Appraisal of water resources in the East Central Florida Region ( FGS: Report of investigations 61 )

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 Investigations No. 61

APPRAISAL OF WATER RESOURCES
IN THE EAST CENTRAL FLORIDA REGION

By
William F. Lichtler

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
EAST CENTRAL FLORIDA REGIONAL PLANNING COUNCIL

TALLAHASSEE, FLORIDA
1972

J-7- 74

Completed manuscript received
February 23, 1972
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by
Rose Printing Company
Tallahassee, Florida

Tallahassee
1972

^ 2- v^ /

FLRD GEOLIOWC( ICA SURflViEWY~

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CONTENTS

Abstract ..................... . .......
Introduction . . . . . . . .
Purpose and scope ..........................
Previous reports .... . . . . . .. .
Description of the Region ......................
Location and extent .......................
Topography ............................
Climate ...............................
Drainage .............................. .
Surface drainage .......................
St. Johns River basin ....................
Kissimmee River basin ...................
Coastal basins ........................
Subsurface drainage .....................
Geology ..............................
Formations ...........................
Lake City Limestone ....................
Avon Park Limestone ..................
Ocala Group .......................
Oligocene Limestone ....................
Hawthorn Formation ..................
Undifferentiated sediments ...............
Structure .............................
Hydrology ...............................
Surface water ............................
Stream s .............................
Lakes ...............................
Water quality ..........................
Ground water ..............................
Nonartesian aquifer .......................
Aquifer properties ....................
Water levels ........................
Water quality .......................
Yield ............................
Secondary artesian aquifers .................
Aquifer properties .....................
Water quality .......................
Floridan aquifer .........................
Aquifer properties ................. .
Recharge and discharge .. . . . .
Confined potentiometric surfaces . . .
Water quality ......................
Yield ............................
Water Use ................................

Page
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. .. . .. .. .. 15
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.. .... .. .. .. .. 16
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.. .. ... .. .. 19
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.. .... .... .... 21
.. .. ........ .. 21

Public supplies ......................................... 35
Rural .............................................. 35
Irrigation ............................................ 35
Self-supplied industrial .................................... 39
Demand and supply ........ .. ...... ... ..... ... ... ......... 39
Problems and alternate solutions in water-resource management ............. 41
Problem s ............................................ 41
Solutions ............................................. 42
Most effective recharge areas .............................. 43

iii

. . . .

............

Moderate to poor recharge areas ........................... 46
Very poor recharge areas . . . . . . . .49
Conclusions . ... . . .. .. . . .. .. . .. 50
References . . . . . . . . . . . 52

ILLUSTRATIONS

Figure Page
1. Map showing topographic divisions ............................ 4
2. Map showing drainage system ................................ 7
3. Map showing altitude of top of Floridan aquifer . . . . ... 14
4. Map showing recharge areas of Floridan aquifer .... .. .. .. ... Inside Back Cover
5. Map showing confined potentiometric surface
of Floridan aquifer May 1970 ............................... 27
6. Map showing water-level changes in the Floridan
aquifer July 1961-May 1970 ................................ 29
7. Map showing water-level changes in the Floridan
aquifer May 1969-May 1970 ................................ 30
8. Map showing dissolved solids in water from the
upper part of the Floridan aquifer ............................ 32
9. Map showing hardness in water from the upper
part of the Floridan aquifer ................................ 33
10. Map showing chloride in water from the upper
part of the Floridan aquifer ................................. 34
11. Sketch showing tentative design of connector well . . . . . 48

TABLES

Table
1. Land and water area in the East Central Florida Region
2. Drainage areas and discharges of streams in the Region .
3. Summary of the properties of the geologic formations
penetrated by water wells in the East Central
Florida Region ......................
4. Estimated water used for public supplies, by counties .
5. Estimated water for rural use, by counties ........
6. Estimated water used for irrigation, by counties .. .
7. Estimated use of self-supplied industrial water,
by counties ........................

Page
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. . . . .. 9

. .. . .. .. 12
. . . . .. 36
. . . . . 37
. . . . .. 38

.... ... .. .. .. .. .. 40

APPRAISAL OF WATER RESOURCES

IN THE EAST CENTRAL FLORIDA REGION
By
William F. Lichtler

ABSTRACT
The East Central Florida Region includes seven counties with a total area of
7,051 square miles. The continuing rapid development of the Region has
resulted in an increasing demand upon its water resources.
All water supplies come from rainfall in or near the Region-therefore,
water-resources management is essential to insure an adequate supply for present
and future needs. The ground-water system that underlies the entire Region-the
Floridan aquifer and the overlying unconfined aquifer-if by far its largest and
most efficient water reservoir. Surface reservoirs are mostly shallow and subject
to high evaporation losses and contamination and are fed by streams that have
very low flow during droughts.
In certain areas of the region natural geologic and hydrologic conditions are
favorable for harvesting rainfall as recharge to the Floridan aquifer. These areas
are most of Lake County and the western parts of Orange, Seminole and Volusia
counties. In other areas, most of Osceola, Brevard, and Indian River counties,
and the eastern parts of Orange, Seminole, and Volusia counties, the aquifer
contains highly mineralized water.
The total recharge to the Floridan aquifer, under natural conditions, is
estimated to be about 1,000 million gallons per day. Projections for the year
1990 indicate that ground-water usage may total about 60 percent of the natural
recharge rate. This appraisal indicated that sound water-management practices
will be necessary to maintain the projected 1990 usage without aquifer depletion
and damage.
The principal water-management objectives of the Region are to develop
land-use controls and artificial-recharge techniques that will preserve or increase
recharge in naturally efficient rainfall-harvesting areas, increase recharge in poor
rainfall-harvesting areas, and at the same time protect or improve the quality of
the water in the aquifer. Possible land-use controls include zoning, tax rebates,
subsidies, and public ownership of the best recharge areas. Artificial recharge
techniques include construction of connector wells that connect the nonartesian
aquifer to the Floridan aquifer, augmentation of recharge by importing water
from surface runoff areas, use of recharge wells for accepting treated storm
water, and land spreading of treated sewage effluent.

REPORT OF INVESTIGATIONS NO. 61

INTRODUCTION
The rapidly expanding population and economic growth in the seven
counties of the East Central Florida Regional Planning Council as shown in
Figure 1, herein called the East Central Florida Region or the Region, has
resulted in increasing demands on its water resources. Although there is
abundant water in the Region as a whole, the water in some areas of the Region
is of unacceptable quality for most uses. As the population increases the demand
for water will become much greater and the available supply may be reduced by
pollution and increased drainage necessitated by urbanization and other land
development. Ground-water supplies can be increased by capturing and storing
water underground that now drains to the sea or evaporates from swamp areas.
Research is needed, however, to develop artificial-recharge methods that are
feasible and which will preserve or improve the quality of water in the aquifer.
PURPOSE AND SCOPE
The purpose of this investigation is to summarize recently available
information concerning the water resources of the Region and to appraise the
water situation in the light of this additional information. The report points out
the need for sound management of the water resources of the Region as a whole
and discusses various practices and techniques that can preserve and enhance its
water resources.
This report identifies the problem areas of the Region and indicates which
methods of artificial recharge are probably best suited to the various areas,
depending on the types of problems involved. Problems are different from place
to place because of differences in geology, topography, and population
concentrations. Possible methods of water-resources management that would
optimize water development are described toward the end of the report.
For the present investigation, much basic information was obtained from
recently published reports and some additional field work was done. The
investigation was made by the U.S. Geological Survey in cooperation with the
East Central Florida Regional Planning Council. The work was done under the
general supervision of Clyde S. Conover, District Chief, and under the
immediate supervision of Joel 0. Kimrey, Subdistrict Chief.
PREVIOUS REPORTS
Reports containing information on the water resources of the Region have
been published by many different agencies.
An annotated bibliography containing 113 items that were available in 1964
is given as appendix 4 in the Planning Council's 1965 Research Series 11-65
(Water Needs and Resources). That bibliography is not included with this report.
Since 1964 additional reports have been prepared by Lichtler, Anderson, and
Joyner of the U.S. Geological Survey. These and several other recent reports are
included in the bibliography at the end of this paper.

REPORT OF INVESTIGATIONS NO. 61 3

DESCRIPTION OF THE REGION

LOCATION AND EXTENT

The Region is in the east central part of peninsular Florida within the
boundaries of 27033' and 29026' latitude and 80019' and 81057' longitude. It
includes the seven counties of the East Central Florida Regional Planning
Council: Brevard, Indian River, Lake, Orange, Osceola, Seminole, and Volusia.
The Region contains 7,051 square miles of which 6,216 square miles are land
area and 835 square miles are water. The seven-county area is shown on Figure 1
and the land and water areas of each of the seven are listed in Table 1. In 1970,
the population was 1,121,800.
The principal industries are tourism, agriculture, and space related indus-
tries. The principal agricultural products are citrus products, cattle, vegetables,
ornamental plants, poultry, and timber or pulpwood.

Table l.-Land and water areas in the East Central Florida Region.

Land Total Fresh Total Salt Total Total
Area Water Area Water Area Water Area Area
County (sq mi) (sq mi) (sq mi) (sq mi) (sq mi)
Lake 996 167 167 1,163
Volusia 1,115 65 27 92 1,207
Seminole 321 31 31 352
Orange 916 87 87 1,003
Brevard 1,032 57 222 279 1,311
Osceola 1,325 142 142 1,467
Indian River 511 35 2 37 548
Total 6,216 584 251 835 7,051

Source: Unpublished data, courtesy Mr. N.C. Landrum, Director, Florida Outdoor Recreation
Planning Committee.

TOPOGRAPHY

On the basis of topographic differences, the East Central Florida Region is
divided into three divisions in this report. They are (1) a lowlands division where
altitudes are generally less than 35 feet, (2) the intermediate division where
altitudes are generally between 35 and 105 feet, and (3) a highlands division
where altitudes are generally greater than 105 feet. These divisions are shown in
Figure 1.
The lowlands division includes the coastal areas, the St. Johns River valley
and tributaries to the St. Johns River (fig. 1). At an altitude of about 35 feet

REPORT OF INVESTIGATIONS NO. 61

ar4S' so s aroo 45

30' 80Ios

EXPLANATION

SLOWLANDS DIVISION
Atiudns range fltr sa m evel to
about 35 lee abo sea stel.
INTERMEDIATE DIVISION
Antubso range from 35 to 105 fee
obove Mo tmel but ar mostly bel
50 and 5B foal.
1 HIGHLANDS DIVISION
Alttituds genAral above 105 feet

a a MAA.u

Area shown is East Central Florida
Regional Planning Council Region

Figure l.-Map showing topographic divisions.

28*o

REPORT OF INVESTIGATIONS NO. 61

there is a relatively steep scarp in many places. A few elongate areas in eastern
Brevard and Indian River Counties having altitudes greater than 35 feet have
been included in the lowlands division. These are mostly fossil sand dune
deposits on ancient coast lines.
The intermediate division occupies most of the middle part of the Region
(fig. 1) between the lowlands on the east and the highlands on the west. With
the exception of the lakes along the mainstem of the St. Johns River, most of
the large lakes of the Region are in the intermediate division.
Although altitudes in the intermediate division are generally between 35 and
105 feet, most land lies between 50 and 85 feet above sea level. A characteristic
area of gentle ridges and intervening lower areas parallel to the Atlantic Coast is
best developed east of Orlando in Orange County. These ridges are believed to be
fossil beach ridges.
The highlands division occupies much of the western part of the Region.
Streams are less common than in the other two divisions except in Green Swamp
in the southwestern part of Lake County. Altitudes range from less than 50 feet
to more than 300 feet above mean sea level and are generally above 105 feet.
Relief in the highlands division is much greater than in the rest of the Region.
For example, local relief of as much as 225 feet occurs in Lake County. The
highlands contain many lakes and depressions, most of which do not have
surface outlets.
The water resources of the Region are directly related to the topography. In
general, the highlands are the most effective natural ground-water recharge areas,
although geologic and hydrologic conditions in Green Swamp prevent the rapid
downward movement of rainwater even though the area is one of the highest in
the peninsula. Pride, Meyer, and Cherry (1966, p. 129) state that "High
piezometric levels in the southern part of the Green Swamp are believed to be
the result of a relatively slow rate of ground-water outflow which is probably
caused by sand-filled fractures, caverns and sinkholes. These act as a natural
grout which decreases the transmissibility of the aquifer." They further state (p.
21) "The surface drainage of the Green Swamp area is poor because of the flat
topography and lack of well developed stream channels." Elsewhere in the
highlands division most of the rainfall that is not lost by evapotranspiration
percolates downward to recharge the aquifers.
The intermediate topographic division varies from very good to very poor as
a ground-water recharge area. There are extensive, highly effective recharge areas
within the intermediate division especially in Volusia, Seminole and in northern
Lake counties. There are many lakes and closed depressions in some parts but
none in others. Most surface streams either go dry or decline to very low flow
after relatively short periods of drought.
In contrast to the other two divisions, the lowlands division is generally a
ground-water discharge area. Streamflow is better sustained than in the other

REPORT OF INVESTIGATIONS NO. 61

divisions because of spring flow and seepage of ground water from both the
water-table and artesian aquifers.

CLIMATE

The Region has a subtropical climate with two pronounced seasons, winter
and summer. By virtue of its proximity to the Atlantic Ocean and the Gulf of
Mexico and the many lakes and swamps, relative humidities remain high the year
round.
In 1969 the average rainfall at 16 stations in the Region was 59.5 inches. The
rainfall ranged from 50.22 at Daytona Beach to 71.72 at Titusville. At Orlando,
near the center of the Region, it was 55.18 inches or 3.81 inches above normal.
Summer thunderstorms accounted for most of the rainfall. Thunderstorms occur
on the average of 83 days per year, one of the highest incidents of
thunderstorms in the United States (U.S. Weather Bureau, Annual Report 1960).
The average temperature of nine stations in the Region for 1969 was 70.8F
and ranged from 69.7*F at Daytona Beach to 71.6F at Orlando.

