Comparative Hydrology, Water Quality, 

and Ecology of Selected Natural and 

Augmented Freshwater Wetlands in 

West-Central Florida

By T.M. Lee, K.H. Haag, P.A. Metz, and L.A. Sacks

Prepared in cooperation with

Pinellas County

Southwest Florida Water Management District

Tampa Bay Water

Professional Paper 1758

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Lee, T.M., Haag, K.H., Metz, P.A., Sacks, L.A., 2009, Comparative Hydrology, Water Quality, and Ecology of Selected 

Natural and Augmented Freshwater Wetlands in West-Central Florida: U.S. Geological Survey Professional Paper 

1758, 152 p.

Library of Congress Cataloging-in-Publication Data

Comparative hydrology, water quality, and ecology of selected natural and augmented freshwater wetlands in 

west-central Florida / by T.M. Lee ... [et al.] ; prepared in cooperation with Pinellas County, Southwest Florida Water 

Management District, Tampa Bay Water.

 p. cm. -- (Professional paper ; 1758)

 Includes bibliographical references.

 ISBN 978-1-4113-2353-7 (papercover)

 1. Wetland hydrology--Florida. 2. Water quality--Florida. 3. Wetland ecology--Florida. I. Lee, T. M. (Terrie Mackin) 

II. Pinellas County (Fla.) III. Southwest Florida Water Management District (Fla.) IV. Tampa Bay Water (Fla.) V. 

Geological Survey (U.S.) VI. Series: U.S. Geological Survey professional paper ; 1758. 

 GB705.F5C66 2009

 577.6809759--dc22

 2009015428
Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................3

Purpose and Scope ..............................................................................................................................5

Description of Study Area ...................................................................................................................7

Rainfall Patterns and Regional Ground-Water Withdrawals ........................................................7

Description of Study Design ...............................................................................................................9

Acknowledgments..............................................................................................................................11

Wetland Hydrogeologic Setting ................................................................................................................13

Regional Hydrogeology......................................................................................................................13

Hydrogeologic Methods ....................................................................................................................15

Basin Stratigraphy..............................................................................................................................21

Sub-Wetland Stratigraphy ...........................................................................................................21

Radium-226 .....................................................................................................................................32

Evidence of Karst Features in Wetland Basins ........................................................................35

Ground-Water Flow Patterns in Wetland Basins ..........................................................................37

Overview of Wetland Hydrogeologic Settings...............................................................................43

Wetland Water Budgets .............................................................................................................................45

Methods of Computation ...................................................................................................................46

Rainfall and Evapotranspiration..................................................................................................48

Wetland Stage, Volume, and Area..............................................................................................48

Wetland Leakage ................................................................................................................................49

Effect of Downward Head Differences on Wetland Leakage .....................................................50

Effect of Hydraulic Conductivity on Wetland Leakage.................................................................52

Case Studies of Wetland Leakage ...................................................................................................53

Duck Pond Augmented Marsh....................................................................................................53

S-63 Augmented Cypress.............................................................................................................54

W-5 Augmented Cypress .............................................................................................................56

Runoff to Wetlands .............................................................................................................................59

Overview of Wetland Water Budgets..............................................................................................60

Wetland Water Quality and Geochemistry of Wetland Basins ............................................................63

iii
Water-Quality and Geochemical Methods.....................................................................................63

Water-Quality Constituents...............................................................................................................64

Field Properties and Major Ions..................................................................................................64

Nutrients and Dissolved Organic Carbon..................................................................................68

Stable Isotopes ..............................................................................................................................69

Basin Geochemistry ...........................................................................................................................70

Field Properties and Major Ions..................................................................................................70

Nutrients and Dissolved Organic Carbon..................................................................................73

Stable Isotopes ..............................................................................................................................73

Overview of Water Quality and Geochemistry...............................................................................75

Wetland Flooding Characteristics.............................................................................................................77

Methods of Flooded Area Determination .......................................................................................78

Changes in Extent of Flooded Area..................................................................................................78

Marshes ..........................................................................................................................................79

Cypress Wetlands .........................................................................................................................81

Comparison of Recent and Historical Flooded Area Duration Distributions ............................83

Natural Wetlands ..........................................................................................................................84

Augmented Wetlands ...................................................................................................................87

Impaired Wetlands........................................................................................................................87

Seasonal Average Flooding Patterns ..............................................................................................91

Overview of Flooding Characteristics .............................................................................................93

Wetland Ecology ..........................................................................................................................................95

Methods of Ecological Data Collection and Interpretation .........................................................95

Periphyton.......................................................................................................................................95

Wetland Vegetation.......................................................................................................................96

Macroinvertebrates ......................................................................................................................97

Periphyton............................................................................................................................................98

Biomass and Chlorophyll-a ..........................................................................................................98

Community Composition...............................................................................................................99

Wetland Vegetation..........................................................................................................................102

Comparison of Vegetation Communities .................................................................................102

Species Richness ........................................................................................................................104

Relative Abundance of Wetland Plants by Indicator Category ...........................................105

Plant Biomass in Marshes .........................................................................................................109

Tree Density and Size in Cypress Wetlands............................................................................109

Effects of Environmental Stressors on Wetland Plant Communities..................................109

Macroinvertebrates..........................................................................................................................112

Marsh Macroinvertebrate Communities .................................................................................112

Cypress Macroinvertebrate Communities ..............................................................................119

Functional Feeding Groups ........................................................................................................119

Macroinvertebrates as Ecological Indicators in Wetlands .................................................127

Overview of Wetland Ecology.........................................................................................................130

Summary and Conclusions.......................................................................................................................131

References Cited........................................................................................................................................135

Glossary.......................................................................................................................................................145

iv

Contents (Continued)
Appendixes

1. Monthly rainfall at the marsh wetlands...........................................................................................147

2. Monthly rainfall inside the canopy at the cypress wetlands.......................................................148

3. Relation between rainfall measurements inside and outside of the tree canopy at 

 the cypress wetlands........................................................................................................................149

4. Evapotranspiration estimates for marsh and cypress wetlands.................................................150

5. Bathymetric maps for the 10 study wetlands showing location of vegetation plots .......151-152

Figures

1. Diagram showing conceptualized isolated wetland showing the changing size 

 of the flooded area...........................................................................................................................4

2. Map showing location of study wetlands in the northern Tampa Bay area, 

 west-central Florida.........................................................................................................................6

3-5. Graphs showing:

3. Regional annual rainfall departures from the long-term average, 2000 to 2004............8

4. Annual rainfall measured at the marsh and cypress wetlands during 

 2001 to 2003 compared to the long-term average rainfall .................................................8

5. The average annual daily ground-water withdrawal from the 11 Tampa 

 Bay Water well fields, 1988 to 2004.......................................................................................8

6-8. Diagrams showing: 

6. Approximate time line of data collection in the two wetland types ................................9

7. Landscape features and hydrogeologic framework of mantled karst 

 terrain in west-central Florida .............................................................................................14

8. Example of dissolution and subsidence forming wetlands in mantled 

 karst terrain.............................................................................................................................14

9. Maps showing location of data-collection sites for the marsh wetlands.............................22

10. Maps showing location of data-collection sites for the cypress wetlands..........................23

11-18. Generalized hydrogeologic sections and vertical head distribution for:

