Environmental Setting and Water-Quality Issues of the

Mobile River Basin, Alabama, Georgia, Mississippi,

and Tennessee

Water-Resources Investigations Report 02-4162

National Water-Quality Assessment Program

U.S. Department of the Interior

U.S. Geological Survey
Cover photos: Left photo is the Cahaba River east of Centerville, Alabama, courtesy of Dan Brothers, 

Alabama Department of Conservation and Natural Resources. Right photo is aerial view of Birmingham, 

Alabama, copyrighted by Alabama Air Foto (published with permission).
Environmental Setting and Water-Quality Issues 

of the Mobile River Basin, Alabama, Georgia, 

Mississippi, and Tennessee

By Gregory C. Johnson, Robert E. Kidd, Celeste A. Journey, 

Humbert Zappia, and J. Brian Atkins

U.S. GEOLOGICAL SURVEY

National Water-Quality Assessment Program

Water-Resources Investigations Report 02-4162

Montgomery, Alabama

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

Any use of trade, product, or firm name in this report is for identification

purposes only and does not constitute endorsement by the

U.S. Geological Survey.

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

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

2350 Fairlane Drive, Suite 120 Box 25286

Montgomery, Alabama 36166 Denver, Colorado 80225-0286
FOREWORD

Foreword iii

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific information that helps enhance and protect the 

overall quality of life, and facilitates effective management of water, biological, energy, and mineral 

resources. Information on the quality of the Nation’s 

water resources is of critical interest to the USGS 

because it is so integrally linked to the long-term 

availability of water that is clean and safe for drinking 

and recreation and that is suitable for industry, irrigation, and habitat for fish and wildlife. Escalating population growth and increasing demands for the multiple 

water uses make water availability, now measured in 

terms of quantity and quality, even more critical to the 

long-term sustainability of our communities and ecosystems.

The USGS implemented the National WaterQuality Assessment (NAWQA) Program to support 

national, regional, and local information needs and 

decisions related to water-quality management and 

policy. Shaped by and coordinated with ongoing 

efforts of other Federal, State, and local agencies, the 

NAWQA Program is designed to answer: What is the 

condition of our Nation’s streams and ground water? 

How are the conditions changing over time? How do 

natural features and human activities affect the quality 

of streams and ground water, and where are those 

effects most pronounced? By combining information 

on water chemistry, physical characteristics, stream 

habitat, and aquatic life, the NAWQA Program aims to 

provide science-based insights for current and emerging water issues. NAWQA results can contribute to 

informed decisions that result in practical and effective water-resource management and strategies that 

protect and restore water quality.

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more than 50 

of the Nation’s most important river basins and aquifers, referred to as Study Units. Collectively, these 

Study Units account for more than 60 percent of the 

overall water use and population served by public 

water supply, and are representative of the Nation’s 

major hydrologic landscapes, priority ecological 

resources, and agricultural, urban, and natural sources 

of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and 

analysis. The assessments thereby build local knowledge about water-quality issues and trends in a particular stream or aquifer while providing an 

understanding of how and why water quality varies 

regionally and nationally. The consistent, multi-scale 

approach helps to determine if certain types of waterquality issues are isolated or pervasive, and allows 

direct comparisons of how human activities and natural processes affect water quality and ecological health 

in the Nation’s diverse geographic and environmental 

settings. Comprehensive assessments on pesticides, 

nutrients, volatile organic compounds, trace metals, 

and aquatic ecology are developed at the national 

scale through comparative analysis of the Study-Unit 

findings. 

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available 

knowledge about water resources can be applied in 

management and policy decisions. We hope this 

NAWQA publication will provide you the needed 

insights and information to meet your needs, and 

thereby foster increased awareness and involvement in 

the protection and restoration of our Nation’s waters. 

The NAWQA Program recognizes that a 

national assessment by a single program cannot 

address all water-resource issues of interest. External 

coordination at all levels is critical for a fully integrated understanding of watersheds and for cost-effective management, regulation, and conservation of our 

Nation’s water resources. The Program, therefore, 

depends extensively on the advice, cooperation, and 

information from other Federal, State, interstate, 

Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder 

groups. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch

Associate Director for Water
Contents v

CONTENTS

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

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

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

Acknowledgments ....................................................................................................................................................... 2 

Environmental Setting of the Mobile River Basin................................................................................................................. 2 

Natural Factors ............................................................................................................................................................ 4 

Physiography ..................................................................................................................................................... 5 

Non-Coastal Plain Physiographic Provinces ........................................................................................... 5 

Blue Ridge and Piedmont Physiographic Provinces ..................................................................... 5 

Valley and Ridge Physiographic Province..................................................................................... 5 

Cumberland Plateau....................................................................................................................... 5 

Coastal Plain Physiographic Province..................................................................................................... 7 

Geology ............................................................................................................................................................. 7 

Soils ................................................................................................................................................................... 9 

Climate............................................................................................................................................................... 11

Hydrology.......................................................................................................................................................... 13

Surface Water........................................................................................................................................... 13

Streamflow Characteristics............................................................................................................ 13

Mean Annual Runoff ..................................................................................................................... 17

Ground Water........................................................................................................................................... 17

Southeastern Coastal Plain Aquifer System .................................................................................. 17

Valley and Ridge Aquifers............................................................................................................. 22

Appalachian Plateaus Aquifers...................................................................................................... 22

Piedmont and Blue Ridge Aquifers............................................................................................... 22

Ecoregions ......................................................................................................................................................... 23

Aquatic Ecology ................................................................................................................................................ 25

Cultural Factors ........................................................................................................................................................... 25

Study Unit Stratification.................................................................................................................................... 26

Reservoirs .......................................................................................................................................................... 26

Land Use............................................................................................................................................................ 26

Agriculture............................................................................................................................................... 26

Urban ....................................................................................................................................................... 32

Mining ..................................................................................................................................................... 34

Water Use........................................................................................................................................................... 39

Water-Quality Issues.............................................................................................................................................................. 42

State 305(b) Reports .................................................................................................................................................... 42

Toxics Release Inventory............................................................................................................................................. 48

Summary................................................................................................................................................................................ 48

References ............................................................................................................................................................................. 51

Appendix A. Aquatic species extirpated from or extinct in the Mobile River Basin ............................................................ 57

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973 ....................... 59
vi Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

FIGURES

1–10. Maps showing:

1. Location of the Mobile River Basin, Alabama, Georgia, Mississippi, and Tennessee................................. 3

2. Topography of the Mobile River Basin......................................................................................................... 4

3. Physiography of the Mobile River Basin...................................................................................................... 6

4. Generalized geology of the Mobile River Basin........................................................................................... 8

5. Major land resource areas within the Mobile River Basin ........................................................................... 10

6. Mean annual precipitation for the Mobile River Basin and 

mean monthly precipitation for selected sites, 1961-90 ............................................................................... 12

7. Mean annual temperature for the Mobile River Basin and 

mean monthly temperature for selected stations, 1961-90 ........................................................................... 14

8. Major river systems and dam locations in the Mobile River Basin .............................................................. 15

9. Mean annual runoff (1961-90) and mean annual discharge (1923-99) for the Mobile River Basin ............ 16

10. Locations and box plots of mean daily discharges for selected streamgaging stations for 

duration analysis representing the different physiographies in the Mobile River Basin .............................. 18

11. Graph showing duration curves for selected streamgaging stations representing the 

different physiographies in the Mobile River Basin ............................................................................................. 19

12–16. Maps showing:

12. Major aquifer systems and generalized section in the Mobile River Basin.................................................. 20

13. Ecological regions of the Mobile River Basin.............................................................................................. 24

14. Study unit stratification of the Mobile River Basin ...................................................................................... 27

15. Land use in the Mobile River Basin ............................................................................................................. 31

16. Agricultural crop production by county area in the Mobile River Basin for 1992....................................... 33

17. Graph showing agricultural crop production by strata for the Mobile River Basin in 1992 ................................ 34

18. Maps showing livestock production by county in the Mobile River Basin for 1992............................................ 35

19. Graph showing livestock production by strata for the Mobile River Basin for 1992 ........................................... 36

20–23. Maps showing:

20. The 1990 population density and metropolitan statistical areas in the Mobile River Basin......................... 37

21. Coal fields of the great Appalachian coal basin located in the Mobile River Basin..................................... 38

22. Location of abandoned coal surface mines in the Mobile River Basin ........................................................ 40

23. Surface-water use in million gallons per day by county area in the Mobile River Basin, 1995................... 41

24. Graphs showing water use by strata in the Mobile River Basin, 1995 ................................................................. 43

25. Maps showing ground-water use in million gallons per day by county area 

for the Mobile River Basin, 1995.......................................................................................................................... 44

26-28. Graphs showing:

26. Causes for segments of rivers in the Mobile River Basin to be placed 

on the 1996 State 303(d) lists ....................................................................................................................... 45

27. Classification of assessed river miles for supporting intended use in the Mobile River Basin

from 1996 State 305(b) reports..................................................................................................................... 46

28. Sources of contamination causing segments of rivers in the Mobile River Basin 

to be placed on the 1996 State 303(d) lists ................................................................................................... 47

29. Map showing U.S. Environmental Protection Agency Toxic Inventory Release 

sites in the Mobile River Basin for 1998 .............................................................................................................. 49

TABLES

1. Summary of climatic data for cooperative weather stations in the Mobile River Basin, 1961-90 ......................... 13

2. Generalized major aquifers in the Mobile River Basin .......................................................................................... 21

3. Dams and associated impoundments in the Mobile River Basin............................................................................ 28

4. Population in the Mobile River Basin by strata, 1970-90....................................................................................... 39

5. Estimated water use in the Mobile River Basin, 1995............................................................................................ 39
Contents vii

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Temperature in degrees Fahrenheit (oF) can be converted to degrees Celsius (oC) by use of the following equation: oC = (oF - 32)/ 1.8

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly 

called Sea Level Datum of 1929.

Abbreviations and Acronyms

303(d) reports List of each State’s surface waters which are classified as impaired by pollutants as required by 

section 303(d) of the Federal Clean Water Act of 1972

305(b) reports State water-quality assessment documents required by section 305(b) of the 

Federal Clean Water Act of 1972

MLRA Major land resource area

MSA Metropolitan statistical area

NAWQA National Water-Quality Assessment Program

PCB Polychlorinated biphenyls

TRI Toxic release inventory

U.S. EPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Multiply By To obtain

inch per year (in/yr) 2.54 centimeters per year 

foot 0.3048 meter

foot per mile (ft/mi) 0.1894 meter per kilometer

mile 1.609 kilometer

cubic foot per second (ft3/s) 448.831 gallons per minute

cubic foot per second (ft3/s) 28.32 liters per second

cubic foot per second (ft3/s) 0.646317 million gallons per day

acre 0.4047 hectacre

acre-foot 43,560 cubic foot

pound, avoirdupois (lb) 0.4536 kilogram

billion tons 1.016 x 1012 kilograms

pounds per year (lbs/yr) 0.4536 kilograms per year

cubic foot per second per square mile [(ft3/s)/mi2] 0.01363 liters per second per square kilometer

square mile (mi2) 2.590 square kilometer
Abstract 1

Environmental Setting and Water-Quality Issues 

of the Mobile River Basin, Alabama, Georgia, 

Mississippi, and Tennessee

By Gregory C. Johnson, Robert E. Kidd, Celeste A. Journey, Humbert Zappia, 

and J. Brian Atkins

ABSTRACT

The Mobile River Basin is one of over 50 

river basins and aquifer systems being investigated as part of the U.S. Geological Survey 

National Water-Quality Assessment (NAWQA) 

Program. This basin is the sixth largest river basin 

in the United States, and fourth largest in terms of 

streamflow, encompassing parts of Alabama, 

Georgia, Mississippi, and Tennessee. Almost twothirds of the 44,000-square-mile basin is located 

in Alabama. Extensive water resources of the 

Mobile River Basin are influenced by an array of 

natural and cultural factors. These factors impart 

unique and variable qualities to the streams, rivers, and aquifers providing abundant habitat to 

sustain the diverse aquatic life in the basin. 

Data from Federal, State, and local agencies 

provide a description of the environmental setting 

of the Mobile River Basin. Environmental data 

include natural factors such as physiography, 

geology, soils, climate, hydrology, ecoregions, 

and aquatic ecology, and human factors such as 

reservoirs, land use and population change, water 

use, and water-quality issues. Characterization of 

the environmental setting is useful for understanding the physical, chemical, and biological 

characteristics of surface and ground water in the 

Mobile River Basin and the possible implications 

of that environmental setting for water quality. 

The Mobile River Basin encompasses parts 

of five physiographic provinces. Fifty-six percent 

of the basin lies within the East Gulf section of 

the Coastal Plain Physiographic Province. The 

remaining northeastern part of the basin lies, from 

west to east, within the Cumberland Plateau section of the Appalachian Plateaus Physiographic 

Province, the Valley and Ridge Physiographic 

Province, the Piedmont Physiographic Province, 

and the Blue Ridge Physiographic Province.

Based on the 1991 land-use data, about 

70 percent of the basin is forested, while agriculture, including livestock (poultry, cattle, and 

swine), row crops (cotton, corn, soybeans, sorghum, and wheat), and pasture land accounts for 

about 26 percent of the study unit. Agricultural 

land use is concentrated along the Black Prairie 

Belt district of the Coastal Plain. Urban areas 

account for only 3 percent of the total land use; 

however, the areal extent of the metropolitan statistical areas (MSA) may indicate more urban 

influences. The MSAs include urban areas outside 

of the city boundaries and can include adjacent 

counties. Seven MSAs are delineated in the 

Mobile River Basin, including Montgomery, 

Mobile, Tuscaloosa, Birmingham, Gadsden, 

Anniston, and Atlanta. The total population for the 

Mobile River Basin was about 3,673,100 in 1990.

State water-quality agencies have identified 

numerous causes and sources of water-body 

impairment in the Mobile River Basin. In 1996, 

organic enrichment, dissolved oxygen depletion, 

elevated nutrient concentrations, and siltation 

were the most frequently cited causes of impairment, affecting the greatest number of river miles. 

Bacteria, acidic pH, and elevated metal concentrations also were identified as causes of impairment. 

The sources for impairment varied among river 

basins, were largely a function of land use, and 

were attributed primarily to municipal and industrial sources, mining, and agricultural activities.
2 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

INTRODUCTION

The Mobile River Basin is the sixth largest river 

basin in the United States, encompassing parts of Alabama, Georgia, Mississippi, and Tennessee (fig. 1) 

(Lamb, 1979), and the fourth largest river basin in 

streamflow. Almost two-thirds of the 44,000-squaremile basin is located in Alabama. Extensive water 

resources of the Mobile River Basin are influenced by 

an array of natural and cultural factors. These factors 

impart unique and variable qualities to the water in 

streams, rivers, and aquifers, which provide abundant 

habitats that sustain the diverse aquatic life in the 

basin. 

The Mobile River is formed by the confluence 

of two large rivers, the Tombigbee and Alabama Rivers, near Mount Vernon, Alabama. Downstream from 

the confluence, the Mobile River flows about 30 miles 

to the south before splitting into several distributaries. 

After flowing across a deltaic plain, these distributaries discharge to Mobile Bay (fig. 2), contributing 

approximately 95 percent of the freshwater inflow to 

the bay (Loyacano and Smith, 1979). Streamflows in 

these distributaries are affected cyclically by tidal processes, creating a unique and complex fluvialestuarine system. 

The Mobile River Basin is one of over 50 river 

basins and aquifer systems (Study Units) being studied 

as part of the U.S. Geological Survey National WaterQuality Assessment (NAWQA) Program. Full-scale 

implementation of the NAWQA Program was initiated 

in 1991. Information from the different study units 

will help Federal, State, and local agencies to make 

management, regulatory, and monitoring decisions to 

better protect, enhance, and use water resources 

(Hirsch and others, 1988). The NAWQA Program is 

designed so that the study units constitute the principal 

building blocks of the Program. Equivalent information from individual study units can be aggregated to 

assess water-quality issues on both a regional and 

national scale. 

The long-term goals of the NAWQA Program 

are to (1) describe the water-quality conditions of a 

large representative part of the Nation’s freshwater 

streams, rivers, and aquifers; (2) describe how the 

water-quality conditions are changing over time; and 

(3) provide a sound, scientific understanding of the 

major natural and human factors that affect these 

water-quality conditions (Leahy and others, 1990; 

Leahy and Wilbur, 1991). The NAWQA Program uses 

an integrated approach to assess water quality. 

Multiple lines of evidence, including physical, chemical, and biological information, are collected to determine water-quality conditions.

Design of a water-quality assessment generally 

considers the environmental setting of the hydrologic 

system because interactions between the different components of the system determine the degree of difference in water-quality conditions throughout the basin. 

An effective regional water-quality assessment strategy 

is based on the environmental setting, which incorporates many interrelated features, including physiography, geology, land use, climate, and hydrology.

Purpose and Scope

This report describes the natural and cultural 

factors that are believed to control or have a large-scale 

or regional influence on the current water quality of 

the Mobile River Basin. This information defines the 

environmental setting, which will be evaluated as the 

first step in designing and conducting a multidisciplinary water-quality assessment of the basin. Historical and recent information collected from Federal, 

State, and local agencies are used as baseline information in the report. The information also is available for 

future data analyses that could address specific waterquality issues of the study unit. A description of physiography, geology, soils, climate, hydrology, habitat, 

and aquatic biology that largely determine the natural 

background quality of water is included in this report. 

