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 2016

Open-File Report 2018–1084

U.S. Department of the Interior

U.S. Geological Survey
Cover. U.S. Geological Survey streamgage at Quonopaug Brook at State Route 116 near North Scituate, Rhode Island; photograph by the 

U.S. Geological Survey.
Streamflow, Water Quality, and 

Constituent Loads and Yields, Scituate 

Reservoir Drainage Area, Rhode Island, 

Water Year 2016

By Kirk P. Smith

Prepared in cooperation with the Providence Water Supply Board

Open-File Report 2018–1084

U.S. Department of the Interior

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

RYAN K. ZINKE, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2018

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Suggested citation:

Smith, K.P., 2018, Streamflow, water quality, and constituent loads and yields, Scituate Reservoir drainage area, 

Rhode Island, water year 2016: U.S. Geological Survey Open-File Report 2018–1084, 32 p., https://doi.org/10.3133/

ofr20181084.

ISSN 2331-1258 (online)
iii

Contents

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

Introduction.....................................................................................................................................................1

Streamflow Data Collection and Estimation..............................................................................................3

Water-Quality Data Collection and Analysis.............................................................................................3

Data Collected by the U.S. Geological Survey.................................................................................3

Data Collected by the Providence Water Supply Board................................................................8

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

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

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

Chloride and Sodium 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..........................................................11

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

Constituent Concentrations and Daily Loads and Yields.....................................................11

Bacteria.......................................................................................................................................12

Chloride and Sodium .................................................................................................................13

Nutrients......................................................................................................................................13

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

Figures

1. Map showing locations of tributary-reservoir subbasins and stations in the 

Scituate Reservoir drainage area, Rhode Island, in water year 2016..................................2

2. Graph showing flow-duration curve and streamflow on the dates when waterquality samples were collected for the U.S. Geological Survey continuous 

streamgage on Rush Brook near Elmdale Road North Scituate, Rhode Island, 

in water year 2016.........................................................................................................................8

3. Graph showing measured daily mean streamflow for October 1, 2015, through 

September 30, 2016, and the 10th percentile, median, and 90th percentile values 

of daily streamflow for October 1, 1994, through September 30, 2015, for the 

U.S. Geological Survey continuous-record streamgage on the Ponaganset River 

at South Foster in the Scituate Reservoir drainage area, Rhode Island...........................10

4. Graph showing annual loads of chloride and sodium estimated from streamflow 

and specific conductance data for water year 2016 and associated minimum, 

maximum, and median annual loads for water years 2009–15 at 14 Providence 

Water Supply Board stations in the Scituate Reservoir drainage area, 

Rhode Island................................................................................................................................12
iv

Tables

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

samples, and available streamflow and specific conductance monitoring in the 

Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, to September 30, 2016 ....................................................................................................................................4

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

Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through 

September 30, 2016.......................................................................................................................6

3. Regression equation coefficients used to estimate concentrations of chloride 

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

monitoring stations in the Scituate Reservoir drainage area, Rhode Island, from 

October 1, 2015, through September 30, 2016 ..........................................................................7

4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the 

Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through 

September 30, 2016.....................................................................................................................25

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

measurements of specific conductance in the Scituate Reservoir drainage area, 

Rhode Island, from October 1, 2015, through September 30, 2016 .....................................14

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

stations in the Scituate Reservoir drainage area, Rhode Island, from October 1, 

2015, through September 30, 2016............................................................................................16

7. Monthly estimated chloride and sodium loads for sampling stations in the 

Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through 

September 30, 2016.....................................................................................................................17

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

Board stations in the Scituate Reservoir drainage area, Rhode Island, from 

October 1, 2015, through September 30, 2016 ........................................................................19

9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from 

October 1, 2015, through September 30, 2016 ........................................................................21
v

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2)

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

ton, short (2,000 lb) 0.9072 metric ton (t)

Datum

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

Supplemental Information

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

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

Loads of chemical constituents in water are given in kilograms (kg), and daily loads are given 

in grams per day (g/d), kilograms per day (kg/d), kilograms per year (kg/yr), or million colony 

forming units per day (MCFU/d).

Yields are given in grams per day per square mile (g/d/mi2), kilograms per day per square mile 

(kg/d/mi2), kilograms per year per square mile (kg/yr/mi2), or million colony forming units per day 

per square mile (MCFU/d/mi2).

Abbreviations

E. coli Escherichia coli

MOVE.1 Maintenance of Variance Extension type 1

NWIS National Water Information System

PWSB Providence Water Supply Board

RIDEM Rhode Island Department of Environmental Management

USGS U.S. Geological Survey

WY water year

Streamflow, Water Quality, and Constituent Loads and 

Yields, Scituate Reservoir Drainage Area, Rhode Island, 

Water Year 2016

By Kirk P. Smith

Abstract

As part of a long-term cooperative program to monitor 

water quality within the Scituate Reservoir watershed, the 

U.S. Geological Survey in cooperation with the Providence 

Water Supply Board collected streamflow and water-quality 

data at the Scituate Reservoir and tributaries. Streamflow 

and concentrations of chloride and sodium estimated from 

records of specific conductance were used to calculate loads 

of chloride and sodium during water year (WY) 2016 (October 1, 2015, through September 30, 2016) for tributaries to 

the Scituate Reservoir, Rhode Island. Streamflow was measured or estimated by the U.S. Geological Survey following 

standard methods at 23 streamgages; 14 of these streamgages 

are equipped with instrumentation capable of continuously 

monitoring water level, specific conductance, and water 

temperature. Water-quality samples were collected by the 

Providence Water Supply Board at 34 sampling stations that 

also include 14 continuous-record streamgages maintained 

by the U.S. Geological Survey during WY 2016 as part of a 

long-term sampling program; all stations are in the Scituate 

Reservoir drainage area. Water-quality data collected by the 

Providence Water Supply Board 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 2016.

The largest tributary to the reservoir, the Ponaganset 

River, which was monitored by the U.S. Geological Survey, 

contributed a mean streamflow of 18 cubic feet per second to 

the reservoir during WY 2016. For the same period, annual 

mean streamflows measured (or estimated) for the other 

monitoring stations in this study ranged from about 0.27 to 

about 12 cubic feet per second. Together, tributaries equipped 

with instrumentation capable of continuously monitoring 

specific conductance transported about 2,100,000 kilograms 

of chloride and 1,300,000 kilograms of sodium to the Scituate 

Reservoir during WY 2016; chloride and sodium yields for the 

tributaries ranged from 14,000 to 95,000 kilograms per square 

mile and from 8,600 to 56,000 kilograms per square mile, 

respectively.

At the stations where water-quality samples were 

collected by the Providence Water Supply Board, the 

medians of the median concentrations were 27.9 milligrams 

per liter for chloride, 0.002 milligram per liter as nitrogen 

for nitrite, 0.13 milligram per liter as nitrogen for nitrate, 

0.07 milligram per liter as phosphate for orthophosphate, and 

700 and 10 colony forming units per 100 milliliters for total 

coliform bacteria and Escherichia coli (E. coli), respectively. 

The medians of the median daily loads of chloride, nitrite 

nitrogen, nitrate nitrogen, orthophosphate, and total coliform 

and E. coli bacteria were 170 kilograms per day, 8.9 grams 

per day, 570 grams per day, 320 grams per day, 41,000 million 

colony forming units per day, and 680 million colony forming 

units per day. The medians of the median yields of chloride, 

nitrite nitrogen, nitrate nitrogen, orthophosphate, total 

coliform, and E. coli bacteria were 53 kilograms per day per 

square mile, 4.7 grams per day per square mile, 130 grams 

per day per square mile, 165 grams per day per square mile, 

23,000 million colony forming units per day per square mile, 

and 340 million colony forming units per day per square 

mile, respectively.

Introduction

The Scituate Reservoir is the primary source of drinking 

water for more than 60 percent of the population of Rhode 

Island. The Scituate Reservoir drainage area consists of six 

subbasins and covers an area of about 94 square miles in 

parts of the towns of Cranston, Foster, Glocester, Johnston, 

and Scituate, Rhode Island (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 
2 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

NARRAGANSETT BAY

BLOCK ISLAND

SOUND

41o45'

71o

45' 71o30'

41o

30'

42o

00'

0 10 MILES

0 10 KILOMETERS

RHODE ISLAND

Study

basin

71O45'

71O

37'30"

41O

52'30"

41O

45'

Base from U.S. Geological Survey

1:24,000-scale digital data

State Plane Feet Zone 5176

Westconnaug 

Reservoir

Ponaganset 

Reservoir

Regulating 

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

34

19

16 20

14

15

17

18

23

27

25 26

24

10

11

7

30

35

36

37

Ponaganset Reservoir subbasin

Regulating Reservoir subbasin

Westconnaug Reservoir subbasin

Basin boundary

Subbasin boundary

Water-quality sampling

 subbasin boundary

Barden Reservoir subbasin

Direct Runoff subbasin

Moswansicut Reservoir subbasin

Subbasins and reservoir areas

Unsampled area draining 

 directly to Scituate Reservoir

Streamflow or water-quality monitoring 

 station and identifier

Providence Water Supply Board 

 water-quality sampling station and number

 Primary roads, including

 arterial and collector roads

Providence Water Supply Board water-quality 

 sampling station and U.S. Geological Survey 

 continuous streamgage and water-quality 

 monitoring station

22

35

7

4

Providence Water Supply Board water-quality 

 sampling station and U.S. Geological Survey 

 continuous water-quality monitoring station

Providence Water Supply Board water-quality 

 sampling station and U.S. Geological Survey 

 partial-record station—Downstream order 

 numbers shown in table 1

EXPLANATION

Figure 1. Locations of tributary-reservoir subbasins and stations in the Scituate Reservoir drainage area, Rhode Island, in water 

year 2016.
Water-Quality Data Collection and Analysis 3

streamflow in tributaries to the Scituate Reservoir. Streamflow 

has been continuously measured at 10 streamgages in the 

drainage area (table 1) since 2009 by the USGS. Streamflow 

also was continuously measured at four streamgages during 2009–14 and periodically measured at nine additional 

streamgages on tributaries in the drainage area. At the 

13 streamgages without continuous flow data (partial-record 

streamgages; table 1), daily mean1 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 

(table 1). Equations that relate specific conductance to concentrations of chloride and sodium in stream water were developed as part of previous cooperative studies of the USGS and 

PWSB (Nimiroski and Waldron, 2002; Smith, 2015b, 2018a). 

These equations used together with measured (or estimated) 

streamflows allow for nearly continuous estimation of chloride 

and sodium loads to the reservoir.

