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 Preface
 Table of Contents
 Acknowledgement
 Main
 Back Cover














Group Title: Biological report
Title: An Ecological characterization of the Tampa Bay watershed
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00000113/00001
 Material Information
Title: An Ecological characterization of the Tampa Bay watershed
Series Title: Biological report
Physical Description: xiv, 334 p. : ill. ; 28 cm.
Language: English
Creator: Wolfe, Steven H.
Wolfe, Steven H
Drew, Richard D
National Wetlands Research Center (U.S.)
United States -- Minerals Management Service. -- Gulf of Mexico OCS Region
Publisher: U.S. Dept. of the Interior, Fish and Wildlife Service
Place of Publication: Washington D.C.
Publication Date: 1990
 Subjects
Subject: Ecology -- Florida -- Tampa Bay Watershed   ( lcsh )
Natural history -- Florida -- Tampa Bay Watershed   ( lcsh )
Genre: federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 254-279).
Statement of Responsibility: edited by Steven H. Wolfe and Richard D. Drew.
General Note: "Performed for U.S. Deparment of the Interior, Fish and Wildlife Service, Research and Development, National Wetlands Research Center and Minerals Management Service, Gulf of Mexico Outer Continental Shelf Office."
General Note: "December 1990."
 Record Information
Bibliographic ID: UF00000113
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 - AAA0268
ltuf - AJQ0173
oclc - 26147970
alephbibnum - 001826123
lccn - 93133200
 Related Items
Other version: Alternate version (PALMM)
PALMM Version

Table of Contents
    Front Cover
        Front Cover
    Front Matter
        Page i
        Page ii
    Preface
        Page iii
    Table of Contents
        Page iv
        Page v
        Page vi
        Page vii
        Page viii
        Page ix
        Page x
        Page xi
        Page xii
    Acknowledgement
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        Page xiv
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Full Text






Biological Report 90(20)
December 1990


An Ecological Characterization

of the Tampa Bay Watershed


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Biological Report 90(20)
December 1990




An Ecological Characterization

of the
Tampa Bay Watershed




edited by


Steven H. Wolfe
and
Richard D. Drew
State of Florida
Department of Environmental Regulation
2600 Blairstone Road
Tallahassee, Florida 32301



Project Officer
Larry Handley
U.S. Fish and Wildlife Service
National Wetlands Research Center
1010 Gause Boulevard
Slidell, Louisiana 70458


Performed for
U.S. Department of the Interior
Fish and Wildlife Service
Research and Development
National Wetlands Research Center
Washington, D.C. 20240
and
Minerals Management Service
Gulf of Mexico Outer Continental Shelf Office
1201 Wholesalers Parkway
New Orleans, Louisiana 70123-2394












DISCLAIMER


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 desig-
nated by other authorized documents.































This report may be cited:
Wolfe, S.H., and R.D. Drew, eds. 1990. An ecological characterization of the Tampa Bay watershed.
U.S. Fish Wildl. Serv. Biol. Rep. 90(20). 334 pp.












PREFACE


This report is one in a series that provides an ecological description of Florida's gulf coasts. The
watersheds described herein, with their myriad subtropical communities, produce many benefits. The
maintenance of this productivity through enlightened resource management is a major goal of this
series. This report will be useful to the many people who have to make decisions regarding the use of the
natural resources of the area.


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





Information Transfer Specialist
U.S. Fish and Wildlife Service
National Wetlands Research Center
NASA Slidell Computer Complex
1010 Gause Boulevard
Slidell, Louisiana 70458












CONTENTS

Page
PREFACE ........................................................................................................... .......................... iii
FIGURES ........................................................................ ........................................... .............vii
TABLES ..................................................................................................................................................... x
CONVERSION FACTORS ............................. ............................................... ........................... xii
ACKNOW LEDGM ENTS ............................................................................. .................................. xiii
AUTHORS ..............................................................................................................................................xiv
Chapter 1. Introduction
1.1 Purpose and Organization......................... ............................................................................. 1
1.2 The Tampa Bay W watershed ............................................................ ........................ 1
Chapter 2. Geology and Physiography
2.1 Structure and Geologic Setting.............................................................. ..........................3
2.2 Tertiary Stratigraphy ............................ ....................................................................... 6
2.3 Pleistocene Marine Terraces............................................. ..................................................... 6
2.4 Physiography ..................... .................................. ............................................... ......... 8
2.4.1 Central Lake District.............................................................. ............................. 8
2.4.2 Ocala Uplift District ........................................... ............................................... 11
2.4.3 Southwestern Flatwoods ............................. ..... ............... ........................... 11
2.5 Recent Sediments and Soils................................................................. ........................... 13
Chapter 3. Climate
3.1 Introduction ..................... .................................. ........................................................25
3.2 Rainfall ..................... ..................................... ................ ...............................26
3.3 Winds ................................................................................................................................... 34
3.4 Temperature................................................................................ .......................... 38
3.5 Relative Humidity ..................................................................... ........................... 39
3.6 Solar Radiation ....................................................................................................................40
3.7 Evapotranspiration........................................................................ ...........................41
3.8 Hurricanes................................... .........................................................................................45
3.9 Air Pollution ............................ ............................................................................. 48
Chapter 4. Hydrology and Water Quality
4.1 Introduction ..................... ..................................................................................... 56
4.2 Ground W after ............................................................. .......................................................57
4.3 Surface Water .... ................. ................................................................................ 70
4.3.1 Anclote River Basin ...................... ..................................................................73
4.3.2 Western Pinellas Peninsula ......................................................................................74
4.3.3 Old Tampa Bay and Southeastern Pinellas County Peninsula .................................... 78
4.3.4 Hillsborough River Basin ........................................................................................ 85
4.3.5 Alafia River Watershed ................................................................................ 103
4.3.6 Manatee and Little Manatee River Basins................................................................ 109
4.3.7 Manasota Coastal Area ......................................................... ........................... 117
4.3.8 Tampa Bay ........................................................... ................ ........................ 126
Chapter 5. Vegetation Communities (Habitats)
5.1 Introduction ........................................................................ .............................................. 134

iv











Page
5.2 T terrestrial H habitats ........................................................................... ................................. 134
5.2.1 Pine-Oak Woodlands .............................. .... ................. .......................... 136
5.2.2 Pine Flatwoods (Typical Flatwoods) ....................................... ............... 137
5.2.3 Prairies ......................................................................................................................... 138
5.2.4 H am m ocks ............................................................................. ................................ 139
5.3 Freshwater Wetland Habitats ............................. .... ................ ........................... 140
5.3.1 Sw am p Forests .............................................. ......................................................... 140
5.3.2 Wet Prairies and Marshes ............................................................... 143
5.3.3 Lakes, Ponds, and Rivers............................................. .............. 147
5.4 Estuarine, Saltwater Wetland, and Coastal Habitats ....................................................... 154
5.4.1 Salt Prairies and Marshes...................................................................154
5.4.2 M angrove Forests ............................................. ............................................... 155
5.4.3 Oscillating-Salinity Open Waters .............................. .............. .......................162
5.4.4 Beach, Dune and Coastal Strand .....................................................179
5.5 Disturbed Communities.........................................................................................184
5.5.1 Exotic Plant Communities ...................... ...............................186
5.5.2 Agricultural Communities .......................................................... 191
5.5.3 Urban-Industrial Communities ........................................ ................ 194
5.5.4 Canals and Other Artificial Structures................................................ 195
5.5.5 Phosphate-Mined Lands ........................................................................ 196
5.5.6 Spoil Islands................................. ... ................................206
5.6 Endangered and Threatened Plant Communities. ........................... ..........................214
Chapter 6. Fauna
6.1 Introduction .............................................................................................................................216
6.2 Invertebrates ............................................................................................................................216
6.2.1 Freshw after Invertebrates........................................................ ................................ 216
6.2.2 Estuarine Invertebrates .......................... ............................... ........................... 218
6.3 Fishes .......................................................................................................................................222
6.3.1 Freshw after Fishes ............................................ ................................................ 222
6.3.2 Estuarine and Marine Fishes ................................................. ...........................229
6.4 Amphibians and Reptiles.............................................................................................234
6.5 B irds ............................................................................................... ................................... 238
6.5.1 Forest (A rboreal) Birds ......................................................... .................................238
6.5.2 Wading Birds ......................................................................... 242
6.5.3 Floating and Diving Water Birds ...........................................................................243
6.5.4 B irds of Prey ........................................................................... ...............................245
6.5.5 Probing Shorebirds ........................................ ................................................ 246
6.5.6 Aerially Searching Birds........................................................................................247
6.6 Mammals ............................... ..........................................................249
L literature C ited .................................. ............................................................ ........................ 254
Appendix
Table A-1. Cenozoic units and formations underlying the Tampa Bay watershed...............................280
Table A-2. Point-source emission summary for west-central Florida. ................................................282
Table A-3. Summary of point- and areal-source emissions in west-central Florida............................283
Table A-4. Areal source emissions of particulates and SO2 in west-central Florida .............................284

V











Appendix Page
Table A-5. Municipal, domestic, and industrial dischargers in the lower Hillsborough River
w atershed.................................................................................................................................................286
Table A-6. Domestic and industrial dischargers in the Tampa Bypass Canal drainage system. ...........286
Table A-7. Industrial dischargers in the Alafia River watershed...................................................287
Table A-8. Summary of 1982 and 1983 Tampa Bay water-quality characteristics.............................288
Table A-9. Aquatic macrophytes collected from the Alafia and Little Manatee Rivers......................289
Table A-10. Bloom species of algae detected in Tampa Bay during 1981..........................................291
Table A-11. Rare, threatened, and endangered plant species in the Tampa Bay watershed; their status
and distribution among major habitats. ...............................................................................................293
Table A-12. Habitat distribution and relative abundance of freshwater fish in the Tampa Bay
w atershed............................................................................................................ ................................299
Table A-13. Composite list of fish species reported from Tampa Bay................................................302
Table A-14. Habitat distribution and relative abundance of terrestrial reptiles in the Tampa Bay
w atershed.................................................................................................................................................306
Table A-15. Wetland and aquatic habitat distribution and relative abundance of reptiles in the Tampa
B ay w watershed. ................................................................................................................................... 308
Table A-16. Terrestrial habitat distribution and relative abundance of amphibians in the Tampa Bay
w atershed.................................................................................................................................................310
Table A-17. Wetland and aquatic habitat distribution and relative abundance of amphibians in the
Tam pa B ay w watershed. ....................................................................................................................... 311
Table A-18. Terrestrial habitats in which forest (arboreal) birds in the Tampa Bay watershed are
found, including distribution, relative abundance, and seasonal occurrence........................................312
Table A-19. Wetland habitats in which forest (arboreal) birds are found in the Tampa Bay watershed,
including relative abundance and seasonal occurrence ..............................................................................317
Table A-20. Aquatic habitats in which forest (arboreal) birds are found in the Tampa Bay watershed,
including relative abundance and seasonal occurrence........................................................................321
Table A-21. Habitat distribution, relative abundance, and seasonal occurrence of wading birds in the
T am pa B ay w watershed. ............................. ............................................................................................ 322
Table A-22. Habitat distribution, relative abundance, and seasonal occurrence of floating and diving
water birds in the Tampa Bay watershed. ............................................................................................ 324
Table A-23. Aquatic habitat distribution, relative abundance, and seasonal occurrence of birds of
prey in the Tam pa Bay watershed. ..................................................................................................... 325
Table A-24. Wetland habitat distribution, relative abundance, and seasonal occurrence of birds of
prey in the Tam pa Bay w atershed ............................................................ ........................................ 326
Table A-25. Terrestrial habitat distribution, relative abundance, and seasonal occurrence of birds of
prey in the Tam pa Bay w atershed ............................................................ ........................................ 327
Table A-26. Habitat distribution, relative abundance, and seasonal occurrence of probing shorebirds
in the Tampa Bay watershed .......................................................................... ...................................328
Table A-27. Habitat distribution, relative abundance, and seasonal occurrence of aerially searching
birds in the Tam pa Bay watershed ....................................................................................................... 330
Table A-28. Terrestrial habitat distribution and relative abundance of mammals known or expected
to occur in the Tam pa Bay watershed .................................................................................................. 331
Table A-29. Wetland habitat distribution and relative abundance of mammals known or expected to
occur in the Tam pa Bay watershed ................................................................................................. 333
Table A-30. Aquatic habitat distribution and relative abundance of mammals known or expected to
occur in the Tampa Bay watershed. .................................................................................................. 334









FIGURES

Figure Page
1. Tam pa B ay w watershed. ............................................................................. ................................. 2
2. Stratigraphic nom enclature of Florida. ......................................................... .............................4
3. Major structural features of southeastern Coastal Plain.....................................................5
4. Glacial ecstatic sea-level chronology for Florida. ........................................ .............................7
5. Terraces of west-central Florida....................................................................... ........................... 9
6. Physiographic division of the Tampa Bay watershed. ................................... .........................10
7. Tampa Bay estuary physiographic divisions................................................ ................................ 13
8. Distribution of the major soil orders in Florida. ........................................ ................................... 15
9. Recent sediment cross section of Sanibel Island ........................................................................... 17
10. Soil associations in the Tampa Bay watershed. ........................................ ................................ 19
11. Bathym etry of Tam pa Bay. .......................................................................................................... 22
12. Texture of bottom sediments in Tampa Bay...................................... ... ........................ 23
13. Calcium carbonate content of bottom sediments (%) in Tampa Bay ............................................24
14. Florida clim atic divisions. ........................................................................... ........................... 25
15. Average annual precipitation in the Tampa Bay watershed, 1941-70.............................................28
16. March and November average rainfall in the Tampa Bay watershed..............................................29
17. Average July rainfall in the Tampa Bay watershed .............................................................................31
18. Average number of days when rainfall exceeds 0.025 cm (0.01 in) and average number of
m monthly thunderstorm s. .................................................. .... ..................................32
19. Average monthly rainfall in the Tampa Bay watershed.............................. ............ ............... 33
20. Average number of days per month when rainfall exceeds 0.25 cm (0.1 in)...................................33
21. Frequency distribution of rainfall in southwest Florida over a 5-year period..................................33
22. Thirty-year annual rainfall for Lakeland................................. ......... ............................ 34
23. Rainfall deviation from normal over 30 years at Lakeland ............................ ..........................35
24. Seasonal wind directions and speed at the 950-mbar level in Florida, 1957-67...............................36
25. Average monthly divergence curves for June, July, and August 1963, over the Florida Peninsula.. 37
26. Prevailing wind speed and direction. ............................................................ ......................... 38
27. Annual, January, and August average temperatures in south-central Florida..................................39
28. Average number of days per year in Florida when air temperatures exceed 320C..........................40
29. Average monthly relative humidity at different times of the day ..............................................40
30. Percent of possible sunshine, daytime sky cover, and solar insolation in southwest Florida. ...........42
31. Average seasonal cloudiness in southwest Florida. .................................... ...........................43
32. Average number of days with heavy fog in southwest Florida.........................................................44
33. Estimated evapotranspiration patterns in Florida....................................................................... 44
34. Average monthly evaporation and solar radiation in eastern Tampa Bay watershed......................45
35. Comparative average potential evapotranspiration in the middle Gulf area as calculated by four
m models .............................................................................................................. ............................46
36. Paths of hurricanes striking the Tampa Bay area 1885 to 1990..................................... ............ 47
37. One-hundred-year hurricane flood surge in Little Manatee River (assuming mean annual river-
discharge rate). ......................................................................................... ................................. 48
38. Seasonal average nutrient concentrations in rainwater at Tamiami Trail and Forty-Mile Bend. ......50
39. Average daily concentrations of airborne sulfur dioxide in the rural and urban Tampa area for the
years 1970-83. ...................................... ................................................................................. 53
40. Annual suspended-particulate emissions in the Tampa area during 1973-83.................................53
41. Number of days each year on which ozone concentration exceeded 80 ppb and 120 ppb in the
Tam pa area during 1971-83. .............................................................................................................55
42. Generalized hydrogeology in the Southwest Florida Management District ....................................58

vii











Figure Page
43. Generalized hydrogeologic relation between surficial and Floridan aquifers. ................................59
44. Hydrographs of wells open to the surficial aquifer in the Tampa Bay watershed ........................... 60
45. Potentiometric surface of Floridan aquifer. ................................................................................. 62
46. Water levels at the Mullet Key tide station and in a southwest St. Petersburg well open to the
lower part of the Floridan aquifer. .................................................................. .............................. 63
47. Groundwater levels, irrigation pumpage, and rainfall in the central Tampa Bay watershed.............64
48. Generalized conceptual model of groundwater flow in the Tampa Bay watershed......................... 66
49. Hydrochemical facies in the Floridan aquifer's upper permeable zone...........................................67
50. Median water quality in the surficial aquifer and upper and lower units of the Floridan aquifer. .... 68
51. Chloride concentration in groundwater from the upper and lower Floridan aquifer .......................69
52. Section through Floridan aquifer showing chloride concentrations in the coastal margin of
Pinellas and central Hillsborough County ............................. ..... ............................................70
53. Major drainage basins of the Tampa Bay watershed. ....................................................................71
54. Ten-year average monthly flows of major rivers and streams in the Tampa Bay watershed............72
55. Anclote River basin .... ........................................................ ... .... ..........................73
56. W est Pinellas peninsula basin. ..................................................................................................75
57. East Pinellas Peninsula and Old Tampa Bay basin .......................................................................79
58. Dissolved oxygen values in Tanglewood Estates canals, northeast St. Petersburg .........................81
59. Hillsborough River and Tampa Bypass Canal drainage basins. ............................... ............. 86
60. Discharge hydrographs for two gauging stations on the Hillsborough River..................................88
61. Flow, current velocity, and residence times for the Tampa Reservoir.............................................95
62. Salinity (ppt) in the lower Hillsborough River .................................................. .........................96
63. Dissolved oxygen in lower Hillsborough River................................................. ..........................98
64. Fecal coliform in the lower Hillsborough River. ............................................... ..........................99
65. Orthophosphate in the lower Hillsborough River ....................................................................... 100
66. Alafia River drainage basin and Alafia River to Little Manatee River coastal area basin. ........... 104
67. Ammonia concentrations in the North Prong Alafia River, February 2, 1982 .............................. 106
68. Dissolved phosphorus trends in Hillsborough Bay and the Alafia River ...................................... 107
69. Seasonal water-quality conditions in the lower Alafia River. ..................................................... 108
70. Conductivity, stage, and streamflow stations on Lower Alafia River and Bullfrog Creek.............. 109
71. Conductivity profiles (pmhos/cm) in the lower Alafia River ........................................................110
72. Little Manatee River basin and Terra Ceia and Cockroach Bays coastal area drainage basins..... 111
73. Seasonal water quality conditions in the Little Manatee River...................................................... 112
74. M anatee River drainage basin .................................................................................................. 115
75. Wet- and dry-season salinity variation in the Lower Manatee River............................................ 117
76. Upper Manasota coastal area drainage basin. ...................................................... 119
77. Lower Manasota coastal area drainage basin......................................................................... 120
78. Blackburn, Lyons, Dona, and Roberts Bays and their tributaries ............................................... 121
79. Dry season hydrography in Dona, Roberts, and Lyons Bays ...................................................... 122
80. Wet season hydrography in Dona, Roberts, and Lyons Bays ..................................................... 123
81. Average monthly concentrations of total phosphorus and color in Phillippi Creek ...................... 125
82. Circulation pattern in Tampa Bay. ............................................................................................ 127
83. Location of evenly distributed particles after 30 days of mixing in Tampa Bay........................... 127
84. General water quality index of Tampa Bay for 1982............................................................. 129
85. General water quality index of Tampa Bay for 1983.................................................................. 130
86. Total phosphate concentrations in the Tampa Bay estuary, 1974-83.............................................. 131
87. Biochemical oxygen demand (BOD) in the Tampa Bay estuary, 1974-83................................... 131











Figure Page
88. Maximum surface and minimum bottom DO concentrations in Tampa Bay, 1974-83 ................ 132
89. Turbidity in the Tampa Bay estuary, 1974-83.............................................................................. 132
90. Chlorophyll a concentrations, light penetration, and color in the Tampa Bay estuary, 1974-83....133
91. Vegetation and land use in the Tampa Bay drainage basin........................................................ 135
92. Typical cypress dome with associated plants.......................................................... 142
93. Typical wet prairie with associated plants. ......................................................... 145
94. Typical freshwater marsh with associated plants.......................................... ............... 146
95. Typical freshwater aquatic plant habitat. ................................................... ........................... 148
96. Seasonal variation of periphytic algal genera in Lake Tarpon, 1973-1977................................... 151
97. Distribution of fish farms in the Tampa Bay watershed. .............................................................. 152
98. Vertical distribution of selected algae and invertebrates on red mangrove prop roots .................. 156
99. Successional relations of mangrove communities and some associated plant communities in
relation to approxim ate tide levels............................................... ......................................... 157
100. Mangrove forest types represented in the Tampa Bay watershed............................................... 158
101. Leaf-litter production rates in mangrove forest categories. .........................................................161
102. Diagrammatic representation of the principle of protein enrichment of red mangrove debris
during degradation. ......................................................................................................................... 161
103. Distribution of major seagrass species in Tampa, Florida during July 1983 survey. .................. 163
104. Generalized schematic of species zonation among seagrasses in Tampa Bay relative to depth
and salinity........................................................................... ..................................................... 164
105. Seasonal growth pattern for Thalassia in Tampa Bay. ........................................................... 167
106. Five types of seagrass beds identified for Tampa Bay.............................................................. 168
107. Seagrass distribution in 1943. ............................ ........................................ ........................ 170
108. Seagrass distribution in 1983. ........................................................................................................ 171
109. Average levels of chlorophyll a in the Tampa Bay system 1981................................................. 178
110. Yearly trends in chlorophyll a concentrations in four areas of Tampa Bay................................. 179
111. Monthly trends in chlorophyll a concentrations in four areas of Tampa Bay during 1982-83...... 180
112. High energy beach community showing major zones relating to sand motion. .......................... 181
113. Two patterns of spatial succession of vegetation community types on west coast barrier
island ds. .............................................................................................................. ........................ 185
114. Schematic of effect of canal development on hydrology and habitat structure ........................... 197
115. Location of central Florida phosphate district in relation to Tampa Bay watershed ................... 198
116. Stratigraphic units of concern in phosphate mining .............................................................. 199
117. Generalized flowsheet of Florida phosphate-mining plants..................................................... 200
118. Generalized habitat succession on dredged material islands in Florida.......................................208
119. Generalized vegetation map of a dredged disposal island in Tampa Bay................................... 11
120. Plant community succession on filled land, Boca Ciega Bay................................................213
121. Seasonal distribution of selected juvenile fishes within the nursery areas of Tampa Bay. ...........230
122. Estuarine fish com m unities ...................................................................................................... 232
123. Relative abundance of amphibian and reptile species in various habitat categories within the
T am pa B ay w watershed. ........................................ .... ...................... ...........................................236
124. Number of species of breeding land birds in the Florida Peninsula. ...........................................240
125. Nesting patterns of colonial shorebirds on Florida spoil islands. ...............................................249









TABLES

Tables Page
1. Deep strata of Florida................................. ....... ..................................................3
2. Tertiary strata of the Tampa Bay watershed .................................. ...... .......................... 6
3. Morphometric features of Tampa Bay estuary and some of its bays.............................................. 14
4. Soil Conservation Service soil orders. ........................................................... .......................... 15
5. Typical soil types on west-central Florida coastal barrier islands ................................................ 18
6. Plant community and soil series associations in the Tampa Bay watershed......................................20
7. Wet-season, dry-season, and total annual rainfall in the Tampa Bay watershed...............................27
8. Major hurricane storm tides in the Tampa Bay watershed. ............................................................48
9. Coastal areas most vulnerable to hurricane flooding in the Tampa Bay watershed ..........................49
10. Maximum winds reported in the Tampa Bay watershed............................... ............................. 49
11. Major air pollutants in the Tampa Bay watershed and their probable sources ................................52
12. Summary of fluoride point-source and areal-source (pond) emissions in Polk, Hillsborough, and
M anatee counties. .......................... .............................................................. ................................. 54
13. Ground-water and surface-water use by county in 1978.................................................................65
14. Ground-water withdrawal rates and predicted rates for major users in Hillsborough, Manatee, and
Sarasota counties, 1975, 1985, and 2000. .................................................... .............................. 65
15. Point sources discharging to eastern Old Tampa Bay and Upper Tampa Bay ................................80
16. Point-source dischargers in the western Old Tampa Bay drainage area..........................................87
17. Description and water-quantity data for four continuous-record gauging stations in the
Hillsborough River. ...............................................................................................................................94
18. Summary statistics for dissolved oxygen levels in the lower Hillsborough River...........................97
19. Stormwater and baseline flow water quality data from three drainage basins to the lower
H illsborough R iver. .........................................................................................................................101
20. Primary productivity and chlorophyll a concentrations in the lower Manatee River. ................... 118
21. Typical lentic aquatic vascular plants in the Tampa Bay watershed. .............................................. 150
22. Typical lotic aquatic vascular plants in the Tampa Bay watershed ............................................... 150
23. Phytoplankton genera collected in the Alafia and Little Manatee Rivers...................................... 153
24. Reproductive strategy differences between three species of mangrove found in the Tampa Bay
w watershed. ........................................................................................................................................ 159
25. A comparison of nutritive values for various plant parts of turtlegrass in the Tampa Bay area......166
26. Biomass values for seagrasses in the Tampa Bay area. ................................................................ 166
27. Changes in seagrass distribution in the Tampa Bay system from ca. 1940 to 1983, based on
aerial m apping. ........................................... ...... ............................................. ............................ 172
28. Changes in seagrass distribution in Sarasota County bay systems between 1948 and 1974. ...........173
29. Net primary production (NPP) of major estuarine habitat components ........................................ 175
30. Major vegetational changes from savannah to cabbage palm forests on a coastal barrier island.... 182
31. Characteristic species of the tropical hammock association on a coastal barrier island ................ 184
32. Species composition of the wetland subassociations on a coastal barrier island........................... 184
33. Water bodies containing Hydrilla within the Tampa Bay watershed. ............................................. 192
34. Previous community associations of major or representative urban centers in the Tampa Bay
w watershed. ............................................................................................................................... 195
35. Structural and functional changes in natural communities in response to gross changes brought
about by urbanization. ........ ........................................................... ......................................... 196
36. Revegetation and land-use possibilities for various landfill types................................................201











Tables Page
37. Occurrence of plant species in phosphate-mined areas of Florida.................................................202
38. Types of reclamation recently completed or approved for implementation in the central Florida
phosphate district. ........................................... .............. ................................. ........................... 205
39. Major plant species associated with the generalized plant succession pattern on dredged
m material islands in Florida. .................................................. ....................................................209
40. Summary of physiochemical soil parameters associated with vegetated community types on
dredge spoil islands. .............................................................................................................................210
41. Dominant fish species, in order of abundance, collected in selected areas of Tampa Bay and
the percentage of the catch represented by those species.......................................................... 234
42. Amphibians and reptiles of biological significance ......................................................................239
43. Species and feeding strategies of forest birds using flatwoods in the Tampa Bay area.................241
44. Number of wading bird nests by county in the Tampa Bay watershed from 1976 to 1978.............243
45. Birds designated as endangered, threatened, rare, or of special concern.......................................250
46. Marine mammals sighted or stranded in Tampa Bay and in Gulf of Mexico coastal waters
between Pasco and Sarasota counties....................................................................................... .. 252
47. Mammals of special concern in the Tampa Bay watershed......................... ......................253












CONVERSION FACTORS


Metric to U.S. Customary
Multiply by To Obtain
millimeters (mm) ................................ 0.03937 ........................... inches (in.)
centimeters (cm) ................................. 0.3937 ............................. inches (in.)
meters (m) ........................................... 3.281 ............................... feet (ft)
kilometers (km).................................. 0.6214............................. miles (mi)

square meters (m2) ............................ 10.76................................. square feet (ft2)
square kilometers (km2) ...................... 0.3861 ............................. square miles(mi2)
hectares (ha)..........................................2.471 .................................acres

liters (1) ............................................... 0.2642 ............................. gallons (gal)
cubic meters (m3) .............................. 35.31 ................................. cubic feet (ft3)
cubic meters (m3) ................................ 0.0008110 ....................... acre-feet

milligrams (mg) ....................................0.00003527 .......................ounces (oz)
grams (g)...............................................0.03527 .............................ounces (oz)
kilograms (kg) ................. .2......................2.205.................................pounds (lb)
metric tons (t) ................................ 2205.0 ................................... pounds (lb)
metric tons (t)...................................... 1.102............................... short tons

kilocalories (kcal)................................ 3.968............................... British thermal units (BTU)
Celsius degrees (OC) .......................... 1.8(C) + 32 .................... Fahrenheit degrees (F)


U.S. Customary to Metric
Multiply by To Obtain
inches..................................................25..................... .............. millimeters
inches.................................................. 2.54...................................centimeters
feet (ft)..................................................0.3048...............................meters
fathoms ............................................... 1.829................................. meters
miles (mi) ............................................. 1.609.................................kilometers
nautical miles (nmi) .............................. 1.852.................................kilometers

square feet ........................................... 0.0929............................. square meters
acres ......................................................0.4047 ...............................hectares
square miles ..........................................2.590................................. square kilometers

gallons ............................................... 3.785................................. liters
cubic feet ..............................................0.02831 .............................cubic meters
acre-feet ........................................ 1233.0................................... cubic meters

ounces (oz)........................................28.35................................. grams
pounds (lb)............................................0.4536...............................kilograms
short tons (ton) .................................... 0.9072 ............................ metric tons

British thermal units ............................ 0.2520 ............................. kilocalories
Fahrenheit degrees ................................0.5556(F -32) ..................Celsius degrees










ACKNOWLEDGMENTS


The authors and editor 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 unpublished data sources. Noteworthy among these were the staffs of
Southwest Florida Water Management District, Hillsborough County Environmental Protection Com-
mission, Tampa Bay Regional Planning Council, Marine Research Laboratory and Bureaus of Geology
and Mine Reclamation in the Florida Department of Natural Resources, University of South Florida,
New College at Sarasota, Florida Institute of Oceanography at St. Petersburg, the University of
Florida's Center for Wetlands, Archbold Biological Research Station, Mote Marine Laboratory, and
Sarasota County Environmental Services Laboratory.
We would also like to thank Robin R. Lewis of Mangrove Systems, Inc. for access to data and figures
from their studies, and Ken Haddad, Bureau of Marine Resources of the Florida Department of Natural
Resources; Eric Shaw and Mark Friedemann, Florida Department of Environmental Regulation; Robert
R ogers, Mineral Management Service; Tom Kunneke, Martel Labs, Inc.; Lorna Patrick, Channing
Bennett, and Beth Vairin of the U.S. Fish and Wildlife Service; as well as Loretta Wolfe and Bonnie
Boynton for review and editing. Thanks also to Sue Lauritzen for review of and assistance with
graphics.