11. HRSP Natural Marsh at Hillsborough River State Park ...................................................24

 12. Duck Pond Augmented Marsh at Cross Bar Well Field...................................................25

13. W-3 Augmented Marsh at Cypress Creek Well Field.......................................................26

14. W-29 Impaired Marsh at Cypress Creek Well Field..........................................................27

15. S-68 Natural Cypress at Starkey Well Field.......................................................................28

16. S-63 Augmented Cypress at Starkey Well Field................................................................29

17. W-5 Augmented Cypress at Cypress Creek Well Field....................................................30

18. W-19 Impaired Cypress at Cypress Creek Well Field.......................................................31

19-22. Graphs showing:

19. Vertical profiles of bulk gamma density and grain size in sediment cores 

 from GS Natural Marsh and W-29 Impaired Marsh.........................................................33

20. Average, minimum, and maximum radium-226 activity from surface 

 sediment samples collected in July 2002 and May 2004 .................................................34

21. Vertical profiles of radium-226 activity in sediment cores taken from 

 W-3 Augmented Marsh, W-29 Impaired Marsh #1, W-29 Impaired 

 Marsh #2, and GS Natural Marsh........................................................................................34

22. Ground-penetrating radar profiles with interpreted geologic features 

 below W-29 Impaired Marsh, Duck Pond Augmented Marsh, S-63 

 Augmented Cypress basin, and Duck Pond Augmented Marsh basin ........................ 36

v
vi

23. Diagram showing conceptualized interactions of wetlands with 

 ground-water recharge and ground-water flow through .......................................................37

24. Maps showing ground-water flow patterns around the marsh wetlands during 

 representative dry-season conditions........................................................................................38

25. Graphs showing wetland stage and ground-water levels in selected surficial 

 and Upper Floridan aquifer wells in the marsh wetland basins.............................................39

26. Maps showing ground-water flow patterns around cypress wetlands during 

 representative dry-season conditions........................................................................................41

27. Graphs showing wetland stage and ground-water levels in selected surficial and 

 Upper Floridan aquifer wells in the cypress wetland basins..................................................42

28-31. Box plots of:

28. Daily linear leakage rates in the study wetlands ........................................................... 49

29. Downward head differences at each wetland during its 

 water-budget period ............................................................................................................ 50

30. Elevation differences between the bottom of the wetland and the 

 head in the Upper Floridan aquifer at W-29 Impaired Marsh for three 

 time periods, marshes from December 2000 through September 2002, 

 and cypress wetlands from November 2002 through July 2004................................. 51

31. Leakance below the study wetlands ................................................................................ 53

32-36. Graphs showing:

32. Annual water budget for Duck Pond Augmented Marsh in 2001................................ 54

33. Daily water-budget residual for Duck Pond Augmented Marsh 

 and head in the Upper Floridan aquifer during December 2000–

 September 2002 .................................................................................................................... 54

34. Daily average head in the Upper Floridan aquifer in relation to daily linear 

 leakage rate from Duck Pond Augmented Marsh.......................................................... 54

35. Daily rainfall, daily water-budget residual, and head in the Upper 

 Floridan aquifer at S-63 Augmented Cypress wetland during 

 November 2002–July 2004 ................................................................................................. 55

36. Daily average head in the Upper Floridan aquifer in relation to daily linear 

 leakage rate at S-63 Augmented Cypress wetland....................................................... 55

37. Maps showing water-table configuration at W-5 Augmented Cypress 

 wetland on May 10, 2004 before augmentation, and on June 1, 2004 after 

 23 days of augmentation ...............................................................................................................57

38-40. Graphs showing:

38. Daily augmentation volume and flooded area in W-5 Augmented Cypress 

 wetland during the augmentation experiment ............................................................... 58

39. Response of the water table below W-5 Augmented Cypress wetland to 

 augmentation......................................................................................................................... 58

40. Daily linear leakage rate and flooded area in W-5 Augmented Cypress 

 wetland during the augmentation experiment ............................................................... 58

41. Stiff diagrams for surface water in marsh and cypress wetlands .........................................65

42. Box plots of field properties and chemical constituents in surface waters of 

 augmented and unaugmented wetlands....................................................................................67

43. Plot showing organic nitrogen and dissolved organic carbon in wetland 

 surface water..................................................................................................................................69

44. Box plot of nitrogen to phosphorus ratio in wetland surface water......................................70
vii

45. Plot showing delta deuterium and delta 18O in wetland surface water and 

 augmentation water.......................................................................................................................70

46. Stiff diagrams for surface water and shallow ground water at selected 

 wetlands...........................................................................................................................................71

47. Plots showing delta deuterium and delta 18O in wetland surface water, shallow 

 ground water, and augmentation water from the Upper Floridan 

 aquifer at W-5 Augmented Cypress, S-63 Augmented Cypress, and 

 S-68 Natural Cypress.....................................................................................................................74

48. Graphs showing percentage of the total wetland area flooded on average each 

 week in the natural, augmented, and impaired marshes from December 12, 2000 

 to September 30, 2002....................................................................................................................80

49. Plot showing soil moisture content in HRSP Natural Marsh and W-29 Impaired 

 Marsh during the same time period............................................................................................81

50. Plot showing the relation between daily average soil moisture in the top 

 one foot of soil and the daily average water-table depth below W-29 

 Impaired Marsh ..............................................................................................................................81

51. Graphs showing percentage of the total wetland area flooded on average each 

 week in the natural, augmented, and impaired cypress wetlands from 

 December 11, 2002 to July 27, 2004 .............................................................................................82

52. Graph showing hourly variation in flooded area at S-63 Augmented Cypress from 

 December 24, 2003 to December 31, 2003..................................................................................82

53. Diagrams showing conceptualized wetland showing the boundary of the flooded 

 area located in different 20-percent intervals of the total wetland area..............................83

54-58. Graphs showing the recent and historical flooded-area duration distributions and 

 maps showing the shapes of these flooded areas in:

54. GS Natural Cypress and S-68 Natural Cypress.............................................................. 85

55. HRSP Natural Marsh and GS Natural Marsh.................................................................. 86

56. Duck Pond Augmented Marsh and W-3 Augmented Marsh........................................ 88

57. W-5 Augmented Cypress and S-63 Augmented Cypress............................................. 89

58. W-29 Impaired Marsh and W-19 Impaired Cypress .........................................................90

59-65. Graphs showing:

59. Historical monthly average flooded area in the study wetlands ................................ 92

60. Relative abundance of dominant algal groups in marsh and cypress 

 wetlands................................................................................................................................. 99

61. Relative abundance of obligate, facultative wet, facultative, and facultative 

 upland plants in marsh and cypress wetlands ............................................................. 108

62. Number of tolerant and intolerant plant species at natural, impaired, and 

 augmented wetlands ..........................................................................................................110

63. Biomass, density, and taxa richness of macroinvertebrates in marsh 

 wetlands................................................................................................................................112

64. Shannon diversity of macroinvertebrates in marsh and cypress 

 wetlands................................................................................................................................113

65. Biomass, density, and taxa richness of macroinvertebrates in cypress 

 wetlands............................................................................................................................... 120

66. Pie chart showing the proportion of macroinvertebrate functional feeding groups 

 in marsh and cypress wetlands.................................................................................................121

67. Graph showing abundance of Chironomidae, all Diptera, and all macroinvertebrates

 in marsh and cypress wetlands.................................................................................................128
viii

Tables

1. Average ground-water withdrawal rates at selected Tampa Bay Water regional

 well fields during the study .................................................................................................................9