A description of the cultural features of population, 

and land- and water-use practices defining the human 

influence on water quality also is included. 

Acknowledgments

The authors are grateful for the assistance provided by members of the Mobile River Basin 

NAWQA Liaison Committee who represent Federal, 

State, local, and private agencies in Alabama, Georgia, 

Mississippi, and Tennessee. Additionally, the authors 

recognize Chris Jackson, Joanne Richardson, 

Joseph F. Connell, and Amy C. Gill for their data 

compilation efforts.

ENVIRONMENTAL SETTING OF THE 

MOBILE RIVER BASIN

The environmental setting of the Mobile River 

Basin is a complex combination of natural and human 
Environmental Setting of the Mobile River Basin 3

Tenn.

Ga.

Miss. Ala.

Figure 1. Location of the Mobile River Basin, Alabama, Georgia, Mississippi, and Tennessee.

TENN.

MISS.

ALA.

GA.

H. Neely Henry L.

William 'Bill' Dannelly

Reservoir

Jordan L.

Mitchel L.

Lay L.

Smith L.

Weiss L.

Lake Tuscaloosa

Lake

Purdy

Allatoona

Reservoir

Carters L.

R. L. Harris

Reservoir

Logan Martin L.

Martin L.

Mobile R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coosawattee R.

Conasauga R.

Oostanaula R.

Etowah R.

Ta ll a p o osa R.

Coosa R.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

50 MILES

0 50 KILOMETERS

0

Mount

Vernon

Base from U.S. Geological Survey

digital line graph, 1:2,000,000, 1972

National Water-Quality Assessment study units Index map

Study Unit

Mobile River Basin Study Unit
4 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Tuscaloosa

Birmingham

Gadsden

Anniston Atlanta

Montgomery

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Shaded relief modified from U.S.

Geological Survey digital elevation data, 30-arc seconds.

Elevation, in feet

EXPLANATION

0

650

2,300

4,100

TENN.

ALA.

GA.

FLA.

MISS.

Figure 2. Topography of the Mobile River Basin.

Mobile

50 MILES

0 50 KILOMETERS

0

factors. This diversity, in part, comes from the basin 

landscape, which ranges from steep mountains and 

plateaus in the northeast to broad, flat plains and rolling hills to the south and west (fig. 2). This variable 

landscape correlates with natural changes in geology 

and hydrology. Cultural influences in the basin include 

abundant rural expanses of forested areas, cropland, 

and pastures that are interspersed with cities and small 

towns. These combinations of natural and human factors are the principal influences on water quality. 

Natural Factors

The physiography, geology, soils, climate, 

hydrology, and ecology of the Mobile River Basin all 

combine to create a unique, diverse setting. The geology and soils are the primary factors affecting the 

chemical composition of ground and surface waters. 

These natural factors discussed in this report are those 

which generally control water-quality characteristics 

in the absence of human activities.
Environmental Setting of the Mobile River Basin 5

Physiography

The Mobile River Basin encompasses parts of 

five physiographic provinces (fig. 3). Fifty-six percent 

of the basin lies within the East Gulf Coastal Plain section of the Coastal Plain Physiographic Province 

(referred to in this report as the Coastal Plain Physiographic Province). The northeastern part of the basin 

lies, from west to east, within the Cumberland Plateau 

section of the Appalachian Plateaus Physiographic 

Province (referred to in this report as the Cumberland 

Plateau), the Valley and Ridge Physiographic Province, the Piedmont Physiographic Province, and the 

Blue Ridge Physiographic Province. 

Non-Coastal Plain Physiographic Provinces

About 44 percent of the Mobile River Basin lies 

within the non-Coastal Plain Provinces. Of these provinces, the Valley and Ridge accounts for 16 percent of 

the basin; the Piedmont, 15 percent; the Cumberland 

Plateau, 12 percent; and the Blue Ridge, 1 percent. 

These four provinces occupy the northern part of the 

study unit and include a wide range of geologic and 

topographic settings. 

The boundary between the Coastal Plain and the 

non-Coastal Plain Provinces is marked by the Fall 

Line, or more accurately a zone along which the rivers 

and streams flow across resistant rocks that mark the 

boundary between these two provinces. River channels along the Fall Line are characterized by shoals 

and rapids produced by preferred erosion of the poorly 

consolidated Coastal Plain sediments (Journey and 

Atkins, 1997). 

Blue Ridge and Piedmont Physiographic Provinces

The northeastern corner of the Mobile River 

Basin lies within the southern tip of the Blue Ridge 

Physiographic Province and is dominated by rugged 

mountains and ridges as high as 4,100 feet above sea 

level. The Piedmont borders the Blue Ridge Physiographic Province to the south (fig. 3). The Blue Ridge 

and Piedmont Physiographic Provinces are underlain 

mostly by Precambrian-age and older Paleozoic-age 

crystalline rocks that form the core of the ancient 

Appalachian Mountains. When first formed, the 

mountains would have rivaled the present day 

Himalayas in elevation. Over the intervening 200 million years, however, the mountains have eroded to 

their present level (McConnell, 1998). The Piedmont 

Physiographic Province is the nonmountainous part of 

the older Appalachians. Rarely is the land surface parallel to bedrock, and nowhere is the original surface 

preserved (Sanders and others, 1999). The Blue Ridge 

is distinguished from the Piedmont primarily by its 

greater topographic relief (Clark and Zisa, 1976). The 

Piedmont forms a well-dissected upland characterized 

by rounded interstream areas to the north and by rolling topography, indicative of a dissected peneplain of 

advanced erosional maturity, to the south (Chandler 

and Lines, 1974). Land-surface altitude in the Piedmont ranges from about 500 to 1,500 feet above sea 

level.

Valley and Ridge Physiographic Province

The Valley and Ridge Physiographic Province 

consists of a series of northeast-trending linear ridges 

and valleys underlain by alternating beds of hard and 

soft Paleozoic sedimentary rocks, which are highly 

faulted and folded and range in age from Cambrian to 

Pennsylvanian. Resistant sandstone and chert underlie 

the ridges, and softer shale and limestone underlie the 

valleys. Altitudes in the Mobile River Basin range 

from 600 to 1,600 feet above sea level on the ridges to 

400 to 900 feet in the valleys (Robinson and others, 

1997). 

Cumberland Plateau

The north-central part of the Mobile River Basin 

lies within the Cumberland Plateau section of the 

Appalachian Plateaus Physiographic Province. The 

Appalachian Plateaus includes nearly horizontal layers 

of Mississippian- and Pennsylvanian-age rocks formed 

adjacent to the ancient Appalachians. Sediment eroded 

from the mountains was carried westward by streams 

and deposited in deltas in the area now called the 

Appalachian Plateaus (McConnell, 1998). The Cumberland Plateau consists of rock similar to the Valley 

and Ridge, but lacks the many folds and faults of the 

Valley and Ridge. This region is a submaturely to 

maturely dissected upland underlain by nearly flatlying rocks of Pennsylvanian age, but the region also 

contains anticlinal valleys of older Paleozoic-age 

limestone and dolomite. Altitudes range from 1,500 to 

2,000 feet above sea level in the northeast to about 

500 feet above sea level in the western part of the 

Cumberland Plateau.
6 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TENN.

MISS.

ALA.

GA.

Mobile

R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coosawattee R.

Conasauga R.

Oostanaula R.

Etowah R.

Ta ll a p o osa R.

Coosa R.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

Figure 3. Physiography of the Mobile River Basin.

50 MILES

0 50 KILOMETERS

0

Modified from Stephenson and Monroe, 1940;

Sapp and Emplaincourt, 1975; and O'Hara, 1996

Base from U.S. Geological Survey

1:2,000,000 digital data, 1972

Physiography

Blue Ridge Physiographic Province

Piedmont Physiographic Province

Valley and Ridge Physiographic Province

Cumberland Plateau Section of the

Appalachian Plateau Physiographic Province

Fall Line Hills District

Black Prairie Belt District

Alluvial-Deltaic Plain District

EXPLANATION

East Gulf Coastal Plain Section of the

Coastal Plain Physiographic Province

Southern Hills District

Chunnenuggee Hills/

Pontotco Ridge

Southern Red Hills/

North Central Hills

Lime Hills

Southern Pine Hills

Fall line
Environmental Setting of the Mobile River Basin 7

Coastal Plain Physiographic Province

The Coastal Plain Physiographic Province is 

separated into four districts: (1) Fall Line Hills, 

(2) Black Prairie Belt, (3) Southern Hills, and 

(4) Alluvial-Deltaic Plain (fig. 3). The Coastal Plain is 

underlain by Mesozoic- and Cenozoic-age sediments 

and sedimentary rocks that dip gently westward and 

southward at about 20 to 40 feet per mile (ft/mi) and 

increase to as much as 50 ft/mi near the coast (Davis, 

1988). Outcrops of resistant beds form asymmetrical 

ridges that gently slope southward forming a series of 

curved, hilly belts trending southeast to east. The location of each district is determined largely by the geologic character of the underlying sediments.

The Fall Line Hills is a dissected upland with a 

few broad, flat ridges separated by valleys ranging 

from 100 to 200 feet deep. The Fall Line Hills occupies a zone where streams descend from resistant sedimentary and crystalline rocks of the Piedmont, Valley 

and Ridge, and Cumberland Plateau Physiographic 

Provinces to the less resistant sand and clay of the 

Coastal Plain. Altitudes range from more than 700 feet 

above sea level in the northwestern part of the basin to 

about 250 feet above sea level along the northern edge 

of the Black Prairie Belt.

The Black Prairie Belt lies to the south and west 

of the Fall Line Hills and occupies a crescent-shaped 

area, extending from northeastern Mississippi into 

central Alabama. The area is characterized by an 

undulating, deeply weathered plain of low relief. Valley bottoms lie at altitudes of about 250 feet above sea 

level (Davis, 1988). The Black Prairie Belt is underlain by chalk of Cretaceous age.

The Alluvial-Deltaic Plain is a flat expanse 

characterized by sinuous stream courses, swamps, and 

poorly defined drainage divides. The district is separated into Quaternary-age alluvial deposits of sand, 

gravel, clay, and silt that make up the flood plains and 

river terraces along the major rivers in the Mobile 

River system (Stephenson and Monroe, 1940), and 

deltaic deposits that form the flood plains along the 

tidally influenced streams in the southernmost part of 

the basin (fig. 3). 

The Southern Hills (fig. 3) lies west and south of 

the Black Prairie Belt and is characterized by a series 

of hills underlain by sediments and poorly consolidated sedimentary rocks (O’Hara, 1996; Sapp and 

Emplaincourt, 1975). The northernmost series of hills 

is the Pontotoc Ridge in northeastern Mississippi and 

the Chunnenuggee Hills in Alabama. The Pontotoc 

Ridge and Chunnenuggee Hills are a pine-forested 

series of sand hills and cuestas (or hogback ridges) 

developed on chalk beds to the west and on more 

resistant clay, siltstone, and sandstone to the east. The 

North Central Hills and Southern Red Hills lie at an 

altitude of about 600 feet above sea level, with local 

relief of several hundred feet. Contained within this 

area is a somewhat flat-lying surface known as the 

Flatwoods.

The Lime Hills extend eastward from near the 

Alabama-Mississippi State line. Resistant sedimentary 

rocks contribute to relief of 200 to 250 feet from valley floors to ridge crests.

The Southern Pine Hills is the southernmost of 

the series of hills in the Southern Hills district. Developed on Miocene-age estuarine deposits to the north 

and on sand and gravel of Pliocene age to the south, 

the Southern Pine Hills form an elevated southward 

sloping dissected plain, which ranges in altitude from 

about 100 to 400 feet above sea level.

Geology

The major geologic units comprising the basin 

and described in this report were modified from King 

and Beikman (1974) (fig. 4). The study area can be 

divided into four broad categories of geologic structure: (1) flat-lying Paleozoic-age sedimentary rocks 

that underlie the Cumberland Plateau; (2) Paleozoicage sedimentary rocks folded into a series of anticlines 

and synclines in the Valley and Ridge Physiographic 

Province, where resistant rocks form ridges and more 

easily eroded rocks underlie the valleys; (3) intensely 

deformed metamorphic rocks that have been intruded 

by small to large bodies of igneous rocks in the Piedmont and Blue Ridge Physiographic Provinces; and 

(4) gently dipping, poorly consolidated to unconsolidated sediments of the Coastal Plain (Miller, 1990).

The Valley and Ridge Physiographic Province is 

characterized by a succession of subparallel northeasttrending ridges that are composed of cherty limestone, 

dolomite, and sandstones; the valleys are developed in 

more soluble limestone, dolomite, and shale 

(DeBuchananne and Richardson, 1956). These 

Paleozoic-age rocks of fluvial and marine origin are 

folded, faulted, and thrusted clastic and carbonate 

rocks that have been only locally metamorphosed 

(Mooty and Kidd, 1997). Predominant rock types are, 

in order of abundance, carbonate rock (dolomite and 

limestone), shale, and sandstone (Colton, 1970).
8 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Quarternary clastic sediments

Pliocene and Miocene clastic sediments

Oligocene, Eocene, Paleocene clastic

sediments and porous limestone

Cretaceous clastic sediments

Cretaceous chalk

Pennsylvanian siliclastic rocks

Mississippian carbonate rocks

Devonian through Cambrian sedimentary

rocks

Upper Paleozoic cataclastic rocks

Silurian through Cambrian phylite,

quartzite, and mica schist

Lower Paleozoic and Precambrian felsic

gneiss and granite

Precambrian quartzite, mica schist,

and gneiss

EXPLANATION

TENN.

MISS.

ALA.

GA.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston Atlanta

Montgomery

Mobile

50 MILES

0 50 KILOMETERS

0

Figure 4. Generalized geology of the Mobile River Basin.

Base map from U.S. Geological Survey

digital data, 1:2,000,000

Geology modified from King

and Beikman, 1974
Environmental Setting of the Mobile River Basin 9

The Cumberland Plateau Physiographic Province also is underlain by rocks of Paleozoic age. These 

rocks are similar to those in the Valley and Ridge, but 

deformation of rocks is less intense than that found in 

the Valley and Ridge (Robinson and others, 1997). The 

bedrock is a sequence of mostly horizontal Pennsylvanian sandstone, shale, conglomerate, and coal and is 

underlain by Mississippian-age and older shale and 

carbonates. The Pennsylvanian-age rocks have low 

permeability except where fractured (Zurawski, 1978).

The Piedmont and Blue Ridge Provinces are 

underlain by complex sequences of igneous rocks, 

mostly granites and lesser amounts of diorite and gabbro, of Precambrian to Paleozoic age and extensively 

folded and faulted metamorphic rocks of late Precambrian to Permian age (Miller, 1990); in the Piedmont, 

isolated igneous rocks of Mesozoic age also are 

present (Chapman and Peck, 1997). The rocks are 

characterized by a complex outcrop and subsurface 

distribution pattern, and can vary significantly on the 

scale of a few tens of feet within the same lithologic 

unit. The Piedmont contains major fault zones that 

generally trend northeast-southwest and form the 

boundaries between major rock groups (Georgia Geologic Survey, 1976). The regolith covering these crystalline igneous and metamorphic rocks ranges in 

thickness from a few to more than 150 feet, depending 

upon the type of parent rock, topography, and hydrogeologic history. Regolith thickness generally is less in 

the Blue Ridge Province than in the Piedmont because 

of the steeper slopes (Schmitt and others, 1989; Brackett and others, 1991).

The Coastal Plain Physiographic Province is 

underlain by a thick wedge of unconsolidated to 

poorly consolidated clastic and carbonate rocks, which 

dip generally toward the west and southwest in the 

western part of the study area and toward the Gulf of 

Mexico in the southern part. Cyclic transgressions and 

regressions of the sea occurred during the Cretaceous 

and Tertiary periods, which deposited the sediments 

that now make up the Coastal Plain Physiographic 

Province (Mallory, 1993). The Cretaceous sediments 

are of fluvial and marine origin. Older units are 

exposed near the Fall Line, and progressively younger 

units crop out at land surface to the west and south 

toward the Gulf of Mexico. The thickness of sediments 

increases downdip to an estimated 21,000 feet near the 

coast (Davis, 1988).

Soils

Soil is a natural mixture of mineral and organic 

ingredients. The type of soil formed in a particular 

region is strongly influenced by the climate, parent 

material, landscape relief, and biological factors. These 

factors interact dynamically over a period of time ranging from recent events to ancient times to produce soil 

profiles that vary with depth and complexity. 

The wide range of geologic, topographic, and 

climatic conditions in the Mobile River Basin produce 

widely varying soil types. The various soil types are 

used to divide the basin into seven Major Land 

Resource Areas (MLRA): the Eastern Gulf Coast Flatwoods, Southern Coastal Plain, Blackland Prairies, 

Southern Appalachian Ridges and Valleys, Sand 

Mountain, Southern Piedmont, and Blue Ridge 

(fig. 5). An MLRA is a geographic land area characterized by a particular combination or pattern of soils, 

climate, water-resources, land-use, and agricultural 

practices. Detailed county-scale soil surveys identify 

several major soil series within each MLRA. A soil 

series is a part of the land area with similar soil properties, such as color, texture, soil horizons, and depth to 

bedrock (U.S. Department of Agriculture, Soil Conservation Service, 1981).

