U.S. Department of the Interior

U.S. Geological Survey

Ground-Water Flow and Saline Water in the 

Shallow Aquifer System of the Southern

Watersheds of Virginia Beach, Virginia

Water-Resources Investigations Report 03-4258

Prepared in cooperation with:

The City of Virginia Beach Department of Public Utilities
U.S. Department of the Interior

U.S. Geological Survey

Ground-Water Flow and Saline Water in the 

Shallow Aquifer System of the Southern 

Watersheds of Virginia Beach, Virginia

By Barry S. Smith

Water-Resources Investigations Report 03-4258

Prepared in cooperation with:

The City of Virginia Beach Department of Public Utilities

Richmond, Virginia

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of trade or product names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Government.

For additional information write to: Copies of this report can be purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

1730 East Parham Road Box 25286, Federal Center

Richmond, VA 23228 Denver, CO 80225-0286

e-mail: GS-W-VArmd DC

Information about water resources in Virginia is available on the World Wide Web at http://va.water.usgs.gov
Contents III

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

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

Background ..................................................................................................................................................................................... 3

Purpose and scope ........................................................................................................................................................................ 3

Description of the study area ....................................................................................................................................................... 3

Surficial geology ............................................................................................................................................................................. 4

Approach ......................................................................................................................................................................................... 7

Previous studies ............................................................................................................................................................................. 7

Acknowledgments ......................................................................................................................................................................... 9

Shallow Aquifer System of the Southern Watersheds ........................................................................................................................ 9

Hydrogeologic framework ............................................................................................................................................................ 9

Columbia aquifer ................................................................................................................................................................. 9

Yorktown confining unit ..................................................................................................................................................... 10

Yorktown-Eastover aquifer ................................................................................................................................................ 12

St. Marys confining unit ..................................................................................................................................................... 12

Hydraulic properties ...................................................................................................................................................................... 15

Horizontal hydraulic conductivities ................................................................................................................................. 15

Vertical hydraulic conductivities ...................................................................................................................................... 15

Ground-water recharge ..................................................................................................................................................... 20

Ground-water levels ...................................................................................................................................................................... 21

Saline Water in the Shallow Aquifer System ........................................................................................................................................ 25

Definitions ........................................................................................................................................................................................ 25

Chloride concentrations in the shallow aquifer system .......................................................................................................... 25

Conceptual model of ground-water flow ................................................................................................................................... 29

Simulation of Ground-Water Flow and Solute Transport .................................................................................................................... 30

Model assumptions and assumed properties ........................................................................................................................... 30

Boundaries and layers .................................................................................................................................................................. 32

Calibration and parameter estimation ........................................................................................................................................ 36

Sensitivity analyses ........................................................................................................................................................................ 41

Analyses of Ground-Water Flow and Saline-Water Intrusion ........................................................................................................... 44

Ground-water budget .................................................................................................................................................................... 44

Ground-water-flow patterns and chloride distributions .......................................................................................................... 44

Drawdowns near hypothetical well fields ................................................................................................................................. 47

Intrusion of saline water near a hypothetical well field .......................................................................................................... 47

Drawdowns around hypothetical open-pit mines .................................................................................................................... 52

Summary and Conclusions ...................................................................................................................................................................... 56

References Cited ....................................................................................................................................................................................... 58

Figures

1-8. Maps showing:

1. Location of the southern watersheds of Virginia Beach, Virginia, and the study area ........................................... 2

2. Land use in the southern watersheds .............................................................................................................................. 5

3. Surficial geology of the southern watersheds ............................................................................................................... 6

4. Land-surface altitudes of the southern watersheds ..................................................................................................... 11

5. Altitudes of the top of the Yorktown confining unit ........................................................................................................ 13

6. Altitudes of the top of the Yorktown-Eastover aquifer .................................................................................................. 14

7. Altitudes of the top of the St. Marys confining unit ....................................................................................................... 16

CONTENTS
IV Contents

8. Location of monitoring wells and selected aquifer-test wells ..................................................................................... 19

9-10. Graphs showing:

9. Long-term trends in ground-water levels of the shallow aquifer system .................................................................. 23

10. Seasonal trends in ground-water levels at Bellwood Estates Park (A), Bayside 

High School (B), Blackwater Park (C), and Creeds Elementary School (D) .............................................................. 24

11-13. Graphs showing:

11. Chloride distribution in the Columbia aquifer ................................................................................................................. 26

12. Chloride distribution in the Yorktown confining unit ...................................................................................................... 27

13. Chloride distribution in the Yorktown-Eastover aquifer ................................................................................................ 28

14. Toth's theoretical ground-water flow-patterns ...................................................................................................................... 29

15. Conceptual model of ground-water flow in the shallow aquifer system ........................................................................... 31

16. Grid, boundaries, and drains of the ground-water-flow and solute-transport models ................................................... 34

17. Layers and hydraulic properties of the calibrated model of the shallow aquifer system ............................................... 35

18. Simulated freshwater displacement of saline water, as indicated by chloride concentrations ................................... 38

19-22. Graphs showing:

19. Root mean square errors, absolute residual means, and residual means (A) and 

normalized root mean square errors (B) between measured and simulated chloride 

concentrations ..................................................................................................................................................................... 39

20 Differences between simulated and measured chloride concentrations (A) and 

simulated and measured water levels (B) ....................................................................................................................... 40

21. Sensitivity of the ground-water-flow model to changes in hydraulic conductivity ................................................. 42

22. Sensitivity of the ground-water-flow model to mutual changes in recharge 

rates and extinction depths ............................................................................................................................................... 43

23-28. Maps showing:

23. Simulated flow vectors and water levels in the lower half of the Columbia aquifer ............................................... 45

24. Simulated flow vectors and water levels in the sand aquifer of the 

Yorktown confining unit ...................................................................................................................................................... 46

25. Simulated flow vectors and water levels in the upper half of the 

Yorktown-Eastover aquifer ................................................................................................................................................ 48

26. Simulated chloride concentrations in the upper half the Yorktown-Eastover aquifer ............................................ 49

27. Simulated chloride concentrations in the lower half of the Yorktown-Eastover aquifer ........................................ 50

28. Drawdowns around two hypothetical well fields, each pumping 1,900 cubic meters per day .............................. 51

29. Horizontal view of simulated chloride concentrations approaching a hypothetical well field pumping 

1,900 cubic meters per day at start of pumping (A), after 33 years of pumping (B), after 67 years 

of pumping (C), and after 100 years of pumping (D) ............................................................................................................... 53

30. Vertical view of simulated changes in chloride concentrations near a hypothetical well field after 

100 years of pumping 1,900 cubic meters per day ................................................................................................................. 54

31. Simulated flow directions and drawdowns around two hypothetical open-pit mines .................................................... 55

Tables

1. Geologic age, geologic units, and hydrogeologic units of the shallow aquifer 

system at Virginia Beach, Virginia ............................................................................................................................................ 10

2. Horizontal hydraulic conductivities of the shallow aquifer system .................................................................................... 17

3. Vertical hydraulic conductivities of the shallow aquifer system ......................................................................................... 18

4. Ground-water-recharge rates in and near the southern watersheds ................................................................................ 20

5. Construction and water-level data for selected wells in the shallow aquifer system ..................................................... 22

6. Definition of water types with regard to seawater and chloride concentrations ............................................................ 25

7. Chloride concentrations in the shallow aquifer system ........................................................................................................ 61
Contents V

CONVERSION FACTORS, DATUMS, TRANSMISSIVITY, HYDRAULIC CONDUCTIVITY,

AND ABBREVIATED WATER QUALITY UNITS

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows: °F = 1.8 x °C + 32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). In this report, that vertical reference also is 

called sea level.

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

*Transmissivity: In this report transmissivity is expressed as square meter per day (m2/d)--The standard unit for transmissivity (T) is cubic meter per 

day per square meter times meter of aquifer thickness "[(m3

/d)/m2]m" or cubic foot per day per square foot times foot of aquifer thickness 

"[(ft3/d)/ft2]ft." These mathematical expressions reduce to square meter per day "(m2/d)" or square foot per day "(ft2/d)."

*Hydraulic conductivity: The standard unit for hydraulic conductivity is cubic meter per day per square meter of aquifer cross-sectional area 

(m3/d)/m2

. In this report, the mathematically reduced form, meter per day (m/d), is used for convenience.

Abbreviated water-quality units: Chemical concentration is reported in milligrams per liter (mg/L) or micrograms per liter (μg/L). Milligrams per liter 

is a unit expressing the concentration of chemical constituents in solution as mass (milligrams) of solute per unit volume (liter) of water. One thousand 

micrograms per liter is equivalent to 1 milligram per liter. For concentrations less than 7,000 mg/L, the numerical value is the same as for 

concentrations in parts per million. Specific conductance of water is reported in microsiemens per centimeter at 25 degrees Celsius (μS/cm).

Multiply By To obtain

millimeter (mm) 0.03937 inch (in)

centimeter (cm) 0.3937 inch (in)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

square centimeters (cm2) 0.155 square inch (in)

square kilometer (km2) 0.3861 square mile (mi2)

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 35.31 cubic foot (ft3)

kilogram (kg) 2.205 pounds (lbs)

grams per cubic centimeter (g/cm3) 62.43 pounds per cubic foot (lbs/ft3)

liter per second (L/s) 15.85 gallon per minute (gal/min)

cubic meter per day (m3/d) 264.2 gallon per day (gal/d)

meter per day (m/d)* 3.281 foot per day (ft/d)

square meter per day (m2/d)* 10.76 square foot per day (ft2/d)
Abstract 1

ABSTRACT

Population and tourism continues to grow in 

Virginia Beach, Virginia, but the supply of freshwater is limited. A pipeline from Lake Gaston supplies water for northern Virginia Beach, but 

ground water is widely used to water lawns in the 

north, and most southern areas of the city rely 

solely on ground water. Water from depths greater 

than 60 meters generally is too saline to drink. 

Concentrations of chloride, iron, and manganese 

exceed drinking-water standards in some areas. 

The U.S. Geological Survey, in cooperation with 

the city of Virginia Beach, Department of Public 

Utilities, investigated the shallow aquifer system 

of the southern watersheds to determine the distribution of fresh ground water, its potential uses, 

and its susceptibility to contamination.

Aquifers and confining units of the southern 

watersheds were delineated and chloride concentrations in the aquifers and confining units were 

contoured. A ground-water-flow and solute-transport model of the shallow aquifer system reached 

steady state with regard to measured chloride concentrations after 31,550 years of freshwater 

recharge. Model simulations indicate that if freshwater is found in permeable sediments of the 

Yorktown-Eastover aquifer, such a well field could 

supply freshwater, possibly for decades, but eventually the water would become more saline. The 

rate of saline-water intrusion toward the well field 

would depend on the rate of pumping, aquifer 

properties, and on the proximity of the well field to 

saline water sources. The steady-state, 

ground-water-flow model also was used to simulate drawdowns around two hypothetical well 

fields and drawdowns around two hypothetical 

open-pit mines. The chloride concentrations simulated in the model did not approximate the measured concentrations for some wells, indicating 

sites where local hydrogeologic units or unit properties do not conform to the simple hydrogeology 

of the model. 

The Columbia aquifer, the Yorktown confining 

unit, and the Yorktown-Eastover aquifer compose 

the hydrogeologic units of the shallow aquifer 

system of Virginia Beach. The Columbia and 

Yorktown-Eastover aquifers are poorly confined 

throughout most of the southern watersheds of 

Virginia Beach. The freshwater-to-saline-water 

distribution probably is in a dynamic equilibrium 

throughout most of the shallow aquifer system. 

Freshwater flows continually down and away from 

the center of the higher altitudes to mix with saline 

water from the tidal rivers, bays, salt marshes, and 

the Atlantic Ocean. Fresh ground water from the 

Columbia aquifer also leaks down through the 

Yorktown confining unit into the upper half of the 

Yorktown-Eastover aquifer and flows within the 

Yorktown-Eastover above saline water in the lower 

half of the aquifer. Ground-water recharge is minimal in much of the southern watersheds because 

the land surface generally is low and flat.

INTRODUCTION

The city of Virginia Beach encompasses 803 km2 of 

coastal lowlands and wetlands in southeastern Virginia. 

Land area of the city is 670 km2 and water 133 km2

(City of Virginia Beach Department of Economic 

Development, 2002, p.1). It is the most populous city in 

Virginia (425,257 citizens in the 2000 census) and 

attracted nearly 3 million tourists in the year 2000. 

Population and tourism continue to grow in Virginia 

Beach, but the supply of freshwater is limited. A pipeline from Lake Gaston supplies water for northern Virginia Beach, but ground water is widely used to water 

lawns in the north and most southern areas of the city 

rely solely on ground water (fig. 1).

Ground-Water Flow and Saline Water in the Shallow Aquifer 

System of the Southern Watersheds of Virginia Beach, Virginia

By Barry S. Smith
2 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 1. Location of the southern watersheds of Virginia Beach, Virginia, and the study area.

60

64

CHESAPEAKE

BAY

ATLANTIC

OCEAN

Intracoastal

Waterway

Landing

River

Back

Bay

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

Cape Henry

STUDY AREA

EXPLANATION

VIRGINIA

Lake Gaston

Chesapeake

Virginia Beach

Base from Mixon and others, 1989, 1:250,000

GREEN LINE—Boundary between northern and 

southern service areas of Virginia Beach

NORTH CAROLINA

STUDY

AREA

Western Reservoirs

Hampton

Roads

Currituck County,

North Carolina

COASTAL PLAIN

36o40'

36o

50'

76o 76o 10'

James River Lynnhaven Bay

64

13

60

264 Norfolk

North

TRANSITION AREA

TRANSITION AREA—Zoned for recreation, parks, 

and limited residential growth

Boundary of the Back Bay and North Landing 

River watersheds

West

Neck

Creek

Pembroke

Creek Bridge

London

Bypass

Canal
Introduction 3

Wells in Virginia Beach provide water from depths 

generally less than 60 m. The shallow aquifers supply 

water for drinking, lawn watering, irrigation, and heat 

pumps. The water-table aquifer also is partially dewatered, in places, by open-pit sand-and-gravel mines that 

can lower the water levels in nearby wells.

Supplies of fresh ground water are limited in many 

areas of Virginia Beach. Concentrations of chloride, 

iron, and manganese exceed drinking-water standards 

in some areas and water from depths greater than 60 m 

generally is too saline to drink. “Water that generally is 

considered unsuitable for human consumption or for 

irrigation because of high content of dissolved solids” 

is called saline (U.S. Geological Survey, 1985, p. 461). 

Most high production wells in and around Virginia 

Beach have had a history of increasing chloride concentrations with higher pumping rates.

Background

The city of Virginia Beach has a keen interest in 

preserving the limited supply of usable water in the 

shallow aquifers beneath the city. The U.S. Geological 

Survey (USGS), in cooperation with the Virginia Beach 

Department of Public Utilities, has revised the conceptual hydrogeologic framework of the shallow aquifer 

system beneath the city and has established a network 

of wells to measure water levels and water quality in 

the city (Smith and Harlow, 2002, p. 23). The purpose 

of this continuing cooperative project is to better understand the distribution of fresh ground water, its potential uses, and its susceptibility to contamination 

(Johnson, 1999, p. 2). 

Specific objectives of this phase of the investigation 

were to (1) map chloride concentrations in the southern 

watersheds of Virginia Beach within the context of the 

revised framework of the shallow aquifer system, (2) 

determine the patterns of ground-water flow in the 

southern watersheds, and (3) evaluate potential changes 

in drawdowns and chloride concentrations, representing saline-water intrusion, resulting from hypothetical 

withdrawals of ground water in the southern watersheds of Virginia Beach.

Purpose and Scope

Ground-water flow and the distribution of saline 

water in the southern watersheds of Virginia Beach are 

described in this report. A ground-water-flow and solute-transport model also is documented.

Chloride concentrations in the shallow aquifer system were mapped in the context of the revised hydrogeologic framework. The chloride data and average 

water levels were used to calibrate a ground-water-flow 

and solute-transport model. The calibrated model then 

was used to simulate drawdowns and potential changes 

in chloride concentrations (saline-water intrusion) 

resulting from hypothetical withdrawals of ground 

water. In this investigation, saline water was inferred 

from measured concentrations of naturally occurring 

chloride.

 This phase of the investigation focused on the 

southern watersheds of Virginia Beach. Ground water 

is the sole source of freshwater in the southern watershed and the distribution of land to water in the southern watersheds is more aggregated than that of the 

north, where many bays, lakes, rivers, and reservoirs 

separate the shallow aquifers into numerous local 

ground-water-flow regimes. More extensive well-data 

networks and a more detailed hydrogeologic framework would be needed for a similar analysis of the 

northern watersheds. Also, the rural nature of the 

southern watersheds renders a simpler conception of 

ground-water recharge with fewer hydrologic variables 

and assumptions to consider than that of the urban 

north.

Description of the Study Area

The southern watersheds of Virginia Beach encompass the coastal lowlands and wetlands draining into 

the North Landing River and the Back Bay (fig. 1). The 

watersheds and the study area, which constitutes most 

of the watersheds, are in the Coastal Plain Physiographic Province of southeastern Virginia. The average 

altitude of Virginia Beach is 4 m above sea level. From 

1895 to 2001, the average annual air temperature was 

15o C (59o F) and average annual precipitation was 120 

cm at Norfolk, Va., which is adjacent to Virginia Beach 

(National Climatic Data Center, 2002). About 18 cm of 

snow falls each year.

The North Landing River and the Back Bay are 

tidal. The North Landing River is connected to the 

Intracoastal Waterway to the west through the city of 

Chesapeake, Va., by the Intracoastal Waterway (Albemarle and Chesapeake Canal) and to the north, just 

beyond the southern watersheds, through northern 
4 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Virginia Beach by West Neck Creek, London Bridge 

Creek, and the Bypass Canal. The North Landing River 

and the Back Bay are connected to Currituck Sound 

south of the study area in Currituck County, N.C.

The Back Bay watershed includes wetlands, barrier 

beaches, and dune sands adjacent to the Atlantic 

Ocean, but the narrow strip of land adjacent to the 

ocean east of the bay probably is isolated from the rest 

of the watershed with respect to ground-water flow, and 

was not included as a part of the study area. The watershed of the North Landing River also includes the part 

of the city of Chesapeake, Va., that is immediately west 

of Virginia Beach. Currituck County, N.C. is immediately south of the study area.

The northern and western perimeters of the watersheds are within the commercial, residential, and transportation sectors of Virginia Beach and Chesapeake, 

Va., which generally were built on or raised to slightly 

higher altitudes than the surrounding areas (fig. 2). The 

watershed boundaries generally follow the higher altitudes, but also can follow subtle changes in altitude 

along and across roads or drainage ditches adjacent to 

roads and air-strip runways.

A “Green Line” and Transition Area mark a 

planned separation between the populated, urban northern service area of Virginia Beach and the relatively 

unpopulated, rural southern service area (fig. 1). Pungo 

and Blackwater boroughs, which together form most of 

the southern service area, had an estimated 5,200 residents combined in 1996 (City of Virginia Beach 

Department of Planning, 1996, p. 10). 

Agriculture and wetlands dominate land use in the 

southern watersheds. Pasture, hay, and row crops are 

common on higher ground whereas woody and herbaceous wetlands remain at the lower altitudes.

Surficial Geology

Holocene (recent) and Pleistocene (glacial and 

interglacial) sediments form the present landscape of 

Virginia Beach. The Holocene sediments have been 

deposited in the estuaries, swamps, marshes, rivers, and 

on the banks of streams, dunes, and shorelines since the 

end of the last major glacial advance about 11,500 

years ago. Before then, Pleistocene sediments were 

deposited in similar coastal settings. The Pleistocene 

deposits of the Tabb Formation form most of the landscape of the southern watersheds of Virginia Beach 

(fig. 3). The Tabb has been divided from oldest to 

youngest into the Sedgefield, Lynnhaven, and Poquoson Members (Johnson and Berquist, 1989, p. 16).

The Sedgefield Member of the Tabb Formation 

rises to about 6 to 8 m above sea level in the southern 

watersheds. It forms Oceana Ridge in Virginia Beach, 

the southernmost tip of which marks the northeastern 

juncture of the southern watersheds. The Sedgefield 

also forms much of the higher ground west of Hickory 

Scarp in Chesapeake, Va., marking the northwestern 

boundary of the southern watersheds north of the Albemarle and Chesapeake Canal and the high ground near 

the western boundary south of the Canal. The Sedgefield Member was deposited in a shallow sea about 

70,000 years ago (Mixon and others, 1989, sheet 1, 

description of map units).

