/d) (80 kilograms per day per square mile (kg/d/mi2)); 10 grams 

per day (g/d) (6.3 grams per day per square mile (g/d/mi2)); 110 g/d (29 g/d/mi2); 610 g/d 

(270 g/d/mi2); 4,600 million colony forming units per day (CFUx106/d) (2,500 CFUx106/d/mi2); and 

1,800 CFUx106/d (810 CFUx106/d/mi2), respectively.

1

 The arithmetic mean of the individual daily mean discharges for the year noted or for the designated period. 
2 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

Introduction

The Scituate Reservoir is the primary source of drinking 

water for more than 60 percent of the population of Rhode 

Island (R.I.). It covers about 94 square miles (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 tributaries is important for management 

of the water supply and for the protection of human health. 

The Providence Water Supply Board (PWSB), 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 60 years.

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

cooperating with the PWSB and the Rhode Island Department 

of Environmental Management (RIDEM) to measure 

streamflow in tributaries to the Scituate Reservoir. Since 2009, 

streamflow has been continuously measured at 14 streamgages 

in the drainage area and periodically measured at 9 additional 

streamgages on tributaries in the drainage area. At these 

9 partial-record streamgages, daily mean streamflow has been 

estimated by using methods developed by the USGS (Hirsch, 

1982). The USGS also has been continuously measuring 

specific conductance at 14 monitoring stations since 2009. 

Equations that relate specific conductance to concentrations 

of sodium and chloride in streamwater were developed as part 

of a previous USGS/ PWSB 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.

Currently (2011), the PWSB regularly collects waterquality samples from 37 tributaries, either monthly or 

quarterly. Water-quality results are summarized by station 

number and constituent or parameter in annual reports 

published by the PWSB. In addition, the USGS has published 

reports that have compiled and tabulated streamflow 

(measured or estimated by the USGS) and water-quality 

data (collected by the PWSB) (Breault and others, 2000; 

Nimiroski and others, 2008; Breault, 2010; Breault and 

Campbell, 2010a,b,c,d; Breault and Smith, 2010; Smith and 

Breault, 2011).

This report presents data on streamflow, water quality, 

and loads and yields of selected constituents for water year 

(WY) 20112 in the Scituate Reservoir drainage area. These 

data were collected as parts of studies done by the USGS in 

cooperation with the PWSB and the RIDEM. A summary 

of measured and estimated streamflows is presented for 

the 14 continuous-record and 9 partial-record streamgages 

in the drainage area. Estimated monthly and annual loads 

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

14 streamgages at which specific conductance is continuously 

monitored by the USGS. Summary statistics for water-quality 

2

 October 1, 2010, to September 30, 2011.

data collected by the PWSB for 37 sampling stations 

during WY 2011 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 the PWSB (table 1). Streamflow was measured 

or estimated by the USGS at 23 streamgages. Measured 

and estimated streamflows are necessary to estimate water 

volume and water-quality constituent loads and yields from 

tributary basins. Stream stage is measured every 10 minutes 

at most continuous-record streamgages. Streamflow is 

computed with a stage-discharge relation (or rating), which 

is developed on the basis of periodic manual measurements 

of streamflow. Daily mean streamflow at a streamgage is 

calculated by dividing the total volume of water that passes 

the streamgage each day by 86,400, the number of seconds in 

a day. Periodic manual streamflow measurements at partialrecord streamgages are used with concurrent continuousrecord measurements from streamgages in hydrologically 

similar drainage areas to estimate a continuous record at 

the partial-record streamgage. Specifically, continuous 

streamflow records for the nine partial-record 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/). The upper and lower 

90-percent confidence limits about the estimated mean annual 

streamflows, as described by Tasker and Driver (1988), also 

are presented in table 2. These data indicate that there is a 

90-percent chance that the estimated mean annual streamflow 

is somewhere between the upper and lower 90-percent 

confidence limits.

Continuous-record streamgages were operated and 

maintained by the USGS during WY 2011 in cooperation with 

RIDEM (USGS streamgage01115098) and the PWSB (fig. 1, 

table 1). Streamflow data for these streamgages wee collected 

at 10 or 15-minute intervals (near-real-time streamflow 

data), were updated at 1-hour intervals on the World Wide 

Web (WWW), and are available through the NWIS Web 

Interface (NWIS Web; U.S. Geological Survey, 2007). Error 

associated with measured streamflows was generally within 

about 15 percent (U.S. Geological Survey, unpublished data); 

upper and lower 90-percent confidence limits calculated by 

methods described by the National Institute of Standards and 

Technology/SEmiconductor MAnufacturing TECHnology 

(2003) are shown in table 2.
Streamflow Data Collection and Estimation 3

NARRAGANSETT BAY

BLOCK ISLAND

SOUND

41°45'

71°45' 71°30'

41°30'

42°00'

0 10 MILES

0 10 KILOMETERS

RHODE ISLAND

Study

basin

71°45'

71°37'30"

41°52'30"

41°45'

Base from USGS Digital Data

State Plane Feet Zone 5176

1:24,000 Scale

Madison

Pond

Pine

Swamp

Westconnaug 

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

GLOCESTER

SCITUATE

FOSTER

JOHNSTON

CRANSTON

Danielson Pike

116

6

14

101

12

3

29 28

8

9

12

5

4

6

33

1 2

32

31 13

22

21

19 34

20

16 14

15

17

18

23

27

25

26

24

10

11

7

30

35

36

37

Ponaganset Reservoir subbasins

Regulating Reservoir subbasins

Westconnaug Reservoir subbasins

EXPLANATION

Town Boundry

Basin Boundry

Subbasin Boundry

Water-quality sampling

subbasin boundary

Barden Reservoir subbasins

Direct Runoff subbasins

Moswansicut Reservoir subbasins

Subbasins and reservoir areas

Uunsampled area draining 

directly to Scituate Reservoir

Streamflow or water-quality monitoring station 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

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

Reservoir drainage area, Rhode Island.
4 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

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, 2010, to 

September 30, 2011.

[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; mi2, square miles; QW, water quality; M, monthly; Q, quarterly; Y, yes; 

N, no; Na, sodium; Cl, chloride; --, none; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]

PWSB 

station 

no.

USGS 

station no. Station name

Drainage 

area 

(mi2

)

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Estimated 

streamflow calculated

Barden Reservior Subbasin

24 01115190 Dolly Cole Brook 4.90 M 10 Y N

25 01115200 Shippee Brook 2.35 Q 3 N Y

26 01115185 Windsor Brook 4.32 Q 4 N Y

27 011151845 Unnamed Tributary to Ponaganset River (Unnamed 

Brook B, Unnamed Brook West of Windsor Brook)

0.10 Q 2 N N

28 01115265 Barden Reservoir (Hemlock Brook) 8.72 M 12 Y N

29 01115271 Ponaganset River (Barden Stream) 33.0 M 12 N N

35 01115187 Ponaganset River 14.0 M 11 Y N

Direct Runoff Subbasin

1 01115180 Brandy Brook 1.57 M 11 N Y

2 01115181 Unnamed Tributary 2 to Scituate Reservoir 

(Unnamed Brook North of Bullhead Brook)

0.15 Q 1 N N

3 01115280 Cork Brook 1.79 M 11 Y N

4 01115400 Kent Brook (Betty Pond Stream) 0.85 M 11 N Y

5 01115184 Spruce Brook 1.22 Q 3 Y N

6 01115183 Quonapaug Brook 1.96 M 11 Y N

7 01115297 Wilbur Hollow Brook 4.32 M 10 Y N

8 01115276 Westconnaug Brook (Westconnaug Reservoir) 5.18 M 9 Y N

9 01115275 Bear Tree Brook 0.62 Q 2 Y N

30 01115350 Unnamed Tributary 4 to Scituate Reservoir 

(Coventry Brook, Knight Brook)

0.78 Q 2 N N

31 01115177 Toad Pond 0.04 Q 1 N N

32 01115178 Unnamed Tributary 1 to Scituate Reservoir 

(Pine Swamp Brook)

0.45 Q 3 N Y

33 01115182 Unnamed Tributary 3 to Scituate Reservoir 

(Hall’s Estate Brook)

0.28 Q 4 N Y

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

37 -- Fire Tower Stream 0.15 Q 2 N N

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir (Moswansicut Stream North, 

Moswansicut Pond)

3.25 M 11 Y N

20 01115160 Unnamed Tributary 1 to Moswansicut Reservoir 

(Blanchard Brook)

1.18 M 10 N N

21 01115165 Unnamed Tributary 2 to Moswansicut Reservoir 

(Brook from Kimball Reservoir)

0.29 Q 2 N Y

22 01115167 Moswansicut Reservoir (Moswansicut Stream South) 0.22 M 9 N N

34 01115164 Kimball Stream 0.27 Q 1 N N
Streamflow Data Collection and Estimation 5

PWSB 

station 

no.