In 2016, the PWSB regularly, either monthly or quarterly, 

collected water-quality samples from 34 tributaries within 

the Scituate Reservoir drainage area. Compiled and tabulated 

streamflow (measured or estimated by the USGS) and waterquality data (collected by the PWSB) have been published 

in Breault and others (2000), Nimiroski and others (2008), 

Breault (2010), Breault and Campbell (2010a–d), Breault and 

Smith (2010), Smith and Breault (2011), Smith (2013, 2014, 

2015a,b, 2016, 2018a–c).

This report presents data on streamflow, water quality, 

and loads and yields of selected constituents for water year 

(WY)2 2016 in the Scituate Reservoir drainage area. These 

data were collected as part 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 

10 continuous-record and 13 partial-record streamgages in the 

drainage area. Estimated monthly and annual loads and yields 

of chloride and sodium are presented for the 14 streamgages at 

which specific conductance is continuously monitored by the 

USGS. Summary statistics for water-quality data collected by 

the PWSB for 34 of the 37 sampling stations (table 1) during 

WY 2016 also are presented, and these data were used to calculate loads and yields of selected water-quality constituents.

Streamflow Data Collection and 

Estimation

Streamflow was measured or estimated by the USGS at 

23 streamgages (table 1). Measured and estimated streamflows 

are necessary to estimate water volume and water-quality 

constituent loads and yields from tributary basins. Stream 

1

The arithmetic mean of the individual daily mean discharges for the year 

noted or for the designated period.

2

A water year is the period between October 1 and September 30 and is 

designated by the year in which it ends.

stage was measured every 10 minutes at most continuousrecord streamgages. Streamflow was computed with a stagedischarge relation (known as a rating), which was developed 

on the basis of periodic manual measurements of streamflow. 

Daily mean streamflow at a streamgage was calculated by 

dividing the total volume of water that passed the streamgage 

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

Periodic manual streamflow measurements at partial-record 

streamgages were used concurrently with continuous-record 

measurements from streamgages in nearby hydrologically 

similar drainage areas to estimate a continuous daily record 

at the partial-record streamgages. Specifically, continuousstreamflow records for the 13 partial-record sites in the 

Scituate Reservoir drainage area (table 1) were estimated 

by using the Maintenance of Variance Extension type 1 

(MOVE.1) method, as described by Ries and Friesz (2000) 

and Smith (2015b); data needed to estimate streamflows at 

partial-record sites were retrieved from the USGS National 

Water Information System (NWIS; U.S. Geological Survey, 

2016). The upper and lower 90-percent confidence limits 

for the estimated mean annual streamflows, as described by 

Tasker and Driver (1988), are listed in table 2. These data 

indicate that there is a 90-percent chance that the estimated 

mean annual streamflow is between the upper and lower 

90-percent confidence limits.

Continuous-record streamgages were operated and 

maintained by the USGS during WY 2016 in cooperation with 

RIDEM (USGS streamgage 01115187) and the PWSB (fig. 1; 

table 1). Streamflow data for these streamgages were collected at 10- or 15-minute intervals (near-real-time streamflow 

data), were updated at 1-hour intervals on the internet, and are 

available through the NWIS web interface (U.S. Geological 

Survey, 2016). Error associated with measured streamflows 

was generally within about 15 percent as noted in the annual 

water year summary for each USGS streamgage.

Water-Quality Data Collection and 

Analysis

Water-quality data were collected by the USGS and the 

PWSB. Concentrations of sodium and chloride were estimated 

by the USGS from continuous records of specific conductance from 14 of the 21 streamgages. Water-quality samples 

were collected monthly or quarterly at 34 sampling stations 

in the Scituate Reservoir drainage area by the PWSB during 

WY 2016 as part of a long-term sampling program (table 1).

Data Collected by the U.S. Geological Survey

The USGS collected and analyzed specific conductance 

data at the 14 continuous-record streamgages (fig. 1; table 1). 

Measurements of specific conductance were recorded automatically at 10- or 15-minute intervals at each streamgage. 
4 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

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

specific conductance monitoring in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, to September 30, 2016.

[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water 

Supply Board (PWSB). Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; mi2, square mile; QW, water quality; Na, sodium; Cl, chloride; M, monthly; Q, quarterly; Y, yes; N, no; Continuous, recorded at 10- or 15-minute intervals; --, none]

PWSB 

station 

number

USGS 

station 

number

Station name

Drainage 

area 

(mi2

)

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Streamflow 

availability

Specific 

conductance 

availability

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 4.90 M 12 Y Continuous Continuous

25 01115200 Shippee Brook 2.35 Q 3 N Estimated None

26 01115185 Windsor Brook 4.32 Q 2 N Estimated None

27 011151845 Unnamed tributary to Ponaganset River 

(unnamed brook B, unnamed brook west 

of Windsor Brook)

0.10 Q 2 N None None

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

29 01115271 Ponaganset River (Barden Stream) 33.0 M 9 N None None

35 01115187 Ponaganset River 14.0 M 10 Y Continuous Continuous

Direct Runoff subbasin

1 01115180 Brandy Brook 1.57 M 12 N Estimated None

2 01115181 Unnamed tributary #2 to Scituate Reservoir 

(unnamed brook north of Bullhead 

Brook)

0.15 Q 1 N None None

3 01115280 Cork Brook 1.79 M 11 Y Continuous Continuous

4 01115400 Kent Brook (Betty Pond Stream) 0.85 M 9 N Estimated None

5 01115184 Spruce Brook 1.22 Q 3 Y Estimated Continuous

6 01115183 Quonapaug Brook 1.96 M 10 Y Continuous Continuous

7 01115297 Wilbur Hollow Brook 4.32 M 12 Y Estimated Continuous

8 01115276 Westconnaug Brook (Westconnaug 

Reservoir)

5.18 M 8 Y Continuous Continuous

9 01115275 Bear Tree Brook 0.62 Q 2 Y Estimated Continuous

30 01115350 Unnamed tributary #4 to Scituate Reservoir 

(Coventry Brook, Knight Brook)

0.78 Q 1 N None None

31 01115177 Toad Pond 0.04 Q 0 N None None

32 01115178 Unnamed tributary #1 to Scituate Reservoir 

(Pine Swamp Brook)

0.45 Q 2 N Estimated None

33 01115182 Unnamed tributary #3 to Scituate Reservoir 

(Halls Estate Brook)

0.28 Q 2 N Estimated None

36 -- Outflow from King Pond 0.77 Q 3 N None None

37 -- Fire Tower Stream 0.15 Q 3 N None None
Water-Quality Data Collection and Analysis 5

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

specific conductance monitoring in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, to September 30, 2016.

—Continued

[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water 

Supply Board (PWSB). Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; mi2, square mile; QW, water quality; Na, sodium; Cl, chloride; M, monthly; Q, quarterly; Y, yes; N, no; Continuous, recorded at 10- or 15-minute intervals; --, none]

PWSB 

station 

number

USGS 

station 

number

Station name

Drainage 

area 

(mi2

)

Frequency 

of QW 

sample 

collection

Number of 

samples 

collected by 

Providence 

Water1

Daily 

estimated 

Na and Cl 

loads

Streamflow 

availability

Specific 

conductance 

availability

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

3.25 M 10 Y Continuous Continuous

20 01115160 Unnamed tributary #1 to Moswansicut 

Reservoir (Blanchard Brook)

1.18 M 9 N None None

21 01115165 Unnamed tributary #2 to Moswansicut 

Reservoir (brook from Kimball 

Reservoir)

0.29 Q 1 N Estimated None

22 01115167 Moswansicut Reservoir (Moswansicut 

Stream South)

0.22 M 7 N None None

34 01115164 Kimball Stream 0.27 Q 1 N None None

Ponaganset Reservoir subbasin

23 011151843 Ponaganset Reservoir 1.92 M 8 N None None

Regulating Reservoir subbasin

13 01115176 Regulating Reservoir 22.1 M 8 N None None

14 01115110 Huntinghouse Brook 6.23 M 10 Y Continuous Continuous

15 01115114 Rush Brook 4.70 M 11 Y Continuous Continuous

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

17 01115119 Dexter Pond (Paine Pond) 0.22 Q 0 N None None

18 01115120 Unnamed tributary to Regulating Reservoir 

(unnamed brook A)

0.28 Q 0 N Estimated Continuous

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 1.48 M 10 N Estimated None

11 01115273 Unnamed tributary to Westconnaug 

Reservoir (unnamed brook south of 

Westconnaug Reservoir)

0.72 Q 2 N Estimated None

12 011152745 Unnamed tributary to Westconnaug Brook 

(unnamed brook north of Westconnaug 

Reservoir)

0.16 Q 3 N None None

1

Not all samples were analyzed for all water-quality properties or constituents.
6 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

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

Island, from October 1, 2015, through September 30, 2016.

[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence 

Water Supply Board (PWSB). Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; ft3/s/mi2, cubic foot 

per second per square mile]

PWSB 

station 

number

USGS 

station 

number

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 6.0 6.8 5.2 1.2

25 01115200 Shippee Brook 3.5 12 1.0 1.5

26 01115185 Windsor Brook 5.4 22 1.3 1.2

28 01115265 Barden Reservoir (Hemlock Brook) 12 14 11 1.4

35 01115187 Ponaganset River 18 20 16 1.3

Direct Runoff subbasin

1 01115180 Brandy Brook 1.8 3.3 1.0 1.2

3 01115280 Cork Brook 2.2 2.5 1.8 1.2

4 01115400 Kent Brook (Betty Pond Stream) 0.99 4.7 0.21 1.2

5 01115184 Spruce Brook 1.6 3.2 0.85 1.3

6 01115183 Quonapaug Brook 2.7 3.0 2.4 1.4

7 01115297 Wilbur Hollow Brook 5.7 11 3.0 1.3

8 01115276 Westconnaug Brook (Westconnaug Reservoir) 6.8 7.5 6.2 1.3

9 01115275 Bear Tree Brook 1.1 2.0 0.67 1.9

32 01115178 Unnamed tributary #1 to Scituate Reservoir 

(Pine Swamp Brook)

0.45 0.89 0.22 1.0

33 01115182 Unnamed tributary #3 to Scituate Reservoir 

(Halls Estate Brook)

0.27 0.77 0.10 0.97

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut Stream North, 

Moswansicut Pond)

3.3 3.7 3.0 1.0

21 01115165 Unnamed tributary #2 to Moswansicut Reservoir 

(Blanchard Brook)

0.47 1.0 0.21 1.6

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 7.6 8.7 6.4 1.2

15 01115115 Rush Brook 6.0 7.0 5.0 1.3

16 01115098 Peeptoad Brook (Harrisdale Brook) 6.7 7.6 5.7 1.3

18 01115120 Unnamed tributary to Regulating Reservoir 

(unnamed brook A)

0.36 1.5 0.09 1.3

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 1.6 2.8 0.87 1.0

11 01115273 Unnamed tributary to Westconnaug Reservoir 

(unnamed brook south of Westconnaug Reservoir)

0.93 1.6 0.54 1.3
Water-Quality Data Collection and Analysis 7

Measurements were made by using an instream probe and 

standard USGS methods for continuous water-quality monitoring at streams (Wagner and others, 2006). The specific conductance measurement data are available through the NWIS 

web interface (U.S. Geological Survey, 2016).

