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 Consumption of ground water
 Problems of development and...
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Ground water in Florida ( FGS: Information circular 3 )
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Permanent Link: http://ufdc.ufl.edu/UF00001063/00001
 Material Information
Title: Ground water in Florida ( FGS: Information circular 3 )
Series Title: ( FGS: Information circular 3 )
Physical Description: 6 p., 1 l. : plate. 6 fold. maps. ; 23 cm.
Language: English
Creator: Cooper, Hilton Hammond, 1913-
Springfield, Victor Timothy, 1902-
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1950]
 Subjects
Subjects / Keywords: Groundwater -- Florida   ( lcsh )
Water-supply -- Florida   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by H. H. Cooper, Jr. and V. T. Springfield.
General Note: "Prepared for presentation at the meeting of the Florida Section of the Soil Conservation Society of America, Orlando, Florida, February 10-11, 1950."
General Note: "References": leaf at end.
Funding: Digitized as a collaborative project with the Florida Geological Survey, Florida Department of Environmental Protection.
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 001692729
oclc - 01729963
notis - AJA4803
lccn - gs 51000118
System ID: UF00001063:00001

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Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page 1
        Title Page 2
    Table of Contents
        Table of Contents
    Introduction and occurrence of ground water
        Page 1
        Fig.1
        Page 2
    Source and movement of ground water
        Fig.2
        Page 2
        Page 3
    Consumption of ground water
        Fig. 3
        Page 3
        Fig. 4
        Page 4
    Problems of development and conservation
        Page 5
        Page 6
        Page 4
    References
        Page 7
        Copyright
            Main
Full Text
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LORIDA GEOLOGIC AL SURVEY

HERIMAN GUNTER. DIRECTOR


GROUND


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IN LOJRIDA


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H. H. COOPE R,


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AND

V.T. STRINGFIELD


ST ,, L TNlAHASSEE, FLORIDA

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J/lMlll n IIC gi i H fl ilJl iI r.. J









GROUND WATER IN FLORIDA (1)


By


H. Hi. C'oor.'r, Jr. (2) and V. T. Stringfield (3)
















Prepared for presentation at the meeting of the
Florida Section of the Soil Conservation Society
of America, Orlando, Florida, February 10-11, 1950



















(1) Published by permission of the Director of the U. S. Geological
Survey and the Director of the Florida Geological Survey.
(2) District Engineer, U. S. Geological Survey, Tallahassee, Florida.
(3) Senior Geologist, U. S. Geological Survey, Washington, D. C.


Rerun (500 copies) April 1, 1951




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W,tll Flowing 6,500 Gallons Per Minute
Near Yukon, Duval County, Fla.


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CONTENTS


Page
Introduction . . . . . . 1

Occurrence of ground water .. ... . . . 1

Source and movement of the water. . . . 2

Consumption of ground water.. . . . . 3

Problems of development and conservation ........... 4


ILLUSTRATIONS

Figure 1. Map of Florida showing areas in which artesian water
having a chloride content of more than 100 parts per
million occurs at moderate depths. Following page.

2. Structure-contour map of Florida showing the top of
the Ocala limestone. (Based on a map prepared by
David B. Erickson, Assistant Geologist, Florida
Geological Survey, 1945). Following page. ..

3. Map showing the piezometric surface in Florida and
southeastern Georgia. Following page. . .

4. Map showing areas of artesian flow. Following page.










GROUND WATER IN FLORIDA


By: H. H. Cooper, Jr., and V. T. Stringfield


INTRODUCTION


lGround water in Florida is the principal source of supply for
industrial, municipal, agricultural, and domestic uses. During
the last half century large developments of ground water have been
made, and new developments are currently being added However, although
problems of supply, some of them critical, have arisen in certain areas,
vast quantities of ground water are:yet available for development over a
major part of the State. It is quite conceivable that the availability
of large developed water resources in Florida, in contrast with the
shortages of supply in many other parts of the country, may play a dominant
role in the agricultural and industrial growth of the State.

