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 Title Page
 Letter of transmittal
 Table of Contents
 List of Illustrations
 Tables
 Abstract
 Introduction
 Purpose and scope - Area of investigation...
 Well numbering system
 Acknowledgements
 Hydrologic data
 Monitoring network
 Hydrologic framework
 Hydrologic conditions and...
 The potentiometric surface of the...
 Surface-water use - Streamflow
 Lake levels
 Water problems
 Summary and conclusions
 Back Cover



















STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Randolph Hodges, Executive Director



DIVISION OF INTERIOR RESOURCES
Robert 0. Vernon, Director



BUREAU OF GEOLOGY
Charles W. Hendry, Jr., Chief



Report of Investigation No. 64


HYDROLOGIC CONDITIONS
IN THE LAKELAND RIDGE AREA
OF POLK COUNTY, FLORIDA


By
Alton F. Robertson



Prepared by
UNITED STATES GEOLOGICAL SURVEY
in cooperation with
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
THE CITY OF LAKELAND, FLORIDA
and the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES


TALLAHASSEE, FLORIDA
1973







63 6r

C- 3


DEPARTMENT
OF
NATURAL RESOURCES



REUBIN O'D. ASKEW
Governor


RICHARD (DICK) STONE
Secretary of State



THOMAS D. O'MALLEY
Treasurer



FLOYD T. CHRISTIAN
Commissioner of Education


ROBERT L. SHEVIN
Attorney General



FRED 0. DICKINSON, JR.
Comptroller



DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Executive Director









LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee
June 27, 1973

Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

The growth of industry, phosphate mining, and citrus production
as well as population growth during the last two decades has
resulted in an increase in ground-water pumpage from about 11
billion gallons in 1950 to 27 billion gallons in 1970. Declines in
artesian water levels due to this pumpage are a subject of concern
to water managers.

The purposes of this report are to reveal existing hydrologic
data, determine trends of ground-water use, and identify potential
problems which may result from these trends.

It is hoped that this investigation will be of significant value to
water managers in the development and protection of the
fresh-water resources.

Respectfully yours,

Charles W. Hendry, Jr., Chief
Bureau of Geology













































Completed manuscript received
March 13, 1973
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by News-Journal Corporation
Daytona Beach, Florida

Tallahassee
1973



iv










CONTENTS
Page
Abstract................................... .. ............................................. 1
In trod u ctio n .......................................................................... ........................ 2
P purpose and scope .............. .. ........................... .... ...................... 3
Area of investigation ............................ ........................ .. ...................... 3
Methods of investigation..................... ....................... 3
W ell num being system ........................ ....... ..................... 5
Acknowledgem ents ................................... ..................... ... ................... 7
H ydrologic data ........................................................................ ................... 8
Previous investigations ............................................................................... 8
M monitoring netw ork ................. ...................................... ....................... 9
G round w ater ....................... .................... .................... 9
Surface w ater .................................... .... .................... 9
Hydrologic fram work .......................... .... ...................... 11
G eology .................................... .............. .................... .... 11
A q u ifers .............................................................................. ....................... 11
Hydraulic properties of the Floridan Aquifer .............................................. 12
Hydrologic conditions and trends ............................................ ...................... 15
G round-w ater use .................................................................. ..................... 15
The potentiometric surface of the Floridan Aquifer ........................................ 19
G round-w ater quality......................................................... ....................... 19
Surface-w ater use ................................................. .................................... 32
Stream flow ........... ........ .................. ... .................. .............. 32
L ake lev els ............................................................................ ..................... 37
W after problem s ........................................ ................................................... 43
W ater-level declines.............................................................. ..................... 43
Lakeland's w ater supply......................................................... ...................... 43
Sum m ary and conclusions ............................................................................... 46
Selected references........................... ... .. ....................... 51









ILLUSTRATIONS
Figure Page
1. Map of Polk County showing location of the area of investigation .................... 4
2. Map showing locations of gaging stations and selected wells in the
Lakeland ridge area ...................................................... ........................ 6
3. Diagram illustrating the U. S. Geological Survey well-numbering
system .......... ..... ........... ....... ............................................................. 7
4. Block diagram showing generalized ground-water geology in the
Lakeland ridge area .........................................................Facing Page 12
5. Map showing depth to zone of solution cavities in the lower part of the
Floridan aquifer .......................... ........ ... ... ... ........ .... ................ ... 13
6. Graph showing industrial, municipal, and irrigation pumpage and
citrus acreage under cultivation in the area of investigation, 1950-70 ........... 15
7. Bar graph of mean monthly municipal pumpage and mean monthly
precipitation at Lakeland, Florida, 1950-70 ........................................ .... 18
8. Contour map of the potentiometric surface of the Floridan aquifer,
M ay 1971 ..................................................... ...... ......... ................... 20
9. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer, September 1949 to June 1969 ........................ ................. 21
10. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer, June 1969 to May 1971............. ............... 22
11. Geophysical logs and water quality at various depths in Well 2. ................... 25
12. Geophysical logs and water quality at various depths in Well 25 .................. 26
13. Geophysical logs and water quality at various depths in Well 21 .................. 27
14. Geophysical logs and water quality at various depths in Well 14 ..... ............... 28
15. Schematic diagram of the quality-monitoringinstallation at Lakeland,
F lorida .............................................. ....................................... ....... 29
16. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer. June 1956 to June 1969. and locations of selected
water-quality-monitoring wells..................................... ..................... ......... 31
17. Bar graphs of mean annual flows of the Peace River at Bartow, North
Prong Alafia River near Keysville, and Blackwater Creek near
Knights. and mean annual precipitation over these basins; 1961-1970 .......... 38
18. Graphs of cumulative precipitation and flow of Peace River at Bartow,
North Prong Alafia River at Keysville, and Blackwater Creek near
Knights. 1951-1969 ............................................................... ............ 39
19. Graphs of mean monthly lake levels of Lake Parker at Lakeland and
Lake Hancock at Bartow and bar graph of annual precipitation at
Lakeland, 1961-1971 ...................................... .................... ............... 41
20. Graphs of water level in Well 26 tapping the Floridan aquifer and stage
of Scott Lake near Lakeland, 1960-1970 ................................................ 42
21. Map showing generalized drawdown due to Lakeland's municipal
pum page, 1970 ..................................................................................... 45
22. Maps showing predicted generalized drawdown south of Lakeland due
to projected municipal pumpage in 1980 and 1990 ...................................... 47
23. Maps showing predicted generalized drawdown north of Lakeland due
to projected municipal pumpage in 1980 and 1990 ............................... 48









TABLES
Table Page
1. Surface=water gaging stations, Lakeland ridge area ...................................... 10
2. Municipal pumpage by cities in and near the Lakeland ridge area, 1970 ............ 17
3. Chemical analyses of water samples from Well 24 ........................................ 30
4. Chemical analyses of water samples from selected wells in the
Lakeland ridge area ............................................................................. 33
5. Record of wells sampled for water quality analysis in the Lakeland
rid ge area ................ ........... ...................... .... ... ............. ............... ........ 36
6. Runoff from six drainage basins in and adjacent to the Lakeland Ridge
area .... ............. .... ....... ... ................ ... .. .... ... .. ..... .... ..... ..... ........ 40























































































~r.












HYDROLOGIC CONDITIONS IN THE LAKELAND RIDGE
AREA OF POLK COUNTY, FLORIDA


By
Alton F. Robertson

ABSTRACT
The Lakeland ridge area of this investigation covers about 300
square miles in northwest Polk County in central Florida. The
growth of industry, phosphate mining, and citrus production as
well as population growth during the last two decades has resulted
in an increase in ground-water pumpage from about 11 billion
gallons in 1950 to 27 billion gallons in 1970.
Decline in artesian water levels due to this pumpage is most
pronounced in the southern part of the area of investigation where
water levels have declined 50 feet or more in the last 20 years.
These declines may be accompanied by several effects of concern
to water managers. The most obvious of these is the necessity to
lower pump intakes to prevent the loss of suction. The hazard of
upward movement of water of poor quality is also increased by the
declines in fresh-water level. Current water analyses, however,
have revealed no widespread changes in quality of ground-water
that can be correlated with water-level decline.
The water levels of some lakes in the area were lower in June 1970
than in June 1961. For instance, the level of Scott Lake declined
about 4 feet. This decline may have been caused, at least in part, by
the decline in artesian levels, but rainfall deficiency during the
current drought is also a factor. However, not all lake levels
declined; the levels at Lakes Parker and Hancock were about the
same in June 1970 as they were in June 1961.
Municipal pumpage by Lakeland increased from 1 billion gallons
in 1950 to 5 billion gallons in 1970 and may reach 9 billion gallons by
1990, based on the established trend. The greatest drawdown
attributed to the city's pumpage in 1970 was about seven feet. This
drawdown was centered southwest of Lake Parker. If the
additional pumpage required to supply the city's needs for 1990
were drawn from wells south of Lakeland, the greatest drawdown







BUREAU OF GEOLOGY


would be about nine feet and would be centered near Scott Lake. If'
the additional pumpage were drawn from wells northeast of
Lakeland, the greatest drawdowns would be about nine feet, and
the center of pumping would shift to the northeast. As a result
water levels south of Lakeland would not be significantly affected
by the increase in city pumpage.
A widespread zone of solution features in the limestone of the
Floridan aquifer occurs at about 450 feet below mean sea level in
the northeast part of the area of investigation and at about 650 feet
below mean sea level in the south part of the area. Most wells open
to this zone yield several thousand gpm (gallons per minute) with
relatively small drawdowns.


INTRODUCTION
Lakeland, the largest city in Polk County, has grown from a
population of 27 when it was incorporated in 1885, to 41,550 in 1970.
The water resources of the area have played an important role in
this development.
The production and processing of citrus, which began late in the
1800's. draw upon the water resources both for irrigation supplies
and supplies for processing. At present (1970) more than 150,000
acres in Polk County are producing citrus. Polk County's
phosphate industry began in the 1800's. Production increased from
about 3.000 tons during the first years to over 30 million tons in 1967.
Tourism is another economically important industry, which, along
with many smaller industries, depends upon the area's water
resources for continued growth.
Central Florida is underlain by aquifers that contain large
quantities of fresh water. These aquifers supply most of water
needs in the Lakeland ridge area. The increased use of
ground-water to support agricultural and industrial operations and
to supply municipal needs has resulted in a continued decline in
ground-water levels in the area.
Changes in land-use patterns in the area that have taken place, or
may be expected to take place as the area develops, also have a
significant affect on the water resources. For example, as
phosphate deposits are depleted, less water will be pumped from
the aquifers to support the industrial operations associated with
phosphate mining. Industrial water use presently (1970) repre-
sents the greatest demands upon the aquifers. Likewise, suburban
developments have displayed citrus groves, thus reducing the
irrigation requirements.







REPORT OF INVESTIGATION NO. 64


PURPOSE AND SCOPE
Recognizing the importance of the water resources to the
continued development of the Lakeland ridge area and the need for
additional technical evaluation to aid in management of the
resources, the Southwest Florida Water Management District, the
city of Lakeland, and the Florida Bureau of Geology entered into a
cooperative investigation with the U. S. Geological Survey, to
evaluate current hydrologic conditions in the ridge area.
The specific purposes of this report are to:
1. Review, assemble, and summarize existing hydrologic data to
determine the adequacy of these data and the data-collection
network for defining present-day hydrologic conditions and for
monitoring possible changes in these conditions that may result
from possible changes in patterns of water-use.
2. Determine present-day conditions and trends of ground-water
quality, the potentiometric surface and water use.
3. Identify problems and anticipated problems resulting from
current hydrologic conditions and trends.
The 4-year investigation upon which this report is based began in
1967. It was made by the U. S. Geological Survey under the general
supervision of C. S. Conover, district chief for Florida and under
the immediate supervision of J. S. Rosenshein, chief of the Tampa
Subdistrict.

AREA OF INVESTIGATION
The Lakeland ridge area of this investigation includes about 300
square miles of northwest Polk County in central Florida (fig. 1).
The area is marked by a distinct topographic ridge more than 150
feet high that generally parallels the coastline. This ridge begins
rather abruptly about 10 miles northwest of Lakeland and extends
southeast about 35 miles to the vicinity of Fort Meade.
The Lakeland ridge is the drainage divide between the Peace
River basin on the east and the Hillsborough and Alafia River
basins on the west (fig. 1). To the north, the Withlacoochee River
has its headwaters in the Green Swamp area.

METHODS OF INVESTIGATION
An evaluation of hydrologic data and a comprehensive well
inventory, formed a base for expanding the network for monitoring
ground-water levels. Included in this network were five continuous
water-level recording stations.
Specific conductivity-measuring instruments were installed in a




































Figure 1. Map of Polk County showing the area of investigation.







REPORT OF INVESTIGATION NO. 64


well at Lakeland to monitor changes in the quality of the ground
water. Twenty wells, which had been sampled for water quality
during previous investigations, were again sampled to determine
water-quality changes. Water samples were obtained from 16 lake
and stream sites to establish the quality of the surface waters.
An inventory of ground-water withdrawals was made for 1970.
The owners or managers of industrial enterprises in the area of
investigation provided information concerning their water use.
Municipal water-use was obtained from the various city
water-plant supervisors. Estimates of citrus-irrigation with-
drawals were made by establishing a pilot study area, a 300-acre
grove. A relation between pumpage and electrical power use was
established. This relation provided a basis for computing annual
irrigation pumpage from power-consumption records, where
direct determinations were not possible.
In a series of packer tests, various intervals in the aquifer were
isolated, from which samples were pumped for water-quality
analyses. Geophysical logs were run on 10 wells, and geologic data
were obtained from 6 wells to extend the geologic coverage of
previous investigations.

WELL NUMBERING SYSTEM
For convenience of reference, all wells referred to in this report
are numbered serially and referred to serially on the figures and
tables of the report. The locations of wells referred to in this report
and U.S. Geological Survey surface-water gaging stations in the
area of investigation are shown on figure 2.
In addition to the serial numbers used in this report, all the
referenced wells are catalogued by the well-numbering system of
the Water Resources Division of the U.S. Geological Survey. This
latter well number should be used by the reader seeking further
information or exact locations of the wells. A cross reference
between the serial number of the well used in this report and the
Geological Survey number is provided as a part of table 5.
The Geological Survey number used to catalog wells is a
16-character number that defines the latitude and longitude of the
southeast corner of a 1-second quadrangle in which the well is
located. The first six characters of the well number include the
digits of the degrees, minutes, and seconds of latitude, in that
order. The six digits defining the latitude are followed by the letter
N which indicates north latitude for wells in the northern
hemisphere. The seven digits following the letter N give the
degrees, minutes, and seconds of longitude. The last digit, set off by








BUREAU OF GEOLOGY


*2*03. 20oo s5 ale so t*419'


EXPLANATION
a


0 I 2 3 4 MILES


Lae stage station and number

SIream-flow station and number

Will and number


Figure 2. Map showing locations of gaging stations and selected wells in the
Lakeland ridge area.

a period from the rest of the number, is assigned sequentially to
identify wells inventoried within a 1-second quadrangle.


26*00







REPORT OF INVESTIGATION NO. 64


An example of the well number is illustrated in figure 3. The
designation 275134N0815220.1 indicates the first well inventoried in
the 1-second quadrangle bounded by latitude 27051'34" on the south
and longitude 081052'201" on the east.

ACKNOWLEDGEMENTS
The writer wishes to express his appreciation to the many
citizens of the area, who permitted the sampling of water and
measuring of water levels in their wells, and to the well drillers,
who provided much helpful information. Appreciation is also


Figure 3. Diagram illustrating the U. S. Geological Survey well-numbering
system.







BUREAU OF GEOLOGY


expressed to the city and industry officials, who supplied
information on water use and power consumption.
Special thanks are given Mr. Tom Williams, whose cooperation
by furnishing information concerning Lakeland's water system
and special operation of the wells to provide specific information,
was especially helpful.

HYDROLOGIC DATA
The considerable amount of hydrologic data available for the
area of investigation can be grouped into two categories. The first
of these consists of geologic and hydrologic information gathered
as a result of previous investigations in and near the Lakeland
ridge area. The second consists of periodic measurements of
hydrologic parameters made on a continuing basis.
These hydrologic data and the additional data collected as a part
of this investigation are sufficient in general to define the
present-day hydrologic conditions.

