GROUND-WATER RESOURCES OF THE

MIDDLE CHATTAHOOCHEE RIVER BASIN IN 

GEORGIA AND ALABAMA, AND UPPER FLINT RIVER 

BASIN IN GEORGIA—SUBAREA 2 OF THE

APALACHICOLA-CHATTAHOOCHEE-FLINT AND

ALABAMA-COOSA-TALLAPOOSA RIVER BASINS

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

ALABAMA DEPARTMENT OF ECONOMIC AND COMMUNITY AFFAIRS

OFFICE OF WATER RESOURCES

GEORGIA DEPARTMENT OF NATURAL RESOURCES

ENVIRONMENTAL PROTECTION DIVISION

NORTHWEST FLORIDA WATER MANAGEMENT DISTRICT

U.S. ARMY CORPS OF ENGINEERS, MOBILE DISTRICT

Open-File Report 96-492

GROUND-WATER RESOURCES OF THE MIDDLE 

CHATTAHOOCHEE RIVER BASIN IN GEORGIA 

AND ALABAMA, AND UPPER FLINT RIVER BASIN IN 

GEORGIA—SUBAREA 2 OF THE 

APALACHICOLA-CHATTAHOOCHEE-FLINT AND 

ALABAMA-COOSA-TALLAPOOSA RIVER BASINS

By Melinda J. Chapman and Michael F. Peck

U.S. GEOLOGICAL SURVEY

Open-File Report 96-492

Prepared in cooperation with the

ALABAMA DEPARTMENT OF ECONOMIC AND COMMUNITY AFFAIRS

OFFICE OF WATER RESOURCES

GEORGIA DEPARTMENT OF NATURAL RESOURCES

ENVIRONMENTAL PROTECTION DIVISION

NORTHWEST FLORIDA WATER MANAGEMENT DISTRICT

U.S. ARMY CORPS OF ENGINEERS, MOBILE DISTRICT

Atlanta, Georgia

1997
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

For further information, please write to

District Chief

U.S. Geological Survey

Peachtree Business Center

3039 Amwiler Road, Suite 130

Atlanta, GA 30360-2824

Copies of this report may be purchased from

U.S. Geological Survey

Branch of Information Services

Denver Federal Center

Box 25286

Denver, CO 80225-0286

_____________________________________________________________________________________________
iii

CONTENTS

Abstract 1

Introduction 2

Purpose and scope 4

Physical setting of study area 4

Physiography 4

Climate 4

Ground-water use 6

Previous investigations 6

Well and surface-water station numbering systems 9

Approach and methods of study 10

Mean-annual baseflow analysis 10

Drought-flow analysis 13

Acknowledgments 13

Conceptual model of ground-water flow and stream-aquifer relations 14

Hydrologic setting 15

Ground-water system 15

Geology 16

Aquifers 17

Ground-water levels 20

Regolith wells 20

Bedrock wells 22

Surface-water system 22

Ground-water discharge to streams 25

Mean-annual baseflow 26

Drought flow for 1941, 1954, and 1986 28

Ground-water utilization and general development potential 37

Ground-water exploration-program example 38

Summary 38

Suggestions for further study 40

Selected references 40
iv

ILLUSTRATIONS

Figures 1-2. Maps showing:

 1. Subareas and major streams in the Apalachicola-Chattahoochee-Flint and Alabama-CoosaTallapoosa River basins 3

 2. Physiographic provinces and subareas in the Apalachicola-Chattahoochee-Flint and AlabamaCoosa-Tallapoosa River basins 5

Figure 3. Graph showing a streamflow hydrograph, separated by program SWGW 12

4. Schematic diagrams showing (A) distribution of ground-water flow in an areally extensive, isotropic, 

homogeneous aquifer system and (B) example of local, intermediate, and regional groundwater flow 14

5. Map showing major aquifers and subareas in the Apalachicola-Chattahoochee-Flint and AlabamaCoosa-Tallapoosa River basins 18

 6. Schematic diagram showing the conceptual ground-water and surface-water systems in Subarea 2: 

fracture-conduit aquifer in the igneous and metamorphic rocks of the Piedmont Province 19

Figures 7-8. Graphs showing:

7. Water-level fluctuations in regolith well 11AA01, Spaulding County, Georgia, during 

(A) 1943-95; and (B) the drought of 1954 21

8. Water-level fluctuations in bedrock well 08CC08, Fulton County, Georgia, during (A) 1979-86; 

and (B) the drought of 1981 23

Figure 9. Map showing selected stream-gaging stations and observation wells 08CC08 and 11AA01, 

Subarea 2 24

10. Graph showing relations among mean-annual stream discharge, mean-annual baseflow, and drought 

flow, Chattahoochee River, Subarea 2 36 

TABLES

Table 1. Estimated ground-water use, by category, Subarea 2, 1990 6

2. Generalized geologic units in Subarea 2, and water-bearing properties, chemical characteristics, and 

well yields 17

3. Selected active and discontinued continuous-record stream-gaging stations in the middle 

Chattahoochee River basin in Georgia and Alabama, and upper Flint River basin in Georgia, 

Subarea 2 24

4. Major impoundments in the middle Chattahoochee River basin, Georgia and Alabama, Subarea 2 25

5. Mean-annual stream discharge, estimated annual and mean-annual baseflow, and unit-area meanannual baseflow at selected gaged streams in the middle Chattahoochee River basin in Georgia 

and Alabama, and upper Flint River basin in Georgia, Subarea 2 27

6. Stream discharge during the month of October of the drought of 1941, Subarea 2 28

7. Stream discharge during the months of September and October of the drought of 1954, Subarea 2 29

8. Stream discharge during the month of July of the drought of 1986, Subarea 2 32

9. Estimated mean-annual baseflow and drought flows entering and exiting the middle Chattahoochee 

River basin in Georgia and Alabama, and exiting the upper Flint River basin in Georgia, 

Subarea 2 34

10. Estimated drought flows and mean-annual baseflow in the middle Chattahoochee River basin in 

Georgia and Alabama, and upper Flint River basin in Georgia; and ratio of average drought 

flow to mean-annual baseflow, Subarea 2 35

11. Relation between 1990 ground-water use and ground-water discharge during mean-annual baseflow, 

average selected drought-flow conditions, and drought flow from Alabama and Georgia, 

Subarea 2 37
v

CONVERSION FACTORS, ABBREVIATIONS AND ACRONYMS,

AND VERTICAL DATUM

CONVERSION FACTORS

Multiply by to obtain

Length

inch (in.) 25.4 millimeter

inch per year (in/yr) 25.4 millimeter per year

foot (ft) 0.3048 meter 

square foot (ft2) 0.0929 square meter

mile (mi) 1.609 kilometer

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

Area

acre 4,047 square meter

square mile (mi2) 2.59 square kilometer

Volumetric rate and volume

cubic foot per second (ft3/s) 0.02832 cubic meter per second

448.831 gallon per minute 

0.6463 million gallons per day

cubic foot per second per square mile (ft3/s/mi2) 0.01093 cubic meter per second per square kilometer

gallon per minute (gal/min) 6.309 x 10-5 cubic meter per second

2.228 x 10-3 cubic foot per second

0.06308 liter per second

1,440 gallon per day

gallon per day (gal/d) 3.785 x 10-3 cubic meters per day

million gallons per day (Mgal/d) 1.547 cubic foot per second

63.09 cubic meter per second

694.44 gallons per minute

gallon per minute per foot 

of drawdown (gal/min/ft)

1.24 x 10-2 cubic meters per minute per minute 

per meter of drawdown

acre-foot 325,900 gallon

Transmissivity

foot squared per day (ft2/d) 0.0929 meter squared per day

Temperature

Temperature in degrees Fahrenheit (° F) can be converted to degrees Celsius as follows:

° C = 5/9 x (° F - 32)
vi

ABBREVIATIONS AND ACRONYMS

ACF Apalachicola-Chattahoochee-Flint River basin

ACT Alabama-Coosa-Tallapoosa River basin

ADAPS Automated Data Processing System

Corps U.S. Army Corps of Engineers

MOA Memorandum of Agreement

GWSI Ground Water Site Inventory database

RORA A computer program (Rutledge, 1993)

SWGW Surface Water-Ground Water—a computer program (Mayer and Jones, 1996) 

USGS U.S. Geological Survey

VERTICAL DATUM

Sea Level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NVGD 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.
vii

GLOSSARY

Alluvium—Sediment transported and deposited by flowing water.

Altitude—As used in this report, refers to the distance above sea level.

Anisotropic—Condition having varying hydraulic properties of an aquifer according to flow direction.

Annual—As used in this report, refers to a water year.

Aquifer—A formation, group of formations, or part of a formation that contains sufficient saturated permeable material to 

yield significant quantities of water to wells and springs.

Artesian—Synonymous with confined.

Baseflow—That part of the stream discharge that is not attributable to direct runoff from precipitation or melting snow; it 

is usually sustained by ground-water discharge.

Bedrock—A general term for the consolidated rock that underlies soils or other unconsolidated surficial material.

Clastics—Rocks composed of fragments of older rocks, for example, sandstone.

Colluvium—Heterogeneous aggregates of rock detritus resulting from the transporting action of gravity.

Cone of depression—A depression of the potentiometric surface, often in the shape of an inverted cone, that develops 

around a well which is being pumped.

Confined aquifer—An aquifer bounded above and below by impermeable beds or by beds of distinctly lower permeability 

than that of the aquifer itself; ground water in the aquifer is under pressure significantly greater than that of the 

atmosphere.

Continuous-record gaging station—Complete records of discharge obtained using a continuous stage-recording device 

through which either instantaneous or mean-daily discharge may be computed for any time, or any period of time, 

during the period of record.

Crystalline rock—A general term for igneous and metamorphic rocks.

Darcian flow—Flow that is laminar and in which inertia can be neglected.

Dendritic drainage—A branching stream pattern that resembles the branching of trees.

Drought—There is no accepted definition of drought. As used in this report, a period of deficient rainfall extending long 

enough to cause streamflow to fall to unusually low levels for the period of record.

Evapotranspiration—The combined evaporation of water from the soil surface and transpiration from plants.

Faults—Fractures in the Earth along which there has been displacement parallel to the fault plane.

Foliation—A planar or layered structure in metamorphic rocks that is caused by parallel orientation of minerals or bands 

of minerals.

Fluvial—Pertaining to the actions of rivers.

Fracture—Breaks in rocks due to intense folding or faulting.

Geologic contact—The boundary surface between one body of rock or sediment and another.

Ground-water recharge—The process of water addition to the saturated zone or the volume of water added by this 

process.

Head, static—The height above a standard datum of the surface of a column of water (or other liquid) that can be 

supported by the static pressure at a given point. The static head is the sum of the elevation head and the pressure head.

Head, total—The total head of a liquid at a given point is the sum of three components:

(a) the elevation head, which is equal to the elevation of the point above a datum, (b) the pressure head, which is the 

height of a column of static water that can be supported by the static pressure at the point, and (c) the velocity head, 

which is the height to which the kinetic energy of the liquid is capable of lifting the liquid.

Heterogeneous—Pertaining to a substance having different characteristics in differing locations.

Hydraulic conductivity—The capacity of a rock to transmit water. It is expressed as the volume of water that will move 

through a medium in a unit of time under a unit hydraulic gradient through a unit area measured perpendicular to the 

direction of flow.
viii

Hydraulic gradient—A change in the static pressure of ground water, expressed in terms of the height of water above 

a datum, per unit of distance in a given direction.

Hydrograph separation—Division of the stream hydrograph into components of aquifer discharge and surface 

runoff.

Igneous rock—Rocks which have solidified or crystallized from a hot fluid mass called magma. 

Intergranular porosity—Porosity resulting from space between grains.

Intrusive igneous rocks—Masses of igneous rock formed by magma cooling beneath the surface.

Isotropic—Condition in which hydraulic properties of an aquifer are equal in all directions.

Joints—Fractures in rocks, often across bedding planes, along which little or no movement has taken place.

Mafic—Applied to the ferromagnesian minerals or to igneous rocks relatively rich in such minerals.

Mean annual—As used in this report, refers to the average of the annual values for a specified period of record.

Metamorphic rock—Rocks derived from pre-existing rocks by mineralogical, chemical, and structural alterations due 

to endogenetic processes.

Partial-record gaging station—Is a particular site where limited streamflow and/or water-quality data are collected 

systematically over a period of years.

Permeability—The property of a porous medium to transmit fluids under an hydraulic gradient.

Porosity—The amount of pore space and fracture openings, expressed as the ratio of the volume of pores and 

openings to the volume of rock.

Potentiometric surface—An imaginary surface representing the static head of ground water and defined by the level 

to which water will rise in a tightly cased well.

Primary porosity—Porosity due to the soil or rock matrix; the original interstices created when a rock was formed.

Recession index—The number of days required for discharge to decline one complete log cycle.

Regolith—Loose, unconsolidated and weathered rock and soil covering bedrock.

Residuum—The material resulting from the decomposition of rocks in place and consisting of the nearly insoluble 

material left after all the more readily soluble constituents of the rocks have been removed.

Rock—Any naturally formed consolidated material consisting of two or more minerals.

Run-off—Precipitation that flows from the surface of the land and into streams and rivers.

Saprolite—Surficial deposits produced by the decay of rocks and remaining as residuals.

Secondary openings—Voids produced in rocks subsequent to their formation through processes such as solution, 

weathering, or movement.

Secondary porosity—Porosity due to such phenomena as dissolution or structurally controlled fracturing.

Soil —The layer of unconsolidated material at the land surface that supports plant growth.

Specific capacity—The rate of discharge of water from the well divided by the related drawdown of the water level 

within the well.

Specific yield—The ratio of the volume of water which the porous medium after being saturated, will yield by gravity 

to the volume of the porous medium.

Storage coefficient—The volume of water an aquifer releases from or takes into storage per unit surface area of the 

aquifer per unit change in head (virtually equal to the specific yield in an unconfined aquifer).

Stream discharge—The volume of water flowing past a given point in a stream channel in a given period of time.

Transmissivity—The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of 

an aquifer under a unit hydraulic gradient. It equals the hydraulic conductivity multiplied by the aquifer thickness.

Trellis drainage—A river system resembling a trellis or rectangular pattern and characteristic of areas of folded 

sedimentary rocks where tributaries cut channels through less resistant beds.
ix

Unconfined aquifer—An aquifer in which the water table is a free surface at atmospheric pressure.

Unit-area discharge—Stream or ground-water discharge divided by the drainage area.

Water table—Upper surface of a zone of saturation under atmospheric pressure.

Water year—The standard water-year used by the U.S. Geological Survey is from October 1 to September 30 of the 

second calendar year.

1

GROUND-WATER RESOURCES OF THE MIDDLE CHATTAHOOCHEE 

RIVER BASIN IN GEORGIA AND ALABAMA, AND UPPER FLINT 

RIVER BASIN IN GEORGIA—SUBAREA 2 OF THE 

APALACHICOLA-CHATTAHOOCHEE-FLINT AND 

ALABAMA-COOSA-TALLAPOOSA RIVER BASINS

By Melinda J. Chapman and Michael F. Peck

ABSTRACT

Drought conditions in the 1980’s focused attention on the multiple uses of the surface- and ground-water 

resources in the Apalachicola-Chattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River basins in 

Georgia, Alabama, and Florida. State and Federal agencies also have proposed projects that would require additional 

water resources and revise operating practices within the river basins. The existing and proposed water projects create 

conflicting demands for water by the States and emphasize the problem of water-resource allocation. This study was 

initiated to describe ground-water availability in the middle Chattahoochee River in Georgia and Alabama, and upper 

Flint River in Georgia, Subarea 2 of the ACF and ACT River basins, and to estimate the possible effects of increased 

ground-water use within the basin.

