Prepared in cooperation with the 

Southwest Florida Water Management District

Hydrology, Water Budget, and Water Chemistry 

of Lake Panasoffkee, West-Central Florida

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5237
Hydrology, Water Budget, and Water 

Chemistry of Lake Panasoffkee, 

West-Central Florida

By W. Scott McBride, Jason C. Bellino, and Amy Swancar

Prepared in cooperation with the

Southwest Florida Water Management District

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5237
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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reproduce any copyrighted materials contained within this report.

Suggested citation:

McBride, W.S., Bellino, J.C., and Swancar, Amy, 2011, Hydrology, water budget, and water chemistry of Lake 

Panasoffkee, west-central Florida: U.S. Geological Survey Scientific Investigations Report 2010–5237, 96 p.
iii

Contents

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

Introduction............................................................................................................................................................3

Purpose and Scope.....................................................................................................................................3

Previous Studies ..........................................................................................................................................5

Description of Study Area..........................................................................................................................5

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

Tributaries and Springs...............................................................................................................................9

Methods of Investigation...................................................................................................................................15

Measurement of Streamflow and Spring Flow....................................................................................15

Measurement of Groundwater Levels ..................................................................................................17

Geospatial Techniques .............................................................................................................................20

Calculation of Evaporation and Groundwater Inflow.........................................................................21

Collection of Precipitation Data..............................................................................................................22

Determination of Lake Volume and Change in Storage.....................................................................22

Geophysical Measurements ...................................................................................................................25

Water Chemistry Sampling Methods and Analysis............................................................................25

Hydrogeology.......................................................................................................................................................30

Surficial Aquifer.........................................................................................................................................35

Intermediate Confining Unit.....................................................................................................................35

Upper Floridan Aquifer .............................................................................................................................35

Middle Confining Units I and II................................................................................................................36

Lower Floridan Aquifer.............................................................................................................................39

Groundwater Levels, Contributing Areas, and Differences in Head...............................................39

Geophysics..................................................................................................................................................48

Surface-Water Hydrology .................................................................................................................................49

Streamflow..................................................................................................................................................49

Spring Inflows ............................................................................................................................................51

Ungaged Flow.............................................................................................................................................51

Lake Level....................................................................................................................................................51

Streamflow Gains and Losses.................................................................................................................53

Water Budget.......................................................................................................................................................55

Precipitation................................................................................................................................................56

Evaporation.................................................................................................................................................57

Onsite Septic Wastewater-Treatment Systems ..................................................................................58

Groundwater Inflow..................................................................................................................................58

Comparisons to Earlier Water-Budget Study.......................................................................................63

Water Chemistry..................................................................................................................................................64

Major Ions ...................................................................................................................................................64

Sources of Sulfate.....................................................................................................................................67
iv

Isotopes .......................................................................................................................................................67

Strontium............................................................................................................................................67

Deuterium and Oxygen-18..............................................................................................................71

Age Dating...................................................................................................................................................73

Carbon-14 and Tritium .....................................................................................................................73

Sulfur Hexafluoride..........................................................................................................................73

Summary...............................................................................................................................................................77

AcknowMedgments ...............................................................................................................................................80

References Cited.................................................................................................................................................80

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer 

potentiometric-surface maps.............................................................................................................85

Appendix 2. Major ion, nutrient, and field parameter water-quality data from the 

Lake Panasoffkee study area, July 2007, and December 2008 through January 2009 ...........93

Figures

1–5. Maps showing:

1. Location of Lake Panasoffkee in west-central Florida.....................................................4

2. Lake Panasoffkee surface-water drainage basin and watershed boundary .............6

3. Physiographic regions of west-central Florida..................................................................7

4. Lake regions of north-central Florida...................................................................................8

5. Location of springs, spring complexes, and sinks in the Lake Panasoffkee 

 study area .................................................................................................................................10

6. Photograph of Fenney Spring pool..................................................................................................11

7. Map showing location of spring vents and surface-water gaging stations near 

 Melton’s Millpond Spring Complex..................................................................................................12

8. Photograph of Maintenance Spring pool.......................................................................................13

9–14. Maps showing:

9. Location of springs in the Canal Springs Complex ..........................................................14

10. Location of surface-water stations in the Lake Panasoffkee study area .................16

11. Location of wells in the Lake Panasoffkee study area...................................................18

12. Location of rain gages and current and historic lake-stage gages in the 

 Lake Panasoffkee study area.............................................................................................. 23

13. Lake Panasoffkee bathymetric model............................................................................... 24

14. Location of water-quality sampling stations in the Lake Panasoffkee 

 study area ................................................................................................................................ 26

15. Chart showing relation of stratigraphic and hydrogeologic units in the Lake 

 Panasoffkee watershed.....................................................................................................................30

16. Hydrogeologic cross sections of the shallow groundwater system near 

 Lake Panasoffkee................................................................................................................................31

17A. Map showing location of hydrogeologic section lines of the deep groundwater

 system in the region surrounding Lake Panasoffkee ..................................................................32

17B. Hydrogeologic cross sections of the deep groundwater system in the region 

 surrounding Lake Panasoffkee ........................................................................................................33

18. Map showing regional transmissivity of the Upper Floridan aquifer .......................................37
v

19. Hydrostratigraphy at four wells installed in the Lower Floridan aquifer near Lake 

 Panasoffkee .........................................................................................................................................38

20–25. Maps showing:

20. Areal extent of middle confining units I and II near the Lake Panasoffkee 

 study area with reinterpretation using new hydrogeologic information................. 40

21. Regional groundwater flow system in the Upper Floridan aquifer, 

 September 2007.......................................................................................................................41

22. Generalized potentiometric surface of the Upper Floridan aquifer in the 

 Lake Panasoffkee study area during May 2007 and September 2007...................... 43

23. Generalized potentiometric surface of the Upper Floridan aquifer in the 

 Lake Panasoffkee study area during May 2008 and September 2008...................... 44

24. Areas of recharge and discharge potential between the surficial aquifer 

 and the Upper Floridan aquifer in the Lake Panasoffkee study area for 

 May 2007 and September 2007....................................................................................... 45

25. Areas of recharge and discharge potential between the surficial aquifer 

 and the Upper Floridan aquifer in the Lake Panasoffkee study area for 

 May 2008 and September 2008 .......................................................................................... 46

26–27. Graphs showing:

26. Difference in hydraulic head between the surficial aquifer and Upper 

 Floridan aquifer near Lake Panasoffkee LP-6 and Wysong Dam well nests, 

 Big Jones Creek and Little Jones Creek well nests, and LP-4 and LP-5 

 well nests, October 2006 through September 2008 ...................................................... 47

27. Lake stage and discharge at Pana Vista Lodge, October 2006 through 

 September 2008...................................................................................................................... 53

28. Map showing relative flow contributions from each stream reach to total 

 streamflow during four seepage runs, December 2007 through September 2008 ................54

29. Graphs showing hydraulic head data for Shady Brook and Outlet River, October 2006 

 through September 2008....................................................................................................................55

30. Diagram of water-budget terms.......................................................................................................56

31. Graph showing monthly total rainfall in the Lake Panasoffkee watershed from 

 October 2006 through September 2008 compared to the average monthly rainfall 

 measured at the National Climatic Data Center station at Inverness, Florida, 

 October 1930 through September 2008...........................................................................................57

32. Map showing location of onsite septic wastewater-treatment systems within 

 100 meters of Lake Panasoffkee or canals....................................................................................60

33. Graph showing summary of monthly water-budget data for Lake Panasoffkee 

 during water years 2007 through 08................................................................................................62

34. Trilinear diagram showing water types from water-quality samples collected in 

 the Lake Panasoffkee watershed during July 2007 and December 2008 through 

 January 2009 ........................................................................................................................................66

35–36. Graphs showing relation between:

35. Strontium isotope ratios and the reciprocal of the strontium concentration 

 in water samples from the Lake Panasoffkee study area for July 2007 and

 December 2008 through January 2009............................................................................. 68

36. Deuterium and oxygen isotope data in the Lake Panasoffkee study area 

 for July 2007 and December 2008 through January 2009............................................ 72

37. Diagram showing generalized conceptual model of the Lake Panasoffkee 

 watershed based on geochemical analyses.................................................................................74
vi

Tables

1. Location and name of springs in the Lake Panasoffkee study area ...............................................11

2. Location of surface-water stations in the Lake Panasoffkee study area ......................................17

3. Additional wells in the Lake Panasoffkee study area used to augment regional 

 potentiometric-surface and water-table maps ............................................................................ 19–20

4. Location of water-quality sampling stations in the Lake Panasoffkee study area.......................27

5. Elevation of land-surface datum, total depth, and depth to various formations for 

 selected wells used in the construction of hydrogeologic cross sections ...................................34

6. Average monthly surface-water discharge and total volume of monthly discharge 

 to and from Lake Panasoffkee, April 2006 through September 2008...............................................50

7. Summary of measured discharge at spring and surface-water stations in the Lake 

 Panasoffkee study area during four seepage runs from December 2007 through 

 September 2008..........................................................................................................................................52

8. Monthly rainfall statistics for the Lake Panasoffkee watershed for water years 

 2006 through 2008 compared to the average monthly rainfall at Inverness, Florida, 

 1930 through 2008 ......................................................................................................................................58

9. Summary of energy-budget data for Lake Panasoffkee from October 2006 through 

 September 2008..........................................................................................................................................59

10. Summary of monthly water-budget data for Lake Panasoffkee during water years 

 2007 through 2008 ......................................................................................................................................61

11. Comparison of the May 1992 through April 1993 and May 2007 through April 2008 

 Lake Panasoffkee water budgets...........................................................................................................63

12. Strontium, hydrogen, and oxygen isotope data collected from select groundwater, 

 surface-water, and spring sites in the Lake Panasoffkee study area, July 2007 and 

 December 2008 through January 2009........................................................................................... 69–70

13. Carbon and tritium isotope data with adjusted carbon-14 groundwater data collected 

 from select groundwater sites in the Lake Panasoffkee study area, December 2008................75

14. Mean concentrations, mean calculated atmospheric mixing ratios, mean piston 

 flow model years of sulfur hexafluoride data and dissolved gas data in groundwater 

 in the Lake Panasoffkee study area, December 2008 through January 2009................................76
vii

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.004047 square kilometer

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3) 

Velocity

inch per day (in/d) 0 .0254 meter per day (m/d)

inch per year (in/yr) 0 .0254 meter per year (m/yr)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per year (ft3/yr) 0.02832 cubic meter per year (m3/yr)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

Pressure

millibar (mb) 0.01450 pound per square inch (lb/in2)

Energy flux density

calories per square centimeter per day 

(cal/cm2/day)

0.04187 megajoules per square meter (Mj/m2)

Transmissivity *

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d) 

*Transmissivity: The standard unit 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.

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 National Geodetic Vertical Datum of 1929 (NGVD 29).

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).
viii

Acronyms and Additional Abbreviations

μg/L micrograms per liter

μS/cm microsiemens per centimeter

cal/cm3 calories per cubic centimeter

cal/g calories per gram

CHIRP compressed high intensity radar pulse

cm3/L cubic centimeters per liter

°C degree Celsuis

fMol/L femtomols per liter

g/cm3 grams per cubic centimeter

GIS Geographic Information System

GMWL global meteoric water line

HMLL High Minimum Lake Level

LGL Low Guidance Level

LGM Last Glacial Maximum

LMWL local meteoric water line

mb/°C millibars per degree Celsius

mg/L milligrams per liter

MLL Minimum Lake Level

MWL meteoric water line

NCDC National Climatic Data Center

OWTS onsite septic wastewater-treatment system

pptv parts per trillion by volume

per mil parts per thousand

ROMP Regional Observation and Monitoring-Well Program

SWFWMD Southwest Florida Water Management District

TU tritium units

USGS U.S. Geological Survey

VSMOW Vienna Standard Mean Ocean Water
Abstract

A study of Lake Panasoffkee and the surrounding watershed was conducted between October 2005 and September 

2009 to gain a better understanding of how this large lake 

fits within the regional hydrogeologic setting of west-central 

Florida. Lake Panasoffkee is part of the headwaters of the 

Withlacoochee River and has a major influence on the 

hydrology and ecology of that basin. The study defined the 

interaction between surface water and groundwater, and the 

magnitude of lake evaporation and groundwater inflow to 

the lake and how these relate to the Lake Panasoffkee water 

budget. Geochemical and isotopic analyses were used with 

water-budget results to describe water sources for the lake.

Lake Panasoffkee, the underlying surficial aquifer, and 

the Floridan aquifer system are hydraulically connected. 

An area of focused groundwater-discharge potential, where 

groundwater levels are higher than surface-water levels, is 

present beneath Lake Panasoffkee and extends several miles 

northwest and southeast of the lake. Although the size and 

intensity of the discharge area varied with the seasons and 

with hydrologic conditions, discharging conditions remained 

constant throughout the study period. 

The sandy uplands farther northeast and southeast of 

Lake Panasoffkee showed the greatest potential for surfacewater to groundwater recharge within the study area. The Lake 

Panasoffkee watershed lacks a well-developed surface-water 

drainage system because rainfall rapidly infiltrates the sandy 

soils in the uplands and recharges the surficial aquifer. 

The intermediate confining unit is discontinuous in the study 

area, but even in areas where the confining unit is present, 

there is a well-developed internal drainage system that 

compromises the integrity of the unit. The internal drainage 

system consists of an interconnected network of karst features 

that includes sinkholes, fissures, and conduits. The discontinuous intermediate confining unit and internal drainage 

features allow the surficial aquifer to rapidly recharge the 

Upper Floridan aquifer in recharge areas.

Little Jones Creek and Shady Brook were the primary 

contributors of surface-water flow to Lake Panasoffkee during 

the study period. The average monthly discharge from Little 

Jones Creek to Lake Panasoffkee ranged from 6.56 cubic 

feet per second in June 2007 to 75.8 cubic feet per second in 

August 2008, whereas the contribution of Shady Brook to 

Lake Panasoffkee ranged from 8.28 cubic feet per second in 

June 2007 to 59.6 cubic feet per second in September 2008. 

The combined flow from both tributaries accounted for 51 and 

47 percent of total input from all sources during water years 

2007 and 2008, respectively. The U.S. Geological Survey 

water year begins October 1st and ends September 30th. 

Water-budget calculations indicated that Lake 

Panasoffkee received 29 percent of its total inflow as groundwater inflow during the study period. Groundwater inflow is 

defined as diffuse flow (or discharge) from the groundwater 

Hydrology, Water Budget, and Water 

Chemistry of Lake Panasoffkee, 

West-Central Florida

By W. Scott McBride, Jason C. Bellino, and Amy Swancar
2 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

system to Lake Panasoffkee through the lakebed. Monthly 

groundwater inflow to Lake Panasoffkee ranged from 11 to 

50 percent of total inflow during the 2-year data-collection 

period, excluding 2 months when groundwater inflow was 

negligible. Comparatively, the volume of surface-water 

inflow for the 2-year data-collection period was 50 percent 

of the total inflow, and rainfall accounted for 21 percent. 

Lake Panasoffkee lost 21 percent of its outflow through 

evaporation and 79 percent through surface-water outflow. 

The percentage of total inflow received by Lake Panasoffkee 

from groundwater is not unusual among central Florida 

lakes, but the source and volume are atypical. A previous 

U.S. Geological Survey study showed that most lakes in 

central Florida receive groundwater inflow from the surficial 

aquifer, but Lake Panasoffkee primarily receives groundwater 

inflow from the Upper Floridan aquifer. The large volume 

of groundwater inflow also is unusual for a lake the size of 

Panasoffkee, which received 1.4 billion cubic feet of groundwater inflow in water year 2008. In addition, the groundwater 

flow system also is the source of much of the surface-water 

flow to Lake Panasoffkee. Four synoptic streamflow measurements completed between December 2007 and September 

2008 determined that 60 to 78 percent of the total surfacewater inflow to Lake Panasoffkee during baseflow conditions 

originated from spring discharge. 

The Floridan aquifer system contributes water to, and 

interacts with, the surface-water system and the surficial 

aquifer in the Lake Panasoffkee watershed. In the study area, 

the Floridan aquifer system consists of the Upper Floridan 

aquifer and the Lower Floridan aquifer, separated by two 

confining units, middle confining unit I and middle confining 

unit II. The distribution of the two middle confining units has 

substantial effect on the availability of potable groundwater in 

the study area. Middle confining unit I is shallower and leaky 

and found mostly east of the lake. Middle confining unit II 

is deeper, less permeable, and found mostly west of the lake. 

Both confining units are found south of the lake.

Water samples were collected in July 2007 and December 

2008 through January 2009 from Lake Panasoffkee, selected 

tributaries and springs that flow into Lake Panasoffkee, and 

groundwater wells installed in the surficial, Upper Floridan, 

and Lower Floridan aquifers in the Lake Panasoffkee watershed. Every water sample collected in the study area was 

classified either as a calcium-bicarbonate, calcium-sulfate, 

or mixed calcium-bicarbonate/calcium-sulfate water type. 

Calcium-bicarbonate type waters form where groundwater 

dissolves the carbonate limestone of the shallow Upper 

Floridan aquifer. Calcium-sulfate type waters form through the 

dissolution of the mineral gypsum; geochemical mass-balance 

modeling performed in a previous U.S. Geological Survey 

study of the area indicated that the source of the gypsum (and 

the high sulfate water) is likely found near the base of the 

Upper Floridan aquifer. The mixed-water type is found in 

areas where the calcium-sulfate type water upwells from this 

unit into the shallow Upper Floridan aquifer, where it mixes 

with calcium-bicarbonate type water. 

The calcium-sulfate and mixed calcium-bicarbonate/

calcium-sulfate type waters were found in samples from 

Lake Panasoffkee and from the groundwater system south 

and southwest of Lake Panasoffkee during the 2007 sampling 

event, but were only found in samples from the groundwater 

system during the 2008–09 sampling event. The latter 

sampling event followed a wet period when surface-water 

levels were higher and aquifer levels in the surficial and Upper 

Floridan aquifers had recovered slightly from earlier severe 

drought conditions. 

Surface-water and groundwater samples that were 

analyzed for strontium isotope content confirmed that 

groundwater from the Upper Floridan aquifer interacts with 

both the surficial aquifer and surface waters within the Lake 

Panasoffkee watershed. Strontium isotope data indicated that 

all of the sampled sites were affected by water from the Upper 

Floridan aquifer, with the exception of one surficial aquifer 

site during each sampling event. The observed strontium–87/

strontium–86 ratios of the water samples were between 0.7077 

and 0.7085, which is consistent with the range of strontium 

isotope ratios found in the Upper Floridan aquifer within the 

Ocala Limestone and Avon Park Formation. 

Water samples analyzed for the stable isotopes 

of hydrogen and oxygen confirm that rainfall is the 

primary source of groundwater recharge within the Lake 

Panasoffkee watershed. Water samples collected from Lake 

Panasoffkee and its surface-water outflow stream were 

isotopically enriched from evaporation, but the majority of 

the groundwater and spring isotope data resemble that of 

isotopically depleted rainfall, indicating that the watershed 

drainage is primarily internal. Water samples from some 

of the deepest wells in the study area, installed in both the 

Upper and Lower Floridan aquifers, indicate slight isotopic 

enrichment of hydrogen and oxygen isotopes compared to 

shallower groundwater. This is probably not an indication 

that these waters underwent enrichment before recharge, 

but that they contain a fraction of water recharged during 

the Last Glacial Maximum. Groundwater deep in the 

Upper Floridan aquifer is part of a regional flow system 

that was recharged thousands of years ago. 

Deeper, older, and more mineralized groundwater flows 

upward into shallower aquifers on the west side of Lake 

Panasoffkee but not on the east side. Adjusted carbon–14 

isotope data collected from a 240-foot deep well installed in 

the Avon Park Formation west of Lake Panasoffkee indicate 

water that was recharged about 23,485 to 26,455 years 

before present. Water from two wells at the same location 

but at different depths 7 miles east of Lake Panasoffkee 

was younger. Water from the 338-foot-deep Upper Floridan 

aquifer well installed in both the Ocala Limestone and Avon 

Park Formation recharged about 7,022 to 7,579 years before 

present, whereas water from the 1,000-foot-deep Lower 

Floridan aquifer well installed in the Avon Park Formation 

below middle confining unit I recharged about 8,703 to 

9,413 years before present.
Introduction 3

Lake Panasoffkee is located near the western extent 

of middle confining unit I and the eastern extent of middle 

confining unit II. Because no deep exploratory drilling has been 

performed in the immediate vicinity of Lake Panasoffkee, it is 

uncertain which of these confining units are present beneath the 

lake. The high concentration of sulfate and the radiocarbon age 

of the water sample from the well west of Lake Panasoffkee 

indicate that the upwelling water probably comes into contact 

with middle confining unit II somewhere along its flow path. 

Middle confining unit II is the only formation in the area 

with a mineral composition capable of producing the high 

concentration of sulfate (1,700 milligrams per liter) found in 

the upwelling groundwater west of Lake Panasoffkee. Because 

middle confining unit II is composed primarily of gypsiferous 

dolomite, deeply circulating groundwater flowing across, or 

through, this unit could produce high sulfate groundwater. 

Water samples from the deep Upper Floridan and Lower 

Floridan aquifer wells east of Lake Panasoffkee were similar 

to one another both chemically and in radiocarbon age. These 

similarities indicate that on the east side of the lake water from 

the Upper Floridan aquifer mixes with water from the Lower 

Floridan aquifer through middle confining unit I, which is 

leaky throughout much of its extent. In the area of these wells, 

the Upper Floridan aquifer recharges the Lower Floridan 

aquifer, whereas closer to the lake, heads reflect upward 

discharge conditions.

Introduction

Lake Panasoffkee is located in northwestern Sumter 

County, west-central Florida (fig. 1), and is the largest lake in 

the county as well as the third largest of about 1,800 lakes in 

west-central Florida (Lake Panasoffkee Restoration Council, 

2008). The area surrounding the lake is predominately rural, 

with nearly 160,000 acres of land countywide dedicated to 

agriculture (U.S. Department of Agriculture, 2007). The most 

highly developed land in the study area is located along the 

western shoreline of the lake in and near the town of Lake 

Panasoffkee. The original settlement of Panasoffkee was on the 

southern end of the lake, where older maps show its location.

The Florida Department of Environmental Protection 

has designated Lake Panasoffkee as an “Outstanding Florida 

Water.” Only water bodies with exceptional recreational 

or ecological significance are awarded this status, which is 

intended to help preserve their existing water quality (Florida 

Department of Environmental Protection, 2009). To help 

protect the water quality in Lake Panasoffkee, as well as 

improve its ecology, the Lake Panasoffkee Restoration Council 

was formed in 1998. The restoration effort primarily involved 

dredging the lake bottom to remove sediments and emergent 

aquatic vegetation, and was completed in 2009.

Water managers and local residents have expressed 

concern that population growth in the Lake Panasoffkee 

watershed could affect local groundwater resources (Southwest 

Florida Water Management District, 2000). In the past, 

development of groundwater resources in some parts of Florida 

was poorly managed because growth was rapid and unplanned. 

Groundwater is susceptible to contamination in the Lake 

Panasoffkee watershed and other parts of Florida because of the 

karstic terrain. Karst features, such as sinkholes, conduits, and 

swallets, allow surface water to recharge directly to the Upper 

Floridan aquifer without filtering through the sands of the surficial aquifer. In addition to its filtering capacity, the surficial 

aquifer supports many microbial and geochemical reactions 

that break down potentially harmful contaminants before they 

reach the Upper Floridan aquifer below. 

Previous studies have already shown that a hydraulic 

connection is present between the surface- and groundwater 

systems in the Withlacoochee River Basin, which includes 

Lake Panasoffkee (Trommer and others, 2009). In this and 

other hydraulically connected systems, excessive groundwater 

withdrawals can result in surface-water drawdowns. As part of 

the headwaters of the Withlacoochee River, Lake Panasoffkee 

affects the hydrology and ecology of the river. A better 

understanding of the interaction between groundwater and 

surface water and how this relates to Lake Panasoffkee and 

the Withlacoochee River is essential to water managers for the 

sound development and management of local water resources, 

especially as demand for freshwater increases.

In October 2005, the U.S. Geological Survey (USGS) 

began a cooperative study with the Southwest Florida 

Water Management District (SWFWMD) to gain a better 

understanding of the surface-water hydrology, groundwater 

interactions, water budget, and geochemistry of the Lake 

Panasoffkee watershed. This study provides information that 

can be used to better understand spring flow, streamflow, 

and groundwater levels as future groundwater supplies are 

developed in the Lake Panasoffkee watershed. Results of the 

study also provide important information to more effectively 

manage the surface- and groundwater resources of the Lake 

Panasoffkee watershed as one integrated system. Studies that 

include surface- and groundwater interaction, water-supply 

watersheds, and source-water protection information are a high 

priority of the USGS Federal Water Cooperative Program, and 

the investigative methods of this study have transfer value to 

other watersheds located in karst areas.

Purpose and Scope

The purpose of this report is to document the surfacewater hydrology, groundwater interactions, water budget, and 

geochemistry of the Lake Panasoffkee watershed. The interaction between groundwater and Lake Panasoffkee is evaluated 

using multiple approaches, and the water budget of the lake is 

refined by incorporating onsite measurement of lake evaporation rates. Geochemical analyses are used to help describe the 

interaction of surface water and groundwater in the watershed.
4 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0 10 20 MILES

0 10 20 KILOMETERS

GILCHRIST

COUNTY

UNION COUNTY COLUMBIA

COUNTY

SUWANNEE

COUNTY

POLK COUNTY

MARION COUNTY

LAKE

COUNTY

LEVY COUNTY

ALACHUA COUNTY

DIXIE COUNTY

PASCO

COUNTY

ORANGE

COUNTY

CITRUS

COUNTY

SUMTER

COUNTY

HILLSBOROUGH

COUNTY

PUTNAM COUNTY

OSCEOLA

COUNTY

VOLUSIA COUNTY

FLAGLER

COUNTY

HERNANDO

COUNTY

CLAY COUNTY TAYLOR COUNTY

LAFAYETTE COUNTY SAINT JOHNS

COUNTY

PINELLAS COUNTY

SEMINOLE

COUNTY

BRADFORD

COUNTY

Ocala

Tampa

Orlando

Wildwood

Bushnell

Inverness

Dunnellon

Dade

City

Ridge

Manor

Gainesville

Zephyrhills

High Springs

Lake

Panasoffkee Brooksville

Bartow

GULF OF MEXICO

Lake

Panasoffkee River

Ocklawaha

Lake

George

Crescent

Lake

Tsala

Apopka

Lake

Lake

Apopka

Hillsborough

River

W River

ithlacoochee

Tampa

Bay

Lake

Calm

Reedy

Lake

Lake

Starr

Wildwood

Lake

Panasoffkee Double Sink

Walled Sink

82°15 ́ 82°10 ́ 82°05 ́ 82°00 ́

28°55 ́

28°50 ́

28°45 ́

0 2 MILES

0 2 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Spring data from Florida Department of Environmental Protection; 2000

Universal Transverse Mercator projection, Zone 17 North

75

44

CITRUS COUNTY SUMTER COUNTY

301

470

Wysong

Dam

Shady Brook

Withlacoochee

River

Jumper

Outlet River

BIG

PRAIRIE

FLORIDA'S

TURNPIKE

Chitty

Chatty

Creek Big

Prairie

Canal

Lake Panasoffkee

Hogeye

Sink

Lake

Okahumpka

Creek

Carlson

Coleman

Sumterville

Warnel

Creek

AREA SHOWN

IN FIGURE

83°30 ́ 83°00 ́ 82°30 ́ 82°00 ́ 81°30 ́

29°30 ́

29°00 ́

28°30 ́

28°00 ́

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Universal Transverse Mercator projection, Zone 17 North

STUDY

AREA

Big

Jones

Creek Little

Jones

Creek

Unnamed

Creek

Figure 1. Location of Lake Panasoffkee in west-central Florida.
Introduction 5

Hydrologic and geologic data were collected during the 

course of the 3.5-year study (April 2006–September 2009), 

and historical data were compiled from the records of the 

USGS and the SWFWMD, and from previously published 

reports. The study required the design and implementation of 

a surface-water and groundwater level monitoring network, 

the installation of an open-water evaporation station, and 

the measurement of surface-water flows and spring flows 

to quantify the volume of flow reaching Lake Panasoffkee. 

Surface-water and spring-flow measurements also were used 

to quantify the exchange rate of surface water and groundwater along stream reaches. Water samples were collected 

from select surface-water sites, springs, and groundwater wells 

to define the geochemistry of the area. Seismic-reflection 

surveys were performed to determine the depth and thickness 

of geologic units beneath the lake. Continuous groundwaterlevel data were collected in the surficial and Upper Floridan 

aquifers to define groundwater flow patterns in the watershed.

Although Lake Panasoffkee restoration efforts by 

the SWFWMD were in progress during this study (Lake 

Panasoffkee Restoration Council, 2008), the effects of these 

restoration efforts were considered in data collection and 

analysis. For example, the water-budget calculations were 

affected by the removal of sediment from the lake bottom, 

because large volumes of water were removed with the sediments. This pumpage from the lake was accounted for as a 

term in the water-budget calculation because accurate records 

of pumpage were maintained by the dredge operators.

The data in this report are typically discussed in terms 

of water years. A water year is the 12-month period from 

October 1 through September 30, and the year is designated 

by the calendar year in which it ends; for example, October 1, 

2008, through September 30, 2009, constitutes water year 2009. 

Previous Studies

The geology and geomorphology of the Lake 

Panasoffkee area were described by White (1958, 1970) 

and Campbell (1989). The hydrogeologic framework of the 

Floridan aquifer system in the Lake Panasoffkee region was 

defined by Miller (1986). Arthur and others (2001) created 

lithostratigraphic and hydrostratigraphic cross sections that 

dissect the Lake Panasoffkee area. The hydrology and hydrogeology of the area have been studied by Taylor (1977), 

Greiner Engineering Sciences (1978), Adams (1985), Ryder 

(1985), and Camp and Barcelo (1988). Bays and Crisman 

(1981) evaluated the water quality of Lake Panasoffkee. 

CH2M Hill (1995) created a water and nutrient budget for 

Lake Panasoffkee. Belanger and others (1993) determined 

the thickness of the bottom sediments in Lake Panasoffkee 

and analyzed the sediments for chemical composition. 

Sources of sediment and rates of sediment accumulation in 

Lake Panasoffkee were evaluated by Belanger and others 

(1995) using lead–210 as an isotopic dating tool. Sacks 

(1996) studied the geochemistry and isotopic composition of 

groundwater near Lake Panasoffkee with special emphasis 

on potential sources of unusually high sulfate concentrations 

near the lake. Elliot and others (1998) studied the quality 

of groundwater around Lake Panasoffkee and calculated 

the nutrient load to the lake contributed by spring flow. 

The water quality and hydrology of springs in the Lake 

Panasoffkee basin have been described by Champion and 

Starks (2001). Brenner and others (2006) studied the role of 

submerged aquatic vegetation in the sedimentation of organic 

matter and phosphorous using carbon/nitrogen ratios and 

stable isotopes of carbon and nitrogen in Lake Panasoffkee.

Description of Study Area

The study area primarily encompasses the land around 

Lake Panasoffkee that directly contributes surface-water 

runoff to the lake (fig. 2), and is referred to herein as the Lake 

Panasoffkee watershed (as defined by Taylor, 1977). The Lake 

Panasoffkee watershed differs from the Lake Panasoffkee 

basin, which is a much larger area that could theoretically 

contribute surface-water flow to Lake Panasoffkee based on 

physiography, but does not because of the karst terrain and its 

well developed internal drainage system. Some of the analyses 

performed in this study extend beyond the Lake Panasoffkee 

watershed boundary, such as the calculations to determine the 

groundwater contribution area to Lake Panasoffkee, but data 

were primarily collected inside the watershed boundary.

A vast floodplain swamp is situated between the eastern 

shoreline of Lake Panasoffkee and Interstate–75 (I–75). 

The SWFWMD purchased nearly 10,000 acres of the swamp 

during the 1990s. This purchase helped protect the water 

quality in Lake Panasoffkee by ensuring the preservation of 

the land in its undeveloped state (Kelly, 1996). 

All four of the tributaries to Lake Panasoffkee (Big Jones 

Creek, Little Jones Creek, Shady Brook, and Warnel Creek; 

figs. 1 and 2) traverse the SWFWMD lands for some or all 

of their lengths. At present, most of this property is managed 

jointly by the SWFWMD and the Florida Fish and Wildlife 

Conservation Commission as the Lake Panasoffkee Wildlife 

Management Area (Kelly, 1996).

The Lake Panasoffkee area has warm, humid summers 

and cool, dry winters associated with a subtropical climate. 

The mean annual air temperature is about 72 °F, with summer 

temperatures that occasionally rise above 95 °F, and winter 

temperatures that occasionally fall below 32 °F (National 

Climatic Data Center, 2009). The rainy season lasts from 

June through September, with rain events mostly in the form 

of intense localized thunderstorms and occasional tropical 

storms. Summer rains account for about 60 percent of the 

annual rainfall, which averages 54.26 in/yr, although annual 

totals vary substantially between years (National Climatic 

Data Center, 2009). The other 40 percent of rainfall is generated by winter frontal systems, primarily from December 

through March.
6 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Physiography

Lake Panasoffkee, the Tsala Apopka chain of lakes, and 

much of the Withlacoochee River are located within the Tsala 

Apopka Plain (fig. 3), which extends from Dunnellon south 

to east of Dade City. The Tsala Apopka Plain is a subregion 

of flat lowlands within the Western Valley physiographic 

region (White, 1970). The Western Valley parallels the west 

coast of Florida from High Springs south to Zephyrhills 

(figs. 1 and 3), and is bounded by the Brooksville Ridge 

to the west and various distinct upland areas to the east, 

including both the Sumter and Lake Uplands (figs. 1 and 3) 

(White, 1970). 

White (1958) theorized that the Tsala Apopka Plain is 

a relict feature of a much larger lake and river system that 

originally flowed southward into the Hillsborough River, 

75

301

44

40

50

41

Ocala

Tavares

Wildwood

Bushnell

Inverness

Dunnellon

Ridge Manor

Brooksville

Lake

Panasoffkee

ORANGE

COUNTY

LAKE COUNTY

MARION COUNTY

CITRUS COUNTY

SUMTER COUNTY

HERNANDO COUNTY

0 5 10 MILES

0 5 10 KILOMETERS

Jumper

Lake

Yale

Lake

Panasoffkee

Lake Harris

Lake

Eustis

Lake

Lake

Apopka

Tsala

Apopka

Lake

Lake Griffin

Lake

Weir

LAKE PANASOFFKEE WATERSHED--From

Taylor (1977)

SURFACE-WATER DRAINAGE BASIN--From

digital elevation model

Lake

Okahumpka

Outlet

River

Creek

Withlacoochee River

Little Jones

Creek

Shady Brook

Ocklawaha River

Big

Jones

Creek

Dora

Little Withlacoochee River

FLORIDA'S TURNPIKE

82°15 ́ 82°00 ́ 81°45 ́

29°00 ́

28°45 ́

28°30 ́

Base modified from U.S. Geological Survey digital data; 1:2,000,000, 1998.

Universal Transverse Mercator projection, Zone 17 North

EXPLANATION

Figure 2. The Lake Panasoffkee surface-water drainage basin and watershed boundary.
Introduction 7

and ultimately, into Tampa Bay. The Brooksville Ridge 

formed the western boundary of this large lake and river 

system, but as flowing groundwater dissolved the limestone 

bedrock along a postulated fault line, the Dunnellon Gap 

was formed across the Brooksville Ridge (Faulkner, 1973). 

The subterranean passage eventually expanded to the point 

where the overlying material collapsed into the void, splitting 

the ridge laterally and forming the gap. Surface-water flow 

in the river system then reversed and began flowing northward from the present-day headwaters of the Green Swamp 

(fig. 4) on the route of the modern-day Withlacoochee River, 

which flows west through the Dunnellon Gap (fig. 3) before 

emptying into the Gulf of Mexico (White, 1958).

The Sumter Upland and Lake Upland are northeast and 

southeast of Lake Panasoffkee, respectively (fig. 3), and are up 

to 150 ft above NGVD 29. To the west of Lake Panasoffkee is 

Dade

City

Ridge

BrooksvilleManor

Ocala

Tampa

Orlando

Wildwood

Bushnell

Inverness

Dunnellon

Gainesville

Zephyrhills

Lake

Panasoffkee

HIGHLANDS

RIDGE

COASTAL LOWLANDS

SOUTHERN GULF

COASTAL

LOWLANDS

ESPANOLA

HILL BROOKSVILLE RIDGE

WESTERN 

VALLEY

OSCEOLA

PLAIN

CENTRAL

VALLEY

LAKE

WESTERN

UPLAND

VALLEY

BROOKSVILLE

RIDGE

MARION

UPLAND

SUMTER UPLAND

TSALA APOPKA PLAIN

MOUNT DORA

DELAND RIDGE

CRESCENT CITY RIDGE

NORTHERN

COASTAL

SWAMPS

LAKE

TARPON

ORLANDO

RIDGE

PALATKA

HILL

WELEKA

HILL

COTTON

BELL

RIDGE

GENEVA

HILL

ATLANTIC

COASTAL

PLAIN

LAKELAND

RIDGE

WINTER HAVEN RIDGE

POLK UPLAND

MOUNT

DORA

RIDGE

PLANT RIDGE

LAKE

WALES

RIDGE

POLK

COUNTY

MARION

COUNTY FLAGLER

COUNTY

PINELLAS

COUNTY

CITRUS

COUNTY

GILCHRIST COUNTY

ST. JOHNS

COUNTY

SUMTER

COUNTY

LAKE

COUNTY

LEVY COUNTY

ALACHUA COUNTY DIXIE COUNTY

ORANGE COUNTY

PUTNAM COUNTY

OSCEOLA COUNTY

VOLUSIA COUNTY

HERNANDO COUNTY

SEMINOLE

COUNTY

HILLSBOROUGH

COUNTY

PASCO COUNTY

83°00 ́ 82°45 ́ 82°30 ́ 82°15 ́ 82°00 ́ 81°45 ́ 81°30 ́ 81°15 ́ 81°00 ́

29°30 ́

29°15 ́

29°00 ́

28°45 ́

28°30 ́

28°15 ́

28°00 ́

0 20 MILES

0 20 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005 and

Southwest Florida Water Management District digital data 1:2,000,000, 1993

Universal Transverse Mercator projection, Zone 17 North

Dunnellon

Gap

EXPLANATION

PHYSIOGRAPHIC LANDFORM

RIDGE

UPLAND

VALLEY OR PLAIN

LOWLAND / OTHER

ATLANTIC OCEAN

River

Lake

George

Withlacoochee

Tampa

Bay

Ocklawaha

Withlacoochee River

River

GULF OF MEXICO Hillsborough

River

Tsala

Apopka

Lake

Lake

Apopka

Lake

Panasoffkee

Crescent

Lake

Figure 3. Physiographic regions of west-central Florida (from White, 1970).
8 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0 10 20 MILES

0 10 20 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Lake regions data from U.S. Environmental Protection Agency, WED, 1996.

Universal Transverse Mercator projection, Zone 17 North

EXPLANATION

LAKE REGIONS

Regions shown are based upon water-quality characteristic classification (Griffith and others, 1997)

65-06 NORTHERN PENINSULA KARST PLAINS

75-01 GULF COAST LOWLANDS

75-03 UPPER SANTA FE FLATWOODS

75-04 TRAIL RIDGE

75-05 NORTHERN BROOKSVILLE RIDGE

75-06 BIG BEND KARST

75-07 MARION HILLS

75-08 CENTRAL VALLEY

75-09 OCALA SCRUB

75-10 EASTERN FLATLANDS

75-11 CRESCENT CITY/DELAND RIDGES

75-12 TSALA APOPKA

75-15 MOUNT DORA RIDGE

75-16 APOPKA RIDGE

75-17 APOPKA UPLAND

75-18 WEBSTER DRY PLAIN

75-19 CLERMONT UPLANDS

75-21 ORLANDO RIDGE

75-26 GREEN SWAMP

75-13 SOUTHERN BROOKSVILLE RIDGE

75-14 LAKE WEIR/LEESBURG UPLAND

AREA SHOWN

IN FIGURE

75-04

65-06

75-08

75-08

75-10

75-08

75-07

75-06

75-09

65-06

75-13

75-01

75-05

75-12

75-16

75-18

75-19

75-04

75-14

75-03

75-21

75-11

75-17

75-26

75-15

82°30 ́ 82°00 ́ 81°30 ́

29°30 ́

29°00 ́

75-11

75-11

75-11

Green

Swamp

Area

GULF OF MEXICO

Lake

Okahumpka

Lake

George

Tsala

Apopka

Lake

Lake

Apopka

Lake

Harris

Crescent

Lake

Lake

Griffin Lake

Eustis

Orange

Lake

Lake

Weir

Lake

Yale

Newnans

Lake

Lochloosa

Lake

Lake

Ocklawaha

Lake

Panasoffkee

Lake

Geneva

Withlacoochee

River

Ocklawaha

River

Figure 4. Lake regions of north-central Florida (from Griffith and others, 1997).
Introduction 9

the Brooksville Ridge, which has the most irregular surface of 

any surface feature of comparable size in peninsular Florida. 

The elevation of the Brooksville Ridge is as high as 200 ft 

above NGVD 29, but can vary from 70 to 200 ft above NGVD 

29 within short distances (White, 1970). 

In addition to the physiographic regions described above, 

Florida has been further divided into lake regions (fig. 4) 

that reflect differences in water quality, water quantity, and 

hydrology (Griffith and others, 1997). Lake Panasoffkee is 

within the Central Valley lake region (fig. 4, region 75–08), 

which includes the Ocklawaha chain of lakes to the east 

(Lakes Apopka, Harris, Griffin, Eustis, and Yale) and three 

lakes to the north (Newnans Lake, Lochloosa Lake, and 

Orange Lake). Lake Panasoffkee lies at the western end of 

a conspicuous narrow offshoot of the Central Valley lake 

region that extends from the Ocklawaha chain of lakes into 

the eastern part of the Tsala Apopka lake region (region 

75–12). 

The lakes in the Central Valley region are typically large, 

shallow, and eutrophic, with abundant macrophytes or algae 

and low water transparency. Water chemistry varies greatly 

among the Central Valley group of lakes, although this variation generally reflects the broad range in mineral content of 

their waters (Griffith and others, 1997). Those lakes with high 

mineral content waters interact with a source of mineralized 

groundwater. Lake Panasoffkee, with a high mineral content, 

receives a large volume of water from the carbonate Floridan 

aquifer system through both spring discharge and groundwater inflow. Lakes with low mineral content water typically 

receive a large percentage of their inflow from rainfall or from 

shallow groundwater that is low in mineral content (Griffith 

and others, 1997).

The 360-mi2 surface-water drainage basin containing 

Lake Panasoffkee, as defined by topographic maps, is long and 

narrow. The lake is situated along the west-central boundary of 

the basin, and is about 6 mi long by 1.5 mi wide (fig. 2). When 

the lake surface is at an elevation of 41.0 ft above NGVD 29, 

it covers an area of nearly 5,700 accres, with an average depth 

of 7 ft and a maximum depth of 10 ft (Taylor, 1977; Southwest 

Florida Water Management District, 2006). The topographic 

basin trends in a northwesterly/southeasterly direction, 

extending from the Ocala area south to an area east of Ridge 

Manor (fig. 2).

The effective surface-water contribution area to Lake 

Panasoffkee is substantially smaller than the topographically 

defined basin because of internal drainage to the groundwater 

system. The sandy soils overlying the surficial aquifer and the 

lack of an effective confining unit above the Upper Floridan 

aquifer allow precipitation to rapidly recharge the groundwater 

system. Streams (and stream channels) have little opportunity 

to form under these conditions because surface-water runoff 

across the landscape is minimal. 

Tributaries and Springs

Lake Panasoffkee has four tributaries, all of which 

except Big Jones Creek originate at springs. Although local 

residents have reported that springs were located along Big 

Jones Creek, none were discovered during this study. The inlet 

for both Big Jones Creek and Little Jones Creek is located 

at the northern end of the lake (fig. 5). Big Jones Creek is an 

intermittent stream that originates in a wetland south of State 

Road (S.R.) 44 and about 8 mi west of Wildwood. Little Jones 

Creek is a perennial stream that originates at Henry Green 

Spring (SP20, fig. 5 and table 1) on private property west of 

I–75. Wayne Lee Spring (SP19, fig. 5 and table 1), located on 

private property east of Florida’s Turnpike, also forms a run 

that empties into Little Jones Creek about 1 mi below Henry 

Green Spring. An unnamed tributary to Wayne Lee Spring run 

originates in the I–75 median south of the I–75 and Florida’s 

Turnpike junction. The tributary joins Wayne Lee Spring run 

just west of I–75. Sepulveda (2002) measured flows on the 

unnamed tributary (where it crosses under I–75) of 8, 5, and 

3 ft3/s between August 1993 and July 1994, and indicated 

that the flow originated from a spring. The channel at this site 

was mostly dry during this study, and no flow was observed 

when the channel was wet. Reconnaissance of the dry channel 

during the current study did not reveal a spring vent. The most 

likely source of flow in this channel is groundwater inflow 

when groundwater levels are above land surface. 

Warnel Creek and Shady Brook discharge into the 

southern end of Lake Panasoffkee. Warnel Creek branches 

off of Shady Brook and discharges into Lake Panasoffkee 

northeast of where Shady Brook flows into the lake. Shady 

Brook originates on private property at Fenney Spring (SP18, 

fig. 5 and table 1), about 2 mi east of Coleman, and terminates 

about 5 mi to the southwest. Fenney Spring (fig. 6) is largely 

undeveloped, although the surrounding banks have been 

eroded by cattle. Other springs that discharge into Shady 

Brook, in downstream order, include Blue Spring (SP17, fig. 5 

and table 1), Belton’s Millpond Spring Complex (SP4–SP8, 

fig. 5 and table 1), and Maintenance Spring (SP3, fig. 5 and 

table 1). 