PREVIOUS INVESTIGATIONS
Various aspects of the water resources of central Florida have
been investigated and the results of these investigations published
by the Florida Geological Survey and the U.S. Geological Survey.
These investigations provide a considerable amount of hydrologic
data useful in describing both historical and current hydrologic
conditions
Stewart (1966) provided the most recently published information
on the ground-water resources of Polk County. His work drew upon
many previous investigations describing the geology and
hydrology of central Florida, most of which are cited in the list of
selected references in this report. An investigation of ground water
in peninsula Florida by Stringfield (1936) provided some of the
early data.
The surface-water resources of Polk County were described by
Heath (1961), who presented hydrographs and stage-duration
curves for 107 gaging stations throughout the county. The chemical
quality of the ground water and surface water was discussed by
Black and Brown (1951) and Wander and Reitz (1951).
Kenner (1964) provided a map showing depth contours of
selected Florida lakes, one of which, Lake Parker, was in the area
of investigation. Stewart (1966) made a comprehensive study of the
hydrology of Lake Parker and Scott Lake. His evaluation indicated
that Lake Parker was underlain by sand and sandy clay and that







REPORT OF INVESTIGATION NO. 64


water from the lake leaked downward through these materials to
recharge the underlying aquifers.
The Withlacoochee River basin was described by Pride, Meyer,
and Cherry (1966). Streamflow rates and flow-duration curves
were given along with the results of chemical analyses of the water.
Although highly colored, the water in the streams was low in
mineral content.
Menke, Meredith, and Wetterhall (1961) discussed the Hills-
borough and Alafia River basins. Streamflow and water quality
were described. Both basins had surface water that was more
highly mineralized than the surface water in the Withlacoochee
basin.
Toler (1967) found fluoride concentrations to be abnormally high
in the surface waters of the Alafia and Peace River basins; he
discussed the source, amounts, and effects of fluoride in the
streams of these two basins.
Other investigations which were made of nearby areas in the
state or which provide additional information related to the water
resources of the area are listed in the selected references.


MONITORING NETWORK
GROUND WATER
The ground-water level monitoring network in the area of
investigation consists of 18 wells measured periodically by the U. S.
Geological Survey in cooperation with various state and local
agencies. The locations of these wells are shown on figure 2. As a
part of this investigation, about 50 other wells were measured to
define in greater detail the potentiometric surface of the Florida
aquifer, (fig. 8).
SURFACE WATER
The locations of the 18 stream and lake gaging stations
maintained by the U.S. Geological Survey in the area covered by
this report are shown on figure 2 and listed in table 1. Included in
table 1 are the maximum and minimum water levels or flow for the
period of record at each gaging station. The most recent (1970)
information on these gaging stations is tabulated in "Water
Resources Data for Florida," an annual publication of the U. S.
Geological Survey. These gaging stations adequately portray the
surface-water conditions in the area of investigation.








Table 1. Surface-water gaging stations in the Lakeland ridge area
(msl mean sea level)

EXTREME OF RECORD

Number (seetation Station Name Period of Maximum Gage Height Minimum Gage Height
Fig. 2) Lakes Record (feet above msl) Date (feet above msl) Date
1 Lake Deeson near Lakeland 1954-60, 1965-67 135.39 9/28/54 122.52 7/31/67
2 Lake Gibson near Lakeland 1954-59 145.1 10/8/57 141.4 7/5/56 W
3 Lake Parker at Lakeland 1949-69 131.81 8/2/60 127.92 5/24/49
9/13/60
4 Mirror Lake at Lakeland 1954-59 178.72 5/17/57 178.23 10/28/54
5 Wire Lake at Lakeland 1954-60 198.22 7/16/59 194.00 5/1/56
6 Lake Bonny at Lakeland 1954-60 131.92 9/11/59 123.12 7/10/56
7 Lake Beulah at Lakeland 1954-59 180.47 5/15/57 178.23 7/9/56 0
8 Lake Morton at Lakeland 1954-59 179.54 3/23/59 176.30 3/10/55
9 Lake Hunter at Lakeland 1954-59 162.97 4/17/57 160.95 4/27/56
10 Lake Hollingsworth at Lakeland 1954-59 133.2 5/17/57 131.9 5/1/56
10/21/58 0
11 Crystal Lake near Lakeland 1951-52, 1954-59 137.24 11/23/59 127.04 6/10/51
12 Lake Hancock near Highland City 1950-51, 1958-69 101.88 9/16/60 93.98 5/23/68
13 Scott Lake near Lakeland 1953-69 169.19 9/13/60 160.50 6/5/68

Maximum Flow Minimum Flow
Streams (cubic feet per second) (cubic feet per second)

14 Lake Parker Outlet at Lakeland 1955-59 12.2 5/2/57 0 Various occasions
15 Saddle Creek near Lakeland 1955-56 45.2 9/15/55 .38 3/8/56
16 Fox Branch near Socrum 1963-67 685 9/11/64 0 Various occasions
17 Saddle Creek at Structure 1963-67 516 9/13/65 0 Various occasions
P-11 near Bartow
18 Peace River at Bartow 1939-69 4140 9/24/47 1.1 4/27/68







REPORT OF INVESTIGATION NO. 64


HYDROLOGIC FRAMEWORK
The hydrologic framework consists of the natural elements
supplying water to the area and the medium through which the
water moves. These elements are described in the following
sections on the geology and aquifers. All surface water and water in
the aquifers are derived from precipitation that either falls on the
area or on upgradient areas.

GEOLOGY
The Lakeland ridge area is underlain by several thousand feet of
heterogeneous limestone and dolomite. In most of the area these
consolidated rocks are overlain by phosphatic clay beds which are,
in turn, overlain by surficial sand beds.
Vernon (1951) and many others have described the consolidated
rock units present in Polk County. The water-bearing strati-
graphic units in this area are: Lake City Limestone, Avon Park
Limestone, the Ocala Group, Suwannee Limestone, Tampa
Formation, and Hawthorn Formation. These units range in age
from Eocene to Miocene and are solution riddled and faulted. The
phosphatic clay and surficial material overlying the limestone are
described by Cathcart (1966) and others.
The stratigraphic nomenclature used in this report conforms to
the usage of the Florida Bureau of Geology. It conforms also to the
usage of the U. S. Geological Survey, with the exception of the
Ocala Group and its subdivisions and the Tampa Formation.

AQUIFERS
The ridge area is underlain by four aquifers, as described by
Stewart (1966); (1) the water-table aquifer, (2) the uppermost
artesian aquifer, (3) the secondary artesian aquifer, and (4) the
Floridan aquifer. Figure 4 shows the generalized geology and
relation of the aquifers.
Permeable zones in the sandy and clayey surficial materials
constitute the water-table aquifer, which is used for some domestic
supplies but is relatively unimportant as a source of water for other
uses. The sand of the aquifer is Miocene and Holocene (in older
literature called "Recent") in age.
The pebble phosphate deposits underlying the surficial deposits
form the uppermost artesian aquifer. Like the water-table aquifer,
this aquifer is used only for domestic and small irrigation supplies.
Limestone of the Hawthorn Formation constitutes the secondary
artesian aquifer, which is confined by the clay beds of the







BUREAU OF GEOLOGY


Hawthorn Formation above and the Tampa Formation below. The
secondary artesian aquifer is a source of water for domestic and
small irrigation supplies.
The water-bearing characteristics of these first three aquifers
are not well known, and they are not used extensively as sources of
supply.
The Floridan aquifer is the major source of water in the ridge
area and is comprised of limestones that range from Eocene to
Miocene in age. The Suwannee Limestone underlies most of the
Lakeland ridge area and constitutes the uppermost part.of the
Floridan aquifer in much of the area of investigation. In places,
limestone of the Tampa Formation is sufficiently connected
hydraulically with the underlying rocks to be included as part of the
aquifer.
Where the Suwannee Limestone is not present, the limestone
units of the Ocala Group constitute the uppermost part of the
Floridan aquifer. The base of the Avon Park Limestone is, for
practical purposes, the base of the aquifer, although some wells
penetrate the Lake City Limestone. Many wells in the Lakeland
ridge area are terminated in cavities in the limestone of the
Floridan aquifer. Such wells characteristically yield several
thousand gallons per minute with small drawdown.
Cavities in the aquifer develop over a long period of time as the
limestone is slowly dissolved by water moving through the aquifer.
Fissures and other structural features, which provide preferential
flow paths for water, localize solution activity and allow it to
proceed more rapidly. Cavities occur at various depths throughout
the area. In the northeast part of the area of investigation, many
wells penetrate a cavity zone at about 450 feet below msl (mean sea
level). This zone of solution cavities is deeper toward the south and
west and occurs rather uniformly at about 650 feet below msl in the
south part of the study area. Figure 5 shows the approximate depth
below land surface to this cavity zone. Although, as a general
feature, the zone seems to be continuous, individual wells at any
given site may not tap cavities at the mapped depth. At most sites
cavities occur at shallower depths, but, on the basis of information
supplied from drillers' logs, few cavities occur below the depths
indicated on figure 5.

Hydraulic Properties of the Floridan Aquifer
Transmissivity pertains to the water-conducting capacity of an
aquifer and is defined as the rate at which water is transmitted
through a unit width of the aquifer under a unit hydraulic gradient.


















EXPLANATION
---- wllIr ef M Me Iof I* Florida. # ,N


Figure 4. Block diagram showing generalized ground-water geology in the Lakeland ridge area.


Undiff em"flated Wait, table aquifer
d60:50% ( SdAdv 41410,
111"o pestle phosphate
can I Uliciffficof artesian aquifer j,
114.1"or. r.,.41,0h end secondary artal'on aquifer
T1.04 Formation H
Il.wAN Limestone s
Ofold Group Floridan aquifer 0
draft Poth Limestone AP
able 6""
"Ims"' '"If"


e t


4tQLoClC UNIT


MHYOROLOGIC UNIT


SYMBOL










REPORT OF INVESTIGATION NO. 64


28012'





26010'


28O00













55'







27 52'


8203' 82*00, 55'


8150' 82*49'


EXPLANATION O 1 2 3 4 MILES
600 I I- I
Line of equal depth
Shows depth to top of solution zone
Interval 50 feet
Datum is land surface


Figure 5. Map showing depth to zone of solution cavities in the lower part of the
Floridan aquifer.






BUREAU OF GEOLOGY


The storage coefficient is the volume of water an aquifer releases
from or takes into storage per unit surface area per unit change in
head.
The specific capacity of a well, that is, the quantity of water the
well yields for each foot of drawdown of the water level, can be used
as an indication of transmissivity (Brown, 1963, p. 336-338). Stewart
(1966) compiled data on the specific capacities of 173 wells in Polk
County. These values range from more than 2,000 gpm per ft
(gallons per minute per foot of drawdown) to less than 10 gpm per ft
in the area of investigation. The specific capacities in some places
varied considerably for wells a few hundred feet apart, especially
where one of the wells tapped a cavity system. The storage
coefficient cannot be determined from specific capacity but the
transmissivity can be estimated as suggested by Brown (1963, p.
336-338). Based on the range of specific capacities given above, the
transmissivity ranges from 536,000 ft2/day (square feet per day) to
about 2,700 ft2/day. These values are equivalent to 4,000,000 gpd per
ft (gallons per day per foot) and 20,000 gpd per ft in the units
formerly used to express transmissivity.
Aquifer tests in which pumping rates are controlled and the
resultant drawdowns are measured in observation wells provide a
more reliable method for determining transmissivity and storage
coefficient. Transmissivity of the Floridan aquifer has been
determined in various parts of the State by such tests. Menke,
Meredith, and Wetterhall (1961) reported a transmissivity of 29,500
ft2/day (220,000 gpd per ft) from tests near Plant City, about 10
miles west of Lakeland. The storage coefficient determined from
this test was 0.002. Stewart (1966) reported a value of 134,000 ft2/day
(1,000,000 gpd per ft) from tests northeast of Lake Parker, but did
not determine the storage coefficient.
As part of this investigation, an aquifer test was made west of
Lake Parker. From this test, a transmissivity of 100,000 ft2/day
(750,000 gpd per ft) and a storage coefficient of 0.0009 were
determined. These values compare favorably with those recently
determined from aquifer tests in Hillsborough and Pasco Counties
(J. W. Stewart, oral commun., Jan., 1971; and L. H. Motz, oral
commun., July, 1971, both of U.S. Geological Survey).
Transmissivity and storage-coefficient determinations for the
Floridan aquifer are applicable over a wide area but may not be
applicable for a specific location because of the heterogeniety of
the aquifer. However, the values determined in this investigation
are probably representative of the area and can be applied to
predict drawdowns caused by pumping from the Floridan aquifer.









REPORT OF INVESTIGATION NO. 64


EXPLANATION

Q Total pumpage
O Industrial pumpage
0 Citrus acreage
+ Phosphate pumpage
* Total municipal pumpage
X Lakeland's municipal pumpage
A Irrigation pumpage


I i I ,
1955 1960 1965


Figure 6. Graph showing industrial, municipal, and irrigation pumpage and
citrus acreage under cultivation in the area of investigation, 1950-70.



HYDROLOGIC CONDITIONS AND TRENDS

Ground-water Use

Ground water has historically been the most widely used source
of water supply in the area of investigation and in 1970 accounted


30





(r
Id



a-
V)

Z20
0
-j



Z
z
215-
_J
-1j

CD
4
0. 10-

a-

_J

z
z 5-
4


20-


15-
IS

0
z



Q .
4
Vt)



U,
10-



Id
QC
4

0
4
5-
U)

M



0-


1
1950


1970







BUREAU OF GEOLOGY


for about 90 percent of the total water used. Most wells that produce
more than 150 gpm (gallons per minute) are terminated in the
Floridan aquifer although numerous smaller wells used for
domestic and stock supplies are terminated in the shallower
aquifers.
Pumpage from the Floridan aquifer in the Lakeland ridge area
increased from about 11 billion gallons in 1950 to about 27 billion
gallons in 1970. The greatest demand for ground water is for
industrial use, principally for phosphate mining and processing.
Other industries that require large quantities of ground water are
citrus processing plants, ice plants, and commercial laundries.
The amount of water withdrawn for industrial use during 1970 was
estimated to be 18 billion gallons. This water-use figure was
derived from information supplied by various industries and from
discharge measurements of selected wells used for industrial
supply. Most of Florida's phosphate industry is south of the area of
investigation, but five mines are located within this area. Water
used by these five mines was estimated to be 25 percent of the water
used by all phosphate operations in central Florida. Water supplied
to industries through municipal systems is not included in this
figure.
Industrial water-use requirements have grown steadily over the
last two decades (fig. 6). Estimates of the amount of water pumped
before 1970 were adapted from Peek (1951), Stewart (1966), and
Kaufman (1967). Industrial water use is generally distributed
equally throughout the year, although some seasonal variations in
total industrial withdrawals are caused by citrus-processing
requirements.
Pumpage of ground water for irrigation varies considerably both
annually and seasonally, depending principally upon the
distribution of precipitation and the acreage under cultivation.
Citrus is the principal irrigated crop. In 1969, about 14,500 acres of
citrus were under cultivation in the area of investigation, as
compared with about 15,100 acres in 1965. The decrease is
principally due to replacement of citrus acreage by subdivision
development south of Lakeland. Citrus acreage inventories are not
available for years earlier than 1965. Acreage for these earlier
years were computed through use of county-wide inventories of
tree age and acreage (Florida Department of Agriculture Crop and
Livestock Reporting Service, 1970). About 10 percent of the Polk
County acreage was within the area of investigation during 1965,
1967, and 1969. Applying this percentage figure to the citrus
acreage totals in the county for the last two decades, an estimate of
the acreage within the area of investigation before 1965 was







REPORT OF INVESTIGATION NO. 64


obtained (fig. 6). An inventory of citrus irrigation wells indicated
that about 70 percent of the acreage was irrigated in 1970.
To determine withdrawals for irrigation, the discharge of many
wells were measured and rated against electric-power input to the
pump motors. The pumps, whose discharges were measured and
rated, were used to irrigate a total of about 2,000 acres.
Extrapolation of the unit-acreage water use for these citrus groves
to the irrigated acreage in the area of investigation indicated that
about 3 billion gallons were withdrawn for irrigation in 1970.
In 1970, most of the water for irrigation was pumped in May,
June, August, and December. Little irrigation was done in
February, March, September, and October.
The increase in irrigation water use over the last two decades is
shown on figure 6. Pumpage figures for the period before 1970 were
adapted from Kaufman (1967).
Lakeland is the largest municipal supplier of water in the area of
investigation. In 1970, Lakeland's pumpage was 5.23 billion gallons,
and the total municipal pumpage was 6.18 billion gallons.
Municipal withdrawals for cities in and adjacent to the area are
shown in table 2. Total annual municipal pumpage by Lakeland,
Bartow, and Mulberry is shown in figure 6 for 1950-1970. For the
period that pumpage records were not available for the two
smaller cities, their withdrawals were estimated on the basis of
Lakeland's pumpage.
Municipal pumpage varies considerably during the year mainly
because of higher demands for lawn irrigation during the dry
months. The relation of municipal pumpage to precipitation is
shown on figure 7.
The trend of increasing water use for municipal supplies will
probably continue with population growth. The trend for other
water users is extremely difficult to anticipate. The decrease in
citrus acreage since 1965 indicates that the irrigation demand has
temporarily stabilized and will probably decrease with increasing
urbanization. Annual and seasonal precipitation variations, of
course, are the principal control on annual water-use demands for
irrigation.
Table 2. Municipal pumpage by cities in and near the Lakeland ridge area, 1970
Million Million
Gallons Gallons
Lakeland 5230 Winter Haven 1685
Bartow 865 -' Haines City 554
Mulberry 84 Lake Wales 653
Plant City 805 Auburndale 320








18 BUREAU OF GEOLOGY


Industrial water use may increase as new industries develop.
However, this increase will be offset as phosphate deposits in the
area of investigation are depleted and the center of phosphate
mining moves farther south. In addition, many of the mining
operations have increased the use of recirculated water from
settling ponds thus reducing their pumpage from the aquifer.






