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STATE OF FLORIDA
STATE BOARD OF CONSERVATION



DIVISION OF GEOLOGY
Robert O. Vernon, Director






REPORT OF INVESTIGATIONS NO. 49






HYDROLOGIC EFFECTS OF GROUND-WATER
PUMPAGE IN THE PEACE AND ALAFIA
RIVER BASINS, FLORIDA, 1934-1965

By
Matthew I. Kaufman


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
and the
DIVISION OF GEOLOGY


1967













FLORIDA STATE BOARD
OF
CONSERVATION





CLAUDE R. KIRK, JR.
Governor


TOM ADAMS
Secretary of State




BROWARD WILLIAMS
Treasurer




FLOYD T. CHRISTIAN
Superintendent of Public Instruction


EARL FAIRCLOTH
Attorney General




FRED 0. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director


Soo, 9


AGRI-
CULTURAL
LIBRARY








LETTER OF TRANSMITTAL


Division of Geology
Tallahassee
July 27, 1967

Honorable Claude R. Kirk, Chairman
State Board of Conservation
Tallahassee, Florida

Dear Governor Kirk:
The Division of Geology, of the State Board of Conservation, is
publishing in its regular series of publications a report prepared by
Matthew I. Kaufman entitled "Hydrologic Effects of Ground-Water
Pumpage in the Peace and Alafia River Basins, Florida, 1934-1965.
This report was prepared as part of the cooperative program to
study the water resources of Florida in cooperation with the United
States Geological Survey.
The pollution problems of the Peace and Alafia rivers have be-
come alarmingly large. This study was undertaken to try to relate
the reaction of surface streams to ground water pumpage and to
understand the cause of lowered artesian water levels and the ef-
facts on the total hydrologic system. It was found that there was
opportunity for an upward migration of saline water from the sub-
surface; that a dewatering of the subsurface resulted in the forma-
tion of sinkholes; that there were increased costs due to a loss of
suction and increased pumping lifts; and that some sections of the
rivers changed from ground water discharge to ground water re-
charge.
The facts developed in this study will be needed in the full un-
derstanding of the total hydrologic system of this area.

Respectfully yours,
Robert 0. Vernon
Director and State Geologist



























































Completed manuscript received
July 27, 1967
Published for the Division of Geology
By E. O. Painter Printing Company
DeLand, Florida

iv











CONTENTS

Abstract __ 1
Introduction _____ __ 2
Purpose and scope -- ____ ___ _---- 2
Acknowledgments 3
Location and extent of area ______ 3
Source of water and magnitude and trends of ground-water pumpage ---- 5
Hydrologic effects of the increasing withdrawal of ground water ___- 9
Long-term artesian water-level trends and seasonal
water-level fluctuations _____ 9
Areal patterns of long-term artesian water-level changes 13
Relation between the piezometric surface and lake levels in the
Lake McLeod area ____ 25
Loss of suction in deep wells 26
Reversal of the hydrologic conditions along the Peace River in
Polk County ___ 26
Salt-water encroachment ___--_ __ ___ 27
Sinkhole occurrence _________28
Summary and conclusions .__._______ -. 29
References --___------ -- 32

ILLUSTRATIONS
Figure Page
1 Location of area, control wells, and generalized outline of main
phosphate industrial area, and ridge and sinkhole lake area ___ 4
2 Total and irrigated citrus acreage, phosphate rock production,
and estimated ground-water pumpage, 1934 to 1965 6
3 Long-term water-level trends in four selected areas, 1934 to 1965 10
4 Annual rainfall at Lakeland, Bartow, and Brewster, 1933 to 1964 12
5 Rainfall, pumpage, and ground-water levels in the Lakeland area
(Dec. 1963 to May 1965) __- 14
6 Extremes in fluctuation of water levels in the Floridan aquifer
1965 _____ 15
7 Piezometric surface of the Floridan aquifer in southwest Polk
County, 1934 ___ --___ 16
8 Piezometric surface of the Floridan aquifer showing centers of
selected pumpage in southwest Polk County, early May 1965 ___- 18
9 Profiles of the piezometric surface of the Floridan aquifer
across Polk County, 1934, 1959 to 1960, and May 1965 22
10 Decline of water levels in the Floridan aquifer, 1934 to late
May 1965 ------_--_-- ---- -- ----- ------- 24

TABLE
Table Page
1 Minimum ground-water levels in feet above sea level with ref-
erence to mean sea level --- --- 13











HYDROLOGIC EFFECTS OF GROUND-WATER
PUMPAGE IN THE PEACE AND ALAFIA
RIVER BASINS, FLORIDA, 1934-1965

by
MATTHEW I. KAUFMAN


ABSTRACT

Accelerated industrial and agricultural growth in the Peace and
Alafia River basins, east-southeast of Tampa, Florida, has led to
an increased use of water from the Floridan aquifer, causing a
Progressive decline of artesian water levels. The largest declines
underlie the phosphate industrial area of southwest Polk County,
where concentrated pumpage has lowered artesian water levels
more than 50 feet since 1934.
A regional decline of artesian levels, centered in the phosphate
industrial complex, and extending over an area of approximately
1,000 square miles, has deepened and has expanded until it
presently (1965) reaches the ridge and sinkhole lake region to the
northeast. Preliminary evidence indicates retardation of the
growth of the cone in this direction, probably as a result of
recharge from the lakes. Pumpage from the Floridan aquifer has
increased the hydraulic gradient between the lake surfaces and the
piezometric surface and may be responsible in part for lowered
lake levels in this area.
Additional effects of lowered artesian water levels on the
hydrologic system include: (1) loss of suction and increased
pumping lifts in wells; (2) reversal of hydrologic conditions along
the Peace River between Bartow and Ft. Meade in Polk County
from one of discharge from the Floridan aquifer in 1934 to one
of potential recharge in 1965; (3) opportunity for upward
migration of the saline-fresh water interface; and (4) collapse
of the subsurface resulting in the formation of sinkholes. A
quantitative evaluation of the Floridan aquifer within the Peace
and Alafia basins, especially in the heavily pumped areas, is needed
in order to provide information required to develop efficiently the
water resources.