Early recognition of the potential economic importance of
Florida's ground-water resources is indicated by the fact that the
first report of the Florida Geological Survey (1), published in
1908, was a report on the ground water of central Florida. In the
following years, several other contributions (2, 3, 4, 5) to the ground-
water literature were made by the Florida Geological Survey and the
U. S. Geological Survey. By 1930, problems of development and conserva-
tion of the ground-water resources pointed to the need for a continuing,
systematic program of investigations, and, accordingly, the State and
Federal Geological Surveys began at that time the cooperative investigations
that are now in progress.


OCCURRENCE OF GROUND WATER

The ground water in Florida may be divided into two classes:
(1) that generally known as the artesian water, which occurs in
the extensive limestone aquifer of Eocene, Oligocene, and Miocene
age that underlies almost all of Floridaf the coastal area of Georgia,
and the southernmost parts of South Carolina and Alabama; and(?2) that
occurring in several younger aquifers of relatively small areal extent,
which consist chiefly of limestone, coquina, sand, and gravel in formations
that range in age from Miocene to Recent;\

The extensive artesian limestone aquifer is the principal source
of water, except in Escambia and Santa Rosa Counties, where it is
absent, and in that area in which the artesian water is too salty for
most uses (fig. 1). The area in which the artesian water is generally
salty includes a band about 20 miles wide along the east coast from
St. Augustine south and practically all that part of Florida south of
Lake Okeechobee. At a few places within this area, however, the arte-
sian water is sufficiently fresh to be suitable for municipal use.






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...... chloric
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I


EXPLANATION


n which artesian water having a
le content of more than 100 part
II ion occurs at moderate depths,






5 50 75 100 Miles
Approximote Scale


Map of Florida showing areas in which artesian water having a chloride content of more than 100 parts per million
occurs at moderate depth.


Figure 1.


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MANATEE HARDEE OKEECHOBEE^
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Among the public supplies derived from the artesian water within
this area are those of Daytona Beach, DeLand, and Everglades City.

The artesian aquifer consists of the Ocala limestone and some
of the underlying limestones of Eocene agel, and, in some parts of
the State, of overlying limestones of Oligocene and Miocene age.
The geologic structure of the formations that comprise the aquifer
is indicated in a general way by the top of the Ocala limestone.
The Ocala is at or near the land surface in an area centered around
Levy County, in the northwestern part of the peninsula, and in the
northern parts of Holmes and Jackson Counties in western Florida.
(fig. 2). It dips southward to more than 1,200 feet below sea level
in southern and western Florida.

'he artesian aquifer is the source of most of the large springs,
such as Silver Springs, whose discharge, according to measurements
by the U. S. G logical Survey, has ranged from 419 to 756 million
gallons a day/ In part of Seminole County alone, the aquifer yields
water to more than 1,000 flowing wells used for irrigation. The
natural flow of some of the individual wells that penetrate the aquifer
is large. One well drilled at Jacksonville in 1942 yielded a flow
of 6,500 gallons a minute, or about 9.5 million gallons a day. Some
of the pumped wells yield slightly more water; one well in Polk County
is reported to have yielded 7,500 gallons a minute -- about 10.5
million gallons a day -- with a drawdown of only 9 feet. Wells that
produce such large quantities of water are generally those which pene-
trate solution channels in the limestone. Drillers report that in
most parts of the Stt.te caverns are penetrated by some of the wells
that end in limestone. Some of the caverns in the central part of the
State are reported to have a height of as much as 20 feet.

,"The younger formations that overlie the artesian aquifer are the
principal source of water in southern Florida and along the east
coast from St. Augustine south, where the artesian water is generally
salty (fig. 1), and in Escambia and Santa Rosa Counties, where the
artesian aquifer is absent. In comparison with the artesian aquifer,
most of these shallow formations have relatively small capacities
to yield water to wells# Among them, however, is the Tamiamil
formation of Pliocene age, one of the most productive aquifer in
the world, and the source of supply for Miami and other cities in Dade
County. Ground water in the sand and gravel formations is generally
much softer than that in the artesian aquifer. Water from a sand
about 200 feet deep at Pensacola, for example, has only 41 parts per
million of dissolved solids and a hardness of only 12 parts per million.
*The artesian water is relatively free from iron, but some of the
shallow ground water has as much as several parts per million.