2. Names, locations, and physical characteristics of study wetlands ............................................10

3. Well characteristics and data collected for wells used in the study...........................................16

4. Water-budget characteristics and selected flux rates for the study wetlands .........................47

5. Wetland leakage rate statistics..........................................................................................................49

6. Regression results relating the daily rainfall volume to the daily change in wetland 

 volume at the unaugmented wetlands.............................................................................................59

7. The volume ratio of runoff to rainfall in the study wetlands..........................................................59

8. Range and median water quality for surface water in wetlands .................................................66

9. Range and median water quality for ground water in wetland basins........................................72

10. Description of stage data used for the historical flooding analyses ...........................................79

11. Percentage of the historical time each wetland area interval was flooded ..............................87

12. The percentage of time that more than half of the total wetland area was flooded, 

 based on stage data from 1996 to 2003 ............................................................................................93

13. Average duration of flooding at deepest point in wetland, in months per year, 

 based on stage data from 1996 to 2003 ............................................................................................93

14. Median biomass of periphyton samples collected in study wetlands, 2002-04 .........................98

15. Median biomass and chlorophyll-a of periphyton samples collected in study 

 wetlands during September–October 2003.....................................................................................98

16. Median diatom species richness and most abundant diatom species in study 

 wetlands..............................................................................................................................................100

17. Van Dam Ecological Indicator values for diatoms in study wetlands........................................101

18. Jaccard’s Similarity Index matrices (using all species greater than 1 percent of 

 abundance) for vegetation in fixed plots in marsh wetlands, 2000–04.....................................102

19. The percentage of time that fixed vegetation plots were flooded during the 

 recent period (2000–02 or 2002–04), based on stage data and bathymetry.............................103

20. Jaccard’s Similarity Index matrices (using all species greater than 1 percent of 

 abundance) for vegetation in fixed plots in cypress wetlands, 2000–04..................................104

21. Jaccard’s Similarity Index comparing vegetation in fixed plots sampled during 

 2000-02 (the period of average rainfall) with vegetation in fixed plots sampled 

 during 2002–04 (the period of above-average rainfall and reduced ground-water 

 pumping)..............................................................................................................................................105

22. Plant species in fixed and randomly located plots in marsh wetlands .....................................106

23. Plant species in fixed and randomly located plots in cypress wetlands ..................................107

24. Biomass of vegetation in marsh wetlands .....................................................................................109

25. Wetland plants that tend to decrease or increase in abundance with disturbance...............111

26. Summary of macroinvertebrate community assessment ............................................................113

27. Mean density, frequency of occurrence, and functional feeding group 

 classification of macroinvertebrates in marsh wetlands ...................................................114-118

28. Mean density, frequency of occurrence, and functional feeding group 

 classification of macroinvertebrates in cypress wetlands ................................................122-126

29. Occurrence of fish and larval amphibians (tadpoles) in study wetlands..................................129
ix

Conversion Factors, Acronyms, and Abbreviations

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3) 0.028316 cubic meter (m3)

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

million gallons per day (Mgal/d) 0.04381 cubic meter per day (m3 /d)

Radioactivity

disintegration per minute per gram (dpm/g) 0.45 picocurie per gram (pCi/g)

disintegration per minute per liter (dpm/L) 0.45 picocurie per liter (pCi/L)

Hydraulic conductivity

foot per year (ft/yr) 0.3048 meter per year (m/yr)

Leakage

inch per day (in/d) 2.54 centimeter per day (cm/d)

inch per hour (in/hr) 2.54 centimeter per hour (cm/hr)

Leakance

foot per day per foot [(ft/d)/ft] 1 meter per day per meter

inch per year per foot [(in/yr)/ft] 83.33 millimeter per year per meter [(mm/yr)/m]

Temperature

Celsius (°C) °F = (1.8 × °C) + 32 Fahrenheit (°F)
x

Vertical coordinate information is referenced to National Geodetic Vertical Datum of 

1929 (NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1983 

(NAD 83).

Elevation, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).

All data and interpretive results in the Wetland Ecology section of the report use metric units.

Terms for which definitions are provided in the Glossary are presented in boldface type.

 Acronyms and Additional Abbreviations

ANC acid neutralizing capacity

cm3/cm3 cubic centimeter per cubic centimeter

δ delta notation for isotopic composition

δD delta deuterium

δ18O delta oxygen-18

DOC dissolved organic carbon

g/cm3 grams per cubic centimeter

GPR ground penetrating radar

GS Green Swamp

HRSP Hillsborough River State Park

mg/L milligrams per liter

mg/m2 milligrams per square meter

μg/cm2 micrograms per square centimeter

mg/cm2 milligrams per square centimeter

μS/cm microsiemens per centimeter

NWQL National Water Quality Laboratory

SWFWMD Southwest Florida Water Management District

USGS U.S. Geological Survey
Comparing altered wetlands to natural wetlands in the same region 

improves the ability to interpret the gradual and cumulative effects of 

human development on freshwater wetlands. Hydrologic differences 

require explicit attention because they affect nearly all wetland functions 

and are an overriding influence on other comparisons involving wetland 

water quality and ecology. This study adopts several new approaches 

to quantify wetland hydrologic characteristics and then describes and 

compares the hydrology, water quality, and ecology of 10 isolated 

freshwater marsh and cypress wetlands in the mantled karst landscape of 

central Florida. Four of the wetlands are natural, and the other six have 

water levels indirectly lowered by ground-water withdrawals on municipally owned well fields. For several decades, the water levels in four of 

these altered wetlands have been raised by adding ground water in a mitigation process called augmentation. The two wetlands left unaugmented 

were impaired because their water levels were lowered. Multifaceted 

comparisons between the altered and natural wetlands are used to examine 

differences between marshes and cypress wetlands and to describe the 

effects of augmentation practices on the wetland ecosystems.

In the karstic geologic setting, both natural and altered wetlands 

predominantly lost water to the surficial aquifer. Water leaking out of the 

wetlands created water-table mounds below the wetlands. The smallest 

mounds radiated only slightly beyond the vegetated area of the wetlands. 

The largest and steepest mounds occurred below two of the augmented 

wetlands. There, rapid leakage rates regenerated a largely absent surficial 

aquifer and mounds encompassed areas 7-8 times as large as the wetlands. 

Wetland leakage rates, estimated using a daily water-budget 

analysis applied over multiple years and normalized as inches per day, 

varied thirtyfold from the slowest leaking natural wetland to the fastest 

leaking augmented wetland. Leakage rates increased as the size of the 

flooded area decreased and as the downward head difference between 

Comparative Hydrology, Water Quality, and 

Ecology of Selected Natural and Augmented 

Freshwater Wetlands in West-Central Florida

By T.M. Lee, K.H. Haag, P.A. Metz, and L.A. Sacks

Abstract
2 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

the wetland and the underlying Upper Floridan aquifer 

increased. Allowing one of the augmented wetlands to dry up 

for about 2.5 months in the spring of 2004, and then refilling 

it, generated a net savings of augmentation water despite the 

amount of water required to recreate the water-table mound 

beneath the wetland. Runoff from the surrounding uplands 

was an important component of the water budget in all of the 

unaugmented wetlands and two of the augmented wetlands. 

At a minimum, runoff contributed from half (45 percent) 

to twice (182 percent) as much water as direct rainfall 

at individual wetlands.