J F M A M J J A S 0 N D


Cn
U
2:
03
z
--I
-I--
z


L-
a_
00




0
UJ
C-
a-


J F M A


M J J A S 0 N D


Figure 7. Bar graph of mean monthly municipal pumpage and mean monthly
precipitation at Lakeland, Florida, 1950-1970.


400

ZH-




-w 200
Wa-Q

az







REPORT OF INVESTIGATION NO. 64


THE POTENTIOMETRIC SURFACE
OF THE FLORIDAN AQUIFER
The level to which water rises in wells penetrating an aquifer
forms a surface referred to as the potentiometric surface. The
altitude of the potentiometric surface varies locally in response to
variations in both recharge to and discharge from the aquifer.
The potentiometric surface of the Floridan aquifer has been
mapped during several previous investigations, which included the
area of investigation (Stringfield, 1936; Black, Brown and Pearce,
1953; Stewart, 1966; Pride, Meyer and Cherry, 1966; Healy, 1962;
and Kaufman, 1967).
The potentiometric surface was mapped as a part of this
investigation in November 1968, near the end of the seasonal
water-level recovery, and in June 1969, May 1970, and May 1971,
near the end of seasonal water-level declines. The potentiometric
surface for May 1971 is shown on figure 8 and reflects the lowest
water levels in the aquifer in most of the area during this
investigation. The low water levels to the south of the area of
investigation are the result of heavy pumpage there.
Changes in the potentiometric surface from the time it was
mapped in September 1949 to the measurements made in June 1969
are shown on figure 9. These lowered levels indicate a reduction of
the quantity of water in storage in the aquifer. Changes have been
greatest in the south part of the area of investigation, where
pumpage is greatest. Water-levels have declined there by 50 feet or
more. In the northeast part, water-level declines have been
generally less than 10 feet.
Pumpage of ground water has resulted in additional water-level
declines from those shown in figure 9. Areas where water levels
lowered between June 1969 and May 1971 are shown in figure 10.

GROUND-WATER QUALITY
Although the water withdrawn from the Floridan aquifer
underlying the Lakeland ridge area is hard, it generally meets the
drinking-water quality standards established by the U. S. Public
Health Service (1962). Municipal supplies for cities in and near the
area are obtained from the aquifer. The water is normally
chlorinated and aerated for municipal use.
Lakeland maintains 27 public-supply wells throughout the city
and in nearby communities. Some of these wells yield water that
contains objectionable quantities of hydrogen sulfide. Hydrogen
sulfide imparts an unpleasant taste and odor to water. The gas can
be detected by smell in concentrations of less than 1 mg/1








BUREAU OF GEOLOGY


EXPLANATION
-- 50- 0 1 2 3 4 MILES
Potenliometlrc contour. I I I 1 I
Shows litstude of the potentiometric urfaoce.
Contour Inlerval 10 fest.
Datum is mean sea level


Figure 8. Contour map of the potentiometric surface of the Floridan aquifer, /
May 1971.







REPORT OF INVESTIGATION NO. 64


28*10'


28600











55'






27 52'


0 2 3 4 MILES
EXPLANATION I I I 1
20
Line of equal water-level decline.
Interval 10 feet


Figure 9. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer, September 1949 to June 1969.








BUREAU OF GEOLOGY


EXPLANATION 0 I 2 3 4 MILES

Line of equal water-lIvel decline.
Intervaol 10 feet


Figure 10. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer, June 1969 to May 1971.






REPORT OF INVESTIGATION NO. 64


milligrams per liter) (Hem, 1959). Hydrogen sulfide is not
Generally present in water from wells less than about 450 feet deep
n the area of investigation; its occurrence may be restricted to
certainn zones in the geologic section.
Water samples were obtained from two wells drilled about
one-quarter mile west of Lake Parker for city supply. One of these
wells was drilled to 920 feet below land surface and cased to 660 feet
(well 23, fig. 2). The concentration of hydrogen sulfide in this water,
as determined by the Lakeland city chemist, was 2.5 mg/1. The
second well, drilled about 1,000 feet farther west from the lake, is
650 feet deep (well 21, fig. 2). The concentration of hydrogen sulfide
in water from this well was negligible. Because the altitude of land
surface for both wells is nearly the same, the gas seems to be
present in the immediate area somewhere between 650 and 920 feet
below land surface and, therefore, between 150 and 400 feet below
the top of the Avon Park Limestone. However, no precise
correlation between the occurrence of hydrogen sulfide and depth
of wells could be established within the scope of this investigation.
Highly mineralized water containing chloride in concentrations
greater than 1,000 mg/1 is present near the area of investigation at
depths about 1,500 feet below mean sea level (Pride, Meyer, and
Cherry, 1966). The depth to this highly mineralized water is related
to the level of the less dense fresh water in the aquifer. Declines of
the fresh-water levels in the aquifer theoretically would allow the
highly mineralized water to move upward, depending upon the
amount of the water-level decline and the vertical permeability of
the aquifer.
In the area, no wells are accessible that are deep enough to locate
precisely the depth to the highly mineralized water. However,
based upon the relative densities of fresh water and sea water,
about 1 foot of decline in the fresh-water levels would allow the
highly mineralized water to move upward 40 feet in a homogeneous
aquifer. In central Polk County, south of the area of investigation,
water levels declined by 50 feet or more between September 1949
and May 1969 (Stewart and others, 1971). These declines indicate a
high potential for upward movement of the highly mineralized
water. No such movement was evident in the water samples taken
during the investigation. Two possible explanations for the
apparent lack of upward movement of the highly mineralized
water are (1) insufficient time has elapsed, or (2) the vertical
permeability of the lower formations is low. Probably both are
involved. Although no data are available to determine the vertical
permeability of the rock units underlying the Avon Park






BUREAU OF GEOLOGY


Limestone, observations by Stewart (1966, p. 26-30) indicate that
the permeability is low.
A well drilled and properly finished to the depth of the highly
mineralized water would allow monitoring of the possible upward
movement of this water. Construction of the well to allow
simultaneous measurements of the artesian pressure at the depth
of the highly mineralized water and artesian pressure in the
fresh-water zones of the Floridan aquifer would provide much
useful information.
To determine the quality of water at various depths in the
Floridan aquifer, a series of packer tests were undertaken. The
packer equipment consisted of two inflatable bladders, which
could be separated by intervals up to 40 feet. A submersible pump
was mounted between the bladders so that, when the bladders were
inflated by compressed gas, the isolated zone could be pumped for
water samples. Before the tests, geophysical logs were made of the
wells. The caliper log, which indicates variations in the size of the
borehole, was used as a basis for selecting the depth settings for the
packers. Cavity zones within the depth range 27 to 618 feet below
msl were selected for sampling. Figures 11, 12, 13, and 14 are
geophysical logs of the four wells selected for the tests. Also shown
on the figures are the results of chemical analyses of water
samples taken at the depths indicated. The fluid resistivity logs
indicate little difference in the total mineral content of the water
with depth, and the samples taken show no significant difference in
the quality of water in the aquifer down through the tested depths.
The heterogeneous nature of the aquifer and the results of these
tests suggest that water circulates freely within the aquifer
through the depths tested.
As a part of this investigation a pump was installed in an unused
city supply well 1,200 feet deep near Mirror Lake in Lakeland to
obtain periodic water samples for chemical quality analyses (well
24. fig. 2). The pump installation in the well, as shown in figure 15,
allows water samples to be taken at two depths in the aquifer, 500
feet and 1.100 feet below land surface. The water at the 500-foot
depth is not isolated from the water at the 1,100-foot depth, but
water from the two depths differed considerably in mineral
content. Chemical analyses for water samples taken from Well 24
are given in table 3. Water from the lower depth emits an odor of
hydrogen sulfide; water from the 500 ft depth does not.
From 1955 to 1962, water samples were collected for analysis
from several wells. Some were sampled again in 1969, and their
locations are shown in figure 16. The change in water level in the
Floridan aquifer between May 1956 and May 1969 is shown in figure






e smot m ss" ..... r
Si T V -
&M.n S,~^ f,"S


*A ~ ~ -- - ,-- !1
>













bp 1 UHIIO


,i =^ = = ::r


C&tnieal am..ls.s gI itrlgranms per luter exetfi for pa, temperature (4m togrees C),


!pdatb va
Tate water,fc


Fe s54


Alkain-fl ard-
It7 =95


Cmad7t
AITty


Tmp.


,4:@
1 0 i








Sc '"-I
1______~


, rl


fin fl71 nS7~ 27.O~


I 30'U.-32~
I ~
I 24~S-flfl

0~n7 I~,


fi -~ -


Oml, tap
finlflated I


Figure 11. Geophysical logs and water quality at various depths in Well 2.


0'


0









.0'S


177 1n54

fu IUI I6.5




B78 ET


t 18 B5


11


its,

31 a








3120


M

t3I

V
0









Ca2





I



0


. .1 -I .. n a l I u a "7t777


mi m e e











S s- ,l Ze o ne I
O~bn~~1WW 3Vu47 *IE lne


oi I


1 T --:: I--






- l- _EE E= : E -
q!i: ;== :


S lapled, ft


260-285


320-345
345-370







505-50


Chemicatl anlyees in milligrams per tler *a ept for pH, temperature (in degrees C),
4n4 conductivity (in microahos)


I Date


6-15-70


6-16.70
6-16-70







6-17-70


'Deplh to
vaerl I Fe I


SO, I


CL I


PO, I


Alktlfan Hard-
Ily ines


Conduct-
tlty I pH


S260


Figure 12. Geophysical logs and water quality at various depths in Well 25.


I Tamp,


26.5


25.0
25.0







25.0


7.7


7.6
7.7







7.7


0




0

0

p~e~


-4


I.I .... I _1 I I I I







"am Re ruam er
SStW.'^&S &fUM


ma -
wa -~


Chemicl! analyses in milltgrams per liter except for pH. tmperature (in degres C),
and conductivity (in hcraombos)
Zone Depth to AlltR- Hard- Conduct.
Sampted,ft Datte ert.ft Fe SOt Ci 70 F ty nes tvity pR Tep.
I P ISo,.. C. 1P 1T IM i Ra.


17 -4
-
















!


=,- -

"i iEi

::z! :, :: :


At 105
Packers C
inflated


200-225-




300-325




415-440
450-475


S-


4.0


354


25.0




26.0




26.0




26.0
26.0


4-29-70




5-11-70




5-11-70




5-11-70
5-11-70


Figure 13. Geophysical logs and water quality at various depths in Well 21.


L i W II i 1 II


8.0
8.0













as -se a war
6OWIL WW a~e' 94" 11


I L I
1 h,_ ^ _- d .




-0- 1 1 .1!= ^==









I J1 P U ^^Z^i ^ ^


Chemical analyses in mlligrams per liter except for pil, cemperature (in degrees C),
and conducilvity (In microahos)


Zone D pth to Alkalin- Hard- Conduct-
Sampied, ft nate -ater, t Ire 504 Cl P04 F ly neI I vity pH Temp.


At 120
packers
not Inflate




260-285


7-2-70






7-2-70





7-2-70


7.4 0.20






9.0 .30


7.4 24.5


Figure 14. Geophysical logs and water quality at various depths in Well 14.











REPORT OF INVESTIGATION NO. 64


WATER-LEVEL FLOAT




WELL CASING






OPEN HOLE IN LIMESTONE


-PUMP AND SWITCHING VALVE


UPPER LEVEL INTAKE


LOWER LEVEL INTAKE


NOTE: NOT TO SCALE


100-

SEA
LEVEL -



-168 -










-560 -


-920
-979 -








Table 3. Chemical analyses of water samples from Well 24
(Results in milligrams per liter except as indicated, Analyses by U.S. Geological Survey)











REPORT OF INVESTIGATION NO. 64


2812'




2810


2800.


82 03' 82t00' 55' 81Io50 82*49'


EXPLANATION


Boundary, dashed where
inferred


WATER LEVEL DECLINE,


0-5


IN FEET *I
Well sampled for wo-tr-
S quality anol, ilh
well number listed in
t10-I l 4


0 1 2 3 4 MILES
I I I I I


5-10


15-20


Greater than 20

Figure 16. Map showing generalized decline in the potentiometric surface of the
Floridan aquifer, June 1956 to June 1969, and locations of selected
water quality monitoring wells.






BUREAU OF GEOLOGY


16 for recognition of a possible relation between quality change and
water-level change. A comparison of the earlier analyses with
those of 1969 (table 4) shows no extensive deterioration of water
quality and little correlation between water-quality changes and
water-level changes for this period. The specific conductance of
water from wells 1, 3, and 18 increased by more than 10 percent.
Wells 1 and 3 are within the area where water levels declined 15 to
20 feet, and well 18 is within the area where the water level decline
was 0 to 5-foot. However, the specific conductance of water from
the other wells throughout the area of investigation either has not
changed or has decreased by more than 10 percent. The depths of,
and other information about these wells are given in table 5.
Any correlation between water-level declines and quality
changes may be overshadowed by other effects, such as
inadequate well construction or localized recharge. These effects
could allow more rapid downward movement of water into the
Floridan aquifer near the well from the water-table aquifer. That
such effects have produced rapid downward movement of water
into the Biscayne aquifer has been shown by Parker (1955, p. 609).

SURFACE-WATER USE
Surface water in the study area is used principally for recreation.
Surface water is also used as a coolant for power plants and for
transportation and dilution of municipal and industrial wastes.
Two electric-power plants on the shores of Lake Parker pumped
about 40 billion gallons from the lake in 1970. The water was
returned to the lake at a slightly higher temperature.
Lakeland's municipal sewage-treatment plant discharges into
Banana Lake, which discharges into Lake Hancock, and from
there flows into Peace River. The discharge from the treatment
plant was about 2.37 billion gallons in 1970. Discharge from the
plant varies throughout the year in about the same manner as the
municipal pumpage.
Bartow's sewage-treatment plants discharge into tributaries of
the Peace River. In 1970 the discharge was about 0.4 billion gallons.

STREAMFLOW
The volume of streamflow is dependent mainly upon the amount
of precipitation. This relation can be seen in figure 17. Conditions
that cause a significant increase in the downward percolation of
streamflow through the stream bed may reduce the annual volume
of flow. Declines of water levels in the Floridan aquifer have





Table 4. Chemical analyses of water samples from selected wells in the Lakeland ridge area
(Results in milligrams per liter except as indicated. Analyses by U.S. Geological Survey)
(Water level: a, from recorder chart; e, estimated; m, measured.)


8 Hardness
as CaCO3 2

> 6 'M o P I
oo o) oU q, o .o < S g.. ^ U)


U)01 CUU) C UCrfn4 li
~ 3~ -- u.. Ca" 0 0 Cn~- Q ~~Z E~


5-08-59
9-11-69
8-4-71
5-07-59
11-07-69
6-11-56
9-16-69
6-11-56
4-15-66
9-10-69
6-11-56
6-9-69
11-07-69
6-07-66
9-17-69
6-09-56
9-18-69


31e
61e

18a
34a
37e
55e
79m
101e
104e
33m
43a
31a
54e
55e
32e
37e


3.2
18
16
17
4.4
16
14


16






.16


0.01
.18


.03
.08
.54




0.0
0.12

2.4

.48


20
95
97
46
20
54
82


39


23

49

59


11
24
25
11
11
11
14


12


4.8

6.1

10


8.2
8.9
10.0
6.8
8.4
13
16


6.0


4.1



8.0


0.8
1.1
1.2
.8
1.0
.7
1.1


.6






.9


48
182
180
178
112
192
260


180


96



206


54
174
200
14
4.0
8.8
52

3.6
.0

8.0
0.3
.8
.4

.0


12
12
13
8.5
6.0
24
20

7.0
7.0

10.0
5.0
10
11

10


0.2
.6
0.3
.4
.3
.0
.2

.3
.2

0.3
0.6
.4
.5

.3


10


0.05


.2


.0

.2
.0
0.1
.2


.3
.5


157
491
473
191
117
227
336
178

176
286

102

212
237
221


95 56
339 190
348 201
160 14
96 4
180 23
262 49
156 --
158 -
148 0
216 -

77 0
150 -
148 -
188 -
188 19


234
650
673
326
205
396
485
299
319
290
418

170
325
310
383
350


7.4
7.6
7.0
7.7
7.3
7.4
7.5
7.2

7.9
7.4
7.3
7.8

7.6
7.2
8.2


25.0
25.0
26.0
25.0

25.0


25.0

24.4
24.5

24.5

25.0






Table .1, Ch'lemicial nulyses of water samples from selected wells







,' = r E o ,.
g 0I
^^ ~ ~ ~ U ag O.& 0S 5iS 3


3-16-62 18
3-25-63 -
9-18-69 1 10e 19
6-11-56 67e -
9-17-69 73e -
2-14-55 lie -
11-11-69 7m 22
2-15-55 28e -
9-17-69 23e -
9-26-56 28e -
9-17-69 29e -
12-05-55 27e -
11-09-59 15a 12
11-10-69 20m 16
6-09-56 57e -
9-18-69 59e -
6-11-56 100m -
9-19-69 110e -
6-09-56 86m -
'.- -G C o -


0.01

0.30

0.14
0.06
0.0
0.03
0.48

1.2

1.2
0.20

0.48

0.00

U.6


54 14 6.9
59 13 6.5
59 14 7.8

41 13 -
38 21 -
40 18 15
46 21 -
43 20 -
4.5 28 -
33 19 -
64 12 4.7
24 7.8 5.2
63 7.9 5.2

38 12 -

30 9.0 -

42 15 6.0


1.0
1.2
0.4



0.8






.5
.8


230
232
238


216
222
237

260

241
118
226





196


3.6 8.5 0.2
10.0 9.0 -
0.0 9.0 0.2

0.1 10 0.5
7.0 12 -
4.0 12 1.0
5.0 10 -
0.1 21 0.5
- 18 -
0.1 23 -
1.0 10 -
2.0 6.5 0.2
0.0 8.0 0.6

0.1 14 0.8

0.1 9.0 0.4

0.0 8.0 0.4


in the Lakeland ridge area, (cont'd.)


