THE MIDWESTERN BASINS AND ARCHES

REGIONAL AQUIFER SYSTEM IN PARTS OF

INDIANA, OHIO, MICHIGAN, AND ILLINOIS SUMMARY

dence 

uses

for a changing world

PROFESSIONAL PAPER 1423-A
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The Midwestern Basins and Arches 

Regional Aquifer System in Parts of 

Indiana, Ohio, Michigan, and Illinois 

Summary

B)iE.F. BUGLIOSI

REGIONAL AQUIFER-S\STEM ANALYSIS MIDWESTERN BASINS AND ARCHES

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1423-A
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, Director

Any use of trade, product, or firm names in this publication is for

descriptive purposes only and does not imply endorsement by the

U.S. Government.

Reston, Virginia 1999

Library of Congress Cataloging in Publication Data

Buliosi, Edward F.

The Midwestern basins and arches regional aquifer system in parts of Indiana, Ohio, Michigan, and Illinois : summary / by E. F. Bugliosi.

p. cm. (U.S. Geological Survey professional paper; 1423-A) 

Includes bibliographical references (p. ). 

ISBN 0-607-92591-4

1. Aquifers Middle West. 2. Groundwater flow-Middle West. I. National Regional Aquifer Systems Analysis Program (U.S.) II. Title. III. Series. 

GB1199.3.M54B84 1999

551.49'0977 dc21 99-33374

CIP

For sale by U.S. Geological Survey, Branch of Information Services, Box 25286,

Federal Center, Denver, CO 80225
FOREWORD

THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM

The Regional Aquifer-System Analysis (RASA) Program represents a 

systematic effort to study a number of the Nation's most important aquifer 

systems, which, in aggregate, underlie much of the country and which represent an important component of the Nation's total water supply. In general, 

the boundaries of these studies are identified by the hydrologic extent of each 

system and, accordingly, transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for 

each study is to assemble geologic, hydrologic, and geochemical information; 

to analyze and develop an understanding of the system; and to develop predictive capabilities that will contribute to the effective management of the 

system. The use of computer simulation is an important element of the RASA 

studies to develop an understanding of the natural, undisturbed hydrologic 

system and the changes brought about in it by human activities, and to provide a means of predicting the regional effects of future pumping or other 

stresses.

The final interpretive results of the RASA Program are presented in a 

series of U.S. Geological Survey Professional Papers that describe the geology, 

hydrology, and geochemistry of each regional aquifer system. Each study 

within the RASA Program is assigned a single Professional Paper number 

beginning with Professional Paper 1400.

Charles G. Groat 

Director

CONTENTS

	Page

Forward......................................................................................... Ill

Abstract......................................................................................... Al

Introduction................................................................................... A2

Regional analysis of the Midwestern Basins and Arches

aquifer system.................................................................. A2

Objectives and approach................................................... A2

Purpose and scope of Professional Papers 1423-A, B,

and C................................................................................. A2

Summary of previous work..................................................... A3

Acknowledgements.................................................................. A3

Physical setting............................................................................. A4

Extent of study area ............................................................... A4

Physiography........................................................................... A5

Climate.................................................................................... A5

Hydrogeology................................................................................. A5

Geologic setting....................................................................... A5

Bedrock units.................................................................... A7

Ordovician rocks ......................................................... A7

Silurian and Lower and Middle Devonian rocks ...... A13

Page

Middle and upper Devonian and Mississippian

rocks...................................................................... A13

Surficial deposits....................................................................... A16

Hydrogeologic units................................................................... A16

Surficial aquifer..................................................................... A16

Carbonate-rock aquifer.......................................................... A19

Regional ground-water flow.......................................................... A19

Hydrogeologic boundaries......................................................... A20

Potentiometric surfaces............................................................ A21

Recharge and discharge............................................................ A21

Ground-water-flow simulations.................................................... A25

Regional simulation.................................................................. A25

Subregional simulations........................................................... A31

Regional water chemistry............................................................. A34

Dissolved solids trends.............................................................. A34

Hydrochemical facies................................................................ A37

Relation of isotopic composition of ground water to

regional flow......................................................................... A37

Ground-water use.......................................................................... A41

References cited............................................................................. A44

ILLUSTRATIONS

FIGURES 1-5. Maps of the Midwestern Basins and Arches Region showing:

1. Location of the area of data collection, study area, and structural arches and basins........................................ A4

2. Generalized topography........................................................................................................................................... A6

3. Mean annual precipitation...................................................................................................................................... A7

4. Major drainage basins ............................................................................................................................................. A8

5. Generalized bedrock geology and major faults....................................................................................................... A9

6. Generalized hydrogeologic sections A-A', B-B', and C-C', Midwestern Basins and Arches Region .................................... A10

7. Chart showing time- and rock-stratigraphic framework, nomenclature, and model layers for the Midwestern Basins

and Arches Region.................................................................................................................................................... All

8-12. Maps of the Midwestern Basins and Arches Region showing:

8. Thickness of the basal confining unit of the carbonate-rock aquifer..................................................................... A12

9. Thickness of the carbonate-rock aquifer and approximate limit of ground water with dissolved-solids

concentration greater than 10,000 milligrams per liter......................................................................... A14

10. Altitude of the top of the upper confining unit of the carbonate-rock aquifer...................................................... A15

11. Glacial deposits, extent of glaciation, and approximate location of the main stem and principal tributaries

of the buried Teays-Mahomet River system ........................................................................................... A17

12. Generalized thickness of glacial deposits ............................................................................................................... A18

13. Conceptual hydrogeologic section showing the relation between local, intermediate, and regional flow............................. A20

14-22. Maps of the Midwestern Basins and Arches Region showing:

14. Generalized ground-water level configuration for the surficial aquifer................................................................ A22

15. Potentiometric surface configuration for the carbonate-rock aquifer.................................................................... A23

16. Calculated mean and mean sustained ground-water discharge to selected reaches along major streams in

the study area........................................................................................................................................... A24

17. Model areas for regional and subregional ground-water-flow models................................................................... A26

18. Boundary conditions used in the regional ground-water-flow model of the surficial and carbonate-rock

aquifers..................................................................................................................................................... A27

19. Measured and simulated hydraulic heads for the carbonate-rock aquifer in the regional model....................... A29

20. Measured and simulated mean sustained ground-water discharge to selected stream reaches for the study

area........................................................................................................................................................... A30

21. Recharge and discharge areas based on output from the calibrated ground-water-flow model.......................... A32

22. Ground-water-flow paths based on particle-tracking of regional ground-water flow........................................... A33
VI CONTENTS

Page

23. Ground-water-flow paths based on particle-tracking results for a cross-sectional model representing regional groundwater flow from a regional recharge area in central-western Ohio to a regional discharge area at Lake Erie ... A34 

24-28. Maps of the Midwestern Basins and Arches Region showing:

24. Distribution of dissolved-solids concentrations in the surficial aquifer................................................................ A35

25. Distribution of dissolved-solids concentrations in the carbonate-rock aquifer..................................................... A36

26. Hydrochemical fades based on concentrations of major anions and cations in water from the surficial

aquifer....................................................................................................................................................... A38

27. Hydrochemical fades based on concentrations of major anions and cations in water from the carbonaterock aquifer............................................................................................................................................... A39

28. Ground-water-withdrawal sites where the potential pumpage is 100,000 gallons per day or more................... A42

29-30. Graphs showing:

29. Total monthly ground-water withdrawals for parts of Indiana and Ohio in the Midwestern Basins and

Arches Region........................................................................................................................................... A43

30. Total monthly ground-water use, by category, among users capable of withdrawing 100,000 gallons per

day or more in parts of Indiana and Ohio in the Midwestern Basins and Arches Region................... A43

TABLES

Page

TABLE 1. Regional ground-water-flow model boundaries and the areas to which each boundary is applied ...................................... A28

2. Relative sensitivity and calibrated model simulation values of hydrologic parameters for the regional ground-waterflow model of the Midwestern Basins and Arches Region....................................................................................... A28

3. Simulated ground-water budget for regional flow in the Midwestern Basins and Arches aquifer system .......................... A31

4. Hydrochemical facies, geochemical processes controlling reactions, and predominant area of hydrochemical facies in

the surficial and carbonate-rock aquifers in the Midwestern Basins and Arches Region..................................... A40

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

inch (in)

foot (ft)

mile (mi)

square mile (mi 2 )

inch per year (in/yr)

foot per day (ft/d)

foot squared per day (ft2/d)

cubic feet per second (ft3/s)

gallon per minute (gal/min)

gallon per minute per foot (gal/min/ft)

gallon per day (gal/d)

million gallons per day (Mgal/d)

25.4 

0.3048 

1.609 

2.590 

0.254 

0.3048 

0.09290 

0.02832 

0.06309 

0.207

4.381 x 10" 

0.04381

millimeter

meter

kilometer

square kilometer

millimeter per year

meter per day

meter squared per day

liter per second

liter per second

liter per second per meter

cubic meter 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 both the United States and 

Canada, formerly called "Sea Level Datum of 1929".

Water-quality units used in this report: Concentrations of dissolved solids are given in milligrams per liter (mg/L), 

a unit expressing the concentration of chemical constituents as mass (millegrams) of solute per unit of volume 

(liter) of water.
CONTENTS VII

Stable isotope ratios are expressed as a departure of the ratio of two isotopes of an element in a given sample 

from the same ratio in an established standard; values are given in permil (parts per thousand). 

Symbols and standards are the following:

5 13C Carbon-13/carbon-12 ratio, referenced to Pee Dee Formation of South Carolina 

5 D Deuterium/hydrogen ratio, referenced to SMOW (Standard Mean Ocean Water) 

5 18O Oxygen-18/oxygen-16 ratio, referenced to SMOW 

5 34S Sulfur-34/sulfer-32 ratio, referenced to Canyon Diablo meteorite standard

REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

THE MIDWESTERN BASINS AND ARCHES 

REGIONAL AQUIFER SYSTEM IN PARTS OF 

INDIANA, OHIO, MICHIGAN, AND ILLINOISSUMMARY

BY E.F. BUGLIOSI

ABSTRACT

The Midwestern Basins and Arches aquifer system is composed of 

surficial deposits of Pleistocene and Holocene age and of Silurian and 

Devonian age carbonate rock in parts of Indiana, Illinois, Michigan, 

and Ohio. The study area encompasses a complex of structural 

arches the Cincinnati, Findlay, and Kankakee Arches and is 

bounded on the east, north and west by the Appalachian, Michigan 

and Illinois Basins, respectively. This report summarizes the major 

results of a 6-year study of this regional aquifer system. Because the 

rock units that compose the carbonate-rock aquifer are not truncated as 

they dip away from the arches and into the basins, the regional aquifer 

system has no definite stratigraphic boundaries. Thus, an area of "principal hydrologic interest" was defined that is bounded by the contact 

between carbonate bedrock and overlying shale bedrock of Upper 

Devonian age, and by various major water bodies. This area of intensive study includes about 44,000 square miles within a larger area of 

data collection that encompasses more than 90,000 square miles.

The hydrogeologic framework of the Midwestern Basins and 

Arches aquifer system is defined in terms of the extent and thickness of 

the lower confining unit, the carbonate-rock aquifer, the upper confining unit, and the surficial aquifer. The lower confining unit, which 

underlies the entire study area, consists of interbedded calcareous 

shales and limestone of Ordovician age that are much less impermeable than the overlying aquifer units. The lower confining unit ranges 

in thickens from an average of 200 feet in northwestern Indiana to 

more than 1,400 feet in central Ohio. The carbonate-rock aquifer consists primarily of limestone and dolomite of Silurian and Devonian 

age. The aquifer is absent in southwestern Ohio and southeastern Indiana along the axis of the Cincinnati Arch, but it is as much as 2,500 feet 

thick in southeastern Michigan at the edge of the Michigan Basin. The 

upper confining unit is composed of Upper Devonian and Mississippian calcareous shales but is present only along the lateral margins of 

the study area (a transitional area from arches to basins). The maximum thickness of the upper confining unit is about 700 feet in northeastern Ohio, at the edge of the Appalachian Basin. Glacial and alluvial 

deposits composing the surficial aquifer unconformably overlie 97 percent of the study area except in the extreme southeast, where the area is 

unglaciated. These deposits are more than 400 feet thick in northwestern Indiana, where they fill the buried, ancient Teays-Mahomet river 

system in the central part of the study area; however, they are only a 

few feet thick over bedrock highs, and are generally no greater than 50 

feet thick in the southern and northeastern parts of the study area.

Ground water in the surficial aquifer is mostly unconfined but may 

be locally semiconfined or confined by layers of till. Ground water in

the carbonate-rock aquifer is confined where the aquifer is directly 

overlain by the upper confining unit along the margins of the structural basins; otherwise, ground water in the carbonate-rock aquifer is 

semiconfined by the surficial deposits. Ground-water flow in the aquifer system is primarily through secondary porosity, mainly through 

fractures within the upper 100 feet of the carbonate-rock aquifer.

Surface-water and ground-water data were used to characterize 

the components of the regional ground-water-flow system within the 

Midwestern Basins and Arches Region and to provide information to 

calibrate a regional ground-water-flow model of the system. The analysis of data from long-term streamflow records indicates that most base 

flow (50 to 97 percent among selected stream reaches) is from localized 

ground-water discharge to streams rather than from regional groundwater flow. Synoptically measured ground-water levels in July and 

August 1990 that represent long-term, steady-state conditions in the 

carbonate-rock aquifer show that the configuration of the potentiometric surface of the carbonate-rock aquifer generally mimics the topography within the area of principle hydrologic interest.