SOURCE AND MOVEMENT OF GROUND WATER

Most of the shallow aquifers of the State have relatively small
areas of extent and are recharged more or less locally, but the arte-
sian aquifer underlies almost all of Florida and extends into three
other States. Much of the water that enters the artesian aquifer in






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limestone with reference to se level. Contour interval 00 feet. ESOTO
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26
22 5 0 5 0 MNle1 BKeyAR Wt



EXPLANATION
MONROE D
Contour lines represent approximately the top of the Ocalo OADE
limestone with reference to sea level. Contour interval 100 feet.


SArea in which Ocalo limestone is at or near the surface.
2 5 '



Approximate Scale E .E o'

U.S. GEOLOGICAL SURVEY, TALLAHASSEE. FLORIDL


Structure contour map of Florida showing the top of the Ocala limestone. (After David B. Ericson)


FIGURE 2.










Among the public supplies derived from the artesian water within
this area are those of Daytona Beach, DeLand, and Everglades City.

The artesian aquifer consists of the Ocala limestone and some
of the underlying limestones of Eocene agel, and, in some parts of
the State, of overlying limestones of Oligocene and Miocene age.
The geologic structure of the formations that comprise the aquifer
is indicated in a general way by the top of the Ocala limestone.
The Ocala is at or near the land surface in an area centered around
Levy County, in the northwestern part of the peninsula, and in the
northern parts of Holmes and Jackson Counties in western Florida.
(fig. 2). It dips southward to more than 1,200 feet below sea level
in southern and western Florida.

'he artesian aquifer is the source of most of the large springs,
such as Silver Springs, whose discharge, according to measurements
by the U. S. G logical Survey, has ranged from 419 to 756 million
gallons a day/ In part of Seminole County alone, the aquifer yields
water to more than 1,000 flowing wells used for irrigation. The
natural flow of some of the individual wells that penetrate the aquifer
is large. One well drilled at Jacksonville in 1942 yielded a flow
of 6,500 gallons a minute, or about 9.5 million gallons a day. Some
of the pumped wells yield slightly more water; one well in Polk County
is reported to have yielded 7,500 gallons a minute -- about 10.5
million gallons a day -- with a drawdown of only 9 feet. Wells that
produce such large quantities of water are generally those which pene-
trate solution channels in the limestone. Drillers report that in
most parts of the Stt.te caverns are penetrated by some of the wells
that end in limestone. Some of the caverns in the central part of the
State are reported to have a height of as much as 20 feet.

,"The younger formations that overlie the artesian aquifer are the
principal source of water in southern Florida and along the east
coast from St. Augustine south, where the artesian water is generally
salty (fig. 1), and in Escambia and Santa Rosa Counties, where the
artesian aquifer is absent. In comparison with the artesian aquifer,
most of these shallow formations have relatively small capacities
to yield water to wells# Among them, however, is the Tamiamil
formation of Pliocene age, one of the most productive aquifer in
the world, and the source of supply for Miami and other cities in Dade
County. Ground water in the sand and gravel formations is generally
much softer than that in the artesian aquifer. Water from a sand
about 200 feet deep at Pensacola, for example, has only 41 parts per
million of dissolved solids and a hardness of only 12 parts per million.
*The artesian water is relatively free from iron, but some of the
shallow ground water has as much as several parts per million.


SOURCE AND MOVEMENT OF GROUND WATER

Most of the shallow aquifers of the State have relatively small
areas of extent and are recharged more or less locally, but the arte-
sian aquifer underlies almost all of Florida and extends into three
other States. Much of the water that enters the artesian aquifer in








an area of recharge travels On mo than 50 mile foa-Lt escape
through wells or s rings. General recognition of the fact that
n--Aht-~stteran waier travels over long distances may be partly re-
sponsible for the false notion that the artesian water of Florida
is derived from very remote places, such as the Appaachian
Mountains, the Great Lakes, or the Rocky Mountains./ The fact is,''
of course, that most of the ground water in the Florida peninsula
is derived from rain that falls within the State, although the
ground water in northern and western Florida is derived partly
from local rainfall and partly from recharge in southern Georgia
and Alabama.

