Front Cover
 Title Page
 Table of Contents
 List of Figures
 List of Tables
 Geology and physiography
 Hydrology and water quality
 Watershed energetics
 Plant communities
 Back Matter
 Back Cover

Group Title: ecological characterization of the Caloosahatchee RiverBig Cypress watershed
Title: An ecological characterization of the Caloosahatchee RiverBig Cypress watershed
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00000112/00001
 Material Information
Title: An ecological characterization of the Caloosahatchee RiverBig Cypress watershed
Alternate Title: Report - Minerals Management Service and Fish and Wildlife Service, U.S. Dept. of the Interior ; FWS/OBS-82/58.2
Physical Description: xvi, 225 p. : ill., maps ; 28 cm.
Language: English
Creator: Drew, Richard D
Schomer, N. Scott
National Coastal Ecosystems Team (U.S.)
United States -- Minerals Management Service. -- Gulf of Mexico OCS Region
Florida -- Dept. of Environmental Regulation
Publisher: Minerals Management Service
Fish and Wildlife Service, U.S. Dept. of the Interior
Place of Publication: Metaire, LA
Washington, D. C.
Publication Date: 1985
Subject: Wetland conservation -- Florida -- Big Cypress National Preserve   ( lcsh )
Wetland conservation -- Florida -- Caloosahatchee River Watershed   ( lcsh )
Wetland ecology -- Florida -- Big Cypress National Preserve   ( lcsh )
Wetland ecology -- Florida -- Caloosahatchee River Watershed   ( lcsh )
Genre: bibliography   ( marcgt )
federal government publication   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 203-225.
Funding: State of Florida, Department of Environmental Regulations.
General Note: Distributed to depository libraries in microfiche.
General Note: "September 1984."
Statement of Responsibility: by Richard D. Drew and N. Scott Schomer ; performed for National Coastal Ecosystems Team, Division of Biological Services, Research and Development, Fish and Wildlife Service, U.S. Department of the Interior and Gulf of Mexico Outer Continental Shelf Office, Minerals Management Service.
 Record Information
Bibliographic ID: UF00000112
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA0267
notis - AME7134
alephbibnum - 002441921
oclc - 12604798

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Title Page
        Page i
        Page ii
        Page iii
        Page iv
    Table of Contents
        Page v
        Page vi
    List of Figures
        Page vii
        Page viii
        Page ix
        Page x
        Page xi
    List of Tables
        Page xii
        Page xiii
        Page xiv
        Page xv
        Page xvi
        Page 1
        Page 2
        Page 3
    Geology and physiography
        Page 4
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    Hydrology and water quality
        Page 50
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    Watershed energetics
        Page 87
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    Plant communities
        Page 95
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    Back Matter
        Page 226
        Page 227
    Back Cover
        Page 228
Full Text

h ~

September 1984


0 5 10 20 30

Minerals Management Service
Fish and Wildlife Service
U.S. Department of the Interior

September 1984



Richard D. Drew
N. Scott Schomer

State of Florida
Department of Environmental Regulation
2600 Blairstone Road
Tallahassee, FL 32301

Project Officer
Ken Adams
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
1010 Gause Boulevard
Slidell, LA 70458

Performed for
National Coastal Ecosystems Team
Division of Biological Services
Research and Development
Fish and Wildlife Service
U.S. Department of the Interior
Washington, DC 20240


Gulf of Mexico Outer Continental Shelf Office
Minerals Management Service
3301 North Causeway Boulevard
U.S. Department of the Interior
Metaire, LA 70010


The opinions, findings, conclusions, or recommendations expressed in
this report are those of the authors and do not necessarily reflect the
views of the U.S. Fish and Wildlife Service unless so designated by other
authorized documents.

Library of Congress Card Number 83-600628

This report should be cited:

Drew, R.D., and N.S. Schomer. 1984. An ecological characterization of
the Caloosahatchee River/Big Cypress watershed. U.S. Fish Wild]. Serv.
FWS/OBS-82/58.2. 225 pp.


This report is one in a series that provides an ecological description
of Florida's gulf coast. The watershed described herein, with its myriad
tropical and subtropical communities, produces many benefits to man. The
maintenance of this productivity through enlightened resource management
is a major goal of this series. This report will be useful to the many
participants that govern the use of the natural resources of the watershed.

Any questions or comments about or requests for this publication should
be directed to:

Information Transfer Specialist
National Coastal Ecosystems Team
U.S. Fish and Wildlife Service
NASA Slidell Computer Complex
1010 Gause Boulevard
Slidell, Louisiana 70458


Southwest Florida contains a variety of natural resources that have
contributed to the development of the area into an important industrial,
shipping, agricultural, sport and commercial fishing, recreational, and
retirement center in the eastern Gulf of Mexico. As growth continues the
finite natural resources of the area will diminish in both quality and
quantity. Future management of the remaining resources requires careful
consideration to preserve a productive balance between man and nature.
Often, in deciding where this line lies, there is considerable uncertainty
about the composition, interaction, and value of the living resources in an
area. This report is an extensive review and synthesis of the available
literature on the ecology of the Caloosahatchee River/Big Cypress watershed.
The report will be used by the U.S. Fish and Wildlife Service, and the
Mineral Management Service to plan for the development of oil and gas
reserves offshore of southwest Florida. This document is divided into two
parts. The first part describes the geology, physiography, climate, and the
characteristics of ground and surface waters. The remainder of the report
focuses on plant succession and communities, and with the watershed's fish
and wildlife, their habits and habitat preferences.


PREFACE . . . . . . . . . . . . . . . . iii
SUMMARY . . . . . . . . . . . . . . . . iv
FIGURES . . . . . . . . . . . . . . . . vii
TABLES . . . . . . . . . . . . . . . . xii
ACKNOWLEDGMENTS . . . . . . . . . . . . . xvi


1.1 Purpose and Organization of the Report . . . . . . 1
1.2 The Caloosahatchee River/Big Cypress Watershed . . . . 1


2.1 Structure and Geologic Setting . . . . . . . . 4
2.2 Tertiary Stratigraphy . . . . . . . . . . 7
2.3 Pleistocene Series . . . . . . . . . . . 11
2.4 Physiography ... ... ........ ........ . 15
2.5 Recent Sediments and Soils . . . . . . . . . 18


3.1 Introduction . . . . . . . . . . . . 25
3.2 Rainfall ... .. .... . . . .. . .... . 26
3.3 Winds . . . . . . . . . . . . . . 32
3.4 Temperature .. ...... ............... . 36
3.5 Relative Humidity .. . ... .. . .. .. .. 38
3.6 Solar Radiation . .. . .. .. .. .. . . . 39
3.7 Evapotranspiration . . . . . . . . . . . 41
3.8 Hurricanes . . . . . . . . . . . . . 42
3.9 Air Pollution . .. ... . . . . . . .... 46


4.1 Introduction . . . . . . . . . . . . 50
4.2 Caloosahatchee River Watershed . . . . . . . . 53
4.2.1 Freshwater Caloosahatchee River . . . . . 53
4.2.2 Tidal Caloosahatchee River . . . . . . . 60
4.3 Estero Bay Watershed . . . . . . . . . . 64
4.4 Golden Gate Canal Watershed . . . . . . . . . 65
4.5 Southern Big Cypress Swamp . . . . . . . . . 83


5.1 Energy and Material Flow Through The Coastal Watershed . .*. 87
5.2 Conceptual Models of Regional Ecological Processes . . . 89


6.1 Introduction . . . . . . . . . . . . 95
6.2 Terrestrial and Freshwater Wetlands . . . . . . . 95
6.2.1 Pinelands . . . . . . . . . . . . 97
6.2.2 Hammocks ....... ........ ...... 103
6.2.3 Cypress and Mixed Swamp Forests . . . . . .. 104
6.2.4 Prairies, Marshes, Sloughs, and Ponds . . . . 110
6.2.5 Riverine Communities . . . . . . . . 112
6.3 Estuarine and Saltwater Wetland Habitats . . . . . 114
6.3.1 Salt Prairies and Marshes . . . . . . . 114
6.3.2 Mangrove Forests . . . . . . . . . 115
6.3.3 Oscillating-Salinity Open Waters . . . . . 123
6.3.4 Beach, Dune, Sea Wrack, and Coastal Strand . . . 130
6.4 Disturbed Communities . . . . . . . . . . 131
6.4.1 Exotic Plant Communities . . . . . . . 132
6.4.2 Agricultural Communities . . . . . . . 138
6.4.3 Urban/Industrial Communities . . . . . . 139
6.4.4 Canals . . . . . . . . . . . . 141


7.1 Introduction . . . . . . . . . . . . 145
7.2 Invertebrates . . . . . . * . * * * 145
7.2.1 Terrestrial and Wetland Invertebrates . . . . 145
7.2.2 Marine and Estuarine Invertebrates . . . . . 146
7.3 Fishes . . . . . . . . . . . . . . 160
7.3.1 Freshwater Fishes . . . . . . . . . 160
7.3.2 Estuarine and Marine Fishes . . . . . . . 168
7.3.3 Endangered Species . . . . . . . . . 175
-7.4 Amphibians and Reptiles . . . . . . . . . . 175
7.5 Birds . . . . . . . . . . . . . . 179
7.5.1 Arboreal Birds . . . . . . . . . . 180
7.5.2 Wading Birds .. . .. . . . . . .. 184
7.5.3 Floating and Diving Water Birds. . . . . . 187
7.5.4 Birds of Prey .. ... ..... ... . .. . 190
7.5.5 Probing Shorebirds . . . . . . . . . 193
7.5.6 Aerially Searching Birds . . . . . . . 196
7.6 Mammals . . . . . . . . . . . . . . 199

REFERENCES . . . . . . . . . . . . . . . 203


Figure Page

1 The Caloosahatchee River/Big Cypress watershed. 2

2 The Floridan Plateau. 4

3 South Florida oil fields. 7

4 Stratigraphic nomenclature of pre-Cenozoic strata in
the Florida peninsula. 8

5 Generalized geologic column of Cenozoic rocks. 9

6 West to east schematic geologic cross section of
Caloosahatchee River outcrops in the area near
Fort Denaud, Fort Thompson, and Ortona Lock. 12

7 Distribution of surface-exposed Pleistocene formations. 13

8 Pleistocene terraces and shorelines of south Florida. 14

9 Major physiographic features of the lower Florida peninsula. 15

10 Geological cross section of the Ten Thousand Islands with
environmental interpretations. 17

11 Generalized soil-type distribution in southwest Florida. 19

12 Environmental mechanisms involved in forming subaerial
crusts. 22

13 Florida climatic divisions. 25

14 Average annual rainfall for the Caloosahatchee River/
Big Cypress watershed. 26

15 Average dry-season rainfall, November through April,
in the Caloosahatchee River/Big Cypress watershed. 28

16 Average wet-season rainfall, June through September,
in the Caloosahatchee River/Big Cypress watershed. 29

17 Average monthly rainfall at three locations in the
Caloosahatchee River/Big Cypress watershed. 29

18 Frequency distribution of rainfall at Clewiston, 1975-1979. 30

Figure Paqe

19 Frequency distribution of rainfall at Fort Myers, 1975-1979. 31

20 Average annual maximum rainfall for one day in south Florida. 31

21 Severe droughts from 1890 to 1980 at Fort Myers,
Lake Trafford, and Miami. 32

22 Representative seasonal streamlines and isotachs over
the Florida Peninsula. 34

23 Average monthly divergence curves over the Florida Peninsula
for June, July, and August, 1963. 35

24 Annual wind rose for Fort Myers. 36

25 Isotherms for south Florida annually, and in January
and August. 37

26 Average annual number of days with maximum temperatures
of 900 F or above throughout Florida. 38

27 Diurnal patterns of relative humidity at three selected
sites over south Florida in April and September. 40

28 Predicted evapotranspiration patterns in Florida. 42

29 Points of entry and probabilities of hurricanes at
selected coastal locations. 44

30 Average chemical concentrations of precipitation at
sampling sites in and adjacent to the watershed. 47

31 Subdrainage basins within the Caloosahatchee River/
Big Cypress watershed. 51

32 Monthly average stream flow at three Caloosahatchee River
stations. 53

33 The East Caloosahatchee River Basin. 54

34 Algal concentrations in the upper and lower Caloosahatchee
River in 1978. 59

35 The tidally influenced portion of the Caloosahatchee River. 60

36 Temporal variations in salinity and water temperature along
the Caloosahatchee River. 62

Figure Page

37 Temporal variations in water quality data along the
Caloosahatchee River. 63

38 Chlorophyll a concentrations in the Caloosahatchee River 1
estuary. 64

39 Canals in western Collier County. 65

40 Water levels near the Golden Gate Canal. 67

41 The Golden Gate Highlands area. 68

42 Diurnal dissolved oxygen and temperatures for
Corkscrew Swamp, September 1975. 71

43 Average monthly flow in the Cocohatchee River Canal. 72

44 Average monthly flow in the Golden Gate Canal. 73

45 Types of canal development in the Naples Bay area. 74

46 Typical canal flushing curves in and around Naples Bay. 75

47 The Rookery Bay estuarine system. 77

48 Average monthly flow in Henderson Creek from 1970 to 1980. 77

49 The Marco Island estuarine system. 79

50 Diagram of flow conveyance channels in the Marco Island
estuarine system. 79

51 Hydrologic cross section in the vicinity of Marco Island. 81

52 Fahkahatchee Bay and Fahka Union Bay. 82

53 Major physiographic regions of south Florida. 83

54 Monthly water levels at bridge 105 at the Tamiami Canal. 84

55 Average monthly flow in the Barron River Canal from
1970 to 1980. 84

56 Wet and dry season water-level contours in the Big Cypress
National Preserve. 85

157 Conceptual model of a terrestrial ecosystem in south Florida. 91

Figure Page

58(o Conceptual model of an ecosystem influenced by man
in south Florida. 91

59 Conceptual model of the Caloosahatchee River/Big Cypress
watershed. 93

60 Major plant communities in the Caloosahatchee River/
Big Cypress watershed. 96

61 Successional patterns in south Florida plant communities. 98

62 Successional stages in inland plant communities in
south Florida. 99

.63 South Florida successional stages without fire:
-- shallow-water marsh to hammock. 100

64 South Florida successional stages without fire:
deep-water marsh to hammock. 100

65 The annual cycle of a slash pine stand. 101

66a Plant community profiles in the Big Cypress swamp:
wet prairie into cypress stand. 106

66b Plant community profiles in the Big Cypress swamp:
pine-palm-palmetto forest through cypress tree community. 106

66c Plant community profiles in the Big Cypress Swamp:
wet prairie, hammock, swamp forest, and lake. 107

66d Plant community profiles in the Big Cypress Swamp:
wet prairie into hardwood hammock. 107

67 Mangrove prop root communities. 116

68 Mangrove community associations and forest types along the
southwest coast of Florida. 117

69 Mangrove community associations and forest types along the
southwest coast of Florida. 118

70 Mangrove community productivity as related to salinity. 122

71 Diagramatic representation of protein enrichment of mangrove
detritus during degradation. 123

Figure Pa

72 Monthly trends in gross production and respiration in
Naples Bay canals. 129

73 A high-energy beach community, showing major zones
relating to sand motion. 130

74 The effects of canal development on hydrology and habitat
structure. 143

75 Seasonal trends in plankton numbers and biomass. 147

76 Representative benthic invertebrates living among
mangrove prop roots. 150

77 Representative benthic invertebrates living among
oyster reefs. 150

78 Simplified model of shrimp migratory patterns in south
Florida. 152

79 Numbers and biomass of pink shrimp (Penaeus duorarum)
and grass shrimp (Palaemonetes spp.) taken from combined
catches of surface and otter trawls in Fahka Union and
Fahkahatchee Bays, 1972. 154

80 Abundance of postlarval shrimp at Whale Harbor Channel
in the upper Keys. 155

81 Continuum of mangrove environments and associated fish
communities. 169

82 Numbers of species of breeding land birds in the Florida
peninsula. 183

83 Seasonal habitat use by birds of various species. 183

84 Number of wading birds at colony sites active in 1974-1975. 186


Table Page

1 Geological eras and formations of the Floridan Plateau. 5

2 Recognized sea-levels during the Pleistocene era in
Florida. 11

3 Wet season, dry season, and total annual precipitation
for the Caloosahatchee River/Big Cypress watershed. 27

4 Mean number of days with rainfall greater than
0.01 inch and 0.10 inch in the Caloosahatchee River/
Big Cypress watershed. 30

5 Most common wind direction and speed by month for the
Fort Myers first order station. 36

6 Summary of severe freezes recorded in the Caloosahatchee
River/Big Cypress watershed. 38

7 Mean monthly relative humidities for 0100, 0700, 1300,
and 1900 hours, and 24-hour average. 39

8 Solar radiation and related climatological data for Miami
and Fort Myers first-order weather stations. 41

9 Major hurricane storm surges between Fort Myers and
Everglades City. 45

10 Caloosahatchee River/Big Cypress watershed maximum
hurricane rainfall data. 46

11 Seasonal averages of nutrient concentrations in
rainwater at Tamiami Trail, 40 Mile Bend. 48

12 Major upstream tributaries (above Ortona Lock)
associated with the Caloosahatchee River watershed. 52

13 Major downstream tributaries (below Ortona Lock)
associated with the Caloosahatchee River watershed. 52

14 Monthly average downstream and upstream flow for the
Townsend Canal, 1970-1980. 55

15 Average constituent concentrations in wet and
dry seasons. 58

16 Tidal prisms in Estero Bay on February 8, 1976. 65

Table Paqe

17 Wet season flow ranges and extremes for Golden Gate
Canal, Henderson Creek, and Fahka Union Canal. 68

18 Salinity, temperature, and dissolved oxygen in
Naples Bay, August 1977. 76

19 Migration rate of Keewaydin Island seaward of Rookery Bay. 78

20 Explanation of energy circuit language symbols used in
the conceptual models. 90

21 Habitats corresponding to conceptual model zonations. 92

22 Physical and biological features of pinelands that
simultaneously promote and limit fire. 102

23 Energetics of cypress forests in the Caloosahatchee River/
Big Cypress watershed. 109

24 Plant species dominating the dry and wet prairies,
marshes and sloughs, and ponds of the Caloosahatchee
River/Big Cypress watershed. 110

25 Plant communities dominated by herbaceous species in
Lake Okeechobee near Moore Haven. 111

26 Major plant species in the Caloosahatchee River oxbow lakes. 113

27 Essential differences in reproduction in Florida mangroves. 121

28 Leaf litter production rates of mangrove forests. 122

29 Algal species collected in the watershed. 124

30 Benthic metabolism in Naples Bay. 127

31 Chlorophyll a in Big Cypress estuaries at high and
low tides during selected months in 1977. 127

32 Plankton metabolism estimates for estuaries of
the Big Cypress watershed. 128

33 Plant communities affected by major urban centers in the
Caloosahatchee River/Big Cypress watershed. 141

Table Page

34 Structural and functional changes in natural communities
caused by urbanization. 142

35 List of aquatic plants found in the waterways of central
and northern Collier County. 144

36 Numbers of decapod crustaceans collected in various habitats
in the Ten Thousand Islands, Florida, 1972. 152

37 Seasonal variation in pink shrimp post-larvae with depth. 155

38 Recurrent groups of benthic fauna in Naples Bay,- 159

39 Benthic habitat ranking in Naples Bay based on average
number of recurrent groups abundance and diversity of
fauna. 160

40 Benthic habitat ranking of canal troughs and berms
based on average number of recurrent groups abundance
and diversity of fauna. 160

41 Differences in benthic community structure and species
composition between Fahka Union and Fahkahatchee Bays. 161

42 Freshwater fishes of southern Florida. 162

43 Relative fish species abundance for six estuarine bays
within the watershed. 172

44 Seasonal occurrences of midwater fish groups in Naples Bay. 173

45 Seasonal occurrences of icthyoplankton in Naples Bay. 174

46 Ranking of recurrent groups of midwater fishes and
icthyoplankton in Naples Bay. 174

47 Endangered, threatened, rare, or special concern species
of fishes found in the Caloosahatchee River/Big Cypress
watershed. 175

48 Habitat importance to amphibian and reptile species in
the Big Cypress watershed. 176

49 Endangered, threatened, rare and special-concern amphibian
~- and reptile species in the Caloosahatchee River/Big Cypress
watershed. 179

Table Page

50 Habitat use and importance to breeding arboreal birds. 180

51 Habitat use and importance to non-breeding arboreal birds. 182

52 Habitat use and importance to wading birds. 185

53 Colony sites and number of wading bird nests in southern
Florida, September 1974 to August 1975. 186

54 Seasonality of nesting by wading birds and associated
species in south Florida. 187

55 Habitat use and importance to floating and diving birds
in the Big Cypress watershed. 188

56 Habitat use and importance to birds of prey in the
Big Cypress watershed. 191

57 Habitat use and importance to probing shorebirds in the
Big Cypress watershed. 194

58 Habitat use and importance to aerially searching birds in
the Big Cypress watershed. 197

59 Endangered, threatened, rare, and special concern
species of birds in the Caloosahatchee River/Big
Cypress watershed. 198

60 Habitat use and importance to land mammals in the
Caloosahatchee River/Big Cypress watershed. 199

61 Aquatic and marine mammals found in the Caloosahatchee
River/Big Cypress watershed. 201

62 Endangered, threatened, rare, and special concern
species of mammals in the Caloosahatchee River/Big
Cypress watershed. 201



The authors wish to acknowledge the assistance of a number of people who
contributed to the preparation of this document. Many public and private
agency representatives cooperated with our search for published and unpub-
lished data sources. Noteworthy among these were the staffs of Everglades
National Park, the South Florida Water Management District, the National
Marine Fisheries Service, the Southwest Florida Regional Planning Council,
the University of Florida's Center for Wetlands, and the University of Miami
Rosenstiel School of Marine and Atmospheric Sciences. Two Individuals in
particular, Alison Lewis and Carol Knox provided continual and invaluable
support to the completion of this work. Ms. Lewis's persistence and effi-
ciency in managing a virtual mountain of computerized bibliographic informa-
tion greatly simplified our task. Ms. Knox's patient revision and completion
of the tables and figures was carried out in an expert and timely manner.
Valuable editorial review and comment was provided by Mr. Joe Carroll,
Mr. Donald Hankla, Dr. Jeffrey Spendelow, Mr. John Parsons, and Ms. Gaye
Farris of the U.S. Fish and Wildlife Service, and Mr. Paul Johnson of the
Florida Department of Environmental Regulation. Grateful appreciation is
extended to Tish Elliott, who prepared draft manuscripts of the synthesis
paper and the bibliography, and to Francie Stoutamire who prepared the final
manuscript. The authors also wish to express special thanks to our project
officer, Mr. Ken Adams, for his constant support and expert guidance in
directing our efforts and bringing this document to publication.



In recent years man's cultural
and economic development has accel-
erated at an unprecedented pace.
Inevitably this development precipi-
tates rapid change in the environ-
ment. Major examples are habitat
alteration, such as urbanization
and dredging, sewage and industrial
effluent discharge, ground and sur-
face water diversion, and urban and
agricultural runoff.

Within the highly developed and
rapidly changing coastal regions of
southwest Florida, a fine line is
emerging between vigorous economic
development and the preservation of
a productive balance between man and
nature. Often, in deciding where
this line lies, there is consider-
able uncertainty about the compo-
sition, interaction, and value of
the living resources in a particular
area. This report is an extensive
review and synthesis of the avail-
able literature on the ecology of
and environmental alterations in
the Caloosahatchee River/Big Cypress

In contrast to most literature
reviews and syntheses, this report
deliberately crosses disciplinary
boundaries in an attempt to focus
on how -a watershed functions as an
integrated ecological system. At
the core of this focus is the basic
question, "How do energies and mate-
rials flow through the Caloosahatch-
ee River/Big Cypress watershed?"

This report is divided into two
parts, one on physical/chemical
background conditions, and the other

on biological resources. The first
part (Chapters 2 through 4) de-
scribes the geology and physiography
of the study area, its climate, and
the characteristics of ground and
surface waters. Chapter 5 discusses
the concept of watershed energetic
for the Caloosahatchee River/Big
Cypress watershed and attempts to
describe the meshing of man's socio-
economic structure with the area's
natural setting. Chapter 6 describes
plant succession and communities,
and Chapter 7 deals with fish and
wildlife, their habits, and habitat


This region (Figure 1) consists
of the watersheds and estuaries of
the Caloosahatchee River, the Big
Cypress Swamp, Estero Bay, and
Corkscrew Swamp, and corresponds to
United States Geological Survey
hydrologic units 03090205 and
03090204. The upper watershed is
dominated by the canalized Caloosa-
hatchee River that runs from Lake
Okeechobee to the Franklin Locks.
A series of three lock structures
control flow and stage in the river.
Many of the tributaries to the
Caloosahatchee River have also been
canalized for drainage and irriga-
tion purposes and are equipped
with weirs and pumps for localized

The upper reach of the Caloo-
sahatchee River estuary is the
salinity-control structure (Franklin
Locks) near the town of Olga. This
long and narrow estuary borders the


.,J \o\oo,
S,,o.S.o \ > \


o 5 20




Figure 1. The Caloosahatchee River/Big Cypress watershed.




