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Hydrology of three sinkhole basins in southwestern Seminole County, Florida ( FGS: Report of investigations 81 )
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 Material Information
Title: Hydrology of three sinkhole basins in southwestern Seminole County, Florida ( FGS: Report of investigations 81 )
Series Title: ( FGS: Report of investigations 81 )
Physical Description: vi, 35 p. : ill., graphs ; 23cm.
Language: English
Creator: Anderson, Warren
Hughes, Gilbert Homer ( joint author )
Geological Survey (U.S.)
Seminole Co., Fla -- Board of County Commissioners
Publisher: State of Florida, Dept. of Natural Resources, Division of Resource Management, Bureau of Geology
Place of Publication: Tallahassee
Publication Date: 1975
 Subjects
Subjects / Keywords: Hydrology -- Florida -- Seminole County   ( lcsh )
Sinkholes -- Florida -- Seminole County   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Warren Anderson and G. H. Hughes.
Bibliography: Bibliography: p. 35.
General Note: "Prepared by the United States Geological Survey in cooperation with the Bureau of Geology... and the Board of County Commissioners of Seminole County."
 Record Information
Source Institution: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000152397
oclc - 02412099
notis - AAR8656
System ID: UF00001268:00001

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STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Harmon Shields, Executive Director



DIVISION OF RESOURCE MANAGEMENT
Charles M. Sanders, Director



BUREAU OF GEOLOGY
Charles W. Hendry, Chief


REPORT OF INVESTIGATIONS NO. 81



HYDROLOGY OF THREE SINKHOLE BASINS IN

SOUTHWESTERN SEMINOLE COUNTY, FLORIDA



By
Warren Anderson and G. H. Hughes
U. S. Geological Survey


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
DIVISION OF RESOURCE MANAGEMENT
FLORIDA DEPARTMENT OF NATURAL RESOURCES
and the
BOARD OF COUNTY COMMISSIONERS OF SEMINOLE COUNTY


Tallahassee, Florida
1975








Fn- 3 /





DEPARTMENT
OF
NATURAL RESOURCES


REUBIN O'D. ASKEW
Governor


BRUCE A. SMATHERS
Secretary of State


PHILIP F. ASHLER
Acting Treasurer


RALPH D. TURLINGTON
Commissioner of Education


ROBERT L. SHEVIN
Attorney General


GERALD A. LEWIS
Comptroller


DOYLE CONNER
Commissioner of Agriculture


HARMON W. SHIELDS
Executive Director





LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee
November 3, 1975



Governor Reubin O'D. Askew, Chairman
Florida Department of Natural Resources
Tallahassee, FL 32304


Dear Governor Askew:
The Bureau of Geology, Division of Resource Management, Department
of Natural Resources, is publishing as its Report of Investigations No. 81,
the "Hydrology of Three Sinkhole Basins in Southwestern Seminole County,
Florida".
The recent spread of urban development has tended to encroach on the
flood plains of lakes in these sinkhole basins and cause concern over the flood
hazard that results. The purpose of this investigation was to document or
evaluate 1) the highest known lake levels in the sinkhole area; 2) the inner-
relation of topography, geology, climate, and hydrology as they pertain to
water level fluctuations; 3) the effects of cultural development on water levels,
and 4) the possible methods of controlling lake levels.
This report contains information that should be useful to local officials
in planning for maximum utilization of land resources of the area with mini-
mum risk of flood damage to the attendant cultural development or of de-
gradation of the hydrologic system.

Sincerely,



C. W. Hendry, Jr., Chief












































Completed manuscript received
June 16, 1975
Printed for the
Florida Department of Natural Resources
Division of Resource Management
Bureau of Geology

Tallahassee
1975


iv





CONTENTS


Page

Abstract ...................................... ............................................................. .......... ......-... 1

Introduction ........................................................................................................................................ ................. 2

Purpose and scope .............................................................. ................. ....................... 2

Acknowledgments .....................................................................................................................

Description of the area ............................................................................................................. 3

L location and extent ........................................................................................................................... 3

Geologic setting ............................ .................................................................................... 5

Topographic setting .... ........... ........................................................................... ............... 5

Climatological setting ................................................................................................. 7

Hydrologic relations .......................... ..................................................... .................-........ 7

Peak stages and probability of occurrence .................................. ............... .......... 9

Hydrologic setting on September 30, 1960 .................. ........ ......................... ......... 17

Stage fluctuations and seepage rates ..... .... ........................... ............... .............2..... 1

Effects of cultural development in the sink basins ...............................................................29

Control of water levels in the sink basins ........................ ..........................................31

Summary and conclusions.............................................................................................................. 32

Selected references .................... ...................... ...............-...... ........ .... 35






ILLUSTRATIONS

Figure Page
1. Map of Seminole County showing location of area
of investigation ....... ........ ......................................... ...... .... .......... ....... 4
2. Map of southwestern Seminole County showing the
generalized configuration of the potentiometric surface
of the Floridan aquifer September 80, 1960 ....---.. 6
3. Graph of departure from normal rainfall at Orlando, Fla.,
1893-1973 water years (National Weather Service) ..................
4. Graph of monthly average discharge of Wekiva River
near Sanford, month-end water level in well 841-121-1
near Island Lake, and monthly rainfall at Orlando,
September 1951 to December 1961 ............................................... ...........11
5. Graph of annual discharge of Wekiva River near
Sanford, Fla. 1936-72 water years; drainage area, 189
square m iles ....................................... ............ ....................................... ....12
6. Graph of average annual discharge of Cypress Creek at
Vineland, Fla., 1946-72 water years; drainage area,
30.3 square miles .................. ................................. .
7. Graph of average annual discharge of Econlock-
hatchee River near Chuluota, Fla., 1936-72 water
years; drainage area, 241 square miles..................................... .......... 14
8. Graph of relation between average annual discharge
of Wekiva River near Sanford, Fla., as computed
from gaging-stations records and as computed
from rainfall records for Orlando by regression
methods, 1936-62 water years .............................................. .............15
9. Graph of average annual discharge of Wekiva River
near Sanford, Fla., computed from rainfall records
for Orlando by regression methods, 1895-1973 water
years .......................................... ......... ....... ...................... ............. ....16
10. Section A-A' showing altitudes of surface-water
bodies and estimated altitudes of water table and
potentiometric surface of the Floridan aquifer,
Septem ber 30, 1960 ......................................................................... ...........18
11. Hydrographs for Island Lake and well 841-121-1 .........................22
12. Hydrographs for Lake Orienta and well 841-121-1 .....................24
13. Hydrographs for Grace Lake and well 841-121-1 ...........................26
14. Hydrographs for Cranes Roost and well 841-121-1 ...................28
15. Hydrographs for Eleventh Hole Pond and well 841-121-1.........80






HYDROLOGY OF THREE SINKHOLE BASINS IN
SOUTHWESTERN SEMINOLE COUNTY, FLORIDA

by

Warren Anderson and G. H. Hughes


ABSTRACT

The southwestern part of Seminole County-in east-central Florida-is
characterized by sinkholes formed by the subsidence of surficial deposits into
solution cavities in the underlying limestone deposits. The area includes three
sinkhole basins created by such subsidence: Cranes Roost, Palm Springs, and
Grace Lake.
Cranes Roost basin (drainage area, 5.02 square miles) contains a closed
drainage system of lakes and swamps-including Lakes Adelaide, Florida.
and Mobile--that terminates at Cranes Roost sink. It also contains Lake
Orienta and two unnamed sinks which do not overflow into Cranes Roost
sink.
Palm Springs basin (drainage area, 1.77 square miles) includes Lake
Marion, Eleventh Hole Pond, and several small unconnected sinks.
Grace Lake basin (drainage area, 1.64 square miles) includes Island Lake
which overflows into Grace Lake.
The recent spread of urban development has tended to encroach on the
flood plains of lakes in these sinkhole basins and cause concern over the flood
hazard that results. An investigation was made of the area to document the
highest known lake levels, to examine possible effects of urbanization with
regard to increasing the flood hazard, and to appraise the possibilities of
controlling lake levels to reduce or limit the flood hazard.
The highest lake stages of record in the three sinkhole basins occurred in
September 1960. Analyses of the hydrologic relations between lake stages,
ground-water levels, stream discharges, and rainfall in the area indicated that
the lake stages of September 1960 probably were the highest attained since
at least 1895.
Cultural development that increases the percentage of a sink basin covered
by impervious materials will cause more rapid runoff of a larger part of the
rainfall in the basin. Thus, as development progresses, lake stages seldom
reached under natural conditions may be reached more frequently unless the
lake levels are controlled.