A two-layer, steady-state, numerical model representing the surficial and carbonate-rock aquifers was constructed to simulate regional 

ground-water flow within most of the area of principle hydrologic 

interest. The ground-water system was simulated to help interpret the 

rates and distribution of regional ground-water recharge and discharge. Modeling results indicate that virtually all recharge to the 

regional ground-water-flow system (99 percent) is from precipitation 

that enters the ground-water system at the water table and that about 

78 percent of the ground water simulated in the regional aquifer system discharges to major streams within the study area, whereas less 

than 3 percent discharges to the Ohio River, Lake Erie, or downdip into 

the Illinois Basin. Additionally, model simulations indicate that 

recharge and discharge areas generally alternate within 10 miles except 

in the northeastern part of the study area, a former swamp that 

remains a large regional discharge area. The longest flow paths (about 

50 miles long) are in the northeastern part of the study area, starting at 

a topographic high in central-western Ohio and terminating in Lake 

Erie.

Computer programs for tracking of ground-water-particles were 

used to indicate directions of regional ground-water flow. Particletracking results were used in conjunction with analyses of stable isotopes, carbon-14, and tritium concentrations of ground water from 

wells in the regional aquifer system to substantiate the concept of 

ground-water flow throughout tine regional aquifer system. Carbon-14 

data indicate that relatively old water (about 13,000 years old) is at the 

end of the longest flow paths (50 miles) near Lake Erie. In contrast,

Al
A2 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

older waters (about 38,000-45,000 years old) were associated with 

ground-water-flow paths only 10 miles long in the Maumee River 

Basin, an indication that recharge is restricted in this area, probably by 

surficial lacustrine deposits.

Patterns of ground-water chemistry were defined by use of available data and by collection of additional information along regional 

ground-water-flow paths determined from the potentiometric-surface 

map of the carbonate-rock aquifer. The chemistry of ground water from 

wells that tap the regional aquifer system was classified into several 

types based on the percentage of the major cations and anions and by 

the concentration of dissolved solids in the water. The Ca-Mg-HCOs 

and Ca-Mg-SO4 water types dominate the chemistry of ground water 

in the study area. The patterns of chemistry in water from wells within 

the carbonate-rock aquifers were compared and related to the 

geochemistry of the bedrock units within the Midwestern Basins and 

Arches Region. The chemistry of ground water throughout most of the 

study area is generally controlled by the dissolution of calcite and dolomite and produces Ca-Mg-HCO3 type waters except where the oxidation of pyrite is responsible for Ca-Mg-SO4 type waters.

The ground-water chemistry of the surficial aquifer is similar to 

that of the carbonate-rock aquifer within the study area. Dissolved-solids concentrations of ground water in the surficial aquifer range from 

about 100 to 2,600 milligrams per liter and those within the carbonaterock aquifer from about 100 to 3,800 milligrams per liter (although concentrations increase substantially as the carbonate-rocks dip into the 

structural basins).

Ground-water withdrawals within the study area were compiled 

from existing state water-use data reported by users capable of withdrawing more than 100,000 gallons per day. The ground-water-withdrawal estimates were used to determine the average amount of 

ground water that was potentially withdrawn in 1990 in the Indiana 

and Ohio parts of the study area; ground-water withdrawals were also 

categorized by the type of use. The reported monthly total groundwater withdrawal for parts of Indiana and Ohio within the study area 

for 1990 was 433 million gallons per day. Monthly totals of groundwater withdrawals indicate a seasonal trend of ground-water use. 

Almost three-fourths of reported ground-water use in 1990 was for 

public supply, similar to the proportion of public-supply use for the 

same area in 1980.

INTRODUCTION

As a result of a congressional mandate to develop 

quantitative appraisals of the nations most important 

regional aquifers (Sun, 1986), the U.S. Geological Survey (USGS) began the Regional Aquifer Systems Analysis (RASA) program in 1978. The objective of this 

program was the systematic study of the quantity and 

quality of the ground water in these regional aquifer 

systems.

In 1988, the RASA program began an analysis of the 

Midwestern Basins and Arches Region in part of the 

east-central portion of the United States (fig. 1). The 

surficial and carbonate-rock aquifers in this region are 

an economically significant supplement to surfacewater supply throughout the region and are economically and culturally important natural resources for this 

area. The regional aquifers supply water not only for 

human consumptive purposes, but also for agricultural, 

industrial, and recreational uses.

REGIONAL ANALYSIS OF THE MIDWESTERN BASINS 

AND ARCHES AQUIFER SYSTEM

OBJECTIVES AND APPROACH

The overall objective of the The Midwestern Basins 

and Arches RASA study was to develop an understanding of the hydrogeologic, hydraulic, and water-quality 

characteristics of the regional surficial and carbonaterock aquifers within their natural hydrogeologic boundaries. An additional objective was to create digital data 

bases of cartographic and spatially-registered information that could be used by regional planners and earth 

scientists to help manage the area's water resources. 

The study was designed primarily to make use of available data; however, additional data were collected 

where needed to supplement or clarify available information. The information was used to (1) describe the 

geometry (thickness, extent, and configuration of surfaces) of the surficial and carbonate-rock aquifers 

within the regional system, and types of deposits and 

rocks and their hydraulic properties; (2) determine the 

natural physical boundaries of the surficial and carbonate-rock aquifers; (3) describe regional ground-water 

flow and estimate regional recharge rates by the use of a 

finite-difference, three-dimensional, ground-water-flow 

model and base-flow analysis of unregulated streams 

within the region; (4) describe the quality of water in 

the surficial and carbonate-rock aquifers in terms of 

anion and cation facies and dissolved-solids trends and 

the relationship of the geochemistry to ground-water 

flow in the region; and (5) determine the current 

ground-water use.

PURPOSE AND SCOPE OF PROFESSIONAL PAPERS 1423 A, B, 

ANDC

Professional Paper 1423 describes the hydrogeologic 

framework, hydrology, and geochemistry of the Midwestern Basins and Arches Region. Because regional 

ground-water flow is considered to be in a state of 

dynamic equilibrium (steady state) and because there 

are no apparent regional stresses on this system, comparative analysis of predevelopment and postdevelopment periods was not done.

The Professional Paper 1423 series consists of three 

papers:

Professional Paper 1423-A (this report) summarizes 

the basic aspects of study-area geology, hydrology, water quality, and geochemistry that are 

reported in more detail in the other papers, 

Professional Paper 1423-B describes the hydrogeologic framework of the glacial and carbonaterock regional aquifer system (Casey, 1997).
INTRODUCTION A3

Professional Paper 1423-C discusses the hydrologic 

aspects of the glacial and carbonate-rock regional 

aquifer system, with emphasis on regional 

recharge and three-dimensional flow modeling; a 

separate section describes general water-quality 

trends and relates the isotopic composition of 

ground water to regional ground-water flow 

(Eberts and George, in press).

These and other reports prepared as part of the Midwestern Basins and Arches RASA project are indicated 

by an asterisk in the section "Selected References" of 

this report.

SUMMARY OF PREVIOUS WORK

Although ground water has become an increasingly 

important resource within the Midwestern Basins and 

Arches Region, comprehensive studies of the geology, 

hydrology, and water chemistry of the area are few. The 

bulk of the hydrologic literature for the region focuses 

on small areas, cities, or counties. One reason for the 

scarcity of regional information, especially with respect 

to the geohydrology, is that some bedrock units are discontinuous across the region from east to west (Shaver, 

1985). Nevertheless, several reports have addressed 

specific aspects of parts of the Midwestern Basins and 

Arches RASA area.

The bedrock geology of the Midwestern Basins and 

Arches Region has been described only for parts of the 

area; however, a project team led by Shaver (1985) compiled a stratigraphic correlation of the Midwest Arches 

area that includes the Midwestern Basins and Arches 

RASA project area. Droste and others (1975), Droste and 

Shaver (1983 and 1985), and Ault and others (1976) discussed the orientation and paleogeography of the carbonate reef banks that underlie much of the study area 

in Indiana and central-western Ohio. The stratigraphy 

of Ohio was originally compiled and produced as a geologic map by Bownocker (1920): this map was not comprehensively updated until 1990 (Hull) and 1991 

(Larsen).

Works by Norris and Fidler (1973) and Norris (1974), 

and by the Ohio Department of Natural Resources, 

Division of Water (1970) detailed the occurrence of 

water in the carbonate-rock aquifer in the western half 

of Ohio. The only other regional appraisal was a generalized report by Bloyd (1974), part of a USGS summary 

of the Nation's ground-water resources. Additionally, 

the Ohio Department of Natural Resources, Division of 

Water has issued a series of ground-water resources 

maps for many of the counties in Ohio at the scale of 

1:62,500.

The regional hydrology of Indiana has been 

addressed somewhat systematically by the basinwide 

studies of ground water within the Whitewater River 

and Kankakee River Basins (Indiana Department of 

Natural Resources, 1988 and 1990, respectively). A 

statewide reconnaissance of available hydrologic information was compiled in 1982 (Geosciences Research 

Associates Inc.), and a ground-water atlas of Indiana 

compiled by the USGS shows the relation between surficial and bedrock aquifers within the State (Fenelon and 

others, 1994).

Regional water-quality in Indiana and Ohio has 

been addressed in several reports . A statewide compilation of water-quality information within bedrock and 

glacial aquifers in Indiana was produced by Geosciences Research Associates Inc. (1982) in cooperation 

with the U.S. Environmental Protection Agency. Several 

regional reports on the dissolved-solids concentration 

of water from bedrock aquifers have been produced for 

Indiana (Keller, 1983; Rupp and Pennington, 1987) and 

Ohio (Stout and others, 1932; Stith,1979). Comprehensive water-quality studies have been conducted on 

smaller parts of the Midwestern Basins and Arches 

Region, primarily in Ohio (Ohio Department of Natural 

Resources, Division of Water, 1970; Norris and Fidler, 

1973; Norris, 1974; Breen and Dumouchelle, 1992). A 

state atlas of nitrate and pesticides in private wells in 

Ohio was compiled by Baker and others (1989).

ACKNOWLEDGMENTS

The author and staff of the Midwestern Basins and 

Arches RASA acknowledge the cooperation of state 

agencies in Ohio, Indiana, Michigan, and Illinois in providing geologic, hydrologic, and chemical data that 

enabled the completion of the project. The agencies 

include the Ohio, Indiana, Michigan, and Illinois 

Departments of Natural Resources, the Ohio Environmental Protection Agency, the Indiana Department of 

Environmental Conservation, and the Ohio and Indiana 

State Geological Surveys. Thomas Berg and Norman 

Hester, State Geologists of Ohio and Indiana, respectively, provided encouragement and access to many scientists on their respective staffs, who provided help in 

compiling and analyzing the geohydrologic framework 

of the surficial and carbonate-rock aquifers.

William Steen and Rebecca Petty of the Divisions of 

Water, Indiana and Ohio Departments of Natural 

Resources, respectively (and their staffs), and the staff at 

the Illinois Department of Natural Resources, Division 

of Water assisted in measuring more than 450 wells in 

July and August 1990 to produce a synoptic potentiometric-surface map of the carbonate-rock aquifer; in
A4 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

WISCONSIN -(piwaukee 

^1 £

Base from U.S. Geological Survey digital data, 0 20 40 60 MILES 

1:2,000,000,1972 | , h H '

0 20 40 60 KILOMETERS

EXPLANATION 

Data-collection area

 Boundary of study area

f^-""~~-J\^ Direction of dip into

* *" ^*^ structural basins

FIGURE 1. Location of the Midwestern Basins and Arches Region, area of data collection, study area, and structural arches and basins.

addition, these persons provided access to hydrologic 

information that was instrumental in the formulation of 

a regional numerical ground-water-flow model of the 

Midwestern Basins and Arches Region.

The staff of the Midwestern Basins and Arches 

RASA project are also grateful to landowners of Ohio, 

Indiana, Michigan and Illinois for allowing measurement and sampling of wells.

PHYSICAL SETTING

EXTENT OF STUDY AREA

The Midwestern Basins and Arches RASA study 

area encompasses a complex of three structural 

arches the Cincinnati, Findlay, and Kankakee Arches
HYDROGEOLOGY A5

in Ohio, Indiana, and parts of Michigan and Illinois and is surrounded by three structural basins the 

Michigan, Appalachian, and Illinois Basins (fig. 1). The 

area's location within an arch and basin complex dictates that the lateral boundaries of the regional carbonate-rock aquifer are not truncated by geologic strata as 

they would be in a single structural basin or in a continental shelf setting. Therefore, the boundary of the Midwestern Basins and Arches RASA study area is a 

combination of hydrogeologic, hydrologic, and chemical boundaries that enclose an area of approximately 

44,000 mi2 (fig. 1).

The boundary of the study area is coincident with 

either major surface-water bodies (large rivers or Lake 

Erie) or the contact between Devonian limestones and 

younger, overlying Devonian shales. An additional 

boundary defined for the study was the line between 

ground water with a dissolved-solids concentration less 

than 10,000 mg/L and water that is more saline within 

the carbonate-rock aquifer units that dip into each of the 

three structural basins; this boundary was delineated to 

aid in ground-water-flow modeling (see the section 

"Regional Ground-water Flow").

