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 Title Page
 Florida Board of Conservation
 Letter of transmittal
 Preface
 Table of contents
 Abstract and introduction
 Physical description
 Relation of ground water to...
 Water budget
 Methods of controlling Brooklyn...
 Conclusions
 Copyright


FGS



Hydrology of Brooklyn Lake near Keystone Heights, Florida ( FGS: Report of investigations 33 )
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 Material Information
Title: Hydrology of Brooklyn Lake near Keystone Heights, Florida ( FGS: Report of investigations 33 )
Series Title: ( FGS: Report of investigations 33 )
Physical Description: viii, 43 p. : maps, diagrs., profiles, tables. ; 24 cm.
Language: English
Creator: Clark, William E
Geological Survey (U.S.)
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1963
 Subjects
Subjects / Keywords: Hydrology -- Florida -- Brooklyn Lake region   ( lcsh )
Brooklyn Lake   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by William E. Clark and others
General Note: "Prepared by the United States Geological Survey in cooperation with the Florida Geological Survey."
 Record Information
Source Institution: University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000958529
oclc - 01723222
notis - AES1339
lccn - a 63007692
System ID: UF00001220:00001

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Table of Contents
    Title Page
        Page i
    Florida Board of Conservation
        Page ii
    Letter of transmittal
        Page iii
        Page iv
    Preface
        Page v
        Page vi
    Table of contents
        Page vii
        Page viii
    Abstract and introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
    Physical description
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
    Relation of ground water to lake
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 15
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
    Water budget
        Page 36
        Page 37
        Page 38
        Page 39
        Page 35
    Methods of controlling Brooklyn Lake
        Page 40
        Page 41
        Page 42
        Page 39
        Page 43
    Conclusions
        Page 43
    Copyright
        Copyright
Full Text



STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director





REPORT OF INVESTIGATIONS NO. 33








HYDROLOGY OF BROOKLYN LAKE
NEAR
KEYSTONE HEIGHTS, FLORIDA

By
William E. Clark, Rufus H. Musgrove,
Clarence G. Menke, and Joseph W. Cagle, Jr.


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY


Tallahassee
1963






vo, 33

AGRI.
FLORIDA STATE BOARD JLTURAL
LIBRARY
OF

CONSERVATION


FARRIS BRYANT
Governor


TOM ADAMS
Secretary of State



THOMAS D. BAILEY
Superintendent of Public Instruction



RAY E. GREEN
Comptroller


J. EDWIN LARSON
Treasurer



RICHARD ERWIN
Attorney General



DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director






LETTER OF TRANSMITTAL


Jlorida ceoloilcal Survey

Callahassee

February 18, 1963

Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida

Dear Governor Bryant:

The Florida Geological Survey is publishing, as Report of In-
vestigations No. 38, a study on the "Hydrology of Brooklyn Lake
near Keystone Heights, Florida." This report was prepared by a
number of geologists and engineers, working with the U. S. Geo-
logical Survey, in cooperation with the Florida Geological Survey.
The study was undertaken, because of the serious depletion of
water levels during the severe drought of 1954-58, as a means of
determining the relationship of the lake water to shallow ground-
water levels and to artesian water levels. This is a comprehensive
study of these lakes and water levels, which will be helpful in de-
signing control structures for the control of the levels of the series
of lakes that extend from Blue Pond to Lake Geneva.

Respectfully yours,
Robert 0. Vernon
Director and State Geologist























































Completed manuscript received
December 20, 1962
Published for the Florida Geological Survey
Tallahassee, Florida
1963

iv








PREFACE


This report was prepared by the Water Resources Division of
the U. S. Geological Survey in cooperation with the Florida
Geological Survey. The investigation was under the general
supervision of M. I. Rorabauigh and C. S. Conover, successively
district engineer, Branch of Ground Water; A. 0. Patterson, district
engineer, Branch of Surface Water; and J. W. Geurin, district
chemist; and K. A. MacKichan, succeeding district engineer,
Branch of Quality of Water, U. S. Geological Survey.










TABLE OF CONTENTS

Abstract ....--- .. --..................... ... ........................................-.....-............-- 1
Introduction .-------------....... -----.............. -------........................ ---------....................... ..... 2
Purpose and scope .--.---..........-------------..... -----.............----------..-.......-.......----.....--- 2
Rainfall -...... ......................... ................. ...........................-.. ...- 4
Physical description ...........................................................-----------------------------.............----..6------6
Surface drainage ...--- --------------------.................. .......... ................-......-- ..---------.....----- 6
Stage fluctuations ..--...............-- ..-....---- --.--.. -------....---..... --............----- -..---...... 6
Depths and storage ---..........-----....................... ................---...----.........--------- -- 9
Chemical quality and temperature of water .-.---.....-----....--......--.......--. 10
Relation of ground water to lake ...........-....-....------...----.....-------.......-----.....-.............---.. 15
Water-table aquifer ......-....-----..--....------.. ----...-....--..... --------------.. .................------. 19
Confining bed --...------..................------....................................----- .....-..--............- 31
Floridan aquifer --------..-..-...------......----.............................---------..--..............-....--..---------..--... 32
Water budget ..---...-..-....--------------......-.....------- ---------............. -------.................-- .--.---. 35
Methods of controlling Brooklyn Lake ..-.............-----------------....---------............--- 39
Conclusions ---..-------....---........ ..-------------..-.---- ...-.......--.--.......------ 43


ILLUSTRATIONS

Figure Page
1 Location of Brooklyn Lake area -----..-..-.....--............-......----------................--------........ 3
2 Bar graph of annual rainfall for the period 1900-60 at
Gainesville, Florida ....--..----.......................-----------....... ..............-- ...-------.. 5
3 Surface drainage of Etonia Creek basin ......-------..---.....................------.. -- 7
4 Profile and location of chain of six lakes in the upper Etonia
Creek basin ........---.---......---..-------................. -----.......... -----........ --............... 8
5 Stage graph of Brooklyn Lake ....-.......-.....-----..------.......-----........-..-......................------------.... 9
6 Brooklyn Lake showing lines of equal depth at lake-surface
elevation of 117 feet above sea level --.---............ .-............-- .......----...............------ 11
7 Brooklyn Lake showing lines of equal depth at the record-low
elevation of 97.2 feet above sea level ...--.--..--..............----..............--...------... 12
8 Curve showing relation of lake stage to lake storage ..--..--....----....--....--- 13
9 Relation of pH to depth of water occurrence, near Brooklyn Lake _. 15
10 Temperature profiles in Brooklyn Lake on May 9, 1960 and
November 28, 1960 .--.........-------.....................--......--........---------...--.....-..------...----..-..--... 16
11 Brooklyn Lake area showing locations of wells and giving
an explanation of the well-numbering system --.-------------- 17
12 Brooklyn Lake area showing the locations of sections A-A',
B-B', C-C', and D-D' -----------...........-...-.....-......--.............-----------..............---..-...--. 19
13 Section showing geologic formations, hydrologic units, and
types of material in the Brooklyn Lake area along line A-A'
in figure 12 ..........------------.............................................................................. 20
14 Section showing hydrologic units in the Brooklyn Lake area
along line B-B' in figure 12 ...-......-----------------................................--..............-------------... 20
15 Section showing hydrologic units in the Brooklyn Lake area
along line C-C' in figure 12 -... ..-....--. ..... .... 21
16 Section showing hydrologic units in the Brooklyn Lake area
through a filled sink along line D-D' in figure 12 .........-------------........--......... 22







ILLUSTRATIONS (Continued)

17 Brooklyn Lake area showing contours on base of the water-
table aquifer ..-------.... -......................................---------------............................... 24
18 Brooklyn Lake area showing contours on the water table on
March 22, 1960 ..............-------.............---------------.....-----.......-.........-...............................---------..... 25
19 Brooklyn Lake area showing contours on the water table
on October 17, 1960 .------------..--...........------...............--..........-...................---------------......--....-...-.. 26
20 Hydrographs of well 947-202-14 and Brooklyn Lake .-....-...-...--.-------...-..... 28
21 Hydrographs of wells 948-202-5 and 948-202-7, and
Brooklyn Lake ..-..-......-----------------...........................--.....-.............--------......-..--..---..-.......... 29
22 Hydrographs of wells 948-201-8, 948-201-10, and 948-201-13,
and Brooklyn Lake -....-.............-.....................------------------..-..-.....----..................-.....---.--.--..... 30
23 Hydrograph showing the water level in well 947-201-4 ......-..-...-.......----------. 34
24 Brooklyn Lake area showing contours on the piezometric
surface of the Floridan aquifer in June 1960 --..--...........--.--...........-.........-- 36
25 Water budget of Brooklyn Lake for the period October 1957
to September 1960 -......--....---.........-----------..................---.--.--..-......................--------.......------. 38
26 Stage graph of Santa Fe Lake and profile from Santa Fe
Lake to Brooklyn Lake ....--------.. ---.. --...-..-------...-....--....-...------ 42


Table Page
1 Average, maximum, and minimum mineral content and tem-
perature of Brooklyn, Magnolia, and Sandhill lakes ...-....-.........-------.....-..... 14
2 Geologic formations, hydrologic units, and their water-
bearing characteristics in the Brooklyn Lake area, Clay
County, Florida ..-..........--- .----- --................................ ...... .....-----------------..........-... 18


viii







HYDROLOGY OF BROOKLYN LAKE
NEAR KEYSTONE HEIGHTS, FLORIDA

By
William E. Clark, Rufus H. Musgrove
Clarence G. Menke, and Joseph W. Cagle, Jr.