BUREAU OF GEOLOGY


In Cranes Roost basin, the levels of Lakes Mobile, Adelaide, and Florida
could be controlled by enlarging their surface outlets and adding control struc-
tures; however, such measures might be ineffective unless the level of Cranes
Roost also was controlled. The level of Cranes; Roost could be controlled by
removal of water by pumping or by providing a surface outlet; pumping
might be ineffective during extreme wet periods because of the sudden surface
inflow from upstream lakes and the potential for ground-water inflow from the
Floridan aquifer. The level of Lake Orienta could be controlled by removal
of water by pumping or by providing a surface outlet.
In the Palm Springs sink basin, the levels of Lake Marion and the several
small sinks could be controlled by removal of water by pumping or by pro-
viding surface outlets. For the several sinks, however, providing a surface
outlet would require an extensive excavation and pumping might prove im-
practical because of seepage induced from the Floridan aquifer.
The level of Island Lake-in Grace Lake sink basin-could be controlled by
enlarging its surface outlet and providing a control structure. The peak stage
of Grace Lake could be reduced by lowering its outlet to the north, but release
of water during wet periods might cause downstream flooding.

INTRODUCTION
Seminole County, an area of 321 square miles in east central Florida,
has developed rapidly since the mid-1960's, especially in the southern part
adjacent to the Orlando metropolitan area in Orange County. Land values are
rising with consequent pressure to develop land in the limestone sinkhole area
in southwestern Seminole County. Knowledge of physiographic and hydrologic
characteristics of this area is needed to evaluate both the suitability of the
lands for cultural development and the measures that may be taken by local
officials to enhance the suitability of the lands. Consequently, the U. S. Geo-
logical Survey in cooperation with the Board of County Commissioners con-
ducted an investigation of the sinkhole area from October 1, 1970 to Septem-
ber 30, 1971.
Purpose and Scope
The purpose of the investigation was to document or evaluate:
(1) the highest known lake levels in the sinkhole area; (2) the interrelation
of topography, geology, climate, and hydrology as they pertain to water-level
fluctuations; (3) the effects of cultural development on water levels; and (4)
the possible methods of controlling lake levels. This report contains informa-
tion that should be useful to local officials in planning for maximum utilization
of land resources of the area with minimum risk of flood damage to the at-
tendant cultural development or of degradation of the hydrologic system.






REPORT OF INVESTIGATION NO. 81


The scope of the study was such that all pertinent available water-level,
streamflow, and rainfall records were evaluated, but field work and collection
of new water records were minimal. Periodic water-level data were obtained,
however, for five surface-water bodies and one artesian well.

Acknowledgments
Special thanks are extended to William Bush, Jr., Seminole County Engi-
eneer, who provided valuable information throughout the study and to Julian
Johnson of the County Engineer's Office, who determined the datums of the
gauges and the altitudes of flood marks pointed out by local citizens. The
authors appreciate the cooperation of the citizens of the area who gave infor-
mation on high-water levels and obtained water-level data.
Many of the background data used in the preparation of this report
are contained in an interim report by Heath and Barraclough (1954) and a
comprehensive report by Barraclough (1962a) on the ground-water resources
and geology of Seminole County. These reports contain references to many
reports by earlier investigators dating back to 1913.
The investigation and preparation of this report were under the direct
supervision of Joel 0. Kimrey, subdistrict chief, Winter Park, and under the
general supervision of C. S. Conover, District Chief, Water Resources Division,
U. S. Geological Survey, Tallahassee, Florida.
For the use of those readers who may prefer to use International System
(metric) units rather than English units, the conversion factors for the terms
used in this report are listed below:

Multiply English unit By To obtain metric unit

inches 25.4 millimetres
.0254 metres
feet .3048 metres
miles 1.609 kilometres
acres 4047 square metres
square miles 2.590 square kilometres
cubic feet per second .02832 cubic metres per second
acre-feet 1233 cubic metres

DESCRIPTION OF THE AREA
Location and Extent
The area of investigation, in the southwest part of Seminole County, is
shown on figure 1. Within this area, the study was restricted to three sink
















-O SANGFORD tO o










o'0 IS' 10' 5 81oo' o 55
-nation


I SEMINOLE COUNTY _
ORANGE COUNTY

2 20 15' id 05' 8100' 8P55
Figure l.-Seminole County showing location of area of investigation.






REPORT OF INVESTIGATION NO. 81


basins, as delineated by the basin-boundary lines in figure 2. The three sink
basins are called, in this report, Cranes Roost sink basin. Palm Springs sink
basin, and Grace Lake sink basin, in order from south to north. In the aggre-
gate, these basins occupy 8.43 square miles.

Geologic Setting
The area is underlain by limestone of Eocene age from about sea level to
70 feet below sea level. The limestone is overlain by about 80 to 150 feet of
calcareous clay and sandy limestone of the Hawthorn Formation of Miocene
age. The Hawthorn Formation is overlain by 10 to 60 feet of clay (Barra-
clough, 1962a, fig. 3). The Eocene limestone and hydrologically connected
permeable zones in the lower part of the Hawthorn Formation are collectively
known as the Floridan aquifer.

Topographic Setting
The area is a fairly level plain generally 85 to 100 feet above mean sea
level except at the southern edge of the area where one sand hill exceeds 120
feet in altitude. The plain has been extensively altered by the subsidence of
the surface materials into cavities in the underlying limestone of the Floridan
aquifer. The cavities are caused by solution of limestone by water. The three
sink basins studied in this report were formed by such subsidence.
In the three sink basins, circulation of water through the limestone is great
because little of the rainfall there escapes as surface outflow. The rainfall
which does not return to the atmosphere by evaporation eventually infiltrates
to the Floridan aquifer and subsequently is discharged outside the area, mostly
at Palm and Sanlando Springs. The voids and cavities, caused by water pass-
ing through the Floridan aquifer, in time are enlarged to such an extent that
the overlying Hawthorn and younger deposits slump or collapse into them.
Because of differences in permeability of the limestone and the overlying
deposits, infiltration of water and the attendant land subsidence have been
greater in the western parts of Cranes Roost and Palm Springs sink basins and
in the northern part of Grace Lake sink basin than in other parts of the basins.
The extent and configuration of each of three sink basins was determined
by the course that surface outflow would ultimately take if the water level in
the individual sink basins were to reach a high enough stage to cause the basin
to overflow (fig. 2). Cranes Roost sink basin, the southernmost of the three, is
5.02 square miles in area and consists of a system of lakes and sinks. Surface
drainage begins in several swamps south of Lake Seminole, about halfway
between Altamonte Springs and Longwood. This drainage is joined by over-
flow from Lake Mobile just before it enters Lake Florida. Overflow from Lake






BUREAU OF GEOLOGY


Florida passes through Lake Adelaide which overflows
Lake Orienta and two smaller sinks, though not connected
the surface, would drain into Cranes Roost sink if their


into Cranes Roost.
to Cranes Roost on
stages were to rise


a.i I' *3' II' 11' rto'
sl
A--m ~ 1- I -TV- P v ti
'..wwc. ^- o^i- k n- /-M-^*.'- A ^-' *


Figure 2.-Map of southwestern Seminole County showing the generalized
configuration of the potentiometric surface of the Floridan aqui-
fer September 30, 1960.
to about 77 feet above mean sea level. Although this basin does not overflow,
Cranes Roost sink would flow into the Little Wekiva River 0.6 mile south of
Sanlando Springs were the basin ever to fill.