The Sedgefield Member is a pebbly to bouldery, 

clayey sand and fine to medium shelly sand grading 

upward to sandy and clayey silt. Paleochannel fill up to 

15 m thick composes the bottom of the Sedgefield 

Member found beneath some of the major tidal rivers 

of southeastern Virginia. This fill is a fine to coarse, 

cross-bedded sand and clayey silty peat, interbedded 

with tree stumps and wood fragments of ancient forests. The fill has been identified at the base of the lower 

member of the Great Bridge Formation of Oaks and 

Coch (1973, p. 67), which correlates to the base of the 

Sedgefield Member (Peebles and others, 1984, p. 14). 

One such paleochannel lies beneath the North Landing 

River in the southern watersheds. The bottom of the 

broad paleochannel is 18 to 21 m below sea level (Oaks 

and Coch, 1973, fig. 13, p. 50). Broad tidal wetlands 

along the North Landing River identified as soft mud 

on the map of surficial geology probably are a geomorphic expression of the ancient paleochannel.

The Lynnhaven Member of the Tabb Formation 

forms much of the low, flat, poorly drained ground of 

Virginia Beach and the southern watersheds. The Lynnhaven forms the surficial deposits of the North Landing 

River watershed generally less than 6 m above sea 

level. It stretches from the west side of Pungo Ridge to 

Hickory Scarp and from Lynnhaven Bay beyond the 

northern boundary of the southern watersheds to the 

southern city limits along the North Carolina border. It 

is a gray, pebbly and cobbly, fine to coarse sand, grading upward into clayey and silty fine sand and sandy 

silt. Channel fill and abundant plant material are found 

at the base of the unit in some places. 

The Poquoson Member of the Tabb Formation 

forms the east side of Pungo Ridge just west of the 

Back Bay of Virginia Beach from sea level to about 
Introduction 5

Figure 2. Land use in the southern watersheds of Virginia Beach, Virginia.3.3 m above sea level (Mixon and others, 1989, sheet 1). 

36o40'

36o

50' 76o

10' 76o

Residential

Commercial/Industrial/

Transportation

Beaches/Sand/Clay

Transitional/Quarries/

Borrow pits

Evergreen forest

Deciduous forest

Pasture/Hay

Row crops

Urban grasses

Woody wetlands

Emergent herbaceous

wetlands

EXPLANATION

LAND USE

GREEN LINE—Boundary between northern and 

southern service areas

North

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Base from Mixon and others, 1989, 1:250,000

Virginia and State and Federal land from Virginia 

Council on the Environment, 1992, 1:100,000

Land use from U.S. Environmental Protection

Agency Multi-Resolution Land Characteristics 

National Land Cover Data, 1995, 30 meter 

resolution

Intracoastal

Waterway

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

Boundary of the Back Bay and North Landing 

River watersheds
6 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 3. Surficial geology of the southern watersheds of Virginia Beach, Virginia.

Lynnhaven Member

Poquoson and Lynnhaven Member 

Poquoson Member

Sedgefield Member

Soft mud

Sand

Artificial fill

HOLOCENE

TABB FORMATION

EXPLANATION

36o

40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Back

Bay

Intracoastal

Waterway

North

Chesapeake

Virginia Beach

Geology from Mixon and others, 1989, Virginia Geology, 1:250,000

Boundary of the Back Bay and North Landing 

River watersheds

PLEISTOCENE

Erosional scarp

PUNGO

RIDGE

RIDGE

OCEANA

HICKORY

SCARP

West

Neck

Creek

Creek Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS
Introduction 7

It is a gray, medium to coarse, pebbly sand grading 

upward into a clayey, fine sand and silt. Some of the 

sand deposits of Pungo Ridge were formed as a coastal 

barrier and are a part of the Poquoson Member. 

Approach

The revised conceptual hydrogeologic framework 

of the shallow aquifer system was based primarily on 

continuous cores and downhole geophysical logs from 

7 sites, each approximately 60 m deep (Smith and Harlow, 2002, p. 8 and 9). That framework was extended in 

this study to other sites in and around the southern 

watersheds using lithologic descriptions and geophysical logs collected by previous investigators and filed in 

local, State, and Federal databases.

The basic geometry of the shallow aquifer system 

was contoured by linear variogram Kriging using 

Surfer®7 from Golden Software, Inc. Concentrations of 

chloride collected during this investigation and from 

previous studies also were contoured by linear Kriging 

using Surfer7 to map the general distribution of chloride concentrations and to infer freshwater to saline 

water gradients in the hydrogeologic units of the shallow aquifer system. 

 The land-surface altitudes of the southern watersheds of Virginia Beach likewise were contoured using 

data from USGS digital elevation models; the contoured surfaces then were imported into Visual MODFLOW®, Waterloo Hydrogeologic, Inc., to represent 

the basic framework of the shallow aquifer system and 

the geometry of the ground-water-flow and solutetransport model. A regionally continuous marine 

deposit of generally low permeability was contoured to 

mark the bottom of the shallow aquifer system and of 

the model. Three conceptual hydrogeologic units that 

constitute the shallow aquifer system were divided further into seven layers to represent the most common 

local configuration of the aquifers and confining units 

of the southern watersheds.

Average water levels from 38 wells and the chloride 

measurements from 123 wells were imported into 

Visual MODFLOW to provide calibration points. The 

parameter estimator WinPEST® as incorporated into 

Visual MODFLOW was used with the water-level data 

to adjust the hydraulic conductivities of the units. 

(Windowsis a trademark of Microsoft Corporation. 

PEST is a trademark of Watermark Numerical Computing.)

Limits to the horizontal and vertical hydraulic conductivities for WinPEST were determined from the 

data reported in previous studies in and around Virginia 

Beach. For the calibration, the ground-water-flow 

model was assumed to be in steady state with average 

annual water levels. 

Initially, saline water was assigned throughout the 

solute-transport model. Freshwater recharge was 

applied steadily to the simulated land surface of the 

model for about 35,000 years, until a new steady state 

with measured concentrations of chlorides was approximated. The calibrated ground-water-flow and solute-transport model then was used to simulate 

drawdowns around hypothetical well fields and 

open-pit mines and the movement of chloride concentrations toward a hypothetical well field.

Previous Studies

Geraghty and Miller (1978, p. 11) defined a leaky 

aquifer system beneath Virginia Beach composed of 

the “Water-Table Aquifer (mostly Columbia Group)” 

and the confined “Yorktown Aquifer (upper part of the 

Yorktown Formation),” as well as units below the shallow aquifer system that were presumed to contain 

“brackish to salty water.” Based on geology and a controlled test of the “Yorktown Aquifer” at the Pembroke 

well field in Virginia Beach, Geraghty and Miller 

(1979, p. 5 and 35) reported the potential for upconing 

of “brackish water known to be present at depths of 100 

to 200 ft below land surface” (fig. 1).

Betz-Converse-Murdoch, Inc. (1981, p. II-1), conducted an investigation for fresh ground water in Virginia Beach, particularly in the southern watersheds of 

the city. Dewatering of large sand pits indicated possible supplies of freshwater from the water-table aquifer 

(p. IV-6). However, large productive well fields from 

the “upper Yorktown aquifer” were precluded over 

much of the city by the limited extent of permeable 

sediments (p. IV-7). Some southern areas of the city 

possibly could supply ground-water supplies, if treated 

to remove iron and manganese (p. II-1 and II-2), but 

problems with finding enough ground water to support 

the city’s needs were limited primarily because of the 

potential for upconing or intrusion of “salt water” 

(p. IV-7). 

Geotrans Inc. (1981, p. 12 and 13) analyzed aquifer 

tests at four sites in the southern watersheds using solute-transport simulations. Fair to poor potential for 
8 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

water supplies were reported based on water-level 

declines. All of the sites were at risk of “brackish 

water” upconing (p. ii and p. 12). Increases in chloride 

concentrations observed in some “deeper” wells during 

the aquifer tests were not caused, however, by upconing, but were possibly contributed by clay deposits 

within the aquifer.

Siudyla and others (1981, p. 18-27) defined a 

“water-table aquifer” and three generally continuous 

sand units in the “Yorktown aquifer” of southeastern 

Virginia, including Virginia Beach, on the basis of geophysical and geologic logs, including some research 

wells. The thickness, permeability, and coarseness of 

the units, however, varied considerably from one point 

to another. They also noted that well fields in the Yorktown aquifer could cause “lateral salt water encroachment, and upconing of brackish water from underlying 

strata” (p. 84 and 85). 

Leahy (1986, p. 44) summarized the potential for 

desalinating brackish water and seawater for southeastern Virginia and Virginia Beach. He compared the 

long-term price of finished water from desalination to 

that of building a pipeline to Lake Gaston (p. 43).

 Meng and Harsh (1988, p. C52) defined the 

regional aquifer system of the Coastal Plain of Virginia 

including Virginia Beach. They recognized the unconfined Columbia aquifer, the Yorktown confining unit, 

and the confined Yorktown-Eastover aquifer, as well as 

deeper units in the Coastal Plain. 

Hamilton and Larson (1988, p. 4) analyzed the 

aquifer systems of southeastern Virginia by use of a 

three-dimensional, digital ground-water-flow model. 

They reported vertical recharge to the Yorktown-Eastover aquifer beneath the higher ground of Virginia 

Beach, but upward discharge from the aquifer beneath 

the low areas, back bays, and off shore (fig. 74, p. 108). 

They also showed some areas in and near Virginia 

Beach where ground-water discharge to the water-table 

aquifer was reduced because of local pumping (fig. 66, 

p. 100) and noted that saline water probably began 

infiltrating the shallow confined aquifers offshore 

beneath the Atlantic Ocean, Chesapeake Bay, and the 

James River estuary in the 1950’s (p. 169).

Harsh and Laczniak (1990, p. F4) described the 

hydrogeologic units of the Coastal Plain of Virginia 

and analyzed ground-water flow in the region and adjacent parts of North Carolina by use of a three-dimensional, digital ground-water-flow model. They showed 

downward flow of ground water into the Yorktown-Eastover aquifer in the northern parts of Virginia 

Beach and upward flow from the Yorktown-Eastover in 

most of the southern parts prior to pumping (fig. 41, 

p. F50). Pumping simulated for 1980 indicated downward flow into the Yorktown Eastover aquifer that had 

been upward prior to pumping in a small area of the 

southwestern part of Virginia Beach (fig. 63, p. F71).

As part of the USGS National Water-Quality 

Assessment (NAWQA) Program, Spruill and others 

(1998, p. 24) analyzed the ground-water chemistry of 

the shallow aquifers in the southern watersheds of Virginia Beach. They indicated that concentrations of dissolved solids under the urban area of the southern 

watersheds of Virginia Beach were ranked between the 

median and the 75th percentile of the national average 

of the 20 aquifer systems sampled (p. 24-25).

After the discovery of the Chesapeake Bay impact 

crater at the mouth of the Chesapeake Bay, Powars 

(2000, p. 4) refined the geologic framework of southeastern Virginia. He indicated that the Yorktown, Eastover, and St. Marys Formations are continuous across 

the region, but that the Chowan River Formation is not 

extensive in Virginia (p. 37). Powars also correlated the 

geologic units to the hydrogeology south of the James 

River in three core holes, which showed the need for 

further refinements of the hydrogeologic framework. 

He indicated that the Columbia aquifer of previous 

investigators is in the Tabb and Yorktown Formations 

in the core holes near Virginia Beach, and that the Calvert confining unit of Hamilton and Larson (1988) predominantly is within the St. Marys Formation (Powars, 

2000, p. 42).

Smith and Harlow (2002, p. 23) refined the conceptual framework of the shallow aquifer system primarily 

on the basis of seven continuous cores and geophysical 

logs. They confirmed that the unconfined Columbia 

aquifer, the Yorktown confining unit, and the confined 

Yorktown-Eastover aquifer compose the shallow aquifer system at Virginia Beach and that the shallow system is separated from deeper units by the St. Marys 

confining unit. They also noted that some sand deposits 

in the Yorktown confining unit supply “small to moderate amounts of freshwater in some areas” but that on a 

regional scale the confining unit is leaky (Smith and 

Harlow, 2002, p. 26). They reported deposits of biofragmental sand in the Yorktown-Eastover aquifer at 

some sites and noted that the extent and hydraulic properties of the biofragmental sand needed further study 

(Smith and Harlow, 2002, p. 30).
Shallow Aquifer System of the Southern Watersheds 9

Acknowledgments

The author thanks the citizens of Virginia Beach 

and the Virginia Beach Department of Public Utilities, 

Water Resources Division, for their cooperation and 

support of the shallow ground-water study. Thomas M. 

Leahy, III, and Rebecca L. Mitchel of the Department 

of Public Works particularly were helpful.

Various USGS employees contributed to this study 

and report. Former project chiefs Alan R. Brockman 

and Henry M. Johnson, IV, organized much of the 

background information, previous data, and resources 

for the initial phases of the project. Previous project 

chief George E. Harlow, Jr., organized and managed the 

coring, well installation, and water sampling and was 

the principal hydrologist of the revised hydrogeologic 

framework. USGS employees Roger M. Moberg and 

Karl M. Dydak collected water-level and water-quality 

data and maintained the network wells. R. Brent 

Banks, III, coded and entered information into USGS 

databases and prepared the illustrations of this report. 

Ted B. Samsel of the USGS also is acknowledged for 

preparing base maps, illustrations, and for his assistance with geographic information systems. Martha L. 

Erwin of the USGS edited this report. Colleagues Mark 

D. Kozar and William Fleck of the USGS provided 

technical review comments.

SHALLOW AQUIFER SYSTEM OF THE 

SOUTHERN WATERSHEDS

The revised conceptual hydrogeologic framework 

of the shallow aquifer system from Smith and Harlow 

(2002, p. 23) was extended in this study to other sites in 

and around the southern watersheds on the basis of 

lithologic descriptions and geophysical logs collected 

by previous investigators and filed in local, State, and 

Federal databases. 

Hydrogeologic Framework

The shallow aquifer system is composed of the 

Columbia aquifer, the Yorktown confining unit, and the 

Yorktown-Eastover aquifer (table 1). The St. Marys 

confining unit separates the shallow aquifer system 

from deeper units.

Columbia Aquifer

The Columbia aquifer of the Virginia Coastal Plain 

is defined as the predominantly sandy surficial deposits 

above the Yorktown confining unit (Meng and Harsh, 

1988, p. C52). The Columbia sediments are, for the 

most part, of the Holocene and Pleistocene ages but 

also can include sandy sediments of Pliocene age above 

the Yorktown confining unit.

The Holocene sediments have been deposited in the 

estuaries, swamps, marshes, rivers, and on the riverbanks, stream banks, dunes, and shorelines since the 

end of the last major glacial advance about 11,500 

years ago. Before then, Pleistocene sediments were 

deposited in similar coastal settings, primarily during 

marine transgressions as the continental ice sheets 

melted and during high stands of the ancient seas of the 

Late Pleistocene (Peebles and others, 1984, p. 20). 

Pleistocene deposits of the Tabb Formation form much 

of the Columbia aquifer, as well as much of the landscape of the southern watersheds of Virginia Beach.

 The Columbia aquifer is unconfined generally, and 

the top of the aquifer is the water table. In a humid climate, the water table closely follows the contours of 

the land surface; therefore, altitudes of the land surface 

can be used to approximate the top of the aquifer. For 

the top of the study area, digital elevation models of 

7.5-minute quadrangles were merged from the National 

Elevation Database of the USGS in 2002 (fig. 4). The 

merged data were contoured by linear Kriging using 

Surfer7 and imported as the top of the groundwater-flow model of the southern watersheds.

Although the Columbia aquifer is unconfined generally, deposits of silt, clay, and peat within the aquifer 

can cause confined or semi-confined conditions, locally 

inhibiting infiltration of freshwater. In other areas, the 

clayey fine sand and silt that form semi-confining beds 

in the Columbia are absent, and the aquifer is composed of dune sand nearly 24 m thick (Smith and Harlow, 2002, p. 26). The Columbia aquifer reaches a 

maximum thickness where the sand dunes are large, 

along the shores of the Atlantic Ocean, and in the older 

sand banks such as Pungo Ridge.

The Columbia aquifer is recharged by local precipitation. Dunes and sand ridges allow precipitation to 

infiltrate readily and ground water percolates downward to the water table. The water table tends to mound 

beneath the dunes and the mound forces freshwater to
10 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

flow downward and outward toward the nearest tidal 

stream or shore, where the freshwater flows into and

mixes with saline water. Betz-Converse-Murdoch, Inc. 

(1981, p. IV-6 and IV-7), noted that “large quantities of 

water have been and are being pumped from many of 

the sand pits of Virginia Beach, which indicates that the 

’water-table’ aquifer potentially could yield significant 

quantities of water . . .”. However, the water-table aquifer is vulnerable to contamination from various land 

uses and generally is used for irrigation, lawn watering, 

or for heat pumps. The Columbia is used for domestic 

drinking water where no other sources of freshwater 

are available. Concentrations of dissolved chloride, 

iron, and manganese greater than the Secondary Drinking Water Regulations of the U.S. Environmental Protection Agency (USEPA) (2002, p. 10) have been 

reported in some areas of Virginia Beach in previous 

reports.

Yorktown Confining Unit

The Yorktown confining unit is defined as a series 

of coalescing clay layers at or near the top of the Yorktown Formation (Meng and Harsh, 1988, p. C51). The 

Yorktown confining unit is not a single continuous 

layer but a series of very fine, sandy to silty clay units 

of various colors at the top of the Yorktown Formation 

(p. C51). The Yorktown Formation was deposited during a succession of marine advances in the Early and 

Late Pliocene Epoch (Johnson and Berquist, 1989, 

p. 11). The top of the Yorktown Formation in southeastern Virginia was mapped by Oaks and Coch (1973,

Table 1. Geologic age, geologic units, and hydrogeologic units of the shallow aquifer system at Virginia Beach, Virginia

Series Geologic unit1 Hydrogeologic unit

Holocene

Pleistocene

Pliocene

Chowan River Formation

Tabb Formation

Post-glacial deposits

Miocene

Yorktown Formation

Eastover Formation

St. Marys Formation

Yorktown confining unit

Yorktown-Eastover aquifer

St. Marys confining unit

Columbia aquifer

Shallow Aquifer System

1After Powars (2000, p. 45-52).
Shallow Aquifer System of the Southern Watersheds 11

Figure 4. Land-surface altitudes of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

High value: 5

Low value: 0

VALUE, IN METERS

EXPLANATION

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

North

Base from Mixon and others, 1989, 

Virginia Geology, 1:250,000

Digital Elevation Model data from

U.S. Geological Survey, National 

Elevation Database, 2002, 30 meter resolution

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

Boundary of the Back Bay and North Landing 

River watersheds

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS
12 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

fig. 13, p. 50), who described a fossiliferous clay facies 

with minor amounts of sand and coquina at the top of 

the Yorktown Formation south and east of Portsmouth 

and Norfolk, Va. Ancient streams and estuaries cut valleys into the top of the Yorktown Formation and subsequently filled the channels with sediments, forming 

paleochannels upon the surface, one of which was 

mapped below the North Landing River.

The uppermost competent clays that form the Yorktown confining unit were deposited on a shallow 

marine shelf in broad lagoons and bays (Meng and 

Harsh, 1988, p. C52). Locally, the fine-grained sediments of the Pleistocene Tabb Formation and possibly 

the Pliocene Chowan River Formation (Powars, 2000, 

fig. 13, p. 42) may lie upon and in effect be a part of the 

Yorktown confining unit (table 3). The Chowan River 

Formation is difficult to distinguish from the Yorktown; 

the Chowan River Formation is an interbedded, silty 

fine sand, clayey silt, and bioclastic sand of limited 

extent in southeastern Virginia (Powars, 2000, p. 37).

The Yorktown confining unit varies in thickness 

and in composition (Smith and Harlow, 2002, p. 26). 

The top of the Yorktown confining unit ranges from 

about 7 to 18 m below sea level in and near the southern watersheds of Virginia Beach (fig. 5). Some of the 

lower altitudes of the top of the Yorktown confining 

unit could indicate paleochannels carved into the surface. The altitudes were plotted and contoured by linear 

variogram Kriging.

