Title: Florida's Water Resources - An Evaluation and Management Philosophy
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From Georgia and Alabama
25 bgd


Rain
150 bgd


Evapotranspiration
107 bgd


Runoff 65 bgd
Consumed 2 bgd
Others 1 bgd
Total 68 bgd

Florida's Water Resources

An Evaluation and Management Philosophy




Prepared by
Black, Crow & Eidsness, Inc.
Engineers
for
Pinellas County, Florida


Project No. 272-75-80


November, 1975



















Florida has an adeqaute source of water for all
needs-now and in the future-as long as technology and
conservation keep pace with our growing demand.
Sound conservation practices can preserve and utilize,
with as little waste as possible, our present fresh water
supplies and their replenishment. Technological advances
will be able to make available for reuse water that has
become contaminated and probably in the near future
can convert salt water economically into fresh water.
Since there is such an abundance of this most
important natural resource, what are the problems?
Why the growing concern over it?
The problems associated with our water resources
arise from the mismatching of man's needs to the
available supply. Therefore, problems of Florida's
water resources, for the most part, are not from lack
of water but from not having the water arrive at the
place at the time it is needed, although flooding,
pollution, contamination, and heavy mineralization are
locally troublesome.
Source: Florida Geological Survey, "Your Water
Resources," Water Leaflet No. 1, Tallahassee, 1963.

























2











FLORIDA'S


WATER


RESOURCES


AN EVALUATION

AND

MANAGEMENT PHILOSOPHY


Prepared for
Pinellas County, Florida

by


J. I. Garcia-Bengochea, Ph.D., P.E.
R. David G. Pyne, P.E.
Emily W. Black, P.E.











BLACK, CROW AND EIDSNESS, INC.
Engineers


Project No. 272-75-80


qov/ 377 2< 2.


November, 1975


1975 Black, Crow and Eidsness, Inc. All rights reserved.

This report has been prepared by Black, Crow and Eidsness, Inc., Consulting Engineers, as a professional service to our client.
Reproductions are prohibited without approval and consent of the engineers.













TABLE OF CONTENTS


Page
LIST OF TABLES iv

LIST OF FIGURES v

PREFACE vi

Section

1 SUMMARY AND CONCLUSIONS 1 1

1.1 Summary

1.2 Conclusions

2 INTRODUCTION AND PURPOSE 2 1

2.1 Introduction 2 1

2.2 Purpose and Scope 2 2

3 HYDROLOGIC PRINCIPLES 3 1

3.1 The Hydrologic Cycle 3 1

3.2 The Water Budget 3 3

3.3 Water Use and Water Consumption 3 3

4 FLORIDA'S FRESHWATER RESOURCES 4 1

4.1 Rainfall 4 1

4.2 Groundwater 4 4

4.2.1 Aquifers 4 4
4.2.2 Springs 4 4

4.3 Surface Water 4 7

4.3.1 Lakes 4 7
4.3.2 Streams 4 10

4.4 Evapotranspiration 4 10

4.5 Florida's Water Budget 4 14










TABLE OF CONTENTS-Continued


Section Page

5 UTILIZATION OF FLORIDA'S FRESHWATER RESOURCES

5.1 Freshwater Withdrawal and Consumption in Florida 5 1

5.2 Freshwater Withdrawal and Consumption in the U.S.A. 5 3

6 HISTORICAL WATER SUPPLY PROBLEMS IN FLORIDA

6.1 Saltwater Intrusion 6 1

6.2 Land Subsidence 6 3

6.2.1 The Sinkhole Problem 6 3
6.2.2 Sinkhole Development 6 4
6.2.3 Groundwater Role 6 5
6.2.4 Can the Problem Be Avoided? 6 5

6.3 Environmental Effects and Hydrological Changes
in Surface Waters 6 7

7 THE WATER CROP CONCEPT

7.1 Definition of Water Crop 7 1

7.2 Applicability of the Water Crop Concept-Large
and Small Areas 7 2

7.3 Ramifications of the Water Crop Concept 7 3

7.4 How Many Existing Municipal Water-Supply Systems
in Florida Comply with the Water Crop Regulation? 7 4

8 POSITIVE WATER MANAGEMENT-CRUX OF THE PROBLEM

8.1 What Is Positive Water Management? 8 1

8.2 Contrast with Present Regulations 8 1

8.3 Alternative Management Tools in Local Problem Areas 8 3

REFERENCES

APPENDIX















LIST OF TABLES


Table Page

4-1 First-Magnitude Springs of Florida-With Period of Record,
Discharge, Representative Temperatures, and Dissolved Solids 4 8

4-2 Drainage Basins and Discharge of Surface Water from the
State of Florida to the Atlantic and to the Gulf 4 12

5-1 Summary of Freshwater Withdrawal in Florida (1970) 5 2

5-2 Summary of Consumptive Use in Florida (1970) 5 2

5-3 Summary of Precipitation and Freshwater Withdrawal and
Consumption in the U.S.A. by States 5 4

5-4 List of States by Decreasing Ratios of Withdrawal and
Consumption to Total Precipitation 5 5

7-1 Comparison of Actual Well Field and Service Areas of Water
Systems in Florida with Water Crop Requirements 7 7

7-2 Systems Not Meeting Water Crop Requirements Even When
Total Service Area on Mainland is Included as "Otherwise
Controlled by Applicant" 7 9

7-3 Systems with Service Areas on Mainland Within 20 Percent of
Required Water Crop Area 7 10

7-4 Information from Water System Survey in Florida-September,
1975 7 11














LIST OF FIGURES


Figure

3-1 The hydrological cycle

4-1 Geological cross section of southern Florida

4-2 Hydrological cycle in Florida

4-3 Mean annual rainfall, 1931-1955

4-4 Water table and artesian aquifer

4-5 Potentiometric contours of the Floridan aquifer and extent of
the Biscayne and the Sand-and-Gravel (Panhandle) aquifers

4-6 Drainage basins and discharge of surface water from the state
of Florida to the Atlantic and to the Gulf

4-7 Average annual lake evaporation

4-8 Florida's water budget

6-1 Effects of controlled and uncontrolled coastal canals on
saltwater intrusion

6-2 Formation of sinkhole by cavern roof collapse

6-3 Formation of sinkhole by the unplugging of vertical voids or
breaches above a cavernous system















PREFACE


At the request of Pinellas County, Black, Crow and Eidsness, Inc.,
has prepared this report evaluating Florida's water resources and management
philosophy.

Black, Crow and Eidsness, Inc., has provided consultant engineering
and hydrological services to Pinellas County since 1951. During the past
25 years the firm has provided similar services to numerous other counties,
municipalities, industries, and local and state agencies responsible for
water supply and water resources management in Florida, as well as in many
other states and countries.

The firm's extensive capabilities and experience in the areas of water
resources and water quality have been directed to the most beneficial
utilization of the state's water resources. The firm has consistently sup-
ported the concept of regional management of these resources and believes
firmly that this concept, established by the Florida Water Resources Act
of 1972, and to be implemented by the water management districts, offers the
greatest potential for achieving the desired objective.

The report provides an evaluation of current water management practices
in Florida and the future impact of these practices. An alternative approach
to some of those practices is proposed that, in our opinion, will lead to the
optimum utilization of the state's water resources at minimum cost, consistent
with the need for protection of the resource and the environment.














SECTION 1


SUMMARY AND CONCLUSIONS

1.1 SUMMARY

The purpose of this report is to present a general evaluation of the
water resources of the state of Florida and a philosophy of their management.
Comparison is made of Florida's freshwater assets and demands with those of the
other 48 continental states of our nation.

The source of fresh water on earth for all practical purposes is
precipitation. In Florida, rainfall is the main source of precipitation.
Precipitation on land and inflow from adjacent areas replenish Florida's fresh-
water resources. Evaporation from freshwater bodies, outflow to the sea,
transpiration of water by plants, and man's consumptive use deplete these
resources. These sources of replenishment or depletion can be thought of as
assets and liabilities which must balance in what is called the water budget.

Hydrology is the science which studies water in the stages described above.
Those stages form part of a cycle starting with evaporation to the atmosphere.
Water vapor in the atmosphere forms clouds which eventually discharge back to
earth in the form of precipitation. Precipitation on land is either retained
by the soil to be lost by evapotranspiration, runs off to lakes and rivers and
eventually back to the seas, or infiltrates into the ground from where, if not
used, it is also eventually returned to the seas. That part of hydrology which
relates to water in the ground is called groundwater hydrology or in more
sophisticated terms: hydrogeology. The cycle of water from evaporation to
rainfall, infiltration, runoff, and return to water bodies for evaporation is
called the hydrologic cycle.

Hydrologic studies in Florida indicate the following water budget in
billion gallons per day (bgd):

Assets or Income Liabilities or Expense

Rainfall 150 Evapotranspiration 107

Inflow from Georgia Surface runoff 65
and Alabama 25
Consumptive use (1970) 2

Others (groundwater runoff) 1

175 bgd 175 bgd


1 -1








These figures immediately indicate that man's consumptive use for 1970
(the last year with available information) represented only a very small per-
centage of our total water budget. Actually the figure of 2 bgd rounds off
1.848, which is divided as follows:


Summary of Consumptive Use in Florida (1970)

Total bgd % of Total

Irrigation (agriculture) 1.270 69
Municipal 0.235 13
Industry (self-supplied) 0.163 9
Rural 0.160 8
Thermoelectric 0.020 1

1.848 100


From the preceding information two main observations can be made:

1. The larp t r-nnsumDtive use of fresh water in the state is for
agricultural Purposes which represent 69 percent of the tota -on
-sumptive use or more than five times t unt water cons
by municipalities, the second largest consumntive usp_

2. The total consumptive use for the entire state (1.848 bgd) represents
only nu =,,l ur irotal freshwater income of the state k17/
bgd and I. percent ot the total amount of precipitation (150 bgd).
The largest use, irrigation, requires only 0.8 percent of the total
amount oT precipitation.

In Section 5 of this report comparison is made of the state of Florida
with the other 48 continental states in regard to freshwater withdrawal and
consumptive use expressed as a percentage of the total annual precipitation of
each state. This comparison indicates that Florida ranks thirty-third in the
ratio of withdrawal to precipitation and eighteenth in the ratio of consumption
to precipitation (see Table 5-4, Section 5).

It is extremely important to realize that Florida is blessed with abundant
freshwater resources. The average annual precipitation in Florida. 54 inches,
is exceeded by only one other state, Louisiana, which has an annual average
precipitation of 55 inches. Our state is also blessed with one of the richest,
if not the richest, groundwater systems in the world. Springs are the natural
surface evidence of this system. The combined flow of the over 200 known
springs in the state amounts to a yearly average of about 7~ba or almost four
times t he consumptive ue for the state in 1970. The flow rom each ofthe two
largest springs, Silver Springs and Rainbow Springs in Marion County, is in
excess of 500 million gallons per day (0.5 bgd), and the flow of either was more
than twice the municipal consumptive use for the entire state in 1970 (0.235
bgd). These springs are natural manifestations of our abundant groundwater
resources.


1 -2










Despite Florida's abundant water resources, there are areas within the
state with persistent and periodic water shortage problems. Why is it that we
hear and read almost every day about water problems in the state?

SThe answer, in our opinion, relates to three points:

l1. Inadequate analysis and perspective of local problems.
2. Lack of knowledge and understanding of our state's water resources.

3. Historical lack of overall water resources management.

Two examples follow:

About the year 1940, consideration was given to the abandonment of the
city of Miami well field and the utilization of surface waters due to saltwater
intrusion attributed to overdraft of the aquifer. At that time the Miami
well field served approximately 170,000 people, and the average daily pumpage
was 23 million gallons per day (mgd). Sound hydrological investigations
disproved the alleged cause and have allowed average daily pumpage, strictly
from groundwater, to reach the 1974-1975 rate of 188 mgd. The change to surface
waters would have cost the citizens of the area considerably more money for
chemicals and treatment.

A major water shortage occurred in south Florida in the spring of 1971.
That crisis prompted the Governor's Conference on Water Management in South
Florida in September, 1971. Just one year before, during the 12-month period
from July, 1969, to July, 1970, a total of 4.5 million acre-feet (1,500 billion
gallons) of excess water had to be discharged to the sea from storage in Lake
Okeechobee and the three conservation areas of southeast Florida (Haeussner,
1970). That volume of fresh water, discharged to the sea because of lack of
storage, represents 21 times the present average annual water supply of the
metropolitan Miami-Dade water system.

Much of Florida's population is concentrated in coastal, urban areas.
Historically, development of these areas has been facilitated by drainage canals,
which have been constructed generally without regard for overall water resources
management. These canals drain vast quantities of fresh water from urbanized
coastal as well as inland areas, thereby losing this resource to the sea. The
general response to many local water shortages reflects a lack of knowledge and
understanding of our state's water resources. Measures taken typically suaapt
that nir Wtar sn urces are ouite limited. whereas I act tnh-v arP nntiful
but require positive management to ensure their optimum utilizatinn

Until approximately 15 years ago water management in Florida was directed
to flood control because this was the main problem at the time. The first
major water management district in the state was created for that purpose.
As competition for the easiest and nearest freshwater sources arose, the water
management districts began to concentrate more heavily on water supply problems.
In 1968, the state's first water regulatory district was formed, within the
responsibility of the Southwest Florida Water Management District (SWFWMD).


1 -3









A major step in the development of water management for the state of
Florida was the enactment of the Water Resources Act of 1972 by the Florida
legislature. The first two of its objectives are "to provide for the manage-
ment of water and related resources," and "to promote the conservation,
development, and proper utilization of surface and groundwater." It also led
to the creation of five water management districts within the state to implement
the objectives of the act. Subsequently a sixth interim district was created.
All areas of the state are within the six districts.

Under the apparent influence of Qrowth control: philosophy, water management
districts have established regulations which seem to be directed more toward
Limiting growth, particularly in the areas of dense population, than toward
management of water resources. These regulations utilize the "water crop"
concept, under which issuance of a permit to withdraw water will be denied if
the amount of water consumptively used will exceed the water crop of lands
owned, leased, or otherwise controlled by the applicant. Except where deter-
mined otherwise, the water crop (precipitation less evapotranspiration)
throughout the SWFWMD is assumed to be 365,000 gallons per year per acre, which
is equivalent to about 13 inches of rainfall. In the Central and Southern
Florida Flood Control District, the water crop is assumed to vary according to
location, with estimates ranging from 6 to 18 inches of rainfall.

A survey was conducted, as part of the investigations for this report, to
determine how many existing Florida municipal water supply systems comply with
the SWFWMD water crop regulation. The questionnaire was sent to 150 systems
using groundwater. Of the 97 responding systems, none complied with the water
crop on well field property owned or controlled by the municipality.

Florida has ample fresh water for the present and foreseeable future.
Positive management is needed to supply our people with the required volumes of
fresh water at the lowest cost. As part of that management, Floridians need to
be encouraged not only in the municipal supply sector, but in all other sectors
(especially agricultural irrigation), to prevent losses and waste. Positive
management also must provide leadership in sound water resources conservation
practices such as artificial recharge and water reuse.

Positive water resources management may be defined as the making of sound
decisions to encourage reasonable conservation and use of existing water
sources, as well as to plan future supplies, in such a way as to minimize total
economic and environmental costs while promoting equitable distribution of!
available water supplies. When based upon sound technical evaluation and
economic analysis, such decisions will tend to achieve optimum utilization of
Florida's water resources.

In addition to conserving and replenishing our water supplies, care must
also be taken to avoid degradation of the quality of these waters. In our
opinion, the recent consolidation by the Florida legislature of water resources
and water quality control under one agency can, if properly managed with a
positive attitude, be another big step forward in solving Florida's water
resources problems.


1 -4









.2 CONCLUSIONS


Florida has a high average annual rainfall, an abundant groundwater
supply, and a wealth of lakes, rivers, and springs. For the benefits of these
renewable resources to be realized, they must be utilized. Use of one type may
preclude other types of uses or may detract from other intrinsic values of the
resource. Sound, positive management decisions must be made to ensure the most
reasonable and beneficial use of these resources for the benefit of the people
of Florida and the generations yet to come.