REPORT OF INVESTIGATION NO. 81


Just north of Cranes Roost sink basin lies the Palm Springs sink basin, which
contains Lake Marion and several smaller sinks. The area of this sink basin is
1.77 square miles. None of the sinks are connected on the surface, but if they
were, they would constitute a drainage system which upon filling would
overflow into the Little Wekiva River at Palm Springs. None of the smaller
sinks are named on the map of figure 2. The pond for which stage data were
obtained during this investigation is herein referred to as Eleventh Hole Pond
because it is near the 11th hole of a golf course.
Grace Lake sink basin, the northernmost, contains Island and Grace Lakes
and occupies 1.64 square miles in the northern part of the sinkhole area. Island
Lake overflows into Grace Lake; Grace Lake at times overflows into Lake
Myrtle and two intervening sinks which lie outside the area of investigation
(fig. 2). Flow from Grace Lake sink basin, should it occur in sufficient quan-
tity to cause the intervening sinks to overflow, would ultimately reach Soldier
Creek, which is tributary to Lake Jessup and the St. Johns River.

Climatological Setting
The climate of the area is characterized by hot, humid summers and cool,
dry winters that are separated by short periods of mild, dry weather in spring
and fall. Wide deviations from these normal conditions occur, especially as
regards rainfall. Any month can be extremely dry or wet.
Average rainfall, as measured at Orlando, is 51.37 inches per year. Since
1893, rainfall totals for water years (which begin October 1 of the year
previous to the designated year and end September 30 of the designated year)
have ranged from 18.31 inches below normal in 1927 to 21.94 inches above
normal in 1905 (figure 3).
Mean monthly air temperatures range from 60.40F in January to 81.80 F
in August and average 71.50F. The lowest recorded temperature was 200F
and the highest, 1000F. Evaporation from a water surface is estimated to
average 50 inches per year. Departures of more than 2 inches from average
during a year probably occur in less than 10 percent of the years (Anderson
and others, 1965).

HYDROLOGIC RELATIONS
The pattern of fluctuation in the water level of a lake is the resultaiiof
several climatological and physiographic factors. Some of these tend to cause
a lake level to rise while others tend to cause it to fall. Lakes in the area of
investigation gain water from rain on their surfaces; surface inflow; and
ground water derived from the water table aquifer, the Floridan aquifer, or
both aquifers. The lakes lose water by evaporation, transpiration, and seepage









I I I I I I 1 I I I I I
NOTE NORMAL RAINFALL EQUALS 51.37 INCHES


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Figure 3.-Departure from normal rainfall, National Weather Service Office,
Orlando, Fla, 1893-1973 water years.


10


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REPORT OF INVESTIGATION NO. 81


to the aquifers; some of the lakes are landlocked but others overflow to another
lake or sink at a lower altitude. The effects of rainfall and surface flow on
lakes are extremely variable and intermittent whereas the effects of ground-
water seepage, evaporation, and transpiration are relatively stable and contin-
uous. The balance between input and output is continually changing; hence.
the level of the lake is nearly always either rising or falling.
During and for a short time after rainfall, surface inflow to the lakes
occurs as overland flow and street and sewer drainage; if the lakes are suffici-
ently filled, surface outflow occurs as overflow to down-gradient lakes or sinks.
Water moves from the lakes to the water-table aquifer if lake levels are
above the water table, and moves into the lakes from the water-table aquifer
if lake levels are below the water table. Similarly, water moves from the lakes
into the Floridan aquifer if lake levels are above the potentiometric surface of
the Floridan aquifer, and moves into the lakes from the Floridan aquifer if
lake levels are below the potentiometric surface. Rates of flow vary with hydro-
static head and with the permeability of materials along the path of flow.

PEAK STAGES AND PROBABILITY OF OCCURRENCE
The approximate peak stages reached by one or more of the water bodies
in the area of investigation in 1954, 1960, and 1970 are given in the table
below. Highwater lines for the peak stages of 1960 are also indicated in figure
2. These data were obtained from a report of a previous investigation, records
in the files of the Seminole County Engineer, highwater lines pointed out by
local residents, and levels to stain marks and wash lines by the Seminole
County Engineer's office.

Altitude, feet above mean sea level
Water Body January 1954 September 1960 March 1970
Lake Orienta 60.5(a) 67.9(b) 61.8(b)
Cranes Roost 60.7(c) 55.3(d)
First sink south 61.4 (c)
of Cranes Roost
Second sink south 64.1 (c)
of Cranes Roost
Grace Lake 66 (c) 65.2(d)
(a) From Barraclough (1962a)
(b) High-water mark pointed out by Glen D. Humes, 134 Hattaway Drive.
Altamonte Springs.
(c) From Department of Transportation plans for Interstate Highway 4.
Data supplied by Seminole County Engineer.
(d) Stains on posts and wash lines on highway fills.







BUREAU OF GEOLOGY


The available lake-stage data are insufficient for evaluating the frequency
of occurrence of specific lake stages. However, lakes, streams, and aquifers are
part of a hydrologic system, and rainfall provides the water than keeps the
system viable. As a consequence, fluctuations of lake levels are tied to the
fluctuations of ground-water levels and stream discharges. Therefore, some
insight as to the frequency of occurrence of selected lake stages can be gained
from a study of the available records of ground-water levels, stream discharges,
and rainfall, which together span a large number of years and a wide range
of hydrologic conditions.
From November 1953 to December 1956 the trend of the water level of
Lake Orienta was generally the same as the trend of the level of the potentio-
metric surface of the Floridan aquifer, which is represented by the level of
water in well 841-121-1 (fig. 4). The potentiometric surface of the Floridan
aquifer was substantially higher in September 1960 than in January 1954, or
in the last few months of 1953. This is consistent with the fact that the stage of
Lake Orienta was substantially higher in September 1960 than in January
1954 as the table shows.
The flow of Wekiva River consists partly of overland runoff and partly
of ground water discharged from the Floridan aquifer at various springs
along the river, including Palm and Sanlando Springs (fig. 2) which dis-
charge into the Little Wekiva River. The discharge of the Wekiva River
follows the trend of the water level in well 841-121-1 (fig. 4). Sharp upswings
of the discharge and water-level graphs generally correspond with large
monthly rainfalls at Orlando and sustained downswings of the graphs gen-
erally corresponds with a series of small monthly rainfalls; the exceptions are
an indication that rainfall over the drainage basin of concern was not uni-
formly the same as rainfall at Orlando.
The average annual discharge of Wekiva River near Sanford (fig. 5)
was substantially greater in the 1960 water year than in any year since at
least 1936. Similarly, the average annual discharge of Cypress Creek at Vine-
land in 1960 was the greatest measured since at least 1946 (fig. 6). The
Cypress Creek drainage area above Vineland encompasses 30.3 square miles
centered about 10 miles east of Orlando. About 25 percent of the Cypress
Creek drainage area consists of lakes.

