U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2006–1226

Prepared in cooperation with the 

Rhode Island Department of Environmental Management

Simulation of Hydrologic-System Responses to 

Ground-Water Withdrawals in the Hunt-AnnaquatucketPettaquamscutt Stream-Aquifer System, Rhode Island 

Simulation of Hydrologic-System 

Responses to Ground-Water Withdrawals 

in the Hunt-Annaquatucket-Pettaquamscutt 

Stream-Aquifer System, Rhode Island

By Paul M. Barlow and Lance J. Ostiguy

Prepared in cooperation with the 

Rhode Island Department of Environmental Management

Open-File Report 2006–1226

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2007

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Barlow, P.M., and Ostiguy, L.J., 2007, Simulation of hydrologic-system responses to ground-water withdrawals in the 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island: U.S. Geological Survey Open-File Report 

2006–1226, 51 p.

Library of Congress Cataloging-in-Publication Data

Author1LastName, Author1FirstName Q.

Title of book/ Author List

p. cm. –(U.S. Geological Survey professional paper ; 0000)

Includes bibliographic references.

1. Subject heading. 2. Subject heading. 3. Subject heading. I. Main entries. 

II.Main entries. III. Main entries.

TN24.M9 M55 2002

553’.09786’6—dc21

2001051109

ISBN 0-607-97815-9 (Set)

ISBN 0-607-97815-7 (Volume 1)
iii

Contents

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

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

Purpose and Scope ........................................................................................................................... 3

Description of the Study Area and Water-Supply Wells............................................................. 3

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System... 7

Overview of the Original Numerical Models................................................................................. 7

Modifications to the Original Numerical Models ....................................................................... 12

Conversion of Models to MODFLOW-2000 ......................................................................... 12

Increase in the Active Area of the Models ........................................................................ 12

Simulation of Flow at Ground-Water Drainage Divides in the 

Annaquatucket River Basin..................................................................................... 15

Modification of Aquifer Hydraulic Properties near Lafayette State Fish 

Hatchery and Town of North Kingstown Well 11 ................................................. 15

Conversion to Constant Saturated Thickness and Transmissivity.................................. 16

Simulation of Hydrologic-System Responses in the Stream-Aquifer System................................ 16

Simulation Results for Original Withdrawal Conditions ............................................................ 16

Simulation Results for Alternative Withdrawal and Recharge Conditions ............................ 20

Simulations for Long-Term Average Recharge Conditions.............................................. 20

Simulations for a Drought...................................................................................................... 42

Limitations of Numerical Models ........................................................................................................... 45

Summary and Conclusions...................................................................................................................... 45

References Cited....................................................................................................................................... 47

Appendix 1: Withdrawals from Selected Production Wells, 1999–2004 ....................................49–51

Figures

1–3. Maps showing—

1. Location of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer 

system, Rhode Island.............................................................................................................4

2. Drainage boundaries to the Hunt-Annaquatucket-Pettaquamscutt 

stream-aquifer system ..........................................................................................................5

3. Altitude and configuration of the water table in the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, October 7–9, 1996 ...........................................6

4. Graph showing average monthly withdrawal rates in the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, 2003............................................................................7

5–8. Maps showing—

5. Spatial extent of active area of simulation models of the 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system......................................8

6. Grid and boundary conditions of the active areas of the modified simulation models

of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system for

(A) rows 3-125, and (B) rows 126-205......................................................................... 10–11

7. Stream sites discussed in text for the Hunt-Annaquatucket-Pettaquamscutt

stream-aquifer system ........................................................................................................14

8. Model-calculated steady-state water table with 1996 withdrawal rates, HuntAnnaquatucket-Pettaquamscutt stream-aquifer system..............................................17
iv

9–11. Graphs showing—

9. Model-calculated mid-monthly streamflow at the outflow 

locations of the Hunt and Annaquatucket Rivers ............................................................20

10. Model-calculated end-of-month streamflow in Queens 

Fort Brook at its outflow (site J)..........................................................................................24

11. Model-calculated end-of-month streamflow in the Annaquatucket 

River at its outflow (site P)...................................................................................................25

12–14. Maps showing—

12. Model-calculated steady-state water table for simulation 

set 3 (2003 withdrawal rates), Hunt-AnnaquatucketPettaquamscutt stream-aquifer system............................................................................26

13. Model-calculated steady-state drawdowns for simulation set 3 

(2003 withdrawal rates), Hunt-Annaquatucket-Pettaquamscutt 

stream-aquifer system .........................................................................................................29

14. Model-grid locations of wetlands near Lafayette State Fish Hatchery...............................30

15. Graphs showing model-calculated end-of-month ground-water 

levels at (A) State Fish Hatchery well 3, (B) State Fish Hatchery well 4, 

and (C) wetland site A ...................................................................................................................31

16–21. Maps showing—

16. Model-calculated steady-state contributing areas to water-supply wells 

in (A) the Hunt River Basin and (B) the Annaquatucket and Pettaquamscutt 

River Basins, for simulation set 3 (2003 withdrawal rates) ..................................... 34–35

17. Model-calculated steady-state drawdowns for simulation set 4 (hatchery 

wells pumping at half their 2003 rates), Hunt-Annaquatucket-Pettaquamscutt 

stream-aquifer system .........................................................................................................37

18. Model-calculated steady-state drawdowns for simulation set 5 (with State 

Fish Hatchery well 4 pumping), Hunt-Annaquatucket-Pettaquamscutt 

stream-aquifer system .........................................................................................................38

19. Model-calculated steady-state water table for simulation set 6 (with State 

Fish Hatchery well 4 and town of North Kingstown well 11 pumping), HuntAnnaquatucket-Pettaquamscutt stream-aquifer system...............................................39

20. Model-calculated steady-state drawdowns for simulation set 6 (with State Fish 

Hatchery well 4 and town of North Kingstown well 11 pumping), 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system.....................................40

21. Model-calculated steady-state contributing areas to water-supply wells 

in the Annaquatucket River Basin for simulation set 6 (with State 

Fish Hatchery well 4 and town of North Kingstown well 11 pumping).........................41

22–24. Graphs showing—

22. Long-term (1941–2003) average and 1957 monthly recharge rates, 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system.....................................42

23. Model-calculated end-of-month streamflow at the outflow sites of (A) Queens 

Fort Brook and (B) Annaquatucket River for simulated long-term (1941–2003) 

average and drought conditions.........................................................................................43

24. Model-calculated end-of-month ground-water levels at (A) State Fish Hatchery 

well 4 and (B) wetland site A for simulated long-term (1941–2003) average and 

drought conditions ................................................................................................................44
Tables

1. Proposed monthly withdrawal rates at Lafayette State Fish Hatchery well SFH4 in the HuntAnnaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island ................................7

2. Model grid-cell locations for stream sites discussed in text for the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system.....................................................................................12

3. Streamflows specified in the steady-state model of the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system.....................................................................................13

4. Model-calculated steady-state water-level altitudes and measured water-level 

altitudes on October 8, 1996, at observation wells in the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system.....................................................................................18

5. Model-calculated steady-state average annual hydrologic budgets for the HuntAnnaquatucket-Pettaquamscutt stream-aquifer system........................................................19

6. Model-calculated steady-state streamflows at outflow locations from the HuntAnnaquatucket-Pettaquamscutt stream-aquifer system........................................................19

7. Withdrawal rates (2003) specified for water-supply wells in the steady-state model of the 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system..............................................22

8. Specified ground-water withdrawals and model-calculated streamflows for 

steady-state simulations...............................................................................................................23

9. Model-calculated ground-water levels near Lafayette State Fish Hatchery for 

steady-state simulations...............................................................................................................28

10. Model-calculated steady-state flows to and from the aquifer in wetland areas near

Lafayette State Fish Hatchery......................................................................................................32
vi

Conversion Table, Datums, and Abbreviations

Multiply By To obtain

Length / Area

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.59 square kilometer (km2)

Volume

gallon (gal) 3.785 liter (L) 

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per day (ft/d) 0.3048 meter per day (m/d)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

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

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Mass

pound (lb) 4.536 kilogram (kg)

Transmissivity

gallon per day per foot [(gal/d)/ft] 0.01242 cubic meter per day per meter [(m3/d)/m]

TEMPERATURE

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F-32)/1.8

VERTICAL DATUM

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD29), formerly called the Sea Level Datum of 1929.

HORIZONTAL DATUM

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27), 

unless otherwise noted.

ABBREVIATIONS

KCWA Kent County Water Authority

NK Town of North Kingstown, Rhode Island

RIDEM Rhode Island Department of Environmental Management

RIEDC Rhode Island Economic Development Corporation

SFH Lafayette State Fish Hatchery
Abstract

A numerical-modeling study was done to better understand hydrologic-system responses to ground-water withdrawals in the Hunt-Annaquatucket-Pettaquamscutt (HAP) 

stream-aquifer system of Rhode Island. System responses 

were determined by use of steady-state and transient numerical ground-water-flow models. These models were initially 

developed in the late 1990s as part of a larger study of the 

stream-aquifer system. The models were modified to incorporate new data made available since the original study and to 

meet the objectives of this study. Changes made to the models 

did not result in substantial changes to simulated ground-water 

levels, hydrologic budgets, or streamflows compared to those 

calculated by the original steady-state and transient models.

Responses of the hydrologic system are described primarily by changes in simulated streamflows and ground-water 

levels throughout the basin and by changes to flow conditions in the aquifer in three wetland areas immediately east 

of the Lafayette State Fish Hatchery, which lies within the 

Annaquatucket River Basin in the town of North Kingstown. 

Ground water is withdrawn from the HAP aquifer at 14 largecapacity production wells, at an industrial well, and at 3 wells 

operated by the Rhode Island Department of Environmental 

Management at the fish hatchery. A fourth well has been 

proposed for the hatchery and an additional production well is 

under development by the town of North Kingstown.

The primary streams of interest in the study area are the 

Hunt, Annaquatucket, and Pettaquamscutt Rivers and Queens 

Fort Brook. Total model-calculated streamflow depletions 

in these rivers and brook resulting from withdrawals at the 

production, industrial, and fish-hatchery wells pumping at 

average annual 2003 rates are about 4.8 cubic feet per second 

(ft3/s) for the Hunt River, 3.3 ft3/s for the Annaquatucket River, 

0.5 ft3/s for the Pettaquamscutt River, and 0.5 ft3/s for Queens 

Fort Brook. The actual amount of streamflow reduction in the 

Annaquatucket River caused by pumping actually is less, 

1.1 ft3/s, because ground water that is pumped at the fishhatchery wells (2.2 ft3

/s) is returned to the Annaquatucket 

River after use at the hatchery.

One of the primary goals of the study was to evaluate the 

response of the hydrologic system to simulated withdrawals 

at the proposed well at the fish hatchery. Withdrawal rates 

at the proposed well would range from zero during April 

through September of each year to a maximum of 260 gallons 

per minute [about 0.4 million gallons per day (Mgal/d)] in 

March of each year. The average annual withdrawal rate at 

the fish hatchery resulting from the addition of the proposed 

well would increase by only 0.13 ft3/s, or about 5 percent of 

the 2003 withdrawal rate. The increased pumping rate at the 

hatchery would further reduce the average annual flow in 

Queens Fort Brook by less than 0.05 ft3/s and in the Annaquatucket River by about 0.1 ft3

/s (which includes some 

model error).

A new production well in the Annaquatucket River 

Basin is under development by the town of North Kingstown. 

A simulated pumping rate of 1.0 Mgal/d (1.6 ft3/s) at this new 

well resulted in additional streamflow depletions, compared 

to those calculated for the 2003 withdrawal conditions, of 

0.8 and 0.2 ft3/s in the Annaquatucket and Pettaquamscutt 

Rivers, respectively. The source of water for about 30 percent 

of the well’s pumping rate, or about 0.5 ft3/s, is derived from 

ground-water inflow from the Chipuxet River Basin across a 

natural ground-water drainage divide that separates the Annaquatucket and Chipuxet River Basins; the remaining 0.1 ft3

/s 

of simulated pumping consists of reduced evapotranspiration 

from the water table.

Model-calculated changes in water levels in the aquifer 

for the various withdrawal conditions simulated in this study 

indicate that ground-water-level declines caused by pumping 

are generally less than 5 feet (ft). However, ground-waterlevel declines of as much as 20 ft were calculated near the fish 

hatchery and of as much as 18 ft were calculated near 

the new production well in the Annaquatucket River Basin. 

The larger water-level declines in these two areas are attributed to relatively low values of the transmissivity of the 

aquifer in these two areas. Average annual ground-water-level 

declines in the aquifer resulting from the increased withdrawal 

in the hatchery area are not substantially greater than those for 

the 2003 average annual pumping conditions.

Simulation of Hydrologic-System Responses to 

Ground-Water Withdrawals in the Hunt-AnnaquatucketPettaquamscutt Stream-Aquifer System, Rhode Island

By Paul M. Barlow and Lance J. Ostiguy
Model-calculated hydrologic budgets for the aquifer in 

the three wetland areas near the fish hatchery indicate that the 

total inflow rate to each area is reduced by a maximum of 

0.3 ft3/s for the 2003 average annual pumping conditions; 

these reductions are a maximum of 13 percent of the total 

inflow rate to each area for non-pumping conditions. The rates 

of reductions in ground-water flows to the wetland areas are 

not substantially different for the proposed additional withdrawals at the hatchery.

The transient model also was used to evaluate the effects 

of a simulated drought condition on streamflow and groundwater levels. The simulated drought condition was based on 

hydrologic conditions during 1957, which was determined 

by the Rhode Island Department of Environmental Management to represent a 1-in-25 year drought. For the withdrawal 

conditions evaluated, the simulated drought caused modelcalculated monthly streamflows in the Annaquatucket River to 

be reduced by 1.0 to 3.1 ft3/s compared to those streamflows 

calculated for long-term average simulation conditions (that is, 

non-drought conditions). Model-calculated ground-water levels at the proposed well site at the fish hatchery for the drought 

condition declined by 1.0 to 3.7 ft compared to those levels 

calculated for non-drought conditions.

Results of the study must be viewed within the 

limitations of the quality of the data that are available for the 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system 

and representation of the system with simulation models. 

Uncertainties in the model simulations result from a variety 

of factors, including uncertainties in the exact values of the 

hydraulic properties of the aquifers, rates of recharge to the 

aquifer, and the approaches used to simulate the many features 

of the hydrologic system (streams, evapotranspiration, flow 

conditions at ground-water drainage divides, and so forth). 

The precision of the numerical models used in this study 

to determine hydrologic-system responses to ground-water 

withdrawals could benefit from refinement of localized information on the wetlands and the geology of the area near the 

fish hatchery. Model results in the area of the hatchery also 

would be improved by the use of a finer model-grid discretization to better simulate wetland-aquifer interactions and the 

impacts of withdrawals on wetlands and streamflow. Use of a 

finer discretization could be done as part of a broader datacollection and analysis study of wetland and hydrologic 

conditions at or near the hatchery. As a consequence of the 

spatial-discretization limitations of the numerical models 

developed for the HAP stream-aquifer system, the ability of 

the numerical models to predict hydrologic responses in the 

vicinity of the hatchery wells is limited. Furthermore, groundwater-flow conditions near the ground-water drainage divide 

that separates the Annaquatucket and Chipuxet River Basins 

are largely unknown. The understanding of hydrologic conditions near this divide would be improved by collection of 

hydrogeologic data in that area.

Introduction

The State of Rhode Island Department of Environmental Management (RIDEM) operates the Lafayette State Fish 

Hatchery in the town of North Kingstown, Rhode Island, 

where about 80,000 lb of rainbow, brown, and brook trout 

are raised annually for stocking in state rivers, streams, and 

ponds. Currently (2005), about 1.5 Mgal/d of ground water is 

pumped from three water-supply wells at the hatchery (wells 

SFH1, SFH2, and SFH3; fig. 1). The water is used for hatchery operations and then discharged to the headwater of the 

Annaquatucket River. RIDEM has proposed to install a fourth 

well (SFH4) at the hatchery that would be pumped from 

October through March at a maximum rate of about 

260 gal/min (0.4 Mgal/d).

The hatchery is located in the Hunt-AnnaquatucketPettaquamscutt (HAP) River Basin of central Rhode Island, a 

39.6-mi2 area that lies primarily in the towns of North Kingstown, East Greenwich, and Exeter (fig. 1). The principal 

ground-water unit in the basin is the HAP aquifer, which is a 

generally unconfined aquifer composed of stratified sand and 

gravel sediments that were deposited by glacial meltwater. The 

stratified deposits are bounded laterally in most locations by 

till and bedrock uplands; however, in a few areas, the deposits 

extend into adjoining surface-water and ground-water basins, 

notably the Usquepaug-Queen and Chipuxet River Basins 

(fig. 2). A key aspect of the aquifer is its hydraulic connection with overlying rivers, brooks, and ponds, and, in most 

places, water can move readily between the ground-water 

and surface-water systems. Because of the importance of this 

connection, the linked ground-water/surface-water system has 

been referred to as the HAP stream-aquifer system (Barlow 

and Dickerman, 2001).

Ground-water withdrawals at the fish hatchery are from 

the HAP aquifer, which also is the source of water to several 

production wells in the basin that are operated by the town 

of North Kingstown, the Rhode Island Economic Development 

Corporation (RIEDC), and the Kent County Water 

Authority (KCWA) (fig. 1). Withdrawals from these and other 

wells in the basin lower ground-water levels in the aquifer, 

reduce streamflow in the hydraulically connected rivers and 

brooks, and can change ground-water-flow conditions within 

and beneath wetlands. In response to a concern by the RIDEM 

about the effects of existing and proposed withdrawals at the 

Lafayette State Fish Hatchery on the hydrology of the 

HAP stream-aquifer system, the U.S. Geological Survey 

(USGS) worked in collaboration with the RIDEM during 

2005 and 2006 on a study to better understand hydrologicsystem responses to ground-water withdrawals throughout the 

HAP River Basin.