In our opinion, the right of a citizen to use water should not rest upon
his ownership of land but should be considered a common holding, just as the
seashores and navigable bodies of water are considered to be held by the state
in the public trust for the use and enjoyment of the people of Florida. The
citizen's use should not endanger the resource or cause adverse environmental
effects, and should be a reasonable beneficial use consistent with the public
interest.

Implementation of the water use rules and regulations recently promulgated
_ by Florida's water management districts utilizes the concept of the "water crop"
to determine availability of water in any area. In addition, water management
authorities have frequently interpreted "reasonable use" to mean that a land-
owner will be entitled to the full water crop on his property whenever, if ever,
he applies for a reasonable and beneficial use. This interpretation of the law
effectively ties the amount of water allocated to an applicant to te extent of
the lands he owns, leases, or otherwise controls. In our opinion, such an
interpretation is a clear and significant change in direction from the concept
ot reclTiunTdbe seT t e association of water rights with land ownership and
goes far beyond the mandate of the Florida Water Resources Act of 1972.

Such water management philosophy can only lead to less than optimum
utilization of our water resources and increase costs unnecessarily for the
people of Florida. If growth limitation is the objective, it should be
achieved by direct measures, such as zoning and land planning, implemented by
appropriate planning agencies, rather than by indirect measures such as limiting
utilization of available water supplies. In the long run the water crop will
not control growth but will force municipalities to purchase land or water
rights at substantial cost increases for public water users.

The water crop concept, utilized in the implementation of rules and
regulations prepared by the water management districts, is a hydrologic "rule of
thumb" applicable only for estimating water availability within a large, well-
defined hydrologic area such as a basin. Its use in small areas, such as well
fields and housing developments, is inappropriate and highly misleading.
Continued reliance upon the water crop concept will lead to under-utilization
of our water resources in small areas and higher costs to all the people of
Florida.

An alternate approach to water management is needed. Such an approach is
proposed in Section 8 of this report. "Reasonable use" of water should be
interpreted by management authorities as the use of water in a manner consis-
tent with the interest of all the people of Florida, based upon the premise
that water is held in the public trust. Management decisions made in this


1 -5









manner will reflect positive water management principles designed to ensure
optimum utilization of our plentiful and renewable water resources. Such
decisions will require greater use of judgment by management authorities as
discussed in Section 8.

Florida's water law is based upon the legal concept of "reasonable use,"
which is common to most states east of the Mississippi River. However,
its development through passage of legislation and court decisions has
not resulted in well-defined legal interpretations clearly applicable to most
of the current water problems in the state. Consequently, Florida's water
management in the future can take either of two directions: (1) the doctrine of
water rights associated with land ownership can be followed, as would result
from continuation in the new direction of the past two years; and (2) alterna-
tively, water can be held by the state in the public trust with the people of
Florida as the beneficiaries of that trust. Allocation of water would be made,
in the second alternate, according to the criteria suggested previously,
including reasonable, beneficial use. In our opinion, the latter direction is
y one that can meet the objective of the 1972 Water Resources Act, which
provided for reasonable, beneficial use consistent with the public interest,
and still ensure optimum utilization of our ample and renewable water resources
at minimum cost and maximum benefit to the people of Florida. Florida s wa er
law and subsequent court decisions should reflect the state's hydrogeology and
ample water resources, rather than be patterned upon case law developed for
states with less plentiful resources and different hydrogeology.

It is suggested that one approach to achieving this redirection of water
management would be legislative action clarifying the intent of the "reasonable
use" criterion contained within the Water Resources Act of 1972, to ensure full
understanding that Florida's water resources are held in the public trust for
the benefit of the people of the state.

C Many of the water problems in the state result less from a shortage of
water than from a shortage of positive water management. Consistent with
positive water management principles would be measures to replenish available
water supplies by recharge and reuse, to prevent overdrainage and consequent
loss of fresh water, and other innovative approaches to attaining full utili-
zation of this renewable resource. Such measures can alleviate many water
.resource problems that have arisen in Florida during the past few years.

A statement (Florida Geological Survey, 1963) which we firmly believe
still holds true is quoted below:

The problems associated with our water resources arise from the
mismatching of man's needs to the available supply. Therefore,
problems of Florida's water resources, for the most part, are not from
lack of water but from not having the water arrive at the place at the
time it is needed, although flooding, pollution, contamination, and
heavy mineralization are locally troublesome.














SECTION 2


INTRODUCTION AND PURPOSE

2.1 INTRODUCTION

The state of Florida is blessed with abundant freshwater resources. It
is also blessed with other natural resources which attract many people not
only as tourists but also as permanent residents. Such attractions have caused
Florida's population to grow at one of the fastest rates in the nation.

Population growth has not only been at a fast rate but has taken place
in and around certain areas. This has concentrated population and also the
problems associated with such rapid growth. One of the most important
problems related to fast and concentrated population growth is freshwater
supply.

Saltwater intrusion is the most critical threat to Florida's freshwater
resources and has been so reported for many years (Thompson, 1931). Saltwater
intrusion was reported in the Biscayne aquifer in the vicinity of the Miami
well field between 1935 and 1939. Consideration was given in the early forties
to the abandonment of that well field and to the utilization of surface waters
to supplement the public supply for the metropolitan area of Miami (Cross and
Love, 1942). In 1940 the city of Miami served a population of approximately
170,000 and the average daily pumpage was 22.5 million gallons per day (mgd).
Hydrological investigations conducted by the U.S. Geological Survey (USGS)
concluded that saltwater intrusion in the area was caused by the construction
of drainage canals, not by an overdraft of the aquifer, and that large addi-
tional volumes of water, several times those being used, could be safely pumped
from the Biscayne aquifer (Parker, 1951).

The abandonment or even the limitation of additional pumpage in 1942
from the Miami municipal wells would have been a grave error. Average daily
pumpage in 1974-75 from wells in the same aquifer for the Miami-Dade water
system was 188 mgd (8 times larger than that in 1940). Proper hydrological
and water resources planning of the area has allowed such an increase and
could even allow further increases.

A major water crisis occurred in south Florida in the spring of 1971.
That crisis prompted the Governor's Conference on Water Management in South
Florida in September, 1971. Just one year before, during the 12-month period
of July, 1969, to July, 1970, a total of 4.5 million acre-feet (1,500 billion
gallons) of excess water had to be discharged to the sea from Lake
Okeechobee and the three conservation areas of southeast Florida (Haeussner,


2 1









1970). This volume of fresh water, discharged to the sea during one single
year because of lack of available safe storage capacity, represents 21 times
the present average annual demand of the metropolitan Miami-Dade water system.

Consecutive and alternating water shortages and excessive drainage are
incontestable evidence of the need for positive water management.


2.2 PURPOSE AND SCOPE

The purpose of this report is to present a general evaluation of the
freshwater resources of the state of Florida and a philosophy of management
requirements. The freshwater resources are presented with a description of the
fundamental principles involved and how they apply to the state of Florida.

A summary of the available information on the state's freshwater demands
is also presented. A comparison is made of Florida's freshwater assets and
demands with those of the other forty-eight continental states (Hawaii is not
included). Finally, an objective critique is made of the political and
administrative tools available for the management of the state's water
resources and the philosophy that seems to support the use of those tools.


2-2















SECTION 3


HYDROLOGIC PRINCIPLES

3.1 THE HYDROLOGIC CYCLE

Fresh water on earth has, for practical purposes, one source:
precipitation. In tropical and semitropical climates such as Florida, precipi-
tation occurs mainly as rainfall, whereas in colder climates, precipitation
occurs as rainfall and snowfall.

Solar energy acting on each body of water on earth produces evaporation.
Evaporation is the source of moisture in the.atmosphere which, when condensed,
causes precipitation. Evaporation of oceans and all other bodies of water is
a huge and continuous distillation process which stores fresh water in the
atmosphere in the form of water vapor. Fresh water is continuously produced in
the world by this process, regardless of where evaporation takes place, be it
in fresh or saltwater bodies.

Precipitation on land constitutes an asset to the freshwater resources
of the area. Evaporation from freshwater bodies inland constitutes a
liability. Another liability to the freshwater resources of an area is
transpiration from plants, which take up considerable amounts of fresh water
from the ground and transpire it to the atmosphere.

Figure 3-1 is a diagrammatic representation of the principles stated.
It describes the general circulation of water from seas to atmosphere (evap-
oration), to land (precipitation), and back to the seas again (runoff). Such
circulation is referred to as the hydrologic cycle.

A portion of the precipitation falling on the land is retained by the
soil, in surface depressions, and by plants and vegetation until it is
returned to the atmosphere by evaporation and transpiration. The combined
action of evaporation and transpiration is referred to as evapotranspiration.
Use of such a term is very advantageous because many times it is not possible
to differentiate evaporation and transpiration amounts in an area; therefore
they are added together.

The remainder of rainfall on land either infiltrates into the ground
to constitute groundwater or moves to rivers, swamps, and lakes to
constitute surface water. If not used, both ground and surface water either
evaporate or eventually reach the seas, where the cycle starts over again.

The foregoing description of the hydrologic cycle is oversimplified.
Actually, all phases of the cycle occur continuously and simultaneously
when considered worldwide. Water, just like matter and energy, is neither


3-1


_ I I I ;~--3P


















Clouds

==


C Clouds

Q-^j


0


LI
m


Rivers -Runofr


Groundwatei


FIGURE 3-1. The hydrological cycle.


0
'4-1

i

I
o


c
C
0
4-'
.m
(+)

a-


T
0
o
Q_


iOwate.
chiare


_7










created nor destroyed, it is just transformed. On a worldwide and long-term
basis, the amount of water involved in each phase of the cycle is relatively
constant; but in terms of a limited area, the amount in any part of the cycle
at certain times can vary significantly. Such variations are the primary
subjects of study in the science of hydrology.


3.2 THE WATER BUDGET

Understanding the concept of the hydrologic cycle leads us to another
concept of utmost importance in water resources management: the water budget.
This is simply the balancing of income with expenditures.

Income of an area, from a hydrological point of view, is precipitation
(Pt) and inflow (If) from an adjacent area or areas. Expenditures are evapo-
transpiration (Et) and outflow (Of) to any other adjacent area or areas.
When totally balanced, the water budget is expressed as:


Pt + If = Et + Of (1)

Water budgets are usually applied for water years (October 1 to
September 30) and very seldom are balanced as shown above. Another term is
needed to keep the balance and this is AS, or change in water storage within
the area. The equation then becomes:


Pt + If = Et + Of AS (2)

Change in water storage would mean high water levels in surface waters
(lakes, rivers, etc.) and groundwaters (water-bearing formations, most
usually referred to as aquifers) after a year or years of heavy precipitation.
It would mean low water levels after a year or years of scarce precipitation.

Up to this point, water withdrawal by man has not been considered. We
have assumed virgin conditions.


3.3 WATER USE AND WATER CONSUMPTION

If man's withdrawal is totally returned to the source after use, our last
equation does not need to be changed. This type of withdrawal is referred to
as water use. One example of this type is "closed, once-through cooling systems."

If man's withdrawal is not returned to the area, then it has to be
entered into the equation as an expenditure or loss. This type of withdrawal
is referred to as water consumption or consumptive use (CO).

Equation 2 is then written:


Pt + If = Et + Of + C, AS (3)


3-3


I __~___I










We must realize that, at least to this date, precipitation (Pt) cannot
be significantly controlled by man. Therefore, in order to balance for
consumption, either inflow (If) from another area is increased, or we must
reduce evapotranspiration (Et), outflow (Of), or storage (S). In practice,
a combination of reduction in outflow and evapotranspiration takes place after
a small reduction in storage.

A reduction in storage (S) is necessary to bring additional flow to
replace that withdrawn. This is more evident in groundwater sources where
drawdown (lowering of the water level or potentiometric head) is needed to
create a gradient toward the point of withdrawal. This drawdown can be both
damaging and beneficial. It can be damaging when it:

1. Occurs in the immediate vicinity of salt water and induces
saltwater intrusion.

2. Is excessive enough to induce land subsidence, adversely affect the
utilization of surface-water bodies due to lowering of flows and
water levels, or alter vegetation where this is unacceptable.

It can be beneficial by:

1. Decreasing the rate of groundwater outflow to seas or other surface
waters where it would be lost from the area.

2. Decreasing the rate of evaporation from soils or transpiration from
plants in areas where changes in vegetation would not be detrimental.

3. Providing storage for rainfall that otherwise would be discharged
to the sea.

It is not reasonable to brand drawdown as damaging, even if it is signif-
icant, when all the conditions for each particular area have not been evaluated.
Significant drawdowns in certain areas can be beneficial; small drawdowns
in others can be damaging. Such judgment is a responsibility of sound water
management based on thorough knowledge of the conditions in the area involved.

Another point to consider when analyzing the water budget equation of
an area is the significance of the term evapotranspiration. Evaporation is
continuously acting on all exposed water bodies and soils with available
moisture. The closer the water table is to the surface of the ground, the
greater is the evapotranspiration. Therefore, strictly from a water-loss
standpoint, it is much more advantageous to store water underground, preferably
deep, than on the surface.

Finally, we can see by analyzing equation (3) that if we cannot increase
our water income, precipitation (Pt) or inflow (If), we must reduce either
evapotranspiration (Et), outflow (Of), or storage (S), or a combination of
them, in order to increase the consumptive use (Cp) of an area. If we have
a fixed income and we need to incur additional expenditures (Cp), we need to
reduce other expenditures, evapotranspiration (Et) or outflow (0O), preferably
those that can be considered as wastes or of the least beneficial use. Contin-
uously reducing the storage will either deplete the resource or induce
saltwater encroachment in coastal areas.


3-4


_ ___~L














SECTION 4

FLORIDA'S FRESHWATER RESOURCES


The state of Florida is blessed with abundant freshwater resources. The
rainfall is plentiful and the groundwater system is one of the richest in the
world. Figure 4-1 is an artist's cross section of the peninsula of Florida
showing the limestone formations underlying the entire peninsula which include
the groundwater system referred to above (Raiz, 1964). Figure 4-2 is a more
detailed cross section of the peninsula in a coastal zone depicting the
hydrologic cycle as it applies to Florida. Rain falling on the ground supplies
soil moisture for vegetation. The excess either runs off into swamps, lakes,
and streams, or infiltrates into the ground and saturates it to constitute
groundwater. Surface waters not evaporated or consumed eventually discharge
as runoff into saltwater bodies. Groundwater not consumed also eventually
reaches the coast and is discharged into the sea in the form of springs.
Evaporation from surface waters and from the sea returns fresh water to the
atmosphere to form clouds and to produce more rain.

Water resource factors of significance in Florida are briefly described
in the following discussion.


4.1 RAINFALL

Based on U.S. Weather Bureau climatological data collected at numerous
stations throughout the state from 1931 through 1974, the average annual
rainfall is approximately 54 inches. Florida has the second largest average
annual precipitation in the continental U.S.A. Louisiana is the state with
the highest average: 55 inches per year. Average annual rainfall in Florida
for individual years varies from 50 to 65 inches. In the Keys, average annual
rainfall is only about 40 inches. High annual rainfall is recorded for
stations in the western part of the panhandle and in the southeastern part of
the peninsula. Geographical distribution of the average annual rainfall in
Florida is shown in Figure 4-3.

Rainfall in Florida varies greatly in seasonal distribution. In the
peninsula, the most striking features of the seasonal distribution are the
predominance of summer rainfall and the rather abrupt start and end of the
summer rainy season. In general, about one-half of the annual rainfall occurs
in a four-month period from June through September. In the northwestern part
of the state there are two rainy seasons, late winter or early spring, and the
summer. October is the driest month in northwest Florida, but in the Keys and
along the southeast coast, October is one of the wet months.


4 1


__ _~












































"Atlas of Florida," E. Raiz, p. 6.


FIGURE 4-1. Geological cross section of southern Florida.




dt,


Lagoon




-~ache nc


"Atlas of Florida," E. Raiz, p. 11.


FIGURE 4-2. Hydrological cycle in Florida.

























































0 50
Miles


Source: USGS Map Series No. 40, 1971.


FIGURE 4-3. Mean annual rainfall, 1931-1955.








Of the 54 inches of rainfall, which is the annual average for the
state, about 14 inches is surface runoff. The remainder is lost to the
atmosphere through evapotranspiration or recharges the groundwater by perco-
lation through the soil or by flowing into sinkholes.