The Eastern Gulf Coast Flatwoods, the Southern 

Coastal Plain, and the Blackland Prairies MLRAs are 

located within the Coastal Plain Physiographic Province. The Eastern Gulf Coast Flatwoods overlaps the 

Alluvial-Deltaic Plain district in the southern part of 

the Mobile River Basin. The soil series comprising 

this MLRA consist primarily of the peaty, mucky Dorovan, the sandy loamy Osier, and the loamy Cahaba 

series, all of which are poorly drained. The Southern 

Coastal Plain includes the Southern Hills district and 

the Fall Line Hills district of the Coastal Plain Physiographic Province. A distinction exists between soil 

characteristics in the Fall Line Hills and the Southern 

Hills districts. The soils of the Fall Line Hills district 

consist mainly of the Smithdale, Luverne, and Savannah soil series, which have a sandy loam or loam surface and loamy or clayey subsoil underlain by a dense, 

impermeable layer or fragipan. The soils of the Southern Hills district in the study area consist mainly of the 

Smithdale and Luverne series, which have a clayey 

loamy subsoil (U.S. Department of Agriculture, Natural Resources Conservation Service, 2001).

The Black Prairie Belt district and the corresponding Blackland Prairie MLRA were named for 

the dark surface colors of the clayey soils, which are 

formed from alkaline chalk or acid marine clay 
10 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Figure 5. Major land resource areas within the Mobile River Basin.

Base map from U.S. Geological Survey

digital data,1:2,000,000

Modified from U.S. Department of Agriculture,

Soil Conservation Service, 1981

50 MILES

0 50 KILOMETERS

0

Major Land Resource Area

EXPLANATION

Eastern Gulf Coast Flatwoods

Southern Coastal Plain

Blackland Prairies

Southern Appalachian Ridges and Valleys

Sand Mountain

Southern Piedmont

Blue Ridge
Environmental Setting of the Mobile River Basin 11

deposits. These clayey soils (vertisols) have low infiltration; they shrink and crack when dry and swell 

when wet. Sumter soil series typically overlie the 

chalk deposits and the Oktibbeha soil series are typical 

of the marine clay. 

The Valley and Ridge Physiographic Province is 

included in the Southern Appalachian Ridges and Valleys MLRA. Soils formed in the valleys in this region 

differ from those formed on the ridges. Soils in the 

valleys of the Southern Appalachian Ridges and Valleys were formed mainly in residuum of weathered 

limestone and are predominantly red, iron- and clayrich types with silt loam surface textures. Decatur and 

Dewey soils are common soil series in the valleys. The 

ridges consist of cherty limestones that produce a 

gravelly loam and gravelly clay subsoil and a gravelly 

silt loam surface layer. Bodine and Fullerton soil series 

cover an extensive part of this landscape.

The Sand Mountain MLRA consists of soils 

formed on the Cumberland Plateau. The soils are 

derived from the predominant sandstone and shale 

units. The soils are gravelly to clayey loam of the 

Montevallo and Townley series, which are found 

along the steep slopes, and loamy to clayey loamy 

soils of the Hartselle, Wynnville, and Albertville, 

which are present in the valleys and found along flatter 

slopes. 

The soils of the Southern Piedmont MLRA are 

formed from the weathering of crystalline rocks, such 

as granite, gneiss, mica schists, and slate. The soil 

types range from clayey loamy soils over schist and 

slate to gravelly loamy soils over gneiss and granite. 

The clayey loamy soils are predominantly Cecil, Tallapoosa, and Madison series, and the gravelly loamy 

soils are of Appling, Cecil, and Gwinnett series. These 

soils tend to be acidic and low in nitrogen and phosphorus.

The Blue Ridge MLRA comprises soils that 

formed within the Blue Ridge Physiographic Province 

from the weathering of crystalline and metamorphic 

rocks. Dominant soils of the Blue Ridge are moderately deep and medium textured. Ashe, Chandler, 

Edneyville, Porters, and Saluda series are the principal 

soils found on steep slopes. Clifton, Edneyville, 

Evard, Fannin, and Hayesville series are found on the 

ridge tops and side slopes of the rolling foothills. 

Bradson, Brevard, Dyke, Tate, and Tusquitee series 

are formed on foot slopes and in coves. Boulders and 

outcrops of bedrock are conspicuous but not extensive 

on mountain slopes (U.S. Department of Agriculture, 

Natural Resources Conservation Service, 1992).

Climate

The climate in the Mobile River Basin is warm 

and humid, ranging from temperate at higher elevations to subtropical near the coast. The land-surface 

altitude and distance from the Gulf of Mexico are 

major factors influencing climate in the basin. In the 

summer months, the Gulf of Mexico produces warm, 

humid air masses that move inland and provide precipitation in the form of thunderstorms, especially near 

the coast. Arctic fronts that move south from the midwestern part of the continent contribute most of the 

precipitation in the winter months. 

Precipitation in the Mobile River Basin is 

mainly rainfall with amounts evenly distributed 

throughout the year; a distinct dry period usually 

occurs during midsummer to late fall (fig. 6), but the 

pattern may be disrupted by tropical depressions, 

storms, and hurricanes, which enter the Gulf of Mexico and move inland in the late summer and early fall. 

These storms may produce an overabundance of rainfall and flooding. Snowfall accumulation is rare, with 

annual averages generally less than an inch. Areas of 

the basin with higher altitudes, such as Rome, Ga., and 

Birmingham, Ala., have an average annual snowfall of 

about 2 inches. 

Mean annual precipitation (fig. 6, table 1) from 

1961 through 1990, ranged from 53.4 in/yr in Montgomery, Ala., in the eastern part of the basin, to 

64 in/yr in Mobile, Ala., near the coast (National Oceanic and Atmospheric Administration, 1998). Mean 

monthly precipitation data were obtained for five 

National Weather Service cooperative stations located 

within or near the Mobile River Basin at Mobile, 

Montgomery, and Birmingham, Ala., Atlanta, Ga., and 

Tupelo, Miss. The lowest mean monthly precipitation 

occurred in October, and ranged from 2.45 to 

3.42 inches for Montgomery and Tupelo, respectively. 

Generally, the highest mean monthly precipitation 

occurred in March and ranged from 5.77 to 6.26 inches 

for Atlanta and Montgomery, respectively. Exceptions 

included Mobile, where the highest mean monthly precipitation occurred during the periods of greatest tropical activity in July and August (6.85 and 6.96 inches, 

respectively), and Tupelo, where the highest mean 

monthly precipitation was in December (6.16 inches) 

and the lowest was in August (3.05 inches).
12 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TE

MISS.

ALA.

GA.

89

34

85

88

87 86

35

85

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Tupelo

Birmingham

Gadsden

Anniston

Atlan

Montgomery

Mobile

Base map from U.S. Geological Surveydigital data, 1:2,000,000

54

60

62

64

60

56

58

58

56

60

56

54

54

56

58

56

58

58

56

56

54

60

52

62

50 MILES

0 50 KILOMETERS0

01234567

0

2

3

4

5

6

7

Mean monthly precipitation, in inches

01234567

Birmingham, Ala.

Mean monthly precipitation, in inches 0

1234567

Tupelo, Miss.

January

February

March

April

May

June

July

August

September

October

November

December

01234567

Mobile, Ala.

Figure 6. Mean annual precipitation for the Mobile River Basin and mean monthly precipitation for selected sites, 1961-90. (Source: P

National Oceanic and Atmospheric Administration, 1998.)

EXPLANATION

Mean Annual Precipitation—Contour

interval is 2 inches
Environmental Setting of the Mobile River Basin 13

Mean annual temperatures for the Mobile River 

Basin ranged from 56 o

F in the northeastern part of the 

basin to 68 o

F near the coast for the period of 1961 to 

1990 (fig. 7). Mean monthly temperature data were 

obtained for the five National Weather Service cooperative stations. The lowest mean monthly temperature 

was in January for all five sites and ranged from 

39.9 o

F in Tupelo to 49.9 oF in Mobile. The highest 

mean monthly temperature was in July for all five sites 

and ranged from 78.8 oF in Atlanta to 82.3 oF in 

Mobile, near the coast. 

Hydrology

The Mobile River Basin has abundant water 

resources. The streams and rivers provide water for 

many uses, and ground water is available from numerous aquifers throughout the basin. Flow in the two 

major rivers, the Alabama and Tombigbee Rivers, is 

generally regulated by upstream reservoirs, floodcontrol and navigational locks, and dams and hydroelectric plants. 

Surface Water

The Mobile River Basin comprises seven major 

rivers. The Mobile River is formed by the confluence 

of two of these major rivers (fig. 8) near Mount Vernon, Ala. (fig. 1)—the Tombigbee River to the west, 

which has headwaters in northeastern Mississippi, and 

the Alabama River to the east, which has headwaters 

in northwestern Georgia and the southeastern corner of 

Tennessee. These two river basins can be further 

divided into seven subbasins. The Black Warrior River 

is a major tributary to the Tombigbee River with the 

confluence near Demopolis, Ala. The Alabama River 

is formed by the confluence of the Coosa and Tallapoosa Rivers near Montgomery, Ala.; and the 

Cahaba River, also a major tributary, joins the Alabama River downstream from Selma, Ala. Downstream from the confluence of the Tombigbee and 

Alabama Rivers, the Mobile River has formed a deltaic plain across which flow several distributaries that 

drain into Mobile Bay and, subsequently, into the Gulf 

of Mexico (fig. 2). The Mobile River system has been 

estimated to contribute approximately 95 percent of 

the freshwater inflow to Mobile Bay (Loyacano and 

Smith, 1979).

Streamflow Characteristics

The total average annual surface-water discharge from the Mobile River Basin is estimated to be 

about 62,100 ft3

/s (U.S. Army Corps of Engineers, 

written commun., 1974). Approximately 47 percent of 

this discharge is contributed from the Tombigbee 

River and 52 percent from the Alabama River. Mean 

annual discharge data from 1923 to 1999 (fig. 9) was 

calulated by using available discharge data from 

USGS streamgaging stations. About 2,800 ft3

/s (8 percent) of the Alabama River’s discharge comes from 

the Cahaba River, 7,300 ft3

/s (22 percent) from the 

Tallapoosa River, and about 16,400 ft3/s (49 percent) 

from the Coosa River. The Black Warrior River is the 

Table 1. Summary of climatic data for cooperative weather stations in the Mobile River Basin, 1961-90

[

oF, degree Fahrenheit; Data from National Oceanic and Atmospheric Administration, 1998]

National Weather Service cooperative station Mean annual 

temperature

(

oF)

Mean annual 

precipitation

Location Number (inches)

Birmingham Municipal Airport

Birmingham, Alabama.

010831 61.8 54.6

Montgomery Dannelly Airport

Montgomery, Alabama.

015550 64.9 53.4

Mobile Regional Airport

Mobile, Alabama.

015478 67.5 64.0

Tupelo Lemons Airport

Tupelo, Mississippi.

229003 61.7 55.9

Atlanta Hartsfield Airport

Atlanta, Georgia.

090451 61.3 50.8
14 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TE

MISS.

ALA.

GA.

Mobile R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coo

Conasauga R

Oostanaula R.

Etowah 

Ta ll a p o osa R.

Coosa R.

89

34

85

88

87

86

35

85

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Tupelo

Birmingham

Gadsden

Anniston

Atlan

Montgomery

Mobile

58

58

59

61

65

66

67

64

61

60

63

60

59

59

62

66

50 MILES

0 50 KILOMETERS0

January

February

March

April

May

June

July

August

September

October

November

December30

405060708090

Mobile, Ala.

30405060708090

Birmingham, Ala.

30405060708090

Tupelo, Miss.

Mean monthly temperature, in degrees Fahrenheit

Figure 7. Mean annual temperature for the Mobile River Basin and mean monthly temperature for selected stations, 1961-90. (Smodified from National Oceanic and Atmospheric Administration, 1998.)

Base map from U.S. Geological Surveydigital data, 1:2,000,000

EXPLANATION

Mean Annual Temperature—Contour

interval is 1 degree fahrenheit
Environmental Setting of the Mobile River Basin 15

Figure 8. Major river systems and dam locations in the Mobile River Basin.

TN.

MISS.

ALA.

GA.

Mobile R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coosawattee R.

Conasauga R.

Oostanaula R.

Etowah R.

Ta ll a p o osa R.

Coosa R.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tombigbee

Alabama

Black Warrior

Tallapoosa

Coosa

Cahaba

Mobile

Dam locations modified from

Ruddy and Hitt, 1990

Base map from U.S. Geological Survey

digital data, 1:2,000,000

Drainage Basin

EXPLANATION

50 MILES

0 50 KILOMETERS

0

1

2 26 32

31

30 4 3

29

25 23

5

27 19 15 6

24 20 33

21

7 34

22 8

12 9 14 10 13

35

16

17

36 18

11

28

11 Dam location and

number (see table 3)

Demopolis

Selma
16 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TENN.

MISS.

ALA.

GA.

20 Line of equal annual

runoff, in inches

EXPLANATION

Base map from U.S. Geological Survey

digital data 1:2,000,000

Runoff data modified from Gebert

and others, 1987

Mobile R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Ta ll a p o osa R.

Coosa R.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

Figure 9. Mean annual runoff (1961-90) and mean annual discharge (1923-99) for the Mobile River Basin.

70,000

30,000

10,000

5,000

1,000

Discharge, in cubic

feet per second

24

30 28 26

24

18

20

22

24

25

26

30

25

22

20

22

20

18

28

24

50 MILES

0 50 KILOMETERS

0
Environmental Setting of the Mobile River Basin 17

major contributor to the Tombigbee River, providing 

about 33 percent of the mean annual flow (9,900 ft3

/s). 

Six streamgaging stations were selected to be 

representative of streamflow characteristics in the different physiographic settings in the Mobile River 

Basin (fig. 10). Variations in streamflow were determined by analyzing discharge data collected from the 

six streamgaging stations. Streamflow varies seasonally in response to precipitation and evapotranspiration. The mean daily discharge shows a consistent 

trend across the basin with the highest median discharge occurring in February and the lowest median 

occurring during the summer months. Maximum mean 

daily discharges for the six sites occurred from January through March. Flow duration curves for the six 

sites were normalized for the contributing drainage 

areas to eliminate the effect of the different basin sizes 

(fig. 11). The shapes of the curves reflect the underlying soil type and geologic characteristics typical of the 

different physiographies in the basin. For instance, 

Catoma Creek in the Black Prairie Belt district has a 

lower base flow and tends to go dry more frequently 

than streams in other areas of the Mobile River Basin. 

Mulberry Creek in the Fall Line Hills district and the 

Cahaba River in the Valley and Ridge Physiographic 

Province have higher base flows than streams in other 

areas of the Mobile River Basin. 

Mean Annual Runoff

Runoff is the water that drains from the land surface into stream or river channels after precipitation. 

Runoff is influenced by precipitation amounts, topography, geology, soil moisture, and other factors. Mean 

annual runoff per square mile of basin, which is computed by dividing the mean annual volume of water 

leaving the basin (measured as streamflow at a gaging 

station) by the area of that basin, is commonly used to 

compare runoff characteristics between basins. 

Mean annual runoff within the Mobile River 

Basin (Gebert and others, 1987) ranges from 18 in/yr 

in the Montgomery area to 30 in/yr in the Birmingham 

area and in the Blue Ridge Mountains (fig. 9). The 

mean annual runoff increases in the southern part of 

the basin reflecting increased annual precipitation 

from the proximity of this area to the Gulf of Mexico. 

The mean annual runoff in the Birmingham area is 

influenced partly by the amount of urbanization and 

subsequent increase in impermeable area. The higher 

mean annual runoff in the northeastern corner of the 

study unit is the result of greater precipitation and 

steeper slopes in the Blue Ridge Mountains, which are 

underlain by less permeable rocks than other parts of 

the basin.

Ground Water

The numerous aquifers in the Mobile River 

Basin range in composition from unconsolidated sand 

to hard, fractured crystalline rocks. These aquifers, 

grouped into four major aquifers or aquifer systems on 

the basis of the different rock types and ground-water 

flow systems, are the Southeastern Coastal Plain aquifer system, Valley and Ridge aquifers, the Appalachian Plateaus aquifers, and Piedmont and Blue Ridge 

aquifers (fig. 12, table 2) (U.S. Geological Survey, 

1998). In general, ground-water flow in all of the aquifers in the Mobile River Basin is south-southwest 

towards the Gulf of Mexico.

Southeastern Coastal Plain Aquifer System

The Southeastern Coastal Plain aquifer system 

includes four regional aquifers (fig. 12; table 2) and 

three intervening regional confining units. Rocks 

forming these confining units are exposed at the land 

surface as a series of curved bands (Miller, 1990). The 

regional aquifers are composed mostly of sand with 

minor gravel and limestone beds that locally may contain clay beds. The regional confining units are primarily clay, silt, or chalk, but locally may contain sand 

beds. Each of the four regional aquifers that compose 

the Southeastern Coastal Plain aquifer system includes 

several smaller aquifers. Even though the regional 

aquifers contain clayey confining units that locally can 

subdivide the regional aquifers, the overall wateryielding characteristics of the regional aquifers are 

similar throughout their extent. 