USGS 

station no. Station name

Drainage 

area 

(mi2)

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Estimated 

streamflow calculated

Ponaganset Reservoir Subbasin

23 011151843 Ponaganset Reservoir 1.92 M 12 N N

Regulating Reservoir Subbasin

13 01115176 Regulating Reservoir 22.1 M 11 N N

14 01115110 Huntinghouse Brook 6.23 M 10 Y N

15 01115114 Rush Brook 4.70 M 11 Y N

16 01115098 Peeptoad Brook (Harrisdale Brook) 4.96 M 11 Y N

17 01115119 Dexter Pond (Paine Pond) 0.22 Q 2 N N

18 01115120 Unnamed Tributary to Regulating Reservoir 

(Unnamed Brook A)

0.28 Q 1 Y N

Westconnaug Reservoir Subbasin

10 01115274 Westconnaug Brook 1.48 M 10 N Y

11 01115273 Unnamed Tributary to Westconnaug Reservoir 

(Unnamed Brook south of Westconnaug Reservoir)

0.72 Q 2 N Y

12 011152745 Unnamed Tributary to Westconnaug Brook (Unnamed 

Brook north of Westconnaug Reservoir)

0.16 Q 1 N N

1

Not all samples were analyzed for all water-quality properties or constituents.

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, 2010, to 

September 30, 2011.—Continued

[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; mi2, square miles; QW, water quality; M, monthly; Q, quarterly; Y, yes; 

N, no; Na, sodium; Cl, chloride; --, none; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]
6 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

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

October 1, 2010, through September 30, 2011.

[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; ft3/s, cubic feet per second; ft3/s/mi2, cubic feet per second per square 

mile; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by the Providence 

Water Supply Board]

PWSB 

station no.

USGS 

station no. Station name

Annual 

mean 

streamflow 

(ft3/s)

Upper 

90-percent 

confidence 

interval 

(ft3/s)

Lower 

90-percent 

confidence 

interval 

(ft3/s)

Annual 

mean 

streamflow 

(ft3/s/mi2)

Barden Reservoir Subbasin

24 01115190 Dolly Cole Brook 11 13 10 2.3

25 01115200 Shippee Brook 5.8 20 1.6 2.5

26 01115185 Windsor Brook 8.8 36 2.2 2.0

28 01115265 Barden Reservoir (Hemlock Brook) 21 24 19 2.4

35 01115187 Ponaganset River 37 41 34 2.7

Direct Runoff Subbasin

1 01115180 Brandy Brook 2.5 4.6 1.4 1.6

3 01115280 Cork Brook 3.4 3.9 2.9 1.9

4 01115400 Kent Brook (Betty Pond Stream) 2.5 12 0.52 2.9

5 01115184 Spruce Brook 2.3 2.4 2.1 1.9

6 01115183 Quonapaug Brook 4.0 4.4 3.7 2.1

7 01115297 Wilbur Hollow Brook 8.2 8.9 7.5 1.9

8 01115276 Westconnaug Brook (Westconnaug Reservoir) 7.5 7.8 7.1 1.4

9 01115275 Bear Tree Brook 1.4 1.5 1.3 2.2

32 01115178 Unnamed Tributary 1 to Scituate Reservoir 

(Pine Swamp Brook)

0.64 1.3 0.32 1.4

33 01115182 Unnamed Tributary 3 to Scituate Reservoir 

(Hall’s Estate Brook)

0.59 1.6 0.21 2.1

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

6.3 6.7 5.8 1.9

21 01115165 Unnamed Tributary 2 to Moswansicut Reservoir 

(Blanchard Brook)

0.69 1.5 0.31 2.4

Regulating Reservoir Subbasin

14 01115110 Huntinghouse Brook 13 15 11 2.2

15 01115115 Rush Brook 9.7 11 8.3 2.1

16 01115098 Peeptoad Brook (Harrisdale Brook) 11 13 9.7 2.3

18 01115120 Unnamed Tributary to Regulating Reservoir 

(Unnamed Brook A)

0.51 0.59 0.43 1.8

Westconnaug Reservoir Subbasin

10 01115274 Westconnaug Brook 2.4 4.2 1.3 1.6

11 01115273 Unnamed Tributary to Westconnaug Reservoir 

(Unnamed Brook South of Westconnaug Reservoir)

1.3 2.3 0.79 1.9
Water-Quality Data Collection and Analysis 7

Water-Quality Data Collection 

and Analysis

Water-quality data were collected by the USGS or 

PWSB. Concentrations of sodium and chloride were estimated 

(by the USGS) from continuous or partial records of specific 

conductance from 14 of the 23 streamgages. Water-quality 

samples were collected monthly or quarterly at 37 sampling 

stations in the Scituate Reservoir drainage area by the 

PWSB during WY 2011 as part of a long-term sampling 

program. Daily loads of bacteria, chloride, nitrite, nitrate, and 

orthophosphate were calculated for 23 streamgages where 

streamflow data were collected by the USGS, and waterquality samples were collected by the PWSB. 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 10- or 15-minute intervals at 

the 14 continuous-record streamgages (fig. 1). Measurements 

were made by using an instream probe and standard USGS 

methods for continuous streamwater-quality monitoring 

(Wagner and others, 2006).

Concentrations of sodium and chloride were estimated 

from continuous or periodic 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, 

1992) on the basis of concurrent measurements of specific 

conductance along with sodium and chloride concentrations 

measured in water-quality samples collected by the USGS 

from tributaries in the Scituate Reservoir drainage area (U.S. 

Geological Survey, 2001):

C Spc b Cl

m = ( )× , (1)

C Spc b Na

m = ( )× , (2)

where

CCl is the chloride concentration, in milligrams 

per liter (mg/L);

CNa is the sodium concentration, in mg/L; and

Spc is the specific conductance, in microsiemens 

per centimeter at 25° Celsius;

m is the slope from the MOVE.1 analysis 

(table 3); and

b is the intercept from the MOVE.1 analysis 

(table 3).

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, values 

of specific conductance were estimated by proportional 

distribution between recorded values.

Data Collected by the Providence Water 

Supply Board

Water-quality samples were collected at fixed stations 

on 37 tributaries by the PWSB. Sampling was done monthly 

at 19 stations and quarterly at another 18 stations (table 1) 

during WY 2011. Water-quality samples were not collected 

during specific weather conditions; rather, a strictly periodic 

water-quality sampling schedule was followed so that waterquality samples would be representative of various weather 

conditions. However, sometimes samples could not be 

collected because tributaries at the sampling stations were 

dry or frozen. When possible, water-quality samples were 

collected by dipping the sample bottle into the tributary 

at the center of flow (Richard Blodgett, PWSB, written 

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

PWSB water-quality laboratory 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 

bacteria (Escherichia coli (E. coli) and total coliform). More 

information on sample-collection, analytical, and qualitycontrol procedures can be found in the Providence Water 

Supply Board Quality Assurance Program Manual (Providence 

Water Supply Board Water Quality Laboratory, 2003).

The PWSB collected samples during a wide range of 

flow conditions. The daily mean flow-duration curve for 

the Quonapaug Brook at North Scituate (USGS streamgage 

01115183) for WY 2011 is shown in figure 2. The curve 
8 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

represents the percentage of time that each flow was exceeded 

at this station. The flows at this station on days when waterquality samples were collected are represented by the plotted 

points superimposed on the curve. Samples were collected 

at flow durations ranging from the 3rd percentile to the 98th 

percentile; this range indicates that the water-quality samples 

collected in WY 2011 represented a wide range of flow 

conditions during that water year.

Estimating Daily, Monthly, and Annual 

Loads and Yields

Daily, monthly, and annual sodium and chloride loads 

in kilograms were estimated for all streamgages for which 

continuous-streamflow and specific-conductance data were 

available for WY 2011. 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 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). Daily data was summed to estimate monthly or 

annual loads.

Daily loads of water-quality constituents (in samples 

collected by the PWSB) were calculated for all sampling dates 

during WY 2011 (table 4, 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 or colony forming units (CFU) 

per liter in single samples by the daily discharge (in liters per 

day) for the day on which each sample was collected. The 

flows, which in some cases were estimates, were assumed 

to be representative of the flow at the time of the sample 

collection. Loads in grams or kilograms (or millions of 

CFUs for bacteria) per day and yields in grams or kilograms 

(or millions of CFUs for bacteria) per day per square mile 

were calculated for bacteria, chloride, nitrite, nitrate, and 

orthophosphate from this water-quality data. Censored data 

(or concentrations reported as less than method detection 

limits) were replaced with concentrations equal to one-half the 

method detection limit.

Table 3. Regression equation coefficients used to estimate concentrations of chloride and sodium from values of specific 

conductance for each U.S. Geological Survey monitoring station in the Scituate Reservoir drainage area, Rhode Island, October 1, 

2010, through September 30, 2011.

[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; RMSE, root mean square error]

PWSB 

station no.

USGS 

station no.

