Interim report on the water resources of Orange County, Florida ( FGS: Information circular 41 )

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY

FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director

INFORMATION CIRCULAR NO. 41

INTERIM REPORT ON THE WATER RESOURCES
OF
ORANGE COUNTY, FLORIDA

By
William F. Lichtler, Warren Anderson, and Boyd F. Joyner
U. S. Geological Survey

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BOARD OF COUNTY COMMISSIONERS OF ORANGE COUNTY
and the
FLORIDA GEOLOGICAL SURVEY

TALLAHASSEE

1964

409Y

AGRIf
CULTURAL
LIBRARY

Completed manuscript received
February 15, 1963
Printed by the Florida Geological Survey
Tallahassee

CONTENTS

Abstract

Intr

Des

Hyd

oduction..............................
oduction
Purpose and scope of investigation . . .
Acknowledgments ......................
Previous investigations . . . . .
Well-numbering system . . . . .
cription of the area .. . . .
Climate . .... .. . ... ....
Sinkholes . . . . . . .
Drainage . .. . . . .. .
Geology . . .... .........
irology . . . . . . .
Surface water . . . . . .
Kissimmee River basin .. ....
Reedy Creek .. .. . . .
Bonnet Creek . ... . .
Shingle Creek .. . . .. .
Boggy Creek . ... . .
Jim Branch . . . . .
Ajay-East Tohopekaliga Canal......
St. Johns River basin . . . .
St. Johns River . .. .....
Small tributaries draining to east .
Lake Pickett . . . . .
Econlockhatchee River . .. .. .
Little Econlockhatchee River ... .
Howell Creek ................
Wekiva River . . .. . .
Apopka-Beauclair Canal . ... .
Lakes, swamps, and marshes . .. .. .
Ground water ....................... .
Nonartesian aquifer . .. . .
Aquifer properties. .. ....... .
Water levels . . . . .
Recharge and discharge . . .
Quality of water . . .. .
Shallow artesian aquifers. . . .
Aquifer properties . . . .
Water levels . . . .
Recharge and discharge ...... .

I I o

o

o
. o

o o

Page
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35
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35

Floridan aquifer .. ........
Aquifer properties ... .. .
Piezometric surface. ... ........
Recharge and discharge ...........
Quality of water........... .......
Pumping test .. ................ .....
Water budget .. ..... ...... .........
Use of water .. .........................
References ........................

............. 35
S . ... 36
............. 36
39
... ..... . 39

...... ...... 41

. ........... 44

... 47
.... ... .... 47

ILLUSTRATIONS

1 Florida showing location of Orange County ... .... . .
2 Physiographic regions of Orange County, Florida ... ..... .
3 Distribution of drainage wells in Orange County, Florida ..... .
4 List and duration of records at surface-water gaging stations in
or near Orange County, Florida . . . . . .
5 Drainage basins and surface-water data collection points in
Orange County, Florida .......................
6 Relation of specific conductance to stream flow, St. Johns River
at station 36, near Cocoa, Florida, 1958-61 . . . .
7 Cumulative frequency curves of specific conductance for the
Econlockhatchee River at station 18, near Bithlo, Florida, 1960-61
8 Hydrographs of observation wells in Orange County and rainfall at
Orlando, Florida .......... ......... ............
9 Orange County, Florida, showing location of inventoried wells
other than drainage wells.......... ........... .
10 Orange County, Florida, showing the contours of the piezometric
surface at high water conditions, September 1960 ... .. .
11 Orange County, Florida, showing the contours of the piezometric
surface at about normal conditions, July 1961 . . . .
12 Orange County, Florida, showing general range of dissolved
solids of the water in wells in the Floridan aquifer . . .
13 Composition of mineral content of water from selected wells in
the Floridan aquifer in Orange County, Florida . .... .

Table
1 Temperature and rainfall at Orlando, Florida .. . . ..
2 Summary of the properties of the geologic formations penetrated
by water wells in Orange County, Florida ..... .......... .
3 Sites where miscellaneous surface-water data have been
collected in and near Orange County, Florida ...

6
7
11

16

17

23

26

32

.34

37

38

40

42

9

13

18

4 Data on small tributaries draining the eastern part of Orange
County, Florida . . . . . .. .24
5 Discharge measurements of springs in Orange County, Florida... 29
6 Results of pumping well 831-122-4, Orlando, Florida, February 17,
1961 . . . . . . . . .. . 43

I

INTERIM REPORT ON THE WATER RESOURCES

OF

ORANGE COUNTY, FLORIDA

By
William F. Lichtler, Warren Anderson, and Boyd F. Joyner

ABSTRACT

The population and industry of Orange County are expanding
rapidly but the demand for water is expanding even more rapidly. This
progress report on the first half of a 6-year investigation provides in-
formation for use in the development and management of the water
resources of the area.

The county lies in three physiographic regions: (1) Eastern
Lowlands, (2) Parallel Ridges, and (3) Rolling Highlands. The Rolling
Highlands, also known as the Orlando Ridge, are characterized by
numerous sinkhole lakes and depressions.

Surface runoff forms the principal drainage in the Eastern Lowlands
and Parallel Ridges, whereas underground drainage prevails in the
Rolling Highlands.

Surface water is temporarily stored in lakes, swamps, and streams.
Lakes are the most reliable sources of surface water as the swamps and
most of the streams, except the St. Johns, Wekiva, and Little Econlock-
hatchee rivers, go dry or nearly dry during droughts.

Approximately 90 of the 1,000 square miles in Orange County are
covered by water. The southwestern 340 square miles of the county
drain to the south by the Kissimmee River system. The eastern and
northern 660 square miles of the county drain to the north by the St. Johns
River.

i. -<

FLORIDA GEOLOGICAL SURVEY

The water in the lakes and streams in Orange County generally is
soft, low in mineral content, and high in color. The quality of the water
in most of the lakes remains fairly constant.

Ground water is obtained from: (1) a nonartesian aquifer composed
of c!astic material of late Miocene to Recent age; (2)several discon-
rir.uous shallow artesian aquifers in the Hawthorn Formation of middle
Miocene age; and (3) the Floridan aquifer composed of the Ocala Group,
the Avon Park Limestone, and the Lake City Limestone, all of Eocene
age.

The surficial nonartesian aquifer produces relatively small quanti-
ties of soft water that is sometimes high in color. The shallow artesian
aquifers produce moderate quantities of generally moderately hard to
hard water.

The Floridan aquifer is the principal source of ground water in
Orange County. It comprises more than 1,300 feet of porous limestone
and dolomite and underlies sand and clay deposits that range in thick-
ness from about 40 feet to more than 350 feet. Wells in the Floridan
cquifer can yield more than 4,000 gpm (gallons per minute).

Artesian heads in the Floridan aquifer range from about 10 feet
above to more than 60 feet below the land surface. The quality of the
water ranges from moderately hard in the western and central parts to
saline in the extreme eastern part of the county.

INFORMATION CIRCULAR NO. 41

INTRODUCTION

The rapid increase of population and industry of Orange County
has created a rapidly increased demand for water. Not only are there
more people and more uses for water, but also the per-capita use of
water is increasing. Central Florida is becoming a major center in
missile development and space exploration and the increase in demand
for water is expected to continue and even to accelerate.

PURPOSE AND SCOPE OF INVESTIGATION

The purpose of this investigation is to furnish data that will be
useful in the conservation, development, and management of the water
resources of Orange County. Water is among the most important natural
resources of Florida. Orange County, with more than 50 inches of
annual rainfall, is blessed with an abundant supply. However, this
supply is not evenly distributed throughout the year, or from year to
year, nor are there adequate storage reservoirs in all parts of the county.

An evaluation of all factors affecting the water resources of an
area is necessary for the protection, efficient development, and manage-
ment of water supplies. Recognizing this fact, the Board of County
Commissioners of Orange County entered into a cooperative agreement
with the U. S. Geological Survey to investigate the water resources
of Orange County. The investigation is a joint effort by the three
branches of the Water Resources Division of the Survey. The report
was prepared under the supervision of M. I. Rorabaugh, succeeded
by C. S. Conover, Tallahassee; A. O. Patterson, Ocala; and K. A.
MacKichan, Ocala.

This interim report summarizes the findings of the first half of
a planned 6-year investigation. The report contains information on
the quantity, quality, and occurrence of surface and ground water in
and near Orange County. The information contained herein will be
incorporated in a final report to be published by the Florida Geological
Survey.

FLORIDA GEOLOGICAL SURVEY

ACKNOWLEDGMENTS

The authors express their appreciation to the many residents of
Orange County who gave information about their wells and to various
public officials whose cooperation greatly aided the investigation.
Special appreciation is expressed to Fred Dewitt, county engineer;
to Robert Simons and Jesse Burkett of the city of Orlando water and
sewer department; and to Gene Pou, Ross Snyder, and Russ Mills of
the city of Orlando engineering department for their assistance.

Appreciation is given the well drillers in or near Orange County
who furnished geologic and hydrologic data and permitted collection of
water samples and drill cuttings and measurements of water I.evels
during drilling operations.

Albert Schwartz and other staff members of the U. S. Soil Conserva-
tion Service gave advice and information.

PREVIOUS INVESTIGATIONS

Two previous investigations of the water resources of Orange
County have been made. A report by the U. S. Geological Survey (19.43)
gives the results of a study of lakes as a source of municipal water
supply for Orlando. A detailed investigation by Unklesbay (1944)
deals primarily with drainage and sanitary wells in Orlando and vicinity
and their effect on the ground-water resources of the area.

Other investigators have included Orange County in geologic and
hydrologic studies. Fenneman (1938), Cooke (1939), MacNeil (1950),
and White (1958) describe the topographic and geomorphic features of
central Florida. Cole (1941, 1945), Cooke (1945), Vernon (1951), and
Puri (1953) describe the general geology of central Florida and make
many references to Orange County. Sellards (1908), Sellards and Gunter
(1913), Matson and Sanford (1913), Gunter and Ponton (1931), Parker,
Ferguson, Love, and others (1955), Brown, Kenner, and Brown (1957),
and Brown (1962) discuss the geology and water resources of Brevard
County. Stringfield (1935, 1936) and Stringfield and Cooper (1950)
investigated the artesian water in peninsular Florida, including Orange
County. Collins and Howard (1928), Black and Brown (1951), Wander
and Reitz (1951), and the Florida State Board of Health (1961) give
information about the chemical quality of water in Orange County.

INFORMATION CIRCULAR NO. 41 5

WELL-NUMBERING SYSTEM

The well-numbering system used in this report is based on latitude
and longitude coordinates derived from a statewide grid of 1-minute
parallels of latitude and meridians of longitude. Wells within these
quadrangles have been assigned numbers consisting of the last digit
of the degree and the two digits of the minute of the line of latitude
on the south side of the quadrangle, the last digit of the degree and
the two digits of the minute of the line of longitude on the east side
of the quadrangle, and the numerical order in which the well within
the quadrangle was inventoried. For example, well 832-122-4 is the
fourth well that was inventoried in the 1-minute quadrangle north of
28032' north latitude and west of 81022' west longitude. By this system
wells referred to by number in the text can be located on figure 9.

DESCRIPTION OF THE AREA

Orange County is in the east-central part of the Florida Peninsula
(fig. 1). It has an area of es-entially 1,000 square miles of which
about 910 square miles are land and about 90 square miles are water.
It is bounded on the east by Brevard County, on the north by Seminole
and Lake counties, on the west by Lake County, and on the south by
Osceola County.

The population of Orange County in 1960 was 263,540. In that
year Orlando, the largest city-in the __ounty, had a population of 88,135,
while Winter Park, the second largest city, hcidti popu!otiono__f 17,160.