Recharge enters the Southeastern Coastal Plain 

aquifer system primarily from precipitation in outcrop 

areas of the aquifers. After reaching the water table, 

most of this water moves laterally and either discharges to small streams, evaporates, or is transpired 

by plants. In areas where the aquifer is unconfined, 

water moves downward generally along short flowpaths, and then horizontally towards discharge areas. 

A small percentage of ground water moves into confined parts of the aquifer where most of the movement 

is horizontal and downdip of the aquifers, along generally long flowpaths, until the water approaches discharge points, where its movement again becomes 

predominantly vertical to discharge to shallower aquifers or surface-water bodies (Miller, 1990). Near the 
18 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Figure 10. Locations and box plots of mean daily discharges for selected streamgaging stations for duration analysis representingthe different physiographies in the Mobile River Basin.

Base map from U.S. Geological Surveydigital data 1:2,000,000

Modified from Stephensonand Monroe, 1940; Sapp andEmplaincourt, 1975

50 MILES

0 50 KILOMETERS

0 

December

January

February

March

April

May

June

July

August

September

October

November

December

January

February

March

April

May

June

July

August

September

0

400

800

1,200

Mean daily discharge, in cubic feet per second Satilpa Creek near Coffeville, Ala.

Mean daily discharge, in cubic feet per second

0

2,0004,0006,0008,000

10,000 Cahaba River at Centerville, Ala.

October

November

0

1,0002,0003,0004,000

Mulberry Fork near Garden City, Ala.

Mean daily discharge, in

cubic feet per second

October

November

December

January

February

March

April

May

June

July

August

September

0

500

1,0001,5002,000 Mulberry Creek near Jones, Ala.

Mean daily discharge, in

cubic feet per second

Drainage area

164 mi2

Drainage area

365 mi2

Drainage area

1,027 mi2

Drainage area

203 mi2

02412000

02422500

02424000

02421000

02450000

02469800
Environmental Setting of the Mobile River Basin 19

02424000 Cahaba River Valley and Ridge 1027

02421000 Catoma Creek Black Prairie Belt 290

02450000 Mulberry Fork Cumberland Plateau 365

02422500 Mulberry Creek Fall Line Hills 203

02469800 Satilpa Creek Southern Hills 164

02412000 Tallapoosa River Piedmont 448

Percentage of time that flow was equaled or exceeded

Discharge per unit area, in cubic feet per second per square mile

EXPLANATION

Station

number

Stream Physiography Drainage area

(mi2)

Line

type

Figure 11. Duration curves for selected streamgaging stations representing the different physiographies

in the Mobile River Basin.

0 20 40 60 80 100

0.01

0.1

1

10

100
20 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TENN.

MISS.

ALA.

GA.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

Pliocene-Miocene aquifer

Tertiary sedimentary aquifer

system

Southeastern Coastal Plain aquifer system

Appalachian Plateaus aquifers

Floridan aquifer system

Piedmount and Blue Ridge aquifers

Valley and Ridge aquifers-siliciclastic rock

Valley and Ridge aquifers-carbonate rock

Line of geologic section

EXPLANATION

Base map from U.S. Geological Survey

digital data 1:2,000,000

Cretaceous aquifer system

Modified from Renken, 1998; Miller, 1990; and

U.S. Geological Survey, 1984

50 MILES

0 50 KILOMETERS

0

Figure 12. Major aquifer systems and generalized section in the Mobile River Basin.

A'

A

A A'

Generalized cross section (A-A') not to scale

A A'

? ? Sea Level ?

-1,000 ft

1,000 ft
Environmental Setting of the Mobile River Basin 21

coast, horizontal flow is blocked either by saltwater or 

by fine-grained sediments that reduce the permeability 

of the aquifer.

The Cretaceous aquifer system (table 2) is the 

basal aquifer of the Southeastern Coastal Plain aquifer 

system and is the most widespread of the regional 

aquifers in the system. The Cretaceous aquifer system 

consists of sand beds in the Providence Sand and the 

Ripley and Eutaw Formations and the Tuscaloosa 

Group, which includes the Gordo and Coker Formations (U.S. Geological Survey, 1984). The aquifers in 

this system are also known as the Chattahoochee River 

aquifer and the Black Warrior River aquifer (Miller, 

1990). The confining units consist of chalk and clay 

beds in the western part of the Mobile River Basin and 

marine clay beds in the eastern part of the basin 

(Davis, 1988).

The Tertiary sedimentary aquifer system 

(table 2) is a thick sequence of sand with minor sandstone and gravel and a few limestone beds. The sediments composing the aquifer range in age from 

Paleocene to late Eocene and were deposited mostly in 

marine environments. The aquifer is equivalent to the 

Mississippi embayment aquifer system to the west and 

southwest and to the Pearl River aquifer in Alabama. 

The Tertiary sedimentary aquifer system and the Floridan aquifer system are hydraulically connected. 

Locally, the upper part of the Tertiary sedimentary 

aquifer system is known as the Lisbon aquifer and the 

lower part as the Nanafalia-Clayton aquifer.

The Floridan aquifer system (table 2) consists of 

limestone of Eocene and Oligocene age. The solutionconduit aquifer occurs in sandy carbonate rocks that 

have little primary porosity or permeability. Water 

moves through secondary porosity features, such as 

solution-enlarged fractures and bedding planes that 

form a system of interconnected conduits (Kidd and 

others, 1997). The Floridan aquifer system is a minor 

contributor of ground water in the Mobile River Basin, 

but is an important, high yielding aquifer in southeastern Alabama, Georgia, and Florida.

The Pliocene-Miocene aquifer (table 2) is 

present in the southern part of the Mobile River Basin 

in southwestern Alabama (fig. 12). This aquifer, the 

youngest regional aquifer in the Southeastern Coastal 

Plain aquifer system, consists of sand and gravel beds 

in the Citronelle Formation of Pliocene age and sand 

beds in the undifferentiated Miocene Series (U.S. Geological Survey, 1984). The aquifer is a source of 

domestic and public water supplies over extensive 

Table 2. Generalized major aquifers in the Mobile River Basin

[From: U.S. Geological Survey, 1984; Mooty and Kidd, 1997; Robinson and others, 1997; Kidd and others, 1997; and Journey and Atkins, 1997.]

Major aquifer Lithology Geologic age Aquifer type

Southeastern Coastal Plain 

aquifer system 

Cretaceous aquifer system

Sand and gravel of the Gordo, 

Coker, Eutaw, and Ripley 

Formations.

Upper Cretaceous Porous media

Tertiary sedimentary aquifer 

system

Sand, clay, gravely sand Paleocene to Eocene Porous media

Floridan aquifer system Limestone Eocene and Oligocene Solution conduit

Pliocene-Miocene aquifer Sand and gravel beds of Citronelle Formation. 

Undifferentiated deposits of 

Miocene Series.

Pliocene

Miocene

Porous media

Valley and Ridge aquifers Limestone, dolomite, chert Paleozoic Solution conduit

Sandstone, shale, siltstone Paleozoic Fracture conduit

Sand and gravel, sandstone, 

sandy chalk and clay.

Cenozoic Porous media

Appalachian Plateaus aquifers Limestone, dolomite, chert Paleozoic Solution conduit

Sandstone, shale, siltstone Paleozoic Fracture conduit

Piedmont and Blue Ridge 

aquifers

Quartzite, slate, gneiss, schist, 

marble, phyllite, and granite.

Precambrian to Paleozoic Fracture conduit

Regolith, soil, alluvium, colluvium, and saprolite.Various ages Porous media
22 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

areas of southern Alabama (Kidd and others, 1997). 

The Citronelle Formation is a water-table aquifer with 

discontinuous sand beds controlling water levels 

locally (Davis, 1988). The Pliocene-Miocene aquifer 

is also known as the Chickasawhay River aquifer and 

is considered part of the Coastal Lowlands aquifer 

system.

Valley and Ridge Aquifers

Aquifers in the Valley and Ridge Physiographic 

Province consist of permeable geologic formations 

within folded and faulted Paleozoic sedimentary rocks. 

The rocks range in age from early to late Paleozoic. 

Most of the Valley and Ridge aquifers consist of limestone or dolomite. The carbonate rocks are productive 

aquifers primarily because of the solution openings in 

the easily dissolved limestone and dolomite. These 

openings, which originate as bedding planes and joints 

in the carbonate rocks, are enlarged by percolating 

slightly acidic ground water, and become linked as a 

series of conduits that rapidly transmit large volumes 

of ground water through the carbonate rocks. The easily eroded carbonate rocks form wide valley floors, 

which are favorable areas for recharge. Other aquifers 

consist of sandstone formations but yield less water 

than do the carbonate rocks. Much of the water from 

the sandstone is obtained from fractures (Mooty and 

Kidd, 1997). Regolith, which acts as a porous media 

aquifer above the carbonate-rock aquifers, contains 

chert rubble of Cenozoic age that stores and transmits 

water slowly to the underlying fractured-rock aquifer 

(Robinson and others, 1997).

Appalachian Plateaus Aquifers

Aquifers in the Cumberland Plateau section of 

the Appalachian Plateaus Physiographic Province consist of permeable stratigraphic units within flat-lying 

sedimentary rocks of Paleozoic age. Rocks comprising 

the aquifers are mostly sandstone, conglomerate, and 

coal of Pennsylvanian age, but in places include beds 

of limestone and chert of Mississippian age. A thick 

sequence of shale, sandstone, and coal overlies Mississippian limestone. Sandstone beds yield small volumes 

of water, but supply water to a large number of domestic wells because sandstone caps most of the upland 

plateaus in the Mobile River Basin (Stricklin, 1989).

Most of the water in both limestone and sandstone is present in fractures. In the limestone, the circulation of slightly acidic ground water has enlarged 

fractures by dissolution of the carbonate rock. Where 

vertical fractures extend to the land surface, the 

enlarged solution conduits may become completely or 

partially filled with sediment transported into them by 

surface streams. Where unfilled, these solution openings convey large volumes of water (Miller, 1990). 

Flow in the Appalachian Plateaus aquifers is 

affected primarily by topography, structure, and the 

development of solution openings in the rocks. 

Recharge to the aquifers is by precipitation on the flat, 

mesa-like plateau tops. Water then percolates down 

through the interbedded Pennsylvanian rocks, primarily along steeply inclined joints and fractures. In 

places, shale beds retard the vertical flow and some 

water flows laterally along bedding planes, mostly in 

sandstone and conglomerate beds, and discharges as 

spring flow along steep valley walls. Some of the 

water migrates down across the thick shale confining 

unit into the underlying limestone aquifer (Miller, 

1990).

Piedmont and Blue Ridge Aquifers

The crystalline-rock aquifers that underlie the 

Piedmont and Blue Ridge Physiographic Provinces in 

the northeastern part of the Mobile River Basin are 

collectively called Piedmont and Blue Ridge aquifers 

(Miller, 1990). Although there are considerable differences in the mineralogy and texture of the rocks composing the Piedmont and Blue Ridge aquifers, the 

overall hydraulic characteristics of the aquifers are 

similar. Locally, however, the occurrence and availability of ground water varies greatly because of the 

complex variability in rock type. Such variability of 

rock type makes describing regional ground-water 

flow impractical. 

The Piedmont and Blue Ridge aquifers consist 

of crystalline bedrock overlain by regolith (unconsolidated material). Included in the regolith are: saprolite, 

which is a layer of earthy, decomposed rock developed 

by weathering of the bedrock; alluvium, which is 

mainly confined to stream valleys; colluvium, which 

consists of material transported downslope by weathering; and soil that develops on top of these layers. 

Because the crystalline rocks are formed under intense 

heat and pressure, they have few primary pore spaces, 

and the porosity and permeability of the unweathered 

and unfractured bedrock are extremely low. This does 

not mean, however, that these rocks will not yield 

water. Ground water can be obtained from the regolith 

and fractures in the rock. Locally, where the crystalline 

rocks consist of marble, the dissolving action of 
Environmental Setting of the Mobile River Basin 23

slightly acidic ground water has created solution openings that yield large volumes of water (Miller, 1990).

Water in the rocks of the Piedmont and Blue 

Ridge aquifers generally is unconfined. Locally, artesian conditions exist where wells penetrate deeply buried fractures that are hydraulically connected to 

recharge areas of higher altitudes or in places where 

the regolith is clayey and forms a confining unit (Kidd, 

1989). Water enters the ground in recharge areas, 

which include all the land surface except the lower 

parts of valleys, and then percolates vertically downward through the unsaturated zone. Water reaches the 

saturated zone (water table) and moves laterally to 

points of discharge. Water discharges as springs, 

seeps, base flow to streams, and seepage to lakes. The 

water table is a subdued replica of the surface topography. The depth to the water table varies, depending 

mainly on topography and to a lesser extent on rainfall 

(Robinson and others, 1997). 

Ecoregions

Areas where ecological systems are generally 

similar are identified as ecoregions. Ecoregions are 

based on coincident patterns of natural factors such as 

geology, physiography, vegetation, climate, soils, land 

use, wildlife, and hydrology (Omernik, 1987; Griffith 

and others, 1998). Ecoregions can provide a framework for assessing ecological conditions with respect 

to the natural environmental setting.

In an ecoregion hierarchy established by Omernik (1987), a Roman numeral classification scheme 

was adopted to prevent confusion caused by terminology associated with the different hierarchical levels. 

Level I divides the North American continent into 15 

major ecological regions. Level II subdivides the 15 

major ecological regions into 52 classes, and Level III 

further subdivides the 52 classes into 120 classes. The 

U.S. Environmental Protection Agency (U.S. EPA) 

has identified the following six Level III ecoregions 

(fig. 13) within the Mobile River Basin: (1) Southern 

Coastal Plain ecoregion lies within the deltaic part of 

the Alluvial-Deltaic Plain Physiographic district; 

(2) Southeastern Plains ecoregion lies within the 

remaining Coastal Plain Physiographic Province; 

(3) Southwestern Appalachians ecoregion is located in 

the Cumberland Plateau Physiographic Province and 

extends into the noncarbonate rock (ridges) of the Valley and Ridge Physiographic Province and the western 

part of the Piedmont Physiographic Province; 

(4) Ridge and Valley ecoregion includes the carbonate 

valleys of the Valley and Ridge Physiographic Province; (5) Piedmont ecoregion includes the eastern part 

of the Piedmont Physiographic Province; and (6) Blue 

Ridge Mountains ecoregion covers the higher altitude 

areas of the Piedmont, Valley and Ridge, and Blue 

Ridge Physiographic Provinces in the northeastern 

part of the basin (U.S. Environmental Protection 

Agency, 2000). The degree of overlap between the 

ecoregions and the physiography and geology of the 

basin indicates that the natural variations in the physiography and geology are reflected in the ecological 

systems.

The Southern Coastal Plain extends from South 

Carolina and Georgia, through much of central Florida, and along the Gulf coast lowlands of the Florida 

Panhandle, Alabama, and Mississippi (Omernik, 

1987). In the Mobile River Basin, the ecoregion is 

drained by the distributaries of the Mobile Delta and 

freshwater streams which, in turn, drain to Mobile 

Bay. These meandering, low-gradient, and sandybottomed streams flow across flat, swampy plains and 

bottomlands that characterize the topography in this 

ecoregion. Surface elevation ranges from sea level to 

approximately 100 feet above sea level. The Southern 

Coastal Plain landscape supports forest and woodland 

areas with some cropland and pasture. Once covered 

by a forest of beech, sweetgum, southern magnolia, 

slash pine, loblolly pine, white oak, and laurel oak, 

land cover in the ecoregion is now mostly longleafslash pine forest, oak-gum-cypress forest in some lowlying areas, pasture for beef cattle, and urban areas 

(Glenn Griffith, U.S. Environmental Protection 

Agency, written commun., 2000).

The Southeastern Plains ecoregion covers an 

extensive part of the Mobile River Basin. The landscape is smooth to irregular plains or flatlands separated in some places by curved bands of asymmetrical 

ridges and rugged hills. Surface elevation ranges from 

as little as 25 feet above sea level in the southernmost 

plains to over 400 feet above sea level in the hills. The 

streams draining this ecoregion are generally low gradient with silty and sandy substrates. Forest and woodland areas are prevalent and are a part of the mosaic of 

cropland, pasture, and urban areas which dot the landscape. The natural vegetative cover includes oak, hickory, pine, and southern mixed forests. The dominant 

soils are formed from the weathering of the underlying 

clastic sediments and are better drained than soils of 

the Southern Coastal Plain. Soils overlying clayey or 

chalk deposits, however, are poorly drained.
24 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

TENN.

MISS.

ALA.

GA.

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

Ridge and Valley

Piedmont

Southeastern Plains

Southwestern Appalachians

Blue Ridge Mountains

Southern Coastal Plain

Ecological Region

Figure 13. Ecological regions of the Mobile River Basin. (Modified from Omernik, 1987.)

EXPLANATION

50 MILES

0 50 KILOMETERS

0

Base map from U.S. Geological Survey

digital data, 1:2,000,000
Environmental Setting of the Mobile River Basin 25

The Southwestern Appalachians ecoregion 

extends from Kentucky to Alabama. These open low 

mountains contain a mosaic of forest and woodland 

with some cropland and pasture. The landscape is 

dominated by plateaus, hills, and mountains and is 

drained by streams of moderate gradient with cobble, 

gravel, and bedrock substrates. The surface elevation 

ranges from about 250 feet above sea level in the 

southwest to about 1,100 above sea level in the northeast. Oak, hickory, pine, and mixed forest of maple, 

tuliptree, oak, and linden are the natural forest cover 

for this area (Omernik, 1987). 