Other springs in the lake watershed that appear to 

discharge into Shady Brook are shown on the Wildwood 

USGS 7.5-minute topographic quadrangle, which incorporates 

most of the eastern half of the study area. All of the springs 

listed on the Wildwood quadrangle were investigated during 

the course of this study. Dixie Lime and Stone Company 

Spring (SP1, fig. 5 and table 1) does not directly contribute 

flow to Lake Panasoffkee, and was therefore not included in 

the study. Shady Brook Head Spring 4 (SP2, fig. 5 and table 1) 

was not accessible because it is located on private property 

and the owner could not be located. Because reconnaissance 

of adjacent public property did not reveal a spring run, it is 

unlikely that this spring contributes substantial flow to Shady 

Brook. Shady Brook Head Spring 3 (SP16, fig. 5 and table 1) 
10 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Double Sink

Walled Sink

Walled Sink

Complex

SP9 SP8 SP7 SP6

SP5

SP2 SP1

SP15

SP14

SP20

SP19

SP18

SP17

SP12 SP16

SP4

SP3

SP13

SP10

SP11

0 2 MILES

0 2 KILOMETERS EXPLANATION

Wildwood

Lake

Panasoffkee

Carlson

Coleman

Sumterville

44

301

75 470

301

470

CITRUS

COUNTY

SUMTER

COUNTY

Brook

Lake

Okahumpka

Little Jones Creek

Big Jones

Creek

Shady

Withlacoochee

River

Jumper

Creek

Outlet

River

Hogeye

Sink

Chitty

Chatty

Creek

Prairie

Unnamed

Creek

Big

Canal

Warnel

Creek

Lake Panasoffkee

Tsala

Apopka

Lake

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Spring data from Florida Department of Environmental Protection; 2000

Universal Transverse Mercator projection, Zone 17 North

Wysong Dam

Canal Springs

Complex

Belton's Millpond

Spring Complex

FLORIDA'S

TURNPIKE

82°15 ́ 82°10 ́ 82°05 ́ 82°00 ́

28°55 ́

28°50 ́

28°45 ́

BIG

PRAIRIE

SPRING LOCATION AND INDEX

NUMBER--Data provided in

table 1

BIG PRAIRIE WATERSHED

SP4

Figure 5. Location of springs, spring complexes, and sinks in the Lake Panasoffkee study area. Site identification 

numbers and names are given in table 1.
Figure 6. Fenney Spring pool; photo by W. Scott McBride.

Table 1. Location and name of springs in the Lake Panasoffkee study area.

[n/a, not applicable]

Reference 

number 

(fig. 5)

USGS site 

identification 

number

Spring name Latitude Longitude

SP1 284515082032301 Dixie Lime & Stone Co. Spring 28°45′16′′ 82°03′19′′

SP2 284515082050001 Shady Brook Head Spring 4 28°45′15′′ 82°05′00′′

SP3 284524082040501 Belton's Millpond (Maintenance Spring) 28°45′24′′ 82°04′05′′

SP4 284526082034401 Belton's Millpond Head Spring 1 28°45′26′′ 82°03′44′′

SP5 284527082034301 Belton's Millpond Head Spring 2 28°45′27′′ 82°03′43′′

SP6 284528082034801 Belton's Millpond Head Spring 2a 28°45′28′′ 82°03′48′′

SP7 284529082034501 Belton's Millpond Head Spring 2b 28°45′29′′ 82°03′45′′

SP8 284529082034502 Belton's Millpond Head Spring 3 -main boil 28°45′29′′ 82°03′45′′

SP9 284533082055401 Big Hole (Dead Spring) 28°45′33′′ 82°05′55′′

SP10 284607082070101 Canal 485 Spring 5 28°46′07′′ 82°07′01′′

SP11 n/a Canal 485a Spring 1a 28°46′10′′ 82°07′05′′

SP12 284610082070401 Canal 485a Spring 1b 28°46′10′′ 82°07′05′′

SP13 284612082070301 Canal 485a Spring 2 28°46′13′′ 82°07′03′′

SP14 n/a Canal 485a Spring 3 28°46′13′′ 82°06′56′′

SP15 n/a Canal 485 Spring 4 28°46′07′′ 82°07′01′′

SP16 284646082023701 Shady Brook Head Spring 3 28°46′46′′ 82°02′37′′

SP17 284708082024401 Shady Brook Head Spring 2 (Blue Spring) 28°47′08′′ 82°02′44′′

SP18 284742082021901 Fenney Spring 28°47′42′′ 82°02′19′′

SP19 285104082051701 Wayne Lee Spring 28°51′04′′ 82°05′17′′

SP20 285138082054001 Henry Green Spring 28°51′38′′ 82°05′40′′

was investigated and was not flowing during August 

2006. The spring vent was silted in and did not appear to 

have flowed for many years. 

Blue Spring (SP17), also called Shady Brook 

Head Spring 2, is situated in a remote swamp on private 

property about 0.75 mi southwest of Fenney Spring 

(SP18) (also called Shady Brook Head Spring 1). An 

undeveloped pond surrounds the Blue Spring vent, and a 

spring run less than 0.2 mi in length flows west from the 

pond and empties into Shady Brook. 

Belton’s Millpond Spring Complex (SP4–SP8) is 

located about 0.25 mi northwest of the intersection of 

U.S. 301 and S.R. 470 at Sumterville (figs. 5 and 7). 

The complex consists of four springs (one spring has 

two vents) that form a pond that flows west over a gated 

spillway. Maintenance Spring (SP3) is located about 

0.25 mi southwest of Belton’s Millpond, and forms a 

circular pool (figs. 5 and 8) that overflows through a 

culvert pipe installed in a berm on the northwestern side 

of the pool. Both Belton’s Millpond Spring Complex and 

Introduction 11
12 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Maintenance Spring have been substantially modified from 

their undeveloped states by the addition of berms to increase 

the size of the pools around the spring vents. 

The runs formed by both Belton’s Millpond and 

Maintenance Spring flow northwestward into a large 

lowland swamp south of Shady Brook near the intersection 

with Lake Panasoffkee. Near their respective springs, 

Belton’s Millpond Spring run and Maintenance Spring run 

are well defined, but the channels quickly lose their definition as they flow through the swamp. Ultimately, water 

from these springs reaches Shady Brook by way of diffuse 

overland flow through the neighboring swamplands. 

EXPLANATION

Base from Southwest Florida Water Management District True Color Orthophotography; 2006.

Spring data modified from Florida Department of Environmental Protection, 2000.

Universal Transverse Mercator projection, Zone 17 North

0 250 500 FEET

0 50 100 METERS

SPRING LOCATION AND INDEX NUMBER--Data

provided in table 1

SURFACE-WATER STATION LOCATION AND INDEX

NUMBER--Data provided in table 2

SP8

SP7

SP6

SP5

SP4

SP3

SW13

SW12

AREA SHOWN

IN AERIAL

PHOTOGRAPH

SUMTER 301

COUNTY

470

301

Lake Panasoffkee

44

75

Belton's Millpond

Spring Complex

Belton's Millpond

Maintenance

Spring

COUNTY

CITRUS

SP4

SW12

Figure 7. Location of spring vents and surface-water gaging stations near Belton’s Millpond Spring Complex. 

Site identification numbers and names are given in tables 1 and 2.
Introduction 13

Dead Spring (SP9, fig. 5 and table 1), also called Big 

Hole, is located about 0.1 mi west of I–75 and 0.1 mi south 

of Shady Brook. No spring flow was detected at Dead Spring 

during this study, but drought conditions prevailed during the 

data-collection period and this spring may flow under wetter 

conditions. Elliot and others (1998) suggest that Dead Spring 

may be a karst window rather than a spring. A karst window 

is a subterranean passage exposed at land surface. Karst 

windows may be wet or dry, but no groundwater discharges 

from them because the potentiometric surface of the aquifer 

containing the karst window is below land surface.

Other notable karst features in the Lake Panasoffkee 

study area include Hogeye Sink, Walled Sink, and Double Sink 

(fig. 5). Hogeye Sink is located about 1 mi northeast of Fenney 

Spring (SP18) near the southwest shore of Lake Okahumpka. 

Hogeye Sink intercepts all or part of the water flowing in 

Chitty Chatty Creek toward Lake Okahumpka when the 

potentiometric surface of the Upper Floridan aquifer is below 

land surface. Hogeye Sink may be a source of water to Lake 

Okahumpka when the potentiometric surface is above land 

surface (Simonds and German, 1980). Hogeye Sink is probably hydraulically connected to Fenney Spring (SP18, fig. 5) 

through subterranean passageways based upon their proximity and the orientation of both features along a northeast/

southwest trending axis. During the study it was observed 

that after heavy rains, the color of the water emanating from 

Fenney Spring changes from blue to brown. The blue water 

is typical of discharge from the Upper Floridan aquifer, 

whereas the brown tannic-stained water is probably recently 

recharged surface water. Hogeye Sink and its associated karst 

features are a probable source of the tannic water, but further 

study would be needed to confirm this hypothesis. 

Walled and Double Sinks, plus at least two other 

unnamed sinks collectively referred to herein as the Walled 

Sink Complex, are located near Sumterville about 2.5 mi 

east-southeast of the intersection of U.S. 301 and S.R. 470 

(fig. 5). A 2-mi long unnamed creek flows northward into 

the sink complex where it recharges directly to the Upper 

Floridan aquifer. In the late 1960s or early 1970s, a network 

of canals was dug along the Lake and Sumter County border 

to drain parts of the Big Prairie watershed (Inwood Consulting 

Engineers, 2006). Big Prairie Canal flows northwestward out 

of the Big Prairie watershed and intersects the Walled Sink 

Complex. Big Prairie Canal probably only flows after excessive 

rainfall during flooding conditions, because most of the Big 

Prairie watershed appears to be internally drained. In recent 

years, mining activities around the Walled Sink Complex have 

affected the hydrology of the area. Satellite imagery indicates 

that mining activities have encroached on the sinks and may 

eventually eliminate them altogether (Southwest Florida Water 

Management District, 2010). A dry channel crosses under 

U.S. 301 just south of the intersection with S.R. 470 downstream from the sink complex; it is unclear whether this channel 

is natural or part of the Big Prairie Canal. In the past, water was 

likely conveyed along this channel during periods of high water 

Figure 8. Maintenance Spring 

pool; photo by W. Scott McBride.

Eastern cottonmouth moccasin; (Agkistrodon piscivorus piscivorus) at 

Maintenance Spring near Sumterville, Fla.; photo by W. Scott McBride
14 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

when the sink complex did not have the capacity to accept 

all of the flow from the Big Prairie watershed. After crossing 

under U.S. 301, flows would have intersected the Belton’s 

Millpond Spring Complex and Shady Brook before finally 

emptying into Lake Panasoffkee. 

Over the course of this study, no hydrologic data 

were collected at Hogeye, Walled, or Double Sinks or their 

related tributaries. None of these sinks appear to contribute 

flow directly to Lake Panasoffkee or its tributaries under 

normal hydrologic conditions. Some or all of these features 

may contribute flows to Lake Panasoffkee during periods of 

high water, but no connection was observed during the study 

period.

A series of residential canals and the Outlet River are 

located on the western shore of Lake Panasoffkee. Canals 

485 and 485A (fig. 9), located on the southwestern shore, 

contain at least six small spring vents, collectively known 

as Canal Springs Complex, which contribute flow to the 

0 250 500 FEET

0 50 100 METERS

SP11

SP15

SP13 SP14

SP12

SP10

EXPLANATION

Canal 485A

Canal 485

Base from Southwest Florida Water Management District True Color Orthophotography; 2006.

Spring data modified from Florida Department of Environmental Protection, 2000.

Universal Transverse Mercator projection, Zone 17 North

SP15

SPRING LOCATION AND INDEX

NUMBER--Number refers to

table 1 designation

AREA SHOWN

IN AERIAL

PHOTOGRAPH

SUMTER

COUNTY

Lake Panasoffkee

COUNTY

CITRUS

44

470 75

301

470

Figure 9. Location of springs in the Canal Springs Complex.
Methods of Investigation 15

lake (SP10-SP15, figs. 5 and 9, table 1). Outflow from Lake 

Panasoffkee is through the Outlet River midway along the 

western shore of the lake. A rock spillway, with two narrow 

breaks for the passage of boat traffic, lies across the head of 

Outlet River. Although the spillway was probably built in the 

1880s as a navigational improvement, the historical record 

is not clear as to who built the spillway and why (Wharton, 

1982). The Outlet River flows west for about 2 mi before 

emptying into the Withlacoochee River (fig. 2). 

Lake Panasoffkee contributes a substantial volume of 

water to the Withlacoochee River, and this water is especially 

important during periods of low river flow (Trommer and 

others, 2009). The Wysong-Coogler Dam (often condensed 

to “Wysong Dam”) is an inflatable bladder dam (fig. 5) 

located about 2.1 mi downstream from the confluence of 

the Outlet River and Withlacoochee River near the town of 

Carlson. This dam helps control stage in the Outlet River 

and Lake Panasoffkee in addition to the upper part of the 

Withlacoochee River.

Methods of Investigation

Multiple approaches were used to quantify the hydrology 

and surface-water/groundwater interactions in the Lake 

Panasoffkee watershed. This section describes the techniques 

and locations used to (1) measure flow, water level, evaporation, and precipitation, and (2) collect and process waterquality and geochemical samples. Geospatial techniques and 

water-budget methods also are described.

Measurement of Streamflow and 

Spring Flow

Surface-water data collection included continuous 

streamflow and spring stage measurements, and periodic 

spring flow measurements. Two USGS streamflow gages used 

in this study were in operation prior to the study period—one 

since the early 1960s (Outlet River, SW7) and the other since 

the early 1990s (Shady Brook, SW3) (fig. 10 and table 2). 

The streamflow gaging network was expanded for this 

study by adding continuous recorders at Little Jones Creek 

(SW6), Big Jones Creek (SW5), Warnel Creek (SW1), and an 

additional gage on Shady Brook (SW2) (fig. 10 and table 2). 

The second Shady Brook gage was added downstream of the 

existing station to capture inflow from springs downstream of 

the original gage. Spring stage monitoring sites were installed 

at Fenney Spring (SW10), Blue Spring (SW11), Belton’s 

Millpond Spring Complex (SW12), and Maintenance Spring 

(SW13) (fig. 10 and table 2). 

The Canal Springs Complex (fig. 9) was not instrumented 

because backwater conditions at the springs prevented accurate discharge measurements using acoustic Doppler velocity 

meters or acoustic Doppler current profilers. Advanced 

discharge measurement techniques, such as index velocity 

methods, would need to be applied to accurately measure the 

flow under these conditions, but application of these advanced 

techniques was beyond the scope of this study.

Periodic discharge measurements were made at each 

of the surface-water and spring sites mentioned previously. 

Rating curves that describe the relation of stage to discharge 

over the range of observed stages were developed for Little 

Jones Creek (SW6), Shady Brook (SW2), and Warnel Creek 

(SW1) (fig. 10 and table 2). Rating curves were necessary at 

these sites to calculate a water budget for Lake Panasoffkee. 

Big Jones Creek was not rated because the channel was dry or 

did not flow during the majority of the study period because 

of drought conditions. A previously established rating curve 

for Outlet River (SW7) was used for this study (fig. 10 and 

table 2).

In addition to the surface-water and spring sites where 

stage was continuously monitored, periodic discharge 

measurements were made at one surface-water site and two 

spring sites. The surface-water site was located on Shady 

Brook (SW4) and the spring sites were Henry Green Spring 

(SW8) and Wayne Lee Spring (SW9) (fig. 10 and table 2). 

Access to these springs was not granted by the private owners, 

but discharge from the springs was measurable where the 

spring runs crossed public land. These sites were measured 

during the four synoptic streamflow runs (seepage runs) 

conducted during this study.

Seepage runs are used to quantify gains and losses of 

water under baseflow conditions, which occur during periods 

of little rainfall when a stream is contained within its banks 

and stream stage is static. Under these conditions, nearly all 

of the water entering or leaving a stream is contributed by 

groundwater, either as spring flow, groundwater inflow, or 

both. To perform the seepage runs, each stream was divided 

into reaches and at least one discharge measurement was made 

within every reach. The length of each reach was primarily 

Streamgage showing continuous recorder; photo by W. Scott McBride
16 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Figure 10. Location of surface-water stations in the Lake Panasoffkee study area. Site identification numbers 

and names are given in table 2.

FLORIDA'S

TURNPIKE

44

470 75

301

301

CITRUS COUNTY

SUMTER COUNTY

0 2 MILES

0 2 KILOMETERS

82°15 ́ 82°10 ́ 81°00 ́

28°50 ́

28°45 ́

81°05 ́

28°55 ́

Tsala

Apopka

Lake Lake Panasoffkee

Jumper

Creek

Little Jones Creek

BigJones

Creek

Shady

Brook

Withlacoochee

River

Outlet

River

Big Prairie

Canal

SURFACE WATER STATION LOCATION

AND INDEX NUMBER--Data provided

in table 2

SW4

EXPLANATION

Base modified from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005.

Universal Transverse Mercator projection, Zone 17 North

Wysong

Dam

Wildwood

Lake

Panasoffkee

Carlson

Coleman

Sumterville

SW9

SW8

SW7

SW6

SW5

SW4 SW3

SW2

SW1

SW13

SW12

SW11

SW10

Hogeye

Sink

Lake

Okahumpka

Warnel

Creek

470

Chitty

Chatty

Creek

Unnamed

Creek

determined by the location of stream cross sections suitable 

for discharge measurements, often at bridge crossings where 

streamflow is funneled into well-defined channels. Net gains 

or losses of flow to the main channel from other sources of 

flow, such as tributaries and springs, also had to be measured. 

Net gains or losses of flow in excess of the discharge 

measurement error were attributed to groundwater inflow or 

outflow from the stream. All of the discharge measurements 

during a seepage run were performed within as short a time 

frame as possible, and were typically collected in upstream 

to downstream order. Seepage runs are usually made only 

during the dry season, but because of the drought conditions 

during this study, it also was possible to make them during the 

summer months, when the conditions are typically wetter and 

stage is not static.

Sources of discharge data included records of streamflow 

at USGS gages, acoustic Doppler velocity meter measurements, and acoustic Doppler current profiler measurements. 
Methods of Investigation 17

Streamflow at each location was either measured directly 

or taken from an established rating curve developed for 

that site. Standard USGS methods, as described in Rantz 

and others (1982) and Oberg and others (2005), were used 

to make discharge measurements and compute streamflow. 

Small differences in streamflow were not always considered 

significant for calculating seepage gains and losses. When 

differences in streamflow between stations were greater 

than 5 percent and the streamflow was greater than 0.5 ft3/s, 

the gain or loss was considered significant (Hortness and 

Vidmar, 2005).

Measurement of Groundwater Levels

Groundwater levels were recorded at six paired monitoring well sites consisting of at least one surficial aquifer 

monitoring well and one Upper Floridan aquifer monitoring 

well (fig. 11 and table 3). Temporal patterns of recharge and 

discharge were evaluated for each site by comparing differences in groundwater levels in each well pair. Two well sites 

were installed specifically for this study: Big Jones Creek 

(GW5–GW6) and Little Jones Creek (GW7–GW8) (fig. 11 

and table 3). The remaining paired well sites are part of the 

SWFWMD Regional Observation and Monitoring Well 

Program (ROMP). These include ROMP wells LP–4 (GW24 

and GW26), LP–5 (GW31–GW32), LP–6 (GW37–GW38), 

and Wysong Dam (GW14–GW15) (fig. 11 and table 3). 

The “LP” well designation stands for “Lake Panasoffkee,” 

and was assigned to each well by the SWFWMD. At the 

start of this study, the USGS installed pressure transducers 

in the wells at Big Jones Creek, Little Jones Creek, LP–4, 

LP–5, and Wysong Dam; LP–6 was already instrumented by 

the SWFWMD. In January 2007, the SWFWMD replaced 

the USGS instruments with their own at ROMP sites LP–4 

(GW24 and GW26) and LP–5 (GW31–GW32) as part of a 

long-term groundwater-level monitoring project. 

Three drivepoint piezometers (temporary, small diameter 

wells used to determine the elevation of the water table) were 

installed along the shore of Lake Panasoffkee (GW18, GW22, 

and GW39) to study the relation between the lake elevation 

and the water table in the shallow surficial aquifer beneath the 

lake (fig. 11 and table 3). A fourth piezometer was installed 

on the bank of Shady Brook about 0.5 mi upstream of Lake 

Panasoffkee (GW30). One piezometer (GW39) was destroyed 

shortly after installation by lake restoration activities and 

was never replaced because of continued restoration activity 

in the area. The drivepoint piezometers consisted of 0.75-in. 

diameter stainless-steel drivepoints about 9 in. long that were 

perforated with holes backed with a fine stainless-steel screen. 

The drivepoints were screwed onto a 0.75-in. diameter steel 

pipe and manually driven to depth, typically between 3 and 

10 ft below land surface. Water levels in some of the first 

piezometers installed were slow to equilibrate to surrounding 

surficial aquifer water levels after installation, sometimes 

requiring 1 full day to equilibrate. Upon removal, one of the 

first piezometers installed was inspected and found to have 

the drivepoint openings sealed over with clayey sand. After 

this discovery, all of the piezometers were flushed with water 

using a 0.375-in. diameter threaded steel rod as a surging 

tool. Three rubber washers were sandwiched between steel 

nuts at one end of the rod. The rubber washers created a tight 

seal inside the piezometer bore, and when the steel rod was 

lowered to the bottom of the piezometer and plunged up and 

Table 2. Location of surface-water stations in the Lake Panasoffkee study area.

[USGS, U.S. Geological Survey]

Reference 

number 

(fig. 10)

USGS site identification 

number Station name Latitude Longitude

SW1 284554082052700 Warnel Creek 350 feet above I–75 at Lake Panasoffkee 28°45′54′′ 82°05′27′′

SW2 284534082054400 Shady Brook 350 feet above I–75 at Lake Panasoffkee 28°45′34′′ 82°05′44′′

SW3 02312667 Shady Brook near Sumterville 28°46′12′′ 82°03′50′′

SW4 284619082032700 Shady Brook 0.7 mile above U.S. 301 near Sumterville 28°46′19′′ 82°03′27′′

SW5 285126082085200 Big Jones Creek 2 miles above Lake Panasoffkee near Carlson 28°51′26′′ 82°08′52′′

SW6 02312675 Little Jones Creek near Rutland 28°50′33′′ 82°07′49′′

SW7 02312700 Outlet River at Panacoochee Retreats 28°48′00′′ 82°09′11′′

SW8 285207082054100 Henry Green Spring Run at Wildwood 28°52′07′′ 82°05′41′′

SW9 285133082053100 Wayne Lee Spring Run at I–75 near Wildwood 28°51′33′′ 82°05′31′′

SW10 02312664 Fenney Springs near Coleman 28°47′42′′ 82°02′19′′

SW11 284709082024100 Blue Spring at Sumter County 28°47′09′′ 82°02′41′′

SW12 284530082034800 Belton’s Millpond Complex near Sumterville 28°45′31′′ 82°03′50′′

SW13 284525082040600 Maintenance Spring Run near Sumterville 28°45′25′′ 82°04′06′′
18 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Figure 11. Location of wells in the Lake Panasoffkee study area. Site identification numbers and names are 

shown in table 3.

CITRUS COUNTY

SUMTER COUNTY

FLORIDA'S

TURNPIKE

44

470

75

301

301

0 2 MILES

0 2 KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005.

Universal Transverse Mercator projection, Zone 17 North

Wysong

Dam

82°15 ́ 82°10 ́ 81°00 ́

28°50 ́

28°45 ́

81°05 ́

28°55 ́

Little Jones Creek

Big Jones Creek

Shady

Brook

Withlacoochee River

Jumper

Outlet

River

Lake

Panasoffkee

Wildwood

Lake

Panasoffkee

Carlson

Coleman

Sumterville

GW9

GW8

GW7

GW6

GW5 GW3

GW2

GW1

GW48

GW47

GW46

GW45

GW44

GW43

GW41

GW40

GW39

GW36

GW35

GW34

GW33

GW32

GW31

GW30

GW29 GW28

GW27

GW26

GW25

GW24

GW23

GW21 GW22

GW20

GW19

GW17 GW18 GW16

GW15

GW14

GW13

GW12

GW11

GW10

GW4

GW42

GW38

GW37

Creek

Hogeye

Sink

Lake

Okahumpka

Warnel

Creek

EXPLANATION

WELL LOCATION AND INDEX

NUMBER--Data provided in

table 3

GW28

Big Prairie

Canal

470

Chitty

Chatty

Creek

Unnamed

Creek

Tsala

Apopka

Lake

down, the resulting change in pressure forced water in and 

out of the drivepoint openings. The flushing water cleared the 

drivepoint perforations of debris encountered during the installation process. Afterwards, water levels in the piezometers 

equilibrated within a few hours instead of days. 

Surficial aquifer water levels were measured in these 

piezometers using a graduated steel tape to measure the 

distance from a permanently inscribed measuring point at the 

top of the steel casing down to the equilibrated groundwater 

level inside the casing. If the piezometers were standing in 

lake water at the time of the measurement, the lake level was 

recorded by measuring the distance from the measuring point 

on the piezometer down to the lake water surface. If lake 

levels were low and the piezometers were on dry ground, the 

lake levels were measured using a nearby independent reference point permanently mounted over the lake water surface. 
Methods of Investigation 19

Table 3. Additional wells in the Lake Panasoffkee study area used to augment regional potentiometric-surface and water-table maps.

[USGS, U.S. Geological Survey; WMA, wildlife management area; UFA, Upper Floridan aquifer; SA, surficial aquifer; ft, feet]

Reference 

number 

(fig. 11)

USGS site 

identification 

number

Well name Latitude Longitude

Measuring 

point 

elevation, 

ft above 

NGVD 29

Well depth, 

ft below 

land 

surface

Aquifer

GW1 285232082054801 Wildwood Truck Wash 92 ft UFA well 28°52′32′′ 82°05′48′′ 52.91 92 UFA

GW2 285241082075001 The Preserve 99 ft UFA well 28°52′41′′ 82°07′50′′ 70.48 99 UFA

GW3 285142082080801 Lake Panasoffkee WMA fenceline UFA well 28°51′42′′ 82°08′08′′ 68.03 80 UFA

GW4 285128082082501 Lake Panasoffkee WMA house UFA well 28°51′28′′ 82°08′25′′ 64.68 81 UFA

GW5 285125082085301 Big Jones Creek 48 ft UFA well 28°51′25′′ 82°08′53′′ 50.73 48 UFA

GW6 285125082085302 Big Jones Creek 7 ft SA well 28°51′25′′ 82°08′53′′ 50.76 7 SA

GW7 285035082075401 Little Jones Creek 48 ft UFA well 28°50′35′′ 82°07′54′′ 47.78 48 UFA

GW8 285035082075402 Little Jones Creek 11 ft SA well 28°50′35′′ 82°07′54′′ 47.68 11 SA

GW9 285118082093801 Santana House 70 ft UFA well 28°51′18′′ 82°09′38′′ 58.89 70 UFA

GW10 285119082120601 Sumter 13 replacement well 28°51′19′′ 82°12′06′′ 52.61 32 UFA

GW11 285130082102901 7018 CR470 181 ft UFA well 28°51′30′′ 82°10′29′′ 58.00 181 UFA

GW12 285048082101101 Tree Farm 67 ft UFA well 28°50′48′′ 82°10′11′′ 53.50 67 UFA

GW13 285011082103201 Vach House 37 ft UFA well 28°50′11′′ 82°10′32′′ 55.19 37 UFA

GW14 284924082105501 Wysong Dam 84 ft UFA well 28°49′24′′ 82°10′55′′ 44.38 84 UFA

GW15 284924082105502 Wysong Dam 10 ft SA well 28°49′24′′ 82°10′55′′ 44.19 10 SA

GW16 284900082101101 Lewis House 171 ft UFA well 28°49′0′′ 82°10′11′′ 51.19 171 UFA

GW17 284840082093501 SWFWMD W470 81 ft UFA well 28°48′40′′ 82°09′35′′ 50.25 81 UFA

GW18 284847082082701 Pfettscher 5 ft shallow well* 28°48′47′′ 82°08′27′′ 41.70 5 SA

GW19 284811082091301 (ROMP) LP-3 152 ft UFA well 28°48′12′′ 82°09′13′′ 54.06 152 UFA

GW20 284741082084601 Register 38 ft UFA well 28°47′41′′ 82°08′46′′ 47.63 38 UFA

GW21 284736082075001 Cowrat 84 ft UFA well 28°47′36′′ 82°07′50′′ 50.57 84 UFA

GW22 284734082071201 Tracy’s Point 5 ft shallow well1 28°47′34′′ 82°07′12′′ 41.20 5 SA

GW23 284653082084201 Haley Ray 52 ft UFA well 28°46′53′′ 82°08′42′′ 48.96 52 UFA

GW24 284628082073801 (ROMP) LP-4 240 ft UFA well 28°46′29′′ 82°07′38′′ 52.82 240 UFA

GW25 284628082073802 (ROMP) LP-4 120 ft UFA well 28°46′29′′ 82°07′38′′ 52.82 120 UFA

GW26 284628082073803 (ROMP) LP-4 30 ft SA well 28°46′29′′ 82°07′38′′ 52.80 30 SA

GW27 284541082071101 Marthas Lane 49 ft UFA well 28°45′41′′ 82°07′11′′ 58.90 49 UFA

GW28 284518082070901 CR489A 45 ft UFA well 28°45′18′′ 82°07′09′′ 59.72 45 UFA

GW29 284528082055201 Sumter County 170 ft UFA well 28°45′28′′ 82°05′52′′ 50.41 170 UFA

GW30 284535082054701 Lake Panasoffkee at I-75 crossing1 28°45′35′′ 82°05′47′′ 41.32 10 SA

GW31 284456082053101 (ROMP) LP-5 139 ft UFA well 28°44′57′′ 82°05′31′′ 67.27 139 UFA

GW32 284456082053102 (ROMP) LP-5 40 ft SA well 28°44′57′′ 82°05′31′′ 66.52 40 SA

GW33 284455082041401 Barber Shop 105 ft well 28°44′55′′ 82°04′14′′ 66.91 105 UFA

GW34 284437082033901 841 CR539A 140 ft UFA well 28°44′37′′ 82°03′39′′ 79.83 140 UFA

GW35 284619082035101 ROMP 111 deep well at Tompkins Park 28°46′20′′ 82°03′51′′ 63.50 185 UFA

GW36 284658082040301 1849 U.S. 301 50 ft UFA well 28°46′58′′ 82°04′03′′ 60.08 50 UFA

GW37 284759082054101 (ROMP) LP-6 154 ft UFA well 28°48′01′′ 82°05′41′′ 55.98 154 UFA

GW38 284759082054102 (ROMP) LP-6 25 ft SA well 28°48′01′′ 82°05′41′′ 56.17 25 SA

GW39 284756082061301 Coleman Landing 5 ft shallow well1 28°47′56′′ 82°06′13′′ 41.27 5 SA
20 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Reference 

number 

(fig. 11)

USGS site 

identification 

number

Well name Latitude Longitude

Measuring 

point 

elevation, 

ft above 

NGVD 29

Well depth, 

ft below 

land 

surface

Aquifer

GW40 284755082061101 Coleman Landing SA monitor well 28°47′55′′ 82°06′11′′ 41.78 13 SA

GW41 284810082033501 Spurling Dr 84 ft UFA well 28°48′10′′ 82°03′35′′ 64.79 84 UFA

GW42 284731082023801 Fenney Spring 53 ft UFA well 28°47′31′′ 82°02′38′′ 58.97 53 UFA

GW43 284720082024801 Fenney Spring 18 ft SA well 28°47′20′′ 82°02′48′′ 54.97 18 SA

GW44 285020082023701 Sleep Inn 85 ft UFA well 28°50′20′′ 82°02′37′′ 61.77 85 UFA

GW45 285202082042001 Caruthers 130 ft UFA well 28°52′02′′ 82°04′20′′ 70.05 130 UFA

GW46 285227082044301 Caruthers Windmill 132 ft UFA well 28°52′27′′ 82°04′43′′ 112.24 132 UFA

GW47 284912082092901 3847 CR470 39 ft UFA well 28°49′12′′ 82°09′29′′ 53.16 39 UFA

GW48 284536082080701 CR416N 200 ft UFA well 28°45′49′′ 82°07′59′′ 47.14 200 UFA

1

Temporary piezometer.

Table 3. Additional wells in the Lake Panasoffkee study area used to augment regional potentiometric-surface and water-table maps.—

Continued

[USGS, U.S. Geological Survey; WMA, wildlife management area; UFA, Upper Floridan aquifer; SA, surficial aquifer; ft, feet]

Water-level measurements at 31 Upper Floridan aquifer 

wells around Lake Panasoffkee were coordinated to coincide with the measurement of the more than 1,100 wells 

used to create the May (dry season) and September (wet 

season) regional potentiometric-surface maps of the Upper 

Floridan aquifer throughout central Florida (Kinnaman and 

Dixon, 2008; Ortiz, 2008a, b, c, and 2009). The additional 

31 wells in the vicinity of Lake Panasoffkee were combined 

with about 340 of the regional wells (app. 1) to create more 

detailed potentiometric-surface maps within the study 

area. The number of wells measured during each synoptic 

water-level survey varied slightly because of difficulties in 

measuring water levels in certain wells, and because new 

wells were sometimes added to the surveys when gaps in 

data coverage were identified. In addition to the monitoring 

wells, domestic (household) wells were frequently used to 

help define the Upper Floridan aquifer potentiometric surface 

within the study area because many of these wells were available in suitable condition for use. Surficial aquifer water levels 

were also measured during the synoptic surveys at the three 

piezometer and six paired well sites described above.

Geospatial Techniques

Each of the Upper Floridan potentiometric-surface 

and surficial aquifer water-table maps was created in a 

geographic information system (GIS) environment using the 

tension-splines interpolation method (Buto and Jorgensen, 

2007; Environmental Systems Research Institute, Inc., 

2009). This is an exact interpolator technique that allows 

the resulting raster surfaces to match the values of the input 

datapoints used to create the surface. The resulting Upper 

Floridan aquifer potentiometric-surface raster grid was then 

subtracted from the surficial aquifer water-table raster grid 

to estimate the difference in water level between the two 

aquifers. Positive water-level differences resulted in areas 

where Upper Floridan aquifer water levels exceeded the 

surficial aquifer water levels, indicating potential for upward 

groundwater discharge. Negative water-level differences 

indicated areas of groundwater recharge potential from the 

surficial aquifer to the Upper Floridan aquifer. The raster 

grids also were used to draw water-level contour lines, which 

were then modified in GIS to remove artifacts of the interpolation process.

A geostatistical cross validation was then run on the 

input datasets used to create the raster grids in which each 

water-level datapoint was removed iteratively and the raster 

was interpolated using the remaining datapoints. The resulting 

difference between each removed point and the interpolated 

value at that location is the error. These methods are set forth 

in the National Standard for Spatial Data Accuracy (Federal 

Geographic Data Committee, 1998). 

The surface-water drainage basin was delineated using 

the best available data from the National Elevation Dataset 

(Gesch and others, 2002; Gesch, 2007). The digital elevation 

model was derived from cartographic contours and mapped 

hydrography, and was resampled to a horizontal resolution 

of 10 m (32.8 ft). The data were downloaded from the USGS 

National Map Seamless Server and processed using ArcHydro 

(Maidment, 2002) within the ArcGIS (Environmental Systems 

Research Institute, 2006) working environment.
Methods of Investigation 21

L is latent heat of vaporization, a function of air 

temperature, in calories per gram; and

BR is the Bowen ratio (the ratio of sensible to latent 

heat) calculated from: 

γP(To - Ta) / (eo - ea) (2)

where

γ is the psychrometric constant, which varies from 0.66 

to 0.67 depending on atmospheric pressure and 

temperature, in millibars per degree Celsius;

P is atmospheric pressure, set to 1,013 millibars;

Ta is air temperature, in degrees Celsius;

eo is saturation vapor pressure at water-surface temperature, in millibars; and

ea is vapor pressure at air temperature, in millibars.

When considering the energy content of a water body 

of varying mass, a base temperature, Tb, must be selected 

to calculate the advected energy term, Qv (Anderson, 1954; 

Saur and Anderson, 1956). For this application, the average 

temperature of the largest unknown flux, groundwater 

inflow, was used as the base temperature to reduce the 

effect of errors in quantifying this term on the calculated 

evaporation.

Groundwater inflow, QGWin, is the diffuse flow (or 

discharge) of groundwater to Lake Panasoffkee through the 

porous lakebed. Groundwater inflow also occurs through 

the streambeds of the tributaries that feed Lake Panasoffkee, 

Floating data-collection raft on Lake Panasoffkee, carrying a suite of 

instrumentation to measure air and water temperature, relative humidity, 

windspeed, and net radiation; photo by W. Scott McBride

Calculation of Evaporation and 

Groundwater Inflow

Previous water-budget studies of Lake Panasoffkee 

used estimates of evaporation and diffuse groundwater 

inflow in their calculations (CH2M Hill, 1995). In this 

study, lake evaporation was measured by installing a 

floating data-collection raft over the deepest section of the 

lake. The suite of instrumentation on the raft collected the 

data necessary for calculating the lake evaporation rate 

using an energy-budget method. The raft included sensors 

for measuring air temperature, water temperature at 1-ft 

intervals, relative humidity, windspeed, and net radiation. Thermal surveys were performed every other week 

at nine stations on Lake Panasoffkee to determine if the 

lake water temperature was well mixed vertically, and to 

ensure that water-temperature data collected at the raft were 

representative of the entire lake system. At each of the nine 

thermal stations, a weighted thermistor was lowered to the 

lake bottom and then raised 3 to 6 in. above the sediment. 

Temperature readings were recorded at 1-ft intervals from 

the lake bottom to the water surface. The instrumentation 

was serviced on the same days the thermal surveys were 

performed. The SWFWMD has previously performed 

bathymetric surveys that were used to calculate the lake 

volume. More detailed descriptions of equipment and 

energy-budget equations are presented in Swancar and 

others (2000) and Allander and others (2009).

Evaporation from the lake surface was calculated 

using the energy-budget equation, originally described 

by Anderson (1954) and applied more recently in Florida 

by Swancar and others (2000). Evaporation is calculated 

as the residual term of a lake-energy budget for which all 

other terms are either measured or estimated, using the 

equation:

EEB = Qn+ Qv - Qx / [c(To – Tb) + ρ(L * (1 + BR))] (1)

where

EEB is energy-budget evaporation rate, in centimeters 

per day;

Qn is net radiation, in calories per square centimeter 

per day;

Qv is advected energy from all inflows and outflows, 

in calories per square centimeter per day;

Qx is change in stored energy, in calories per square 

centimeter per day;

c is the specific heat of water, 1 cal/cm3;

To is water-surface temperature, in degrees Celsius;

Tb is the base temperature, in degrees Celsius;

ρ is the density of water, 1 g/cm3;
22 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

but this inflow is accounted within the lake water budget as 

discharge measured at stream gages located near the mouth of 

each tributary. Groundwater fluxes are dependent on the relations among the lake water level, surficial aquifer water level, 

and the Upper Floridan aquifer water level (Schiffer, 1998). 

If the elevation of the potentiometric surface of the Upper 

Floridan aquifer is greater than the lake water level, there is 

potential for groundwater inflow into the lake. Groundwater 

inflow occurs within the surficial aquifer, if present, or directly 

from the Upper Floridan aquifer where the lake is in direct 

contact with the aquifer (Schiffer, 1998). Seepage losses from 

Lake Panasoffkee to the underlying aquifer are assumed to be 

negligible because of the upward difference. This is atypical of 

most Florida lakes, which have both groundwater inflow and 

outflow (Sacks and others, 1998; Schiffer, 1998). 

Groundwater inflow to the lake was calculated as the 

residual term of the lake water-budget equation:

QGWin = ΔS - Pr + EEB - QSWin + QSWout - QOWTSin (3)

where

QGWin is monthly groundwater inflow, in cubic feet;

ΔS is monthly change in lake storage, in cubic feet;

Pr is monthly rainfall on the lake, in cubic feet;

EEB is monthly energy-budget evaporation, in 

cubic feet;

QSWin is monthly surface-water inflow, in cubic feet;

QSWout is monthly surface-water outflow (including 

dredging outflow), in cubic feet; and

QOWTSin is monthly groundwater inflow from onsite 

wastewater-treatment systems, in cubic feet.

All water-budget terms are expressed in both cubic feet 

and as inches of water over the average lake surface area for 

each month. Errors in each term were based on a previous 

study conducted in central Florida (Swancar and others, 2000) 

and were combined to estimate the error in groundwater 

inflow using the following equation (Sacks and others, 1998):

ErrGWin =[[(0.05(ΔS))]2

+ (0.05(Pr))2 + (0.15(EEB))2

+ (0.10(QSWin))2 + (0.05(QSWout))2

+ (1.00(QOWTSin))2]]0.5 (4)

Errors in monthly water-budget terms were assumed to 

be 5 percent for change in stage/volume, monthly rainfall, and 

surface-water outflows; 10 percent for surface-water inflows; 

15 percent for evaporation; and 100 percent for onsite septic 

wastewater-treatment system (OWTS).

Collection of Precipitation Data 

The average monthly rainfall for the Lake Panasoffkee 

region was calculated using rainfall data compiled by the 

National Climatic Data Center (NCDC) from the Inverness 

3E weather station (084289) at Inverness, Florida, from 1930 

to 2008 (fig. 12). Nine missing data records in the Inverness 

location were filled by using data from other nearby NCDC 

weather station sites (Ocala 2NE station (086419) near Ocala, 

Florida, or the Bushnell 1E station (081163) near Bushnell, 

Florida) (fig. 12). The average 78-year monthly rainfall for 

the region was computed to assess the variability in wet or dry 

season rainfall during the study period compared to long-term 

average rainfall.

During water years 2007 and 2008, the USGS collected 

rainfall data at three stations within the Lake Panasoffkee 

watershed using electronic tipping-bucket sensors. These 

sensors were located at Little Jones Creek (station 02312675), 

Outlet River (station 02312700), and Withlacoochee River 

at Wysong Dam (station 02312720) (fig. 12). The sensors 

were calibrated annually in the laboratory both before and 

after deployment to track data quality; no corrections to the 

data were needed. While deployed in the field, the sensors 

were regularly checked for debris and obstructions and 

tested for operability. Once the rainfall data were collected, 

daily rainfall totals were summed to determine the monthly 

rainfall for each station. The average of the three monthly 

rainfall totals was used as the total monthly rainfall for the 

entire Lake Panasoffkee watershed. The same procedure was 

used to determine the total rainfall in the Lake Panasoffkee 

watershed for water year 2006, using rainfall data collected at 

two SWFWMD stations, LP–6 (2760) and Lake Panasoffkee 

(6087), because the USGS rain sensors were not yet installed 

(fig. 12).

Determination of Lake Volume and Change 

in Storage 

To calculate lake volume and the change in storage as 

lake levels fluctuated, it was necessary to know the shape 

and depth of the lake. A triangulated irregular network (TIN) 

model of the bottom of Lake Panasoffkee was developed by 

the SWFWMD in 2005 using point-depth measurements along 

1,000-ft transects across the lake. The TIN model incorporates 

areas susceptible to inundation around the lake, with elevations up to 44 ft above NGVD 29 (fig. 13). This model was 

obtained by the USGS and used to interpolate volumes and 

surface areas at 0.01-ft intervals of lake stage. These calculations were then used in the water- and energy-budget equations as required.

Water and sediment were removed from the lake 

throughout much of this study by a dredge that operated on an 

intermittent schedule, up to 24 hours a day, as part of the Lake 

Panasoffkee restoration effort. Full scale restoration efforts 

began in December 2003 and were completed in October 2008 
Methods of Investigation 23

CITRUS

COUNTY

SUMTER COUNTY

MARION COUNTY

LEVY

COUNTY

HERNANDO COUNTY

LAKE COUNTY

Tsala

Apopka

Lake

Lake

Panasoffkee

Withlacoochee

River

Lake Harris

Lake

Weir

Lake Griffin

Ocala

Bushnell

Wildwood

Dunnellon

Inverness

Lake Panasoffkee

6087

2760

081163

086419

084289

02312720

02312700

02312675

02555

670277

02312698

081163

670277

EXPLANATION

SURFACE-WATER STATION

LOCATION AND NUMBER

RAINFALL SENSOR LOCATION

AND STATION NUMBER

Base modified from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005.

Universal Transverse Mercator projection, Zone 17 North

Outlet

River

Little

Creek

Shady Brook

Big

Jones

Creek Jones

Jumper

Creek

0 5 MILES

0 5 KILOMETERS

82°20 ́ 82°10 ́ 82°00 ́ 81°50 ́

29°10 ́

29°00 ́

28°50 ́

28°40 ́

Ocklawaha River

Figure 12. Location of rain gages and current and historic lake-stage gages in the Lake Panasoffkee study area. 
24 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Figure 13. Lake Panasoffkee bathymetric model.

Lake bathymetry data from Southwest Florida Water Management District; 2005

Universal Transverse Mercator projection, Zone 17 North

Wysong Dam

EXPLANATION

LAKE BOTTOM ELEVATION,

IN FEET ABOVE NGVD 29

82°10 ́ 82°05 ́

28°50 ́

0 2 MILES

0 2 KILOMETERS

FLORIDA'S TURNPIKE

75

470

301

Tsala

Apopka

Lake

Little Jones Creek

Shady

Brook

Withlacoochee

River

Outlet

River

Warnel Creek

Big

Jones Creek

Big Prairie Canal

CITRUS

COUNTY

SUMTER COUNTY

Lake Panasoffkee

Carlson

Coleman

LAKE PANASOFFKEE BOUNDARY--Digitized

from U.S. Geological Survey High

Resolution Orthoimagery for Coastal

Florida, 2006

42.1 to 44.0

40.1 to 42.0

38.1 to 40.0

36.1 to 38.0

34.1 to 36.0

32.1 to 34.0

29.6 to 32.0
Methods of Investigation 25

(Lake Panasoffkee Restoration Council, 2008). A detailed 

daily log of the number of hours of pumping was kept by the 

dredge operator. The number of hours of daily pump operation 

was multiplied by the nominal pumping rate to estimate the 

volume of water and sediment removed from the lake each 

day. The average solids content of the pumpage was estimated 

by the SWFWMD to be 10–13 percent by weight. Using a 

rough estimate of 2.66 g/cm3 for the density of silt particles, 

the average solids content of the pumpage was calculated to be 

about 5 percent by volume. This factor was applied to the total 

daily pumpage to estimate the volume of water and sediment 

removed from the lake. Daily water and sediment calculations 

were then summed by month, and estimates of water removed 

were incorporated into the water-budget calculations.

Three stations with continuous water-level recorders have 

been used to measure stage at Lake Panasoffkee (fig. 12). One 

station was operated by the USGS (02312698 – Lake Panasoffkee 

near Lake Panasoffkee, Florida) from 1955 through 2006. In 

February 2007, after the USGS station was discontinued, the 

SWFWMD installed a station with a water-level recorder 

on Lake Panasoffkee (670277 – Lake Panasoffkee-Jeffcoat). 

A third station, also operated by the SWFWMD, is located on 

the Outlet River about 800 ft downstream of Lake Panasoffkee 

(02555 – Pana Vista Outlet River). This station was in operation throughout the entire study period. Although this station 

is located on the Outlet River, the data collected differed 

minimally from data collected at the Jeffcoat gage. The average 

difference between the water-level data at Pana Vista Outlet 

River and Lake Panasoffkee-Jeffcoat was 0.03 ft. Because it 

was equally representative of lake stage and covered the entire 

study period, the water-level data from the Pana Vista Outlet 

River station were used to represent lake stage for this analysis.

Geophysical Measurements

The shallow hydrogeologic framework underlying Lake 

Panasoffkee was investigated using high-resolution seismic 

sub-bottom profiling equipment. The survey was conducted 

using a C–Products low-voltage seismic-reflection boomer 

with Teledyne Instruments SDS–55 10-receiver hydrophones. 

An EdgeTech 3200–XS sub-bottom profiler with SB 424 

compressed high intensity radar pulse (CHIRP) towfish also 

was used. Both units are towed behind a motor boat and 

collect continuous data. 

