Simulated Ground-Water Flow for a

Pond-Dominated Aquifer System near

Great Sandy Bottom Pond, Pembroke,

Massachusetts

By Carl S. Carlson and Forest P. Lyford

In cooperation with the Drinking Water Program, 

Massachusetts Department of Environmental Protection

Scientific Investigations Report 2004-5269

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Carlson, C.S., and Lyford, F.P., 2005, Simulated ground-water flow for a pond-dominated aquifer system near Great 

Sandy Bottom Pond, Pembroke, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2004-5269, 

43 p.
iii

Contents

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

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

Description of Study Area ........................................................................................................................... 2

Geology and Hydraulic Properties .................................................................................................... 5

Bedrock ........................................................................................................................................ 5

Till .................................................................................................................................................. 5

Stratified Sediments ................................................................................................................... 5

Alluvium and Swamp Deposits ................................................................................................. 6

Characteristics of Ponds ................................................................................................................... 6

Water Use and Wastewater Disposal .............................................................................................. 6

Runoff, Recharge, and Evapotranspiration ..................................................................................... 7

Data Collection and Compilation ................................................................................................................ 9

Simulation of Ground-Water Flow ........................................................................................................... 11

Model Extent, Boundary Conditions, and Discretization ........................................................... 12

Model-Simulated Streams ............................................................................................................... 15

Model-Simulated Stresses ............................................................................................................. 15

Hydraulic-Property Zones ................................................................................................................ 18

1998–2003 Transient Model ............................................................................................................. 19

Regional Hydrologic Context of 1998–2003 Transient Model ..................................................... 24

Sensitivity and Limitations for the 1998–2003 Transient Model ................................................. 25

Steady-State Model ......................................................................................................................... 27

Simulated Water Budgets and Pond Stages for Average Conditions and Various 

Water-Use Scenarios ................................................................................................................... 27

Changes in Water Withdrawals under Average Conditions ...................................................... 27

Changes in Climatic Conditions ....................................................................................................... 30

Summary ..................................................................................................................................................... 32

Acknowledgments ...................................................................................................................................... 34

References Cited ........................................................................................................................................ 34
iv

Figures

 1–4. Maps showing:

1. Ponds, streams, production wells, pond diversion and export points, and 

pumping rates in 2002 for the study area around Great Sandy Bottom 

Pond, Pembroke, southeastern Massachusetts ...........................................................3

2. General distribution of geologic materials at the land surface and 

bedrock-surface contours in the study area around Great Sandy 

Bottom Pond, Pembroke ....................................................................................................4

3. Data-collection sites in the study area around Great Sandy Bottom Pond, 

Pembroke, 2002–03. ..........................................................................................................10

 4. Model boundary conditions, stream cells, ponds, and hydraulic

conductivity zones for model layers 1 and 2 (surficial materials), 

Pembroke area ..................................................................................................................13

5. Generalized north-south cross section through the model area showing model 

layers and hydraulic-conductivity zones in the study area around Great Sandy 

Bottom Pond, near Pembroke .................................................................................................. 14

 6. Map showing average yearly recharge (1998–2002), in inches per year, 

representative of recharge applied to the transient 1998–2003 model and 

Year 2000 census tracts, near Pembroke .............................................................................. 17

 7. Graph showing model-simulated and measured ground-water levels, pond 

and lake levels, and stream discharge and simulated monthly base recharge, 

near Pembroke ........................................................................................................................... 20

 8. Map showing water-table altitudes near Pembroke ........................................................... 21

 9–15. Graphs showing:

 9. Measured streamflow and model-simulated monthly streamflow for 

variations in model hydraulic characteristics for Herring Brook at 

Route 36 in Pembroke, October 1, 2002–September 30, 2003. ...................................22

 10. Monthly outflow for model stream nodes and constant-head nodes and 

measured streamflow for the Indian Head, Jones, and Taunton Rivers .................24

 11. Measured water levels for the model period January 1998–September 

2003 in well MA-HGW 76 (well depth = 26.6 ft) near Wampatuck Pond, 

Hanson ................................................................................................................................25

 12. Simulated and measured water level of Great Sandy Bottom Pond in 

Pembroke, October 1, 2002–September 30, 2003. ........................................................26

 13. Simulated average monthly water levels in Great Sandy Bottom Pond for 

five water-use scenarios based on average monthly recharge from the 

period 1949–2002, Pembroke ...........................................................................................29

 14. Simulated monthly water-level altitude in Great Sandy Bottom Pond for 

average recharge conditions and for two periods of reduced recharge 

resulting from the historical droughts of 1979–82 and 1963–66 ...............................31

 15. Simulated water-level altitude of Great Sandy Bottom Pond, near 

Pembroke, with average 2002 pumping, diversion, and export rates 

(scenario 1) and the 180-day simulation with no recharge (scenario 8) .................32
v

Multiply By To obtain

acre 0.4047 hectare (ha)

cubic foot (ft3) 0.02832 cubic meter (m3) 

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

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

cubic foot per second per square

 mile [(ft3

/s)/mi2]

 0.01093 cubic meter per second per square

 kilometer [(m3

/s)/km2]

foot (ft) 0.3048 meter (m)

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) 

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3

) 

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

gallon per day per square mile

 [(gal/d)/mi2

]

 0.001461 cubic meter per day per square

 kilometer [(m3

/d)/km2]

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

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

inch per month (in/mo) 25.4 millimeter per month (mm/mo)

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

mile (mi) 1.609 kilometer (km)

million gallons (Mgal) 3,785 cubic meter (m3

)

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

/s)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Conversion Factors, Datums, and Abbreviations

Tables

 1. Summary of average daily water use near Pembroke, southeastern 

Massachusetts, for average 1998–2002 and average 2002 .................................................. 7

 2. Cranberry bog water-use schedule and rates, Pembroke area .......................................... 8

 3. Precipitation, streamflow, pond-stage measurement sites, and summary of 

data collection near Pembroke ............................................................................................... 11

 4. Summary of properties for the Pembroke-area model ........................................................ 16

 5. Average monthly and monthly recharge rates used for model calibration and 

model simulations of average and drought seasonal conditions near Pembroke ......... 18

 6. Summary of results for sensitivity model runs by the 1998–2003 model for 

simulated yearly streamflow for Herring Brook at Route 36 and Herring Brook 

at Mountain Avenue, Pembroke, October 1, 2002 through September 30, 2003 ............. 23

 7. Cumulative budgets for simulations of average transient (water-use scenario 1) 

and steady-state conditions for model simulation in the Pembroke area ....................... 30

 8. Record for selected wells near Pembroke ............................................................................ 39
vi

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 coordinate information is referenced to the North American Vertical Datum of 1929 

(NGVD 29).

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

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

aquifer thickness in feet [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

ACCL Acceleration variable for SIP solver in MODFLOW

GIS Geographic information system

GSB Great Sandy Bottom

LMG Algebraic multigrid solver in the Link-AMG (LMG) Package of MODFLOW

MDEP Massachusetts Department of Environmental Protection

PET Potential evapotranspiration

SIP Strongly Implicit Procedure Package in MODFLOW

SMR Sensitivity model run

USGS U.S. Geological Survey

YMCA Young Men’s Christian Association
Abstract

A ground-water flow simulation for a 66.4-square-mile 

area around Great Sandy Bottom (GSB) Pond (105 acres) near 

Pembroke, Massachusetts, was developed for use by local and 

State water managers to assess the yields for public water supply of local ponds and wells for average climatic and drought 

conditions and the effects of water withdrawals on nearby 

water levels and streamflows. Wetlands and ponds cover 

about 30 percent of the study area and the aquifer system 

is dominated by interactions between ground water and the 

ponds. The three largest surface-water bodies in the study area 

are Silver Lake (640 acres), Monponsett Pond (590 acres), 

and Oldham Pond (236 acres). The study area is drained by 

tributaries of the Taunton River to the southwest, the South 

and North Rivers to the northeast, and the Jones River to the 

southeast. In 2002, 10.8 million gallons per day of water was 

exported from ponds and 3.5 million gallons per day from 

wells was used locally for public supply.

A transient ground-water-flow model with 69 monthly 

stress periods spanning the period from January 1998 through 

September 2003 was calibrated to stage at GSB Pond and 

nearby Silver Lake and streamflow and water levels collected 

from September 2002 through September 2003. The calibrated 

model was used to assess hydrologic responses to a variety of 

water-use and climatic conditions. Simulation of predevelopment (no pumping or export) average monthly (1949–2002) 

water-level conditions caused the GSB Pond level to increase 

by 6.3 feet from the results of a simulation using average 

2002 pumping for all wells, withdrawals, and exports. Most 

of this decline can be attributed to pumping, withdrawals, and 

exports of water from sites away from GSB Pond. The effects 

of increasing the export rate from GSB Pond by 1.25 and 

1.5 times the 2002 rate were a lowering of pond levels by a 

maximum of 1.6 and 2.8 feet, respectively. Simulated results 

for two different drought conditions, one mild drought similar 

to that of 1979–82 and a more severe drought similar to that of 

1963–66, but with current (2002) pumping, were compared to 

results for average monthly recharge conditions (1949–2002). 

Simulated mild drought conditions showed a reduction of 

GSB Pond level of about 1.3 feet and a lower streamflow 

of about 1.7 percent in the nearby stream. Simulated severe 

drought conditions reduced the pond level at GSB Pond by 

almost 7 feet and lowered streamflow by about 37 percent. 

Varying cranberry-irrigation practices had little effect on 

simulated GSB Pond water levels, but may be important in 

other ponds. The model was most sensitive to changes in areal 

recharge. An increase and decrease of 22 percent in recharge 

produced changes in the GSB Pond water level of +1.4 feet 

and -2.4 feet, respectively. 

The accuracy of simulation results was best in the central 

portion of the study area in the immediate location of GSB 

Pond. The model was developed with the study-area boundary 

far enough away from the GSB Pond area that the boundary 

would have minimal effect on the water levels in GSB Pond, 

nearby ponds, and the underlying aquifer system. The model 

is best suited for use by local and State water managers to 

assess the effects of different withdrawal scenarios for wells 

and ponds near GSB Pond and for general delineation of 

areas contributing recharge to wells and ponds in the vicinity 

of GSB Pond. The model in its current form may not be well 

suited to detailed analyses of water budgets and flow patterns 

for parts of the study area farther from GSB Pond without 

further investigation, calibration, and data collection.

Simulated Ground-Water Flow for a Pond-Dominated 

Aquifer System near Great Sandy Bottom Pond, 

Pembroke, Massachusetts

By Carl S. Carlson and Forest P. Lyford
Introduction

The Massachusetts Department of Environmental 

Protection (MDEP) is concerned that increased water demands 

with population growth will adversely affect water supplies, 

pond levels, and streamflow in the area of Pembroke, MA. A 

numerical ground-water-flow model for a region that includes 

numerous public-supply sources of water near Pembroke, MA, 

would be useful to local and State water managers to assess 

effects of alternative water-development options on water 

resources in the region, particularly pond levels, ground-water 

levels, and streamflows. Hydraulic interactions between ponds, 

streams, wetlands, and an extensive aquifer system require a 

model-simulation approach that accounts for all water that is 

available to enter ponds and recharge the aquifer system under 

variable climatic conditions and conditions of increasing water 

withdrawals. The modeling strategy for the hydrologic system 

near Pembroke accounts for all water that is available to enter 

ponds and recharge the aquifer system, and is potentially 

applicable to low-relief (elevations ranging from about 10 ft to 

150 ft above NGVD 29) terrains elsewhere. 

An area that encompasses most of the towns of Pembroke 

and Hanson and parts of Duxbury, Plympton, Halifax, 

Kingston, and East Bridgewater, near the headwaters of the 

Jones, North, South, and Taunton Rivers in southeastern 

Massachusetts (fig. 1), has been a major source of water 

for public supply since the late 1800s. Ponds are prominent 

features in this low-relief landscape and the hydrologic system 

is dominated by interactions between ground water and the 

ponds. Silver Lake, Furnace Pond, and Monponsett Pond 

have been sources of water for the city of Brockton, and Great 

Sandy Bottom (GSB) Pond has been a source of water for 

the towns of Abington and Rockland for decades. Various 

other ponds are used for recreation. Additionally, a sand and 

gravel aquifer system underlying most of the area is the main 

water source for all of the towns within the study area (fig. 2). 

Cranberry growers also pump ground water or divert water 

from ponds periodically. The numerous withdrawals and 

exports of water potentially affect streamflow and, thus, the 

habitat of anadromous fish species. The MDEP is concerned 

that increased water demands with population growth will 

adversely affect water supplies. An understanding of transient water budgets for average and drought periods would 

help local officials manage their water resources effectively. 

A numerical model of ground-water flow for the area around 

GSB Pond would help managers to assess the effects of 

alternative water-development options on water resources, 

particularly pond levels, ground-water levels, and streamflows. 

A study was begun in 2002 by the U.S. Geological Survey 

(USGS) in cooperation with the MDEP, where such a model 

was developed.

The purpose of this report is to describe ground-water 

flow in a pond-dominated aquifer system near Pembroke, 

Massachusetts. This report describes the geohydrology of the 

study area, documents the ground-water-flow model that was 

developed, and demonstrates model applications for simulating pond stages, ground-water levels, and streamflows, the 

possible effects of water withdrawals on these resources, and 

water budgets for average climatic and drought conditions. 

Water-level data were collected for a one year period and 

steady-state and transient ground-water-flow models were 

developed.

Description of Study Area

The focus of this investigation is an area containing 

numerous ponds in the vicinity of Pembroke and Hanson, MA, 

and centered approximately on GSB Pond (fig. 1). The study 

area is 66.4 mi2 and extends beyond the vicinity of GSB Pond 

to minimize possible simulated boundary effects in the modeled area near the pond. The study-area boundary coincides 

approximately with major streams and ground-water divides 

that were identified on the basis of simulated water levels from 

a preliminary regional numerical model developed as part of 

this study. Altitudes in the study area range from about 10 ft 

above NGVD 29 on the north side to a maximum of about 

150 ft on till hills throughout the study area. Major streams 

within or on the boundary of the study area include the Indian 

Head River, Herring Brook (a tributary of Indian Head River), 

Jones River, Pine Brook (a tributary of the Jones River), 

Stump Brook (a tributary of the Satucket River in the Taunton 

River Basin), and Poor Meadow Brook (a tributary of the 

Satucket River). Ponds and wetlands, including cranberry 

bogs, are dominant features in the landscape and collectively 

cover about one-third of the study area. Most residents in 

the study area live in single-family homes. The population, 

based on census tracts from the 2000 census, is approximately 

80,000 in the study area (MassGIS, 2003). The population 

has been gradually increasing in these suburban communities 

about 30 mi southeast of Boston.

2 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal conic projection,

1983 North American datum

WHITMAN

HANSON

Taunton River Basin

South Coastal Basin

North River Subbasin

Jones River Subbasin

South River

 Subbasin

PEMBROKE

HANOVER

EAST

BRIDGEWATER

HALIFAX

BRIDGEWATER

PLYMPTON

KINGSTON

DUXBURY

Robbins Pd

Burrage

Pd

Indian

 Head

Pd

Great

Sandy

Bottom

Pd

Little

Sandy

Bottom Pd

Stetson

Pd

Oldham

Pond

Jones River

Silver Lake

Furnace Pd

Maquan

Pond

Wampatuck

Pond

Mill Brook

Monponsett Pond

Herring Br

Poor Meadow Br

Indian Head River

Stump Br.

Pine Br.

Pudding Br.

Satucket River

58

58

14

14

14

3

27

36

36

53

27

106

106

GSBP

export

1.21

Furnace Pond

inflow

Pleasant St.

To

Brockton

To AbingtonRockland

Pond St.

0.151

Hudson St.

0.31

Crescent St.

0.25

Brook St.

Silver Lake

export

9.61

Furnace Pond

inflow

Monponsett

Pond withdrawal 

to Silver Lake

6.12

Monponsett

Pond inflow

Pembroke 4

Pembroke 2

0.51 Pembroke 3

0.28

Crystal Spring

0.73

(combined)

Furnace Pond

withdrawal to Silver Lake

0.77 Pembroke 1

0.113

Pembroke 5

0.011

0.45

Lake Shore

0.17

Richmond 

Park 1

0.11

Richmond Park 2 0.08

YMCA

0.35

Pleasant St.

