STATE BOARD OF CONSERVATION
FLORIDA GEOLOGICAL SURVEY
Herman Gunter, Director
REPORT OF INVESTIGATIONS
GROUND WATER IN
CENTRAL AND NORTHERN FLORIDA
H. H. Cooper, Jr., W. E. Kenner and Eugene Brown
UNITED STATES GEOLOGICAL SURVEY
THE FLORIDA GEOLOGICAL SURVEY
LETTER OF TRANSMITTAL
florida geological ?fuivey
November 10, 1953
Mr. Charles Bevis, Supervisor
Florida State Board of Conservation
Dear Mr. Bevis:
The Interior and Insular Affairs Committee of the House of
Representatives, United States Congress, encouraged members of
the United States Geological Survey, and the United States Weather
Bureau, "to prepare graphic descriptions of the geologic, topo-
graphic and hydrologic features of eight type areas, chosen to show
in detail on a sample area basis characteristics which are typical
of extensive areas," throughout the United States.
Florida was fortunate in being selected as the type area of
artesian groundwater occurring in carbonate aquifers. The report
on the central and northern Florida area was prepared by Messrs.
Cooper, Kenner and Brown of the United States Geological Survey
and was considered to be so readable, factually true, and excel-
lently illustrated that it should be made available to the citizens
of Florida, as part of the service by this Department.
I am pleased to submit this fine report with the request that
it be published as Report of Investigations No. 10.
Herman Gunter, Director
FLORIDA STATE BOARD
CHARLEY E. JOHNS
R. A. GRAY
Secretary of State
CLARENCE M. GAY
THOMAS D. BAILEY
Superintendent of Public
J. EDWIN LARSON
Commissioner of Agriculture
Supervisor of Conservation
TABLE OF CONTENTS
Letter of Transmittal ----..... ...--------------------....---....----.... 3
Acknowledgments -6---------------......----------... ...-------------------.... __ 6
The general setting .......--------------.. ...... ---------- 7
Precipitation .._- --.__- -.............. -------........- -__________ 8
Streams in northern and central Florida 9............---------------.. --......... 9
Ground water --------------------.-..-..- ........--------------..........------ 17
Artesian water ------------------ ---------- _17
Aquifer functions as a giant reservoir ----------- 20
Aquifer functions as a system of pipelines _------... --. 24
Chemical quality of ground water ___ -------------------- 29
Current draft of water has made only minor subtractions
from the total supply ---------------..... ----------.----...-........ 31
Studies needed ............--- ...-- ................ ...............---------.---.....--- ...-. 34
References -..------..----.-------. ...----. ..... -....--------- ---- --..... .. .7..37
1 Florida's rainfall is plentiful .....---------.. --.. ---.---------.... 9
2 Variations in monthly precipitation at Gainesville __----- -- 10
3 Variations in yearly rainfall at Gainesville, 1901-1950 1-- --
4 Flow of the Santa Fe River passes underground in a 3-mile
reach between Worthington and High Springs .----...... 12
5 Flow of Santa Fe River upstream and downstream from
its underground reach ----_-----------.......... __....... ----- .. 13
6 Streams of northern and central Florida and their flow _--- 14
7 Size and frequency of floods, Suwannee River near Bell --- 15
8 Hardness of stream waters in central and northern Florida -- 16
9 Expanse of the Floridan aquifer --. __ -------...._.. ---- 18
10 Areas of recharge to the Floridan aquifer ..--..-----------.- -. 19
11 Florida's large springs --............-......... ------- ...- 20
12 Geology controls recharge and movement of the water ..- ------------... 21
13 Model explaining the piezometric surface .-------------------.-.._ --- 22
14 Effect of rain on ground-water levels ....-------------......---- __.. 23
15 Recharge through sinkhole ... ..... ......------ --------------.....--..- 2.... 24
16 Typical recharging sinkholes ___---.....-----.......-..........__ ....____....____. 25
17 Piezometric surface of the Floridan aquifer, 1952 --....-........------- 26
18 Areas of artesian flow ---.......................-_ -------_ .---------..---. 27
19 Salty water in the Floridan aquifer ----.....------ ...-_.-----.___-----. 28
20 Hardness of water from upper part of the Floridan aquifer --....._... 29
21 Artesian pressures have diminished at Jacksonville ---.....----_.--- 30
22 A large spring ceases to flow --__------ __..__ ...--- ----33
23 Why Kissengen Spring stopped flowing ..----..--- ----- --- ----- --- ._... 34
This report was published as Chapter Nine of part four of
the series of studies of natural resources prepared for the Interior
and Insular Affairs Committee, House of Representatives, United
States Congress. Part four of the series was prepared under the
supervision of Arthur M. Piper of the Federal Survey.
The permission to publish the chapter on Florida was kindly
given by Dr. Nelson Sayre, Chief, Groundwater Branch, U. S.
Geological Survey. The subject matter and the scope of the project
is at the heart of the delegated responsibilities of the United States
Geological Survey, but heavy responsibilities and limited manpower
keep the Survey from making many studies that are needed.
The activities required in the preparation of these reports
were undertaken by members of the regular staffs of the various
branches of the U. S. Geological Survey, but much of the work
accomplished was a result of overtime activity.
Many individuals have participated in the preparation of the
report, "Ground Water in Central and Northern Florida." Those
with the chief responsibility for preparing the report are listed
as authors, but many individuals in the various offices prepared
diagrams, tabulated data or contributed to the report in other
ways. In particular A. O. Patterson, District Engineer, Surface
Water Branch, Ocala, Florida, and Ralph Heath, Acting District
Geologist, Groundwater Branch, Tallahassee, Florida, contributed
specific items to the report.