4.2 GROUNDWATER

Two fundamental subjects to discuss about groundwater are water-bearing
formations (aquifers) and springs. Their discussion follows.

4.2.1 Aquifers

Water-bearing zones under the earth's surface capable of receiving,
storing, and transmitting water are called aquifers. In Florida most aquifers
are cavernous limestone, and sand and shell beds, while clays and shales are
aquicludes (watertight). Aquifers in Florida may be divided into two classes:
(1) nonartesian, which occur in unconfined or water-table conditions and in
which the water surface is free to rise and fall; and (2) artesian,* which
occur where water is confined under pressure, beneath a relatively impermeable
formation (aquiclude), so that the surface is not free to rise and fall. If a
well is drilled into an artesian aquifer, the water will rise in the well above
the top of the aquifer. The imaginary surface to which water will rise in a
tightly cased well penetrating an artesian aquifer is called the potentiometric
or piezometric surface. Figure 4-4 is a graphical representation of these
concepts.

Nonartesian aquifers accept and store recharge water by allowing water
to infiltrate and fill previously unsaturated voids throughout the aquifer.
Artesian aquifers are recharged in areas where the aquifers crop out at the
earth's surface and in areas where the confining layers have been breached by
erosion or penetrated by sinkholes, through which water can pass freely into
the aquifer.

Most of the shallow aquifers of the state have relatively small areas
of extent and are recharged primarily by local rainfall. An exception is the
Biscayne aquifer of southeast Florida, the most productive of this type. The
principal artesian aquifer (the Floridan aquifer) underlies almost all of the
state. Figure 4-5 shows the contours of the potentiometric surface of the
Floridan and the extent of the Biscayne. Contours indicate the elevation to
which water will rise in wells penetrating the Floridan aquifer and also the
general direction of the groundwater flow (perpendicular to the contours).
Both are cavernous limestone aquifers with not uncommon yields of five million
gallons per day per well. Areas dotted in red on Figure 4-5 indicate brackish
water in the Floridan aquifer. In most of those areas, however, water-table
or secondary aquifers offer moderate yields of fresh water.

4.2.2 Springs

Springs are the result of a natural overflow of the groundwater storage
system. Springs in Florida are of two basic types:

*The first free-flowing well was drilled in the year 1126 AD in the province
of Artios, France, from which the name "artesian" was derived.


4-4










Black, Crow and Eidsness, Inc., Engineers


Potentiometric level


Artesian Recharge
artesian


Source: Ground Water and Wells, Johnson Division, Universal Oil
Products Co., 1966, p. 17.


FIGURE 4-4. Water table and artesian aquifer.





























































FIGURE 4-5. Potentiometric contours of the Floridan aquifer and extent of the Biscayne
and the Sand-and-Gravel (Panhandle) aquifers.









1. Artesian springs, which occur when the potentiometric surface
intersects the earth's surface and water flows under hydrostatic
pressure through openings in the confining bed of the aquifer.

2. Nonartesian springs, which occur when percolating water reaches a
relatively impervious bed and then flows parallel to this bed until
the bed intersects the earth's surface, where it issues forth as a
spring.

The majority and most important springs in Florida are of the first
type. They are well known for their beauty and for their abundance of water
in seasons of drought as well as in seasons of heavy rainfall. The Floridan
aquifer, the source of most of the large springs, acts as a huge reservoir
which tends to equalize the flow of water, regardless of the wet or dry
seasons.

The total number of springs in Florida is not known, but there are well
over 200. The combined flow of these springs is about 11,000 cubic feet per
second (cfs), or about 7 billion gallons per day (bgd). As a comparison, in
1971 public water systems provided 800 million gallons per day (mgd), which
is only about one-ninth of the water being discharged from known springs in
Florida each day (Rossenau and Faulkner, 1975). The two largest springs in
the state are located in Marion County. Silver Springs, one of the largest
springs in the world, has an average discharge of 823 cfs (532 mgd) and
Rainbow Springs has an average discharge of 788 cfs (509 mgd). Springs with
an average flow of 100 cfs or more are classified as first-magnitude springs.
Table 4-1 lists these springs, their locations, and their average flows.

Florida has more first-magnitude springs than any other state in the
nation. There are 25 of these first-magnitude springs in the state, with a
total flow of 8,700 cfs (5.6 bgd) or 79 percent of the average flow of all
springs in Florida (Rossenau and Faulkner, 1975).

Either of Florida's largest springs (Silver or Rainbow) would have
sufficient water to supply a city with a population of over 3 million and any
one of the first-magnitude springs could supply a city of 500,000.


4.3 SURFACE WATER

For the purposes of this discussion, lakes and streams are considered
to be surface water, although portions of the water in most lakes and streams
are, or have been, groundwater.

4.3.1 Lakes

Florida is blessed with thousands of lakes scattered throughout most of
the state from the northern extremity to as far south as Lake Okeechobee. The
total number is estimated at 30,000 (Raiz, 1964, p. 10). There are many lakes in
Florida which rival the ocean beaches in terms of attraction and recreational
value.

Most of Florida's lakes are located in the central sand ridge, especially
between Gainesville to the north and Lake Placid, two hundred miles farther


4-7








TABLE 4-1. First-Magnitude Springs of Florida-With Period of Record, Discharge,
Representative Temperatures, and Dissolved Solids

Average
Period Discharge Water Dissolved
Spring and County of Average Range Number of Temperature Solids
of Location Record (cfs) (cfs) Measurements OC F (mg/1)


Alachua County
Hornsby Spring 1972-73 163 76-250 2 22.5 73 230
Bay County
Gainer Springs 1941-72 159 131-185 7 22.0 72 60
Citrus County
Chassahawitska Springs 1930-75 139 32-197 81 23.5 74 740
Crystal River Springs 1964-75 878 t 25.0 75 144
Homosassa Springs 1932-75 192 125-257 75 23.0 73 1,800
Columbia County
Ichetucknee Springs 1917-75 358 241-578 359 22.5 73 170
Hernando County
Weekiwachee Springs 1917-75 176 101-275 354 23.5 74 150
Jackson County
Blue Springs 1929-73 190 56-287 10 21.0 70 116
Jefferson County
Wacissa Springs Group 1971-73 374 255-596 14 20.5 69 150
Lafayette County
Troy Spring 1942-73 166 148-205 4 22.0 72 171
Lake County
Alexander Springs 1931-72 120 74-162 13 23.5 74 512
Leon County
Natural Bridge Spring 1942-73 106 79-132 5 20.0 68 138
St. Marks Spring 1956-75 519 310-950 130 20.5 69 154
Levy County
Fannin Springs 1930-72 102 64-137 7 22.0 72 194
Manatee Spring 1932-73 181 110-238 9 22.0 72 215
Madison County
Blue Spring 1946-73 123 78-145 5 21.0 70 146
Marion County
Rainbow Springs 1898-1975 788 487-1,230 386 23.0 73 93
Silver Springs 1906-75 823 59) 1,290 139 23.0 73 245
Silver Glen Springs 1931-72 112 90 129 11 23.0 73 1,200
Suwannee County
Falmouth Spring 1933-73 125 00-159 1 21.0 70 218
Volusia County
Blue Spring 1932-75 162 63-214 352 23.0 73 826
Wakulla County
Kini Spring 1972-73 176 -- 1 21.0 70 105
River Sink Spring 1942-73 164 102-215 6 21.0 70 105
Spring Creek Springs 1974 2,003 1 22.5 73 2,400
Wakulla Springs 1907-75 375 25-1,870 266 21.0 70 153

Source: J. C. Rossenau and G. L. Faulkner, "An Index to Springs of Florida," U.S. Geological Survey Map Series
No. 63,1975.
*Tidal affected.
tContinuous record, vane gage.


4-8









south. The area to the south of Lake Okeechobee is the only major portion
of the state which does not have well-defined lakes, since it is covered by
freshwater marshes and swamps.

The lack of well-defined lakes in the southern end of the peninsula and
the abundance of lakes in the central part of the state are due to the
geomorphology of the state. All of the peninsula is underlain at various
depths by porous limestone, formed by marine sediments. Solution of the lime-
stone by groundwater has created subterranean cavities. When part of the roof
of a cavity collapses, a sinkhole is developed and a lake may be formed if the
limestone was overlain by surficial deposits of sufficient depth to form a bed
to contain the lake (see Figures 6-2 and 6-3 in Section 6).

Although many of the lakes in Florida have been formed by the above
process, not all of them were formed in this way. The large lakes, such as
Lake Okeechobee, Lake Istokpoga, and Lake Kissimmee, are believed to have
been created by receding seas of geologic times. Other large lakes, such as
those in north Florida, were parts of streambeds which were abandoned by
meandering streams.

Lakes in Florida may be grouped into three broad categories: (1)
perched lakes, (2) water-table lakes, and (3) artesian lakes. Perched lakes
have an impervious layer of material under them which may be "perched" above
the water table. Because of this impervious layer, water from the lake does
not freely communicate with the groundwater, and lake levels fluctuate inde-
pendently of the water-table fluctuations. Damage to the impervious layer
underlying a perched lake can cause a drastic decline in the lake level or
possibly drain the lake altogether.

Water-table lakes are very common in Florida. The bottoms of these
lakes extend below the water table. When the lake level is higher than the
water table, water flows out of the lake into the groundwater. When the lake
level is lower than the water table, water flows from the water table into
the lake.

Artesian lakes, sometimes called sinkhole lakes or spring-fed lakes,
are also numerous in Florida. These lakes are directly connected to the
artesian aquifer and water flows upward into the lake due to hydrostatic
pressure. Since the pressure in the aquifer may fluctuate, the level of an
artesian lake will fluctuate accordingly.

Florida's lakes are intrinsically valuable for many reasons, among
which are: recreation, commerce, land development and enhancement, water
supply for irrigation, wildlife preserves, water storage, and recharge of
the groundwater. Lakes also serve to moderate local climatic conditions,
which is beneficial to adjacent agricultural developments. Like any other
resource, however, lakes must be used if their benefits are to be realized.
Some types of uses preclude others and, therefore, sound management
decisions must be made to insure the most reasonable and beneficial use of
these resources.


4-9








4.3.2 Streams


In Florida, a major stream is considered to be one that has an average
flow of at least 1,000 cfs (646 mgd). There are 11 major streams in Florida
(Kenner et al., 1969).

The average flow of a stream depends on the size of the drainage basin,
topography, climate, geology, and land development. In northern Florida the
drainage basins are generally larger than in the rest of the state, the
topography is steeper, and the evapotranspiration rate is less; therefore,
the average streamflow in northern Florida is greater. Four of the five
largest streams in the state are in northern Florida. These are the Apalach-
icola, Suwannee, Choctawatchee, and Escambia rivers. The third largest
stream, the St. Johns River, drains portions of both northern and southern
Florida. In central peninsular Florida, the largest stream is the Kissimmee
River. Other large streams in central Florida include the Withlacoochee
River, the Hillsborough River, and the Peace River. In south Florida streams
are, for the most part, poorly developed and most drainage is through a
system of canals.

Figure 4-6 shows the major drainage basins in the state and the basins
which drain into the state fiom Georgia and Alabama. Average streamflows
into the Atlantic and the Gulf are shown in Table 4-2.


4.4 EVAPOTRANSPIRATION

Surface-water bodies lose water in four principal ways: (1)
transpiration, (2) outflow through streams, (3) underground outflow, and
(4) evaporation. Transpiration (plant use) varies seasonally. It is low
during the fall and winter and high during the growing season. Evaporation
also varies seasonally, and is dependent on such factors as humidity, cloud
cover, solar radiation, wind movement, and air temperature. Figure 4-7 shows
the average yearly evaporation rate from free water surfaces in Florida.

Evaporation and transpiration occur on land surfaces as well as on
water bodies. Evaporation of soil moisture near the surface of the earth
occurs when the vegetative cover is not too dense. In areas of vegetation,
water is taken up from the ground by the root system of plants and transpired
into the atmosphere through the leaves. The depth from which plants will
take up groundwater varies with the species of plant and type of soil, but
it ranges from a few inches for ordinary grasses to 50 feet or more for certain
types of desert plants.

Direct determinations of evapotranspiration for large areas of diversified
soils, topography, and vegetative cover cannot be made with present technology.
However, it is known that areas covered by vegetation with a water table contin-
uously at or near ground surface can produce evapotranspiration losses
significantly higher than evaporation from free water surfaces and, of course,
much higher than in areas where the water table is significantly below ground
level.

Experiments in Belle Glade, at the southeast corner of Lake Okeechobee,
indicate that the mean annual evapotranspiration from sawgrass land, with the
water table ranging from ground level to an average of about two feet below, is


4 10





























































FIGURE 4-6. Drainage basins and discharge of surface water from the state of Florida to
the Atlantic and to the Gulf.















TABLE 4-2. Drainage Basins and Discharge of Surface Water from the
State of Florida to the Atlantic and to the Gulf.


Drainage
Area Total Discharge
Basin No. (sq mi) (cfs) (bgd)

Discharge to the Atlantic
St. Johns 1 8,500 8,900 5.75

Cape Kennedy to Cape Sable 2 9,000 5.82

Discharge to the Gulf
Cape Sable to Alligator Creek 3 2,500. 1.62

Peace River to New River 4 26,100 27,200 17.58

Apalachicola River 5 20,000 26,700 17.26

Wetappo Creek to Perdido River 6 14,200 25,100 16.22

Total 99,400 64.25

Source: USGS, Hydrologic Investigations, Atlas HA-282, 1969.

Note: Surface inflow from Georgia and Alabama is estimated to be 25 bgd.

*Drainage area not computed.


4 12



























Goop OF
rr'


o
48



50


52







54 N





Miles




Source: USGS, Map Series No. 32, 1969.


FIGURE 4-7. Average annual lake evaporation.








approximately 60 inches (Clayton et al., 1942). This average annual evapo-
transpiration rate of 60 inches is approximately the same as the average
annual rainfall for the area (Figure 4-3). This means that the full amount of
annual rainfall is lost by evapotranspiration. Evapotranspiration from pine-
and-grass land south of Miami with a lower water table is estimated at
approximately 35 inches per year (Parker et al., 1955, p. 55).


4.5 FLORIDA'S WATER BUDGET

By comparing annual "income" and "expenses" of water in the state, a
"budget" can be prepared. The annual rainfall (54 inches) taken over the
entire state (58,560 square miles) is equal to 150 billion gallons per day
(bgd). Another source of income is the surface inflow into the state from
Georgia and Alabama. This amounts to another 25 bgd (see Figure 4-6). The
credit side of the ledger now has 175 bgd. On the debit side is evapotranspi-
ration and surface outflow. From Table 4-2, the annual surface outflow is
65 bgd. An average figure of 38 inches per year is a reasonable assumption
for evapotranspiration throughout the state. This would amount to 107 bgd,
so the total debit evapotranspirationn and surface outflow) is 172 bgd.

The difference in the total income (175 bgd) and the expenses (172 bgd)
is 3 bgd. These 3 bgd amount to approximately 1.0 inch of rain per year or
1.7 percent of the total water income. Such a relatively small difference
could be attributed to either consumptive use, coastal groundwater outflow,
or lack of better refinement in the generalized estimate for evapotranspiration;
or most probably to a combination of these. In any case the difference is well
within the margin of accuracy of these estimates.

Groundwater inflow from the north across the state line has not been
included in this budget since estimates for such volume are relatively low
(0.05 bgd).

Adjusting the expenses side of the budget equation to take care of the
differences for Florida's water budget, we arrive at the following figures in
bgd:


INCOME EXPENSES

Rainfall + inflow = Evapotranspiration + outflow

150 + 25 = 107 + 68*

A graphical representation of the above concept is presented in Figure
4-8.


*Including consumptive use and coastal groundwater outflow.


4 14
















SECTION 5


UTILIZATION OF FLORIDA'S FRESHWATER RESOURCES


5.1 FRESHWATER WITHDRAWAL AND CONSUMPTION IN FLORIDA

Distinction between freshwater withdrawal, use, and consumption was
established in paragraph 3.3. Water withdrawal returned to the original
source or area after utilization is referred to as water use. If the with-
drawal is not returned to the area after utilization but is either evaporated
or discharged into salt water, it is referred to as consumption or consumptive
use.

