EVALUATION OF GROUND-WATER FLOW BY 

PARTICLE TRACKING, WRIGHT-PATTERSON 

AIR FORCE BASE, OHIO

by William L Cunningham, Rodney A. Sheets, and Charles W. Schalk

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 94-4243

Prepared in cooperation with 

WRIGHT-PATTERSON AIR FORCE BASE

Columbus, Ohio 

1994
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

GORDON P. EATON, Director

For additional information Copies of this report may 

write to: be purchased from:

District Chief U.S. Geological Survey 

U.S. Geological Survey Earth Science Information Center 

975 West Third Avenue Open-File Reports Section 

Columbus, OH 43212-3192 Box 25286, MS 517

Denver Federal Center 

Denver, CO 80225
CONTENTS

Abstract................................................................................................................................................................^ 1

Introduction...............................................^ 1

Model description and limitations......................................................................................................................................... 3

Model description........................................................................................................................................................ 3

Particle-tracking postprocessor.................................................................................................................................... 5

Limitations............................................................................................................................................................^ 5

Evaluation of ground-water flow by particle tracking........................................................................................................... 5

Ground-water-flow directions...................................................................................................................................... 5

Areas contributing recharge......................................................................................................................................... 8

Summary.........................................................................................^^ 8

References cited..................................................................................................................................................................... 11

FIGURES

1-6. Maps showing:

1. Location of Wright-Patterson Air Force Base and administrative areas............................................................ 2

2. Locations of wells active in August 1994 and withdrawal rates at pumping centers........................................ 4

3. Particle pathlines from Base boundary to discharge points............................................................................... 6

4. Directions of flow from hazardous-waste sites within Operable Units to discharge points.............................. 7

5. Areas contributing recharge to selected wells and Mad River, Wright-Patterson Air Force Base.................... 9

6. Traveltime-related areas contributing recharge to discharge points in and around

Wright-Patterson Air Force Base.................................................................................................................... 10

TABLE

1. Rates of pumping near Wright-Patterson Air Force Base. 1987 and 1994............................................................. 3

CONVERSION FACTORS

Multiply By To obtain

Distance 

mile (mi) 1.609 kilometer

Flow

gallons per minute (gal/min) 3.785 liters per minute 

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

Contents III
Evaluation of Ground-Water Flow by Particle Tracking, 

Wright-Patterson Air Force Base, Ohio

By William L. Cunningham, Rodney A. Sheets, and Charles W. Schalk

Abstract

The U.S. Geological Survey (USGS) and 

Wright-Patterson Air Force Base (WPAFB) began 

a Basewide Monitoring Program (BMP) in 1992. 

The purpose of the BMP was to establish a longterm ground-water and surface-water sampling 

network in order to (1) characterize current 

ground-water and surface-water quality;

(2) describe water-quality changes as water 

enters, flows across, and exits Base boundaries;

(3) conduct statistical analyses of water quality; 

and (4) estimate the effect of WPAFB on regional 

water quality.

As part of the BMP, the USGS conducted 

ground-water particle-tracking analyses based on 

a ground-water-flow model produced during a 

previous USGS study. This report briefly 

describes the previous USGS study, the inherent 

assumptions of particle-tracking analyses, and 

information on the regional ground-water-flow 

field as inferred from particle pathlines. Pathlines 

for particles placed at the Base boundary and particles placed within the identified Installation 

Restoration Program sites are described.

INTRODUCTION

Wright-Patterson Air Force Base (WPAFB or 

"the Base") is in parts of Greene, Clark, and Montgomery Counties near the city of Dayton in southwestern Ohio (fig. 1). The Base overlies highly permeable 

glacial-drift deposits of the Mad River buried-valley 

aquifer. Near the Base, the aquifer is used as a source

of drinking water for the nearby cities of Dayton and 

Fairborn, as well as for WPAFB.

Landfilling and other forms of waste disposal 

associated with aviation and research activities have 

been practiced in the WPAFB area since the 1920's. 