15 20

4 "c4;

cities of Fort Myers and Cape Coral,
and empties into San Carlos Bay in
the lee of Sanibel and Pine Islands.
These islands are considered part
of the Charlotte Harbor estuarine

The Big Cypress watershed
hydrologicc unit 03090204) consists
of the Estero Bay watershed, the
Corkscrew Swamp watershed, and the
Big Cypress Swamp. The Estero Bay
watershed encompasses the drainage

of small streams into Estero Bay.
The ill-defined Corkscrew Swamp
watershed begins near Lake Trafford
and runs southwesterly toward the
coast. The Big Cypress Swamp in-
cludes the numerous cypress domi-
nated sloughs and strands flowing
roughly southwest and perpendicular
to the Tamiami Canal. The surface
waters of this gently sloping area
discharge into the Gulf of Mexico
through the Ten Thousand Islands



The Floridan Plateau (Figure
2), originally named by Vaughan
(1910), is the land mass that sepa-
rates the Gulf of Mexico from the
Atlantic Ocean. It includes not
only the State of Florida but an
equal area of submerged ocean shelf
west to a depth of 50 fathoms (91 m
or 300 ft). The plateau underlies
the Caloosahatchee River/Big Cypress
watershed as well as a large area of
the Gulf of Mexico. In the Gulf,
the plateau's bottom slopes gently

away from the west coast of Florida,
but it drops off sharply just south
of the Keys into the Straits of
Florida. The median axis of the
plateau passes through Key West,
Bradenton, Sarasota, Cedar Keys, and
Madison, Florida (Cooke 1945).

A reference chart for the
ensuing discussion of geologic
structure and stratigraphy is given
in Table 1. More detailed tables
correlating specific rock formations
and facies in Florida with geologic
periods may be found in Cooke (1945)
and Puri and Vernon (1964).

Figure 2. The Floridan Plateau (adapted from Chen 1965).

Table 1. Geological eras and formations of the Floridan Plateau.

QUATERNARY Pleistocene
CENOZOIC (glacial) mankind
Pl iocene
TERTIARY Ol igocene
Paleocene 70,000,000 placental
marna I s
Lower birds cereals
JURASSIC 160,000,000 flowering
mammals plants
TRIASSIC ginkgoes

PERMIAN 230,000,000 cycads

390,000,000 plants:
SILURIAN lycopodiums
500,000,000 mosses

CAMBRIAN 620,000,000

inverte- spores of
PROTEROZOIC brates uncertain
NOT DIVIDED relationship
1,420,000,000 algae

Structurally, the area under
consideration in this report lies
within what Pressler (1947) refers
to as the Florida Peninsula sedimen-
tary province. This province is one
of two distinct sedimentary facies,
clastic (panhandle Florida) and non-
clastic (peninsula Florida), that
segregate Florida's early Tertiary
stratigraphy (Paleocene and Eocene) .
These two sedimentary faces were
separated by the Suwannee Channel
(Figure 2), which served as a nat-
ural sedimentational and faunal
barrier. It occupied a narrow NE
to SW trending belt, from southern
Georgia to northern Florida's
Apalachicola Bay, during the late
Cretaceous to upper Eocene (Chen
1965). Nonclastic sediments, which
dominate the Florida peninsula, are
primarily carbonates and anhydrites,
that are chemically or biologically
produced, in contrast to sediments
generated by weathering or erosional

Of particular significance in
the watershed is the structural
feature of the peninsula identified
as the South Florida Shelf. This
term was applied by Applin and
Applin (1964) to a shallow shelf
generally paralleling and inclusive
of the lower southwest coast (Puri
and Vernon 1964). Pressler (1947)
believes that anticlinal folds are
the most prevalent type of struc-
tures within the South Florida
Shelf. Although probably occurring
as secondary structural features,
faults should also be common in this
area. Based on the configuration of
the surface of the submerged areas,
Pressler (1947) believes the Florida
Peninsula is bounded on the south
and east by major fault zones. These
faults are probably due to conti-
nental movements in addition to
settling, compacting, and continuous
downwarping of the sedimentary fill.
These factors contribute localized

structural features significant to
the accumulation of oil (Winston

The oil deposits of south
Florida are generally confined to
the Sunniland Limestone of the lower
Cretaceous Trinity Age found in the
Big Cypress watershed, as illus-
trated in Figure 3. Of the 72 holes
drilled in the Big Cypress National
Preserve, as of 1977, only 12 pro-
duced oil. The current status of
each well, permit changes, and
drilling progress are summarized
in a weekly newsletter, "Florida
Petroleum Report", which may be
obtained from the Florida Bureau of
Geology in Tallahassee. The oil-
producing zone of the Sunniland
Limestone varies in depth (2,925 to
3,590 m or 9,597 to 11,779 ft) and
in lithology. A comparison of two
of the more productive fields illus-
trates the stratigraphic variation.
The Bear Island Field represents an
elongated, low-relief anticline,
whereas the Sunniland Field lies
over a slight dome, possibly a reef
structure, which may be associated
with natural adjustments of rock
masses within the earth's crust and
associated faults. In both fields,
the oil traps are gentle anticlines
associated with biostromal reefs
(Duever et al. 1979). More detail
on the south Florida oil field
geology may be obtained from the
Florida Division of Resource Manage-
ment or from reports listed in the
Florida Bureau of Geology "List of

According to Applin and Applin
(1964), the floor of the coastal
plain in the Florida Peninsula is
the truncated surface of a variety
of igneous and sedimentary rocks
that are chiefly Precambrian and
early Paleozoic in age. Unfortu-
nately, most of the work conducted
on underlying pre-Mesozoic rocks in

Figure 3. South Florida oil fields
(adapted from Duever et al. 1979).

Florida is restricted to northern
Florida. One of the primary reasons
for this is the volume of sedimen-
tary fill overlying the coastal
plain floor in southern Florida. A
number of investigators (Pressler
1947, Antoine and Harding 1963,
Applin and Applin 1964, Applin and
Applin 1965) place the pre-Mesozoic
floor at 3,658 to 6,096 m (12,000
to 20,000 ft) below mean sea level.
Figure 4 (from Purl and Vernon
1964) summarizes the stratigraphic
relationships of the pre-Cenozoic
Floridan Peninsula.


The generalized geologic column
for Cenozoic rock in the watershed
is illustrated in Figure 5. The
oldest Tertiary rock layer beneath
the Caloosahatchee River/Big Cypress
watershed is the Cedar Keys Forma-
tion, a light-gray mixture of dolo-
mites and evaporites (gypsum and
anhydrite) of marine origin belong-
ing to the Midway Group of the
Paleocene Series of Florida (Chen
1965). In central and southern Flor-
ida, the formation is essentially
nonfossiliferous with a relatively
high evaporite content ranging from
25% to greater than 40%. The thick-
ness of the Cedar Keys Formation
exceeds 610 m (2,000 ft) in the
study area near the Sunniland oil

The Oldsmar Limestone of the
Sabine Stage overlies the Cedar Keys
formation. This chalky white to
light-brown, rather pure, finely
fragmented, and fossiliferous lime-
stone unit represents the earliest
formation of the Eocene. A thick
dolomite section of the Lake City
Limestone overlies it. The Oldsmar
Limestone is of marine and deltaic
clastic origin and ranges from
less than 244 to over 366 m (800 to
1,200 ft) thick in the watershed
(Chen 1965). The Clairborne Stage
(middle Eocene), which overlies
the Oldsmar Limestone, is composed
almost entirely of dolomite and
limestone with minor amounts of
evaporite and thin beds of com-
pressed peat. Two formations, the
Lake City Limestone and the Avon
Park Limestone, form the Clairborne
Stage in the study area. The older
of the two, the Lake City Limestone,
is a dark-brown, chalky limestone
faces which gradually thins from
central Florida southwestward (Chen
1965, Purl and Winston 1974). The
Avon Park Limestone is a cream col-






BEDS OF TAYLOR AGE. ..................... NE ......A. [..AL .G.

AL11 Q1 AL IN AGE.. . .N. ...B3D OF AULTIN AGE ...

w ,U A[ UPPEH BEDS OF EAGLE FORD AGE ..............





BEDS F TRN Y Alc..........













Figure 4. Stratigraphic nomenclature of pre-Cenozoic strata in the
Florida peninsula (adapted from Purl and Vernon 1964).

Figure 5. Generalized geologic
column of Cenozoic rocks (adapted
from Puri and Winston 1974).

ored chalky limestone, and brown to
dark-brown, rather porous dolomite,
which reaches a maximum thickness
exceeding 244 m (800 ft). The last
and most recent stage of the Eocene
series is the Jackson, represented
by limestones of the Ocala group.
These limestones are chalky white to
light brown, porous, and poorly
consolidated, and reach a maximum
thickness of more than 122 m (400
ft). Included in this group, in
ascending order are: Inglis, Willis-
ton, and Crystal River Formations.
Only the Crystal River Formation

underlies the entire watershed,
whereas the Williston and Inglis
Formations thin out southward (Puri
and Vernon 1964).

The sole representative of the
Oligocene series is the Suwannee
Limestone, which is a white to
cream-colored, compact, finely po-
rous, fossiliferous limestone (Jakob
and Waltz 1980). The formation
generally thickens to the south,
varying from 61 to 107 m (200 to
350 ft) in the watershed (Puri and
Winston 1974, Jakob and Waltz 1980,
Burns 1983, Peacock 1983).

The Suwannee Limestone is over-
lain unconformably by either the
Tampa or Hawthorn Formations of the
Miocene series. These formations

consist of approximately 213 m
(700 ft) of intermixed clastic and
nonclastic materials with varying
lithologies, including mixtures of
sandstone, olive-drab siltstone,
brown or olive shale, loose shells,
and white, sandy limestone, with
phosphorite or plastic clay (Puri
and Winston 1974). Clay portions of
the Miocene formations exhibit very
low permeability and act as an aqui-
clude over the porous and permeable
Suwannee Limestone. These formations
contain the first substantial depos-
its of clastic sediments from the
Cenozoic era, marking a distinct
shift of the Floridan peninsula's
depositional environment. In the
interval between the Suwannee Lime-
stone (Oligocene) and the Tampa
Formation (early Miocene), the Ocala
Uplift developed. During subsequent
formations deposition was controlled
by this uplift, as evidenced by the
thinning and pinching out of younger
strata from south (Key Largo) to
north (Ocala) or towards the crest
of the uplift (Jakob and Waltz
1980). Shorelines during this time
(Miocene) extended as far south as
central Florida.

The lower Miocene is represent-
ed by the Tampa Limestone which is a
grayish-yellow to cream, sandy lime-
stone containing some marl. The
sand content (predominantly quartz)
increases to the north as the forma-
tion thins. In southwest Florida
the Tampa Limestone thickens from
northeast Glades County to western
Lee County (Jakob and Waltz 1980,
Burns 1983).

Above the Tampa Limestone is
the Hawthorn Formation, which is an
interbedding of marine, light-green
to gray, sandy days and sandy
limestones containing numerous fish
and invertebrate fossils. In the
watershed the formation varies in
thickness from 30 to 245 m (100 to
800 ft), and like the Tampa Lime-
stone below it, thins toward the
crest of the Ocala Uplift. In the
western coastal areas, the formation
most closely approaches the surface,
ranging from 15 to 46 m (50 to 150
ft) below mean sea level (msl)
(Puri and Vernon 1964, Jakob and
Waltz 1980).

The upper Miocene to late Plio-
cene is represented in south Florida
by the Tamiami Formation, which con-
sists of approximately 46 m (150 ft)
of limestone, calcareous clay,
green-aluminous clay, and sand. The
formation thickens to the south and
east of the Caloosahatchee River
basin and represents the oldest
formation of its era to exhibit out-
crops In the watershed, specifically
along the Caloosahatchee River and
in ditches along the Tamiami Trail
(State Highway 41) for which it was
named. Elsewhere the formation
varies in depth from about 5 to 30 m
(15 to 100 ft) below land surface
(Puri and Vernon 1964, Dubar 1974,
Hunter 1978, Jakob and Waltz 1980,
Jakob 1983).

The post-Eocene stratigraphy in

southwest Florida has recently been
revised by some authors based on
lithologic, rather than paleontolog-
ic criteria (King and Wright 1979,
Mooney et al. 1980, Peacock 1983).
The result is a recognition of the
Tampa Limestone Formation only in
west-central Florida, as specially
described by King and Wright (1979),
and not in south Florida. The strata
normally assigned to the Tampa Lime-
stone is instead considered part of
the Hawthorn Formation (Peacock
1983). Peacock (1983) also expands
the Hawthorn to include the upper
Suwannee Limestone (Cole 1941), and
all but the upper Tamiami Formation
(Parker 1951). The latter revision
(reduction of the Tamiami Formation)
is based on a recent redefinition of
the Tamiami Formation by Hunter and
Wise (1980).

In south Florida the Tamiami
Formation extends to the late Plio-
cene (Dubar 1974, Hunter 1978). The
only other formation that suggests a
Pliocene origin is the Caloosahatch-
ee Marl. The uncertainty reflects a
current debate over the Caloosa-
hatchee Formation's placement in the
Pliocene (Parker et al. 1955), the
Pleistocene (Dubar 1958a), or an
undefined transition zone referred
to as the Plio-Pleistocene (Brooks
1974). Hunter (1978) concurs with
Dubar (1958a) and further suggests
it be considered as a member of the
Fort Thompson Formation, as such
encompassing all the interbedded
marine, brackish, and fresh water
deposits of roughly Pleistocene age
(10,000 to 1,800,000 years B.P.).
The Pliocene (1.8 to 5.0 million
years B.P.) would be represented
only by the Tamiami Formation.
Figure 5 illustrates Hunter's (1978)
suggested stratigraphic classifica-
tion and reported radiometric dates.
Dubar's (1974) scheme is .in agree-
ment with a Pleistocene origin for
the Caloosahatchee, but recognizes

the deposit as a formation in itself
rather than as a member of the Fort
Thompson Formation. For purposes of
this report, the Caloosahatchee will
be recognized as a formation of the
early Pleistocene.


Sea level prior to the initial
Pleistocene glacial melt lay approx-
imately 82 m (270 ft) above the
present shoreline. Dry land on the
Floridan Plateau was restricted to a
few small islands lying in what is
now Polk County, and another group
in the vicinity of the Trail Ridge
area near Jacksonville. Subsequent
sea-level fluctuations gradually
left more and more of the Floridan
Plateau exposed. This successive
dampening of sea-level rise Is prob-
ably the result of sea-floor spread-
ing, which concurrently increased
the global volume of the oceans
(Cooke 1945). Names of recognizable
sea-level fluctuations of the Pleis-
tocene in Florida and the respective
heights to which they extended above
present day sea-level are listed in
Table 2. The Talbot and Pamlico are
the only terraces important to the

The various elevations of the
Pleistocene shorelines and the
alternation of marine and freshwater
beds in certain limestone and marl
formations provide a record of sea-
level fluctuations during the great
ice age. The advances and retreats
of great ice sheets over the North
American continent alternately
raised and lowered the regional sea
levels that resulted in a variety of
Pleistocene deposits, including
quartz sands, shell beds, limestone,
and marl (Klein et al. 1964).

In southern Florida the strata
of the Pleistocene are composed of
the sands of marine terraces; the

Table 2. Recognized sea-levels dur-
ing the Pleistocene era in Florida
(adapted from Cooke 1945).

Height above present
Name sea level (ft)
Brandywine 270
Coharie 215
Sunderland 170
Wicomico 100
Penholoway 70
Talbot 42
Pamli co 25
Silver Bluff (tentative) 5

Caloosahatchee, Anastasia, and Fort
Thompson Formations; the Key Largo
Limestone; and the Miami Formation.
Of these, only the Caloosahatchee
and Fort Thompson Formations, and
two of the four to seven recognized
marine terraces are located in the
watershed. The Anastasia Formation
may underlie a major portion of the
Caloosahatchee River/Big Cypress
watershed (Klein et al. 1964), but a
lack of core data and the difficulty
of distinguishing it from Caloosa-
hatchee and Fort Thompson Formations
makes it difficult to verify this
claim (Missimer 1978).

The most ancient of the Pleis-
tocene rock layers in south Florida
is the Caloosahatchee Formation,
which is primarily a grayish-green,
silty, sandy, shell marl with inter-
bedded layers and lenses of sand,
silt, clay, and marl. The formation
occurs only in the eastern part of
the watershed, ranging in thickness
from a few meters to greater than
15 m (50 ft) near the western edge
of Lake Okeechobee. It continues to
thicken towards Florida's east coast
(Dubar 1974, Jakob and Waltz 1980).
The Caloosahatchee Formation con-
sists of three members which col-
lectively comprise a lithologic
record of a transgressive-regressive
depositional cycle (Figure 6). The


' __---- BELLE GLADE

I- 20,9001

' 75.000//

$ o120,000
to 140,000

Figure 6. West to east schematic geologic cross section of Caloosahatchee
River outcrops in the area near Fort Denaud, Fort Thompson, and Ortona Lock
(adapted from Hunter 1978).

oldest (Fort Denaud Member) was de-
posited in fresh and brackish water
during the early transgressive
phase. A younger member (BeeBranch
Member) represents a deposit of
shallow-shelf and high-salinity bay
origin, and corresponds to the
maximum Caloosahatchee sea trans-
gression. The most recent (Ayers
Landing Member) occurred during a
regression of the sea, in brackish
to high-salinity bays and freshwater
environments (Dubar 1974).

The Caloosahatchee Formation
is typically overlain by the Fort
Thompson Formation--a name applied
by Sellards (1919) to beds of fresh-
water marl and limestone, which
alternate with beds of marine shell
marl in the vicinity of Fort Thomp-
son on the Caloosahatchee River
(Dubar 1974). Deposits of this for-
mation provide the best picture of
the changing environments associated
with sea-level fluctuations during
Pleistocene glacial events (Jakob
and Waltz 1980). The Fort Thompson
Formation is often represented by
discontinuous beds, particularly
in the Big Cypress Swamp to the
southwest. In this region the
Tamiami Formation surface is thinly
overlain by recent sediments, pock-
ets of the Fort Thompson Formation,
or terrace sands (Duever et al.
1979). The beds vary in size and
thickness, and reflect the sub-
surface irregularity of the deeper
Caloosahatchee and Tamiami Forma-
tions (Dubar 1974). Areal distribu-
tion of the formation is illustrated
in Figure 7, in relation to more
recent Pleistocene strata of south
Florida. The deposit's thickness
ranges from absent (0) to 5 m (15
ft) in the study area, increasing
southeastward toward Miami, where
it reaches a maximum thickness of
21 m or 70 ft (Klein et al. 1964,
Dubar 1974, Jakob and Waltz 1980).
The Fort Thompson Formation contains

Figure 7. Distribution of surface-
exposed Pleistocene formations
(adapted from Dubar 1974).

two distinct members, the younger
Coffee Mill Hammock Member and the
Okaloacoochee Member (Dubar 1958b)
(Figure 6). The older Okaloacoochee
Member is represented by two fresh-
water gray-marl units separated by a
thin layer of brackish water marl
and marine shell. This member was
deposited during the initial trans-
gression of the Fort Thompson sea in
a bay-margin and freshwater environ-
ment. Over this member is the Coffee
Mill Hammock Member, a marine shell
bed, which was deposited in a shal-
low semirestricted, high-salinity
bay similar to present-day Florida
Bay (Dubar 1974, Jakob and Waltz
1980). The tops of the freshwater
beds have been hardened into brittle
limestone, but are perforated by
solution holes that are filled with
marine shells from succeeding
strata. The Fort Thompson Formation
is of special importance to the
human population of south Florida
because it forms a large part of the
Biscayne Aquifer, the sole drinking-
water source for the southeast

coast. The Lake Flirt Formation is
reported either as the youngest Fort
Thompson Formation member (Hunter
1978) or as the youngest Pleistocene
Formation whose deposition continued
into the Recent epoch or Holocene
epochs (Dubar 1974). Taking the
latter case, this deposit lies
unconformably on the Fort Thompson
Formation and represents freshwater
sediments deposited along the Caloo-
sahatchee River. It consists of thin
beds of mucky dark sands and marl
shell that typically range in thick-
ness from 1 to 3 m (3 to 8 ft).

Pleistocene marine terrace
deposits. During the high Pleisto-
cene sea level stands, terraces were
formed over Florida by wave, cur-
rent, and erosional actions. Today
belts of these terrace sands extend
around Florida, parallel to the
present coastline. These belts are

found in step-like formation, rising
inland from the coasts with the
oldest sediment being the highest in
elevation. The actual number of
terraces in Florida is the subject
of much debate: estimates range
from four to nine (Puri and Vernon
1964). The terraces and shorelines
identified in the watershed, from
the lowest in elevation to the
highest, are Silver Bluff, Pamlico,
Talbot, Penholoway, and Wicomico
Terraces (Healy 1975). These Pleis-
tocene terraces and shorelines are
illustrated in Figure 8 and are
accompanied by their approximate
shoreline elevations. The terraces
in the study area are composed of
quartz sand and lie discontinuously
upon the Fort Thompson, Caloosa-
hatchee, and Tamiami Formations.
Overlain unconformably by the Lake
Flirt Formation and recent deposits,
these sands typically range from

Figure 8. Pleistocene terraces and shorelines of south Florida (adapted from
Healy 1975).

0.5 to 1 m (2 to 3 ft) in thickness,
although pockets exceeding 5 m
(15 ft) have been observed (Klein
et al. 1964).


The dominant physiographic
feature of the Caloosahatchee River
watershed Is the Caloosahatchee
River Valley (Puri and Vernon 1964,
White 1970). The axis of the valley
follows the Caloosahatchee River
from Lake Okeechobee to San Carlos
Bay. The valley "wall" known as the
Caloosahatchee Incline (White 1970)
slopes very gradually upward to the
north of the river. At the peak of
the -valley wall lies the De Soto
Plain, a very flat terrace extending
down from the Polk Uplands of the
Central Florida Highlands. To the
south of the Caloosahatchee River
the valley wall is formed by the
Immokalee Rise, an elevated flat
area of predominantly sandy soils.
Both the Caloosahatchee Incline and
the Immokalee Rise formed as ero-
sional submarine terraces of the
Pamlico shoreline. The De Soto
Plain is generally regarded as a
submarine terrace formed below the
Wicomico shoreline.

The Big Cypress watershed
(Figure 9) contains all or part of
four major physiographic features of
the lower Florida peninsula: (1) The
Immokalee Rise, (2) The Big Cypress
Spur, (3) The Southern Slope, and
(4) Coastal Swamps and Lagoons.

As the Pamlico sea level drop-
ped, the Immokalee Rise emerged as
a sloping sand shoal south of the
Caloosahatchee Valley. A somewhat
parallel situation would occur today
off Cape Romano, should sea-level

Southeast of the Immokalee Rise
is the Big Cypress Spur, a sloping

Figure 9. Major physiographic
features of the lower Florida
peninsula (adapted from Purl and
Vernon 1964).
area transitional between the rise,
the Everglades trough to the east,
and the southwestern slope to the
west. The spur is best characterized
by its abundant dwarf cypress on
marl soils to the west and its saw-
grass/Everglades slough vegetation
to the east.

The spur receives runoff from
the north, off relatively higher
lands of the Immokalee Rise. His-
torically, flow was probably in two
directions (and fairly rapid): one
to the Everglades trough, then down
and out Shark River, and the other
to the Southwestern Slope and out
through the back bays north of Lost-
man's River. Today SFWMD levee
L-28 tieback canal insures this
drainage pattern by accentuating the
naturally low ridge that separates
Big Cypress Spur from the South-

western Slope. L-28 was breached
by culverts in 1983 to restore
the high-water basin connection at
certain times.

The Southwestern Slope is a
northwest-southeast trending area
that is gently tilted toward the
Gulf of Mexico. Toward the south, a
drainage pattern perpendicular to
the coast is evident in the elonga-
tion of slough and strand vegeta-
tion. Here the substrate is thin
sands overlying a dissected Tamiami
Limestone. Toward the north sands
are more prevalent and often deeper,
as evidenced by increasing pineland
vegetation and less distinct coast-
perpendicular drainage.

Coastal swamps and laqoons.
The Big Cypress estuarine and salt-
water wetland zone is made up of
two major components: (1) a coastal
reentrant zone from Gullivan Bay
south to Lostman's River, and (2) a
coastal protuberant zone from Cape
Romano north to Fort Myers Beach.
The northern boundary of the coastal
reentrant zone includes the Ten
Thousand Islands. These numerous
mangrove-covered islands appear to
coalesce south along the coastline,
eventually forming larger solid
blocks. Dissected lagoons (back
bays) characterize the upland side
of this zone. These blocks are
separated from one another by in-
creasingly distinct drainage ways.
Concurrently the inland extent of
brackish vegetation (mangroves and
salt marshes) increases north to
south from about 4.8 km (3 mi) to
8.8 km (5.5 mi) from Gullivan Bay
to Lostman's River.