Two electromagnetic seepage meters were installed in 

Lake Panasoffkee to directly quantify groundwater inflow into 

the lake. The seepage meters consisted of aluminum domes 

of known volume that were driven into the lake bottom with 

as little disturbance to the underlying sediments as possible. 

All trapped air was released from inside the domes by way of 

a valve. The domes are essentially upside-down funnels that 

concentrate the bidirectional exchange of groundwater and 

surface water through a narrow neck fitted with an electromagnetic flow meter capable of detecting seepage velocities as 

low as 4 in/d (Swarzenski, 2004). 

Water Chemistry Sampling Methods and 

Analysis

Water-chemistry data are helpful in evaluating the 

sources of water and groundwater flow paths within the 

watershed, and for assessing the processes controlling the 

surface-water and groundwater quality. In particular, isotopic 

and age dating parameters can be useful for determining the 

transport mechanisms of flow through a hydrologic system. 

Sources of water to Lake Panasoffkee include rainfall, springs, 

tributaries, and the surficial aquifer and Floridan aquifer 

system. All of these sources affect the chemistry of the lake 

water and provide information about the water’s origin. 

Samples were collected in July 2007, and in December 

2008 through January 2009 to characterize the water quality 

in the Lake Panasoffkee watershed. Samples were collected 

from Lake Panasoffkee, tributaries, springs, and groundwater. 

Groundwater samples were collected from wells installed in 

the surficial aquifer and Upper Floridan aquifer, and a single 

sample was collected from the Lower Floridan aquifer below 

middle confining unit I. 

The first round of samples was collected in July 2007 at 

12 groundwater sites, 5 spring sites, and 7 surface-water sites 

(fig. 14 and table 4). Samples were analyzed for dissolved 

major ions and some trace metals, dissolved organic carbon, 

nutrients, and the isotopic ratios of strontium (87Sr/86Sr), oxygen 

(

18O/16O), and hydrogen (2

H/H). Dissolved major ions and trace 

metals, dissolved organic carbon, and nutrient samples were 

analyzed by the USGS National Water-Quality Laboratory in 

Denver, Colorado. The 87Sr/86Sr ratios were determined by 

the USGS Water Resources Radiogenic Isotope Laboratory in 

Menlo Park, California. The USGS Stable Isotope Laboratory in 

Reston, Virginia, analyzed samples for 18O/16O and 2H/H.

The second round of water-quality samples was collected 

from December 2008 through January 2009. Samples were 

collected at 17 groundwater sites, 4 spring sites, and 5 surfacewater sites (fig. 14 and table 4). Compared to July 2007, five 

additional groundwater sites were sampled and one spring 

and two surface-water sites were dropped. The samples were 

collected using the same USGS protocols described earlier and 

samples were analyzed for the same properties, but additional 

age dating and isotope samples were collected at select sites. 

Chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) 

age dating samples were collected at 11 groundwater sites and 

were analyzed at the USGS Chlorofluorocarbon Laboratory in 

Reston, Virginia. Samples from the three deepest monitoring 

wells were analyzed for the radioactive isotopes of carbon 

(

14C) and hydrogen (3H, tritium). Analysis of the 14C samples 

was done at the National Ocean Sciences Accelerator Mass 

Spectrometry Facility in Woods Hole, Massachusetts, whereas 

the 3H samples were analyzed at the University of Miami 

Tritium Laboratory in Miami, Florida. Water-quality samples 

were collected following methods described in the USGS 

National Field Manual for the Collection of Water-Quality 

Data (U.S. Geological Survey, variously dated).
26 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0 2 MILES

0 2 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Universal Transverse Mercator projection, Zone 17 North

FLORIDA'S

470

44

301

301

75 TURNPIKE

Little Jones Creek

Big Jones Creek

Shady

Brook

Withlacoochee

River

Jumper

Outlet

River

Creek

Hogeye

Sink

Lake

Okahumpka

Warnel

Creek

Wildwood

Lake

Panasoffkee

Carlson

Coleman

Sumterville

QW29

QW28

QW27

QW26

QW25

QW24

QW23

QW22

QW21

QW19

QW18

QW17 QW16

QW15

QW14

QW13

QW12

QW11

QW10

QW09

QW08

QW07

QW05

QW04

QW03

QW02

QW01

QW20

QW06

Wysong

Dam

WATER QUALITY SAMPLING LOCATION

AND INDEX NUMBER--Data provided

in table 4

EXPLANATION

CITRUS COUNTY

SUMTER

COUNTY

82°15 ́ 82°10 ́ 82°05 ́ 82°00 ́

28°55 ́

28°50 ́

28°45 ́

QW4

Big Prairie

Canal

470

Chitty

Chatty

Creek

Unnamed

Creek

Tsala

Apopka

Lake

Figure 14. Location of water-quality sampling stations in the Lake Panasoffkee study area. Site identification 

numbers and names are given in table 4.

Groundwater and spring-water samples were collected 

using a submersible pump with polytetrafluoroethylene 

(Teflon®) tubing to minimize cross contamination between 

sampling sites. Wells were purged a minimum of three casing 

volumes before samples were collected. Specific conductance, 

water temperature, dissolved oxygen, pH, and turbidity were 

monitored during the removal of the third well-casing volume 

to determine if the water chemistry was stable before water 

samples were collected. Springs were sampled by lowering a 

submersible pump head into the spring vent to ensure that the 

spring water did not mix with surface water before the sample 

was collected. The same field properties as groundwater 

samples, minus turbidity, were monitored for stability before 

spring-water samples were collected. 

Surface-water samples were collected using a stainless-steel 

weighted bottle sampler with a 1-liter Teflon® collection 

bottle and nozzle. The stainless-steel sampler was slowly 

lowered through the water column while the sampler was 
Methods of Investigation 27

Table 4. Location of water-quality sampling stations in the Lake Panasoffkee study area.

[GW, groundwater; SW, surface water, UFA, Upper Floridan aquifer; SA, surficial aquifer; LFA, Lower Floridan aquifer; —, not available; ft, feet; 

n/a, not applicable] 

Reference 

number 

(fig. 14)

USGS site 

identification 

number

Station name Latitude Longitude

Land 

surface 

elevation, 

ft above 

NGVD 29

Well 

depth, 

ft below 

land 

surface

Screened 

interval, 

ft below 

land 

surface

Water 

type Aquifer

QW1 285125082085301 Big Jones Creek 48 ft UFA well 28°51′25′′ 82°08′53′′ 48 48 20–48 GW UFA

QW2 285125082085302 Big Jones Creek 7 ft SA well 28°51′25′′ 82°08′53′′ 48 7 2–7 GW SA

QW3 285035082075401 Little Jones Creek 48 ft UFA well 28°50′35′′ 82°07′54′′ 45 48 27–47 GW UFA

QW4 285035082075402 Little Jones Creek 11 ft SA well 28°50′35′′ 82°07′54′′ 45 11 2–11 GW SA

QW5 284811082091301 (ROMP) LP-3 152 ft UFA well 28°48′12′′ 82°09′13′′ 51 152 110–150 GW UFA

QW6 284628082073801 (ROMP) LP-4 240 ft UFA well 28°46′29′′ 82°07′38′′ 52 240 200–240 GW UFA

QW7 284628082073802 (ROMP) LP-4 120 ft UFA well 28°46′29′′ 82°07′38′′ 52 120 100–120 GW UFA

QW8 284628082073803 (ROMP) LP-4 30 ft SA well 28°46′29′′ 82°07′38′′ 52 30 15–30 GW SA

QW9 284528082055201 Sumter County 170 ft UFA well 28°45′28′′ 82°05′52′′ 50 170 — GW UFA

QW10 284456082053102 (ROMP) LP-5 40 ft SA well 28°44′57′′ 82°05′31′′ 63 40 20–40 GW SA

QW11 284759082054101 (ROMP) LP-6 154 ft UFA well 28°48′01′′ 82°05′41′′ 54 154 42–154 GW UFA

QW12 284759082054102 ROMP LP-6 25 ft SA well 28°48′01′′ 82°05′41′′ 54 25 18–23.5 GW SA

QW13 284734082071201 Tracys Point 5 ft shallow well 28°47′34′′ 82°07′12′′ 39 5 4–5 GW SA

QW14 284756082061301 Coleman Landing 5 ft shallow well 28°47′57′′ 82°06′13′′ 39 5 4–5 GW SA

QW15 284922082075901 Lake Panasoffkee 7 ft shallow well 

near Shell Point

28°49′26′′ 82°07′55′′ — 7 6–7 GW SA

QW16 284949082000501 ROMP 117 1000 ft LFA well 28°49′51′′ 82°00′04′′ 70 1,002 600–1,002 GW LFA

QW17 284949082000502 ROMP 117 338 ft UFA well 28°49′51′′ 82°00′04′′ 70 338 83–338 GW UFA

QW18 02312664 Fenney Springs near Coleman 28°47′42′′ 82°02′19′′ n/a n/a n/a SW n/a

QW19 284709082024100 Blue Spring at Sumter County 28°47′09′′ 82°02′41′′ n/a n/a n/a SW n/a

QW20 284530082034800 Belton’s Millpond Complex near 

Sumterville

28°45′31′′ 82°03′50′′ n/a n/a n/a SW n/a

QW21 284525082040600 Maintenance Spring Run near 

Sumterville

28°45′25′′ 82°04′06′′ n/a n/a n/a SW n/a

QW22 284613082070500 Canal Spring Complex near 

Panasoffkee

28°46′13′′ 82°07′05′′ n/a n/a n/a SW n/a

QW23 284534082054400 Shady Brook 350 ft above I-75 at 

Lake Panasoffkee

28°45′34′′ 82°05′44′′ n/a n/a n/a SW n/a

QW24 02312675 Little Jones Creek near Rutland 28°50′33′′ 82°07′49′′ n/a n/a n/a SW n/a

QW25 02312700 Outlet River at Panacoochee Retreats 28°48′00′′ 82°09′11′′ n/a n/a n/a SW n/a

QW26 284922082075900 Lake Panasoffkee near Shell Point at 

Panasoffkee

28°49′22′′ 82°07′59′′ n/a n/a n/a SW n/a

QW27 284630082062700 Lake Panasoffkee near SSE Shore at 

Panasoffkee

28°46′00′′ 82°06′27′′ n/a n/a n/a SW n/a

QW28 284718082070000 Lake Panasoffkee near Tracy’s Point at 

Panasoffkee

28°47′18′′ 82°07′00′′ n/a n/a n/a SW n/a

QW29 284852082082000 Lake Panasoffkee near Idlewild Camp 

at Panasoffkee

28°48′52′′ 82°08′20′′ n/a n/a n/a SW n/a
28 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

filling in order to collect a depth-integrated sample. At stream 

sites, water samples were collected with respect to both water 

depth and at multiple points across the stream channel to 

ensure that samples were representative of the entire stream 

cross section. At surface-water sites, specific conductance, pH, 

temperature, and dissolved oxygen were measured at middepth at each sampling point. 

Alkalinity (as calcium carbonate) was measured in the 

field for all samples using fixed end-point titration methods. 

Sampling equipment was cleaned onsite after the collection of 

each sample using dilute phosphate-free detergent, followed 

by three rinses with deionized water. 

High-precision measurements of the ratio of 87Sr/86Sr in 

carbonate sedimentary rock can be correlated to specific units 

within an aquifer (DePaolo and Ingram, 1985). The 87Sr/86Sr 

ratio of a water sample can be used to determine the hydrogeologic units the water sample has been in contact with. Samples 

with the lowest strontium isotope ratios typically have been in 

contact with the oldest aquifer materials. This result is possible 

because many marine organisms build their shells from 

carbonate minerals precipitated from seawater that record 

the ratio of 87Sr/86Sr in seawater at the time of shell formation. The isotopic ratio of 87Sr/86Sr does not vary spatially in 

modern seawater, but it has slowly changed over millions of 

years. It is possible to determine the source of a groundwater 

sample by comparing the 87Sr/86Sr ratio of a water sample 

with that of the individual lithologic units of the Floridan 

aquifer system.

The stable isotopes of oxygen and hydrogen, 18O and 

2H, are useful in determining sources of water, flow patterns, 

and mixing of waters. Their stability and incorporation into 

water molecules make these isotopes excellent tracers of 

water origin and movement. Other common tracers, such as 

dissolved constituents, may undergo chemical reactions or 

move through a flow system at a different rate than the water 

itself. Deuterium (2H) is a heavy isotope of hydrogen that 

accounts for about 0.015 percent of the hydrogen on Earth, 

whereas oxygen–18 (18O), the heavy form of oxygen, accounts 

for about 0.204 percent of the oxygen on Earth (Clark and 

Fritz, 1997). Because of their low concentrations on Earth, 

these isotopes are not measured directly. Instead, the ratio of 

the heavy to light form of the isotope is measured and reported 

relative to a reference in delta (δ) notation: 

δsample = 1,000 [(Rsample / Rref)-1)] (5)

where R is 2H/H for hydrogen or 18O/16O for oxygen. Results 

are reported in units of per mil (parts per thousand or ‰). 

The reference used for both deuterium and oxygen–18 isotopic 

ratios is Vienna Standard Mean Ocean Water (VSMOW) 

(Sacks, 2002), which has δ2H and δ18O of 0‰ by definition.

The relative amounts of 2H and 18O in the environment 

vary depending on water phase and location, including latitude, elevation, and the distance from the ocean. 2H and 18O 

preferentially condense out of water because of their greater 

masses, making rainfall isotopically enriched compared to 

water vapor in the atmosphere (Sacks, 2002). The lighter and 

more numerous isotopes of oxygen and hydrogen, 1H and 16O, 

have higher vapor pressures and diffusivities, causing them 

to preferentially evaporate compared to the heavier isotopes. 

Consequently, surface water becomes enriched in 2H and 

18O compared to water vapor and atmospheric moisture. 

Rainfall around the world has a consistent relation between 

δ2H and δ18O, as delineated by the global meteoric water line 

(GMWL), because of the global balance between evaporation 

and condensation (Craig, 1961; Sacks, 2002).

In 1999, Sacks (2002) determined the local meteoric 

water line (LMWL) for west-central Florida by collecting 

and compositing monthly rainfall samples and then analyzing 

the samples for δ2H and δ18O. The LMWL represents the 

ambient variability of δ2H and δ18O in the rainfall of westcentral Florida from that of the GMWL and seawater. Sacks 

determined that there was no statistical difference between 

the GMWL and LMWL in west-central Florida. The LMWL 

was defined as δ2H = 7.73 δ18O + 11.62, whereas Craig (1961) 

defined the GMWL as δ2H = 8.0 δ18O + 10. 

Water influenced by evaporation is offset to the right 

of the meteoric water line (MWL) when δ2H is graphically 

plotted against δ18O because of differences in how the 

two isotopes fractionate during evaporation (Sacks, 2002). 

The local evaporation trend line provides useful information 

as to the sources of water in a watershed. Waters with the 

longest residence times at land surface plot farthest to the 

right because they have undergone the most evaporation. 

Once water recharges to the groundwater system it undergoes 

little to no additional evaporation and therefore, groundwater 

maintains the isotopic signature it had at the time of recharge 

as long as it remains in the groundwater system. Sources of 

groundwater recharge can be determined by comparing a 

groundwater sample position on a graph with that of local 

surface waters and the MWL. Groundwater samples that 

plot on or near the MWL recharged quickly after deposition, 

whereas samples that contain isotopically enriched water 

remained at land surface for a period of time before recharge. 

Four age-dating analyses were added to the December 

2008 through January 2009 sampling event to better define 

flow paths within the Lake Panasoffkee groundwater system 

and to assess if mixing was occurring between shallow and 

deep groundwater systems. Analyses included carbon–14 

(

14C), tritium (3H), sulfur hexafluoride (SF6), and CFCs. 

The term “age dating” refers not to the age of the water itself, 

but to the time elapsed since the water recharged the groundwater system. 

Carbon–14 is a naturally occurring radioactive isotope 

of carbon that is created when cosmic ray protons bombard 

nuclei in the Earth’s upper atmosphere. The resultant neutrons, 

in turn, blast nitrogen atoms, composed of seven protons and 

seven neutrons, into the radioactive isotope 14C, composed 

of six protons and eight neutrons. 14C is then incorporated 

into the planetary carbon cycle where the vast majority is 

incorporated into atmospheric carbon dioxide. All biomass at 

Earth’s surface contains 14C at atmospheric levels, but once 
the 14C drops out of the biological cycle, such as through 

burial or dissolution in water that recharges an aquifer, it 

begins to decay. Once the concentration of 14C is measured in 

a groundwater sample, the time elapsed since recharge can be 

calculated by knowing the half-life of 14C (5,568 years), and 

making assumptions about the initial 14C concentration at the 

time of recharge. For every half-life since the recharge event, 

the concentration of 14C decreases by half. It is assumed that 

a “parcel” of water is at equilibrium with the atmospheric 

concentration of 14C at the time of recharge (Kalin, 2000). 

The geochemical mass-balance model NETPATH 

(Plummer and others, 1991) was used to apply adjustments 

to the 14C data in the manner of Ingerson and Pearson (1964), 

Tamers (1975), Fontes and Garnier (1979), and Eichinger 

(1983). Geochemical reactions, such as dedolomitization, 

calcium carbonate recrystallization, microbial oxidation of 

organic matter, and cation exchange reactions, can all lower 

the 14C activity of dissolved inorganic carbon, leading to 

unrealistically old apparent radiocarbon ages (Plummer and 

Sprinkle, 2001). The apparent radiocarbon ages from this 

study were analyzed using the NETPATH model, and the 14C 

age data were corrected for geochemical reactions that cause 

erroneous apparent ages. The model output reflected a range 

of maximum 14C ages for each water sample.

The primary 3H input to groundwater was from aboveground nuclear testing of hydrogen bombs that began in 1952, 

although low tritium concentrations are naturally produced in 

the atmosphere by cosmic radiation. Atmospheric concentrations of 3H peaked between 1962 and 1965 after the ban of 

above-ground nuclear testing, and have declined since then 

(University of Miami Tritium Laboratory, 2009). The short 

half-life of 3H (12.43 years) makes it an ideal tracer of young 

groundwater (Solomon and Cook, 2000). The 3H isotope 

is commonly reported in tritium units (TU), where 1 TU is 

defined as the presence of one tritium atom in 1018 atoms of 

hydrogen. If water samples contain concentrations of 3H above 

naturally occurring background concentrations, typically 5 to 

10 TU, then at least a fraction of the sample was recharged 

after 1952. In this report, groundwater recharged after 

1952 is referred to as “young” groundwater, whereas “old” 

groundwater was recharged prior to 1952.

Sulfur hexafluoride is a trace atmospheric gas that is 

mostly anthropogenic in origin (Busenberg and Plummer, 

2000). The primary use of SF6 is in the production of high 

voltage electrical switches. Substantial industrial usage began 

in the 1960s and the atmospheric concentration of SF6 has 

risen steadily, and at known rates, ever since. Atmospheric 

moisture equilibrates to the concentration of SF6 in air before 

falling back to the Earth as precipitation. Water recharging 

to groundwater maintains the concentration of SF6 present 

in the atmosphere at the time of recharge, which makes it a 

useful tool for dating groundwater that has recharged in the 

last 35 years. SF6 also is conservative chemically, meaning 

it reacts little with other compounds in the environment 

(Plummer and Busenberg, 2000; Reston Chlorofluorocarbon 

Laboratory, 2009). 

Chlorofluorocarbons also were used to age-date selected 

samples of groundwater. CFCs are anthropogenic in origin and 

were widely used as refrigerants, solvents, and in plastic foam 

production until being banned in the United States in 1996 

because of the damage they cause to the Earth’s ozone layer. 

Since the 1996 ban, atmospheric CFC concentrations have 

declined. Similar to SF6, CFCs are useful for dating young 

groundwater because their concentrations in the atmosphere 

rose steadily and at known rates after their introduction, and 

because of their conservative behavior in the subsurface. Once 

water enters the groundwater system, the concentration of 

CFCs remains constant, effectively tagging the parcel of water 

with the date of recharge. By comparing the amount of each 

CFC compound dissolved in a groundwater sample with a plot 

of yearly atmospheric CFC concentration, a date of recharge 

can be derived (Plummer and Busenberg, 2000; Reston 

Chlorofluorocarbon Laboratory, 2009). 

All of the water samples analyzed for SF6 and CFCs 

also were analyzed for dissolved gas content. The low 

solubility of SF6 and CFCs in water requires that excess 

air be accounted for in order to calculate accurate apparent 

sample ages. Excess air is introduced when air trapped in the 

unsaturated zone dissolves into groundwater during a rapid 

rise of the water table in the surficial aquifer. This introduces 

SF6 in excess of atmospheric concentration and makes the 

apparent age of samples appear erroneously young (Reston 

Chlorofluorocarbon Laboratory, 2009). 

Methods of Investigation 29

Osprey nest
30 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Hydrogeology

The hydrogeologic units of interest to this study are the 

surficial aquifer, intermediate confining unit, and the Floridan 

aquifer system, which includes the Upper Floridan aquifer, 

the middle confining units I and II, and the Lower Floridan 

aquifer (fig. 15). Well data used to construct the hydrogeologic 

cross sections in figures 16 and 17A–B are contained in table 5. 

The cross sections schematically depict the orientation of the 

hydrogeologic units. Cross sections are used because they 

illustrate trends in the study area’s hydrogeology that are 

not readily apparent in figure 15. Detailed structural maps 

of the area of these sections are not available, which is why 

substantially less is known about the lateral extent and vertical 

position of some of the units. Locally, the Upper Floridan 

aquifer is comprised primarily of the Ocala Limestone and the 

upper part of the Avon Park Formation. The Ocala Limestone 

is highly transmissive because of secondary porosity from 

karstification, whereas the transmissivity of the dolomitic 

limestone of the Avon Park Formation mostly depends on the 

extent of fracturing. Floridan aquifer system

Cypresshead

Formation

Phosphatic sands

and clays

Holocene and

Pleistocene

Undifferentiated

sands and clays

Fine sand; interbedded

clay, shell, limestone Surficial aquifer

SYSTEM SERIES /

EPOCH

STRATIGRAPHIC

UNIT LITHOLOGY HYDROGEOLOGIC UNIT

Pliocene

Miocene Hawthorn Group Clay, sand, dolomite Intermediate

confining

unit

Oligocene Suwannee

Limestone

Limestone, sandy

limestone, fossiliferous

Upper Floridan aquifer

Upper Ocala Limestone

Limestone, chalky,

foraminiferal,

dolomitic near bottom

Middle Avon Park

Formation

Upper part, soft to

hard, porous, granular

to chalky, fossiliferous

limestone; crystaline

dolomite within middle

confining unit I

?? Middle confining unit I (middle

semi confining unit)

Lower part, soft to

hard, porous to dense,

granular to chalky,

fossiliferous limestone;

crystalline dolomite,

intergranular gypsum

and anhydrite within

middle confining unit II

Middle confining unit II ?? Lower Floridan aquifer

below middle confining

unit I

Lower Floridan aquifer below

middle confining unit II

Lower confining unit

Lower Oldsmar

Formation

Limestone and

dolomite; some

evaporites and chert

Paleocene Cedar Keys

Formation

Dolomite and

limestone with

evaporites and

anhydrites

Intermediate

confining

unit

Intermediate

confining

unit

Intermediate

confining

unit

Eocene

Tertiary Quaternary

Figure 15. Relation of stratigraphic and hydrogeologic units in the Lake Panasoffkee watershed (Modified from 

Ryder, 1985; Sacks, 1996; and O’Reilly and others, 2002). The intermediate confining unit and the Suwannee Limestone 

are of limited areal extent in the study area.
Hydrogeology 31

EXPLANATION

HERNANDO

COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

LAKE

COUNTY

Base modified from U.S. Geological Survey digital data; 1:2,000,000, 1998.

Universal Transverse Mercator projection, Zone 17 North

BJC

LJC LP-6 LP-5

Surficial

aquifer

SOUTH

W-3

B′

A

WEST

110

-100

Intermediate

confining unit

LP-3 LP-6

Surficial

aquifer

EAST

117

-563

A′ Lake Panasoffkee

Intermediate

confining

unit

FEET

Upper

Withlacoochee

River

Lake Okahumpka

-50

0

50

-152 -154 -2,037

Floridan aquifer

Upper Floridan aquifer

-154 -139 -3,090

-100

FEET

-50

0

50

B

NORTH Big Jones Creek

Little Jones Creek Shady Brook

Big

Jones

Creek

Jumper

Creek

Outlet

River

Lake

Panasoffkee

Brook

Shady

River

Withlacoochee

Little

Jones

Creek

Lake

Okahumpka

Tsala

Apopka

Lake

A

A′

B

B′

82°15 ́ 82°10 ́ 82°05 ́ 82°00 ́’ 81°55 ́

28°55 ́

28°50 ́

28°45 ́

28°40 ́

FLORIDA'S

LJC

BJC

W-3

117

LP-5

LP-3

110

LP-6

TURNPIKE

Wysong

Dam

0 2 MILES

0 2 KILOMETERS

ROADS

RIVERS

SECTION LINE

WELL LOCATION AND

INDEX NUMBER--Data

provided in table 5

A A′

EXPLANATION

110

VERTICAL SCALE GREATLY EXAGGERATED

DATUM IS NGVD 29

Panacoochee

Retreats

Bushnell

Wildwood

Lake

Panasoffkee

Carlson

Coleman

Sumterville

HYDROGEOLOGIC UNIT

CONTACT DASHED

WHERE INFERRED

NUMBER AT TOP IS WELL

NAME; NUMBER AT

BOTTOM IS WELL

DEPTH, IN FEET -563

110

44

75 470

Figure 16. Hydrogeologic cross sections of the shallow groundwater 

system near Lake Panasoffkee.
32 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0 50,000 FEET

0 10,000 METERS

119.5

LK-9

CI-1 CI-3

CI-2

LK-7

117

OR-1

AL-6

AL-4

HER-4

LK-10

MAR-8

MAR-7

MAR-3

PAS-4

WR-6B

83°00 ́ 82°30 ́ 82°00 ́ 81°30 ́ 81°00 ́

29°30 ́

29°00 ́

28°30 ́

Lake

Panasoffkee

Base modified from U.S. Geological Survey digital data; 1:2,000,000, 1998

.Universal Transverse Mercator projection, Zone 17 North

Lake

Apopka

Lake

George

EXPLANATION

!

C

C′

D′

D

E

F

G

E′

F′

G′ GULF OF MEXICO

ATLANTIC OCEAN

POLK COUNTY

MARION

COUNTY

LAKE COUNTY

LEVY COUNTY

VOLUSIA COUNTY

ORANGE COUNTY

ALACHUA

COUNTY

DIXIE

COUNTY

PASCO

COUNTY

PUTNAM COUNTY

CLAY COUNTY

HILLSBOROUGH

COUNTY

COLUMBIA

COUNTY

CITRUS COUNTY

SUWANNEE

COUNTY

SUMTER COUNTY

ST. JOHNS

COUNTY

FLAGLER

COUNTY

LAFAYETTE

COUNTY

HERNANDO

COUNTY

GILCHRIST\

COUNTY

SEMINOLE COUNTY

UNION

COUNTY

BRADFORD

COUNTY

PINELLAS

COUNTY

OSCEOLA COUNTY

RIVERS

SECTION LINE

WELL LOCATION AND INDEX

NUMBER--Data provided in

table 5

C C′

PAS-4

Figure 17A. Location of hydrogeologic section lines of the deep groundwater system in the region surrounding Lake 

Panasoffkee. 
Hydrogeology 33

HYDROGEOLOGIC UNIT CONTACT

DASHED WHERE INFERRED

NUMBER AT TOP IS WELL NAME;

NUMBER AT BOTTOM IS WELL

DEPTH, IN FEET

EXPLANATION

-3,457

CI-2

-500

0

-1,000

-1,500

-2,000

-2,500

-4,791 -4,493 -4,637 -4,101

Lower Floridan

aquifer

Upper

Floridan

aquifer

Middle confining unit I

Middle

confining

unit II

Surficial

aquifer Intermediate

confining unit

Surficial

aquifer

E E′

CI-3 CI-1 119.5 MAR-7MAR-8

?

?

WEST EAST

FEET

-500

0

-1,000

-1,500

-2,000

-2,500

Lower Floridan aquifer

Middle confining unit I

Middle confining

unit II

Upper

Floridan

aquifer

F F′

CI-2

Surficial

aquifer

Intermediate

confining unit

117 LK-9

-5,565 -4,891

?

?

WEST EAST

FEET

C-C′

-500

0

-1,000

-1,500

-2,000

-2,500

-3,000-8,477

G G′

HER-4

Surficial

aquiferIntermediate

confining unit

WR-6B LK-10

Surficial

aquifer Intermediate

confining unit OR-1

Lower Floridan aquifer

Middle

confining

unit II

Middle

unit I Upper Floridan aquifer

VERTICAL SCALE GREATLY EXAGGERATED

DATUM IS NGVD 29

WEST EAST

FEET

confining

D-D′

?

?

NORTH

AL-6

-500

Surficial

aquifer

SOUTH

PAS-4

Intermediate

confining unit

0

-1,000

-1,500

-2,000

119.5 WR-6B

Upper

Floridan

aquifer

Upper

Floridan aquifer

Middle confining unit II

Lower Floridan aquifer

-3,454

?

C C′

FEET

Intermediate

confining unit

F-F′

-2,500

-3,000

Intermediate

confining unit

Surficial

aquifer

Surficial

aquifer

Intermediate

confining unit

NORTH SOUTH

AL-4

MAR-3 MAR-7 117 LK-7

Middle

confining

unit II

Lower

Upper

Floridan

aquifer

Middle confining unit I

Upper Floridan aquifer

-500

0

-1,000

-1,500

-2,000

-2,500

-3,116 -3,845 -4,637 -5,780

?

D D′

FEET

Floridan aquifer

G-G′

Figure 17B. Hydrogeologic cross sections of the deep groundwater system in the region surrounding Lake 

Panasoffkee.
34 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida Table 5. Elevation of land-surface datum, total depth, and depth to various formations for selected wells used in the construction of hydrogeologic cross sections. [Hydrologic cross sections are shown in figures 16 and 17A–B; UFA, Upper Floridan aquifer; LFA, Lower Floridan aquifer; FGS, Florida Geological Survey; ft, feet; —, not available; n/a, not applicable; TD, total depth] Reference number (figs. 16 and 17A–B) USGS site identification number Well name Land surface elevation, ft above NGVD 29 Well depth, ft below land surface Formation interval, ft below land surface Surficial aquifer Intermediate confining unit Floridan aquifer system Middle confining unit I Middle confining unit II A–A ′ 110 284513082131201 ROMP 110 150 ft UFA well 50 563 0–16 n/a 16 TD

—

—

LP-3 284811082091301 (ROMP) LP-3 152 ft UFA well 51 152 0–4.5 4.5–9.6 9.6 TD

—

—

LP-6 284759082054101 (ROMP) LP-6 154 ft UFA well 54 154 0–24 24–34 34 TD

—

—

117 n/a ROMP 117 2,037 ft LFA well 70 2,037 0–10 10–55 55 TD 357–614 n/a

B–B ′

BJC 285125082085301 Big Jones Creek 48 ft UFA well 48 48 0–7 7–10.5 10.5 TD

—

—

LJC 285035082075401 Little Jones Creek 48 ft UFA well 45 48 0–8 8–14.2 14.2 TD

—

—

LP-6 284759082054101 (ROMP) LP-6 154 ft UFA well 54 154 0–24 24–34 34 TD

—

—

LP-5 284456082053101 (ROMP) LP-5 139 ft UFA well 63 139 0–56 n/a 56 TD

—

—

W-3 n/a FGS well W-3 77 3,090 0–30 n/a 30–1,450

—

—

C–C ′

AL-6 n/a Texaco #1 A.M. Creighton 67 3,524 0–70 70–205 205–1,684 n/a n/a119.5 n/a ROMP 119.5 Ross Pond 66 1,466

—

—

—

— 623–981

WR-6B n/a ROMP WR-6B Withlacoochee Transect 53 1,290

—

— 27 TD n/a 513–1,122

PAS-4 n/a Dade City Krisman 176 1,434 n/a 0–96 96 TD n/a 996–1,206

D–D ′

AL-4 n/a Tidewater #1 J.A. Phifer 122 3,238 0–10 10–258 258–1,714 n/a n/aMAR-3 n/a Sun #1 H.T. Parker 69 3,845

—

— 60–1,750 219–409 n/a

MAR-7 n/a Sun #1 Henry N. Camp 64 4,637 n/a n/a 0–1,840 229–469 n/a117 n/a ROMP 117 2,037 ft LFA well 70 2,037 0–10 10–55 55 TD 357–614 n/aLK-7 n/a Amoco #1 Arnold Industries 114 5,780 0–37 37–52 52–2,381 452–1,027 1,027–1,197

E–E ′

CI-3 n/a Mobil #1 Harbond 14 4,791

—

— 13–2,100 n/a 860–1,290

CI-1 n/a Mobil #1 Camp Phosphate 106 4,493

—

— 73–2,226 n/a 765–941

119.5 n/a ROMP 119.5 Ross Pond 66 1,466

—

—

—

— 623–981

MAR-7 n/a Sun #1 Henry N. Camp 64 4,637 n/a n/a 0–1,840 229–469 n/aMAR-8 n/a Amoco #1 USA Unit 6-4 63 4,101

—

— 84–1,864 271–463 n/a

F–F ′

CI-2 n/a Mobil #1 Garby 5 5,565

—

— 0–2,324 n/a 830–1,335

117 n/a ROMP 117 2,037 ft LFA well 70 2,037 0–10 10–55 55 TD 357–614 n/aLK-9 n/a Amoco #1-A USA 44 (29-13) 43 4,891

—

— 43–2,001 395–580 n/a

G–G ′

HER-4 n/a Ohio Oil #1 Hernasco 35 8,477

—

— 0–2,977 n/a 727–1,393

WR-6B n/a ROMP WR-6B Withlacoochee Transect 53 1,290

—

— 27 TD n/a 513–1,122

LK-10 n/a Griffin Groves 106 728 0–36 36–112 112 TD 378–646 n/aOR-1 n/a Plymouth Citrus 75 1,070

—

— 75 TD 470–785 n/a
Hydrogeology 35

Surficial Aquifer

The surficial aquifer is the uppermost hydrogeologic 

unit in the study area (fig. 15). It is an unconfined aquifer, 

consisting of a thin layer of undifferentiated fine sand interbedded with clay, shell, and limestone, overlying a thick 

sequence of Tertiary carbonate rocks that form the Floridan 

aquifer system (Campbell, 1989). Within the study area, the 

surficial aquifer tends to be thickest near the uplands and thinnest in low-lying areas (Trommer and others, 2009). The most 

recent sediments in the surficial aquifer are undifferentiated 

Holocene and Pleistocene quartz sands, clayey sands, and clay 

(Campbell, 1989). Surficial aquifer deposits were between 4.5 

and 56 ft in thickness in seven core samples collected by the 

SWFWMD in the study area. The surficial aquifer was 16 ft 

thick or less at wells GW5, GW7, GW19, and GW24, 24 ft 

thick at well GW37, and 56 ft thick at wells GW31 and GW35 

(fig. 11 and table 3). In parts of the study area, the surficial 

aquifer may be missing entirely where the underlying limestone units crop out at land surface. 

The surficial aquifer is recharged by rainfall that infiltrates the unsaturated zone and moves down to the water table. 

Throughout this study, the water table in the Lake Panasoffkee 

watershed was generally within 20 ft of land surface, and 

during brief wet periods it was at or near land surface in 

low-lying areas. The elevation of the water table fluctuates 

seasonally based on rainfall patterns, evapotranspiration, 

and the stage of nearby surface-water bodies (Miller, 1986). 

The lack of a continuous confining unit between the surficial 

aquifer and the Upper Floridan aquifer in the study area allows 

water in the surficial aquifer to recharge the Upper Floridan 

aquifer directly. In those areas where there is confinement, 

water percolates downward through the unsaturated zone 

to the water table and then flows laterally along the top of 

the intermediate confining unit until it either discharges to a 

surface-water feature or recharges the Upper Floridan aquifer 

if a pathway through the intermediate confining unit is reached 

(Miller, 1986). 

The transmissivity of the surficial aquifer varies in 

west-central Florida depending on its saturated thickness and 

lithology (Ryder, 1985). No aquifer tests have been performed 

in the surficial aquifer within the study area, but limited 

tests performed outside the study area within the SWFWMD 

indicate that transmissivity is typically low compared to that 

of the underlying Upper Floridan aquifer. Surficial aquifer test 

results either performed or gathered by the SWFWMD from 

various agencies and consulting firms in west-central Florida 

indicate that transmissivity varies from 8 to 5,348 ft2/d when 

the thickness of the aquifer is 55 ft or less (Robert Peterson, 

Southwest Florida Water Management District, written 

commun., 2010).

Regionally, the phosphatic sands and clays of the 

Pliocene-age Cypresshead Formation are found below the 

undifferentiated sands and clays of the surficial aquifer, and 

above the clayey Hawthorn Group. Throughout its spatial 

extent, the permeable sands of the Cypresshead Formation act 

as part of the surficial aquifer (Scott, 2001). The Cypresshead 

Formation was identified in the study area west of Lake Panasoffkee in a core sample collected at ROMP LP–3 (GW19) by 

the SWFWMD (fig. 11 and table 3) at a depth of 4.5 ft below 

land surface and with a thickness of 5.1 ft. Campbell (1989) 

determined that the Cypresshead Formation is rarely present 

within the study area.

Intermediate Confining Unit

Where present in northern west-central Florida, the clays 

of the Hawthorn Group form the intermediate confining unit 

between the surficial aquifer and the Upper Floridan aquifer. 

Within the Lake Panasoffkee watershed, the clay, sand, and 

dolomite of the Miocene Hawthorn Group are discontinuous 

(Scott, 2001) due to weathering, erosion, and breaching from 

karst activity. Hawthorn Group clays were present in core 

samples collected in the study area at sites GW19 and GW37 

(fig. 11 and table 3). Clays were present in these samples 4.5 

to 24 ft below land surface and were 5.1 to 10 ft thick, respectively. Clay was not found at site GW31, and only a thin clay 

horizon was found at sites GW5, GW7, GW24 and GW35. 

Upper Floridan Aquifer

The Upper Floridan aquifer is present throughout most 

of Florida and is composed of high porosity limestones. In the 

study area, the aquifer lies beneath the surficial aquifer and 

is semiconfined or unconfined because of the incomplete 

coverage of the Hawthorn Group clays. The Oligocene age 

Suwannee Limestone is the uppermost limestone found in the 

region, but it is not areally extensive and is not an important 

aquifer unit in the study area. Remnant boulders of Suwannee 

Limestone are common in the southern part of Sumter County, 

and pockets of this unit are present in low spots in the top 

of the underlying Ocala Limestone throughout the county 

(Campbell, 1989). However, the Suwannee Limestone has 

mostly been eroded away within the study area. 

The Ocala Limestone is of late Eocene age and is the 

uppermost unit of the Upper Floridan aquifer within the study 

area where the Suwannee Limestone is absent. The chalky, 

fossiliferous Ocala Limestone is porous and highly karstified, 

with some dolomite near the base of the unit. The top of the 

Ocala Limestone was from 9.6 to 56 ft below land surface 

within the study area at well sites GW5, GW7, GW19, GW24, 

GW31, GW35, and GW37 (fig. 11 and table 3). The Ocala 

Limestone was from 34 to 84 ft thick at the four sites where 

a complete core sample was recovered and where the well 

was drilled to sufficient depth to fully penetrate the formation 

(GW19, GW24, GW35, and GW37). 

Beneath the Ocala Limestone is the Avon Park Formation 

of middle Eocene age. Regionally, the top of the Avon Park 

Formation lies at about 150 to 500 ft below land surface, 

and the formation has a thickness of about 950 to 1,280 ft 
36 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

(Campbell, 1989). In the study area, cores collected at ROMP 

sites GW19, GW24, GW31, GW35, and GW37 indicate 

that the top of the formation is from 44.5 to 140 ft below 

land surface (fig. 11 and table 3), but none of the wells fully 

penetrate the formation. The upper part of the Avon Park 

Formation is soft to hard, porous, granular to chalky, fossiliferous limestone and dolostone, whereas the lower part of 

the Avon Park Formation is porous to dense and has more 

dolostone than limestone. The Avon Park Formation spans 

both the Upper and Lower Floridan aquifers, depending on 

the presence or absence of confining units within the formation. When no middle confining units are present, all of the 

Avon Park Formation is considered part of the Upper Floridan 

aquifer (Miller, 1986). The Avon Park Formation is the deepest 

geologic unit in the region commonly used for public water 

supply because waters in deeper formations are often highly 

mineralized.

A lack of confinement and downward head differences 

between the surficial and Upper Floridan aquifers allows 

water from the surficial aquifer to recharge the Upper Floridan 

aquifer in the southwestern and northeastern parts of the study 

area (Aucott, 1988). Karst features in the study area, such as 

sinkholes, fractures, and conduits, also can serve as direct 

pathways for recharge between the land surface and the Upper 

Floridan aquifer. Bush and Johnston (1988) estimated that 

transmissivity ranges from about 50,000 to 1,000,000 ft2/d in 

the Upper Floridan aquifer in Sumter County, with the lowest 

transmissivity values found in the southeast near the Lake 

Upland, and the highest values found in the northeast under 

the Sumter Upland (figs. 3 and 18). Aquifer tests performed by 

the SWFWMD at site GW35 (fig. 11 and table 3) within the 

study area indicated Upper Floridan aquifer transmissivities 

of about 9,100 ft2/d, but transmissivity data collected from 

12 other aquifer tests conducted in Sumter or surrounding 

counties ranged from 28,000 to 1,850,000 ft2/d (Robert 

Peterson, Southwest Florida Water Management District, 

written commun., 2010). Unconfined or semiconfined areas 

of the Upper Floridan aquifer typically have higher aquifer 

transmissivities than areas that are confined (Johnston and 

Bush, 1988). The Upper Floridan aquifer in unconfined or 

semiconfined areas undergoes greater chemical weathering 

than in confined areas because acidic near-surface water and 

rain reaches the aquifer faster in these areas and therefore 

dissolves more carbonate. Those areas with the highest aquifer 

transmissivities typically have extensively developed solution 

features that act as secondary pathways for the flow of water. 

Secondary porosity is more important than primary porosity 

to increasing the transmissivity of the Floridan aquifer system 

(Miller, 1986). The karstic Ocala Limestone is more transmissive than the Avon Park Formation because of extensive 

secondary porosity. The many springs found in the study area 

result from this secondary porosity and indicate that a large 

volume of water can be transported through these pathways. 

Middle Confining Units I and II

Two distinct confining units within the Avon Park 

Formation in central Florida separate the Floridan aquifer 

system into the Upper Floridan and Lower Floridan aquifers 

(Miller, 1986). Although middle confining unit I lies primarily 

to the east of the Lake Panasoffkee area, its western extent 

is poorly defined throughout its range because few wells in 

the area extend to this depth. Middle confining unit I, the 

leakiest of the eight middle confining units within the Floridan 

aquifer system, is composed of soft, less permeable crystalline 

dolomite within the Avon Park Formation that inhibits flow, 

but does not prevent it (Miller, 1986). The lithology of middle 

confining unit I does not vary greatly from that of the Upper 

and Lower Floridan aquifers above and below it, except that 

there is secondary mineralization of the pore spaces within the 

unit, which slightly reduces the permeability. Differences in 

water levels between wells installed above and below middle 

confining unit I confirm its definition as a confining unit 

(O’Reilly and others, 2002). The top of middle confining unit I 

is 357 ft below land surface about 7 mi east of Lake Panasoffkee 

at ROMP 117, where the unit is 257 ft thick (fig. 19) (Jason 

LaRoche, Southwest Florida Water Management District, 

written commun., 2009). 

Middle confining unit II is less permeable than middle 

confining unit I, and is composed of hard, crystalline dolomitic limestone and gypsiferous dolomite of the Avon Park 

Formation. Gypsum and anhydrite have largely filled the pore 

spaces of the dolomite matrix composing middle confining 

unit II, resulting in low permeability (Miller, 1986). This 

unit is present primarily west of Lake Panasoffkee, although 

its eastern boundary is not well defined because few wells 

extend deep enough to penetrate this unit. Middle confining 

unit II was not found at ROMP 117 east of Lake Panasoffkee 

where middle confining unit I was found. Hydraulic data 

indicate that middle confining unit II is essentially non-leaky 

(Miller, 1986). At ROMP WR-6B, about 15 mi southwest 

of Lake Panasoffkee (fig. 19), the top of middle confining 

unit II was 513 ft below land surface, and the unit was 609 ft 

thick (Jason LaRoche, Southwest Florida Water Management 

District, written commun., 2009). At ROMP 119.5, about 

20 mi northwest of Lake Panasoffkee (fig. 19), the top of 

middle confining unit II was 623 ft below land surface, 

and the unit was 358 ft thick (Jason LaRoche, Southwest 

Florida Water Management District, written commun., 2009). 

Middle confining unit I was not found at ROMP WR-6B nor 

ROMP 119.5.

At ROMP 102.5, located about 10 mi south of Lake 

Panasoffkee (fig. 19), both middle confining units I and II 

were found. The top of middle confining unit I lies 431 ft 

below land surface and the unit is 119 ft thick, whereas the top 

of middle confining unit II lies 792 ft below land surface and 

the unit is 323 ft thick. Two zones of slightly higher permeability found within middle confining unit II at ROMP 102.5 
Hydrogeology 37

EXPLANATION

ESTIMATED TRANSMISSIVITY--In

feet squared per day

Hillsborough

River

Newmans

Lake

Lake

Geneva

Orange

Lake

Lochloosa

Lake

Withlacoochee

River

OcklawahaRiver

Tampa

Bay

Geor

Lake

ge

Crescent

Lake

Lake

Apopka

Lake

Panasoffkee GULF OF MEXICO

ATLANTIC OCEAN

Lake

Panasoffkee

Bushnell

Brooksville

Ocala

Tampa

Bartow

Orlando

Tavares

Wildwood

Inverness

Dunnellon

Dade

City

Ridge

Manor

Gainesville

Zephyrhills

High

Springs

50,001 to 100,000

100,001 to 250,000

250,001 to 1,000,000

Greater than 1,000,001

10,001 to 50,000

0 10 20 MILES

0 10 20 KILOMETERS

83°00 ́ 82°30 ́ 82°00 ́ 81°30 ́ 81°00 ́

29°30 ́

29°00 ́

28°30 ́

28°00 ́

Base from U.S. Geological Survey digital data, 1:2,000,000, 1998 and

Southwest Florida Water Management District digital data 1:2,000,000, 2002

Universal Transverse Mercator projection, Zone 17 North

BREVARD COUNTY

POLK

COUNTY

MARION

COUNTY

FLAGLER

COUNTY

PINELLAS

COUNTY

CITRUS

COUNTY

GILCHRIST

COUNTY

SAINT JOHNS

COUNTY

SUMTER

COUNTY

LAKE

COUNTY

LEVY COUNTY

ALACHUA

COUNTY DIXIE COUNTY

ORANGE COUNTY

PUTNAM

COUNTY

OSCEOLA COUNTY

VOLUSIA COUNTY

HERNANDO

COUNTY

SEMINOLE

COUNTY

HILLSBOROUGH

COUNTY

PASCO COUNTY

LAFAYETTE COUNTY CLAY COUNTY BRADFORD COUNTY

Figure 18. Regional transmissivity of the Upper Floridan aquifer (from Bush and Johnston, 1988).
38 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Figure 19. Hydrostratigraphy at four wells installed in the Lower Floridan aquifer near Lake Panasoffkee.