Concentrations of chloride and sodium were estimated 

from continuous measurements of specific conductance by 

using equations that were developed by the USGS to relate 

specific conductance to concentrations of chloride and sodium, 

as follows:

CCl = SPCm × b and (1)

CNa = SPCm × b, (2)

where

CCl is the chloride concentration, in milligrams 

per liter;

CNa is the sodium concentration, in milligrams per 

liter;

SPC is the specific conductance, in microsiemens 

per centimeter;

m is the slope from the MOVE.1 analysis 

(table 3); and

b is the intercept from the MOVE.1 analysis 

(table 3).

These regression equations were developed by using the 

MOVE.1 method (also known as the line of organic correlation; Helsel and Hirsch, 2002) on the basis of concurrent 

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

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

2015, through September 30, 2016.

[Locations of stations are shown on figure 1. U.S. Geological Survey (USGS) parameter codes: specific conductance, 90095; chloride, 00940; sodium, 00930. 

PWSB, Providence Water Supply Board]

PWSB 

station 

number

USGS 

station 

number

Samples used in analyses Chloride Sodium

Sample data range 

(month/day/year)

Sample 

count Slope Intercept

Standard error 

of regressions 

(percent)

Slope Intercept

Standard error 

of regressions 

(percent)

24 01115190 03/08/2000; 03/29/2005; 

01/22/2009 to 07/06/2017

26 1.2571 0.06894 3.8 1.2244 0.04913 7.3

28 01115265 03/28/2001; 03/30/2005; 

01/22/2009 to 07/06/2017

26 1.2270 0.07901 5.5 1.1326 0.07443 9.0

35 01115187 03/28/2001; 03/29/2005; 

01/22/2009 to 07/06/2017

26 1.2428 0.07282 6.3 1.1751 0.06094 8.4

3 01115280 03/08/2000; 03/30/2005; 

01/22/2009 to 07/19/2017

26 1.2217 0.07704 4.9 1.0722 0.09611 7.8

5 01115184 03/05/2009 to 07/20/2017 23 1.2558 0.06221 6.5 1.0813 0.08318 6.1

6 01115183 03/08/2000; 03/30/2005; 

01/22/2009 to 07/20/2017

34 1.1920 0.07872 6.7 1.2291 0.03842 9.2

7 01115297 03/28/2001; 03/30/2005; 

01/22/2009 to 07/20/2017

25 1.0552 0.13303 6.3 0.89330 0.16852 8.6

8 01115276 01/22/2009 to 07/19/2017 23 1.1016 0.13513 4.9 1.0463 0.10969 5.9

9 01115275 03/08/2000; 03/30/2005; 

01/22/2009 to 07/20/2017

25 1.0600 0.17564 4.2 1.0734 0.09639 5.6

19 01115170 03/08/2000; 03/29/2005; 

01/22/2009 to 07/20/2017

29 1.2410 0.06537 4.0 1.1927 0.04976 4.7

14 01115110 03/28/2001; 03/29/2005; 

01/22/2009 to 07/19/2017

30 1.2030 0.07202 12 1.0670 0.07766 11

15 01115114 01/22/2009 to 07/20/2017 31 1.1748 0.09355 4.0 1.0885 0.08810 7.5

16 01115098 03/28/2001; 03/29/2005; 

01/22/2009 to 07/20/2017

27 1.2748 0.05402 6.9 1.0919 0.08072 9.6

18 01115120 01/22/2009 to 07/19/2017 18 1.2098 0.07604 4.5 1.0879 0.08393 5.1
8 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

measurements of specific conductance3 along with chloride4

and sodium5

 concentrations measured in water-quality samples 

collected by the USGS from tributaries in the Scituate Reservoir drainage area (U.S. Geological Survey, 2016).

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 by the PWSB at 34 

of the 37 fixed stations on tributaries draining to the Scituate Reservoir during WY 2016. Sampling visits typically are 

conducted monthly at 19 stations and quarterly at another 

15 stations (table 1). No quarterly water samples were collected at Toad Pond (PWSB station 31), Dexter Pond (PWSB 

station 17), and unnamed tributary to Regulating Reservoir 

(PWSB station 18) during WY 2016.

Water-quality samples were not collected during specific 

weather conditions; instead, a strictly periodic water-quality 

sampling schedule was followed so that water-quality samples 

would be representative of various weather conditions. 

3

Specific conductance is USGS parameter code 90095.

4

Chloride is USGS parameter code 00940.

5

Sodium is USGS parameter code 00930.

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. Waterquality properties and constituent concentrations were 

measured by using unfiltered water samples. These waterquality properties included pH, alkalinity, color, turbidity, and 

concentrations of chloride, nitrite, nitrate, orthophosphate, 

and bacteria (Escherichia coli [E. coli] and total coliform); 

the data are published in Smith (2018c). Analytical methods 

used for the determination of values or concentrations of pH, 

color, turbidity, alkalinity, and chloride are documented by 

Eaton and others (2017). Concentrations of nitrite and nitrate 

were determined by U.S. Environmental Protection Agency 

method 353.2 (U.S. Environmental Protection Agency, 1993). 

Concentrations of orthophosphate were determined by the 

Hach PhosVer Method (Hach Method 8048; Hach Company, 

2000). Before August 2016, Standard Method 9222 was used 

for the determination of concentrations of bacteria in water 

samples, and thereafter, Standard Method 9223 was used for 

the determination of concentrations of bacteria (Eaton and 

others, 2017).

Water-quality samples were collected by the PWSB 

during a wide range of flow conditions. The daily mean 

flow-duration curve for Rush Brook near Elmdale Road near 

North Scituate (USGS streamgage 01115114) for WY 2016 

is shown in figure 2. The curve represents the percentage 

0.01

0.1

1

10

100

.05 1 10 40 70 95 99.5

Percentage of time streamflow was equaled or exceeded

Streamflow, in cubic feet per second

Water-quality sample 

collected at Rush Brook

Figure 2. Flow-duration curve and 

streamflow on the dates (represented 

by points) when water-quality samples 

were collected for the U.S. Geological 

Survey continuous streamgage on 

Rush Brook near Elmdale Road North 

Scituate (01115114), Rhode Island, in 

water year 2016. Location of station is 

shown on figure 1.
Water Quality and Constituent Loads and Yields 9

of time that each flow duration was equaled or 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 1.5 percentile to the 

84th percentile; this range indicates that the water-quality 

samples collected in WY 2016 represented a wide range of 

flow conditions during that water year. About 15 percent of the 

flows at this station were equal to or less than 0.01 cubic foot 

per second (ft3/s) during WY 2016.

Estimating Daily, Monthly, and Annual 

Loads and Yields

Daily, monthly, and annual chloride and sodium loads 

(in kilograms) were estimated for all streamgages for which 

continuous-streamflow and specific-conductance data were 

available for WY 2016. Daily flow-weighted concentrations of chloride and sodium were calculated by multiplying 

instantaneous flows by concurrent concentrations of chloride and sodium (estimated from measurements of specific 

conductance) for each day and dividing by the total flow for 

that day. At the four continuous monitoring stations, where 

instantaneous flow was unavailable (table 1), daily mean 

concentrations of chloride and sodium were calculated from 

the daily mean value of specific conductance for each day. 

The latter method may result in less accurate concentrations 

because instantaneous measurements of specific conductance 

may change (decrease or increase) with surface water runoff; 

however, the variability of instantaneous measurements of 

specific conductance at these streamgages was generally small 

and daily mean values did not differ substantially from daily 

flow-weighted values estimated during prior water years when 

instantaneous flow data were available. Daily loads of chloride 

and sodium were estimated by multiplying daily concentrations of chloride and sodium (in milligrams per liter) by daily 

discharge (in liters per day). Daily data were 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 2016 (table 4, in 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 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 million colony forming units, kilograms, 

or grams per day) and yields (in million colony forming units, 

kilograms, or grams per day per square mile) were calculated 

for bacteria, chloride, nitrite, nitrate, and orthophosphate. 

Censored data (concentrations reported as less than method 

detection limits) were replaced with concentrations equal to 

one-half the method detection limit.

Streamflow

Monitoring streamflow is a necessary step 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 annual streamflow 

at the streamgage on the Ponaganset River (PWSB station 35; 

USGS streamgage 01115187) for the entire period of its operation (mean of the annual mean streamflows for the period of 

record, WY 1994–2015) before WY 2016 was about 29 ft3/s 

(U.S. Geological Survey, 2016). During WY 2016, annual 

mean streamflow of 18 ft3/s was lower than the mean of the 

annual mean streamflows for the period of record. Daily 

mean streamflow was often below the 10th percentile for the 

daily mean streamflows for the period of record (fig. 3) for 

much of September through December 2015 and for lesser 

periods through WY 2016 (fig. 3). Streamflow recovered to 

more typical rates of flow during the winter of WY 2016, 

with short periods exceeding the 90th percentile for the daily 

mean streamflows for the period of record later in WY 2016. 

Mean annual streamflow at the Peeptoad Brook streamgage 

(PWSB station 16, streamgage 01115098), the other longterm continuous-record streamgage in the Scituate Reservoir 

drainage area, for its period of record (WY 1994–2015) before 

WY 2016 was about 10.5 ft3/s (U.S. Geological Survey, 2016). 

Annual mean streamflow at the Peeptoad Brook streamgage 

during WY 2016 also was lower at 6.7 ft3/s than the mean 

annual streamflow for its period of record.

Water Quality and Constituent Loads 

and Yields

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

properties, 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 high flows 

tend to have high loads because the greater volume of water 

can carry more of the constituent to the reservoir per unit time 

than tributaries with low flows. 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 

for 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 also are useful for examining potential 

differences among basin properties that may contribute to 

water quality in the reservoir.
10 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

2015 2016

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

Water year

EXPLANATION

0.1

1

10

100

1,000

Streamflow, in cubic feet per second

Daily mean streamflow, water year 2016

Median daily streamflow, water years 1994–2015

Unshaded area shows the range between the 10th and 90th

 percentile values of daily streamflow, water years 1994–2015

Figure 3. Measured daily mean streamflow 

for October 1, 2015, through September 30, 

2016, and the 10th percentile, median, and 

90th percentile values of daily streamflow for 

October 1, 1994, through September 30, 2015, 

for the U.S. Geological Survey continuousrecord streamgage on the Ponaganset River 

at South Foster (01115187) in the Scituate 

Reservoir drainage area, Rhode Island. 