On a regional scale, the Yorktown confining unit is 

leaky. Some sand layers within the confining unit that 

had been mapped previously as the upper and middle 

Yorktown-Eastover aquifers are considered, in this 

report, to be local discontinuous sand units within the 

more regional confining unit. These discontinuous sand 

deposits are capable of producing small to moderate 

amounts of freshwater in some areas. The supply of 

freshwater in the discontinuous sands of the Yorktown 

confining unit is limited, however, by concentrations of 

dissolved iron, manganese, and chloride that are greater 

than the Secondary Drinking Water Regulations of the 

USEPA (2002, p. 10). The potential for upconing or 

intrusion of brackish or saline water into the sand units 

of the Yorktown also is a concern in some areas.

Yorktown-Eastover Aquifer

The Yorktown-Eastover aquifer is defined as the 

predominantly sandy deposits of the Yorktown Formation and the upper part of the Eastover Formation above 

the confining clays of the St. Marys Formation (Meng 

and Harsh, 1988, p. C50). The Yorktown-Eastover 

aquifer previously was called the Yorktown aquifer by 

some investigators in Virginia (Geraghty & Miller, Inc., 

1978, p. 12) and in North Carolina (Meng and Harsh, 

1988, pl. 1). The Yorktown-Eastover aquifer as defined 

in this report is equivalent generally to the lower Yorktown aquifer of some previous investigators (Siudyla 

and others, 1981, p. 27). 

The Yorktown Formation is a bluish-gray, greenishand dark greenish-gray, very fine to coarse sand, in part 

glauconitic and phosphatic, commonly very shelly and 

interbedded with sandy and silty clay (Powars, 2000, p. 

37). The Yorktown also includes abundant microfauna 

and cross-bedded, biofragmental lenticular sand bodies, which locally may be overlain by and difficult to 

distinguish from the Chowan River Formation. The 

Yorktown Formation was deposited in the Pliocene.

 The Eastover Formation is dark gray, bluish-to 

greenish-gray, muddy fine sand interbedded with finer 

and coarser grained sand (Powars, 2000, p. 37). It can 

include shells, shell hash, and indurated beds. Locally, 

it may be glauconitic and micaceous. The Eastover was 

deposited in restricted to open shallow seas of the 

Miocene (Powars, 2000, p. 37). 

In the southern watersheds of Virginia Beach, the 

top of the Yorktown-Eastover aquifer varies from about 

23 to about 37 m below sea level (fig. 6). The top surface undulates and generally is higher to the west and 

along Pungo Ridge than elsewhere.

On a regional scale, the Yorktown-Eastover aquifer 

generally thickens towards the east. At Virginia Beach, 

it generally ranges from about 30 to 60 m thick, but 

attains a maximum known thickness at the shoreline of 

Virginia Beach of about 73 m, according to Meng and 

Harsh (1988, p. C50), to 85 m, according to Hamilton 

and Larson (1988, p. 33).

The Yorktown-Eastover aquifer generally is confined. Freshwater is limited to the upper part of the 

Yorktown-Eastover aquifer, and “upconing [of saline 

water] as a result of excessive withdrawal rates from 

wells has occurred at several locations in the city” 

(Betz-Converse-Murdoch, Inc., 1981, p. IV-7). 

St. Marys Confining Unit

The top of the St. Marys confining unit, a regionally 

continuous deposit of generally low permeability, 

marks the bottom of the shallow aquifer system 

(Powars, 2000, p. 37). The St. Marys Formation is
Shallow Aquifer System of the Southern Watersheds 13

Figure 5. Altitudes of the top of the Yorktown confining unit of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

Boundary of the Back Bay and North Landing 

River watersheds

Study area

-10

-12

-14

-8

-12

-14

-10

-8

-12

-14

-10

-14

-12

-14

-8

-10

-16

-6

-12

-7

-12

-8

-14

-12

-14

-9

-16

-12 -15

-14

-13

-16

-7

-14

-11

-9 -7

-15 -18

-16 -14

-10

-9

-8

-9

-12

-7

-8

-11

-11 -15

-17

-11

-12 -6

-12

-12

-11

-9

-10

-7 -8

-7

-14

-15

-13 -11 -14

-13 -14

-14

-14

-15

LINE OF EQUAL ALTITUDE—Contour interval 2 meters.

Vertical datum is NGVD 29

TEST HOLE AND ALTITUDE OF TOP OF THE 

YORKTOWN CONFINING UNIT—Altitude in meters. 

Vertical datum is NGVD 29

-8

-10

EXPLANATION

North

Base from Mixon and others, 1989, 1:250,000

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS
14 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 6. Altitudes of the top of the Yorktown-Eastover aquifer of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

Boundary of the Back Bay and North Landing 

River watersheds

Study area

LINE OF EQUAL ALTITUDE—Contour interval 2 meters.

Vertical datum is NGVD 29

TEST HOLE AND ALTITUDE OF TOP OF THE 

YORKTOWN-EASTOVER AQUIFER—Altitude in meters. 

Vertical datum is NGVD 29

-36

-24

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

-34

-32

-30

-26

-28

-24

-32

-30

-26

-28

-34

-24

-26

-32

-30

-26

-34

-27

-30

-33

-33

-35

-25

-26

-23

-28

-26

-29

-29

-33 -37 -37

-25

-22

-24

-23

-37

-30 -27

-26 -25

-28

-30

-27

-27

-31 -28

-28 -36

-27

-27

-28

-27 -27 -26

-36

-29

-28

-28

-27 -28

-27

EXPLANATION

North

Base from Mixon and others, 1989, 1:250,000

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal
Shallow Aquifer System of the Southern Watersheds 15

composed of mostly muddy, very fine sand and sandy 

clay and silt deposits of marine origin (Powars, 2000, 

p. 37). The St. Marys confining unit, in places, also 

includes clays of the overlying Eastover Formation 

(Meng and Harsh, 1988, p. C50). Within the southern 

watersheds of Virginia Beach, the top of the St. Marys 

confining unit, which is the bottom of the shallow aquifer system, varies from about 80 to 110 m below sea 

level. 

Hydraulic Properties

The sediments that compose the shallow aquifer 

system were deposited in shifting currents of an everchanging coastal environment. The extent of and the 

hydraulic properties of such poorly sorted (heterogeneous) units can vary considerably over relatively short 

distances. Previous investigators have estimated the 

hydraulic properties of the aquifers and confining units 

of the shallow aquifer system in southeastern Virginia 

by various methods. However, the sampled volume of 

the aquifer or confining unit tested depends on the 

method. Sample volumes can range from cubic centimeters analyzed by sieves and permeameters, to cubic 

meters of single-well (slug) tests or specific-capacity 

tests, to the field scales of aquifer tests with multiple 

wells, to ground-water-flow models that usually represent hydraulic properties from the field scale to the 

watershed or even regional scales. For this study, the 

hydraulic conductivities estimated by previous investigators were used to set minimum, initial, and maximum limits for a parameter estimator (WinPEST) that 

was used to calibrate the ground-water-flow model.

Horizontal Hydraulic Conductivities

 Horizontal hydraulic conductivities of the Columbia aquifer from previous studies in southeastern Virginia ranged from 1 to 23 m/d (table 2). The average 

hydraulic conductivity probably was in the range from 

6 to 9 m/d. 

Horizontal hydraulic conductivities of the Yorktown confining unit varied, depending on the material 

tested. In the previous studies, clay and silt units ranged 

from 0.0003 to 6 m/d. Sand units in the Yorktown 

ranged from 0.4 to 16 m/d with an average probably 

from 6 to 9 m/d.

Horizontal hydraulic conductivities of the Yorktown-Eastover aquifer ranged from 0.4 to 7.7 m/d in 

previous studies. The average hydraulic conductivity 

probably was about 4 m/d.

Vertical Hydraulic Conductivities

Vertical hydraulic conductivities of the Columbia 

aquifer in southeastern Virginia ranged from 0.000052 

to 0.052 m/d (table 3) and averaged about 0.02 m/d. 

The maximum and minimum of the range came from 

five permeameter tests of sediment cores with a median 

of 0.02 m/d. A vertical conductivity of 0.02 m/d also 

was used to calibrate a ground-water-flow model of the 

same area where the cores were taken (Smith, 2001, 

p. 9). 

An aquifer test encompassing confining beds in the 

Columbia aquifer, 62B 9 (fig. 8), within the southern 

watersheds of Virginia Beach had a narrower range 

from 0.0030 m/d in the lower confining bed to 0.015 

m/d in the upper confining bed (Geotrans, Inc., 1981, 

p. 16) and would have an average of 0.0090 m/d if 

combined. 

Vertical hydraulic conductivities of the Yorktown 

confining unit ranged from 0.000004 m/d to 0.002 m/d 

in previous studies and averaged 0.00058 m/d. The 

lowest value was from a laboratory analysis of a sediment core (Richardson, 1994a, p. 19) and the highest 

value was from a calibrated ground-water-flow model 

(Smith, 2001, p. 9). Results from calibrated flow models of southeastern Virginia, however, indicated lower 

vertical hydraulic conductivities of 0.00026 m/d 

(Hamilton and Larson 1988, p. 60; Harsh and Laczniak, 1990, p. F94). Values from two aquifer tests of 

the Yorktown confining beds in the southern watersheds of Virginia Beach, 63C 25 and 62C 25 (fig. 8), 

were in and near the middle range (Geotrans, 

Inc.,1981, p.16).

Vertical hydraulic conductivities of the Yorktown-Eastover aquifer ranged from 0.0000052 m/d to 

0.15 m/d in previous studies and averaged 0.0014 m/d. 

The maximum and minimum of the range came from 

23 permeameter tests of sediment cores. The median of 

the sediment cores was 0.0021 m/d (Smith, 2001, p. 9). 

A vertical conductivity of 0.002 m/d also was used to 

calibrate a ground-water-flow model of the area where 

the cores were taken (Smith, 2001, p. 9). The aquifer 

test encompassing confining beds in the Yorktown-Eastover aquifer, 62C 63 (fig. 8), in the southern watersheds of Virginia Beach had the same vertical hydraulic
16 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 7. Altitudes of the top of the St. Marys confining unit of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

-88

-108

-104

-100

-96

-92

-88

-84

-112

-92

-81

-108

-106

EXPLANATION

North

-108

Base from Mixon and others, 1989, 1:250,000

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

Boundary of the Back Bay and North Landing 

River watersheds

Study area

LINE OF EQUAL ALTITUDE—Contour interval 4 meters.

Vertical datum is NGVD 29

TEST HOLE AND ALTITUDE OF TOP OF THE ST. 

MARYS CONFINING UNIT—Altitude in meters. 

Vertical datum is NGVD 29

-108

-96
Shallow Aquifer System of the Southern Watersheds 17

Unit

Method

Median of specificcapacity test

(meters per day)

Aquifer-test analyses

(meters per day)

Calibrated ground-water-flow mo

(meters per day)

Columbia aquifer – 7.3 2 to 9 4.6 5.5 to 6.4 23 1 – 5.5 Yorktown confiningunit

3.2 (U)

5.2 (M)

–

2.1 (U)

16 (M)

– 7.0 to 7.3 (M)

12

9 (Sand)

6 (Silt)

0.0003 (silt, clay)

0.4 and 16 (U)

1.3 (P) (M)

0.4 and 13 (M)

– 1

Yorktown-Eastover aquifer 2.7 (L) 7.7 – 6.1 – 5.5 1 0.4 and 2.6 (L) 4.5 Source citation 1 2 3 4 5 6 7 1 4, 8 

Table 2. Horizontal hydraulic conductivities of the shallow aquifer system in and near Virginia Beach, Virginia[–, no data; U, Upper; P, Paleochannel; M, Middle; L, Lower]

1. Richardson (1994a, p. 19 and 50).2. Laczniak and Meng (1988, p. 57).3. Malcolm Pirnie (1997a, p. 1-4, 1-6,1-8, 2-4, and 2-5).4. Harsh and Laczniak (1990, p. F17 and F94).5. Malcolm Pirnie (1997b, p. 1-4, 1-6, 2-4, and 2-6).6. Geotrans, Inc. (1981, p. 15 and 16).7. Smith (2001, p. 8 and 9).8. Hamilton and Larson (1988, p. 49). 9. Robinson and Reay (2002, p. 126).
18 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia Unit Method Aquifer tests of confining beds (meter per day) Laboratory analyses of sediment cores (meter per day) Calibrated grou

flow mod

(meter per 

Columbia aquifer William Oliver 62B 9 max. 0.150 (U) med. 0.0090 (2) min. 0.0030 (L)

– – –

max. 0.052

med. 0.021 (5)

min. 0.000052

0.02 – 

Yorktown confining unit

 Redwing Park 63C 25

max. 0.00046 (U)

med. 0.00046 (2)

min. 0.00046 (L)

Cameron Munden 62C 25

max. 0.0015 (U)

med. 0.00083 (2)

min. 0.00015 (L)

0.00000424 (1)

max. 0.0012

med. 0.00069 (2)

min. 0.00018

0.000263(A?)

max. 0.0023

med. 0.000037 (6)

min. 0.0000040

0.002 0.00026

Yorktown-Eastover aquifer

Oceana II 62C 63

max. 0.000055 (U)\

med. 0.000055 (2)

min. 0.000055 (L)

– – –

max. 0.15

med. 0.0021 (23)

min. 0.0000052

0.002 – 

St. Marys confining unit – max. 0.00000497 med. 0.00000442 (2) min. 0.00000387 max. 0.0000061 med. 0.0000035 (2) min. 0.00000085 0.000126(A?) – – 0.00012Source citation 1 2 3 4 5 5 6 

Table 3. Vertical hydraulic conductivities of shallow aquifer system in and near Virginia Beach, Virginia.[max., maximum; med., median; min., minimum; U, upper; L, lower; –, no data; A, average; figures in parentheses are the number of samples or tests; ?, numbe

1 Geotrans, Inc. (1981a, p. 16). See figure 8 for site locations.2 Richardson (1994a, p. 19).3 Harsh and Laczniak (1990, F92).4 Laczniak and Meng (1988, p. 68 and 70).5 Smith (2001, p. 9).6 Hamilton and Larson (1985, p. 60).7 Harsh and Laczniak (1990, p. F94).
Shallow Aquifer System of the Southern Watersheds 19

Figure 8. Location of monitoring wells and selected aquifer-test wells in the shallow aquifer system of the southern 

watersheds of Virginia Beach, Virginia.

CHESAPEAKE

BAY

ATLANTIC

OCEAN

Intracoastal

Waterway

Landing

River

Back

Bay

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

Cape Henry

Chesapeake

Virginia Beach

36o40'

36o

50'

76o 76o 10'

James River Lynnhaven Bay

Norfolk

North

61B 6

61C 4

61C 29

62A 2

62A 3

62A 22

62A 23

(Blackwater

Park)

62B 15

62B 16

(Creeds

Elementary

School)

62B 18

(Pungo 2)

62B 1

62B 2

62B 22 (Pungo 1)

61B 7

61B 2

61B 17

61B 18

61B 19

62B 7

62B 9

62B 21

62C 5

62C 8

62B 3

62C 2

62C 3 63C 2

63C 3 63C 4

63C 5

63C 13

63C 19

63C 25

63C 11 

(Red Wing 

Park)

62C 9

62C 10

62C 11

62C 12

62C 63

61C 28

61C 27

61C 23

62C 32

62C 33

(Lynnhaven Pump 

Station)

63C 20

61C 25

61C 45

61C 46

(Bayside High 

School)

61C 43

61C 44

Continuous electronic data logger

Periodic measurement with chalked tape

Aquifer-test site

62A 2

62B 9

62A 3

62A 22

62A 23

EXPLANATION

WELL NUMBER DATA-COLLECTION METHOD

62A 5 

62A 6

(Seneca)

(Bellwood Estates Park)

Base from Mixon and others, 1989, 1:250,000

62C 25

West

Neck

Creek

Creek Bridge

London

Bypass

Canal

(Kempsville)
20 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

conductivities above and below the aquifer, 0.000055 

m/d (Geotrans, Inc., 1981, p. 16).

Vertical hydraulic conductivities of the St. Marys 

confining unit in southeastern Virginia generally were 

much less than those of the shallow aquifer system 

(table 3). The vertical hydraulic conductivities of the 

St. Marys ranged from 0.00000085 m/d to 0.00013 

m/d. 

Ground-Water Recharge

Ground-water recharge is that part of precipitation 

that reaches the water table. Recharge rates from previous studies of the shallow aquifer system in southeastern Virginia were used to set reasonable limits for 

calibrating the ground-water-flow model of this study.

Previous studies have estimated ground-waterrecharge rates of the shallow aquifer system by hydrologic budget analyses, streamflow-separation techniques, hydrogeologic unit area regression, and by 

calibration of ground-water-flow models. Those 

recharge rates ranged from 10 to 30 cm/yr (table 4). 

The average and median of the previous studies is 

about 20 cm/yr. 

The lowest values of 10 to 13 cm/yr were estimated 

by hydrologic budget analyses for a site in the southern 

watersheds of Virginia Beach (Malcolm Pirnie, 1997a, 

p. 2-7). An average recharge rate of 19.1 cm/yr was 

estimated from 1970 to 1990 at the stream gage nearest 

the study area using streamflow-separation techniques 

(Richardson, 1994b, p. 5, fig. 3 and p. 6, table 1). The 

stream gages in the Coastal Plain of Virginia, however, 

are above the tidal zone and probably estimate 

ground-water-recharge rates higher than those of Virginia Beach. Extensive wetlands and clayey soils in 

much of Virginia Beach inhibit freshwater recharge. A 

recharge rate of 20 cm/yr was estimated for an area that 

included the southern watersheds of Virginia Beach by 

hydrogeologic-area regression, assuming that 

ground-water discharge equals ground-water recharge 

(Richardson, 1994b, p. 12, fig. 5). This rate, however, 

was based on the same long-term hydrographs as that 

used for the streamflow-separation method and also 

could have over-estimated the ground-water recharge 

for Virginia Beach. Recharge rates of 15 to 30 cm/yr 

were used to calibrate previous ground-water-flow 

models of southeastern Virginia (table 4). The recharge 

rates ranged from local site applications of flow models 

within the southern watersheds of Virginia Beach (Malcolm Pirnie, 1977a, p. 2-7; Malcolm Pirnie 1977b, p. 

2-6) to regional analyses of the Coastal Plain of southeastern Virginia (Hamilton and Larson, 1988, p. 61). 

 Evapotranspiration rates generally reach a maximum at the land surface (McDonald and Harbaugh, 

1988, p. 10-5). For simulation of ground-water flow in 

this study, it was assumed that recharge would be zero 

where the water table was at land surface. Where the 

water table was below the land surface, the evapotranspiration rate would decrease from the land surface to a 

specified extinction depth, as depicted by McDonald 

and Harbaugh (1988, p. 10-3). Ground-water recharge, 

therefore, would increase when the water table was 

below land surface to an extinction depth below which 

recharge again would drop to zero.

 A maximum recharge rate of 20 cm/yr was 

assumed initially for the ground-water-flow model of 

this study, equal to the average annual ground-water 

discharge estimated for southeastern Virginia and for

Method Recharge Estimate

(centimeters per year) Source

Hydrologic budget analysis 10 to 13 Malcolm Pirnie (1997a, Permit Part 14, p. 2-7).

Streamflow separation at gage nearest

to study area (02043500) 19.1

After Richardson (1994, p. 5, fig. 3 and p. 6, 

table 1) assuming ground-water recharge equals 

discharge.

Hydrogeologic-unit area regression 20 After Richardson (1994, p. 12, fig. 5), assuming

ground-water recharge equals discharge.

Calibrated ground-water-flow models

15 Malcolm Pirnie (1997b, Permit Part 14, p. 2-6).

23 Smith (2001, p. 15).

30 Hamilton and Larson (1988, p. 61).

30 Malcolm Pirnie (1997a, Permit Part 14, p. 2-7).

Table 4. Ground-water-recharge rates in and near the southern watersheds of Virginia Beach, Virginia.
Shallow Aquifer System of the Southern Watersheds 21

the southern watersheds of Virginia Beach. This initial 

maximum recharge rate, however, produced simulated 

water levels much higher than measured. Model calibration and subsequent sensitivity tests indicated a better approximation of measured water levels if a 

maximum recharge rate of 10 to 15 cm/yr was 

assumed.

Ground-Water Levels

Average water levels from 38 wells were used to 

calibrate the ground-water-flow model for this study 

(table 5). Long-term records of selected wells show 

trends in water levels from 1984 to 2002 in the southern watersheds of Virginia Beach (fig. 9).