 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Purpose and Scope

This report describes the results of the USGS/RIDEM 

study on the effects of existing and proposed withdrawals at 

the Lafayette State Fish Hatchery and at the other production 

wells in the basin on the hydrology of the HAP stream-aquifer 

system. System responses were determined by use of steadystate and transient numerical ground-water-flow models that 

were developed originally as part of a larger study of the 

basin by Dickerman and Barlow (1997) and Barlow and 

Dickerman (2001). The models were modified as part of the 

current study to account for new hydrogeologic and groundwater-withdrawal data made available since the original 

study. Responses of the hydrologic system are described in 

this report primarily by changes in simulated ground-water 

levels and streamflows throughout the basin and by changes 

to ground-water-flow conditions in three wetland areas 

immediately east of the hatchery (fig. 1). Contributing areas 

and sources of water to simulated wells also are reported for 

selected withdrawal conditions. 

Description of the Study Area and WaterSupply Wells

In this report, the study area, which is also referred to as 

the HAP River Basin, is defined as the entire 39.6-mi2 drainage area shown in figures 1 and 2. Of this total area, the HAP 

stream-aquifer system covers a 19.0-mi2 area that lies within 

parts of the Hunt, Annaquatucket, Cocumcossuc, Pettaquamscutt, Usquepaug-Queen, and Chipuxet River Basins (fig. 2). 

The Pettaquamscutt River is called the Mattatuxet River in its 

headwater reaches. The remaining 20.6 mi2 of the basin consists of upland areas of till, bedrock, and discontinuous areas 

of stratified sand and gravel. Till and bedrock also underlie 

the HAP aquifer. The surface-water drainage area (35.6 mi2) 

is smaller than the total drainage area of the system (39.6 mi2) 

because ground-water and surface-water drainage boundaries are not coincident in the Chipuxet and Usquepaug-Queen 

River Basins where they adjoin the western boundary of the 

Annaquatucket River Basin (fig. 2). Surface-water runoff in 

these two basins drains to the west of the study area, whereas 

some of the ground water recharged in the basins flows eastward to the HAP aquifer. 

The study area consists of a relatively flat valley that 

contains several large but generally shallow ponds and lakes. 

Land-surface altitudes in the valley range from about 5 ft 

above NGVD29 at the downstream end of the Hunt and 

Pettaquamscutt River Basins to a maximum of about 250 ft in 

the headwaters of the Usquepaug-Queen River Basin. The valley is bounded by uplands where land-surface altitudes reach 

a maximum of about 480 ft. Average annual total precipitation 

at a National Oceanic and Atmospheric Administration climatological station in Kingston, Rhode Island, approximately 

6.5 mi southwest of the center of the study area, was 48.2 in. 

during the 63-year period 1941–2003.

A map of the water table was prepared for the HAP aquifer on the basis of water-level measurements made throughout the aquifer on October 7–9, 1996 (fig. 3), which was a 

period of near-average water-level conditions (Dickerman 

and Barlow, 1997). Ground water moves through the aquifer 

in the direction of lower water-level altitudes. The altitude 

and configuration of the water-table contours (fig. 3) indicate that the general direction of ground-water flow is from 

the western contact of the HAP aquifer with till and bedrock 

uplands toward the east, northeast, and southeast. The aquifer 

is recharged by precipitation, stream leakage, ground-water 

inflow from adjacent till-bedrock uplands, and by a small 

amount of wastewater discharge. Under natural conditions, 

most ground water flows toward, and is discharged at, the 

streams, ponds, and wetlands in the basin; some ground water 

also is discharged from the aquifer by evapotranspiration at 

the water table and by underflow to adjacent ground-water 

systems. Water-supply wells, however, intercept ground water 

that would have flowed to natural discharge areas.

Ground water currently is withdrawn from the HAP 

aquifer from 18 large-capacity water-supply wells. These 

consist of 14 production wells, an industrial well (well IW, 

fig. 1), and the 3 fisheries wells. The town of North Kingstown 

has 10 supply wells (wells NK1–NK10, fig. 1), the RIEDC has 

3 wells (wells 3A, 9A, and 14A, fig. 1), and the KCWA has a 

single well (well KC1, fig. 1). The town of North Kingstown 

also has an 11th well (NK11) in the Annaquatucket River 

Basin that has been approved for pumping at a rate of 

1.0 Mgal/d (Fay, Spofford, and Thorndike, 2005; Susan 

Licardi, Director of Water Supply, Town of North Kingstown 

Water Department, written commun., 2005).

Current withdrawals at the fish hatchery average about 

1.4 to 1.5 Mgal/d, and peak at about 1.6 Mgal/d during 

December through February (Peter Angelone, Rhode Island 

Department of Environmental Management, oral commun., 

2005). The distribution of total withdrawals among the three 

wells is approximately 17 percent from well SFH1, 33 percent 

from well SFH2, and 50 percent from well SFH3 (James 

McGinn, Rhode Island Department of Environmental Management, written commun., 2005). Withdrawals at the proposed 

fourth hatchery well would vary through the year, from a rate 

of zero during April through September to a maximum rate of 

about 260 gal/min (0.4 Mgal/d) during March (table 1).

Average daily withdrawals from all existing wells during 

2003 were about 6.3 Mgal/d, which was typical for recent 

(1999–2004) years. Total withdrawals ranged from about 

5.1 Mgal/d during November and December to a maximum of 

about 8.1 Mgal/d during July (fig. 4). Withdrawals are largest 

in the Hunt River Basin and smallest in the Pettaquamscutt 

River Basin. Total monthly withdrawals for each of the 

14 production wells during 1999 through 2004 are provided in 

appendix 1; withdrawals at each well prior to 1999 are 

provided in Barlow and Dickerman (2001).

Abstract 
 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

Figure 1. Location of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island.

0 .5 1 MILE

0 .5 1 KILOMETER

STRATIFIED DEPOSITS

TILL AND BEDROCK

WETLANDS NEAR LAFAYETTE

 STATE FISH HATCHERY—Other

 wetlands in the study area are not shown

BOUNDARY OF THE

 STREAM-AQUIFER SYSTEM

GROUND-WATER DRAINAGE 

 BOUNDARY—Where it differs

 from the surface-water drainage basin

 boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

U.S. GEOLOGICAL SURVEY STREAMFLOW-

 GAGING STATION AND IDENTIFIER—Contin-

 uous-record streamflow-gaging station

WATER-SUPPLY WELL AND

 IDENTIFIER

WEST

WARWICK

WEST GREENWICH

EAST GREENWICH

EXETER

NORTH KINGSTOWN

WARWICK

EXPLANATION

NK2

01117500

41°37'30"

71°32'30"

71°27'30"

41°32'30"

NK10 NK9

14A KC1

9A

3A

IW

NK6

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK8 NK3

NK7

SFH4

NK11

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

0 10 MILES

0 10 KILOMETERS

71°45' 71°30'

41°30'

42°00'

RHODE

ISLAND

MASSACHUSETTS

MASSACHUSETTS

CONNECTICUT

01117500

Study Area

Kingston

River

River

Hunt

River

Cocumcossuc Brook

Queens Fort Brook

Reuben Brown Brook

Annaquatucket

Sandhill Brook

Fry Brook

Frenchtown Brook

Scrabbletown Brook

Unnamed Tributary

Unnamed Tributary

Pettaquamscutt

Carr

Pond

Silver

 Spring Lake

Secret

 Lake

Belleville

Pond

Potowomut 

Pond

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection
Figure 2. Drainage boundaries to the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system. 

Narragansett

Bay

Greenwich

Bay

Unnamed Tributary

Queen River

Chipuxet River

Carr River

Carr

Pond

Silver

Spring Lake

Secret

 Lake

Carr

Pond

Potowomut 

Pond

Belleville

Pond

WARWICK

WARWICK

COVENTRY EAST GREENWICH

WEST GREENWICH

NORTH KINGSTOWN

SOUTH KINGSTOWN

EXETER

SOUTH KINGSTOWN

WEST GREENWICH

EAST GREENWICH

EXETER

WEST GREENWICH

NORTH KINGSTOWN

 EAST GREENWICH

NORTH

KINGSTOWN

WARWICK

WEST

WARWICK

Hunt River

Basin

Cocumcossuc

Brook Basin

Annaquatucket

River Basin

Pettaquamscutt

River Basin

UsquepaugQueen

River

Basin

Basin

Chipuxet

River

River

Hunt

Annaquatucket

River

Cocumcossuc Brook

Scrabbletown

Brook

Fry Brook

Frenchtown Brook

Queens Fort Brook

River

Pettaquamscutt

Pettaquamscutt River

Sandhill

Brook

01117000

01117100

Base from U.S. Geological Survey,

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

41°

37'

30"

71°32'30" 71°27'30"

41°

32'

30"

0 .5 1 MILE

0 .5 1 KILOMETER

AREA WHERE SURFACE

 WATER DRAINS WEST AND

 GROUND WATER DRAINS

 EAST TO THE AQUIFER

BOUNDARY OF THE

 STREAM-AQUIFER SYSTEM

DRAINAGE BOUNDARY—

 Ground-water drainage

 boundary where it differs

 from the surface-water

 drainage-basin boundary 

 Ground-water and surface-water

 drainage boundary

 Surface-water subbasin drainage

 boundary

U.S. GEOLOGICAL SURVEY

 STREAMFLOW-GAGING

 STATION—Continuous-record

 streamflow-gaging station

U.S. GEOLOGICAL SURVEY

 STREAMFLOW-GAGING

 STATION—Discontinued,

 continuous-record streamflow-

 gaging station 

EXPLANATION

01117000

01117100

Abstract 
40

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STRATIFIED DEPOSITS

TILL AND BEDROCK

WATER-TABLE CONTOUR —

 Shows altitude of water table in

 feet above NGVD29. Dashed

 where approximately located.

 Contour interval is variable

BOUNDARY OF THE STREAM-

 AQUIFER SYSTEM

GROUND-WATER DRAINAGE 

 BOUNDARY—Where it differs

 from the surface-water drainage

 basin boundary

GROUND-WATER AND

 SURFACE-WATER DRAINAGE

 BOUNDARY

WATER-SUPPLY WELL AND

 IDENTIFIER

EXPLANATION

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford,Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

41°37'30"

71°32'30"

71°27'30"

41°32'30"

0 .5 1 MILE

0 .5 1 KILOMETER

100

NK2

Figure 3. Altitude and configuration of the water table in the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode 

Island, October 7–9, 1996. (Modified from Dickerman and Barlow, 1997, fig. 5.)

 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Numerical Models to Simulate 

Hydrologic-System Responses in the 

Stream-Aquifer System

Ground-water flow in the HAP aquifer was simulated 

with the USGS modular three-dimensional finite-difference 

ground-water-flow model, commonly known as MODFLOW 

(McDonald and Harbaugh, 1988; Harbaugh and McDonald, 

1996; Harbaugh and others, 2000). The original models of the 

study area used the 1996 version of MODFLOW, but were 

updated to the 2000 version in the study described here.

Overview of the Original Numerical Models

The numerical models of the HAP stream-aquifer system are basin-scale models that were developed to simulate 

ground-water flow throughout the entire HAP system. A brief 

overview of the original steady-state and transient models of 

the basin is provided here as background for the modifications 

to the models described later in this report; Barlow and Dickerman (2001) provide a complete description of the development and calibration of the original models.

Ground-water flow was only simulated in the stratified 

deposits (fig. 5). The grid used for both the steady-state and 

transient models was aligned approximately parallel to the 

northeast-trending valleys of the Hunt River and Sandhill 

Brook and southwest-trending valley of the Pettaquamscutt 

River (fig. 6). The models simulated average flow conditions 

that were presumed to represent the 56-year period 1941–96. 

The steady-state model simulated long-term average conditions in which there are no storage changes in the simulated 

system. The transient model simulated average annual conditions using monthly stress periods (January through December). The transient model was designed to simulate dynamic 

equilibrium, which is the condition in which there is no net 

change in storage in the simulated system over the average 

annual hydrologic cycle. Calculated water-level altitudes 

and streamflows vary over the annual cycle, but at the end of 

the cycle, the system returns to the condition that existed at 

the beginning of the cycle. Because initial conditions affect 

the transient response of the simulated system, it was necessary to repeat the 1-year cycle until there was no change in 

0

1

2

3

4

5

6

7

8

9

MONTH

WITHDRAWALS, IN MILLION GALLONS 

PER DAY 

TOTAL

HUNT RIVER BASIN

ANNAQUATUCKET

RIVER BASIN

PETTAQUAMSCUTT

RIVER BASIN

EXPLANATION

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

Figure 4. Average monthly withdrawal rates in the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, 2003.

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System 

Table 1. Proposed monthly withdrawal rates at Lafayette 

State Fish Hatchery well SFH4 in the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island.

[Withdrawal rate: Proposed withdrawal rates from James McGinn, Rhode 

Island Department of Environmental Management, written commun., 2005. 

Well location shown in figure 1]

Month

Withdrawal rate

Gallons per

minute

Million gallons

per day

January 120 0.17

February 200 .29

March 260 .37

April 0 0

May 0 0

June 0 0

July 0 0

August 0 0

September 0 0

October 20 .03

November 20 .03

December 90 .13
 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

NK10 NK9

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NK11

River

River

Hunt

River

Queens Fort Brook

Reuben Brown Brook

Annaquatucket

Sandhill Brook

Fry Brook

Frenchtown Brook

Scrabbletown Brook

Unnamed Tributary

Unnamed Tributary

Pettaquamscutt

Cocumcossuc Brook

Belleville

Pond

STRATIFIED DEPOSITS

TILL AND BEDROCK

ACTIVE AREA OF MODIFIED

 SIMULATION MODELS

NEW ACTIVE AREA IN MODIFIED

 MODEL

BOUNDARY OF THE

 STREAM-AQUIFER SYSTEM

GROUND-WATER DRAINAGE

 BOUNDARY—Where it differs

 from the surface-water drainage

 basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

WATER-SUPPLY WELL AND

 IDENTIFIER

NK2

EXPLANATION

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

Figure 5. Spatial extent of active area of simulation models of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer 

system, Rhode Island. (Modified from Barlow and Dickerman, 2001, fig. 11.)
storage over the simulated year. It was found that five annual 

cycles (60 monthly stress periods) were adequate to produce 

dynamic equilibrium.

The grid consisted of 205 rows and 197 columns of 

square cells that are 200 ft on each side (fig. 6). In the vertical 

dimension, the grid consists of a maximum of four layers that 

extend from the water table to the contact of the HAP aquifer 

with underlying bedrock. The top layer extends to a maximum 

depth of 10 ft below the October 1996 elevation of the water 

table in each cell. This uppermost layer is relatively thin in 

order to simulate shallow ground-water flow near surfacewater bodies as accurately as possible. The maximum 

thickness of each of the second and third layers is 30 ft; the 

fourth layer extends from the bottom of the third layer to the 

HAP aquifer/bedrock contact. Because the thickness of the 

aquifer varies laterally, the number of active layers within 

each vertical stack of cells varies laterally as well. Areas of 

the HAP aquifer where saturated thickness was less than 

5 ft were made inactive to ensure numerical stability of the 

models. This criterion resulted in many cells near the boundary between the HAP aquifer and adjoining till and bedrock 

uplands being made inactive, and an active area that was 

smaller than the measured extent of the aquifer (compare 

boundary of the HAP stream-aquifer system to active area of 

model in fig. 5).

Horizontal hydraulic conductivity of the simulated 

stratified deposits of the aquifer ranged from 25 to 587 ft/d. 

The average horizontal hydraulic conductivity of each layer 

of the calibrated models ranged from 169 to 191 ft/d. 

A uniform anisotropic ratio of horizontal to vertical hydraulic 

conductivity of 5.0 was used throughout the simulated area. 

Uniform values of the specific yield and storage coefficient of 

the aquifer of 0.28 and 3.0 x 10-4, respectively, were specified 

for the stratified deposits. Ponds and lakes were simulated in 

the top layer of each model by specifying an arbitrarily high 

value of horizontal hydraulic conductivity (50,000 ft/d) and 

a specific yield of 1.0 in those cells in which ponds and lakes 

are located.

The active area of the models was surrounded laterally 

by no-flow boundaries. These boundaries were based on the 

water-table map of the aquifer developed by Dickerman and 

Barlow (1997) and hydrogeologic information provided in 

Rosenshein and others (1968), who completed the first comprehensive study of the aquifer. Recharge to the water table 

was represented as a specified flow rate applied to the uppermost active cell in each vertical stack of cells. A long-term 

average precipitation recharge rate of 28.0 in/yr was applied 

to all areas of the HAP aquifer except those overlain by ponds 

and lakes, where a recharge rate of 19.5 in/yr was specified. 

For the transient model, long-term average monthly recharge 

rates were specified for all areas of the model except ponds 

and lakes, where recharge rates were reduced in proportion to 

seasonal free-water-surface evaporation rates. Recharge from 

wastewater was specified in those areas of the model that 

receive water supplies but are unsewered; total recharge from 

wastewater was about 1.2 ft3/s (or 3 percent of the total 

average annual simulated recharge of 35.5 ft3/s), and was 

specified at a constant rate throughout the year.

Ground-water inflow from upland areas not drained by 

streams was accounted for by injecting water into simulated 

wells located in the first and second layers of the models just 

inside the boundary between the HAP aquifer and adjoining 

till and bedrock; total steady-state inflow along these boundaries was calculated by multiplying the precipitation recharge 

rate to the aquifer of 28.0 in/yr by the total area of undrained 

till and bedrock uplands. For the transient model, these inflow 

rates were varied in proportion to the monthly precipitation recharge rate to the aquifer. Ground-water underflow 

where it leaves the system near the Annaquatucket River was 

accounted for by withdrawing 1.0 ft3/s of water from simulated 

wells in the top layer of the steady-state model in that area; for 

the transient model, this rate was adjusted for each month in 

proportion to the monthly recharge rate to the aquifer.