The Ridge and Valley ecoregion ranges in elevation from 600 to over 1,600 feet above sea level and is 

drained by moderate to high-gradient streams with 

cobble, gravel, and bedrock substrates. As a result of 

extreme folding and faulting, the roughly parallel 

ridges and valleys vary in width, height, and geologic 

materials, including limestone, dolomite, shale, siltstone, sandstone, chert, mudstone, and marble. Springs 

and caves are numerous. Cropland and pasture are 

prevalent with some woodland and forest. The dominant vegetative cover is Appalachian oak forest. 

The northeast-southwest trending Piedmont 

ecoregion, considered the nonmountainous part of the 

old Appalachian Highlands by physiographers, is a 

transitional area between the mostly mountainous 

ecoregions of the Appalachians to the northwest and 

the relatively flat coastal plain to the southeast. The 

area is underlain by Precambrian and Paleozoic metamorphic and igneous rocks with moderately dissected 

irregular plains with some hills. Surface elevation 

ranges from about 500 to 600 feet above sea level to 

the southwest in Alabama, to 1,500 to 1,700 feet above 

sea level in Georgia near the foot of the Blue Ridge 

Mountains. Once largely cultivated, much of this 

region has reverted to pine and hardwoods. The soils 

are finer textured and lower in organic matter and 

nutrients than the soils of the coastal plain regions.

The Blue Ridge Mountains ecoregion extends 

from southern Pennsylvania to northern Georgia, varying from narrow ridges to hilly plateaus to more massive mountainous areas with high peaks. The Blue 

Ridge Mountain part of the Mobile River Basin is in 

the northeasternmost part of the basin. This ecoregion 

accounts for only a small amount of the entire basin 

but has distinctive characteristics. The rugged mountains and ridges have surface elevations ranging from 

about 3,000 to 4,700 feet above sea level and are 

drained by high-gradient streams with cobble, gravel, 

and bedrock substrates. The landscape is covered 

mostly by ungrazed woodlands and forests. 

Aquatic Ecology

The diverse aquatic habitats in the Mobile River 

Basin sustain one of the richest aquatic fauna in North 

America. The basin’s endemic fauna include 40 fishes, 

33 mussels, 110 aquatic snails, as well as a variety of 

turtles, aquatic insects, and crustaceans (U.S. Fish and 

Wildlife Service, 1998a). However, contaminants and 

modification of aquatic habitat such as impoundments, 

channelization, dredging, and mining over the past few 

decades have resulted in the presumed extinction of at 

least 15 mussels and 38 aquatic snails (Appendix A). 

The basin also has 39 species of aquatic animals and 

plants that are currently protected under the Endangered Species Act of 1973 (U.S. Fish and Wildlife Service, 1986), including 11 fish, 17 mussels, 7 snails, 

2 turtles, and 2 plants (Appendix B). A review of other 

candidate species may substantially increase the number of species listed under the act (U.S. Fish and Wildlife Service, 1998b).

The Endangered Species Act of 1973 was established by the Federal government to protect endangered species. This act groups species in peril into two 

categories: endangered or threatened. A species is considered endangered when it is in danger of becoming 

extinct throughout all or a significant portion of its 

range. A threatened species is likely to become endangered in the near future in all or a significant part of 

their range (U.S. Fish and Wildlife Service, 1986).

Cultural Factors

Human activities have affected water quality 

and quantity in the Mobile River Basin. A series of 

locks and dams on rivers throughout the basin have 

increased flood control, improved navigation, provided hydroelectric power, and promoted many recreational activities. These dams also have had negative 

effects on the aquatic ecology of the region. The presence of the dams have resulted in lowered temperatures and dissolved oxygen concentrations in the 

tailwaters of the dams, thus adversely affecting the 

natural aquatic population and the distribution of fish. 

The lakes impounded by these dams now support different arrays of aquatic ecology than would be found 

in naturally free-flowing rivers. In addition to the 

physical alterations of the river system, as population 

growth in the Mobile River Basin has increased, 
26 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

forested and agricultural land use has changed to more 

urban and industrial applications, resulting in an 

increase in demand for water and other resources.

Study Unit Stratification

An environmental framework was developed 

for the Mobile River Basin to isolate the effects of natural and human factors that are thought to be the most 

important in affecting water quality and quantity. 

Characterizing this environmental framework is an 

important element in each study-unit investigation of 

the NAWQA Program. The environmental framework 

divides a study unit into several subareas (not necessarily contiguous) that have homogeneous combinations of those natural and human factors believed to be 

relevant to water quality (Gilliom and others, 1995). 

This process is called stratification. The identified 

strata provide a unique spatial framework to be used 

for (1) conducting a retrospective analysis of water 

quality, (2) evaluating study priorities and approaches 

for assessing water-quality conditions, (3) designing 

the monitoring program, and (4) making comparative 

assessments of water quality and ecosystems within 

the Mobile River Basin and among the hydrologic systems across the Nation. Natural factors in the Mobile 

River Basin include geology, physiography and aquifer systems. Human factors include agricultural land 

use, mining, forested land use, and urbanization. 

The Mobile River Basin was stratified based on 

the physiography with the Alluvial-Deltaic Plain district of the Coastal Plain Physiographic Province separated into the Deltaic deposits and the Alluvial aquifer 

(fig. 14). Land and water use in the Mobile River 

Basin are evaluated based on this stratification. 

County-level data for agricultural and water-use activities and population distribution were weighted to provide estimates for each strata based on the area of the 

county within each strata. These weighting approaches 

may give inaccurate results in areas where the population distribution, water-use, or agricultural activities 

vary greatly across a county, but the error introduced 

in this step is not significant for the strata encompassing large areas and multiple counties.

Reservoirs

The surface-water system in the Mobile River 

Basin is regulated by 36 dams that influence the 

hydrology of the basin (fig. 8, table 3). Streamflow in 

the Alabama River is affected by 10 reservoirs and 

hydroelectric plants upstream in the Coosa River 

Basin; 4 reservoirs and hydroelectric plants on the Tallapoosa River; and 3 navigational locks and dams on 

the Alabama River. The Cahaba River, a major tributary to the Alabama River, drains 1,820 square miles 

in central Alabama and is the largest free-flowing river 

in the Mobile River Basin. The Cahaba River Basin 

has only one reservoir, Lake Purdy (table 3), on the 

Little Cahaba River. The Tombigbee River is affected 

by 12 navigational locks and dams on the main stem. 

The Black Warrior River, a main tributary to the Tombigbee River, is affected by four navigational locks 

and dams and two reservoirs, Lake Tuscaloosa and the 

Lewis Smith Reservoir (table 3). The Tombigbee 

River is part of the Tennessee-Tombigbee waterway.

The Tennessee-Tombigbee waterway, a 

234-mile navigation channel connecting the Tombigbee River to the Tennessee River, was completed in 

1985 and is the largest manmade water-resource 

project built in the United States. The major features 

of the waterway are 12 locks and dams, a 12-foot-deep 

and 280-foot-wide canal, and 234 miles of navigation 

channels. The 12 locks are used to raise or lower 

barges and boats a total of 341 feet, the difference in 

elevation between the two ends of the waterway (The 

Tennessee Tombigbee Waterway Development 

Authority, 2001).

Land Use

Based on 1991 land-use data (U.S. Environmental Protection Agency, 1992), about 70 percent of the 

basin is forested, while agriculture, including livestock, aquaculture, row crops, and pastureland, 

accounts for about 26 percent of the study unit. Agricultural land use (fig. 15) is concentrated in an area 

corresponding to the Black Prairie Belt district of the 

Coastal Plain Physiographic Province. No agricultural 

activities are associated with the Deltaic deposits due 

to the prevalence of poorly drained soils. Urban areas 

account for only 3 percent of the total land use; however, the areal coverage of the metropolitan statistical 

areas (MSA) may indicate more urban influences.

Agriculture

The primary row crops produced in the Mobile 

River Basin include corn, soybeans, cotton, wheat, and 

sorghum. Cultivation of corn is well distributed 

throughout the Coastal Plain Physiographic Province 

with the greatest acreage in the Southern Hills and Fall 
Environmental Setting of the Mobile River Basin 27

TENN.

MISS.

ALA.

GA.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

50 MILES

0 50 KILOMETERS

0

Piedmont

Valley and Ridge

Cumberland Plateau

Fall Line Hills

Black Prairie Belt

Southern Hills

Alluvial aquifer

EXPLANATION

Deltaic deposits

Blue Ridge

Study Unit Strata

Figure 14. Study unit stratification of the Mobile River Basin.

Base map from U.S. Geological Survey

digital data, 1:2,000,000

Modified from Stephenson and Monroe, 1940; Sapp and

Emplaincourt, 1975; and Mallory, 1993
28 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Table 3. Dams and associated impoundments in the Mobile River Basin—Continued

No.

(see 

fig. 8)

Name of 

dam

Associated 

impoundment

River Agency

Date 

constructed 

or 

operational

Principal 

use

Location River

mile

Total

drainage 

area

(mi2)

Full power or 

normal pool data

Surface

area

(acres)

Storage

capacity

(acrefeet)

Coosa River Subbasin

1 Carters Carters Lake Coosawatte

River

USACOE 1974 P, FC, 

R

Murray 

County, 

Ga.

526.8 4373 43,220 1472,800

2 Carters

re-regulation 

-- Coosawatte

River

USACOE 1975 P, FC, 

R

Murray 

County, 

Ga.

5

25.3 5520 -- 117,600

3 Allatoona Allatoona

Lake

Etowah

River

USACOE 1949 P, FC, 

R

Bartow 

County, 

Ga.

547.0 41,120 419,200 1367,000

4 Weiss Weiss Lake Coosa

River

APC 1961 P, FC, 

R

Cherokee 

County, 

Ala.

2226.1 25,270 428,300 2360,400

5 H. Neely 

Henry 

H. Neely 

Henry Reservoir

Coosa

River

APC 1966 P, FC, 

R

Calhoun 

County, 

Ala.

2

146.8 26,596 411,235 2120,850

6 Logan Martin Logan Martin 

Reservoir

Coosa

River

APC 1964 P, FC,

R

St. Clair 

County, 

Ala.

2

98.5 27,743 415,260 2273,300

7 Lay Lay Lake Coosa

River

APC 1914

1968

P, FC Chilton 

County, 

Ala.

251.0 29,053 -- 46,7002144,994

2262,774

8 Mitchell Mitchell Lake Coosa

River

APC 1923 P, R Chilton 

County, 

Ala.

236.8 2

9,778 45,800 2172,000

9 Jordan Jordan Lake Coosa

River

APC 1929 P, R Elmore 

County, 

Ala.

2

18.9 210,102 44,800 2236,200

10 Walter 

Bouldin

Jordan Lake 

Diversion

Coosa

River

APC 1967 P Elmore 

County, 

Ala.

-- -- 4920 4230,000

Tallapoosa River Subbasin

11 Harris Harris ReservoirTallapoosa

River

APC 1982 P, FC, 

R

Randolph 

County, 

Ala.

2

139.0 21,453 -- --

12 Martin Lake Martin Tallapoosa

River

APC 1926 P, FC, 

R

Tallapoosa 

County, 

Ala.

2

60.6 22,984 438,300 4250,000

13 Thurlow Thurlow ReservoirTallapoosa

River

APC 1930 P Tallapoosa 

County, 

Ala.

649.7 63,308 4585 411,000

14 Yates Thurlow ReservoirTallapoosa

River

APC 1928 P, R Tallapoosa 

County, 

Ala.

6

52.7 63,293 41,920 426,000

Table 3. Dams and associated impoundments in the Mobile River Basin

[mi2, square miles; --, data not available; FC, flood control; N, navigation; P, power; WS, water supply; WQ, water quality; FW, fish and wildlife; R, recreation; 

USACOE, U.S. Army Corps of Engineers; APC, Alabama Power Company] 
Environmental Setting of the Mobile River Basin 29

Cahaba River Subbasin

15 Lake Purdy Lake Purdy Little

Cahaba

River

Birmingham

Water 

Works

Board

1911

(

41964)

WS, R,

FC

Jefferson 

County, 

Ala.

8

4.3 446.0 41,050 317,500

Alabama River Basin

16 Robert F. 

Henry Lock 

and Dam

4Jones Bluff 

Lake

Alabama

River

USACOE 1971 P, N, 

R

Lowndes 

County, 

Ala.

6245.4 416,300 412,510 4234,200

17 Millers 

Ferry Lock, 

Dam, and 

Powerhouse

William “Bill” 

Dannelly Lake

Alabama

River

USACOE 1970 P, N, 

R

Wilcox 

County, 

Ala.

6

142.3 420,700 417,200 4331,800

18 Claiborne 

Lock and 

Dam

Claiborne 

Lake

Alabama

River

-- 1969 N Monroe 

County, 

Ala.

6

81.8 621,473 45,930 496,360

Black Warrior Subbasin

19 John Hollis 

Bankhead 

Lock and 

Dam

Lake BankheadBlack

Warrior

River

APC 1928

(1975)

N Jefferson 

County, 

Ala.

2153.6 2

3,981 49,200 112,000

(usable

capacity)

4288,000

20 Holt Lock 

and Dam

Holt Lake Black

Warrior

River

USACOE 1976 N Tuscaloosa 

County, 

Ala.

2

135.1 24,219 43,296 115,000

(usable

capacity)

21 William 

Bacon 

Oliver Lock 

and Dam

William 

Bacon Oliver 

Lake

Black

Warrior

River

USACOE 41940 N Tuscaloosa 

County, 

Ala.

2125.9 2

4,820 42,220 412,500

22 Selden Lock 

and Dam

Warrior Lake Black

Warrior

River

USACOE 1946 N Hale 

County, 

Ala.

2

49.6 25,810 47,800 454,000

23 Lewis 

Smith 

Lewis Smith 

Reservoir

Sipsey

Fork

River

APC 1960 P, FC Walker 

County, 

Ala.

213.5 2945 421,000 394,000

24 Lake Tuscaloosa DamLake 

Tuscaloosa

Black

Warrior

River

City of

Tuscaloosa

1971 WS, 

FC,

R

Tuscaloosa 

County, 

Ala.

-- 2416 45,885 4130,000

Tombigbee River Basin

25 Aberdeen 

Lock and 

Dam

Aberdeen 

Lake

Tombigbee

River

USACOE 1981 N Monroe 

County, 

Miss.

6

363.0 42,170

6

2,047

4

4,121 431,564

26 Whitten 

Lock and 

Dam

Bay Springs 

Lake

Tombigbee

River

USACOE 1985 N Tishomingo 

County, 

Miss.

-- 468.2 46,700 4180,000

Table 3. Dams and associated impoundments in the Mobile River Basin—Continued

No.

(see 

fig. 8)

Name of 

dam

Associated 

impoundmentRiver Agency

Date 

constructed 

or 

operational

Principal 

use

Location River

mile

Total

drainage 

area

(mi2)

Full power or 

normal pool data

Surface

area

(acres)

Storage

capacity

(acrefeet)
30 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

1

 Stokes and McFarlane (1994)

2 Pearman and others (1997)

3

 Strickland (1994)

4 Ruddy and Hitt (1990)

5 U.S. Army Corps of Engineers (1985b)

6

 U.S. Army Corps of Engineers (1985a)

7 The Tennessee Tombigbee Waterway Development Authority (2001)

8 Rollins and others (1987)

Tombigbee River Basin—Continued

27 Stennis 

Lock and 

Dam

Columbus 

Lake

Tombigbee

River

USACOE 1978 N Lowndes 

County, 

Miss.

6

325.3 44,440 48,910 459,483

28 Amory 

Lock

Lock “A” 

Pool

Tombigbee

River

USACOE 1981 N Monroe 

County, 

Miss.

-- -- 7914 --

29 Glover 

Wilkins 

Lock

Lock “B” Pool Tombigbee

River

USACOE 1981 N Monroe 

County, 

Miss.

-- 41,226 42,718 419,039

30 Fulton Lock Lock “C” Pool Tombigbee

River

USACOE 1981 N Lowndes 

County, 

Miss.

-- -- 41,642 413,221

31 John 

Rankin 

Lock

Lock “D” 

Pool

Tombigbee

River

USACOE 1985 N Itawamba 

County, 

Miss.

-- -- 41,992 424,869

32 G.V. 

“Sonny” 

Montgomery Lock

Lock “E” Pool Tombigbee

River

USACOE 1985 N Itawamba 

County, 

Miss.

-- -- 4851 46,926

33 Tom 

Belville 

Lock and 

Dam

Aliceville 

Lake

Tombigbee

River

USACOE 1979 N, R Pickens 

County, 

Ala.

6

287.4 45,750 48,300 460,400

34 John C. 

Heflin Lock 

and Dam

Gainesville 

Lake

Tombigbee

River

USACOE 1978 N, R Greene 

County, 

Ala.

6238.8 47,220 46,400 445,290

35 Demopolis 

Lock and 

Dam

Demopolis 

Lake

Tombigbee

River

USACOE 1928

(

4

1955)

N Marengo 

County, 

Ala.