REPORT OF INVESTIGATIONS NO. 49


INTRODUCTION

PURPOSE AND SCOPE

The Floridan aquifer, composed of formations of Tertiary age, is
the major source of water in the Peace and Alafia River basins in
west-central Florida. Within the basins, the increasing needs of in-
dustry, agriculture, and municipalities have resulted in an increas-
ing rate of withdrawal of water from the artesian Floridan aquifer.
Ground-water pumpage increased approximately tenfold during
the period 1934-65. An estimated minimum rate of withdrawal of
350 mgd (million gallons per day) in 1965 attests to the importance
of the ground-water resources to the growth and economy of the
Peace and Alafia River basins. Located within the basins are one of
the major phosphate industrial complexes in the United States,
numerous citrus canning plants, and extensive citrus acreage.
The long-term pumpage increase in the Peace and Alafia River
basins has resulted in declines of artesian water level over most
of the area. The largest declines are centered in the phosphate
industrial complex of southwestern Polk County, where pumpage
has lowered artesian water levels more than 50 feet since 1934.
Phenomena which occurred in the northeastern Peace River
basin in the spring of 1965 and which may be closely related to
the heavy ground-water pumpage and declining artesian water
levels include lowered lake levels, occurrence of sinkholes, and the
loss of suction in wells in the Floridan aquifer. Questions which
arise include the adequacy of the long-term water supply, future-
trends in ground-water conditions, and the effects on the hydrologic
system of a progressively increasing demand for ground water.
The purposes of this report are to: (1) determine the effects
of ground-water pumpage on the hydrologic system for the period
1934-65, with special reference to artesian water levels; (2)
determine the areal pattern and magnitude of seasonal water-level
fluctuations and long-term water-level trends; (3) predict possible
future trends in ground-water conditions; (4) portray some of
the hydrologic effects of lowered artesian water levels with respect
to lake levels, sinkhole occurrence, position of the saline-fresh
water interface, and (5) provide hydrologic information that will
assist in the planning and development of the area's water
resources and which will serve as a brief hydrologic background
for more detailed studies, such as a quantitative evaluation of
the aquifer system.





HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 3

This report is not an intensive study, but rather a summary
in order to portray the problem and help determine what additional
information is needed to insure the maximum development and
utilization of the area's abundant water resources.
The investigation was carried out in cooperation with the
Alafia and Peace River Basin Boards of the Southwest Florida
Water Management District as part of the cooperative program
with the Division of Geology, Florida Board of Conservation, to
evaluate the water resources of Florida.
The investigation was under the direct supervision of J. W.
Stewart, Hydrologist-in-Charge of the U. S. Geological Survey
Tampa Field Office, and under the general supervision of C. S.
.Conover, District Chief, Water Resources Division, U. S. Geological
Survey, Tallahassee, Florida.

ACKNOWLEDGMENTS

The author is grateful to L. Johnson, consultant to the
Southwest Florida Water Management District, and to W. S.
Wetterhall, J. W. Stewart, R. N. Cherry, and N. P. Dion of the
U. S. Geological Survey for helpful advice and suggestions in the
preparation of this report.
Special thanks are extended to the phosphate companies for their
cooperation in furnishing pumpage data. Appreciation is expressed
to the U. S. Department of Agriculture, Florida Citrus Mutual,
and the various county agents for their assistance in determining
the total and irrigated citrus acreage figures, and to the city of
Lakeland and other municipalities for providing pumpage data.
The author also wishes to thank the many well owners who
allowed access for water-level measurements. Without the coopera-
tion of those mentioned above, this report would not have been
possible.

LOCATION AND EXTENT OF AREA

The Peace and Alafia River basins, east-southeast of Tampa,
encompass an area of approximately 3,000 square miles in west-
central Florida, figure 1. The basins include parts of Polk,
Hillsborough, and Charlotte counties and all of Hardee and
DeSoto counties. The Peace and Alafia River basins are part of
the Southwest Florida Water Management District and their
boundaries approximate the natural drainage basin divides.








REPORT OF INVESTIGATIONS NO. 49


MANATEE CO.
Manatee
92


C)
0


EXPLANATION

Control well used to
construct long-term
water-level trend graphs

* Generalized outline of the
main phosphate industrial
area

.- Generalized outline of the
S ridge and sinkhole lake
area


0 10 20 miles
I I


Figure 1.-Location of area, control wells, and generalized outline of main
phosphate industrial area, and ridge and sinkhole lake area.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS


Shaded patterns show the generalized outlines of the ridge
and sinkhole lake region, believed to be a major source of recharge
for the Floridan aquifer in this area, and the area of the main
phosphate industrial complex, representing an area of heavy
ground-water withdrawals from the Floridan aquifer.

SOURCE OF WATER AND MAGNITUDE AND
TRENDS OF GROUND-WATER PUMPAGE

The Floridan aquifer, one of the most productive in the United
States, is the major source of water in the report area. The aquifer
is composed of about 1,000 feet of limestone and dolomite,
consisting of several geologic formations which range in age from
Eocene to Miocene.
Throughout most of the area, these formations act as a gross
aquifer system. Formations included within the aquifer are the
upper part of the Lake City Limestone, the Avon Park Limestone,
the Ocala Group (Crystal River, Williston, and Inglis Formations),
the Suwannee Limestone, the Tampa Formation, and the lower
part of the Hawthorn Formation. The nomenclature used in this
report is that of the Florida Geological Survey and not necessarily
that of the U. S. Geological Survey.
The major water-producing formation within the aquifer in
the Peace and Alafia River basins is the Avon Park Limestone.
Wells penetrating this formation yield as much as several thousand
gpm (gallons per minute). For recent geologic and hydrologic
discussions pertaining to parts of the report area and immediately
adjacent areas, see Bishop (1956), Menke, et al (1961), Pride, et
al (1966), and Stewart (1966).
Ground water is estimated to account for approximately 90
per cent of the water used in the Peace and Alafia River basins.
A partial inventory of water users, which included municipalities,
irrigators of citrus, and phosphate industries, indicated an average
ground-water use of approximately 350 mgd (million gallons per
day) in 1965. The 350 mgd does not include water used for the
citrus canning industry, other industries, irrigation (excluding
citrus), and domestic use, and hence represents a minimum figure
for total water use in the basins.
S Owing to the seasonal nature of ground-water pumpage by
irrigators of citrus, by municipalities, and by the canning industry,
the quantity of water used may vary considerably for any given
period. The municipal water use of about 27 mgd in 1965 accounts







REPORT OF INVESTIGATIONS NO. 49


for less than 8 per cent of the minimum total ground water used
in the area.
Increases in citrus acreage, phosphate rock production, and
municipal use from 1934 through 1965 have resulted in large
increases in ground-water withdrawals'as shown in figure 2. The
city of Lakeland uses about 50 per cent of the total ground water
pumped by municipalities in the Peace and Alafia River basins.
The insignificance of the municipal demand with respect to the
ground-water demands of industry and agriculture is readily-seen
in figure 2.
The phosphate rock production data are from Florida Board
of Conservation biennial reports and U. S. Bureau of Mines
Minerals Yearbooks, and represent production for the entire State
of Florida. However, the bulk of the State's phosphate is mined
and produced within the Peace and Alafia River basins, and the
data are believed to be a good measure of the production in these
basins.


oo 0

"I I I I
EXPt.AN TION
To Tal amh in Ift0iodr ,f of
4o, ill~borou"h H'dr Desoto,
and Charlt. 0lie..
Irprigated Cenre in the oaove c ct(218 .
+ nd fthce~d tratip, PpoW far irrigation.
I- tioton reqjitenerim based an am fact
of mter (3251.850gallons) per yer per am))
__x- Phosphat rocv production in atilliaris of
Wq his arrar
_*---Ew-fild W.d ..IOl P921q by thb
phosphate industryd
fi G-d enate, Powtooge. City of Lakeland.