ABSTRACT

Brooklyn Lake receded about 20 feet during 1954-58 and reached
its lowest stage of record (97.2 feet) in February 1958; this was
the lowest stage in the memory of longtime residents. This un-
usually large recession was a result of deficient rainfall during
more than a 3-year period, January 1954 to May 1957. However,
by October 1959, after 21/. years of above normal rainfall, the
lake had recovered and water was flowing through the surface
outlet.
Brooklyn Lake is the fourth lake from the head of a chain of
lakes situated in a group of high sandhills in the upper Etonia
Creek basin. The sands covering this part of the basin are porous.
Consequently, seepage rates are high and surface runoff is exceed-
ingly low.
The dissolved solids content of Brooklyn Lake water ranged
from 19 to 34 ppm (parts per million) during the period July 1957
to June 1960. The pH values of the water ranged from 5.1 to 5.7.
Seepage from the lake is apparently effective in localized lowering
of the pH of the ground water. Temperature measurements
during November 1957 and May 1960 indicate seasonal variation
in temperature and degree of stratification.
The sediments that underlie Brooklyn Lake comprise three
hydrologic units-the water-table aquifer, the confining bed, and
the Floridan aquifer. The water-table aquifer, the uppermost unit,
is composed of sand, clay, limestone, and marl beds that have an
aggregate maximum thickness of about 100 feet. The underlying
confining bed is composed of relatively impermeable deposits that
are as much as 130 feet thick. The lowermost unit, the Floridan
aquifer, is composed of a series of permeable limestone, dolomite,
and dolomitic limestone beds that are more than 900 feet thick. At
places, the confining bed has been breached by collapse of the
underly Floridan limestone, or displaced by what may be faults or
fractures.






FLORIDA GEOLOGICAL SURVEY


Brooklyn Lake both loses and gains water from the water-table
aquifer. During the period March through October 1960, about 400
acre-feet more water left the lake than entered the lake through
the water-table aquifer. Water leaks from the lake into the
Floridan aquifer through old filled sinks that perforate the confining
bed, and water also probably seeps downward to the Floridan aqui-
fer through the confining bed especially where it is thin.
A water budget computed for a 3-year period, October 1957
through September 1960, indicated about 30,000 acre-feet of water
entered the lake by surface inflow and precipitation directly to the
lake. This is more than twice the amount of water than can be
stored in the, lake at any time. Slightly more than 10,000 acre-feet
of the water entering the lake went to lake storage. The remaining
20,000 acre-feet was removed from the lake in three ways:
seepage, 55 percent; evaporation, 35 percent; and surface outflow,
10 percent. Seepage accounted for an average daily loss of about
3 million gallons during the 3-year period. An average of about 8
mgd (million gallons per day) recharged the Floridan aquifer
during the 8-month period, March to October 1960. The amount of
water evaporated from the lake surface was essentially equal to
that contributed directly by rainfall.
Three possible methods of increasing inflow to help maintain a
normal lake stage during periods of deficient rainfall are: (1) by
carefully pumping from the Floridan aquifer at strategic sites; (2)
by increasing storage in upper lakes during periods of excess rain-
fall; and (3) by diversion of water from Santa Fe Lake. Plans to
control the stage of Brooklyn Lake should be based on detailed
engineering studies.




INTRODUCTION

PURPOSE AND SCOPE
The level of Brooklyn Lake, near the city of Keystone Heights
in southwestern Clay County, fluctuates widely (fig. 1). As a
consequence both permanent and summer residents, who have
built many houses on its shores are concerned. Local organizations
and officials realized the need for determining the reason for the
wide fluctuations and prompted an investigation. This report ex-
plains why the lake level fluctuates widely and furnishes informa-
tion for planning methods of regulating the lake level.






REPORT OF INVESTIGATIONS No. 33


8e*os


Figure 1. Location of Brooklyn Lake area.


The investigation was made by the U. S. Geological Survey at
the request of and in cooperation with the Florida Geological Sur-
vey. The investigation of the lake was part of an investigation of
the water resources of Alachua, Bradford, Clay, and Union
counties. The results of this four-county study are contained in
reports entitled "Water Resources of Alachua, Bradford, Clay, and






FLORIDA GEOLOGICAL SURVEY


Union Counties, Florida," and "Water Resources Data of Alachua,
Bradford, Clay, and Union Counties, Florida" by William E. Clark,
Rufus H. Musgrove, Clarence G. Menke, and Joseph W. Cagle, Jr.
to be published by the Florida Geological Survey. The report of
the Brooklyn Lake area was prepared chiefly for the convenience
of the reader who is interested primarily in that aspect of the
investigation.
Information is given in this report on the surface drainage,
fluctuation of stage, depth, mineral content, and temperature of
Brooklyn Lake. The earth materials underlying and surrounding
the lake are described, and the movement of water into and out
of the lake from these materials is discussed. Various ways that
the lake gains and loses water are discussed and evaluated to de-
termine if downward leakage occurs. Finally, some methods for
regulating the stage of the lake are considered.


RAINFALL

Brooklyn Lake receives all its water either directly or indirectly
from rainfall. Rain falling on the lake surface is the direct source.
The indirect source is surface inflow and ground-water inflow. The
rainfall on Brooklyn Lake averages 52 inches per year, based on
records from three U. S. Weather Bureau stations within 30 miles
of the lake-Gainesville, Glen St. Mary, and Federal Point. This
amount is essentially equal to that at Gainesville. Records for
the period 1900-60 at Gainesville show that the rainfall there
averages 51 inches and has ranged from 32.79 to 73.30 inches.
Figure 2 shows annual rainfall for the period 1900-60 at
Gainesville. Periods of excessive and deficient rainfall occur in
unpredictable cycles. Rainfall at Gainesville in 1953 was 73.30
inches, the highest annual rainfall of record for the area, and in
1954 the rainfall was 36.24 inches, the second lowest annual rain-
fall of record for the area. Also, 1954 marked the beginning of a
prolonged period of deficient rainfall.
A period of more than 3 years of deficient rainfall from Janu-
ary 1954 to May 1957, coupled with high rates of seepage, caused
Brooklyn Lake to recede to the low levels that existed in 1957-58.
Rainfall during the 3-year period 1954 to 1956 was below normal by
nearly 23 inches. Above-normal rainfall started in March 1957, but
Brooklyn Lake did not begin to rise until March 1958 when surface
inflow started.












221---

20

____IS MAXIMUU






41

-I-
zz1
4 0 6;A


10 02


W HIAilZ!rIIjII i lll llTll llllllli jA I II I il I
0 0 0 0 0 2 o 0 O n o w 0


Figure 2. Bar graph of annual rainfall for the period 1900-60
Florida.


at Gainesville,






FLORIDA GEOLOGICAL SURVEY


PHYSICAL DESCRIPTION

Brooklyn Lake is not unique in its behavior or physical struc-
ture, but it is somewhat unusual in both respects. Its range in
stage is quite large for a Florida lake-about 20 feet-and it is
one of the many lakes located in a group of high sandhills. Some
of these lakes are landlocked; that is, they have no surface outlet;
others are connected by surface channels and form a chain of
lakes. Brooklyn Lake is in a chain of lakes. This lake region is
characterized by hills and valleys covered with a thick mantle of
sand. The highest of these hills, north of Blue Pond, is 225 feet
above sea level. The highest land surface near Brooklyn Lake is
about 170 feet above sea level.

SURFACE DRAINAGE

Brooklyn Lake is the fourth from the head of a chain of six
lakes that form the headwaters of Etonia Creek in southwestern
Clay County. The upper Etonia Creek basin lies between the Santa
Fe River basin to the west and the Black Creek basin to the north-
east (fig. 3). The lakes, in a downstream order, are: Blue Pond,
Sandhill Lake, Magnolia Lake, Brooklyn Lake, Keystone Lake, and
Lake Geneva. The upper three of these are in the Camp Blanding
Military Reservation. The lower three-Brooklyn Lake, Keystone
Lake, and Lake Geneva-are at Keystone Heights.
Surface runoff from this group of lakes is exceedingly low.
Surface flow occurs from the lower of these lakes only after pro-
longed periods of excess rainfall, even though the differences in
lake elevations and slopes of the channels connecting them are
sufficient to allow rapid runoff. In January 1961, after 31/ years of
above-normal rainfall, the level of Lake Geneva was still below the
outlet level. A profile showing water-surface elevations of these
six lakes on two dates is given in figure 4. Brooklyn and Keystone
lakes were lower than Lake Geneva in October 1958 even though
they are above Lake Geneva in the chain. Low runoff from these
lakes indicates that seepage into the ground and evapotranspiration
from the basin take a heavy toll of the rainfall.

STAGE FLUCTUATIONS

Lake surface elevations, and how they fluctuate with seasons,
are important characteristics of any lake. If the rate of
replenishment were to equal the rate of loss, the amount of water







REPORT OF INVESTIGATIONS No. 33


Figure 3. Surface drainage of Etonia Creek basin.


stored in a lake would remain constant and the lake surface would
not fluctuate. However, no lake remains at a constant stage. All
lakes in Florida have some seasonal fluctuations. When stage
fluctuations become so great that the utility of the lake is
hampered, control measures are sought. In 1957 and 1958, Brooklyn
Lake was at such a low level that control measures were desirable.







FLORIDA GEOLOGICAL SURVEY


A' 165


M CAML *STAMMC. M tES
Figure 4. Profile and location of chain of six lakes in the upper Etonia Creek
basin.
A stage graph of Brooklyn Lake for the period July 1957 to
December 1960 is given in figure 5.
In 1957, after 31/1 years of deficient rainfall, Brooklyn Lake
had receded about 20 feet below a desirable stage. However, at the
end of 1959, after 21/ years of excessive rainfall, the lake had filled
and water was flowing from the outlet to Keystone Lake. Brooklyn
Lake began its recovery in mid-March 1958 when surface flow from
Magnolia Lake first started. The recovery was erratic during the
last 9 months of 1958, partly because at the lowest stages the lake
consisted of 10 separate pools that had to be filled. After these
pools were filled and the lake became one continuous body of water,
the recovery was fairly uniform through 1959.
Surface outflow from the lake began at elevation 115.2 feet in
October 1959, after which the stage leveled off for several months.
From October 1959 to December 1960, the stage fluctuated through
a range of 2.2 feet. The highest known stage of Brooklyn Lake,
which occurred in 1948, is 118.2 feet, 3 feet above the bottom of the
outlet.
Flood and drought conditions occur in unpredictable cycles.
These cycles coincide with periods of high and low rainfall. It is







REPORT OF INVESTIGATIONS NO. 33


-j








1028 -.... .. .
104

98 top .






