Hydrogeology and Simulated 

Ground-Water Flow Through the 

Unconsolidated Aquifers of Northeastern 

St. Joseph County, Indiana

By E.R. BAYLESS and LD. ARIHOOD

Prepared in cooperation with the

INDIANA DEPARTMENT OF NATURAL RESOURCES

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 95-4225

Indianapolis, Indiana 

1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For additional information, write to: 

District Chief 

U.S. Geological Survey 

Water Resources Division 

5957 Lakeside Boulevard 

Indianapolis, IN 46278-1996

Copies of this report can be purchased from:

U.S. Geological Survey

Earth Science Information Center

Open-File Reports Section

Box25286, MS 517

Denver Federal Center

Denver, CO 80225
CONTENTS

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

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

Purpose and Scope..................................................................... 2

Previous Investigations ................................................................. 4

Acknowledgments..................................................................... 4

Description of the Study Area ............................................................... 4

Hydrogeologic Setting...................................................................... 5

General Geology ...................................................................... 5

Aquifer Properties ..................................................................... 5

Recharge and Discharge ................................................................ 7

Water Levels ......................................................................... 14

Ground-Water Flow.................................................................... 17

Simulated Ground-Water Flow Through the Unconsolidated Aquifers ................................ 17

Model Conceptualization................................................................ 20

Boundary and Inactive Cells ........................................................ 20

Active Model Cells................................................................ 22

Other Model Inputs ............................................................... 23

Model Assumptions ............................................................... 23

Model Calibration ..................................................................... 23

Model Sensitivity...................................................................... 28

Simulation Results..................................................................... 28

Simulated Ground-Water Availability ................................................. 28

Simulated Particle Transport ........................................................ 30

Model Limitations..................................................................... 34

Summary and Conclusions .................................................................. 36

References Cited .......................................................................... 38

Supplemental Data......................................................................... 41

FIGURES

1. Location of study area, monitoring-well network, and geologic sections ......................... 3

2. Distribution of aquifer systems in northeastern St. Joseph County, Indiana ....................... 6

3. Generalized geologic sections showing conceptual layers used in the ground-water-flow model

for northeastern St. Joseph County, Indiana................................................ 8

Contents iii
CONTENTS

FIGURES Continued

4-14. Maps showing:

4. Location and thickness of aquifer 1................................................... 9

5. Location and thickness of aquifer 2................................................... 10

6. Location and thickness of aquifer 3................................................... 11

7. Location and thickness of confining unit 1 ............................................. 12

8. Location and thickness of confining unit 2 ............................................. 13

9. Locations of significant (ground) water-withdrawal facilities in 1993 ........................ 15

10. Ground-water levels during water year 1991 at well sites 1 and 16, northeastern St. Joseph

County, Indiana .................................................................. 16

11. Altitude and configuration of the ground-water-level surface in aquifer 2..................... 18

12. Altitude and configuration of the ground-water-level surface in aquifer 3 ..................... 19

13. Model grid, boundary conditions, and river reaches used in the simulation of ground-water

flow............................................................................ 21

14. Simulated steady-state ground-water-level surface and absolute error for calibrated model

at well sites in aquifer 3 ............................................................ 27

15. Graphs showing relation between simulated errors and variation in parameter values for the

ground-water-flow model, northeastern St. Joseph County, Indiana ............................. 29

16. Water-level decline in aquifer 3 caused by a 50-percent increase in ground-water withdrawals

at all sites .......................................................................... 31

17. Simulated flow paths from selected points of recharge to significant water-withdrawal facilities ...... 32

18. Starting locations for flow paths that end at significant water-withdrawal facilities ................. 33

19. Row paths from sites of contamination to points of discharge ................................. 35

TABLES

1. Ground-water levels measured in northeastern St. Joseph County, Indiana, water years 1991-92 ....... 42

2. Ground-water-withdrawal site numbers, geographic locations, model cell locations, 1993 groundwater withdrawals and withdrawal capacities, northeastern St. Joseph County, Indiana ............... 46

3. Water budget for the calibrated ground-water-flow model, northeastern St. Joseph County,

Indiana.............................................................................. 26

iv Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
CONVERSION FACTORS AND VERTICAL DATUM

Multiply

inches (in.)

inches per year (in/yr)

foot (ft)

mile (mi)

square mile (mi2)

foot per day (ft/d)

cubic foot per second (ft3/s)

gallons per minute (gal/min)

gallons per day (gal/d)

million gallons per day (Mgal/d)

By

0.0254

0.0254

0.3048

1.609

2.590

0.3048

28.32

0.06309

0.0000438

0.04380

To obtain

meter

meter per year

meter

kilometer

square kilometer

meter per day

liter per second

liter per second

liter per second

cubic meter per second

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) 

a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, 

formerly called Sea Level Datum of 1929.

Conversion Factors v
Hydrogeology and Simulated Ground-Water Flow 

Through the Unconsolidated Aquifers of 

Northeastern St. Joseph County, Indiana

By E.R. Bayless and L.D. Arihood

ABSTRACT

The U.S. Geological Survey investigated 

the ground-water resources of northeastern 

St. Joseph County, Indiana, during 1990-93. 

The investigation included field measurements 

of water levels and numerical models of the 

ground-water-flow system. This report documents the results of that work and includes 

a description of (1) the hydrogeologic framework, (2) water levels, (3) model sensitivity 

to variations in hydrogeologic parameters, 

(4) simulated aquifer response to increased 

ground-water withdrawals, (5) contributing 

areas for significant water-withdrawal facilities, 

and (6) flow paths for hypothetical solute 

particles originating beneath known contamination sites.

Water levels were measured in a spatially 

distributed network of 53 monitoring wells. 

Wells were installed at 36 sites to depths of 

18 to 173 feet below land surface. At 15 sites, 

nested monitoring wells were installed to describe hydraulic gradients between shallow 

and deep parts of the aquifer system. Water 

levels were measured during January 1991- 

November 1992. Water-level measurements 

indicated that (1) regional ground-water flow 

is towards the St. Joseph River, (2) depth to 

water generally is small in the St. Joseph aquifer 

system compared to that in the Hilltop and

Nappanee aquifer systems, and (3) water levels 

in the deep and shallow parts of the aquifer 

system are not equal at sites where a confining 

unit is present.

Simulation of aquifer response to various 

stresses was examined by use of a numerical model of ground-water flow. A quasi 

three-dimensional numerical model of the 

ground-water-flow system was constructed 

from geologic, hydrologic, and water-use 

information. The model was calibrated by an 

adjustment to the hydrogeologic parameter 

values within known ranges until a suitable 

correspondence between simulated and 

measured ground-water levels was achieved. 

Steady-state ground-water-flow simulations 

were used to identify sites where increased 

withdrawals might cause significant aquifer 

dewatering or induce migration of pollutants 

from known contamination sites.

Results of the study indicate that an 

increase in withdrawals by 50 percent at 

significant water-withdrawal facilities would 

cause drawdowns generally less than 6 feet in 

the one-quarter square mile surrounding area. 

In this simulation, ground-water flows to Juday 

Creek and the St. Joseph River were reduced by 

23 percent and 6 percent, respectively.

Abstract 1
The results of particle-tracking analyses 

indicate that flow paths from recharge areas 

to significant water-withdrawal facilities 

operating at 1993 withdrawal rates generally 

are less than 5 miles long in the upper aquifer 

but may be more than 12 miles long in the 

lower aquifer. Travel times between recharge 

and discharge points are less than 10 years 

in the upper aquifer but may be as much as 

100 years in the lower aquifer.

Particle-tracking analyses indicate that 

flow paths for solutes originating beneath 

known contamination sites may pass near 

to, or be intercepted by, significant waterwithdrawal facilities. Most particles are 

discharged to the St. Joseph River, but some 

may be discharged to Juday Creek.

INTRODUCTION

During January 1,1990-December 31,1994, 

the U.S. Geological Survey (USGS), in cooperation 

with the Indiana Department of Natural Resources 

(IDNR), studied the ground-water resources of 

northeastern St. Joseph County, Ind. The most 

productive source of ground water in the study 

area is the St Joseph aquifer system, Indiana's 

only designated sole-source aquifer (Anna Miller, 

U.S. Environmental Protection Agency, oral 

commun., 1995). The St. Joseph aquifer system 

is a thick, glacially deposited sand and gravel 

sequence that is locally interbedded with poorly 

permeable, clay-rich sediment (Beaty, 1987). 

Because the uppermost parts of the aquifer system 

are highly permeable and the water table occurs 

at shallow depths, the St. Joseph aquifer system 

is susceptible to ground-water contamination. 

Furthermore, as ground-water withdrawals from 

the St. Joseph aquifer system increase, the possibility of ground-water contamination and resource 

depletion increases.

For the USGS study, a 221-mi2 area of northeastern St. Joseph County was identified (fig. 1) 

where an increased understanding of the regional 

hydrogeology and aquifer-system response to 

increased ground-water withdrawals would benefit 

land-use planners and resource managers. A 

further consideration of the study was to describe 

contributing areas for significant water-withdrawal 

facilities (SWWF's) facilities capable of 

pumping at rates greater than 100,000 gal/d 

(U.S. Geological Survey, 1990) and discharge 

points for water originating beneath known sites 

of contamination.

The goals of this study were accomplished 

primarily by use of a numerical model of the 

ground-water-flow system in northeastern 

St. Joseph County. The numerical model is an 

efficient way to examine the effects of varying 

hydrologic stresses, such as drought or increased 

ground-water withdrawals, on regional groundwater levels. The area considered in the numerical 

model was the 227-mi2 study area plus the area 

3.5 mi north of the Indiana/Michigan State line 

and 3 mi east of the St. Joseph County/Elkhart 

County political boundary. The enlarged study 

area was necessary to incorporate numericalmodel boundary conditions.

Purpose and Scope

This report describes the hydrogeologic 

framework and simulation of the ground-water 

flow in the unconsolidated aquifers of northeastern 

St. Joseph County. The study was accomplished 

by (1) a compilation and synthesizing of available 

geologic, hydrologic, and climatic information; 

(2) a development of numerical models of groundwater flow based on the acquired hydrogeologic 

information; (3) use of the models to identify 

contributing areas to SWWF's; and (4) use of the 

models to identify flow paths for ground water 

originating beneath known sites of contamination.

2 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86°15' 86°07'30"

41°45

41°37'30" -

41°30' -

01 2345 MILES Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86°

EXPLANATION

01 2345 KILOMETERS

AI I A1 Trace of hydrogeologic section (sections shown in figure 3) Study Area

22

St. Joseph River drainage divide 

Well site and identifier

Figure 1. Study area, monitoring-well network, and geologic sections.

Purpose and Scope 3
The geological data base for the model 

includes more than 370 well logs. In addition, 

53 monitoring wells were installed at 36 sites 

where geologic information was unavailable. 

Surface-geophysical measurements were made at 

six additional sites. Water levels were measured 

synoptically in the 53-well network at least seven 

times during water years 1 1991 and 1992. Waterlevel measurements were integrated into composite 

water-level maps previously compiled by Beaty 

(1987).

Other data required to develop the numerical 

model, such as recharge rates, hydraulic conductivity of the aquifers, vertical leakance of confining 

units, streambed conductance, and ground-wateruse information, were collected from available 

sources. These data were used as input information 

to a computer algorithm that solves the physical 

equations describing ground-water flow. Solution 

of the algorithm produced a non-unique numerical 

model of the regional water table. The difference 

between simulated and measured water levels was 

used as an indicator of model accuracy. Individual 

parameter values were varied within known or 

acceptable ranges to demonstrate the effect on 

simulated water levels. The model was calibrated 

by minimizing the differences between calculated 

and measured water levels for the 53 monitoring 

wells in the network. The calibrated model was 

used to examine (1) aquifer response to increased 

withdrawals at SWWF's, (2) contributing areas for 

SWWF's, and (3) flow paths and discharge points 

for solute particles originating beneath known 

contamination sites.

Rosenshein and Hunn, 1962; Klaer and Stallman, 

1948). These reports summarize available data 

describing geologic setting, aquifer recharge, 

climatic variables, hydraulic properties of the 

geologic units, land use, water use, water levels, 

and ground-water quality. Bleuer and Melhom 

(1989) provide additional geologic information.