The average annual discharge of Econlockhatchee River near Chuluota
(fig. 7) also was greater in 1960 than in any year since at least 1936. In
relation to Wekiva River, Econlockhatchee River has a larger surface-water
component and a smaller ground-water component. The annual discharge of
Econlockhatchee River tends to reflect more directly the variations in the
yearly rainfall.









REPORT OF INVESTIGATION NO. 81


1200


1000 8
ioo

o a
800 ^

w
U-
600o


400 W


200


0


951 1 952 1953 1954 1955 1956 1957 1958 1959 1960 1961
Figure 4.-Monthly average discharge of Wekiva River near Sanford, month-
end water level in well 841-121-1 near Island Lake, and monthly
rainfall at Orlando, September 1951 to December 1961.

Thus, from the general relation apparent between lake levels, ground-
water levels, and the measured discharges of different types of streams of
different sizes, it reasonably can be concluded that the stages of Lake Orienta
and other lakes in the area of investigation, especially lakes in closed basins.
were higher in September 1960 than they were at any time since at least 1936.

On the assumption that the discharge of Wekiva River near Sanford pro-
vides a valid index of the general level of nearby lakes, the average annual







12 BUREAU OF GEOLOGY

discharge of Wekiva River was estimated for years before 1936 by regression
methods (Riggs, 1968) using the following equation as a model: (1)
Q, = a + boP0 + bP, + bP,
Where Qo = average annual discharge of Wekiva River (water years), in
cubic feet per second.
Po = annual rainfall at Orlando in the year corresponding to Qo, in
inches.


P, = annual rainfall at Orlando in first preceding year,
P2 = annual rainfall at Orlando in second preceding year,
and, a, bo, b1, and b2 are regression coefficients.


500


400


300


200


in inches;
in inches;


o r
qt .
a) 0


Figure 5.-Average annual discharge of Wekiva River near Sanford, Fla.,
1936-72 water years; drainage area, 189 square miles;.








REPORT OF INVESTIGATION NO. 81


50


40


30


20


10


0


o o 0 0 U 0 o O
4- tO rNt LO (
0) 0) 0) O) 0) 0) 0


Figure 6.-Average annual discharge of Cypress Creek at Vineland, Fla., 1946-
72 water years; drainage area, 30.3 square miles.

On basis of double-mass analyses of rainfall and streamflow, the annual
discharge of Wekiva River near Sanford (fig. 5) in recent years appears to
be larger than it was in the past, both in relation to rainfall in the general
area and in relation to the discharge of nearby streams; consequently, only
the data for 1936-62 was used in the regression analysis. The resulting regres-
sion equation was:
Qo = 4.19Po + 3.71P, + 1.45P2 209 (2)
The annual discharges computed by equation 2 are generally within 15
percent of the discharges measured during 1936-62 (fig. 8). The estimated
.1,







BUREAU OF GEOLOGY


discharge for 1960 was substantially greater than that computed for any year
since 1895. (fig. 9).
Similar regression analyses were made using the average of rainfall at
Orlando and Sanford, the average of rainfall at Orlando and Eustis-Eustis
is about 30 miles northwest of Orlando-and the average of rainfall at all
three stations. The rainfall record for Sanford begins in 1914; that for Ens-
tis in 1891. The pattern of the computed annual discharges in each case was
similar to that shown in figure 9: the computed discharge for 1960 was always
substantially greater than any other.


800


700


600


500


400


300


200


100


_t 0 t0


Figure 7.-Average annual discharge of Econlockhatchee River near Chuluota,
Fla, 1936-72 water years; drainage area, 241 square miles.

In the different analyses the regression coefficients for Po and P1 varied
some with the choice of rainfall data but were of the same general magnitude
and always of the same sign (positive). The coefficient for Pa was relatively







REPORT OF INVESTIGATION NO. 81


small in each case but was negative when the average of rainfall at Orlando
and Sanford was used.


450


DISCHARGE COMPUTED FROM GAGING-STATION RECORDS,
CUBIC FEET PER SECOND
Figure 8.-Relation between average annual discharge of Wekiva River near
Sanford, Fla., as computed from gaging-station records and as
computed from rainfall records for Orlando by regression
methods, 1936-62 water years.

According to Riggs (1968, p. 19, 20), as variables are added to or de-
leted from a regression, a change in sign of the coefficient of one of the
variables indicates that the effect of the variable is small in relation to the
sampling error. Seemingly, the same conclusion would apply if the use of
different but comparable data in a regression produces a change in sign of the
coefficient of one of the variables. The effect of antecedent rainfall on the
current year's discharge doubtless decreases with each preceding year. Thus,
for the purpose at hand, there is no need to consider the effect of rainfalls
past the second preceding year.
On basis of the foregoing analysis of the average annual discharge of
Wekiva River near Sanford, and other hydrologic data and relations pre-
viously described, it is concluded that the peak stages attained by lakes in

















0 500 i Ii I I I II



U C
00- -

2 100 1 1


8 10 In 0 to 0 0 W) 0 0 in 0o0
0o 0 o CY o o g o o _







Figure 9.--Average annual discharge of Wekiva River near Sanford, Fla., com-
puted from rainfall records for Orlando by regression methods,
1895-1973 water years.







REPORT OF INVESTIGATION NO. 81


southwest Seminole County in 1960 probably were higher than any occurring
since at least 1895.

HYDROLOGIC SETTING ON SEPTEMBER 30, 1960
In the area investigated the potentiometric surface of the Floridan aquifer
in 1960 was recorded in only one well (number 841-121-1 at Island Lake)
which has served as a monitor well since 1951. Consequently, the maximum
altitude of the potentiometric surface elsewhere in the area can only be
estimated.
The estimated altitude and configuration of the potentiometric surface on
September 30, 1960 (fig. 2) are based on the altitudes of water levels in wells
observed by Barraclough (1962b) in January 1954 and June 1956. The 1960
altitudes of water levels in these wells were estimated on the assumption that
the ratio of the difference between their 195-1 and 1956 water levels to
the difference between their 1956 and 1960 water levels was the same as the
ratio of these differences for well 841-121-1. This assumption is reasonable
because experience has indicated that correlation from well to well is fairly
tight for wells tapping the Floridan aquifer, not only in this area but else-
where in Florida as well. Along the western and southern boundaries of the
area the potentiometric contours as shown in figure 2 conform with the po-
tentiometric contours presented by Lichtler (1968, p. 102) for the September
1960 high-water conditions in Orange County.
Figure 10 shows the estimated altitudes of the water-table aquifer and the
potentiometric surface of the Floridan aquifer at the end of September
1960 along section A-A' (fig. 2) passing through Lake Orienta.
The high water table east of Lake Orienta (fig. 10) is typical of the con-
dition existing east of a line running in an arc from just east of Lake Orienta,
northeast to the area between Lakes Florida and Mobile, and thence northwest
around the west side of Island Lake where it curves east. The Hawthorn de-
posits in the area of investigation lying east of this line must be relatively
impermeable in order to permit head differences as much as 30 feet between
the water table and Floridan aquifers. West of the line, smaller head differ-
ences (5 to 8 feet) between the aquifers indicate that the Hawthorn deposits
are much more permeable than those to the east.
Ordinarily, evapotranspiration is sufficient to prevent the water table
from rising to land surface in places where the terrane slopes to the lakes and
sinks west of the area of high water table previously described. During wet
periods, however, ground water comes to the surface along these slopes, as
evidenced by the stench of septic-tank effluent in the subdivision east of Lake
Orienta in the spring of 1970 (William Bush, Jr., oral commun., 1971).
