Wetland flooded areas, derived using wetland water 

levels and bathymetric data and presented as a percentage 

of total wetland area, were used to compare and contrast 

hydrologic conditions among the 10 wetlands. The percentages of the natural wetland areas that flooded during the 

study were comparable, despite differences in the sizes of 

the wetlands. The percent flooded area in each wetland was 

calculated daily over the study period and monthly for up to 

16 years using historical water-level data. Historical flooding 

in the natural wetlands spanned a greater range in area and 

had more pronounced seasonality than historical flooding at 

either the impaired or augmented wetlands. Flooding in the 

impaired and natural wetlands was similar, however, during 

2 years of the study with substantially reduced well-field 

pumping and above average rainfall.

communities in natural marsh and cypress wetlands also 

were similar. Vegetation is inherently different between 

marsh and cypress wetlands, and among wetland sites of 

the same type there was a large variety and small overlap 

of vegetation species. Macroinvertebrate taxa richness and 

density were generally greater in natural marshes than in 

natural cypress wetlands.

The hydrology and water quality of augmented 

wetlands differed substantially from natural wetlands, but 

ecological differences were less apparent. Augmentation 

preserved between 40 and 80 percent of the original surface 

areas of four wetlands. The water levels in augmented 

wetlands, however, fluctuated less than in natural wetlands 

and augmented wetlands dried out far less frequently, 

accelerating sediment accumulation. Year-round augmentation of the deepest and fastest leaking wetland, Duck Pond 

Augmented Marsh, required a volume equivalent to a 60-foot 

column of water over an area of about 3 acres. The bottom 

sediments in augmented wetlands did not show enrichment 

of radium-226, as has been reported in augmented lakes in 

the area. Augmentation shifted wetland water quality from an 

acidic, dilute, and sodium-chloride dominated chemistry to 

a calcium-carbonate rich water with much higher alkalinity, 

specific conductance, and pH. The abundance of periphyton 

species known to prefer higher pH, conductivity, and 

nutrient concentrations was greater in augmented wetlands. 

“Freshwater wetlands and their interaction with ground water 

play a pivotal role in the water resources of Florida”

Comparisons indicated several hydrologic differences 

between the marsh and cypress wetlands in this study. 

The natural and impaired marshes leaked at about half the 

rate of the natural and impaired cypress wetlands, and the 

marshes collectively were underlain by geologic material with lower vertical leakance values than the cypress 

wetlands. The natural marshes had higher evaporation rates 

compared to cypress wetlands, and their more isotopicallyenriched surface waters indicated longer water residence 

times than the cypress wetlands. Over the same 8-year 

period, marshes spent from 16 to 30 percent more time 

(or about 15 to 29 months more) than cypress wetlands 

with greater than half of their total areas flooded. Cypress 

wetlands were nearly dry a greater percentage of time than 

marshes; however, more than 80 percent of their area was 

flooded a greater percentage of time than marshes. The water 

quality of natural marsh and cypress wetlands was similar, 

with a low pH, low conductivity, minimal alkalinity, and 

low concentrations of major ions; therefore, periphyton 

Plant species richness and biomass were higher in the 

augmented wetlands than in unaugmented wetlands, most 

likely in response to more prolonged flooding and greater 

availability of nutrients released by accumulated decaying 

plant material. The natural variability of macroinvertebrate 

communities in marsh and cypress wetlands in this study 

exceeded the differences attributable to augmentation, 

although the presence of gastropods at augmented wetlands 

of both types was due to inherent water-quality differences. 

The comparisons of macroinvertebrate communities between 

natural and augmented wetlands would be more useful if a 

larger population of wetlands was available for study.

Quantifying wetland hydrology along with water quality 

and ecological indicators makes the results from the comparative analyses of these 10 wetlands generic. The approaches 

used in this study can be applied to future studies and those 

results can be compared to this initial study population, 

allowing the comparative analyses to describe an increasing 

number of wetlands.
Freshwater wetlands and their interaction with ground water play 

a pivotal role in the water resources of Florida. Wetlands occupy a 

greater percentage of the land surface in Florida (29 percent) than any 

other state in the conterminous United States. A mantled karst terrain 

characterized by sinkhole subsidence and permeable aquifers, together 

with a wet subtropical to warm-temperate climate, produces a landscape 

where surface water and ground water can be viewed as a single resource 

(Winter and others, 1998). Ground water has been pumped in increasing 

quantities from below these surface waters in recent years, supplying 

more than 92 percent of the drinking water for more than 17 million 

Florida residents (in 2005) and 72 million tourists estimated to visit the 

State annually (in 2000) (Marella, 2004). 

Large tracts of land, some containing numerous wetlands, have been 

set aside by municipalities across Florida for use as ground-water reservoirs and “well fields” where ground water is pumped for potable supply 

(Marella, 2004). Ground-water withdrawals at municipal well fields in 

west-central Florida have reduced the depth and duration of flooding in 

overlying wetlands (Mortellaro and others, 1995; Hancock and Smith, 

1996). To mitigate the reduction in wetland flooding frequency and duration, a small fraction of the ground water pumped from a well field has 

been used to augment water levels in affected wetlands. The augmentation water thus replaces the water lost when leakage through the wetland 

bottom is accelerated by local ground-water withdrawal. Water levels in 

some of these mitigated wetlands have been augmented since the 1980s 

(Berryman and Hennigar, Inc., 2000). The augmentation rates needed 

to sustain targeted water levels depend on yearly climate conditions and 

ground-water pumping rates from the underlying aquifer. 

Understanding the long-term effects of wetland augmentation and 

other mitigation practices on wetlands in Florida requires systematically 

comparing the hydrology, water quality, and ecology of both natural 

Introduction
4 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

and augmented systems. A few comprehensive studies of 

natural wetlands in southern Florida have been published, 

including studies of Big Cypress Swamp (Klein and others, 

1975; McPherson and others, 1976) and Corkscrew Swamp 

(Duever and others, 1975). Ewel and Odum (1984) presented 

a number of indepth studies of cypress wetlands in Florida 

and the eastern United States. The Florida Everglades has 

been studied in great detail (Davis and Ogden, 1994; Porter 

and Porter, 2002), and numerous studies are underway as 

part of the Comprehensive Everglades Restoration Plan 

(U.S. Army Corps of Engineers and South Florida Water 

Management District, 2000). In west-central Florida, however, 

conditions in marsh and cypress wetlands have not been 

rigorously studied using consistent methods uniformly 

applied to both natural wetlands and those wetlands that have 

experienced anthropogenic effects. 

Comparative assessments of vegetation in wetlands are 

numerous and have been documented in detail. In fact, names 

for different kinds of wetlands are often derived from the 

name of the dominant plant (for example, “maidencane marsh” 

and “cypress swamp”). In addition, a number of studies 

have focused on wetland water quality and biogeochemistry, 

although many of these studies were designed to assess the 

ability of wetlands, both natural and constructed, to assimilate 

and process nutrients and contaminants in wastewater (Mitsch 

and Gosselink, 2000), a focus outside the scope of this study. 