The principal agricultural crops are citrus, vegetables, and cattle.
In 1960 there were about 67,000 acres of citrus groves, about 6,000
acres of vegetables, mostly in the Zellwood muck lands, and about
15,000 head of cattle.

Orange County is in the Atlantic Coastal Plain physiographic
province described by Meinzer (1923, pl. 28). The county is subdivided
into three physiographic regions: the Eastern Lowlands, the Parallel
Ridges, and the Rolling Highlands (fig. 2).

The Eastern Lowlands include the St. Johns River marsh, the
northern part of the Econlockhatchee River basin and the northeastern
part of the county east of Rock Springs. Elevations range from about

FLORIDA GEOLOGICAL SURVEY

________^ ____________ ^ ___ A

I) 0 020 3040 50miles

\I I
9;-:^

a g',j. /e v.- -

Figure 1. Florida showing location of Orange County.

I

INFORMATION CIRCULAR NO. 41 5

WELL-NUMBERING SYSTEM

The well-numbering system used in this report is based on latitude
and longitude coordinates derived from a statewide grid of 1-minute
parallels of latitude and meridians of longitude. Wells within these
quadrangles have been assigned numbers consisting of the last digit
of the degree and the two digits of the minute of the line of latitude
on the south side of the quadrangle, the last digit of the degree and
the two digits of the minute of the line of longitude on the east side
of the quadrangle, and the numerical order in which the well within
the quadrangle was inventoried. For example, well 832-122-4 is the
fourth well that was inventoried in the 1-minute quadrangle north of
28032' north latitude and west of 81022' west longitude. By this system
wells referred to by number in the text can be located on figure 9.

DESCRIPTION OF THE AREA

Orange County is in the east-central part of the Florida Peninsula
(fig. 1). It has an area of es-entially 1,000 square miles of which
about 910 square miles are land and about 90 square miles are water.
It is bounded on the east by Brevard County, on the north by Seminole
and Lake counties, on the west by Lake County, and on the south by
Osceola County.

The population of Orange County in 1960 was 263,540. In that
year Orlando, the largest city-in the __ounty, had a population of 88,135,
while Winter Park, the second largest city, hcidti popu!otiono__f 17,160.

The principal agricultural crops are citrus, vegetables, and cattle.
In 1960 there were about 67,000 acres of citrus groves, about 6,000
acres of vegetables, mostly in the Zellwood muck lands, and about
15,000 head of cattle.

Orange County is in the Atlantic Coastal Plain physiographic
province described by Meinzer (1923, pl. 28). The county is subdivided
into three physiographic regions: the Eastern Lowlands, the Parallel
Ridges, and the Rolling Highlands (fig. 2).

The Eastern Lowlands include the St. Johns River marsh, the
northern part of the Econlockhatchee River basin and the northeastern
part of the county east of Rock Springs. Elevations range from about

3 ^30 25' 5 10' 05' 8100' 55 80 50
'1

-30'

C
r"
25'

0
0 C E 0 L A 20'
L I

35' 253 22 1 10' 05' 8100 8065av
0 I 2 3 4_5 6 7 1 9 milos

Figure 2. Physiographic regions of Orange County, Florida

FLORIDA GEOLOGICAL SURVEY

5 feet above msi (mean sea level) near the St. Johns River to about
35 feet above msi where the lowlands merge with the Parallel Ridges.

The Parallel Ridges occupy most of the middle portion of the
county between the Eastern Lowlands and the Rolling Highlands.
EEevations range from 35 to 105 feet above msl but are mostly between
50 and 85 feet above msl. The ridges and intervening lower areas
parallel to the Atlantic coast are best developed in the area between
Orlando and the Econlockhatchee River.

The Rolling Highlands occupy the western part of Orange County
with an island outlier in the vicinity of Orlando. Elevations range
from about 50 feet in the Wekiva River basin to about 210 feet above
msl near the Avalon lookout tower in the southwestern part of the county.
This area contains many lakes and depressions that usually have no
surface outlets.

The three physiographic regions described above are approximately
equivalent to the Pleistocene terraces postulated by MacNeil (1950) as
the Pamlico terrace from about 8 feet to about 30 feet above msl, the
Wicomico terrace from about 30 feet to about 100 feet above msl, and
the Okefenokee terrace from about 100 to 150 feet above msl.

Cooke (1939) has called the surface defined by the 42- and 70-
foot shorelines the Penholoway terrace and the surface defined by
the 70- and 100-foot shorelines the Wicomico terrace. The altitudes
above 150 feet in Orange County probably represent sandhills or altered
remnants of higher terraces.

CLIMATE

Orange County has a subtropical climate with only two pronounced
seasons winter and summer. The average annual temperature at
Orlando is essentially 720F and the average annual rainfall is 51.4
inches. Summer thunderstorms account for most of the rainfall. Thunder-
storms occur on an average of 83 days per year (U. S. Weather Bureau,
annual report, 1960); one of the highest incidences of thunderstorms in
the United States.

INFORMATION CIRCULAR NO. 41

Table 1. Temperature and Rainfall at Orlando, Florida

Normal Normal Normal Normal Maximufa Minimur
maximum minimum average rainfall rainfall rainfall
temp.2 ('F) :temp.2 (F) temp. (*F) (inches) (inches) (year) (inches) (year)

Jan. 70.7 50.0 60.4 2.00 6.44 1948 0.15 1950

Feb. 72.0 50.7 61.4 2.42 5.64 1960 .10 1944

Mar. 75.7 54.0 64.9 3.41 10.54 1960 .16 1956

April 80.5 59.8 70.2 3.42 6.18 1953 .28 1961

May 85.9 66.2 76.1 3.57 8.58 1957 .43 1961

June 89.1 i 71.4 80.3 6.96 11.61 1947 1.97 1948

July 89.9 73.0 81.5 8.00 19.57 1960 4.35 1957
Aug. 90.0 73.5 81.8 6.94 15.19 1953 3.40 1958

Sept. 87.6 i 72.4 80.0 7.23 15.87 1945 1.65 1958

Oct. 82.6 65.3 74.0 3.96 14.51 1950 1.51 1949

Nov. 75.6 56.2 65.9 1.57 4.86 1951 .09 1950
Dec. 71.6 51.2 61.4 1.89 4.30 1950 trace 1944

Yearly 80.9 62.0 71.5 51.37 68.74 1960 39.61 1943

1
Average for 10 or more years.
2U.S. Weather Bureau records, 1921-60.
U.S. Weather Bureau records, 1943-60.

SINKHOLES

Sinkholes are common in areas underlain by limestone formations.
Rainfall combines with carbon dioxide in the atmosphere to form a weak
carbonic acid. As the water percolates through the limestone, solution
takes place and cavities of irregular shape are gradually formed. When
the cavities enlarge to the extent that the roof can no longer support
the overburden, the surface deposits, generally sand, collapse into
the cavity and a sinkhole is formed. Many of Orange County's natural
lakes, ponds, and closed depressions are the surface expression of
such collapse. Sinkholes range in size from small pits a few feet in
diameter to large depressions several square miles in area. Large
depressionsare usually formed by the coalescence of several sinkholes.

Sinkholes may form either suddenly by collapse of the roof of a
large caverr or slowly by a gradual sinking of the ground surface. The

FLORIDA GEOLOGICAL SURVEY

5 feet above msi (mean sea level) near the St. Johns River to about
35 feet above msi where the lowlands merge with the Parallel Ridges.

The Parallel Ridges occupy most of the middle portion of the
county between the Eastern Lowlands and the Rolling Highlands.
EEevations range from 35 to 105 feet above msl but are mostly between
50 and 85 feet above msl. The ridges and intervening lower areas
parallel to the Atlantic coast are best developed in the area between
Orlando and the Econlockhatchee River.

The Rolling Highlands occupy the western part of Orange County
with an island outlier in the vicinity of Orlando. Elevations range
from about 50 feet in the Wekiva River basin to about 210 feet above
msl near the Avalon lookout tower in the southwestern part of the county.
This area contains many lakes and depressions that usually have no
surface outlets.

The three physiographic regions described above are approximately
equivalent to the Pleistocene terraces postulated by MacNeil (1950) as
the Pamlico terrace from about 8 feet to about 30 feet above msl, the
Wicomico terrace from about 30 feet to about 100 feet above msl, and
the Okefenokee terrace from about 100 to 150 feet above msl.

Cooke (1939) has called the surface defined by the 42- and 70-
foot shorelines the Penholoway terrace and the surface defined by
the 70- and 100-foot shorelines the Wicomico terrace. The altitudes
above 150 feet in Orange County probably represent sandhills or altered
remnants of higher terraces.

CLIMATE

Orange County has a subtropical climate with only two pronounced
seasons winter and summer. The average annual temperature at
Orlando is essentially 720F and the average annual rainfall is 51.4
inches. Summer thunderstorms account for most of the rainfall. Thunder-
storms occur on an average of 83 days per year (U. S. Weather Bureau,
annual report, 1960); one of the highest incidences of thunderstorms in
the United States.

INFORMATION CIRCULAR NO. 41

Table 1. Temperature and Rainfall at Orlando, Florida

Normal Normal Normal Normal Maximufa Minimur
maximum minimum average rainfall rainfall rainfall
temp.2 ('F) :temp.2 (F) temp. (*F) (inches) (inches) (year) (inches) (year)

Jan. 70.7 50.0 60.4 2.00 6.44 1948 0.15 1950

Feb. 72.0 50.7 61.4 2.42 5.64 1960 .10 1944

Mar. 75.7 54.0 64.9 3.41 10.54 1960 .16 1956

April 80.5 59.8 70.2 3.42 6.18 1953 .28 1961

May 85.9 66.2 76.1 3.57 8.58 1957 .43 1961

June 89.1 i 71.4 80.3 6.96 11.61 1947 1.97 1948

July 89.9 73.0 81.5 8.00 19.57 1960 4.35 1957
Aug. 90.0 73.5 81.8 6.94 15.19 1953 3.40 1958

Sept. 87.6 i 72.4 80.0 7.23 15.87 1945 1.65 1958

Oct. 82.6 65.3 74.0 3.96 14.51 1950 1.51 1949

Nov. 75.6 56.2 65.9 1.57 4.86 1951 .09 1950
Dec. 71.6 51.2 61.4 1.89 4.30 1950 trace 1944

Yearly 80.9 62.0 71.5 51.37 68.74 1960 39.61 1943

1
Average for 10 or more years.
2U.S. Weather Bureau records, 1921-60.
U.S. Weather Bureau records, 1943-60.

SINKHOLES

Sinkholes are common in areas underlain by limestone formations.
Rainfall combines with carbon dioxide in the atmosphere to form a weak
carbonic acid. As the water percolates through the limestone, solution
takes place and cavities of irregular shape are gradually formed. When
the cavities enlarge to the extent that the roof can no longer support
the overburden, the surface deposits, generally sand, collapse into
the cavity and a sinkhole is formed. Many of Orange County's natural
lakes, ponds, and closed depressions are the surface expression of
such collapse. Sinkholes range in size from small pits a few feet in
diameter to large depressions several square miles in area. Large
depressionsare usually formed by the coalescence of several sinkholes.

Sinkholes may form either suddenly by collapse of the roof of a
large caverr or slowly by a gradual sinking of the ground surface. The

FLORIDA GEOLOGICAL SURVEY

latter condition is illustrated by the formation of a sinkhole in the
Orlando area in April 1961. The sinking was first noted as a depression
in a graded road. By the following day a hole about 6 feet in diameter
had formed. Within 2 days the hole gradually increased to about 60 feet
in diameter and to about 15 feet in depth. The hole was filled and no
further development has been noted.