Most hydrographs of wells at Virginia Beach indicate periodic and seasonal fluctuations in water levels, 

but unchanging or steady states when viewed over several years. A steady state indicates that ground-water 

recharge is in balance with ground-water discharge. 

Such a steady state also is called a dynamic equilibrium. Wells 61C 27 in the Yorktown-Eastover and 

62A 2 in the Yorktown confining unit indicate typical 

long-term, steady states (fig. 9). However, hydrographs 

of two other wells in the Yorktown-Eastover–62C 10 

and 63C 4–show generally lower or declining water 

levels over the period of record. Such long-term 

declines typically are the result of ground-water withdrawals.

Continuous recorders installed in seven wells in 

April 2001 show seasonal changes in water levels at 

Virginia Beach (fig. 10). The continuous records indicate generally higher water levels in the spring, followed generally by months of decline through the 

summer. Such declines typically are caused by the 

emergence of leaves and high rates of evapotranspiration. Precipitation and pumping wells, mostly for irrigation, cause short-term fluctuations in the water levels 

that are superimposed on the longer cycles and contribute to or detract from the seasonal patterns, in kind.

 Water levels in wells 61C 43 and 61C 44 at Bellwood Estates Park and 61C 46 at Bayside High School 

declined until the summer of 2001, reaching seasonal 

lows in July and early August. The declines generally 

were followed by gradual water-level recoveries that 

increased after the leaves fell in October. In 2002, similar seasonal patterns were repeated in those wells, but 

the fall recoveries began in late August and early September. The water levels at Bellwood Estates Park fluctuate through greater amplitudes than the other wells 

and the water levels have declined below sea level, 

indicating the possible effects of a pumping well.

Water levels in wells 62A 22 and 62A 23 at Blackwater Park and 62B 15 and 62B 16 at Creeds Elementary School declined through the summer of 2001, but 

continued to decline through the fall and winter of 

2001 until January 2002. Water levels in those wells 

recovered until April and May 2002 when the normal 

seasonal declines began again.
22 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Landsurface 

altitude

(meters 

above

NGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Top of 

screen

(meters

below

land 

surface)

Bottom of 

screen

(meters

below

land 

surface)

Average 

water

level

(meters

above or

below

NGVD 

1929)

Hydrogeologic

unit

61B 19 na 364227076074713 234-00198 36 42 27 76 07 47 4.57 6.10 3.05 6.10 3.51 Columbia aquifer

61B 7 SOW 091D 364227076074704 234-00067 36 42 27 76 0 747 4.57 6.71 5.18 6.71 3.51 Columbia aquifer

62A 3 SOW 097B 363537076061002 228-00171 36 33 55 76 06 17 3.05 7.32 6.10 7.32 2.13 Columbia aquifer

62B 1 SOW 098A 364126076003501 228-00167 36 41 27 76 00 35 3.05 7.32 6.10 7.32 1.86 Columbia aquifer

63C 19 na 364721075591701 228-00248 36 47 21 75 59 17 2.74 9.14 7.62 9.14 .59 Columbia aquifer

62C 11 SOW 172C 364745076004303 228-00253 36 47 46 76 00 43 6.09 10.67 6.10 9.14 3.96 Columbia aquifer

63C 3 SOW 100C 364613075583202 228-00207 36 46 14 75 58 29 2.44 10.67 9.14 10.67 .30 Columbia aquifer

63C 2 SOW 100B 364613075583201 228-00206 36 46 14 75 58 29 2.44 16.46 14.94 16.46 .55 Columbia aquifer

62C 8 SOW 127 364529076031501 228-00078 36 45 33 76 03 20 4.57 18.29 15.24 16.76 1.83 Columbia aquifer

62B 7 na 364354076005401 228-00265 36 43 54 76 00 55 2.59 19.81 15.24 18.29 .54 Columbia aquifer

62B 21 na 364353076005401 228-00264 36 43 53 76 00 54 3.11 19.81 15.24 18.29 .69 Columbia aquifer

62C 3 SOW 092B 364715076030801 228-00133 36 47 14 76 03 07 4.27 17.68 16.15 17.68 1.91 Yorktown confining unit

62B 3 SOW 128 364455076032801 228-00079 36 44 55 76 03 28 3.05 19.81 16.76 19.81 .30 Yorktown confining unit

62C 5 SOW 093 364504076031301 228-00135 36 44 56 76 03 01 4.27 19.81 18.29 19.81 .15 Yorktown confining unit

61B 18 na 364227076074712 234-00197 36 42 27 76 07 47 4.57 20.42 17.37 20.42 2.29 Yorktown confining unit

62B 9 na 364352076005401 228-00263 36 43 52 76 00 54 3.26 20.42 15.85 18.90 .58 Yorktown confining unit

62C 12 SOW 172D 364745076004304 228-00253 36 47 47 76 00 44 5.18 22.86 18.29 21.34 3.35 Yorktown confining unit

62A 2 SOW 097A 363537076061001 228-00170 36 33 56 76 06 17 3.05 23.16 20.12 23.16 1.83 Yorktown confining unit

62B 16 na 363812076021202 228-00432 36 38 12 76 02 12 4.27 23.47 19.81 22.86 1.09 Yorktown confining unit

63C 11 na 364728075591401 228-00245 36 47 28 75 59 14 2.77 25.91 21.34 24.38 .47 Yorktown confining unit

62A 5 na 363325076005201 228-00046 36 33 27 76 00 27 1.52 26.82 17.68 25.30 -.53 Yorktown confining unit

63C 5 SOW 173B 364722075591802 228-00243 36 47 22 75 59 18 2.74 28.96 24.38 27.43 .91 Yorktown confining unit

62B 2 SOW 098B 364126076003502 228-00168 36 41 26 76 00 35 3.05 29.87 26.82 29.87 1.83 Yorktown confining unit

61B 8 SOW 134 364231076140801 234-00118 36 42 31 76 14 08 6.10 30.48 25.60 28.65 4.27 Yorktown confining unit

62A 23 na 363714076063502 228-00430 36 37 14 76 06 35 3.17 30.48 26.82 29.87 1.50 Yorktown confining unit

61C 29 SOW 175 364837076092001 228-00318 36 48 37 76 09 21 4.57 32.00 27.43 30.48 2.13 Yorktown confining unit

61B 2 SOW 091A 364227076074701 234-00136 36 42 27 76 07 47 4.57 29.57 28.04 29.57 2.13 Yorktown-Eastover aquifer

62C 2 SOW 092A 364713076030701 228-00132 36 47 14 76 03 07 4.27 31.09 29.57 31.09 .91 Yorktown-Eastover aquifer

61B 17 na 364227076074711 234-00196 36 42 27 76 07 47 4.57 32.92 26.82 29.87 2.44 Yorktown-Eastover aquifer

62B 18 na 364126076013401 228-00269 36 41 26 76 01 34 3.05 41.15 36.58 39.62 1.67 Yorktown-Eastover aquifer

62B 22 na 364325076011501 228-00268 36 43 25 76 01 15 3.05 41.15 36.58 39.62 -.42 Yorktown-Eastover aquifer

62C 4 SOW 083 364711076060001 228-00120 36 47 11 76 06 00 3.96 45.42 35.97 39.01 .91 Yorktown-Eastover aquifer

62C 9 SOW 172A 364745076004301 228-00250 36 47 46 76 00 42 5.18 51.82 47.24 50.29 1.98 Yorktown-Eastover aquifer

62A 22 na 363714076063501 228-00429 36 37 14 76 06 35 3.19 54.25 43.59 51.21 1.52 Yorktown-Eastover aquifer

63C 13 na 364721075591601 228-00364 36 47 21 75 59 16 2.29 62.48 57.91 60.96 .42 Yorktown-Eastover aquifer

62B 15 na 363812076021201 228-00431 36 38 12 76 02 12 4.20 63.40 58.83 61.87 .84 Yorktown-Eastover aquifer

62C 10 SOW 172B 364745076004302 228-00315 36 47 45 76 00 43 5.18 85.34 82.30 85.34 1.52 Yorktown-Eastover aquifer

63C 4 SOW 173A 364722075591801 228-00314 36 47 21 75 59 16 2.50 88.70 85.65 88.70 1.06 Yorktown-Eastover aquifer

Table 5. Construction and water-level data for selected wells in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia

[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; na, not applicable;

See figure 8 for location of wells.]
Shallow Aquifer System of the Southern Watersheds 23 Figure 9. Long-term trends in ground-water levels of the shallow aquifer system in the southern watersheds of Virginia Beach, Virginia.

1.5

1.2

0.6

1.8

2.1

2.4

2.7

3.0

3.3

3.6

4.2

3.6

3.0

2.4

1.8

5.4

4.8

3.6

4.2

0.6

1.2

1.8

2.4

3.0

-0.6

0

3.0

2.7

2.4

2.1

1.8

1.5

1.2

0.9

0.9

0.6

2.1

1.8

1.5

1.2

0.3

0.6

0.9

1.2

1.5

1.8

2.1

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 1984 1986 1988 1990 1992 1994 1996 19

1980 1985 1990 1995 

GROUND-WATER LEVEL, IN METERS BELOW LAND SURFACE

GROUND-WATER LEVEL, IN METERS BELOW LAND SURFACE

ALTITUDE OF GROUND-WATER LEVEL, IN METERS ABOVE OR BELOW NGVD 1929

61C 27 SOW 174A

Yorktown-Eastover aquifer

62A 2 SOW 097A

Yorktown confining unit

62C 10 SOW 172B

Yorktown-Eastover aquifer

63C 4 SOW 173A

Yorktown-Eastover aquifer
24 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 10. Seasonal trends in ground-water levels at Bellwood Estates Park (A), Bayside High School (B), Blackwater Park (C), and Creeds Elementary Schooin the southern watersheds of Virginia Beach, Virginia, 2001-2002.

0

-1.0

-2.0

-3.0

-4.0

-5.0

-7.0

-6.0

0

-1.0

-2.0

-3.0

-4.0

-5.0

-7.0

-6.0

0

-1.0

-2.0

-3.0

-4.0

-5.0

-7.0

-6.0

2001

Apr May Jun Jul Aug Sep Oct Nov Dec

2

Jan Feb Mar Apr M

62B 15

62B 16

G

0

-1.0

-2.0

-3.0

-4.0

-5.0

2001

Apr May Jun Jul Aug Sep Oct Nov Dec

2002

Jan Feb Mar Apr May Jun Jul Aug Sep

61C 43

61C 44

(A)

GROUND-WATER LEVEL, IN METERS BELOW LAND SURFACE

2001

Apr May Jun Jul Aug Sep Oct Nov Dec

2002

Jan Feb Mar Apr May Jun Jul Aug Sep

62A 22 62A 23

(C)

2001

Apr May Jun Jul Aug Sep Oct Nov Dec

2

Jan Feb Mar Apr M

61C 46

-7.0

-6.0

Sea level

Sea level
Saline Water in the Shallow Aquifer System 25

SALINE WATER IN THE SHALLOW 

AQUIFER SYSTEM

“Water that generally is considered unsuitable for 

human consumption or for irrigation because of high 

content of dissolved solids” is called saline (U.S. Geological Survey, 1985, p. 461). Chloride concentrations 

commonly are used to indicate the proximity or the 

presence of saline water. In this study, chloride concentrations were contoured by linear Kriging to indicate 

the general distribution of saline water in the Columbia 

aquifer, the Yorktown confining unit, and the Yorktown-Eastover aquifer. The chloride concentrations 

subsequently were used to calibrate a ground-waterflow and solute-transport model. 

Definitions

Definitions for water types with regard to seawater 

are based on dissolved solids concentrations (U.S. 

Department of the Interior, 1989, p. 22). Water with 

less than 1,000 mg/L is considered fresh, and water 

with dissolved solids from 1,000 to 35,000 mg/L is 

defined as saline. Seawater is assumed to contain 

approximately 35,000 milligrams of dissolved solids 

per liter. 

A table to relate equivalent concentrations of chloride to those of dissolved solids was made for this 

report based on the proportion of each to seawater 

(table 6). Seawater has about 19,000 milligrams of 

chloride per liter (Hem, 1989, p. 7).

High concentrations of dissolved solids and chlorides can impart an undesirable taste to drinking water. 

The USEPA (2002, p. 10) recommends a maximum of 

250 mg/L for chloride under the Secondary Drinking 

Water Regulations. People can become accustomed to 

concentrations in excess of 250 mg/L (World Health 

Organization, 1993, p. 22). However, a chloride concentration of 400 mg/L renders a salty taste for most 

people (Hem, 1989, p. 212).

Chloride Concentrations in the Shallow 

Aquifer System

In the southern watersheds of Virginia Beach, the 

Columbia aquifer generally contains freshwater and the 

average chloride concentration is about 25 mg/L 

(table 7, at end of report). However, water from three 

wells open to the Columbia aquifer on the eastern edge 

of the Back Bay watershed had concentrations greater 

than 200 mg/L (fig. 11). All of the wells in the Columbia aquifer had concentrations less than 250 mg/L. Two 

wells (not shown) adjacent to a road salt storage area 

near Pungo were not included on the map because they 

probably were contaminated by anthropogenic sodium 

and (or) potassium chloride. 

The Yorktown confining unit also contains freshwater in the southern watersheds, similar in distribution to 

that of the Columbia aquifer, as indicated by chloride 

concentrations (fig. 12). Chloride concentrations in 

water from wells open to the Yorktown confining unit 

were less than the 250 mg/L except for samples from 

two wells in the northern Back Bay watershed and one 

other sample from a well west of the southern watersheds and outside of the study area. 

The Yorktown-Eastover aquifer contains saline 

water over much of the southern watersheds, as indicated by chloride concentrations in water from wells 

open to the aquifer (fig. 13). Freshwater, however, has 

Water type1

Dissolved solids 

concentrations

(milligrams per liter)

Equivalent chloride concentrations

(milligrams per liter)

Freshwater2 Less than 1,000 Less than 500

Saline3

water

Brackish4 water Slightly saline3 1,000 to less than 3,000 500 to less than 1,600

Moderately saline3 3,000 to less than 10,000 1,600 to less than 5,400

Very saline3 10,000 to less than 35,000 5,400 to less than 19,000

Seawater1 35,000 19,000

Brine3 Greater than 35,000 Greater than 19,000

Table 6. Definition of water types with regard to seawater and chloride concentrations

1 U.S. Department of the Interior (1989, p. 22).

2 Also defined by Davis and Dewiest (1966, p. 118).

3 Krieger and others (1957, p. 5).

4 U.S. Geological Survey (1985, p. 460) and Davis and Dewiest (1966, p. 118).
26 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 11. Chloride distribution in the Columbia aquifer of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

25

100

50

200

50

25

150

16

20

19 21

23 23

21

15

7

19

24

25

77

20

5

50

22

30

203

210

205

23

23 23

30

25

EXPLANATION

North

Base from Mixon and others, 1989, 1:250,000

Boundary of the Back Bay and North Landing 

River watersheds

Study area

LINE OF EQUAL CHLORIDE CONCENTRATION—

Interval, in milligrams per liter, is variable.

Dashed where approximate

WELL AND CHLORIDE CONCENTRATION, IN

MILLIGRAMS PER LITER

20

25
Saline Water in the Shallow Aquifer System 27

Figure 12. Chloride distribution in the Yorktown confining unit of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

50

25

100

150

200

250

50

25

50

25

50

25

300

250

200

150

100

25

50

286

14

14

189

45

64

91

27

45

53

27 84

69

11

23

30

45 454 53 53

24

41

197

30

30

23

265

22

30

102

9 10

12 21

113

31

49 56

38

43

36

30

30

15

15

19

23 23

30

23

15

EXPLANATION

North

Base from Mixon and others, 1989, 1:250,000

Boundary of the Back Bay and North Landing 

River watersheds

Study area

LINE OF EQUAL CHLORIDE CONCENTRATION—

Interval, in milligrams per liter, is variable.

Dashed where approximate

WELL AND CHLORIDE CONCENTRATION, IN

MILLIGRAMS PER LITER

43

25
28 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 13. Chloride distribution in the Yorktown-Eastover aquifer of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

West Neck

Creek

Creek

Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

SALINE WATER—Chloride concentration greater 

than 500 and less than 19,000 milligrams per liter

Study area

LINE OF EQUAL CHLORIDE CONCENTRATION—

Interval, in milligrams per liter, is variable.

Dashed where approximate

WELL AND CHLORIDE CONCENTRATION, IN

MILLIGRAMS PER LITER

98

25

EXPLANATION

25

250

500

1,000

500

500

1,000

1,500

2,000

2,500

500

1,000 1,500

2,000

250

25

98

701

3,080

576

420

71

95

464

198

3,380

134 212

283

530

2,094

168 1,220

424

209

677

1,121

45

91

4,115

252

23

61

364

30

502 23

22

45

38

129

76

23

72730

23

38

30

30 61

64

30

45

38

30

North

Base from Mixon and others, 1989, 1:250,000

Boundary of the Back Bay and North Landing 

River watersheds

1,500

2,000

2,500

3,000

1,500
Saline Water in the Shallow Aquifer System 29

leaked down into the top of the Yorktown-Eastover 

aquifer, near the watershed divides in the north along 

Oceana and Pungo Ridges, and possibly along and near 

the divides in the western parts of the watershed of the 

North Landing River in Chesapeake, Va. The contour 

lines around some sites are the average of sample concentrations from two or more wells open to different 

depths in the aquifer. 

Two of the highest concentrations of chloride, 

3,080 mg/L in well 61C 43 at Creeds Elementary 

School and 3,380 mg/L in well 62B 16 at Bellwood 

Estates Park, were measured in the southern watersheds in the year 2000. Both concentrations were in 

areas where continuous cores indicated generally 

fine-grained sediments (Smith and Harlow, 2002, p. 21, 

fig. 11). These wells were sampled again in 2001, at 

2,940 and 3,340 mg/L, respectively, indicating virtually 

no change in chloride concentration (White and Powell, 2001, p. 313). The highest concentration of chloride measured in the southern watersheds was 4,242 

mg/L in water from well 63C 4 at Red Wing Park during an aquifer test in 1981 (Betz-Converse-Murdoch, 

1981, v. 2b). That well was sampled again in 2002 at 

4,115 mg/L indicating virtually no change in concentration over a period of 21 years.

Virtually of the chloride concentrations measured 

under natural flow conditions in the shallow aquifers of 

the southern watersheds, including the highest measurements, showed no changes in concentration 

through time. These results indicate that the natural 

freshwater and saline water interfaces probably are in 

equilibrium in the southern watersheds.

Overall, the maps generally confirm what most previous investigations have indicated; the Columbia aquifer and the Yorktown confining unit generally contain 

freshwater although concentrations of chloride can be 

higher than average in places. The top of the Yorktown-Eastover aquifer may contain freshwater in 

places, but most of the Yorktown-Eastover aquifer contains saline water, particularly with increasing depth. 

Conceptual Model of Ground-Water Flow

A general conception of ground-water flow in the 

shallow aquifer system at Virginia Beach was reported 

by Smith and Harlow (2002, p. 27). That general conceptual model has been refined in light of the chloride 

maps and the simulations of ground-water flow documented in this report.

Ground-water-flow patterns in shallow aquifers of 

Virginia Beach reflect the topography. Tóth defined 

intergraded local, intermediate, and regional 

ground-water-flow patterns resulting from undulating 

topography (Freeze and Cherry, 1979, p. 196). 

Regional patterns are defined by deep, long concentric 

paths from the watershed divides to the farthest extent 

of the discharge areas (fig. 14). Local patterns are shallow, short concentric paths at the nearest edge of the 

discharge areas and intermediate patterns are the concentric paths between. 

The shallow aquifer system at Virginia Beach is 

recharged by local precipitation. Rainwater or snowmelt that soaks through the soil and is not captured and 

transpired by plants seeps through the unsaturated zone 

Figure 14. Toth's theoretical ground-water flow patterns effected by topography. (Taken from Sanford, 2002.) ELEVATION

DISTANCE

Recharge Recharge Recharge Recharge Recharge

Potential distribution representing the water table 

on the surface of the theoretical flow region

Equipotential line

Line of flow

EXPLANATION NOT TO SCALE
30 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

to recharge the water table. During the growing season, 

ground-water recharge generally is slight because trees 

and shrubs capture most of the precipitation and transpire that back to the atmosphere. The water table is 

more readily recharged in the late fall and winter when 

plants are dormant.