We would especially like to thank Lawrence Handley and the late Millicent Quammen of the U.S.
Fish and Wildlife Service for review, review coordination, and general assistance...and persistence.
















Conventional graphics by Carol Knox
Computer graphics and layout by Steve Wolfe













AUTHORS


Richard D. Drew
State of Florida
Department of Environmental Regulation
2600 Blair Stone Road
Tallahassee, Florida 32399-2400





N. Scott Schomer
107 Strawberry Patch
Chapel Hill, North Carolina 27514





Paul Johnson
State of Florida
Office of the Governor
Tallahassee, Florida 32399

















Chapter 1. Introduction


1.1 Purpose and Organization

In recent years, development in west-central
Florida has accelerated at an unprecedented pace,
precipitating a rapid change in the environmental
conditions that characterize the area. Widespread
habitat destruction, sewage and industrial effluent
discharge, ground and surface water diversion, and
urban and agricultural runoff are but a few of the
inevitable by-products of economic expansion that
alter the regional ecology.
In the highly developed and rapidly changing
coastal zone of west-central Florida, a fine line is
emerging between vigorous economic growth and the
preservation of the natural environment. Often, in
deciding where this line is to be drawn, there is
considerable uncertainty about the composition, inter-
actions, and value of the living resources in an area.
This report attempts to resolve some of the uncertain-
ty and to assist in future resource development and
management by providing an extensive review and
synthesis of available literature on the ecology of the
Tampa Bay drainage basin In contrast to conven-
tional literature reviews and syntheses, the report
deliberately crosses disciplinary boundaries to focus
on the manner in which the drainage basin functions
as an integrated ecological system.
Chapters 2 through 4 describe the geology and
physiography of the study area, the climate, and the


characteristics of ground and surface waters. Chapter
5 describes plant communities and their succession.
Chapter 6 deals with fish and wildlife, their habits,
and their habitat preferences.

1.2 The Tampa Bay Watershed

This area (Figure 1) consists of the drainage basins
and estuaries of Hillsborough, Tampa, Old Tampa,
and Sarasota Bays, and the coastal provinces from the
Anclote River south to and including the Manasota
Peninsula. These drainage basins and their corre-
sponding United States Geological Survey hydrolo-
gic units are as follows:


Hydrologic
Unit
03100201
03100202
03100203


Geographic Areas
Sarasota Bay, Manasota Peninsula
Manatee River basin
Little Manatee River basin


03100204 Alafia River basin
03100205 Hillsborough River basin
03100206 Tampa Bay and coastal areas
03100207 Coastal Pinellas County and Anclote
River basin (southern portion).

The drainage basin encompasses over 176 km of
coastline and 7,700 km2 of west central Florida.










Tampa Bay Ecological Characterization


So S

I ,
0 't^












S. T B Manasota
Peninsula






Figure 1. Tampa Bay watershed.


















Chapter 2. Geology and Physiography

Richard D. Drew


2.1 Structure and Geologic Setting

The Tampa Bay watershed is underlain by 1,200 m
(north-central Pasco County) to 4,000 m (southwest
Sarasota County) of sedimentary rocks that overlie a
pre-Mesozoic basement complex of crystalline, igne-
ous, and metamorphic rock (Rainwater 1960; Hickey
1981a; Deuerling and MacGill 1981). The sedimen-
tary rock consists of sandstone, anhydrite, and dolo-
mite of Mesozoic age, and underlies limestone, dolo-
mite, clay, and sand strata of the Cenozoic age
(Menke etal. 1961; Lane 1980; Lane et al. 1980). The
deep strata of Florida (Table 1) consist of sedimentary
rock over the pre-Mesozoic basement rock. A thick
and relatively homogeneous layer of carbonate mate-
rials found in the deep stratigraphy reflects a relative-
ly long, stable period that was conducive to the forma-
tion and growth of a massive carbonate bank between
the Gulf of Mexico and the Atlantic Ocean. Reefs
formed near old shorelines, carbonate sediments were
deposited in shallow coastal waters, and marine,
brackish, and freshwater habitats contributed to the
beds of marl, limerock, sands, and organic such as
peats and mucks. When eustatic sea-level changes
occurred, the accumulated sediment masses subsided
to produce three major structural features that domi-
nated the subsequent geology of the peninsula. These
are the Suwannee Channel (Chen 1965), the South
Florida Basin (Applin and Applin 1964), and the Pen-
insula Arch and Ocala Uplift (Puri and Vernon 1964).
Figure 2 summarizes the stratigraphic relationships of
the pre-Cenozoic Florida Peninsula. More detailed
analyses of Florida's pre-Cenozoic strata may be
found in Cooke (1945), Puri and Vernon (1964),
Chen (1965), and Brooks (1973).


Table 1. Deep strata of Florida (after Rainwater
1960).

Division Composition
Cedar Keys (lower) Dolomite, anhydrite, lime-
stone
Navarro Dolomite, limestone, chalk
Taylor Chalk, dolomite, limestone
Austin Chalk and argillaceous
limestone
Eagleford-Tuscaloosa Shale, argillaceous lime-
stone
Washita-Fredricksburg Anhydrite dolomite and
dolomite limestone
Glen Rose (upper) Dolomite, limestone and
anhydrite
(middle) Anhydrite, some limestone
and dolomite
(lower) Limestone, dolomite,
anhydrite, some shale



From the late Cretaceous to upper Eocene, the
Suwannee Channel (Figure 3) was a narrow water-
way extending from southeast Georgia to Apalachi-
cola Bay. For the entire Tertiary period, the channel
represented a natural biological and sedimentological
barrier that caused the development of a southern
sedimentary province quite distinct from its northern
continental counterpart. Northwest and north of the
channel, a plastic faces composed of sandstone,
shale, and limestone developed; south and southeast
of the channel, the Florida Peninsula sedimentary
province formed as a nonclastic facies consisting of
















Tampa Bay Ecological Characterization


PANHANDLE PENINSULA

WEST EAST NORTH CENTRAL SOUTH


g.



0 0
I"

c
_;


-'-I


ow
0 ~
Lw



z
LU



00
0


EUTAW


BED3 Or NAVAPPn AGE (?) (ABSENT !J APT)................LAWSON LIMESTONE .........................



BEDS OF TAYLOR AGE...................................BEDS OF TAYLOR ACGE.......................



BEDS OF AUSTIN AGE...................................BEDS OF AUISTIN AGE.......................


EUTAI..


UPPER

MILLER SAND

SM APIE(
0


M'YE (PILOT) SAND


BED COF EAGLE FORD AGE...................







BEDS OF WOODBINE AGE.....................


I LO::ED

COMANCHE THIN CONTACT
OR GPEEN SHALE
GULF

I BEDS OF WASHITA AGE............


UNDIFFERENTIATED


UNDIFFERENTIATED REDS CF FREDRICKSBURG AGE......


I 2EDS OF TRINITY hGE............
0PDunta Gorda Anhydrite
Sunni and Limestone

UPPER
JURASSIC JURASSIC
OR FT. PIERCE
RETACEOUS R LOWER FORMATION
CRETACEOUS

u)
w UNDIFFEPENTIATED
c: (I Well)
-


RED AND VARICOLORED PLASTIC ROCKS CONTAINING,
IN SOME WELLS, INTRUSIONS OF DIABASE AND BASALT.


DIABASE INTRUSIONS
AND/OR FLOWS


-i -'-. I


TERRESTRIAL DEPOSITS (I WELL)


- t


BLACK SHALE


-v-I


BLACK SHALE


0
a LU QUARTZITIC SANDSTONE
rC : AND SOME DARK SHALE
0 o


PRE-CAMBRIAN OR
PORPHYRITIC RHYOLITE (I WELL) RHYOLITIC LAVA AND PYROCLASTIC ROCKS

LOWER PALEOZOIC


PRE-CAMBRIAN ? GRANITE AND DIORITE




HIGHLY ALTEPED IGNEOUS
AGE UNKNOWN ROCK (I WELL)




Figure 2. Stratigraphic nomenclature of Florida (after Puri and Veron 1964).


Lu
-J

1
S


SILURIAN









2. Geology and Physiography


Figure 3. Major structural features of southeastern Coastal Plain (after Chen
1965).


carbonate, evaporites, and anhydrides (nonclastic
sediments are those formed from biological and/or
chemical actions, while erosion of preexisting rocks
forms plastic sediments). The barrier effect of the
Suwannee Channel gradually disappeared near the
end of the Eocene epoch (Chen 1965).
During this time interval from the late Cretaceous
to the upper Eocene, a downwarping took place in
south-central Florida, forming the shallow structural
South Florida Basin (Figure 3). The downwarping
resulted from differential compaction within the basin
throughout the Tertiary, and a late Tertiary tectonic
uplift along the east and northeast margins of the
basin to further tilt the basin in a northwesterly direc-
tion. This resulted in a subsequent thickening of the


tertiary carbonate strata in a southwest direction into
the basin (Menke et al. 1961; Applin and Applin
1965).
The Peninsular Arch, formed by regional tecton-
ism and differential sediment compaction, "trends
south-southeast and extends from southeastern Geor-
gia through Florida into the Great Bahamas" (Chen
1965). Murray (1963) suggested that "the Arch is a
mobile 'swell or welt' in the developing Gulf-Atlantic
Coastal geosynclinal province." The Ocala Uplift is
the late Tertiary flexure in central peninsular Florida,
centered around the upper Eocene (Ocala) and the late
middle Eocene (Avon Park) group (Chen 1965).
Applin (1951) found no close structural relation
between the Cenozoic Uplift and Paleozoic Arch.









Tampa Bay Ecological Characterization


Because of the downdipping of the South Florida
Basin and the uplifting of the central peninsular anti-
cline, Tertiary and Quaternary rocks that are several
hundred meters deep in the Charlotte Harbor area are
found as exposed surface sediments less than 150 km
north in central Florida (Gorelick 1975). The Penin-
sula Arch, the "backbone of the Florida Platform"
(Chen 1965), and the Ocala uplift are responsible for
higher midstate elevations or ridges.
Pressler (1947) believed that anticlinal folds are the
most prevalent structures in the South Florida Shelf.
Although identified as secondary structural features,
faults are prevalent within this area. Based on con-
figuration of the surface of the submerged areas,
Pressler and others have concluded that the Florida
Peninsula is bounded on the south and east by major
fault zones. These faults are probably due to conti-
nental plate movements, in addition to settling, com-
pacting, and continuous downwarping of the sedi-
mentary fill.

Tampa Bay sits on the southwest flank of the
Peninsular Arch and just southwest of the Ocala
Uplift. Fracture patterns in carbonate rock associated
with the Ocala Uplift show preferred fracture orienta-
tion with azimuths from 301 to 325 just north of
Tampa Bay (Hickey 1981a). Also, fracture patterns
are found in the northern part of Pinellas County but


absent in the southern part. They are also found in
reduced numbers in southern Hillsborough County
(Vernon 1951).

2.2 Tertiary Stratigraphy

Tertiary strata in the Tampa Bay watershed are
illustrated in Table 2 and described in Appendix
Table A-1.

2.3 Pleistocene Marine Terraces

In the Quaternary (Recent) Period, there were at
least five major intervals of worldwide climatic cool-
ing (glacial) and four warming interglaciall) periods,
with many less pronounced climatic changes super-
imposed on each of the major periods. The majority
of these climatic fluctuations (Figure 4) took place in
the Pleistocene Epoch or "Great Ice Age," primarily
from 2 million to 40,000 years B.P. (before present).
Each interglacial period brought sea levels up as high
as 60 m above present-day mean sea level (m.s.1.), and
created a warm, tropical and subtropical marine envi-
ronment conducive to sediment accumulation from
resident biota (nonclastic) and weathered and eroded
materials plasticc). With the onset of glacial periods,
the sea levels receded. The accompanying aridity of
terrestrial environments created episodes of erosion,


Table 2. Tertiary strata of the Tampa Bay watershed (after Hickey 1981a).

Erathem System Series Formation
Quaternary Pleistocene Surficial Sand
Pliocene Tamiami Formation
Bone Valley Formation
Miocene Middle Hawthorne Formation
Lower Tampa Limestone
Tertiary Oligocene Suwannee Limestone
Upper Ocala Limestone
Eocene Middle Avon Park Limestone
Lower Oldsmar Limestone
Paleocene Cedar Keys Limestone
Mesozoic Cretaceous Undifferentiated for this report
Pre-Mesozoic Undifferentiated for this report











LATE PLIOCENE PLEISTOCENE
Pre-glacial Classical
Pamlico Terrace
c Talbot Terrace 200
_" En Penholoway Terrace
v Okeefenokee Terrace Silver Bluff Terrace
(8 _q Ca S Princess Ann Terrace >
SBone Valley Formation, Tamiami icomico Terrae 100
Formation, Jackson Bluff Formation '
"m C and "Pinecrest" Beds
Ca S a I ,, s
> > I,,," Sea i
Level
o"
Note: Anastasia Coquina, Miami Oolite, and Key Largo 0 -100 =
Limestone (reef) are part of the Fort Thompson o 'E
and Coffee Mill Hammock Formations 0
o o
Note: A Mid-Wisconsin stand of sea level at -200
about 10 ft lower than present probably ? l
occurred 45,000 to 23,000 B.P. E
Nebraskan Glaciar Stage -------- -300
Kansan Glacial Stage -------------
Illinoian Glacial Stage -------------
Wisconsin Glacial Stage ---------------------
5 4 3 2 1
Time in Millions of Years Before Present (B.P.)


Figure 4. Glacial eustatic sea-level chronology for Florida (after Brooks 1968).









Tampa Bay Ecological Characterization


weathering, and the reworking of sediments of the
Suwannee, Tampa, Hawthorne, and Bone Valley
Formations, along shorelines of previously deposited
materials (Roush 1985). The end result of these depo-
sitional, erosional, and reworking processes was the
series of terraces and ancient shorelines that today
typify the state's geomorphology. Each terrace repre-
sents (at least initially) a level plain having a slight
seaward dip. The landward margin is the abandoned
shoreline, which is generally marked by a low scarp
line (Heath and Smith 1954). Belts of ancient terrace
and shoreline sands occur in steplike formation typi-
cally running parallel to and rising inland from the
Florida coastline. The highest represents the oldest
deposit. The actual number and origin of terraces in
Florida are the subject of much debate. Healy (1975)
summarizes the history of terrace classification and
origin and adopts for illustration the terrace terminol-
ogy used by Cooke (1939, 1945).
Of the eight terraces and shorelines Cooke (1945)
identified in Florida, six occur in the Tampa Bay
watershed (Figure 5) (Healy 1975; Roush 1985).
Altschuler and Young (1960) question the Plei-
stocene marine terrace origin of the surface sands in
the central Florida uplands (more than 30 m above
m.s.l.), particularly those associated with the Bone
Valley Formation in eastern Hillsborough and Mana-
tee counties and western Polk County. Instead, they
suggest that the sands are a residual weathered prod-
uct of the underlying Bone Valley Formation. This
"residual" hypothesis is supported by later work indi-
cating that much of the higher terrain (30-50 m) in
Florida represents older Pliocene and upper Miocene
age deposits and not terrace deposits associated with
the advance of Pleistocene seas (Healy 1975).
The terrace-sand lithology and thickness vary
slightly from one terrace to the next. The greatest
difference is between the younger deposits (Pamlico)
and the older, more inland deposits (Peek 1959;
Altschuler et al. 1964; Knapp 1980). Generally, the
sands are quartose, fine to medium grained (fine to
coarse north of Seminole and NW of Largo),
subangular to subrounded, well sorted, white to light
tan or buff, and hardened to sandstone in places
(Heath and Smith 1954; Peek 1959; King and Wright


1979; Knapp 1980; Sinclair 1982). The younger
Pamlico deposits, found along the Tampa Bay shores
and near coastal areas, consist of shell and limestone
and range in thickness from zero to 6 m. Older depos-
its consist of quartz sand and some clay, and range in
thickness from 0 to 20 m (Peek 1959; Knapp 1980).
Terrace sands may contain organic debris, 1%-3%
phosphate, silts (particularly in older deposits), iron
oxides as stain, and clay in minor amounts (King and
Wright 1979; Sinclair 1982).


2.4 Physiography

Tampa Bay and its drainage system lie within the
sand-rich central or midpeninsular zone of Florida.
The watershed is characterized by the following three
physiographic districts and nine divisions (Figure 6)
(Brooks 1982b) based on rock and soil type, geologic
sSuvec Oef detidm 'igfoc g gWororpfifc proceg-
ses that constructed or sculptured the landscape, and
relief.
A. Central Lake District
1. Lakeland Ridge (Lakeland Ridge)
B. Ocala Uplift District
1. Webster Limestone Plains (Western Valley)
2. Dade City Hills (Brooksville Ridge)
3. Hillsborough Valley (Zephyrhills Gap)
4. Tampa Plain (Gulf Coastal Lowlands)
C. Southwestern Flatwoods District
1. Bone Valley Uplands (Polk Uplands)
2. De Soto Slope (De Soto Plain)
3. Pinellas Peninsula (Gulf Coastal Lowlands)
4. Barrier Island Coastal Strip (Gulf Coastal
Lowlands, Lagoons and Barrier Chain)
The names in parentheses denote similar physio-
graphic divisions described by Cooke (1939) and
White (1970), who based their divisions primarily on
features associated with higher stands of sea level.

2.4.1 Central Lake District
Sandhills that form the Lakeland Ridge extend
from just southeast of Bartow to approximately 16 km
north of Lakeland. This ridge lies along the northeast-
ern edge of the watershed, reaches a maximum











820


I CO


Sf
)





Terrace elevations (ft) .- .( b(

a Silver Bluff Terrace < 1-10 _
b Pamlico Terrace 8-25 ,
c Talbot Terrace 25-42
d Penholoway Terrace 42-70 '
e Wicomico Terrace 70-100
f Sunderland Terrace 100-170 "
g Coharie Terrace 170-215 4,
h Hazelhurst Terrace 215-320 ',

I i.=3mi.


Figure 5. Terraces of west-central Florida (after Healy 1975).










Tampa Bay Ecological Characterization


3 d rrv-m Scarp
Sarasota -- Ocala Uplift Boundary
SBay Division Boundary
Division Codes
3 Southwestern Flatwoods District
0o a Pinellas Peninsula
b Barrier Island Coastal Strip
-0- 3b c Bone Valley Uplands
O d DeSotoSlope
S4 Central Lake District
o \ a Lakeland Ridge
5 Ocala Uplift District
a Tampa Plain
b Hillsborough Valley



S) 3b




Figure 6. Physiographic division of the Tamp Bay watershed (after Brooks 1982).

Figure 6. Physiographic division of the Tampa Bay watershed (after Brooks 1982b).


10









2. Geology and Physlography


elevation (m.s.l.) of 80 m, and averages about 60 m.
Very deep weathering of phosphatic silty sands has
resulted in a thick, residual sand soil. The Lakeland
Ridge is part of the Central Lake District of Florida
and consists of uplifted limestones of the Floridan
aquifer lying uncomfortably below surficial sands.
This region is sandhill karst with solution basins and
is Florida's most active region for new sinkhole
development. Internal drainage within the sandy hills
serves as an important recharge route for the Floridan
aquifer.


2.4.2 Ocala Uplift District
a. Dade City Hills. Only a small portion of the
Dade City Hills extends into the northern Hillsbor-
ough River watershed, while most of this feature lies
north of the study area. Dade City Hills is a spectacu-
lar ridge of high hills dissected from upper Miocene
and silty sands. It is an active recharge and karst
region where deep weathering has produced thick
sand soils. Elevations range from 53 to 60 m and are
quite irregular, with the highest areas to the south and
west. Despite the height of the ridge, the irregular
topography prevents the formation of persistent
valleys; hence, the surface drainage pattern is not well
defined.
The position of the ridge correlates well with out-
crops of Bone Valley and Alachua Formations and
exhibits relatively greater resistance to solution than
the limestones that lie to the east and west. The Dade
City Hills is part of the Ocala Uplift District, which
encompasses all of the Big Bend area of Florida from
Tampa Bay to Tallahassee and into south Georgia.
Known as the "Lime Sink Region," the structure of
the area is a broad uplift of early Tertiary limestones
that occurred during the middle and late Tertiary.
Much of the limestone is near or at the surface in the
region.
b. Webster Limestone Plains. West of the Dade
City Hills is an erosional plain of low relief, less than
30 m in elevation, and consisting of a northern dry
plain and a southern wet plain. The wet plain is distin-
guished by a water table at or above the land surface


and exhibits a landscape of swamps and wet pine
flatwoods. The headwaters of both the Withlacoo-
chee River and the Hillsborough River are formed in
this region.
c. The Hillsborough Valley. The Hillsborough
River watershed is an erosional basin where sluggish
surface drainage is still dominant, but where there are
many karst features from which much of the surficial
plastic sediment has been removed. The greatest
relief in the "plain" is found in the headwaters, where
elevations reach 43 m above m.s.l.
d. The Tampa Plain. Along with the Hillsbo-
rough Valley, the Tampa Plain is the southernmost
extension of the Ocala Uplift District. The plain
covers much of western Hillsborough, northern
Pinellas, and central and western Pasco Counties, and
is characterized by lowland karst features related to
the Tampa Limestone Formation (Figure 6).
Land-O-Lakes encompasses a plain at 15 to 25 m
above m.s.l., with many small lakes, despite the pres-
ence of a moderately thick silty sand layer over the
limestone. The area lies directly north of Tampa and
extends into central Pasco County and then west to the
gulf coast, taking on a crescent shape. The crescent's
two cusps define the northern, eastern, and southeast-
em borders of the Odessa Flats or the Anclote River
watershed. Flatwoods dominate the poorly dissected
low sand plain of the Odessa Flats except near the
coast, where some paleodunes persist.
South of both the Odessa Flats and the Land-O-
Lakes lies the Lake Tarpon Basin, an erosional basin
less than 10 m in elevation. This basin, which is
partially backfilled with late Pleistocene sediments,
extends along the northern shore of Old Tampa Bay
from Tampa to Lake Tarpon.

2.4.3 Southwestern Flatwoods
a. De Soto Slope. This feature, along with the
Bone Valley Uplands, Pinellas Peninsula, and Barrier
Island Coastal Strip, is a member of the Southwestern
Flatwoods District. The district is distinguished by
Miocene and Pliocene sedimentary rock and sedi-
ments with nonexistent or thin Quatemary deposits.
Wetlands and flatwoods characterize the area.









Tampa Bay Ecological Characterization


Brooks (1982b) defines the De Soto Slope as a plain
that gradually slopes from a maximum of 30 m
(Wicomico Terrace) to 9 m (Talbot Terrace). Surface
drainage within this plain is frequently interrupted by
cypress swamps underlain by clay deposits. The De
Soto Slope gradually narrows in width from north to
south. To the north, particularly northwest, the slope
dramatically pinches to a narrow belt running parallel
to the eastern Tampa Bay shoreline. Along this belt,
terracing is more evident, as is the slope, and is best
observed in the Alafia River watershed.

b. The Bone Valley Uplands. The headwaters of
the Alafia, Little Manatee, and Manatee Rivers are
contained in the Bone Valley Uplands, a poorly
drained plateau underlain by deeply weathered sand
and clayey sand of the Bone Valley Formation.
Flatwoods with cypress heads and strands are
common. The upland margin, which generally
exceeds 40 m m.s.l. contains excessively drained
thick white sands.

c. The Pinellas Peninsula. The peninsular fore-
land between the limestone coast to the north and the
middle-Miocene to Recent plastic sediments south-
ward along the coast is called the Pinellas Peninsula.
Residual deeply weathered sandhills occur in the
northern portion of the peninsula, and sand and shell
of Plio-Pleistocene age underlie the central and south-
em lower terraces.

d. The Barrier Island Coastal Strip. The coastal
strip is bordered to the west by lagoons and islands of
Recent origin, and inland, to an elevation of approxi-
mately 6 m, by coastal flatwoods. The coastal areas,
particularly islands and inlets, are very dynamic and
prone to shifts in position, size, and shape.

In the southern half of the watershed, drainage to
the coastal lagoons of Lemon Bay, Dona Bay, and
Little Sarasota Bay is ill-defined and originates
entirely from gently sloping lowlands. These
lowlands roughly correspond to terraces of the
Pamlico and Talbot shorelines. Cow Pen Slough to
Dona Bay is the most distinct freshwater drainage
system in this area. A number of low-lying lakes are
found upland of these lagoons. Drainage from


Phillippi Creek into Roberts Bay and the Bracken
River into Sarasota Bay is restricted to a narrow belt
of lowlands adjacent to the estuarine embayments.