Studies began in the 1980's to identify and control 

environmental contamination on and off the Base 

(Weston, Incorporated, 1983,1985,1989; Dames and 

Moore, 1986a, 1986b; IT Corporation, 1990). The 

USGS reported the results of using a numerical model 

to simulate ground-water flow in the region; the model 

was based on results of hydrogeologic and geochemical investigations (Dumouchelle and others, 1993). As 

a result of these studies, 65 potential wastedisposal sites termed Installation Restoration Program (IRP) Sites have been identified and grouped 

into 12 Operable Units (OU's).

In 1992, the USGS entered into an agreement 

with WPAFB for a Basewide Monitoring Program 

(BMP). The purpose of the BMP was to establish a 

long-term Basewide ground-water and surface-water 

sampling network in order to (1) characterize current 

ground-water and surface-water quality; (2) describe 

water-quality changes as water enters, flows across, 

and exits Base boundaries; (3) analyze water quality 

statistically; and (4) estimate the effect of WPAFB on 

regional water quality. As part of the BMP, the USGS 

analyzed ground-water pathlines by means of the previously developed ground-water-flow model.

The purpose of this report is to provide particlepathline information to illustrate directions of groundwater flow across the Base with respect to OU's and 

IRP sites. These results may be used by WPAFB in 

planning for (1) future base-wide monitoring studies, 

(2) a ground-water OU, (3) future remediation 

schemes, and (4) ongoing OU studies. This report

Introduction
84°07'30' 84° 00'

39°52'30" 

39°45'

Base map digitized from U.S. Geological Survey 

Bellbrook. photorevised 1987; Dayton North, 

photorevised 1981; Dayton South, photorevised 

1981; Donnelsvilte, photoinspected 1983; Fairbom, 

photorevised 1988; New Carlisle, photoinspected 1984; 

Tipp City, photoievised 1982, Xenia, photorevised 

1987; Yellow Springs, photorevised 1975 

Polyconic projection

4 MILES

J

\ I I

234 KILOMETERS

EXPLANATION

MUNICIPALITY

WELL

MODELED AREA

WRIGHT-PATTERSON AIR FORCE 

BASE BOUNDARY

Figure 1. Location of Wright-Patterson Air Force Base and administrative areas. (Modified from 

Dumouchelle and others, 1993, fig. 1.)

2 Evaluation of Ground-Water Flow by Particle Tracking, Wright-Patteraon Air Force Base, Ohio
briefly describes the previous USGS study, the 

assumptions inherent to this and to any particletracking analyses, and information on the regional 

ground-water-flow field as inferred from particle pathlines. Pathlines for particles placed at the Base boundary and particles placed within the identified IRP sites 

are described.

MODEL DESCRIPTION AND LIMITATIONS

Model Description

A three-dimensional ground-water-flow model 

calibrated to steady-state ground-water-flow conditions of October-December 1987 was developed by 

Dumouchelle and others (1993) for an area including 

the Base. The USGS computer code MODFLOW 

(McDonald and Harbaugh, 1988) was used for the 

simulation. The purpose of the model was, in part, to 

determine and evaluate sources and sinks of regional 

ground-water flow. These sources and sinks included 

the Mad River and its tributaries.

The Base overlies a productive buried-valley 

aquifer system that incises less permeable shales and 

shaley limestones. Upland areas adjoining the buried 

valleys are capped by limestone units that are used 

locally for ground-water supply. The model consists of 

three layers that simulate ground-water flow in the 

buried-valley aquifer as well as in the upland bedrock. 