Land surface


"Water table






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


_,100
W
Id
>
a
-j
49
W
'I,
(0
280


W
LU


S60
W
W
IL
4i
IL
0
i-40
F
? 40
5


IMile
I I I i I I


(See figure 2 for location of section)


Figure 10.-Section A-A' showing altitudes of surface-water bodies and
estimated altitudes of water table and potentiometric surface of
Floridan aquifer, September 30, 1960.


A

I


n


surface


0
I 1


___ _I ______ I___ __


-


-







REPORT OF INVESTIGATION NO. 81


Described below are the processes that were probably going on in some of
the water bodies on September 30, 1960, when their stages were at or near
their maximum known altitudes. Rainfall in the general area was about 0.7
inch on September 29 and 30, 1960; whether overland flow occurred on the
30th would depend on how late in the day rain fell on the 29th:

Cranes Roost Sink Basin

Lake Mobile
Surface inflow Street and storm-sewer drainage, possibly overland
inflow.
Surface outflow Overflow to down-gradient lakes.
Ground-water inflow -Lateral seepage from surrounding water-table
aquifer.
Ground-water outflow Minor vertical seepage through the bottom to
the aquifers beneath the lakes.
Note.-Lake levels were higher than the potentiometric surface of the
Floridan aquifer but probably lower than the surrounding water table.

Lakes Adelaide and Florida
Surface inflow Street and storm-sewer drainage, overflow from up-
gradient lakes, possibly minor overland inflow.
Surface outflow Overflow to Cranes Roost.
Ground-water inflow Lateral seepage from the surrounding water-table
aquifer; vertical seepage through the bottom from the aquifers be-
neath the lake.
Ground-water outflow None.
Note.-Lake levels probably were below both surrounding water table
and potentiometric surface.

Cranes Roost
Surface inflow Street and storm-sewer drainage, inflow from Lake
Adelaide, possibly minor overland inflow.
Surface outflow None.
Ground-water inflow Probably none.
Ground-water outflow Lateral seepage to the surrounding water-table
aquifer and vertical seepage through bottom to the aquifers beneath
the sink.
Note.-Sink water level probably higher than both surrounding water
table and potentiometric surface.







BUREAU OF GEOLOGY


Lake Orienta
Surface inflow Street and storm-sewer drainage, overflow from lakes
to the east, possibly minor overland inflow.
Surface outflow None.
Ground-water inflow Lateral seepage from the water-table aquifer.
Ground-water outflow Vertical seepage through bottom to the aquifers
beneath the lake.
Note.-The adjacent water table probably was higher than the lake. The
lake level was higher than the potentiometric surface beneath the
lake.


Palm Springs Sink Basin

Lake Marion
Surface inflow Street and storm-sewer drainage, possibly minor over-
land flow.
Surface outflow None.
Ground-water inflow Lateral seepage from the adjacent water-table
aquifer on east.
Ground-water outflow Lateral seepage to adjacent water-table aquifer
on west and vertical seepage through the bottom to the aquifers
beneath the lake.
Note.-Lake level probably lower than adjacent water table at east end
but higher than water table at west end. Lake level higher than
potentiometric surface.

Palm Springs sinks (including Eleventh Hole Pond)
Surface inflow Street and storm-sewer drainage, possibly some over-
land runoff from lawns and golf course fairways.
Surface outflow None.
Ground-water inflow Lateral seepage from the surrounding water-table
aquifer and vertical seepage through bottom from the aquifers beneath
the sinks if the sink levels were below the potentiometric surface.
Ground-water outflow Vertical seepage through bottom to the aquifers
beneath the sinks if the sink levels were above the potentiometric
surface.
Note.-Sink levels probably were slightly above potentiometric surface
if the stage was falling and slightly below if the stage was rising.







REPORT OF INVESTIGATION NO. 81


Grace Lake Sink Basin
Island Lake
Surface inflow Street and storm-sewer drainage, possibly overland
inflow.
Surface outflow Overflow to down-gradient lakes.
Ground-water inflow Lateral seepage from surrounding water-table
aquifer.
Ground-water outflow Minor vertical seepage through the bottom to the
aquifers beneath the lakes.
Note.-Lake levels were higher than the potentiometric surface but
probably lower than the surrounding water table.

Grace Lake
Surface inflow Overflow from Island Lake, highway drainage, possibly
minor overland inflow.
Surface outflow Possibly overflowing to down-gradient sinks and
lakes.
Ground-water inflow Probably none.
Ground-water outflow Vertical seepage through the bottom to the
aquifers beneath the lake.
Note:-Lake level probably higher than both surrounding water table
and potentiometric surface.

STAGE FLUCTUATIONS AND SEEPAGE RATES
To provide some insight to the nature of water-level fluctuations of the
surface-water bodies and their relation to the Floridan aquifer, stage data
were collected during the investigation for five water bodies and well 841-
121-1 which taps the Floridan aquifer near Island Lake. These data are shown
in figures 11-15; the hydrograph for the well is repeated on the hydrograph
for each of the water bodies for comparison. For three of the water bodies-
Lake Orienta, Cranes Roost, and Grace Lake-the approximate altitude is
shown for the peak stages occurring about mid-March, 1970.
A similarity in the pattern of fluctuation in the water levels of Island
Lake and well 841-121-1 is evident in figure 11, although the range of fluctu-
ation is much less for the lake than for the well. The lake level being about
40 feet higher than the well level suggests a poor connection between the lake
and the Floridan aquifer. This would preclude an appreciable amount of
seepage from the lake to the aquifer.
On the assumption that seepage from Island Lake to the Floridan aquifer
is insignificant, the hydrologic conditions at Island Lake between January 1








BUREAU OF GEOLOGY


84
ISLAND LAKE

83 ___ ___'
-- -- -- --6 ___-- -- -- -- -- -- --

82


81 --..



47


46
/____WELL 841-121-I AT ISLAND LAKE

45
44 --- ---_--- ___---__--- ______

44----


43-




1-- --
42


41
A n t-- -- -- -- -- -- -- -


NOV.
197


DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT OCT. NOV. DEC.