Chloride Sodium

Intercept Slope RMSE Intercept Slope RMSE

24 01115190 0.1334 1.1013 0.030 0.1074 1.0431 0.035

28 01115265 0.1334 1.1013 0.030 0.1074 1.0431 0.035

35 01115187 0.1334 1.1013 0.030 0.1074 1.0431 0.035

3 01115280 0.1334 1.1013 0.030 0.1074 1.0431 0.035

5 01115184 0.0772 1.1901 0.037 0.0760 1.0808 0.037

6 01115183 0.1334 1.1013 0.030 0.1074 1.0431 0.035

7 01115297 0.0772 1.1901 0.037 0.0760 1.0808 0.037

8 01115276 0.1334 1.1013 0.030 0.1074 1.0431 0.035

9 01115275 0.1334 1.1013 0.030 0.1074 1.0431 0.035

19 01115170 0.1334 1.1013 0.030 0.1074 1.0431 0.035

14 01115110 0.0772 1.1901 0.037 0.0760 1.0808 0.037

15 01115114 0.1334 1.1013 0.030 0.1074 1.0431 0.035

16 01115098 0.1334 1.1013 0.030 0.1074 1.0431 0.035

18 01115120 0.1334 1.1013 0.030 0.1074 1.0431 0.035
Estimating Daily, Monthly, and Annual Loads and Yields 9

Water-quality sample collected at Quonapaug Brook

0.001

0.01

0.1

1

10

100

Percentage of time streamflow was equaled or exceeded

Streamflow, in cubic feet per second

0.01 1 10 40 70 95 99.5 99.99

Figure 2. Flow-duration curve for the U.S. Geological Survey continuous streamgage on Quonapaug Brook at North 

Scituate (01115183) for water year 2011 and streamflow measurements at this streamgage on the dates (represented by 

points) when water-quality samples were collected.
10 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

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 daily 

streamflow at the streamgage on the Ponaganset River 

(USGS streamgage 01115187) for the entire time period of its 

operation (mean of the daily mean streamflows for the period 

of record, WY 1994–2010) prior to WY 2011 was 29 ft3/s 

(http://waterdata.usgs.gov/nwis). During WY 2011, annual 

mean streamflow was 37 ft3/s (fig. 3). Mean daily streamflow 

in Peeptoad Brook (streamgage 01115098), the other longterm continuous-record streamgage in the Scituate Reservoir 

drainage area, for its period of record (WY 1994–2010) prior 

to WY 2011 was 11 ft3/s (http://waterdata.usgs.gov/nwis). 

Annual mean streamflow in Peeptoad Brook during WY 2011 

also was 11 ft3/s (table 2).

Water Quality and Constituent Loads 

and Yields

Water-quality conditions in the Scituate Reservoir 

drainage area are described by summary statistics for waterquality properties, 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 tributaries. In the case of loads, tributaries with 

higher flows tend to have higher loads because the greater 

volume of water can carry more of the constituent to the 

reservoir per unit time. Yields represent the constituent load 

per unit of drainage area and are calculated by dividing the 

load estimated for a streamgage by the drainage area to the 

monitoring station. Yields are useful for comparison among 

streamgages that have different drainage areas 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 dataset 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 in estimates of constituent masses delivered to 

receiving waters.

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 the PWSB, indicated that tributaries 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 restricted diets need to limit their intake 

of sodium.

Estimated monthly mean3 sodium concentrations in 

tributaries of the Scituate Reservoir drainage area ranged 

from 4.8 to 37.3 mg/L, and estimated monthly mean chloride 

concentrations ranged from 7.4 to 64.4 mg/L (table 5). The 

highest monthly mean concentrations of sodium and chloride 

were measured in Bear Tree Brook (PWSB station number 9) 

in October 2010 (37.3 and 64.4 mg/L, respectively; table 5). 

3

 Monthly mean concentrations were calculated by dividing the total 

monthly load by the total discharge for the month.
Water Quality and Constituent Loads and Yields 11

2010 2011

Streamflow, in cubic feet per second

0.1

1

10

100

1,000

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Water year 2011

Long-term average

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

River at South Foster (01115187) in the Scituate Reservoir drainage area, Rhode Island, for October 1, 2010, through September 

30, 2011, and mean daily streamflow for October 1, 1994, through September 30, 2010.
12 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name October November December January February March Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Barden Reservoir Subbasin 24 01115190 Dolly Cole Brook 22.5 13.8 21.5 13.2 17.9 11.1 20.8 12.8 25.4 15.5 23.1 14.2 28 01115265 Barden Reservoir (Hemlock Brook) 28.2 17.1 20.4 12.6 15.0 9.37 19.5 12.1 18.5 11.5 16.2 10.1 35 01115187 Ponaganset River 18.8 11.7 18.2 11.3 14.4 9.06 18.1 11.2 21.3 13.1 16.5 10.3 Direct Runoff Subbasin

3 01115280 Cork Brook 35.7 21.4 31.6 19.0 21.2 13.0 29.1 17.6 34.6 20.8 27.4 16.65 01115184 Spruce Brook 21.8 12.8 18.3 10.9 12.4 7.66 16.4 9.84 17.0 10.2 14.3 8.716 01115183 Quonapaug Brook 47.5 28.0 46.6 27.5 32.9 19.8 41.5 24.7 45.0 26.6 38.0 22.77 01115297 Wilbur Hollow Brook 15.2 9.20 12.5 7.7 8.59 5.48 9.61 6.07 8.10 5.19 7.98 5.128 01115276 Westconnaug Brook (Westconnaug Reservoir) 32.6 19.6 32.8 19.7 18.5 11.5 19.0 11.8 19.4 12.0 17.3 10.89 01115275 Bear Tree Brook 64.4 37.3 56.6 33.1 43.7 25.8 51.2 30.1 42.6 25.2 37.6 22.5

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

33.1 19.9 33.2 19.9 32.9 19.8 34.2 20.5 34.4 20.7 33.2 20.0

Regulating Reservoir

14 01115110 Huntinghouse Brook 14.8 8.99 10.9 6.80 7.48 4.82 11.9 7.39 10.3 6.44 7.83 5.0315 01115115 Rush Brook 41.5 24.7 31.1 18.7 21.3 13.0 42.2 25.0 43.2 25.6 31.7 19.116 01115098 Peeptoad Brook (Harrisdale 

Brook)

34.9 20.9 36.7 22.0 29.4 17.8 30.7 18.6 35.9 21.5 30.2 18.2

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

32.1 19.3 33.7 20.2 28.1 17.0 46.7 27.6 52.1 30.5 40.4 24.0

Scituate Reservoir Basin

Average 31.7 18.9 28.9 17.3 21.7 13.2 27.9 16.8 29.1 17.5 24.4 14.8

Table 5. Monthly mean concentrations of chloride and sodium estimated from continuous measurements of specific conductance in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; monthly mean concentrations were calculated by dividing the monthly load by the total discharge for the month; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Suply Board]
Water Quality and Constituent Loads and Yields 13

Table 5. Monthly mean concentrations of chloride and sodium estimated from continuous measurements of specific conductance in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; monthly mean concentrations were calculated by dividing the monthly load by the total discharge for the month; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Suply Board]

PWSB 

station 

number

USGS 

station 

number

Station 

name

April May June July August September

Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na

(mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)

Barden Reservoir Subbasin

24 01115190 Dolly Cole Brook 22.8 14.0 23.5 14.4 24.0 14.7 23.6 14.5 20.3 12.5 18.7 11.628 01115265 Barden Reservoir (Hemlock 

Brook)

17.3 10.8 19.0 11.8 19.9 12.3 20.2 12.5 17.0 10.6 14.6 9.17

35 01115187 Ponaganset River 17.2 10.7 18.3 11.3 18.4 11.4 18.3 11.3 15.5 9.70 14.0 8.82

Direct Runoff Subbasin

3 01115280 Cork Brook 26.1 15.9 29.3 17.8 29.5 17.9 26.6 16.2 26.1 15.9 20.1 12.4

5 01115184 Spruce Brook 14.8 8.98 16.1 9.68 17.4 10.4 18.3 10.9 19.0 11.3 16.7 10.06 01115183 Quonapaug Brook 36.9 22.1 37.2 22.2 36.0 21.5 38.2 22.8 40.0 23.8 35.8 21.47 01115297 Wilbur Hollow Brook 9.16 5.81 9.43 5.97 7.44 4.80 8.83 5.62 10.2 6.41 8.38 5.368 01115276 Westconnaug Brook (Westconnaug Reservoir) 18.0 11.2 19.7 12.2 21.1 13.0 24.4 14.9 19.4 12.0 17.4 10.89 01115275 Bear Tree Brook 40.3 24.0 46.5 27.5 51.9 30.5 59.0 34.4 45.7 26.9 43.7 25.9

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

35.6 21.3 36.6 21.9 36.5 21.8 36.6 21.9 36.7 21.9 35.1 21.1

Regulating Reservoir Subbasin

14 01115110 Huntinghouse Brook 9.59 6.05 10.4 6.51 11.4 7.09 12.0 7.41 10.5 6.60 8.80 5.5915 01115115 Regulating Reservoir (Rush 

Brook)

29.3 17.7 36.0 21.6 41.1 24.4 34.6 20.7 27.6 16.7 24.8 15.1

16 01115098 Peeptoad Brook (Harrisdale 

Brook)

34.1 20.5 34.4 20.7 36.9 22.1 38.1 22.8 38.3 22.8 39.3 23.4

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

41.3 24.5 47.8 28.2 38.9 23.2 26.6 16.2 29.4 17.8 31.8 19.1

Scituate Reservoir Basin

Average 25.2 15.3 27.4 16.6 27.9 16.8 27.5 16.6 25.4 15.4 23.5 14.3
14 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

The highest annual mean4 concentrations of sodium and 

chloride also were measured in Bear Tree Brook, 27.0 and 

45.8 mg/L, respectively (table 6). These high concentrations 

are the result of residual sodium and chloride leaching 

from a formerly uncovered salt storage pile to groundwater 

(Nimiroski and Waldron, 2002) and relatively small surfacewater flows. 