ROMP 117

LAKE COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

HERNANDO

COUNTY

Inverness

Bushnell

Wildwood

Brooksville

Lake

Panasoffkee

ROMP 102.5

ROMP WR-6B

ROMP 119.5

82°15 ́ 82°00 ́

29°00 ́

28°45 ́

Tsala

Apopka

Lake

River

Jumper

Lake

Panasoffkee

Lake

Okahumpka

Lake

Weir

Creek

Withlacoochee

Shady

Big

Jones

Creek

Little

Jones

Creek

MARION

COUNTY

Brook

0 5 10 MILES

0 5 10 KILOMETERS

WELL AND INDEX NUMBER--Newly

constructed deep exploratory wells.

Data provided in table 5

Semiconfinement

ROMP WR-6B

(15 miles SW of Lake Panasoffkee)

Upper

Floridan

aquifer

Middle

confining

unit II

Lower Floridan

aquifer

Total depth = 1,290 feet

ROMP 117

(7 miles west of Lake Panasoffkee)

Upper

Floridan

aquifer

Middle confining

unit I

Lower

Floridan

aquifer

Total depth =2,037 feet

ROMP 102.5

(10 miles south of Lake Panasoffkee)

Upper

Floridan

aquifer

Middle

confining

unit II

Lower Floridan

aquifer

Total depth = 2,000 feet 2,000

Lower Floridan

aquifer

ROMP 119.5

(20 miles northwest of Lake Panasoffkee)

Upper

Floridan

aquifer

Middle

confining

unit II

Lower Floridan

aquifer

Total depth = 1,466 feet

1,000

0

FEET

0

1,000

1,500

0

1,000

2,000

1,000

500

1,500

0

FEET

FEET

FEET

500

1,500

500

1,500

500

Base modified from Florida Department of Transportation

digital data; 1:24,000; 2007.

Universal Transverse Mercator projection, Zone 17 North.

2,000

EXPLANATION
Hydrogeology 39

contained water of lower mineral content than in the confining 

unit above and below those zones. This indicates that this site 

is located near the eastern extent of middle confining unit II.

Recent drill coring records by the SWFWMD for ROMP 

sites 117, WR-6B, 119.5, and 102.5 indicate that the westward 

extent of middle confining unit II defined in Miller (1986) was 

originally overestimated, because only middle confining unit I 

is present at ROMP 117 rather than both units I and II based 

on Miller’s (1986) maps. A reinterpretation of the overlapping 

area between the two confining units is shown by the dashed 

line in figure 20. The eastern edge of middle confining unit II 

was simply shifted to the west so that it lies slightly west of 

ROMP 117. ROMP 119.5 and WR-6B cores confirm that 

only middle confining unit II is present at those locations, 

whereas ROMP 102.5 cores confirm that overlap of the middle 

confining units exists at that location. Further drilling would 

be required to more precisely determine the location of middle 

confining units I and II in this area. 

Lower Floridan Aquifer

In the study area, the Lower Floridan aquifer includes 

the lower parts of the Avon Park Formation, the Oldsmar 

Formation, and the upper part of the Cedar Keys Formation. 

The Lower Floridan aquifer is confined at the base by the 

lower confining unit within the Cedar Keys Formation 

(fig. 15). The top of the early Eocene age Oldsmar Formation 

is about 1,450 ft below land surface, and the formation is 

600 to 800 ft thick within Sumter County (Campbell, 1989). 

The Oldsmar Formation is composed of dolomite and 

limestone, with variable porosity and microcrystalline to 

medium crystalline structure with some evaporites and chert 

(Vernon, 1951; Campbell, 1989). The Cedar Keys Formation, 

which underlies the Oldsmar Formation in the study area, is 

Paleocene in age and is mostly composed of microcrystalline to finely crystalline dolomitized limestone with variable 

quantities of evaporites and anhydrites. The top of the Cedar 

Keys Formation ranges from about 1,800 to 2,200 ft below 

land surface, and the unit is between 700 and 1,000 ft thick in 

Sumter County (Vernon, 1951; Campbell, 1989). 

The recent exploratory drilling by the SWFWMD at 

ROMP 117 indicated that the top of the Lower Floridan 

aquifer below middle confining unit I was 614 ft below land 

surface. At ROMP sites 119.5 and WR-6B (fig. 19), the 

top of the Lower Floridan aquifer below middle confining 

unit II was 981 ft below land surface and 1,122 ft below 

land surface, respectively (Jason LaRoche, Southwest 

Florida Water Management District, written commun., 

2009). Tests of basic water-quality constituents such as 

chloride, sulfate, and specific conductance at ROMP 117 

(fig. 19) indicated that potable water was available to a 

depth of at least 1,850 ft below land surface in the Lower 

Floridan aquifer below middle confining unit I; however, 

non-potable water was found in the Lower Floridan aquifer 

below middle confining unit II at ROMP 119.5 and ROMP 

WR-6B. Potable water generally contains less than 250 mg/L 

of chloride and sulfate, and has a specific conductance less 

than 1,000 μS/cm. One possible explanation for the difference 

in water quality between these well sites is the difference 

in the permeability of the middle confining units above the 

Lower Floridan aquifer. Middle confining unit I, which is 

more permeable, allows more interaction between the Lower 

Floridan aquifer and the overlying freshwater in the Upper 

Floridan aquifer. At ROMP 117, the greater interaction has 

helped flush out the minerals that degrade water quality from 

the Lower Floridan aquifer. At ROMP 119.5 and WR-6B, 

however, middle confining unit II is less permeable and, 

therefore, groundwater flow is much slower, resulting in less 

flushing of the Lower Floridan aquifer below middle confining 

unit II (Miller, 1986; O’Reilly and others, 2002). 

The hydrostratigraphy at ROMP 102.5 (fig. 19), where 

both confining units are present, is more complicated than 

at the Lower Floridan wells discussed earlier (ROMP 117, 

ROMP 119.5, and ROMP WR-6B). Below middle confining 

unit I, an upper section of the Lower Floridan aquifer extends 

from 550 ft below land surface to 792 ft below land surface; 

the latter depth corresponds to the top of middle confining 

unit II (Jason LaRoche, Southwest Florida Water Management 

District, written commun., 2010). Water quality, based on 

chloride, sulfate, and specific conductance data, degraded with 

depth in the Lower Floridan aquifer between middle confining 

units I and II, and eventually became non-potable between 

600 and 700 ft below land surface. However, water quality 

began to improve with depth about half-way through middle 

confining unit II between 900 and 1,000 ft below land surface. 

A lower section of the Lower Floridan aquifer was found at 

1,115 ft below land surface, and water quality in this section 

continued to improve with depth until a zone of evaporitic, 

low-permeability rock was reached at 1,391 ft below land 

surface. Below this level, water quality degraded with depth 

to the base of this zone at 1,543 ft below land surface. 

Below 1,543 ft, water quality quickly improved with depth 

to the point of potability and remained potable until at least 

2,000 ft below land surface. Drilling at ROMP 102.5 was still 

underway as of March 2010. Even with the limited data available, it is clear that the presence or absence of the two middle 

confining units has a substantial effect on the distribution and 

availability of potable groundwater in the study area. 

Groundwater Levels, Contributing Areas, and 

Differences in Head

Regional groundwater flow in the Upper Floridan aquifer 

originates from a potentiometric high in the center of the state 

in the Lake and Polk Uplands (figs. 3 and 21), and moves 

northwestward across Lake and Sumter Counties. A second 

regional groundwater-flow system, beginning at the potentiometric high located in the Northern Highlands (figs. 3 and 21), 

flows southward from north-central Florida toward the study 

area. These two regional groundwater-flow systems merge 
40 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

ORANGE

COUNTY

LAKE COUNTY

MARION COUNTY

SUMTER

COUNTY

CITRUS COUNTY

HERNANDO

COUNTY

Inverness

Ocala

Bushnell

Wildwood

Dunnellon

Ridge

Manor

Brooksville

Lake

Panasoffkee

ROMP 100

ROMP 117

ROMP 132

ROMP 102.5

ROMP WR-6B

ROMP 119.5

ROMP 100

CI-1

MAR-7

LK-10

HER-4

HER-4

0

0

10 MILES

10 KILOMETERS

82°30 ́ 82°15 ́ 82°00 ́ 81°45 ́

29°15 ́

29°00 ́

28°45 ́

28°30 ́

Base modified from Florida Department of Transportation digital data; 1:24,000; 2007.

Universal Transverse Mercator projection, Zone 17 North.

EXPLANATION

AREA OF OVERLAP BETWEEN MIDDLE

CONFINING UNITS I AND II

AREA WHERE MIDDLE CONFINING UNITS

ARE ABSENT

REVISED EASTERN EXTENT OF MIDDLE

CONFINING UNIT II

WELL AND INDEX NUMBER--Newly

constructed deep exploratory wells.

Data provided in table 5

WELL AND INDEX NUMBER--Wells used

in original interpretation of areal extent

of middle confining units I and II. Data

provided in table 5

MIDDLE CONFINING UNIT I

MIDDLE CONFINING UNIT II

Tsala

Apopka

Lake

River

Jumper

Lake

Panasoffkee

Lake

Okahumpka

Ocklawaha River

Lake

Weir

Lake Griffin Lake Harris

Lake

Eustis

Lake

Apopka

Creek

Lake

Yale

Lake Dora

Withlacoochee

Lake George

Figure 20. Areal extent of middle confining units I and II near the Lake Panasoffkee study area as interpreted 

by Miller (1986) with reinterpretation using new hydrogeologic information. Inset shows areal extent of middle 

confining units I and II in Florida according to Miller (1986).
Hydrogeology 41

POLK

COUNTY

MARION

COUNTY

LAKE

COUNTY

OSCEOLA

COUNTY

LEVY

COUNTY

VOLUSIA

COUNTY

ORANGE

COUNTY

TAYLOR COUNTY

ALACHUA

COUNTY

DIXIE COUNTY

PASCO

COUNTY

PUTNAM COUNTY

CLAY

COUNTY

HILLSBOROUGH COUNTY

CITRUS

COUNTY

SUMTER

COUNTY

ST. JOHNS

COUNTY

FLAGLER

COUNTY

LAFAYETTE

COUNTY

MANATEE

COUNTY

BREVARD COUNTY

HERNANDO

COUNTY

HARDEE

COUNTY

SUWANNEE COUNTY

UNION COUNTY

BAKER COUNTY

GILCHRIST

COUNTY

SEMINOLE COUNTY

HIGHLANDS

COUNTY

PINELLAS

COUNTY

DUVAL COUNTY

BRADFORD

COUNTY

OKEECHOBEE

COUNTY

COLUMBIA

COUNTY

0 10

0 10

20 MILES

20 KILOMETERS

Lake

Apopka

ATLANTIC OCEAN

GULF OF MEXICO

Tampa Bay

84°00 ́ 83°30 ́ 83°00 ́ 82°30 ́ 82°00 ́ 81°30 ́ 81°00 ́

30°00 ́

29°30 ́

29°00 ́

28°30 ́

28°00 ́

27°30 ́

Base modified from SWFWMD digital data; 2002.

Potentiometric surface data from U.S. Geological Survey, September 2007.

Universal Transverse Mercator projection, Zone 17 North

EXPLANATION

UPLAND AND RIDGE PHYSIOGRAPHIC REGIONS

POTENTIOMETRIC CONTOUR--Shows elevation at

which water level would have stood in tightly cased wells.

Hachures indicate depression. Contour interval 10 feet.

Datum is NGVD 29

DIRECTION OF REGIONAL GROUNDWATER FLOW

60

70

50

40

60

Lake

Panasoffkee

100

60

40

60

120

80

40

20

10

20

10

30

30

50

70

90

110

110

100

90

80 7060

50

50

30

30

70

40

50

50

40

50

60

10

30

10

10

10

30

0

20

20

30

40

20

80 70 70

0

0

10

10

Figure 21. Regional groundwater flow system in the Upper Floridan aquifer, September 2007 (from Kinnaman 

and Dixon, 2008; Ortiz, 2008b).
42 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

in central Marion County where the potentiometric surface 

of the Upper Floridan aquifer flattens out because of high 

aquifer transmissivities reflected by the large volume of spring 

discharge in that area. Lake Panasoffkee is located at the 

northern end of the southern potentiometric high, near where 

flow from both the northern and southern potentiometric highs 

turns westward toward the coast. 

The area that contributed groundwater to Lake 

Panasoffkee covered an average area of 192 mi2 during the 

study period and extends about 15 mi southeast and about 5 mi 

northeast of Lake Panasoffkee. The area is roughly oval in 

shape (figs. 22 and 23) and was defined from the regional 

potentiometric-surface maps of the Upper Floridan aquifer 

(Ortiz, 2008a, b, c, and 2009) and from the detailed potentiometric-surface maps created as part of this study. The potentiometric surface was defined using a simple graphical method 

similar to the way a topographic basin is defined. Water 

flows from the highest point in the groundwater basin and 

the boundaries of the contributing area and flow lines are all 

perpendicular to the lines of equal potential (head). Using this 

method to define the groundwater contribution area probably 

overestimates the actual area that contributes groundwater to 

Lake Panasoffkee because some groundwater farther from the 

lake probably flows vertically to recharge deeper parts of the 

flow system rather than laterally. 

Groundwater-level data collected in May 2007 and 2008 

(figs. 22A and 23A) were used to generate potentiometricsurface maps of the Upper Floridan aquifer at the end of the 

historic annual dry season when water levels are usually low, 

whereas the September 2007 and 2008 maps (figs. 22B and 

23B) illustrate the potentiometric surface at the end of the 

annual wet season when water levels are usually high. Longterm water-level data indicate that, on average, groundwater 

levels are lowest in Florida in May because winter and spring 

are usually the driest seasons of the year, whereas September 

typically has the highest groundwater levels following the wet 

summer months when rainfall and tropical activity are highest.

The groundwater-level data used to draw all four maps 

during the study period were collected during drought conditions. The May 2007 map (fig. 22A) represents peak drought 

conditions. Rainfall was below average during each of the 

preceding 12 months. The potentiometric surface of the Upper 

Floridan aquifer recovered slightly from the drought conditions in September 2007 because the rainfall in September 

2007 was 29 percent above average. The potentiometric 

surface changed little during 2008 in response to sporadic 

rainfall, with some months well above average and others well 

below average.

The discharge potential of the Upper Floridan aquifer 

generally increased during the study period (figs. 24 and 

25). Discharge and recharge potential are quantified by the 

head difference between the surficial aquifer and the Upper 

Floridan aquifer, with positive values for upward flow, and 

negative values for downward flow, respectively. The increase 

in discharge potential was caused by the slow recovery of the 

potentiometric surface of the Upper Floridan aquifer as rainfall 

returned to near normal levels in water year 2008 following 

the exceptionally dry 2006 and 2007 water years. As recharge 

increased in the uplands, so too did discharge in the lowlands. 

Head differences between the surficial and Upper Floridan 

aquifers ranged from -1.47 ft in the Big Jones Creek well nest 

(GW5–GW6) in July 2008 to +3.04 ft at ROMP well nest 

LP–6 (GW37–GW38) in August 2008 (fig. 11 and table 3). 

The central position of the recharge and discharge areas 

was consistent throughout the study period, with only the 

periphery of these areas expanding and contracting depending 

on the hydrologic conditions. The interpolated discharge areas 

generally follow a southeast-northwest trend similar to the 

outline of Lake Panasoffkee and of the Tsala Apopka Lake 

system to the west (figs. 24 and 25). Discharge potential was 

greatest along the eastern and southeastern margins of the 

lake, and is consistent with the presence of an artesian well 

(figs. 24 and 25) that flowed throughout the study period along 

the southeastern periphery of the lake. A secondary discharge 

area was identified northwest of the lake near the town 

of Carlson. Recharge potential was greatest northeast and 

southeast of the study area in the Sumter and Lake Uplands 

(fig. 3) where land-surface elevations are more than 110 ft 

above NGVD 29. 

Continuous water levels were recorded in six of the 

seven well nests mentioned earlier. These data present a 

much more detailed view of temporal changes in head differences between the Upper Floridan and surficial aquifers and 

their responses to individual rainfall events than the twice 

annual water-level data collected for the potentiometricsurface maps. Although head differences fluctuated from 

0 to 2 ft in the ROMP LP–6 (GW37–GW38) and Wysong 

Dam well nests (GW14–GW15) (fig. 11 and table 3), 

discharge potential was consistent (positive head difference) 

from the Upper Floridan aquifer to the surficial aquifer 

throughout the study period (fig. 26A). The higher heads in 

the Upper Floridan aquifer at these two well nests compared 

to other well nests are likely affected by the presence of 

Hawthorn Group clays that create locally confined conditions. Water levels at the Wysong Dam well nest might be 

influenced by the nearby dam; the dam was not in operation 

from the beginning of data collection until about October 

2007, and head differences were more variable starting in 

December 2007 (fig. 26A). The Upper Floridan aquifer head 

was higher than the surficial aquifer water level during the 

entire period the dam was not in operation during this study. 

The well nests at Little Jones Creek (GW7–GW8), Big 

Jones Creek (GW5–GW6), and to some degree ROMP LP–5 

(GW31–GW32) (fig. 11 and table 3) generally had flatter 

head differences than those at ROMP LP–6 (GW37–GW38) 

and Wysong Dam (GW14–GW15), with oscillations between 

recharge and discharge conditions occurring at each well 

nest (figs. 26B and C). Head differences at Big Jones Creek 

well nest, and especially at Little Jones Creek well nest, had 

small fluctuations between October 2006 and the beginning 

of the 2007 wet season in August 2007. From August 2007 

to the end of the study period, however, head differences 
Hydrogeology 43

ORANGE

COUNTY

LAKE

COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

HERNANDO

COUNTY

ORANGE

COUNTY

LAKE

COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

HERNANDO

COUNTY

Lake

Panasoffkee

Lake

Apopka

Withlacoochee

Lake

Apopka

Lake

Eustis

Lake

Eustis

Lake

Yale

Lake

Yale

Lake Griffin

Lake Griffin

Lake

Panasoffkee

Tsala

Apopka

Lake

Tsala

Apopka

Lake

Withlacoochee

River

River

Lake

Weir

Lake

Weir

Lake

Dora

Lake

Dora

Lake

Harris

Lake

Harris

50

40

30

10

20

30

40

50

60

70

80

90

50

40

30

40

30

50

60

20

70

10

80

90

30

20

40

10

20

30

40

20

10

20

50

30

20

50

30

20

60

60

5

3

3 2

5

5

8

6 4

9

7

36

43 45 34 49

38

30

13 44 48 43 47 52 34

53

44 47 23 37

33 15 60 32

36

13

42 43 47

34 36 63 27

36 38 61 13 52

18 48

52 54 72

72

77

56 79

28 72 76 34 16

58

31 70 35 32 78

37 83 70 30

51 11

95 78

46 87 66

43

44

48

49

49

4449 47

46 45

40

39

39

39 38

36

37

36

36

37

37

36

39

39

41

41

40

41 41

41

42 43

76

5

3

3

3

6

5

9

6 5

9

39

42 45 36 48 44 38

31

44 48 44 48

53

35

53 46 45 23 39

14 36 61 32 37 14 42 43

47 37

38 63 29

40

38 62 51 13

36 54 56 49 19 72

77 77 57

29

73

74 36 17

10 61

32

70

36

80

84 32

38 82

70

30

54 75 13 98 78

51 88 71

46

47

52

51

52 46

50

48

46

46

42

41

42 41 42

41 41

38

40

38

41 41 39

42 42

43

44

42

44 44

44

45 45

79

Bushnell

Wildwood

Inverness

Ridge

Manor

Brooksville

Lake

Panasoffkee

Bushnell

Wildwood

Inverness

Ridge

Manor

Brooksville

Lake

Panasoffkee

50

50

44

44

301

301

75

75

FLORIDA'S TURNPIKE

FLORIDA'S TURNPIKE

82°30 ́ 82°15 ́ 82°00 ́ 81°45 ́ 81°30 ́

29°00 ́

28°45 ́

28°30 ́

29°00 ́

28°45 ́

28°30 ́

A

B

60

51

EXPLANATION

WELL LOCATION AND NUMBER--Elevation of water level, in

feet above NGVD 29

POTENTIOMETRIC CONTOUR--Shows elevation at

which water level would have stood in tightly cased wells.

Hachures indicate depression. Contour interval is 10 feet.

Datum is NGVD 29

GROUNDWATER CONTRIBUTION AREA

0 5 10 MILES

0 5 10 KILOMETERS

Base modified from U.S. Geological Survey digital data; 1:100,000, 1983 and 1:2,000,000, 2005.

Universal Transverse Mercator projection, Zone 17 North

Figure 22. Generalized potentiometric-surface map of the Upper Floridan aquifer in the Lake Panasoffkee 

study area during A, May 2007 and B, September 2007. Modified from Ortiz (2008a and b).
44 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

50

50

44

44

301

301

75

75

FLORIDA'S TURNPIKE

FLORIDA'S TURNPIKE

5

3

3

3

5

5

9

5 6

9

8

40

42 46 36 47 44 37 30

45 47

44 48 52

34 52 45 46 24 39

16 35 61 37 39

14

41 42

38 39 64 31 38 62

52

13 38

18 53 48 57

73

73 79 57

80 36 39 17

62

31 36 69 81 84

38

85 69 29

52 73 11 97

77 48

71 86

40

45

46 50

50

45 51

51

48

46 42 41

41

41

4040

38 39 38

40

40

38 40 41

42

42

42

43

43

44 44

7

5

5

4

8

7

8 7

45 47 50 40 51 48

43

33

49 53 48 53

57 36

58 49 52 43 27

19 38 66 43

12

40

18 52 49

56 39 40 66 33 44 39 65 54

16 39 21

55

54

58 77

76 81 59

78

11

79 37 18 41

12

63 32

73

37 83 86

39

86 72 30

61

15 78

99 49 81 73 90

43

43

48

49 54

52 48 56

54

48

47 45 44

43 40

42

40

42

43

44 44

4546

44

46

46 47 48

80

43

83

5050 43 43

40

46

EXPLANATION

WELL LOCATION AND NUMBER--Elevation of water level, in

feet above NGVD 29

POTENTIOMETRIC CONTOUR--Shows elevation at

which water level would have stood in tightly cased wells.

Hachures indicate depression. Contour interval is 10 feet.

Datum is NGVD 29

GROUNDWATER CONTRIBUTION AREA

0 5 10 MILES

0 5 10 KILOMETERS

Base modified from U.S. Geological Survey digital data; 1:2,000,000, 1998.

Universal Transverse Mercator projection, Zone 17 North

Lake

Panasoffkee

Lake

Apopka

Withlacoochee

Lake

Apopka

Lake

Eustis

Lake

Eustis

Lake

Yale

Lake

Yale

Lake Griffin

Lake Griffi

Lake n

Panasoffkee Tsala

Apopka

Lake

Tsala

Apopka

Lake

Withlacoochee

River

River

Lake

Weir

Lake

Weir

Lake

Dora

Lake

Dora

Lake

Harris

Lake

Harris

ORANGE

COUNTY

LAKE

COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

HERNANDO

COUNTY

ORANGE

COUNTY

LAKE

COUNTY

SUMTER

COUNTY

CITRUS

COUNTY

HERNANDO

COUNTY

Inverness

Tavares

Wildwood

Bushnell

Ridge

Manor

Brooksville

Lake

Panasoffkee

Tavares

Wildwood

Bushnell

Inverness

Ridge

Manor

Brooksville

Lake

Panasoffkee 40

30

50

60

20

70

10

80

90

50

40

30

10

20

30

40

50

60

70

80

90

50

40

30

30

20

40

10

20

30

40

20

10

20

50

30

20

50

30

30

82°30 ́ 82°15 ́ 82°00 ́ 81°45 ́ 81°30 ́

29°00 ́

28°45 ́

28°30 ́

29°00 ́

28°45 ́

28°30 ́

A

B

50

Figure 23. Generalized potentiometric-surface map of the Upper Floridan aquifer in the Lake Panasoffkee 

study area during A, May 2008 and B, September 2008. Modified from Ortiz (2008c and 2009).
Hydrogeology 45

301

75

470

301

470 75 301

301

Jumper

Creek

Jumper

Creek

Coleman

Lake

Panasoffkee

Lake Panasoffkee

Coleman

Lake

Panasoffkee

Tsala

Apopka

Lake

Shady

Brook

Shady

Brook

Outlet

River

Outlet

River

Withlacoochee

River

Withlacoochee

River

Little Jones Creek

Little Jones Creek

Lake Panasoffkee

Tsala

Apopka

Lake

Big

Jones

Creek

Big

Jones

Creek

Warnel

Creek

Warnel

Creek

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Universal Transverse Mercator projection, Zone 17 North

EXPLANATION

Head difference, in feet

Carlson

Carlson

Less than -2.0

-2.1 to -1.0

-1.1 to 0.0

0.1 to 1.0

1.1 to 2.0

Greater than 2.1

Flowing artesian well

DISCHARGE

RECHARGE

A

B

0 2 MILES

0 2 KILOMETERS

Figure 24. Areas of recharge and discharge potential between the surficial aquifer 

and the Upper Floridan aquifer in the Lake Panasoffkee study area for A, May 2007 and 

B, September 2007.
46 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0 2 MILES

0 2 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 and 1:2,000,000, 2005

Universal Transverse Mercator projection, Zone 17 North

EXPLANATION

470

301

301

470

75

301

301

Lake

Panasoffkee

Lake

Panasoffkee

Coleman

Coleman

Tsala

Apopka

Lake

Tsala

Apopka

Lake

Lake Panasoffkee

Shady

Brook

Shady

Brook

Outlet

River

Outlet

River

Withlacoochee

River

Withlacoochee

River

Little Jones Creek

Little Jones Creek

Lake Panasoffkee

Jumper

Creek

Jumper

Creek

Warnel

Creek

Big

Jones

Creek

Warnel

Creek

Big

Jones

Creek

Head difference, in feet

Carlson

Carlson

Flowing artesian well

Less than -2.0

-2.1 to -1.0

-1.1 to 0.0

0.1 to 1.0

1.1 to 2.0

DISCHARGE Greater than 2.1

RECHARGE

A

B

Figure 25. Areas of recharge and discharge potential between the surficial aquifer 

and the Upper Floridan aquifer in the Lake Panasoffkee study area for A, May 2008 and 

B, September 2008.
Hydrogeology 47

Big Jones Creek (GW5 - GW6)

Little Jones Creek (GW7 - GW8)

Precipitation

EXPLANATION

EXPLANATION

ROMP LP-4 (GW24 and GW26)

ROMP LP-5 (GW31 - GW32)

Precipitation

ROMP LP-6 (GW37 - GW38)

Wysong Dam (GW14 - GW15)

Precipitation

EXPLANATION

Point measurements taken in the well

after recording equipment was removed

-4

-2

0

2

4

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-4

-2

0

2

4

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-4

-2

0

2

4

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

A

B

C

Oct

Oct

Dec

Dec

Feb

Feb

Apr

Apr

Jun

Jun

Aug

Aug

Oct

Oct

Dec

Dec

Feb

Feb

Apr

Apr

Jun

Jun

Aug

Aug

Oct

Oct

HYDRAULIC HEAD

DIFFERENCE, IN FEET

PRECIPITATION, IN INCHES PRECIPITATION, IN INCHES PRECIPITATION, IN INCHES

DATE

HYDRAULIC HEAD

DIFFERENCE, IN FEET

HYDRAULIC HEAD

DIFFERENCE, IN FEET

Nov

Nov

Jan

Jan

Mar

Mar

May

May

Jul

Jul

Sep

Sep

Nov

Nov

Jan

Jan

Mar

Mar

May

May

Jul

Jul

Sep

Sep

2006

2006

2007

2007

2008

2008

Oct

Nov

Dec

Jan

Feb

MarApr

MayJun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

MayJun

Jul

Aug

Sep

Oct

2006 2007 2008

Big Jones Creek (GW5 - GW6)

Little Jones Creek (GW7 - GW8)

Precipitation

EXPLANATION

EXPLANATION

ROMP LP-4 (GW24 and GW26)

ROMP LP-5 (GW31 - GW32)

Precipitation

ROMP LP-6 (GW37 - GW38)

Wysong Dam (GW14 - GW15)

Precipitation

EXPLANATION

Point measurements taken in the well

after recording equipment was removed

Figure 26. Difference in hydraulic head between the surficial aquifer and Upper 

Floridan aquifer near Lake Panasoffkee A, LP-6 and Wysong Dam well nests; 

B, Big Jones Creek and Little Jones Creek well nests; and C, LP-4 and LP-5 well 

nests, October 2006 through September 2008. Positive hydraulic head values 

indicate potential discharge from the Upper Floridan aquifer, whereas negative 

values indicate recharge potential. Figure 11 and table 3 contain well location and 

well specification information.
48 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

at these well nests oscillated rapidly between recharge and 

discharge conditions, even during the dry season. Headdifference oscillations at ROMP LP–5 were small from the 

beginning of data collection in January 2007 until about 

May 2007, when large, low-frequency oscillations began 

(fig. 26C). These large oscillations ended abruptly around 

November 2007, and differences at ROMP LP–5 remained 

nearly constant with (negative) recharge potential from the 

surficial aquifer to the Upper Floridan aquifer for most of the 

remainder of the study period. The Hawthorn Group clays 

are absent at ROMP LP–5. This absence results in a better 

hydraulic connection between the Upper Floridan aquifer 

and surficial aquifer at ROMP LP–5 than at the Big Jones 

Creek and Little Jones Creek well sites. The lack of confinement at this site explains the nearly constant head differences 

recorded at ROMP LP–5 from November 2007 through the 

end of the study.

During the third week of August 2008, 4 days of heavy 

rainfall (an average of almost 3 in. in the Lake Panasoffkee 

basin) resulted in a sharp recharge peak at ROMP LP–5 

(GW31–GW32), and especially at Little Jones Creek (GW7–

GW8) and Big Jones Creek (GW5–GW6) (figs. 11, 26B

and C, table 3). During the week following this rainfall event, 

the head differences at the Little Jones Creek and Big Jones 

Creek well nests recovered quickly to a state of discharge 

potential from the Upper Floridan aquifer to the surficial 

aquifer. The head differences at ROMP LP–5, however, 

followed a more gradual asymptotic recovery, returning 

after about 7 weeks to a state of recharge potential from the 

surficial aquifer to the Upper Floridan aquifer, similar to 

conditions that existed before the rain event. The difference 

in response between the three well nests can be attributed to 

the thickness of the unsaturated zone and the thickness of the 

surficial aquifer at each site. The surficial aquifer deposits are 

5 ft thick or less at both the Big Jones Creek and Little Jones 

Creek well sites, whereas the surficial aquifer is 56 ft thick at 

site ROMP LP–5. The greater water-storage capacity of the 

surficial aquifer at site ROMP LP–5 compared to the other 

sites results in slower recovery at this site after major rain 

events because the unsaturated zone is thicker. 

The head difference between the Upper Floridan and 

surficial aquifers at ROMP LP–4 (GW24 and GW26) on 

the west side of the lake is slightly positive and shows little 

variation over time, indicating steady, upward groundwater 

discharge potential (figs. 11 and 26C, table 3). Continuous 

data were collected until January 2007 when the data logger 

was removed from the surficial aquifer well; only monthly 

periodic measurements are available thereafter. The periodic 

ROMP LP–4 measurements corroborate the trend of a small 

potential for upward groundwater discharge. Similar to ROMP 

LP–5 (GW31–GW32), the Hawthorn Group is absent or very 

thin at ROMP LP–4, indicating potential hydraulic connection 

between the Upper Floridan and surficial aquifers. Whereas 

the period of low frequency oscillation in head differences 

at ROMP LP–5 occurs after the continuous data collection 

at ROMP LP–4 ended in January 2007, it is still evident in 

figure 26C that head differences at ROMP LP–4 and ROMP 

LP–5 remained similar to each other and, therefore, the 

surficial and Upper Floridan aquifers respond similarly to 

precipitation at these sites. 

The dry-season measurement in 2007 indicated an 

upward head difference in the northwest (GW18) and westcentral (GW22) lake piezometer sites, and a downward head 

difference at the southern site (GW30) (fig. 11 and table 3). 

The September 2007 wet season yielded the opposite condition, with downward (negative) head differences measured 

from the surficial aquifer to the Upper Floridan aquifer at the 

northwestern and west-central sites, whereas the southern 

site experienced upward (positive) head differences from 

the Upper Floridan aquifer to the surficial aquifer. All of the 

measurements made in 2008, during both the wet and dry 

seasons, indicated upward head differences from the Upper 

Floridan aquifer to the surficial aquifer. Both the northwest 

and west-central piezometer sites tended to mirror the relation 

between the Upper Floridan aquifer and surficial aquifer at 

ROMP LP–4 (GW24 and GW26, fig. 11 and table 3). When 

water levels in the surficial aquifer were higher than Lake 

Panasoffkee levels at the lakeshore piezometer sites, the 

head in the Upper Floridan aquifer was also higher than the 

surficial aquifer at nested well site ROMP LP–4, indicating 

upward heads in both the Upper Floridan and surficial aquifers. Head differences at the southern piezometer site were 

usually in the same direction as at ROMP LP–6 (GW37–

GW38, fig. 11 and table 3). During the wet season in 2007, 

however, Lake Panasoffkee water levels were higher than 

the water levels in the surficial aquifer, reflecting recharging 

conditions. At ROMP LP–6, Upper Floridan aquifer heads 

also were higher than water levels in the surficial aquifer, 

reflecting upward discharge conditions.

Geophysics

Direct measurement of groundwater inflow rates using 

electromagnetic seepage meters would have been useful in 

corroborating the groundwater inflow data calculated from 

the water budget. For a period of 1 week in February 2007, 

an attempt was made to directly measure groundwater inflow 

rates in Lake Panasoffkee. Unfortunately, very soft organic 

sediment that constitutes much of the lakebed prevented the 

seepage meters from properly sealing. Because the seals were 

not complete, groundwater discharge probably by-passed the 

electromagnetic flow meter and was lost to the lake, rendering 

the estimates inconclusive. 

Seismic-reflection surveys can be a useful tool for 

qualifying subsurface hydrogeologic features beneath a lake 

(Kindinger, 2002). Although a seismic reflection survey 

does not quantify the volume of water exchanged between 

groundwater and surface water, it can help identify features, 

such as sinkholes, springs, and faults, where exchange may 

occur (Tihansky and others, 1996). Seismic reflection surveys 

also may determine the presence or absence of confining units 

beneath a lake (Tihansky and others, 1996). A continuous 
Surface-Water Hydrology 49

seismic-reflection profiling survey of Lake Panasoffkee 

was first attempted in May 2006, but water levels in Lake 

Panasoffkee were extremely low at that time and floating 

aquatic vegetation covered much of the lake surface. 

The combined low water levels and thick vegetation made boat 

navigation difficult. Attempts were made to survey the lake 

using both the high-frequency CHIRP and the low-frequency 

electromagnetic seismic Boomer. The high-frequency signal 

produced by the CHIRP was attenuated by aquatic vegetation 

before penetrating the lakebed. It is believed that gas bubbles 

trapped by growing vegetation and within the organic debris at 

the lake bottom disrupted the wave form of the acoustic pulse, 

returning spurious signals to the hydrophones. The higher 

energy propagated by the Boomer system was capable of 

penetrating the vegetation, but signal loss was still evident. 

After running various unsuccessful survey lines, the effort was 

abandoned with little usable data collected. 

A second seismic reflection survey was attempted at 

Lake Panasoffkee in May 2008 using the same equipment. 

Lake conditions during this survey were much improved, 

with parts of the lake newly opened by dredging as part of the 

lake restoration effort. Water levels also were much higher 

than in May 2006, resulting in a lake surface free of floating 

aquatic vegetation. The CHIRP was used for the first profile 

attempt, with much the same result as in 2006. Even with the 

lake surface clear of vegetation, the CHIRP was unable to 

efficiently penetrate the vegetation and trapped gas bubbles 

covering most of the lake bottom. The Boomer was used for 

the remainder of the survey. 

Although several potential subsurface features were 

detected beneath Lake Panasoffkee while running the seismic 

survey lines, none of the features could be reproduced when 

they were investigated a second time. Because the features 

could not be reproduced there is doubt that they were real. 

A persistent but faint subsurface feature was detected from 

60 to 100 ft beneath the lakebed under much of the lake, but 

the noise in the data made it impossible to determine if the 

feature was real or perhaps caused by interference between 

the boat and the seismic equipment. Although the depth at 

which the potential geologic feature was detected roughly 

corresponds with the top of the Avon Park Formation in some 

of the wells adjacent to Lake Panasoffkee, the poor quality of 

the data prevented any definite conclusions from being drawn. 

The complete Lake Panasoffkee seismic-reflection survey is 

documented in Harrison and others (2009).

Surface-Water Hydrology

The surface-drainage basin of Lake Panasoffkee 

encompasses roughly 360 mi2 in Sumter, Marion, and Lake 

Counties (fig. 2). The sparseness of surface-water features 

north of S.R. 44, in combination with the low topographic 

relief of the study area, suggests that the effective surface 

drainage area of the lake is much smaller. Lake Panasoffkee 

has two main tributaries, Little Jones Creek and Shady Brook, 

and one outlet, the Outlet River (fig. 10). Warnel Creek, a 

distributary of Shady Brook (fig. 10), also contributes water 

to Lake Panasoffkee, although the net effect on the lake water 

budget from this tributary during the study was small. Big 

Jones Creek (fig. 10), a fourth tributary of Lake Panasoffkee, 

contributed almost no water to the lake during this study 

because it only began to flow during the last month of data 

collection (September 2008). At the Big Jones Creek gaging 

station (SW5, fig. 10), water was pooled in the channel over 

much of the study period and flow over the control was rarely 

observed. An area of diffuse, poorly channelized flow along the 

eastern edge of the lake may contribute substantial amounts of 

surface water to the lake during periods of heavy rainfall, but 

estimations made of surface-water flow from this area during 

this study showed little overall effect on the lake water budget. 

The entire Lake Panasoffkee watershed is a major contributor 

of surface-water inflow to the Withlacoochee River, through 

the Outlet River (Trommer and others, 2009). 

Streamflow

The major contributors of surface water to Lake 

Panasoffkee during the study period were Little Jones Creek 

and Shady Brook (fig. 10 and table 6). Warnel Creek also 

contributed surface-water flow, but only from December 2007 

through September 2008. The average monthly discharge 

from Little Jones Creek to Lake Panasoffkee between April 

2006 and September 2008 ranged from 6.56 ft3/s in June 

2007 to 75.8 ft3/s in August 2008 (U.S. Geological Survey, 

2009). The total discharge from Little Jones Creek to Lake 

Panasoffkee during this period was 2.36 billion ft3. The water 

year 2007 total was 523 million ft3 and the water year 2008 

total was 1.22 billion ft3. The average monthly discharge 

from Shady Brook to Lake Panasoffkee between April 2006 

and September 2008 ranged from 8.28 ft3/s in June 2007 to 

59.6 ft3/s in September 2008 (U.S. Geological Survey, 2009). 

The total discharge from Shady Brook to Lake Panasoffkee 

during this period was 1.65 billion ft3. Shady Brook contributed 357 million ft3 of total flow to Lake Panasoffkee in water 

year 2007 and 897 million ft3 of total flow in water year 2008. 

Average monthly discharge from Warnel Creek (when it was 

flowing) ranged from 0.10 ft3/s in December 2007 to 12.4 ft3/s 

in August 2008. Warnel Creek did not flow in water year 

2007 and it contributed 113 million ft3 of total flow to Lake 

Panasoffkee in water year 2008. The combined discharge from 

Little Jones Creek, Shady Brook, and Warnel Creek was 51 

and 49 percent of the total inflow to Lake Panasoffkee during 

water years 2007 and 2008, respectively. 

The average monthly discharge from Lake Panasoffkee to 

the Outlet River (fig. 10) between April 2006 and September 

2008 ranged from 12.6 ft3/s in June 2007 to 225 ft3/s in August 

2008 (U.S. Geological Survey, 2009; table 6). The total 

discharge from Lake Panasoffkee to the Outlet River during 

the 29-month period was 5.50 billion ft3. Typically, the 
50 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida Table 6. Average monthly surface-water discharge and total volume of monthly discharge to and from Lake Panasoffkee, April 2006 through September 2008. [Big Jones Creek (285126082085200) was omitted from the table because it did not contribute flow to Lake Panasoffkee during the study period. ft3/s, cubic feet per second; ft3, cubic feet; WY, water year] Month and year Little Jones Creek (02312675) Shady Brook (284619082032700) Warnel Creek (284554082052700) Outlet River (02312700) Outflow from dredging1 Average monthly discharge (ft3/s) Total monthly volume (ft3

)

Average 

monthly 

discharge 

(ft3/s)

Total 

monthly 

volume 

(ft3

)

Average 

monthly 

discharge 

(ft3/s)

Total 

monthly 

volume 

(ft3

)

Average 

monthly 

discharge 

(ft3/s)

Total 

monthly 

volume 

(ft3

)

Total 

monthly 

volume 

(ft3

)

Percentage of 

monthly outflow 

from dredging2

Apr-06 64.0 165,888,000 40.5 104,892,909 0 0 107 277,344,000 21,924,046 7.9

May-06 46.0 123,206,400 29.6 79,324,523 0 0 57.3 153,472,320 23,548,966 15

Jun-06 34.8 90,201,600 22.4 58,094,971 0 0 86.6 224,467,200 21,371,611 9.5

Jul-06 34.3 91,869,120 21.2 56,686,496 0 0 94.4 252,840,960 22,581,253 8.9

Aug-06 27.2 72,852,480 17.9 47,935,662 0 0 62.7 167,935,680 22,783,177 14

Sep-06 27.2 70,502,400 17.1 44,302,896 0 0 64.4 166,924,800 15,807,258 9.5

Oct-06 19.6 52,496,640 12.4 33,211,433 0 0 46.7 125,081,280 23,933,766 19

Nov-06 19.7 51,062,400 11.9 30,748,615 0 0 48.9 126,748,800 22,558,393 18

Dec-06 17.8 47,675,520 12.9 34,600,152 0 0 38.3 102,582,720 20,440,091 20

Jan-07 16.5 44,193,600 13.7 36,749,813 0 0 39.5 105,796,800 20,809,651 20

Feb-07 19.6 47,416,320 15.0 36,257,399 0 0 42.5 102,816,000 20,626,776 20

Mar-07 19.0 50,889,600 12.0 32,079,531 0 0 36.3 97,225,920 15,171,005 16

Apr-07 14.8 38,361,600 10.0 25,850,051 0 0 21.5 55,728,000 21,358,276 38

May-07 9.53 25,525,152 8.31 22,263,378 0 0 13.1 35,087,040 22,449,811 64

Jun-07 6.56 17,003,520 8.28 21,465,122 0 0 12.6 32,659,200 8,149,367 25

Jul-07 10.5 28,123,200 9.60 25,706,641 0 0 26.1 69,906,240 0 0

Aug-07 17.4 46,604,160 10.8 28,912,110 0 0 37.4 100,172,160 0 0

Sep-07 28.4 73,612,800 11.3 29,169,660 0 0 37.4 96,940,800 0 0

Oct-07 54.1 144,901,440 25.0 66,959,214 0 0 20.4 54,639,360 11,292,531 21

Nov-07 31.7 82,166,400 19.8 51,341,610 0 0 34.3 88,905,600 23,296,751 26

Dec-07 30.1 80,619,840 16.4 43,940,716 0.10 267,840 63.7 170,614,080 19,224,734 11

Jan-08 31.2 83,566,080 16.5 44,226,069 1.15 3,080,160 96.8 259,269,120 21,085,868 8.1

Feb-08 27.0 67,651,200 21.1 52,845,204 2.38 5,963,328 111 278,121,600 18,862,794 6.8

Mar-08 34.7 92,940,480 31.5 84,460,882 4.61 12,347,424 122 326,764,800 20,127,680 6.2

Apr-08 37.3 96,681,600 24.8 64,277,626 2.62 6,791,040 70.6 182,995,200 20,567,723 11

May-08 17.3 46,336,320 12.8 34,343,334 0.45 1,205,280 20.3 54,371,520 21,144,922 39

Jun-08 16.5 42,768,000 16.6 43,066,365 1.61 4,173,120 77.3 200,361,600 23,489,913 12

Jul-08 32.9 88,119,360 37.2 99,679,723 7.01 18,775,584 162 433,900,800 23,404,190 5.4

Aug-08 75.8 203,022,720 59.1 158,272,263 12.4 33,212,160 225 602,640,000 22,049,772 3.7

Sep-08 74.8 193,881,600 59.6 154,544,380 10.7 27,734,400 213 552,096,000 20,215,307 3.7

WY 2007 total 16.6 522,964,512 11.3 357,013,905 0 0 33.4 1,050,744,960 175,497,137 17WY 2008 total 38.6 1,222,655,040 28.4 897,957,385 3.59 113,550,336 101 3,204,679,680 244,762,186 7.6Apr 2006–Sept 2008 total 29.9 2,360,139,552 20.8 1,646,208,746 1.43 113,550,336 69.6 5,498,409,600 548,275,633 10

1 Outflow from dredging is the monthly volume of water pumped from Lake Panasoffkee as a result of lake restoration activities.2 Percentage of monthly outflow from dredging is the percentage of the total monthly outflow from Lake Panasoffkee attributed to lake restoration activities.
Surface-Water Hydrology 51

Outlet River accounts for almost all of the surface-water 

discharge from the lake, but during the study period, water 

was being pumped from the lake as part of the lake-restoration 

activities. The pumpage lowered the lake level, and therefore, 

decreased the volume of outflow from Lake Panasoffkee to 

the Outlet River, so discharge may appear low for the study 

period compared to other periods with similar climatic conditions. Monthly outflow from dredging from April 2006 through 

September 2008 totaled 548 million ft

3

 and average monthly 

pumpage ranged from 8.15 million ft

3

 in June 2007 to 23.9 

million ft

3

 in October 2006 (table 6). Dredging accounted for 

a minimum of 3.7 percent of the total monthly surface-water 

outflow, in both August and September 2007, and a maximum 

of 64 percent of the total outflow in May 2007. No dredging 

occurred in July, August, and September 2007 because the 

drought resulted in unusually low lake levels. On average, 

dredging accounted for 10 percent of the total surface-water 

outflow from Lake Panasoffkee from April 2006 through 

September 2008. 

Spring Inflows

Spring discharge measurements were made during four 

seepage runs to determine the groundwater contributions 

of each spring to Lake Panasoffkee (table 7). During the 

December 2007, July 2008, and September 2008 seepage 

runs, about 67 to 76 percent of the discharge in Little Jones 

Creek and Shady Brook (fig. 10) was derived from springs. 