Location of station is shown on figure 1.

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 loads of 

chloride and sodium (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 than small datasets. 

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.

Uncertainties associated with measuring streamflow and 

specific conductance and with chloride and sodium 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 

chloride and sodium inputs from tributaries or their drainage 

basins, based on the available data and analysis methods. 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 

streamflow are commonly assumed to affect load and yield 

calculations more than the errors associated with measuring specific conductance and (or) chemical analysis, and the 

uncertainties associated with estimated streamflow are greater 

than those associated with measured streamflow. 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.

Chloride and Sodium Loads and Yields 

Estimated From Specific-Conductance 

Monitoring Data

Chloride and sodium 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). Nimiroski and Waldron (2002) 

indicated that tributaries in basins with State-maintained roads 

had substantially higher concentrations of chloride and sodium 

than tributaries in basins with low road density, presumably 

because of deicing activities. In addition, sodium is a constituent of potential concern for human health; some persons on 

restricted diets might need to limit intake of sodium.
Water Quality and Constituent Loads and Yields 11

Estimated monthly mean6 chloride concentrations in 

tributaries of the Scituate Reservoir drainage area ranged 

from 9.3 to 97 milligrams per liter (mg/L), and estimated 

monthly mean sodium concentrations ranged from 6.2 to 

59 mg/L (table 5). The highest monthly mean concentrations 

of chloride and sodium were estimated to be 97 and 59 mg/L, 

respectively, at Quonapaug Brook (PWSB station 6) in 

October 2015 and 91 and 52 mg/L, respectively, at Rush 

Brook (PWSB station 15) in September 2016. The estimated 

monthly mean concentrations at all stations were greater 

during summer and early fall compared with the estimated 

monthly mean concentrations during the winter months. The 

highest annual mean7 concentrations of chloride and sodium 

were estimated to be 57 and 34 mg/L, respectively, at Bear 

Tree Brook (table 6). These high concentrations at Bear Tree 

Brook are the result of residual chloride and sodium leaching 

from a formerly uncovered salt storage pile to groundwater 

(Nimiroski and Waldron, 2002) and relatively small surfacewater flows. Annual mean concentrations of chloride and 

sodium estimated to be 54 and 31 mg/L, respectively, at 

unnamed tributary to Regulating Reservoir and 53 and 

31 mg/L, respectively, at Moswansicut Reservoir also were 

relatively high (table 6). Both of these stations are located 

in the more developed, northeastern part of the Scituate 

Reservoir drainage area (fig. 1).

During WY 2016, the Scituate Reservoir received about 

2,100,000 kilograms (kg; about 2,300 short tons) of chloride 

and 1,300,000 kg (about 1,400 short tons) of sodium from 

tributaries that are equipped with instrumentation capable of 

continuously monitoring specific conductance. The highest 

chloride and sodium loads in the drainage area during 

WY 2016 were estimated to be 380,000 and 230,000 kg, 

respectively, at the Ponaganset River station (PWSB 

station 35; table 6). Monthly estimated chloride and sodium 

loads were highest in February (table 7), except at Wilbur 

Hollow Brook (PWSB station 7) and Westconnaug Brook 

(PWSB station 8) where the monthly estimated loads were 

higher during April and at Peeptoad Brook (PWSB station 16) 

where the monthly estimated load was highest during January. 

Monthly estimated chloride and sodium loads for Quonapaug 

Brook (PWSB station 6) were the same in February and April. 

From January through April, the sum of the monthly loads of 

chloride and sodium at each station accounted for 69 percent 

of the annual load for the monitored area in the Scituate 

Reservoir drainage area. The highest annual chloride and 

sodium yields were 95,000 and 56,000 kilograms per square 

mile, respectively, measured at Bear Tree Brook (PWSB 

station 9; table 6). During WY 2016, estimated annual loads 

of chloride and sodium at the continuous monitoring stations 

were less than the median annual loads for WY 2009–15 at all 

stations except for Spruce Brook (PWSB station 5; chloride 

only), Quonapaug Brook (PWSB station 6), Westconnaug 

6

Monthly mean concentrations were calculated by dividing the total 

monthly load by the total discharge for the month.

7

Annual mean concentrations were calculated by dividing the total annual 

load by the total discharge for the year.

Brook (PWSB station 8), and Bear Tree Brook (PWSB 

station 9) in the Direct Runoff subbasin and Peeptoad 

Brook (PWSB station 16) in the Regulating Reservoir 

subbasin (fig. 4).

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, and color, were routinely measured to characterize 

water quality in each of the six subbasins in the Scituate 

Reservoir drainage area (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 5.3 to 7.0; the median of the medians for all stations was 6.3. Median values of color ranged 

from 12 to 140 platinum cobalt units; the median for all stations was 35 platinum cobalt units. Median values of turbidity ranged from 0.27 to 1.8 nephelometric turbidity units; the 

median for all stations was 0.62 nephelometric turbidity units. 

Median alkalinity values in tributaries were low, ranging from 

2.3 to 15 mg/L as calcium carbonate (CaCO3); the median for 

all stations was 4.8 mg/L as CaCO3 (table 8).

Constituent Concentrations and Daily Loads and 

Yields

Fecal indicator bacteria, chloride, and nutrients such as 

nitrogen and phosphorus are commonly detected in natural 

water; at elevated concentrations, these constituents can cause 

or contribute to water-quality impairments. 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 stream water from 

precipitation, weathering, or human activities such as waste 

disposal, use of septic systems, and road deicing. Sources 

of nutrients in tributary stream water include atmospheric 

deposition, leaching of naturally occurring organic material, 

discharge of groundwater that is enriched with 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 listed in tables 8 and 9.
12 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

EXPLANATION

Chloride load

Median annual load for water years 2009−15

Sodium load

Maximum annual load for water years 2009−15

Minimum annual load for water years 2009−15

Annual load for water year 2016

Providence Water Supply Board station number and subbasin name

 24 28 35 3 5 6 7 8 9 19 14 15 16 18 

Direct Runoff Moswansicut 

Reservoir

Regulating

 Reservoir

Barden

Reservoir

6,500

65,000

650,000

Load, in kilograms per year

Figure 4. Annual loads of chloride and 

sodium estimated from streamflow and 

specific conductance data for water year 

2016 and associated minimum, maximum, and 

median annual loads for water years 2009–15 

at 14 Providence Water Supply Board stations 

in the Scituate Reservoir drainage area, 

Rhode Island. Location of stations shown on 

figure 1.

Bacteria

Median concentrations of total coliform bacteria were 

above the detection limit (10 colony forming units per 

100 milliliters [CFU/100 mL]) at all sites (table 8); median 

concentrations of E. coli were equal to or greater than the 

detection limit of 10 CFU/100 mL before August 2016 and 

1 CFU/100 mL thereafter at 14 of the 34 sites for which 

samples were collected. Total coliform bacteria concentrations were greater than E. coli concentrations (as expected 

because total coliform is more inclusive); the medians of 

median concentrations for all sites in the drainage area 

were 700 CFU/100 mL for total coliform bacteria and 

10 CFU/100 mL for E. coli (table 8). The median concentration of total coliform bacteria was highest at unnamed 

tributary #2 to Moswansicut Reservoir (PWSB station 21) 

at 8,400 CFU/100 mL. The highest median concentration of 

E. coli (105 CFU/100 mL) was measured in samples collected 

at Quonapaug Brook (PWSB station 6) and Huntinghouse 

Brook (PWSB station 14). Median concentrations of fecal 

indicator bacteria were lowest at Kimball Stream (PWSB 

station 34). Median concentrations of E. coli were equivalent 

to or greater than 10 CFU/100 mL at more than half of the 

sampling stations.

Median daily loads and yields of total coliform bacteria 

and E. coli varied by about two orders of magnitude; the 

highest median daily yield of total coliform bacteria at 

480,000 million colony forming units per day per square 

mile (MCFU/d/mi2) and the highest median daily yield of 

E. coli of 4,500 MCFU/d/mi2 were at unnamed tributary #2 to 

Moswansicut Reservoir (PWSB station 21; table 9). Although 

relatively high for sampling stations in the Scituate Reservoir 

subbasin, median daily bacteria yields at Moswansicut 

Reservoir are low to moderate for yields of indicator bacteria 

in sewage-contaminated stream water or stream water 

affected by stormwater runoff in an urban environment 
Water Quality and Constituent Loads and Yields 13

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

coliform bacteria for all subbasins in the Scituate Reservoir 

drainage area ranged from 730 to 350,000 million colony 

forming units per day (MCFU/d), and yields ranged from 

860 to 480,000 MCFU/d/mi2; E. coli loads ranged from less 

than 160 to 4,900 MCFU/d, and yields ranged from 89 to 

4,500 MCFU/d/mi2 (table 9).

Chloride and Sodium

The highest median chloride concentration of 92.5 mg/L 

was measured in the Direct Runoff subbasin at unnamed 

tributary #2 to Scituate Reservoir (PWSB station 2; 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 daily 

chloride yield for monitored areas within the drainage 

area was 53 kilograms per day per square mile (kg/d/mi2). 

Ponaganset River (PWSB station 35) had the largest median 

daily chloride load at 1,100 kilograms per day. The largest 

median daily chloride yield was determined to be 370 kg/d/mi2

at Bear Tree Brook (PWSB station 9). The estimated annual 

mean yields of chloride and sodium for the drainage areas 

above the 14 USGS continuous-record streamgages, which 

represent nearly 66 percent of the Scituate Reservoir drainage 

area, were 93 and 56 kg/d/mi2, respectively. These estimated 

annual mean yields of chloride and sodium for WY 2016 

were about 13 percent lower than the estimated annual mean 

yields of 108 and 64 kg/d/mi2, respectively, for WY 2015 

(Smith, 2018a).

Nutrients

Median concentrations of nitrite and nitrate (table 8) were 

0.002 and 0.13 mg/L as nitrogen, respectively. The highest median concentration of nitrite nitrogen was 0.012 mg/L 

measured in a sample collected at Moswansicut Reservoir 

(PWSB station 22). The highest median concentration of 

nitrate nitrogen was 0.65 mg/L measured in a sample collected at unnamed tributary #2 to Scituate Reservoir (PWSB 

station 2). The median concentration of orthophosphate for 

the entire study area (table 8) was 0.07 mg/L as phosphate 

(PO4). The maximum median concentration of orthophosphate 

was 0.23 mg/L as PO4 measured in Kimball Stream (PWSB 

station 34). Median daily nitrite nitrogen and orthophosphate 

loads were largest at Ponaganset River (PWSB station 35) 

at 67 and 2,700 grams per day (g/d), respectively (table 9). 

