U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5072

Prepared in cooperation with the

Georgia Department of Natural Resources

Environmental Protection Division

Geohydrology of the Aucilla–Suwannee–

Ochlockonee River Basin, South-Central Georgia 

and Adjacent Parts of Florida

G E O R G I A

F L O R I D A

Study area boundary

Gulf Trough–Apalachicola Embayment

OKEFENOKEE

BASIN
Cover. See figure 15 of this report.
Geohydrology of the Aucilla–Suwannee–

Ochlockonee River Basin, South-Central Georgia 

and Adjacent Parts of Florida

By Lynn J. Torak, Jaime A. Painter, and Michael F. Peck

Prepared in cooperation with the

Georgia Department of Natural Resources

Environmental Protection Division

Scientific Investigations Report 2010–5072

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Torak, L.J., Painter, J.A., and Peck, M.F., 2010, Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, 

south-central Georgia and adjacent parts of Florida: U.S. Geological Survey Scientific Investigations Report 

2010–5072, 78 p.
iii

Contents

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

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

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

Previous Studies ...................................................................................................................................2

Well and Climatological-Station Identification and Surface-WaterStation-Numbering System ..................................................................................................4

Study Area..............................................................................................................................................4

Climate and Precipitation Variability ........................................................................................4

Physiography and Drainage.......................................................................................................6

Geohydrology................................................................................................................................................10

Geologic Setting..................................................................................................................................10

Structural Features....................................................................................................................11

Geologic Units ............................................................................................................................17

Hydrologic Setting ..............................................................................................................................22

Hydrochemistry...................................................................................................................................27

Hydrologic Characteristics ...............................................................................................................28

Surficial Aquifer System...........................................................................................................28

Hydraulic Properties ........................................................................................................28

Groundwater Levels and Fluctuations ..........................................................................28

Upper Semiconfining Unit ........................................................................................................30

Thickness ...........................................................................................................................30

Vertical-Leakage Potential..............................................................................................31

Upper Floridan Aquifer..............................................................................................................31

Thickness Variations ........................................................................................................31

Hydraulic Properties and the Effects of Limestone Dissolution and the 

Gulf Trough–Apalachicola Embayment on Groundwater Flow....................34

Transmissivity and Hydraulic Conductivity..........................................................34

Storage Coefficient and Specific Yield.................................................................35

Groundwater Levels and Fluctuations .................................................................38

September 2006 Potentiometric Surface.............................................................40

Lower Confining Unit.................................................................................................................44

Conclusions...................................................................................................................................................45

References Cited..........................................................................................................................................48

Appendix. Geohydrologic Data ..............................................................................................................53
iv

Figures

1. Map showing location of study area in the Aucilla–Suwannee–Ochlockonee 

River Basin and lower Apalachicola–Chattahoochee–Flint River Basin, and of 

continuous-recorder observation wells and climatological and streamgaging 

stations in south-central Georgia and northwestern Florida................................................5

2. Graphs showing period-of-record monthly mean, minimum, and maximum 

precipitation at climatological stations 92266, Cordele, Georgia, 1948–2005; 

99186, Waycross, Georgia, 1930–2005; 84731, Lake City, Florida, 1931–2006; 

and 88758, Tallahassee, Florida, 1948–2005..............................................................................7

3. Map showing physiographic divisions in the Aucilla–Suwannee–Ochlockonee 

River Basin.....................................................................................................................................8

4. Correlation chart showing geologic and geohydrologic units and groundwater 

quality of the Upper Floridan aquifer and hydraulically connected sediments in the 

Aucilla–Suwannee–Ochlockonee River Basin......................................................................10

5–6. Maps showing—

5. Structural features affecting the Floridan aquifer system .........................................11

6. Approximate location of the Gulf Trough–Apalachicola Embayment 

in the Aucilla–Suwannee–Ochlockonee River Basin in southern Georgia 

and adjacent parts of Florida...........................................................................................12

7. Geologic sections across northeastern Florida showing relations between 

geologic units and the Floridan aquifer system along A–A’, from west of Lake City, 

Florida, to the Atlantic Ocean; and B–B’, from Duval County, Florida, to 

Fernandina Beach, Florida ........................................................................................................13

8. Geologic section across Colquitt County, Georgia, showing sediment 

thickening in the area of the Gulf Trough–Apalachicola Embayment ...............................14

9. Geologic section across Thomas County, Georgia, showing sediment 

thickening in the area of the Gulf Trough–Apalachicola Embayment ...............................15

10. Geologic sections across northeastern Florida showing accumulation of 

Eocene sediment over the Peninsular Arch along A–A’, from western Jefferson 

County, Florida, to Columbia County, Florida; and B–B’, from Taylor County, Florida, 

near Gulf of Mexico, to Bradford County, Florida..................................................................16

11. Geologic section across Crisp and Wilcox Counties, Georgia, showing 

reduction of Suwannee Limestone thickness to Flint River residuum...............................18

12. Geologic section of Floridan aquifer system from Calhoun County, Georgia, 

southeast to Clay County, Florida, showing hydrostratigraphic relations and 

structure of sediments in the Aucilla–Suwannee–Ochlockonee River Basin .................19

13. Conceptual diagram of groundwater and surface-water flow in the 

interconnected stream-lake-aquifer flow system of the Aucilla–Suwannee–

Ochlockonee River Basin ..........................................................................................................22
v

14–17. Maps showing—

14. Areal extent of surficial aquifer system in the Aucilla–Suwannee–

Ochlockonee River Basin .................................................................................................23

15. Overburden thickness and leakage potential of the upper semiconfining 

unit in the Aucilla–Suwannee–Ochlockonee River Basin..........................................24

16. Altitude of the top of the Upper Floridian aquifer in the Aucilla–Suwannee–

Ochlockonee River Basin .................................................................................................25

17. Potentiometric surface of the surficial aquifer system in the Aucilla–

Suwannee–Ochlockonee River Basin, September 2006.............................................29

18. Groundwater hydrographs of wells 16M015, 16N006, 17L028, and 18K051, 

completed in the surficial aquifer system, for the period 2001–2007.................................30

19–21. Map showing—

19. Thickness of the Upper Floridan aquifer in the Aucilla–Suwannee–

Ochlockonee River Basin .................................................................................................32

20. Altitude of the base of the Upper Floridan aquifer in the Aucilla–

Suwannee–Ochlockonee River Basin............................................................................33

21. Hydraulic properties of the Upper Floridan aquifer in the Aucilla–Suwannee–

Ochlockonee River Basin hydraulic conductivity and transmissivity.......................36

22. Hydrograph showing seasonal groundwater-level fluctuation in well 15L020, 

Sylvester, Georgia, 1996–1999 ..................................................................................................38

23. Hydrographs showing daily mean depth to water level and period-of-record 

median daily groundwater level for wells 12F036, 1964–2008; 15L020, 1972–2008; 

18H016, 1965–2008; 18K049, 1978–2008; 19E009, 1957–2008; 27E004, 1978–2008;

and 27G003, 1982–2008...............................................................................................................39

24. Maps showing potentiometric surface of the Upper Floridan aquifer in 

southern Georgia and northern Florida, September 2006; and enlarged view 

of the potentiometric surface of the Upper Floridan aquifer in southern Georgia, 

September 2006, showing groundwater divide and flow directions..................................42

Tables

1. Center-pivot irrigation in the lower Apalachicola–Chattahoochee–Flint River 

Basin during 1993 and 1999 in Georgia counties co-located along the basin divide 

with the Aucilla–Suwannee–Ochlockonee River Basin ........................................................3

2. Period-of-record monthly average precipitation at Lake City and Tallahassee, 

Florida, and at Cordele and Waycross, Georgia......................................................................6

3. Precipitation for selected years and climatological stations located in 

the Aucilla–Suwannee–Ochlokonee River Basin .................................................................41

A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.....................54
vi

Conversion Factors and Datums

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

acre 0.4047 hectare (ha)

square mile (mi2

) 259.0 hectare (ha)

square mile (mi2

) 2.590 square kilometer (km2) 

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Mass

ton, short (2,000 lb) 0.9072 megagram (Mg) 

Specific capacity

gallon per minute per foot 

[(gal/min)/ft)]

 0.2070 liter per second per meter 

[(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

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

Transmissivity*

foot squared per day (ft2

/d) 0.09290 meter squared per day (m2/d) 

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

°F = (1.8 × °C) + 32

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

°C = (°F – 32) / 1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3

/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
Geohydrology of the Aucilla–Suwannee–

Ochlockonee River Basin, South-Central Georgia 

and Adjacent Parts of Florida

By Lynn J. Torak, Jaime A. Painter, and Michael F. Peck

Abstract

Major streams and tributaries located in the Aucilla–

Suwannee–Ochlockonee (ASO) River Basin of south-central 

Georgia and adjacent parts of Florida drain about 8,000 square 

miles of a layered sequence of clastic and carbonate sediments and carbonate Coastal Plain sediments consisting of 

the surficial aquifer system, upper semiconfining unit, Upper 

Floridan aquifer, and lower confining unit. Streams either flow 

directly on late-middle Eocene to Oligocene karst limestone or 

carve a dendritic drainage pattern into overlying Miocene to 

Holocene sand, silt, and clay, facilitating water exchange and 

hydraulic connection with geohydrologic units.

Geologic structures operating in the ASO River Basin 

through time control sedimentation and influence geohydrology and water exchange between geohydrologic units and 

surface water. More than 300 feet (ft) of clastic sediments 

overlie the Upper Floridan aquifer in the Gulf Trough–

Apalachicola Embayment, a broad area extending from the 

southwest to the northeast through the center of the basin. 

These clastic sediments limit hydraulic connection and water 

exchange between the Upper Floridan aquifer, the surficial 

aquifer system, and surface water. Accumulation of more 

than 350 ft of low-permeability sediments in the Southeast 

Georgia Embayment and Suwannee Strait hydraulically 

isolates the Upper Floridan aquifer from land-surface 

hydrologic processes in the Okefenokee Basin physiographic 

district. Burial of limestone beneath thick clastic overburden 

in these areas virtually eliminates karst processes, resulting 

in low aquifer hydraulic conductivity and storage coefficient 

despite an aquifer thickness of more than 900 ft. Conversely, 

uplift and faulting associated with regional tectonics and the 

northern extension of the Peninsular Arch caused thinning 

and erosion of clastic sediments overlying the Upper Floridan 

aquifer southeast of the Gulf Trough–Apalachicola Embayment near the Florida–Georgia State line. Limestone 

dissolution in Brooks and Lowndes Counties, Ga., create 

karst features that enhance water-transmitting and storage 

properties of the Upper Floridan aquifer, promoting groundwater recharge and water exchange between the aquifer, land 

surface, and surface water.

Structural control of groundwater flow and hydraulic 

properties combine with climatic effects and increased 

hydrologic stress from agricultural pumpage to yield unprecedented groundwater-level decline in the northwestern and 

central parts of the ASO River Basin. Hydrographs from 

continuous-record observation wells in these regions document declining groundwater levels, indicating diminished 

water-resource potential of the Upper Floridan aquifer through 

time. More than 24 ft of groundwater-level decline occurred 

along the basin’s northwestern boundary with the lower 

Apalachicola–Chattahoochee–Flint River Basin, lowering 

hydraulic gradients that provide the potential for groundwater flow into the ASO River Basin and southeastward 

across the Gulf Trough–Apalachicola Embayment region. 

Slow-moving groundwater across the trough-embayment 

region coupled with downward-vertical flow from upper to 

lower limestone units composing the Upper Floridan aquifer 

resulted in 40–50 ft of groundwater-level decline since 1969 

in southeastern Colquitt County. Multi-year episodes of dry 

climatic conditions during the 1980s through the early 2000s 

contributed to seasonal and long-term groundwater-level 

decline by reducing recharge to the Upper Floridan aquifer 

and increasing hydrologic stress by agricultural pumpage. 

Unprecedented and continued groundwater-level decline since 

1969 caused 40–50 ft of aquifer dewatering in southeastern 

Colquitt County that reduced aquifer transmissivity and the 

ability to supply groundwater to wells, resulting in depletion 

of the groundwater resource.
2 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Introduction

Episodic-drought conditions and increased pumpage 

since the mid-1970s have caused unprecedented groundwaterlevel decline in the Upper Floridan aquifer in much of the 

roughly 8,000-square-mile (mi2) Aucilla–Suwannee–

Ochlockonee (ASO) River Basin (fig. 1). During 2007, 

record-low groundwater levels occurred in Charlton, Cook, 

Tift, Ware, and Worth Counties. The groundwater level in 

Lowndes County declined nearly 25 feet (ft) during the first 

10 months of 2006, after recovering nearly that much and 

holding stable since 2003. An eastward shift in location of 

municipal groundwater withdrawal at Cairo, Ga., reversed a 

35-ft declining groundwater-level trend that occurred during 

1966–1973, although groundwater-level fluctuations of as 

much as 20 ft occurred in multiyear cycles since that time.

Since the early 1990s, increased center-pivot irrigation 

along the basin divide with the neighboring Apalachicola–

Chattahoochee–Flint (ACF) River Basin (Litts and others, 

2001) has intercepted groundwater that, prior to irrigation 

pumpage, was available to recharge the ASO River Basin as 

regional (interbasin) groundwater flow. Pumpage increases 

along the boundary of the ASO and ACF River Basins have 

accelerated groundwater-level declines in the Upper Floridan 

aquifer and reduced the hydraulic gradient, thus reducing 

the amount of regional groundwater flow (interbasin flow) 

to the south and east into the ASO River Basin (Torak and 

Painter, 2006). Long-term groundwater-level decline in the 

Upper Floridan aquifer has the potential to reduce springflow, 

decrease groundwater discharge to streams (baseflow), and 

diminish interbasin flow from the north and west, threatening 

the ability of the basin’s water resources to meet current and 

future demand.

As a result of these concerns, the U.S. Geological 

Survey (USGS), in cooperation with the State of Georgia, 

Department of Natural Resources, Environmental Protection 

Division (GA-EPD), began a study in September 2006 to 

acquire, compile, and interpret geohydrologic information in 

the ASO River Basin. Study results would enable development of science-based, cause-and-effect relations between 

groundwater withdrawal for agricultural, municipal, industrial, 

and drinking-water purposes and groundwater-level and 

streamflow trends. Hydrologic relations developed from this 

study would enable evaluation of emerging resource issues 

related to groundwater-level and streamflow declines, such 

as aquatic-habitat degradation and potential local or regional 

groundwater shortages resulting from excessive groundwater 

withdrawal and dry climatic conditions.

Purpose and Scope

This report describes the geohydrologic investigation 

of the ASO River Basin performed primarily in Georgia; 

however, adjacent areas of the panhandle of northwestern 

Florida have been included as needed (fig. 1). Investigative 

results described herein provide a framework for evaluation of 

groundwater level and streamflow decline in the ASO basin, 

as jointly developed by the GA-EPD and USGS. Objectives of 

this investigation and report accomplish the following tasks,

1. Describe the lithology and hydraulic properties of the 

Upper Floridan aquifer and hydraulically connected 

geologic units that would enable assessment of water 

exchange between the Upper Floridan aquifer and other 

geohydrologic units and surface water.

2. Develop a hydrogeologic framework and conceptual 

model for evaluating agricultural pumpage and groundwater and surface-water exchange between the Upper 

Floridan aquifer and other geohydrologic units connected 

to surface water.

3. Present an overview of 2006 groundwater-level and 

streamflow conditions.

4. Explain hydrologic concepts of the groundwater and 

surface-water exchange mechanisms that control causal 

relations between groundwater pumpage in the Upper 

Floridan aquifer, climatic variations, groundwater-level 

decline, reductions in streamflow and springflow, and 

changes in interbasin flow.

Previous Studies

Early investigations provided general descriptions of the 

geology and groundwater in the area (McCallie, 1898, 1908; 

Stephenson and Veatch, 1915; Cooke, 1943; and Herrick 

and Vorhis, 1963). Cooke (1943) mapped the geology of the 

coastal plain of Georgia, and MacNeil (1947) mapped Tertiary 

and Quaternary formations in the study area. Wait (1960) 

published water-chemistry analyses of selected wells in the 

basin. Herrick (1961) compiled detailed lithologic and paleontological logs of wells throughout the Georgia Coastal Plain.

Previous hydrologic investigations in Georgia have 

neither included the entire area of the ASO River Basin nor 

evaluated causal relations between groundwater pumpage 

and declining groundwater level, streamflow, and springflow. 

Studies performed for the National Water-Quality Assessment 

(NAWQA) Program, Georgia–Florida Coastal Plain Drainages 

study unit (U.S. Geological Survey, 2006), included evaluation 

of nutrient loads of several major rivers, including the main 

rivers of the ASO River Basin in Georgia and Florida; however, none of these studies compiled geologic and hydrologic 

data into a comprehensive geohydrologic framework in the 

study area. A NAWQA Program study by Pittman and Berndt 

(2003) focused on water-quality issues related to herbicide 

degradation in the surficial aquifer and streams located in the 

upper part of the basin.

Priest (2004) evaluated the groundwater contribution to 

streamflow in the coastal area of Georgia and adjacent Florida 

and South Carolina; however, the study area encompassed 
Introduction 3

only part of the Suwannee River Basin and excluded the 

Aucilla and Ochlockonee Rivers to the west. Falls and others 

(2005) investigated the hydrogeology of the Lower Floridan 

aquifer in 24 coastal counties in Georgia and adjacent Florida 

and South Carolina, which included only the extreme eastern 

part of the ASO River Basin. Payne and others (2005) 

compiled additional geologic information for a larger study 

area than that of Falls and others (2005) still excluding the 

western parts of the ASO River Basin. Studies by Torak and 

Painter (2006) and Jones and Torak (2006), investigated 

stream-aquifer relations in the neighboring ACF River Basin 

to the north and west, and only marginally investigated the 

geohydrology of the Ochlockonee River and upper Suwannee 

River Basins inasmuch as it affected groundwater flow in the 

western basin of interest.

McConnell and Hacke (1993) and Plummer and 

others (1998a, b) performed hydrologic studies of the water 

chemistry of the karst area in the Upper Floridan aquifer at 

Valdosta, Ga. Katz and others (1995a,b, 1997), Katz (1998), 

and Crandall and others (1999) investigated hydrochemistry 

of stream-lake-aquifer interaction in karst areas of northern 

Florida. Studies describing the geochemistry and groundwater 

quality of the Upper Floridan aquifer include Sever (1965), 

Sprinkle (1989), and Katz (1992).

A geohydrologic investigation by Torak and Painter 

(2006) and simulation of groundwater and surface-water 

exchange by Jones and Torak (2006) indicate that irrigation 

pumpage in outcrop and recharge areas of the Upper Floridan 

aquifer in the lower ACF River Basin intercepts groundwater 

that once was available to recharge the ASO River Basin as 

regional (interbasin) groundwater flow. The geohydrologic 

investigation by Torak and Painter (2006) indicates that 

reduced interbasin flow from irrigation pumpage in the ACF 

River Basin limits groundwater availability and development 

potential in the ASO River Basin and can reduce baseflow of 

streams located along the basin’s northwestern boundary and 

interior. Lithologic descriptions given in the study by Torak 

and Painter (2006) indicate that large variations in hydraulic 

conductivity of the Upper Floridan aquifer exist at regional 

and local scales that could alter the amount of groundwater 

and surface-water exchange between the aquifer and surface 

water within short distances.

Previous investigations provided water-use information 

in the ASO River Basin and documented increases in rates 

of groundwater withdrawal for irrigation, industry, and 

public supply. Thomson and others (1956) noted increases in 

statewide irrigation following the 1954 drought. Carter and 

Johnson (1974) compiled statewide estimates of irrigated 

acres based on a 1969 U.S. Census Bureau national summary 

of agriculture and compiled water-use estimates according to 

Area Planning and Development Commission regions. Pierce 

and others (1984) documented large increases in agricultural 

irrigation in southwestern Georgia during the 1970s, differentiated groundwater- and surface-water-irrigation withdrawal, 

and identified locations of center-pivot irrigation systems in a 

“High Irrigation Water Use Zone” during 1980 that included 

the ACF and ASO River Basins. Harrison and Tyson (1999) 

and Harrison (2001) reported results of the Georgia Irrigation 

Survey that identified steadily increasing trends in agricultural 

water-use statewide and increased use of center-pivot irrigation. Turlington and others (1987), Fanning and others (1992), 

and Fanning (1997, 2003) compiled water-use data by county 

and type of use, and provided summaries of water use, by 

county, for 1985, 1990, 1995, and 2000, respectively. Litts 

and others (2001) reported significant increases in centerpivot-irrigation systems during the 1990s within and along 

the boundary between the ASO and lower ACF River Basins 

(table 1). Unfortunately, the investigation by Litts and others 

(2001) only reported irrigated acreage and acreage change 

associated with the lower ACF River Basin, although seven 

Georgia counties are located partially in both basins.

Geologic nomenclature used herein is consistent with 

previous geologic and hydrologic investigations performed in 

the study area and adjacent regions to the north and west, and 

described in reports by Sever (1964, 1965), Sever and Herrick 

(1967), Miller (1986), Torak and McDowell (1996), Torak 

and others (1996, 2006), Albertson and Torak (2002), Mosner 

(2002), and Jones and Torak (2004, 2006). Consistent nomenclature with that used in the neighboring ACF River Basin and 

recent investigations, referenced above, promotes increased 

understanding of the role of geologic units during assessment 

of water resources in the ASO River Basin and emphasizes 

regional importance of these units northward and westward to 

the outcrop areas. Alternate naming conventions of geologic 

units are presented and cited for reference where appropriate.

Table 1. Center-pivot irrigation in the lower Apalachicola–

Chattahoochee–Flint River Basin during 1993 and 1999 in 

Georgia counties co-located along the basin divide with the 

Aucilla–Suwannee–Ochlockonee River Basin (see fig. 1 for 

county locations; modified from Litts and others, 2001).

[—, not applicable]

County

Center-pivot irrigationa

(acres)

1993 to 1999 

increase 

(acres)

Percent 

increase

1993 1999

Crisp 3,895 11,951 8,056 207

Decatur 47,870 59,579 11,709 24

Dooly 6,984 12,487 5,503 79

Grady 2,828 3,254 426 15

Mitchell 47,610 58,425 10,815 23

Turner 211 1,384 1,173 556

Worth 9,552 15,675 6,123 64

Total 118,950 162,755 43,805 —

a

Acreage located in Apalachicola–Chattahoochee–Flint River Basin only.
4 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Well and Climatological-Station Identification 

and Surface-Water-Station-Numbering System 

A system based on USGS topographic maps identifies 

wells in Georgia. Each 71⁄2-minute topographic quadrangle 

map in Georgia has been given a number and letter designation beginning at the southwestern corner of the State. 

Numbers increase eastward through 39, letters advance 

northward through “Z,” then double-letter designations “AA” 

through “PP” are used. The letters “I,” and “O” are not used. 

Wells inventoried in each quadrangle are numbered sequentially beginning with “1.” Thus, the 49th well inventoried in 

the Tifton East quadrangle (designated 18K) is designated 

18K049 (fig. 1). Wells in Florida are numbered with a 

four-digit numerical code that is assigned by the Northwest 

Florida Water Management District (Christopher J. Richards, 

Northwest Florida Water Management District, Havana, Fla., 

written commun., April 2000).

Climatological stations are given a name that corresponds 

to the nearest city, town, or locality; figures and letters 

following the name indicate the distance in miles and compass 

direction from the post office or town community center, such 

as Albany 3 SE (National Oceanic and Atmospheric Administration, 2002), located 3 miles (mi) southeast of the town 

center. Additionally, climatological stations are “identified 

by a six-digit number that constitutes the National Weather 

Service (NWS) Cooperative Station Network. The first two 

digits designate a state or territory code. The last four digits 

are assigned to stations within a state in general accordance 

with the alphabetical order of the station name. A station in 

this network, as designated by a single Cooperative Station 

Identifier, can be one site or a series of sites whose locations 

fall within 2 mi horizontal or 100 ft vertical distance. There 

are exceptions to this rule, with ‘climatic compatibility,’ as 

determined by the NWS field manager, being the overriding 

factor” (National Oceanic and Atmospheric Administration, 

2008). For example, station number 092266 corresponds to 

the station “CORDELE,” located in Cordele, Ga. (fig. 1). The 

leading “0” of the state or territory code has been omitted in 

this report.

Partial- and continuous-record surface-water stations 

are given an identification number, which is assigned in 

“downstream order” (Stokes and others, 1990). No distinction 

is made between partial-record stations and other stations; 

therefore, the number for a partial-record station indicates 

downstream-order position in a list made up of both types 

of stations. The complete number for each station, such as 

02314500, includes a 2-digit part number “02” plus a sixdigit downstream-order number, “314500.”

Study Area

The study area is located in the Coastal Plain Physio

graphic Province of south-central Georgia and adjacent 

Florida, and consists mainly of the land area and geologic 

units contributing to the headwaters of the Aucilla, Suwannee, 

and Ochlockonee Rivers, and similar headwater drainage to 

the St. Marks River (fig. 1). Drainage basins of the Alapaha, 

Little, and Withlacoochee Rivers, and tributaries to the 

Suwannee River, are contained wholly within the study area. 

The Alapaha, Little, and Withlacoochee Rivers and their 

tributaries either flow directly over the limestone aquifer on a 

gentle, seaward-sloping karst plain, or incise sandy to clayey 

sediments overlying the limestone, carving a dendritic drainage pattern in the landscape.

Climate and Precipitation Variability

Long summers and mild winters characterize the climate 

of the ASO River Basin, which ranges from temperate in 

the northwestern part to humid subtropical in the southern 

and southeastern parts. Proximity of the basin to the Gulf of 

Mexico and Atlantic Ocean influences the seasonal variation 

of temperature and precipitation. Mean-annual temperatures 

for the climatic period 1971–2000 vary about 3 degrees 

Fahrenheit (°F), from about 69 °F in the southern and southeastern parts of the basin near the Gulf of Mexico and Atlantic 

Ocean (Tallahassee and Lake City, Florida, respectively; 

fig. 1) to about 66 °F inland in the northwestern and eastern 

parts of the basin (Cordele and Waycross, Ga., respectively) 

(Southeast Regional Climate Center, 2008a, b, c, d). Winterlow temperatures during December and January vary from 

the mid- to upper-30s °F in the northwestern and eastern 

parts of the basin, to the low- to mid-40s °F to the south and 

southeast. Summer-high temperatures occur during June, July, 

and August and vary from the low-90s °F in the northwestern 

and eastern parts of the basin, to the mid- to upper-90s °F to 

the south and southeast. Occasional freezing temperatures 

occur throughout the study area during fall through spring. 

Temperatures approaching 100 °F and above generally occur 

during late-spring through early-fall within much of the study 

area except to the south, where summertime cloudiness and 

thunderstorms limit high temperatures to the low-90s °F.

Precipitation varies geographically and temporally in 

the ASO River Basin according to the seasonal influence of 

weather patterns that bring humid subtropical and maritime air 

northward from the Gulf of Mexico and Atlantic Ocean and 

that move continental air masses into the basin from the north 

and west. Long-term records indicate nearly an 18-inch variation in total annual precipitation, from about 62.5 inches in 

Tallahassee, Fla., to the south, to about 44.9 inches in Cordele, 

Ga., to the northwest (table 2) (Southeast Regional Climate 

Center, 2008a, c). Summertime southwesterly winds bring 

tropical moisture inland from the Gulf of Mexico causing 

higher precipitation in the southern part of the study area (near 

Tallahassee, Fla.) than to the northwest (near Cordele, Ga.). 

Coastal storms from the Atlantic Ocean increase precipitation 

along the eastern part of the study area (near Waycross, Ga.). 

The southeastern part of the study area receives precipitation 

from the remains of coastal and gulf storms that move inland 
Introduction 5

85° 84° 83° 82°

31°

32°

30°

BAKER MITCHELL

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER

STEWART

SCHLEY

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

CHARLTON

WHEELER

PULASKI

DODGE

MONTGOMERY

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE

TIFT

BERRIEN

ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

BROOKS

THOMAS

BRADFORD

UNION

SUMTER

QUITMAN

BRANTLEY

TOOMBS

JEFF DAVIS

WARE

St Marks River

Aucilla River

Withlacoochee River

Suwannee River

Ochlockonee River

Little River

Alapaha River

Okefenokee Swamp

Alapaha

Rise Holton

Spring

Lake Jackson 

Lake Iamonia

 Lake

Miccosukee

Flint River

15L020

18K049

02317500 02318500

023177483

02318000

02316000

02318700

02327500

02329342 02314500

12F036

18H016

19E009 27E004 93465

27G003

Sylvester

Cordele

Moultrie

Valdosta

Tallahassee

Ellaville

Attapulgus

Quincy

Lake City

Waycross

92266

92728

90406 93386

98703

96244

96087

92783

96879

93312

98974

99186

93325

94429

97276

98666 91463

90586

91500

88758

84731

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Ochlockonee River Basin

Boundary of lower Apalachicola–

 Chattahoochee–Flint River Basin 

 study (Torak and Painter, 2006)

Groundwater well and site name

Streamgaging station and number

Aucilla River Basin

Suwannee River Basin

Study area 19E009

02317500

Figure 1. Location of study areas in the Aucilla–Suwannee–Ochlockonee River Basin and lower Apalachicola– 

Chattahoochee–Flint River Basin, and of continuous-recorder observation wells and climatological and 

streamgaging stations in south-central Georgia and northwestern Florida.