Evapotranspiration from the water table was simulated 

with the evapotranspiration package of MODFLOW. A maximum steady-state evapotranspiration rate from the water table 

of 21.0 in/yr and a maximum depth below the land surface at 

which evapotranspiration takes place of 4 ft were assumed. 

For the transient model, maximum monthly evapotranspiration rates from the water table were specified as 3.5 inches per 

month during the May–October growing season and zero for 

the remaining months of the year.

Average annual and monthly ground-water withdrawals during 1996 were specified at simulated supply wells for 

the steady-state and transient models, respectively. These 

withdrawal rates were determined by Barlow and Dickerman 

(2001, p. 27) to be representative of the 1941–96 period.

Streams were simulated in the models with the streamrouting package developed by Prudic (1989). This package 

simulates hydraulic interaction between an aquifer and adjoining streams, and tracks the amount of water in each simulated 

stream. Most of the simulated streams flow through ponds 

and lakes that are in hydraulic connection with the aquifer; 

these ponds and lakes also were simulated with the streamrouting package. The grid locations of the several stream sites 

discussed in this report are summarized in table 2, and their 

locations are shown in figure 7. Streamflow that enters the 

HAP stream-aquifer system from upland till and bedrock areas 

and at the headwater of the Annaquatucket River where water 

is discharged to the stream at the fish hatchery was specified in 

the steady-state and transient models. These streamflow rates 

were either measured directly or were estimated by correlation 

of streamflows measured at the stream sites to long-term continuous-record streamflow-gaging stations. Locations of specified streamflow are shown in figure 6; the rates of streamflow 

specified for the steady-state model are given in table 3.

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System 
10 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

9A

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BOUNDARY OF ACTIVE AREA OF MODELS

SIMULATED STREAM 

SPECIFIED FLOW FROM TILL AND BEDROCK

 TO AQUIFER—Flow specified in layers 1 or 2

SPECIFIED FLOW OUT OF AQUIFER—Ground-

 water underflow near Annaquatucket River

HEAD-DEPENDENT FLOW ALONG

 GROUND-WATER DRAINAGE DIVIDE

INACTIVE CELL

SPECIFIED STREAM SITE AND

 IDENTIFIER—See table 3

WATER-SUPPLY WELL AND IDENTIFIER

A

EXPLANATION

NK2

A

0 .5 1 MILE

0 .5 1 KILOMETER

Unnamed Tributary

Fry Brook

Frenchtown Brook

Scrabbletown Brook

Sandhill

Brook

Cocumcossuc Brook

Hunt

River

Potowomut

Pond

Unnamed

Tributary

Figure 6. Grid and boundary conditions of the active areas of the modified simulation models of the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island, for (A) rows 3-125 and (B) rows 126-205. (Modified from Barlow and Dickerman, 

2001, fig. 12.)
6

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Brook

Annaquatucket

River

Pettaquamscutt River

Queens

Fort

Brook

0 .5 1 MILE

0 .5 1 KILOMETER

Figure 6. Grid and boundary conditions of the active areas of the modified simulation models of the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island, for (A) rows 3-125 and (B) rows 126-205. (Modified from Barlow and Dickerman, 

2001, fig.12.)—Continued

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System 11
12  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

uniform ratio of horizontal to vertical hydraulic conductivity 

of 5.0 was specified for all four layers of the models, which 

was the same ratio used to calculate vertical conductance in 

the original models. The second change that was required was 

the addition of a discretization (DIS) file. Most of the data 

specified in the DIS file was moved there from the original 

Basic (BAS) and BCF package files. A top elevation for each 

cell of layer 1 of the models also was specified in the DIS file; 

these elevations were set to the estimated water-table elevations during October 1996, which were the elevations used to 

derive the model-layering intervals in the original model.

Increase in the Active Area of the Models

The lateral extent of the active area of the models was 

increased to provide improved representation of the aquifer 

near the State Fish Hatchery. This was done in two general 

areas (fig. 5): (1) west of the hatchery toward Queens Fort 

Brook in the Usquepaug-Queen River Basin and (2) south 

Table 2. Model grid-cell locations for stream sites discussed in text for the Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island.

[Site identifiers are shown in figure 7]

Stream site 

identifier Stream name

Model cell

Layer Row Column

Hunt River Basin

A Scrabbletown Brook 1 119 35

B Unnamed tributary #1 to Hunt River 1 103 37

C Frenchtown Brook 1 74 13

D Fry Brook 1 59 8

E Unnamed tributary #2 to Hunt River 1 28 6

F Hunt River outflow 1 6 35

Cocumcossuc Brook Basin

G Cocumcossuc Brook outflow 1 104 86

Usquepaug–Queen River Basin

H Reuben Brown Brook 1 166 30

Queens Fort Brook:

I At upland contact 1 161 29

J At outflow 1 187 73

Annaquatucket River Basin

Annaquatucket River:

K Below State Fish Hatchery 1 160 78

L Between State Fish Hatchery and Hatchery Road 1 148 79

M Between State Fish Hatchery and Hatchery Road 1 141 71

N At Hatchery Road 1 133 85

O Belleville Pond outflow 1 135 117

P At outflow (Route 1) 1 131 129

Pettaquamscutt River Basin

Q Unnamed tributary to Pettaquamscutt River 1 180 177

R Pettaquamscutt River outflow 1 157 197

Modifications to the Original Numerical Models

Several modifications were made to the original models 

to incorporate new data made available since the original 

study, or to meet the objectives of this study. These modifications are described below.

Conversion of Models to MODFLOW-2000

The first step in updating the models was to convert 

them to the 2000 version of MODFLOW (Harbaugh and 

others, 2000), so that they run with a more current version of 

the MODFLOW code. The most substantial change that was 

required was to replace the Block-Centered Flow (BCF) package of MODFLOW-96 with the Layer-Property Flow (LPF) 

package of MODFLOW-2000. This change required replacing 

the vertical conductance of the aquifer specified in the original BCF package by the ratio of horizontal to vertical hydraulic conductivity of the aquifer specified in the LPF package. A 
of the hatchery and west of Belleville Pond. These changes 

increased the active area of the models by about 1.1 mi2.

Changes to the lateral extent of the active area of the 

models necessitated two additional changes to the original 

models: (1) the locations and rates of inflow from upland 

areas of till and bedrock and (2) the simulation of two streams 

in the Usquepaug-Queen River Basin west of the hatchery. 

As described previously, ground-water inflow from upland 

areas of till and bedrock that are not drained by streams was 

simulated by use of injection wells just inside the boundary between active and inactive areas. The amount of inflow 

from undrained upland areas was decreased from the original 

model to account for the smaller extent of these areas in the 

new model. The total reduction in the amount of inflow from 

upland areas for the steady-state model was about 2.3 ft3/s, 

which is consistent with a recharge rate in the upland areas of 

28.0 in/yr (as used in the original models) applied over the 

1.1-mi2 active area added to the model. For the transient 

model, monthly rates of lateral inflow along these boundaries 

were specified in proportion to the monthly recharge rates to 

the aquifer, as was done in the original model.

The revised active area of the model also necessitated 

changes to the simulation of Queens Fort and Reuben Brown 

Brooks in the Usquepaug-Queen River Basin. Streamflow had 

been simulated for part of Queens Fort Brook in the original 

models. In the modified models, the length of that brook that 

was simulated was increased, and a short reach of Reuben 

Brown Brook, which is tributary to Queens Fort Brook, was 

included. Streamflow from upland areas drained by these two 

brooks was specified in the first reach of each brook. For the 

steady-state model, these flows were calculated on the basis 

of the drainage area to the first reach of each brook and an 

assumed average runoff rate of 28.0 in/yr, as was done in the 

original models. Average annual flows of 0.64 and 0.98 ft3/s 

were specified for Queens Fort Brook and Reuben Brown 

Brook, respectively. These specified flows to the streams 

were compensated for in the modified models by reducing the 

specified amounts of ground-water inflow from upland areas 

where these streams enter the active area of the model by 

about 1.6 ft3/s. 

Specified monthly inflows for Queens Fort and Reuben Brown Brooks for the transient model were determined 

by use of the annual distribution of specified flows for Fry 

Brook, which is a small brook that drains upland areas in 

the Hunt River Basin and whose flow was measured during 

the original study (site D, fig. 7). The drainage area of this 

brook is underlain almost entirely by till, as are the drainage 

areas of Queens Fort and Reuben Brown Brooks upgradient 

to the active area of the models. Therefore, it was assumed 

that the annual distribution of monthly inflows to the model 

would be similar for the three brooks. Long-term average 

monthly streamflows at the Fry Brook measurement site for 

the 1941–96 period were estimated in the original study by 

use of correlation graphs between streamflows measured in 

the brook and those measured at a continuous-record streamflow-gaging station on the Pawcatuck River at Wood River 

Junction, Rhode Island. The ratio of each estimated average 

monthly flow to the estimated long-term average annual flow 

for the brook was multiplied by the estimated average annual 

flows for Queens Fort Brook and Reuben Brown Brook to 

determine the distribution of monthly inflows to the model for 

the two brooks. The monthly ratios ranged from a low of 

0.14 in September to 2.20 in March.

Table 3. Streamflows specified in the steady-state model of the Hunt–Annaquatucket–Pettaquamscutt stream-aquifer 

system, Rhode Island.

[Site identifiers are shown in figures 6 and 7]

Stream site 

identifier Stream name

Model cell Streamflow

Layer Row Column Cubic feet 

per second

Million gallons 

per day

Hunt River Basin

A Scrabbletown Brook 1 119 35 2.25 1.45

B Unnamed tributary #1 to Hunt River 1 103 37 2.95 1.91

C Frenchtown Brook 1 74 13 13.50 8.73

D Fry Brook 1 59 8 6.40 4.14

E Unnamed tributary #2 to Hunt River 1 28 6 .80 .52

Usquepaug–Queen River Basin

H Reuben Brown Brook 1 166 30 .98 .64

I Queens Fort Brook 1 161 29 .64 .41

Annaquatucket River Basin

K Annaquatucket River 1 160 78 1.95 1.26

Pettaquamscutt River Basin

Q Unnamed tributary to Pettaquamscutt River 1 180 177 .62 .40

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System 13
Chipuxet

River

Basin

Hunt River

Basin

UsquepaugQueen

River

Basin

Annaquatucket

River

Basin

Pettaquamscutt

River

Basin

Cocumcossuc

Brook

Basin

H

I

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F

0 .5 1 MILE

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STRATIFIED DEPOSITS

TILL AND BEDROCK

WETLANDS NEAR LAFAYETTE

 STATE FISH HATCHERY—Other

 wetlands in the study are not shown

BOUNDARY OF THE

 STREAM-AQUIFER SYSTEM

BOUNDARY OF ACTIVE AREA

 OF MODEL

DRAINAGE BOUNDARY—

 Ground-water drainage

 boundary where it differs

 from the surface-water drainage

 basin boundary

 Ground-water and surface-water

 drainage boundary

 Surface-water subbasin drainage

 boundary

STREAM SITE

WEST

WARWICK

WEST GREENWICH

EAST GREENWICH

EXETER

NORTH KINGSTOWN

WARWICK

EXPLANATION

A

41°37'30"

71°32'30"

71°27'30"

41°32'30"

Queens Fort Brook

Reuben Brown Brook

Fry Brook

Frenchtown Brook

Scrabbletown Brook

Cocumcossuc Brook

Sandhill

Brook

Hunt River

River

Hunt

River

Unnamed Tributary

Unnamed Tributary

Annaquatucket

River

Pettaquamscutt

Carr

Pond

Secret

 Lake

Belleville

Pond

Potowomut 

Pond

Silver

 Spring Lake

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

Figure 7. Stream sites discussed in text for the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island. 

14  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Simulation of Flow at Ground-Water Drainage 

Divides in the Annaquatucket River Basin

As noted previously, ground-water and surface-water 

drainage divides do not coincide along the western boundary 

of the Annaquatucket River Basin where it is in contact with 

the Usquepaug-Queen and Chipuxet River Basins. Because of 

this, the active area of the original models was extended into 

these adjoining basins where they are underlain by stratified 

deposits. In the original model, the ground-water divides were 

simulated as no-flow boundaries, which prevented ground 

water from flowing between the Annaquatucket River Basin 

and adjoining basins regardless of hydrologic stresses that 

might occur within the Annaquatucket River Basin. This 

assumption of no ground-water flow across the drainage 

divides is valid as long as the locations of ground-water withdrawals in the Annaquatucket River Basin are relatively far 

from the boundary, which was valid for conditions simulated 

in the original models. However, the addition of the new well 

NK11, which was approved since development of the original 

model, made it necessary to change the type of boundary condition used to simulate flow along the ground-water drainage 

divides that separate the Annaquatucket River Basin from the 

Chipuxet River Basin and a small length of the UsquepaugQueen Basin (fig. 6). Instead of the original no-flow boundary 

condition, head-dependent boundary conditions were specified along these drainage divides by use of the General-Head 

Boundary (GHB) package of MODFLOW. The use of headdependent boundary conditions allows ground water to flow 

across the simulated divides in response to changing stress 

conditions within the model area (but not in the other two 

basins).

The use of this type of boundary condition requires that 

ground-water heads be specified at each of the boundary cells. 

Because of a lack of detailed water-level data in these areas, 

heads in model cells in all four layers of the model along the 

boundary were specified on the basis of water-table contours 

on the October 1996 water-table map and those available 

in Hahn (1959) and Johnson and Marks (1959). It was also 

necessary to specify hydraulic conductance at each of these 

boundary cells. These conductances were calculated as the 

product of the transmissivity of the aquifer at each cell and the 

width of each cell (200 ft) divided by the length of each cell 

(200 ft), which was assumed to be the distance over which the 

head loss across each drainage divide occurs. The transmissivity of each cell was calculated as the product of the hydraulic 

conductivity and saturated thickness of the aquifer at each 

cell, as estimated from maps prepared as part of the study by 

Rosenshein and others (1968).

Modification of Aquifer Hydraulic Properties 

near Lafayette State Fish Hatchery and Town of 

North Kingstown Well 11

The saturated thickness and hydraulic conductivity of the 

aquifer were modified in the area near the Lafayette State Fish 

Hatchery to improve their representation in the model. The 

modifications were based on a re-evaluation of aquifer conditions near the hatchery as a result of new hydrogeologic data 

collected during 1995 and 2002 (James McGinn, Rhode Island 

Department of Environmental Management, written commun., 

2005). The modifications consisted of reducing the simulated 

saturated thickness of the aquifer (by raising the simulated 

altitude of the bedrock surface) and reducing the simulated 

hydraulic conductivity of the aquifer near the hatchery from 

a value of 350 ft/d specified in the original model to 200 ft/d, 

which is more consistent with the sand and gravel aquifer sediments found at the hatchery.

Changes also were made to the hydraulic conductivity and transmissivity of the aquifer near well NK11. These 

changes were made on the basis of new data made available 

from the results of an aquifer test done at the site by Fay, Spofford, and Thorndike (2005). They calculated transmissivity of 

the aquifer to be 18,000 (gal/d)/ft at the site (about 2,400 ft2/d) 

based on the results of a 72-hour aquifer test. 

This transmissivity is low compared to those estimated for 

some other well locations in the Annaquatucket River 

Basin, but is consistent with an estimated transmissivity of 

20,000 (gal/d)/ft for the aquifer near NK11 given in Rosenshein and others (1968, plate 2). NK11 is in an area mapped 

as mixed till and outwash (stratified deposits) by Johnson 

and Marks (1959), who describe these deposits as “till and 

outwash that grade into one another or are mixed in varying 

proportions.” These deposits are discontinuous and extend 

generally westward from an area west of Belleville Pond and 

Secret Lake toward the Chipuxet River Basin (Johnson and 

Marks, 1959; Hahn, 1959). The mixed sediment type in which 

the well is apparently located may explain the relatively low 

transmissivity of the aquifer in that area. 

An average hydraulic conductivity of the aquifer at well 

NK11 can be calculated to be about 24 ft/d on the basis of 

the saturated thickness of the aquifer at the site (about 102 ft) 

estimated from data provided in Fay, Spofford, and Thorndike 

(2005). Based on these data, the hydraulic conductivity of the 

simulated aquifer near the well site was reduced such that the 

simulated transmissivity of the aquifer in the area of the well 

is about 2,300 ft2/d.

Numerical Models to Simulate Hydrologic-System Responses in the Stream-Aquifer System 15
Conversion to Constant Saturated Thickness and 

Transmissivity

The modifications made to increase the active area of 

the models caused the updated steady-state model to become 

numerically unstable. It is assumed that this instability was 

caused by the relatively thin saturated thickness of the aquifer 

(generally less than about 30 ft) in the area west of the State 

Fish Hatchery in the Usquepaug-Queen River Basin. In fact, 

the original model was made inactive in that area to avoid 

these instabilities. Because of the importance of the area in 

meeting study objectives, it was necessary to simulate the 

aquifer as having constant saturated thickness and transmissivity at each cell. This approach allows the saturated 

thickness and transmissivity of the aquifer to vary spatially 

throughout the model domain, but not in response to changing 

stress conditions, which include changing withdrawal rates. 

This assumption often is made in the simulation of water-table 

aquifers and is considered valid because the saturated thickness (and therefore the transmissivity) of the aquifer does 

not change substantially in response to changing withdrawal 

conditions, except within the immediate vicinity of each well 

(generally less than the 200-ft width of each cell).

This change also required modification to the storage 

properties of the aquifer for the transient simulations. The 

storage properties specified in the original transient model 

were the storage coefficient and specific yield of the aquifer. 

In the modified transient model, the uniform value of the storage coefficient specified for layers 2-4 of the original model 

(3.0 x 10-4) was replaced by a uniform value of specific storage equal to 1.0 x 10-5 ft-1, which was the value used in the 

original study to calculate storage coefficient. Uniform values 

of specific yield equal to 0.28 for stratified deposits and 1.0 

for ponds and lakes were specified for layer 1 of the original 

model. For the modified model, these values were divided by 

10 ft, the original saturated thickness for each cell of layer 1, 

to obtain a storage property that has units that are consistent 

with specific storage (ft-1), but that retains the high storagecapacity characteristic of a specific yield.