Another sinkhole occurred in April 1961 in Pine Hills, west of
Orlando. A depression about 1 foot deep and 50 feet in diameter formed
during April 23 and 24 and was marked only by a faint line in the sand
except where the outer edge intersected two houses. The floor of one
room, the carport, and the concrete driveway of one house was badly
cracked. The corner of the other house dropped about 6 inches.

The slow rate of settlement was probably caused by a gradual
funneling of the overlying sand and clay into relatively small solution
channels in the limestone. The channels eventually became filled
and the subsidence stopped.

DRAINAGE

The eastern and southern parts of Orange County are drained
principally by surface streams. The St. Johns River and its tributaries
drain the eastern part of the county while Shingle Creek, Reedy Creek,
Boggy Creek, and canals in the upper Kissimmee River basin drain
most of the south-central and southwestern part. Many swamps and
sloughs occur in the eastern and southern parts of the county because
of the poorly developed drainage.

In the western and northwestern parts of the county much of the
drainage is to closed depressions and thence by seepage to the under-
lying limestone or by evaporation from the lakes and ponds. A few
sinkholes have open connections with solution channels in the limestone.
Water that collects in these sinkholes drains directly into the solution
channels. Most of the sinkholes, however, are floored with relatively
impermeable sediments and the rate of seepage through these lake-
filled sinkholes may not be much greater than in areas adjacent to the
lakes.

More than 300 drainage wells were drilled between 1906 and 1961
in the upland area of the county, especially in Orlando and vicinity,
to drain surface water directly into the artesian aquifer (fig. 3).

FLORIDA GEOLOGICAL SURVEY

latter condition is illustrated by the formation of a sinkhole in the
Orlando area in April 1961. The sinking was first noted as a depression
in a graded road. By the following day a hole about 6 feet in diameter
had formed. Within 2 days the hole gradually increased to about 60 feet
in diameter and to about 15 feet in depth. The hole was filled and no
further development has been noted.

Another sinkhole occurred in April 1961 in Pine Hills, west of
Orlando. A depression about 1 foot deep and 50 feet in diameter formed
during April 23 and 24 and was marked only by a faint line in the sand
except where the outer edge intersected two houses. The floor of one
room, the carport, and the concrete driveway of one house was badly
cracked. The corner of the other house dropped about 6 inches.

The slow rate of settlement was probably caused by a gradual
funneling of the overlying sand and clay into relatively small solution
channels in the limestone. The channels eventually became filled
and the subsidence stopped.

DRAINAGE

The eastern and southern parts of Orange County are drained
principally by surface streams. The St. Johns River and its tributaries
drain the eastern part of the county while Shingle Creek, Reedy Creek,
Boggy Creek, and canals in the upper Kissimmee River basin drain
most of the south-central and southwestern part. Many swamps and
sloughs occur in the eastern and southern parts of the county because
of the poorly developed drainage.

In the western and northwestern parts of the county much of the
drainage is to closed depressions and thence by seepage to the under-
lying limestone or by evaporation from the lakes and ponds. A few
sinkholes have open connections with solution channels in the limestone.
Water that collects in these sinkholes drains directly into the solution
channels. Most of the sinkholes, however, are floored with relatively
impermeable sediments and the rate of seepage through these lake-
filled sinkholes may not be much greater than in areas adjacent to the
lakes.

More than 300 drainage wells were drilled between 1906 and 1961
in the upland area of the county, especially in Orlando and vicinity,
to drain surface water directly into the artesian aquifer (fig. 3).

I ,s ".'' OA' '' 05' 81'oo' o5' 8.oso I

I o

8 4

I -d 4 i 45I

4 r, 4
EXPLANATION 45'

d-U, -.i ? L ---------. -----------

3 I N
So
7 I

..... -

2- 25.
An"::^
U A c I A -L A^1^^

rc- NTl- Mr M 1 11 L^-^::^^ ::

Base token from U.S. Geological
Survey topographic quadrangles
1124,000

0 1 2 3 4 5 6 7 8 9 10 mill

al

Well inventory by W if Llch r

Figure 3. Distribution of drainage wells in Orange Countyj Florida.

28

W0'

17'

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0 05 9P00 SS 80 56

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4 4 3 36 28

FLORIDA GEOLOGICAL SURVEY

The greatest activity was during 1960 when about 35 drainage
wells were drilled. Considerable quantities of water are disposed of
in this manner, but figures on the total amount are not available. The
quality of the water that enters the aquifer through drainage wells ranges
from pure rainwater to water used to flush cow barns.

GEOLOGY

The materials penetrated by water wells in Orange County range
in age from middle Eocene (about 50 million years ago) to Recent.
The formations, in ascending order of age, include the Lake City Lime-
stone, the Avon Park Limestone, and the Ocala Group1 of middle Eocene
age; the Hawthorn Formation of middle Miocene age; and undifferentiated
post-Miocene deposits.

Sand and clay of the Hawthorn Formation and younger deposits
generally cover the limestones to depths ranging from a few feet in
the northern part of the county to about 100 to 150 feet in the Orlando
area and more than 350 feet in the eastern part of the county. Vernon
(1950) has postulated that the western two-thirds of the county is part
of the upthrown side of a faulted block called the Kissimmee faulted
flexure. Indications of another fault exist in the St. Johns River marsh
area with the upthrown side to the east. Further geologic data will be
collected to aid in solving the complex structure underlying Orange
County. Table 2 summarizes the properties of the geologic formations
penetrated by water wells in Orange County.

HYDROLOGY

All natural supplies of fresh water are derived from precipitation.
The cycle of precipitation, evaporation, and the intervening movements
of water is known as the hydrologic cycle. Some precipitation returns
almost immediately to the atmosphere by evaporation, some is transpired
by plants, some is stored in surface or underground reservoirs before
being returned to the atmosphere by evapotranspiration, and some moves
to the sea by surface or underground routes, eventually to be evaporated
again.
1The stratigraphic nomenclature used in this report conforms generally
to the usage of the Florida Geological Survey. It conforms also to the
nomenclature of the U. S. Geological Survey, except that Ocala Group
is used in this report instead of Ocala Limestone.

Table 2. Summary of the Properties of the Geologic Formations Penetrated by Water Wells in Orange County, Florida

Formation Thickness, Description of Water-bearing
Series. name in feet material properties Aquifer Water level
Recent Undifferen-
and tiated; may
Pleistocene include 0-200 Mostly quartz sand with Varies widely in onartesian 0-20 feet below the
Caloosa- varying amounts of quantity and land surface but
hatchee clay ahd shell quality of water generally less than
Pliocene (.) Marl produced 10 feet
Gray-green, clayey, Generally imper- Shallow artesian Piezometric surface not
quartz sand and silt; meable except for lower limestone defined, water level .
Miocene Hawthorn 0-200 phosphatic sand; and .limestone, shell, beds may be part generally is lower than"
buff, impure, phosphatic or gravel beds of Floridan nonartesian aquifer and
limestone, mostly in a quifer higher than Floridan
lower' part aquifer
Cream to tan, fine, soft Moderately high trans-
Ocala 0-125 to medium hard, granu- missibility, most
Group lar, porous,'sometimes wells also penetrate
dolomitic limestone underlying formations
Upper section mostly Overall transmissibilit
cream to tan, granular, very high, contains Piezometric surface
Eocene Avon Park 400-600 porous limestone. Often many interconnected Floridan shown in figures 10
Limestone, contains abundant cone- solution cavities, and 11
shaped Foraminifera. Many large capacity
Lower section mostly wells draw water fror
dense, hard, brown,crys- this formation
talline dolomite
Dark brown crystalline Similar to Avon Park
Lake City Over 700. layers of dolomite alter- Limestone. Municipal
Limestone Total un-' nating with chalky fossili- supply of City of
known' ferous layers of limestone Orlando obtained from
this formation

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O

FLORIDA GEOLOGICAL SURVEY

The greatest activity was during 1960 when about 35 drainage
wells were drilled. Considerable quantities of water are disposed of
in this manner, but figures on the total amount are not available. The
quality of the water that enters the aquifer through drainage wells ranges
from pure rainwater to water used to flush cow barns.

GEOLOGY

The materials penetrated by water wells in Orange County range
in age from middle Eocene (about 50 million years ago) to Recent.
The formations, in ascending order of age, include the Lake City Lime-
stone, the Avon Park Limestone, and the Ocala Group1 of middle Eocene
age; the Hawthorn Formation of middle Miocene age; and undifferentiated
post-Miocene deposits.

Sand and clay of the Hawthorn Formation and younger deposits
generally cover the limestones to depths ranging from a few feet in
the northern part of the county to about 100 to 150 feet in the Orlando
area and more than 350 feet in the eastern part of the county. Vernon
(1950) has postulated that the western two-thirds of the county is part
of the upthrown side of a faulted block called the Kissimmee faulted
flexure. Indications of another fault exist in the St. Johns River marsh
area with the upthrown side to the east. Further geologic data will be
collected to aid in solving the complex structure underlying Orange
County. Table 2 summarizes the properties of the geologic formations
penetrated by water wells in Orange County.

HYDROLOGY

All natural supplies of fresh water are derived from precipitation.
The cycle of precipitation, evaporation, and the intervening movements
of water is known as the hydrologic cycle. Some precipitation returns
almost immediately to the atmosphere by evaporation, some is transpired
by plants, some is stored in surface or underground reservoirs before
being returned to the atmosphere by evapotranspiration, and some moves
to the sea by surface or underground routes, eventually to be evaporated
again.
1The stratigraphic nomenclature used in this report conforms generally
to the usage of the Florida Geological Survey. It conforms also to the
nomenclature of the U. S. Geological Survey, except that Ocala Group
is used in this report instead of Ocala Limestone.

FLORIDA GEOLOGICAL SURVEY

All natural waters dissolve mineral matter from the soils and
rocks contacted. The quantity of mineral matter dissolved depends
mainly upon the type of material contacted and the length of the time
of contact. The solvent action upon mineral substances is greatly
increased when the water contains dissolved gases, such as carbon
dioxide, which may be introduced from the atmosphere or from decaying
organic material. The most common mineral constituents dissolved in
water are silica, iron, calcium, magnesium, sodium, potassium, car-
bonate and bicarbonate, sulfate, chloride, nitrates, and fluorides. Other
mineral constituents may be present in minor amounts.

Dissolved organic material which is introduced into water when
it contacts living and decaying vegetation imparts color to the water.
The color is generally more prevalent in surface water and shallow
ground water than in deep ground water.

At a particular, location ground water generally contains more
dissolved mineral matter than surface water because it is in intimate
contact with the soil and rock. However, the quality of ground water
does not vary as much as that of surface water. During dry periods,
the mineral content of surface water usually increases because of a
higher percentage of ground-water inflow and a longer time of contact
with soil and rock.

Dissolved mineral constituents in water are generally reported
in parts per million. One part per million (ppm) is one unit weight of
a constituent in a million unit weights of water. Hardness of water
is caused by the presence of alkaline earth metals such as calcium
and magnesium and is expressed as an equivalent quantity of calcium
carbonate. The hardness scale generally used by the U. S. Geological
Survey classifies water with a hardness of 0 to 60 ppm as soft; 61 to
120 ppm as moderately hard; 121 to 200 ppm as hard; and over 200 ppm
as very hard. Specific conductance is a measure of the ability of water
to conduct an electric current and may be used in estimating the total
dissolved mineral content. The total dissolved mineral content of most
surface water in Orange County is between 50 and 60 percent of the
conductivity. Thus, by making a simple conductivity measurement,
the mineral content can be estimated by multiplying the specific con-
ductance by a factor of 0.55. The mineral content of ground water in
Orange County can be estimated by multiplying the specific conductance
by a factor of 0.62. Color is expressed in units of the platinum-cobalt
scale. Hydrogen-ion concentration (pH) is a measure of the acidity or

INFORMATION CIRCULAR NO. 41

alkalinity of a solution. A pH value of 7.0 is neutral. Progressive
values of pH above 7.0 denote increasing alkalinity, and regressive
values below 7.0 denote increasing acidity.