When and where ground-water recharge is ample, 

the water table rises as a subsurface mound and water 

begins flowing away from the center of the mound. The 

mound forces the water beneath to flow downward and 

outward toward the nearest tidal stream or shore, where 

the fresh ground water flows into and mixes with saline 

water (fig. 15). In the humid climate of Virginia Beach, 

the periodic recharge of freshwater through the shallow 

aquifer system occurs often enough to create a 

steady-state balance or a dynamic equilibrium whereby 

freshwater flows continually down and away from the 

center of the higher ground and the sand ridges to mix 

with saline water from the tidal rivers, bays, salt 

marshes, and the Atlantic Ocean.

Recharge and mounding beneath much of the 

southern watersheds is limited by the general flatness 

and low altitude of the terrain and by the proximity and 

extent of wetlands, bays, open waterways, and tidal rivers, streams, and channels, where ground water readily 

discharges. Extensive lowlands and wetlands to the 

west of Virginia Beach and Chesapeake, Va., limit 

ground-water recharge over much of the southeastern 

region of Virginia as well. Infiltration of water falling 

on the land surface is hindered further in much of the 

southern watersheds of Virginia Beach by shallow layers of clayey soils and the limited depth of permeable 

sediments beneath the soils (Wolman and others, 1942, 

p. H-2). Extensive systems of ditches have been built to 

lower the water table beneath poorly drained soils that 

cover much of the agricultural areas of Virginia Beach. 

Paved surfaces, drains, and stormwater sewers, particularly in urban areas along the northern perimeter of the 

southern watersheds, also inhibit ground-water 

recharge. Thus, ground-water recharge is limited and 

ground-water-flow lines tend to be short and shallow in 

much of the southern watersheds. 

The shallow aquifer system is recharged in some 

places through permeable soils and sand dunes, particularly beneath some of the higher altitudes, such as 

Pungo Ridge. The areas of greatest recharge are those 

where the land surface is broad and high.

 Semi-confining and confining sediments, particularly those of the Yorktown confining unit, hinder fresh 

ground-water recharge to deeper units. Pockets of 

saline water may be trapped within impermeable sediments in some areas (fig. 15). Where recharge of fresh 

ground water is inhibited, saline water is at shallower 

depths. The fresh ground water that does recharge the 

deeper sediments of the shallow aquifer system flows 

over and above heavier saline water in the bottom of 

the shallow aquifer system. In the confined and poorly 

confined aquifers of the southern watersheds, freshwater probably has displaced saline water generally from 

the higher ground in the north and west toward the 

south and east so that saline water probably remains in 

the confined aquifers in the southeast beneath Pungo 

Ridge. Freshwater from Hickory Ridge to the west 

probably discharges to the broad flood plain and wetlands of the North Landing River.

SIMULATION OF GROUND-WATER FLOW 

AND SOLUTE TRANSPORT

The Columbia and Yorktown-Eastover aquifers are 

poorly confined throughout most of the southern watersheds of Virginia Beach, and the freshwater to saline 

water distribution is in a dynamic equilibrium (steady 

state) with average ground-water levels, measured concentrations of dissolved salts (chlorides), and modern 

sea levels. A three-dimensional, steady-state, 

ground-water-flow and solute-transport model was 

used to simulate that dynamic equilibrium.

Model Assumptions and Assumed 

Properties

A primary goal was to devise the simplest model 

possible that would meet the objectives of the project. 

As the number of variables and assumptions in a model 

increase, errors multiply, creating greater uncertainty. 

The principle of parsimony (also called the principle of 

simplicity, or Ockham’s razor) suggests that the simpler approach to an objective should be tried first in 

order to reduce errors and uncertainty. However, there 

is a tradeoff between the simplicity of design and the 

complexity of possible realities, because measured data 

can be more precisely approximated if there are more 

variables to adjust.

Visual MODFLOW® version V.3.0 (Waterloo 

Hydrogeologic, Inc., 2002, p. 25) was used to simulate 

ground-water flow and solute transport. Version V.3.0 

incorporates MODFLOW 2000, a finite-difference
Simulation of Ground-Water Flow and Solute Transport 31 Figure 15. Conceptual model of ground-water flow in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia. (Modified from Johnson, 1999.)

EXPLANATION

Columbia aquifer

Yorktown confining unit

Yorktown-Eastover aquiferSt. Marys confining unit

Silty or clayey unit

Saline water

Generalized ground-waterflow direction

HICKORY 

RIDGE

Chesapeake North Landing River

Virginia

Beach

PUNGO RIDGE

WEST 
32 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

ground-water-flow model (or MODFLOW 96) and 

MODPATH, a particle-tracking routine designed by the 

USGS, as well as MT3DMS, a multi-species transport 

model for simulation of advection, dispersion, diffusion, and some chemical reactions designed at the University of Alabama, and completed, in part, in 

cooperation with the Army Corps of Engineers Waterways Experiment Station (Zheng and Wang, 1998, 

p. 1-4). Calibration and sensitivity analyses of the 

model were aided by the parameter estimator WinPEST and various other mapping, contouring, graphing, and statistical routines that are also incorporated 

into Visual MODFLOW (Waterloo Hydrogeologic, 

Inc., 2002, p. 222 and 244). VMOD 3D-Explorer also 

is incorporated into Visual MODFLOW V.3.0. Except 

as noted, the default settings of Visual MODFLOW 

were applied for the model simulations.

The usual assumptions associated with 

ground-water flow and solute transport simulations of 

layered aquifer systems as applied to these programs 

are valid for the objectives of this study. The assumptions are appropriate as used for the system conceptualization of this study; however, before applying the 

model for other purposes the appropriateness of the 

assumptions should be evaluated.

Ground-water flow is assumed to be laminar (not 

turbulent). The aquifers are assumed to be homogeneous (uniform in composition) and isotropic (aquifer 

properties are directionally uniform) within representative elemental volumes (cells). However, horizontal 

hydraulic conductivity of each unit was assumed to be 

higher than vertical because the sediments of the southern watersheds generally were deposited in stratified 

layers (Jacob, 1963, p. 274). 

Temperature and density gradients were assumed to 

be uniform in the shallow aquifer system. The simulations do not incorporate density-dependent flow— the 

pressure gradients produced by mixing waters of different mass (weights). Such pressure gradients are negligible because the differences in density between the 

freshwater and slightly saline water of the southern 

watersheds is small generally and concentration gradients tend to increase gradually with depth. The greatest 

chloride concentration measured in a well of the shallow aquifer system was 4,242 mg/L (moderately 

saline) at Red Wing Park at a depth of 286 m in 1981.

Dispersion in the direction of principal velocity 

generally is much greater than the dispersion perpendicular to the principal velocity (Henry, 1964, p. C-73). 

The longitudinal dispersivity of the calibrated model 

was 1.0 m. The longitudinal dispersivity was assumed 

to be one order of magnitude (10 times) greater than 

the transverse dispersivity in the horizontal direction 

and 2 orders of magnitude (100 times) greater than the 

transverse in the vertical direction. The diffusion coefficient was assumed to be that of chloride, 20.3 X 10-6 

square centimeters per second (Domenico and 

Schwartz, 1990, p. 369).

Effective porosity of the aquifers was assumed to be 

30 percent, representing some shell hash, biofragmental sand, and beach sand in the units; porosity of confining units was assumed to be 40 percent, representing 

mostly fine sand, silt, and clay deposits (Davis and 

DeWeist, 1966, p. 375, table 11.1; Todd, 1980, p. 28, 

table 2.1). Fine-grained sediments such as silt and clay 

tend to have poorly connected but larger void spaces 

than sands (Freeze and Cherry, 1979, p. 37).

The simulation method assumes steady state with 

respect to modern eustatic (average global) sea level, 

which has fluctuated with regional and global climate 

changes over the last 70,000 years (Mixon and others, 

1982 or See explanation of Sedgefield Member of Tabb 

Formation from Mixon and others, 1989, Sheet 1). The 

aquifer system was in equilibrium with measured average water levels. Such a steady state was indicated 

from numerous hydrographs covering decades of periodic measurements in wells and by continuous records 

of transducers in wells. A few hydrographs from wells 

in Virginia Beach, however, were not indicative of 

steady states, but indicated local anomalies, probably 

caused by unreported ground-water withdrawal for irrigation, and such water levels were not used to calibrate 

to the average water levels. It also was assumed that the 

freshwater-saline-water interfaces were in dynamic 

equilibrium with modern sea levels, as indicated by the 

unchanging measurements of chloride in the southern 

watersheds. 

Boundaries and Layers 

The boundaries of the southern watersheds of Virginia Beach were derived from hydrologic unit boundaries of Virginia that rely on USGS 1:24,000-scale 

7.5-minute topographic maps. The outlines of the 

southern watersheds of Virginia Beach were imported 

into Visual MODFLOW® and referenced to known 

locations on topographic maps using Universal Transverse Mercator coordinates (Waterloo Hydrogeologic, 

Inc., 1999, p. 20). Maps of land use (fig. 2) and surfi-
Simulation of Ground-Water Flow and Solute Transport 33

cial geology (fig. 3) also were overlaid in Visual MODFLOW to guide placement of internal and external 

boundaries and hydrogeologic properties, including 

wetland areas and the generally sandy Poquoson Member of the Tabb Formation.

A square finite-difference grid of 80 rows and 80 

columns was set over the southern watersheds of Virginia Beach, except for the narrow strip of land adjacent to the Atlantic Ocean east of the Back Bay that 

was assumed to be isolated with respect to 

ground-water flow from the rest of the watershed 

(fig. 16). Each individual cell of the model was 

400.0 m (1,312 ft) per side. 

The outer perimeters of the southern watersheds 

were assumed to be no-flow boundaries because of the 

shallow flowpaths of the aquifer system. The short 

southern boundaries of the watersheds are drawn at the 

Virginia-North Carolina State line, which runs perpendicular to the North Landing River and the higher 

ground on either side, following natural ground-water 

flowpaths that define no-flow boundaries. The limits of 

the model area to the east also are assumed to be 

no-flow boundaries by definition, but those boundaries 

were set far enough from the land areas to allow unimpeded discharge to the Atlantic Ocean and the Back 

Bay, which were assumed to be constant water levels. 

The potential effect of moving the boundary closer to 

the shore was tested and the simulated water levels 

were found to be insensitive to the change.

Constant water levels of zero altitude and constant 

chloride concentrations of 19,000 mg/L were assumed 

for modern sea levels and maximum salinity representing the Atlantic Ocean in the simulations (Hem, 1989, 

p. 7, table 2). Constant water levels of 0.3 m (1.0 ft) 

above sea level and constant chloride concentrations of 

10,000 mg/L were used to represent the average tide 

levels and maximum salinities expected for the Back 

Bay, the North Landing River, the Intracoastal Waterway, and West Neck Creek (Bales and Skrobialowski, 

1994, p. 10, fig. 5; Caldwell, 2001, p. 9, fig. 2, and 

p. 19, fig. 6).

Flowing non-tidal streams and major ditches were 

simulated as drain cells in the model. Drain bottoms 

were determined from points along streams and ditches 

marked on USGS 7.5-minute, topographic maps. The 

bottoms of the drain cells were set equal to the altitudes 

where the land-surface contours crossed over the 

streams and ditches.

Conductances of the drain cells were estimated by 

multiplying the hydraulic conductivity by the width 

and length of the cells and dividing by the thicknesses 

of the drain bottoms in much the same way as river bottoms for MODFLOW are documented (MacDonald 

and Harbaugh, 1988, p. 6-4, fig. 34). The length of each 

drain was assumed to be equal to the length of each cell 

of the model in which the drain was represented (400 

m) the width was assumed to be 3.0 m, and the thickness of the drain bottom was assumed to be 1.0 m. 

Drain hydraulic conductivities initially were assumed 

to be 1.0 m/d.

Four contoured surfaces define the conceptual 

hydrogeologic framework of the shallow aquifer system and constitute the layered geometry of the 

ground-water-flow and solute-transport model (fig. 17). 

The contours of the land surface form the limits to the 

top of the Columbia aquifer. The bottom of the Columbia is the contact with the top of the Yorktown confining unit. The bottom of the Yorktown confining unit is 

the contact with the top of the Yorktown-Eastover aquifer. The top of the St. Marys confining unit, a regionally continuous marine deposit of low permeability, 

forms the bottom of the Yorktown-Eastover aquifer, the 

shallow aquifer system, and the no-flow bottom of the 

ground-water-flow and solute-transport model. 

The four contoured surfaces that form the geometry 

of the shallow aquifer system were imported into 

Visual MODFLOW to form the three conceptual units 

of the model. The three conceptual units of the shallow 

aquifer system were divided further into seven layers to 

represent the most common local configuration of shallow aquifers and confining units of the southern watersheds. The model layers representing aquifers 

(Columbia and the Yorktown-Eastover aquifers) each 

were divided evenly into two layers, one upper and one 

lower. The Yorktown confining unit was divided evenly 

into three layers to approximate two confining units 

with an aquifer in between, which is the simplest configuration of the local hydrogeology throughout much 

of the southern watersheds of Virginia Beach. 

Most model layers were assigned uniform hydraulic 

conductivities. The transmissivities of each layer, however, varied with the thickness. The upper layer of the 

Columbia aquifer was assigned three separate zones for 

hydraulic conductivities: wetland, upland, or Poquoson 

(Pungo Ridge), assuming increasing values, respectively (fig. 17). Layer 6, representing the upper layer of 

the Yorktown-Eastover aquifer, was assigned a single 

zone of hydraulic conductivity for most of the watersheds. Two areas known to be generally less permeable 

from test drilling and driller’s information, one in and 
34 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 16. Grid, boundaries, and drains of the ground-water-flow and solute-transport model of the shallow aquifer system of the 

southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

North

CONSTANT-HEAD CELL DRAIN CELL INACTIVE CELL

EXPLANATION

Base from Mixon and others, 1989, 1:250,000

West Neck

Creek

Creek

Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS
Simulation of Ground-Water Flow and Solute Transport 35 Figure 17. Layers and hydraulic properties of the calibrated model of the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia.

307.90.3236.1167.621

0.00010.00010.300.0520.00230.00030.0020.00030.0003

HYDRAULIC CONDUCTIVITY,

IN METERS PER DAY

Horizontal Vertical

EXPLANATION

Upland Wetland Poquoson Wetland

NO
36 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

around Bellwood Estates Park and the other in and 

around Creeds Elementary School, were assigned 

lower hydraulic conductivities than elsewhere in that 

layer.

The model layers were designated Type 3 convertible, meaning that the transmissivity was calculated 

from saturated thickness and hydraulic conductivity 

(McDonald and Harbaugh, 1988, p. 5-38). Inter-block 

(cell) conductance was calculated by harmonic means 

and all cells were non-wettable (Harbaugh and others, 

2000, p. 57).

Calibration and Parameter Estimation

Average water levels from 38 wells (table 5), most 

of which were long-term averages, and chloride concentrations of water sampled from 123 wells (table 7) 

were used for calibration of the ground-water-flow and 

solute-transport model. The average water levels were 

used in WinPEST, a parameter estimation routine for 

calibrating Visual MODFLOW.

Ground-water-recharge rates were calibrated independently of parameter estimation so that a more 

unique solution to the ground-water-flow equation 

could be determined. Recharge rates were taken from 

previous studies that covered all or parts of southeastern Virginia (table 4). To take advantage of information 

from digital elevation models, recharge rates were 

assumed to be dependent on land surface altitudes. 

Evapotranspiration rates were assumed to be equal to 

recharge rates at the land surface and to decrease with 

depth to an extinction point.

Evapotranspiration rates generally reach maximum 

values at the land surface. The evapotranspiration rates 

were assumed to be zero where the water table was at 

land surface. Evapotranspiration rates in the model 

decrease with depth (and, thus, recharge rates increase) 

up to a predetermined extinction point. Initially, the 

extinction point was assumed to be 2.0 m, within the 

range of 1.8 to 2.4 m commonly assumed–although 

considerable variation can be expected because of such 

factors as climate and vegetation (McDonald and Harbaugh, 1988, p. 10-5).

The maximum recharge rate initially was assumed 

to be about 20 cm/yr, equal to the average annual 

ground-water discharge for the southern watersheds of 

Virginia Beach (Richardson, 1994b, p. 12, fig. 5). This 

initial maximum recharge rate, however, produced simulated water levels much higher than measured. Calibration and subsequent sensitivity tests indicated a 

better approximation of measured water levels if a 

maximum recharge rate of 10 cm/yr was assumed for 

the model with an extinction depth of 3 m.

The model was calibrated to average water levels 

by adjusting hydraulic conductivities with the aid of the 

parameter estimator, WinPEST. Minimum and maximum limits for horizontal and vertical hydraulic conductivities for WinPEST were taken from tables 2 and 

3, respectively. Much of the calibration process 

involved checking the limits to WinPEST so that horizontal hydraulic conductivities of individual units 

always were greater than or equal to vertical. Units 

known or presumed to be of lower hydraulic conductivity than others—such as the wetlands compared to 

upland—also were checked and controlled by limiting 

those parameter limits for WinPest. (Hydraulic conductivities of the wetlands in the southern watersheds are 

undetermined and a value of 0.3 m/d was presumed.) 

After calibration, most of the horizontal and vertical 

conductivities of the calibrated model were at the maximum or minimum limits assigned to WinPEST.

The default values for the mathematical parameters 

of WinPEST were adequate for almost every model 

simulation. PCG2, the preconditioned conjugate gradient solution package, version 2.4, was the solver chosen for MODFLOW. Default values for the solver also 

were adequate for almost every run.

The hydraulic parameters from the WinPEST calibration also were calibrated to measured chloride concentrations. The solute-transport model initially was 

assumed to contain very saline water (chloride concentrations of 10,000 mg/L) from the late Pleistocene 

when shallow seas and estuaries covered the study area 

and saturated the shallow aquifer system. Freshwater 

displacement of that saline water in the watersheds was 

simulated until a new steady state with regard to the 

measured chlorides was reached (fig. 18). Constant 

concentrations of 10,000 mg/L were assigned to the 

Back Bay, the North Landing River, and the Intracoastal Waterway, because those tidal waters still are 

saline to very saline. Constant chloride concentrations 

of 19,000 mg/L, representing seawater, were assigned 

to the Atlantic Ocean. 

Freshwater recharge was applied to the top layer of 

the ground-water-flow and solute-transport model until 

the simulated chloride concentrations approximated 

measured chloride concentrations as indicated by statistical methods. In the calibrated model, the new 

steady state was approximated after 31,500 years of 
Simulation of Ground-Water Flow and Solute Transport 37

freshwater recharge. The solute-transport model 

approached steady state with regard to measured chloride concentrations after 31,550 years of freshwater 

recharge. Freshwater displaced saline water that had 

filled the shallow aquifer system during the last major 

interglacial period more than 70,000 years ago when 

the shallow waters and estuaries of the Sedgefield Sea 

covered the study area (Mixon and others, 1989, 

sheet 1).

The steady state is indicated by chloride concentrations in the upper layers of the model that show little or 

no change in concentrations over periods of 10,000 

years or more, particularly between times of 30,000 

and 40,000 years (fig. 18). Freshwater continued to 

slowly replace saline water in the lower layers of the 

model beyond 30,000 years as indicated by simulated 

chloride concentrations, but few data points are available from those depths as calibration points. 

The third-order total variation diminishing (TVD) 

scheme was selected to solve the advective term of the 

MT3DMS transport equation because it is mass conservative, minimizes numerical dispersions, and essentially is free of artificial oscillations (Zheng and Wang, 

1998, p. 3-6). The TVD scheme uses the ULTIMATE 

(Universal Limiter for Transient Interpolation Modeling of the Advective Transport Equations) algorithm 

(Zheng and Wang, 1998, p. 3-5).

The root mean squared errors (RMSE’s) of measured to simulated water levels and chloride concentrations were used to calibrate the model (Waterloo 

Hydrologic, Inc., 2002, p. 250). The RMSE is calculated by subtracting each measured water level and 

chloride concentration from the equivalent simulated 

water level and chloride concentration. Each measured 

to model-simulated difference is squared. All of the 

squared differences then are summed, divided by the 

number of measurements, and then the square root is 

taken. The lower the RMSE, the better the approximation between measured and simulated water levels and 

chloride concentrations. The RMSE is determined for 

each simulated run and compared to the last run to 

determine whether the changes in parameters improve 

the approximation. The RMSE of measured to simulated water levels for the first run was 161 cm and the 

RMSE of the calibrated model was 60.7 cm. The normalized RMSE (the RMSE divided by the range 

between the maximum and minimum observations) 

was 30.2 percent for the first run and 12.7 percent for 

the calibrated model. 