Railroad

0 1 2 3 MILES

0 1 2 3 KILOMETERS

42o05'

70o52'30" 70o47'30"

42o00'

Lake Shore

0.17

9.61 PRODUCTION WELL AND LOCAL 

NAME—Number is average 2002 pumping 

rate, in million gallons per day

INACTIVE PRODUCTION WELL AND

LOCAL NAME

POND WITHDRAWAL OR EXPORT 

AND INFLOW POINT—Number is average 

2002 rate in million gallons per day

EXPLANATION

STUDY-AREA

BOUNDARY

DRAINAGE-BASIN

BOUNDARY

SUBBASIN

BOUNDARY

WATER TRANSFER

EASTERN

MASSACHUSETTS

Boston

Study 

area

71o00'

41o30'

42o30'

70o00'

Figure 1. Ponds, streams, production wells, pond diversion and export points, and pumping rates in 2002 for the study area 

around Great Sandy Bottom Pond, Pembroke, southeastern Massachusetts.

Description of Study Area 3
Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal conic projection,

1983 North American datum

Robbins

Pd

Burrage

Pd

Indian

 Head

Pd

Great 

Sandy

Bottom

Pd

Little

Sandy

Bottom Pd

Stetson

Pd

Oldham

Pond

Jones River

Silver Lake

Furnace Pd

Maquan

Pond

Wampatuck

Pond

Mill Brook

Monponsett Pond

Herring Br

Poor Meadow Br

Indian Head River

Stump Br.

Pine Br.

Pudding Br. +

++++

+

+

+

+

+++

++

++

+++ +

+

+ +

+ +

+

+

+

+

+

++

+

+

+

+

+

+

+

+

+

+ +

+

+

+ + +

+

+

+

++

+ +

+

+

++ +

+

+ + +

+

+

+

+

+ +

+

+

+

+ +

+ +

+

+

+

+ +

+

+

+

++ +

+

+

+

+

+

++ +

+

+

+

+

+

+

+ + +

+ +

+

+

+

+

+

+

+

+

+

+ + +

+

++

+ +

+

+

+

+

+

+

+ +

+

+

+

+

+

+

+ + + + +

+

+ +

+

+

+

+ + + +

+

+

+

+

++

+ +

+

+

+

+

+ +

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+ +

+

+

+ ++

+

+

+++

+

+

+

+

++

+

++

+

+ +

+

+

+

+

+

+

+

+

+++

+

+

+

+

+

+

+

+

+

+

+

+

++

+

+

+

+

+

+

+ +

+ +

+

+

+

+

+

+

+

+

+

+

+ + +

+

++

+

+ + +

+

+

+

+ +

+ +

+

+

+

+

+

+

+

+

+

+

+

+

++

++

+

+

+

+

+

+

+

+

+

+ +

+

+

+

+

+

+

+

+

+

+

+

+

80

60

40

60

60

80

40

40

60

20

20

0

40

40

60

40

20

-20

-20

0

0

20

40

60

-40

0

-20

-20

20

20 0

20

-20

0

0

20

40

60

20

40

60

200

0

0

40

-40

-80

60

40

20

20

-20

-20

60

80

80

0 1 2 3 MILES

0 1 2 3 KILOMETERS

42o05'

70o52'30"

70o47'30"

42o00'

EXPLANATION

STUDY-AREA

BOUNDARY

WATERSHED

BOUNDARY

BOUNDARY 

BETWEEN

PENNSYLVANIAN

SEDIMENTARY

ROCKS AND PREPENNSYLVANIAN

GRANITE (Shaw and 

Peterson, 1967)

PREDOMINANTLY

SAND AND GRAVEL

PREDOMINANTLY

SWAMP DEPOSITS AND

LACUSTRINE FINES

TILL

WATER BODIES

BEDROCK-SURFACE

CONTOUR—Interval is 20

feet. Datum is NGVD 29. Dashed

where uncertain

BEDROCK-SURFACE DATA

POINT

20

Pennsylvanian 

sedimentary rocks

Pre-Pennsylvanian

Granite

Figure 2. General distribution of geologic materials at the land surface and bedrock-surface contours in the 

study area around Great Sandy Bottom Pond, Pembroke, southeastern Massachusetts.

4 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Geology and Hydraulic Properties

In approximately 80 percent of the study area, the 

bedrock is overlain by glacially derived stratified sediments, 

alluvium, swamp deposits, and in the remainder of the study 

area by till. Bedrock exposures are limited to a few outcrops, mostly on hills. Bedrock geologic units in the study 

area include Pennsylvanian-age sedimentary rocks and older 

granitic rocks (fig. 2). Considerable relief of more than 120 ft 

for the bedrock surface resulted from preglacial erosion and 

glacial scouring. The bedrock surface shown in figure 2 was 

modified from maps presented by Shaw and Petersen (1967), 

Petersen and Shaw (1967), and Williams and Willey (1973) on 

the basis of additional drillers’ logs available in State files and 

consultants’ engineering and environmental reports (Amory 

Engineers, 1993; Camp Dresser & McKee, 1992; GZA 

GeoEnvironmental, 1991; Ground Water Associates, 1997; 

Inland Professional Corporation, 1999; Nangle Consulting 

Associates, 2002). Uncertainties in the bedrock surface result 

from sparse data from some areas, particularly areas underlain 

by till and areas of weathered Pennsylvanian-age sedimentary 

rocks that are difficult to distinguish from surficial materials 

on drillers’ logs. Thicknesses of surficial deposits exceed 

120 ft in some areas underlain by buried valleys, but generally 

are less than 100 ft thick. 

Bedrock

Pennsylvanian-age sedimentary rocks underlie most of 

the study area (fig. 2) and include shale, sandstone, and thin 

beds of conglomerate (Hartshorn, 1960). The Pennsylvanian 

rocks lie unconformably on older granitic rocks. An area 

underlain by granitic rocks on the east side of the study area 

coincides approximately with a bedrock high.

Information about the hydraulic properties of bedrock 

units is limited to driller-reported yields and pumping levels. 

A review of drillers’ logs for approximately 60 wells completed in bedrock in Pembroke and Hanson revealed yields 

that ranged from 5 to 100 gal/min with a geometric mean of 

17 gal/min. Driller-reported specific-capacity data (well yield 

divided by drawdown) that were analyzed using a formula 

of Cooper and Jacob (1946) (in Fetter, 1994) give a range 

of transmissivities from 6 to 1,700 ft2

/d and a geometric 

mean of 94 ft2/d. Most of the data are for wells completed in 

Pennsylvanian-age sedimentary rocks. Limited data for wells 

completed in granite indicate that yields and transmissivities 

are not notably different than for sedimentary rocks. Williams 

and others (1973) also reported that well yields for domestic 

wells in sedimentary rocks in the Taunton River Basin are not 

notably different than for wells in igneous rocks, but yields for 

industrial wells were typically higher for sedimentary rocks 

than for igneous rocks. Domestic wells completed in bedrock 

typically are less than 200 ft deep.

Till

A discontinuous layer of till was deposited on the 

bedrock surface during the last glacial period. Limited data 

indicate that the till thickness generally is less than 30 ft, but 

may be greater in some drumlins. Most till in the study area 

is poorly compacted, has a wide range of particle sizes from 

silt to boulders, and has a predominantly sandy or silty matrix 

(Hartshorn, 1960). Till is often difficult to distinguish on drillers’ logs and geologic logs from overlying stratified sediments 

and underlying sedimentary rocks. 

The hydraulic properties of till have not been described 

for the study area. For tills in Connecticut, Melvin and others 

(1992) report a wide range of hydraulic conductivities from 

0.0028 to 65 ft/d. Loose surface till has a median hydraulic 

conductivity of 2.7 ft/d and a specific yield of 0.28. Lower 

median values of 0.06 ft/d for hydraulic conductivity and 0.04 

for specific yield are reported for compact (drumlin) till.

Stratified Sediments

Surficial stratified sediments include sand and gravel 

deposited near ice (ice-contact deposits), coarse materials 

deposited as outwash in streams and as deltas in ponded water, 

and fine-grained materials deposited in lakes and ponds. 

Stratified sediments in the northeastern portion of the study 

area were largely deposited near or on glacial ice and include 

mostly sand and gravel. The depositional surface on ice was 

40 ft or more above the current land surface in many places, 

and sediments eventually collapsed to their current position as 

the ice melted (Shaw and Petersen, 1967). Most of the ponds 

in the study area occupy depressions left by melted ice blocks. 

Some of the depressions overlie buried bedrock valleys where 

ice blocks apparently were thicker than elsewhere. 

Fine-grained sand and silt are common in the southwestern part of the study area that was occupied by Glacial Lake 

Taunton. This lake persisted at an altitude of 55 to 65 ft above 

NGVD 29 during deglaciation of the region (Hartshorn, 1960; 

Larson, 1982). Extensive flat areas below altitudes of about 65 

ft are the former lake bottom covered with fine-grained sediments. The thickness of these sediments depends on the subsurface distribution of ice-contact deposits, ice-block depressions formed during or prior to deposition of lacustrine fines, 

and bedrock-surface topography, and can vary appreciably. 

The rail line that runs diagonally from northwest to southeast 

through the study area (fig. 1) approximately marks the transition from predominantly coarse sediments in the northeast to 

interbedded fine and coarse sediments in the southwest. 

Description of Study Area 5
Areas of stratified sediments that are above the glaciallake altitude of approximately 65 ft represent ice-contact 

deposits or outwash deltas and are coarser than sediments at 

or near the land surface in surrounding lower areas. In some 

areas, deltaic deposits overlie lacustrine fines. Lithologic logs 

indicate that the fines commonly abut or overlie ice-contact 

materials. Natural water bodies, such as Monponsett and 

Robbins Ponds, occupy depressions that were not completely 

filled prior to draining of the glacial lake or were formed 

by collapse over ice blocks that persisted for the lifetime of 

Glacial Lake Taunton (Hartshorn, 1960). The generalized distribution of materials at the land surface shown in figure 2 was 

determined from publicly available geographic information 

system (GIS) maps of till and wetland areas (MassGIS, 1999 

and 2002c) and surficial geologic maps by Peterson and Shaw 

(1967), Shaw and Peterson (1967), Hartshorn (1960), and 

Chute (1965). Recent alluvial deposits have a limited distribution in areas flooded by modern streams and are not shown as 

a separate unit on figure 2.

The hydraulic conductivity of glacially derived stratified sediments ranges widely from less than 1 ft/d for silt 

and varved clay to more than 200 ft/d for sand and gravel 

(Morris and Johnson, 1967). Reported aquifer transmissivities 

at production wells and exploration sites range from values 

that exceed 8,000 ft2/d near Pembroke, Halifax YMCA, and 

Duxbury Lake Shore production wells to lower values of 

about 1,400 to 6,000 ft2/d at other well sites (table 8, at back 

of report). These values may result from the fact that exploration programs for the siting of production wells often identify 

sites with highly transmissive sediments. Vertical hydraulicconductivity values for collapsed sediments and ice-contact 

deposits have not been measured. Lower values of vertical 

hydraulic conductivity of 10 ft/d or less are estimated for areas 

of interbedded silts and sands that are common in the southwestern part of the study area. Specific yields from 0.2 to 0.25 

are estimated for all stratified sediments (Morris and Johnson, 

1967).

Alluvium and Swamp Deposits

Swamp and alluvium deposits are widespread in the study 

area and consist of fine-grained sediments and organic matter. 

Peat and peaty materials described on geologic logs typically 

are less than 2 ft thick, but some thicknesses exceeding 

10 ft have been reported (Williams and Willey, 1970). Average 

thicknesses may be greater than those reported on drillers’ 

and geologic logs because wells typically are not drilled in 

swamps. For example, Hartshorn (1960) reports 60 ft of muck 

and peat in bogs near the southwest boundary of the study 

area. 

Information about hydraulic properties for swamp and 

alluvium deposits is not available for the study area. Morris 

and Johnson (1967) report an average vertical hydraulic 

conductivity for peat of about 20 ft/d and a specific yield of 

0.4. Hydraulic-conductivity values summarized by Mitsch and 

Gosselink (1993, table 4-6) range from 0.03 ft/d for highly 

decomposed wetland soils to 14 ft/d for slightly decomposed 

or fibrous peat. A low vertical hydraulic conductivity is 

needed to maintain ponded conditions in cranberry bogs, but 

an approximate value is not available.

Characteristics of Ponds 

The three largest surface-water bodies in the study area 

are Silver Lake (640 acres), Monponsett Pond (590 acres), 

and Oldham Pond (236 acres). Other ponds in the vicinity 

of GSB Pond (105 acres) (fig. 1) are Indian Head Pond 

(124 acres), Furnace Pond (115 acres), Stetson Pond 

(94 acres), Wampatuck Pond (68 acres), Little Sandy Bottom 

Pond (61 acres), and Maquan Pond (48 acres). Bathymetric 

data indicate that maximum pond depths are less than 10 ft in 

Furnace Pond; less than 20 ft in Oldham, Great Sandy Bottom, 

Little Sandy Bottom, Maquan, and Monponsett Ponds; nearly 

30 ft in Stetson Pond; and 70 ft in Silver Lake (Baystate 

Environmental Consultants, Inc., 1993; Coler & Colantonio, 

Inc., 2003; Tim Hall, Weston & Sampson Engineers, Inc., 

written commun., 2003; Massachusetts Division of Fisheries 

and Wildlife, 2002). Bathymetric data are not available for 

other ponds in the area, but depths of less than 20 ft are likely. 

Soft-sediment thicknesses of 10 ft or more have been 

mapped for deeper parts of Oldham, Furnace, Little Sandy 

Bottom, and Stetson Ponds (Baystate Environmental 

Consultants, Inc., 1993). They report that soft sediments 

typically are absent near the shore and at depths of less 

than 6 ft.

Maximum pond levels at Furnace Pond, Monponsett 

Pond, Silver Lake, and Wampatuck Pond are controlled by 

outlet structures. Other ponds in Pembroke and Hanson have 

natural controls. GSB Pond and Hobomock Pond in Pembroke 

have no surface outlet, and natural outflow from Little Sandy 

Bottom Pond to GSB Pond appears to be limited.

Levels for most ponds fluctuate over a range of about 

2 ft (Petersen, 1962; data collected during this study). Larger 

fluctuations from 3 to 5 ft are observed in GSB Pond and 

Silver Lake. Withdrawals from Furnace Pond and Monponsett 

Ponds to Silver Lake are managed to minimize variations in 

pond stage (Brian Creedon, Brockton Water System Manager, 

oral commun., 2002). The hydraulic properties of pond-bottom sediments have not been measured in the study area. For 

a pond in Natick, MA, in a similar geologic setting, Friesz and 

Church (2001) report vertical hydraulic-conductivity values 

from 1.1 to 2.9 ft/d for coarse pond-bottom sediments.

Water Use and Wastewater Disposal

Water use in the study area is principally for public 

supply and cranberry irrigation. All towns in the study area 

provide public-supply water to residents. In 2002, waterproduction reports provided to MDEP by towns indicated that 

6 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
pumping from 13 production wells for use within the area 

averaged 3.51 Mgal/d, export from Silver Lake to Brockton 

averaged 9.61 Mgal/d, and export from Great Sandy Bottom 

Pond to Abington and Rockland averaged 1.21 Mgal/d 

(table 1, fig. 1). Of the water withdrawn for export from Silver 

Lake, a small amount, 0.1 Mgal/d, was used within the study 

area in Hanson. In addition, appreciable withdrawals were 

made from Furnace (0.77 Mgal/d) and Monponsett 

(6.12 Mgal/d) Ponds to Silver Lake (fig. 1, table 1). 

Use of water in Pembroke, Hanson, and Halifax during 

1998–2002, determined from town-reported pumpage and 

population served, averaged about 70 gal/person/d, which 

is near an estimate of statewide use of 66 gal/person/d from 

public supplies (Korzendorfer and Horn, 1995). Horn (2000) 

estimates a consumptive use (water that is consumed and not 

returned to the immediate water environment) of 15 percent 

for domestic users.

Water is diverted from ponds and pumped from wells 

for cranberry farming in about 2 mi2, or about 3 percent, of 

the area. The U.S. Department of Agriculture reports that 

farmers typically flood cranberry bogs six times a year for 

frost protection, summer irrigation, and harvesting (Dan 

Barnett, U.S. Department of Agriculture, written commun., 

2002). The cumulative flood depth totals 7 ft/yr for a typical 

bog (table 2). Most water used for flooding is diverted from 

ponds, but irrigation wells also supply water when pond levels 

are low or in some areas where pond water is not available 

(Robert Clark, cranberry grower, oral commun., 2003). Most 

of the water is returned to ponds, released downstream, or 

infiltrates to recharge ground water. Cranberry bogs near and 

east of GSB Pond are irrigated by diversions from Furnace 

Pond. Larger areas to the east are irrigated from ponds and 

water is released to Herring Brook. Active cranberry bogs 

northwest of GSB Pond are irrigated by diversions from Indian 

Head Pond. Flood water from these areas is periodically 

released to Furnace Pond. Cranberry bogs between Stetson 

Pond and Little Sandy Bottom Pond are irrigated from Stetson 

Pond. The evaporation of ponded water from cranberry bogs 

may be greater than from other wetland areas, but is not 

considered to be a major additional component of the water 

budget for the study area. 