SURFACE WATER

Most of the surface water in Orange County is from rain within the
county, but some of it is from rain on adjacent areas of higher elevation
that flows into the county. The surface water is only temporarily stored
in the lakes, swamps, and stream channels. The amount in storage
continuously changes because the rate of replenishment differs from the
rate of depletion.

Permanent lakes are the most reliable sources of surface water
in Orange County. Swamps and marshes are intermittent sources that
go dry after relatively short periods of drought.

The St. Johns River, the Wekiva River, and the Little Econlock-
hatchee River north of State Highway 50 are the only streams in the
county that do not either go dry or recede to extremely low base flows
in most years. The flow of the St. Johns River is sustained in all but
extreme droughts by water stored in several large lakes that are a part
of its main stem. The Wekiva River is sustained at relatively high
base flow by several springs. The lower Little Econlockhatchee River
receives water from the Orlando sewage system.

Surface-water data have been collected at 62 sites in the county.
Figure 4 lists the sites where data have been collected systematically
and shows the periods of record. Table 3 lists the sites where miscel-
laneous data have been collected.

Surface water from the southwestern 340 square miles of Orange
County drains to the south into the Kissimmee River. Surface water
from the eastern and northern 660 square miles of the county drains
to the north into the St. Johns River. Figure 5 shows the drainage
basins and the surface-water data collection points in Orange County.

KISSIMMEE RIVER BASIN

Reedy Creek: Reedy Creek drains 49 square miles in the south-
:west corner of Orange County. The drainage from about 22 square miles
of this basin in Lake County flows into Orange County.

FLORIDA GEOLOGICAL SURVEY

Stiii
Station

I AdarLke.at Orlando
Z Ajy-East Tohopekaliga Canal nr Narcoossee '
3 Apopha- ciir Canal at control t Astotula
a aeo oai Canal at State .448 nc Astatula
SApopa. Lake at Winter Garden
SBass Lake ni Orlando
7 Bssie, Lake, at Windermere
8 Big Sand Lake at Doctor Phillips
9 Bog Creek n Kissimmee

10 Bagy Creek nt Taft
SBuftler, Lake, at Windermere

- I 1.I i

Concord, Lake, at Orlando
Conway, Lake, nc Pinecastle
Corrine, Lake, or. Orlando
Cypress Creek at Vineland
Disston Canal nr Wewahotee
ra Laker, at Mount Dora
Econlockhatchee River nc Bithlo
Econlockhatchee River nr Chuluota
Fairview, Lake, at Orlando
Hart, Lake, nt Narcoossee
Nighland, Lake, at Orlando __
Ivanhoe, Loa at Orlando _
lim Creek nr Christmas
Johns Lake at Oakland
Little Econockhatchee River nr Union Park

27 i Lake Fairview at Orlando _
2 Molandi Lake, at Winter Park
29 ar Jane Lake n. Norcoossee
30 Mr Jane-Hart Canal nr. Narcoossee
13 Myr.e-Mary Jane Canal nr Narcoossee

32 i Lake at Orlando
33 Pinsett, Lake, nr Cocoa
34 awena, Lake, at Orlando
35 t Johns River nr. Christmas
,36 S Johns River no Cocoa
37 S Johns River Flood Profile
38 Shle Creek ot airport, nr. Kissimmee

39 IShingle Creek nr. Vineland

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; T 'T linDBiii

40 Silver Lake, at Orlando- --_-
4 t Spie; Lake, nr Orlando
42 Spring Lake at Orlando
43 Sue, Lake, at Orlando
44 Susannah Lake, nr. Orlando
45 Udthill, Lake, at Orlando
46 Yhiova River nr. Sanford S
47 Wenonah (Frmnci) Lake nr Plymouth
EXPLANATION
Oaily to weekly stage
Monthly stage or annual flood crest 1n |
Periodic discharge measurements i". *''-.......'**...* *.....................
Daily stage and discharge M %::. ::+::::::::::::::

Figure 4. List and duration of records at surface-water gaging stations in or

near Orange County, Florida.

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el 35 30 2 20 0 05 l 55 o 5'

3r~ e, 2a17'
e' 1o 26 10. 5c e e0'sd I
Base tken from US. GeologlCol 0 i 2 2 4 5 6 L I1O mles
SUrvey lopogrophic quodronglos,
1;24,000

Figure 5. Drainage basins and surface-water data collection points in Orange County, Florida. %

_ __ ---

INFORMATION CIRCULAR NO. 41

alkalinity of a solution. A pH value of 7.0 is neutral. Progressive
values of pH above 7.0 denote increasing alkalinity, and regressive
values below 7.0 denote increasing acidity.

SURFACE WATER

Most of the surface water in Orange County is from rain within the
county, but some of it is from rain on adjacent areas of higher elevation
that flows into the county. The surface water is only temporarily stored
in the lakes, swamps, and stream channels. The amount in storage
continuously changes because the rate of replenishment differs from the
rate of depletion.

Permanent lakes are the most reliable sources of surface water
in Orange County. Swamps and marshes are intermittent sources that
go dry after relatively short periods of drought.

The St. Johns River, the Wekiva River, and the Little Econlock-
hatchee River north of State Highway 50 are the only streams in the
county that do not either go dry or recede to extremely low base flows
in most years. The flow of the St. Johns River is sustained in all but
extreme droughts by water stored in several large lakes that are a part
of its main stem. The Wekiva River is sustained at relatively high
base flow by several springs. The lower Little Econlockhatchee River
receives water from the Orlando sewage system.

Surface-water data have been collected at 62 sites in the county.
Figure 4 lists the sites where data have been collected systematically
and shows the periods of record. Table 3 lists the sites where miscel-
laneous data have been collected.

Surface water from the southwestern 340 square miles of Orange
County drains to the south into the Kissimmee River. Surface water
from the eastern and northern 660 square miles of the county drains
to the north into the St. Johns River. Figure 5 shows the drainage
basins and the surface-water data collection points in Orange County.

KISSIMMEE RIVER BASIN

Reedy Creek: Reedy Creek drains 49 square miles in the south-
:west corner of Orange County. The drainage from about 22 square miles
of this basin in Lake County flows into Orange County.

18 FLORIDA GEOLOGICAL SURVEY

Table 3. Sites Where Miscellaneous Surface-Water Data Have Been Collected
In And Near Orange County, Florida
(Station number corresponds to that shown for figure 5.)

Station number Station
48 Bonnet Creek near Vineland

49 Christmas Creek near Christmas
50 Howell Creek near Maitland

51 Jim Branch near Narcoossee

52 Little Wekiva River near Forest City

53 Mills Creek near Chuluota

54 Reedy Creek near Vineland

55 Roberts Branch near Bithlo

56 Rock Springs near Apopka

57 Second Creek near Christmas

58 Settlement Creek near Christmas

59 Taylor Creek near Cocoa

60 Tootoosahatchee Creek near Christmas

61 Wekiva Springs near Apopka

62 Witherington Spring near Apopka

Elevations in Reedy Creek basin in Orange County range from
75 feet at the southern county line to 210 feet at Avalon fire lookout
tower. The eastern part of the basin is relatively flat swampy terrain
interspersed with islands of low relief. The western part is rolling
hills interspersed with lakes and swamps. The divide between Reedy
Creek basin and Bonnet Creek basin to the east is rather indefinite,
and some interchange of water occurs between basins.

At Reedy Creek near Vineland (station 54), 1 mile south of the
county line, the minimum flow observed was less than 0.01 cfs (cubic
feet per second) in May 1961. The maximum flow was 1,940 cfs at the
peakof the flood in September 1960.

Analyses of water collected from Reedy Creek at station 54 at
low flows on June 15, 1960, and May 23, 1961, show the water to be
very soft and low in mineral content. At almost zero flow on May 23,

INFORMATION CIRCULAR NO. 41

1961, the hardness was 11 ppm, and the mineral content, based on a
conductivity measurement, was estimated at 24 ppm.

Bonnet Creek: Bonnet Creek and its tributary, Cypress Creek,
drain 55 square miles of Orange County, east of Reedy Creek basin.
The part of the Bonnet Creek basin that is drained by Cypress Creek
differs hydrologically from the rest of the basin.

Elevations in Bonnet Creek basin range from 75 feet at the county
line to 195 feet near Windermere. Elevations in the western part of the
basin, the part excluding Cypress Creek basin, range from 75 to 100
feet. This area is flat and swampy but contains several lakes of moderate
size and islands of low relief.

The minimum flow observed at Bonnet Creek near Vineland (station
48), 1 mile south of the county line, was 0.4 cfs in May 1961 and the
maximum flow was 1,180 cfs at the peak of the flood in September 1960.

The water in Bonnet Creek has a slightly higher mineral content
and less color than the water in most other streams in the county. On
November 24, 1959, the mineral content was 107 ppm, the hardness was
66 ppm, and the color was. 10 units. The higher mineral content and
lower color are probably due to ground-water inflow.

Cypress Creek basin is comprised of about 8 square miles of lakes,
2 square miles of swamps, and 22 square miles of rolling hills in the
eastern part of Bonnet Creek basin. Elevations range from 90 feet at
its junction with Bonnet Creek to 195 feet near Windermere.

The flow from Cypress Creek basin has been gaged at Vineland
(station 15) since 1945. The average annual runoff is about 4 inches
and ranged from a minimum of 0.3 inch in 1955 to a maximum of 17.72
inches in 1960. In 10 of the 15 years of complete record, at least one
period of no flow occurred. The longest period of no flow was 107 days
in 1956. The maximum flow recorded was 354 cfs in September 1960.

Shingle Creek: Shingle Creek drains 83 square miles of Orange
County west of U.S. Highway 441 and south of State Highway 50.

Elevations range from 70 feet at the county line to 175 feet near
Windermere. The basin is relatively flat and altitudes are generally
less than 105 feet except for rolling hills on the western fringe. A closed
'depression occupies 3.3 square miles of the northern part of the basin.

FLORIDA GEOLOGICAL SURVEY

Continuous records of stage and discharge for Shingle Creek near
Kissimmee (station 38) have been obtained since October 1958. The
maximum discharge of record at this station was 3,320 cfs in March 1960.
Periodic observations of stage and discharge near Vineland (station 39)
have been obtained since September 1959. At this station, the maximum
discharge was 1,740 cfs in March 1960. In most years there is no flow
for many days at either site.

The water in Shingle Creek near Vineland (station 39) has low
mineral content and is soft. Dissolved organic material, usually about
50 percent of the dissolved solids, causes high color, especially during
the early periods of high flow. The dissolved solids, including organic
material, are less than 165 ppm and the hardness is usually less than
30 ppm. Color ranges from 55 to 200 units.

Boggy Creek: Boggy Creek drains 86 square miles of the county
in and south of Orlando. An area of about 11 square miles in the upper
part of the basin has no surface outlet and drains underground.

Elevations range from 60 feet at the county line to about 125 feet
in the upper basin. The lower part of the basin is flat and contains
many swamps and marshes but relatively few lakes. The upper part
of the basin is rolling hills interspersed with many lakes.

Periodic measurements of the discharge of Boggy Creek near
Kissimmee (station 9) were made from January 1955 to September 1959.
Since September 1959, continuous records of the discharge of Boggy
Creek near Taft (station 10) have been collected. The maximum discharge
during the period of record was 3,680 cfs in March 1960, and the minimum
was 0.1 cfs in June 1961.