The solute-transport model approached steady-state 

conditions with regard to measured chloride concentrations within about 30,000 to 40,000 years depending on 

simulated hydraulic properties. The model was calibrated after several iterations of adjusting hydraulic 

properties to water levels followed by calibration to 

chloride concentrations and then back to water levels. 

For the transient (chloride) calibration, the calibration 

time was chosen from the lowest RMSE near the absolute residual mean of the simulated to measured concentrations (nearest zero). The absolute residual mean 

is calculated by subtracting each measured concentration from the equivalent simulated concentration, dropping the sign (positive or negative), then summing all 

of the differences and dividing by the number of wells. 

Positive or negative bias is at a minimum at the lowest 

absolute residual mean. The residual mean is similar 

except that the sign is not dropped so that positive and 

negative values cancel.

The RMSE of measured to simulated concentrations of chloride for the calibrated model was 

636 mg/L at the lowest absolute residual mean, which 

was at 31,550 years (fig. 19A). The normalized RMSE 

with respect to chloride was 15 percent at that time 

(fig. 19B).

The calibrated model approximated the measured 

water levels (13-percent normalized RMSE) slightly 

more accurately than the chloride concentrations (15- 

percent normalized RMSE). The simulated chloride 

concentrations did not approximate the measured concentrations in the water from some wells. In particular, 

the simulated concentrations of chloride were much 

greater than those measured for three wells—Pungo1 

(62B 22), Pungo 2 (62B 18), and a well at Seneca

(62A 6). In contrast, the chloride simulated for one 

well at Redwing Park (63C 4) and one at Bellwood 

Estates Park (61B 43) were much less than those measured (fig. 20A). (See figure 8 for well locations.) The 

differences indicate that these sites do not conform to 

the simple geometry of the watershed model, or to the 

hydraulic properties estimated for the model units at 

those sites, or possibly both. Actual vertical changes in 

chloride concentrations within the individual units at 

these locations probably contribute to most of the error. 

More information or a different model conception and 

geometry at the local scale would be needed to simulate ground-water flow and solute transport more accurately in those areas.

Calibration of the model to the average annual 

water levels (fig. 20B) and to most of the measured
38 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 18. Simulated freshwater displacement of saline water, as indicated by chloride concentrations, in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia.

AFTER 20,000 YEARS

AFTER 30,000 YEARS

AFTER 40,000 YEARS

0 4,000 8,000 12,000 16,000 20,000 24,000 

0 4,000 8,000 12,000 16,000 20,000 24,000 

0 4,000 8,000 12,000 16,000 20,000 24,000 

North Landing River West Neck Creek North Landing River West Neck Creek North Landing River West Neck Creek 

WEST 

10

0

-110

-55

10

0

-110

10

0

-110

10

0

-110

ALTITUDE, IN METERS ABOVE AND BELOW SEA LEVEL

0 4,000 8,000 12,000 16,000 20,000 24,000 

AFTER 10,000 YEARS

DISTANCE, IN METERS

North Landing River West Neck Creek 

CONSTANT CHLORIDE CONCENTRATION OF 10,000 MILLIGRAMS PER LITER

LINE OF EQUAL CHLORIDE CONCENTRATION—Interval, in milligrams per liter, is variable

25

EXPLANATION

25

6,000 3,000 1,500 500 9

25

3,000 1

500

25

3,000 1,500

500

9,000 

25

1,500 500 

25

500

1,500 3,0

25 500 

25

500

6,000

1,500 

25

SALINE WATER—Chloride concentration greater than 500 and less than 19,000 milligrams per liter

-55-55

-55
Simulation of Ground-Water Flow and Solute Transport 39

Figure 19. Root mean square errors, absolute residual means, and residual means (A) and normalized root mean 

square errors (B) between measured and simulated chloride concentrations approaching equilibrium and the 

calibration point for the simulation of ground-water flow of the southern watersheds of Virginia Beach, Virginia.

250

200

100

50

0

150

NORMALIZED ROOT MEAN SQUARE ERROR, IN PERCENT

1 10,000 20,000 30,000 40,000

TIME, IN YEARS

Calibration point: 15 percent 

at 31,550 years

(A)

(B)

TIME, IN YEARS

1 10,000 20,000 30,000 40,000

8,000

10,000

6,000

4,000

2,000

0

ERROR, IN MILLIGRAMS PER LITER

Root mean squared error

Absolute residual mean

Residual mean

Calibration point: chloride 

concentration of 637 milligrams

per liter at 31,550 years
40 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 20. Differences between simulated and measured chloride concentrations (A)

and simulated and measured water levels (B) of the calibrated model of the southern 

watersheds of Virginia Beach, Virginia.

5

4

3

2

1

0

-1

-1 0 1 2 3 4 5

SIMULATED WATER LEVEL, IN METERS ABOVE OR BELOW NGVD 1929

MEASURED WATER LEVEL, IN METERS ABOVE OR BELOW NGVD 1929

95% interval

95% confidence interval

5,000

4,000

3,000

2,000

1,000

0

0

SIMULATED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

1,000 4,000 2,000 3,000 5,000

MEASURED CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

95% interval

95% confidence interval

(A)

(B)

62B 18 (Pungo 2)

(Pungo 1)

62A 6 

61C 43 (Bellwood Estates Park)

63C 4 (Redwing Park)

(Seneca)

62B 22
Simulation of Ground-Water Flow and Solute Transport 41

chloride concentrations, however, indicates that the 

model is an adequate estimator of ground-water-flow 

and saline-water movement for watershed planning. 

Also, approximations of the water levels and chloride 

concentrations of water sampled from most of the wells 

indicate that the freshwater and saline water interfaces 

of the shallow aquifer system probably are in dynamic 

equilibrium with average water levels and modern sea 

levels.

Sensitivity Analyses

The RMSE of measured to simulated water levels 

also was used to test the sensitivity of the calibrated 

model to changes in aquifer properties. Horizontal and 

vertical hydraulic conductivities were tested in multiples of the calibrated values. Simulated water levels of 

the calibrated model were more sensitive to changes in 

hydraulic conductivity in the Columbia aquifer than in 

deeper units (fig. 21). Water levels were moderately 

sensitive to changes in the horizontal hydraulic conductivity of all of the other units. Simulated water levels 

were sensitive to decreases in the vertical hydraulic 

conductivity of the Yorktown confining unit, but were 

not sensitive to increases in the vertical conductivity of 

the Yorktown confining unit or the Yorktown-Eastover 

aquifer.

The sensitivity of the ground-water-flow model to 

mutual changes in recharge rates and evapotranspiration extinction depths was delineated by plotting and 

contouring RMSE’s of the measured to simulated water 

levels (fig. 22). A recharge rate of 10 cm per year with 

an extinction depth of 3.0 m was chosen as a reasonable calibration point. Recharge rates less than 

10 cm/year were not expected, as indicated by previous 

studies, and extinction depths greater than 3.0 m, 

although possible, were considered less likely. However, the model was not sensitive to changes in 

recharge rates and extinction depths beyond those of 

the calibration point. Different rates and depths corresponding to the area where RMSE’s are less than 61 cm 

also could have been chosen as calibration points with 

regard to measured and simulated water levels. 
42 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 21. Sensitivity of the ground-water-flow model of the southern watersheds of Virginia Beach, Virginia, to changes 

in hydraulic conductivity.

2.25

2.30

2.20

2.15

2.10

2.05

2.00

1.95

ROOT MEAN SQUARED ERROR OF WATER LEVELS, IN FEET

69

70

68

67

66

65

64

ROOT MEAN SQUARE ERROR OF WATER LEVELS, IN CENTIMETERS

63

62

61

60

0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0

MULTIPLE OF CALIBRATION

61.0

61.9

62.8

68.3

60.8

61.6

63.4

68.9

69.2

60.7

61.0

61.6

64.3

63.1

61.0

61.6

60.7

60.9

61.7

61.3

61.0

61.3

61.6

62.2

60.7

61.6

61.9

63.7

64.3

Columbia aquifer (horizontal)

Yorktown confining unit (horizontal)

Yorktown confining unit (vertical)

Yorktown-Eastover aquifer (horizontal)

Yorktown-Eastover aquifer (vertical)

Columbia aquifer (vertical)

EXPLANATION

ROOT MEAN SQUARED ERROR OF MEASURED TO 

CALIBRATED WATER LEVEL, IN CENTIMETERS, 

AT THE CALIBRATION POINT

ROOT MEAN SQUARED ERROR OF MEASURED TO 

CALIBRATED WATER LEVEL, IN CENTIMETERS

63.4

60.7
Simulation of Ground-Water Flow and Solute Transport 43

Figure 22. Sensitivity of the ground-water-flow model of the southern watersheds of Virginia Beach, Virginia, to mutual changes 

in recharge rates and extinction depths.

1

2

3

14

13

12

11

10

9

8

7

6

5

4

15

0.3

1.0

2.0

4.6

4.0

3.0

RECHARGE, IN INCHES PER YEAR

RECHARGE, IN CENTIMETERS PER YEAR

0 1 2 3 4 5 6 7 8 9 10

61.6

64.3 60.7

61.0

64.3

62.5

62.2

61.0

61.3

64.0 61.9

61.0

60.9

60.7

60.7

61.0

64.0

67.7

70.1

60.7

64.3

62.8

61.6

61.0

60.7

66.4

64.6

62.2

61.3

65.5

64.0

62.5

62.5

61.0

64.0

EXTINCTION DEPTH, IN FEET

EXTINCTION DEPTH, IN METERS

LINE OF EQUAL ROOT MEAN SQUARE ERROR, 

IN CENTIMETERS—Interval is variable

ROOT MEAN SQUARE ERROR OF MEASURED TO 

SIMULATED WATER LEVEL, IN CENTIMETERS, 

AT THE CALIBRATION POINT

ROOT MEAN SQUARE ERROR OF MEASURED TO 

SIMULATED WATER LEVEL, IN CENTIMETERS

64.0

60.7

62.5

EXPLANATION

0 5 10 15 20 25
44 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

ANALYSES OF GROUND-WATER FLOW 

AND SALINE-WATER INTRUSION

The periodic recharge of freshwater to the Columbia aquifer sustains annual ground-water levels in the 

shallow aquifer system. Steady annual water levels sustain a dynamic equilibrium whereby freshwater flows 

continually down and away from the center of the 

higher ground and the sand ridges to mix with saline 

water from the tidal rivers, salt marshes, inlets, bays, 

and the Atlantic Ocean. Some freshwater also leaks 

down through the Yorktown confining unit into the top 

of the Yorktown-Eastover aquifer, but saline water generally is found in the lower parts of the aquifer.

Once calibrated to the dynamic equilibrium, the 

ground-water-flow and solute-transport model was 

used to estimate a ground-water budget of the southern 

watersheds and to simulate patterns of ground-water 

flow and the distribution of chloride concentrations in 

the aquifers. The steady-state ground-water-flow and 

solute-transport model was used to simulate declines in 

water levels (drawdowns) around two hypothetical well 

fields and to simulate the potential movement of chloride concentrations representing saline-water intrusion 

near one of those hypothetical well fields. The model 

also was used to simulate drawdowns around two 

hypothetical open-pit mines. 

Ground-Water Budget

A ground-water budget for the southern watersheds 

can be estimated from the mass balance of the calibrated ground-water-flow model of the shallow aquifer 

system. Rates of 10 cm/yr applied to the top cells of the 

calibrated model resulted in a volumetric recharge of 

145,000 m3/d to the watersheds. Evapotranspiration 

removed 119,000 m3/d, or about 82 percent of the 

recharge, leaving 26,000 m3/d (7 million gal/d), or 

about 18 percent, as effective recharge to the water 

table. Inflow from constant heads, representing freshwater lakes and ponds, provided another 400 m3/d.

 Of the water that effectively recharged the shallow 

aquifer system, 23,000 m3/d (6 million gal/d) discharged to the tidal zones and open waterways, including the Intracoastal Waterway, North Landing River, 

West Neck Creek, the Back Bay, and the Atlantic 

Ocean, represented by constant heads in the model. A 

smaller portion of recharge–3,700 m3/d (1 million 

gal/d)–discharged to drain cells of the model representing non-tidal, freshwater ditches and streams.

 Some ground water also is removed from the 

watersheds by pumping for domestic drinking water 

and irrigation, but those withdrawals are a negligible 

percentage of the total annual withdrawals. Domestic 

ground-water use was small, estimated at 1,400 m3/d 

(0.38 million gal/d) for southern Virginia Beach 

(Johnson, 1999), and irrigation use for agriculture and 

golf courses was sporadic, estimated at 790 m3/d 

(0.21 million gal/d) in all of Virginia Beach in 2000 

(U.S. Geological Survey, 2003, Aggregate Water Use 

Data System). 

Ground-Water-Flow Patterns and Chloride 

Distributions

Ground-water-flow patterns in shallow aquifers 

reflect the topography. Simulated water levels and flow 

vectors of the calibrated ground-water model show the 

general patterns of flow in the aquifers of the southern 

watersheds. In the Columbia aquifer, water from the 

higher land surface of the watersheds flows downward 

and outward toward the nearest drains and tidal streams 

where the flow changes abruptly upward indicating 

where most of the ground water discharges (fig. 23).

 Along the ground-water divide of the two watersheds, near and along Pungo Ridge, the flow is downward and outward in the Columbia aquifer west to the 

wetlands along the North Landing River and east to the 

Back Bay or the Atlantic Ocean where the ground 

water discharges near the shore. Farther out in the Back 

Bay and the Atlantic Ocean, negligible flow velocities 

are indicated by small vectors (dots). Some ground 

water also leaks downward through the confining units 

beneath the Columbia into the confined aquifers.

 In the model layer representing the sand aquifer 

between the two confining units of the Yorktown, the 

flow patterns are similar to that of the Columbia aquifer, but upward leakage over a broader area indicates a 

more intermediate pattern for the sand unit of the Yorktown (fig. 24). Much of the water that leaks downward 

into the confined sand unit of the Yorktown leaks back 

upward into the Columbia aquifer and discharges 

locally to the nearest wetland or tidal creek, or to the 

Back Bay and the Atlantic Ocean. Some small amount 

of water, however, leaks further downward from the 

sand unit and the confining unit beneath into the Yorktown-Eastover aquifer beneath.
Analyses of Ground-Water Flow and Saline-Water Intrusion 45

Figure 23. Simulated flow vectors and water levels in the lower half of the Columbia aquifer of the southern watersheds of 

Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

North

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

Study area

LINE OF EQUAL WATER LEVEL—Contour 

interval is 1 meter

DOWNWARD GROUND-WATER FLOW

UPWARD GROUND-WATER FLOW

1.0

EXPLANATION

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

4.0

3.0

2.0

1.0

1.0

1.0

2.0

3.0

Base from Mixon and others, 1989, 1:250,000

Boundary of the Back Bay and North Landing 

River watersheds
46 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 24. Simulated flow vectors and water levels in the sand aquifer of the Yorktown confining unit of the southern watersheds of 

Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

EXPLANATION

North

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

4.0

3.0

1.0

2.0

2.0

Base from Mixon and others, 1989, 1:250,000

Study area

LINE OF EQUAL WATER LEVEL—Contour 

interval is 1 meter

DOWNWARD GROUND-WATER FLOW

UPWARD GROUND-WATER FLOW

1.0

Boundary of the Back Bay and North Landing 

River watersheds
Analyses of Ground-Water Flow and Saline-Water Intrusion 47

In the model layer representing the upper half of the 

Yorktown-Eastover aquifer, the basic flow patterns are 

more regional than those of the shallower aquifers. 

Almost all of the flow is from the west and north 

toward the east or south as opposed to some westward 

flow paths toward West Neck Creek and the North 

Landing River in the shallower aquifers (fig. 25). 

Ground water is leaking upward from the Yorktown-Eastover aquifer over a broad area along the wetlands and tidal rivers of West Neck Creek and North 

Landing River and to the Atlantic Ocean. To the southeast, negligible flow velocities are indicated by small 

vectors in and around the Back Bay. Most of the 

upward leakage from the Yorktown-Eastover aquifer 

would be expected to discharge within the wetlands of 

the North Landing River. Saline water, not displaced by 

freshwater, probably remains in the Yorktown-Eastover 

aquifer in the south and east, as indicated by the 

ground-water flow and solute simulations. The simulated flow patterns indicate that the freshwater to saline 

water components of the shallow aquifer system probably are in or are approaching a dynamic equilibrium.

The simulated distributions of chloride indicate that 

freshwater has been displaced in some areas in the 

upper half of the Yorktown-Eastover aquifer (fig. 26), 

but saline water predominates in the lower half of the 

Yorktown-Eastover (fig. 27). The simulated distribution of chloride concentrations in the Yorktown-Eastover aquifer approximate those measured and contoured 

(fig. 13). Both the simulated and measured distributions of chloride indicate that freshwater in the Yorktown-Eastover aquifer probably is limited to isolated 

areas below the higher altitudes in the west and north 

along the watershed divide and along the divide of the 

two southern watersheds beneath the northern parts of 

Pungo Ridge. 

Drawdowns Near Hypothetical Well Fields

The aquifers of the shallow aquifer system were 

deposited in shifting coastal environments, and the sediments that comprise the aquifers can change over relatively short distances from sand and gravel to fine sand, 

including some silt, to silt and clay. Recharge to the 

aquifers is limited in large tracts of the watersheds by 

clayey soils and extensive wetlands. Also, the quality 

of the water available from the aquifers can vary considerably from one location to another. All of these factors have limited large-scale production of ground 

water in the watersheds, and in the rest of Virginia 

Beach and the surrounding area as well.

One of the most productive well fields in Virginia 

Beach was at Pembroke about 3 km north of the study 

area (fig. 1). The Pembroke well field produced sustained freshwater supplies from a depth of about 38 m 

beginning in 1963. A total of about 1,100 m3 of water 

per day (300,000 gal/d) was pumped from seven active 

wells at Pembroke in 1979 (Geraghty and Miller, 1979, 

p. 1-3). Well production could have been increased at 

Pembroke, but the risk of upward movement or intrusion of “brackish water” limited the supply (Wiley and 

Wilson, Inc., 1979, p. 7).

Using the Pembroke well field as an indicator, 

about 1,900 m3/d (0.5 million gal/d) was assumed to be 

the maximum sustained production for simulating well 

fields in this report. To compare drawdowns from different permeable zones, two hypothetical well fields, 

each steadily pumping 1,900 m3/d from the upper half 

of the Yorktown-Eastover aquifer, were simulated with 

the calibrated model (fig. 28). Both well fields were 

located on the ground-water divide of the two watersheds, but the well field to the north probably would 

have a higher hydraulic conductivity (7.6 m/d in the 

model) whereas the well field to the south would be in 

an area of the Yorktown-Eastover aquifer identified by 

coring and by local drillers as generally having lower 

hydraulic conductivity (2 m/d in the model). 

The hypothetical well fields pump at the same rates, 

but the depth and extent of the water-level declines 

(drawdowns) in and around the well fields would be 

different at the new steady state, as indicated by the 

simulated contours. Pumping the hypothetical well 

field in the north, in more permeable sediments, would 

result in a smaller drawdown affecting a smaller area in 

the confined aquifer than the well field in the south. 

Pumping from the confined aquifer in the south, in less 

permeable sediments, would result in a deeper drawdown and the area affected would be greater than that 

in the north. The drawdown in the southern well field 

also is affected by hydraulic boundaries around the site, 

causing some elongation in the shape of the simulated 

concentric contours.