During the March 2008 seepage run, 82 and 91 percent of 

the discharge in Little Jones Creek and Shady Brook, respectively, was contributed by spring flow. The flow in excess of 

these percentages probably derives from diffuse groundwater 

inflow. A small percentage may be attributed to overland 

flow, but overland flow was assumed to be minimal because 

the seepage runs were completed under baseflow conditions. 

The seepage runs are detailed below in the section titled 

“streamflow gains and losses.”

During the seepage runs, the single largest spring 

contributor to Lake Panasoffkee was Henry Green Spring 

(SP20, fig. 5 and table 1), which forms the head of Little Jones 

Creek near the intersection of S.R. 44 and I–75. Measured 

discharge at Henry Green Spring ranged from 7.98 ft3/s in 

April 2007 to 23.6 ft3/s in September 2008; the April 2007 

Henry Green Spring discharge measurement was not part of 

a seepage run (U.S. Geological Survey, 2009). The second 

and third largest contributors were Fenney Spring (SP18) and 

Wayne Lee Spring (SP19), respectively (fig. 5 and table 1). 

Measured discharge at Fenney Spring ranged from 3.07 ft3/s 

in December 2007 to 28.4 ft3/s in September of 2008, and 

discharge at Wayne Lee Spring ranged from 6.55 ft3/s in July 

2008 to 24.2 ft3/s in September 2008 (table 7). 

A maximum discharge of 80 ft3/s at Fenney Spring 

(SP18) was based on the period-of-record maximum gage 

height of 54.86 ft above NGVD 29 on August 28, 2008 (fig. 5 

and table 1) (U.S. Geological Survey, 2009). Discharge at 

Fenney Spring was estimated using a 2nd-order polynomial 

curve that was fit to a plot of spring discharge in relation to 

water-level measurements made in a surficial aquifer monitoring well (GW43) adjacent to the spring pool (R2 = 0.98):

y = 16.928x2 - 1785.4x + 47,078 (6)

where 

y is spring discharge and 

x is the water level in the monitoring well, in feet above

 NGVD 29 (fig. 5 and table 1). 

Surficial aquifer water levels were used to develop the 

regression equation because of a lack of gage-height measurements defining the upper end of the gage height-discharge 

relation. Because surficial aquifer water levels were used to 

estimate maximum discharge, it was necessary to compare 

these water levels to gage height in order to determine the 

suitability of using water levels as a proxy for gage height. 

Differences between water levels and gage heights were less 

than 0.20 percent or 0.10 ft, with a maximum expected error of 

0.1 ft3/s. No-flow conditions were observed at Fenney Spring 

during a site inspection on June 6, 2007, at a gage height of 

51.48 ft (U.S. Geological Survey, 2009). Based on the hydrograph for this site for the study period, no-flow conditions 

probably occurred from April through July 2007.

Ungaged Flow

The land along the eastern margin of Lake Panasoffkee 

is generally flat and is composed of mucky soils interspersed 

with small, sandy islands. Overland flow in this region is 

typified by poorly channelized sheetflow that is constrained 

by culverts that divert flow underneath a dirt access road. 

The road runs north and south, parallel to the eastern shore 

of Lake Panasoffkee, and acts as a berm in low-lying areas. 

All of the overland flow into Lake Panasoffkee from east of 

this road is routed through the culverts before emptying back 

into the swamp west of the dirt road. Discharge was observed 

at some of these culverts early in the reconnaissance phase 

of the study, but was not measured at that time. Water was 

only flowing through a single culvert during the first three 

seepage runs, with flows of 1.22, 3.14, and 0.53 ft3/s measured 

in December 2007, March 2008, and July 2008, respectively. 

In September 2008, water was found to be flowing through 

two culverts with a combined flow of 12.6 ft3/s (table 7).

Lake Level

The SWFWMD has drafted a new set of Minimum and 

Guidance Levels for Lake Panasoffkee that will supersede the 

current set of Guidance Levels adopted in 1982 (Southwest 

Florida Water Management District, 2006). The SWFWMD 

proposes three guidance levels and two minimum levels―all 

of which are based on needs for recreational use, maintenance 

of aquatic habitat, and lakeshore development. Of particular 
52 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

interest to this study are the new Low Guidance Level (38.9 ft 

above NGVD 29), Minimum Lake Level (39.4 ft above NGVD 

29), and High Minimum Lake Level (40.8 ft above NGVD 29).

The Low Guidance Level (LGL) is defined as “the 

elevation that a lake’s water levels are expected to equal or 

exceed 90 percent of the time (P90) on a long-term basis” 

(Southwest Florida Water Management District, 2006). This 

corresponds roughly to the existing “Extreme Low Level” 

(38.5 ft above NGVD 29) under the current set of Guidance 

Levels. The P90 of the lake from April 2006 to September 

2008 was 37.2 ft above NGVD 29, and the proposed LGL was 

exceeded only 40 percent of the time (fig. 27). The Minimum 

Lake Level (MLL) of 39.4 ft above NGVD 29 is the P50 level, 

the water level expected to be equaled or exceeded 50 percent 

of the time on a long-term basis. The MLL was exceeded only 

30 percent of the time between April 2006 and September 

2008. The measured P50 of the lake during the study period 

was only 38.2 ft above NGVD 29. The High Minimum Lake 

Level (HMLL) was not reached during the study period; the 

maximum stage recorded during the study period was 40.42 ft 

above NGVD 29.

 Lake stage fluctuated 3.44 ft between October 2006 and 

September 2008, with a minimum stage of 36.98 ft above 

NGVD 29 and a maximum stage of 40.42 ft above NGVD 

29 (fig. 27). Lake levels fell consistently from 37.66 ft above 

NGVD 29 on October 1, 2006, to 36.98 ft above NGVD 29 

on June 30, 2007. Around October 1, 2007, lake levels 

began to rise quickly without a commensurate increase in 

discharge at Outlet River. This occurred because water in the 

Withlacoochee River was impounded by the Wysong Dam 

(fig. 1), which caused backwater effects all the way up Outlet 

River into Lake Panasoffkee. In all, lake levels rose from 

37.86 ft above NGVD 29 on October 1, 2007, to a maximum 

of 39.23 ft above NGVD 29 on October 31, 2007. This rise 

in lake stage equates to an increase in storage of roughly 200 

million ft3 (1.5 billion gallons).

Table 7. Summary of measured discharge at spring and surface-water stations in the Lake Panasoffkee study area during four 

seepage runs from December 2007 through September 2008.

[ft3/s, cubic feet per second; n/a, not applicable; E, estimated value]

Reference 

number 

(fig. 10)

USGS site 

identification 

number

Station name

Discharge, ft3/s

Dec-07 Mar-08 Jul-08 Sep-08

Inflows to Lake Panasoffkee

SW1 284554082052700 Warnel Creek 350 ft above I-75 at Lake Panasoffkee 0.00 3.75 6.23 12.7

SW2 284534082054400 Shady Brook 350 ft above I-75 at Lake Panasoffkee 18.9 32.0 38.8 70.9

SW3 02312667 Shady Brook near Sumterville 12.4 24.4 23.7 53.8

SW4 284619082032700 Shady Brook 0.7 mile above U.S. 301 near Sumterville 11.2 21.9 21.8 55.1

SW5 285126082085200 Big Jones Creek 2 miles above Lake Panasoffkee near Carlson 0.00 0.00 0.00 6.09

SW6 02312675 Little Jones Creek near Rutland 40.7 30.8 25.9 69.0

n/a n/a Discharge from swampy area east of Lake Panasoffkee (culverts) E 1 E 3 E 0.5 E 13

Outflows from Lake Panasoffkee

SW7 02312700 Outlet River at Panacoochee Retreats 86.5 86.6 150 261

Springs that contribute flow to Little Jones Creek

SW8 285207082054100 Henry Green Spring Run at Wildwood 15.1 13.4 12.0 23.6

SW9 285133082053100 Wayne Lee Spring Run at I-75 near Wildwood 12.2 11.8 6.55 24.2

Springs that contribute flow to Shady Brook

SW10 02312664 Fenney Spring near Coleman 3.07 15.5 8.90 28.4

SW11 284709082024100 Blue Spring at Sumter County 5.98 4.95 6.35 6.00

SW12 284530082034800 Belton’s Millpond Spring Complex near Sumterville E 3 7.87 12.0 18.8

SW13 284525082040600 Maintenance Spring Run near Sumterville 0.76 0.71 1.07 0.93

Percentage of flow from Little Jones Creek to Lake Panasoffkee contributed by spring flow 67 82 72 69

Percentage of flow from Shady Brook to Lake Panasoffkee contributed by spring flow 68 91 73 76

Percentage of total inflow to Lake Panasoffkee contributed by spring flow 66 78 66 60
Surface-Water Hydrology 53

Streamflow Gains and Losses

Although all seepage runs were conducted during 

baseflow conditions when hydrologic conditions were static, 

the later seepage runs reflected higher water conditions 

compared to the earlier ones, which were affected by the 

antecedent drought. The highest documented flows during 

the seepage runs were in September 2008, when Outlet River 

discharge measured 261 ft3/s. The lowest flows during the 

seepage runs were measured in December 2007 when Outlet 

River discharge was 86.5 ft3/s. The relative contribution from 

each stream reach to total streamflow during the four seepage 

runs is shown in figure 28. The range of flows presented here 

is probably lower than it would be for a typical year because 

of an ongoing drought. The drought began in 2005 before data 

collection started for this study and continued until the end of 

data collection in September 2008.

Seepage run data indicate that the primary tributaries 

to Lake Panasoffkee, Little Jones Creek and Shady Brook, 

are both gaining streams. Henry Green Spring (SW8) and 

Wayne Lee Spring (SW9) are the primary sources of water 

to Little Jones Creek (fig. 10 and table 2). In all four seepage 

runs (fig. 28), Little Jones Creek also gained additional flow 

between the springs and the downstream gage. In September 

2008, the combined discharge for Henry Green Spring (SW8) 

and Wayne Lee Spring (SW9) was 47.8 ft3/s. Less than 3 mi 

downstream, the measured discharge was 69.0 ft3/s at the 

Little Jones Creek stream gage (SW6). Thus, Little Jones 

Creek gained an additional 21.2 ft3/s of flow along this reach, 

nearly the volume of flow provided by Wayne Lee Springs 

(24.2 ft3/s) and Henry Green Springs (23.6 ft3/s) (table 7). 

The additional flow is either from unidentified springs, or, 

more likely, from groundwater inflow into the creek channel. 

This conclusion was corroborated by comparing continuous 

water-level data collected at the Shady Brook and Outlet River 

surface-water stations (fig. 29) to nearby groundwater-level 

data. Water-level data indicate a continuous upward head 

difference from the groundwater system into the streams. 

Surface-water runoff also likely contributed small amounts of 

flow during this seepage run, because the swamp adjacent to 

Little Jones Creek contained shallow standing water.

The headwater for Shady Brook is Fenney Spring (SW10, 

fig. 10 and table 2). Blue Spring (SW11) forms a run that 

empties into Shady Brook about 0.75 mi downstream from the 

headwater. The combined flow from these springs in September 

2008 was 34.4 ft3/s. A little more than 1 mi downstream 

from Fenney Spring, the discharge of Shady Brook (SW4) 

was measured at 55.1 ft3/s, which corresponds to a gain of 

20.7 ft3/s. Discharge at the streamflow gage at U.S. 301 (SW3) 

was 53.8 ft3/s, for a difference of 1.3 ft3/s (table 7). The small 

difference is statistically insignificant and should be interpreted 

as neither a net loss nor gain. West of U.S. 301, the combined 

flow from Belton’s Millpond Spring Complex (SW12) and 

36

37

38

39

40

41

42

LAKE STAGE, IN FEET ABOVE NGVD 29

-50

0

50

100

150

200

250

300

350

400

450

DISCHARGE, IN CUBIC FEET PER SECOND

High Minimum Lake Level (40.8 feet)

Minimum Lake Level(39.4 feet)

Low Guidance Level (38.9 feet)

Lake stage

Discharge at Outlet River

EXPLANATION

DATE

Oct

Dec

Feb

Apr

Jun

Aug

Oct

Dec

Feb

Nov

Jan

Mar

May

Jul

Sep

Nov

Jan

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

2006 2007 2008

Figure 27. Lake stage and discharge at Pana Vista Lodge (SWFWMD Gage 23142 Pana Vista Outlet 

River), October 2006 through September 2008. SWFWMD is Southwest Florida Water Management 

District.
54 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

FLORIDA'S

TURNPIKE

44

301

301

75

470

470

Base modified from Florida Department of Transportation digital data; 1:24,000; 2007.

Universal Transverse Mercator projection, Zone 17 North

0 2 MILES

0 2 KILOMETERS EXPLANATION

SUM OF ALL SYNOPTIC STREAMFLOW DISCHARGE

MEASUREMENTS--In cubic feet per second

SW4

No flow or negative contribution

10.01 - 100.00

100.01 - 250.00

250.01 - 645.36

SURFACE-WATER GAGING STATION

AND INDEX NUMBER--Data

provided in table 2

82°15 ́ 82°10 ́ 82°05 ́ 82°00 ́

28°55 ́

28°50 ́

28°45 ́

Warnel Creek

Tsala

Apopka

Lake

Brook

Lake

Okahumpka

Little Jones Creek

BigJones

Creek

Shady

Withlacoochee

River

Outlet

River Lake Panasoffkee

Coleman

Wildwood

Lake Panasoffkee

Wysong

Dam CITRUS

COUNTY

SUMTER COUNTY

SW9

SW8

SW7

SW6

SW5

SW3 SW4

SW2

SW1

SW13

SW11

SW10

SW12

Carlson

Sumterville

Hogeye

Sink

Figure 28. Relative flow contributions from each stream reach to total streamflow during four seepage runs, 

December 2007 through September 2008. 
Maintenance Spring (SW13) empties into Shady Brook. Flow 

from these springs in September 2008 was 18.8 and 0.9 ft3/s, 

respectively. Warnel Creek (SW1) diverges from Shady Brook 

upstream of the I–75 gage (SW2), and the flow at Warnel Creek 

at I–75 in September 2008 was 12.7 ft3/s. With the addition of the 

spring flow from Belton’s Millpond and Maintenance Spring, 

and the loss of flow to Warnel Creek, discharge at Shady Brook 

near I–75 was 70.9 ft3/s. The combined flow from Warnel Creek 

and Shady Brook, both near I–75, was 83.6 ft3/s (table 7). This 

corresponds to a net gain of flow of 8.8 ft3/s over what can be 

explained by the addition of spring flow from Belton’s Millpond 

Spring Complex and Maintenance Spring. The increase in 

discharge is most likely groundwater inflow to Shady Brook.

Water Budget

Lake Panasoffkee interacts with the atmosphere, the 

subsurface, and other surface-water features. The lake gains 

water from rainfall, streamflow, spring flow, and groundwater 

seepage, and loses water by evaporation, surface outflow, and 

groundwater seepage (Healy and others, 2007; fig. 30). Under 

wet conditions, the lake also gains flow from overland runoff, 

a difficult component to compensate for in the water budget 

because there is no method available to accurately measure 

the volume of this input. The drought precluded this process 

from being a concern during the study period. The balance 

between water inputs and outputs to Lake Panasoffkee 

40

41

42

43

44

45

46

47

SHADY BROOK

35

37

39

41

43

45

47

OUTLET RIVER

HYDRAULIC HEAD, IN

FEET ABOVE NGVD 29

HYDRAULIC HEAD, IN

FEET ABOVE NGVD 29

A

B

Upper Floridan aquifer

Surficial aquifer

Surface water

EXPLANATION

Upper Floridan aquifer

Surface water

EXPLANATION

DATE

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

2006 2007 2008

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

2006 2007 2008

Figure 29. Hydraulic head data for A, Shady Brook and B, Outlet River, October 2006 through 

September 2008. 

Water Budget 55
56 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

results in changes in lake water level, except when inflows 

equal outflows. Lake water levels rise when inflows exceed 

outflows, and they fall when outflows exceed inflows.

A monthly water budget was developed for Lake 

Panasoffkee for water years 2007 and 2008. Groundwater 

inflow was calculated as the residual term in the water budget 

and is considered to be the change in lake stage not accounted 

for by precipitation, surface-water inflows and outflows, and 

evaporation (fig. 30). Surface-water inflows and outflows 

to Lake Panasoffkee and changes in lake stage have been 

discussed earlier herein. Precipitation, evaporation, and the 

effects of OWTS on groundwater inflow are discussed in the 

following sections. 

Precipitation

The average rainfall for water years 1930–2008 at the 

Inverness weather station (084289) (fig. 12) was 54.26 in/yr 

(National Climatic Data Center, 2009). Comparatively, the 

average rainfall was 52.74 in/yr at Ocala (station 086414) 

during water years 1932–2008, and was 51.79 in/yr at 

Bushnell (081163) during water years 1938–2005 (National 

Climatic Data Center, 2009). Rainfall totaled 38.27 and 

53.44 in/yr during water years 2007 and 2008, respectively 

(fig. 31 and table 8), within the Lake Panasoffkee watershed. 

Total rainfall during the study period was 15 percent below 

average when compared to the historical data from Inverness. 

EXPLANATION

SURFICIAL AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN AQUIFER

EEB

Pr

QGWin

QGWout

QOWTSin

QSWout

QRESout

QSWin

QSPin

QSWin

EEB

Restoration Outflow

Surface-water Inflow

Spring Inflow

Groundwater Inflow

Onsite Wastewater Treatment

System Inflow

Surface-water Outflow

Evaporation Outflow

Change in storage

Flow direction

Groundwater Outflow

Pr Precipitation

QGWin

QGWout

QOWTSin

QRESout

QSPin

QSWin

QSWout

Figure 30. Diagram of water-budget terms.
Water year 2006 (just prior to the beginning of this study) was 

24 percent below average. During the first year of the study 

(water year 2007), rainfall was 29 percent below average, 

with most of the rain occurring in a short period from July 

to September. During the second year of the study (water 

year 2008), rainfall was near average, but again, most of the 

rain fell during a few exceptionally wet months. Rainfall for 

October and December 2007 was 56 and 39 percent above 

average, respectively, whereas rainfall in January and August 

2008 was 27 and 29 percent above average, respectively.

Evaporation 

Lake evaporation was 90.50 in. for the 24-month study 

period, or 45.96 and 44.54 in/yr for water years 2007 and 2008, 

respectively (table 9). These values are about 17 to 28 percent 

lower than values measured at other central Florida lakes, 

which range from 54 to 63 in/yr (Lee and Swancar, 1997; 

Swancar and others, 2000; D.M. Sumner, U.S. Geological 

Survey, written commun., 2008). After comparison with data 

from three other lakes in central Florida (Lake Calm, Lake 

Starr, and Reedy Lake; fig. 1), it was determined that most of 

the difference in evaporation at Lake Panasoffkee was due to 

the lower net radiation measured at the lake. Of all the terms 

in the energy-budget equation (table 9), evaporation is most 

sensitive to radiation fluxes (Sacks and others, 1994; Lee and 

Swancar, 1997). Although the cause of the reduced evaporation 

at Lake Panasoffkee is not completely understood because only 

net radiation was measured instead of measuring all radiation 

components separately, it is probably due to the increased 

reflectance of the water. Radiation differences between Lake 

Panasoffkee and other lakes are greatest during the middle of 

the day, when incoming solar radiation is greatest. The effect 

of increased reflectance (higher albedo) also would be greatest 

during midday. Compared to other lakes where evaporation 

has been measured, Lake Panasoffkee is shallow, and the 

fine-grained tan-colored carbonate bottom sediments are 

readily resuspended into the water column when it is windy. 

0

2

4

6

8

10

12

14

RAINFALL, IN INCHES

WY2006 WY2007 WY2008

Monthly measured

rainfall, in inches

Average monthly rainfall

(1930-2008), in inches

EXPLANATION

2005 2006 2007 2008

DATE

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Figure 31. Monthly total rainfall in the Lake Panasoffkee watershed from October 2006 through 

September 2008 compared to the average monthly rainfall measured at the National Climatic Data 

Center station at Inverness, Florida (station 084289), October 1930 through September 2008.

Water Budget 57
58 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

In addition, restoration dredging increased the water turbidity 

during this study, which also may have affected the evaporation 

measurement.

Onsite Septic Wastewater-Treatment Systems

To accurately quantify groundwater inflow, all processes 

that might affect lake stage, including the effects of OWTS, 

were examined. The towns surrounding Lake Panasoffkee do 

not offer centralized wastewater disposal, thus, it is assumed 

that all houses in the area utilize an OWTS for residential 

waste. Most OWTS in the Lake Panasoffkee watershed 

consist of a septic tank in which solid wastes are trapped, 

and an absorption field where discharged fluids infiltrate the 

surrounding soil (Landers and Ankcorn, 2008). It also was 

assumed that each parcel of land had one house, and, thus, 

one OWTS located within its boundaries. A geospatial query 

of all parcels on the west side of Lake Panasoffkee was run 

to identify those parcels that were located within 100 m 

(328 ft) of a canal or the lake itself. A visual inspection of 

these parcels of land using digital orthophotography was 

then conducted to determine if each parcel did indeed have 

a house on it. The result of this process returned a total of 

737 parcels, and hence OWTS, that met the criteria (fig. 32). 

A high estimate of average household indoor water usage of 

300 gal/d was used to calculate the annual volume of water 

recharged to the surficial aquifer. This value was based on 

a Sumter County residential per capita public water-supply 

usage of 162 gal/d (Southwest Florida Water Management 

District, 2009). A high estimate was used in the calculations to 

compensate for uncounted OWTS and to test whether nearly 

doubling per capita water usage would have a significant 

effect on the water budget. According to this high estimate, 

the annual volume of water recharging the surficial aquifer 

would be about 80.7 Mgal (10.8 million ft3), minus losses due 

to evapotranspiration. In terms of the overall water budget and 

ignoring evapotranspiration, potential contribution to the lake 

from OWTS accounts for less than 1 percent of the total water 

inflow to the lake. Based on this annual estimate and assuming 

no seasonal variability, about 899,000 ft3 of monthly inflow 

is contributed to Lake Panasoffkee from OWTS. This was 

accounted for in the water budget as a component of the total 

groundwater inflow. 

Groundwater Inflow

The water-budget calculations confirmed that Lake 

Panasoffkee nearly always gained water from groundwater 

inflow, with the exceptions of June and September 2007 

when monthly net groundwater inflow was -0.001 and 

-0.97 in., respectively (-13,251 ft3 and -11.5 million ft3; 

table 10). These totals are within the error of the water 

budget, and indicate little to no groundwater flux or that 

inflows and outflows were balanced (fig. 33). For all the 

remaining values that exceed the water-budget error, monthly 

River otter (Lutra canadensis) at Shady Brook near 

Sumterville, Fla.; photo by W. Scott McBride

Table 8. Monthly rainfall statistics for the Lake Panasoffkee 

watershed for water years 2006 through 2008 compared to the 

average monthly rainfall at Inverness, Florida, 1930 through 2008.

[NCDC, National Climatic Data Center; WY, water year; SWFWMD, 

Southwest Florida Water Management District]

Month

NCDC mean 

monthly 

rainfall, in 

inches 

(1930 through 

2008)a

Mean monthly rainfall in the 

Lake Panasoffkee watershed for

 WY 2006 through 2008, in inches

WY 2006b WY 2007c WY 2008c

October 2.80 3.25 2.49 6.45

November 1.75 2.62 1.73 0.21

December 2.48 3.06 2.19 4.05

January 2.85 0.57 1.48 3.91

February 3.15 4.01 2.06 2.74

March 4.18 0.00 1.12 3.08

April 2.56 0.62 0.55 2.49

May 3.32 3.14 0.00 0.19

June 7.76 7.11 5.52 8.64

July 8.42 5.14 7.26 8.15

August 8.65 8.05 4.98 12.14

September 6.32 3.60 8.90 1.39

Total 54.26 41.17 38.27 53.44

a Rainfall data collected at the NCDC station 084289 (Inverness). 

Data gaps were filled using data collected at NCDC stations 086414 

(Ocala) or 081163 (Bushnell).

b Mean monthly rainfall based on data collected at SWFWMD stations 

2760 (LP-6) and 6087 (Lake Panasoffkee).

c Mean monthly rainfall based on data collected at USGS stations 

02312675 (Little Jones Creek), 02312700 (Outlet River), and 02312720 

(Withlacoochee River at Wysong Dam).
Water Budget 59

Table 9. Summary of energy-budget data for Lake Panasoffkee from October 2006 through September 2008.

[Ta, air temperature; To, surface-water temperature; Ea, vapor pressure at air temperature; Eo, saturation vapor pressure at water-surface temperature; 

cal/cm2/d, calories per square centimeter per day; mb, millibars; °C, degrees Celsius; Qx, change in stored energy; Qv, energy advected to the lake from 

rainfall; cal/g, calories per gram; cm/day, centimeters per day; in., inch; WY, water year]

Month 

and 

year

Ta, °C To, °C Ea, mb Eo, mb

Net 

radiation, 

cal/cm2/d

Psychrometric 

constant, 

λ , mb/°C

Qx, 

cal/cm2/d

Qv, 

cal/cm2/d

Latent 

heat of 

vaporization, 

cal/g

Bowen 

ratio, 

dimensionless

Daily 

average 

evaporation, 

cm/d

Evaporation, 

in.

Water Year 2007

Oct-06 23.0 26.5 21.88 34.93 177 0.67 -13 -3 583.36 0.181 0.27 3.29

Nov-06 17.2 19.8 15.53 23.40 129 0.67 -3 -2 586.55 0.224 0.18 2.15

Dec-06 18.0 19.9 17.26 23.43 81 0.67 -2 -1 586.10 0.204 0.12 1.42

Jan-07 16.3 19.5 14.86 22.92 97 0.66 -17 -1 587.04 0.269 0.15 1.85

Feb-07 14.3 17.5 12.06 20.08 162 0.66 19 -1 588.15 0.267 0.19 2.12

Mar-07 18.9 22.5 15.25 27.46 244 0.67 8 -2 585.58 0.197 0.33 4.08

Apr-07 20.1 23.9 15.49 30.07 303 0.67 8 -2 584.96 0.180 0.42 5.01

May-07 23.5 27.0 19.01 35.76 335 0.67 1 -1 583.08 0.141 0.50 6.06

Jun-07 26.0 30.0 24.80 42.68 318 0.67 12 0 581.70 0.152 0.45 5.34

Jul-07 26.7 31.4 27.58 46.15 266 0.67 -6 2 581.33 0.174 0.40 4.82

Aug-07 28.0 32.7 28.30 49.65 323 0.67 3 -1 580.62 0.151 0.47 5.73

Sep-07 26.1 30.2 26.65 43.09 234 0.67 -2 1 581.63 0.169 0.34 4.08

WY 2007 total 45.96

Water Year 2008

Oct-07 24.3 27.7 24.33 37.39 161 0.67 3 2 582.64 0.179 0.23 2.83

Nov-07 18.4 21.4 16.23 25.67 128 0.67 -6 -2 585.90 0.220 0.19 2.19

Dec-07 18.1 20.7 16.88 24.62 99 0.67 -2 -3 586.03 0.228 0.14 1.67

Jan-08 14.8 17.0 13.38 19.53 100 0.66 -12 -3 587.87 0.242 0.15 1.83

Feb-08 17.4 20.4 14.86 24.00 149 0.67 1 -3 586.40 0.216 0.20 2.32

Mar-08 18.4 21.5 15.10 25.73 236 0.67 19 -5 585.87 0.194 0.30 3.71

Apr-08 20.8 25.1 17.04 32.07 309 0.67 2 -4 584.55 0.193 0.43 5.11

May-08 24.4 27.9 20.76 37.68 356 0.67 12 -1 582.60 0.142 0.51 6.24

Jun-08 26.1 30.7 25.52 44.34 316 0.67 2 -3 581.63 0.167 0.45 5.33

Jul-08 26.0 30.8 26.79 44.57 269 0.67 -1 -9 581.69 0.184 0.37 4.57

Aug-08 26.4 29.9 27.28 42.54 246 0.67 11 -6 581.50 0.159 0.34 4.10

Sep-08 26.0 29.4 25.59 41.08 259 0.67 -18 -11 581.68 0.147 0.39 4.65

WY 2008 total 44.54

WY 2007-08 total 90.50

groundwater inflow ranged from 2.53 in. (43.6 million ft3) 

in December 2007 to 12.85 in. (239 million ft3) in August 

2008. The percent contribution of groundwater inflow to total 

inflows for months when groundwater inflow exceeded the 

error ranged from 11 percent in October 2007 to 50 percent 

in May 2007, with a total contribution of 29 percent over the 

2-year data-collection period. By comparison, surface-water 

inflow for the 2-year study period was 50 percent of the total 

inflow and rainfall was 21 percent of the total inflow.

The percentage of total inflow received from groundwater 

inflow (29 percent) at Lake Panasoffkee is typical for lakes in 

central Florida. Sacks (2002) used the isotope mass-balance 

approach to calculate the groundwater inflow to 81 lakes in 

Alligator; photo by W. Scott McBride central Florida, categorizing lakes as low, medium, or high 
60 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

groundwater inflow lakes depending on the percentage of total 

inflow received as groundwater inflow. “Low” lakes receive 

less than 25 percent, “medium” lakes receive between 25 and 

50 percent, and “high” lakes receive greater than 50 percent of 

total inflow as groundwater inflow. Lake Panasoffkee is within 

the “medium” category because it receives between 25 and 50 

percent of its total inflow as groundwater inflow. Sacks (2002) 

found that lakes in upland areas typically fall in the “medium” 

to “high” category of groundwater inflow lakes, whereas lakes 

in the coastal lowlands usually fall into the “low” groundwater 

inflow lakes category. Lakes selected for the Sacks (2002) 

study were mostly seepage lakes, however, with no surfacewater inflows or outflows. So although Lake Panasoffkee falls 

in the “medium” category, the comparison is hampered by 

the fact that it is a more surface water dominated system than 

many Florida lakes.

Panacoochee Retreats

82°09 ́ 82°08 ́ 82°07 ́ 82°06 ́ 82°05 ́

28°50 ́

28°49 ́

28°48 ́

28°47 ́

28°46 ́

Lake Panasoffkee

Base modified from Florida Department of Transportation digital data; 1:24,000; 2007.

Universal Transverse Mercator projection, Zone 17 North

Outlet River

EXPLANATION

ONSITE SEPTIC WASTEWATER-TREATMENT SYSTEMS

0 1 MILES

0 1 KILOMETERS

75

470

Warnel Creek

County Road 514

Little

Jones

Creek

Figure 32. Location of onsite septic wastewater-treatment systems within 100 meters (328 feet) of Lake Panasoffkee 

or canals.
Water Budget 61

Table 10. Summary of monthly water-budget data for Lake Panasoffkee during water years 2007 through 2008. [Positive values indicate flow into the lake; negative values indicate flow out of the lake. Inflows and outflows are reported in inches of water over the monthly average surface area of the lake and in cubic feet.ft2, square feet; in., inches of water over average monthly surface area of lake; ft3, cubic feet; WY, water year]

Month 

and 

year

Average 

surface 

area, ft2

Inflows

Total 

inflow, 

in.

Total 

inflow, 

ft3

Outflows

Total 

outflow, 

in.

Total outflow, 

ft3

Change 

in 

storage, 

in.

Change 

in 

storage, 

ft3

Surfacewater 

inflow, 

in.

Surface-water 

inflow, ft3

Groundwater 

inflow, 

in.

Groundwater 

inflow, ft3

Precipitation,

 in.

Precipitation,

 ft3

Surfacewater 

outflow, 

in.

Surfacewater 

outflow, 

ft3

Evaporation, in. Evapora- tion, ft3

Water Year 2007

Oct-06 140,397,243 7.33 85,708,073 4.17 48,753,954 2.49 29,132,428 13.98 163,594,455 -12.74 -149,015,046 -3.29 -38,519,018 -16.03 -187,534,064 -2.05 -23,939,609

Nov-06 139,902,748 7.02 81,811,015 4.14 48,320,651 1.73 20,169,313 12.89 150,300,979 -12.81 -149,307,193 -2.15 -25,075,787 -14.96 -174,382,981 -2.07 -24,082,002

Dec-06 138,088,009 7.15 82,275,672 3.24 37,261,702 2.19 25,239,419 12.58 144,776,793 -10.69 -123,022,811 -1.42 -16,375,734 -12.11 -139,398,546 0.47 5,378,248

Jan-07 136,783,775 7.10 80,943,413 3.12 35,610,020 1.48 16,832,003 11.70 133,385,436 -11.11 -126,606,451 -1.85 -21,142,801 -12.96 -147,749,252 -1.26 -14,363,816

Feb-07 135,407,840 7.42 83,673,719 3.89 43,863,543 2.06 23,188,593 13.36 150,725,855 -10.94 -123,442,776 -2.12 -23,882,082 -13.06 -147,324,858 0.30 3,400,997

Mar-07 132,936,367 7.49 82,969,131 4.47 49,502,271 1.12 12,407,394 13.08 144,878,796 -10.15 -112,396,925 -4.08 -45,172,984 -14.22 -157,569,909 -1.15 -12,691,113

Apr-07 126,217,173 6.10 64,211,651 4.60 48,421,907 0.55 5,732,363 11.25 118,365,921 -7.33 -77,086,276 -5.01 -52,657,985 -12.34 -129,744,261 -1.08 -11,378,340

May-07 115,750,331 4.95 47,788,530 4.99 48,160,286 0.00 0 9.95 95,948,816 -5.96 -57,536,851 -6.06 -58,457,613 -12.03 -115,994,464 -2.08 -20,045,648

Jun-07 108,851,367 4.24 38,468,642 0.00 -13,251 5.52 50,071,629 9.76 88,527,020 -4.50 -40,808,567 -5.34 -48,477,968 -9.84 -89,286,535 -0.08 -759,515

Jul-07 123,192,816 5.24 53,829,841 4.81 49,414,307 7.26 74,531,654 17.32 177,775,802 -6.81 -69,906,240 -4.82 -49,528,933 -11.63 -119,435,173 5.68 58,340,629

Aug-07 138,285,807 6.55 75,516,270 3.26 37,579,850 4.98 57,388,610 14.79 170,484,730 -8.69 -100,172,160 -5.73 -66,010,116 -14.42 -166,182,276 0.37 4,302,454

Sep-07 142,675,059 8.64 102,782,460 -0.97 -11,478,814 8.90 105,757,887 16.57 197,061,534 -8.15 -96,940,800 -4.08 -48,480,201 -12.23 -145,421,001 4.34 51,640,533

WY 2007 131,540,711 79.24 879,978,417 39.73 435,396,427 38.27 420,451,293 157.24 1,735,826,137 -109.87 -1,226,242,097 -45.96 -493,781,222 -155.83 -1,720,023,319 1.41 15,802,819

Water Year 2008

Oct-07 172,688,341 14.72 211,860,654 2.61 37,591,239 6.45 92,772,015 23.78 342,223,907 -4.58 -65,931,891 -2.83 -40,771,885 -7.41 -106,703,776 16.37 235,520,131

Nov-07 201,755,578 7.94 133,508,010 2.91 48,902,149 0.21 3,530,723 11.06 185,940,882 -6.67 -112,202,351 -2.19 -36,770,512 -8.86 -148,972,863 2.20 36,968,019

Dec-07 206,647,617 7.25 124,828,396 2.53 43,643,219 4.05 69,743,571 13.83 238,215,186 -11.02 -189,838,814 -1.67 -28,778,485 -12.70 -218,617,299 1.14 19,597,886

Jan-08 210,193,105 7.47 130,872,309 7.50 131,420,524 3.91 68,546,307 18.89 330,839,140 -16.01 -280,354,988 -1.83 -31,967,462 -17.83 -312,322,450 1.06 18,516,690

Feb-08 212,514,757 7.14 126,459,732 9.64 170,792,885 2.75 48,612,751 19.53 345,865,367 -16.77 -296,984,394 -2.32 -41,129,203 -19.09 -338,113,597 0.44 7,751,769

Mar-08 211,430,163 10.77 189,748,786 8.58 151,253,711 3.08 54,178,979 22.43 395,181,476 -19.69 -346,892,480 -3.71 -65,330,634 -23.40 -412,223,113 -0.97 -17,041,638

Apr-08 207,110,791 9.72 167,750,266 3.24 55,873,705 2.49 42,975,489 15.45 266,599,460 -11.79 -203,562,923 -5.11 -88,160,460 -16.90 -291,723,383 -1.46 -25,123,923

May-08 201,602,288 4.87 81,884,934 3.70 62,175,629 0.19 3,192,036 8.76 147,252,600 -4.49 -75,516,442 -6.24 -104,809,674 -10.73 -180,326,116 -1.97 -33,073,516

Jun-08 204,371,413 5.28 90,007,485 8.27 140,874,148 8.64 147,147,418 22.20 378,029,051 -13.14 -223,851,513 -5.33 -90,835,601 -18.48 -314,687,114 3.72 63,341,937

Jul-08 211,274,394 11.73 206,574,667 11.46 201,751,436 8.15 143,490,526 31.34 551,816,629 -25.97 -457,304,990 -4.57 -80,408,980 -30.54 -537,713,970 0.80 14,102,659

Aug-08 222,939,082 21.23 394,507,143 12.85 238,689,078 12.14 225,540,038 46.22 858,736,259 -33.62 -624,689,772 -4.10 -76,111,143 -37.72 -700,800,916 8.50 157,935,344

Sep-08 222,474,256 20.29 376,160,380 5.18 95,998,262 1.39 25,831,733 26.86 497,990,375 -30.87 -572,311,307 -4.65 -86,216,506 -35.52 -658,527,813 -8.66 -160,537,438

WY 2008 207,083,482 128.43 2,234,162,761 78.48 1,378,965,986 53.44 925,561,585 260.35 4,538,690,332 -194.64 -3,449,441,866 -44.54 -771,290,545 -239.19 -4,220,732,411 21.17 317,957,920WY 2007-08 169,312,097 207.67 3,114,141,178 118.22 1,814,362,413 91.71 1,346,012,878 417.59 6,274,516,469 -304.52 -4,675,683,963 -90.50 -1,265,071,767 -395.02 -5,940,755,730 22.58 333,760,739
62 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

-600

-400

-200

0

200

400

600

500

300

100

-100

-300

WA

-500

TER VOLUME, IN MILLIONS OF CUBIC FEET PER MONTH

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

DATE

2006 2007 2008

Oct

Surface-water inflow

Groundwater inflow

Precipitation

Surface-water outflow

Evaporation

EXPLANATION

Groundwater inflow error

Figure 33. Summary of monthly water-budget data for Lake Panasoffkee during water years 2007 through 2008. 

The source of the groundwater inflow to Lake 

Panasoffkee is also unusual among lakes in central Florida. 

Lake Panasoffkee receives most of its groundwater inflow 

from the Upper Floridan aquifer. Sacks (2002) found that both 

the upland and lowland lakes in that study received groundwater inflow from the surficial aquifer. Most of the seepage 

lakes studied by Sacks (2002) were formed by karst processes 

when cavities in the underlying limestone collapsed, causing 

overlying sands and clays to subside into the collapse feature 

and leaving depressions at land surface (Tihansky and others, 

1996). The depressions then filled with water from the surficial aquifer, creating the lakes. These lakes are in a recharge 

setting with respect to the Upper Floridan aquifer, and water 

from the lakes recharges the Upper Floridan aquifer preferentially through disruptions in the intermediate confining unit 

caused by the initial collapse (Lee and Swancar, 1997).

The volume of groundwater inflow received by Lake 

Panasoffkee also distinguishes it from other lakes in central 

Florida. Although the percentage of total inflow received 

by Lake Panasoffkee from groundwater inflow is similar to 

that of other lakes, the volume of groundwater inflow is not. 

The largest lowland lake studied by Sacks (2002) had a surface 

area of 267 acres and an estimated groundwater inflow of 

19.3 in/yr (19 million ft3/yr); the largest highland lake, with 

a surface area of 5,074 acres, had an estimated groundwaterinflow rate of 16 in/yr (294 million ft3

/yr). Both lakes receive 

smaller volumes of groundwater inflow than Lake Panasoffkee, 

which had an average surface area of 3,020 acres in water year 

2007 and 4,753 acres in water year 2008. Groundwater inflow 

to Lake Panasoffkee was 39.73 in/yr (435 million ft3/yr) during 

water year 2007 and 78.48 in/yr (1.38 billion ft3/yr) during 

water year 2008 (table 10). This was double that of the lake 

with the largest groundwater inflow reported by Sacks (2002). 

The volume of groundwater contributed from the 

Upper Floridan aquifer to Lake Panasoffkee is even more 

pronounced if the sources of the surface-water inflows are 

considered, because as much as 78 percent of the total surfacewater inflow during the four seepage runs was contributed 

by spring flow. If 78 percent of the total surface-water 

inflow to Lake Panasoffkee for March 2008 (8.40 in. or 
Water Budget 63

148 million ft3) is added to the total groundwater inflow for 

that month, the volume of groundwater contributed to Lake 

Panasoffkee nearly doubles from 8.58 in. (151 million ft3) 

to 16.98 in. (299 million ft3). The combined spring flow and 

groundwater inflow into Lake Panasoffkee is the equivalent 

of a first-magnitude spring. A spring must produce at least 

261 million ft3 per month (100 ft3/s) to be classified as a firstmagnitude spring (Spechler and Schiffer, 1995). Under wetter 

hydrologic conditions, groundwater inflow alone would meet 

these criteria at Lake Panasoffkee and nearly did so in August 

2008 when groundwater inflow averaged about 91 ft3/s.

Comparisons to Earlier Water-Budget Study

A water budget was calculated for Lake Panasoffkee 

by CH2M Hill (1995) from May 1992 through April 1993 

(table 11). Water-budget data from the current study were 

computed for the May 2007 through April 2008 period so that 

the results of the two studies could be compared. The comparison is given only in cubic feet of water, not in inches of water 

over the average surface area of the lake, because 3 months of 

lake stage data were missing during the earlier study. Data from 

the earlier study were converted from acre feet to cubic feet.

Table 11. Comparison of the May 1992 through April 1993 and May 2007 through April 2008 Lake Panasoffkee water budgets. 

[Positive values indicate flow into the lake; negative values indicate flow out of the lake. All flows are expressed in cubic feet. Table values are rounded from 

the values used in the actual water budget calculations]

Month Precipitation Surface-water 

inflow

Groundwater 

inflow Total inflow Surface-water outflow Evaporation Total outflow

Change in 

storage

May 1992 through April 1993

May 11,151,360 41,033,521 149,236,562 201,421,443 -123,710,402 -96,354,721 -220,065,123 -18,643,680

June 62,247,241 51,400,801 101,886,841 221,807,523 -117,394,202 -81,108,721 -198,502,923 23,304,600

July 59,764,321 70,436,521 60,112,801 190,313,643 -108,725,762 -101,364,121 -210,089,883 -19,776,240

August 111,426,482 113,343,122 54,754,921 279,524,524 -152,111,522 -71,569,081 -223,680,603 55,887,481

September 80,368,201 166,529,882 86,379,481 333,277,565 -244,632,964 -58,370,401 -303,003,364 30,274,200

October 67,343,761 186,044,763 195,497,283 448,885,806 -361,504,445 -51,313,681 -412,818,126 36,067,681

November 55,364,761 166,050,722 128,589,122 350,004,605 -305,791,204 -46,522,081 -352,313,285 -2,308,680

December 7,100,280 148,321,802 192,143,163 347,521,685 -337,415,765 -29,925,720 -367,341,485 -19,776,240

January 52,664,041 171,844,202 181,645,203 406,109,886 -334,715,045 -41,120,641 -375,835,685 30,274,200

February 44,823,241 170,145,362 158,209,922 373,178,525 -316,855,445 -43,516,441 -360,371,885 12,806,640

March 99,752,401 271,640,164 118,483,202 489,875,767 -356,146,565 -73,224,361 -429,370,926 60,548,401

April 18,643,680 252,517,324 168,969,242 440,130,246 -370,564,925 -87,032,881 -457,597,807 -17,467,560

12-month total 670,606,210 1,815,580,826 1,595,907,743 4,082,094,779 -3,129,568,245 -781,466,411 -3,910,947,536 171,147,242

May 2007 through April 2008

May 0 47,788,530 48,160,286 95,948,816 -57,536,851 -58,457,613 -115,994,464 -20,045,648

June 50,071,629 38,468,642 -13,251 88,527,020 -40,808,567 -48,477,968 -89,286,535 -759,515

July 74,531,654 53,829,841 49,414,307 177,775,802 -69,906,240 -49,528,933 -119,435,173 58,340,629

August 57,388,610 75,516,270 37,579,850 170,484,730 -100,172,160 -66,010,116 -166,182,276 4,302,454

September 105,757,887 102,782,460 -11,478,814 197,061,534 -96,940,800 -48,480,201 -145,421,001 51,640,533

October 92,772,015 211,860,654 37,591,239 342,223,907 -65,931,891 -40,771,885 -106,703,776 235,520,131

November 3,530,723 133,508,010 48,902,149 185,940,882 -112,202,351 -36,770,512 -148,972,863 36,968,019

December 69,743,571 124,828,396 43,643,219 238,215,186 -189,838,814 -28,778,485 -218,617,299 19,597,886

January 68,546,307 130,872,309 131,420,524 330,839,140 -280,354,988 -31,967,462 -312,322,450 18,516,690

February 48,612,751 126,459,732 170,792,885 345,865,367 -296,984,394 -41,129,203 -338,113,597 7,751,769

March 54,178,979 189,748,786 151,253,711 395,181,476 -346,892,480 -65,330,634 -412,223,113 -17,041,638

April 42,975,489 167,750,266 55,873,705 266,599,460 -203,562,923 -88,160,460 -291,723,383 -25,123,923

12-month total 668,109,614 1,403,413,895 763,139,810 2,834,663,319 -1,861,132,460 -603,863,471 -2,464,995,931 369,667,388
64 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

The volume of precipitation received by Lake Panasoffkee 

during the two periods was similar, as both studies were 

conducted during a drought. Inflow to Lake Panasoffkee directly 

from rainfall was 671 million ft3/yr during the preceding study 

and 668 million ft3/yr during May 2007 through April 2008 

(table 11). Total rainfall was 41.01 in/yr at Lake Panasoffkee 

during the earlier study (CH2M Hill, 1995) and 49.59 in/yr 

from May 2007 through April 2008 (table 8). The discrepancy 

in the amount of rainfall between the two periods compared to 

the volume of inflow received from rainfall probably results 

from a difference in average lake surface area between the two 

studies. During the first study, Lake Panasoffkee remained 

above 38.50 ft NGVD 29 for the entire study period and was 

above 39.50 ft NGVD 29 for more than half of the study period. 

During this study, water levels were about 37.50 ft NGVD 29 

during the summer of 2007, rose to about 39.00 ft NGVD 29 

in the fall, and mostly remained between 39.00 and 39.50 ft 

NGVD 29 through April 2008. Small changes in water level can 

result in large changes in lake surface area when the topographic 

relief of a region is low. Because water levels were higher, on 

average, during the earlier study, the surface area of the lake 

was presumably greater, resulting in similar volumes of input 

received directly from rainfall despite an approximate 8.5-in. 

difference in rainfall.