The Scituate Reservoir received about 1,600,000 kg 

(about 1,800 tons) of sodium and 2,600,000 kg (about 

2,900 tons) of chloride from tributaries—equipped with 

instrumentation capable of continuously monitoring specific 

conductance—during WY 2011. The highest sodium 

and chloride loads in the watershed during WY 2011—

360,000 kg and 580,000 kg, respectively—were measured 

at the Ponaganset River station (PWSB station number 35; 

table 6). Monthly estimated sodium and chloride loads were 

highest in March at 13 stations and in February at 1 station 

(Ponaganset River; table 7). For these months, the estimated 

load of sodium and chloride at each station accounted for 

12–23 percent of the annual load for each constituent at the 

respective stations. The highest annual sodium and chloride 

yields were 53,000 and 90,000 kg/mi2, respectively, and 

were measured at Bear Tree Brook (PWSB station number 9; 

table 6).

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 the most likely values 

for sodium and chloride coming from tributaries or their 

drainage basins. It may be best to discuss loads and yields in 

terms of a range within which the true values lie; 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. 

The uncertainties associated with estimating streamflow are 

commonly assumed to affect load and yield calculations more 

than the errors 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 tributaries and their 

drainage basins.

4

 Annual mean concentrations were calculated by dividing the total annual 

load by the total discharge for the year.

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 from each basin 

(table 8). 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 acid-neutralizing capacity of water.

The median pH in tributaries in the Scituate Reservoir 

drainage area ranged from 5.6 to 6.8; the median of the 

medians for all stations was 6.2. Median values of color 

ranged from 12 to 210 platinum cobalt units (PCU); the 

median for all stations was 55 PCU. Median values of 

turbidity ranged from 0.21 to 1.9 nephelometric turbidity units 

(NTU); the median for all stations was 0.68 NTU. Median 

alkalinity values in tributaries were low, ranging from 2.5 to 

15 mg/L as CaCO3; the median for all stations was 4.9 mg/L as 

CaCO3 (table 8).

Constituent Concentrations and Daily Loads 

and Yields

Fecal indicator bacteria, chloride, and nutrients such as 

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 such as waste 

disposal, use of septic systems, 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 tributaries is drinking water, which must meet specific 

water-quality standards. For this reason, the PWSB and the 

USGS closely monitor concentrations of these constituents in 

tributaries. Median concentrations, loads, and yields of waterquality constituents are given in tables 8 and 9.
Water Quality and Constituent Loads and Yields 15

Table 6. Annual mean chloride and sodium concentrations, loads, and yields by sampling station in the Scituate Reservoir drainage 

area, Rhode Island, October 1, 2010, through September 30, 2011.

[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; mg/L, milligrams per liter; kg, kilograms; kg/mi2, kilograms per square 

mile; Cl, chloride; Na, sodium; annual mean concentrations were calculated by dividing the annual load by the total discharge for the year; alternate station 

names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]

PWSB 

station 

no.

USGS 

station 

no.

Station name

Concentration Load Yield

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(kg)

Na 

(kg)

Cl 

(kg/mi2)

Na 

(kg/mi2)

Barden Reservoir Subbasin

24 01115190 Dolly Cole Brook 22.1 13.6 220,000 140,000 45,000 28,000

28 01115265 Barden Reservoir (Hemlock Brook) 17.6 10.9 330,000 200,000 38,000 23,000

35 01115187 Ponaganset River 17.5 10.9 580,000 360,000 41,000 26,000

Direct Runoff Subbasin

3 01115280 Cork Brook 27.1 16.4 82,000 50,000 46,000 28,000

5 01115184 Spruce Brook 15.7 9.47 32,000 19,000 26,000 16,000

6 01115183 Quonapaug Brook 38.9 23.2 140,000 83,000 71,000 42,000

7 01115297 Wilbur Hollow Brook 9.16 5.80 67,000 42,000 15,000 9,800

8 01115276 Westconnaug Brook (Westconnaug Reservoir) 19.7 12.2 130,000 81,000 25,000 16,000

9 01115275 Bear Tree Brook 45.8 27.0 56,000 33,000 90,000 53,000

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir, (Moswansicut Stream 

North, Moswansicut Pond)

34.7 20.8 190,000 120,000 60,000 36,000

Regulating Reservoir Subbasin

14 01115110 Huntinghouse Brook 9.50 5.99 110,000 71,000 18,000 11,000

15 01115115 Rush Brook 32.2 19.3 280,000 170,000 59,000 35,000

16 01115098 Peeptoad Brook (Harrisdale Brook) 33.7 20.3 330,000 200,000 67,000 40,000

18 01115120 Unnamed Tributary to Regulating Reservoir 

(Unnamed Brook A)

40.0 23.8 18,000 11,000 64,000 38,000

Scituate Reservoir Basin

Average Total Average

26.0 15.7 2,600,000 1,600,000 48,000 29,000
16 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name October November December January February March Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) Barden Reservoir Subbasin 24 01115190 Dolly Cole Brook 7,200 4,400 13,000 8,200 19,000 12,000 18,000 11,000 41,000 25,000 44,000 27,000 28 01115265 Barden Reservoir (Hemlock Brook) 14,000 8,700 17,000 10,000 25,000 16,000 30,000 19,000 41,000 25,000 56,000 35,000 35 01115187 Ponaganset River 23,000 14,000 29,000 18,000 40,000 25,000 59,000 37,000 130,000 81,000 98,000 61,000 Direct Runoff Subbasin

3 01115280 Cork Brook 2,300 1,400 4,400 2,700 7,200 4,400 6,500 4,000 10,000 6,200 16,000 9,5005 01115184 Spruce Brook 810 480 1,300 780 2,700 1,600 2,400 1,400 3,300 2,000 6,100 3,7006 01115183 Quonapaug Brook 5,900 3,500 9,600 5,700 13,000 7,700 12,000 7,400 18,000 11,000 25,000 15,0007 01115297 Wilbur Hollow Brook 4,400 2,700 5,000 3,100 6,300 4,000 5,000 3,200 6,300 4,000 9,700 6,2008 01115276 Westconnaug Brook (Westconnaug Reservoir) 5,900 3,600 6,700 4,000 9,400 5,800 11,000 6,700 12,000 7,500 16,000 10,0009 01115275 Bear Tree Brook 2,900 1,700 3,100 1,800 4,400 2,600 4,200 2,400 4,300 2,500 7,200 4,300

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

5,800 3,500 9,700 5,800 18,000 11,000 15,000 9,000 17,000 10,000 34,000 21,000

Regulating Reservoir

14 01115110 Huntinghouse Brook 3,500 2,100 5,900 3,700 9,500 6,100 8,600 5,300 16,000 10,000 21,000 13,00015 01115115 Rush Brook 9,000 5,300 14,000 8,500 20,000 12,000 23,000 14,000 45,000 27,000 51,000 31,00016 01115098 Peeptoad Brook 

(Harrisdale Brook)

14,000 8,400 28,000 17,000 38,000 23,000 19,000 11,000 39,000 24,000 69,000 42,000

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

240 150 330 200 1,300 760 1,700 1,000 3,100 1,800 4,200 2,500

Scituate Reservoir Basin

Total 99,000 60,000 150,000 89,000 210,000 130,000 220,000 130,000 390,000 240,000 460,000 280,000

Table 7. Monthly estimated chloride and sodium loads by sampling station in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; Cl, chloride; Na, sodium; kg, kilogram; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
Water Quality and Constituent Loads and Yields 17

PWSB 

station 

number

USGS 

station 

number

Station 

name

April May June July August September

Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na

(Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg)

Barden Reservoir Subbasin

24 01115190 Dolly Cole Brook 28,000 17,000 13,000 8,000 6,000 3,700 3,000 1,800 13,000 8,100 15,000 9,60028 01115265 Barden Reservoir 

(Hemlock Brook)

39,000 24,000 25,000 15,000 15,000 9,400 6,700 4,100 26,000 16,000 32,000 20,000

35 01115187 Ponaganset River 63,000 39,000 36,000 23,000 19,000 12,000 7,200 4,500 31,000 19,000 43,000 27,000