Layer 1 simulates the unconfined nature of flow in the 

uppermost part of the buried-valley aquifer and the 

entire permeable thickness of the upland bedrock aquifer. Layer 2 of the model simulates the central part of 

the buried-valley aquifer, in which most of the watersupply wells are completed. Layer 3 of the model simulates the part of buried-valley aquifer that is bounded 

by the bottom of layer 2 and by the impermeable bedrock underlying the valley. Layers 2 and 3 were modeled as confined aquifers. The presence of discontinuous deposits of poorly permeable clays and silts 

defines the boundaries between layers I and 2 and 

between layers 2 and 3. Lateral boundaries to groundwater flow were based on the locations of groundwater divides and surface-water bodies, and on calculated flux through valley cross sections. The model 

was calibrated to water levels measured in 1987, 

results of a gain-loss study of the major rivers and tributaries, and vertical-gradient data collected at nested 

wells. A sensitivity analysis indicated that the simulated hydraulic heads and flows in the model were 

most sensitive to the hydraulic conductivity of the 

uppermost layer and to the riverbed hydraulic conductivity. Details of model parameters, construction, and 

calibration are described in the report by Dumouchelle 

and others (1993, p. 55-100).

Pumping rates for the period of model calibration were obtained for all pumping centers producing 

more than approximately 10 gal/min. These centers 

are primarily in industrial areas, in municipalities, and 

on the Base. The city of Dayton's Mad River Well 

Field (fig. 2) was the largest pumping center included 

in the model; withdrawals were approximately 

50 Mgal/d. For the steady-state calibration of the 

model, the Skeel Road and East Well Fields at 

WPAFB were pumped at 1.9 and 1.1 Mgal/d, respectively. Area B wells at WPAFB were not active for the 

time period used for the calibration.

Since model calibration (1988), wells designed 

to produce about 20 Mgal/d have been constructed on 

the downstream side of Huffman Dam, and a well producing approximately 0.9 Mgal/d has been completed 

about 1 mi northeast of Huffman Dam (fig. 1). Currently (1994), the Huffman Dam Well Field is pumping a combined total of approximately 2 Mgal/d. In a 

predictive simulation, these pumping centers and the 

current (1994) rates of pumping were added to the 

model that was produced by Dumouchelle and others 

(1993). Particle pathlines are based on this predictive 

simulation. Active centers of withdrawal for the model 

simulation on which the particle-tracking results are 

based are shown in figure 2. The pumping centers and 

rates for this predictive simulation (1994) are summarized in table 1. Area B wells were not active for the 

time period used for the calibration; the East Well 

Field has not been active since 1988, so was not 

simulated here.

Table 1. Rates of pumping near Wright-Patterson Air Force 

Base, 1987 and 1994 [Mgal/d, million gallons per day]

Weil field

Mad River

AreaB

East

Skeel Road

Huffman Dam

OU5 Extraction

Pumping rate, 

1987 (Mgal/d)

50

0

1.1

1.9

0

0

Pumping rate, 

1994 (Mgal/d)

50

1.7

0

1.9

2

.9

Mode! Description and Limitations
84°07'30-

39" 501

39°47'30°

fl40 03'45-

I

<

/ Huffman Dam \ 

\ / Well Field

Mad RiveTr Well Field \ '

Base map digitized from U.S. Geological Survey 

Dayton North, photorevised (981; Fairbom, 

photorevised 1988. Polyconic projection

2 MILES

I

1

2 KILOMETERS

EXPLANATION

WELL FIELD Production, in million gallons per day,

is given below: 

Mad River 50 

Skeel Road 1.9 

Area B 1.7 

Huffman Dam 2.0 

Extraction Well -9

 WRIGHT-PATTERSON AIR FORCE BASE BOUNDARY 

*GR-155 WELL LOCATION AND IDENTIFIER

Figure 2. Locations of wells active in August 1994 and withdrawal rates at pumping centers. 

4 Evaluation of Ground-Water Flow by Particle Tracking, Wright-Pattereon Air force Baee, Ohio
Particle-Tracking Post Processor

Particle pathlines were computed on the basis of 

flow in each cell of the regional model by use of the 

USGS particle-tracking code MODPATH (Pollock, 

1989). MODPATH is a three-dimensional postprocessing program for particle tracking designed for 

use with output from simulations obtained with the 

computer code MODFLOW. MODPATH uses a semianalytical particle-tracking scheme based on the 

assumption that the directional ground-water-velocity 

components within a model cell vary linearly. The 

velocity components are based on the intercell flow 

volumes computed by MODFLOW. The average 

linear velocity component across each face in a model 

cell is obtained by dividing the flow volume at a cell 

face by the cross-sectional area of the cell and the 

effective porosity of the material within the cell. 