Most wastewater is discharged to ground water through 

septic systems. There are no sewage-collection and -treatment 

systems in the area.

Runoff, Recharge, and Evapotranspiration

Major components of the water budget for the region are 

precipitation, evapotranspiration, and runoff. Precipitation 

averages about 47 in/yr (Randall, 1996). Average annual 

runoff ranged from 25 in/yr in the Taunton River near 

Bridgewater for the combined periods 1930–75, 1986–87, and 

1998–2002 and 28 in/yr in the Indian Head River at Hanover 

for 1965–2002 and the Jones River downstream from Silver 

Lake in Kingston (Socolow and others, 2002) for 1965–2002. 

Losses to evapotranspiration, therefore, were in the range of 

16 to 19 in/yr for these periods. The runoff and evapotranspiration estimates are affected by water transfers between basins 

and wastewater discharges, particularly in the Taunton River 

(Socolow and others, 2002). Exports to Brockton and the 

Abington/Rockland Joint Water Works, from 2002 water-use 

data and an assumed runoff rate of 27 in/yr, total about 13 

percent of runoff for the study area.

Table 1. Summary of average daily water use near Pembroke, 

southeastern Massachusetts, for 1998–2002 and 2002. 

[Data from Joe Cerutti, Massachusetts Department of Environmental 

Protection, written commun., 2003. Type: GW, ground-water pumping; 

SWE, surface-water export; SWW, surface-water withdrawal. No., number; 

Mgal/d, million gallons per day]

Town and diversion point Type

 Average, 

1998–2002 

(Mgal/d)

 Average, 

2002 

(Mgal/d)

 Duxbury

Lake Shore Drive Well GW

 

 0.16 

 

 0.17 

Halifax

YMCA-03G, Lingan Street GW

 

 .33 

 

 .35 

RP1-01G, Plymouth Street GW .12 .11 

RP2-02G, Plymouth Street GW .07 .08 

Pembroke

Hobomock Street (GPW #1) GW

 

 .09 

 

 .11 

Center Street (GPW #2) GW .43 .51 

School Street (GPW #3) GW .28 .28 

Sandy Lane (GPW #4) GW .48 .45 

Windswept Bog (GPW #5) GW .002 .01 

East Bridgewater

Pond Street, Well No. 1 GW

 

 .10 

 

 .15 

Hudson Street, Well No. 4 GW .30 .31 

Crescent Street, Well No. 2 GW .27 .25 

Hanson

Crystal Spring GW

 

 .71 

 

 .73 

Abington–Rockland

Great Sandy Bottom Pond SWE

 

 1.34 

 

 1.21 

Brockton

Silver Lake SWE

 

 9.92 

 

 9.61 

Furnace Pond withdrawal to 

Silver Lake SWW

 

 1.38 

 

 .77 

Monponsett Pond withdrawal to 

Silver Lake SWW

 

 5.27 

 

 6.12 

Total 21.25 21.22 

Description of Study Area 7
Conceptually, surface runoff is minimal for areas underlain by sand and gravel, and average annual recharge rates 

approach average annual runoff rates. Hansen and Lapham 

(1992) report recharge rates of 27 in/yr for the PlymouthCarver area just south of this study area, and Masterson and 

others (1997; 1998) report recharge rates of 26 in/yr for 

western Cape Cod. Recharge rates to till in New England are 

poorly defined but may be nearly the same as recharge rates 

to sand and gravel for the sandy tills that characterize the 

study area. In areas of extensive wetlands where water is at or 

above the land surface, the water available for recharge may 

discharge into streams. Some wetlands may become recharge 

areas seasonally. The net effect of wetlands is to reduce the 

total regional recharge.

Lake evaporation typically is larger than evapotranspiration. Regional maps of lake evaporation show rates of about 

26 in/yr for the study area, about 76 percent of which is lost 

from May through October (Kohler and others, 1955). Higher 

annual rates of 40 in. or more are predicted on the basis of 

evaporation formulas described by Fennessey and Vogel 

(1996). By using monthly average temperature data collected 

at the Brockton climate station for the period 1948–93 and 

longitude and elevation data at GSB Pond, the formulas yield 

the following average monthly (in/mo) and annual (in/yr) 

pond-evaporation rates used in this study (Stacey Archfield, 

U.S. Geological Survey, written commun., 2004): 

Table 2. Cranberry bog water-use schedule and rates, Pembroke area, southeastern Massachusetts.

[Water is used during times shaded. Souce of data, U.S. Department of Agriculture–Natural Resources Conservation Service in cooperation with University of 

Massachusetts Cranberry Experiment Station, and Cranberry Growers. Modified from Dan Barnett, U.S. Department of Agriculture, written commun., 2002]

Water

use

Water

application,

in acre-feet

per acre

JanuaryFebruary

March April May June July August September October November

December

Second winter flood 1

Spring frost 

protection

 1

Chemigation1 Negligible

Summer irrigation 

and bog cooling

 2

Fall frost protection 1

Harvest flood 1

Winter flood 1

Total 7

1

Chemigation: agricultural chemicals added to irrigation water applied to bog.

January February March April May June July August September October November December Year

(in/yr)

1.26 1.56 2.65 3.95 5.75 6.78 7.21 6.20 4.30 2.72 1.55 1.17 45.1

8 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Evapotranspiration rates are poorly defined for wetland 

areas in temperate regions. Literature-reported values for 

Massachusetts range from 20 to 40 in/yr (O’Brien, 1977; 

Hemond, 1980). Mitsch and Gosselink (1993) point out that 

studies have not demonstrated that evapotranspiration losses 

from wetlands are different (higher or lower) than evaporation 

losses from open bodies of water. Runoff rates that are similar 

to regional rates (Randall, 1996) indicate that evapotranspiration rates in this area of extensive wetlands are not appreciably 

different from regional evapotranspiration rates. 

Data Collection and Compilation

Hydrologic data needed for model calibration were 

collected by USGS personnel for approximately 1 year and 

concurrently by Weston & Sampson, Inc., as part of their 

monitoring program for Pembroke (fig. 3; tables 3 and 8). 

The city of Brockton routinely collects precipitation and stage 

data for Silver Lake, Furnace Pond, and Monponsett Pond, 

and the Abington and Rockland Joint Water Works collects 

stage data for Great Sandy Bottom Pond. Water levels are 

measured regularly by Hanson and Halifax near production wells. Additional water levels were available for the 

Cumberland Farms site in Hanson (Xan Riddle, Environmental 

Compliance Services, written commun., 2002), the Wal-Mart 

site in Halifax (Corporate Environmental Advisors, 2002), 

and the former Pembroke landfill site in Pembroke (Nangle 

Consulting Associates, written commun., 2003). Water-table 

maps for the following environmental sites and well sites 

were used for comparison to simulated water levels and flow 

patterns: Shaws in Hanson (Jaworski Geotech, Inc., 1995); 

Cumberland Farms in Hanson (Environmental Compliance 

Services, 1993, 1995, 2002); 318 Main St., Hanson (Fluor 

Daniel GTI, Inc., 1995); Pleasant St. well site, Hanson (Camp 

Dresser & McKee, 1998); Pembroke landfill, Pembroke (GZA 

GeoEnvironmental, 1991; Nangle Consulting Associates, Inc., 

1996); Dave’s Automotive, Hanson (Hydro-Environmental 

Technologies, 1988); Wal-Mart, Halifax (Corporate 

Environmental Advisors, 2002). Historical ground-water 

levels and pond stages for 1957–61 reported by Peterson 

(1962) define ranges of water-level fluctuations that were 

used to support the transient model calibration. 

Daily pond stages and diversions from Silver Lake, 

Furnace Pond, and Monponsett Pond, and records from 

the precipitation gage near Silver Lake for 1996 through 

September 2003 were provided by Brian Creedon (Manager, 

Brockton Water System, written commun., 2003), and daily 

pond stages and diversions for Great Sandy Bottom Pond 

for 1998–2003 were provided by Dan Callahan (Manager, 

Abington/Rockland Joint Water Works, written commun., 

2003). Monthly pumping rates for production wells were 

compiled from annual reports submitted by towns to MDEP. 

Recent pumping rates for town wells within the study area 

(January through September 2003) were provided by town 

water-system managers.

Data Collection and Compilation 9
58

14

27

36

36

27

HANSON

HALIFAX

KINGSTON

PEMBROKE

Indian

 Head

Pd

Great 

Sandy

Bottom

Pd

Little

Sandy

Bottom Pd

Stetson Pd

Oldham Pond

Silver Lake

Furnace Pd

Maquan

Pd Wampatuck

Pd

Herring Br

Indian Head R

Queensbrook St.

drive point Camp

Kiwanee

drive point Maquan Pond

staff gage

Maquan Pond

staff gage

Indian Head Pond

staff gage

TW 4-99

MA-HGW 76

MA-HGW 76

Stetson pond

staff gage

Indian Head Brook

staff gage

Indian Head Brook

staff gage

Wampatuck Pond

staff gage

Oldham Pond

outlet

Stetson

Pond

well

Brockton 

measuring points

C2

81-83

81-82

79-6

79-6

Ambient 

(DPW garage)

Herring Brook at

Mountain Ave.

Herring Brook at

Route 36

Herring Brook at

Route 36

GSBP staff gage

Furnace Pond 

R

R

R

R

R R

0 0.5 1 MILE

0 0.5 1 KILOMETER

70o50' 70o

47'30"

42o02'30"

42o01'

Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal conic projection,

1983 North American datum

PRECIPITATION GAGE

OBSERVATION WELL AND 

IDENTIFIER

OBSERVATION WELL WITH

RECORDER AND IDENTIFIER

EXPLANATION

CONTINUOUS-RECORD GAGING STATION AND 

IDENTIFIER—Streamflow-measurement site with 

continuous recorder, 2002–03

STREAMFLOW-MEASUREMENT SITE WITHOUT 

RECORDING GAGE AND IDENTIFIER

POND-STAGE MEASUREMENT STATION AND 

IDENTIFIER

Figure 3. Data-collection sites in the study area around Great Sandy Bottom Pond, Pembroke, southeastern 

Massachusetts, 2002–03.

10 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Simulation of Ground-Water Flow

The finite-difference ground-water-flow-modeling code, 

MODFLOW-2000 (Harbaugh and others, 2000) was used for 

this analysis. Pre- and post-processing were accomplished by 

using Argus ONE (Argus Holdings Ltd., 1992–2002) with the 

MODFLOW-GUI PIE Version 4 (Winston, 2000). Groundwater-flow models are commonly designed to account for only 

the ground-water component of the water budget and ignore 

storm runoff. Conceptually, surface or overland runoff for the 

sandy soils in the project area is minimal and storm runoff is 

largely from ponds and wetland areas. To simulate the water 

budgets for ponds, such as GSB Pond that has no surface 

outflow and Silver Lake that has limited surface outflow, all 

of the water that enters the ponds should be accounted for in 

model simulation. Also, pumping stresses can cause wetlands 

that are principally areas of ground-water discharge to convert 

to areas that are principally areas of ground-water recharge. 

Thus, the model should have the capability to receive recharge 

that might discharge from areas of high water tables under 

non-pumping conditions. To account for all of the water 

available for recharge, the modeling required adjustments 

from actual conditions. Ponds were simulated as high hydraulic-conductivity zones with stream nodes near the centerline 

to maintain a nearly flat water table and provide a means 

for routing water to downgradient model cells. An alternative approach might have been to use the Lake Package in 

MODFLOW (Merritt and Konikow, 2000) and the Streamflow 

Table 3. Precipitation, streamflow, pond-stage measurement sites, and summary of data collection near Pembroke, southeastern 

Massachusetts. 

[Latitude and longitude: In degrees, minutes, and seconds. NA, not available; SG, staff gage; topo, topographic map; USGS, U.S. Geological Survey; 

ft, foot]

Site name Latitude

° ′ ′′

Longitude

° ′ ′′

Altitude of reference point (ft) above 

NGVD 29

Source of data Period

of record

Measurement 

frequency

Silver Lake 42 01 26 70 48 52 NA Brockton Water 

Commission

01/02–10/03 Daily

Great Sandy Bottom Pond 42 03 22 70 50 06 NA USGS 10/02–10/03 Continuous

Herring Brook at Center Street 42 03 14 70 48 53 53.04 at reading of 

3.23 on SG

USGS 10/02–10/03 Continuous

Herring Brook at Mountain Avenue 42 03 43 70 48 09 From topo: 33 USGS 10/02–10/03 Periodic

Indian Head Brook at Indian Head 

Street

 42 02 54 70 51 32 68.65 at reading of 

1.85 on SG

USGS 10/02–10/03 Periodic

Oldham Pond outlet 42 03 32 70 49 58 58.18 at reading of 

57.75 on SG

USGS 10/02–10/03 Periodic

Indian Head River at Hanover 42 06 02 70 49 23 3.16 USGS 7/66–10/03 Continuous

Great Sandy Bottom Pond 42 03 22 70 50 06 58.98 Abington-Rockland

Joint Water Works

1998–2003 Daily

Oldham Pond (same as Oldham Pond 

outlet)

 42 03 32 70 49 58 58.18 at reading of 

57.75 on SG

USGS 10/02–10/03 Periodic

Stetson Pond 42 01 28 70 49 49 62.66 at reading of 

61.14 on SG

USGS 10/02–10/03 Periodic

Indian Head Pond 42 02 54 70 51 12 From topo: 68 USGS 6/03–10/03 Periodic

Maquan Pond 42 03 25 70 51 10 74.09 at reading of 

74.74 on SG

USGS 10/02–10/03 Periodic

Wampatuck Pond 42 03 54 70 52 03 70.32 USGS 10/02–10/03 Periodic

Little Sandy Bottom Pond 42 02 38 70 49 53 69.63 (measuring 

point)

Weston & Sampson 

Engineers, Inc.

6/02–4/03 Periodic

Silver Lake 42 01 26 70 48 52 From topo: 47 Brockton Water 

Commission

1996–2003 Daily

Furnace Pond 42 03 08 70 49 10 From topo: 56 Brockton Water 

Commission

1996–2003 Daily

Monponsett Pond 41 59 57 70 49 51 From topo: 52 Brockton Water 

Commission

1996–2003 Daily

Simulation of Ground-Water Flow 11
Routing Package (Prudic and others, 2004), but these packages did not have provisions for connecting streams and lakes 

when model simulation for this study began. Wetlands, like 

ponds, were treated as high hydraulic-conductivity zones with 

streams through the center to maintain a nearly flat water table 

near the land surface and to route the appropriate discharge 

quantities of water to ponds and areas downgradient where 

recharge might be possible. This method of simulating wetlands uses unrealistically high values of hydraulic properties 

for wetlands but retains water quantities. A more traditional 

approach of assigning realistic wetland properties and assuming no recharge in wetland areas might cause unrealistically 

high water levels in those areas and omit that quantity of 

water, an important component of the water budget in this 

setting, from inclusion in the wetland-area water budget or 

elsewhere downstream. For the intended uses of the model, it 

was decided that accurate simulation of water levels and water 

budgets was more important than accurate simulation of flow 

through wetland sediments. 

The 1998–2003 transient model spanned the period from 

January 1998 through September 2003 with 69 monthly stress 

periods. Calibration data included water levels in ponds and 

wells from January 1998 through September 2003. Monthly 

stress periods were chosen for model calibration. For this 

approximately 6-year period, the effects of estimated initial 

water-level conditions diminished within the first 2 years of 

model-run time. Model calibration focused on the period of 

intensive data collection, September 2002–September 2003. 

Reliable water-level and streamflow data for calibration were 

mostly available for the area near GSB Pond (fig. 3). Waterlevel data for calibration were limited for other areas. The 

limited data available for areas relatively far (more than about 

3 mi) from the GSB Pond area were used as a check on the 

plausibility of model-simulated water levels (heads).

Model Extent, Boundary Conditions, and 

Discretization 

The model area corresponding to the study area of 

66.4 mi2 (fig. 1) was selected on the basis of preliminary 

numerical modeling. The preliminary steady-state regional 

model developed as an initial model for this study covered an 

area of about 221 mi2 centered on GSB Pond. Drainage-divide 

and flow-line-convergence locations from particle tracking 

(Pollock, 1994) in the preliminary model defined the boundary locations for the model described in this report. Boundary 

locations included ground-water divides and streams where 1) 

numerical boundary effects on the hydrologic response at GSB 

Pond to changes in model-simulated stresses would be negligible, and 2) the maximum lateral extent of areas contributing 

recharge to wells and ponds near GSB Pond would not be near 

the model boundary. Boundary conditions at the edge of the 

model include no-flow cells near ground-water divides and 

constant-head cells at streams (fig. 4). 