Climatological data station

Hourly precipitation data station

Climatological and hourly

 precipitation data station

70586

96879

90406

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

Figure 1. Location of study area in the Aucilla–Suwannee–Ochlockonee River Basin and lower Apalachicola–Chattahoochee–

Flint River Basin, and of continuous-recorder observation wells and climatological and streamgaging stations in south-central 

Georgia and northwestern Florida.
6 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

to the northern-peninsular and eastern-panhandle region near 

Lake City, Fla. Continental storms associated with frontal 

passages bring precipitation to the central and northwestern 

parts of the basin during late fall through early spring. Annual 

precipitation is fairly uniformly distributed throughout the 

year; however, slightly less precipitation occurs during April 

and May and during October through December than during 

the remaining months of the year.

Variations in monthly mean, minimum, and maximum 

precipitation measured at National Oceanic and Atmospheric 

Administration climatological stations that encompass the 

ASO River Basin (Cordele and Waycross, Ga., and Lake City 

and Tallahassee, Fla.) give an indication of the susceptibility 

of the basin to extremely dry or wet conditions (fig. 2). 

Monthly precipitation records at Cordele and Waycross, 

Ga., and at Lake City and Tallahassee, Florida, indicate dry 

conditions from September through May. Each of these 

stations recorded no precipitation for at least 1 month during 

the fall, and Cordele, Ga., listed no precipitation during 

October, November, and December during the period of record 

1948–2006. June, July, and August have the highest minimum 

precipitation amounts of the year, most likely the result of 

summer thunderstorms and tropical storms, such as hurricanes.

The highest maximum precipitation recorded at Cordele 

and Waycross, Ga., and at Lake City and Tallahassee, Florida, 

occurred during September, which also can be one of the driest 

months (fig. 2). All four weather stations listed a maximum 

precipitation during September of at least 18 inches, perhaps 

the result of tropical storms. One such storm deposited nearly 

8 inches of rain at Lake City, Florida, and nearly 5 inches 

of rain at Waycross, Ga., on September 7, 2004, which 

contributed to the September period-of-record maximum 

precipitation at each station (Southeast Regional Climate 

Center, 2008b, d). Most other months recorded maximum 

precipitation in the 10–15-inch range, with the exception of 

Cordele, Ga., where the maximum precipitation of 7–8 inches 

occurred during February, April, October, and November. 

The southern and southeastern parts of the basin (Tallahassee 

and Lake City, Florida) historically have recorded monthly 

maximum precipitation in excess of 10 inches year-round, 

with two minor exceptions occurring at Lake City, Florida, 

during February (about 9.9 inches) and November (about 

9 inches) during the period of record 1931–2006.

Physiography and Drainage

Three distinct regions of the Coastal Plain Physiographic 

Province define unique landforms and surface drainage in the 

study area: a region of dissected hills and sand-hill ridges; an 

area of low relief that decreases to the southeast and contains 

numerous swamps; and a relatively flat, coastal-sediment 

region with karst limestone at or near land surface. The hilly 

region—termed the Tifton Upland District in Georgia and 

the Tallahassee Hills District (Puri and Vernon, 1964) and 

Northern Highlands (Cooke, 1939) in Florida—contains 

headwater drainage to the Alapaha, Aucilla, Ochlockonee, and 

Withlacoochee Rivers (fig. 3). The Tifton Upland is bounded 

to the west by the Solution Escarpment (MacNeil, 1947) and 

to the east by the eastern drainage divide of the Alapaha River. 

The swampy area of low relief to the east of the Tifton Upland 

and Tallahassee Hills is termed the Okefenokee Basin District 

(Clark and Zisa, 1976) and is drained by the Suwannee River.

Table 2. Period-of-record monthly average precipitation at Lake City and Tallahassee, Florida, and at Cordele and 

Waycross, Georgia (Southeast Regional Climate Center 2008a, b,c, d; see fig. 1 for location).

Month

Period-of-record average precipitation, in inches

Cordele, 

Georgia (92266)

1948–2006

Waycross 4 NE, 

Georgia (99186)

1930–2005

Lake City 2 E, 

Florida (84731)

1931–2006

Tallahassee, WSO AP, 

Florida (88758)

1948–2005

January 4.10 3.89 3.67 4.42

February 4.20 3.57 3.73 4.81

March 4.98 4.49 4.50 5.98

April 3.37 3.21 3.15 3.72

May 3.14 3.40 3.50 4.35

June 4.21 5.63 6.58 7.14

July 5.00 6.56 7.27 8.50

August 3.89 5.95 7.12 7.21

September 3.83 4.68 5.48 5.69

October 1.97 2.84 2.95 3.16

November 2.74 2.32 2.24 3.36

December 3.54 3.10 3.01 4.11

 Annual 44.86 49.63 53.19 62.46
Introduction 7

The Cody Scarp, called the “most persistent topographic 

break in the state” by Puri and Vernon (1964), denotes a transition between the Tallahassee Hills and Northern Highlands and 

the relatively flat coastal region of the Gulf Coastal Lowlands, 

which frames the southern study area boundary. Above the 

escarpment, the thin, clastic cover is commonly breached by 

erosion, both from above by streams and from below by subsidence sinkholes. This erosional dissection has broadened the 

escarpment into a transition zone. Where the cover is breached, 

virtually all surface drainage flowing off the highlands disappears underground; numerous springs occur a short distance 

below the escarpment. Several of these, such as the Alapaha 

Rise, constitute discrete resurgences apparently connected to 

the sinking point by continuous conduits, although this has 

not been absolutely documented. The outflow is frequently 

turbid, reddish-brown, river-type water; however, there is also a 

substantial groundwater component to this flow (Ceryak, 1977).

The Tifton Upland, Tallahassee Hills, and Northern 

Highlands are parts of a nearly continuous series of 

topographically high uplands containing gently rolling 

hills with broad rounded summits situated between the 

low-lying Dougherty Plain to the northwest, Gulf Coastal 

Lowlands to the south, and Okefenokee Basin to the east 

(fig. 3). The upland regions appear to be disconnected 

remnants of a once-continuous residual highland (Yon, 

1966). Stream valleys divide the Northern Highlands into 

a series of local geomorphic subzones. The Tallahassee 

Hills was the name proposed by Cooke (1939) for the 

region bounded by the Georgia State line to the north, 

coastal terraces to the south, the Withlacoochee River 

to the east, and the Apalachicola River to the west 

(Rupert, 1990). The hilly regions contain resistant clayey 

sands, silts, and clays (Arthur and Rupert, 1989), which 

slope gently to the southeast.

C. Lake City, Florida, 1931–2006 D. Tallahassee, Florida, 1948–2005

A. Cordele, Georgia, 1948–2006 B. Waycross, Georgia, 1930–2005

PRECIPITATION, IN INCHES

30

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

15

20

25

0

5

10

30

15

20

25

0

5

10

Figure 2. Period-of-record monthly mean, minimum, and maximum precipitation at climatological stations (A) 92266, 

Cordele, Georgia, 1948–2006; (B) 99186, Waycross, Georgia, 1930–2005; (C) 84731, Lake City, Florida, 1931–2006; and 

(D) 88758, Tallahassee, Florida, 1948–2005 (Southeast Regional Climate Center; 2008a,b,c,d).

EXPLANATION

Precipitation—Period-of-

 record monthly value

Minimum Mean Maximum

Figure 2. Period-of-record monthly mean, minimum, and maximum precipitation at climatological stations (A) 92266, 

Cordele, Georgia, 1948–2005; (B) 99186, Waycross, Georgia, 1930–2005; (C) 84731, Lake City, Florida, 1931–2006; and 

(D) 88758, Tallahassee, Florida, 1948–2005 (Southeast Regional Climate Center, 2008a, b, c, d).
8 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

TALLAHASSEE HILLS

DOUGHERTY PLAIN

TIFTON UPLAND 

OKEFENOKEE

BASIN BARRIER ISLAND SEQUENCE

VIDALIA UPLAND

BACON TERRACES

NORTHERN

HIGHLANDS

FALL LINE HILLS

GULF COASTAL LOWLANDS

Cody

Scarp

Solution

Escarpment

85° 84° 83° 82°

31°

32°

30°

St Marks River

Aucilla

River

Withlacoochee R

Suwannee River

Ochlockonee River

Little River

Okefenokee Swamp

Alapaha

Rise Holton

Spring

Alapaha River

Flint River

Apalachicola River

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

EXPLANATION 50 KILOMETERS

Ochlockonee River Basin

Aucilla River Basin

Suwannee River Basin

Red Hills region

Study area

Figure 3. Physiographic divisions in the Aucilla–Suwannee–Ochlockonee River Basin (modified from Cooke, 1939; 

and Clark and Zisa, 1976).

Bainbridge

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

COASTAL PLAIN

Figure 3. Physiographic divisions in the Aucilla–Suwannee–Ochlockonee River Basin (modified from Cooke, 1939; 

and Clark and Zisa, 1976).
Introduction 9

The Tifton Upland is a distinct cuesta that begins just 

west of the study area with a prominent escarpment (the 

Solution Escarpment) nearly 150 ft high overlooking the Flint 

River (Fenneman, 1938) (fig. 3). Land-surface altitude in the 

Tifton Upland ranges from about 480 ft in the north to about 

150 ft to the southeast, which is indicative of the regional dip 

of underlying sediments (Clark and Zisa, 1976). Land-surface 

altitude in the Florida counterpart to the Tifton Upland, the 

Tallahassee Hills, ranges from about 330 ft near the Florida–

Georgia State line to about 100 ft in the southern part of the 

region. The high- altitude areas of the Tifton Upland contain 

solution features, some of which are abundant in a broad eastwest strip along the Florida–Georgia State line (Fenneman, 

1938). Dendritic drainage of many surface streams dissects 

the hills and forms deeply incised valleys and ravines (Rupert, 

1990) in the otherwise broad, flat plain.

The Tifton Upland and Tallahassee Hills contain the 

927-mi2 Red Hills region, which encompasses the Aucilla 

and Ochlokonee River Basins in Florida and Georgia and is 

bounded on the south by the Cody Scarp (Cox and others, 

2001) (fig. 3). The Red Hills region comprises part of a belt of 

Eocene hilly terrain that extends across Alabama and Mississippi and contains ravines and clay-capped ridges (Schwaner 

and Mount, 1970; Davis, 1996b) that, in Florida and Georgia, 

drain to the Aucilla and Ochlockonee Rivers. Sandy loam soil 

supports sandhill vegetation that covers ridge tops composed 

of uneroded clay (Schwaner and Mount, 1970). Ravines form, 

however, from selective clay erosion. Surface runoff and 

dissolution subsidence control topography, and small karst 

depressions hold temporary ponds (Davis, 1996a). 

The Red Hills region of the Aucilla and Ochlockonee 

River Basins provides habitat to rare flora and fauna. This 

region may contain the only known localities in Florida and 

Georgia for the salamander Phaeognathus hubrichti, which 

has been located in equivalent hilly regions in Alabama 

(Schwaner and Mount, 1970). One of the largest remaining 

populations of federally endangered red-cockaded wood

peckers (Picoides borealis) is present in the Red Hills region, 

as well as some of the best examples of old-growth longleaf 

pine (Pinus palustris) remaining in the southeastern United 

States (Cox and others, 2001).

The Aucilla River is a distinctive blackwater stream 

that rises in central Thomas County, Ga., and drains marshes 

and lakes before flowing over karst limestone east of Talla

hassee, Fla., where it disappears in sinkholes located along 

the Cody Scarp, only to reappear downstream as springflow 

(1,000 Friends of Florida, 2006). Blackwater streams have a 

naturally dark appearance or are tea-colored due to dissolved 

organic matter carried by the stream (Wakulla County Tourist 

Development Council, 2007).

The Ochlockonee River rises just south of Sylvester, 

Ga., and flows southward about 300 mi over clayey sediments 

of the Tifton Upland and Tallahassee Hills to an estuary 

before emptying to the Gulf of Mexico (fig. 1). Transported 

sediment and organic matter give the Ochlockonee River a 

distinct yellow color. The organic matter nourishes numerous 

species of fish and shellfish, which sustain recreational and 

commercial fishing in the estuary and Gulf of Mexico. The 

Ochlockonee River is State-designated as Outstanding Florida 

Water and is a well-known canoe trail (Wakulla County 

Tourist Development Council, 2007).

The Okefenokee Basin District (fig. 3) contains numerous 

swamps and low relief that decreases to the southeast (Clark 

and Zisa, 1976). Land-surface altitude ranges from about 

240 ft in the northwest on Pliocene-Pleistocene deposits to 

about 75 ft to the southeast on Pleistocene deposits; relief 

varies from about 50 ft to about 5 ft. The swamps range in size 

from a few hundred square feet to the 660-mi2

 Okefenokee 

Swamp. The Suwannee River rises in the Okefenokee Basin 

District of southeastern Georgia, where a series of southeasterly flowing tributaries joins the main channel and drains the 

Okefenokee Swamp as the river flows southwest into northcentral Florida (fig. 1).

The Suwannee River receives major tributary flow from 

the Alapaha and Withlacoochee Rivers, which rise on the 

Tifton Upland and join the Suwannee River in the northern 

panhandle of Florida near Ellaville (fig. 1). The Alapaha 

River flows through a mature karst terrain of numerous 

sinkholes, stream sinks, and springs on the Tifton Upland and 

Northern Highlands before disappearing into several large 

sinkholes (Raulston and others, 1998). The subterranean river 

flows through solution channels in the limestone for about 

19 mi before emerging at two springs—Alapaha Rise and 

Holton Spring—and before joining the Suwannee River. The 

Suwannee River contains the second largest streamflow in 

Florida, after the Apalachicola River in northwestern Florida 

(Raulston and others, 1998). In Florida, a few northwesterly 

flowing tributaries drain the Northern Highlands before the 

Suwannee River crosses the Cody Scarp and flows onto the 

Gulf Coastal Lowlands.

The Gulf Coastal Lowlands (fig. 3) is a sandy, flat, 

seaward-sloping feature shaped mostly by wave and current 

activity from Pleistocene high sea-level stands (Arthur and 

Rupert, 1989). Land surface in the lowlands contains relic 

Pleistocene marine bars, terraces, spits, and sandbar dunes 

(Leitman and others, 1984) with limestone at or near the 

surface. Streams entering the Gulf Coastal Lowlands from the 

Northern Highlands disappear into the limestone aquifer at the 

Cody Scarp, only to reappear downstream as springflow. 
10 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Geohydrology

Geologic and hydrologic settings within the ASO River 

Basin define distinct lithologic and fluid-flow characteristics 

that control groundwater movement and interaction with 

surface water. The Upper Floridan aquifer and overlying and 

underlying semiconfining units contain geologic formations, 

the hydraulic properties of which combine with human-induced 

stress to influence water-resource availability, groundwater and 

surface-water exchange, and development potential. 

The following sections describe geologic and hydrologic 

characteristics of the Upper Floridan aquifer, and overlying 

and underlying semiconfining units, that improve current 

understanding of the lithology and hydraulic properties of the 

aquifer and hydraulically connected geologic units. Such an 

understanding enables conceptualization of water exchange 

among the Upper Floridan aquifer, hydraulically connected 

geologic units, and surface water in the ASO River Basin 

and promotes development of causal relations between 

groundwater pumpage in the Upper Floridan aquifer and 

groundwater-level decline and reductions in streamflow 

and springflow.

Geologic Setting

A thick Jurassic to Holocene sequence of sedimentary 

rocks and unconsolidated to semiconsolidated sediments 

underlies the Coastal Plain Physiographic Province in the 

ASO River Basin and forms a tilted wedge of permeable and 

semipermeable layers that thickens seaward from a featheredge in outcrop areas to the northwest to more than 20,000 ft 

in southern Alabama and Florida (Miller, 1986). Miller (1986) 

identified the section of mostly Paleocene to early Miocene 

carbonate and clastic geologic units, variously hydraulically 

connected, as the Floridan aquifer system of the southeastern 

United States. The Eocene to Holocene sequence of geologic 

units defines the Upper Floridan aquifer and hydraulically 

connected sediments that contribute to groundwater and 

surface-water exchange in the study area (fig. 4). Middle Miocene to Holocene clastic sediments overlie the Floridan aquifer 

system nearly everywhere except where erosion has removed 

poorly consolidated sediments and exposed carbonates at land 

surface. Dissolution by infiltrating precipitation forms local 

to regional karst features where carbonates presently lie at or 

near land surface, or where now-buried carbonates previously 

were exposed at land surface on the paleo landscape.

Geologic unit Geologic unit

West East West East

Tampa 

Limestone

St.

Marks

Formation

Chattahoochee

 Formation

Hawthorn

Group Corrosive

Moderately soft

to moderately

hard, high

magnesium

Moderately hard

to hard, high

magnesium

and sulfate

Avon Park

Formation

Avon Park Formation

Hard to very

hard, high

magnesium

 and sulfate; high

iron along Solution Escarpment

Geohydrologic 

unit Surficial

aquifer system

Terrace and 

undifferentiated 

(surficial) deposits

Terrace and 

undifferentiated 

(surficial) deposits

FLORIDA GEORGIA 

Groundwater

quality

Upper 

semiconfining

unit

Ocala Limestone Ocala Limestone

Suwannee 

Limestone

Lisbon

Formation

Lisbon

Formation

Suwannee Limestone

Chattahoochee

Formation

St. Marks

Formation

Byram

Formation

Marianna

Limestone

Byram

Formation

Marianna

Limestone

Tallahatta

Formation

Tallahatta

Formation

Holocene

and

Pleistocene

SERIES

Oligocene

Miocene

Pliocene

Citronelle Fm Miccosukee Fm

Jackson Bluff Fm

Eocene

Lower

confining

unit

Upper

Floridan

aquifer

Moderately 

hard, sulphurous

Hard to very

hard

Very hard; high iron,

sulfate, and fluoride 

Not determined

Hawthorn Group–

Torreya Formation

Figure 4. Geologic and geohydrologic units and groundwater quality of the Upper Floridan 

aquifer and hydraulically connected sediments in the Aucilla–Suwannee–Ochlockonee River 

Basin (modified from Miller1986; Rupert1990; and Torak and Painter2006)

Figure 4. Geologic and 

geohydrologic units and 

groundwater quality of the 

Upper Floridan aquifer and 

hydraulically connected 

sediments in the Aucilla–

Suwannee–Ochlockonee 

River Basin (modified from 

Miller, 1986; Rupert, 1990; and 

Torak and Painter, 2006).
Geohydrology 11

Structural Features

Local tectonics in the ASO River Basin associated with 

altered crystalline basement rocks, differential compaction, 

and solution and collapse of limestone affected the accumu

lation and lithology of Coastal Plain sediments that constitute 

the aquifers and confining units of the Floridan aquifer 

system. Upwarping during early Mesozoic to late Cretaceous 

produced by compressional tectonics associated with the 

seaward extension of the Appalachian and (or) Ouachita 

structural belts (Chen, 1965) formed the Peninsular Arch 

in north-central Florida, which dominated sedimentation 

in the southeastern part of the study area (Miller, 1986) 

(fig. 5). Clastic and carbonate sediments accumulated on 

the flanks of the Peninsular Arch to the northeast, north, 

northwest, and west since at least the Early Cretaceous in 

depositional features termed, respectively, the Southeast 

Georgia (or Savannah) Embayment, Suwannee Strait, 

Gulf Trough (fig. 6), and Apalachicola (or Southwest 

Georgia) Embayment, (Miller, 1986). The Southeast Georgia 

Embayment represents a shallow east-to-northeast-plunging 

syncline that subsided at a moderate rate allowing an 

accumulation of clastic and carbonate sediments (Miller, 

1986) (fig. 7). In contrast, a nearly continuous sequence of 

late Jurassic clastic sediments fill the southwest-plunging 

syncline of the Apalachicola Embayment and Gulf Trough 

(Miller, 1986), followed by thickening of Oligocene 

to Miocene sediments (figs. 8 and 9).

Figure 5. Structural features affecting the Floridan aquifer system (Miller, 1986).

Figure 5. Structural features affecting the 

Floridan aquifer system (Miller ,1986).
12 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Kellam and Gorday (1990) describe the Gulf Trough–

Apalachicola Embayment as part of a subsurface paleomarine channel system in the Georgia Coastal Plain, with 

the former (Gulf Trough) a northeastward extension of the 

latter. Declining sea level restricted circulation within this 

channel, allowing deposition of a thick accumulation of 

fine-grained material (Davis, 1996a). Miller (1986) describes 

the Gulf Trough as a series of boundary faults to grabens 

that position low water-bearing clastic sediments opposite 

limestone of the Floridan aquifer system. The low watertransmitting ability of these features allows them to be 

discussed in this report as a single geohydrologic entity 

termed the Gulf Trough–Apalachicola Embayment 

(fig. 6).

85° 84° 83° 82°

31°

32°

30°

MITCHELL

BAKER

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

UNION

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER STEWART

QUITMAN

SCHLEY

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

WARE

BRANTLEY

CHARLTON

WHEELER

PULASKI

DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE TIFT

BERRIEN

ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

THOMAS BROOKS

BRADFORD

JEFF DAVIS

Figure 6. Approximate location of the Gulf Trough–Apalachicola Embayment in the Aucilla–Suwannee–Ochlockonee 

River Basin in southern Georgia and adjacent parts of Florida (modified from Kellam and Gorday, 1990; Davis, 1996a).

EXPLANATION

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

Approximate location of the Gulf Trough–

 Apalachicola Embayment

Study area

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

Figure 6. Approximate location of the Gulf Trough–Apalachicola Embayment in the Aucilla–Suwannee–Ochlockonee 

River Basin in southern Georgia and adjacent parts of Florida (modified from Kellam and Gorday, 1990; Davis, 1996a).
Geohydrology 13

31°

30°

82° 81°

Map

area

ALABAMA GEORGIA

FLORIDA

Gulf of Mexico Atlantic Ocean

HAMILTON

WARE

CLAY

DUVAL

CLINCH

ALACHUA PUTNAM

BAKER

COLUMBIA

SUWANNEE

NASSAU

CHARLTON

CAMDEN

ST JOHNS

ECHOLS

UNION

GILCHRIST

BRADFORD

FLORIDA

Atlantic

Ocean

A

B’

B

A’

Figure 7. Geologic sections across northeastern Florida showing relations between geologic units and the Floridan aquifer 

system along A–A’, from west of Lake City, Florida, to the Atlantic Ocean; and B–B', from Duval County, Florida, to 

Fernandina Beach, Florida (modified from Leve, 1968).

Cedar Keys Formation

Hawthorn Group Avon Limestone

Undiff.

clastic

sediments

(Alachua)

Avon Park Fm

Oldsmar

Lake

Park

Ocala

City

Limestone

Limestone

Formation

2,600

2,400

2,200

2,000

1,800

1,600

1,400

1,200

FEET

1,000

800

600

400

200

Sea level

200

A A' Baker Co. Duval Co. Baker Co. Columbia Co.

Nassau Co.

St Johns River

Alligator Lake

Upper Miocene or

Pliocene deposits

Pleistocene and

recent deposits

Suwannee

Limestone

Suwannee

Limestone

Ocala Limestone

0 20 MILES

0 20 KILOMETERS

10

10

Hawthorn Group

Ocala Limestone

2,600

2,400

2,200

2,000

1,800

1,600

1,400

1,200

FEET

1,000

800

600

400

200

Sea level

200

B B’ Duval Co. Nassau Co.

St Johns 

River Fernandina

Beach

0 10 MILES

0

5

5 10 KILOMETERS

Late

Miocene

or Pliocene

deposits

Pleistocene

and recent

deposits

Lake

City Limestone

Formation

Avon

Cedar Keys Formation

Oldsmar Limestone

Park

GEORGIA

St Johns River

0 40 MILES

0 20 40 KILOMETERS

Base from U.S. Geological Survey 20

1:100,000-scale digital data

VERTICAL SCALE 

GREATLY EXAGGERATED

VERTICAL SCALE GREATLY EXAGGERATED

?

?

Fault—Queried where 

 vertical. Short dash 

 where inferred

Approximate axis of

 Southeast Georgia Embayment

?

Approximate boundary of Gulf 

 Trough–Apalachicola Embayment

EXPLANATION

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Lower confining unit Study area boundary

Geologic contact—

 Dashed where 

 inferred

A A’ Line of section

MAP CROSS SECTION

Control point

Figure 7. Geologic sections across northeastern Florida showing relations between geologic units and the Floridan 

aquifer system along A–A’, from west of Lake City, Florida, to the Atlantic Ocean; and B–B’, from Duval County, Florida, 

to Fernandina Beach, Florida (modified from Leve, 1968).
14 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

FEET

600

400

200

Sea level

400

200

A A’

Tallahatta Formation Tallahatta Formation

Lisbon Formation

Ocala Limestone Ocala Limestone

Lisbon Formation

Marianna Limestone equivalent

Byram Formation

Alum Bluff Group

Ochlockonee

River

Ochlockonee

fault

Tampa Limestone equivalent

Suw

Potentiometric surface December 1969 anee Limestone

0 5 10 MILES

0 5 10 KILOMETERS

319

319

75

37

133

133

37

10 MILES

10 KILOMETERS

0 5

0 5

VERTICAL SCALE GREATLY EXAGGERATED

Base modified from U.S. Geological Survey 

1:100,000-scale digital files

EXPLANATION

Figure 8. Geologic section across Colquitt County, Georgia, showing sediment thickening in the 

area of the Gulf Trough–Apalachicola Embayment (modified from Zimmerman, 1977).

N

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Lower confining unit

Study area boundary

Geologic contact—

 Dashed where inferred

Line of section

Approximate location of 

 Gulf Trough–Apalachicola 

 Embayment

A A’

MAP CROSS SECTION

COLQUITT

WORTH TIFT

COOK

THOMAS BROOKS

MITCHELL

A

A’

Moultrie

Riverside

Berlin

Norman Park

Doerun

Funston

GEORGIA

FLORIDA

Gulf of Mexico

Atlantic Ocean

ALABAMA

Map area

below

Figure 8. Geologic section across Colquitt County, Georgia, showing sediment thickening in the 

area of the Gulf Trough–Apalachicola Embayment (modified from Zimmerman, 1977).
Geohydrology 15

ALABAMA GEORGIA

FLORIDA

Gulf of Mexico Atlantic Ocea

Map area n

below Meigs

Ochlocknee

Thomasville

Boston

Barwick

BROOKS

THOMAS

MITCHELL COLQUITT

GRADY

FEET

100

100

200

Sea level

300

200

VERTICAL SCALE GREATLY EXAGGERATED

A A’

Ochlockonee

fault

19

84

319

FLORIDA

84

Barwick arch

Figure 9. Geologic section across Thomas County, Georgia, showing sediment thickening in the area of the 

Gulf Trough–Apalachicola Embayment (modified from Sever, 1966).

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Study area boundary

Geologic contact—

 Dashed where inferred

Line of section

EXPLANATION

Approximate location of Gulf 

 Trough–Apalachicola Embayment

N

Fault—Short dash 

 where inferred

A A’

Base modified from U.S. Geological Survey 

1:100,000-scale digital files

0 5 10 MILES

0 5 10 KILOMETERS

0 5 10 MILES

0 5 10 KILOMETERS

MAP

CROSS SECTION

Ochlockonee fault—Relative 

 fault movement; U, upthrown;

 D, downthrown

D

U

D

U

A

A’

Citronelle Formation

Alum Bluff

Tampa

Group

Alum

Alum

Bluff Group

Bluff Group

Alum

Bluff Group

Limestone

Suwannee

Limestone

(upper

member)

(upper

(upper

zone)

(lower

(undiff)

zone)

(lower

member)

Limestone

Limestone

Tampa

Tampa

member)

Suwannee Limestone

Ochlockonee 

Barwick

fault 

arch

Figure 9. Geologic section across Thomas County, Georgia, showing sediment thickening in the area of the 

Gulf Trough–Apalachicola Embayment (modified from Sever, 1966).
16 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

The Ocala “Uplift,” a comparatively younger structure 

than the Peninsular Arch (fig. 5), first began to develop 

southwest of the arch during post-Oligocene or lower Miocene, based on the configuration of Miocene sediment that 

directly overlies upper Eocene carbonates (fig. 10) and the 

lack of thinning of Eocene sediments along the crest of the 

uplift (Chen, 1965). Winston (1976) attributed the uplift to 

an anomalous buildup of middle Eocene carbonates. Miller 

(1986) suggested that differential compaction of these sediments shortly after deposition had given rise to the Ocala 

“Uplift.” Often confused and used synonymously with the 

Peninsular Arch, the Ocala “Uplift” represents a gentle and 

local flexure parallel to the Peninsular Arch in central Florida 

where middle to upper Eocene sediments outcrop on the west 

coast of the peninsula (Chen, 1965).