Simple linear interpolation is used to compute the 

principal velocity components within a cell.

The particle-tracking scheme used by MODPATH is valid only for computing and interpolating 

advective velocities from intercellular flows such as 

those output by MODFLOW. Accordingly, the particle 

pathlines are based on advective particle movement 

and traveltimes no diffusion, dispersion, or chemical 

or microbiological retardation is incorporated into the 

movement of particles that trace the particle pathlines. 

The analyses presented herein are based on a model of 

steady-state conditions. Changes in pumping or other 

stresses in the system over time will likely affect the 

particle pathlines and traveltimes.

Limitations

The most significant limiting factor in particle 

tracking is the numerical model on which the analyses 

are based. The numerical model from which the heads 

and flows are generated and used in particle tracking is 

a numerical representation of the physical flow system. Numerical approximations, convergence tolerances, and scale limitations all affect how well the 

model represents the physical flow system. Grid 

design, boundary conditions, and calibration data also 

can affect the accuracy of the model and, therefore, the 

particle-tracking analysis. Errors from numerical 

approximations are assumed to be minimized by trialand-error adjustment during calibration (Dumouchelle 

and others, 1993, p. 78-86), but a discussion of the 

scale limitations is required here. The model developed previously was designed to investigate regional 

ground-water flow. Local flow, such as flow to small 

streams or flow adjacent to sources and sinks, may not 

be well represented by the model. However, the analyses presented by Sheets (1994) indicate that local flow, 

at the scale of particle pathlines, is well represented in 

the regional model. A complete discussion of the limitations of the ground-water-flow model is given in 

Dumouchelle and others (1993, p. 96-100).

EVALUATION OF GROUND-WATER FLOW 

BY PARTICLE TRACKING

Ground-Water-Flow Directions

Particle pathlines from the Base boundary to 

particle-discharge points are shown in figure 3. Particles were placed initially at the water table along the 

Base boundary. The following characteristics of the 

ground-water-flow field under the stated pumping conditions can be identified from the particle pathlines:

 Generally, ground water flows from the northeastern boundary of the Base to the Skeel Road 

Well Field.

 A ground-water-flow divide between discharge 

to the Mad River and flow beneath Huffman 

Dam exists near the middle of Area A and C, 

just south of well clusters USGS 4 and 33. 

Flow north of the divide is to the Mad River; 

flow south of the divide is to the downgradient 

ground-water-flow system.

 A topographic and bedrock upland feature near 

well cluster USGS 9 restricts regional groundwater flow in the area.

 In the southwestern part of Area B, a groundwater-flow divide exists between flow to the 

Mad River Well Field at Rohrer's Island and 

flow downgradient into other wells within the 

Mad River Well Field. The divide is near well 

cluster DG1.

Particle pathlines from the identified IRP 

hazardous-waste sites within OU's to particle discharge points are shown in figure 4. Particles were 

placed at the water table within the areas delineated as 

IRP sites. The following characteristics of the flow 

field can be identified from the particle pathlines:

 Ground water flows from OU2, at the northeastern boundary of the Base, through OU3 to 

the Mad River.

Evaluation of Ground-Water Flow by Particle Tracking 5
84°07'30' 84"03'45'

39° SO1 

39°47'30'

Base map digitized from U.S. Geological Survey 

Dayton North, photorevised 1981; Fairbom, 

photorevised 1988. Pohyconic projection

2 MILES

h T

2 KILOMETERS

EXPLANATION

1=1 WELL FIELD

 WRIGHT-PATTERSON AIR FORCE BASE BOUNDARY

SIMULATED PARTICLE PATHLINE-Arrow indicates 

<sr'^ direction of flow

UG8 UPGRADIENT CLUSTER LOCATION AND NAME

^1 INTERIOR CLUSTER LOCATION AND NAME

%DG3 DOWNGRADIENT - CLUSTER LOCATION AND NAME

Figure 3. Particle pathlines from Base boundary to discharge points. 