Intrusion of Saline Water Near a 

Hypothetical Well Field

Beneath the divide of the watersheds along the 

northern stretch of Pungo Ridge, freshwater recharges
48 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 25. Simulated flow vectors and water levels in the upper half of the Yorktown-Eastover aquifer of the southern watersheds of 

Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

EXPLANATION

North

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

Study area

LINE OF EQUAL WATER LEVEL—Contour 

interval is 1 meter

DOWNWARD GROUND-WATER FLOW

UPWARD GROUND-WATER FLOW

1.0

Boundary of the Back Bay and North Landing 

River watersheds

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

3.0

2.0

1.0

Base from Mixon and others, 1989, 1:250,000
Analyses of Ground-Water Flow and Saline-Water Intrusion 49

Figure 26. Simulated chloride concentrations in the upper half of the Yorktown-Eastover aquifer of the southern watersheds of 

Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

Base from Mixon and others, 1989, 1:250,000

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

EXPLANATION

North

West Neck

Creek

Creek

Bridge

London

Bypass

Canal

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

25

25

250

250

500

1,500

3,000

9,000

6,000

3,000

500

1,500

250

SALINE WATER—Chloride concentration greater 

than 500 milligrams per liter

Study area

LINE OF EQUAL CHLORIDE CONCENTRATION—

Interval, in milligrams per liter, is variable

25

Boundary of the Back Bay and North Landing 

River watersheds
50 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 27. Simulated chloride concentrations in the lower half of the Yorktown-Eastover aquifer of the southern watersheds of 

Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

EXPLANATION

North

Base from Mixon and others, 1989, 1:250,000

West Neck

Creek

Creek

Bridge

London

Bypass

Canal

SALINE WATER—Chloride concentration greater 

than 500 milligrams per liter

Study area

LINE OF EQUAL CHLORIDE CONCENTRATION—

Interval, in milligrams per liter, is variable

Boundary of the Back Bay and North Landing 

River watersheds

500

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

1,500

1,500

500

1,500

3,000

3,000

6,000

9,000

6,000
Analyses of Ground-Water Flow and Saline-Water Intrusion 51

Figure 28. Drawdowns around two hypothetical well fields, each pumping 1,900 cubic meters per day (0.5 million gallons per day), on the 

boundary of the watersheds from the upper half of the Yorktown-Eastover aquifer of the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

LINE OF EQUAL DRAWDOWN, 

IN METERS—Contour interval 

is 2 meters

HYPOTHETICAL WELL FIELD

1.0

EXPLANATION

North

HYDRAULIC CONDUCTIVITY

2 METERS PER DAY

HYDRAULIC CONDUCTIVITY

7.6 METERS PER DAY

Waterway

Study area

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

Base from Mixon and others, 1989, 1:250,000

1.0

3.0

1.0

3.0

5.0

West Neck

Creek

Creek

Bridge

London

Bypass

Canal
52 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

the water table (Columbia aquifer) and, in some places, 

leaks into the top of the Yorktown-Eastover aquifer. 

Supplies of freshwater from the Yorktown-Eastover are 

a possibility in Virginia Beach and in the surrounding 

area; however, such supplies have been limited because 

of saline-water intrusion. “With little exception, all 

large scale pumping operations (> 300,000 gpd 

[1.1 Ml/day]) have resulted in brackish or saline water 

intrusion and upconing” (Leahy, 1986, p. 3). The 

potential intrusion of saline water toward the northern 

hypothetical well field of the previous scenario was 

simulated. Intrusion of saline water toward the southern 

well field was not simulated because of low permeability and the lack of freshwater in the Yorktown-Eastover 

aquifer there.

 Chloride movement toward the hypothetical northern well field of the previous scenario was simulated 

for 100 years with the calibrated ground-water-flow 

and solute-transport model to indicate the potential for 

saline-water intrusion in the confined aquifer. Pumping 

from the top half of the Yorktown-Eastover aquifer 

beneath the ridge would remove freshwater. The result 

would be to allow saline water in the aquifer to begin 

moving slowly toward the well field, as indicated by 

simulated chloride concentration gradients in the aquifer from just after the start of pumping (A), after 33 

years of pumping (B), after 67 years of pumping (C), 

and after 100 years of pumping (D) (fig. 29). The nearest source of saline water in the aquifer would be from 

the southwest beneath West Neck Creek. (Saline water 

probably was not displaced by freshwater beneath West 

Neck Creek at the end of the Pleistocene, and the creek 

is tidal and remains a possible source of saline water.)

After 100 years, the 250-mg/L chloride line would 

be within the simulated pumping cell approaching the 

center of the well field and the 500 mg/L chloride line 

would be close behind. In the simulation, chloride concentrations in the center of the pumping cell changed 

from 90 mg/L to 150 mg/L over the 100-year span. 

Saline water to the east also would move toward the 

well field. The eastern source, however, is farther away 

than the southwestern source and it would not approach 

the well field in 100 years.

A vertical view of the simulated pumping cell, 

exaggerated 10 times, indicates that upward movement 

of saline water from deeper units beneath the well field 

probably would not take place in 100 years (fig. 30). 

Changes in chloride concentrations to the east of the 

well also were negligible in the vicinity of the well. To 

the west of the pumping cell, however, the saline water 

would begin moving slowly eastward toward the well 

field, as shown by the changes in lines of equal chloride 

concentrations of 250, 500, and 1,000 mg/L. Much of 

the apparent upward movement of chloride concentration gradients in this view is an artifact of the vertical 

exaggeration of the illustration. 

The simulation indicates that if freshwater is found 

in sediments of the Yorktown-Eastover aquifer and if 

those sediments are permeable enough to supply 

1,900 m3/d (0.5 million gal/d), such a well field could 

sustain freshwater for a considerable time (possibly 

decades), but eventually the supply would become 

more saline. The rate of saline-water intrusion toward 

the freshwater supply would depend on the rate of 

pumping, the aquifer properties in and around the site, 

and the proximity of the well field to saline-water 

sources. Desalination could, however, extend the use 

such a well field.

Drawdowns Around Hypothetical Open-Pit 

Mines

The sand-and-gravel deposits that form some of the 

most permeable aquifers of the shallow system also are 

sources of building materials. Open pit mining of sand 

and gravel has been a common practice in the southern 

watersheds and throughout Virginia Beach in the recent 

past. Dewatering of the open pits can affect the water 

supplies of surrounding areas.

To analyze the potential affects of dewatering from 

the Columbia aquifer, two cells, each 400 m2, in the top 

layer of the calibrated model were pumped steadily. 

Both cells were on the divide between the two southern 

watersheds, at the same locations as in the previous 

simulations, but the dewatering would be from the 

unconfined Columbia aquifer, which has different 

hydraulic properties than the deeper confined aquifer. 

The pumping rates required to dewater each cell to 

approximately the same depth was determined by trial 

and error. The simulated well screen was 1.5 m in 

length at the bottom of each cell.

Differences in the simulated pumping rates required 

to dewater the cells to approximately the same depth 

reflect differences in the local hydrogeology, primarily 

the hydraulic conductivity of the Columbia aquifer at 

each site (fig. 31). The site to the north is in an upland 

area that was represented in the model as having a 

hydraulic conductivity of 7.9 m/d. To dewater the cell 

to the north, 545 m3/d (100 gal/min) was required. The 
Analyses of Ground-Water Flow and Saline-Water Intrusion 53

Figure 29. Horizontal view of simulated chloride concentrations approaching a hypothetical well field pumping 1,900 cubic meters per day

at start of pumping (A), after 33 years of pumping (B), after 67 years of pumping (C), and after 100 years of pumping (D), on the boundary

of the watersheds from the upper half of the Yorktown-Eastover aquifer of the southern watersheds of Virginia Beach, Virginia.

2,400

2,000

1,600

1,200

800

400

0

2,400

2,000

1,600

1,200

800

400

0 0 400 800 1,200 1,600 2,000 2,400 2,800 3,200 0 400 800 1,200 1,600 2,000 2,400 2,800 3,200

250

2,000

1,000

500

250

2,000

1,000

500

250

2,000

1,000

500

250

2,000

1,000

500

DISTANCE, IN METERS

DISTANCE, IN METERS

PUMPING CELL AND WELL-FIELD CENTER

LINE OF SIMULATED CHLORIDE CONCENTRATION, 

IN MILLIGRAMS PER LITER—Contour interval 

is variable

DOWNWARD GROUND-WATER FLOW

250 WATERSHED BOUNDARY

EXPLANATION

START OF PUMPING

AFTER 67 YEARS OF PUMPING (C)

AFTER 33 YEARS OF PUMPING (B)

AFTER 100 YEARS OF PUMPING (D)

(A)
54 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

Figure 30. Vertical view of simulated changes in chloride concentrations near a hypothetical well field after 100 years of pumping 1,900 cubic meters per day (0.5 mper day) in the upper half of the Yorktown-Eastover aquifer of the southern watersheds of Virginia Beach, Virginia.

25

250

500

1,000

CHANGE IN CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER,AFTER 100 YEARS OF PUMPINGLINE OF EQUAL CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER(BEFORE PUMPING)—Contour interval is variableLINE OF EQUAL CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER(AFTER 100 YEARS OF PUMPING)—Contour interval is variableAPPROXIMATE GROUND-WATER FLOW DIRECTION

6

100

109

0

-80

-60

-40

-20

0

HYPOTHETICAL PUMPING WELL

MODEL CELL IN WHICH WELL FIELD IS LOCATED WELL SCREEN INTERVAL

300 600 900 1,200 1,500 1,800 

DISTANCE, IN METERS

EXPLANATION

2525

V

500

250

250
Analyses of Ground-Water Flow and Saline-Water Intrusion 55

Figure 31. Simulated flow directions and drawdowns around two hypothetical open-pit mines pumping on the watershed boundary

from the water table (Columbia aquifer) in the southern watersheds of Virginia Beach, Virginia.

36o40'

36o

50' 76o

10' 76o

ATLANTIC

OCEAN

Landing

River

Chesapeake

Virginia Beach

Back

Bay

Intracoastal

Waterway

0 1 2 3 4 MILES

0 1 2 3 4 KILOMETERS

WELL FIELD AND PUMPING RATE, IN 

CUBIC METERS PER DAY 

LINE OF EQUAL DRAWDOWN, 

IN METERS—Contour interval 

is variable

1.0

EXPLANATION

North

West

Neck

Creek

Creek

Bridge

London

Bypass

Canal

0.3

1.0

0.5

0.3

0.5

1.0

2.0

545

1,226

545

Base from Mixon and others, 1989, 1:250,000
56 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

drawdown at the center of the cell was 5 m and the 

radius of the 0.3-m drawdown contour was about 1 km.

The site to the south was in the Poquoson Member 

of the Sedgefield Formation that had the highest permeability in the model, a hydraulic conductivity of 

30 m/d, almost four times that of the site to the north. 

To dewater this site would require about 1,200 m3/d 

(225 gal/min) or more than twice the pumping rate of 

the site to the north. The drawdown at the center of the 

cells was 4.1 m and the radius of the 0.3-m drawdown 

contour was about 2.5 km at the maximum elongation.

Drawdown at the center of each well was approximately the same but the shape of the cone of depression, indicated by the contoured declines in water 

levels around each site, was different. The dewatering 

of the southern site would affect a larger area, as indicated by the 0.3-m (1-ft) drawdown contour. A notch in 

the 0.3-m drawdown contour to the west resulted from 

encountering a wetland cell, which was designated 

with a hydraulic conductivity of 0.3 m/d. To the east, 

the 0.3-m contour reached the hydraulic boundary of 

the constant-head cells of Back Bay.

The model simulations indicate that the pumping 

rate required to dewater a site depend on the aquifer 

properties and on the hydrologic boundaries in and 

around the site. More pumping is required to dewater a 

site where sediments are more permeable, and a larger 

area around the site would be affected than at a site 

where materials are less permeable.

SUMMARY AND CONCLUSIONS

Population and tourism continues to grow in Virginia Beach, but the supply of freshwater is limited. A 

pipeline from Lake Gaston supplies water for northern 

Virginia Beach, but ground water is widely used to 

water lawns in the north, and most southern areas of the 

city rely solely on ground water. Supplies of fresh 

ground water are limited by high concentrations of 

chloride, iron, and manganese in some areas. Water 

from depths greater than 60 m generally is too saline to 

drink. The city of Virginia Beach and the U.S. Geological Survey began a cooperative study to (1) refine the 

hydrogeologic framework of the shallow aquifer system, and (2) better understand the distribution of fresh 

ground water, its potential uses, and its susceptibility to 

contamination.

Specific objectives of this phase of the investigations were to (1) map chloride concentrations in the 

shallow aquifers of the southern watersheds of Virginia 

Beach, (2) determine the patterns of ground-water flow 

in the shallow aquifers of the southern watersheds, and 

(3) evaluate potential changes in drawdowns and chloride concentrations, representing saline-water intrusion, resulting from hypothetical withdrawals of 

ground water in the southern watersheds of Virginia 

Beach.

The Columbia aquifer, the Yorktown confining unit, 

and the Yorktown-Eastover aquifer compose the hydrogeologic units of the shallow aquifer system of Virginia 

Beach. The top altitudes of these units were extended 

from continuous core sites reported previously, to other 

sites in the southern watersheds, where geophysical 

logs and lithologic descriptions of sediments had been 

recorded. The top altitudes of the units were contoured 

by linear Kriging. Chloride data collected during this 

investigation and from previous studies were contoured 

also by linear Kriging to map the general distribution of 

chlorides for each unit.

The Columbia and Yorktown-Eastover aquifers are 

poorly confined throughout most of the southern watersheds of Virginia Beach and the freshwater-tosaline-water distribution is in a dynamic equilibrium 

with average ground-water levels, measured concentrations of dissolved salts (chlorides), and modern sea levels. The chloride concentrations measured in water 

from wells open to the shallow aquifers and confining 

units of the southern watersheds showed virtually no 

changes in concentration through recent time.

In the humid climate of Virginia Beach, the periodic recharge of freshwater through the shallow aquifer 

system occurs often enough to create a steady-state balance or a dynamic equilibrium whereby freshwater 

flows continually down and away from the center of the 

higher ground and the sand ridges to mix with saline 

water from the tidal rivers, bays, salt marshes, and the 

Atlantic Ocean. Fresh ground water from the Columbia 

aquifer also leaks down through the Yorktown confining unit into the upper half of the Yorktown-Eastover 

aquifer and then flows within the Yorktown-Eastover 

above saline water that remains in the lower half of the 

shallow aquifer system.

Ground-water-flow patterns in shallow aquifers of 

Virginia Beach reflect the topography. Ground-water 

recharge is limited in much of the southern watersheds 

because the land surface generally is low and flat, 

whereas bays, wetlands, tidal rivers, and tidal streams 

where fresh ground water discharges extend throughout 

the watershed area. Also, soils over much of the water-
Summary and Conclusions 57

sheds are rich in clay and ditching has been used to 

lower the water table for agriculture. Where sand 

ridges do allow greater recharge, generally unconfined 

conditions prevail. Ground-water flow can be deeper 

below the ridges, but discharge areas are nearby in wetlands, tidal creeks, or just off shore in the Back Bay or 

the Atlantic Ocean. Thus, ground-water-flow lines tend 

to be short and shallow in much of the southern watersheds.

A three-dimensional, steady-state, ground-waterflow and solute-transport model was used to simulate 

the dynamic equilibrium between freshwater and saline 

water in the shallow aquifer system as indicated by 

water-level hydrographs and chloride concentrations. 

The equilibrium was approached after 31,550 years of 

freshwater recharge and displacement of saline. Saline 

water saturated the shallow aquifer system during the 

last major interglacial period more than 70,000 years 

ago when estuaries and shallow seas covered the area. 

At model calibration, average water levels were 

approximated slightly more accurately than chloride 

measurements (13-percent normalized RMSE of 38 

water levels compared to 15-percent normalized RMSE 

of 123 chloride measurements). The chloride concentrations in the model did not approximate the measured 

concentrations for some wells, indicating sites where 

local hydrogeologic units or unit properties do not conform to the simple hydrogeology simulated with the 

model.

The calibrated steady state, ground-water-flow and 

solute-transport model was used to simulate hypothetical scenarios. The simulation indicates that if freshwater is found in sediments of the Yorktown-Eastover 

aquifer, and if those sediments are permeable enough to 

supply 1,900 m3/d (0.5 million gal/d), such a well field 

could sustain freshwater, possibly for decades, but 

eventually the water would become more saline. The 

rate of saline-water intrusion toward the freshwater 

supply would depend on the rate of pumping, aquifer 

properties, and the proximity of the well field to saline 

water sources. 

Steady-state simulations with the calibrated model 

also indicate that a pumping rate of 545 m3/d 

(100 gal/min) would be required to dewater to a depth 

of 5 m in a hypothetical open-pit mine in the upland 

part of the Columbia aquifer and that the 0.3-m drawdown contour around the site would be about 1 km in 

radius. A pumping rate of 1,200 m3/day (225 gal/min) 

would be needed to dewater an open-pit mine about 

4.1 m deep in the Columbia aquifer where materials are 

more permeable, and a large area around the site, about 

2.5 km at the maximum elongation, would be drawn 

down about 0.3 m.

The aquifers of the shallow aquifer system were 

deposited in shifting coastal environments, and the sediments that comprise the aquifers can change over relatively short distances from sand and gravel to fine sand, 

including some silt, to silt and clay. Also, the quality of 

water available from the aquifers can vary considerably 

from one location to another. Because it is difficult to 

correlate the discontinuous sediments from one site to 

another, the hydrogeologic framework of the shallow 

aquifer system is not well defined in many areas of the 

southern watersheds, as well as the rest of the city of 

Virginia Beach. Additional field information such as 

geophysical logs, coreholes, water-level observations, 

and water-quality data could improve the conceptual 

framework at the local (site-specific) scale in many 

areas of Virginia Beach. Such detailed information 

would be needed for any field explorations or site-specific ground-water-flow and solute-transport simulations.

 The usual assumptions associated with 

ground-water-flow and solute-transport simulations of 

layered aquifer systems as applied to the models used 

in this study are valid for the objectives of this study. 

The assumptions are appropriate as used for the system 

conceptualization; however, before applying the model 

for other purposes, the appropriateness of the assumptions, particularly the boundary conditions, should be 

evaluated.

The ground-water-flow and solute-transport model 

of the southern watersheds documented in this report is 

a simple representation of a complex, and in some 

places, an uncertain hydrogeologic framework. The 

calibrated steady-state ground-water flow and solute-transport model does, however, combine a large 

amount of field information with sound hydraulic and 

transport principles to produce reasonable results on 

the watershed scale. 
58 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia

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 61

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

above

NGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

61C 52 na 364846076121701 228-00008 364846 761217 -12.96 15 3.66 29.87 Columbia aquifer 3/11/80 Siudyla and othe62C 71 na 364836076002201 228-00033 364836 760022 2.59 5 6.10 21.95 Columbia aquifer 1/13/77 Siudyla and othe61C 49 na 364843076105301 228-00051 364843 761053 -11.89 19 8.23 18.29 Columbia aquifer 10/31/72 Siudyla and othe62A 25 na 363623076051001 228-00055 363623 760510 -5.49 21 3.66 26.21 Columbia aquifer 4/12/78 Siudyla and othe63B 6 na 364330075581401 228-00057 364330 755814 -12.20 203 .91 20.12 Columbia aquifer 4/12/78 Siudyla and othe63B 7 na 364334075581301 228-00058 364334 755813 -9.15 210 .91 9.14 Columbia aquifer 4/12/78 Siudyla and othe63C 27 na 364633075582001 228-00128 364633 755820 -6.10 50 1.52 7.92 Columbia aquifer 12/28/77 Siudyla and othe62A 26 na 363324076001901 228-00137 363324 760019 -3.96 20 3.05 9.14 Columbia aquifer 4/06/78 Siudyla and othe62A 27 na 363617076013401 228-00138 363617 760134 -1.52 19 3.05 7.62 Columbia aquifer 4/06/78 Siudyla and othe62B 36 na 364154076032801 228-00147 364154 760328 -3.81 22 3.05 7.32 Columbia aquifer 10/27/78 Siudyla and othe62C 67 na 364714076030401 228-00169 364714 760304 -2.29 20 4.27 7.32 Columbia aquifer 1979 Siudyla and othe62A 3 SOW 097B 363537076061002 228-00171 363355 760617 -3.66 16 3.05 20.73 Columbia aquifer 7/26/79 Siudyla and othe61C 57 na 364810076114201 228-00182 364810 761142 -13.41 7 6.10 3.96 Columbia aquifer 6/15/79 Siudyla and othe62C 69 na 364846076043701 228-00195 364846 760437 -.15 77 3.35 9.14 Columbia aquifer 4/03/81 Siudyla and othe62C 21 na 364515076012101 228-00288 364515 760121 -2.90 23 3.96 19.81 Columbia aquifer 3/9/81 Betz-Converse-M63B 5 na 364459075595401 228-00294 364459 755954 -13.72 23 3.05 17.37 Columbia aquifer – Converse-Ward-62C 70 na 364522076001701 228-00298 364522 760017 -12.96 23 3.66 19.81 Columbia aquifer – Converse-Ward-63C 12 na 364515075584101 228-00359 364515 755841 -15.24 205 1.52 .00 Columbia aquifer – Converse-Ward-62C 11 SOW 172C 364745076004303 228-00257 364746 760043 -1.52 23 6.09 9.14 Columbia aquifer 2/13/81 Betz-Converse-M63C 19 na 364721075591701 228-00248 364721 755917 -5.64 23 2.74 19.81 Columbia aquifer – Converse-Ward-62B 27 na 364443076010702 228-00280 364443 760107 -12.96 30 4.57 18.29 Columbia aquifer – Converse-Ward-62B 11 na 364414076003901 228-00260 364414 760039 -13.57 30 2.44 20.42 Columbia aquifer 3/14/81 Betz-Converse-M62B 29 na 364352076004301 228-00262 364352 760043 -14.02 15 3.35 20.42 Columbia aquifer 3/14/81 Betz-Converse-M