Proceeding north, the Manatee, Little Manatee,
and Alafia Rivers traverse a steeper and narrowing
coastal strip. Still farther north, the Coastal Strip
grades into the Hillsborough Valley.
Seaward of the mainland from Marco Island to
Anclote Key is the Gulf Barrier Island Chain, which is
a product of a plentiful terrigenous sand supply and
sufficient wave energy to transport sand to and from
the coastline. Miocene siliclastic rocks provide the
local supply of sand for the high-energy coastal
processes. The area's protruding coastline and
steeper slope allow more of the Gulf of Mexico's
wave energy to be expended on the shoreline and not
dampened by extended shallow flats characteristic of
low-energy coasts (e.g., Big Bend, TenThousand
Islands). However, a great deal of the coastline has
been stabilized during development.
e. Gulf-coastal estuaries and lagoons. A signi-
ficant fraction of the watershed behind the barrier
island chain is made up of submerged lands that are
drowned river valleys and relict lagoons. Together,
these form the Tampa Bay estuary and the narrow line
of nearly continuous lagoons, including (from north
to south) Palma Sola, Sarasota, Roberts, Little
Sarasota, Dona, and Lemon Bays.

The Tampa Bay estuary is a roughly Y-shaped
system 55 km long and 15 km wide, covering
approximately 900 km2 and having a shoreline
340 km long (Olson and Morrill 1955). The estuary
(Figure 7) is divided into Old Tampa, Hillsborough,
Middle Tampa, LowerTampa, Boca Ciega, and Terra
Ceia Bays, the Manatee River, and Anna Maria
Sound (Olson and Morrill 1955; Simon 1974; Lewis
and Whitman 1985). The Tampa estuarine system is
crisscrossed and modified by four major causeways
and an extensive network of dredged channels (Figure
7). The disposal of dredged materials over the years
has resulted in the formation of numerous spoil
"islands" in the estuary. Table 3 presents a summary
of morphometric features of the Tampa Bay estuary.









2. Geology and Physiography


- 28 00'







The










m.a



C)
0







ri



- 2P 30'


Subdivisions of Tampa Bay
( ---- Demarcation Line)
1. Old Tampa Bay
2. Hillsborough Bay
3. Middle Tampa Bay
4. Lower Tampa Bay
5. Boca Ciega Bay
6. Terra Ceia Bay
7. Manatee River
8. Anna Maria Sound


Figure 7. Tampa Bay estuary physiographic divisions (after Lewis and Whitman 1985).


2.5 Recent Sediments and Soils

Soils are described and classified based on measur-
able and visible differences in surficial soil profile
characteristics down to a depth of 2 m (Carlisle
1982a). The profile is composed of one or more soil


horizons and is characterized by the nature of the
parent rock, weathering processes, the transport
mechanisms involved, biology, and stage of decom-
position. In central and south Florida, the soils or
uppermost sediments are geologically young and are
surficial (Estevez 1981); that is, the soil profiles


13









Tampa Bay Ecological Characterization

Table 3. Morphometric features of Tampa Bay estuary and some of its bays (after Simon 1974).
Morphometric Old Tampa HIllsborough Tampa Boca Clega Tampa Bay
feature Bay Bay Bay Bay Estuary
Length (km) 21 14.5 56
Average width (km) 3-10 7 11-16 16
Area (km2) 203 105 519 56 882
Volume (km3) 2.862
Maximum depth (m) 11 5.5 12.8 17.4
Mean depth (m) 3.4
Modal depth (m) 2.4 2.1 4.3 0.6 3
Length of shoreline (km) 87 59 159 -
% of total system (area) 23 12 59 6 100


reflect changes in sediment types rather than develop-
ment of chemically or mechanically produced hori-
zons. For example, one is more likely to observe
sands layered over marsh-produced calcareous marl,
particularly in the coastal regions. Apart from the
common quality of "newness" of Florida's peninsular
soils, each soil is a unique fingerprint of the preexist-
ing conditions; i.e., parent materials. Soils are orga-
nized into a taxonomic classification system by the
U.S. Soil Conservation Service (SCS) in which each
soil is categorized by order, suborder, great group,
subgroup, family, and soil series (Collins and
Caldwell 1982). Nationwide, there are 10 orders of
soil, of which 7 are found in Florida. Entisols,
Spodosols, Ultisols and Histosols dominate the
State's landscape. Table 4 presents a general descrip-
tion for each of the 10 orders and their relative abun-
dance in Florida. The distribution of four major soil
orders in Florida is illustrated in Figure 8. The figure
indicates only the dominance of a soil order in an area.
For example, Histosols (peats and mucks) dominate
the regional soil groups only in an area south of Lake
Okeechobee, but are found in 42 of 67 Florida coun-
ties.
Soil information in the Tampa Bay watershed is
available in the Florida General Soil Atlas and the
County Soil Survey. The Florida General Soil Atlas
presents a soil-association map for each county in the


State (DSP 1975a,b). A soil association is a group of
one or more major soils and at least one minor soil
that are found naturally together to form a distinctive
landscape. These soil association maps provide a
statewide coverage of soil types, but lack the detail
required for site-specific work, as only the dominant
soil types are reported. However, for some areas of
the State, the atlas may be the only current and really
comprehensive soil data base available (Carlisle
1982b). The other, more detailed, source of soil data
is the SCS County Soil Surveys. These are at various
stages of completion in the State. Soils, at the soil
series level, are delineated on 1:20,000-scale
photomosaics. A description of each soil series is
provided, as well as associated soil types, flora, drain-
age characteristics, and suitability for various land
uses (Carlisle 1982b).
In the Tampa Bay watershed, all six counties have
published surveys, the latest, Polk County, in 1986
(USDA 1981). Although these surveys appear to
provide an excellent soil data base, two of the five
published surveys (Hillsborough and Sarasota Coun-
ties) were completed during the late 1950's (USDA
1958,1959). Since that time, the survey methodology
has been changed significantly to modify the taxo-
nomic structure and soil series names, include previ-
ously undescribed soil series for wetland areas, and
describe alteration of existing soils by development.









2. Geology and Physiography


Table 4. Soil Conservation Service soil orders (after Collins and Caldwell 1982).

Order name Principal diagnostic property(ies) (simplified definitions)
Alfisolsa Mineral soils, relatively low in organic matter, relatively high base saturation; an illuvial hori-
zon of silicate clays; moisture available to mature a crop.


Aridisolsb


Entisols
Histosols
InceptisolsC



Mollisolsc


Oxisolsb
Spodosols


Ultisols

Vertisolsb


Mineral soils, relatively low in organic matter; inadequate moisture to mature a crop without
irrigation in most years, some pedogenic horizons.
Mineral soils, weak or no pedogenic horizons, no deep wide cracks in most years.
Organic in more than half of upper 80 cm.
Mineral soils, some pedogenic horizons and some weatherable minerals, moisture available
to mature a crop in most years, no horizon of illuvial clays, relatively low in either organic
matter or base saturation, or in both.
Mineral soils, thick dark surface horizon, relatively rich in organic matter, high base saturation
throughout, no deep wide cracks in most years.
Mineral soils, no weatherable minerals; inactive clays; no illivial horizon of silicate clays.
Mineral soils, an illuvial horizon of amorphous aluminum and organic matter, with or without
amorphous iron.
Mineral soils, an illuvial horizon of silicate clays; low base saturation, moisture available to
mature a crop in most years.


Clayey soils; deep wide cracks at some time in most years.


areas; b None recognized in Florida; c Minor occurrence.


Even in the 1972 Pinellas County soil survey, the wet-
land soils were generally classed as swamp or marsh.
Only Pasco and Manatee (revised) County surveys
provide a current and complete inventory and analysis
of the soils. Revision of some of the older surveys is
under way, including remapping of Hillsborough
County. Another valuable informational source on
regional soils is an annual publication, Proceedings of
the Soil and Crop Society of Florida, which provides
a scientific forum for the most recent soil research in
the State.
Sands and organic dominate the soils in the water-
shed and much of the coastal-plain region of Florida.
Such soils are a product of the wet, semitropical cli-
mate; the flat terrain; and the short geologic time the
parent materials (sands) have been exposed to the soil
development processes (USDA 1983). High rainfall,
short, mild winters, and high summer temperatures
encourage rapid oxidation and leaching of deposited


1. Entisols
2. Ultisols
3. Spodosols
4. Histosols


Figure 8. Distribution of the major soil orders in
Florida (after Goodins et al. 1982).


15


a Widely interspersed









Tampa Bay Ecological Characterization


organic materials in the poorly drained sandy soils. In
partially or completely inundated wetland areas,
leaching is reduced and the high productivity of a
subtropical climate causes rapid generation of organic
materials and a buildup of peat and/or muck. The
relatively short time surface sediments have been
exposed to soil-making processes has generally
resulted in an absence of developed soil horizons in
the watershed and a predominance of relatively
poorly developed and/or geologically young soils,
such as Spodosols, Entisols, and Histosols (DSP
1975a,b; USDA 1982, 1983).
The Tampa Bay watershed is dominated by
Entisols along the more elevated eastem and northern
margins, and by Spodosols elsewhere. Entisols are
mineral soils that have not formed definite soil hori-
zons, or have only rudimentary horizons. These soils
are typically sandy, acidic, very poorly to excessively
drained (depending on water-table depth), and have a
low cation-exchange capacity (CEC). The CEC
affects soil ability to retain various ions, including
needed plant nutrients. The higher the CEC the
greater the soil's capacity to retain ions. Soils with
low CEC (e.g., sands) limit productivity unless stor-
age sites such as organic topsoils (e.g., peats and
mucks) or a low permeable horizon (e.g., a spodic
horizon which "catches" the leached ionic materials)
develop to reduce the loss of nutrients and minerals.
Spodosols, the dominant soil order in the water-
shed, exhibit a spodic horizon or subsurface layer that
contains an accumulation of organic matter and
precipitated oxides of aluminum and iron. Soils over-
lying this organic layer are generally well-leached
sands that exhibit a low CEC and base saturation and
are moderately to strongly acidic. The low pH is a
result of the neutrality and poor buffering characteris-
tics of the parent material (terrace sands), the presence
of surficially decomposed organic materials, and the
natural acidity of rain. Pine flatwoods are well suited
for these soils; their litter is low in metallic ions and
has a low neutralization potential. Both characteris-
tics promote soil acidity. Spodic soils range from well
drained to very poorly drained, dependent on water
depth and the degree of organic pan (hardpan) devel-
opment at the spodic horizon. A well-developed
hardpan substantially slows or blocks the downward


movement of water, forcing the water to move later-
ally. Because these soils are typically found in areas
with little or no slope, lateral movement is slow, and
the waters back up, causing seasonal ponding. Inten-
sive drainage networks are constructed in these areas
to make them suitable for a variety of agricultural pur-
poses. Soils of this order are found in every county in
the watershed and dominate in all but Polk County
(DSP 1975a,b).
Histosols are peat and muck organic substrates
formed of partially decomposed plant material and a
mixture of inorganic sand, clay, and silt. While this
soil order is not a dominant substrate in the watershed,
it frequently occurs in wetlands. Water inundating the
wetlands creates an anaerobic layer at the sediment-
water interface that promotes an accumulation of
partially decomposed organic materials.
The difference between the two organic forms,
peat and muck, is the degree of decomposition. Peat
is a fibrous organic substrate only slightly altered
from the original plant structure and retains identifi-
able plant parts (e.g., leaves, stems, seeds, and roots).
The parent material is local autochthonouss), and the
ash and inorganic content is typically low. In
contrast, muck is a thoroughly decomposed, fine-
grained, nonfibrous, organically rich substrate that is
high in ash content and is often mixed with inorganic
sedimentary material. Source material for muck may
be autochthonous or allochthonous (transported from
outside the decomposition site).
The origin, structure, chemical qualities, decompo-
sition rates, environments, and patterns, as well as
other characteristics of organic are well studied,
particularly in south Florida. Davis (1946) provides
an extensive review of peat deposits in Florida includ-
ing information on their nature, origin, type, and
composition. 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 peat deposits in the watershed are
located in the riverine swamps of the Bracken,
Manatee, Anclote, Little Manatee, and Hillsborough
Rivers; Lake Thonotosassa; and the coastal man-
groves and saltwater marshes (Davis 1946; Reynolds
1976; Herwitz 1977; USDA 1958, 1982, 1983).









2. Geology and Physiography


Some small deposits are typically found in the nu-
merous swamps, marshes, ponds, and sloughs, and
along some stream margins. Regionally, organic de-
posits range in depth from a few centimeters to 3 m
and are high in carbon and nitrogen, but low in other
nutrient forms (e.g., phosphorus) (Davis 1946). The
type and condition of peat is dependent on water
depth, pH, hydroperiod, parent vegetation, topogra-
phy, thickness, degree of decomposition, characteris-
tics of the underlying sediment, inorganic content,
and presence of incorporated layers such as marl,
shell, limerock, or sand. Peats are most often classi-
fied by their parent material, e.g., mangrove peat,
Conocarpus (buttonwood) peat, Spartina peat, and
others (Cohen and Spackman 1974). Mangrove peat,
which forms in the southwestern coast's tidal area,


usually retains much more of the original plant struc-
ture than its freshwater and brackish-water counter-
parts. It also exhibits a greater ash content caused by
the intermixing of shells and sands transported into
the swamps by tides and storm waves.
Soils associated with the barrier island group of the
Tampa Bay watershed are commonly mixtures of the
region's three dominant soil orders, with the sandy
Entisols dominating the group. Sediment from the
Pleistocene terraces, mostly Pamlico sands and
reworked marine sediments, have been molded into
the existing islands by erosion and deposition (Brooks
1973; Missimer 1973; Herwitz 1977; Morrill and
Harvey 1980; Estevez 1981). The characteristics of
sediments common to the barrier islands of the region
are illustrated in Figure 9. Beach and dune sand and


+4-
0 Gulf of Mexico '^^ 0gO' Pine Island Sound

:o O o


12 o -K M 0


0 1 2 3 4 5
Miles-

Modern estuarine Recent peat deposits
sediments \ Recent estuarine deposits: organic matter,
1/// A sand, mud, and shell


O Oxidized barrier-island sand and shell
Shelly sand unit
She.ly sUnoxidized barrier-island sand and shell


Muddy, shelly sand unit X Relict estuarine deposits: organic matter,
Sand, mud, and shell

Pleistocene Pleistocene sandy limestone
limestone unit
o Unoxdize barir-sln san and shell' .
Mudselysn nt eitesurn epst:ogai atr
sand, mud, and shell\
Pleistocen Pleistcene sand limeston


Figure 9. Recent sediment cross section of Sanibel Island (after Missimer 1973).









Tampa Bay Ecological Characterization


shell normally prevail on the western island faces,
where greater tidal, wind, and current forces are
exerted. These tan-colored, well-oxidized sediments
are composed of mixed carbonate shell material and
fine to medium-grained quartz sand. Sands include
heavy minerals, phosphorite, shell materials, and or-
ganics. South of Tampa Bay, sand, shell, and clay
content increases lagoonward and only the gulf-fac-
ing side has relatively thick sequences of sand. Gulf
beaches south of Sarasota, particularly near Venice,
contain appreciable phosphorite in sizes up to gravels
(Knapp 1980). On the eastern side, a quieter environ-
ment encourages the deposition of mangrove forest
and Spartina marsh peats. In the sheltered bays,
lagoons, and harbors, a muddy-shelly sand is found
that varies in its composition (fine-grained quartz
sand, silt,clay, shell material, and organic matter),
depth, and thickness (Missimer 1973; Estevez 1981).
Lagoons are bounded by a medium to fine sand and
silt lithology north of Tampa Bay and by sand, shell,
and clay to the south (Knapp 1980).


Soil types on the barrier islands are known largely
through the work of Herwitz (1977)-Cayo Costa,
Morril and Harvey (1980)-North Captiva, and the
U.S. Department of Agriculture, SCS (1983)-Mana-
tee County. Soils series that are generally representa-
tive of barrier island soils in the watershed are
presented in Table 5 and are further described by
Reynolds (1976).
Florida soils have generally developed from a
mantle of noncalcareous sands and clays overlying
limestone deposits. The sand and clay mantle varies
in thickness, but, in the watershed, generally thins in
the coastal lowlands and wetlands. Soil series found
in close association with underlying mars or lime-
stone often exhibit alkaline qualities even under
anaerobic conditions (e.g., Kesson, Parkwood Vari-
ant, Manatee, and Felda [USDA 1983]). Commoner
representative soil associations in the watershed are
presented in Figure 10 (Caldwell and Johnson 1982).
The lowland and inland flatwood soils are dominated


Table 5. Typical soil types on west-central Florida coastal barrier islands (adapted from Herwitz 1977; Morrill
and Harvey 1980; Estevez 1981; USDA 1982, 1983).

Soil type Local soil series Characteristics
Quartzipsammentsa Canaveral Fine Most abundant, moist mineral soils, sand and shell fragments with thin
accumulation of organic materials at or near the surface; moderate to well
drained; coastal strand, savannah, cabbage-palm forest, tropical ham-
mock, Australian-pine forest; beach soil is similar but has higher shell
content and is disturbed by wave action.
Psammaquents8 Captiva Poorly drained, but very permeable; sandy texture, gray; associated with
shallow sloughs and seasonally wet depressions; marshes, wetlands in
general, cabbage-palm forests (in depressions).
Sulfaquentsa Kesson Poorly drained mineral soils, like Captiva but has sulfidic horizon (associ-
ated with salt-water intrusion) close to surface; found on bay fringes asso-
ciated with salt flat and mangrove communities; Batis maritima and
Sesuvium portulacastrum indicator plants.
Sulfihemistsb Wulfert Organic soil; muck, decomposed roots; associated with flat, tidally-
flooded mangrove forests along shallow backwaters on island baysides.
Medisapristsb Terra Ceia Organic soil, muck, associated with hardwood swamps.
Various Arents Well-drained, human-disturbed soils without discernible horizons, e.g.,
Indian shell mounds.
a Entisols-Mineral soils lacking pedogenic horizons (see Table 4).
b Histosols-Organic soils saturated most of the year (see table 4).

18










2. Geology and Physiography


O


Soil Associations
Arredondo-Kendrick-Hillhopper (Blichton, Lake, Sparr)* 5
Candler-Apopka-Astatala (Arredondo, Tavares)
Adamsvllle-Felda (Delray, Pompano) 1
Coastal Beach and Dunes (Palm Beach, Paola, Canaveral) / :..::
Myakka-lmmokalee-Waveland (Basinger, Pomello, Pompano) / I
Oldsmar-lmmokalee-Malabar (Adamsville. Eau Gallie, Myakka)
Wabarso-Felda-Pompano (Delray, Holopaw, Pomona)
Minor soils in parentheses.


Figure 10. Soil associations in the Tampa Bay watershed (after Caldwell and Johnson 1982).


19









Tampa Bay Ecological Characterization


by Spodosols and Entisols soil orders. The single
spodic soil association of Myakka-Waveland-
Cassia, for example, represents 33% of Manatee
County soils. Ridge, knoll, and hill soils are generally
sandy and well-drained Entisols, often associated
with regional terraces and prehistoric dune ridges.
An individual soil series can be associated with one
or more plant communities, since plant communities


reflect several factors, including drainage conditions,
chemical and mineral composition, and climate.
Table 6 presents common plant-soil series relation-
ships for the watershed.
Arent soils (i.e., soils disturbed by human activity
to a point of altering the soil profile) are found in asso-
ciation with mine pits, dredge-and-fill activities, and
other urban developments. Phosphate mining in


Table 6. Plant community and soil series associations in the Tampa Bay watershed (after USDA 1958, 1972,
1981, 1983; Eco Impact, Inc. 1979; Carlisle et al. 1981; Carlisle and Brown 1982).


Plant community


Pine flatwoods

Pine and cabbage palm
forests
Prairies
A. Saw palmetto
B. Seasonally wet
Scrub forests
A. Sand pine scrub
B. Longleaf pine and
turkey oak hills
Hammock forests


Soil series associations


Myakka, Eau Gallie, Waveland, Immokalee, Pomona, Ona, St. Johns, Wabasso,
Zolfo, Wauchula.
Adamsville, Felda, Pinellas, Bradenton, Hallandale, Parkwood Variant, Aripeka.



Myakka, Immokalee.
Pompano, Delray, Basinger, Placid, Sellars.

Cassia, Duette, Orsino, Pomello, Astatula, Paola, St. Lucie.
Orlando, Tavares, Candler.

Felda-Palmetto, Bradenton, Parkwood Variant, Aripeka (along elevated margins),
Paisley (Variant Sand), Arredondo.


Freshwater hardwood and Chobee, Tomoka, Okeelanta, Terra Ceia, Aripeka (along elevated margins),
cypress swamps Sellars, Canova, Anclote.


Freshwater marshes

Tidal marshes

Mangrove swamps


Delray, Floridana, Gator, Manatee, Tomoka, Okeelanta, Terra Ceia, Sellars,
Zephyr.
Myakka (tidal), Okeelanta (tidal), Gator, Homosassa, Weekiwachee, Lacoochee,
Pahokee, Tisonia, Aripeka (along elevated margins).
Estero, Wulfert, Kesson, Bessie, Weekiwachee, Hallandale (variant), Peckish.


Coastal beaches/dunes Canaveral, Satellite.


Floodplains and sloughs

Cypress domes and small
grassed ponds


Delray, Felda, Palmetto, Pineda, Basinger, Pompano, Anclote, Canova, Okeelanta,
Chobee.
Delray, Floridana, Gator, Tomoka, Basinger, Anclote, Placid, Sellars, Zephyr,
Okeelanta-Terra Ceia.









2. Geology and Physiography


western Polk, eastern Hillsborough, and northeastern
Manatee Counties has created and continues to create
large areas of aren't soils. The disturbed soils occur as
mixed overburden (substrate overlying the phosphate
matrix), quartz sand tailings used as pit fill or to cap
clay settling areas, and, the most pervasive, consoli-
dated clay slimes (Schnoes and Humphrey 1980; U.S.
Bureau of Mines 1982). Urban activities, particularly
those requiring extensive dredging and filling, have
altered much of the coastal lowland soil in Pinellas,
Hillsborough, Manatee, and Sarasota counties
(Estevez 1981; USDA 1983). In 1973, approximately
15% of Pinellas County soils were classed as made
land or urban land (DSP 1975a). About 730 ha of
Manatee County barrier islands are aren't soils classed
as Canaveral sand-filled or organic substratum
created from dredged sand and shells deposited on
tidal swamp or marshes (USDA 1983).
Estuarine sediments of the Tampa Bay watershed
consist primarily of quartz sand and calcareous shell
material (Pyle et al. 1972; Brooks 1973; Mote Marine
Lab 1975). The sands, and to some extent, the calcar-
eous material, result from a backfilling of offshore
sediments that began about 8,000 years ago. The off-
shore sediments were, in turn, an earlier product of
erosion from the Tampa Bay watershed river valleys,
exposed during a lower sea-level stand (Stahl 1970;
Brooks 1973). Pliocene and Miocene marl, lime-
stone, and sand underlie unconsolidated Holocene
deposits that are generally 12 to 15 m thick in Tampa
Bay, but increase to as much as 30 m in channels.
Shallow (less than 1.8 m deep) sand flats gradually
slope to channels which exceed 5 m near the bay axis
(Figure 11). The scoured Egmont Channel at the
mouth of Tampa Bay reaches an 18 m depth (Brooks
1973). In the last century people have made numer-
ous alterations in the smooth bottom topography,
including enlargement of natural channels and
creation of new channels, spoil areas, turning basins,


and causeways. Sand-sized particles dominate the
estuary bottom sediments, except in Hillsborough
Bay, where silt is abundant, and in high velocity chan-
nels, where coarser sediments are found (Figure 12).
Silts and other fines also increase significantly in
association with human modifications. For example,
silt and clay fractions in the Anclote River estuary
rarely exceed 1%, but in the adjacent Port Tarpon
Marina, silts alone account for more than 3% of the
sediment composition (Pyle et al. 1972). The typi-
cally homogeneous vertical composition of the
sediment's top 0.5 m in Tampa Bay is caused by mix-
ing by currents (tidal and wind driven) and benthic
fauna bioturbation. Sediments of the shallow flats
along bay margins are composed of an almost pure
fine quartz sand. Calcium carbonate content, mainly
fragments of mollusk shells, increases along the slope
bordering the channels near the bay mouth (Figure
13). Kyanite, staurolite, and sillimanite are the more
commonly observed heavy minerals. Clay minerals
such as kaolinite and montmorillonite are rare
(Goodell and Gorsline 1961; Pyle et al.1972).
Stormwater discharge from areas of intense urban
development contribute large quantities of suspended
solids and significantly increase the nearshore
sediment's percentage of organic matter. The
increase is most pronounced in areas without signifi-
cant tributaries (e.g., creeks, sloughs, rivers), such as
the Intracoastal Waterway, Dona and Roberts Bay,
eastern portions of Sarasota Bay, Old Tampa Bay,
and southeast Pinellas County. Waterway sediment
composition is affected by instream hydrologic modi-
fications (e.g., channelization, saltwater barriers, con-
trol structures, reservoirs) and the upland land uses
(Lopez and Michaelis 1979; Lopez and Giovannelli
1984). Cow Pen Slough, for instance, exhibits a low
level of organic matter except where it runs near a
county landfill (Mote Marine Lab 1975).








Tampa Bay Ecological Characterization


8230
82 30,


Hillsborough River


- 28000'


City of
Tampa


Pinellas
Peninsula


Alafia River


City of
St. Petersburg


0



0


Manatee River


- 27030'


~:.. .......


Figure 11. Bathymetry of Tampa Bay (ft) (from NOAA National Ocean Survey chart #11412).


22


d








2. Geology and Physiography


. I
82P 309


Hillsborough River


City of
Tampa


Pinellas
Peninsula


1 Inter-
eay
Peninsula


--- 28000'



















IM


0
0


k2 elttManatee River


Manatee River


27'30'


Very coarse-coarse sand
Medium sand


Fine sand
Very fine sand


Figure 12. Texture of bottom sediments in Tampa Bay (after Goodell and Gorsline 1961).


23


Alafia River


City of
St. Petersburg


I
Lullt


Silt


r

ly


WV









Tampa Bay Ecological Characterization


1
82J~ 30'


River


City of
Tampa


Pinellas.
Peninsula


Manatee River


Figure 13.
1961).


Calcium carbonate content of bottom sediments (%) in Tampa Bay (after Goodell and Gorsline


24


- 28000'

























0
0
0S


River


- 27030'


aw-.-



















Chapter 3. Climate

Richard D. Drew


3.1 Introduction

The National Weather Service classification
system divides Florida into seven climatic divisions.
Each division encompasses an area in which basic
climatic variables, 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 differ-
ences within a division exceed divisional variation,
particularly between coastal and inland areas.
Despite these differences, climatic divisions are a
means of organizing watershed and statewide
climatic indicators. Most of the Tampa Bay water-
shed is in the south central division, with a small part
in the north central division (Figure 14). The loca-
tions of first-order weather stations operated by the
National Weather Service in Florida are also shown in
Figure 14. Each station provides the most complete
weather data base available, including statistics on
temperature, rainfall, cloud cover, relative humidity,
wind, barometric pressure, and solar radiation. For
the watershed, only the Tampa Station provides this
level of detail, while first-order station data from
Lakeland and Fort Myers provide information on the
inland and southwestern coastal areas, respectively,
for the general region. This data base is supplemented
by cooperative and research stations that provide
weather data of a more limited nature (e.g., rainfall
and air temperature). These secondary weather
stations monitor the climate for a variety of applica-
tions; water management, agriculture, and aviation
are three of the most important. For a more complete
review of the weather stations adjacent to and in the


watershed, refer to the publications of USDC (1953,
1964), FBC (1954), Thomas (1970, 1974), Palmer
and Miller (1976), Whalen (1977, 1979), Wyllie
(1981), and Heath and Conover (1981).