-Hardness
ns CaCO







0.2 238 192 4 395 7.3 -

12 245 205 i 389 7.6 26.0
0. 211 172 322 78 -
0.05 185 156 280 7.9 28.0
-0.2 238 12 36695 7.9 -
0.6 0.1 225 12 40370 8.0 23.5
-0.1 24411 172 380 7.8 -
0.04 218 156 320 8.1 24.0
-- 280 182 435 7.2 -
0.6 0.02 225 174 .0 310 7.6 23.0
211 202 362 7.6 -

115 92 196 7.9 -
1.2 0.2 218 190 365 8.0 23.5
168 228 14 4280 7.3 -
0.04 171 145 290 7.7 24.5
-0. 151 209 239 7.6 -

0.0 142 112 200 7.9 24.5
0.1 298 260 526 7.6 25.5
188 167 6 315 8.2 1 26. j


I18
S (


15

16










Table 4. Chemical analyses of


water samples from selected wells in the Lakeland ridge area. (cont'd.)


I
Cu


E


z
'oZ'


E
U55
tC3


0
MW


~-0
CA,-


v
S-~
U-.


V
5 ,
0


U)


1
'3 v'
M'0
V};=
SS


T


Hardness
as CaCO0


) cu

.3C ff
ro 'cc J


P

Cu
o ..~. 'Cu

Cu cr


-4 ~


- 0.01 35
- 50
22 0.05 60

- 0.15 26
14 0.31 40


18
12
22
28

5.3
4.4


14 0.61 39 5.0


5.2
3.7
7.9
12



4.8
4.7


166
174
252
322



142
146


1.0
0.10
1.0
0.0

0.1
2.8
0.0


7.0 -
4.0 0.3
12 -
17 0.3

11 0.4
6.0 0.4
6.0 0.3


0.6

0.05


0.0 0.07 1147 119
I


295
250
412


U)
5-
Cu
5-
U)
0.

0.


24.0


566 8.0 23.0
223 7.7 -
190 7.4 26.0
241 8.1 -
240 7.6 24.0


C.,
Cu
.5-
U,

,~Cu

Cu~


En
En c
C,0-


17

18

19

20


1-02-56
11-11-69
1-30-56
11-10-69
6-11-56
9-19-69
6-14-62
9-19-69


21m
22m
13m
18e
52m
61e

30e


I







36 BUREAU OF GEOLOGY


Table. 5. Record of wells sampled for water-quality analyses in the Lakeland ridge
area

Approximate thickness
of formation open to
well (feet)
Latitude-
Longitude
-- f= I 0fl| 2'
-- :rC -- o o


1 121 600 (a) 1904 0 56 173 171 275353N-0815033.1
2 100 710 237 ? ) 13 214 24r; 275326N-0815858.1
3 12- 252 90 1936 0 105 57 0 275751N-0815220.1
4 1 4 325 163 1955 0 0 162 0 275759N-0815813.1
122 1220 243 1948 0 0 207 770 275959N-0815525.1
6 137 300 (a) 1940 0 14 86 0 280159N-0820156.1
7 135 746 16O 1948 0 90 200 296 280254N-0815525.1
8 201 828 280 1945 0 34 203 311 280246N-0815704.1
9 158 635 114 1951 35 85 226 175 280227N-0815918.1
10 117 193 36 1954 62 95 0 0 280336N-0815128.1
11 123 355 55 1953 55 122 123 0 280325N-0815345.1
12 134 126 78 1953 0 33 15 0 280407N-0815443.1
13 138 311 265 1955 0 0 46 0 280503N-0815528.1
14 158 550 6(7 1939 51 97 115 220 280559N-0815748.1
15 207 261 203 1954 0 0 58 0 280529N-0815947.1
16 128 1285 375 1950 0 0 0 910 280606N-0815232.1
17 139 103 63 1956 0 40 0 0 280614N-0815636.1
18 135 411 53 1956 17 118 178 45 280702N-0815422.1
19 160 198 88 1952 27 83 0 0 280727N-0820113.1
20 145 140 135 1955 0 5 0 0 280922N-0815412.1
21 173 647 185 1968 280416N-0815719.1
22 173 660 198 1969 280416N-0815719.2
23 167 920 660 1968 280420N-0815707.1
24 188 1167 356 1925 280244N-0815708.1
25 216 820 262 1945 275646N-0815645.1
'Casing depth estimated to be 2<00 feet.


increased the head differential between the stream levels and the
water levels in the aquifer, thereby providing conditions favorable
for increasing stream losses. To investigate this possibility, graphs
were prepared in which cumulative annual precipitation (an
really weighted mean over the individual basin) was plotted
against cumulative annual flows of three streams Peace River
at Bartow, North Prong Alafia River at Keysville, and Blackwater
Creek near Knights (fig. 18). Because streamflow is dependent
mainly upon precipitation, any significant changes in the
streamflow-precipitation relationship, such as increases in stream






REPORT OF INVESTIGATION NO. 64


losses, would be indicated by a change in slope of the graph. No
significant changes in this relationship are evident for the period
considered, 1951-69. However, the effects of increased losses by
downward percolation from the streams may be offset by
increased outflow from settling ponds created by mining
operations during this period. No data were available to assess this
possibility.
Unit-area runoff from six drainage areas in or adjacent to the
area of investigation vary considerably. The unit-area runoff for
each of the six drainage areas is listed in table 6. The unit-area
runoff from the smaller drainage areas upstream from the gaging
stations, Peace Creek drainage canal near Alturas, and Lake Lulu
outlet near Eloise is much lower than from the four larger drainage
areas during 1947-69. These smaller areas contribute significantly
more recharge per unit area than the four larger ones. The many
lakes in the smaller drainage areas may cause higher evaporation
as well as higher unit-area recharge to the shallow aquifers.

LAKE LEVELS
Lake levels in this area respond more rapidly to local
precipitation than to any other hydrologic factor, rising during
extended periods of above normal rainfall and declining during
extended periods of below normal rainfall. This general relation
can be seen by comparing mean annual rainfall at Lakeland and
Bartow to mean monthly levels of Lakes Parker and Hancock (fig.
19). Although the outflow of these lakes is controlled, long-term
trends of mean water level can be defined adequately.
In addition to responding to variations in rainfall, the level of
some lakes, for example Scott Lake, also respond noticeably to
declines in ground-water level. The hydrograph of mean monthly
water level in Scott Lake (fig. 20), indicates that the lake level was
about 4 feet lower in June 1970 than in June 1961. On the other hand,
the mean water levels in Lakes Parker and Hancock were about the
same or somewhat higher in June 1970 than in June 1961. The trend
of lowered water levels in Scott Lake follows closely the trend of
lowered water levels in the Floridan aquifer during this period.
This correlation is apparent from the hydrograph of water levels in
well 26 (fig. 20). The well is about 4 miles north of Scott Lake (fig.
2). Stewart (1966) discussed the various influences that affect the
water level in Scott Lake and correlated the lake-level fluctuations
to water-level fluctuations in the secondary artesian aquifer.
Because fluctuations of the water level in the secondary artesian
aquifer are closely related to fluctuations of the water level in the









PRECIPITATION,
INCHES
N


gr4







.01.









pi
?aS4







Ito


z
0

z

z
m.1


mr
rn~
n-i





r
m


MEAN ANNUAL FLOW,
INCHES
o am 5 u


PRECIPITATION,
INCHES
o ."


MEAN ANNUAL FLOW,
INCHES
o 5 5


MEAN ANNUAL FLOW, INCHES
0 W 0 ( 0 W


PRECIPITATION,
INCHES
o S





400


A Blackwater Creek


near Knights


o 0
00 0
0a
oO A
AA


400
400


600
600


00 0
0o


800
800


I
1000


1200


CUMULATIVE PRECIPITATION, INCHES
Figure 18. Graphs of cumulative precipitation and flow of Peace River at Bartow, North Prong Alafia River at Keysville, and
Blackwater Creek near Knights, 1951-69.


I I I
EXPLANATION
0 Peace River at Bartow
0 North Prong Alafio river near Keyesville ,9


uJ
0
z
C.,
z


300-


200-






100 -


I
200


qos2








Table (. Runoff from six drainage basins In and adjacent to the Lukeland Ridge area"


Area 160 sqmi,
Peace Creek
Drainage canal
near Alturas
(cfsm)


1.056
1.312
1.031
.410
.631
.451
.981
1.025
.198
.081
.462
.550
1.356
1.762
.618
.195
.302
.296
.182
.483
.26
.33
.33


Area 23 sq.mi.
Lake Lulu
Outlet near
Eloise
(cfsm)


0.543
.878
.573
.255
.242
.203
.243
.756
.083
.048
.447
.556
1.447
1.652
.416
.163
.120
.160
.232
.865
.27
.18
.38


Area 207 sq.mi.
Peace River
near
Bartow
(cfsm)


1.239
1.313
.796
.456
1.089
.686
1.204
1.355
.436
.376
1.476
1.213
2.133
2.386
.982
.449
.685
.999
.688
1.003
.396
.560
.517


Area 253 sq,mi,
Peace River
near Zolfo
Springs
(cfsm)


3.490
2.166
2.434
1.193
1.146
.905
3.316
2.873
1.094
.750
1.798
1.952
3.324
3.126
1.343
1.379
1.596
1.537
1.324
1.217
1.024
1.822
1.478


1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
.1968
1969

Mean


Area 135 sq.mi.
North Prong
Alafia River
near Keyes-
ville(cfsm)


1.370
1.370
1.370
1.370
.619
.577
1.711
1.459
.822
.574
1.600
1.348
2.740
2.740
1.074
1.133
1.325
1.488
1.237
1.703
1.19
1.56
1.22


Area 110 sq.cmi.
Blackwater
Creek near
Knights
(cfsm)


-

0.55
.68
1.45
1.06
.42
.38
1.04
.61
2.15
2.34
.51
.52
.61
1.00
.78
.85
.46
.76
.86


1.37


a In cubic feet per second per square mile.


Water Year


1.84







ANNUAL PRECIPITATION,
INCHES


LAKE STAGE, FEET ABOVE MEAN SEA LEVEL


LAKE STAGE, FEET
ABOVE MEAN SEA LEVEL


C-'O

S-




s-8.







e CD






-. CD*

sDI


-







0 lo




d cl_


I I



S- m
V










BUREAU OF GEOLOGY


I I I I I I I I I I I


PERIODIC \
MEASUREMENTS


1960 1 1962 I 1964 1966 '


1968 1 1970


Figure 20. Graphs of water level in Well 26 tapping the Floridan aquifer and stage
of Scott Lake near Lakeland, 1960 to 1970.


170 r


62-



66-



70 -



74-


102 -



106


>168
LJ







166 -

U
Lit

cn





6LJ
!--


IL.


160 L-


82 -



8 -



90-






REPORT OF INVESTIGATION NO. 64


Floridan aquifer (Stewart 1966), a long-term trend of lowered
artesian water levels may result in a long-term lowering of some
lake levels.

WATER PROBLEMS
WATER-LEVEL DECLINES
The most immediate effect of declining water levels in wells is
loss of suction to pumps, requiring that pump intakes be lowered.
Continued water-level declines further increase the potential for
upward movement of highly mineralized water. Lowered water
levels in the Floridan aquifer increase recharge rates to the aquifer
in direct proportion to the head differential between the water level
in the Floridan aquifer and the higher water levels in the overlying
aquifers. The recharge increase supplied by the overlying aquifers
and, ultimately, the water-table aquifer results in some places in
the decline of lake levels.
Any increase in the amount of water used likely will be obtained
from the Floridan aquifer. Water levels in the aquifer will continue
to decline as withdrawals increase. These declines may be
modified somewhat if above-average precipitation occurs,
reducing the need for irrigation. Some increase in pumpage for
municipal and industrial purposes is probable; therefore,
continued water-level declines are anticipated.

LAKELAND'S WATER SUPPLY
Lakeland's water supply comes from 27 wells in the city and in
nearby communities. Water supplying the distribution system is
stored momentarily in small pressure tanks near each well. As
additional supplies are needed, new wells are drilled generally
near the area of need. Growth of the city has been toward the south,
where long-term water-level changes are most pronounced, thus
creating the necessity to drill wells near that area.
When a well is pumped, a cone of depression, or lowered water
levels, is created in the aquifer and is centered around the pumping
well. The shape of this cone of depression is dependent upon the
pumping rate and period and the hydraulic characteristics of the
aquifer and confining beds. Knowing these characteristics, the
shape of the cone can be defined for various rates for any given
period of pumping. After steady pumping has continued for a
sufficiently long time, the cone approaches an equilibrium
condition in which recharge induced into the aquifer is about equal
to the pumpage. Under these equilibrium conditions, water-level
declines due to steady pumping, cease. However, an increase in






BUREAU OF GEOLOGY


pumpage causes additional declines until a new equilibrium
condition is again established. When numerous wells are pumped
in an area, the individual cones of depression may overlap and
interfere with one another, resulting in a complex pattern of
drawdown, which becomes more difficult to describe and analyze
as the number of wells increase.
If only those wells pumped for municipal supply by Lakeland are
considered, the pattern of drawdown caused by their pumping can
be determined with reasonable accuracy. Utilizing the leaky-
aquifer method (Ferris and others 1962, p. 110-118) to determine
steady-state drawdowns, the cone of depression due to Lakeland's
pumpage of 5.23 billion gallons in 1970 was determined (fig. 21). The
greatest decline due to the city's pumpage was about 7 feet,
southwest of Lake Parker. The cone of depression bounded by the
5-foot decline line was elongated and extended from the north to
beyond the south of the city limits. Northwest of Scott Lake the
decline was about 6 feet.
To calculate drawdown, transmissivity of 100,000 ft2/day (750,000
gpd/ft) was used because it is assumed to be representative for the
Floridan aquifer underlying the area. The yield of each well was
taken as the continuous rate which, if maintained for 1 year, would
yield the actual quantity of water withdrawn during 1970. Because
actual pumping rates and time of pumping varied during the year,
the cone of depression shown in figure 21 is an approximation and
could not be expected to depict the actual drawdown at any specific
time.
The leakage factor used in calculating drawdown was 0.001
gpd/ft3 (gallons per day per square feet of surface area per foot of
head difference). This is about 6 inches per year under a head
difference of ten feet. Inasmuch as only Lakeland's well system
was considered, the drawdown shown on figure 21 is only a part of
the total drawdown of water levels in the area, as reflected in the
potentiometric-surface map for May 1971, (fig. 8).
To predict the drawdown that could be expected due to future
increases in the city's pumpage, the trend of annual pumpage
shown in figure 6 was extrapolated linearly to 1990. From this
extrapolation, the total annual municipal pumpage in 1980 and 1990
would be about 7 billion and 9 billion gallons, respectively.
Using these projected municipal withdrawals and following the
same method as above, the cone of depression resulting from
Lakeland's projected pumpage in 1980 and 1990 was determined.
The drawdowns shown on figure 22 would occur if the additional
pumpage required to meet the projected municipal needs in 1980
and 1990 were equally distributed among five city wells now used









REPORT OF INVESTIGATION NO. 64


EXPLANATION
5
Lines of equal water-leve
decline. Interval, I foot

Figure 21. Map showing generalized drawdown due to Lakeland's municipal
pumpage, 1970.






BUREAU OF GEOLOGY


south of Lakeland. All other wells were assumed to be pumped at
the same rate as during 1970. The general pattern of the cone of
depression is similar to that of 1970 (fig. 21), but the greatest
decline, 9 feet in 1990, occurs near Scott Lake south of Lakeland.
If the additional pumpage for 1980 and 1990 were supplied from
wells drilled northeast of Lakeland, the predicted cone of
depression due to the city's pumpage would be as shown in figure
23. Again it was assumed that existing city wells would be pumped
at the same rate as in 1970. The greatest decline, 9 feet in 1990,
occurs northeast of Lakeland near. the pumped wells. However,
water-level declines south of Lakeland in this case are about the
same as in 1970.
The cones of depression in figures 21, 22, and 23 are due only to
pumping for Lakeland's municipal supply. Pumping for industrial
and irrigation use in and near the area of investigation also produce
cones of depression, and the interaction of these drawdowns
produce the present configuration of the potentiometric surface
(fig. 8). Because most of the industrial and irrigation pumpage is
south of Lakeland, water-level changes have been more
pronounced there (fig. 10). Municipal wells drilled north of
Lakeland to supply increased demands would be more distant from
this center of pumping and would experience less interference
from other wells. Such a distribution would reduce the amount of
further water-level declines south of Lakeland, where industrial
and irrigation pumpage are more likely to increase through 1990.