2

171.2 215,385 41,000 4150,000

36 Coffeville 

Lock and 

Dam

Coffeville 

Lake

Tombigbee

River

USACOE 1960

(

4

1962)

N Choctaw 

County, 

Ala.

274.7 218,417 8,500 4190,800

Table 3. Dams and associated impoundments in the Mobile River Basin—Continued

No.

(see 

fig. 8)

Name of 

dam

Associated 

impoundmentRiver Agency

Date 

constructed 

or 

operational

Principal 

use

Location River

mile

Total

drainage 

area

(mi2)

Full power or 

normal pool data

Surface

area

(acres)

Storage

capacity

(acrefeet)
Environmental Setting of the Mobile River Basin 31

EXPLANATION

Urban

Forest

Agriculture

Wetlands

Open water

TENN.

MISS.

ALA.

GA.

89

34 34

85

88 87

86

35

85

35

33

86 32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston Atlanta

Montgomery

Mobile

50 MILES

0 50 KILOMETERS

0

Modified from U.S. Environmental Protection Agency,

Multi-Resolution Land Characteristics Consortium,

30-meter data, 1992

Base map from U.S. Geological Survey

digital data 1:2,000,000

Figure 15. Land use in the Mobile River Basin.
32 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Line Hills districts (figs. 16 and 17). Soybeans cover 

the greatest acreage and is almost as well distributed 

as corn with the greatest concentrations in Mississippi. 

Cotton is the second highest acreage crop and is concentrated in selected areas in the Valley and Ridge and 

Cumberland Plateau Physiographic Provinces and in 

the Coastal Plain Physiographic Province (Fall Line 

Hills district, Black Prairie Belt district, Southern Hills 

district, and Alluvial aquifer). The greatest acreage of 

wheat is concentrated in selected areas in the Southern 

Hills district, Black Prairie Belt district, and the Alluvial aquifer of the Coastal Plain Physiographic Province. Sorghum acreage is not as prevalent as other 

crops but is evenly distributed across the basin, except 

in the Blue Ridge Physiographic Province and in Deltaic deposits where no sorghum is produced (U.S. 

Department of Agriculture, National Agricultural Statistics Service, 1997).

Livestock production in the Mobile River Basin 

includes poultry, cattle, and swine. The greatest density of swine production is in the Cumberland Plateau 

Physiographic Province (figs. 18 and 19). Poultry 

operations are concentrated in the northern part of the 

Mobile River Basin in Alabama and Georgia. Chicken 

production is greatest throughout the Blue Ridge and 

Cumberland Plateau Physiographic Provinces but also 

is prevalent in the Valley and Ridge and the Piedmont 

Physiographic Provinces. Broilers by far comprise the 

largest chicken operations. Cattle production is ubiquitous with the highest density of production in the Blue 

Ridge, Cumberland Plateau, and Valley and Ridge 

Physiographic Provinces. Few large cattle feedlots 

operate in the Mobile River Basin, and the majority of 

cattle are raised for beef on pastureland (U.S. Department of Agriculture, National Agricultural Statistics 

Service, 1997).

Urban

The total population for the Mobile River Basin 

was about 3,673,100 people in 1990 based on estimates of county population (U.S. Bureau of the Census, 2001). Urban areas account for only 3 percent of 

the total land use; however, the areal extent of the 

MSAs may indicate more urban influences. The MSAs 

include urban areas outside metropolitan boundaries 

and can include adjacent counties. Seven MSAs are 

delineated in the Mobile River Basin and include 

Montgomery, Mobile, Tuscaloosa, Birmingham, 

Gadsden, Anniston, and Atlanta (fig. 20). The cities 

with their entire MSAs included in the study area are 

Birmingham with a 1990 population of 839,942; 

Montgomery, 292,517; Tuscaloosa, 150,522; Anniston, 116,032; and Gadsden, 99,840 people (U.S. 

Bureau of the Census, 1998). Anniston lies entirely 

within the Valley and Ridge Physiographic Province 

whereas Birmingham and Gadsden lie mostly within 

the Valley and Ridge Physiographic Province with 

some area in the Cumberland Plateau Physiographic 

Province. Montgomery and Tuscaloosa lie mostly 

within the Alluvial aquifer of the Coastal Plain Physiographic Province, and Mobile lies mostly within the 

Southern Hills district of the Coastal Plain Physiographic Province. Part of the Atlanta MSA lies in the 

Piedmont Physiographic Province of the Mobile River 

Basin. The most concentrated areas of population lie 

within the Valley and Ridge and Cumberland Plateau 

Physiographic Provinces in Alabama and the Piedmont Physiographic Province in Georgia. The Blue 

Ridge Physiographic Province has the lowest overall 

population density but has the highest rate of growth, 

reflecting a 62-percent increase in population from 

1970 to 1990 (table 4). The Piedmont Physiographic 

Province experienced a 60-percent growth from 1970 

to 1990, resulting from urban sprawl in the Atlanta 

area. The Mobile River Basin experienced an overall 

growth of 23 percent for the same time period. 

The population in urban areas is increasing 

faster than in rural areas, resulting in increasing waterquality concerns. Urban and residential areas can 

affect the quality and quantity of water resources by 

altering the physical hydrology and by adding waste 

products to water bodies. As urbanization increases, 

the amount of impervious area increases, thus decreasing the amount of water that would naturally infiltrate 

into the soil. Increased runoff can alter the magnitude 

and timing of storm peaks, increasing the likelihood of 

localized flooding. Urban runoff also can transport 

large nonpoint-source loads of sediment and inorganic 

and organic constituents from paved surfaces, parks, 

lawns, and golf courses. Point sources of contamination from urban areas can include sewage-treatment 

facilities, industrial discharges, landfills, and leaking 

underground storage tanks. 

Nonpoint-source contamination in urban areas 

is a common contributor to water body impairment. 

Although associated with agricultural activities, pesticides and fertilizers are applied to urban land at greater 

rates per unit area than typically applied to agricultural 

land, thus contributing to water-quality impairment. 

Lawns, gardens, parks, and golf courses are subject to 

intense pesticide application. Insecticides used largely 
Environmental Setting of the Mobile River Basin 33

0 - 4,999

5,000 - 9,999

10,000 - 14,999

15,000 - 20,000

Greater than 20,000

Acres of cotton

Figure 16. Agricultural crop production by county area in the Mobile River Basin for 1992. (Modified from U.S. Department

of Agriculture, National Agricultural Statistics Service, 1997.)

0 - 4,999

5,000 - 9,999

10,000 - 19,999

20,000 - 30,000

Greater than 30,000

Acres of soybeans

Base map from U.S. Geological Survey

digital data 1:2,000,000

0 - 1,999

2,000 - 3,999

4,000 - 5,999

6,000 - 8,000

Greater than 8,000

Acres of wheat

0 - 249

250 - 499

500 -1,000

Greater than 1,000

Acres of sorghum

0 - 1,999

2,000 - 3,999

4,000 - 7,999

8,000 - 16,000

Greater than 16,000

Acres of corn

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.
34 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Soybeans

Cotton

Corn

Wheat

Sorghum

0

50

100

150

200

250

300

350

0

10

20

30

40

50

60

70

Area harvested, in thousands of acres Percentage of total crop production in each strata

EXPLANATION

Southern Hills

Black Prairie Belt

Fall Line Hills

Piedmont

Valley and Ridge

Cumberland Plateau

Blue Ridge

Alluvial aquifer

Figure 17. Agricultural crop production by strata for the Mobile River Basin in 1992.

around homes and in gardens, parks, and commercial 

areas are frequently detected in urban streams at levels 

of concern for aquatic life and may be a significant 

obstacle for restoring urban streams. Because chemical applications for urban use are not as stringently 

regulated as for agricultural purposes, the levels of 

pesticides found in streams in urban areas nationally 

generally is comparable to levels of pesticides found 

in streams in agricultural areas, with higher levels of 

herbicides in agricultural areas and higher levels of 

insecticides in urban areas (U.S. Geological Survey, 

1999).

Mining

Coal mining, the predominant mineral extraction activity for the Mobile River Basin, is concentrated in the Cumberland Plateau and the Valley and 

Ridge Physiographic Provinces and some adjacent 

areas in the Fall Line Hills district in Alabama 

(fig. 21). Alabama ranks 15th in coal production 

among coal-producing states, yielding high-volatile A 

bituminous coal (U.S. Office of Surface Mining, 

2000). Alabama has four coal fields that are part of the 

great Appalachian coal basin—Plateau, Warrior, 

Cahaba, and Coosa fields (fig. 21). Total coal reserves 

in Alabama are estimated at 4.8 billion tons; of that 

amount, an estimated 3.1 billion tons are recoverable 

reserves. Prior to 1986, surface mining was the predominate extraction method; but in 1999, about 

75 percent of the coal was mined from underground. 

As of September 30, 2000, 27 permitted surface mines 

and 10 permitted underground mines were actively 
Environmental Setting of the Mobile River Basin 35

0 - 9,999

10,000 - 19,999

20,000 - 29,999

30,000 - 39,999

40,000 - 50,000

Greater than 50,000

Number of cattle

Miss.

Ala.

Tenn.

Ga.

0 - 4,999

5,000 - 9,999

10,000 - 19,999

20,000 - 30,000

Greater than 30,000

Number of swine

Base map from U.S. Geological Survey

digital data 1:2,000,000

Miss.

Ala.

Tenn.

Ga.

Figure 18. Livestock production by county in the Mobile River Basin for 1992. (Modified from U.S. Department of

Agriculture, National Agricultural Statistics Service, 1997.)

0 - 99,999

100,000 - 499,999

500,000 - 999,999

1,000,000 - 1,999,999

Greater than 5,000,000

Number of chickens

2,000,000 - 5,000,000

Miss.

Ala.

Tenn.

Ga.
36 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Figure 19. Livestock production by strata for the Mobile River Basin for 1992.
Environmental Setting of the Mobile River Basin 37

TENN.

MISS.

ALA.

GA.

Mobile R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coosawattee R.

Conasauga R.

Oostanaula R.

Etowah R.

Ta ll a p o osa R.

Coosa R.

89

34 34

85

88 87

86

35

85

35

33

32 86

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

50 MILES

0 50 KILOMETERS

0

Less than 100

101 - 500

501 - 1,000

1,001 - 5,000

Greater than 5,000

EXPLANATION

Figure 20. The 1990 population density and metropolitan statistical areas in the Mobile River Basin.

(Modified from Price and Clawges, 1999.)

Metropolitan statistical area boundary

Population density, per square mile

Base map from U.S. Geological Survey

digital data 1:2,000,000
38 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Figure 21. Coal fields of the great Appalachian coal basin located in the Mobile River Basin.

Modified from Harkins and others, 1980; Harkins

and others, 1981; Harkins and others 1982

Base map from U.S. Geological Survey

digital data 1:2,000,000

1

2

3

4

5

6

7

TENN.

MISS.

ALA.

GA.

H. Neely Henry L.

William 'Bill' Dannelly

Reservoir

Jordan L.

Mitchel L.

Lay L.

Smith L.

Weiss L.

Lake Tuscaloosa

Lake

Purdy

Allatoona

Reservoir

Carters L.

R. L. Harris

Reservoir

Logan Martin L.

Martin L.

Mobile

R.

Tombigbee R.

Cahaba R.

Tombigbee R .

Black Warrior R.

Alabama R.

Coosawattee R.

Conasauga R.

Oostanaula R.

Etowah R.

Ta ll a p o osa R.

Coosa R

Tuscaloosa .

Birmingham

Gadsden

Anniston

Atlanta

Montgomery

Mobile

1 - Bibb

2 - Cullman

3 - Jefferson *

4 - Marion

5 - Shelby

6 - Tuscaloosa *

7 - Walker *

8 - Winston

Counties producing

coal in 2000

EXPLANATION

* Counties with highest production

Coal Field

Plateau Field

Warrior Field

Cahaba Field

Coosa Field

50 MILES

0 50 KILOMETERS

0

8
Environmental Setting of the Mobile River Basin 39

producing coal in nine Alabama counties: Bibb, Cullman, Jackson (not in Mobile River Basin), Jefferson, 

Marion, Shelby, Tuscaloosa, Walker, and Winston. 

Approximately 85 percent of the coal comes from Jefferson, Tuscaloosa, and Walker Counties. In Alabama, 

approximately 103,300 acres have been identified as 

disturbed by surface coal mining and reclamation 

operations (U.S. Office of Surface Mining, 2000) 

(fig. 22). The abandoned strip mine areas are potential 

sources of acid mine drainage and sediment. 

Water Use

The Mobile River Basin has abundant surfacewater and ground-water resources. Water from streams 

and aquifers in the Mobile River Basin is used for 

municipal, industrial and rural water supplies, irrigation, and the generation of energy. Instream water uses 

include hydroelectric-power generation, wastewater 

assimilation, recreational boating, fish and wildlife 

habitat, and swimming. 

Basinwide, surface-water use (excluding power 

generation) is about three and a third times greater 

than ground-water use (table 5) (Price and Clawges, 

1999). The greatest surface-water use is for thermoelectric power generation where water is withdrawn 

for cooling and then discharged back into the water 

body. Consumptive water use for power generation in 

Alabama in 1995 was about 1 percent of the total 

water withdrawn for thermoelectric power generation 

(Price and Clawges, 1999). Water withdrawn for 

power generation is about an order of magnitude 

greater than that for any other water-use category and 

is greatest in the middle and southern parts of the 

Mobile River Basin (fig. 23). The next largest surfacewater uses are industry and commercial use and public 

water supply. Most of the industrial and commercial 

usage is in the southern part of the study unit and near 

Gadsden, Ala., in the northern part of the study unit 

(fig. 23). Most (72 percent) of the public drinkingwater supply in the basin is withdrawn from surfacewater resources, and the spatial distribution generally 

corresponds to population densities. Mining and agricultural water use also correspond to those land-use 

activities. 

Table 4. Population in the Mobile River Basin by strata, 1970-90

[Data from the U.S. Bureau of the Census, 2001; mi2, square miles; pop, population]

Strata

Population Area 

(mi2)

Density

1990

(pop/mi2)

Population change

1970 1980 1990 1970-90 Percent

Deltaic deposits 38,900 45,900 50,000 508 98 11,100 29

Alluvial aquifer 140,800 156,300 159,000 3,123 51 18,200 13

Blue Ridge 14,700 18,800 23,800 542 44 9,100 62

Southern Hills district 361,700 402,500 411,700 9,156 45 50,000 14

Fall Line Hills district 296,300 344,800 353,700 7,497 47 57,400 19

Black Prairie Belt 

district

242,500 271,800 280,600 4,271 66 38,100 16

Cumberland Plateau 637,600 711,300 713,100 5,335 134 75,500 12

Valley and Ridge 836,100 963,000 1,024,900 6,820 150 188,800 23

Piedmont 411,200 515,600 656,300 6,427 102 245,100 60

Total for Mobile River Basin 2,979,800 3,430,000 3,673,100 43,679 84 693,300 23

Table 5. Estimated water use in the Mobile River Basin, 1995

[Mgal/d, million gallons per day; data from Price and Clawges, 1999]

Category

Total withdrawal (Mgal/d)

Surface water Ground water

Public water supply 518 200

Domestic water supply 0 50.3 

Power generation 3,035 2.6

Industrial and commercial 457.6 47.1

Mining 7.4 4.1

Livestock 94.3 16.4

Irrigation 40.6 15.0

Total 4,152.9 335.5
40 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

EXPLANATION

Abandoned coal mine

Figure 22. Location of abandoned coal surface mines in the Mobile River Basin.

Base map from U.S. Geological Survey

1:2,000,000 digital data

Study Unit Strata

Piedmont

Valley and Ridge

Cumberland Plateau

Fall Line Hills

Black Prairie Belt

Southern Hills

Alluvial aquifer

Blue Ridge

Deltaic deposits

TENN.

MISS.

ALA.

GA.

89

34 34

85

88 87

86

35

85

35

33

86

32

87

31

88

31

32

89

33

Tuscaloosa

Gadsden

Anniston

Atlanta

Montgomery

Mobile

Birmingham

50 MILES

0 50 KILOMETERS

0

Modified from Stephenson and Monroe, 1940;

Sapp and Emplaincourt, 1975; and U.S. Office

of Surface Mining, 1998
Environmental Setting of the Mobile River Basin 41

Public supply water use, inmillion gallons per day (Mgal/d)

0 - 0.91.0 - 6.97.0 - 19.920 - 80

Greater than 80

Industrial/commercial wateruse, in Mgal/d

00.01 - 4.95.0 - 29.930 - 70Greater than 70

Mining water use, in Mgal/d

00.01- 0.090.10 - 0.991.0 - 2Greater than 2

Irrigation water use, in Mgal/d

0 - 0.090.1 - 0.991.0 - 1.992.0 - 5Greater than 5

Figure 23. Surface-water use in million gallons per day (Mgal/d) by county area in the Mobile River Basin, 1995.

Base map from U.S. Geological Survey1:2,000,000 digital data

Miss.

Ala.

Tenn.

Ga.

Miss. Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.