Figure 2.-Total and irrigated citrus acreage, phosphate rock production, and
estimated ground-water pumpage-1934 to 1965.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 7

The estimated ground-water pumpage by the phosphate
industry from 1934 to 1950 is after Peek (1951, p. 79). The
pumpage data for 1962 was furnished by the phosphate industry.
The accuracy of the pumpage estimates is shown by the close
agreement of the rock production curve and the ground-water
pumpage curve. On the basis of these curves, the production of
1 million long tons of phosphate requires approximately 4 billion
gallons of ground water under present operating conditions; that
is, processing of 1 long ton of phosphate rock requires 4,000 gallons
of ground water. Ground water use by the phosphate industry has
increased from about 8 bgy (billion gallons per year) in 1934 to
about 72 bgy in 1965.

In a recently published study (Florida Board of Conservation,
1966) water use data for the area under discussion are reported.
Polk County is shown to have the highest industrial use of water.
The high demand for water reflects the presence of the phosphate
and electric power generating industries. Total industrial water
use in Polk County was reported to be 133.5 bgy (366 mgd) in
1962. Most of this use of water occurs within the Peace and Alafia
River basins. According to the Florida Board of Conservation,
projection to 1980 indicates an industrial water use of 316 bgy
(868 mgd), an increase of 2.3 times the 1962 demand.

Estimates of water requirements for citrus irrigation vary.
According to personnel at the citrus experiment station in Lake
Alfred, an average of 1 foot of water per acre (325,850 gallons)
per year is required for irrigation. This figure is based on studies
covering different kinds of citrus and soil types, including soil
moisture tests to determine the optimum requirements (Johnson,
1965). Based on data compiled by the Soil Conservation Service
(U. S. Department of Agriculture, 1965), 1.95 acre feet of water
per acre is used for citrus irrigation under average conditions in
west-central Florida. The water-use data for irrigated citrus
acreage shown in figure 2 are based on the value of 1 acre foot
per acre. An estimated 82 per cent of the water used for citrus
irrigation is derived from ground-water sources, and the remaining
from surface-water sources. Water use for citrus has increased
from about 20 bgy in 1956 to about 52 bgy in 1965. According
to the Soil Conservation Service, the projected agricultural water
use by 1980 will be 2.4 times the present (1965) demand in the
5-county area included in the Peace and Alafia River basins, or
approximately 125 bgy. As parts of Polk and Hiilsborough






REPORT OF INVESTIGATIONS NO. 49


counties lie outside the Peace and Alafia River basins, the quantities
presented above are too large, however, the trends are significant.
The total fresh water use by industry, agriculture, and munici-
palities within the Peace River basin during 1963 was estimated
at 196 bgy (Florida Board of Conservation, 1966). In addition,
projections to 1980 indicated a total water use of 478 bgy, an
overall increase of approximately 2.4 times over the 1963 water use.
With respect to the availability of water in Polk County, Stewart
(1966, p. 119) states:
"The tabulation of recharge to the limestone aquifers
in 1959 shows that runoff exceeded recharge in the various
drainage basins by amounts ranging upward from a factor
of 3. Thus it is clear that the water available for recharge
is vastly more than that required by the ground-water
system to supply present (1959) demands."
It must be borne in mind in evaluating the above statement
that 1959 was the wettest year on record during the past 30 years,
with rainfall almost 20 inches above normal over the basins as a
whole and almost 27 inches above normal at Bartow, site of one
of the gaging stations in Polk County; consequently, conditions in
1959 did not represent a picture of long-term average conditions.
Runoff was excessive and ground-water pumpage was considerably
reduced.
In contrast to Stewart's conclusions, the Florida Board of
Conservation (p. 146, op. cit) using the assumption that water
available for use is equal to the runoff from the basins, and
using the total industrial, agricultural, and municipal water use
states:
'"he most critical water short area indicated by these
studies appears to be the Polk County area where approxi-
mately 860 mgd will be available. The projected water need
for the area is 1,200 mgd for 1980 .......... This would
mean a water shortage in the area of 340 mgd by
1980 .......... "
In summary, the above discussion and figure 2 illustrate the
increasing rate of ground-water withdrawal in the Peace and Alafia
River basins during the period 1934-65 and point out the expected
increases in demand in the future. A correlation between ground-
water use and phosphate production and citrus acreage is shown
to exist.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 9

HYDROLOGIC EFFECTS OF THE INCREASING
WITHDRAWAL OF GROUND WATER

LONG-TERM ARTESIAN WATER-LEVEL TRENDS
AND SEASONAL WATER-LEVEL FLUCTUATIONS
Within the Peace and Alafia River basins, artesian water levels
show a declining trend attributable to the increasing withdrawal
of ground water from the Floridan aquifer. Hydrographs of wells
tapping the Floridan aquifer in four areas are plotted in figure 3.
Only the annual high and low water levels are plotted. These hydro-
graphs depict the long-term declines of ground-water levels in
four selected areas (Eagle Lake, Lakeland, Mulberry, and south-
central Manatee County) for the period 1934 to 1965. Water-level
data were compiled from Stringfield (1936), and U. S. Geological
Survey and U. S. Army Corps of Engineers records. Locations of
the wells are shown in figure 1.
Examination of the hydrographs indicate that the annual rate
of ground-water level decline is progressively increasing. The
period 1957-60 was a notable exception to the general downward
trend in water level. Water levels generally rose from their 1956
lows and remained relatively steady. The rise was due primarily
to excessive rainfall and consequent increased recharge and
concomitant decreased demand for ground water. Stewart (1966,
p. 104) conclid ud-that pumpage was nearly equal to recharge in
southwestern Polk County in 1959-60. At the end of the wet
cycle, water levels again declined. By the spring of 1965, water
levels at Lakeland and Mulberry were considerably below their
1956 levels.
In order to better assess the effects of precipitation on water
levels, three records of long-term rainfall are plotted in figure 4.
Calculations of average rainfall for three successive 10-year
periods are as follows:

Average Rainfall
Station 10-Year Period in Inches
Lakeland 1935-44 49.3
1945-54 50.9
1955-64 49.5
Bartow 1935-44 52.3
1945-54 55.9
1955-64 58.4






REPORT OF INVESTIGATIONS No. 49


Figure 3.-Long-term water-level trends in four selected areas-1934 to 1965.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 11