85° 84° 83° 82°

31°

32°

30°

MITCHELL

BAKER

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

NASSAU

DUVAL

CLAY BRADFORD

UNION

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

QUITMAN

TERRELL

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER

STEWART

SCHLEY

TURNER

COLQUITT

EVANS

LONG

WAYNE

TATTNALL

BACON

PIERCE

CAMDEN WARE BRANTLEY

CHARLTON

WHEELER

PULASKI

DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE

JEFF DAVIS

TIFT

BERRIEN ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

BROOKS

THOMAS

Map area

FLORIDA

Gulf of Mexico Atlantic Ocean

ALABAMA GEORGIA

A

A’

B

B’

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Approximate location 

 of Gulf Trough–

 Apalachicola Embayment

Approximate axis of 

 Southeast Georgia 

 Embayment

Approximate axis of 

 Peninsular Arch

Study area boundary

Line of section

Pleistocene and

recent deposits

Pleistocene and

recent deposits

Geologic contact

Approximate boundary 

 of Southeast Georgia 

 Embayment

A A’

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Lower confining unit

CROSS SECTION

MAP

Figure 10. Geologic sections across northeastern Florida showing accumulatioin of Eocene sediment over the 

Peninsular Arch along A–A’, from western Jefferson County, Florida, to Columbia County, Florida; and B–B’, from 

Taylor County, Florida, near Gulf of Mexico, to Bradford County, Florida (modified from Kellam and Gorday, 1990; 

Davis, 1996a; and Raulston and others, 1998).

FEET

700

600

400

500

300

200

Sea level

100

200

100

A A' B B'

Avon Park Formation

Ocala Limestone

Suwanee

Limestone

Hawthorn

Group

St Marks

Formation

Hawthorn

Group

Ocala Limestone

Suwanee Limestone

Avon Park Formation

Miccosukee

Formation

VERTICAL SCALE GREATLY EXAGGERATED

No data

VERTICAL SCALE GREATLY EXAGGERATED

Figure 10. Geologic sections across northeastern Florida showing accumulation of Eocene sediment over the Peninsular Arch 

along A–A’, from western Jefferson County, Florida, to Columbia County, Florida; and B–B’, from Taylor County, Florida, near 

Gulf of Mexico, to Bradford County, Florida (modified from Kellam and Gorday, 1990; Davis, 1996a; Raulston and others, 1998).
Geohydrology 17

The Suwannee Strait (Dall and Harris, 1892) represents 

a negative feature, such as a closed basin or trough, within 

which several stratigraphic units are anomalously thin (Miller, 

1986). Paleocene to Eocene environmental stress and sea-level 

rise possibly suppressed carbonate-sediment production, 

prohibiting accumulation rates from keeping pace with 

tectonic subsidence (Hine and others, 2001). Dall and Harris 

(1892) described the Suwannee Strait as a northeast-trending 

trough extending from the Suwannee River in Florida through 

the Okefenokee Swamp. Well data indicate a closed depression on the top of the Paleocene, compatible with an extension 

of the Southeast Georgia Embayment but separated from the 

embayment by a sill-like ridge (Miller, 1986). Miller (1986) 

suggested that during early Eocene, the Suwannee Strait 

ceased to be an actively subsiding basin and accordingly, had 

little effect on the Floridan aquifer system except that the 

aquifer thickens slightly within the strait. Deltaic sedimentation by rivers draining off the Appalachian Mountains during 

late Oligocene probably caused infilling of the seaway. This 

deltaic sedimentation extended southward and onlapped 

carbonates of northern Florida (Hine and others, 2001).

Applin and Applin (1944) suggested the existence of 

“a channel or trough extending southwestward across Georgia 

through the Tallahassee area to the Gulf of Mexico.” “This 

channel cut nearly at right angles to the trend of the Peninsular 

Arch and lay between the carbonate-evaporite facies to the 

southeast and the terrigenous clastic facies to the north and 

northwest” (Chen, 1965). Jordan (1954) termed this channel 

the Suwannee Strait, in apparent conflict with the previous 

usage of the term by Dall and Harris (1892). 

The Suwannee Strait possibly formed beneath the 

Suwannee Seaway and combined with the Gulf Trough to 

form consecutive seaways linking the Gulf of Mexico with 

the Atlantic Ocean (Hine and others, 2001). Chen (1965) 

attributes the continuous existence of the Suwannee Strait (or 

“Channel”) during Paleocene and lower Eocene to current 

action that “considerably reduced the rate of accumulation of 

fine sediments ... and would have prevented the spread of fine 

terrigenous sediments over the peninsula area to the southeast.” Applin (1951) recognized distinct clastic and non-clastic 

sedimentary facies in the area of the Suwannee Strait; these 

facies have shifted northward and northwestward through 

geologic time (Chen, 1965).

A number of investigators have expressed various explanations about the nomenclature associated with the structural 

feature known as the Gulf Trough as well as its origin. Herrick 

and Vorhis (1963) associated the name Gulf Trough of Georgia 

(or Gulf Trough, figs. 5 and 6) with the same structural feature 

described previously as the Suwannee Strait by Dall and 

Harris (1892) and Jordan (1954) (fig. 8). Sever (1966) defined 

the Meigs Basin as a local synclinal sedimentary structure of 

the larger Suwannee Strait, or Gulf Trough, in northwestern 

Thomas County, Ga. (fig. 9). The principal hypotheses for the 

origin of the Gulf Trough have been summarized by Patterson 

and Herrick (1971) and listed by Zimmerman (1977). These 

hypotheses are that the Gulf Trough defines (1) a buried 

submarine valley or strait analogous to the Straits of Florida; 

(2) a graben; (3) a syncline; or (4) a buried solution valley 

analogous to the Flint River valley (fig. 11).

In the Flint River valley, solution and weathering 

of carbonate rocks transformed the Oligocene Suwannee 

Limestone into a residuum (Flint River residuum) of greatly 

reduced thickness (fig. 11). Weathering completely leached the 

Suwannee Limestone and replaced it with silica that formed 

chert boulders in the residuum (Vorhis, 1972). By analogy, 

the Marianna Limestone and Byram Formation supplanted the 

Lisbon Formation and Ocala Limestone in the Gulf Trough 

region by sedimentation, rather than through solutioning and 

weathering as in the Flint River valley. The resulting formation consisted of a thick, low-water-transmitting zone in the 

aquifer containing poor water quality.

Herrick and Vorhis (1963), Gelbaum (1978), and 

Gelbaum and Howell (1982) identified a series of northeasterly trending boundary faults in the Gulf Trough region. Miller 

(1986) described a process where low-permeability clastic 

sediments fill grabens in the fault zone and are juxtaposed 

with high-permeability limestone units in the Floridan aquifer 

system. Zimmerman (1977) described the pinch-out of highpermeability Upper Eocene fossiliferous limestone along the 

trend of the Gulf Trough and deposition of low-permeability 

Oligocene dolomitic limestone and marl in its place (fig. 8). 

The juxtaposition of low-permeability sediments of the Gulf 

Trough with high-permeability limestone presents a barrier 

to groundwater flowing southeastward in the Upper Floridan 

aquifer from outcrop/recharge areas located to the northwest 

of the study area (figs. 9 and 12).

Geologic Units

Structural control of sedimentation in the ASO River 

Basin resulted in a vertically layered sequence of clastic and 

carbonate sediments that also grades laterally within these 

layers to define geologic units. The sequence of middle 

Eocene and younger geologic units provide the setting for 

groundwater and surface-water exchange within the Upper 

Floridan aquifer, lower and upper semiconfining units, and 

surficial aquifer (fig. 4).

A lithostratigraphic-transition zone in south-central 

Gadsden County, Fla., divides late Eocene calcareous and 

clastic facies and separates low-permeability middle Eocene 

carbonates of the Avon Park Formation of northern and peninsular Florida from the age-equivalent, glauconitic, sandy, and 

clayey limestone and sand of the Lisbon (Rupert, 1990) and 

Tallahatta Formations to the west (Miller, 1986) (fig. 4). The 
18 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

85° 84° 83° 82°

31°

32°

30°

A’

A

A

A’

VERTICAL SCALE GREATLY EXAGGERATED

Feet

1,000

800

600

600

400

400

200

Sea level

200

A A' 15P249 16P251 17P142 20N2110 20N349

Water level surface

Suwannee Limestone

Tallahatta Formation

McBean Formation

Clinchfield Sand

Ocala Limestone

Wilcox Formation

Hawthorn Group

Flint River residuum

Providence Sand

Porters Creek equivalent

Clayton Limestone

197 ft 173 ft

107 ft 250 ft

230 ft

300 ft

Residuum

0 5 KILOMETERS

N

SUMTER

LEE

WORTH TURNER

WILCOX

DOOLY

CRISP

BEN HILL

DODGE

15P1030

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0 25

25 50 MILES

50 KILOMETERS

Figure 11. Geologic section across Crisp and Wilcox Counties, Georgia, showing reduction of 

Suwannee Limestone thickness to Flint River residuum (modified from Vorhis, 1972).

Base modified from U.S. Geological Survey 

1:100,000-scale digital data

0 5

5

10 MILES

0 5 MILES

0 10 KILOMETERS

EXPLANATION

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Lower confining unit

Study area boundary

Geologic contact—

 Dashed where inferred

Line of section

Well and identification number

Approximate location of 

 Gulf Trough–Apalachicola 

 Embayment

A A’

MAP

CROSS SECTION

Map area below

ALABAMA GEORGIA

FLORIDA

Gulf of Mexico Atlantic Ocean

Map area

at right

15P1030 15P249

16P251

16P251

17P142 20N2110

20N349

Flint River

valley

Flint River valley

Figure 11. Geologic section across Crisp and Wilcox Counties, Georgia, showing reduction of 

Suwannee Limestone thickness to Flint River residuum (modified from Vorhis, 1972).
Geohydrology 19

85° 84° 83° 82°

31°

32°

30°

MITCHELL

BAKER

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN LEON JEFFERSON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE COLUMBIA BAKER

NASSAU

DUVAL

CLAY

BRADFORD

UNION

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

QUITMAN

TERRELL

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER

STEWART

SCHLEY

TURNER

COLQUITT

EVANS

LONG

WAYNE

TATTNALL

BACON

PIERCE

CAMDEN WARE

BRANTLEY

CHARLTON

WHEELER

PULASKI

DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN

HILL

IRWIN

APPLING

COFFEE

JEFF DAVIS

TIFT

BERRIEN

ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

THOMAS BROOKS

Moultrie

Cairo

Quincy

Attapulgus Valdosta

Tifton

Alapaha

Adel

A

A’

Feet

2,000

1,500

2,500

3,000

1,000

Sea level

500

500

A A' GEORGIA FLORIDA

Rocks of Cretaceous age

Rocks of early Eocene age

Rocks of Cretaceous age

Rocks of middle Eocene age

Rocks of late Eocene age

Oligocene age

Avon Park Formation

Rocks of 

Rocks of Miocene age Post-Miocene rocks

VERTICAL SCALE GREATLY EXAGGERATED

Okefenokee Swamp

Map area

FLORIDA

Gulf of Mexico

Atlantic Ocean

ALABAMA GEORGIA

Figure 12. Geologic section of Floridan aquifer system from Calhoun County, Georgia, southeast to Clay County, 

Florida, showing hydrostratigraphic relations and structure of sediments in the Aucilla–Suwannee–Ochlockonee 

River Basin (modified from Miller, 1986).

Gulf Trough–

Apalachicola

Embayment

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

Fault—Arrows indicate

 relative movement

EXPLANATION

Surficial aquifer system

Hydrologic unit

Upper semiconfining unit

Upper Floridan aquifer

Middle and lower confining unit

Lower Floridan aquifer

Study area boundary

Geologic contact—

 Dashed where inferred

Line of section

Approximate location of 

 Gulf Trough–Apalachicola 

 Embayment

A A’

MAP

CROSS SECTION

Lisbon Formation Figure 12. Geologic section of Floridan aquifer system from Calhoun County, Georgia, southeast to Clay County, Florida, 

showing hydrostratigraphic relations and structure of sediments in the Aucilla–Suwannee–Ochlockonee River Basin 

(modified from Miller, 1986).
20 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

middle third of the Avon Park Formation in the eastern half of 

the Florida peninsula and in much of southeastern Georgia is 

micritic, finely pelletal limestone; the lower half of the Avon 

Park Formation in west-central peninsular Florida consists of 

gypsiferous limestone and dolomite. In the Florida peninsula 

and southeastern Georgia, the variable lithology of the Avon 

Park Formation constitutes a subregional confining unit 

within the Floridan aquifer system (Miller, 1986). The Lisbon 

Formation defines the lower confining unit of the Upper 

Floridan aquifer (Miller, 1986) in the northern, western, and 

north-central parts of the study area; the Avon Park Formation 

defines the lower confining unit of the Upper Floridan aquifer 

to the south and east. 

The middle Eocene Lisbon and Avon Park Formations 

hydraulically separate water-bearing carbonates of the 

Floridan aquifer system into two major permeable zones 

termed the Upper and Lower Floridan aquifers (Miller, 1986) 

(fig. 12). The area of separation of these permeable units 

occurs in a region bounded by Moultrie, Ga., to the north, the 

Okefenokee Swamp and Baker County, Fla., to the east, and 

Attapulgus, Ga., and Quincy, Fla., to the west. Miller (1986) 

indicates the occurrence of a Lower Floridan aquifer near 

Valdosta, Ga. Here, the Lisbon and Avon Park Formations 

form a middle confining unit to the Upper and Lower Floridan 

aquifers; however, gypsiferous rocks of the intervening 

confining unit grade downward into low-permeability clastic 

sediments of the aquifer system’s lower confining unit, where 

total confining-unit thickness exceeds 200 ft. Well data limit 

the definition and areal extent of these confining units because 

neither unit crops out in the study area. This separation 

sufficiently impedes groundwater and surface-water exchange 

with Paleocene-to-middle-Eocene rocks of the Lower Floridan 

aquifer in the ASO River Basin; thus, these units are not 

discussed in this report. Further, the middle confining unit of 

Miller (1986) functions as and is termed the lower confining 

unit of the Upper Floridan aquifer. Accordingly, only latemiddle Eocene-to-Holocene geologic units (fig. 4) define 

the hydrologic setting for groundwater and surface-water 

exchange in the basin.

The mostly carbonate middle-to-late Eocene Ocala Limestone and late Oligocene Suwannee Limestone (fig. 4) form 

a single, vertically continuous, permeable layer in the Upper 

Floridan aquifer in updip parts of the ASO River Basin toward 

the northwestern boundary. The Ocala Limestone consists of 

an upper part containing white, soft, friable porous coquina, 

large forams, bryozoan fragments, and echinoid remains in 

a micritic limestone matrix. A lower part contains cream-towhite, fine, soft to semi-indurated micritic limestone with 

miliolid remains and scattered forams, and glauconite locally. 

To the east of the Flint River in Dooly and Crisp Counties, the 

Suwannee Limestone weathered into the Flint River residuum 

(fig. 11) or Flint River Formation, “making a porous permeable unit that favors recharge” (Vorhis, 1972).

In the southwestern part of the basin near Cairo, Grady 

County, Ga., nearly 400 ft of middle Oligocene sediments 

separate the Suwannee and Ocala Limestones. These sediments 

consist of the stratigraphically equivalent Marianna Limestone 

and Byram Formation, which were known previously to exist 

only in Florida. Formerly considered part of the late Eocene 

Ocala Limestone (Sever and Herrick, 1967), sediments of 

the Marianna Limestone and Byram Formation have been 

included in the Suwannee Limestone (Davis, 1996a). The 

Byram Formation consists predominantly of yellowish-brown, 

dense, clayey, finely crystalline dolomite and is similar to the 

Byram Formation described by Puri and Vernon (1964) at an 

outcrop in Jackson County, Fla. (Sever and Herrick, 1967). 

The Marianna Limestone consists of interbedded pale orange to 

cream, soft, granular, fossiliferous limestone, cream fossiliferous marl, and thin beds of pale-grown dolomite and dolomitic 

limestone. Foraminiferal evidence correlates part of the nearly 

500 ft of middle Oligocene sediments penetrated in a test well 

at Cairo, Ga., with the Marianna Limestone of Florida, as well 

as with part of a 635-ft section of sediments from a well in 

Coffee County, Ga. (Sever and Herrick, 1967). The northeastward trend of these sediments from Grady to Coffee Counties 

coincides with the location of the Gulf Trough–Apalachicola 

Embayment (fig. 6), inferring continuous separation of the 

Suwannee and Ocala Limestones by geologic units of similar 

lithology as the Byram Formation and Marianna Limestone in 

a southwest-to-northeast corridor.

The Suwannee Limestone consists of hard to soft, 

yellowish-gray, calcitized, crystalline fossiliferous limestone 

in the western part of the study area near Cairo, Grady County, 

Ga. (Sever and Herrick, 1967). In southwestern Georgia, 

along the Solution Escarpment, and in the eastern panhandle 

of Florida, the Suwannee Limestone consists of cream to tan, 

crystalline, vuggy limestone with gastropod and pelecypod 

casts and molds. Another facies contains white to cream, finely 

pelletal limestone with small foraminifers, pellets of micrite 

bound by a micritic to finely crystalline limestone matrix. Fine 

sand in cast and mold facies is present locally. The micritic 

pelletal facies contains trace amounts of fine to medium, light 

to dark-brown phosphate (Miller, 1986). South and west of 

the Solution Escarpment, and in Florida, dolomitic, silty, and 

sandy limestone layers of early-to-middle Miocene Tampa 

Limestone and Chattahoochee and St. Marks Formations 

(fig. 4) represent permeable zones that contribute locally to 

aquifer thickness; although clastic sediments mostly compose 

Miocene and younger units (Miller, 1986). A transition zone 

near south-central Gadsden County, Fla., separates the calcareous downdip (southeastward) facies of the Tampa Limestone, 

termed the St. Marks Formation (Puri, 1953; Rupert, 1990), 

from the clastic updip (northwestward) facies, termed the 

Chattahoochee Formation (Puri and Vernon, 1964; Rupert, 

1990; Scott, 1986, 1992). Stratigraphically, the Chattahoochee 

Formation grades upward into the siliciclastic and clayey 
Geohydrology 21

middle-to-late Miocene Hawthorn Group–Torreya Formation 

in Florida (Rupert, 1990) and the basal part of the Hawthorn 

Group in Georgia (Huddlestun, 1988).

Middle-to-late Miocene deposits termed the Torreya 

Formation (Banks and Hunter, 1973) in the eastern panhandle 

of Florida, and the Hawthorn Group (Huddlestun, 1988) in 

Georgia and in the remaining parts of the study area in Florida 

(fig. 4), contain very fine-to-medium, clayey sand, silty 

clay, limestone, dolomite, and phosphate grains. Beyond the 

study area, to the west of the Apalachicola River in Florida, 

Hawthorn Group sediments transition to a thinly bedded, 

fine-to-coarse clastic, shelly sequence termed the Alum Bluff 

Group (Miller, 1986). In Georgia, the Alum Bluff Group 

was identified by previous investigators in Colquitt County 

(Zimmerman, 1977) (fig. 8) and Thomas County (Sever, 1966) 

(fig. 9); however, Sever (1965) described equivalent geologic 

units of the Alum Bluff Group as the “Hawthorne Formation.” 

Hawthorn Group sediments range in thickness from a feather

edge in northwestern Colquitt County to about 300 ft in or 

near the Gulf Trough–Apalachicola Embayment (Zimmerman, 

1977). The “Hawthorne Formation” thickens to 500 ft in Ware 

County, where very sticky, cohesive, greenish-blue clay in 

the upper part of the formation confines sandy and phosphatic 

dolomite and limestone of the middle and lower parts, in 

addition to confining the underlying Upper Floridan aquifer 

(Matthews and Krause, 1984).

Carbonate sediments of the Hawthorn Group-Torreya 

Formation (fig. 4) consist of clayey limestone or dolomitic 

limestone, which grade downward to a predominantly limestone base in the western part of the study area in Gadsden 

County, Fla. Fossiliferous and phosphatic sand and fuller’s 

earth (palygorskite) clay, montmorillonite, and kaolin clay 

interfinger with limestone and dolomite (Rupert, 1990). Dense, 

crystalline, dolomitic limestone, and limonitic and phosphatic 

clay interbedded with limestone characterize the Hawthorn 

Group in south-central Georgia near Adel, Ga. (Herrick, 

1961). Sever (1966) divided the Hawthorn-equivalent Alum 

Bluff Group into three mappable zones: a sandy marl lower 

zone, a sandy limestone middle zone, and a fuller’s earth clay 

upper zone that is mined commercially in the Gulf Trough–

Apalachicola Embayment region. Clastic sediments in the 

“Hawthorne Formation” may contain minor surficial and 

intermediate aquifers; however, the clastic sediments primarily 

function as confining units, restricting local recharge to the 

Upper Floridan aquifer (Pratt and others, 1996).

The Pliocene Jackson Bluff Formation (fig. 4) crops out 

to the west of the study area in Gadsden County, Fla., and 

consists of three clayey, sandy shell beds (Schmidt, 1984; 

Puri and Vernon, 1964). The Jackson Bluff Formation overlies 

either the Tampa Limestone or the Hawthorn Group–Torreya 

Formation, depending on the presence of each unit, and 

functions as a semiconfining unit, impeding vertical movement 

of water into and out of deeper water-bearing units (Torak and 

McDowell, 1996).

The Citronelle Formation exists only in the southwestern 

part of the ASO River Basin and consists of late Pliocene, 

orange to red, clayey, medium to coarse, quartz sand 

containing clay lenses and beds of friable quartz pebbles. 

About 90 ft of Pliocene gravel and coarse sand termed the 

Citronelle Formation overlies Hawthorn-equivalent sediments 

of the Alum Bluff Group in northwestern Thomas County 

(fig. 9). In the absence of Holocene and Pleistocene deposits, 

sediments of the Citronelle Formation exist at land surface, 

capping many of the hills in Gadsden County, Fla. In Decatur, 

Grady, and Seminole Counties, Ga., Sever (1965) described 

a Citronelle-equivalent, unnamed red clayey sand and gravel 

containing hematite concretions, and in Thomas County, Sever 

(1966) described the Citronelle Formation as cross-bedded, 

yellow to red gravel, sand, and clay. Thickness varies from 

about 20 to 100 ft; although the original thickness is uncertain 

because of removal by erosion throughout much of its areal 

extent. Zimmerman (1977) noted small isolated patches of the 

Citronelle Formation in Colquitt County, Ga. To the east, the 

reddish siliciclastic sediments are lithologically similar to the 

late Pliocene Miccosukee Formation (Rupert, 1990) (fig. 4). 

Clay lenses in the Citronelle Formation impede groundwater 

recharge from precipitation and limit vertical leakage to the 

underlying Hawthorn Group and Upper Floridan aquifer.

The Miccosukee Formation contains interbedded clay, 

silt, sand, and gravel, similar in overall lithology to the 

Citronelle Formation, except that the Miccosukee contains less 

gravel and more fine-to-medium clayey sand than the Citronelle (Rupert, 1990). Sediments of the Miccosukee Formation 

extend eastward from Gadsden County, Fla., and northeastward into Georgia, pinching out in the south-central part of 

the study area in eastern Madison County, Fla. (Rupert, 1990). 

The Miccosukee Formation caps topographically high areas 

on the Tifton Upland and lies unconformably on the Miocene 

Hawthorn Group–Torreya Formation. The Red Hills region of 

the Ochlockonee and Aucilla River Basins most likely owes its 

name to the distinct reddish color of siliciclastic sediments of 

the Miccosukee and Citronelle Formations, which contribute 

to the sediment load of those streams giving them a distinct 

yellow color. The predominantly clayey quartz sand and 

sandy clay identified in exposures and core of the Miccosukee 

Formation can impede groundwater recharge to the underlying 

Hawthorn Group and Upper Floridan aquifer; although locally 

sandy zones can yield groundwater to domestic wells.

Pleistocene and Holocene undifferentiated sand and 

clay mantle most of the surface of the study area forming the 

uppermost water-bearing zones of the surficial aquifer system 

(fig. 4). Marine-terrace deposits consisting of Pleistocene 

undifferentiated quartz sand and clay lie unconformably 

on the Citronelle, Miccosukee, Torreya, or Chattahoochee 

Formations in the western part of the study area in Florida. 

Holocene alluvial deposits thinly blanket stream valleys and 

commonly are indistinguishable from Pleistocene sediments 

(Rupert, 1990).
22 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Hydrologic Setting

Groundwater flow and exchange with surface water in 

the ASO River Basin occur within a hydraulically connected 

sequence of middle Eocene to Holocene sediments grouped 

according to similarities in hydraulic properties to form 

geohydrologic units termed the surficial aquifer system, 

upper semiconfining unit, Upper Floridan aquifer, and lower 

confining unit (fig. 4). Differences in hydraulic characteristics 

within and among geologic units form geohydrologic-unit 

boundaries that transcend time-stratigraphic and paleon

tological divisions. Geohydrologic units define the hydrogeologic framework for conceptualizing groundwater and 

surface-water exchange in the basin (fig. 13).

system and the surface-water level determine the potential for 

recharge to the surficial aquifer system from surface-water or 

for groundwater discharge to surface water from the surficial 

aquifer system. 

The surficial aquifer system interacts hydraulically 

with the Upper Floridan aquifer through direct contact, in 

the absence of the upper semiconfining unit, or indirectly 

by vertical leakage through a thin upper semiconfining unit 

(fig. 13). Miller (1986) noted the occurrence of a “surface 

veneer” of post-Miocene sediments, generally 10–50-ft thick, 

overlying the Upper Floridan aquifer within most of the 

ASO River Basin. Erosion of Oligocene-to-middle-Miocene 

sediment associated with the Ocala Uplift near Lake City, 

Fla. (fig. 14), caused the surficial aquifer to contact the Upper 

Floridan aquifer, providing a mechanism for direct recharge 

of the Upper Floridan aquifer by infiltrating precipitation 

and vertical leakage. Erosion of Pliocene-to-Miocene 

geologic units and deposition of Holocene-to-Pleistocene 

undifferentiated sediments places the surficial aquifer system 

in contact with the Upper Floridan aquifer in southeastern 

Thomas County, Ga. (Sever, 1966). In extreme northwestern 

Colquitt County, Ga., erosion to a featheredge of outcropping 

Hawthorn Group-equivalent sediments of the Alum Bluff 

Group provides nearly direct contact of isolated remnants of 

the Pliocene Citronelle Formation with the Upper Floridan 

aquifer. These permeable clastic sediments function hydrologically the same as the upper part of the Alum Bluff in northwestern Colquitt County, Ga. (Zimmerman, 1977). 

Indirect interaction of the surficial aquifer with the 

Upper Floridan aquifer occurs in Brooks, western Echols, and 

Lowndes Counties, Ga., where vertical leakage from overlying 

clastic sediment of the surficial aquifer to the underlying 

Upper Floridan aquifer occurs through clay confining layers 

(Krause, 1979). Interior drainage through deep sands of the 

surficial aquifer system in Columbia and Suwannee Counties, 

Fla., enhances recharge to the overlying Upper Floridan 

aquifer (Raulston and others, 1998). Less than 50 ft of postOligocene sediment composing the surficial aquifer system 

and upper semiconfining unit occur in contact with the Upper 

Floridan aquifer along the lower half of the Withlacoochee 

River in Brooks and Lowndes Counties, Ga. (fig. 14). The 

condition of a relatively thin surficial aquifer system in direct 

contact with the Upper Floridan aquifer extends into Florida 

along the flood plains of the Alapaha, Aucilla, Suwannee, and 

Withlacoochee Rivers, enhancing recharge-discharge relations.

Potentially high recharge to the Upper Floridan aquifer 

by vertical leakage from the surficial aquifer system exists 

where a relatively thin (less than 50 ft) upper semiconfining 

unit separates the two aquifers (fig. 15), and where the water 

table in the surficial aquifer system lies above the potentiometric surface of the Upper Floridan aquifer. Subtracting 

estimates for the altitude of the top of the Upper Floridan 

aquifer (fig. 16) from the USGS National Elevation Dataset 

digital-elevation model of land surface (U.S. Geological 

Survey, 2008) yielded a distribution of the combined thickness 

of the surficial aquifer system and upper semiconfining unit, 

The uppermost water-bearing zone to provide groundwater and surface-water exchange in the ASO River Basin 

consists of late Miocene-to-Holocene sediments termed 

the surficial aquifer system by the Southeastern Geological 

Society Ad Hoc Committee on Florida Hydrostratigraphic 

Unit Definition (Florida Geological Survey, 1986) and by 

Miller (1990) (fig. 13). The surficial aquifer system covers the 

study area except where erosion exposes geologic units of the 

upper semiconfining unit or Upper Floridan aquifer (fig. 14). 