Peters and Renn (1988) and Peters (1987) 

used aquifer-test data to calculate values of 

hydraulic properties of the aquifers. Bailey and 

others (1985), Lindgren and others (1985), and 

Imbrigiotta and Martin (1981) used numerical 

models to investigate ground-water flow in 

adjacent areas of the St. Joseph River Basin. 

The model described in this report refers to these 

studies for measured and calculated values of 

hydrologic parameters.

Acknowledgments

The authors received assistance from many 

people during this study. Personnel from the 

Indiana Department of Natural Resources, Division 

of Water, provided guidance, water use and geologic information, and manuscript reviews. The 

citizens and officials of South Bend, Mishawaka, 

and northeastern St. Joseph County allowed access 

to their properties for well installation and data 

collection. A special appropriation from the Indiana 

General Assembly partially funded this study.

Previous Investigations DESCRIPTION OF THE STUDY AREA

The hydrogeology of the unconsolidated 

aquifers of northeastern St. Joseph County is 

described in several reports published by State 

and Federal agencies (Beaty, 1987; Crompton 

and others, 1986; Reussow and Rohne, 1975; 

Hunn and Rosenshein, 1969; Pettijohn, 1968;

lrThe water year is the 12-month period October 1- 

September 30; the water year is designated by the calendar 

year in which it ends.

The study area is the part of St. Joseph County 

that lies within the St. Joseph River drainage basin 

(fig. 1). The east boundary of the study area is the 

political boundary that separates St. Joseph County 

and Elkhart County, Ind. The north boundary of the 

study area is the Indiana/Michigan State line. The 

St. Joseph River drainage basin divide is the south 

and west boundary.

4 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
Within the study area are two metropolitan 

areas, South Bend and Mishawaka, and several 

smaller communities. Population of the study 

area is approximately 210,000 persons (Beaty, 

1987). Major industries in the basin include 

machinery, rubber and plastics, lumber and wood, 

fabricated metal, and printing and publishing 

(Beaty, 1987). Agricultural land use (primarily 

corn, soybeans, and other row crops) accounts 

for 59.2 percent of the study area (Beaty, 1987).

In 1989, a total of 16 public-supply well fields 

and 30 noncommunity well fields (such as those at 

schools and mobile home parks) were in operation. 

Rural homes and several residential neighborhoods 

in St. Joseph County that are beyond corporate 

limits rely on domestic wells.

As many as 79 potential ground-watercontamination sites are in the study area (Michiana 

Area Council of Governments, 1989). These 

sites include landfills, dump sites, waste-treatment 

sites, sludge ponds, waste lagoons, auto-salvage 

yards and junkyards, recycling stations, and 

land-reclamation sites. Ground-water contamination has been documented at 13 of these sites 

(Michiana Area Council of Governments, 1989).

HYDROGEOLOGIC SETTING

Several hydrogeologic factors affect the 

distribution of ground-water levels and directions 

of ground-water flow in northeastern St. Joseph 

County. Most of those factors are included in 

the numerical model, either explicitly or as 

lumped parameters that represent a combination 

of factors. Aquifer recharge is an example of a 

lumped parameter that describes the integrated 

effect of precipitation, evaporation, transpiration, 

and vertical hydraulic conductivity of surficial 

deposits. The following description of the hydrogeologic setting examines many of these variables 

and provides a basis for understanding the groundwater hydrology of northeastern St. Joseph County.

General Geology

Physiographic provinces are regions of similar 

topography and geology. Northeastern St. Joseph 

County lies entirely within the physiographic 

provinces known as the Kankakee Outwash and 

Lacustrine Plain and the Steuben Morainal Lake 

Area (Malott, 1922). The northern two-thirds of 

the study area lies within the Kankakee Outwash 

and Lacustrine Plain, a large outwash plain formed 

by sediment-laden rivers that drained Pleistocene 

Epoch glaciers (Malott, 1922). Glacial outwash 

typically is composed of sand and gravel that grades 

into finer materials with increasing distance from 

the source (Thombury, 1969). The outwash plain in 

northeastern St. Joseph County is gently undulating 

flat land that locally descends 15 to 30 ft into the 

St. Joseph River Valley. Land-surface altitudes on 

the outwash plain range from about 680 to 800 ft 

above sea level.

The Steuben Morainal Lake Area, which 

covers the southern one-third of the study area, 

is a gently undulating till plain (Malott, 1922). 

Glacial till is a heterogeneous ice-contact deposit 

that contains clay, silt, sand, and gravel and has a 

larger fraction of fine-grained sediment than outwash does (Thornbury, 1969; Krumbein and Sloss, 

1951). Local relief is about 170 ft along the 

boundary between the Kankakee Outwash and 

Lacustrine Plain and the Steuben Morainal Lake 

Area. Altitudes are as great as 920 ft above sea level 

in the Steuben Morainal Lake Area.

Aquifer Properties

The thickness of unconsolidated deposits 

in the study area ranges from less than 30 ft in 

the Mishawaka area (Beaty, 1987) to more 

than 200 ft in areas a great distance from the 

St. Joseph River Valley. The deposits form three 

distinct aquifer systems the St. Joseph aquifer 

system, the Hilltop aquifer system, and the 

Nappanee aquifer system in northeastern 

St. Joseph County (fig. 2) (Beaty, 1987).

Hydrogeologic Setting 5
86° 15' 86°07'30"

41°45'

41°37'30" -

41°30' -

n i r

012345 KILOMETERS

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30'. 45°30', central meridian -86'

EXPLANATION

I" ' I St. Joseph aquifer system

 M Hilltop aquifer system

 Nappanee aquifer system

 St. Joseph River drainage divide

 22 Well site and identifier

Figure 2. Distribution of aquifer systems in northeastern St. Joseph County, Indiana (modified from 

Beaty, 1987, pi. 2).

6 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
Unconsolidated deposits in the northern 

half of the study area are designated primarily 

as the St. Joseph aquifer system and are composed 

of outwash (fig. 2). In many places, outwash 

deposits of the St. Joseph aquifer system are 

separated by lesser thicknesses of clay-rich 

deposits. The clay-rich deposits probably are till 

or glacial-lacustrine deposits (Beaty, 1987). Where 

present, the clay-rich deposits may be confining 

units and may inhibit vertical ground-water flow 

between aquifers. Geologic evidence in northeastern St. Joseph County, Ind., indicated the 

existence of three main aquifers, each of which 

is separated from the other by a confining unit; 

the entire sequence is underlain by the Ellsworth 

Shale (fig. 3).

For purposes of this report, the outwash 

deposits are identified as aquifers 1,2, and 3; 

the interlayered clay-rich deposits are identified 

as confining units 1 and 2. Aquifer 1 occupies 

relatively small areas in the western and southern 

parts of the study area. Thickness of aquifer 1 

ranges from 0 to about 50 ft (fig. 4). Aquifer 2 is 

present in all of the study area except the southeastern and southwestern corners. The thickness 

of aquifer 2 ranges from 0 to more than 150 ft; 

in most places, however, thickness is 25 to 100 ft 

(fig. 5). Aquifer 3 is absent in the southeastern 

part of the study area, primarily designated as the 

Nappanee aquifer system, but is present elsewhere 

throughout the study area (fig. 6). The thickness of 

aquifer 3 ranges from 0 to 225 ft; the greatest thickness is in northeastern St. Joseph County. The 

horizontal hydraulic conductivity of outwash aquifers in northeastern St. Joseph County ranges from 

280 to 600 ft/d (Peters, 1987), and ground-water 

production rates range from 100 to 1,500 gal/min 

(Beaty, 1987).

Thickness of the confining units ranges from 

0 to about 100 ft; in most places, however, thickness is 10 to 50 ft. Thickness of confining unit 1 

ranges from 0 to 125 ft; greatest thickness is in the 

southeastern and western parts of the study area. 

The southeastern wedge of confining unit 1 represents till deposits primarily of the Nappanee aquifer 

system (fig. 7). A large area north of the Indiana/ 

Michigan State line also is overlain by confining

unit 1. Thickness of confining unit 2 ranges from 

0 to 125 ft in the study area and may be as great 

as 150 ft north of the State line (fig. 8). Confining 

unit 2 is absent from the northeastern and 

northwestern comers of the study area, as well as 

the southern areas where confining unit 1 is 

thickest. Water-level data indicate that vertical 

flow between aquifers may be inhibited where 

confining units are relatively thick or particularly 

clay rich. Vertical hydraulic conductivity of the 

confining units ranges from 0.04 to 0.21 ft/d 

(Lindgren and others, 1985).

The Hilltop and Nappanee aquifer systems 

are south and west of the St. Joseph aquifer system 

(fig. 2). The Hilltop aquifer system is composed 

of sand and gravel deposits overlain by 5 to 50 ft 

of clay-rich deposits (Beaty, 1987, p. 50). Pumping 

rates in the Hilltop aquifer system range from 10 

to 250 gal/min (Beaty, 1987, p. 50). The Nappanee 

aquifer system, in the southeastern part of the study 

area, consists of thin sand and gravel units (3 to 

20 ft thick) contained within thick sequences of till 

(Beaty, 1987, p. 49). Area! extent of the aquifers 

is less than 2 mi2 (Beaty, 1987, p. 49). Pumping 

rates in the Nappanee aquifer system range from 

50 to 600 gal/min (Beaty, 1987, pi. 2). The Nappanee aquifer system rarely is used for nondomestic 

or nonagricultural purposes.

The Ellsworth Shale of Devonian-Mississippian age underlies the unconsolidated deposits in 

the study area (Schneider and Keller, 1970). The 

upper part consists of the grayish-green shale and 

lenses of dolomite or laminated dolomite (Shaver 

and others, 1986). The lower part of the Ellsworth 

Shale consists of alternating grayish-green and 

brownish-black shale. The Ellsworth Shale dips 

toward the Michigan Basin (to the north-northeast) 

at an angle of less than 1°. The Ellsworth Shale is 

relatively poorly permeable and rarely used as a 

source of ground water.

Recharge and Discharge

Annual mean precipitation in the entire 

St. Joseph River Basin is 35 in/yr; the range is 21 

to 54 in/yr (Beaty, 1987, p. 19). About 38 in. of 

precipitation fall on the study area each year.

Recharge and Discharge 7
FEET NAPPANEE AQUIFER SYSTEM

A

900 -i

800 -

700 -

600 -

500

ST JOSEPH AQUIFER SYSTEM

FEET NAPPANEE 

AQUIFER

900 -i

800 -I

HILLTOP 

AQUIFER 

SYSTEM

ST JOSEPH AQUIFER SYSTEM

700 - B Aquifer3

600

500

NAPPANEE 

AQUIFER 

FEET SYSTEM

HILLTOP 

AQUIFER 

SYSTEM

ST JOSEPH AQUIFER SYSTEM

700

600

500

DATUM IS SEA LEVEL 

VERTICAL SCALE IS GREATLY EXAGGERATED

Figure 3. Generalized geologic sections showing 

conceptual layers used in the the ground-water-flow 

model for northeastern St. Joseph County, Indiana. 

(Aquifer 1 is not intersected by any of the sections.)

EXPLANATION

HC3 Sand and gravel 

i I Clay-rich deposits

6 MILES

KILOMETERS

8 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86°15' 86°07'30"

41°45

41°37'30" -

41°30' -

 __ ^- ~- -f»

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30'. 45°30'. central meridian -86'

012345 KILOMETERS

EXPLANATION

 ' - St. Joseph River drainage divide

^25" Isopach -- Shows thickness of geologic unit. Contour interval is 25 feet.

 22 Well site and identifier

Figure 4. Location and thickness of aquifer 1.

Recharge and Discharge 9
86°15' 86°07'30"

41°45'

41°37'30" -

41°30' -

Base from U.S. Geological Survey digital data, 1983 12345 MILES

Albers projection

standard parallels 29°30', 45°30', central meridian -86' I I T 

012345 KILOMETERS

EXPLANATION

 St. Joseph River drainage divide

^25- Isopach -- Shows thickness of geologic unit. Contour interval is 25 feet.

 22 Well site and identifier

Figure 5. Location and thickness of aquifer 2.

10 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86°15' 86°07'30"

41°45'

41°37'30"

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29D30', 45°30', central meridian -86C

0 1 345 MILES

n i i i i

012345 KILOMETERS

EXPLANATION

 St. Joseph River drainage divide

^25^ Isopach -- Shows thickness of geologic unit. Contour interval is 25 feet.