Simulation of Hydrologic-System 

Responses in the Stream-Aquifer 

System

The modified steady-state and transient models described 

in the previous section were used to simulate several alternative basin-wide withdrawal and recharge conditions. First, the 

modified models were run using the original 1996 withdrawal 

conditions to determine how the results of the modified models compare to those of the original models. Then, the modified models were run for several new withdrawal and recharge 

conditions.

Simulation Results for Original Withdrawal 

Conditions

The only change that was made to the models after the 

modifications described in the previous section was to increase 

the ground-water levels specified at the head-dependent 

boundary cells used to simulate the ground-water drainage 

divide between the Annaquatucket and Chipuxet River Basins. 

These increases were a maximum of about 7 ft, and were made 

to cause the model-calculated steady-state flow across the 

divide to be as close to zero as possible, because the boundary is conceptualized as having no ground-water flow across 

it. The process of having to increase the ground-water levels 

at this boundary indicates the uncertainty of the exact location 

of the divide between the Chipuxet and Annaquatucket River 

Basins.

Calculated water-level altitudes for the original and 

modified models at each of 22 observation wells used for 

model calibration are shown with the measured values on 

October 8, 1996, in table 4. The mean of the absolute value of 

the difference between calculated and measured water-level 

altitudes, which is referred to as the mean water-level residual, 

is about 2.7 ft for each of the two models, which indicates 

the general similarity between the two models. A map of the 

simulated water table for steady-state conditions is shown 

in figure 8. In most areas, differences between the simulated 

water tables for the original and modified models are small. 

The areas of noticeable change are those where the lateral 

extent of the model was increased, west and south of the State 

Fish Hatchery.

Steady-state average annual hydrologic budgets 

calculated by the original and modified models are shown 

in table 5. The total amount of simulated inflow to the two 

models is identical, although the distribution of flows among 

the different inflow components differs because of changes 

made to the lateral extent of the model. In the modified model, 

lateral ground-water inflow from uplands (15.5 ft3/s) is 4.0 

ft3/s less than the original model, but this decrease is made 

up by an increase of 2.4 ft3/s in simulated recharge to the 

aquifer and 1.6 ft3/s in specified streamflow from the uplands 

at Queens Fort and Reuben Brown Brooks. Ground-water 

inflows along the two simulated drainage divides between the 

Annaquatucket River Basin and adjoining Usquepaug-Queen 

and Chipuxet River Basins for the modified model are about 

zero; outflows along these drainage divides for the modified 

model are about 0.2 ft3/s (table 5).

The total amount of simulated steady-state outflow from 

the modified model is higher than the original model by 

0.6 ft3/s, but the budget error (total inflows minus total outflows) for the modified model is improved over that of the 

original model. Streamflows calculated by the original and 

modified models at the five outflow sites reported for the 

original model are shown in table 6. Differences in calculated streamflows between the original and modified models 

for the Hunt, Cocumcossuc, and Pettaquamscutt Rivers are 

16  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
WCW-29

WCW-270

NKW-45

NKW-41 EGW-41

NKW-641

NKW-1321

NKW-1320

NKW-512

NKW-602

EGW-77

NKW-627

NKW-591

NKW-1319

NKW-1335

NKW-1333

NKW-452

NKW-1316

NKW-543 NKW-1330

NKW-543

EXW-86

NKW-255

NK10

NK9 14A

KC1

9A

3A

IW

NK6

SFH3

SFH2

SFH1

NK1

NK2 NK4

NK5

NK3

NK8

NK7

NK11

SFH4

120

140

160

180

100

100

60

80

60

60

50

50

40

30

10

30

20

50

60

80

100

50

50

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

50

60

50

200

220

240

20

40

30

20

10

60

40

80

10

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-

 STATE WATER-TABLE CONTOUR—

 Shows altitude of water table in feet above

 NGVD29. Contour interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

OBSERVATION WELL AND U.S. GEOLOGICAL

 SURVEY IDENTIFIER—Site where model-calculated

 and measured water-table altitudes were compared.

 See table 4

NK2

EXPLANATION

100

Figure 8. Model-calculated steady-state water table with 1996 withdrawal rates, Hunt-Annaquatucket-Pettaquamscutt 

stream-aquifer system, Rhode Island.

Simulation of Hydrologic-System Responses in the Stream-Aquifer System 17
18  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

Table 4. Model-calculated steady-state water-level altitudes and measured water-level altitudes on October 8, 

1996, at observation wells in the Hunt–Annaquatucket–Pettaquamscutt stream-aquifer system, Rhode Island.

[Well locations are shown in figure 8. USGS well identifier: EGW, East Greenwich well; EXW, Exeter well; NKW, North 

Kingstown well; WCW, Warwick well; USGS, U.S. Geological Survey]

USGS well 

identifier

Model location

(layer, row, column)

Water-level altitude

(feet above NGVD29)

Measured Original model Modified model

WCW-29 1, 8, 33 1.4 6.9 5.8

WCW-270 1, 23, 31 19.6 16.0 16.0

NKW-41 1, 29, 49 14.1 15.1 15.2

NKW-45 1, 43, 43 29.5 28.5 28.5

EGW-41 1, 54, 19 31.2 30.8 30.8

NKW-627 1, 66, 28 38.7 39.5 39.5

NKW-641 1, 69, 43 41.4 41.9 42.2

NKW-1321 1, 93, 53 45.3 49.5 49.7

EGW-77 1, 96, 39 43.2 43.0 43.0

NKW-591 1, 102, 72 52.1 53.3 54.3

NKW-602 1, 111, 53 47.3 53.8 54.1

NKW-1320 1, 117, 60 52.0 59.4 60.3

NKW-512 1, 130, 71 63.1 66.4 67.9

NKW-1319 1, 139, 83 67.6 69.0 68.9

NKW-452 1, 135, 133 44.0 43.4 43.9

NKW-1335 2, 146, 102 57.9 52.4 53.1

NKW-1333 3, 150, 112 50.1 49.7 50.2

NKW-1316 1, 160, 148 37.1 37.8 38.0

NKW-1330 2, 170, 128 68.4 65.9 65.1

NKW-255 1, 170, 159 36.3 40.7 44.4

NKW-543 2, 177, 111 93.7 89.5 91.6

EXW-86 2, 180, 69 172.4 169.2 172.4
Table 5. Model-calculated steady-state average annual hydrologic budgets for the Hunt–

Annaquatucket–Pettaquamscutt stream-aquifer system, Rhode Island. 

[Budget components are in cubic feet per second]

Hydrologic budget component Original model Modified model

Inflow

Recharge 35.5 37.9

Lateral ground-water inflow from uplands 19.5 15.5

Streamflow from uplands 26.5 28.1

Discharge to Annaquatucket River at the State Fish Hatchery 2.0 2.0

Inflow along ground-water drainage divides .0 .0

Total inflow 83.5 83.5

Outflow

Streamflow 69.3 69.5

Evapotranspiration 4.6 4.8

Ground-water underflow near Annaquatucket River 1.0 1.0

Ground-water withdrawal 8.1 8.1

Outflow along ground-water drainage divides .0 .2

Total outflow 83.0 83.6

Budget error (inflow-outflow) .5 -.1

Table 6. Model-calculated steady-state streamflows at outflow locations from the Hunt–

Annaquatucket–Pettaquamscutt stream-aquifer system, Rhode Island.

[Streamflow rates are in cubic feet per second; stream site identifiers are shown in figure 7]

Stream site 

identifier Stream name

Streamflow

Original model Modified model

F Hunt River 42.3 42.4

G Cocumcossuc Brook 2.9 2.9

J Queens Fort Brook .6 1.3

P Annaquatucket River 13.8 13.3

R Pettaquamscutt River 9.7 9.6

Simulation of Hydrologic-System Responses in the Stream-Aquifer System 19
less than or equal to 0.1 ft3

/s, whereas those for the Annaquatucket River and Queens Fort Brook are -0.5 ft3

/s and 

+0.7 ft3/s, respectively. These differences most likely result 

from changes made to the model in the Annaquatucket River 

Basin, particularly those related to extending the active area 

of the model in the areas west and south of the State Fish 

Hatchery. Although there is no long-term streamflow gage for 

the Queens Fort Brook where it leaves the modeled area, a 

long-term average streamflow of 1.02 ft3/s has been estimated 

for a site on the brook about 0.9 mi downstream from the 

model boundary (USGS streamflow-gaging station 01117365) 

(Gardner Bent, U.S. Geological Survey, written commun., 

2005).

Calculated ground-water levels and streamflows for 

the modified transient model also are very similar to those 

calculated for the original transient model. The similarity in 

model-calculated mid-monthly streamflows for the Hunt and 

Annaquatucket Rivers at their outflow locations can be seen in 

figure 9. Mid-monthly streamflows calculated by the modified 

model for the Annaquatucket River are from 0.3 to 0.9 ft3/s 

lower than those calculated by the original model, which is 

consistent with the lower streamflow calculated for the river 

by the modified steady-state model. Model-calculated groundwater inflows along the simulated ground-water drainage 

divides at the end of each month range from zero in February 

through June to a maximum of 0.4 ft3/s in October; groundwater outflows range from zero in September and November 

to a maximum of about 0.7 ft3/s in April.

Simulation Results for Alternative Withdrawal 

and Recharge Conditions

The modified models were used to simulate several alternative withdrawal and recharge conditions. The majority of 

simulations are for long-term (1941–2003) average recharge 

conditions; two additional simulations were made to evaluate 

the effects of drought on the hydrologic system.

Simulations for Long-Term Average Recharge 

Conditions

Six sets of simulations were made with the steadystate and transient models for long-term average recharge 

conditions to determine the effects of alternative basin-wide 

withdrawal conditions on the ground-water and surface-water 

resources of the HAP stream-aquifer system. Simulation 

conditions represent long-term average annual and average 

monthly hydrologic conditions. Long-term average hydrologic conditions are defined as those that existed during the 

63-year period 1941–2003, which extends the 56-year period 

(1941–96) used in the original models. The simulations 

progress from a condition of minimum stress, in which there 

are no ground-water withdrawals anywhere in the HAP Basin, 

to a condition of maximum stress in which withdrawals occur 

simultaneously at all existing supply wells in the basin and at 

two proposed or new wells in the Annaquatucket River Basin. 

20 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

HUNT RIVER, ORIGINAL

MODEL

HUNT RIVER, MODIFIED

MODEL

ANNAQUATUCKET RIVER, 

ORIGINAL MODEL

ANNAQUATUCKET RIVER,

MODIFIED MODEL

EXPLANATION

MONTH

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

0

20

40

60

80

100

STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 9. Model-calculated mid-monthly streamflow at the outflow locations of the Hunt and Annaquatucket Rivers, Rhode Island.
The alternative stress conditions allow the effects of different 

groups of wells and of different pumping rates on the hydrologic system to be isolated. The effects of withdrawals are 

described in terms of their effects on ground-water levels and 

streamflows in the basin and on the flow rates to the aquifer 

underlying three wetland areas near the fish-hatchery wells. 

The six sets of simulations are:

No withdrawals at any supply wells;

Withdrawals at 2003 rates at existing production wells 

only;

Withdrawals at 2003 rates at existing production and 

State Fish Hatchery wells;

Withdrawals at existing production wells at 2003 rates 

and State Fish Hatchery wells at half their 2003 rates;

Withdrawals at 2003 rates at existing production and 

State Fish Hatchery wells and additional withdrawals at 

proposed State Fish Hatchery well; and

Withdrawals at 2003 rates at existing production and 

State Fish Hatchery wells and additional withdrawals at 

the proposed State Fish Hatchery well and new town of 

North Kingstown well.

Long-term average recharge rates to the aquifer were 

calculated for the 1941–2003 period by use of the computer 

program RORA (Rutledge, 1993). The program calculates 

average annual and monthly recharge rates on the basis of 

continuous streamflow records available for the Hunt River at 

its outflow location from the study area (USGS streamflowgaging station 01117000; location shown in fig. 2). The average annual recharge rate calculated for the 63-year period was 

25.5 in., or 0.1 in. greater than the value of 25.4 in. 

calculated for the 56-year period in the original study. 

Average monthly recharge rates for the 63-year period ranged 

from a minimum of 0.6 in. for September to 4.3 in. for March, 

as they did for the 1941–96 period. The maximum difference 

in the average monthly recharge rate between the 1941–96 

and 1941–2003 periods was 0.1 in. for the month of June. 

Because of the similarity in the long-term average annual and 

monthly recharge rates estimated for the two time periods, 

recharge rates simulated in the original steady-state and transient models were not changed for the simulations described 

below. Moreover, other flow-related boundary conditions 

specified in the steady-state and transient models also were 

not changed from the original models. These include 

(1) specified rates of lateral ground-water inflow from 

uplands; (2) specified rates of streamflow from upland areas 

to streams entering the modeled area; (3) ground-water 

underflow near the Annaquatucket River outflow from the 

basin; and (4) evapotranspiration rates from the water table. 

Approaches used to estimate each of these boundary conditions are described in detail by Barlow and Dickerman (2001). 

Because wastewater recharge is a small part of the total 

recharge to the aquifer, the rate of wastewater recharge was 

1.

2.

3.

4.

5.

6.

not varied for the six sets of simulations. Discharge rates from 

the hatchery to the headwater of the Annaquatucket River at 

stream site K (location shown in fig. 7) were set equal to total 

withdrawal rates from the hatchery wells, as was done in the 

original study; these discharge rates were varied from simulation to simulation, as described below.

Most of the simulations described below are based on the 

2003 average annual and average monthly pumping rates for 

each well, which were obtained from the three water suppliers in the basin (Town of North Kingstown, RIEDC, and 

KCWA) and from the RIDEM. The pumping rate specified 

for the industrial well (site IW in fig. 1) was not changed from 

the original model (0.25 Mgal/d). Average annual withdrawal 

rates at each well simulated in the models are shown in table 7 

and are fairly typical for recent years (1999–2004). Withdrawals at the hatchery represent about 54 percent of the 2003 total 

average annual withdrawals from the Annaquatucket River 

Basin. Total average annual ground-water withdrawals from 

each basin were greater in 2003 than in 1996, increasing from 

2.78 to 3.28 Mgal/d in the Hunt River Basin, from 2.25 to 

2.71 Mgal/d in the Annaquatucket River Basin, and from 0.21 

to 0.33 Mgal/d in the Pettaquamscutt River Basin.

Steady-state contributing areas also were delineated for 

the production and fish-hatchery wells for two of the simulation conditions described below. The contributing area of 

a well is the surface area of the water table where recharge 

water entering the ground-water system eventually flows to 

the well. Contributing areas were delineated with the computer program MODPATH (Pollock, 1994), which calculates 

three-dimensional flow paths from the results of the MODFLOW steady-state simulation. MODPATH uses a particletracking scheme to track the movement of hypothetical 

particles of water through the simulated ground-water-flow 

system. MODPATH requires specification of the porosity of 

the aquifer for each cell of the model grid. As in the original 

study, a uniform porosity of 0.35 was specified for the stratified deposits simulated by the model, and a porosity of 1.0 

was specified for the simulated ponds and lakes. The contributing area to each well was delineated by overlaying a 2 x 2 

array of particles onto the simulated water table in each model 

cell. Particles were then tracked from the water table to their 

points of discharge from the simulated aquifer. The origin 

of those particles that were captured by each simulated well 

defined the contributing area to that well.

Simulation Set 1: No Withdrawals at Any Supply 

Wells—The first set of model runs, which simulated the 

condition of no ground-water withdrawals at any of the supply wells in the HAP Basin, was done primarily to provide 

base-line conditions against which the alternative withdrawal 

scenarios could be compared. Because there were no withdrawals from the hatchery wells for this simulation set, there 

was no discharge of water from the hatchery specified to the 

headwater of the Annaquatucket River. Under this condition, 

the steady-state model indicates that the Annaquatucket River 

would be dry from its headwater to below the Hatchery Road 

stream site (site N, table 8), which is just above Belleville 

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  21
Pond (fig. 7). Results of the transient simulation also indicated 

that the river would be mostly dry in this reach during an 

average year (that is, the condition simulated by the transient 

model). These dry conditions result from the fact that modelcalculated ground-water levels in the aquifer are lower than 

the stream stage along most of this reach. Because discharge 

from the hatchery occurred during all measurement periods in 

the original study, there are no data to confirm these simulation results directly; however, existing data indicate that the 

river is losing water to the aquifer under some flow conditions 

in the reach from just below the hatchery to the Hatchery 

Road stream site (site N) (Dickerman and Barlow, 1997; 

Barlow and Dickerman, 2001). This implies that ground-water 

levels beneath the river are lower than the stream stage in this 

reach; this was confirmed by water-level data measured at 

the Hatchery Road stream site (site N) in October 1996 that 

showed that the water table was more than 4.5 ft below the 

stream stage in this area. This losing condition suggests that if 

discharge from the hatchery was discontinued, the river would 

be dry, or at least intermittent, above the Hatchery Road site 

for most hydrologic conditions.

There are large model-calculated increases in groundwater discharge to the Annaquatucket River from below the 

Hatchery Road stream site, through Belleville Pond, to the 

river’s outflow location from the study area (table 8). These 

increases, which are supported by field measurements made 

22  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

Table 7. Withdrawal rates (2003) specified for water-supply wells in the steady-state model of the 

Hunt–Annaquatucket–Pettaquamscutt stream-aquifer system, Rhode Island. 