DRAINAGE

In comparison with the rest of the United States, East Central Florida is
unusual in its drainage characteristics. Its underground drainage is much greater
than its surface drainage. This is because the porous surface sand readily allows
rainfall to percolate downward and the underlying cavernous limestone
facilitates the flow of water to points of discharge such as springs, seeps and to
the ocean.

SURFACE DRAINAGE

ST. JOHNS RIVER BASIN

The St. Johns River is the most prominent surface drainage feature of the
Region, as shown in Figure 2. Its source is south of the Region at an altitude of
less than 25 feet in a broad swampy area west of Fort Pierce in St. Lucie

REPORT OF INVESTIGATIONS NO. 61 7

Figure 2.-Map of Region showing drainage system.

REPORT OF INVESTIGATIONS NO. 61

County. Its mouth is at Mayport about 300 river miles from the source and its
course across the Region is generally north-northwest. From the headwaters a
marsh extends northward approximately 50 miles before a natural channel
becomes recognizable, upstream from Lake Hellen Blazes. This marsh area has
been modified extensively by canals and dikes so that considerable interchange
of water takes place with. the Lake Okeechobee basin to the south and the
Coastal Basins to the east. Of the total 9,430-square-mile St. Johns River basin,
about 3,600 square miles are within the East Central Florida Region. Normally,
the St. Johns is tidal as far upstream as Lake George in northern Volusia County.
Under combined conditions of drought and high tide, tidal effects may occur as
far upstream as Lake Monroe in Seminole and Volusia counties, about 160 miles
from its mouth. Much of the land bordering the river is swamp or marshland.
During the rainy season a strip as much as 7 miles wide is flooded. The average
flow of the St. Johns River where it leaves the Region is about 3,000 cfs (cubic
feet per second). Average runoff from the part of the drainage basin within the
Region is about 1.2 cfs per square mile or about 16 inches of runoff per year.
This is equal to about 30 percent of the average annual rainfall in the area.
However, the variability of the St. Johns is indicated by observations of no flow
in the river at State Road 50 bridge for periods during March, April and June
1939.

KISSIMMEE RIVER BASIN

The Kissimmee River and its tributaries drain about 1,100 square miles of
the East Central Florida Region including more than half of Osceola County.
Headwaters streams begin south of Orlando and drain southern and southwes-
tern Orange County, and a small area in southeastern Lake County. Headwaters
streams of the Kissimmee River include Boggy Creek, Shingle Creek, Cypress and
Bonnet creeks, and Reedy Creek.

COASTAL BASINS

The streams draining the coastal area of the Region have relatively small
drainage basins. Tomoka River drains only 152 square miles. Water from the
coastal area drains into lagoons which connect to the ocean through inlets.
Drainage areas and discharges for the major streams in the St. Johns River,
Kissimmee River and Coastal basins are shown in Table 2.

SUBSURFACE DRAINAGE

The total amount of subsurface drainage in the East Central Florida. Region

Table 2.-Drainage areas and discharges of streams in the Region.

Drainage Area
(sq mi)

Maximum

cfs cfs/sq mi

Discharge
Minimum

cfs cfs/sq mi

Average

efs cfs/sq mi

Average Runoff
(in/yr)

ST. JOHNS RIVER BASIN
Oklawaha River at Moss Bluff
Econlockhatchee River near Chuluota
Wekiva River near Sanford
Apopka-Beauclair Canal near Astatula
Palatlakaha Creek near Mascotte
Deep Creek near Osteen
Taylor Creek near Cocoa
Wolf Creek near Deer Park
Jane Green Creek near Deer Park
Deep Creek near Barberville
Jim Creek near Christmas

KISSIMMEE RIVER BASIN
Ajay-East Tohopekaliga Canal
Shingle Creek near Kissimmee
Boggy Creek near Taft
Reedy Creek near Vineland
Bonnet Creek near Vineland
Cypress Creek at Vineland

COASTAL BASINS
Turkey Creek near Palm Bay
Tomoka River near Holly Hil
Spruce Creek near Samsula
Crane Creek at Melbourne

910
241
189
184
180
120
55.2
25.7
248
23.0
22.7

171
89.2
83.6
75.0
56.1
30.3

95.5
76.8
32.0
12.6

1,630
11,000
2,060
754
458
2,630
3,000
7,700
18,400
1,100
3,750

1,420
3,320
3,680
1,910
1,180
354

2,790
2,170
1,610
665

1.8
45.6
10.9
4.1
2.5
21.9
54.4
300
74.2
47.8
165

8.3
37.2
44.0
25.5
21.0
11.7

29.2
28.3
50.3
52.8

8.0 .01 370
6.7 .03 281
105 281
0 0 94.3
.2 0 104
.4 0
0 0
0 0 40.4
0 0 306
.1 0
0 0

170
62.5
54.5
55.0
33.0
8.4

15.0
0
0
1.8

.16 137
64.2

.14 15.9

5.5
15.8
20.2
7.0
7.8

1.6 21.4
1.2 16.7

13.5
9.5
8.8
10.0
8.0
3.8

1.4 19.5
.8 11.3

1.3 17.1

Stream

REPORT OF INVESTIGATIONS NO. 61

ranges from all of the excess of rainfall over evapotranspiration to none of it.
There are two principal types of subsurface drainage in the Region. In the
first type, rain water that escapes evapotranspiration or does not run off
percolates downward until it reaches the water table and then moves more or
less laterally through sandy material until it emerges at the surface in lakes,
streams, or swamps at a lower altitude. The water usually does not travel very
far, moves in a non-artesian system, and is discharged by gravity springs or seeps.
In the second type of subsurface drainage, rainwater continues downward
into the limestone of the Floridan aquifer and then moves laterally through the
limestone to points of discharge through artesian springs and seeps on land or on
the floor of the ocean. In this type of drainage the water usually moves greater
distances and is under artesian pressure. The artesian pressure that causes the
springs to flow results from recharge in the topographically higher areas of the
hydrologic system.
The first or nonartesian type of subsurface drainage contributes most of the
flow to streams and lakes. During dry weather, this system is the sole source of
water to maintain the flow in the streams and the levels in the lakes of the
Region. The artesian system is the source of most of the municipal, industrial,
and domestic water supplies and a significant part of the irrigation supplies. In
addition, the large springs of the Region such as Rock, Wekiva, Sanlando and
Alexander derive water from the artesian system.
Factors that determine the amount of subsurface drainage in a given area are
the permeability of the surface and subsurface materials, the topography of the
land surface, and the altitude of the potentiometric surface in relation to the
altitude of the land surface. If the surface materials are of low permeability, the
rain cannot infiltrate as fast as it falls and surface runoff occurs. Also, if the
surface materials are permeable but the subsurface materials have a low
permeability, the surface materials become saturated and surface runoff occurs.
Where the slope of the land surface is sufficient the water will move laterally
through the permeable surface material. This can result in the water table being
at or near the surface on the crests of broad, dome-shaped hills and deeper on
the flanks of the hill.
The effects of a breach in the clay layer by sinkhole formation are shown by
the water levels in two test holes that were drilled about a mile apart. The
land-surface altitudes at each site were about the same but one test site was near
a small sinkhole depression while the other was not. At the site about a mile
from the sinkhole the water table was about 1 foot below the land surface
while at the site near the sinkhole the water table was 20 feet below the surface.
The possibility of creating artificial breaches in the clay layer to lower the water
table and provide adequate storage for rainfall is discussed later in this report.
Poor subsurface drainage occurs in areas where the potentiometric surface is
near or above the land surface. In these areas there is little or no head difference

REPORT OF INVESTIGATIONS NO. 61

to induce excess water to move downward to the artesian aquifer. All subsurface
drainage must occur through the nonartesian aquifer and unless there is
significant local relief with nearby points of discharge such as a stream drainage
system, subsurface drainage will be poor. In addition, upward leakage from the
artesian aquifer may add water to the nonartesian aquifer and further reduce its
ability to drain excess surface water. The St. Johns River marsh is an example of
this condition. Methods of increasing ground-water recharge in areas where the
surface materials have low permeability or where the potentiometric surface is
near or above the land surface are also discussed in this report.

GEOLOGY

The occurence, movement, availability, quality and quantity of ground water
in the Region are closely related to its geology.
The Region is underlain mostly by marine limestone, dolomite, shale, sand
and anhydrite that range in total thickness from about 5,500 to 12,000 feet in
different parts of the Region. Below these depths the granites and other
crystalline rocks of the basement complex occur. Only about the top 2,000 feet
of sediments, which have been penetrated by water wells, will be discussed in
this report. A summary of the properties of the formations is given in Table 3.

FORMATIONS
LAKE CITY LIMESTONE

The oldest formation penetrated by water wells in the Region is the Lake
City Limestone of middle Eocene age.
The Lake City Limestone underlies the entire Region and consists of
alternating layers of hard, brown, porous to dense, crystalline dolomitic
limestone and soft to hard, cream to tan, chalky, fossiliferous limestone and
dolomitic limestone.
The Lake City Limestone is lithologically and hydrologically similar to the
overlying Avon Park Limestone, from which it is distinguished by the presence
of the fossil Forminifera Dictyoconus Americanus in the Lake City Limestone.
Dolomitization has destroyed or damaged the fossils in many areas of the Region
making it difficult to determine the depth to the top of the formation.
Relatively few wells penetrate the Lake City Limestone, and no water wells
are known to penetrate its total thickness, but the formation is more than 700
feet thick. The Lake City Limestone yields very large amounts of water-5,000
to 10,000 gpm (gallons per minute)-to many wells and is the principal source of
water for the cities of Orlando and Winter Park.

Table 3,-Summary at the properties of the geologic formations penetrated by water wells in the East Central Florida Region.

Formation
Series name

Recent
Pleistocene,
Pllocene,
and
Miocene

Undiffer.
entiated,
may Include
Caloosahatchee
Mad

Miocene Hawthorn

0-200 Mostly quartz sand
with varying amounts
of clay and shell,

0-250 Gray.green, clayey
quartz sand and silt;
phosphatic sand; and
buff, Impure, phos-
phatic limestone,
mostly in lower part.

Eocene Ocala
Group

Eocene Avon
Park
Limestone

Eocene Lake
City
Limestone

0400 Cream to tan, fine,
soft to medium hard,
granular, porous,
sometimes dolomitic
limestone

100- Upper section mostly
1,000 cream to tan, granu-
lar, porous limestone.
Often contains abund-
ant cone-shaped
Foraminifers. Lower
section mostly dense,
hard, brown, crystal-
line dolomite.

Over Dark brown crystal-
700 line layers of
Total dolomite alternating
unknown with chalky fossili-
iferous layers of
limestone.

Moderately high
transmlssibiUty,
most wells also
penetrate under-
lying formations.

Overall transmis-
sibility very high,
contains many inter-
connected solutions
cavities. Many large
capacity wells
draw water from
this formation.

Similar to Avon
Park Limestone.
Municipal supply
of City of Orlando
obtained from
this formation.

Thick.
neas,
in
feet

Description of
material

Water-bearing
properties

Aquifer

Water level

Varies widely in
quantity and qual.
ity of water
produced

Generally imper.
meable except for
limestone, shell,
or gravel beds,

Non.
artesian

Secondary
artesian, lower
limestone
beds may be
part of
Floridan

0 to 0S feet
below the land
surface but
generally leas
than 10 feet

Plezometric
surface not de-
fined, water
level generally
is lower than
nonarteslan
aquifer and
higher than
Floridan
aquifer.

Floridan

Potentiometric
surface shown
in figure 6.

Floridan

REPORT OF INVESTIGATIONS NO. 61

AVON PARK LIMESTONE
The Avon Park Limestone of middle Eocene age appears to conformably
overlie the Lake City Limestone and is composed of similar materials. The
formation, which probably underlies the entire Region, is generally dis-
tinguished from overlying strata by the occurrence of many sand-sized,
cone-shaped foraminifera and is distinguished from the underlying Lake City
Limestone by the absence of Dictyoconus Americanus.
The thickness of the Avon Park Limestone is not known accurately except in
a few places because few wells penetrate the entire formation. Known
thicknesses range from less than 100 feet in Indian River County to more than
1,000 feet in southern Lake County. Depths to the top of the formation range
from less than 30 feet in parts of Lake County to more than 800 feet in parts of
Indian River County.
The Avon Park Limestone is a principal source of ground water throughout
most of the Region. In Orange, Osceola, Seminole and Lake Counties and parts
of other counties many of the largest well yields are from the hard, brown,
dolomitic limestone layers in the Avon Park Limestone. Although fragments
from drill cuttings indicate that the dolomitic limestone is very dense, the layers
usually contain interconnected solution channels of up to 90 feet in height that
yield more than 5,000 gpm. In areas where the dolomitic layers do not contain
solution channels, they probably inhibit the vertical movement of water.
OCALA GROUP
The Ocala Group' unconformably overlies the Avon Park Limestone and
contains the Crystal River, Williston and Inglis Formations of late Eocene age.
The Ocala Group was deposited on the eroded and irregular surface of the Avon
Park Limestone and was subjected to a very long period of subaerial erosion that
removed the entire group in some areas of the Region, especially in southern
Orange County and parts of Lake County. The erosion accounts for some of the
varying thickness and altitude of the group. The thickness of the group varies
from 0 to more than 200 feet in the Region. The lithology is similar to that of
the underlying Avon Park Limestone except that the Ocala usually contains less
dolomitic limestone and is softer and lighter in color. Where present, the Ocala
usually constitutes the uppermost part of the Floridan aquifer and in areas
where it is appreciably thick it will yield moderate to large amounts of water.
The contours on the top of the Floridan aquifer shown in Figure 3 reflect, for
the most part, the top of the Ocala group. Depth to the top of the Ocala varies
from less than 25 feet in parts of Lake County to more than 600 feet in Indian
River County.