Median daily nitrate nitrogen loads were largest at Bear Tree 

Brook (PWSB station 9) at 2,200 g/d. The largest median 

daily yields for nitrite and nitrate nitrogen were 9.9 and 

3,500 grams per day per square mile (g/d/mi2), respectively, at 

Bear Tree Brook. The largest median daily yield for orthophosphate was 660 g/d/mi2

 at Pine Swamp Brook (PWSB station 32; table 9). The medians of median daily loads and yields 

were 8.9 g/d and 4.7 g/d/mi2 for nitrite nitrogen, 570 g/d and 

130 g/d/mi2 for nitrate nitrogen, and 320 g/d and 165 g/d/mi2

for orthophosphate.
14 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 5. Monthly mean concentrations of chloride and sodium estimated from continuous measurements of specific conductance in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016. [Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water Supply Board (PWSB); locations of stations are shown on figure 1. Monthly mean concentrations were calculated by dividing the monthly load by the total discharge for the month. USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; mg/L, mil- ligram per liter; --, no flow] PWSB station number USGS station number Station name October November December January February March Cl (mg/L) Na (mg/L) Cl (mg/L) Na (mg/L) Cl (mg/L) Na (mg/L) Cl (mg/L) Na (mg/L) Cl (mg/L) Na (mg/L) Cl (mg/L) Na (mg/L) Barden Reservoir subbasin 24 01115190 Dolly Cole Brook 50 30 40 24 36 22 30 18 30 18 35 21 28 01115265 Barden Reservoir (Hemlock Brook) 50 29 43 25 33 19 23 14 21 13 26 15 35 01115187 Ponaganset River 35 21 33 20 28 17 22 13 21 13 24 15 Direct Runoff subbasin

3 01115280 Cork Brook 64 35 59 33 46 26 33 20 36 21 41 245 01115184 Spruce Brook 52 27 40 22 30 17 22 13 23 14 23 136 01115183 Quonapaug Brook 97 59 79 48 63 38 39 23 39 23 40 247 01115297 Wilbur Hollow Brook 26 15 18 11 13 8.2 10 6.4 9.3 6.2 11 7.08 01115276 Westconnaug Brook (Westconnaug Reservoir) 33 21 35 22 33 20 21 13 21 13 24 159 01115275 Bear Tree Brook 75 44 69 41 61 36 52 30 49 29 56 33

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

53 31 53 31 52 31 52 30 52 31 53 31

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 21 12 19 11 15 8.9 12 7.4 13 7.7 14 8.115 01115114 Regulating Reservoir (Rush Brook) 81 47 68 40 50 30 32 20 36 22 47 2816 01115098 Peeptoad Brook (Harrisdale Brook) 55 30 55 30 60 33 55 30 47 27 46 2618 01115120 Unnamed tributary to Regulating Reservoir 

(Unnamed brook A)

-- -- 47 27 58 33 52 30 53 30 59 33

Scituate Reservoir drainage area

Average 53 31 47 27 41 24 32 19 32 19 36 21
Water Quality and Constituent Loads and Yields 15

Table 5. Monthly mean concentrations of chloride and sodium estimated from continuous measurements of specific conductance in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water Supply Board (PWSB); locations of stations are shown on figure 1. Monthly mean concentrations were calculated by dividing the monthly load by the total discharge for the month. USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; mg/L, milligram per liter; --, no flow]

PWSB 

station 

number

USGS 

station 

number

Station name

April May June July August September

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Cl 

(mg/L)

Na 

(mg/L)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 33 20 35 21 37 22 41 25 44 26 39 2428 01115265 Barden Reservoir (Hemlock Brook) 22 13 26 16 30 18 38 22 33 19 37 2235 01115187 Ponaganset River 22 14 25 15 26 16 28 17 28 17 26 16

Direct Runoff subbasin

3 01115280 Cork Brook 37 22 40 23 40 23 43 25 58 32 60 335 01115184 Spruce Brook 20 12 21 13 25 15 35 19 46 25 62 326 01115183 Quonapaug Brook 37 22 41 24 44 26 46 27 63 38 82 507 01115297 Wilbur Hollow Brook 9.9 6.5 11 7.3 11 7.3 14 8.4 12 7.6 14 8.58 01115276 Westconnaug Brook (Westconnaug 

Reservoir)

23 14 25 16 23 14 35 21 33 20 32 20

9 01115275 Bear Tree Brook 51 30 59 35 74 44 79 47 75 45 80 48

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

54 31 55 32 56 33 56 33 63 37 62 36

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 13 7.9 15 8.6 17 9.7 17 9.8 16 9.4 15 9.015 01115114 Regulating Reservoir (Rush Brook) 38 23 47 28 56 33 87 50 73 42 91 5216 01115098 Peeptoad Brook (Harrisdale Brook) 45 26 46 26 50 28 54 30 55 30 56 3118 01115120 Unnamed tributary to Regulating Reservoir 

(unnamed brook A)

53 30 55 31 57 32 -- -- -- -- -- --

Scituate Reservoir drainage area

Average 33 19 36 21 39 23 44 26 46 27 51 29
16 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

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

area, Rhode Island, from October 1, 2015, through September 30, 2016.

[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence 

Water Supply Board (PWSB). Locations of stations are shown on figure 1. Annual mean concentrations were calculated by dividing the annual load by the total 

discharge for the year; annual mean yields were calculated by dividing the sum of individual loads by the sum of the drainage area. USGS, U.S. Geological 

Survey; Cl, chloride; Na, sodium; mg/L, milligram per liter; kg/yr, kilogram per year; kg/yr/mi2, kilogram per year per square mile]

PWSB 

station 

number

USGS 

station 

number

Station name

Concentration Load Yield

Cl

(mg/L)

Na

(mg/L)

Cl

(kg/yr)

Na

(kg/yr)

Cl

(kg/yr/mi2)

Na

(kg/yr/mi2)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 33 20 180,000 110,000 36,000 22,000

28 01115265 Barden Reservoir (Hemlock Brook) 25 15 280,000 170,000 32,000 19,000

35 01115187 Ponaganset River 24 14 380,000 230,000 27,000 17,000

Direct Runoff subbasin

3 01115280 Cork Brook 39 23 75,000 44,000 42,000 24,000

5 01115184 Spruce Brook 24 14 36,000 21,000 29,000 17,000

6 01115183 Quonapaug Brook 45 27 110,000 64,000 55,000 33,000

7 01115297 Wilbur Hollow Brook 11 7.3 58,000 37,000 14,000 8,600

8 01115276 Westconnaug Brook (Westconnaug Reservoir) 24 15 150,000 92,000 28,000 18,000

9 01115275 Bear Tree Brook 57 34 59,000 35,000 95,000 56,000

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut Stream 

North, Moswansicut Pond)

53 31 160,000 94,000 49,000 29,000

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 13 8.0 91,000 54,000 15,000 8,700

15 01115114 Rush Brook 41 25 220,000 130,000 47,000 28,000

16 01115098 Peeptoad Brook (Harrisdale Brook) 49 28 300,000 170,000 60,000 34,000

18 01115120 Unnamed tributary to Regulating Reservoir 

(unnamed brook A)

54 31 17,000 9,800 62,000 35,000

Scituate Reservoir drainage area

Mean Total Mean

35 21 2,100,000 1,300,000 34,000 20,000
Water Quality and Constituent Loads and Yields 17

Table 7. Monthly estimated chloride and sodium loads for sampling stations in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.[Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water Supply Board (PWSB). Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; kg, kilogram]

PWSB 

station 

number

USGS 

station 

number

Station name

October November December January February March

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Cl 

(kg)

Na 

(kg)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 1,900 1,100 6,800 4,100 13,000 7,600 26,000 16,000 44,000 27,000 23,000 14,00028 01115265 Barden Reservoir (Hemlock 

Brook)

5,500 3,100 11,000 6,400 25,000 15,000 38,000 23,000 62,000 38,000 32,000 19,000

35 01115187 Ponaganset River 9,000 5,300 11,000 6,700 25,000 15,000 55,000 34,000 86,000 53,000 52,000 32,000

Direct Runoff subbasin

3 01115280 Cork Brook 1,200 640 2,900 1,600 5,800 3,300 8,700 5,100 18,000 11,000 12,000 6,8005 01115184 Spruce Brook 890 460 2,000 1,100 3,000 1,700 5,100 3,000 6,700 4,000 4,700 2,8006 01115183 Quonapaug Brook 4,600 2,800 9,800 5,900 15,000 8,700 13,000 7,900 18,000 10,000 13,000 7,4007 01115297 Wilbur Hollow Brook 2,900 1,600 5,200 3,100 6,700 4,200 6,900 4,600 8,500 5,600 7,300 4,7008 01115276 Westconnaug Brook (Westconnaug Reservoir) 4,500 2,800 4,100 2,500 4,700 2,900 16,000 9,900 26,000 16,000 24,000 15,0009 01115275 Bear Tree Brook 1,700 1,000 1,400 820 1,500 880 6,500 3,800 10,000 5,900 9,100 5,400

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

630 370 1,300 740 8,200 4,800 23,000 14,000 35,000 21,000 26,000 15,000

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 740 420 1,800 1,000 5,100 3,000 14,000 8,600 23,000 14,000 12,000 7,40015 01115114 Regulating Reservoir (Rush 

Brook)

4,100 2,300 9,800 5,700 21,000 12,000 28,000 17,000 52,000 31,000 33,000 20,000

16 01115098 Peeptoad Brook (Harrisdale 

Brook)

3,700 2,100 4,500 2,500 31,000 17,000 65,000 36,000 49,000 28,000 39,000 22,000

18 01115120 Unnamed tributary to 

Regulating Reservoir (unnamed brook A)

-- -- 45 26 540 300 3,000 1,700 5,800 3,300 1,800 1,000

Scituate Reservoir drainage area

Total 41,000 24,000 72,000 42,000 170,000 100,000 310,000 180,000 440,000 270,000 290,000 170,000
18 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 7. Monthly estimated chloride and sodium loads for sampling stations in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through Septem- ber 30, 2016.—Continued [Alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the Providence Water Supply Board (PWSB). Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; Cl, chloride; Na, sodium; kg, kilogram] PWSB station number USGS station number Station name April May June July August September Cl (kg) Na (kg) Cl (kg) Na (kg) Cl (kg) Na (kg) Cl (kg) Na (kg) Cl (kg) Na (kg) Cl (kg) Na (kg) Barden Reservoir subbasin 24 01115190 Dolly Cole Brook 37,000 22,000 14,000 8,700 5,100 3,100 2,600 1,600 2,700 1,600 910 550 28 01115265 Barden Reservoir (Hemlock Brook) 50,000 30,000 25,000 15,000 9,200 5,500 1,600 960 14,000 8,200 3,800 2,200 35 01115187 Ponaganset River 70,000 43,000 34,000 21,000 16,000 9,500 8,400 5,100 14,000 8,300 2,600 1,600 Direct Runoff subbasin