1957 1958 1959 1960
Figure 5. Stage graph of Brooklyn Lake.

possible for the cumulative deficiency for several consecutive years
of slightly below-normal rainfall to cause a more serious drought
condition than a large rainfall deficiency in a single year. Like-
wise, in this lake region, it is possible for the cumulative effect of
slightly above-normal rainfall for several consecutive years to
cause greater floods than those caused by 1 year of exceedingly
high rainfall. Figure 2 shows that the rainfall at Gainesville was
below normal during 1954-56. The end of the period of below-
normal rainfall corresponds with the low lake levels that were
measured in 1957. The graph in figure 2 also shows that the rain-
fall was below normal from 1906-11, 1914-18, and 1931-34. Pre-
sumable, the lake level was also low near the end of these periods.

DEPTHS AND STORAGE

Other physical aspects of Brooklyn Lake are shape, size, depth,
and the related factor of storage. At the lake-full stage of 115.2






FLORIDA GEOLOGICAL SURVEY


feet, the area of the lake is 1.0 square mile and the length of shore-
line is 8.4 miles. At the low stage of 97.2 feet in February 1958,
the composite water-surface area of the 10 separate pools for the
lake was only 0.5 square mile.
The map given in figure 6 shows lines of equal depth at the
stage of 117 feet. The map was drawn from data obtained from
traverses of the lake with a sonic depth recorder. Maximum depths
of the main body of the lake range from 20 to 34 feet. Several arms
of the lake extend outward from the main body. The arm extending
southwest toward Keystone Heights is the shallowest, with a depth
of 20 feet. The deepest point in the lake, 47 feet, is the middle
of the series of three depressions extending to the northwest.
Brooklyn Bay, to the southeast of State Highway 21, has a depth
of 40 feet.
The lake divided into 10 separate pools when it was at its lowest
stage of 97.2 feet in February 1958. The maximum depth at that
stage was 27 feet. Figure 7 shows the outline of the lake and lines
of equal depth at the low stage of 97.2 feet.
Storage, or volume, of water in the lake is related to stage and
has ranged from 2,200 to 13,000 acre-feet. (An acre-foot is the
volume needed to cover 1 acre to a depth of 1 foot.) The storage;
curve in figure 8 shows the storage of Brooklyn Lake at any lake
stage.

CHEMICAL QUALITY AND TEMPERATURE OF WATER

Chemical quality and temperature of Brooklyn Lake water for
the period of record, July 1957 to June 1960, were determined by
sampling about twice yearly. Table 1 shows the results of chemical
analyses of water in Brooklyn Lake, Magnolia Lake, and Sandhill
Lake. During periods when surface inflow occurs, water in
Brooklyn Lake is a blend of waters from the upper lakes and
possibly shallow ground water. Data for ground water were
obtained as a part of the four-county study.
The water in Brooklyn Lake has a low dissolved solids content.
The maximum concentration of dissolved solids was 34 ppm as
determined by the weight of residue on evaporation at 1800C
(table 1). The maximum change in dissolved solids content was
15 ppm as determined by the weight of residue. The chemical
content appears to have a general inverse relation to lake stage.
None of the individual constituents varied markedly during the
period of record. The most highly concentrated constituent was
chloride with a maximum of 7 ppm.






































Figure 6. Brooklyn Lake


showing lines of equal depth at lake-surface elevation
of 117 feet above sea level.












ii.
a' I.,


1 /

Sheefilme of e ae-ifeie *lgitign
19? Feet tKre mean sea fere.


Figure 7. Brooklyn Lake showing lines of equal depth at the record-low
elevation of 97.2 feet above sea level.


0


0
0
0
9.4
0

02


'.4


_ __


/'""'>
SS-.






REPORT OF INVESTIGATIONS NO. 33


STORAGE, IN THOUSANDS OP ACRE-FEET
Figure 8. Curve showing relation of lake stage to lake storage.

The pH of the lake was low, averaging 5.5 with a range of 0.6
pH units. Figure 9 shows the relation of pH of the lake to that
of ground water in the area. The data suggest that water from the
lake has a slight effect on the pH of the ground water. In the
vicinity of the lake, the average pH value of the water in the
shallow aquifer is 0.1 to 0.2 units lower than the average pH
value for water in that aquifer throughout Clay County. The total
contribution of the lake and water-table aquifer to the secondary
artesian aquifer apparently is effective in lowering the pH about
0.4 units in the vicinity of the lake. No direct chemical quality
relation is obviously apparent between the Floridan aquifer and
recharge sources in the vicinity of Brooklyn Lake.
The temperature of Brooklyn Lake fluctuates seasonally. Rain
causes minor fluctuations in temperature of the lake surface. The
temperature of shallow ground water that enters Brooklyn Lake
ranges from 650 to 800F. During the recent period of high lake
stages, temperature measurements were made at selected spots
in Brooklyn Lake to correlate water temperature with depth of
water. The results of temperature measurements at the selected
spots within the lake are shown as vertical temperature profiles
in figure 10.












TABLE 1. Average, Maximum, and Minimum Mineral Content and Temperature of
Brooklyn, Magnolia, and Sandhill Lakes. (Chemical analyses in parts per million
except specific conductance, pH and color, July 1957 to June 1960.)

an CaCO,
.g Hardness








Brooklyn Lake near Keystone Heights, Florida b

Average 75 0.9 0.03 1.3 0.7 3.6 0.2 3 4.1 5.8 0.0 0.1 0.0 I 18 .28 5 6 4 85 5.5 4
Maximum 88 1.4 .06 1.6 1.2 4.4 .4 4 6.5 7.0 .1 .2 .1 21 84 13 9 8 41 6.7 10
Minimum 60 .2 .02 1.0 .2 2.6 .0 1 2.6 4.8 .0 .0 .0 14 19 1 4 2 26 5.1 2

Magnolia Lake near Keystone Heights, Florida e
-i S to















Average 67 1.3 00 1.0 0. .8 0.1 8 2.4 6 0.0 0.1 0.0 1 20 6 4 1 6 11
Maximum 83 1.0 .07 1.2 .6 2.9 .2 4 2.8 6.0 .1 .6 .0 15 28 14 4 2 28 6.1 20
Minimum 66 .8 .02 .8 .1 2.6 0 2 1.8 4.0 .0 .0 .0 13 1 2 4 0 24 5.1

Sandhill Lake near Keystone Heights, Florida b
Average 74 2. 0.09 0.9 0. 3.2 0.1 3 2.0 5.0 0.1 0.1 1 0.0 17 223 6 4 2 28 5.4 10




Maximum I87 4.0 .23 1.4 .7 .6 4 3 4 5.6 .8 .1 .2 .0 20 26 11 6 4 37 11 .7
Minimum 65 1.3 .01 .4 .4 2.8 .0 1 .8 4.2 .0 .0 .0 14 16 2 4 0 24 4.8 2


MUnits, platinum-cobalt scale
bSix analyses
cFour analyses







REPORT OF INVESTIGATIONS NO. 33


8.0 1-1 1


S


7.0 -- -- -
S EXPLANATION
Averoge PH value
pH Average plotted data -
Plotted data are for wells In vicinity of Brooklyn Lake
A Water table aquifer, 48 analyses
6.0 B Secondary artesIan aquiter, 45 analyses -
C Florldan aqulter, 97 onalyses
pH BROOKLYN LAKE

WATER-TABLE SECONDARY ARTESIAN I FLORIOAN AQUIFER
AQUIFER AQUIFER I
5 0I I1 I I
0 100 200 300 400 500
DEPTH OF WELL, IN FEET
Figure 9. Relation of pH to depth of water occurrence, near Brooklyn Lake.


The temperature measurements for the two profiles were made
at times of equal lake stages (about 117 feet above mean sea level)
and reflect seasonal temperature fluctuations. Stratification was
much more pronounced on May 9 than on November 28, 1960,
which was probably due to the slower rate of warming of the
deeper water during the spring months. On November 26, 1957,
when the lake stage was about 20 feet lower, water temperature
throughout the lake was essentially uniform; the maximum
temperature of 670F being near the lake surface and the minimum
temperature of 650F being near the lake bottom.


RELATION OF GROUND WATER TO LAKE

The following sections describe the principal hydrologic units
that underlie the Brooklyn Lake area-the water-table aquifer,
the confining bed, and the Floridan aquifer-and describe the
movement of ground water in the aquifers in relation to Brooklyn
Lake. The two major aquifers, the water-table aquifer, and the
Floridan -aquifer, are separated by the confining bed. The geologic
formations, the nature of the earth materials that comprise each
hydrologic unit, and the hydrologic characteristics of each hydro-
logic unit are described. The interpretations of the relation of







FLORIDA GEOLOGICAL SURVEY


0 0



10 10



20 0
I. L.



S3O0 I 30
a.-0.


40 40



50 1 50
50 60 70 80 50 60 70 80
TEMPERATURE *F TEMPERATURE "F
Figure 10. Temperature profiles in Brooklyn Lake on May 9, 1960 and
November 28, 1960.




ground water to Brooklyn Lake, and also of the character and
composition, thickness and structure, and extent of the geologic
formations and hydrologic units are based on data from 39 test
wells and many private wells. The locations of wells in the
Brooklyn Lake area and an explanation of the well-numbering
system are given in figure 11. Table 2 lists the geologic formations
that comprise each hydrologic unit and summarizes the water-
bearing characteristics of each unit.
Figure 12 shows the locations of sections A-A', B-B', C-C' and
D-D'. Section A-A' (fig. 13) shows graphically the lithology of the
formations and relates the geology to the hydrologic units and to
the lake. Sections B-B' (fig. 14), C-C' (fig. 15), and D-D' (fig. 16)
show the hydrologic units that underlie the Brooklyn Lake area.
Figure 16 also shows a section through a filled sink.