In general terms, the mild subtropical climate of
the watershed is a product of its low topography, its
proximity to the Gulf of Mexico and the Atlantic
Ocean, and its relatively low latitude (Bradley 1972;
USDC 1981). The slight relief allows uninterrupted
movement of winds and rains across the terrain. The
adjacent waters moderate temperatures, acting as a
heat source in winter and a heat sink in summer, and
provide a source of moisture for clouds and rain. The
temperature differential between the water and the


Jackson ille


Atlantic
Ocean


Gulf of Mexico


South Central
1 . ---- -" %\ est
\ "'/ y Palm
,M, rs Beach
SEverglades Lower
and East
SW Coast,' Coast
\ JMiami

-Toria-aKeys,
Key West CP )


Figure 14. Florida climatic divisions (after Bradley
1972).


25









Tampa Bay Ecological Characterization


land also drives the land and sea breezes. The inland
areas are typically cooler in winter and warmer in
summer than the adjacent coastal regions. The low
latitude provides for moderate winter temperatures
(Palmer 1978). Rainfall in the area is characteristic of
a humid mesothermal climate with a warm, wet sum-
mer dominated by thundershowers and a moderate to
slight dry season during the winter (Hela 1952;
USDC 1981).


3.2 Rainfall

Mean annual precipitation for the Tampa Bay
watershed is approximately 140 cm (Heath and
Conover 1981). The entire region is characterized by
a relatively long period (6 to 8 months) of low rainfall
and a shorter period (4 to 6 months) of heavy rains.
Dry-season rains vary from 5 to 6.5 cm per month.
Wet-season rainfall is much more variable, both
spatially and temporally, and ranges from about 13 to
over 20 cm per month (Palmer 1978). From Novem-
ber to April, the dry season provides 24% to 34% of
the annual rainfall, derived primarily from middle-
latitude cyclonic or frontal rainfall systems (Thomas
1974; Echtemacht 1975; Palmer 1978). The wet-
season rains are a daily phenomenon caused by con-
vective rainfall systems (e.g., cumulonimbus thunder-
showers) that, in the summer months alone (June to
September), account for over 60% of the watershed's
annual rainfall. Wet-season, dry-season, and total
annual rainfall for individual stations in and adjacent
to the watershed are given in Table 7. Annual average
rainfall isohyets for the watershed are illustrated in
Figure 15. Rainfall exceeds 140 cm in the eastern half
of Pasco and Hillsborough Counties and most of the
Manatee River watershed in Manatee County.
A 5-year cyclic rainfall patten observed in south
Florida (e.g., Florida Keys or along the southeast
coastal ridge) is not evident in the Tampa Bay water-
shed (Thomas 1970). The only long-term rainfall
pattern apparent in this area is a recent (1960-75) pe-
riod of deficit rainfall when monthly rainfall was con-
sistently lower than normal (Palmer 1978; TI 1978a).
The weather over much of the eastern United
States is dominated by a succession of low- (cyclone)


and high- anticyclonee) pressure systems that move
generally west to east and collectively result in winds
known as the prevailing westerlies (Palmer 1978;
U.S. Air Force 1982). The zones of contact between
these pressure systems are called fronts. Rare during
the wet season in the Tampa Bay area, fronts domi-
nate south and central Florida's dry season in
response to the general atmospheric circulatory
system's shift southward over the state (Blair and Fite
1965; Palmer 1978). The fronts, also called synoptic-
scale systems, pass over the region an average of once
a week and exhibit rainfall patterns quite distinct from
the wet-season convection storms (Echtemacht 1975;
Palmer 1978; Bamberg 1980). Synoptic rains typi-
cally fall over a more uniform area of the front and
depend only on the temporal passage of the system
(Gruber 1969; Echteracht 1975; Palmer 1978).
Frontal rainfall usually extends along a line from
northeast to southwest over the Florida peninsula and
sweeps south to southeast. Convergence of warm,
humid air masses to the south and the cooler, drier air
carried with the front generates rainfall along the fron-
tal path. Rainfall intensities depend on the strength of
the interacting air masses and motions of individual
precipitation "pockets" within the front. Occasion-
ally, large amounts of rain will fall in a narrow band
when the front becomes stationary.
Figure 16 illustrates the average monthly rainfall
for the wettest dry-season month, March, and the
driest dry-season month, November. The disappear-
ance of summer convection systems, frontal systems
that remain to the north, and the shift in tropical storm
movement to the west of Florida create an environ-
ment conducive to November's low rainfall. In
November, the average rainfall in the watershed
varies from less than 2.5 cm to just over 3 cm, and
generally increases from south to north. Monthly
average rainfall tends to increase gradually through
March, when there is maximum development of fron-
tal rainfall. Average rainfall ranges from less than 5
cm near Venice to the south to greater than 7.5 cm in
the extreme northwest around Lakeland.
In midspring, the frontal systems move north of
west-central Florida and local sea-breeze/convection
circulation becomes the dominant force controlling
wet-season rainfall (Echtemacht 1975; Palmer 1978;









3. Climate

Table 7. Wet-season, dry-season, and total annual rainfall in the Tampa Bay watershed.

Dry season Wet season Annual
Station location Nov. to Apr May to Oct average
(N)a (cm) %0 (cm) % (cm) Ref.c
Alafia River
Lakeland WB City 54 38.48 30 91.21 70 129.69 1
Lakeland 37 38.40 31 87.15 69 125.55 2
Pierce 30 35.84 26 104.11 74 139.95 3
Plant City 74 39.60 28 100.66 72 140.26 1
Hillsborough River
Hillsborough St. Park 23 41.78 29 101.32 71 143.10 1
St. Leo 69 41.71 29 101.17 71 165.74 1
Manatee River
Bradenton 77 36.80 26 102.90 74 139.70 1
Bradenton Exp. Stat. 78 37.52 27 102.18 73 139.70 4
Ft. Green 14 40.67 28 103.23 72 143.89 1
Parrish 14 42.16 28 108.31 72 150.47 1
Sarasota Bay
Long Boat Key 15 56.67 34 109.02 66 165.68 1
Sarasota S.E. 16 32.92 24 105.66 76 138.58 1
Venice 20 34.67 29 86.03 71 120.70 1
Phillippi Creek
Sarasota 26 39.42 29 95.76 71 135.18 1
Tampa Bay
Bay Lake 16 45.34 32 98.60 68 143.94 1
Pinellas Park 25 38.38 27 104.44 73 142.82 1
St. Petersburg 55 39.42 29 96.27 71 135.69 1
Tampa 93 35.56 28 93.27 72 128.83 1
Tampa Airport 29 38.51 31 86.92 69 125.43 5
Tampa AFB 31 34.29 30 78.49 70 112.78 6


a (N) = Years of record. c References: 1) Thomas 1974 2) USDC 1978
b % = Percent of total annual rainfall. 4) USDC 1964 5) USDC 1981


Bamberg 1980). Convection rainfall is a product of
the sea-breeze system and the direction and intensity
of the general wind system. The pattern of shower
formation in the region is described by Palmer (1978)
as follows:

During the course of a summer day the land in
a coastal area warms up more rapidly than adja-
cent water bodies. The warm land heats the
overlying air which, in turn, becomes light and
buoyant relative to the air over the water. In
terms of atmospheric pressure, a low pressure


3) FBC 1954
6) USAFETAC 1974


area develops over the land with relative high
pressure over the water. Since winds are the
result of atmospheric pressure differences, an
onshore wind develops, commonly called the
sea breeze. Development of the sea breeze
begins a few hours after sunrise and continues to
mid or late afternoon. At the time of maximum
development, the front (landward edge) of the
sea breeze may have pushed 30-40 km inland
and is marked by cumulus clouds. Under favor-
able conditions these may develop into cumu-
lonimbus clouds producing shower activity.









Tampa Bay Ecological Characterization


- - County Boundary
...-- Basin Boundary


Go







O V
0 -'7





Precipitation Stations
A Record period >60 years
* Record period 30-60 years
* Record period <30 years


Figure 15. Average annual precipitation (cm) in the Tampa Bay watershed, 1941-70 (cm/yr) (after Palmer
1978).


28
































0


C S
o




* Precipitation Stations


Figure 16. March and November average rainfall (cm) in the Tampa Bay watershed (after Palmer 1978).


C)


ae









Tampa Bay Ecological Characterization


The local sea breezes interact with large-scale
(synoptic) airflow (prevailing southeasterlies and
southwesterlies) to form lines of convergence where
rainstorm development is greatest (Frank et al. 1967;
Gruber 1968; Pielke 1973). While the dry-season
rainfall tends to increase from south to north, the wet-
season rainfall exhibits (from north to south) a ridge-
and-trough pattern of higher and lower areas of rain-
fall (Figure 17). A ridge of seasonally and monthly
high rainfall values extends from the Bradenton area
eastward to encompass southern Polk County and
northern Hardee County (Figure 17). 'Troughs" or
areas of minimal rainfall characterize the southern
(Charlotte Harbor) and northern (Tampa) portions of
the watershed (Palmer 1978).
Convective wet-season storms exhibit the greatest
spatial and temporal variations of any rainfall regime.
Extreme differences in annual rainfall of as much as
10 cm in 1.5 km and 35 cm in 6.5 km have been
reported in the region (Woodley et al. 1974). Monthly
variations of more than 13 cm occur in areas situated
only a few kilometers apart (Duever et al. 1975;
Palmer 1978; Buono et al. 1978). The difference in
rainfall is related not only to the physical placement of
the clouds but also to moisture content and size of in-
dividual storm clouds. The natural variability of rain-
fall from a single cumulonimbus cloud in south and
central Florida ranges from 200 to 2,000 acre-ft
(Woodley 1970).
A predominant form of the convective wet-season
storm is the thundershower. These storms are brief
(1-2 h), usually intense, and occasionally attended by
strong winds or hail (Bradley 1972). Thunderstorms
in the Tampa Bay watershed are more frequent (87 to
over 100 days per year) than any other section of the
continental United States, and most frequent (about
75%) during the summer months (Jordan 1973;
Palmer 1978). Wet-season storms lasting more than a
few hours are infrequent and generally associated
with tropical disturbances. The short-duration, high-
intensity thundershowers are related to cyclic, land/
sea-breeze convective processes. Rain from these
storms generally falls during the late afternoon or
early evening hours, a period of maximum atmo-
spheric convergence (Gruber 1969; Echtemacht


1975; Gannon 1978). Figure 18 shows the average
number of days when rainfall exceeds 0.025 cm and
the average number of thunderstorms per month as
reported by the area's three first-order weather sta-
tions.
Distribution of rainfall over west-central and
southwest Florida during the year exhibits a bimodal
pattern (Figure 19). The first and smaller of two
peaks is in February or March and the second in July
and August (Thomas 1974). This bimodal seasonal
distribution of rainfall is associated with times of
maximum frontal (March) and thunderstorm (July)
activity (Palmer 1978).
A commonly reported precipitation statistic of in-
terest for air pollution and ecological studies is the
number of days on which certain amounts of rainfall
are reported, i.e., rainfall greater than or equal to
0.25 cm. A summary of the mean number of days per
month with rainfall exceeding 0.025 cm and 0.25 cm,
respectively, is given in Figures 18 and 20 (Bradley
1974; Gutfreund 1978; TI 1978a). The monthly and
seasonal distribution of rainfall is relatively uniform.
Storm events exceeding or equal to 1.3 and 2.5 cm
exhibit the same temporal patterns shown in Figure 20
for smaller threshold storms (Gutfreund 1978).
Rainfall frequency distributions developed from 5
years of record (1975-1979) for Fort Myers, Orlando,
and Tampa are illustrated in Figure 21. This figure
shows that approximately 75% of the rainfall events
in the watershed contribute less than 1.5 cm per event.
Drought is occasionally experienced even in the
"wet" season (Bradley 1972). The effect of drought is
aggravated or ameliorated by variations of tempera-
ture that affect transpiration, evaporation, and soil
moisture. One of the more noteworthy studies of this
situation is that of Gannon (1978), whose 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 redistribute rainfall by changing 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 the daily sea-breeze circulation in









3. Climate


- County Boundary
SBasin Boundary


C)

0O

CI

0
0


* Precipitation Stations


Figure 17. Average July rainfall (cm) in the Tampa Bay watershed (after Palmer 1978).


31









Tampa Bay Ecological Characterization

30-
Days with >0.025 cm rain Tampa
E] Avg. number of thunderstorms
20 . .......-.- -- -. .



20





Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30

Days with >0.025 cm rain Lakeland
O Avg. number of thunderstorms
20 ----o- -- ---- ...-- ----

0

10 ... ..........


I

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30
Days with >0.025 cm rain Fort Myers
O Avg. number thunderstorms r My
20 --- -r--- -
20








Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month

Figure 18. Average number of days when rainfall exceeds 0.025 cm (0.01 in) and average number of monthly
thunderstorms (data from Bradley 1974; TI 1978a).

32











3. Climate


12

10

3 8
r-
6

45


Month


Figure 19. Average monthly rainfall in the Tampa Bay watershed (after Thomas 1974).




15
Ft. Pierce
O St. Petersburg
E1 Winter Haven .
10 ...................................................................................... ....

p' iS~ Iiii


Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Month


Figure 20. Average number of days per month when rainfall exceeds
Gutfreund 1978).




1 -


0.25 cm (0.1 in) (after


.01
00
.r.001


.0001


1 2 3
Event Volume (inches)


Figure 21. Frequency distribution of rainfall in southwest Florida over a 5-year period (after
Anderson 1982).


33


15






0









Tampa Bay Ecological Characterization


Gannon's model. Surface albedo 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 increas-
ing 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 implications of temperature change for fish
and wildlife, as well as for the human population of
south Florida, have recently been noted by Marshall
(described in Boyle and Mechum 1982). His hypoth-
esis is that development and drainage have slowly
replaced Florida's wet season "rain machine" with a
relatively drier "heat machine" during summer
months. The wet-season rains that are so vital to
south Florida's ecosystems are less frequent because
of massive changes in the daily heat budget.
Rainfall has been deficient in west-central Florida
since 1961 (Palmer and Bone 1977). The drought is
most severe in an area that runs from Tampa eastward
through Bartow and northeast to Orlando; within this


200






100-






0


region, the 16-year cumulative deficits range as high
as 218 cm. Southward, the cumulative deficit
decreases to less than 25 cm at Fort Myers. The defi-
cit is attributed to the urbanization between Tampa
and Orlando, which reduces soil moisture; the
absence of "normal" hurricane activity during the 16-
year period; and a permanent climatic change (Palmer
1978). A 30-year annual rainfall profile for Lakeland
is presented in Figures 22 and 23. This figure clearly
shows the recent shift of annual rainfall from an even
distribution of wet to dry years before 1961 to a
lopsided distribution of dry to normal years since that
time.

3.3 Winds

Wind patterns in the Tampa Bay watershed are
determined by the interaction of wind forces of a
long- and short-term temporal nature. Seasonal large-
scale (synoptic) atmospheric patterns represent the
long-term phenomenon, such as the Atlantic anticy-
clone, whose western edge influences the lower-
altitude winds of the Florida peninsula during the
summer months. In this position, the anticyclone
causes southeasterly winds in the southern part of the
watershed and southerly winds in the northern


Figure 22. Thirty-year annual rainfall for Lakeland (data from Palmer 1978).

34









3. Climate
60


Wet
40

High
20. Normal


0 Normal


20Low
Normal
Dry


1946 1950 1955 1960 1965 1970 1975
Year
Figure 23. Rainfall deviation from normal over 30 years at Lakeland (data from Palmer 1978).


watershed (Figure 24). In the winter months (Figure
24), prevailing easterly trade winds dominate the re-
gion south of latitude 270N, while its counterpart, the
westerlies, influence the area north of latitude 290N.
The region between is quite varied (Gruber 1969).
Short-term atmospheric phenomena include local-
ized diumal land/sea breeze convective processes
during the wet season and synoptic-scale frontal
systems during the dry season (Echtemacht 1975;
Femandez-Partagas and Mooers 1975; Palmer 1978).
In a comprehensive examination of seasonal differ-
ences in the large-scale wind fields for the Florida
peninsula, Gruber (1969) described the seasonal
streamlines at three vertical levels: 950 millibars
(mbar) at 0 to 600 m; 500 mbar at 5,500 to 6,000 m;
and 200 mbar at approximately 12,000 m. His work
was summarized by Echtemacht (1975), who uses the
wind-field patterns to describe potential air pollution
problems affecting south Florida. The four seasonal
wind-field patterns adapted by Echtemacht (1975) at
the 950-mbar level (i.e., for low-level winds) are illus-
trated in Figure 24. The Tampa Bay watershed is in a
transition area of changing wind directions, especially
in winter, when winds vary from southeasterly to the
south and southwesterly to the north. Spring and
summer generally exhibit more southerly winds, and
fall is characterized by east or northeasterly winds.


The prevailing winds interact with the wet- and dry-
season short-term system processes (e.g., convective
and frontal) to produce the day-to-day wind patterns
over the watershed.
In the wet season (May to October), convective-
scale winds (initiated by thermal gradients at the land-
sea interface) mix with the prevailing southeasterly
winds (Pielke 1973). The recurrent wind-cycle and
maritime influence (discussed under the rainfall
section) is significant to the watershed's wet-season
climate because of the flat terrain and proximity to the
water (Bradley 1972; Echtemacht 1975). The daily
changes in divergence (in this case, a measure of
surface airflow away from a sinking column of air)
over the Florida peninsula for June, July, and August
were monitored by Frank et al. (1967). A pronounced
diural pattern shows very strong convergence (nega-
tive divergence, indicating surface winds flowing
towards an upwelling-in this instance likely to be a
convective updraft) peaking around 1200 to 1400
hours (Figure 25). This pattern demonstrates that the
convective scale is the fundamental scale of motion in
the watershed during the wet season (Echtemacht
1975).
In the dry season (November to April), the influ-
ence of convection diminishes as the sun's angle of


E
.2

E
0
c
.2_


.5.-


I


I









Tampa Bay Ecological Characterization


Figure 24. Seasonal wind directions and speed at the 950-mbar level in Florida, 1957-67 (after Echtemacht
1975).


36









3. Climate


20


10 August .- August
June -- June
July J u. ... ly
0-
o- ......



-10-


-2 0 -


-30 -.


-40 -I I I I
1:00 4:00 7:00 10:00 13:00 16:00 19:00 22:00 1:00 4:00
Time (e.s.t.)
Figure 25. Average monthly divergence curves for June, July, and August 1963, over the Florida Peninsula
(after Frank et al. 1967).


incidence decreases. This reduces the daytime radiant
heating of the land and minimizes the thermal gradi-
ent between the land and sea surfaces (Blair and Fite
1965; Donn 1975). Dry-season wind patterns are
influenced by synoptic-scale systems or winter
frontals moving cold airmasses southward. Although
the watershed lies far enough to the south to remain
affected by the easterlies year round (see Figure 24,
winter), a northerly component related to the synop-
tic-scale systems affects the daily weather pattern
(Echtemacht 1975). Winter cold fronts typically pass
over the watershed approximately once a week
(Palmer 1978). An average cold front affects wind
patterns for 4 to 5 days, involving a slow 360' clock-
wise 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. Maximum
winds preceding the front are from the southwest and
reach about 8 m/s. Maximum winds from an
exceptional cold front may reach 20 to 26 m/s
(Warzeski 1976).


Prevailing monthly wind speed and direction for
first-order weather stations in or adjacent to the water-
shed are summarized in Figure 26. Although the con-
cept of "prevailing" winds does not take into account
diurnal shifts in wind direction and speed caused by
differential heating of air and water surfaces or the
passage of winter frontal systems, it does indicate the
predominant seasonal factors that control wind.
Seasonally, highest average wind speeds are likely
in late winter and early spring, and lowest speeds are
most likely in summer. Winds near the coast, domi-
nated by stronger land/sea breezes, are generally
stronger than winds farther inland. Localized high
winds of short duration (35-50 km/h) are generated
by summer thundershowers and cold fronts (Bradley
1972). Wind speeds associated with convective
systems follow a diurnal pattern. On a typical day,
wind speeds are lowest at night, increase during
daylight to a peak (which seldom exceeds 8-10 m/s)
in the late afternoon, and then decrease in the evening
(Mooers et al. 1975; Gutfreund 1978).









Tampa Bay Ecological Characterization


-- Tampa
-- Fort Myers
-e- Lakeland


i dam


~~u"F3


,-----*^


N

WOE

S
0
s


p--^


I I I I I I I I I I I i I
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Month
Figure 26. Prevailing wind speed and direction (data from Bradley 1974; TI 1978a).


--2


pm


Synoptic-scale influences are associated with 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 evidenced by the northerly compo-
nent of the prevailing wind directions for the months
of October through January (Figure 26).
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 relatively flat
terrain of the Tampa Bay watershed (Gutfreund
1978).


3.4 Temperature

The southern latitude and the moderating influence
of the Gulf of Mexico control the air temperature
regime in the Tampa Bay watershed. The climate is
subtropical marine, characterized by long, warm
summers and mild, moderately dry winters (Bradley
1972).


Isotherms for the average annual temperatures and
for the coolest month (January) and the warmest
month (August) in south-central Florida are given in
Figure 27. Differences between coastal and inland
areas are highlighted by isotherm contours that follow
the coastline. Along coastal areas the maritime influ-
ence causes low daily fluctuations of air temperature
and rapid warming of cold air masses that pass to the
south and east of the state (USDC 1981). Inland areas
generally display a greater range of temperatures
because of more rapid heating and cooling of ground
surfaces (Gerrish 1973; Gutfreund 1978; TI 1978a).
In winter, advective and radiational cooling pro-
cesses following the passage of cold fronts cause
sharp drops intemperature (Bamberg 1980). As rain-
fall diminishes with the passage of a front, cool, dry
arctic air from Canada causes brisk northwesterly
winds, which at maximum strength (velocity) cause
the lowest daytime temperatures. Nighttime speeds
cooling when large quantities of heat are radiated
from land surfaces (water is a poor radiator),
particularly in periods of clear skies and calm winds.
Radiational cooling reaches a maximum a day or two


10.5


S9.5


8.5 .
E
*o
a
- 7.5 -


6.5


S5.5


A









3. Climate


30 20 7,02 after a front has passed, as the surface high-pressure
3o ope system moves over or near Florida from the north-
7 enney west. This cooling begins after sunset and results in
2 the lowest temperatures for the entire front at dawn.
280 Tampo Nighttime air-temperature gradients of 30C to 80C are
7 \ 730 common a few kilometers inland from the west-
0 F Pi740 central Florida coastline with the passage of synoptic
30 Frccold systems, as a result of radiational cooling. In
S \ addition to the coastal/inland air-temperature gradi-
T 73 -,C ents, a similar gradient (30C to 60C) is found between
740 relatively high, dry land and adjacent moist lowlands
ers \(Bamberg 1980). Another temperature gradient
S72 forms between urban and rural areas. Rural Lakeland,
for example, typically experiences 2 days of freezing
30 820 30 temperatures per year, while the city suburbs freeze
o 210 an average of 11 days per year (USDC 1978).
Kennedy The rare freeze, once or twice a year on calm, cold,
6", 6p \ p630 clear nights (maximum radiational cooling), is gener-
Tompa
20 620 ally not too destructive (TI 1978a). When sustained
640 freezing temperatures are combined with strong
\t P erce northwest winds, the penetration of cold is near maxi-
S65" mum and crop and citrus damage is most severe. A
66 -0 severe freeze is experienced about once every 20
63 OKEC \ years. Crops are most severely damaged if the freeze
640 is followed by warm, dry weather. Water bodies act
6 o as natural heat sources during the freezes, moderating
63 / the surrounding air temperature by conduction.
Summer air-temperature gradients associated with
810, wet-season convective processes develop more
30d Cope rapidly, are more frequent, and show greater spatial
810 Kenn/ variation than the winter temperature changes associ-
810 820
2 ated with fronts. Air temperatures typically rise to the
S ampr upper 90's in the vicinity of developing thundershow-
w2 \ ers, and drop 50C-170C when cool downdrafts gener-
o30\ ated from the thunderstorms precede a downpour
810 (Bradley 1972; Bamberg 1980). In the Tampa Bay
S/ watershed, particularly the eastern edge, temperatures
82 \ CHBE reach or exceed 320C an average of 100 days per year
S(Gutfreund 1978). Temperatures along the coastal
'/Myes regions are more moderate (Figure 28).
S\ 18,0 0

3.5 Relative Humidity
Figure 27. Annual, January, and August average
temperatures (oF) in south-central Florida (after A precise description of relative humidity is gener-
Thomas 1974). ally difficult because of large diurnal and seasonal


39









Tampa Bay Ecological Characterization


0 9060 variations (USDC 1981). Still, in Florida, and espe-
6~ c--ially south Florida, the situation is less complex
30ao3 \\\ because of the abundance of moisture throughout the
20 60 year (Gutfreund 1978). Average monthly relative
2030 humidities for 0100, 0700, 1300, and 1900 hours at
1 the Tampa International Airport are summarized in
Figure 29.
The mean annual relative humidity is quite
uniform throughout the watershed, averaging about
75% (USDC 1981). Relative humidities are normally
12 highest during the early morning hours, about 80%-
90%, and lowest in the afternoon hours, about 50%-
70%. Although seasonal differences are not great,
mean relative humidities tend to be lowest in the
60 spring (April and May) and highest in summer and
0-" 30
C>6'" fall.


Figure 28. Average number of days per year in 3.6 Solar Radiation
Florida when air temperatures exceed 320C (after
Gutfreund 1978). Atmospheric solar radiation varies little across the
Tampa Bay watershed (Gutfreund 1978). Factors that
do vary are cloud cover, air pollution (particulate load



100
1300 0 0100
O 1900 O 0700
.42 daily average

S 8 0 ..................... .................................................................................................................................................. .....................................................





60 -44.......





40
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Figure 29. Average monthly relative humidity at different times of the day (USDC 1981 data).









3. Climate


or dustiness), and relative humidity. These factors
modify the transmission, absorption, and reflection of
solar energy (Blair and Fite 1965; Bamberg 1980),
and largely determine the amount of solar radiation
reaching the land and water surface. Solar radiation
data collected at the Tampa and Lakeland first-order
weather stations are presented in Figure 30 (Bradley
1972). The average daily solar radiation is 444
langleys (gram-calories per square centimeter).
Monthly variations range from 293 langleys in Janu-
ary to 599 langleys in May (Bradley 1972). Higher
values are reported in middle to late spring rather than
during the summer solstice (when the angle of inci-
dence is smallest) because of increased precipitation
and cloud cover associated with the beginning of the
south-central Florida wet season (Figures 19, 30 and
31). Information on the frequency of fog in the
Tampa Bay area is presented in Figure 32.