Much of our information on the source and movement of water
in the artesian aquifer is revealed through a map of the piezo-
metric surface, which represents by contour lines the approximate
height to which the artesian water will rise in wells with refer-
ence to sea level. Such a map is compiled by measuring the depth
to water -- or, in areas of artesian flow, the pressure head --
with reference to selected measuring points in many wells through-
out the State, and by establishing the altitudes of the measuring
points by instrumental leveling. The control points so obtained
are used in plotting the contour lines that represent the piezo-
metric surface. Generally, recharge of the artesian system occurs
where the piezometric surface is high, and discharge occurs where
it is low. A map prepared (6, 7, 8) as a part of the cooperative
ground-water investigations of the Florida Geological Survey and
the U. S. Geological Survey represents the piezometric surface of
the artesian water throughout most of Florida and the coastal area
of Georgia (fig. 3). This map probably represents the piezometric
surface over a larger area than any other yet prepared, and it is
notable in that it indicates generally the areas of recharge and
discharge and the direction of movement of the artesian water over
hundreds of miles. Furthermore, it has revealed areas of recharge
that were not recognized before its preparation. Among these is
the large area of recharge centered around Polk County, from which
most of the artesian water in central and southern Florida is derived.

Over roughly a third of the State, the piezometric surface is
higher than the land surface, and wells will flow (fig. 4). However
over a large part of the area of artesian flow the artesian water
is relatively highly mineralized.


CONSUMPTION OF GROUND WATER

At the turn of the century the development of the artesian
aquifer in Florida had barely begun. The history of the develop-
ment indicates that the first successful artesian well in Florida
was drilled at St. Augustine during the period 1880 to.1882. Shortly
afterward, the first of the artesian wells for the Jacksonville
municipal supply was drilled.

The average daily consumption of ground water in Florida to-
day is estimated to be about 500 million gallons, of which about
20 percent is consumed by supplies used for irrigation. The consump-





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327 o 2


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26- EXPLANATION
Contour Lines Represent Approximately the Height, in Feet,- 2
to Which Water Will Rise With Reference to Mean Sea Level in .. 26
Tightly Cased Wells That Penetrate the Principal Artesian Aquifer. :40
Contour Intervals 20 Feet 1 Miami


250 25 0 25 50 75 1o00 L 2






870 860 85 84- 83 820 81 80*
FIGURE 3. Map showing the piezometric surface in Florida and southeastern Georgia.








an area of recharge travels On mo than 50 mile foa-Lt escape
through wells or s rings. General recognition of the fact that
n--Aht-~stteran waier travels over long distances may be partly re-
sponsible for the false notion that the artesian water of Florida
is derived from very remote places, such as the Appaachian
Mountains, the Great Lakes, or the Rocky Mountains./ The fact is,''
of course, that most of the ground water in the Florida peninsula
is derived from rain that falls within the State, although the
ground water in northern and western Florida is derived partly
from local rainfall and partly from recharge in southern Georgia
and Alabama.

Much of our information on the source and movement of water
in the artesian aquifer is revealed through a map of the piezo-
metric surface, which represents by contour lines the approximate
height to which the artesian water will rise in wells with refer-
ence to sea level. Such a map is compiled by measuring the depth
to water -- or, in areas of artesian flow, the pressure head --
with reference to selected measuring points in many wells through-
out the State, and by establishing the altitudes of the measuring
points by instrumental leveling. The control points so obtained
are used in plotting the contour lines that represent the piezo-
metric surface. Generally, recharge of the artesian system occurs
where the piezometric surface is high, and discharge occurs where
it is low. A map prepared (6, 7, 8) as a part of the cooperative
ground-water investigations of the Florida Geological Survey and
the U. S. Geological Survey represents the piezometric surface of
the artesian water throughout most of Florida and the coastal area
of Georgia (fig. 3). This map probably represents the piezometric
surface over a larger area than any other yet prepared, and it is
notable in that it indicates generally the areas of recharge and
discharge and the direction of movement of the artesian water over
hundreds of miles. Furthermore, it has revealed areas of recharge
that were not recognized before its preparation. Among these is
the large area of recharge centered around Polk County, from which
most of the artesian water in central and southern Florida is derived.

Over roughly a third of the State, the piezometric surface is
higher than the land surface, and wells will flow (fig. 4). However
over a large part of the area of artesian flow the artesian water
is relatively highly mineralized.