Subarea 2 encompasses about 4,100 square miles (mi2), which includes about 2,250 mi2 of the Chattahoochee 

River basin and 1,850 mi2 of the Flint River basin in the Piedmont physiographic province of west-central Georgia 

and eastern Alabama. Subarea 2 includes about 26 percent of the total 8,740 square-mile area of the Chattahoochee 

River basin and about 22 percent of the total 8,460 square-mile area of the Flint River basin. The study area is underlain by a two-component aquifer system composed of a fractured, crystalline-rock aquifer characterized by little or no 

primary porosity or permeability; and the overlying weathered regolith (saprolite), which generally behaves as a 

porous-media aquifer. In some areas, a transition zone lies between the regolith and unweathered crystalline bedrock.

The conceptual model described for this study qualitatively subdivides the ground-water flow system into 

local (shallow), intermediate, and regional (deep) flow regimes. Ground-water discharge to tributaries mainly is from 

local and intermediate flow regimes and varies seasonally. The regional flow regime probably represents steady-state 

conditions and discharges chiefly to major drains such as the Chattahoochee and Flint Rivers. Ground-water 

discharge to major drains originates from all flow regimes. Mean-annual ground-water discharge to streams 

(baseflow) is considered to represent the long-term, average recharge to ground water. The mean-annual baseflow 

was estimated using an automated hydrograph-separation method, and represents discharge from the local, 

intermediate, and regional flow regimes of the ground-water flow system. Mean-annual baseflow exiting Subarea 2 

was estimated to be 5,800 cubic feet per second. Mean-annual baseflow represented about 68 percent of total meanannual stream discharge in the Chattahoochee River basin and 49 percent in the Flint River basin at the Subarea 2–

Subarea 3 boundary. 
2

Stream discharge for selected sites on the Chattahoochee River and its tributaries were compiled for the years 

1941, 1954, and 1986, during which sustained severe droughts occurred throughout most of the ACF-ACT area. 

Stream discharge was assumed to be sustained entirely by baseflow during the latter periods of these droughts. Estimated baseflow (unregulated) near the end of the individual drought years averaged about 13 percent of the estimated 

mean-annual baseflow in the Chattahoochee River basin and 8.7 percent in the Flint River basin in Subarea 2.

The potential exists for the development of ground-water resources on a regional scale throughout Subarea 2. 

Estimated ground-water use in 1990 was about 1.2 percent of the estimated mean-annual baseflow in Georgia and 1.7 

percent in Alabama; and 11.4 and 14.5 percent of the average drought flow in Georgia and Alabama, respectively. 

Because ground-water use in Subarea 2 represents a relatively minor percentage of ground-water recharge, even a 

large increase in ground-water use in Subarea 2 in one State is likely to have little effect on ground-water and surfacewater occurrence in the other. Indications of long-term ground-water level declines were not observed; however, the 

number and distribution of observation wells for which long-term water-level measurements are available in Subarea 

2 are insufficient to draw conclusions. 

INTRODUCTION

Increased and competing demands for water and the droughts of 1980-81, 1986, and 1988 in the ApalachicolaChattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River basins have focused the attention of water 

managers and users in Alabama, Florida, and Georgia, on the water resources in the two basins. The ACF-ACT River 

basins encompass about 42,400 square miles (mi2

) and extend from near the Georgia-Tennessee State line, through 

most of central and southern Alabama and Georgia and part of the Florida panhandle to the Gulf of Mexico (fig. 1). 

Ground- and surface-water systems of the ACF-ACT River basins behave as an integrated, dynamic flow system 

comprised of an interconnected network of aquifers, streams, reservoirs, control structures, floodplains, and estuaries. 

The degree of hydrologic interaction between ground water and surface water suggests that the water resources be 

investigated and managed as a single hydrologic entity, to account for the climatic and anthropogenic factors that 

influence the flow systems.

Recent water projects and resource allocations, and other actions proposed by Federal, State, and local 

agencies, have resulted in conflicts among the States of Alabama, Florida, and Georgia, and the U.S. Army Corps of 

Engineers (Corps). The Corps has been given the authority to regulate the Nation’s surface waters through the Rivers 

and Harbors Act of 1927, in accordance with the U.S. House of Representatives Document Number 308, 69th U.S. 

Congress. Proposed projects designed to increase development and to re-allocate surface-water supplies in Georgia, 

based on revised operating practices of control structures for flood control, navigation, and hydropower generation, 

and a proposal to construct a dam and reservoir have met with opposition from Alabama and Florida. As a result, in 

1991, the U.S. Congress authorized the Corps to initiate a Comprehensive Study of the ACF-ACT River basins that 

would “develop the needed basin and water-resources data and recommend an interstate mechanism for resolving 

issues” (Draft Plan of Study, Comprehensive Study, Alabama-Coosa-Tallapoosa and Apalachicola-ChattahoocheeFlint River basins, prepared by: The Comprehensive Study Technical Coordination Group, July 1991, U.S. Army 

Corps of Engineers, Mobile District).

In 1992, the Governors of Alabama, Florida, and Georgia; and the U.S. Army, Assistant Secretary for Civil 

Works, signed a Memorandum of Agreement (MOA) establishing a partnership to address interstate water-resource 

issues and promote coordinated systemwide management of water resources. An important part of this process is the 

Comprehensive Study of the ACF and ACT River basins. Since this signing, the Study Partners defined scopes of 

work to develop relevant technical information, strategies, and plans, and to recommend a formal coordination 

mechanism for the long-term, basinwide management and use of water resources needed to meet environmental, 

public health, and economic needs (U.S. Army Corps of Engineers, written commun., 1993). The U.S. Geological 

Survey (USGS) was requested to assist in the development of a scope of work for the ground-water-supply element of 

the Comprehensive Study, and in June 1993, was asked to conduct that study element.

Eight subareas of the ACF-ACT River basins were identified by the Study Partners and the USGS on the basis 

of hydrologic and physiographic boundaries. Addressing the study at the smaller, subarea scale within the ACF-ACT 

River basins facilitated evaluation of the ground-water resources on a more detailed scale. This report is one of a 

series of eight reports that present results of ground-water studies of the ACF-ACT subareas. 
3
4

Purpose and Scope

This report describes the ground-water resources of the middle Chattahoochee River in Georgia and Alabama, 

and upper Flint River in Georgia—Subarea 2 of the ACF-ACT River basins. The report provides an analysis of 

ground-water resources that can be used to address resource-allocation alternatives created by existing and proposed 

uses of the water resources in the river basins. Specific objectives of this study were to:

• describe a conceptual model of ground-water flow and stream-aquifer relations;

• describe the hydrologic setting of Subarea 2;

• quantify mean-annual and drought period ground-water contributions to the Chattahoochee 

River from Whitesburg, Ga., to Columbus, Ga., and to the Flint River from the headwaters 

to Culloden, Ga., and the ground water exiting Subarea 2; including separate computations 

of the contributions from Georgia and from Alabama; and

• describe and evaluate ground-water utilization and general development potential.

 Findings contained herein are but one component of a multidiscipline assessment of issues related to the 

basinwide utilization and management of water. This report is not intended to provide definitive answers regarding 

the acceptability of ground-water-resource utilization or the potential for additional resource development. Such 

answers are dependent on the synthesis of results from all components of the Comprehensive Study and on 

subsequent consideration by the State and Federal water managers responsible for decision making within the basin.

The report scope includes literature and data searches and an assessment of existing geologic data. A 

conceptual model that describes the hydrologic processes governing the ground- and surface-water flow was 

developed, and an evaluation of ground-water utilization was made by compiling and evaluating existing hydrologic, 

geologic, climatologic, and water-use data. Field data were not collected during this study.

Physical Setting of Study Area

The Subarea 2 study area encompasses about 4,100 mi2 in west-central Georgia and eastern Alabama (fig. 1). 

The study area is bounded to the northeast by the upper Chattahoochee River basin (Subarea 1) in Georgia, to the 

south by the lower Chattahoochee and Flint River basins (Subarea 3) in Georgia and Alabama, to the east by the 

Altamaha River basin, and to the west by the Tallapoosa River basin of the ACT River basins (Subarea 5) in Alabama 

and Georgia (fig. 1).

Physiography

Ninety-nine percent of Subarea 2 lies within the Piedmont Province (fig. 2). A small part of Subarea 2 along 

the downstream section of the Chattahoochee River, is located in the Coastal Plain Province. For purposes of this 

discussion, Subarea 2 is considered to be comprised entirely of a Piedmont hydrologic setting. Land-surface altitudes 

in the study area range from about 360 feet (ft) above sea level in southern Talbot County, Ga., to 1,395 ft in Harris 

County, Ga. The altitude of intermountain plateaus within the province ranges from about 1,600 to 1,700 ft (Brackett 

and others, 1991). Most streams are characterized by a dendritic drainage pattern. Piedmont topography is 

characterized by low, rolling hills in the north and a broad rolling upland or plateau in the south (Cressler and others, 

1983). The Piedmont is comprised of metamorphic and igneous rocks that are overlain by regolith of varying 

thickness. The regolith in the study area is composed of semi-consolidated to unconsolidated saprolite (weathered 

bedrock), soil, and other surficial deposits (Clarke and Peck, 1991).

Climate

The climate in Subarea 2 is moist and temperate. The area receives an average of 51 inches (in.) of 

precipitation annually (Cressler and others, 1983; Carter and Stiles, 1983). Precipitation occurs primarily during the 

winter and early spring. The average annual temperature is about 63 ° F. Average daily temperature ranges from 

about 44 ° F during the winter to 83 ° F during the summer (U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, 1992).
5
6

Ground-Water Use

The estimated ground-water use in Subarea 2 during 1990 was about 26 million gallons per day (Mgal/d) or 

about 40 cubic feet per second (ft3/s) (Marella and others, 1993). Of this total, about 18 percent was for public water 

supply, about 36 percent for domestic water supply, 5 percent for self-supplied industrial and commercial activities, 

and 41 percent for agricultural use. The largest ground-water use in the middle Chattahoochee River basin in Georgia, 

Subarea 2, is for domestic water supply and in Alabama, is for agricultural supply. For the upper Flint River basin, 

Georgia, Subarea 2, both domestic and agricultural use is about 8 percent (table 1).

Table 1. Estimated ground-water use, by category, Subarea 2, 1990

[Mgal/d, million gallons per day; ft3/s, cubic feet per second]

Public water supply Self-supplied industrial 

and commercial Agricultural Domestic Total

(Mgal/d) (ft3/s) (Mgal/d) (ft3/s) (Mgal/d) (ft3/s) (Mgal/d) (ft3/s) (Mgal/d) (ft3/s)

Chattahoochee River basin

Georgia 1.1 1.7 0.6 0.9 0.9 1.4 4.0 6.3 6.6 10.2

Alabama .8 1.2 .1 .2 4.6 7.1 .4 0.6 5.9 9.1

Flint River basin

Georgia 2.8 4.3 .6 .9 5.2 8.0 4.9 7.6 13.4 20.7

Subarea 2 total 4.7 7.2 1.3 2.0 10.6 16.5 9.3 14.5 25.9 40.0

Ground-water use reported by Marella and others (1993) is by county; ground-water use in those counties that 

are partially in Subarea 2 are reported herein for Subarea 2 only. Ground-water use for public water supply, and selfsupplied industrial and commercial uses were determined by using site-specific data. Ground-water pumpage for 

domestic purposes was determined by subtracting the population served by public supply facilities from the total 

population of the county or hydrologic unit, then multiplying that number by a water-use coefficient of 75 gallons per 

day (gal/d) per person. Agricultural ground-water use was estimated by multiplying the reported county use by the 

percentage of the land area of the county in Subarea 2.

Most small communities outside the Metropolitan Atlanta area use ground water as their primary water 

supply. Rapid increases in population in the Metropolitan Atlanta area, along with the variability of surface-water 

supplies during drought conditions, have caused some municipalities to investigate the possibility of supplementing 

surface-water supplies with ground water. The city of Fayetteville, Fayette County, Ga., installed three wells in 1988 

to supplement their surface-water supply during periods of peak demand and during droughts.

Previous Investigations

The results of several regional studies have described ground-water resources in crystalline-rock 

hydrogeologic settings in the Piedmont Province of the southeastern United States. The major objectives of regional 

studies were to formulate concepts regarding the availability of ground water and to determine possible controlling 

factors that affect or control well yield and ground-water quality. Conceptual models of hydrogeologic frameworks of 

the crystalline-rock aquifers in this region evolve as information increases (Chapman and others, 1993). 

Some of the earliest reports describing ground-water resources in the crystalline rocks of the Piedmont were 

by McCallie (1898, 1908), who concluded that the yield of wells completed in bedrock would be sufficient only for 

rural use, and would not be a viable source for large cities such as Atlanta and Macon. In urban areas, wells would be 

susceptible to contamination from “local drainage”; an Atlanta public supply well (2,175 ft deep), apparently was 

contaminated after only a few years of use (McCallie, 1898).

Herrick and LeGrand (1949) inventoried a large number of wells in the Atlanta region and conducted regional 

geologic mapping to determine possible factors influencing ground-water availability and quality. They concluded 

that the occurrence of ground water in the Metropolitan Atlanta area depended largely on factors, such as rock type, 

structural features, degree of weathering, and topography. Geologic settings considered to be favorable for 

developing high-yielding wells were discussed for a variety of rock types, geologic structural conditions, and 
7

topographic settings. Although the study represented a reconnaissance rather than a detailed evaluation, Herrick and 

LeGrand (1949) recognized that variations in the rock character and attitude strongly influence the availability of 

ground water, and distinct differences could be observed within intervals of feet in the Piedmont region. Herrick and 

LeGrand (1949) also related the quality of ground water to rock type. Ground water from granitic rocks was 

substantially less mineralized compared to water from amphibolites and hornblende gneisses, which contained 

elevated concentrations of calcium and magnesium. 

Carter and Herrick (1951) evaluated water use and sources of water supply (including surface water) in the 

Metropolitan Atlanta area and estimated future water-supply needs. Historically, dug wells were the primary sources 

of water supply in the Atlanta area until the late 1800’s, when surface-water sources were developed to meet 

increasing water-supply demands. The study examined the relation between ground-water availability and certain 

geologic factors, such as joints, faults, and other fractures. The investigators evaluated well yield, total depth of wells, 

and the importance of aquifer tests in assessing sustained yield and potential well interference. The report concluded 

that the potential for ground-water development in the Atlanta area was considerable, and that wells could serve as 

sole sources of water supply for rural communities and some industries throughout the Piedmont region. Carter and 

Herrick (1951) related hardness of ground water to mafic rocks, such as amphibolites and hornblende gneisses, and 

determined that granitic rocks contained softer water. 

Thomson and Carter (1955) presented streamflow data for the 1954 drought throughout Georgia, including the 

Chattahoochee and Flint Rivers in Subarea 2. The authors included a discussion of the lack of rainfall—the rainfall 

deficit in most areas was at least 15 in. Streamflow was below normal in the Piedmont region by July 1954. Record 

low flows were recorded during September and early October.

A later report by Thomson and Carter (1963) continued a discussion of the 1954 drought streamflow data for 

Georgia. The authors stated that the 1954 data may be the last available extreme drought streamflow data representing 

natural flow conditions. For the Chattahoochee and Flint Rivers in Subarea 2, the 1954 drought was the second most 

severe in 57 years. The most severe drought for the West Point station occurred in 1925 (Thomson and Carter, 1963). 

Stewart and others (1964) and Stewart (1962, 1964) conducted an investigation to determine the effects of 

waste-disposal migration in weathered crystalline rocks at the Georgia Nuclear Laboratory, Dawson, Ga. Infiltration 

tests were conducted in a saprolite disposal pit to determine the rate and areal extent of possible waste leakage into 

the shallow ground-water system. The purpose of the study was to determine the feasibility of using infiltration pits 

constructed in weathered crystalline rocks for the disposal of liquid wastes. The three water-bearing units evaluated 

were near-surface alluvium, regolith, and unweathered crystalline bedrock. The investigation of regolith material 

included estimates of saprolite porosity and permeability and ion-exchange capacity from core samples, the 

measurement of infiltration rates, and shallow aquifer testing. Bedrock wells also were drilled and estimates of 

transmissivity were made from aquifer-test data. A noticeable increase in ground-water mounding was observed 

along the strike of schistosity in the regolith. Other fieldwork included surficial geologic mapping and the collection 

of ground-water quality samples, streamflow data, and continuous ground-water levels in wells. During aquifer 

testing, the largest drawdowns in the saprolite wells were along the strike of schistosity. Rates of ground-water 

movement were calculated from hydraulic gradient data and estimates of porosity and permeability in the saprolite.