1971


0'


Figure 11.-Hydrographs for Island Lake and well 841-121-1.


and May 31, 1971 were favorable for making an estimate of the difference
between rainfall and lake evaporation for the same 5-month period. The lake
level was low enough that there was no surface-water outflow. Surface-water
inflow probably was minimal because the highly permeable surficial sand in
most parts of the contributing drainage area is conducive to the infiltration of
rainfall. Rainfall during this period-10.7 inches at Orlando; 15.8 inches at
Sanford; mostly in February and May-was not great enough to cause large
quantities of runoff but was sufficient to account entirely for the few rises
in lake level indicated by the hydrograph. Small quantities of runoff would







REPORT OF INVESTIGATION NO. 81


not contribute appreciably to a rise in lake level because the runoff would
be distributed over the entire lake area which takes up a large percentage of
the total drainage area. Ground-water inflow to the lake from the water-table
aquifer probably was small because rainfall was over 11 inches below normal
in the 6 months preceding January 1971. Thus, the 0.6 foot decline in the
stage of Island Lake between January and May 1971 is considered to be a
good measure of the excess of evaporation over rainfall for that period.
The estimate of 0.6 foot for the excess of evaporation over rainfall between
January and May 1971 probably is applicable to other water bodies in the
area for the same period. For example, the hydrograph for Lake Orienta (fig-
ure 12) shows that during this period the lake level declined about 1.1 feet.
Therefore, the net of seepage into the lake from the water-table aquifer and
out of the lake to the water-table and Floridan aquifers plus any surface-water
inflow that occurred was 0.5 foot. (Although figure 10 shows that the ground-
water level in the adjacent water-table aquifer is above the level of Lake Ori-
enta on both the east and west sides of the lake, as it probably was at the end
of the unusual wet period ending September 1960, during dry periods, such
as January-May 1971, the water table probably slopes continuously downward
from Lake Orienta toward the nearby sink to the west; if so, during dry
periods some water would move from Lake Orienta through the water-table
aquifer to the sink.) Inasmuch as the rainfall on the lake was sufficient to
account for the few rises in lake level indicated by the hydrograph, surface-
water inflow probably was minimal during this period. The magnitude of the
individual components of seepage moving into and out of the lake cannot be
determined from the data at hand.
Water probably moves always downward from Lake Orienta to the Flori-
dan aquifer but the rate of movement varies appreciably between wet and
dry periods. The level of Lake Orienta is several feet above the level of the
potentiometric surface of the Floridan aquifer at Island Lake from the com-
parison of the lake-level graph with the water-level graph for well 841-121-1
(figs. 4 and 12); however, the level of the potentiometric surface changes
appreciably over a distance of a few miles. Water-level data for 1954-56 (Bar-
raclough, 1962b, p.ll, 12, 40) indicate that the level of the potentiometric
surface at Lake Orienta-as represented locally by the water level in well 839-
121-5 (fig. 2)-on January 11, 1954, was 5.2 feet higher than the water level
in well 841-121-1, and on January 5, 1956, was 4.2 feet higher. Thus, it is
evident from figure 4 that the level of Lake Orienta locally was about 4 feet
higher than the potentiometric surface in January 1954 and about 8 feet
higher in January 1956. This indicates that from January 1954 to January
1956 the head differential between the two water bodies-and the resultant
rate of water movement-increased by a factor of about 2.










V


ii
--H


Die r. L LAKE ORIENTAL

60 -- - -- W- 9 r- F;- W -- --7-- -

58---- -



54


52
,e50-- -- --- -- ---=P -- ----





51



S44---------------------------------------------------------------------
40

46-
MLL 841-121-1 AT ISLAND LAKE



42

4 0
JAN. FEB. MAR APR. MAY JUNE JULY AUG. SEPT OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT OCT. NOV. DEC.
1970 1971

Figure 12.-Hydrographs for Lake Orients and well 841-121-1.


w
-J







Ld
U,

w
0
I-


0


Io
0
0z



M


)--------i ---t----)---( ---i----t'-----)- -1







REPORT OF INVESTIGATION NO. 81


Just as the level of the potentiometric surface declined more than the level
of Lake Orienta in 1954-56, so it would have risen more than the lake level
as they both rose to their peak stages of September 1960. Consequently, the
head differential between the two water bodies--and the resultant rate of water
movement-in September 1960 would have been substantially less than in
1956 or at other times when water levels were generally lower.
The fluctuation in the water level of the water table aquifer adjacent to
the lake between wet and dry periods also probably is greater than the fluctu-
ation in level of Lake Orienta. Consequently, the inflow to the lake increases
during wet periods and decreases during dry periods. Thus at a time when
ground-water outflow from Lake Orienta to the Floridan aquifer is at its
least, ground-water inflow to Lake Orienta from the water-table aquifer is at
its greatest.
Whereas ground-water outflow from Lake Orienta was greater than
ground-water inflow during the relative dry period of January-May 1971,
the opposite condition may have prevailed at the height of the wet period
ending September 1960. In any event, the high level of Lake Orienta, and
otier lakes as well, in 1960 was caused by an increase in ground-water in-
flow to the lake, a decrease in ground-water outflow from the lake, in combina-
tion with a large excess of rainfall over lake evaporation, and some surface-
water inflow.
The net of inseepage from the water-table aquifer and outseepage to the
Floridan aquifer also can be estimated for Grace Lake for the period January
1 to May 31, 1971. During this period the level of Grace Lake declined about
3.1 feet, as shown in figure 13. There was no surface inflow from Island
Lake and probably no runoff of consequence from rainfall on the drainage
basin downstream from Island Lake. If lake evaporation exceeded rainfall by
0.6 foot, net seepage from Grace Lake was 2.5 foot for the 5-month period, or
about 0.5 .foot per month. Inseepage from the water-table aquifer probably
was minimal during this relatively dry period; thus outseepage from the
lake to the Floridan aquifer probably was only slightly greater than 0.5 foot
per month.
Outseepage from Grace Lake varies considerably between extreme wet and
dry periods. For example, when the peak stage of Grace Lake was 66 feet in
the September 1960 wet period, the altitude of the potentiometric surface of
the Floridan aquifer at Grace Lake probably was about 53 feet (fig. 2); thus,
locally the head differential between the two water bodies probably was about
13 feet. In the January-May 1971 dry period the level of Grace Lake was about
17 feet higher than the water level in well 841-121-1 at Island Lake (fig. 13);
however, figure 2 shows that the potentiometric surface of the Floridan aqui-








-F V } 'F' F 'F'+-


/GRACE LAKE


82 1 i_
8g-------- ------------------- --------------------------------- ----------------------* ---------'--------------------------I-----------------










5 o



L 841-121-1 AT ISLAND LAE




A1A
462- -------------------------------------- ----- __








JAN. FEB. MAR. APR MAY JUNE JULY AUG. SEPT OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPt OCT. NOV. DEC.
1970 1971
Figure 13.-- ydrographs for Grace Lake and well 841-121-1.


_1







<

LL
U)
I-



I--
-j


w]


0
'S


F


Cf;-i







REPORT OF INVESTIGATION NO. 81


fer is about 3 to 4 feet lower at Grace Lake than at Island Lake. In January-
May 1971, therefore, the level of Grace Lake was probably about 20 feet
above the potentiometric surface locally. The rate of outseepage from the
lake to the Floridan aquifer is proportional to the head differential between the
two water bodies. Thus, if the area of the hydraulic connection between the
lake and the Floridan aquifer remains the same irrespective of lake stage,
outseepage from the lake to the Floridan aquifer was about one-third less in
September 1960 than it was in January-May 1971. In terms of effect on the
lake level, the difference in outseepage would be even greater because the
lake area was considerably greater in September 1960 than in January-May
1971.
Grace Lake apparently overflows to sinks north of the lake during rel-
'atively wet periods. In August 1974 one of the authors observed water flowing
at a rate of about 10 cfs through a normally dry culvert under the road north
of the lake. Antecedent rainfall in the general area was ample but not out-
standingly great. The occasional overflowing of Grace Lake accounts for the
peak stage of 1960 being only slightly greater than the peak stage attained in
1970; in contrast, the 1960 stages of other water bodies, such as Lake Orienta
and Cranes Roost, were much above those attained in 1970.
The fluctuation in the water level of Cranes Roost is greater than that of
any of the other water bodies investigated and is controlled primarily by sur-
face inflow from Lake Adelaide and outseepage to the Floridan aquifer. From
January 1 to May 31, 1971, the water level in Cranes Roost declined about
5.3 feet as shown in figure 14. Both the surface-water inflow from Lake Adel-
aide and inseepage from the water-table aquifer probably were minimal during
this period; hence, if 0.6 foot is allowed for the excess of evaporation over
rainfall, about 4.7 feet of the decline in level was caused by outseepage from
Cranes Roost to the Floridan aquifer.
Analysis of the 1960 and 1971 water levels indicates that the level of Cranes
Roost on May 31, 1971 was not very far above the potentiometric surface of
the Floridan aquifer. On September 30, 1960, the stage of Cranes Roost at
60.7 feet in altitude probably was about 11 feet above the potentiometric sur-
face of the Floridan aquifer at the western end of the water body (fig. 2). The
water level in well 841-121-1 at Island Lake was about 14 feet higher in alti-
tude on September 30, 1960, than on May 31, 1971. In general, the range of
fluctuation in the level of the potentiometric surface of a confined aquifer
decreases down gradient. If the range of fluctuation in the level of the poten-
tiometric surface at Cranes Roost were 80 percent of that at Island Lake, the
level of the potentiometric surface at Cranes Roost would have been about 11
feet lower on May 31, 1971 than on September 30, 1960, or at an altitude of
about 39 feet at the western end of the water body. Thus, at an altitude of 42