Brewster 1935-44 53.0
1945-54 54.4
1955-64 54.6

.. Figure 4 and the above data indicate that/although the rainfall
is highly erratic from year to year or for a series of years to
series of years, -no apparent long-term change in rainfall has
occurred during the past 30 years. Deficient precipitation thus is
not a major cause for long-term declines of the artesian water
levels. The cyclic wet and dry periods, however, contribute to short-
term water-level fluctuations, as evidenced by the sharp rise in
ground-water levels during the 1957-60 wet period following the
dry period of 1954-56.
As brought out by Stewart (1966), observed declines of
artesian water levels do not necessarily constitute dewatering of
the aquifer. Nevertheless, water is being removed from the aquifer
and the overall effects on the hydrologic system of the lowered
artesian water-levels must be taken into account.
Periods of severe drought are associated with greatly increased
water demand and consequent lowering of water levels. These
periods of drought are the most critical for the water user. The
numbered points on figure 3 represent the annual low-water levels
which occurred during drought periods. Connecting these points
results in "minimum water-level trends." By projecting these
trends, an estimation of the low ground-water levels to be expected
during future critical periods of peak water demand may be
obtained.
The minimum annual water-level data presented in the above
graphs along with data from three other areas are listed in table 1.
The magnitude of the annual water-level fluctuations has
increased with time for most of the wells studied, reflecting the
increased effect of seasonal pumpage on the hydrologic system.
The seasonal relation between rainfall, pumpage, and ground-
water levels in the Lakeland area is shown in figure 5. The
correlation between water level and pumpage appears to be better
than that between water level and rainfall. The amount of rainfall
probably affects the magnitude of pumpage in the area; increased
rainfall resulting in decreased pumpage and vice-versa. Water
levels in turn respond most directly to pumpage. A rise in water
level corresponds primarily to reduced pumpage and a lowering
of water level to increased pumpage.








12 REPORT OF INVESTIGATIONS NO. 49


SI 0 i0 0 int


LAKELAND I
65 Average annual rainfall
1933-64, 50.52"

60


55







40







75
I i -iI i Ii





L L BARTOW
~ 70

Average annual rainfall
65 1933-64, 56.23"




55




z 45
z
C////X////// ////II~tIIII~l Y ~ /


Figure 4.-Annual rainfall at Lakeland, Bartow, and Brewster-1933 to 1964.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 13

Table 1.-Minimum ground-water levels in feet above sea level.









1934/35 121 1121 105 104 101 92
1939/40 118 98 -
1942 ----- 42
1945 40
1950 86 86
1953 .. . 84
1955!56 87 78 72 72 83 32
1939/40 118 __ 98 __ ___ _-





1963 ....26
1965 95 68 64 53 54 .78

1 Estimated from 1934 piezometric map.


The areal pattern and magnitude of seasonal water-level
fluctuations for 1965, as exemplified by extremes in water-level
fluctuations, is shown in figure 6. The fluctuation represents the
general seasonal fluctuation of levels which is a reflection of
changes in pumpage and recharge and not a change in water level
from non-pumping to pumping levels (drawdown) in pumped
wells. The magnitude of the fluctuations is greatest in the highly
developed central area) Figure 6 was constructed by taking the
difference between the highest and lowest water levels in 1965 in
selected wells as illustrated by interval A on figure 3.
The range in fluctuations reflects primarily the influence of
seasonal pumpage for irrigation and for municipal use. As the
amount of pumpage is expected to increase, the magnitude of the
annual fluctuations also is expected to continue to increase.


AREAL PATTERNS OF LONG-TERM ARTESIAN
WATER-LEVEL CHANGES

The areal effects of ground-water withdrawal can be portrayed
by changes in the piezometric surface over a period of time. (The
piezometric surface is an imaginary surface that coincides with
the static water level in the artesian aquifer). Figure 7 is a map







14 REPORT OF INVESTIGATIONS No. 49


1963 1964 1965
D J F M A M J J A S 0 N D J F M A M


12

Monthly rainfall at Lakeland



- 6











C

o 300

.0 400

500-
Monthly ground-water pumpage
o in millions of gallons, city of
S600 Lakeland.
Note: scale inverted




I 74

0 7

82
| 82--------- -------- -- ,^____
-Z 8- Monthly water-levels in the Floridan
aquifer. 2 miles SW of Lakelond,
(Polk 759-158-214)
^- 90-----------------------\ --


S D J3 F M A M J J A S O N OJ F M A M
1963 1964 1965

Figure 5.--Rainfall, pumpage, and ground-water levels in the Lakeland area
(December 1963-May 1965).







HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS


MULBERRY

17.5


BARTOW


S19.7


17.O*BREWSTER


0 FT. MEADE


/

I -

S1.II


EXPLANATION
Line represents the extreme
- 10---- water-level fluctuation in
feet during 1965.
Interval 5 feet. Dashed where
inferred.
Control well with water-level record
017.5 ing gage. Number represents e)
treme water-level fluctuation in
feet.
S17.0+ Control well. Number represents rr
imum water-level fluctuation in fe


19.9


WAUCHULA
C


o ARCADIA


03.0+ 2.9


S 0 5 mitesd


Figure 6.-Extremes in fluctuation of water levels in the Floridan aquifer,
1965.









REPORT OF INVESTIGATIONS NO. 49


Green


N


EXPLANATION 75
e75
Contour represents the altitude of
1 the piezmmetnc surface, in feet
aoove mean sea level, 1934.
Contour intervl 10 feet. Doshed
where inferred. (Adopted from Stringfid, 1934)
1T07 Control well. Number represents water-
level, in. feet above mean sea level.
21 Spring. Number represents mean annual
now, in mgd in 1934.
S Generalized outline of the ridge and
sinkhole lake area.

5' 800 5'I I0
82"05B 82*00 55' 50'


0 5 10miles
I I


Figure 7.-Piezometric surface of the Floridan aquifer in southwest Polk
County-1934.


28*00'






55'






50'






45'






40'






27-35'