REPORT OF INVESTIGATIONS No. 33


82*02'


EXPLANATION
.9
Inventoried well and well number


Test well


Well-numbering system


The area of study is divided into 1-minute quadrangles by the latitudinal
and longitudinal lines. Each veil is numbered consecutively within a quadrangle
in the order that it is inventoried. This is shown by the quadrangle outlined
by a heavy black line on the map, in which the wells are numbered consecutively.
Each quadrangle is designated by the 1-minute latitudinal line on the south and
by the 1-minute longitudinal line on the east. The quadrangle outlined on the
map is described by latitude 29*47' and by longitude 82*01'. A well within this
quadrangle, such as number 9 shown by the arrow on the map, is numbered according
to the quadrangle designation. The number is 29*47' 82*01' 9. This number
is simplified by dropping off the first digit of the degrees from the latitudinal
and longitudinal lines and by omitting the degree and minute symbols. The well
number above is"thus written 947 201 9.





I 0 I mile


Base taken from U.S.G.S.
topographic quadrangle
1949

Figure 11. Brooklyn Lake area showing locations of wells and giving an
explanation of the well-numbering system.










TABLE 2. Geologic Formations, Hydrologic Units, and Their Water-Bearing Charac- 0
teristics in the Brooklyn Lake Area, Clay County, Florida'


Formation

Older Plesltocene
terrace deposits


Unnamed coarse
elastics


Choctawhatchee
Formation




Hawthorn Formation





Crystal River Fm.
Ocala Willliston Frm.
Group Inglis Formation
(Undifferentiated)


Avon Park Limestone


Lake City Limestone

Oldsmar Limestone


Normal
range in
thickness

0-15


30-67


10-20


115-155


210


4504.

?


Physical characteristics


Sand, tan, yellow and brown, loose.


Sand and clayey sand, varicolored, lo-
cally contains quarts gravels, inter-
bedded thin lenses of clay or kaolin.
Upper few feet in places is red and
yellow sandy clay bed.


Clay and marl, yellow and cream, indu-
rated in part, phosphate grains and
pebbles, thin limestone and sand layers.


Clay and sandy clay, varicolored, inter-
bedded thin sands and sandy phosphatic
limestones, disseminated grains and
pebbles of phosphate. Some thick sand
beds with limestone layers.


The lowermost 25 feet of the Hawthorn
is composed of very hard tan and gray
limestone and dolomitic limestone with
interbedded clay and sand lenses.


Limestone, white, cream, and tan, soft,
granular, porous, fossiliferous, coqui-
noid in part. Some hard layers of tan
and gray crystalline limestone, dolo-
mitic in part.
Dolomite, dark brown and tan, granu-
lar, hard, dense to porous; interbedded
tan and cream limestone and dolomitic
limestone.
Limestone, dolomite, and dolomitic
limestone.
Limestone, dolomite, and dolomitic
limestone.


Water-bearing characteristics




Water in the aquifer is unconfined. The
sands and sandy clays are of low to moder-
ate permeability. The Choctawhatchee con-
tains a few permeable zones,


Relatively impervious clays and limestone
confine water in the Floridan aquifer under
artesian pressure. Some sand and lime-
stone beds that are interbedded in clay are
of low to moderate permeability.


Water in the FIorldan aquifer is under ar-
tesian pressure. Beds in the lower part of
the Hawthorn are the least permeable part
of the aquifer. Limestones in the Ocala
Group are highly porous and permeable and
constitute the most productive part of the
aquifer. The Avon Park, Lake City, and
Oldsmar Limestones contain many rela.
tively impervious beds, but the formations
are generally moderately to highly perme-
able.


iThe stratigraphic nomenclature used in this report conforms t tthe usage of the Florida Geological
Survey.


Ilydrologie
unit





Water-table
aquifer


Confining
bed


Floridan
aquifer


Series


Pleistocene


Miocene


Eocene


I.--------


_I I----------I


I I -


--


--- -







REPORT OF INVESTIGATIONS NO. 33


Base taken from U.S.G.S.
topographic quadrangle 1
1949 i 0 I mile

Figure 12. Brooklyn Lake area showing the locations of sections A-A', B-B',
C-C', and D-D'.

WATER-TABLE AQUIFER

The upper and middle parts of the water-table aquifer are
composed predominantly of sands and clayey sands. These sands
and clayey sands grade into soft clay and marl beds in the bottom
part of the aquifer. From the surface downward the aquifer is
made up of the older Pleistocene terrace deposits, the unnamed
coarse plastics of Pleistocene age, and the Choctawhatchee Forma-
tion of Miocene age.
The older Pleistocene terrace deposits which lie at the surface
are yellow, tan, and brown, fine to coarse; loose sands that are as
much as 15 feet thick.
The underlying unnamed coarse plastic unit is composed of two
parts. At most places, the upper part is a bed of coarse, red, yel-
low, and orange sandy clay that is from 6 to 16 feet thick. The








FLORIDA GEOLOGICAL SURVEY


A
+200



+160



+120o



S+80"



+40.



S0-



; -40


oA





Older Plel toceng
terrace d&po00&1

SBrooklyn Lak







SWATER- TA.BL /


'*s t /"" .... CONFINING/ /

Hawthorn / Formation




JP OF FLORIDAN AOUIFER '
Hawlhorn Formation
--------------------------------

Ocala Group
0 1000 2000 lit
Siooo


EXPLANATION

Sand

f s R d, Yeiio. one ortlat
soand cloy
Vlo0i1o0rid Wlrd
and clyed ltord,
thi;hi lay tonilI
Yellow Clay Oan moml
pl^ thole r an Ito

SClay nda saondy cloay
wlth thllln 1iiItinr rOyll,




pno0 Mett ioo Solic
i Snd ao"< fo and
phOlhtiOlic

Dolomilic limltior

SWK,1 aem oetnam
folldilttOi$ limeistone


-120

Figure 13. Section showing geologic formations, hydrologic units, and types
of material in the Brooklyn Lake area along line A-A' in figure 12.





+200 -


a) -
+1600 -- 0

W WA IER- ER-






+80 AOUI






Fr %WBrooklyn Lake Wr




0 1000 2000 feet
S-40 -

FLORIDAN AQUIFER
Total depth 395 ft. Total depth 307 ft.


Figure 14. Section showing hydrologic units in the Brooklyn Lake area along

line B-B' in figure 12.






REPORT OF INVESTIGATIONS NO. 33


_J
> C =

< +160 t N
0
Z
< WATER-
2 +120 -a t er Loch
o--l~oe omn
P ^ TABLE -.
SPiezometric surface
a +80 AQUIFER
w
UL
W

w +40
U / CON FINING, BED/

L 1-
0


W FLORIDAN AQUIFER
_J
lu -40
0 10,00 2000 feet
Figure 15. Section showing hydrologic units in the Brooklyn Lake area along
line C-C' in figure 12.

bed was not penetrated at the sites of test wells 947-201-4 (east
side of lake), 947-202-13 (southwest side of lake), and 948-200-1
and 4 (northeast side of lake near Loch Lommond), and 948-201-7
(north side of lake). The sandy clay either changes character or is
absent in the area northeast from the lake and in the area generally
north of test wells 948-201-9 and 948-202-4. The sediments that lie
beneath the sandy clay bed and comprise the lower part of the un-
named coarse plastic unit are varicolored micaceous sands and
clayey sands that contain thin lenses of kaolin clay and sandy clay,
and locally contain quartz gravel. Where the sandy clay in the
upper part of the unnamed coarse plastics units is absent, the
varicolored sands and clayey sands are continuous with the over-
lying loose surface sands. Test wells penetrated 20 to 58 feet of
the varicolored sands and clayey sands. The thickness of the







22 FLORIDA GEOLOGICAL SURVEY



0 Go
N ft
D N0

+15 0 -
0-) Brooklyn /
-JJ

,L +100 Piezometric ,-_ surface
WATER TABLE AQUIFER

--_
i +50 /


< /CON FINING BED



Ll1



o -100 "I
0"
U -100

FLORIDAN AQUIFER













-300 -A

0 1000 2000 Feet
-350
Figure 16. Section showing hydrologic units in the Brooklyn Lake area through
a filled sink along line D-D' in figure 12.







REPORT OF INVESTIGATIONS NO. 33


unnamed coarse plastics including the sandy clay bed ranged from
30 to 67 feet.
The basal part of the aquifer, the Choctawhatchee Formation,
is composed of 10 to 20 feet of soft, yellow, and olive sandy clay
and partly indurated marl with some sand, red and brown phos-
phorite and silica gravel, thin limestone, and a few poorly pre-
served mollusk shells and impressions.
The water-table aquifer, as a composite of the above described
materials and formations ranged in thickness in test wells from
50 to 85 feet. However, where deep filled sinks occur the aquifer
is much thicker, as at the site of test well 947-202-13 (section
D-D', fig. 16) where 319 feet of sediments were penetrated.
The sands that comprise the unnamed coarse elastic unit, the
main part of the water-table aquifer, have a low to moderate
permeability owing to clay that is disseminated in the bed. The
predominantly clayey Choctawhatchee Formation, though it con-
tains a few permeable zones, will transmit only very small amounts
of water.
Figure 17 shows the configuration of the base of the water-table
aquifer. Comparison of figure 17 with the contour map of the
bottom of Brooklyn Lake (fig. 6) and figures 13, 14, 15, and 16
shows that nearly everywhere the bottom of the lake is in the
water-table aquifer. The lake bottom generally lies from 15 to 25
feet above the base of the aquifer. Only in its deepest parts does
the lake bottom extend to or slightly below the base of the water-
table aquifer.
Water in the water-table aquifer is unconfined so that its
surface is free to rise and fall. The water in the aquifer is derived
from local rainfall and from water that at times flows into the
aquifer from lakes and perhaps from streams. The clayey sand or
sandy clay layer in the upper part of the aquifer, shown in figure 13,
does not prevent water from moving downward. While test wells
were being drilled near the lake, no water was found in the loose
sand above this layer. Moreover, water placed in casings ending
in the layer soon disappeared.
Figures 18 and 19 show the general configuration of the water
table on March 22 and October 17, 1960, respectively. The water
table and Brooklyn Lake on October 17 was higher than on March
22. In general, the water table slopes toward the lake on the
northern, northwestern, western, and southwestern sides of the
lake and slopes away from the lake on the eastern and southeastern
sides of the lake. In March, a trough existed in the water table
near the lake on the northern and northwestern sides of the lake.