3 01115280 Cork Brook 16,000 9,300 6,600 3,800 1,900 1,100 700 400 1,300 740 360 200.05 01115184 Spruce Brook 5,300 3,200 3,500 2,100 1,600 940 1,400 770 1,100 600 570 2906 01115183 Quonapaug Brook 18,000 10,000 10,000 6,100 3,500 2,100 2,600 1,600 1,200 720 150 947 01115297 Wilbur Hollow Brook 9,600 6,300 6,300 4,000 2,300 1,500 2,000 1,200 630 400 98 618 01115276 Westconnaug Brook 

(Westconnaug Reservoir)

28,000 17,000 16,000 9,800 12,000 7,500 4,100 2,500 4,900 3,000 4,300 2,700

9 01115275 Bear Tree Brook 10,000 6,100 6,200 3,700 6,500 3,900 1,700 980 2,000 1,200 1,900 1,100

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

34,000 20,000 19,000 11,000 8,400 4,900 1,100 620 680 400 550 320

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 20,000 12,000 9,300 5,500 2,400 1,400 1,100 650 480 280 91 5315 01115114 Regulating Reservoir 

(Rush Brook)

42,000 26,000 22,000 13,000 6,800 4,000 1,700 990 1,100 620 42 24

16 01115098 Peeptoad Brook 

(Harrisdale Brook)

62,000 35,000 26,000 15,000 5,800 3,300 5,100 2,800 3,600 2,000 960 530

18 01115120 Unnamed tributary to 

Regulating Reservoir (unnamed brook A)

4,900 2,800 1,100 620 120 70 -- -- -- -- -- --

Scituate Reservoir drainage area

Total 410,000 240,000 200,000 119,000 80,000 50,000 30,000 20,000 48,000 28,000 16,000 10,000
Water Quality and Constituent Loads and Yields 19

Table 8. Median values for water-quality data collected at Providence Water Supply Board stations in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; PCU, platinum cobalt unit; NTU, nephelometric turbidity unit; CFU/100mL, colony forming unit per 100 milliliters; E. coli, Escherichia coli; mg/L, milligram per liter; CaCO3, calcium carbonate; N, nitrogen; PO4, phosphate; <, less than; --, no data]

PWSB 

station 

number

USGS 

station 

number

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 PO4)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 6.4 36 0.60 2,300 30 4.5 34.5 0.002 <0.05 0.06

25 01115200 Shippee Brook 6.4 33 0.53 1,600 <10 4.3 14.3 0.001 <0.46 0.09

26 01115185 Windsor Brook 6.3 29 0.51 6,000 <20 4.8 37.5 0.002 <0.06 0.11

27 011151845 Unnamed tributary to Ponaganset River 

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

5.3 20 0.38 6,300 <10 2.9 18.9 0.002 0.53 0.11

28 01115265 Barden Reservoir (Hemlock Brook) 5.8 100 0.71 560 <10 4.7 34.1 0.003 0.05 0.09

29 01115271 Ponaganset River (Barden Stream) 6.3 45 0.87 490 <10 4.2 26.6 0.002 <0.05 0.05

35 01115187 Ponaganset River 6.2 39 0.67 1,900 <10 4.0 24.9 0.002 <0.05 0.07

Direct Runoff subbasin

1 01115180 Brandy Brook 7.0 80 1.1 1,200 20 11 14.2 0.002 0.21 0.07

2 01115181 Unnamed tributary #2 to Scituate 

Reservoir (unnamed brook north of Bullhead Brook)

5.9 15 0.49 200 <10 4.3 92.5 0.002 0.65 0.05

3 01115280 Cork Brook 6.3 48 0.44 2,400 20 5.0 43.1 0.001 0.15 0.10

4 01115400 Kent Brook (Betty Pond Stream) 6.8 20 0.84 200 <10 7.7 6.1 0.002 <0.05 0.04

5 01115184 Spruce Brook 6.2 40 0.45 520 <10 4.0 19.8 0.002 0.29 0.05

6 01115183 Quonapaug Brook 6.4 69 0.66 1,300 105 8.4 40.5 0.002 0.28 0.07

7 01115297 Wilbur Hollow Brook 6.4 73 0.82 1,900 31 4.1 12.8 0.003 <0.05 0.08

8 01115276 Westconnaug Brook (Westconnaug 

Reservoir)

6.2 14 0.60 540 <10 3.5 15.6 0.001 <0.05 0.05

9 01115275 Bear Tree Brook 6.4 33 0.75 530 <45 5.8 58.0 0.002 0.56 0.06

30 01115350 Unnamed tributary #4 to Scituate Reservoir (Coventry Brook, Knight Brook) 6.0 32 0.34 360 <10 3.4 29.5 0.002 <0.06 0.03

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

32 01115178 Unnamed tributary #1 to Scituate Reservoir (Pine Swamp Brook) 6.5 48 0.71 1,100 <40 5.9 16.9 0.002 0.43 0.20

33 01115182 Unnamed tributary #3 to Scituate Reservoir (Halls Estate Brook) 6.1 22 0.32 280 <15 4.9 13.0 0.001 0.17 0.07

36 -- Outflow from King Pond 6.6 20 0.34 690 10 4.0 4.4 0.001 <0.05 0.04

37 -- Fire Tower Stream 5.6 15 0.35 400 30 5.0 3.2 0.001 <0.05 0.11
20 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 8. Median values for water-quality data collected at Providence Water Supply Board stations in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; PCU, platinum cobalt unit; NTU, nephelometric turbidity unit; CFU/100mL, colony forming unit per 100 milliliters; E. coli, Escherichia coli; mg/L, milligram per liter; CaCO3, calcium carbonate; N, nitrogen; PO4, phosphate; <, less than; --, no data] PWSB station number USGS station number 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 PO4

)

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut 

Stream North, Moswansicut Pond)

6.7 17 1.2 710 <10 11 53.9 0.002 0.07 0.05

20 01115160 Unnamed tributary #1 to Moswansicut 

Reservoir (Blanchard Brook)

5.9 140 0.50 650 <10 6.0 76.3 0.004 0.10 0.14

21 01115165 Unnamed tributary #2 to Moswansicut Reservoir (brook from Kimball 

Reservoir)

6.6 35 0.87 8,400 80 10 50.3 0.001 0.42 0.10

22 01115167 Moswansicut Reservoir (Moswansicut 

Stream South)

6.6 18 1.8 710 20 15 59.9 0.012 0.61 0.11

34 01115164 Kimball Stream 6.1 45 0.92 70 <10 12 25.8 0.003 0.13 0.23

Ponaganset Reservoir subbasin

23 011151843 Ponaganset Reservoir 6.2 12 0.55 210 <10 2.7 20.5 0.001 0.06 0.03

Regulating Reservoir subbasin

13 01115176 Regulating Reservoir 6.6 29 0.98 990 <10 8.0 45.2 0.002 <0.05 0.04

14 01115110 Huntinghouse Brook 6.4 35 0.64 2,700 105 8.0 15.9 0.002 <0.06 0.07

15 01115114 Rush Brook 6.6 55 1.1 2,100 30 8.2 66.2 0.002 0.05 0.07

16 01115098 Peeptoad Brook (Harrisdale Brook) 6.5 34 0.89 3,700 <10 12 51.3 0.002 0.07 0.05

17 01115119 Dexter Pond (Paine Pond) -- -- -- -- -- -- -- -- -- --

18 01115120 Unnamed tributary to Regulating Reservoir (unnamed brook A) -- -- -- -- -- -- -- -- -- --

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 5.7 23 0.27 190 15 2.3 29.1 0.001 0.05 0.10

11 01115273 Unnamed tributary to Westconnaug 

Reservoir (unnamed brook south of Westconnaug Reservoir)

5.5 60 0.40 190 10 2.8 5.80 0.002 0.05 0.03

12 011152745 Unnamed tributary to Westconnaug 

Brook (unnamed brook north of Westconnaug Reservoir)

5.8 48 0.41 490 10 4.4 64.9 0.001 0.05 0.04

Scituate Reservoir drainage area

Minimum 5.3 12 0.27 70 <10 2.3 3.2 0.001 <0.05 0.03

Median 6.3 35 0.62 700 10 4.8 27.9 0.002 0.13 0.07

Maximum 7.0 140 1.8 8,400 105 15 92.5 0.012 0.65 0.23
Water Quality and Constituent Loads and Yields 21

Table 9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; MCFU/d; million colony forming units per day; MCFU/d/mi2, million colony 

forming units per day per square mile; E. coli, Escherichia coli; kg/d, kilogram per day; kg/d/mi2, kilogram per day per square mile; N, nitrogen; PO4, phosphate; g/d, gram per day; g/d/mi2, gram per day per 

square mile; <, less than; --, no data]

PWSB 

station 

number

USGS 

station 

number

Station name

Total coliform 

bacteria E. coli Chloride Nitrite (as N) Nitrate (as N) Orthophosphate (as PO4)

Load

(MCFU/d)

Yield

(MCFU/d/mi2)

Load

(MCFU/d)

Yield

(MCFU/d/mi2)

Load

(kg/d)

Yield

(kg/d/mi2)

Load

(g/d)

Yield

(g/d/mi2)

Load

(g/d)

Yield

(g/d/mi2)

Load

(g/d)

Yield

(g/d/mi2)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 110,000 22,000 1,800 360 190 38 12 2.3 <180 <36 350 70

25 01115200 Shippee Brook 16,000 6,800 <390 <170 120 51 7.8 3.3 <270 <110 700 30026 01115185 Windsor Brook 190,000 44,000 <2,500 <580 310 71 9.4 2.2 <260 <59 1,200 280

28 01115265 Barden Reservoir 120,000 14,000 <2,200 <250 480 55 45 5.2 530 60 1,600 18035 01115187 Ponaganset River 330,000 23,000 3,400 240 1,100 80 67 4.8 <1,200 <86 2,700 190

Direct Runoff subbasin

1 01115180 Brandy Brook 22,000 14,000 310 190 54 34 8.7 5.5 690 440 210 130

3 01115280 Cork Brook 40,000 22,000 580 320 34 19 4.6 2.6 230 130 160 89

4 01115400 Kent Brook 730 860 <210 <250 7.5 8.8 2.9 3.4 <57 <67 23 275 01115184 Spruce Brook 28,000 23,000 <270 <220 38 31 11 9.0 1,300 1,100 190 160

6 01115183 Quonapaug Brook 38,000 19,000 2,700 1,400 260 130 18 9.2 1,900 940 330 170