A survey was completed in 1973 (Pride, 1973) on the water withdrawal
and consumption in Florida during 1970. Table 5-1 summarizes the data from
the survey on freshwater withdrawal from the two main sources, groundwater
and surface water. Table 5-2 summarizes consumptive use of fresh water for
the five different types of users.

From the information presented in Tables 5-1 and 5-2 the following
observations can be made:

1. The largest consumptive use of fresh water in the state is that
for agricultural purposes. It represents 69 percent of the total
consumption and is more than 5 times larger than the amount of
water consumed by municipalities, the second largest consumptive
user listed in Table 5-2.

2. Approximately the same amount of withdrawal is obtained from
groundwater sources (49.7 percent) as from surface-water sources
(50.3 percent).

3. The total consumptive use for the entire state was 1.848 bgd.
This amount represents only 1.1 percent of the total freshwater
income of the state (175 bgd) and 1.2 percent of the total amount
of precipitation (rainfall) in the state (150 bgd). Freshwater
income and precipitation figures are given in paragraph 4.5,
Florida's Water Budget.

4. The total consumptive use for the state, 1.848 bgd, represents
32 percent of the total freshwater withdrawal, 5.762 bgd. This
means that 68 percent of the total amount of water withdrawn is
returned to the freshwater resources of the state.


5-1








TABLE 5-1. Summary of Freshwater Withdrawal in Florida (1970)


Groundwater Surface Water
Total % of Total % of Total
User bgd % bgd Withdrawal bgd Withdrawal

Irrigation 2.070 37 1.172 20.3 .898 15.6

Thermoelectric 1.686 29 .011 0.2 1.675 29.0

Industry* .927 16 .736 12.8 .191 3.3

Municipal .884 15 .759 13.2 .125 2.2

Rural .195 3 .183 3.2 .012 0.2

State 5.762 100 2.861 49.7 2.901 50.3


Source: Florida Bureau of Geology I. C. No. 83, Tallahassee, 1973.

Notes: In billion gallons per day (bgd), 1 bgd = 1,000 mgd (million gallons
per day) = 1 x 109 gpd (gallons per day).

*Self-supplied.


TABLE 5-2.


Summary of Consumptive Use in Florida (1970)


Total


Irrigation

Municipal

Industry*

Rural

Thermoelectric

State


1.270

.235

.163

.160

.020

1.848


69

13

9

8

1

100


Source: Florida Bureau of Geology I. C. No. 83, Tallahassee, 1973.

Notes: In billion gallons per day (bgd), 1 bgd = 1,000 mgd (million gallons
per day) = 1 x 109 gpd (gallons per day).

*Self-supplied.
5 2









What is the significance of the percentages given in observations 3 and
4 above? The total consumptive use of the state when compared to the total
amount of precipitation seems to be very low (1.2 percent). This means that
in 1970 Florida was only consuming 1.2 percent of its freshwater income from
precipitation. The total amount of water returned to the freshwater resources
of the state when compared to the total amount of withdrawal seems to be
relatively high (68 percent).

The two preceding considerations (very low and relatively high) could
be misleading unless viewed in light of what other states in the nation are
doing. This comparison is included in the following paragraph.


5.2 FRESHWATER WITHDRAWAL AND CONSUMPTION IN THE U.S.A.

Table 5-3 summarizes information on a survey completed in 1973 (Murray
et al., 1972) on the water withdrawn and consumed in the United States in 1970.
Table 5-3 includes all continental states. Hawaii is not included because the
information for that state would represent a number of islands, rather than
one body of land. Population data from the 1970 U.S. census have been
included to assist in the an-lysis of the information.

Figures in column 4, precipitation total volume per day (PTV), are
obtained by multiplying the average yearly precipitation (column 3) by the
area (column 2) and by the proper unit conversion factors. Figures in column
9 are the ratio of fresh water withdrawn per day (FWW, column 7) to the precip-
itation total volume per day (PTV, column 4). Figures in column 12 are the
ratio of fresh water consumed per day (FWC, column 10) to the precipitation
total volume per day (PTV, column 4).

Figures in columns 9 and 12 represent, respectively, the ratio of
fresh water withdrawn and the ratio of fresh water consumed to the total
volume of precipitation. In common terms,figures in columns 9 and 12 tell
us how much fresh water each state withdraws and consumes, expressed as a
percentage of the total amount of precipitation each receives. These figures
do not consider water importation from other neighboring states, but on the
other hand they can be used as a fairly good indicator of how effectively
each state is using its water resources.

A tabulation has been prepared listing the states in decreasing ratios for
withdrawal and consumption (from columns 9 and 12 of Table 5-3). This tabulation
is shown as Table 5-4. The left-hand side of the table shows the ratio of
fresh water withdrawn (FWW) to precipitation total volume (PTV). The right-
hand side shows the ratio of fresh water consumed (FWC) to precipitation total
volume (PTV). Table 5-4 shows that Florida ranks thirty-third for the total
withdrawal ratio and eighteenth for the consumptive use ratio. This, in turn,
indicates that our consumption rating is much higher than our withdrawal
rating; that is, Florida in relation to its total precipitation withdraws a
relatively small amount of water but consumes more than other states.

There is no question that our peninsular geography, with the longest
coastline of any state except Alaska, contributes to the higher consumptive
ratio. However, our groundwater systems properly managed can, in our opinion,
substantially offset the geographical handicap.


5-3
















TABLE 5-3. Summary of Precipitation and Freshwate


Precipitation 1970 Population
Total
Volume
Average Per Day Tol
Area Per Year (bgd) Density (bg
State (sq mi) (in) PTV Inhabitants (inh/sq mi) FW
1 2 3 4 5 6 7

1 Alabama 51,609 54.57 135.2 3,444,165 66.74 6
2 Alaska 586,412 36.07 1,015.3 302,173 0.52 0.
3 Arizona 113,909 12.36 57.6 1,772,482 15.56 6.
4 Arkansas 53,104 48.65 124.0 1,923,295 36.22 3.
5 California 158,693 28.98 182.7 19,953,134 125.73' 39.
6 Colorado 104,247 15.14 75.8 2,207,259 21.17 13.
7 Connecticut 5,009 47.13 11.3 3,032,217 605.35 1.
8 Delaware 2,057 45.60 4.5 548,104 266.46 0.
9 Florida 58,560 52.46 147.5 6,789,443 115.94 5.'
10 Georgia 58,876 48.85 138.1 4,589,575 77.95 5.
11 Idaho 83,557 14.97 60.0 713,008 8.53 16.1
12 Illinois 56,400 37.42 101.3 11,113,976 197.06 16.1
13 Indiana 36,291 39.57 58.9 5,193,669 143.11 8.(
14 Iowa 56,290 31.26 84.5 2,825,041 50.19 2.'
15 Kansas 82,264 26.38 104.2 2,249,071 27.34 3.
16 Kentucky 40,395 45.78 88.8 3,219,311 79.70 4.!
17 Louisiana 48,523 56.37 131.3 3,643,180 75.08 8.1
18 Maine 33,215 42.46 67.7 993,663 29.92 0.5
19 Maryland 10,577 43.14 21.9 3,922,399 370.84 1.6
20 Massachusetts 8,257 44.89 17.8 5,689,170 689.01 2.0
21 Michigan 58,216 31.17 97.1 8,875,083 152.45 13.0
22 Minnesota 84,068 25.82 104.2 3,805,069 45.26 3.4
23 Mississippi 47,716 54.03 123.7 2,216,912 46.46 1.6
24 Missouri 69,686 40.12 134.2 4,677,399 67.12 3.5
25 Montana 147,138 14.54 102.7 694,409 4.72 8.0
26 Nebraska 77,227 22.13 82.0 1,483,791 19.21 6.0
27 Nevada 110,540 7.42 39.4 488,738 4.42 3.3
28 New Hampshire 9,304 41.60 18.6 737,681 79.29 0.51
29 New Jersey 7,836 44.72 16.8 7,168,164 914.77 3.1
30 New Mexico 121,666 12.78 74.6 1,016,000 8.35 3.2
31 New York 49,576 38.86 92.5 18,241,266 367.95 9.1
32 North Carolina 52,586 48.51 122.4 5,082,059 96.64 5.7
33 North Dakota. 70,665 16.92 57.4 617,761 8.74 0.63
34 Ohio 41,222 37.30 73.8 10,652,017 258.41 18.0
35 Oklahoma 69,919 32.74 109.9 2,559,253 36.60 1.5
36 Oregon 96,981 34.49 160.6 2,091,385 21.56 5.9
37 Pennsylvania 45,333 41.78 90.9 11,793,909 260.16 20.0
38 Rhode Island 1,214 43.02 2.5 949,723 782.31 0.15
39 South Carolina 31,055 48.80 72.7 2,590,516 83.42 3.3
40 South Dakota 77,047 18.39 68.0 666,257 8.65 0.44
41 Tennessee 42,244 50.95 103.3 3,924,164 92.89 6.4
42 Texas 267,339 27.51 353.0 11,196,730 41.88 19.0
43 Utah 84,916 11.67 47.6 1,059,273 12.47 4.2
44 Vermont 9,609 40.14 18.5 444,732 46.28 0.11
45 Virginia 40,817 42.82 83.9 4,648,494 113.89 4.7
46 Washington 68,192 41.66 136.4 3,409,169 49.99 7.1
47 West Virginia 24,181 43.95 51.0 1,744,237 72.13 5.8
48 Wisconsin 56,154 30.67 82.7 4,417,933 78.68 6.3
49 Wyoming 97,914 14.67 68.9 332,416 3.39 5.7


5-4















Dr Withdrawal and Consumption in the U.S.A. by States


Freshwater Withdrawal Fresh Water Consumed
Ratio Over Ratio Over
Total Precipitation Total Precipitation
?tal Per Day Total Per Day Ratio
igd) Per Capita (%) (bgd) Per Capita (%) (%)
NW (gpd/inh) FWW/PTV FWC (gpd/inh) FWC/PTV FWC/FWW
7 8 9 10 11 12 13


1,858.2
827.3
3,836.4
1,559.8
1,954.6
5,889.7
494.7
328.4
869.0
1,133.0
22,440.1
1,439.6
1,655.9
743.4
1,689.6
1,397.8
2,223.3
563.6
407.9
351.5
1,464.8
893.5
721.7
748.3
11;520.6
4,043.7
6,752.1
718.5
432.5
3,149.6
498.9
1,121.6
1,019.8
1,689.8
586.1
2,821.1
1,695.8
157.9
1,273.9
660.4
1,630.9
1,696.9
3,965.0
247.3
1,011.1
2,082.6
3,325.2
1,426.0
17,147.2


4.73
0.02
11.81
2.42
21.35
17.15
13.27
4.00
4.00
3.77
26.67
15.79
14.60
2.49
3.65
5.07
6.17
0.83
7.31
11.24
13.39
3.26
1.29
2.61
7.79
7.32
8.38
2.85
18.45
4.29
9.84
4.66
1.10
24.39
1.36
3.67
22.0
6.0
4.5
0.65
6.20
5.38
8.82
0.59
5.60
5.21
11.37
7.62
8.27


0.23
0.016
4.8
1.2
22.0
6.8
0.18
0.026
1.85
0.42
4.70
0.36
0.39
0.24
2.6
0.18
2.2
0.061
0.14
0.14
0.33
0.31
0.41
0.31
5.5
3.7
1.5
0.018
0.38
1.5
0.66
0.48
0.20
0.46
0.83
2.60
0.45
0.013
0.18
0.25
0.20
9.6
2.2
0.013
0.15
2.5
0.066
0.18
2.4


66.8
52.9
2,708.1
623.9
1,102.6
3,080.7
59.4
47.4
272.0
91.5
6,591.8
32.4
75.1
84.9
1,156.0
55.9
603.9
61.4
35.7
24.6
37.2
81.5
184.9
66.3
7,920.4
2,493.6
3,069.1
24.4
53.0
1,476.4
36.2
94.4
323.7
43.2
324.3
1,243.2
38.2
13.7
69.5
375.2
50.9
857.4
2,076.9
29.2
32.3
733.3
37.8
40.7
7,219.9


0.17
0.002
8.33
0.97
12.04
8.97
1.59
0.58
1.29
0.30
7.83
0.36
0.66
0.28
2.50
0.20
1.68
0.09
0.64
0.79
0.34
0.30
0.33
0.23
5.36
4.51
3.81
0.10
2.26
2.01
0.71
0.39
0.35
0.62
0.76
1.62
0.50
0.52
0.25
0.37
0.19
2.72
4.62
0.07
0.18
1.83
0.12
0.22
3.48


3.59
6.40
70.6
40.0
56.4
52.3
12.0
14.4
31.4
8.08
29.4
2.25
4.53
11.43
68.4
4.00
27.2
10.9
8.75
7.00
2.54
9.12
25.62
8.86
6.70
61.7
45.5
3.40
12.3
46.9
7.25
8.42
31.7
2.56
55.3
44.1
2.25
8.67
5.45
56.8
3.12
50.5
52.4
11.8
3.19
35.2
1.14
2.86
42.1


I







TABLE 5-4.


List of States by Decreasing Ratios of Withdrawal and
Consumption to Total Precipitation


FWW/PTV (%) State Rank I State FWC/PTV (%


26.67
24.39
22.00
21.35
18.45
17.15
15.79
14.60
13.39
13.27
11.81
11.37
11.24
9.84
8.82
8.38
8.27
7.79
7.62
7.32
7.31
6.20
6.17
6.00
5.60
5.38
5.21
5.07
4.73
4.66
4.50
4.29
4.00
4.00
3.77
3.67
3.65
3.26
2.85
2.61
2.49
2.42
1.36
1.29
1.10
0.83
0.65
0.59
0.02


Idaho
Ohio
Pennsylvania
California
New Jersey
Colorado
Illinois
Indiana
Michigan
Connecticut
Arizona
West Virginia
Massachusetts
New York
Utah
Nevada
Wyoming
Montana
Wisconsin
Nebraska
Maryland
Tennessee
Louisiana
Rhode Island
Virginia
Texas
Washington
Kentucky
Alabama
North Carolina
South Carolina
New Mexico
Florida
Delaware
Georgia
Oregon
Kansas
Minnesota
New Hampshire
Missouri
Iowa
Arkansas
Oklahoma
Mississippi
North Dakota
Maine
South Dakota
Vermont
Alaska


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
S18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49


Note: FWW/PTV = ratio of fresh water withdrawn to precipitation total volume.
FWC/PTV = ratio of fresh water consumed to precipitation total volume.
5 5


California
Colorado
Arizona
Idaho
Montana
Utah
Nebraska
Nevada
Wyoming
Texas
Kansas
New Jersey
New Mexico
Washington
Louisiana
Oregon
Connecticut

Arkansas
Massachusetts
Oklahoma
New York
Indiana
Maryland
Ohio
Delaware
Rhode Island
Pennsylvania
North Carolina
South Dakota
Illinois
North Dakota
Michigan
Mississippi
Georgia
Minnesota
Iowa
South Carolina
Missouri
Wisconsin
Kentucky
Tennessee
Virginia
Alabama
West Virginia
New Hampshire
Maine
Vermont
Alaska


12.04
8.97
8.33
7.83
5.36
4.62
4.51
3.81
3.48
2.72
2.50
2.26
2.01
1.83
1.68
1.62
1.59
1.20
0.97
0.79
0.76
0.71
0.66
0.64
0.62
0.58
0.52
0.50
0.39
0.37
0.36
0.35
0.34
0.33
0.30
0.30
0.28
0.25
0.23
0.22
0.20
0.19
0.18
0.17
0.12
0.10
0.009
0.007
0.002













SECTION 6


HISTORICAL WATER SUPPLY PROBLEMS IN FLORIDA


6.1 SALTWATER INTRUSION

Saltwater intrusion, which was discussed previously in section 2.1,
Introduction, is and has been the most serious threat to Florida's freshwater
resources.

A comprehensive investigation was made in the early fifties on the extent
of saltwater intrusion in Florida. That investigation showed 28 areas of the
state already affected by the problem. It was concluded that saltwater
intrusion in those areas was the direct result of not only large local with-
drawals but of excessive drairage in areas where groundwater levels were close
to sea level (Black et al., 1953). We must repeat that concurrent local large
water withdrawals and excessive drainage, together with water shortages in an
area, are evidence of lack of adequate water management.