 22 Well site and identifier

Figure 6. Location and thickness of aquifer 3.

Recharge and Discharge 11
86° 15' 86°07'30"

41°45'

41°37'30" -

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45 30', central meridian -86°

0 1 2345 MILES

I I I I

01 2345 KILOMETERS

EXPLANATION

-< St. Joseph River drainage divide

-- 25" Isopach -- Shows thickness of geologic unit. Contour interval is 25 feet.

- 22 Well site and identifier

Figure 7. Location and thickness of confining unit 1.

12 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86° 15' 86°07'30"

41°45' -

41°37'30"

41°30'

Base from U.S. Geological Survey digital data, 1983

Alters projection

standard parallels 29°30', 45°30', central meridian -86'

01 2345 MILES

I I I I I

1 T \ \ \ I 

012345 KILOMETERS

EXPLANATION

-* St. Joseph River drainage divide

25 " Isopach -- Shows thickness of geologic unit. Contour interval is 25 feet.

 22 Well site and identifier

Figure 8. Location and thickness of confining unit 2.

Recharge and Discharge 13
Fifty-seven percent of the annual precipitation 

falls during the growing season (May-October) 

(Beaty, 1987, p. 19). The annual mean potential 

evapotranspiration in north-central Indiana is 

greatest during the growing season and amounts 

to about 27 in/yr (Newman, 1981).

Previous studies indicate recharge to the 

St. Joseph aquifer system from precipitation is 

about 10.6 in/yr (Beaty, 1987). The Hilltop and 

Nappanee aquifer systems receive less recharge, 

6.4 and 3.7 in/yr, respectively (Beaty, 1987), 

because the poorly permeable till that overlies the 

aquifers promotes runoff and inhibits infiltration. 

Precipitation that does not recharge the groundwater system evaporates or transpires into the 

atmosphere or becomes storm runoff to rivers 

and ditches. Recharge to the aquifers eventually 

is withdrawn for public and domestic water uses, 

commercial and industrial operations, and agricultural irrigation, or it discharges as base flow to the 

St. Joseph River and its tributaries.

The St. Joseph River is the primary drainage 

in the study area (fig. 1). The river enters the study 

area on the eastern county line, meanders westward 

and slightly southward to the middle of South Bend, 

and then turns northward and flows into Michigan. 

The stage and discharge of the St. Joseph River 

are controlled by dams built for power generation. 

Major tributaries of the St. JosephRiver in the study 

area are Juday Creek and Baugo Creek (fig. 1). 

Smaller streams and ditches also are part of the 

surface-water-drainage systems in St. Joseph 

County. Few lakes are in the study area, but 

numerous lakes are immediately north and west 

of the drainage-basin divide. Lakes and ponds 

also may be points of local ground-water recharge 

or discharge.

In addition to ground-water discharges to 

rivers, streams, lakes, and ditches, large volumes 

of ground water are extracted by SWWF's. Sixtytwo SWWF's were registered with IDNR in 1993 

(fig. 9; table 2, at back of report). Ground-waterwithdrawal capabilities reported in 1986 for 53 sites 

(14 percent not reporting) were 122.31 Mgal/d.

Actual use at those 53 sites was 34.67 Mgal/d 

(Beaty, 1987, p. 61). Estimated withdrawals by 

unregistered users in 1987, primarily domesticwell owners in rural St. Joseph County, accounted 

for less than 9 percent of the total ground-water 

production.

Water Levels

During this study, 53 monitoring wells 

were installed at 36 sites; clusters of 2 or 3 wells 

were constructed at 15 sites. Thirty-nine of the 

monitoring wells were north and east of the 

St. Joseph River. This area currently is experiencing rapid commercial and residential growth 

and is facing increased demands by SWWF's and 

domestic well users. The Hilltop and Nappanee 

aquifer systems are not used as heavily for highcapacity well fields; consequently, these aquifer 

systems received less attention during this study. 

Water levels were measured synoptically in the 

53-well network at least seven times during water 

years 1991 and 1992 (table 1, at back of report).

Hydrographs of ground-water levels in the 

St. Joseph aquifer system indicate similarities 

and differences between sites where confining 

units are and are not present. Water-level altitudes 

in deep wells (completed below the confining unit 

or at depths greater than 70 ft) and shallow wells 

(completed above the confining unit or at depths 

less than 70 ft) at clustered-well sites generally are 

similar if confining units do not separate upper 

and lower aquifers. At site 1, for example, the 

maximum difference in water levels in wells 1-25, 

1-85, and 1-173, during water year 1992 was 0.09 ft 

(fig. 10 and table 1). At sites where a confining 

unit is present, however, the difference between 

water-level altitudes in deep and shallow wells is 

greater. At sites 2,5,16,22, and 31, for example, 

clay-rich deposits are a definite barrier to vertical 

ground-water flow, and the altitudes of water levels 

in deep wells are lower than those in shallow wells

14 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86° 15' 86°07'30"

41°45'

41°37'30" -

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29"30', 45°30', central meridian -86°

01 2345 MILES

i I I I I I

012345 KILOMETERS

EXPLANATION

 - St. Joseph River drainage divide

 ?2 Well site and identifier

Water withdrawal facilities-Size of symbol is proportional to annual 

volume of water withdrawn from aquifer 1 .

O >0 - 100,000,000 (gallons per year) withdrawn

>1 00,000,000 - 1 ,000,000,000 (gallons per year) withdrawn 

>1 ,000,000,000 (gallons per year) withdrawn

Figure 9. Locations of significant (ground) water-withdrawal facilities in 1993.

Water Levels 15
5)

|CL i

1

0) 3Q.

SimulateQ.

0

i3Q.t<D n

i53.D) 8i(/)

c_O

13"

o

§

v?

^_3Q. 5'

0)

01y 786.055to

§ 785.5

oi01LLZ 785.001

§CC 784 5 S ' 1

784.0 

S(

i i i i i i i i i | i i i i | i i i i | i i i i | i i i i | i i i i | i i i i | i i i . i

" "- S n en 5J E2 ~: m '.: : -- '

- 8; 9 ;

1 Eg - -~_ 1 1 1 1 1 1 1 , 1 1 1 1 1 , 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ! 1 1

EXPLANATION

+ Well 1-25

X Well 1-85

n Well 1-1 73

3pt Oct Dec Jan Mar May June Aug Oct Nov

1991 1991 1991 1992 1992 1992 1992 1992 1992 1992

745 ...... . ... .........

dai 740 2i to

£J 735Smoi 730ffi

zuj 72501 i

a:OIt? 720

: ' ' ' ' ' ' ' '+' ' ' ' + ' ' + ' ' + ' - +- i . . . . -^ . . . . . . . , .- _i_ 'i- .- - --_ ___ "--- EXPLANATION + Well 16-28 O Well 16- 173

Figure 10. Ground-water levels during water year 1991 at well sites 1 and 16, northeastern St. Joseph County, Indiana.
by an average 1.28 ft, 3.56 ft, 24.67 ft, 24.11 ft, 

and 13.84 ft, respectively. (A hydrograph for 

site 16 is shown in figure 10.) A confining unit also 

separates shallow and deep aquifers at site 8; but at 

this location, the water levels are higher in the deep 

well by an average of 0.35 ft. This exception to the 

usual pattern is probably the effect of Juday Creek, 

which is less than 20 ft from site 8, drawing down 

the local water levels in the shallow aquifer.

Temporal variability of water levels in deep 

and shallow wells was approximately constant 

during the period of study, regardless of the 

presence or absence of a confining unit. At site 1, 

for example, the variability of water levels was 

1.48 ft, 1.49 ft, and 1.55 ft in wells completed at 

25 ft, 85 ft, and 173 ft, respectively; at site 16, 

water-level variability was 1.88 ft and 1.71 ft for 

wells screened at 28 ft and 173 ft, respectively 

(fig. 10). Proximity of a well site to the St. Joseph 

River did not seem to affect the temporal variability 

of water levels. Ground-water levels at all sites are 

highest in the winter and spring; they decline during 

summer and begin to recover towards the end of 

autumn (for example, see fig. 10).

Two wells in the USGS network were in 

the Nappanee aquifer system (wells 14-135 and 

A6-152) and one was in the Hilltop aquifer system 

(37-150) (fig. 1). Hydrographs for wells 14-135 and 

A6-152 varied by 13.67 ft and 0.55 ft, respectively. 

The highest levels at site 14-135 occurred during 

summer and may reflect delayed recharge of the 

aquifer or irrigation that was not observed during 

site visits. Water lev els at well site 37-150 were 

measured three times during the study period and 

varied by 0.93 ft. Compared to the St. Joseph 

aquifer system, depth to water generally is great 

in the Hilltop and Nappanee aquifer systems.

Ground-Water Flow

Ground-water-level maps were assembled 

for aquifers 2 and 3. No attempt was made to create 

a ground-water-level map for aquifer 1 because 

data were available for only one well site. The 

composite water-level map by Beaty (1987) was 

the foundation for constructing the ground-waterlevel maps shown in figures 11 and 12; measured

water levels in the deep and shallow wells were 

used to adjust the composite map to create 

individual maps for aquifers 2 and 3.

Ground water generally flows from regional 

recharge areas to regional discharge areas and 

local discharge sites. Ground-water discharge may 

occur at natural features such as creeks, rivers, 

lakes, and ponds, or ground water may discharge 

at manmade features such as drainage ditches and 

well fields. Regional ground-water flow in northeastern St. Joseph County is toward the St. Joseph 

River, the ultimate discharge point in the study area 

(Beaty, 1987). Local ground-water-flow patterns 

may be directed toward creeks, lakes, ponds, 

drainage ditches, and high-capacity well fields. 

Ground-water flow in deep aquifers typically 

follows regional flow paths, which may be as long 

as tens of miles. Ground-water flow in shallow 

aquifers, by comparison, may be affected by local 

discharge points; consequently, local flow paths 

may be as short as a few hundred feet.

SIMULATED GROUND-WATER FLOW 

THROUGH THE UNCONSOLIDATED 

AQUIFERS

A numerical model of ground-water flow 

was constructed to examine (1) simulated aquifer 

response to increased ground-water withdrawals, 

(2) contributing areas of SWWF's, and (3) flow 

paths and discharge points for hypothetical water 

particles originating beneath known contamination 

sites. The numerical model was based on a quasi 

three-dimensional finite-difference computer 

algorithm by McDonald and Harbaugh (1988). 

Fundamental assumptions of the model include 

a steady-state ground-water-flow system and a 

homogeneous, isotropic porous medium within 

each model layer. Model-parameter values were 

constrained by available hydrogeological information. The model was calibrated by minimizing 

the differences between simulated and fieldmeasured water-table elevations.

Ground-Water Flow 17
86°15' 86°07'30"

41°45'

41 037'30" -

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86°

01 2345 MILES

I I I I I

I I I I 

012345 KILOMETERS

EXPLANATION

-< St. Joseph River drainage divide

-720" Water-level contour-Shows altitude of water level. Contour interval 5 feet. 

Datum is sea level.

- 22 Well site and identifier

Figure 11. Altitude and configuration of the ground-water-level surface in aquifer 2.
86°15' 86°07'30"

41°45

41°37'30'

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86'

01 2345 MILES

I I I

' I I I T 

01 2345 KILOMETERS

EXPLANATION

 St. Joseph River drainage divide

-72o" Water-level contour-Shows altitude of water level. Contour interval 5 feet. 

Datum is sea level.

 22 Well site and identifier

Figure 12. Altitude and configuration of the ground-water-level surface in aquifer 3.
Model Conceptualization

The area represented in the numerical model, 

the "modeled area," is considerably larger than the 

study area described in the "introduction" section. 

The north boundary of the modeled area was 3.5 mi 

north of the Indiana/Michigan State line, and the 

east boundary was 3.0 mi east of the St. Joseph 

County/Elkhart County line (fig. 13). The southwest boundary of the modeled area was the 

St. Joseph River drainage basin divide.

The study area was divided into a model 

grid of rectangular cells (fig. 13), each with an 

area of one-quarter mi2. The center of the cell 

the "node" is the location where the numerical 

calculations of water level and flow direction were 

applied.