3.7 Evapotranspiration

Evaporation and transpiration evapotranspirationn,
ET) are two processes that move moisture, in the form
of water vapor, into the atmosphere. Evaporation is
defined as the passage of vapor to the atmosphere di-
rectly from the surface of water bodies, from surface
and near-surface soils, or from impervious surfaces
on which moisture has collected (Bamberg 1980).
Transpiration is the movement of water vapor from a
living body through membranes, pores, and/or cellu-
lar 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, vegeta-
tion is the primary source.
Two major factors that control evapotranspiration
are solar energy and relative humidity. Solar energy
provides the fuel necessary to transform liquid water
into water vapor. The amount of solar energy reach-
ing the earth's surface is modified by cloud cover, air
pollution, and angle of incidence. Relative humidity
is a measure of the air's moisture saturation. The rela-
tive humidity of fog, for example, usually is 100%,
whereas that during rainfall may be less. Evapotrans-
piration is inversely related to relative humidity: as


relative humidity increases, evapotranspiration
decreases. Other factors controlling evapotranspira-
tion are wind (velocity and duration), wave action,
ground cover (type and density), shade, barometric
pressure, temperatures (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 1981).
Evapotranspiration, especially when soils are satu-
rated, becomes an important controller of sea-breeze
intensity and, ultimately, the formation of convective
storms. The heat consumption associated with high
evaporation rates slightly increases temperature
gradients between cooler inland areas and warmer
coastal-urban strips (Gannon 1978; Bamberg 1980),
especially for a day or two 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 that tends to even the spatial
distribution of seasonal rainfall (Bamberg 1980).
Estimates of evapotranspiration in west-central
Florida range from 75 cm to 120 cm per year
(Dohrenwend 1977; Palmer 1978). Predicted evapo-
transpiration patterns for Florida are given in Figure
33. Estimated annual values range from more than
100 cm in the southern part of the watershed to less
than 90 cm in the north (Dohrenwend 1977).
Although this is a first-order approximation, it closely
agrees with the areawide 100 cm per year generally
used by the Southwest Florida Water Management
District (SWFWMD) in regional water-use calcula-
tions (Palmer 1978; Seabum and Robertson, Inc.
1980). Both values are rough estimates for a region
whose physical environment exhibits high spatial
variability. Palmer (1978) categorized the geographic
variation into four major evapotranspiration surface
environments: lakes and open surface water bodies,
wetlands, well-drained upland areas, and urban areas.
Open surface waters exhibit evaporation rates that
range from 120 cm in the northern watershed to
130 cm in the south. Wetlands show the greatest
potential for moisture loss of any of the surface envi-
ronments, with qualities that maximize both










Tampa Bay Ecological Characterization


o lampa


c 60














60 Lakeland
[3 FortMvers














5 0 0 . .. . .. .. .. . .. ..
50.


















,- 400
0 -

u 20













Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
7 Tampa
o Lakeland















Month
Figure 30. Percent of possible sunshine, daytime sky cover, and solar insolation in southwest Florida (after
Bradley 1972; USDC 1978, 1981).
42
100



0









Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec





42









3. Climate


20
STampa Average number of clear days
O Lakeland
15 Fort Myers
S15


10
0







Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

20
Tampa Average number of partly-cloudy days
O Laeiland
SH Forln MJ,er=
15-


E 10



d0


0
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
20
Tampa Average number of cloudy days
E O Lakeland
S15 Fort Myers



E o
S15

0





Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Month
Figure 31. Average seasonal cloudiness in southwest Florida (after Bradley 1972; USDC 1978, 1981).

43









Tampa Bay Ecological Characterization
20
Tampa
O Lakeland
>. ] Fort Myers
. 15 -



E 10

ac






Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Month
Figure 32. Average number of days with heavy fog in southwest Florida (after Bradley 1972; USDC 1978,
1981).


Evapotranspiration
(millimeters)


Figure 33. Estimated evapotranspiration patterns in
Florida (after Dohrenwend 1977).


evaporation and transpiration (e.g., shallow surface
waters and abundant aquatic vegetation). Well-
drained uplands exhibit the most variable evapotrans-
piration rates in response to the variety of vegetative
covers, soil types, and water-table depths. Urban
areas, in which water is removed through stormwater-
drainage systems, retain less water for evapotranspi-
ration than any of the other surface environments.
The monthly pan evaporation at the Lake Alfred
Experimental Station in the extreme northern water-
shed is shown in Figure 34. The pan evaporation is
measured using a ventilated pan that is representative
of evaporative losses from small, isolated natural
shallow pools in the general vicinity of the pan where
similar exposure conditions prevail (Parker et al.
1955). The seasonal variation shown in Figure 34
closely follows the monthly solar radiation reported at
the Lakeland National Weather Station. A slight lag
is probably related to the seasonal availability of
moisture. Maximum pan evaporation is in May when
the sun approaches summer solstice, spring winds are
still strong, cloud cover is still minimal, heavy mom-
ing fogs are infrequent, and the relative humidity is
near the yearly minimum.









3. Climate


22 575

20 -525

E 18 -
2 475
0 16 -
S425 "
0 14 -
S-*. Solar radiation (Lakeland) 375
> 375 M
w 12-
-o- Evaporation (Lake Alfred c6
10 /Experimental Station) 325

8 -275
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Figure 34. Average monthly evaporation and solar radiation in eastern Tampa Bay watershed (adapted
from Parker et al. 1955; USDC 1978).


To estimate localized evapotranspiration rates, the
SWFWMD has developed a model that is sensitive to
spatial and climatic variations within the district
boundaries (Palmer 1978). The model uses four
existing evapotranspiration-predictive equations,
those of Thomthwaite (1948), Blaney and Criddle
(1962), Christiansen (1966), and Penman (1948).
The Penman equation considers solar radiation, cloud
cover, relative humidity, and wind, and appears most
suited for the watershed. However, all four equations
are used to estimate really averaged values of both
potential and actual evapotranspiration on a square-
kilometer grid-cell level (Wyllie 1981; Bob Evans,
SWFWMD; personal communicationn. This
approach enables the user to choose one or a combi-
nation of the four values predicted. The data are
incorporated into a monthly water-balance calcula-
tion for each cell (Wyllie 1981). The average
monthly potential evapotranspiration for the gulf-
coast area from Tampa Bay to Crystal River for each
of the equations is illustrated in Figure 35. The
Penman and modified Christiansen equations predict
an earlier seasonal rise in potential evapotranspiration
rates that corresponds to Lake Alfred pan evaporation
data (Figure 34) and to evapotranspiration data from
Tampa (Seabum and Robertson, Inc. 1980). It was
concluded that these two equations most accurately


reflect conditions typical of southwest Florida
(Wyllie 1981).

3.8 Hurricanes

The climatic conditions of south Florida may be
divided into three energy levels or intensities
(Warzeski 1976): prevailing mild easterly winds,
winter cold fronts, and tropical storms and hurricanes.
The first two were discussed in the sections on wind
and rainfall. Tropical storms and hurricanes, because
of their relative rarity, their importance as an ecologi-
cal force, and their unique climatic characteristics, are
treated as a separate climatic element.
In summer and fall, low-pressure areas originate in
the warm, moist air of the equatorial trough. In these
areas, the winds are light and usually drift from east to
west. Atmospheric waves form in the easterly flow
between 50N and 20N and proceed westward at 15 to
25 km/h (Blair and Fite 1965). From this point, the
easterly wave development may go through one to
four stages of a tropical cyclone (formative, imma-
ture, mature, decaying) as described by Riehl (1954).
In the immature and mature stages, the systems
generally move westward at 15 to 50 km/h with winds
ranging from 61 km/h (38 mph) (tropical depression)









Tampa Bay Ecological Characterization
on-


18-

16-

S14
-
S12-
S10-
to


2 I DI I I I I I I I
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept
Month

Figure 35. Comparative average potential evapotranspiration in the middle Gulf area as calculated by four
models (after Wyllie 1981).


to more than 400 km/h (great hurricane). The typical
path is parabolic, although the actual path of any
given storm is governed by the winds above it, which
cause a multitude of speed and directional changes
(Riehl 1954; Blair and Fite 1965; Gentry 1974). 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
rapidly, while the wind increases from a gentle breeze
to hurricane force, and the clouds thicken from cirrus
and cirrostratus to dense cumulonimbus, 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 stabilizes at its
lowest value. This phase may last 30 minutes or
longer, and then the storm begins again in all its sever-
ity, as before, except that the wind is from the oppo-
site direction and the pressure rises rapidly. As this
continues, the wind gradually decreases in violence
until the tempest passes and the tropical oceans


resume their normal repose. The violent portion of
the storm may last 12-24 hours.
South Florida has been visited more often by hurri-
canes and tropical storms than any other equal-sized
area of the United States (Gentry 1974). The Tampa
Bay watershed is exposed to both Atlantic and Carib-
bean hurricanes, but is more vulnerable to late-season
tropical cyclones moving northeasterly after recurva-
ture (Cry 1965; Bradley 1972; Ho et al. 1975). Points
of entry of hurricanes are shown in Figure 36. The
Tampa Bay watershed is most often hit in the latter
part of the hurricane season, usually September and
October. The probability of huricane-force winds in
any year decreases from 1 in 11 at Fort Myers to 1 in
25 at Tampa (TI 1978a). Only 10 or 11 storms of
hurricane intensity in 87 years of record have passed
inland on the west coast of Florida from Cedar Key to
Fort Myers (Heath and Conover 1981). The average
forward speed for hurricanes affecting the watershed
is 10 knots, with a radius of maximum winds extend-
ing an average of 20 nmi from the center (Ho et al.
1975). Detailed descriptions of the passage of
specific hurricanes and tropical storms through the


-- Thornthwaite (Annual total = 116 cm)
- Penman (Annual total = 128 cm)
-a- Blaney-Criddle (Annual total = 132 cm)
-- Christiansen (Annual total = 147 cm)









3. Climate


Figure 36. Paths of hurricanes striking the Tampa
Bay area 1885 to 1990 (after Jordan 1984; Monthly
Weather Review 1980-1991).


watershed (as well as the rest of the country) are
published in the journal Monthly Weather Review.

The primary forces associated with hurricanes are
wind, storm surge, and rain. Sustained winds higher
than 120 km/h are necessary for a tropical storm to
qualify as a hurricane. Sustained winds over 200 km/h
put a hurricane into the "Great Hurricane" category.
Winds over 200 km/h have been reported in central
and south Florida on several occasions in the last
century (Sugg et al. 1971). The most notable was the
Labor Day hurricane in 1935, which passed over the
Florida Keys with high sustained winds estimated at
320-400 km/h according to Bradley (1972).


The ecological significance of hurricanes is clear
when one considers that wind force increases by the
square of the wind speed. In other words, 150-km/h
wind exerts four times as much force as a 75-km/h
wind. When hurricane winds exceed 400 km/h, as
was estimated for the Labor Day hurricane, their
strength becomes almost inconceivable (Gentry
1974). Ball et al. (1967), Pray (1966), and Perkins
and Enos (1968) describe the passages of two recent
Great Hurricanes, Donna (September 1960) and
Betsy (September 1965), through the Florida Keys
and how they affected the ecology.
A storm surge is a meteorologically induced tide
produced by a combination of high storm winds and
low barometric pressure. The low pressure at the
storm center or eye creates a vacuum that lifts the
waters about 0.3 m for every 2.5 cm of pressure
difference or 0.6-1 m for a major hurricane (Bruun et
al. 1962). Winds generated by a hurricane cause
heavy seas that travel as swell waves in all directions
from the eye. Waves to the right of the storm center
and running in the direction of the storm movement
are generally the highest. As these waves encounter
shallow coastal waters, they peak, break, and add to
the overall water level toward the coast (referred to as
the wave setup). Winds also act on the water surface
(shear stress and normal pressure) to push the surface-
water layers forward. In deeper offshore waters, this
force is balanced by return flow in deeper layers, but
in shallower coastal areas, the waters tend to pile up
toward the shore. This pileup effect is most signifi-
cant in the shallow inland lakes and broad continen-
tal-shelf bays, and more pronounced when the storm
moves directly onshore (right angle to the shoreline).
Other factors, such as the offshore slope of the
bottom, storm speed and size, and shoreline configu-
ration (e.g., bays, embayments, river estuaries), affect
the size and duration of the storm surge (Jelesnianski
1972).
The total storm tide is a combination of the storm
surge and the astronomical tide. Added to the top of
the storm tide are storm waves, whose pounding
forces severely damage coastal structures (Gentry
1974). In Florida, about 75% of all damage related to
tropical storms is caused by tidal flooding, with the
remaining 25% attributed to winds and rainfall


47









Tampa Bay Ecological Characterization


(Bruun et al. 1962). The U. S. Fish and Wildlife
Service has maps showing maximum areas subject to
flooding in southwest Florida (Kunneke 1983). Some
of the higher storm tides reported along the central
Florida gulf coast are presented in Table 8.
One of the highest recorded storm tides along the
Florida gulf coast occurred on September 25, 1848,
when a 4.5-m tide struck Tampa, destroying much of
the port, but causing no loss of life. Seventeen days
later a second hurricane caused a 3.0-m storm tide.
The first of these two storms was the 100-year hurri-
cane and has been used to estimate potential hurricane
flooding in the watershed (Figure 37). A worst-case
scenario (a storm the size and intensity of the 1935
Labor Day Hurricane) predicted a coastal storm surge
of about 8 m for coastal Pinellas County (Seijo et al.
1979). The most vulnerable coastline areas in the
watershed are given in Table 9.
The amount of rainfall from tropical storms varies
according to the rate of ascent in the storm circulation,
the forward movement, the temperature and lapse
rates in the storm, and the moisture content of the air,
which must be continuously renewed. Because of the
violent nature of the storm, the error in the rainfall
measurements may be as high as 50% (Dunn 1967).
Usually, 12 to 25 cm of rain are recorded at any one
point during the passage of a tropical storm (Gentry


Table 8. Major hurricane storm tides in the Tampa
Bay watershed.

Storm tide
Location height" (m) Date Referenceb
Tarpon Springs 3.0 Oct. 1921 1
Caladesi Island 1.9 Oct. 1921 2
Clearwater 2.9 Oct. 1921 2
St. Petersburg 2.3 Oct. 1921 2
St. Petersburg 2.2 Sept.1950 3
Tampa 4.3 Sept.1848 2
Tampa 3.0 Oct. 1848 2
Bradenton 2.1 Oct. 1921 2
Sarasota 2.1 Oct. 1921 2
aStorm tide height = Astronomical tide and storm surge.
bReferences: (1) USDC 1957; (2) Bruun et al. 1962;
(3) Jelesnianski 1972.


Figure 37. One-hundred-year hurricane flood surge
in Little Manatee River (assuming mean annual river-
discharge rate) (after Dames and Moore 1975).


1974). One of the wetter hurricanes to affect Tampa
was Brenda (1960) which dropped more than 30 cm
of rain within 24 hours (Dames and Moore 1975).
Although Great Hurricane Donna (1960) passed over
this coastline, it was a comparatively "dry" hurricane.
Precipitation was only 5 to 8 cm. Great Hurricane
Donna's winds, however, reached 240 km/h at Ever-
glades City and caused extensive storm surge damage
along the southwest coast (Bamberg 1980). Maxi-
mum winds reported in the watershed during hurri-
cane conditions are given in Table 10.


3.9 Air Pollution

The sea breeze, moderate inland winds, abundance of
sunshine (driving convective processes), and rela-
tively high morning and afternoon mixing heights
provide the Tampa Bay watershed with climatic char-
acteristics that enhance the dispersion of pollutants
and generally result in good air quality (ESE 1975; TI
1978a). However, portions of the watershed, particu-
larly Hillsborough, northern Pinellas, and western


48









3. Climate

Table 9. Coastal areas most vulnerable to hurricane flooding in the Tampa Bay
watershed (after Bruun et al. 1962).

Maximum
Coastal region Specific areas) elevation(s) (m)
South of Sarasota Siesta Key Generally <1.5

Sarasota to Tampa Lido Keya 1.2-1.8
Bay Longboat Key 0.9-1.5
Anna Maria Key 0.6-1.5

Tampa Bay area Areas bordering Tampa, Old Tampa, and Most <2.4
Hillsborough Bay (e.g., Shell Isle and Much <1.5
Davis Island). MacDill Air Force Base,
and shore area north of Ballast Point
to Hillsborough River.

Egmont Channel Long Key 1.7-1.8
to Anclote Keys Treasure Island 1.7
Clearwater Beach Island 1.5
aNew Pass formed from 1848 hurricane breakthrough.


Polk Counties, have consistently shown high levels of
air pollutants that violate State and Federal air quality
standards (EPA 1972; Ped Co. 1976; Bowman 1977;
Urone and Chadboume 1977; FDER 1978, 1979a,b;
Gutfreund 1978; TI 1978a; HCEPC 1984). Else-
where in the watershed, local or transient air-pollution
problems associated with intense urbanization (e.g.,
construction, vehicular traffic, and fossil-fuel power
plants) cause localized poor air quality, but not at the



Table 10. Maximum winds reported in the Tampa
Bay watershed (after USDC 1957; Bruun et al.
1962; Seijo etal. 1979).

Wind
Location speed (km/h) Date
Tampa 130 Oct. 18,1910
135 Oct. 19,1944
138 Sept. 4, 1935
Tarpon Springs 129 Oct. 25, 1921
(129-160)
Sarasota 124 Oct. 19, 1944


levels observed in the industrialized areas of Hillsbor-
ough, Pinellas, and Polk Counties.
The atmospheric emission-transport mechanisms
that convey contaminants from the air to the earth's
surface depend on the nature of the substance and the
regional weather patterns. Atmospheric contami-
nants take three forms: small particulate matter that
can form condensation nuclei, suspended particulate
matter or liquid aerosols that can be scavenged by
falling raindrops, and solutes dissolved in condensa-
tion particles or cloud droplets (Echtemacht 1975;
Brezonik et al. 1982; ESE 1984). The sources for the
three forms and their geographic distribution depend
on weather patterns.
Large-scale synoptic (or pressure) systems that
pass over the watershed in the dry season (November
to April) may contain pollutants from sources far
removed from the State (Echtemacht 1975), in addi-
tion to localized sources (Holle 1971; TI 1978a;
Edgerton 1981). Wet-season diural land/sea breezes
carry atmospheric contaminants, primarily from local
sources such as automobile emissions; stack gases;
road, fertilizer, and pesticide dusts; and phosphate









Tampa Bay Ecological Characterization


mining, transport, and processing emissions (Holle
1971; Echtemacht 1975; TI 1978a; HCEPC 1984).
Airborne contaminants from the atmosphere are
carried to the land and water surface by either wet or
dry fallout (Irwin and Kirkland 1980). Materials
subject to dry fallout are in a continuous flux of
suspension and deposition (e.g., wind generated dust,
bacteria, spores, pollens, car emissions) (HCEPC
1984). Materials deposited during wet fallout or rain-
fall, in either a dissolved or particulate form, are
affected by two processes referred to as rainout and
washout (Echtemacht 1975). Semonim and Adams
(1971) describe rainout as the removal of aerosols in
the rainmaking process, and washout as the process of
falling rain scavenging airborne particulates. In cen-
tral and south Florida, phosphate (P04) in particulate
form is subject to washout as well as to dry fallout
year round (Echtemacht 1975; Brezonik et al. 1982).
In contrast, nitrogen as NOx is primarily a soluble gas
and is, therefore, removed in the rainout process.
Edgerton (1981) found NOx to be a significant
airborne contaminant in the Tampa area, and levels of


NO03, NH4+, and S042- were observed to decrease
with distance from the urban-industrial center. Total
atmospheric fallout is commonly reported as bulk
precipitation and includes all soluble and insoluble
materials (Irwin and Kirkland 1980). Highest rates of
total atmospheric fallout are commonly observed in
agricultural areas and near major point sources; i.e.,
fossil-fuel power plants (Brezonik et al. 1982;
HCEPC 1984). Lowest nutrient fallout amounts are
reported in undeveloped coasts and forested areas.
Although most of the total annual bulk-precipita-
tion load is deposited in the wet season, pollutant
concentrations in rainfall are highest in the dry season
(Echteracht 1975; Waller and Earle 1975). The
South Florida Water Management District's rain-
water chemistry data illustrate this seasonal differ-
ence of nitrogen and phosphorous concentrations.
Peak concentrations in the spring months, character-
ized by high winds and low rainfall, are representative
of high dry-fallout conditions (Figure 38). Fire is also
believed to be a factor in inhancing the concentration
of dry fallout in the dry season (Holle 1971; Waller


SAmmonium
Nitrate
O Nitrite
[ Orthophosphate




o

0
0d
00 o


Summer


00
o 0
01 0
C6


Winter


Spring


Season
Figure 38. Seasonal average nutrient concentrations in rainwater at Tamiami Trail and Forty-Mile
Bend (after Echtemacht 1975).


2.0


a.
a-
0

c 1.0 -
o
C
0
0


_I


0.0 -.-









3. Climate


and Earle 1975). Summer months, during peak rain-
fall and maximum dilution, show the lowest concen-
trations of dry fallout.
An important factor controlling the ecosystem's
exposure to air pollutants is the frequency and dura-
tion of atmospheric inversions. The temperatures
normally decrease with increasing altitude, but occa-
sionally the reverse is true; that is, the temperature
increases with height in a given atmospheric layer or
between layers. This phenomenon is called an inver-
sion of temperature or simply an inversion, and is
common on calm, clear nights when the surface cools
rapidly by radiant heat loss. The near-surface air is
cooled by conduction and radiation faster than the air
above it, creating an inversion-a stable equilibrium
in the air column with cooler air at the surface. When
air temperatures decrease with height (a condition
favorable to convection), the air column is unstable
(Blair and Fite 1965). The significance of inversions
to air quality is that they reduce mixing, dilution, and
dispersion of air pollutants, because air within an
inversion is trapped. The near-ground pollutants,
such as vehicle emissions, can build up to levels that
constitute a health hazard (Gutfreund 1978).
Low-level inversions are least frequent and short-
est in the southern part of the watershed, increasing in
duration and frequency from the coast inland (Hosler
1961; Gutfreund 1978). Inversion frequency typical-
ly decreases with height and is observed most often in
the surface-to-26-m layer. Seasonally, they are more
common in winter and fall and least common in
spring. They frequently form between 2200 and 0700
hours, with minimum frequency at 1000 hours. Land/
sea breezes generally prevent the significant buildup
of atmospheric pollutants in the watershed (Gut-
freund 1978; TI 1978a).
Several studies, including the Hillsborough
County Environmental Protection Commission
(HCEPC) biannual reports, the State of Florida air
quality statistical reports, and several privately and
publicly funded studies (i.e., TI 1978a,b,c areawide
impact assessment program) focus on air pollution in
the Tampa Bay watershed. Although not as current as
the State or local program reports, the EPA-funded TI
(1978a) study is the most comprehensive. It is a


compilation of the major air-pollutant sources, moni-
toring sites, and dispersion characteristics of west-
central Florida (excluding Pinellas County). The
following information is largely drawn from this
report, and is supplemented by more current and site-
specific data (e.g., HCEPC 1982, 1984).
The air pollutants of primary concern in the Tampa
bay watershed and their probable sources are listed in
Table 11. The sources are generally reported as point
sources (e.g., exhaust stacks), or areal sources (e.g.,
forest fires, dust from unpaved roads). As shown in
Appendix Table A-2, fossil fuel power plants and the
phosphate industry are the most important SO2 and
total suspended particulates (TSP) point-sources,
accounting for 97% of the SO2 emissions and 80% of
the TSP emissions (TI1978a).
Power plants in 1976, particularly in Hillsborough
County, accounted for 77% of the SO2 point-source
emissions (Appendix Table A-2), and 76% of the total
(point- and areal-source) emissions in the region
(Appendix Table A-3). The only SO2 nonattainment
area in Florida is situated in northern Pinellas County,
where 22 violations were reported from July 1977 to
April 1978 (FDER 1978). Probable point sources are
a phosphate-processing plant, a fossil-fuel power
plant, and an asphalt batch plant. Many of the 3-hour
violations were observed in evening and early mom-
ing (1700 to 0600) when inversion frequency is the
greatest. Annual sulfate load in Hillsborough County
decreased from 1974 to 1978, and from 1978 to 1983
has stabilized in spite of an increase in the number of
point sources (TI 1978a; HCEPC 1984). The
decrease in loading was caused by implementation of
air pollution abatement practices (e.g., higher stack
heights, lower sulfur fuels), particularly from 1974 to
1976 (Appendix Table A-2, Figure 39). No violations
of Federal or State standards were reported in Hills-
borough County in 1982 and 1983 (HCEPC 1984).
Additional sources of SO2 not addressed in the TI
(1978) study include imported atmospheric sulfur
from both continental and maritime areas, and natural
biogenic sources of sulfur within the region. These
may represent significant inputs into an area's total
sulfur budget, particularly in nonindustrialized, rural
regions (Adams et al. 1980; Edgerton 1981; ESE
1982a,b, 1984; Brezonik et al. 1982).









Tampa Bay Ecological Characterization


Table 11. Major air pollutants in the Tampa Bay watershed and their probable sources (after TI 1978a).

Pollutant Probable source Activity Referencesa
Sulfur dioxide Fossil fuel power plants Burning of sulfur containing fossil fuels. 1,10,12.
Phosphate industry Burning sulfur-containing fossil fuels. 2,10.
Manufacture of sulfuric acid (an acid mist is also 9.
generated).
Other Mobile emissions, stationary fuel combustion, 1,3,10,12
incineration, citrus heaters, cement producers.
Dust b Fossil fuel power plants Fuel burning. 1,3,10.
Phosphate industry Fuel burning, drying, grinding, and material transport; 8,10.
other stages of mining.
Other Small single-family or apartment heaters and 10,11.
incinerators, mobile sources, citrus heaters, bacteria,
soil and meteoritic dust, spores and pollen, salt, cement
processing, factory dust, and traffic.
Fluorides Phosphate industry Various chemical processes, drying and calcining, 4,5,6,10.
fluoride removal for feed preparation, gypsum, and
cooling-water ponds.
2Radon Phosphate industry Ground disturbance associated with strip mining leads 7.
to a redistribution of uranium-238 and its decay
products.
Lead Industry Lead smelting and refining, scrap-metal recovery, and 10.
battery manufacture.
Other Burning of leaded gasoline. 10.
Nitrogen oxides Fossil fuel power plants Fuel burning 10,12.
and carbon
monoxide
Other Mobile emissions, any industrial process burning fuels. 10,12
Ozone Product of reaction Autos, gas stations, gas terminals, gas tankers, car- 10.
between hydrocarbons undercoating operations, paint manufacturers, dry
and nitrogen oxides cleaners, auto refinishers.


a References:


(1) Ped Co. 1976
(2) USEPA 1977
(3) Ped Co. 1975
(4) ESE 1977a


(5) Tessitore 1975
(6) Tessitore 1976
(7) Guimond and Windham 1975
(8) FDER 1977


(9) USEPA 1976
(10) HCEPC 1982, 1984
(11) TI 1978a
(12) ESE 1982b


b as total suspended particulates (TSP).


Although in 1976 the phosphate industry domi-
nated the TSP point-source emissions (54%) in west-
central Florida (Table 11), it contributes only about
17% of the total TSP loading to the watershed (Tables
11 and Appendix Table A-2). Vehicular emissions,
dust from paved and unpaved roads, trash and
garbage incineration, agricultural burning, and forest
fires are areal sources that account for the largest part
(56%) of the TSP emissions (Appendix Tables A-2 -
A-4). Hillsborough County is one of the two Florida
counties designated as a TSP nonattainment area by
the U.S. Environmental Protection Agency (FDER
1978). Several stations located in the Hillsborough


Bay area have reported primary (Federal) and second-
ary (State) 24-hour and annual geometric mean value
violations in 1982 and 1983 (HCEPC 1984). The
primary sources that contribute to these violations are
National Sea Products, Hookers Point, and Gardinier
Park, and to a lesser extent, fugitive dust from traffic
and dust-producing industries (e.g., General Portland
Cement, Florida Steel Corporation). Implementation
of pollutant-control devices between 1974 and 1976
significantly reduced TSP and SO2point-source emis-
sions (Appendix Table A-2, Figure 39 and 40) (TI
1978a; Gutfreund 1978; HCEPC 1984). Fluoride
emissions in the watershed are confined to mining










3. Climate


1.0
Rural
Urban
0.8 ....... ................ .. ..... . .............. ..


E 0.6 .. .-- ............... .......