-- -----------












5H 11















--Figr-- -- 4.-H----drogr--phs for Cranes Roost and e 8 1-121-. -
42-- WE L
WELL 841-121-1 IT ISMLA LKE







JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPI OCT. NOV DEC. JAN. FEB. MAR.- APR. MAY JUNWE JULY AUG. SEPT OCT. NOV. DEC.
".-70 1971
Figure 14.-Hydrographs for Cranes Roost and well 841-121-1.


J




z
w
_J








4
w




0
I-
8-
3


w




0)
'1

8z







REPORT OF INVESTIGATION NO. 81


feet in May 1971 the water level of Cranes Roost probably was only about 3
feet above the potentiometric surface.
At the end of a dry period the potentiometric surface of the Floridan aqui-
fer in response to rainfall probably rises faster than the lake level until such
time as rainfall is sufficient to cause surface inflow from Lake Adelaide. Under
such conditions the potentiometric surface may briefly rise above the water
level in Cranes Roost, thereby causing water to move upward from the Flori-
dan aquifer into Cranes Roost. Had there been no surface inflow from Lake
Adelaide, the water level in Cranes Roost still would have reached an altitude
greater than 50 feet because the water level in the sink cannot naturally decline
below the level of the potentiometric surface.
Conditions in the Palm Springs sink area are such that the pond levels,
including Eleventh Hole Pond, probably are always close to the level of the
potentiometric surface of the Floridan aquifer. The many sink holes and the
extent of land subsidence in this area indicates a good hydraulic connection
between the surficial material and the Floridan aquifer. The pond levels are
about the same in altitude which indicates that movement of water through
the Floridan aquifer is relatively unrestricted in this area.
In February-March 1971 the level of Eleventh Hole Pond (figure 15)
declined slightly more rapidly than the water level in well 141-121.1 at Island
Lake; this indicates that the pond level was above the local potentiometric sur,
face at that time. However, the rise in the pond level in July-August 1971 was
much greater than that of any of the other surface-water bodies investigated,
and it follows closely the trend of the water level in well 841-121-1; this sug-
gests that the potentiometrie surface in the Palm Springs sink area probably
was above the pond level during this period. The water level in the Palm
Springs sinks probably are controlled almost exclusively by the potentiomeric
surface of the Floridan aquifer; water seeps out of the pond into the Floridan
aquifer when the potentiometric surface is falling and seeps into the pond
from the Floridan aquifer when it is rising.

EFFECTS OF CULTURAL DEVELOPMENT
IN THE SINK BASINS

The preceding remarks concerning water-l.vel fluctuations and peak stages
of different water bodies are applicable under the physiographic conditions
that existed in the area at the time of the investigation and in some instances
before 1960. The area has undergone considerable urbanization since 1960
and doubtless will be further urbanized; this development will affect the
hydrologic relations in the basin.








BUREAU OF GEOLOGY


.Cultural development that increases the percentage of a basin covered by
impervious materials, such as roofs and pavement, causes more of the rainfall
to run off. Replacement of the natural soil cover with grass sod also may
cause more rapid and voluminous runoff. The higher velocities associated with
greater and more rapid runoff can cause greater erosion, especially where the
soil is disturbed during construction. Eroded organic matter and clay accumu-



45- 00
ooOo
44 A-. .


43
_j ... \ ...
L\
> 42-----
_1 \ WELL 841-121-1 AT ISLAND LAKE
< --


> '
z --- - r ----- -- -- -



S39---


U 3 i8 .. .
LLu 0

S371


< 36- ___


NOV DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.
1970 1971
Figure 15.-Hydrographs for Eleventh Hole Pond and well 841-121-1.


lating in the bottoms of sinks or lakes may reduce the rate of seepage out of
the sinks and lakes.The reduction in seepage coupled with the increased rate
and volume of inflowing water can cause higher than normal water levels.
Conceivably, lake stages that are seldom reached or exceeded under natural
conditions could be reached or exceeded frequently under conditions of full
cultural development. The hydrologic effects of future developments could be







REPORT OF INVESTIGATION NO. 81


considered before setting altitudes which supposedly, represent a specified or
limited degree of flood hazard.
Because of the increasing value of land in the sink basins, proposals have
been made to increase the amount of usuable property in the sink basins by
raising the level of part of the property by filling along the lip of a sink and
using material excavated from the bottom of the sink. This procedure would
increase the acreage above a designated flood level without reducing the stor-
age capacity of the sink. Such a procedure would necessarily increase the slope
of the sink wall and could cause the embankment of fill to slump if it should
become saturated. Removal of material from the bottom of the sink would
probably increase the rate of seepage from the sink, but would reduce the
amount of filtration the water received before entering the Floridan aquifer.
If the excavated material were removed from over a cavity, the roof of the
cavity could be weakened to the point of collapse. If the excavated material
were deposited over a cavity, the added weight could cause the roof of the
cavity to collapse.

CONTROL OF WATER LEVELS IN SINK BASINS
A greater part of the property in the sink basins could be culturally de-
veloped if water levels were controlled to prevent their rising to high altitudes
such as those reached in 1960. In Cranes Roost basin, the level of Lake Mobile
could be controlled by enlarging the existing surface outlet and providing an
adjustable control structure. The levels of Lakes Adelaide and Florida could
be similarly controlled, but such measures might become ineffective if the level
of Cranes Roost should rise to the altitude reached in 1960. The peak stages of
Lake Orienta and Cranes Roost could be reduced slightly by improving the
permeability of their bottoms, but effective control would require removal of
water by pumping or by providing a surface outlet. Removal of water by
pumping probably would prove impractical at Cranes Roost; during extreme
wet periods massive pumping would be required to limit the magnitude of
relatively sudden rises in level caused by surface inflow from upstream lakes;
also, inseepage from the Floridan aquifer might be induced into Cranes Roost
if its water level were drawn down below an altitude of about 55 feet.
Improving the permeability of the lake bottoms probably would have the unde-
sirable effect of lowering water levels below desirable stages during dry
periods. -'
In Grace Lake sink basin, the water level of Island Lake could be controlled
by enlarging its surface outlet and providing an adjustable control structure.
The peak stage of Grace Lake could be reduced easily by lowering the swales
in the divide between the lake basin and the sinks to the north. However, this
would tend to increase the flood hazard in the sinks and lakes downstream.