Additional data were collected beyond the study 

area to define (1) the geometry of the geologic units and 

(2) the physiochemical limit of the fresh ground water 

as the regional ground-water-flow system extends into 

the structural basins (fig. 1). This larger area represents 

the geographical extent for which information was 

obtained to determine the geometry and chemistry of 

the regional aquifer system in the Midwestern Basins 

and Arches Region. Most of the analyses discussed 

herein, however, were limited to the study area because 

that is the area of active, fresh ground-water flow in the 

regional system and because little hydrologic information is available for the carbonate-rock aquifer outside 

the study area.

PHYSIOGRAPHY

The study area is mostly within the Midwestern 

Basin and Arches Region defined by the American 

Association of Petroleum Geologists (Shaver, 1985). 

This area lies within the Central Lowlands Physiographic Province east of the Mississippi River (Fenneman, 1938). Erosion has reduced the low, broad 

bedrock arches to a fairly flat plain throughout most of 

the area, with the exception of: (1) the southern part of 

the region, which has been dissected by numerous 

streams, and (2) two topographically high areas, one in 

central-western Ohio and another along the Ohio-Indiana state line (fig. 2).

Land-surface altitude in the area ranges from more 

than 1,400 ft near the central-western Ohio to about 500 

ft near the Ohio River (USGS 1:500,000 state topographic maps) (fig. 2). Abroad lowland along the ancestral glacial Lake Maumee and Lake Whittlesey plains 

(Flint, 1971, fig. 26-b) is the former "Black Swamp", an 

area of peat-like soil that has been drained by numerous 

ditches since the late 1800's (Kaatz, 1952). About 24 mi 

of coastline along the southwestern part of Lake Erie is 

included in the study area (fig. 1).

CLIMATE

The Midwestern Basins and Arches Region has a 

humid, temperate climate and a weather pattern dominated by pressure cells emanating either from the Gulf 

of Mexico (bringing warm, moisture-laden air northward up the Mississippi and Ohio River Valleys) or 

from the Canadian interior (bringing cooler, drier air).

The source of freshwater in the Midwestern Basins 

and Arches Region is precipitation, primarily as rain 

and snow, and secondarily as hail and dew. The mean 

annual precipitation, computed from National Oceanographic and Atmospheric Administration (NOAA) 

records of meteorological stations with at least 50 years 

of data, ranges from 33 to 43 in (fig. 3). Precipitation patterns are probably influenced by evaporation from lakes 

Erie and Michigan, and (or) flow of moist air northeastward through the Ohio River Valley.

Parts of three major river systems drain the study 

area: the Ohio River drainage (Wabash River, White 

River, East Fork White River, Great Miami River, Little 

Miami River, and Scioto River), the St. Lawrence River 

drainage (Maumee River, Sandusky River, River Rasin, 

and Huron River), and the Upper Mississippi River 

drainage (fig. 4). Additionally, a divide within the study 

area separates water draining to the Atlantic Ocean 

through the Great Lakes and the St. Lawrence Seaway 

from water draining to the Gulf of Mexico through the 

Ohio and Mississippi Rivers (fig. 4).

HYDROGEOLOGY

GEOLOGIC SETTING

The geology of the Midwestern Basin and Arches 

region is composed of sedimentary rocks that underlie 

the area and range in age from Cambrian through Permian. However, only Late Ordovician through Pennsylvanian rocks crop out within the study area (fig. 5). The 

units dip away from the crests of the arches toward the 

three structural basins, thickening differently within
A6 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

60 MILES

0 20 40 60 KILOMETERS

EXPLANATION

Topographic contours from U.S. Geological Survey 1:500,000 

topographic maps of Ohio, Indiana, Michigan, and Illinois

m/fl^m Generalized altitude of land surface Contour interval

'soo is 200 feet. Datum is sea level

 Boundary of study area

FIGURE 2. Generalized topography of the Midwestern Basins and Arches Region.

each basin depending upon the structural and depositional history of that basin (figs. 5 and 6). The degree of 

dip ranges from less than 1° on the flanks of the Arches 

to greater than 5° toward the center of the structural 

basins (G.D. Casey, U. S. Geological Survey, written 

commun, 1994). Depositional environments within the 

structural basins, where restriction of inter- and intrabasin circulation differed, produced various accumulations of sediments within each basin. The different pattern of circulation within the basins, caused by 

restrictions in inflow into these basins, also affected the 

type of sediments deposited, especially the types and 

amounts of evaporites. Most of the tectonic events that 

led to the formation of the arches and basins within the 

region occurred from at least Early Ordovician through 

Permian time and include the Taconic, Acadian, 

Alleghey, and Ouachita orogenies (Beaumont and others. 1988).
HYDROGEOLOGY A7

88°

40° -

Base from U.S. Geological Survey digital data, 

1:2,000.000.1972

0 20 40 60 KILOMETERS

EXPLANATION

Equal mean annual precipitation, in inches 

Interval is 1 inch. Data from meteorological stations 

with greater than 50 years of record

Boundary of study area

FIGURE 3. Mean annual precipitation in the area of principal hydrologic interest, Midwestern Basins and Arches Region.

BEDROCK UNITS

ORDOVICIAN ROCKS

The basal confining unit of the carbonate-rock aquifer consists of Upper Ordovician units that unconformably overlie the Trenton Limestone in Indiana and

northwestern and central Ohio (Gray, 1972; Janssens, 

1977; Droste and Shaver, 1985), and are overlain unconformably by the Sexton Creek Limestone or Brassfield 

Limestone and Cataract Formation of Silurian age 

(LaFerriere and others, 1986) (fig. 7). The rocks that 

comprise the basal confining unit are the Maquoketa
A8 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000.1972 i I 

0 20 40 60 KILOMETERS

Basin boundaries from The National Atlas of the United States, 

Hydrologic Units map, 1:3,500,000,1998

EXPLANATION 

Regional drainage basins

I St. Lawrence River-Great Lakes

Upper Mississippi River 

I Ohio River

Major surface-water divide Separates surface water that flows northward 

toward the Atlantic Ocean from surface water that flows southward toward 

the Gulf of Mexico

Regional drainage-basin divide 

Subregional drainage-basin divide 

Other drainage basin divides 

Boundary of study area

FIGURE 4. Major drainage basins in the Midwestern Basins and Arches Region.
HYDROGEOLOGY A9

38°

Base from U.S. Geological Survey digital data. 

1:2,000,000,1972

0 20 40 60 MILES Geology modified from Bownocker, 1920; Willman and others, 1967;

I___ I ___ I______| Burger and others, 1971; Gray, 1972b; Gray and others, 1972; Gray

1 ' ' ' and others, 1979; Gray and others, 1987; Milstein, 1987

0 20 40 60 KILOMETERS

EXPLANATION 

Geologic time units Contact

I Pennsylvanian

Mississippian 

, Devonian 

^^1 Silurian 

[ j Ordovician

-Z~~ Bowling Green Fault Zone 

From Van Wagner, 1988

T i r Fault Locations from various sources. 

Hachures on downthrown side

FIGURE 5. Generalized bedrock geology and locations of major faults in the Midwestern Basins and Arches Region.
A10 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

VERTICAL SCALE GREATLY EXAGGERATED

e

VERTICAL SCALE GREATLY EXAGGERATED

FEET 

1,200

VERTICAL SCALE GREATLY EXAGGERATED

60 MILES

20 40 60 KILOMETERS

LOCATION OF HYDROGEOLOGIC SECTIONS

88° 86° 84° 82°

EXPLANATION 

[ | Glacial deposits 

^^J Upper confining unit 

| j Carbonate-rock aquifer 

^^1 Basal confining unit

n Undifferentiated older rock (not 

included in this investigation)

Contact

A'.

60 MILES 

' 

60 KILOMETERS

Trace of hydrogeologic section

FIGURE 6. Generalized hydrogeologic sections A-A, B-B', and C-C1 ; Midwestern Basins and Arches Region (modified from Casey, 1997).
HYDROGEOLOGY All

GENERALIZED GEOLOGIC UNITS

SYSTEM

QUATERNARY

<

D_ 

D_

MISSISS

DEVONIAN

SILURIAN

\^ ORDOVICIAN

SERIES

PLEISTOCENE

LOWER

UPPER

MIDDLE

LOWER

CAYUGAN

NIAGARAN

ALEXANDRIAN

CINCINNATIAN

Mil ^'" ^

Southeastern 

Indiana

Glacial 

deposits

Borden 

Group

Rockfncd 1 imfiStPnP\ai

New Albany 

Shale

V - -,__--

Muscatatuck 

Group

, ~~ ~ Salina1 

: Group

 Salamonie1 

Dolomite^xBrassfield \ 

Limestone_N,

^-^^

Maquoketa1 

Group ^^_

^minton £

 <*0»»J g

^*«c^U

Northwestern 

to east-central 

Indiana

Glacial 

deposits

Bordorft 

Group ]

Rockford U.

NU6W -Ei^

Albany Shale 

Shale ' 

Antrim 

Shale

Muscatatuck 

Group

Salina1 

Group

Salamonie1 

Dolomite

i

*- c

 ° °

Sexfon^^. 2 to 

Creek Ls?^ g g 

Brassfield " £ 

Limestone

/

Maquoketa1 

Group

Trent^r^* 

W~'^ Limestone

Northern 

Indiana

Glacial 

deposits

Coldwater Shali"" ~ 

SunburySh.

Ellsworth Shale

Antrim Shale

./

Traverse ^ 

Formation o

CD^.

Detroit ^ 

River g 

Formation %

^

Salina1 

Group

Salamonie1 

Dolomite

*- c 

 t3 o

co ' >-- 

SE

Brassfield o £ 

Limestone

Maquoketa1 

Group

^* Trenton 

I imestone *^^>» ~>^^_

Northwestern 

Ohio and 

southeastern 

Michigan

Glacial 

deposits

Bedford Shale

Antrim 

Shale

Traverse 

Formation

BmvJeeTlT[Deiawarel^ 

Columbus Limestone

Detroit River 

Formation

Salina

Group

Lockport 

Dolomite

Rochester Shale equrv.

 ~ _N_^Da^tonL».

Brassfield Cataract 

Limestone Formation

Trenton 

Limestone

Central and 

western 

Ohio

Glacial 

deposits

Ohio 

Shale

Olentangy Shale

Delaware 

Limestone

Columbus 

Limestone

Detroit River 

Group

Salina 

Group

Guelph 

t 2 Dolomite2

£-§ Goat Island 

8 o Dolomite2

-1 "-1 Gasport 

Dolomite2

Rochester Shale equrv.

 ->_^^Da£onLs

Brassfield Cataract 

Limestone Formation

Trenton 

Limt; stone

Southwestern 

Ohio

Glacial 

deposits

Bedford Shale

Ohio 

Shale

Olentangy Shafe

Hillsboro Sandstone

Salina Group

Lockport 

Dolomite

Rochester Shale equiv.

Dayton Limestone

Brassfield Limestone

Trentor 

Limestone

GENERALIZED 

GEOHYDROLOGIC 

UNITS

Glacial aquifers 

and 

confining unit

Upper 

confining 

unit

Carbonate 

rock 

aquifer

Basal 

confining 

unit

 

MODEL 

LAYERS

Layer 1

Layer 2

/^^

LURIAN DEVONIAN CARBONATE-ROCK AQUIFER SYSTEM AND 

CO

V

1 Follows usage of the Indiana Geological Survey (Gray and others, 1985} 

2 Follows usage of th Ohio Geological Suvery (Hull, 1990; Larsen, 1991)

^_ Non-deposition or erosion

EXPLANATION 

Intervals not included in investigation

Modified from Casey, 1997

Unconformity

FIGURE 7. Time- and rock-stratigraphic framework, nomenclature, and model layers for the Midwestern Basins and Arches Region.
A12 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

Group (Indiana usage) and undifferentiated Cincinnatian rocks (Ohio usage) and are similar time-stratigraphic rocks. The rocks that comprise the basal 

confining unit generally are composed of grey calcareous shale with alternating limestone layers in the upper 

20 percent of the unit (Gray, 1972).

The thickness of the Ordovician rocks that comprise 

the basal confining unit (Maquoketa Group and undifferentiated Cincinnatian rocks) ranges from 200 ft in

northwestern Indiana to about 1,000 ft 25 mi east of the 

Ohio-Indiana border, gradually thickening to more than 

1,200 ft as they dip into the Appalachian Basin and to 

more than 600 ft as they dip into the Michigan Basin 

(fig. 8). In southeastern Indiana and southwestern Ohio 

the basal confining unit thins to less than 700 ft near the 

updip limit of rock of Silurian age and to less than 100 ft 

near the Ohio River (Casey, 1997) (fig. 8).