Sediments of the surficial aquifer system represent “the 

permeable hydrogeologic unit contiguous with land surface 

that is comprised principally of unconsolidated to poorly 

indurated clastic deposits” (Florida Geological Survey, 1986), 

although the surficial aquifer system contains gravel, sandy 

limestone, limestone, clay, and silt in places (Miller, 1986). 

Complex interbedding of fine- and coarse-textured sediments 

characterizes the system (Miller, 1990).

Groundwater and surface-water exchange in the surficial 

aquifer system occurs where aquifer material directly contacts 

surface-water features, such as in stream valleys or flood 

plains or in the bottom of sinkhole ponds or lakes (fig. 13). 

The relative positions of the water table in the surficial aquifer 

Figure 13. Conceptual diagram of groundwater and 

surface-water flow in the interconnected stream-lake-aquifer 

flow system of the Aucilla–Suwannee–Ochlockonee River Basin 

(modified from Torak and Painter, 2006).

Lower confining unit (Lisbon Formation, no vertical leakage)

Discharge

to stream or lake

Potentiometric surface of

Upper Floridan aquifer Lake or stream

water level

Surficial

aquifer

system

Water

table

Regional flow

Recharge to aquifer

Solution feature 

Springflow

NOT TO SCALE

Vertical leakage 

Upper Floridan aquifer

Upper 

semiconfining 

unit

Figure 13. Conceptual diagram of groundwater and surfacewater flow in the interconnected stream-lake-aquifer flow 

system of the Aucilla–Suwannee–Ochlockonee River Basin 

(modified from Torak and Painter (2006).
Geohydrology 23

85° 84° 83° 82°

31°

32°

30°

MITCHELL

BAKER

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE COLUMBIA

BAKER

UNION BRADFORD

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER

STEWART

SCHLEY

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

WARE

BRANTLEY

CHARLTON

WHEELER

PULASKI DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE

JEFF DAVIS

TIFT

BERRIEN ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

BROOKS

THOMAS

QUITMAN

St Marks River

Aucilla River

Withlacoochee River

Suwannee River

Ochlockonee River

Alapaha River

Okefenokee Swamp

Alapaha

Rise Holton

Spring

Lake Jackson 

Lake Iamonia

 Lake

Miccosukee

Little River

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Surficial aquifer

Basin boundary

Study area

Figure 14. Areal extent of surficial aquifer system in the Aucilla–Suwannee–Ochlockonee River Basin 

(modified from Sever, 1966; Krause, 1979; Miller, 1990; and Raulston and others, 1998).

17L028 Surficial-aquifer well and site name

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

18K051

17L028

16M015

16N007

Lake City

Sylvester

Cordele

Moultrie

Tallahassee

Ellaville

Attapulgus

Quincy

Figure 14. Areal extent of surficial aquifer system in the Aucilla–Suwannee–Ochlockonee River Basin 

(modified from Sever, 1966; Krause, 1979; Miller, 1990; and Raulston and others, 1998).
24 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

MITCHELL

BAKER

DECATUR

LIBERTY

FRANKLIN

GADSDEN

LEON

WAKULLA

TAYLOR

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

UNION

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

CLAY

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WAYNE

TATTNALL

BACON

PIERCE

WARE

BRANTLEY

CHARLTON

WHEELER

PULASKI

DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN HILL APPLING

COFFEE

ATKINSON

WILCOX

BRADFORD

GRADY

MADISON

TURNER

COLQUITT

IRWIN

TIFT

BERRIEN

LANIER

COOK

LOWNDES ECHOLS

BROOKS

THOMAS

JEFFERSON HAMILTON

CLINCH

JEFF DAVIS

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

Figure 15. Overburden thickness and leakage potential of the upper semiconfining unit in the 

Aucilla–Suwannee–Ochlockonee River Basin.

Base from U.S. Geological Survey 

1:100,000-scale digital data

Approximate location 

 of Gulf Trough–Apalachicola

 Embayment

Study area boundary

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

N/A—Not applicable; direct recharge to Upper Floridan aquifer

None—No vertical leakage or water exchange

*Contains up to 50 feet of surficial aquifer system overlying

 upper semiconfining unit

Potential

Absent

Vertical

leakage

Water

exchange

Overburden thickness,

in feet*

N/A

High

Moderate

Low

Extremely low

None

High

High

Moderate

Low

Extremely low

None

EXPLANATION

Less than 50

50 to 100

100 to 200

200 to 300

Greater than 300

OKEFENOKEE

BASIN

85° 84° 83° 82°

31°

32°

30°

Valdosta

Figure 15. Overburden thickness and leakage potential of the upper semiconfining unit in the 

Aucilla–Suwannee–Ochlockonee River Basin.
Geohydrology 25

l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l

l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l

l

l l l l l l

l

l l l l l l

l l

l l l l l

l l

l l l l l l l l

l

l l l l l l l l l l l

l l l l l l l l

l l l l l l l

l l

l

l

l l l l

l l l

l l l l

l l l l

l l l l l l l l l l l l l l l l l l l l l

l l l l l l l l l l l l l l l l l

l

l

l l l l l l l l l

l l l l l l l l l l l l l l l l l l

l

l

l l l l l

l

l l l l

l l

l

l

l l l

l l l

l l l l

85° 84° 83° 82°

31°

32°

30°

EXPLANATION

Study area

Figure 16. Altitude of the top of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin.

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

500

Data point

Structure contour—Shows altitude of the top of the

 Upper Floridan aquifer. Hachures indicate depression. 

 Interval 100 feet. Datum is NGVD 29

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

100

100

100

100

100

100

200

200

200

200

200

200

100

300

300

300

300

100

0

0

0

0

0

0

0

100

–100

–200

–300

–100

–200

–300

–400

–500

Figure 16. Altitude of the top of the Upper Floridian aquifer in the Aucilla–Suwannee–Ochlockonee River Basin.
26 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

termed “overburden.” Differentiation of constituent thickness 

of the surficial aquifer system and upper-semiconfining-unit 

within the overburden was not possible from the geohydrologic data (Appendix); therefore, overburden thickness of less 

than 50 ft can consist entirely of sediments constituting either 

the surficial aquifer system or upper semiconfining unit, as 

noted by Miller (1990). Overburden thickness of 50–100 ft 

can contain up to 50 ft of surficial aquifer system sediments; 

these areas warranted classification as a moderate potential 

for recharge by vertical leakage. Areas of low leakage and 

recharge potential exist where overburden thickness of 

100–200 ft occurs; extremely low leakage and recharge 

potential exists where overburden thickness of 200–300 ft 

occurs. No potential for leakage or recharge exists where 

more than 300 ft of overburden thickness occurs. 

The potential exists for the surficial aquifer system to 

receive upward vertical leakage of groundwater from the 

Upper Floridan aquifer in areas where the potentiometric 

surface of the aquifer lies above the water table in the surficial 

aquifer system. In some areas, however, extensive thickness 

of the upper semiconfining unit and low-permeability clay 

and other clastic sediments limit vertical leakage between the 

surficial aquifer system and Upper Floridan aquifer (fig. 15).

The surficial aquifer system generally does not yield 

much water (Miller, 1990), although groundwater occurs under 

mostly unconfined conditions. The thin and discontinuous 

distribution of the surficial aquifer system yields sufficient 

amounts of water for domestic and small-farm supply from 

dug, jetted, or shallow drilled wells (Krause, 1979). Surficial 

aquifer system sediments of the Alum Bluff Group in Colquitt 

County, Ga., are considered unreliable because these sediments 

only receive recharge from precipitation (Zimmerman, 1977).

The upper semiconfining unit consists of a thick 

sequence of low-permeability clastic and carbonate rocks 

that hydraulically separate the overlying surficial aquifer 

system from the underlying Upper Floridan aquifer (fig. 13). 

Depending on hydraulic characteristics and occurrence, terrace 

and undifferentiated (surficial) deposits and the Citronelle, 

Miccosukee, and Jackson Bluff Formations constitute part 

of the upper semiconfining unit. Thin permeable zones in the 

Miccosukee Formation supply water for domestic needs in 

northeastern Lowndes County, Ga. (McConnell and Hacke, 

1993); however, the predominantly clayey lithology and 

potential thickness of 100–200 ft for the Miccosukee and 

other Pliocene formations impede recharge of groundwater 

by precipitation and vertical leakage (fig. 15). The dense, 

clayey, dolomitic, and phosphatic lithology of the Hawthorn 

Group–Torreya Formation and thickness of more than 100 ft 

combine with low-permeability layers in overlying geologic 

units to provide an effective barrier preventing recharge of 

groundwater to the Upper Floridan aquifer by vertical leakage 

from the surficial aquifer system or by infiltration of precipitation directly onto and through the upper semiconfining unit. 

Erosion and carbonate dissolution, however, removes this 

upper semiconfining unit and exposes the Upper Floridan 

aquifer to karstification near Valdosta, Ga., and along the 

Florida–Georgia State line, promoting recharge through karst 

features situated at or near land surface.

Hydrologic conditions of the Upper Floridan aquifer 

vary from semiconfined to unconfined and hydraulic connection with surface water equally varies depending on 

location in the ASO River Basin. The aquifer transitions from 

unconfined conditions in the southern part of the study area to 

semiconfined conditions to the north in karst areas along the 

Florida–Georgia State line in Brooks and Lowndes Counties. 

Unconfined conditions also occur in southern Colquitt and 

northeastern Thomas Counties, where uplift along the flanks 

of the Peninsular Arch (fig. 5) and smaller structural features 

provided sufficient relief for late Eocene rocks and younger 

to be stripped away by erosion (Miller, 1986), subjecting the 

Suwannee and Ocala Limestones to dissolution. The Cody 

Scarp, located along the southern boundary of the study area 

(fig. 3), denotes an area of active limestone dissolution where 

erosion also removed overlying geologic units, exposing the 

Upper Floridan aquifer at or near land surface. In these karst 

areas, limestone dissolution increases aquifer transmissivity 

through the formation of solution cavities and conduit-flow 

conditions (fig. 13) and also increases the hydraulic connection of the aquifer with surface water.

Exposure of the Upper Floridan aquifer at land surface 

causes the most dynamic interaction of groundwater and 

surface-water exchange in the ASO River Basin. Mature 

karst features such as springs, steep-sided sinkholes, disappearing streams, lakes that periodically drain downward, and 

resurgences of disappearing streams characterize the Upper 

Floridan aquifer along the Cody Scarp (Raulston and others, 

1998). Major rivers, such as the Withlacoochee, Alapaha, 

and Suwannee Rivers, flow over limestone that crops out in 

streambeds and freely exchange surface water and ground

water depending on the relative water levels of the aquifer 

and streams. 

North of the Cody Scarp and karst areas in southern 

Georgia, thick clastic sediments of the upper semiconfining 

unit overlie and separate the Upper Floridan aquifer (fig. 13) 

from karst processes, groundwater and surface-water 

exchange, and recharge by infiltration of precipitation. 

Limited karstification in this area causes a precipitous 

decrease in aquifer transmissivity (Miller, 1986) and groundwater exchange with surface water. To the north of karst 

areas in Brooks and Lowndes Counties, upper semiconfining 

unit thickness in excess of 100 ft decreases aquifer recharge 

by infiltration of precipitation and by vertical leakage from 

recharge received by direct infiltration of precipitation and 

surface-water leakage from streams (fig. 15). 

In the northern part of the ASO River Basin, along the 

boundary with the ACF River Basin, recharge to the Upper 

Floridan aquifer occurs where the Suwannee Limestone 

weathered into the Flint River residuum (fig. 11). This 

residuum, termed the Flint River Formation by Vorhis (1972), 

facilitates recharge to the Upper Floridan aquifer in a limited 

area in Dooly and Crisp Counties along the boundary of both 

basins east of the Flint River (fig. 1).
Geohydrology 27

Lithostratigraphic separation of the Upper and Lower 

Floridan aquifers by geologic units constituting the lower 

confining unit, that is, the Avon Park, Lisbon, and Tallahatta 

Formations (figs. 4; 12), creates an effective hydraulic barrier 

to groundwater flow that isolates permeable zones underlying 

the lower confining unit from above-lying units and restricts 

groundwater flow (Leve, 1968). In the northern, western, and 

north-central parts of the study area, the Avon Park Formation 

contains micritic, low permeability limestone that grades into 

a clayey, micritic, glauconitic limestone. This lithology, in 

turn, grades into calcareous, glauconitic, commonly shelly 

sand and clay beds of the Lisbon and Tallahatta Formations 

(Miller, 1986). The micritic limestone and gypsiferous 

carbonate beds constitute important subregional confining 

beds within the Floridan aquifer system (Miller, 1986), 

and represent an impermeable base to the Upper Floridan 

aquifer. Near Valdosta, Ga., low-permeability rocks of the 

lower confining unit coalesce with deeper clastic sediments 

to form a confining unit of more than 200 ft in thickness. The 

lower confining unit yields only small amounts of water to 

wells and contains high sulfide concentrations—attesting to 

the confining and hydraulic isolation of this unit from deep 

formations containing mineralized water—therefore, it functions as the lower boundary to groundwater flow and surfacewater exchange in the ASO River Basin (fig. 13). 

Hydrochemistry

Limestone, dolomite, and gypsum composing the Upper 

Floridan aquifer supply groundwater with ions derived from 

dissolution of calcium carbonate, magnesium carbonate, 

and calcium sulfate, respectively (Torak and others, 2006). 

Glauconite and pyrite contained in the residuum and Upper 

Floridan aquifer contribute potassium, iron, silica, and sulfate 

ions to the chemical composition of groundwater through 

dissolution (Sever, 1965). Clastic Miocene and younger 

sediments weathered from crystalline host rocks of the 

Piedmont contain uranium and radioactive minerals such as 

monazite, a cerium-lanthanum thorium-neodymium-yttrium 

phosphate (Kellam and Gorday, 1990; Mineral Gallery, 2008). 

Groundwater derived from Miocene sediments contains the 

highest natural radioactivity in the Gulf Trough–Apalachicola 

Embayment area, specifically in Tift and Berrien Counties, Ga. 

(Kellam and Gorday, 1990).

The general chemical composition of groundwater in the 

Upper Floridan aquifer is a calcium-magnesium-bicarbonate 

type; however, local recharge mechanisms and lithologic 

variations in the geohydrologic units alter the water chemistry. 

Hard, calcium-magnesium-bicarbonate-type water exists near 

the western boundary of the ASO River Basin. In the Tifton 

Upland, very hard water containing sulfate occurs in some 

places. High iron concentration exists in a 100-mi2

 region 

that trends roughly parallel with the Solution Escarpment and 

Flint River, southeast of Bainbridge, Ga. (fig. 3) (Sever, 1965, 

fig. 2). Inferior-quality water once thought to occur in the 

Ocala Limestone in Grady County, Ga., actually occurs in the 

overlying Byram Formation and consists of extremely hard 

water having high concentrations of sulfate, iron, fluoride, and 

dissolved solids (Sever and Herrick, 1967). Water in geologic 

units underlying the Upper Floridan aquifer in the western 

part of the study area emits a moderate hydrogen-sulfide odor 

because of pyrite and gypsum contained in these rocks, and 

probably contains high sodium and chloride concentrations as 

well as high concentrations of iron and sulfur (Sever, 1965).

Unstable decay of several radioactive isotopes, or 

daughter products, of uranium-238 cause elevated gammaray activity in the ASO River Basin that can help identify 

subsurface zones of high radiation emission. High-radioactive 

zones are represented as peaks, kicks, or points on naturalgamma geophysical logs (Wait, 1960). Laboratory results 

indicate that radium-226 is the dominant alpha emitter in 

the Gulf Trough–Apalachicola Embayment area, and that 

radium-228 activity is negligible (Kellam and Gorday, 1990). 

Radon-222 exists naturally in virtually all soil and rock as a 

decay product of radium-226, the fifth daughter in the decay 

of uranium-238 (Torak and others, 2006). As radon-222 forms, 

some atoms leave the soil or rock and enter the surrounding air 

or water (Samet and Nero, 1989). 

Highly phosphatic sediment in the Hawthorn Group and 

phosphatic sandy Oligocene limestone and dolomite from 

coastal areas of Georgia are proportionately more radioactive 

than other local geologic units, indicating that they are a source 

of radon to groundwater (Torak and others, 2006). Not all wells 

in the Gulf Trough–Apalachicola Embayment area contain high 

levels of radioactivity, or gross alpha activity. Highest levels of 

radioactivity occur near Tifton, Tift County, and near Alapaha, 

Berrien County, Ga. (fig. 12). Here, municipal wells tapping 

Oligocene carbonates of the Upper Floridan aquifer produced 

higher-than-normal amounts of radioactivity. One well, City 

of Tifton municipal well 5, was removed from production 

because of high radioactivity levels. Wells containing high 

gross alpha activity in Tift and Berrien Counties seem to 

be associated with the low altitude of the top of the Upper 

Floridan aquifer, which contains high relief in this area (Kellam and Gorday, 1990). The structural lows in the top of the 

aquifer at these locations probably result from erosion or dissolution, which created a favorable environment for deposition 

of post-Oligocene, radioactive, phosphatic clastic sediments.

Organic material mixed with surface water enters the 

Upper Floridan aquifer by direct recharge in karst areas of 

the ASO River Basin, altering the natural water chemistry 

of groundwater. In the Valdosta, Ga., area, large quantities 

of organic material from the Withlacoochee River enter the 

aquifer through a sinkhole area that has been formed in the 

streambed, providing a source of soluble organic carbon to 

groundwater. About 2.6 tons of total organic carbon (TOC) was 

estimated to enter the Upper Floridan aquifer daily through 

sinkholes in the streambed from 1972 to 1989 (McConnell 

and Hacke, 1993). Increased concentrations of TOC, chloride, 

total sulfide, and methane in wells located downgradient from 

the sinkhole area in the Withlacoochee River, compared with 
28 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

lower concentrations in upgradient wells, indicate that mixing 

of organic-rich river water catalyzes the growth of microbiota 

in the aquifer, which in turn produces methane and hydrogen 

sulfide. Humic substances associated with organic material 

in the water can form trihalomethane during chlorination of 

groundwater for drinking-water supplies.

Water samples collected from the Little and Withlacoochee Rivers (fig. 1) and from wells completed in the 

surficial aquifer adjacent to agricultural fields in the ASO 

River Basin contained herbicide-degradation compounds 

derived from land application of the herbicides metolachlor and 

alachlor, indicating an active flow system consisting of groundwater and surface-water exchange (Pittman and Berndt, 2003). 

While streams contained mostly degradation compounds of 

metolachlor and alachlor, some groundwater samples contained 

the parent compound metolachlor; however, no groundwater 

samples contained alachlor. Concentrations of metolachlor in 

groundwater did not exceed 0.13 microgram per liter (μg/L), 

although its degradation products, metolachlor ethane sulfonic 

acid and metolachlor oxanilic acid, attained maximum concentrations of 19 μg/L and 0.13 μg/L, respectively.

The lower confining unit yields small amounts of water 

containing a high sulfate concentration, which results from 

dissolution of gypsum (Sprinkle, 1989). Underlying units to 

the lower confining unit contain slow-moving, poor-quality 

water (Miller, 1986).

Hydrologic Characteristics

Variations in physical properties of geologic units 

composing the surficial aquifer system, upper semiconfining 

unit, Upper Floridan aquifer, and lower confining unit determine the degree of hydraulic connection among these units 

and control groundwater and surface-water exchange in the 

ASO River Basin. Areal and vertical distribution of physical 

properties within geohydrologic units define heterogeneities in 

hydrologic characteristics that improve current understanding 

of the relative contribution of each unit to groundwater and 

surface-water exchange and that refine the hydrogeologic 

framework and conceptual model of groundwater flow and 

water exchange in the basin.

Surficial Aquifer System

Hydraulic properties and groundwater level control the 

exchange of groundwater in the surficial aquifer system with 

surface water and determine the potential for vertical leakage 

to and from the Upper Floridan aquifer (fig. 13). Variations in 

thickness and areal extent determine the resource potential of 

the surficial aquifer system (figs. 14 and 15)

Hydraulic Properties

The surficial aquifer system blankets most of the ASO 

River Basin with a thin veneer of late Miocene-to-Holocene 

sediments typically less than 50-ft thick (Miller, 1990) (fig. 15). 

Thickness of the surficial aquifer system in the southwestern 

part of the study area in Florida generally ranges from 30 to 

50 ft (Moore, 1955; Scott, 1992). In southeastern Georgia, 

thickness of about 60 ft has been mapped (Miller, 1990).

Transmissivity of the surficial aquifer system in the study 

area ranges from 1,000 to 10,000 feet squared per day (ft2

/d) 

(Miller, 1990). Miller (1990) attributed large transmissivity values to beds of shell and limestone that constitute the 

surficial aquifer system in eastern and southern peninsular 

Florida beyond the study area. 

Wells completed in the surficial aquifer system generally 

yield less than 50 gallons per minute (gal/min) in the study 

area (Miller, 1990). The surficial aquifer system in the Florida 

part of the study area yields only small amounts of water 

when pumped and generally is not used (Davis, 1996a). The 

surficial aquifer system in Colquitt County, Ga., generally 

extends less than 50 ft below land surface and supplies small 

amounts of water for domestic and stock use (Zimmerman, 

1977). In Thomas County, Ga., one well drilled in a Miocene 

phosphatic sandy limestone constituting the surficial aquifer 

system yielded a maximum of 6 gal/min of moderately hard, 

good-quality water. Dug wells in Miocene sand beds produced 

corrosive water containing excessive dissolved iron (Sever, 

1966). Holocene flood plain deposits up to 40-ft thick contain 

water-sorted sand and gravel that could supply domestic or 

light industrial needs; however, swampy conditions and the 

potential for flooding render these deposits untested as a water 

resource (Zimmerman, 1977). 

Hawthorn-equivalent sediment constituting the surficial 

aquifer system in Cook County contains as much as 85 ft of 

medium to very coarse phosphatic sand. Wells installed in 

this sediment produce moderate amounts of corrosive water 

that contain excessive dissolved iron suitable for domestic, 

irrigation, and industrial uses (Sever, 1972). Dug and bored 

wells completed in Pleistocene-to-Holocene alluvial deposits 

provide moderate amounts of water from quartz sand and 

gravel up to 30-ft thick.

Groundwater Levels and Fluctuations

Groundwater levels measured synchronously with 

stream-stage altitudes during September 2006 agree favorably 

and depict a potentiometric surface having a strong surfacewater influence as well as topographic control (fig. 17). The 

similarities in groundwater levels and stream stages indicate 

hydraulic connection and water exchange between the surficial 

aquifer system and surface water. The water table in the 

surficial aquifer system parallels topography in a subdued 

manner and generally lies within 10 ft of land surface (Planert, 

2007). Steep gradients occur between streams and ridges or 

hills; gentle gradients exist in broad, flat interstream areas and 

under broad topographic highs. Groundwater that enters the 

system as precipitation moves quickly along short flowpaths 

perpendicular to potentiometric contours and discharges to 

streams as baseflow (Miller, 1990). Hydraulic gradients and 

groundwater-flow directions change within short distances in 

the surficial aquifer system.
Geohydrology 29

0 10 20 MILES

0 10 20 KILOMETERS

Base from U.S. Geological Survey 

1:100,000-scale digital data

EXPLANATION

Groundwater well and water-level altitude, in feet

Streamgaging station and stage altitude, in feet Gulf of Mexico

Atlantic Ocean

Figure 17. Potentiometric surface of the surficial aquifer system in the Aucilla–Suwannee–Ochlockonee River Basin, 

September 2006.

Study area

200 Potentiometric contour—Shows altitude at which water level 

would have stood in tightly cased wells. Contour interval 10 feet. 

Dashed where approximate. Datum is NGVD 29

174

386

225

171

151

211

203

248

174

186

276

157

262

323

230

298

311

170

158

294

166

165

163

264

LEE 286

WORTH

COFFEE

TIFT

IRWIN

COLQUITT

TELFAIR

MITCHELL BERRIEN

CLINCH

CRISP

WILCOX

COOK

SUMTER

TURNER

ATKINSON

BAKER

GRADY THOMAS

TERRELL

BEN HILL

LANIER

DOUGHERTY

BROOKS LOWNDES

DODGE

JEFF

DAVIS

DOOLY

281 298 300 261

313

303 303

312

314

338 403 313

355 281

312

199

382

409 413

348

353

382

386

403

326 305

323

200

300

300

300

300

400

350 350

350

350

400

200

150

250

250

400

84° 83°

31°

32°

ALABAMA GEORGIA

Map

area

FLORIDA

Figure 17. Potentiometric surface of the surficial aquifer system in the 

Aucilla–Suwannee–Ochlockonee River Basin, September 2006.
30 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Periodic groundwater-level measurements in four wells 

indicate that the water table in the surficial aquifer system 

responds seasonally to precipitation and changes in evapotranspiration rates (fig. 18). High groundwater levels occur during 

late fall through early spring, when frequent precipitation from 

long-duration, low-intensity storms associated with frontal 

passages promotes infiltration. Sparse vegetation from minimal 

crop activity and leaf fall gives rise to low evapotranspiration 

rates during this time, allowing groundwater levels to recover 

(recharge) from the spring and summer growing season. During 

mid-spring through mid-fall, high evapotranspiration rates 

from crop vegetation and trees combine with high runoff and 

low infiltration of precipitation to cause seasonal groundwaterlevel decline. The limited number of water-level measurements 

at the four wells demonstrated the severity of dry climatic 

conditions during 2006 and 2007 by recording unprecedented 

low groundwater levels in the surficial aquifer system.

Upper Semiconfining Unit

The thickness of low-permeability clay and clastic 

sediments constituting the upper semiconfining unit creates 

a hydraulic barrier to groundwater that limits recharge to the 

Upper Floridan aquifer by downward vertical leakage from 

the surficial aquifer system (fig. 15). A low vertical-leakage 

potential exists where thick sequences (100–200 ft) of 

sediment in the upper semiconfining unit overlie the Upper 

Floridan aquifer.

Thickness

Thickness of the upper semiconfining unit ranges from 

absent in karst areas along the Florida–Georgia State line to 

more than 300 ft in the Gulf Trough–Apalachicola Embayment 

region to the northwest and in the Okefenokee Basin to the 

east (fig. 15). 

Davis (1996a) indicated that several hundred feet of 

fine-grained, low-permeability material of the upper semiconfining unit exists in the Apalachicola Embayment–Gulf 

Trough region of the ASO River Basin (fig. 6). Thickness 

of the Hawthorn Group–Torreya Formation of the upper 

semiconfining unit ranges from about 100 to 230 ft in the 

northern and western parts of the study area (Sever, 1966; 

Zimmerman, 1977; and Rupert, 1990). Additional thickness 

of up to 100 ft of low-permeability sediment from the Citronelle, Miccosukee, and Jackson Bluff Formations creates a 

substantial barrier to groundwater recharge from infiltration or 

vertical leakage from the surficial aquifer system. Erosion and 

carbonate dissolution, however, remove this upper semiconfining unit and expose the Upper Floridan aquifer at some 

locations in the study area, such as in southeastern Colquitt 

and Thomas Counties, Ga. (figs. 8 and 9, respectively), along 

the Withlacoochee River near Valdosta, Ga., and in karst areas 

along the Florida–Georgia State line.

2001 2002 2003 2004 2005 2006

10

8

6

16

Well 16N006

14

12

412

414

416

406

408

410

10

8

4

Well 17L028

Well 18K051

Well 16M015

6

10

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8

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6

10

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8

6

316

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318

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406

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402

404

GROUNDWATER LEVEL, IN FEET BELOW LAND SURFACE

ALTITUDE OF WATER LEVEL, IN FEET ABOVE NGVD 29

Provisional data subject to revision

Provisional data subject to revision

Provisional data subject to revision

Provisional data subject to revision

Figure 18. Groundwater hydrographs of 

wells 16M015, 16N006, 17L028, and 18K051, 

completed in the surficial aquifer system, 

for the period 2001–2007. 

Figure 18. Groundwater hydrographs of 

wells 16M015, 16N006, 17L028, and 18K051, 

completed in the surficial aquifer system, 

for the period 2001–2007.
Geohydrology 31

Vertical-Leakage Potential

Thickness variations cause the upper semiconfining 

unit to range in hydrologic function from an impermeable 

boundary to allowing vertical leakage between the Upper 

Floridan aquifer and the surficial aquifer system or surface 

water (fig. 15). The upper semiconfining unit contains a 

high vertical-leakage potential where it is relatively thin 

and generally less than 50-ft thick, allowing recharge to the 

Upper Floridan aquifer by infiltrating precipitation or by 

groundwater flow from the surficial aquifer system. Areas 

of relatively thin upper semiconfining unit promote groundwater exchange between the Upper Floridan aquifer and 

surface water, such as in some upland stream valleys of the 

ASO River Basin north of Tifton, Ga., and northwest of the 

Gulf Trough–Apalachicola Embayment. 