6 Evaluation of Ground-Water Flow by Particle Tracking, Wrlght-Patterson Air Force Base, Ohio
840 07'30' 84"03'45'

39" 50' 

39°4T30m

Basa map digitized from U.S. Geological Survey 

Dayton North, photorevised 1981; Fairbom, 

photorevised 1988. Polyconic projection

T

2 MILES

I

0 1 2 KILOMETERS

EXPLANATION

APPROXIMATE FLOW-PATH ZONE

 j HAZARDOUS-WASTE SITE

__ OPERABLE UNIT (OU) BOUNDARY

 WRIGHT-PATTERSON AIR FORCE BASE BOUNDARY

< GENERAL DIRECTION OF FLOW

£ WELL LOCATION

Flgur* 4. Directions of flow from hazardous-waste sites within Operable Unite to discharge points.

Evaluation of Ground-Water Flow by Particle Tracking 7
 Ground water flows from OU1 through 

Areas A and C and men through OU5.

 Ground-water flows from OU9 to the Mad 

River Well Field.

 Ground water flow from OU6 is divided: someground water discharges to the Mad River Well 

Field at Rohrer's Island and downgradient to 

other Mad River wells.

 Many BMP wells are completed within 

ground-water-flow paths from OU's.

Areas Contributing Recharge

Figure 5 illustrates areas within the model mat 

contribute recharge to wells and streams. Particles 

were placed at the water table throughout the BaseParticles are color-coded according to their point of 

discharge. As figure 5 indicates, most of Areas A and 

C contribute recharge to the Mad River, a gaining 

stream in this reach along the buried valley. Areas that 

contribute recharge to the Skeel Road Well Field, the 

OU5 extraction well, and interceptor wells near Huffman Dam are also within Areas A and C. Most of Area 

B contributes recharge to the Mad River Well Field at 

Rohrer's Island. Area B also contributes recharge to 

the Area B Well Field and the interceptor wells near 

Huffman Dam.

Traveltime-related areas contributing rechargeto the- Mad River, Skeel Road, Area B, and Huffman 

Dam Well Fields, the, OU5 Extraction Well, and the 

Mad River are shown in figure 6. Particles were placed 

at the- water table- and tracked to their discharge- points. 

Traveltime-related areas were determined by assigning 

an effective porosity to each cell in the flow model. 

The- effective porosity used for the particle-tracking 

simulation was 0.20,0.25, and 0.15 for model layers 1, 

2, and 3, respectively. The effective porosity within a 

model cell has a linear effect on the traveltime of a 

particle but has no effect on the particle- pathlines. For 

example, an increase in the effective porosity would 

decrease the area associated with each traveltime 

listed in figure 6.

SUMMARY

As part of the BMP, the USGS analyzed groundwater pathlines by means of a ground-water-flow 

model produced during a previous USGS study. 

Results of this pathline analysis are summarized 

below.

 The most significant limiting factor in particle 

tracking is the numerical model on which the 

analyses are based; accordingly, all results 

described herein are limited by the assumptions of the numerical ground-water-flow 

model employed.

 At the northeastern boundary of the Base, 

ground water flows from OU2 through OU3 to 

the Mad River. Some ground-water flow is 

captured by the Skeel Road Well Field. A 

ground-water-flow divide between discharge to 

the Mad River and flow beneath Huffman Dam 

exists near the middle of Area A and C just 

south of well clusters USGS 4 and 33. Flow 

north of the divide is to the Mad River; flow 

south of the divide is to the downgradient 

ground-water-flow system.

 Ground water flows from OU1 through 

Areas A and C and then through OU5.

 Ground-water flow from OU6 is divided; some 

ground water discharges to the Mad River Well 

Field at Rohrer's Island, and the rest flows 

downgradient to other Mad River wells.

 Ground water flows from OU9 to the Mad 

River Well Field. A topographic and bedrock 

upland feature near well cluster USGS 9 

restricts regional flow in the area.