1 The term "Ocala Group" has not been adopted by the U.S. Geological Survey. The
Florida Geological Survey uses Ocala as a group name as proposed by Puri (1953) and
divided into three formations-Crystal River, Williston and Inglis Formations.

REPORT OF INVESTIGATIONS NO. 61

14

29*15

29'0F

EXPLANATION

-0-

act.f a te too of
he Floridan Aquifer
ICAWAr & ao 4ft;

? MILK$1.1

Figure 3.-Map of Region showing altitude of top of Floridan aquifer.

8a4s'

I5' 81*00' 45'

0
0
,

REPORT OF INVESTIGATIONS NO. 61

OLIGOCENE LIMESTONE

Limestone of Oligocene age occurs only in a small area in eastern Indian
River County where it overlies the Ocala Group. Although the limestone is as
much as 280 feet thick it has low permeability and is not an important part of
the Floridan aquifer.

HAWTHORN FORMATION

Where present, the Hawthorn Formation of middle Miocene age uncon-
formably overlies the Ocala group except where the Ocala is missing and in the
small area of Indian River County where Oligocene rocks overlie the Ocala. The
Hawthorn Formation consists of varying proportions of quartz sand and silt,
clay, phosphorite, phosphatic limestone and sandstone. These materials generally
have less permeability than the limestones of the Floridan aquifer or the sands of
the nonartesian aquifer, and tend to separate the two aquifers. In recharge areas
as shown in Figure 4, the formation retards the downward movement of water
into the Floridan aquifer and in discharge areas it retards the upward movement
of water and confines it under pressure. Locally it may be a part of the Floridan
aquifer [p. 40].
The Hawthorn Formation contains numerous lenses and discontinuous layers
of shell and coarse sand that yield large quantities of water in some places. A
well tapping a 13-foot shell bed in eastern Orange County yielded 1,000 gpm
with about 50 feet of drawdown. The shell bed occurs between 75 and 88 feet
below the land surface, and pump tests indicated its poor hydraulic connection
with the Floridan aquifer and the nonartesian aquifer. This illustrates the
productivity and the possible extent of isolation of permeable beds that occur
within the Hawthorn Formation.
The Hawthorn Formation is apparently absent in Volusia County and parts
of Seminole and Lake County. Within the Region its thickness ranges from 0 to
about 250 feet.

UNDIFFERENTIATED SEDIMENTS

The sediments above the Hawthorn Formation include the Caloosahatchee
Marl (which has been designated upper Miocene, Pliocene and Pleistocene by
various workers), thick deposits of variegated red clayey sand, and marine
terrace deposits. Surface deposits throughout the Region have generally been
designated Holocene and Pleistocene; however, recent identification of fossils
from a clay pit 7 miles northwest of Orlando and a shell bed 13 feet below the
surface in eastern Orange County have shown that the sediments are equivalent

REPORT OF INVESTIGATIONS NO. 61

to the Pinecrest Sand member of the upper part of the Tamiami Formation
(Mio-Pliocene age).
The thickness of the undifferentiated sediments ranges from 0 to 200 feet.
These sediments yield small (5-15 gpm) supplies to screened wells and small
diameter open wells in most parts of the Region.

STRUCTURE
The generalized configuration of the top of the Floridan aquifer is shown on
Figure 3. The top of the aquifer conforms roughly to the top of the limestone
formations of Eocene age. The Eocene formations represented by Figure 3
include the Crystal River Formation, the Williston Formation, the Inglis
Formation and the Avon Park Limestone. Figure 3 is not bated on a single
uneroded horizon such as the top of a conformable formation or a marker bed;
however, in a gross sense it reflects underlying structure. Figure 3 does not show
the presence of faults although they undoubtedly occur in the Region. Faulting
can affect the movement of water in the ground and also alter surface drainage;
however, more information will be necessary before the faults can be delineated
and their effects on the hydrology of the Region can be assessed.
The depth to the Floridan aquifer below land surface may be obtained by
adding the altitude of the land surface to the altitude of the surface of the
aquifer in areas where the top of the aquifer is below mean sea level. In areas
where the top of the aquifer is above mean sea level, this altitude should be
subtracted from the land surface altitude to obtain the depth to the aquifer.

HYDROLOGY

The water supply of the earth, whether it is on the surface or below the
ground, has its origin in precipitation. Of the precipitation that reaches the
ground, part is returned to the atmosphere by evapotranspiration; part remains
above ground and is stored temporarily in lakes, ponds, and swamps, or moves to
the sea as streamflow; and part percolates into the ground, some to replenish the
soil moisture and some to enter the saturated zone and recharge ground-water
supplies. Ground water moves in the aquifers (ground-water reservoirs) under the
influence of gravity, toward areas of discharge such as streams, lakes, springs,
wells, and the oceans.

SURFACE WATER

Important factors in considering surface water as a potential source of
supply are its dependability and chemical quality. Dependability includes the

REPORT OF INVESTIGATIONS NO. 61

average amount of water available and the extremes of variation in the amount.
Even if a stream has an average flow of 100 cfs it may have little value as a
source of supply if the extremes of flow vary from 0 to 300 cfs. Usually the
heaviest demand for water occurs during droughts when the flow may be zero.

STREAMS

Extreme variability of flow is one of the most serious factors limiting the use
of the streams of the Region for water supply. Even the St. Johns River, which is
the largest stream in the Region, at times had no flow at the State Road 50
bridge between Orange and Brevard Counties.
Most streams of the Region have little or no flow after only moderate
droughts. The exceptions are streams that are fed by artesian-spring discharge;
however, this flow cannot be considered a long-term dependable supply because
ground-water pumpage, especially in areas upgradient from the springs, may
lower the potentiometric surface sufficiently to reduce or stop the flow of the
springs.
Most streams in the Region go dry or have very low flow because their
channels are not deeply incised and the water table declines below the stream
bed after short drought periods. Thus there is little or no ground-water seepage
to maintain the base flow of the stream. The high, low, and average flows of the
major streams of the Region are listed in Table 2.
Storage facilities are necessary to insure a dependable surface-water supply
during minimum flow periods. Channel storage is small in the poorly defined
channels, but lakes and swamps in the stream valley can provide considerable
storage space and help reduce the extremes of flow. Most lakes in stream valleys
are shallow and evaporation rates are high in comparison to the amount of water
stored. If the depths of the lakes can be increased by lowering the lake bottom
or raising the lake shore, their storage capacity can be increased without
increasing evaporation losses. However, ground-water seepage losses may be
increased. The St. Johns River valley is one of the most favorable locations for
increasing surface-water storage because of the large area of low, flat,
undeveloped land adjacent to the river.
Lake Washington, in the main stem of the St. Johns River 8 miles northwest
of Melbourne, is the principal source of water for the Melbourne area. During
droughts there is little or no flow into the lake and its level is lowered by
continuing withdrawal. The quantity of water in storage was increased by
damming the river below the lake in 1961. In addition the proposed upland
reservoirs (Jane Green, Blue Cypress and Fort Drum) will store considerable
quantities of water, some of which could be released to augment the flow of the
St. Johns River or could be used directly from the reservoirs.

REPORT OF INVESTIGATIONS NO. 61

The primary function of the upland reservoirs is flood control. If
implemented as planned, the works in the upper St. Johns River basin would
store only limited quantities of surface water because they would have to be
nearly empty prior to the rainy season to be available to store flood runoff.
The water in Lake Washington and the upland reservoirs is low in mineral
content but high in color. If withdrawal from these water bodies becomes too
great they may suffer from stagnation and eutrophication.
Downstream from Lake Washington, the St. Johns River becomes pro-
gressively more mineralized, partly because of seepage of mineralized artesian
water into the bed of the river, but mostly because of inflow of mineralized
irrigation water from flowing wells in the Floridan aquifer. Because of the highly
mineralized water, the prospects of developing municipal supplies of surface
water downstream of Lake Poinsett are poor, but the water may be suitable for
irrigation of salt-tolerant crops.

LAKES

A considerable volume of water is stored in the many lakes of the
Region-although it is only a fraction of the total amount of water in storage at
any given time. The usefulness of these lakes as sources of water is severely
limited because of the desirability of lake front property as homesites.
Homeowners like to have a stable lake level for esthetic purposes and to
facilitate boating and swimming. These needs conflict directly with flood-control
requirements: storage reservoirs are raised to their highest possible level during
flood times and drawn down during droughts.

WATER QUALITY

A second factor limiting the use of surface water in the Region is its quality.
Water-treatment plants can be designed to treat most of the different kinds of
fresh surface water found in the Region; however, operation of such plants is
extremely difficult when the quality of the water changes from day to day.
Water in streams is usually higher in mineral content during periods of low
flow and higher in color during early periods of high flow. The pH of the water
often changes seasonally. The concentration of pollutants in a stream will vary
with the volume of flow and the composition of the pollutants can also vary.
Lakes such as Lake Apopka, which is in an advanced stage of eutrophication,
often have algal blooms during the summer which make treatment difficult.
The salt (chloride) content of the St. Johns River at State Highway 520
exceeds public health standards for potable water about 15 percent of the time.

REPORT OF INVESTIGATIONS NO. 61

The brackish water results from upward leakage of highly mineralized water
from the Floridan aquifer through the relatively thin confining beds overlying
the Floridan aquifer in parts of the St. Johns River valley, and from the flow of
such water from artesian wells in the valley.

GROUND WATER

Ground water in the East Central Florida Region occurs under both
nonartesian and artesian conditions. Nonartesian conditions occur where the
upper surface of the zone of saturation is not confined and, accordingly, is free
to rise and fall directly in response to variations in recharge and discharge.
Artesian conditions occur where the water is confined and rises in wells above
the point at which it is first encountered. The heights to which water rises in
tightly cased wells that penetrate an artesian aquifer define its confined
potentiometric surface. The altitude of the confined potentiometric surface is
not necessarily directly related to the altitude of the water table (unconfined
potentiometric surface); the confined potentiometric surface may be above,
below, or at the same level as the water table.

NONARTESIAN AQUIFER
AQUIFER PROPERTIES

The nonartesian aquifer consists mostly of the undifferentiated sediments. It
extends over most of the Region and is composed mainly of quartz sand with
varying amounts of clay, hardpan, and shell. It is an important source of water
where only small quantities are needed for domestic use, stock watering, and
lawn irrigation. The thickness and character of the aquifer are highly variable.
For example, in the St. Johns River basin the nonartesian aquifer is as little as 3
feet thick whereas in the ridge area in the western part of the Region it is more
than 100 feet thick. In most parts of the Region the base of the aquifer is
probably about 40 to 50 feet below the land surface. The productivity of the
aquifer varies with its hydraulic conductivity (field permeability) and thickness,
and there are areas where it yields very little water. Most wells in the nonartesian
aquifer are small-diameter well, finished with sandpoint or screen that are 20 to
40 feet deep and yield sufficient water for domestic use (5 to 10 gpm).
Open-end wells can be constructed in the nonartesian aquifer in some areas
by seating the casing in a hardpan or clay layer and then drilling through the
hard layer and pumping out sand until a small cavity or "pocket" is formed
below the hard layer. The well is then pumped at a slightly higher rate than the
normal rate until it is virtually sand free so that it will not yield sand when in
normal use. Wells of this type usually yield more water (up to 30 gpm) and

REPORT OF INVESTIGATIONS NO. 61

require less maintenance than sand-point or screened wells but in many areas of
the Region geologic conditions are not favorable for their development.

WATER LEVELS

The water table is at the land surface in some parts of the Region and more
than 70 feet below the land surface in other parts of the Region. In the sand hills
in the western part of the Region it may be as much as 100 feet deep. The water
table conforms in a general way to the configuration of the land surface. In the
lowlands and flatwoods sections of the Region the water table is usually within a
few feet of the surface but is usually at greater depths under the hills than under
the lowlands. The degree to which the water table conforms to the configuration
of the land surface depends to a large extent on the hydraulic conductivity of
the nonartesian aquifer and of the materials below it. Other factors being equal,
the water table follows the land surface most closely where the hydraulic
conductivity is lowest. The water table fluctuates in response to changes in
recharge and discharge in a manner analogous to the fluctuations in the levels of
lakes and reservoirs. Natural fluctuations of the water table range from a few
feet in flat areas of the Region to 15 feet or more in hilly areas.
In areas where the water table is near the land surface it reacts quickly to
local showers and, with prolonged rainfall, rises to the surface so that surface,
runoff occurs. Between rains the water table declines to a 'few feet below the
land surface as surface drainage and evaporation rapidly remove water from the
area. However, once the water table is 3 or 4 feet below the surface, further
decline is slowed because most streams in the Region have shallow channels and
cease to flow, evaporation practically ceases, and transpiration by shallow rooted
vegetation diminishes. Further, lateral ground-water flow from most areas is slow
in the flat terrain and downward leakage into the underlying artesian aquifer
through the underlying relatively impermeable muck or clay and clayey sand is
slight. In places the hydraulic head in the artesian aquifer is equal to or greater
than the water-table head, and inhibits downward flow.
Where the water table is a considerable distance below the land surface,
fluctuations in its level reflect long periods of excess and deficient rainfall.
Responses to wet or dry conditions often lag a month or more behind the event.
Brief showers after a dry period have little or no effect on the water table
because rain is held as soil moisture and returned to the atmosphere by
evapotranspiration. In much of the ridge or sandhill area the surface sand can
absorb even a heavy and prolonged rainfall and little or no surface runoff occurs.
The water that infiltrates below the root zone eventually reaches the water table.
After this water reaches the water table, it either seeps laterally into nearby
ponds or streams or moves downward into the artesian aquifer.