Analyses of water collected periodically from Boggy Creek show
that the water is soft, low in mineral content, and high in color. The
total dissolved material ranged from 59 to 115 ppm, and the dissolved
mineral content ranged from 29 to 62 ppm which indicates that about
50 percent of the total dissolved material is organic. Color intensity
ranged from 45 to 140 units and was usually highest during the early
part of flood periods. The hardness of the water is less than 20 ppm.

Jim Branch: Jim Branch drains 5.8 square miles in the south-
central port of Orange County. Elevations in the basin range from 75
to 85 feet.

INFORMATION CIRCULAR NO. 41

The maximum flow of Jim Branch near Narcoossee (station 51)
has not been determined. A dry stream channel has been observed at
this station.

Water collected from Jim Branch at low flow on May 23, 1961
was very soft (9 ppm) and low in mineral content (30 ppm, estimated
from its conductivity).

Ajay-East Tohopekaliga Canal: This canal drains approximately
171 square miles, of which 54.5 square miles are in Orange County
and 116.5 square miles are in Osceola County.

Elevations of the drainage area in Orange County range from 60
to 90 feet. The topography is fairly flat and is characterized by swamps
in the northern part and by lakes in the southern part.

Periodic measurements of the flow in Ajay-East Tohopekaliga
Canal near Narcoossee (station 2) have been made since 1942. The
maximum measured discharge was 1,420 cfs in March 1960. A reverse
flow of 0.25 cfs was measured in February 1946. The average dis-
charge, based on the relation between drainage area and average discharge
at several points on the main stem of the Kissimmee River, is estimated
to be about 170 cfs.

The flow into Orange County from an area of 111 square miles in
Osceola County has been measured in Myrtle-Mary Jane Canal near
Narcoossee (station 31) since November 1949. The maximum flow into
the county via this canal was 990 cfs in September 1960. In September
1956, the flow reversed for 2 days and flowed out of the county at the
rate of 17 cfs. The average discharge in this canal for the period 1950
to 1960 was 129 cfs.

Water from Ajay-East Tohopekaliga Canal, collected at station 2
during low flow on May 23, 1961, was very soft (16 ppm) and low in
mineral content (39 ppm, estimated from its conductivity).

ST. JOHNS RIVER BASIN

St. Johns River: The St. Johns River is the eastern boundary of
Orange County. Small tributaries drain 174 square miles of Orange
County directly to the St. Johns River. An additional 490 square miles
,of the county are drained to the St. Johns River by tributaries which
flow across the county line before joining the main stem.

FLORIDA GEOLOGICAL SURVEY

The St. Johns River slopes very little in its approximately 20-mile
reach along the border of Orange County. At flood stages, the river
falls from an elevation of about 17.5 feet at Lake Poinsett to about 10.5
feet at the northern county line. At the minimum stages in 1945, the
river fell from 8.0 feet to minus 0.4 foot in this reach.

Stage and discharge records have been collected at St. Johns
River near Christmas (station 35) since December 1933 and at St. Johns
River near Cocoa (station 36) since October 1953. The average discharge
for the period of record at station 35 was 1,431 cfs. For the 7-year
period October 1953 to September 1960, the average discharge at station
35 was 1,689 cfs; and at station 36, 1,431 cfs. The maximum flow at
station 35 was 11,700 cfs in October 1953. There was no flow at station
35 for periods during March, April, and June 1939.

Large quantities of water may be stored in the wide channel and
in lakes in the St. Johns River valley.

Analyses of water collected daily from the St. Johns River at
station 36 from October 1953 to September 1960 and a continuous record
of its conductivity since June 1959 show that the quality of the water
varies greatly.

Figure 6 shows the relation of specific conductance to stream
flow for the St. Johns River at station 36 from June 1958 to July 1961.
The mineral content in the water varies inversely with stream flow be-
cause the percentage of mineralized ground water in the stream is greatest
during low flows. The scatter of the plotted points may be due to the
variable inflow of highly mineralized artesian water though possibly in
part to the problem of representative sampling. Inflow from one well
occurs just above the conductivity recorder, but it is doubtful if water
from this single well causes all of the variations in conductivity. During
the period 1953-60, the dissolved solids in water from the St. Johns
River ranged from 103 ppm October 21-31, 1953, to 998 ppm July 11-20,
1956; the hardness ranged from 30 ppm October 21-31, 1953, to 294 ppm
June 11-20, 1956; specific conductance ranged from 107 micromhos
October 10, 1953, to 1,620 micromhos June 18, 1956; and the water
temperature ranged from 460F January 9-12, 1956, to 950F August 9,
1956. The chloride content reached a maximum of 403 ppm at a mean
discharge of 41 cfs during the period June 11-20, 1956. This chloride
concentration is enough to taste slightly salty to most people (Hem,
1959).

0
S60oo

S400

S200

U

100 200 400 600 1000 2000 4000 7000 1I
Mean discharge in cubic feet per second

Figure 6. Relation of specific conductance to stream flow, St.Johns River at station 36, near Cocoa, Florida, 1958-61.

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24 FLORIDA GEOLOGICAL SURVEY

Small tributaries draining to east: The eastern part of the county
between the main stem of the St. Johns River and the Econlockhatchee
River, amounting to about 180 square miles, is drained to the St. Johns
River by numerous small tributaries. Table 4 shows data pertinent to
these tributaries.

During the low flow period from June 14 to 17, 1960, the dissolved
mineral content of the water in the small tributaries draining eastward
into the St. Johns River was estimated from conductivity measurements
to range from 33 ppm in Taylor Creek to 86 ppm in Second Creek. The
mineral content of the water in Christmas Creek was estimated to be
52 ppm on May 24, 1961, when the other small tributaries were dry.

Table 4. Data on Small Tributaries Draining the Eastern Part of Orange County,
Florida

Drainage
area Elevation
Station (square (feet) Discharge (cfs)
Subdivision of area number miles) Max. Min. Max. Date Min. Date
Taylor Creek near
Cocoa 59 8.74 75 14 3,000 Mar. 0 *
1960
Sweetwater Branch -- 4.31 50 16 --- ---0 *

Ji Creek near
Christmas 4 31.4 75 11 3, 750 Mar. 0 *
1960
Second Creek near
Christmas 57 17.3 76 17 1,500 Sept. 0 *
1960
Settlement Creek
near Christmas 58 8.86 76 17 --- -- 0 *

Tootoosahatchee Creek
near Christmas 60 23.6 76 14 --- --- *

Near Creek -- 6.52 72 13 --- --- *

Unnamed Creek -- 4.37 61 12 -- ---0

Christmas Creek 49 15.0 71 11 --- --- 0.04 June
1961
Buscombe Creek I -- 2.15 56 11 --- --- 0

Roberts Branch 55 5.05 72 37 --- -- 0 *

Area without
definite channels -- 13.4 46 14 --- ---0 *

St. Johns River
flood plain 40. 18 4

Many days in most years.

INFORMATION CIRCULAR NO. 41

Lake Pickett: Lake Pickett and its contributory drainage area
occupy 8.1 square miles. Mills Creek drains Lake Pickett to the Econ-
lockhatchee River. Elevations in the Lake Pickett drainage basin range
from 60 to 75 feet.

The hardness of the water in Mills Creek at Chuluota (station 53)
on May 24, 1961, was 7 ppm. and the mineral content, estimated from
its conductivity, was 21 ppm. The pH of the water was 5.9 indicating
that it is slightly corrosive. The water quality of Lake Pickett probably
is similar to that of Mills Creek.

Econlockhatchee River: The Econlockhatchee River drains 117
square miles of Orange County. The drainage basin ranges from 2.5 to
9.5 miles wide and the average width of the basin in Orange County
is 6.2 miles. The basin is about 14 miles east of Orlando and spans
the county from south to north. The drainage from 17 square miles of
the basin in Osceola County enters Orange County. Elevations in the
Econlockhatchee River basin in Orange County range from 20 to 90
feet.

The Econlockhatchee River basin and the area drained by small
tributaries to the St. Johns River are unusual for Orange County in that
they contain only three lakes of significant size. These basins do,
however, contain many swamps and marshes.

Continuous records of the flow of the Econlockhatchee River
near Chuluota (station 19) have been collected since 1936, and periodic
measurements of the flow of the Econlockhatchee River near Bithlo
(station 18) have been made since September 1959. The maximum flow
at station 19 was 11,000 cfs and at station 18, 7,840 cfs. The minimum
flow at station 19 was 6.7 cfs in June 1945. The river flow ceases at
station 18 in most dry years. The average flow at station 1.9 was 266
cfs for the period 1936 to 1960.

A continuous conductivity record since October 1959 and analyses
of water collected periodically from the Econlockhatchee River near
Bithlo show the water to be high in color, soft, and low in mineral con-
tent. The conductivity ranged from 24 to 189 micromhos and the color
ranged from 45 to 240 units. The color is always greatest during the
early part of high flow periods.

Figure 7 shows the cumulative frequency curves of specific con-
iductance for the Econlockhatchee River at station 18 for the 1960 and

FLORIDA GEOLOGICAL SURVEY

ISO

160

S140
o
10

2 100
E
o

g 80
0
0

a
01
U)

1 2 5 10 30 50
Percent of time specific conductance
that shown

70 90 99
was equal to or less than

Figure 7. Cumulative frequency curves of specific conductance for the Econ-
lockhatchee River at station 18, near Bithlo, Florida, 1960-61.

and 1961 water years (October 1 to September 30). These curves may
be used to estimate the mineral content of water in the river for any
percentage of time. For example, the conductivity was 130 micromhos or
less for 80 percent of the time in the 1961 water year whereas in 1960
the conductivity never exceeded 120. The mineral content of water in
the Econlockhatchee River averages about 0.55 of the conductivity;
therefore, the dissolved mineral content would be 72 ppm (130 x 0.55)
or less for 80 percent of the time during the 1961 water year. The mineral
content of the water in the Econlockhatchee River was lower in 1960
than in 1961 because of greater dilution by surface runoff in 1960.

I1961

i /1960

1,/

INFORMATION CIRCULAR NO. 41

Little Econlockhatchee River: The Little Econlockhatchee River
drains 71 square miles of Orange County east of Orlando. Elevations
in this basin range from about 35 feet near the county line to 127 feet
at the eastern edge of Orlando.

A few lakes exist along the western rim of the basin but none
exist elsewhere. Many swamps and marshes temporarily store water
and thereby reduce the magnitude of peak flows in the river.

The flow from the upper 27 square miles of the basin has been
gaged since October 1959 at Little Econlockhatchee River near Union
Park (station 26). The maximum and minimum flows at this station
were 1,640 cfs in March 1960 and 0.1 cfs in June 1961. The average
flow for the period October 1959 to May 1961 was 36 cfs.

Effluent from the Orlando sewage plant is discharged into the
river just north of State Highway 50. The amount of effluent ranges
from 5 to 12 mgd (million gallons per day) and averages about 7 mgd
oral communication, Mr. Reed Terry, Orlando Sewage Plant).

Analyses of water collected from the Little Econlockhatchee
River at station 26 show that the quality is similar to that of the Econ-
lockhatchee River. Color ranged from 30 to 32 units and was highest
during high flow periods. The dissolved solids content of the water
ranged from 83 to 140 ppm, mineral content ranged from 35 to 75 ppm,
and the water hardness did not exceed 48 ppm.

Howell Creek: Howell Creek drains about 20 square miles in
Orange County, mostly in the suburban areas of Maitland, Winter Park,
and the northern half of Orlando. Elevations in the Howell Creek basin
range from about 55 to 125 feet.