REPORT OF INVESTIGATIONS NO. 33


8.0 1-1 1


S


7.0 -- -- -
S EXPLANATION
Averoge PH value
pH Average plotted data -
Plotted data are for wells In vicinity of Brooklyn Lake
A Water table aquifer, 48 analyses
6.0 B Secondary artesIan aquiter, 45 analyses -
C Florldan aqulter, 97 onalyses
pH BROOKLYN LAKE

WATER-TABLE SECONDARY ARTESIAN I FLORIOAN AQUIFER
AQUIFER AQUIFER I
5 0I I1 I I
0 100 200 300 400 500
DEPTH OF WELL, IN FEET
Figure 9. Relation of pH to depth of water occurrence, near Brooklyn Lake.


The temperature measurements for the two profiles were made
at times of equal lake stages (about 117 feet above mean sea level)
and reflect seasonal temperature fluctuations. Stratification was
much more pronounced on May 9 than on November 28, 1960,
which was probably due to the slower rate of warming of the
deeper water during the spring months. On November 26, 1957,
when the lake stage was about 20 feet lower, water temperature
throughout the lake was essentially uniform; the maximum
temperature of 670F being near the lake surface and the minimum
temperature of 650F being near the lake bottom.


RELATION OF GROUND WATER TO LAKE

The following sections describe the principal hydrologic units
that underlie the Brooklyn Lake area-the water-table aquifer,
the confining bed, and the Floridan aquifer-and describe the
movement of ground water in the aquifers in relation to Brooklyn
Lake. The two major aquifers, the water-table aquifer, and the
Floridan -aquifer, are separated by the confining bed. The geologic
formations, the nature of the earth materials that comprise each
hydrologic unit, and the hydrologic characteristics of each hydro-
logic unit are described. The interpretations of the relation of








FLORIDA GEOLOGICAL SURVEY


29*49'


Keystcne \
Lake
EXPLANATION

Well


Upper number is well number
Lower number is base of the
water-table aquifer, in feet
referred to mean sea level




Contour represents the
elevation of the base of the
water-table aquifer, in feet
Dashed line represents inferred
position of contour. Contour
interval 10 feet. Datum is mean
sea level


Base taken from U. S. G. S.
topogroahic quadrangle ..
1949 I 2 0 o mile

Figure 17. Brooklyn Lake area showing contours on base of the water-table
aquifer.








REPORT OF INVESTIGATIONS NO. 33


Base taken from U. S. G.S.
topographic quadrangle
1949

Figure 18. Brooklyn Lake area showing contours on the water table on March
22, 1960.







FLORIDA GEOLOGICAL SURVEY


EXPLANATION


Well

15
117
Upper number is well number
Lower number is water level,
in feet above mean sea level
Number in lake is lake level,
in feet. above mean sea level



Contour represents the
approximate elevation of the
water table, in feet, October
17, 1960. Contour interval 5
feet. Datum is mean sea level.


S1 0 I mile


Base taken from U S. G. S
rooograohic quadrangle
1949


Figure 19. Brooklyn


Lake area showing contours on the water table on
October 17, 1960.


I rr






REPORT OF INVESTIGATIONS No. 33


Also, a depression exists on the water table on the western side
of the lake.
Ground water moves downgradient in a direction at right angles
to the contours on the water table. Thus, in general, water in the
water-table aquifer moves toward the lake on the northern, north-
western, western, and southwestern sides of the lake and from the
lake on the eastern and southeastern sides. While the trough in
the water table on the northern and northwestern sides exists,
however, water moves from the lake toward the trough. Also,
water moves from the lake toward the depression in the water table
on the western side of the lake.
Some conditions under which water moves into the lake from
the water-table aquifer and from the lake into the water-table
aquifer are illustrated by the movement of water in the aquifer
at three sites near the lake.
The water levels in the wells and the contours north and north-
west of the lake on the water table (fig. 18, 19) show that water
in the aquifer several hundred feet north and northwest of the
lake moved toward the lake during the period March through
October 1960. However, near the lake as evidenced by the low
ground-water levels, water moved from the lake into the aquifer.
Before the rapid rise of the stage of the lake in 1959 (fig. 5),
water probably moved into the lake in most places on the north
and northwest sides of the lake.
The steepest slope of the water table toward the lake is on the
southwestern side of the lake. On this side of the lake, water
moved from the lake into the aquifer in most places for a time
during and after the rapid rise of the lake level (fig. 5), but after
a few months, water again began moving into the lake from the
aquifer, except near well 947-202-13 where the confining bed has
been breached as shown on figure 16.
Some conditions under which water moves into the lake from
the water-table aquifer and from the lake into the water-table
aquifer are illustrated by the movement of water in the aquifer at
three sites near the lake.
The first site is at wells 947-202-13 and 947-202-14, which are
about 3 feet apart and about 100 feet from the southwestern edge
of the lake (fig. 11). Well 947-202-13 penetrated the filled sink
shown in figures 16 and 17 and well 947-202-14 taps the water-table
aquifer. A comparison of the fluctuation of the water level in well
947-202-14 and the fluctuation of the stage of the lake is shown in
figure 20. The water level in well 947-202-14, reflects the water
table of the water-table aquifer and seems to stay about 2 feet






FLORIDA GEOLOGICAL SURVEY


= 117
C
0
(-
E
S116
0
.3

115
0-


. 114


113


1960
Figure 20. Hydrographs of well 947-202-14 and Brooklyn Lake.

lower than the level of the lake. Thus, the water table slopes from
the lake toward the filled sink, and accordingly water moves from
the lake into the water-table aquifer in the vicinity of the filled
sink shown in figures 16 and 17.
The second site is at wells 948-202-7 and 948-202-8, which are
about 3 feet apart. Well 948-202-8, which is shown on section A-A'
in figure 13, penetrated a normal sequence of material. Figure 21
shows hydrographs of water-table well 948-202-5, which is about
1,500 feet northwest of the lake, and well 948-202-7, which is about
300 feet northwest of the lake, and a stage graph of Brooklyn Lake
(fig. 11). The water level in well 948-202-5 stayed above the level
of the lake; whereas, the water level in well 948-202-7 was slightly
below the level of the lake from March through October 1960,
indicating that during most of that period water at the second site
moved from the lake into the aquifer. A reversal in the direction
of water movement at this site is indicated in mid-October 1960
when the water level in well 948-202-7 reached a stage higher than
that of the lake.
The third site is at wells 948-201-7 and 948-201-8, which are
north of the lake and about 3 feet apart (fig. 11). Well 948-201-7
penetrated the Floridan aquifer at an unusually high elevation as


Brooklyn Lake











Well 947-202-14
____ (Well tops water-
table aquifer about
100 feet southwest
of lake.)
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec






REPORT OF INVESTIGATIONS No. 33


> Well 948-202-5
- 119 (Well taps water-
o table aquifer about
Z 1500 feet northwest /
c of lake.)
- 118 J







--IWell 948-202-7
4sie- ---- / --


0 /Well 948-202-7
j 115 / (Well tops water-
,- table aquifer about
300 feet northwest
of lake.)
Jon Feb Mar Apr May June July Aug Sept Oct Nov Dec
1960
Figure 21. Hydrographs of wells 948-202-5 and 948-202-7, and Brooklyn Lake.


shown in figure 14. The hydrographs of wells 948-201-8, 948-201-10,
and 948-201-13, and a stage graph of Brooklyn Lake are shown in
figure 22. As indicated by the hydrographs the water level in well
948-201-13 stayed at about half a foot below the level of the lake,
the water level in well 948-201-8 about 2 feet below the level of the
lake, and the water level in 948-201-10 from 1 to 3 feet higher than
the level of the lake. The water levels in these wells indicate that
the water table slopes generally toward well 948-201-8 from the
north and from the lake and that water probably moves toward
well 948-201-8 from all directions.
The data at the three sites indicate that the water in the water-
table aquifer moved from the lake, where normally it would have
moved into the lake. This reversal of direction may have been
caused by: (1) water percolating downward from the aquifer at, or
near, these sites; (2) the water table being in the process of
adjusting itself to the rapid rise of the level of the lake; or (3)
both of the preceding two conditions.






FLORIDA GEOLOGICAL SURVEY


121


120


119


118


117


116


115


114


113


Well 948-201-10
(Well taps water-table
-aquifer about 1500feet -
north of lake)






Brooklyn Lake








Well 948-201-13 (Well taps _-
water-table aquifer about- -
300 feet north of lake)






Well 948-201-8 (Well taps
water-table aquifer about 700 feet
north of. lake)
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
1960


Figure 22. Hydrographs of wells 948-201-8, 948-201-10, and 948-201-13, and
Brooklyn Lake.