REPORT OF INVESTIGATIONS NO. 61

WATER QUALITY

The quality of water from wells in the nonartesian aquifer varies greatly
depending on the composition of the aquifer and other factors. Water from wells
developed in clean quartz sand is usually very soft (hardness generally less than
25 mg/l) and its mineral content less than 25 to 50 mg/l. Where the aquifer
materials have a high calcium carbonate or iron content the water tends to be
hard or high in iron. Where the water moves through organic matter and
dissolves carbon dioxide or organic acids it has a low pH and is corrosive.

YIELD

Where dithe nonartesian aquifer is composed of clean sand and is not subject
to contamination, it is a dependable source of water if the need does not exceed
about 5 to 10 gpm. Wells yielding 30 gpm or more have been constructed in the
nonartesian aquifer. However, the variable nature of the aquifer makes it
difficult to predict where higher yielding wells might be expected. A problem
encountered in many localities is clogging of well points or screens by deposition
of iron or calcium compounds, sometimes within a year after construction. This
requires removal, cleaning and reinstallation of the well point or screen, or
construction of a new well.
The total amount of water in storage in the nonartesian aquifer, assuming an
average thickness of 50 feet and a specific yield of 0.2 is about 3 billion gallons
per square mile or about 17 trillion gallons under the 6,216 square miles of land
in the Region. This huge quantity may perhaps be better comprehended as the
volume of water pumped over a period of 1,000 years by 25 wells, each pumping
at a constant rate of 1,500 gpm.
Hydraulic conductivity as determined from several tests in the Region ranged
from 5.4 ft per day (40 gpd per ft2) to 40 ft per day (300 gpd per ft2). The
lower values are from sites in the lowlands parts of the Region and the higher
values are from the highlands and coastal areas in Brevard County that may
include dune sand.

SECONDARY ARTESIAN AQUIFERS
AQUIFER PROPERTIES

Several artesian aquifers occur within the confining beds of the Hawthorn
formation and less extensively in the undifferentiated sediments above the
Hawthorn. These aquifers, of secondary importance, are usually found at depths
ranging from 60 feet to about 300 feet below land surface. They are composed
of discontinuous shell beds, thin limestone lenses or layers, and zones of sand

REPORT OF INVESTIGATIONS NO. 61

and gravel. Little is known about the extent and characteristics of these aquifers
but recent exploratory wells drilled in the City of Cocoa well field in eastern
Orange County show that they will yield as much as 1,000 gpm. At this location
a well that produced 1,000 gpm penetrated a 13-foot shell bed from 75 to 88
feet. The well also has 100 feet of screen developed in sand, shell and clay
between 70 and 170 feet. However, a current meter survey showed that 95
percent of the water produced by the well came from the shell bed. A screened
well about half a mile from the first well did not penetrate the shell bed and the
yield of this well was only 300 gpm. Ninety percent of its yield came from a
15-foot section of the well between depths of 140 and 155 feet.
Construction costs are usually higher for wells in the secondary artesian
aquifer than for wells in the underlying Floridan aquifer, and yields are lower;
however, in areas where the quality of the Florida aquifer water is unsatisfactory
the secondary aquifer may be a valuable source of water. The exploratory wells
in the Cocoa well field indicated the secondary artesian aquifer to be extremely
variable in lateral extent and thickness. Extensive exploratory drilling and testing
of the aquifer at any given site appears necessary before the dependable yield at
that site can be estimated. As stated previously the secondary artesian aquifer at
the Cocoa well field appears to have an extremely poor hydraulic connection to
the nonartesian aquifer and to the underlying Floridan aquifer. Thus, if it were
to yield water on a permanent basis it would have to be recharged at a rate equal
to withdrawal. Further studies will be necessary in the Cocoa well field area to
determine the optimum well spacings and pumping rate to assure a steady supply
of water and to avoid dewatering the aquifer.
A porous shell bed 12 feet thick was penetrated by a well 6 miles north of
the Cocoa well field. It is not known whether this shell bed, which is about 75
feet below the surface, is connected to the shell bed of the Cocoa well field. In
southern Seminole County a 4-inch test well yielded 100 gpm from the
secondary artesian aquifer. This well was 205 feet deep and was cased to a depth
of 63 feet. Most of the water appeared to come from a layer of coarse
phosphatic sand and gravel at about 175 feet.
Secondary artesian aquifers composed of limestone occur in western Indian
River County at depths of 190 to 300 feet. Most layers are about 20 feet thick.
A well in this zone near Fellsmere flows at the rate of 10 gpm.

WATER QUALITY

The quality of water from the secondary artesian aquifers in the Region
varies with location, depth, and the local hydrology. In general, water from the
secondary artesian aquifers is less mineralized than water from the underlying
Floridan aquifer and more mineralized than water from the nonartesian aquifer.

REPORT OF INVESTIGATIONS NO. 61

Downward leakage from the nonartesian aquifer can occur in areas where the
confined potentiometric surface of the secondary artesian aquifer is below the
water table, and the water in the Floridan aquifer tends to be similar in quality
to the nonartesian water except that some additional solution of mineral matter
takes place. In areas where the confined potentiometric surface of the secondary
artesian aquifer is below the confined potentiometric surface of the Floridan
aquifer, upward leakage can occur from the Floridan aquifer and the water in
the secondary artesian aquifer tends to be similar in quality to the water in the
Floridan aquifer. In instances where the secondary artesian aquifer is composed
of highly soluble materials, water in the secondary artesian aquifer can be more
mineralized than the water in the other aquifers.
The secondary artesian aquifers are the least likely to be polluted because the
overlying, low-permdability beds protect them from surface pollution, and
because drainage wells are usually cased through the secondary artesian aquifer
zone into the deeper Floridan aquifer.

FLORIDAN AQUIFER

The Floridan aquifer underlies all of Florida and parts of Alabama, Georgia
and South Carolina. In the East Central Florida Region it includes the Lake City
Limestone, Avon Park Limestone, Ocala Group Limestone and permeable parts
of the Hawthorn formation that are in hydraulic contact with the rest of the
aquifer.

AQUIFER PROPERTIES

The Floridan aquifer, as much as 2,000 feet thick in parts of the Region, is
one of the most productive aquifers in the world. The lithologic and hydrologic
character of the Floridan aquifer is not uniform, either horizontally or vertically.
In general, layers of limestone alternate with layers of dolomite or dolomitic
limestone. Most of the limestone layers are softer and lighter in color than the
dolomite layers. The aquifer stores large quantities of water and also acts as a
conduit, conveying water slowly through openings in the rock from areas of
recharge to areas of discharge. The entire aquifer has been affected to some
degree by the solvent action of ground water as it moves through the rock, so
that the aquifer is somewhat analogous to an enormous sponge.
Some of the largest known caverns in Florida have been found within the
Floridan aquifer in the East Central Florida Region. A 90-foot deep cavern was
penetrated by a well in Orlando between depths of 573-663 below land surface.
The cavern was filled with water and there was 12 feet of black organic muck on

REPORT OF INVESTIGATIONS NO. 61

its floor. There was no surface indication of the cavern and its areal extent is
unknown, but several deep wells located about 1,000 feet north did not
penetrate it. One of the deepest and largest known caverns in Florida is a
sinkhole northwest of Orlando known as Emerald Springs. The sinkhole was
measured in 1956 and found to extend at least 334 feet below the water surface,
which is 45 feet below the surrounding land surface. Many wells in the Region
penetrate 5-to 10-foot caverns and most wells penetrate one or more soluhition
channels at least several inches in diameter.
The solution channels are interconnected, and current-meter traverses of
wells show that most of the yield comes from the cavities. Cavities can occur in
any part of the aquifer, but are usually more prevalent and productive in the
hard, dolomitic layers. Exceptions occur locally in Volusia County where the
dolomitic layers are relatively impermeable and tend to separate the aquifer into
discrete upper and lower zones.
In most of the Region in Volusia County, as noted above, water levels do not
change appreciably with depth in the aquifer unless there is heavy pumpage in
the area. In the Orlando area, water levels in the lower zone of the aquifer
(1,300-1,500 feet) are always one to several feet lower than water levels in the
upper zone (100 to 400 feet) because of heavy pumpage from the lower zone by
the cities of Orlando and Winter Park. Another factor contributing to temporary
differences in water levels is the injection of storm water directly into the upper
zone of the aquifer through several hundred drainage wells in the Orlando area.
This causes water levels in the upper zone to rise more rapidly than those in the
lower zone. The effect is largely dissipated within a few days.

RECHARGE AND DISCHARGE

Most of the ground-water recharge in the Region originates as rainfall within
the Region. The major exception to this is Osceola County which receives a
major part of its recharge by underground flow from eastern Polk County. In
addition, minor amounts of groundwater recharge enters the Region by
underground flow from northern Polk County into southern Lake and
southwestern Orange Counties; by underground flow from southeastern Marion
County into the northern tip of Lake County; and by flow from southern
Flagler County into the northeastern tip of Volusia County. Exact figures on the
percentage of recharge entering the Floridan aquifer by underground flow from
outside the Region and from rainfall on the Region are not known as it is
extremely difficult to measure flow in the highly variable aquifer; however, it is
likely that 80 to 90 percent or possibly more of the recharge is from rainfall on
the Region and the remainder from rainfall nearby. The most efficient recharge
areas are the porous sand hills in the highlands in the north central and

REPORT OF INVESTIGATIONS NO. 61

northwest part of the Region, as shown in Figures 1 and 4, where the water table
is always at least 5 feet below the surface and where there is little or no surface
runoff. In these areas evapotranspiration is low and the water that escapes
evapotranspiration seeps through the relatively thin and permeable confining
beds to the Floridan aquifer. Infiltration rates are high in the sandy soils; rates as
high as 50 inches per hour have been reported for the most porous soils in an
undisturbed state.
Figure 4, which shows recharge areas, is based in part on soils maps of the
Soil Conservation Service, U.S. Department of Agriculture. The soils are shown
on these soils maps as four general groups on the basis of their surficial drainage
characteristics.
Because water that drains downward from the soil must go either into the
underlying artesian aquifer or seep into nearby streams, soils types were used in
conjunction with streamflow patterns to define the relative effectiveness of
recharge of the different areas as indicated in Figure 4. In addition to soil type
and streamflow patterns, the altitude of the confined potentiometric surface in
relation to land surface was considered in delineating the areas.
The movement of water from the surface sand to the Floridan aquifer is a
complex and imperfectly understood process. In some instances sinkhole lakes
provide the principal avenue of movement. In other instances the lake bottom
has been partially sealed with clay and organic matter, and the principal recharge
avenue may be under the slope of the surrounding land where the confining beds
were breached by formation of the sinkhole. In other areas there are no
sinkholes and recharge is by seepage through the semipermeable confining beds
overlying the aquifer. Important factors in determining the effectiveness of a
recharge area are the thickness of the permeable beds overlying the semi-
permeable confining beds and their height above the confined potentiometric
surface,
If the permeable beds are thick enough and sufficiently above the confined
potentiometric surface, the water table can build up until there is sufficient head
difference to move all the water in excess of evapotranspiration through the
semipermeable confining bed. As an example, two areas, "A" and "B," may have
equal recharge rates even though the permeability of the confining beds at "A"
is only 1/20th that of "B" if the head difference between the water table and
the confined potentiometric surface in area "A" is 20 times that in "B."
An accurate determination of the amount of recharge occurring in the Region
is impossible because of the difficulty in measuring evapotranspiration and the
great variability of evapotranspiration rates both really and seasonally. However
it is possible to make some rough estimates. Over most of the 1,200 square miles
designated as "most effective recharge areas" on Figure 4 the water table is well
below the land surface and evapotranspiration rates are relatively low. Much of
this area is planted in citrus trees which are moderate users of water (about 30

REPORT OF INVESTIGATIONS NO. 61

inches per year). Numerous small lakes and swamps are included in the effective
recharge area shown on Figure 4, and the higher evapotranspiration rates from
these areas would raise the average rate somewhat, possibly to 33 inches per
year. Surface runoff is small or nonexistent in most of the area, and probably
averages not more than 3 inches per year. This leaves an average of about 15
inches per year of recharge to the Floridan aquifer in the most effective recharge
areas. This amounts to about 310 billion gallons per year or about 850 million
gallons per day. Some additional recharge can be induced by pumping which
lowers the confined potentiometric surface and increases leakage from the
nonartesian aquifer. This lowers the water table and salvages some water that
would otherwise be lost to surface runoff or evapotranspiration. However, in
most parts of the most effective recharge areas (fig. 4) the water table is already
more than 5 feet below the surface and further lowering would not appreciably
reduce runoff and evapotranspiration losses.
Some recharge to the Floridan aquifer occurs wherever the water table is
above the confined potentiometric surface because there are no completely
impermeable materials in nature; however, in some places, as where extensive
clay layers exist, the amount of recharge may be extremely small. In the
moderately effective recharge areas (fig. 4) recharge rates probably range from 5
to 15 inches per year and in the poor recharge areas rates probably vary from
zero to 5 inches per year. Most of the very poor recharge areas (fig. 4) are areas
of artesian flow and no recharge can occur. No attempt has been made to
evaluate recharge quantitatively in moderately effective and poor recharge areas.
In some such areas, such as the East Lake Tohopekaliga vicinity in Osceola
County, recharge may be quite significant. Reports from local drillers indicate
that some wells in this area have penetrated sand with virtually no clay from the
land surface to the top of the aquifer. In addition, many lakes in the area have
no natural surface outflow except in very wet weather, indicating that at least
moderate recharge to the Floridan aquifer occurs. Total recharge in the
moderately effective areas and in the poor recharge areas is probably between
100 and 300 mgd. Total recharge then within the Region is in the order of 1
billion gallons per day. Pumping will increase recharge somewhat in the
moderate, poor and very poor recharge areas where permeable materials overlay
the Floridan aquifer, but the high confined potentiometric levels and the low
permeability of the confining beds greatly retard recharge in most of these areas.
Discharge of ground water from the Floridan aquifer in the East Central
Florida Region is by spring flow; by upward seepage into the St. Johns River
valley and other low areas; by outflow to Sumter, Marion and Flagler counties
and to the Atlantic Ocean, and by pumpage within the Region. Major springs are
Wekiva Springs and Rock Springs in Orange County; Sanlando Springs, Palm
Springs, and Sheppard Springs in Seminole County; Blue Springs, De Leon
Springs, and Green Springs in Volusia County; and Alexander Springs in Lake
County (fig. 2).