LeGrand (1967) proposed a rating system, based on topographic setting and soil (regolith) thickness, to assess 

ground-water conditions in the Piedmont and Blue Ridge Provinces of the southeastern United States. LeGrand 

(1967) developed the concept of a statistical percentage chance of obtaining a certain yield under various conditions. 

Actual quantifiable yields were said to be difficult to estimate because well yields were shown to vary substantially 

within 100 ft of lateral distance. LeGrand (1967) also stated that fractures seemed to diminish with increasing depth, 

and that the relation between well yield and depth was complex.

Cressler and others (1983) conducted a study of ground-water in the Atlanta area to assess the availability, 

quality, and quantity of ground water in crystalline rocks and to devise methods for locating sites for high-yielding 

wells that could serve as alternative or supplemental sources of water supply. Results from that study indicated that 

the highest well yields in the Atlanta area seemed to be associated with wells tapping contact zones between rocks of 

contrasting lithology, fault zones, stress-relief (horizontal) fractures, drainage features controlled by local structural 

characteristics, concentrated jointing within folded rocks, and shear zones. Results of this study indicated that 

topographic drainage features may or may not be related to underlying water-bearing features in the rocks. From data 

gathered using borehole geophysical logs of wells, Cressler and others (1983) determined that the size, spacing, and 
8

interconnection of water-bearing openings differed greatly from one rock type to another. The range in well yield 

within an identified water-bearing unit was highly variable, and high-yielding wells were present in each unit. Local 

features in the rocks were recognized as generally controlling well yield. The authors also noted that water from wells 

open to mafic rock types contained higher concentrations of iron, magnesium, manganese, dissolved solids, and 

possibly chloride, than water from wells open to granitic rocks in the Metropolitan Atlanta area. The pH of water 

samples collected from wells completed in mafic rocks also was relatively high compared to samples collected from 

wells completed in granitic rocks.

Hale and others (1989) presented streamflow data for the 1986 drought in Alabama, Georgia, North Carolina, 

South Carolina, Tennessee, and Virginia. Minimum flows occurred in midsummer during 1986, which was several 

months earlier than the regional droughts of 1954 and 1981. The source of this drought was a rainfall deficit that 

began in 1985 and persisted until late summer 1986. The range of 7-month precipitation totals was about 30 to 85 

percent of normal. The authors reported minimum low flows for 1, 7, 30, 60, and 90 days from April 1, 1986 through 

March 31, 1987.

Gorday (1989) conducted a study of ground-water resources in Lamar County, near the eastern boundary of 

Subarea 2. Gorday described ground-water occurrence in discontinuities, (such as faults, geologic contacts, stressrelief fractures, foliation, and joints), in the crystalline bedrock. A survey of well yields provided information on a 

low-yielding schist and gneiss unit. Gorday (1989) also noted that water from wells open to mafic rock types had 

higher concentrations of iron, manganese, dissolved solids, and possibly chloride, and a higher pH than water from 

wells open to granitic rocks in the Metropolitan Atlanta area. Recommendations for well site selection were made in 

relation to topography and topographic lineaments. The Towaliga fault zone was identified as being the most 

favorable area for ground-water exploration due to the highly fractured texture of the mylonite within the fault zone. 

The thickness of the regolith, which provides storage for ground water, was noted to be thicker within the fault zone 

(Gorday, 1989).

Clarke and Peck (1991) conducted a study of a nine-county area south of the Metropolitan Atlanta area. The 

study consisted of a general evaluation of the existing and possible future development of ground-water resources. 

Data collection consisted of the compilation of geologic, hydrologic, and water-quality data. An extensive inventory 

of wells and springs was assembled. The study followed the same method as that used by Cressler and others (1983). 

Many high-yielding wells were inventoried; reported yields for two of which were 600 and 700 gallons per minute 

(gal/min). Clarke and Peck (1991) concluded that ground water is a viable resource that had been underutilized in the 

variety of hydrogeologic settings in the area. Ground-water quality problems included elevated concentrations of 

iron, manganese, fluoride, and radon.

As part of an investigation of the hydrogeologic controls on the occurrence and movement of ground water in 

the Piedmont and Blue Ridge physiographic provinces of Georgia, the Georgia Geologic Survey conducted local 

investigations at 10 hydrologic test sites (Brackett and others, 1991). Two of the sites were located in Subarea 2. 

Geologic and aquifer-test data were collected at a well site in Newnan, Coweta County, Ga. Another study conducted 

in Coweta County, included the collection of geologic data, surface and borehole geophysical data, and aquifer-test 

data (Brackett and others, 1991).

A study conducted by the Georgia Geologic Survey (O’Connor and others, 1993) assessed ground-water 

availability in Carroll, Douglas, Haralson, Polk, and Paulding Counties, Ga., located at the northwestern boundary of 

Subarea 2. Objectives of the study were to estimate the quantity of the ground-water resource that would be available 

to municipal and industrial users, and identify favorable areas for ground-water exploration. The estimated 

availability of ground water for the Piedmont in the five-county West-Georgia study area was 24 Mgal/d (37 ft3/s). 

The authors used geographic information system (GIS) methods to overlay hydrogeologic and environmental data. 

Considered hydrogeologic factors included topographic slope, soils, geology, topographic lineaments, and perennial 

streams. Environmental factors included population density, solid-waste disposal sites, hazardous-waste disposal 

sites, land application sites, wastewater treatment plants, and abandoned sulfide mines and other heavy metal 

anomalies. Favorable ground-water exploration areas were identified based on the ranking of those factors.

The most recent investigation of ground-water resources near the study area was by Chapman and others 

(1993). A study of the relation of geologic controls, well yields, and ground-water quality was conducted in the area 

of Zebulon, Pike County, Ga. Well yields and potential ground-water quality problems were similar to those indicated 

by Cressler and others (1983) and Clarke and Peck (1991).
9

The Geological Survey of Alabama recently developed a ground-water database of bedrock wells drilled in 

the Alabama Piedmont to statistically evaluate the effects of well construction, topography, and hydrogeologic factors 

on well yields. The distribution of well yields was mapped (Guthrie and others, 1994). More than 1,200 well records 

were evaluated for that study. Well yields varied significantly with total depth, use, diameter, topographic setting, 

depth to the water table, hydrogeologic unit, and tectonic belt. Well use and diameter were determined to be the most 

significant factors controlling the variation in reported yields. High-yielding wells appeared to be located in areas 

characterized by structurally-controlled surface drainage and less than 100 ft of regolith cover, in topographic settings 

such as slopes, draws, and valleys, and in areas generally coinciding with lineaments observed from regional satellite 

images. The distribution of high-yielding wells (more than 50 gal/min) suggests a correlation with regional geologic 

trends (Guthrie and others, 1994).

Most recently, Steele and others (1994) conducted a local-scale study at a research site in Lamar County, Ga., 

near the eastern boundary of Subarea 2. The major study objective was to determine the influence of pumping from a 

test production well for the city of Barnesville. Observation wells were installed within the regolith and bedrock near 

the pumping well and across a stream. Field studies included geologic mapping, geologic core collection, 

magnetometer surveys, ground-water level monitoring, collection of aquifer-test data, and the collection of groundwater-quality data. The regolith was determined to provide primary storage for water that supplies the production 

well. The primary pathway for recharge was in the transition zone between the regolith and the bedrock; the 

production well taps both the transition zone and the bedrock. Pumping of the production well caused drawdown in 

both the regolith and bedrock wells located across Big Towaliga Creek. The features controlling ground-water flow to 

the production well in the bedrock were determined to be parallel to the strike of the rocks along foliation and in the 

direction of the dip of foliation. Another general conclusion of the study was that water that recharges the aquifer 

under pumping conditions may not reach the aquifer under unstressed conditions. Delineation of the recharge area of 

the fractured bedrock and transition-zone aquifer was determined to be more complex than the general assumptions 

of the area of influence coinciding with drainage basin boundaries. Under pumping conditions, the area of influence 

of the production well extended across the creek (Steele and others, 1994)

Reports describing methods of estimating streamflow and ground-water discharge to streamflow include 

Bingham (1982), Hirsch (1982), Hoos (1990), Rorabaugh (1960, 1964), Rutledge (1991, 1992, 1993), and Mayer 

and Jones (1996). Data collected as part of the ongoing surface-water monitoring program of the USGS are published 

annually in the reports “Water-Resources Data, Georgia.” Other reports containing information about the surfaceand ground-water resources of the ACF-ACT River basin area are listed in the “Selected References” section of 

this report.

Well and Surface-Water Station Numbering Systems

Wells in Georgia are numbered by a system based on U.S. Geological Survey topographic maps. Each 7 1/2-

minute topographic quadrangle map in Georgia has been assigned a number and letter designation beginning at the 

southwest corner of the State. Numbers increase sequentially eastward through 39; letters advance northward through 

“Z,” then double-letter designations “AA” through “PP” are used. The letters “I,” “O,” “II,” and “OO” are not used. 

Wells and springs inventoried in each quadrangle are numbered sequentially beginning with “1.” Thus, the second 

well inventoried in the Zebulon quadrangle (designated 11Y) is designated 11Y002.

Wells in the USGS Ground-Water Site Inventory (GWSI) data base are assigned a 15-digit identification 

number based on the latitude and longitude grid system. The first six digits denote the degrees, minutes, and seconds 

of latitude. The next seven digits denote the degrees, minutes, and seconds of longitude. The last two digits (assigned 

sequentially) identify wells within a one-second grid.

The USGS established a standard identification numbering system for all surface-water stations in 1950. 

Stations are numbered according to downstream order. Stations on a tributary entering upstream of a main-stream 

station are numbered before and listed before the main-stream station. No distinction is made between continuousrecord and partial-record stations. Each station has a unique eight-digit number that includes a two-digit part number 

(02 refers to natural drainage into the Eastern Gulf of Mexico) and a six digit downstream order number. Gaps are left 

in the series of numbers to allow for new stations that may be established; hence, the numbers are not consecutive. 

The complete number for each station includes a two-digit part number “02” plus the downstream-order number, 

which can be from 6 to 12 digits. All records for a drainage basin, encompassing more than one State, can easily be 

correlated by part number and arranged in downstream order. 
10

Approach and Methods of Study

This study included several work elements used to appraise the ground-water resources of Subarea 2, 

including the description of a conceptual model of ground-water flow and stream-aquifer relations, and an assessment 

of ground-water availability. The approach and methods used to accomplish these tasks included:

• compilation of information and data from pertinent literature, including geologic, groundwater, streamflow, and ground-water use data;

• separation of streamflow hydrographs to estimate mean-annual ground-water contribution to 

the Chattahoochee and upper Flint Rivers and their tributaries;

• evaluation of streamflow records and periodic discharge measurements during drought 

periods to estimate “worst-case” streamflow conditions; and

• comparison of 1990 ground-water use with mean-annual and drought-flow conditions to 

evaluate ground-water availability.

Literature and data reviews provided information necessary to describe a conceptual model of groundwater/surface-water relations. Much of the conceptual model is based on results of previous investigations by Toth 

(1962, 1963), Freeze (1966), Freeze and Witherspoon (1966, 1967, 1968), Winter (1976), Heath (1984, 1989), Faye 

and Mayer (1990), and Miller (1990). These studies suggest that large rivers, such as the Chattahoochee, and their 

tributaries function as hydraulic drains for ground-water flow, and that during significant droughts, most of the 

discharge in these streams is contributed by ground water.

Streamflow data were compiled from the USGS Automated Data Processing System (ADAPS) database. 

Streamflow records from continuous-record and miscellaneous discharge-measurement stations were used for 

hydrograph-separation analyses and drought streamflow evaluation.

Stream-aquifer relations were quantified using two approaches: (1) the hydrograph-separation method of 

Rorabaugh (1960, 1964) and Daniel (1976), called the recession-curve-displacement method; and (2) a drought-flow 

mass-balance analysis of streamflow. The hydrograph-separation method was used to estimate the mean-annual 

discharge of ground water (baseflow) to the basins. An estimate also was made of the mean-annual volume of ground 

water discharged from Subarea 2 to Subarea 3 as baseflow in the middle Chattahoochee River basin in Georgia and 

Alabama, and upper Flint River basin, Georgia. The mean-annual baseflow was used as a base or reference with 

which to compare and evaluate droughts under “worst-case” conditions. The mass-balance analysis was used to 

estimated the baseflow contributions to the surface-water system during historically significant droughts and the 

ground water delivered as baseflow from Subarea 2 to Subarea 3 near the end of these droughts.

Mean-Annual Baseflow Analysis

Discharge data from continuous-record gaging stations along the Chattahoochee and Flint Rivers and their 

tributaries were selected for baseflow analysis based on the period of record of unregulated flow. Streamflow 

representative of low, average, and high years of stream discharge were evaluated by hydrograph-separation methods 

to estimate annual baseflow. The mean-annual baseflow was then computed as the average baseflow of the three 

representative flow years.

The selection process for the most representative year of low, average, and high stream discharge involved 

objective statistical examination of the discharge data, followed by some subjectivity in the final choice of the water 

year selected. Hydrographs acceptable for separation were characterized by relatively normal distributions of daily 

stream discharge, small ranges of discharge, and the absence of extremely high, isolated peak stream discharge. For 

each station, the mean annual stream discharge was computed for the period of record of unregulated flow and used 

as a reference mean for low-, average-, and high-flow conditions for that station. The mean- and median-annual 

stream discharge for those water years identified as acceptable were compared to the reference mean. Because 

extremely high discharge during a water year could greatly influence the mean but not the median (which is similar to 

the geometric mean for positively skewed data sets, such as discharge), the process of selecting representative water 

years for low-, average-, and high-flow conditions considered the position of the mean discharge for the selected year 

relative to the median and the reference mean. The hydrographs for these representative water years were examined 

and separated. True subjectivity in the selection process entered only at this point, such that, if acceptable 

hydrographs were available for several years, one year arbitrarily was chosen over the others.
11

The separation analyses were conducted using the computer program SWGW (Mayer and Jones, 1996); which 

is an automated version of the recession-curve-displacement method, often referred to as the Rorabaugh or 

Rorabaugh-Daniel method. The SWGW program was applied to a water-year period of streamflow data. SWGW 

utilizes daily mean discharge data collected at unregulated stream-gaging sites and requires at least 10 years of record 

to accurately estimate a recession index necessary for hydrograph-separation analysis.

The hydrograph-separation method estimates the ground-water component of total streamflow. In general, the 

streamflow hydrograph can be separated into two components — surface runoff and baseflow (ground-water 

discharge to streams). Figure 3 shows the graphical output from the SWGW program. Surface runoff is the quick 

response (peaks) of stream stage to precipitation and nearby overland flow.

Application of the recession-curve-displacement method requires the use of the streamflow recession index. 

The streamflow recession index is defined as the number of days required for baseflow to decline one order of 

magnitude (one log cycle), assuming no other additional recharge to the ground-water system. The streamflow 

recession index is a complex number that reflects the loss of ground water to evapotranspiration (Daniel, 1976) or 

leakage, and the influence of geologic heterogeneities in the basin (Horton, 1933; Riggs, 1963). The slope of the 

streamflow recession is affected by evapotranspiration, such that the streamflow recession index varies from a 

maximum during the major rise period to a minimum during the major recession period (fig. 3). The major rise period 

of streamflow generally occurs from November through March or April, when precipitation is greatest and 

evapotranspiration is least. The major recession period occurs during late spring through fall and coincides with a 

period of lesser precipitation, higher temperatures, and greater evapotranspiration (fig. 3). Two recession indices were 

estimated for streamflow observed at each continuous-record gaging station used in the mean-annual baseflow 

analysis; one index for the major rise period and one for the major recession period.