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 17

of the piezometric surface in 1934 (after Stringfield, 1936) before
significant development of the aquifer occurred. This figure shows
a piezometric-high centered near Winter Haven. Stringfield
(1936) considered that the piezometric-high and sinkhole lake
region represented a major recharge area for the Floridan aquifer.
The direction of ground-water flow is generally downgradient,
perpendicular to the contours in an isotropic aquifer.
The piezometric surface in early May 1965 and major centers
of ground-water pumpage (greater than 5 mgd) are shown in
figure 8.
A comparison of figure 8 with figure 7 shows the persistence
of the piezometric high near Winter Haven and a sharpening of a
ridge, or ground-water divide, running from Lake Alfred to
Frostproof./The piezometric high and ground-water divide
underlie the sinkhole lakes and indicate the ridge and sinkhole lake
area to be a major source of recharge to the Floridan aquifer in
the Peace and Alafia River basins. Under natural conditions,
ground water moves through an aquifer from areas of recharge,
where water levels are high, to areas of discharge, where water
levels are low. In general, the average rate of movement is slow,
possibly a few feet per day, and is controlled by the permeability
of the aquifer materials, by the temperature of the water, and
by the hydraulic gradient, or slope, of the piezometric surface.
Additionally, in limestone aquifers, progressive solution enlarges
the subsurface conduits, thus changing the flow characteristics of
the water. /According to Stewart (1966), horizontal flow through
fracture controlled cavern systems may result in troughs in the
piezometric contours due to the reduction of pressure head.
The piezometric high and the southeastward trending ground-
water ridge extend into Highlands County underlying the
Highlands Ridge. According to Bishop (1956), the entire ridge
section of Highlands County is in the recharge area for the
Floridan aquifer; he states (p. 60) ". . .Most of the
recharge to the aquifer occurs north of Sebring (located 20 miles
southeast of Frostproof). Cuttings from wells in the area north of
Sebring indicate that the beds overlying the limestones of the
Floridan aquifer are thin and fairly permeable. The recharge area
extends northward into Polk County where the principal recharge
to the aquifer occurs." Stewart (1966 p. 72) reports "the entire
length of the Lake Wales Ridge in this county is packed with
and flanked by innumerable closed basin lakes. There are also
many sinkhole basins without lakes ........ It seems likely that







REPORT OF INVESTIGATIONS NO. 49


.Wales



1u


EXPLANATION
Cantour represents the altitude
of the piezametric surface in
feet above mean sea level,
May 3-5, 1965. Contour
interval 10 feet.
Control well. Number represents
* water-levl, in fee above
mean sea level.
* Control well with water-level
recordin gage


I v


S- Ground water divide
eneralized outline of the ridge
and sinkhole lake area
S Centers of selected industrial


5-10

k 1-20


>20


ground-waoer pumpoge in excess
of 5 million gallons per day


mgd
0 5 10 miles


27*35'


82MS 82*00 55' 50' 45' 40' 81*35'

Figure 8.-Piezometric surface of the Floridan aquifer showing centers of
selected pumpage in southwest Polk County-early May 1965.






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 19

in much of this area, ground water percolating down the slopes
of these dry basins is going into the artesian limestone aquifers
as recharge." In a detailed investigation of the hydrology of the
Green Swamp area, bordering the Peace River basin on the north,
Pride, et al (1966, p. 82) states "the drawdown is confined to the
southern boundary of Green Swamp, suggesting that the area of
the sinkhole-riddled ridges around southern Green Swamp is a
recharge area."
Runoff from the northeastern Peace River basin, containing the
areas of the ridge and sinkhole lake complex, is considerably lower
than runoff from the remainder of the basin. The Florida Board
of Conservation (1966, p. 32) reports that the headwater region
of the Peace River is "composed of many sinkhole lakes which
limit surface runoff and provide storage and avenues for recharge
of the aquifers .......... Runoff is least (5 to 10 inches annually)
in the northeastern part of the area because of the high evaporation
losses from the many lakes and recharge to the aquifers. It is
greatest (nearly 15 inches annually) in the lower part of the area
because of the small number of lakes and because of discharge
from the aquifers."
Additional data indicating that the sinkhole dotted ridges
represent significant areas of recharge are the relatively low
hardness of water from the Floridan aquifer underlying the
Winter Haven and Lake Wales ridges (personal communication,
A. E. Coker and N. P. Dion) and a calcium carbonate per cent
saturation map (Pride, et al., 1966, p.91). This map shows waters
from the Floridan aquifer to be undersaturated with respect to
calcium carbonate (thus implying a recharge area), in part
extending south and southeast from Winter Haven, in general
conformance with the piezometric high and ground-water ridge
as portrayed by figure 8.
Recharge to the Floridan aquifer, however, is not restricted to
the ridge and sinkhole lake region. As pointed out by Stewart
(1966) recharge occurs over all areas of the county (Polk) where
hydrologic conditions are favorable for the downward leakage of
water through the semi-permeable confining beds. Evidence
supporting this view arises from the studies of Pride et al (1966).
They report that total mineral content and calcium carbonate
saturation in water in the Floridan aquifer indicate that recharge
is occurring over much of central Florida.
Based in part on water-budget computations and the existence
of piezometric troughs underlying some sinkhole lakes in the






REPORT OF INVESTIGATIONS NO. 49


Lakeland area, Stewart (1966) further concluded that recharge
through sinkholes was a relatively small part of the total annual
recharge to the aquifer and that the amount of recharge in the
principal sinkhole areas did not necessarily equal or exceed the
amount of recharge in adjacent nonsink areas of comparable size.
This conclusion appears questionable for several reasons:

1. In calculating recharge values of approximately 5 inches
over the 650 sq. mi. of the Peace River basin within Polk
County in 1959, Stewart assumed uniform runoff over the
basin. However, published data indicate that runoff is
significantly lower in the sinkhole lake region than the
remainder of the basin (Florida Board of Conservation,
1966, p. 32, and U. S. Geological Survey, 1963, pp. 132,
134). The gaging station at Bartow, used by Stewart in
his computations, reflects runoff from both the sinkhole
and nonsink areas. In oder to assess the runoff from the
different areas of the drainage basin, it is necessary to
separate the contributions from the different areas. To
accomplish this separation, data from the gaging station
north of Alturas which reflects the runoff from the
sinkhole lake area must be used and the data from the
Bartow gaging station must be corrected so as to reflect
only the runoff from the remainder of the area.
Reworking the water budget for the year 1959 in the
same general manner as Stewart, but in accordance with
the above discussion, calculations show 9.4 inches of
recharge over the 150 sq. mi. ridge and sinkhole lake area
and 4 inches of recharge over the remaining 500 sq. mi.
of the basin. This indicates recharge values 2.3 times as
great in the sinkhole area as in the nonsink area per unit
area.

2. The occurrence of piezometric troughs underlying some
sinkhole lakes in the Lakeland area (Stewart, 1966)
appear to be caused in part by the contouring of pumping
water levels. Hence, these troughs are artificial and not
related to recharge aspects. Other troughs may be due to
the reduction in pressure head caused by localized high
flow velocities in solution channels and the rate of
downward leakage of lake water may be insufficient to
counterbalance this. It is pertinent to observe that figure
8 of this report shows a well defined-linear piezometric