This basin contains a chain of lakes connected by natural channels,
canals, and culverts, beginning at Spring Lake at Orlando (station 42),
at an elevation of about 88 feet and ending at Lake Maitland at Winter
Park (station 28), at an elevation of about 66 feet. Several other lakes
are connected to the chain of lakes by canals or culverts. Lake Under-
hill at Orlando (station 45), in the Boggy Creek basin, is connected
to Lake Highland in the Howell Creek basin by a culvert.

The flow of Howell Creek near Maitland (station 50) has been
measured several times. The maximum discharge was about 160 cfs

FLORIDA GEOLOGICAL SURVEY

in September 1960. Flow at this site ceases when the level of Lake
Maitland is below about 65.5 feet with the center board of the control
out or about 66.0 feet with the center board in. The levels of many
of the lakes in the basin are partly controlled by drainage wells and
the flow from the basin is accordingly modified.

The water in Howell Creek and Lake Maitland are similar and
are of good quality except for moderate hardness. Hardness at high
and low lake levels was 65 and 81 ppm, respectively. The dissolved
solids at high and low lake levels were 128 and 147 ppm, respectively.

Wekiva River: The Wekiva River and its tributaries, the Little
Wekiva River and Rock Springs Run, drain about 130 square miles in
Orange County. Elevations in this basin range from about 15 feet at
the northern county line to about 195 feet near Windermere.

The area near the stream channels is flat and swampy, and ranges
in elevation from about 15 to 30 feet. From the edges of these flat
swamps, rolling hills rise abruptly to elevations ranging between 60 and
100 feet. More than half of the Wekiva River basin in Orange County
consists of rolling hills interspersed with lakes and sinks. There is
no surface outflow from this area.

Records of the daily stage and discharge of the Wekiva River
near Sanford (station 46) have been collected since October 1935. The
contributing drainage area at this station is about 200 square miles.
The average discharge for the period 1935-60 was 273 cfs. The maximum
discharge was 2,060 cfs in September 1945 and the minimum, 105 cfs in
June 1939.

The flows of Rock Springs, Wekiva Springs, and Witherington
Spring (stations 56, 61, and 62) near Apopka in the Wekiva River basin,
have been measured occasionally since 1931. Table 5 shows the results
of these measurements.

During low flow on May 25, 1961, the hardness of the water of the
Little Wekiva River at Forest City (station 52) was 41 ppm and the
mineral content, estimated from the conductivity of the water, was 90 ppm.

The quality of water from Rock Springs, and Wekiva Springs, is
similar to the ground water in the area, and variations with flow are
small.

INFORMATION CIRCULAR NO. 41 29

Table 5. Discharge Measurements of Springs in Orange County, Florida

Downstream location
of,measuring section
Name of spring and Date of Discharge in relation to head of
station number measurement (cfs) (mgd) spring (feet)

Rock Springs (56)

Wekiva Springs (61)

Witherington Spring
(62)

Z- 5-31
.3- 8-32
2-10-33
1-30-35
11- 7-35
12- 6-35
1- 4-36
1- 4-36
6- 7-45
5- 9-46
4-26-56
11-24-59
11-24-59
6-17-60
10-17-60
5-25-61

3- 8-32
2-10-33
11- 7-35
6- 7-45
5- 9-46
4-27-56
11-25-59
6-17-60
10-17-60
5-25-61

8- 8-45
10-19-60

55. 9
51.9
54.2
62.8
57.1
62. 8
54.9
56.2
52. 5
59.1
54.7
70.0
72.4
78.2
83.2
68.4

63.9
66.9
72.5
64.8
67.5
62.0
88.8
86.0
91.7
86.6

4.69
12.0

36.1
33.5
35.0
40.6
36.9
40.6
35.5
36.3
33.9
38.2
35.4
45. 2
46.8
50.5
53.8
44.2

41.3
43. 2
46.9
41.9
43.6
40.1
57.4
55.6
59.3
56.0

3.03
7.76

50
50
40
80
50
500
600
60
5b
30
1,000
150
1,200
1,250
1,250
1,300

1ob
100--
300
200
150
200
300
200
150
150

4,224
4,752.

Apopka-Beauclair Canal: This canal drains Lake Apopka and

the surrounding areas. The total area drained by the canal is about
180 square miles, of which about 120 square miles is in Orange County.
Elevations in this basin range from about 65 feet in the mucklands ad-

jacent to Lake Apopka to m6re than 210 feet near Avalon lookout tower.

The flow in Apopka-Beauclair Canal near Astaula was measured
periodically at station 3 from 1942 to 1948. Since July 1958 the daily
flow has been determined at station 4. The maximum flow at station 4

was 754 cfs in March 1960 and the minimum flow was estimated to be
about 5 cfs during periods when a control structure in the canal was
closed.

FLORIDA GEOLOGICAL SURVEY

LAKES, SWAMPS, AND MARSHES

Orange County has about 1,100 permanent bodies of open water
and hundreds of intermittent marshes and swamps. The vast majority
of the lakes are in the western half of the county. Swamps and marshes
occur in all parts of the county but are less prevalent in the northwestern
part than elsewhere in the county.

The lakes range in altitude from about 20 to 155 feet and in size
from less than 1 acre to nearly 47 square miles. Records of the levels
for the lakes listed in figure 4 have been collected by the U.S. Geolog-
ical Survey for the periods shown. Records for many additional lakes
have been collected by the engineering departments of the city of Orlando
and Orange County.

Because of relatively large volumes of water stored in lakes,
the quality does not change as rapidly as in streams. Some changes
in the quality of the water in lakes occur because of dilution, by high
runoff, and because of ground-water inflow and concentration of mineral
matter by evaporation.

Water from Lake Hart near Narcoossee (station 21) has been ana-
lyzed semiannually since October 1954. This water has high color, low
pH values, and low dissolved mineral content. The color ranged from
50 units on October 8, 1958, to 170 units on November 8, 1956. The pH
values, which ranged from 5.5 to 6.2, indicate that the water is slightly
corrosive. The dissolved mineral content was low and ranged from 20
to 34 ppm.

The water in Lake Apopka at Winter Garden (station 5) is hard
and high in calcium bicarbonate, indicating large quantities of ground-
water inflow. During the low stage in May 1961 the calcium content
was 29 ppm, the bicarbonate was 123 ppm, and the water hardness was
126 ppm.

Water collected from Johns Lake at Oakland (station 25) during
high stage on October 29, 1959, had a hardness of 30 ppm, a mineral
content of 77 ppm, and a color of 80 units.

INFORMATION CIRCULAR NO. 41

GROUND WATER

Ground water is the subsurface water in the zone of saturation -the
zone in which all the openings of the soil or rock are completely filled
with water under atmospheric or greater pressure. Ground water occurs
under nonartesian or artesian conditions. Nonartesian conditions occur
when the upper surface of the zone of saturation (the water table) is not
confined and accordingly is free to rise and fall. Artesian conditions
occur when an aquifer (water-bearing formation or group of formations)
is confined by relatively impermeable beds and the water is under greater
than atmospheric pressure.

The heights to which water will rise in tightly cased wells that
penetrate an artesian aquifer define its pressure or piezometric surface.
The piezometric surface is not directly related to the water table and
may be above, below, or at the same level as the water table. Where
the water table is above the piezometric surface the nonartesian water
may infiltrate through the confining layer to the artesian aquifer. Such
areas are recharge areas to the artesian aquifer. Conversely, where
the piezometric surface is above the water table, the artesian water
moves upward and the area is a discharge area of the artesian aquifer.
As no confining bed is completely impermeable, some leakage up or
down usually occurs; however, where the confining bed is composed
of a thick section of dense material, such as clay, the amount of leakage
is relatively small.

Ground water in Orange County occurs in a shallow nonartesian
aquifer, in several shallow artesian aquifers, and in the Floridan aquifer,
which is artesian in Orange County.

NONARTESIAN AQUIFER

Aquifer properties: The nonartesian aquifer in Orange County
extends from the water table to about 30 or 40 feet below land surface.
It is composed mainly of quartz sand with varying amounts of clay,
hardpan, and shell material. The nonartesian aquifer extends over
most of the county, but its composition and thickness and consequently
its productivity vary and there may be many local areas where it will
not produce enough water to supply a well. Most wells in the nonartesian
aquifer are small diameter sand-point or screened wells, 20 to 30 feet
deep, that yield small to moderate quantities of water.

32 FLORIDA GEOLOGICAL SURVEY

Water levels: The depth to the water table in Orange County
ranges from 0 to about 40 feet below the land surface. The data avail-
able indicate that the yearly fluctuations of the water table range from
a few feet in low-lying parts of the county to more than 20 feet in higher
areas. Figure 8 shows the hydrograph of one well (832-105-3) in the

38 i

l -do-, Fo
42-

_.L._,

zC-4 T j r
|^-+ 4--p--^^^

i i i "s '

6i- I I--i---
IT I Of 0000CCT COUNTY SHOWIAG

-6 4 ~- 1 '-- O -W -EL
^ rl i | i, .- iL _i

Figure 8. Ilydrographs of observation wells in Orange County and rainfall at
OrlandLo, Florida.
Fig-ure8 yrgah fosevto el nOageCut n anala
Or~ano, Flrida

INFORMATION CIRCULAR NO. 41

nonartesian aquifer in comparison with the hydrographs of observation
wells in the artesian aquifer in Orange County. The graph shows that
at that location the water level fluctuated less than 2 feet in 1961.
The lowest level was in early June, the beginning of the wet season.

Recharge and discharge: Practically all the recharge to the non-
artesian aquifer in Orange County comes from rainfall within or near
the county. Most of the county is blanketed with permeable sand which
allows the water to infiltrate rapidly. In much of the eastern and southern
parts of the county, where the land is flat and an impermeable layer of
hardpan is near the surface, the overlying surface sands are quickly
saturated during the rainy season and many swamps and sloughs are
formed.

Discharge from the nonartesian aquifer in Orange County is by
evapotranspiration, seepage into surface-water bodies, downward leakage
to underlying aquifers, seepage out of the county, and pumpage. The
hydrographs of wells 832-105-1, 2, and 3, in figure 8, show that in the
the vicinity of these wells (fig. 9) the water table was consistently
above the pressure surfaces in the underlying artesian aquifers and
accordingly some shallow water probably discharged downward.

Quality of water: Water collected from a selected number of wells
in the nonartesian aquifer shows a range in chemical composition. The
water.from wells developed in clean quartz sand is usually very soft
(hardness generally less than 25 ppm) and low in mineral content (about
20 to 50 ppm). The very soft water often has low pH value indicating
that it is corrosive.

Total mineral content as high as about 500 ppm (estimated from
conductivity measurements) and high concentrations of some constituents
indicate that the water in some wells in the nonartesian aquifer is pol-
luted. The water from well 822-138-3 (fig. 9) had concentrations of
potassium (10 ppm), sulfate (107 ppm), and nitrate (173 ppm), which
definitely indicates a possible nearby source of pollution. Use of water
containing an excess of 45 ppm of nitrate for feeding formulas for infants
results in methemoglobinemia or cyanosis (blue babies) in the infants.
A high concentration of nitrate was found only in well 822-138-3. The
waterfrom some of the nonartesian wells had as much as 90 units of color.

Mb 4W 40 3b, 30 O h 20 A 0W0
Io .4 .. .... ... .. . . o, -.