Available ground-water-level data indicate that long-term changes in ground-water storage are minimal in 

Subarea 2. Because long-term storage changes are minimal, mean-annual ground-water discharge, estimated using 

the hydrograph-separation method, is considered an estimate of minimum mean-annual recharge. Also, aquifers at a 

regional scale in the middle Chattahoochee River basin in Georgia and Alabama, and upper Flint River basin in 

Georgia, Subarea 2 are considered, for purposes of analysis, to respond as homogeneous and isotropic media.

Results of the mean-annual baseflow analysis are based on measured and estimated data, and the analytical 

methods to which they are applied. Drainage areas were measured using the most accurate maps available at the time 

of delineation (Novak, 1985), and are reported in units of square miles. Drainage areas are reported to the nearest 

square mile for areas greater than 100 mi2; to the nearest tenth of a square mile for areas between 10 and 100 mi2; and 

to the nearest hundredth of a square mile for areas less than 10 mi2, if the maps and methods used justify this degree 

of accuracy (Novak, 1985). Annual stream discharge, the sum of the daily mean stream discharges for a given water 

year, is reported in units of cubic foot per second (ft3/s), to the nearest cubic foot per second. Daily mean discharge is 

reported to the nearest tenth of a cubic foot per second for discharge between 1.0 and 9.9 ft3

/s; to the nearest unit for 

discharge between 10 and 100 ft3/s; and is reported using three significant figures for discharge equal to or greater 

than 100 ft3

/s (Novak, 1985).

The accuracy of stream-discharge records depends primarily on: (1) the stability of the stage-discharge 

relation or, if the control is unstable, the frequency of discharge measurements; and (2) the accuracy of measurements 

of stage and discharge, and the interpretation of records. Accuracy of records of streamflow data used in this report 

can be found in annually published USGS data reports, for example, Stokes and McFarlane (1994). The accuracy 

attributed to the records is indicated under “REMARKS” in the annual data reports for each station. “Excellent” 

means that about 95 percent of the daily discharges are within 5 percent of the true discharge; “good,” within 10 

percent; and “fair,” within 15 percent. Records that do not meet these criteria are rated “poor.” The accuracy of 

streamflow records at a station may vary from year to year. In addition, different accuracies may be attributed to 

different parts of a given record during a single year (Novak, 1985).

Results of the mean-annual baseflow analyses are inherently uncertain. The hydrograph-separation method of 

analysis is partly subjective, relying on the input of several user-selected variables. As such, the results of the 

analyses derived and reported herein, are difficult to independently confirm and are presented as estimates of 

unknown quality and confidence. However, because the values in this report are used in several water budgets, not 

only within Subarea 2 but also from subarea to subarea, hydrograph-separation results may be reported to a greater 

significance than the data and analyses warrant to maintain the numerical balance of the water budget; implication of 

accuracy to the extent shown is not intended.
12
13

Drought-Flow Analysis

Daily mean streamflow data collected at gaging stations during periods of low flow and corresponding 

periodic measurements of stream discharge collected at partial-record stations were compiled for the drought years 

1941, 1954, and 1986. These data included nearly concurrent daily measurements of streamflow in the Chattahoochee 

River and periodic measurements of tributary discharge. Data from the Flint River basin were too sparse for a 

detailed analyses of tributary discharge.

Standard periods of analyses for drought studies were selected for all ACF-ACT subareas. The period of 

analysis selected for compiling 1954 drought data was September 15 through November 1, 1954. The selected period 

for the 1986 drought was July 1 through August 14, 1986. Streamflow during these periods was considered to 

represent the “worst-case” of ground-water storage and availability throughout the ACF-ACT study area. Discharge 

data were sparse during the 1941 drought; therefore, a standard period of analysis was not selected for the entire 

ACF-ACT study area. 

The period of “worst-case” conditions may not include the minimum streamflow that occurred during a 

drought at a streamflow measurement site. Minimum drought flows typically occur at different times at different 

stations within large watersheds, such as the Chattahoochee and Flint River basins. Rather, the “worst-case” 

evaluation was designed to describe streamflow during the advanced stages of each drought; thus, providing a 

near-contemporaneous summary of streamflow conditions during periods of low flow throughout the ACF–ACT 

study area.

The estimated “worst-case” distribution of Chattahoochee River streamflow near the end of the 1941, 1954, 

and 1986 drought periods was determined by balancing mass in the stream network in a general downstream 

direction during a relatively short interval of time. The tributary discharge to the Chattahoochee River during 

drought periods was calculated using a unit-area discharge extrapolated to the entire drainage area of the tributary. 

Unit-area discharges are based on streamflow measurements that generally are inclusive of only part of the tributary 

drainage, and may not be representative of an average unit-area discharge for the entire tributary drainage. Therefore, 

most unit-area discharges used to estimate discharge at ungaged and unmeasured tributaries were based on 

streamflow data measured at the most downstream point of tributaries to better represent the entire tributary 

contributing area.

Acknowledgments

The authors appreciate BCI Geonetics of Laconia, New Hampshire; and HydroSource Associates of 

Ashland, New Hampshire, for providing information on the results of the ground-water exploration program in 

Fayetteville, Ga.
14

CONCEPTUAL MODEL OF GROUND-WATER FLOW

AND STREAM-AQUIFER RELATIONS

The conceptual model of the ground-water flow and stream-aquifer relations in middle Chattahoochee River 

basin in Georgia and Alabama, and upper Flint River basin in Georgia, Subarea 2, is based on previous work done in 

other areas by Toth (1962, 1963), Freeze (1966), Freeze and Witherspoon (1966, 1967, 1968), Winter (1976), and 

Faye and Mayer (1990). These studies suggest that recharge originates from precipitation that infiltrates the land 

surface, chiefly in upland areas, and percolates directly, or leaks downward to the water table. Ground water 

subsequently flows through the aquifer down the hydraulic gradient and either discharges to a surface-water body or 

continues downgradient into confined parts of an aquifer. Major elements of this conceptual model include descriptions of flow regimes, stream-aquifer relations, recharge to ground water, and ground-water discharge to streams.

Toth (1963) observed that most ground-water flow systems could be qualitatively subdivided into paths of 

local (shallow), intermediate, and regional (deep) flow. Local flow regimes are characterized by relatively shallow 

and short flow paths that extend from a topographic high to an adjacent topographic low. Intermediate flow paths are 

longer and somewhat deeper than local flow paths and contain at least one local flow path. Regional flow paths (fig. 

4) begin at or near the major topographic (drainage) divide and terminate at regional drains, which are the 

Chattahoochee and Flint Rivers in Subarea 2. Depending on local hydrogeologic conditions, all three flow regimes 

may not be present everywhere within the subarea.
15

The water table in Subarea 2 probably is a subdued replica of the land-surface topography but generally has 

less relief. The presence of ground-water flow regimes depends largely on the configuration of the water table, such 

that recharge occurs in highland areas and discharge occurs in lowland areas. Quantities of recharge to the water table 

and ground-water discharge to streams are variably distributed throughout the local, intermediate, and regional flow 

regimes. Local regimes receive the greatest ground-water recharge from the water table and provide the most groundwater discharge to streams. Ground-water discharge to tributary drainages primarily is from local and intermediate 

flow regimes; ground-water discharge to regional drains, such as the Chattahoochee and Flint Rivers, includes 

contributions from the regional as well as local and intermediate regimes.

Seasonal variation in rainfall affects the local ground-water flow regime most significantly, and affects the 

regional flow regime least significantly. Generally, regional flow probably approximates steady-state conditions, and 

long-term recharge to and discharge from this regime will not vary significantly.

Continuum methods of analysis of ground-water flow, such as hydrograph separation, are based on 

assumptions of laminar flow through a medium characterized by systematic changes in primary porosity and 

permeability. Such media generally are classified as porous media. Ground-water flow through porous media is 

commonly termed Darcian flow. Fractured rock media in the Blue Ridge and Piedmont Provinces contain virtually no 

primary porosity or permeability and virtually all ground-water flow occurs through secondary openings. For 

purposes of analysis, continuum methods based on assumptions of Darcian flow are applied to ground-water flow 

through fractured rock media. Such approaches commonly are justified on a regional scale because fracture systems 

typically are ubiquitous and intersecting. 

Results of smaller-scale studies also demonstrate the continuity of ground-water flow through fractured 

media. For example, long-term ground-water pumping operations near Ridgeway, S.C., began in the fall of 1988 to 

dewater fractured Piedmont rocks to accommodate open-pit mining of gold-bearing ore (Glenn and others, 1989). 

Detailed ground-water monitoring around and within the mined areas indicated that after less than one year of 

pumping, drawdown extended in an oblong distribution for more than 1 mi beyond the center of pumping. 

Drawdown decreased uniformly with distance from pumped wells. Nelson (1989) used water-level data from 

numerous monitoring wells at a 120-acre study site constructed in fractured Piedmont rocks to describe streamaquifer relations (non-pumping conditions) near the Rocky River in North Carolina. Nelson (1989) concluded that the 

Rocky River was a drain for ground water discharged from Piedmont rocks, and that observed hydraulic relations 

between the fractured-rock aquifer and the river and within the aquifer at various depths, were consistent with 

porous-media concepts of ground-water flow, as described by Toth (1962, 1963). Under pumping conditions, 

drawdown can extend across surface-water drainage divides in a fractured-rock aquifer, similar to drawdown 

conditions observed in porous media. As part of an ongoing ground-water-resources investigation in the 

Lawrenceville, Ga., area (in the Piedmont Province), drawdown across drainage divides was observed at a distance of 

about 0.9 mi during a 96-hour constant-discharge aquifer test (U.S. Geological Survey, unpublished data from 1995). 

A study of 18 bedrock wells in the Piedmont Province in Virginia showed the influence of a pumping well across 

drainage-basin divides, where significant drawdown was observed in a nonpumping well located 1,900 ft from a 

pumping well in an adjacent drainage basin (Tinkham and others, 1989).

HYDROLOGIC SETTING

The hydrologic framework of Subarea 2 contains dynamic hydrologic systems consisting of aquifers, streams, 

reservoirs, and floodplains. These systems are interconnected and form a single hydrologic entity that is stressed by 

natural hydrologic and climatic factors and by anthropogenic factors. For this discussion, the hydrologic framework 

is separated into two systems: the ground-water system and surface-water system. 

Ground-Water System

The ground-water system forms as geology and climate interact. Geology primarily determines the aquifer 

types present, as well as the natural quality and quantity of ground water. Climate primarily influences the quantity of 

ground water. 
16

Geology

A detailed description of the diverse and complex geology of Subarea 2 is beyond the scope of this study; 

however, a brief description of the geology of the subarea is presented, based on selected published descriptions of 

various geologic investigations. The “Selected References” section of this report lists selected geologic 

investigations.

The Piedmont Province is characterized by complex sequences of igneous rocks of Precambrian to Paleozoic 

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

rocks of Mesozoic age also are present (D.C. Prowell, U.S. Geological Survey, oral commun., 1996). Collectively, 

these rocks are called crystalline rocks. The metamorphic rocks originally were sedimentary, volcanic, and 

volcaniclastic rocks that have been altered by several stages of regional metamorphism to slate, phyllite, schist, 

gneiss, quartzite, and marble; a variety of cataclastic rocks also are present. The metamorphic rocks are extensively 

folded and faulted. The intrusive igneous rocks, dominantly granites and lesser amounts of diorite and gabbro, occur 

as widespread plutons. The rocks are characterized by a complex outcrop and subsurface distribution pattern, as 

shown on geologic maps of various scales (Szabo and others, 1988). Because rock characteristics can vary 

significantly on the scale of a few tens of feet within the same lithologic unit, detailed geologic-unit differentiation 

can be accomplished only on the scale of a topographic quadrangle, or larger. The Piedmont contains major fault 

zones that generally trend northeast-southwest and form the boundaries between major rock groups (Georgia 

Geologic Survey, 1976). One such fault is the Brevard Zone of Cataclasis, which extends from Cornelia in 

northwestern Georgia, through the Metropolitan Atlanta area; and to Whitesburg, near the boundary with Subareas 1 

and 2 (Georgia Geologic Survey, 1976). The Chattahoochee River generally is within or parallel to the Brevard Zone 

of Cataclasis in the upper Chattahoochee River basin (Subarea 1) having trellised and rectangular drainage patterns 

which reflect geologic control. However, the middle Chattahoochee River basin in Georgia and Alabama, and the 

upper Flint River basin in Georgia, generally exhibit a dendritic pattern, indicating a superimposed drainage. 

Regional fault structures mapped in Subarea 2 include the Brevard Zone of Cataclasis near Whitesburg, Ga., and the 

Towaliga, and Goat Rock Faults near Lake Harding (Georgia Geologic Survey, 1976). 

The crystalline igneous and metamorphic rocks largely are covered by a layer of weathered rock and soil 

known as regolith. The regolith ranges in thickness from a few to more than 150 ft, depending upon the type of parent 

rock, topography, and hydrogeologic history. From the land surface, the regolith consists of a porous and permeable 

soil zone that grades downward into a clay-rich, relatively impermeable zone that overlies and grades into porous and 

permeable saprolite, generally referred to as a transition zone (Heath, 1989). The transition zone grades downward 

into unweathered bedrock. 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). In general, the massive granite 

and gabbro rocks are poorly fractured and are characterized by a thin soil cover; in contrast, the schists and gneisses 

are moderately to highly fractured. The weathering of the rocks is erratic and usually deep; remnants of the original 

texture and foliation are retained in the saprolite in many places (Clarke, 1963). 

The ground-water system in the crystalline rocks of the Piedmont Province of Georgia and Alabama is 

controlled largely by geology. Various textural and structural properties in the rocks control permeability characteristics; however, hydraulic head gradients and recharge may be influenced by topography and climatic factors. 
17

Aquifers

The principal aquifers in Subarea 2 are fracture-conduit aquifers in igneous and metamorphic rocks of the 

Piedmont Province (fig. 5); the general physical characteristics of these aquifers are given in table 2. As a result of 

intense heat and pressure during metamorphism and structural deformation, bedrock aquifers of the Piedmont 

Province contain little or no primary porosity (less than two percent), and are poorly permeable. In the bedrock, 

water-bearing zones occur in areas where differential weathering along geologic features produces openings that 

enhance permeability and enable the storage and flow of ground water (Chapman and others, 1993). Geologic 

features favorable for the development of secondary openings include lithologic contacts, foliation, joints, fractures, 

faults, folds, quartz veins, and pegmatites. 

Table 2. Generalized geologic units in Subarea 2, and water-bearing properties, chemical characteristics, and well 

yields

[—, no available data]

Physiographic 

province Geologic age and lithology Aquifer type Water-bearing properties and chemical characteristics Well yield

Piedmont and 

Blue Ridge

regolith: soil, alluvium, colluvium, and 

saprolite derived from various-aged rocks

porous-media; 

preferential flow

generally suitable for 

domestic use only

—

Precambrian to Paleozoic—bedrock: 

quartzite, slate, gneiss, schist, marble, 

phyllite, granite, amphibolite

fracture-conduit local, discontinuous 

properties, well yields 

variable, water quality 

generally good

1 to 25 gallons per minute 

typical; may exceed 700 

gallons per minute (Kidd, 

1989; Clarke and Peck, 1991)

Fracture-conduit aquifers in the Piedmont Province consists of two water-bearing zones—a shallow, regolith 

zone and a deeper, bedrock zone (fig. 6). The regolith may consist of soil, alluvium, colluvium, and saprolite 

(weathered bedrock retaining geologic structural characteristics). In general, the regolith consists of a porous, 

permeable soil at land surface, grading downward into a highly weathered, clay-rich relatively impermeable zone that 

overlies a less-weathered and more permeable transition zone (Heath, 1989). In some instances, ground water in the 

regolith is similar to that in porous media, where intergranular porosity is present in the soil or alluvium, or where 

rocks have been deeply weathered, and retain few structural characteristics. Porosity of the regolith can range from 

20 to 30 percent (Heath, 1984). The transition zone between the saprolite and bedrock contains weathered material 

and boulders, and along structural features, such as foliation and jointing, generally is more permeable than the 

saprolite. Ground-water flow can be preferential in saprolite, where weathered rock retains relict structural features 

(Stewart, 1962, 1964; Stewart and others, 1964). 