Miss. Al

Miss. Al
42 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

In the Coastal Plain Physiographic Province 

(Fall Line Hills, Black Prairie Belt, Southern Hills, 

Alluvial aquifer, and Deltaic deposits), surface-water 

use is low in Mississippi, but high in Alabama and 

usually is related to industrial use (fig. 23). Generally, 

surface-water use is greatest in the Valley and Ridge, 

Cumberland Plateau, Southern Hills, and Piedmont 

because of power generation, public water supply, and 

industrial and commercial withdrawals (fig. 24). Water 

use for these four areas is related to the presence of 

urban areas and the resulting population distribution.

Basinwide, ground-water use is less than 

surface-water use for all categories with the exception 

of domestic water supply, which consists of rural wells 

and springs (table 5) (Price and Clawges, 1999). Public drinking-water supply constitutes 60 percent of all 

ground-water withdrawals. Ground water is the main 

public water-supply source for the Fall Line Hills district, Black Prairie Belt district, and the Alluvial aquifer in the Coastal Plain Physiographic Province 

(fig. 24). In the other physiographic provinces, surface 

water is the main source of public water supply. 

Domestic and public water-supply use (fig. 25) corresponds to areas with the largest population densities. 

Industrial and commercial ground-water use is greatest 

in the Fall Line Hills and Black Prairie Belt districts of 

the Coastal Plain Physiographic Province in Mississippi, the Southern Hills district of the Coastal Plain 

Physiographic Province in Alabama, and the Valley 

and Ridge Physiographic Province in Georgia. Agricultural water use for livestock is greatest in the Fall 

Line Hills, Black Prairie Belt, and Southern Hills districts, and the Alluvial aquifer of the Coastal Plain 

Physiographic Province and Cumberland Plateau 

Physiographic Province. Ground-water use for irrigation is greatest in the Southern Hills district and the 

Deltaic deposits of the Coastal Plain Physiographic 

Province. Ground-water use for mining has a greater 

spatial distribution than does surface-water use for 

mining.

WATER-QUALITY ISSUES

Water quality in the Mobile River Basin is 

highly variable and influenced by many natural and 

human factors. One valuable source of information 

about water quality in basins in each State is the State 

305(b) report to Congress, which is prepared every 

2 years. Another source of information is the Toxics 

Release Inventory (TRI), published by the U.S. EPA, 

which provides insight into the potential sources of 

contaminants present in the Mobile River Basin. 

State 305(b) Reports

Impairment of the water quality in stream and 

ground-water systems can cause the water to be designated as partially supporting or nonsupporting their 

intended use. Impairment can be caused by both point 

and nonpoint sources of contamination, such as runoff 

from urban, agricultural, or forested land, flow regulation, and industrial point sources. In 1994 and 1995, 

over 9,460 river miles within the Mobile River Basin 

were assessed. These assessments were made available in the 305(b) water-quality reports to Congress by 

the Alabama Department of Environmental Management (1996), the Georgia Department of Natural 

Resources—Environmental Protection Division 

(1996), and the Mississippi Department of Environmental Quality (1996). 

Based on the 1996 State 305(b) water-quality 

reports, approximately 74 percent of the assessed river 

and stream miles within the Mobile River Basin were 

considered to be fully supporting of their classified 

uses; 15 percent, partially supporting; and 11 percent, 

nonsupporting. Nonsupporting and partiallysupporting stream miles are placed on the State 303(d) 

list. Several factors were identified as the source for 

the impairment of the partially and nonsupporting 

river miles. In 1996, organic enrichment and dissolved 

oxygen depletion, elevated nutrient concentrations, 

and siltation were cited most frequently as the sources 

of impairment for the greatest number of river miles 

(fig. 26). Bacteria, acidic pH, and elevated metal concentrations also contributed a large percentage to the 

impairment. 

The percentage of river miles that support the 

designated use classification, and the causes and 

sources of impairment of the rivers varied among subbasins. Only 64 percent and 67 percent of the river 

miles assessed in the Cahaba River Basin and Coosa 

River Basin, respectively, were considered fully supporting of their intended use (fig. 27). The cause of 

impairment for the Cahaba River Basin was similar to 

the Mobile River Basin in general; organic enrichment, low dissolved oxygen, elevated nutrient concentrations, and siltation were cited as primary causes of 

impairment. The sources for the impairment in the 

Cahaba River Basin were attributed primarily to urban 

sources, including construction, storm sewers, and 
Water-Quality Issues 43

Blue Ridge

PIedmont

Valley andRidge

CumberlandPlateau

Fall Line Hills

Black PrairieBelt

SouthernHills

Alluvialaquifer

Deltaicdeposits

0

50

100

150

Public supply

Industrial/commercial

Mining

Irrigation

Livestock

Surface-water use

0

20

40

60

S

Ground-water use

Water use, in million gallons per day

EXPLANATION

Public supply

Industrial/commercial

Mining

Irrigation

Livestock

Domestic

EXPLANATION

0

400

800

1,200 Surface-water use for

power generation

Figure 24. Water use by strata in the Mobile River Basin, 1995.
44 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee Public Supply water use, in million gallons per day (Mgal/d) 0 - 0.99 1.0 -1.99 2.0 - 5.99

6.0 -15.0Greater than 15.0

Industrial/commercial wateruse, in Mgal/d

0 - 0.090.10 - 0.991.0 - 1.992.0 - 3.0Greater than 3.0

Figure 25. Ground-water use in million gallons per day (Mgal/d) by county area for the Mobile River Basin, 1995.

Base map from U.S. Geological Survey1:2,000,000 digital data 

Mining water use, in Mgal/d

00.01 - 0.090.10 - 0.390.40 - 0.70Greater than 0.7

Irrigation, in Mgal/d

00.01- 0.090.10 - 0.991.0 - 4.0Greater than 4.0

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Miss.

Ala

Ga. 

Miss.

Ala

Miss.

Ala.

Tenn.

Ga.

Miss.

Ala.

Tenn.

Ga.
Water-Quality Issues 45

0

Alabama River

Basin

Black Warrior River

Basin

Cahaba River

Basin

Coosa River

Basin

Metals

Siltation

OE/DO

Bacteria

Nutrients

Ammonia

Pro. Org

Flow Mod

Habitat Mod

Non Pri Org

Pesticides

Toxins

Temperature

Bio impairments

Tallapoosa River

Basin

Metals

Siltation

OE/DO

Bacteria

Nutrients

Ammonia

Pro. Org

Flow Mod

Habitat Mod

Non Pri Org

Pesticides

Toxins

Temperature

Bio impairments

Tombigbee River

Basin

Figure 26. Causes for segments of rivers in the Mobile River Basin to be placed on the

1996 State 303(d) lists.

100

200

300

400

0

100

200

300

400

0

100

200

300

400

Acidic pH

Acidic pH

Number of river miles classified as nonsupporting or partially supporting of designated use

EXPLANATION

Organic enrichment/dissolved

oxygen depletion

Priority organics (mostly

polychlorinated biphenyls)

Flow modification

Habitat modification

Non-priority organics

Biological impairments

OE/DO

Pro. Org

Flow Mod

Habitat

Mod

Non Pri

Org

Bio impairments
46 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

Alabama Tombigbee Black Warrior Cahaba Coosa Tallapoosa

0

500

1,000

1,500

2,000 Fully supporting

Partially supporting

Nonsupporting

Assessed river miles

Figure 27. Classification of assessed river miles for supporting intended use in the Mobile River Basin

from the 1996 State 305(b) reports.

Percentage of assessed river

miles in basin

EXPLANATION

67

13

20

82

14

4

64

22

15

79

15

6

81

13

6

69

20

11

69

surface runoff (fig. 28). Priority organics [mainly 

polychlorinated biphenyls (PCBs)] and pathogens 

were considered the primary causes of impairment in 

the Coosa River Basin and were attributed to industrial 

sources. In the Black Warrior River Basin, 69 percent 

of the assessed river miles were classified as fully supporting their intended use. Impairment of the Black 

Warrior River Basin was attributed more to elevated 

metals, acidic pH, and siltation associated with the 

greater surface mining activities in that region than in 

the other basins (figs. 26 and 28). The three remaining 

subbasins in the Mobile River Basin had percentages 

of fully supporting river miles greater than that of the 

entire Mobile River Basin (74 percent): Tallapoosa 

River Basin (82 percent), Alabama River Basin 

(79 percent), Tombigbee River Basin (81 percent). 

Impairment of surface-water segments in the Tallapoosa River Basin primarily was attributed to siltation and habitat modification resulting from dredging 

and mining activities. The Alabama River’s problems 

stemmed primarily from siltation, organic enrichment 

and nutrients resulting from agricultural and municipal 

activities, and flow modification from dams. The 

sources of impairment in the Tombigbee River Basin 

were identified as acidic pH, organic enrichment, 

reduced dissolved oxygen levels, and nutrients resulting from municipal sources, dams, mining, and other 

unknown or unlisted sources.

The utilization of the State 305(b) reports to 

summarize water-quality conditions in the basin has 

some limitations. Assessments and reporting methodologies vary from state to state, and the extent of the 

investigations are influenced by available funding levels and other local issues. Areas with known waterquality problems are targeted for investigation, which 

results in a somewhat biased representation of the 

prevalence of impaired water bodies. Additionally, 

classification of the causes of impairment and sources 

of contamination vary among states. Nevertheless, 

these reports are the most comprehensive ongoing 

summarization of water-quality conditions available. 

These reports incorporate data collected by many 
Water-Quality Issues 47

Black Warrior

River Basin Alabama River

Basin

Cahaba River

Basin Coosa River

Basin

Tallapoosa River

Basin

Tombigbee River

Basin

Figure 28. Sources of contamination causing segments of rivers in the Mobile River Basin to be placed

on the 1996 State 303(d) lists.

Number of river miles listed in State 303(d) reports as nonsupporting or partially supporting designated usage

0

50

100

150

200

250

300

350

0

50

100

150

200

250

300

350

0

50

100

150

200

250

300

350

Crop Pasture/Range

CAFOs

Silviculture

Roads

Construction

Storm Sewers

CSOs

Surface Runoff

Mining Dredge

Tailings

Landfill

Septic Tanks

Channel

Dams

Flow Reg Vegetation

Industrial

Municipal

Point-storm sewers

Nonpoint

Unknown

Crop Pasture/Range

CAFOs

Silviculture

Roads

Construction

Storm Sewers

CSOs

Surface Runoff

Mining Dredge

Tailings

Landfill

Septic Tanks

Channel

Dams

Flow Reg Vegetation

Industrial

Municipal

Point-storm sewers

Nonpoint

Unknown

EXPLANATION

Combined animal feedlot

operations

Combined sewerers

overflows

Dredging operations

Channel modifications

Flow regulation

CAFOs

CSOs

Dredge

Channel

Flow Reg
48 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

governmental agencies and provide biennial snapshots 

of conditions throughout the basin and the Nation. 

Toxics Release Inventory

The Toxics Release Inventory (TRI), published 

by the U.S. EPA, is a valuable source of information 

regarding toxic chemicals that are being used, manufactured, treated, transported, or released into the environment. The TRI requires the reporting of estimated 

amounts of toxic chemical releases but does not mandate that facilities monitor these releases. In 1998, 

releases included a combination of atmospheric releases 

(81,800,000 pounds), landfill (11,300,000 pounds), and 

discharges directly into the water (3,030,000 pounds). 

The TRI provides the first comprehensive overview of 

toxic chemical contamination from manufacturing 

facilities in the United States; however, the TRI does 

not cover toxic chemicals that reach the environment 

from non-industrial sources, such as dry cleaners or 

auto service stations. The TRI also does not distinguish between amounts that could have been released 

continuously over the course of the year or possibly in 

a single large release. Though the TRI data base is a 

starting point for assessing possible health effects 

resulting from industrial chemical use, the user cannot 

ascertain levels of exposure or risk without combining 

TRI information with information from other sources. 

The location and magnitude of toxic chemical releases 

reported in the TRI for 1998 in the Mobile River Basin 

are shown in figure 29 (U.S. Environmental Protection 

Agency, 2001). 

SUMMARY

The Mobile River Basin is the sixth largest river 

system in the United States covering about 

44,000 square miles and is the fourth largest in terms 

of flow, having an average annual discharge of about 

62,100 ft3

/s. The basin encompasses parts of Alabama, 

Georgia, Mississippi, and Tennessee. The Mobile 

River is formed from the confluence of the Tombigbee 

and the Alabama River systems. These rivers are regulated by dams and reservoirs that strongly influence 

the hydrology of the basin. 

The physiography and geology were used to 

stratify the Mobile River Basin into nine subunits that 

represent areas of relative geologic and physiographic 

homogeneity. This stratification provides a spatial 

framework in which natural variability in water quality can be quantified and the effects of human-related 

factors can be assessed. Five physiographic provinces 

are included in the Mobile River Basin. The southern 

part of the basin is located in the East Gulf Coastal 

Plain section of the Coastal Plain Physiographic Province. The northeastern part of the basin lies within the 

Cumberland Plateau section of the Appalachian Plateaus Physiographic Province, the Valley and Ridge, 

the Piedmont, and the Blue Ridge Physiographic Provinces. The study unit can be divided into four broad 

categories of geologic structure that relate to the physiography. From north to south these are (1) flat-lying 

Paleozoic sedimentary rocks that underlie the Cumberland Plateau Physiographic Province, (2) Paleozoic 

rocks folded into a series of anticlines and synclines in 

the Valley and Ridge Physiographic Province where 

resistant rocks form ridges and soft rocks underlie valleys, (3) intensely deformed metamorphic rocks of the 

Piedmont and Blue Ridge Physiographic Provinces 

that have been intruded by small to large bodies of 

igneous rocks, and (4) gently dipping, poorly consolidated to unconsolidated sediments of the Coastal Plain 

Physiographic Province. 

The wide range of geologic, topographic, and 

climatic conditions in the Mobile River Basin produce 

widely varying soil conditions. These different soil 

conditions are used to divide the basin into seven geographic land areas (Major Land Resource Areas) characterized by a particular combination or pattern of 

soils, climate, water resources, land use, and agricultural practices. 

The climate in the Mobile River Basin is warm 

and humid, ranging from temperate to subtropical near 

the coast. In the summer, precipitation moves inland 

from the Gulf of Mexico. In the winter, precipitation is 

attributed to arctic fronts that move south from the 

midwestern part of the continent. Mean annual precipitation for 1961 through 1990, ranged from 

53.4 inches per year in Montgomery, Ala., to 64 inches 

per year in Mobile, Ala. Mean annual runoff ranged 

from 18 inches per year in the Montgomery area to 

30 inches per year in the Birmingham area and in the 

Blue Ridge Mountains. The mean annual runoff 

increases in the southern part of the basin reflecting 

increased annual precipitation. Runoff in the Birmingham area is influenced partly by increased urbanization and the resulting increase in impermeable areas. 

The higher runoff in the northeastern corner of the 

study unit is a result, in part, of high precipitation, 

increased slopes, and the low permeability of the soil 
Summary 49

EXPLANATION

Chemical releases, in pounds

per year

City location

TENN.

MISS.

ALA.

GA.

89

34 34

85

88

87

86

35

85

35

33

86

32

87

31

88

31

32

89

33

Tuscaloosa

Birmingham

Gadsden

Anniston Atlanta

Montgomery

Mobile

30,000,000

2,000,000

100,000

10,000

1,000

Base map U.S. Geological Survey

digital data, 1:2,000,000

50 MILES

0 50 KILOMETERS

0

Figure 29. U.S. Environmental Protection Agency Toxic Inventory Release sites in the Mobile River Basin

for 1998. (Modified from U.S. Environmental Protection Agency, 2001.)
50 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

and rock underlying the Blue Ridge Mountains. For 

the same time frame (1961 through 1990), the mean 

annual temperatures ranged from 56 oF in the northeastern part of the basin to 68 o

F near the coast. 

The aquifers in the Mobile River Basin range in 

composition from unconsolidated sand of the Southeastern Coastal Plain aquifer system to hard crystalline 

rocks of the Piedmont and Blue Ridge aquifers. These 

aquifers have been grouped into four major aquifers or 

aquifer systems on the basis of rock types and groundwater flow systems: Southeastern Coastal Plain aquifer system, Valley and Ridge aquifers, Appalachian 

Plateaus aquifers, and Piedmont and Blue Ridge aquifers. 

Six Level III ecoregions are designated within 

the Mobile River Basin: (1) Southern Coastal Plain 

ecoregion, (2) Southeastern Plains ecoregion, 

(3) Southwestern Plains ecoregion, (4) Ridge and Valley ecoregion, (5) Piedmont ecoregion, and (6) Blue 

Ridge Mountains ecoregion. The degree of homogeneity among the ecoregions, and the physiography and 

geology in the Mobile River Basin indicates that the 

natural variations in the physiography and geology are 

reflected in the variations of the ecological systems of 

the basin.

The diverse aquatic habitats in the Mobile River 

Basin sustain one of the richest aquatic fauna in North 

America. Endemic fauna include 40 fishes, 33 mussels, 110 aquatic snails, as well as a variety of turtles, 

aquatic insects, and crustaceans. However, contaminants and modification of aquatic habitat such as 

impoundments, channelization, dredging, and mining 

have resulted in the presumed extinction of at least 

15 mussels and 38 aquatic snails. The basin is habitat 

for 39 species of aquatic animals and plants that are 

currently protected under the Endangered Species Act, 

including 11 fish, 17 mussels, 7 snails, 2 turtles, and 

2 plants. 