SUMMARY AND CONCLUSIONS
Hydrologic data collected as a part of this and previous studies
are sufficient to define in general the present-day hydrologic
conditions in the area of investigation. The data-collection network
adequately measures artesian water levels and streamflow and
lake stages. Changes in the quality of the ground water can be
monitored by periodic sampling of selected wells. No observation
well is presently available to measure and monitor directly the
depth to the highly mineralized water underlying the fresh water of
the Floridan aquifer. A well drilled and properly finished to the
depth of this highly mineralized water in the area of greatest
water-level declines .would allow monitoring of the possible upward
movement of this water. Such monitoring would warn of possible
deterioration from this source before the fresh-water supply is
threatened. This well would need to be a multi-zone well to allow
simultaneous measurements of the artesian heads in the Floridan
aquifer and in the zone containing highly mineralized water.


























0
ir- -








"Id aroW *so *J' ; T
Sq .t i a i 1' ," Aei, its J J

1980 1990

EXPLANATION
-5
Lines of equal water-level
decline. Interval, i foot

0
Well

Figure 22. Maps showing predicted generalized drawdown south of Lakeland due to projected municipal pumpage in 1980 and
1990.








I If I tiI j


IS t -


ll'Dage, 1 0, ",













aIL9 Z a S

1980 1990

EXPLANATION
5-
Lines of equal water-level
decline. Interval, I foot
Figure 23. Maps showing predicted generalized drawdown north of Lakeland due to projected municipal pumpage in 1980 and
Ig 0090




Hydrologic conditions in the Lakeland Ridge area of Polk County, Florida ( FGS: Report of investigations 64 )
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Series Title: ( FGS: Report of investigations 64 )
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Creator: Robertson, Alton F.
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Table of Contents
    Copyright
        Copyright
    Front Cover
        Front Cover
    Title Page
        Page i
        Page ii
    Letter of transmittal
        Page iii
        Page iv
    Table of Contents
        Page v
    List of Illustrations
        Page vi
    Tables
        Page vii
    Abstract
        Page 1
    Introduction
        Page 2
    Purpose and scope - Area of investigation - Methods of investigation
        Page 3
        Page 4
    Well numbering system
        Page 5
        Page 6
    Acknowledgements
        Page 7
    Hydrologic data
        Page 8 (MULTIPLE)
    Monitoring network
        Page 9
        Page 10
    Hydrologic framework
        Page 11 (MULTIPLE)
        Page 12
        Page 12a
        Page 13
        Page 14
    Hydrologic conditions and trends
        Page 15 (MULTIPLE)
        Page 16
        Page 17
        Page 18
    The potentiometric surface of the Floridian aquifer - Ground-water quality
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
    Surface-water use - Streamflow
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
    Lake levels
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
    Water problems
        Page 43 (MULTIPLE)
        Page 44
        Page 45
    Summary and conclusions
        Page 46
        Page 47
        Page 48
    Back Cover
        Back Cover
Full Text
1|) FLORIDA GEOLOGICAL SURVEY^
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STATE OF FLORIDA DEPARTMENT OF NATURAL RESOURCES Randolph Hodges, Executive Director
DIVISION OF INTERIOR RESOURCES Robert O. Vernon, Director
BUREAU OF GEOLOGY Charles W. Hendry, Jr., Chief
Report of Investigation No. 64
HYDROLOGIC CONDITIONS IN THE LAKELAND RIDGE AREA OF POLK COUNTY, FLORIDA
By
Alton F. Robertson
Prepared by UNITED STATES GEOLOGICAL SURVEY in cooperation with SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT THE CITY OF LAKELAND, FLORIDA and the BUREAU OF GEOLOGY FLORIDA DEPARTMENT OF NATURAL RESOURCES
TALLAHASSEE, FLORIDA 1973


5-5-7.
DEPARTMENT OF
NATURAL RESOURCES
REUBIN O'D. ASKEW Governor
RICHARD (DICK) STONE
Secretary of State
ROBERT L. SHEVIN
Attorney General
THOMAS D. O'MALLEY
Treasurer
FRED O. DICKINSON, JR.
Comptroller
FLOYD T. CHRISTIAN
Commissioner of Education
DOYLE CONNER
Commissioner of Agriculture
W. RANDOLPH HODGES
Executive Director


LETTER OF TRANSMITTAL
Bureau of Geology Tallahassee June 27, 1973
Honorable Reubin O'D. Askew, Chairman Department of Natural Resources Tallahassee, Florida
Dear Governor Askew:
The growth of industry, phosphate mining, and citrus production as well as population growth during the last two decades has resulted in an increase in ground-water pumpage from about 11 billion gallons in 1950 to 27 billion gallons in 1970. Declines in artesian water levels due to this pumpage are a subject of concern to water managers.
The purposes of this report are to reveal existing hydrologic data, determine trends of ground-water use, and identify potential problems which may result from these trends.
It is hoped that this investigation will be of significant value to water managers in the development and protection of the fresh-water resources.
Respectfully yours,
Charles W. Hendry, Jr., Chief Bureau of Geology


Completed manuscript received March 13, 1973 Printed for the Florida Department of Natural Resources Division of Interior Resources
Bureau of Geology by News-Journal Corporation Daytona Beach, Florida
Tallahassee 1973


CONTENTS
Page
Abstract.......................................................................................................... 1
Introduction.................................................................................................... 2
Purpose and scope........................................................................................3
Area of investigation..................................................................................... 3
Methods of investigation................................................................................ 3
Well numbering system................................................................................. 5
Acknowledgements....................................................................................... 7
Hydrologicdata............................................................................................... 8
Previous investigations................................................................................. 8
Monitoring network...................................................................................... 9
Groundwater............................................................................................ 9
Surface water............................................................................................ 9
Hydrologic framework.....................................................................................U
Geology.......................................................................................................H
Aquifers.......................................................................................................H
Hydraulic properties of the Floridan Aquifer................................................12
Hydrologic conditions and trends......................................................................15
Ground-water use.........................................................................................15
The potentiometric surface of the Floridan Aquifer..........................................19
Ground-water quality....................................................................................I9
Surface-water use..........................................................................................32
Streamflow..................................................................................................32
Lake levels...................................................................................................37
Water problems...............................................................................................43
Water-level declines......................................................................................43
Lakeland's water supply................................................................................43
Summary and conclusions................................................................................46
Selected references..........................................................................................51


ILLUSTRATIONS
Figure P&P
1. Map of Polk County showing location of the area of investigation....................4
2. Map showing locations of gaging stations and selected wills in the
Lakeland ridge area...............................................................................6
3. Diagram illustrating the U. S. Geological Survey well-numbering
system.................................................................................................... 7
4. Block diagram showing generalized ground-water geology in the
Lakeland ridge area.........................................................Facing Page 12
5. Map showing depth to zone of solution cavities in the lower part of the
Floridan aquifer.................................................................................... 18
6. Graph showing industrial, municipal, and Irrigation pumpage and
citrus acreage under cultivation in the area of investigation, 1950-70...........15
7. Bar graph of mean monthly municipal pumpage and mean monthly
precipitation at Lakeland, Florida, 1950-70...............................................18
8. Contour map of the potentiometrie surface of the Floridan aquifer,
May 1971...............................................................................................20
9. Map showing generalized decline in the potentiometrie surface of the
Floridan aquifer, September 1949 to June 1969..........................................21
10. Map showing generalized decline in the potentiometrie surface of the
Floridan aquifer, June 1969 to May 1971....................................................22
11. Geophysical logs and water quality at various depths in Will 2.......................25
12. Geophysical logs and water quality at various depths in Well 25.....................26
13. Geophysical logs and water quality at various depths in Well 21.....................27
14. Geophysical logs and water quality at various depths in Well 14.....................28
15. Schematic diagram of the quality-monitoring installation at Lakeland.
Florida.................................................................................................29
t6. Map showing generalized decline in the potentiometrie surface of the Floridan aquifer, June 1956 to June 1969, and locations of selected water-quality-monitoring wells................................................................ 31
17. Bar graphs of mean annual flows of the Peace River at Bartow, North
Prong Alafia River near Keysville, and Blackwater Creek near
Knights, and mean annual precipitation over these basins; 1961-1970 .......... 38
18. Graphs of cumulative precipitation and flow of Peace River at Bartow,
North Prong Alafia River at Keysville, and Blackwater Creek near Knights. 1951-1969..............................................................................39
19. Graphs of mean monthly lake levels of Lake Parker at Lakeland and
Lake Hancock at Bartow and bar graph of annual precipitation at Lakeland, 1961-1971................................................................................41
20. Graphs of water level in Well 26 tapping the Floridan aquifer and stage
of Scott Lake near Lakeland, 1960-1970 ..................................................... 42
2t. Map showing generalized drawdown due to Lakeland's municipal
pumpage, 1970.......................................................................................45
22. Maps showing predicted generalized drawdown south of Lakeland due
to projected municipal pumpage in 1980 and 1990...................................... 47
23. Maps showing predicted generalized drawdown north of Lakeland due
to projected municipal pumpage in 1980 and 1990 ......................................48


TABLES
Table
1. Surface-watergtgingstations,Lakeland ridgearea..........................
2. Municipal pumpage by cities in and near the Lakeland ridge area, 1970
3. Chemical analysts of water samples from Well 24...........................
4. Chemical analyses of water samples from selected wells in the
Lakeland ridge area...................................................................
5. Record of wells sampled for water quality analysis in the Lakeland
ridgearea.................................................................................
6. Runoff from six drainage basins in and adjacent to the Lakeland Ridge
area.......................,...................................................................


HYDROLOGIC CONDITIONS IN THE LAKELAND RIDGE AREA OF POLK COUNTY, FLORIDA
By
Alton F. Robertson
ABSTRACT
The Lakeland ridge area of this investigation covers about 300 square miles in northwest Polk County in central Florida. The growth of industry, phosphate mining, and citrus production as well as population growth during the last two decades has resulted in an increase in ground-water pumpage from about 11 billion gallons in 1950 to 27 billion gallons in 1970.
Decline in artesian water levels due to this pumpage is most pronounced in the southern part of the area of investigation where water levels have declined 50 feet or more in the last 20 years. These declines may be accompanied by several effects of concern to water managers. The most obvious of these is the necessity to lower pump intakes to prevent the loss of suction. The hazard of upward movement of water of poor quality is also increased by the declines in fresh-water level. Current water analyses, however, have revealed no widespread changes in quality of ground-water that can be correlated with water-level decline.
The water levels of some lakes in the area were lower in June 1970 than in June 1961. For instance, the level of Scott Lake declined about 4 feet. This decline may have been caused, at least in part, by the decline in artesian levels, but rainfall deficiency during the current drought is also a factor. However, not all lake levels declined; the levels at Lakes Parker and Hancock were about the same in June 1970 as they were in June 1961.
Municipal pumpage by Lakeland increased from 1 billion gallons in 1950 to 5 billion gallons in 1970 and may reach 9 billion gallons by 1990, based on the established trend. The greatest drawdown attributed to the city's pumpage in 1970 was about seven feet. This drawdown was centered southwest of Lake Parker. If the additional pumpage required to supply the city's needs for 1990 were drawn from wells south of Lakeland, the greatest drawdown


would be about nine feet and would be centered near Scott Lake. II the additional pumpage were drawn from wells northeast o) Lakeland, the greatest drawdowns would be about nine feet, and the center of pumping would shift to the northeast. As a result water levels south of Lakeland would not be significantly affected by the increase in city pumpage.
A widespread zone of solution features in the limestone of the Floridan aquifer occurs at about 450 feet below mean sea level in the northeast part of the area of investigation and at about 650 feet bHow mean sea level in the south part of the area. Most wells open to this zone yield several thousand gpm (gallons per minute) with relatively small drawdowns.
INTRODUCTION
Lakeland, the largest city in Polk County, has grown from a population of 27 when it was incorporated in 1885, to 41,550 in 1970. The water resources of the area have played an important role in this development.
The production and processing of citrus, which began late in the 1800's. draw upon the water resources both for irrigation supplies and supplies for processing. At present (1970) more than 150,000 acres in Polk County are producing citrus. Polk County's phosphate industry began in the 1800's. Production increased from j about 3,000 tons during the first years to over 30 million tons in 1967. I Tourism is another economically important industry, which, along j with many smaller industries, depends upon the area's water resources for continued growth.
Central Florida is underlain by aquifers that contain large quantities of fresh water. These aquifers supply most of water needs in the Lakeland ridge area. The increased use of ground-water to support agricultural and industrial operations and to supply municipal needs has resulted in a continued decline in ground-water levels in the area.
Changes in land-use patterns in the area that have taken place, or may be expected to take place as the area develops, also have a significant affect on the water resources. For example, as phosphate deposits are depleted, less water will be pumped from the aquifers to support the industrial operations associated with phosphate mining. Industrial water use presently (1970) represents the greatest demands upon the aquifers. Likewise, suburban developments have displayed citrus groves, thus reducing the irrigation requirements.


PURPOSE AND SCOPE
Recognizing the importance of the water resources to the continued development of the Lakeland ridge area and the need for additional technical evaluation to aid in management of the resources, the Southwest Florida Water Management District, the city of Lakeland, and the Florida Bureau of Geology entered into a cooperative investigation with the U. S. Geological Survey, to evaluate current hydrologic conditions in the ridge area.
The specific purposes of this report are to:
1. Review, assemble, and summarize existing hydrologic data to determine the adequacy of these data and the data-collection network for defining present-day hydrologic conditions and for monitoring possible changes in these conditions that may result from possible changes in patterns of water-use.
2. Determine present-day conditions and trends of ground-water quality, the potentiometric surface and water use.
3. Identify problems and anticipated problems resulting from current hydrologic conditions and trends.
The 4-year investigation upon which this report is based began in 1967. It was made by the U. S. Geological Survey under the general supervision of C. S. Conover, district chief for Florida and under the immediate supervision of J. S. Rosenshein, chief of the Tampa Subdistrict.
AREA OF INVESTIGATION
The Lakeland ridge area of this investigation includes about 300 square miles of northwest Polk County in central Florida (fig. 1). The area is marked by a distinct topographic ridge more than 150 feet high that generally parallels the coastline. This ridge begins rather abruptly about 10 miles northwest of Lakeland and extends southeast about 35 miles to the vicinity of Fort Meade.
The Lakeland ridge is the drainage divide between the Peace River basin on the east and the Hillsborough and Alafia River basins on the west (fig. 1). To the north, the Withlacoochee River has its headwaters in the Green Swamp area.
METHODS OF INVESTIGATION
An evaluation of hydrologic data and a comprehensive well inventory, formed a base for expanding the network for monitoring ground-water levels. Included in this network were five continuous water-level recording stations.
Specific conductivity-measuring instruments were installed in a


Figure 1. Map of Polk County showing the area of investigation.


well at Lakeland to monitor changes in the quality of the ground water. Twenty wells, which had been sampled for water quality during previous investigations, were again sampled to determine water-quality changes. Water samples were obtained from 16 lake and stream sites to establish the quality of the surface waters.
An inventory of ground-water withdrawals was made for 1970. The owners or managers of industrial enterprises in the area of investigation provided information concerning their water use. Municipal water-use was obtained from the various city water-plant supervisors. Estimates of citrus-irrigation withdrawals were made by establishing a pilot study area, a 300-acre grove. A relation between pumpage and electrical power use was established. This relation provided a basis for computing annual irrigation pumpage from power-consumption records, where direct determinations were not possible.
In a series of packer tests, various intervals in the aquifer were isolated, from which samples were pumped for water-quality analyses. Geophysical logs were run on 10 wells, and geologic data were obtained from 6 wells to extend the geologic coverage of previous investigations.
WELL NUMBERING SYSTEM
For convenience of reference, all wells referred to in this report are numbered serially and referred to serially on the figures and tables of the report. The locations of wells referred to in this report and U.S. Geological Survey surface-water gaging stations in the area of investigation are shown on figure 2.
In addition to the serial numbers used in this report, all the referenced wells are catalogued by the well-numbering system of the Water Resources Division of the U.S. Geological Survey. This latter well number should be used by the reader seeking further information or exact locations of the wells. A cross reference between the serial number of the well used in this report and the Geological Survey number is provided as a part of table 5.
The Geological Survey number used to catalog wells is a 16-character number that defines the latitude and longitude of the southeast corner of a 1-second quadrangle in which the well is located. The first six characters of the well number include the digits of the degrees, minutes, and seconds of latitude, in that order. The six digits defining the latitude are followed by the letter N which indicates north latitude for wells in the northern hemisphere. The seven digits following the letter N give the degrees, minutes, and seconds of longitude. The last digit, set off by