The fracture-conduit aquifers are anisotropic and heterogeneous because of the highly complex and locally 

variable geologic characteristics controlling the presence of the water-bearing units in the bedrock and regolith. Rock 

type, structural features, and regolith thickness vary locally and affect the storage capacity and hydraulic conductivity 

of an aquifer (LeGrand, 1967, 1989; Daniel, 1987; Guthrie and DeJarnette, 1989; Schmitt and others, 1989; Chapman 

and others, 1993; Guthrie and others, 1994). 

Recent studies have shown that a thorough evaluation of hydrogeologic settings in areas characterized by 

fracture-conduit aquifers can lead to an increased likelihood of successful development of ground-water resources. 

Most municipal, industrial, and commercial ground-water exploration plans now include consultation with 

hydrogeologists, who evaluate surficial geology, including structural features, topographic relations to geologic 

features, existing well information, and land use. Surface and borehole geophysical surveys also may be conducted 

to delineate subsurface features that indicate the sources of water to wells and the water-bearing properties of the 

rocks.

Ground water in the study area is obtained from either shallow, bored wells that are completed in the regolith, 

or deeper, drilled wells that are completed in the bedrock. Public supply wells are completed in the bedrock and 

casing is grouted about 5 ft into the bedrock to avoid possible contamination from surface runoff and direct 

infiltration through the weathered regolith. Wells drilled for industrial or commercial use generally also are 

completed in the bedrock primarily due to the potential for higher yields. Domestic wells are completed in both the 

regolith (bored wells) and bedrock (drilled wells) (fig. 6). Shallow bored wells that are completed in the regolith can 

be susceptible to contamination and to water-level decline during droughts. 
18
19
20

Well depth in Subarea 2 generally ranges from 100 to 700 ft. Wells may yield water from several fractures 

throughout a borehole, or from a single productive fracture. Conversely, a borehole may not intersect a fracture, or 

the fracture may not be water bearing, and thus, may yield little or no water. Because of the complex nature of the 

secondary permeability in fracture-conduit aquifers, production zones generally are of limited extent. Quantitative 

estimates of aquifer properties such as transmissivity, hydraulic conductivity, and storage coefficient are difficult to 

assess because of the highly localized geologic controls on secondary permeability.

Fracture-conduit aquifers formed in crystalline rocks may yield quantities of water suitable for public or 

industrial supply. Yields from wells completed in the fractured crystalline-rock aquifers of Subarea 2 are highly 

variable. A high-yielding well produces 100 gal/min or greater and yields of as much as 550 gal/min have been 

reported in Subarea 2; typical well yields, however, are 1 to 25 gal/min (table 2). Bedrock wells often are more able 

to sustain yields during droughts.

Ground-water movement in fracture-conduit aquifers mainly is through secondary openings, such as fractures 

and joints, or other enhanced openings along lithologic contacts. Secondary porosity is created by faulting and 

fracturing and is enhanced by weathering along these openings. The bedrock below the weathered zone and laterally 

beyond fractures typically has little or no matrix porosity or primary permeability. Ground-water storage primarily is 

in the overlying weathered rock (regolith or saprolite, which behaves like a porous-media aquifer). The volume of 

water in storage in the regolith is controlled by the porosity and thickness. To a lesser degree, the volume of water in 

storage in the bedrock is controlled by the degree of fracturing. Because of the limited storage in fractures, water 

levels in fracture-conduit aquifers typically respond rapidly to pumping.

Ground water pumped from fracture-conduit aquifers in Subarea 2 generally is suitable for drinking. 

However, elevated concentrations of iron, manganese, sulfate, dissolved solids, and nitrates are known to occur in 

some areas. Other potential problems include acidic water that can corrode copper water lines, and the presence of 

radon gas in the water from the decay of elemental radium in the rocks.

Ground-Water Levels

Ground-water levels fluctuate in response to natural and anthropogenic processes, such as seasonal changes in 

rainfall, interaction with the surface-water system, and ground-water withdrawal. These fluctuations indicate changes 

in the amount of water in storage in an aquifer. In the Piedmont Province, ground-water levels in wells may represent 

differing degrees of confinement. Because of their shallow depth, wells completed in the regolith are highly 

influenced by climatic changes, such as variations in evapotranspiration and precipitation. During droughts, shallow 

bored wells temporarily may go dry when the water table falls. Water-level changes in bedrock wells may exhibit 

both semiconfined and confined behavior; the former responding most directly to recharge. Flowing bedrock wells, 

however, exhibit more confined conditions and related yields probably are less influenced by climatic variability.

As part of the evaluation of ground-water levels, observation well data were analyzed for wells completed in 

regolith and fractured bedrock. Long-term ground-water-level data are available for only one regolith well in 

Subarea 2, and one bedrock well in Subarea 1 near the boundary with Subarea 2. Figures 7 and 8 show water levels 

in wells 11AA01 and 08CC08, located in the Piedmont Province in Georgia (fig. 9).

Regolith Wells

Regolith wells respond to recharge from precipitation, and the highest ground-water levels generally occur 

during the winter and spring. Long-term, ground-water-level data are available for a shallow, regolith well 11AA01, 

located at Griffin, Spalding County, Ga., east of the Subarea 2 boundary (figs. 7 and 9). The water level in well 

11AA01 has been monitored continuously since 1943 (fig. 7a). Ground-water levels tend to decline during the late 

spring through fall, as losses to evapotranspiration increase and recharge is less. However, if significant and 

numerous storms occur during the summer months, ground-water levels may rise. Annual fluctuations in groundwater levels range from 5 to 10 ft in well 11AA01.
21

During droughts in 1981 and 1986, water levels were the lowest of the period of record in well 11AA01 (fig. 

7a). Overall seasonal water levels fluctuated about 4 to 6 ft. Comparing the annual high water levels for various 

hydrologic conditions (high, average, and low mean annual water levels); high water levels for the drought year,1988, 

were about 16.5 ft below land surface; high water levels were about 13 ft below land surface during an average year, 

1969; and high water levels were about 9.5 ft below land surface for a wetter year, such as 1975. Many regolith wells 

in the Piedmont were dry during the later months of the droughts of the 1980’s. An example of the annual water-level 

decline during a drought year is shown for well 11AA01 for 1954 (fig. 7b). A continuous water-level decline was 

observed as a result of decreased precipitation and increased evapotranspiration losses during the year.
22

Bedrock Wells

Although continuous ground-water-level data were not available for bedrock wells within Subarea 2, a well 

located near the boundary with Subarea 1 is considered to be representative. Well, 08CC08 (fig. 9) in southern Fulton 

County, Ga., was drilled as part of an investigation by Cressler and others (1983) and water-level data were collected 

from 1979 through 1986 (fig. 8a). The well is located on the flood plain of a tributary to the Chattahoochee River.

The major rock type tapped by well 08CC08 is a biotite gneiss interlayered with a minor schist unit. The 

biotite gneiss is weathered deeply and casing was set at 78 ft. Total depth of the well is 243 ft. The initial well yield 

was estimated to be 45 gal/min, with most of the water being derived from fractures at depths of 103 and 176 ft. 

Geologic core collected at this site confirmed the presence of horizontal fractures and weathering along foliation near 

lithologic contacts (Cressler and others, 1983).

The water level in well 088CC08 ranged from slightly above land surface to about 4.5 ft below land surface 

during the period of record (fig. 8a). During the 1981 drought, the water level in the well declined only about 3.5 ft, 

and the minimum water level occurred in late July (coincident with the period of minimum streamflow throughout the 

ACF basin). The 1981 water-level hydrograph for this bedrock well is very different from ground-water levels 

observed in the regolith well (fig. 8b) during the 1954 drought. Water levels in the bedrock well (08CC08) exhibited 

sharp peaks, possibly in response to nearby stream levels or rainfall. The drought years of 1980 and 1986 produced 

the lowest water levels observed during the period of record; however, the lowest water levels were only about 1 ft 

below average-year minimums. The relatively small fluctuation in water levels probably is due to the location of the 

well in a floodplain, an area of ground-water discharge. 

Surface-Water System

The two major river systems in Subarea 2 are the Chattahoochee and Flint Rivers (fig. 9). Headwaters of the 

Chattahoochee are located near Helen, Ga. (Subarea 1) (fig. 1), and the river enters Subarea 2 near Whitesburg, Ga., 

along the Carroll and Coweta County line. Headwaters of the Flint River are in Subarea 2 in Clayton County, Ga. In 

Subarea 2, the Chattahoochee River forms the State line with Alabama in Heard County, Ga., and Randolph County, 

Ala. The Subarea 2-3 boundary (figs. 1, 2) is near the Columbus, Ga., gaging station on the Chattahoochee River 

(02341500), and near the Culloden, Ga., gaging station on the Flint River (02347500) (fig. 9). Gaging stations on 

rivers discussed in this report are listed in table 3.

Table 3. Selected active and discontinued continuous-record stream-gaging stations in the middle Chattahoochee 

River basin in Georgia and Alabama, and upper Flint River basin in Georgia, Subarea 2

[I, fracture-conduit aquifer in igneous or metamorphic rock; —, not applicable]

Station 

number Station name Drainage area (square miles)

Type 

of 

stream

Major 

aquifer 

drained

Period of record of 

unregulated flow 

(water years)

Mean-annual stream 

discharge

1/Stokes and McFarlane (1994).

1/

(cubic feet per second)

Chattahoochee River basin

02338000 Chattahoochee River near Whitesburg, Ga. 2,420 regional I 1939-53

2/Unregulated flow.

2/3,740

02338660 New River near Corinth, Ga. 127 tributary I 1978-present 152

02338840 Yellowjacket Creek near Hogansville, Ga. 91.0 do. I 1979-85 116

02339000 Yellowjacket Creek near LaGrange, Ga. 182 do. I 1951-71 225

02339500 Chattahoochee River at West Point, Ga. 3,550 do. I 1897-1955 2/5,625

02340500 Mountain Oak Creek near Hamilton, Ga. 61.7 do. I 1943-71 82.3

02341500 Chattahoochee River at Columbus, Ga. 4,670 do. I —

3/Regulated flow.

3/6,794

Flint River basin

02347500 Flint River near Culloden, Ga. 1,850 regional I 1912-22

1929-31

1938-present

2,344
23
24
25

For this report, the mean-annual stream discharge of a surface-water drainage measured at a gaging station is defined 

as the arithmetic average of all reported annual discharges for the period of record. Note that, by definition, the stream 

discharge includes both surface runoff and baseflow. The estimated mean-annual stream discharge of the Chattahoochee River 

from Subarea 2 to Subarea 3 is about 6,794 ft3

/s; and for the Flint River, mean-annual stream discharge is about 2,344 ft3/s at 

the Subarea 2–Subarea 3 boundary.

Three major storage reservoirs are located on the Chattahoochee River in the Piedmont physiographic province. These 

reservoirs are used for flood control, power generation, recreation, and water supply. The northernmost impoundment is Lake 

Sidney Lanier (Forsyth, Hall, Gwinnett, and Lumpkin Counties, Ga.), in Subarea 1 of the ACF basin. Usable storage capacity 

for Lake Sidney Lanier is 1,686,000 acre-feet between elevations of 1,035 and 1,085 ft. The other two reservoirs are in 

Subarea 2 (table 4): West Point Lake (Troup and Heard Counties, Ga.-Chambers County, Ala.) and Lake Harding (Harris 

County, Ga.–Lee and Chambers Counties, Ala.) (fig. 9). Storage began in October 1974 at West Point Lake, which has a total 

capacity of 774,800 acre-ft at an elevation of 641 ft (maximum flood-control pool level) (Stokes and McFarlane, 1994). Lake 

Harding, where storage began in 1926, is downstream of West Point Lake on the Chattahoochee River, north of Columbus, 

Ga. Total storage capacity of Lake Harding is 181,000 acre-ft at an elevation of 521 ft (Stokes and McFarlane, 1994). Watersupply withdrawal and wastewater returns are common along the Chattahoochee River in Subarea 2. Although, no major 

storage reservoirs are on the Flint River in Subarea 2, minor withdrawal and returns occur throughout the river corridor.

Table 4. Major impoundments in the middle Chattahoochee River basin, Georgia and Alabama, Subarea 2

Impoundment structure Station 

number Location Installation date Major uses

Total storage 

capacity1/ 

(acre-feet) 

West Point 02339400 Troup and Heard Counties, Ga.—

Chambers County, Ala.

1975 flood control and power 

generation

774,800

Bartletts Ferry 

(Lake Harding)

02339820 Harris County, Ga.—Lee and 

Chambers Counties, Ala.

1926 power generation 181,000

1/Stokes and McFarlane (1994).

GROUND-WATER DISCHARGE TO STREAMS

Streamflow is comprised of two major components—a typical hydrograph integrates these components as: 

• overland or surface runoff, represented by peaks, indicating rapid response to precipitation; 

and 

• baseflow, represented by the slope of the streamflow recession, indicating ground-water 

discharge to the stream. 

In relation to the conceptual model, baseflow in streams is comprised of contributions from the local, 

intermediate, or regional ground-water flow regimes. Estimates of recharge to the ground-water system are minimum 

estimates because the budgets were developed as ground-water discharge to streams, and do not include ground water 

discharged as evapotranspiration, to wells, or ground water that flows downgradient into other aquifers beyond the 

topographic boundary defining Subarea 2. Local flow regimes likely are the most affected by droughts. Discharge 

measured in unregulated streams and rivers near the end of a drought should be relatively steady and composed 

largely of baseflow. 
26

Mean-Annual Baseflow

Mean-annual baseflow was determined by estimating mean-annual ground-water discharge to the 

Chattahoochee and Flint Rivers and selected major tributaries. Streamflow data used to determine mean-annual 

ground-water discharge at continuous-record gaging stations were selected according to periods of record when flow 

was unregulated. The hydrograph-separation program SWGW (Mayer and Jones, 1996) was applied to estimate 

mean-annual baseflow at three continuous-record gaging stations in the middle Chattahoochee River in Georgia and 

Alabama, and upper Flint River in Georgia (table 5). For each gaging station, two recession indices are listed in table 

5; one represents the rate of streamflow recession during the major rise period, generally in winter; and the other 

during the major recession period, generally in summer. Some variables that are supplied by the user to SWGW for 

each hydrograph separation are not listed in table 5, but can be obtained from the U.S. Geological Survey, Georgia 

District Office, Atlanta, Ga. These variables include the time-base (in days) from the peak to the cessation of surface 

runoff, the time period (the beginning and ending months) for application of the summer recession index, and the 

adjustment factor for the displacement of the recession curve. See Rutledge (1993) for a discussion of time-base, and 

Mayer and Jones (1996) for a discussion of the other user-supplied variables.

The mean-annual baseflow, in cubic feet per second, and the related unit-area baseflow, in cubic feet per 

second per square mile, were computed for each station. Mean unit-area baseflow estimated for three stations 

representing discharge from igneous and metamorphic rocks along the middle Chattahoochee River in Georgia and 

Alabama, and upper Flint River in Georgia, Subarea 2, ranged from 0.627 to 1.06 ft3/s/mi2 (table 5).

Data for gaging stations located downstream of Lake Sidney Lanier (Subarea 1) on the Chattahoochee River 

in Subarea 2 (fig. 9) were evaluated for the period prior to its impoundment by Buford Dam in 1956. Where possible, 

data for the same years were used for the hydrograph-separation analyses for each station throughout the study area. 

In general, in the middle Chattahoochee River basin in Georgia and Alabama, and upper Flint River basin in 

Georgia, the lowest streamflow occurred during the drought of 1941; the highest streamflow occurred in 1949. The 

average flow year selected for analysis varied for each station with regard to the available period of record for 

unregulated flow. 