REPORT OF INVESTIGATIONS NO. 61

8145'

81'O00 45' 30 80*15'

EXPLANATION 1

Poteniionetric contour shows
oalitude to which- water rose
during May, 1970, in lightly
cased wells that penetrole
the FloiOoan Aquifer.
(Conlow kirvol 5 fIeel;
dotum is meon sea lerelJ

0 10 2? MILES

Figure 5.-Map of Region showing confined potentiometric surface of Floridan
aquifer May 1970.

C.,

0 ,
-0

REPORT OF INVESTIGATIONS NO. 61

CONFINED POTENTIOMETRIC SURFACE

The artesian pressure or confined potentiometric surface is the height to
which water will rise in tightly cased wells that penetrate an artesian aquifer. In
general, the confined potentiometric surface of the Floridan aquifer is highest in
the western part of the Region and slopes toward the east and northeast, as
shown in Figure 5. An exception is Volusia County which is a local high area
from which water moves out in all directions. Water moves down slope, or down
gradient, from areas of high potentiometric levels. In general, the direction of
movement shown by arrows in Figure 5 is at right angles to the contours,
although locally the direction of flow may be different because of differences in
permeability such as those associated with changes in the orientations of cavern
systems.
Figure 5 shows the confined potentiometric surface foi the Region in May
1970 after a short period of drought (April-May). There was heavy pumpage in
some areas and this is reflected in Figure 6, which shows the change in water
levels between July 1961 and May 1970. Water levels on the two dates are not
directly comparable because July is in the early part of the rainy season, when
water levels are normally rising, and May is at the end of the dry period when
water levels are at their lowest; some useful observations may, however, be made
from such comparisons. The effects of heavy pumping on the lower east coast of
the Region and near Daytona Beach are shown by Figure 6. This condition is
probably temporary, and experience has shown that water levels may change as
much as 5 to 10 feet in a few days or weeks in response to changes in pumping.
Figure 6 shows that there has been little change in water levels over most of the
Region during the approximately 9-year period.
Figure 7 shows the change in the water levels from May 1969 to May 1970.
This map also shows that water levels have risen in the northwest (recharge) part
of the area and have declined in the southern and eastern (discharge) part of the
area. This indicates either (1) that water levels in and near the recharge areas
have recovered from the 1961-68 drought, while those far from the recharge
areas have not yet had time to recover; or (2) that pumping rates far from
recharge areas are exceeding the ability of the aquifer to transmit water under
the existing hydraulic gradients. The most likely cause is a combination of the
two.

WATER QUALITY

The quality of water in the Floridan aquifer varies greatly throughout the
Region, but varies little with time at a particular location and depth. Exceptions
occur in wells that penetrate a stratum partially filled with highly mineralized
water, or in wells near drainage wells or open sinkholes. Water of poor quality

REPORT OF INVESTIGATIONS NO. 61

to the Pinecrest Sand member of the upper part of the Tamiami Formation
(Mio-Pliocene age).
The thickness of the undifferentiated sediments ranges from 0 to 200 feet.
These sediments yield small (5-15 gpm) supplies to screened wells and small
diameter open wells in most parts of the Region.

STRUCTURE
The generalized configuration of the top of the Floridan aquifer is shown on
Figure 3. The top of the aquifer conforms roughly to the top of the limestone
formations of Eocene age. The Eocene formations represented by Figure 3
include the Crystal River Formation, the Williston Formation, the Inglis
Formation and the Avon Park Limestone. Figure 3 is not bated on a single
uneroded horizon such as the top of a conformable formation or a marker bed;
however, in a gross sense it reflects underlying structure. Figure 3 does not show
the presence of faults although they undoubtedly occur in the Region. Faulting
can affect the movement of water in the ground and also alter surface drainage;
however, more information will be necessary before the faults can be delineated
and their effects on the hydrology of the Region can be assessed.
The depth to the Floridan aquifer below land surface may be obtained by
adding the altitude of the land surface to the altitude of the surface of the
aquifer in areas where the top of the aquifer is below mean sea level. In areas
where the top of the aquifer is above mean sea level, this altitude should be
subtracted from the land surface altitude to obtain the depth to the aquifer.

HYDROLOGY

The water supply of the earth, whether it is on the surface or below the
ground, has its origin in precipitation. Of the precipitation that reaches the
ground, part is returned to the atmosphere by evapotranspiration; part remains
above ground and is stored temporarily in lakes, ponds, and swamps, or moves to
the sea as streamflow; and part percolates into the ground, some to replenish the
soil moisture and some to enter the saturated zone and recharge ground-water
supplies. Ground water moves in the aquifers (ground-water reservoirs) under the
influence of gravity, toward areas of discharge such as streams, lakes, springs,
wells, and the oceans.

SURFACE WATER

Important factors in considering surface water as a potential source of
supply are its dependability and chemical quality. Dependability includes the

REPORT OF INVESTIGATIONS NO. 61

81*45' 30'

15' 81o0'o 45'

EXPLANATION

WATER LEVEL DECLINE, FEET
S0 ( small rite In Some aeas)
0-5
5-10
more than 10

0 0 2 MILES
I I I I I I

Figure 6.-Map of Region showing water-level changes in the
Floridan aquifer July 1961-May 1970.

30' 80" 15

29.15'l-

290oo I-

REPORT OF INVESTIGATIONS NO. 61

ert*' so' is' 81*00'

EXPLANATION

CHNAGE IN WATER LEVEL. FEET

0 O to .*

3 -4 to -2
SGreQte, than -4

Figure 7.-Map of Region showing water level changes in the
Floridan aquifer May 1969-May 1970.

30' 80W I'

0
0
I"
f
t

REPORT OF INVESTIGATIONS NO. 61

injected in a drainage well may move rapidly through the cavernous limestone
and enter a nearby supply well.
Geology is the major factor influencing the natural quality of water in the
Floridan aquifer in the Region. The limestone that forms the aquifer is soluble
and the presence of carbon dioxide in the water, dissolved from the atmosphere
or vegetation, increases the rate of solution. As water moves through the aquifer
it becomes more mineralized until it reaches saturation or even supersaturation.
In addition to becoming more mineralized by dissolving the rock through which
it passes, fresh water mingles with highly mineralized ocean water that entered in
previous ages but has not yet been completely flushed from the aquifer.
Figures 8, 9, and 10 show the dissolved solids, hardness and chloride content
of water from the upper part of the Floridan aquifer. The patterns shown on the
figures are changeable. Heavy pumpage in areas where salty water exists at depth
in the aquifer can expand the areas of high mineralization. Artificial recharge of
fresh water can expand the areas of low mineralization.

YIELD

The yields of wells in the Floridan aquifer are as high as several thousand
gallons per minute. The yields of individual wells usually do not indicate the
ability of the aquifer to yield water because in addition to the transmissivity of
the aquifer, the yield of an individual well depends on the diameter and depth of
the well, the capacity of the pump, the condition of the well, the proportion of
total aquifer thickness, and the size and number of solution cavities penetrated
by the individual well.
Although, in general, wells constructed in the most effective recharge areas
of the Region (fig. 4), where solution cavities are most prevalent, yield large
amounts of water, there are many exceptions. For example, some 8-inch wells in
the St. Johns River valley area of Brevard County yield more than 3,000 gpm by
natural flow, and a 12-inch well about 1,000 feet deep, in western Orange
County, yields less than 1,000 gpm because it is located in a sinkhole where sand
extends to a depth of more than 650 feet below the normal top of the Floridan
aquifer in that area.
In most parts of the Region large quantities of potable water can be obtained
from the Floridan aquifer if there is water of good quality in at least the top
1,000 feet of the aquifer and if withdrawal does not induce upward movement
of water or poor quality from greater depths.

WATER USE

A detailed inventory of water use in all parts of the Region was not available
in September 1970. However, a county-by-county inventory of water use in the

REPORT OF INVESTIGATIONS NO. 61

a S45 30' is' a8oo' 45' 30' 80*15

4! I-

28O-f I-

EXPLANATION

DISSOLVED SOLIDS. MILLIGRAMS
E Less man 250
1 250-500
E 501-1000
3 Greater than 1000

0 0 2 UILES
S I I I

Figure 8.-Map of Region showing dissolved solids in water from
the upper part of the Floridan aquifer.

It'Xft-

REPORT OF INVESTIGATIONS NO. 61

8P45' 3O'

IS' 8100' 45'

0 D 2 M ILES
I I I I I l

Figure 9.-Map of Region showing hardness in water from the upper
part of the Floridan aquifer.

29"15 I-

30 80 15

29o00 -

20'Od ,-

REPORT OF INVESTIGATIONS NO. 61

r4s' 30'

2roo -

-Oso-

EXPLANATION
CHLORIDE CONCENTRATION. MILLIGRAMS PER LITER
0 Less Wn 50

S251 -1 00
E Gr#.ow Iton 1000

Figure 10.-Map of Region showing chloride in water
from the upper part of the Floridan aquifer.

IV5s a*00'

80 15

REPORT OF INVESTIGATIONS NO. 61

State of Florida during 1970 was completed early in 1971 by the U.S.
Geological Survey. This information, used in conjunction with forecasts of the
development of population, industry and agriculture in the Region, will make it
possible to make reasonably accurate forecasts of future water needs in the
Region. Because this information was not available when this report was written
the following discussion of water use depends heavily on values from a 1965
survey, and, therefore, is preliminary and subject to substantial revision. The
estimates of water use in 1965 for the following discussions were made by the
Geological Survey, whereas the projections of population and water use to 1990
were made by the East Central Florida Regional Planning Council.

PUBLIC SUPPLIES

Water for public supply includes that furnished by both public and private
utilities for all uses including domestic, fire fighting, street flushing, irrigation of
lawns and parks, commerce and industry. Water used for public supply in the
Region in 1965 was an estimated 102 mgd (million gallons per day), serving a
population of about 640,000. Of this total about 98.6 mgd, serving a population
of about 597,000, was ground water and about 3.6 mgd, serving a population of
about 40,000, was surface water. Average water use per capital in areas served by
public supply was about 150 gallons a day per person.
Water used for public supply in the Region is expected to increase to about
269 mgd by 1990 and will serve a population of about 1,685,500. The foregoing
estimates do not include industrial and commercial water from public supplies.
Water for these uses was about 37 mgd in 1965 and estimated to be about 99
mgd by 1990.

RURAL

Water for rural use includes that from private, individual wells used for
domestic purposes, by livestock, and for gardening uses not included under
irrigation. Water for rural use in the Region in 1965 was estimated to be about
18 mgd serving a population of about 220,000, as shown in Table 5. All rural
water use except a small part (less than 1.5 mgd) was from ground-water sources.
Surface-water sources were used principally for livestock water.
It is estimated that water for rural use will increase to about 28 mgd by 1990
and will serve a population of about 352,450 with ground water sources
furnishing all but about 2.1 mgd.

IRRIGATION

Water used for irrigation in the Region in 1965 was estimated to be about

Table 4.-Estimated water used for public supplies, by counties.