7 01115297 Wilbur Hollow Brook 130,000 30,000 1,800 420 180 41 35 7.9 <880 <200 660 1508 01115276 Westconnaug Brook 160,000 30,000 <780 <150 180 35 24 4.6 <800 <150 940 180

9 01115275 Bear Tree Brook 22,000 35,000 <1,600 <2,600 230 370 6.2 9.9 2,200 3,500 220 350

32 01115178 Unnamed tributary #1 

to Scituate Reservoir (Pine Swamp Brook)

19,000 43,000 <510 <1,100 26 58 2.5 5.4 640 1,400 300 660

33 01115182 Unnamed tributary #3 

to Scituate Reservoir (Halls Estate Brook)

3,000 11,000 <160 <560 13 46 1.1 3.8 210 750 81 290

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir 

(Moswansicut Stream North, Moswansicut Pond)

16,000 4,900 330 100 190 60 6.8 2.1 140 43 210 64

21 01115165 Unnamed tributary #2 

to Moswansicut Reservoir (brook from Kimball Reservoir)

140,000 480,000 1,300 4,500 84 290 1.7 5.9 700 2,400 170 590
22 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 9. Median daily loads and yields of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Locations of stations are shown on figure 1. USGS, U.S. Geological Survey; MCFU/d; million colony forming units per day; MCFU/d/mi2, million colony forming units per day per square mile; E. coli, Escherichia coli; kg/d, kilogram per day; kg/d/mi2, kilogram per day per square mile; N, nitrogen; PO4, phosphate; g/d, gram per day; g/d/mi2, gram per day per square mile; <, less than; --, no data] PWSB station number USGS station number Station name Total coliform bacteria E. coli Chloride Nitrite (as N) Nitrate (as N) Orthophosphate (as PO4

)

Load

(MCFU/d)

Yield

(MCFU/d/mi2

)

Load

(MCFU/d)

Yield

(MCFU/d/mi2

)

Load

(kg/d)

Yield

(kg/d/mi2

)

Load

(g/d)

Yield

(g/d/mi2

)

Load

(g/d)

Yield

(g/d/mi2

)

Load

(g/d)

Yield

(g/d/mi2

)

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 290,000 46,000 4,900 780 140 23 53 8.4 <610 <97 970 150

15 01115114 Regulating Reservoir 

(Rush Brook)

350,000 74,000 2,000 430 900 190 13 2.8 410 87 700 150

16 01115098 Peeptoad Brook (Harrisdale Brook) 98,000 20,000 440 89 420 85 9.1 1.8 650 130 260 52

18 01115120 Unnamed Tributary to 

Regulating Reservoir (unnamed brook A)

-- -- -- -- -- -- -- -- -- -- -- --

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 28,000 19,000 470 310 150 98 4.5 3.0 <100 <69 79 53

11 01115273 Unnamed tributary to 

Westconnaug Reservoir (unnamed brook south of Westconnaug Reservoir)

42,000 58,000 460 630 21 29 6.4 8.8 170 230 370 510

Scituate Reservoir drainage area

Minimum 730 860 <160 89 7.5 8.8 1.1 1.8 <57 <36 23 27

Median 41,000 23,000 680 340 170 53 8.9 4.7 570 130 320 165

Maximum 350,000 480,000 4,900 4,500 1,100 370 67 9.9 2,200 3,500 2,700 660
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 OpenFile Report 2009–1041, 25 p. [Also available at

https://pubs.er.usgs.gov/publication/ofr20091041.]

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

quality, and constituent loads and yields, Scituate Reservoir 

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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. [Also available at https://pubs.er.usgs.gov/publication/ofr20101044.]

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quality, and constituent loads and yields, Scituate Reservoir 

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drainage area, Rhode Island, water year 2009: U.S. Geological Survey Open-File Report 2010–1275, 24 p. [Also available at https://pubs.er.usgs.gov/publication/ofr20101275.]

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Streamflow, water quality, and contaminant loads in the 

lower Charles River watershed, Massachusetts, 1999–2000: 

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

basin characteristics in the Scituate Reservoir basin, Rhode 

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manual, rev. 2: Loveland, Colo., Hach Company, 657 p.

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water resources: U.S. Geological Survey Techniques of 

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straight line to data—Examples in water resources: Water 

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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 

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[Also available at https://pubs.er.usgs.gov/publication/

sir20085060.]

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 2002–4149, 16 p. [Also available at 

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Providence Water Supply Board Water Quality Laboratory, 

2012, Quality assurance program manual: Providence Water 

Supply Board, [variously paged].

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low-flow statistics for Massachusetts streams: U.S. Geological Survey Water-Resources Investigations Report 2000–

4135, 81 p. [Also available at https://pubs.er.usgs.gov/

publication/wri004135.]

Smith, K.P., 2013, Streamflow, water quality, and constituent 

loads and yields, Scituate Reservoir drainage area, Rhode 

Island, water year 2011: U.S. Geological Survey OpenFile Report 2013–1127, 32 p. [Also available at 

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

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loads and yields, Scituate Reservoir drainage area, Rhode 

Island, water year 2013: U.S. Geological Survey Open-File 

Report 2015–1082, 31 p., accessed June 3, 2015, at 

https://doi.org/10.3133/ofr20151082.
24 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016

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sir20155058.]

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Smith, K.P., 2018c, Water quality data from the Providence 

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publication/tm1D3.
Table 4 25

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available]

PWSB 

station 

number

USGS 

station 

number

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total coliform 

bacteria 

(MCFU/d)

E. coli

(MCFU/d)

Chloride 

(kg/d)

Nitrite 

(g/d as N)

Nitrate 

(g/d as N)

Orthophosphate 

(g/d as PO4)

Barden Reservoir subbasin

24 01115190 Dolly Cole Brook 10/02/15 0.37 110,000 6,700 32 0.91 59 120

11/06/15 1.1 27,000 2,100 120 2.6 <66 29012/04/15 2.4 110,000 1,100 170 11 <140 40001/04/16 5.8 8,500 1,400 480 14 <350 57002/12/16 8.8 64,000 <1,100 630 21 1,600 1,30003/11/16 6.8 160,000 <830 510 33 <410 1,30004/01/16 6.6 330,000 6,500 590 16 <410 81005/06/16 18 2,400,000 130,000 810 860 <1,100 1,30006/03/16 2.4 830,000 230,000 200 12 <150 24007/15/16 0.94 290,000 2,300 80 6.9 200 14008/05/16 0.31 73,000 130 30 1.5 91 3809/16/16 0.24 15,000 82 21 0.59 49 23

25 01115200 Shippee Brook 01/25/16 3.2 14,000 <390 120 7.8 6,800 700

04/29/16 4.4 180,000 3,200 150 11 <270 75007/22/16 0.06 16,000 <7.6 1.7 0.30 -- 20

26 01115185 Windsor Brook 04/29/16 7 230,000 4,900 560 16 <410 2,300

07/13/16 0.57 150,000 <69 56.0 2.8 100 110
26 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available] PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (MCFU/d) E. coli (MCFU/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as PO4

)

Barden Reservoir subbasin—Continued

28 01115265 Barden Reservoir (Hemlock Brook) 10/29/15 12 11,000,000 440,000 1,100 88 1,500 2,600

11/10/15 4.9 30,000 4,800 490 36 600 1,80012/08/15 2.8 36,000 2,700 250 20 <170 94001/12/16 57 280,000 110,000 2,100 280 7,100 15,00002/09/16 29 92,000 <3,500 1,400 140 <1,800 4,20003/08/16 13 84,000 <1,600 850 62 <780 2,20004/12/16 27 190,000 <3,300 1,400 67 <1,700 2,00005/17/16 7.4 190,000 <900 470 54 <450 54006/16/16 2.1 690,000 <250 170 25 290 1,40007/12/16 0.80 150,000 <98 69 7.8 160 18008/09/16 0.08 19,000 2.0 7.1 0.39 35 9.809/13/16 1.1 15,000 130 100 10 230 390

35 01115187 Ponaganset River 12/04/15 5.1 260,000 <620 470 12 <310 620

01/04/16 15 25,000 <1,800 950 72 <900 2,50002/12/16 32 280,000 <3,900 1,800 78 8,500 14,00003/11/16 23 530,000 <2,800 1,300 56 33,000 6,10004/01/16 25 370,000 6,100 1,500 61 3,200 3,60005/06/16 39 2,900,000 <4,700 3,000 190 <2,400 2,80006/03/16 14 5,000,000 860,000 830 100 <830 1,70007/15/16 24 13,000,000 1,400,000 1,600 350 <1,500 8,20008/05/16 0.92 220,000 450 49 6.8 170 25009/16/16 0.81 34,000 480 49 4.0 <50 140
Table 4 27

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available]

PWSB 

station 

number

USGS 

station 

number

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total coliform 

bacteria 

(MCFU/d)

E. coli

(MCFU/d)

Chloride 

(kg/d)

Nitrite 

(g/d as N)

Nitrate 

(g/d as N)

Orthophosphate 

(g/d as PO4)

Direct Runoff subbasin

1 01115180 Brandy Brook 10/6/2015 0.31 9,500 150 1.8 0.76 320 69

11/3/2015 0.67 7,200 330 27 3.3 830 15012/1/2015 1.3 1,300 <160 50 6.4 830 4501/5/2016 1.8 3,000 <220 57 13 960 3002/2/2016 2.3 18,000 <280 0.57 11 1,200 573/1/2016 3.4 26,000 8,300 90 17 110 5804/5/2016 3.5 140,000 3,400 110 25 1,100 5105/3/2016 3.3 100,000 16,000 330 24 810 7306/7/2016 2.0 840,000 <250 73 25 550 1507/15/2016 0.68 310,000 1,700 60 5.0 400 2708/15/2016 1.1 130,000 2,600 37 2.7 570 1409/6/2016 0.04 1,400 13 1.4 0.17 16 6.1

3 01115280 Cork Brook 10/01/15 0.22 310,000 5,900 33 <0.27 97 54

11/05/15 0.21 12,000 100 34 0.51 <13 5112/03/15 1.2 25,000 910 160 3.0 150 6101/07/16 1.1 2,100 270 27 5.3 640 32002/04/16 11 91,000 17,000 860 55 4,100 1,70003/03/16 4.8 40,000 <580 410 12 230 70004/07/16 36 1,600,000 18,000 3,800 270 12,000 8,90005/05/16 6.6 420,000 16,000 640 32 2,900 2,90006/02/16 0.95 110,000 <120 22 4.6 230 16007/22/16 0.07 18,000 <8.6 8.4 0.17 72 1908/04/16 0.05 750 8.6 6.8 0.12 51 16
28 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available] PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (MCFU/d) E. coli (MCFU/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as PO4

)