The position of the saltwater front in a coastal aquifer is controlled
mainly by the elevation of the fresh groundwater levels above sea level. The
most serious cases of saltwater encroachment into well field areas have
occurred by the upstream movement of salt water into the aquifer from uncon-
trolled tidal streams and canals. Where salinity control structures have been
built, the saltwater front not only has been halted but pushed back (Parker,
1951). Figure 6-1 shows the effects of controlled and uncontrolled coastal
canals on saltwater intrusion (Sherwood et al., 1973).

The theoretical basis of saltwater intrusion is the Ghyben-Herzberg
Principle.which establishes the relationship between seawater (specific gravity,
1.025) and fresh water (specific gravity, 1.000). Fresh water, being lighter
than seawater, will tend to float on top of seawater and also to be displaced
by it. A detailed explanation of the Ghyben-Herzberg Principle is given in the
Appendix of this report.

Clear understanding of the Ghyben-Herzberg Principle, sound hydrological
knowledge, and proper monitoring can allow for the development of substantial
volumes of fresh water in coastal areas without any water quality degradation.
Positive water management with artificial and/or induced recharge can allow for
significant additional volumes of fresh water to be developed in those areas.
In addition, the more recent possibility of wastewater reuse after treatment
for nonpotable uses is one more factor to further increase freshwater devel-
opment in such areas.


6 1











Black. Crow and Eidsness, Inc., Engineers
n.


Seawater and fresh water in coastal area before
construction of canals.




h


The construction of uncontrolled tidal canals
causes seawater intrusion in two ways: it
lowers freshwater levels and it provides open
channels to convey seawater inland. The salt
front in the aquifer shifts inland adjacent to
the new canal.


An uncontrolled canal that extends into an area
of heavy pumpage can convey salt water inland
to contaminate freshwater supplies.


Source: Sherwood et al., 1973.


In contrast a controlled canal can provide a
perennial source of fresh water to prevent
saltwater intrusion and to replenish the well
field by bringing in fresh water from outside
the area.


FIGURE 6-1. Effects of controlled and uncontrolled coastal canals on saltwater intrusion.








6.2 LAND SUBSIDENCE


Land subsidence due to groundwater withdrawal is a phenomenon observed
in areas underlaid by unconsolidated aquifers (sands, gravels, and shells)
when the withdrawal has been large and prolonged. It commonly occurs as a
slow process which pretty evenly spreads over the area where the potentio-
metric surface has been significantly lowered. This type of subsidence does
not have any present significance in Florida because major groundwater with-
drawals take place in consolidated (limestone) aquifers. Examples of that
type are in the Houston-Galveston area of Texas, the San Joaquin and Santa
Clara valleys in California, and in Mexico City. Such occurrences are not
discussed in this report.

Land subsidence due to groundwater withdrawal can also occur in areas
underlaid by consolidated calcareous (limestone) aquifers. The appearance of
this phenomenon is markedly different from that mentioned in the preceding
paragraph. Land subsidence of this second type appears in the surface of the
ground rather suddenly, usually in the form of an inverted cone with land
surface diameters in the range of several feet to one hundred feet or more.
There are exceptions, of course, but the inverted cone, or near-inverted cone
type, is most common.

Land subsidence of this nature causes typical holes in the ground which
in the United States are referred to as sinkholes or sometimes only as sinks.

When the water table is higher than the bottom of a sinkhole, a lake is
formed. Some authors (Ardaman, 1969) elaborate that over 90 percent of the
30,000 lakes in the state of Florida (Raiz, 1964) are a result of sinkholes.

6.2.1 The Sinkhole Problem

Sinkholes appeared on the surface of the earth long before man started
withdrawing water from the ground. It is, then, a natural process; but it can
be accelerated by man's water withdrawal.

Development of sinkholes has caused serious local problems in buildings,
highways, bridges, and utilities (entire homes have collapsed and fallen into
sinkholes in the Lakeland, Bartow, Mulberry area of Florida). The sinkhole
problem is usually very localized and small compared to other natural disasters
such as hurricanes and earthquakes. However, when it happens, it seriously
affects the property value of the person or agency involved.

In order to evaluate the sinkhole problem, it is necessary to understand
the limestone dissolution process which causes it. This is a natural process;
not a result of man's ill-treatment of his environment; not a result of poor
construction or poor engineering practices; not a result of poor planning or
management; but a natural hydrogeologic process. The peninsula of Florida,
where the phenomenon is very common, is an area with extensive limestone
formations, relatively low relief, relatively poor surface drainage, and prin-
cipal erosion toward base level accomplished by internal drainage and
dissolution of the carbonate plateau. In this dissolution process, certain
subsurface and surface features are not only characteristic but are inevitable.


6-3










Among these features are subsurface caverns or voids and surface sinkholes. It
is not the intent of this report to describe the worldwide occurrence of these
features, the various types, and the origins ascribed to them; but rather to
focus only on Florida and to suggest a mode of formation for the principal
shallow cavernous zones and the more commonly encountered type of sinkhole.

6.2.2 Sinkhole Development

As previously indicated, caverns or void spaces result from the
dissolution of carbonates (limestones) by the slight acidic action of rain and
surface waters. This activity is believed to be most concentrated near the
water table when the water table stands within the carbonate section. Above
the water table, the principal orientation of solution voids is vertical,
enlarging fractures, joints, faults, etc.; while below the water table, the
principal orientation becomes horizontal. Through geologic time this has
resulted in a stacked system of caverns or cavernous -zones; each zone developed
where the water table stood for long periods of time, separated by sequences of
less-affected carbonates where land surface or sea level was less stable.
Immediately above the horizontal cavernous zone occur vertically oriented voids
that appear to occupy a section ranging from a few feet to about 50 feet in
thickness. The top of this zone is usually marked by an unconformity (another
formation, clay, or marls above) representing an old erosion surface.

During the Miocene epoch, the development of Florida's terrains changed
from one of chemical carbonate deposition to one of detrital plastic (clays,
sands, and shell) deposition. This resulted in the uppermost cavernous zone
being covered with unconsolidated to poorly consolidated quartz sands and
clays. The structural competency of the roof of the cavernous zones is highly
variable, ranging from thick competent limestones to thin incompetent lime-
stones either with clastic-filled or plugged breaches of the roof. The top of
the limestone section can also be covered with quite variable thicknesses of
sands and clays to the present-day land surface.

Within the limits of this premise, let us look at Florida's landscape
today. Where the sand cover is minimal (0-15 feet ), numerous small sinkholes
occur; where the detrital clastics (sand and clays) are of intermediate
thickness (15-100 feet ), scattered large sinkholes occur; where the detrital
clastics are thick (more than 100 feet), few sinkholes are present, however,
scattered large circular structural sags occur; and where the detrital clastics
are not only thick (more than 100 feet) but are consolidated to the degree of
structural stability, no sinkholes or subsidence is evident. This latter
category coincides fairly well with down-dip areas where erosional unconfor-
mities are more difficult to recognize and may reflect nonemergent areas where
cavernous systems are poorly developed. Concerning the first three categories,
significant differences are apparent. In the 0-15 feet of plastic overburden
areas, the sinkholes are small enough for existing structures to bridge without
catastrophic collapse, resulting in less property damage; in the areas with
more than 100 feet of plastic overburden, catastrophic collapse is extremely
rare, however structural sagging may occur and be extremely difficult to
recognize. With 15-100 feet of plastic overburden, both catastrophic collapse
and sagging are common and result in major structural damage to real property.


6-4








The most commonly reported type of sinkhole developing in Florida today
does not result from the expansive collapse of cavern roofs (Figure 6-2), but
rather as small breaches of the cavern roof by solution and/or collapse and by
the unplugging of breaches filled with plastic plugs (Figure 6-3). This allows
unconsolidated sediments to move downward into the underlying caverns and
results in a rapidly progressive enlarging void in the overlying unconsolidated
clastics. The development of this void may be to any degree and at any rate,
depending on the capacity of the caverns to accept the unconsolidated clastics
and the ability of the unconsolidated clastics to move downward. The end
result varies from minor structural sags, usually accompanied by concentric
cracks, to a collapse of the overburden.

6.2.3 Groundwater Role

Groundwater, in addition to its role in solution, plays other important
roles in the formation of sinkholes if the preceding potentially unstable
conditions exist. Groundwater can function as a lubricant or flow medium for
plastic particle movement, as a drive mechanism or erosive agent where head
differences occur and downward recharge to the aquifer is accelerated through
a breach in the limestone top. and as a triggering device in transmitting
shock waves to unplug breaches. The last roles, requiring head differentials,
are more active when head differentials are greater. Significant head differ-
entials can occur and have occurred naturally over the centuries by climatic
conditions: droughts or heavy rainfalls following a drought.

The preceding natural climatic conditions are the reason why the great
majority of the 30,000 lakes in Florida were formed long before man started
withdrawing water from the ground. Man-made stresses on the system occur
where the potentiometric surface is being lowered by pumping, or when ground
surface is flooded and a marked differential in hydraulic head (water level
difference) is created with the water table of the area.

6.2.4 Can the Problem Be Avoided?

The preferable answer is one which avoids the problem as opposed to an
after-the-fact financial remuneration to sustained losses. To this end, the
Bureau of Geology of the state of Florida has investigated in substantial
detail a variety of direct and indirect methods to determine the stability of
a particular area. The key element is the measure of the competency of the
section overlying the cavernous zone. Competency in this sense is not just a
measure of the engineering strength of a thickness of limestone, but whether
the limestone is breached and where. Experience has shown that a sinkhole
approximately 100 feet in diameter at the top developed through a breach as
small as 4 inches in diameter. Investigations have been pursued utilizing
refraction seismic, electric resistivity, gravity, core drilling, piezometers,
aerial photography, remote sensing, topographic analysis including frequency
distribution-elevations and frequency distribution-land forms, structure
mapping, and isopach mapping (Windham, 1974).

At the present time, no suitable methodology has as yet been fully
demonstrated to make the preceding evaluation possible in Florida's environment,
except for localized soil investigation based mainly on core drilling and/or


6-5












Black, Crow and Eidsness, Inc., Engineers


ARTESIA
HEAD


FIGURE 6-2. Formation of sinkhole by cavern roof collapse (generalized
concept).


1 2


WATER
TABLE,
ARTESIAN
HEAD


FIGURE 6-3. Formation of sinkhole by the unplugging of vertical voids or
breaches above a cavernous system.









ground settlement under preliminary surcharge. This exception, of course, is
much more applicable for man-made stresses than for natural ones. A good
understanding of the principles involved in sinkhole development, together
with proper testing and the use of some of the above-mentioned investigations,
can minimize damage resulting from the formation of sinkholes that could be
produced by man's groundwater withdrawal.


6.3 ENVIRONMENTAL EFFECTS AND HYDROLOGICAL CHANGES IN SURFACE WATERS

In addition to the threat of saltwater intrusion and land subsidence,
declining artesian water levels can also affect the flow of water in streams,
the level of water in lakes, aquatic fauna and flora, and the vegetation of
the surrounding lands.

Water flowing in a stream is primarily direct surface runoff from
precipitation. However streamflow can also include water discharged from
surface reservoirs or lakes, and sometimes groundwater. Groundwater from
springs discharges into many Florida streams, and groundwater from the water
table augments streamflow when the water table level is higher than the level
of the stream.

Declining artesian pressures due to groundwater production may cause
decreased contribution of groundwater to streamflows. Spring flow will be
diminished and also the water table level may decline. The resultant decline
in streamflow has occurred in several areas of Florida due to direct water
diversion or groundwater production. Aquatic fauna and flora may be affected
by these hydrologic changes throughout the course of the stream, and in parti-
cular near the mouth where the saltwater interface will move upstream as the
freshwater flow decreases. Such an effect may be considered detrimental from
some points of view but from a strictly water-resources standpoint it is highly
beneficial because it reduces water losses (surface and groundwater outflow to
saltwater bodies). Sound management must determine which alternate is most
beneficial to society and how to minimize the adverse effects caused by the
most beneficial solution.

As discussed in Section 4, lakes can be classified as artesian, water
table, or perched. Artesian lakes derive part of their waters from springs.
When artesian water levels decline then spring flow is diminished and the
lake level will be lowered. The levels of water table lakes rise and fall
with the water table level. A permanent lowering of the water table results
in a permanent lowering of the lake level unless artificial means of main-
taining the lake level are employed. In perched lakes a different situation
may exist since the waters of the lake are not interconnected with the water
table or with artesian springs. A truly perched lake is dependent upon the
precipitation occurring within its drainage basin and upon the evaporation
occurring from its surface. However, if the impermeable seal beneath the
perched lake is damaged, such as by dredging, water will flow out of the lake.
Perched lakes in some areas have actually been completely drained. Changes to
the aquatic life in lakes such as these, as well as the impact on some species
of terrestrial life near the shores of such lakes, are evident.


6-7









Terrestrial effects may also occur in the vicinity of major water
withdrawals in areas where hydrogeological characteristics are such that the
water table is lowered substantially and the existing vegetation is highly
sensitive to lowering of the water table. Generally the most significant
effects that have been observed are the damage to trees where the water table
is lowered at a rate faster than the root system can extend. Trees may also
be damaged severely by windstorms and fire in areas where dried muck provides
insufficient support following significant lowering of the water table.

Many of these adverse effects can be alleviated by careful evaluation of
each situation followed by implementation of positive steps to maintain higher
water levels. Some solutions may involve surface irrigation through small
ditches as used in pasture irrigation. Substantially greater quantities of
water can be withdrawn from the aquifer than is necessary for replenishment of
the water table to prevent adverse environmental effects.


6-8













SECTION 7


THE WATER CROP CONCEPT

7.1 DEFINITION OF WATER CROP

The water crop for any given area is the amount of rainfall falling on
that area less the amount lost by evapotranspiration. From-the water budget
discussion in Section 3, it is apparent that the water crop is therefore the
amount of water available for aquifer recharge or for maintaining streamflow.
On a statewide basis, the water crop is about 0.683 million gallons per day per
square mile (mgd/sq mi), excluding surface water inflow across the state line.

In theory, if this amount of water were withdrawn uniformly across the
state and if evapotranspiratioi were to remain the same, streamflow would
cease. Obviously, this is too simplified. Rainfall and evapotranspiration vary
each month of the year and also vary according to location. Furthermore,
demand for water varies throughout the year for different water users. Another
significant variable is evapotranspiration. In many parts of Florida the water
table is at or within about 5 feet of ground surface. In such areas, a small
decline in the water table caused by pumping can reduce evapotranspiration
losses. The amount of reduction depends upon many factors and is difficult to
estimate; however, previous studies suggest that the amount may vary in a
typical range of 0 to 4 inches/year. The higher end of this range is equiv-
alent to about 0.19 mgd/sq mi.

Based upon a regional water budget study conducted by the U.S. Geological
Survey (USGS), the Southwest Florida Water Management District (SWFWMD) has
estimated that the water crop within that district is 640,000 gpd/sq mi
(365,000 gallons per year per acre). This estimate includes a reserve factor
of about 25 percent to provide a buffer against possible adverse effects in
local areas. The water crop is equivalent to about 13 inches of rainfall per
year.

The Central and Southern Florida Flood Control District (CSFFCD) has
followed a different approach to estimating the water crop. This approach
assumes that evapotranspiration loss in any area can be approximated by that
for St. Augustine grass, which in turn has been related to the evaporation loss
from open water surfaces. Since both rainfall and lake evaporation vary
according to location in the district, the calculated water crop varies from 6
inches to 18 inches of rainfall. While this approach is superior to the
regional average approach followed by SWFWMD, its application in the water
management decision-making process has been most conservative. In particular,
much of the area within Dade, Broward and southern Palm Beach counties that is
credited with a water crop of 18 inches, is in fact not a recharge area at all
since the aquifer is very thin and has little underground storage capacity most


7- 1









of the time. The CSFFCD Conservation Areas comprise much of this part of the
district. The water crop from these areas is released in drainage canals to
supplement the more permeable coastal ridge aquifer. However, water use permit
applicants are allocated only the water crop on their property, with no credit
for a reasonable portion of the water crop from inland conservation and storage
areas.

The other water management districts have not yet developed rules and
regulations for the management of water resources; however, we believe that
unless there is a change in direction, it is reasonable to assume that the
water crop concept will be adopted in these other districts.