The water level in well 947-202-14 at the site of the filled sink
showed no indication of rising above the level of the lake, suggesting
that most, if not all, of the time water probably percolates down-
ward from the aquifer at this site. At the second site, where the
normal sequence of materials was present, the water table was
rising in such a way as to indicate that it might rise above the level






REPORT OF INVESTIGATIONS No. 33


of the lake. The water table at this site, during the period March
through October 1960, was probably in the process of adjusting
itself to a higher stage of the lake. At the third site, where the
Floridan aquifer extends to an unusually high elevation, the water
table was rising, but whether the water table would rise above the
level of the lake is problematical. Water at this site probably was
percolating downward and the water table was probably adjusting
itself to a higher level of the lake.
The relationship between water in the water-table aquifer and
water in the lake is complex. The movement of water in the aquifer
northwest of the lake at the second site, where the normal sequence
of materials is present below the surface, is probably typical of the
movement of water around most of the lake. At the second site
water moved from the lake into the water-table aquifer during most
of the period, March through October 1960. The normal direction
of flow on the northern, northwestern, and southwestern sides of
the lake is probably from the aquifer into the lake and was probably
reversed by the rapid rise in lake stage in 1959. The flow from the
lake into the aquifer was accelerated on the eastern and south-
eastern sides of the lake. This acceleration and the reversal of
flow in some places around the lake are temporary conditions that
will exist only while the water table is adjusting itself to a higher
level of the lake. At other places near the lake, such as the first
site at the location of the filled sink, water probably normally moves
from the lake into the water-table aquifer and thence percolates
downward.

CONFINING BED

Relatively impermeable deposits of the Hawthorn Formation of
Miocene age make up the confining bed. Limestone and dolomitic
limestone beds in the bottom part of the Hawthorn, however, do
not belong to the confining bed but are a part of the Floridan
aquifer. The confining bed locally includes secondary artesian
aquifers. The confining bed is composed mostly of various shades
of green, gray, yellow, and blue phosphatic clay and sandy clay,
containing sand and limestone lenses. The limestone lenses, which
range in thickness from a few inches to about 6 feet, are gray,
white and bluish gray, and are usually sandy and phosphatic.
In the southwestern half of the lake, which includes sections
A-A' and D-D' (fig. 13, 16), the middle and lower parts of the
confining bed, in most places, contain a bed of tan and gray, fine
to coarse, sand and clayey sand. The middle and lower part of the






FLORIDA GEOLOGICAL SURVEY


confining bed also contain some interbedded thin limestone layers
whose thickness, permeability and relative position within the
confining bed are variable. The sand is thickest and most permeable
southwest of the lake. In well 947-202-11, shown on section D-D',
figure 16, a thickness of 45 feet of fine to medium-grained sand and
clayey sand was penetrated between depths of 135 and 180 feet,
overlain by 75 feet of clay and limestone of the confining beds.
In the northeastern half of the lake, which includes sections
B-B' and C-C' (fig. 14, 15), the confining bed is composed mostly
of relatively "tight" clay and limestone. The limestone contains
small cavities and, together with thin bedded sands, forms zones of
relatively high permeability within the clay beds.
The confining bed is thinnest in the northeastern part at the
site of test well 948-201-7 (section B-B',, fig. 14) where only about
30 feet of clayey materials that comprise the bed overlie the
Floridan aquifer. The greatest thickness of the confining bed was
120 feet in test well 947-202-11. The maximum thickness of the
confining bed in the Brooklyn Lake area is estimated to be about
130 feet.
The confining bed is ordinarily the hydraulic barrier that
separates the water-table aquifer from the Floridan aquifer.
Although the bed is not completely impermeable, the vertical
permeability of the bed is low and it will normally pass only
comparatively small amounts of water. However, in the vicinity
of Brooklyn Lake at two sites where test wells were drilled, water
probably moves through the confining bed relatively easily. These
two sites are at wells 947-202-13 and 948-201-7. Well 947-202-13
was drilled into a filled sink (fig. 16) and at the site of well
948-201-7 the confining bed is thin. At other sites around the lake
and beneath the lake, similar conditions probably exist.

FLORIDAN AQUIFER

The Floridan aquifer below the confining bed consists from top
to bottom, of limestone in the bottom part of the Hawthorn For-
mation and limestone, dolomite, and dolomitic limestone in
formations of Eocene age that include the Ocala Group, the Avon
Park Limestone, the Lake City Limestone, and, in part, the Oldsmar
Limestone. Nine wells shown on figure 11, 947-201-1, 2, and 4;
947-202-13 and 18; 948-201-1, 2, and 7; and 948-202-8 penetrate
the Floridan aquifer. The deepest penetration of the aquifer, by
well 948-201-1 (section B-B', fig. 14), is to the approximate base of
the Ocala Group at 262 feet below mean sea level.







REPORT OF INVESTIGATIONS NO. 33


Wells drilled into the Floridan aquifer usually penetrate a tan
to gray or brown, very hard limestone or dolomitic limestone of the
Hawthorn Formation at the top of the aquifer. Interbedded with
the hard limestones in the lower part of the Hawthorn are clays
and thin sand lenses, the unit being about 25 feet thick. Beneath
the limestones and clays of the Hawthorn is the Ocala Group, which
is about 210 feet thick and composed predominantly of white and
cream, soft, fossiliferous limestones. The underlying Avon Park
Limestone, estimated to be about 210 feet thick, the Lake City
Limestone more than 450 feet thick, and the lowermost Floridan
unit, the Oldsmar Limestone which is of undetermined thickness,
are composed of a series of dolomite, limestone, and dolomitic
limestone beds. Limestone of the Hawthorn Formation is relatively
impermeable, that of the Ocala Group is highly permeable, and the
limestone of the Avon Park, Lake City, and Oldsmar Limestones is
moderately to highly permeable.
Results of test drilling near Brooklyn Lake show that the
Floridan aquifer probably had been breached. At test well
947-202-13 (fig. 16) the Floridan aquifer has been breached by a
collapse of the underlying Eocene limestone. The breach has been
filled with sediments of the confining bed and the water-table
aquifer.
At test well 948-201-7 (fig. 14) where the Floridan aquifer is at
an unusually high elevation, the Floridan aquifer and the confining
bed seems to be breached. During the drilling of well 948-201-7,
the water level rose to an elevation that corresponded to the eleva-
tion of the Floridan piezometric surface when the drill had pene-
trated only 30 feet of the confining bed at a depth of 96 feet below
the land surface. The relatively thin 30-foot layer of clayey sedi-
ments of the confining bed that here separates the Floridan aquifer
from the water-table aquifer is apparently underlain by about 54
feet of materials that normally would be a part of the confining bed
but instead are hydrologically a part of the Floridan aquifer. The
apparent breaching of the beds in well 948-201-7 that has allowed
the hydrologic connection with the confining bed does not
necessarily involve collapse as in well 947-202-13 but might be
attributed to the displacement of the beds by faulting or fracturing.
Three conditions must exist if Brooklyn Lake is to leak sub-
stantial amounts of water to the Floridan aquifer: (1) the
piezometric surface or the pressure head in the Floridan aquifer
must be below the level of the lake; (2) a relatively permeable
route from the lake to the Floridan aquifer must exist; and, (3) the







FLORIDA GEOLOGICAL SURVEY


Floridan aquifer must be capable of transmitting the leaked water
to other areas.
The piezometric surface of the Floridan aquifer is probably
always below the water level of Brooklyn Lake. In October 1960,
the piezometric surface of the Floridan aquifer near Brooklyn Lake
was about 90 feet above mean sea level, more than 25 feet below the
water level of the lake but about 20 feet above the bottom of the
deepest part of the lake. Figure 23 shows a hydrograph of the
water level in well 947-201-4, which taps the Floridan aquifer and
is near Brooklyn Lake. During 1958 when the level of the lake was
97.2 feet above mean sea level, the lowest on record, the piezometric
surface was presumably lower than it was during the period August
through October 1960. Accordingly, the piezometric surface of the
Floridan aquifer is probably never less than about 10 feet below
the level of the lake and probably has never been below the bottom
of the deeper parts of the lake.
The second condition, that a relatively permeable route from
the lake to the Floridan aquifer exists, seems to be fulfilled. As
has been discussed, a relatively permeable route to the Floridan

90

I890-------------------------------------(------

_I /
Well 947-201-4
CD Floridan aquifer

(D
E88


(D
88-.- -- -








86 Aug Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug ISept Oct NovDec
1959 1960
Figure 23. Hydrograph showing the water level in well 947-201-4.
ai / -







-------------------------- __1960_______
Figure 23. Hydrograph showing the water level in well 947-201-4.







REPORT OF INVESTIGATIONS NO. 33


aquifer apparently exists at the site of well 947-202-13, which is
at the site of a filled sirk, and at well 948-201-7, which is at a site
where the confining bed is thin and the Floridan aquifer extends to
an unusually high elevation.
The third condition, that the Floridan aquifer be capable of
transmitting large amounts of water away from the lake, seems
to be fulfilled also. The capability of the aquifer to transmit water
is demonstrated by the ease with which large amounts of water are
released to wells tapping the aquifer. Although no figures for the
transmissibility, a measure of the ease with which the aquifer
transmits water, are available for the Brooklyn Lake area, the
transmissibility is probably more than 100,000 gpd (gallons per
day) per foot.
Because these conditions are fulfilled with little question, it
seems likely that Brooklyn Lake leaks substantial amounts of water
to the Floridan aquifer. Further, Brooklyn Lake is in an area where
the piezometric surface is high (fig. 24) indicating the artisian
aquifer receives recharge and that substantial amounts of water
enter the aquifer in the general vicinity of the lake.

WATER BUDGET
A water budget for Brooklyn Lake is the accounting of water
entering and leaving the lake. The difference in the amount of
water entering and leaving the lake is reflected in the rise or fall
of the lake level.
Water entering the lake is from three sources: (1) rainfall (R),
(2) surface inflow (Is), and (3) ground-water inflow (Ig). Water
leaving the lake is represented by: (1) evaporation from the sur-
face of the lake (E), (2) surface outflow (Os), and (3) ground-
water outflow (Og). These factors may be expressed in a formula
as follows:
AS = (R + Is + Ig) (E + Os + Og)
where AS is change in lake storage
Rainfall records were collected near the south shore of the
lake by the Florida Forest Service (fig. 4). The rain gage was a
plastic tube type, nonstandard gage. The records were adjusted to
be consistent with records from three U.S. Weather Bureau stations
(Gainesville, 20 miles southeast; Glen St. Mary, 35 miles north; and
Federal Point, 30 miles east). It was assumed that the records
from this gage were indicative of the amount of rain falling evenly
on the lake surface, the area of which was adjusted for changes in
lake level.