Surface-water inflow was similar during both study 

periods, whereas groundwater inflow was not. CH2M Hill 

(1995) reported surface-water inflows of 1.8 billion ft3/yr, 

compared to 1.4 billion ft3/yr for May 2007 through April 

2008 (table 11). The 12-month period prior to each period 

was substantially different. Rainfall at the NCDC weather 

station at Inverness, Florida (fig. 12), from May 1991 through 

April 1992 was well above average with 68.88 in/yr of 

rainfall, whereas rainfall was only 38.29 in/yr between May 

2006 and April 2007. The rainfall surplus during the earlier 

study and the deficit during the recent period are reflected 

in the differences in groundwater inflow data for each study 

period. Lake Panasoffkee received almost 1.6 billion ft3/yr of 

groundwater inflow between May 1992 and April 1993, and 

only half that amount, 763 million ft3/yr, between May 2007 

and April 2008 (table 11). 

Total inflows to Lake Panasoffkee for the recent period 

were about 69 percent of the total inflows determined during 

the 1992–93 study period, mostly because of the decrease in 

groundwater inflow, but also because the lake received no 

flow from Big Jones Creek (fig. 1) between May 2007 and 

April 2008 during the current study. Big Jones Creek was not 

flowing because surficial aquifer levels, the primary water 

source for this stream, were lower than the elevation of the 

creek channel during this time. Total outflows from Lake 

Panasoffkee, including both surface water and evaporation, 

were 3.9 billion ft3/yr from May 1992 through April 1993 

and 2.5 billion ft3/yr from May 2007 through April 2008 

(table 11). The lower total outflows for the latter period are 

primarily a result of the lower volumes of surface-water and 

groundwater inflow to Lake Panasoffkee, with groundwater 

inflow being the largest difference. Lake evaporation was 

estimated to be 781 million ft3/yr in the 1992–93 study 

period, whereas measured evaporation was 604 million ft3/yr

for the 2007–8 period. The CH2M Hill study (1995) may 

have overestimated the volume of evaporation from Lake 

Panasoffkee because that study used pan evaporation values 

that were not determined at Lake Panasoffkee. This study 

established that the evaporation rate at Lake Panasoffkee is 

less than that of other lakes in the area. 

Water Chemistry

This section describes the water chemistry of Lake 

Panasoffkee, its tributaries, and selected springs and wells in 

the watershed. Included in the discussion are conditions in the 

surficial aquifer and Upper Floridan aquifer, and, to a lesser 

extent, the Lower Floridan aquifer below middle confining 

unit I. Results of water chemistry, isotopic, and age-dating 

analyses of surface and groundwaters in the Lake Panasoffkee 

watershed provide independent information to support the 

hydrologic data discussed earlier, or in some cases provide 

new information, that aid in our understanding of the Lake 

Panasoffkee hydrologic system. 

Drought conditions prevailed during the two sampling 

periods, with surface water and groundwater at below-average 

levels. Water-chemistry data from samples collected during 

non-drought conditions would likely result in appreciably 

different water chemistry because surface water and the 

surficial aquifer would have a greater effect on the hydrologic 

system. The advantage of collecting samples during the 

drought is that the effects of the deep groundwater system on 

Lake Panasoffkee can be easily determined from data analysis. 

The effect of deep groundwater on the lake would be more 

difficult to determine under wet conditions because of dilution 

of lake water from surface water and shallow groundwater.

Major Ions

Major ions are those ions commonly found in ambient 

waters in concentrations exceeding 1 mg/L (Hem, 1992); they 

form as the result of innate processes such as geochemical 

weathering and atmospheric deposition. Major ions include 

positively charged cations, such as calcium, magnesium, 

sodium, and potassium, and negatively charged anions, such as 

sulfate, chloride, fluoride, nitrate, bicarbonate, and carbonate. 

Rainfall typically contains low concentrations of major ions, 

but these increase in concentration after water reaches land 

surface and begins to interact with soils, rocks, and minerals. 

The concentration of major ions in a water sample can be an 

indication of the “maturity” of the water, and helps delineate 

the flowpath it has taken through the hydrologic system. 

As water percolates through soil, it becomes increasingly acidic (lowering the pH) as it reacts with carbon dioxide 

(CO2) in the soil to form carbonic acid (H2CO3). Natural 

organic acids, such as humic acid, also can increase the 
Water Chemistry 65

acidity of water. Carbonic acid reacts with limestone in the 

groundwater system to liberate calcium (Ca2+) and bicarbonate 

(HCO3-) ions (Jones and others, 1996). As water enters the 

slower moving groundwater-flow system, concentrations 

of major ions further increase because the water is in close 

contact with Earth materials for long time periods.

Major ion data from the Lake Panasoffkee water samples 

that were collected during July 2007 and December 2008 

through January 2009 are plotted on trilinear diagrams (fig. 34, 

app. 2). In this study, despite the widely varying sources of 

water sampled, the majority of samples were calcium-bicarbonate water types. The primary source of calcium bicarbonate 

in the study area is limestone of the Floridan aquifer system; 

therefore, almost all of the water samples contain at least some 

percentage of groundwater. Groundwater can interact with 

surface water by way of spring discharge or through diffuse 

inflow of groundwater through stream or lakebeds when the 

head in the Upper Floridan aquifer is higher than that of the 

overlying surficial aquifer.

Trilinear diagrams indicate three distinct groups of 

samples. Groups A and B are similar chemically and appear 

adjacent to one another on the plots. Group A samples plot in 

the lower left corner of the trilinear diagram, indicating that 

these samples are “pure” calcium-bicarbonate type waters. 

Group B samples plot just above group A samples and are 

still calcium-bicarbonate type waters, but contain a higher 

fraction of sulfate than group A, indicating mixing with a 

calcium-sulfate type water. Water from ROMP LP–4 (QW6), 

the sole sample in group C, plots in the upper tip of the 

trilinear diagram and was a calcium-sulfate type water for both 

samples (fig. 34, table 4, and app. 2). The most likely source 

of calcium sulfate is gypsum, which is found deep in the 

Upper Floridan aquifer in the Avon Park Formation. 

In July 2007, group A samples included all of the 

groundwater samples collected in the surficial aquifer, all of 

the springs except site QW22, three Upper Floridan aquifer 

samples (QW1, QW3, and QW11), and one surface-water 

sample (QW23) (fig. 34A, table 4, and app. 2). The three 

Upper Floridan aquifer samples in group A are all from 

wells located near the northern and eastern shoreline of Lake 

Panasoffkee in recharge areas. Group B samples included all 

of the surface-water samples (lake and tributary), except the 

aforementioned QW23 sample. QW22 is the sole spring in 

group B, and is located in a canal on the southwestern shore 

of Lake Panasoffkee with five other spring vents. These are 

the only springs in the lake watershed located west of Lake 

Panasoffkee. The final three samples in group B were from 

Upper Floridan aquifer wells located near the western shore of 

Lake Panasoffkee. 

The December 2008 through January 2009 trilinear plot 

reveals the same three sample groups as in July 2007, but 

some of the sites shifted between groups A and B (fig. 34B). 

Group B, the mixed calcium-bicarbonate/calcium-sulfate 

water type, contained the same Upper Floridan aquifer and 

spring sites as in July 2007 as well as QW13 and QW15, 

two new surficial aquifer sites not previously sampled in 

July 2007. Group A contained all remaining samples except 

the aforementioned Upper Floridan aquifer sample in Group C

from QW6. All of the surface-water sites that had been in 

group B in July 2007 shifted to group A in the second sampling 

event. Group A also included sites QW17, a deep Upper 

Floridan aquifer well, and QW16, a Lower Floridan aquifer 

well installed below middle confining unit I. Neither of these 

sites was sampled in July 2007 (figs. 14 and 34B, table 4, and 

app. 2). 

The lower sulfate concentrations detected in most of the 

surface-water samples collected in December 2008 through 

January 2009 were likely the result of higher aquifer levels. 

In July 2007, aquifer levels in both the surficial and Upper 

Floridan aquifers were at the lowest point of the study period. 

By the second sampling event, aquifer levels had recovered 

partially because of rainfall during the summer of 2008, 

which resulted in greater volumes of groundwater inflow 

to the lake from the surficial and shallow Upper Floridan 

aquifers (fig. 33). The water containing higher concentrations 

of sulfate likely comes from deep within the Upper Floridan 

aquifer. Lake Panasoffkee probably regularly receives a small 

percentage of its groundwater inflow from the deep Upper 

Floridan aquifer, but this source would be difficult to detect 

under normal hydrologic conditions because of dilution from 

shallow and surface sources. 

Differences in head and major ion data indicate that the 

primary source of spring flow in the watershed is the shallow 

part of the Upper Floridan aquifer, which is generally low in 

sulfate. However, the groundwater chemistry of the Upper 

Floridan aquifer is distinctly different in a small area south 

and southwest of Lake Panasoffkee compared to conditions 

elsewhere in the watershed. Water in the Upper Floridan 

aquifer in west-central Florida is usually chemically stratified, with higher sulfate concentrations present deeper in the 

aquifer because of an increase in gypsum and anhydrite rocks 

with depth (Faulkner, 1973). Sacks (1996) analyzed data from 

rock cores collected from the shallow Upper Floridan aquifer 

near Lake Panasoffkee, and determined that gypsum was not 

present in sufficient quantities to explain the observed sulfate 

concentrations found in water samples from that formation. 

Sulfate concentrations in west-central Florida are typically 

less than 30 mg/L in surface waters, the surficial aquifer, 

and the Upper Floridan aquifer. Sacks used the geochemical 

mass-balance model NETPATH (Plummer and others, 1991) 

to determine that the most likely source of water containing 

greater than 30 mg/L of sulfate in the shallow Upper Floridan 

aquifer is water upwelling from deep within the Upper 

Floridan aquifer. Observed values of sulfate are consistent 

with those found in middle confining unit II or near the 

base of the Upper Floridan aquifer. Water deep in the Upper 

Floridan aquifer is part of a much slower regional flow system 

that typically bypasses inland discharge areas to discharge 

near or offshore from the coast (Southwest Florida Water 

Management District, 1991). 
66 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

LOWER FLORIDAN AQUIFER

UPPER FLORIDAN AQUIFER

SURFICIAL AQUIFER

SPRING

SURFACE WATER

EXPLANATION

CaSO

(gypsum,

anhydrite)

4

NaCl

(halite)

CaCO

CaMg (CO )

(calcite,

dolomite)

3

3 2

NaHCO3

Magnesium

Type

Calcium

Type

Sodium/

Potassium

Type

No

Dominant

Type

No

Dominant

Bicar- Type

bonate

Type

Chloride

Type

Sulfate

Type

CALCIUM

100

80

60

40

20

0

0

20

40

60

80

100

MAGNESIUM

0

20

40

60

80

100

SODIUM PLUS POTASSIUM

CHLORIDE, FLUORIDE, NITRITE PLUS NITRATE

0

20

40

60

80

100

100

80

60

40

20

0

CARBONATE PLUS BICARBONATE

100

80

60

40

20

SULFATE

0

20

40

60

80

100

SULFATE PLUS CHLORIDE

0

20

40

60

80

CALCIUM PLUS MAGNESIUM

80

60

40

20

0

100

80

60

40

20

0

PERCENT

PERCENT

Group A

Group B

Group C

PERCENT

CALCIUM

100

80

60

40

20

0

0

20

40

60

80

100

MAGNESIUM

0

20

40

60

80

100

SODIUM PLUS POTASSIUM

CHLORIDE, FLUORIDE,

NITRITE PLUS NITRATE

0

20

40

60

80

100

100

80

60

40

20

0

CARBONATE PLUS BICARBONATE

100

80

60

40

20

0

SULFATE

0

20

40

60

80

100

SULFATE PLUS CHLORIDE

0

20

40

60

80

100

CALCIUM PLUS MAGNESIUM

100

80

60

40

20

0

100

80

60

40

20

0

PERCENT

PERCENT

Group A

Group B

Group C

PERCENT

100 100

A

B

0

Figure 34. Water types from water-quality samples collected in the Lake Panasoffkee watershed during A, July 2007 and 

B, December 2008 through January 2009.
Water Chemistry 67

Sources of Sulfate

Most of the region around Lake Panasoffkee is an aquifer 

recharge area, but there are focused areas of discharge associated with Lake Panasoffkee and the Withlacoochee River. 

One possible mechanism driving the upwelling of water from 

deep within the Upper Floridan aquifer is aquifer discharge to 

Lake Panasoffkee and the Withlacoochee River (Sacks, 1996). 

Rapid groundwater flow within the shallow, more permeable 

parts of the Upper Floridan aquifer may contribute to the 

upwelling. However, similar groundwater upwelling anomalies also have been observed in recharge areas of Marion 

County (Sacks, 1996). 

Upwelling groundwater might also be related to vertical 

groundwater flow through fractures and faults associated with 

the Ocala structural high, which connect deeper and shallower 

parts of the Floridan aquifer system (Southwest Florida Water 

Management District, 1991). Jones and others (1996) noted 

an area of high sulfate concentrations in the Upper Floridan 

aquifer distributed along a northeast-southwest trending 

line stretching from northwest of Ocala to near Dunnellon 

(fig. 2). Vernon (1951) mapped possible fracture traces on the 

Florida peninsula based on physiographic expressions. Five of 

these traces pass near or through the Lake Panasoffkee area, 

trending in both northeast-southwest and northwest-southeast 

directions. The long, narrow shape of Lake Panasoffkee 

suggests that it may have formed along a fault, but there is no 

physical evidence of this other than topography.

Recent deep core samples collected by the SWFWMD 

at well sites ROMP 119.5, about 20 mi northwest of Lake 

Panasoffkee, and ROMP WR-6B, about 15 mi southwest of 

Lake Panasoffkee, did not intercept middle confining unit I 

(figs. 19–20) (Jim Clayton and Jason LaRoche, Southwest 

Florida Water Management District, written commun., 

2008–2009). Middle confining unit II was present at both 

sites, but was absent 7 mi west of Lake Panasoffkee at site 

QW16 (fig. 14 and table 4). The SWFWMD collected waterquality samples while drilling ROMP sites 119.5 and WR-6B 

and found the water beneath middle confining unit II to be 

highly mineralized and nonpotable without treatment (Jason 

LaRoche, Southwest Florida Water Management District, 

written commun., 2008). At site QW16 (fig. 14 and table 4), 

the quality of the water in the Lower Floridan aquifer (beneath 

middle confining unit I) was similar to that found deep in the 

Upper Floridan aquifer at QW17 (above middle confining 

unit I). This result is an indication that middle confining unit I 

is leaky, and that water exchange occurs between the Upper 

and Lower Floridan aquifers in this area. O’Reilly and others 

(2002) studied the hydrogeology and water-quality characteristics of the Lower Floridan aquifer in east-central Florida 

below middle confining unit I, and found head differences 

between the Upper and Lower Floridan aquifers to be highly 

variable throughout east-central Florida. The differences in 

head were attributed to the integrity (or lack thereof) of middle 

confining unit I. O’Reilly reclassifies middle confining unit I 

as the middle semiconfining unit based on this new data that 

were not available to Miller (1986).

Isotopes 

Isotopic analyses of water samples are powerful tools for 

describing groundwater-flow patterns and surface-water and 

groundwater interactions. In a hydrologic system like the Lake 

Panasoffkee watershed, where major ion chemistry is similar 

throughout the system, isotopes are useful for identifying 

sources of groundwater to the lake. 

Strontium

The similarity between the 87Sr/86Sr ratios found in 

water samples from Lake Panasoffkee and water samples 

from Upper Floridan aquifer wells installed in the Avon 

Park Formation south and southwest of Lake Panasoffkee 

suggests that water originating from this part of the Avon 

Park Formation contributes groundwater inflow to Lake 

Panasoffkee. Ratios of 87Sr/86Sr in all water samples collected 

in July 2007 varied from 0.70776 to 0.70856 (fig. 35A and 

table 12). The 87Sr/86Sr ratio is inversely related to the age of 

the aquifer materials the water samples have been in contact 

with: older samples have lower 87Sr/86Sr ratios. Water samples 

from Upper Floridan aquifer wells QW5, QW6, and QW9 

(fig. 14 and table 4), located south and southwest of Lake 

Panasoffkee, had the lowest 87Sr/86Sr ratios in the study area. 

The 87Sr/86Sr ratio data collected in December 2008 

through January 2009 were similar to the data collected in 

July 2007 (fig. 35B and table 12). Spring site QW22 and 

surface-water samples QW25 and QW27 had only a slightly 

higher overall ratio of 87Sr/86Sr than the corresponding July 

2007 samples (fig. 14 and table 4). DePaolo and Ingram 

(1985) analyzed rock cores from the Avon Park Formation and 

determined that the strontium isotope ratio of this formation 

ranged from 0.7077 to 0.7078. This value is consistent with 

the 87Sr/86Sr ratios obtained in the groundwater, spring, and 

surface-water samples in this study. 

Water samples from both Shady Brook and Little Jones 

Creek, the primary contributors of surface-water flow to Lake 

Panasoffkee, both had higher strontium isotope ratios than 

samples from Lake Panasoffkee. This suggests that although 

the lake receives water from the Avon Park Formation, this 

water does not come from the lakes tributaries. Site QW22 

supplies water directly to Lake Panasoffkee and has a similar 

87Sr/86Sr ratio as the lake water, but these springs are a minor 

source of water compared to the tributaries. The 87Sr/86Sr 

ratios in water samples from piezometers driven into the 

lakebed in December 2008 (QW13 and QW15) were nearly 

identical to samples collected from the deeper Upper Floridan 

aquifer wells south and southwest of Lake Panasoffkee (QW5, 

QW6, and QW9) (figs. 14 and 35B, and tables 4 and 12). 
68 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

0.7076

0.7077

0.7078

0.7079

0.7080

0.7081

0.7082

0.7083

0.7084

0.7085

0.7086

0.7087

0 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

A

AVON PARK FORMATION

0.7076

0.7077

0.7078

0.7079

0.7080

0.7081

0.7082

0.7083

0.7084

0.7085

0.7086

0.7087

0 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020

B

OCALA LIMESTONE

AVON PARK FORMATION

1/Sr, IN MILLIGRAMS PER LITER

87 86 Sr/ Sr

1/Sr, IN MILLIGRAMS PER LITER

87 86 Sr/ Sr

EXPLANATION

EXPLANATION

OCALA LIMESTONE

UPPER FLORIDAN AQUIFER

SURFICIAL AQUIFER

SPRINGS

LAKE

STREAMS

LOWER FLORIDAN AQUIFER

UPPER FLORIDAN AQUIFER

SURFICIAL AQUIFER

SPRINGS

LAKE

STREAMS

QW16 QW3

QW1

QW5

QW7

QW6 QW11

QW9

QW17

QW4

QW2

QW8

QW12

QW10

QW14

QW13

QW15

QW19 QW18

QW21

QW22

QW26

QW27

QW25

QW24

QW23

QW3

QW1

QW5

QW7

QW6

QW11

QW9

QW4

QW2 QW8

QW12

QW10

QW18

QW19

QW21

QW22

QW20

QW26

QW27

QW28 QW29

QW25

QW24 QW23

Figure 35. Relation between strontium isotope ratios and the reciprocal of the strontium 

concentration in water samples from the Lake Panasoffkee study area for A, July 2007 and 

B, December 2008 through January 2009. Blue bands indicate the range of values measured 

in rock cores collected from the specified formations.
Water Chemistry 69

Table 12. Strontium, hydrogen, and oxygen isotope data collected from select groundwater, surface-water, and spring sites in the Lake 

Panasoffkee study area, July 2007 and December 2008 through January 2009.

[yyyy/mm/dd, year/month/day; EST, Eastern Standard Time; ft, feet; per mil, parts per thousand; UFA, Upper Floridan aquifer; SA, surficial aquifer; SPG, 

spring; SW, surface water; LFA, Lower Floridan aquifer]

Reference 

number 

(fig. 14)

Site 

type

USGS site 

identification 

number

Station name Date 

(yyyy/mm/dd)

Time 

(EST)

Strontium 

87/86 ratio

Delta

hydrogen 

2/1 ratio 

(per mil)

Delta 

oxygen

18/16 ratio 

(per mil)

July 2007 Sampling Event

QW1 UFA 285125082085301 Big Jones Creek 48 ft UFA well 20070723 1200 0.70788 -17.35 -3.39

QW2 SA 285125082085302 Big Jones Creek 7 ft SA well 20070723 1500 0.70796 -16.37 -3.25

QW3 UFA 285035082075401 Little Jones Creek 48 ft UFA well 20070719 1200 0.70794 -16.77 -3.24

QW4 SA 285035082075402 Little Jones Creek 11 ft SA well 20070719 1300 0.70799 -18.86 -3.39

QW5 UFA 284811082091301 (ROMP) LP-3 152 ft UFA well 20070717 1500 0.70776 -5.31 -1.31

QW6 UFA 284628082073801 (ROMP) LP-4 240 ft UFA well 20070716 1700 0.70776 -10.51 -2.45

QW7 UFA 284628082073802 (ROMP) LP-4 120 ft UFA well 20070717 1100 0.70798 -20.62 -4.04

QW8 SA 284628082073803 (ROMP) LP-4 30 ft SA well 20070716 1500 0.70792 -22.76 -4.18

QW9 UFA 284528082055201 Sumter County 170 ft UFA well 20070718 1400 0.70777 -13.13 -2.9

QW10 SA 284456082053102 (ROMP) LP-5 40 ft SA well 20070724 1100 0.70828 -20.86 -4.04

QW11 UFA 284759082054101 (ROMP) LP-6 154 ft UFA well 20070724 1600 0.70793 -14.38 -2.77

QW12 SA 284759082054102 (ROMP) LP-6 25 ft SA well 20070726 1100 0.70856 -11.93 -2.18

QW18 SPG 02312664 Fenney Springs near Coleman 20070730 1400 0.70789 -15.72 -3.11

QW19 SPG 284709082024100 Blue Spring at Sumter County 20070731 1100 0.70789 -16.24 -3.08

QW20 SPG 284530082034800 Belton’s Millpond Complex near Sumterville 20070726 1500 0.70793 -4.34 -0.88

QW21 SPG 284525082040600 Maintenance Spring Run near Sumterville 20070726 1300 0.70803 -12.95 -2.6

QW22 SPG 284613082070500 Canal Spring Complex near Panasoffkee 20070730 1100 0.70782 -17.22 -3.14

QW23 SW 284534082054400 Shady Brook 350 ft above I-75 at Lake Panasoffkee 20070709 1305 0.70785 -15.08 -2.53

QW24 SW 02312675 Little Jones Creek near Rutland 20070709 945 0.70785 -16.83 -3.19

QW25 SW 02312700 Outlet River at Panacoochee Retreats 20070709 1115 0.70782 8.71 2

QW26 SW 284922082075900 Lake Panasoffkee near Shell Point at Panasoffkee 20070710 1230 0.70791 7.93 1.84

QW27 SW 284630082062700 Lake Panasoffkee near SSE Shore at Panasoffkee 20070710 1310 0.70778 -3.16 -0.37

QW28 SW 284718082070000 Lake Panasoffkee near Tracy’s Point at Panasoffkee 20070710 1255 0.70784 5.15 1.38

QW29 SW 284852082082000 Lake Panasoffkee near Idlewild Camp at Panasoffkee 20070710 1205 0.70784 5.22 1.26

December 2008 through January 2009 Sampling Event

QW1 UFA 285125082085301 Big Jones Creek 48 ft UFA well 20081203 1230 0.70784 -18.08 -3.35

QW2 SA 285125082085302 Big Jones Creek 7 ft SA well 20081203 1600 0.70790 -16.54 -3.23

QW3 UFA 285035082075401 Little Jones Creek 48 ft UFA well 20081202 1230 0.70783 -18.1 -3.36

QW4 SA 285035082075402 Little Jones Creek 11 ft SA well 20081202 1430 0.70790 -17.19 -3.37

QW5 UFA 284811082091301 (ROMP) LP-3 152 ft UFA well 20081204 1130 0.70773 -7.11 -1.4

QW6 UFA 284628082073801 (ROMP) LP-4 240 ft UFA well 20081208 1700 0.70777 -12.26 -2.5

QW7 UFA 284628082073802 (ROMP) LP-4 120 ft UFA well 20081208 1400 0.70794 -21.31 -3.98

QW8 SA 284628082073803 (ROMP) LP-4 30 ft SA well 20081204 1400 0.70795 -21.26 -4.16
70 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Together with the sulfate data, 87Sr/86Sr evidence suggests 

that water upwelling from deep within the Upper Floridan 

aquifer contributes substantial amounts of groundwater 

inflow to Lake Panasoffkee, at least during times of drought. 

The results of the strontium isotope analyses (figs. 35) are 

consistent with the trilinear plots of major ion data because 

the water-quality sampling sites with the highest sulfate values 

generally had the lowest strontium isotope ratios. 

There also were geochemical indications of upward 

leakage from the Ocala Limestone to the surficial aquifer. July 

2007 samples from surficial aquifer wells QW10 and QW12 

(fig. 14 and table 4) showed evidence of flow from the Ocala 

Limestone, with 87Sr/86Sr ratios of 0.70828 and 0.70856, 

respectively (fig. 35B). Katz and Bullen (1996) determined 

that the range of 87Sr/86Sr ratios in the Ocala Limestone was 

between 0.7081 and 0.7085. The Upper Floridan aquifer 

heads were higher than surficial aquifer heads in July 2007, 

and the Ocala Limestone is the uppermost member of the 

Upper Floridan aquifer at this well site. It is also possible that 

these samples represent young groundwater that had not yet 

come into equilibrium with the Ocala Limestone, but upward 

leakage seems most likely because of the upward head difference in the Upper Floridan aquifer and overall carbonate water 

quality in the surficial aquifer.

The remainder of the water samples of all types had a 

narrower range of 87Sr/86Sr ratios, from 0.70785 to 0.70803. 

These ratios fall between those of the Ocala Limestone and 

the Avon Park Formation, and probably represent mixtures 

of water from these formations. Many of the Upper Floridan 

aquifer wells that were sampled have long open intervals that 

span both formations. Flow from springs also would likely 

contact both formations, because much of the spring flow in 

the area has been attributed to conduits that form along the 

interface between the formations (Miller, 1986). 

Table 12. Strontium, hydrogen, and oxygen isotope data collected from select groundwater, surface-water, and spring sites in the Lake 

Panasoffkee study area, July 2007 and December 2008 through January 2009.—Continued

[yyyy/mm/dd, year/month/day; EST, Eastern Standard Time; ft, feet; per mil, parts per thousand; UFA, Upper Floridan aquifer; SA, surficial aquifer; SPG, 

spring; SW, surface water; LFA, Lower Floridan aquifer]

Reference 

number 

(fig. 14)

Site 

type

USGS site 

identification 

number

Station name Date 

(yyyy/mm/dd)

Time 

(EST)

Strontium 

87/86 ratio

Delta

hydrogen 

2/1 ratio 

(per mil)

Delta 

oxygen

18/16 ratio 

(per mil)

QW9 UFA 284528082055201 Sumter County 170 ft UFA well 20081216 1330 0.70772 -14.98 -3.02

QW10 SA 284456082053102 (ROMP) LP-5 40 ft SA well 20081216 1500 0.70825 -21.29 -4.17

QW11 UFA 284759082054101 (ROMP) LP-6 154 ft UFA well 20081210 1300 0.70787 -14.34 -2.8

QW12 SA 284759082054102 (ROMP) LP-6 25 ft SA well 20081210 1700 0.70842 -11.95 -2.35

QW13 SA 284734082071201 Tracy’s Point 5 ft Shallow well 20081229 1600 0.70773 -6.36 -1.29

QW14 SA 284756082061301 Coleman Landing 5 ft Shallow well 20081229 1230 0.70862 -16.57 -3.31

QW15 SA 284922082075901 Lake Panasoffkee 7 ft Shallow well near Shell Point 20090106 1230 0.70772 -14.29 -3.12

QW16 LFA 284949082000501 ROMP 117 1000 ft LFA well 20081217 1300 0.70778 -10.31 -2.22

QW17 UFA 284949082000502 ROMP 117 338 ft UFA well 20081217 1530 0.70787 -12.5 -2.78

QW18 SPG 02312664 Fenney Springs near Coleman 20081218 1030 0.70790 -16.32 -3.38

QW19 SPG 284709082024100 Blue Spring at Sumter County 20081218 1300 0.70784 -16.07 -3.23

QW21 SPG 284525082040600 Maintenance Spring Run near Sumterville 20081218 1530 0.70792 -15.77 -2.85

QW22 SPG 284613082070500 Canal Spring Complex near Panasoffkee 20081218 1700 0.70775 -15.8 -3.17

QW23 SW 284534082054400 Shady Brook 350 ft above I-75 at Lake Panasoffkee 20081222 1400 0.70784 -12.37 -2.33

QW24 SW 02312675 Little Jones Creek near Rutland 20081222 1030 0.70789 -14.88 -3.05

QW25 SW 02312700 Outlet River at Panacoochee Retreats 20081221 1700 0.70777 -7.36 -1.42

QW26 SW 284922082075900 Lake Panasoffkee near Shell Point at Panasoffkee 20081221 1345 0.70778 -8.75 -1.94

QW27 SW 284630082062700 Lake Panasoffkee near SSE Shore at Panasoffkee 20081221 1515 0.70783 -7.6 -1.56
Water Chemistry 71

Water in wells west of Lake Panasoffkee is probably 

influenced by water upwelling from deep within the Upper 

Floridan aquifer near middle confining unit II, whereas the 

water in wells 7 mi east of Lake Panasoffkee is not. Samples 

from ROMP 117 (QW16 and QW17), the Lower Floridan 

aquifer and deep Upper Floridan aquifer wells east of Lake 

Panasoffkee, had 87Sr/86Sr ratios slightly higher (younger) 

than the deep Upper Floridan aquifer wells west of Lake 

Panasoffkee (QW5, QW6, and QW9) (figs. 14 and 35B, 

and tables 4 and 12). Despite being finished almost 100 ft 

deeper in the Upper Floridan aquifer than the deepest Upper 

Floridan aquifer well west of Lake Panasoffkee, water from 

ROMP 117 UFA (QW17) had a slightly higher 87Sr/86Sr ratio 

than all three of the deep Upper Floridan aquifer wells west 

of the lake. ROMP 117 LFA (QW16), about 750 ft deeper 

than the deepest western well and finished in the Lower 

Floridan aquifer below middle confining unit I, also had a 

higher 87Sr/86Sr ratio than two of the western wells (QW5 and 

QW9) and was similar (but slightly higher in ratio) than the 

third well (figs. 14 and 35B, and tables 4 and 12). The higher 

87Sr/86Sr ratio east of Lake Panasoffkee indicates a change 

in the hydrogeology of the system from west to east, perhaps 

related to fracturing or faulting. Unfortunately, at the time of 

this study, there were no wells west of Lake Panasoffkee that 

penetrated as deep as middle confining unit II or the Lower 

Floridan aquifer to clarify where this transition in the subsurface occurs. Somewhere beneath Lake Panasoffkee, middle 

confining unit I thins or is leaky enough that it no longer 

acts even as a semiconfining unit, because mineralized water 

associated with deeper formations, likely middle confining 

unit II, moves upward to the Upper Floridan aquifer.

Deuterium and Oxygen–18

Deuterium and oxygen isotope ratios in groundwater 

samples, together with head data from the Upper Floridan 

and surficial aquifers, indicate that recharge occurs quickly 

following rainfall in the Lake Panasoffkee watershed, and 

support the assumption that the watershed is primarily 

internally drained. The δ2H and δ18O composition of the 

majority of the groundwater samples collected in the Lake 

Panasoffkee watershed during both the July 2007 and 

December 2008 through January 2009 sampling events plot 

at or slightly to the right of the intersection of the MWLs and 

evaporation trend lines (fig. 36). The low level of enrichment 

in groundwater samples indicates that water recharges quickly 

in the watershed before much evaporation can occur at land 

surface. Samples collected from Lake Panasoffkee and the 

Outlet River were the most enriched of all the δ2H and δ18O 

samples collected in the watershed (samples QW25, QW26, 

QW28, and QW29, fig. 14 and table 4). Groundwater samples 

that plot at the base of the evaporation trend line are the least 

enriched (most depleted) in the watershed. Samples that plot 

along the evaporation trend line contain mixtures of these two 

end members (enriched water and depleted water). 

Samples collected at greater depths within the Upper 

and Lower Floridan aquifers during both sampling events 

(fig. 36) also were generally more enriched in δ2H and δ18O 

than samples from shallower depths. Enrichment in this situation is related to water age. Water deep within the Floridan 

aquifer system was recharged thousands of years ago under 

different climatic conditions than are present today (Plummer 

and Sprinkle, 2001). During the Last Glacial Maximum 

(LGM) about 20,000 years ago, water in coastal areas of the 

southeastern United States were enriched in δ2H and δ18O 

as much as 2.3‰. The enrichment was most likely caused 

by the large volume of isotopically light water trapped in 

glaciers. Continental interiors during the LGM were typically isotopically depleted, because of cooler temperatures. 

Even though most of the water sampled from the Floridan 

aquifer system was recharged much more recently than the 

LGM, these samples likely contain fractions of water that 

was recharged during the LGM (Plummer and Sprinkle, 

2001; L.N. Plummer, U.S. Geological Survey, written 

commun., 2010).

Samples from sites QW5 and QW27 (figs. 14 and 36A, 

tables 4 and 12) contain mixtures of water from different 

sources (groundwater and surface water) because they plot 

near the middle of the evaporation trend line. Site QW5, a 

152-ft deep Upper Floridan aquifer well located near the 

Outlet River, likely receives recharge from the Outlet River 

(QW25) because the isotopic content of the sample plots 

about midway between the MWLs and the sample from Outlet 

River (figs. 14 and 36A, tables 4 and 12). The sample from 

site QW27 was collected from Lake Panasoffkee near the 

confluences of Shady Brook and Warnel Creek (figs. 14 and 

36A, tables 4 and 12). The isotopic composition of the sample 

likely results from a mixture of enriched lake water and water 

discharging from the two streams. Water emanating from the 

two streams primarily originates from spring flow. 

The δ2H and δ18O data from the samples collected in 

December 2008 through January 2009 (fig. 36B) followed 

a similar pattern to the July 2007 data (fig. 36A), but there 

was less variability. The lack of variability was probably 

because of the time of the year the samples were collected, 

and the continuing drought at the time of sampling. During 

winter, there is less evaporation from surface water because of 

cooler temperatures and shorter days, so surface water is less 

enriched in δ2H and δ18O. The months preceding the sampling 

event in December 2008 through January 2009 also had been 

very dry, so groundwater inflow from the Upper Floridan 

aquifer was a larger component of the overall lake water 

budget compared to July 2007, which also contributed to a less 

enriched δ2H and δ18O isotopic signature. 

Sample QW13 (figs. 14 and 36B, tables 4 and 12), 

the most isotopically enriched sample during the second 

sampling event, was collected from a piezometer installed 

about 5 ft beneath the lakebed along the western shore of 

Lake Panasoffkee. Enrichment of δ2H and δ18O indicates 

that Lake Panasoffkee was recharging the surficial aquifer at 

this location. The recharge/discharge potential maps (figs. 24 
72 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Figure 36. Relation between deuterium and oxygen isotope data in the Lake Panasoffkee study area 

for A, July 2007 and B, December 2008 through January 2009. 

-30

-25

-20

-15

-10

-5

0

5

10

-5 -4 -3 -2 -1 0 1 2 3

LOWER FLORIDAN AQUIFER

UPPER FLORIDAN AQUIFER

SURFICIAL AQUIFER

SPRINGS

LAKE

STREAMS

B

-30

-25

-20

-15

-10

-5

0

5

10

-5 -4 -3 -2 -1 0 1 2 3

UPPER FLORIDAN AQUIFER

SURFICIAL AQUIFER

SPRINGS

LAKE

STREAMS

A

y = 4.9094x - 0.8363

R = 0.9883 2

Local Meteoric

Water Line

(Sacks, 2002)

Global Meteoric

Water Line

(Craig, 1961)

Evaporation Trend Line

y = 5.2785x + 0.6834

R = 0.9719 2

Evaporation Trend Line

Local Meteoric

Water Line

(Sacks, 2002)

Global Meteoric

Water Line

(Craig, 1961)

DELTA DEUTERIUM, PER MIL DELTA DEUTERIUM, PER MIL

EXPLANATION

EXPLANATION

DELTA OXYGEN-18, PER MIL

DELTA OXYGEN-18, PER MIL

QW4

QW1

QW3

QW2

QW18

QW19

QW22

QW24

QW5

QW6

QW7

QW11

QW9

QW8

QW10

QW12

QW20

QW21

QW28

QW26

QW29

QW27

QW23

QW25

QW16

QW3

QW1

QW5

QW7

QW6

QW11

QW9

QW17

QW4 QW2

QW8

QW12

QW10

QW14

QW13

QW15

QW18

QW19

QW21

QW22

QW26

QW27

QW25

QW24

QW23
Water Chemistry 73

and 25) created for the study area indicated that sample QW13 

was collected near the boundary of a recharge/discharge area. 

In contrast, data from sites QW14 and QW15 (fig, 14 and 

36B, tables 4 and 12), also shallow piezometers, indicated that 

the lake was receiving groundwater inflow at those locations. 

QW14 was installed 5 ft beneath the lakebed on the western 

shore of Lake Panasoffkee, whereas QW15 was installed 

7 ft beneath the lakebed about 300 ft from the northeastern 

shoreline of the lake. These results are consistent with the 

lake water budget, which indicated that the lake was receiving 

more groundwater inflow than it was losing in December 

2008. The recharge/discharge potential maps created for the 

study area indicated that the QW14 and QW15 samples were 

collected in a discharge area.

Age Dating

Samples from select groundwater and spring sites were 

analyzed for 14C, 3H, SF6, and CFC concentrations. These four 

environmental tracers are useful for determining the time that 

has passed since a parcel of water recharged the groundwater 

system. Knowledge of the age of a groundwater sample helps 

determine if mixing is occurring between different aquifers, 

for determining sources of groundwater, and helps in locating 

recharge areas (Cook and Böhlke, 2000). 

Carbon–14 and Tritium

Samples from QW6, QW16, and QW17 (fig. 14 and 

table 4) were analyzed for 14C, because they were the deepest 

wells in the study area and would likely yield water too 

old to be dated by any other readily available age dating 

method. Well QW6, located near the western shore of Lake 

Panasoffkee, penetrates 240 ft below land surface deep into 

the Upper Floridan aquifer (fig. 37). ROMP 117 wells (QW16 

and QW17) are located about 7 mi east of Lake Panasoffkee 

on the northeast shore of Lake Okahumpka (fig. 37). ROMP 

117 UFA (QW17) penetrates 338 ft below land surface to the 

bottom of the Upper Floridan aquifer and is finished near 

the top of middle confining unit I. ROMP 117 LFA (QW16) 

penetrates 1,000 ft below land surface through middle 

confining unit I and is finished in the upper part of the Lower 

Floridan aquifer. 

Four adjusted 14C ages were calculated within the 

NETPATH model for each water sample using the formulas 

developed by Ingerson and Pearson (1964), Tamers (1975), 

Fontes and Garnier (1979), and Eichinger (1983). Groundwater 

ages can be presented in this report as either an “apparent” age 

or as an “adjusted” age. Apparent ages are those ages given 

as part of the analytical results, whereas adjusted ages have 

been modified from the analytical results using geochemical 

models to compensate for degradation of the tracer in the 

hydrologic system. Apparent ages are typically used when no 

proof of degradation is evident. The adjusted 14C ages from the 

NETPATH model ranged from 7,022 to 7,579 years before 

present for the water samples from ROMP 117 UFA (QW17), 

from 8,703 years to 9,413 years before present for ROMP 117 

LFA (QW16), and from 23,485 to 26,455 years before present 

for ROMP LP–4 UFA (QW6) (fig. 14 and tables 4 and 13). All 

of the calculated ages are considered maximum ages because 

recrystallization of carbonates was not considered in any of 

the model formulas. Only the water sample from ROMP LP–4 

UFA (QW6) showed substantial signs of recrystallization, 

which for carbonates, makes a sample appear older than it 

actually is. The ROMP LP-4 UFA (QW6) sample could be 

several thousand years younger than was calculated by the 

models. 

Water samples from QW6, QW16, and QW17 also were 

analyzed for 3H to determine if a mixture of both young 

(recharged post-1952) and old groundwater (recharged 

pre-1952) was present in the samples (fig. 14, tables 4 and 13). 

3H was detected in all of the samples, but all results were near 

the method detection limit of 0.09 TU. QW6 had the highest 

detection at 0.31 TU, whereas QW16 and QW17 had detections of 0.14 and 0.12 TU, respectively. Because naturally 

occurring “pre-hydrogen bomb” background concentrations 

of 3H have been estimated at 5–10 TU, groundwater with 

concentrations less than about 1 TU are considered older than 

1952 (Clark and Fritz, 1997). The detected 3H levels were 

sufficiently low in all three water samples that mixing of 

young and old groundwater can be considered insignificant in 

these samples. 

The similarity in radiocarbon age of samples from QW16 

and QW17 (fig. 14, tables 4 and 13) indicates that middle 

confining unit I is leaky east of Lake Panasoffkee. The similarities in radiocarbon ages and in major ion chemistries at these 

sites indicate exchange of water between the Upper Floridan 

aquifer and Lower Floridan aquifer in this area. The 14C water 

sample collected at QW6 (fig. 14, tables 4 and 13) is older than 

the samples collected at QW16 and QW17, even though both 

of these wells are much deeper than QW6. The increase in 

age of the groundwater west of Lake Panasoffkee at shallower 

depths in the Upper Floridan aquifer is further evidence of 

water upwelling from deep within the Floridan aquifer system 

west of Lake Panasoffkee. The 14C age data, together with the 

sulfate data presented earlier, indicate that the upwelling water 

probably contacts middle confining unit II somewhere along 

its flow path. Middle confining unit II is the only formation in 

the study area known to contain enough gypsum to explain the 

sulfate concentrations found in the sample, and the age of the 

sample indicates a deep flow source. 

Sulfur Hexafluoride

A piston flow model was used to derive the SF6 ages 

presented in this report; it is assumed in the model that 

a parcel of water is recharged to an aquifer and travels 

through the aquifer to a point of discharge while remaining 

unaltered by transport processes along the way (Busenberg 

and Plummer, 2000). It is unlikely, however, that piston 

flow is maintained in the karst topography of the study area 
74 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

because of potential “short circuits” in unconfined karst areas 

where flow enters the system midway along the flow path. 

The apparent age of the water likely reflects a mixture of 

waters recharged to the groundwater system at different points 

in time. The SF6 ages presented here are therefore averages of 

the mixtures of groundwaters collected in a sample. 

Eleven surficial aquifer and Upper Floridan aquifer wells 

were sampled for SF6 and dissolved gases (table 14). Except 

for wells QW6, QW15, and QW17 (fig. 14 and table 4), all 

of the wells sampled for SF6 have a component of young 

groundwater that has recharged the groundwater system within 

the last 35 years, which is the effective dating range of SF6

(Busenberg and Plummer, 2000). The water sample from well 

QW15 did not contain detectable levels of SF6, and samples 

from wells QW6 and QW17 both contained 0.1 fMol/L of 

SF6, which is just above the analytical detection limit for SF6. 

One fMol/L is equal to 10-15 moles in 1 liter of water. None of 

the samples from these three wells contained enough SF6 to 

accurately determine an age of recharge; however, all can be 

considered free of young water recharged in the last 35 years. 

Excluding surficial aquifer well QW15, mean modeled 

recharge years for the water samples from the surficial aquifer 

wells ranged from 1989 to 2001. Water samples from the two 

Upper Floridan aquifer wells 154 ft deep or less had mean 

UPLANDS

Lake

Panasoffkee

SOUTHWEST NORTHEAST

VERTICAL SCALE GREATLY EXAGGERATED EXPLANATION

SURFICIAL AQUIFER

INTERMEDIATE CONFINING UNIT

UPPER FLORIDAN AQUIFER

MIDDLE CONFINING UNIT I

MIDDLE CONFINING UNIT II

LOWER FLORIDAN AQUIFER

GROUNDWATER

FLOW DIRECTION

WATER TABLE

CONTACT

ROMP LP-4

(WELL QW6)

240 feet

Upper Floridan aquifer well

(recharged ~ 25, 000 years ago)

ROMP 117

(Well QW17)

338 feet

Upper Floridan Aquifer well

(recharged ~ 7,300 years ago)

ROMP 117

(Well QW16)

1,000 feet

Lower Floridan aquifer well

(recharged ~ 9,100 years ago)

UNDIFFERENTIATED

SANDS AND CLAYS

AVON PARK

LIMESTONE

OCALA

LIMESTONE

AVON PARK LIMESTONE

Spring

Hawthorn

Group

High Sulfate Water

SEMICONFINEMENT

Figure 37. Generalized conceptual model of the Lake Panasoffkee watershed based on geochemical 

analyses. Figure 14 and table 4 show well locations and specifications.
Table 13. Carbon and tritium isotope data with adjusted carbon-14 groundwater data collected from select groundwater sites in the Lake Panasoffkee study area, December 2008.

[USGS, U.S. Geological Survey; EST, Eastern Standard Time; yyyy/mm/dd, year/month/day; per mil, parts per thousand; pct, percent; ams, accelerator mass spectrometry; δ13C, delta carbon-13; DIC, dissolved inorganic carbon; 14C, carbon-14; UFA, Upper Floridan aquifer; LFA, Lower Floridan aquifer]

Reference 

number 

(fig. 14)

Site 

type

USGS 

site identification 

number

Station name Date (yyyy/ mm/dd) Time (EST)

Carbon 

13/12 

ratio 

(per 

mil)

Carbon14 ams 

(pct)

Carbon14 

ams 

(pct 

error)

Tritium 

unit

Unadjusted age1 Ingerson and Pearson (1964) Tamers (1975) Fontes and Garnier (1979) Eichinger (1983)

δ13C 

of DIC

Initial 

14C 

(pct 

modern)

Unadjusted age 

(14C 

years)

Computed 14C 

(pct 

modern)

Adjusted 

age 

(14C 

years)

Computed 14C 

(pct 

modern)

Adjusted 

age 

(14C 

years)

Computed 14C 

(pct 

modern)

Adjusted 

age 

(14C 

years)

Computed 14C 

(pct 

modern)

Adjusted 

age 

(14C 

years)

QW6 UFA 284628082073801 (ROMP) LP-4 240 ft 

UFA well

20081208 1700 -3.94 2.2 0.1 0.31 -3.94 1.85 30,660 40.80 25,585 45.32 26,455 40.24 25,471 31.64 23,485

QW16 LFA 284949082000501 ROMP 117 1,000 ft 

LFA well

20081217 1300 -9.40 16.8 .1 .14 -9.4 16.44 14,315 50.45 9,267 51.34 9,413 50.4 9,260 47.12 8,703

QW17 UFA 284949082000502 ROMP 117 338 ft 

UFA well

20081217 1530 -10.49 21.0 .1 .12 -10.49 20.33 12,541 50.46 7,516 50.85 7,579 50.44 7,513 47.54 7,022

1Apparent age of the water sample before compensation for environmental degradation.