This reentrantt" physiography
is caused by a combination of off-
shore profile, substrate composi-
tion, and rising sea-level. Off-
shore bottom topography decreases
In steepness toward the south of

the watershed. The 5-fathom isobath
only rarely lies more than 0.8 km
(0.5 mi) offshore north of Marco
Island, but in the coastal reentrant
zone the 5-fathom isobath lies as
much as 13 to 19 km (20 to 30 mi)
offshore. The 5-fathom depth is
considered close to the maximum
depth at which waves scour oceanic
shores. Where the 5-fathom isobath
lies far from shore, wave energy
is not sufficient to throw barrier
sands onto the shoreline.

Another factor influencing the
nature of the reentrant coastline
is source of materials. Near-shore
substrates in the reentrant section
are more limey than sandy; limestone
is not a good source material for
building barrier beaches and is-
lands. The effect of substrate is
also seen by comparing (1) the
highly dissected nature of the Ten
Thousand Island area, which sits
on erodable Tamiami Limestone with
(2) the more solid blocks to the
south, which rest on Pleistocene
(Anastasia) sands. The latter are
less soluble and more influenced
(historically) by freshwater Ever-
glades discharge (White 1970).

Recent sediments in the Ten
Thousand Islands (Figure 10) have
been deposited over the last 5,000
years during a more or less contin-
uous marine transgression. Maximum
sediment thickness reaches 7.6 m
(25 ft) and consists of a mixture of
clean, slightly peaty basal sands,
relic vermitid gastropodd) reefs,
silts, sands, oyster bars, and thick
mangrove peats (Shier 1969). The
Miocene Tamiami Formation forms the
bedrock that underlies the entire
Ten Thousand Islands area, and is
discontinuously overlain by marsh
sediments clayeyy sands) that were
deposited during the Wisconsin low
sea-level stand, or during the
subsequent sea-level rise. As the

of the
with Environmental


Figure 10. Geological cross section
environmental interpretations (adapted

post-Wisconsin sea-level rose over
the gradual seaward slope of the
Tamiami Limestone (5 to 10 cm per
1.6 km or 2 to 4 In per mi) a wide,
shallow coastal sea formed. Along
its outer edge ecological conditions
favored the growth of a vermitid
reef-forming gastropod, Vermetus
(Thylaeodus) nigricans Dall (Shier
1969). A chain of vermitid reefs
formed parallel to the coastline and
created a lagoon as much as 6.4 km
(4 mi) wide. A complex of bay
bottom sands and silts, tidal pass
sands, oyster bars, and thick man-
grove peats has accumulated behind
the reef barrier. Recent sediments
along a landward-seaward transect of
the Ten Thousand Islands are illus-
trated in Figure 10. The two basic
island forms consist of (1) the
outer or seaward vermitid reef based
islands, and (2) the inner oyster

of the Ten Thousand Islands with
from Shier 1969).

reef-based islands. The former often
exhibits an exposed vermitid-reef
rock beach on the seaward side. Both
are forested by mangroves. Sediments
of the lagoonal and island environ-
ments are brought in by normal tidal
currents and by waves and storm
tides that accompany severe storms
and hurricanes; they are also pro-
duced autochthonously (e.g. oyster
shells, foraminifera, mangrove de-
tritus, and peat).

To the north of Ten Thousand Is-
lands and Cape Romano the brackish-
zone vegetation decreases rapidly in
lateral extent from 4.8 km (3 mi)
in width at Gullivan Bay to only a
fringing remnant along inner bays
and barrier island lagoons north of
Naples. High-energy barrier beaches
and sheltered coastal embayments are
prominent coastline features north

of Marco Island.

The four major areas of gulf
coastal lagoons behind barrier is-
lands in the Big Cypress watershed
are as follows:
(1) The Marco Island/Cape Romano
leeward estuary (including
Rookery Bay).
(2) The Gordon River estuary and
Naples Bay near the town of
(3) Wiggins Say at the down-
stream end of the Coco-
hatchee River.
(4) Estero Bay at the northern
boundary of the basin.
Because of its size, shape, and
hydrography the Caloosahatchee River
estuary is considered a somewhat
unique coastal lagoon. Though it
is clearly protected by Sanibel
and Pine Islands, its great length
and relative straightness indicate
a much more profound river drain-
age influence than in the more
restricted estuarine embayments to
the south.


Holocene sediments in the Ca-
loosahatchee River/Big Cypress wa-
tershed were products of a seasonal
abundance of rainfall and a warm
subtropical climate. This has, over
the last 5,000 years, stimulated
both luxuriant plant growth and case
hardening of periodically exposed
limestone rock. Much of the water-
shed "soils" are not actually soils
in the textbook sense, that is,
layers of mixed mineral and organic
materials with characteristic pro-
files. Instead they represent only
slightly weathered parent material,
or modern sediments, some of which
are still being formed; consequently
the soils are generally described
as surficial sediments. Horizons
or layers that occur in the water-

shed usually reflect changes in
sediment type, e.g., sand overlying
calcareous marl, and are caused by
successional sea-level transgres-
sions and regressions or more subtle
changes in wet and dry climatic

Chemical and biological pro-
cesses have, within a relatively
short period of time (5,000 years),
modified the geologic features of
the watershed. Rainwater, which
combines with organic materials to
form an acidic solution, accelerates
limestone dissolution. Depending on
the water-table height, the dis-
solved calcium carbonate may: (1)
recrystallize within or on the rock
surface to form a cap rock or (2)
with the assistance of periphyton,
be reprecipitated in low wet areas
as calcitic marl (Duever et al.
1979). Roots, algae, fungi, storms,
and fire provide forces that crack,
tunnel, and otherwise destroy the
structural integrity of the rock,
exposing a greater surface area to
dissolution processes. Exposed por-
tions of the Tamiami Formation often
exhibit these characteristics, par-
ticularly in the Big Cypress water-
shed (Duever et al. 1979).

The generalized soil-type dis-
tribution within the Caloosahatchee
River/Big Cypress watershed is Il-
lustrated in Figure 11. Greater
detail on the physical and chemical
nature of soils is available from
soil surveys published by the U.S.
Soil Conservation Service (SCS
1975). These surveys contain
1:20,000 photomosaics overlain by
soil series delineations; physio-
chemical descriptions of soil pro-
files down to a 2-m (6-ft) depth,
where possible; and, a description
of the soil series suitability for
various land uses (Carlisle 1982).
County soil surveys are at various
stages of completion, which range

Figure 11. Generalized soil-type distribution in southwest Florida (adapted
from Jakob and Waltz 1980).

from total absence of soils work in
Glades County to the completed, but
antiquated, Collier County soil sur-
vey. Another valuable information
source on regional soils is reported
in an annual publication, Proceed-
ings of the Soil and Crop Society of
Florida, which provides an academic
forum for the most recent soil re-
search in the state.

The soil types in the watershed
(Figure 11) generally fall into one
of the following five major sub-
strate-sediment groups; limestone
rock, calcareous muds (marls), sands
(marine terraces), organic materials
(peats and mucks), and mixed solids
(Duever et al. 1979, SFWMD 1980).

Although this classification departs
from the more classical SCS county
soil series, it is a much more prac-
tical system for the unique sediment
characteristics of southwest Flor-
ida. The absence of either updated
(e.g., Collier County), or completed
county soil surveys also prevents a
watershed or region-wide application
of the soil series (Duever et al.
1979, Carlisle and Brown 1982). The
five substrate groups differ from
one another in terms of grain or
particle size, homogeneity, chemical
composition, and in many other chem-
ical and physical properties that
affect the type of plant communities
found associated with them, and
their suitability for use by man.

An additional substrate not
specifically addressed in Figure 11
is man-altered or aren't soils, e.g.,
dredge and fill, shell mounds, and
landfills (Herwitz 1977). The soil
composition is extremely diverse and
its relationship to the surrounding
environment has only begun to be
studied. One example of this soil
modification is in the inland and
coastal man-made canals in the
watershed. Modification of natural
tidal tributaries to finger canals
is prevalent in developments around
Marco Island, Naples, Cape Coral,
and numerous other coastal commu-
nities. Wanless (1974) and Wanless
et al. (1975) studied the variation
of sediments in natural and artifi-
cial waterways in the Marco Island
area and noted numerous differences
in the form and production of sedi-
ment. Possibly the most important
distinction is the shift away from
autochthonous sediment production in
the natural waterways to a primarily
allochthonous source of sediments in
canal systems, carried into the ca-
nals by tidal and storm water move-
ments. Also, decreases in particle
size and bioturbation (infaunal)
in the canals result in a more
homogeneous and biologically sterile
sediment composition (Wanless 1974).
In situ sediment production in natu-
ral waterways was not only signifi-
cant quantitatively, but also di-
verse in its composition. Sediment
contributors include oysters and
barnacles (prop root and bottom,
along bay and tributary margins),
mollusks, foraminifera, diatoms,
benthic invertebrates in bays and
channel-margin flats, seagrasses,
and brown, green, and blue-green
algae benthicc flora that provide

Marls are a muddy deposit of
calcium carbonate silts, with occa-
sional shells and shell fragments.
In Florida, surface marl soils are

basically the product of three pro-
cesses: (1) physiochemical or bio-
chemical precipitation of calcite
crystals by freshwater periphytic
blue-green algae that grow on sedi-
ment surfaces or as sheaths covering
vegetation; (2) storm deposition
of aragonitic marine muds in the
mangrove keys, swamps, and other
coastal areas; and (3) weathering
of surficial limestone outcrops.
Marl soils are often associated or
mixed with sands or peats, depending
upon local influences. For example,
in mangrove forests, marls may occur
along the margins of the mangrove
peat. These marls are referred to as
marly peat or peaty marl, depending
upon the soils' major constituent.
Marly sands or sandy marls are often
found in the Big Cypress watershed
and represent erosional products
of the Tamiami Formation limestone
outcrops. The production of calcite
by blue-green algae generally occurs
in seasonally wet marshes or wet
prairies having sparse to medium
density of vegetative cover and
where limited shade permits pene-
tration of sunlight to the surface

The major surficial marl depos-
its are located in the Big Cypress
Swamp and in the marsh and prairie
areas to the south. Marls and sand
marls generally range In depth from
15 to 90 cm (6 to 36 in), exhibit
a low-level relief, and, because
of their low permeability to water,
are often wet (Leighty et al. 1954,
Duever et al. 1979, SFWMD 1980).
Marl soils account for almost
400,000 acres or 29% of the soils
surveyed in Collier County (Leighty
et al. 1954).

Sands, which represent the dom-
inant surficial soil in the Caloosa-
hatchee River/Big Cypress watershed,
are derived from old shoreline de-
posits, weathering of limestone, and

the relocation of sands by wind and
storm surges. Deposits are generally
thicker and more extensive north and
west of the Big Cypress Swamp, and
consist either of marine quartz
sands, carbonate sands, or a mixture
of the two.

Marine quartz sands of the
Pamlico, Penholoway, and Talbot
Terraces dominate the surficial
deposits from mid-Collier County to
the northern reaches of the Caloosa-
hatchee River watershed in Charlotte
and Glades Counties. Surrounding
Immokalee on the Immokalee Rise
(White 1970) are sands, regarded as
bars and swales, which thin to the
south, east, and west, and eventual-
ly grade into the irregular western
boundary of the Big Cypress Swamp to
the east (Duever et al. 1979). Near
the coasts is some carbonate sand
fraction formed from shell material
(SFWMD 1980). A mixture of the two
sands has probably existed at one
time in the terrace formations with
the carbonate fraction subsequently
being removed by dissolution and/or

The vegetation associated with
sand soils exhibits tremendous
variety in relation to (1) depth to
water table, (2) presence of a hard-
pan, (3) character and depth of sub-
strata, (4) grain size, (5S) mixture
of silt, clay, and organic material,
and (6) elevation and slope. Vege-
tative communities range from sea-
sonally inundated low-lying pine/
palmetto flatwoods and prairies to
elevated xeric dunes and ridges
which support scrub oak and sand

Limestone rock provides for one
of the most unique and visually
obvious surficial substrates in the
Caloosahatchee River/Big Cypress
watershed. The rock's appearance
is caused by erosion, dissolution,

and reprecipitation, which creates
an irregular, undulating surface of
hard, dense, and impermeable cap-
rock. The processes involved in the
caprock's formation are illustrated
in Figure 12.

The Tamiami Formation dominates
the surface rock substrates in the
Big Cypress watershed. The faces
which represent the formation are
distinguished by several factors
including sand content, fossil con-
tent, porosity or fragment size,
degree of surface hardening, and
topography (SFWMD 1980). The cap-
rock is typically well laminated,
thick, and highly Indurated. The
surfaces are perforated with solu-
tion features which contain caliche
(dark-tan colored, finely laminated
crusts), solution breccias, later
marine deposits, sands, marls, and
post-depositional cements (Duever et
al. 1979). Of secondary importance,
really, are the Fort Thompson and
Miami Limestone outcrops, which make
up some of the surficial rocks along
the eastern edge of Collier County
and occur in isolated pockets in the
Big Cypress watershed. Pinnacle
rocks, which provide the most overt
signs of these latter formations,
exhibit a very irregular caprock or
crust with sharp-pointed projections
and small conical depressions (Cooke
1945, SFWMD 1980).

Vegetation associated with the
rock outcrops include slash pine,
cabbage palmetto, saw-palmetto,
shrubs, grasses, and dwarf cypress.
In Collier County, where most of the
area's limerock substrate occurs,
the rocklands (also referred to as
pine rocklands) account for 6.4%
(83,000 acres or 33,590 hectares)
of the area (Leighty et al. 1954).
Hardwood hammocks often appear on
elevated limestone outcrops in the
southern Everglades region of the
Big Cypress watershed. Craighead

Figure 12. Environmental mechanisms involved in forming subaerial crusts
(adapted from Multer and Hoffmeister 1968).

(1974) and Duever et al. (1979) sug-
gest that the hammock develops along
a self-destructive course. The outer
trees in the circular or tear-drop
shaped hammocks are more susceptable
to fire or wind damage. When the
dead outer trees are blown down
(windthrown) their extensive root
systems gouge or crack the existing
caprock, which accelerates dissolu-
tion of the limerock. The opened
cavities eventually encircle the
hammock, forming a moat. Only sparse
aquatic or emigrant vegetation lives
around the moat's shaded inner wall
to stabilize the rock and provide
organic material. That, in combina-
tion with the organic acids produced
from the hardwood litter decomposi-
tion, causes continued undermining

of the hammock rock. The end result
is the elimination of the hammock
and the upper rock unit. Pine rock-
lands are characterized by extremely
irregular, exposed, and elevated
bedrock surfaces. The pines root in
sediment-filled solution holes or
crevasses as do the hardwoods in
hammocks. Hardwoods are generally
excluded from the pine rocklands
because of the frequent fires that
prevent an accumulation of organic
litter in the soil. The low level
of organic material and the alkaline
nature of the limerock reduces the
acid dissolution of the limestone.
Also, the amount of marl in the
soils is minimal because of the
relatively elevated and drained
conditions of these pinelands.

The organic substrates, peat
and muck, are formed of partially
decomposed plant material and a
mixture of inorganics such as sand,
clay, or silt. These substrates
often develop in wetland environ-
ments where the inundation of water
creates an anaerobic layer at the
sediment-water interface. This per-
mits and encourages the accumulation
of partially decomposed organic
materials. The difference between
peat and muck is primarily the
degree of decomposition. Peat rep-
resents a fibrous organic substrate
that is only slightly altered from
the original structure, retaining
Identifiable plant parts, (e.g.,
leaves, stems, seeds, and roots).
The parent material is local (au-
tochthonous), and the ash and
inorganic content is typically low.
In contrast, muck is a thoroughly
decomposed, fine-grained, nonfi-
brous, organically-rich substrate,
which is high in ash content and
often mixed with inorganic sedimen-
tary material. Source material for
muck is either autochthonous or
allochthonous (transported from
outside the decomposition site).

The origin, structure, chemical
qualities, deposition rates, envi-
ronments/patterns, and other charac-
teristics of organic sediments are
well studied, but because of their
complexity they will be only briefly
mentioned here. A number of excel-
lent reviews are reported in the
literature. Davis (1946) gives an
extensive review of peat deposits in
Florida, including information on
their nature, origin, type, and com-
position. This work is supplemented
by Cohen and Spackman's (1974)
description of south Florida peats,
and Stone and Gleason's (1976) and
Kropp's (1976) work in the Corkscrew
Swamp Sanctuary.

The major surface peat deposits
in the Caloosahatchee River/Big
Cypress watershed are located along
the southwest coast from Gordon Pass
south, in the far eastern Caloosa-
hatchee River region which borders
Lake Okeechobee, and in the Cork-
screw Swamp Sanctuary near Lake
Trafford (Davis 1946, Leighty et al.
1954). In addition, small deposits
are typically found in the area's
numerous swamps, marshes, ponds,
and sloughs, and along some stream
margins. These smaller deposits
are particularly common in the Big
Cypress Swamp, where they are con-
tained in wet depressions throughout
the rockland, sand, and marl areas.
Organic deposits range in depth from
a few centimeters to 3 meters (up
to 9 feet or more), and are high in
carbon and nitrogen, but low in
other nutrients, e.g., phosphorus
(SFWMD 1980). The type and condi-
tion of a peat is dependent on the
water depth, pH, hydroperiod, parent
vegetation, topography, thickness,
degree of decomposition, character
of the underlying sediment, inor-
ganic content, and pressure of
incorporated layers such as marl,
shell, limerock, or sand. Peats
are most often classified by their
parent material, e.g., mangrove
peat, Conocarpus (buttonwood) peat,
Spartina peat, and others (Cohen and
Spackman 1974). Mangrove peat,
which forms in much of the south-
western coast's tidal areas, typi-
cally retains much more of the
original plant structure than its
freshwater and brackish water coun-
terparts. It also exhibits a greater
ash content caused by the intermix-
ing of shells and sands, which are
transported into the swamps by tides
and storms.

Compared to the freshwater peats
of the Everglades, the Corkscrew

Swamp peats are more degraded and
mucky, with less identifiable plant
tissue structure. This condition
may be indicative of a poorer pre-
serving environment at the Corkscrew
Swamp, possibly a shorter hydro-
period, or a deeper zone of aeration
(Stone and Gleason 1976). The basal
peat samples dated from this deposit
have been carbon-14 dated in the
range of 4700 to 5700 years B.P.,
the latter being the oldest peat
deposit recorded in south Florida

(Kropp 1976, Duever et al. 1979).

Along the eastern edge of the
Caloosahatchee River watershed,
brown to black peat and muck de-
posits reach a maximum thickness
of 3 m. Westward these deposits
integrate with quartz sands which
originate from the major terraces
(Klein et al. 1964). This deposit
is the western extension of the
large Everglades Peat Bed (Davis



A classification system devised
by the National Weather Service
divides Florida into seven climatic
divisions. The Caloosahatchee River/
Big Cypress watershed is contained
entirely within the Everglades and
Southwest Coast climatic division as
illustrated in Figure 13. This
division and each of the other cli-
matic divisions encompass an area
within which basic climatic vari-
ables, primarily temperature and
rainfall, are generally consistent
when averaged over extended periods
of record. Obviously the boundary
lines between the climatic divisions
approximate general lines of change.
Sometimes station-to-station dif-
ferences within a division exceed
divisional variation. This is par-
ticularly true between coastal and
inland areas. Despite these dif-
ferences, climatic divisions are a
means for organizing statewide and
basinwide climatic indicators.

The location of Florida's first-
order weather stations operated by
the National Weather Service are
shown in Figure 13. These stations
provide the most inclusive weather
data base available. Each station's
data base is supplemented by cooper-
ative and research stations that
provide weather data of a more lim-
ited nature (e.g., rainfall and
air temperature). These secondary
weather stations monitor the climate
for a variety of applications.
Agriculture, water management, and
aviation are three of the most
important. For the Caloosahatchee
River/Big Cypress watershed, detail-
ed meteorological information is
available only from the Fort Myers
station. For a more in-depth review

Figure 13. Florida dimatic divisions
(adapted from Gutfreund 1978).

of the weather stations adjacent to
and within the watershed, refer to
the publications of Parker et al.
(1955), Thomas (1970), Bradley
(1972), Thomas (1974), Duever et al.
(1979), Bamberg (1980), and MacVicar
(1981) and (1983).

In general terms, the mild sub-
tropical climate of the watershed is
a reflection of a low geographical
relief, the encirclement by the
large water masses of the Gulf of
Mexico, the Everglades, and Lake
Okeechobee, and a relatively low
latitude (Bradley 1972, Pielke 1973,
Gannon 1978). The slight relief
permits the uninterrupted movement
of winds and rains across the ter-
rain. These movements are obstructed
instead by the atmospheric changes



caused by the surrounding water
masses. The water bodies moderate
temperatures (acting as a heat
source in winter and a heat sink
in summer) and provide a valuable
source of moisture for rains. The
inland areas are typically cooler
(in the winter) or warmer (in the
summer) than the adjacent coastal
regions. The latitude indicates
moderate winter temperatures.

Of the three climatic patterns
that Hela (1952) associated with
south Florida, two are applicable to
the reference area. All of the Big
Cypress watershed and the southern
half of the Caloosahatchee River
watershed are characterized by a
tropical savannah climate, which has
a relatively long and severe dry
season and a wet season. North of
the Caloosahatchee River a humid
mesothermal climate predominates,
characterized by a warm, moist sum-
mer and a moderate dry season.


Mean annual precipitation for
the Caloosahatchee River/Big Cypress
watershed Is about 135 cm (53 in)
(Bradley 1972). The dry season,
from November to April (Riebsame
et al. 1974), provides between 16%
and 26% of the annual rainfall, and
the wet season (June-September)
accounts for over 60%. The rela-
tionship between wet season, dry
season, and total annual rainfall
for individual stations and for
geographical groupings (Coastal-
Inland-Lake and North-South) is
shown In Table 3. Mean annual rain-
fall patterns for the watershed are
illustrated in Figure 14. Average
annual rainfall exceeding 152 cm
(60 in) is reported for coastal
locations south of Sanibel Island
(Bonita Springs and Marco Island)
and northeast of Immokalee (Fig.

14). Near Estero, the annual aver-
age rainfall is greater than 178 cm
(70 in). Overall, the average annual
rainfall decreases from the coast to
Lake Okeechobee and from south to
north (Table 3). Rainfall is lowest
(less than 125 cm or 49 in) north
of the Caloosahatchee River from
Charlotte Harbor to the Franklin
Locks at Olga (Bamberg 1980). The
region around and north of the
Caloosahatchee River exhibits a more
even annual distribution of rainfall
than the tropical-savannah climate
in the southern portion of the area.
Contrary to a 5-year cycle of rain-
fall along the southeast Florida
coast, and in the Everglades and
Florida Keys, there are no dis-
cernible long-term cycles in the
reference area (Gee and Jensen 1965,
Thomas 1974, Duever et al. 1978).

Figure 14. Average annual rainfall
(inches) for the Caloosahatchee
River/Big Cypress watershed
(adapted from Bamberg 1980).

Table 3. Wet season, dry season, and total annual precipitation
for the Caloosahatchee River/Big Cypress watershed.

Rainfall in Inches Annual Mean
Station Location n1 Dry Season (%) Wet Season (%) Rainfall (inches) Ref2
(S)Everglades 43 10.38 (19) 44.49 (81) 54.87 1
C (S)Marco Island 10 12.26 (19) 51.98 (81) 64.24 2
O (S)Naples Caribe Gardens 27 10.74 (20) 42.99 (80) 53.73 1
A (S)Bonita Springs 13 9.53 (17) 47.26 (83) 56.79 1,2
S (N)Estero 10 16.12 (23) 54.14 (77) 70.26 2
T (N)Captiva 29 12.44 (26) 36.30 (74) 48.74 1,2
A (N)Ft. Myers 98 11.52 (22) 41.48 (78) 53.00 1
L (N)Ft. Myers Airport 40 11.37 (21) 42.58 (79) 53.95 3
[N)Punta Gorda 4ENE 48 12.64 (25) 39.05 (75) 51.69 1,2
I 'S)Tamiami Trail 40 mi. 26 10.10 (18) 47.00 (82) 57.10 1
N (N)Big Cypress Res. 15 10.87 (21) 41.54 (79) 52.41 1
L (N)Lake Trafford 21 11.31 (23) 38.54 (77) 49.85 1
A (N)Devils Garden Tower 25 12.70 (22) 45.63 (78) 58.33 2
N (N)Felda 9 11.52 (26) 32.30 (74) 43.82 1
D (N)Olga Lock 12 12.29 (26) 34.35 (74) 46.64 2
[N)La Belle 40 12.22 (23) 40.41 (77) 52.63 1,2
L LIcwiston 22 10.61 (23) 36.26 (77) 46.87 1,2
A lewiston U.S. Eng. 21 11.30 (22) 39.21 (78) 50.51 1
K Iore Haven Lock 1 51 11.36 (23) 39.04 (77) 50.40 1,2
Groupings Dry Season % Wet Season % Total
Coastal 11.89 21 44.47 79 56.36
Inland 11.58 22 41.25 78 52.83
Lake 11.09 23 38.17 77 49.26
South 10.60 18 46.74 82 57.35
North 12.35 23 41.40 77 53.75
In = years of record, (S) = Southern half of watershed, (N) = Northern half of watershed.
2References: 1) Thomas 1974; 2) Bamberg 1980; 3) USDC 1981a.