The southwest corner of the model grid is located at 

latitude 41o 58’ 0.4” and longitude 70o 55’ 7.3”. The grid is 

rotated about its southwest corner 5 degrees counterclockwise. 

The grid consists of square cells 250 ft on a side with a total of 

185 rows and 205 columns for best representation of aquifer 

system features and a reasonable solution time. The Strongly 

Implicit Procedure (SIP) solver in MODFLOW-2000 was 

used for transient simulations with an acceleration parameter 

(ACCL in MODFLOW-2000) of 0.92 or 0.96. The steady-state 

model was solved by using the algebraic multigrid (AMG) 

Link-AMG (LMG) package in MODFLOW-2000 (German 

National Research Center for Information Technology, 2001; 

Mehl and Hill, 2001).

The location of geologic materials, their proximity to 

land surface, and their location relative to an average hydraulic-head surface simulated with a preliminary steady-state 

model were the basis for the determination of layer elevation 

boundaries. The surficial sand and gravel aquifer and areas of 

till and bedrock within 20 ft of land surface are represented in 

layers 1 and 2. Three layers were used to simulate the aquifer 

system: the top two layers (layers 1 and 2) represent surficial 

materials and bedrock within 20 ft of land surface, and the 

bottom layer (layer 3) represents bedrock (fig. 5). The surficial 

materials were divided into two layers to simulate pond and 

wetland geometries in layer 1 more accurately. Layer 2 represents the remainder of the surficial materials between layer 

1 and above bedrock. Layer 3 represents bedrock where the 

bedrock surface is at least 20 ft below land surface. The threelayer model approximates most physical features of the aquifer 

system and was found to be reasonably numerically stable. 

The top of layer 1 is defined by land-surface elevations 

from the Contours datalayer (MassGIS, 2002a). This datalayer, 

produced by MassGIS, is a combination of 1:25,000 USGS 

Digital Line Graph 10-ft contours and 3-meter contours created from Digital Terrain Model data points collected during 

the production of 1:5,000 black-and-white digital orthophoto 

images, with additional processing. Except for Silver Lake, the 

bottom of layer 1 was determined by subtracting 20 ft from 

an average hydraulic-head surface simulated with the preliminary steady-state model (fig. 5). This approach generally 

yielded a smooth surface between layers 1 and 2 and gave a 

reasonable initial saturated thickness for layer 1. Bathymetric 

data for Silver Lake (Coler & Colantonio Inc., 2003) below a 

depth of 20 ft defined the bottom surface of layer 1 at Silver 

Lake (fig. 5). The thickness range for layer 1 was 20–105 ft. In 

some areas, bedrock is within 20 ft of land surface and crops 

out at others. Bedrock at and within 20 ft of land surface was 

assigned to layer 1 but was accounted for in the hydraulicconductivity zone for till and bedrock.

The top surface of layer 2 was set equal to the bottom 

surface of layer 1. The bottom surface of layer 2 was the 

bedrock-surface elevation (fig. 2). The thickness of layer 2 

was set equal to 1 foot in areas where bedrock is within 20 ft 

of land surface or where layer 2 would have pinched out and 

under Silver Lake (fig. 5). The thickness for layer 2 ranged 

from 1 to 103 ft. 

12 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
MATERIAL, LAYER, AND MODELASSIGNED HYDRAULIC 

CONDUCTIVITY, IN FEET PER DAY 

 Till and bedrock within 20 ft

 of land surface, Layers 1

 and 2; 10

 Sand and gravel, Layers 1

 and 2; 45

 Sand and gravel (high 

 hydraulic conductivity

 zone), Layers 1 and 2; 80

 Wetland, Layer 1; 1,000

 Pond, Layer 1; 50,000

Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal

 conic projection, 1983 North American datum

A

A'

EXPLANATION

0 1

1

205

185

150

1

2 3 MILES

0 1 2 3 KILOMETERS

42o05'

70o52'30" 70o

47'30"

42o00'

100

50

50

100

150

Robbins

Pd

Burrage

Pd

Indian

 Head

Pd

Great Sandy

Bottom

Pd

Little

Sandy

Bottom Pd

Stetson

Pd

O

Po

ldham

nd

Jones River

Silver Lake

Maquan Furnace Pd

Pond

Wampatuck

Pond

Mill Brook

Monponsett Pond

Herring Br

Poor Meadow Br

Indian Head River

Stump Br.

Pine Br.

Pudding Br.

STREAM CELL

CONSTANT-HEAD CELL—Placed at 

stream locations 

NO-FLOW CELL—Placed at drainagedivide locations

LINE OF CROSS SECTION (shown 

on fig. 5)

A A'

Columns

Rows

Figure 4. Model boundary conditions, stream cells, ponds, and hydraulic-conductivity zones for model layers 1 and 2 (surficial materials), Pembroke area, southeastern Massachusetts. A constant value of 1 ft/d for hydraulic conductivity is assigned to model layer 3 

(represents bedrock underlying entire study area).

Simulation of Ground-Water Flow 13
1 0 2 MILES

1 0 2 KILOMETERS

2 L

2

 IN FEET ABOVE OR BELOW NGVD 29 , LTITUDE A

Preliminary steady-state water table Layer 2, 1 foot thick where 

b d k i ithi 20 f t f

Bedrock surface

A A'

EXPLAN

ATION

Area of till and bedrock at and within 20 ft of land surface

L

Layer 1,y Layer L 1, ayer 1,

surficial i l icial urficial materials

Layer 1 L yer 1 

Layer Layer 1

y

2

Layer 3, bedrock

(to 200 feet belo

w

bedrock surface)

-20-40-60

0

80604020

160140120100

Till and bedrock within 20 ft of land surface, Layers 1 and 2Sand and gravel, Layers 1 and 2Sand and gravel (high hydraulicconductivity zone), Layers 1 and 2

Wetland, Layer 1Pond, Layer 1

 HYDRAULIC-CONDUCTIVITY ZONE MATERIAL AND LAYER

Bedrock, Layer 3

North South

Vertical exaggeration x 80

Figure 5. Generalized north-south cross section through the model area showing model layers and hydraulic-conductivity zones in the study area around Great Sandy Bottom Pond, near Pembroke, southeastern Massachusetts. Line of section shown on figure 4.

14 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
The top surface of layer 3 was set equal to the bottom 

surface of layer 2. The bottom surface of layer 3 was set 

200 ft below the bedrock surface (fig. 5). A bedrock thickness of up to 200 ft was chosen as a reasonable representation of the underlying layer of generally poorly permeable 

bedrock. The altitude of the bottom of layer 3 was calculated 

by subtracting 200 ft from the bedrock surface. In locations 

where the bedrock surface is within 20 ft of land surface, 

the thickness of layer 3 was reduced to less than 200 ft. This 

reduction was done to maintain the simulated minimum thickness for model layers 1 and 2 of 20 ft and 1 ft, respectively, in 

areas where the actual bedrock surface is above the bottoms 

of model layers 1 and 2. Again, bedrock within 20 ft of land 

surface was incorporated into the hydraulic-conductivity zone 

for till and bedrock in layers 1 and 2. The total thickness range 

for layer 3 was 151–200 ft. Thicknesses between 151–180 ft 

were assigned to areas near the model boundary, where data 

on bedrock depth are sparse.

Layers 1 and 2 were simulated as convertible between 

confined and unconfined layer types. If a simulated head was 

above a layer, it functioned as a confined layer; if the simulated head was below the top of a layer, it functioned as an 

unconfined layer. Layer 3 was simulated as confined.

Model-Simulated Streams

The locations of all streams were determined from 

stream-centerline data (MassGIS, 2002b) and were simulated 

with the Stream Package (Prudic, 1989) of MODFLOW-2000. 

A total of 199 stream segments were used (fig. 4). Streamstage elevations were derived from the Contours datalayer 

(MassGIS, 2002a). Streams that entered and exited ponds were 

simulated as continuously flowing through the ponds, but were 

divided into segments where the stream centerline crossed the 

pond shore. Most simulated streams were assigned a width of 

10 ft. In some segments furthest upstream, width was adjusted 

downward to as low as 3 ft both to simulate the narrow widths 

characteristic of upstream segments and to restrict flow into 

the stream segment to maintain model stability in upstream 

areas. Most streams through Silver Lake and the ponds in 

the vicinity of GSB Pond were assigned a width of 25 ft to 

minimize resistance to flow between pond and stream reach. 

Both stream depth and streambed thickness were set equal to 

1 ft. Streambed hydraulic conductivity ranged from 1 to 3 ft/d 

and values were consistent with those for streams draining 

stratified glacial deposits at locations in central Massachusetts, 

southern Rhode Island, Long Island, New York, and northern 

New Jersey (Rosenshein, 1968; deLima, 1991; Prince and 

others, 1988; Dysart and Rheaume, 1999). Lower conductivity 

values typically were assigned to segments furthest upstream 

to restrict flow into the segment. Values of streambed hydraulic conductivity greater than 3 ft/d caused numerical instabilities, mainly in areas where streams and wetland areas were 

coincident. The segments through Silver Lake were assigned 

a value of 5 ft/d to minimize resistance to flow between the 

lake and the simulated stream reach passing through the lake 

(table 4). Indian Head Pond is the only pond in the study area 

with two surface-water outlets. Stream segments were simulated for both the canal flowing to the east and Indian Head 

Brook flowing out the west side of the pond. 

Model-Simulated Stresses 

 Model-simulated stresses include production wells, 

surface-water withdrawals and exports (fig. 1), and recharge 

(fig. 6). Monthly average pumping rates from wells, surface 

withdrawals, and exports from ponds were obtained from State 

and town records. Sixteen production wells were located to 

simulate the vertical location of the screened portion of the 

well accurately. Injection wells assigned to specific modeled 

pond cells were used to simulate inflow to Silver Lake from 

Furnace and Monponsett Ponds, and wells assigned to specific 

modeled pond cells were used to simulate withdrawals from 

Furnace Pond and Monponsett Pond and exports from GSB 

Pond and Silver Lake. The withdrawal from Furnace Pond and 

exports from GSB Pond and Silver Lake were simulated with 

one well each. High withdrawal rates from Monponsett Pond 

during some periods caused a single extraction well to go dry. 

To sustain pumping for all periods, 16 wells, distributed over 

the area of Monponsett Pond, were used to simulate the 

withdrawal from Monponsett Pond. 

Simulated monthly recharge rates accounted for precipitation, soil-moisture capacity, evapotranspiration, wastewater 

discharge to ground water, and pond evaporation. Temperature 

and precipitation data from the Brockton weather station for 

1949–2003 were used to estimate monthly recharge rates for 

that period. Missing data were estimated from weather-station 

records from Hingham and Plymouth. 

Monthly recharge from precipitation was calculated by 

subtracting potential evapotranspiration (PET) from precipitation and including soil-moisture capacity (moisture retained 

in the soil after excess moisture is drained through gravity 

drainage). Monthly values of PET were calculated by the 

Thornthwaite method (Chow, 1964), where the latitude and 

monthly temperature data are used. Monthly areal recharge 

was then calculated using PET, monthly precipitation, and 

a value for soil-moisture capacity. Calculations were made 

to assess the sensitivity of recharge calculations to varying 

values (4, 6, and 8 in/yr) of soil-moisture capacity. Recharge 

values for soil-moisture capacities of 4 and 8 in/yr were about 

6 percent greater and about 3 percent less, respectively, when 

compared to recharge calculated for 6 in/yr. Because recharge 

values determined from these three different soil-moisture 

capacity values were similar, recharge values resulting from a 

soil-moisture capacity of 6 in/yr were selected for use in this 

study. 

Simulation of Ground-Water Flow 15
Recharge is increased in much of the study area by wastewater discharge from septic systems. The quantity of recharge 

from septic systems was estimated from per person water 

use, consumptive use, and population density. Additional 

recharge of about 59 gal/person/d was estimated by reducing the total estimated water-use value of 70 gal/person/d by 

15 percent (10.5 gal) to account for consumptive use. The 

additional water was calculated and distributed over the study 

area (fig. 6) on the basis of a population-per-square-foot value 

determined for each census tract from year 2000 census data 

(MassGIS, 2003). The amounts of additional water for each 

census tract were constant values (values did not vary over 

the duration of the simulation) that were added to the actual 

recharge calculated for each month covering the period from 

January 1998 through September 2003 and recharge calculated 

for the steady-state model and the various water-use scenarios 

(discussed later in the report). The range of average yearly 

total recharge that is representative of the actual recharge 

applied to the 1998–2003 transient model for the period from 

January1998 through December 2002 by model cell and year 

2000 census tracts is shown in figure 6. The recharge value for 

ponds (8.6 in/yr) (fig. 6) takes into account actual precipitation 

amounts for the period from January 1998 through December 

2002 and pond evaporation. Census-tract areas of dense population correspond to areas where recharge values are 40.0 in/yr 

and greater (fig. 6). All recharge was applied to the uppermost 

active cell in the model.

Table 4. Summary of properties for the Pembroke-area model, southeastern Massachusetts. 

[ft, foot; ft/d, foot per day; ft-1, per foot]

Model property Description or value

Top and bottom of layers

Layer 1 (surficial aquifer) Top at land surface from land-surface contours from MassGIS, bottom at 20 ft below potentiometric 

surface from preliminary steady-state model.

Layer 2 (surficial aquifer) Top at bottom of layer 1; bottom at top of bedrock surface or 1 ft below the bottom of layer 1 in areas 

of shallow bedrock.

Layer 3 (bedrock) Top at bottom of layer 2; bottom at 200 ft below the bedrock surface.

Horizontal hydraulic conductivity

Layer 1 (surficial aquifer) 45 ft/d for sand and gravel areas; 80 ft/d in high-transmissivity zone between Great Sandy Bottom 

Pond and Little Sandy Bottom Pond; 10 ft/d for till and shallow bedrock; 1,000 ft/d for wetland 

areas; 50,000 ft/d for pond areas.

Layer 2 (surficial aquifer) Same as layer 1, but wetland and pond areas absent.

Layer 3 (bedrock) 1 ft/d

Vertical hydraulic conductivity

Layer 1 (surficial aquifer) 2 ft/d at pond and wetland areas, 5 ft/d elsewhere.

Layer 2 (surficial aquifer) 5 ft/d

Layer 3 (bedrock) 1 ft/d

Storage coefficient

Layer 1 (surficial aquifer) Primary (specific yield), 1 for ponds and wetlands, 0.6 for band of nearshore pond cells around Silver 

Lake and Great Sandy Bottom Pond, 0.2 elsewhere; secondary (specific storage) 0.00001 ft-1.

Layer 2 (surficial aquifer) Specific yield is 0.2; specific storage is 0.00001 ft-1.

Layer 3 (bedrock) Specific storage is 0.00001 ft-1.

Stream properties

Water-surface altitude From MassGIS land-surface contours.

Water depth 1 ft below land surface.

Thickness of stream bottom 1 ft 

Width 10 ft in most reaches, to a minimum of 3 ft in some upstream reaches; 25 ft in pond locations in and 

near Great Sandy Bottom Pond and in Silver Lake.

Streambed hydraulic conductivity 1 to 3 ft/d; 5 ft/d at simulated stream through Silver Lake

16 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal conic projection,

1983 North American datum

0 1 2 3 MILES

0 1 2 3 KILOMETERS

42o05'

70o52'30"

70o47'30"

42o00'

Robbins

Pd

Burrage

Pd

Indian

 Head

Pd

Great Sandy

Bottom Pd

Little

Sandy Bottom Pd

Stetson Pd

O

Po

ldham nd

Jones River

Silver Lake

Furnace Pd

Maquan

Pond

Wampatuck

Pond

Mill Brook

Monponsett Pond

Herring Br

Poor Meadow Br

Indian Head River

Stump

Br.

Pine Br.

Pudding Br.

27.1 - 29.0

 8.6 (surface-water bodies)

29.1 - 32.0

32.1 - 36.0

36.1 - 40.0

40.0 and greater (census tracts

 of greatest population density)

EXPLANATION

RECHARGE—Average yearly recharge (1998–2002),

in inches per year (a single value, within the indicated 

range, applied to each cell), representative of monthly 

recharge applied to the transient 1998–2003 model.

 YEAR 2000 CENSUS TRACT

 MODEL GRID

DRAINAGE-BASIN

BOUNDARY

Figure 6. Average yearly recharge (1998–2002), in inches per year, representative of recharge applied to the transient 1998–2003 

model and Year 2000 census tracts, near Pembroke, southeastern Massachusetts. Applied recharge is a sum of recharge calculated from precipitation and wastewater disposal.