High to moderate leakage potential exists between the 

Gulf Trough–Apalachicola Embayment region and the State 

line in areas where the combined thickness of surficial aquifer 

and upper semiconfining unit total 50 to 100 ft (fig. 15). These 

areas can contain up to 50 ft of surficial aquifer, increasing 

the potential for vertical leakage from moderate to high in the 

absence of the upper semiconfining unit. 

Moderate to low vertical-leakage potential exists in areas 

located between the Gulf Trough–Apalachicola Embayment 

and karst areas along the Florida–Georgia State line (fig. 15). 

In these areas, thick (more than 50 ft) upper-semiconfiningunit sediments overlie the Upper Floridan aquifer, limiting 

or preventing groundwater exchange with surface water or 

recharge from the surficial aquifer system.

 Moderate, to low, to extremely low potential for vertical 

leakage and groundwater and surface-water exchange exists 

in a broad region of the ASO River Basin trending northeast 

to southwest, beginning along the western and northwestern 

basin boundary and extending northeast to Atkinson, Coffee, 

and Irwin Counties, Ga. (fig. 15). A band of increased thickness of low-permeability clastic sediments identifies the Gulf 

Trough–Apalachicola Embayment in this area. Little or no 

potential for vertical leakage and groundwater and surfacewater exchange exists in the center of this area where thickness of the upper semiconfining unit reaches 250 ft or more.

Extremely low to no potential for vertical leakage and 

groundwater and surface-water exchange exists in the eastern 

part of the study area defined by the Okefenokee Basin (fig. 3). 

More than 300 ft of low-permeability clastic sediments overlie 

the Upper Floridan aquifer in parts of Charlton, Clinch, and 

Ware Counties, Ga. (fig. 15) and effectively isolate the aquifer 

from groundwater and surface-water exchange and infiltration 

of precipitation.

Upper Floridan Aquifer

The Upper Floridan aquifer contains Eocene-to-Miocene 

carbonate sediments consisting of the Tampa, Suwannee, 

Marianna, and Ocala Limestones and the Chattahoochee, 

St. Marks, and Byram Formations (figs. 4, 7–12). Natural and 

human-induced factors affect the hydrologic characteristics of 

the Upper Floridan aquifer. Aquifer thickness, hydraulic properties, limestone dissolution, connection with surface water, 

climatic effects, and groundwater withdrawal simultaneously 

affect the water resources of the Upper Floridan aquifer and 

influence groundwater flow and exchange with surface water.

Thickness Variations

Thickness variations for the Upper Floridan aquifer 

(fig. 19) correspond with geologic structural control of 

sediment accumulation in the basin. Subtraction of the areal 

distribution of the base of the Upper Floridan aquifer (fig. 20) 

from the altitude of the aquifer top (fig. 16) yielded the thickness distribution of the Upper Floridan aquifer in the study 

area. The aquifer thins at the updip limits in the northwestern 

part of the basin, just east of the Solution Escarpment (fig. 3), 

and thickens substantially into the Gulf Trough–Apalachicola 

Embayment region (fig. 6) and seaward to the Gulf of Mexico 

and Atlantic Ocean, corresponding with the regional dip of 

geologic units. Thickness of the Upper Floridan aquifer ranges 

from about 150 ft in Worth County, Ga., to more than 900 ft 

in parts of Atkinson, Clinch, Grady, and Lanier Counties, 

Ga., and Gadsden, Hamilton, and Leon Counties, Fla. Clastic 

and carbonate sediments accumulated in the Gulf Trough–

Apalachicola Embayment in Grady and Leon Counties, setting 

the altitude of the base of the Upper Floridan aquifer at nearly 

–1,000 ft (fig. 20). Similar sedimentation in the Suwannee 

Strait (fig. 5) in Clinch County, set the altitude of the base 

of the Upper Floridan aquifer slightly deeper than –1,100 ft. 

Accumulation of sediment in the Apalachicola Embayment 

extends southward through Jefferson and Leon Counties, Fla., 

and beyond the study area in Wakulla County, Fla., where 

thickness of the undifferentiated Floridan aquifer system 

reaches about 2,800 ft (Pratt and others, 1996). Thickness of 

the Upper Floridan aquifer varies by about 300 ft locally in 

Leon County, Fla., owing to limestone dissolution and channel 

erosion of the Suwannee Limestone and St. Marks Formation 

(Hendry and Sproul, 1966). Regional seaward thickening of 

Coastal Plain sediments (Miller, 1986) increases the thickness 

of the Upper Floridan aquifer from near zero in the northwest 

to more than 750 ft in the southeast in Hamilton and Columbia 

Counties, Fla.
32 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

85° 84° 83° 82°

31°

32°

30°

MITCHELL

BAKER

GRADY

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

UNION BRADFORD

SEMINOLE

JACKSON

CALHOUN

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

SUMTER

LEE

DOOLY

DOUGHERTY

CRISP

WEBSTER

STEWART

SCHLEY

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

WARE

BRANTLEY

CHARLTON

WHEELER

PULASKI DODGE

MONTGOMERY

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE

JEFF DAVIS

TIFT

BERRIEN ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

THOMAS BROOKS

QUITMAN

Solution

Escarpment

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Figure 19. Thickness of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin.

Thickness of the Upper 

 Floridan aquifer, in feet

150 to 300

300 to 450

450 to 600

600 to 750

750 to 900

Greater than 900

Approximate location of 

 Gulf Trough–Apalachicola

 Embayment

Study area boundary

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

Figure 19. Thickness of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin.
Geohydrology 33

l l l l l l l l l l l

l l l l l l l l l

l l l l l l

l l l l l l l l l

l l

85° 84° 83° 82°

31°

32°

30°

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Data point 

Figure 20. Altitude of the base of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin.

–500

Study area

Structure contour—Shows altitude of the base of the

 Upper Floridan aquifer. Hachures indicate depression. 

 Interval 100 feet. Datum is NGVD 29

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

–500

–500

–500

–1,000

–1,000

–1,000

–1,000

–2,000

–1,500

0

l l l l l l l l l l l l

l l l l l l l l l l l l l

l l l l l l l l l l l

l l l l l l l l l l l l l l

Figure 20. Altitude of the base of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin. 
34 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Hydraulic Properties and the Effects of Limestone 

Dissolution and the Gulf Trough–Apalachicola Embayment 

on Groundwater Flow

Karst areas located along the Florida–Georgia State line 

and near Valdosta, Ga. (fig. 1) contain dissolution-enhanced 

hydraulic properties that facilitate groundwater flow and 

exchange with surface water. Limestone dissolution by water 

percolating through carbonate sediments enlarges subsurface 

pathways for groundwater flow, increasing hydraulic properties of aquifer transmissivity, hydraulic conductivity, storage 

coefficient, and specific yield in the Upper Floridan aquifer. 

Interconnected systems of solution channels and conduits, 

cavities, and enlarged pore space, joints, and fractures form 

the principal mechanisms for transmitting and storing large 

quantities of groundwater in the Upper Floridan aquifer in 

karst areas. Groundwater readily mixes and exchanges with 

surface water in karst areas where solution features increase 

the hydraulic connection of the Upper Floridan aquifer with 

streams and lakes. Ongoing limestone dissolution alters the 

landscape and reconfigures subsurface pathways, re-forming 

and re-orienting preferential directions of groundwater flow 

and enhancing groundwater and surface-water connection.

In contrast to dissolution-enhanced hydraulic properties 

that exist in karst areas, geologic structure and thick 

accumulation of clastic sediment and dense carbonate layers 

affect the hydraulic properties of the Upper Floridan aquifer 

in the Gulf Trough–Apalachicola Embayment region (fig. 6). 

The low water-transmitting and storage values for the Upper 

Floridan aquifer in the Gulf Trough region represent a 

limestone matrix nearly devoid of dissolution features and 

other groundwater-flow and storage enhancement. Joints or 

faults cut all or part of the Upper Floridan aquifer, juxtaposing 

low permeability sediment with the Upper Floridan aquifer 

(figs. 7–9), effectively decreasing the permeability of the 

aquifer and disrupting groundwater flow (Miller, 1986). The 

absence of secondary water-transmitting and storage features 

in the limestone creates an area of slow-moving groundwater, 

low storage capacity, and low well yield.

Transmissivity and Hydraulic Conductivity

Transmissivity of the Upper Floridan aquifer varies 

throughout the ASO River Basin according to changes in 

thickness and hydraulic conductivity because transmissivity is 

computed as the product of hydraulic conductivity and aquifer 

thickness. Generally, transmissivity increases with increased 

aquifer thickness (fig. 19) and (or) increased hydraulic 

conductivity. Geologic structure, depositional environment, 

and limestone dissolution affect the distribution of aquifer 

thickness and hydraulic conductivity within geohydrologic 

units constituting the Upper Floridan aquifer.

Hydraulic conductivity of the Upper Floridan aquifer 

increases northwestward and southeastward off the flanks 

of the Gulf Trough–Apalachicola Embayment, as the 

thick accumulation of low-permeability clastic, carbonate, 

and clayey sediments overlying the aquifer in the troughembayment region diminishes. Up to 500 ft of low watertransmitting carbonates of the Byram Formation and Marianna 

Limestone supplant the high water-transmitting Suwannee and 

Ocala Limestones in the trough-embayment region (fig. 8). 

Northwest of the Gulf Trough–Apalachicola Embayment, 

hydraulic conductivity ranges from about 26–120 feet per 

day (ft/d) in Ben Hill County, Ga., to about 220–450 ft/d in 

Tift County, Ga., to an exceptional regional high value of 

about 5,700 ft/d in Decatur County, Ga. (Kellam and Gorday, 

1990) (fig. 21A). In the trough-embayment region, Kellam and 

Gorday (1990) indicate typical hydraulic conductivity values 

in the range of about 0.7–140 ft/d. Two exceptions produced 

atypical values of hydraulic conductivity in the troughembayment region: south of Moultrie, Colquitt County, Ga. 

(about 770 ft/d); and east of Cairo, Grady County, Ga. (about 

5,800 ft/d), where wells tap highly productive zones in the 

Upper Floridan aquifer.

Limestone dissolution increases the water-bearing 

capacity of the Upper Floridan aquifer in karst areas along 

the Florida–Georgia State line where limestone exists at or 

near land surface. The aforementioned 5,700-ft/d estimate of 

hydraulic conductivity in Decatur County (fig. 21A) demonstrates the high water-yielding potential of the Upper Floridan 

aquifer caused by limestone dissolution. A 6-ft vertical zone 

of cavities and other solution features located within 130 ft of 

land surface produced nearly 90 percent of the groundwater 

pumped from the well associated with this large value of 

hydraulic conductivity, although aquifer thickness at this location totals about 350 ft (Torak and Painter, 2006). Transmis

sivity understandably attained a high value of 1,300,000 ft2/d 

as a result of this hydraulic conductivity value (fig. 21B).

Aquifer transmissivity varies widely in the ASO River 

Basin, more in response to limestone dissolution than to 

changes in aquifer thickness. Transmissivity values in the 

range 100,000–200,000 ft2/d (McConnell and Hacke, 1993) 

exist in karst areas of Valdosta, Ga. (fig. 21B), although less 

than 300 ft of aquifer thickness exists in this area (fig. 19). 

By comparison, aquifer thickness of 500 to 900 ft in the 

Gulf Trough–Apalachicola Embayment region produces 

aquifer transmissivity values that range from about 5 ft2/d in 

Gadsden County, Fla. (Bush and Johnston, 1988), to 160 ft2/d 
Geohydrology 35

in Tift County, Ga., to 390 ft2/d in Grady County, Ga., and 

to about 3,000 ft2/d in Colquitt and Thomas Counties, Ga. 

(Kellam and Gorday, 1990). On the northwestern flank of the 

trough-embayment region and within 10 mi north and west 

of the 160-ft2/d transmissivity value in Tift County, Kellam 

and Gorday (1990) reported transmissivity values in the range 

1,200–180,000 ft2/d. Bush and Johnston (1988) reported 

a value of 1,300 ft2/d in Leon County, Fla., just east of the 

Gulf Trough–Apalachicola Embayment.

Limestone dissolution enhances hydraulic conductivity 

and disrupts any regional trend in transmissivity defined 

solely by changes in aquifer thickness. Kellam and 

Gorday (1990) indicate the occurrence of a large void in 

aquifer material penetrated by a well in Grady County that 

yielded a hydraulic-conductivity value of about 5,800 ft/d 

(fig. 21A); this well produced a corresponding transmissivity 

value of 430,000 ft2/d. Two wells in Berrien County, Ga., 

penetrate about 600–700 ft of aquifer thickness and produce 

transmissivity values of about 360,000 ft2/d (Kellam and 

Gorday, 1990). The lithologic description of one of these 

wells lists a 17-ft zone of no samples located at the top of 

the Ocala Limestone (McFadden and others, 1986, p. 92), 

most likely the result of solution cavities, which caused poor 

sample return. By comparison, a well located in the Gulf 

Trough–Apalachicola Embayment region south of Moultrie, 

Colquitt County, Ga., produced a transmissivity value of 

about 89,000 ft2/d from about 600–700 ft of aquifer thickness. 

Construction records associated with this well indicate that 

most of the production of about 600 gal/min was derived 

from a 40-ft zone of soft limestone penetrated at a depth of 

425–465 ft below land surface (by S.B. Milligan, Jr., then 

resident engineer, E.P. McLean Engineering Company, to 

W.F. Ladson, then City Manager, City of Moultrie, Ga., 

written commun., January 29, 1949). Most likely, the 

Suwannee Limestone of the Upper Floridan aquifer supplied 

water to this well. Other high values of transmissivity in 

the range 100,000–600,000 ft2/d, attributed to limestone 

dissolution, occur in Berrien, Coffee, and Cook Counties, 

Ga. (Kellam and Gorday, 1990), and in Hamilton County, 

Fla. (Ceryak and others, 1983).

Storage Coefficient and Specific Yield

Storage properties of the Upper Floridan aquifer vary 

by several orders of magnitude in the ASO River Basin 

and surrounding area depending on the degree of limestone 

dissolution and whether groundwater occurs under confined 

or unconfined conditions. Confined- (or artesian-) aquifer 

conditions use the storage coefficient and occur when the 

groundwater level exceeds the top of the aquifer; unconfinedor water-table-aquifer conditions use the specific yield and 

occur when the groundwater level lies below the top of the 

aquifer. Various degrees of semiconfined (leaky artesian) to 

confined conditions cause storage coefficient values to vary 

by several orders of magnitude in the Upper Floridan aquifer. 

This variability of storage coefficient values causes differences 

in vertical-leakage rates through the upper semiconfining unit 

during non-steady, or transient, groundwater flow. Results of 

aquifer testing in the study area and in coastal Georgia indicate 

that values for the confined (or artesian) storage property, or 

storage coefficient, range from 0.00004 to 0.04 (Clarke and 

others, 2005). 

For unconfined, or water-table, conditions, the specific 

yield controls the release or uptake of water by the aquifer. In 

contrast to storage-coefficient values, a value of 0.1 derived 

from an aquifer-performance test in Bainbridge, Ga. (Sever, 

1965), located a few miles to the west of the ASO River Basin 

(fig. 1), indicates unconfined conditions in the Upper 

Floridan aquifer.

 The position of the groundwater level relative to the top 

of the aquifer determines which storage property controls the 

release or uptake of groundwater during transient groundwater 

flow. Seasonal or short-term water-level fluctuations can 

cause aquifer conversion between artesian and water-table 

conditions. Unconfined conditions also occur where erosion 

has removed the upper semiconfining unit and surficial aquifer 

system from overlying the Upper Floridan aquifer (fig. 15). 

Where erosion exposes the aquifer at or near land surface, 

the aquifer contains a water table that reflects a subdued 

expression of topography.

Pumping, climatic conditions, and exchange with surface 

water cause temporal variations in groundwater levels on local 

and regional scales throughout the basin which, in turn, can 

cause conversion from confined to unconfined, or from unconfined to confined conditions depending on the type, extent, 

and duration of hydrologic stress or change in stress imposed 

on the Upper Floridan aquifer. Transient groundwater flow 

occurs at the onset of hydrologic stress applied to the aquifer 

or whenever rates of existing hydrologic stress change, such as 

(1) during the initial stages of pumping or changes in pumping 

rates, (2) during changes in stream stage and (or) groundwater 

level that control groundwater and surface-water exchange, or 

(3) during changes in recharge by infiltration of precipitation 

or vertical leakage. Water is released from or taken up into 

storage in the aquifer according to the artesian or water-table 

storage properties as groundwater levels adjust to changes in 

hydrologic stress, such as those described.
36 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

85° 84° 83° 82°

31°

32°

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

5,700 5,800

0.70

770

140

220

450

90

120 26

1.4

5.1 1.3

MONTGOMERY

DOOLY

SCHLEY PULASKI

MITCHELL

BAKER

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

UNION

SEMINOLE

JACKSON

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

SUMTER

LEE

DOUGHERTY

CRISP

WEBSTER STEWART

QUITMAN

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

WARE

CHARLTON

DODGE WHEELER

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

TIFT COFFEE

BERRIEN ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

THOMAS BROOKS

BRADFORD

JEFF DAVIS

CALHOUN

BRANTLEY

GRADY

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

EXPLANATION

Approximate location of Gulf Trough–Apalachicola Embayment

Study area boundary

Figure 21. Hydraulic properties of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin 

(A) hydraulic conductivity and (B) transmissivity (modified from Ceryak and others, 1983; Bush and Johnston, 1988; 

Kellam and Gorday, 1990; and McConnell and Hacke, 1993).

A. Hydraulic conductivity

Atlantic Ocean

140 Well—Number is estimated hydraulic conductivity in feet per 

 day (ft/d). Range of hydraulic conductivity from 10 ft/d or lower

 to greater than 100 ft/d

Moultrie

Cairo

Figure 21. Hydraulic properties of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin 

(A) hydraulic conductivity and (B) transmissivity (modified from Ceryak and others, 1983; Bush and Johnston, 1988; 

Kellam and Gorday, 1990; and McConnell and Hacke, 1993).
Geohydrology 37

85° 84° 83° 82°

31°

32°

Base from U.S. Geological Survey 

1:100,000-scale digital data

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

B. Transmissivity

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

3,300

1,200 180,000

1,700

13,000

160

390

EXPLANATION

Approximate location of Gulf Trough–Apalachicola Embayment

Study area boundary

Figure 21. Hydraulic properties of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin 

(A) hydraulic conductivity and (B) transmissivity (modified from Ceryak and others, 1983; Bush and Johnston, 1988; 

Kellam and Gorday, 1990; and McConnell and Hacke, 1993).—Continued

Well—Number is estimated transmissivity in feet squared per 

 day (ft2/d). Range of transmissivity values from less than 

 5,000 ft2/d to greater than 50,000 ft2/d

390

430,0000

5

3,100

89,000

1,300,000

170,000

100,000–

 200,000

94,000

360,000

600,000

1,300

190,000

MONTGOMERY

DOOLY

SCHLEY PULASKI

MITCHELL

BAKER

DECATUR

LIBERTY

FRANKLIN

GADSDEN

JEFFERSON

LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE

COLUMBIA

BAKER

UNION

SEMINOLE

JACKSON

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

WORTH

SUMTER

LEE

DOUGHERTY

CRISP

WEBSTER STEWART

QUITMAN

TURNER

COLQUITT

WAYNE

TATTNALL

BACON

PIERCE

WARE

CHARLTON

DODGE WHEELER

TOOMBS

TELFAIR

BEN HILL

IRWIN

APPLING

COFFEE

TIFT

BERRIEN ATKINSON

CLINCH

LANIER

COOK

LOWNDES

ECHOLS

WILCOX

THOMAS BROOKS

BRADFORD

JEFF DAVIS

CALHOUN

BRANTLEY

GRADY

Figure 21. Hydraulic properties of the Upper Floridan aquifer in the Aucilla–Suwannee–Ochlockonee River Basin 

(A) hydraulic conductivity and (B) transmissivity (modified from Ceryak and others, 1983; Bush and Johnston, 1988; 

Kellam and Gorday, 1990; and McConnell and Hacke, 1993).—Continued
38 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Groundwater Levels and Fluctuations

Annually, groundwater levels in the Upper Floridan 

aquifer respond to normal hydrologic stress, such as seasonal 

precipitation and groundwater pumping, and to unseasonable 

or abnormal hydrologic stress caused by climatic and (or) 

pumpage extremes. Groundwater levels attain a seasonal high 

during early spring because the combination of infiltrating 

precipitation, low irrigation demand, and low evapotranspiration rates raises groundwater levels from the low water-level 

conditions of the previous season (fig. 22). Groundwater levels 

decline from late spring to early fall in response to increased 

irrigation pumpage and evapotranspiration, and decreased 

infiltration of precipitation from rates in early spring. Summertime convective storms produce high-intensity, shortduration precipitation events that cause more runoff and less 

infiltration to recharge groundwater levels than the relatively 

long-duration, low-intensity storms associated with frontal 

passages during mid-fall to early spring. The long duration, 

low-intensity storms cause low runoff and high infiltration 

conducive to recharging groundwater levels. Precipitation 

during the growing season temporarily curtails irrigation 

pumpage and slows the seasonal decline in groundwater level 

until dry conditions cause pumping to resume. Groundwater 

levels rise by year’s end and continue rising into the following 

spring in response to seasonal precipitation beginning during 

mid-fall and extending into early spring.

In the absence of unseasonable climatic and/or pumpage variability, groundwater levels usually fluctuate within 

the range of previous years’ levels, rising to nearly the same 

seasonal-high values each spring and declining to about the 

same seasonal-low values each fall. Daily median, or 50th 

percentile, groundwater levels, computed for the period of 

record and superposed on a hydrograph showing daily mean 

groundwater levels (fig. 22), define “normal” seasonal fluctuations and allow comparison of daily mean groundwater levels 

to a statistical representation of normal conditions. Small 

deviations from the median statistic indicate typical variations 

in groundwater levels caused by normal climatic variability 

and short-term changes in hydrologic stress. Consistently 

increasing or decreasing high or low groundwater levels in 

relation to the median daily statistic indicate a trend in groundwater levels that requires explanation with regard to changes 

in climate or hydrologic stress that might signal an irreversible 

groundwater-level condition. For example, the hydrograph of 

well 15L020 during 1996–1999 indicates a declining trend in 

groundwater level of about 6 ft in 4 years, or an average yearly 

groundwater-level decline of about 1.5 ft. The significance of 

this decline is evaluated with regard to a period of observation 

and hydrologic stresses that have changed during this time, as 

discussed below.

Hydrographs from continuous-recorder wells completed 

in the Upper Floridan aquifer depict varying magnitudes of 

seasonal groundwater-level fluctuations in the ASO River 

Basin (fig. 23). Unseasonable climate and (or) pumpage 

variations either amplify or diminish groundwater-level 

fluctuations from normal conditions, depending on the severity 

and duration of the climatic and (or) pumpage variation. 

Multiseason or multiyear deviations from normal climatic 

conditions and (or) pumping rates cause rising or declining 

groundwater-level trends, evidenced on the hydrographs as 

divergence of groundwater levels from median values. Rising 

or declining groundwater-level trends affect groundwater and 

surface-water exchange and recharge and discharge relations 

between hydrologic components that contribute to the water 

resources of the basin (fig. 13).

Consistent deviation from normal seasonal groundwaterlevel fluctuations could indicate a rising or declining trend in 

groundwater levels triggered by a corresponding increase or 

decrease in hydrologic stress on the Upper Floridan aquifer. 

Dry climatic conditions during the fall and winter hinder 

recovery of groundwater levels, and groundwater levels that 

do not recover from seasonal-low values in the fall begin the 

spring at a lower level than the previous year. Consistently 

dry conditions during periods of aquifer recharge—mid-fall 

through early spring—cause lower groundwater levels each 

spring than during the previous spring and could signal a 

declining groundwater-level trend. Low-groundwater-level 

conditions that occur during late spring continue throughout 

the year to perpetuate the declining groundwater-level trend.

WATER LEVEL, IN FEET 

BELOW LAND SURFACE 206

204

202

208

210

212

1996 1997 1998 1999

Jan July Jan July Jan July Jan July Jan

2000

Figure 22. Hydrograph showing seasonal groundwaterlevel fluctuation in well 15L020, Sylvester, Georgia, 

1996–1999.

Median daily statistic

Daily mean depth to water level

EXPLANATION

Figure 22. Hydrograph showing seasonal groundwater-level 

fluctuation in well 15L020, Sylvester, Georgia, 1996–1999.
Geohydrology 39

Figure 23. Hydrographs showing daily mean depth to water level and median daily groundwater level for wells 

(A) 12F036, 1964–2008; (B) 15L020, 1972–2008; (C) 18H016, 1965–2008; (D) 18K049, 1978–2008; (E) 19E009, 1957–2008; 

(F) 27E004, 1978–2008; and (G) 27G003, 1982–2008.

Estimated daily mean depth to water level

Median daily statistic

Daily mean depth to water level

Period of provisional data 

Period of approved data

EXPLANATION

1976 1982 1988 1994 2000 1964 1970 1976 1982 1988 1994 2000

19851982 1988 1991 1994 2000 2003 1997

19851982 1988 1991 1994 2000 2003 1997

19701965 1976 1982 1988 1994 2000 2006

197619701964 1982 1988 2000 2006 1994

2006 2006

2006

2006 1957

2008

1991198819851982 1994 1997 2003 2006 2000 2008

2008

2008

2008

1972

1978

2008

1978

2008

C. Well 18H016, 1965–2008 D. Well 18K049, 1978–2008

E. Well 19E009, 1957–2008

G. Well 27G003, 1982–2008

F. Well 27E004, 1978–2008

A. Well 12F036, 1964–2008 B. Well 15L020, 1972–2008

DAILY DEPTH TO WATER LEVEL, IN FEET BELOW LAND SURFACE

DAILY DEPTH TO WATER LEVEL, IN FEET BELOW LAND SURFACE

130

135

140

145

150

155

160

165

170

175

180

185

165

115

145

120

125

130

135

140

95

110

105

100

60

75

70

65

110

105

115

120

125

130

135

140

145

190

195

200

205

210

215

Figure 23. Hydrographs showing daily mean depth to water level and period-of-record median daily groundwater 

level for wells (A) 12F036, 1964–2008; (B) 15L020, 1972–2008; (C) 18H016, 1965–2008; (D) 18K049, 1978–2008; (E) 19E009, 

1957–2008; (F) 27E004, 1978–2008; and (G) 27G003, 1982–2008.
40 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

The effectiveness of precipitation to raise groundwater 

levels the Upper Floridan aquifer varies in the basin, 

depending on the type and thickness of overlying sediment 

and degree of hydraulic connection of the aquifer with 

land surface or surface water (fig. 15). Although thickness 

of the overlying material can control water-level recovery 

by affecting infiltration of precipitation, regional pumpage 

and climatic conditions also influence water-level recovery. 

High-precipitation months do not necessarily generate high 

groundwater levels, especially in areas where relatively thick 

overburden hydraulically disconnects the aquifer from land 

surface and limits recharge by infiltration of precipitation. 

Similarly, the magnitude of precipitation that occurs near each 

well during the fall through early spring does not always affect 

the magnitude of seasonal water-level recovery if infiltrating 

precipitation first satisfies a thick unsaturated zone in the 

overburden before reaching the Upper Floridan aquifer.

Unseasonably frequent or high precipitation during the 

growing season can reduce or eliminate seasonal groundwaterlevel decline even in areas where a relatively thick upper 

semiconfining unit limits or prevents recharge to the aquifer. 

Irrigation pumping rates usually decrease during wet periods 

of the growing season, causing less pumpage-induced 

groundwater-level decline than during normal or dry periods. 

Climatic variation triggers changes in agricultural pumping 

rates, which increase during periods of low precipitation, 

lowering unseasonably low groundwater levels, and decrease 

during periods of high precipitation, reducing or eliminating 

groundwater-level declines.

Groundwater levels in continuous recorder wells 

completed in the Upper Floridan aquifer responded to 

regional drought during 1980–1981, 1986, 1998–2002, and 

2006 (figs. 23A–F). The hydrograph of continuous recorder 

well 27G003 (fig. 23G) showed effects of regional drought 

conditions similar to groundwater levels in wells previously 

cited, except that the period of record began during 1982 

and, therefore, did not exist to record drought conditions 

during 1980–1981. Some climatological stations recorded 

above-normal precipitation during a few months of 1986 and 

2001, which were drought years, and during 1987 following 

the drought of 1986 (table 3, as noted). Conversely, all 

observation wells exhibited unseasonably high groundwater 

levels during 1987, although some climatological stations 

located near the observation wells recorded less-thanaverage precipitation.

Annual precipitation during 1986, 1987, and 2001, 

recorded at climatological stations located near continuous 

recorder wells, compared favorably with the period-of-record 

mean-annual precipitation (table 3), which seems to refute that 

drought conditions ever occurred during two of these years. 

Unseasonably high precipitation during specific months of 

these years skewed total annual precipitation to near meanannual values. Groundwater levels seemed to respond more 

to regional climatic conditions than to local conditions, as 

evidenced by the low water levels recorded on well hydrographs during drought years (fig. 23).