Rainfall in the dry season
(November to April) is derived pri-
marily from large-scale (synoptic)
cold frontal systems that move into
the area about once a week (Thomas
1970, Echternacht 1975, Bamberg
1980). Rainfall related to these
fronts has a characteristic distri-
bution pattern distinct from that
observed in convective-type thunder-
showers. Synoptic rains typically
fall over a more uniform area of the
front and are dependent only on the
temporal passage of the system
(Echternacht 1975). Frontal rainfall
typically extends along a line from
the northeast to the southwest over
Florida's peninsula, sweeping south
or southeast. The warm, humid air
masses to the south converge with

the cooler, drier air carried with
the front, generating rainfall along
the frontal path. As a front passes,
individual radar responses (areas of
rainfall) move perpendicular to the
frontal motion (Bamberg 1980). Data
reported during its passage would
be expected to come from a number
of meteorological stations simulta-
neously (Gruber 1969), and would be
independent of the diurnal cycles
reported for convective storms
(Asplidin 1967). Rainfall intensi-
ties depend on the strength of the
interacting air masses and motions
of individual precipitation 'pock-
ets' within the front. Occasionally,
large amounts of rainfall can fall
within a narrow areal band if the
front becomes stationary.

The dry season mean rainfall
for the watershed is given in Figure
15. Rainfall is higher near the
coast and decreases inland. Highest
values (>41 cm or 16 in) are report-
ed from Estero. Rain in the remain-
der of the watershed averages be-
tween 25 and 30 cm (10 and 12 in).

By mid-spring the incidence of
frontal systems moving in from the
north decreases in southwest Flor-
ida, and local sea-breeze/convection
circulation becomes the dominant
force controlling wet-season rain-
fall (Echternacht 1975, Bamberg
1980). The local sea breezes inter-
act with large-scale (synoptic) air
flow (primarily southeasterlies and

Figure 15. Average dry-season rain-
fall (inches), November through
April, in the Caloosahatchee River/
Big Cypress watershed (adapted from
Bamberg 1980).

southwesterlies) to form lines of
convergence. These lines of conver-
gence are the most probable sites
for rainstorm development (Frank
et al. 1967, Gruber 1968, Pielke
1973). The predominant form of the
convective wet-season storm is the
thunderstorm. These storms are brief
(1 to 2 hours), usually intense, and
occasionally attended by strong
winds or hail (Bradley 1972). Thun-
derstorms in the Fort Myers area are
more frequent (over 100 annually)
than anywhere else along the eastern
gulf coast and most frequent (75%)
during the summer months (Jordan
1973, Duever et al. 1979). Day-long
wet-season storms are infrequent
and are generally associated with
tropical disturbances. Since the
short duration-high intensity thun-
dershowers are related to cyclic
land-sea breeze convective process-
es, the rainfall follows a diurnal
pattern usually peaking during the
late afternoon or early evening
hours, a period of maximum atmo-
sphere convergence (Gruber 1969,
Echternacht 1975). The most intense
convergence takes place a short
distance from the west coast, where
maximum wet season rainfall reaches
127 cm (50 inches) at Estero and 76
to 102 cm (30 to 40 inches) along
the remainder of the coast. Rainfall
patterns for the watershed's wet
season are illustrated in Figure 16.
Because of the enormous size of Lake
Okeechobee, a lake breeze (similar
to coastal sea breezes) develops to
form an area of divergence over the
lake (air and moisture diverging
away from the center of the lake)
that restricts vertical raincloud
development and wet-season rainfall
(Figure 16). The net effect mini-
mizes wet-season rainfall directly
over the lake (Pielke 1974, Riebsame
et al. 1974, Woodley et al. 1974,
Bamberg 1980). Convective wet-sea-
son storms show greater spatial and

Figure 16. Average wet-season
rainfall (inches), June through
September, in the Caloosahatchee
River/Big Cypress basins (adapted
from Bamberg 1980).

temporal variation than the synoptic
dry-season regime. Extreme gradients
of 10 cm in 1.6 km (4 inches in
1 mi) and 36 cm in 6.4 km (14 inches
in 4 mi) were reported by Woodley
et al. (1974). Variations over 12
cm (5 in) in one month at stations
less than 8 km (5 mi) apart at Cork-
screw Swamp Sanctuary were reported
by Duever et al. (1975). Woodley
(1970) estimates the natural vari-
ability of rainfall from a single
cumulonimbus cloud in south Florida
to range from 200 to 2,000 acre-

Distribution of rainfall over
southern Florida in the wet season
follows a bimodal pattern (Figure

17). The first of two peaks comes
in May or June and the second in
September or October (Thomas 1974).
This biomodal seasonal distribution
of rainfall is associated with an
upper air trough that extends south-
ward from the middle latitudes in
June and centers itself over south-
ern Florida. The trough is displaced
westward into the Gulf of Mexico in
July and August and returns again in
September or October (Thomas 1970,
Gruber 1969). Rainfall is heaviest
when this trough is overhead (Riehl

A precipitation statistic com-
monly reported and of interest for
air pollution and ecological studies
is the number of days on which cer-
tain amounts of rainfall are report-
ed, i.e., rainfall greater than or
equal to 0.254 cm (0.10 inches).
Mean number of days per month having
rainfall greater than 0.0254 cm
(0.01 inches) and 0.254 cm (0.10
inches) at stations in or near the
watershed or shown in Table 4.

Figure 17. Average monthly rainfall
at three locations in the Caloosa-
hatchee River/Big Cypress watershed
(adapted from Thomas 1974 and USDC

Table 4. Mean number of days per month with rainfall greater than 0.0254 cm
(0.01 Inch) and 0.254 an (0.10 inch) at stations in the Caloosahatchee River/
Big Cypress watershed (adapted from Gutfreund 1978).

DIVISION __________________________
Station Jan Feb Mar A My |un t J- U S5d Oct Nov Dec Annual
Evernlades and SW
CoasL I
Fort Myers 5 6 5 5 8 15 18 18 16 8 4 5 113

DIVISION __________________________
Station Ian Feb Mar Apr May J.n J LL Au g OCt Nov Dec Annual
EveriIlades and SW
Belle Glade 4 4 4 4 6 12 12 12 12 8 3 3 84
Naples 3 3 3 3 6 10 13 12 12 6 2 3 76

The monthly and seasonal dis-
tribution of rainfall is relatively
uniform. The mean annual rainfall
and the number of days with rainfall
greater than or equal to 1.27 and
2.54 cm (0.5 and 1.0 inch) for the
Everglades and Southwest Coastal
climatic division follow the same
temporal patterns that are shown in
Table 4 (Gutfreund 1978).

Rainfall frequency-distribution
curves developed from the 1975 to
1979 rainfall records for Clewiston
and Fort Myers are illustrated in
Figures 18 and 19, respectively,
(Anderson 1982). These figures
and the data in Table 4 show that
approximately 75% of the rainfall
events in the watershed contribute
less than 1.27 cm (0.50 inch) each.

The SFWMD has recently com-
pleted the first phase of a project
that provides an important addition
to the rainfall data base. MacVicar
(1981) has produced a series of
rainfall-frequency maps summarizing
the predicted maximum precipitation
for durations ranging from 1 to 5
days, and wet, dry, and annual se-
ries for 1-, 3-, 5-, 10-, 25-, 50-,
and 100-year return periods. The
average annual maximum for 1-day

rainfall is given in Figure 20.
These rainfall-frequency maps cover
south Florida and include data from
all rain gauges with a minimum of 20
years of available daily records.

sFROM 1975-1979


0 0..

Figure 18. Frequency distribution of
rainfall at Clewiston, 1975 to 1979
(adapted from Anderson 1982).

S0 4 FROM 1975-1979

I 0.


U 001 -
S0005 -
0 00`1
0 5 10 15 20 25 30 3 5 40 0
Figure 19. Frequency distribution of
rainfall at Fort Myers, 1975 to 1979
(adapted from Anderson 1982).

Despite the usually abundant
wet-season rainfall, drought may
occur in south Florida even during
the wet season (Bradley 1972). Dur-
Ing one of the worst droughts on
record, in 1971, only 87.9 cm (34.6
inches) of precipitation was record-
ed in the Everglades and Southwest
Coast Climatic Division, and wild-
fire caused severe damage throughout
the Big Cypress watershed (Duever
et al. 1979). Longterm spatial and
temporal variation of droughts in
south Florida is given in Figure 21.
Of the nine droughts recorded from
1940 to 1980 for Lake Trafford (48
km or 30 mi ESE of Fort Myers) only
four were concurrently observed at
Fort Myers. The only drought to
affect both Lake Trafford and Miami
was in 1949. Miami and Fort Myers
show no overlap of the ten worst
droughts recorded at either station.
This illustrates how localized even
severe droughts are and how cautious

Figure 20. Average annual maximum
rainfall (inches) for one day in
south Florida (adapted from MacVicar

we must be in extrapolation of
weather data from first-order weath-
er stations (Fort Myers and Miami)
to nearby areas (Duever et al.
1979, MacVicar 1983).

The effect of drought is aggra-
vated or ameliorated by variations
of temperature which affect transpi-
ration, evaporation, and soil mois-
ture. One of the more noteworthy
studies on this is that of Gannon
(1978). His model of the daily sea-
breeze circulation over the south
Florida peninsula showed that
developments on the land surface,
such as urbanization and wetland
drainage, inadvertently modify
weather patterns by redistributing

1930 1940 1950 1960 1970 1980




I Severe droughts
Severe droughts at
two stations
H Period of record
for each station


Figure 21. Severe droughts from 1890 to 1980 at Fort Myers, Lake Trafford,
and Miami (adapted from Duever et al. 1979).

rainfall via changes in the overall
daily heat budget. Soil moisture
and surface albedo (the ratio of
reflected radiation to total radia-
tion) are the two most important
factors influencing the strength of
daily sea-breeze circulation in
Gannon's model. Surface albedo in
turn is inversely related to soil
moisture; consequently, wetland
drainage may exert something of a
self-accelerating effect on the
daily hydrologic cycle by lowering
soil moisture (which itself changes
the heat budget), by providing less
moisture for evapotranspiration, and
by increasing surface albedo (which
increases daytime heating). The
total removal of wetlands from the
weather cycle through asphalt and
concrete paving and other urban
development further amplifies the
shift toward higher temperatures.

The insidious implications of
temperature change for fish and
wildlife as well as for the human
population of south Florida have

recently been noted by A. Marshall
(Boyle and Mechum 1982). His hy-
pothesis is that development and
drainage have slowly replaced Flor-
ida's wet season "rain machine" with
a relatively drier "heat machine".
The wet-season rains, which are
so vital to south Florida's eco-
systems, are less frequent because
of massive changes in the daily heat


Wind patterns in south Florida
are determined by the interaction of
prevailing easterly tradewinds and
localized diurnal factors produced
by land-sea convection patterns in
the wet season and synoptic-scale
cold fronts during the dry season
(Echternacht 1975). In a compre-
hensive examination of seasonal dif-
ferences in the large-scale wind
fields for the Florida peninsula,
Gruber (1969) described the seasonal
streamlines at three vertical lev-
els: 950 millibars (mb), at 0 to

I I50


YEAR i 9" 1100 1W AM

I I ,

to 610 m (0 to 2,000 ft); 500 mb, at
5,486 to 6,096 m (18,000 to 20,000
ft); and 200 mb, at approximately
12,192 m (40,000 ft). His work was
summarized by Echternacht (1975) in
an attempt to apply the wind-field
patterns to potential air-pollution
problems affecting south Florida.
The four seasonal wind-field pat-
terns adapted by Echternacht (1975)
at the 950-mb level (i.e., for low-
level winds) are illustrated in
Figure 22. A dominant easterly in-
fluence varying from east-northeast
and east-southeast in fall and
winter seasons, to southeast and
south-southeast in spring and summer
characterizes the Caloosahatchee
River/Big Cypress watershed.

The prevailing easterly winds
interact with the two seasonal wind
patterns described previously. For
the wet season (May to October)
convective-scale winds initiated by
thermal gradients at the land-sea
interface counter the prevailing
southeasterly winds (Pielke 1973).
The heating of the land surface pro-
motes sea-breeze circulation during
the day, causing a convergence of
warm moist air over the peninsula
(Gannon 1978, Gutfreund 1978). At
night the circulation reverses as
the land cools faster than the
ocean, and air tends to diverge away
from the peninsula. The recurrent
wind cycle and maritime influence is
significant to the reference areas'
wet-season climate because of the
flat terrain and proximity to the
water (< 40 km or 25 mi) (Bradley
1972, Echternacht 1975). The daily
changes in divergence over the
Florida peninsula from June through
August were monitored by Frank
et al. (1967). As illustrated in
Figure 23, a pronounced diurnal pat-
tern shows very strong convergence
(i.e., negative divergence) peaking

from 12:00 to 2:00 P.M. This pattern
demonstrates that the convective
scale is the fundamental scale of
motion during the watershed's wet
season (Echternacht 1975).

In the dry season (November to
April) the convective influence
diminishes as the sun's angle of
incidence decreases. This reduces
the radiant heating of the land
surface during the day and minimizes
the thermal gradient between the
land-sea surfaces (Blair and Fite
1965). In the dry season, the wind
patterns are influenced by synoptic-
scale systems or winter frontals
moving cold air masses southward.
Although south Florida is far enough
to the south to remain under the
influence of the easterlies year
round (Figure 22; winter), a north-
erly component, related to the
synoptic-scale systems, affects the
daily weather patterns (Echternacht
1975). Winter cold fronts typically
pass over the watershed once a week
during the dry season (Bamberg
1980). Warzeski (1976) describes
the cold front in south Florida as

An average cold front affects wind
patterns in the Biscayne Bay region
for 4 to 5 days, involving a slow
3600 clockwise rotation of wind
direction (direction from which the
wind is blowing). Winds rise above
ambient throughout this period,
reaching maxima roughly half a day
before and after passage of the
front itself. Maximum winds ahead
of the front are from the southwest
and reach 8 m/sec. Maximum winds
during on exceptional cold front can
reach 20 to 26 m/sec.

Monthly wind speed and direc-
tion for the watershed's first-order

Figure 22. Representative seasonal streamlines and isotachs over the Florida
Peninsula (adapted from Echternacht 1975).


Figure 23. Average monthly divergence curves over the Florida Peninsula for
June, July, and August. 1963 (adapted from Frank et al. 1967).

weather station (Fort Myers) is sum-
marized in the wind rose in Figure
24 (Gutfreund 1978). Wind direc-
tions most frequent each month are
given in Table 5. These two methods
of presentation (Figure 24 and Table
5) do not give an adequate depiction
of diurnal shifts in wind direction
and speed caused by differential
heating of air and water surfaces
during the wet season, or the pas-
sage of individual winter frontal
systems; however, Figure 24 and
Table 5 do indicate the predominance
of different seasonal factors con-
trolling wind. On a seasonal basis,
highest average wind speeds are
likely in late winter and early
spring, and lowest speeds are most
likely in the summer. Localized
high winds of short duration are

generated by summer thundershowers
and cold fronts (Bradley 1972).
Wind speeds associated with con-
vective systems follow a diurnal
pattern. On a typical day, wind
speeds are lowest in the nighttime,
increase during the daylight hours
to a peak in the late afternoon, and
then decrease again in the evening
(Gutfreund 1978).

Synoptic-scale influences are
related to the passage of the front,
as previously described, rather than
with diurnal patterns (Warzeski
1976). The influence of synoptic-
scale systems on prevailing wind
direction is shown by the northerly
component of the prevailing wind
directions from October through
January (Table 5).


oncentric crces represent S percent frequency intervals.
Average n speed (mph) fur each direction is shown along
Period of record: 1969-1973.
Figure 24. Annual wind rose for Fort
Myers (adapted from Gutfreund 1978).

Wind direction and speed tend
to vary with height above the
ground. The variation of wind
direction with height is not always
uniform, but wind speed generally
increases with height over the flat
terrain of the Caloosahatchee River/
Big Cypress watershed (Gutfreund
1978). Seasonal variations in wind
speed and direction at the 950-mb
level (0 to 610 m or 0 to 2,000 ft)
are given in Figure 22.


The southern latitude and mar-
itime influences are the primary
controls on air temperatures in the
Caloosahatchee River/Big Cypress
watershed. The climate is basically
subtropical/marine characterized by
a long, warm summer followed by a
mild, dry winter (Bradley 1972).

Isotherms developed for south
Florida (Thomas 1970) describing the
mean annual temperature, and the
mean monthly temperature for the

Table 5. Most common wind direction
and speed by month for the Fort
Myers first order weather station
(adapted from USDC 1981a).

Ft. Myers International Airport

Wind Prevailing
Month Speed (mph) Direction
J 8.5 E
F 9.1 E
M 9.4 SW
A 9.0 E
M 8.2 E
J 7.4 E
J 6.8 ESE
A 6.8 E
S 7.7 E
0 8.5 NE
N 8.3 NE
D 8.2 NE

Average 8.2 E

coolest month (January) and the
warmest month (August) are illus-
trated in Figure 25. Differences
between coastal and inland areas are
highlighted by isotherm contours
that follow the coastline. Typical-
ly, the lower west-coast air temper-
atures vary about 1F from Punta
Gorda to the Everglades. Along
coastal areas the maritime influence
causes low daily fluctuations of air
temperature and rapid warming of
cold air masses that pass to the
east of the State (USDC 1981a).
Inland areas generally display a
greater range of air temperatures
because of more rapid heating and
cooling of ground surfaces (Gerrish
1973, Gutfreund 1978).

Aw..A u ks .!

Figure 25. Isotherms for south Flor-
ida annually, and in January and
August (adapted from Thomas 1974).

In winter, advective and radi-
ational cooling processes, which
follow frontal passages, cause sharp
drops in temperature. As rainfall
diminishes with the passage of a
front, the cool, dry artic air from
Canada causes brisk northwesterly
winds, which at maximum velocity
cause the lowest daytime tempera-
tures. Nighttime cooling is preva-
lent when large quantities of heat
are lost by radiation from the land

surfaces (water is a poor radiator)
during clear skies and calm winds.
Cooling reaches a maximum a day or
two after a front has passed, as the
surface high-pressure system moves
over or near Florida from the north-
west. This cooling begins soon after
sunset; and the lowest temperatures
for the entire front are reached at
dawn. Nighttime air-temperature
gradients of 3.30C to 8.30C (60F to
15F) are typical a few miles inland
from the southwest Florida coastline
during the passage of the synoptic
cold systems as a result of radia-
tion. In addition to coastal/inland
air temperature gradients, a similar
gradient (3.3C to 5.6*C or 6F to
10F) occurs between relatively
high, dry land and adjacent moist

During calm, cold, clear nights
(maximum radiation cooling), frost
may form, particularly in low-lying
inland areas. The frequency of
frost varies from infrequent near
Everglades City to seven or eight
times a year just west of Lake Okee-
chobee. When sustained freezing
temperatures are combined with
strong northwest winds, the pene-
tration of cold is near maximum and
crop and citrus damage is most
severe. A severe freeze has been
reported about once every 20 years
(Table 6). Crops are most severely
damaged if the freeze is followed
by warm, dry weather. Water bodies
are a natural heat source during
these freezes, and moderate (via
conduction) the surrounding air

Summer air-temperature gradi-
ents may be as great as or greater
than those reported for the winter.
The air-temperature variation in the
wet season, compared to the winter's
synoptic-scale frontals, is short-
term, frequent, and spatially spo-
radic, i.e., tied to the behavior of

Table 6. Summary of severe freezes recorded in the Caloosahatchee River/
Big Cypress watershed (adapted from Bamberg 1980).

Stations and Minimum Temperatures'

Dec. 12-13, 1934 24 23 28 20 28 Tender truck
crops destroyed
Jan. 27-29, 1940 29 23 24 24 29 34 Cold winter, ctrus dormant;
ai tender and mach hardy
truck crops killed
Dec. 12-13, 1957 28 29 32 27 29 34 Strong winds and excessive
rains; moderate to severe
damage to cane and vegetable
Jan. 8-10. 1958 23 33 37 29 33 37
Dec. 13-14, 1962 26 24 30 22 25 29 Warm dry weather followed
heavy citrus damage.

jan. 20-22, 1977 30 25 29 21 26 Cold weather, citrus dormant
Snow all counties, air
tender, hardy truck and cane
ki lled.

*Includes minimum temperatures of each freeze occurrence from Weather Bureau data (1930-19791.

the wet-season thunderstorms. Air
temperatures generally rise to the
upper 90's (Figure 26) as a thunder- 90
storm develops nearby, and drop 6g
5.6C to 16.70C (10OF to 300F) when
cool downdrafts generated from the 60
thunderstorm precede the downpour
(Bradley 1972, Bamberg 1980). The 20 60
area between the southwest coast of 20 12
Florida and Lake Okeechobee is one
of two areas in the southeastern
United States where air temperatures
exceed 32.20C (90F) more than 120
days a year (Figure 26). 120


A general description of rela- so
tive humidity is difficult for many 30
areas because of large diurnal and
seasonal variations (USDC 1981a); Figure 26. Average annual number
however, in Florida, and especially of days with maximum temperatures
south Florida, the situation is less of 90*F or above (adapted from
complex because of the abundance of Gutfreund 1978).

moisture throughout the year (Gut-
freund 1978). Mean monthly relative
humidities at the Fort Myers first-
order weather station are summarized
in Table 7.

The mean annual relative humid-
ity is quite uniform throughout
the watershed, averaging about 75%
(USDC 1981a). Relative humidities
are generally highest In early morn-
ing, about 80% to 90%, and generally
lowest in the afternoon, about 50%
to 70%. Although seasonal differ-
ences are not great, mean relative

Table 7. Mean monthly relative hu-
midities (%) for 0100, 0700, 1300,
and 1900 hours, and 24 hour average
(adapted from USDC 1981a).

Ft. Myers, Page Field 24-hr
Month 0100 0700 1300 1900 Avg

JAN 86 88 58 73 76

FEB 84 88 55 70 76

MAR 84 89 52 68 73

APR 84 88 48 65 71

MAY 85 88 51 67 73

JUN 88 88 59 74 77

JUL 88 88 60 75 78

AUG 88 89 61 77 79

SEP 88 90 62 78 80

OCT 86 88 57 73 76

NOV 87 89 56 74 77

DEC 87 89 56 75 77
AVERAGE 86 89 56 72 76

humidities tend to be lowest in the
spring (April) and highest in the
summer and fall.

The daily variation in relative
humidity for the Caloosahatchee
River/Big Cypress watershed is much
greater than reported for the lower
Florida east coast and Keys, par-
ticularly during the dry season
(Figure 27). This variation is
caused by the prevailing easterly
winds that bring more moderate and
stable Gulf Stream air over the
southeastern coast as opposed to
alternating moist and dry air masses
carried over the southwest coast.


Atmospheric solar radiation
varies little in the Caloosahatchee
River/Big Cypress watershed (Gut-
freund 1978). Factors that do vary
are cloud cover, air pollution
(particulates) and relative humid-
ity, which modify the transmission,
absorption, and reflection of solar
energy (Blair and Fite 1965, Bamberg
1980). These factors largely de-
termine the amount of solar radia-
tion reaching the land and water

Miami is the only first-order
weather station that collects solar
radiation data in or near the water-
shed (Bradley 1972). The average
daily solar radiation is 447 lang-
leys (gm-cal/cm2). Monthly varia-
tions range from 319 langleys in
December to 572 langleys in April
(Bradley 1972, Multer 1977). The
higher values are reported during
middle to late spring rather than
during the summer solstice (when the
angle of incidence is least) because
of increased precipitation and cloud
cover preceding and during south
Florida's wet season.