POPULATION SERVED

WATER WITHDRAWN

INDUSTRIAL AND COMMERCIAL

COUNTY YEAR Ground
Water
(thou-

1965
1970
1990
1965
1970
1990

sands)
107,700
120,600
289,400
12,500
13,250
57,000

1965 44,200
1970 47,600
1990 114,200

1965 260,000
1970 288,600
1990 634,900

1965
1970
1990

13,000
14,000
59,200

1965 33,100
Seminole 1970 39,100
1990 129,000

1965 126,200
1970 140,000
1990 294,000

1965 597,000
1970 664,000
1990 1,578,000

Surface All

Water Water Water
(thou- (thou- (mid)
sands) sands)
40,000 147,700 20.9
44,800 165,400 23.4
107,500 396,900 48.0
0 12,500 1.5
0 13,250 1.6
0 57,000. 6.9

0 44,200 8.0
0 47,600 8.6
0 114,200 20.5

0 260,000 49.0
0 288,600 54.4
0 634,900 119.7

0 13,000 2.0
0 14,800 2.3
0 59,200 9.2

0 33,100 4.2
0 39,100 5.0
0 129,000 16.5

0 126,200 13.0
0 140,000 14.4
0 294,000 30.2

40,000 637,000 98.6
44,800 709,000 109.7
107,500 1,685,500 251.1

Ground Surface All

Water USES
(mgd) (mgd)

3.6
4.0
17.8
0
0
0

Per (from public supplies) WATER
Capita Air cond. Other All uses CONSUMED
(mgd) (mgd) (mgd) (mgd) (mgd)

24.5
27.4 166
65.8
1.5
1.6 120
6.9

8.0
8.6 180
20.5

49.0
54.4 188
119.7

0 2.0
0 2.3 155
0 9.2

0 4.2
0 5.0 127
0 16.5

4.0
4.5
10.8
8
.1
.1

7.7
9.5
20.4
.3
.3
1.4

12.0
13.4
32.2
.3
.3
1.3

.1 1.9 2.0 5.0
.1 2.0 2.1 5.4
.2 4.8 5.0 13.0

4.9
5.4
11.9

5.0
5.5
12.1

10.0
11.1
24.4

.1 1.9 2.0 1.3
.1 2.2 2.3 1.5
.4 8.8 9.2 6.0

.03 .57 .6 2.0
.04 .7 .74 2.4
.1 2.3 2.4 7.9

13.0
14.4 103
30.2

3.6 102.2 4.73 14.9
4.0 113.7 .148 5.24 16.4
17.8 268.9 28.8 42.5

6.0
6.7
14.1

19.6 36.6
21.64 40.8
71.3 98.9

Brevard

Indian
River

Lake

Orange

Osceola

Volusia

Totals

Table 5.-Estimated water for rural use, by counties.

COUNTY YEAR POPULA-
TION

1965 52,000
Brevard 1970 58,000
1990 58,000

1965 20,000
Indian 1970 21,300
River 1990 29,750

1965 18,000
Lake 1970 19,500
1990 29,700

1965 50,000
Orange 1970 55,200
1990 70,300

1965 9,000
Osceola 1970 10,200
1990 29,300

1965 37,000
Seminole 1970 43,800
1990 58,500

DOMESTIC USE (MGD) LIVESTOCK USE (MGD) DOMESTIC AND LIVESTOCK (MGD)
WATER WITHDRAWN Water WATER WITHDRAWN Water Water Withdrawn All Water

Ground Surface
water water
4.0 0
4.5 0
4.5 0

1.0 0
1.1 0
1.5 0

1.8 0
1.9 0
2.8 0

4.0 0
4.4 0
5.6 0

.4 0
.5 0
1.4 0

1.8 e
2.1 e
2.8 e

Consumed Ground Surface Consumed Ground Surface Water
water water water water

Consumed

1.4 .6
1.5 .7
2.9 1.0

1965 34,000-
1970 37,100
1990 76,900

1965 220,000
1970 245,100
1990 352,450

e less than 0.05 mgd.

1.7 0
1.9 0
3.9 0

14.7 e
16.4 e
22.5 e

1.9 .2 2.1
2.) .2 2.3
.8 4.3 .4

11.4 2.2
12.5 2.3
17.5 3.3

17.0 1.4
18.7 1.5
25.8 2.1

18.4 14.7
20.2 16.2
27.9 22.9

Volusia

Totals

Table 6.-Estimated water used for ripgation, by counties

ACRES
YEAR IRRIGATED

Brevard

1965
1970
1990

1965
1970
1990

1965
1970
1990

1965
1970
1990

1965
1970
1990

1965
1970
1990

1965
1970
1990

1965
1970
1990

WATER WITHDRAWN

Ground
water

Surface Total

water

(mgd) (mgd)

24,000
26,000
50,000

50,600
60,000
120,000

20,000
28,000
35,000

31,500
33,000
40,000

45,500
50,000
100,000

10,000
11,000
15,000

3,700
4,500
10,000

185,300
212,500
370.000

50.4
37.1
71.4

26.2
40.2
80.4

14.0
22.5
28.1

22.2
22.1
26.8

42.3
33.5
67.0

4.8
7.4
10.0

6.2
6.4
14.3

166.1
169.2
298.0

4.6
9.3
17.9

39.3
40.2
80.4

12.0
15.0
18.8

21.8
22.1
26.8

42.3
33.5
67.0

5.9
7.4
20.0

1.2
1.6
3.6

127.1
129.1
224.5

COUNTIES

(mgd)

55.0
46.4
89.3

65.5
80.4
160.8

26.0
37.5
46.9

44.0
44.2
S3.6

84.6
67.0
134.0

10.7
14.8
10.0

7.4
8.0
17.9

293.2
298.3
522.5

Indian River

Lake

Orange

Osceola

Seminole

Volusia

Totals

CONSUMED
(mgd)

35.2
37.1
71.4

25.9
40.2
80.4

9.5
15.0
18.8

19.6
22.1
26.8

42.8
33.5
67.0

4.8
7.4

5.4
6.4
14.3

143.2
161.7
288.7

REPORT OF INVESTIGATIONS NO. 61

293 mgd (328,000 acre-feet), applied to about 185,300 acres, as shown inTable
6. Of this total, about 166 mgd was from ground-water sources and 127 mgd
from surface water sources. Of the water withdrawn for irrigation, an estimated
143 mgd, or 49 percent, was consumed.
It is estimated that by 1990 water for irrigation use will increase to about
522 mgd (585,000 acre-feet) and acreage irrigated will increase to about 370,000
acres, with most of the increases in the southern part'of the Region. Most of the
increase in water use for irrigation is expected to come from irrigation of
existing agricultural land not now irrigated rather than an increase in total land
used for agriculture.

SELF-SUPPLIED INDUSTRIAL

About 13.6 mgd, as shown in Table 7, of self-supplied industrial water was
used in the Region in 1965. Of this about 0.2 mgd was saline. All water used in
this category was withdrawn from wells.
Self-supplied industrial use of water was the smallest use in the Region,
probably because most industry in the area is located near public water-supply
systems.
It is estimated that by 1990 self-supplied industrial use will increase to about
24 mgd. This estimate, as are all the others, is preliminary and subject to
substantial revision as more information becomes available.

DEMAND AND SUPPLY

Total water used in the Region in 1990, as shown in Tables 4-7 is estimated
to be 843.1 mgd, of which 589.7 mgd (71 percent) will be from ground-water
sources. Of the 244.4 mgd (29 percent of total use) from surface-water sources,
more than 90 percent is used for irrigation. Virtually all public, industrial, and
rural water supplies, and more than half of the irrigation-water supplies, are
expected to come from ground-water sources.
The expected 1990 draft of 598.7 mgd from ground-water sources
(principally the Floridan aquifer) will be approximately 60 percent of the
estimated natural recharge to the Floridan aquifer. If water levels in the Floridan
aquifer and flow in the springs are to be maintained and salt-water encroachment
from the ocean prevented, it may be necessary to preserve at least half of the
natural recharge for these purposes.
From the above it is thus apparent that by 1990 the draft on the Floridan
aquifer may equal or exceed the quantity of water that can be withdrawn
without causing undesirable consequences, unless steps are taken to increase
recharge and reuse water. As most of the natural ground-water recharge takes
place in the western part of the Region and much of the water use is in the

Table 7.-Estimated use of self-supplied industrial water, by counties.

WATER WITHDRAWN, MILLION GALLONS PER DAY

Ground Water
Fresh Saline

Surface Water
Fresh Saline

All Water

Air Cond. Consumed

Fresh Saline (mgd) Fresh (mgd)

0 0
.4 0
1.0 0

65
70
90

65
70
90

65
70
90

65
70
90

65
70
90

65S
70
90

65
70
90

65
70
90

13.4 .2
14.7 .2
23.8 .2

0 0
.2 0
.8 0

I .1
.1 .4

13.4 .2
14.7 .2
23.8 .2

COUNTIES

Brevard

Indian River

0 0
.2 0
.8 0

0 0
.3 0
1.0 0

Lake

Orange

Osceola

Seminole

Volusia

Totals

REPORT OF INVESTIGATIONS NO. 61

coastal part, one solution may be to transport increasing amounts of water from
the western to the eastern part of the Region. This is now being done in central
Brevard County, which imports water from eastern Orange County, and the
practice will probably become more widespread in the future.
Total rainfall on the Region is about 18 billion gpd (gallons per day) and
only about 6 percent of this amount is now being captured and stored in
ground-water reservoirs. If the amount of capture could be increased to 10
percent of total rainfall, the supply of ground water would be sufficient for the
foreseeable future; this assumes, of course, that the estimates of future needs
and of amounts of recharge cited above are valid.

PROBLEMS AND SOLUTIONS IN WATER-RESOURCE MANAGEMENT
PROBLEMS

Taken in its entirety, the East Central Florida Region has large quantities of
good-quality water at the present time. The major water problems in the Region
are:
(1) Rainfall in the Region is not distributed uniformly either seasonally or
from year to year. Thus it is necessary to store water for months or years, from
periods of abundant rainfall to periods of deficient rainfall.
(2) Although rainfall, which is the source of virtually all freshwater supplies,
is reasonably uniform over the different areas of the Region on a long-term basis,
the natural facilities to collect and store the rainfall are not uniformly
distributed. In most areas surface-water reservoirs are impractical because of the
flat terrain, high evaporation rates, and changing water quality. The Floridan
aquifer, which is the most productive ground-water source and, together with
the overlying aquifers, forms the largest and most efficient storage reservoir in
the State, underlies the entire Region. However, owing to differences in
topography and geology the natural capacity of the land to absorb rainfall is
greater in some areas than in others. Parts of the Region that are efficient in
harvesting rainfall for recharge to the Floridan aquifer are delineated in Figure 4,
which shows that Lake County and the western parts of Orange, Seminole and
Volusia counties are efficient recharge areas, and that Indian River, Osceola, and
Brevard counties and the eastern parts of Orange, Seminole and Volusia counties
are poor recharge areas. The hydrologic situation in Volusia County is a
small-scale replica of the hydrologic situation in the rest of the Region, in that
most of the recharge is in the western part of the county and must move through
the aquifer to population centers along the coast. The principles of water
management that apply in the rest of the Region are equally applicable in
Volusia County.
(3) In parts of the Region the Floridan aquifer contains water of poor
quality (figs. 8, 9, and 10). In most cases this situation is directly related to

REPORT OF INVESTIGATIONS NO. 61

injected in a drainage well may move rapidly through the cavernous limestone
and enter a nearby supply well.
Geology is the major factor influencing the natural quality of water in the
Floridan aquifer in the Region. The limestone that forms the aquifer is soluble
and the presence of carbon dioxide in the water, dissolved from the atmosphere
or vegetation, increases the rate of solution. As water moves through the aquifer
it becomes more mineralized until it reaches saturation or even supersaturation.
In addition to becoming more mineralized by dissolving the rock through which
it passes, fresh water mingles with highly mineralized ocean water that entered in
previous ages but has not yet been completely flushed from the aquifer.
Figures 8, 9, and 10 show the dissolved solids, hardness and chloride content
of water from the upper part of the Floridan aquifer. The patterns shown on the
figures are changeable. Heavy pumpage in areas where salty water exists at depth
in the aquifer can expand the areas of high mineralization. Artificial recharge of
fresh water can expand the areas of low mineralization.

YIELD

The yields of wells in the Floridan aquifer are as high as several thousand
gallons per minute. The yields of individual wells usually do not indicate the
ability of the aquifer to yield water because in addition to the transmissivity of
the aquifer, the yield of an individual well depends on the diameter and depth of
the well, the capacity of the pump, the condition of the well, the proportion of
total aquifer thickness, and the size and number of solution cavities penetrated
by the individual well.
Although, in general, wells constructed in the most effective recharge areas
of the Region (fig. 4), where solution cavities are most prevalent, yield large
amounts of water, there are many exceptions. For example, some 8-inch wells in
the St. Johns River valley area of Brevard County yield more than 3,000 gpm by
natural flow, and a 12-inch well about 1,000 feet deep, in western Orange
County, yields less than 1,000 gpm because it is located in a sinkhole where sand
extends to a depth of more than 650 feet below the normal top of the Floridan
aquifer in that area.
In most parts of the Region large quantities of potable water can be obtained
from the Floridan aquifer if there is water of good quality in at least the top
1,000 feet of the aquifer and if withdrawal does not induce upward movement
of water or poor quality from greater depths.