Simulation of Ground-Water Flow 17
Net recharge in pond areas is less than elsewhere because 

of high evaporation rates. Monthly values of pond evaporation were subtracted from monthly precipitation values to 

determine monthly recharge rates at ponds. In some months, 

negative net recharge values were the result. Monthly recharge 

applied to pond areas for the period 1998–2003 ranged from 

-6.7 to 9.3 in/mo. Recharge applied in wetland areas was the 

same as recharge applied to nearby areas of other surficial 

geologic materials. 

In the 1998–2003 transient model, monthly recharge 

applied to the model was the actual recharge calculated for 

each month covering the period from January 1998 through 

September 2003. In the steady-state model, the applied model 

recharge was the annual average recharge calculated for the 

period 1949–2002. For water-use scenario runs 1 through 5, 

the applied model recharge was the average monthly recharge 

calculated from the period 1949–2002. For water-use scenario 

runs 6 and 7, the applied model recharge is the actual recharge 

calculated for each month from the period January 1979 to 

December 1982 and from January 1963 to December 1966. 

Average monthly recharge in inches for periods 1949–2002 

(22.28 in/yr) and 1998–2002 (27.16 in/yr) and monthly 

recharge for years 1965 (8.13 in/yr), 1980 (13.24 in/yr), and 

2002 (24.53 in/yr) are shown in table 5.

Hydraulic-Property Zones

Horizontal hydraulic-conductivity zones for layer 1 

include areas of till and bedrock within 20 ft of land surface, 

sand and gravel deposits, a zone of high hydraulic conductivity 

between GSB Pond and Little Sandy Bottom Pond, wetland 

areas, and pond areas (fig. 4). The area of till deposits from the 

Surficial-Geology datalayer (MassGIS, 1999) was extended to 

include areas where bedrock is within 20 ft of land surface to 

produce one hydraulic-conductivity zone representing till and 

bedrock (10 ft/d). This relatively high value is reasonable for 

fractured and weathered bedrock near the surface. One zone 

was used to represent sand-and-gravel deposits (45 ft/d). The 

limited data available do not indicate differences in hydraulic 

conductivity between predominantly coarse sediments in the 

northeast and areas of fine-grained sediments at the surface 

in the southwestern portions of the study area. A zone of high 

hydraulic conductivity (80 ft/d) between GSB Pond and Little 

Sandy Bottom Pond was based on a similar zone used in a previous calibrated model of the GSB Pond area (Ground Water 

Associates, Inc, 1997) and available transmissivity data from 

various high-yielding production wells (table 8). The pond 

and wetland areas were derived from the Wetlands datalayer 

(MassGIS, 2002c). Hydraulic-conductivity values for pond 

and wetland areas were 50,000 and 1,000 ft/d, respectively. 

The zones for layer 2 included till and bedrock within 20 

ft of land surface, the zone of high hydraulic conductivity, 

and sand and gravel deposits, all of which were assigned the 

same hydraulic-conductivity values as in layer 1. A uniform 

hydraulic conductivity of 1 ft/d was assigned to layer 3 that 

represented bedrock (table 4, fig. 4). All zones in layers 1 and 

2 were assigned a vertical hydraulic-conductivity value of 

5 ft/d, except for ponds and wetlands, which were assigned a 

value of 2 ft/d to simulate less transmissive bottom sediments. 

Bedrock in layer 3 was assigned a vertical hydraulic conductivity of 1 ft/d.

For transient simulations, a uniform value for specific 

storage (Ss) of 0.00001 ft-1 was used for all layers. Specific 

yield (Sy) was specified as 1 for both ponds and wetlands and 

Table 5. Average monthly and monthly recharge rates used for model calibration and model simulations of average and drought 

seasonal conditions near Pembroke, southeastern Massachusetts. 

Month Average monthly recharge (inches) Monthly recharge (inches)

1949–2002 1998–2002 1965 1980 2002

January 3.74 5.11 1.84 1.07 3.13

February 3.67 4.53 2.89 1.26 2.47

March 3.96 5.91 1.82 6.37 4.33

April 2.51 2.17 1.58 4.33 .60

May .97 1.64 .00 .00 3.81

June .48 2.16 .00 .00 .00

July .07 .00 .00 .00 .00

August .17 .00 .00 .00 .00

September .21 .11 .00 .00 .00

October .82 .80 .00 .00 .00

November 1.89 1.52 .00 .00 3.76

December 3.79 3.21 .00 .21 6.43

Total (inches/year) 22.28 27.16 8.13 13.24 24.53

18 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
0.2 for surficial materials in layer 1. In GSB Pond and Silver 

Lake, a band of cells near the shoreline was assigned a Sy

of 0.6 in layer 1 to account for the decrease in specific yield 

along the pond bottom that would be exposed if the water level 

in the pond dropped 7 ft from the water level shown on the 

topographic map. A uniform value for Sy of 0.2 was applied to 

layer 2.

1998–2003 Transient Model 

The numerical model described above produced results 

that approximately simulated observed ground-water levels 

and streamflow for 1998–2003. In the 1998–2003 transient 

model, simulated monthly recharge was the actual recharge 

calculated for each month covering the period from January 

1998 through September 2003. Other combinations of 

hydraulic properties, however, could have yielded a suitable 

alternative solution. In the calibration process, the final run of 

the 1998–2003 transient model used the ending heads (water 

levels) for layer 3 from the previous model run as starting 

heads to minimize the effects of initial head conditions on the 

results. The calibrated 1998–2003 transient model provided 

the base for the steady-state-model and transient-model runs 

for average conditions and various water-use scenarios.

Graphs comparing simulated to observed water levels 

in two ponds (GSB Pond and Silver Lake) and two wells 

(Stetson Pond well and 79-6) (fig. 3) and comparing 

simulated to observed streamflow in Herring Brook at Route 

36 and Herring Brook at Mountain Avenue are shown in 

figure 7, along with base recharge values in inches per month. 

Locations of all the wells and surface-water points that were 

used to compare results with measured data are shown in 

figures 3 and 8. Calibration to stage in GSB Pond focused 

on the period from October 2002 through September 2003 

because of an uncertain reference elevation for earlier 

measurements. 

The transient ground-water model simulated the timing of 

changes in the surface-water level of GSB Pond for the model 

calibration period correctly, but did not simulate the magnitude of these changes. The modeled head is about 1ft too 

high for January–November 2002 and about 1 ft too low for 

June–September 2003. A change in the amount and timing of 

monthly recharge may have resulted in a better match between 

observed and simulated heads. At Silver Lake, the model-simulated heads approximately matched the timing of observed 

high and low water levels, but the magnitudes of high and low 

water-level elevations were not matched accurately. Simulated 

heads in the Stetson Pond well were nearly 1.5 ft lower than 

the observed head measurements. This discrepancy could 

indicate either a transmissivity for layers 1 and 2 that is too 

high or a recharge rate that is too low in the area. At well 

79-6, the magnitude of measured head change from low to 

high is approximately matched by the simulated heads, but 

the simulated heads are slightly lower during the September 

2002–September 2003 period. This discrepancy could also 

indicate an areal recharge rate that is too low in the area. 

Streamflow at Herring Brook at Route 36 was 

measured by both periodic- and continuous-measurement 

methods. Streamflow at Herring Brook at Mountain Avenue 

was measured by periodic measurement methods. The continuous record for the Route 36 location is missing for the period 

after flooding of the recorder housing on July 10, 2003. Data 

recorded before July 10, 2003, is included (fig. 9). Therefore, 

comparisons are made between estimated and simulated 

streamflow for two periods: from October 2002 through July 

2003 and from October 2002 through September 2003. Total 

estimated streamflows in cubic feet per day from monthly 

instantaneous data as used in the following comparisons with 

simulated streamflows (figs. 7 and 9) were calculated by the 

following method: the instantaneous flow data (one daily flow 

value in cubic feet per day for each month) were plotted and 

a flow value for the middle of each month was determined by 

linear interpolation between actual data points; the monthly 

values were then added over each period to obtain a total flow 

value in cubic feet (MODFLOW output of one cubic foot per 

day flow value corresponding to the middle of each monthly 

stress period). In the period from October 2002 through July 

2003, total model-simulated streamflow is 2,723,000 ft3

compared to total streamflows estimated from continuous 

data (4,110,000 ft3, 51 percent more than simulated) and total 

streamflow estimated from instantaneous data (2,350,000 ft3, 

14 percent less than simulated). For the period from October 

2002 through September 2003, estimated total streamflow 

from instantaneous data was 2,678,000 ft3 compared to simulated streamflow of 2,946,000 ft3

. The model overestimated 

streamflow by about 10 percent (table 6) at the Route 36 location. Total streamflow at Herring Brook at Mountain Avenue 

was estimated only from instantaneous measurements; for 

the period from October 2002 through September 2003, total 

flow was estimated as 6,840,000 ft3 compared to simulated 

streamflow of 6,489,000 ft3 for the same period. Simulated 

streamflow was underestimated by about 5 percent (table 6) at 

the Mountain Avenue location. 

At Indian Head Pond, two streams are simulated as flowing from the pond. One is a canal flowing from the pond to the 

northeast, and the other is Indian Head Brook flowing from 

the west side of the pond (figs. 3 and 4). In the 1998–2003 

model, simulated streamflow along the canal segment typically decreased to zero during the summer months, but flow 

in Indian Head Brook from Indian Head Pond was sustained 

throughout the simulation. Infiltration from the canal segment 

to the aquifer system may be hydrologically important in the 

GSB Pond area.

Simulation of Ground-Water Flow 19
0

2

4

6

8

10

12

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

2

4

6

8

10

12

0

2

4

6

8

10

12

1998 1999 2000 2001 2002 2003

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Stetson well Well 79-6

Silver Lake

Streamflow in Herring Brook at Route 36 Streamflow in Herring Brook at Mountain Avenue

Simulated

Simulated

Simulated

Simulated

Simulated

Simulated

Daily measurements, uncertain

 reference elevation Periodic 

measured pond level

Periodic measured 

ground-water altitude

Periodic 

measured

discharge

Periodic measured

discharge

Measured lake level

Periodic 

measurements

by consultant

Continuous 

measurements

by consultant

50

52

54

56

58

60

Great Sandy Bottom Pond

100,000

500,000

200,000

1,000,000 100,000

1,000

 10,000

1,000,000

40

42

44

46

48

50

WATER-LEVEL ALTITUDE, IN FEET 

ABOVE NGVD 29

WATER-LEVEL ALTITUDE, IN FEET 

ABOVE NGVD 29

WATER-LEVEL ALTITUDE, IN FEET 

ABOVE NGVD 29

WATER-LEVEL ALTITUDE, IN FEET

ABOVE NGVD 29 

FLOW IN CUBIC FEET PER DAY

FLOW, IN CUBIC FEET PER DAY

55

57

59

61

63

65

53

55

57

59

61

63

RECHAR

GE, IN INCHES PER MONTH

RECHAR

GE, IN INCHES PER MONTH RECHAR

GE, IN INCHES PER MONTH RECHARGE, IN INCHES PER MONTH

RECHAR

GE, IN INCHES PER MONTH RECHAR

GE, IN INCHES PER MONTH

EXPLANATION

SIMULATED DAILY OR MORE

FREQUENT

MEASUREMENTS

PERIODIC 

MEASUREMENTS

MONTHLY 

RECHARGE

Figure 7. Model-simulated and measured ground-water levels, pond and lake levels, and stream discharge and simulated monthly 

base recharge, near Pembroke, southeastern Massachusetts. Measured levels in Great Sandy Bottom Pond prior to 2002 are 

uncertain because of uncertain reference elevation.

20 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Base from U.S. Geological Survey digital

data, 1:25,000, 1991, Lambert conformal conic projection,

1983 North American datum

Robbins

Pd

Burrage

Pd

Indian

 Head

Pd

Great 

Sandy

Bottom

Pd

Little

Sandy

Bottom Pd

Stetson

Pd

Oldham

Pond

Jones River

Silver Lake

Furnace Pd

Maquan

Pond

Wampatuck

Pond

Mill Brook

Monponsett Pond

Herring Br

Poor Meadow Br

Indian Head River

Stump Br.

Pine Br.

Pudding Br.

10

20

30

30

30

40

40

40

40

40

50

40

50

50

50

50

50

50

60

60

60

60

60

60

60

70

70

70 70

70

70

80

80 80

90

90

90

90

100

100

110

120

10

20

30

30

30

40

40

40

40

40

40

50

40

50

50

50

50

50

50

60

60

60

60

60

60

60

70

70

70 70

70

70

80

80 80

90

90

90

90

100

100

110

120

PEW 218

62-72 ft

12/57-11/60

PEW 362

80-82 ft

9/97-6/02

PEW 354

78-79 ft

11/02-9/03

HGW 165

79-82 ft

10/98-5/02

HGW 152

77-80 ft

10/02-9/03

PEW 361

60-70 ft

8/02-9/03

PEW 359

52-62 ft

8/02-9/03

PEW 360

48-59 ft

8/02-9/03

HBW 27

50-55 ft

4/57-9/59

KGW 92

56-62 ft

12/57-9/59

PEW 217

98-104 ft

12/57-11/60

PEW 351

119-122 ft

1/99-7/99;

6/03-9/03

PEW 132

28-34 ft

5/58-9/59

PEW 239

22-28 ft

5/58-10/59

HGW 23

66-73 ft

12/57-9/59 HGW 45

53-55 ft

5/58-11/60

HGW 76

64-68 ft

6/64-9/03

HGW 163

38-50 ft

6/83-9/03

EBW 27

67-75 ft

12/57-9/59

HBW 28

47-60 ft

12/57-9/59

HBW 124

61-68 ft

6/98-12/01 HBW 127

42-51 ft

1/98-4/03

HBW 126

47-50 ft

1/98-4/03

PEW 356

52-59 ft

8/02-9/03

PEW 358

61-67 ft

8/02-9/03

HBW 29

45-57 ft

9/57-8/59

PEW 219

79-91 ft

10/57-10/59

PEW 175

16-24 ft

10/57-10/59

PEW 218

62-72 ft

12/57-11/60

PEW 362

80-82 ft

9/97-6/02

PEW 354

78-79 ft

11/02-9/03

HGW 165

79-82 ft

10/98-5/02

HGW 152

77-80 ft

10/02-9/03

PEW 361

60-70 ft

8/02-9/03

PEW 359

52-62 ft

8/02-9/03

PEW 360

48-59 ft

8/02-9/03

HBW 27

50-55 ft

4/57-9/59

KGW 92

56-62 ft

12/57-9/59

PEW 217

98-104 ft

12/57-11/60

PEW 351

119-122 ft

1/99-7/99;

6/03-9/03

PEW 132

28-34 ft

5/58-9/59

PEW 239

22-28 ft

5/58-10/59

HGW 23

66-73 ft

12/57-9/59 HGW 45

53-55 ft

5/58-11/60

HGW 76

64-68 ft

6/64-9/03

HGW 163

38-50 ft

6/83-9/03

EBW 27

67-75 ft

12/57-9/59

HBW 28

47-60 ft

12/57-9/59

HBW 124

61-68 ft

6/98-12/01 HBW 127

42-51 ft

1/98-4/03

HBW 126

47-50 ft

1/98-4/03

PEW 356

52-59 ft

8/02-9/03

PEW 358

61-67 ft

8/02-9/03

HBW 29

45-57 ft

9/57-8/59

HBW 29

45-57 ft

9/57-8/59

PEW 219

79-91 ft

10/57-10/59

PEW 175

16-24 ft

10/57-10/59

0 1 2 3 MILES

0 1 2 3 KILOMETERS

42o05'

70o52'30"

70o47'30"

42o00'

EXPLANATION

STUDY-AREA

BOUNDARY

WATERSHED

BOUNDARY

SUBBASIN

BOUNDARY

SIMULATED WATER 

TABLE—Contour shows 

altitude of water table. Contour

interval is 10 feet. Datum is

NGVD 29.

OBSERVATION POINT—Upper number is 

U.S. Geological Survey identifier, middle 

numbers denote range of observed water-level 

altitude in feet above NGVD 29, and lower numbers 

denote the observation period.

KEY TO OBSERVATION POINTS:

SURFACE WATER

MODEL-SIMULATED STEADY-STATE 

WATER LEVEL RELATIVE TO MEASURED 

WATER-LEVEL RANGE:

 Higher

 Within range

 Lower

Taunton River Basin

South Coastal Basin

North River Subbasin

Jones River Subbasin

South River

 Subbasin

Figure 8. Water-table altitudes near Pembroke, southeastern Massachusetts. Water-table contours drawn from modelsimulated steady-state levels in layer 1 and observed range of water-level altitudes.