FLORIDA GEOLOGICAL SURVEY


29'40' \ \ 4 mes29*40'

1 1 2 4 m les
10' 05' 82*00' 55'
EXPLANATION
Well
870 3
Upper number is well number.
Lower number is water level,
in feet above mean sea level.
80--.O
Contour represents the approximate
elevation of the piezometric surface,
In feet above mean sea level. Contour
interval 5 feet.
Figure 24. Brooklyn Lake area showing contours on the piezometric surface
of the Floridan aquifer in June 1960.

Surface inflow was computed from a stage-discharge curve
drawn on the basis of the stage record of Magnolia Lake and 12
discharge measurements made about 1 mile from Brooklyn Lake
(fig. 4).
Surface outflow was computed from a stage-discharge curve
drawn on the basis of the stage record of Brooklyn Lake and seven
discharge measurements made at the outlet (fig. 4).
Lake evaporation was computed from records from a Class A
pan collected at Gainesville by the U.S. Weather Bureau. The pan







REPORT OF INVESTIGATIONS NO. 33


evaporation was about 67.04 inches for the 1958 water year; about
61.50 inches for the 1959 water year; and about 66.49 inches for
the 1960 water year. Records from the Class A pan were adjusted
by monthly coefficients developed for the period 1940-46 for Lake
Okeechobee, Florida, by Kohler (Kohler, M. A., 1954, Water loss
investigations: Lake Hefner Studies, Technical Report: U.S. Geol.
Survey Prof. Paper 269, p. 128.) These coefficients ranged from
0.69 for February to 0.91 for July and August. The mean annual
coefficient was 0.81. Adjustments in evaporation were made to
take account of the variation in lake surface due to changes in lake
level.
Changes in lake storage were computed from the stage-storage
curve given in figure 8. Data used to develop the stage-storage
curve and the depth-contour map given in figure 6 were collected
with a sonic depth recorder.
Data were not available, however, to determine ground-water
inflow (Ig) and ground-water outflow (Og), they were combined
into one factor net ground-water flow. This net ground-water flow
was determined as a residual for three water years, October 1957
to September 1960. A water year is from October 1 to September
30. Annual figures for the water budget are given in the following
table:


Values, In Acre-Feet, By Water Years
1958 1959 1960
Rainfall 1,600 3,100 3,400
Surface inflow 360 8,800 12,800
Surface outflow 0 0 2,000
Evaporation 1,600 2,200 3,000
Change in storage +360 +7,800 +2,000
Net ground-water flow from lake 0 1,900 9,100


A schematic presentation of the water budget during the 3-year
period is given in figure 25.
The net ground-water flow may be composed of ground-water
inflow and outflow to and from the water-table aquifer and to and
from the Floridan aquifer. Because the piezometric surface of
the Floridan aquifer remains below the level of the lake, water
cannot flow from the Floridan aquifer to the lake. Thus, the net
ground-water flow is composed only of ground-water inflow and
outflow to and from the water-table aquifer and ground-water
outflow to the Floridan aquifer.







FLORIDA GEOLOGICAL SURVEY


Figure 25. Water budget of Brooklyn Lake for the period October 1957 to
September 1960.
In order to determine where the water that left the lake went,
the ground-water inflow and outflow to and from the water-table
aquifer were computed for the period for which data are available,
March to October 1960. The flow was computed by the formula:
Q= TIW
where:
Q = the rate of movement of the water
T = Coefficient of transmissibility of the aquifer
I = the hydraulic gradient
W = the width of the flow section
The coefficients of transmissibility were computed from the
permeability of samples of the materials composing the aquifer.
The coefficients were determined by multiplying the permeability of
each sample by the interval represented by the sample and by
adding these products. The coefficients of transmissibility were
computed at the sites of wells 947-201-18, 947-202-18, 948-200-7,
and 948-202-8.
The width of the flow sections was taken from the map showing
contours on the water table. The width of the sections through
which water moves into the filled sink and into the area where the
confining is thin was estimated to be about 1,000 feet. The hy-
draulic gradient was taken to be the slope of the water table
between the lake and a nearby well.


WATER BUDGET







REPORT OF INVESTIGATIONS No. 33


The movement of water into the lake, and from the lake,
through the water-table aquifer was estimated for monthly inter-
vals for the period March through October 1960. During this
period about 70 acre-feet of water was estimated to have moved
into the lake from the water-table aquifer on the southwestern
side of the lake and about 200 acre-feet was estimated to have left
the lake on the eastern side of the lake. During this period about
400 acre-feet more water was estimated to have left the lake than
entered the lake through the water-table aquifer.
The lateral movement of water through the water-table aquifer
from Brooklyn Lake, during the period March through October
1960, was computed to be less than 10 percent of the loss to the
aquifers. Therefore, most of the net ground-water flow from the
lake was to the Floridan aquifer.
The net ground-water outflow, most of which was outflow to the
Floridan aquifer, was the largest loss from the lake. The net
ground-water outflow was zero during the 1958 water year when the
lake was low, and increased rapidly during 1959 and 1960 as the
lake surface rose. The increase in the net ground-water outflow
as the level of the lake rose may be accounted for by: (1) a decrease
in inflow from and an increase in outflow to the water-table aquifer;
and (2) an increase in outflow to the Floridan aquifer.
When the level of the lake was low, undoubtedly the flow to the
Floridan aquifer was least; the inflow from the water-table aquifer
was probably more, and the outflow less. The outflow to the
Floridan aquifer is related to the difference in head between the
lake level and the piezometric surface of the Floridan aquifer. An
exact relation between the head difference and the outflow to the
Floridan aquifer could not be determined. The difference in head
was undoubtedly much less in 1958 than it was in 1960. The inflow
from the water-table aquifer was probably larger when the lake
was low because the gradient of the water table to the lake was
probably greater. Likewise, the outflow was probably less because
the gradient was probably smaller. Thus, the amount of inflow
required to maintain the lake at a high stage is greater than that
required to maintain the lake at a low stage.

METHODS OF CONTROLLING BROOKLYN LAKE

Both high and low stages must be considered in any plan to
control Brooklyn Lake. The problem is to prevent the stage from
falling below or rising above desirable levels. Additional water
diverted into the lake to supplement the natural inflow would







REPORT OF INVESTIGATIONS NO. 33


aquifer apparently exists at the site of well 947-202-13, which is
at the site of a filled sirk, and at well 948-201-7, which is at a site
where the confining bed is thin and the Floridan aquifer extends to
an unusually high elevation.
The third condition, that the Floridan aquifer be capable of
transmitting large amounts of water away from the lake, seems
to be fulfilled also. The capability of the aquifer to transmit water
is demonstrated by the ease with which large amounts of water are
released to wells tapping the aquifer. Although no figures for the
transmissibility, a measure of the ease with which the aquifer
transmits water, are available for the Brooklyn Lake area, the
transmissibility is probably more than 100,000 gpd (gallons per
day) per foot.
Because these conditions are fulfilled with little question, it
seems likely that Brooklyn Lake leaks substantial amounts of water
to the Floridan aquifer. Further, Brooklyn Lake is in an area where
the piezometric surface is high (fig. 24) indicating the artisian
aquifer receives recharge and that substantial amounts of water
enter the aquifer in the general vicinity of the lake.

WATER BUDGET
A water budget for Brooklyn Lake is the accounting of water
entering and leaving the lake. The difference in the amount of
water entering and leaving the lake is reflected in the rise or fall
of the lake level.
Water entering the lake is from three sources: (1) rainfall (R),
(2) surface inflow (Is), and (3) ground-water inflow (Ig). Water
leaving the lake is represented by: (1) evaporation from the sur-
face of the lake (E), (2) surface outflow (Os), and (3) ground-
water outflow (Og). These factors may be expressed in a formula
as follows:
AS = (R + Is + Ig) (E + Os + Og)
where AS is change in lake storage
Rainfall records were collected near the south shore of the
lake by the Florida Forest Service (fig. 4). The rain gage was a
plastic tube type, nonstandard gage. The records were adjusted to
be consistent with records from three U.S. Weather Bureau stations
(Gainesville, 20 miles southeast; Glen St. Mary, 35 miles north; and
Federal Point, 30 miles east). It was assumed that the records
from this gage were indicative of the amount of rain falling evenly
on the lake surface, the area of which was adjusted for changes in
lake level.







FLORIDA GEOLOGICAL SURVEY


prevent critically low stages, but if allowed to remain during periods
of high water, could overtax the conveyance of the natural outlet
channel and cause flooding. Conversely, if the outlet channel was
lowered and its capacity increased to carry off more water and
prevent flooding, lake storage would be reduced and additional
lowering of the lake during periods of deficient rainfall would
result. A detailed engineering study would be required to determine
the overall feasibility and cost of controlling the lake and to work
out the details of hydraulics. The following is a general discussion
of several possibilities for controlling the lake.
Low lake stages have created more serious problems in recent
years than have flood stages. The extremely low stages that existed
in 1957-59 were brought about because the rate of movement of
water from the lake exceeded the rate at which it was entering the
lake from rainfall and surface inflow. The solution to the problem
would then seem to be to retard the losses or increase the inflow.
The water budget analysis indicates that water is removed from
the lake by the following processes and in the following proportions:
surface outflow, 10 percent; evaporation, 35 percent; and the net
ground-water outflow, 55 percent. The amount flowing through the
surface outlet is the only one that could be reasonably retarded.
However, the control of the surface outflow would not solve the
problem of low lake levels as outflow occurs only at high stages. In
fact, surface outflow is then necessary as a relief measure to
prevent flooding. Reduction of seepage and evaporation losses is
not easily accomplished and probably not feasible. Therefore,
measures other than preventing the usual natural water losses
must be considered.
Increasing inflow is a possible method by which Brooklyn Lake
could be prevented from falling below a desired level. In considering
this method of control, the amount and source of supplemental
inflow need to be determined.
Lake storage was reduced about 10,000 acre-feet during the
recession of lake levels that ended in 1958. It is reasonable to
assume that the period of this recession coincided with the 31-year
period of deficient rainfall. Therefore, a reduction in lake storage
of 10,000 acre-feet during a 31/-year period is equivalent to an
average rate of about 4 cubic feet per second, which is the average
rate of loss and the apparent minimum rate of supplemental inflow
needed to prevent such a recession. However, the greater difference
in head between the lake surface and ground-water level that would,
be induced by control measures could cause a substantial increase