8
l-

0 0.4 .......
U)


0.2


0.0
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983
Year
Figure 39. Average daily concentrations of airborne sulfur dioxide in the rural and urban Tampa area for the
years 1970-83 (after HCEPC 1984).




80








60 .. ...... .








40
1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983

Year
Figure 40. Annual suspended-particulate emissions in the Tampa area during 1973-83 (after HCEPC 1984).



53









Tampa Bay Ecological Characterization


activities, principally in eastem Hillsborough County
and western Polk County (Table 12). The areal-
source emissions (from holding ponds) are approxi-
mately five times as great as reported for point-source
emissions. These emissions have, in some areas,
increased pasture-grass fluoride content to levels
exceeding 45 ppm (level considered to be hazardous
to foraging cattle) (TI 1978a; HCEPC 1984).
Ozone (03) production at ground level is related
primarily to a photochemical atmospheric reaction
between reactive volatile organic compounds
(RVOC), nitrogen oxides, and sunlight (HCEPC
1984). Reactive volatile organic compounds, which
vaporize into the atmosphere as reactive hydrocar-
bons, are emitted from such stationary sources as
gasoline storage and transfer operations and indus-
tries that use solvents and surface coatings containing
organic compounds. Most reactive hydrocarbons,
however, come from motor-vehicle exhaust systems.
Nitrogen oxides result almost entirely from combus-
tion in electric-power generation units or gasoline,
diesel, and jet engines (FDER 1979b). Hillsborough,
Pinellas, and seven other Florida counties were identi-
fied as photochemical-oxidant nonattainment areas
by EPA (FDER 1979b). From January 1977 to Octo-
ber 1977, Pinellas County had 11 violation periods.
After September 7, 1982, the 1-hour ozone stan-
dard in the State was increased from 80 to 120 ppb,


Table 12. Summary of fluoride point-source and
areal-source (pond) emissions in Polk, Hillsbor-
ough, and Manatee counties (after TI 1978a).

Total emissions (t/vr)
Pond emissions Point sources
County 1974 1976 1976
Polka 1,120 1,211 244
Hillsborougha 320 346 69
Manatee 15 15 2
Total 1,455 1,573 315
a Fluoride product recovery at one plant in Polk County
and two plants in Hillsborough County tend to reduce
pond emissions. Since no quantitative data exist on the
extent of the reduction, it is not reflected in the numbers
tabulated.


matching the Federal standard. Even with the laxer
standard, several sites in the Hillsborough Bay area
reported violations (e.g., Davis Island in 1983,
[HCEPC 1984]). From 1973 to 1983 the number of
days each year that exceeded 80 ppb in Hillsborough
County remained fairly constant; slightly fewer days
have exceeded the new standard of 120 ppb (Figure
41) (HCEPC 1984). Ozone levels show a strong diur-
nal pattern corresponding to increases in sunlight and
vehicular traffic. Hourly ozone averages generally
peak between 1200 and 1800 hours.

Additional air pollutants whose concentrations are
tied to the diurnal pattern of vehicular traffic in the
area are lead, carbon monoxide, and the nitrogen
oxides. All these pollutants have decreased since
1973, apparently the result of the use of catalytic
burners and lead-free gasoline in automobiles, and the
implementation of air-pollution abatement practices
at fossil-fueled power plants (HCEPC 1984).
Although higher levels of all three pollutants corre-
spond to the areas within the Tampa Bay watershed
with higher populations and more traffic, no viola-
tions were reported in 1982 or 1983 (HCEPC 1984).
The pH of "pure" rain is controlled by the dissolu-
tion of atmospheric C02, forming a weak carbonic
acid (H2CO3) with a pH of about 5.6. When factors
such as alkaline dust and ocean spray that are charac-
teristic of the Tampa Bay watershed are taken into
account, the pH of rain approaches 7.0 (Brezonik et
al. 1982). However, with the release of sulfur and
nitrogen acids to the atmosphere (forming H2SO4 and
HN03) from anthropogenic sources, (e.g. fossil-fuel
combustion) and from biogenic sources (e.g., salt
marshes), rainwater pH (particularly in urban-indust-
rial areas) is drastically lowered (Brezonik et al. 1982;
ESE 1984). The resulting acidic rainfall increases
soil- and surface-water acidity and alters the capacity
of the soils and organic materials to retain nutrients,
metals, and exotics such as organochlorinated hydro-
carbons. Although a released nutrient may boost
plant food supply, the effect is short-lived, for the
released nutrients are also more susceptible to leach-
ing. Thus, on a long-term basis, the shift in acidity
and subsequent loss of nutrients mean use of more
fertilizer to sustain crop yields. In addition, toxic









3. Climate


'71 '72 '73 '74 '75 '76 '77 '78 '79 '80 '81 '82 '83
Year
Figure 41. Number of days each year on which ozone concentration exceeded 80 ppb and 120 ppb
in the Tampa area during 1971-83 (after HCEPC 1984).


metals and exotics become available to the hydrologic
cycle, either by percolation into ground water or by
dissolution back into the surface waters from bottom
or suspended sediments (Brezonik et al. 1982).
Edgerton (1981) studied the problem of atmospheric
acid deposition in the Tampa Bay watershed by com-
paring sulfur, nitrogen, and acid fallout at seven sites
in the area. Although all samples exhibited acidities
higher than pure water in equilibrium with atmo-
spheric CO2, the area's rainfall was no more acidic
than observed at most other locations in Florida (ex-
treme south Florida was higher). However, the anions
S042- and NO3- and cations Ca2+ and Mg2+ were re-
ported in much higher concentrations in the Tampa
area than elsewhere in the State. High levels of
SO42-, Ca2+, and NH4+ in the area were tied back to
the region's intensive industrial and surface activity
(Edgerton 1981). These ions and others, e.g., NO3-,
generally decreased a relatively short distance from
the urban-industrial center, as, surprisingly, did the


pH values. The decrease of pH in rainfall away from
the industrial area was explained in the following
manner (ESE 1982b):
...the mix of atmospheric emissions in the
immediate area is such that the majority of
acidity in Tampa area rain is neutralized by lo-
cally suspended particulate matter, principally
calcium carbonate. Such particles, however,
have significant deposition velocities and are
redeposited close to Tampa, while the acid pre-
cursors (SO2 and NOx) may travel much
greater distances."
Other studies (Brezonik et al. 1982; ESE 1982b,
1984) observed pH values from the Tampa Bay
region to average less than 4.7. Summer rains were
generally 0.2 to 0.3 pH units lower than winter
precipitation. Sulfuric (H2SO4) and nitric (HNO3)
acids account for 70% and 30%, respectively, of the
excess acidity (Brezonik et al. 1982).


















Chapter 4. Hydrology and Water Quality

Richard D. Drew


4.1 Introduction

Perhaps nowhere else in Florida are conflicts over
water supply and optimum use more sharply defined
than in the west-central region. The large and rapidly
growing urban populations of Tampa, St. Petersburg,
Clearwater, and Sarasota place increasing demands
on potable water resources and compete with water-
intensive industrial and agricultural users for the re-
gional water supply. The development of reservoirs
and well fields to meet existing and projected de-
mands alters the magnitude and timing of freshwater
discharge to the estuarine environment. Shortfalls in
local sources have inspired some investigators to pro-
pose importing water from as far north as the
Suwannee River (Geraghty and Miller, Inc. 1977).
Once the water's immediate usefulness ends, it is
disposed of in the form of sewage and industrial
waste, urban runoff, mine processing waste, and agri-
cultural runoff to the local surface and ground waters.
For Tampa Bay, waste disposal has resulted in fish
kills, algal blooms, phosphate slime pond spills,
sewer overflows, closed shellfish areas, reduced
seagrass meadows, and the loss of aesthetic appeal
(Simon 1974; FDER 1980,1983; Metcalf and Eddy,
Inc. 1980, 1983; HCEPC 1982, 1984).
In addition to upland urban, industrial, and agricul-
tural development, the Bay itself has been physically
modified to facilitate real estate development, traffic
flow, and waterbome commerce. In 1974 a total of
65 km of dredged channels, ranging in depth from 6
to 11 m, cut across the Tampa Bay system (Simon
1974). The 60 km of causeways that cross the bay
system reduce flushing of bay waters to a third of the


natural rate. Shoreline real estate development has
created extensive finger canals and seawalls where
there were once mangroves and salt marshes. Old
Tampa Bay, Hillsborough Bay, and Boca Ciega Bay
are the areas most affected by these modifications
(Getter et al. 1983).
The Tampa Bay system's ability to support and
produce fish and wildlife is often reduced in this
ongoing water supply and water-use struggle.
Upstream water diversion, land development, and
increased consumption alters the timing and magni-
tude of freshwater supply to the freshwater wetland
and estuarine ecosystems, while urban and agricul-
tural runoff and sewage and industrial discharge
change its chemical nature. Dredging, filling, and
shoreline modifications of the bay and its major tribu-
taries chronically remove valuable breeding and
nursery habitats, destroy bottom communities, and
resuspend settled nutrients.
Describing water quality and quantity in the
Tampa Bay watershed is very difficult, considering
the wealth of past studies and the great number of on-
going or recently completed studies. This chapter
attempts to summarize the available information by
geographic divisions or major river and receiving
water drainage areas. The Tampa Bay watershed, for
this purpose, is divided into eight drainage areas,
including the Anclote River, West Pinellas Peninsula;
Eastern Pinellas Peninsula/Old Tampa Bay; Hillsbor-
ough River/Tampa Bypass Canal; Alafia, Manatee,
and Little Manatee Rivers; and Manasota Coastal
area. Tampa, Old Tampa, and Hillsborough Bays are
discussed separately. Land use, point sources, and
nonpoint sources are briefly described for each









4. Hydrology and Water Quality


drainage area to provide an insight into what is enter-
ing the waters (either natural or of human origin),
followed by a review of the area hydrology and water
quality.
Ground water is treated from a general watershed
perspective. It is included in the Tampa Bay water-
shed characterization because of its direct connection
to the watershed surface waters via springs, seepage,
sinkholes, water supply, and subsurface disposal.
Information is presented vertically by aquifer and
horizontally with changes in geologic strata and saline
interaction.


4.2 Ground Water

Ground water in the Tampa Bay watershed is
present in two aquifers, the surficial and the Floridan,
generally separated by a confining bed of dense clay.
The thickness, lithology, depth, and distribution of
these units are spatially quite variable (Figure 42).
The generalized hydrogeologic relationship among
these units is illustrated in Figure 43.
The surficial aquifer is nonartesian and consists
predominantly of fine to very fine sand and clayey
sand interbedded with clay, marl, shell, limestone,
and phosphorite of primarily Pliocene to Recent ori-
gin (Figure 42). Typically, it ranges from 6 to 12 m in
thickness, but may reach 30 m under ridges near the
northern and eastern boundaries of the watershed
(Motz 1975; Wehle 1978; Wilson and Gerhart 1980;
Brown 1982b; Henderson 1983). The surficial aqui-
fer is absent where the limestone of the Floridan aqui-
fer or the confining layer nears or reaches the surface.
Yield from the aquifer is as variable as its thick-
ness. Transmissivity is a measure of an aquifer's abil-
ity to have water pumped from a well without lower-
ing the water table. Transmissivity for the water table
surficiall) aquifer ranges from zero, where the thick-
ness is less than a few meters, to about 2,000 m2/day
(Geraghty and Miller, Inc. 1976, 1977; Wilson and
Gerhart 1980).
Water-table gradients and direction of flow usually
conform to local topography, so that steeper gradients
adjoin major stream courses and gentle gradients


characterize the broad interstream areas (Wehle 1978;
SWFWMD 1981). Water in the surficial aquifer
flows laterally toward local points of discharge (e.g.,
lakes, streams, ditches, wells, sinks) grading down
toward the Gulf of Mexico or Tampa Bay, and down-
ward as leakage through the confining layer to
recharge the Floridan aquifer (Stewart et al. 1978). In
poorly drained areas, the water table is at or near the
land surface (e.g., Cypress Creek, Green Swamp), but
generally it lies 1.5-15 m below (Motz 1975; Wehle
1978; Hickey 1981a; Brown 1982a,b).
Seasonal changes in the height of the water table
typically range from 0.5 to 1.5 m, with peak heights
reached in the rainy season and midwinter. Lower
levels correspond to the end of the dry season,
commonly May (Tibbals et al. 1980; Hickey 1981a;
SWFWMD 1981; Brown 1982a,b). Along coastal
margins, daily fluctuations are caused by tides
(Hickey 1981a). Two hydrographs, illustrated in
Figure 44, show no significant trends in water levels
from 1965 to 1976, other than that expected from
annual rainfall variation.
In some areas of the Tampa Bay watershed, the
surficial aquifer has been affected permanently by
human activities. One example, the construction of
the Tampa Bypass Canal from 1970 to 1982, diverted
high-flow flood waters away from the middle Hills-
borough River to the Six Mile Creek/Palm River
system. The canal penetrated a ridge separating the
two river systems and cut through a wet, flat upland
area called Hamey Flats. The lower water level in the
canal has increased drainage from the surficial aquifer
on lands adjacent to the canal, lowering the water
table. The canal also broke through the confining
layer, creating a new, larger outflow point for the
artesian aquifer that reduced flow to Eureka Springs
and seepage springs in Harney Flats. The net effect of
the canal, even with control structures to maintain
water-level heights in the canal, was a 0.5 to 1.5-m
lowering of the surficial aquifer in Hamey Flats and
Eureka Springs area (Motz 1975; Duerr and Stewart
1980; USGS 1983).
The confining layer that separates the surficial
from the Floridan aquifer is typically formed by a
carbonate and plastic sequence composed of clay, silt,













Mlion STRATA GENERAL HYDROLOGY IN SWFWMD
Million STRATA
Years NORTH NORTH-CENTRAL SOUTH-CENTRAL SOUTH
Ere Period Epoch Before North 4 South (North of Mid-Pascc (Mid-Pasco to South (South Hillsborough (South of
Present County) Hillsborough County) to Mid-Sarasota Mid-Sarasota
(MYBP) County) County)


QUATERNAR'


HOLOCENE
(Recent)


PLEISTOCENE


PLIOCENE


MIOCENE


Undifferentiated Deposits


CALOOSAHATCHEE



BONE VALLEY/
TAMIAMI


HAWTHORN/
ALACHUA


OLIGOCENE SUWANNEE



36
OCALA


AVON PARK

LAKE CITY


Surficial
Aquifer





Boundary
of Floridan Aquifer
(by definition)










Floridan
Aquifer


Surficial
Aquifer


Surficial
Aquifer


Surficial
Aquifer


Uontniner


Zone 1a


Confining Layer


Confining Layer


Floridan
Aquifer


Confining Layer


Upper
Floridan
Aquifer


Confining Layer


Lower
Floridan
Aquifer


Zone 2


Confining Layer


Zone 3 a


Confining Layer


Zone 4a


Confining Layer


Zone 5


a Zones 1 and 2 are considered by some authors to be intermediate aquifers, and Zones 3, 4, and 5 to represent the Floridan
aquifer in Manatee and Sarasota counties (Brown 1982b; Sutcliffe and Thompson 1983; Wolansky et al. 1983).


-I


m
0
0
0
rn
0
0


=.


N
0
-I
0


p.
0


Figure 42. Generalized hydrogeology in the Southwest Florida Management District (after Wehle 1978).


F


a


a.


-I


TAMPA


EOCENE


-4. - - i I


,













,, L X. ~ ..

..........
. . . .. .
.... % .. .. ... ......
- < ..,*._ i ( \^ ^ ^"""* ^: .....;Z ^ *-^


/ / / / / 1 / / *// / // /
/ I / / I / I / / / i I
I / / I / / / / I
/ / / I

/ Precipitation / / /
/ # i 1 / / / t / i / /,
/ I I / / / / / / / /
I I / / /I ii I

Flowing Artesian
Well I / / I / /
----- --- ------ Artesiar
Stream Water-table Well -'.
or Lake ln ni :


"';.ii Surficial aquifer
.0.,., o .(unconfined) *.
So' a ".o'n a o 6 .O
confining bed


Evapotranspiration
SWell
Floridan aquifer
potentiometric surface
Surficial aquifer
.- water table

o'",0.'0 Seep or Spring
*, **- .- Sinkhole and interconnected
-- **.-\ underwater conduits (caves)


Figure 43. Generalized hydrogeologic relation between surficial and Floridan aquifers.


i / /
/ / /
/i I
/ / II


/ / /
/ //
///i;.
ii/









Tampa Bay Ecological Characterization


(0 164
Z

0
.0 162


160
g160 -----------------------------------------
4) NGVD = National Geodetic Vertical Datum, 1929
64 I I I I I I I I I
SVerna Well Field at Verna, Sarasota County

0 62


__ 60


58-


56 I I I I I
1964 66 68 70 72 74 76 1977
Year
Figure 44. Hydrographs of wells open to the surficial aquifer in the Tampa Bay watershed (Wilson and Gerhart
1980).


marl, limestone, and dolomite of the upper Haw-
thorne Formation, and undifferentiated deposits that
include all or parts of the Caloosahatchee Marl, Bone
Valley Formation, and Tamiami Formation, and to
the east, the sand and clay unit of the Tampa Lime-
stone (Wehle 1978; Wilson and Gerhart 1980; Brown
1982a). Although quite variable, the thickness of the
confining layer tends to increase toward the south
(Buono et al. 1979). North of Tampa, it ranges from
zero to 20 m, averaging 7.5-15 m (Hickey 1981a;
Brown 1982b; Henderson 1983). The confining layer
was absent at 12 of 59 test-well sites in northwest
Hillsborough and south Pasco Counties (Sinclair
1974). South of Tampa Bay to southeast of Sarasota,


the layer may reach a thickness of about 120 m
(Hickey 1981a). In southern Hillsborough County
and much of Manatee and Sarasota Counties, the
confining layer contains intermediate aquifers that
provide much of the area's domestic, home irrigation,
and public water supply (Brown 1982b).
Penetration of the confining bed results in a direct
linkage between the surficial and Floridan aquifers.
This may be caused by sinkholes (Figure 43), uncased
well holes, and hydrologic modifications such as the
Tampa Bypass Canal (Motz 1975; Stewart et al.
1978). Typically, the confining layer restricts vertical
hydraulic conductivities to about 1 mm/day (Hickey
1981a; Brown 1982a). In an area around Tarpon









4. Hydrology and Water Quality


Springs, conductivities ranged from 2 to 0.1 mm/day.
This rate of exchange, however, varies greatly,
temporally and spatially, and may be affected by
height of the water table, potentiometric surface
elevation, local lithology, and topography.
Beneath the confining layer, the Floridan aquifer
consists of limestone and dolomite that extends from
the Lake City Limestone (early Eocene) up through
the permeable beds of the Hawthorn Formation.
These strata contain solution-enlarged fractures and
bedding planes that provide abundant water for the
watershed's industrial, agricultural, and domestic
needs.
The top of the Floridan aquifer lies near the surface
in the northeastern portion of the watershed (Green
Swamp) and gradually dips to about 120 m below the
National Geodetic Vertical Datum (NGVD) of 1929
just south of Sarasota (Figure 45) (Buono and
Rutledge 1979). The bottom ranges from 335 m
below the NGVD in the north to about 550 m below
the NGVD at Sarasota Bay, and generally corre-
sponds to the beginning of vertically consistent inter-
granular evaporites that are in either the Avon Park,
Lake City, or Oldsmar Limestones of Eocene age
(Wolansky et al. 1979). Transmissivity for the aqui-
fer is variable, ranging from an average of 3,700 m2/
day in the Cypress Creek watershed to an average of
9,300 m2/day along southeast Hillsborough and east-
ern Manatee counties (Wilson and Gerhart 1980;
Henderson 1983).
Potentiometric surface maps of the Floridan aqui-
fer, showing water levels for most of the Tampa Bay
watershed, have been produced since January 1964,
and for all of the watershed since 1975 (Stewart et al.
1971; Mills and Laughlin 1976; Brown 1982b).
Potentiometric surfaces of intermediate aquifers and
water-table heights have been recorded since 1975
(Gombers 1975; Wolansky et al. 1978; Brown
1982b).
Potentiometric levels of the Floridan aquifer
exhibit strong seasonal changes similar to those
observed in the surficial aquifer, that is, high in the fall
and low in the spring (Brown 1982b; Causseaux and
Fretwell 1982). Changes are caused by seasonal
water use, rainfall, tidal variations in the Gulf of


Mexico and Tampa Bay, barometric changes, and
earth tides (Wilson and Gerhart 1980; Hickey 1981a;
Causseaux and Fretwell 1982).
Tides and barometric pressure changes are short-
term phenomena that affect the surficial aquifer and
the Floridan aquifer potentiometric altitude on a daily
or weekly basis, as illustrated in Figure 46. Changes
are generally restricted to coastal margins (Sinclair
1979; Hickey 1981a).
Water users (e.g., industry, agriculture, municipal)
and rainfall are, by far, the most influential factors
controlling changes in the Floridan's potentiometric
surface in the watershed. Both affect levels on a
seasonal and long-term (several-year) basis (Brown
1982b). Seasonally, spring low aquifer levels corre-
spond to maximum irrigationpumpage and minimum
rainfall, while maximum levels, reported in late
summer and early fall, correspond to the end of the
wet season when irrigation is minimal, as illustrated
in Figure 47 (Robertson 1973; Reichenbaugh 1977;
Tibbals et al. 1980; Wilson and Gerhart 1980;
Causseaux and Fretwell 1982). Long-term declines
in the Floridan aquifer have been reported from sever-
al wells, and have been attributed to increases in
population, irrigation for agriculture, and the number
and variety of industrial users (Duerr and Trommer
1981; Hickey 1981a,b; Rollins 1981; Brown 1982b;
Yobbi 1982; Causseaux and Fretwell 1982). The
introduction of deep turbine pumps in the early
1960's greatly accelerated water use in the watershed
and has been singled out as a major cause for the drop
in the potentiometric surface in the last 20 years (Wil-
son and Gerhart 1980; Hickey 1981a). Deficit annual
rainfalls over this period (1960-1980) have also been
blamed for the long-term drop in the Floridan aquifer
(Palmer 1978; Wilson and Gerhart 1980).
Ground-water and surface-water use by county in
the Tampa Bay watershed is presented in Table 13.
Agricultural irrigation, mainly for citrus and veg-
etable crops, is the largest ground-water use in the
watershed, followed by public supply and industry
(Duerr and Trommer 1981). Public wateruse is great-
est in Pinellas and Hillsborough Counties, where
more than 90% of the total watershed's public supply
needs are met (Henderson 1983). Potable water is









Tampa Bay Ecological Characterization


0O


Contour showing altitude (m.s.1.)
of potentiometric surface.


Depression contour.


Figure 45. Potentiometric surface of Floridan aquifer (after Buono and Rufledge 1979).


5IF~Tn









4. Hydrology and Water Quality


Mullet Key
Tide Station


-3.5 Lags Mullet Key tide station
-----~WellB3 by 105 minutes

-4.0

NGVD = National Geodetic Vertical Datum, 1929
I II I I I I I I I I


1600


2000 2400 0400 0800


1200 1600 1900


March 9, 1977


March 10, 1977


Figure 46. Water levels at the Mullet Key tide station and in a southwest St. Petersburg well open to the lower
part of the Floridan aquifer (Hickey 1982).


increasingly being imported from other counties such
as Pasco County, (e.g., Cypress Creek wellficid).
Most significant of the industrial water users are
phosphate mines; citrus, chemical, and food process-
ing; and air conditioning (Causseaux and Fretwell
1982).
Future ground-water consumption in the Tampa
watershed will increase significantly by the year
2000, as shown in Table 14 (Wilson and Gerhart
1980). Even these estimates appear to be very conser-
vative when the values predicted for 1985 in Table 14
are compared to the actual levels reported in 1978
(Table 13). The most abrupt change is expected to be
caused by expanded phosphate mining operations in
eastern Hillsborough and Manatee counties. The net


effect of the increased ground-water consumption is
expected to decrease the Floridan's potentiometric
surface by 1.5-3.0 m by the year 2000 (Wilson and
Gerhart 1980).

Although the surficial aquifer is not widely used as
a water supply, it is a major source of recharge for the
Floridan aquifer. The rate of leakage and even its
direction is dependent on the Floridan potentiometric
surface, the surficial aquifer altitude, the land surface
elevation, and the characteristics of the confining
layer.

Downward leakage is common in most inland
areas of the watershed, while upward leakage occurs
along coastal areas and along the incised valleys of


.J









Tampa Bay Ecological Characterization


a 44
z


.2
2 36




l 20


Irrigation pumpage
al Joshua Grove


Rainfall at
Fort Green


I I
I I
I I
I LI
I II
I II iii ill


Figure 47. Ground-water levels, irrigation pumpage, and rainfall in the central Tampa
Bay watershed (Wilson and Gerhart 1980).

64









4. Hydrology and Water Quality


Table 13. Ground-water and surface-water use by county in 1978 (after Rollins 1981).

Amount of water used for indicated purpose
Public Thermo-
County supply Rural Industrial Irrigation electric Subtotal Total
GW SW GW SW GW SW GW SW GW SW GW SW
Hillsborough 21 45 15 0 75 9 57 3 1 2,292s 169 2,349 2,518
Manatee 0 17 7 0 5 0 46 5 0 3 58 25 83
Pasco 4 0 13 0 15 0 26 0 0 670s 58 670 728
Pinellas 98 0 1 0 1 0 19 0 0 796s 119 796 915
Sarasota 9 8 6 0 0 0 31 3 0 0 46 11 57

Subtotal 132 70 42 <1 96 9 179 11 1 3,761 449 3,851 4,301

Total 202 42 105 190 3,762 4,301
a GW ground water; SW surface water; all is freshwater except for 39.8 mgd of saline ground water used
by industry in Hillsborough County. All measurements are in million gallons per day (mgd).


Table 14. Ground-water withdrawal rates and predicted rates for major users in Hillsborough, Manatee, and
Sarasota counties, 1975, 1985, and 2000 (after Wilson and Gerhart 1980).