[Well locations are shown in figure 1; KCWA, Kent County Water Authority; NK, town of North Kingstown; 

SFH, Lafayette State Fish Hatchery]

Water supply 

well identifier

Model cell Withdrawal rate

Layer Row Column Cubic feet 

per second

Million 

gallons per 

day

Hunt River Basin

KC1 4 35 21 1.00 0.64

3A 4 58 22 .34 .22

9A 2 30 21 .33 .21

14A 3 30 23 .37 .24

NK6 3 109 53 .99 .64

NK9 4 36 21 1.67 1.08

NK10 4 38 21 0 0

IW 3 79 26 .39 .25

Total for basin 5.09 3.28

Annaquatucket River Basin

SFH11 2 161 78 0.37 0.24

SFH21 2 160 77 .74 .48

SFH3 2 160 76 1.11 .72

SFH4 2 163 76 0 0

NK1 2 149 114 .76 .49

NK2 2 150 115 .31 .20

NK4 2 154 117 .48 .31

NK5 3 161 118 .42 .27

NK11 4 178 122 0 0

Total for basin 4.19 2.71

Pettaquamscutt River Basin

NK3 3 151 187 0.17 0.11

NK7 3 153 188 .17 .11

NK8 3 153 187 .17 .11

Total for basin .51 .33

Total for all basins 9.79 6.32

1

Row assignments for wells SFH1 and SFH2 were modified from the original model on the basis of new data 

(James McGinn, Rhode Island Department of Environmental Management, oral commun., 2005).
during the original study, are the result of the large groundwater drainage area west of the pond and upgradient to the 

outflow location.

The average annual (steady-state) flow in Queens Fort 

Brook at its outflow location from the study area (site J, 

fig. 7) calculated by the model for the no-withdrawal condition is 1.7 ft3

/s (table 8), and ranges from zero from August 

through December to a maximum of 5.9 ft3/s in March 

(fig. 10). The zero-streamflow calculations from August 

through December are consistent with streamflow data 

provided in Kliever (1995, p. 65) for Queens Fort Brook at 

the USGS streamflow-gaging station 01117365 about 0.9 mi 

downstream from the model boundary. Those data indicate 

that of 13 streamflow measurements made during August 

through December from 1988 through 1991, only one (on 

November 20, 1989) was greater than zero. It should be noted 

that the numerical model only calculates the ground-water 

discharge component (referred to as the base-flow component) of streamflow in Queens Fort Brook, and does not 

simulate direct surface-water runoff. Nevertheless, the agreement between the model-calculated zero flow and the available streamflow data suggests that surface-water runoff to the 

brook, at least from August through December, is a relatively 

small component of total flow in the brook. 

Table 8. Specified ground-water withdrawals and model-calculated streamflows for steady-state simulations.

[Withdrawals and streamflows are in cubic feet per second. Stream site identifiers (in parentheses) are shown in figure 7; NK, town of North Kingstown; 

SFH, Lafayette State Fish Hatchery]

Wells or

stream name

Simulation conditions

Set 1: No

withdrawals

at any wells

Set 2:

Withdrawals

at all existing

production

wells only at 

2003 rates

Set 3:

Withdrawals

at all existing

wells at 2003

rates

Set 4:

Withdrawals

at all existing

wells;

SFH wells at

half their 2003 rates

Set 5:

Withdrawals

at all existing 

wells at 2003

rates and at well 

SFH4

Set 6:

Withdrawals

at all existing 

wells at 2003

rates

and at wells 

SFH4 and

NK11

Withdrawals

Production wells 0.0 7.6 7.6 7.6 7.6 9.1

State Fish Hatchery wells .0 .0 2.2 1.1 2.4 2.4

Streamflows

Hunt River outflow (F) 46.6 41.8 41.7 41.8 41.7 41.7

Cocumcossuc Brook outflow (G) 2.9 2.9 2.8 2.9 2.8 2.8

Queens Fort Brook outflow (J) 1.7 1.7 1.2 1.5 1.2 1.1

Annaquatucket River:

Below State Fish Hatchery (K) .0 .0 2.2 1.1 2.4 2.4

Below wetland area A (L) .0 .0 2.0 .9 2.1 2.1

Below wetland area B (M) .0 .0 1.8 .7 1.9 1.9

At Hatchery Road (N) .0 .0 1.3 .2 1.5 1.5

Belleville Pond outflow (O) 7.9 7.2 8.0 7.3 8.1 7.9

At outflow (Route 1) (P) 14.2 12.4 13.1 12.4 13.2 12.4

Pettaquamscutt River outflow (R) 9.9 9.4 9.4 9.4 9.4 9.2

Model-calculated steady-state inflows and outflows 

along the simulated ground-water drainage divides between 

the Annaquatucket River Basin and the adjoining Usquepaug-Queen and Chipuxet River Basins are 0.0 and 0.1 ft3

/s, 

respectively; for transient conditions, they range to a maximum inflow of 0.4 ft3

/s in October and maximum outflow of 

0.8 ft3/s in April. 

Simulation Set 2: Withdrawals at 2003 Rates at Existing 

Production Wells Only—In this second set of model runs, 

withdrawals were specified at 2003 rates from the 14 existing 

production wells and the industrial well; withdrawals were set 

to zero at the hatchery wells. These simulations were done to 

isolate the effects of the existing production-well withdrawals on the hydrologic system. Total simulated average annual 

withdrawals from the supply wells were 4.9 Mgal/d (7.6 ft3/s), 

and ranged from 3.6 Mgal/d in December to 6.7 Mgal/d 

in July.

For long-term average steady-state conditions, nearly all 

of the water withdrawn by the wells (7.1 ft3/s) is derived from 

depletion of streamflow throughout the HAP Basin, with the 

remainder derived from reduced ground-water evapotranspiration (0.1 ft3

/s) or from undetermined model errors (0.4 ft3/s). 

These model errors are generally small mass-balance errors 

caused by a number of factors, including rounding of the 

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  23
numbers calculated by the models and model-convergence (or 

closure) errors resulting from the iterative process used in the 

numerical calculations. Total steady-state streamflow 

depletions at each of the outflow locations of the streams are 

4.8 ft3/s for the Hunt River, 1.8 ft3/s for the Annaquatucket 

River, 0.5 ft3/s for the Pettaquamscutt River, and less than 

0.1 ft3/s for the Cocumcossuc River. Streamflow depletions are largest in the Hunt River because ground-water 

withdrawal rates are largest in the Hunt River Basin. In the 

Annaquatucket River Basin, model-calculated streamflow 

depletions at the outflow location of the Annaquatucket River 

(site P, fig. 7) range from a minimum of 1.5 ft3/s in January 

and February to a maximum of 2.6 ft3/s in July. Model-calculated end-of-month streamflows in the Annaquatucket River 

at site P are shown in figure 11. Simulated streamflows in 

Queens Fort Brook and the Annaquatucket River above the 

0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

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

MONTH

NO WITHDRAWALS AT ANY WELLS (SET 1) 

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES (SET 3) 

WITHDRAWALS AT ALL EXISTING WELLS; STATE FISH HATCHERY

 WELLS AT HALF THEIR 2003 RATES (SET 4) 

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES AND AT

 STATE FISH HATCHERY WELL 4 (SET 5)

EXPLANATION

STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 10. Model-calculated end-of-month streamflow in Queens Fort Brook at its outflow (site J).

Hatchery Road stream site were unaffected by withdrawals at 

the production and industrial wells.

Simulation Set 3: Withdrawals at 2003 Rates at Existing Production and State Fish Hatchery Wells—In this set of 

model runs, withdrawals were simulated at all of the existing production, industrial, and fish-hatchery wells, at their 

2003 pumping rates. Total long-term average (steady-state) 

withdrawal rates were 4.9 Mgal/d (7.6 ft3/s) for the production wells and 1.5 Mgal/d (2.2 ft3

/s) at the hatchery wells. A 

constant discharge rate of 2.2 ft3/s also was specified at the 

headwater of the Annaquatucket River just below the hatchery 

to represent discharge of water from the hatchery to the river. 

Steady-state and transient model results indicate that the 

Annaquatucket River loses water to the underlying aquifer in 

the reach that extends from the hatchery to the Hatchery Road 

stream site. This was shown by simulated average annual 

24  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
EXPLANATION

NO WITHDRAWALS AT ANY WELLS (SET 1)

WITHDRAWALS AT ALL EXISTING PRODUCTION WELLS ONLY AT

 2003 RATES (SET 2)

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES (SET 3)

WITHDRAWALS AT ALL EXISTING WELLS; STATE FISH HATCHERY

 WELLS AT HALF THEIR 2003 RATES (SET 4)

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES AND AT

 STATE FISH HATCHERY WELL 4 (SET 5)

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES AND AT

 STATE FISH HATCHERY WELL 4 AND TOWN OF NORTH

 KINGSTOWN WELL 11 (SET 6)

0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

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

MONTH

STREAMFLOW, IN CUBIC FEET PER SECOND 

Figure 11. Model-calculated end-of-month streamflow in the Annaquatucket River at its outflow (site P).

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  25
NK10

NK9 14A

KC1

9A

3A

IW

NK6

SFH3

SFH2

SFH1

NK1

NK2 NK4

NK5

NK3

NK8

NK7

NK11

SFH4 140

160

180

100

100

60

80

60

60

50

50

40

30

10

30

20

50

80

60

100

50

50

50

60

50

200

220

240

20

40

30

20

10

60

40

80

10

120

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-

 STATE WATER-TABLE CONTOUR—

 Shows altitude of water table in feet above

 NGVD29. Contour interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

EXPLANATION

100

NK2

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

Figure 12. Model-calculated steady-state water table for simulation set 3 (2003 withdrawal rates), Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island.

26  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
(table 8) and monthly streamflows that decrease by a constant 

rate of about 0.9 ft3/s in this reach. As described above for 

the results of simulation set 1, these model-calculated losing 

conditions are supported by streamflow measurements made 

during the original study, which showed a loss of streamflow 

in this reach during October 1996. The loss of streamflow in 

this reach may reflect an increase in the transmissivity of the 

aquifer east of the hatchery to Belleville Pond, which would 

result in a relative lowering of the altitude of the water table 

with respect to the altitude of the streambed and stream stage 

of the river. Although an increase in the transmissivity of the 

aquifer in this area cannot be supported directly with available 

data, an increase in the aquifer’s transmissivity is suggested 

by the relatively flat gradient of the water table east of the 

hatchery to Belleville Pond (fig. 12).

Below the Hatchery Road site, the Annaquatucket River 

becomes gaining, and, as in the previous simulations, there is 

a substantial increase in the river’s flow between the Hatchery 

Road site and the outflow location from the basin (table 8). 

Model results indicate that the flow at the river’s outflow location is actually higher (by about 0.7 ft3

/s) than for the previous 

simulation in which the hatchery wells were not pumping. 

The reason for this is that some of the water that is withdrawn 

by the hatchery wells is captured from Queens Fort Brook and 

then discharged to the Annaquatucket River at the hatchery; 

in the absence of withdrawals at the hatchery, this water 

would not have been available to the Annaquatucket River, 

and would have continued to flow to the Usquepaug-Queen 

River Basin. The amount of captured streamflow from Queens 

Fort Brook for steady-state conditions is 0.5 ft3/s, which is 

the difference between model-calculated streamflow in the 

brook for non-pumping conditions at the hatchery (1.7 ft3/s, 

simulation sets 1 and 2) and pumping conditions (1.2 ft3/s, 

this simulation). The remaining increase in the rate of outflow 

from the Annaquatucket River (about 0.2 ft3/s for steady-state 

conditions) is likely due to decreased rates of ground-water 

evapotranspiration in the Annaquatucket River Basin and to 

model error. The range in streamflow depletion calculated for 

Queens Fort Brook caused by pumping at the hatchery wells 

ranges from zero during August through December (when 

simulated baseflow in the river is zero) to 0.7 ft3/s in January; 

model-calculated monthly streamflows in the brook are shown 

in figure 10.

Note that if all of the water that is discharged from the 

hatchery to the Annaquatucket River had discharged from the 

basin at the Annaquatucket River outflow location, the river’s 

flow would have been 14.6 ft3/s for the long-term average 

conditions, which is determined by summing the flow of 

the river for the condition of no withdrawals at the hatchery 

(12.4 ft3/s; simulation set 2, table 8) and the total withdrawal 

rate from the hatchery wells (2.2 ft3/s). However, because the 

model-calculated flow rate for the river is only 13.1 ft3/s, it 

can be determined that about 1.5 ft3/s of the water discharged 

by the wells consists of water that would have discharged 

to the Annaquatucket River in the absence of pumping at 

the hatchery. Overall, the sources of water to the hatchery 

wells for the steady-state simulation consist of about 0.5 ft3/s 

reduced flow in Queens Fort Brook, 1.5 ft3/s reduced flow 

in the Annaquatucket River, 0.1 ft3/s reduced ground-water 

evapotranspiration, and about 0.1 ft3/s undetermined sources 

(which include model-rounding error). Total streamflow 

depletion in the Annaquatucket River at its outflow location caused by withdrawals at all wells (both production and 

hatchery wells) is 3.3 ft3/s.

A map of the model-calculated water table for the 2003 

annual average (steady-state) pumping conditions is shown 

in figure 12. Overall, the water-table contours are not substantially different from those shown for the 1996 withdrawal 

conditions (fig. 8). This results from the fact that although 

pumping rates are somewhat greater for the 2003 simulation 

conditions than those for the 1996 simulation conditions, 

the aquifer is highly transmissive in those areas of the Hunt 

and Annaquatucket River Basins where many of the production wells are located; therefore, changes in the altitude of 

the water table resulting from the increased withdrawals are 

generally small.

A map of water-table drawdowns (that is, ground-water 

level declines) for the 2003 average annual pumping rates is 

shown in figure 13. Drawdowns were calculated as the change 

in ground-water levels resulting from the condition of no 

ground-water pumping (simulation set 1) to that with the 2003 

pumping rates. Drawdowns calculated for each cell of the 

model represent a single drawdown value over the entire 200-

ft by 200-ft area of each cell; drawdowns calculated at cells 

that include pumping wells do not represent the maximum 

drawdown that occurs at the location of withdrawal. 

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  27
The drawdown map indicates that ground-water level declines 

are generally less than 5 ft, with the exception of the area near 

the hatchery, where drawdowns are as much as 19.3 ft at the 

cell containing well SFH3 (table 9; the locations of observation points shown in table 9 are given in fig. 14). Drawdowns 

are most likely greater in the hatchery area than in other parts 

of the aquifer because of the generally lower transmissivity of 

the aquifer near the hatchery wells than in other parts of the 

aquifer where withdrawals occur. For example, Rosenshein 

and others (1968, plate 2 and p. 11) report transmissivities of 

about 1,340 to 6,700 ft2/d near the hatchery wells, compared 

to transmissivities that range from about 13,400 to 50,800 

ft2/d along the Hunt and Annaquatucket River valleys where 

most of the production wells are located. The relatively large 

drawdowns at the fish-hatchery wells are consistent with 

water-level declines that have been measured at the hatchery 

wells during aquifer tests. For example, the drawdown at well 

SFH2 was 26.5 ft at the end of a 48-hour aquifer test during 

September 1994 in which well SFH2 was pumped at a rate of 

400 gal/min for the first 24 hours and at a rate of 450 gal/min 

during the second 24 hours (R.E. Chapman Company, written 

communication to Rhode Island Department of Environmental 

Management, November 1994). Also, the drawdown at well 

SFH3 was 32.7 ft at the end of a 166-hour aquifer test during 

June 1996 in which well SFH3 was pumped at a rate of 

720 gal/min (R.E. Chapman Company, written commun., 

July 1996).

Model-calculated end-of-month ground-water levels at 

three locations within and near the fish hatchery (wells SFH3 

and SFH4 and wetland site A) are shown in figure 15. The 

graphs indicate the declines in water levels that occur at each 

of the three locations from non-pumping conditions (simulation set 1) to pumping conditions (simulation set 3). The 

annual range of water-level fluctuations at the three points for 

non-pumping conditions is 1.9 ft at wells SFH3 and SFH4 and 

2.5 ft at wetland site A; for pumping conditions, the ranges 

are 2.2 and 2.1 ft at wells SFH3 and SFH4, respectively, and 

2.4 ft at wetland site A. Because simulated pumping rates at 

wells SFH1, SFH2, and SFH3 are constant throughout the 

year, water-level declines at each of the three locations are 

relatively constant throughout the year.

Hydrologic budgets were calculated for the aquifer 

within the three wetland areas near the hatchery by use of the 

Zonebudget computer program for MODFLOW (Harbaugh, 

1990). These budgets provide information on how simulated 

flow conditions in the aquifer underlying the wetland areas 

change in response to pumping at the hatchery wells. Modelsimulated sources of water to the aquifer in the wetland areas 

include recharge to the water table underlying the wetlands, 

streamflow seepage from the Annaquatucket River, and 

ground-water inflow; model-simulated outflow components 

include evapotranspiration from the water table, discharge 

to the Annaquatucket River, and ground-water outflow. The 

areas for which budgets were calculated include only the top 

Table 9. Model-calculated ground-water levels near Lafayette State Fish Hatchery for steady-state simulations.