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 21

high underlying the main ridge and sinkhole lake
complex extending from Winter Haven to Frostproof.
3. Water budget studies made on four different lakes all
indicate downward leakage to the underlying limestone
aquifers during periods of declining piezometric levels.
These studies will .be discussed in detail in a subsequent
section of this report.
It appears therefore that a large amount of recharge to the
Floridan aquifer in the Peace and Alafia River basins does occur
in the ridge and sinkhole lake area and that recharge values in
the principal sinkhole areas exceed those in nonsink areas per
unit area. As the nonsink areas are of much greater areal extent,
significant quantities of recharge can occur outside the main
sinkhole areas.
More detailed work is needed to assess with greater accuracy
the relative quantities of recharge from the different areas. Studies
presently underway by the U. S. Geological Survey utilizing
calcium carbonate saturation and age-dating of ground water by
carbon-14 may prove valuable in this respect.
Concentrated heavy ground-water pumpage, the effects of
which are shown by a shift in the contours on the piezometric
surface map depicted in figure 8, has resulted in a considerable
lowering of the piezometric surface southwest of Bartow. The
increased hydraulic gradient between Winter Haven and Bartow
from about 2 ft/mile in 1934 to 5 ft/mile in 1965 is the result
of the increasing withdrawal of ground water in southwest Polk
County during the above period. The resultant changes in
hydraulic gradients have altered the direction of ground-water
movement and increased the rate of movement toward the centers
of pumpage. Also, Kissengen Spring (figure 7) which had a mean
annual flow of 21 mgd in 1934, ceased to flow in 1950 (Peek, 1951)
when the piezometric surface declined below the spring outlet.
The 1965 ground-water flow pattern, as portrayed by figure 8, is
a result of both the regional gradient and heavy pumpage.
A hydrologic profile across Polk County, from northeast to
southwest, showing the changes that have occurred in the piezo-
metric surface from 1934 to 1965 in relation to land surface and
sea level is shown in figure 9. Lowered water levels caused the
piezometric surface in May 1965 to fall below the bottom of Lake
McLeod and increased the head differential between lake levels
and the piezometric surface of the Floridan aquifer in the sinkhole-































B- tO 1 mliii


Figure 9.-Profiles of the piezometric surface of the Floridan aquifer across
Polk County-1934, 1959-60, and May 1965.


n---- Gnerplied orog of ---
ridge and Lnkhola liake


160


120






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 23

lake area south of Winter Haven. The level of Lake Otis, at
Winter Haven, appears to correspond closely to the decline in the
piezometric surface.
Pumping creates a depression in the piezometric surface. The
decline in water levels is essentially directly proportional to the
rate of pumping and inversely proportional to the logarithm of
the distance from the center of pumping. When many wells within
an area are pumped, the depressions overlap to cause a regional
lowering of water levels (i.e. regional decline in the piezometric
surface). The extent of the individual or regional declines in water
levels is a function of pumping rate, aquifer characteristics, and
resultant changes in discharge and recharge.
Ground-water pumpage within the Peace and Alafia River
basins has produced a large regional depression in the piezometric
surface, figure 10, of more than 50 feet. The depression is
centered southwest of Bartow and covers an area of about 1,000
square miles out to the 20-foot contour. Thousands of wells tap
the Floridan aquifer within this area and mutually contribute to
the lowering of the piezometric surface. Beyond the 20-foot line,
it is difficult to distinguish between seasonal and long-term effects.
The greatest decline in water levels is the result of concentrated
ground-water pumpage in the phosphate mining area southwest
of Bartow.
Figure 10 was prepared by plotting changes in water level in
individual deep wells and by comparing the 1934 piezometric map
(Stringfield, 1936) with well measurements in late May 1965 and
with the 1965 piezometric map. The decline in water levels mapped
in figure 10 is defined by the interval "B" on figure 3, that is the
decline is the difference in water levels from 1934 to the lowest
levels in May 1965.
Pumpage of ground water necessitates that water levels
progressively decline until enough water is diverted toward the
areas of concentrated pumpage from areas of recharge or natural
discharge to balance the rate of withdrawal. When this balance
occurs, water levels in the Floridan aquifer will tend to remain
steady and a state of equilibrium can be said to exist. Should the
pumping rate be increased, either before or after equilibrium
conditions are reached, water levels will decline, reflecting the
adjustment to the new pumping rate. Equilibrium conditions in
general do not exist at the present time (1965) within the Peace
and Alafia River basins.






REPORT OF INVESTIGATIONS NO. 49


Figure 10.-Decline of water levels in the Floridan aquifer, 1934 to late
May 1965.

It is pertinent to observe the relative steepness of the gradient
of decline northeast from Bartow. The lowering of water levels
apparently is being retarded in this area, possibly by increased
recharge from the sinkhole lake region around Winter Haven.
The increased pumpage from the Floridan aquifer may therefore
be one of the causes of declines in some lake levels in this area.
Also, the steep gradients of decline, west and northwest of






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 25

Mulberry, indicate that the lowering of water levels also is being
retarded in this direction, possibly by a reduction in the natural
discharge occurring along the Alafia River. This natural discharge
manifests itself, in part, in the flow of Lithia Springs, one of the
large limestone springs of Florida with a total flow of 72.2 cubic
feet per second (46.7 mgd) on September 30, 1958.
The continuing increase in pumpage will cause further artesian
pressure declines. In addition, the distribution of pumpage is
expected to expand southward owing to the increased use of water
for irrigation and possible migration of phosphate mining to the
southern Peace River basin. This shift in the pumpage pattern
may cause additional water-level declines to the south and south-
west.


RELATION BETWEEN THE PIEZOMETRIC SURFACE AND
LAKE LEVELS IN THE LAKE McLEOD AREA

Record low ground-water levels throughout most of the area
occurred during the spring of 1965. Lake levels in the northeastern
Peace River basin also declined, leading to complaints from
residents, especially in the vicinity of Lake McLeod in Polk
County, about the extreme low water levels in several lakes. Lake
McLeod, for example, declined from 131 feet above msl (mean sea
level) in May 1961 to 122 feet above msl in June 1965.
Lake McLeod, because of its circular shape and location,
appears to be a sinkhole lake. The progressive decline of the
piezometric surface near the lake (from approximately 110 feet
above msl in 1961 to 95 feet above msl in late May 1965) has
increased the head differential between the lake level and the
piezometric surface, thereby contributing to an increase in down-
ward leakage from the lake and apparently a consequent lowering
of lake level.
A water budget for Lake McLeod was computed for the period
May 1, 1961 to June 4, 1965 (Johnson, 1965). While the values
obtained are approximate, they do provide an indication of the
quantities of water involved and the cause of the decline in lake
level. Johnson's results indicate that about 7 feet of water was
unaccounted for in the four years. He attributed this to leakage
to the underlying aquifers. This means that the average downward
leakage of water from the lake was about 0.8 mgd during the above
4-year period.