Central and Northern Florida*
By H. H. COOPER, Jr., W. E. KENNER and EUGENE BROWN,
United States Geological Survey
THE GENERAL SETTING
Florida affords a happy contrast to thirsty regions of the
Southwest. Over most of the State vast quantities of water await
development. Precipitation is abundant. Streams empty substantial
volumes of water into the ocean, their flows virtually undiminished
by man's minor extractions. Numerous limestone springs, some
among the largest in the world, contribute their share to the water
that escapes unused. Myriad lakes and large swamps yield an un-
told levy to evaporation and to the transpiration of native vege-
Beneath the State lies a part of one of the most extensive and
productive ground-water reservoirs in the Nation-the Floridan
aquifer. This aquifer plays a dual role in the water-resources pic-
ture. On one hand it serves as a giant reservoir, storing water
in periods of excessive rainfall against gradual release during
droughts. On the other, it acts as a system of pipelines, trans-
mitting water to points distant from the areas of recharge and
distributing it conveniently to cities and industries and to isolated
farms and rural homes.
Although the total available supply of water is very large as
compared with the present demand, water of good quality is not
adequate in some localized areas. The lack is becoming especially
acute at some places along the coast where most of the ground
water is too salty for ordinary uses, and where the surface sup-
plies are scanty or are themselves salty.
Florida's economy is expanding rapidly. Ranking first among
sources of income is the State's tourist trade, but other sources,
including citrus growing and citrus processing, truck farming,
cattle raising, mining of phosphate and heavy minerals, and timber
* Reprinted from Part V, Subsurface facilities of water management and
patterns of supply-Type area studies: The Physical and Economic Found-
ation of Natural Resources, Interior and Insular Affairs Committee, House
of Representatives, United States Congress, 1953, 206 pp.
and pulpwood production, contribute substantially. Attracted in
part by the availability of large dependable supplies of water, man-
ufacturers of paper, rayon, and nylon are establishing many mills
in the northern part of the State.
The State's mild climate has, of course, been predominantly in-
strumental to its agricultural development and to its popularity
as a winter resort. Generally, the State is frost free more than 9
months of the year. With average temperatures of 81 F. in July
and 590 F. in January, the climate is usually neither excessively
hot nor excessively cold. Only once has a subzero temperature
been recorded in the State: a low of -2 F. nipped Tallahassee dur-
ing the unprecedented, nationwide cold wave of February 1899.
The highest temperature on record is 1070 F., but yearly maxima
of 1000 F. and minima of 200 F. are by no means common any-
where in the State. Snow is so rare that many adult natives have
never seen it.
The 1950 census recorded in Florida a permanent population
of 2,770,000, which represents a growth of 46 percent since 1940.
Part of the growth has come from an influx of elderly people,
who are retiring and establishing permanent residence in the
As shown in figure 1, no part of the State has been slighted
in the distribution of rain. In the extreme southeastern and north-
western sections of the State the average is 64 inches and at other
places is generally more than 48 inches. The average over the
State as a whole is 53 inches a year.
Although there are well-defined wet seasons and occasional
droughts, ordinarily the rainfall is fairly well distributed through
the year. The seasonal distribution at Gainesville is typical of that
at most stations (fig. 2). The period of greatest rainfall generally
begins in June and ends in September but extends into October on
the southeast coast, owing to the far-reaching influences of tropi-
cal disturbances in the Atlantic Ocean.
Long-term trends of rainfall at Gainesville are represented in
figure 3. During the 50-year period from 1901 to 1950 the yearly
rainfall averaged 50 inches but ranged from as little as 32 inches
in 1917 to as much as 65 inches in 1941. From 1901 through 1918
the rainfall was generally less than average; from 1919 through
1943 it was about average; and from 1944 through 1950 it was
generally higher than average.
FIGURE 1.-Florida's rainfall is plentiful.
The lines define zones of equal average yearly rainfall, which ranges from
46 to 64 inches. From "Climate and man," U. S. Department of Agriculture
STREAMS IN NORTHERN AND CENTRAL FLORIDA
The area which will be discussed comprises about 22,000 square
miles in the north-central part of Florida, including all or parts
of 32 of the State's 67 counties. This area consists principally of
low coastal lands divided slightly east of center by Trail Ridge, a
series of rolling hills that rise no higher than about 200 feet above
In few other areas of the United States is the distinction be-
tween surface water (streams, lakes, and ponds) and ground water
more transient. Also, in few other areas is the land surface more
obviously drained in part by movement of water underground. The
water of a stream or lake may infiltrate through the bed of that
stream or lake and become ground water. Elsewhere, perhaps miles
Mean 4.23 inches
Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept
FIGURE 2.-Variations in monthly precipitation at Gainesville.
Average rainfall in the driest month, November, is 24 percent of that in
the wettest month, July. Extremes vary widely in each month, especially
from October through April.
away, it may issue from a large spring and form a stream. In
north Florida, for example, the Santa Fe River disappears under-
ground to reappear several miles away and continue again as a
surface stream (see figs. 4 and 5). The water is the same; only
Average by periods shown below, inches
45.95 50.43 --56.59h-
50 year average, 50.63 inches
o 0 C 0
o ._ CMJ a -
2 0 I I I I I I I I I I I I I l I I I I I I I I I I I I i ii i i ii i
average in 1917 to 128 percent of average in 1941; this percentage range
is much less than is common in the drier parts of the Nation. The lower
graph shows a dry period from 1906 through 1918 and a wet period beginning
with 1941; the intervening period was neither notably wet nor notably dry.