Direct Runoff Subbasin

3 01115280 Cork Brook 11,000 6,700 6,600 4,000 3,100 1,900 1,900 1,200 6,600 4,000 6,200 3,8005 01115184 Spruce Brook 4,700 2,900 3,200 1,900 1,700 1,000 1,100 630 1,600 940 2,800 1,7006 01115183 Quonapaug Brook 18,000 11,000 12,000 7,000 5,100 3,000 1,700 1,000 6,900 4,100 12,000 7,3007 01115297 Wilbur Hollow Brook 9,100 5,800 6,400 4,100 2,600 1,600 820 520 4,400 2,700 7,000 4,5008 01115276 Westconnaug Brook (Westconnaug Reservoir) 15,000 9,400 15,000 9,500 11,000 6,500 6,400 3,900 8,400 5,200 14,000 8,5009 01115275 Bear Tree Brook 6,300 3,800 5,600 3,300 4,300 2,500 3,300 1,900 4,200 2,500 5,700 3,400

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

28,000 17,000 19,000 11,000 11,000 6,500 6,000 3,600 11,000 6,600 19,000 11,000

Regulating Reservoir Subbasin

14 01115110 Huntinghouse Brook 17,000 11,000 9,600 6,000 4,600 2,900 1,600 1,000 6,500 4,100 9,300 5,90015 01115115 Regulating Reservoir 

(Rush Brook)

37,000 22,000 24,000 14,000 11,000 6,400 4,800 2,900 17,000 10,000 22,000 13,000

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

34,000 21,000 13,000 7,600 15,000 8,900 4,300 2,600 26,000 15,000 34,000 20,000

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

3,000 1,800 1,500 910 530 320 230 140 690 420 1,300 760

Scituate Reservoir Basin

Total 310,000 190,000 190,000 120,000 110,000 67,000 49,000 30,000 160,000 99,000 220,000 140,000

Table 7. Monthly estimated chloride and sodium loads by sampling station in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.—Continued[PWSB, Providence Water Supply Board; USGS, U.S. Geological Survey; no., number; Cl, chloride; Na, sodium; kg, kilogram; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
18 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station no. USGS station no. Station name Properties Constituents pH (units) Color (PCU) Turbid- ity (NTU) Total coli- form 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 6.1 68 0.78 23 14 4.5 26 0.002 0.01 0.0725 01115200 Shippee Brook 6.0 45 0.75 23 23 3.1 15 0.002 <0.01 0.0526 01115185 Windsor Brook 6.2 44 0.43 240 23 2.8 16 0.001 0.01 0.1527 011151845 Unnamed Tributary to Ponaganset River 

(Unnamed Brook B, Unnamed Brook West of Windsor Brook)

5.8 21 0.25 12 2.8 4.6 14 0.001 <0.01 0.02

28 01115265 Barden Reservoir (Hemlock Brook) 5.8 80 0.63 1,100 310 2.8 20 0.003 <0.01 0.0829 01115271 Ponaganset River (Barden Stream) 6.1 55 0.78 23 23 4.1 20 0.002 <0.01 0.0835 01115187 Ponaganset River 6.2 72 0.64 23 23 4.1 19 0.002 <0.01 0.08

Direct Runoff Subbasin

1 01115180 Brandy Brook 6.7 70 1.2 150 21 9.4 12 0.002 0.01 0.12 01115181 Unnamed Tributary #2 to Scituate Reservoir 

(Unnamed Brook North of Bullhead Brook)

6.3 18 0.26 23 23 3.4 14 0.001 0.03 0.07

3 01115280 Cork Brook 6.3 45 0.4 >2,400 240 4.9 30 0.002 0.01 0.054 01115400 Kent Brook (Betty Pond Stream) 6.3 32 0.68 23 1.5 7.6 5.7 0.001 <0.01 0.055 01115184 Spruce Brook 6.0 70 0.43 23 23 4.2 19 0.002 0.01 0.066 01115183 Quonapaug Brook 6.4 84 1 43 43 8.8 38 0.002 <0.01 0.17 01115297 Wilbur Hollow Brook 6.1 85 0.84 1,100 33 5.9 16 0.003 <0.01 0.088 01115276 Westconnaug Brook (Westconnaug Reservoir) 6.1 18 0.59 23 23 3.5 19 0.001 0.01 0.089 01115275 Bear Tree Brook 6.4 48 0.35 58 6.5 5.4 34 0.002 0.04 0.07

30 01115350 Unnamed Tributary #4 to Scituate Reservoir 

(Coventry Brook, Knight Brook)

6.0 57 0.37 33 23 4 24 0.002 0.02 0.07

31 1115177 Toad Pond 6.5 45 0.78 93 23 4.9 87 0.002 0.13 0.0832 01115178 Unnamed Tributary #1 to Scituate Reservoir 

(Pine Swamp Brook)

6.3 65 0.74 23 23 4.9 15 0.001 0.01 0.09

33 01115182 Unnamed Tributary #3 to Scituate Reservoir 

(Hall’s Estate Brook)

6.2 55 0.48 240 20 2.9 19 0.002 0.03 0.04

36 -- Outflow from King Pond 6.2 20 0.26 23 4 3.4 5.1 0.001 0.01 0.0437 -- Fire Tower Stream 5.8 44 0.28 4 4 3.8 4.6 0.001 0.03 0.03

Table 8. Median values for water-quality data collected at Providence Water Supply Board stations, by tributary reservoir subbasin in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.[Water-quality data are from samples collected and analyzed by Providence Water (PWSB); no., number; USGS, U.S. Geological Survey; 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, nitrogen; P, phosphorus; <, less than; >, greater than; --, no data; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]
Water Quality and Constituent Loads and Yields 19

PWSB 

station 

no.

USGS 

station no. Station name

Properties Constituents

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)

6.8 28 1.2 23 4 7 32 0.001 0.01 0.06

20 01115160 Unnamed Tributary #1 to Moswansicut 

Reservoir (Blanchard Brook)

6.1 210 0.93 350 240 7.9 43 0.003 0.01 0.13

21 01115165 Unnamed Tributary #2 to Moswansicut 

Reservoir (Brook from Kimball Reservoir)

6.6 85 1.4 630 29 6 19 0.003 0.03 0.06

22 01115167 Moswansicut Reservoir (Moswansicut Stream 

South)

6.6 60 1.9 1,100 1,100 15 40 0.005 0.06 0.15

34 01115164 Kimball Stream 6.5 65 0.57 23 9 8.8 31 0.002 <0.01 0.06

Ponaganset Reservoir Subbasin

23 011151843 Ponaganset Reservoir 6.0 12 0.46 12 1.5 2.6 12 0.001 0.01 0.03

Regulating Reservoir Subbasin

13 01115176 Regulating Reservoir 6.7 29 0.76 9 4 3.7 30 0.001 <0.01 0.0614 01115110 Huntinghouse Brook 6.5 47 0.74 200 84 9.6 8.9 0.002 <0.01 0.0815 01115115 Rush Brook 6.6 74 0.8 150 39 13 35 0.002 0.01 0.0716 01115098 Peeptoad Brook (Harrisdale Brook) 6.5 42 0.98 75 39 10 34 0.001 0.01 0.0617 01115119 Dexter Pond (Paine Pond) 5.9 60 0.6 120 5.3 5 33 0.002 <0.01 0.1118 01115120 Unnamed Tributary to Regulating Reservoir 

(Unnamed Brook A)

6.5 70 0.76 >2,400 43 8.9 43 0.002 0.01 0.07

Westconnaug Reservoir Subbasin

10 01115274 Westconnaug Brook 5.6 33 0.21 110 19 2.5 23 0.001 <0.01 0.065

11 01115273 Unnamed Tributary to Westconnaug Reservoir 

(Unnamed Brook South of Westconnaug Reservoir)

5.7 100 0.64 23 23 4.1 32 0.005 0.03 0.035

12 011152745 Unnamed Tributary to Westconnaug Brook 

(Unnamed Brook north of Westconnaug Reservoir)

6.2 62 0.69 23 23 4.9 6.1 0.003 0.05 0.03

Scituate Reservoir Basin

Minimum 5.6 12 0.21 4 1.5 2.5 4.6 0.001 <0.01 0.02Median 6.2 55 0.68 33 23 4.9 20 0.002 0.01 0.07Maximum 6.8 210 1.9 >2,400 1,100 15 87 0.005 0.13 0.15

Table 8. Median values for water-quality data collected at Providence Water Supply Board stations, by tributary reservoir subbasin in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water (PWSB); no., number; USGS, U.S. Geological Survey; 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, nitrogen; P, phosphorus; <, less than; >, greater than; --, no data; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]
20 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name Total coliform bacteria E. Coli Chloride Nitrite (as N) Nitrate (as N) Orthophos- phate (as P) (CFU×106/d) (CFU×106/mi2

) (CFU×106/d) (CFU×106/mi2

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

) (g/d) (g/d/mi2

) (g/d) (g/d/mi2

) (g/d) (g/d/mi2

)