40°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0

I 

0 20 40 60 KILOMETERS

Modified from Casey 1997

EXPLANATION

. 200 Thickness of the basal confining unit 

'. BOO II Lines of equal thickness dashed where

- soo inferred. Interval 200 feet. Darker colors

-;'200-I indicate greater thickness

Subcrop of Ordovician rocks beneath surfical deposits 

Boundary of study area

FIGURE 8 Thickness of the basal confining unit of the carbonate-rock aquifer, Midwestern Basins and Arches Region.
HYDROGEOLOGY A13

SILURIAN AND LOWER AND MIDDLE DEVONIAN ROCKS

The Carbonate-rock aquifer throughout the study 

area is composed of Silurian and Devonian bedrock 

units (fig. 7). The physical characteristics of these rocks 

are principally a result of tectonic forces that resulted in 

basin subsidence and arch formation in the Midwestern 

Basins and Arches Region. The depositional environments within each of the structural basins and near the 

arches affected the accumulation of carbonate sediment 

and resulted in different types of these deposits, for 

example, reef-bank and reef flank deposits that differ 

somewhat from the pelagic, carbonate deposits elsewhere within the study area. Beds of gypsum and 

other evaporitic deposits are present locally in northwestern Ohio; otherwise, the majority of the rocks that 

compose the carbonate-rock aquifer are either limestone 

or dolomite with widely-scattered, discontinuous 

evaporitic deposits.

The Silurian rocks that overlie the Ordovician rocks 

are composed of sediment that was deposited during 

Alexandrian, Niagaran and Cayugan time (fig. 7). The 

Cataract Formation directly overlies the basal confining 

unit in northwestern Indiana and eastward to centralwestern Ohio. In parts of western and northern Indiana, 

the Ordovician rocks are overlain by the Sexton Creek 

Limestone, and in southeastern Indiana and southwestern Ohio by the Brassfield Limestone. These rocks, in 

turn, are unconformably overlain by the Salamonie 

Dolomite in Indiana and the Dayton Limestone in Ohio 

(fig. 7). During late Niagaran and early Cayugan time 

the rocks representing the Salina Group were deposited 

in Indiana, and from mid Niagran to early Cayugan 

time the rocks representing the Lockport Group and 

Salina Group were deposited in Ohio. The Rochester 

Shale Equivalent is interbedded between the underlying Brassfield Limestone, Cataract Formation, and the 

Dayton Limestone and the overlying Lockport Group in 

Ohio. The Silurian carbonate rocks are composed of 

dolomite, argillaceous dolomite, and limestone, whereas the relatively thin Rochester Shale Equivalent is composed of interbedded shale, limestone, and dolomite.

The Devonian rocks that make up the upper portion 

of the carbonate-rock aquifer were deposited during the 

later part of Lower Devonian, and during Middle Devonian time (fig. 7). These rocks are somewhat thinner 

than the Silurian-aged rocks due to uplift and subsequent erosion, especially along the crests of the arches 

in the study area. The Silurian and Devonian rocks are 

separated by a major unconformity during late Silurian 

(Cayugan) and Lower Devonian time. The rocks of Middle Devonian age are composed of the Detroit River 

Formation or Detroit River Group in northern Indiana, 

northwestern, and central-western Ohio, and are overlain by the Delaware Limestone and Columbus Limestone in northwestern and central-western Ohio, 

respectively. In most of northern Indiana the Middle 

Devonian rocks are overlain by the Traverse Formation, 

but in northwestern, east-central, and southeastern and 

part of northern Indiana, the entire Middle Devonian 

carbonate sequence is classified as the Muscatatuck 

Group (Shaver, 1974).

The rock units of Silurian and Devonian age that 

make up the carbonate-rock aquifer in the Midwestern 

Basins and Arches Region are offset by several faults 

within the study area (figs. 5 and 6). The Royal Center, 

Fortville, and Mount Carmel Faults cut the carbonaterock units of Silurian and Devonian age in Indiana 

along the northeastern and eastern edge of the Illinois 

Basin, and represent movement during Mississippian 

and Pennsylvanian time (Melhorn and Smith, 1959; 

Shaver and Austin, 1972). The faults are normal and 

have maximum displacements of less than 200 ft. In 

Ohio, the Bowling Green Fault Zone is composed of 

multiple faults that have been mapped within this zone 

(VanWagner, 1988). Movement along this zone is uncertain, occurring either during early Paleozoic time or as 

recently as Cenozoic time (Onasch and Kahle, 1991) and 

vertical displacement along these faults ranges from 90 

-300 ft (VanWagner, 1988). Nowhere in the Midwestern 

Basins and Arches Region do these faults juxtapose a 

confining unit alongside the carbonate-rock aquifer, 

therefore there is no regional disruption of groundwater flow by these faults.

The thickness of the rocks of Silurian and Devonian 

age that make up the carbonate-rock aquifer range from 

0 ft in the south-central part of the study area, at the 

contact with the rocks of Ordovician age in southeast 

Indiana and southwest Ohio, to more than 2,500 ft in 

southeastern Michigan as the units dip northwestward 

into the Michigan Basin. Generally the carbonate-rock 

aquifer thins where it crops out along the crests of the 

Arches and thickens downdip into the Appalachian, 

Michigan and Illinois Basins. The rate and degree of 

thickening however, differs within each basin (fig. 9). 

The units that make up the carbonate-rock aquifer also 

are absent where the buried ancient Teays-Mahomet 

River System completely dissects these units and is 

incised into the basal confining unit of Ordovician age 

within the study area. The greatest thickness of the carbonate-rock aquifer within the Midwestern Basins and 

Arches Region is along the east and west flanks of the 

Findlay Arch (figs. 1 and 9).

MIDDLE AND UPPER DEVONIAN AND MISSISSIPPIAN ROCKS

The rocks that overlie and confine the carbonaterock aquifer consist of shales of late Middle and Upper
A14 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

38'

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modifiedfcom Casey, 1997

20 40 60 KILOMETERS

EXPLANATION

Thickness of the carbonate-rock 

aquifer Lines of equal thickness 

dashed where inferred. Interval 200 

feet. Darker colors indicate greater 

thickness

Approximate limit of dissolved-solids concentration greater 

than 10,000 milligrams per liter Dashed where inferred. 

Pattern along limit indicates side with higher concentration

Subcrop of Ordovician rocks beneath surficial deposits 

Boundary of study area

FIGURE 9. Thickness of the carbonate-rock aquifer and approximate limit of ground water with dissolved-solids concentration greater 

than 10,000 milligrams per liter in the Midwestern Basins and Arches Region.

Devonian age, and shales and siltstones of Lower Mississippian age. It is important to understand, however, 

that these rocks have been eroded over most of the 

study area (figs. 6 and 10), and that they confine only a 

small part of the carbonate-rock aquifer around the 

flanks of the Arches, where the carbonate-rock-aquifer

units dip into each structural basin (fig. 10). The tectonic 

forces that caused the depositional environments during late Middle Devonian, Upper Devonian, and Lower 

Mississippian time were a result of the continued collision between the North American craton and the Avalon terrane, known as the Acadian orogeny (Ettensohn,
HYDROGEOLOGY A15

40° -

Base from U.S. Geological Survey digital data. 

1:2,000,000,1972

Modified from Casey. 1997

20 40 60 KILOMETERS

- 7,200^

EXPLANATION

-7,000 

 soo Altitude of the top of the upper confining

H w -- unit Contour interval 200 feet. Dashed

 200 where inferred. Datum is sea level. Darker

SEA LEVEL 0 . ,. . . . .. ,

greens indicate greater elevation above sea

level; darker blues indicate greater depth

 200 

 wo 

 soo below sea level 7,000 

 7,200 

 7,400 

Subcrop of Ordovician rocks beneath surficial deposits 

Boundary of study area

FIGURE 10. Altitude of the top of the upper confining unit of the carbonate-rock aquifer in the Midwestern Basins and Arches Region.

1985). In northern Indiana, these rocks consist of the 

Antrim, Ellsworth, Sunbury, and Coldwater Shales. 

South of the Kankakee Arch, in southeastern Indiana, 

the New Albany Shale is equivalent to the Antrim, 

Ellsworth, and Sunbury Shales. In Ohio, the rocks

which comprise the upper confining unit south of the 

Findlay Arch are the Olentangy, Ohio, and Bedford 

Shales; north of the Findlay Arch the upper confining 

unit is grouped into the Antrim Shale and the Bedford 

Shale.
A16 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

The rock units of Devonian age that make up the 

upper confining unit of the carbonate-rock aquifer (fig. 

7) are generally composed of clay-rich shale, in some 

areas fissile, and occasionally interlayered with argillaceous material, thin sheets of micaceous sandstone, and 

pyrite (Hoover, 1960). Natural gas is produced in moderate quantities from units such as the Ohio Shale and 

its equivalent (Janssens and de Witt, 1976). The Mississippian units are generally silty shales or argillaceous 

siltstones and shales with some fine grained sandstones 

and interbedded, discontinuous limestone lenses 

(Shaver and others, 1986).

The thickness of the upper confining unit of the carbonate-rock aquifer system ranges from 0 ft along the 

crests of the Kankakee, Findlay and Cincinnati Arches 

where the upper confining unit has been subjected to 

several extensive periods of erosion, to more than 1,000 

ft on the western flank of the Appalachian Basin and the 

southern flank of the Michigan Basin. In general, the 

thickness of the upper confining unit increases from the 

contact between the Devonian carbonates and the 

updip edge of the Devonian shales and thickens downdip toward the three structural basins. The upper confining unit is cut by only one major fault, the Mount 

Carmel Fault, in Indiana. Vertical displacement along 

this fault is generally thought to be less than 200 feet; 

therefore, the confining unit does not appear to be 

breached along the Mount Carmel Fault. Additionally, 

there is no evidence that there is any perturbation of 

ground-water-flow patterns in the carbonate-rock aquifer associated with this fault.

SURFICIAL DEPOSITS

The surficial deposits of the Midwestern Basins and 

Arches Region include the glacial deposits that cover 

most of the study area and alluvium that is concentrated along stream valleys. More than 95 percent of the 

area is covered by Pleistocene glacial deposits, except in 

the southeastern part of the study area (southcentral 

Ohio) (fig. 11). The deposits generally consist of end 

moraine and ground moraines (till), outwash sediments, and lacustrine deposits, and represent three 

major stages of Wisconsinan age glaciation: Early, Middle, and Late Wisconsinan. Advances by the Late Wisconsinan Laurentide ice sheet removed surficial 

evidence of earlier glaciations in most places except 

south of the Wisconsinan glacial limit (fig. 11) (Fullerton, 1986). The resulting landscape and internal structure of the glacial deposits is a mixture of 

unconsolidated deposits from multiple glacial advances 

and retreats.

The direction of ice flow, determined from erosional 

and depositional features, indicates that ice advances

during the Late Wisconsinan time crossed the Lake Erie 

Basin and the interstadial lakes accounting for much of 

the clay component in the tills (Flint, 1971 and Whillans, 

1985). Because much of the ice overrode the Lake Erie 

Basin, the mineral composition of tills within the study 

area mostly is representative of the local bedrock underlying the basin (Strobel and Faure, 1987); generally 

being clay-rich because of the types of rocks (limestone, 

dolomite, and shale) and their low resistance to glacial 

erosion.

The thickness of glacial deposits varies throughout 

the Midwestern Basins and Aches region, ranging from 

0 ft where the deposits are absent in parts of southwest 

Ohio and southeast Indiana to more than 400 ft in outwash areas in west-central and northwest Indiana and 

within the buried Teays-Mahomet valleys (fig. 12) (Soller, 1986 and Bleuer, 1991). A prominent area of thin 

deposits, generally less than 50 ft thick, which is coincident with the Glacial Lake Maumee plain, is present in 

the northeastern part of the study area (fig. 12).

A system of pre-Pleistocene, buried-river valleys 

extends throughout the study area. The most prominent 

of these is the Teays-Mahomet system (Goldthwait, 

1991; Bleuer, 1991; Gray, 1991)(fig. 11). These buried valleys are filled with deposits ranging from lacustrine 

clays to sands and gravels depending on their location 

and local depositional history. Generally, though, the 

main stem of the Teays-Mahomet buried valley is filled 

with finer-grained deposits from southcentral Ohio to 

near the Ohio-Indiana border, where the fill generally 

changes to coarser sand and gravel-type deposits (Bingham and others, 1991; Bleuer, 1991).

HYDROGEOLOGIC UNITS 

SURFICIAL AQUIFER

The surficial aquifer typically glacial outwash or 

thin, discontinuous lenses of permeable material within 

till is generally composed of sands and gravels. The 

surficial aquifer also includes alluvium of Holocene age 

that lies along streams and their flood plains. The 

deposits are mostly unconfined (for example, where 

outwash sediments are present along the major rivers in 

the study area) but locally may be semiconfined or confined by layers of till. Transmissivities of these deposits 

generally range from 300 to 69,700 ftVd (Joseph and 

Eberts, 1994). In some parts of the study area, especially 

in northwestern and central-western Ohio, the vertical 

flow of water is greater than would be expected because 

the fractures in the tills allows flow to depths as great as 

30 ft (Strobel, 1993). In these areas the vertical hydraulic 

conductivity can be more than 1 ft/d (Strobel, 1993); 

however, average vertical hydraulic conductivities gen-
HYDROGEOLOGY A17

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES

I ' 

0 20 40 60 KILOMETERS

EXPLANATION

Geology from Bennison, 1978

^" » Buried Teays-Mahomet valley system Main stem 

and principal tributaries

 Southern extent of glaciation

 Southern extent of Wisconsin glaciation

 Boundary of study area

Glacial deposits

Ground moraine 

End moraine

|| Lacustrine deposits 

Outwash deposits

III Undifferentiated glacial deposits 

(thin or absent)

FIGURE 11. Glacial deposits, extent of glaciation, and approximate location of the main stem and principal tributaries of the buried 

Teays-Mahomet valley system in the Midwestern Basins and Arches Region.

erally range from 0.0001 to 0.77 ft/d in till (Joseph and 

Eberts, 1994).