10 0 20 Miles
I i I I
FIGURE 4.-Flow of the Santa Fe River passes underground in a 3-mile
reach between Worthington and High Springs.
Several of the rivers in northern Florida, including the Santa Fe and the
Suwannee, have cut channels into the limestone formations that compose
the principal ground-water reservoir. During low flows, these rivers are fed
by the ground water. During high flows, water from the rivers pours into
its name, "surface water" or "ground water," changes according
to mode of occurrence at the moment.
Lakes and ponds, scattered over the area, number in the thous-
ands. Large swamps border most of the west coast and occupy
much of the St. Johns River basin. The principal streams of the
area include the Suwannee, St. Marys, St. Johns, Oklawaha, Santa
Fe, Hillsborough, and Waccasassa Rivers, two rivers named With-
lacoochee, and Olustee and Black Creeks (see fig. 6). The St.
Johns River is one of the few rivers of the world that flow north-
ward throughout their courses.
The figure shows the average flows of these streams so far as
is indicated by the few data available. A notable deficiency is the
lack of records on the flow of the lower St. Johns River-the flow
is unknown over a reach of 150 miles. The flow of the Suwannee
River near Bell, Fla., averaging 8,000 cubic feet a second, is by
far the largest of any on which adequate data are available, but
During the 7 months covered, flow of the river at Worthington, upstream
from the underground reach, ranged from 7 to 1,930 mgd (million gallons a
or 11 to 290 1. N r High Springnr irng r
FIGURE 5at high flow this reach of Santa Fe River upstream and downstream from its
ground water. During rising stages at high flow, it loses moderately to ground
During the 7 months cover St. Johs t rir at Worthington, upstream
from the underground reach, ranged from 7 to 1,930 mgd (million gallons a
day), or 11 to 2,980 cfs. Near High Springs, downstream, it ranged from
94 to 1,630 mgd, or 146 to 2,520 cfs. Evidently, during low flow and falling
stages at high flow this reach of the river gains very substantially from
ground water. During rising stages at high flow, it loses moderately to ground
the flow of the lower St. Johns may turn out to be even larger
Most of the major streams-including the Suwannee, St. Johns,
Oklawaha, Santa Fe, Hillsborough, and Waccasassa Rivers and the
two Withlacooche Rivers-receive a part of their flow from arte-
sion springs. At high stages, water from the Suwannee River
backs into many of the numerous springs along its course. The
flows of the Oklawaha and the southern Withlacoochee Rivers are
sustained at medium and low stages by Silver Springs and Rain-
bow Springs, respectively-the State's largest two springs. The
operation of a hydroelectric plant on the Withlacooche owes its
existence to the discharge of Rainbow Springs. The Hillsborough
River is the source of supply for Tampa, the third largest city of
Inundating floods of the Suwannee River (see fig. 7) doubtless
have helped to retard economic development in the river basin.
Optimum design of control structures will require an adequate un-
derstanding of the effects of water movement in the limestone for-
mations through which the river has cut its channel. The flow of
water through open solution channels in the limestone would cause
difficulty in confining the flood waters to surface reservoirs, but,
on the other hand, voids in the limestone would add substantially
to the storage capacities of reservoirs.
The lakes are used extensively for irrigating citrus groves and
truck farms during the winter and early spring, when rains are
FIGURE 6.-Streams of northern and central Florida and their flow.
Where known from measurements, average flow of the streams is indi-
cated by the symbols-a dotted line for flow less than 500 cfs (cubic feet
a second), a solid line for each 500 cfs of flow in the larger streams. For
example, the flow of the Suwannee River below the Santa Fe River is about
8,000 cfs. Flow is not measured in numerous long reaches of certain streams,
and cannot be shown here.
101 11 15 2 5 10 25 50 100
RECURRENCE INTERVAL, YEARS
FIGURE 7.-Size and frequency of floods, Suwannee River near Bell.
Drainage area 9,260 square miles. Here, water yield per square mile is only
moderate. For a flood of 10-year expectancy, flow near Bell would be about
46,000 cfs. In contrast, the 10-year flood of the St. Joe River at Calder,
Idaho is 4.7 times larger per square mile. On the streams of Florida, flooding
is more a result of low channel gradients and relatively slow runoff, than
of the amount of runoff.
relatively infrequent. They serve also to moderate the tempera-
ture, providing frost protection for citrus and vegetables during
The recreational facilities offered by the surface waters are
substantial contributors to the economy of the area, and the large
limestone springs of the area are among the State's major tourist
attractions. Fishing in the lakes and streams lures many anglers
from border States and other parts of the Nation. Pleasure boating
on the Oklawaha River and its headwater lakes is a favorite recrea-
tion among local inhabitants and visitors.
The proposed Florida cross-State barge canal would run east
from the Withlacooche River to the Oklawaha and thence into the
St. Johns. The successful operation of the locks of the canal would
depend on the flows of the large springs.
Gaging stations on the small streams of the area are far too
few and have been operated only for short periods. Before these
streams are developed for municipal, industrial, and agricultural
supplies, records of their flows will be needed. Also, records of
the flow of smaller streams are prerequisite to estimates of ground-
The chemical character of Florida's lakes and streams is quite
FIGURE 8.-Hardness of stream waters in central and northern Florida.