Simulation of Ground-Water Flow 21
EXPLANATION

SMR 1. Horizontal hydraulic conductivity increased by 

10 percent

SMR 2. Horizontal hydraulic conductivity decreased by 

10 percent

SMR 3. Specific yield increased by 25 percent to 0.25

SMR 4. Specific yield decreased by 25 percent to 0.15

SMR 5. Vertical hydraulic conductivity in ponds and 

wetlands increased by 50 percent to 3 feet per day

SMR 6. Vertical hydraulic conductivity in ponds and 

wetlands decreased by 50 percent to 1 foot per day

SMR 9. Cranberry irrigation added

CALIBRATED 1998-2003 MODEL

RECHARGE INCREASED BY 6 

INCHES PER YEAR

RECHARGE DECREASED BY 6 

INCHES PER YEAR

PERIODIC MEASUREMENT

AVERAGE DAILY CONTINUOUS 

RECORDED DISCHARGE 

MEASUREMENT

MONTHLY AVERAGE OF 

CONTINUOUS MEASUREMENT

RANGE OF SIMULATED STREAMFLOW RESULTING

FROM THE FOLLOWING INDIVIDUAL CHANGES TO

CALIBRATED MODEL FOR EACH SENSITIVITY MODEL

RUN (SMR)

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

STREAMFLOW, IN CUBIC FEET PER DAY

Missing continuous 

discharge record

Water stored in 

ice and snow

Oct.

Nov.

Dec.

Jan. 

Feb.

Mar.

Apr.

May 

June

July

Aug.

Sept. 

2002 2003

Figure 9. Measured streamflow and model-simulated monthly streamflow for variations in model hydraulic characteristics for 

Herring Brook at Route 36 in Pembroke, southeastern Massachusetts, October 1, 2002–September 30, 2003.

22 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Table 6. Summary of results for sensitivity model runs by the 1998–2003 model for simulated yearly streamflow for Herring Brook at 

Route 36 and Herring Brook at Mountain Avenue, Pembroke, southeastern Massachusetts, October 1, 2002 through September 30, 

2003. 

[in/yr, inches per year; --, no change]

Sensitivity model run

Annual flow

October 2002–

September 2003

(cubic foot)

Percent difference 

from 1998–2003

calibrated model

Herring Brook at Route 36

Estimate from instantaneous (hand) measurement data 2,678,000 -9.11

Simulated by calibrated 1998–2003 model 2,946,000 --

Decrease horizontal hydraulic conductivity by 10 percent 3,137,000 6.46

Increase horizontal hydraulic conductivity by 10 percent 2,734,000 -7.22

Decrease vertical hydraulic conductivity in ponds and wetlands to 1 ft/d 2,937,000 -.33

Increase vertical hydraulic conductivity in ponds and wetlands to 3 ft/d 2,897,000 -1.68

Increase recharge by 6 in/yr 5,327,000 80.80

Decrease recharge by 6 in/yr 806,000 -72.65

Lower specific yield to 0.15 2,970,000 .79

Increase specific yield to 0.25 2,922,000 -.84

Add cranberry irrigation west of Great Sandy Bottom Pond and south of 

Little Sandy Bottom Pond

 2,929,000 -.57

Herring Brook at Mountain Avenue

Estimate from instantaneous (hand) measurement data 6,840,000 5.41

Simulated by calibrated 1998–2003 model 6,489,000 --

Decrease horizontal hydraulic conductivity by 10 percent 6,673,000 2.84

Increase horizontal hydraulic conductivity by 10 percent 6,334,000 -2.39

Decrease vertical hydraulic conductivity in ponds and wetlands to 1 ft/d 6,507,000 .28

Increase vertical hydraulic conductivity in ponds and wetlands to 3 ft/d 6,468,000 -.32

Increase recharge by 6 in/yr 9,701,000 49.50

Decrease recharge by 6 in/yr 3,655,000 -43.67

Lower specific yield to 0.15 6,553,000 .99

Increase specific yield to 0.25 6,487,000 -.03

Add cranberry irrigation west of Great Sandy Bottom Pond and south of 

Little Sandy Bottom Pond

 6,489,000 --

Simulation of Ground-Water Flow 23
Regional Hydrologic Context of 1998–2003 

Transient Model

Simulated monthly outflows for the model area were 

computed for a qualitative comparison to monthly flows in the 

Indian Head River at Hanover, MA, Jones River at Kingston, 

MA, and Taunton River near Bridgewater, MA (fig. 10); actual 

outflows from the study area are not known. Outflows were 

examined by adding model-simulated outflow to streams 

and constant heads and subtracting model-simulated inflow 

from streams and constant heads. For January 1998 through 

December 2002, the patterns of simulated outflows are similar 

to observed streamflows (fig. 10), but simulated flows during 

high-flow periods were lower than observed flows and simulated flows during low-flow periods were higher than observed 

flows. Total simulated outflow was less than the total outflow 

for the three rivers. Some of the differences may be attributable to physical conditions in the model area that are different 

from conditions in the three drainage basins upstream from 

the three sites mentioned above. For example, a combination 

of exporting water and refilling numerous ponds and wetlands 

that were depleted during summer months reduced simulated 

runoff in the study area relative to other areas during highflow periods. For low-flow periods, simulated outflow may be 

sustained by water stored in ponds and wetlands. Alternatively, 

simulated recharge rates may be high, aquifer storage properties may be high, or both. Total simulated runoff lower than 

the estimated outflow from the three rivers is partly attributable to exportation of water.

The range of long-term (period from 1964 through 2003) 

normal monthly water levels (range between highest and lowest 25 percent of levels) in the USGS monitoring-network well 

MA-HGW 76, near Wampatuck Pond, Hanson, MA (fig. 3), 

was compared to measured water levels for the model period 

January 1998–September 2003 (fig. 11). Except for some measurements that are outside of the normal range in the spring 

and fall, most measurements are within or near the normal 

range of monthly water levels. The model-simulation period 

(January 1998–September 2003) is, therefore, reasonably 

representative of normal conditions in the study area.

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

FLOW IN, CUBIC FEET PER MONTH PER SQUARE MILE

Indian Head River at Hanover, MA

Jones River at Kingston, MA 

Taunton River near Bridgewater, MA

Total model-simulated outflow to stream nodes and 

constant-head nodes

INDEX MAP

Taunton River

Jones River

Indian Head River

Model and Study Area

Figure 10. Monthly outflow for model stream nodes and constant-head nodes and measured streamflow for the Indian 

Head, Jones, and Taunton Rivers, southeastern Massachusetts. Flows are normalized by dividing by drainage area. 

24 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Sensitivity and Limitations for the 

1998–2003 Transient Model

A sensitivity test was performed on the 1998–2003 

transient model to determine changes in results when selected 

model properties were increased or decreased within reasonable limits. Nine sensitivity model runs (SMR) were made 

to examine the effects on water level at GSB Pond and 

streamflows in Herring Brook at Route 36 and at Herring 

Brook at Mountain Avenue for comparison of sensitivity-test 

results of each of the following changes in model properties: 

SMR 1) Increase of 10 percent in horizontal hydraulic conductivity; 

SMR 2) Decrease of 10 percent in horizontal hydraulic conductivity; 

SMR 3) Increase of 25 percent in specific yield to 0.25; 

SMR 4) Decrease of 25 percent in specific yield to 0.15; 

SMR 5) Increase of 50 percent in vertical hydraulic conductivity in wetland and pond areas to 3 ft/d; 

SMR 6) Decrease of 50 percent in vertical hydraulic conductivity in wetland and pond areas to 1 ft/d; 

SMR 7) Increase of 6 in/yr in recharge values (22 percent); 

SMR 8) Decrease of 6 in/yr in recharge values (22 percent); 

and, 

SMR 9) Addition of cranberry irrigation.

The final sensitivity test (SMR 9) simulated the effect of 

cranberry farming at bogs north of Indian Head Pond northwest of GSB Pond and five bogs between Little Sandy Bottom 

Pond and Stetson Pond. The total size of this area is about 

190 acres. The timing and per-acre quantity of monthly water 

use for cranberry-bog irrigation from table 2 was combined 

with estimated bog areas and infiltration rates to determine the 

monthly quantities of water to divert from ponds and apply 

to bog areas. Months in which no cranberry irrigation was 

simulated were January, March, September, and November. 

For other seasons, it was assumed that half of the applied 

water infiltrated to recharge ground water and half returned to 

ponds or streams. All water applied for summer irrigation and 

bog cooling was assumed to be lost to evapotranspiration. The 

method used to simulate the movement of water in the cranberry-irrigation process for seven bogs follows: (1) two wells 

were added, one in Indian Head Pond and one in Stetson Pond, 

to simulate removal of water, (2) seven injection wells—one at 

each of the bogs north of Indian Head Pond and northwest of 

GSB Pond, and five in the bogs between Little Sandy Bottom 

Pond and Stetson Pond, were added to simulate application, 

and (3) an injection well was located in Furnace Pond to 

simulate the release of irrigation water from the bogs north 

of Indian Head Pond and northwest of GSB Pond to Furnace 

Pond. No direct return to Stetson Pond was simulated.

WATER-LEVEL ALTITUDE, IN 

FEET ABOVE NGVD 29

Monthly measured water level in observation well MA-HGW 76

68

67

66

65

Below normal water level (lowest 25 percent of levels)

Above normal water level (highest 25 percent of levels) Normal water-level range

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

Jan. 

May 

Sept. 

1998 1999 2000 2001 2002 2003

Figure 11. Measured water levels for the model period January 1998–September 2003 in well MA-HGW 76 (well 

depth = 26.6 ft) near Wampatuck Pond, Hanson, southeastern Massachusetts. Location of well shown in figure 3. The 

range of long-term normal monthly water levels at the well is repeated for each of the years shown. Normal water levels 

were computed for the period June 1964–September 2003. Normal water levels are those measurements between the 

highest and lowest 25 percent of water levels.

Simulation of Ground-Water Flow 25
Of the characteristics altered for the sensitivity analysis 

(fig. 12), modifying recharge rates for the period 1998–2003 

(SMR 7 and SMR 8) had the greatest effect on water levels 

in GSB Pond. Increasing recharge by 6 in/yr (0.5 in/mo) 

resulted in a simulated head increase in GSB Pond of up to 

1.4 ft, whereas decreasing recharge by 6 in/yr (0.5 in /mo) 

resulted in a decrease in head of up to 2.4 ft. Sensitivity model 

runs, which included the increase and decrease of horizontal 

hydraulic conductivity by 10 percent (SMR 1 and SMR 2), 

specific yield by 25 percent (SMR 3 and SMR 4), and vertical 

hydraulic conductivity by 50 percent (SMR 5 and SMR 6), 

produced a maximum difference in head at GSB Pond of about 

0.6 ft from the head value from the calibrated 1998–2003 

transient model. Increasing horizontal hydraulic-conductivity 

values by more than 10 percent caused numerical instabilities 

for unknown reasons. Increasing horizontal hydraulic conductivity by 10 percent (SMR 1) and increasing and decreasing 

vertical hydraulic conductivity in ponds and wetlands by 

50 percent (SMR 5 and SMR 6) produced nearly identical 

head patterns. In the process of sensitivity testing, lowering 

specific yield by 25 percent to 0.15 (SMR 4) yielded a slightly 

closer match of observed to simulated heads at GSB Pond 

(fig. 12). The magnitude of total water-level change at GSB 

Pond from November 2002 through June 2003 (about 3.7 ft) 

was not matched in the model runs conducted with the alternative model parameters in the sensitivity analyses.

51

52

53

54

55

56

57

58

GREAT SANDY BOTTOM POND WATER-LEVEL 

ALTITUDE, IN FEET ABOVE NGVD 29

EXPLANATION

SMR 1. Horizontal hydraulic conductivity increased by 

10 percent

SMR 2. Horizontal hydraulic conductivity decreased by 

10 percent

SMR 3. Increase of 25 percent in specific yield to 0.25

SMR 5. Vertical hydraulic conductivity in ponds and 

wetlands increased by 50 percent to 3 feet per day

SMR 6. Vertical hydraulic conductivity in ponds and 

wetlands decreased by 50 percent to 1 foot per day

SMR 9. Cranberry irrigation added

POND ELEVATION 1998-2003 

CALIBRATED MODEL

RECHARGE INCREASED BY 6 

INCHES PER YEAR

RECHARGE DECREASED BY 6 

INCHES PER YEAR

SPECIFIC YIELD DECREASED TO 

0.15

MEASURED WATER LEVEL 

PERIODIC MEASUREMENT

RANGE OF SIMULATED POND ELEVATION

RESULTING FROM THE FOLLOWING 

INDIVIDUAL CHANGES TO CALIBRATED MODEL

FOR EACH SENSITIVITY MODEL RUN (SMR) Jan. Feb.

Mar.

Apr.

May 

June

July

Aug.

Sept. 

Oct.

Nov.

Dec.

2002 2003

Figure 12. Simulated and measured water level of Great Sandy Bottom Pond in Pembroke, southeastern Massachusetts, 

October 1, 2002–September 30, 2003.

26 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
The effect on simulated heads of adding cranberry-irrigation water transfers in the local ponds was minimal. Simulated 

water levels at Little Sandy Bottom Pond and nearby wells 

were about 1 ft higher and water levels in Stetson Pond and 

the nearby Stetson Pond well were about 3 ft lower. Not 

accounting for all water inflows to Stetson Pond, underestimating recharge, or overestimating cranberry-irrigation water 

usage could account for the difference in head at Stetson 

Pond. Streamflow at Herring Brook at Route 36 was about 

0.6 percent lower when compared to streamflow results of the 

1998–2003 model (fig. 9), with no difference in streamflow 

noted at Herring Brook at Mountain Avenue (table 6).

The greatest percentage change in streamflow for the 

period October 2002–September 2003 in Herring Brook at 

Route 36 and at Herring Brook at Mountain Avenue resulted 

from altering recharge by 6 in/yr, whereas altering horizontal 

hydraulic conductivity had the next greatest effect (fig. 9, 

table 6). All other variations used for sensitivity analysis 

resulted in percentage changes of less than about 1 percent in 

streamflow at the two locations. 

The match between simulation results and observed data 

is best for the central part of the study area in the immediate 

vicinity of GSB Pond. The model is best suited for evaluating 

effects of different extraction scenarios for wells and ponds 

near GSB Pond on water levels and streamflow and for delineation of areas contributing recharge to these same wells and 

ponds. Elsewhere, the model simulation is useful for a preliminary analysis of potential effects of water withdrawals on pond 

levels, streamflow, and general ground-water-flow patterns, 

but additional data against which to calibrate the model, such 

as water levels and streamflow, are needed for more rigorous 

applications of the model outside the vicinity of GSB Pond. 

As for most model properties, there is uncertainty 

associated with the values calculated for pond evaporation 

and recharge. Pond evaporation and recharge values were 

estimated from data collected at the Brockton weather station, 

which is the closest station (about 15 mi) to the GSB Pond 

area. Some local weather data were recorded at GSB Pond 

during the period of intensive data collection, but no longterm record is available for GSB Pond; such a record would 

be needed to estimate recharge rates and possibly local pond 

evaporation more accurately. In general, longer records of 

streamflow, pond-level data, and local precipitation are needed 

to refine recharge and pond-evaporation estimates. Values of 

streambed hydraulic conductivity greater than 3 ft/d caused 

numerical instabilities, mainly in areas where streams and 

wetland areas were coincident.

Steady-State Model 

A steady-state model was developed from the 1998–2003 

transient model with average 2002 extraction rates and the 

average annual base recharge value (22.28 in/yr; table 4) for 

the period 1949–2002 to determine a potentiometric surface 

for average stress conditions. Other parameters in the model 

were the same as in the 1998–2003 transient model. The 

resulting head in layer 1 was chosen to represent the water 

table for the model area under average 2002 stress conditions 

(fig. 8). Head differences of less than 1 ft between layer 1 

and layer 2 and between layer 1 and layer 3 occur in 99.8 and 

97.9 percent of the model cells. The resulting water-table map 

with the observed ranges of heads and corresponding dates 

for wells and ponds is shown in figure 8. Comparison of the 

water-table contours and the topographically defined basin 

boundaries shows a good correspondence between surfaceand ground-water divides. Most water levels at the observation 

points were within the range of measured values. Water-level 

values that were higher or lower than the measured values are 

found scattered over the study area. 

Simulated Water Budgets and Pond 

Stages for Average Conditions and 

Various Water-Use Scenarios

Model application was demonstrated by simulating 

monthly water levels in GSB Pond for eight water-use scenarios for each of which a 4-year transient model was developed. The scenarios fall into two categories: (1) changes in 

water withdrawal under average conditions (scenarios 1, 2, 3, 

4, and 5); and (2) changes in climatic conditions, specifically, 

recharge (scenarios 6, 7, and 8). 