Estimated mean-annual baseflow in the upper Chattahoochee River basin ranges from about 50 to 61 percent 

of mean-annual stream discharge in Subarea 2. The contribution of mean-annual baseflow from Subarea 2 to Subarea 

3 was estimated using data from the West Point, Ga., (02339500), gaging station on the Chattahoochee River, and the 

gaging station near Culloden, Ga., (02347500), on the Flint River (fig. 9; table 5). The discharge to the Chattahoochee 

River at the Subarea 2–3 boundary at Columbus, Ga., was estimated to be about 4,640 ft3/s. For the Flint River basin, 

with headwaters in Subarea 2 in Georgia, the transfer of water from Subarea 2 to Subarea 3 near Culloden, Ga., is 

estimated to be about 1,160 ft3

/s (750 Mgal/d). The discharge was estimated by applying the unit-area discharge 

computed at the West Point, Ga., station (02339500), to the entire drainage area at the Columbus, Ga., station 

(02341500). The baseflows exiting Subarea 2 represent about 68 percent of the mean-annual (regulated, table 3) 

stream discharge for the Chattahoochee River and 49 percent for the Flint River at Columbus, Ga., and near 

Culloden, Ga., respectively.

 Data representative of unregulated streamflow were used to estimate mean-annual baseflow for all gaging 

stations in Subarea 2. All gaging stations on the Chattahoochee River in Subarea 2 (table 3) are downstream of 

Lake Sidney Lanier (Buford Dam), located northeast of Atlanta, Ga., (fig. 1, Subarea 1). Data used for 

hydrograph-separation analyses from these stations were evaluated for the period prior to the lake’s completion in 

1956. The station at West Point, Ga., is downstream of West Point Lake (West Point Dam) (fig. 9), which was 

completed in 1974. Streamflow-discharge data at Columbus, Ga., were not used for the analyses due to regulation 

upstream from Lake Harding, which began operation in 1926. Although regulation occurs along the Flint River in 

Subarea 2, no specific record periods were eliminated as there are no major reservoirs within or upstream of the 

study area, and the influence of regulation on streamflow at the station near Culloden, Ga., is minimal.
27

Table 5. Mean-annual stream discharge, estimated annual and mean-annual baseflow, and unit-area mean-annual baseflow at selected gageChattahoochee River basin in Georgia and Alabama, and upper Flint River basin in Georgia, Subarea 2

Station 

number Station name Type of stream

Drainage 

area 

(square 

miles)

Major 

aquifer 

type

Recession index

Water 

year

Flow 

conditions

Mean-annual 

stream 

discharge1/

(cubic feet per 

second)

Annual

baseflow2/,3/

(cubic feet per 

second)

Mean

basef

(cubic 

sec

Winter 

(days)

Summer 

(days)

Chattahoochee River basin

02338000 Chattahoochee River near Whitesburg, Ga. regional 2,420 regional 120 100 1941 Low 2,166 1,370

1952 Average 4,170 2,460 21949 High 6,221 3,890 

02339500 Chattahoochee River at West Point, Ga. do. 3,550 do. 140 100 1941 Low 3,036 1,960

1943 Average 5,947 3,660 31929 High 10,100 4,970

02341500 Chattahoochee River at Columbus, Ga. do. 4,670 do. — — — — — — 6/4

Flint River basin

02347500 Flint River near Culloden, Ga. do. 1,850 do. 85 55 1941 Low 1,043 654

1943 Average 2,617 1,350 11949 High 3,262 1,480

Mean-annual baseflow exiting middle Chattahoochee 

River basin, Georgia and Alabama; and upper Flint River basin, Georgia, Subarea 2

7/5

1/From annually published U.S. Geological Survey data reports; for example, Stokes and McFarlane (1994). 2/Estimated using the computer program SWGW (Mayer and Jones, 1996). 3/Values are reported to three significant digits to maintain the numerical balance of the water budget; implication of accuracy to the degree sh4/Estimated by averaging discharges for low, average, and high flow years for the period of unregulated flow. 5/Discharge divided by drainage area. 6/Mean-annual baseflow estimated by multiplying drainage area by unit-area baseflow for the Chattahoochee River at West Point, Ga. (see tex7/Represents entire Chattahoochee and Flint River basins in Subarea 2.
28

 Because of the absence of continuous-record streamflow data in Alabama, the contribution of mean-annual 

baseflow in the Chattahoochee River from Alabama in Subarea 2 was computed using the following approximation. 

The Chattahoochee River forms the State line between Georgia (east) and Alabama (west) beginning at West Point 

Lake (fig. 9; net drainage area is about 2,250 mi2). Baseflow from Alabama to the Chattahoochee River in Subarea 2 

was estimated by determining the percentage of drainage area in Alabama (26 percent or about 590 mi2) 

contributing to the total drainage area between stations near Whitesburg, Ga., and at Columbus, Ga., (2,250 mi2

); and 

then multiplying this percentage by the net gain in mean-annual baseflow estimated between the Whitesburg and 

Columbus, Ga., gaging stations. (This extrapolation is considered valid because of similar overall hydrogeologic 

conditions throughout the study area.) The total net gain in mean-annual baseflow was about 2,070 ft3/s (1,340 

Mgal/d) between the Whitesburg and Columbus gaging stations. The contributing area in Alabama was 26 percent of 

the total drainage area between the stations. Therefore, the estimated mean-annual baseflow contribution to the 

Chattahoochee River from Alabama is 26 percent of 2,070 ft3

/s (1,340 Mgal/d), or about 540 ft3/s (350 Mgal/d). 

Accordingly, the estimated mean-annual baseflow contribution to the Chattahoochee River from Georgia is about 

1,530 ft3/s (982 Mgal/d) between the stations near Whitesburg, Ga., and at Columbus, Ga.

Drought Flow for 1941, 1954, and 1986

Regional drought periods of 1938-45, 1950-63, and 1984-88 were marked by severe droughts in the years of 

1941, 1954, and 1986 in the ACF and ACT River basins. Typically, the lowest mean-annual streamflow for the period 

of record occurred during one of these years. Streamflow was assumed to be sustained entirely by baseflow near the 

end of these droughts. Near-synchronous discharge measurements at partial-record gaging stations or daily mean 

streamflow at continuous-record gaging stations during these periods were assumed to provide a quantitative estimate 

of near minimum baseflow from Subarea 2 into Subarea 3. Where available, streamflow data for an interval of a few 

days were compiled; and where not available, streamflow was estimated using various techniques—discussed below.

Estimated and measured streamflow near the end of the 1941, 1954, and 1986 drought years at selected sites 

on the middle Chattahoochee River in Georgia and Alabama and its tributaries and the upper Flint River in Georgia 

are shown in tables 6, 7, and 8, respectively, and summarized in table 9. Most of the data presented represent 

minimum daily mean streamflow from continuous-record gaging stations. Some miscellaneous streamflow 

measurements were used for the analyses.

Table 6. Stream discharge during the month of October of the drought of 1941, Subarea 2

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/ 

(square 

miles)

Date

Stream 

discharge2

/ 

(cubic feet 

per second)

Unit-area 

discharge3/ 

(cubic feet per 

second per 

square mile)

Chattahoochee River basin

02338000 Chattahoochee River near Whitesburg, Ga. regional 2,420 10-26-41 468 0.193

02339500 Chattahoochee River at West Point, Ga. do. 3,550 10-25-41 540 .152

02341500 Chattahoochee River at Columbus, Ga. do. 4,670 — 4/710 .152

Drainage area and stream discharge exiting Chattahoochee River basin, Subarea 2 4,670 — 4/710 —

Flint River basin

02347500 Flint River at Culloden, Ga. regional 1,850 10-26-54 98 .053

Drainage area and stream discharge exiting Flint River basin, Subarea 2 1,850 — 98 —

Drainage area and stream discharge exiting Subarea 25/ 6,520 — 808 —

1/From Carter and others (1989), except for Chattahoochee River drainage areas downstream from New River, 

which are from Carter (1959).

2/Daily mean discharge.

3/Discharge divided by drainage area.

4/Estimated unregulated discharge multiplying drainage area by unit-area discharge for Chattahoochee River at 

West Point, Ga.

5/Represents entire Chattahoochee and Flint River basins.
29

Table 7. Stream discharge during the months of September and October of the drought of 1954, Subarea 2

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/

(square 

miles)

Date

Stream 

discharge2/ 

(cubic feet 

per second)

Unit-area 

discharge3/

(cubic feet per 

second per 

square mile)

Chattahoochee River basin

02338000 Chattahoochee River near Whitesburg, Ga. regional 2,420 09-15-54 4/461 0.190

— intermediate area between Chattahoochee River near Whitesburg, 

Ga., and mouth of Wahoo Creek

— 6 — 5/0.1 —

02338100 Wahoo Creek near Sargent, Ga. tributary 20.4 09-24-54 4/.44 .022

— Wahoo Creek at mouth do. 34.6 — 6/.8 —

— intermediate area between Wahoo Creek and Acorn Creek — 16 — 5/1.1 —

02338220 Acorn Creek near Whitesburg, Ga. tributary 8.7 09-20-54 4/.62 .071

— Acorn Creek at mouth do. 11.2 — 6/.8 —

— intermediate area between Acorn Creek and Whooping Creek — 6 — 5/.3 —

02338280 Whooping Creek near Lowell, Ga. tributary 26.6 09-20-54 4/1.53 .058

— Whooping Creek at mouth do. 31.4 — 6/1.8 —

— intermediate area between Whooping Creek and Yellowdirt Creek — 2 — 5/.3 —

02338310 Yellowdirt Creek near Roopville, Ga. tributary 4.3 09-20-54 4/.71 .165

— Yellowdirt Creek at mouth do. 25.7 — 6/4.2 —

— intermediate area between Yellowdirt Creek and Centralhatchee 

Creek

— 62 — 5/6.0 —

02338400 Centralhatchee Creek at U.S. Highway 27 near Franklin, Ga. tributary 56.7 10-11-54 4/5.42 .096

— Centralhatchee Creek at mouth do. 58.8 — 6/5.6 —

— intermediate area between Centralhatchee and New River — 123 — 5/13 —

— New River above Messiers Creek tributary 10.5 — 7/2.6 —

02338620 Messiers Creek near Grantville, Ga. do. 4.0 09-24-54 4/1.01 .252

— Messiers Creek at mouth do. 10.5 — 6/2.6 —

— New River below Messiers Creek do. 21 — 8/5.2 —

— New River above Carey Creek do. 98.5 — 9/12.4 .126

02338650 Caney Creek near Corinth do. 12.6 10-12-54 4/0 0

— Caney Creek at mouth do. 22.8 — 6/0 0

— New River below Caney Creek do. 121 — 10/12.4 .102

— New River at mouth do. 151 — 11/15 —

— intermediate area between New River and Yellowjacket Creek — 65 — 5/4.3 —

02339000 Yellowjacket Creek near LaGrange, Ga. tributary 182 10-19-54 12 .066

— Yellowjacket Creek at mouth do. 202 — 6/13 —

02339130 Whitewater Creek near LaGrange, Ga. do. 27 10-20-54 4/.24 12/.009

02339350 Wedhadkee Creek at Georgia Highway 244 near Abbotsford, Ga. do. 97.6 10-20-54 4/.20 12/.002

— intermediate area between Yellowjacket Creek and Chattahoochee 

River at West Point, Ga.

— 338 — 13/21 —

02339500 Chattahoochee River at West Point, Ga. regional 3,550 10-19-54 2/,14/548
30

— intermediate area between Chattahoochee River at West Point, 

Ga., and Long Cane Creek

— 0.2 — 5/0.0 —

02339640 Long Cane Creek at U.S. Highway 27 near LaGrange, Ga. tributary 22.5 10-20-54 4/1.37 .061

— Long Cane Creek at mouth do. 83.8 — 6/5.1 —

— intermediate area between Long Cane Creek and Flat Shoal Creek — 8 — 5/.9 —

02340250 Flat Shoal Creek at State Route 18 near West Point, Ga. tributary 202 10-20-54 4/22.4 .111

— Flat Shoal Creek at mouth do. 220 — 6/24 —

— intermediate area between Flat Shoal Creek and Mountain Oak 

Creek

— 78 — 5/8.9 —

02340500 Mountain Oak Creek near Hamilton tributary 61.7 10-20-54 7.0 .114

— Mountain Oak Creek at mouth do. 69.7 — 6/7.9 —

— intermediate area between Mountain Oak and Mulberry Creek — 270 — 15/45 —

02341070 Mulberry Creek at State Route 85 near Waverly Hall, Ga. tributary 123 10-21-54 4/0 0

— Mulberry Creek above Dowdell Creek do. 43.2 — 16/.6.6 —

02341110 Dowdell Creek near Waverly Hall, Ga. do. 27.9 10-21-54 4/8.54 .306

— Dowdell Creek at mouth do. 32.3 — 6/9.9 —

— Mulberry Creek below Dowdell Creek do. 75.5 — 17/16.5 .219

— Mulberry Creek above Palmetto Creek do. 88.5 — 18/19.4 —

02341130 Palmetto Creek near Hamilton do. 9.2 10-21-54 4/2.74 .298

— Palmetto Creek at mouth do. 20.5 — 6/6.1 —

— Mulberry Creek below Palmetto Creek do. 109 — 19/25.5 .234

— Mulberry Creek above Ossahatchie Creek do. 115 — 20/26.9 —

02341200 Ossahatchee Creek near Hamilton do. 42.8 10-21-54 4/.15 .004

— Ossahatchee Creek at mouth do. 46.1 — 6/.2 —

— Mulberry Creek below Ossahatchee Creek do. 161 — 21/27.1 .168

— Mulberry Creek at mouth do. 228 — 22/38 —

— intermediate area between Mulberry Creek and Standing Boy 

Creek

— 42 — 5/.3 —

02341330 Standing Boy Creek near Rehobeth tributary 9.7 10-21-54 4/.02 .002

— Standing Boy Creek above Heiferhorn Creek do. 46.6 — 23/.1 —

02341340 Heiferhorn Creek near Rehobeth do. 2.4 10-21-54 4/.04 .017

— Heiferhorn Creek at mouth do. 23.1 — 6/.4 —

— Standing Boy Creek below Heiferhorn Creek do. 69.7 — 24/.5 .007

— Standing Boy Creek at mouth do. 71.3 — 25/.5 —

Table 7. Stream discharge during the months of September and October of the drought of 1954, Subarea 2—Continued

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/

(square 

miles)

Date

Stream 

discharge2/ 

(cubic feet 

per second)

Unit-area 

discharge3/

(cubic feet per 

second per 

square mile)
31

1/From Carter and others (1989), except for Chattahoochee River drainage areas downstream from New River, which are 

from Carter (1959).

2/Daily mean discharge.

3/Discharge divided by the drainage area.

4/Miscellaneous discharge measurement.

5/Estimated by multiplying drainage area of the intermediate area by the unit-area discharge that was computed using the 

discharge at the next downstream miscellaneous measurement site or daily mean-discharge site. 6/Estimated by multiplying the drainage area at the tributary’s mouth by the unit-area discharge that was computed using the 

discharge at that tributary’s miscellaneous measurement site or daily mean-discharge site. 7/Estimated by multiplying drainage area by Messiers Creek unit-area discharge.

8/Sum of discharges estimated for New River above Messiers Creek and Messiers Creek at mouth.

9/Estimated by multiplying the drainage area by the average unit-area discharge of Messiers Creek and Caney Creek. 10/Sum of the estimated discharges for New River above Caney Creek and Caney Creek at mouth. 11/Estimated by multiplying drainage area by unit-area discharge for New River below Caney Creek. 12/

Unit-area discharge not used to estimate tributary or intermediate discharges. 13/Estimated by multiplying drainage area by mean-unit area discharge of Yellowjacket Creek and Long Cane Creek. 14/Daily mean discharge and sum of estimated upstream discharges at intermediate drainage areas and tributary mouths. 15/Estimated by multiplying drainage area by unit-area discharge of Mulberry Creek below Ossahatchee Creek. 16/Estimated by multiplying drainage area by mean unit-area discharge of Mulberry Creek at State Route 85 near Waverly 

Hall and Dowdell Creek.

17/Sum of the estimated discharges for Mulberry Creek above Dowdell Creek and Dowdell Creek at mouth.