01:00 07:00 13:00 19:00
Hours (EST)

rFT ?Mys September


\ /

01:00 07:00 13:00 19:00
Hours (EST)

Figure 27. Diurnal patterns of relative humidity at three selected sites
over south Florida in April and September (adapted from USDC 1981a, 1981b,

Although atmospheric solar
radiation is consistent in the
watershed, the insolation (radiation
reaching the ground/water surface)
varies depending upon local atmo-
spheric differences (Bamberg 1980).
Climatic data observed at Fort Myers
and Miami first-order stations are
shown in Table 8. These data are
either direct measurements of incom-
Ing solar radiation or observations
that measure the factors affecting
the passage of solar energy through
the atmosphere (Bradley 1972, USDC
1981a, 1981b). Since the Miami
station is located approximately 9
miles inland, data from this station
is probably representative of the
southwest Florida inland environment
(USDC 1981b). It is also assumed

that Fort Myers is representative
of the coastal environment of the
watershed. The coastal areas exhibit
less cloud cover and more clear days
than inland areas, especially in the
dry season (Nov. to Apr.), when the
highest number of clear days are re-
ported. The number of days of heavy
fog increases in south Florida from
south to north, and from east to
west (Table 8). In the dry season,
fog is usually an early-morning or
late-night phenomenon, and usually
dissipates or thins soon after sun-
rise (USDC 1981a, 1981b). Heavy
daytime fog is seldom observed in
south Florida (Bradley 1972). The
mean annual total sunshine for the
watershed averages approximately
3000 hours (Gutfreund 1978).

Table 8. Solar radiation and related
Fort Myers first-order weather stations
1981a. 1981b).


Evaporation and transpiration
(together called evapotranspiration,
ET) describe two processes that
move moisture into the atmosphere in
the form of water vapor. Evaporation
describes the passage of vapor to
the atmosphere directly from the
surface of water bodies, from
surface and near-surface soils, and
from impervious surfaces on which
moisture has collected (Bamberg
1980). Transpiration describes the

climatological data for Miami and
(adapted from Bradley 1972; USDC

movement of water vapor from a liv-
ing body through membranes, pores,
and/or cellular interstitial spaces
by diffusion to the external surface
and then to the atmosphere, or the
evaporation of water from living
surfaces directly into the atmo-
sphere. Although all living surfaces
transpire, vegetation is the primary

The two major factors that
control ET are solar energy and
relative humidity. Solar energy

Miami International Airport Ft. Myers Page Field
Month (1) (2) (3) (4) (5) (6) (7) (1) (21 (31 (4) (5) (6)
JAN 61 5.3 10 12 9 1 334 5.0 11 12 8 5

FEB 61 5.3 9 11 8 1 397 4.9 11 10 7 3

MAR 78 5.4 8 15 8 1 475 4.9 12 11 8 3

APR 80 5.4 8 15 7 1 572 4.6 11 13 6 2

MAY 66 6.0 6 15 10 540 5.0 9 15 7 1

JUN 76 6.8 3 14 13 0 506 6.1 5 15 10 *

JUL 78 6.6 2 17 12 539 6.5 2 18 11 *

AUG 74 6.6 2 18 11 510 6.3 3 18 10 *

SEP 73 6.8 2 15 13 440 6.2 4 15 11 *

OCT 70 6.0 6 14 11 387 5.0 11 12 8 1

NOV 63 5.4 8 14 8 1 350 4.7 12 11 7 2

DEC 60 5.3 9 13 9 1 319 4.9 12 11 8 4

AVERAGE 70 5.9 73 173 119 9 447 5.3 103 151 101 21
(1) Percent of possible sunshine (5) Mean number of cloudy days
(2)Mean sky cover sunrise to sunset (tenths) (6) Mean number of days with heavy
(3)Mean number of clear days fog
(4)Mean number of partly cloudy days (7) Average daily solar radiation
in langleys

provides the heat necessary to
transform liquid water into vapor.
The amount of solar energy reaching
the earth's surface is modified by
cloud cover, air pollution, and
angle of incidence to the earth's
surface. Relative humidity (RH) is
a measure of air moisture percentage
saturation. The RH of fog, for
example, usually is 100%, whereas
the RH during rainfall may be less.
ET is inversely related to RH; as
RH increases, ET decreases. Other
factors controlling ET are wind (ve-
locity and duration), wave action,
ground cover (type and density),
shade, barometric pressure, temper-
ature (air and surface), soil type,
soil moisture content, and water
table depth (Parker et al. 1955,
Dohrenwend 1977, Palmer 1978, Duever
et al. 1979, Bamberg 1980, Wyllie

Evapotranspiration, especially
during saturated soil conditions,
becomes an important control of sea
breeze intensity and ultimately the
formation of convective storms. The
heat-consumptive process associated
with high evaporation rates causes
slightly higher temperature gradi-
ents between cooler inland areas
and warmer coastal urban strips
(Gannon 1978, Bamberg 1980). These
conditions are more prevalent one to
two days following a heavy rainfall.
Because ET is a cooling phenomenon,
land-water gradients are reduced,
convective processes are reduced,
and the recently rained-on area
receives less rainfall. The overall
effect is the creation of a natural
feedback mechanism which results in
a more even spatial distribution of
seasonal rainfall (Bamberg 1980).

Estimates of evapotranspiration
in southwest Florida range from 76.2
cm (30 inches) per year to 121.9 cm
(48 inches) per year (Dohrenwend

1977, Palmer 1978). Predicted evapo-
transpiration patterns for Florida
are given in Figure 28. Estimated
annual values range from greater
than 100 cm (39.4 inches) in the
central southern watershed to less
than 95 cm (37.4 inches) in the
north (Dohrenwend 1977).


The climatic conditions of
south Florida may be divided into
three energy levels or intensities
(Warzeski 1976). They are prevail-
ing mild southeast and east winds,
winter cold fronts, and tropical
storms and hurricanes. The first
two were discussed before in the
sections on wind and rainfall. Trop-
ical storms and hurricanes, because
of their destructive capacity,
importance as an ecological force,
and unique climatic characteristics,
are described here as a separate
climatic element.


Figure 28. Predicted evapotranspi-
ration patterns in Florida (adapted
from Dohrenwend 1977).

In summer and fall, low-pressure
areas that originate in the warm,
moist air of the equatorial trough
are relatively common. The winds
are light and usually drift from
east to west. At that time atmo-
spheric waves appear in the easterly
flow and proceed westward at 16 to
24 km per hr (10 to 15 mph) (Blair
and Fite 1965). These easterly
waves usually form between 50 and
200 north of the equator. From this
point easterly wave developments may
go through one or all four stages of
a tropical cyclone as described by
Riehl (1954):
(1) Formative stage. Winds usu-
ally remain below hurricane
force. The strongest winds
are generally in one quad-
rant, poleward and east of
the center of a deepening of
the barometric trough. Areas
of weak wind circulation
(less than 61 km or 38 mi
per hour) are referred to as
"tropical depressions" or
"tropical disturbances".
These disturbances move in a
very rough counterclockwise
direction and may travel
great distances organized as
such (Gentry 1974).
(2) Immature stage. If the shal-
low depressions intensify
with winds exceeding 61 km
per hour (38 mph) the "trop-
ical depression" has become
a "tropical storm" charac-
terized by barometric pres-
sures dropping to 1000 mb
and below, and winds forming
tighter concentric bands
around the center or eye.
The cloud and rain patterns
also change from disorganiz-
ed squalls to narrow orga-
nized bands spiraling inward
(Riehl 1954). If the winds
intensify to 119 km per hour
(74 mph) or more, a tropical

hurricane is born (Gentry
1974). Still only a rela-
tively small area is in-
volved, i.e., a hurricane
force wind radius of 32
to 48 km (20 to 30 miles)
(Riehl 1954).
(3) Mature stage. The surface
pressure at the center is no
longer falling and the maxi-
mum wind speed no longer
increases (Riehl 1954). In-
stead the circulation ex-
pands, extending the radius
of hurricane force winds.
(4) Decaying stage. Tropical
cyclones, both mature and
immature, generally move
westward in the prevailing
westward drift of the east-
erlies. They enter the
decaying stage as they re-
curve from the tropics and
enter the belt of wester-
lies, usually decreasing in
size (Riehl 1954, and Blair
and Fite 1965).

During the immature and mature
stages the general westward movement
ranges from 16 to 48 km per hr (10
to 30 mph). The typical path is
parabolic, although the actual path
of any given storm is governed by
the winds existing above it, causing
a multitude of speed and directional
changes (Blair and Fite 1965). Blair
and Fite (1965) provide a concise
description of the passage of a
hurricane over south Florida:

As such a storm approaches, the
barometer begins falling, slowly at
first and then more and more rapid-
ly, while the wind increases from a
gentle breeze to hurricane force,
and the clouds thicken from cirrus
and cirrostratus to dense cumulo-
nimbus, attended by thunder and
lightning and excessive rain. These
conditions continue for several

hours, spreading destruction in
their course. Then suddenly the eye
of the storm arrives, the wind and
the rain cease, the sky clears, or
partly so, and the pressure no lon-
ger falls but remains at its lowest.
This phase may last thirty minutes
or longer, and then the storm begins
again in all its severity, as be-
fore, except that the wind is from
the opposite direction and the pres-
sure is rising rapidly. As this
continues, the wind gradually de-
creases in violence until the tem-
pest is passed and the tropical
oceans resume their normal repose.
The violent portion of the storm
may last from twelve to twenty-four

South Florida is subjected to
more hurricanes and tropical storms
than any other area of equal size in
the United States (Gentry 1974). The
Caloosahatchee River/Big Cypress wa-
tershed is exposed to both Atlantic
and Carribean hurricanes. Generally,
tropical cyclones strike the east
coast of south Florida from an ESE
direction a predominant direction
for Atlantic hurricanes before
recurvature (Jordan 1973, Ho et al.
1975). The west coast of south
Florida is vulnerable to late-season
tropical cyclones moving in a north-
eastward direction after recurvature
(Cry 1965, Bradley 1972). Figure
29 illustrates the frequency of
hurricanes along the Atlantic coast-
line for 5 of 58 coastal segments
delineated by Simpson and Lawrence
(1971). Of the 38 hurricanes that
passed over Florida's southwest
coast from 1901 to 1971, 30 were
in August, September, or October
(Jordan 1973). Points of entry of
tropical storms and hurricanes in
south Florida are shown in Figure
29. Tropical storms cause destruc-
tion once every 3 years south of the
Everglades and once every 5 years
farther north in the watershed

Figure 29. Points of entry and prob-
abilities of hurricanes at selected
coastal locations (adapted from
Jordan 1973).
(Bamberg 1980). The average forward
speed for hurricanes affecting south
Florida is 10 knots; the radius of
maximum winds extends an average of
20 nautical miles from the center
(Ho et al. 1975). Detailed descrip-
tions of the passage of specific
hurricanes and tropical storms
through south Florida are reported
in the U.S. Department of Commerce
"Monthly Weather Review". This
review summarizes all meteorological
data on the passage of tropical
waves, disturbances, storms, and
hurricanes for each year's hurricane

The three primary forces asso-
ciated with the passage of a hur-
ricane are wind, storm surge, and
rain. Sustained winds over 200 km
per hour (125 mph) are necessary for
a hurricane to be classified a
"Great Hurricane". Ball et al.
(1967), Pray (1966), and Perkins and
Enos (1968) describe the passages of

two Great Hurricanes, Donna (Sept.
1960) and Betsy (Sept. 1965),
through the Florida Keys. Winds
over 200 km per hour (125 mph) have
been reported in south Florida on
several occasions during the last
century (Sugg et al. 1971, see Fig-
ure 29). The most notable was the
"Labor Day" hurricane in 1935, which
passed over Long Key with highest
sustained winds estimated at between
322 and 402 km per hr (200 to 250
mph), according to Bradley (1972).

The ecological significance of
hurricanes can best be understood
when it is known that the wind force
increases by the square of the wind
speed. In other words, a 150-km-per-
hour (93 mph) wind exerts four times
as much force as a 75-km-per-hour
(47 mph) wind. When hurricane winds
exceed 400 km per hour (249 mph), as
was estimated for the "Labor Day"
hurricane, their strength becomes
almost inconceivable (Gentry 1974).

A storm surge, of high tides
and rough seas, is caused by a
complex interaction of wind, air
pressure, and the bottom topography
of waters adjacent to the land
(Gentry 1974). The effects are more
pronounced when the storm moves
onshore, as opposed to moving along
the coastline. Since 1873, eight
hurricanes have caused record storm
tides in south Florida (Simpson
et al. 1969). Some of the most
pronounced surges along the coast
are given in Table 9 (Jordan 1973).
No discernible pattern of these
great storms is apparent all areas
of the coast were equally affected.
Record storm-surge tides range be-
tween 2.9 and 5.5 m (9.5 to 18 ft)
above undisturbed waters (Simpson
et al. 1969). In addition to high
tides, coastal areas are also sub-
ject to strong wave action that

Table 9. Major hurricane storm
surges between Fort Myers and Ever-
glades City (adapted from Jordan

Surge height Month of
Location (feet) occurrence
Ft. Myers 9 Oct. 1921
Punta Gorda 14 Oct. 1873
Naples 11 Oct. 1944
Marco Island 10 Oct. 1910
Everglades 10 Oct. 1910

causes waters to reach even further
inland than indicated by tide
heights alone (Gentry 1974). The
highest recorded storm surge along
Florida's southwest coast occurred
in 1873 when a 4.3 m (14 ft) tide
destroyed the island community of
Punta Rassa (Sugg et al. 1971).

The amount of rainfall from
tropical storms varies according to
the intensity of rainfall, the rate
of forward movement, and the size of
the storm (Gentry 1974). Because of
the violent nature of the storm, the
error in the rainfall measurements
may be as high as 50%. Usually 12.5
to 25 cm (5 to 10 inches) of rain
are recorded at any one point during
the passage of a tropical storm
(Gentry 1974). Reports of excessive
rainfall (> 20 cm or 8 inches) in
conjunction with hurricanes crossing
the coast near the Caloosahatchee
River/Big Cypress watershed are
given in Table 10. Although Great
Hurricane Donna (1960) passed over
this coastline, it was a compara-
tively "dry" hurricane. Precipita-
tion was only 5 to 8 cm (2 to 3
inches). Donna's winds, however,
reached 241 km per hour (150 mph)
and caused extensive damage to Ever-
glades City and other areas along
the coast (Bamberg 1980).

Table 10. Maximum hurricane rainfall for the Caloosahatchee River/Big
Cypress watershed (adapted from Bamberg 1980).

Stations* Oct. 1929 Sept. 1926 Sept. 1929 Sept. 1948

Moore Haven 9.14 - - 10.26

Everglades 15.66 8.02 9.37 8.76

Ft. Myers - - 7.66 -

La Belle - - 8.69 11.15

Punta Gorda - - 8.00 10.26

*Rainfall listed only if any single station received a total rainfall
equal to or exceeding 8 inches during hurricane passage.


The three natural and man-made
sources of atmospheric contaminants
in south Florida are: (1) sources
for small particulate matter that
can form condensation nuclei, (2)
sources for particulate matter
suspended in the air that can be
scavenged by falling raindrops, and
(3) sources of solutes which are
dissolved in condensation particles
or cloud droplets (Echternacht
1975). Their geographic distribution
is dependent on watershed weather
patterns. For the Caloosahatchee
River/Big Cypress watershed it is a
wet-dry season variation. Passage
of large-scale synoptic (or pres-
sure) systems during the dry season
(Nov. to Apr.) may contain pollut-
ants from sources far removed from
the State (Echternacht 1975), in
addition to localized sources (Holle
1971). Wet-season convective sys-
tems, exhibiting diurnal activity
related to land-sea breeze inter-
actions, convey atmospheric contami-
nants primarily from local sources,
i.e., automobile emissions, stack
gases, fertilizer and pesticide
dusts, and ash from burned marsh

grasses and sugar cane residue
(Holle 1971, Echternacht 1975).

Two mechanisms are involved in
the movement of air-borne contami-
nants from the atmosphere to the
land and water surface. The mate-
rial, inorganic and organic, is
transported either by wet or dry
fallout (Irwin and Kirkland 1980).
Material associated with dry fallout
is in a continuous flux of suspen-
sion and deposition, e.g., wind-
generated dust and car emissions.
Those materials deposited during wet
fallout or rainfall, either in a
dissolved or particulate form, are
affected by two processes referred
to as rainout and washout (Echter-
nacht 1975). Semonim and Adams
(1971) describe rainout as the re-
moval of aerosols in the rainmaking
process, and washout as the process
of falling rain scavenging air-borne
particulates. For instance, in
south Florida, Echternacht (1975)
concluded that with nutrient fall-
out, total phosphate (TPO4) in the
particulate form is subject to the
washout process, i.e., scavenging of
particulates by falling rain, and as
dry fallout year round. In contrast,

nitrogen as NOx is primarily in
the solute form and is therefore
removed in the rainout process.
Total atmospheric fallout, wet plus
dry, is commonly reported as bulk
precipitation and consists of dis-
solved materials in aqueous precipi-
tation, the water-soluble component
of dry precipitation, and the water-
insoluble component of either wet
or dry precipitation (Irwin and
Kirkland 1980).

Qualitative rainfall character-
istics at selected USGS study sites
in Florida, including six sites
within or adjacent to the Caloosa-
hatchee River/Big Cypress watershed,

04 Station location and number N

Na+ K .-CI

0.2 0.1 0 0.1 0.2

Diagrams show general chemical
character of bulk precipitation.
The ionic concentrations are
plotted for sodium and potassium
(Na+K), calcium (Ca), magnesium
(Mg), chloride (Cl), bicarbonate
(HC03), and sulfate (SO4). Anions
are plotted to the right of the
centerline and cations to the left.
The area of a diagram is an in-
dication of the dissolved-solids
concentration--larger areas reflect
greater dissolved solids concentration.

were summarized by Irwin and
Kirkland (1980). The mean chemical
composition of the more common inor-
ganic ions in rainfall are illus-
trated in Figure 30. Site 4 (40 Mile
Bend, Tamiami Trail) in the extreme
southern end of the basin exhibits a
predominantly calcium bicarbonate
water type. Site 14 (Sanibel Island)
is a sodium chloride water type
reflecting the maritime influence on
the island. The Moore Haven sites
at Lake Okeechobee show a mixture of
both types. Higher calcium/bicar-
bonate levels observed in this basin
(site 4) are believed to be derived
from fine rock and marl soils
(Waller and Earle 1975).

Figure 30. Average chemical concentrations of precipitation at sampling sites
in and adjacent to the watershed (adapted from Irwin and Kirkland 1980).


Bulk precipitation comprises as
much as 78% of the total annual in-
put of nitrogen and 90% of the input
of phosphorus to the conservation
areas north of the Everglades Na-
tional Park (Waller 1975). Davis
and Wisniewski (1975) reported that
nutrient loading via rainfall ac-
counted for 19% and 11% of the total
nitrogen and phosphorus loading to
Lake Okeechobee. The majority of
the loading is during the wet sea-
son. Concentrations in dry fallout
tend to increase during the dry
season (Waller and Earle 1975, Ech-
ternacht 1975). The South Florida
Water Management District's rain-
water chemistry data illustrates
this seasonal difference of nitrogen
and phosphorus concentrations (Ech-
ternacht 1975). Peak concentrations
in the spring, characterized by
high winds and low rainfall, are
representative of high dry fallout
conditions (Table 11). Fire is also
believed to be a factor in enhancing
the concentration of dry fallout in
the dry season (Holle 1971, Waller
and Earle 1975). Summer months,
during peak rainfall and maximum
dilution, show the lowest concen-

Spatially, nitrates in south
Florida exhibit a north-south gradi-
ent and a maximum in the area east
of Lake Okeechobee. Phosphorus is
even more variable, but still shows
a similar north-south gradient (with
several maximums) around Lake Okee-
chobee (Echternacht 1975, Davis and
Wisniewski 1975).

Most trace metals in bulk pre-
cipitation are derived from dry
soils and fine rock material wafted
Into the air by winds. Mercury and
arsenic, however, are believed
related to pesticide use In nearby
agricultural operations (Waller and
Earle 1975). Lead and iron are at-
tributed to motor vehicle emissions
(Irwin and Kirkland 1980). Site 4
(Tamiami Trail, 40 Mile Bend) is the
only site in the watershed monitored
for trace metals in bulk precipita-
tion. Of all trace metals, cadmium
and zinc show up in the most poten-
tially hazardous concentrations, but
these concentrations are believed to
result from contamination by nearby
galvanized metals (Waller and Earle
1975). Single samples were analyzed
from sites 14, 16, and 17; sites 16
& 17 (from Moore Haven) exhibited

Table 11. Seasonal averages of nutrient concentrations in rainwater
at Tamiami Trail, 40 Mile Bend (adapted from Echternacht 1975).

Arnonium Nitrate Nitrite Orthophosphate Total phosphate
NH+ N03 N02 OP TP
Season ppm ppm ppm ppm ppm

Sunmner 0.30 0.28 0.01 0.03 0.04

Fall 0.61 0.26 0.02 0.06 0.07

Winter 1.91 0.27 0.02 0.08 0.09

Spring 2.20 0.49 0.06 0.13 0.30

much higher concentrations of lead
than site 4 (40 Mile Bend, Tamiami
Trail). Trace-metal sampling sites
for measuring local phenomena are
usually located near highways, so it
is unlikely that they are represen-
tative (Irwin and Kirkland 1980).

The reported pH of rainfall
at sites 4, 14, 16, and 17 in the
watershed ranged from 5.5 to 8.8
(Irwin and Kirkland 1980). This data
should be viewed as only approximate
due to the holding times imposed.
Data on selected pesticides and
industrial compounds monitored are
rather limited. Trace amounts of
malathion and diazinon were reported
at 40 Mile Bend (site 4).

Airborn sulfur dioxides in the
state of Florida have been monitored
in Hillsborough, Duval, and Escambia
counties and to a lesser extent in
the remaining Florida counties.
This survey showed very low sulfur-
dioxide emission rates for the
counties in the watershed. The
largest source is the fossil-fueled
power plant at Fort Myers. At this
location the 24-hour maximum con-
centrations of SO2 have been and
should continue to be far below
Florida and national air-quality
standards, even at locations where
the maximum combined effects are

Normally, air temperature de-
creases with an increase In alti-
tude, but occasionally the reverse
occurs, i.e., the temperature in-
creases with height within a given
atmospheric layer or between layers.
This phenomena is called an inver-
sion of temperature or simply an

inversion. Inversion is most common
on calm, clear nights, when the soil
cools rapidly by radiation. The
adjacent near-surface air is cooled
by conduction and radiation more
rapidly than the air above it,
creating an inversion. During the
inversion, the air column involved
is stable, but when air temperatures
decrease with height (a condition
favorable to convection) the air
column is considered unstable (Blair
and Fite 1965). The significance of
an inversion to air quality is its
effect on mixing, dilution, or
dispersion of air pollutants. Air
within an inversion is trapped and
near-ground pollutants, e.g., vehi-
cle emissions, can build up and
create a health hazard in the more
common near-surface inversions
(Gutfreund 1978).

The general pattern of inver-
sion frequency is consistent from
season to season. Low-level inver-
sions are least frequent in the
south of the watershed, but Increase
to the north. Annual variation
ranges from 10% at 40 Mile Bend
along Tamiami Trail to about 30% of
the time north of the Caloosahatchee
River (Hosler 1961). Seasonally,
inversions are more common in fall
and winter and least common in sum-
mer. In addition to the north-south
gradient, inversions tend to in-
crease and are much stronger inland
than along coastal areas (Gerrish
1973, Gutfreund 1978); however,
because of the diurnal nature of
inversion phenomenon, significant
atmospheric pollutant build-up sel-
dom occurs. The daily inversions
are quickly dispersed by the dynamic
wind and rain patterns over the
watershed (Gutfreund 1978).



The surface-water drainage of
the Caloosahatchee River/Big Cypress
watershed consists of a mixture of
diffuse waterways (strands), rela-
tively few distinct stream channels,
and an extensive network of man-made
canals. The identifiable drainage
basins shown in Figure 31 are as
(1) The Caloosahatchee Valley &
River watershed.
(2) The Estero Bay and Imperial
River watershed.
(3) The Golden Gate Canal/Gordon
River/Cocohatchee River Ca-
nal drainage to Cocohatchee
Bay, Rookery Bay, Naples
Bay, and the Ten Thousand
(4) The Turner and Barron River
Canals and the Big Cypress
National Preserve drain-
age to Chokoloskee Bay and

Fresh groundwater for domestic,
agricultural, and industrial pur-
poses has a number of sources. In
the upper Caloosahatchee Valley, a
combination of shallow aquifers,
including the shallow water table,
the Tamiami, and the lower Hawthorn
and Floridan aquifers are sources of
groundwater. These same sources
plus the upper Hawthorn Aquifer
supply groundwater to the Estero Bay
watershed. In southern Collier Coun-
ty, groundwater is drawn from the
shallow water table and the Tamiami
and Floridan Aquifers (SFWMD 1980,
Burns 1983, Jakob 1983).