Points indicate sampling stations; numerals indicate hardness in parts per
million. These are momentary values of hardness, from single "spot" sam-
ples; they are not average values.
FIGURE 10.-Areas of recharge to the Floridan aquifer.
The aquifer is replenished by infiltration of rain over about 13,000 square
miles. In the darkly-shaded areas almost all the rainfall is offered to the
aquifer but some is rejected when the aquifer becomes full. In the lightly
shaded areas the aquifer is blanketed by watertight material but receives
recharge through sinkholes that penetrate the blanket.
This aquifer is the source of Florida's many large springs, such
as Silver Springs, whose discharge averages 500 mgd, or 775 cfs.
It is also the source of water from many thousand wells. In Sem-
inole County alone it yields water to more than 2,500 irrigation
wells. The natural flows of some of the wells are quite large; one
well at Jacksonville, in Duval County, yielded a flow of almost 10
mgd, enough water to supply a city of 75,000 people.
FIGURE 11.-Florida's large springs.
The discharge of springs gives an inkling of the large potential yield of
the Floridan aquifer. In the aggregate about 6,000 cfs flows from the
springs represented here. But a much larger quantity of water escapes from
the aquifer beneath the sea, unobserved and unmeasured.
Aquifer Functions as a Giant Reservoir
The artesian water is replenished by rain in areas where the
limestone aquifer lies at the surface and where it is covered only
by pervious material (fig. 10). Within these areas the water that
falls as rain is stored over long periods of time sustaining the flow
of springs and rivers during long droughts, and endowing a peren-
nial supply to wells. No one knows how much recoverable water is
stored in the aquifer-there is not sufficient information to enable
a well-founded estimate-but we do know that it is very large.
Rough calculations put the volume of fresh water in the aquifer
at about 10 times the capacity of Lake Mead, the Nation's largest
man-made reservoir, impounded behind Hoover Dam on the Col-
orado River. But only a fraction of the water stored can be claimed
Neither do we know how much replenishment the aquifer re-
ceives each year, although the total discharge of the large springs
indicates that it, too, is large. The aggregate discharge of the
springs represented in figure 11 is about 6,000 cubic feet a second.
But this is only a small fraction of the whole. Probably most of
the discharge goes directly into the sea, through countless springs
and widespread seepage. This submarine discharge cannot be ob-
served or measured, but we believe that it exceeds by several times
the discharge of the terrestrial springs. Thus, we conclude that the
discharge from the aquifer, and hence the replenishment to it,
must be reckoned in the tens of thousands of cubic feet a second,
and that the replenishment easily exceeds the flow into Lake Mead.
The areas of recharge aggregate about 13,000 square miles in
central and northern Florida. Full development and use of the ar-
/ ---- .. ...-,,
Reltd rharp. Maxmum recharge Rechire ntilroh Ate fow:
Aquer exposed but Aquifer exposed or covered snk holes Piezometri srae
full of water with porous material above ond
Vercal relief greatly exau erted
FIGURE 12.-Gology controls recharge and movement of the water.
The Floridan aquifer is a thick section of limestone which crops out at
the land surface in some areas, but which is blanketed by watertight ma-
terial in other areas. Recharge occurs most readily where the aquifer crops
out, but a substantial amount of water enters through sinkholes which breach
the watertight blanket.
Flowing wells may be obtained wherever the piezometric surface (see fig.
13) is above the land surface, as in the right-hand part of the section shown.
Here the water is confined beneath the watertight blanket, and the aquifer
is essentially a conduit. Where the aquifer is unconfined (left half of the
section) it functions as a reservoir. At the far left of the section the aquifer
is full and, therefore, is rejecting recharge.
tesian water will require that we distinguish between two types of
recharge areas. In one, the aquifer is exposed at the land surface
or is covered only with porous sand through which water may in-
filtrate to the aquifer quite readily. (See figs. 12 and 13.) In such
an area a large percentage of the rainfall is available to the aqui-
fer. Where the aquifer is not full, it accepts the water offered to
it, leaving little or none to run off in streams. (See fig. 14.) Where
the aquifer is full to overflowing, however, it rejects a part of the
rainfall. Of that rejected, some runs off in streams and some
returns to the atmosphere through evaporation and transpiration.
Where the aquifer is rejecting water, recharge may be increased
by the simple expedient of drilling wells and pumping water for
use, thereby unwatering the aquifer and providing space to be
occupied by additional recharge. When this is done, some of the
streamflow and some of the water that otherwise would be evap-
orated or transpired is captured by the wells. Certain species of
vegetation, when so robbed of their perennial supply of water, be-
In the second type of recharge area the aquifer is overlain by
a blanket of relatively impervious material that tends to confine
the aquifer and preclude recharge. Here it is only where the blank-
et is breached that appreciable quantities of water reach the aqui-
fer. In certain areas the blanket of impervious material is per-
forated with sinkholes, which form when limestone caverns, grow-
ing ever larger as the limestone gradually dissolves away, eventu-
ally collapse (fig. 15). These sinkholes are the avenues through
which water finds its way down into the artesian aquifer (String-
FIGURE 13.-Model explaining the piezometric surface.
In this laboratory model, the piezometric surface is the plane passing
through the water surfaces in the tank and in the vertical tubes. In nature,
it is an imaginary surface coinciding everywhere with the height to which
water will rise in wells, owing to its pressure head. Water moves in the
direction of downward slope on the piezometric surface.
FIGURE 14.-Effect of rain on ground-water levels.