7.2 APPLICABILITY OF THE WATER CROP CONCEPT-LARGE AND SMALL AREAS

The water crop concept is an accepted hydrologic tool for determining
"rule of thumb" estimates of water availability in hydrologically isolated or
very large areas (several hundred square miles, or larger). It is inappropriate
as a tool for water resources allocation in small areas, such as a well field, a
packing plant, or a housing development.

The assumptions underlying basin averages that set the water crop equal
to a percentage of the average rainfall less the average evapotranspiration
are not applicable for a finite piece of property within a basin. While
surface and groundwater inflow and outflow may be considered equal in the
water budget formula to arrive at the water crop value, they may vary widely
for each finite parcel within the basin. The regional water crop calculation
of the SWFWMD assumes a constant evapotranspiration rate, while it may actually
vary widely both with the type of vegetation and the depth to the water table
in finite parcels. In areas where large withdrawals take place, a lowering of
the water table occurs and evapotranspiration can be substantially reduced.

The present method of regulation according to the water -crop concept
permits withdrawal of only that much water determined by water crop calculations
for the applicant's land ownership. There is no consideration of the fact that
local geology and aquifer productivity vary widely, such that recovery of the
water crop from some areas is difficult and costly, while in other areas
production in excess of the water crop is possible and desirable from a water
management standpoint. By limiting production to the water crop for all permit
applications, it is our opinion that ultimately there will be much less than full
utilization of the resource since significant yields from wells in some areas
will not be feasible or economical, while in some other areas, full use of
available supplies will not be required by the existing water user or landowners.

In many areas, pumping in excess of the water crop with alleviation of
adverse effects on the property of adjacent landowners, resulting from such
production, would represent a reasonable use of the water, consistent with the
public interest. However, experience to date suggests that regulatory agencies
often view such withdrawals as being unreasonable and inconsistent with the
public interest.


7-2









By taking this position, we believe that regulatory agencies have
substantially reduced the use of judgment as to whether a proposed use is
reasonable. The public interest has been interpreted to mean that the indi-
vidual landowner's reasonable use of his water is the full amount available'on
his property, whether he uses it or not and regardless of the proposed use.
While this management policy is easier to implement, it can only lead to much
less than optimum utilization of the resource, and higher costs to the people
of Florida. Ownership or purchase of water rights on large tracts of land,
with construction of numerous small well fields, pipelines, and treatment
facilities, is an unnecessary major expense that will result from this manage-
ment policy.


7.3 RAMIFICATIONS OF THE WATER CROP CONCEPT

The Water Resources Act of 1972 requires that in order to obtain a
consumptive use permit, an applicant must show that the intended use is a
reasonable, beneficial use; will not interfere with any legal use of water
existing at the time of the application; and is consistent with the public
interest. The act does not refer to either the water crop concept or to water
rights associated with land ownership. Water management authorities have, in
our opinion, frequently gone significantly beyond the mandate of the act by
introducing the water crop as a management tool, and by judging that a land-
owner's use of the full water crop from his property is a reasonable use,
regardless of whether or not such use is requested or likely to be requested,
and regardless of possible alternative uses by others. Ramifications of this
new direction are significant.

The immediate result is a limitation of density on new residential
developments. For example, assuming a domestic water consumption of 125 gallons
per capital per day, and the Southwest Florida Water Management District water
crop of 640,000 gpd/sq mi, a total population of 5,120 people per square mile
results. Assuming 2.9 people per unit, 1,766 residential units can occupy one
square mile. Each unit would require 0.36 acres, including its share of roads,
drainage facilities, etc. This is equivalent to a density of 2.8 units per
acre.

While this degree of constraint may have some short-term merit to slow
down growth and provide time for adequate future planning, there is no firm
indication that any intent exists to adjust these contraints in order to ensure
proper water management consistent with the long-term public interest. The
long-term impact of this management approach will be under-utilization of our
water resources with significant increases in cost to the people of Florida.
Municipal water systems will be forced to pay higher costs in order to develop
the water supplies needed by the community. These added costs are now begin-
ning to be felt, as new well fields, treatment and pumping facilities, and
pipelines are being planned, designed, and built to obtain water from new
areas. In some areas where alternative water sources are too expensive or
difficult to obtain, conservation and reuse measures are being implemented. To
the extent that these plans are based upon unnecessarily high alternative costs
due to administrative rules creating artificial water-supply shortages, they are
not in the public interest. As discussed in previous sections, Florida has ample
water resources requiring only proper management to ensure optimum utilization.


7-3








7.4 HOW MANY EXISTING MUNICIPAL WATER-SUPPLY SYSTEMS IN FLORIDA
COMPLY WITH THE WATER CROP REGULATION?

One of the conditions for issuance of a consumptive use permit by the
Southwest Florida Water Management District is in paragraph 16J-2.11 (3) of
its rules and regulations. This paragraph states:

Issuance of a permit will be denied if the amount of water consumptively
used will exceed the water crop of lands owned, leased, or otherwise
controlled by the applicant. (Except where determined otherwise, the
-water crop {precipitation less evapotranspiration} throughout the
District will be assumed to be three hundred sixty-five thousand
{365,000} gallons per year per acre.)

A requirement such as this does not appear in the rules and regulations
of the Central and Southern Florida Flood Control District. However, water
crop calculations have been used by staff members as one of the criteria to
grant or deny a consumptive permit to a municipality. As discussed previously,
the SWFWMD water crop estimate is equivalent to about 13 inches of rainfall.
This is also considered to be a reasonable estimate of the average water
crop calculated by CSFFCD for the coastal areas of that district, where
most of the municipalities are concentrated.

As part of this study, a survey was conducted to determine how many of
the existing municipal water systems in Florida comply with the water crop
regulation.

A letter questionnaire was sent August 20, 1975, to 150 municipal water
systems in the state of Florida which use groundwater as the only or main source
of supply.* The data requested were:

1. Average daily flow during last year.

2. Maximum daily flow during last year.

3. Total number of service connections as of July 1, 1975.

4. Number of wells in system. Other source?

5. Area owned or leased by system for well fields and any other ground-
water sources.

6. Extent of franchise area served.

7. Extent of number 6 above not on mainland, but on islands, keys,
beyond Intracoastal Waterway, etc.


*86 percent of the water withdrawn in Florida for municipal supply is ground-
water (see Table 5-1).


7-4









The results of 97 responses received within the time limit established
for the survey are in Table 7-4 at the end of this section. Table 7-1 compares
the actual well field or water resource area in acres owned or controlled by
each system (column 2) with that required by the water crop concept in acres
(column 4). Some systems show zero acres for well fields. This is because
their wells are along rights-of-way of streets, parks, golf courses, and other
municipal facilities, which are not mainly dedicated to water supply.

Of the 97 systems inventoried not a single one complies with the water
crop regulation in its strict interpretation. This actually means that of
those systems (including the largest ones in the state) none could presently
obtain a consumptive use permit if the water crop regulation was strictly
applied. The city of Fort Lauderdale (No. 29 on Table 7-1) would require
46,410 acres for well fields, while it actually has only 32.3 acres. The city
of Miami (No. 59: Miami-Dade Water & Sewer Authority) would require 187,700
acres, while it actually has only 540 acres.

A more relaxed interpretation of the water crop regulation is to consider
as "otherwise controlled by applicant" the entire area served or to be served
by the system, provided it is on the mainland. This interpretation is used
entirely at the discretion of the Board of SWFWMD and is applied in some cases
and not in others. Areas on keys, islands, and beyond the Intracoastal Waterway
are not considered as a part of the total service area, within this application
of the water crop regulation.

This relaxation in the interpretation of the water crop concept makes it
easier for the applicant to obtain a consumptive use permit. However, in our
opinion, this relaxation has serious legal ramifications. That is, if the
entire service area is considered as "otherwise controlled by the applicant,"
then owners within the area would have to surrender the "alleged right" of
their water crop allotment. If they do so, we cannot foresee how those owners
could have their own individual wells for lawn irrigation, cooling, self-
supplied industry, or whatever other consumptive use they may desire or
actually have under operation, without exceeding the water crop in the service
area.

Even when the service area on the mainland is included in the more
relaxed interpretation, there are 11 systems of those inventoried which do not
meet the area requirements, considering the average flow for the past year.
These systems are shown on Table 7-2. Included in the group are two of the
largest systems in the state: No. 29, Fort Lauderdale and No. 59, Miami-Dade
Water and Sewer Authority.

Table 7-3 includes 10 additional systems whose service areas are within
20 percent of the water crop requirements, considering last year's water
production. This means that those ten systems could not ever produce more
than a maximum of 20 percent over what they produced last year, even if the
relaxed interpretation is applied.

The difference between the service area on the mainland (in square miles)
and that required by the relaxed interpretation of the water crop regulation
can be noted by comparing columns 3 and 5 of Tables 7-2 and 7-3.


7-5










In general, the requirements for well fields owned or leased by the
responding water systems range from less than 1 percent to 25 percent of the
water crop requirements; while their service areas on the mainland range from
10 to 230 percent. The additional requirements to meet the water crop would
force Florida's water systems to purchase or condemn large quantities of land
for additional well fields, or the alleged water rights in the service area, or
both. This would be a very serious burden economically to those systems and
their users, most of them citizens of Florida.

Another significant issue regarding the relaxed interpretation of the
water crop regulation is that it excludes those portions of the service area
not on the mainland, such as keys, islands, and areas beyond the Intracoastal
Waterway. These areas include many of the state's urbanized or potential urban
communities. In order for these people to obtain water under the new regu-
lations, they would have to acquire water rights to large tracts of land on the
mainland, or make water supply arrangements with mainland communities that
would in turn acquire these additional water rights. As residents of Florida,
these people should have an equal right to water as those persons living on the
mainland.


7-6











TABLE 7-1. Comparison of Actual Well Field arid Service Areas of Water Systems in Florida
with Water Crop Requirements

Average Service
Daily Actual Well Area on Water Crop
Flow Field Area Mainland Requirements
No. City or System (mgd) (acres) (sq mi) (acres) (sq mi)


1 Alachua 0.245 0.3 2.0 245 0.38
2 Apalachicola 0.465 2.0 2.5 465 0.73
3 Archer 0.121 1.5 1.5 121 0.19
4 Auburndale 2.496 0.9 7.0 2,496 3.9
5 Avon Park 1.000 16.0 30.0 1,000 1.56
6 Bartow 2.940 2.0 13.5 2,940 4.59
7 Boca Raton 15.50 0.0 52.8 15,500 24.22
8 Boynton Beach 6.200 10.0 11.8 6,200 9.69
9 Brooksville 0.605 2.0 3.0 605 0.95
10 Broward County Utilities 17.00 40.0 32.0 17,000 26.56

11 Bunnell 0.221 7.0 2.0 221 0.35
12 Casselberry 1.400 4.2 8.0 1,400 2.19
13 Cedar Key Special W&S District 0.087 13.0 0.0 87 0.14
14 Chiefland 0.240 1.0 3.5 240 0.38
15 Chipley 0.400 0.0 3.3 400 0.63
16 Clermont 0.955 1.1 4.2 955 1.49
17 Cocoa 14.95 174.0 140.0 14,950 23.36
18 Cooper City 0.600 3.0 5.0 600 0.94
19 Dade City 0.800 2.0 -- 800 1.25
20 Daytona Beach 10.20 0.0 26.0 10,200 15.94

21 Deerfield Beach 6.100 0.0 9.7 6,100 9.53
22 DeFuniak Springs 0.580 0.0 -- 580 0.91
23 DeLand 3.900 0.0 12.0 3,900 6.09
24 Delray Beach 8.200 1.0 9.2 8,200 12.81
25 Dunedin 3.500 0.0 7.7 3,500 5.47
26 Edgewater 0.350 5.0 10.0 350 0.55
27 Eustis 2.100 6.0 8.0 2,100 3.28
28 Fernandina Beach 1.966 15.0 0.0 1,966 3.07
29 Fort Lauderdale 46.41 32.3 35.3 46,410 75.52
30 Fort Pierce 5.477 0.3 13.1 5,477 8.56

31 Frostproof 0.367 6.0 3.0 367 0.57
32 Gainesville 15.32 20.0 75.9 15,320 23.94
33 Green Cove Springs 0.392 0.0 1.0 392 0.61
34 Groveland 0.310 3.0 4.0 310 0.48
35 Haines City 1.688 -- 1,688 2.64
36 Hallandale 4.900 3.0 4.0 4,900 7.66
37 Havana 0.187 3.0 2.0 187 0.29
38 High Springs 0.320 1.0 5.0 320 0.50
39 Holly Hill 0.856 15.0 3.5 856 1.34
40 Hollywood 14.12 12.0 24.0 14,120 22.06

41 Immokalee 0.826 40.0 8.0 826 1.29
42 Jacksonville 56.41 1.1 168.0 56,410 88.14
43 Jasper 0.450 2.0 16.0 450 0.70
44 Key West-Florida Keys Aqueduct 7.800 0.0 0.0 7,800 12.19
45 Kissimmee 2.500 7.0 8.0 2,500 3.91
46 LaBelle 0.216 10.0 4.0 216 0.34
47 Lake Alfred 0.877 .- 877 1.37
48 Lake City 1.704 5.0 10.0 1,704 2.66
49 Lakeland 17.93 196.4 84.5 17,930 28.02
50 Lake Park-Palm Beach Co. Utilities 7.671 20.8 14.0 7,671 11.99


7-7










TABLE 7-1. Comparison of Actual Well Field and Service Areas of Water Systems in Florida
with Water Crop Requirements-Continued



Average Service
Daily Actual Well Area on Water Crop
Flow Field Area Mainland Requirements
No. City or System (mgd) (acres) (sq mi) (acres) (sq mi)

() 0 3 ) 3
51 Lake Wales 2.400 2.0 6.0 2,400 3.75
52 Lake Worth 5.440 65.0 5.5 5,440 8.50
53 Lauderhill 3.500 0.0 8.5 3,500 5.47
54 Leesburg 4.106 0.0 6.5 4,106 6.42
55 Lehigh Acres 0.576 -- 6.0 576 0.90
56 Lynn Haven 1.267 0.0 3.0 1,267 1.98
57 Madison 1.107 0.8 2.8 1,107 1.73
58 Margate 4.135 8.0 10.0 4,135 6.46
59 Miami-Dade W&S Authority 187.7 540.0 285.0 187,700 293.28
60 Milton 1.000 5.0 8.0 1,000 1.56

61 Mims-Brevard Co. Utilities 0.462 0.5 4.0 462 0.72
62 Miramar 2.574 0.9 10.0 2,574 4.02
63 Monticello 0.500 2.0 7.0 500 0.78
64 Naples 9.600 0.0 17.0 9,600 15.00
65 New Port Richey 1.790 600.0 4.5 1,790 2.80
66 New Smyrna Beach 2.253 80.0 8.2 2,253 3.52
67 Niceville 0.900 1.5 6.0 900 1.41
68 Ocala 6.000 32.0 22.0 6,000 9.38
69 Orlando Utilities Commission 40.96 60.0 150.0 40,960 64.00
70 Ormond Beach 3.300 20.0 31.0 3,300 5.16

71 Oviedo 0.350 0.0 50.0 350 0.55
72 Palatka 2.000 0.0 5.0 2,000 3.13
73 Palm Springs 1.546 5.0 2.3 1,546 2.42
74 Pensacola 23.90 0.0 100.7 23,960 37.44
75 Pinellas County Water System 34.51 6,600.0 175.0 34,510 53.92
76 Plant City 2.100 0.0 13.0 2,100 3.28
77 Pompano Beach 16.51 945.0 11.2 16,510 25.80
78 Port Orange 1.700 10.0 17.0 1,700 2.66
79 Quincy 1.220 0.0 6.0 1,220 1.91
80 Riviera Beach 5.500 0.0 4.7 5,500 8.59

81 St. Augustine 2.700 70.0 20.0 2,700 4.22
82 St. Petersburg 33.70 1,810.0 58.0 33,700 52.66
83 Sanford 4.300 0.0 11.0 4,300 6.72
84 Sarasota 7.290 2,000.0 12.4 7,290 11.39
85 Sebring 4.400 4.0 30.0 4,400 6.88
86 Siesta Key Utilities-Sarasota 1.200 1.0 0.0 1,200 1.88
87 Stuart 2.470 0.2 8.2 2,470 3.86
88 Sunrise 3.750 100.0 18.0 3,750 5.86
89 Tamarac 3.900 10.0 11.4 3,900 6.09
90 Tequesta 1.434 61.0 3.0 1,434 2.24