Cell orientation is parallel to the primary 

directions of ground-water ^ow. Regional 

ground-water flow in the study area is towards 

the St. Joseph River. Because the St. Joseph River 

reaches are mostly oriented north-south and 

east-west, the selected cell orientation (which 

coincidental^ parallels the political boundaries) 

is acceptable. Variable sizing of model cells 

(commonly used to give detailed information 

about a small site that lies within a modeled area) 

was not used in this study because the emphasis 

was on the regional flow system.

Boundary and Inactive Cells

Accurate identification of boundary conditions can greatly affect simulation results near the 

boundary, particularly in steady-state simulations 

such as this one (Anderson and Woessner, 1992). 

Boundary conditions for the modeled area were 

established where natural hydraulic boundaries 

were located; where natural boundaries did not 

exist, artificial boundaries were established at a 

sufficient distance from the study area so that they 

would not affect the simulated water levels. All 

model boundary cells were identified as "constanthead" cells; water levels were held constant in these 

cells during all simulations.

The southwestern boundary of the modeled 

area, the St. Joseph River drainage basin divide, is 

a hydraulic boundary. Although the surface-water 

drainage divide may not exactly coincide with the 

ground-water drainage-basin divide, the surfacewater drainage divide generally is accepted as 

a close approximation for a regional model. 

Boundary cells along the surface-water drainage 

divide, marking the southwest boundary of the 

modeled area, were identified in the numerical 

model as constant-head cells. The hydraulic heads 

assigned to the constant-head cells along the 

southwest boundary of the modeled area were 

based on maps of the ground-water-level surface 

(figs. 11 and 12). Assignment of constant heads 

to these cells was considered acceptable because 

(1) the boundary was at least 3 mi from the nearest 

SWWF; (2) the Hilltop and Nappanee aquifer systems, which are adjacent to this boundary, are rarely 

used by SWWF's; and (3) the main focus of this 

study is the area north and east of the St. Joseph 

River. These cells were identified in the numerical 

model as a constant-head boundary, as opposed to a 

constant-flux boundary that is sometimes used to 

simulate drainage divides, because accurate data 

needed to calculate ground-water fluxes were not 

available. Cells southwest of the drainage divide 

were identified as inactive cells and were not 

considered in the model calculations (fig. 13).

The land beyond the north and northwest 

boundaries of the modeled area is marked by 

several lakes, ponds, and poorly drained areas. 

This boundary extends due north approximately 

3.5 mi from the intersection of the St. Joseph River 

surface-water drainage divide and the Indiana/ 

Michigan State line. The northern boundary of 

the modeled area is oriented east-west and is 

positioned 3.5 mi north of the Indiana/Michigan 

State line. Boundary cells marking the north and 

northwest limits of the modeled area are identified 

in the numerical model as constant-head cells. 

The hydraulic heads assigned to these cells were 

based on ground-water-level surface maps and

20 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86°15' 86J07'30"

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30'. 45°30'. central meridian -86°

EXPLANATION

Active model cell 

£3 River cell 

0 Constant head cell 

[/] Inactive cell

 St. Joseph River drainage divide

 22 Well site and identifier

2345 MILES

II i I

n i

012345 KILOMETERS

Figure 13. Model grid, boundary conditions, and river reaches used in the simulation 

of ground-water flow.
water levels in the surface-water bodies. These 

boundary-cell assignments were considered 

acceptable because the cells are more than 4 mi 

from the nearest SWWF.

The eastern boundary of the modeled area 

is an artificial boundary established 3.0 mi east of 

the St. Joseph County/Elkhart County political 

boundary. The cells that mark the eastern boundary 

of the modeled area were identified in the numerical 

model as constant-head cells. Hydraulic heads 

assigned to boundary cells that mark the eastern 

limit of the modeled area were based on the groundwater-level surface maps assembled for this study. 

The boundary cells identifying the eastern limit of 

the modeled area were considered acceptable 

because (1) the nearest SWWF is more than 3 mi 

west of the boundary; (2) similar to the northern 

boundary, the eastern boundary is in the productive 

outwash of the St. Joseph aquifer system; and 

(3) previous studies and the water-level surface 

map indicated that ground-water flow is primarily 

from north to south in the area north and east of the 

St. Joseph River. Therefore, the contributing areas 

for SWWF's would affect primarily areas due north 

of their pumping stations. The evidence of a small 

east-west component of ground-water flow was 

enough justification to identify these cells as the 

constant-head type rather than the no-flow type 

that is sometimes used for cells positioned along a 

ground-water streamline (Anderson and Woessner, 

1992).

The Ellsworth Shale underlies the study area 

and probably is much less permeable than the 

glacial-drift deposits. The Ellsworth Shale was 

identified as a no-flow boundary, which allows 

no transfer of water across its interface with active 

model cells.

Active Model Cells

The stratigraphy represented in the active 

model cells was described from geophysical logs 

that were recorded during an earlier phase of this 

study (Bayless and others, 1995) and from more

than 370 well-driller's logs on file with IDNR. 

Geology in the modeled area is portrayed as three 

aquifers, separated by confining units the entire 

sequence underlain by the Ellsworth Shale (fig. 3). 

Stratigraphy of the St. Joseph aquifer system has 

been similarly conceptualized in previous model 

studies of ground-water flow in Elkhart County, 

Ind. (Imbrigiotta and Martin, 1981; and Lindgren 

and others, 1985). Isopach maps, constructed for 

each modeled stratigraphic unit, were used as a 

basis for assigning cell thicknesses.

Horizontal hydraulic conductivities of the 

modeled stratigraphic units were selected from 

ranges published in previous studies. Horizontal 

hydraulic conductivity of aquifer cells was constant 

within each layer.

Vertical leakances were used to represent 

vertical ground-water flow through the confining 

units. Vertical leakance is the vertical hydraulic 

conductivity divided by confining-unit thickness. 

Use of vertical leakance is acceptable if horizontal 

flow through the confining unit is small; this 

assumption has been made in similar stratigraphic 

settings (Imbrigiotta and Martin, 1981; Anderson 

and Woessner, 1992). Representative hydraulic 

conductivities were adopted from previous studies 

(Imbrigiotta and Martin, 1981; Lindgren and 

others, 1985). Vertical hydraulic conductivity 

was held constant within each confining unit, and 

the same value was used for all confining units.

Vertical hydraulic conductivity of streambed 

sediments in the St. Joseph River and Juday Creek 

(the two streams included in the model) was 

initially set to 0.07 ft/d (Imbrigiotta and Martin, 

1981, p. 41). Streambed conductance represents the 

stream-aquifer connection and is calculated as 

the product of streambed area and the vertical 

hydraulic conductivity of the streambed sediments 

divided by the thickness of the bed material. 

Imbrigiotta and Martin (1981) estimated streambed 

conductance by matching simulated seepage rates 

to measured rates in nine reaches of St. Joseph 

River tributaries; however, they were not able to 

calculate streambed conductance for the St. Joseph

22 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
River because of limitations in the accuracy of 

flow measurements along the river. The average 

length and width of a stream reach was determined 

by averaging the dimensions of reaches in several 

model cells. Average length of a reach below the 

dammed pool (fig. 1) was estimated to be 3,500 ft, 

and average width of a reach below the dammed 

pool was 200 ft. Reaches in the dammed-pool 

area were of similar length but stream width 

was estimated to be 400 ft. As in the model by 

Imbrigiotta and Martin (1981), astreambed 

thickness of 1 ft was assumed for all simulations.

Other Model Inputs

Aquifer recharge in the numerical model 

represents the difference between infiltration and 

evapotranspiration. Seasonal variations in precipitation and evapotranspiration were not required 

because computations were made only for the 

time-averaged steady-state model. Time-averaged 

recharge (infiltration minus evapotranspiration) 

has been estimated to be 10.6, 6.4, and 3.7 in/yr 

for the St. Joseph aquifer system, the Hilltop aquifer 

system, and the Nappanee aquifer system, respectively (Beaty, 1987).

Initial head arrays for the numerical model 

were based on water-level maps described in 

the section, "Ground-Water Flow." Groundwater-level maps of aquifer 2 and aquifer 3 were 

distinguished at only a few locations where fieldmeasured water levels differed between the two 

layers (table 1, at back of report).

All simulations were done by use of the data 

input and equations required for a steady-state 

system. A steady-state system generally is considered to be a reflection of long-term conditions. 

The steady-state conditions were simulated to meet 

the purpose of this study to describe the long-term 

effects of additional stresses on the aquifer system.

Model Assumptions

The computer program by McDonald and 

Harbaugh (1988), used to create the numerical

model, uses a finite-difference approximation for 

solving a set of equations that describe groundwater flow.

The results of a numerical model reflect 

the accuracy and precision of (1) the input data; 

(2) the fundamental equations that describe groundwater flow through a porous medium; (3) the finitedifference approximations; and (4) the simplifying 

assumptions concerning the spatial distribution of 

hydraulic parameters, such as homogeneity and 

isotropy. Values for some hydrologic variables 

used in the model were taken from measurements 

or estimates published in previous reports on the 

St. Joseph River Basin. The accuracy of those 

measurements and estimates and the spatial density 

of values affect the numerical model's ability to 

represent the flow system. Unavoidably, certain 

steps in model development such as construction 

of water-level maps and isopach maps are subject 

to the modeler's judgement and level of expertise. 

Inherent in the finite-difference method is the 

assumption that hydrogeologic parameter values 

are uniform within individual cells; the accuracy 

of this assumption is related to the cell dimensions. 

Generally, the accuracy of a numerical model based 

on the finite-difference method improves with 

decreasing cell size because additional data can be 

included and the hydrogeologic geometry can 

be more closely simulated. The additional accuracy, 

however, requires the availability of detailed hydrogeologic information and increased computing 

capabilities.

Model Calibration

The calibration process consisted of adjusting 

model-parameter values until the differences between simulated and measured ground-water levels 

and simulated and measured stream discharges 

were minimized. The parameter values adjusted 

were the horizontal hydraulic conductivity of 

aquifer 2, the horizontal hydraulic conductivity 

of aquifer 3, the vertical hydraulic conductivity of

Model Calibration 23
the confining units, the vertical hydraulic conductivity of the streambed, and the recharge 

rates to the three different aquifer systems. Thirty 

water-level measurements in aquifer 2 and 22 

measurements in aquifer 3 were used for model 

calibration; two discharge measurements along 

Juday Creek also were used.

Initial values of the model parameters were 

based on the values selected for a ground-water 

model of adjacent Elkhart County (Imbrigiotta and 

Martin, 1981). The aquifer system in St. Joseph 

County is contiguous with the aquifer system in 

Elkhart County, and the hydraulic characteristics 

should be similar. Initial values were 400 ft/d for 

horizontal hydraulic conductivity of the sand and 

gravel aquifers, 0.07 ft/d for the vertical hydraulic 

conductivity of the confining unit, 12 in/yr for 

recharge rate to the outwash, and 0.5 ft/d for the 

vertical hydraulic conductivity of the streambed.

The first of three significant changes made 

to the model during calibration was to reduce the 

number of aquifers being simulated. The initial 

conceptual model was based on drillers' records 

and included three sand and gravel aquifers. During 

calibration, however, the observations were made 

that (1) aquifer 1 covers only a small percentage 

of the modeled area, (2) aquifer 1 is not present 

in the area north and east of the St. Joseph River, 

(3) no measured water levels for aquifer 1 were 

available for comparison with simulated values, 

and (4) aquifer 1 probably has little effect on the 

regional flow system. Aquifer 1 was inactivated 

during subsequent runs of the model.

The second significant change to the model 

concerned the vertical hydraulic conductivity of 

the confining unit beneath the St. Joseph River. 

In a previous study by Marie (1975, p. 7), a detailed 

geologic section indicated erosion of the confining 

unit and refilling with coarse-grained sediments. 

Downcutting and refilling with coarse-grained 

sediments by large rivers, such as the St. Joseph 

River, has been recorded in other hydrogeologic 

studies in Indiana (Planert, 1980; Meyer and others, 

1975). During calibration, the model results

indicated that simulated water levels in the lower 

aquifer were consistently higher than measured 

water levels near the river if a vertical hydraulic 

conductivity of 0.07 ft/d were used. As a result 

of this observation and the data from Marie (1975), 

the vertical hydraulic conductivity of the confining unit was increased to 0.7 ft/d beneath the 

St. Joseph River; this resulted in a decreased 

gradient across the confining unit and water levels 

in aquifer 3 that were lower and more similar to 

measured water levels.