Land use in the Mobile River Basin is a heterogeneous mixture of forest, agricultural, and urban 

areas. Most (about 70 percent) of the basin is forested; 

agriculture, including livestock (poultry, cattle, and 

swine), aquaculture, row crops (cotton, corn, soybeans, sorghum, and wheat), and pasture land, 

accounts for about 26 percent of the study unit. The 

highest concentration of agricultural land use is along 

the Black Prairie Belt district of the Coastal Plain 

Physiographic Province. Urban areas account for only 

3 percent of the total land use; however, the areal 

extent of the metropolitan statistical areas may indicate more urban influences. 

The total population for the Mobile River Basin 

was about 3,673,100 people in 1990. The highest population density is within the Valley and Ridge and 

Cumberland Plateau Physiographic Provinces in Alabama and the Piedmont Physiographic Province in 

Georgia. The Piedmont Physiographic Province experienced a 60-percent increase in population from 1970 

to 1990, as a result of urban sprawl in the Atlanta area. 

The Blue Ridge Physiographic Province has the lowest overall population density, but had the highest rate 

of population growth from 1970 to 1990. The Mobile 

River Basin experienced an overall population growth 

of 23 percent for the same time period.

Coal extraction has been the primary mining 

activity in the Mobile River Basin. Coal mining is concentrated in Alabama in the Cumberland Plateau and 

Valley and Ridge Physiographic Provinces and some 

adjacent areas in the Fall Line Hills district. Alabama 

ranks 15th in coal production among coal-producing 

states. Alabama has four coal fields that are part of the 

great Appalachian coal basin: Plateau, Warrior, 

Cahaba, and Coosa fields.

The Mobile River Basin has abundant water 

resources. Water from streams and aquifers in the 

Mobile River Basin is used for municipal, industrial 

and rural water supplies, irrigation, and the generation 

of energy. Other water uses include hydroelectricpower generation, wastewater assimilation, recreational uses, and fish and wildlife habitat. Hydroelectric power generation uses the greatest amount of 

surface water where the water is withdrawn for cooling and then discharged back into the water body. Basinwide, surface-water use (excluding hydroelectricpower generation) is about three and a third times 

greater than ground-water use. 

Water quality in the Mobile River Basin is influenced by many natural and human factors. Impairment 

of water quality can cause water bodies to be designated as partially supporting or nonsupporting of their 

intended uses. Impairment can be caused by point and 

nonpoint sources of contamination, such as runoff 

from urban, agricultural, or forested land, flow regulation, and industrial point sources. The 1996 State 

305(b) reports documented the assessment of over 

9,460 river miles within the Mobile River Basin by 

State environmental agencies. Approximately 74 percent of the assessed river and stream miles were considered to be fully supporting of their classified uses; 
References 51

15 percent, partially supporting; and 11 percent, nonsupporting. The U.S. Environmental Protection 

Agency Toxic Release Inventory serves as a source of 

information about toxic chemicals released into the 

environment. A number of Toxic Release Inventory 

sites are located in the Mobile River Basin and 

reported total releases of about 93 million pounds in 

1998. These toxic chemical releases are self-reported 

estimates by industry and are a combination of atmospheric, land, and water releases, all of which may 

potentially affect water quality.

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accessed February 7, 2001, at http://www.epa.gov/tri/

U.S. Fish and Wildlife Service, 1986, Endangered species: 

U.S. Fish and Wildlife Service, FWS-OES-8/86.

———1998a, Technical/Agency draft Mobile River Basin 

Ecosystem Recovery Plan, Jackson Mississippi, 112 p.

———1998b, The Endangered Species Program, accessed 

November 7, 2000, at http://endangered.fws.gov/

U.S. Geological Survey, 1984, National water summary, 

Hydrologic events and selected water-quality trends 

and ground-water resources: U.S. Geological Survey 

Water-Supply Paper 2275, 467 p.

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States, accessed February 9, 2001, at http://

www-atlas.usgs.gov/aquifers.html

———1999, The quality of our Nation's waters—nutrients 

and pesticides: U.S. Geological Survey Circular 1225, 

82 p. 

U.S. Office of Surface Mining, 1998, Abandoned mine land 

inventory system—High priority coal-related problems 

database, accessed August 1, 2001, at 

http://www.osmre.gov/aml/inven/zamlis.htm

———2000, Annual evaluation summary report for the 

regulatory and abandoned mine lands reclamation programs administered by the State of Alabama for evaluation year 2000, October 1, 1999 to September 30, 

2000, 28 p.

Zurawski, A., 1978, Summary appraisals of the Nation’s 

ground-water resources—Tennessee Region: U.S. 

Geological Survey Professional Paper 813-L, 35 p.

APPENDIXES

Appendix A 57

Appendix A. Aquatic species extirpated from or extinct in the Mobile River Basin—Continued

Common name Scientific name Federal status

FISH

Lake sturgeon Acipenser fulvescens Extirpated

MUSSELS

Deertoe mussel Truncilla truncata Extirpated

Coosa elktoe Alasmidonta maccordi Extinct

Tombigbee moccasinshell Medionidus macglameriae Extinct

Warrior pigtoe Pleurobema rubellum Extinct

Highnut Pleurobema altum Extinct

N/A Pleurobema hartmanianum Extinct

Longnut Pleurobema nucleopsis Extinct

True pigtoe Pleurobema verum Extinct

Yellow pigtoe Pleurobema flavidulum Extinct

Alabama pigtoe Pleurobema johannis Extinct

N/A Pleurobema aldrichianum Extinct

Hazel pigtoe Pleurobema avellanum Extinct

Alabama clubshell Pleurobema troschelianum Extinct

Brown Pigtoe Pleurobema hagleri Extinct

Coosa pigtoe Pleurobema murrayense Extinct

Warrior pigtoe Pleurobema rubellum Extinct

SNAILS

Umbilicate pebblesnail Clappia umbilicata Extinct

Cahaba pebblesnail Clappia cahabensis Extinct

Short-spire elimia Elimia brevis Extinct

Fusiform elimia Elmia fusiformis Extinct

High-spired elimia Elimia hartmaniana Extinct

Constricted elimia Elimia impressa Extinct

Hearty elimia Elimia jonesi Extinct

N/A Elimia lachryma Extinct

Ribbed elimia Elimia laeta Extinct

N/A Elimia macglameriana Extinct

Rough-lined elimia Elimia pilsbryi Extinct

Pupa elimia Elimia pupaeformis Extinct

Pygmy elimia Elimia pygmaea Extinct

Cobble elimia Elimia vanuxemiana Extinct

Closed elimia Elimia clausa Extinct

N/A Elimia gibbera Extinct

Appendix A. Aquatic species extirpated from or extinct in the Mobile River Basin

[All taxa listed are endemic to the Mobile River Basin. Extinct species have not been reported for 20 or more years. N/A, No recorded 

common name for these species (Source: U.S. Fish and Wildlife Service, 1998a)]
58 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

SNAILS—Continued

Excised slitshell Gyrotoma excisa Extinct

Striate slitshell Gyrotoma lewisii Extinct

Pagoda slitshell Gyrotoma pagoda Extinct

Ribbed slitshell Gyrotoma pumila Extinct

Pyramid slitshell Gyrotoma pyramidata Extinct

Round slitshell Gyrotoma walkeri Extinct

Agate rocksnail Leptoxis clipeata Extinct

Interrupted rochsnail Leptoxis foremanii Extinct

Maiden rocksnail Leptoxis formosa Extinct

Rotund rocksnail Leptoxis ligata Extinct

Lirate rocksnail Leptoxis lirata Extinct

Black mudalia Leptoxis melanoidus Extinct

Bigmouth rocksnail Leptoxis occultata Extinct

Coosa rocksnail Leptoxis showalterii Extinct

N/A Leptoxix torrefacta Extinct

Striped rocksnail Leptoxis vittata Extinct

Oblong rocksnail Leptoxis compacta Extinct

Shoal sprite Amphigyra alabamensis Extinct

N/A Neoplanorbis carinatus Extinct

N/A Neoplanorbis smithi Extinct

N/A Neoplanorbis tantillus Extinct

N/A Neoplanorbis umbilicatus Extinct

Appendix A. Aquatic species extirpated from or extinct in the Mobile River Basin—Continued

Common name Scientific name Federal status
Appendix B 59

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973—Continued

Common name Scientific name Federal status General endemic range Cause 

FISH

Alabama sturgeon Scaphirhynchus 

suttkusi

Endangered Mobile River system, in Alabama and Georgia.Attributed to over fishing, loss and fragmentation of habitat, and 

water degradation.

Amber darter Percina antesella Endangered Conasauga River, Ga. and 

Tenn., and Etowah River and 

Shoal Creek, Ga.

Limited range, proposed reservoir, and 

water-quality degradation.

Blue shiner Cyprinella caerulea Threatened Cahaba River, Ala. and 

Coosa River and tributaries 

in Ala., Ga., and Tenn.

Due in part to loss and 

fragmentation of habitat 

associated with reservoir construction as 

well as degradation of 

water quality.

Cahaba shiner Notropis cahabae Endangered Main stem of Cahaba River, 

Ala. in Bibb, Perry, and 

Shelby counties.

Adverse habitat alterations and water-quality 

degradation from residential, industrial, and 

commercial development.

Cherokee darter Etheostoma scotti Threatened Upper Etowah River and two 

of its tributaries (Long 

Swamp and Amiclala Creek) 

in Ga.

Impoundments, 

degraded water quality, 

and loss of benthic habitat by siltation.

Conasauga logperch Percina jenkinsi Endangered Upper Conasauga River, 

Tenn. and Ga.

Limited range, proposed reservoir, and 

water-quality degradation.

Etowah darter Etheostoma etowahae Endangered Upper Etowah River and two 

of its tributaries (Long 

Swamp and Amiclala Creek) 

in Ga.

Degraded water quality 

and loss of benthic habitat by siltation.

Goldline darter Percina aurolineata Threatened Cahaba and Coosa River 

drainages; including the Little Cahaba, Coosawatte, Ellijay, and Cartecay Rivers.

Water-quality degradation and loss of habitat.

Gulf sturgeon Acipenser oxyrhynchus 

desotoi

Threatened Historical range extends 

from Lake Pontchartrain, La. 

to Tampa Bay, Fla.

Over-exploitation by 

fishermen, habitat modification, and waterquality degradation. 

Impoundments may 

restrict reproduction.

Pygmy sculpin Cottus pygmaeus Threatened Coldwater Spring, Calhoun 

County, Ala.

Water contamination of 

the subsurface aquifer 

for Coldwater Spring.

Watercress darter Etheostoma nuchale Threatened Four springs in the Black 

Warrior River watershed, 

Jefferson County, Ala.

Limited range, increasing urbanization, and 

potential ground-water 

contamination.

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973 

[From U.S. Fish and Wildlife Service, 1998b]
60 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

MUSSELS

Inflated heelsplitter Potamilus inflatus Threatened Tombigbee, Black Warrior, 

and Coosa Rivers, Ala.

Impacts to habitat from 

channel modification, 

impoundments, pollution, and dredging.

Alabama moccasinshell Medionidus acutissimus Threatened Mobile River drainage basin, 

which includes the Alabama, 

Tombigbee, Black Warrior, 

Cahaba, and Coosa Rivers 

and their tributaries.

Habitat modification, 

sedimentation, eutrophication, and pollution.

Black clubshell Pleurobema curtum Endangered Tombigbee River above 

Pickensville, Ala. and in 

Miss.

Habitat modification 

including impoundments and channelization.

Coosa moccasinshell Medionidus parvulus Endangered Mobile River drainage basin, 

which includes the Cahaba 

River, Sipsey Fork, Black 

Warrior River, and Coosa 

River.

Habitat modification, 

sedimentation, eutrophication, and pollution.

Dark pigtoe Pleurobema furvum Endangered Mobile River drainage in 

parts of Ala., Ga., Miss., and 

Tenn.

Loss of habitat and 

water-quality degradation.

Fine-lined pocketbook Lampsilis altilis Threatened Mobile River drainage basin, 

which includes the Alabama, 

Tombigbee, Black Warrior, 

Cahaba, Tallapoosa and 

Coosa Rivers and their and 

tributaries.

Habitat modification, 

sedimentation, eutrophication, and pollution.

Flat pigtoe Pleurobema marshalli Endangered Tombigbee River between 

Columbus, Miss. and Epes, 

Ala.

Habitat modification 

from navigational 

impoundments.

Heavy pigtoe Pleurobema taitianum Endangered Main stem Tombigbee, Alabama, Cahaba, and Coosa 

Rivers, Ala. and Miss.

Impoundments, agricultural runoff, sand and 

gravel mining.

Orangenacre mucket Lampsilis perovalis Threatened Alabama River and tributaries; tributaries of the Tombigbee and Black Warrior 

Rivers; Cahaba River and 

tributaries.

Habitat modification, 

sedimentation, eutrophication, and pollution.

Ovate clubshell Pleurobema perovatum Endangered Tombigbee River Basin, Ala. 

and Miss., Black Warrior and 

Cahaba River Basins, Ala., 

Alabama River, Ala., Coosa 

River Basin, Ala., Ga., and 

Tenn., Chewacla, Uphapee, 

and Opintlocco Creeks in the 

Tallapoosa River Basin, Ala.

Habitat modification, 

sedimentation, eutrophication, and waterquality degradation.

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973—Continued

Common name Scientific name Federal status General endemic range Cause 
Appendix B 61

MUSSELS—Continued

Southern acornshell Epioblasma othcaloogensisThreatened Coosa and Cahaba River 

Basins above the Fall Line, 

Ala., Ga., and Tenn.

Habitat modification, 

sedimentation, eutrophication, and water-quality degradation from 

point and nonpoint 

sources.

Southern clubshell Pleurobema decisum Endangered Entire Mobile River Basin 

except for the Mobile Delta.

Habitat modification, 

sedimentation, and 

water-quality degradation.

Southern combshell Epioblasma penita Endangered Alabama, Cahaba, and Coosa 

Rivers, Ala., Tombigbee 

River Basin, Miss. and Ala., 

Black Warrior River below 

Fall Line, Ala.

Channelization and 

impoundment, sedimentation, and waterquality degradation. 

Sand and gravel mining 

and agricultural runoff.

Southern pigtoe Pleurobema georgianumEndangered Mobile River drainange in 

parts of Ala., Ga., Miss., and 

Tenn.

Loss of habitat and 

water-quality degradation.

Stirrupshell Quadrula stapes Endangered Tombigbee, Alabama, and 

Black Warrior Rivers, Ala. 

and Miss.

Impoundments and 

nonpoint source pollution.

Triangular kidneyshell Ptychobrancus greeni Endangered Mobile River drainange in 

parts of Ala., Ga., Miss., and 

Tenn.

Loss of habitat and 

water-quality degradation.

Upland combshell Epioblasma metastriata Endangered Black Warrior and Cahaba 

River Basins, Ala., Coosa 

River Basin, Ala., Ga., and 

Tenn.

Habitat modification, 

sedimentation, eutrophication, and waterquality degradation 

from point and nonpoint 

sources.

SNAILS

Cylindrical lioplax Lioplax cyclostomaformisEndangered Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Ala.

Impoundments and 

water-quality degradation.

Flat pebblesnail Lepyrium showalteri Endangered Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Ala.

Impoundments and 

water-quality degradation.

Lacy elimia Elimia crenatella Threatened Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Ala.

Impoundments and 

water-quality degradation.

Painted rocksnail Leptoxis taeniata Threatened Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Ala.

Impoundments and 

water-quality degradation.

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973—Continued

Common name Scientific name Federal status General endemic range Cause 
62 Environmental Setting and Water-Quality Issues of the Mobile River Basin,

Alabama, Georgia, Mississippi, and Tennessee

SNAILS—Continued

Plicate rocksnail Leptoxis plicata Endangered Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Alabama.

Impoundments and 

water-quality degradation.

Round rocksnail Leptoxis ampla Threatened Black Warrior, Cahaba, Alabama, and Coosa Rivers and 

their tributaries in central 

Alabama.

Impoundments and 

water-quality degradation.

Tulotoma snail Tulotoma magnifica Endangered Coosa River Basin from St. 

Clair Co., Ala. to Alabama 

River, Clarke/Monroe Co., 

Ala.

Impoundments and 

point and nonpoint 

source pollution.

TURTLES

Alabama red-belly turtle Pseudemys alabamensis Endangered Mobile Delta Habitat alterations of 

rivers for navigation 

and flow modifications.

Flattened musk turtle Sternotherus depressus Threatened Locust Fork, Mulberry Fork, 

and Sipsey Fork of the Black 

Warrior River, Ala.

Habitat modification, 

sedimentation, and 

water-quality degradation.

PLANTS

Harperella Ptilimnium nodosum Endangered Little River on Lookout 

Mountain and Town Creek 

on Sand Mountain, Ga. and 

Ala.

Flow and stream bank 

modification, siltation, 

and pollution.

Kral’s water-plantain Sagittaria secundifolia Threatened Little River on Lookout 

Mountain, Town Creek on 

Sand Mountain, Sipsey Fork 

of the Black Warrior River, 

Ga. and Ala.

Stream bank modification, siltation, and pollution.

Appendix B. Aquatic species in the Mobile River Basin listed under the Endangered Species Act of 1973—Continued

Common name Scientific name Federal status General endemic range Cause