CONSUMPTION OF GROUND WATER

At the turn of the century the development of the artesian
aquifer in Florida had barely begun. The history of the develop-
ment indicates that the first successful artesian well in Florida
was drilled at St. Augustine during the period 1880 to.1882. Shortly
afterward, the first of the artesian wells for the Jacksonville
municipal supply was drilled.

The average daily consumption of ground water in Florida to-
day is estimated to be about 500 million gallons, of which about
20 percent is consumed by supplies used for irrigation. The consump-



























































EXPLANATION


:::: Area of artesian flow
....::......: ...ii~~ii~


U.S. GEOLOGICAL SURVEY. TALLAHASSEE, FLORIDA


FIOURE,'4. :Map showing, areas of aartesian flow.


0
Q,









tion by the four principal types of supplies is as follows:

(Gallons)
a day

Public supplies serving 100 or more people 160,000,000

Industrial supplies 200,000,000

Agricultural supplies 100,000,000

Domestic supplies 40,000,000

Total 500,000,000

According to the U. S. Bureau of the Census, 4,631 flowing wells
and 1,686 pumped wells were being used for irrigation in 1940.
Many additional wells have, of course, been drilled during the 10
years since this census was made.

According to data compiled by the Florida State Board of
Health, of about 357 public water supplies in Florida that serve
100 or more people, about 325 obtain their water entirely from wells.
The public supplies serve a total population of 1,980,000, of which
79 percent is served by supplies obtained exclusively from wells,
and an additional 6 percent is served by supplies that are obtained
partly from surface sources and partly from ground water. Practically
all the nonpublic domestic supplies in Florida are obtained from wells.

The consumption of 500 million gallons of water a day.is, of
course, a heavy draft on the ground-water resources, but this draft
should not be a cause for concern in regard to the State as a whole
when it is realized that the ground-water reservoirs are naturally
discharging many hundreds of millions of gallons of water a day,
much of which can be salvaged and used whenever it is needed. The
tremendous discharges of Florida's large limestone springs, which
rank among the largest in the world, forcibly demonstrate the large
capacity of the ground-water reservoirs. The average flow of Silver
Springs alone is equal to the estimated total consumption of ground
water in the State.


PROBLEMS OF DEVELOPMENT AND CONSERVATION

However plentiful the undeveloped supply of ground water in the
State as a whole may be, one cannot escape the fact that in some areas
in Florida the demand for ground water is approaching the capacity of
the aquifers to yield water perennially. The lack of an adequate quan-
tity of water of suitable quality has become especially acute in a
few coastal areas where overdevelopment or artificial drainage has per-
mitted sea water to enter the aquifers and ruin some of the well sup-
plies. The availability of water in those areas in which the ground
water is salty from natural causes is likewise a critical problem (fig.
1). The problem of salt-water encroachment should not be confused








with the problem of development where ground water is salty as
a result of natural proq6sses that occurred long before man's
time. The first is a problem of avoiding the overdevelopment
or the overdrainage that would permit the encroachment of sea
water; the other is a problem of finding supplies of fresh
water in areas where the water was naturally salty before the
first wells were drilled.

It is well known that salt-water encroachment occurs as the
result of a disturbance of a previously established balance be-
tween ground water and sea water (9). Prior to any artificial
disturbance, ground water and sea water, occurring under condi-
tions that have remained essentially unchanged for a long period
of time, perhaps for many centuries, have assumed a state of dy-
namic balance. The occurrence of the two, under this balance, is
determined by such factors as the relative densities of the two
waters, the height of the water table (or piezometric surface)
with reference to sea level, and the character and structure of the
geologic formations. The balance between ground water and sea water
is generally explained through an analogy with a hollow U-tube
containing two liquids of different densities, the lighter liquid
representing fresh water and the heavier, sea water. In such a tube
the lighter liquid will stand higher than the heavier liquid, and
the interface between the two will occur at a certain depth below
the surface of the lighter liquid, this depth being determined by
the relative densities and the difference in levels of the two liquids.