-- ....
46. ^ .. ; -- .. "

A Kf I COU1T "
G- : ^T j --- 7*
f W T-W ""^ --- *Ti- l

.. .. .- -- ---- ----4---

7 PI r' --T
Ap o jC U NTY
--- .
0 r u. _-----T -
:- ~ a ,i3- gpi ,_. ,-- ,, --.I-----. r

I, 30 -
1\ 1~ ~Ji~r[-. ..-- ~ ~ I'N, I ,.- "

C NT -- L
2d :: ^ : ;:::: :': :;:72: : : :
C'UN S l Y "'. I I I- I- L IE E- _-5-I I-- -- -

I I I i

I l I i l

ftw+

rL i,,'L /
horemLu

I I i\ I I

I I I 1 I I

, ' '' ' [' ' ' ..
w --

Base taken from US. Geological
Survey topographic quadrangles
1124,000

0 1 23 4 5 6 7 9 9 Omlles

Figure 9. Orange County, Florida, showing location of Inventoried wells other than drainage wells.

I

81'4

a

Size

i i L-CIR-I '' ' '-;?J-~lki.~--l-l-l--t-I-3--

Y--~ ~ ~--~ ---~--~ --.-,--,---ccc--n--

r,o..

0so0

'I

i
I

fl

/

15 10 ow 8lUo

EXPLANATION
Wil and wel mrnbn

_ -- I-----

i

INFORMATION CIRCULAR NO. 41

SHALLOW ARTESIAN AQUIFERS

Aquifer properties: Several shallow artesian aquifers occur within
the confining beds of the Hawthorn or younger formations at depths
ranging from about 60 feet to more than 150 feet below land surface.
These aquifers are composed of discontinuous shell beds, thin limestone
layers, or permeable sand zones. The shallow artesian aquifers are
most productive in the area east and south of Orlando, where they yield
quantities of water sufficient for domestic use to screened or open-end
wells.

Water levels: The only record of water-level fluctuations in a
shallow artesian aquifer is from well 832-105-2 (depth 75 feet) (fig. 8).
The range of fluctuation in this well, for the period of record, was about
3.5 feet, or from 7 to 10.5 feet below land surface. At this location the
shallow artesian water level is 6 to 12 feet below the nonartesian water
level and 6 to 14 feet above the water level in the Floridan aquifer.

Recharge and discharge: Recharge to the shallow artesian aquifers
is mostly by leakage through overlying beds or by upward leakage from
underlying beds where the piezometric surface in the Floridan aquifer is
above the piezometric surface in the shallow artesian aquifer. A small
amount of water probably flows into the county from surrounding counties
within the shallow artesian aquifers.

Discharge from the shallow artesian aquifers is by downward
leakage to the Floridan aquifer, upward leakage to the nonartesian
aquifer where the piezometric surface is above the water table, under-
ground flow out of the county, and pumpage.

FLORIDAN AQUIFER

The principal artesian aquifer that underlies Orange County is a
part of the Floridan aquifer which underlies Florida and parts of Alabama,
Georgia, and South Carolina. The Floridan aquifer, as defined by Parket
(1955, p. 189), includes "parts or all of the middle Eocene (Avon Park
and Lake City limestones), upper Eocene (Ocala limestone), Oligocene
(Suwannee limestone), and Miocene (Tampa limestone) and permeable
parts of the Hawthorn formation that are in hydrologic contact with the
rest of the aquifer."

FLORIDA GEOLOGICAL SURVEY

Aquifer properties: The Floridan aquifer in Orange County is
covered by a layer of sand and clay which ranges in thickness from
about 40 to 350 feet. The total thickness of the aquifer is unknown
and it may include formations older than the Lake City Limestone.
Supply wells for the city of Orlando penetrate more than 1,300 feet of
the aquifer.

The lithology of the Floridan aquifer is variable but, in general,
it is composed ofalternating layers of limestone and dolomite, or dolomitic
limestone. The limestone layers are usually softer and of lighter color
than the dolomitic layers. The upper part of the aquifer is mostly cream to
tan limestone and the lower part is mostly light to dark brown dolomite or
dolomitic limestone. In many parts of the county persistent layers of
dense, hard, dark brown, dolomitic limestone occur between depths of.
about 400 and 600 feet below land surface.
Although the permeability of the dolomite is extremely low, the
dolomitic zones contain many interconnected solution cavities and chan-
nels that make its overall permeability very high. Tests made by Unkles-
bay (1943, p. 13) show that wells with open hole between depths of
60 and 450 feet and wells with open hole between 550 and 1,000 feet
below land surface have the same water level and fluctuate together,
indicating that the solution channels are interconnected vertically as
well as horizontally.

Solution channels, ranging in diameter from a fraction of an inch
to many feet probably occur throughout the aquifer but are most preva-
lent at depths between 200 and 600 feet and between 1,100 and 1,500
feet below the land surface. Cavities 15 feet or more in depth have
been reported by drillers. Large diameter wells in the Floridan aquifer
will yield more than 4,000 gpm.

Piezometric surface: The piezometric surface of the Floridan
aquifer in Orange County slopes to the east and northeast from its highest
point in the southwestern part of the county (fig. 10,11). Water moves
downgradient, from areas of high piezometric level to areas of lower
piezometric level. In general, the direction of movement is at right angles
to the contour lines. The arrows in figures 10 and 11 show the general
direction of movement of water in the Floridan aquifer. Because of the
cavernous nature of the aquifer the actual direction of movement of water
at particular locations may be different than the general direction indicated
by the configuration of the piezometric surface, The flattened ridge on
the piezometric surface in the vicinity of Orlando is caused by recharge
through the drainage wells in the area. Figure 10 depicts the piezometric

Figure 10. Orange County, Florida, showing the contours of the piezometric surface at high water conditions, September 1960.

___ ___ _I ___I I_

Bb s0' 20b 0 N b I 05 Boo0 bb 800'
-'T7 1-1 T 1 '-1 4r-1 / 1111111 ==1III'I I I 1r- -I -I-I I I T-T-1 -7 1 12
--"4 .1 N N
KL lY3 EXPLANATION

Nlimor Ii A\r er level, kin el
above mien III level.

Ca-nour (epresenls tIh pliiom lrrle surfuce,
In fell ob0 1 moeon Ile 10\1, in .ul, 1IS6, Dohid
hore inferred Arrow nd, ie duirrm of m.A or fIo.w..-
SAPOP Ceontour Inlevol a fef '
4d 40'
o SEMINOLE

is, 0 0 UT T Y

5 1- 3
'S4 .1 0

.A 0 '-2

S SCE OLA ,, t t, C 0UNTY
044 1,51 ow

45 40 35 30 25 20 15' 10 05 81'00 55 80'50'
Bose token from US Geologicol 0 I 2 3 4 5 6 7 8 9 I0 mie
Survey topographr' qUOdronglos --
I124,000

Figure 11. Orange County, Florida, showing the contours of the piezometric surface at about normal conditions, July 1961.
Figure 11. Orange County, Florida, showing the contours of the piezometric surface at about normal conditions, July 1961.

INFORMATION CIRCULAR NO. 41

levels in September 1960, the highest observed during the investigation.
The high levels of September 1960 equaled or exceeded the highest
previous recorded levels, which occurred in the early 1930's. Figure 11,
which shows the piezometric surface in July 1961, about 10 months later,
represents about normal conditions.

The magnitude of fluctuations of the piezometric surface ranges
from place to place in the county. The greatest fluctuations occur in
Orlando, where more than 300 drainage wells in and around the city
permit direct and immediate recharge to the aquifer (fig. 3) and where
pumping is concentrated. Hydrographs of five artesian wells in figure 8
illustrate this condition. The water level in well 833-120-3 at the
Orlando Air Base varied 23 feet in 1960-61, from a high of 75 feet on
September 11, 1960, to a low of 52 feet on June 6, 1961, whereas the
fluctuation in the other wells in the Floridan aquifer was small.

Recharge and discharge: Most of the recharge to the Floridan
aquifer in Orange County is from infiltration of rain through the relatively
thin semipermeable confining beds in the highlands section of the county
and through the more than 300 drainage wells in the county. A lesser
quantity enters the county by underground flow from southern Lake County
and a very small amount enters from Osceola County. The best data
available in 1961 suggest that most of the ground water in the artesian
aquifer in Orange County originates within the county.

Discharge of ground water from the Floridan aquifer in Orange
County is by (1) outflow into northern Lake County, Seminole County,
and Brevard County; (2) upward leakage into the St. Johns marsh; (3) use
within the county; and (4) spring outflow. Preliminary estimates ofthe
amount of recharge of artesian water from various sources and discharge
to various areas are given in the section on water budget.

Quality of water: The quality of the water in the Floridan aquifer
ranges greatly throughout the county, but varies little at a particular
location and depth. The total dissolved solids, as estimated from
conductivity measurements, ranged from 60 ppm in water from well
843-131-1 in the northwestern part of the county to 1,810 ppm in water
from well 829-056-1 in the eastern part of the county.

Figure 12 shows that in the western part of the county most of
the water in the Floridan aquifer is relatively low in mineral content,
and the dissolved solids are less than 150 ppm. The mineral content
of the water increases toward the eastern part of the county, and the

Figure 12. Orange County, Florida, showing general range of dissolved solids of the water in wells in the Floridan aquifer.

INFORMATION CIRCULAR NO. 41

dissolved solids exceed 1,000 ppm in the flowing wells along the St.
Johns River. The high mineral content of artesian water in the eastern
part of the county is probably due to incomplete flushing of saline water
that entered the aquifer when the sea last covered Florida.

Figure 13 shows the principal mineral constituents in water from
selected wells in the Floridan aquifer in Orange County. The total
alkalinity (carbonate plus bicarbonate) is reported as carbonate. Car-
bonate is present in natural water when the pH value exceeds 8.2. Some
of the artesian water in Orange County contains small amounts of carbon-
ate, but most of the alkalinity is due to bicarbonate.

The composition of water from well 843-136-1 in northwestern
Orange County and from well 832-058-1 in eastern Orange County (fig.13)
indicates that artesian water in western OrangeCounty is high in calcium
carbonate whereas the highly mineralized water in the eastern part of the
county is high in sodium chloride.

Except for high hardness, most water from the Floridan aquifer
in western and central Orange County is of good chemical quality.
However, water from flowing wells to the east along the St. Johns River
is very hard and contains large amounts of sodium, sulfate, and chloride.
West of longitude 81003' the hardness ranged from 48 to 335 ppm and
averaged 153 ppm. The water from well 832-058-1, near the east edge
of Orange County, had a hardness of 590 ppm, contained 354 ppm of
sodium, 250 ppm of sulfate, and 630 ppm of chloride on July 3, 1957.
Water from the same well had a hardness of 580 ppm and contained 640
ppm of chloride on October 24, 1960. Hydrogen sulfide gas is generally
present in water from the flowing wells, and can be detected by the
characteristic odor and taste. Hydrogen sulfide can be eliminated by
aeration.

PUMPING TEST

The ability of an aquifer to transmit water is referred to as the
coefficient of transmissibility (T); defined as the quantity of water,
in gallons per day, that will move through a vertical section of the
aquifer 1 foot wide and extending the full saturated height of the aquifer,
under a unit hydrologic gradient at the prevailing temperature of the
water (Theis, 1938, p. 892). A measure of the capacity of the aquifer
to store water is referred to as the coefficient of storage (S); defined
as the volume of water released from or taken into storage per unit

FLORIDA GEOLOGICAL SURVEY

42

o
o

*o
o

D

o

o

1.

Figure 13. Composition of mineral content of water from selected wells in the
Floridan aquifer in Orange County, Florida.

100

90

80

70

60

50

40

30

20

10

0

INFORMATIONC.IRCULAR NO. 41

surface area of the aquifer per unit change in head normal to that surface.
The leakage coefficient (P/m) is a measure of the ability of the confining
beds above and below the aquifer to transmit water to the main producing
zone. It is defined as the quantity of water that moves through a unit
area of the confining bed with a head difference across the bed of unity.