Barden Reservoir Subbasin

24 01115190 Dolly Cole Brook 3,100 630 2,200 440 360 73 25 5.1 110 23 1,100 22025 01115200 Shippee Brook 3,200 1,400 1,900 810 230 98 31 13 110 47 630 27026 01115185 Windsor Brook 75,000 17,000 4,000 920 300 69 28 6.5 200 46 4,600 1,10028 01115265 Barden Reservoir 

(Hemlock Brook)

290,000 33,000 160,000 18,000 770 88 92 10 220 25 2,900 330

35 01115187 Ponaganset River 11,000 790 11,000 790 1,400 100 88 6.3 490 35 3,600 260

Direct Runoff Subbasin

1 01115180 Brandy Brook 6,700 4,300 1,400 890 73 46 9 6 28 18 610 3903 01115280 Cork Brook >65,000 >36,000 65,000 36,000 76 42 5.4 3 54 30 200 1104 01115400 Kent Brook 850 1,000 320 380 15 18 2.2 2.6 22 26 170 2005 01115184 Spruce Brook 2,800 2,300 490 400 36 30 2.3 1.9 13 11 92 756 01115183 Quonapaug Brook 4,600 2,300 4,400 2,200 310 160 14 7.1 81 41 730 3707 01115297 Wilbur Hollow Brook 210,000 48,000 4,700 1,100 290 67 41 9.4 130 29 1,200 2808 01115276 Westconnaug Brook 1,800 350 1,600 310 390 75 24 4.6 120 23 820 1609 01115275 Bear Tree Brook 1,200 1,900 170 270 140 230 6.7 11 200 320 230 370

32 01115178 Unnamed Tributary #1 

to Scituate Reservoir (Pine Swamp Brook)

570 1,300 100 220 38 84 2.5 5.6 25 56 220 490

33 01115182 Unnamed Tributary #3 

to Scituate Reservoir (Hall’s Estate Brook)

700 2,500 70 250 16 56 1.2 4.1 25 88 34 120

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

2,800 860 770 240 260 80 10 3 61 19 430 130

Table 9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin, in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; N, nitrogen; P, phosphorus; kg/d, kilograms per day; kg/d/mi2, kilograms per day per square mile; g/d, grams per day; g/d/mi2, grams per day per square mile; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]
Water Quality and Constituent Loads and Yields 21

PWSB 

station 

number

USGS 

station 

number

Station 

name

Total coliform bacteria E. Coli Chloride Nitrite (as N) Nitrate (as N) Orthophos- phate (as P)

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

21 01115165 Unnamed Tributary #2 

to Moswansicut Reservoir (Brook from Kimball Reservoir)

31,000 110,000 1,200 4,200 85 290 5.7 20 140 480 140 490

Regulating Reservoir

14 01115110 Huntinghouse Brook 25,000 3,900 16,000 2,500 250 39 40 6.4 160 25 2,300 36015 01115115 Rush Brook 26,000 5,500 2,600 550 650 140 30 6.4 120 26 1,000 21016 01115098 Peeptoad Brook (Harrisdale Brook) 18,000 3,600 4,200 850 570 110 22 4.4 120 24 720 15018 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

>100,000 >350,000 1,800 6,400 180 640 8 30 42 150 290 1,000

Westconnaug Reservoir Subbasin

10 01115274 Westconnaug Brook 4,000 2,700 700 470 120 78 4.6 3.1 26 18 400 270

11 01115273 Unnamed Tributary 

to Westconnaug Reservoir (Unnamed Brook South of Westconnaug Reservoir)

620 860 620 860 120 170 7 9.7 150 200 43 59

Scituate Reservoir Basin

Minimum 570 350 70 220 15 18 1.2 1.9 13 11 34 59Median 4,300 2,500 1,800 810 230 80 10 6.3 110 29 610 270Maximum 290,000 >350,000 160,000 36,000 1,400 640 92 30 490 480 4,600 1,100

Table 9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin, in the Scituate Reservoir drainage area Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; N, nitrogen; P, phosphorus; kg/d, kilograms per day; kg/d/mi2, kilograms per day per square mile; g/d, grams per day; g/d/mi2, grams per day per square mile; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water]
22 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011

Bacteria

Median concentrations of total coliform and E. coli

bacteria were above the detection limit (3 CFU/100 mL) at 

nearly all sites (table 8). 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 for all sites in the 

drainage basin were equal to 33 CFU/100 mL for total 

coliform bacteria and 23 CFU/100 mL for E. coli bacteria. 

Median concentrations of total coliform bacteria were 

highest at Cork Brook (PWSB station number 3; table 8) 

and at Unnamed Tributary to Regulating Reservoir (PWSB 

station number 18; table 8) at more than 2,400 CFU/100 mL. 

Median concentrations of E. coli bacteria were highest at 

Moswansicut Reservoir (PWSB station number 22; table 8) at 

1,100 CFU/100 mL.

Concentrations of fecal indicator bacteria were 

lowest at sampling stations Regulating Reservoir (PWSB 

station number 13), Ponaganset Reservoir (PWSB station 

number 23), Unnamed Tributary to Ponaganset River 

(PWSB station number 27), and Fire Tower Stream (PWSB 

station number 37). In addition to these sampling stations, 

concentrations of E. coli bacteria also were relatively low 

at Dexter Pond (PWSB station number 17), Moswansicut 

Reservoir (PWSB station number 19), and Outflow from 

King Pond (PWSB station number 36). Median daily loads 

and yields of total coliform and E. coli bacteria varied by 

about three orders of magnitude; the highest median daily 

yield of total coliform bacteria was at Unnamed Tributary to 

Regulating Reservoir (PWSB station number 18; table 9), 

and the highest median daily yield of E. coli bacteria was 

at Cork Brook (PWSB station number 3; table 9). Although 

relatively high for sampling stations in the Scituate Reservoir 

Subbasin, median daily bacteria yields at this station are 

low to moderate compared to yields of indicator bacteria in 

sewage-contaminated streamwater or streamwater affected 

by stormwater runoff in an urban environment (Breault 

and others, 2002). The median daily loads of total coliform 

bacteria for all subbasins in the Scituate Reservoir drainage 

area ranged from 570 to 290,000 CFUx106/d, and yields 

ranged from 350 to greater than 350,000 CFUx106/d/mi2; 

E coli loads ranged from 70 to 160,000 CFUx106/d, and 

yields ranged from 220 to 36,000 CFUx106/d/mi2 (table 9) 

. These median daily loads were substantially greater than 

the values in the previous water year, when the median 

daily loads of total coliform bacteria ranged from 360 to 

29,000 CFUx106/d, and loads of E coli bacteria ranged from 

57 to 8,700 CFUx106/d (Smith and Breault, 2011).

Chloride

The highest median chloride concentration 

(87.0 mg/L) was measured in the Direct Runoff 

Subbasin at Toad Pond (PWSB station number 31; 

table 8). Median daily chloride loads and yields estimated 

from samples collected by the PWSB varied among 

monitoring stations in the drainage area (table 9); the 

median chloride yield for the overall drainage area 

was about 80 kilograms per day per square mile (kg/d/mi2). 

Ponaganset River (PWSB station number 35) had the largest 

median daily chloride load (1,400 kilograms per day (kg/d)). 

The largest median daily chloride yield (640 kg/d/mi2) was 

determined for Unnamed Tributary to Regulating Reservoir 

(PWSB station number 18); this yield is greater than the mean 

daily chloride yield [64,000 kilograms per year per square 

mile (kg/yr/mi2)(table 6) or about 175 kg/d/mi2] estimated 

for that station by using continuously measured specificconductance records. The mean annual yield of chloride 

and sodium for the drainage areas above the 14 USGS 

continuous-record streamgages, which represent nearly 

66 percent of the Scituate watershed, was 113 kg/d/mi2 and 

70 kg/d/mi2,respectively.

Nutrients

Median concentrations of nitrite and nitrate (table 8) 

were 0.002 and 0.01 mg/L as nitrogen (N), respectively. 

Higher concentrations of nitrite and nitrate at some 

monitoring sites, such as Moswansicut Reservoir (PWSB 

station number 22) in the Moswansicut Reservoir Subbasin 

(0.005 mg/L as N and 0.06 mg/L as N, respectively), may 

have been affected by nutrient-enriched runoff or groundwater 

(Nimiroski and others, 2008). The median concentration 

of orthophosphate for the entire study area (table 8) was 

0.07 mg/L as P. The maximum median concentration of 

orthophosphate (0.15 mg/L as P) was measured in Windsor 

Brook (PWSB station number 26). Median daily nutrient 

loads from the Ponaganset River (PWSB station number 35) 

into the Scituate Reservoir—nitrite (88 g/d), nitrate (490 g/d), 

and orthophosphate (4,600 g/d)—were among the largest 

for all the sampled stations. Median daily nitrite loads for 

WY 2011 were larger at only one station, Barden Reservoir 

(PWSB station number 28; 92 g/d). The largest median daily 

yield for nitrite (30 g/d/mi2) was determined for Unnamed 

Tributary to Regulating Reservoir (PWSB station number 

18). The largest median daily yield for nitrate (480 g/d/mi2) 

was determined for Unnamed Tributary 2 to Moswansicut 

Reservoir (PWSB station number 21), and the largest median 

daily yield for orthophosphate (1,100 g/d/mi2) was determined 

for Windsor Brook (PWSB station number 26; table 9). 