EXPLANATION
IB I
Ut otooo notion and numbar
A
Sirtam-floa notion and iwntbor
Will and numbtr
Figure 2. Map showing locations of gaging stations and selected wells in the Lakeland ridge area.
a period from the rest of the number, is assigned sequentially to identify wells inventoried within a 1-second quadrangle. '


An example of the well number is illustrated in figure 3. The designation 275134N0815220.1 indicates the first well inventoried in the 1-second quadrangle bounded by latitude 2751'34" on the south and longitude 08152'20" on the east.
ACKNOWLEDGEMENTS
The writer wishes to express his appreciation to the many citizens of the area, who permitted the sampling of water and measuring of water levels in their wells, and to the well drillers, who provided much helpful information. Appreciation is also
Figure 3. Diagram illustrating the U. S. Geological Survey well-numbering system.


expressed to the city and industry officials, who supplied information on water use and power consumption.
Special thanks are given Mr. Tom Williams, whose cooperation by furnishing information concerning Lakeland's water system and special operation of the wells to provide specific information, was especially helpful.
HYDROLOGIC DATA
The considerable amount of hydrologic data available for the area of investigation can be grouped into two categories. The first of these consists of geologic and hydrologic information gathered as a result of previous investigations in and near the Lakeland ridge area. The second consists of periodic measurements of hydrologic parameters made on a continuing basis.
These hydrologic data and the additional data collected as a part of this investigation are sufficient in general to define the present-day hydrologic conditions.
PREVIOUS INVESTIGATIONS
Various aspects of the water resources of central Florida have. been investigated and the results of these investigations published by the Florida Geological Survey and the U.S. Geological Survey. These investigations provide a considerable amount of hydrologic data useful in describing both historical and current hydrologic conditions
Stewart (1966) provided the most recently published information on the ground-water resources of Polk County. His work drew upon many previous investigations describing the geology and hydrology of central Florida, most of which are cited in the list of selected references in this report. An investigation of ground water in peninsula Florida by Stringfield (1936) provided some of the early data.
The surface-water resources of Polk County were described by Heath (1961), who presented hydrographs and stage-duration curves for 107 gaging stations throughout the county. The chemical quality of the ground water and surface water was discussed by Black and Brown (1951) and Wander and Reitz (1951).
Kenner (1964) provided a map showing depth contours of selected Florida lakes, one of which, Lake Parker, was in the area of investigation. Stewart (1966) made a comprehensive study of the hydrology of Lake Parker and Scott Lake. His evaluation indicated that Lake Parker was underlain by sand and sandy clay and that


water from the lake leaked downward through these materials to recharge the underlying aquifers.
The Withlacoochee River basin was described by Pride, Meyer, and Cherry (1966). Streamflow rates and flow-duration curves were given along with the results of chemical analyses of the water. Although highly colored, the water in the streams was low in mineral content.
Menke, Meredith, and Wetterhall (1961) discussed the Hillsborough and Alafia River basins. Streamflow and water quality were described. Both basins had surface water that was more highly mineralized than the surface water in the Withlacoochee basin.
Toler (1967) found fluoride concentrations to be abnormally high in the surface waters of the Alafia and Peace River basins; he discussed the source, amounts, and effects of fluoride in the streams of these two basins.
Other investigations which were made of nearby areas in the state or which provide additional information related to the water resources of the area are listed in the selected references.
MONITORING NETWORK GROUND WATER
The ground-water level monitoring network in the area of investigation consists of 18 wells measured periodically by the U. S. Geological Survey in cooperation with various state and local agencies. The locations of these wells are shown on figure 2. As a part of this investigation, about 50 other wells were measured to define in greater detail the potentiometric surface of the Florida aquifer, (fig. 8).
SURFACE WATER
The locations of the 18 stream and lake gaging stations maintained by the U.S. Geological Survey in the area covered by this report are shown on figure 2 and listed in table 1. Included in table 1 are the maximum and minimum water levels or flow for the period of record at each gaging station. The most recent (1970) information on these gaging stations is tabulated in "Water Resources Data for Florida," an annual publication of the U. S. Geological Survey. These gaging stations adequately portray the surface-water conditions in the area of investigation.


Table 1. Surface-water gaging stations In the Lakeland ridge area (msl mean sea level)
EXTREME OF RECORD
Gaging Station t. Number (see Station Name Period of Maximum Gage Height Minimum Gage Height
Fig. 2) Lakes Record (feet above msl) Date (feet above msl) Date
1 Lake Deeson near Lakeland 1954-60, 1965-67 135.39 9/28/54 122.52 7/31/67
2 Lake Gibson near Lakeland 1954-59 145.1 10/8/57 141.4 7/5/56
CO Lake Parker at Lakeland 1949-69 131.81 8/2/60 127.92 5/24/49
9/13/60
4 Mirror Lake at Lakeland 1954-59 178.72 5/17/57 178.23 10/28/54
5 Wire Lake at Lakeland 1954-60 198.22 7/16/59 194.00 5/1/56
6 Lake Bonny at Lakeland 1954-60 131.92 9/11/59 123.12 7/10/56
7 Lake Beulah at Lakeland 1954-59 180.47 5/15/57 178.23 7/9/56
8 Lake Morton at Lakeland 1954-59 179.54 3/23/59 176.30 3/10/55
to Lake Hunter at Lakeland 1954-59 162.97 4/17/57 160.95 4/27/56
H> Lake Hollingsworth at Lakeland 1954-59 133.2 5/17/57 131.9 5/1/56
10/21/58
11 Crystal Lake near Lakeland 1951-52, 1954-59 137.24 11/23/59 127.04 6/10/51
12 Lake Hancock near Highland City 1950-51, 1958-69 101.88 9/16/60 93.98 5/23/68
13 Scott Lake near Lakeland 1953-69 169.19 9/13/60 160.50 6/5/68
Maximum Flow Minimum Flow
Streams (cubic feet per second) (cubic feet per second)
14 Lake Parker Outlet at Lakeland 1955-59 12.2 5/2/57 0 Various occasions
15 Saddle Creek near Lakeland 1955-56 45.2 9/15/55 .38 3/8/56
16 Fox Branch near Socrum 1963-67 685 9/11/64 0 Various occasions
17 Saddle Creek at Structure 1963-67 516 9/13/65 0 Various occasions
P-H near Bartow
18 Peace River at Bartow 1939-69 4140 9/24/47 1.1 4/27/68
O


HYDROLOGIC FRAMEWORK
The hydrologic framework consists of the natural elements supplying water to the area and the medium through which the water moves. These elements are described in the following sections on the geology and aquifers. All surface water and water in the aquifers are derived from precipitation that either falls on the area or on upgradient areas.
GEOLOGY
The Lakeland ridge area is underlain by several thousand feet of heterogeneous limestone and dolomite. In most of the area these consolidated rocks are overlain by phosphatic clay beds which are, in turn, overlain by surficial sand beds.
Vernon (1951) and many others have described the consolidated rock units present in Polk County. The water-bearing strati-graphic units in this area are: Lake City Limestone, Avon Park Limestone, the Ocala Group, Suwannee Limestone, Tampa Formation, and Hawthorn Formation. These units range in age from Eocene to Miocene and are solution riddled and faulted. The phosphatic clay and surficial material overlying the limestone are described by Cathcart (1966) and others.
The stratigraphic nomenclature used in this report conforms to the usage of the Florida Bureau of Geology. It conforms also to the usage of the U. S. Geological Survey, with the exception of the Ocala Group and its subdivisions and the Tampa Formation.
AQUIFERS
The ridge area is underlain by four aquifers, as described by Stewart (1966); (1) the water-table aquifer, (2) the uppermost artesian aquifer, (3) the secondary artesian aquifer, and (4) the Floridan aquifer. Figure 4 shows the generalized geology and relation of the aquifers.
Permeable zones in the sandy and clayey surficial materials constitute the water-table aquifer, which is used for some domestic supplies but is relatively unimportant as a source of water for other uses. The sand of the aquifer is Miocene and Holocene (in older literature called "Recent") in age.
The pebble phosphate deposits underlying the surficial deposits form the uppermost artesian aquifer. Like the water-table aquifer, this aquifer is used only for domestic and small irrigation supplies.
Limestone of the Hawthorn Formation constitutes the secondary artesian aquifer, which is confined by the clay beds of the


Hawthorn Formation above and the Tampa Formation below. The secondary artesian aquifer is a source of water for domestic and small irrigation supplies.
The water-bearing characteristics of these first three aquifers are not well known, and they are not used extensively as sources of supply.
The Floridan aquifer is the major source of water in the ridge area and is comprised of limestones that range from Eocene to Miocene in age. The Suwannee Limestone underlies most of the Lakeland ridge area and constitutes the uppermost part.of the Floridan aquifer in much of the area of investigation. In places, limestone of the Tampa Formation is sufficiently connected hydraulically with the underlying rocks to be included as part of the aquifer.
Where the Suwannee Limestone is not present, the limestone units of the Ocala Group constitute the uppermost part of the Floridan aquifer. The base of the Avon Park Limestone is, for practical purposes, the base of the aquifer, although some wells penetrate the Lake City Limestone. Many wells in the Lakeland ridge area are terminated in cavities in the limestone of the Floridan aquifer. Such wells characteristically yield several thousand gallons per minute with small drawdown.
Cavities in the aquifer develop over a long period of time as the limestone is slowly dissolved by water moving through the aquifer. Fissures and other structural features, which provide preferential flow paths for water, localize solution activity and allow it to proceed more rapidly. Cavities occur at various depths throughout the area. In the northeast part of the area of investigation, many wells penetrate a cavity zone at about 450feet below msl (mean sea level). This zone of solution cavities is deeper toward the south and west and occurs rather uniformly at about 650 feet below msl in the south part of the study area. Figure 5 shows the approximate depth below land surface to this cavity zone. Although, as a general feature, the zone seems to be continuous, individual wells at any given site may not tap cavities at the mapped depth. At most sites cavities occur at shallower depths, but, on the basis of information supplied from drillers' logs, few cavities occur below the depths indicated on figure 5.
Hydraulic Properties of the Floridan Aquifer
Transmissivity pertains to the water-conducting capacity of an aquifer and is defined as the rate at which water is transmitted through a unit width of the aquifer under a unit hydraulic gradient.


Figure 4. Block diagram showing generalized ground-water geology in the Lakeland ridge area.


EXPLANATION (
-600 i-1
Line of equal depth. Shows depth to top ol solution zone Interval 50 feet Datum it land lurtace
Figure 5.
Map showing depth to zone of solution cavities in the lower part of the Floridan aquifer.


The storage coefficient is the volume of water an aquifer releases from or takes into storage per unit surface area per unit change in head.
The specific capacity of a well, that is, the quantity of water the well yields for each foot of drawdown of the water level, can be used as an indication of transmissivity (Brown, 1963, p. 336-338). Stewart (1966) compiled data on the specific capacities of 173 wells in Polk County. These values range from more than 2,000 gpm per ft (gallons per minute per foot of drawdown) to less than 10 gpm per ft in the area of investigation. The specific capacities in some places varied considerably for wells a few hundred feet apart, especially where one of the wells tapped a cavity system. The storage coefficient cannot be determined from specific capacity but the transmissivity can be estimated as suggested by Brown (1963, p. 336-338). Based on the range of specific capacities given above, the transmissivity ranges from 536,000 ftVday (square feet per day) to about 2,700 ftVday. These values are equivalent to 4,000,000 gpd per ft (gallons per day per foot) and 20,000 gpd per ft in the units formerly used to express transmissivity.
Aquifer tests in which pumping rates are controlled and the resultant drawdowns are measured in observation wells provide a more reliable method for determining transmissivity and storage coefficient. Transmissivity of the Floridan aquifer has been determined in various parts of the State by such tests. Menke, Meredith, and Wetterhall (1961) reported a transmissivity of 29,500 ftVday (220,000 gpd per ft) from tests near Plant City, about 10 miles west of Lakeland. The storage coefficient determined from this test was 0.002. Stewart (1966) reported a value of 134,000 ftVday (1,000,000 gpd per ft) from tests northeast of Lake Parker, but did not determine the storage coefficient.
As part of this investigation, an aquifer test was made west of Lake Parker. From this test, a transmissivity of 100,000 ftVday (750,000 gpd per ft) and a storage coefficient of 0.0009 were determined. These values compare favorably with those recently determined from aquifer tests in Hillsborough and Pasco Counties (J. W. Stewart, oral commun., Jan., 1971; and L. H. Motz, oral commun., July, 1971, both of U.S. Geological Survey).
Transmissivity and storage-coefficient determinations for the Floridan aquifer are applicable over a wide area but may not be applicable for a specific location because of the heterogeniety of the aquifer. However, the values determined in this investigation are probably representative of the area and can be applied to predict drawdowns caused by pumping from the Floridan aquifer.


| i i i i | i i i i | I I I I | I I I I
1950 1955 I960 1965 1970
Figure 6. Graph showing industrial, municipal, and irrigation pumpage and citrus acreage under cultivation in the area of investigation, 1950-70.
HYDROLOGIC CONDITIONS AND TRENDS
Ground-water Use
Ground water has historically been the most widely used source of water supply in the area of investigation and in 1970 accounted


for about 90 percent of the total water used. Most wells that produce more than 150 gpm (gallons per minute) are terminated in the Floridan aquifer although numerous smaller wells used for domestic and stock supplies are terminated in the shallower aquifers.
Pumpage from the Floridan aquifer in the Lakeland ridge area increased from about 11 billion gallons in 1950 to about 27 billion gallons in 1970. The greatest demand for ground water is for industrial use, principally for phosphate mining and processing. Other industries that require large quantities of ground water are citrus processing plants, ice plants, and commercial laundries. The amount of water withdrawn for industrial use during 1970 was estimated to be 18 billion gallons. This water-use figure was derived from information supplied by various industries and from discharge measurements of selected wells used for industrial supply. Most of Florida's phosphate industry is south of the area of investigation, but five mines are located within this area. Water used by these five mines was estimated to be 25 percent of the water used by all phosphate operations in central Florida. Water supplied to industries through municipal systems is not included in this figure.
Industrial water-use requirements have grown steadily over the last two decades (fig. 6). Estimates of the amount of water pumped before 1970 were adapted from Peek (1951), Stewart (1966), and Kaufman (1967). Industrial water use is generally distributed equally throughout the year, although some seasonal variations in total industrial withdrawals are caused by citrus-processing requirements.
Pumpage of ground water for irrigation varies considerably both annually and seasonally, depending principally upon the distribution of precipitation and the acreage under cultivation. Citrus is the principal irrigated crop. In 1969, about 14,500 acres of citrus were under cultivation in the area of investigation, as compared with about 15,100 acres in 1965. The decrease is principally due to replacement of citrus acreage by subdivision development south of Lakeland. Citrus acreage inventories are not available for years earlier than 1965. Acreage for these earlier years were computed through use of county-wide inventories of tree age and acreage (Florida Department of Agriculture Crop and Livestock Reporting Service, 1970). About 10 percent of the Polk County acreage was within the area of investigation during 1965, 1967, and 1969. Applying this percentage figure to the citrus acreage totals in the county for the last two decades, an estimate of the acreage within the area of investigation before 1965 was


obtained (fig. 6). An inventory of citrus irrigation wells indicated that about 70 percent of the acreage was irrigated in 1970.
To determine withdrawals for irrigation, the discharge of many wells were measured and rated against electric-power input to the pump motors. The pumps, whose discharges were measured and rated, were used to irrigate a total of about 2,000 acres. Extrapolation of the unit-acreage water use for these citrus groves to the irrigated acreage in the area of investigation indicated that about 3 billion gallons were withdrawn for irrigation in 1970.
In 1970, most of the water for irrigation was pumped in May, June, August, and December. Little irrigation was done in February, March, September, and October.
The increase in irrigation water use over the last two decades is shown on figure 6. Pumpage figures for the period before 1970 were adapted from Kaufman (1967).
Lakeland is the largest municipal supplier of water in the area of investigation. In 1970, Lakeland's pumpage was 5.23 billion gallons, and the total municipal pumpage was 6.18 billion gallons. Municipal withdrawals for cities in and adjacent to the area are shown in table 2. Total annual municipal pumpage by Lakeland, Bartow, and Mulberry is shown in figure 6 for 1950-1970. For the period that pumpage records were not available for the two smaller cities, their withdrawals were estimated on the basis of Lakeland's pumpage.
Municipal pumpage varies considerably during the year mainly because of higher demands for lawn irrigation during the dry months. The relation of municipal pumpage to precipitation is shown on figure 7.
The trend of increasing water use for municipal supplies will probably continue with population growth. The trend for other water users is extremely difficult to anticipate. The decrease in citrus acreage since 1965 indicates that the irrigation demand has temporarily stabilized and will probably decrease with increasing urbanization. Annual and seasonal precipitation variations, of course, are the principal control on annual water-use demands for irrigation.
Table 2. Municipal pumpage by cities in and near the Lakeland ridge area, 1970
Million Gallons
Million Gallons
Lakeland Bartow
5230 865 84 805
Winter Haven
1685 554 653 320
Mulberry Plant City
Haines City Lake Wales Auburndale


Industrial water use may increase as new industries develop. However, this increase will be offset as phosphate deposits in the area of investigation are depleted and the center of phosphate mining moves farther south. In addition, many of the mining operations have increased the use of recirculated water from settling ponds thus reducing their pumpage from the aquifer.
M
M
CO LU X
o
oo
<
- or
o cr
CL-
IO
400
X
-200 0
< CO
M
M
Figure 7. Bar graph of mean monthly municipal pumpage and mean monthly precipitation at Lakeland, Florida, 1950-1970.