Declining groundwater-level trends of any duration 

indicate a systematic lowering of the potentiometric surface 

of the Upper Floridan aquifer and a depletion of groundwater 

resources, compared with previous conditions (fig. 23). 

Abnormally dry climatic conditions reduce infiltration of 

precipitation to the Upper Floridan aquifer from conditions 

of normal precipitation, limiting aquifer recharge and causing 

unseasonably low groundwater levels in recharge areas of the 

Upper Floridan aquifer, such as along the northwestern basin 

boundary and in karst areas along the Georgia–Florida State 

line and to the south and east of the Gulf Trough–Apalachicola 

Embayment. Drought-induced increases to irrigation pumping 

rates cause declining groundwater-level trends wherever 

pumping stresses the Upper Floridan aquifer beyond its ability 

to recharge by regional groundwater flow, infiltration of 

precipitation, or induced surface-water leakage. Unseasonably 

low groundwater levels in aquifer-recharge areas, in turn, lower 

hydraulic gradients and regional groundwater-flow rates in 

downgradient, or outward, directions from the recharge area.

Rising groundwater-level trends of any duration can 

result from a reduction of hydrologic stress to the aquifer, 

such as above-normal precipitation sustained during several 

seasons or years and (or) pumpage reduction or relocation, 

and represent an accretion of groundwater resources. In a 

reverse process from that previously described for declining 

groundwater-level trends, precipitation that infiltrates areas 

favorable for recharge to the Upper Floridan aquifer (fig. 15) 

locally raises groundwater levels, increases regional groundwater flow out of recharge areas, and raises downgradient 

groundwater levels. Relocation of municipal pumpage at 

Cairo, Ga., for example, during October 1973 caused a 25-ft 

rise in the groundwater level in well 12F036 by February 1974 

(fig. 23A). A declining trend during 1976–1982 negated this 

water-level increase; however, a rising trend in groundwater 

levels during the next 6 years restored water levels to the 1976 

level by 1988. The hydrograph for well 15L020 (fig. 23B) 

depicts other groundwater-level trends during 1988–1991 

(declining), 1991–1995 (rising), and 1995–2003 (declining), 

characterized by amplified seasonal water-level fluctuations 

that exceeded median values.

September 2006 Potentiometric Surface

Potentiometric contours of the Upper Floridan aquifer 

during September 2006 indicated complex patterns of 

groundwater flow in the ASO River Basin and across the 

basin boundary in the ACF River Basin (fig. 24). Groundwater 

generally flows southward to Florida and the Gulf of Mexico 

and eastward to coastal Georgia and the Atlantic Ocean from 

a groundwater divide located along the northern and western 

boundary of the ASO River Basin with the ACF River Basin 

(fig. 24B). Groundwater mounds near the Withlacoochee 

River in Brooks and Lowndes Counties, Ga., and groundwater 

depressions in southern Colquitt and Cook Counties, Ga., define 

diverging and converging groundwater-flow patterns, respectively, indicative of recharge and discharge, which alter the 

regional pattern of southward and eastward groundwater flow.
Geohydrology 41

Table 3. Precipitation for selected years and climatological stations located in the Aucilla–Suwannee–Ochlokonee River Basin.

Station

name

Station 

number

(fig. 1)

Nearest 

observation 

well (fig. 1)

Precipitation, in inches

Mean Remarks

annual 1986 1987 2001

Ashburn 3 

ENE

90406 15L020 48.3 48.21 63.18 43.04 Total precipitation during 2001 skewed by precipitation of 11.84 inches during March; data from 

Southeast Regional Climate Center, 2008e.

Cairo 2 N 91463 12F036 51.25 — — 53.53 Precipitation of 11.34 and 15.67 inches occurred 

during March and June 2001, respectively; data 

from Southeast Regional Climate Center, 2008f.

Cordele 92266 15L020 44.86 31.12 38.82 43.87 Precipitation of 9.61, 10.58, and 8.55 inches occurred during March, June, and September 2001, 

respectively; data from Southeast Regional 

Climate Center, 2008c.

Folkston 9 

SW

93465 27E004 52.64 58.66 48.1 41.29 Precipitation of 11.52 inches occurred during 

June 2001; data from Southeast Regional 

Climate Center, 2008g.

Homerville 94429 27G003 52.31 61.44 54.87 37.26 Precipitation of 8.03, 10.15, 9.31, and 8.28 inches

occurred during February, June, July, and 

December 1986, respectively; precipitation of 

8.28 and 9.22 inches occurred during July and 

September 1987, respectively; precipitation of 

10.84 inches occurred during June 2001; data 

from Southeast Regional Climate Center, 2008h.

Lake City 

2 E

84731 27E004 53.19 55.72 59.26 42.31 Precipitation of 10.34 and 12.89 inches occurred 

during August 1986 and 1987, respectively; 

precipitation of 9.95 inches occurred during 

September 2001; data from Southeast Regional 

Climate Center, 2008b.

Moultrie 2 

ESE

96087 18H016 49.9 51.65 46.07 43.54 Precipitation of 11.84 inches occurred during 

March 2001; data from Southeast Regional 

Climate Center, 2008i.

Quitman 2 

NW

97276 19E009 52.5 39.25 — 39.84 Precipitation of 15.4 inches occurred during 

June 2001; 11 days of precipitation missing 

during July 2001; data from Southeast Regional 

Climate Center, 2008j.

Tifton Exp 

Stn

98703 18K049 47.23 48.01 49.59 42.64 Precipitation of 15.14 inches occurred during 

June 2001; data from Southeast Regional 

Climate Center, 2008k.

Waycross 4 

NE

99186 27G003 48.98 40.54 44.98 37.60 Precipitation of 8.73, 8.03, and 8.55 inches occurred during June, July, and September 2001, 

respectively; data from Southeast Regional 

Climate Center, 2008d.
42 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

85° 84° 83° 82°

31°

32°

30°

A

200

250

100

50

50

50

50

100

150

200

200

50

50

50

50

50

50

150

250

200

Okefenokee

Swamp

MITCHELL

GRADY

DECATUR

LIBERTY

GADSDEN

SUMTER

LEE

CRISP

COLQUITT

CHARLTON

BEN

HILL

IRWIN

TIFT

BERRIEN

COOK

BROOKS THOMAS

WORTH

MONTGOMERY

DOOLY

SCHLEY PULASKI

BAKER

FRANKLIN

JEFFERSON LEON

WAKULLA

MADISON

TAYLOR

HAMILTON

SUWANNEE

LAFAYETTE COLUMBIA

BAKER

UNION

SEMINOLE

JACKSON

MILLER

EARLY

CALHOUN

RANDOLPH

CLAY

TERRELL

DOUGHERTY

WEBSTER

STEWART

QUITMAN

TURNER

WAYNE

TATTNALL

BACON

PIERCE

WARE

DODGE WHEELER

TOOMBS

TELFAIR

APPLING

COFFEE

ATKINSON

CLINCH

LANIER

LOWNDES

ECHOLS

WILCOX

BRADFORD

JEFF DAVIS

CALHOUN

BRANTLEY

ALABAMA GEORGIA

FLORIDA

Map area

Gulf of Mexico

Atlantic Ocean

0

0

10

10

20

20

30

30

40

40

50 MILES

50 KILOMETERS

Figure 24. (A) Potentiometric surface of the Upper Floridan aquifer in southern Georgia and northern Florida, 

September 2006; and (B) enlarged view of the potentiometric surface of the Upper Floridan aquifer in southern 

Georgia, September 2006, showing groundwater divide and flow directions.

Base from U.S. Geological Survey 

1:100,000-scale digital data

EXPLANATION

Approximate location of the Gulf 

 Trough–Apalachicola Embayment—

 (modified from Kellam and

 Gorday, 1990; Davis, 1996a)

Study area boundary Direction of groundwater flow

Groundwater divide

Approximate axis of Peninsular Arch

150 Potentiometric contour—Shows altitude at 

which water level would have stood in 

tightly cased wells during September 2006. 

Hachures indicate depression. Contour 

interval 10 feet. Datum is NGVD 29

Apalachicola–Chattahoochee–

 Flint River basin boundary

Area of map in Figure 24B

Figure 24. (A) Potentiometric surface of the Upper Floridan aquifer in southern Georgia and northern Florida, 

September 2006; and (B) enlarged view of the potentiometric surface of the Upper Floridan aquifer in southern 

Georgia, September 2006, showing groundwater divide and flow directions.
Geohydrology 43

84° 83°

31°

32°

B

100

150

200

50

60

60

70

80

90

50

50

50

50

150

250

200

200

MITCHELL

SUMTER

LEE

DOUGHERTY

CRISP

TURNER

COLQUITT

BEN HILL

IRWIN

TIFT

BERRIEN

COOK

WILCOX

BROOKS

THOMAS

GRADY

LANIER

LOWNDES

WORTH

DODGE

TELFAIR

0

0

10

10

20 MILES

20 KILOMETERS

Base from U.S. Geological Survey 

1:100,000-scale digital data

Figure 24. (A) Potentiometric surface of the Upper Floridan aquifer in southern Georgia and northern 

Florida, September 2006; and (B) enlarged view of the potentiometric surface of the Upper Floridan 

aquifer in southern Georgia, September 2006, showing groundwater divide and flow 

directions.—Continued

EXPLANATION

Approximate location of the Gulf Trough–

 Apalachicola Embayment—(modified 

 from Kellam and Gorday, 1990; Davis, 1996a)

Study area boundary

Groundwater divide Direction of groundwater flow

Approximate axis of Peninsular Arch

150 Potentiometric contour—Shows altitude at 

which water level would have stood in 

tightly cased wells during September 2006. 

Hachures indicate depression. Contour 

interval 10 feet. Datum is NGVD 29

Apalachicola–Chattahoochee–Flint River 

 basin boundary

Figure 24. (A) Potentiometric surface of the Upper Floridan aquifer in southern Georgia and northern Florida, 

September 2006; and (B) enlarged view of the potentiometric surface of the Upper Floridan aquifer in southern 

Georgia, September 2006, showing groundwater divide and flow directions.—Continued
44 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Southward bending of the 60–190-ft potentiometric 

contours established a groundwater divide east of the basin 

boundary in the ASO River Basin in Colquitt, Grady, Mitchell, 

Thomas, and southern Worth Counties (fig. 24B). In Decatur 

and Grady Counties, Ga., and in Gadsden and Leon Counties, 

Fla., the 60–90-ft potentiometric contours trend nearly east to 

west across the basin boundary defining southward groundwater flow from the ACF River Basin into the ASO River 

Basin (fig. 24A). The northwestern trend of the 100–150-ft 

potentiometric contours across the basin boundary indicates 

southwestward groundwater flow along the basin boundary 

in southern Mitchell County. The 160–190-ft potentiometric 

contours align more northward than the 100–150-ft contours, 

indicating westward groundwater flow across the basin boundary from the ASO River Basin into the ACF River Basin in 

northwestern Colquitt and southwestern Worth Counties.

The 210–260-ft potentiometric contours during 

September 2006 positioned the groundwater divide in the 

ACF River Basin west of the basin boundary in central Crisp 

and northern Worth Counties (fig. 24B). Groundwater flows 

eastward to southeastward into the ASO River Basin from 

the ACF River Basin in northern and central Worth County. 

The 200-ft potentiometric contour positioned the groundwater 

divide coincident with the basin boundary in southern Worth 

County where groundwater diverges from the divide and basin 

boundary and flows into both basins.

Tightly spaced 70–190-ft contours on the September 

2006 potentiometric surface defined high hydraulic gradients 

but relatively slow-moving groundwater in the Gulf Trough–

Apalachicola Embayment area (fig. 24A). Low hydraulic 

conductivity and transmissivity in the trough-embayment area 

(fig. 21) limit southeastward groundwater flow from recharge 

areas across the basin boundary in the ACF River Basin in the 

northwestern part of the study area.

Closed patterns of 40- and 50-ft cotours on the 

September 2006 potentiometric surface located southeast of 

the Gulf Trough–Apalachicola Embayment region in eastern 

Colquitt and Cook Counties defined depressions that indicate 

groundwater discharge (fig. 24A). The depression in south

eastern Colquitt County coincides with northeastern extensions of the Ochlockonee fault and Barwick arch, as identified 

by Sever (1966) (fig. 9). Miocene folding and faulting 

displaced the Upper Floridan aquifer upward by as much as 

190 ft on the southeastern side of the fault, juxtaposing the 

top unit of the aquifer (the Suwannee Limestone) with the 

low-water-bearing Tampa Limestone on the northwestern side 

of the fault. “Rocks on the southeast side of the fault [have 

been] upthrown with the amount of displacement increasing 

[from Thomas County] to the northeast” (Sever, 1966, p. 8). 

Sever (1966) described a condition in Thomas County during 

March 1964 where the groundwater level of the Suwannee 

Limestone was 10–20 ft higher than groundwater levels of the 

underlying Byram Formation, Marianna Limestone equivalent, 

and Ocala Limestone (fig. 4). Very little groundwater flowed 

across the Ochlockonee fault. Rather, groundwater flowed 

down the fault into underlying geologic units. 

The depression in the September 2006 potentiometric 

surface in southeastern Colquitt County (fig. 24A) coincided 

with the location of a recharge mound during December 1969, 

where groundwater diverged from an area enclosed by 

80- and 90-ft potentiometric contours (Zimmerman, 1977, 

fig. 5). A groundwater level of 80–90 ft during December 

1969 coincided with the top altitude of the Upper Floridan 

aquifer in this area (fig. 16). Therefore, groundwater levels of 

40–50 ft during September 2006 indicated that about 40–50 ft 

of aquifer dewatering had occurred since December 1969. 

Such dewatering can lead to depletion of the groundwater 

resource as saturated aquifer thickness decreases with 

increased dewatering. Other depressions in the September 

2006 potentiometric surface seem to be pumpage related 

rather than indicative of vertically downward leakage from 

the Suwannee Limestone to deeper geologic units of the 

Upper Floridan aquifer.

Closed 80–90-ft contours of the September 2006 potentiometric surface located in Brooks and Lowndes Counties 

defined diverging groundwater flow indicative of recharge 

mounds in the Upper Floridan aquifer (fig. 24). In these areas, 

the aquifer lies near or slightly below land surface because of 

uplift by the northern extension of the Peninsular Arch and 

subsequent erosion of overlying sediments. Limestone dissolution formed sinkholes and other karst features in this area 

that promote infiltration of precipitation and surface-water 

exchange (Krause, 1979).

Sparse groundwater-level measurements in the eastern 

part of the study area during 2006 resulted in a general 

potentiometric surface defined by widely spaced 40- and 50-ft 

potentiometric contours (fig. 24A). This area contains the 

Okefenokee Swamp, where more than 300 ft of low-waterbearing clastic sediments overlie the Upper Floridan aquifer 

(fig. 15), limiting if not eliminating hydraulic connection of 

the aquifer with land surface and surface water.

Lower Confining Unit

The Lisbon Formation defines the lower confining unit of 

the Upper Floridan aquifer in the northern, western, and northcentral parts of the study area (Miller, 1986). The carbonaceous 

clay and glauconitic limestone of the Lisbon Formation that, 

in turn, grades into micritic, low-permeability, finely pelletal 

limestone interbedded with fine-to-medium crystalline, 

slightly vuggy dolomite of the Avon Park Formation to the 

south and east in the ASO River Basin represents an important 

subregional confining unit within the Floridan aquifer system 

(Miller, 1986). These geologic units define the lower confining 

unit to the Upper Floridan aquifer (fig. 4) and create a hydrologic barrier to groundwater flow. The lower confining unit 

prevents poor-quality water in deeper water-bearing units from 

entering the Upper Floridan aquifer in the study area.

Thickness of the lower confining unit varies greatly in 

the ASO River Basin (figs. 7, 8, 10–12). At least 100 ft of the 

Lisbon Formation extends from the western boundary with 

the ACF River Basin, across the Gulf Trough–Apalachicola 
Conclusions 45

Embayment region, northeastward to northern Coffee County, 

Ga., just to the northeast of the study area Miller (1986) 

(fig. 6). The lower confining unit increases in thickness 

southeastward from about 500 ft in Coffee County to more 

than 2,200 ft in Clinch County, Ga., in the eastern part of the 

study area. Thickness of the lower confining unit increases 

northeastward from about 200–300 ft in Madison County, Fla., 

to nearly 2,000 ft in Echols County, Ga. (figs. 10 and 12). The 

low stratigraphic position of these low permeable units in the 

southeastern part of the study area (fig. 12) creates the base 

of the Floridan aquifer system, above which a local confining 

unit about 100–150-ft thick separates the Upper Floridan 

aquifer from permeable units of the Lower Floridan aquifer. 

Conclusions

The objectives addressed in this report are restated from 

the section “Purpose and Scope” prior to each conclusion.

1. Describe the lithologic and hydraulic properties of the 

Upper Floridan aquifer and hydraulically connected 

geologic units that would enable assessment of water 

exchange between Upper Floridan aquifer and other 

geohydrologic units and surface water.

Tectonic forces underlying the Coastal Plain played a 

major role in determining the type of sediment in the 20,000-ft 

sequence of clastic and carbonate sediments deposited in the 

ASO River Basin. Structural control of sedimentation also 

affected the geohydrology and water exchange of geohydrologic units with surface water. Differential compaction and 

limestone dissolution and collapse affected the accumulation 

and lithology of late-middle Eocene and younger sediments 

constituting the surficial aquifer system, Upper Floridan 

aquifer, and intervening upper semiconfining unit. An early 

Mesozoic uplift, the Peninsular Arch, established various 

depocenters along its flanks and dominated sedimentation 

patterns throughout most of the study area. Deposition and 

accumulation of more than 300 ft of low-permeability clastic 

sediments on the northeastern flank of the Peninsular Arch 

in the Southeast Georgia Embayment and Suwannee Strait, 

and along the northwestern flank of the Arch in the Gulf 

Trough–Apalachicola Embayment, virtually isolated the 

Upper Floridan aquifer from land surface and recharge by 

infiltrating precipitation. Burial of limestone beneath thick 

clastic overburden in these regions virtually eliminated 

the potential for ongoing karst processes, resulting in low 

aquifer hydraulic conductivity and storage coefficient despite 

increased aquifer thickness of more than 900 ft. Accumulation 

of up to 500 ft of low-water-bearing Oligocene carbonates in 

the Gulf Trough–Apalachicola Embayment stratigraphically 

and hydraulically separated two principal water-bearing strata 

of the Upper Floridan aquifer—the Oligocene Suwannee 

Limestone and the late Eocene Ocala Limestone. Conversely, 

uplift and faulting associated with the Peninsular Arch thinned 

overlying clastic sediments and exposed the Suwannee 

Limestone of the Upper Floridan aquifer to land surface near 

the Florida–Georgia State line, creating a karst region of active 

limestone dissolution and vigorous exchange of groundwater 

with surface water.

The Ochlockonee fault and Barwick arch produce more 

than 100 ft of uplift on the southeastern flank of the Gulf 

Trough–Apalachicola Embayment, juxtaposing the top of 

the Upper Floridan aquifer (Suwannee Limestone) with 

low-water-bearing geologic units of the overlying upper 

semiconfining unit in Colquitt and Thomas Counties, Ga. 

Contours of the altitude of geologic units prepared by previous investigators for Colquitt County demonstrate structural 

control of the top of the Upper Floridan aquifer; disparate 

values of the aquifer-top altitude within short distances result 

from deposition and faulting rather than limestone dissolution. Similar data disparities for the top altitude of the Upper 

Floridan aquifer in Cook County result from variable lithology 

and water-bearing characteristics of the early Miocene Tampa 

Limestone, which either transmits water as the top geologic 

unit of the Upper Floridan aquifer or semiconfines the 

underlying aquifer, depending on location. Close inspection of 

geohydrologic data in other counties in the ASO River Basin 

indicates similar variability of water-transmitting characteristics and presence of geologic units constituting the top of the 

Upper Floridan aquifer.

2. Develop a hydrogeologic framework and conceptual 

model for evaluating agricultural pumpage and groundwater and surface-water exchange between the Upper 

Floridan aquifer and other geohydrologic units connected 

to surface water.

Various hydrologic processes contribute to groundwater 

flow in the ASO River Basin, conveying water to pumped 

wells and facilitating groundwater and surface-water exchange 

between the Upper Floridan aquifer and other geohydrologic 

units connected to surface water. Recharge to the Upper 

Floridan aquifer occurs by infiltration of precipitation, 

vertical leakage through the surficial aquifer system and 

undifferentiated overburden, inflow across stream channels or 

lake bottoms, and regional flow. Discharge processes include 

vertical leakage, outflow across stream channels or lake 

bottoms, regional flow, and well pumpage. Geohydrologic 

units containing these processes consist of the surficial aquifer 

system, upper semiconfining unit, Upper Floridan aquifer, and 

lower confining unit. Hydraulic gradients and properties of 

aquifer transmissivity and storage govern the rate of groundwater flow to pumped wells.

Climate and pumpage changes create complex and 

dynamic relations with groundwater levels and with groundwater and surface-water exchange in the ASO River Basin. 

Groundwater levels recover during late fall and winter from 

declines incurred during the growing season (spring through 

early fall) caused by high evapotranspiration and runoff, low 

infiltration of precipitation, and irrigation pumpage. Low 

evapotranspiration and crop demand during the fall, winter, 

and early spring coupled with infiltration of precipitation and 
46 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

little runoff contribute to raising groundwater levels. Droughts 

require additional agricultural irrigation pumpage from 

normal irrigation pumping rates to maintain crop production; 

increased irrigation pumping rates lower groundwater levels 

more than would occur during a growing season having 

normal precipitation. Extended dry or drought conditions 

lower groundwater levels from normal water-level conditions 

by reducing recharge to the Upper Floridan aquifer from 

infiltration of precipitation, from vertical leakage through the 

upper semiconfining unit and (or) the surficial aquifer system, 

and from regional flow. Abnormally large groundwater-level 

declines reduce the base flow of streams and either limit 

or eliminate hydraulic connection of the aquifer with the 

stream. Most of the continuous-recorder hydrographs indicate 

abnormally low groundwater levels during the following 

years of extremely dry conditions or drought: 1980–81, 1986, 

1998–2002, and 2006.

3. Present an overview of 2006 groundwater-level and 

streamflow hydrologic conditions.

Groundwater levels and streamflows measured during 

September 2006 provide an overview of then-current hydrologic conditions. Water-table conditions occurred in two areas 

of the ASO River Basin: north and west of the Gulf Trough–

Apalachicola Embayment region, and south and east of the 

trough-embayment region but west of the Okefenokee Basin. 

To the north and west of the trough-embayment region, headwater streams to the Alapaha, Little, and Withlacoochee Rivers 

incise through relatively thin overburden, further reducing 

overlying sediment thickness to the Upper Floridan aquifer 

and enhancing groundwater and surface-water exchange and 

aquifer recharge. South and east of the trough-embayment 

region, more than 40 ft of aquifer dewatering occurred since 

the late 1960s in southeastern Colquitt County, as defined by 

the area contained within the 40-ft potentiometric contour 

of the September 2006 potentiometric surface. Here, and 

in Cook and Thomas Counties, Ga., uplift of Coastal Plain 

sediments associated with the Peninsular Arch and erosion of 

Oligocene and younger geologic units positioned the Upper 

Floridan aquifer near or just below land surface. In karst 

areas of Brooks and Lowndes Counties, this uplift created a 

recharge area, water-table conditions, and active groundwater 

and surface-water exchange along the Withlacoochee River 

near Valdosta, Ga.

The Upper Floridan aquifer exhibited artesian-aquifer 

conditions during September 2006 in two distinct areas of 

the ASO River Basin—along the trace of the Gulf Trough–

Apalachicola Embayment and in the Okefenokee Basin and 

Swamp. The low-water-transmitting ability of the Upper 

Floridan aquifer in the trough-embayment region limits 

groundwater flow, resulting in elevated groundwater levels and 

artesian conditions in this area. Groundwater levels declined 

about 100 ft in 20 mi across the trough-embayment region 

from the northwest to the southeast in northern Colquitt and 

southern Tift and Worth Counties. Confinement of the Upper 

Floridan aquifer with up to 300 ft of overburden consisting 

of the surficial aquifer and upper semiconfining unit causes 

hydraulic separation of the Upper Floridan aquifer with land 

surface, limiting recharge, spring discharge, and surface-water 

exchange from affecting the potentiometric surface and 

possibly creating water-table conditions. In the Okefenokee 

Basin and Swamp, limited groundwater development and 

more than 300 ft of low-water-transmitting overburden limited 

interaction of the Upper Floridan aquifer with land surface 

and streams, allowing artesian conditions to exist during 

September 2006.

4. Explain hydrologic concepts of the groundwater and 

surface-water exchange mechanisms that control causal 

relations between groundwater pumpage in the Upper 

Floridan aquifer, climatic variations, groundwater-level 

decline, reductions in streamflow and springflow, and 

changes in interbasin flow.

Groundwater levels in the Upper Floridan aquifer and 

streamflows fluctuate seasonally and exhibit long-term decline 

in response to complex interactions of natural and humaninduced hydrologic stress imposed on the water resources of 

the ASO River Basin. Changes in groundwater and surfacewater withdrawal, climatic conditions, and the degree and 

areal extent of hydraulic connection of the aquifer with land 

surface and surface water combine to influence groundwater 

levels and streamflows. Groundwater levels resolve and 

manifest hydrologic stresses into a unique temporal record: 

the groundwater hydrograph. Likewise, streamflow and 

streamflow hydrographs reflect and resolve to varying degrees 

the combined effects of hydrologic stresses imposed on the 

groundwater- and surface-water-flow system.

The effect of climate on groundwater levels in the 

Upper Floridan aquifer varies depending on the potential of 

the overlying sediment to provide recharge to the aquifer by 

vertical leakage or by infiltration of precipitation. Increased 

precipitation above normal amounts raises groundwater levels 

in the Upper Floridan aquifer above normal, or median, values 

and increases groundwater recharge and hydrologic processes 

that deliver water to streams and wells. High-precipitation 

months do not necessarily coincide with groundwater-level 

increases shown on hydrographs, however, and the magnitude 

of precipitation that occurs near each well during fall and 

winter does not seem to affect the magnitude of groundwaterlevel increases. Storage properties and moisture conditions 

of the aquifer and overburden sediments can dampen the 

response of groundwater levels to recharge from infiltration of 

precipitation in the same manner as storage properties delay 

pumpage-induced groundwater-level decline.

Increased hydrologic stress caused by dry climatic 

conditions and (or) increased pumpage initiated a steady 

groundwater-level decline along the northwestern boundary 

of the ASO River Basin in Worth County, Ga., during the 

mid-1970s that extended through the mid-2000s. Increases in 

center-pivot irrigation systems during the mid-to-late 1990s 

and drought conditions during the mid-1980s and 1998–2002 

contributed to groundwater-level declines indicated on 
Conclusions 47

hydrographs of wells located in the northwestern and central 

parts of the study area.

Groundwater-level declines lower the hydraulic gradient 

toward the ASO River Basin from recharge areas northwest 

of the basin boundary in the adjacent ACF River Basin and 

reduce the potential for regional groundwater to flow southeastward across the Gulf Trough–Apalachicola Embayment. 

Low-water-bearing clastic sediments overlying the Upper 

Floridan aquifer in the Gulf Trough–Apalachicola Embayment 

and the low-water transmitting properties of the aquifer in the 

trough-embayment region divide the ASO River Basin into 

distinct regions of groundwater flow.

The trough-embayment region restricts recharge in the 

northwestern parts of the ASO River Basin from flowing 

southeastward as regional groundwater flow and isolates 

groundwater-level changes that occur on either side. Waterlevel declines in the trough-embayment region associated 

with relatively heavy pumping in Colquitt and Tift Counties, 

Ga., cause local depressions in the potentiometric surface 

that seem isolated from water levels on the distal side of the 

trough-embayment region, about 15–20 mi to the northwest. 

Areas southeast of the trough-embayment region receive 

insufficient recharge by regional groundwater flow from the 

northwest, resulting in pumpage-induced groundwater-level 

declines. Vertical downward leakage of groundwater from 

the Suwannee Limestone of the Upper Floridan aquifer to 

deeper limestone units in southeastern Colquitt County, Ga., 

has caused 40–50 ft of groundwater-level decline and aquifer 

dewatering since December 1969.

Relatively low aquifer transmissivity in the Gulf Trough–

Apalachicola Embayment region not only limits the effects 

of pumpage to a local area, but amplifies pumpage-induced 

groundwater-level changes near pumped wells. For example, 

the groundwater-level rise during late 1973 to early 1974 

in the trough-embayment region near Cairo, Grady County, 

Ga., represented a local response to relocation of municipal 

pumpage about 2 mi east of the city. Groundwater-level 

changes in the trough-embayment region provide unreliable 

information about groundwater-level trends in other parts of 

the Upper Floridan aquifer, such as northwest and southeast 

of the trough-embayment region, as demonstrated by distinct 

groundwater-level trends on hydrographs of continuousrecorder wells located in these areas.