REPORT OF INVESTIGATIONS NO. 33


in the rate of seepage to the ground, which would increase the in-
flow requirements necessary to hold the lake at a constant level.
Also, the greater average lake surface brought about by the higher
average lake stage would increase the evaporation. The increase
in evaporation would be essentially offset by the evaporation on the
larger lake surface. Though the exact rate of inflow needed to hold
the lake at a higher level is uncertain, any amount would be helpful.
Three possible ways in which additional water may be provided
to Brooklyn Lake are: (1) by pumping from the Floridan aquifer;
(2) by increasing the storage capacity of the lakes that are
connected by channels above Brooklyn Lake (fig. 3); and, (3) by
diverting water from Santa Fe Lake. A study would be necessary
to determine the feasibility and cost of these methods and to de-
termine the effects that each of these methods would have on the
related bodies of water.
Enough water may be pumped from the Floridan aquifer to
stabilize the level of the lake if the pumping of water from the
aquifer does not induce appreciable increases in leakage. The
leakage from the lake is proportional to the head difference between
the lake and the Floridan aquifer. The pumping of water from the
aquifer will create a cone of depression in the piezometric surface.
If the cone of depression extends to where the lake leaks, it will
create an additional head difference between the lake and the
aquifer. Thus, the downward flow of water to the Floridan aquifer
would increase and, in effect, part of the water pumped would be
circulated.
The amount of additional leakage that will be induced by
pumping from the Floridan aquifer was not studied. The greater
the distance of the pumped wells from the lake the less additional
leakage the pumping will induce. If, however, the water from the
lake leaks into an extensive system of solutional channels, such as
might be expected where large quantities of water enter a limestone
aquifer, the pumping of water from wells may induce only small
amounts of additional leakage from the lake. Accordingly, it may
be feasible to supply the lake with the needed water by pumping
from wells located at strategic sites adjacent to the lake.
Magnolia Lake (average surface area, 0.31 sq. mi.), Sandhill
Lake (average surface area 1.95 sq. mi.), and Blue Pond (average
surface area, 0.31 sq. mi.) are at higher elevations than Brooklyn
Lake and are connected by channels. Storage in these upper lakes
may be increased by low-head controls in the outlet channels. The
combined area of these three lakes in 2.57 square miles compared







FLORIDA GEOLOGICAL SURVEY


to the 1.00 square mile area of Brooklyn Lake. These lakes would
supply only a relatively small amount of water.
Another possible source of supply is Santa Fe Lake which is in
in the headwaters of the Santa Fe River basin, the adjoining basin
west of Brooklyn Lake. Santa Fe Lake has a surface area of 8.05
square miles and had a range in stage of 4.2 feet from 1957 to 1960.
Santa Fe Lake fluctuated through a range in stage of only 4.2 feet
(luring the period August 1957 to December 1960 while Brooklyn
Lake fluctuated through a range of 20 feet (fig. 5, 26). The stage
of Santa Fe Lake is higher than that of Brooklyn Lake by about
40 feet at low stages and about 25 feet at high stages. The map in
figure 2 shows possible location of a diversion canal from Santa Fe
Lake to Brooklyn Lake. The canal would extend from the northeast
end of Little Santa Fe Lake through Silver Lake and Mid Lake and
into the westernmost end of Brooklyn Lake. A profile showing
elevations from Santa Fe Lake to Brooklyn Lake, and a stage depth
graph of Santa Fe Lake, are given in figure 26.






STAGE OF SANTA FE LAKE




j .. [ 1j*I l 956l 1 99.9!l 1 l I L _I __ 1 960 .L__L


30


120
- .

"'0


195


DISTANCE, IN MILES
Figure 26. Stage graph of Santa Fe Lake and profile from Santa Fe Lake to
Brooklyn Lake.


I It959 1960


I I







REPORT OF INVESTIGATIONS No. 33


The movement of water into the lake, and from the lake,
through the water-table aquifer was estimated for monthly inter-
vals for the period March through October 1960. During this
period about 70 acre-feet of water was estimated to have moved
into the lake from the water-table aquifer on the southwestern
side of the lake and about 200 acre-feet was estimated to have left
the lake on the eastern side of the lake. During this period about
400 acre-feet more water was estimated to have left the lake than
entered the lake through the water-table aquifer.
The lateral movement of water through the water-table aquifer
from Brooklyn Lake, during the period March through October
1960, was computed to be less than 10 percent of the loss to the
aquifers. Therefore, most of the net ground-water flow from the
lake was to the Floridan aquifer.
The net ground-water outflow, most of which was outflow to the
Floridan aquifer, was the largest loss from the lake. The net
ground-water outflow was zero during the 1958 water year when the
lake was low, and increased rapidly during 1959 and 1960 as the
lake surface rose. The increase in the net ground-water outflow
as the level of the lake rose may be accounted for by: (1) a decrease
in inflow from and an increase in outflow to the water-table aquifer;
and (2) an increase in outflow to the Floridan aquifer.
When the level of the lake was low, undoubtedly the flow to the
Floridan aquifer was least; the inflow from the water-table aquifer
was probably more, and the outflow less. The outflow to the
Floridan aquifer is related to the difference in head between the
lake level and the piezometric surface of the Floridan aquifer. An
exact relation between the head difference and the outflow to the
Floridan aquifer could not be determined. The difference in head
was undoubtedly much less in 1958 than it was in 1960. The inflow
from the water-table aquifer was probably larger when the lake
was low because the gradient of the water table to the lake was
probably greater. Likewise, the outflow was probably less because
the gradient was probably smaller. Thus, the amount of inflow
required to maintain the lake at a high stage is greater than that
required to maintain the lake at a low stage.

METHODS OF CONTROLLING BROOKLYN LAKE

Both high and low stages must be considered in any plan to
control Brooklyn Lake. The problem is to prevent the stage from
falling below or rising above desirable levels. Additional water
diverted into the lake to supplement the natural inflow would






REPORT OF INVESTIGATIONS NO. 33


The methods suggested herein for controlling the stage of
Brooklyn Lake.have been based on the hydrologic data that have
been collected for this study. Additional detailed engineering
studies will be required to determine the most feasible method and
to prepare plans for the construction and operation of any struc-
tures that are required.

CONCLUSIONS

Brooklyn Lake receded about 20 feet during the period 1955-58.
This period of recession coincided with, and was a direct result of,
a period of deficient rainfall. Rainfall was deficient by nearly 23
inches during this period. The lack of rainfall upset the hydrologic
balance that normally keeps the lake stage from falling, and allowed
the rate of loss from the lake to far exceed the rate of
replenishment.
The lake's source of replenishment is rain that falls directly on
the lake surface and surface inflow from Magnolia Lake. During
prolonged periods of deficient rainfall surface inflow ceases, which
was the case during 1955-58. The lake received about twice as
much water from the surface inflow as it did from rain directly on
the lake surface during the 3-year period covered by this report.
Water leaves the lake through evaporation, surface outflow, and
seepage. From October 1957 to September 1960, seepage was by far
the greatest loss, accounting for 55 percent of all losses, or an
average of more than 3 mgd. Evaporation took 35 percent, and
surface outflow took 10 percent, of the total loss.
To prevent Brooklyn Lake from falling below a desirable stage
during prolonged periods of deficient rainfall it will be necessary to
divert water into the lake from other sources. Three possible ways
to divert water into the lake are: (1) by pumping from the Floridan
aquifer; (2) by increasing the storage in the three upper lakes
during periods of excess rainfall and releasing it to Brooklyn Lake
when needed; and (3) by diversion from Santa Fe Lake. Careful
and thorough engineering studies should precede the adoption of
any of these methods or any combination of them.






REPORT OF INVESTIGATIONS NO. 33


The methods suggested herein for controlling the stage of
Brooklyn Lake.have been based on the hydrologic data that have
been collected for this study. Additional detailed engineering
studies will be required to determine the most feasible method and
to prepare plans for the construction and operation of any struc-
tures that are required.

CONCLUSIONS

Brooklyn Lake receded about 20 feet during the period 1955-58.
This period of recession coincided with, and was a direct result of,
a period of deficient rainfall. Rainfall was deficient by nearly 23
inches during this period. The lack of rainfall upset the hydrologic
balance that normally keeps the lake stage from falling, and allowed
the rate of loss from the lake to far exceed the rate of
replenishment.
The lake's source of replenishment is rain that falls directly on
the lake surface and surface inflow from Magnolia Lake. During
prolonged periods of deficient rainfall surface inflow ceases, which
was the case during 1955-58. The lake received about twice as
much water from the surface inflow as it did from rain directly on
the lake surface during the 3-year period covered by this report.
Water leaves the lake through evaporation, surface outflow, and
seepage. From October 1957 to September 1960, seepage was by far
the greatest loss, accounting for 55 percent of all losses, or an
average of more than 3 mgd. Evaporation took 35 percent, and
surface outflow took 10 percent, of the total loss.
To prevent Brooklyn Lake from falling below a desirable stage
during prolonged periods of deficient rainfall it will be necessary to
divert water into the lake from other sources. Three possible ways
to divert water into the lake are: (1) by pumping from the Floridan
aquifer; (2) by increasing the storage in the three upper lakes
during periods of excess rainfall and releasing it to Brooklyn Lake
when needed; and (3) by diversion from Santa Fe Lake. Careful
and thorough engineering studies should precede the adoption of
any of these methods or any combination of them.










FLRD GEOLIOWC( ICA SURflViEWY~


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