THE POTENTIOMETRIC SURFACE OF THE FLORIDAN AQUIFER
The level to which water rises in wells penetrating an aquifer forms a surface referred to as the potentiometrie surface. The altitude of the potentiometrie surface varies locally in response to variations in both recharge to and discharge from the aquifer.
The potentiometrie surface of the Floridan aquifer has been mapped during several previous investigations, which included the area of investigation (Stringfield, 1936; Black, Brown and Pearce, 1953; Stewart, 1966; Pride, Meyer and Cherry, 1966; Healy, 1962; and Kaufman, 1967).
The potentiometrie surface was mapped as a part of this investigation in November 1968, near the end of the seasonal water-level recovery, and in June 1969, May 1970, and May 1971, near the end of seasonal water-level declines. The potentiometrie surface for May 1971 is shown on figure 8 and reflects the lowest water levels in the aquifer in most of the area during this investigation. The low water levels to the south of the area of investigation are the result of heavy pumpage there.
Changes in the potentiometrie surface from the time it was mapped in September 1949 to the measurements made in June 1969 are shown on figure 9. These lowered levels indicate a reduction of the quantity of water in storage in the aquifer. Changes have been greatest in the south part of the area of investigation, where pumpage is greatest. Water-levels have declined there by 50 feet or more. In the northeast part, water-level declines have been generally less than 10 feet.
Pumpage of ground water has resulted in additional water-level declines from those shown in figure 9. Areas where water levels lowered between June 1969 and May 1971 are shown in figure 10.
GROUND-WATER QUALITY
Although the water withdrawn from the Floridan aquifer underlying the Lakeland ridge area is hard, it generally meets the drinking-water quality standards established by the U. S. Public Health Service (1962). Municipal supplies for cities in and near the area are obtained from the aquifer. The water is normally chlorinated and aerated for municipal use.
Lakeland maintains 27 public-supply wells throughout the city and in nearby communities. Some of these wells yield water-that contains objectionable quantities of hydrogen sulfide. Hydrogen sulfide imparts an unpleasant taste and odor to water. The gas can be detected by smell in concentrations of less than 1 mg/1


Figure 8. Colour map of the potentiometric surface of the Floridan aquifer,,


0 12 3 4 MILES EXPLANATION -1-1--"
-20-
Lin* ot tqual walir-ltvtl dtciint. InHrvol 10 (lit
Figure 9. Map showing generalized decline in the potentiometric surface of the Floridan aquifer, September 1949 to June 1969.


Figure 10. Map showing generalized decline in the potentiometrie surface of the Floridan aquifer, June 1969 to May 1971.


milligrams per liter) (Hem, 1959). Hydrogen sulfide is not generally present in water from wells less than about 450 feet deep n the area of investigation; its occurrence may be restricted to certain zones in the geologic section.
Water samples were obtained from two wells drilled about one-quarter mile west of Lake Parker for city supply. One of these wells was drilled to 920 feet below land surface and cased to 660 feet {well 23, fig. 2). The concentration of hydrogen sulfide in this water, as determined by the Lakeland city chemist, was 2.5 mg/1. The second well, drilled about 1,000 feet farther west from the lake, is 650 feet deep (well 21, fig. 2). The concentration of hydrogen sulfide in water from this well was negligible. Because the altitude of land surface for both wells is nearly the same, the gas seems to be present in the immediate area somewhere between 650 and 920 feet below land surface and, therefore, between 150 and 400 feet below the top of the Avon Park Limestone. However, no precise correlation between the occurrence of hydrogen sulfide and depth of wells could be established within the scope of this investigation.
Highly mineralized water containing chloride in concentrations greater than 1,000 mg/1 is present near the area of investigation at depths about 1,500 feet below mean sea level (Pride, Meyer, and Cherry, 1966). The depth to this highly mineralized water is related to the level of the less dense fresh water in the aquifer. Declines of the fresh-water levels in the aquifer theoretically would allow the highly mineralized water to move upward, depending upon the amount of the water-level decline and the vertical permeability of the aquifer.
In the area, no wells are accessible that are deep enough to locate precisely the depth to the highly mineralized water. However, based upon the relative densities of fresh water and sea water, about 1 foot of decline in the fresh-water levels would allow the highly mineralized water to move upward 40 feet in a homogeneous aquifer. In central Polk County, south of the area of investigation, water levels declined by 50 feet or more between September 1949 and May 1969 (Stewart and others, 1971). These declines indicate a high potential for upward movement of the highly mineralized water. No such movement was evident in the water samples taken during the investigation. Two possible explanations for the apparent lack of upward movement of the highly mineralized water are (1) insufficient time has elapsed, or (2) the vertical permeability of the lower formations is low. Probably both are involved. Although no data are available to determine the vertical permeability of the rock units underlying the Avon Park


Limestone, observations by Stewart (1966, p. 26-30) indicate that the permeability is low.
A well drilled and properly finished to the depth of the highly mineralized water would allow monitoring of the possible upward movement of this water. Construction of the well to allow simultaneous measurements of the artesian pressure at the depth of the highly mineralized water and artesian pressure in the fresh-water zones of the Floridan aquifer would provide much useful information.
To determine the quality of water at various depths in the Floridan aquifer, a series of packer tests were undertaken. The packer equipment consisted of two inflatable bladders, which could be separated by intervals up to 40 feet. A submersible pump was mounted between the bladders so that, when the bladders were inflated by compressed gas, the isolated zone could be pumped for water samples. Before the tests, geophysical logs were made of the wells. The caliper log, which indicates variations in the size of the borehole, was used as a basis for selecting the depth settings for the packers. Cavity zones within the depth range 27 to 618 feet below msl were selected for sampling. Figures 11, 12, 13, and 14 are geophysical logs of the four wells selected for the tests. Also shown on the figures are the results of chemical analyses of water samples taken at the depths indicated. The fluid resistivity logs indicate little difference in the total mineral content of the water with depth, and the samples taken show no significant difference in the quality of water in the aquifer down through the tested depths. The heterogeneous nature of the aquifer and the results of these tests suggest that water circulates freely within the aquifer through the depths tested.
As a part of this investigation a pump was installed in an unused city supply well 1,200 feet deep near Mirror Lake in Lakeland to obtain periodic water samples for chemical quality analyses (well 24, fig. 2). The pump installation in the well, as shown in figure 15, allows water samples to be taken at two depths in the aquifer, 500 feet and 1,100 feet below land surface. The water at the 500-foot depth is not isolated from the water at the 1,100-foot depth, but water from the two depths differed considerably in mineral content. Chemical analyses for water samples taken from Well 24 are given in table 3. Water from the lower depth emits an odor of hydrogen sulfide; water from the 500 ft depth does not.
From 1955 to 1962, water samples were collected for analysis from several wells. Some were sampled again in 1969, and their locations are shown in figure 16. The change in water level in the Floridan aquifer between May 1956 and May 1969 is shown in figure'


Figure 11. Geophysical logs and water quality at various depths in Well 2.




anna, itnttr__
iao ocout snjMV >"x **"T ctsw dot* mrr
Bleal aoal?aas In milligram* par liur axcept for pB. tenpararaia (In dagraaa C),
and ccoAietlYiey (in ntleromhoa)
*ls*TNrrr Zone



>_ i
-!= -I
t



f
-r a
-2 .*=
-* mm
i-
-J 3"-
= 1
Zone SampUd, ft Data Dtpth to water.ft Fa S04 CI K>4 r Alkalinity Rard-naaa pR Too.
At 105 4-29-70 82 0.01 4.0 8.0 0.02 0 234 196 354 7.6 25.0
Paefcara sot
inflated
200-225- 5-11-70 85 .01 3.0 8.0 .01 0 212 152 315 7.9 26.0
300-325 5-11-70 85 .01 3.0 8.0 .02 0 239 198 360 7.5 26.0
415-MOi 5-11^70 85 .01 3.0 8.0 0 o' 212 153 288 7.8 26.0
450-475 5-11-70 85 .01 3.0 8.0 0 0 242 218 35S 7.3 26.0
Figure 13. Geophysical logs and water quality at various depths in Well 21.


CheaUel enelyeei In nilllgrue per liter except far pH, teapereturc (in degree* C),
end conductivity (In nlcroeihoi)








>











7












Stapled, ft
At 120 7-2-70
packer* noc Inflated
Depth to weter, ft
) 260-285
AUalln
ity
Herd-neie
Conductivity
Tenp,


188
777"
100
sea level
-168
560 -
920 -979 -
-6=
water level recorder
-jyj- land surface
-water-level float
well casing
open hole in limestone
pump and switching valve
upper level intake
lower level intake
note: not to scale
Figure 15. Schematic diagram of the quality-monitoring installation at Lakeland, Florida.


(Results
Table 3. Chemical analyses of water samples
In milligrams per liter except as Indicated. Analyses
from Well 24
by U.S. Geological Survey)
Hardness
Bicarbonate Date of sample and depth taken Water level feet above msl Silica (Sio2) Calcium (Ca) Magnesium (Mg) Sodium (Na) Potassium (K) Sulfate (S04) Chloride (CI) Fluoride | (F) Nitrate (N03) Dissolved solids Calcium Magnesium Non-carbonate Q. Color
3-21-68 500 87.6 20 60 19 6.5 0.9 200 59 14 0.3 0.4 275 229 65 448 7.6 5
600 87.6 20 52 17 6.6 0.9 188 46 14 CO .4 247 201 47 408 7.5 5
720 87.6 19 56 19 6.8 1.0 196 56 14 .4 .2 268 219 58 439 7.6 5
3-22-68 820 87.6 18 104 23 9.4 1.5 270 130 18 .4 .2 449 358 136 700 7.5 20
1080 87.6 18 98 23 9.7 1.5 260 122 16 .4 .2 424 342 130 650 7.5 15
1116 87.6 18 106 22 9.6 1.7 264 144 16 .4 .2 462 359 142 700 7.5 20
3-6-70 500 97.9 360 1610 290 1825
1150 97.9
4-15-70 500 95.2 *
1150 95.2
5-18-70 500 95.0 __ 980 1340
1150 95.0
9-25-70 500 985
1150 2180
12-28-70 960 91.5 23 430 90 16 2.5 202 1200 26 1.4 6.5 1900 1460 1290 2200 7.9 0
1-20-71 500 92.5 440 2250
1150 92.5 ---


82' 03' 82*00'
8I50' 8249'
EXPLANATION
____ WATER LEVEL DECLINE, IN FEET t
a. _>,... i I Will tempted tor olr-
Boundory, doihtd h*r rrrrn |y anolytltt wilh
inferrtd |_| I 1
0-5 10-15
0 12 3 4 MILES
1 I_I_I-1
0
GrioKr than 20
Figure 16. Map showing generalized decline in the potentiometric surface of the Floridan aquifer, June 1956 to June 1969, and locations of selected water quality monitoring wells.


16 for recognition of a possible relation between quality change and water-level change. A comparison of the earlier analyses with those of 1969 (table 4) shows no extensive deterioration of water quality and little correlation between water-quality changes and water-level changes for this period. The specific conductance of water from wells 1, 3, and 18 increased by more than 10 percent. Wells 1 and 3 are within the area where water levels declined 15 to 20 feet, and well 18 is within the area where the water level decline was 0 to 5-foot. However, the specific conductance of water from the other wells throughout the area of investigation either has not changed or has decreased by more than 10 percent. The depths of, and other information about these wells are given in table 5.
Any correlation between water-level declines and quality changes may be overshadowed by other effects, such as inadequate well construction or localized recharge. These effects could allow more rapid downward movement of water into the Floridan aquifer near the well from the water-table aquifer. That such effects have produced rapid downward movement of water into the Biscayne aquifer has been shown by Parker (1955, p. 609).
SURFACE-WATER USE
Surface water in the study area is used principally for recreation. Surface water is also used as a coolant for power plants and for transportation and dilution of municipal and industrial wastes. Two electric-power plants on the shores of Lake Parker pumped about 40 billion gallons from the lake in 1970. The water was returned to the lake at a slightly higher temperature.
Lakeland's municipal sewage-treatment plant discharges into Banana Lake, which discharges into Lake Hancock, and from there flows into Peace River. The discharge from the treatment plant was about 2.37 billion gallons in 1970. Discharge from the plant varies throughout the year in about the same manner as the municipal pumpage.
Bartow's sewage-treatment plants discharge into tributaries of the Peace River. In 1970 the discharge was about 0.4 billion gallons.
STREAMFLOW
The volume of streamflow is dependent mainly upon the amount of precipitation. This relation can be seen in figure 17. Conditions that cause a significant increase in the downward percolation of streamflow through the stream bed may reduce the annual volume of flow. Declines of water levels in the Floridan aquifer have,


Table 4. Chemical analyses of water samples from selected wells in the Lakeland ridge area (Results in milligrams per liter except as indicated. Analyses by U.S. Geological Survey; (Water level: a, from recorder chart; e, estimated; m, measured.)
Well Date Sampled Water level ft. below land surface Silica (Si02) Iron (Fe) Calcium (Ca) Magnesium (Mg) Sodium (Na) Potassium (K) Bicarbonate (HC03) Sulfate (S04) -i Chloride (CI) Fluoride j (F) 1 Nitrate Phosphate (PO.) Dissolved solids Hardness as CaCOg Specific Conductance (micro-mhos at 258C) EC a Temperature (C)
Calcium, Magnesium Non-carbonate
1 5-08-59 31e 3.2 0.01 20 11 8.2 0.8 48 54 12 0.2 0.0 157 95 56 234 7.4 _
9-11-69 61e 18 .18 95 24 8.9 1.1 182 174 12 .6 .7 0.05 491 339 190 650 7.6 25.0
8-4-71 16 97 25 10.0 1.2 180 200 13 0.3 0.5 473 348 201 673 7.0 25.0
2 5-07-59 18a 17 46 11 6.8 .8 178 14 8.5 .4 .0 191 160 14 326 7.7 26.0
11-07-69 34a 4.4 .03 20 11 8.4 1.0 112 4.0 6.0 .3 1.1 .2 117 96 4 205 7.3 25.0
3 6-11-56 37e 16 .08 54 11 13 .7 192 8.8 24 .0 1.5 227 180 23 396 7.4 25.0
9-16-69 55e 14 .54 82 14 16 1.1 260 52 20 .2 .3 336 262 49 485 7.5
4 178 156 299 7.2
4-15-66 lOle 3.6 7.0 .3 158 319
9-10-69 104e 16 39 12 6.0 .6 180 .0 7.0 .2 .9 .2 176 148 0 290 7.9 25.0
5 6-11-56 33m .0 286 216 418 7.4
6-9-69 43a 0.0 _ _ 8.0 10.0 0.3 0.1 7.3 24.4
11-07-69 31a 0.12 23 4.8 4.1 96 0.3 5.0 0.6 .2 102 77 0 170 7.8 24.5
6 6-07-66 54e _ _ __ .8 10 .4 150 325
9-17-69 55e 2.4 49 6.1 .4 11 .5 212 148 310 7.6 24.5
7 6-09-56 32e .3 237 188 383 7.2
9-18-69 37e .16 .48 59 10 8.0 .9 206 .0 10 .3 10 .5 221 188 19 350 8.2 25.0



cn cn 4> co co o to co Well j
3-16-62 3-25-63 9-18-69 6-11-56 9-17-69 2-14-55 11-11-69 2-15-55 9-17-69 9-26-56 9-17-69 12-05-55 11-09-59 11-10-69 6-09-56 9-18-69 6-11-56 9-19-69 6-09-56 1 Date Sampled
1 lUc 67e 73e lie 7m 28e 23e 28e 29e 27e 15a 20m 57e 59e I 100m UOe 86m Water level ft. below land surface
III || || 5 | || || to j || 5 | Silica (Stty
0.01 0.30 0.14 0.06 0.0 0.03 0.48 1.2 1.2 0.20 0.48 0.00 1 Iron fFe)
4~i co | co | ctoQ>col..ct4>iUco.U| cn cn cn to 1 o 1 col Wiu. ui^ un on ^ 1 co co 3*. cn Calcium (Ca) 1
h--, n- >' h-itO to to ''CO > *~ Ui 1 COl tO 1 Sl^lM (DM Of 09-> CO b co co 1 Magnesium (Mg)
SI II II II IIs! II O to to ll II II bo cn 1 II II col II lutob 1 Potassium (K)
to ?-' to to to toto to to to CD j to >-' 1 CO 1 CO to CO CO CO 05 1 II 11 CT CO ? 1 O 1 -J tO 34 1 1 CO tO O Bicarbonate 'HC03)
o | p| p| OMH.pl o cn 4*. -o o | oou b v-. i-t. bbb >1 > b b b > boon Sulfate (SO.) 4
i 1 (O '. to <* '' ' co 1 to 1 4- 1 oopocoooi->ototoopcooo b b b cn b b cn Chloride (CI)
p j p 1 pi op | it p i j Oj00 'u I 1c 1 bo 1 onto' r' cn' o cn to 1 Fluoride IF)
I 1 1 I I 1 I I I I gl I I s 1 g Nitrate (NO,)
0 01 0.1 0.05 0.1 0.04 0.02 0.2 0.04 0.0 0.0 0.1 Phosphate (Po4)
tO f h~h~ to > tO tO tO tO tO tO tO tO tO Kg co co 4* cn sio) i- co 4>. to i coi^ii^ I to CC OO tO - i- CO COUIM 4*. O CO 4^ Ul4> OIHW 1 55 1 Dissolved solids
-.tO i i h tO tO * tO i tO CT3 MM 4*. 4> CO CD O CT9 bp tOO J OO tn-JO O CO o toto CJ1 o to to -'OO o to 4^ CO cn to m to to Calcium. Magnesium 1 S3 =-go
.1 II II cnM 1 4t 1 1 bl M05. Non-carbonate
Co 01 10 to tOtp CO i. CO CO 4i COCO CO CO to CO CO 4^ CO to 0 Co co bo cn to cn t- co to Co -j 00 to oo Q co iii cn 0 to 00 cn cn to o cn oo o cn o to to o cn Specific Conductance (micro-mhos at 250
oe -- bo b to b bob enco --1 pH
26.0 28.0 23.5 24.0 23.0 23.5 24.5 24.5 25.5 Temperature <*:)