Water Chemistry 75
76 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida Table 14. Mean concentrations, mean calculated atmospheric mixing ratios, mean piston flow model years of sulfur hexafluoride data and dissolved gas data in groundwater in the Lake Panasoffkee study area, December 2008 through January 2009. [SF6, sulfur hexafluoride; fMol/L, femtomols per liter; pptv, parts per trillion by volume; USGS, U.S. Geological Survey; °C, degrees Celsius; NGVD 29, National Geodetic Vertical Datum of 1929; mg/L, milligrams per liter; cm3/L at STP, cubic centimeters per liter at standard temperature and pressure; mean concentration typically calculated from two replicate samples collected at each site; UFA, Upper Floridan aquifer; SA, surficial aquifer] Mean SF6 Mean concentration, mg/L Reference number (fig. 14) Site type USGS site identification number Station name Concen- tration in solution (fMol/L) Calcu- lated atmos- pheric mixing ratio (pptv) Piston flow model mean recharge year (year) Water tempera- ture at time of collection

(°C)

Nitrogen 

(N2) 

Argon 

(Ar) 

Oxygen 

(O2) 

Carbon 

dioxide 

(CO2) 

Methane 

(CH4)

Estimated 

recharge 

altitude 

(feet 

above 

NGVD 29)

Mean 

calculated 

recharge 

temperature 

(cm3/L at 

STP)

Mean 

calculated 

excess air 

in water 

sample 

(cm3/L at 

STP) 

Mean 

estimated 

excess 

nitrogen 

gas in 

water 

sample 

(mg/L) 

QW1 UFA 285125082085301 Big Jones Creek 48 ft UFA Well 0.4 0.9 1981 22.51 17.30 0.57 0.21 14.11 0.06 60 24.03 3.56 0.00QW2 SA 285125082085302 Big Jones Creek 7 ft SA Well 0.8 2.2 1989 19.27 17.06 0.58 0.23 24.33 0.20 60 21.71 2.74 0.00QW6 UFA 284628082073801 (ROMP) LP-4 240 ft UFA Well 0.1 0.3 1970 24.52 13.48 0.48 0.19 10.70 0.03 60 28.43 0.64 0.00QW7 UFA 284628082073802 (ROMP) LP-4 120 ft UFA Well 1.4 4.1 1998 24.78 16.31 0.55 0.50 4.54 0.00 60 25.10 2.80 0.00QW8 SA 284628082073803 (ROMP) LP-4 30 ft SA Well 1.5 4.9 2001 25.21 15.44 0.54 1.60 3.38 0.00 60 24.43 1.75 0.00

QW11 UFA 284759082054101 (ROMP) LP-6 154 ft UFA Well 0.3 0.7 1979 22.93 17.31 0.59 0.21 22.24 1.19 60 21.40 2.92 0.00

QW12 SA 284759082054102 (ROMP) LP-6 25 ft SA Well 1.3 3.4 1995 23.08 17.24 0.59 0.23 26.07 1.05 60 20.31 2.55 0.00QW13 SA 284734082071201 Tracy’s Point 5 ft Shallow Well 1.4 4.5 2000 21.94 20.71 0.54 0.17 26.18 0.03 60 25.27 2.22 5.00QW14 SA 284756082061301 Coleman Landing 5 ft Shallow 

Well

1.1 3.2 1994 19.88 11.94 0.42 0.15 113.81 1.70 60 36.14 0.50 0.00

QW15 SA 284922082075901 Lake Panasoffkee 7 ft Shallow 

Well near Shell Pt.

0.0 0.0 1952 22.77 17.19 0.59 0.23 8.65 0.02 60 20.39 2.52 0.00

QW17 UFA 284949082000502 ROMP 117 338 ft UFA Well 0.1 0.3 1971 22.98 17.39 0.59 0.21 6.13 0.10 70 21.11 2.92 0.00
Summary 77

modeled recharge years ranging from 1979 to 1998. None of 

the Upper Floridan aquifer wells that were sampled at greater 

than 240 ft below land surface contained enough SF6 to model 

an accurate age of recharge and, using the aforementioned 

reasoning, can be considered free of modern water recharged 

to the Upper Floridan aquifer in the last 35 years.

Water from two of the three shallow drivepoint piezometers (QW13 and QW14) that were installed in the surficial 

aquifer beneath Lake Panasoffkee had apparent recharge years 

of 2000 and 1994, respectively, based on SF6 concentrations. 

Water from the third well (QW15) was recharged prior to 

1973 (fig. 14 and tables 4 and 14). The older recharge date 

from QW14 is probably an indication of greater groundwater 

inflow at that site than the other sites. An increase in the 

volume of water upwelling from the Upper Floridan aquifer 

into the surficial aquifer would result in an older apparent 

date of recharge. The sample from well QW15 was the only 

groundwater sample analyzed for SF6 that had no measurable 

SF6 concentration. Although it is possible that the SF6 was 

degraded by the geochemical conditions beneath the lake, 

SF6 is typically resistant to change under highly reducing 

conditions and from biodegradation (Busenberg and Plummer, 

2000). The water sample from well QW15 appears to be 

composed entirely of water greater than 35 years in age.

Three of the well nests sampled for SF6 included at least 

one surficial aquifer well and one Upper Floridan aquifer well. 

All of the nested well samples indicated an older apparent 

age in the Upper Floridan aquifer compared to water from 

the surficial aquifer. QW1 and QW2, the nested wells northeast of Lake Panasoffkee at Big Jones Creek, had apparent 

recharge years of 1981 and 1989, respectively (fig. 14 and 

tables 4 and 14). QW6, QW7, and QW8, which are all part 

of the ROMP LP-4 well nest west of Lake Panasoffkee, had 

apparent recharge years of 1970, 1998, and 2001 for the deep 

Upper Floridan aquifer, shallow Upper Floridan aquifer, 

and surficial aquifer wells, respectively (fig. 14 and tables 4 

and 14). Samples from QW11 and QW12, located near the 

eastern shore of Lake Panasoffkee, had apparent recharge 

years of 1979 and 1995, respectively (fig. 14 and tables 4 

and 14). Despite descriptions of a thin intermediate confining 

unit in drillers’ logs for many of these wells, the presence of 

SF6 below the confining unit confirms that the intermediate 

confining unit is leaky or discontinuous throughout much of 

the study area. 

Throughout the study area, the calculated years of 

recharge tended to be older than anticipated for shallow surficial aquifer wells. However, these surficial aquifer samples 

were collected during a time of drought when heads in the 

Upper Floridan aquifer were higher than those in the surficial 

aquifer over much of the study area. During a period of wetter 

weather when the Upper Floridan aquifer is being recharged 

by the surficial aquifer, water samples from the surficial 

aquifer would likely date younger than during dry periods.

None of the analyses of CFCs in water samples were 

valid because of environmental degradation that reduces CFC 

concentrations after recharge to the groundwater system. 

Several environmental processes are known to degrade CFCs. 

Unfortunately, all but two of the 11 surficial aquifer and Upper 

Floridan aquifer well-water samples were degraded under 

reducing conditions (indicated by the presence of methane), 

rendering the data unreliable. This degradation typically 

occurs when methane-producing bacteria biodegrade CFCs 

at the groundwater/surface-water interface under anoxic 

conditions (Happell and others, 2003). 

Summary

Lake Panasoffkee is a 5,700-acre water body located in 

west-central Florida on the western border of Sumter County. 

The study area includes Lake Panasoffkee and the surrounding 

watershed.

The uppermost part of the groundwater system in the 

Lake Panasoffkee watershed consists of a thin, unconfined 

surficial aquifer composed primarily of sand. Discontinuous 

clays and sands of the Hawthorn Group compose the intermediate confining unit, which separates the surficial aquifer from 

the Upper Floridan aquifer within the study area. The Upper 

Floridan aquifer in this area consists of the Ocala Limestone 

and the upper part of the Avon Park Formation. In west-central 

Florida, the Upper Floridan aquifer is separated from the 

Lower Floridan aquifer by either middle confining unit I, 

middle confining unit II, or both in areas where the units 

overlap. Middle confining unit I lies primarily east of Lake 

Panasoffkee, whereas middle confining unit II lies mostly west 

of Lake Panasoffkee. Middle confining unit I is typically more 

leaky than middle confining unit II.

Lake Panasoffkee exhibits a strong hydraulic connection 

with the underlying Floridan aquifer system. Examination of 

hydrologic data indicates there is potential for exchange of 

water between the surface-water and groundwater systems. 

Differences in water level from paired surficial and Upper 

Floridan aquifer wells indicate that recharge conditions were 

present during the study period northeast and southeast of 

Lake Panasoffkee in the nearby uplands, whereas discharge 

conditions were present around Lake Panasoffkee and in 

adjacent areas southeast and northwest of the lake. 

The recharge areas coincide with lands of high surface 

elevation, such as the ridges of the Sumter and Lake Uplands. 

Precipitation rapidly infiltrates the sandy uplands and 

recharges the surficial aquifer. The lack of a continuous intermediate confining unit in much of the study area allows water 

from the surficial aquifer to freely recharge the limestone of 

the Upper Floridan aquifer, and even where the intermediate 

confining unit is present, recharge can still quickly reach 

(in days or hours) the Upper Floridan aquifer because of the 

karst features in the area. Sinkholes, fissures, and conduits are 

all parts of an internal drainage system that breaches the intermediate confining unit and allows surface water to recharge 

directly into the Upper Floridan aquifer. 
78 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Piezometers driven into the bed of Lake Panasoffkee 

generally indicated an upward head difference between the 

surficial aquifer and the lake during synoptic measurements. 

Upward head differences between the Upper Floridan aquifer 

and the surficial aquifer indicate the potential for water to 

discharge from the Upper Floridan aquifer into the overlying 

surficial aquifer. Similarly, groundwater discharges into 

surface-water bodies through porous bed materials when 

hydraulic head in the Upper Floridan aquifer is higher than 

surface-water levels. 

A drought that extended from 2005 through the end 

of data-collection activities in September 2008 resulted 

in below-normal groundwater levels for most of the study 

period. During the study period, wetter conditions resulted in 

more intense recharge in the recharge areas and more intense 

discharge in the discharge areas. The spatial relation between 

groundwater recharge and discharge areas remained relatively 

constant throughout the study period.

Monthly water-budget calculations were used to 

determine groundwater-inflow rates. Based on rainfall data 

collected at three stations within the Lake Panasoffkee 

watershed, rainfall totaled 91.71 in. between October 2006 

and September 2008 (water years 2006–8). For the 1930–2008 

water years, annual average precipitation for the area is 

54.26 in. Five surface-water gaging stations were used to 

determine the monthly volume of surface-water inflow and 

outflow to Lake Panasoffkee, of which Little Jones Creek and 

Shady Brook were the main contributors. Discharge at Little 

Jones Creek ranged from 6.56 ft3/s in June 2007 to 75.8 ft3/s 

in August 2008, whereas flows at Shady Brook ranged from 

8.28 ft3/s in June 2007 to 59.6 ft3/s in September 2008. 

Discharge from Lake Panasoffkee to Outlet River ranged from 

a low of 12.6 ft3/s in June 2007 to a high of 225 ft3/s in August 

2008. During water years 2007 and 2008, a combined total of 

90.50 in. of water evaporated from Lake Panasoffkee, or 45.96 

and 44.54 in/yr, respectively. Lake Panasoffkee evaporation 

rates were about 17 to 28 percent lower than those measured at 

other lakes in central Florida. Most of the difference in evaporation rates can be attributed to lower net radiation measured 

at Lake Panasoffkee. Lower net radiation is assumed to be the 

result of greater reflectance of solar radiation (albedo) caused 

by the naturally occurring and lightly colored carbonate sediments that compose the lakebed and that are easily suspended 

in the shallow water column during windy periods. This 

increased reflectance may have been exacerbated during the 

study period by the ongoing lake-restoration work. 

Water-budget calculations indicate that Lake Panasoffkee 

gained substantial water from groundwater inflows during the 

study period. Monthly groundwater inflows as a percentage of 

total inflows during the 2-year data-collection period ranged 

from 11 percent in October 2007 to 50 percent in May 2007, 

with a total contribution of 29 percent of all inflow over the 

2-year data-collection period. Comparatively, the total volume 

of surface-water inflow for the 2-year data-collection period 

was 50 percent of total inflow, and rainfall accounted for 21 

percent. The percentage of groundwater inflow received by 

Lake Panasoffkee is not unusual compared to other central 

Florida lakes, but the source and the volume of groundwater 

inflow are atypical. A previous USGS study of groundwater 

inflow to 81 lakes in central Florida rated each lake as a 

“low,” medium,” or “high” groundwater inflow lake. Lake 

Panasoffkee falls in the medium category of lakes because 

it received an average of 29 percent of its total inflow from 

groundwater during the 2-year data-collection period. What 

is unusual is that the primary source of groundwater inflow 

to Lake Panasoffkee is the Upper Floridan aquifer. All of the 

lakes in the previous study received their groundwater inflow 

from the surficial aquifer. The total volume of groundwater 

inflow received by Lake Panasoffkee also differs from other 

lakes. Calculations indicate that Lake Panasoffkee received 

1.38 billion ft3/yr of groundwater inflow during water 

year 2008. The largest (5,074 acres) of the 81 lakes in the 

previous USGS study received only 294 million ft3/yr. Lake 

Panasoffkee also receives much of its surface-water inflow 

from groundwater, because as much as 78 percent of the 

surface-water inflow originated as spring discharge during the 

study period. 

Two sets of water samples were collected from Lake 

Panasoffkee, its tributaries, and selected groundwater and 

spring sites in July 2007 and December 2008 through January 

2009. Trilinear diagrams indicate three distinct water types 

within the Lake Panasoffkee watershed: calcium-bicarbonate 

type waters, mixed calcium-bicarbonate/calcium-sulfate 

type waters, and two groundwater samples (from the same 

well) that were composed of calcium-sulfate type water. 

The presence of calcium-bicarbonate and calcium-sulfate type 

waters in the surficial aquifer, spring, and lake water samples 

indicates that the Upper Floridan aquifer contributes inflow to 

the overlying hydrogeologic units and surface-water bodies in 

the Lake Panasoffkee watershed.

Sulfate concentrations in west-central Florida are typically low (less than 30 mg/L) in surface waters, the surficial 

aquifer, and the shallow parts of the Upper Floridan aquifer. 

Water samples collected from Lake Panasoffkee in July 2007 

exceeded 30 mg/L. A previous USGS study of the Lake 

Panasoffkee area concluded that the most likely source of 

the high sulfate waters in and around Lake Panasoffkee was 

water upwelling from near the base of the Upper Floridan 

aquifer. This upwelling suggests that there is a mechanism 

that allows water to move from the Avon Park Formation deep 

in the Upper Floridan aquifer to the shallow Upper Floridan 

and surficial aquifers. Vertical groundwater flow in the area is 

likely related to fractures and faults associated with the Ocala 

structural high. Physiographic expressions at land surface, 

including the shape of Lake Panasoffkee, indicate that one 

or more faults may be present in the Lake Panasoffkee area, 

although no physical evidence has been found to date. 

Water samples collected in July 2007 and December 

2008 through January 2009 were analyzed for the isotopic 

ratios of strontium, oxygen, and hydrogen. Strontium 

isotope ratios were higher in samples from both of the main 

surface-water tributaries to Lake Panasoffkee and in all of 
Summary 79

the springs, suggesting that the lake receives groundwater 

inflow that originates in hydrogeologic units that are geologically older than the surficial aquifer or shallow parts of the 

Upper Floridan aquifer (Ocala Limestone). The strontium 

isotope data indicate that Lake Panasoffkee receives water that 

originates deep in the Upper Floridan aquifer in the Avon Park 

Formation. Strontium isotope ratios found in samples from 

Lake Panasoffkee were similar to samples taken from Upper 

Floridan aquifer wells finished in the Avon Park Formation 

south and southwest of Lake Panasoffkee. 

Hydrogen and oxygen isotopic ratios (δ2H and δ18O) 

indicate that rainfall rapidly recharges the groundwater system 

in the Lake Panasoffkee watershed. The isotope data collected 

in July 2007 and December 2008 through January 2009 

mostly plot near the LMWL, indicating a lack of enrichment 

and, therefore, that rainfall infiltrates the groundwater system 

rapidly near Lake Panasoffkee. This result is consistent 

with the assumption that water is internally drained in the 

watershed. Samples collected from Lake Panasoffkee and its 

tributaries showed the most isotopic enrichment, as might be 

expected of surface water that has undergone evaporation. 

Two δ2H and δ18O samples collected in December 2008 from 

the surficial aquifer beneath Lake Panasoffkee, one near the 

northeast shoreline and one near the east-central shoreline, 

indicated that the lake was receiving groundwater inflow in 

those areas. This result is consistent with the Lake Panasoffkee 

water budget, which indicates that the lake was receiving 

water through groundwater inflow. The recharge/discharge 

potential map created for the study area indicates that both 

these samples were collected in discharge areas. A third surficial aquifer sample from beneath Lake Panasoffkee, collected 

near the west-central shoreline, indicated the presence of 

lake water in the surficial aquifer in the vicinity of that well. 

The recharge/discharge potential map for September 2008 

indicates that this sample was collected from a well located 

near the boundary of a recharge/discharge area. 

In December 2008, water samples were collected for 

analysis of 14C and 3H from the three deepest (240, 338, 

and 1,000 ft deep) monitoring wells in the study area. These 

wells included an Upper and Lower Floridan aquifer well 

east of Lake Panasoffkee and an Upper Floridan aquifer well 

west of Lake Panasoffkee. The shallower well east of Lake 

Panasoffkee is finished above middle confining unit I deep 

in the Upper Floridan aquifer, whereas the Lower Floridan 

aquifer well is finished below middle confining unit I. 

The Upper Floridan aquifer well west of Lake Panasoffkee is 

finished above middle confining unit II. 

After the analyses of the 14C samples was completed, 

the apparent 14C ages were adjusted using a geochemical 

mass-balance model to correct the apparent ages for error 

caused by geochemical changes that result in samples because 

of contact with aquifer materials. The water sample from the 

eastern Upper Floridan aquifer well recharged from about 

7,022 to 7,579 years before present, whereas the sample from 

the eastern Lower Floridan aquifer well recharged from about 

8,703 to 9,413 years before present. The adjusted age since 

recharge for the sample from the western Upper Floridan 

aquifer well ranged from about 23,485 to 26,455 years before 

present. None of the sample ages were corrected for recrystallization of carbonates, but only the western well showed 

any indication of recrystallization. The western well sample 

is probably dated several thousand years too old because of 

recrystallization of carbonates. The 3H data indicate that none 

of the three well water samples include a substantial volume 

of “young” groundwater recharged since 1952.

The similarities in both the radiocarbon age of the water 

and the major ion chemistry of the samples indicate that water 

exchanges occur between the Upper and Lower Floridan 

aquifers in the vicinity of the wells east of Lake Panasoffkee. 

Despite the Lower Floridan aquifer well on the east side of 

Lake Panasoffkee being much deeper than the Upper Floridan 

aquifer well on that side of the lake (1,000 and 338 ft, respectively), the modeled radiocarbon age of the deep sample was 

only about 1,500 years older. This small age difference is an 

indication that middle confining unit I is leaky east of the 

study area. 

In a small, poorly defined area west/southwest of Lake 

Panasoffkee, water upwells from deep parts of the Upper 

Floridan aquifer to shallower parts of the Upper Floridan 

aquifer. Despite both the Upper and Lower Floridan aquifer 

wells east of Lake Panasoffkee being deeper than the Upper 

Floridan aquifer well west of the lake, the radiocarbon sample 

from the well to the west was much older. The difference in 

the age of the groundwater east and west of Lake Panasoffkee 

indicates that the upwelling water west/southwest of Lake 

Panasoffkee does not gain its chemical signature from middle 

confining unit I or from the Lower Floridan aquifer below 

middle confining unit I. The upwelling water probably comes 

in contact with middle confining unit II somewhere along its 

flow path. Middle confining unit II is the only hydrogeologic 

unit in the study area that contains sufficient quantities of 

gypsum to explain the sulfate concentration (1,700 mg/L) 

found in the sample from west of Lake Panasoffkee. 
80 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Acknowledgments

The authors thank the citizens of the Lake Panasoffkee 

community and surrounding area who granted access to their 

private properties. Without their cooperation this study would 

not have been possible. Special thanks are offered to Tracy’s 

Point Fishing Lodge for use of their boat ramp and Mr. and 

Mrs. Bill Pfettscher for use of their property as a staging 

area for the installation of hydrologic equipment on Lake 

Panasoffkee. 

Numerous individuals from the Southwest Florida 

Water Management District provided support for this study, 

including Ron Basso, Jerry Mallams, Jason LaRoche, Angel 

Martin, Tamera McBride, Jim Clayton, Dave DeWitt, and 

Roberta Starks.

Thanks also are offered to U.S. Geological Survey staff 

who provided technical assistance with this study, including 

Brian Katz, Niel Plummer, Arturo Torres, Terrie Lee, 

Patty Metz, Tyler Coplen, Dann Yobbi, Lari Knochenmus, 

Tom Lopes, John Trommer, Jim Flocks, Dana Wiese, Pete 

Swarzenski, Chris Reich, Robert Renken, Gary Mahon, 

and the Data Sections in Orlando and Tampa. Ryan Hollins 

deserves special recognition for working long days in the field 

assisting with data collection. 

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Laboratory: Accessed online October 29, 2009, at http://

www.rsmas.miami.edu/groups/tritium/.
84 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

U.S. Department of Agriculture, 2007, Census of agriculture, 

Sumter County - Florida: Accessed online March 4, 2010, at 

http://www.agcensus.usda.gov/Publications/2007/Online_

Highlights/County_Profiles/Florida/cp12119.pdf.

U.S. Geological Survey, variously dated, National field 

manual for the collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A1-A9: Available online at http://pubs.

water.usgs.gov/twri9a.

U.S. Geological Survey, 2009, Water-resources data for the 

United States―Water year 2008: Available online at http://

wdr.water.usgs.gov/wy2008/search.jsp.

Vernon, R.O., 1951, Geology of Citrus and Levy Counties, 

Florida: Tallahassee, Florida Geological Survey Geological 

Bulletin 33, 256 p.

Wharton, B.R., 1982, Historic analysis of the rock spillway at 

Outlet River and Lake Panasoffkee, Sumter County, Florida: 

Brooksville, Southwest Florida Water Management District 

report, 6 p.

White, William, 1958, Some geomorphic features of central 

peninsular Florida: Tallahassee, Florida Geological Survey 

Geological Bulletin 41, 92 p.

White, William, 1970, The geomorphology of the Florida 

Peninsula: Tallahassee, Florida Geological Survey 

Geological Bulletin 51, 164 p.
Appendix 1. Elevation of water levels in all wells used to 

create Upper Floridan aquifer potentiometric-surface maps
86 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric-surface maps.

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

285232082054801 Wildwood Truck Wash 92 ft FLRD well nr Royal 28°52′32′′ 82°5′48′′ 43.75 45.99 44.90 48.04

285241082075001 The Preserve 99 ft FLRD nr Royal 28°52′41′′ 82°7′50′′ 42.74 45.14 44.31 47.92

285142082080801 Lake Panasoffkee WMA fenceline FLRD well nr Royal 28°51′42′′ 82°8′8′′ 41.79 44.31 43.33 46.44

285128082082501 Lake Panasoffkee WMA house FLRD well nr Carlson 28°51′28′′ 82°8′25′′ 41.59 44.12 43.17 46.30

285125082085301 Big Jones Creek 48 ft FLRD well nr Carlson 28°51′25′′ 82°8′53′′ 41.63 44.51 43.21 46.03

285035082075401 Little Jones Creek 48 ft FLRD well nr Carlson 28°50′35′′ 82°7′54′′ 40.98 42.95 42.40 44.55

285118082093801 Santana House 70 ft FLRD well nr Carlson 28°51′18′′ 82°9′38′′ 41.04 44.42 42.59 46.12

285130082102901 7018 CR470 181 ft FLRD well nr Carlson 28°51′30′′ 82°10′29′′ 41.16 43.96 42.69 45.68

285048082101101 Tree Farm 67 ft FLRD well nr Carlson 28°50′48′′ 82°10′11′′ 39.60 42.77 41.33 44.89

285011082103201 Vach House 37 ft FLRD well nr Carlson 28°50′11′′ 82°10′32′′ 39.11 42.51 40.98 44.76

284924082105501 Wysong Dam 84 ft FLRD well at Carlson 28°49′24′′ 82°10′55′′ 36.26 39.34 38.82 40.97

284900082101101 Lewis House 171 ft FLRD well at Carlson 28°49′0′′ 82°10′11′′ 37.60 41.51 40.13 43.17

284840082093501 SWFWMD W470 81 ft FLRD well nr Carlson 28°48′40′′ 82°9′35′′ 37.99 41.53 40.31 42.98

284811082091301 LP-3 152 ft FLRD well nr Panacoochee Retreats 28°48′12′′ 82°9′13′′ 36.19 38.55 38.79 40.32

284741082084601 Register 38 ft FLRD well at Panacoochee Retreats 28°47′41′′ 82°8′46′′ 36.22 40.34 38.88 42.04

284736082075001 Cowrat 84 ft FLRD well at Panacoochee Retreats 28°47′36′′ 82°7′50′′ 37.19 38.71 39.27 40.06

284653082084201 Haley Ray 52 ft FLRD well nr Panacoochee Retreats 28°46′53′′ 82°8′42′′ 36.05 41.22 38.42 —

284628082073801 (ROMP) LP-4 240 ft FLRD well nr Panacoochee Retreats 28°46′29′′ 82°7′38′′ 38.37 41.78 40.47 43.36

284628082073802 (ROMP) LP-4 120 ft FLRD well nr Panacoochee Retreats 28°46′29′′ 82°7′38′′ 38.33 42.18 40.44 43.61

284541082071101 Marthas Lane 49 ft FLRD well nr Lake Panasoffkee 28°45′41′′ 82°7′11′′ 39.03 41.74 41.03 43.92

284518082070901 CR489A 45 ft FLRD well at Lake Panasoffkee 28°45′18′′ 82°7′9′′ 39.69 42.32 41.77 44.65

284528082055201 Sumter County 170 ft FLRD well at Lake Panasoffkee 28°45′28′′ 82°5′52′′ 39.62 41.11 41.62 43.50

284456082053101 (ROMP) LP-5 139 ft FLRD well at Lake Panasoffkee 28°44′57′′ 82°5′31′′ 40.78 42.55 42.98 45.96

284455082041401 Barber Shop 105 ft well at Sumterville 28°44′55′′ 82°4′14′′ 45.16 46.01 46.31 47.77

284437082033901 841 CR539A 140 ft FLRD well at Sumterville 28°44′37′′ 82°3′39′′ 46.18 46.91 48.12 48.22

284619082035101 ROMP 111 FLRD well at Sumterville 28°46′20′′ 82°3′51′′ 47.48 48.52 48.48 50.45

284658082040301 1849 U.S. 301 50 ft FLRD well nr Coleman 28°46′58′′ 82°4′3′′ 49.03 50.52 51.09 54.72

284759082054101 (ROMP) LP-6 154 ft FLRD well nr Coleman 28°48′1′′ 82°5′41′′ 44.05 46.51 45.84 48.71

284810082033501 Spurling Dr 84 ft FLRD well at Coleman 28°48′10′′ 82°3′35′′ 49.62 52.51 51.73 56.76

284731082023801 Fenney Spring 53 ft FLRD well nr Coleman 28°47′31′′ 82°2′38′′ 49.34 51.56 50.83 52.36

285020082023701 Sleep Inn 85 ft FLRD well at Wildwood 28°50′20′′ 82°2′37′′ 48.19 52.43 50.65 54.35

285202082042001 Caruthers 130 ft FLRD well nr Wildwood 28°52′2′′ 82°4′20′′ 44.66 47.16 46.50 49.49

285227082044301 Caruthers Windmill 132 ft FLRD well nr Royal 28°52′27′′ 82°4′43′′ 43.79 46.37 45.14 48.56

284912082092901 3847 CR470 39 FLRD well nr Carlson 28°49′12′′ 82°9′29′′ — — 40.75 43.06

284536082080701 CR416N 200 ft FLRD well nr Lake Panasoffkee. 28°45′49′′ 82°7′59′′ — — — 43.59

280446082390701 East Lake dp well 17 nr Tarpon Springs 28°4′45′′ 82°39′5′′ 14.58 16.28 15.24 17.18

280503082143702 ROMP 68 Swnn well nr Antioch 28°5′2′′ 82°14′35′′ 41.98 47.24 43.26 45.50

280510082043801 T-2 dp well nr Crystal Springs 28°5′10′′ 82°4′36′′ 90.75 96.89 92.78 96.07

280531081431601 Lake Alfred 12-inch UFA well at Lake Alfred 28°5′25′′ 81°43′16′′ 116.20 120.30 115.42 121.10

280520081575201 Cresent St FLRD well at Lakeland 28°5′21′′ 81°57′52′′ 87.58 93.99 86.99 94.71

280504082365501 St Pete FLRD well E-102 nr Citrus Park 28°5′8′′ 82°36′55′′ 17.08 20.71 18.24 21.72

280558081314801 805131–Kimbell well nr Lake Mari 28°5′52′′ 81°31′48′′ 67.54 70.67 68.42 71.50

280556081532601 Tennorock Rd well nr Lakeland 28°5′50′′ 81°53′26′′ 113.70 115.11 113.29 115.89

280550082202901 Morris Bridge FLRD well 10 nr Branchton 28°5′53′′ 82°20′27′′ 20.76 26.77 24.20 25.24

280548082355701 St Pete FLRD well E-100 nr Citrus Park 28°5′49′′ 82°35′57′′ 19.71 23.84 20.81 26.26

280546082390701 East Lake dp well 14 nr Tarpon Springs 28°5′47′′ 82°39′7′′ 15.01 17.26 15.82 18.66

280605082184101 Morris Bridge FLRD well 12 nr Branchton 28°6′6′′ 82°18′39′′ 20.54 27.43 24.54 25.52

280602082333001 ROMP-05 dp well nr Citrus Park 28°5′58′′ 82°33′31′′ 22.48 27.20 24.15 22.88

280603082385401 ROMP-19 dp well nr Oldsmar 28°5′59′′ 82°38′55′′ 17.03 18.70 17.10 20.27

280632082455001 NW Pinellas injection monitoring dp well nr Tarpon Springs 28°6′31′′ 82°45′52′′ 2.06 2.61 2.76 3.39
Appendix 1 87

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

280659082175201 Morris Bridge FLRD well 13 nr Branchton 28°6′58′′ 82°17′50′′ 22.88 31.49 28.77 28.60

280655082193001 Morris Bridge FLRD well 3A nr Branchton 28°7′1′′ 82°19′41′′ 24.05 31.17 29.09 27.56

280708082074801 T-1 dp well nr Crystal Springs 28°7′11′′ 82°7′50′′ 82.16 89.03 84.42 86.60

280659082294302 Berger FLRD well nr Citrus Park 28°7′0′′ 82°29′42′′ 38.23 42.88 41.20 47.26

280702082302801 Sec 21-13 FLRD well nr Lutz (Hillsborough 13) 28°7′2′′ 82°30′27′′ — 35.33 35.48 44.14

280740082105201 Blackwater Creek ELAPP UFA well 28°7′40′′ 82°10′52′′ 66.66 72.61 68.91 70.34

280738082282701 Lorena Tamp well nr Lutz 28°7′35′′ 82°28′30′′ 47.62 49.44 47.72 52.58

280734082313301 Goodwin Tamp well nr Lutz 28°7′36′′ 82°31′28′′ 33.93 39.01 37.36 44.63

280740082271001 Debuel Rd FLRD well nr Lutz 28°7′40′′ 82°27′2′′ 50.38 52.32 50.34 53.02

280734082442101 ROMP TR 15-3 dp well nr Tarpon Springs 28°7′33′′ 82°44′20′′ 4.19 4.22 5.30 5.47

280747082452001 ROMP TR 15-2 dp well nr Tarpon Springs 28°7′45′′ 82°45′28′′ 2.71 3.40 3.09 4.02

280753082465201 ROMP TR 15-1 dp well nr Tarpon Springs 28°8′3′′ 82°46′50′′ 2.15 2.54 2.72 3.25

280819082374301 ROMP-03 dp well nr Citrus Park 28°8′20′′ 82°37′42′′ 20.85 22.71 19.75 25.59

280905081270101 Reedy Cr overlook 6 UFA nr south 28°8′59′′ 81°27′1′′ 55.23 59.16 56.72 61.59

280849082053701 T-3 dp well nr Crystal Springs 28°8′51′′ 82°5′36′′ 87.35 93.26 90.10 91.73

280852082135601 Hills St Pk Tamp well nr Zephyrhills 28°8′54′′ 82°13′53′′ 36.39 39.18 37.67 38.92

280901082310401 ROMP-01 dp nr Citrus Park 28°9′1′′ 82°31′0′′ 41.28 42.61 42.81 48.66

280852082414301 North Lake Tarpon dp well nr Tarpon Springs 28°8′55′′ 82°41′47′′ 10.28 12.10 11.17 13.86

280856082401201 Eldridge-Wilde dp well 2 South nr Tarpon Springs 28°8′58′′ 82°40′13′′ 14.61 16.81 15.00 19.52

280907082424801 Tarpon Rd dp well nr Tarpon Springs 28°9′7′′ 82°42′46′′ 6.95 9.05 8.36 10.21

280926082162101 USGS Tamp well 532 nr Branchton 28°9′26′′ 82°16′19′′ 38.43 44.13 41.75 44.05

280920082322101 Lutz-Lake Fern FLRD well nr Lutz 28°9′21′′ 82°32′18′′ 37.49 41.10 40.42 46.86

281008081441801 PO0006 Lake Alfred 6 UFS nr Lake Alfred 28°10′2′′ 81°44′18′′ 123.72 126.09 123.72 126.84

280944082380501 Eldridge-Wilde dp well N-4 nr Tarpon Springs 28°9′45′′ 82°38′7′′ 20.06 24.64 22.27 27.81

280942082390601 Eldridge-Wilde shallow well N-1 nr Tarpon Springs 28°9′45′′ 82°39′4′′ 14.08 17.06 14.21 18.07

281031082071801 Alston Track dp 28°10′31′′ 82°7′18′′ 78.79 82.57 81.65 84.54

281022082400201 Eldridge-Wilde dp well N3 nr Tarpon Springs 28°10′23′′ 82°40′2′′ 14.61 17.71 15.72 19.31

281058081495003 USGS 4 annual monitor at Polk 28°10′52′′ 81°49′50′′ — 124.09 — —

281057081495002 ROMP 76A 6 UFA, Polk Co 28°10′51′′ 81°49′50′′ 123.33 — 123.59 126.51

281023082450701 Coastal Pasco well 13 nr New Port Richey 28°10′23′′ 82°45′12′′ 4.36 4.73 6.35 6.53

281035082305701 Pasco FLRD well 42 nr Land O′ Lakes 28°10′38′′ 82°30′58′′ 40.33 40.52 44.24 53.26

281052082052601 Alston 1 Deep (UFA) well 28°10′53′′ 82°5′26′′ 89.52 94.27 92.72 —

281046082470801 Fpc well 1 nr Tarpon Springs, Fla 28°10′48′′ 82°47′7′′ 1.51 1.41 1.59 1.15

281124082274101 Winter Qtrs RV Park nr Land O’ Lakes 28°11′24′′ 82°27′38′′ 56.15 58.13 57.11 59.81

281138082120201 Zephyrhills Prison FLRD 28°11′38′′ 82°12′2′′ 56.81 59.30 59.56 61.77

281202081391701 PO0001 Thornhill 4 inch UFA nr Davenport 28°11′56′′ 81°38′47′′ 121.70 125.07 122.71 125.56

281144082100402 ROMP 86A Suwannee 28°11′44′′ 82°10′4′′ 56.24 58.67 58.10 59.05

281143082304702 SR 54 dp well nr Land O’ Lakes (SWFWMD 97 and 363) 28°11′44′′ 82°30′49′′ 44.21 43.55 47.89 54.66

281312082011601 ROMP 87 nr Lakeland 28°13′6′′ 82°1′16′′ 96.41 101.36 99.69 101.52

281317081491301 813149423 26S25E16 312 28°13′11′′ 81°49′13′′ 121.84 123.32 122.46 125.08

281322082084501 Chancey Rd Floridan 28°13′22′′ 82°8′46′′ 65.12 69.80 70.87 72.06

281325082215301 Fl-2-1000 well nr Lutz 28°13′26′′ 82°21′54′′ 52.32 56.47 59.30 56.88

281353082110401 Zephyrhills Park FLRD 28°13′53′′ 82°11′4′′ 59.78 62.33 63.75 64.94

281429081290501 Mercantile Ln (OSF-254) nr Poinciana 28°14′23′′ 81°29′5′′ 55.90 59.76 57.24 62.04

281440081431701 814143232 26S26E04 333 28°14′34′′ 81°43′17′′ 122.63 124.99 123.32 125.88

281424082192702 ROMP 85 FLRD well nr Zephyrhills 28°14′25′′ 82°19′25′′ 72.34 77.30 75.76 77.13

281420082344701 PZ-1 dp well nr Elfers 28°14′19′′ 82°34′47′′ 32.83 33.30 35.44 39.04

281443082055501 Howard Blvd UFA well 28°14′44′′ 82°5′54′′ 73.15 76.58 79.53 80.28

281437082271401 Nininger dp well 857 at Drexel 28°14′38′′ 82°27′14′′ 68.03 70.42 69.92 70.95

281448082301801 Bexley well 2 nr Drexel (Recorder)**Potmap** 28°14′49′′ 82°30′18′′ 57.72 59.62 59.71 61.72

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
88 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

281504082104801 ROMP 86 dp well nr Zephyrhills 28°15′3′′ 82°10′49′′ 68.14 67.20 66.16 66.01

281446082354101 MW-1 dp well nr Elfers 28°14′48′′ 82°35′40′′ 24.92 24.94 30.89 33.89

281457082334301 PZ-3 dp well nr Elfers 28°14′52′′ 82°33′43′′ 37.87 40.27 41.22 43.34

281451082380701 Starky 10 dp well nr Elfers 28°14′51′′ 82°38′7′′ 22.89 22.79 24.69 27.40

281458082330701 PZ-5 dp well nr Elfers 28°14′59′′ 82°33′5′′ 39.23 41.68 41.98 43.91

281532081345001 Loughman UFA 28°15′26′′ 81°34′50′′ 86.79 89.80 88.67 90.23

281532081493001 USGS shallow well W5470 nr Polk Co 28°15′26′′ 81°49′30′′ 120.09 121.57 121.06 122.85

281532081345001 Loughman dp (Orlando also) 28°15′34′′ 81°34′50′′ 86.79 89.80 88.67 90.23

281533082130601 Austin Smith Rd FLRD 28°15′33′′ 82°13′6′′ 61.69 63.82 65.71 66.65

281559081260701 Shingle Creek 4 inch UFA, SR 531A 28°15′53′′ 81°26′7′′ 49.47 53.38 50.65 57.18

281518082424301 ROMP TR 16-2 Van Buren - SWNN 28°15′18′′ 82°42′40′′ 4.64 6.05 5.32 6.30

281535082241301 Cypress Creek dp well Tmr-5 nr San Antonio 28°15′35′′ 82°24′14′′ 50.63 51.91 53.64 54.54

281531082352901 PZ-4 dp well nr Elfers 28°15′32′′ 82°35′34′′ 28.71 28.43 33.45 36.76

281556082104701 Wire Rd FLRD 28°15′56′′ 82°10′47′′ 60.51 64.39 64.30 65.01

281558082264601 Pasco well 13 nr Drexel 28°15′60′′ 82°26′46′′ 68.92 70.44 70.38 71.68

281622082241301 Cypress Creek dp well 3 nr San Antonio 28°16′23′′ 82°24′12′′ 49.26 49.14 52.00 52.58

281631082261601 Catchings well nr Drexel 28°16′29′′ 82°26′14′′ 62.87 64.68 64.03 67.61

281654082065901 US 98 well nr Dade Co 28°16′48′′ 82°6′59′′ 72.45 73.85 75.92 75.36

281654082201601 Carr dp well nr San Antonio 28°16′49′′ 82°20′17′′ 71.39 73.65 — —

281636082372001 Moon Lake dp well nr New Port Richey 28°16′42′′ 82°37′15′′ 27.67 27.56 27.94 29.80

281650082244501 Cypress Creek dp well TMR-4 nr San Antonio 28°16′51′′ 82°24′45′′ 50.75 51.29 53.51 54.13

281642082440201 Coastal Pasco dp well 04 atPort Richey 28°16′42′′ 82°44′2′′ 0.42 0.00 0.93 -0.51

281715082164401 SR 577 dp well nr San Antonio 28°17′16′′ 82°16′44′′ 78.99 80.91 82.89 83.78

281837081544101 ROMP 88 nr Rockridge 28°18′31′′ 81°54′41′′ 105.01 101.60 104.07

281918082264601 SR 52 dp well nr Gowers Corner 28°19′19′′ 82°26′46′′ 66.66 68.97 67.31 69.76

281923082252201 ROMP 93 dp well nr Gowers Corner 28°19′24′′ 82°25′21′′ 64.09 66.42 65.15 67.34

281926082212901 Jct SR 52 & 581 well nr Darby 28°19′27′′ 82°21′18′′ 63.46 65.52 66.53 67.56

281917082420901 ROMP TR 17-1 dp well at Bayonet Pt 28°19′17′′ 82°42′7′′ 3.67 4.07 4.17 3.82

281922082403901 ROMP TR 17-3 dp well nr Bayonet Pt 28°19′21′′ 82°40′40′′ 2.78 2.66 3.33 2.74

281938082141501 ROMP BR-3 Lake Pasadena dp 28°19′38′′ 82°14′14′′ 69.50 70.07 71.98 70.86

281951082012001 Green Swp well L11MD nr Dade Co 28°19′45′′ 82°1′20′′ 83.26 89.04 88.07 88.50

281949082332001 SR 52 dp well nr Fivay Jct 28°19′50′′ 82°33′0′′ 48.94 49.93 49.48 52.20

281948082415301 Withlacoochee elec well #1 at Bayonet Pt 28°19′51′′ 82°41′50′′ 1.17 2.31 1.61 2.09

281954082413401 Ponderosa Dev well at Bayonet Pt 28°19′57′′ 82°41′36′′ 1.98 2.85 — 1.70

282009082373801 SR 52 dp well nr Hudson 28°20′14′′ 82°37′28′′ 21.55 22.25 22.73 23.96

282035082283701 Serw-D dp well nr Masaryktown 28°20′35′′ 82°28′35′′ 63.07 65.38 63.53 67.19

282044082312401 H Kent dp well nr Gowers Corner 28°20′45′′ 82°31′23′′ 55.24 56.39 55.63 58.89

282121082071101 Cummer office well 28°21′15′′ 82°7′11′′ 68.09 70.30 71.10 70.54

282202081384601 OR0064 Lake Oliver 6 UFA nr Lake Oliver 28°21′56′′ 81°38′46′′ 105.06 106.24 105.65 107.22

282154082142401 Haycraft well nr Dade Co 28°21′48′′ 82°14′24′′ 60.32 61.86 63.57 64.10

282148082281801 Crossbar WFA-1 dp 28°21′49′′ 82°28′17′′ 53.19 56.02 52.92 56.36

282221082103001 Collura well #1 28°22′15′′ 82°10′30′′ 60.58 62.07 — —

282202082270801 Serw-D well nr Masaryktown 28°22′10′′ 82°27′10′′ 54.47 56.77 54.97 59.78

282241081443901 L-0051 sand mine UFA 28°22′35′′ 81°44′39′′ 112.64 113.32 112.70 115.65

282245081492601 L-0057 Eva 6 inch UFA at Eva (dp) 28°22′39′′ 81°49′26′′ 106.39 108.31 107.45 110.12

282229082405801 Coastal Pasco dp well 02 at Hudson 28°22′30′′ 82°40′56′′ 1.87 1.78 2.23 1.94

282238082362101 Justice dp nr Hudson 28°22′42′′ 82°36′17′′ 19.70 21.52 — 23.80

282318081544003 L-0555 Green Swamp test 28°23′12′′ 81°54′40′′ 98.42 100.96 100.64 102.58

282331081370801 USGS well Hartzog Rd 28°23′25′′ 81°37′8′′ — 101.19 99.04 101.85

282354081313001 Disney World Buena Vista Blvd 28°23′48′′ 81°31′30′′ 72.65 — — —

282324082285101 Wrw-D well nr Masaryktown 28°23′25′′ 82°28′52′′ 39.27 40.08 39.28 43.93

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
Appendix 1 89

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

282434081283102 Sea World Dr well replacement nr Vineland 28°24′28′′ 81°28′31′′ 50.03 53.79 50.93 59.73

282428082134501 Lee Well 28°24′22′′ 82°13′45′′ 58.50 60.22 61.56 61.91

282430082112101 Dale Self 28°24′24′′ 82°11′21′′ 58.14 59.89 61.14 61.36

282434082200301 Travelers Rest FLRD well nr Darby 28°24′36′′ 82°20′0′′ — 57.23 58.99 58.90

282434082283601 D Sutyak dp well nr Masaryktown 28°24′44′′ 82°28′33′′ 23.37 24.07 32.80 27.59

282528081340901 Bay Lake dp well nr Bay Lake 28°25′22′′ 81°34′9′′ 80.23 82.73 81.08 85.49

282543081385801 82513801 Hickory Nut Lake, Mathias 28°25′37′′ 81°38′58′′ 93.07 93.39 92.13