[Water levels are for top layer of model. Water levels are in feet above NGVD29. Values in parentheses are drawdowns from simulation set 1, in feet. NK, 

town of North Kingstown; SFH, Lafayette State Fish Hatchery]

Location

Simulation conditions

Set 1: No

withdrawals

at any wells

Set 2:

Withdrawals

at all existing

production 

wells only at 

2003 rates

Set 3:

Withdrawals

at all existing

wells at 2003

rates

Set 4:

Withdrawals

at all existing

wells; SFH wells at

half their 2003 rates

Set 5:

Withdrawals

at all existing 

wells at 2003

rates and at 

well SFH4

Set 6:

Withdrawals

at all existing

wells at 2003 rates 

and at wells

SFH4 and NK11

Well SFH1 115.0 114.9 (0.1) 99.5 (15.5) 108.3 (6.7) 98.6 (16.4) 98.5 (16.5)

Well SFH2 114.1 114.1 (0.0) 95.9 (18.2) 106.2 (7.9) 95.0 (19.1) 94.9 (19.2)

Well SFH3 115.8 115.8 (0.0) 96.5 (19.3) 107.2 (8.6) 95.6 (20.2) 95.5 (20.3)

Well SFH4 122.8 122.7 (0.1) 109.6 (13.2) 117.2 (5.6) 108.1 (14.7) 108.0 (14.8)

Wetland site A 93.0 92.9 (0.1) 86.7 (6.3) 90.9 (2.1) 86.3 (6.7) 86.2 (6.8)

Below wetland A

(stream site L)

81.2 81.1 (0.1) 78.4 (2.8) 80.8 (0.4) 78.1 (3.1) 78.1 (3.1)

Wetland site B 78.1 78.0 (0.1) 76.9 (1.2) 78.3 (-0.2) 76.7 (1.4) 76.7 (1.4)

Below wetland B

(stream site M)

74.6 74.4 (0.2) 73.8 (0.8) 75.0 (-0.4) 73.6 (1.0) 73.6 (1.0)

Wetland site C 91.9 91.8 (0.1) 87.2 (4.7) 90.1 (1.8) 86.8 (5.1) 86.6 (5.3)

28  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
1

4

2

1 2

1

2

4

6

10

14

6

4

2

1

NK10

NK9 14A

KC1 9A

NK6

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK8 NK3

NK7

NK11

SFH4

3A

IW

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-STATE

 DRAWDOWN CONTOUR—Shows decrease

 in altitude of water table in feet. Contour

 interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

EXPLANATION

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

NK2

4

Figure 13. Model-calculated steady-state drawdowns for simulation set 3 (2003 withdrawal rates), Hunt-AnnaquatucketPettaquamscutt stream-aquifer system, Rhode Island.

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  29
EXPLANATION

MODEL GRID

SIMULATED STREAM

WETLAND A

WETLAND B

WETLAND C

STREAM SITE

WETLAND SITE

WELL

SFH1

M

A

M

L

K

B

A

C

SFH1

SFH3 SFH2

SFH4

0 1,000

0 300

2,000 FEET

600 METERS

70 80 90 100

140

150

160

170

60

60 70 80 90 100

140

150

160

170

R O W

C O L U M N

Figure 14. Model-grid locations of wetlands near Lafayette State Fish Hatchery, Rhode Island. Simulated stream is the 

Annaquatucket River.

30 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
WATER-LEVEL ALTITUDE, IN FEET ABOVE NGVD29 

90.0

100.0

110.0

120.0

100.0

110.0

120.0

130.0

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

80.0

90.0

100.0

110.0

MONTH

A

B

C

 EXPLANATION

NO WITHDRAWALS AT ANY WELLS (SET 1)

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES (SET 3)

WITHDRAWALS AT ALL EXISTING WELLS AT 2003 RATES AND AT

 STATE FISH HATCHERY WELL 4 (SET 5)

Figure 15. Model-calculated end-of-month ground-water levels at (A) State Fish Hatchery well 3, (B) State Fish Hatchery well 4, 

and (C) wetland site A.

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  31
32  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

Table 10. Model-calculated steady-state flows to and from the aquifer in wetland areas near Lafayette State Fish Hatchery.

[All values are in cubic feet per second. Total inflow may not equal total outflow for each simulation because of rounding errors; SFH, Lafayette 

State Fish Hatchery]

Flow Simulation Set 1: No withdrawals at any wells

Wetland A Wetland B Wetland C

Inflow

Recharge 0.3 0.3 0.4

Streamflow seepage .1 .0 .0

Ground-water inflow 1.9 1.6 1.4

Total inflow 2.3 1.9 1.8

Outflow

Evapotranspiration 0.0 0.0 0.1

Streamflow discharge .1 .0 .0

Ground-water outflow 2.1 1.9 1.7

Total outflow 2.2 1.9 1.8

Flow

Simulation Set 3: Withdrawals at all existing wells at 2003 rates

Wetland A Wetland B Wetland C

Inflow

Recharge 0.3 0.3 0.4

Streamflow seepage .3 .2 .0

Ground-water inflow 1.4 1.4 1.2

Total inflow 2.0 1.9 1.6

Outflow

Evapotranspiration 0.0 0.0 0.0

Streamflow discharge .0 .0 .0

Ground-water outflow 2.0 1.8 1.5

Total outflow 2.0 1.8 1.5

Flow

Simulation Set 4: Withdrawals at all existing wells; SFH wells at half their 2003 rates

Wetland A Wetland B Wetland C

Inflow

Recharge 0.3 0.3 0.4

Streamflow seepage .3 .2 .0

Ground-water inflow 1.6 1.4 1.3

Total inflow 2.2 1.9 1.7

Outflow

Evapotranspiration 0.0 0.0 0.0

Streamflow discharge .0 .0 .0

Ground-water outflow 2.1 1.9 1.6

Total outflow 2.1 1.9 1.6

Flow

Simulation Set 5: Withdrawals at all existing wells at 2003 rates and at well SFH4

Wetland A Wetland B Wetland C

Inflow

Recharge 0.3 0.3 0.4

Streamflow seepage .3 .2 .0

Ground-water inflow 1.4 1.4 1.1

Total inflow 2.0 1.9 1.5

Outflow

Evapotranspiration 0.0 0.0 0.0

Streamflow discharge .0 .0 .0

Ground-water outflow 2.0 1.8 1.5

Total outflow 2.0 1.8 1.5
layer of the model (layer 1), although ground-water inflows 

and outflows to and from these areas are from both layers 1 

and 2 of the model. It is important to note that these areas of 

the aquifer were not simulated any differently than other areas 

of the model; they are simply areas of the aquifer that are overlain by wetlands, from which ground-water discharge can take 

place by evapotranspiration from the water table and by discharge to the Annaquatucket River, and to which ground-water 

recharge and streamflow seepage from the Annaquatucket 

River can take place.

Steady-state model results indicate that for nonpumping conditions (simulation set 1), total steady-state 

inflows to these aquifer areas are 2.3 ft3/s for wetland A, 1.9 

ft3/s for wetland B, and 1.8 ft3/s for wetland C; in each case, 

the majority of water that flows to and from these areas is from 

ground-water inflows and outflows (table 10). With pumping 

at the three hatchery wells at 2003 rates (this simulation), 

the average rate of reduction in ground-water inflow to the 

wetlands is 0.5 ft3/s for wetland A, 0.2 ft3/s for wetland B, and 

0.2 ft3/s for wetland C (table 10). However, because of losing 

conditions along the Annaquatucket River, there is actually 

an increase in the amounts of streamflow that seep into 

wetlands A and B for the pumping and hatchery-discharge 

conditions simulated in this model run; as a consequence, 

there is an overall reduction in flow to wetlands A and B 

caused by pumping at the hatchery wells of only 0.3 and 

0.0 ft3/s, respectively.

Model-calculated rates of ground-water evapotranspiration from the aquifer in the wetland areas are very small for 

both pumping and non-pumping conditions (less than 0.1 ft3/s 

in all cases). These low rates of ground-water evapotranspiration result from the fact that model-calculated ground-water 

levels in the wetland areas are generally below the specified 

4-ft maximum depth below land surface at which groundwater evapotranspiration occurs. Unfortunately, there are few 

ground-water-level measurements in the wetland areas to

support or refute these simulation results. Data provided by 

R.E. Chapman Company to RIDEM (written commun., 

December 5, 1995) indicate that the depth to water at an 

observation well in the southern part of wetland A near wells 

SFH1 and SFH2 (test well 2), was about 4.6 ft below land 

surface in December 1995; ground-water-level data from a 

second well (test well 6), which also appears to be within or 

just west of wetland A, indicates a depth to water of 6.0 ft 

below land surface in December 1995. Both of these measured 

water levels are below the 4-ft maximum depth below landsurface criterion at which ground-water evapotranspiration is 

assumed to cease.

Hydrologic budgets calculated for the aquifer in the 

wetland areas using the transient model show pumping effects 

that are similar to those calculated by the steady-state model; 

that is, most changes that occur in the budgets consist of 

reductions in the amounts of ground-water inflow and outflow 

to and from the aquifer in the wetlands.

Contributing areas delineated for the wells are shown 

in figure 16. Contributing areas for some of the wells are 

grouped into single areas. This was done where wells are 

close together and their contributing areas were difficult to 

differentiate well-by-well because of the presence of weak 

internal sinks. Weak internal sinks are model cells that 

contain simulated streams, wells, or areas of evapotranspiration in which the amount of water removed by the internal 

sink is less than the total amount of water that flows into the 

cell. Weak sinks cause some ambiguities in the delineation of 

contributing areas because it cannot be determined whether a 

particle that enters a cell with a weak sink should be removed 

by the sink or should continue through the flow system (Pollock, 1994).

Contributing areas delineated for each well are specific 

to the simulated pumping rates at each well, as well as pumping rates and other stresses simulated at other locations in the 

model. Several of the contributing areas extend to the boundary of the active area of the model, which implies that some 

of the water captured by the wells is derived from the upland 

areas of till and bedrock. Contributing areas to wells 9A, 14A, 

KC1, NK9, and 3A are very similar to those delineated in the 

original study because the 2003 pumping rates at the wells 

did not differ substantially from the 1996 pumping conditions simulated in the original study. The contributing area to 

well NK6 is larger than that delineated in the original study 

because the 2003 pumping rate at the well was more than 

twice that during 1996. Contributing areas to wells SFH1, 

SFH2, and SFH3 are larger than those delineated for the 

1996 pumping rates. Moreover, contributing areas delineated 

for the hatchery wells overlie the wellheads, which they did 

not do in the original study. This is most likely because of 

the higher 2003 pumping rates at the wells and the changes 

that were made to the simulated aquifer conditions near the 

hatchery that resulted in less saturated thickness of the aquifer 

at the wells. Contributing areas to wells NK1, NK2, NK4, 

and NK5 are different from those determined in the original 

study because of changes made to the lateral extent of the 

active area of the model in the area south of the hatchery and 

west of Belleville Pond. Also, the total 2003 pumping rate at 

wells NK1, NK2, and NK4 was about twice that at the wells 

in 1996, whereas the rate at well NK5 was almost half that in 

1996. As seen on figure 16, the contributing area to well NK5 

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  33
State Highway 1

State Highway 1

State Highway

4

State Highway 102

State Highway 2

100

60

60

50

40

30

10

30

20

50

50

60

50

60

40

80

60

50

80

Fry

Brook

Cocumcossuc

Brook

Sandhill

Brook

River

River

Hunt River

Hunt River

Hunt

Frenchtown Brook

Annaquatucket

Belleville

Pond

Secret Lake

Potowomut

 Pond

NORTH

KINGSTOWN

NORTH KINGSTOWN

State Highway 4 

EAST

GREENWICH

WARWICK

3A

NK9

9A

14A

KC1

NK6

EXPLANATION

180

MODEL-CALCULATED STEADY-STATE CONTRIBUTING AREAS

BOUNDARY OF ACTIVE AREA OF MODEL—Dashed where active 

 area extends beyond area shown

MODEL-CALCULATED STEADY-STATE WATER-TABLE 

 CONTOUR—Shows altitude of water table, in feet above NGVD29.

 Contour interval is variable

TOWN BOUNDARY

WATER-SUPPLY WELL AND IDENTIFIER

NK6

0 .5 1 MILE

0 .5 1 KILOMETER

3A

Contributing area

A

34  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

Figure 16. Model-calculated steady-state contributing areas to water-supply wells in (A) the Hunt River Basin and (
140

160

180

100

80

60

50

50

60

80

100

50

200

220

240

20

40 30

20

10

10

120

40State Highway 1

State Fish Hatchery

State Highway 4

Belleville

Pond

Secret 

 Lake

Silver

Spring

Lake

Carr

Pond

Pettasquamscutt

Queens Fort Brook

River

Annaquatucket

River

NORTH KINGSTOWN

EXETER

State Highway 102

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK3

NK8 NK7

Part of NK1 and NK4

Contributing areas

NK5

Contributing area

Part of NK6 Contributing area

( see part A )

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

0 .5 1 MILE

0 .5 1 KILOMETER

B

State Highway 138

(B) the Annaquatucket and Pettaquamscutt River Basins, Rhode Island, for simulation set 3 (2003 withdrawal rates). 

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  35
36  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals

an increased ground-water-level decline of about 1.5 ft is calculated at the proposed supply well (SFH4) and less than 1 ft 

at the three existing wells. Ground-water levels calculated with 

the transient model show the effects of increased withdrawals at well SFH4, particularly at well SFH4 during December 

through March (fig. 15B). Model-calculated changes in flow 

rates to the three wetland areas for average annual conditions 

for pumping at well SFH4 also are not substantially different from those calculated for 2003 pumping rates (table 10). 

Decreases in total flows of less than 0.05 ft3/s from the 2003 

rates were calculated for each of the three wetlands; these 

reductions in flow are less than the accuracy of the values 

calculated by the model.

Simulation Set 6: Withdrawals at 2003 Rates at Existing Production and State Fish Hatchery Wells and Additional 

Withdrawals at the Proposed State Fish Hatchery Well and 

New Town of North Kingstown Well—All aspects of this last 

set of model simulations are the same as for the previous set, 

with the addition of pumping at new well NK11 in the 

Annaquatucket River Basin at a rate of 1.0 Mgal/d 

(1.5 ft3/s) for both steady-state and transient simulation conditions. For this withdrawal condition, steady-state flow in the 

Annaquatucket and Pettaquamscutt Rivers at their outflow 

locations are reduced by 0.8 ft3/s and 0.2 ft3/s, respectively, 

over the previous simulation (table 8). The steady-state 

sources of water to the new well calculated on the basis 

of model results consist of this total of 1.0 ft3/s reduced 

streamflow in the Annaquatucket and Pettaquamscutt Rivers, 

0.5 ft3/s induced ground-water flow into the Annaquatucket 

River Basin across the ground-water divide that separates the 

Annaquatucket and Chipuxet River Basins, and about 0.1 ft3/s 

reduced evapotranspiration from the water table. Results of 

the transient model indicate that the increased flow rate across 

the Annaquatucket/Chipuxet ground-water divide is constant 

at a rate of 0.5 ft3/s throughout the year; this constant flow rate 

likely results from the constant withdrawal rate of 1.0 Mgal/d 

simulated at the well throughout the year.

Steady-state water-table and drawdown contours in the 

aquifer calculated for these pumping conditions are shown 

in figures 19 and 20, respectively. Model-calculated drawdowns near NK11 are as much as 18 ft. These relatively large 

drawdowns near the well are consistent with those measured 

during the 2005 aquifer test at the site by Fay, Spofford, and 

Thorndike (2005). The pumping rate at well NK11 during that 

test was 750 gal/min (1.08 Mgal/d). Drawdown at the well at 

the end of the 72-hour test was 73 ft; drawdowns at the end 

of the test at observation wells located 10 ft, 70 ft, and 350 ft 

from the pumped well were about 31 ft, 5 ft, and 2 ft, respectively (Fay, Spofford, and Thorndike, 2005). The relatively 

large drawdowns at the site reflect the relatively low transmissivity of the aquifer at the site as calculated by Fay, Spofford, 

and Thorndike (2005) and described earlier in this report. 

Drawdowns calculated by the model may not be completely 

accurate west of the well toward the simulated Annaquatucket/

Chipuxet ground-water drainage divide. This divide is an area 

does not overlie the wellhead, which is consistent with the 

results of the original study.

Simulation Set 4: Withdrawals at Existing Production 

Wells at 2003 Rates and State Fish Hatchery Wells at Half 

Their 2003 Rates—In this set of model runs, simulated withdrawals at the fish-hatchery wells were reduced by half their 

2003 rates (to 1.1 ft3/s), while withdrawals at all production 

wells were maintained at their 2003 rates. This simulation set 

was done to evaluate the effects of lower pumping rates at the 

hatchery on the hydrologic system. The simulated reductions 

in withdrawals resulted in an increase in streamflow in Queens 

Fort Brook at its outflow location from the basin to 1.5 ft3/s 

for steady-state conditions (table 8); streamflows calculated 

for transient conditions also are higher (fig. 10). Flow rates 

along the Annaquatucket River, however, actually decrease 

from the previous set of simulations because the amount 

of water that is discharged to the river below the hatchery 

is reduced from 2.2 to 1.1 ft3/s. The sources of water to the 

hatchery wells for the steady-state simulation consist of about 

0.2 ft3/s reduced flow in Queens Fort Brook and about 1.1 ft3/s 

reduced flow in the Annaquatucket River; these values contain 

some model error, including rounding error.

Drawdowns in the altitude of the water table near the 

hatchery are substantially less for these withdrawal conditions 

than for the 2003 withdrawal rates (table 9 and fig. 17). The 

maximum ground-water-level decline, which is at well SFH3, 

is 8.6 ft, or about 11 ft less than that calculated for the 2003 

withdrawal rates. The total reductions in flow to the aquifer in 

the wetland areas resulting from these withdrawal conditions 

at the hatchery wells (compared to the condition of no withdrawals at the wells) are about 0.1 ft3

/s to each of wetlands A 

and C and less than 0.1 ft3/s to wetland B (table 10).

Simulation Set 5: Withdrawals at 2003 Rates at Existing Production and State Fish Hatchery Wells and Additional 

Withdrawals at the Proposed State Fish Hatchery Well—In 

this set of model runs, pumping at proposed well SFH4 was 

simulated in addition to withdrawals at 2003 rates at all 

existing wells in the basin. Monthly pumping rates specified 

at well SFH4 are given in table 1, and range from a minimum 

of zero from April through September to 260 gal/min 

(0.4 Mgal/d) in March. Because the well is anticipated to be 

used during only 6 months of the year, the average annual 

pumping rate of the well is only 0.13 ft3/s (0.08 Mgal/d), 

which increases the total average annual withdrawal rate at 

the hatchery (and associated discharge to the headwater of the 

Annaquatucket River) from approximately 2.24 ft3/s in 2003 

to 2.37 ft3/s in the future, or by about 5 percent. The increased 

withdrawals at the hatchery reduce the average annual flow in 

Queens Fort Brook at its outflow from the basin by less than 

0.05 ft3/s from its simulated 2003 rate (set 3) and in the Annaquatucket River at its outflow from the basin by about 0.1 ft3

/s 

(which includes an undetermined amount of model error). 