Some of the characteristics of
the surface water drainage in the
Caloosahatchee River watershed have
been modified by agricultural prac-

tices and navigational channels.
Sixty (60) tributaries make up the
Caloosahatchee River watershed. The
major tributaries are listed in
descending (upstream to downstream)
order in Tables 12 and 13. The
Caloosahatchee River watershed (USGS
Hydrologic Unit 03090205) is divided
Into the East Caloosahatchee basin,
the West Caloosahatchee basin, the
Telegraph Swamp basin, and the
Caloosahatchee River Tidal Basin.

At one time the Caloosahatchee
River was a natural water course
that began in the vicinity of Lake
Hicpochee and flowed about 78.8 km
(49 mi) to the Gulf of Mexico.
In 1884 a canal was constructed,
connecting the river with Lake
Okeechobee at Moore Haven. In 1918
three combination lock and spillway
structures were constructed at Moore
Haven, Citrus Center, and Fort
Thompson. By 1937, after improve-
ments authorized by the 1930 River
and Harbors Acts, the Caloosahatchee
River had a navigable channel about
2 m (6.6 ft) deep and 24 m (80 ft)
wide (Miller et al. 1982). From
1962 to 1968 the last major improve-
ments were completed under the
auspices of the Central and Southern
Florida Flood Control Project. The
old lock structures were replaced by
three primary facilities: S-77,
S-78, and S-79. Farthest upstream
at Moore Haven, Lake Okeechobee
waters are released through a
combination spillway (S-77) and
navigation lock (HGS No.1). West of
S-77 about 24 km (15 mi), a second
lock and spillway (S-78, Ortoona
Lock) controls water levels on
adjacent upstream lands. The W.P.
Franklin Lock and Dam (S-79) at Fort
Myers prevents saltwater intrusion
from the west and controls water





a co

Figure 31. Subdrainage basins within the Caloosahatchee RiverlBig Cypress
watershed (adapted from SFWMD 1980).

Table 12. Major upstream tributaries (above Ortona Lock) associated
with Caloosahatchee River drainage (adapted from SFWMD 1980).

Tributaries entering from:

Moore Haven South North
Diston Island Canal C-19 Canal
Nine Mile Canal Rangeline Canal
Whidden Corner Canal Bayce Canal
Lake Hicpochee Canal Meander Line Canal
downstream to Grassy Marsh East Canal Citrus Center Canal
Grassy Marsh West Canal Turkey Branch
42' Canal (Beautiful Hammock)
Long Hammock Canal
Goodno Canal
Ortona Lock

Table 13. Major downstream tributaries (below Ortona Lock) associated
with Caloosahatchee River drainage (adapted from SFWMD 1980).

Tributaries entering from:

Ortona Lock South North
Goodno #2 Canal Cypress Branch
Goodno #1 Canal Deadman's Branch
Okaloacoochee Branch East Spoil Canal
LaBelle Canal West Spoin Canal
Messer Canal North LaBelle Canal
downstream to Crawford Canal Pollywog Creek
Roberts Canal Bee Branch
Townsend Canal Jacks Branch
State Road 80 Bedman Creek Mouth Canal
State Road 80 Mouth
Mouth, Spanish Creek
Mouth, Cypress Creek
Franklin Lock Minor Basin
Mouth, Telegraph Creek

levels for the remaining 42 km (26
mi) reach, west of S-78.

Presently the Caloosahatchee
River (C-43) is an improved canal,
104.6 km (65 mi) long, 50 to 130 m
(55 to 142 yd) wide, and 6 to 9 m
(20 to 30 ft) deep (Miller et al.
1982). Since 1945 many of the river
oxbows have fallen victim to the
channelization. Thirty-five oxbows
still remain between the town of

LaBelle and the Franklin Locks
(Milleson 1980).

Water flow and stage heights in
the Caloosahatchee River canal are
maintained for a variety of needs,
including local drainage and flood
control, irrigation and municipal
water supply, navigation, salinity
control, and maintenance of the
Lake Okeechobee regulation schedule
(SFWMD 1980). The canal stage is

maintained at about 3 m (11 ft)
above mean sea level at the Ortona
Lock (S-78) and 1 m (3 ft) above msl
at Franklin Lock (S-79). A summary
of monthly average flows at several
Caloosahatchee River stations is
given in Figure 32.


4.2.1 Freshwater Caloosahatchee

Structure-78 (Ortona Lock) sep-
arates the freshwater portion of the
Caloosahatchee River watershed into
two distinct hydrologic units, the
East and West Basins.


100 -----------


The East Basin or upperpool
(Figure 33), encompasses an area of
875 km2 (216,133 acres). Average
discharge near its upstream end,
at Moore Haven is 27.0 m3/s (954
cfs). The maximum recordeddischarge
is 235 m3/s (8290 cfs) and minimum
discharge is -56.9 m3/s (-2,010
cfs). The minus values indicate
back pumping to the lake. Estimated
seepage when the locks are closed
averages as much as 0.142 m3/s
(5.0 cfs) according to USGS

Tributary drainage in the East
Basin is more complex than the
drainage of the West Basin, primari-
ly because of the land use and water
control (Miller et al. 1982). Land
use in the East Basin is primarily
agricultural; consequently, irri-
gation of croplands is the most
important water use. Irrigation is
controlled by extensive canal net-
works that drain flood waters during
the wet season and recharge the
shallow water table during the dry
season. Tributary streams that drain
into the east Caloosahatchee River
are listed in Table 12.

To the north of the river in
Glades County, four canals dominate
the watershed. These, in descending
order downstream are the C-19 Canal,
the Bayce Canal, the Meander Line
Canal, and the Citrus Center Canal.
Turkey Branch enters the Caloosa-
hatchee River from the north a few
miles upstream from the Ortona
Locks. To the south of the Caloo-
sahatchee River, in Hendry County,
the Whidden Corner Canal, the Lake
Hicpochee Canal, the Grassy Marsh
East and West Canals, and Long
Hammock Canal dominate the water-
shed. The Goodno Canal enters the
Caloosahatchee River at the Ortona

SF A M J J A 0 N D
Figure 32. Monthly average stream
flow (cfs) at three Caloosahatchee
River stations (adapted from
SFWMD 1980).

Figure 33. The East (upper) Caloosahatchee River basin (adapted from
SFWMD 1980).

Drainage by these and numerous
other canals and ditches opens much
of the marginal and seasonal wet-
lands of the East Basin to intensive
agriculture, and the crops grown on
these predominantly sandy and highly
permeable soils require rather in-
tensive irrigation. A fine balance
between drainage and irrigation must
be maintained. The canals lower
the shallow water table to allow
cultivation and yet, during the wet
season (summer), some of this water
must be reused to irrigate the
crops. In general, canals accelerate
runoff and evaporation and decrease
groundwater storage.

Maintaining the drainage/irri-
gation balance is made easier by
external sources of water that were
not historically a part of the near-
surface water balance. These new

external sources are the Floridan
aquifer and the overflow of Lake
Okeechobee. Because of the drainage
operations, over half the predrain-
age storage capacity of the water-
shed has been lost (Debellvue 1976).
Historically, the shallow surface
water table and the slough-like
drainage were able to hold consider-
ably more water before agricultural
development. During the dry season
the watershed has an average 23 cm
(9.2 inches) deficit that requires
much of the wet season's 32 cm
(12.4 inches) excess to be retained
in order to sustain natural and
cultivated vegetation. The loss of
the natural storage capacity of the
basin and increased consumption in
the dry season sometimes makes it
necessary to import water (e.g.,
backpumping) for recharge and

The Floridan aquifer in the
East Basin is composed of limestone
ranging in age from middle Miocene
to Eocene. The Tampa Formation and
the Suwannee Limestone are the major
strata that contribute to the water
holding capacity of the aquifer,
along with some interbedded lime-
stone of the lower Hawthorn. These
strata are overlain by clay, marl,
and sandy clay of the Hawthorn For-
mation. Replenishment of this arte-
sian aquifer comes largely from the
Highlands Ridge area to the north
(Klein et al. 1964).

Use of the Floridan aquifer
for irrigation is limited because
its excess of total dissolved solids
is detrimental for most crops,
although some crops (e.g., citrus)
tolerate the high ionic content bet-
ter than others. On the other hand,
dilution from rainfall helps reduce
mineral concentrations and makes the
Floridan aquifer more useful for
irrigation in the East Basin.

The shallow aquifer is general-
ly of better quality than the Flor-
idan aquifer because it is higher
in calcium and bicarbonates but
lower in concentrations of sodium,
magnesium, sulfate, and chloride.
The shallow aquifer is contaminated
where there is seepage from the
Floridan aquifer through unplugged
or improperly cased wells (near
LaBelle) and where surface waters
contact rock bearing connate sea
water near Lake Okeechobee (Burns

The West Basin, including Tele-
graph Swamp, encompasses an area of
1,287 km2 (318,253 acres). Land
use is largely agricultural, so the
balance between adequate drainage
and adequate recharge for irrigation
is a primary concern of regional
water management. In the West Basin
the Caloosahatchee River water
serves as a primary and secondary

source of drinking water, which
focuses greater public concern on
the river water quality (SFWMD

The average annual upstream
discharge to the West Basin through
the Ortona Locks is 20.5 m3/s
(724 cfs). Flow ranges from 0 to
275 m3/s (9,720 cfs). A list of
tributary watersheds that drain into
the West Basin is given in Table 13
and Figure 33. The monthly average
flow in the West Basin at the inflow
(Ortona Locks) and outflow (Franklin
Locks) stations is given in Figure
32. The control of flow in response
to the demands for water in the West
Basin often leads to an irregular
pattern of flow in tributary canals.
The monthly average flow and stan-
dard deviation for the Townsend
Canal during the water years 1970 to
1980 is shown in Table 14 and also
illustrates the back-and-forth flow
action in the canal. The river reg-
isters a net negative average flow
in 7 months of the year, indicating
heavy consumption for irrigation and
surface loss to groundwater and/or

Table 14. Monthly average downstream
and upstream (-) flow for the Town-
send Canal 1970-1980 (SFWMD 1980).
Townsend Canal Sta. 02292780


JAN 30 147
FEB -23 76
MAR -47 152
APR -151 114
MAY -15 181
JUN <-1 188
JUL 121 122
AUG 117 202
SEP 153 260
OCT -45 192
NOV -27 122
DEC 14 155

Groundwater in the West Basin
is supplied by the surficial aqui-
fer, the Hawthorn aquifer, and the
Floridan aquifer (Boggess et al.
1981, Burns 1983). The surface
aquifer is contained within terrace
deposits (Pleistocene to Holocene
origin) and the Tamiami Formation
(Pleocene). Unconsolidated quartz
sands, shell beds, calcareous clays,
and interfingering limestones char-
acterize the terrace deposits. Sandy
biogenic limestones that identify
the Tamiami Formation are occasion-
ally separated from the terrace
deposits by a semi-confining calcar-
eous clay bed.

The surface aquifer ranges from
25 ft to 125 ft, thickening to the
west and southwest in Lee County.
Rainfall, surface waters, and dis-
charge from deep wells recharge this
aquifer, and the top of the aquifer
fluctuates about 1 m (3 ft) season-
ally. Major areas of recharge are
Telegraph Swamp, north of the Caloo-
sahatchee River, and the region
around the Immokalee Rise, south of
Lehigh Acres.

The Hawthorn aquifer consists
of three semi-confining beds and two
sub-aquifers, the Sandstone and the
Mid-Hawthorn (Sproul et al. 1972,
Boggess and Missimer 1975, Burns
1983). The upper Hawthorn acts as
the upper confining layer. The Sand-
stone aquifer, the upper water-bear-
ing unit of the Hawthorn aquifer, is
absent in Cape Coral and northwest
Lee County and thickens to 200 ft
to the east. Potentiometric peaks
correspond to the surface aquifer
recharge areas. The water quality
is good except in northeast and
southwest Lee County where chlorides
exceed 250 mg/I.

The mid-Hawthorn is more exten-
sive than the Sandstone aquifer but
rarely exceeds 75 ft In thickness.

Chloride content of the mid-Hawthorn
is higher, exceeding 1000 mg/I along
the west coast (Burns 1983). Recent
intensive pumping from the aquifer
has reduced its artesian pressure to
below mean sea level in most of the
West Basin. Average seasonal fluc-
tuations range from 6.2 m (17 ft) in
heavily pumped areas to about 1.0 m
(3 ft) where pumping is minimal
(Boggess et al. 1981).

Deepest of the three aquifers
is the Floridan aquifer, and the
only zone of consequence to the West
Basin's water supply is the lower
Hawthorn/Tampa producing zone. This
zone, located in the upper Floridan
aquifer, ranges from 75 ft to 250 ft
thick and provides water for agri-
culture and for the Cape Coral, Pine
Island and Sanibel reverse osmosis
plants. Chlorides range from 250
mg/I to 5,000 mg/I (Burns 1983).

Water quality of the East and
West Basin. Water quality in the
Caloosahatchee River is controlled
largely by the low relief, semitrop-
ical climate, discharge from Lake
Okeechobee, and land use. Where
shallow sands are underlain by clay
or marl hardpans, water may pond
up because of the extremely low
relief of the land, and form sloughs
or seasonal wetlands that affect
surface water quality and rate of
runoff. Wet and dry seasons alter-
nately dilute and concentrate sur-
face water constituents. Agriculture
and urbanization have caused ex-
tensive channelization that changed
the hydrologic cycle of the water-
shed, as well as its surface water

Water quality data for the
Caloosahatchee River is available
from (1) USGS and Florida Depart-
ment of Environmental Regulation
(FDER) monitoring stations, (2) an
extensive sampling and analysis

program that assessed the effect of
runoff on the river and its tribu-
taries (ESE 1977), and (3) most
recently, a series of studies aimed
at developing a comprehensive water-
management plan for the Caloosa-
hatchee River watershed (SFWMD 1980,
Miller et al. 1982).

The upper Caloosahatchee River,
from Moore Haven to the Lee-Hendry
County line, is classified as Class
III waters by the FDER. This clas-
sification requires that water qual-
ity meet standards for recreational
contact and the propagation of fish
and wildlife. From the Lee County
line to Franklin Lock, waters are
classified I-A, suitable for potable
or drinking water use. The City
of Fort Myers pumps surface water
from the Caloosahatchee River into
a nearby shallow-well field to
augment groundwater recharge. Lee
County takes water directly from
the river, treats it, and uses it
for domestic supply purposes (Klein
et al. 1964).

Water quality in the Caloosa-
hatchee River (Moore Haven to Frank-
lin Lock) is dominated by Lake Okee-
chobee discharges and tributary
drainage from the surrounding agri-
cultural lands (McPherson and La
Rose 1982, Miller et al. 1982).
Based on a 1978 to 1980 sampling
program, inflow from Lake Okeechobee
contributed 55% of the Caloosahatch-
ee River water, 62% of the total
nitrogen, and 64% of the chloride
load (Miller et al. 1982). The East
Basin contributed the least amount
of water (21%) and the greatest
amount of total phosphorus (43%).

Total phosphorus at S-77 (Moore
Haven) exhibits a seasonal pattern
which is sensitive to flow releases
from Lake Okeechobee. Concentrations
are lowest in winter when the Moore
Haven structure is discharging and
are highest in the summer when there

is no discharge. Total phosphorus
along the river increases between
S-77 and S-78 (Ortona Lock) and
decreases downstream to S-79, the
Franklin Lock and Dam (FDER 1980,
Miller 1980). The change in concen-
tration is related to the nutrient
levels observed in the East and West
Basin tributaries. The East Basin
tributaries contain phosphorus con-
centrations that are higher than
observed in the upper river, whereas
the West Basin tributary levels are
lower than the river's total phos-
phorus levels. The difference be-
tween basins is probably related to
land-use practices that vary between
the two areas. Although agricultural
activities (improved pasture, crop-
land, and citrus) are similar in the
East and West Basins (Isern and
Brown 1980), the intensity and
drainage practices between the two
basins are not. Nutrient polishing
ponds and water reuse systems are
used in the West Basin but not in
the East Basin (ESE 1977, Miller
et al. 1982).

Total nitrogen gradually de-
creases from Lake Okeechobee (S-77)
to the Franklin Lock (S-79). The
tributaries in both East and West
Basins exhibit lower concentrations
than those observed in the river
except for the five easternmost
tributaries that drain organic or
muck soils high in nitrogen. Organic
nitrogen, the dominant nitrogen
form, represents 81% and 90% of the
total nitrogen in the East and West
Basins, respectively. An inverse
relationship was found between the
inorganic nitrogen species (ammonia
and nitrate). Moving downstream from
S-77 to S-79 ammonia decreased while
nitrate increased. In the East Basin
83% of the inorganic nitrogen is in
the form of ammonia, and 77% of the
West Basin's inorganic nitrogen is
nitrate. No seasonal trend is ap-
parent as illustrated in Table 15
(Miller et al. 1982).

Table 15. Average constituent concentrations during the wet (sum-
mer) and dry (winter) seasons (adapted from Miller 1980).

mg P/L mg N/L mg I
Wet Dry Wet Dry Wet Dry
STATION (summer) (winter) (sumner) (winter) (summer) (winter)

S-77 0.109 0.057 2.37 2.15 82.4 90.3
S-78 0.145 0.082 2.10 1.92 61.6 71.5
S-79 0.119 0.078 1.78 1.77 64.6 77.0

East Basin 0.161 0.109 2.90 3.10 77.9 77.4
West Basin 0.055 0.038 1.47 1.41 66.8 73.2

East Basin 0.112 0.064 2.29 2.07 74.2 78.9
West Basin 0.130 0.077 1.90 1.95 65.9 72.0

Chloride follows a trend be-
tween S-77 and S-79 that is the
opposite of the pattern observed for
phosphorus. Chloride decreases from
S-77 to S-78 and then increases to
S-79. Tributary flow is partially
responsible for this trend, particu-
larly in the West Basin. However,
the lower river increases did not
compensate for the upstream dilu-
tion, and chloride concentrations
at S-79 were generally lower than at
S-77. A seasonal trend showed slight
decreases of chloride concentrations
in the summer and high concentra-
tions in the winter. High chloride
concentrations are caused by salt-
water intrusion, particularly near
Franklin Lock, and by unplugged,
abandoned, and poorly constructed
wells that mix the poorer aquifer
waters (high in dissolved ions) with
surface or ground waters (Boggess
1972, Burns 1983).

Water temperature, pH, and
specific conductance are generally
well mixed along the vertical pro-
file, and only water temperature
showed a significant seasonal trend

that peaked in summer. Mean water
temperatures in the West Basin trib-
utaries are generally lower than
in the East Basin, particularly in
Jack's Branch and Cypress Creek,
where littoral and streambank vege-
tation shades much of the stream.

Dissolved oxygen profiles are
responsive to both flow and time of
year. Both East and West Basins ex-
hibit higher dissolved oxygen (DO)
concentrations in winter than sum-
mer. Generally, there is no vertical
stratification of DO in winter dur-
ing either high or low flow condi-
tions. A gradient forms in the sum-
mer during low flow but is rapidly
dissipated with an increase in flow.

Chlorophyll a concentrations,
which serve as a measure of phyto-
plankton, are usually higher in
the East Basin (McPherson and La
Rose 1982). Seasonal minimum con-
centrations of less than 10 mg/m3
during autumn and winter correspond
to seasonal low temperatures. In
May and early June concentrations
increase and reach a maximum mean

level of 40 mg/m3. Decreases of
nitrate and flow, in addition to
increases in water temperature, cor-
relate with increases in chlorophyll
a (Milleson 1980, McPherson and La
Rose 1982, Miller et al. 1982).
When chlorophyll a concentrations
reach a level that is visually
obvious it denotes an algal bloom.
This condition often results in a
massive die-off of the plankton,
and the subsequent decomposition
depletes the water of oxygen and
occasionally causes a fish kill.
One such algal bloom was observed in
the West Basin, adjacent to the Lee
County Water Treatment Plant, in
early June 1976 when concentrations
reached 753 mg/m3 (Milleson 1980).
The blue-green algal species Ana-
baena flosaquae and Microcystis
aeruqinosa dominated the bloom. Sub-
sequent blooms were reported In May,
June and July 1977 and June 1980
(Miller et al. 1982). In all cases
the bloom was reduced by freshwater
releases from Lake Okeechobee. The
relationship between chlorophyll a
and the rate of flow in the Caloosa-
hatchee River in late spring of 1978
is shown in Figure 34. Although
higher chlorophyll a levels are
reported annually in the East Basin,
the reported algal blooms are locat-
ed in the West Basin just upstream
from the Franklin Lock. One possible
reason for this is the presence of a
nutrient-rich, low-volume source of
water entering the Caloosahatchee
River between Alva and S-79 (Miller
et al. 1982). This supposition is
based on dramatic increases of the
river's total phosphorus, orthophos-
phorus, ammonia, and nitrate in the
4-mile reach from S-79 to Alva. The
increase is most pronounced in the
wet season and probably is caused by
agricultural runoff from intensive
flower nurseries and citrus groves
close to the river. The influence
of this runoff on the Caloosahatchee
River is a decrease of chloride



chlorophyll d


Figure 34. Algal
sured as mg of
m3 in the upper
hatchee River in
SFWMD 1980).

concentrations mea-
chlorophyll a per
and lower Caloosa-
1978 (adapted from

concentrations west of Alva.

The _agricultural pesticides
Aldrin, Dieldrjn, DDT, and chlordane
exceeded Florida Water Quality Stan-
dards in October 1979 at S-77 and
S-78 (Miller et al. 1982). In April
1981 only chlordane exceeded State
standards. Of the heavy metals only
total iron and zinc exceeded State
standards, on occasion.

Urban stormwater runoff from
Fort Myers, LaBelle, and other popu-
lation centers along the Caloosa-
hatchee River contribute suspended
and settleable solids, pathogenic
microbes, nutrients, heavy metals,
and pesticides (ESE 1977). Lead

A- 20 M0 1

Io 20

and mercury are among those metals
detected at relatively high concen-
trations. The effect that urban
stormwater has upon the Caloosa-
hatchee River is either poorly
documented near the major urban
center of Fort Myers or dwarfed by
the inflow of agricultural runoff
and Lake Okeechobee discharge.

4.2.2 Tidal Caloosahatchee River

The portion of the Caloosa-
hatchee River influenced by tides
extends about 45 km (28 mi) down-
stream from Franklin Lock to San
Carlos Bay (Figure 35). The upstream
portion is dominated by the Okeecho-
bee waterway, a channel maintained
at a 2.43 m (8 ft) depth. Sporadic

flow releases apparently have scour-
ed the channel to depths up to 6.7 m
(22 ft). At Orange River, about
11.3 km (7 mi) downstream from the
locks, the winding Caloosahatchee
River widens considerably. Dredged
bottom sediments are deposited on
either side of the channel from
Beautiful Island downstream to
the Highway 41 bridge, a distance
of about 9.6 km (6 mi). These
spoil deposits are more extensive
on the north side of the channel
than on the south side. The width
of the river in this section
averages 2.0 km (1.25 mi). The
cities of East Fort Myers and Fort
Myers are on the south bank, and
North Fort Myers is on the north

Figure 35. The tidally influenced portion of the Caloosahatchee River.

Water depths toward the middle
of the river exceed 1.82 m (6 ft)
beginning near the Highway 41
bridge. The Okeechobee waterway
is shunted along the south side of
the river near the Fort Myers Port
facilities. The depth of these
waters once averaged between 0 and
1.5 m (5 ft), but the average range
now is 2.4 to 3.3 m (8 to 11 ft).
The Caloosahatchee fixed bridge
is located 0.8 km (0.5 mi) down-
stream from the Highway 41 bridge.
On the north side of the river,
some prominent spits of land jut
out from the bank between the two

About 4.8 km (3 mi) below the
second bridge the river widens to a
maximum of 3.05 km (1.75 mi), then
narrows again at Fourmile Point.
Most of this oscillation in geogra-
phy is on the northern side of the
river, creating a broad, shallow
shelf, whereas on the south side
the main channel reunites with the
Okeechobee Waterway at depths from
2.7 to 4.3 m (9 to 14 ft). The
nearshore shelf of shallow water
is much less extensive along the
southern bank. The city of Fort
Myers continues along the southern
bank of this stretch and the eastern
end of the Cape Coral subdivision
lies on the north side.

From Fourmile Point to Shell
Point, a distance of about 18.5 km
(11.5 mi), the Caloosahatchee River
estuary oscillates in width between
1.6 and 2.9 km (1.0 and 1.8 mi).
The diversity of the depth contours
increases in this stretch, particu-
larly near Redfish Point. Islands
of shallow water (< 1.82 m) located
in deeper water suggests that some
strong and complex currents flow
toward the mouth of the estuary. A

third bridge traverses the estuary
near the midpoint of this segment,
connecting the relatively undevelop-
ed south bank with the extensively
canalized city of Cape Coral sub-
division along the northern bank.