282534082222802 Barthle Ranch dp well nr Darby 28°25′36′′ 82°22′29′′ 39.59 39.37 — —

282540082275701 Masaryktown dp well at Masaryktown 28°25′41′′ 82°27′56′′ 23.71 25.10 24.02 27.00

282557082364301 County line Trade Center 28°25′56′′ 82°36′42′′ 11.38 13.13 12.03 14.66

282620082193801 Lakewood Retreat 28°26′14′′ 82°19′38′′ 72.55 83.54 66.51

282605082345801 ROMP 97 dp well nr Aripeka 28°26′6′′ 82°34′58′′ 12.87 14.65 13.60 16.99

282613082381701 ROMP TR 18-3 FLRD well nr Aripeka 28°26′17′′ 82°38′11′′ 10.09 11.42 10.51 12.32

282636082221401 Weeki well 11 nr Masaryktown 28°26′37′′ 82°22′14′′ 35.74 37.81 35.96 35.35

282717081553101 ROMP 101 UFA nr Bay Lake 28°27′11′′ 81°55′31′′ 93.44 94.93 94.99 97.81

282717082142001 Rossini UFA west of Trilby 28°27′11′′ 82°14′20′′ 49.66 51.82 51.74 51.47

282659082391104 ROMP TR 18-2 Aripeka U AVPK 28°27′0′′ 82°39′11′′ 7.02 7.93 7.34 8.17

282738081341401 USGS well nr Lake Sawyer 28°27′32′′ 81°34′14′′ — 77.58 74.83 81.54

282741081585701 With St for Green Swp well nr Bay Lake 28°27′35′′ 81°58′57′′ 89.75 93.58 93.07 93.96

282740082012101 Green Swp well L12BD nr Bay Lake 28°27′34′′ 82°1′21′′ 83.88 88.82 89.22 90.23

282742082375901 ROMP TR 18-1 dp well nr Aripeka 28°27′43′′ 82°37′59′′ 11.51 12.97 11.99 14.04

282816082123701 Tomkow Hay Barn well 28°28′10′′ 82°12′37′′ 45.90 48.50 48.03 48.22

282835081305201 USGS well Palm Lake Dr 28°28′32′′ 81°30′26′′ 59.78 65.99 61.65 69.95

282839082190801 Blackett well nr Lake Neff 28°28′33′′ 82°19′8′′ 67.87 69.25 64.20 61.84

282851082035301 Boyette well 28°28′45′′ 82°3′53′′ 77.08 82.30 — —

282923081282801 Ivey's Nursery Trukey Lake Rd 28°29′17′′ 81°28′28′′ 57.38 61.58 57.05 66.80

283001082064702 Richloam Fire Tower well 28°29′55′′ 82°6′47′′ 66.05 71.72 71.79 73.16

283019081455701 LCFD STAT 109 28°30′13′′ 81°45′57′′ 87.46 88.35 86.64 90.19

283036082105501 Ridge Manor ROMP 99 28°30′30′′ 82°10′55′′ 46.59 51.36 48.99 49.83

283128081404701 L-0052 Johns Lake 4 inch UFA 28°31′22′′ 81°40′47′′ 78.99 78.67 77.88 81.57

283100082342501 Weeki Wachee Springs nr Brooksville 28°31′4′′ 82°34′24′′ 8.11 8.52 7.96 9.00

283144081254201 831-125-04 Lake Mann Drain well 28°31′38′′ 81°25′42′′ 41.42 44.92 40.96 54.45

283204081544901 L-0062 Mascotte UFA nr Mascotte 28°31′58′′ 81°54′49′′ 95.98 98.23 97.93 99.70

283201082315601 Weeki Wachee well nr Weeki Wachee 28°32′1′′ 82°31′58′′ 11.43 13.67 11.80 15.66

283232081394101 L-0146 Edgewater Bch 832-139-02 UFA 28°32′26′′ 81°39′41′′ — 75.22 73.97 78.10

283253081283401 OR0047 6 inch UFA, Orla Vista 28°32′47′′ 81°28′34′′ 51.73 54.87 52.18 61.53

283243082365701 ROMP TR 19-2 dp well nr Bayport 28°32′43′′ 82°36′56′′ 5.98 5.56 6.16 5.20

283333081233502 OR0046 Lake Adair 10 4 inch UFA, Orlando 28°33′27′′ 81°23′35′′ 40.80 44.18 39.84 51.93

283340081222803 OR0468 Lake Ivanhoe UFA 28°33′34′′ 81°22′28′′ 40.04 43.46 39.30 50.49

283321082241601 ROMP 105 dp well a Brooksville 28°33′22′′ 82°24′16′′ 30.60 30.33 29.96 30.47

283355081411701 L-0199 Turnpike 28°33′49′′ 81°41′17′′ 70.47 70.31 69.62 72.49

283432081592401 Hugh Iley well nr Mabel 28°34′26′′ 81°59′24′′ 83.23 82.89 85.38 86.53

283510082133701 Croom RR Siding well nr Croom 28°35′4′′ 82°13′37′′ 37.05 38.36 38.12 39.15

283530081514501 Dr. Phillips & Sons UFA nr Mascotte 28°35′24′′ 81°51′45′′ — — 84.34 —

283508082215101 Clarence Smith 28°35′2′′ 82°21′51′′ 32.71 32.75 — —

283539082000301 JC 67 28°35′33′′ 82°0′3′′ — — 81.67 —

283537082151501 ROMP 103 nr Brooksville 28°35′31′′ 82°15′15′′ 35.45 36.54 36.43 37.25

283608081403001 L-0658 City of Montverde 28°36′2′′ 81°40′30′′ 70.48 70.33 69.95 73.63

283613082184301 Delmas Nix 28°36′7′′ 82°18′43′′ 31.29 32.00 31.94 32.69

283638082025702 Town of Webster UFA 2 28°36′32′′ 82°2′57′′ 76.64 79.12 80.00 83.04

283637082081501 JC48B Seaboard Coastline RR use 28°36′31′′ 82°8′15′′ 58.86 61.53 62.24 63.89

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
90 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

283650082313301 ROMP Centralia dp well nr Weeki Wachee 28°36′52′′ 82°31′32′′ 7.63 10.24 8.37 12.16

283804082211001 Russano at Lake Lyndsey 28°38′4′′ 82°22′5′′ 16.70 17.32 17.38 18.32

283829082123701 JC 47 Jumper Crk well 47 nr No 28°38′23′′ 82°12′37′′ — — 39.78 —

283840082154801 Barnhart well CE25 at Nobleton 28°38′34′′ 82°15′48′′ 34.94 36.32 36.49 37.64

283904082001601 JC 65 28°38′58′′ 82°0′16′′ 76.11 74.73 — 79.21

283924082272301 ROMP 107 dp well nr Brooksville 28°39′25′′ 82°27′23′′ 9.09 9.59 9.57 11.50

283952082022001 JC 42 28°39′46′′ 82°2′20′′ 72.56 73.19 80.62 78.48

283957082181001 W Blizzard 28°39′51′′ 82°18′10′′ 28.59 29.05 — —

284106081594001 Replacement well Stuart Ranch nr Cntr Hill 28°41′5′′ 81°59′43′′ 79.36 — — —

284115082062601 JC 27A 28°41′9′′ 82°6′26′′ 56.28 57.43 57.22 59.47

284122081534401 L-0095 Groveland Twr UFA 28°41′16′′ 81°53′44′′ 77.77 77.82 79.92 81.83

284119082034501 JC 44 4 inch UFA nr Bushnell 28°41′13′′ 82°3′45′′ 72.39 77.19 73.50 76.28

284126082034501 JC 45 28°41′26′′ 82°3′45′′ 72.79 72.63 73.59 77.47

284146082061401 JC 32 28°41′40′′ 82°6′14′′ 54.84 56.71 57.10 58.81

284212082071701 JC 63 28°42′6′′ 82°7′17′′ 52.24 54.20 53.47 54.89

284230081345301 OR0106 Plymouth Twr UFA 28°42′24′′ 81°34′53′′ 48.67 49.30 48.33 55.51

284238081275803 OR0548 Wekiwa Sp St Pk UFA nr Forest City 28°42′32′′ 81°27′58′′ 18.62 19.49 18.98 21.86

284317082142601 Wynnhaven Camp well 28°43′11′′ 82°14′26′′ — 36.15 38.57 39.57

284330082215401 ROMP 109 N Storey Mine 28°43′24′′ 82°21′54′′ 13.00 13.51 13.88 16.04

284317082330601 Chassahowitzka well 1 nr Chassahowitzka 28°43′19′′ 82°33′6′′ 4.95 5.89 5.50 7.07

284339082270401 Lecanto well 1 nr Chassahowitzka 28°43′38′′ 82°27′5′′ 6.12 6.88 6.80 8.95

284435082011701 Linda Lee Wood 28°44′29′′ 82°1′17′′ 52.51 51.52 52.65 54.09

284445081462101 L-0043 Lake Yale Groves 28°44′39′′ 81°46′21′′ 61.68 62.66 62.22 65.92

284439082131401 Trail's End well 28°44′33′′ 82°13′14′′ 36.42 38.83 38.85 39.79

284449082055201 JC 71 Woodward well off 470 28°44′43′′ 82°5′52′′ 38.88 40.06 — 44.43

284508082174601 Ferris Pkg Co well at Floral City 28°45′2′′ 82°17′46′′ 27.84 29.81 31.45 33.21

284528081530201 Church of God of Prophecy 28°45′22′′ 81°53′2′′ 63.14 63.68 64.32 66.10

284519082150701 Lammlein 28°45′13′′ 82°15′7′′ 36.33 38.81 39.15 40.16

284532082371001 Homosassa well 1 nr Homosassa, Fla 28°45′34′′ 82°37′10′′ 1.14 1.37 1.86 2.17

284609082163001 Duval Island well nr Floral City 28°46′3′′ 82°16′30′′ 34.97 37.58 38.67 39.70

284619082035101 JC 56 ROMP 111 UFA, Thomplin's Park nr Coleman 28°46′13′′ 82°3′51′′ 47.58 47.92 48.54 50.62

284703082001701 Burnt House well Lowe 28°46′57′′ 82°0′17′′ — — — 56.26

284725081361901 L-0600 Wolf Sink 6 inch UFA LCWA 28°47′19′′ 81°36′19′′ 43.21 43.88 42.96 52.68

284757081320701 L. Knowles 4 inch UFA, 30845 CR 435, Mt. Plymouth 28°47′51′′ 81°32′7′′ 42.07 42.74 41.70 49.78

284752082202501 Highlands VFD nr Inverness 28°47′46′′ 82°20′25′′ 13.93 14.75 14.96 18.57

284809082080701 Kent well at Lake Panasoffkee 28°48′3′′ 82°8′7′′ 36.95 37.79 39.33 40.38

284805082225701 WSF-Holder Mine Campground 28°47′59′′ 82°22′57′′ 8.13 9.23 9.02 12.43

284803082351701 Norris well at Homosassa Springs 28°48′5′′ 82°35′17′′ 1.31 1.77 1.84 2.14

284844082282801 WSF-Perryman Tract well 28°48′38′′ 82°28′28′′ 5.04 5.80 5.66 7.62

284929081294901 10′′ UFA Artesian off SR46A nr Sorrento 28°49′23′′ 81°29′49′′ 32.73 32.87 37.47 43.43

284955081595801 Byrd Trailer well nr Orange Home 28°49′49′′ 81°59′58′′ 60.23 61.16 61.87 66.42

285020082365301 Ozello well 3 nr Crystal River 28°50′21′′ 82°36′54′′ 0.64 1.47 1.34 1.53

285037082213801 Inverness Village east well 28°50′31′′ 82°21′38′′ 15.15 14.61 16.06 19.76

285105082135802 Citrus 11 USGS-west with river 28°50′55′′ 82°13′58′′ 33.38 36.69 35.38 38.79

285102082204001 FDOT Hwy 41 observation well at Inverness 28°50′56′′ 82°20′40′′ 23.92 23.62 24.18 27.63

285102082361001 Ozello well 4 nr Crystal River 28°51′3′′ 82°36′12′′ 1.60 2.05 2.28 —

285119082120601 Sumter 13 replacement nr Wildwood 28°51′19′′ 82°12′6′′ 37.24 39.42 39.57 43.19

285121082245401 ROMP 113 replacement nr Inverness 28°51′15′′ 82°24′54′′ 5.47 6.00 5.94 8.24

285112082354401 ROMP TR 21-2 dp well nr Homosassa Springs 28°51′12′′ 82°35′49′′ 1.19 1.30 1.74 1.84

285150082044001 JC 58 USGS CE3 28°51′44′′ 82°4′40′′ 47.31 45.73 45.99 49.15

285207082014501 JC 57 Masters Ave cty well at WI 28°52′1′′ 82°1′45′′ 44.97 46.33 46.92 52.28

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
Appendix 1 91

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

285257081434201 L-0373 J Eichelburg UFA 28°52′51′′ 81°43′42′′ 53.00 53.36 52.89 58.02

285248082183201 Elmer Heath SR581 no of Inverness 28°52′42′′ 82°18′32′′ 34.64 35.16 34.36 36.83

285234082341901 ROMP TR 21-3 dp well nr Crystal River 28°52′35′′ 82°34′17′′ 2.51 2.68 3.09 3.67

285254082323001 Lecanto well 7 nr Lecanto 28°52′56′′ 82°32′30′′ 2.85 3.43 3.46 4.77

285357081472801 L-0620 Cabbage Hammock UFS 28°53′51′′ 81°47′28′′ 52.98 53.10 52.90 57.58

285420081571901 Smith #2 UFA nr Cherry Lake 28°54′14′′ 81°57′19′′ 47.45 48.25 48.53 53.90

285422082001901 Katz well at Lake Miona 28°54′16′′ 82°0′19′′ 43.01 44.20 44.42 48.98

285414082284201 NORTH LECANTO DP WELL nr LECANTO 28°54′8′′ 82°28′42′′ 3.18 3.82 3.65 5.46

285454081241201 Lwr Wekiva Rvr St Presv 2 inch UFA #1 (no.) artesian 28°54′48′′ 81°24′12′′ 24.86 25.86 25.17 30.19

285421082361602 Crystal River dp well at Crystal Rvr 28°54′22′′ 82°36′14′′ 0.88 1.31 1.73 1.13

285504081405901 L-0380 Austin Groves 8 inch UFA, Umatilla 28°54′58′′ 81°40′59′′ 48.94 48.16 47.59 53.18

285539081262901 South Pine Lakes 4 inch UFA, SR 44 28°55′33′′ 81°26′29′′ 32.23 32.59 31.79 38.34

285536082044001 GN Smith west of Oxford 28°55′30′′ 82°4′40′′ 44.05 44.25 45.40 49.77

285608082233401 Camp mining well CE64 nr Holder 28°56′2′′ 82°23′34′′ 13.45 — — —

285612082294201 Pine Ridge #3 28°56′6′′ 82°29′42′′ 3.27 3.62 3.66 5.59

285720082201301 ROMP dp well 116 nr Tsala Apopka 28°57′14′′ 82°20′13′′ 30.55 31.48 30.97 33.00

285810081234101 Lwr Wekiva Rvr St Presv 4 inch UFA artesian 28°58′4′′ 81°23′41′′ 18.32 18.81 22.95 28.02

285827081331401 L-0390 Paul Shokly UFA 858-133-01 28°58′21′′ 81°33′14′′ 38.21 38.30 37.63 43.10

285812082360901 USGS well CE 7 nr Crystal Rvr 28°58′6′′ 82°36′9′′ 9.05 8.93 8.83 12.98

285900082072001 M-0031 USGS observation well CE36 at Pedro 28°58′54′′ 82°7′20′′ — 44.53 44.78 48.63

285930081430901 M-0062 KOA UFA SR 42 west of Altoona 28°59′24′′ 81°43′9′′ 49.01 48.18 47.36 51.74

285933082192501 CE 24 Drake Ranch 28°59′27′′ 82°19′25′′ 34.61 36.05 36.59 40.28

285930082283702 Citrus Sprgs golf course well 28°59′24′′ 82°28′37′′ 5.30 5.66 5.57 7.76

285953081590101 M-0467 Lake Weir Middle School 6 inch UFA 28°59′47′′ 81°59′1′′ 45.07 45.89 46.18 50.60

285951082350901 CE 6 SR488 E of Red Level 28°59′45′′ 82°35′9′′ 16.61 16.23 15.69 18.86

290000081380001 Pitman work center UFA - USFS 29°0′38′′ 81°38′28′′ 43.35 42.97 42.32 47.84

290052081271201 Central Baptist Youth Camp 4 inch UFA off CR42 29°0′46′′ 81°27′12′′ 40.19 39.57 39.15 45.09

290023082393601 USGS CE 89 US 19-98, so. of CFBC 29°0′17′′ 82°39′36′′ 9.79 10.04 10.17 14.57

290106082191001 USGS UFA CE23 nr Dunnellon 29°1′0′′ 82°19′10′′ 36.90 39.53 40.23 45.43

290107082400501 CE 88 US 19-98, no. of CFBC 29°1′1′′ 82°40′5′′ 1.62 1.60 2.04 5.16

290215082152401 Observation well CE74 nr Ocala 29°2′9′′ 82°15′24′′ 41.16 41.50 42.12 46.41

290200082432301 ROMP 124 D 8 inch UFA nr Yankeetown 29°1′54′′ 82°43′23′′ 2.10 2.22 2.48 3.81

290216082292001 QW observation well CE77 nr Dunnellon 29°2′10′′ 82°29′20′′ 10.91 9.81 10.00 12.68

290244081302601 Alexander Spgs Ck 4′′ UFA, Ocala NF FSR552B boat ramp 29°2′38′′ 81°30′26′′ 13.33 13.51 13.28 18.63

290227082250801 CE 75 29°2′21′′ 82°25′8′′ 51.23 49.27 50.51 53.03

290230082412501 ROMP 125 D 6 inch UFA, Crackertown 29°2′24′′ 82°41′25′′ 2.37 1.89 2.82 5.21

290306082032101 M-0465 Belleview Elem Sch 6 inch UFA 29°3′0′′ 82°3′23′′ 43.64 44.38 44.71 48.33

290306082232802 Fire Twr UFA CE73 at Dunnellon 29°3′0′′ 82°23′28′′ 50.49 49.10 51.32 53.26

290312082190601 QW UFA CE22 nr Dunnellon 29°3′6′′ 82°19′6′′ 43.26 45.12 46.23 50.12

290312082250801 CE 14 nr Dunnellon 29°3′6′′ 82°25′8′′ — — 36.96 —

290327081562001 M-0445 (prev. M-0380) Tiger Den nr Ocklawaha 29°3′30′′ 81°56′21′′ 46.39 46.91 — —

290400082091001 M-0041 CE33 4 inch UFA nr Ocala 29°3′54′′ 82°9′10′′ 42.32 42.90 43.26 46.89

290451081344401 L-0066 Alexander Springs UFA nr Astor 29°4′45′′ 81°34′44′′ 15.64 15.61 15.26 17.87

290455081530401 90415301 USGS observation well at Moss Bluff Park 29°4′49′′ 81°53′4′′ — — 49.51 —

290447082250901 QW observation well CE13 nr Rainbow Springs 29°4′41′′ 82°25′9′′ 34.95 34.88 35.16 —

290503082323101 T & J Ranch 4 inch UFA, SR 336 29°4′57′′ 82°32′31′′ 70.12 69.36 68.91 71.54

290514082270701 Rainbow Spg well nr Dunnellon 29°5′8′′ 82°27′7′′ 30.55 30.72 30.68 32.55

290628081425301 M-0061 Lookout Twr Bombing Rng UFA 29°6′22′′ 81°42′53′′ 46.08 45.28 44.62 50.90

292713082493601 H.E. MILLS 10′′ UFA nr Chiefland 29°27′7′′ 82°49′36′′ 19.45 17.75 18.04 18.44

292817081483602 M-0410 USGS 6 inch UFA, SW c/o FSR88/31, Ocala NF 29°28′11′′ 81°48′36′′ 19.12 19.57 19.16 21.51

292744082375201 Bronson High Sch 29°27′45′′ 82°37′53′′ 45.89 43.92 — —

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
92 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

USGS site 

identification 

number

Well name Latitude Longitude

Water level elevation, ft above NGVD 29

May-07 Sep-07 May-08 Sep-08

292816082234501 Smith Bros nr Raleigh 29°28′10′′ 82°23′45′′ 54.36 52.25 52.15 52.65

290633081375201 L-0407 Camp Ocala 6 inch UFA, Lake Sellars, Ocala NF 29°6′27′′ 81°37′52′′ 38.89 38.97 38.02 43.64

290605082372601 Goethe Rd 2′′ UFA, LCR 320 29°5′59′′ 82°37′26′′ 26.84 26.77 27.14 28.14

290646081314001 L-0441 USFS so. of Astor 29°6′40′′ 81°31′40′′ 15.58 15.89 15.90 19.96

290647081342101 L-0040 Alexander Sping 4 inch UFA 29°6′41′′ 81°34′21′′ 37.08 37.30 36.28 41.11

290739082245701 CE 12 29°7′33′′ 82°24′57′′ 33.94 33.74 34.25 37.15

290743082341501 Tidewater 12′′ UFA #1 29°7′37′′ 82°34′14′′ 52.20 51.39 51.84 55.03

290752082271101 SCE 116 Rainbow Acres 29°7′46′′ 82°27′11′′ 34.08 33.60 33.98 36.85

290820082032001 M-0037 USGS CE37 4 inch UFA nr Ocala 29°8′14′′ 82°3′20′′ — 42.27 42.12 45.13

290900081342002 (City of) Astor Park 8 inch UFA. 29°8′54′′ 81°34′20′′ 31.62 31.60 28.59 32.96

290910081360001 Camp McQuarrie (4-H Club Found) 6 inch UFA off SR40, 

Ocala NF

29°9′5′′ 81°36′2′′ 42.71 43.48 42.51 47.38

290913082245601 SCE 118 Lake Tropicana Ranchette 29°9′7′′ 82°24′56′′ 35.82 35.20 35.74 39.54

290910082315001 SCE 158 Little Lake Bonable well 29°9′4′′ 82°31′50′′ 41.98 40.48 41.28 46.16

291002081330601 L-0455 Astor 6 inch UFA 29°9′56′′ 81°33′6′′ 15.28 16.42 15.41 19.15

290953082031301 M-0038 USGS UFA CE79 nr Silver Springs 29°9′49′′ 82°3′13′′ 39.37 40.01 39.78 42.52

291004082382901 Dixie Lime 4 inch UFA, Lebanon Sta 29°9′58′′ 82°38′29′′ 21.81 18.43 20.92 25.52

291059082190801 M-0059 ROMP 120 nr cotton plant 29°10′53′′ 82°19′8′′ 41.98 41.73 42.23 45.79

291056082263201 Hershel Kyper so. of Romeo 29°10′50′′ 82°26′32′′ 37.45 36.58 37.15 41.27

291117081540501 M-0044 Redwater Lake UFA nr Lynne 29°11′11′′ 81°54′5′′ 45.75 46.06 46.60 49.54

291115082102901 M-0321 CE31 Golden Flake UFA, Ocala 29°11′9′′ 82°10′29′′ 41.77 41.95 42.07 45.20

291130082015001 M-0026 CE47 6 inch UFA nr Silver Springs 29°11′24′′ 82°1′50′′ 45.75 41.19 40.88 43.24

291448081381601 L-0340 Juiper Hunt Club UFA supply 29°14′42′′ 81°38′16′′ 0.27 1.12 0.19 2.30

291414082560901 USGS 6 inch UFA, Rosewood 29°14′8′′ 82°56′9′′ 9.46 9.50 9.78 11.00

291508082432901 Jiffy (141620) Cty Gulf Hammock 4 inch UFA 29°15′2′′ 82°43′29′′ 9.06 9.45 9.46 10.80

291625082085901 M-0419 Marion Co Sherritt UFA U.S. 301 29°16′19′′ 82°8′59′′ 41.57 41.83 41.85 44.57

291728081390501 Ponderosa Club CE30A 2 inch UFA Artesian (M-0316) 

nr Lisk Point

29°17′22′′ 81°39′5′′ 13.63 13.55 13.75 17.45

291712082351801 Robinson 4 inch UFA, SR 337 and LCR 158 29°17′6′′ 82°35′18′′ 48.99 48.37 47.24 46.92

291740081562001 M-0025 Gores Landing CE54 6 inch UFA nr Ocala 29°17′34′′ 81°56′20′′ 43.22 43.31 43.47 45.73

291849081411401 M-0021 Lake George UFA nr Salt Springs 29°18′43′′ 81°41′14′′ 14.33 14.69 14.39 18.23

291806082545601 USGS 6IN nr Rosewood 29°18′6′′ 82°54′56′′ 7.66 17.46 17.84 —

291910082341101 Bullock-Huber 4 inch UFA nr Williston 29°19′4′′ 82°34′11′′ 43.29 41.54 42.80 47.30

292146082182501 SR 316 west of Fairfield 29°21′40′′ 82°18′25′′ 47.51 46.97 47.60 48.19

292200081510001 M-0024 USGS UFA CE84 nr Salt Springs 29°21′54′′ 81°51′0′′ 23.75 23.66 24.48 24.56

292143082282201 Williston Airport 6 inch UFA 29°21′37′′ 82°28′22′′ 44.41 42.89 43.09 47.39

292204082022801 M-0052 Ft McCoy Fire Tower UFA 29°21′59′′ 82°2′29′′ 48.22 47.28 47.76 49.96

292310081582201 M-0463 Ft. McCoy Elemen School 6 inch UFA 29°23′4′′ 81°58′22′′ 49.13 49.17 48.83 55.51

292310082373701 Weems 6 inch UFA nr Bronson 29°23′4′′ 82°37′37′′ 51.39 51.85 50.25 54.25

292430082283001 Devils Den Sink CE-08 nr Williston 29°24′24′′ 82°28′30′′ 44.93 43.30 43.58 47.08

292507082560201 Neil Phillips 4 inch 29°25′6′′ 82°56′3′′ 4.98 3.92 2.68 11.80

292554082034501 M-0443 Citra Ranch nr Island Grove 29°25′49′′ 82°3′47′′ 52.41 51.30 52.09 54.67

292622082131801 M-0367 Huff UFA, McIntosh 29°26′16′′ 82°13′18′′ 49.49 48.06 48.91 51.73

292615082272601 ROMP 134 6 inch UFA nr Willison 29°26′9′′ 82°27′26′′ 44.80 43.15 43.17 46.96

292718082202601 Mahaffey UFA 29°27′12′′ 82°20′26′′ 52.05 50.90 51.03 52.12

Appendix 1. Elevation of water levels in all wells used to create Upper Floridan aquifer potentiometric surface maps. — Continued

[USGS, U.S. Geological Survey; NGVD 29, National Geodetic Vertical Datum of 1929; FLRD, Upper Floridan aquifer (UFA) well; WMA, wildlife 

management area; SWFWMD, Southwest Florida Water Management District; ft, feet; nr, near; dp, deep; —, no data]
Appendix 2. Major ion, nutrient, and field parameter 

water-quality data from the Lake Panasoffkee study 

area, July 2007, and December 2008 through January 2009
94 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Appendix 2. Major ion, nutrient, and field parameter water-quality data in the Lake Panasoffkee watershed, July 2007 and December 

2008 through January 2009. The columns of this table showing constituent values continue on the following two pages.

[USGS, U.S. Geological Survey; <, less than; E, estimated; ft, feet; nr, near; CaCO3, calcium carbonate; °C, degrees Celcius; NA, not applicable; LFA, Lower 

Floridan aquifer; mg/L, milligrams per liter; SA, surficial aquifer; SPG, spring; SW, surface water; UFA, Upper Floridan aquifer; μS/cm, microsiemens per 

centimeter; μg/L, micrograms per liter]

Reference 

number 

(fig. 14)

Site 

type

USGS site 

identification 

number

Station name

Well 

depth 

(ft below 

land 

surface)

Date 

(yyyy/mm/dd)

Time 

(EST)

Oxygen, 

dissolved 

(mg/L)

Field pH 

(standard 

units)

Specific 

conductance, 

field 

(μS/cm)

July 2007 Sampling Event

QW1 UFA 285125082085301 Big Jones Creek 48 ft UFA well 48 20070723 1200 0.2 7 326

QW2 SA 285125082085302 Big Jones Creek 7 ft SA well 7 20070723 1500 2.8 6.7 520

QW3 UFA 285035082075401 Little Jones Creek 48 ft UFA well 47 20070719 1200 0.1 7.2 328

QW4 SA 285035082075402 Little Jones Creek 11 ft SA well 11 20070719 1300 0.3 6.8 346

QW5 UFA 284811082091301 LP-3 152 ft UFA well 150 20070717 1500 0.1 7 857

QW6 UFA 284628082073801 LP-4 240 ft UFA well 240 20070716 1700 0.2 7.2 2,650

QW7 UFA 284628082073802 LP-4 120 ft UFA well 120 20070717 1100 3 7.5 272

QW8 SA 284628082073803 LP-4 30 ft SA well 30 20070716 1500 4.7 7.6 216

QW9 UFA 284528082055201 Sumter County 170 ft UFA well 170 20070718 1400 0.4 7.1 453

QW10 SA 284456082053102 LP-5 40 ft SA well 40 20070724 1100 1.9 6.2 197

QW11 UFA 284759082054101 LP-6 154 ft UFA well 154 20070724 1600 0.2 6.9 414

QW12 SA 284759082054102 LP-6 25 ft SA well 24 20070726 1100 1.1 6.6 285

QW18 SPG 02312664 Fenney Springs nr Coleman NA 20070730 1400 0.2 7.5 294

QW19 SPG 284709082024100 Blue Spring at Sumter County NA 20070731 1100 0.1 7.4 294

QW20 SPG 284530082034800 Belton's Millpond Complex nr Sumterville NA 20070726 1500 0.3 7.1 355

QW21 SPG 284525082040600 Maintenance Spring Run nr Sumterville NA 20070726 1300 1.1 6.6 444

QW22 SPG 284613082070500 Canal Spring Complex nr Panasoffkee NA 20070730 1100 0.2 7.4 431

QW23 SW 284534082054400 Shady Brook 350 ft above I–75 at Lake Panasoffkee NA 20070709 1305 5.4 7.3 392

QW24 SW 02312675 Little Jones Creek nr Rutland NA 20070709 945 5.5 7.3 412

QW25 SW 02312700 Outlet River at Panacoochee Retreats NA 20070709 1115 9.2 8.8 249

QW26 SW 284922082075900 Lake Panasoffkee nr Shell Point at Panasoffkee NA 20070710 1230 7.5 9 228

QW27 SW 284630082062700 Lake Panasoffkee nr SSE Shore at Panasoffkee NA 20070710 1310 7.7 8.3 280

QW28 SW 284718082070000 Lake Panasoffkee nr Tracy's Point at Panasoffkee NA 20070710 1255 7.2 8.1 252

QW29 SW 284852082082000 Lake Panasoffkee nr Idlewild Camp at Panasoffkee NA 20070710 1205 8.1 8.6 251

December 2008 through January 2009 Sampling Event

QW1 UFA 285125082085301 Big Jones Creek 48 ft UFA well 48 20081203 1230 0.2 7.4 355

QW2 SA 285125082085302 Big Jones Creek 7 ft SA well 7 20081203 1600 0.4 7.2 421

QW3 UFA 285035082075401 Little Jones Creek 48 ft UFA well 47 20081202 1230 0.2 7.6 331

QW4 SA 285035082075402 Little Jones Creek 11 ft SA well 11 20081202 1430 0.2 7.5 335

QW5 UFA 284811082091301 LP-3 152 ft UFA well 150 20081204 1130 0.1 7.2 826

QW6 UFA 284628082073801 LP-4 240 ft UFA well 240 20081208 1700 0.2 7.3 2,680

QW7 UFA 284628082073802 LP-4 120 ft UFA well 120 20081208 1400 3 7.8 281

QW8 SA 284628082073803 LP-4 30 ft SA well 30 20081204 1400 3.4 7.8 195

QW9 UFA 284528082055201 Sumter County 170 ft UFA well 170 20081216 1330 0.7 7.5 431

QW10 SA 284456082053102 LP-5 40 ft SA well 40 20081216 1500 1.7 6.6 193

QW11 UFA 284759082054101 LP-6 154 ft UFA well 154 20081210 1300 0.1 7.2 412

QW12 SA 284759082054102 LP-6 25 ft SA well 24 20081210 1700 0.1 7 309

QW13 SA 284734082071201 Tracys Point 5 ft shallow well 7.5 20081229 1600 0.3 7 371

QW14 SA 284756082061301 Coleman Landing 5 ft shallow well 5 20081229 1230 5.3 6.7 651

QW15 SA 284922082075901 Lake Panasoffkee 7 ft shallow well nr Shell Point 7 20090106 1230 0.3 7.5 427

QW16 LFA 284949082000501 ROMP 117 1000 ft LFA well 1,000 20081217 1300 0.2 7.6 390

QW17 UFA 284949082000502 ROMP 117 338 ft UFA well 338 20081217 1530 0.1 7.6 299

QW18 SPG 02312664 Fenney Springs nr Coleman NA 20081218 1030 0.5 7.4 294

QW19 SPG 284709082024100 Blue Spring at Sumter County NA 20081218 1300 0.1 7 294

QW21 SPG 284525082040600 Maintenance Spring Run nr Sumterville NA 20081218 1530 0.2 6.8 441

QW22 SPG 284613082070500 Canal Spring Complex nr Panasoffkee NA 20081218 1700 0.1 7.2 448

QW23 SW 284534082054400 Shady Brook 350 ft above I-75 at Lake Panasoffkee NA 20081222 1400 3.4 7.5 372

QW24 SW 02312675 Little Jones Creek nr Rutland NA 20081222 1030 4.5 7.4 345

QW25 SW 02312700 Outlet River at Panacoochee Retreats NA 20081221 1700 12.7 8.5 392

QW26 SW 284922082075900 Lake Panasoffkee nr Shell Point at Panasoffkee NA 20081221 1345 11.1 8.2 384

QW27 SW 284630082062700 Lake Panasoffkee nr SSE Shore at Panasoffkee NA 20081221 1515 10.9 8.2 406
Appendix 2 95

Appendix 2. Major ion, nutrient, and field parameter water-quality data in the Lake Panasoffkee watershed, 

July 2007 and December 2008 through January 2009. — Continued

[USGS, U.S. Geological Survey; <, less than; E, estimated; ft, feet; nr, near; CaCO3, calcium carbonate; °C, degrees Celcius; NA, 

not applicable; LFA, Lower Floridan aquifer; mg/L, milligrams per liter; SA, surficial aquifer; SPG, spring; SW, surface water; UFA, 

Upper Floridan aquifer; μS/cm, microsiemens per centimeter; μg/L, micrograms per liter]

Reference 

number 

(fig. 14)

Site 

type

USGS site 

identification 

number

Temperature, 

water 

(°C)

Calcium, 

dissolved 

(mg/L)

Magnesium, 

dissolved 

(mg/L)

Potassium, 

dissolved 

(mg/L)

Sodium, 

dissolved 

(mg/L)

Alkalinity,

field 

(mg/L as 

CaCO3)

Bromide, 

dissolved 

(mg/L)

Chloride, 

dissolved 

(mg/L)

Silica, 

dissolved 

(mg/L)

July 2007 Sampling Event

QW1 UFA 285125082085301 23.3 53.8 5.2 0.26 4.21 144 0.03 6.49 8.03

QW2 SA 285125082085302 25 87.5 6.88 0.3 6.5 254 0.06 9.22 9.7

QW3 UFA 285035082075401 23.2 48.9 5.77 1.37 11 125 E 0.01 6.18 11.9

QW4 SA 285035082075402 25.3 57.8 5.98 0.24 4.09 138 0.03 6.11 10.5

QW5 UFA 284811082091301 24.5 139 27.6 1.16 6.38 253 0.04 8.98 13.8

QW6 UFA 284628082073801 26 528 123 2.8 11.4 117 0.07 14.9 14.3

QW7 UFA 284628082073802 25.8 42.1 2.46 0.97 5.24 87 E 0.02 7.08 4.76

QW8 SA 284628082073803 26.5 38.7 3.42 1.19 1.85 89 <0.02 3.16 3.86

QW9 UFA 284528082055201 25.4 78.2 8.47 0.72 5.25 152 0.03 7.62 10.2

QW10 SA 284456082053102 25.1 28.9 1.74 1.09 7.19 81 0.04 7.19 6.72

QW11 UFA 284759082054101 23.4 78.8 2.64 0.27 4.1 210 0.03 6.62 9.45

QW12 SA 284759082054102 23.9 52.5 1.94 0.3 4.11 135 0.04 8.27 8.4

QW18 SPG 02312664 23.3 50.7 2.49 0.63 4.33 134 0.02 7.72 8.85

QW19 SPG 284709082024100 23.4 51.8 2.08 0.59 4.48 131 0.03 7.83 8.27

QW20 SPG 284530082034800 21.8 62.4 2.73 0.66 4.92 162 0.04 8.25 5.73

QW21 SPG 284525082040600 23.7 82.9 3.04 0.58 4.92 216 0.03 8.17 6.79

QW22 SPG 284613082070500 23.7 73.9 5.21 0.76 4.75 144 0.05 8.08 6.86

QW23 SW 284534082054400 27.5 74.2 3.03 0.63 5.26 161 0.04 9.04 8.66

QW24 SW 02312675 26.1 72.4 6.05 0.76 5.97 137 0.04 9.41 11.2

QW25 SW 02312700 31.8 32.9 6.01 1.03 7.49 59 0.07 12.5 8.4

QW26 SW 284922082075900 32.4 28.4 6.36 0.41 7.41 45 0.05 12 9.76

QW27 SW 284630082062700 33.1 46.3 4.24 0.29 5.37 93 0.05 9.14 6.23

QW28 SW 284718082070000 32.7 37.1 5.11 0.17 6.11 61 0.06 10.5 3.37

QW29 SW 284852082082000 31.6 34 6.04 0.79 7.03 64 0.07 11.5 11.2

December 2008 through January 2009 Sampling Event

QW1 UFA 285125082085301 22.5 61.3 5.4 0.26 4.67 164 0.03 7.46 8.17

QW2 SA 285125082085302 19.3 76.2 5.98 0.23 5.72 210 0.03 8.91 8.7

QW3 UFA 285035082075401 21.8 53.2 6.05 0.52 5.09 132 0.03 6.04 11

QW4 SA 285035082075402 21.6 56.3 5.98 0.3 4.18 136 0.05 6.13 10

QW5 UFA 284811082091301 22.7 144 25.9 1.15 6.93 280 0.04 9.72 12

QW6 UFA 284628082073801 24.5 554 130 2.91 11.9 120 0.06 14.5 13.2

QW7 UFA 284628082073802 24.8 45 2.66 1.04 5.24 86 E 0.02 7.09 4.96

QW8 SA 284628082073803 25.6 33.4 2.64 0.88 2.01 76 E 0.02 3.3 3.5

QW9 UFA 284528082055201 24.2 75.2 8.31 0.86 5.31 138 0.03 8.31 9.47

QW10 SA 284456082053102 26.6 31.3 1.94 1.23 6.74 78 0.04 7.19 6.07

QW11 UFA 284759082054101 22.9 79.5 2.74 0.27 4.18 205 0.02 6.65 8.47

QW12 SA 284759082054102 23.1 55.1 2.14 0.34 4.24 145 0.03 7.64 9.24

QW13 SA 284734082071201 21.9 60.1 9.75 2.9 12.1 127 0.03 21.3 5.66

QW14 SA 284756082061301 19.9 130 2.68 2.06 4.86 346 0.09 5 3.94

QW15 SA 284922082075901 22.8 66.1 11.7 0.81 5.07 142 0.04 7.71 10.5

QW16 LFA 284949082000501 24 66.3 10.2 1.12 5.36 165 0.04 8.21 13.8

QW17 UFA 284949082000502 23 53.9 4.3 0.71 4.8 142 0.04 7.5 12.3

QW18 SPG 02312664 23.4 52.8 2.55 0.67 4.32 131 0.03 8.4 8.62

QW19 SPG 284709082024100 23.5 54.1 2.02 0.61 4.25 128 0.03 8.24 8.06

QW21 SPG 284525082040600 23.6 86.7 3.05 0.64 5.06 213 0.03 9.08 6.98

QW22 SPG 284613082070500 23.8 83.8 5.65 0.86 4.69 158 0.07 8.6 7.03

QW23 SW 284534082054400 17.4 76 3.06 0.55 5.57 177 0.03 9.78 8.18

QW24 SW 02312675 16.9 63.4 5.47 0.47 6.1 157 0.03 10.4 10.6

QW25 SW 02312700 20.1 75.7 5.43 1.5 6.79 179 <0.02 11.8 14.9

QW26 SW 284922082075900 20.4 71.5 5.45 1.14 6.48 169 E 0.01 11.4 13.3

QW27 SW 284630082062700 20.3 77.4 4.41 1.35 6.3 177 <0.02 11.6 12.9
96 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida

Appendix 2. Major ion, nutrient, and field parameter water-quality data in the Lake Panasoffkee watershed, 

July 2007 and December 2008 through January 2009. — Continued

[USGS, U.S. Geological Survey; <, less than; E, estimated; ft, feet; nr, near; CaCO3, calcium carbonate; °C, degrees Celcius; NA, 

not applicable; LFA, Lower Floridan aquifer; mg/L, milligrams per liter; SA, surficial aquifer; SPG, spring; SW, surface water; UFA, 

Upper Floridan aquifer; μS/cm, microsiemens per centimeter; μg/L, micrograms per liter]

Reference 

number 

(fig. 14)

Site 

type

USGS site 

identification 

number

Sulfate, 

dissolved 

(mg/L)

Ammonia 

+ organic 

nitrogen 

(mg/L)

Ammonia 

(mg/L)

Nitrate 

+ nitrite 

(mg/L)

Nitrite 

(mg/L)

Orthophosphate 

(mg/L)

Phosphorus 

(mg/L)

Organic 

carbon, 

dissolved 

(mg/L)

Strontium, 

dissolved 

(μg/L)

July 2007 Sampling Event

QW1 UFA 285125082085301 15.1 E 0.08 0.044 <0.06 0.001 0.044 0.09 2.2 251

QW2 SA 285125082085302 2.68 0.51 0.326 <0.06 0.002 0.015 <0.04 8.5 274

QW3 UFA 285035082075401 31.5 <0.1 0.029 <0.06 E 0.001 0.095 0.09 1.4 312

QW4 SA 285035082075402 26.3 0.12 0.117 <0.06 E 0.001 0.047 0.06 0.8 314

QW5 UFA 284811082091301 206 0.38 0.244 <0.06 <0.002 0.059 0.07 5.1 6950

QW6 UFA 284628082073801 1,670 0.25 0.177 <0.06 <0.002 0.039 <0.08 1.8 10,600

QW7 UFA 284628082073802 18.9 <0.1 <0.02 4.98 <0.002 0.042 0.05 0.5 53.4

QW8 SA 284628082073803 12.7 E 0.08 <0.02 1.18 <0.002 0.145 0.11 1.3 87.5

QW9 UFA 284528082055201 67.3 <0.1 0.03 0.36 0.007 0.062 0.05 1 5,900

QW10 SA 284456082053102 4.8 <0.1 <0.02 0.16 <0.002 0.072 0.06 1.2 53

QW11 UFA 284759082054101 0.56 0.19 0.134 <0.06 <0.002 0.142 0.12 2.9 142

QW12 SA 284759082054102 3.3 0.18 0.039 <0.06 <0.002 0.062 0.08 2.6 59.5

QW18 SPG 02312664 5.6 E 0.06 0.053 0.14 <0.002 0.087 0.08 0.9 76.8

QW19 SPG 284709082024100 6.18 <0.1 <0.02 0.34 <0.002 0.074 0.06 0.8 86

QW20 SPG 284530082034800 12.5 0.34 0.159 <0.06 <0.002 0.056 0.06 2.6 142

QW21 SPG 284525082040600 8.61 0.1 <0.02 E 0.05 <0.002 0.045 0.05 1.1 99.6

QW22 SPG 284613082070500 56.7 E 0.05 E 0.016 0.9 <0.002 0.052 0.05 0.6 641

QW23 SW 284534082054400 24.3 0.26 E 0.011 0.11 E 0.001 0.052 0.06 4.9 231

QW24 SW 02312675 56.4 0.23 <0.02 0.47 E 0.001 0.027 0.04 2.6 330

QW25 SW 02312700 40.5 1 E 0.013 <0.06 <0.002 E 0.005 <0.04 11.6 312

QW26 SW 284922082075900 38.8 0.9 E 0.011 <0.06 <0.002 <0.006 <0.04 10.4 295

QW27 SW 284630082062700 32.4 0.47 0.02 <0.06 <0.002 E 0.004 E 0.02 6.3 376

QW28 SW 284718082070000 39.8 0.62 0.02 <0.06 <0.002 E 0.003 E 0.03 7.9 342

QW29 SW 284852082082000 37.9 0.81 0.02 <0.06 <0.002 E 0.005 E 0.02 11 286

December 2008 through January 2009 Sampling Event

QW1 UFA 285125082085301 12.4 0.12 0.044 <0.04 <0.002 0.049 0.09 2.2 257

QW2 SA 285125082085302 6.27 0.23 0.057 <0.04 <0.002 0.112 0.12 5.9 248

QW3 UFA 285035082075401 27.3 0.1 E 0.014 <0.04 <0.002 0.068 0.07 E 0.4 310

QW4 SA 285035082075402 27 E 0.07 0.039 <0.04 <0.002 0.046 0.06 0.5 312

QW5 UFA 284811082091301 183 0.45 0.249 <0.04 <0.002 0.058 0.06 5.7 5970

QW6 UFA 284628082073801 1,700 0.42 0.171 <0.04 <0.002 0.033 0.04 5.9 11,100

QW7 UFA 284628082073802 19.7 <0.1 0.02 4.31 E 0.001 0.042 0.05 E 0.4 65.8

QW8 SA 284628082073803 14.3 E 0.06 0.02 1.03 0.002 0.086 0.09 0.8 75.7

QW9 UFA 284528082055201 65.1 E 0.06 0.022 0.73 0.002 0.059 0.06 0.8 6150

QW10 SA 284456082053102 5.44 <0.1 0.02 0.13 0.002 0.08 0.09 0.6 58.4

QW11 UFA 284759082054101 <0.18 0.22 0.119 <0.04 0.002 0.136 0.12 2.4 140

QW12 SA 284759082054102 1.64 0.19 0.09 0.06 E 0.001 0.174 0.21 2.4 59.3

QW13 SA 284734082071201 51.8 0.2 0.021 0.17 0.036 0.462 0.44 2.5 926

QW14 SA 284756082061301 E 0.18 4.5 3.92 <0.04 <0.002 0.058 0.18 24.6 99.1

QW15 SA 284922082075901 62.1 0.13 0.075 <0.04 <0.002 0.049 0.05 1.8 950

QW16 LFA 284949082000501 29.5 0.11 0.059 <0.04 <0.002 0.03 E 0.04 0.9 758

QW17 UFA 284949082000502 2.15 0.14 0.081 <0.04 <0.002 0.081 0.09 1.1 122

QW18 SPG 02312664 6.33 0.11 0.02 0.59 0.067 0.078 0.08 1.6 72.6

QW19 SPG 284709082024100 6.71 <0.1 0.02 0.68 <0.004 0.078 0.08 0.8 82.2

QW21 SPG 284525082040600 9.63 E 0.09 0.02 0.22 0.014 0.044 0.05 0.7 102

QW22 SPG 284613082070500 56 E 0.06 0.02 1.04 E 0.002 0.053 0.06 0.7 697

QW23 SW 284534082054400 7.57 0.35 E 0.014 0.08 E 0.001 0.045 0.05 7.1 184

QW24 SW 02312675 11.9 0.38 E 0.012 0.64 0.002 0.028 E 0.04 7.5 294

QW25 SW 02312700 20.8 0.82 0.02 <0.04 <0.002 E 0.005 <0.04 14.1 381

QW26 SW 284922082075900 18.9 0.59 0.02 <0.04 <0.002 E 0.006 <0.04 12.1 345

QW27 SW 284630082062700 20.9 0.64 0.02 <0.04 <0.002 E 0.005 <0.04 13.5 345
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W. Scott McBride and others – – USGS/SIR 2010–5237 Hydrology, Water Budget, and Water Chemistry of Lake Panasoffkee, West-Central Florida