Average annual ground-water-level declines in the 

aquifer resulting from the increased withdrawal in the hatchery 

area (table 9; fig. 18) are not substantially greater than those 

for the 2003 average annual pumping conditions. For example, 
1

4

2

1 2

1

2

4

8

6

1

2

1

NK10

NK9 14A

KC1 9A

NK6

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK8 NK3

NK7

NK11

SFH4

3A

IW

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-STATE

 DRAWDOWN CONTOUR—Shows decrease

 in altitude of water table in feet. Contour

 interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

EXPLANATION

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

NK2

4

Figure 17. Model-calculated steady-state drawdowns for simulation set 4 (hatchery wells pumping at half their 2003 rates), 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island.

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  37
1

4

2

1 2

1

2

4

10

6

1

2

14

18

6

4

NK10

NK9 14A

KC1 9A

NK6

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK8 NK3

NK7

NK11

SFH4

3A

IW

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-STATE

 DRAWDOWN CONTOUR—Shows decrease

 in altitude of water table in feet. Contour

 interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

EXPLANATION

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

NK2

4

Figure 18. Model-calculated steady-state drawdowns for simulation set 5 (with State Fish Hatchery well 4 pumping), 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island.

38  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
NK10

NK9 14A

KC1

9A

3A

IW

NK6

SFH3

SFH2

SFH1

NK1

NK4 NK2

NK5

NK3

NK8

NK7

NK11

SFH4 140

160

180

100

100

60

80

60

60

50

50

40

30

10

30

20

50

80

60

100

50

50

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

50

60

50

200

220

240

20

40 30

20

10

60

40

80

10

120

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-

 STATE WATER-TABLE CONTOUR—

 Shows altitude of water table in feet above

 NGVD29. Contour interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

NK2

EXPLANATION

100

Figure 19. Model-calculated steady-state water table for simulation set 6 (with State Fish Hatchery well 4 and the town of North 

Kingstown well 11 pumping), Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island.

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  39
1

4

2

1 2

1

2

4

10

6

1

2

14

18

6

4

14

10

18

6

4

2

1 NK10

NK9 14A

KC1 9A

NK6

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK8 NK3

NK7

NK11

SFH4

3A

IW

0 .5 1 MILE

0 .5 1 KILOMETER

41°37'30"

71°32'30"

71°27'30"

41°32'30"

STRATIFIED DEPOSITS

TILL AND BEDROCK

BOUNDARY OF THE

 STREAM-AQUIFER

 SYSTEM

BOUNDARY OF ACTIVE 

 AREA OF MODEL

GROUND-WATER

 DRAINAGE BOUNDARY—

 Where it differs from the surface-

 water drainage basin boundary

GROUND-WATER AND 

 SURFACE-WATER DRAINAGE

 BOUNDARY

MODEL-CALCULATED STEADY-STATE

 DRAWDOWN CONTOUR—Shows decrease

 in altitude of water table in feet. Contour

 interval is variable

WATER-SUPPLY WELL AND IDENTIFIER

EXPLANATION

NK2

4

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

Figure 20. Model-calculated steady-state drawdowns for simulation set 6 (with State Fish Hatchery well 4 and the town of North 

Kingstown well 11 pumping), Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island.

40 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Figure 21. Model-calculated steady-state contributing areas to water-supply wells in the Annaquatucket River Basin for simulation set 

6 (with State Fish Hatchery well 4 and the town of North Kingstown well 11 pumping), Hunt-Annaquatucket-Pettaquamscutt streamaquifer system, Rhode Island. 140160

180

100

80

60

50

50

60

80

100

50

200

240

20

40 30

20

10

40

10

120

220

Belleville

Pond

Secret 

 Lake

Silver

Spring

Lake

Carr

Pond

Pettaquamscutt

Queens Fort Brook

River

River

Annaquatucket

State Highway 1

State Fish Hatchery

State Highway 4

NORTH KINGSTOWN

EXETER

State Highway 102

State Highway 138 

SFH3

SFH2

SFH1

NK1

NK2

NK4

NK5

NK3

NK8 NK7

SFH4

NK11

0 .5 1 MILE

0 .5 1 KILOMETER

EXPLANATION

180

MODEL-CALCULATED STEADY-STATE CONTRIBUTING AREAS

BOUNDARY OF ACTIVE AREA OF MODEL—Dashed where active area

 extends beyond area shown

MODEL-CALCULATED STEADY-STATE WATER-TABLE 

 CONTOUR—Shows altitude of water table, in feet above NGVD29.

 Contour interval is variable

TOWN BOUNDARY

WATER-SUPPLY WELL AND IDENTIFIER

NK4

NK11

Contributing area

NK5

Contributing area

Part of NK1

Contributing area

Base from U.S. Geological Survey

East Greenwich, Slocum, Wickford, Crompton, 1:24,000, 1988–94

Rhode Island state plane projection

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  41
in which future studies are needed to better define the hydrogeologic conditions of the aquifer.

Contributing areas delineated for wells in the Annaquatucket River Basin for the steady-state simulation are 

shown in figure 21. Contributing areas delineated for wells 

in the Hunt and Pettaquamscutt River Basins are identical to 

those delineated for simulation set 3 (2003 pumping rates; see 

fig. 16) and therefore are not shown on figure 21. Contributing 

areas to wells SFH1, SFH2, and SFH3 are largely unchanged 

from those delineated for the condition of no withdrawal at 

well SFH4 (that is, simulation set 3; fig. 16B) because pumping at well SFH4 does not increase the total pumping stress in 

the area of the hatchery by very much. The contributing area 

delineated for well NK11 extends to the ground-water divide 

between the Chipuxet and Annaquatucket River Basins and, 

as mentioned previously, some of the water captured by well 

NK11 is derived from induced ground-water flow across the 

boundary from the Chipuxet River Basin. Contributing areas 

to wells NK1, NK2, NK4, and NK5 are different for this simulation than those delineated in simulation set 3 because of the 

withdrawal simulated at well NK11 in this simulation.

Simulations for a Drought

Two additional simulations were made with the transient 

model to evaluate the effects of a drought on streamflow and 

ground-water levels in the Annaquatucket River Basin. Staff at 

the RIDEM used available precipitation data to determine that 

hydrologic conditions in 1957 were representative of a 1-in-25 

year drought (Alisa Richardson, Rhode Island Department of 

Environmental Management, written commun., May 2005). 

Total precipitation during that year was 32.5 in. Total recharge 

to the aquifer during that year is estimated to have been 

15.9 in., as determined from streamflow records of the Hunt 

River using the RORA analysis method (Rutledge, 1993). This 

total recharge rate is about 10 in. lower than the long-term 

average recharge determined from the streamflow records for 

the 1941–2003 period. Month-by-month recharge rates during 

1957 are shown with the long-term average monthly recharge 

rates in figure 22. Estimated monthly recharge rates during 

1957 were lower than the long-term average monthly recharge 

rates for every month except April, when recharge was about 

0.5 in. greater than for long-term average conditions.

Three changes were made to the transient model to simulate the drought. First, monthly recharge rates during the last 

16 months of the 60-month simulation period were modified 

to reflect the estimated recharge conditions from September 

1956 through December 1957. The period September through 

December 1956 was added to provide the simulated system 

some time to adjust to the modified drought conditions. Simulated monthly recharge rates for these 16 months were calculated by multiplying each of the calibrated-model monthly 

recharge rates by the ratio of the estimated 1956–1957 

recharge rate to the long-term (1941–2003) average recharge 

rate. These ratios ranged from a minimum of 0.17 in September 1957 to a maximum of 1.16 in April 1957. The remaining 

two changes to the model were to modify the monthly rates 

of specified ground-water inflow and streamflow from the till 

and bedrock uplands for the last 16 months of the transient 

simulation (again, September 1956 through December 1957). 

These flows also were calculated on the basis of the ratio of 

the estimated 1956–1957 recharge rate to the long-term average recharge rate for each month. Other boundary conditions 

simulated by the model, including evapotranspiration conditions, were not modified.

Two withdrawal conditions were simulated for the 

drought scenario: the 2003 withdrawal rates at existing wells 

(simulation set 3 above) and the 2003 withdrawal rates at 

existing wells plus withdrawals at proposed well SFH4 and 

new well NK11 (simulation set 6 above). As can be seen in 

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

MONTHLY RECHARGE, 

IN INCHES 

MONTH

LONG-TERM AVERAGE

1957

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

Figure 22. Long-term (1941–2003) average and 1957 monthly recharge rates, Hunt-Annaquatucket-Pettaquamscutt streamaquifer system, Rhode Island. 

42  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Figure 23. Model-calculated end-of-month streamflows at the outflow sites of (A) Queens Fort Brook and 

(B) Annaquatucket River, Rhode Island, for simulated long-term (1941–2003) average and drought conditions. STREAMFLOW, IN CUBIC FEET PER SECOND

MONTH

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

0

1

2

3

4

5

6

6

8

10

12

14

16

18

EXPLANATION

LONG-TERM AVERAGE CONDITIONS

 Withdrawals at all existing wells at 2003 rates (set 3)

 Withdrawals at all existing wells at 2003 rates at State Fish Hatchery 

 well 4 and the town of North Kingstown well 11 (set 6)

DROUGHT CONDITIONS

 Withdrawals at all existing wells at 2003 rates (set 3)

 Withdrawals at all existing wells at 2003 rates at State Fish Hatchery 

 well 4 and the town of North Kingstown well 11 (set 6)

A

B

Simulation of Hydrologic-System Responses in the Stream-Aquifer System  43
LONG-TERM AVERAGE CONDITIONS

 Withdrawals at all existing wells at 2003 rates (set 3)

 Withdrawals at all existing wells at 2003 rates and at State Fish Hatchery

 well 4 and town of North Kingstown well 11 (set 6)

DROUGHT CONDITIONS

 Withdrawals at all existing wells at 2003 rates (set 3)

 Withdrawals at all existing wells at 2003 rates and at State Fish Hatchery 

 well 4 and the town of North Kingstown well 11 (set 6)

WATER-LEVEL ALTITUDE, IN FEET ABOVE NGVD29 

EXPLANATION

MONTH

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

A

90

100

110

120

B

70

80

90

100

Figure 24. Model-calculated end-of-month ground-water levels at (A) State Fish Hatchery well 4, and (B) wetland site A, Rhode 

Island, for simulated long-term (1941–2003) average and drought conditions.

44  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
figure 23, streamflows at the outflow locations of Queens 

Fort Brook and the Annaquatucket River are reduced by the 

drought conditions. The months during which there is no 

ground-water discharge (base flow) to Queens Fort Brook for 

the drought condition are January and July through December 1957, as compared to only the months of August through 

December for the long-term average simulation conditions. 

Streamflows in the Annaquatucket River are reduced by 

1.2 to 2.9 ft3/s for the 2003 withdrawal rates and by 1.0 to 

3.1 ft3/s for the 2003 withdrawal rates with SFH4 and NK11 

also pumping.

Model-calculated ground-water levels at well SFH4 and 

at wetland site A are shown in figure 24. For the 2003 withdrawal rates, water-level declines at well SFH4 for the simulated drought (fig. 24A) range from 1.0 to 3.7 ft more than 

the declines during the non-drought condition. Similar results 

were determined at wetland site A (fig. 24B), where waterlevel declines ranged from 0.9 to 3.0 ft more than the declines 

during the non-drought condition. Water-level declines for the 

drought condition with 2003 withdrawal rates and pumping 

at wells SFH4 and NK11 are of similar magnitude at the two 

locations as those for the 2003 withdrawals.

Limitations of Numerical Models

The numerical models of the HAP stream-aquifer system are basin-scale models that were developed to simulate 

ground-water flow throughout the entire HAP system. Therefore, results of the models are most appropriate for evaluating 

hydrologic conditions such as ground-water-level declines, 

ground-water discharge rates to streams, and ground-water 

flow beneath wetland areas that result from the net effects of 

withdrawals that occur throughout the entire basin. This basinscale approach was necessary to determine the relative effects 

of withdrawals from the different types of wells (hatchery and 

production wells) pumping throughout the basin on the basinscale hydrologic system.

Model results indicate the need for improved understanding of the hydrologic conditions at the State Fish Hatchery. 

Conditions should be tested by the collection of water-level, 

lithologic, and vegetation data in the wetlands. Model results 

in the area of the hatchery also would be improved by the use 

of a finer model-grid discretization to better simulate wetland-aquifer interactions and the impacts of withdrawals on 

wetlands and streamflow. Use of a finer discretization could be 

done as part of a broader data-collection and analysis study of 

wetland and hydrologic conditions at and near the hatchery. As 

a consequence of the spatial-discretization limitations of the 

numerical models developed for the HAP stream-aquifer system, interpretations drawn from the study related to changes 

in wetland conditions simulated by the models should not be 

applied to other wetlands of the State.

Summary and Conclusions

In response to concern by the Rhode Island Department 

of Environmental Management (RIDEM) about the effects 

of existing and proposed withdrawals at the Lafayette State 

Fish Hatchery, a cooperative study by the U.S. Geological 

Survey and RIDEM was done to better understand hydrologic-system responses to ground-water withdrawals in the 

Hunt-Annaquatucket-Pettaquamscutt (HAP) stream-aquifer 

system of Rhode Island. System responses were determined by 

use of steady-state and transient numerical ground-water-flow 

models. Responses of the hydrologic system are described 

primarily by changes in simulated streamflows and groundwater levels throughout the basin and by changes to flow 

conditions in the aquifer in three wetland areas immediately 

east of the Lafayette State Fish Hatchery, which lies within the 

Annaquatucket River Basin in the town of North Kingstown. 

Ground water is withdrawn from the HAP aquifer at 14 largecapacity production wells that are operated by the town of 

North Kingstown, the Rhode Island Economic Development 

Corporation, and the Kent County Water Authority. Ground 

water also is withdrawn at an industrial well in the basin and 

at three wells operated by the RIDEM at the fish hatchery. A 

fourth well has been proposed for the hatchery and an additional production well is under development by the town of 

North Kingstown.

The numerical models used in the study were initially 

developed in the late 1990s as part of a larger study of the 

stream-aquifer system. The numerical models of the HAP 

stream-aquifer system are basin-scale models that were 

developed to simulate ground-water flow throughout the entire 

HAP system. The models were modified to incorporate new 

data made available since the original study and to meet the 

objectives of this study. Changes made to the models did not 

result in substantial changes to simulated ground-water levels, 

hydrologic budgets, or streamflows compared to those calculated by the original steady-state and transient models.

The primary streams of interest in the study area are the 

Hunt, Annaquatucket, and Pettaquamscutt Rivers and Queens 

Fort Brook. Total model-calculated streamflow depletions 

in these rivers and brook resulting from withdrawals at the 

production, industrial, and fish-hatchery wells pumping at 

average annual 2003 rates are about 4.8 cubic feet per second 

(ft3/s) for the Hunt River, 3.3 ft3/s for the Annaquatucket River, 

0.5 ft3/s for the Pettaquamscutt River, and 0.5 ft3/s for Queens 

Fort Brook. The actual amount of streamflow reduction in 

the Annaquatucket River caused by pumping is less, 1.1 ft3/s, 

because ground water that is pumped at the fish-hatchery wells 

(2.2 ft3/s) is returned to the Annaquatucket River after use 

at the hatchery. Model results also indicate that the Annaquatucket River loses water to the underlying aquifer in the 

reach from just below the fish hatchery to just above Belleville 

Pond; these results are supported by field data.

Summary and Conclusions  45
One of the primary goals of the study was to evaluate the 

response of the hydrologic system to simulated withdrawals 

at the proposed well at the fish hatchery. Withdrawal rates at 

the proposed well would range from zero during April through 

September of each year to a maximum of 260 gallons per 

minute [about 0.4 million gallons per day (Mgal/d)] in March 

of each year. The average annual withdrawal rate at the fish 

hatchery resulting from the addition of the proposed well 

would increase by 0.13 ft3/s, or about 5 percent of the 2003 

withdrawal rate. The increased pumping rate at the hatchery 

would further reduce the average annual flow in Queens Fort 

Brook by less than 0.05 ft3/s and in the Annaquatucket River 

by about 0.1 ft3/s (which includes some model error).

A new production well in the Annaquatucket River 

Basin is under development by the town of North Kingstown. 

A simulated pumping rate of 1.0 Mgal/d (1.6 ft3/s) at this new 

well resulted in additional streamflow depletions over those 

calculated for the 2003 withdrawal conditions of 0.8 and 

0.2 ft3/s in the Annaquatucket and Pettaquamscutt Rivers, 

respectively. The source of water for about 30 percent of the 

well’s pumping rate, or about 0.5 ft3/s, is derived from groundwater inflow from the Chipuxet River Basin across a natural 

ground-water drainage divide that separates the Annaquatucket 

and Chipuxet River Basins; the remaining 0.1 ft3/s of simulated pumping consists of reduced evapotranspiration from the 

water table.

Model-calculated changes in water levels in the aquifer 

for the various withdrawal conditions simulated in this study 

indicate that ground-water-level declines caused by pumping 

are generally less than 5 feet (ft). However, ground-waterlevel declines of as much as 20 ft were calculated near the fish 

hatchery and of as much as 18 ft were calculated near the new 

production well in the Annaquatucket River Basin. The larger 

water-level declines in these two areas are attributed to relatively low values of the transmissivity of the aquifer in these 

two areas. Average annual ground-water-level declines in the 

aquifer resulting from the increased withdrawal in the hatchery 

area are not substantially greater than those for the 2003 average annual pumping conditions.