The median daily yield for orthophosphate for Unnamed 

Tributary to Regulating Reservoir (PWSB station number 18; 

1,000 g/d/mi2) also was high compared with the other stations 

in the monitoring network.
References Cited 23

References Cited

Breault, R.F., 2010, 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, 25 p.

Breault, R.F., and Campbell, J.P., 2010a, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, water year 2003: U.S. 

Geological Survey Open-File Report 2010–1043, 24 p.

Breault, R.F., and Campbell, J.P., 2010b, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, Water Year 2004: U.S. 

Geological Survey Open-File Report 2010–1044, 24 p.

Breault, R.F., and Campbell, J.P., 2010c, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, water year 2005: U.S. 

Geological Survey Open-File Report 2010–1045, 24 p.

Breault, R.F., and Campbell, J.P., 2010d, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, water year 2006: U.S. 

Geological Survey Open-File Report 2010–1046, 25 p.

Breault, R.F., and Smith, K.P., 2010, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, water year 2009: U.S. 

Geological Survey Open-File Report 2010–1275, 24 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.

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.

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, 2012, NIST/

SEMATECH e-Handbook of Statistical Methods: U.S. 

Department of Commerce, accessed April 17, 2013, at 

http://www.itl.nist.gov/div898/handbook/.

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.

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.

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.

Smith, K.P. and Breault, R.F., 2011, Streamflow, water 

quality, and constituent loads and yields, Scituate Reservoir 

drainage area, Rhode Island, water year 2010: U.S. 

Geological Survey Open-File Report 2011–1076, 20 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, 2001, National Water Information 

System data available on the World Wide Web (Water 

Data for the Nation): U.S. Geological Survey, accessed 

November 10, 2010, at http://waterdata.usgs.gov/nwis/.

U.S. Geological Survey, 2007, Water-resources data for the 

United States, Water Year 2006: U.S. Geological Survey 

Water-Data Report WDR–US–2006, accessed November 5, 

2009, at http://wdr.water.usgs.gov/.

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.
24 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011. [Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board] PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (CFU×106/d) E. Coli (CFU×106/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as P) Barden Reservoir Subbasin 24 01115190 Dolly Cole Brook 10/29/10 1.4 51 51 52 10 68 34 11/05/10 5.6 63,000 63,000 300 41 68 1,200 12/03/10 21 48,000 48,000 1,200 100 260 2,600 01/07/11 5.7 560 1,300 450 28 140 700 03/04/11 17 620 620 1,100 42 420 2,500 04/01/11 9.1 53,000 53,000 640 45 220 18,000 05/06/11 6.6 3,700 3,700 420 16 81 1,300 06/15/11 4.4 2,500 430 290 22 650 650 07/01/11 1.6 900 59 100 12 20 270 09/02/11 4.2 47,000 47,000 190 21 51 920 25 01115200 Shippee Brook 10/15/10 6.4 170,000 38,000 230 31 160 630 04/15/11 8.6 3,200 1,900 240 42 240 1,100 07/15/11 0.15 83 83 6.2 0.36 350 58 26 01115185 Windsor Brook 10/15/10 9.7 260,000 57,000 240 24 5.2 1,200 01/21/11 14 520 520 360 35 81 8,000 04/15/11 13 150,000 7,400 710 32 280 250 07/15/11 0.21 120 120 12 0.52 1,100 81
References Cited 25

PWSB 

station 

number

USGS 

station 

number

Station 

name

Date

Daily 

mean 

streamflow 

(ft3/s)

Total 

coliform bacteria

(CFU×106/d) 

E. Coli

(CFU×106/d) 

Chloride

(kg/d)

Nitrite

(g/d as N)

Nitrate

(g/d as N)

Orthophosphate

(g/d as P)

28 01115265 Barden Reservoir (Hemlock Brook) 10/12/10 3.3 190,000 12,000 210 48 88 7,300 11/09/10 23 >620,000 >1,400,000 1,100 110 220 18,000

12/14/10 94 >5,500,000 2,500,000 3,800 920 3,700 1,20001/11/11 7.2 4,100 700 230 18 120 44002/15/11 18 9,200 660 950 44 130 240,00003/08/11 200 340,000 84,000 5,500 370 320 1,50004/12/11 0 5,600 370 640 24 210 2,20005/10/11 11 12,000 12,000 790 27 100 12,00006/14/11 26 >1,500,000 290,000 1,000 250 3,500 3,50007/12/11 8.4 230,000 230,000 520 100 910 1,00008/09/11 8.5 >500,000 >500,000 310 83 910 6,70009/13/11 16 430,000 430,000 740 160 930 2,500

35 01115187 Ponaganset River 10/29/10 9.3 2,000 910 230 68 490 13,000

11/05/10 37 2,200,000 140,000 1,800 360 680 4,60012/03/10 38 430,000 430,000 2,000 190 440 2,00001/07/11 20 11,000 11,000 920 49 310 9,60003/04/11 56 2,100 2,100 2,800 140 510 160,00004/01/11 36 20,000 20,000 1,500 88 50 3,70005/06/11 25 920 920 1,400 61 3.9 3,60006/15/11 21 12,000 12,000 1,500 100 220 1,00007/01/11 4.1 900 150 81 30 17 7008/05/11 0.32 3,600 3,600 5.9 0.78 19 3,50009/02/11 18 200,000 200,000 730 88 92 170

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
26 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (CFU×106/d) E. Coli (CFU×106/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as P) Direct Runoff Subbasin

1 01115180 Brandy Brook 10/05/10 1.4 800 800 7.3 3.5 72 300

11/16/10 1.5 1,600 110 65 3.8 160 1,30012/16/10 3.8 14,000 100,000 85 28 79 72001/04/11 2.9 6,700 6,700 87 22 140 1,30003/01/11 6.5 24,000 1,400 280 32 12 1,40004/05/11 3.2 19,000 1,800 96 16 10 70005/03/11 2.8 17,000 1,500 84 7.0 0.43 19006/07/11 0.96 1,800 35 31 9.4 28 14007/05/11 0.42 240 15 6.6 3.1 45 5.208/02/11 0.04 210 1.3 0.71 <0.01 16 61009/16/11 2.3 26,000 26,000 73 11 140 450

3 01115280 Cork Brook 10/07/10 3.7 >100,000 >220,000 43 18 78 190

11/04/10 1.3 >35,000 >76,000 7.6 3.2 75 2,00012/02/10 5.7 >330,000 >330,000 72 42 150 20001/06/11 1.6 94,000 5,900 130 3.9 56 7503/03/11 6.1 >360,000 >360,000 600 15 54 2,60004/13/11 12 >700,000 70,000 940 88 13 28005/15/11 2.3 62,000 8,400 170 5.6 0.49 5406/02/11 1.1 >65,000 620 76 2.7 13 12007/07/11 0.18 2,000 170 11 1.3 110 0.2408/04/11 0.02 >1,200 11 2.1 <0.01 5.1 35009/01/11 1.1 >65,000 >65,000 89 5.4 57 480

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
References Cited 27

PWSB 

station 

number

USGS 

station 

number

Station 

name

Date

Daily 

mean 

streamflow 

(ft3/s)

Total 

coliform bacteria

(CFU×106/d) 

E. Coli

(CFU×106/d) 

Chloride

(kg/d)

Nitrite

(g/d as N)

Nitrate

(g/d as N)

Orthophosphate

(g/d as P)

4 01115400 Kent Brook 10/05/10 0.46 850 850 15 1.1 44 61

11/16/10 0.42 15 15 3.8 1.0 110 17012/16/10 2.3 14,000 14,000 19 11 110 22001/04/11 1.8 180 66 25 4.4 19 21002/08/11 8.7 850 320 130 43 22 44003/01/11 9.1 53,000 330 220 44 1.1 16004/05/11 1.6 900 900 20 7.8 0.50 11005/03/11 0.9 500 33 11 2.2 11 2006/07/11 0.09 52 3.4 1.5 0.23 13 6.007/05/11 0.04 1,100 23 0.72 0.20 130 26009/06/11 0.9 5,300 5,300 12 2.2 20 40

5 01115184 Spruce Brook 10/19/10 0.27 150 150 12 0.66 22 640

04/19/11 5.2 2,900 2,900 200 25 300 9207/19/11 0.47 2,800 490 36 2.3 430 470

6 01115183 Quonapaug Brook 10/05/10 1.6 >43,000 >94,000 86 3.9 81 750

11/16/10 1.8 1,900 1,900 200 4.4 320 1,50012/16/10 6.2 70,000 70,000 450 30 240 97001/04/11 4.4 4,600 1,600 380 22 310 16002/08/11 6.6 1,800 3,700 66 32 11 1,90003/01/11 13 48,000 24,000 1,200 32 3.7 49004/05/11 5.0 5,300 5,300 470 24 33 1,00005/03/11 4.2 4,400 4,400 390 10 120 25006/07/11 0.94 340 34 100 14 55 10007/05/11 0.3 3,400 3,400 5.0 9.5 130 73009/06/11 2.7 >160,000 >160,000 310 13 150 2,000