The density of sea water differs slightly from one place to
another but is generally considered to be about 1,025. The density
of fresh ground water is, for practical purposes, 1.000. Thus, the
ratio of the two densities is 1.025:1.000, or 41:40. It is evident,
therefore, that if fresh water and sea water were placed in a U-tube
in such a way that they did not mix with one another, a column of
the fresh water 41 units in height would balance a column of salt water
40 units in height. With respect to ground water in some coastal
areas this relationship may be stated in another way: for each foot
that the water table (or piezometric surface) stands above sea level
there will be an additional 40 feet of fresh water below-sea level.
Thus we have the familiar criterion, commonly referred to as the
Ghyben-Herzberg principle, by which, under proper conditions, one may
judge the depth to salt water in a coastal area. In many areas, prob-
ably most, the relationship is applicable only if it is modified to
allow for vitiating conditions. These conditions might include: (1)
the presence of one or more strata of impervious material within
or contiguous to the water-bearing formations, which would act to con-
fine the two bodies of water; (2) the occurrence of a wide zone of
diffusion between the fresh water and the salt water, caused by the
agitation of tides and fluctuations of the water table; (3) a tran-
sient condition, possibly of many years duration, in which the original
balance has been destroyed and a new balance is being established.

In Florida, the problem of salt-water encroachment is most pro-
nounced in Dade and Pinellas Counties. The encroachment in Dade
County has occurred principally as the result of artificial drainage
to reclaim land for agriculture, pasture, and urban development (10).
As a result many wells that once yielded fresh water will yield only









brackish or salty water. Much of the encroachment came from a movement
of sea water up the mouths of the drainage canals during droughts. The
problem in the Dade County area has been improved considerably since
the County undertook to control the levels of the canals several years ago.

The encroachment of salt water in Pinellas County has been caused by
the withdrawal of ground water for irrigation and municipal supply (11).
Over most of the southern part of the county and in some areas along the
west coast wells are now yielding water having a chloride content of from
100 parts per million to several thousand parts per million. It appears
probable that further migration of salt water in Pinellas County can be
prevented only by limiting the withdrawal of ground water, although
artificial recharge of the aquifer with water from surface streams might
alleviate the problem to some extent.

Other places in the State at which salt-water encroachment has occurred
include Fort Myers, Fort Pierce, Tampa, Daytona Beach, Panama City, and
Pensacola (12). The encroachment at Tampa forced the abandonment of the
old municipal supply wells about 25 years ago, and since that time Tampa
has obtained its water supply from the Hillsborough River. However, the
geologic and hydrologic conditions indicate that an adequate supply of
ground water for Tampa could be obtained at a safe distance from Tampa Bay.

At many places along the east coast from St. Augustine south, and in
southern Florida, where the artesian water is naturally salty, shallow
aquifers that will yield water of good quality have been found, as in Dade
County and at Fort Myers, Fort Pierce, and Titusville. At a few places,
however, adequate supplies of fresh ground water have not yet been found,
as at Cocoa, on the east coast. Apparently the fact that the artesian water
is salty in some areas has not greatly limited its use for irrigation.
Hundreds of flowing wells that yield water too salty for municipal and most
industrial uses are being used for irrigation along the east and west
coasts. Many yield water having a chloride content of more than 1,000
parts per million.

In the central part of the Florida peninsula from Lake Okeechobee north,
and in northern and western Florida, largo quantities of fresh ground water
are available for future development. In these regions, where problems of
salt water contamination are not likely to develop, the available supply
within any given area probably will be limited only by the extent to which
the water levels in wells may be lowered by pumping before economical pump-
ing limits are exceeded. A:lowering of water levels will, of course, inev-
itably accompany the withdrawal of water from an aquifer, the amount of
lowering being more or less in proportion to the withdrawal. Thus, in a
given area, as the withdrawal is increased water levels will be lowered fur-
ther until eventually no further lowering is feasible. So far, this condi-
tion is being approached in only a few local areas, as at Fernandina, where
the withdrawal of 30 million gallons a day by an industry has lowered the
artesian head over a wide area (13). The withdrawal at Fernandina has
caused the artesian head to decline 8 feet at Yulee, which is about 8 miles
from the heavily pumped wells. Even so, it appears that additional quanti-
ties of water may be..developed in the vicinity of Fernandina provided that
new wells are dispersed over a sufficiently broad area.









tion by the four principal types of supplies is as follows:

(Gallons)
a day

Public supplies serving 100 or more people 160,000,000

Industrial supplies 200,000,000

Agricultural supplies 100,000,000

Domestic supplies 40,000,000

Total 500,000,000

According to the U. S. Bureau of the Census, 4,631 flowing wells
and 1,686 pumped wells were being used for irrigation in 1940.
Many additional wells have, of course, been drilled during the 10
years since this census was made.