In areas where ground water is unconfined, the 

water table generally is within the surficial aquifer and 

the water-table configuration closely mimics topography throughout the study area. The depth to the water 

table generally increases in topographically high areas 

and decreases in regionally low areas, such as stream 

valleys and near Lake Erie. A detailed discussion of the 

relation between land-surface altitude and water-table
A18 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Casey, 1997

0 20 40 60 KILOMETERS

EXPLANATION

Thickness of glacial deposits

Less than 100 feet 

H 100 to 200 feet 

H 201 to 400 feet 

H Greater than 400 feet

 Southern extent of glaciation

 Boundary of study area 

FIGURE 12. Generalized thickness of glacial deposits in the Midwestern Basins and Arches Region.
REGIONAL GROUND-WATER FLOW A19

altitude in the surficial aquifer (with reference to longterm steady-state conditions) can be found in Eberts (in 

press). Most fluctuations of the ground-water levels 

within these deposits are seasonal and generally are less 

than 10 ft (Clark, 1980; Shindel and others, 1991a, 

1991b).

The potential yield of wells producing water from 

the surficial aquifer varies over small distances because 

of differences in the composition, continuity, and structure of the deposits (Strobel, 1993). Specific capacity of 

wells tapping the surficial aquifer within the study area 

ranges from 0.01 to 420 gal/min/ft. Yields of wells generally range from 0.5 to 7,700 gal/min.

CARBONATE-ROCK AQUIFER

The carbonate-rock aquifer is composed primarily of 

limestone and dolomite of Middle Devonian to Alexandrian age; thin shale units are present in places (fig. 7). 

Most of the regional carbonate-rock aquifer is semiconfined by the surficial aquifer mostly by till within 

the study area, primarily along the structural arches; a 

small part of the carbonate-rock aquifer is confined outside of the study area by Upper Devonian and Lower 

Mississippian shale (figs. 5, 6 and 7). The carbonaterock aquifer is confined below by shale and shaley limestone of Cincinnatian age (fig. 7).

Water in the underlying carbonate-rock aquifer 

occurs primarily in fractures, bedding joints, and other 

openings as secondary permeability within the rock. 

Arihood (1994) reported that most of the active flow 

within fractures is within the upper 50 ft in three wells 

tested in northwest Indiana. Similarly, data from the 

USGS's Ground Water Site Inventory (GWSI) data base 

indicates that 86 percent of more than 1,100 wells within 

the study area in the carbonate-rock aquifer were 

drilled to less than 100 ft into bedrock; thus most of the 

secondary permeability is within at least the upper 100 

ft of the carbonate-rock aquifer. The carbonate-rock 

aquifer ranges in thickness from 0 ft to more than 2,300 

ft within the study area, and it thickens from the crest of 

the arches into the adjacent structural basins within the 

region (Norris and Fidler, 1973; Rupp, 1991; Casey, 

1997) (fig 8).

The limit of freshwater within the carbonate aquifer, 

considered for this study to be less than 10,000 mg/L 

dissolved solids (U.S. Environmental Protection 

Agency, 1984), has been found in carbonate bedrock of 

Silurian and Devonian age as far as 70 mi west of the 

study area within the Illinois Basin (Rupp and Pennington, 1987; D. Schnoebelen, U.S. Geological survey, written commun., 1992). The limits of freshwater also occur 

within areas 5 mi north of the northern limit of the 

study area in the Michigan Basin (D. J. Schnoebelen,

written commun., 1992) and within several miles of the 

eastern boundary of the study area on the margin of the 

Appalachian Basin (fig. 9).

Some units, or zones, within the carbonate-rock 

aquifer are more productive than others. The Newburg 

Zone (Strobel and Bugliosi, 1991) is one such example. 

Most of the carbonate-rock aquifer, however, functions 

as a single hydrologic unit at the scale of the Midwestern Basins and Arches Region. In a regional discharge 

area in northwestern Indiana, for example, vertical 

hydraulic gradients were less than 3 ft in three, 600-ftdeep wells that penetrate the entire thickness of the carbonate-rock aquifer (Arihood, 1994).

Few wells tap the carbonate-rock aquifer where it 

dips beneath the Devonian shales because shallower 

freshwater sources are available. Within the study area, 

the potential yield from wells drilled into the carbonaterock aquifer differs areally and is related to the degree 

of secondary permeability. The specific capacity of wells 

within the carbonate-rock aquifer ranges from 0.1 to 90 

gal/min/ft; yields range from 0 to about 1, 000 gal/ 

min.

REGIONAL GROUND-WATER FLOW

Ground-water flow in the Midwestern Basins and 

Arches Region is affected by topography and by the 

hydraulic characteristics of the surficial and carbonaterock aquifers and confining units that compose the 

regional aquifer system. Water flows from areas of 

recharge to areas of discharge, but at local, intermediate, and regional scales (Toth,1963) (fig. 13). This study 

focused primarily on ground water that flows at least 

several miles before discharging to streams, lakes, or 

wells that are drilled into the surficial deposits and, 

especially, the carbonate-rock aquifer. The limited focus 

was a consequence necessitated by the large area of 

study and the subsequent coarse discretization (4 by 4 

mi) of the numerical model used for analysis of the 

regional ground-water-flow system. Local flow to small 

perennial streams could not be simulated because of the 

coarse discretization necessary for the model.

Throughout most of the study area, the carbonaterock aquifer is considered to be in a state of quasi-equilibrium (steady-state condition). No component of storage at a regional scale was considered. However, in 

northwestern Indiana an area of intensive agricultural 

development intensive pumping from the carbonaterock aquifer during periods of irrigation has stressed 

the ground-water system. Seasonal, subregional transient conditions in which the potentiometric surface in 

the carbonate-rock aquifer declines below the top of the 

aquifer, creates locally unconfined conditions and
A20 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

Area of greater relief 

-dominated by local ground-water flow

Area of lesser relief 

dominated by regional ground-water flow

Lake Erie

-100

Modified from Hanover, 1994

- 1,300

- 1,200

- 1,100

- 1,000

-900

- 800

- 700

- 600

- 500

- 400

- 300

- 200

- 100

- SEA LEVEL 

-100

10 20 KILOMETERS

EXPLANATION

Surficial deposits (unsaturated) 

Surficial aquifer 

Carbonate-rock aquifer 

Undifferentiated older rock 

Contact

General direction of ground-water flow

Local flow 

Intermediate flow 

* Regional flow

FIGURE 13 Conceptual hydrogeologic section showing the relation between local, intermediate, and regional flow in the 

Midwestern Basins and Arches Region (trace of section shown in figure 17).

ground water is pumped from storage in the aquifer 

(Arihood, 1994). Because the transient conditions occur 

in only a small part of the regional aquifer system and 

are seasonal, no additional investigations of transient 

conditions in this area of the carbonate-rock aquifer 

were made.

HYDROGEOLOGIC BOUNDARIES

The boundaries of regional ground-water flow in the 

Midwestern Basin and Arches Region are defined physically by the hydrogeologic framework and geochemically by the 10,000-mg/L dissolved solids limit within 

the carbonate-rock aquifer (fig. 9). The 10,000-mg/L dissolved solids limit was selected to represent the lateral 

extent of the regional ground-water-flow system 

because (1) 10,000 mg/L is the minimum recommended

secondary standard for consumptive use (U. S. Environmental Protection Agency, 1984), (2) the multiple-density ground-water-flow simulations necessary for 

waters with dissolved-solids concentrations greater 

than 10,000 mg/L were beyond the scope of this study, 

and (3) hydrogeologic information available for the 

area beyond this boundary is sparse. The carbonaterock aquifer is confined above by either the surficial 

deposits throughout most of the study area or by shales 

of Devonian and Mississippian age on the flanks of the 

structural arches, where the rock units of Silurian and 

Devonian age dip into the structural basins. The aquifer 

is confined below by shales and shaley limestones of 

Ordovician age. The water table is the uppermost 

boundary of regional ground-water flow.

Discharge boundaries for regional ground-water 

flow include Lake Erie and most of the major streams
REGIONAL GROUND-WATER FLOW A21

within the area. The Kankakee and Iroquois Rivers in 

northwestern Indiana and east-central Illinois function 

as a regional ground-water discharge area that separates the flow system in the carbonate-rock aquifer in 

northwest Indiana from a regional flow system further 

northward in Illinois and Wisconsin (figs. 5, 6, and 10) 

(Young, 1992; Mandle and Kontis, 1992). The Scioto 

River is a major discharge boundary for the carbonaterock aquifer along much of the eastern part of the study 

area in central Ohio. Additionally, former swamps, such 

as those in northwestern Ohio that are extensively 

drained by tile and ditches, function as regional discharge areas (Kaatz, 1952). The Ohio River is a major 

hydrologic boundary within the area, but only a small 

portion of the carbonate-rock aquifer extends to this 

boundary (fig. 5).

Internal boundaries include the ancestral TeaysMahomet River system where it is filled with glacial 

deposits of varied permeabilities that contrast with the 

permeability of the surrounding carbonate-rock aquifer, 

especially where the valleys incise the entire carbonaterock aquifer (figs. 5, 6, and 10); however, these valleys 

function primarily as local discharge boundaries 

throughout most of the region (Sheets and Yost, 1994), 

especially where they are filled with highly permeable 

sand and gravel; as in the central and western part of 

the study area (Bleuer, 1991) (fig. 11). In contrast, part of 

the buried Teays Valley in southwestern Ohio is filled 

with fine-grained deposits and it is relatively impermeable (Sheets and Yost, 1994). These valleys appear to 

have no effect on the direction of ground-water flow at 

a regional scale, (Eberts, in press) and they were not 

considered explicitly as internal boundaries in the 

regional ground-water-flow model constructed for this 

study.

POTENTIOMETRIC SURFACES

Ground-water levels within the Midwestern Basins 

and Arches Region, not only in the surficial aquifer, but 

also in the carbonate-rock aquifer generally mimic the 

topography of the area. Where ground water is unconfined, the water table is within the surficial aquifer 

except in areas where the surficial deposits are thin or 

absent, in which case the water table is within the carbonate-rock aquifer. Depth to water generally increases 

with increasing land-surface altitude (as, for example, 

near the highest point in the study area in central-western Ohio) and decreases with decreasing altitudes (as, 

for example, near Lake Erie or the Ohio or Kankakee 

Rivers) (Hanover, 1994; Eberts, in press).

A regional water-level map (fig. 14) representing the 

aggregate water levels from wells drilled in surficial

deposits in the Midwestern Basins and Arches Region 

shows the same general configuration as the topography (fig. 2). Configuration of the potentiometric surface 

of the carbonate-rock aquifer (fig. 15) is similar to that of 

the water-level surface in the surficial aquifer. Two predominant potentiometric high areas in the carbonaterock aquifer are in central-western Ohio and near the 

southern limit of the aquifer along the border between 

Indiana and Ohio (fig. 15). Potentiometric low areas, 600 

ft or less, are along the major regional drains to the 

aquifer system (the Wabash and the Ohio Rivers and 

Lake Erie). Potentiometric contours within the region 

characteristically wrap around the major rivers, pointing upstream, indicating that ground-water discharges 

to most of the major rivers. The potentiometric surface 

flattens around the area of the Maumee River Basin, in 

the north-central and northeastern part of the study 

area (fig. 4).

RECHARGE AND DISCHARGE

The mean regional ground-water discharge for a 

long-term period (tens of years) approximates the mean 

recharge to the regional ground-water-flow systems 

within the Midwestern Basins and Arches Region 

because the regional aquifer system is in steady state 

(equilibrium) over these long periods. All recharge to 

the regional ground-water-flow system is from precipitation either directly on the surficial deposits throughout most of the study area or directly on the carbonate 

bedrock where it is exposed at, or within a few feet of, 

the surface. Few regional estimates of recharge have 

been made; however, a few local estimates have been 

reported in the literature: (1) recharge to the surficial 

aquifer, estimated as recharge through unsaturated glacial till at 1.4 and 1.8 in/yr (Daniels and others 1991), (2) 

12 and 12.4-15.8 in/yr through outwash deposits (Walton and Scudder, 1960; Dumouchelle and others,1993) 

respectively, and (3) 8 and 2 in/yr through till on 

uplands in the Great Miami River Basin (Walton and 

Scudder, 1960; Dumouchelle and others,1993). Recharge 

to the carbonate-rock aquifer has been estimated to 

range from 0.14 to 6.3 in/yr (Watkins and Rosenshein, 

1963; Rowland and Kunkle, 1970; Cravens and others, 

1990; Roadcap and others, 1993).

Regional ground-water discharge from the Midwestern Basins and Arches aquifer system is mainly to the 

major rivers and lakes within the area; a lesser amount 

of discharge is by evapotranspiration. Ground-water 

discharge to the unregulated reaches of large streams 

within the study area was estimated from streamflow 

data by separating out daily mean base flow to these 

streams from streamflow hydrographs (Eberts, in press)
A22 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

38° ~

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Eberts, in press

0 20 40 60 KILOMETERS

EXPLANATION

 1,200 

"£00011 Altitude of composite water level in surficial

 900 -- deposits Contour interval 100 feet.