Groundwater levels exhibited a basin-wide response to 

regional hydrologic stress imposed on the Upper Floridan 

aquifer. Hydrographs recorded lowering of groundwater 

levels in and downgradient from recharge areas in response 

to extremely dry conditions that occurred during 1980–1981, 

1986, 1998–2002, and 2006.

In contrast to pumpage- and drought-induced groundwater-level decline, above-average precipitation following 

drought conditions raised groundwater levels in recharge 

areas in the northwestern and south-central parts of the basin. 

The groundwater-level rise, in turn, raised the potentiometric 

surface of the Upper Floridan aquifer in the Okefenokee 

Basin, although several hundred feet of low-permeability 

clastic sediments hydraulically isolate the aquifer from 

infiltrating precipitation and surface-water interaction there. 

Groundwater-level fluctuations in the eastern part of the ASO 

River Basin also indicate a strong relation to fluctuations that 

occur in wells completed in the Upper Floridan aquifer located 

along the coast.

Declining groundwater-level trends indicate a systematic 

lowering of the potentiometric surface of the Upper Floridan 

aquifer and a depletion of groundwater resources, compared 

with previous conditions. Abnormally dry climatic conditions 

limit aquifer recharge by infiltration of precipitation from 

conditions of normal precipitation, causing unseasonably low 

groundwater levels in recharge areas of the ASO River Basin, 

such as along the northwestern basin boundary, in karst areas 

along the Georgia–Florida State line, and south and east of 

the Gulf Trough–Apalachicola Embayment. Drought-related 

increases in irrigation pumpage and pumpage associated 

with increased agricultural, industrial, and (or) municipal 

development has the potential to cause declining trends in 

groundwater levels in the Upper Floridan aquifer as pumpage 

and climatic stress exceed the ability to replenish groundwater resources by regional groundwater flow, infiltration of 

precipitation, and (or) surface-water leakage. Unseasonably 

low groundwater levels in aquifer-recharge areas stressed 

by dry climatic conditions and pumpage cause a lowering 

of hydraulic gradients and regional groundwater-flow rates 

in downgradient, or outward, directions from the recharge 

area. This hydrologic condition has occurred in the Gulf 

Trough–Apalachicola Embayment region, where dry climatic 

conditions and increased agricultural pumpage lowered 

groundwater levels northwest of the trough-embayment 

region, reducing the potential for groundwater to flow across 

the trough-embayment region to recharge southeastern 

parts of the basin.

Groundwater-level decline affects streamflow by reducing 

hydraulic gradients to streams, thus reducing groundwater 

discharge to (or base flow of) streams. As groundwater levels 

attempt to equilibrate to agricultural groundwater withdrawal 

from the previous growing season, similar effects occur 

during the current growing season, compounding residual 

groundwater-level decline and contributing toward a temporal 

trend of groundwater-level and streamflow decline.

Long-term, groundwater-level decline in the northwestern 

part of the basin portends diminished water-resource potential 

for future development. Excessive groundwater-level decline 

can lower the potentiometric surface of the Upper Floridan 

aquifer below the top of the geohydrologic unit, which reduces 

aquifer transmissivity from that associated with artesian 

conditions, creating water-table and aquifer-dewatering 

conditions. Aquifer dewatering can degrade groundwater 

resources by reducing saturated thickness of the aquifer, 

compacting water-bearing units (subsidence), and collapsing 

solution-enlarged features that once transmitted groundwater 

prior to dewatering. 
48 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

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Appendix. Geohydrologic Data
54 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Florida 

Alachua FLA-BRA-1g 29.63084595 –82.29292489 132 3,167 3,167 

Baker FLA-BA-1g 30.48772863 –82.320641592 124 3,348 3,348 

Baker FLA-BA-2g 30.43913052 –82.292940415 116 902 902 

Baker FLA-BA-4g 30.25993411 –82.272038242 158 722 722 

Bradford FLA-BRA-2g 29.93914104 –82.109527365 165 283 283 

Bradford FLA-BRA-3g 30.13773875 –82.062330567 175 3,171 3,171 

Clay FLA-CL-7g 30.06273955 –82.033128393 175 3,439 3,439 

Columbia FLA-BA-3g 30.16273460 –82.460941324 145 3,043 3,043 

Columbia FLA-CO-1g 30.47522165 –82.59984844 124 4,285 4,285 

Columbia FLA-CO-3g 30.15853306 –82.57484386 164 2,828 2,828 

Columbia FLA-CO-4g 30.06413507 –82.595643121 115 2,929 2,929 

Columbia FLA-CO-9g 30.27272922 –82.618146147 144 3,198 3,198 

Duval FLA-DUV-2g 30.23353829 –82.037331871 85 3,521 3,521 

Gadsden AT180n 30.69019166 –84.805919259 174 — — 

Gadsden City of Quincy 

No. 2g

30.59852791 –84.579910278 150 1,346 — 

Gadsden FLA-GA-10g 30.53849362 –84.785716052 262 4,223 4,223 

Gadsden FLA-GA-11g 30.54439511 –84.614912247 197 4,196 4,196 

Gadsden McDonald No 1n 30.58991623 –84.656028748 284 4,223 — 

Gadsden O-347n 30.68119297 –84.596913653 294 — — 

Gadsden Owenby Farm 

oil testn

30.54186249 –84.561019897 201 7,028 7,028 

Gadsden W-12078n 30.60409575 –84.468208678 198 — — 

Gadsden W-15468n 30.67439477 –84.409607133 210 447 447 

Gadsden W-15795n 30.51959753 –84.464307553 200 402 402 

Gadsden W-1768n 30.58989286 –84.777716913 291 4,240 4,240 

Gadsden W-3276n 30.58419443 –84.614912807 279 — — 

Gadsden W-3504n 30.62769572 –84.414106806 240 692 692 

Gadsden W-3577n 30.55630493 –84.886581421 — — 4,025 

Gadsden W-3776n 30.54659347 –84.780716153 256 — — 

Gadsden W-4404n 30.65629243 –84.690515977 295 — — 

Gadsden W-4925n 30.56189494 –84.604912226 216.60 185 4,185 

Gadsden W-4n 30.60019467 –84.573011883 149.75 898 898 

Gadsden W-5201n 30.60599358 –84.656014246 288.17 467 467 

Gadsden W-7472n 30.55439553 –84.570711213 255 472 472 

Gadsden W-7528n 30.58079655 –84.431606979 230 442 442 

Hamilton FLA-HAM-1g 30.43632120 –82.770651692 128 1,418 1,418 
Appendix. Geohydrologic Data 55

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Florida

FLA-BRA-1g –63 –938 — — — — — —

FLA-BA-1g –196 –1,089 — — — — — —

FLA-BA-2g –272 — — — — — — —

FLA-BA-4g –150 — — — — — — —

FLA-BRA-2g –101 — — — — — — —

FLA-BRA-3g –189 –533 — — — — — —

FLA-CL-7g –226 –642 — — — — — —

FLA-BA-3g –68 –884 — — — — — —

FLA-CO-1g –57 –467 — — — — — —

FLA-CO-3g — –838 — — — — — —

FLA-CO-4g 35 –885 — — — — — —

FLA-CO-9g –22 –828 — — — — — —

FLA-DUV-2g — –764 — — — — — —

AT180n 60 –634 — — — — — —

City of Quincy 

No. 2g

–185 — — — — — — —

FLA-GA-10g 142 –830 — — — — — —

FLA-GA-11g — –988 — — — — — —

McDonald No 1n –286 –696 — — — — — —

O-347n –100 –600 — — — — — —

Owenby Farm 

oil testn

–279 — — — — — — —

W-12078n –219 — — — — — — —

W-15468n –205 — — — — — — —

W-15795n –160 — — — — — — —

W-1768n –80 — — — — — — —

W-3276n –258 — — — — — — —

W-3504n –266 — — — — — — —

W-3577n –135 –845 — — — — — —

W-3776n –208 — — — — — — —

W-4404n –77 — — — — — — —

W-4925n –303 — — — — — — —

W-4n –230 –880 — — — — — —

W-5201n –179 — — — — — — —

W-7472n –180 — — — — — — —

W-7528n –179 — — — — — — —

FLA-HAM-1g 10 –878 — — — — — —
56 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Florida 

Jefferson FLA-JEF-1g 30.37350382 –83.983187522 39 7,913 7,913 

Leon FLA-LN-1g 30.31190320 –84.116591778 30 6,520 6,520 

Leon FLA-LN-2g 30.31190240 –84.194894845 17 10,466 10,466 

Leon FLA-LN-4g 30.38739714 –84.645710696 41 525 525 

Leon Hopkins Plant #3g 30.45519829 –84.397956848 138 406 425 

Leon Lake Talquin coren 30.41130829 –84.599906921 95 422 422 

Leon W-6599n 30.38759714 –84.645010682 61 525 525 

Leon W-6902n 30.51829888 –84.324302177 80 158 158 

Leon W-6937n 30.59269903 –84.05459255 245 248 248 

Leon W-6998n 30.58849858 –84.151296202 237 227 227 

Leon W-7181n 30.58459822 –84.227999085 249 262 262 

Liberty AT095n 30.29119736 –84.982915394 52 — — 

Liberty O-83n 30.37819684 –84.68691154 89 — — 

Liberty O-93n 30.42219591 –84.874915112 173 — — 

Liberty W-15497n 30.59579365 –84.901618615 245 302 302 

Liberty W-15498n 30.57689391 –84.897718089 264 504 504 

Liberty W-15499n 30.58269394 –84.914118434 255 501 501 

Liberty W-15500n 30.50619569 –84.975916911 212 348 348 

Liberty W-15501n 30.54489483 –84.95071781 245 404 404 

Liberty W-6025n 30.42919634 –84.97791626 168 — — 

Liberty W-6901n 30.46909605 –84.979316546 82 527 527 

Madison FLA-MAD-1g 30.40021588 –83.236563825 86 3,333 3,333 

Madison FLA-MAD-2g 30.43021249 –83.358167708 102 5,385 5,385 

Madison FLA-MAD-3g 30.30691821 –83.260663294 84 3,450 3,450 

Suwannee FLA-LAF-1g 30.14462146 –83.230460443 43 4,235 4,235 

Suwannee FLA-SUW-4g 30.28632600 –82.822050206 152 3,572 3,572 

Suwannee FLA-SUW-6g 30.20022274 –83.133157457 85 3,819 3,819 

Suwannee FLA-SUW-7g 30.07382990 –82.826248372 86 3,139 3,139 

Taylor FLA-TAY-4g 29.95521819 –83.439864512 57 4,877 4,877 

Taylor FLA-TAY-7g 30.02801141 –83.812377031 126 3,036 7,502 

Union FLA-UN-2g 30.04193712 –82.531541396 126 3,036 3,036 

Wakulla FLA-WAK-1g 30.22520347 –84.19989402 28 5,766 5,766 

Wakulla FLA-WAK-2g 30.27379969 –84.533206441 85 11,735 11,735 

Wakulla O-75n 30.30019819 –84.682910219 75 — — 
Appendix. Geohydrologic Data 57

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Florida

FLA-JEF-1g 29 –860 — — — — — —

FLA-LN-1g 20 –1,895 — — — — — —

FLA-LN-2g — –1,685 — — — — — —

FLA-LN-4g –87 — — — — — — —

Hopkins Plant #3g 35 — — — — — — —

Lake Talquin coren –289 — — — — — — —

W-6599n –291 — — — — — — —

W-6902n –51 — — — — — — —

W-6937n 8 — — — — — — —

W-6998n 19 — — — — — — —

W-7181n 11 — — — — — — —

AT095n –120 –680 — — — — — —

O-83n –220 — — — — — — —

O-93n –195 –680 — — — — — —

W-15497n –56 — — — — — — —

W-15498n –98 — — — — — — —

W-15499n –69 — — — — — — —

W-15500n –136 — — — — — — —

W-15501n –157 — — — — — — —

W-6025n –50 — — — — — — —

W-6901n –218 — — — — — — —

FLA-MAD-1g — –703 — — — — — —

FLA-MAD-2g 102 –707 — — — — — —

FLA-MAD-3g — –764 — — — — — —

FLA-LAF-1g 43 — — — — — — —

FLA-SUW-4g — –768 — — — — — —

FLA-SUW-6g 55 — — — — — — —

FLA-SUW-7g — –761 — — — — — —

FLA-TAY-4g 57 — — — — — — —

FLA-TAY-7g 11 — — — — — — —

FLA-UN-2g 11 –980 — — — — — —

FLA-WAK-1g — –2,102 — — — — — —

FLA-WAK-2g –110 –1,770 — — — — — —

O-75n –250 –710 — — — — — —
58 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Atkinson 22J001g 31.26687050 –82.9498672485352 217 4,296 4,296 

Ben Hill 18N001e 31.77240372 –83.4084930419922 365 240 240 

Ben Hill 18N002n 31.81101418 –83.4237747192383 378 202 202 

Ben Hill 18N003e 31.79684830 –83.4348831176758 374 215 215 

Ben Hill 19J009n 31.27361107 –83.2694473266602 255 217 217 

Ben Hill 19M001n 31.71546364 –83.2618179321289 357 612 — 

Ben Hill 19M025n 31.74583244 –83.2925033569336 369 310 310 

Ben Hill 19M026n 31.74111176 –83.2602767944336 372 310 310 

Ben Hill 19M027n 31.68972206 –83.3011093139648 354 370 370 

Ben Hill 19M028n 31.70750046 –83.2641677856445 335 716 716 

Ben Hill 19M029b 31.70555496 –83.2750015258789 355 390 390 

Ben Hill 19N003e 31.75657272 –83.2965469360352 361 310 310 

Ben Hill 20M002n 31.71740913 –83.244873046875 354.56 825 825 

Ben Hill 20M003n 31.71768570 –83.244873046875 359.28 739 750 

Ben Hill 20M007e 31.71185303 –83.1682052612305 345 368 368 

Ben Hill 20M008e 31.65879822 –83.2390441894531 334 420 420 

Ben Hill 20N002e 31.83101654 –83.1579284667969 197 390 390 

Ben Hill 20N004e 31.77546120 –83.2201538085937 251 232 232 

Ben Hill 21N002n 31.77601814 –83.1059799194336 262 240 240 

Berrien 19H024n 31.20742035 –83.2548751831055 222.13 333 333 

Berrien 19J002b 31.29944420 –83.2569427490234 252 317 317 

Berrien 19K002e 31.46333122 –83.3467025756836 311 575 — 

Berrien 19K003e 31.46806145 –83.3380966186523 308 500 500 

Berrien 19K004f 31.41388893 –83.2744445800781 319 530 530 

Berrien 20G005e 31.09325600 –83.2118225097656 214 310 310 

Berrien 20H002e 31.15880966 –83.2373733520508 224 340 340 

Berrien 20H003e 31.20964241 –83.2309875488281 239.60 485 485 

Berrien 20J001n 31.36575127 –83.2273788452148 276 500 — 

Berrien 20K002e 31.38380623 –83.22265625 291 550 550 

Berrien 20K005n 31.37991714 –83.2193222045898 285 580 580 

Brantley 29J002g 31.25916672 –82.0552749633789 69 850 850 

Brantley 30H021g 31.1875 –81.9655532836914 75 950 950 

Brantley 30J005g 31.28972244 –81.9499969482422 42 4,513 4,513 

Brantley 31H017g 31.14644432 –81.8580093383789 60 764 — 

Brooks 16D001n 30.73305511 –83.7347259521484 178 180 180 
Appendix. Geohydrologic Data 59

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

22J001g –22 –597 — — — — — —

18N001e 185 — — 185 — — — —

18N002n 248 — 248 218 — — — —

18N003e 164 — — 164 — — — —

19J009n 215 — 215 165 75 — — —

19M001n 169 — 169 67 — — — —

19M025n 189 — 189 129 — — — —

19M026n 232 — 232 162 — — — —

19M027n 164 — 164 104 4 — — —

19M028n 165 — 165 103 15 –263 — —

19M029b 165 — 165 95 –5 — — —

19N003e 221 — 221 181 61 — — —

20M002n 150 — 150 103 10 –275 –365 —

20M003n 149 — 149 103 19 –271 –361 —

20M007e 75 — — 75 –5 — — —

20M008e 104 — — 104 –6 — — —

20N002e 99 — — 99 –18 — — —

20N004e 121 — — 121 41 — — —

21N002n 142 — 142 92 52 — — —

19H024n — — — — — — — —

19J002b 82 — 82 — — — — —

19K002e — — — –129 — — — —

19K003e — — — –162 — — — —

19K004f 37 — 37 –54 –161 — — —

20G005e — — — –16 — — — —

20H002e — — — –16 — — — —

20H003e 30 — 30 –20 –205 — — —

20J001n 30 — 30 –73 –189 — — —

20K002e 1 — 1 –119 –199 — — —

20K005n 16 — 16 –113 –237 — — —

29J002g –511 — — — — — — —

30H021g –550 — — — — — — —

30J005g –478 –843 — — — — — —

31H017g –555 — — — — — — —

16D001n 93 — 93 73 — — — —
60 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Brooks 16D003n 30.71027756 –83.6811141967773 192 220 220 

Brooks 16D004n 30.66416740 –83.6369476318359 105 147 147 

Brooks 16D006e 30.74214172 –83.6626586914062 196 220 220 

Brooks 16D007n 30.68527794 –83.6577758789062 135 196 196 

Brooks 16D010n 30.67936516 –83.6868286132812 170 180 292 

Brooks 16E001n 30.83186150 –83.7171096801758 225 226 226 

Brooks 16E002n 30.85213661 –83.7348861694336 232 231 231 

Brooks 16E004n 30.78111076 –83.6697235107422 138 153 153 

Brooks 16E006e 30.75805473 –83.6719436645508 193 225 225 

Brooks 16F003n 30.99629974 –83.7201690673828 245 265 265 

Brooks 16F006e 30.88388824 –83.7074966430664 228 240 240 

Brooks 16F009e 30.88074875 –83.6362762451172 230 230 230 

Brooks 16F016e,f 30.94055557 –83.7350006103516 220 748 748 

Brooks 16F017g 30.94056129 –83.7350006103516 200 335 335 

Brooks 16G009e 31.01768875 –83.7229461669922 251.83 300 300 

Brooks 16G042e,f 31.01638794 –83.7311019897461 260 856 856 

Brooks 16Q004n 31.03417015 –83.6277770996094 225 482 482 

Brooks 17D001e 30.69361115 –83.5366668701172 203 205 205 

Brooks 17D002n 30.72138977 –83.6102752685547 155 200 200 

Brooks 17D008n 30.68222237 –83.5202789306641 204 201 201 

Brooks 17E004e 30.82611084 –83.5961074829102 230 250 250 

Brooks 17E008e 30.80277824 –83.5580520629883 142 200 200 

Brooks 17E009e 30.86833382 –83.5250015258789 212 218 218 

Brooks 17E012n 30.78380775 –83.5640487670898 183 304 304 

Brooks 17E027e 30.79972267 –83.6005554199219 165 200 200 

Brooks 17F007e 30.91685867 –83.5798873901367 202 186 186 

Brooks 17F008e 30.89833260 –83.5272216796875 238 250 250 

Brooks 17F009n 30.95574570 –83.6110000610352 200 3,850 3,850 

Brooks 17F013n 30.98638916 –83.6144409179687 161 821 821 

Brooks 17G003n 31.00769043 –83.5143280029297 257 228 — 

Brooks 18D001e 30.66222191 –83.495002746582 163 200 200 

Brooks 18D002n 30.69305611 –83.4769439697266 194 310 310 

Brooks 18E001e 30.81908607 –83.4893264770508 244 205 205 

Brooks 18E002n 30.80305481 –83.4738922119141 180 156 156 

Brooks 18E014n 30.86936378 –83.3945999145508 173 180 180 
Appendix. Geohydrologic Data 61

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

16D003n 72 — 72 62 — — — —

16D004n 73 — 73 54 — — — —

16D006e 106 — 106 76 — — — —

16D007n 70 — 70 53 — — — —

16D010n 90 — 90 65 –48 — — —

16E001n 125 — 125 80 — — — —

16E002n 147 — 147 117 — — — —

16E004n 98 — 98 68 — — — —

16E006e 108 — 108 83 — — — —

16F003n 130 — 130 75 — — — —

16F006e 138 — 138 108 — — — —

16F009e 60 — 60 40 — — — —

16F016e,f — — 100 71 –43 –524 — —

16F017g 57 — — — — — — —

16G009e 162 — 162 102 — — — —

16G042e,f — –490 — 61 –104 –490 — —

16Q004n 285 — — — — — — —

17D001e 118 — 118 98 — — — —

17D002n 65 — 65 55 — — — —

17D008n 84 — 84 74 — — — —

17E004e 70 — 70 50 — — — —

17E008e 62 — — 62 — — — —

17E009e 102 — 102 42 — — — —

17E012n 88 — 88 33 –7 — — —

17E027e 105 — — 105 — — — —

17F007e 102 — — 102 — — — —

17F008e 138 — 138 88 — — — —

17F009n — –675 — — — –675 — —

17F013n 100 –622 100 86 –46 –622 — —

17G003n 117 — 117 — — — — —

18D001e 83 — 83 63 — — — —

18D002n 94 — 94 19 –114 — — —

18E001e 129 — 129 74 — — — —

18E002n 120 — 120 60 — — — —

18E014n 141 — 141 111 — — — —
62 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Brooks 18F006e,f 30.94435883 –83.4996032714844 223 296 296 

Brooks 18F007e 30.88463974 –83.4509887695312 238 220 220 

Brooks 18F008e 30.93027687 –83.4822235107422 175 182 182 

Brooks 18F023n 30.87853050 –83.4293212890625 224 236 238 

Charlton 30E010g 30.79333305 –81.9933319091797 25 4,578 4,578 

Clinch 23F001g 30.92854309 –82.7979202270508 167 3,848 3,848 

Clinch 23G005g 31.01944351 –82.8016662597656 182 570 570 

Clinch 23H001g 31.15187263 –82.8637542724609 205 4,232 4,232 

Clinch 24E002g 30.85576820 –82.7212448120117 139 4,088 4,088 

Clinch 24F006g 30.97722244 –82.7083358764648 162 3,410 3,410 

Clinch 26E001g 30.78355408 –82.4406814575195 110 4,588 4,588 

Coffee 20K017g 31.45138931 –83.1350021362305 280 4,340 4,340 

Coffee 22M004g 31.71268654 –82.8940353393555 308 4,130 4,130 

Coffee 22M005g 31.68546677 –82.8887557983398 260 4,151 4,151 

Coffee 22M006k 31.71546555 –82.897087097168 295 3,556 3,556 

Coffee 22N004g 31.76129723 –82.9401473999023 193 — 1,903 

Coffee 23L020g 31.52416992 –82.8555603027344 245 650 650 

Coffee 23M001g 31.70610809 –82.8499984741211 300 1,605 1,605 

Coffee 24L005g 31.51583290 –82.6350555419922 195 — — 

Colquitt 14G010n 31.07907486 –83.8948974609375 274 400 400 

Colquitt 14G016g 31.06879807 –83.9612808227539 303 385 — 

Colquitt 14H001a,e,g 31.18490791 –83.9012832641602 287 650 4,916 

Colquitt 14H006g 31.22101784 –83.9921188354492 280 426 426 

Colquitt 14H008n 31.13629723 –83.9579544067383 307 850 850 

Colquitt 14H013n 31.19796181 –83.9398956298828 290 460 460 

Colquitt 14H026e,g 31.23777771 –83.913330078125 348 6,901 6,901 

Colquitt 14J011n 31.31907082 –83.9454574584961 360 240 240 

Colquitt 14J036e 31.29833412 –83.8988876342773 350 1,142 1,142 

Colquitt 15G044g 31.04527855 –83.7694473266602 238 835 835 

Colquitt 15H007n 31.16768646 –83.7860107421875 317 752 1,000 

Colquitt 15H033e,g 31.15851974 –83.8323974609375 305 780 797 

Colquitt 15H038e,f 31.23277855 –83.82861328125 306 840 840 

Colquitt 15H066e 31.21805573 –83.8152770996094 290 1,321 1,321 

Colquitt 15H067e,g 31.21694374 –83.815559387207 290 790 790 

Colquitt 15J003n 31.31879425 –83.8690643310547 340 380 380 
Appendix. Geohydrologic Data 63

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

18F006e,f 129 — 129 76 — — — —

18F007e 168 — 168 148 — — — —

18F008e 85 — — 85 — — — —

18F023n 166 — 166 141 — — — —

30E010g –385 — — — — — — —

23F001g –173 –1,043 — — — — — —

23G005g –176 — — — — — — —

23H001g –109 — — — — — — —

24E002g –195 — — — — — — —

24F006g –233 –1,143 — — — — — —

26E001g –220 — — — — — — —

20K017g –119 –1,005 — — — — — —

22M004g –140 –946 — — — — — —

22M005g –173 –955 — — — — — —

22M006k –100 –935 –65 –176 –765 –935 — –1,325

22N004g –97 –607 — — — — — —

23L020g –155 — — — — — — —

23M001g –175 –960 — — — — — —

24L005g –250 — — — — — — —

14G010n — — 14 — — — — —

14G016g — — 20 — — — — —

14H001a,e,g –103 –783 — –103 –173 –783 — –888

14H006g 11 — — 11 –21 — — —

14H008n –158 — — — — — — —

14H013n 22 — — — — — — —

14H026e,g –62 –602 — –62 –152 –602 — —

14J011n 184 — — — — — — —

14J036e 34 –464 — 34 –348 –464 –765 —

15G044g 62 –476 96 62 –12 –555 — —

15H007n –143 — — — — — — —

15H033e,g –107 — — –107 –276 — — —

15H038e,f –90 — — –91 –135 — — —

15H066e — –870 — — –686 –870 — —

15H067e,g –106 –349 65 –106 –145 –349 — —

15J003n 13 — — — — — — —
64 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Colquitt 15J013n 31.27879524 –83.8168411254883 370 640 640 

Colquitt 16G043g 31.10638809 –83.7372207641602 270 770 770 

Colquitt 16G044e 31.10638809 –83.7372207641602 270 908 908 

Colquitt 16H014e,g 31.18768501 –83.7457275390625 305 579 579 

Colquitt 16H077g 31.13999939 –83.663330078125 245 868 868 

Colquitt 16H078e 31.13999939 –83.663330078125 245 870 870 

Colquitt 16J002n 31.26712990 –83.6857299804687 370 705 817 

Colquitt 16J004e,f 31.26194382 –83.6727752685547 330 1,213 1,213 

Colquitt 17J015e,f,g 31.31129646 –83.5776672363281 333 1,017 1,047 

Cook 17G008n 31.12102127 –83.5354385375977 225.68 330 — 

Cook 17H013n 31.19166756 –83.5208358764648 200 140 140 

Cook 17H025e 31.22083282 –83.5041656494141 222 300 300 

Cook 18G018e,f 31.04602623 –83.3943252563477 244.42 308 — 

Cook 18G019g 31.04444504 –83.3986129760742 231 230 230 

Cook 18H002n 31.14269066 –83.4240493774414 238.14 386 — 

Cook 18H003e 31.22296906 –83.4046020507812 274.22 291 — 

Cook 18H005n 31.13796997 –83.4259948730469 240.82 375 — 

Cook 18H008e 31.12750053 –83.4188919067383 230.12 359 359 

Cook 18H015g,l 31.16852379 –83.4334945678711 236.29 407 — 

Cook 18H016e 31.13713455 –83.4340515136719 241.42 865 865 

Cook 18H033g 31.14046860 –83.4282150268555 240.11 393 393 

Cook 18H036e 31.21102333 –83.4490509033203 263.77 210 223 

Cook 18H040e 31.23583412 –83.4700012207031 268 315 320 

Cook 18J001n 31.25657654 –83.4629364013672 263.61 288 — 

Cook 18J003e 31.27324295 –83.4615478515625 286.12 501 — 

Cook 18J011f 31.27083397 –83.4661102294922 291.26 382 382 

Cook 18J027e,f 31.33472252 –83.4408340454102 298 580 580 

Cook 18J046e 31.28858948 –83.4926910400391 295 360 360 

Crisp 15N001n 31.82684326 –83.7698974609375 364 — 5,008 

Crisp 15P001n 31.96017456 –83.7748947143555 340 540 816 

Crisp 15P003n 31.93406296 –83.764892578125 317 265 265 

Crisp 15P007n 31.97045136 –83.7746124267578 316 600 677 

Crisp 15P020n 31.98888969 –83.788330078125 287 75 75 

Crisp 15Q011n 32.00933838 –83.7918395996094 336 — 255 

Crisp 15Q016n 32.02999878 –83.8522186279297 330 170 170 
Appendix. Geohydrologic Data 65