In the area of free recharge ground-water levels rise quickly owing to
local rain. As shown, in a well east of Orlando the water level rose more
than 6 feet in less than 24 hours after 2 inches of rain fell. A rise so rapid
indicates that water infilters readily to the aquifer. In most wells the water
level responds to rainfall more slowly.
field, 1936, p. 148). Ordinarily, they are not open holes but are
floored with sand, and the sand allows water to filter through slow-
ly (fig. 16). Thus, the rate of recharge is limited by the number
of sinkholes and by the permeability of the sand and other material
they contain. It may be observed that in this case the recharge is
limited neither by the amount of rainfall nor by the capacity of
the aquifer to receive water, but by the rate at which water may
seep through the overlying material. The aquifer would receive
more water if it were offered. Accordingly, the water running off
in surface streams and being evaporated and transpired cannot be
regarded as having been rejected by the aquifer. One could not
expect, then, to induce much additional recharge merely by pump-
ing. Additional recharge can be effected only by causing more
water to pass through the water-tight blanket. This might be done
by drilling artificial-recharge wells, through which surplus water
may be diverted from the land surface into the aquifer.
Aquifer Functions as a System of Pipelines
One attractive feature of the artesian water, and of ground
water in general, is its proximity to places where water is in de-
mand. Generally, the isolated rural dweller, the farmer, the city
or industry needs only to drill a few hundred feet to obtain an ade-
quate supply. The aquifer through which the artesian water moves
is a natural conduit, a distribution system reaching almost every-
where in the region. From where it enters the aquifer the water
may travel long distances, commonly 50 miles and more, to where
it is withdrawn for use. Not only does it move to the very prem-
ises of the consumers-over a large part of the State it is deliv-
ered under artesian pressure, so that the consumers are saved the
expense of pumping.
We have learned the general directions in which the water
moves by mapping the height of water levels in many wells
FIGURE 15.-Recharge through sinkhole.
Limestone is slightly soluble in water and gradually dissolves as water
moves through it. Over the ages this process of solution creates large cav-
erns, and forever enlarges them until ultimately they collapse under the
load of rock and earth above. Collapse of a cavern causes the overlying ma-
terial to subside, and so breaches the watertight blanket that confines the
aquifer. Water from the land surface and in the thin sandy mantle then has
a portal through which it may drain into the aquifer.
FIGURE 16.-Typical recharging sinkholes.
Florida's landscape is dotted with hundreds of sinkholes such as this. Some contain water and others do not. Those that are dry
evidently drain freely and hence contribute a larger share of recharge to the Floridan aquifer. Those that contain water gener-
ally do so because their bottoms are covered with an accumulation of muck that slows drainage. Recharge to the aquifer might
be increased by dredging the muck away.
throughout the State. The result is the map shown in figure 17,
which represents approximately the height to which the artesian
water will rise in a well at any given place (Stringfield, 1936, pp.
146-154). We may observe, for example, that near the center of
the peninsula the water in wells stands 120 feet above sea level-
higher than at any other place in the State. Generally, recharge
occurs in areas such as this, where the water stands high, and dis-
charge occurs where it stands low. The water moves laterally from
the areas of recharge toward areas of discharge, generally at right
angles to the lines shown on the map. The water passes, in some
directions, beneath the blanket of relatively impervious material,
FIGURE 17.-Piezometric surface of the Floridan aquifer, 1952.
Lines connect points of equal head on the ground water, in feet above
sea level. The piezometric surface, so shown, is highest where there is re-
charge and slopes downward in the direction that water moves toward places
of escape. The general coastward slope of this surface indicates that most
of the water moving in the aquifer wastes into the sea.
which not only impedes downward percolation from the land sur-
face, but also confines the water within the aquifer and preserves
its head. In low areas, water so confined has enough head to flow
at the land surface when the confining blanket is punctured by a
well. As indicated in figure 18, flowing wells may be obtained over
roughly a third of the State.
Where the artesian water is confined, the aquifer cannot func-
tion efficiently as a reservoir, because it is already full and cannot
store additional water in large quantity. An effort to conserve
n ~ -
FIGURE 18.-Areas of artesian flow.
Flowing wells may be obtained over roughly a third of Florida, commonly
with yields of several hundred gallons a minute. Such wells are a boon to
farmers and citrus growers as they obviate an expense of pumping water
for irrigation. Flowing wells used for irrigation number in the tens of thous-
ands. The area of flow is contracting locally because of the heavy draft of
flood water by artificially recharging a confined aquifer would be
comparable to an attempt on the part of a city to use the pipes of
its distribution system as a storage reservoir. True, the artesian
pressure would be increased around the area of artificial recharge
so long as the injection of water were continued, and to this ex-
tent beneficial results would accrue, but these effects would dis-
sipate rapidly whenever the injection were interrupted. Thus, if
surplus water is available for recharge only intermittently, as dur-
FIGURE 19.-Salty water in the Floridan aquifer.
Shaded area is that within which the water contains more than 1000 ppm
of chloride at moderate depths. This is almost as large as the area of ar-
tesian flow. At some places the water is only slightly salty and is being used
for irrigation and municipal supply, but only because better water is lacking.
At other places the water is much too salty for all but a few unusual pur-
poses. Some hydrologists think the salty water is a remainder of sea water
that moved into the aquifer thousands of years ago when the sea stood higher
ing wet seasons, it ordinarily cannot be stored in a confined aqui-
fer for withdrawal during subsequent droughts.