Changes in Water Withdrawals under 

Average Conditions

The aquifer system properties determined as a result 

of the model-calibration process of the 1998–2003 transient 

model were used for the scenario runs. Head values calculated 

by the steady-state model were used as starting heads for the 

scenario runs. As in the 1998–2003 transient model, a monthly 

time step was used in the scenario model runs; however, each 

Simulated Water Budgets and Pond Stages for Average Conditions and Various Water-Use Scenarios 27
scenario model was run for a span of 4 years. The water-use 

scenarios in the category “changes in water withdrawal under 

average conditions” are: 

 1. Average 2002 pumping for all wells, withdrawals, and 

exports and average monthly recharge calculated from 

the period 1949–2002; 

 2. No pumping, withdrawals, or exports and average 

monthly recharge calculated from the period 1949–

2002; 

 3. No exports from GSB Pond, but all other pumping, 

withdrawals, and exports at 2002 rates, and average 

monthly recharge calculated from the period 1949–

2002; 

 4. Increase in the average 2002 GSB Pond export rate, as 

used in scenario 1, by 1.25 times; and 

 5. Increase in the average 2002 GSB Pond export rate, as 

used in scenario 1, by 1.5 times. 

Scenario 1 represents the average monthly water levels that would be found at GSB Pond under 2002 pumping, 

withdrawal, and export conditions and average monthly 1949 

to 2002 recharge. This scenario is used for comparison to 

scenarios 2–7. Scenarios 2 and 3 show the effect of pumping, 

withdrawal, and export of water on GSB Pond water levels. 

Scenario 2 represents the area-wide predevelopment average 

monthly water-level condition that would have been found 

before pumping, withdrawals, and exports of water began 

in the GSB Pond area with average monthly 1949 to 2002 

recharge; wastewater disposal as reflected in the partially varying recharge array was not changed. With no exports from the 

GSB Pond itself, scenario 3 represents the effect that nearby 

pumping, withdrawals, and exports at average 2002 rates have 

on water levels at GSB Pond. Scenarios 4 and 5 represent the 

GSB Pond water-level condition if the GSB Pond export rate 

was increased (perhaps because of a future increase in water 

demand) by 1.25 and 1.5 times, respectively, with surrounding pumping, withdrawals, and exports at average 2002 rates. 

These scenarios demonstrate the applicability of the model 

to simulate head at GSB Pond for water-use rates that range 

from predevelopment conditions to possible future increases 

in water demand and also provide insight into aquifer-system 

response to alternative stresses.

Water-use scenarios 1, 2, 3, 4, and 5 are considered 

dynamic-equilibrium model simulations, in that the same 

model stresses are repeated for each year of model-run time. 

After effects of initial conditions are overcome, the results 

are cyclic in nature and show the same repeatable water-level 

pattern for each simulated year. The last year of results for 

scenarios 1, 2, 3, 4, and 5 and the average monthly 1949–2002 

recharge rates are shown in figure 13. The heads calculated for 

scenarios 2 and 3 are 6.3 ft and 5.0 ft higher, respectively, than 

for scenario 1. The effects of increasing the 2002 GSB Pond 

export rate by 1.25 times (scenario 4) and 1.5 times (scenario 

5), were a lowering of pond levels by a maximum of 1.6 and 

2.8 ft, respectively, from those of scenario 1 (fig. 13). 

If the specific capacity (well yield divided by drawdown) 

is calculated for GSB Pond by dividing the average export 

rate from GSB Pond for 2002 (1.21 Mgal/d) by the drawdown 

(final head from scenario 1 subtracted from the final head 

of scenario 3, which equals 5.03 ft), and this calculation is 

repeated for scenarios 4 and 5 (increasing the 2002 GSB Pond 

export rate by 1.25 and 1.5 times) a nearly constant value 

is found (0.24, 0.23, and 0.23). This value corresponds to a 

specific capacity for GSB Pond of about 0.2 Mgal/day/ft of 

drawdown for the range of pumping rates simulated for 

average recharge conditions. 

 For scenarios 1 and 3 (average and no GSB Pond withdrawals) the water budgets are essentially identical. Because 

scenario 2 lacks pumping stresses, more water discharges to 

streams. Cumulative water budgets for scenario 1 (average 

transient) and the steady-state model are shown in table 7, 

where values are shown in inches per year and gallons per day. 

Recharge, wells, withdrawals and exports, and streamflows are 

the largest components of the cumulative water budget for the 

steady-state and average transient models (table 7). The major 

differences between the water budgets for average transient 

and steady-state model runs are the storage terms. About 22 

percent of the total flow through the aquifer system is represented in the seasonal changes in storage.

28 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
1

0

2

3

4

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

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

46

48

50

52

54

56

58

60

62

64

WATER-LEVEL ALTITUDE, IN 

FEET ABOVE NGVD 29

AVERAGE 1949–2002 RECHARGE, 

IN INCHES PER MONTH

MONTH

MONTH

SCENARIO

1. Average 2002 pumping, diversion, and 

export rates and average monthly 

 1949–2002 recharge

2. No pumping, diversions, or exports, 

average monthly 1949–2002 recharge

3. No Great Sandy Bottom Pond exports, 

all other pumping, diversions, and exports

at 2002 rates, and average monthly 1949–

2002 recharge

4. Increase 2002 Great Sandy Bottom 

Pond export rates by 1.25 times

5. Increase 2002 Great Sandy Bottom

Pond export rates by 1.5 times

EXPLANATION

Figure 13. Simulated average monthly water levels in Great Sandy Bottom Pond for five water-use scenarios based on average monthly recharge from the period 1949–2002, Pembroke, southeastern Massachusetts.

Simulated Water Budgets and Pond Stages for Average Conditions and Various Water-Use Scenarios 29
Changes in Climatic Conditions

The water-use scenarios that fall into the category of 

“changes in climatic conditions” are: 

 6. Average 2002 pumping for all wells, withdrawals, and 

exports and actual calculated monthly recharge values 

from the period 1979–82, considered a mild drought in 

Massachusetts; 

 7. Average 2002 pumping for all wells, withdrawals, and 

exports and actual calculated monthly recharge values 

from the period 1963–66, considered the drought of 

record in Massachusetts; and 

 8. Average 2002 pumping, withdrawal, and export rates 

and no recharge for 180 days. 

Scenarios 6 and 7 were run to simulate the response in 

water levels at GSB Pond if mild and more severe drought 

conditions were imposed on the aquifer system while water 

extraction was maintained at current (average 2002 pumping, withdrawal, and export) rates. For scenarios 6 and 7, the 

decrease in recharge caused more inflow from storage for 

the simulated period as well as lower streamflows. Simulated 

drought conditions for 1979–82 (scenario 6) showed a reduction of pond level at GSB Pond of about 1.3 ft (fig. 14) and a 

lower streamflow of about 1.7 percent at Herring Brook 

at Mountain Avenue for 2002 pumping conditions. Simulated 

drought conditions for 1963–66 (Scenario 7) created a 

reduction of pond level at GSB Pond of almost 7 ft (fig. 14) 

and a lower streamflow of about 37 percent at Herring Brook 

at Mountain Avenue for 2002 pumping conditions. Average 

monthly recharge rates for 1949 to 2002 and 1998 to 2002 

conditions and monthly recharge for selected drought conditions (in 1965 and 1980) and year 2002 are shown in table 5. 

Water-level results for GSB Pond for scenarios 6 and 7 are 

shown in figure 14, along with the simulated average transient 

water levels (scenario 1). Recharge was greater in the early 

time of scenario 6 than in scenario 1, then declined during a 

2-year drought, and ended with a water level 1.3 ft lower 

than that for average conditions at the end of the 4-year 

simulation. The maximum difference in simulated water levels 

between average and 1979–82 conditions was about 4 ft. The 

water levels in scenario 7 declined throughout an extended 

drought such as the period 1963–66 and ended 6.9 ft lower 

than the water levels for average transient conditions (scenario 1). These scenarios demonstrated the applicability of 

the model to simulate water levels at GSB Pond for drought 

conditions of varying severity, while maintaining current water 

demand.

Table 7. Cumulative budgets for simulations of average transient (water-use scenario 1) and steady-state conditions for model simulation in the Pembroke area, southeastern Massachusetts. 

[gal/d, gallons per day; in/yr, inch per year]

Water-budget components

Scenario 1

Average transient

conditions

(in/yr)

Steady state

(in/yr)

Scenario 1

Average transient

conditions

(gal/d)

Steady state

(gal/d)

IN:

Storage 7.79 0 24,608,000 0

Constant head 1.45 1.45 4,595,000 4,570,000

Withdrawals to Silver Lake 2.18 2.18 6,893,000 6,878,000

Recharge 22.22 21.49 70,213,000 67,921,000

Stream leakage 1.56 1.64 4,914,000 5,187,000

Total IN 35.20 26.76 111,223,000 84,556,000

OUT:

Storage 7.38 0 23,308,000 0

Constant head 2.32 2.31 7,345,000 7,315,000

Withdrawals and exports from ponds 5.60 5.60 17,690,000 17,690,000

Wells 1.11 1.11 3,506,000 3,506,000

Recharge .83 0 2,625,000 0

Stream leakage 18.14 17.74 57,325,000 56,048,000

Total OUT 35.38 26.76 111,799,000 84,559,000

IN minus OUT -0.19 0 -576,000 -3,000

Percent discrepancy -0.56 0 -0.56 0

30 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
An additional transient run (scenario 8) was made for 

a period of 180 days with 2002 pumping, withdrawal, and 

export rates and no recharge (fig. 15). The rapid early decline 

in pond level during the first few days of simulation time 

resulted from the sudden elimination of recharge (Rorabaugh, 

1964) and initial conditions in the model. After the rapid 

early decline, the simulated water level in GSB Pond declined 

almost linearly. This simulation began with January pumping 

rates and ended with June pumping rates. The level in GSB 

Pond at the end of 180 days of no recharge was about 1.6 ft 

lower than the water level under average transient conditions 

(scenario 1). The water-level decline from start to finish of the 

180-day simulation, not including the drop because of initial 

conditions, was 1.2 ft. If the 180-day simulation began in a 

month other than January, the water-level result may have been 

different, because of different initial head conditions and 

44

46

48

50

52

54

56

58

0 1 2 3 4

 WATER-LEVEL ALTITUDE, 

IN FEET ABOVE NGVD 29 RECHARGE, IN INCHES PER MONTH

YEAR

MONTHLY RECHARGE

1979–82

1979–82

1963–66

1963–66

1. Average monthly recharge rates for the period 1949–2002

6. Monthly recharge from historical drought period 1979–82 

7. Monthly recharge from historical drought period 1963–66 

EXPLANATION

Simulated monthly water level

0

4

8

12

16

0

4

8

12

16

1963 1964 1965 1966

1979 1980 1981 1982

SIMULATED WATER-LEVEL ALTITUDE OF GREAT SANDY BOTTOM POND FOR 

EACH WATER-USE SCENARIO (1, 6, AND 7) WITH AVERAGE MONTHLY 2002 

PUMPING, DIVERSION, AND EXPORT RATES AND:

Figure 14. Simulated monthly water-level altitude in Great Sandy Bottom Pond for average recharge conditions and for 

two periods of reduced recharge resulting from the historical droughts of 1979–82 and 1963–66 in Massachusetts. 

Simulated Water Budgets and Pond Stages for Average Conditions and Various Water-Use Scenarios 31
varying pumping rates that are specific to the month in which 

the simulation would start. The effects of model boundaries, 

such as the constant-head boundaries at the Jones and North 

Rivers, are minimal because the boundaries of the study area 

are far from the location of GSB Pond. For the 180-day norecharge simulation, most water extracted at pumping wells 

and from ponds was from storage.

Summary 

The Massachusetts Department of Environmental 

Protection (MDEP) is concerned that increased water demands 

resulting from population growth will adversely affect water 

supplies, pond levels, and streamflow in the area of Pembroke, 

MA. The U.S. Geological Survey (USGS), in cooperation 

with the MDEP, began a study in 2002 to develop a numerical ground-water-flow model for use by local and State water 

managers to assess the effects of alternative water-development options on the water resources in the region, particularly 

pond levels, ground-water levels, and streamflows. 

The study area of 66.4 mi2 includes numerous ponds. 

Altitudes range from about 10 ft above NGVD 29 on the north 

side to about 150 ft on hills. Pennsylvanian-age sedimentary 

rocks underlie most of the study area. A discontinuous layer 

of till was deposited on the bedrock surface. The till generally 

is less than 30 ft thick. The hydraulic conductivity of glacially 

derived stratified sediments ranges widely from less than 

1 ft/d for silt and varved clay to more than 200 ft/d for sand 

and gravel. Natural water bodies occupy depressions that were 

not completely filled with sediment prior to the draining of 

Glacial Lake Taunton or were formed by collapse over ice 

blocks that persisted for the lifetime of the glacial lake. The 

three largest surface-water bodies in the study area are Silver 

Lake (640 acres), Monponsett Pond (590 acres), and Oldham 

Pond (236 acres). Levels for some ponds fluctuate over a 

range of about 2 ft. 

Water use in the study area is principally for public supply and cranberry irrigation. Water use in Pembroke, Hanson, 

and Halifax averaged about 70 gal/person/d during the period 

1998–2002. Major components of the water budget for the 

study area are precipitation, evapotranspiration, and runoff. 

Precipitation averages about 47 in/yr. Average annual runoff 

50

0 20 40 60 80 100 120 140 160 180

52

54

56

58

60

WATER-LEVEL ALTITUDE, IN FEET ABOVE NGVD 29

DAYS

SCENARIO:

 1. Average monthly 1949–2002 recharge starting in January

 8. No recharge, 180-day model simulation

Figure 15. Simulated water-level altitude of Great Sandy Bottom Pond, near Pembroke, 

Massachusetts, with average 2002 pumping, diversion, and export rates (scenario 1) and 

the 180-day simulation with no recharge (scenario 8). The rapid early decline in pond 

level during the first few days of simulation time resulted from the sudden elimination of 

recharge (Rorabaugh, 1964) and initial conditions in the model.

32 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
ranged from 25 to 28 in/yr. Lake evaporation typically is larger 

than evapotranspiration. Hydrologic data (water levels, pond 

stages, and streamflows) for ground-water-flow model calibration were collected by USGS personnel for approximately 

1 year and concurrently by Weston & Sampson, Inc., as part 

of their monitoring program for Pembroke.

A numerical ground-water-flow model covering an area 

around Great Sandy Bottom (GSB) Pond, Pembroke, MA, 

was developed for use by water managers to assess yields of 

local ponds and wells for supplying water for recent average 

climatic and drought conditions. The model was also used to 

assess the effects of water diversions on nearby water levels 

and streamflow. Wetlands and ponds cover about 30 percent of 

the study area and the aquifer system is dominated by interactions between ground water and the ponds. The model was calibrated to historical water-level data from available reports and 

town databases, and to streamflows and water levels collected 

from September 2002 through September 2003. A transient 

model with 69 monthly stress periods spanning the period 

from January 1998 through September 2003 was calibrated to 

measured pond levels in GSB Pond and Silver Lake, selected 

wells, and streamflows by varying hydraulic properties. 

A sensitivity analysis was completed by systematically 

varying selected model properties and assessing the changes 

in simulated water levels and streamflows. Model properties 

included horizontal hydraulic conductivity, vertical hydraulic conductivity at ponds and wetlands, specific yield, and 

recharge. A hypothetical scenario of water use for cranberry 

farming was also considered. Of the properties varied during 

the sensitivity analysis, an increase and decrease of recharge 

by 6 in/yr (22 percent) had the greatest effect on simulated 

water levels at GSB Pond and streamflows at Herring Brook 

at Route 36 and at Mountain Avenue as compared to the 

results from simulations by the 1998–2003 calibrated model. 

Collectively, the other hydraulic properties that were varied 

produced a maximum change in simulated GSB Pond water 

level of about 0.6 ft from the level calculated by the 1998–

2003 calibrated transient model. The inclusion of simulated 

cranberry irrigation had little effect on GSB Pond water levels 

but may have more effect on nearby ponds. 

Simulation of predevelopment (no pumping or water 

export) average monthly (1949–2002) water-level conditions with average monthly 1949–2002 recharge caused the 

water level in GSB Pond to increase by 6.3 ft compared to a 

simulation of average conditions (average 2002 pumping for 

all wells, surface-water withdrawals, and exports and average monthly recharge calculated from the period 1949–2002). 