REPORT OF INVESTIGATIONS No. 49


Kohout and Meyer (1959) investigated the hydrologic features
of Lake Placid (located to the southeast of Lake McLeod in
Highlands County in a similar hydrogeologic setting) and con-
eluded that downward leakage from the lake during the first half
of 1956 (a drought period) amounted to about 2 to 3 inches per
month (6.4 to 9.5 mgd).
They noted that the recession curve for Lake Placid for
1955-56 deviated from those for previous years and attributed this
to increased downward leakage from the lake because of lowered
water levels in the Floridan aquifer.
Studies to determine the relations between the lakes of Polk
County and the underlying limestone aquifers were conducted by
Stewart (1966), who reports (p. 1) :
"Water budget analyses for two lakes near Lakeland,
during the first 6 months of 1956, show that the lakes
recharged the underlying limestone aquifers. Lake Parker
recharged water to the Floridan aquifer at a rate of about
2.5 inches per month and Scott Lake recharged water to the
limestones of the Hawthorn Formation at a rate of about
5 inches per month. Data suggest that other lakes in the
county may also recharge the aquifers at slow rates."

LOSS OF SUCTION IN DEEP WELLS

In the spring of 1965 many "deep" wells "went dry" (that is
the pumps lost suction when water levels declined below the pump
intake) in parts of the study area. The city of Eagle Lake in Polk
County lost its water supply for several days and water had to be
transported by truck to meet the needs of the residents.
These occurrences are expected to continue in the future and
many well owners will need to lower their pump intakes in order
to obtain water. Lowered water levels increase the lift and power
required to pump water and thereby increase the cost.

REVERSAL OF THE HYDROLOGIC CONDITIONS ALONG
THE PEACE RIVER IN POLK COUNTY

In 1934 an area of artesian flow existed along the Peace
River from just north of Bartow southward to the Polk-Har-
dee county line. The water levels in the Floridan aquifer were
about 10 to 20 feet above land surface along the Peace River
between Bartow and Ft. Meade. This area of artesian flow from






HYDROLOGIC EFFECTS--PEACE AND ALAFIA RIVER BASINS 27

the Floridan aquifer manifested itself in the flow of Kissengen
Springs, southeast of Bartow. This spring ceased to flow in 1950
(Peek, 1951) when the piezometric surface declined below the
spring outlet.
In May 1965 the water level in the Floridan aquifer was about
20 to 25 feet below land surface along the Peace River between
Bartow and Ft. Meade. This decline in the water level has caused
a reversal of the hydrologic conditions, in that a potential now
(1965) exists for water to move from the Peace River and the
shallow water table to the Floridan aquifer, as opposed to the
flow of water from the Floridan aquifer into the river in 1934.


SALT-WATER ENCROACHMENT

The entire study area is underlain by saline water (greater
than 1,000 ppm total dissolved solids) at varying depths below the
fresh water in the aquifer. The depth at which this saline water
occurs and the conditions governing its movement are not
adequately known but depend upon the characteristics of the
aquifer. The altitude of the piezometric surface above msl is one
of the factors which appears to govern the depth to saline water.
Using the approximate relation that for every foot of fresh
water above mean sea level, there is 40 feet of fresh water below
sea level, that is 40 feet of fresh water above the saline water,
a depth to saline water underlying Mulberry and Brewster of 2,140
feet below msl is calculated to exist in late May 1965. Information
pertaining to the actual depth of the saline fresh-water interface
underlying southwest Polk County is not available. An oil explora-
tory well, located north of the Peace and Alafia River basins in
southern Lake County, encountered saline water at approximately
2,300 feet (personal communication: R. N. Cherry and B. F.
Joyner). Pride, et al (1966, p. 92) report "Data from a few scat-
tered deep wells indicate that fresh water extends to about 1,500
feet below sea level in much of the interior of central Florida from
Marion County to Highlands County."
A possible avenue for upward migration of saline water exists
along the Peace River. The ground-water circulation pattern is
such that upward movement of artesian water occurs. Stewart
(1966) reports that piezometric troughs along the Peace River
in Polk County are caused by upward leakage along the river
and that these troughs extended to the northwest of Bartow during






REPORT OF INVESTIGATIONS NO. 49


the 1959-60 wet years. In studying the chemical characteristics of
artesian water in the southern Peace River basin, Kaufman
and Dion (in preparation) mapped a linear zone of relatively
warm, highly mineralized calcium-magnesium sulfate water in the
vicinity of the Peace River. This appears to reflect the upward
movement of waters after relatively deep circulation through the
aquifer. North-south trending linear patterns of artesian waters
of relatively high mineralization that follow the Peace River in
Polk County have recently been mapped (A. E. Coker and N. P.
Dion, personal communication).
No vertical saline water encroachment has been observed in
the heavily pumped area, however, the possibility exists that with
the continued lowering of the piezometric surface, saline water
may move upward from depth.

SINKHOLE OCCURRENCE

Within the ridge and sinkhole-lake region of the northern
Peace River basin, the Floridan aquifer is overlain predominantly
by sand, with some interbedded clays and limestone which range
in thickness from less than 50 feet to more than 300 feet. In the
spring of 1965 numerous sinkholes developed in the northern Peace
River basin. This was a period of extremely low rainfall, maximum
ground-water withdrawal, and consequent record low water levels.
The formation of collapse sinkholes represent surficial evidence
of solutional activity in the underlying limestone aquifer. Within
a limestone aquifer, such as the Floridan, progressive solution
enlarges the underground conduits, resulting in extensive cavern
systems. As the solutional caverns increase in size or possibly as
support of their roofs is reduced by lowered artesian pressures,
their roofs may become incapable of supporting the overlying ma-
terials and eventually there is a collapse. Although the occurrence of
sinkholes is a natural geologic process in buried limestone terranes,
the periods of recent major sinkhole activity and the areal distribu-
tion of recently formed sinkholes indicate that other factors may
be important.
The occurrence and areal distribution of sinkholes in Polk
County during the period 1953 to 1960 is discussed by Stewart
(1966, p. 65-69). Analyses of the data show that 12 of 18 reported
sinkholes occurred during the drought years of 1954-56, a period
of generally declining artesian water levels. The areal distribution
of these 18 sinkholes was such that 16 out of 18 occurred within






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 29

the 20-foot line of the northeast quadrant of the regional decline
of water levels portrayed in figure 10. This area represents that part
of the hydrologic system between the main recharge area to the
northeast and the main discharge area to the southwest. The
steepest hydraulic gradients and consequently the greatest ground-
water velocities occur within this area. (See piezometric map,
figure 8).
It appears, therefore, that a causal relation may exist between
lowered artesian water levels and the occurrence of sinkholes.