In contrast, the hydrologic characteristics of isolated 

wetlands, particularly in the karst terrain of Florida, are not 

as well known (Kirkman and others, 1999). Methods used 

to compare the water budget and ground-water interactions 

in natural and augmented lakes in Florida provide a useful 

framework for studying wetlands (Metz and Sacks, 2002; 

Swancar and Lee, 2003). However, the classical goal of a lake 

water budget, namely, accounting for inflows and outflows 

to a permanent landscape feature, can lose its equivalence 

when applied to seasonally flooded or altered wetlands. In 

an isolated wetland, the ponded area that is subject to the 

conservation of mass principle can vary in size, disappear, 

and reappear over the timeframe of the water-budget analysis 

(fig. 1). For multiple wetlands undergoing these processes in 

unsynchronized cycles, comparing wetland water budgets based 

on cumulative fluxes for a given time period can explain little 

about the intrinsic similarities and differences between individual wetlands. Water budgets have been applied to relatively 

few natural isolated wetlands (Carter, 1978; LaBaugh, 1986; 

Hayashi and others, 1998), usually over judiciously selected 

time periods with synchronized flooding. Water-budget analyses 

are more commonly available for constructed or mitigation 

wetlands that stay inundated year-round due to surface-water 

inflow or augmentation (Kadlec and Knight, 1996; Choi and 

Harvey, 2000; Biological Research Associates, Inc., and SDI 

Environmental Services, Inc., 2001).

To address the need for a greater understanding of the 

interactions among surface water, ground water, and wetlands 

ecosystems in karst terrain, the U.S. Geological Survey (USGS) 

initiated the current study in 1999 to compare and contrast: 

Figure 1. Conceptualized isolated wetland showing the 

changing size of the flooded area. The volumes of waterbudget components change with the size of the flooded area, 

complicating hydrologic comparisons of isolated wetlands.

I

I

O

O

EXPLANATION

May

O

June

I O

I

April

I

O

O

I

I

O

I O

March

FLOODED WETLAND AREA

DRY WETLAND AREA

VOLUME OF WATER-BUDGET

INFLOW–arrow size

indicates magnitude

Rainfall

VOLUME OF WATER-BUDGET

OUTFLOW–arrow size

indicates magnitude

Evapotranspiration

Leakage to ground water

WETLAND PERIMETER

Runoff
Introduction 5

(1) the hydrogeologic framework of wetlands and wetland/

ground-water interactions; (2) wetland water budgets, focusing 

on the role of leakage and runoff in the water budget; (3) the 

water quality of wetland surface waters and the geochemistry 

of underlying aquifers; (4) the frequency, duration, depth, and 

spatial extent of wetland flooding; and (5) wetland ecology as 

assessed by periphyton, aquatic vegetation, and macroinvertebrates. The current study was conducted in cooperation with 

Pinellas County, the Southwest Florida Water Management 

District (SWFWMD), and Tampa Bay Water. 

The study conducted in west-central Florida examines the 

hydrologic behavior of 10 isolated wetlands in unprecedented 

detail at a daily timescale over a period of several years. 

The daily timescale makes it possible to interpret inundation 

patterns, rainfall/runoff relations, and wetland water budgets 

across a range of hydrologic conditions, and it generates 

comparable results whether a given wetland remains perennially flooded or is dry much of the year. In this approach, 

runoff entering the wetlands is quantified, but only until rainfall and runoff cause water to overflow the wetland perimeter. 

Purpose and Scope

The purpose of this report is to distinguish and categorize 

the long-term effects of augmentation on the hydrology, water 

quality, and ecology of isolated wetlands in the mantled karst 

terrain of Florida. These effects were derived implicitly by 

comparing and contrasting selected natural and augmented 

wetlands to each other, and cataloguing differences. 

The report is divided into five distinct (color coded) 

sections that collectively characterize the hydrology, water 

quality, and ecology of the 10 wetlands. A companion USGS 

scientific investigations report (Haag and others, 2005) and 

two USGS fact sheets (Haag and Lee, 2006; Lee and Haag, 

2006) describe the bathymetry and vegetation in the 10 

wetlands, and provide a framework for describing the floodedarea frequency of wetlands.

The first section begins the hydrologic characterization 

by defining the hydrogeologic setting of the wetlands and 

describing the interactions between wetlands and ground 

water. Hydrogeologic sections describe the hydrogeologic 

framework for 8 of the 10 wetlands and incorporate basin 

topography, wetland bathymetry, basin stratigraphy, groundwater flow patterns, and organic sediment thickness in the 

wetlands. Wetland water quality and the geochemistry of the 

underlying aquifers provide additional evidence of the wetland 

and ground-water interactions. Sediment cores taken in the 

center of three wetlands reveal the thickness and sequence of 

organic and mineralized layers beneath the wetlands. Surface 

geophysical surveys were made in two of the wetland basins, 

and the results are used to describe karst subsidence features 

that occur in these settings.

In the second section, the water-budget approach 

customarily applied to lakes and reservoirs was modified 

and adapted to characterize the small, periodically flooded 

wetlands in this study. The difference between the measured 

water volumes entering and leaving a wetland, and the 

observed change in the wetland volume is used to estimate 

the magnitude of two hydrologic fluxes that are difficult to 

The ponded area in isolated wetlands can vary in 

size, disappear, and reappear through time
6 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 2. Location of study wetlands in the northern Tampa Bay area, west-central Florida.

6

1

2

3

4

5

6

7

8

9

10

S-68 Natural Cypress

W-3 Augmented Marsh

W-5 Augmented Cypress

W-19 Impaired Cypress

W-29 Impaired Marsh

Duck Pond Augmented Marsh

Green Swamp Natural Cypress

Green Swamp Natural Marsh

Hillsborough River State Park Natural Marsh

S-63 Augmented Cypress

GREEN SWAMP SELECTED WETLAND AND NUMBER

PARKS AND WELL FIELDS

PHYSIOGRAPHIC REGIONS

Gulf Coastal Lowlands

Western Valley

Base from U.S. Geological Survey digital data, 1:24,000,

datum NAD83, Albers Equal-Area Conic Projection,

Standard parallels 29°30’ and 45°30’,

Central Meridian -83°00’

28°30’

15’

28°00’

82°45’ 30’ 15’ 82°00’

5 10 MILES

0 5 FLORIDA

LOCATION

OF STUDY

AREA

Northern Tampa Bay Area

10 KILOMETERS

0

EXPLANATION

Hillsborough

River State Park

HERNANDO COUNTY

PASCO COUNTY

HILLSBOROUGH

COUNTY

POLK COUNTY

PINELLAS

COUNTY

SUMTER

COUNTY

LAKE

COUNTY

8

9 10

2

3

4

1

5 6

7

Withlacoochee

OLD

TAMPA

BAY

GULF

OF

MEXICO

River

River

Creek

Blackwater

River

River

Cypress

Creek

Hillsborough

River

Alafia

Anclote

Pithlachascotee

Tampa

New

Port

Richey

Tarpon

Springs

Land O Lakes

Temple

Terrace

Zephyrhills

Plant City Lakeland

Brandon

Clearwater

Brooksville

Dade

City

Starkey

Well Field

Cypress

Creek

Well Field

Cross Bar

Ranch

Well Field
Introduction 7

Description of Study Area 

The study area is located in west-central Florida and 

includes parts of Hernando, Hillsborough, Lake, Pasco, 

Pinellas, Polk, and Sumter Counties (fig. 2). All 10 study sites 

are located in well fields or on publicly owned lands, such 

as wildlife management areas or parks, in two physiographic 

regions (fig. 2). These regions, known as the Gulf Coastal 

Lowlands and Western Valley (White, 1970), have a relatively 

high water table and some surface drainage to rivers. In the 

subsurface, the Upper Floridan aquifer is the principal source 

of all local water supplies.

In west-central Florida, freshwater wetlands consist of 

forested and non-forested types, including riverine swamps, 

lacustrine swamps, cypress domes, marshes, and wet prairies 

(Southwest Florida Water Management District, 1999a). 