18/Estimated by multiplying drainage area by unit-area discharge for Mulberry Creek below Dowdell Creek.19/Sum of the 

estimated discharges for Mulberry Creek above Palmetto Creek and Palmetto Creek at mouth. 20/Estimated by multiplying drainage area by unit-area discharge for Mulberry Creek below Palmetto Creek. 21/Sum of estimated discharges for Mulberry Creek above Ossahatchee Creek and Ossahatchee Creek at mouth.

22/Estimated discharge by multiplying drainage area by unit-area discharge for Mulberry Creek below Ossahatchie Creek. 23/Estimated by multiplying drainage area by unit-area discharge for Standing Boy Creek near Rehobeth. 24/Sum of estimated discharges for Standing Boy Creek above Heiferhorn Creek and Heiferhorn Creek at mouth.

25/Estimated by multiplying drainage area by unit-area discharge for Standing Boy Creek below Heiferhorn Creek. 26/Estimated unregulated flow obtained by summing the discharge for the Chattahoochee River at West Point (02339500), 

estimated discharges for tributaries at their mouths and intermediate area discharges downstream (in boldface type), 

except Dowdell Creek, Palmetto Creek, and Ossahatchie Creek which are tributaries of Mulberry Creek and Heiferhorn 

Creek which is a tributary of Standing Boy Creek. 27/Represents entire Chattahoochee and Flint River basins.

— intermediate area between Standing Boy and Chattahoochee River 

at Columbus, Ga.

— 49 — 25/.3 —

02341500 Chattahoochee River at Columbus, Ga. regional 4,670 — 26/679 —

Drainage area and stream discharge exiting Chattahoochee River basin, Subarea 2 4,670 679

Flint River basin

02347500 Flint River at Culloden, Ga. regional 1,850 10-17-54 97 .052

Drainage area and stream discharge exiting Flint River basin, Subarea 2 1,850 — 97 —

Drainage area and stream discharge exiting Subarea 227/ 6,520 776

Table 7. Stream discharge during the months of September and October of the drought of 1954, Subarea 2—Continued

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/

(square 

miles)

Date

Stream 

discharge2/ 

(cubic feet 

per second)

Unit-area 

discharge3/

(cubic feet per 

second per 

square mile)
32

Table 8. Stream discharge during the month of July of the drought of 1986, Subarea 2

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/ 

(square 

miles)

Date

Stream 

discharge2/ 

(cubic feet 

per second)

Unit-area 

discharge3/

(cubic feet 

per second 

per square 

mile)

Chattahoochee River basin

02338000 Chattahoochee River near Whitesburg, Ga. regional 2,420 — 4/637 0.263

— intermediate area between Chattahoochee River near 

Whitesburg, Ga., and Wahoo Creek

— 6 — 5/1.2 —

02338100 Wahoo Creek near Sargent, Ga. tributary 20.4 07-07-86 4.0 .196

— Wahoo Creek at mouth do. 34.6 — 6/6.8 —

— intermediate area between Wahoo Creek and Centralhatchee 

Creek

— 155 — 7/34 .221

02338400 Centralhatchee Creek near Franklin, Ga. tributary 57 07-07-86 14 .246

02338450 Centralhatchee Creek at mouth do. 58.8 — 6/14.5 —

— intermediate area between Centralhatchee and 

Hillabahatchee Creek

— 4 — 5/1.1 —

02338530 Hillabahatchee Creek near Franklin tributary 77.3 07-07-86 22 .285

— Hillabahatchee Creek at mouth do. 80.2 — 6/22.9 —

— intermediate area between Hillabahatchee Creek and New 

River

— 39 — 5/1.6 —

02338660 New River near Corinth, Ga. tributary 127 07-07-86 8/5.2 .041

— New River at mouth do. 151 — 6/6.2 —

— intermediate area between New River and Yellowjacket 

Creek

— 65 — 5/3.3 —

02338840 Yellowjacket Creek near Hogansville, Ga. tributary 91 07-07-86 4.6 .050

— Yellowjacket Creek at West Point Lake do. 97.2 — 9/4.9 —

02338930 Beech Creek near LaGrange, Ga. do. 52.9 07-07-86 3.5 .066

— Beech Creek at West Point Lake do. 56.5 — 9/3.7 —

02339210 Wehadkee Creek near Pittman, Ala. do. 11.5 07-09-86 3.1 .270

— Wehadkee Creek at West Point Lake do. 97.6 — 9/26.4 —

— intermediate area between New River, backwater effects of 

West Point Lake on inflow tributaries and Chattahoochee 

River at West Point, Ga.

— 289 — 10/37.3 .129

02339500 Chattahoochee River at West Point, Ga. regional 3,550 — 11/801 .226

— intermediate area between Chattahoochee River at West 

Point, Ga., and Flat Shoal Creek

— 92 — 5/15.3 —

02340262 Flat Shoal Creek near West Point, Ga. tributary 211 07-09-86 35 .166

— Flat Shoal Creek at mouth do. 220 — 6/36.5 —

— intermediate area between Flat Shoal and Mountain Oak 

Creek

— 78 — 5/6.7 —

02340500 Mountain Oak Creek near Hamilton, Ga. tributary 61.7 07-09-86 5.3 .086

— Mountain Oak Creek at mouth do. 69.7 — 6/6.0 —

— intermediate area between Mountain Oak and Osanippa 

Creek

— 0 — 5/0 —

02340750 Osanippa Creek near Fairfax, Ala. tributary 99.7 07-08-86 3.7 .037
33

1/From Carter and others (1989), except for Chattahoochee River drainage areas downstream from New River which 

were obtained from Carter (1959).

2/Miscellaneous discharge measurements.

3/Discharge divided by the drainage area.

4/Estimated unregulated discharge entering Subarea 2 (exiting Subarea 1).

5/Estimated by multiplying drainage area of the intermediate area by the unit-area discharge that was computed using 

the discharge at the next downstream miscellaneous measurement site or daily mean-discharge site. 6/Estimated by multiplying the drainage area at the tributary’s mouth by the unit-area discharge that was computed 

using the discharge at that tributary’s miscellaneous measurement site or daily mean-discharge site. 7/Estimated by multiplying the drainage area by average unit-area discharge of Wahoo Creek and Centralhatchee Creek. 8/Daily mean discharge.

9/Estimated at the point the stream enters West Point Lake.

10/Estimated by multiplying drainage area by average unit-area discharge of Yellowjacket Creek, Beech Creek, and 

Wehadkee Creek.

11/Sum of estimated unregulated discharge at Chattahoochee River near Whitesburg, Ga., intermediate area discharges, 

and tributary mouth discharges. 12/Estimated by multiplying drainage area by mean unit-area discharge for Osanippa Creek and Halawakee Creek. 13/Estimated by multiplying drainage area by unit-area discharge for Mulberry Creek. 14/Sum of estimated unregulated discharge at Chattahoochee River at West Point, Ga., intermediate area discharges, and 

tributary discharges at their mouths (in boldface type). 15/Represents entire Chattahoochee and Flint River basins.

— Osanippa Creek at mouth do. 126 — 6/4.7 —

02340900 Halawakee Creek near Opelika, Ala. do. 36.2 07-08-86 1.1 .030

— Halawakee Creek at mouth do. 96.8 — 6/2.9 —

— intermediate area between Osanippa Creek and Mulberry 

Creek

— 48 — 12/1.6 .034

02341220 Mulberry Creek near Mulberry Grove, Ala. tributary 190 07-08-86 9.2 .048

— Mulberry Creek at mouth do. 228 — 6/11 —

— intermediate area between Mulberry Creek and 

Chattahoochee River at Columbus, Ga.

— 42 — 13/2.0 —

02341500 Chattahoochee River at Columbus, Ga. regional 4,670 — 14/888 —

Drainage area and stream discharge exiting Chattahoochee River basin, Subarea 2 4,670 — 888 —

Flint River basin

02347500 Flint River at Culloden, Ga. regional 1,850 07-15-86 107 .058

Drainage area and stream discharge exiting Flint River basin, Subarea 2 1,850 — 107 —

Drainage area and stream discharge exiting Subarea 215/ 6,520 995

Table 8. Stream discharge during the month of July of the drought of 1986, Subarea 2—Continued

[—, not applicable]

Station 

number Station name

Type 

of 

stream

Drainage 

area1/ 

(square 

miles)

Date

Stream 

discharge2/ 

(cubic feet 

per second)

Unit-area 

discharge3/

(cubic feet 

per second 

per square 

mile)
Table 9. Estimated mean-annual baseflow and drought flows entering and exiting the middle Chattahoochee River 

basin in Georgia and Alabama, and exiting the upper Flint River basin in Georgia, Subarea 2

Contributing drainage area

Contributing 

drainage 

area 

(square 

miles)

Unregulated 

mean-annual 

streamflow 

(cubic feet 

per second)

Stream discharge (cubic feet per second)

Estimated 

mean-annual 

baseflow1/

Drought of 

19412/ Drought of 19543/ Drought of 19864/

Chattahoochee River basin

Entering Chattahoochee River basin, Subarea 2 2,420 3,740 2,570 468 461 637

02338000 Chattahoochee River near Whitesburg, Ga. 2,420 3,740 2,570 468 461 637

02339500 Chattahoochee River at West Point, Ga. 3,550 5,625 3,530 540 548 801

02341500 Chattahoochee River at Columbus, Ga. 4,670 5/6,794 4,640 710 679 888

Georgia exiting Subarea 2 5/4,994 3,410 522 499 653

Alabama exiting Subarea 2 5/1,800 1,230 188 180 235

Exiting Chattahoochee River basin, Subarea 2 4,670 6,794 4,640 710 679 888

Flint River basin

02347500 Flint River at Culloden, Ga. 1,850 2,344 1,160 98 97 107

Exiting Flint River basin, Subarea 2 1,850 2,344 1,160 98 97 107

Exiting Chattahoochee and Flint River basins, 

Subarea 2

6,520 5/9,138 5,800 808 776 995

34

1/From table 5.

2/From table 6.

3/From table 7.

4/From table 8.

5/Regulated.

In evaluating streamflow data on the Chattahoochee River during these drought years, regulation and 

withdrawal are evident as abnormally increased streamflow (storage releases) or decreased streamflow (storage 

increases). The Chattahoochee River has been regulated below the Lake Harding Dam since 1926 (Subarea 2), below 

Buford Dam (Subarea 1) since 1955, and below West Point Dam (Subarea 2) since 1974. Therefore, unregulated 

streamflow had to be estimated for sites below these structures to determine streamflow exiting Subarea 2 for the 

1941, 1954, and 1986 droughts; and streamflow entering Subarea 2 for the 1986 drought (Chapman and Peck, 1996).

Streamflow in the Flint River is affected by withdrawals from and return to the river or its tributaries from 

communities such as Griffin, Ga., but no major reservoirs affect the streamflow. The minimal effects caused by the 

lack of major storage reservoirs along the Flint River are indicated by the similarity of streamflow at Culloden, Ga., 

near the end of the droughts of 1941, 1954, and 1986. Due to the lack of tributary data between continuous gaging 

stations near the upper Flint River drainage and the boundary station, data from only the Culloden station is presented 

in this report.

The estimates for the 1954 and 1986 drought flows in the Chattahoochee River were determined by balancing 

mass in a stream in a general downstream direction during two relatively short periods of time for the 1954 drought 

and one relatively short period of time for the 1986 drought. The daily mean-discharge values available from gaging 

stations in Subarea 2 indicate that flows were comparable during the two periods used in the 1954 drought analysis 

and similar discharge contributions were assumed throughout Subarea 2. Accordingly, the tributary discharges to the 

Chattahoochee River during the drought periods were estimated using the unit-area discharge computed at a 

miscellaneous measurement site or gaging station site extrapolated to the entire tributary drainage. These unit-area 

discharges were also applied to the intermediate areas between tributaries. The unit-area discharge for a tributary was 
35

generally applied to the intermediate area immediately upstream from the tributary except for the last intermediate 

area in Subarea 2 for which the unit-area discharge for the last upstream tributary was used (Standing Boy Creek 

below Heiferhorn Creek, 1954; Mulberry Creek near Mulberry Grove, Ala., 1986). Exceptions to this procedure 

occurred when a unit-area discharge was unusually low in which case an average unit-area discharge was used (tables 

7 and 8).

Estimated discharges exiting Subarea 2 from the Chattahoochee River were computed by summation of the 

discrete discharges estimated for the tributary streams and intervening drainage areas between tributaries (tables 7 

and 8). These estimates are identified in boldtype face in tables 7 and 8 (679 ft3/s, 1954; 888 ft3

/s, 1986).

 Baseflow during the later parts of the droughts of 1941, 1954, and 1986 ranged from 15 to 19 percent of the 

estimated mean-annual baseflow to the Chattahoochee River at Columbus, Ga., and averaged 8.7 percent at the Flint 

River at Culloden, Ga. (table 10). Ground-water contribution to streamflow during the drought periods at the Subarea 

2-3 boundary (table 10) was estimated using the computed flows at the Columbus, Ga., gage along the Chattahoochee 

River, and gaged data from the Culloden, Ga., gage along the Flint River. In relation to the conceptual model of 

ground-water flow and stream-aquifer relations, baseflow during droughts represents greatly reduced contributions 

from the local and intermediate flow regimes. Downstream baseflow in the middle Chattahoochee River basin in 

Georgia and Alabama, and upper Flint River basin in Georgia, near the end of the 1941, 1954, and 1986 droughts is 

related to drainage area in figure 10 and summarized in tables 9 and 10.

Table 10. Estimated drought flows and mean-annual baseflow in the middle Chattahoochee River basin in 

Georgia and Alabama, and upper Flint River basin in Georgia; and ratio of average drought flow to mean-annual 

baseflow, Subarea 2

[—, not applicable]

Contributing drainage area

Drought flows (cubic feet per second) Mean-annual 

baseflow1/ 

(cubic feet

per second)

Ratio of average 

drought flow to 

mean-annual 

baseflow 

(percent)

2/1941 3/1954 4/1986

Average of 

1954 and 

1986 droughts

Chattahoochee

River

Flint RiverChattahoochee

River

Flint RiverChattahoochee

River

Flint RiverChattahoochee

River

Flint RiverChattahoochee

River

Flint RiverChattahoochee

River

Flint River

Flow entering subarea, by river 468 — 384 — 637 — 496 — 2,570 — 19 —

Flow gain in subarea, by river 242 98 295 97 251 107 263 101 2,070 1,160 13 8.7

Flow exiting drainage basin, by river 710 98 679 97 888 107 759 101 4,640 1,160 16 8.7

Flow exiting Subarea 2 808 776 995 860 5,800

1/From table 5.

2/From table 6.

3/From table 7.

4/From table 8.
36
37

GROUND-WATER UTILIZATION AND

GENERAL DEVELOPMENT POTENTIAL

Ground-water utilization is defined as the ratio of ground-water use in 1990 to mean-annual ground-water 

recharge. The degree of ground-water utilization is scale dependent. For example, local ground-water pumping may 

result in substantial storage change and water-level declines near a center of pumping; whereas, such pumping 

relative to the entire Subarea would be small compared to mean-annual recharge. Because ground-water use in 

Subarea 2 represents a relatively minor percentage of ground-water recharge, even a large increase in ground-water 

use in Subarea 2 in one State is likely to have little effect on ground-water and surface-water occurrence in the other.

Ground-water use of about 31 ft3/s in Georgia and 9.2 ft3/s in Alabama in 1990 in Subarea 2 represented 1.2 

percent of the mean-annual baseflow in Georgia and 1.7 percent of the mean-annual baseflow in Alabama (table 11). 

Ground-water use represented 10.5 percent of the average drought flow in Georgia and 13.1 percent of the average 

drought flow in Alabama. Local problems of ground-water overuse were not identified. However, long-term waterlevel data at wells in Subarea 2 are few in number and poorly distributed areally; and conclusions regarding regional 

water-level declines or storage change cannot be reasonably drawn.