A third change to the model was to increase 

recharge to the St. Joseph aquifer system above 

values documented in previous studies. The South 

Bend area receives about 38 in/yr of precipitation, 

and aquifer recharge was previously estimated at 

about 12 in/yr (Beaty, 1987). This study found 

that an aquifer recharge value of 24 in/yr provided 

the best model calibration, and that ample evidence 

was available to support this value. For example, 

as part of this study, map and site inspections 

documented few tributaries to Juday Creek or 

the St. Joseph River in the area of the St. Joseph 

aquifer system, indicating that surface runoff is 

an uncommon mechanism for conveying stormwater to the St. Joseph River. The sandy soils and 

relatively flat topography probably have the effect 

of causing most precipitation to infiltrate directly 

into the shallow aquifers. Analysis of storm hydrographs for Juday Creek show that a narrow, runoff 

peak, probably derived from urban runoff, is 

proceeded usually by long-duration ground-watergenerated rise in streamflow (Fowler and Wilson, 

1995). By use of a recharge value of 24 in/yr, 

simulated ground-water discharge to Juday Creek 

(16.5 ft3/s) and measured discharge (18.2 fl3/s) 

were in reasonable agreement for a steady-state 

period in August 1993. In addition, a 24 in/yr 

recharge produced the least deviation of simulated 

and measured ground-water levels in the study area.

Recharge rates to the Nappanee aquifer 

system did not change during model calibration, but 

the rate to the Hilltop aquifer system was increased

24 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
from 6.4 to 9.6 in/yr. The surficial deposits of the 

Hilltop aquifer system are similar to the highly 

permeable surface of the St. Joseph aquifer system.

The streambed sediments of the St. Joseph 

River were assigned a vertical hydraulic conductivity of 5 ft/d. The vertical hydraulic conductivity 

of streambed sediments in tributaries to the 

St. Joseph River was 50 ft/d. Little silt or clay is 

in the surficial deposits of the drainage basins, and 

so the vertical hydraulic conductivity of the streambeds was increased over that used in the model 

study of Imbrigiotta and Martin (1981). By use of 

these values for the vertical hydraulic conductivity 

of streambed sediments, most measured and simulated ground-water levels near streams were in 

agreement.

The downstream reaches of Juday Creek 

were conceptualized as having a relatively low 

vertical hydraulic conductivity. Vertical hydraulic 

conductivity of streambed sediments for the six 

farthest downstream cells of Juday Creek was set 

at 0.05 ft/d to maintain streamflows reported in 

Fowler and Wilson (1995). The downstream 

reaches of Juday Creek are convex upward when 

viewed in profile, a situation that is somewhat 

uncommon for a stream that is approaching a 

confluence with a major stream and that is underlain with glacial drift deposits. The channel of 

Juday Creek, however, is lined with cobble-sized 

rocks that are hindering the creek from eroding 

its channel to a convex down profile that is typical 

of Indiana streams. As a result of this unusual 

stream profile, the simulations indicated that Juday 

Creek would lose water to the aquifer in the last 

six model cells, and there would be no flow in the 

channel if the vertical hydraulic conductivity were 

not reduced. Organic particulates, chemical precipitates, clays, and silts may have accumulated in the 

streambed represented by these six model cells and 

thereby reduced the vertical hydraulic conductivity.

The water budget associated with the 

calibrated model is given in table 3. The final 

values selected for model parameters were the 

following:

Horizontal hydraulic conductivity 

of the aquifers (ft/d)......... 275

Vertical hydraulic conductivity of

the confining unit (ft/d) ...... 0.07

Vertical hydraulic conductivity of 

the confining unit at the St. Joseph 

River (ft/d)................ 0.7

Vertical hydraulic conductivity 

of the streambed of the St. Joseph 

River (ft/d)................ 5

Vertical hydraulic conductivity 

of the streambed of all other 

streams (ft/d) .............. 50

Vertical hydraulic conductivity of 

the streambed at the lower end of 

Juday Creek (ft/d)........... 0.05

Recharge to the St. Joseph aquifer 

system (in/yr).............. 24

Recharge to the Nappanee aquifer 

system (in/yr).............. 3.7

Recharge to the Hilltop aquifer 

system (in/yr).............. 9.6

The accuracy of simulated water levels 

relative to measured water levels was quantified 

by calculating the mean absolute error and the bias 

according to the following equations:

Mean ,, , , ZI simulated head-measured head! absolute error = - - - 

number of measurements

n . E( simulated head - measured head) Bias = - - - 

number of measurements

The mean absolute error and the bias for the 

calibrated model were 5.0 ft and 1.8 ft, respectively. 

The mean absolute error and the bias were divided 

by the range in measured water levels to estimate 

the accuracy of the calibrated model. The range 

in measured water levels was about 100 ft. The 

percent mean absolute error was 5 percent, and 

the percent bias was 2 percent.

Model Calibration 25
Table 3. Water budget for the calibrated ground-water-flow model, northeastern St. Joseph County, 

Indiana

[all values in cubic feet per second]

Inflow

Recharge from precipitation 366 

Ground-water recharge from streams 6.8 

Boundary inflow 128

Outflow

Ground-water withdrawal 57.7

Ground-water discharge to streams 413

Boundary outflow 29.8

Total inflow 501 Total outflow 501

Error generally is less than the average (5 ft) 

for the entire model. The principal anomaly is in 

the vicinity of three proximally located wells in the 

northeastern quadrant of the study area; here, simulated water levels in aquifer 3 are 20 to 30 ft higher 

than the measured water levels (fig. 14). Despite 

close examination of the physical setting near 

these wells, the explanation for the anomalously 

high simulated water levels is unknown. Available 

pumping records for SWWF's near the three 

anomalous well sites do not indicate withdrawals 

sufficient to cause a large cone of depression, and 

depressed water levels are not evident in aquifer 2. 

If these three sites are not considered, the mean 

absolute error is 3.8 ft.

The absolute error of the model (measured 

water level minus simulated water level) and the 

simulated steady-state water levels are depicted for 

aquifer 3 in figure 14. In general, the map of simulated water levels generated from the calibrated 

model closely approximates the map of measured 

water levels (fig. 12). Accuracy of the model predictions is better in parts of the study area where 

monitoring-well information was available for 

calibration.

One area of apparent disagreement between 

figures 12 and 14 is near the confluence of Juday 

Creek and the St. Joseph River. Simulations indicate an area of depressed water levels that isn't 

present in figure 12. The simulated depression is 

a result of higher leakance rates for the confining 

unit near the confluence of Juday Creek and the 

St. Joseph River (described earlier in this section). 

In the vicinity of the confluence, the hydraulic head 

in aquifer 3 is approximately equal to the stage in 

the St. Joseph River. Absolute mean error for the 

observation well in this vicinity is 2 ft.

The confining unit thickens beneath the 

St. Joseph River north of the river's confluence 

with Juday Creek, and the resulting decrease in 

leakance causes the simulated heads in aquifer 3 

to be as much as 30 ft higher than the river stage. 

The effect of the elevated water levels in aquifer 3 

is a concentricity of water-level contours around 

the confluence of the St. Joseph River and Juday 

Creek. Although this water-level contour pattern 

is uncommon near large rivers, boundary conditions and initial head values were examined and 

determined to be unrelated to the model solution. 

Very few measured water levels were available 

for aquifer 3 in Michigan, and figure 12 is largely 

based on lakes, ponds, streams, and shallow 

wells that are more representative of conditions 

in aquifer 2.

Differences between simulated and measured 

water levels in aquifer 2 generally are 5 ft or less 

in the area north and east of the St. Joseph River, 

the area of greatest interest for model simulations. 

South and west of the river, differences between 

measured and simulated water levels in aquifer 2 

south range from 5 to 21 ft. Acquiring and including 

additional hydrogeologic information in the area 

south and west of the river probably would improve 

calibration.

The simulated water-level surface for 

aquifer 2 is not depicted in the report. It was discovered during this study that parts of aquifer 2 are not 

water-bearing deposits a contoured water-level 

surface for aquifer 2 would be discontinuous and 

difficult to interpret. In the parts of aquifer 2 that are 

waterbearing, contours of the water-level surface 

would be similar to those pictured in figure 11. The 

water-level surfaces shown in figures 11 and 12 

were constructed from a composite surface for the

26 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86° 15' 86°07'30"

41°45' -

41 037'30" -

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45"30', central meridian -86°

01 2345 MILES

I I I I I

012345 KILOMETERS

EXPLANATION

-> St. Joseph River drainage divide

-760- Water-level contour-Shows altitude at which water level would have stood in 

tightly cased wells. Contour interval 5 feet. Datum is sea level.

-2 Difference between the simulated and measured water levels 

» 22 Well site and identifier

Figure 14. Simulated steady-state ground-water-level surface and absolute error for 

calibrated model at well sites in aquifer 3.
study area that did not differentiate between 

shallow and deep aquifer deposits as a result, 

the contour lines in figure 11 indicate that the 

ground-water surface is continuous, whereas 

the simulations indicate that this may not be true.

Model Sensitivity

The purpose of the sensitivity analysis was 

to determine the effect of each model parameter 

on simulated water levels. Parameters that substantially affect simulated water levels must be accurate 

for model results to be reliable.

Model sensitivity was examined by incrementally varying each of the parameters from 

one-half to twice the calibrated value and observing 

the mean absolute error and bias that resulted. The 

parameters examined were the same as those 

varied during calibration: horizontal hydraulic 

conductivity of the aquifers, vertical hydraulic conductivity of the confining unit, recharge rates to 

the aquifers, and vertical hydraulic conductivity 

of the streambeds. The model sensitivity of each 

parameter is illustrated in figure 15 (because 

several values are used for vertical hydraulic 

conductivity of the streambeds, the caption for the 

x-axis of the associated graph of sensitivity refers to 

the multiplier of the calibrated values rather than 

the value itself, as done in the other graphs).

On the basis of mean absolute error and 

bias, the analyses indicate the following order of 

parameter sensitivities, from least sensitive to 

most sensitive: vertical hydraulic conductivity 

of the streambeds, vertical hydraulic conductivity 

of the confining units, horizontal hydraulic 

conductivity of aquifer 2, horizontal hydraulic conductivity of aquifer 3, and recharge to aquifer 2. 

This information indicates that accurate estimates 

of the recharge rates and the horizontal hydraulic 

conductivities of the aquifers are the most important data for modeling the ground-water-flow 

system in northeastern St. Joseph County.

If a parameter value greatly differs from 

values used for similar geologic formations or 

hydrogeologic settings, then additional data need 

to be acquired to support use of the selected value. 

In this study, model calibration indicates that 

recharge rates are about twice the previously 

reported rates (Meyer and others, 1975, p. 48; 

Imbrigiotta and Martin, 1981, p. 44; Bergeron, 

1981, p. 34) are required to minimize errors in 

the model of the St. Joseph aquifer system. Additional study would be beneficial to confirm this 

discrepancy.

In addition to recharge, the model is sensitive 

to the horizontal hydraulic conductivity of the 

aquifers. The model probably is more sensitive to 

horizontal hydraulic conductivity of aquifer 3 

than to that of aquifer 2 because ground-water 

withdrawals from aquifer 3 are greater.

Simulation Results

The ground-water model was used to simulate 

(1) aquifer response to increased ground-water 

withdrawals, (2) source areas for SWWF's, and 

(3) flow paths and discharge points for particles 

originating beneath known contamination sites.

Simulated Ground-Water Availability

Ground-water availability was examined 

by simultaneously increasing ground-waterwithdrawal rates by 50 percent at all SWWF's. 

The 50-percent increase over 1993 production 

rates a reasonable estimate of future demands 

on the resource was useful for examining how 

the aquifer might respond.

The simulations of increased ground-water 

withdrawals indicated that maximum drawdowns 

would be about 6 ft in aquifer 2 and 10 ft in 

aquifer 3 (fig. 16). The maximum drawdowns 

were computed only for the cells where the heaviest 

withdrawals were made; however, in both aquifers, 

the area sustaining depressed water levels of 2 ft 

or more was several square miles. Although the

28 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
toLiJ

Li.

Z

ERROR, FED 

SIMULA!