A 1986 inventory of 71 mi2 in the northern Tampa Bay area 

indicates that wetlands account for about 23 percent of the 

total acreage surveyed (Manny Lopez, Southwest Florida 

Water Management District, written commun., 2002). About 

92 percent of the total number of wetlands in the northern 

Tampa Bay area are isolated wetlands, and they constitute 

68 percent of the total wetland acreage. Precipitation and 

shallow ground water supply the majority of water to isolated 

marshes and cypress swamps (Ewel and Odum, 1984; Myers 

and Ewel, 1990; Kirkman and others, 1999). In these isolated 

wetlands, where the water table seasonally approaches 

land surface under ambient conditions, the hydroperiod is 

largely determined by differences between precipitation and 

evapotranspiration, and is mediated by geology and topography. Small changes in wetland stage can cause large changes 

in wetland surface area because these wetlands are relatively 

shallow topographic features. Persistent changes in wetland 

water levels, due to changes in rainfall or human activities, 

could in turn cause a substantial change in the vegetation of 

hundreds or thousands of acres of land (Stewart and Kantrud, 

1972; Poiani and others, 1996; Poiani and Johnson, 2003; 

Swanson and others, 2003).

Wetlands in the central Florida region typically follow 

a hydrologic pattern in which water levels decline during 

the winter and spring, with minimum water levels occurring 

in May and early June. During a year with average rainfall, 

wetland water levels typically begin rising in early summer 

and reach their highest levels in September (Berryman and 

Hennigar, Inc., 2000).

Rainfall Patterns and Regional Ground-Water 

Withdrawals

Surface water and ground water both respond relatively 

quickly to the distributed effects of rainfall and the more 

localized effects of ground-water withdrawals in the karst 

terrain of central Florida. Describing the hydrology of 

wetlands in the region requires identifying trends in both 

of these components of the hydrologic cycle. Rainfall in 

directly quantify: the leakage of wetland surface water into 

the aquifer, and precipitation runoff the wetland receives 

from the surrounding upland area. The modified approach 

focuses on daily rates instead of cumulative volumes and, in 

doing so, generates results that are directly comparable for 

all 10 wetlands, regardless of how much the flooded wetland 

areas expand and contract, and whether or not all 10 wetlands 

remain continually flooded. 

The third section presents wetland water-quality data 

from the 10 wetlands and describes the geochemistry of the 

wetland basins. The wetland water-quality data serve principally 

as supporting information, because surface-water quality is 

a strong determinant of many aspects of wetland ecology. 

Moreover, analyses of wetland water-quality data can be useful 

in describing various aspects of surface-water to ground-water 

interactions that are influenced by basin geochemistry. In addition, levels of radium-226 are measured in wetland water and 

sediment. This naturally occurring radioisotope has been found 

at elevated levels in lakes augmented with ground water in 

central Florida and may pose a human health risk for individuals 

who come in contact with it (Hazardous Substance and Waste 

Management Research, Inc., 2004).

The fourth section continues the hydrologic characterization of the wetlands by comparing flooding patterns in 

the 10 wetlands. Flooded area is determined using detailed 

bathymetric maps of each wetland (described in Haag and 

others, 2005) and observations of wetland water levels. The 

percentage of the total wetland area that was flooded over 

time was compared among the 10 wetlands on a weekly basis 

over the period of study. Time-series data describing the size 

of the flooded area are then condensed to describe the duration 

of flooding over different regions of the total area of a wetland. 

The duration of flooding for the previous 8 to 16 years is reconstructed using long-term water-level data, and these flooding 

conditions are compared to the more recent flooding conditions 

in each wetland.

In the final section, three biological communities (algae, 

wetland plants, and macroinvertebrates) are assessed to interpret 

differences in ecological conditions between natural, impaired, 

and augmented wetlands. The variety and abundance of periphyton, the algae that grow on the surface of submersed plants and 

the wetland bottom, is an indicator of nutrient concentrations 

and overall water quality in wetlands. Periphyton communities 

were assessed quarterly, and differences in these communities 

are used to describe and compare ecological conditions in the 

10 wetlands. Wetland vegetation communities are compared 

in the 10 wetlands, and differences in the macrophytes and 

woody vegetation are discussed in relation to hydrologic factors 

including water depth, water quality, and the spatial extent and 

duration of the flooding. Snails, crayfish, dragonfly nymphs, 

and other macroinvertebrates inhabiting the 10 wetlands were 

sampled quarterly, and macroinvertebrate community structure 

is compared and contrasted among the five marsh wetlands 

and among the five cypress wetlands. In accordance with the 

standard convention for ecological literature, all quantities in 

this section are reported in metric units.
8 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

the region encompassing the study wetlands averages about 

52 in/yr, based on 110 years of regional rainfall record from 

1895 to 2005 for the two climate divisions that bisect the 

study area: Division 3 (52.26 in/yr) and Division 4 (51.84 in/

yr) (National Oceanographic and Atmospheric Administration, 

2007). Annual rainfall during the study ranged substantially 

above and below the long-term average. Regional rainfall was 

about 12 to 15 in. below the average in 2000, and was close to 

the average in 2001 (fig. 3). During the next 3 years (2002-04), 

annual rainfall was about 5 to 10 in. above average (fig. 3). 

The above-average rainfall that began in late 2002 ended a 

5-year drought in Florida (Verdi and others, 2006).

Rainfall was measured over 3 entire years at the study 

wetlands, and the annual totals measured at these sites 

followed the regional trend. The rainfall data are summarized 

monthly in appendixes 1 and 2. The annual rainfall measured 

at five wetland sites during 2001 ranged from below average 

to near the long-term average, whereas rainfall in 2002 and 

2003 ranged from 3 to 15 in. above average at several of the 

wetlands (fig. 4). The Hillsborough River State Park (HRSP) 

Natural Marsh was an exception, because the rainfall measured 

for 2003 was below (instead of above) the long-term average. 

In central Florida, where most of the annual rainfall occurs 

during the summer from small convective thunderstorms and 

larger tropical storms, spatial variability across a region can 

exceed the interannual variability (Chen and Gerber, 1990).

The increase in annual rainfall in the northern Tampa 

Bay area during 2002-04 was accompanied by a steep reduction in ground-water withdrawals from regional well fields 

(fig. 5). Ground-water pumping from 11 well fields in the 

northern Tampa Bay area is coordinated by a regional water 

utility called Tampa Bay Water, which has been the principal 

provider of drinking water for Pasco, Hillsborough, and 

Pinellas Counties since 1998. Between 1998 and 2002, most 

of the regional water demand was supplied using ground 

water pumped from regional well fields. Well-field pumping 

decreased substantially beginning in late 2002 when nearly 

66 Mgal/d of alternative water supply became available 

from a newly created surface-water reservoir. The reductions 

in well-field pumping complied with a master water plan 

that mandated reducing ground-water withdrawals in the 

11 regional well fields from a historical annual average of 

about 158 Mgal/d to 90 Mgal/d by 2008 (Tampa Bay Water, 

2004). The increased rainfall and decreased ground-water 

withdrawal during 2002-04 increased aquifer water levels and 

nearby wetland water levels; these effects are discussed in 

several chapters of the report.

All of the augmented and impaired wetlands in this 

study were located on the three largest well fields operated 

by Tampa Bay Water, namely, Cross Bar Ranch Well Field, 

Cypress Creek Well Field, and Starkey Well Field (fig. 2). 