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, –, sampled between November 1, 1980, and March 10, 1981]
62 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued [USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981] 62B 9 na 364352076005401 228-00263 364352 760054 -14.02 23 3.26 19.81 Columbia aquifer 3/14/81 Betz-Converse-M

62B 21 na 364353076005401 228-00264 364353 760054 -13.72 23 3.11 19.81 Columbia aquifer 3/14/81 Betz-Converse-M62B 7 na 364354076005401 228-00265 364354 760055 -14.02 23 2.59 9.14 Columbia aquifer 3/14/81 Betz-Converse-M62B 24 na 364352076005402 228-00266 364352 760054 -3.51 38 3.20 15.24 Columbia aquifer 3/14/81 Betz-Converse-M62B 32 na 364352076005404 228-00267 364352 760054 -13.72 15 3.05 20.12 Columbia aquifer 3/14/81 Betz-Converse-M61B 21 na 364223076074201 234-00026 364223 760742 -12.65 25 3.96 19.20 Columbia aquifer 1/13/77 Siudyla and other61C 58 na 364515076133001 234-00040 364515 761330 -10.67 21 7.01 6.71 Columbia aquifer 2/13/74 Siudyla and other61B 7 SOW 091D 364227076074704 234-00067 364227 760747 -1.40 24 4.57 32.31 Columbia aquifer 3/22/89 USGS 62C 1 na 364945076051401 228-00007 364945 760514 -26.83 14 3.66 35.66 Yorktown confining unit 12/09/80 Siudyla and other63C 6 na 364824075594601 228-00044 364824 755946 -21.95 11 4.57 31.09 Yorktown confining unit 12/28/77 Siudyla and other62A 6 na 363325076005202 228-00047 363325 760052 -22.41 49 1.52 28.65 Yorktown confining unit 8/10/72 Siudyla and other61C 22 na 364812076094701 228-00050 364812 760947 -20.12 64 6.10 25.91 Yorktown confining unit 10/19/72 Siudyla and other62A 24 na 363617076013301 228-00053 363617 760133 -21.95 113 2.44 18.90 Yorktown confining unit 4/06/78 Siudyla and other62B 33 na 363813076021501 228-00056 363813 760215 -15.70 9 2.44 28.65 Yorktown confining unit 4/06/78 Siudyla and other61C 53 na 364725076080001 228-00076 364725 760760 -23.17 84 3.96 24.08 Yorktown confining unit 9/28/76 Siudyla and other61C 55 na 364904076083401 228-00105 364904 760834 -18.75 91 4.57 27.43 Yorktown confining unit 7/17/58 Siudyla and other62C 13 na 364508076032501 228-00107 364508 760325 -18.60 24 3.05 18.29 Yorktown confining unit 3/25/74 Siudyla and other63C 26 na 364629075582001 228-00127 364629 755820 -15.24 69 1.52 17.68 Yorktown confining unit 12/28/77 Siudyla and other62C 3 SOW 092B 364715076030801 228-00133 364714 760307 -16.92 27 4.27 19.81 Yorktown confining unit 12/12/77 Siudyla and other62C 5 SOW 093 364504076031301 228-00135 364456 760301 -16.92 41 4.27 18.29 Yorktown confining unit 12/19/77 Siudyla and other62B 34 na 363813076054301 228-00136 363813 760543 -13.41 31 3.35 18.29 Yorktown confining unit 4/06/78 Siudyla and other62A 28 na 363507076050201 228-00139 363507 760502 -13.72 12 3.05 19.81 Yorktown confining unit 4/20/78 Siudyla and other63B 8 na 364247075584301 228-00140 364247 755843 -17.53 255 1.52 19.81 Yorktown confining unit 4/21/78 Siudyla and other

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date
 63

63B 9 na 364247075584302 228-00141 364247 755843 -17.53 261 1.52 18.29 Yorktown confining unit 4/21/78 Siudyla and other63B 10 na 364150075582801 228-00144 364150 755828 -15.85 102 .91 24.38 Yorktown confining unit 9/13/79 Siudyla and other62B 35 na 364140076013701 228-00146 364140 760137 -19.05 22 4.57 31.09 Yorktown confining unit 4/20/78 Siudyla and other62A 29 na 363519076010701 228-00148 363519 760107 -26.52 21 3.05 22.56 Yorktown confining unit 10/27/78 Siudyla and other61C 56 na 364839076094801 228-00164 364839 760948 -12.80 14 7.62 23.16 Yorktown confining unit 6/28/79 Siudyla and other62A 2 SOW 097A 363537076061001 228-00170 363356 760617 -18.60 56 3.05 22.86 Yorktown confining unit 7/26/79 Siudyla and other62C 34 na 364909076051101 228-00357 364921 760521 -17.68 27 3.05 20.73 Yorktown confining unit 7/18/02 USGS62C 25 na 364515076012001 228-00283 364515 760120 -14.33 30 3.99 28.04 Yorktown confining unit 3/12/81 Betz-Converse-M62C 35 na 364521076011601 228-00284 364521 760116 -21.04 23 4.08 27.74 Yorktown confining unit 3/9/81 Betz-Converse-M62C 30 na 364514076012001 228-00285 364514 760120 -20.73 23 3.90 27.43 Yorktown confining unit 3/14/81 Betz-Converse-M62C 20 na 364516076012102 228-00286 364516 760121 -20.43 15 3.99 27.43 Yorktown confining unit 3/9/81 Betz-Converse-M62C 26 na 364517076012401 228-00287 364517 760124 -20.43 23 3.84 30.33 Yorktown confining unit 3/9/81 Betz-Converse-M62C 23 na 364515076012102 228-00289 364515 760121 -21.13 30 4.02 27.43 Yorktown confining unit 3/13/81 Betz-Converse-M62B 17 na 364400076014701 228-00363 364400 760147 -21.04 30 3.05 24.38 Yorktown confining unit – Converse-Ward-D61C 28 SOW 174B 364920076093202 228-00317 364914 760919 -16.77 194 4.57 32.00 Yorktown confining unit 7/19/02 USGS61C 29 SOW 175 364837076092001 228-00318 364837 760921 -24.39 45 4.57 35.05 Yorktown confining unit – Converse-Ward-D62C 37 na 364522076002001 228-00292 364522 760020 -27.59 30 3.66 29.57 Yorktown confining unit – Converse-Ward-D63B 3 na 364459075585901 228-00360 364459 755859 -25.00 454 1.52 27.43 Yorktown confining unit – Converse-Ward-D62C 54 na 364455076013201 228-00273 364455 760132 -21.04 19 3.35 33.53 Yorktown confining unit 3/12/81 Betz-Converse-M62C 55 na 364459076012601 228-00274 364459 760126 -25.91 15 4.57 27.43 Yorktown confining unit 3/9/81 Betz-Converse-M62C 41 na 364451076013401 228-00275 364451 760134 -21.04 15 3.44 27.43 Yorktown confining unit 3/9/81 Betz-Converse-M62C 42 na 364501076011201 228-00276 364501 760112 -21.04 45 3.47 23.47 Yorktown confining unit 3/9/81 Betz-Converse-M62C 28 na 364513076013901 228-00277 364513 760139 -17.07 30 3.41 28.65 Yorktown confining unit 3/12/81 Betz-Converse-M

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981]
64 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia 62C 56 na 364505076034201 228-00346 364505 760342 -21.04 53 4.57 22.86 Yorktown confining unit – Converse-Ward-D

62B 25 na 364458076033001 228-00347 364458 760330 -15.24 53 4.57 22.86 Yorktown confining unit – Converse-Ward-D62C 58 na 364744076003001 228-00251 364744 760030 -14.94 30 4.88 22.86 Yorktown confining unit 2/14/81 Betz-Converse-M62C 12 SOW 172D 364745076004304 228-00253 364747 760044 -14.63 30 5.18 24.38 Yorktown confining unit 2/13/81 Betz-Converse-M62C 60 na 364747076004601 228-00254 364747 760046 -16.16 30 5.18 25.91 Yorktown confining unit 2/13/81 Betz-Converse-M62C 46 na 364753076011101 228-00255 364753 760111 -17.07 30 5.79 25.91 Yorktown confining unit 2/13/81 Betz-Converse-M62C 47 na 364736076001001 228-00256 364736 760010 -18.29 30 4.79 20.42 Yorktown confining unit 2/14/81 Betz-Converse-M62C 61 na 364846076033501 228-00344 364846 760335 -12.80 45 4.57 24.99 Yorktown confining unit – Converse-Ward-D62C 62 na 364842076033201 228-00345 364842 760332 -17.38 53 4.57 54.86 Yorktown confining unit – Converse-Ward-D62B 37 na 364450076020902 228-00355 364450 760209 -18.29 197 3.05 21.34 Yorktown confining unit – Converse-Ward-D62B 19 na 364059076012701 228-00270 364059 760127 -13.72 30 1.52 20.42 Yorktown confining unit – Converse-Ward-D62B 13 na 364325076011701 228-00271 364325 760117 -15.55 23 3.05 28.96 Yorktown confining unit – Converse-Ward-D63C 5 SOW 173B 364722075591802 228-00243 364722 755918 -23.17 17 2.74 25.30 Yorktown confining unit 7/17/02 USGS 63C 22 na 364724075593701 228-00244 364724 755937 -18.90 23 3.35 25.91 Yorktown confining unit 2/6/81 Betz-Converse-M63C 11 na 364728075591401 228-00245 364728 755914 -20.12 23 2.77 23.47 Yorktown confining unit 2/6/81 Betz-Converse-M63C 14 na 364720075591701 228-00246 364720 755917 -18.29 15 2.13 23.77 Yorktown confining unit 2/6/81 Betz-Converse-M63C 23 na 364720075591901 228-00247 364720 755919 -18.60 23 2.13 27.13 Yorktown confining unit 2/6/81 Betz-Converse-M63C 25 na 364721075591602 228-00249 364721 755916 -19.21 23 2.44 22.86 Yorktown confining unit 2/6/81 Betz-Converse-M62B 20 na 364432076042701 228-00362 364432 760427 -15.55 45 4.27 30.48 Yorktown confining unit – Converse-Ward-D62A 23 na 363714076063502 228-00430 363714 760635 -25.19 36 3.17 23.47 Yorktown confining unit 9/11/01 USGS62B 16 na 363812076021202 228-00432 363812 760212 -17.07 10 4.27 16.76 Yorktown confining unit 8/15/00 USGS61A 6 na 363620076120001 234-00015 363620 761200 -9.91 43 4.57 29.26 Yorktown confining unit 10/28/74 Siudyla and other60A 4 na 363352076153501 234-00028 363352 761535 -10.67 25 6.40 30.48 Yorktown confining unit 4/10/75 Siudyla and other

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981]
 65

60A 7 na 363413076151101 234-00034 363413 761511 -20.42 38 5.79 21.64 Yorktown confining unit 8/03/70 USGS61B 22 na 364303076073501 234-00045 364303 760735 -16.16 30 4.27 31.70 Yorktown confining unit 2/05/79 Siudyla and other60C 29 na 364536076164301 234-00051 364536 761643 -23.17 286 2.44 36.58 Yorktown confining unit 10/17/61 Siudyla and other62C 64 na 364740076041801 228-00002 364740 760418 -35.82 134 2.13 35.66 Yorktown-Eastover aquifer 6/19/64 Siudyla and other62C 65 na 364739076041401 228-00003 364739 760414 -34.91 209 1.52 36.58 Yorktown-Eastover aquifer 6/30/64 Siudyla and other62C 66 na 364739076041701 228-00004 364739 760417 -35.82 212 2.13 36.58 Yorktown-Eastover aquifer 7/18/64 Siudyla and other61C 42 na 364900076122201 228-00009 364900 761222 -31.40 95 2.13 45.11 Yorktown-Eastover aquifer 12/09/80 Siudyla and other61C 5 na 365221076121301 228-00101 365221 761213 -31.71 464 3.96 38.10 Yorktown-Eastover aquifer 12/04/78 Siudyla and other61C 54 na 364637076093301 228-00103 364637 760933 -33.38 198 2.44 45.42 Yorktown-Eastover aquifer 12/04/78 Siudyla and other62C 4 SOW 083 364711076060001 228-00120 364711 760600 -33.54 283 3.96 31.09 Yorktown-Eastover aquifer 10/13/78 Siudyla and other62C 2 SOW 092A 364713076030701 228-00132 364714 760307 -26.07 168 4.27 60.96 Yorktown-Eastover aquifer 12/18/79 Siudyla and other62C 68 na 364624076011501 228-00192 364624 760115 -55.34 22 4.57 41.15 Yorktown-Eastover aquifer 11/19/80 Siudyla and other62C 24 na 364916076051601 228-00356 364916 760516 -35.06 530 3.05 45.72 Yorktown-Eastover aquifer 7/18/02 USGS62C 27 na 364522076013201 228-00282 364522 760132 -39.02 45 3.66 72.54 Yorktown-Eastover aquifer 3/9/81 Betz-Converse-M62C 36 na 364516076012101 228-00368 364516 760121 -41.01 38 3.90 53.34 Yorktown-Eastover aquifer 3/9/81 Betz-Converse-M61C 27 SOW 174A 364920076093201 228-00316 364920 760930 -45.73 2,094 4.57 35.05 Yorktown-Eastover aquifer 7/19/02 USGS63C 15 na 364535076001001 228-00290 364535 760010 -28.96 30 3.05 42.67 Yorktown-Eastover aquifer – Converse-Ward-D63C 16 na 364528076001201 228-00291 364528 760012 -36.59 64 3.05 35.97 Yorktown-Eastover aquifer – Converse-Ward-D62C 38 na 364512076002601 228-00293 364512 760026 -29.88 61 3.05 39.62 Yorktown-Eastover aquifer – Converse-Ward-D63B 2 na 364451075595601 228-00295 364451 755956 -33.54 23 3.05 36.58 Yorktown-Eastover aquifer – Converse-Ward-D62C 53 na 364525076004401 228-00296 364525 760044 -28.96 30 4.57 41.76 Yorktown-Eastover aquifer – Converse-Ward-D62C 39 na 364522076001801 228-00297 364522 760018 -35.06 30 3.66 38.10 Yorktown-Eastover aquifer – Converse-Ward-D62C 57 na 364608076010001 228-00348 364608 760100 -28.96 23 6.10 36.58 Yorktown-Eastover aquifer – Converse-Ward-D

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981]
66 Ground-Water Flow and Saline Water in the Shallow Aquifer System of the Southern Watersheds of Virginia Beach, Virginia 62C 43 na 364635076001701 228-00350 364635 760017 -29.27 502 1.83 59.44 Yorktown-Eastover aquifer – Converse-Ward-D

62C 15 na 364708076024501 228-00358 364708 760247 -51.83 1,220 4.57 51.82 Yorktown-Eastover aquifer 7/17/02 USGS 62C 9 SOW 172A 364745076004301 228-00250 364746 760042 -43.60 45 5.18 42.67 Yorktown-Eastover aquifer 2/13/81 Betz-Converse-M62C 59 na 364722076000601 228-00252 364722 760006 -35.37 30 4.30 48.77 Yorktown-Eastover aquifer 2/14/81 Betz-Converse-M62C 48 na 364914076002101 228-00352 364914 760021 -39.63 91 6.10 85.34 Yorktown-Eastover aquifer – Converse-Ward-D62C 10 SOW 172B 364745076004302 228-00315 364745 760043 -77.74 364 5.18 44.20 Yorktown-Eastover aquifer 2/13/81 Betz-Converse-M62C 22 na 364746076004301 228-00369 364746 760043 -35.91 30 5.24 42.67 Yorktown-Eastover aquifer 2/13/81 Betz-Converse-M62C 63 na 364746076004302 228-00258 364746 760043 -32.93 38 5.18 54.86 Yorktown-Eastover aquifer 2/14/81 Betz-Converse-M62C 50 na 364851076033901 228-00343 364851 760339 -47.26 424 4.57 54.86 Yorktown-Eastover aquifer – Converse-Ward-D62B 26 na 364450076020901 228-00354 364450 760209 -48.78 1,121 3.05 41.15 Yorktown-Eastover aquifer – Converse-Ward-D62B 22 na 364325076011501 228-00268 364325 760115 -35.06 45 3.05 41.15 Yorktown-Eastover aquifer – Converse-Ward-D62B 18 na 364126076013401 228-00269 364126 760134 -34.15 576 3.05 56.39 Yorktown-Eastover aquifer – Converse-Ward-D63C 21 na 364729075593001 228-00242 364729 755930 -49.63 61 3.66 88.70 Yorktown-Eastover aquifer 2/6/81 Betz-Converse-M63C 4 SOW 173A 364722075591801 228-00314 364721 755916 -84.70 4,115 2.50 62.48 Yorktown-Eastover aquifer 7/16/02 USGS 63C 13 na 364721075591601 228-00364 364721 755916 -57.01 252 2.29 53.34 Yorktown-Eastover aquifer 7/15/02 USGS 63C 24 na 364721075591702 228-00365 364721 755917 -47.87 23 2.44 38.10 Yorktown-Eastover aquifer – Converse-Ward-D62B 14 na 364441076010201 228-00278 364441 760104 -30.49 23 4.57 51.82 Yorktown-Eastover aquifer – Converse-Ward-D62B 12 na 364443076010701 228-00279 364443 760107 -44.21 76 4.57 54.86 Yorktown-Eastover aquifer – Converse-Ward-D62B 28 na 364439076012201 228-00281 364439 760122 -47.26 129 4.57 35.05 Yorktown-Eastover aquifer – Converse-Ward-D62B 23 na 364410076002801 228-00259 364410 760028 -28.96 38 3.05 40.23 Yorktown-Eastover aquifer 3/14/81 Betz-Converse-M62B 8 na 364401076003801 228-00261 364401 760038 -34.45 30 2.68 65.23 Yorktown-Eastover aquifer 3/14/81 Betz-Converse-M62B 30 na 364352076005403 228-00366 364352 760054 -61.74 727 3.32 60.20 Yorktown-Eastover aquifer 3/14/81 Betz-Converse-M61C 43 na 364558076074501 228-00426 364558 760745 -55.43 3,380 1.73 32.61 Yorktown-Eastover aquifer 8/10/00 USGS

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981]
 67

61C 44 na 364558076074401 228-00427 364558 760744 -27.81 677 1.76 54.25 Yorktown-Eastover aquifer 8/09/00 USGS62A 22 na 363714076063501 228-00429 363714 760635 -44.22 701 3.19 63.40 Yorktown-Eastover aquifer 8/16/00 USGS62B 15 na 363812076021201 228-00431 363812 760212 -56.16 3,080 4.20 36.27 Yorktown-Eastover aquifer 8/16/00 USGS60B 26 na 36432707616001 234-00001 364327 761600 -25.76 71 2.74 42.67 Yorktown-Eastover aquifer 5/10/78 Siudyla and other61A 9 na 363637076104901 234-00041 363637 761049 -34.15 98 3.96 29.57 Yorktown-Eastover aquifer 12/15/78 Siudyla and other61B 2 SOW 091A 364227076074701 234-00136 364227 760747 -24.00 420 4.57 29.87 Yorktown-Eastover aquifer 3/22/89 USGS

USGS

well

number

SWCB

well

number

USGS

well

identifier

Storet

identifier Latitude Longitude

Sample

altitude

(meters 

below

NGVD 

1929)

Chloride

(mg/L)

Landsurface 

altitude

(meters 

aboveNGVD 

1929)

Well 

depth

(meters

below

land 

surface)

Hydrogeologic

unit

Sample

date

Table 7. Chloride concentrations in the shallow aquifer system of the southern watersheds of Virginia Beach, Virginia—Continued[USGS, U.S. Geological Survey; SWCB, State Water Control Board; Latitude and longitude in degrees, minutes, and seconds in NAD27; mg/L, milligrams per liter; na, 

–, sampled between November 1, 1980, and March 10, 1981]