Withdrawal rate (mgd)

County User 1975 1985 2000a
Hillsborough Phosphate mines 0.8 20.0 26.0
Municipal 11.9 13.9 14.4
Irrigation 55.0 55.0 55.0
Total 67.7 88.9 95.4

Manatee Phosphate mines 0 34.2 41.7
Municipal 0 1.5 3.8
Irrigation 32.7 37.6 45.0
Total 32.7 73.3 90.5

Sarasota Phosphate mines 0 0 0
Municipal 7.1 7.1 7.1
Irrigation 4.6 5.6 7.0
Total 11.7 12.7 14.1

3-county total 112.1 174.9 200.0
a extrapolated









Tampa Bay Ecological Characterization


major streams (Henderson 1983), or wherever the
potentiometric surface is above the surficial aquifer
(Figure 48). The rate of upward leakage is lower in
May than September, corresponding to the seasonal
fluctuations of the potentiometric surface (Wilson and
Gerhart 1980). Locally, the leakage may be high due
to an absence or thinning of the confining layer, or
breaches in the layer caused by sinkholes (Figure 43)
or other karst features common to the watershed
(Motz 1975; Tibbals et al. 1980; Sinclair 1982;
Henderson 1983). In the northern half of Pasco
County, the confining layer is absent and the Floridan
aquifer is nonartesian (Wehle 1978). In the southern
half of the Tampa Bay watershed, the Floridan aquifer
is more complex (Figure 42) and may be divided into
as many as five distinct aquifers separated by confin-
ing layers and exhibiting different water pressures and
water quality. The upper two of the five aquifers are
considered by some authors to be intermediate aqui-
fers, part of the overlying confining zone, and sepa-
rate from the Floridan aquifer system (Brown 1982b;
Sutcliffe and Thompson 1983; Wolansky et al. 1983).
Ground-water quality is controlled by the compo-
sition and solubility of soil and rock through which
the water passes, the residence time of the water, and
the source of the water (Hutchinson 1978; Tibbals et


Figure 48. Generalized conceptual model of ground-
water flow in the Tampa Bay watershed (after Wilson
and Gerhart 1979, 1980).


al. 1980; Brown 1982b; Sprinkle 1982). In the Tampa
Bay watershed, ground-water quality exhibits two
general trends: one vertical from the surficial aquifer
down to the lower confining bed of the Floridan aqui-
fer, and the other lateral or east to west. Vertically, the
major change is an increase in dissolved solids and
specific conductivity with depth. In the surficial
aquifer, the residence time is relatively short and the
aquifer stratum is composed of minerals (i.e.,
insoluble quartz sand) that contribute low concentra-
tions of ions, and clay particles that adsorb dissolved
solids (Hutchinson 1978).
In the upper layer of the Floridan aquifer, the resi-
dence time of the ground water increases, as does the
solubility of the rock (limestone) through which the
water passes. Dissolved calcium, magnesium, and
bicarbonates dominate the increased dissolved-solid
concentration reported from this major water supply
for west-central Florida. Downward toward the lower
confining layer of the Lake City Limestone, the
ground-water residence time increases and the aquifer
lithology reveals more dolomite and intergranular
gypsum and anhydrites. These factors cause an
increase in specific conductivity, dissolved solids,
and sulfates (gypsum) to a concentration that exceeds
acceptable levels for public water supply and agricul-
ture.
In addition to a vertical pattern, an east-to-west or
northeast-to-southwest gradient is present in the
watershed (Figure 49). Most inland areas (eastern
Pasco, Hillsborough, and Manatee Counties) are in a
zone characterized hydrochemically as a calcium-
bicarbonate facies. The previous vertical-profile
description applies to the ground-water quality
associated with this faces. Dissolved-solid concen-
trations in the surficial aquifer and parts of the
Floridan aquifer from the eastern or upper Alafia
River watershed are shown in Figure 50. In this
facies, the dominant process that controls the concen-
tration and form of dissolved solids in the ground
water is chemical reaction between water and the
aquifer limestone (Sprinkle 1982).
To the west and southwest of this zone is a mixed
hydrochemical facies consisting of calcium, bicar-
bonate, magnesium, sodium, and chloride ions (Fig-
ure 49). It is a transitional area or zone of diffusion


66









4. Hydrology and Water Quality


Calcium-bicarbonate
facies


Calcium-magnesium-
bicarbonate-sulfate
facies


/


Mixed
facies


Sodium-chloride
facies


Calcium-magnesium-
bicarbonate facies


Calcium-magnesium-
sulfate facies


Mixed-bicarbonate
facies


Sodium-bicarbonate
facies


Figure 49. Hydrochemical faces in the Floridan aquifer's upper permeable zone (after Sprinkle 1982).


between saltwater and freshwater ground waters, and
may also be a result of mixing freshwater with resid-
ual saline water, particularly in areas with long resi-
dence times (Sprinkle 1982). The influence of salt-
water increases with depth because of density differ-
ences between saltwater and freshwater, as well as
freshwater recharge from the surficial aquifer.


Along the coastal margin of the Tampa Bay water-
shed is a predominantly sodium chloride hydrochem-
ical facies. The chloride concentrations typically
range from 25 mg/L to 19,000 mg/L, with lower con-
centrations inland and in the upper part of the Floridan
aquifer (Hickey 1982; Causseaux and Fretwell 1983).
Chloride concentrations along the coastal margin of













Surficial aquifer




Upper unit
Floridan aquifer



Lower unit
Floridan aquifer


Tampa Bay Ecological Characterization


| cations Ca: HCO3 anions
Mg : Cl

Na + K S04+F

Ca .: .HCO3
Mg CI
Na + K SO4+ F

Cal HCO,
Mg CI

Na + K S04+F
I I I 2 3 4
3 2 1 0 1 2 3 4


meq/L
Figure 50. Median water quality in the surficial aquifer and upper and lower units of the Floridan aquifer (after
Hutchinson 1978).


the Tampa Bay watershed from the upper and lower
part of the Floridan aquifer are illustrated in Figure
51. Vertical profiles of chloride concentrations in
ground water from the Gulf of Mexico inland and
from Tampa Bay inland 15 km are shown in Figure
52.
Farther to the south, particularly in Sarasota
County, chloride concentrations in the Floridan aqui-
fer generally exceed 250 mg/L (Wilson and Gerhart
1980; Brown 1982b; Causseaux and Fretwell 1983;
Sutcliffe and Thompson 1983). In these areas, public
water supplies are drawn from inland reservoirs (Lake
Manatee, Lake Ward) and intermediate aquifers lo-
cated in the Tamiami and upper Hawthorn Forma-
tions (Brown 1982b; Sutcliffe and Thompson 1983).
Localized contamination of freshwater by dissolv-
ed solids (e.g., chlorides and sulfides) may result from
upward leakage of mineralized waters through
uncased or improperly cased wells or lateral contami-
nation (e.g., saltwater intrusion); may be stimulated
by overuse of local water supplies creating a cone of
depression; or may arise from downward leakage of
storm-driven tides (Tibbals et al. 1980; Causseaux
and Fretwell 1983; Sutcliffe and Thompson 1983).


Other contaminants found in ground water are
nutrients (ammonia, organic nitrogen, orthophos-
phate), organic (total and dissolved organic carbon,
including tannins and lignins), metals and inorganics
(iron, strontium, iodine, barium), pesticides, and
bacteria (Stewart et al. 1978; Brown 1982a; Miller
and Sutcliffe 1982). In addition to the processes
previously described (i.e., dissolution of minerals,
saltwater infiltration), several other mechanisms can
contribute to ground-water contamination in the
Tampa Bay watershed. North of Tampa where the
aquifer lies near the surface, the structural faults and
solution cavities provide direct access to the ground
water by surface storm-water contamination, as illus-
trated in Figure 43 (Stewart et al. 1978; Sinclair
1982). Contamination of the surface aquifer, the
intermediate aquifer, and the Floridan aquifer may
also occur during subsurface injection of sewage
wastes (Rosensheim and Hickey 1977; Hickey
1977a,b, 1981a, 1982; Hickey and Barr 1979; Hickey
and Spechler 1979; Wilson et at 1979; Hickey and
Wilson 1982), land-surface spreading of treated and
untreated wastes (Fernandez 1978; Franks 1981;
Brown 1982a), waste disposal at landfills (Hutchin-
son and Stewart 1978; Fernandez 1978,1983;



















19,000


Chlorle Ba/ Coulurlue
Old Tampa
Bay
0

o ilsborough / Hillsborough 0.
Bay Bay
Tampa
Bay
C
Gulf Gulf p
of of
0 1
Mexico -Mexico 0,







Figure 51. Chloride concentration in groundwater from the upper and lower Floridan aquifer (after Hickey 1982).










Tampa Bay Ecological Characterization


200

0

-200

-400


-600

Z -800
0
a -1,000
,0
a 200

o 0
.0
,: -200

a -400

S-600


-800

-1,000

-1,200

-1,400


I I I I I
Vertical exaggeraton 10X
S ------------------25
--- ^----/ *--25
-

-Z


... 5,000

Pinellas County ----..,
-l G c V l D m of 19,0002
National Geodetic Vertical Datum of 1929


S- ----------------------


*0

4%b


%.4P


----- Top of Floridan aquifer


Line of equal chloride
concentration (mg/L)


Hillsborough County


S1 2 3 4 5
Distance from Coast (mi)


Figure 52. Section through Floridan aquifer showing chloride concentrations in the coastal margin of Pinellas
and central Hillsborough County (after Causseaux and Fretwell 1983).


Femandez and Hallbourg 1978; Duerr and Stewart
1980, 1981; Stewart et al. 1983), and disposal of
phosphate mine waste products such as gypsum
stacks and slime ponds (Miller and Sutcliffe 1982).


4.3 Surface Water

The Tampa Bay watershed encompasses eleven
major river basins or drainage areas (Figure 53).
From north to south these watersheds are the Anclote
River, West Pinellas Peninsula, East Pinellas Penin-


sula-Old Tampa Bay, Hillsborough River, Tampa
Bypass Canal-Palm River, Alafia River, coastal basin
between the Alafia and Little Manatee Rivers, Little
Manatee River, Terra Ceia and Cockroach Bays
coastal basin, Manatee River, and the Manasota
coastal basin.

The monthly 10-year-average flows at major
stations in these river basins are shown in Figure 54.
Seasonally, there tend to be two recurrent peaks in
surface outflow, a small one in February and a larger
one in the wet season (August to October). Variations


70









4. Hydrology and Water Quality


.,*- '


o Tampa
Bay ...../.. -


.. ...











Tampa Bay-area

1. Anclote River basin a
2. West Pinellas Peninsula basin
3. East Pinellas-Old Tampa Bay basin
4. HIIIsborough River basin
5. Palm River-Tampa Bypass Canal basin

6. Alafia River basin


7. Alafia to Little Manatee River coastal basin
8. Little Manatee River basin
9. Terra Ceia and Cockroach Bays basin

11. Manasota coastal basin
Figure 53. Major drainage basins of the Tampa Bay watershed (after Conover and Leach 1975).
1. Anclote River basin --..
2. West P nellas Peninsula basin
3. East Plnellas-Old Tampa Bay basin Bay..atershed ( /f.er .v-.h 17)


71











Tampa Bay Ecological Characterization


Tarpon Canal
800


600 ----------------------------------------


400----------------------------------------


200-


u I I 1 I I I I I I I I7
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Hillsborough River
800 1 I


600-

U, -
400
0
LL


1 1 I 1 1 1 I 1 I I I
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Little Manatee River


Anclote River


600-----------------


400------------------------------------------


200-


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


S 1 1 1 1 1 1 1 1 1 1 1 I I I I I I
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Alafia River


Manatee River
800-


600------------------------------------------


400------------------------------------------


200-


V I I 1 I I
)ec Jan Feb Mar Apr May Jun

Phillipi Creek


800-


600 --------------------------------------------------


400 ----------------------------------------


200------------------------------------------


I I I I I
Jul Aug Sep Oct Nov Dec


0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec


Figure 54. Ten-year average monthly flows of major rivers and streams in the Tampa Bay watershed (after
USGS 1983).


72


-I 4


ft--


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


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









4. Hydrology and Water Quality


in flow are greatest during these periods reflecting the
combined effects of drought and flood years.

4.3.1 Anclote River Basin
The Anclote River originates near Drexel in Pasco
County and flows about 30 km southwesterly through
the northwest comer of Pinellas County to the Gulf of
Mexico near the city of Tarpon Springs (Figure 55).
From its headwaters downstream to the middle
reaches, the river basin is rural, characterized prima-
rily by pine flatwoods, citrus, pasture, and forested
wetlands. The area is sparsely populated, although in
the eastern and southern edge of the watershed,
numerous lakes are ringed by residential development
(Cherry et al. 1970; Turner 1979). In the lower
reaches, the river meanders through swampy, tidally
affected lowlands bordered by several large develop-
ments (e.g., Tarpon Springs). The residential
development along the coastal margin has typically
been built on filled-in salt marshes (ESE 1977b;
Turner 1979).
Three main tributaries flow into the upper Anclote
River. These are the South Branch, Cross Cypress


Branch, and Sandy Branch. The streambeds of all
three tributaries have largely retained their natural
form. In this reach the main river channel is 3-15 m
wide and 1-2 m deep. The river slope averages
0.66 m/km, ranging from 1 m/km at the headwaters to
0.4 m/km near Elfers (Cherry et al. 1970; Seijo et al.
1979).
Very little water-quality data exist for the upper
river. Flow on several days each year is zero, and in
most years the upper river dries up for a number of
days (USGS 1982). Low dissolved-oxygen levels
(<4.0 mg/L) are common, caused by a combination of
low streamflow and decomposition of organic
materials (leaf litter). High levels of organic carbon
are probably contributed by wetlands adjacent to the
river (ESE 1977b).
Downstream of the junction of the main and south
branches, the Anclote River generally exhibits good
water quality. Exceptions to this are occasional high
levels of ammonia and phosphates, probably caused
by livestock on adjacent pasturelands (ESE 1977b).
Near Elfers, where the area drained is approxi-
mately 188 km2, flow averages 2.0 m3/s, ranging


Figure 55. Anclote River basin.


73









Tampa Bay Ecological Characterization


from 142 to 0.01 m3/s (USGS 1982; Foose 1983).
Dissolved solids, mainly calcium bicarbonate, aver-
age 222 mg/L and are derived from ground-water
seepage that annually contributes about 10% to the
total river flow (Cherry et al. 1970; ESE 1977b).
The lower Anclote River is tidally influenced as far
as 23 km upstream. Chloride concentrations range
from 3,000 mg/L at a point 4 km upstream of Salt
Lake, to 18,000 mg/L at the mouth of the river (Baird
et al. 1973; Seabum and Jennings 1976). Water
quality in the lower Anclote River above Tarpon
Springs is generally good. Dissolved oxygen is typi-
cally higher than 5 mg/L. An occasionally high total
phosphorus level (0.39 mg/L) is thought to be a result
of agricultural runoff from pastureland (ESE 1977b).
The river broadens to an average width of 460 m
from Tarpon Springs to the Gulf of Mexico, and its
mean depth, except for a dredged channel, remains
about 1 m. A ship channel about 4.5 m deep has been
dredged from the river mouth to the city of Tarpon
Springs. Additional flow (about 2.8 m3/s), primarily
from ground-water seepage and springs, is contrib-
uted by Kreamer and Whitcomb Bayous just down-
stream of Tarpon Springs (Seabum and Jennings
1976). There, the river also receives both urban run-
off and point-source contributions. Point sources in-
clude the Tarpon Springs sewage treatment plant and
a Stauffer Chemical plant engaged in work using
elemental phosphorus and ferrophosphorous. High
levels of total phosphorus (0.83 mg/L) and biochemi-
cal oxygen demand (BOD) (4.4 mg/L) have been
reported in Whitcomb Bayou slightly downstream
from the Tarpon Springs sewage treatment plant
(ESE 1977b).
Considerable hydrology and water-quality infor-
mation has been collected on the Anclote estuary and
anchorage before and since construction of Florida
Power Corporation's Anclote Plant at the mouth of
the river (Humm et al. 1971; Baird et al. 1972,1973;
FPC 1977).
The estuary and anchorage (behind Anclote Key)
is shallow, ranging from 0.5 to 3.5 m deep. Within the
anchorage, areas less than 0.5 m deep comprise about
35% of the total area. A bathymetric cross section of
the anchorage from the mouth of the river to Anclote


Key is roughly U-shaped with shallower plateaus
toward the mainland and the key. A dredged channel
runs from the deeper central portion of the anchorage
to the mouth of the river.
Currents in the anchorage generally flow north
during flood tides and south during ebb tides. Wind
speed and direction exhibit strong influences on water
currents when speeds reach 4.5 m/s or greater. Mean
flood-tide velocities range between 5 and 40 cm/s,
while ebb-tide velocities range from 5 to 34 cm/s.
Calculated residence time (to 1% of initial concentra-
tion) for the anchorage is 56.75 days.
Salinities in the anchorage vary seasonally with
rainfall and runoff and diurnally with the tides.
Concentrations in the estuary range from 0.8 ppt in
the freshwater side, to 32.7 ppt in the Gulf of Mexico.
In the anchorage, salinities generally fall within the
14- to 31-ppt range. Salinities in the power-plant
intake average only 2-4 ppt less than in the anchor-
age, because over a net tidal cycle considerably more
of the intake water originates from the anchorage
waters than from fresh river waters (FPC 1977).
Average temperatures in the anchorage range
between 20 and 30C. Heated water discharged from
the Anclote Power Plant raises ambient temperatures
more in winter than in other seasons. Seasonally
average maximum increases above ambient were
reported by FPC (1977) as follows: winter 4.70C,
spring 3.50C, summer 3.00C, and fall 3.60C. The
+10C isotherm caused by the thermal effluent consis-
tently covered about 15% of the total anchorage; the
+20C and +3C isotherms covered 10% and 6%,
respectively; and the +40C, +5C, and +6C iso-
therms were not consistently present (FPC 1977).
Nutrients, organic color, chlorophyll a, silicates,
and bacteria (total coliforms) decrease from the river
to the anchorage. Concentrations of these materials
are highest in late summer and early fall and are verti-
cally well mixed except in the deep, open shipping
channels (Baird et al. 1973).

4.3.2 Western Pinellas Peninsula
Seventy-two kilometers of keys or barrier islands
lie between the mouth of the Anclote River and the









4. Hydrology and Water Quality


main entrance to Tampa Bay (Egmont Channel). Sur-
face water bodies are predominantly coastal bays,
lagoons, and bayous; these receive drainage from the
mainland via overland sheetflow, through stormwater
drainage systems, and from a few relatively small
streams. The barrier islands run generally northwest-
southeast in the southern half of the Pinellas County
coast, and almost north-south in the northern half of
the county (Figure 56). The islands are closest to the
mainland at Indian Rocks Beach on Sand Key, where
the lagoon through the Narrows is only 60-90 m
wide. The Narrows connect Boca Ciega Bay on the
south with Clearwater Harbor and St. Joseph Sound
on the north.
Water currents between the barrier islands and the
Pinellas County mainland are mainly tidal (USACE
1966). Tides are mixed, fluctuating between
semidiumal and diural over the course of a month,
and average 0.55 m in amplitude (USACE 1966). In
very shallow areas, winds tend to dominate current
speed and direction. Northern lagoons (St. Joseph
Sound and Clearwater Harbor) are most affected by
winter winds that come from the north and northeast,
running parallel to the lagoons. Winds from the
southeast, common in summer, are more influential
on Boca Ciega Bay, a northwest-to-southeast oriented
lagoon.
The St. Joseph Sound drainage area extends from
just south of Tarpon Springs to just north of
Clearwater in the northwest comer of the Pinellas
Peninsula, and includes Honeymoon and Caladesi
Islands. The eastern margin of the drainage area is
approximately 1.5 km west of Lake Tarpon. Major
land uses, from north to south, are Sutherland Bayou,
citrus and urban; Smith Bayou, urban, residential, and
agriculture; Curlew Creek, urban, agriculture, and
open space; and Cedar Creek, residential and parks.
Urban and residential Dunedin drains to the northern
part of Clearwater Harbor by overland flow and a net-
work of canals.
Much of the coastline from Anclote to Sutherland
Bayou remains in the natural state, (i.e., mangrove
and marsh community). However, south of Suther-
land Bayou, seawalls, filled-sand and gravel beaches,
and riprap have replaced the native shorelines (Getter
et al. 1983).


Figure 56. West Pinellas peninsula basin.


75









Tampa Bay Ecological Characterization


The major tributary to St Joseph Sound is Curlew
Creek, a small stream north of Dunedin that drains
west into the Sound. Its channel slope ranges from
about 11 m/kmn at the headwaters to less than 1 m/km
near the mouth. The headwaters drain a hilly area
northwest of Safety Harbor. Flow at the creek mouth
is estimated at 0.5 m3/s (Cherry et al. 1970).
Water quality in Curlew Creek is greatly influ-
enced by six point-source dischargers and, in
particular, Greenbriar Service Corporation, which
discharges 38.1 mg/L BOD (ESE 1977). Water-qual-
ity data downstream of the point sources show high
levels of total phosphorus (0.41 mg/L), NH3 (0.23
mg/L), total Kjeldahl nitrogen (TKN) (1.55 mg/L),
and total coliforms (TC) and fecal coliforms (FC) (TC
13,700/100 mL; FC 1,010/100 mL) (ESE 1977).
Nitrate, total phosphorus and orthophosphate concen-
trations decrease toward the mouth of the creek.
Dissolved oxygen concentrations are acceptable and
exceed 6.6 mg/L.
The limited data reported for St. Joseph Sound
show an increase of water color and chlorophyll a
levels from north to south in the fall, which corre-
sponds to a north-to-south increase in urbanization
and point-source discharges (ESE 1977). The aquatic
preserve between Caladesi Island and the mainland is
directly offshore from two major point sources, the
Dunedin sewage plant and a citrus processor that
discharges high-BOD wastes.
South of St Joseph Sound is Clearwater Harbor,
which receives drainage from the northwest side of
Pinellas Peninsula, extending from Dunedin south-
ward to the Madeira Beach Bridge. The area contains
barrier beaches, intracoastal waterways, and coastal
lowlands and uplands. Clearwater Harbor separates
Clearwater Beach Island and the northern section of
Sand Key from the mainland. Farther south, the
mainland is separated from the central section of Sand
Key by the "Narrows," and from the southern section
of Sand Key by Boca Ciega Bay. Both the Narrows
and northern Boca Ciega Bay are designated aquatic
preserves.
Drainage on the mainland is generally to the west
through creeks, channelized ditches and streams,


underground storm sewers, and overland flow. Land
northeast of Dunedin drains south through an un-
named creek that empties into Stevenson Creek 1 km
upstream of its mouth. Stevenson Creek flows from
the central hilly part of Pinellas County (northeast of
Largo) to the north and northwest, entering Clear-
water Harbor just north of Clearwater. The lower
reach of the creek is tidal. Flow at its mouth averages
0.5 m3/s (Cherry et al. 1970). From Clearwater to
McKay Point, south of Bellaire Causeway, storm-
water runoff enters Clearwater Harbor by overland
flow and through urban drainage systems and a small
creek. McKay Creek, the other major tributary to
Clearwater Harbor, drains a 3 km stretch southwest of
Largo. Two reservoirs, Walsingham Reservoir and
Taylor Lake, are located in the highly urbanized
upper reaches of McKay Creek. Flow at the creek
mouth is estimated at 0.15 m3/s (Cherry et al. 1970).
The water of the streams and creeks entering
Clearwater Harbor typically exhibits high concentra-
tions of nutrients and coliforms, and depressed
dissolved-oxygen levels. The poor water quality is
caused by a combination of sewage treatment-plant
effluent and storm water. Stevenson Creek, for
example, receives effluent from the Marshall Sewage
Plant in Clearwater. The result is high levels of
suspended solids (<69 mg/L), ammonia (6.0 mg/L),
nitrite (0.42 mg/L), nitrate (0.98 mg/L), TKN
(9.0 mg/L), total phosphate (1.6 mg/L), and BOD
(11.0 mg/L). Fecal coliform counts in a small stream
receiving waste from the Bellaire Sewage Treatment
Plant in Clearwater have been reported as high as
15,300/100 mL. Similar counts have been found in
McKay Creek (ESE 1977b).
Urban storm water also contributes high concen-
trations and loads of pollutants to Clearwater Harbor.
The storm water is generally high in BOD, suspended
solids, nutrients, heavy metals, and bacteria.
Discharge from the Turner Street storm drain in
Clearwater showed high BOD (10.4 mg/L), high total
coliform (3.8 x 105/100mL) and fecal coliform (1.4 x
104/100 mL) counts, and lead (405 ig/L) and zinc
(255 gg/L), all of which exceeded state water quality
standards (Lopez and Giovannelli 1984). High con-
centrations of phosphorus (TP = 0.52 mg/L), nitrogen









4. Hydrology and Water Quality


(TN = 1.5 mg/L), and chemical oxygen demand
(COD = 89 mg/L) were also reported. The long-term
effect of point (sewage) and nonpoint (storm water)
source loadings to Clearwater Harbor has been poor
water quality.
Poor water quality continues into the Narrows,
where the McKay Creek Sewage Treatment Plant
discharges into the Narrows and Boca Ciega Bay
aquatic preserves. High ammonia (0.55 mg/L), total
phosphorus (0.26 mg/L), orthophosphate (0.13 mg/
L), and TKN (1.79 mg/L) levels have been reported
(ESE 1977). Surface drainage is by overland flow
and urban storm-water drainage systems.
The southern half of the Pinellas Peninsula exhibits
low surface relief, with a maximum elevation of only
8 m; consequently, no streams of any appreciable size
develop, and drainage occurs through storm-water
drainage systems, bayous, and small tidal creeks.
Most prominent among these in the southwest penin-
sula are Long Bayou, Cross Bayou Canal, Bear
Creek, and Clam Bayou. Lake Seminole branches off
upstream of Long Bayou, as does Lake Maggiore off
Clam Bayou. Cross Bayou Canal bisects the Pinellas
Peninsula, connecting Boca Ciega Bay to Old Tampa
Bay.
Boca Ciega Bay is possibly the most modified
estuarine system on Florida's gulf coast, both physic-
ally and hydraulically. From 1950 to 1965 about
1,400 ha or 20% of the bay surface area was filled,
and five major causeways cross the bay, connecting
the barrier islands (Sand Key, Treasure Island, Long
Key, and Cabbage Key) to the mainland (Taylor and
Saloman 1969). The bay covers about 70 km2 with a
mean depth of less than 2 m over 80% of the area.
Water exchange between the bay and the Gulf of
Mexico is quite good near the barrier-island passes
and in the Narrows. Away from the passes in Boca
Ciega Bay near Pinellas Bayway and south of Johns
Pass, the water movement is drastically reduced
(Geo-Marine, Inc. 1973a,b; Saloman 1974). The
pattern of water movement in the bay also differs
seasonally (Geo-Marine, Inc. 1973a,b). Cross Bayou
Canal is affected tidally by both Old Tampa Bay and
Boca Ciega Bay, creating a complex tidal pattern;


however, net flow in the canal is toward Boca Ciega
Bay (Hickey 1979).
Water quality in the bay tributaries reflects the
urban character of its drainage area. For example,
77% of the Lake Seminole drainage area and 84% of
the Lake Maggiore drainage area are urban (Myers
and Edmiston 1983).
Lake Seminole was formed in 1950 by damming
the upper reach of Long Bayou. Its chloride concen-
tration decreased from 2,300 mg/L in 1950 to 25 mg/
L in 1957. Since 1957, the concentrations have
ranged from 30 to 180 mg/L. The lake shows mini-
mal seasonal change and no evidence of tidal fluctua-
tion. Outflow to Long Bayou averages 0.3 m3/s
(Cherry et al. 1970). Urban storm water and historic
sewage plant effluent have caused the lake to become
eutrophic, with high chlorophyll a (76 gg/L), total ni-
trogen (2.06 mg/L), and total phosphorus (0.75 mg/L)
concentrations. Several fish kills have been reported
(Myers and Edmiston 1983).
The other major lake in the southwest peninsula,
Lake Maggiore, has outflows to Boca Ciega Bay
(Clam Bayou) and Tampa Bay (Bayboro Bayou via
Salt Creek). Based on water-quality data, Lake
Maggiore is considered one of the ten worst lakes in
Florida. It is characterized by poor light penetration
(0.3 m secchi disk) and high concentrations of chloro-
phyll a (158 gg/L), total nitrogen (4.45 mg/L), and
total phosphorus (0.28 mg/L).
Tributaries to Boca Ciega Bay (e.g., Bear Creek)
have been modified to underground storm sewers or
open ditches (Lopez and Michaelis 1979). The upper
reaches of Joe's Creek, for example, are 67% storm
sewer and 33% open ditch. Background water quality
in these creeks is fair and does not reflect the poor
water quality of storm water that flows to Boca Ciega
Bay through these tributaries, or the contaminants
remaining in the sediments (Lopez and Michaelis
1979; Lopez and Giovannelli 1984).
Bear Creek drains to southern Boca Ciega Bay on
the west side of South Pasadina. Most of the Bear
Creek basin is residential. Storm water from this
creek has high total coliforms (6.8 x 105 counts/100
mL), fecal coliforms (6.6 x 105 counts/100 mL), lead









Tampa Bay Ecological Characterization


(128 gg/L), and zinc (83 ig/L). Pesticides such as
chlordane, Silvex, 2,4-D, and 2,4,5-T have been
detected in the storm water (Lopez and Michaelis
1979; Lopez and Giovannelli 1984). Sediment
samples have shown high levels of volatile solids,
total nitrogen, total phosphorus, and lead, as well as
the presence of several pesticides such as chlordane,
DDD, dieldrin, PCB, and hepta-chlor-epoxide (Lopez
and Michaelis 1979).
Joe's Creek crosses through a mixed urban area
north of St. Petersburg and drains into Cross Bayou
Canal near Boca Ciega Bay. Both storm-water qual-
ity and sediment characteristics are similar to those
found in Bear Creek (Lopez and Michaelis 1979;
Lopez and Giovannelli 1984). The commercial and
light industry influence on the watershed's storm
water is evidenced in much higher concentrations of
the heavy metals, lead (mean concentration = 349 gg/
L) and zinc (mean concentration = 182 g.g/L).
The effect of the tributary storm-water and point-
source loadings on Boca Ciega Bay is dependent on
distance from the tributary mouths and the circula-
tion. Cross Bayou, Long Bayou, Joe's Creek, and
Cross Bayou Canal are surface waters close to pollut-
ant discharges and are restricted hydraulically from
mixing with the bay. These areas, particularly the
upper reaches, exhibit the worst water quality in the
Boca Ciega Bay system, characterized by low oxygen
levels, high nutrient concentrations and BOD, and
high coliform counts (Geo-Marine, Inc. 1973a,b).
Water quality in Boca Ciega Bay is better away
from Long Bayou and Cross Bayou and away from
the point sources along the western shoreline (Taylor
and Saloman 1969; Geo-Marine, Inc. 1973b;
Saloman 1974). Salinity, temperature, and pH of the
bay are similar to that reported for near-shore gulf
waters and lower Tampa Bay. Storm water may
cause temporary stratification or pockets of higher
temperature and lower salinity waters (Geo-Marine,
Inc. 1973b). This stratification causes differences in
surface-to-bottom dissolved-oxygen levels and is
more apparent towards Cross Bayou and in dredged
channels (Taylor and Saloman 1969). Temperature
fluctuates most (diurnally and seasonally) over


shallow seagrass flats and may range from 4.8C
(January) to 36.90C (July).
Seasonal changes in water quality include de-
creased dissolved oxygen and dissolved nutrient
levels, increased BOD, and increased color in late
summer and early fall (Geo-Marine, Inc. 1973b). The
decrease in dissolved nutrients suggests a concurrent
assimilation of nutrients by phytoplankton and
macrophytes.
Water quality offshore is relatively stable and
shows only minor changes with depth, to seaward,
along shore, and by season (Saloman 1974). The
passes act as nutrient sources for the adjacent seaward
areas, as evidenced by higher nutrient concentrations
in and adjacent to the passes during the ebb tide.
Seaward of the Pinellas County beaches are long,
relatively deep borrow pits formed from dredging
sand for use in beach restoration projects. Off Sunset
Beach, one pit runs parallel to the beach for 390 m and
is 130 m wide and 9 m deep (Saloman 1974). Its side
slope is 300 to 45. Unconsolidated soft sediments
about 3 m deep have accumulated on the bottom. The
restricted circulation in the pit and the soft, highly
organic sediments have caused low dissolved-oxygen
levels and a depauperate benthic community.