tO ^ O CO CO ""J Well
1-02-56 11-11-69 1-30-56 11-10-69 6-11-56 9-19-69 6-14-62 9-19-69 Date Sampled
co ( en cn i> i to to O to coco to m ^^|| to | || Silica (Si02)
0.01 0.05 0.15 0.31 0.61 Iron (Fe)
co to | en cn co co co o cn 1 o o cn to Calcium (Ca)
to to * i* cn a cn | co to to co b *- co Magnesium (Mg)
^ t | to co en 1 1 cn 1 II Potassium (K)
>-- WM HH i^>c> to cn -J cn cn to 1 1 to to cn Bicarbonate (HC03)
1.0 0.10 1.0 0.0 0.1 2.8 0.0 Sulfate (S04)
en cn h-. 1 -q to -J b b b b Chloride (CO
o O O 1 O 1 1 CO t 1 CO 1 CO I Fluoride (F)
pp 1 1 p1 II o to >- 1 11 Nitrate (N03)
0.6 0.05 0.07 Phosphate (P04)
!(- h- CO tO (.i 4* to to CO ^00 si os to h- cn cn cn o Dissolved solids
>' >' >> to to >.>. >> ce m eft >' cocn coco o to 1 1 1 o 1 Non-carbonate
C to J to cn k to to > co to cn >-* enco >- o to cn to ocn Specific Conductance (micro-mhos at 259C)
<1 CO SI co pH
24.0 23.0 26.0 24.0 Temperature


Table. 5. Record of wells sampled for water-quality analyses in the Lakeland ridge
area
Well depth i feet 1 Altitude 1 Hawthorn and Tampa Formation Suwannee Limestone Ocala Group Avon Park Limestone i
I 121 BOO (a) 1904 0 56 173 171 275353N-0815033.1
V 100 710 237 > 0 13 214 240 275326N-0815858.1
12 125 252 90 1936 0 105 57 0 275751N-0815220.1
164 325 163 1955 0 0 162 0 275759N-0815813.1
5 122 1220 243 1948 0 0 207 770 275959N-0815525.1
8 137 300 (a) 1940 0 14 86 0 280159N-0820156.1
135 748 160 1948 0 90 200 296 280254N-0815525.1
8 201 828 280 1945 0 34 203 311 280246N-0815704.1
9 158 635 114 1951 35 85 226 175 280227N-0815918.1
10 117 193 36 1954 62 95 0 0 280336N-0815128.1
I! 123 355 55 1953 55 122 123 0 280325N-0815345.1
12 134 126 78 1953 0 33 15 0 280407N-0815443.1
13 138 311 265 1955 0 0 46 0 280503N-0815528.1
14 I5J'. 550 67 1939 51 97 115 220 280559N-0815748.1
IS 207 261 203 1954 0 0 58 0 280529N-0815947.1
IK 128 1285 375 1950 0 0 0 910 280606N-0815232.1
17 139 103 63 1956 0 40 0 0 280614N-0815636.1
18 135 411 53 1956 17 118 178 45 280702N-0815422.1
1!) 160 198 88 1952 27 83 0 0 280727N-0820113.1
20 145 140 135 1955 0 5 0 0 280922N-0815412.1
21 173 647 185 1968 __ 280416N-0815719.1
22 173 660 198 19(59 _ _ 280416N-0815719.2
23 167 920 660 1968 _ 280420N-0815707.1
24 188 1167 356 1925 __ 280244N-0815708.1
25 21B 820 262 1945 275646N-0815645.1
'Casing depth estimated to be 2 feet.
increased the head differential between the stream levels and the water levels in the aquifer, thereby providing conditions favorable for increasing stream losses. To investigate this possibility, graphs were prepared in which cumulative annual precipitation (an areally weighted mean over the individual basin) was plotted against cumulative annual flows of three streams Peace River at Bartow, North Prong Alafia River at Keysville, and Blackwater Creek near Knights (fig. 18). Because streamflow is dependent mainly upon precipitation, any significant changes in the streamflow-precipitation relationship, such as increases in stream


losses, would be indicated by a change in slope of the graph. No significant changes in this relationship are evident for the period considered, 1951-69. However, the effects of increased losses by downward percolation from the streams may be offset by increased outflow from settling ponds created by mining operations during this period. No data were available to assess this possibility.
Unit-area runoff from six drainage areas in or adjacent to the area of investigation vary considerably. The unit-area runoff for each of the six drainage areas is listed in table 6. The unit-area runoff from the smaller drainage areas upstream from the gaging stations, Peace Creek drainage canal near Alturas, and Lake Lulu outlet near Eloise is much lower than from the four larger drainage areas during 1947-69. These smaller areas contribute significantly more recharge per unit area than the four larger ones. The many lakes in the smaller drainage areas may cause higher evaporation as well as higher unit-area recharge to the shallow aquifers.
LAKE LEVELS
Lake levels in this area respond more rapidly to local precipitation than to any other hydrologic factor, rising during extended periods of above normal rainfall and declining during extended periods of below normal rainfall. This general relation can be seen by comparing mean annual rainfall at Lakeland and Bartow to mean monthly levels of Lakes Parker and Hancock (fig. 19). Although the outflow of these lakes is controlled, long-term trends of mean water level can be defined adequately.
In addition to responding to variations in rainfall, the level of some lakes, for example Scott Lake, also respond noticeably to declines in ground-water level. The hydrograph of mean monthly water level in Scott Lake (fig. 20), indicates that the lake level was about 4 feet lower in June 1970 than in June 1961. On the other hand, the mean water levels in Lakes Parker and Hancock were about the same or somewhat higher in June 1970 than in June 1961. The trend of lowered water levels in Scott Lake follows closely the trend of lowered water levels in the Floridan aquifer during this period. This correlation is apparent from the hydrograph of water levels in well 26 (fig. 20). The well is about 4 miles north of Scott Lake (fig. 2). Stewart (1966) discussed the various influences that affect the water level in Scott Lake and correlated the lake-level fluctuations to water-level fluctuations in the secondary artesian aquifer. Because fluctuations of the water level in the secondary artesian aquifer are closely related to fluctuations of the water level in the


<~ 9 h
O
i_cnSO Ml IM9 1970
PEACE RIVER AT BARTOW
Z2Q -
5.0
z z <
a
5f -
WW IMI MS IBTO
BLACKWATER CREEK NEAR KNIGHTS
1961 1969 IVTO
NORTH PRONG ALAFIA RIVER NEAR KEYESVILLE
Figure 17. Bar graphs of mean annual flows of the Peace River at Bartow, North Prong Alafia River near Keysville, and Blackwater Creek near Knights, and mean annual precipitation over these basins; 1961-70.


CO UJ
O 300 -
o
Ul
>
200 ~
3
3 100
o
-1-1-1-
EXPLANATION O Peace River at Bartow
? North Prong Alafia river near Keyesville
A Blackwater Creek near Knights
O o
o A
o a A
?
? o o A
o
O A
-,-1-1-1-1-
0 200 400 600 800 1000 1200
CUMULATIVE PRECIPITATION, INCHES Figure 18. Graphs of cumulative precipitation and flow of Peace River at Bartow, North Prong Alafia River at Keysville, and Blackwater Creek near Knights, 1951-69.


Table (t, Runoff from six drainage basins in and adjacent to the Lakeland Ridge area"
Water Year Area 100 sq.mi, Peace Creek Drainage canal near Alturas (cfsm) Area 23 sq.mi. Lake Lulu Outlet near Eloise (cfsm) Area 207 sq.mi. Peace River near Bartow (cfsm) Area 253 sq.mi. Peace River near Zolfo Springs (cfsm) Area 135 sq.mi. North Prong Alafia River near Keyes-ville(cfsm) Area 110 sq.mi. Blackwater Creek near Knights (cfsm)
1947 1.056 0.543 1.239 3.490 1.370
1948 1.312 .878 1.313 2.166 1.370
1949 1.031 .573 .796 2.434 1.370
1950 .410 .255 .456 1.193 1.370
1951 .631 .242 1.089 1.146 .619 0.55
1952 .451 .203 .686 .905 .577 .68 1.45
1953 .981 .243 1.204 3.316 1.711
1954 1.025 .756 1.355 2.873 1.459 1.06
1955 .198 .083 .436 1.094 .822 .42
1956 .081 .048 .376 .750 .574 .38
1957 .462 .447 1.476 1.798 1.600 1.04
1958 .550 .556 1.213 1.952 1.348 .61
1959 1.356 1.447 2.133 3.324 2.740 2.15
1960 1.762 1.652 2.386 3.126 2.740 2.34
1961 .618 .416 .982 1.343 1.074 .51
1962 .195 .163 .449 1.379 1.133 .52
1963 .302 .120 .685 1.596 1.325 .61
1964 .296 .160 .999 1.537 1.488 1.00
1965 .182 .232 .688 1.324 1.237 .78
1966 .483 .865 1.003 1.217 1.703 .85
1967 .26 .27 .396 1.024 1.19 .46
1968 .33 .18 .560 1.822 1.56 .76
1969 .33 .38 .517 1.478 1.22 .86
Mean .62 .46 .98 1.84 1.37 .90
a In cubic feet per second per square mile.




Figure 20. Graphs of water level in Well 26 tapping the Floridan aquifer and stage of Scott Lake near Lakeland, 1960 to 1970.


Floridan aquifer (Stewart 1966), a long-term trend of lowered artesian water levels may result in a long-term lowering of some lake levels.
WATER PROBLEMS
WATER-LEVEL DECLINES
The most immediate effect of declining water levels in wells is loss of suction to pumps, requiring that pump intakes be lowered. Continued water-level declines further increase the potential for upward movement of highly mineralized water. Lowered water levels in the Floridan aquifer increase recharge rates to the aquifer in direct proportion to the head differential between the water level in the Floridan aquifer and the higher water levels in the overlying aquifers. The recharge increase supplied by the overlying aquifers and, ultimately, the water-table aquifer results in some places in the decline of lake levels.
Any increase in the amount of water used likely will be obtained from the Floridan aquifer. Water levels in the aquifer will continue to decline as withdrawals increase. These declines may be modified somewhat if above-average precipitation occurs, reducing the need for irrigation. Some increase in pumpage for municipal and industrial purposes is probable; therefore, continued water-level declines are anticipated.
LAKELAND'S WATER SUPPLY
Lakeland's water supply comes from 27 wells in the city and in nearby communities. Water supplying the distribution system is stored momentarily in small pressure tanks near each well. As additional supplies are needed, new wells are drilled generally near the area of need. Growth of the city has been toward the south, where long-term water-level changes are most pronounced, thus creating the necessity to drill wells near that area.
When a well is pumped, a cone of depression, or lowered water levels, is created in the aquifer and is centered around the pumping well. The shape of this cone of depression is dependent upon the pumping rate and period and the hydraulic characteristics of the aquifer and confining beds. Knowing these characteristics, the shape of the cone can be defined for various rates for any given period of pumping. After steady pumping has continued for a sufficiently long time, the cone approaches an equilibrium condition in which recharge induced into the aquifer is about equal to the pumpage. Under these equilibrium conditions, water-level declines due to steady pumping, cease. However, an increase in


pumpage causes additional declines until a new equilibrium condition is again established. When numerous wells are pumped in an area, the individual cones of depression may overlap and interfere with one another, resulting in a complex pattern of drawdown, which becomes more difficult to describe and analyze as the number of wells increase.
If only those wells pumped for municipal supply by Lakeland are considered, the pattern of drawdown caused by their pumping can be determined with reasonable accuracy. Utilizing the leaky-aquifer method (Ferris and others 1962, p. 110-118) to determine steady-state drawdowns, the cone of depression due to Lakeland's pumpage of 5.23billion gallons in 1970 was determined (fig. 21). The greatest decline due to the city's pumpage was about 7 feet, southwest of Lake Parker. The cone of depression bounded by the 5-foot decline line was elongated and extended from the north to beyond the south of the city limits. Northwest of Scott Lake the decline was about 6 feet.
To calculate drawdown, transmissivity of 100,000 ftVday (750,000 gpd/ft) was used because it is assumed to be representative for the Floridan aquifer underlying the area. The yield of each well was taken as the continuous rate which, if maintained for 1 year, would yield the actual quantity of water withdrawn during 1970. Because actual pumping rates and time of pumping varied during the year, the cone of depression shown in figure 21 is an approximation and could not be expected to depict the actual drawdown at any specific time.
The leakage factor used in calculating drawdown was 0.001 gpd/ft3 (gallons per day per square feet of surface area per foot of head difference). This is about 6 inches per year under a head difference of ten feet. Inasmuch as only Lakeland's well system was considered, the drawdown shown on figure 21 is only a part of the total drawdown of water levels in the area, as reflected in the potentiometric-surface map for May 1971, (fig. 8).
To predict the drawdown that could be expected due to future increases in the city's pumpage, the trend of annual pumpage shown in figure 6 was extrapolated linearly to 1990. From this extrapolation, the total annual municipal pumpage in 1980 and 1990 would be about 7 billion and 9 billion gallons, respectively.
Using these projected municipal withdrawals and following the same method as above, the cone of depression resulting from Lakeland's projected pumpage in 1980 and 1990 was determined. The drawdowns shown on figure 22 would occur if the additional pumpage required to meet the projected municipal needs in 1980 and 1990 were equally distributed among five city wells now used


REPORT OF INVESTIGATION NO. 64
45
EXPLANATION -5 -
Lines of equal water-leve decline Interva I, I foot
Figure 21. Map showing generalized drawdown due to Lakeland's municipal pumpage, 1970.


south of Lakeland. All other wells were assumed to be pumped at the same rate as during 1970. The general pattern of the cone of depression is similar to that of 1970 (fig. 21), but the greatest decline, 9 feet in 1990, occurs near Scott Lake south of Lakeland.
If the additional pumpage for 1980 and 1990 were supplied from wells drilled northeast of Lakeland, the predicted cone of depression due to the city's pumpage would be as shown in figure 23. Again it was assumed that existing city wells would be pumped at the same rate as in 1970. The greatest decline, 9 feet in 1990, occurs northeast of Lakeland near the pumped wells. However, water-level declines south of Lakeland in this case are about the same as in 1970.
The cones of depression in figures 21, 22, and 23 are due only to pumping for Lakeland's municipal supply. Pumping for industrial and irrigation use in and near the area of investigation also produce cones of depression, and the interaction of these drawdowns produce the present configuration of the potentiometrie surface (fig. 8). Because most of the industrial and irrigation pumpage is south of Lakeland, water-level changes have been more pronounced there (fig. 10). Municipal wells drilled north of Lakeland to supply increased demands would be more distant from this center of pumping and would experience less interference from other wells. Such a distribution would reduce the amount of further water-level declines south of Lakeland, where industrial and irrigation pumpage are more likely to increase through 1990.
SUMMARY AND CONCLUSIONS
Hydrologic data collected as a part of this and previous studies are sufficient to define in general the present-day hydrologic conditions in the area of investigation. The data-collection network adequately measures artesian water levels and streamflow and lake stages. Changes in the quality of the ground water can be monitored by periodic sampling of selected wells. No observation well is presently available to measure and monitor directly the depth to the highly mineralized water underlying the fresh water of the Floridan aquifer. A well drilled and properly finished to the depth of this highly mineralized water in the area of greatest water-level declines would allow monitoring of the possible upward movement of this water. Such monitoring would warn of possible deterioration from this source before the fresh-water supply is threatened. This well would need to be a multi-zone well to allow simultaneous measurements of the artesian heads in the Floridan aquifer and in the zone containing highly mineralized water.




I960 1990
explanation 5 -
Lines of equal water-level decline. Interval, I foot
Figure 23. Maps showing predicted generalized drawdown north of Lakeland due to projected municipal pumpage in 1980 and
toon '