 700 Dashed where inferred. Datum is sea level,

r £00 - Darker blues indicate lower altitude

 Boundary of study area

FIGURE 14. Generalized ground-water level configuration for the surficial aquifer in the Midwestern Basins and Arches Region.

by use of the local-minimum method of Pettyjohn and 

Henning (1979). The mean ground-water discharge to 

stream reaches above the selected streamflow-gaging 

stations was then estimated from the daily mean baseflow data (Eberts, in press). This mean ground-water 

discharge to streams describes long-term (tens of years), 

steady-state conditions within the Midwestern Basins

and Arches aquifer system. The mean ground-water 

discharge for the selected reaches of streams ranged 

from 17 to 80 percent of total mean streamflow (Eberts, 

in press).

Base-flow-duration curves (the frequency that a particular base flow is met or exceeded in a given period) 

were constructed from daily mean base-flow data and
REGIONAL GROUND-WATER FLOW A23

38° - 

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Eberts, in press

I I I I

0 20 40 60 KILOMETERS

 7,200 -

 lisa EXPLANATION 7,;oo--

~J;{Jjj0-- Altitude of potentiometric surface Contour |

 950 interval 50 feet. Dashed where inferred.

700 

650 

600 

Datum is sea level. Darker blues indicate 

lower altitude

Subcrop of Ordivician rocks beneath surficial deposits 

Boundary of study area

FIGURE 15. Potentiometric-surface configuration for the carbonate-rock aquifer in the Midwestern Basins and Arches Region.

used to estimate the regional, sustained component of 

ground-water discharge to a stream, and is referred to 

herein as "sustained base flow" or "sustained groundwater discharge" (Eberts, in press). The mean sustained 

ground-water discharge to stream reaches between 

streamflow-gaging stations was estimated by computing the difference between estimates of mean sustained 

ground-water discharge at adjacent gaging stations (fig. 

16). These mean sustained ground-water discharges 

ranged from 3 to 50 percent of the mean ground-water 

discharge (fig. 16) (Eberts, in press).
A24 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

40° -

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES

I r-h i 

0 20 40 60 KILOMETERS

EXPLANATION

Modified from Eberts and George, in press

25

Base flow to stream reach Numbers are estimates in cubic feet per second. 

Upper number is mean ground-water discharge calculated from hydrograph 

separation. Lower number is mean sustained ground-water discharge

 Stream reach used in base-flow analysis

 Boundary of study area 

A Continuous-record streamflow-gaging station

FIGURE 16. Calculated mean and mean sustained ground-water discharge to selected reaches along major streams

in the Midwestern Basins and Arches Region.
GROUND-WATER-FLOW SIMULATIONS A25

GROUND-WATER-FLOW SIMULATIONS

The focus of this study the regional ground waterflow components of the surficial and carbonate-rock 

aquifers within the Midwestern Basins and Arches 

Region pertained to the ground water that enters the 

study area and flows tens of miles before discharging to 

streams or remaining in the subsurface and flowing 

beyond the 10,000-mg/L dissolved-solids boundary 

The objectives of this study (Bugliosi, 1990), the practicality of collecting and analyzing data for such a large 

area, and the resulting coarseness of the regional-flowmodel grid limited this study to a description of 

regional ground-water flow. Consequently the groundwater-flow simulations were not designed to address 

shallow, local components of ground-water-flow paths 

less than 4 mi. long

One regional and two subregional ground-waterflow simulations were evaluated to test the conceptual 

model of the regional aquifer system; specifically to test 

the conceptualization of external and internal boundaries of ground-water flow (fig. 17). The regional 

ground-water-flow model was constructed to (1) test 

and improve upon the conceptual model of regional 

flow, (2) compute a regional ground-water budget, (3) 

determine recharge and discharge areas, and (4) identify ground-water-flow patterns within the study area. 

Additionally, a two-dimensional, steady-state, crosssectional-flow model was constructed to determine 

ground-water pathlines and traveltimes along a flow 

path from a regional recharge area (a potentiometric 

and topographically high area in central-western Ohio) 

to a regional discharge area (Lake Erie) and to test the 

conceptual model of regional flow along a single flow 

path. A subregional, transient ground-water-flow 

model was previously developed by Arihood (1994) for 

a predominantly agricultural area in northwestern Indiana. This heavily irrigated area exhibits seasonal 

changes in ground-water storage in the carbonate-rock 

aquifer, and is the only known part of the Midwestern 

Basins and Arches Region where transient groundwater conditions occur. The subregional ground-waterflow models had finer grid spacings than the regional 

model (4 mi X 4 mi) and thus represented the flow system in these areas in greater detail.

REGIONAL SIMULATION

The regional ground-water-flow model was 

designed to simulate steady-state, regional flow conditions within the Midwestern Basins and Arches aquifer 

system without explicitly representing local flow systems that are too small and numerous to be adequately 

simulated with a regional-scale model (Eberts and

George, in press). Ground-water withdrawals were not 

simulated because the regional aquifer is not stressed 

enough to produce widespread transient conditions.

Surficial deposits were simulated as layer 1 in the 

model. Rocks of Ordovician age were simulated as part 

of model layer 2 where the carbonate-rock aquifer is 

absent and these Ordovician rocks subcrop beneath 

thin, surficial deposits in the south-central part of the 

study area. The shale subregional confining unit was 

not represented as a separate model layer but rather as 

a resistance to vertical flow between layer 1 and layer 2. 

Each model cell was 16 mi2 (4X4 mi) and parameter 

values, such as hydraulic conductivity, were assumed to 

be constant within individual model cells. The model 

grid was oriented parallel to the contact between carbonate and shale rocks of Devonian age along the margin of the Illinois Basin because no physical hydrologic 

boundary is present in this area (fig. 18). Boundaries 

for the regional flow model were set according to table 1 

and are shown in figure 18. A detailed description of 

these boundaries is given in (Eberts and George, in 

press).

Parameter-estimation and testing codes (Hill, 1992, 

1994) were used to estimate parameter values by nonlinear regression and to test the confidence of the 

hydrologic parameters used in the calibrated regional 

ground-water-flow model, namely (1) horizontal 

hydraulic conductivity or transmissivity, (2) vertical 

hydraulic conductivity, (3) streambed hydraulic conductivity, (4) a conductance term for the general headdependent-flux boundary condition that was used to 

simulate ground-water flux at the regional water-table 

interface, and (5) effective recharge to the regional 

ground-water-flow system (Eberts and George, in 

press). The relative sensitivity of model output to 

changes in these hydrologic parameters used to calibrate the ground-water-flow model and final calibrated 

parameter values are given in table 2.

A comparison of simulated and measured hydraulic 

heads (fig. 19) and comparison of calculated and simulated regional ground-water discharge to major streams 

(fig. 20) indicates that model calibration was achieved 

(Eberts and George, in press).

A regional ground-water-flow budget was estimated 

by use of output from the calibrated ground-water-flow 

model (table 3) (Eberts and George, in press). This budget does not account for localized ground-water flow, 

which is an important part of the overall ground-waterflow budget within the regional aquifer system.

A map of regional ground-water recharge and discharge areas (fig. 21) based on output from the calibrated ground-water-flow model (Eberts and George, in 

press) shows a pattern of alternating recharge and discharge areas, except in and around the Maumee and
A26 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

38° IBase from U.S. Geological Survey digital data. 

1:2,000,000.1972

0 20 40 60 KILOMETERS

EXPLANATION 

Boundaries of ground-water-flow models

Regional ground-water-flow model

 Layer 1 (surficial aquifer)

^ " Layer 2 (carbonate-rock aquifer)

Subregional ground-water-flow models

mTTTTrm Cross-sectional model (Hanover, 1994). (See figure 13 for details)

 Transient model (Arihood, 1994a)

 Boundary of study area 

FIGURE 17. Model areas for regional and subregional ground-water-flow models in the Midwestern Basins and Arches Region.
GROUND-WATER-FLOW SIMULATIONS A27

SURFICIAL AQUIFER (Model layer 1)

86° 84°

38°

Base from U.S. Geological Survey 

digital data. 1:2,000,000,1972

40 80 MILES Modified from Eberts 

 I and George, in press

0 40 80 KILOMETERS

CARBONATE-ROCK AQUIFER (Model layer 2)

88° 86° 84° 82°

42°

40°

Base from U.S. Geological Survey 

digital data, 1:2,000,000,1972

40 80 MILES Modified from Eberts 

 I and George, in press

0 40 80 KILOMETERS

EXPLANATION 

Model boundaries

General head-dependent flux 

Specified head 

Head-dependent flux

Specified flux (carbonate-rock aquifer only) 

No flow 

Boundary of study area

FIGURE 18. Boundary conditions used in the regional ground-water-flow model of the surficial and carbonate-rock aquifers

in the Midwestern Basins and Arches Region.

Sandusky River Basins, where discharge areas dominate. The map (fig. 21) indicates that few regional 

ground-water-flow paths extend from high to low 

regional potentiometric areas over distances greater 

than a few tens of miles; instead, flow is dominated by 

shorter flow paths (fig. 22). The dominant trend of 

shorter ground-water-flow paths within the Midwestern Basins and Arches Region is substantiated by variable-density-modeling results of Gupta (1993), 

indicating that a small volume of ground water, in a 

region that extends further than the boundaries of the 

Midwestern Basins and Arches Region (this study), 

passes through the rocks of Ordovician age (bottom of 

the conceptual model for this study) and flows into the 

surrounding structural basins. It is these very long 

(hundreds of miles) flow paths that are truly "regional." 

However, these very longe flow paths were not considered for this study because they represent a volume of 

ground-water flow that is significantly less than the 

total ground-water flow accounted for in the model 

constructed for this study.

The primary factors controlling the ground-waterflow patterns in the Midwestern Basins and Arches 

Region are the relatively subdued topography and the 

low ratio of depth to lateral extent of the regional aquifer system. The water-table configuration is closely 

associated with the topographic relief in the area, as is 

the potentiometric surface of the carbonate-rock aquifer 

(Eberts and George, in press). Because the range in altitude in the study area is less than 1,000 ft and only two 

small topographically high areas are present (fig. 2), 

short flow paths (a few miles) are dominant throughout 

the region. The low ratio of depth to lateral extent of the 

regional aquifer system also produces shorter ground-
A28 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

TABLE 1. Regional ground-water-flow model boundaries and the areas to which each boundary is applied

[Modified from Eberts and George, in press. Boundaries are shown in figure 18]

Model boundary type Location where boundary is applied

Surficial aquifer (layer 1) Carbonate-rock aquifer (layer 2)

No-flow

(includes streamlines, surface-water 

drainage divides, limit of Wisconsinian 

glaciation, ground-water divides, top of 

Ordovician rocks, Lake Erie shoreline, 

and the 10,000 mg/L dissolved-solidsconcentration boundary).

Specified head

(includes Lake Erie shoreline, 700 foot 

ground-water equipotential, and the 

Ohio River).

Specified flux

(includes flow into Illinois Basin).

Head-dependent flux

(includes most large streams in study area).

General head-dependent flux

(includes interface between water table 

in layer 1 and localized ground-water 

discharge to smaller perennial streams).

All boundaries except along Lake East, north, northeast and northwest. 

Erie shoreline.

Lake Erie shoreline and southernmost part of western boundary.

None.

Principal streams.

Water-table boundary,

Ohio River along southern part of study 

area and southernmost part of western 

boundary where surficial deposits are 

absent or very thin.

Northernmost part of study area where 

flow is into Illinois Basin.

Principal streams (only in areas where 

layer 1 is absent in the model).

Water-table boundary where layer 1 is 

absent; also where layer 1 is absent and 

the carbonate-rock aquifer is isolated 

from shallow flow systems by the 

Devonian and Mississippian upper 

confining shale units, such as along the 

lateral margins of the study area.