SUMMARY AND CONCLUSIONS

The accelerated industrial and agricultural growth in the-Peace
and Alafia River basins has resulted in an increasing rate of
withdrawal of water from the Floridan aquifer; this in turn has
caused an increasing rate of decline of artesian water levels. The
largest declines underlie the industrialized area of southwestern
Polk County where concentrated pumpage has lowered artesian
water levels more than 50 feet since 1934. The demand for water
may more than double by 1980 and declines in artesian water level
are expected to continue into the future. It should be noted that
lowered water levels in themselves may not have an overall adverse
effect when the economic, sociological, and political benefits derived
from the large scale development of the ground-water resources are
taken into consideration.
Seasonal fluctuations of water level within the areas of heavy
pumping are large and are increasing and primarily reflect seasonal
pumpage rather than precipitation or recharge.
Large scale ground-water pumpage within the Peace and Alafia
River basins has produced a large regional lowering of water levels
centered in southwestern Polk County. The area of regional decline
has deepened and expanded until it presently (1965) reaches the
edge of the ridge and sinkhole-lake region to the northeast.
Preliminary evidence indicates retardation of the decline of water
levels in the direction of the sinkhole region, probably as a result
of recharge from the lakes. The declines in some lake levels, such
as occurred in the Lake McLeod area in the spring of 1965, may
be due in part to the lowered artesian water levels resulting from
the increased pumpage from the Floridan aquifer which increased
the downward leakage from the lakes. Water budget studies of
Lake McLeod in Polk County and Lake Placid in Highlands County
indicated downward leakage of 0.80 mgd and 6.4 to 9.5 mgd,






REPORT OF INVESTIGATIONS NO. 49


respectively. Also water budget analyses for Lakes Parker and
Scott near Lakeland show that the lakes recharged the underlying
limestone aquifers.
The increasing citrus acreage and related irrigation in the
southern Peace River basin coupled with a possible future south
and southwestward migration of phosphate mining should cause the
distribution of pumpage to increase in this area with additional
water-level declines.
Some of the effects of lowered artesian water levels, in addition
to the effects on some lake levels as discussed above, are:
(1) The loss of suction in wells when water levels
decline below the pump intakes. This entails adding
pump column and requires a greater pumping lift,
thereby increasing the cost.
(2) The reversal of the hydrologic conditions along the
Peace River between Bartow and Ft. Meade in Polk
County from one of discharge from the Floridan
aquifer in 1934 to one of potential recharge to the
aquifer in 1965.
(3) The position of the saline-fresh water interface,
which in part depends on the altitude of the piezo-
metric surface, may rise and create the possibility
of vertical salt-water encroachment. The depth to
saline water underlying the heavily pumped indus-
trial area of southwest Polk County was estimated
to be about 2,100 feet below msl in May 1965.
(4) The development of numerous sinkholes, caused by
the collapse of the subsurface, in the northern Peace
River basin during the spring of 1965 appears to be
related to the lowered artesian water levels which
increase the effective stress within the confined
aquifer system.
Important questions which arise concern the adequacy of the
long-term water supply and the long-term effects on the hydrologic
system of the progressively increasing demand for ground water.
One of the problems of determining the effects of pumping is
calculating the ultimate drawdown or change of water level that
would result from anticipated rates of pumping. Where knowledge
is available on the permeability, storage characteristics, areal
extent and thickness of a given aquifer, it is possible to quantita-






HYDROLOGIC EFFECTS-PEACE AND ALAFIA RIVER BASINS 31

4vely calculate how a system of wells will function and what will
occur in an aquifer under various assumed patterns of pumping.
SA complete appraisal of the Floridan aquifer within the Peace
and Alafia River basins is not possible at present (1965). Addi-
tional data collection, analyses and interpretation are necessary
for a more comprehensive understanding of the aquifer. A
quantitative evaluation of the Floridan aquifer within the Peace
and Alafia River basins is needed.
Aquifer characteristics such as coefficients of transmissibility,
storage, and leakance are available for areas immediately adjacent
to the north and northwest and for scattered areas throughout
Florida. See for example Menke, et al (1961) and Pride, et al
(1966). However, quantitative studies are not available for the
Peace and Alafia River basins. Geologic and hydrologic data,
including specific information on the amount, distribution, and
use of ground water, are especially needed near the center of
heavy pumpage in southwest Polk County.
The relation between the level of Lake McLeod and the shallow
and deep ground-water system is presently being investigated by
the U. S. Geological Survey. Studies to evaluate the relations
between lakes and the underlying Floridan aquifer are needed.
Additionally, a deep test-well in the center of the phosphate mining
area would be of great value. This well should be drilled to the
saline-fresh water interface and could serve as a monitor of
possible upward salt-water encroachment. It would also determine
the thickness and character of the Floridan aquifer and, if drilled
in a location so as to take advantage of existing wells as observation
wells, could furnish the needed aquifer characteristics through the
use of pumping tests. As pumping tests only represent a "spot"
sampling of the aquifer, an application of flow net analysis may
perhaps provide an integrated and more realistic value of the areal
transmissibility.







REPORT OF INVESTIGATIONS NO. 49


REFERENCES

Bishop, E. W.
1956 Geology and ground-water resources of Highlands County,
Florida: Florida Geol. Surv. Rept. Inv. 15.
Cherry, R. N. (see Pride, R. W.)
Florida Board of Conservation
1961-1964 Biennial Reports.
1966 Florida Land and Water Resources, Southwest Florida.
Florida Geological Survey
1933-1960 Biennial Reports.
Johnson, L.
1965 Investigation of Eagle Lake, Lake McLeod, Spirit Lake, Millsite
Lake, and Grassy Lake, Polk County, Florida: Unpublished
memorandum report to the Peace River Basin Board.
Kohout, F. A.
1959 (and Meyer, F. W.) Hydrologic features of the Lake Placid
area, Highlands County, Florida: Florida Geol. Survey Rept.
Inv. 19, pt II.
Menke, C. G.
1961 (and Meredith, E. W., and Wetterhall, W. S.) Water resources
of Hillsborough County, Florida: Florida Geol. Survey Rept.
Inv. 25.
Meredith, E. W. (see Menke, C. G.)
Meyer, F. W. (see Kohout, F. A. and Pride, R. W.)
Peek, H. M.
1951 Cessation of flow of Kissengen Springs in Polk County, Florida:
Florida Geol. Survey Rept. Inv. 7, pt III.
Pride, R.W.
1966 (and Meyer, F. W., and Cherry, R. N.) Hydrology of Green
Swamp area in central Florida: Florida Geol. Survey Rept.
Inv. 42.
Stewart, H. G. Jr.
1963 Records of wells and other water-resources data in Polk County,
Florida: Florida Geol. Survey Inf. Circ. 38.
1966 Ground-water resources of Polk County: Florida Geol. Survey
Rept. Inv. 44.
Stringfield, V. T.
1936 Artesian water in the Florida peninsula: U. S. Geol. Survey
Water-Supply Paper 773-C.
U. S. Bureau of Mines
1964-65 Minerals Yearbooks, Vol. 1.
U. S. Dept. of Agriculture
1965 Appendix to the report of "Water and related land resources,"
Florida west coast tributaries.
U. S. Geological Survey
1963 Compilation of records of surface waters of the U. S., Oct. 1950-
Sept. 1960, Part 2B: U. S. Geol. Survey Water Supply Paper
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Wetterhall, W. S. (see Menke, C. G.)










































































































f

















































































1