WATER USE

A detailed inventory of water use in all parts of the Region was not available
in September 1970. However, a county-by-county inventory of water use in the

REPORT OF INVESTIGATIONS NO. 61

problem 2 in that the flow of fresh water through the aquifer in these parts has
been insufficient to flush the poor-quality water from the aquifer or, in some
instances, has been insufficient to prevent the intrusion of mineralized water
into areas of large water withdrawal. Most of the water of poor quality is in
coastal areas and in the St. Johns River valley where geologic and hydrologic
conditions severely limit recharge.
(4) The need for water is not uniformly distributed throughout the Region.
For various reasons the need is often greatest where the supply is least. For
example, much development with a large need for water has taken place along
the sea coast where the quality of water is poorest, Lake County, on the other
hand, has a very large supply of water of good quality but is sparsely populated.
Thus, part of the problem is to distribute water supplies where they are needed
throughout the Region.
(5) Many activities of man impair the effectiveness of recharge areas, thereby
reducing the rainfall harvest. Paving increases surface runoff; urbanization of
flood plains around lakes necessitates construction of drainage canals and
pumping stations to move quickly to the ocean water that would otherwise
recharge the ground-water reservoir. Other activities of man pollute existing
reservoirs, further reducing potable water supplies. In some areas, such as
Orlando and the vicinity, uncontrolled drainage wells tend to add pollutants to
the Floridan aquifer; and in other areas, heavy pumping has induced salty water
to move into parts of the aquifer that formerly contained fresh water. Thus,
without proper water-resources management there is the prospect of increasing
demand on a diminishing supply of water.
In brief, the problem facing the East Central Florida Region with respect to
insuring an adequate water supply for the present and for the future is one of
water management. This will entail development of water- and land-control
measures that will increase the water-harvesting and storing capabilities of the
land development in the Region. It may also entail transporting water of suitable
quality to places where it is needed.
SOLUTIONS
There is no single solution or even a group of solutions for all water-resource
management problems. Methods of water management include preservation of
the area in its natural state by such land-use controls as zoning, tax rebates,
subsidies, or public ownership; various types of artificial recharge practices; and
importation of water. Which of these methods is adopted in a particular area
depends on a variety of physical factors, as well as on political, legal, and other
social factors beyond the scope of this report. The physical factors are discussed
below. For convenience the East Central Florida Region is divided into three
subdivisions according to the potential for recharge to the Floridan aquifer; (1)
most effective recharge areas, (2) moderate to poor recharge areas, and (3) very
poor recharge areas. These are the subdivisions shown on Figure 5 except that

REPORT OF INVESTIGATIONS NO. 61

the moderately effective recharge areas and the poor recharge areas shown on
the map have been combined.
MOST EFFECTIVE RECHARGE AREAS
The most effective recharge areas are mainly in Lake County and in the
western parts of Orange, Seminole and Volusia counties (fig. 4). An isolated
recharge area, which appears to be an extension of the Volusia County area, is in
eastern Seminole County.
Maximum recharge occurs where there is no surface runoff and where the
water table remains below the root zone so that evapotranspiration is at a
minimum. For this situation to exist four conditions must be met: (1) The
surface materials must be sufficiently permeable to absorb the heaviest rainfall
without surface runoff; (2) the permeable surface material must be thick enough
to store the water from a prolonged rain without the water table rising to the
root zone; (3) the vertical hydraulic gradient between the water table and the
confined potentiometric surface, and the vertical hydraulic conductivity of any
confining beds between the water table and the Floridan aquifer, must be
sufficient to move all available water (that is, rainfall minus evapotranspiration)
to the aquifer; (4) the transmissivity of the Floridan aquifer and the confined
potentiometric gradient must be sufficient to move the water from the area.
Geologic and hydrologic parameters approximating the above conditions
occur in most of the areas designated as "most effective recharge areas" on
Figure.
Some water in the most favorable areas moves to closed lakes and ponds
where it is temporarily stored before seeping down to the aquifer; but aside from
a higher evapotranspiration loss in the lake area, the net recharge effect is the
same. If these areas are left in their native state or used only for agriculture there
will be little reduction in recharge. The natural quality of the ground water is
excellent for most purposes (see figs. 8, 9, and 10). Problems arise when
urbanization occurs. Houses and paving reduce the infiltration capacity of the
surface materials and increase runoff to the lakes and ponds. Because
urbanization tends to speed the movement of water to lakes and ponds, more of
the flood plains become inundated than before urbanization. Homes are often
built on flood plains during dry periods. When the plains become inundated
during wet periods there is great pressure to dig drainage canals or build pumping
stations to move the excess water to the streams and hence to the ocean.
Drainage wells have been installed, especially in the Orlando area, to convey
surface water directly to the upper zone of the Floridan aquifer. This is useful in
providing recharge to the aquifer and maintaining ground-water levels. However,
there are, at present, no controls on the quality of the water entering the aquifer
and wide-spread pollution of the upper zone has resulted. Fortunately the lower
zone (1,100 to 1,500 ft.) has not as yet been polluted and municipal supplies for
Orlando and Winter Park are withdrawn from this zone.

44 REPORT OF INVESTIGATIONS NO. 61
Recharge through the more than 300 drainage wells in the Orlando-Winter
Park area is undoubtedly the reason why there is no appreciable cone of
depression in the area even though the combined pumpage is at times more than
50 mgd. Observation-well records in Orlando show that the potentiometric head
is always higher in the upper zone than in the lower zone; therefore, it could be
just a matter of time before polluted water moves to the lower zone. A well in
the Orlando-Winter Park area that is 1,300 feet deep and cased to a depth of
1,200 feet has produced raw water high in bacteria count for the past 2 years.
The source of the pollution is unknown at this time, although it probably
represents a local, isolated, condition.
The elimination of drainage wells would be a large step in reducing the
danger of pollution of the aquifer. However, expensive drainage canals and
pumping stations would have to be built to replace the drainage wells, and the
resulting decrease in recharge would cause a larger cone of depression to form
around centers of heavy pumping. This could cause the upward movement of
salty water. In the Orlando-Winter Park area the salty water is only about 500 to
1,000 feet below the bottoms of the municipal supply wells and little is known
about the permeability of the intervening materials. Other areas have or
probably will have similar problems.
Protection of the most-effective recharge areas is one of the most important
aspects of water-resource management. Recharge areas could be protected by
halting or reducing their urbanization. This would tend to preserve a diversified
economy, for much of the most effective recharge area is now planted in citrus
trees. Many methods of discouraging urbanization of the recharge areas have
been proposed. These include: zoning; subsidy of utility and road development
outside recharge areas; tax deferments for land remaining in agricultural pursuits;
and payment to the landowner for net recharge on his land. However, some areas
such as Orlando and vicinity are already heavily urbanized, and further
urbanization may take place in recharge areas. Methods of maintaining recharge
under the pressure of urbanization are (1) transporting storm runoff to natural
recharge basins, (2) treating runoff, then injecting it by gravity or pumping
through recharge wells directly into the Floridan aquifer, and (3) land spreading
of treated sewage effluent.
The first method-transporting storm water from urban areas to natural
recharge basins-is the simplest and possibly the least expensive way of
maintaining recharge, for it utilizes the natural filtering and purifying action of
the surface sand to remove impurities from storm water. There are many closed
basins in the most efficient recharge areas where surplus surface water can be
stored.
This method has many advantages but there are few data to indicate how
much additional downward leakage could be expected for each additional foot
of water added to the recharge basin. This information would be needed to
determine how much runoff the basin could accept during extreme flood

REPORT OF INVESTIGATIONS NO. 61

conditions. All the recharge basins are different and their recharge capabilities
would have to be evaluated individually. Some of the factors requiring
evaluation would be the purifying capabilities of the sand aquifer, the minimum
thickness of sand required to protect the Floridan aquifer from contamination,
possible reduction in infiltration capacity of the basin bottom, and cost in
relation to benefits derived.
Where natural recharge basins are not available or where they cannot
accommodate the storm runoff, recharge wells could be used. Recharge wells can
efficiently convey large amounts of water to the aquifer. As much as 20 cfs (12
million gpd) has been reported to have entered the aquifer by gravity flow
through a single well in the Orlando area, and injection rates of 5 to 10 cfs are
common in many parts of the Region. If contamination is to be avoided, the
quality of the recharge water must be at least as good as that of the aquifer
water before it enters the well because the cavernous limestone affords little
filtering action.
The second method-injection of treated water into the Floridan aquifer
through recharge wells-would require prior study to determine the following:
(1) Optimum quality standards for water entering the well-the standards
should be adequate to prevent contamination of the aquifer.
(2) Effects of the recharge water on the rock of the aquifer and the natural
water contained therein-the recharge water probably would contain different
minerals than the aquifer water and adverse chemical reaction might occur. The
nature of the possible reaction would have to be identified.
(3) Efficient and economical size and design criteria for the holding basins
and water-treatment facilities necessary for recharge of excess rainwater through
wells.
The third method-land spreading of treated sewage effluent-could be very
useful in combating pollution and conserving water in the most effective
recharge areas. Not only is the environment polluted by ordinary methods of
effluent disposal, but loss of the water is a drain on the water resources of an
area. There are no large bodies of water in the Region that are capable of
absorbing the projected 1990 waste load. At present, the trend is toward
pollution and eutrophication of lakes and streams. Even the St. Johns River,
which is the largest river entirely in Florida, does not carry sufficient water to
adequately dilute and disperse the treated wastes expected to be discharged by
the city of Sanford in 1990, and many estuaries and ocean beaches are already
polluted.
Land spreading and irrigation with treated effluent would help to maintain
ground-water levels and provide a means of waste-water disposal. These methods
have been studied in detail and have proved successful and economical in certain
places such as the Hyperion and Whittier Narrows Sewage Treatment Plants in
Los Angeles, California. Numerous investigations have shown the techniques of

REPORT OF INVESTIGATIONS NO. 61

land spreading with cover crops in the spreading area to be effective in removing
nutrients. In many areas land spreading could be the most economical means of
tertiary treatment currently known, as well as providing recharge to ground-
water reservoirs. The Region, with its highly absorbent soils and its almost
continuous growing season, would seem to be a favorable area for the so-called
"plant-soil filter technique of tertiary treatment and artificial recharge of waste
water." Land spreading would be most effective in the highland areas of the
Region (fig. 1) where the surface soils are porous and the water table is at least 5
to 10 feet below the the land surface; however, land spreading might also be
practical in coastal ridge areas which also have porous soils and a low water
table. In coastal areas the recharge would be to the nonartesian aquifer.
Information on land spreading techniques in other parts of the country is
useful in evaluating the practicability of land spreading in the East Central
Florida Region; however each area of the country is different and has different
problems. Studies in different parts of the region to determine the best suited
techniques and the economics of land spreading in particular situations would be
desirable. Information gained from studies in other parts of the country is not
entirely applicable and would not be duplicated, but could be used in designing
the local studies.

MODERATE TO POOR RECHARGE AREAS

Recharge areas classified as moderate to poor occur mostly in eastern
Orange, Osceola, Volusia and Seminole counties and parts of Lake and Brevard
counties (fig. 4). Here the natural recharge capabilities range from very good in
areas adjacent to the most effective recharge areas to virtually nil in areas
adjacent to very poor recharge areas.
Surface runoff occurs from almost all the moderate to poor recharge areas,
and extensive parts of these areas contain intermittent swamps and bayheads.
Average recharge per unit area of the Floridan aquifer is small in comparison to
recharge in the most effective recharge areas; however the total volume of
recharge is appreciable because of the large area involved (2000 sq. mi.).
Relatively small areas, designated as moderately effective recharge areas on
Figure, provide appreciable local recharge; however, such areas depend largely
on recharge that enters the Floridan aquifer in the most effective recharge areas
to replace water lost through discharge and to maintain water levels.
The amount of rainfall is about the same in the poor recharge areas as in the
effective recharge areas. The factors that reduce the recharge rates are geologic,
hydrologic, or a combination of the two. In eastern Orange County and much of
Osceola County the prime factor is geology. The surface sand is permeable but

REPORT OF INVESTIGATIONS NO. 61

the underlying confining beds are thick and their clay content is high. This
considerably reduces the rate of recharge to the aquifer even though the head
difference between the water table and the confined potentiometric surface is 40
feet or more in some sections. In other parts of the poor recharge area, including
central Volusia County and southwestern Lake County, the confining materials
overlying the Floridan aquifer are relatively permeable; however the level of the
confined potentiometric surface is near the level of the water table and there is
little downward hydraulic gradient to move the water to the aquifer. Lateral
movement in the aquifer cannot keep pace with the potential recharge and the
aquifer is, in effect, full and rejecting recharge. Increased pumping of ground
water in these areas will lower the confined potentiometric surface and induce
greater recharge thereby salvaging water that is now being lost to evapo-
transpiration and surface runoff.
In the parts of the poor recharge areas where low permeability is preventing
recharge, lowering of the confined potentiometric surface by pumping will not
appreciably increase recharge and, further, may induce upward movement of
salty water. In these areas the physically most effective methods of artificial
recharge are recharge wells and connector wells.
As discussed in the previous section, recharge wells can be very efficient in
adding water to the Floridan aquifer where the confined potentiometric surface
is 15 feet or more below the land surface. However, feasible methods of
collecting and treating surplus surface water before allowing it to enter the
aquifer would have to be determined. Adding surface water of good quality to
the aquifer would not only tend to prevent salt-water intrusion but also would
reduce the hardness and mineral content of the natural water. A side benefit
might be a reduction in the need for expensive drainage canals and pumping
stations. To store flood water underground for future use may prove less
expensive than to discharge it wastefully into the ocean.
Connector wells are wells that provide a path between the nonartesian
aquifer and the Floridan aquifer. The purpose of such wells is to provide
recharge to the Floridan aquifer in areas where the water table is considerably
above the confined potentiometric surface of the Floridan aquifer and is near
the land surface most of the time. These conditions, where surface runoff and
evapotranspiration are high and the use of the land is restricted, occur in much
of what are designated as poor recharge areas on Figure 4.
Connector wells are cased near the surface, screened in the nonartesian
aquifer, cased through the underlying confining clay layers, and open to the
Floridan aquifer, as shown in Figure 11. Rainwater that has filtered through the
surficial sand enters the well through the screen and flows by gravity into the
Floridan aquifer. This lowers the water table, reduces evapotranspiration, and
provides storage space for the next rainfall. It also reduces the need for surface
drainage and can help preserve the quality of lakes by avoiding the necessity of

REPORT OF INVESTIGATIONS NO. 61

6" Solid Casing

Screen

Solid Casing

} Porous Sand and Shell

Less Permeable Clay Layers
and Clayey Sand and Shell

I I

- Open Hole Limestone
-Sketch showing tentative design of connector we
U I

Figure 1.-Sketch showing tentative design of connector well.

50

100

150

200

REPORT OF INVESTIGATIONS NO. 61

channeling urban runoff through lakes.
The feasibility of connector wells in the Region could be evaluated by a pilot
study. A prototype installation might include, (1) an observation well in the
Floridan aquifer to monitor the quality of the mixed water, (2) water-table
observation wells to monitor the lowering of the water table, the area of
influence of the recharge well, and the quantity and quality of the water
entering the well, and (3) a connector well to provide a conduit between the two
water-bearing strata.