91 Titusville 4.000 10.0 26.0 4,000 6.25
92 Umatilla 0.175 5.0 1.3 175 0.27
93 Wauchula 0.868 10.0 -- 868 1.36
94 Williston 0.450 0.5 3.0 450 0.70
95 Winter Haven 5.629 226.5 34.0 5,629 8.80
96 Winter Park 12.60 8.2 23.4 12,600 19.69
97 Zephyrhills 0.700 2.0 3.5 700 1.09


7-8

















TABLE 7-2. Systems Not Meeting Water Crop Requirements Even When Total Service
Area on Mainland is Included as "Otherwise Controlled by Applicant"



Average Service
Daily Actual Well Area on Water Crop
Flow Field Area Mainland Requirements
No. City or System (mgd) (acres) (sq mi) (acres) (sq mi)


13 Cedar Key Special W&S District 0.087 13.0 0.0 87 0.14

19 Dade City 0.800 2.0 800 1.25

24 Delray Beach 8.200 1.0 9.2 8,200 12.81

29 Fort Lauderdale 46.41 32.3 35.3 46,410 75.52

36 Hallandale 4,900 3.0 4.0 4,900 7.66

44 Key West-Florida Keys Aqueduct 7.800 0.0 0.0 7,800 12.19

52 Lake Worth 5.440 65.0 5.5 5,440 8.50

59 Miami-Dade W&S Authority 187.7 540.0 285.0 187,700 293.28

73 Palm Springs 1.546 5.0 2.3 1,546 2.42

80 Riviera Beach 5.500 0.0 4.7 5,500 8.59

86 Siesta Key Utilities-Sarasota 1.200 1.0 0.0 1,200 1.88


7-9
















TABLE 7-3. Systems with Service Areas on Mainland Within 20 Percent of Required
Water Crop Area



Average Service
Daily Actual Well Area on Water Crop
Flow Field Area Mainland Requirements
No. City or System (mgd) (acres) (sq mi) (acres) (sq mi)

0 0 0 0( 0
8 Boynton Beach 6.200 10.0 11.8 6,200 9.69

10 Broward County Utilities 17.00 40.0 32.0 17,000 26.56

21 Deerfield Beach 6.100 0.0 9.7 6,100 9.53

40 Hollywood 14.12 12.0 24.0 14,120 22.06

50 Lake Park-Palm Beach Co. Utilities 7.671 20.8 14.0 7,671 11.99

54 Leesburg 4.106 0.0 6.5 4,106 6.42

64 Naples 9.600 0.0 17.0 9,600 15.00

82 St. Petersburg 33.70 1,810.0 58.0 33,700 52.66

84 Sarasota 7.290 2,000.0 12.4 7,290 11.39

96 Winter Park 12.60 8.2 23.4 12,600 19.69


7- 10











TABLE 7-4. Information from Water System Survey in Florida-September, 1975



Number of No. of Well Service
Daily Flow Service Wells in Field Area on
Average Maximum Connections System Area Mainland
No. City or System County (mgd) (mgd) (1975) (1975) (acres) (sq mi)


1 Alachua Alachua 0.245 0.500 980 2 0.3 2.0
2 Apalachicola Franklin 0.465 0.642 991 2 2.0 2.5
3 Archer Alachua 0.121 0.158 398 1 1.5 1.5
4 Auburndale Polk 2.496 3.500 3,692 4 0.90 7.0
5 Avon Park Highlands 1.000 1.600 3,400 5 16.0 30.0
6 Bartow Polk 2.940 4.224 5,096 11 2.0 13.5
7 Boca Raton Palm Beach 15.50 24.50 12,579 35 0.0 52.8
8 Boynton Beach Palm Beach 6.200 9.300 15,000 11 10.0 11.8
9 Brooksville Hernando 0.605 0.691 1,999 3 2.0 3.0
10 Broward County Utilities Broward 17.00 28.00 30,309 38 40.0 32.0

11 Bunnell Flagler 0.221 0.379 620 4 7.0 2.0
12 Casselberry Seminole 1.400 2.800 4,415 5 4.2 8.0
13 Cedar Key Special W&S District Levy 0.087 0.208 381 3 13.0 0.0
14 Chiefland Levy 0.240 0.320 700 2 1.0 3.5
15 Chipley Washirnton 0.400 0.500 1,430 3 0.0 3.3
16 Clermont Lake 0.955 2.900 1,646 3 1.1 4.2
17 Cocoa Brevard 14.95 20.99 24,437 19 174.0 140.0
18 Cooper City Broward 0.600 1.000 1,977 3 3.0 5.0
19 Dade City Pasco 0.800 1.800 2,638 4 2.0
20 Daytona Beach Volusia 10.20 12.70 17,265 12 0.0 26.0

21 Deerfield Beach Broward 6.100 10.15 14,932 16 0.0 9.7
22 DeFuniak Springs Walton 0.580 0.750 2,180 3 0.0
23 DeLand Volusia 3.900 5.800 6,037 7 0.0 12.0
24 Delray Beach Palm Beach 8.200 10.90 8,342 18 1.0 9.2
25 Dunedin Pinellas 3.500 6.000 8,095 15 0.0 7.7
26 Edgewater Volusia 0.350 0.529 1,600 2 5.0 10.0
27 Eustis Lake 2.100 3.300 4,230 3 6.0 8.0
28 Fernandina Beach Nassau 1.966 2.591 2,849 8 15.0 0.0
29 Fort Lauderdale Broward 46.41 60.74 46,666 57 32.3 35.3
30 Fort Pierce St. Lucie 5.477 6.543 10,913 24 0.3 13.1

31 Frostproof Polk 0.367 0.633 1,000 2 6.0 3.0
32 Gainesville Alachua 15.32 19.96 22,173 14 20.0 75.9
33 Green Cove Springs Clay 0.392 0.537 1,250 4 0.0 1.0
34 Groveland Lake 0.310 0.597 649 2 3.0 4.0
35 Haines City Polk 1.688 3.394 3,210 4 -
36 Hallandale Broward 4.900 6.970 22,502 7 3.0 4.0
37 Havana Gadsden 0.187 0.211 990 2 3.0 2.0
38 High Springs Alachua 0.320 0.430 1,100 1 1.0 5.0
39 Holly Hill Volusia 0.856 1.100 3,593 5 15.0 3.5
40 Hollywood Broward 14.12 18.10 28,784 19 12.0 24.0

41 Immokalee Collier 0.826 1.953 1,817 5 40.0 8.0
42 Jacksonville Duval 56.41 71.60 85,896 75 1.1 168.0
43 Jasper Hamilton 0.450 0.852 1,275 3 2.0 16.0
44 Key West-Florida Keys Aqueduct Monroe 7.800 8.900 22,000 11 0.0 0.0
45 Kissimmee Osceola 2.500 3.500 3,000 5 7.0 8.0
46 LaBelle Hendry 0.216 0.383 771 3 10.0 4.0
47 Lake Alfred Polk 0.877 1.196 1,100 3 -
48 Lake City Columbia 1.704 2.922 4,547 4 5.0 10.0
49 Lakeland Polk 17.93 32.71 28,400 32 196.4 84.5
50 Lake Park-Palm Beach Co. Utilities Palm Beach 7.671 11.88 9,969 26 20.8 14.0


7- 11










TABLE 7-4. Information from Water System Survey in Florida-September, 1975-Continued



Number of No. of Well Service
Daily Flow Service Wells in Field Area on
Average Maximum Connections System Area Mainland
No. City or System County (mgd) (mgd) (1975) (1975) (acres) (sq mi)

51 Lake Wales Polk 2.400 5.000 4,066 5 2.0 6.0
52 Lake Worth Palm Beach 5.440 10.04 10,152 14 65.0 5.5
53 Lauderhill Broward 3.500 5.000 4,360 6 0.0 8.5
54 Leesburg Lake 4.106 8.271 5,650 9 0.0 6.5
55 Lehigh Acres Lee 0.576 0.808 3,652 9 6.0
56 Lynn Haven Bay 1.267 3.000 1,621 2 0.0 3.0
57 Madison Madison 1.107 1.706 1,490 3 0.8 2.8
58 Margate Broward 4.135 7.282 8,451 8 8.0 10.0
59 Miami-Dade W&S Authority Dade 187.7 230.1 122,000 55 540.0 285.0
60 Milton Santa Rosa 1.000 1.400 3,500 5 5.0 8.0

61 Mims-Brevard Co. Utilities Brevard 0.462 1.200 425 3 0.5 4.0
62 Miramar Broward 2.574 3.015 8,806 9 0.9 10.0
63 Monticello Jefferson 0.500 0.687 1,025 3 2.0 7.0
64 Naples Collier 9.600 14.50 12,647 42 0.0 17.0
65 New Port Richey Pasco 1.790 3.380 5,134 6 600.0 4.5
66 New Smyrna Beach Volusia 2.253 2.738 5,401 5 80.0 8.2
67 Niceville Okaloosa 0.900 2.500 2,200 3 1.5 6.0
68 Ocala Marion 6.000 8.000 8,405 6 32.0 22.0
69 Orlando Utilities Commission Orange 40.96 73.33 63,314 21 60.0 150.0
70 Ormond Beach Volusia 3.300 3.800 8,429 16 20.0 31.0

71 Oviedo Seminole 0.350 0.500 750 3 0.0 50.0
72 Palatkab Putnam 2.000 3.800 4,000 9 0.0 5.0
73 Palm Springs Palm Beach 1.546 2.579 2,496 8 5.0 2.3
74 Pensacola Escambia 23.90 42.30 52,110 24 0.0 100.7
75 Pinellas County Water System Pinellas 34.51 44.54 53,635 64 6,600.0 175.0
76 Plant City Hillsborough 2.100 3.500 5,665 5 0.0 13.0
77 Pompano Beach Broward 16.51 25.00 13,250 16 945.0 11.2
78 Port Orange Volusia 1.700 2.600 4,900 5 10.0 17.0
79 Quincyc Gadsden 1.220 2.330 2,920 1 0.0 6.0
80 Riviera Beach Palm Beach 5.500 7.900 7,318 20 0.0 4.7

81 St. Augustine St. Johns 2.700 3.900 8,904 19 70.0 20.0
82 St. Petersburg Pinellas 33.70 46.30 88,157 37 1,810.0 58.0
83 Sanford Seminole 4.300 6.101 7,476 12 0.0 11.0
84 Sarasota Sarasota 7.290 9.600 15,286 52 2,000.0 12.4
85 Sebring Highlands 4.400 6.200 4,927 5 4.0 30.0
86 Siesta Key Utilities-Sarasota Sarasota 1.200 2.800 2,090 9 1.0 0.0
87 Stuart Martin 2.470 4.320 6,230 22 0.2 8.2
88 Sunrise Broward 3.750 5.980 6,716 15 100.0 18.0
89 Tamarac Broward 3.900 5.890 10,500 9 10.0 11.4
90 Tequesta Palm Beach 1.434 2.190 2,405 22 61.0 3.0

91 Titusville Brevard 4.000 7.000 9,261 49 10.0 26.0
92 Umatilla Lake 0.175 0.250 610 2 5.0 1.3
93 Wauchula Hardee 0.868 1.850 1,700 5 10.0
94 Williston Levy 0.450 3.000 870 1 0.5 3.0
95 Winter Haven Polk 5.629 11.52 11,132 12 226.5 34.0
96 Winter Park Orange 12.60 17.70 18,490 7 8.2 23.4
97 Zephyrhills Pasco 0.700 1.680 3,029 5 2.0 3.5


aSmall plot of land by each well, estimated 100' X 100' per well.
bRavine Gardens is additional source.
CCreek is additional source.
7- 12














SECTION 8


POSITIVE WATER MANAGEMENT-CRUX OF THE PROBLEM


8.1 WHAT IS POSITIVE WATER MANAGEMENT?

Full benefit of Florida's water resources can only be realized if positive
management is exercised by those regulatory agencies charged with the responsi-
bility of managing our water resources. Failure to exercise positive manage-
ment will lead to under-utilization of these renewable resources, with conse-
quent increase in cost to the general public. With the current rapidly
increasing costs in most sectors of the economy, the pursuit of a management
policy that promotes substantial and unnecessary higher costs for water
development and supply is questionable. It is, therefore, appropriate to ask,
"What is positive management?"

Positive water resources management may be defined as the making of sound
decisions to encourage reasonable conservation and use of existing water
sources, as well as to plan future supplies, in such a way as to minimize
total economic and environmental costs while promoting equitable distribution
of available water supplies. When based upon sound technical evaluation and
economic analysis, such decisions will tend to achieve optimum utilization of
Florida's water resources.


8.2 CONTRAST WITH PRESENT REGULATIONS

The control of water in Florida has emerged as a growth control tool.
Consequently, political considerations have substantially increased their
significance in the water resource decision-making process. In our opinion,
technical considerations have often weighed insignificantly in this process.
The result has been a trend toward regulatory decisions inconsistent with
optimum utilization of Florida's water resources. As the power of regulatory
agencies to manage our water resources increases, the consequences of such
decisions become more significant, resulting in rapidly mounting cost to the
people of Florida.

State regulatory agencies have apparently elected to implement, by admin-
istrative procedures, an interpretation of the 1972 Water Resources Act which,
in effect, focuses the thrust of water resources management practice in
Florida upon the use of water as a growth control tool. By limiting, and some-
times reducing, utilization of available water supplies by growth areas, over-
conservation of these supplies has resulted and growth has been temporarily
restrained. In certain areas they have overlooked the fact that growth in Florida
will continue, and that it must be carefully planned and provided for, years in
advance. We believe that these agencies are not promoting optimum utilization of


8 1









Florida's water resources, and are inadvertently introducing a level of
distortion into the public and private long-range decision-making process.
This distortion is based upon a shortage of water supply created by administra-
tive regulations, rather than from inadequate resources.

By contrast, positive water resources management would result in simul-
taneous optimum utilization of available water resources and planning for new
sources of water, with equitable distribution of available supplies and costs.
This approach would achieve minimum cost to the consumer and would encourage
necessary conservation of water and environmental protection as justified by
the increase in cost of supplying water from more distant sources.

The interpretation of existing law by which water may be used as a growth
control tool centers around the issue of "reasonable use." Large water users
have, for many years, pumped water that was often derived primarily from
recharge on surrounding property. In recent years, adverse effects sometimes
resulting from such production have led to development of legislation providing
for reasonable, beneficial use of water, consistent with the public interest.
The 1972 Water Resources Act represents the most recent landmark in the devel-
opment of such legislation. Under the provisions of the act, one interpretation
is that a proposed use of water should be balanced against the need for that
water by other users, in order to determine the most reasonable, beneficial use.
Unfortunately, current interpretation of the law has frequently found municipal
water use for more populated areas to be unreasonable when compared to
existing or possible future use of that water by individual landowners. In
our opinion, this current interpretation of the law effectively removes from
most of the people of Florida their right to reasonable use of available water
resources and gives this right to the landowners of Florida, who may use, not
use or sell it as they wish.

Rules and regulations for management of surface and groundwaters have
been adopted, or are in process of adoption, for each of Florida's water
management districts created by the 1972 Water Resources Act. Each of the
adopted rules is different, reflecting variations in hydrologic characteristics
of the area and differing philosophical and political approaches to water
management. Common to each approach, whether spelled out in the rules or
incorporated into their implementation, is the utilization of the "water crop"
concept, which relates water allocation to land ownership. Other criteria are
also spelled out or utilized, some of which are designed to protect the water
resource and others to protect adjacent landowners from excessive drawdowns or
adverse effects caused by water production. Many of these criteria are
arbitrary and represent an attempt to define indicators which, when exceeded,
are assumed to result in unacceptable adverse effects.