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
28 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (CFU×106/d) E. Coli (CFU×106/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as P)

7 01115297 Wilbur Hollow Brook 10/07/10 <0.01 >270,000 >590,000 360 73 210 1,200

11/04/10 4.5 4,700 4,700 160 11 200 27012/02/10 11 >650,000 >650,000 450 81 78 1,20001/06/11 6.1 600 600 590 30 210 3,70003/03/11 17 1,000,000 3,700 930 42 5.5 1,20004/07/11 8.2 4,600 4,600 250 40 81 94005/15/11 6.4 >170,000 33,000 170 47 56 31006/02/11 4.2 >250,000 2,400 330 10 270 18007/07/11 0.45 1,000 250 24 3.3 370 1,90009/01/11 6.6 >390,000 >390,000 130 48 120 390

8 01115276 Westconnaug Brook 10/08/10 2.3 2,200 2,200 55 5.6 99 810

12/17/10 11 6,200 6,200 270 27 430 3,30003/11/11 15 1,500 550 510 37 68 2,80004/08/11 9.7 360 360 310 24 34 59005/13/11 8.1 1,800 300 390 20 420 4,50006/10/11 8.8 5,000 5,000 410 43 12 82007/08/11 5.6 3,200 3,200 390 14 390 55008/12/11 2.8 1,600 1,600 180 6.8 240 14,00009/09/11 17 620 620 820 42 25 72

9 01115275 Bear Tree Brook 10/19/10 0.49 1,100 110 26 2.4 9.2 390

04/19/11 2.3 1,300 230 260 11 160 26

32 01115178 Unnamed Tributary 1 

to Scituate Reservoir (Pine Swamp Brook)

10/20/10 0.18 100 100 4.0 0.87 40 30001/20/11 1.1 12,000 1,200 40 2.7 1.0 22004/21/11 1.0 570 98 38 2.5 930 9.2

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
References Cited 29

PWSB 

station 

number

USGS 

station 

number

Station 

name

Date

Daily 

mean 

streamflow 

(ft3/s)

Total 

coliform bacteria

(CFU×106/d) 

E. Coli

(CFU×106/d) 

Chloride

(kg/d)

Nitrite

(g/d as N)

Nitrate

(g/d as N)

Orthophosphate

(g/d as P)

33 01115182 Unnamed Tributary 3 

to Scituate Reservoir (Hall’s Estate Brook)

10/27/10 0.13 1,400 120 4.1 0.31 61 5901/31/11 0.8 29 29 36 2.0 44 9304/27/11 0.54 300 20 27 2.6 300 2.407/27/11 0.02 >1,100 110 1.0 0.0 1,000 49

Moswansicut Reservoir Subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

10/14/10 2.0 200 200 170 4.9 340 43011/15/10 2.5 >67000 >150000 210 6.1 49 26012/09/10 1.8 110,000 6,600 140 4.4 42 30002/10/11 6.2 230 230 530 30 37 1,00003/10/11 21 3,600 770 1,100 100 590 11,00004/14/11 14 1,400 510 1,300 68 61 1,20005/12/11 4.0 150 150 350 9.8 280 17006/09/11 3.4 7,700 1,200 260 8.3 0.82 29007/14/11 3.0 1,700 1,700 220 7.3 13 2,30008/16/11 12 22,000 22,000 770 29 590 98009/16/11 5.0 2,800 490 260 12 150 280

21 01115165 Unnamed Tributary 2 to 

Moswansicut Reservoir (Brook from Kimball Reservoir)

04/18/11 2.3 61,000 2,400 170 11 640 4.907/18/11 0.03 120 12 0.68 0.33 3,100 220

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
30 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (CFU×106/d) E. Coli (CFU×106/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as P) Regulating Reservoir Subbasin 14 01115110 Huntinghouse Brook 10/04/10 1.1 4,000 40 30 2.7 160 2,900 11/18/10 24 25,000 25,000 480 120 120 1,200 12/06/10 6.0 22,000 14,000 120 15 150 6,400 01/03/11 26 150,000 150,000 600 64 2,800 62,000 03/07/11 300 >14,800,000 460,000 4,300 1800 57 2,900 04/04/11 13 12,000 1,300 380 32 16 1,600 05/02/11 9.5 10,000 10,000 280 46 4,500 310 06/06/11 2.1 24,000 7,700 210 10 120 15,000 08/15/11 29 >1,700,000 >1,700,000 170 350 390 110 09/15/11 4.7 >280,000 17,000 33 34 3,600 320 15 01115115 Rush Brook 10/04/10 1.3 4,800 730 140 3.2 120 1,000 11/18/10 14 26,000 1,700 700 100 77 840 12/06/10 4.9 >290,000 1,800 420 12 81 2,700 01/03/11 16 9,000 9,000 820 39 1.0 32,000 03/07/11 100 540,000 860,000 6,800 1100 2,500 1,200 04/04/11 9.8 10,000 2,600 1,100 24 48 1,100 05/02/11 6.3 37,000 6,600 650 31 44 220 06/06/11 1.1 400 1,000 140 5.4 1,200 22 07/25/11 0.04 230 230 4.7 <0.01 120 17,000 08/15/11 52 >3,100,000 >3,100,000 2,300 1700 880 290 09/15/11 3.9 100,000 23,000 120 29 7,900 350 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued [Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
References Cited 31

PWSB 

station 

number

USGS 

station 

number

Station 

name

Date

Daily 

mean 

streamflow 

(ft3/s)

Total 

coliform bacteria

(CFU×106/d) 

E. Coli

(CFU×106/d) 

Chloride

(kg/d)

Nitrite

(g/d as N)

Nitrate

(g/d as N)

Orthophosphate

(g/d as P)

16 01115098 Peeptoad Brook (Harrisdale Brook) 10/04/10 3.6 3,800 350 240 8.8 290 7,300 11/18/10 50 26,000 26,000 3,800 370 54 720

12/06/10 4.9 18,000 130,000 410 12 15 2,60001/03/11 18 33,000 33,000 1,500 44 8.3 2,00003/07/11 200 >9,500,000 >9,500,000 11,000 1200 640 2,60004/04/11 12 6,800 1,200 1,000 29 57 54005/02/11 4.4 50,000 4,200 570 22 42 8806/06/11 1.2 680 680 130 5.9 11 22007/25/11 0.68 1,200 1,200 86 1.7 47 1,90008/15/11 13 350,000 350,000 1,000 380 120 11009/15/11 4.7 8,600 1,300 250 11 29 290

18 01115120 Unnamed Tributary to 

Regulating Reservoir (Unnamed Brook A)

04/18/11 1.7 >100,000 1,800 180 8.3 260 11

Westconnaug Reservoir Subbasin

10 01115274 Westconnaug Brook 10/12/10 0.44 1,600 150 21 1.1 23 560

11/09/10 3.8 22,000 22,000 200 19 23 97012/14/10 10 18,000 18,000 580 24 22 27001/11/11 1.2 71,000 120 100 2.9 4.0 2,30003/08/11 11 6,000 390 500 52 88 4704/12/11 1.9 1,100 70 140 4.7 290 32005/10/11 1.9 68 68 130 4.5 1.6 79006/14/11 1.8 >110,000 >110,000 95 4.4 15 4807/12/11 0.33 1,900 1,900 18 0.80 10 48009/13/11 1.8 1,000 1,000 97 18 14 37

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued[Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
32 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2011 PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (CFU×106/d) E. Coli (CFU×106/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as P) 11 01115273 Unnamed Tributary to Westconnaug Reser- voir (Unnamed Brook South of Westconnaug Reservoir) 10/26/10 0.25 140 140 8.2 4.4 83 48 04/26/11 2.0 1,100 1,100 240 9.6 14 820 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate by tributary reservoir subbasin in the Scituate Reservoir drainage area, Rhode Island, October 1, 2010, through September 30, 2011.—Continued [Water-quality data are from samples collected and analyzed by Providence Water Supply Board (PWSB); USGS, U.S. Geological Survey; ft3/s, cubic feet per second; CFUx106/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilograms per day; g/d, grams per day; N, nitrogen; P, phosphorus; <, less than; >, greater than; shaded areas indicate values that were calculated with concentration data censored at half the detection level; alternate station names given in parenthesis for stations where different historical names were used for the same sampling location by Providence Water Supply Board]
Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Office Chief

U.S. Geological Survey

New England Water Science Center 

Massachusetts-Rhode Island Office

10 Bearfoot Road

Northborough, MA 01532

dc_ma@usgs.gov

or visit our Web site at:

http://ma.water.usgs.gov
Smith—Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, Water Year 2011—Open-File Report 2013–1127, ver. 1.1

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20131127