The above coefficients of an aquifer can be determined from-ob-
servation wells at a known distance from a well being pumped at a
constant rate by analyzing the resulting changes in water level.

A. pumping test to determine the coefficients of the Floridan
aquifer was made in Orlando on February 17, 1961'. A 12-inch drainage
well on Lake Davis (841-122-4) was pumped for 11 hours at a rate of
1,100 gpm and changes in water levels were recorded in four nearby
well s.

Background data collected before and after the test were used
to eliminate from the drawdown curves extraneous effects, such as
natural fluctuations of the water levels not related to the pumping.
The corrected drawdown data (s) were plotted versus time (t) since
pumping began, divided by the square of the distance (r) from the pumped
well to the observation well (s versus t/r2). The resulting curves were
compared with a family of leaky aquifer type curves developed by H.H.
Cooper, Jr. (U.S. Geological Survey, Tallahassee, Florida). This family
of curves is based on the equation for nonsteady flow in an infinite
leaky aquifer developed by Hantush and Jacobs (1955, p. 95-100) and
described by Hantush (1956, p. 702-714). The equation assumes a
permeable bed overlain by less permeable beds through which wafer,
under a constant head, can infiltrate to reach the aquifer. The trans-
missibility and storage coefficients obtained by the leaky aquifer method
apply to the main producing zone, and the leaky coefficient applies to the
semipermeable confining beds.

The coefficients and other pertinent data for the Orlando test are
shown in table 6. The range in,determined values reflects in part the
nonhomogeneous and anisotropic conditions of the limestone aquifer.
This test indicates the aquifer has approximately the following coef-
ficients: transmissibility 500,000, storage 0.001, and leakage 0.1. A
transmissibility of 500,000 gpd/ft indicates a very productive aquifer.

44 FLORIDA GEOLOGICAL SURVEY

Table 6. Results of Pumping Well 831-122-4, Orlando, Florida, February 17, 1961

Casing Distance to Transmis- Maximum
Observation Depth Depth observation sibility Leakge drawdown
well number (feet) (feet) well (feet) (gpd/ft) Storage (gpd/ft /ft ) (feet)
831-122-15 350 88 750 455,000 0.00071 0.131 2.90
831-121-6 335 115 950 440,000 .0031 .312 .66
831-121-7 428 315 1,900 745,000 .00083 .074 .26
831-122-18 435 114 3,900 745,000 .00083 .049 .14

WATER BUDGET

The water available for use by man is that stored in surface or
underground reservoirs. If the water in these reservoirs is not used
by man, it eventually leaves the reservoir in which it is stored and
moves to another part of the hydrologic cycle. Over long-term climatic
cycles the amount of water leaving an area must balance the amount
entering it. If the amounts of water entering and leaving an area are
out of balance, a change in the amount of water in storage occurs. An
accounting of the amounts of water entering and leaving an area and
related changes in storage is termed a water budget. An approximate
water budget for Orange County based upon general information presently
available follows. Additional investigation will result in refining the
various figures and they are presentedonly to show the relative magnitude.

Rainfall within Orange County averages about 2,500 mgd. Surface-
water inflow averages about 140 mgd and ground-water inflow, mostly
within the Floridan aquifer, averages about 40 mgd.

Water lost by evapotranspiration is estimated to average about
1,750 mgd, surface runoff from the county averages about 790 mgd, and
about 140 mgd is lost by underground flow to Brevard, Lake, and Seminole
counties.

An average of 814 mgd of water from sources outside the county
flows along the eastern border of the county in the St. Johns River.

INFORMATION CIRCULAR NO. 41 45

USE OF WATER

Use of ground water in Orange County is estimated tohave averaged
about 65 mgd in 1960. Of this total, about 17 mgd were pumped by the
Orlando Utilities Commission to users in and around Orlando, including
the Martin Company; about 9 mgd were pumped by the city of Cocoa from
their well field in Orange County, about 7 mgd were used by privately
supplied industry, mostly for citrus processing and packing;.4 mgd were
pumped by private water companies in the Orlando area; about 3 mgd
'were used for irrigation; and an estimated 25 mgd were used by com-
munities and private individuals outside of the Orlando area.

Use of surface water is estimated to average about 45 mgd. About
30 mgd is used for irrigating citrus trees and about 15 mgd is used for
irrigating row crops mostly in the Zellwood muckland area north of Lake
Apopka.

44 FLORIDA GEOLOGICAL SURVEY

Table 6. Results of Pumping Well 831-122-4, Orlando, Florida, February 17, 1961

Casing Distance to Transmis- Maximum
Observation Depth Depth observation sibility Leakge drawdown
well number (feet) (feet) well (feet) (gpd/ft) Storage (gpd/ft /ft ) (feet)
831-122-15 350 88 750 455,000 0.00071 0.131 2.90
831-121-6 335 115 950 440,000 .0031 .312 .66
831-121-7 428 315 1,900 745,000 .00083 .074 .26
831-122-18 435 114 3,900 745,000 .00083 .049 .14

WATER BUDGET

The water available for use by man is that stored in surface or
underground reservoirs. If the water in these reservoirs is not used
by man, it eventually leaves the reservoir in which it is stored and
moves to another part of the hydrologic cycle. Over long-term climatic
cycles the amount of water leaving an area must balance the amount
entering it. If the amounts of water entering and leaving an area are
out of balance, a change in the amount of water in storage occurs. An
accounting of the amounts of water entering and leaving an area and
related changes in storage is termed a water budget. An approximate
water budget for Orange County based upon general information presently
available follows. Additional investigation will result in refining the
various figures and they are presentedonly to show the relative magnitude.

Rainfall within Orange County averages about 2,500 mgd. Surface-
water inflow averages about 140 mgd and ground-water inflow, mostly
within the Floridan aquifer, averages about 40 mgd.

Water lost by evapotranspiration is estimated to average about
1,750 mgd, surface runoff from the county averages about 790 mgd, and
about 140 mgd is lost by underground flow to Brevard, Lake, and Seminole
counties.

An average of 814 mgd of water from sources outside the county
flows along the eastern border of the county in the St. Johns River.

INFORMATION IRCUL-AR N0.41 47

REFERENCES

Black, A. P.
1951 (and Brown, Eugene) Chemical character of Florida's waters:
Florida State Board Cons., Div. Water Survey and Research Paper 6.

Brown, D. W.
1957 (and Kenner, W. E., and Brown,
resources of Brevard County,
Circ. 11-.

Eugene) Interim report on the water
Florida:- Florida Geol. Survey Inf.

1962 (and Kenner, W. E., Crooks, J. W., and Foster, J. B.) Water resources
of Brevard County, Florida: Florida Geol. Survey Rept. Inv. 28.

Brown, Eugene (see Black, A. P.; Brown, D. W.)

Cole, W. S.
1941

Stratigraphic and paleontologic studies of wells in
Geol. Survey Bull. 19.

1945 Stratigraphic and pa'leontologic studies oflwells in
Florida Geol. Survey Bull. 28.

Collins, .W. D.
1928 (and Howard, C. S.) Chemical character of waters
Geol. Survey Water-Supply Paper 596-G.

Florida: Florida

Florida no. 4:

in Florida: U. S.

Cooke, C. W.
1939 Scenery of Florida: Florida Geol. Survey Bull. 17.

1945 Geology of Florida: Florida Geol. Survey Bull. 29.

Cooper, H. H., Jr. (see Stringfield, V. T.)

Crooks, J. W. (see Brown, D. W.)

Fenneman, N. M. -
1938 Physiography of eastern United States: New York, McGraw-Hill
Book Co., Inc.

Ferguson, G. E. (see Parker, :G..G.) -

48 FLORIDA GEOLOGICAL SURVEY

Florida State Board of Health
1961 Some physical and chemical characteristics of selected Florida
waters: June 1960.

Foster, J. B. (see Brown, D. W.)

Gunter, Herman (also see Sellards, E. H.)
1931 (and Ponton, G. M.) Need for conservation and protection of our
water supply with special reference to waters from the Ocala lime-
stone: Florida Geol. Survey 21st and 22d Ann. Rept.

Hantush, M. C.
1955 (and Jacob, C. E.) Nonsteady radical flow in an infinite leaky dquifer:
Am. Geophys. Union Trans., v. 36, no. 1, p. 95-100.

1956 Analysis of data from pumping tests in leaky aquifers: Am. Geophys.
Union Trans., v. 37, p. 702-714.

Hem, J. D.
1959 Study and interpretation of the chemical characteristics of natural
water: U. S. Geol. Survey Water-Supply Paper 1473.

Howard, C. S. (see Collins, W. D.)

Jacob, C. E. (see Hantush, M. C.)

Kenner, W. E. (see Brown, D. W.)

Love, S. K. (see Parker, G. G.)

MacNeil, F. S.
1950 Pleistocene shorelines in Florida and Georgia: U. S. Geol. Survey
Prof. Paper 221-F.

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

Meinzer, O.E.
1923 The occurrence of ground water in the United States, with a dis-
cussion of principles: U. S. Geol. Survey Water-Supply Paper 489.

INFORMATION CIRCULAR NO. 41

Parker, G. G.
1955 (and Ferguson, G. E., Love, S. K., and others) Water resources of
southeastern Florida: U.S. Geol. Survey Water-Supply Paper 1255.

Ponton, G. M. (see Gunter, Herman)

Puri, H. S.
1953

Contribution to the study of the Miocene of the Florida Panhandle:
Florida Geol. Survey Bull. 36.

Rainwater, F. H.
1960 (and Thatcher, L. L.) Methods for collection and analysis of water
samples: U. S. Geol. Survey Water-Supply Paper 1454.

Reitz, H. J. (see Wander, 1. W-)

Sanford, Samuel (see Matson, G. C.)

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

1913 (andGunter,Herman) The artesian water supply of eastern and southern
Florida: Florida Geol. Survey 5th Ann. Rept.

Stringfield, V. T.
1935 The piezometric surface of artesian water in the Florida Peninsula:
Am. Geophys. Union Trans., 16th Ann. Mtg., Pt. 2, p. 524-529.

1936 Artesian water in the Florida Peninsula: U. S. Geol. Survey Water-
Supply Paper 773-C.

1950 (and Cooper, H. H., Jr.) Ground water in Florida: Florida Geol.
Survey Inf. Circ. 3.

Thatcher, L. L. (see Rainwater, F. H.)

Theis, C. V.
1938 The significance and nature of the cone of depression in ground-
water bodies: Econ. Geology, v. 33, no. 8.

U. S. Geological Survey
1943 Progress report on hydrologic studies of lake sources of municipal
water supplies of Orlando, Florida: Open-file rept.

50 FLORIDA GEOLOGICAL SURVEY

U. S. Weather Bureau
1960 Climatological data, Florida, annual summary, 1960: v. 64, no. 13.

Unklesbay, A. G.
1944 Ground water conditions in Orlando and vicinity, Florida: Florida
Geol. Survey Rept. Inv. 5.

Ver.-on, R. O.
1951 Geology of Citrus and Levy counties, Florida: Florida Geol. Survey
Bull. 33.

Wander, 1. W.
1951 (and Reitz, H.J.) The chemical composition of irrigation water used in
Florida citrus groves: Univ.of Florida Agr. Experiment Station Bull.408.

White, W. A.
1958 Some geomorphic features of central peninsular Florida: Florida
Geol. Survey Bull. 41.

FLRD GEOLOSk ( IC SUfRiW

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	Title Page
	Table of Contents
	Abstract
	Introduction
	Description of area
	Climate
	Sinkholes
	Drainage
	Geology and hydrology
	Surface water
	Ground water
	Water budget
	References