Simulation of the effects of nearby pumping, surface-water 

withdrawals, and exports on water levels at GSB Pond, with no 

export from GSB Pond, all other pumping, withdrawals, and 

exports at 2002 rates, and average monthly recharge calculated 

for the period 1949–2002 caused the pond level to increase 

by 5.0 ft from the result of a simulation of average conditions. The effect of increasing the export rate from GSB Pond 

by 1.25 times and 1.5 times with average monthly recharge 

calculated from the period 1949–2002 was a lowering of pond 

levels by a maximum of 1.6 and 2.8 ft, respectively, from the 

result of a simulation of average conditions. Simulated results 

for two different drought conditions, one mild drought similar 

to that of 1979–82 and a more severe drought similar to that of 

1963–66, but with current (2002) pumping, were compared to 

results of a simulation of average conditions. Simulated mild 

drought conditions showed a reduction of GSB Pond level of 

about 1.3 ft and a lower streamflow of about 1.7 percent at 

Herring Brook at Mountain Avenue for 2002 pumping conditions. Simulated severe drought conditions reduced the pond 

level at GSB Pond by almost 7 ft and lowered streamflow by 

about 37 percent at Herring Brook at Mountain Avenue for 

2002 pumping conditions. 

Uncertainty in rates of recharge and pond evaporation, as 

well as in the extent, depth, distribution, and hydraulic properties of the subsurface materials, can affect simulation results. 

The Thornthwaite approach used in this study to estimate 

recharge is but one method available for recharge calculations; 

results based on other methods might be different. Because 

results of recharge calculations based on the same method 

also depend on the location where weather data was recorded 

(weather can vary over short distances), there is still some possibility of variation in the results. 

The model was developed with the study-area boundary 

far enough away from the GSB Pond area that the boundary 

would have minimal effect on water levels in GSB Pond and 

the underlying aquifer system. Therefore, accuracy of model 

simulation is best in the central portion of the study area in the 

vicinity of GSB Pond. The model is best suited for exploring 

the effects of different extraction scenarios on the yields of 

wells and ponds near GSB Pond and on nearby streamflow, for 

average climatic and drought conditions, and for delineation of 

areas contributing recharge to wells and ponds in the vicinity 

of GSB Pond. Local and State water managers will find the 

model useful for these purposes, as well as for other watersupply calculations related to GSB Pond and the underlying 

aquifer system. The model in its current form may not be well 

suited to detailed analyses of water budgets and flow patterns 

for other parts of the study area away from GSB Pond without 

further investigation of hydrologic properties and conditions in 

those areas, revision of the model to incorporate new information, and recalibration of the model.

Summary 33
Acknowledgments

The authors thank various people who contributed time, 

knowledge, and information for this study. Joe Cerutti, MDEP, 

provided water-use data and reports from wellhead-protection 

and environmental studies from MDEP files. The following 

water managers provided useful data and reports from town 

files and operations information for water-supply systems: 

Daniel Callahan, Abington/Rockland Joint Water Works; 

Brian Creedon, City of Brockton Water Department; Michael 

Valenti, Town of Pembroke Department of Public Works; Glen 

Doherty, Hanson Water Department; Richard Clark, Halifax 

Water Department; Scott McCann, East Bridgewater Water 

Department; and Carl Hillstrom, Duxbury Water Department. 

Blake Martin and Tim Hall of Weston & Sampson, Engineers, 

Inc., provided valuable information about ground-water 

conditions in the Pembroke area and hydrologic data needed 

for model calibration. Mark Ames and Robert Clark, members of the Pembroke Conservation Commission, provided 

information about cranberry farming. Gary Makuch and Jim 

McLaughlin, MDEP, provided useful information on water use 

and cranberry farming in the study area. The Hanson Parks 

Commission provided access to town property for hydrologic 

monitoring at and near Maquan Pond.

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36 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Table 8

Table 8. Record for selected wells near Pembroke, southeastern Massachusetts. —Continued

[All altitudes are above the National Geodetic Vertical Datum of 1929 (NGVD 29). USGS, U.S. Geological Survey; ft, foot; ft2/d, foot squared per day; gal/min, gallons per minute; gal/min/ft, gallons per minute per foot; -- , no data]

Local well number

or name

USGS

number

Year 

drilled

Altitude of

measuring

point above

NGVD 29

(ft)

Altitude

of land 

surface 

above 

NGVD 29 

(ft)

Total

depth

(ft)

Screened 

interval (ft)

depth 

below land 

surface

Range of 

water-level 

altitudes

(ft)

[period]

Transmissivity

(ft2/d)

Source of data Comments

Public-supply wells or well sites

Duxbury Lake Shore 

Drive Well

D4W 72 1955 -- 70 46 -- -- 9,200 IEP, Inc., 1986

East Bridgewater #1 EBW 142 1965 -- 56 64 -- -- -- Williams and Willey, 1970 Also known as the Pond Street 

Well. Well yield 708 gal/min.

East Bridgewater #2 EBW 166 1966 -- 48 40 -- -- -- Williams and Willey, 1970 Also known as the Crescent 

Street Well. Specific capacity 19.3 gal/min/ft.

East Bridgewater #4 EBW 234 -- -- 50 -- -- -- -- -- Also known as Hudson Street 

Well.

Halifax YMCA Well HBW 121 1987 -- 65 109 92–107 -- 13,000 Camp Dresser & McKee, 

1987

Halifax RP #1 HBW 122 1964 -- 50 -- -- -- -- Whitman & Howard, 1964 Specific capacity of 

22.7 gal/min/ft from test on 

cluster of wells.

Halifax RP #2 HBW 123 1964 -- 50 -- -- -- -- Whitman & Howard, 1964

Hanson 10-94 HGW 153 1994 -- 60 64.5 28–40 -- 6,200 Camp Dresser & McKee, 

1994

Brook Street well site.

Hanson 12-94 HGW 154 1994 -- 54 52 28–40 -- 6,000 Camp Dresser & McKee, 

1994

Brook Street well site.

Hanson 5E-8B HGW 156 1991 -- 58 72.5 53–63 -- 3,600 Camp Dresser & McKee, 

1991

Pleasant Street well site.

Hanson 3-5 HGW 157 1992 -- 70 50 36–41 -- 1,440 Camp Dresser & McKee, 

1992

Cranland Airport site.

Hanson 3-3 

(production)

HGW 159 1992 -- 60 52 41–51 -- 4,500 Camp Dresser & McKee, 

1992

Cranland Airport site.

Hanson Crystal Spring 

#1

HGW 160 1980 -- 55 -- -- -- 4,400 Camp Dresser & McKee, 

1981

Transmissivity from well cluster 

test.

Hanson Crystal Spring 

#2

HGW 161 -- -- 50 -- -- -- -- --

Pembroke GPW #2 PEW 240 1962 -- 65 107 82–107 54

[8/1/62]

 17,400 Ground Water Associates, 

1997

Also known as Center Street 

Well.

Table 8 39
Table 8. Record for selected wells near Pembroke, southeastern Massachusetts. —Continued

[All altitudes are above the National Geodetic Vertical Datum of 1929 (NGVD 29). USGS, U.S. Geological Survey; ft, foot; ft2/d, foot squared per day; gal/min, gallons per minute; gal/min/ft, gallons per minute per foot; -- , no data]

Local well number

or name

USGS

number

Year 

drilled

Altitude of

measuring

point above

NGVD 29

(ft)

Altitude

of land 

surface 

above 

NGVD 29 

(ft)

Total

depth

(ft)

Screened 

interval (ft)

depth 

below land 

surface

Range of 

water-level 

altitudes

(ft)

[period]

Transmissivity

(ft2/d)

Source of data Comments

Public-supply wells or well sites—Continued

Pembroke Test Well PEW 346 1981 -- 80 68.3 44–60 69.4 

[10/14/81]

 15,300 USGS files At location of Pembroke GPW 

#4.

Pembroke GPW #4 PEW 349 1984 -- 80 65 50–65 75.7

[5/24/84]

 11,800 Ground Water Associates, 

1997

Also known as Bryantville 

School Well.

Pembroke GPW #5 PEW 352 1999 -- 60 75 50–70 -- 8,500 Ground Water Associates, 

1997

Also known as Windswept Bogs 

Well.

Pembroke GPW #3 PEW 353 -- -- 60 62 -- -- 12,500 Ground Water Associates, 

1997

Also known as School Street 

Well.

Pembroke GPW #1 PEW 41 1955 -- 60 63 48–63 54

[4/1/57]

 4,500 Ground Water Associates, 

1997

Also known as Hobomock Well.

Wells that have multiple water-level measurements for 1998–2003

NAWQA well EBW 233 1998 -- 60 20 -- 52

[10/98]

 -- USGS files

Walmart CEA 1 HBW 124 -- -- 75 -- -- 61-68

[6/98–12/01]

 -- Corporate Environmental 

Advisors, Inc., 2002

Halifax YMCA well A HBW 125 -- -- 65 -- -- 43-47

[1/98–5/03]

 -- Richard Clark, Superintendent, Halifax Water 

Department, written commun., 2003

Halifax YMCA well B HBW 126 -- -- 65 -- -- 47-50

[1/98–4/03]

 -- Richard Clark, Superintendent, Halifax Water 

Department, written commun., 2003

Halifax Richmond Park 

CDM-3

HBW 127 -- -- 56 -- -- 42-51

[1/98–4/03]

 -- Richard Clark, Superintendent, Halifax Water 

Department, written commun., 2003

Camp Kiwanee drive 

point

HGW 152 2002 81 80 6 5.0–6.0 77-80

[10/02–9/03]

 -- This study

40 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Table 8. Record for selected wells near Pembroke, southeastern Massachusetts. —Continued

[All altitudes are above the National Geodetic Vertical Datum of 1929 (NGVD 29). USGS, U.S. Geological Survey; ft, foot; ft2/d, foot squared per day; gal/min, gallons per minute; gal/min/ft, gallons per minute per foot; -- , no data]

Local well number

or name

USGS

number

Year 

drilled

Altitude of

measuring

point above

NGVD 29

(ft)

Altitude

of land 

surface 

above 

NGVD 29 

(ft)

Total

depth

(ft)

Screened 

interval (ft)

depth 

below land 

surface

Range of 

water-level 

altitudes

(ft)

[period]

Transmissivity

(ft2/d)

Source of data Comments

Wells that have multiple water-level measurements for 1998–2003

Hanson C8-80 HGW 162 1981 55.96 53.8 -- -- 38–50

[6/83–9/03]

 -- Glen Doherty, Superintendent, Hanson Water 

Department, written commun., 2003

Hanson B10-80 HGW 163 1981 58.66 57.2 -- -- 38–50

[6/83–9/03]

 -- Glen Doherty, Superintendent, Hanson Water 

Department, written commun., 2003

Hanson T2-81 HGW 164 -- 56.83 54.9 -- -- 39–50

[6/83–9/03]

 -- Glen Doherty, Superintendent, Hanson Water 

Department, written commun., 2003

Cumberland Farms

ECS 12

HGW 165 -- -- 88 -- -- 79–82

[10/98–5/02]

 -- Xan Riddle, Environmental 

Compliance Services, written commun., 2002

USGS Obs. HGW 76 -- 72.5 71 26.6 24.6–26.6 64–68

[6/64–9/03]

 -- USGS files

NAWQA Forest St. well PEW 351 1999 130 130 23 18–23 118–121

[1/99–9/03]

 -- USGS files

Queensbrook Street 

drive point

PEW 354 2002 81 80 6 5.0–6.0 78–79

[11/02–9/03]

 -- This study

Well 3-14 PEW 355 1992 63.31 61.6 57 35–40 -- -- Camp Dresser & McKee, 

1992

Reported yield of 45 gal/min.

TW4-99 PEW 356 1999 64.48 -- 61.5 56.1–61.5 52–59

[8/02–9/03]

 -- Layne Geosciences, Inc., 

1999

Well 81-82 PEW 357 -- 68.14 -- 44 38–42 54–62

[8/02–9/03]

 -- Layne Geosciences, Inc., 

1999

Well C2 PEW 358 -- 70.34 -- 37 -- 61–67

[8/02–9/03]

 -- Layne Geosciences, Inc., 

1999

Well 79-6 PEW 359 -- 71.40 -- 60 50–55 52–62

[8/02–9/03]

 -- Weston & Sampson, 

written commun.

Sounded depth of 45 ft in 2003.

Table 8 41
Table 8. Record for selected wells near Pembroke, southeastern Massachusetts. —Continued

[All altitudes are above the National Geodetic Vertical Datum of 1929 (NGVD 29). USGS, U.S. Geological Survey; ft, foot; ft2/d, foot squared per day; gal/min, gallons per minute; gal/min/ft, gallons per minute per foot; -- , no data]

Local well number

or name

USGS

number

Year 

drilled

Altitude of

measuring

point above

NGVD 29

(ft)

Altitude

of land 

surface 

above 

NGVD 29 

(ft)

Total

depth

(ft)

Screened 

interval (ft)

depth 

below land 

surface

Range of 

water-level 

altitudes

(ft)

[period]

Transmissivity

(ft2/d)

Source of data Comments

Wells that have multiple water-level measurements for 1998–2003—Continued

Well 81-83 PEW 360 -- 64.63 -- 75 69–72 48–59

[8/02–9/03]

 -- Layne Geosciences, Inc., 

1999

Ambient (DPW garage) PEW 361 -- 79.21 -- 29.6 -- 60–70

[8/02–9/03]

 -- Weston & Sampson, 

written commun., 2003.

Sounded depth of 29.6 ft.

Pembroke Landfill 

NC-2A

PEW 362 -- -- 100 131 121–131 80–82

[9/97–6/02]

 -- Nangle Consulting 

Associates, Inc., 2002

Wells that have multiple historical water-level measurements

-- HGW 23 -- -- 83 19.2 -- 66–73

[12/57–9/59]

 -- Peterson, 1962 Depth to water ranged from 

10.03 to 17.45 ft.

-- EBW 27 -- -- 76 16.6 -- 67–75

[12/57–9/59]

 -- Peterson, 1962 Depth to water ranged from 0.99 

to 8.77 ft.

-- HBW 27 1957 -- 64 17.6 -- 50–55

[14/57–9/59]

 -- Peterson, 1962 Depth to water ranged from 9.08 

to 13.96 ft. 

-- HBW 28 -- -- 82 39 -- 47–60

[12/57–9/59]

 -- Peterson, 1962 Depth to water ranged from 

22.08 to 35.20 ft.

-- HBW 29 1957 -- 63 27.9 -- 45–57

[9/57–8/59]

 -- Peterson, 1962 Depth to water ranged from 

10.40 to 17.95 ft. 

-- HGW 45 -- -- 64 14 -- 53–55

[5/58–11/60]

 -- Peterson, 1962 Depth to water ranged from 9.47 

to 11.42 ft. 

-- HGW 55 1958 -- 70 29 -- 59–62

[10/58–10/60]

 -- Peterson, 1962 Depth to water ranged from 8.03 

to 11.10 ft. 

-- KGW 92 -- -- 67 12.1 -- 56–62

[12/57–9/59]

 -- Peterson, 1962 Depth to water ranged from 5.05 

to 10.53 ft. 

-- PEW 132 1900 -- 36 24.8 -- 28–34

[5/58–9/59]

 -- Peterson, 1962 Depth to water ranged 2.36 to 

7.89 ft. 

42 Simulated Ground-Water Flow for a Pond-Dominated Aquifer System near Great Sandy Bottom Pond, Pembroke, MA
Table 8. Record for selected wells near Pembroke, southeastern Massachusetts. —Continued

[All altitudes are above the National Geodetic Vertical Datum of 1929 (NGVD 29). USGS, U.S. Geological Survey; ft, foot; ft2/d, foot squared per day; gal/min, gallons per minute; gal/min/ft, gallons per minute per foot; -- , no data]

Local well number

or name

USGS

number

Year 

drilled

Altitude of

measuring

point above

NGVD 29

(ft)

Altitude

of land 

surface 

above 

NGVD 29 

(ft)

Total

depth

(ft)

Screened 

interval (ft)

depth 

below land 

surface

Range of 

water-level 

altitudes

(ft)

[period]

Transmissivity

(ft2/d)

Source of data Comments

Wells that have multiple historical water-level measurements—Continued

-- PEW 175 -- -- 27 13.6 -- 16–24

[10/57–10/59]

 -- Peterson, 1962 Depth to water ranged from 3.38 

to 10.57 ft. 

-- PEW 217 -- -- 110 12.5 -- 98–104

[12/57–11/60]

 -- Peterson, 1962 Depth to water ranged from 5.83 

to 11.73 ft.

-- PEW 218 -- -- 73 16.7 -- 62–72

[12/57– 11/60]

 -- Peterson, 1962 Depth to water ranged from 0.6 

to 11.2 ft. 

-- PEW 219 -- -- 97 19.2 -- 79–91

[10/57–10/59]

 -- Peterson, 1962 Depth to water ranged from 6.35 

to 18.54 ft. 

-- PEW 239 -- -- 32 15.1 -- 22–28

[5/58–10/59]

 -- Peterson, 1962 Depth to water ranged from 4.47 

to 9.87 ft. 

Table 8 43