Water movement in the Caloosa-
hatchee River estuary has not been
extensively studied. Two attempts
to model water flow and quality
in the estuary have produced only
limited information on flushing
characteristics and circulation
patterns. The straight and narrow
shape of the estuary and the well
controlled inflow at its upstream
boundary suggests ideal conditions
for testing general textbook theo-
ries of estuarine hydrodynamics.
Longitudinal profiles of salinity
and temperature tend to confirm that
there is a distinct increase in
salinity downstream in the estuary,
which varies with the season and the
rate of freshwater inflow (Figure
36a to 36c).

In a detailed study of salini-
ty, DeGrove (1980) was unable to
demonstrate a convincing agreement
between observed and calculated
isohalines along the length of the
estuary from Fort Myers to Shell
Point. Water masses frequently
appear oriented in a direction oppo-
site to that predicted, suggesting
that movement patterns are much more
complex than the model was able to
depict. Limited synoptic data on
tidal relations and water quality
along the length of the river also
ruled out model development. During
low flow the author estimated a
retention time of about 25.3 days
for particles traveling over the
length of the estuary between Fort
Myers central sewage plant discharge
and San Carlos Bay.


Figure 36. Temporal variations in
salinities and water temperature
along the Caloosahatchee River
(adapted from Post, Buckley, Schuh
and Jernigan, Inc. 1976).

Because the estuary is so long
(45 km or 28 mi), it is conceivable
that different sections may be
responding to different local condi-
tions. At the upstream boundary,
lock operations may complicate
expected flow and tidal patterns.
A change in the orientation of the
estuary's axis may influence tidal
movement. Axis orientation relative
to wind direction also causes dif-
ferent hydraulic effects at differ-
ent locations. The location of
causeways, tributaries, extensive
urban centers, and canals also in-

111n " na-tm-l 11_ wl%

fluence the characteristics of local
hydraulic conditions by changing
water storage capacity, velocity,
and runoff.

Water quality in the Caloosa-
hatchee River estuary has been
studied by a number of agencies from
1973 to 1981. Yet routine monitor-
ing of background conditions at
fixed locations is generally lack-
ing. Data collected from synoptic
surveys for specific purposes, such
as the allocation of domestic waste-
loads, is the prevailing information

Water quality data from three
surveys from October 1975 to Feb-
ruary 1976 were reported by Post,
Buckley, Schuh and Jernigan, Inc.
(1976). Their sampling included
transects at eight locations along
the axis of the estuary in addition
to grab samples at selected stations
between the transects. These samples
were taken largely to help model
the dissolved oxygen balance of the
estuary. A summary of the data
collected on these surveys is given
in Figure 37.

In all three surveys the data
reveal a rise in dissolved oxygen
concentration from 12.8 to 16 km
(8 to 10 mi) downstream from the
Franklin Locks and Dam. In October
and December, in the upper reaches
of this segment, concentrations of
dissolved oxygen are generally less
than 4.0 mg/I. A relatively intense
mixing between salt and fresh waters
was observed about 17 km (10.5 mi)
downstream. Upstream from the mix-
ing zone, tidal dampening of river
flow increased residence time,
which increased the probability of
oxygen deficits in the water column.
Because of salinity increases down-
stream, the solubility of oxygen and
dissolved (DO) oxygen decreased.

R4.0fl22m0 FOsnjur M oM se,.od 0,, r W.RFfmli"i,
1 1 1ri00 1 0 I
OCTOBER 30197 aS

c00o~o C -- 4^
N0__o0 ------ --3

. .. -.. .....--....

0 3
\ 40

!--- 1" 0

.1-. AN, 2AMI '
^"^~ ~ --o 5 . ^ o ,

or". ^5 A t t )
oo o )9 ifr



Figure 37. Temporal variations in
water quality data along the Ca-
loosahatchee River (adapted from
Post, Buckley, Schuh and Jernigan,
Inc. 1976).

The average water temperature
in December was about 5C less than
in October, and salinity increased
slightly. The flow in December
dropped sharply, which increased the
residence time of upstream waters.
Higher salinities and resident times
in upstream waters, and lower water

temperatures (and consequently lower
metabolic rates) apparently lowered
DO near the locks. From the locks
to a point 16 km (10 mi) downstream,
the DO increased and seaward of this
point the DO level remained stable.

Continued low flows and low
temperatures by February created a
semi-steady-state condition in which
oxygen concentrations hovered near
4.5 mg/I at the locks and rose fair-
ly rapidly to 7.0 mg/I downstream.
The prolonged suppression of meta-
bolism in cooler waters combined
with increased settling of oxygen
demanding materials (BOD, COD)
during low flow is believed to be

Carbonaceous oxygen demand
(CBOD20) along the estuary
follows a pattern opposite to DO;
the 17 km (10 mi) point appears
to be an inflection point. This
pattern is least obvious in October
when levels of CBOD20 are nearly
uniform along the estuary axis. In
December and February there is a
distinct tendency for CBOD20 to
decline with distance seaward of
this point. Nitrogenous oxygen
demand (NBOD20) also shows a
tendency to decrease with distance
from the Franklin Lock, but this
pattern is less obvious. NBOD20
levels are highest in October
and December and uniformly low in

The seaward changes of dissolved
oxygen, CBOD20, and NBOD20 indi-
cate a conspicuous convergence of
physical and chemical conditions
about 16 to 17 km (10 mi) downstream
from Franklin Lock. This reach is
where the upper Caloosahatchee River
estuary widens. From 19 to 21 km
(12 to 13 mi) the upper estuary is
constricted by two bridges. The
area between receives Inflow from
the Orange River and the city of

Fort Myers waste discharge. These
conditions tend to promote relative-
ly high algal productivity (Figure
38). During high nutrient inflow
(wet season), moderate salinity, and
high temperature, chlorophyll a in
this area may reach bloom concentra-
tions (250 mg/I). In winter and
early spring when river flow and
temperature are low, and salinities
are high, chlorophyll a concentra-
tions tend to be lower (PBSJ 1976).

An analysis of water quality in
the tidal Caloosahatchee River indi-
cates that there are five major
sources of pollution (DeGrove 1981).
These are the downstream flow from
Franklin Lock, the Orange River in-
flow, the Fort Myers sewage treat-
ment plants (central & southern
plants), the Cape Coral subdivision
and sewage treatment plant, and the
Waterway Estates sewage treatment
plant. Most of these areas or loca-
tions are shown on Figures 31 and
35. According to DeGrove (1981) all

R edfish Point F -u M ile Point E diso In
--- -.M.
| 1 Bridge

Eo-kAlla I

Figure 38. Chlorophyll a concentra-
tions in the Caloosahatchee River
estuary (adapted from Post, Buckley,
Schuh and Jernigan, Inc. 1976).

but one of the sewage treatment
plants are required to cease sur-
face-water discharge in the near
future. The remaining plant, Fort
Myers south, is required to treat
and discharge effluents that will
not cause total phosphorus concen-
trations to exceed 0.165 mg/I and
total nitrogen to exceed 1.1 mg/1.
Degrading influences from surround-
ing urban and agricultural nonpoint
sources may be somewhat curbed
through implementation of the recent
stormwater permitting requirements
and voluntary "best management"


Relatively little is known
about hydrology and water-quality
dynamics in the Estero Bay water-
shed. Information on tides, physi-
cal/chemical characteristics, and
nutrients in the northern bay were
reported by Tabb et al. (1974). A
report on water quality in the bay
was made by Duane Hall and Asso-
ciates (1974), and reports on salin-
ity and temperature in the central
and southern bay were provided by
Jones (1980). Data on tides, cur-
rents, and runoff were summarized by
Estevez (1981). In addition, the
Florida Department of Environmental
Regulation (FDER) maintains a water
quality monitoring station at San
Carlos Pass, a major inlet to Estero

Freshwater inflow into the Es-
tero Bay estuary generally peaks in
September (Kenner and Brown 1956).
Flows measured in the Imperial River
from 1940 to 1952 indicate that flow
in the dry months (December to May)
averages only about 7% of the total
annual inflow. Virtually no publish-
ed information on the quality of
this or other freshwater inflow into
Estero Bay is available.

Tidally induced flows in Estero
Bay are far greater (volume and
velocity) than the freshwater inflow
(Jones 1980). The generally mixed
type tides average about 0.54 m
(1.75 ft), or 0.94 times those of
the open coast (Estevez et al.
1981). At the three major passes
between the bay and the Gulf of
Mexico, flood tides can be as high
as 1.07 m (3.5 ft). Velocities in
the pass range from 0.64 m/s (ebb)
to 1.52 m/s (flood). Tidal prisms
(ft3) calculated at the three
major inlets to Estero Bay are shown
in Table 16.

Freshwater inflow into Estero
Bay is so low that even in its upper
reaches salinities seldom fall below
10 ppt in the wet season. In the
dry season, tidal flushing and
freshwater inflow from ungaged
sources apparently is sufficient to
prevent widespread hypersalinity.
Water samples taken over a year's
time at 20 stations in the northern
and central bay revealed salinities
as high as 34.0 ppt (Tabb et al.

Concentrations of inorganic ni-
trate (NO3) and phosphate (PO4)
in the north and central bay are
relatively low. Nitrate ranges from
0 to 0.10 mg/l in the bay and
phosphate ranges from 0.02 to 0.26
mg/1 (Tabb et al. 1974). Concen-
trations of both tend to decrease
toward the Gulf.

Table 16. Tidal prisms in Estero
Bay on February 8, 1976 (adapted
from Estevez 1981).
Big Hickory Pass 1.20 x 100
New Pass 2.71 x 108 2.02 x 108
Bit Carlos Pass 8.19 x 108 5.75 x 108


The drainage areas of the
Golden Gate Canal, Gordon River,
Cocohatchee River Canal, Henderson
Creek Canal, and the Fahka Union
Canal are depicted in Figure 39.
The Fahka Union Canal is the largest
of the artificial drainage systems,
averaging about 30 m (100 ft) in
width and just less than 2.4 m
(8 ft) in depth over a distance of
about 48 km (30 mi). The Golden
Gate Canal is similar in width and
depth but is slightly shorter, 41.6
km (26 mi). The Henderson Creek
and Cocohatchee River Canals are
smaller, averaging 7.6 m (25 ft)
in width, less than 1.5 m (5 ft)
in depth, and 11.2 and 20.8 km (7
and 13 mi) in length, respectively
(McCoy 1972).

Figure 39. Canals in western Collier
County (adapted from McCoy 1972).

Downstream freshwater flow
through this extensive maze of ca-
nals is partially controlled by a
set of 30 weirs ranging in elevation
from 5.16 to 0.6 m (17 to 2 ft)
above mean sea level (msl). These
weirs are designed to prevent exces-
sive drainage during the dry season.
All canals except the Cocohatchee
and Henderson Creek are controlled
by at least one weir.

During the dry season, the
Cocohatchee River Canal drains the
area southwest of Lake Trafford.
During the extremely dry years,
e.g., 1971 and 1974, no flow is
reported (USGS 1980). Outflow from
the canal has averaged 0.82 m3/s
(29.1 cfs).

During very wet periods, the
Cocohatchee River Canal functions as
an overflow valve for excess drain-
age from the Golden Gate area to the
south. Maximum discharge from the
Cocohatchee River Canal is 15.3
m3/s (542 cfs), in August, 1973.
The average peak velocity is 0.4 m/s
(4.3 ft/s) as compared to an average
velocity of 0.02 m/s (0.23 ft/s).

The Golden Gate area and the
Cocohatchee River Canal basin ap-
parently draw from the same water
table. The construction of weirs
W-4 and W-8 in the Golden Gate Canal
in 1964 correlates with an unexpect-
ed rise in the water table at the
Cocohatchee Canal outlet. The water
table at the Cocohatchee River Canal
well rose higher in the 1965 rainy
season than in the two previous
rainy seasons, even though rainfall
in 1965 was below average (McCoy
1972). At the same time, inland
construction of Golden Gate Estates
canals diverted upstream drainage
away from the Cocohatchee River Ca-
nal, effectively reducing peak water
levels and flows downstream. The
net effect of these hydraulic shifts

is that the Cocohatchee River Canal
becomes both a supplier of water to
the Golden Gate area during low flow
and a discharge valve for Golden
Gate Estates during high flows.

the Golden Gate canal was con-
structed in the early 1960's in an
attempt to reduce the hydroperiod of
a vast tract of land known as Golden
Gate Estates. Simultaneously, the
tract was platted and rezoned for
residential development; roads and
auxiliary canals were constructed,
and the land was offered for sale.
In conjunction with concerns over
the environmental effects of such
massive drainage, Collier County
officials in about 1970 initiated
actions to revise the earlier devel-
opment plan. In addition to the
alteration of natural habitats,
there were other shortcomings in the
plan. A typical graph of water
levels in a well 1.12 km (0.7 mi)
from the Golden Gate Canal is shown
in Figure 40. This graph clearly
demonstrates that the Golden Gate
Canal drained these former wetlands
and lowered the water table.

To the southeast of the Golden
Gate Canal, a second grid-like se-
ries of canals was also constructed
in the early 1960's as part of the
same residential development. These
canals, which culminate in the Fahka
Union Canal, discharge into the Ten
Thousand Islands area. The canals
were designed to drain the Remuda
Ranch Grants, a large section of
former wetlands south of State Road
838 (Alligator Alley).

Between these two larger net-
works of canals, a third drainage
way, the Henderson Creek Canal,
flows south/southwest from the
Golden Gate Estates to the Gulf of
Mexico. Like the Cocohatchee River
Canal, Henderson Creek Canal serves

1967 1968
Figure 40. Water levels near the Golden Gate Canal (adapted from Klein
et. al. 1970).

as an overflow valve for Golden Gate
Estates during peak wet periods.

During the dry season (November
to May) most or all of the flow in
the upstream end of the Golden Gate
Canal system may recharge the shal-
low ground-water aquifer. Surface
discharge during the dry season
ranges from 0.28 to 1.27 m3/s
(10 to 45 cfs). Further downstream
dry season flows range from 0.28 to
3.4 m3/sec (10 to 120 cfs). At
Naples reports of no flow were com-
mon in 1975, but on the average,
flows of 1.70 to 8.5 m3/s (60 to
300 cfs) are released to the Gordon
River/Naples Bay estuary during the
dry season. Dry-season flows in
the Henderson Creek Canal range from
0 to 0.71 m3/s (0 to 25 cfs) and
in the Fahka Union Canal, the range
is from 1.27 to 3.54 m3/s (45 to
125 cfs). The ranges and extremes
of wet-season flow in these three
canals are given in Table 17.

The seasonal characteristics
and magnitude of water discharges
from these canals have profound
effects on regional hydrology and
ecology. Tabb et al. (1976) esti-
mate, through a simplified mass bal-
ance technique, that during average

rainfall years there is little if
any surplus runoff from the water-
shed canals. Based on the saturation
capacity of the soils and monthly
rainfall, hydroperiod is estimated
at between 4 and 6 months. These
figures agree well with observations
of long-term residents. These
canals, since their construction,
have effectively drained off surface
waters, shortened the hydroperiod by
about 4 to 6 months, and lowered
groundwater recharge.

A number of topographic clues
suggest that the area underlying the
Golden Gate and Henderson Creek
Canal drainage basins is relatively
impermeable to recharge. Tabb et al.
(1976) call this area the "Golden
Gate Highlands" (Figure 41) and rea-
son that its impermeability is due
to an underlying caprock of the Fort
Thompson Formation. These authors
speculate that recharge of this area
is more likely due to lateral inflow
through cavernous subterranean lime-
stone channels which undergo solu-
tion by acidic fresh waters, rather
than through direct downward seep-
age. The presence of actively form-
ing karst topography is strongly
suggested by Deep Lake (30 m or 97
ft in depth) on the east of the

Table 17. Wet-season flow ranges and extremes for Golden Gate
Canal, Henderson Creek, and Fahka Union Canal.

Wet season
Flow Range Extreme
m3/sec (CFS) m3/sec (CFS)
Golden Gate Canal
Upstream 0.6 2.8 (22-100) 5.1 (181)
Mid reach 1.1 10.5 (40-370) 20.2 (714)
Downstream 3.0 18.7 (105-660) 98.1 (3,460)

Henderson Creek 0.4 0.8 (16-30) 10.0 (353)

Fahka Union
Upstream 0.4 1.1 (15-42) 4.5 (160)
Mid reach 1.4 7.4 (50-260) 10.3 (362)
Downstream 2.8 17.0 (100-600) 90.7 (3,200)

Highlands and a well-defined line of
cypress strands running along their
S.. western margin. These strands are
Sunderlain by deep sands in eroded
.' 'solution channels that are believed
SGod.nGat.e"Highlands" -+ to have connections with deeper
I channel systems.
The area along the eastern
perimeter of the "Highlands" acts as
L a kind of leaky roof for recharging
the underlying aquifer to the west.
The Golden Gate Highlands is less
S- permeable to seepage flow because of
a shallow Fort Thompson caprock that
I overlies deeper Tamiami caprock Of
Sense clays. Removing upstream sur-
i? ,I face waters via canals may therefore
SI ...... l..... ....... amplify the loss of recharge to
I the down-gradient aquifer by short-
41 Li circuiting the leaky roof connec-
Gulf tion. Tabb et al. (1976) estimated
Mof that the construction of the 293 km
Mexico (183 mi) of Golden Gate Estates
D. canals accelerated the rate of
__ __..._- _ _drainage of stored water to about
16 times normal.
Figure 41. The Golden Gate High-
lands area (adapted from Tabb et al. To the south, the Highlands
1976). is drained by what is known as the

Gulf American Corporation (GAC)
canal network into Fahka Union Canal
and Fahka Union Bay. The area
drained by the GAC canal network is
also known as the Remuda Ranch
Grants. The borrow canal of State
Road 84 (Alligator Alley) cuts
across this canal system and con-
nects with the Golden Gate Estates
canals and Henderson Creek Canal.
Further south the Tamiami Canal also
crosses the Fahka Union. Ground-
water levels here have been lowered
approximately 61 to 122 cm (2 to
4 ft) by the more extensive region-
al drainage canals (Klein et al.

To the north and west of the
GAC canal network are five major
strand systems, the Deep Lake
Strand, Okaloacoochee Slough, Fahka-
hatchee Strand, Roberts Lake Strand,
andGumSlough(Flgure31). Although
not directly within the Golden Gate
Estates canals, the Camp Keasis
strand is close enough to the re-
gional drainage system to be affect-
ed by it.

Okaloacoochee Slough begins
near the Hendry-Collier County line
and runs southwest to near Alligator
Alley. Here there appears to be a
short discontinuity between the
slough and Fahkahatchee Strand to
the south, although both Carter et
al. (1973) and Tabb et al. (1976)
believe there is a hydrologic con-
nection between them. The Okaloa-
coochee Slough is crossed in the
north-south direction by the Barron
River Canal and the Fahkahatchee
strand is crossed by the east-west
borrow canal of Alligator Alley.

The hydrology of the Fahka-
hatchee strand was monitored by
Carter et al. (1973) from 1970 to
1972. These authors reported the
curious phenomenon of relatively

high flows emanating from the strand
during 2 years of below normal rain-
fall, followed by a low discharge
during a year of high rainfall. Even
more curious was that ground-water
levels during the high rainfall/low
runoff year decreased rather than
increased, indicating seepage to
deep storage. The easternmost GAC
canal intercepted water from the
Fahkahatchee strand and effective-
ly lowered ground-water levels as

Fresh ground water for domes-
tic, agricultural, and industrial
purposes In the Golden Gate's
Estates canals came from a shallow
unconfined or semi-confined aquifer
(Jakob 1983). The permeable lime-
stones and sands of the Pleistocene
and the upper permeable limestones
of the Miocene-Pliocene Tamiami
Formation are the major components
of the shallow aquifer. The maxi-
mum depth of the aquifer is 39.6 m
(130 ft) near the city of Naples.
It tends to thin toward the north-
east, east, and southeast (McCoy
1962, 1972; Jakob 1983).

Water-quality data in the
Golden Gate Estates canal drainage
area was reported by Little et al.
(1970), McPherson (1970), Carter et
al. (1973), Tabb et al. (1976), and
ESE (1978a). The most prominent in-
fluence on natural background water
quality is rainfall. During the wet
season, abundant rainfall dilutes
most chemical substances, whereas
diminishing rainfall in the dry sea-
son concentrates the sediments and
chemicals in solution. Superimposed
on this cycle are the effects of
drainage canals that tend to alter
the magnitude and timing of natural
flow. Localized variations due to
land use, uneven rainfall distribu-
tion, and inherent physiographic
differences also are evident.

Some water-quality character-
istics, such as conductivity and
chloride concentration, generally
follow the wet/dry season cycle
described by Carter et al. (1973).
Conductivity, which reflects the
ionic content of the water, in-
creases in the dry season as inor-
ganic constituents become more
concentrated. Near the coast the
effect is amplified by the inland
migration of salt water. If uncon-
trolled, canals tend to amplify this
inland migration by providing more
rapid access to coastal aquifers.
The use of weirs and earthen dams
reduces this problem. Wimberly
(1973, 1974) reported short-term in-
creases in conductivity and chloride
concentration near oil-exploration
sites, but no detectable effects at
oil-producing sites.

Other water-quality character-
istics, such as alkalinity, may also
decrease during the wet season but
are strongly influenced by local-
ized drainage (Little et al. 1970).
Canals may release more buffered
ground water into the surface water
drainage system than do uncanalized
sloughs. The water at all canal
stations is higher in alkalinity,
on the average, than at slough sta-
tions (Carter et al. 1973). Little
et al. (1970) also reported higher
levels and greater variation in
alkalinity, hardness, and sulfate at
canal stations. Increased ground-
water influence is again believed

Although pH fails to show any
distinct variation during the gen-
eral wet/dry season cycle, water
color does. Drainage of organic
tannin and lignin-like substances
from swamps during the wet season is
believed to be responsible for this
increase. Apparently the buffering
capacity of surface waters is suf-
ficient to mask seasonal variations
in pH.

Relatively little information
exists on dissolved gases, nutri-
ents, and organic matter from the
Golden Gate Estates canals. Tabb
et al. (1976) report oxygen concen-
trations of 4.2 to 5.4 mg/l during
October 1976 and 3.3 to 7.0 mg/I in
January 1976. Depth of the canal is
a major factor influencing oxygen
concentrations. Deep canals are fed
more by low-oxygen ground-water than
shallow canals. Nitrate concentra-
tions ranged between 0.45 and 1.00
mg/I in October and from 0.60 to
0.75 mg/I in January. Total phos-
phate ranged from 0.04 to 0.21 mg/I
in October and 0.17 to 0.38 mg/I in
January. Once again, higher and more
variable nitrogen and phosphorus
levels are reported from canal sta-
tions than from slough and strand
stations (Little et al. 1970).

Diurnal oxygen and temperature
curves from four locations in the
Corkscrew Swamp are presented in
Figure 42. The cypress locations
and the "pond with floating vegeta-
tion cover" display characteristi-
cally little variation because of
shading. The relatively more open
sawgrass marsh has a more distinct
diurnal cycle, although DO levels
are clearly below saturation. Diur-
nal variations of DO are greatest
in open, mixed-marsh environments
where daily ranges of 7.0 to 7.5
mg/I have been recorded (Duever
et al. 1975).

To the south, in the GAC canal
network, Fahka Union Canal, and
Fahkahatchee Strand, highest oxygen
concentrations have been reported
in March to June at most stations
(Carter et al. 1973), with the
lowest concentrations in September
to October. Fahka Union Canal
station samples were consistently
higher in dissolved oxygen than
water samples from strand stations.
The authors attribute this phenome-
non to higher flow rates and the

SMALL CYPRESS DI..olved ox ygen -



I ----------.


2 1

0000 0400 OOO 1200 100c 2000 24oo00
Figure 42. Diurnal dissolved oxygen
and temperatures for Corkscrew
Swamp, September 1975 (adapted from
Duever et al. 1975).

abundance of aquatic vegetation in
the canals compared to the slower
moving, more shaded waters of the

Water temperatures in shaded
strands and sloughs average about
1.1C (2F) below those in mo e open
canal waters (Little et al. 1970).
This condition could help bring
about lower oxygen concentrations in
canals. Where dense mats of floating
aquatic vegetation thrive in shallow
canals (e.g., Tamiami Canal), oxygen
concentrations, and diurnal varia-
tion may be similar to that in
strands and sloughs.

Comparisons show that the
annual transport of total Kjeldahl
nitrogen (TKN), total phosphorus
(TP), and total organic carbon (TOC)
from the Fahka Union and Barron

River Canals is much higher than
from the relatively undisturbed
Fahkahatchee Strand (Carter et al.
1973). Canals cause a shift in the
timing and relative magnitude of
the delivery of nutrients to the
estuary and an accelerated loss of
water, nutrients, and organic matter
from the uplands.