BUREAU OF GEOLOGY


The peak stage of Lake Marion in the Palm Springs sink basin could be
controlled by removal of water by pumping or by providing a surface outlet.
Peak stages of the Palm Springs sinks, including Eleventh Hole Pond, could
be controlled in the same way; however, a surface outlet to Little Wekiva
River would require a long, deep excavation. Massive pumping would be re-
quired to appreciably lower the peak stages of the sinks because they appear
to be largely controlled by the level of the potentiometric surface of the Flori-
dan aquifer. Any appreciable lowering of the stages of the Palm Springs sinks
would induce seepage into the sinks from the Floridan aquifer.

SUMMARY AND CONCLUSIONS
All water bodies in the sink area in southwestern Seminole County are
affected to about the same degree by rainfall and evaporation, yet the range
in stage differs widely amongst them because some of the lakes are landlocked;
some have surface outlets; in relation to their size, some lakes receive more
surface inflow than others; the lakes differ widely in the extent to which they
lose water by seepage to the Floridan aquifer and gain water by seepage from
the water-table aquifer.
Island Lake, in Grace Lake sink basin, overflows readily through its sur-
face outlet, and loses little water by seepage through the bottom to the Floridan
aquifer; consequently, the lake level fluctuates through a fairly small range.
The peak stage of Island Lake in September 1960 was only 3 to 4 feet above
the low stages of May-June 1971.
The range in stage of Grace Lake is substantially greater than that of Is-
land Lake. The peak stage of September 1960 was about 7 feet above the low
stage of June 1971. Grace Lake receives much more surface inflow than Island
Lake-in relation to its size-and overflows only at a relatively high stage.
Grace Lake also loses a considerable quantity of water-0.5 foot per month in
January-May 1971-by seepage through the bottom to the Floridan aquifer.
Lake Orienta-in Cranes Roost sink basin-has a larger range in stage
than many of the other lakes investigated. The peak stage of September 1960
was about 10 feet higher than the low stages of June-July 1971, and was more
than 11 feet higher than the low stage of October 1, 1956. The lake is land-
locked and normally occupies about 15 percent of its drainage basin. The
rise in lake level probably is caused primarily by the excess of rainfall over
lake evaporation and by seepage from the adjacent water-table aquifer. The
lake loses water by seepage through the bottom to the Floridan aquifer and,
during dry periods, by seepage through the water-table aquifer on the west side
of the lake. The exchange of water between the lake and the aquifers in Jan-
uary-May 1971 resulted in a loss of about 0.5 foot or 0.1 foot per month. The







REPORT OF INVESTIGATION NO. 81


loss decreases during wet periods; with water levels rising generally, inseepage
from the water-table aquifer increases and outseepage to the Floridan aquifer
decreases. Although Lake Orienta probably always loses water to the Floridan
aquifer, inseepage from the water-table aquifer may exceed outseepage to the
Floridan aquifer during extreme wet periods.
Cranes Roost is also landlocked and has the greatest range in stage of all
the water bodies investigated. The peak stage of September 1960 was almost
19 feet higher in altitude than the low stage of June 1971. Cranes Roost prob-
ably receives substantial surface inflow from Lake Adelaide. Cranes Roost
readily loses water by seepage through the bottom to the Floridan aquifer; in
January-May 1971 seepage to the Floridan aquifer averaged almost 1 foot per
month.
The water levels of the Palm Springs sinks, including Eleventh Hole Pond,
also fluctuate considerably. The peak stage of Eleventh Hole Pond in Septem-
ber 1960 was about 12 feet higher in altitude than the low stages of May-June
1971. The sinks in general are landlocked and apparently are well connected
hydraulically with the Floridan aquifer. The water levels of the sinks probably
reflect closely the level of the potentiometric surface of the Floridan aquifer in
the sink area.
The September 1960 peak stages of lakes in southwest Seminole County
probably were the maximum attained since at least 1895. Results of a regres-
sion analysis of 'the annual discharge of Wekiva River near Sanford and rain-
fall at Orlando showed the discharge for the 1960 water year to be markedly
greater than that for any other year since at least 1895. Similarities established
between fluctuations of lake and ground-water levels and variations in dis-
charges of nearby streams suggest that the rainfall which produces an out-
standingly high discharge also will produce lake and ground-water levels that
are equally outstanding.
As cultural development of the sinkhole area progresses, the peak lake
stages that result from a specific amount of rainfall probably will become pro-
gressively greater because of an increase in the percentage of the basin that is
covered by relatively impervious materials and because of other changes that
affect the basin hydrology. With full development, lake stages seldom reached
under natural conditions may be reached more frequently unless lake levels
are controlled.
Control of the water levels of Lakes Mobile, Adelaide, and Florida-in
Cranes Roost sink basin-would require enlargement of their existing surface
outlets and the addition of adjustable control structures. During extreme wet
periods such measures might be ineffective for Lakes Florida and Adelaide
unless the water level of Cranes Roost also was controlled. The level of Cranes






BUREAU OF GEOLOGY


Roost could be controlled by removal of water by pumping or by providing
a surface outlet; pumping probably would be impractical because of the large
pump capacity required to limit rises in level caused by surface inflow from
upstream lakes. Lowering the water level of Cranes Roost below an altitude
of about 55 feet might induce inseepage from the Floridan aquifer during ex-
treme wet periods. The level of Lake Orienta could be effectively controlled by
removal of water by pumping or by providing a surface outlet.
In the Palm Springs sink basin, the levels of Lake Marion and the Palm
Springs sinks could be controlled by removal of water by pumping or by pro-
viding surface outlets. For the Palm Springs sinks, however, providing a sur-
face outlet to Little Wekiva River would require an extensive excavation, and
pumping might prove impractical during wet periods because any appreciable
lowering of the water levels would induce seepage from the Floridan aquifer.
In Grace Lake sink basin, the water level of Island Lake could be controlled
by enlarging its surface outlet and providing an adjustable control structure.
The peak stage of Grace Lake could be reduced by lowering the swales in the
divide between the lake basin and the sinks to the north; however, this would
tend to increase the flood hazard in downstream sinks and lakes.








REPORT OF INVESTIGATION NO. 81 35

SELECTED REFERENCES

Anderson, Warren, Lichtler, W. F.. and Joyner, B. F., 1965, Control of lake
levels in Orange County, Florida: Florida Geol. Survey Inf. Circ. 47,
15 p.
Barraclough, J. T., 1962a, Ground-water resources of Seminole County,
Florida: Florida Geol. Survey Rept. Inv. 27, 91 p.
-1962b, Ground-water records of Seminole County, Florida: Florida
Geol. Survey Inf. Circ. 34, 148 p.

Florida State Board of Conservation, 1954, Summary of observed rainfalls on
Florida to 81 December 1952: Water Survey and Research paper No.
11, 334 p.

Heath, R. C., and Barraclough, J. T., 1954, Interim report on the ground-water
resources of Seminole County, Florida: Florida Geol. Survey Inf. Circ.
5, 43 p.

Lichtler, W. F., Anderson, Warren, and Joyner, B. F., 1968, Water resources
of Orange County, Florida: Florida Geol. Survey Rept. Inv. 50, 150 p.

Riggs H. C., 1968, Some statistical tools in hydrology: U. S. Geol. Survey,
Techniques Water-Resources Inv., Book 4, Chap. Al, 39 p.

U. S. Weather Bureau, 1954-74, Climatological data, Florida, Annual sum-
maries, 1953-78: U. S. Dept. Commerce, National Climatic Center, Ashe-
ville, N. C.