 Many BMP wells are completed within 

ground-water-flow paths from the OU's.

8 Evaluation of Ground-Water Flow by Particle Tracking, Wright-Patterson Air Force Base, Ohio
84"07130" 84"03'45'

39°50'

39°47'30'

fease map digitized from U.S. Geological Survey 

Dayton North, photorevised 1981; Fairbom, 

photorevised 1988. Polyconic projection

2 MILES

I I

1 2 KILOMETERS

EXPLANATION

^ HUFFMAN DAM WELLS CONTRIBUTING AREA

| | MAD RIVER CONTRIBUTING AREA

I I MAD RIVER WELLS CONTRIBUTING AREA

| | OPERABLE UNIT 5 WELL CONTRIBUTING AREA

I I AREA B WELLS CONTRIBUTING AREA

| | SKEEL ROAD WELLS CONTRIBUTING AREA

I I OTHER CONTRIBUTING AREAS

WRIGHT-PATTERSON AIR FORCE BASE

 BOUNDARY

* PRODUCTION WELL

Figure 5. Areas contibuting recharge to selected wells and Mad River, Wright-Patterson Air Force

Base.

Summary 9
840 07'30- 84"03'45-

39" 50' 

39°47'3011

Base map digitized from U.S. Geological Survey 

Dayton North, jphotorevised 1981; Fairbom, 

photorevised 1988. Polyconic projection

2 MILES

2 KILOMETERS

EXPLANATION

|H HAZARDOUS-WASTE SITE

 I 0-1 YEAR CONTRIBUTING AREA

I 1 1-5 YEAR CONTRIBUTING AREA

I I 5-10 YEAR CONTRIBUTING AREA

I I OTHER CONTRIBUTING AREAS

 WRIGHT-PATTERSON AIR FORCE BASE BOUNDARY

Figure 6. Traveltime-related areas contributing recharge to discharge points in and around 

Wright-Patterson Air Force Base.

10 Evaluation of Ground-Water Flow by Particle Tracking, Wright-Pattereon Air Force Bate, Ohio
REFERENCES CITED

Dames & Moore, Incorporated, 1986a, Installation Restoration Program report, site investigation report landfills 

8 and 10: Prepared for Wright-Patterson Air Force 

Base [variously paginated].

 1986b, Installation Restoration Program report, site 

investigation report landfill 12: Prepared for WrightPatterson Air Force Base [variously paginated].

Dumouchelle, D.H., Schalk, C.W., Rowe, G.L., and 

de Roche, J.T., 1993, Hydrogeology, simulated 

ground-water flow, and ground-water quality, WrightPatterson Air Force Base, Ohio: U.S. Geological Survey Water Resources Investigation Report 93-4047, 

152 p.

IT Corporation, 1990, Installation Restoration Program 

report, environmental investigation of ground-water 

contamination at Wright-Patterson Air Force Base, 

Ohio: Dayton, Ohio, Battelle Environmental Management Operations, prepared for Wright-Patterson Air 

Force Base [variously paginated].

McDonald, M.G. and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. Al [variously 

paginated].

Pollock, D.W., 1989, Documentation of computer programs 

to compute and display pathlines using results from the 

U.S. Geological Survey modular three-dimensional 

finite-difference ground-water flow model: U.S. Geological Survey Open File Report 89-38,188 p.

Sheets, R.A., 1994, Contributing recharge areas of watersupply-wells at Wright-Patterson Air Force Base, 

Ohio: U.S. Geological Survey Water Resources Investigations Report 94-4231,35 p.

Weston, Roy F., Incorporated, 1983, Installation Restoration 

Program report, Phase II problem confirmation and 

quantification study: Prepared for Wright-Patterson Air 

Force Base [variously paginated].

 1985, Installation Restoration Program report, Phase 

II Stage 1 study: Prepared for Wright-Patterson Air 

Force Base [variously paginated].

 1989, Installation Restoration Program report, Phase 

II Stage 2 report: Prepared for Wright-Patterson Air 

Force Base [variously paginated].

References Cited 11