Direct Runoff subbasin—Continued

4 01115400 Kent Brook 10/6/2015 0.02 730 <2.8 0.18 0.056 2.8 1.1

11/3/2015 0.05 250 25 2.1 0.25 <3.1 1612/1/2015 0.09 <11 <11 1.9 0.22 <5.4 131/5/2016 0.42 210 210 7.5 2.1 <26 212/2/2016 0.94 230 <120 0.23 4.6 <58 233/1/2016 2.1 8,600 <250 45 5.0 <130 2004/5/2016 3.0 36,000 <360 43 15 <180 5805/3/2016 1.2 15,000 290 14 2.9 <73 886/7/2016 0.94 320,000 2,300 14 4.6 <57 92

5 01115184 Spruce Brook 1/22/2016 2.2 28,000 <270 38 11 1,800 490

4/19/2016 2.6 20,000 <320 130 13 1,300 1907/19/2016 0.38 110,000 <46 32 1.8 270 46

6 01115183 Quonapaug Brook 10/06/15 0.2 24,000 2,700 37 0.49 160 88

11/03/15 0.57 18,000 2,000 11 1.4 350 1412/01/15 1.4 13,000 2,400 250 7.0 2,400 24001/05/16 2.2 18,000 1,600 290 11 3,100 59002/02/16 3.2 15,000 1,500 300 150 3,200 7703/01/16 5.3 52,000 2,600 330 26 390 1,00004/05/16 5.5 230,000 4,000 550 40 4,000 94005/03/16 5.2 160,000 25,000 92 25 3,200 64006/07/16 2.6 630,000 65,000 260 39 1,300 32008/15/16 1.1 130,000 24,000 150 5.6 390 330
Table 4 29

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available]

PWSB 

station 

number

USGS 

station 

number

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total coliform 

bacteria 

(MCFU/d)

E. coli

(MCFU/d)

Chloride 

(kg/d)

Nitrite 

(g/d as N)

Nitrate 

(g/d as N)

Orthophosphate 

(g/d as PO4)

Direct Runoff subbasin—Continued

7 01115297 Wilbur Hollow Brook 10/01/15 4.1 8,000,000 740,000 610 40 2,100 700

11/05/15 1.3 17,000 960 51 3.2 <80 26012/03/15 5.9 80,000 <720 180 29 860 43001/07/16 3.6 2,700 890 400 8.9 980 62002/04/16 17 89,000 25,000 180 85 4,200 1,30003/03/16 12 320,000 3,000 260 61 2,200 1,50004/07/16 22 790,000 <2,700 690 160 <1,400 4,40005/05/16 15 13,000,000 710,000 460 110 <890 3,60006/02/16 4.1 870,000 10,000 31 50 <250 4,40007/22/16 0.57 170,000 <69 20 1.4 <35 32008/04/16 0.20 12,000 720 7.4 1.4 <12 4809/01/16 0.16 19,000 130 4.0 1.2 <9.9 91

8 01115276 Westconnaug Brook 11/20/15 4.5 200,000 <550 170 44 870 870

01/08/16 3.6 <440 <440 130 8.8 970 26002/12/16 10 25,000 <1,200 140 25 2,500 1,20003/11/16 12 17,000 <1,400 450 29 <720 1,70004/08/16 53 710,000 <6,500 2,200 130 <3,200 6,50005/13/16 8.2 110,000 <1,000 300 <10 <500 80006/10/16 4.2 720,000 <510 180 10 <260 1,00008/12/16 4.6 200,000 230 180 23 <280 450
30 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available] PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (MCFU/d) E. coli (MCFU/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as PO4

)

Direct Runoff subbasin—Continued

9 01115275 Bear Tree Brook 1/22/2016 1.5 15,000 3,000 220 3.7 2,600 300

4/19/2016 1.8 28,000 <210 240 8.6 1,800 130

32 01115178 Unnamed tributary #1 to Scituate Reservoir 

(Pine Swamp Brook)

1/21/2016 0.55 2,800 940 24 1.3 720 2904/21/2016 0.73 36,000 <89 28 3.6 550 300

33 01115182 Unnamed tributary #3 to Scituate Reservoir 

(Hall’s Estate Brook)

01/27/16 0.56 4,000 280 15 1.4 360 14004/27/16 0.30 1,900 <36 11 0.72 62 22

Moswansicut Reservoir subbasin

19 01115170 Moswansicut Reservoir (Moswansicut Stream 

North, Moswansicut Pond)

10/08/15 0.08 1,800 20 10 0.39 10 1411/12/15 0.27 400 <33 34 0.66 40 2612/10/15 0.52 1,500 380 68 2.5 140 3801/14/16 8.9 31,000 15,000 1,200 44 2,600 66003/10/16 5.6 4,100 <690 710 28 2,200 69004/14/16 10.0 120,000 2,500 1,300 49 3,500 49005/19/16 2.6 96,000 8,300 350 13 560 38006/10/16 2.3 440,000 <280 320 11 <140 51007/14/16 0.26 21,000 <32 38 2.5 <16 2508/11/16 0.15 11,000 15 21 1.1 <9.2 18

21 01115165 Unnamed tributary #2 to Moswansicut Reservoir 

(brook from Kimball Reservoir)

04/29/16 0.68 140,000 1,300 84 1.7 700 170
Table 4 31

Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued[Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available]

PWSB 

station 

number

USGS 

station 

number

Station name Date

Daily mean 

streamflow 

(ft3/s)

Total coliform 

bacteria 

(MCFU/d)

E. coli

(MCFU/d)

Chloride 

(kg/d)

Nitrite 

(g/d as N)

Nitrate 

(g/d as N)

Orthophosphate 

(g/d as PO4)

Regulating Reservoir subbasin

14 01115110 Huntinghouse Brook 10/02/15 0.15 290,000 13,000 5.4 0.73 34 22

11/06/15 0.58 35,000 2,300 24 2.8 <35 17012/04/15 1.3 50,000 1,600 58 3.2 <79 63001/11/16 64 3,100,000 500,000 1,700 470 130,000 11,00002/16/16 30 240,000 7,400 7.4 74 13,000 3,70003/07/16 10 25,000 <1,300 1,400 50 3,000 1,30004/15/16 15 1,000,000 110,000 540 73 <920 2,90005/13/16 6.3 1,000,000 <770 220 <7.7 <390 62006/06/16 12 7,500,000 840,000 530 120 <730 2,30007/08/16 1.5 280,000 <180 65 55 480 260

15 01115114 Rush Brook 10/02/15 0.99 1,100,000 23,000 220 7.3 130 170

11/06/15 0.62 19,000 300 110 1.5 <38 14012/04/15 2.7 87,000 2,000 440 13 <170 47001/11/16 42 1,600,000 270,000 2,500 310 10,000 6,20002/16/16 52 540,000 13,000 8,500 250 26,000 7,60003/07/16 7.1 31,000 1,700 980 17 2,600 70004/15/16 7.9 760,000 <970 900 39 1,100 97005/02/16 6.6 350,000 15,000 1,000 <8.1 <410 97006/06/16 11 6,600,000 380,000 1,400 140 <680 2,50007/08/16 0.51 110,000 <62 110 5.0 150 8708/05/16 0.02 4,700 120 4.6 0.20 <1.2 3.9
32 Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, WY 2016 Table 4. Daily loads of bacteria, chloride, nitrite, nitrate, and orthophosphate in the Scituate Reservoir drainage area, Rhode Island, from October 1, 2015, through September 30, 2016.—Continued [Water-quality data are from samples collected and analyzed by the Providence Water Supply Board (PWSB); alternate station names are listed in parentheses for stations where different historical names were used for the same sampling location by the PWSB. Shaded areas indicate values that were calculated with concentration data censored at half the detection level. USGS, U.S. Geological Survey; ft3/s, cubic foot per second; MCFU/d; millions of colony forming units per day; E. coli, Escherichia coli; kg/d, kilogram per day; g/d, gram per day; N, nitrogen; PO4, phosphate; <, less than; >, greater than; --, data not available] PWSB station number USGS station number Station name Date Daily mean streamflow (ft3/s) Total coliform bacteria (MCFU/d) E. coli (MCFU/d) Chloride (kg/d) Nitrite (g/d as N) Nitrate (g/d as N) Orthophos- phate (g/d as PO4

)

Regulating Reservoir subbasin—Continued

16 01115098 Peeptoad Brook (Harrisdale Brook) 10/2/2015 0.58 98,000 <71 72 1.4 71 85

11/6/2015 0.38 7,700 <46 57 1.9 <23 11012/4/2015 3.2 43,000 780 420 16 780 5401/11/2016 89 3,800,000 420,000 13,000 660 22,000 4,4003/7/2016 13 65,000 <1,600 750 32 6,800 3,2004/15/2016 14 1,300,000 34,000 790 69 3,400 2,4005/2/2016 7.5 250,000 1,800 900 <9.1 1,300 5506/6/2016 3.6 630,000 <440 420 26 650 2607/8/2016 2.6 760,000 <320 340 6.3 <160 1908/5/2016 0.41 48,000 40 58 3.0 <25 509/9/2016 0.35 41,000 8.6 44 0.86 <21 34

18 01115120 Unnamed tributary to Regulating Reservoir 

(unnamed brook A)

-- -- -- -- -- -- -- --

Westconnaug Reservoir subbasin

10 01115274 Westconnaug Brook 10/29/2015 3.6 4,900,000 150,000 310 8.8 1,200 88

12/8/2015 0.72 12,000 180 63 3.5 <44 701/12/2016 5.7 21,000 1,400 370 42 <350 4202/9/2016 3.2 14,000 <390 250 7.8 470 3903/8/2016 2.2 30,000 540 190 5.4 <130 6504/12/2016 4.6 40,000 <560 330 22 <280 6705/17/2016 1.2 25,000 <150 100 3.0 <74 606/16/2016 0.27 59,000 1,300 19 0.66 <17 667/12/2016 0.45 99,000 <56 34 1.1 <28 449/13/2016 0.004 130 <1 0.24 0.0095 <0.24 0.38

11 01115273 Unnamed tributary to Westconnaug Reservoir 

(unnamed brook south of Westconnaug Reservoir)

1/26/2016 1.2 1,200 <150 22 8.9 240 47004/26/16 1.6 82,000 760 20 3.8 <95 270
For more information about this report, contact:

Director, New England Water Science Center

U.S. Geological Survey

10 Bearfoot Road

Northborough, MA 01532

dc_nweng@usgs.gov

or visit our website at

https://newengland.water.usgs.gov

Publishing support provided by the 

Pembroke Publishing Service Center
Smith—Streamflow, Water Quality, and Constituent Loads and Yields, Scituate Reservoir Drainage Area, Rhode Island, Water Year 2016—OFR 2018–1084

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20181084