Model-calculated hydrologic budgets for the aquifer in 

the three wetland areas near the fish hatchery indicate that 

the total inflow rate to each area is reduced by a maximum 

of 0.3 ft3/s for the 2003 average annual pumping conditions; 

these reductions are a maximum of 13 percent of the total 

inflow rate to each area for non-pumping conditions. Modelcalculated rates of ground-water evapotranspiration from the 

wetlands are very small (less than 0.1 ft3/s in all cases) for 

both pumping and non-pumping conditions. These low rates 

of ground-water evapotranspiration result from the fact that 

model-calculated ground-water levels in the wetland areas are 

generally below the model-simulated 4-ft maximum depth 

below land surface at which ground-water evapotranspiration is assumed to occur. Ground-water-level data generally 

are lacking to support or refute these simulated ground-water 

levels in the wetlands. The rates of reductions in ground-water 

flows to the wetland areas are not substantially different for 

the proposed additional withdrawals at the hatchery.

The transient model also was used to evaluate the effects 

of a simulated drought condition on streamflow and groundwater levels. The simulated drought condition was based on 

hydrologic conditions during 1957, which was determined 

by the RIDEM to represent a 1-in-25 year drought. For the 

withdrawal conditions evaluated, the simulated drought caused 

model-calculated monthly streamflows in the Annaquatucket 

River to be reduced by 1.0 ft3/s to 3.1 ft3/s more than those 

streamflows calculated for long-term average simulation 

conditions (that is, non-drought conditions). Model-calculated 

ground-water levels at the proposed well site at the 

fish hatchery decline by 1.0 ft to 3.7 ft for the drought 

condition compared to those levels calculated for nondrought conditions.

Results of the study must be viewed within the limitations 

of the quality of the data that are available for the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system and representation of the system with simulation models. Uncertainties in 

the model simulations result from a variety of factors, including uncertainties in the exact values of the hydraulic properties of the aquifers, rates of recharge to the aquifer, and the 

approaches used to simulate the many features of the hydrologic system (streams, evapotranspiration, flow conditions at 

ground-water drainage divides, and so forth). 

The precision of the numerical models used in this study 

to determine hydrologic-system responses to ground-water 

withdrawals could benefit from refinement of localized information on the wetlands and the geology of the area near the 

fish hatchery. Model results in the area of the hatchery also 

would be improved by the use of a finer model-grid discretization to better simulate wetland-aquifer interactions and the 

impacts of withdrawals on wetlands and streamflow. Use of a 

finer discretization could be done as part of a broader datacollection and analysis study of wetland and hydrologic 

conditions at or near the hatchery. As a consequence of the 

spatial-discretization limitations of the numerical models 

developed for the HAP stream-aquifer system, the ability of 

the numerical models to predict hydrologic responses in the 

vicinity of the hatchery wells is limited. Furthermore, groundwater-flow conditions near the ground-water drainage divide 

that separates the Annaquatucket and Chipuxet River Basins 

are largely unknown. The understanding of hydrologic 

conditions near this divide would be improved by collection 

of hydrogeologic data in that area. 

46  Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
References Cited

Barlow, P.M., and Dickerman, D.C., 2001, Numericalsimulation and conjunctive-management models of the 

Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, 

Rhode Island: U.S. Geological Survey Professional 

Paper 1636, 88 p.

Dickerman, D.C., and Barlow, P.M., 1997, Water-table 

conditions and stream-aquifer interaction in the HuntAnnaquatucket-Pettaquamscutt aquifer, central Rhode 

Island, October 7–9, 1996: U.S. Geological Survey 

Water-Resources Investigations Report 97–4167, 1 sheet.

Fay, Spofford, and Thorndike, 2005, Well 11 pump test results, 

new public water supply, North Kingstown, R.I., prepared 

for Town of North Kingstown Water Department (January 

2005): Burlington, Massachusetts, variously paginated.

Hahn, G.W., 1959, Ground-water map of the Slocum 

quadrangle, Rhode Island: Rhode Island Water Resources 

Coordinating Board GWM-2, 1 sheet, scale 1:24,000.

Harbaugh, A.W., 1990, A computer program for calculating 

subregional water budgets using results from the U.S. 

Geological Survey modular three-dimensional finite-difference ground-water flow model: U.S. Geological Survey 

Open-File Report 90–392, 24 p.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, 

M.G., 2000, MODFLOW-2000, the U.S. Geological 

Survey modular ground-water model—User guide to 

modularization concepts and the ground-water flow process: 

U.S. Geological Survey Open-File Report 00–92, 121 p.

Harbaugh, A.W., and McDonald, M.G., 1996, User’s 

documentation for MODFLOW-96, an update to the U.S. 

Geological Survey modular finite-difference groundwater flow model: U.S. Geological Survey Open-File 

Report 96–485, 56 p.

Johnson, K.E., and Marks, L.Y., 1959, Ground-water map of 

the Wickford quadrangle, Rhode Island: Rhode Island Water 

Resources Coordinating Board GWM-1, 1 sheet, 

scale 1:24,000.

Kliever, J.D., 1995, Hydrologic data for the Usquepaug-Queen 

River Basin, Rhode Island: U.S. Geological Survey 

Open-File Report 95–305, 68 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 6, chap. A1, 586 p.

Pollock, D.W., 1994, User’s guide for MODPATH/MODPATH-PLOT, version 3—A particle tracking post-processing package for MODFLOW, the U.S. Geological Survey 

finite-difference ground-water flow model: U.S. Geological 

Survey Open-File Report 94–464, 249 p.

Prudic, D.E., 1989, Documentation of a computer program to 

simulate stream-aquifer relations using a modular, finite-difference, ground-water flow model: U.S. Geological Survey 

Open-File Report 88–729, 113 p.

Rosenshein, J.S., Gonthier, J.B., and Allen, W.B., 1968, 

Hydrologic characteristics and sustained yield of 

principal ground-water units, Potowomut-Wickford area, 

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

Paper 1775, 38 p.

Rutledge, A.T., 1993, Computer programs for describing the 

recession of ground-water discharge and for estimating 

mean ground-water recharge and discharge from streamflow 

records: U.S. Geological Survey Water-Resources 

Investigations Report 93–4121, 45 p.

References Cited  47
48    Report Title
APPENDIX 1:

Withdrawals from Selected Production Wells, 

1999–2004
Table 1.1. Summary of monthly withdrawals from selected production wells in the Hunt–Annaquatucket–Pettaquamscutt streamaquifer system, Rhode Island, 1999–2004.—Continued

[Withdrawals are in million gallons. RIEDC, Rhode Island Economic Development Corporation; KCWA, Kent County Water Authority; NK, North Kingstown. Well locations shown in figure 1]

Year January February March April May June July August September October November December

Hunt River Basin

RIEDC well 9A

1999 9.4 6.9 8.5 7.9 5.8 5.1 7.2 9.2 6.4 8.8 9.6 9.7

2000 8.9 4.9 5.9 4.0 5.5 2.6 .0 .0 .0 .0 .0 .0

2001 .8 5.8 7.1 7.1 9.6 4.9 10.5 11.6 9.3 11.3 .0 6.4

2002 8.9 7.4 8.5 10.5 10.0 9.6 9.5 5.8 7.0 5.9 4.8 5.5

2003 6.2 3.4 6.8 5.7 7.5 5.2 4.8 4.0 12.5 8.4 6.1 6.8

2004 7.2 6.0 6.3 6.8 7.1 7.2 7.2 9.3 7.1 4.8 4.8 6.4

RIEDC well 14A

1999 9.1 4.3 2.5 5.4 5.7 7.3 9.9 9.9 6.7 2.9 9.6 4.8

2000 .0 .0 9.1 9.4 4.0 9.3 22.6 11.9 13.9 16.0 11.4 13.3

2001 14.7 5.6 5.1 4.7 6.1 10.3 3.9 7.4 9.5 .2 10.3 6.4

2002 4.5 2.5 3.7 3.0 3.5 4.4 10.7 10.9 8.6 7.4 6.2 5.5

2003 6.1 5.3 8.3 8.2 7.7 8.6 12.0 10.8 1.9 5.3 3.8 8.1

2004 8.2 5.4 7.1 7.5 6.8 7.9 7.6 9.7 7.4 7.5 6.8 6.7

RIEDC well 3A

1999 3.6 7.3 5.2 7.5 5.1 6.9 11.0 9.4 8.5 7.2 .0 5.9

2000 10.3 15.0 6.0 6.3 4.4 6.7 7.4 12.0 7.3 4.3 7.0 8.1

2001 6.2 5.4 6.0 5.4 7.3 8.8 9.7 8.0 6.3 8.2 8.6 5.4

2002 6.1 6.4 5.9 6.4 5.2 7.1 9.3 10.1 5.9 5.5 4.3 3.9

2003 5.1 4.9 7.0 9.5 8.5 7.7 9.2 9.9 5.9 3.2 8.3 1.8

2004 6.2 5.5 4.9 4.1 6.6 7.8 8.9 4.7 7.9 5.6 5.6 5.4

KC well 1

1999 34.0 29.3 31.0 7.0 26.8 34.2 42.2 35.8 13.4 3.5 3.5 2.3

2000 27.1 27.9 28.6 31.0 17.2 14.4 10.7 3.0 1.7 .4 .8 .4

2001 .8 .7 14.8 24.1 24.0 19.3 29.3 21.3 19.1 18.6 11.3 13.8

2002 18.1 13.2 23.8 29.4 29.6 22.5 32.2 34.3 32.7 33.7 26.6 23.1

2003 24.0 21.8 25.7 25.1 27.8 25.7 31.4 32.5 21.1 .0 .0 .0

2004 14.8 10.1 11.1 11.3 24.2 31.1 24.8 22.2 18.2 24.5 22.2 23.6

NK well 9

1999 29.4 17.5 20.0 19.8 33.0 52.6 53.7 45.8 37.3 33.2 17.8 31.1

2000 32.2 29.9 30.3 29.0 41.3 41.4 46.4 33.0 36.4 33.6 26.2 23.9

2001 18.6 24.6 20.4 12.6 34.9 42.2 47.9 37.6 37.6 0 0 0

2002 0 0 3.4 8.1 12.8 22.4 45.4 24.9 12.4 18.0 31.2 35.4

2003 29.5 28.0 17.6 31.1 37.6 35.3 40.7 36.5 37.3 35.2 32.0 34.2

2004 30.9 28.2 32.8 28.3 29.4 31.6 6.4 37.1 11.1 11.3 17.3 18.9

NK well 10

1999 0 0 0 0 0 0 0 0 0 0 0 0

2000 0 0 0 0 0 0 0 0 0 0 0 0

2001 0 0 0 0 0 0 0 0 0 0 0 0

2002 0 0 0 0 0 0 0 0 0 0 0 0

2003 0 0 0 0 0 0 0 0 0 0 0 0

2004 0 1.9 1.7 7.4 7.5 9.7 50.7 4.3 33.6 25.3 23.9 20.3

NK well 6

1999 6.6 9.3 11.3 11.6 15.4 23.9 23.2 16.0 12.1 6.5 11.2 5.6

2000 3.6 3.1 6.1 8.0 5.8 15.6 21.4 13.4 10.4 10.0 9.0 9.8

2001 11.9 6.6 11.7 14.9 21.6 17.5 21.8 21.5 19.0 20.5 18.5 18.7

2002 22.1 21.4 23.6 24.2 28.6 24.7 31.2 28.6 25.4 23.8 17.7 15.1

2003 16.8 15.7 20.9 18.1 19.4 19.9 24.0 21.7 20.6 22.0 17.9 16.9

2004 15.5 17.3 7.7 12.5 23.3 25.2 19.3 22.0 16.5 16.5 10.9 11.3

50 Simulation of Hydrologic-System Responses to Ground-Water Withdrawals
Table 1-1. Summary of monthly withdrawals from selected production wells in the Hunt–Annaquatucket–Pettaquamscutt streamaquifer system, Rhode Island, 1999–2004.—Continued

[Withdrawals are in million gallons. RIEDC, Rhode Island Economic Development Corporation; KCWA, Kent County Water Authority; NK, North Kingstown. Well locations shown in figure 1]

Year January February March April May June July August September October November December

Annaquatucket River Basin

NK well 1

1999 3.7 6.2 9.5 11.1 11.9 20.3 17.5 12.2 5.6 4.9 10.3 5.4

2000 4.7 4.9 4.2 4.6 7.5 7.8 17.9 11.8 5.2 4.6 6.0 8.0

2001 9.9 5.3 8.8 12.9 18.5 13.6 16.8 15.8 14.7 18.2 16.1 16.2

2002 19.2 18.4 20.6 20.2 24.7 21.0 25.6 13.7 23.4 19.4 9.1 7.1

2003 13.9 11.1 19.3 12.2 15.9 15.5 22.6 22.6 15.7 10.2 9.9 10.7

2004 15.0 14.5 18.9 17.6 20.7 21.5 16.2 19.1 15.2 13.1 9.3 9.7

NK well 2

1999 1.6 3.0 .2 0 0 6.0 13.0 9.1 4.7 3.5 3.2 3.8

2000 4.5 3.6 4.0 4.7 3.7 5.7 10.7 5.7 3.4 4.6 4.4 4.9

2001 4.5 3.7 4.2 7.3 9.8 8.0 9.4 8.8 5.9 9.9 8.5 8.6

2002 9.9 9.1 10.3 10.0 12.0 10.3 11.8 12.5 9.7 8.7 5.0 5.5

2003 4.3 4.6 6.4 5.2 4.3 6.7 9.0 8.2 6.9 5.2 5.7 5.5

2004 6.9 5.2 8.1 6.0 7.5 8.5 5.1 6.7 3.6 5.2 2.9 3.4

NK well 4

1999 8.8 6.2 8.1 8.6 12.8 21.7 17.4 7.6 0 1.8 7.7 6.5

2000 5.5 6.5 7.4 8.0 9.5 8.2 15.1 9.0 7.6 9.1 5.6 6.4

2001 5.3 5.9 6.2 6.9 15.0 11.6 16.4 14.8 12.7 10.3 7.0 8.4

2002 9.3 6.2 6.3 8.8 10.6 13.7 25.8 20.2 11.4 10.2 6.8 6.5

2003 6.5 8.0 8.8 7.7 12.0 9.6 14.2 11.7 11.0 8.9 8.3 7.5

2004 6.2 6.1 6.1 6.2 12.1 9.4 13.8 11.4 15.9 11.9 11.4 10.6

NK well 5

1999 5.6 7.5 7.3 11.6 19.1 26.5 26.2 24.6 19.7 12.9 6.8 4.4

2000 5.7 4.6 4.4 4.8 11.6 16.8 24.3 13.8 10.7 7.4 5.7 5.5

2001 5.7 4.7 5.1 9.1 23.1 20.8 21.9 17.7 16.1 18.1 14.2 13.4

2002 8.0 5.9 7.3 7.4 13.0 21.6 38.4 25.1 13.1 9.5 6.5 7.4

2003 6.8 3.5 6.1 5.7 8.4 10.4 17.2 13.9 10.3 6.7 5.6 4.9

2004 6.3 6.3 6.2 8.0 11.9 20.2 19.4 14.5 4.5 4.1 3.1 6.4

Pettaquamscutt River Basin

NK well 3

1999 3.6 1.1 0.8 0 0.7 4.4 5.5 4.4 3.9 3.8 3.6 2.1

2000 1.6 1.6 1.4 1.4 2.0 3.8 4.6 2.6 2.4 1.7 1.5 1.5

2001 1.7 1.3 1.5 1.8 3.2 4.1 5.0 4.6 4.0 2.8 1.1 4.2

2002 4.2 2.2 1.6 1.8 2.3 3.3 9.1 7.2 3.7 3.8 3.0 2.9

2003 2.8 2.5 3.0 3.2 4.2 4.1 4.4 3.6 4.2 2.4 2.3 2.2

2004 2.3 2.0 2.1 2.3 3.0 3.4 4.2 4.1 2.7 3.3 2.3 2.5

NK well 7

1999 .6 0 .3 0 0 6.5 8.2 4.2 5.8 5.8 5.9 3.0

2000 2.1 2.3 1.9 1.9 2.8 5.3 6.3 3.4 3.2 2.2 1.9 1.7

2001 2.2 1.7 1.9 2.1 3.8 4.7 5.6 5.1 4.3 3.8 4.6 4.2

2002 4.1 2.1 1.5 1.7 2.2 3.1 8.6 6.6 3.3 3.4 2.6 2.8

2003 2.7 2.4 2.9 2.9 3.9 3.6 4.4 4.1 1.4 3.9 3.7 3.6

2004 3.7 3.2 3.4 3.6 4.7 5.2 6.2 5.3 4.4 4.0 3.6 4.0

NK well 8

1999 1.0 0 0 .1 .9 4.7 6.0 5.1 3.9 3.4 1.6 2.9

2000 2.1 2.2 1.8 1.8 2.7 5.1 6.0 3.3 3.7 2.1 1.8 1.5

2001 1.9 1.6 1.9 2.0 3.7 4.6 5.4 5.0 4.4 3.8 4.8 4.4

2002 4.3 2.2 1.6 1.8 2.2 3.2 8.9 7.0 3.5 3.6 2.4 2.6

2003 2.5 2.2 2.6 2.8 3.7 3.6 4.4 4.1 4.6 2.8 2.6 2.5

2004 2.5 2.1 2.3 2.5 3.2 3.6 4.3 3.7 3.1 2.8 2.4 2.7

Appendix 1  51

For additional information call or write to:

Deputy Director, U.S. Geological Survey

Massachusetts-Rhode Island Water Science Center

275 Promenade Street

Providence, RI 02908

(401) 331-9050

http://ri.water.usgs.gov
Printed on recycled paper

Barlow and Ostiguy—Simulation of Hydrologic-System Responses to Ground-Water Withdrawals in the Hunt-AnnaquatucketPettaquamscutt Stream-Aquifer System, Rhode Island—Open-File Report 2006–1226