TABLE 2. Relative sensitivity and calibrated model-simulation values ofhydrologic parameters for the regional ground-water-flow model

of the Midwestern Basins and Arches Region

[ft2/d, feet squared per day; ft/d, feet per day; in/yr, inches per year. Modified from Eberts and George, in press, table 3]

Relative sensitivity of 

model output to changes 

in hydrologic parameters

Parameter Parameter value

Most sensitive

1 i

Least sensitive

Transmissivity of the carbonate-rock aquifer 1,610 ft /d 

Horizontal hydraulic conductivity of the morainal deposits 21.3 ft/d

Net recharge necessary to balance sustained ground-water discharge to the 

principal streams associated with the regional ground-water-flow system '2.15 in/yr

Effective vertical hydraulic conductivity of the combined moraine/bedrock areas 0.375 x 10"2 ft/d

Conductance term for the general head-dependent flux boundary condition

used to simulate the regional water table a 0.259

Hydraulic conductivity of streambeds throughout most of the modeled area 0.0149 ft/d

Horizontal hydraulic conductivity of the outwash deposits 168 ft/d

Vertical hydraulic conductivity of the shale subregional confining unit 0.466 x 10~3 ft/d

'Net recharge to regional flow system is computed by subtracting the flux associated with the head-dependent flux boundary conditions from the estimated 

value of the recharge parameter on a cell-by-cell basis.
GROUND-WATER-FLOW SIMULATIONS A29

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES Modified from Eberts and George, in press

I r-h rj '

0 20 40 60 KILOMETERS

EXPLANATION 

Subcrop of Ordovician rocks beneath surficial deposits

 so? Potentiometric contour Shows altitude at which water level would have stood in tightly cased wells,

July-August 1990. Dashed where approximately located. Contour interval 100 feet. Datum is sea level

 so? Potentiometic contour Simulated by regional flow model. Contour interval 100 feet. Datum is sea level

 Boundary of model layer 2

 Boundary of study area

FIGURE 19. Measured and simulated hydraulic heads for the carbonate-rock aquifer in the regional model,

Midwestern Basins and Arches Region.
A30 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

40°

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES

I r-h H '

0 20 40 60 KILOMETERS

EXPLANATION

Modified from Eberts and George, in press

;o 3 12 Ground-water discharge to selected stream reach Color corresponds to deviation of simulated

flow from measured streamflow. Upper number is mean sustained ground-water discharge, in cubic 

feet per second. Lower number is simulated ground-water discharge, in cubic feet per second

Simulated ground-water discharge to streams

 Under simulated Simulated flow less than 3 times the standard deviation of the error associated 

with measured streamflow

 Reasonably simulated Simulated flow within 3 times more, or less than, the standard deviation 

of the error associated with measured streamflow

 Oversimulated Simulated flow more than 3 times the standard deviation of the error associated 

with measured streamflow

^ Boundary of modeled area 

A Continuous-record streamflow-gaging station

FIGURE 20. Measured and simulated mean sustained ground-water discharge to selected stream reaches

in the Midwestern Basins and Arches Region.
GROUND-WATER-FLOW SIMULATIONS A31

TABLE 3. Simulated ground-water budget for regional flow in the Midwestern Basins and Arches aquifer system

[Mgal/d, million gallons per day. Modified from Eberts and George, in press, table 4]

Major regional ground-water-flow components Flow 

(Mgal/d)

Percent 

recharge or 

discharge

Recharge

Across the regional trend of the water table from precipitation

From losing stream reaches

Discharge

To principal streams

Across the regional trend of the water table to seeps, springs, 

small streams, or by means of evapotranspiration

Along the margin of the Illinois (structural) Basin 

To the Ohio River from the carbonate-rock aquifer 

To Lake Erie

Across the northwest boundary of the modeled area 

To the Ohio River from Ordovician rocks

Total

Total

1,277

15

1,292

1,006

242

24

18

1

1

1,292

99

1

100

78

19

2

1

100

water-flow paths, as postulated by Freeze and Witherspoon, 1967). The somewhat hummocky local topography caused by glaciation theoretically contributes to the 

dominance of shallower flow paths (less than 100 ft into 

the carbonate-rock aquifer) within the study area 

(Toth,1963).

SUBREGIONAL SIMULATIONS

A subregional, cross-sectional, steady-state model 

was constructed to simulate regional ground-water 

flow along a path from a potentiometric high in centralwestern Ohio to a regional potentiometric low at 

Sandusky Bay, on the southwestern shore of Lake Erie 

(Hanover, 1994) (Location of the section is shown in fig. 

17) The specific purpose of this model was to describe 

quantities and locations of recharge and discharge 

along this flow path and to account for the apportionment of ground-water flow between the surficial and 

carbonate-rock aquifers along the selected path. Results 

of simulations made with the calibrated model indicate 

that about 84 percent of the water entering the groundwater-flow systems near this cross section travels less 

than 5 mi from the area of recharge to the area of discharge, and that most of the flow is within the surficial 

aquifer (fig. 23). Traveltimes for ground-water particles

calculated by use of a particle-tracking routine (Pollock, 

1989) generally agreed with uncorrected carbon-14 ages 

for ground-water samples collected from deep wells 

near the model columns along the regional flow path 

(fig. 23). Results of this model substantiate results of 

the regional ground-water-flow model, namely that 

much of the flow in the Midwestern Basins and Arches 

aquifer system follows fairly short flow paths and that 

only a small part travels along deep, long paths from 

regional recharge to discharge areas.

The only area where transient conditions develop 

within the carbonate-rock aquifer is in northwestern 

Indiana, where ground-water withdrawals for irrigation impose seasonal stress on the carbonate-rock aquifer. A subregional, transient ground-water-flow model 

was constructed for this area (Arihood,1994) prior to the 

RASA study (fig. 17). Transient model results indicate 

that the specific storage of the carbonate-rock aquifer is 

1.3 x 10"4 and that the transmissivity ranges from 1,000 

to 5,000 ftVd. The transmissivity of the carbonate-rock 

aquifer calculated from the regional steady-state 

ground-water-flow model 1,610 ftVd is well 

within the ranges from transient model results, an indication that similar values of specific storage for the carbonate-rock aquifer can be applied with some 

confidence to other areas within the Midwestern Basins 

and Arches Region having similar aquifer geometry.
A32 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

38° -

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Eberts and George, in press

n r 

0 20 40 60 KILOMETERS

EXPLANATION 

Recharge areas Based on model output of simulated recharge, in inches per year

O 0-0.5

n 0.5-4

B Greater than 4

Discharge areas Based on model output of simulated discharge, in inches per year

n 0-0.5

E Greater than 0.5

Boundary of ground-water-flow model

 Layer 1 (surficial aquifer) 

^^ Layer 2 (carbonate-rock aquifer)

 Boundary of study area

FIGURE 21. Recharge and discharge areas based on model output from the calibrated ground-water-flow model

of the Midwestern Basins and Arches Region.
GROUND-WATER-FLOW SIMULATIONS A33

38° -,

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES

0 20 40 60 KILOMETERS

EXPLANATION

Modified from Eberts and George, in press

 > Simulated regional ground-water-flow path Shows path from 

point of regional recharge to point of regional discharge

 Boundary of model layer 1 (surficial aquifer)

 ^ Boundary of model layer 2 (carbonate-rock aquifer)

 Boundary of study area

FIGURE 22. Ground-water-flow paths based on particle tracking of regional ground-water flow 

in the Midwestern Basins and Arches Region.
A34 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

SOUTHWEST

FEET

1,400-) Area of dominant 

.regional recharge 

1300

NORTHEAST

Modified from Hanover, 1994

-100

15 KILOMETERS

EXPLANATION 

B Layer 1 model cell 

 Layer 2 model cell 

 * Pathline of ground-water flow

FIGURE 23. Ground-water-flow paths based on particle-tracking results for a cross-sectional model representing regional ground-water 

flow from an area in central-western Ohio to a discharge area at Lake Erie (trace of section shown on figure 17).

REGIONAL WATER CHEMISTRY

The chemical character of ground water in the Midwestern Basins and Arches Region reflects the composition of the surficial deposits and carbonate bedrock and 

is affected by the patterns of ground-water flow 

through the aquifer system, especially from recharge 

areas to discharge areas in a carbonate-rich system. As 

ground water flows downgradient from regional 

recharge to discharge areas, the dominant anion generally changes from bicarbonate, to sulfate, to chloride; a 

corresponding increase in dissolved-solids concentration and the age of the water also indicate the relative 

lengths of the ground-water-flow paths and the associated residence time of ground water within the system 

(Chebotarev,1955). The changes in ground-water chemistry from recharge to discharge areas in the Midwestern Basins and Arches Region indicate that the flow

systems consist mainly of short flow paths and that a 

complete evolution of anion species from bicarbonate to 

sulfate to chloride along regional flow paths is not evident in most of the study area.

DISSOLVED SOLIDS TRENDS

Distribution of dissolved-solids concentrations of 

ground water in the Midwestern Basins and Arches 

Region is similar in the surficial aquifer and the carbonate-rock aquifer within the study area where the carbonate-rock aquifer is a subcrop beneath the surficial 

deposits (figs. 24 and 25). The concentration of dissolved solids in ground water within the study area 

ranges from less than 100 to more than 2,600 mg/L in 

the surficial aquifer and from about 170 to 3,830 mg/L 

in the carbonate-rock aquifer (Eberts and George, in
REGIONAL WATER CHEMISTRY A35

press). Dissolved solids concentrations in the carbonaterock aquifer outside of the study area (downdip, in the 

structural basins) range from 4,000 to more than 350,000 

mg/L.

Water in the carbonate-rock aquifer with dissolved 

solids concentrations less than 500 mg/L is generally 

found in Indiana and only locally in the central part of

the study area (fig. 25). Ground-water with dissolved 

solids concentrations less than 500 mg/L is also found 

locally in the northeastern part of the study area (near 

Lake Erie) and is associated with carbonate bedrock of 

Devonian age, such as that along the southern perimeter of the Michigan Basin (fig. 25). Ground water with 

dissolved-solids concentrations between 500 and 1,000

88°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

0 20 40 60 MILES Modified from Eberts and George, in press

0 20 40 60 KILOMETERS

EXPLANATION

 Boundary of study area

Concentration of dissolved solids, in milligrams per liter

0-500 

o 501-1,000

 Greater than 1,000

FIGURE 24. Distribution of dissolved-solids concentrations in the surficial aquifer, Midwestern Basins and Arches Region.
A36 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

38°

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

20 40 60 MILES Modified from Eberts and George, in press

i i I i

0 20 40 60 KILOMETERS

EXPLANATION

 70,000 Approximate line of equal dissolved-solids concentration 

Dashed where inferred. Interval, in milligrams per liter, 

is variable

 Boundary of study area

Concentration of dissolved solids, in milligrams per liter

0-500 

o 501-1,000

 1,001-10,000

 Greater than 10,000

FIGURE 25. Distribution of dissolved-solids concentrations in the carbonate-rock aquifer, Midwestern Basins and Arches Region.
REGIONAL WATER CHEMISTRY A37

mg/L is found primarily in the northeastern part of the 

study area (fig. 25). Water with dissolved-solids concentrations greater than 1,000 mg/L is restricted to the 

north-central and northeastern parts of the study area 

(fig. 25). Ground water with dissolved-solids concentrations greater than 10,000 mg/L is considered to be 

unsuitable for consumption (U. S. Environmental Protection Agency, 1984). As stated earlier in this report, the 

position of the 10,000 mg/L line defines the limit of the 

freshwater part of the carbonate-rock aquifer for this 

study.

Dissolved-solids concentrations greater than 10,000 

mg/L in carbonate-rock waters differ considerably in 

their distribution between the three structural basins 

(fig. 25). The Appalacian Basin exhibits the most rapid 

increase in dissolved-solids concentration downdip into 

the basin; dissolved-solids concentration of the water 

increases to greater than 10,000 mg/L generally within 

5 mi of the contact between the carbonate-rock aquifer 

and the upper confining unit. In the Michigan Basin, 

dissolved-solids concentrations greater than 10,000 mg/ 

L are further downdip into the basin, usually 5 to 25 

miles from the contact between the carbonate-rock aquifer and the upper confining unit (fig. 25). In the Illinois 

Basin, the trend in dissolved-solids concentration is 

anomalous to trends in the Appalacian and Michigan 

Basins. Dissolved-solids concentrations of less than 

10,000 mg/L are found more than 70 mi downdip, from 

the contact between the carbonate-rock aquifer and the 

upper confining unit as it extends into the basin (fig. 

26). Results of work by D.J. Schnoeblen (U. S. Geological Survey, written commun., 1993) indicate that fresher 

water (dissolved-solids concentration less than 10,000 

mg/L) underlies saline ground water (dissolved-solids 

concentration greater than 10,000 mg/L) in areas where 

the carbonate-rock aquifer units dip into the Illinois 

Basin in southwestern Indiana (figs. 1 and 25); however, 

the mechanism that caused and maintains this inversion is not understood, and investigation of this anomalous water-quality trend was beyond the scope of this 

project.

HYDROCHEMICAL FACIES

Ground water in the Midwestern Basins and Arches 

Region was classified into hydrochemical facies on the 

basis of concentrations of major cations and anions in 

solution reported for more than 1,300 chemical analyses 

of ground water from the surficial and carbonate-rock 

aquifers (Eberts and George, in press). The distributions 

of hydrochemical facies for the surficial and carbonaterock aquifers are similar (figs. 26 and 27). The most 

common type of water in both aquifers throughout the

study area is Ca-Mg-HCO3. In the northeastern part of 

the study area where sulfate concentrations are elevated, ground water is dominated by Ca-Mg-SO4-type 

water. Additionally, several areas are characterized by a 

mixture of several ground-water types (referred to as 

"multiple-water-types" in figures 26 and 27).

Water in the carbonate-rock aquifer becomes sodium 

enriched in the northeastern, north-central, northwestern, and west-central parts of the Midwestern Basins 

and Arches Region near the contact between the upper 

confining unit shales and the carbonate-rock aquifer 

(fig. 27 and fig. 7). The increase in sodium and chloride 

ions is probably associated with either (1) mixing with 

more saline water in the adjacent structural basins and 

(or) (2) restricted recharge through the surficial aquifer 

to the carbonate-rock aquifer, because the upper confining unit shales inhibit direct recharge through the surficial deposits (Eberts and George, in press).