433 Old Tampa Bay and Southeastern Pinellas
County Peninsula
This drainage area encompasses eastern Pinellas
County and western Hillsborough County (Figure
57). Drainage for the eastern Pinellas County Penin-
sula and western Interbay Peninsula is characterized
by open-ditch channels and storm sewers emptying
into the tidal creeks and bayous of upper Tampa Bay
and Old Tampa Bay. Most of the area north of Old
Tampa Bay is drained by three creeks, Lake Tarpon
Canal and Brooker Creek, Rocky Creek, and
Sweetwater Creek. Portions of all three creeks have
been channelized, with control structures to regulate
flow and prevent saltwater intrusion (HCEPC 1984).
Two streams, Salt Creek and Booker Creek, drain
the lower southeastern Pinellas County peninsula.
Salt Creek receives the outflow from Lake Maggiore,
and Booker Creek drains south-central St. Petersburg.









4. Hydrology and Water Quality


Pasco County
Island -
Ford Lake:. Lake .-
I Fern Turkey
,,Lake bi I ke, 7
STarpon eO kske

S|&/ Church J>
S Lake Citrus Lake
Ton Park C" Magdalene
Ta rpon ul 0 Lake
Canal D_. b lke
Se I Bay La bke ~Z Carroll
dsmar Doubl Lmlrms
Bridgeport oub. l Lake Ellen
Branch
... .... ..'.jer Cree -
S,'Cabbaj (1 rC .
SM~M) bbl" av ou,
safety Harbor avM r am
C Alligator Ck/Ike Cooper













LMalmo / an 1 -
Bavou
Dellwood eC ausewa mpa

O ldLTampa a






MBay gagbor
Ck LaAFB






SoPointrQntg
\ Q n Y ar vor 0 Q
Seeded ak,
Sa1 tt-g ras" Is. AFB

J10e's eeCrP ^ Placido 01^- BaYou

o *Baayou
f St. Petersbur '\ Coffeepot
o booker Ck Bayou
/ Bayboro

FO 57 East Pn Coquina 'Tampa
0 0 MLake 0 Key

Maximo
0La ^ Point / ,


O 0




Figure 57. East Pinellas Peninsula and Old Tampa Bay basin.


79









Tampa Bay Ecological Characterization


Both creeks flow into Bayboro Bayou and then empty
into lower Tampa Bay. Little water quantity or qual-
ity data are available for Salt Creek; however, Booker
Creek was one of several sites chosen by the USGS
for a study of urban watersheds in the Tampa Bay area
(Lopez and Michaelis 1979; Lopez and Giovannelli
1984). Base flow in Booker Creek, 2.5 km upstream
of the mouth, averages 0.03 m3/s. Under base flow
conditions, the creek is turbid (140 JTU) and high in
nutrients (TP = 0.25 mg/L, TN = 2.0 mg/L).
Compared to the bottom sediments of other urban
watersheds in the Tampa-St. Petersburg area, those of
Booker Creek contain relatively low levels of con-
taminants. One exception is PCB, which, at the time
of the study, averaged 34 g.g/kg of sediment (Lopez
and Giovannelli 1984). Storm water in Booker Creek
exhibits high levels of nutrients (nitrogen and phos-
phorus), BOD, coliforms (fecal and total coliforms),
lead (190 ig/L), and zinc (Lopez and Michaelis 1979;
Lopez and Giovannelli 1984).
Drainage in the southeastern drainage area is
through ditch systems directed east toward Old
Tampa Bay and upper Tampa Bay. There are also
small inland lakes, particularly in northeast St. Peters-
burg and east Pinellas Park. Bays in this predomi-
nantly urban setting (60%) include Big Island Gap,
Snug Harbor Bayou, Riviera Bay, Bayou Grande, and
Smacks Bayou. Agriculture (unimproved pasture)
and wetlands (mangrove) account for about 13% and
20%, respectively, of the land use in the area. Much
of the mangrove wetland is located in the Weedon


Island area (ESE 1977; Getter et al. 1983; Kunneke
and Palik 1984; Dial and Deis 1986).
Point-source discharges to this area's waters are
given in Table 15. The thermal plume from the
Florida Power Corporation (FPC) Bartow station
reportedly follows the shore and enters Masters
Bayou during flood tide.
Water quality in many bayous and finger canals in
the area is poorly documented. Tanglewood Estates
canals, northeast of St. Petersburg and open to upper
Tampa Bay, are one exception. The canals exhibit
dissolved oxygen stratifications that are most pro-
nounced in July and August (Lindall et al. 1973,
1975). Bottom DO levels in the summer often remain
at or near zero, as illustrated in Figure 58. Tempera-
ture and salinity stratifications in the canals were
minor, except after heavy rains in August, when sur-
face and bottom salinities differed by as much as 14
ppt.
The Hillsborough County Environmental Protec-
tion Commission (HCEPC) conducts routine water-
quality sampling in Tampa Bay and has placed a
station at the mouth of Grande Bayou in the vicinity
of the St. Petersburg Northeast Treatment Plant.
Water quality in Grande Bayou is much worse than
adjacent Tampa Bay. High BOD (5 mg/L), and high
concentrations of ammonia (0.5 mg N/L) and total
phosphorus (1.5 mg P/L) are reported near the bayou
mouth, where flushing with the bay water is the great-
est. Farther into the bayou, where flushing decreases,


Table 15. Point sources discharging to eastern Old Tampa Bay and Upper
Tampa Bay (after ESE 1977b; Hartigan and Hanson-Walton 1984).

Receiving waters Treatment facility Effluent volume
(mgd)
Old Tampa Bay Florida Power Corp. Bartow Station 560.0a
Feather Sound Development 0.6
Upper Tampa Bay St. Petersburg Northeastb 6.8
Al Whitted STP 15.27
Artificial lake Monumental Properties 0.03
aOnce-through cooling waters with maximum temperature elevation of 10,C.
bNear mouth of Bayou Grande.










4. Hydrology and Water Quality
8

6 .......................... ......................................................
Station 1 (Control)




0 --*


Station 2


4 .......... ... . ......................








Station 3
SmSurface DO
S -' Bottom DO


Station 4



Figure 58. .Dissolved oxygen values in Tanglewood Estates canals, northeast St. Petersburg (after




indal et a. 1 .



















81
Station 6




0
0800 1200 1600 20b00 2400 0400 0800
Time of day

Figure 58. Dissolved oxygen values in Tanglewood Estates canals, northeast St. Petersburg (after
Lindall et al. 1973).

81









Tampa Bay Ecological Characterization


the water quality is predicted to be worse. At the
bayou mouth, dissolved oxygen has varied from
4 mg/L to 15 mg/L near the surface where high con-
centrations of chlorophyll a were reported (ESE
1977b).
West of these bayous and north of Joe's Creek and
Booker Creek is Sawgrass Lake, which drains eastern
Pinellas Park and northwest St. Petersburg. Although
much of the lake's drainage area is urban (70%), the
lake itself is surrounded primarily by a red maple
swamp and to a lesser extent a mixed-oak ridge
(Rochow 1979, 1982). Outflow from the lake is
routed through canals to Riviera Bay and upper
Tampa Bay. Nutrient loading to the lake was ranked
fourth highest for lakes in Florida, but the in-lake con-
centrations varied considerably, possibly caused by
the dense mats of water hyacinth (Eichhornia
crassipes) that completely cover the lake's surface
and assimilate nutrients into their biomass (Dooris
1979). Dissolved-oxygen concentrations below the
hyacinth mat decrease sharply to near zero.
North of the Sawgrass Lake drainage area, Cross
Bayou Canal bisects the Pinellas Peninsula, connect-
ing Boca Ciega Bay on the Gulf of Mexico to Old
Tampa Bay. The canal receives urban drainage from
Pinellas Park. Complex flow patterns in the canal are
caused by the out-of-phase tidal patterns in Boca
Ciega Bay and Old Tampa Bay, and a higher high tide
of 0.15 m in Old Tampa Bay (Geo-Marine, Inc.
1973b). Maximum currents are near Old Tampa Bay
and approach 0.75 m/s.
Upstream from Old Tampa Bay 1.5 km, DO values
often drop below 4 mg/L and high coliform counts are
reported (Geo-Marine, Inc. 1973b). At the canal
mouth, DO values are typically greater than 4.0 mg/L
even in predaylight hours. Water quality problems in
the canal are attributed to the presence of several mu-
nicipal and industrial point-source dischargers (Ap-
pendix Table A-5).
Five coastal streams lie between Tarpon Canal and
Cross Bayou Canal. These are Bishop, Mullet, Alli-
gator, and Allen Creeks and Long Branch. The first
three streams discharge to the bay north of Courtney
Campbell Causeway, the remaining two between


Courtney Campbell and Howard Franklin Cause-
ways. Urban land uses dominate this drainage area,
which includes the cities of Bridgeport, Dellwood,
Safety Harbor, and portions of Largo and Clearwater.
The area pasturelands are primarily located north of
S.R. 60 in the Alligator, Mullet, and Bishop Creeks
watersheds. The mix of urban, agricultural, and na-
tive upland and wetland areas is about 4:1:1 (ESE
1977b). At least 30% of the watershed is storm
sewered, including most or all of Safety Harbor,
Clearwater, Largo, Oldsmar, and Pinellas Park.
Numerous municipal and industrial sewage treatment
plants discharge to watershed waters as shown in
Appendix Table A-5.
In-stream water quantity and quality data are
limited to tidal and upstream portions of Allen Creek
and Alligator Creek and Alligator Lake. Allen Creek
originates northeast of Largo and flows east to Largo
Inlet and Old Tampa Bay. Flow at the mouth is esti-
mated at 0.4 m3/s (Cherry et al. 1970). The upper
creek is drained to the north by storm sewers and to
the south by open ditches, and is relatively steep-
4.43 m/km (Lopez and Michaelis 1979). Tidal and
upstream portions of Allen Creek have shown wide
fluctuations of dissolved oxygen; high levels of BOD
(10 mg/L); high concentrations of nitrogen (TN =
2.4 mg/L), phosphorus (TP = 0.52 mg/L), lead, and
zinc; and high fecal and coliform counts (ESE 1977b;
Lopez and Michaelis 1979; Lopez and Giovannelli
1984). Excessive plant growth and stagnant or negli-
gible flows prevent flushing of the stream and allow
intermittent accumulation of nutrients and organic
matter (ESE 1977b).
Alligator Creek heads in a hilly area east of Clear-
water and flows east to Alligator Lake just south of
the City of Safety Harbor. Alligator Lake was formed
by damming off a saltwater inlet. Flow 1.5 km up-
stream of Alligator Lake averages 0.6 m3/s and ranges
from 0.007 m3/s to 18 m3/s (Cherry et al. 1970; USGS
1982). Alligator Creek has historically had high num-
bers of coliforms, high concentrations of phosphate,
high BOD, and low dissolved-oxygen levels (ESE
1977b). These conditions have been repeated down-
stream in Alligator Lake where chlorophyll a concen-
trations average 38 gg/L.









4. Hydrology and Water Quality


The westernmost of the three major drainage areas
entering Old Tampa Bay from the north is Lake
Tarpon-Brooker Creek. Before 1969, Lake Tarpon
was hydraulically connected to the Anclote River and
Spring Bayou through a sinkhole on the northwestern
end, and salinities fluctuated widely, ranging from 0
to 5,000 mg/L (Hunn 1974). In 1969, an earthen dike
was built to separate the sinkhole from the lake. The
result was a rapid drop in salinity to about 250 mg/L
and a decrease of nitrogen and phosphorus levels
(Bartos et al. 1977). After removal of the water's
access to the sinkhole, Brooker Creek became the
dominant factor influencing the lake's limnology.
Brooker Creek runs 24 km and drains about
108 km2 of land area. The creek forms in northwest
Hillsborough County, east of the town of Lake Fem,
flows south-southwest to Keystone Lake, north to
Island Ford Lake, and then southwest through
swamps and marshes to Lake Tarpon (Menke et al.
1961; Bartos et al. 1978). From the headwaters to
Lake Tarpon, the creek drops about 12 m. Numerous
lakes, often surrounded by citrus groves, are located
in the headwaters. Keystone Lake (157 ha), Church
Lake (28 ha), and Echo Lake (10 ha) are the three
largest lakes (Menke et al. 1961; Reichenbaugh
1977). Keystone Lake receives overland runoff from
cypress swamps, pastures, citrus groves, and
lakefront residential areas. Dredged shorelines for
residences create nearshore pits as deep as the maxi-
mum center-lake depths of 5.5-7.0 m. The volume of
runoff is low because of internal drainage through
numerous sinkholes (Reichenbaugh 1977). Outflow
is highest in August and September with a minor peak
in March. Turbidity and nutrient concentrations
increase in proportion to the flow from the lake, but
the water is of fairly good quality in and just down-
stream of the lake.
Flow in Brooker Creek near Tarpon Springs and
3 km upstream of its mouth averages 0.6 m3/s and
ranges from 45 m3/s to no flow. Decreased flow in
Brooker Creek since 1960 is attributed to ground-
water withdrawals from several wellfields in and
north of the Brooker Creek watershed (Bartos et al.
1978).
Lake Tarpon has an area of 1,036 ha with an aver-
age depth of 2.7 m and a maximum depth of 4.5 m,


except for dredged holes that are 9.0 m deep. The
155 km2 drainage area is about 11% urban, and the
remainder is split between agriculture and wetlands.
Water quality is generally very good. Dissolved
oxygen ranges from 4.6 to 9.1 mg/L, and neither DO
nor temperature vertical profiles show stratification
(Bartos et al. 1977, 1978). Nutrients, chlorophyll a,
coliforms, turbidity, and BOD levels correspond to a
clean, oligo-mesotrophic lake. Changes in chloride,
iron, color, transparency, and nutrients are propor-
tional to Brooker Creek flow (Bartos et al. 1977).
Lake-stage height peaks in fall and winter and is
lowest in spring and early summer.
Lake Tarpon Canal, completed in 1971, is a flood-
control canal that runs south from the south end of
Lake Tarpon for about 3 km and then southeast to
Safety Harbor and upper Old Tampa Bay (Bartos et
al. 1978). Midway down the canal is a saltwater-
barrier/flood-control structure. Canal flow averages
1.0 m3/s and ranges from 64 m3/s to no flow (USGS
1982). The canal exhibits high DO levels (7.0 to
8.0 mg/L), neutral pH (7.0), generally low nutrient
concentrations, and high conductivities (ESE 1977b;
Dooris and Dooris 1985).
Double Branch Creek is a relatively small, tidally
influenced drainage area sandwiched between the
Lake Tarpon-Brooker Creek and Rocky Creek water-
sheds. The creek drains 7.3 km2 and has an estimated
discharge of 1 m3/s (Simon 1974). The tidal influ-
ence is seen in high salinities (12 ppt) measured at the
Hillsborough Avenue bridge (HCEPC 1983, 1984).
High levels of nutrients, organic (TOC), and coli-
forms peak in the wet season and are caused by urban
storm water (including runoff from the Florida
Downs Racetrack) and pastureland runoff (HCEPC
1983, 1984; Dooris and Dooris 1985). Low fecal-
coliform to fecal-streptococcus ratios (FC/FS) sug-
gest a strong influence of animal waste (HCEPC
1984). The high levels of nutrients, particularly NH3,
(2.2-3.1 mg/L), TOC (21.9 mg/L), and color (153
platinum-cobalt units), keep the average DO at less
than 5.0 mg/L (HCEPC 1983, 1984; Dooris and
Dooris 1985). Urban effects on this drainage area are
still much lower than observed in Rocky Creek,
Channel A, and Sweetwater Creek. Color, much









Tampa Bay Ecological Characterization


higher in Double Branch Creek than the other creeks
to the east, and low to moderate phosphate concentra-
tions indicate the still-strong influence of wetland
areas on the water quality of this stream (HCEPC
1983, 1984).
Rocky Creek begins at Turkey Ford Lake in north-
central Hillsborough County and flows southwest
through several small lakes, then south to upper Old
Tampa Bay. The run and drainage area are about
18 km and 115 km2, respectively (TI 1978c). The
flow rate 9.5 km upstream of Rocky Creek's mouth
averages 1.0 m3/s and ranges from 80 m3/s to zero
(USGS 1982). Land use is mainly agriculture
(pasture) in the upper drainage area, with a sparse
population near lakes. The lower drainage area is
urban north of Hillsborough Avenue, but retains
much of its natural salt marsh-mangrove wetland
southward to the bay (Cherry et al. 1970; Getter et al.
1983; Kunneke and Palik 1984). Brushy Creek is the
major tributary to Rocky Creek, draining about 28
km2 of the eastern drainage area starting near Starva-
tion Lake (Menke et al. 1961). Other lakes in the
upper watershed are Hobbs, Cooper, Thomas, and
Round. All the lake levels in this area have been low-
ered in the past 20 years because of pumpage from
several wellfields to the north, (i.e., Cosme). A flood-
relief channel in the lower drainage area, Channel A,
was constructed in 1966 and carries flood water
southwest into Cabbay Bayou and Old Tampa Bay.
Salinity barriers were built in 1977-78 in Channel A
and Rocky Creek (Dooris and Dooris 1985).
In Brushy Creek and the upper reaches of Rocky
Creek, water quality is generally good with occa-
sional high concentrations of ammonia (NH3) and
total phosphorus (ESE 1977b). Total and fecal colif-
orm bacteria may also reach levels well above State
standards and the FC/FS indicates that the origin of
these bacteria is probably pasture runoff. Dissolved
oxygen in the upper creek is relatively low. Nutrient
concentrations decrease downstream within the
creek's freshwater portion.
Except for Turkey Ford Lake, lakes in the upper
drainage area (e.g., Hobbs, Round, Starvation) exhibit
good water quality with relatively low nutrient
concentrations. Nitrogen concentrations in Turkey


Ford Lake are twice that of the surrounding lakes (TN
= 1.6 mg/L). Water in the lower reach of Rocky
Creek at Hillsborough Avenue exhibits low DO
levels (less than 4.0 mg/L), moderate to high nitrogen
concentrations, and high bacterial counts (HCEPC
1983, 1984; Dooris and Dooris 1985). Relatively low
salinity and color (compared to Double Branch
Creek) reflect decreased influence by wetlands and
tidal waters caused by increased urbanization and
construction of the saltwater barrier. Fecal-coliform
to fecal-streptococcus ratios averaging 0.76 and 1.20
in 1982 and 1983 suggest contamination from.sewage
effluent and urban storm water (HCEPC 1984).
In Channel A, turbidity, five-day BOD (BOD5),
total phosphorus, pH, and dissolved oxygen tend to be
higher than in the lower reaches of Rocky Creek,
while total nitrogen and bacteria levels are lower.
Water-quality differences between these two water-
ways suggest a more prolific phytoplankton commu-
nity in Channel A. Channel A contains twice the
chlorophyll a concentration, very low nitrate levels
(0.05 mg/L), and total nitrogen levels equal to those
found in Rocky Creek (HCEPC 1983, 1984; Dooris
and Dooris 1985). In 1983, Channel A exhibited DO
concentrations that approached zero, caused by do-
mestic waste (discharge from a 0.9-mgd wastewater
treatment facility), urban stonnwater runoff, chan-
nelization (deepening and elimination of shoreline
wetlands), and flood-control structures creating a
stagnant lake-like condition rather than a flowing
stream (ESE 1977b; HCEPC 1984). The absence of
wetlands has also been caused by urbanization, which
is apparent from very low color levels-the lowest
reported from Hillsborough County tributaries in
1982 and 1983 (HCEPC 1984).
Sweetwater Creek forms in western Hillsborough
County near Lake Magdalene, flows west to Bay
Lake, south to Lake Ellen, and then south-southwest
to upper Old Tampa Bay near the eastern end of
Courtney Campbell Parkway. The creek drops from
about 15 m above m.s.l., an average of 2 m/km in the
middle reaches to 0.2 m/km near the creek mouth. In
the upper reach, the land is relatively flat, poorly
drained, and contains many shallow lakes that are
interconnected by canals and culverts (Cherry et al.









4. Hydrology and Water Quality


1970). The largest of these lakes are Lake Magdalene
(93 ha) and Lake Carroll (75 ha). In high-flood condi-
tions, Sweetwater Creek receives some overflow
from Cypress Creek through a low, swampy area
separating the Hillsborough River and Sweetwater
Creek watersheds. Sweetwater Creek is 17 km long
and drains about 65 km2. Flow is affected by an over-
flow structure in the upper reaches (from the Hillsbor-
ough River) and in the lower reaches (through Chan-
nel G to Rocky Creek) by control structure G-1
(USGS 1982). The drainage area is primarily urban
(85%), with single family residences accounting for
61% of the land use (ESE 1977b). The drainage
system receives heated or sewage effluent from 11
municipal or industrial facilities.
Lakes in the upper reaches of the creek are in fair
condition with low concentrations of total phosphorus
(0.02-0.003 mg/L) and moderate levels of total
nitrogen (0.57-0.79 mg/L) and chlorophyll a (4.9-
13.8 gg/L).
Upper Sweetwater Creek data indicate rather poor
water quality; DO averages less than 3.0 mg/L and
BOD5 averages 6.0 mg/L. Downstream DO concen-
trations improve slightly to 3.7 mg/L, in spite of the
added effluent from several point sources. In the tidal
portion of the creek, DO, BOD5, and nutrient concen-
trations indicate degraded conditions (ESE 1977b;
HCEPC 1983, 1984; Dooris and Dooris 1985).
Throughout the creek, coliform counts are the highest
reported for Hillsborough County, and in 1981,8% of
the samples showed an FC/FS ratio in excess of 4.0,
suggesting human-waste contamination (HCEPC
1983). The FC/FS ratio decreased in 1982 and 1983,
but still remained between 0.7 and 4.0, indicating a
continued influence of sewage (HCEPC 1984).
From south of Sweetwater Creek to the southern
point of the Interbay Peninsula is the urban complex
of the City of Tampa. Drainage on the western side of
the peninsula is routed through underground storm
sewers and ditches to Old Tampa Bay. One drainage
system in this area, Gandy Boulevard Drainage Ditch,
was part of a USGS study of urban watersheds in the
Tampa/St. Petersburg region (Lopez and Michaelis
1979; Lopez and Giovannelli 1984). The Gandy
Boulevard watershed is composed of 45% residential,


26% commercial, and 29% open space. Base flow in
the ditch showed relatively high BOD and nutrient
levels, as did the ditch sediments. Nutrient concentra-
tions generally decreased during storms, but NH3
increased from 0.19 mg/L to 0.40 mg/L. High total
coliform (3.0 x 105/100 mL) and fecal coliform (1.5 x
105/100 mL) counts and lead (154 gg/L), and zinc
(103 .g/L) concentrations were reported in storm
water sampled.


43.4 Hillsborough River Basin
The Hillsborough River begins east-northeast of
Zephyrhills in southeastern Pasco and northwestern
Polk Counties (Figure 59). Its headwaters originate in
the southwestern portion of the Green Swamp, where
it also receives overflow from the Withlacoochee
River. The river flows southwest 87 km to upper
Hillsborough Bay and drains more than 1,800 km2.
River-basin elevation ranges from 43 m east of Plant
City to sea level at the river mouth.
Perennially flowing tributaries to the Hillsborough
River are Big Ditch, Blackwater Creek, and Flint
Creek (Figure 59). Intermittent streams are Indian
Creek, New River, Two Hole Branch, Basset Branch,
Hollomans Branch, Clay Gully, Trout Creek, and
Cypress Creek. Flood waters are diverted from the
Hillsborough River at the confluence of Trout Creek
and upstream of the Tampa Reservoir Dam through
the Tampa Bypass Canal to McKay Bay. Sixteen
kilometers upstream of the mouth of the Hillsborough
River is the Tampa Reservoir dam, which creates a
narrow reservoir about 20 km long. This reservoir
provides water for the city of Tampa.
A majority of the land use in the river basin (54%)
is agricultural. The remainder is evenly distributed
between range (14%), wetland (13%), and urban
(15%) areas (Femandez et al. 1984). The northern
and central portions of the drainage area are rural, and
the southern part is mainly urban and industrial.
Major incorporated urban centers include Tampa,
Temple Terrace, Plant City, and Zephryhills. For-
ested areas above Trout Creek are lush and thick and
river banks are heavily wooded. Nearshore habitats
are shaped by fallen trees, wetland floodplain, low




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