Table 11. Relation between 1990 ground-water use and ground-water discharge during mean-annual baseflow, 

average selected drought-flow conditions, and drought flow from Alabama and Georgia, Subarea 2

State

Ground-water 

use, 1990 

(cubic feet per 

second)

Baseflow contributions to Subarea 2

(cubic feet per second)

Ratio of ground-water use to baseflow 

(percent)

Meanannual 

baseflow

1941 

drought 

baseflow

1954 

drought 

baseflow

1986 

drought 

baseflow

Average 

drought 

baseflow

Meanannual 

baseflow

1941 

drought 

baseflow

1954 

drought 

baseflow

1986 

drought 

baseflow

Average 

drought 

baseflow

Georgia 31 2,680 276 314 291 294 1.2 11.2 9.9 10.7 10.5

Alabama 9.2 550 64 78 67 70 1.7 14.4 11.8 13.7 13.1

In general, ground-water resources are underutilized throughout the study area. The rural population relies on 

ground water as their principal source of water supply; whereas, more densely populated areas rely on surface-water 

resources. However, wells supplied water to many communities prior to the development of large surface-water 

reservoirs. In recent years, suburban communities have developed ground-water supplies in response to curtailed 

surface-water supplies.

Ground-water exploration in the Piedmont Province of Georgia historically has been “difficult” and its success 

“unpredictable”. The crystalline-rock aquifers of this region are characterized by little or no primary porosity and 

complex development of secondary permeability. The yield of bedrock wells depends on the characteristics of the 

water-bearing zones penetrated by the open borehole in the bedrock. The aquifers in the Piedmont are extremely 

anisotropic and heterogeneous due to complex geologic controls in the crystalline bedrock (fig. 6). Depth to waterbearing zones is highly variable. Wells may yield water from several fractures throughout a borehole, or from a single 

productive fracture. Conversely, a borehole may not intersect an opening; and thus, may yield little or no water. 

A general assessment of ground-water development potential in Subarea 2 would reflect, in part, the 

cumulative effects of current and anticipated future hydrologic stresses imposed on the ground-water resources, and 

to a lesser extent, the current availability of surface-water supplies. The nature of such an assessment is limited by a 

lack of knowledge of current hydrologic conditions and the lack of agreed upon standards by which Federal, State, or 

local water-resource managers evaluate the effects of additional stress and future development. Current stresses and 

hydrologic conditions might be unknown in some areas; thereby making an evaluation of ground-water development 

potential highly uncertain. Future stresses also might be linked to water-management practices that have yet to be 

formulated, or to water-management decisions that have yet to be made. Therefore, an assessment of ground-water 

development potential provides insight only into one aspect of the broader question of how water-management 

decisions affect ground-water availability. Specifically, whether existing hydrologic data documents the flow-system 

behavior adequately to allow the potential effects of future development on the flow system to be adequately 
38

evaluated and understood. Further, an assessment of ground-water development potential does not account for the 

suitability of existing ground-water resource management approaches or the effects of future approaches on further 

resource development. Such answers partly are dependent on the synthesis of results from the various Comprehensive 

Study components and subsequent consideration by the Federal, State, or local water managers responsible for 

decision-making within the basin.

The identification of areas that could be developed for ground-water supply to replace or supplement surfacewater sources could not be determined from available data for Subarea 2. Because geologic controls affecting groundwater availability are highly variable, even on a local scale, regional evaluations are inherently characterized by a 

high degree of uncertainty. Ground-water resources probably could provide supplemental supplies during peak 

demand periods throughout most suburban areas of Subarea 2. In more rural areas, ground-water supplies could serve 

as a primary resource depending upon demands. Generally, wells need only supply about 5 gal/min for domestic 

users, and may not be drilled to a depth that taps the available ground-water supply at a site. Most municipal or 

industrial users generally require well yields of at least 50 to 100 gal/min or more, and wells for such supplies likely 

are drilled to a depth sufficient to intersect as many water-bearing zones as feasible. Municipal and industrial users 

also tend to drill multiple wells to obtain the required ground-water supply.

Ground-Water Exploration-Program Example

An example of a successful ground-water exploration program in Subarea 2 on a local scale is that 

implemented for the city of Fayetteville, Fayette County, Ga. (fig. 9). The goal of the program, initiated in 1988, was 

to develop a “drought-resistant” water source to be integrated with the city’s surface-water supply system. The 

exploration program utilized several methods of investigation to locate favorable drilling sites, including surficial 

geologic mapping (rock types, structural features, fracture fabric, and joint statistical analysis), reconnaissance 

surface geophysical surveys, photolineament analysis, collection of background well information, drainage basin 

analysis, collection of soils information, and contaminant-potential analysis. The overall assessment of the 

hydrogeologic framework of the Fayetteville area, evaluated as part of this ground-water exploration program, was 

the delineation of two aquifers: a shallow, regolith zone consisting of alluvium and saprolite; and a deeper fractured 

bedrock aquifer. Following well siting, three test wells were completed in a quartz-biotite gneiss and an epidotecalcite-diopside gneiss that yielded a total of 550 gal/min (145, 185, and 220 gal/min each), or about 0.8 Mgal/d 

(1.23 ft3/s). Depth to water-bearing zones in the bedrock was highly variable at these three sites. Borehole 

geophysical logging, including a downhole camera and caliper, were used to evaluate water-bearing-zone 

characteristics. The major water-bearing fractures were horizontal or low-dipping, along the margins of granitic 

bodies, or where significant lithologic changes occurred (BCI Geonetics, 1990).

To determine the development potential of and to monitor recharge to the well during pumping, shallow 

regolith and deeper bedrock observation wells were completed at the three well sites. Based on 72-hr aquifer tests, the 

total maximum safe yield for the three wells was estimated to be about 937,000 gal/d (BCI Geonetics, 1990). During 

pumping of each bedrock well, drawdown in the shallow regolith wells was insignificant, indicating that most of the 

recharge was derived from deeper bedrock fracture zones. The stage of a nearby creek also was monitored, and 

indicated no apparent effects from ground-water withdrawal (BCI Geonetics, 1990). Water levels in observation 

wells completed in the bedrock responded to the pumping at distances of a few thousand feet (BCI Geonetics, 1990).

 SUMMARY

Drought conditions in the 1980’s have focused attention on the multiple uses of the surface- and ground-water 

resources in the Apalachicola-Chattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River basins in 

Alabama, Florida, and Georgia. Federal, State, and local agencies also have proposed projects that are likely to result 

in additional water use and revisions of reservoir operating practices within the river basins. The existing and 

proposed water projects have created conflicting demands for water and emphasized the problem of allocation of the 

resource. This study was initiated to describe ground-water availability in the middle Chattahoochee River basin in 

Georgia and Alabama, and the upper Flint River basin in Georgia, Subarea 2 of the ACF-ACT River basins, and to 

estimate the possible effects of increased ground-water use in the basin.
39

Subarea 2 encompasses about 4,100 mi2 in west-central Georgia and eastern Alabama. Subarea 2 is bounded 

to the northeast by the upper Chattahoochee River basin (Subarea 1) in Georgia, to the south by the lower 

Chattahoochee and Flint River basins (Subarea 3) in Georgia and Alabama, to the east by the Altamaha River basin, 

and to the west by the Tallapoosa River basin of the ACT River basins (Subarea 5) in Alabama and Georgia.

The Piedmont Province is characterized by a two-component aquifer system composed of a fractured 

crystalline-rock aquifer characterized by little or no primary porosity or permeability. The overlying weathered 

regolith (saprolite) behaves as a porous-media aquifer. In some areas, a transition zone lies between the regolith and 

unweathered crystalline bedrock.

The conceptual model of ground-water flow and stream-aquifer relations subdivides the ground-water flow 

system into local (shallow), intermediate, and regional (deep) flow regimes. The regional flow regime probably 

approximates steady-state conditions and water discharges chiefly to the Chattahoochee River. Ground-water 

discharge to tributaries primarily is from the local and intermediate flow regimes. Ground water that discharges to 

regional drains is composed of local, intermediate, and regional flow regimes. Mean-annual ground-water discharge 

to streams (baseflow) is considered to approximate the long-term, average recharge to ground water.

Mean-annual baseflow in Subarea 2 was estimated using an automated hydrograph-separation method. 

Total mean-annual baseflow to the middle Chattahoochee River basin in Georgia and Alabama and upper Flint 

River basin in Georgia and their tributaries was estimated to be about 5,800 cubic feet per second (from the 

headwaters to Subarea 2–Subarea 3 boundary). Mean-annual baseflow represents about 68 percent of the meanannual stream discharge in the Chattahoochee River basin and 49 percent in the Flint River basin at the 

Subarea 2–Subarea 3 boundary. 

Stream discharges for selected sites on the Chattahoochee and Flint Rivers and tributaries were compiled for 

the years 1941, 1954, and 1986, during which historically significant droughts occurred throughout most of the ACFACT River basins. Stream discharge was assumed to be sustained entirely by baseflow during the latter periods of 

these droughts. Estimated baseflow near the end of the individual drought years averaged about 16 percent of the 

estimated mean-annual baseflow in the Chattahoochee River system and 8.7 percent in the Flint River system in 

Subarea 2.

The limited scope, lack of field-data collection, and the short duration of the ACF-ACT River basin study has 

resulted in incomplete descriptions of ground- and surface-water-flow systems, which may affect the future 

management of water resources in the basins. For example, the extent and continuity of local and regional flow 

systems and their relation to geology is largely unknown. Similarly, quantitative descriptions of stream-aquifer 

relations, ground-water flow across State lines, water quality, drought flows, and ground-water withdrawal and 

subsequent effects on the flow systems (the availability and utilization issue) are highly interpretive; therefore, the 

descriptions should be used accordingly.

Estimates of water use and ground-water discharge to streams are dependent on methodologies employed 

during data collection, computation, and analyses. Results reported herein are limited by a lack of recent data and the 

non-contemporaneity of all data. Analyses using limited data may not adequately describe stream-aquifer relations. 

Most importantly, analyses in this report describe only two hydrologic conditions—(1) mean-annual baseflow and 

(2) drought-flow conditions during 1941, 1954, and 1986. Analyses derived from extrapolation to other hydrologic 

conditions, such as much longer drought periods or increased ground-water withdrawal, should be used with caution. 

Special concern also should be directed to the effects of increased post-1990 withdrawal on ground-water discharge 

to streams in Subarea 2. 

The potential exists for the development of ground-water resources on a regional scale throughout Subarea 2. 

Ground-water use in 1990 represented about 1.2 percent of the estimated mean-annual baseflow in Georgia, 1.7

percent in Alabama, and 10.5 and 13.1 percent of the average drought flow in Georgia and Alabama, respectively. 

Because ground-water use in Subarea 2 represents a relatively minor percentage of ground-water recharge, even a 

large increase in ground-water use in Subarea 2 in one State probably would have little effect on the quantity of 

ground-water and surface-water occurrence in the other. Long-term ground-water level declines were not observed; 

however, long-term water-level data at wells in Subarea 2 are few in number and poorly distributed areally, and 

conclusions regarding regional water-level declines or storage changes cannot be reasonably drawn. 
40

SUGGESTIONS FOR FURTHER STUDY

This report presents a discussion of ground-water resources and interaction of ground- and surface-water 

systems in the middle Chattahoochee River basin in Georgia and Alabama, and upper Flint River basin in Georgia, 

Subarea 2, of the ACF-ACT River basins. In Subarea 2, ground-water availability is addressed only from a regional 

perspective using historical data. Data collection was not a part of this study; therefore, lack of streamflow and 

ground-water data necessitated that estimation methods be used extensively to describe stream-aquifer relations. 

Additional data, particularly data describing surface- and ground-water conditions on a local scale, are needed to 

further refine and quantify interaction of ground- and surface-water systems in the Subarea. Analyses of these data 

could better describe stream-aquifer relations, as well as ground-water availability and development potential in 

Subarea 2. 

Although the overall objectives of this study were to evaluate the ground-water resources and supply, the data 

used to accomplish these objectives were stream-discharge data. Stream-discharge data were sufficient to meet study 

objectives; however, such data either were not totally adequate or were not available at critical sites. Future streamdischarge data collection to support resource management should emphasize (1) continuous-record data at critical 

hydrologic and political boundaries for a period of years; and (2) concurrent stream-discharge measurements at 

critical sites during drought periods.

Continuous stream-discharge data collected over a period of years at critical locations provide the basic 

information essential to basinwide water-resource planning and management. Current data coverage is incomplete. 

For example, stream-gaging stations located on major tributary streams would have eliminated or reduced the need to 

extrapolate and interpolate data from stations distant from these boundaries, and consequently, would have improved 

the accuracy of estimates of ground-water contributions from subarea to subarea. 

The collection of drought-flow data obviously is contingent on the occurrence of a drought; thus, collection of 

drought data is not routine and is not easily planned. A contingency plan to collect drought data should be in place. 

The plan could consider, but not be limited to, logistics, manpower needs, and the preselection of stream datacollection locations. For more rigorous planning, field reconnaissance of preselected stream sites could be conducted. 

Data-base development also is critical to resource management. Data elements, such as well construction and 

yield; hydraulic characteristics of aquifers; water quality; and ground-water withdrawals—both areally and by 

aquifer—are particularly important. Seepage runs (detailed streamflow measurements of drainage systems made 

concurrently during baseflow conditions) can be used to identify individual ground-water flow systems and improve 

the understanding of stream-aquifer relations, especially in crystalline and mixed-rock terranes. Once identified, a 

flow system can be studied in detail to define its extent, recharge and discharge areas, movement of water, chemical 

quality, and the amount of water that can be withdrawn with inconsequential or minimal effects. These detailed 

studies might include test drilling, borehole geophysical logging, applications of surface geophysics, aquifer testing, a 

thorough water-withdrawal inventory, and chemical analyses of ground water to delineate the extent of the groundwater-flow system and evaluate its potential as a water supply. Evaluation of several such flow systems would greatly 

improve the understanding of ground-water resources throughout the subarea. Because aquifer properties vary 

substantially on a local scale and data are sparse, field studies are needed to obtain quantitative definitions of the 

hydraulic interactions of aquifers and streams in Subarea 2. 

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46

SELECTED REFERENCES—Continued

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47

SELECTED REFERENCES—Continued

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____1964, Infiltration and permeability of weathered crystalline rocks, Georgia Nuclear Laboratory, Dawson County, 

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Thomson, M.T., 1960, Streamflow maps of Georgia’s major rivers: Georgia Geologic Survey Information Circular 21, 

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Thomson, M.T., and Carter, R.F., 1955, Surface water resources of Georgia during the drought of 1954: Georgia 

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___1963, Effect of a severe drought (1954) on streamflow in Georgia: Georgia Geologic Survey Bulletin 73, 97 p.

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48

 SELECTED REFERENCES—Continued

Trent, V.P., Fanning, J.L., and Doonan, G.A., 1990, Water use in Georgia by county for 1987: Georgia Geologic 

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Turlington, M.C., Fanning, J.L., and Doonan, G.A., 1987, Water use in Georgia by county for 1985: Georgia Geologic 

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U.S. Army Corp of Engineers, 1972, Stream mileage tables with drainage areas: Mobile, Ala., U.S. Army Corps of 

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___1985a, Alabama-Mississippi stream mileage tables with drainage areas: Mobile, Ala., U.S. Army Corps of 

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U.S. Geological Survey, 1960, Compilation of records of surface waters of the United States, through September 1950; 

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___1963, Compilation of records of surface waters of the United States, October 1950 to 1960; Part 2-B. South 

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___1972, Water-resources data for Georgia, water year 1971: U.S. Geological Survey, 259 p.

___1974a, Hydrologic Unit Map, State of Alabama: U.S. Geological Survey Hydrologic Unit Map, scale 1:500,000, 

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___1974b, Hydrologic Unit Map, State of Georgia: U.S. Geological Survey Hydrologic Unit Map, scale 1:500,000, 1 

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___1977, Water resources data for Georgia, water year 1976: U.S. Geological Survey GA-76-1, 411 p.

___1978, Water resources data for Georgia, water year 1977: U.S. Geological Survey GA-77-1, 375 p.

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