1U

8

6 

4

(

2

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1J

i i

> «- .

*" * 

"*~«^

i i

i i i i i

"~*-*-*-*-*.^

i i i i i

i

i

15 175 225 275 325 375 425 475 525 575

HORIZONTAL HYDRAULIC CONDUCTIVITY OF

10

8

6 '

i 

4

2

0

-2

1J

AQUIFER 2, IN FEET PER DAY

i I

-

11111

-

. «- '

"""*-- .

*--- - *_

i i i i i

i

>5 175 225 275 325 375 425 475 525 575

HORIZONTAL HYDRAULIC CONDUCTIVITY OF

10 

8

6 

4

2

0

AQUIFER 3, IN FEET PER DAY

l ill

-

-

-*- »»- --»- -»-- _...__,.

i ill

12 16 20 24 28 32 36 40 44 48 

RECHARGE TO THE UPPER AQUIFER, IN INCHES 

PER YEAR

IU

8

6

4

2

0 

-9

' '

-

-

-

I I

I i 1 I

-

1 1 I 1

0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 

MULTIPLIER OF THE CALIBRATED VERTICAL 

HYDRAULIC CONDUCTIVITY OF THE STREAM BEDS

EXPLANATION

 Mean absolute error for all 

simulated water levels

0.03 0.05 0.07 0.09 0.11 0.13 

VERTICAL HYDRAULIC CONDUCTIVITY OF THE 

CONFINING UNIT, IN FEET PER DAY

0.15

Bias for all simulated water levels

Reference lines for errors and 

calibrated parameter values

Data point for simulated error

Figure 15. Relation between simulated errors and variation in parameter values for the 

ground-water-flow model, northeastern St. Joseph County, Indiana.

Simulation Results 29
maximum drawdowns are averages for the entire 

simulated cell (one-quarter mi2), drawdowns at a 

single well within that cell might be significantly 

greater.

In aquifer 2 and aquifer 3, the area where 

ground-water levels would be depressed by a 

50-percent increase in withdrawals includes 2 to 

3 mi of the lower reaches of Juday Creek (fig. 16). 

If a 50-percent increase in withdrawals were realized, ground water that would usually discharge to 

streams would be unavailable, and a decrease in 

streamflow would be expected. This model indicated that a 50-percent increase in ground-water 

withdrawals would cause a 19-ft3/s loss of streamflow in the St Joseph River and a 3.8-ft3/s loss of 

streamflow in Juday Creek; these losses represent 

a 6-percent and a 23-percent reduction of groundwater flow to the channels of the St. Joseph River 

and Juday Creek, respectively.

Simulated Particle Transport

The particle-tracking program MODPATH 

(Pollock, 1989) was used to determine the source, 

flow path, and travel time of water to the largest 

SWWF's in the study area. The particles whose 

flow paths are examined are inert and hypothetical they could be water molecules or any 

nonreactive constituent in the ground water. 

Particle tracking is a useful way to examine the 

potential pathways that ground water might follow 

enroute to discharge at lakes, ponds, rivers, or 

SWWF's.

The land-surface area that contains the starting 

locations for all flow paths to a single withdrawal 

site is the contributing area for that well. The particle paths shown in figure 17 are not the only ones 

possible; instead, the flow paths shown in figure 17 

describe only the general ground-water-flow paths 

that particles might follow if introduced into the 

system. The number of particles tracked in this 

analysis was limited to improve the clarity of the 

figure, but use of additional particles would not 

substantially affect the contributing areas.

The flow-path lengths and the travel times 

for particles are related to ground-water-withdrawal 

rates and the hydraulic properties of the aquifers 

pumped. In general, the calculated flow paths are 

perpendicular to contours of the ground-water-level 

surface. Simulations indicate that flow paths to 

wells in aquifer 3 can be more than 12 mi long 

and travel times generally are 50 to 100 years. The 

long flow paths and travel times are associated 

with SWWF's withdrawing ground water from 

aquifer 3. Times required for particles to reach 

wells withdrawing water from aquifer 3 are substantially increased because recharge must flow 

through a confining unit, which has lower permeability and retards the flow of water.

Flow paths in aquifer 2 generally are less than 

5 mi, and travel times are usually less than 10 years. 

Exceptions to this general observation are the long 

paths that originate in the southern part of the study 

area and end at a well field that is located near the 

St. Joseph River (fig. 17). This well field withdraws 

a relatively large amount of ground water about 

2,500 gal/min and, as a result, the flow paths 

originate several miles away. The distances 

between 5-year time increments for this S WWF 

are noticeably longer than those associated with 

other well sites and probably indicate increased 

flow velocities caused by water-level gradients 

that are greater than those located north and west 

of the river.

Figure 18 shows the starting locations for 

particles that, in figure 17, were shown to eventually be carried along the flow path to the SWWF's. 

Although not clear from figure 17, figure 18 shows 

that simulated flow paths originate close to and 

distant from the SWWF's. Starting locations for 

particles that eventually flow to the SWWF's north 

and east of the St. Joseph River the primary focus 

of this study can be used to identify the entire 

contributing area for each SWWF. South and west 

of the St. Joseph River, the contributing areas for 

four of five well sites extend beyond the model 

boundary, indicating that the conceptual boundary 

selected for the model may not be appropriate 

south and west of the river or that a more sophisticated model for particle transport is needed to

30 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86°15' 86°07'30"

41°45'

41°37'30" -

41°30

012345 MILES Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86'

EXPLANATION

~ St. Joseph River drainage divide

 2- Line of equal water level decline-Interval 2 feet

 22 Well site and identifier

012345 KILOMETERS

Figure 16. Water-level decline in aquifer 3 caused by a 50-percent increase 

in ground-water withdrawals at all sites.
86°15' 86°07'30"

41°45' -

41°37'30" -

41°30

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86'

EXPLANATION

 St. Joseph River drainage divide

 « Flow path and 5-year time increment

 ~~ Well site and identifier

n Significant ground-water withdrawal facility

rn r i i

012345 KILOMETERS

Figure 17. Simulated flow paths from selected points of recharge to significant 

water-withdrawal facilities.
86°15' 86°07'30"

41°45' -

41°37'30"

41°30' -

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86° i i i

01 2345 KILOMETERS

EXPLANATION

 St. Joseph River drainage divide

 22 Well site and identifier

o Starting location of flow path that enters a simulated production well

PI Significant ground-water withdrawal facility

Figure 18. Starting locations for flow paths that end at significant water-withdrawal facilities.
simulate this setting. The level of pre-model data 

acquisition and analysis for the southwestern part 

of the study area was not as intensive as the area 

north and east of the St. Joseph River. Further 

refinement of the model and its parameter values 

would be needed to resolve discrepancies in the 

simulation in the areas south and west of the 

St. Joseph River.

In addition to its use for determining the 

source of water to wells, MODPATH was used 

to determine the flow paths and ultimate discharge 

points for particles originating beneath documented 

sites of contamination. This analysis does not 

indicate anything about the quality of water along 

the flow path, which can be affected by many 

physical, chemical, and biological processes that 

occur in the subsurface. Simulated flow paths that 

originate beneath contamination sites, however, 

might be used to locate sites where water-quality 

analyses could be done to test for mobile constituents. The contamination sites used in this analysis 

were identified as "known contamination sites" by 

the Michiana Area Council of Governments (1989). 

Model cells containing the contamination sites 

were identified and several particles were distributed across the ground-water-level surface in that 

cell. Starting locations, flow paths, and ultimate 

discharge points for particles originating beneath 

the contamination sites are shown in figure 19.

The flow paths depicted in figure 19 are based 

on the assumption that a particle that enters a cell 

containing a simulated well or stream will not be 

withdrawn or discharged unless all ground water 

flowing into the cell is captured by the well or 

stream; otherwise, the particle continues along a 

flow path towards its ultimate discharge point. 

This conceptual model tends to route most particles 

to the St. Joseph River, the primary point of 

discharge in the study area; some ground water 

discharges to Juday Creek. This conceptual model 

indicates that ground water from known contamination sites does not discharge to any SWWF, but 

flow paths from several contamination sites appear 

to pass near these well fields. Particles in this set of 

simulations require from 1 to 100 years to travel 

from their starting points to their ultimate discharge 

points, but most travel times are less than 10 years.

By use of a different assumption, particles 

were allowed to discharge to the first stream or 

well along their flow paths, regardless of whether 

some or all of the ground water is captured by the 

well or stream. Some results were different than 

those from the previously described model. Numerical simulations based on this conceptual model 

indicate that eight SWWF's would intercept 

some particles that originated beneath known 

contamination sites. Some combination of these 

two conceptual models may represent the actual 

situation.

Model Limitations

Reliability of the results given in this report 

can be judged on the basis of the data and design 

limitations associated with the model. Limitations 

associated with the use of the model for northeastern St. Joseph County are described here.

Model reliability is enhanced if calibration 

data are available for a period when the aquifers 

are heavily stressed. Errors in model-parameter 

values generally are amplified when the flow 

system is modeled for transient conditions. 

Conditions during the 1991-92 well-measurement 

period could not be used to examine a period of 

aquifer stress because withdrawal rates at that 

time did not significantly stress the system. During 

model calibration, however, USGS investigators 

used water levels for several wells near SWWF's 

where some indication of aquifer stress might 

be observed.

Within the study area, the most appropriate 

application of results is to the area north and east 

of the St. Joseph River because (1) data for model 

parameterization and calibration were most 

abundant in the area north and east of the St. Joseph 

River, (2) the river was a permanent hydrologic 

boundary that was suitable as one boundary 

condition, and (3) the model was insensitive to 

the artificially established hydrologic conditions 

along the north and east sides of the modeled area.

34 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
86° 15' 86°07'30"

41°45

41°37'30"

41°30' -

MICHIGAN________

NDIANA.27A Granger

Base from U.S. Geological Survey digital data, 1983

Albers projection

standard parallels 29°30', 45°30', central meridian -86'

EXPLANATION 

['7" River cell

-* St. Joseph River drainage divide

 « Flow path and 5-year time increment

22 Well site and identifier

|~i Significant ground-water withdrawal facility

012345 KILOMETERS

Figure 19. Flow paths from sites of contamination to points of discharge.
In general, the most appropriate application of 

model results is also limited to areas greater than 

the dimensions of one model cell (0.25 mi2); the 

ground-water levels reported for each cell are 

calculated at the node and do not indicate the 

range of ground-water levels that might exist 

within that cell.

Assignment of boundary conditions along 

the north and east sides of the study area as both 

constant head and constant flux nodes produced 

no effect on either the simulated drawdown at 

SWWF's or the model's water-budget calculations. 

Simulated ground-water levels near artificial 

boundary conditions, however, may be less reliable 

than simulated ground-water levels that are distant 

from boundary cells.

Available data indicate that confining unit 2 

is present in most parts of the modeled area. 

Additional lithologic data may reveal locations 

where the unit is absent and change the conceptual 

ground-water exchange between aquifers 2 and 3 

in these simulations. Simulated drawdowns and 

flow directions might be altered at such locations.

Porosity was the only additional hydrogeologic parameter that was required for 

particle-tracking simulations. Porosities used for 

the aquifers (0.35) and confining units (0.45) in the 

particle-tracking analyses were reported averages 

for outwash and interbedded clays (Morris and 

Johnson, 1967, p. D29). Porosities for geologic 

units in the modeled area were not measured in this 

study or in previous investigations. Use of different 

porosities would not affect the size or shape of 

the delineated contributing area but could change 

the location of simulated 5-year time increments.

SUMMARY AND CONCLUSIONS

The water supply for northeastern St. Joseph 

County is withdrawn primarily from permeable 

glacial deposits that are vulnerable to contamination from human activity at land surface. To 

determine the source and availability of future

drinking-water supplies, the USGS and the 

IDNR cooperatively examined the ground-water 

resources of a 227-mi2 area in northeastern 

St. Joseph County, Ind.