VERY POOR RECHARGE AREAS

Very poor recharge areas occur along the Atlantic coast, in the St. Johns
River valley and tributaries, the Kissimmee River valley and other isolated low
areas (fig. 4). This category includes almost all of Indian River and Brevard
counties, parts of Volusia and Osceola County and small parts of the other
counties. In most of the very poor recharge areas the confined potentiometric
surface is above the land surface and no recharge to the Floridan aquifer can
occur under natural conditions. Water must move from recharge areas which are
as much as 80 miles away. Under natural gradients this takes many thousands of
years and the water commonly becomes saturated or even supersaturated with
dissolved minerals from the rock through which it flows. Also, there has not
been time to completely flush sea water that entered the aquifer the last time
the Florida Peninsula was under the sea from some parts of the aquifer. It is in
these areas where most so-called shortages of water have occurred. This is not, of
course, a shortage of water but a shortage of water of suitable quality.
Surface-water sources are utilized in parts of the very poor recharge area
especially in southern Brevard County but most surface sources are unde-
pendable because of the generally intermittent stream flow.
The nonartesian (water-table) aquifer, which is recharged by local rainfall is
utilized to some degree in most of the Region, but because of its thinness and
relatively low water-transmitting ability the nonartesian aquifer cannot sustain
very large yields in most areas. One solution to the problem has been to pipe
water from areas where the Floridan aquifer contains water of suitable quality.
For example, water is piped from eastern Orange County to supply Brevard
County and Cape Kennedy. This can lead to problems with local water users in
the well-field area. A long term solution could be to store surplus surface water
of good quality in the aquifer during wet periods for later use.
The amount of rainfall per acre is about the same in the very poor recharge
areas as in the most effective recharge areas; therefore the potential for recharge
is the same. The problems are technical ones of collecting, treating, and injecting
.the water into the Floridan aquifer and then retrieving it in suitable condition

REPORT OF INVESTIGATIONS NO. 61

for its intended use. One technical problem is injecting the treated water into the
aquifer against the natural pressure in the aquifer. This could be greater than for
gravity injection of recharge water. The increased cost of injection would be at
least partially offset by reduced withdrawal costs as supply wells will flow at the
land surface under natural artesian pressure which would be augmented by the
injection pressure.
A second problem is the mixing of good-quality surface water with the
generally poor-quality ground water existing in the Floridan aquifer in the very
poor recharge areas. When small quantities of good water are injected into zones
containing water of poor quality, the water later withdrawn is a blend of the two
types. However, preliminary tests conducted in the Cocoa Well Field in eastern
Orange County indicate that when large amounts of fresh water are injected into
a water with a high mineral content, the more mineralized water is gradually
pushed back and a bubble of fresh water is formed around the well. Indications
are that as the buffer zone of blended water expands, an increasing percentage of
fresh water can be recovered with each injection-withdrawal cycle. The
percentage may eventually approach 100 percent. The feasibility of storing fresh
water in salt-water aquifers and the determination of the best methods of
collecting and treating surplus surface water could be evaluated by studies at the
most favorable sites.

CONCLUSIONS

Most water supplies in the East Central Florida Region, excluding cooling
water, are obtained from ground water. Large quantities of water are available
from the artesian Floridan aquifer in all parts of the seven member counties of
the East Central Florida Region, but the salt content of the water in
approximately one-third of the Region exceeds U.S. Public Health limits for
public water supplies. Most of this salty water is residual ocean water that has
not, as yet, been flushed from the aquifer by fresh water moving from recharge
areas to discharge areas. Because of this, it is sometimes necessary to transport
water from one part of the Region to another.
The quantity of water entering the Region as rainfall averages about 18,000
mgd, but under natural conditions less than 6 percent of this water enters the
Floridan aquifer. Although a larger percentage of the rainfall is temporarily held
in surface-water bodies, surface reservoirs are very small in comparison to the
ground-water reservoir and most surface water drains to the ocean or evaporates.
Surface water and ground water are the same resource so that a sound
management program would consider making best use of the total water
resources of the Region.
All recharge to the Floridan aquifer in the Region is from rainfall in central
Florida-principally within the Region. The prime recharge areas of the Floridan

REPORT OF INVESTIGATIONS NO. 61

coastal part, one solution may be to transport increasing amounts of water from
the western to the eastern part of the Region. This is now being done in central
Brevard County, which imports water from eastern Orange County, and the
practice will probably become more widespread in the future.
Total rainfall on the Region is about 18 billion gpd (gallons per day) and
only about 6 percent of this amount is now being captured and stored in
ground-water reservoirs. If the amount of capture could be increased to 10
percent of total rainfall, the supply of ground water would be sufficient for the
foreseeable future; this assumes, of course, that the estimates of future needs
and of amounts of recharge cited above are valid.

PROBLEMS AND SOLUTIONS IN WATER-RESOURCE MANAGEMENT
PROBLEMS

Taken in its entirety, the East Central Florida Region has large quantities of
good-quality water at the present time. The major water problems in the Region
are:
(1) Rainfall in the Region is not distributed uniformly either seasonally or
from year to year. Thus it is necessary to store water for months or years, from
periods of abundant rainfall to periods of deficient rainfall.
(2) Although rainfall, which is the source of virtually all freshwater supplies,
is reasonably uniform over the different areas of the Region on a long-term basis,
the natural facilities to collect and store the rainfall are not uniformly
distributed. In most areas surface-water reservoirs are impractical because of the
flat terrain, high evaporation rates, and changing water quality. The Floridan
aquifer, which is the most productive ground-water source and, together with
the overlying aquifers, forms the largest and most efficient storage reservoir in
the State, underlies the entire Region. However, owing to differences in
topography and geology the natural capacity of the land to absorb rainfall is
greater in some areas than in others. Parts of the Region that are efficient in
harvesting rainfall for recharge to the Floridan aquifer are delineated in Figure 4,
which shows that Lake County and the western parts of Orange, Seminole and
Volusia counties are efficient recharge areas, and that Indian River, Osceola, and
Brevard counties and the eastern parts of Orange, Seminole and Volusia counties
are poor recharge areas. The hydrologic situation in Volusia County is a
small-scale replica of the hydrologic situation in the rest of the Region, in that
most of the recharge is in the western part of the county and must move through
the aquifer to population centers along the coast. The principles of water
management that apply in the rest of the Region are equally applicable in
Volusia County.
(3) In parts of the Region the Floridan aquifer contains water of poor
quality (figs. 8, 9, and 10). In most cases this situation is directly related to

REPORT OF INVESTIGATIONS NO. 61

aquifer are mostly in the western part of the Region and water moves through
the aquifer in a general northeasterly direction. An exception is Volusia County
where there is a local recharge area in the central part of the county from which
water moves outward in all directions. Discharge is by springs and seeps within
the Region and on the floor of the Atlantic Ocean and by pumpage from wells.
Natural recharge to the Floridan aquifer within the Region is estimated to be
about 1,000 mgd. Ground-water use in 1970 totaled about 312 mgd or about
one-third of the natural recharge. By 1990 it is estimated that use of ground
water will total about 600 mgd or 60 percent of the natural recharge. Paving and
drainage works in the prime recharge areas may actually reduce recharge
considerably below the natural level.
Preservation of at least 50 percent of the volume of natural recharge to the
aquifer probably would be required to maintain acceptable water levels in wells
and the flow of springs, and to prevent salt-water encroachment. This would
leave only 500 mgd for net withdrawal for water supplies. Therefore,
artificial-recharge measures or other water-conservation practices will be needed
before 1990 to protect the ground-water resources of the Region if water use
increases as projected. Because of local concentration of withdrawal, unequal
distribution of natural recharge, and the poor quality of water in parts of the
aquifer, artificial-recharge measures are needed at the present time (1970) in
many parts of the Region, especially in coastal sections and in the St. Johns
River valley.
Although the principles of artificial recharge are well established, special
studies would be needed to determine the most efficient and economical
methods that apply in the climatic, geologic, and hydrologic conditions that
exist in east central Florida.
Surface reservoirs are important in some parts of the Region, especially the
upper St. Johns River valley. However, because of the relatively flat terrain, high
evaporation rates, changing water quality and the danger of contamination, the
use of surface water, except for irrigation, has declined. As the population of the
Region increases, more homes are built on shores of lakes. These homeowners
object to water withdrawals from the lake during low stages. In addition,
increase in land values make artificial surface reservoirs more costly. During
droughts most streams in the Region dry up, have low flows, or contain water of
poor quality. Spring-fed streams cannot be considered an additional source of
water because they derive most of their flow during droughts from ground
water. Ground-water reservoirs store more than 99 percent of the water in
storage in the Region at any given time and it is likely that most water supplies
in the future will be withdrawn from ground-water reservoirs if adequate
recharge rates can be achieved. Artificial recharge measures will be required to
accomplish this goal of adequate recharge.

REPORT OF INVESTIGATIONS NO. 61

for its intended use. One technical problem is injecting the treated water into the
aquifer against the natural pressure in the aquifer. This could be greater than for
gravity injection of recharge water. The increased cost of injection would be at
least partially offset by reduced withdrawal costs as supply wells will flow at the
land surface under natural artesian pressure which would be augmented by the
injection pressure.
A second problem is the mixing of good-quality surface water with the
generally poor-quality ground water existing in the Floridan aquifer in the very
poor recharge areas. When small quantities of good water are injected into zones
containing water of poor quality, the water later withdrawn is a blend of the two
types. However, preliminary tests conducted in the Cocoa Well Field in eastern
Orange County indicate that when large amounts of fresh water are injected into
a water with a high mineral content, the more mineralized water is gradually
pushed back and a bubble of fresh water is formed around the well. Indications
are that as the buffer zone of blended water expands, an increasing percentage of
fresh water can be recovered with each injection-withdrawal cycle. The
percentage may eventually approach 100 percent. The feasibility of storing fresh
water in salt-water aquifers and the determination of the best methods of
collecting and treating surplus surface water could be evaluated by studies at the
most favorable sites.

CONCLUSIONS

Most water supplies in the East Central Florida Region, excluding cooling
water, are obtained from ground water. Large quantities of water are available
from the artesian Floridan aquifer in all parts of the seven member counties of
the East Central Florida Region, but the salt content of the water in
approximately one-third of the Region exceeds U.S. Public Health limits for
public water supplies. Most of this salty water is residual ocean water that has
not, as yet, been flushed from the aquifer by fresh water moving from recharge
areas to discharge areas. Because of this, it is sometimes necessary to transport
water from one part of the Region to another.
The quantity of water entering the Region as rainfall averages about 18,000
mgd, but under natural conditions less than 6 percent of this water enters the
Floridan aquifer. Although a larger percentage of the rainfall is temporarily held
in surface-water bodies, surface reservoirs are very small in comparison to the
ground-water reservoir and most surface water drains to the ocean or evaporates.
Surface water and ground water are the same resource so that a sound
management program would consider making best use of the total water
resources of the Region.
All recharge to the Floridan aquifer in the Region is from rainfall in central
Florida-principally within the Region. The prime recharge areas of the Floridan

52 REPORT OF INVESTIGATIONS NO. 61

REFERENCES

I-ast Central Florida Regional Planning Council
1965 Availability of fresh water in the East Central il'orida Planning Region: 1965
Research Series.

Knoclenmus, 1). 1).
1968 Surface drainage characteristics in Volusia Countl. l*iorida: Fla. Ikl. Conser-
vation, Div. Geology Map Series 30.
1970 (and Beard, M.I-.) Evaluation of the quantity and quality of the water resources
of Vohisia Counmt. Florida: Fla. Dept. Natural Resources, Bureau of ;Geology
Report Inv. 57.

Lichtler. W. F., Anderson, Warren and Joyner. II. F.
1968 Water resources of Orange (Count. 1l, orida: Fla. 1Bi. Conservation, Div. geologyy
Report Inv. 50.

MacNeil, F. S.
1950 Pi'istocenei shorelines in Ilorida and Georgia: U1.S. Geol. Survey Prol. Paper
221-F, p. 95-107.

Mcinicr. 0. I.
1923 The occurrence of groundwater in the lUnited Slats, with a discussion of
principles: U.S. ;Geol. Survey Wa tr-Supply Paper 489.

Pride. R. W.. Meyer, !*. W., and Ciherry, R. N.
I 9 llyvdrolohr of the Grecen Swamp area in Central 'lorida: Ilorida (Geol. Survey
Rept. Inv. 42

Puri, 1I. S.. and Vernon, 0.
1964 Sumntarv of the geology of 1I'orida amid a gimdehook to the classic exposures:
Florida (Geol. Surv. Spec. Publication 5 (revised).

t5 f~I04530'H0ig5

)rmond Beach

itona Beach

L AKE
,, ,"or

1o I'i

290 15'

2900'

45'

30'

15'

2800'

:APOPKA

-..

EXPLANATION

effective recharge areas
lately effective recharge areas

recharge areas

*1

L..

Very poor recharge areas

Location of recharge- area boundaries
based in part on soil maps of the
Soil Conseivolion Service, U.S.
Deportment of Agriculture.

0 10 20 MILES
1. 1 I-j

-4

*z
-4

C-

I
L
fJ

45'

27030'

D Most
D[ Moderc
Poor

D

LAKE
/I A N

I Vero Beach

1!5 1 fil Q ool

I I
6A lu

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	Title Page
	Copyright
	Contents
	Abstract
	Introduction
	Description of the region
	Hydrology
	Water use
	Problems and solutions in water-resource...
	Conclusions
	References
	Map