Chemical Quality of Ground Water
At times in the geologic past the sea has stood much higher
than it stands today. At those times, the salty water of the sea,
under the thrust of the sea's stronger pressure, moved considerable
distances into the aquifer. Some ground-water hydrologists believe
that it is a consequence of this ancient invasion that the artesian
water is now salty over much of Florida (see fig. 19). Since the
sea was last high, possibly 10,000 to 20,000 years ago, the seaward
circulation of fresh water has been gradually flushing the salty
water out. Eventually the artesian water may become fresh almost
everywhere, but that is too far in the future to be of much interest
Over most of the State deep wells drilled for oil have pene-
trated very salty water, some of it much saltier than the sea, at
depths of several thousand feet. We infer from this that such water
may occur everywhere beneath the State, but our information is
too scanty for us to be sure. Wherever it does occur, the salty
water menaces the fresh artesian water that lies above, for unwise
FIGURE 20.-Hardness of water from upper part of the Floridan aquifer.
Lines connect points of equal hardness, in parts per million.
development might cause the salty water to move up and contamin-
ate the fresh-water resource.
The hardness of the artesian water varies considerably from
one place to another (see fig. 20). It is less than 100 parts per
million in an area west of Gainesville, where recharge enters the
aquifer through sinkholes, but increases progressively as the water
moves away from this area. The hardness is derived mainly by
solution of the limestone and dolomite that make up the Floridan
aquifer. As the water enters the aquifer, it is quite soft but con-
tains carbon dioxide and organic acids that enable it to dissolve
the rocks more readily. During its long journey from the area of
recharge, always in intimate contact with the rocks, the water
picks up several hundred parts per million of hardness.
Where the artesian water is too salty for use, the shallow
ground water and the streams, lakes, and ponds constitute the
principal sources of supply. In some such areas, as around Miami,
the shallow aquifers are highly productive and will very likely sup-
ply the local needs for many years to come. On the other hand,
in areas such as those along the middle east coast, the shallow for-
mations and surface sources do not yield an adequate supply, and
eventually the municipalities must pipe water from sources in ad-
joining areas to supply their steadily growing requirements.
\I .Femandia F rnandia
S__________ J& knville
sAugnt tA st 4/
FIGURE 21.-Artesian pressures have diminished at Jacksonville.
Lines connect points of equal artesian head, in feet above sea level. When
the first wells were drilled, about 1880, the artesian pressure in the vicinity
of Jacksonville was sufficient to raise water 600 feet above sea level (map
at left). Now, owing to a draft of 80 mgd, the pressure is substantially less
(map at right). Large additional supplies of artesian water may be devel-
oped, but at the cost of a further decrease in pressure.
Current Draft of Water Has Made Only Minor
Subtractions From the Total Supply
Considered as a whole, the available supply of artesian water is
scarcely touched by current draft. It is only in certain localities
that the demands for water are approaching the capacity of the
aquifer to supply it.
For example, about 100 million gallons a day is currently being
drawn from wells in the vicinity of Jacksonville for municipal and
industrial uses. As indicated in figure 21, this draft has caused
substantial lessening of artesian pressures, especially around the
town of Fernandina, north of Jacksonville. The decline of water
levels does not, however, indicate a depletion of the reserve, as it
would in some other areas. It merely indicates that the aquifer
lacks sufficient capacity for transmitting water from the area of
recharge. Around Jacksonville the aquifer is confined and is func-
tioning principally as a conduit rather than a reservoir. Just as
the size of a pipeline limits the quantity of water that will flow
through it, so does the capacity of the aquifer to transmit water-
its "transmissibility"-determine the rate of flow of the artesian
water. But the rate of flow is determined also by the steepness of
the piezometric surface; when the piezometric surface is steepened,
water moves through the aquifer more rapidly. Thus, the lessening
of artesian pressures in the Jaksonville area, by steepening the
piezometric surface, has induced more water to move in from the
recharge area. Each time the draft is increased, the pressures will
be further lessened and the gradient steepened proportionately. The
maximum yield of the wells will have been realized when the draft
has grown to the extent that no further lowering is economically
feasible. Other factors being equal, the maximum yield will be
larger if the wells are distributed over a wide area. Also, more
yield may be obtained by drilling wells closer to the recharge area,
thereby shortening the distance the water must travel.
It appears unlikely that any alarming consequences will develop
from heavy withdrawal in the Jacksonville area, providing wells
are not drilled too deep. More likely economic expedience, rather
than disastrous experience, will eventually call a halt to further
development of the artesian water and motivate the development
of a supplemental supply from other sources.
But not everywhere is the outlook so happy. An excessive draft
of ground water can be ruinous if it causes encroachment of salt
water from the sea. A notable example of the places where salt-
water encroachment is becoming acute is the Pinellas County pen-
insula, on the west coast of Florida. Here, sea water is gradually
moving into the aquifer, destroying its worth to the farmers,
municipalities, and industries that have grown to rely on it. One
by one the wells are beginning to yield water unfit for use. Be-
cause of the encroachment, St. Petersburg was forced to develop
a new water supply on the mainland as early as 1928, and indica-
tions are that the other municipalities of the county must follow
suit before many more years. Other places at which salt water has
encroached to a greater or lesser extent are Miami, Fort Myers,
Fort Pierce, Tampa, Daytona Beach, Panama City, and Pensacola.