The ground-water resources of northeastern 

St. Joseph County were investigated by collection 

and analysis of field data, compilation of available 

water-well records, and simulation of ground-water 

flow by use of a numerical model. Field data 

consisted of water-level measurements from 

monitoring wells, streamflow measurements at 

Juday Creek, and surface-geophysical measurements. About 370 well drillers' records, collected 

by IDNR, were combined with logs for 53 wells 

drilled during this study to construct isopach maps 

of aquifers and confining units. The isopach maps 

and other hydrogeologic information were used 

to construct and calibrate a numerical model that 

simulated ground-water flow. The simulations were 

used to determine the effect of increased withdrawals on ground-water levels, local streamflow, 

and ground-water-flow paths. Particle-tracking 

analyses were used to delineate the contributing 

areas for SWWF's and the discharge points for 

known contamination sites.

The ground-water-flow system in northeastern St. Joseph County contains three aquifer 

systems: the St. Joseph, the Hilltop, and the 

Nappanee. The St. Joseph aquifer system consists 

of outwash deposits that can exceed thicknesses of 

200 ft. The outwash aquifers may be separated 

vertically by a confining unit of till or lacustrine 

deposits. South of the St. Joseph aquifer system are 

the topographically higher Hilltop and Nappanee 

aquifer systems. The Hilltop aquifer system consists of sand and gravel deposits overlain by 5 to 

50 ft of clay-rich till. The Nappanee aquifer system 

consists of thin sand and gravel deposits (3 to 30 ft) 

contained within thicker sequences of till.

The ground-water model developed in this 

study represents two extensive aquifers as individual layers; the confining unit is represented by 

a vertical leakage term. Fifty-three measured water 

levels and two streamflow measurements along 

Juday Creek were used to help calibrate the model.

36 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
The closest agreement between simulated and 

measured water levels and fluxes was found with 

the following set of model-parameter values:

Horizontal hydraulic conductivity

of the aquifers (ft/d)......... 275

Vertical hydraulic conductivity of

the confining unit (ft/d) ...... 0.07

Vertical hydraulic conductivity of 

the confining unit near the St. Joseph 

River (ft/d) ................ 0.7

Vertical hydraulic conductivity of

the streambed of the St. Joseph

River (ft/d) ................ 5

Vertical hydraulic conductivity

of the streambed of all other

streams (ft/d)............... 50

Vertical hydraulic conductivity of

the stream be at the lower end of

Juday Creek (ft/d)........... 0.05

Recharge rates to aquifers (in/yr) 3.7-24

This set of parameter values resulted in a 

mean absolute error of 5.0 ft between simulated 

and measured water levels. The sensitivity analyses 

indicated that an accurate estimate of recharge 

rate and horizontal hydraulic conductivity of 

aquifer 3 is the most critical information needed for 

an accurate representation of the flow system 

in the numerical model.

The calibrated recharge rate for the St. Joseph 

aquifer system is higher than that used for most 

ground-water systems in Indiana; additional 

recharge data would be required to improve 

confidence in the calibrated rate. If the measured 

recharge rate were actually lower than the 

calibrated rate, then ground-water availability 

may be less than the model simulations indicate.

The calibrated model was used to determine 

the effect of a 50-percent increase in pumpage at 

all SWWF's. Maximum simulated drawdowns, 

when averaged across an entire 0.25 mi2 cell, 

were 6 ft in aquifer 2 and 10 ft in aquifer 3. The 

50-percent increase in withdrawals caused a loss 

of 19 ft3/s in streamflow of the St. Joseph River 

and loss of 3.8 ftVs in streamflow of Juday Creek.

Flow paths to SWWF's at current withdrawal 

rates were investigated. Flow paths to wells in 

aquifer 3 can be as long as 12 mi, and travel times 

can be 50 to 100 years. Long flow paths and greater 

travel times were simulated at SWWF's, where 

aquifer 2 and aquifer 3 are separated by a confining 

unit and withdrawals were being made from the 

lower aquifer. The longer travel times and the natural filtering properties of the clay- and silt-rich 

confining unit may partially protect water in the 

lower aquifer from human-related contamination. 

Flow paths in aquifer 2 are typically less than 5 mi 

long, and travel times are usually less than 

10 years. Ground water withdrawn from aquifer 2 is 

probably more susceptible to contamination from 

human activities than is water in the lower aquifer.

The flow paths of ground water that originate 

beneath known contamination sites and the ultimate 

discharge points of that ground water also were 

investigated. Ground water originating beneath 

contamination sites generally discharges to the 

St. Joseph River; under some conditions, however, 

this water may be partially captured by 8 of the 

10 largest SWWF's. The flow-path analysis does 

not in any way describe the quality of water along 

the flow paths, but results may be used to locate 

monitoring wells intended to study the transport 

of constituents away from known contamination 

sites.

Summary and Conclusions 37
REFERENCES CITED

Anderson M.P., and Woessner, W.W., 1992, 

Applied groundwater modeling: San Diego, 

Calif., Academic Press, 381 p.

Bailey, Z.C.; Greeman, T.K.; and Crompton, I.E., 1985, 

Hydrologic effects of ground- and surface-water 

withdrawals in the Howe area, LaGrange County, 

Indiana: U.S. Geological Survey Water Resources 

Investigations Report 85-43,130 p.

Bayless, EJR.; Westjohn, D.B.; and Watson, L.R., 1995, 

Use of surface and borehole geophysics to delineate 

the glacial-drift stratigraphy of northeastern 

St. Joseph County, Indiana: U.S. Geological Survey 

Water-Resources Investigations Report 95-4041, 

63 p.

Beaty, Judith, 1987, Water resource availability in the 

St. Joseph River Basin, Indiana: Indiana Department 

of Natural Resources, Division of Water, Water 

Resource Assessment 87-1,139 p.

Bergeron, M.P., 1981, Effect of irrigation pumping on 

the ground-water system in Newton and Jasper 

Counties, Indiana: U.S. Geological Survey WaterResources Investigations Report 81-38,73 p.

Bleuer, Ned, and Melhorn, W.N., 1989, Glacial terrain 

models, north-central Indiana The application 

of downhole logging to analysis of glacial vertical 

sequences: South Bend, Ind., Notre Dame University, Geological Society of America, North-Central 

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Crompton, E.J.; Peters, J.G.; Miller, R.L.; Stewart, J.A.; 

Banaszak, KJ.; and Shedlock, R.J., 1986, Review 

of the hydrologic data-collection network in the 

St. Joseph River Basin, Indiana: U.S. Geological 

Survey Water-Resources Investigations 

Report 86-4157,51 p.

Fowler, K.K., and Wilson, J.T., 1995, Characteristics, 

transport, and yield of sediment in Juday Creek, 

St. Joseph County, Indiana, 1993-94: U.S. Geological Survey Water-Resources Investigations 

Report 95-4135,48 p.

Hunn, J.D., and Rosenshein, J.S., 1969, Geohydrology 

and ground-water potential of St. Joseph County, 

Indiana: Indiana Department of Natural Resources, 

Division of Water, Bulletin 33,20 p.

Klaer, F.H., and Stallman, R.W., 1948, Ground-water 

resources of St. Joseph County, Indiana, Part 1. 

South Bend area: Indiana Department of Conservation Bulletin 3,177 p.

Krumbein, W.C., and Sloss, L.L., 1951, Stratigraphy 

and sedimentation (2d ed.): San Francisco, Calif., 

W.H. Freeman and Company, 660 p.

Imbrigiotta, T.E., and Martin, Angel, Jr., 1981, Hydrologic and chemical evaluation of the ground-water 

resources of northwest Elkhart County, Indiana: 

U.S. Geological Survey Water-Resources Investigations Report 81-53,149 p.

Lindgren, H.A.; Peters, J.G.; Cohen, D.A.; and 

Crompton, E.J., 1985, Hydrologic effects of 

ground- and surface-water withdrawals in the 

Milford area, Elkhart and Kosciusko Counties, 

Indiana: U.S. Geological Survey Water-Resources 

Investigations Report 85-4166,76 p.

Malott, C.A., 1922, The physiography of Indiana, in 

Handbook of Indiana geology: Indiana Department 

of Conservation Publication 21, p. 59-256.

Marie, JJR., 1975, Hydraulic characteristics and watersupply potential of the aquifers in the vicinity of the 

wastewater treatment plant, South Bend, Indiana: 

U.S. Geological Survey Water-Resources Investigations 49-74,26 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular three-dimensional finite-difference ground-water 

flow model: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 6, chap. Al, 

586 p.

Meyer, William; Reussow, J. P.; and Gillies, D. C, 1975, 

Availability of ground water in Marion County, 

Indiana: Open-File Report 75-312, 87 p.

Michiana Area Council of Governments, 1989,

St. Joseph County potential groundwater contamination sites: 1 sheet, scale 1:90,000.

Morris, D. A., and Johnson, A.I., 1967, Summary of 

hydrologic and physical properties of rock and soil 

materials, as analyzed by the Hydrologic Laboratory 

of the U.S. Geological Survey 1948-60: U.S. Geological Survey Water-Supply Paper 1839-D, 42 p.

38 Hydrogeology and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
REFERENCES CITED Continued

Newman, I.E., 1981, Weekly water-use estimates by 

crops and natural vegetation in Indiana: West 

Lafayette, Ind., Purdue University, Agricultural 

Experiment Station Bulletin 344,26 p.

Peters, J.G., 1987, Description and comparison 

of selected models for hydrologic analysis of 

ground-water flow, St. Joseph River Basin, Indiana: 

U.S. Geological Survey Water-Resources Investigations Report 86-4199,125 p.

Peters, J.G., and Renn, D.E., 1988, Effects of agricultural 

irrigation on water resources in the St. Joseph River 

Basin, Indiana, and implications for aquifer yield: 

U.S. Geological Survey Water-Resources Investigations Report 87-4273, 35 p.

Pettijohn, R. A., 1968, Reconnaissance of the groundwater resources of the St. Joseph River Basin in 

Indiana, Appendix to the State water plan of the 

Division of Water: U.S. Geological Survey, 32 p.

Planert, Michael, 1980, Ground-water availability near 

Fort Wayne, Alien County, Indiana: U.S. Geological 

Survey Water-Resources Investigations 80-34,54 p.

Pollock D.W., 1989, Documentation of computer programs to compute and display pathlines using results 

from the U.S. Geological Survey modular threedimensional finite-difference ground-water flow 

model: U.S. Geological Survey Open-File Report 

89-381, 188 p.

Reussow, J.P., and Rohne, P.B., Jr., 1975, Water

resources of the St. Joseph River Basin in Indiana: 

U.S. Geological Survey Hydrologic Investigations 

Atlas HA-537, 3 sheets, scales 1:500,000 and 

1:250,000.

Rosenshein, J.S., and Hunn, J.D., 1962, Ground-water 

resources of northwest Indiana, preliminary 

report St. Joseph County: Indiana Department 

of Conservation Bulletin 15, 318 p.

Schneider, A.F., and Keller, S.J., 1970, Geologic map of 

the 1° x 2° Chicago quadrangle, Indiana, Illinois, 

and Michigan., showing bedrock and unconsolidated 

deposits: Indiana Department of Natural Resources, 

Geological Survey Regional Geologic Map 4, 

1 sheet, scale 1:250,000.

Shaver, R.H.; Ault, C.H.; Burger, A.M.; Carr, D.D.; 

Droste, J.B.; Eggert, D.L;, Gray, H.H.; Harper, 

Denver; Hasenmueller, N.R.; Hasenmueller, W.A.; 

Horowitz, A.S.; Hutchison, H.C.; Keith, B.D.; 

Keller, S.J.; Patton, J.B.; Rexroad, C.B.; and 

Wier, C.E. 1986, Compendium of paleozoic rockunit stratigraphy in Indiana A revision: Indiana 

Department of Natural Resources, Geological 

Survey Bulletin 59,203 p.

Thornbury, W.D., 1969, Principles of geomorphology 

(2d ed.): New York, John Wiley and Sons, 549 p.

U.S. Geological Survey, 1990, National water summary 

1987 Hydrologic events and water supply and use: 

U.S. Geological Survey Water-Supply Paper 2350, 

553 p.

References Cited 39
4o
SUPPLEMENTAL DATA
Table 1. Ground-water levels measured in northeastern St. Joseph County, Indiana, water years 1991-92

[All water levels and land-surface elevations in feet above sea level; *, dry well; , no measurement]

10

X'a

3

8

O

(Q

to

a. 

w

3

c. 

n

I

O

3

a

i

Tl

I

z

O

sw 

<D-«

3 

CO

c.