These rules and regulations provide the governing boards with wide
latitude to select those criteria which they deem pertinent to each
individual case. Unfortunately, experience to date suggests that, with this
latitude and with the current frequent interpretation of "reasonable use"
discussed above, water management decisions are increasingly reflecting an
attempt to control growth by limiting utilization of available water
resources to levels below those which the resource can safely supply.
Such decisions will cost the people of Florida substantial sums of money
for acquiring additional land or "water rights," building new sources,
new pipelines, pumping stations, and related facilities to supply


8-2


__









the balance of the demand not covered by the application of the water crop and
other criteria to existing or proposed fields. Positive water management would
avoid these unnecessary costs.

The application of administrative rule to relate water use to water
rights associated with land ownership will require the public purchase of
"water rights" from the landowner for water pumped from the aquifer under his
land. In essence, the public is being asked to purchase the recharge capability
of the owner's land.


8.3 ALTERNATIVE MANAGEMENT TOOLS IN LOCAL PROBLEM AREAS

Better alternatives to existing management practices are available,
all of which require an understanding of Florida's water resources and
associated problems. The allocation of water based upon land ownership and the
present interpretation of "reasonable use" is a relatively simplistic tool that
avoids the need for consideration of other factors requiring a more thorough
understanding of the problem. It is, therefore, easier to manage with this
approach, but leads to management decisions that, in our opinion, are fre-
quently not in the public interest.

The amount of water available to a water user in any given area is
established by the consumptive use permit process. Each consumptive use permit
should be issued according to certain criteria, many of which are set forth in
the 1972 Water Resources Act. The intended use should: (1) be a reasonably
beneficial use; (2) not interfere with any presently existing legal use;
(3) not harm the resource; (4) not cause significant adverse effects upon the
environment; and (5) be consistent with the public interest.

Based upon these criteria, a reasonable alternative management approach
can be developed that overcomes the problems associated with the present
management practices. This new approach would follow the same general
procedures utilized at present by SWFWMD and by CSFFCD, but with two critical
modifications.

1. The water crop concept would be utilized only as an overall indicator
of water availability in large areas with reasonably well defined
hydrological boundaries, such as a basin, and should not be applied to
each individual permit.

2. When water demand approaches availability within a basin the
management authority would evaluate all technical and related
considerations, and would allocate water between competing users
based upon a reasonable, beneficial use, consistent with the public
interest. This would be based on the concept that the water
resources of the state are held in public trust to serve the best
interest of all the people of Florida. In every case, there would be
provisions for positive measures by the water users, designed to
alleviate adverse effects upon surrounding property, attributable
to water production. Such measures would be an integral part of
the evaluation and management decision regarding the reasonableness
of proposed water uses.


8-3








For instance, a major well field supplying water for several thousand
people quite often causes lower groundwater levels and sometimes lower lake
levels and ecosystem changes on surrounding lands, particularly during dry
weather periods. To reduce production at such a well field to a level consis-
tent with the water crop on well field property or service area would almost
certainly alleviate these adverse effects, but at tremendous cost to develop
alternate water sources.

Reducing well field production to a level greater than the water crop that
still alleviates the adverse effects on adjacent land would ultimately require a
greater number of well fields to supply a given demand for water. By constructing
more well fields and associated pipelines and treatment facilities, the cost of
water to the consumer increases substantially.

A third alternative would be to provide for positive measures by the well
field user to alleviate significant adverse effects on surrounding property, to
the extent that adverse effects are caused by well field production. Adjacent
wells can be deepened and pump modifications can be made; small control struc-
tures can be provided on nearby lakes to retain storm runoff; wells can be
drilled to augment lake levels; water can be diverted from the well field to
maintain a high water table in critical areas; and other innovative measures
can be implemented to alleviate adjacent adverse effects. Experience has
shown that this type of approach is generally far less costly than either of
the previous two alternative approaches. In the event that such measures are
not feasible or become too costly, the well field owner will find it more
economical to build a new well field or to acquire more adjacent land.

In the typical case, all three of these alternatives may be consistent
with protection of the resource and the environment against adverse effects.
However, the first alternative will definitely lead to significant under-
utilization of the resource, and maximum total cost to all water users. The
second alternative may lead to under-utilization and consequent increased cost,
depending upon the constraints imposed. Only the third approach achieves
optimum resource utilization at minimum cost, and should therefore be considered
reasonable and in the public interest.

The third approach is typical of positive water management. It requires
understanding of the problem, careful evaluation of the alternatives, and a
management decision based upon sound hydrologic principles.

Many of Florida's current water shortage problems are in our opinion a
shortage of positive water management. Use of innovative management tools such
as those discussed above, combined with hydrologically sound, long-range
planning for water supplies, can resolve many of our current problems and
provide for future water demands, thereby achieving full utilization of the
resource at minimum cost to the people of Florida.

Many other management tools are available. Improved drainage practices
would provide the necessary flood protection for some developed areas while
maintaining higher groundwater levels, thereby increasing water supplies in
storage. Implementation of constraints upon building or rebuilding in flood-
prone areas will ultimately provide greater flexibility to water management
authorities to maintain more water in ground storage. Due consideration should


8-4









be given to the increase in the regional water availability resulting from
evapotranspiration reduction caused by groundwater withdrawals. Storage of
storm runoff in conservation areas and in Lake Okeechobee would also increase
water availability. Underground storage of storm runoff in aquifers could
facilitate subsequent reuse during dry weather periods to maintain aquifer
levels. Artificial recharge or additional substantial storage with minimum
free surfaces exposed to the atmosphere can significantly increase available
water. Adequately treated effluent from wastewater facilities will soon be used
to irrigate golf courses, public parks, and median strips in the city of St.
Petersburg, thereby significantly reducing municipal demand for potable water
supplies. Similarly, adequately treated effluent can possibly be utilized to
create saltwater intrusion barriers in saline, coastal aquifers. All of these
alternatives cost money, and yet as the cost of other sources of water increases,
these become viable, cost-effective alternatives. Positive water management
will ensure that each is evaluated against the true cost of optimum utilization
of all existing water resources.

The state must clarify the desired objective of reasonable, beneficial
use of this renewable resource consistent with the interest of all the people
of Florida. Such clarification should also provide a management framework
designed to achieve this objective through decisions based primarily upon
sound technical evaluation, as well as full consideration of legal, political,
economic, and other related criteria.


8- 5








REFERENCES


Ardaman, M. E. "Springs and Sinkholes: Blessings and Curses." Journal of the
Florida Engineering Society. November, 1969, pp. 8-10.

Bermes, B. J., G. W. Leve, and G. R. Tarver. "Geology and Ground-Water Resources
of Flagler, Putnam, and St. Johns Counties, Florida." Florida Geological
Survey Report of Investigations No. 32. 1963.

Black, A. P., E. Brown, and J. M. Pearce. "Salt Water Intrusion in Florida."
Water Survey and Research Paper No. 9. State Board of Conservation.
Tallahassee, Florida. 1953.

Brown, D. W., W. E. Kenner, J. W. Crooks, and J. B. Foster. "Water Resources of
Brevard County, Florida." Florida Geological Survey Report of Investi-
gations No. 28. 1962.

Clayton, B. S., J. R. Neller, and R. V. Allison. "Water Control in the Peat
and Muck Soils of the Florida Everglades." Florida Agricultural
Experiment Station Bulletin No. 378. 1942.

Cooper, H. H., Jr. and V. T. Stringfield. "Ground Water in Florida." Florida
Geological Survey Information Circular No. 3. 1950.

Cross, W. P. and S. K. Love. "Ground Water in Southeastern Florida." Journal
of the American Water Works Association. Vol. 34. 1942, pp. 490-504.

Ferguson, G. E., C. W. Lingham, S. K. Love, and R. 0. Vernon. "Springs of
Florida." Florida Geological Survey Geological Bulletin No. 31. 1947.

Florida Geological Survey. "Your Water Resources." Water Leaflet No. 1.
Tallahassee, Florida. 1963.

Groundwater and Wells. Johnson Division, Universal Oil Products Co. St. Paul,
Minnesota. 1972.

Haeussner, T. E. "Water Resources for Central and Southern Florida." Presented
at the annual meeting of the Florida Section of the American Water Works
Association and the Florida Water Pollution Control Association.
Hollywood, Florida, November 2, 1970.

Hyde, L. W. "Principal Aquifers in Florida." U.S. Geological Survey Map Series
No. 16. May, 1965.

Kenner, W. E. "Runoff in Florida." U.S. Geological Survey Map Series No. 22.
July, 1969.

Kenner, W. E. "Stage Characteristics of Florida Lakes." Florida Geological
Survey Information Circular No. 31. 1961.

Kenner, W. E., E. R. Hampton, and C. S. Conover. "Average Flow of Major Streams
in Florida." U.S. Geological Survey Map Series No. 34. 1969.








Landrum, N. C. "Florida's Fresh Water Lakes." Civic Information Series No. 33.
Public Administration Clearing Service of the University of Florida.
1959.

Murray, C. R. and R. E. Bodette. "Estimated Use of Water in the United States
in .1970." U.S. Geological Survey Circular 676. 1972.

Parker, G. P. "Geologic and Hydrological Factors in the Perennial Yield of the
Biscayne Aquifer." Journal of the American Water Works Association.
Vol. 43. 1951, pp. 817-835.

Peek, H. M. "The Artesian Water of the Ruskin Area of Hillsborough County,
Florida." Florida Geological Survey Report of Investigations No. 21.
1959.

Pride, R. W. "Estimated Use of Water in Florida, 1970." Information Circular
No. 83. Bureau of Geology, Department of Natural Resources. Tallahassee,
Florida. 1973.

Raiz, E. et al. Atlas of Florida. University of Florida Press. Gainesville,
Florida. 1964.

Rossenau, J. C. and G. L. Faulkner. "An Index to Springs of Florida." U.S.
Geological Survey Map Series No. 63. 1975.

Thompson, D. G. "Problems of Ground Waters in Florida." Journal of the American
Water Works Association. Vol. 23. 1931, pp. 2055-2100.

Visher, F. N. and G. H. Hughes. "The Difference Between Rainfall and Potential
Evaporation in Florida." U.S. Geological Survey Map Series No. 32.
August, 1969.

Wilson, A. and K. T. Iseri. "River Discharge to the Sea from the Shores of the
Conterminous United States, Alaska and Puerto Rico. United States
Geological Survey Hydrologic Investigations Atlas HA-282. 1969.

Windham, S. R. Florida Bureau of Geology. Personal Communication, 1974.

Wood, Dr. R. and Dr. E. A. Fernald. The New Florida Atlas. Trend House.
Tampa. 1974.













































APPENDIX


~II












APPENDIX *



The Theoretical Basis for Salt Water Intrusion

(The Ghyben-Herzberg Principle)


The basic requirement for the infiltration of salt water into
fresh water is that they be either in direct contact or separated
by a relatively permeable aquifer. This condition exists through-
out much of the perimeter of Florida as the ground water of the
Coastal Lowlands is separated from sea water by formations
that are, for the most part, porous and permit the passage of
water quite readily.

Sea water isheavier than freshwater and when the two come
together in permeable formations there will be a tendency for
the heavier sea water to displace the lighter fresh water.

The piezometric relationship between salt and fresh water,
known as the Ghyben-Herzberg Principle, has been summarized
by Brown.(27) This principle may be expressed mathematically:
H = h + t = hg or h = -T (See Fig. 3) where h is the depth of
fresh water below sea level,t is the height of fresh waterabove
sea level, and g is the specific gravity of sea water. The
value of g varies from 1.024 to 1.026,(4) being heater in the
deeper parts of the ocean and less near coastal areas where
sea water is diluted by fresh water discharged from rivers and
off-shore springs. As applied in actual practice, the equation
indicates that for each foot of fresh water which lies above
mean sea level, salt water will be depressed in the permeable
aquifer to a depth of 38.4 feet to 41.7 feet below mean sea
level. Taking 1.025 as the value commonly found along coastal
areas, it is easily seen that for each foot of fresh water head,
salt wzter is dep essed 40 feet below mean sea level. It may
be safely assured that in a coastal area where the fresh water
head is maintained at a minimum height, for example of 4 feet


above sea level, the maximum height to which salt water will
rise in the underlying formations will be 160 feet below mean
sea level. In the inland portions of the peninsula, salt water
occurs onlyat great depths,due to thehighpiezometric surface,
as well as to intervening impervious layers. In coastal areas,
where the piezometric surface is low, salt water may be found
at moderate depths. In such cases, sea water may invade fresh
water supplies either laterally or vertically, if the fresh water
head is sufficiently lowered. If an impervious formation seals
off the aquifer from the saline water below, only lateral intru-
sion may then occur, either from the ocean itself or by seepage
of saline water directly into the aquifer from tidal canals or
streams. In some of the coastal areas, of course, the piezo-
metric surface is sufficiently high to effectively prevent either
type of intrusion. The draft from a well creates a "cone of de-
pression," or lowering of the piezometric head. The extent of
this cone depends on the permeability of the aquifer and the
rare at which the water is withdrawn from the well. If the draft
is heavy, the cone may vertically deepen to a source of salt
water or laterally extend to salt water. A well that may be safe-
ly pumped at a given rate today may not be pumped at the same
rate in the future, if the overall fresh water head of the area is
lowered, either from excessive withdrawal elsewhere, or ex-
cessive surface drainage into the ocean. In some coastal areas,
salt water intrusion may be controlled by construction of con-
trol works in the canals(28,60'63); in others, the only solu-
tion may be abandonment of the well field and location of
another farther inland, where the tresn water le-ad can oe main-
tained at a sufficiently high level to prevent salt water intru-
sion.


U V





The basic principle is thao of bulonced w ghts.
1 cubic foot of sea water weigh. 64.06 Ibs.
I cubic foot of fresh waolf weighs 62.5 I s.

Thus solt waort 640 o, 1.025 tm.s as heavy
62.5
as Ireshwater ondo column of salt w.atr L fet
in hoght w.ll balance a column of fresh ot.,
(1.025) L fee* in heSght.


A. BASIC PRINCIPLE


Connect the solt and fresh wo!er columns shown
in A by o connecting tube and add a reservoir,
to the top of the so!t water column. The result
.s fhown obove. Then as *KplaIned in A,
H = 1.025 L
or h I 1.025 L = 1.025 h
h : --'- ... = ..- -.'
(1.02S 1) .025
s.n t 1., h 40.
Hen.r for every foot of flesh we., above soee
lvi there or. 40 eelt of flesh eotr below .o
level.


B. BASIC PRINCIPLE APfI'PIFD TO FRESH
WATER HEAD


'2



h2



I





Lower the surface of the fresh water column
shown in and ,e r..esult a shown obove. The
fresh wtelhed Is now t2and- by equoton shown
in B,


As a result of lowernq the fresh woatr surface.
thesolt waItrhos ,lseaol thelelt tub. on amount
oqual to (h h2).
B h t t( t t2
0 25 .025 .025

So whon ( t2) 1 (h h2) 40
Hfnclinr veryfoot of *Irnwd.wn if ofreth *a'*'
toIl. the sotul wait hneaulh the ireh witer ar ll
rQse 40 .eet.

C. BASIC PRINCIP I." APPLIEfD ro DkAW
DOWN


FIGURE 3. Explanation of the Ghyben-Herzberg Principle























FIGURE 3A. General Relation between fresh and salt water. A is a cross section of a small island
or peninsula of permeable sand showing general relationship between fresh and salt water. B
shows relation between fresh and salt water under artlsianr conditions. /ron- Journal AWWA,
October, 195/. "Gpological and Hydrologic Factors Affe-ctirq Perrnnil i>eld of Aqulfers"
by V. T. Sfringfeld and H. H. Cooper. I


REFERENCES


(4)Henry, Clarence R. "Improvements to Hialeah Treatment Plant." JAWWA.
Vol. 41, No. 152. 1949.
(28)
(28)Parker, G. G. "Geologic and Hydrologic Factors in the Perennial Yield of
the Biscayne Aquifers." JAWA. Vol. 43, No. 817. 1951.

(60)Stringfield, F. T. "Ground Water Resources of Sarasota County, Florida;
and Exploration of Artesian Wells in Sarasota County, Florida." FGS,
23-24 Annual Report. 1933.


(63)
( Vorhis, Robert
Florida. FGS,


C. "Geology and Ground Water of the Fort Lauderdale Area,
Report of Investigations 6. 1948.


*Reproduced from: Black, A. P., E. Brown, and J. M. Pearce. Salt Water
Intrusion in Florida 1953. Water Survey and Research Paper No. 9. 1953.




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