The encroachment at Tampa forced the abandonment of the old
municipal wells about 25 years ago, and since then Tampa has
obtained its water from the Hillsborough River. However, avail-
able information indicates that an adequate supply of ground water
for Tampa may yet be obtained close to the city. The encroachment
at Miami was caused, not by pumping of wells, but by drainage
operations (Parker, Ferguson, and Love, 1953).
An encroachment of salt water is especially lamentable because
its effects are long lasting. Having once established inroads into
the aquifer, the salty water will rinse out only very slowly, leaving
traces for many years and perhaps for generations after remedial
measures are undertaken. Convincing evidence of this is the fact
that today, after thousands of years of rinsing, salty water that
entered the aquifer during the ancient high seas is yet very much
in evidence (fig. 19). It would seem, therefore, that among the
various undesirable effects of excessive draft, an encroachment
of salt water is the most hurtful. If it is not checked, it may destroy
all or a part of an aquifer beyond practical recovery.
In the long run, salt-water encroachment can be avoided, when-
ever it impends, only by limiting the total draft from wells, but
the limit can be raised by artificially recharging the aquifer. If
geologic conditions are favorable, artificial recharge might be most
effective if applied immediately adjacent to the coast, where it
would build up a ground-water "ridge" to act as a barrier to the
inland advance of sea water. This approach to the problem prob-
ably would be feasible only if the aquifer were underlain by a
watertight formation at a reasonable depth. It is therefore im-
portant that the geology of the area be understood thoroughly
before such remedial measures are undertaken.
As we have already observed, a withdrawal of water from the
aquifer may, under favorable conditions, cause an increase in re-
charge. Another way in which nature adjusts to withdrawal is
through a lessening of natural discharge. This process is exempli-
fied by the cessation of flow at Kissengen Spring, near Bartow,
formerly one of the large springs of the Florida Peninsula. For
several decades Kissengen Spring was a favorite recreational center
for out-of-State tourists and for residents of the Bartow area. In
February 1950 it became the first of the large artesian springs of
Florida to cease flowing completely (fig. 22). The cause of its
demise was the increasingly heavy draft from wells in the sur-
rounding region (see fig. 23). Currently, about 110 mgd (million
gallons a day) is being drawn from the wells during periods of
peak demand, principally for industrial and agricultural uses. Of
this amount, about 20 mgd is derived from the capture of the flow
of Kissengen Spring. The balance, or 90 mgd, evidently is made
up partly from decreases in other discharge, partly from an in-
crease in recharge, and-so long as the water levels continue to
decline-partly from a slight reduction in the amount of water
stored in the aquifer.
Like the lowering of pressures at Jacksonville, the cessation of
the flow of Kissengen Spring reflects the capacity of the aquifer
to transmit water from the area of recharge, and does not, in the
main, indicate depletion of the resource. The flow will remain ar-
rested as long as the current rate of draft continues, but would re-
sume if, for any reason, the draft were curtailed sufficiently.
The large supplies of unappropriated artesian water in the area
of recharge will doubtless play a prominent part in Florida's fu-
ture development. They beckon to industries that must settle where
large supplies can be had-industries whose thirsts can be satis-
FIGURE 22.-A large spring ceases to flow.
Only a few years ago Kissengen Spring, near Bartow, was a well-known
recreation center. Today it is a hyacinth-covered stagnant pool. (See p. 37)
fied only by drafts of tens of millions of gallons a day. If the trends
of the past decade continue as they doubtless will, we may expect
an accelerating influx of these industries into the State. Moreover,
as the coastal cities grow until their water requirements exceed
the local supplies, many will doubtless begin piping water from
the recharge areas. Thus, however abundant the ground-water
resources may appear today, it seems inevitable that they will
eventually be fully appropriated-at least over much of the area.
Anticipating full development of the artesian water, we should
proceed to learn how much water can be claimed and what can be
done to increase the water yield. But we have only an inkling of
how much water enters the ground and a lesser idea of how much
more recharge could be induced by pumping and by artificial re-
charge. We cannot obtain a reliable estimate of the rate of re-
charge until there is a more complete accounting of all factors in
j -~ I I
FIGUE 23.-Why Kissingen Spring stopped flowing.
From about 1936 to 1950, pumpage of ground water in the region around
the spring increased more than fourfold, from about 8 to 34 billion gallons
a year (25,000 to 105,000 acre-feet a year). As a result, the artesian pressure
diminished until it could no longer sustain the spring flow. There was no
lasting deficiency in rainfall that might explain why the spring stopped
the water budget. We must first know how much water falls on
the recharge area, how much runs off in streams, and how much
returns to the atmosphere through transpiration and evaporation.
Much of Florida's rain comes in short, intense showers that
drench a few square miles at a time while leaving surrounding
areas undampened. Consequently, precipitation stations only a few
miles apart commonly record substantially different quantities of
rain in a given year. Existing stations are much too widely scat-
tered to measure the volume of rainfall. Only when they have been
greatly augmented can the gross supply of water in the recharge
area be known as accurately as is needed.
We must know how much water runs off various parts of the
recharge area. This means that we must gage the flow of many
small tributaries. It means also that we must have topographic
maps to enable us to define the drainage areas of these tributaries
Included in some of the larger drainage basins are sizable areas
having no surface runoff at all-areas in which all the rainfall
not evaporated or transpired filters into the ground. Lacking
topographic maps that would enable us to delineate their boun-
daries, we cannot exclude these areas from the drainage basins of
surface streams, although we know they do not contribute to the
discharge of the streams. Accordingly, we are defeated in our ef-
fort to convert discharge records to meaningful figures represent-
ing runoff per unit area.