Ow

-ST>

£

C

^

a

to

3

to

Date

measured

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92

02/16/92

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92

02/16/92

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

Well number

(land-surface elevation)

1-25

(800.12)

786.62

787.08

785.96

785.77

784.98

-

786.06

785.94

785.62

785.74

785.97

784.58

784.76

-

5-133

(749.66)

723.46

722.31

721.53

721.40

--

721.10

721.88

721.94

721.74

721.65

721.81

721.15

721.22

1-85

(800.14)

-

784.95

-

786.04

785.91

785.59

785.72

785.94

784.55

784.73

-

7-33

(793.99)

-

777.11

776.98

775.87

--

776.41

776.53

776.16

776.10

776.19

775.27

774.97

~

1-173

(799.83)

--

784.99

--

786.07

785.96

785.63

785.75

785.97

784.52

784.82

-

8-22

(765.75)

~

759.89

761.98

--

760.72

760.54

760.87

760.58

760.64

760.41

760.99

2-25

(779.21)

773.32

773.30

772.16

772.02

773.73

--

773.74

773.19

773.32

773.19

773.21

772.17

773.75

-

8-148

(765.74)

762.25

--

-

761.25

760.97

--

761.17

760.98

761.01

760.58

761.35

2-139

(778.19)

-

772.47

-

772.47

--

771.93

772.06

771.92

771.97

770.75

772.48

--

9-25

(770.46)

766.76

766.62

764.62

764.48

--

766.30

-

766.67

765.99

766.01

765.95

766.02

764.65

766.50

--

4-25

(77536)

768.04

767.75

765.94

765.77

-

767.77

767.13

766.91

766.96

769.14

765.76

767.19

-

9-99

(770.47)

--

-

766.34

--

766.73

766.05

--

766.07

766.02

766.08

764.85

766.55

~
Table 1. Ground-water levels measured in northeastern St. Joseph County, Indiana, water years 1991-92 Continued

Ground-Water

Levels Measured inNortI

w

3

w

o w<D a

c

^

6

Date 

measured

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92 

02/16/92 

03/19/92 

04/20/92 

07/14/92 

11/04/92

11/05/92

01/25/91 

06/07/91 

07/25/91 

07/31/91 

08/01/91

10/05/91 

10/06/91

10/07/91 

12/02/91

12/03/91 

01/14/92 

01/16/92

02/16/92 

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

Well number

(land-surface elevation)

11-37

(754.72)

742.56

742.64

741.45

--

741.33

741.20

741.76

--

740.95 

740.98 

741.33 

740.57 

740.77

--

21-23

(758.04)

747.25 

747.10

747.57

748.59

748.15

747.97 

748.01

748.01

747.16

747.91

11-95

(754.51)

742.64

742.40

741.02

--

740.91

741.18

742.23

--

741.59

741.41 

741.44 

741.33 

740.55 

740.77

--

21-133

(757.79)

747.32

748.36

747.93

747.72 

747.77

747.77

746.90

747.71

13-23

(76637)

__

751.55

--

--

--

750.05

--

751.28

--

751.51

751.42 

751.86 

752.23 

750.48 

750.09

--

22-30

(756.68)

750.10 

748.74

747.09

747.15

749.35

748.58

748.33 

748.70

748.70

747.29

747.69

14-135

(844.20)

..

--

--

774.86

775.38

775.46

775.05 

775.14 

775.59 

788.53 

787.57

-

22-148

(756.15)

-

723.47

724.63

724.65

724.44 

724.25

724.25

723.30

723.87

15-35

(751.56)

_.

--

--

734.63

734.49

735.20

735.19

734.86 

734.91 

735.02 

733.80 

734.48

--

23-55 

(790.51)

754.30 

754.13

753.90

753.39

752.90

752.67 

753.04

753.04

752.02

751.32

15-130

(751.18)

_.

--

--

734.51

735.23

735.06

734.88 

734.94 

735.05 

733.93 

734.51

--

23-133

(79031)

753.96

753.52

753.02

752.98 

753.17

753.17

752.07

751.62
Table 1. Ground-water levels measured in northeastern St. Joseph County, Indiana, water years 1991-92 Continued

o

(Q«< 

0)

a

CO

3

O

to

<D

3

L

o 

co

 s

jf

0) 

0)

Date

measured

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92

02/16/92

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92

02/16/92

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

Well number

(land-surface elevation)

26-30

(785.75)

-

766.64

-

765.42

~

766.18

~

765.95

-

765.60

765.52

765.60

764.70

764.44

~

31-138

(732.89)

-

-

-

-

715.45

--

716.38

716.74

-

716.44

716.33

716.58

714.99

715.85

-

27-28

(743.37)

733.00

-

-

732.40

733.71

~

733.05

-

732.64

732.87

733.20

732.55

732.00

-

32-148

(730.55)

~

-

-

-

705.20

706.06

~

706.53

~

705.95

705.86

706.37

704.60

705.74

~

27A-60

(829.32)

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

33-65

(783.10)

730.78

--

730.85

~

--

730.59

~

730.56

730.12

-

730.08

730.03

729.07

--

-

728.37

27A-148

(829.47)

~

-

~

~

-

767.72

767.99

767.88

-

767.64

767.50

767.32

765.81

766.43

--

34-33

(73324)

--

707.26

~

707.15

-

706.46

706.80

706.57

-

706.30

706.29

706.43

705.81

705.69

29-68

(697.19)

~

-

-

-

--

-

687.94

~

688.34

688.02

~

688.10

688.16

688.30

687.43

~

688.43

35-52

(716.67)

--

690.39

690.32

~

--

-

689.01

689.66

-

689.84

~

689.59

689.79

690.04

688.93

689.27

~

30-29

(695.88)

-

-

--

--

-

-

~

-

675.25

674.86

~

674.64

674.85

674.80

673.63

-

674.47

36-168

(760.15)

-

~

--

723.61

--

--

724.94

725.10

-

724.78

724.58

725.01

723.49

724.34

-
Table 1. Ground-water levels measured in northeastern St. Joseph County, Indiana, water years 1991-92 Continued

o

Q.

tt 

<D

I

W

2.

o

Date 

measured

01/25/91

06/07/91

07/25/91

07/31/91

08/01/91

10/05/91

10/06/91

10/07/91

12/02/91

12/03/91

01/14/92

01/16/92

02/16/92

03/19/92

04/20/92

07/14/92

11/04/92

11/05/92

Well number

(land-surface elevation)

39-25

(735.10)

728.43

728.73

727.45

~

--

-

728.08

729.43

-

728.61

-

728.58

728.69

728.61

727.54

728.76

-

40-78 

(736.31)

-

--

--

-

~

721.89

--

723.06

--

722.56

722.45

722.55

722.75

721.71

721.98

-

41-23 

(764.98)

~

754.99

-

-

755.01

755.32

~

755.06

755.30

755.39

755.49

754.85

754.93

--

42-33 

(71333)

-

690.54

~

-

~

690.41

690.57

690.45

690.45

690.45

690.51

690.75

691.12

--

A6-149

(851.78)

~

--

792.17

-

792.61

792.48

792.51

792.46

792.06

791.84

-
Table 2. Ground-water-withdrawal site numbers, geographic locations, model cell locations, 1993 ground-water 

withdrawals, and withdrawal capacities, northeastern St. Joseph County, Indiana

[UTMN, Universal Transverse Mercator northing; UTME, Universal Transverse Mercator easting; gal/yr, gallons per year, gal/min, gallons 

per minute]

Site 

number

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

Geographic location 

UTMN UTME

4612740

4612925

4611450

4611525

4613500

4613450

4614500

4615125

4612750

4611825

4614525

4613925

4614005

4616175

4615350

4617975

4610975

4609475

4620250

4619050

4615525

4615600

4614175

4612920

4622700

4606525

4614690

4614315

4614480

4622750

4622250

4619350

4615700

4619400

4622900

4621300

4621750

4616800

4622550

4622525

4622950

4609700

4610025

4613100

4617080

4617150

4616520

4616370

4616925

4616975

4614000

570550

570525

569975

570050

572950

572950

565750

565950

569050

568550

558650

573425

573425

557525

565525

560550

560850

561875

565350

557475

558850

558850

572375

576390

573105

572175

574395

574505

574000

562950

563250

562825

557500

556700

560850

569425

570425

575000

567150

567425

568200

572500

571575

577675

563700

563810

563820

563100

563220

563100

560000

Row

19

19

18

18

17

17

17

17

18

19

16

17

17

15

16

13

21

22

10

12

15

15

24

18

8

25

18

17

16

8

8

11

15

12

8

9

9

14

8

8

8

25

24

20

14

14

14

15

14

14

19

Model

Column

23

23

22

22

25

25

17

17

21

20

8

26

26

7

16

10

11

12

16

6

8

8

16

30

25

25

28

27

27

13

13

13

6

6

11

21

22

28

18

18

19

25

24

32

14

14

14

13

14

13

9

Layer

3

3

3

3

3

3

3

3

3

3

2

3

3

3

3

2

3

3

3

3

2

2

2

3

2

3

3

3

3

2

2

3

3

3

2

2

2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

1993 

withdrawal 

(1,000 gal/yr)

76,737

1,871,615

217,359

80,008

167,760

168,770

2,039

8,250

9,674

60,000

115,630

18,575

22,872

1,118,501

1,775,650

1,361,886

5,986

740,323

200,837

1,032,965

44,240

36,340

2,133

2,189

1,740

3,552

4,500

21,610

2,635

24,816

2,239

520

880

3,000

670

15,000

15,000

1,232

40,320

72,225

50,400

13,500

8,610

3,739

145,272

228,686

313

12,275

75,905

29,601

152,340

Withdrawal 

capacity 

(gal/mln)

146

1,050

750

1,000

750

750

638

955

85

1,000

80

2,000

2,000

1,388

2,777

2,604

1,042

1,388

400

2,000

600

600

150

235

100

200

300

165

200

239

75

100

150

150

55

1,000

1,000

500

800

300

1,000

500

500

100

1,000

1,000

650

600

500

1,300

349

46 Hydrogeologiy and Simulated Ground-Water Flow, Northeastern St. Joseph County, Indiana
Table 2. Ground-water-withdrawal site numbers, geographic locations, model cell locations, 1993 ground-water 

withdrawals, and withdrawal capacities, northeastern St. Joseph County, Indiana Continued

Site 

number

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

Geographic location

UTMN

4608930

4621125

4621750

4621520

4621520

4621450

4601520

4605525

4618550

4618550

4619000

4619100

4619250

4619625

4619875

4621575

4621575

4621525

4622050

4622100

4622050

4622275

4622350

4622350

4622250

4622250

4622400

4618700

4618999

4618910

4618750

4620075

4607300

4613750

4606125

4606050

4622675

4622750

4622800

4622300

4622375

UTME

571920

568350

569875

572975

573025

573075

563900

568400

567825

567400

567510

570300

570375

568100

568030

573325

573400

573450

573650

573650

573550

573660

573650

573650

573590

573500

573450

567910

567900

567720

567625

577900

564800

561975

565625

565550

573600

573650

573675

573290

573290

Row

26

9

9

9

9

9

27

26

12

12

12

11

11

11

11

9

9

9

10

10

10

10

10

10

10

10

10

12

12

12

12

10

23

20

26

26

9

8

8

9

8

Model

Column

24

20

21

25

25

25

15

20

19

19

19

22

22

19

19

26

26

26

26

26

26

26

26

26

26

26

26

19

19

19

19

31

27

12

17

17

27

27

27

26

26

Layer

3

3

2

2

2

2

2

3

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

3

3

2

2

2

3

3

1993 

withdrawal 

(1,000gal/yr)

2,401

77,580

114,930

27

360

625

59

1,912

1,795

1,127

168

92,236

145,457

301,749

371,858

89,941

88,532

156,586

53,492

58,716

65,985

45,358

40,709

26,328

35,640

35,640

37,852

154

16

23,564

153

387

10,676

79,056

38

1

2,694

991

991

967

67

Withdrawal 

capacity 

(gal/min)

100

1,400

1,500

224

1,503

80

50

100

499

150

55

275

300

1,250

1,000

190

108

360

120

100

100

100

75

75

75

75

75

195

105

525

105

154

101

150

46

254

42

27

27

65

75

* U.S. GOVERNMENT PRINTING OFFICE: 1996 747-764 Ground-Water Withdrawal 47