Combined, these three well fields occupy more than 33 mi2 of 

Pasco County and encompass hundreds of isolated wetlands. 

Although differences in rainfall and ground-water pumping 

affected all of the study wetlands over time, the effects 

were particularly evident in those three well fields where 

Figure 3. Regional annual rainfall departures from the long-term 

average, 2000 to 2004. (NOAA, National Oceanic and Atmospheric 

Administration.)

Figure 4. Annual rainfall measured at the marsh and cypress 

wetlands during 2001 to 2003 compared to the long-term average 

rainfall. NOAA Division 3 average is 52.26 in/yr and NOAA Division 

4 average is 51.84 in/yr. (HRSP, Hillsborough River State Park; 

GS, Green Swamp.)

Figure 5. The average annual daily ground-water withdrawal from 

the 11 Tampa Bay Water well fields, 1988 to 2004.

15

10

5

0

-5

-10

-15

-20 2000 2001 2002 2003 2004

DEPARTURE FROM THE 110-YEAR

AVERAGE ANNUAL RAINFALL, IN INCHES

NOAA Division 3

NOAA Division 4

2001 2002 2003

70

60

50

40

30

20

10

0

HRSP Natural Marsh

W-29 Impaired Marsh

Duck Pond Augmented Marsh

GS Natural Marsh

W-3 Augmented Marsh

W-5 Augmented Cypress

W-19 Impaired Cypress

S-63 Augmented Cypress

HRSP Natural Marsh

W

S-68 Natural Cypress

GS Natural Cypress

-29 Impaired Marsh

HRSP Natural Marsh

W-29 Impaired Marsh

LONG-TERM

AVERAGE

ANNUAL RAINFALL, IN INCHES

AVERAGE ANNUAL DAILY

GROUND-WATER WITHDRAWAL,

IN MILLION GALLONS PER DAY 200

150

100

50

0

1988

1989

137 1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

165

151

131

79

86

1990
Introduction 9

ground-water pumping was concentrated (table 1). Data for all 

five marshes were collected during 2001 and the first 9 months 

of 2002, prior to reductions in ground-water withdrawals and 

when rainfall was at or slightly below average (table 1 and 

fig. 4). The five cypress wetlands were monitored during the 

remainder of 2002 and the subsequent 2 years, when rainfall 

was markedly above average and ground-water withdrawals 

had decreased sharply at Cypress Creek Well Field and Cross 

Bar Ranch Well Field. Ground-water withdrawals, however, 

did not decline at Starkey Well Field (table 2). The timing 

of the pumping reductions provided a unique opportunity 

to examine their effects on wetland hydrology, because the 

reduction in ground-water withdrawals across the 11 Tampa 

Bay Water well fields was unprecedented.

Description of Study Design

Comparing the hydrology of isolated wetlands lacks 

a standardized method. Therefore, this study was designed 

to define approaches to compare the hydrologic condition 

of isolated wetlands equivalently, including wetlands with 

different vegetation types and in differing hydrologic settings. 

Augmentation has been used to mitigate environmental degradation in both isolated marshes 

and in cypress wetlands. To 

capture the potential differences 

in these two wetland types, five 

of the study wetlands are cypress 

wetlands and five are marsh 

wetlands [classified as forested 

wetlands and emergent wetlands, 

respectively, in the Palustrine 

System of Cowardin and others (1979)]. Equivalent methods 

were applied at the 10 study wetlands over a period of 4 years 

so that comparisons would be consistent across the range of 

hydrologic settings and for both wetlands types. Data were 

collected sequentially at the two wetland types, beginning with 

the five marshes during 2000-02. Data were collected at the 

five cypress wetlands (and continued at two of the marshes) 

during 2002–04 (fig. 6).

The isolated wetlands selected for the study range in 

size from about 1 to 9 acres and maximum depth from about 

1 to 8 ft (table 2). Isolated wetlands of this size are common 

throughout the region. Wetland sites with existing data collection programs were given preference in the selection process. 

All of the study wetlands belong to the hydrogeomorphic 

class of depression wetlands—naturally occurring topographic 

depressions with closed contours and low hydraulic energy in 

which the water sources are precipitation, ground water, and 

interflow (seasonal flow between wetlands when rainfall is 

abundant) (Brinson, 1993). Although these wetlands periodically flood beyond their respective perimeters, they lack a 

consistent surface outflow to a down-slope river, and they 

have little surface connectivity with other water bodies during 

years of typical rainfall.

Figure 6. Approximate 

timeline of data 

collection in the two 

wetland types.

Table 1. Average ground-water withdrawal rates at selected Tampa Bay Water 

regional well fields during the study.

[All values are in million gallons per day]

Well-field name

Marsh 

data-collection period

(Dec. 2000–Sept. 2002)

Cypress 

data-collection period

(Nov. 2002–Aug. 2004)

Study wetlands on 

selected well fields

Cross Bar Ranch Well Field 20.7 11.6 Duck Pond 

Augmented Marsh

Cypress Creek Well Field 23.6 11.2

W-3 Augmented Marsh 

W-5 Augmented Cypress 

W-19 Impaired Cypress

W-29 Impaired Marsh

Starkey Well Field 11.2 12.5 S-63 Augmented Cypress 

S-68 Natural Cypress

Total for all 11 well fields 148 85.5

Data collection in marshes

Data collection in cypress wetlands

2000 2001 2002 2003 2004 2005
10 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Table 2. Names, locations, and physical characteristics of study wetlands.

[USGS, U.S. Geological Survey; N, north; W, west; E, east; Sec., section; T, township; S, south; R, range; sta., station; latitude and longitude in degrees (o), 

minutes ( ́), and seconds ( ̋)]

Wetland name, 

location, and USGS

site identification number

Wetland 

name for this 

study

Period of 

hydrologic

record1

County Latitude Longitude Map 

location2

Size

(acres)

Maximum 

depth

(feet)

Mean

depth

(feet)