Another vexing complication is that many surface streams are
fed by artesian springs whose water is derived from rain falling in
the drainage basins of other streams. Obviously, we must evaluate
and isolate the spring flow if we are to compute how much water
is generated within a given drainage area. But the task of isolating
spring flow will not be simple where the flow occurs in multitu-
dinous vents along the bottoms of stream channels, as, for example,
in the Suwannee River. The manner in which considerable quan-
tities of water migrate underground without regard to surface
basins has caused some hydrologists to ponder the wisdom of ac-
cepting surface basins as the logical hydrologic units in Florida.
The problem that will be the most difficult to solve is that of
determining, within permissible limits of error, the amount of
evaporation and transpiration from land surfaces. Techniques for
estimating these quantities directly where manifold types of vege-
tation grow in varying densities have not yet been perfected. Until
they are, progress can be made by studying selected areas wherein
the other factors of the water budget are known. Ordinarily, if we
subtract surface runoff from rainfall, we have a remainder con-
sisting partly of ground-water recharge and partly of evapotrans-
piration, neither of which quantities can be measured. But if we
select an area wherein ground-water recharge is known to be very
small as compared with the other quantities, the difference between
rainfall and runoff will provide an estimate of the evapotranspira-
tion, which estimate can be applied to other areas having similar
vegetation and topography to estimate ground-water recharge.
Although we know in general how and where the Floridan aqui-
fer receives recharge, our knowledge is far from being adequate.
The delineation of areas of recharge shown in figure 10 is based
largely on inference, supported by observation and geologic map-
ping. An investigation, including extensive test drilling, of the
geologic and hydrologic characteristics of the material overlying
the aquifer in the areas of recharge must be made before we can
have an adequate comprehension of the part that controlled re-
charge may play in optimum development of the artesian water.
We understand the recharge through sinkholes only in princi-
ple. We perceive that where sinkholes occur the piezometric sur-
face stands high, and we infer that a substantial amount of re-
charge occurs through them. But beyond this we know very little.
We wonder if appreciable recharge occurs through most of them
or through only a small fraction of their number. Perhaps the
gradual accumulation of muck has rendered a large percentage of
them ineffective as recharge agents, and perhaps recharge could
be increased materially by removing the muck. Studies of a repre-
sentative number of the sinkholes would enable us to eliminate
much of the guesswork from our present concepts.
Most of the wells currently being used for observations of
water levels and artesian pressures in Florida are abandoned sup-
ply wells owned privately and by municipalities. They are used
through the tolerance of the owners. Several valuable records have
been interrupted when the owners rightfully elected to restore
such wells to their own service. To the hydrologist, who recognizes
long-term records as being indispensable to his studies, such in-
terruptions are costly, especially when they terminate long records.
We have only a meager conception of how water moves about
within the Floridan aquifer. For the sake of simplicity we have pic-
tured the aquifer as though it were a hydrologic unit, a homogen-
eous mass of limestone through which water may move with equal
ease in any direction, laterally or vertically. Actually its structure
is far more complex. The aquifer is composed of layer upon layer
of limestones that have different water-transmitting properties.
Within some of these layers water moves quite freely, but it moves
from one layer to another only very slowly and with considerable
loss of pressure head. As a consequence, the artesian pressures
vary considerably from one layer to another. Under this condition
a single map of the piezometric surface, such as that in figure 17,
obviously cannot be truly representative, although it is useful until
more complete information is available. Before we can obtain an
adequate comprehension of how the artesian water moves from the
areas of recharge to areas of discharge, we must map the piezo-
metric surfaces for the individual geologic formations that make up
the aquifer. But we cannot do this by measuring water levels in
existing supply wells. Such wells generally draw from several
layers of limestone, and the water levels in them do not indicate the
pressure in any one layer. To do the mapping will require numer-
ous observation wells drilled under the control of trained hydrolo-
PARKER, GARALD G., 1951, Geologic and hydrologic factors in the perennial
yield of the Biscayne aquifer: Am. Water Works Assoc. Jour., vol. 43, no.
10, pp. 817-835.
PARKER, GARALD G., FERGUSON, G. E., LOVE, S. K., and others, 1953,
Water resources of southeastern Florida, with special reference to the
geology and ground water of the Miami area: U. S. Geol. Survey Water-
Supply Paper 1255 (in preparation).
STRINGFIELD, V. T., 1936, Artesian water in the Florida peninsula: U. S.
Geol. Survey Water-Supply Paper 773, pp. 115-195.
Note added while in press:
From A. O. Patterson, District Engineer, Surface Water Branch, U. S. Geological Survey, Ocala,
the following data was received February 1, 1954: "On January 13, 1954, a discharge measurement was
made of Kissengen Springs and it was flowing 3.55 second-feet. This is the first time it has been found
flowing since it stopped several years ago".
Florida Geological Survey
Report of Investigations No. 10
Ground Water in
Central and Northern Florida
Page 14 -
Page 34 -
(1st line of footnote) PART IV, not Part V.
(9th and 15th lines) WITHLACOOCHEE, not
(Figure 6) ALAPAHA, not Alpha River.
WACASASSA, not Wicissa River.
OKLAWAHA, not Okkawaha River.
(Bottom line) WITHLACOOCHEE, not Withlacooche.
(Title to fig. 12) GEOLOGY, not Gology.
(Figure 21) FERNANDINA, not Fernandia.
(Third line of explanation of
fig. 21) 60, not 600.
(Title to fig. 23) KISSENGEN, not