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

15J013n –86 — — — — — — —

16G043g 48 –396 — — — — — —

16G044e — –591 — — –120 –591 — —

16H014e,g –195 — — –135 –233 — — —

16H077g 65 –497 — — — — — —

16H078e — — — — –81 –588 — —

16J002n –95 — — –95 –139 –334 — —

16J004e,f –144 –740 — –144 –176 –740 — —

17J015e,f,g –290 — — –290 — — — —

17G008n 86 — 86 26 — — — —

17H013n 82 — 82 — — — — —

17H025e 22 — 22 –18 — — — —

18G018e,f –8 — 91 6 — — — —

18G019g 31 — 101 18 — — — —

18H002n 67 — 67 40 — — — —

18H003e 144 — 144 — — — — —

18H005n 59 — 59 32 — — — —

18H008e 11 — 11 –10 — — — —

18H015g,l 52 — 79 50 — — — —

18H016e 47 –286 81 39 –178 –624 — —

18H033g 40 — 117 29 — — — —

18H036e 77 — 77 — — — — —

18H040e 38 — 38 –30 — — — —

18J001n 30 — 30 –17 — — — —

18J003e 36 — 36 26 –174 — — —

18J011f 49 — 49 –29 — — — —

18J027e,f –76 — –76 — — — — —

18J046e 55 — 55 — — — — —

15N001n — –41 — — — — — —

15P001n 241 30 — — — — — —

15P003n 227 — — — — — — —

15P007n 281 61 — — — — — —

15P020n 242 — — — — — — —

15Q011n 236 106 — — — — — —

15Q016n 280 162 — — — — — —
66 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Crisp 16P001n 31.93406487 –83.7318344116211 363 290 290 

Crisp 16P006n 31.91693878 –83.6650009155273 359 260 260 

Crisp 16P007n 31.96100807 –83.7304458618164 423 610 — 

Crisp 17P002n 31.93212128 –83.6179428100586 460 310 — 

Decatur 07D014n 30.71805573 –84.7794418334961 280 795 830 

Decatur 08D093n 30.74833298 –84.6719436645508 300 300 — 

Decatur 08E018b,i 30.80852318 –84.6513061523437 87 — 6,152 

Decatur 09E002g 30.79166985 –84.5555648803711 302 442 442 

Decatur 09E517h,m 30.76324654 –84.5365829467773 287 486 486 

Decatur 09F016n 30.89268875 –84.5699157714844 130 485 — 

Decatur 09F019a 30.97879791 –84.5315780639648 122 3,717 3,717 

Decatur 10D002l,m 30.74741554 –84.4868545532227 311 905 — 

Decatur 10D021l,m 30.70833397 –84.3886108398437 270 4,195 4,195 

Decatur 10F160n 30.91611099 –84.4677810668945 140 420 420 

Decatur 10G001n 31.02296448 –84.3871307373047 141 160 160 

Echols 22D002g 30.73687935 –82.9229125976562 146 3,916 3,916 

Echols 22D003g 30.68305588 –82.8786087036133 181 3,953 3,953 

Echols 22E001g 30.75826645 –82.9098587036133 171 — 4,185 

Echols 23C001g 30.61632729 –82.7826309204102 135 4,003 4,003 

Echols 27D001g 30.69388962 –82.2947235107422 132 4,062 4,062 

Grady 11F083n 30.88611031 –84.3194351196289 238 482 482 

Grady 12E064n 30.87471962 –84.1761016845703 271 427 — 

Grady 12E046l,m 30.76297188 –84.220458984375 165 226 226 

Grady 12F018e 30.87528038 –84.1916656494141 181 1,206 1,206 

Grady 12F020n 30.87685776 –84.2060089111328 238 650 — 

Grady 12F022n 30.87769127 –84.2118453979492 239.36 586 586 

Grady 12F025k 30.87602425 –84.2176818847656 208 540 540 

Grady 12F030k 30.87741280 –84.2107315063477 241 671 870 

Grady 12F035n 30.98296547 –84.1601791381836 285 595 595 

Grady 12F036e,k 30.87657928 –84.2143478393555 204.54 467 971 

Grady 12G028n 31.00388908 –84.2055587768555 307 550 550 

Irwin 18L002n 31.54879761 –83.3937683105469 322 280 — 

Irwin 18L029n 31.60693932 –83.4593963623047 352 204 204 

Irwin 18L030n 31.61333084 –83.4772033691406 330 200 200 

Irwin 18M002n 31.72934914 –83.4146041870117 367 230 — 
Appendix. Geohydrologic Data 67

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

16P001n 231 — — — — — — —

16P006n 309 — — — — — — —

16P007n 329 80 — — — — — —

17P002n 280 — — — — — — —

07D014n — –520 — — — — — —

08D093n –50 –475 — — — — — —

08E018b,i 87 –258 — 87 — –258 –723 —

09E002g –20 — — –20 –135 — — —

09E517h,m –135 — –48 –135 — — –748 —

09F016n 51 –175 — — — — — —

09F019a — — — — — — — –748

10D002l,m –287 — –123 –287 –388 — — —

10D021l,m –320 –955 –190 –320 –630 –955 –1,305 —

10F160n 23 –290 — — — — — —

10G001n 56 — — — — — — —

22D002g –69 –727 — — — — — —

22D003g — –663 — — — — — —

22E001g –28 –732 — — — — — —

23C001g –30 –771 — — — — — —

27D001g –124 –756 — — — — — —

11F083n –167 — — — — — — —

12E064n — — –63 — — — — —

12E046l,m –45 — –5 –45 — — — —

12F018e –261 — –78 –261 — –931 — —

12F020n –261 — — –261 — — — —

12F022n –255 — 20 –255 — — — —

12F025k — — –50 — — — — —

12F030k –268 — –53 –268 — — — —

12F035n –187 — 25 –187 — — — —

12F036e,k –266 — –41 –266 — — — —

12G028n 7 — 167 7 — — — —

18L002n 162 — 162 122 — — — —

18L029n 262 — 262 192 — — — —

18L030n 240 — 240 170 — — — —

18M002n 227 — 227 177 — — — —
68 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Irwin 18M021n 31.64332962 –83.4535980224609 358 256 256 

Irwin 18M022n 31.63083076 –83.3764038085937 371 402 402 

Irwin 19L034n 31.58611107 –83.2538986206055 313 280 280 

Irwin 19L035n 31.50583076 –83.2791976928711 330 340 340 

Irwin 19L036n 31.53888893 –83.2538986206055 328 310 310 

Irwin 19M023n 31.63861084 –83.2758026123047 357 301 301 

Irwin 19M024n 31.65971947 –83.3581008911133 380 300 300 

Irwin 20L002e 31.56296921 –83.1801528930664 300 380 — 

Irwin 20L003n 31.59519005 –83.2473754882812 338 637 — 

Irwin 20L026n 31.59499931 –83.1750030517578 284 280 280 

Irwin 20L027e 31.60778046 –83.2489013671875 353 696 — 

Irwin 21L001e 31.54880333 –83.0804290771484 292 620 — 

Irwin 21M019n 31.62999916 –83.0556030273437 335 494 494 

Lowndes 18F029g 30.93667030 –83.4063873291016 243 5,246 5,246 

Lowndes 19E001n 30.82881355 –83.2815399169922 215 408 408 

Lowndes 19E004b 30.82909012 –83.2823715209961 211.30 367 818 

Lowndes 19E005n 30.86158943 –83.2837600708008 226.33 348 348 

Lowndes 19E006n 30.85992432 –83.2857055664062 213.88 334 339 

Lowndes 19E007n 30.86242294 –83.2884826660156 195 230 230 

Lowndes 19E008n 30.84047890 –83.2920989990234 191 126 — 

Lowndes 19E011d 30.82520294 –83.2804260253906 197 400 — 

Lowndes 19E014n 30.79159164 –83.262092590332 197 200 200 

Lowndes 19E017n 30.80659103 –83.2990417480469 223 251 251 

Lowndes 19E018n 30.84103394 –83.2990417480469 195 220 228 

Lowndes 19E026n 30.83464623 –83.3151550292969 192 213 213 

Lowndes 19E043d,g 30.86381149 –83.2909851074219 178 965 1,014 

Lowndes 19E082d 30.83964539 –83.3209838867187 203 193 193 

Lowndes 19E101d 30.87490082 –83.2882766723633 206 — — 

Lowndes 19F020g 30.98297310 –83.3698806762695 225 360 363 

Lowndes 19F099g 30.90603447 –83.2809829711914 191 — 5,004 

Lowndes 19F140g 30.99028015 –83.2522201538086 157 8,550 8,550 

Lowndes 20E043g 30.84833145 –83.1877822875977 201 4,985 4,985 

Lowndes 20F004g 30.97770119 –83.2040405273437 224 342 — 

Lowndes 21E006g 30.85693932 –83.0563888549805 171 5,052 5,052 

Mitchell 12H008n 31.22434807 –84.215461730957 165 341 346 
Appendix. Geohydrologic Data 69

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

18M021n 226 — 226 204 — — — —

18M022n 169 — 169 139 29 — — —

19L034n 143 — 143 103 — — — —

19L035n 160 — 160 90 — — — —

19L036n 148 — 148 58 — — — —

19M023n 167 — 167 117 — — — —

19M024n 200 — 280 130 — — — —

20L002e 70 — 70 0 — — — —

20L003n 248 — 248 128 –32 — — —

20L026n 104 — — 104 34 — — —

20L027e 153 –343 153 108 42 — — —

21L001e –98 — –98 –308 — — — —

21M019n 30 — 30 –85 — — — —

18F029g 66 –660 — — — — — —

19E001n 60 — — 60 — — — —

19E004b 106 –549 106 21 –159 –549 — —

19E005n 70 — 70 19 –101 — — —

19E006n 27 — 27 11 — — — —

19E007n 30 — 30 10 — — — —

19E008n 92 — 92 70 — — — —

19E011d 7 — 7 –18 –183 — — —

19E014n 27 — 27 17 — — — —

19E017n — — 0 –6 — — — —

19E018n 82 — 82 59 — — — —

19E026n 69 — 69 42 — — — —

19E043d,g 41 –538 41 –2 –198 –538 — —

19E082d 80 — 80 48 — — — —

19E101d 46 — 46 13 –234 — — —

19F020g 23 — — — — — — —

19F099g — –605 — — — — — —

19F140g — –606 — — — — — —

20E043g –12 –428 — — — — — —

20F004g 95 — — — — — — —

21E006g –38 –591 — — — — — —

12H008n 115 –125 — — — — — —
70 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Mitchell 13H004n 31.17193794 –84.0455627441406 319 316 316 

Mitchell 13J003n 31.26296043 –84.0210113525391 372 575 575 

Mitchell 13J009n 31.32250023 –84.053337097168 272 497 497 

Mitchell 13J010n 31.32268143 –84.0532379150391 270 43 48 

Mitchell 13J012n 31.30624962 –84.0525817871094 287 — — 

Mitchell 13K001n 31.43267822 –84.02490234375 275 382 386 

Pierce 28J010g 31.34138870 –82.1488876342773 108 875 875 

Pierce 28J011g 31.27222252 –82.149169921875 75 810 810 

Thomas 10G314n 31.11244392 –84.4037475585937 140 370 370 

Thomas 13E002e 30.96722221 –84.0430526733398 264 423 423 

Thomas 13E010f 30.75297165 –84.0265579223633 195 204 — 

Thomas 13F019e 30.88352394 –84.0535049438477 228 240 — 

Thomas 13F023e 30.99963188 –84.1187896728516 275 408 — 

Thomas 13F024g 30.98685455 –84.0774002075195 230 446 — 

Thomas 13F025f 30.97111130 –84.0511093139648 271 637 637 

Thomas 13G003e 31.04129791 –84.0696182250977 304 905 — 

Thomas 13G006e,f,i 31.07129669 –84.0918426513672 345 832 1,560 

Thomas 13G019e 31.07097244 –84.0953521728516 330 — 1,439 

Thomas 13H008b,f,i 31.14129639 –84.0701751708984 330 7,490 7,490 

Thomas 14E016g,i 30.83361053 –83.9823913574219 258 1,635 1,635 

Thomas 14E047e,g 30.78638840 –83.9622192382812 267 6,672 6,672 

Thomas 14F015e,g 30.92435646 –83.9712829589844 238 325 — 

Thomas 15E017f 30.81083298 –83.7563858032227 205 904 904 

Thomas 15F016f 30.98916626 –83.8088912963867 238 1,206 1,206 

Thomas 15G011e,g 31.01157761 –83.8685073852539 252 383 385 

Thomas 15G043g 31.00194359 –83.8272247314453 248 801 801 

Tift 15K021a,b 31.45750046 –83.8333282470703 355 585 585 

Tift 16J005e 31.35833359 –83.6483306884766 295 — — 

Tift 16J031n 31.33416748 –83.6399993896484 273 1,170 1,170 

Tift 16K010c 31.38444519 –83.628059387207 325 352 352 

Tift 17J004f 31.33944511 –83.5936126708984 325 705 705 

Tift 17J042d,e 31.35416603 –83.5833282470703 324 490 490 

Tift 17K007n 31.49333382 –83.5458297729492 332 260 260 

Tift 17K038c,e 31.48388863 –83.529167175293 392 500 500 

Tift 17K111n 31.44444466 –83.5930557250977 338 350 350 
Appendix. Geohydrologic Data 71

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

13H004n 12 — — — — — — —

13J003n 130 — — — — — — —

13J009n 227 –167 — — — — — —

13J010n 224 — — — — — — —

13J012n 204 — — — — — — —

13K001n 218 –39 — — — — — —

28J010g –424 — — — — — — —

28J011g –420 — — — — — — —

10G314n 75 –210 — — — — — —

13E002e –131 — 29 –131 — — — —

13E010f 35 — — 35 0 — — —

13F019e — — 78 — — — — —

13F023e — — 40 — — — — —

13F024g –170 — -8 –170 — — — —

13F025f –241 — — –241 — — — —

13G003e –201 — — –201 -499 — — —

13G006e,f,i –139 –470 13 –139 –241 –451 — —

13G019e — –615 60 –114 –465 –615 — —

13H008b,f,i –40 –460 100 –40 –65 –460 –620 –895

14E016g,i 67 –767 213 67 –36 –767 — —

14E047e,g — –618 — — — –618 –1,018 –1,368

14F015e,g –48 — — –48 — — — —

15E017f 120 –582 135 79 –75 –582 — —

15F016f 109 –552 143 109 –38 –552 — —

15G011e,g –70 — 30 –70 — — — —

15G043g 89 –537 142 89 –25 –537 — —

15K021a,b 85 — 220 85 15 — — —

16J005e — — — — — — — —

16J031n –28 — — –28 –95 –357 — —

16K010c 17 — 199 17 — — — —

17J004f –36 — — –36 -88 — — —

17J042d,e –146 — — –146 — — — —

17K007n 202 — — 202 — — — —

17K038c,e 138 — — 138 — — — —

17K111n 168 — — 168 18 — — —
72 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Tift 17L001n 31.54935074 –83.5346069335937 370 260 — 

Tift 17L002n 31.50416756 –83.5016632080078 390 350 350 

Tift 17L003n 31.50333405 –83.5430526733398 350 208 208 

Tift 17L004n 31.51861191 –83.559440612793 371 260 260 

Tift 17L005n 31.56944466 –83.575553894043 360 170 170 

Tift 17L006n 31.52194405 –83.5777740478516 352 210 210 

Tift 17L010n 31.54194450 –83.5280532836914 355 408 408 

Tift 17L011n 31.52888870 –83.5727767944336 360 320 320 

Tift 17L012n 31.56212616 –83.6093368530273 311 280 — 

Tift 17L014n 31.50129509 –83.6215591430664 334 250 — 

Tift 17L015n 31.51749992 –83.5663909912109 360 220 220 

Tift 17L062c,e 31.50416756 –83.5541687011719 395 — — 

Tift 18K001f 31.41435242 –83.4898834228516 352 610 — 

Tift 18K003n 31.54796410 –83.4537734985352 322 540 — 

Tift 18K073b,e 31.45138931 –83.4944458007812 330 501 501 

Tift 18L006n 31.50333405 –83.4225006103516 320 250 250 

Tift 18L012n 31.52694511 –83.4250030517578 300 220 220 

Tift 18L031n 31.53166580 –83.4861145019531 335 270 270 

Turner 16M001n 31.73712349 –83.6512756347656 399 350 — 

Turner 16M002n 31.68388939 –83.6447219848633 397 220 220 

Turner 16M008n 31.65601349 –83.6315536499023 410 375 — 

Turner 16M010n 31.70517921 –83.6565551757812 430 485 — 

Turner 16M011n 31.70656967 –83.6546096801758 430 648 — 

Turner 16M013b 31.69712448 –83.6465606689453 430 650 — 

Turner 16M020n 31.67818832 –83.6387329101562 404 501 — 

Turner 16M021b 31.69545746 –83.640998840332 402 770 770 

Turner 16M022n 31.67073631 –83.636833190918 380 525 525 

Turner 16M052n 31.66500092 –83.7344436645508 370 320 320 

Turner 16M053n 31.62833405 –83.7186126708984 390 240 240 

Turner 16M054n 31.63611031 –83.7236099243164 402 402 402 

Turner 16M055n 31.66861153 –83.6324996948242 388 250 250 

Turner 16M056n 31.66444397 –83.7291641235352 395 270 270 

Turner 16N015n 31.75305557 –83.6816635131836 386 225 225 

Turner 16N016n 31.75138855 –83.6630554199219 360.38 565 565 

Turner 17L008n 31.61018181 –83.5437774658203 352 220 — 
Appendix. Geohydrologic Data 73

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

17L001n 170 — 200 170 — — — —

17L002n 150 — 250 150 — — — —

17L003n 170 — 280 170 — — — —

17L004n 191 — — 191 — — — —

17L005n 270 — — 270 — — — —

17L006n 192 — 292 192 — — — —

17L010n 179 — — 179 69 — — —

17L011n 180 — 300 180 — — — —

17L012n 201 — — — — — — —

17L014n 254 — 234 174 — — — —

17L015n 190 — 300 190 — — — —

17L062c,e 195 — — 195 — — — —

18K001f –60 — –6 –46 –171 — — —

18K003n 22 — — 22 –138 — — —

18K073b,e 74 — 206 74 –66 — — —

18L006n 140 — — 140 — — — —

18L012n 105 — — 105 — — — —

18L031n 205 — — 205 — — — —

16M001n 199 — — 199 — — — —

16M002n 227 — — 227 — — — —

16M008n 190 — 220 190 110 — — —

16M010n 150 — — 150 30 — — —

16M011n 302 — — 169 12 — — —

16M013b 218 — — 218 40 — — —

16M020n 235 — — 235 –51 — — —

16M021b 150 — — 150 17 –268 — —

16M022n 219 — — 219 –90 — — —

16M052n 190 — 190 165 — — — —

16M053n 210 — 210 180 — — — —

16M054n 167 — — 167 — — — —

16M055n 228 — — 228 — — — —

16M056n 243 — — 243 — — — —

16N015n 281 — — 281 — — — —

16N016n 226 — — 226 –110 — — —

17L008n 242 — 242 198 — — — —
74 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Turner 17L009n 31.61240578 –83.5368347167969 335 220 — 

Turner 17L063n 31.60916710 –83.5749969482422 325 130 130 

Turner 17L064n 31.59722137 –83.5963897705078 358 260 260 

Turner 17L065n 31.61305618 –83.5008316040039 330 336 336 

Turner 17M007n 31.71462440 –83.5712738037109 382 242 — 

Turner 17M043n 31.67944527 –83.6216659545898 390 270 270 

Turner 17M045n 31.67944527 –83.6202774047852 377 470 470 

Turner 17M046n 31.72138977 –83.5430526733398 380 220 220 

Turner 17M047n 31.67138863 –83.5919418334961 400 235 235 

Turner 17M048n 31.63972282 –83.616943359375 385 250 250 

Turner 17N001n 31.78573608 –83.5073852539062 382 194 194 

Turner 17N002n 31.81323433 –83.6007232666016 365 51 260 

Turner 18N011n 31.83555603 –83.4974975585937 351 220 220 

Turner 18N012n 31.82250023 –83.4888916015625 350 176 176 

Turner 33H016n 31.12717438 –81.5550994873047 365 780 780 

Ware 24P010g 31.97972298 –82.6466674804687 121 701 701 

Ware 27G003g 31.11855698 –82.2654037475586 150 1,856 1,970 

Wilcox 17P008n 31.96805573 –83.5469436645508 405 160 160 

Wilcox 17P009n 31.91361046 –83.5572204589844 371 196 196 

Wilcox 17P010n 31.95277786 –83.5752792358398 351 — 200 

Wilcox 17P011n 31.98444366 –83.5758361816406 352 — 56 

Wilcox 17P012n 31.92861176 –83.5008316040039 365 175 175 

Wilcox 17P013n 31.96361160 –83.5663909912109 372 225 225 

Wilcox 17Q020l 32.11294937 –83.5037841796875 273 293 293 

Wilcox 17Q021l 32.10972214 –83.5038909912109 278 210 210 

Wilcox 18P001b,g 31.95045471 –83.4576644897461 367 335 — 

Wilcox 18P006n 31.97888947 –83.4944458007812 415 255 255 

Wilcox 20N005n 31.84851646 –83.2082061767578 167 642 — 

Wilcox 20N010n 31.86722183 –83.2286148071289 292 173 173 

Wilcox 20N017n 31.84693909 –83.2133026123047 170 — — 

Worth 14J003n 31.33490372 –83.9640655517578 382 280 280 

Worth 14J006c 31.37138939 –83.9397201538086 412 250 250 

Worth 14K001f 31.44434738 –83.8782348632812 430 454 454 

Worth 14K003n 31.46351242 –83.9149017333984 431 370 370 

Worth 14K005e 31.40768051 –83.9662933349609 409 — 280 
Appendix. Geohydrologic Data 75

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

17L009n 203 — — 203 — — — —

17L063n 205 — 205 — — — — —

17L064n 238 — — 238 128 — — —

17L065n 215 — — 215 102 — — —

17M007n 122 — — 122 — — — —

17M043n 230 — — 230 — — — —

17M045n 257 — — 257 27 — — —

17M046n 170 — — 170 — — — —

17M047n 250 — — 260 — — — —

17M048n 245 — — 245 — — — —

17N001n 242 — 282 242 — — — —

17N002n 343 — — — — — — —

18N011n 251 — — 251 — — — —

18N012n 284 — — 284 — — — —

33H016n 175 — — 175 –130 — — —

24P010g –349 — — — — — — —

27G003g –456 –840 — — — — — —

17P008n 265 — — 265 — — — —

17P009n 281 — — 281 — — — —

17P010n 271 — — 271 — — — —

17P011n 296 — — 296 — — — —

17P012n 213 — — 213 — — — —

17P013n 252 — — 252 — — — —

17Q020l 153 — — 153 — — — —

17Q021l 178 — — 178 — — — —

18P001b,g 190 — — 190 102 — — —

18P006n 295 — — 295 — — — —

20N005n 141 –283 — 110 52 –283 –356 —

20N010n 212 — — 212 — — — —

20N017n 95 — — 95 — — — —

14J003n 162 — — — — — — —

14J006c 202 — — 202 — — — —

14K001f 226 — — 226 162 — — —

14K003n 238 60 — 238 — 60 — —

14K005e 187 — — 187 — — — —
76 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

County Well

name

Latitude

(decimal

degrees)

Longitude

(decimal

degrees)

Land-surface

altitude

(feet above

NAVD 88)

Well depth

(feet)

Hole depth

(feet)

Georgia 

Worth 14K053n 31.40830612 –83.9116363525391 385 500 600 

Worth 14K054n 31.49323273 –83.9615707397461 315 465 465 

Worth 14K055n 31.49323273 –83.9615707397461 315 83 87 

Worth 14K058n 31.49323082 –83.9615707397461 315 — — 

Worth 14L002c,e 31.54990005 –83.8776779174805 430 460 460 

Worth 14L003b,e 31.58350945 –83.9407348632812 335 — 315 

Worth 14L007e 31.55156708 –83.9162902832031 355 180 180 

Worth 14L009n 31.58323288 –83.9182357788086 288 238 238 

Worth 14L012n 31.55073357 –83.9212875366211 355 — — 

Worth 14L030n 31.54601097 –83.8818435668945 390 — 214 

Worth 14M001n 31.64295387 –83.9157333374023 263 215 215 

Worth 14M008n 31.71850967 –83.888786315918 289 102 102 

Worth 14N001n 31.82795143 –83.9218444824219 278 325 325 

Worth 14N014n 31.76055527 –83.9191665649414 250 110 110 

Worth 15J015e 31.36518288 –83.8551788330078 400 — 320 

Worth 15J017b,e 31.37240410 –83.8551788330078 412 — 300 

Worth 15K003n 31.43934822 –83.818229675293 391 — 240 

Worth 15K004g 31.37879372 –83.7987899780273 348 — 802 

Worth 15L004f 31.58934593 –83.8435134887695 412 402 402 

Worth 15L005n 31.51823616 –83.8193435668945 380 178 178 

Worth 15L020n 31.52962494 –83.8210067749023 420 450 738 

Worth 15L021n 31.53767967 –83.8457336425781 380 536 536 

Worth 15L032n 31.59055519 –83.8383331298828 410 520 520 

Worth 15L035n 31.58936119 –83.836669921875 410 430 430 

Worth 15N003n 31.80775070 –83.8363037109375 285 50 57 

Worth 15N005n 31.80805588 –83.8363876342773 281 260 260 

Worth 15N006n 31.80791664 –83.8323059082031 288 210 210 

Worth 16J030e 31.32028008 –83.7375030517578 288 5,568 5,568 

Worth 16J047e 31.35472298 –83.6972198486328 340 440 440 

Worth 16K011e 31.40157127 –83.7037811279297 362 620 — 

Worth 16K013e 31.42407227 –83.7096176147461 375 610 — 

Worth 16L011e 31.55073547 –83.7746200561523 332 210 — 

Worth 16L019n 31.51268196 –83.7382278442383 380 — 717 
Appendix. Geohydrologic Data 77

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

[Accuracy of land-surface altitude varies based on method of measurement. Values reported to hundredths of a foot represent measurement made by 

surveying or global positioning techniques; —, no data available]

Well

name

Top

altitude,

Upper

Floridan 

aquifer

Bottom 

altitude, 

Upper 

Floridan

aquifer

Top

altitude,

Tampa

Limestone

Top

altitude, 

Suwannee 

Limestone

Top

altitude,

Ocala

Limestone

Top

altitude,

Lisbon or 

Avon Park 

Formation

Top

altitude, 

Tallahatta 

Formation

Top

altitude,

Wilcox

Group

Feet above or below NAVD 88

Georgia

14K053n 360 — — 360 318 — — —

14K054n 210 –150 — — — — — —

14K055n 228 — — — — — — —

14K058n 224 –145 — — — — — —

14L002c,e 222 — — 222 146 53 — —

14L003b,e 245 — — — 245 — — —

14L007e 285 — — 285 — — — —

14L009n 234 56 — 234 180 56 — —

14L012n — — — — — — — —

14L030n 222 — — 222 — — — —

14M001n 119 — — — — — — —

14M008n 226 — — 226 — — — —

14N001n 226 — — 226 164 — — —

14N014n 220 — — 220 200 — — —

15J015e 100 — — 100 — — — —

15J017b,e 132 — — 132 — — — —

15K003n 175 — — — 175 — — —

15K004g 96 –331 — 96 17 –331 –434 —

15L004f 184 — — — 184 25 — —

15L005n 224 — — 224 — — — —

15L020n 230 — — 230 — — — —

15L021n 250 –146 — — — — — —

15L032n 230 –100 — — 230 –100 — —

15L035n 240 — — — — — — —

15N003n 230 — — — 230 — — —

15N005n 228 70 — — — — — —

15N006n 248 — — — 248 — — —

16J030e –98 –718 — –98 — –718 — —

16J047e –50 — — –50 — — — —

16K011e 2 — — 2 — — — —

16K013e 1 — — 1 — — — —

16L011e 242 — — 242 — — — —

16L019n — — — –46 –180 — — —
78 Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida

a

 Applin and Applin, 1964.

b

 Herrick, 1961.

c

 Kellam and Gorday, 1990.

d

 Mcconnell and Hacke, 1993.

e

 McFadden and others, 1986.

f

 Miller, 1986.

g

 Miller, 1988.

h

 Sever, 1964.

i

 Sever, 1965.

j

 Sever, 1966.

k

 Sever and Herrick, 1967.

l

 Stephenson and Veatch, 1915.

m Torak and Painter, 2006.

n

 Data on file at the U.S. Geological Survey, Georgia Water Science Center, Atlanta, Georgia.

Table A–1. Geohydrologic data for the Aucilla–Suwannee–Ochlockonee River Basin.—Continued

Footnotes
Manuscript approved for publication, April 8, 2010

Edited by Kimberly A. Waltenbaugh

Graphics by Bonnie J. Turcott

Layout by Caryl J. Wipperfurth

For more information concerning the research in this report, contact

USGS Georgia Water Science Center

3039 Amwiler Road

Atlanta, Georgia 30360

telephone: 770-903-9100

http://ga.water.usgs.gov
Torak and others—Geohydrology of the Aucilla–Suwannee–Ochlockonee River Basin, South-Central Georgia and Adjacent Parts of Florida—Scientific Investigations Report 2010–5072