According to data compiled by the Florida State Board of
Health, of about 357 public water supplies in Florida that serve
100 or more people, about 325 obtain their water entirely from wells.
The public supplies serve a total population of 1,980,000, of which
79 percent is served by supplies obtained exclusively from wells,
and an additional 6 percent is served by supplies that are obtained
partly from surface sources and partly from ground water. Practically
all the nonpublic domestic supplies in Florida are obtained from wells.

The consumption of 500 million gallons of water a day.is, of
course, a heavy draft on the ground-water resources, but this draft
should not be a cause for concern in regard to the State as a whole
when it is realized that the ground-water reservoirs are naturally
discharging many hundreds of millions of gallons of water a day,
much of which can be salvaged and used whenever it is needed. The
tremendous discharges of Florida's large limestone springs, which
rank among the largest in the world, forcibly demonstrate the large
capacity of the ground-water reservoirs. The average flow of Silver
Springs alone is equal to the estimated total consumption of ground
water in the State.


PROBLEMS OF DEVELOPMENT AND CONSERVATION

However plentiful the undeveloped supply of ground water in the
State as a whole may be, one cannot escape the fact that in some areas
in Florida the demand for ground water is approaching the capacity of
the aquifers to yield water perennially. The lack of an adequate quan-
tity of water of suitable quality has become especially acute in a
few coastal areas where overdevelopment or artificial drainage has per-
mitted sea water to enter the aquifers and ruin some of the well sup-
plies. The availability of water in those areas in which the ground
water is salty from natural causes is likewise a critical problem (fig.
1). The problem of salt-water encroachment should not be confused









REFERENCES


(1) Sellards, E. H., A preliminary report on the underground water supply
of central Florida: Fla. Geol. Survey Bull. 1, (1908).

(2) Matson, G. C., and Sanford, Samuel, Geology and ground waters of
Florida: U. S. Geological Survey Water Supply Paper 319, (1913).

(3) Sellards, E. H., and Gunter, Herman, The artesian water supply
of eastern Florida: Fla. Geol. Survey 3rd Ann. Rept., pp. 77-195,
(1910).

(4) Sellards, E. H., and Gunter, Herman, The water supply of west-central
and west Florida: Fla. Geol. Survey 4th Ann. Rept., pp. 87-155,
(1912).

(5) Sellards, E. H., and Gunter, Herman,-Artesian water supply of eastern
and southern Florida: Fla. Geol. Survey 5th Ann. Rept. pp. 103-290,
(1913).
(6) Stringfield, V. T., Artesian water in the Florida peninsula:
U. S. Geological Survey Water-Supply Paper 773-C, (1936).

(7) Warren, M. A., Artesian water in southeastern Georgia:
Ga. Geol. Survey Bull. 49, (1944).

(8) Stringfield, V. T., Unpublished map of the piezometric surface of
artesian water in Florida west of the Suwannee River.

(9) Brown, J. S., A study of coastal ground water, with special
reference to Connecticut: U. S. Geol. Survey Water-Supply Paper
537, (1935).

(10) Brown, R. H., and Parker, G. S., Salt water encroachment in
limestone at Silver Bluff, Miami, Florida: Economic Geol.,
Vol. o0, No. 4, (1945).

(11) Heath, R. C., and Smith, P. C., Ground water resources of
Pinellas County, Florida: unpublished manuscript

(12) Jacob, C. E., and Cooper, H. H. Jr., Report on the ground-water
resources of the Pensacola area, Escambia County, Florida:
unpublished manuscript.

(13) Cooper, H. Jr., and Warren, M. A., The perennial yield of
artesian water in the coastal area of Georgia and northeastern
Florida: Economic Geol. Vol. 40, No. (1945).










FLRD GEOLOSk ( IC SUfRiW


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