Descriptions of hydrochemical facies and processes 

likely controlling the development of these facies 

throughout the Midwestern Basins and Arches Region 

are summarized in table 4. It is evident from the hydrochemical-facies maps (figs. 26 and 27) and from table 4 

that the dominant process controlling the geochemistry 

of ground water in the Midwestern Basins and Arches 

Region is dissolution of limestone and dolomite into 

Ca-Mg-HCO3 The similarity of hydrochemical-facies 

distribution between the surficial and carbonate-rock 

aquifers within the study area indicates that (1) these 

aquifers are geochemically similar because the parent 

material in both aquifers was derived from the same 

bedrock source (Strobel and Faure, 1987) and (or) that 

(2) most recharge to the carbonate-rock aquifer is 

through the surficial deposits; thus the chemical signature from the surficial aquifer is present in waters from 

the carbonate-rock aquifer, owing to the hydraulic connection between them.

RELATION OF ISOTOPIC COMPOSITION OF 

GROUND WATER TO REGIONAL FLOW

The absence of systematic changes in dissolved-solids or sulfate concentrations in ground-water along 

directions of regional flow supports other hydrologic 

evidence that the regional aquifer system is characterized by short intermediate-length flow cells (alternating 

recharge and discharge areas) rather than by long 

regional flow paths starting at regional potentiometric 

highs and extending to regional potentiometric lows 

(Eberts and George, in press). Additional insight into 

chemical and hydrologic processes was gained by measuring the stable-isotope ratios, 834S, 818O, 8D, and 

813C, and estimating the age of ground water along
A38 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND AECHES

40° -

38° -,

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Eberts and George, in press

0 20 40 60 KILOMETERS

EXPLANATION 

Hydrochemical facies

Predominantly single water type

Ca-Mg-HCO3 

|B Ca-Mg-SO4

Multiple-water types

10 Ca-Mg-HCO3) Ca-Mg-Na-HCO3 , Cl-influenced 

HI Ca-Mg-HCO3 , Ca-Mg-SO4 , Ca-Mg-Na-HCO3 , and 

HI Ca-Mg-HCO3 , Ca-Mg-SO4 , Ca-Mg-Na-HCO3 , Na-HCO3 , and Ca-Mg-Na-SO4

 - Boundary between hydrochemical facies Dashed where inferred

 Boundary of study area

Well for which chemical data are available

FIGURE 26. Hydrochemical facies based on concentrations of major anions and cations in water from the surficial aquifer

in the Midwestern Basins and Arches Region.
REGIONAL WATER CHEMISTRY A39

38° -

Base from U.S. Geological Survey digital data, 0 20 40 BO MlLbb Modified from Eberts and George, in press 

1:2,000.000.1972

0 20 40 60 KILOMETERS

EXPLANATION 

Hydrochemical facies

Predominantly single water type 

11 Ca-Mg-HCO3 

H Ca-Mg-SO4 

t: Na-Cl

Na-Ca-Cl

Multiple-water types

 Ca-Mg-HCO3 and Ca-Mg-Na-HCO3

Hi Ca-Mg-HCO3 , Ca-Mg-SO4 , Ca-Mg-Na-HCO3 , Na-HCO3 , and Ca-Mg-Na-SO4

B Na-C1 and Na-Ca-Cl

 - Boundary between hydrochemical facies Dashed where inferred

 Boundary of study area

Well for which chemical data are available

FIGURE 27. Hydrochemical facies based on concentrations of major anions and cations in water from the carbonate-rock aquifer

in the Midwestern Basins and Arches Region.
A40 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

TABLE 4. Hydrochemical fades, geochemical processes controlling reactions, and predominant areas of hydrochemical fades 

in the surfidal and carbonate-rock aquifers in the Midwestern Basins and Arches Region

Hydrochemical facies Processes likely controlling chemical reactions Predominant area of hydrochemical facies

Surficial aquifer

Ca-Mg-HCO3 

Ca-Mg-SO4

Ca-Mg-HCO3 ; Ca-Mg-SO4 ; 

Ca-Mg-Na-HCO3; Na-HCO3; 

Ca-Mg-Na-SO4

Ca-Mg-HCO3; Ca-Mg-SO4 ; 

Ca-Mg-Na-HCO3; Na-HCO3

Ca-Mg-HCO3; Ca-Mg-Na-HCO3, 

Cl influenced

Single water type

Dissolution of calcite and dolomite

Dedolomitization and dissolution of dolomite 

by sulfuric acid from oxidized pyrite

Multiple water type

Cation exchange and dissolution of calcite and 

dolomite

Cation exchange; some mixing with Na-Cl waters

Cation exchange; mixing with Na-Cl waters; 

human activity

Most of study area, predominantly in central part 

Northeastern part of study area

North-central part of study area, principally in 

northeastern Ohio along contact between 

Devonian carbonate and shale rocks

Northwestern part of study area in northwest 

Indiana

South-central part of study area

Carbonate-rock aquifer

Single water type

Ca-Mg-HCO3 Dissolution of calcite and dolomite

Ca-Mg-SO4 Dedolimitization and dissolution of dolomite

by sulfuric acid from oxidized pyrite

Multiple water type

Ca-Mg-HCO3; Ca-Mg-SO4; Cation exchange and dissolution of calcite and 

Ca-Mg-Na-HCO3; Na-HCO3; dolomite 

Ca-Mg-Na-SO4

Ca-Mg-HCO3; Ca-Mg-Na-HCO3 Cation exchange

Na-Cl; Na-Ca-Cl; Ca-Na-Cl; 

Cl influenced

Complex processes; related to absence of fresher 

ground-water recharge due to the presence of the 

upper confining unit

Most of study area, predominantly in central part 

Northeastern part of study area

Northern part of study area along the contact 

between Devonian carbonate and shale rock; 

along the margins of the Michigan Basin where 

the carbonate-rock aquifer is overlain by 

Devonian shales

Southwestern part of study area near the contact 

between Devonian carbonates and shales

Along contact between Devonian carbonate and 

shale rocks in structural basins

directions of regional ground-water flow (from regional 

recharge areas to regional discharge areas) by use of the 

radioactive isotopes 14C and tritium (Eberts and 

George, in press).

Values of 834S in ground-water samples collected 

from wells in the study area ranged from -10.4 permil to 

+44.1 permil for 834S(sulfate) and from -53.2 permil to - 

12.2 permil for 834S(suifide) (Eberts and George, in press). 

The heaviest 83 S(suyate) values were most commonly 

found in the northeastern part of the study area in association with gypsum deposits of Silurian and Devonian 

age; lighter 6 S(suyate) values were generally found in 

the western part of the study area where gypsum beds

are absent from the carbonate bedrock. In addition 

S34S(sulfate) values f°r ground-water from the surficial 

aquifer tended to be lighter than those for ground water 

from deep in the carbonate-rock aquifer, an indication 

that recharge entering the surficial aquifer and the fractured, uppermost part of the carbonate-rock aquifer 

does not reach the deeper parts of the regional system 

(Eberts and George, in press).

Values of 818O and 8D were determined for water 

samples collected from wells in the surficial and carbonate-rock aquifers in the study area in the Midwestern 

Basins and Arches Region to determine relative ages of 

recharge to the regional ground-water system (Eberts
GROUND-WATER USE A41

and George, in press). Isotopic compositions of most 

ground-water samples were similar to those of surface 

water sampled in the study area, an indication that climatic conditions at the time of recharge to the regional 

ground-water-flow system were likely similar to 

present climatic conditions. Moreover, water from 

wells in most parts of the study area contains enough 

tritium to indicate that the regional aquifer system in 

these areas is relatively active with respect to flow and 

that it has been recharged since atmospheric testing of 

nuclear weapons began in 1953. In contrast, isotopically 

light ground-water from wells in the northeastern part 

of the study area indicate that water likely recharged 

the regional aquifer system during climatic conditions 

colder than the present, perhaps during Pleistocene 

time. Additionally, tritiated water was not detected in 

any of the isotopically light ground-water samples in 

the northeastern part of the study area (Eberts and 

George, in press), an indication that recharge has not 

entered the regional ground-water system in this area 

since 1953.

Carbon-14 ages were determined for samples from 

wells in the surficial and carbonate-rock aquifers; 813C 

data also were collected to provide information regarding sources of dissolved inorganic carbon in ground 

water so that measured 14C values could be corrected 

for the dilutional effects caused by various geochemical 

processes. The 14C data indicate that ground water 

throughout most of the study area is relatively young, 

from a few hundred to several thousand years old; the 

oldest ground water (about 38,000-45,000 years old) is 

in the northeastern part of the study area (within the 

Maumee River Basin and adjacent to Lake Erie), near 

the regional discharge area surrounding the Wabash 

River in northern Indiana, and at the margin of the Illinois Basin in western Indiana (Eberts and George, in 

press). These data corroborate ground-water-flow-modeling results indicating that the Maumee River Basin, 

Lake Erie, and the Wabash River are regional groundwater-discharge areas, and support the conclusion that 

recharge is restricted in this area, probably by surficial 

lacustrine deposits. Ground water discharging in these 

areas has traveled deeper within the regional system 

along somewhat longer flow paths and is thus older 

than most water within the surficial and carbonate-rock 

aquifers in the Midwestern Basins and Arches Region. 

Carbon-14 data indicate that relatively old water (about

13,000 years old) is at the end of the longest flow paths 

(50 miles) near Lake Erie.

GROUND-WATER USE

The amount of ground water withdrawn for various 

uses was estimated from ground-water-pumpage data 

reported by users in 1990 capable of pumping 100,000 

gal/d or more (Bill Steen, Indiana Department of Natural Resources, Division of Water and Rebecca Petty, 

Ohio Department of Natural Resources, Division of 

Water, written communs., 1992) (fig. 28). To account for 

all other ground-water users (those that pumped less 

than 100,000 gal/d in 1990) would increase the total 

substantially; however, these data were not available. 

The reported ground-water use data can be considered 

conservative estimates of the types and rates of groundwater withdrawals in the Midwestern Basins and 

Arches Region in 1990.

An average of 433 Mgal/d of ground water was 

withdrawn from the surficial and carbonate-rock aquifers in Indiana and Ohio during 1990 (Beary, 1993). In 

contrast, about 280 Mgal/d was withdrawn from the 

aquifers in 1980 (Bugliosi, 1990), an increase of almost 

65 percent in 10 years. The reported increase in groundwater use is probably due at least, in part, to changes in 

reporting policies and user compliance with those 

reporting policies from 1980 to 1990. Monthly total 

ground-water withdrawals in the Indiana and Ohio 

parts of the study area exhibited a seasonal trend in 

1990 (fig. 29); monthly withdrawals in Ohio ranged 

from 6,800 Mgal (February) to about 12,000 Mgal 

(August), whereas those in Indiana ranged from 4,300 

Mgal (February) to about 8,000 Mgal (July).

The greatest use in a particular category (more than 

65 percent) of ground water within the Indiana and 

Ohio parts of the study area in 1990 was for public supply (180.8 Mgal/d) (fig. 30). Industrial and energy-production uses followed (21 and 6 percent, respectively), 

with agriculture/irrigation, miscellaneous and rural 

use accounting for the remainder (about 8 percent). The 

percentages of ground-water use for the various categories are similar to those for 1980 (Bugliosi, 1990), an 

indication that ground-water-use trends remained 

steady during 1980-90 within the Midwestern Basins 

and Arches Region.
A42 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

88°

38'

Base from U.S. Geological Survey digital data, 

1:2,000,000,1972

Modified from Beary, 1993

I i i ____ I I \ ^ r

0 20 40 60 KILOMETERS

EXPLANATION 

Boundary of study area

Ground-water-withdrawal site Locations reported 

from Ohio and Indiana State agencies

FIGURE 28. Ground-water-withdrawal sites where potential pumpage is 100,000 gallons per day or more

in the Midwestern Basins and Arches Region.
GROUND-WATER USE A43

14,000

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

FIGURE 29. Total monthly ground-water withdrawals for parts of Indiana and Ohio 

in the Midwestern Basins and Arches Region, 1990 (modified from Beary, 1993).

Miscellaneous

(7.9 Mgal/d)

Energy production

(17.1 Mgal/d)

x Agriculture/irrigation

Rural use (11-4 Mgal/d)

(1.95 Mgal/d) Mgal/d: Million gallons per day

FIGURE 30. Total monthly ground-water use, by category, among users capable of withdrawing 100,000 gallons per day or more 

in parts of Indiana and Ohio within the Midwestern Basins and Arches Region, 1990 (modified from Beary, 1993).
A44 REGIONAL AQUIFER-SYSTEM ANALYSIS MIDWESTERN BASINS AND ARCHES

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(These and other reports prepared as part of the 

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Bulletin, v. 30, no. 2, p. 205-218.

Arihood, L.D. and Basch, M.E.,1994, Geohydrology and simulated 

ground-water flow in an irrigated area of northwestern Indiana: U.S. Geological Survey Water Resources Investigations 

Report 92-4046,38 p.

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atlas: Tiffin, Ohio, Heidelberg College Water Quality Laboratory, 304 p.

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2 p.

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of water in aquifers in Lucas, Sandusky, and Wood Counties, 

northwestern Ohio: U.S. Geological Survey Water-Resources 

Investigations Report 91-4024, 234 p.

*Bugliosi, E.F., 1990, Plan of study for the Ohio-Indiana carbonatebedrock and glacial-aquifer system: U.S. Geological Survey 

Open File Report 90-151,26 p., 1 plate.

Burger, A.M., Forsyth, J.L, Nicoll, R.S., and Wayne, W.J., 1971, Geological map of the I' x 2' Muncie quadrangle, Indiana and Ohio, 

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1993, Hydrogeology, simulated ground-water flow, and 

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