Most authors who have studied
the water quality of the Golden Gate
Estates canal waters agree that me-
tal and pesticide pollution was not
a problem, nor were mercury, copper,
chromium, arsenic, and nickel de-
tected in the water column in the
GAC canals or the Barron River Canal
(Carter et al. 1973). Zinc and lead
were only rarely detected. Iron con-
centrations ranged from 100 to 1,150
mg/I, but this is not considered
unusual. Wet-season copper concen-
trations in the GAC canals ranged
from 0.20 to 0.30 mg/I (Tabb et al.

Little et al. (1970), Carter
et al. (1973), and Duever et al.
(1978) attribute occasional higher
than normal levels of aluminum,
copper, lead, and zinc to locally
intense vehicle use, urban construc-
tion, and agriculture.

The six estuaries within the
Golden Gate Estates area from north
to south are as follows:
(1) Wiggins Bay at the down-
stream end of the Cocohatch-
ee River; Wild Turkey Bay
and Naples Park lie to the
south of Wiggins Pass.
(2) Naples Bay surrounded by the
city of Naples; Dollar Bay
to the south of Gordon Pass
is considered a part of the
same system.
(3) Rookery Bay, a National
Audubon Society Wildlife
Sanctuary lying downstream
of Henderson Creek directly
behind Marco Island.

(4) The Marco Island estuary
within and surrounding Marco
Island and Cape Romano.
(5) Fahka Union Bay downstream
of the Fahka Union Canal.
(6) Fahkahatchee Bay downstream
of Fahkahatchee Strand.
Gullivan Bay refers to the
embayment behind Cape Romano
and seaward of the Ten Thou-
sand Island area of Fahka
Union and Fahkahatchee Bays.
Very little information is available
on the hydrology and water quality
of Wiggins Bay and Gullivan Bay:
consequently our discussion is

The monthly average water flows
in the Cocohatchee River Canal,
which drains into Wiggins Bay, are
given in Figure 43. Flows from
November to June average less than
0.56 m3/s (20 cfs). Beginning in
July average flows increase, reach-
ing a peak in September (mean = 3.05
m /s or 109 cfs). The convoluted
topography of the natural drainage-
ways and the construction of finger
canals slow the flushing of bay
water through Wiggins Pass.

The existing physical/chemical
quality data on the Wiggins Bay sys-
tem were summarized by ESE (1978a).
Salinities in April and June are
close to those of the Gulf (27.2 to
33.9 ppt). During September, at the
peak of the wet season, salinity
ranges between 17.9 and 21.9 ppt.
Average monthly water temperatures
are 23.10C in April, 30.10C in June,
and 29.5C in September.

The Naples Bay estuarine system
receives freshwater input from the
Golden Gate Canal, the Gordon River,
Haldeman Creek, and Rock Creek. Of
these four, only the Golden Gate
Canal is equipped with a flow gaug-
ing device. Monthly average flows

Figure 43. Average monthly flow
(cfs) in the Cocohatchee River Canal
(adapted from ESE 1978a).

emanating from the Golden Gate Canal
are shown in Figure 44. Toward the
south, Naples Bay connects to the
Gulf through Doctor's Pass and to
Rookery Bay via the Intracoastal

According to van de Kreeke
(1979) salinities upstream from the
U.S. Highway 41 bridge approach zero
during high flow (August to Septem-
ber). The middle section of Naples
Bay may average as low as 20 ppt.
Restricted water exchange between
the mid and upper bay causes salini-
ties to decrease rapidly above the
bridge. Salinity stratification
tends to increase toward the south-
ern end of Naples Bay. The frequent
variations in freshwater inflow and
the short distances within the bay




J F M A M J J A S 0 N D
Figure 44. Average monthly flow
(cfs) in the Golden Gate Canal.

relative to tidal excursion general-
ly preclude stable flow and circula-
tion patterns. Tidal excursions of
4,000 to 6,000 m (4,376 to 6,564 yd)
are estimated for the open portion
of Naples Bay.

One of the more prominent
factors influencing Naples Bay
hydrology and water quality is the
extensive network of finger canals
carved out of the once mangrove-
lined tidal creeks that border the
bay system. The extensive dredge-
and-fill activity, along with shore-
line development, has created a very
irregular bathymetry in and around
the periphery of the bay.

Eight types of canal develop-
ment are based on canal width,
length, depth, proximity to one
another, and type of shoreline sta-
bilization (Figure 45), according to
van de Kreeke (1979). All canal

developments except Port Royal (A)
and Aqualane Shores I (C) exhibit
numerous finger canals branching
off from the main canals. Many of
the finger canals are deeper at
their heads than at their mouths,
effectively trapping high-salinity

In attempting to model the
hydrodynamics of Naples Bay, van de
Kreeke (1979) found that observed
tide ranges and currents fit reason-
ably well with predicted values. A
consistent error in predicting time
lags during flood-tide cycles was
believed to result from underesti-
mating the amount of water storage
capacity in the natural mangrove
areas and small canal systems.

Current velocities and circula-
tion patterns within the canal sys-
tems are extremely complex. Canal
velocities often are larger than
predicted (Monopolis 1978). Winds
are discounted as an important
factor. Rather, current reversals
within the vertical velocity profile
and the existence of lateral cross-
canal currents suggests that the
main driving force is oscillating-
density currents induced by salinity
fluctuations in the main bay. These
oscillating salinities along the
axis of Naples Bay are considered
essential to flush the peripheral
canal systems (van de Kreeke 1979).
In addition, flushing of canals is
highly dependent upon their length
and bathymetry. Shorter canals
exhibit an exponential flushing
curve whereas longer canals show a
level curve for a time, then an
exponential curve as the dye mass
reaches a critical excursion length.
Typical canal flushing curves are
shown in Figure 46.

Water quality in the Naples Bay
estuary is reported by Hicks (1979)
from December 1976 through November

With respect to construction and geometry
DAM the canals connected to Naples Bay are
GORDON GOLDEN GATE CANAL divided into different groups:
RI ER A. Port Royal
41 typical length 1800 m; typical width 70 m
depths vary between 2 m and 6 m
shoreline protected by rip-rap
no finger canals
B. Aqualane Shores I
typical length 700 m; typical width 50 m
typical depth 1.5 m
shoreline protection: mixture of
a *vertical sea walls and rip-rap
finger canals
N I C. Aqualane Shores II
SROCCREEK typical length 700 m; typical width 20 m
typical depth 1.5 m
shoreline protection: mostly wooden
and concrete vertical sea walls, some
areas unprotected
411 no finger canals
E D. Rock Creek
typical length 500 m; typical width 30 m
c NAtE typical depth 0.6 m
DAY shoreline protection: vertical sea
H walls
GUL finger canals
OF AOEMANCREE E. Boat Haven/Golden Shore/Oyster Bay
OF typical length 400 m; typical width 20 m
W \EXCO B typical depth 0.4 m
shoreline protection: vertical sea
wall, rip-rap, natural
finger canals
F. Oyster Bay
typical length 500 m; typical width 20 m
typical depth 0.7 m
shoreline protection: vertical
concrete sea walls
fA inger canals
o 1000 G. Royal Harbor
I typical length 750 m; typical width 20 m
METERS typical depth 1.2 m
shoreline protection: vertical
concrete sea walls
finqer canals
H. Haldeman Creek
typical length 250 m; typical width 20 m
typical depth 0.4 m
shoreline protection: vertical sea
walls, rip-rap, natural
finger canals
Figure 45. Types of canal development in the Naples Bay area (adapted
from van de Kreeke 1979).

1977. Water sampling and analysis
was designed to focus on metabolism
in the bay as opposed to levels of
toxins such as pesticides or heavy
metals. Seasonal and diel trends in
selected physical/chemical constitu-
ents in both water and sediments
were analyzed from samples taken
throughout the bay system.

Salinity and water temperatures
in Naples Bay generally exhibit a

typical response to freshwater in-
flows and air temperature. For
salinity, vertical stratification is
often evident even during the wet
summer season. This stratification
is amplified by freshwater inflow
and restricted circulation; con-
sequently, the head ends of slow-
flushing canals frequently exhibit
a high degree of salinity stratifi-
cation, particularly during the
summer, when freshwater from urban/

75 \O
J 25 \.
Z 0 ---,--

S75 \
50 \

LU 75
50 -

residential runoff tends to "float"
on the more dense, higher salinity
canal waters. Restricted circulation
combined with the density differen-
tial also tends to inhibit gas ex-
change, thereby leading to dissolved
oxygen stratification. The rate of
oxygen consumption in the lower
water mass often exceeds the rate of
oxygen supply, leading to increas-
ingly anoxic conditions toward the
bottom. Hicks (1979) associates
substandard (< 4.0 mg/I) oxygen
concentrations with canal depths
greater than 1.45 m (4 ft).

A summary of salinity, tempera-
ture, and dissolved oxygen in August
1977 at selected locations in Naples
Bay show that salinity and dissolved
oxygen are most variable at the
canal stations (Table 18). The most
moderate and highest average concen-


WIDTH .18.5 m



WIDTH- 46m



Naples Bay (adapted

trations of oxygen occur at the
relatively well-flushed lower bay

During the year of study (1976
to 1977), the seasonal cycles of
inorganic nitrogen and phosphorus
abundance appeared to be reciprocal
to one another in the Gordon River-
Naples Bay system. Inorganic nitro-
gen, particularly NO2-NO3, cor-
relates fairly well in waters with
localized urban runoff. Ground-water
inflow during winter months (when
north winds tend to drain the bay)
is also cited as a possible cause of
reduced nitrogen (NH3) input to
the bay, where the more oxidizing
environment favors conversion to
N02-NO3. Organic nitrogen, on
the other hand, appears to peak
in response to upland runoff during
the wet season. Phosphorus tends

20 o 0 100 140
Figure 46. Typical canal flushing curves in and around
from van de Kreeke 1979).

Table 18. Salinity, temperature, and dissolved oxygen in Naples Bay,
August 1977 (adapted from Hicks 1979).

DO (mg/1) % Sat. Salinity (%) Temperature (OC)
Gordon River 4.3 52 0.4 27.6
(upper) (2.8 5.3) (0.2 0.7)

Mid Bay 4.2 57 13.1 27.6
(1.9 7.6) (4.7 32.9)

Lower Bay 4.9 73 28.0 29.2
(2.3 6.4) (8.1 35.2)

Canals 3.8 56 18.5 29.5
(0.0 12.6) (2.9 35.8)
Numbers in parenthesis represent ranges in parameters.

to peak in the dry season in some
areas, probably in response to point
source inputs.

Nitrogen and phosphorus both
tend to reach highest concentrations
at the head end of the Gordon River.
Concentrations typically decrease
longitudinally toward the gulf. The
longitudinal decline in nitrogen
is probably due to dilution by gulf
waters, whereas the phosphorus
decline is probably due to a combi-
nation of dilution and settling
(Hicks 1979). Sediment concentra-
tions of phosphorus tend to increase
after the wet season, suggesting
flocculation and settling of phos-
phorus imports.

Consistent with the hydraulic
assessment of van de Kreeke (1972a),
Hicks (1979) reports a close corre-
lation between certain chemicals in
the main axis of the estuary and
nearby canals. The canals often act
as carbon traps, importing organic
matter from the river estuary but
not returning it in equal quantity.
Chemical concentrations in short
canals tend to be more closely cor-
related with river concentrations

than do concentrations in long

A distinct vertical stratifica-
tion of total organic carbon (TOC)
is reported by Hicks (1979) in
Naples Bay canals. Concentrations
are relatively high near the sur-
face, lower at mid-depth, and high
again on the bottom. This layering
is believed to be caused by salinity
stratification and deprives Naples
Bay of a useful detrital food source
by prematurely shunting surface
waters to the gulf (Hicks 1979).

Chlorophyll a, like nitrogen
and phosphorus, generally exhibits
a longitudinal decrease in concen-
tration from the head end of the
estuary to the gulf. Peak seasonal
concentrations of chlorophyll a cor-
respond with peak salinity and low
flow. Mean annual concentrations at
canal stations range from 9.5 to
31.0 mg/m3 with a maximum of 87.2
mg/m3, and at river stations range
from 9.7 to 28.9 mg/m3 with a max-
imum of 111.2 mg/ml. The frequency
of algal blooms in the river and bay
decline with the onset of wet-season

runoff. Blooms in canals tend to ex-
tend into the wet season because of
restricted mixing with bay waters.

The Rookery Bay estuary (Figure
47) receives freshwater inflow from
Henderson Creek to the west and
Stopper Creek to the northwest.
Monthly average flows in Henderson
Creek are presented in Figure 48.
Johnson Bay to the south of Rookery
Bay also is considered a part of the
estuary although it is not part of
the Audubon Sanctuary. On the
seaward side, Rookery and Johnson
Bays are bordered by mangrove-
covered islands and long channels
that extend to Little Marco Pass and
Hurricane Pass on either side of
Little Marco Island. Keewaydin
Island is a barrier island lying
seaward of Little Marco Island.

The relatively small size of
the watershed upstream from Rookery


I... i. -. 1

Figure 47. The Rookery Bay estuarine
system (adapted from Lee and Yokel



Figure 48. Average monthly flow
(cfs) in Henderson Creek, from 1970
to 1980.

and Johnson Bays is reflected by the
low flow in Henderson Creek. Any
substantial freshwater dilution in
bay waters is a short-lived phenome-
non. The salinity in Rookery Bay
and lower Henderson Creek sharply
decrease during local rainfall and
runoff (Lee and Yokel 1973).

The water residence time ranges
from 1 to 6 days in Henderson Creek
and 1 to 10 days in Rookery Bay.
The shallow, winding creeks along
the periphery of the bay system are
generally slow flushing. These and
other physical constraints, such as
oyster bars, reduce tidal exchange
of waters. Under drought conditions
hypersalinity (> 35 ppt) is likely
in the upper waters of the bay (Lee
and Yokel 1973).

Rookery Bay lies at a physio-
graphic "inflection point" along the
southwest coast. To the north, high
energy beaches dominate the coast-
line. To the south, coastal swamps
and lagoons are the dominant fea-
ture; consequently, Rookery Bay is a
transitional estuary. The forces
that form and maintain Rookery Bay
are a combination of those that
shape barrier-island estuaries
(e.g., impoundment behind a bar and
coastal erosion) and those that

shape lagoons (e.g., differential
solution and erosion of peat and
marl). Recent sea-level fluctuations
and hurricanes are major forces that
control the development of both
types of shoreline.

Most of the tidal exchange
between Rookery Bay and the gulf is
through Little Marco and Hurricane
Passes. Lee and Yokel (1973) report
that the physical interplay between
Keewaydin Island and Little Marco
Pass is highly dynamic. Aerial
photographs and older survey maps
reveal that the barrier island
has migrated to the south at an
increasing rate from 1885 to 1970
(Table 19).

From March to June 1972 a
72.6 m (200 ft) retreat of Keewaydin
Island was observed (Lee and Yokel
1973). Concurrently, the sand spit
off Little Marco Island migrated
southwest at a rate of 76.3 m
(210 ft)/year. The authors speculate
that the large tidal flows around
Little Marco Island may stabilize
drifts to the south but cause
Keewaydin Island to grow in width.

The Marco Island estuary (Fig-
ure 49) lies in the physiographic
transition zone between the coastal
protuberant and reentrant zones
(White 1970). On the seaward side,
the barrier islands of Marco Island
and Cape Romano provide shelter for
leeward embayments and mangrove

Table 19. Migration rate of Keeway-
din Island seaward of Rookery Bay
(adapted from Lee and Yokel 1973).


1885 1927 15.6m (43 ft)/year
1927 1957 42.5m (117 ft)/year
1957 1970 50.1m (138 ft)/year

lined tidal creeks. South of Cape
Romano the coastline recedes into
the Ten Thousand Islands, a dissect-
ed network of low, mangrove-covered
islands. The open-water embayment
seaward of the islands and in the
lee of Cape Romano is Gullivan
Bay. The leeward estuaries of the
Marco Island system include the Big
Marco River, and Collier, Barfield,
Roberts, and Blue Hill Bays. The
Big Marco River and Collier Bay flow
into the Gulf of Mexico through Big
Marco Pass on the north side of
Marco Island. Roberts and Barfield
Bays flow into the gulf on the south
side of Marco Island through Caxam-
bas Pass. Blue Hill Bay connects to
Barfield Bay, as well as to Gullivan
Bay, through Coon Key Pass.

Freshwater inflow into the
Marco Island estuary from coastal
wetlands ranges between 0.27 x 106
m3/yr and 3.51 x 106 m3/yr
(van de Kreeke and Daddio 1981).
Groundwater inflow from the fresh-
water aquifer to the coastal saline
aquifer averages 489 m3/day/ kilo-
meter (Amy 1981). During the wet
season, daily tidal fluctuations
in culverts draining nearshore
wetlands are nearly obliterated by
high water levels. During the dry
season, daily tidal fluctuations
may range as much as 0.38 m (1.3
ft) between high and low water.
Surface runoff from these wetlands
is approximately 100 to 200 times
subsurface outflow. Total surface
outflow is estimated to be about 53%
of the input from rainfall. This
relatively high percentage Is believ-
ed to be at least partially caused by
drainage operations that accelerate

A simplified stick diagram of
major flow conveyance channels of the
Marco Island estuary is given in Fig-
ure 50. According to van de Kreeke
(1972a), the tidal waves at the Gulf

Figure 49. The Marco Island estuarine system (adapted from
van de Kreeke 1972a).

PAss of Mexico (Big Marco Pass) and Coon
Key on the sheltered side of Gullivan
Bay are about an hour out of phase.
SBLUE The major flow conveyance channel is
JoHN B between Big Marco Pass and Coon Key
TVENSEK Pass along the Big Marco River. The
BIG IEEENK second most important flow pathway
"PA BAy (in terms of volume) is the Caxambas
Pass to Coon Key connection. Numerous
ROBERTS short circuits and dead ends also
contribute to the net circulation
pattern (Figure 49).

CAXAMBAS PASS Tidal excursions through these
major channels are about 4.8 km
Figure 50. Diagram of flow convey- (3 mi) long; not long enough to
ance channels in the Marco Island flow through on one tidal cycle but
estuarine system. nonetheless significant. Current


velocities are generally highest in
the primary channels near the major
passes and lowest where the tidal
waves meet. Three areas in the
estuary where maximum velocities are
barely measurable are Big Marco
River near Goodland, Blue Hill Creek
west, and John Stevens Creek (van de
Kreeke 1972a).

The net effect of urban devel-
opment of Marco Island canals is to
increase velocities in these water-
ways (van de Kreeke 1972a). This in-
crease is brought about by dredging,
which increases the cross sections
of channels and thus their water
storage and transport capacities;
and by filling, which decreases the
upland/wetland storage provided by
shoreline mangroves. In general, the
effect of dredging amplifies the
effect of filling, producing not
only a net increase in canal storage
but faster water movement as well.
Although flushing increases in the
deepened canals, it does not neces-
sarily improve the overall water
circulation in the canals, possibly
because stratification, either due
to salinity or temperature gradients
or the physical structure of the
canal (e.g., presence of sills),
shields the underlying and stagnant
waters, and restricts flushing to
the upper layer (Chesher 1974,
Carpenter and van de Kreeke 1975).

Urban development of shorelines
and wetlands in the vicinity of
Marco Island generally involves the
deepening and/or excavation of
natural waterways. Such activities
may create some unique hydrologic
conditions where the excavated body
of water does not connect with the
Gulf of Mexico (Figure 51). Courtney
(1981) published data on one such
excavated "lake" in the Marco Island
Shores golf course. Due to the
extremely pervasive influence of
saline ground waters, the lake is

permanently stratified. Vertical
diffusion is the only means of chem-
ical exchange between the upper and
lower strata. As a consequence of
such high stability, the lakes func-
tion well as sedimentation basins
for stormwater runoff. The lower
saline stratum ultimately receives
the stormwater runoff, while the
upper freshwater stratum remains
relatively unaffected by the nutri-
ent loading.

In response to intensive urban
development, a number of water-
quality studies have been conducted
on the Marco Island estuary. Base-
line information on dissolved oxy-
gen, salinity, and temperature is
provided by van de Kreeke (1972b).
Carpenter and van de Kreeke (1975),
and van de Kreeke and Roessler
(1975) discuss projected and ob-
served conditions within selected
waterways of the estuary. Weinstein
et al. (1977) gave a detailed sum-
mary of physical, chemical, and
biological data collected from 1971
to 1975. Most recently a series
of papers has appeared (Cross and
Williams 1981) documenting the
relationships between urbanization
and water-quality dynamics in the
Marco Island area.

The relative paucity of rain-
fall at Marco Island compared with
stations on the mainland was de-
scribed by Weinstein et al. (1977).
Low rainfall combined with high
rates of evapotranspiration (and
canalization, which promotes rapid
loss of freshwater) often leads
to seasonally hypersaline condi-
tions in estuarine surface waters.
Minimum salinity usually lags behind
peak rainfall periods by about one
month. A westerly salinity gradient
forms where freshwater inflow is
significant, such as in the Big
Marco River, which receives seasonal



kREA 7




Figure 51. Hydrologic cross section In the vicinity of Marco Island
(adapted from Courtney 1981).

sheet-flow runoff from the Big
Cypress Swamp watershed.

Nutrient concentrations in both
natural and developed estuarine
areas are generally low, although
some artificial waterways may act as
nutrient sinks. Under certain wind
conditions, nutrients may be re-
leased from sediments into the water
column, creating locally high con-
centrations. Maximum nutrient
levels were reported for Henderson
Creek, which drained both natural
and developed areas. Chlorophyll a
concentrations are generally highest
in canal waters that are dominated
by a phytoplankton-based food chain
(Weinstein et al. 1977).

The lake-like coastal excava-
tions upland on Marco Island are
essentially meromictic, with highly
saline, nutrient-rich, deeper
ground water and relatively nutrl-

ent-poor freshwater in the surface
layer. Water quality in these lakes
will probably stabilize in the
mesotrophic to slightly eutrophic
condition. Nutrient overenrichment
reportedly will not be a problem
(Huber and Brezonik 1981), nor will
the discharge of nutrient-laden sur-
face water from the lakes tributary
to the estuary.

The dissolved-oxygen daily min-
ima at several stations and depths
in both artificial and natural
waterways in the Marco Island estu-
ary were compared by van de Kreeke
and Roessler (1975) and Van Belle
(1974). Because of the input of
mangrove detritus and the restricted
backwater circulation, natural areas
frequently exhibit lower oxygen than
disturbed areas. Canal waters tend
to have a greater degree of oxygen
stratification and variability with
depth than waters in natural areas.


Carpenter and van de Kreeke (1975)
conclude that the vertical-mixing
coefficient and detritus-based
respiration are more influential in
the dissolved-oxygen budget of
canals than are atmospheric trans-
fer, water-column photosynthesis,
and respiration.

Fahkahatchee Bay and Fahka
Union Bay (Figure 52) to the south-
east of Marco Island are located
behind a line of dissected mangrove
islands. Fahka Union Bay receives
freshwater inflow from the Fahka
Union Canal, which drains the Remuda
Ranch Grants development. Fahka-
hatchee Bay is less influenced by
freshwater inflow because drainage
is by sheet flow from the Fahka-
hatchee Strand and through the East
River (Carter et al. 1973).

--------- -f-- -------


Figure 52. Fahkahatchee Bay and
Fahka Union Bay (adapted from Carter
et al. 1973).
et al. 1973).

The proximity and physical
similarity of the two bays permit
an interesting comparison on the
effects of hydrologic modification.
Because of higher freshwater inflow
to Fahka Union Bay, salinities there
are lower at all times of the year.
In addition, during high flow in
late summer, rapid delivery of run-
off from GAC canals not only affects
Fahka Union Bay, but western Fahka-
hatchee Bay as well. During low
flow, saltwater intrusion in the
channel in Fahka Union Bay is very
pronounced. Because of greater
freshwater inflow, salinity intru-
sion into Fahkahatchee Bay is much
less pronounced. Salinity stratifi-
cation occurs in both bays during
low flow, but again in Fahka Union
Bay it is greater. In both bays the
wind is a dominant force that gov-
erns tidal flux and water level.
In winter north winds tend to drain
the marshes and shallow bays, where-
as in the summer south winds tend to
pile water up and inhibit flushing
(Carter et al. 1973). Seasonal
salinities for both bays are as low
as 0 to 2 ppt in late summer and as
high as 40 ppt in late spring and
summer during droughts.

Total nutrient loading to Fahka
Union Bay greatly exceeds that of
Fahkahatchee Bay, even though the
mean nutrient concentrations for the
two bays are similar. The differen-
ces in loading are related to the
increased flow from the extensively
ditched and drained Fahka Union Bay
estuary. Although total Kjeldahl
nitrogen (TKN) levels in the two
bays are similar, Fahkahatchee Bay
exhibits an occasional high TKN
value because of local marshland
drainage. Mean total phosphorus con-
centrations and total organic carbon
in Fahka Union Bay are slightly
lower than in Fahkahatchee Bay.

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