Duck Pond Marsh 

Cross Bar Ranch Well Field 

282159082280400

Duck Pond

Augmented 

Marsh

1978 -

present

Pasco 28o21 ́59 ̋N 82o28 ́02 ̋W Sec. 25, T. 24 S., R. 18 E

Ehren

5.2 8.13 3.20

Green Swamp Cypress 

Green Swamp Wildlife 

Management Area

282445081574000

GS Natural

Cypress

1979 -

present

Sumter 28o24 ́47 ̋N 81o57 ́40 ̋W Sec. 12, T. 24 S., R. 23 E

Bay Lake

1.7 1.69 0.46

Green Swamp Marsh 

Green Swamp Wildlife 

Management Area

282114082100100

GS Natural

Marsh

1995 -

present

Sumter 28o21 ́16 ̋N 82o01 ́02 ̋W Sec. 33, T. 24 S., R. 23 E

Branchborough

1.6 1.07 0.62

Hillsborough River 

State Park Marsh

Hillsborough River State 

Park

280848082134400

HRSP

Natural Marsh

1977 -

present

Hillsborough28o08 ́49 ̋N 82o13 ́41 ̋W Sec. 8, T. 27 S., R. 21 E

Zephyrhills

2.2 2.65 0.67

S-63 Cypress 

Starkey Well Field

281455082350000

S-63 

Augmented

Cypress

1983 -

present

Pasco 28o14 ́55 ̋N 82o35 ́00 ̋W Sec. 2, T. 26 S., R. 17 E

Odessa

1.3 1.47 0.58

S-68 Cypress 

Starkey Well Field

281415082343000

S-68 

Natural

Cypress

1983 -

present

Pasco 28o14 ́21 ̋N 82o34 ́31 ̋W Sec. 11, T. 26 S., R. 17 E

Odessa

5.8 1.55 0.79

W-3 Marsh

Cypress Creek Well Field

281812082233800

W-3 

Augmented

Marsh

1978 -

present

Pasco 28o18 ́13 ̋N 82o22 ́40 ̋W Sec. 14, T. 25 S., R. 19 E

Ehren

7.4 5.44 1.89

W-5 Cypress 

Cypress Creek Well Field

281820082225500

W-5 

Augmented

Cypress

1978 -

present

Pasco 28o18 ́18 ̋N 82o22 ́55 ̋W Sec. 14, T. 25 S., R. 19 E

Ehren

8.8 2.11 0.52

W-19 Cypress 

Cypress Creek Well Field 

281642082235000

W-19 

Impaired

Cypress

1978 -

present

Pasco 28o16 ́42 ̋N 82o23 ́52 ̋W Sec. 27, T. 25 S., R. 19 E 

Ehren

2.1 2.70 1.08

W-29 Marsh 

Cypress Creek Well Field 

281754082231300

W-29 

Impaired

Marsh

1978 -

present

Pasco 28o17 ́54 ̋N 82o23 ́13 ̋W Sec. 22, T. 25 S., R. 19 E

Ehren

6.5 2.76 1.44

1

Historical data were collected by regional agencies (Southwest Florida Water Management District; Tampa Bay Water).

2

USGS 1:24,000 topographic map name.
Introduction 11

The marsh and cypress wetlands were grouped depending 

on the principal hydrologic conditions that were used to 

describe them: natural wetlands, impaired wetlands, and 

augmented wetlands.

• Natural wetlands are defined as being unaffected or 

minimally affected by human activities including 

ground-water withdrawal. Four wetlands (two marsh 

and two cypress) were chosen as study sites to 

characterize this group. 

• Impaired wetlands are defined as wetlands affected 

by ground-water withdrawals for several years that 

are typically dry for a longer period of the year than 

natural wetlands. These wetlands have never been 

augmented. Two wetlands (one marsh and one cypress) 

represent this group.

• Augmented wetlands are defined as wetlands affected 

by ground-water withdrawals and augmented with 

ground water for at least 5 years. Four augmented 

wetlands (two marshes and two cypress) were selected 

as study sites to characterize the altered hydroperiod 

and biota of augmented wetlands.

Defining the hydrologic and ecological conditions in 

the natural wetlands was fundamental to the study design. 

Conditions recorded in the four natural wetlands create 

a provisional baseline data set of typical conditions in 

regional wetlands in an undeveloped setting. Comparing 

and contrasting the conditions in the natural wetlands with 

the four historically augmented wetlands provides the basis 

for inferring changes resulting from wetland augmentation. 

A final aspect of the study design was to define conditions 

at two wetlands that are neither natural nor augmented, but 

are considered impaired because they are located in well 

fields and their water levels have been indirectly lowered by 

ground-water pumping. Studies of the two impaired wetlands 

are instructive, because these wetlands share attributes with 

both natural and augmented wetlands. In some respects, the 

impaired wetlands represent a more common contemporary 

hydrologic condition than the natural wetlands, because 

ground-water withdrawals affect wetlands to varying degrees 

throughout the northern Tampa Bay area, not just on its 

well fields. 

Two of the ten wetlands, Green Swamp (GS) Natural 

Marsh and GS Natural Cypress, were studied less intensively 

than the others (fig. 2) because of their remote location. 

Specifically, ground-water flow paths could not be defined 

and hydrogeologic sections could not be drawn at either site 

because new monitoring wells were not constructed. 

Acknowledgments

The authors thank Ted Rochow and Michael Hancock of 

the Southwest Florida Water Management District, and Patty 

Fesmire and Chris Shea of Tampa Bay Water for providing 

historical hydrologic data and knowledgeable advice on area 

wetlands. Lauren Pusateri and Donald Herndon, formerly of 

the USGS Tampa office, provided valuable assistance with 

many aspects of data collection and analysis. Michael Deacon 

provided an excellent editorial review and Patty Fesmire, 

Michael Hancock, Warren Hogg, James LaBaugh, Chris 

Shea, Dave Slonena, Amy Swancar, and Douglas Wilcox 

provided technical review comments that greatly improved 

the report. Michael Hancock generously provided many of 

the wetland photographs used in the report. James Tomberlin 

and Kimberly Swidarski provided graphics support and 

layout design. Twila Darden Wilson provided guidance and 

evaluation in organization and design of the final product. 

Pipeline delivering ground water to

 augment a marsh

Photograph above provided by K. Haag, USGS; photograph at left provided by M. Hancock, SWFWMD
12 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
Wetland hydrology is strongly controlled by the geologic setting 

and the depth and direction of ground-water flow beneath wetland 

basins (Winter and Woo, 1990). The permeability of geologic deposits 

and the ground-water flow patterns around wetlands directly affect their 

rates of ground-water exchange and indirectly affect the magnitude of 

runoff they receive from the surrounding upland areas. The regional 

hydrogeology of the study area and the influence of karst terrain on 

wetland formation are addressed in this section, followed by a description of the hydrogeologic framework of 8 of the 10 wetland basins. 

The stratigraphy in the upland areas around the wetlands are compared 

and contrasted with the stratigraphy directly beneath wetlands. Groundwater flow patterns around the wetlands are described and contrasted 

for natural, impaired, and augmented wetlands, and the effects of 

augmentation on these differences are discussed.

Regional Hydrogeology

The regional landscape of west-central Florida is a mantled karst 

terrain, and in the low-lying areas north of Tampa Bay, wetlands are one 

of the dominant landforms (Schmidt, 1997; Sinclair and others, 1985). 

Mantled karst terrain is characterized by numerous topographic depressions, or sinkholes, that occur where thick, soluble limestone is overlain 

by a mantle of relatively insoluble sands and clays. Rainfall dissolves 

the limestone, forming sinkholes, solution pipes, and other karst features 

that are partially covered by the sand and clay deposits (Sweeting, 1973). 

Where the water table is close to land surface, the limestone dissolution is 

relatively shallow and the resulting land subsidence can create wetlands 

and lakes (fig. 7) (Sinclair and others, 1985; Ewel, 1990; Winter and Woo, 

1990). As the limestone dissolves and forms cavities, the overlying clay 

layer collapses and sand infiltrates or “pipes” into these openings (fig. 8) 

Wetland Hydrogeologic Setting
14 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 7. Landscape features and hydrogeologic framework of mantled karst terrain in 

west-central Florida. (Modified from Tihansky, 1999.)

Figure 8. Example of dissolution and subsidence forming wetlands in mantled karst terrain. (Modified from Tihansky, 1999.)

Overburden (sand and a thin layer

of clay)

Carbonate

bedrock

water table

water table

water

table

Granular sediments spall into

secondary openings in the

underlying carbonate bedrock.

A column of overlying sediments

settles into the vacated spaces

(a process termed piping).

The slow downward erosion

eventually forms a shallow

depression several feet in depth

that intersects the water table.

Dissolution and infilling continue,

forming a depression in the land

surface.

Over time, sediment deposition,

surface drainage, and the cyclical

ponding of the depression aid in

the formation of a wetland.

Mantle or overburden

(sand/clay)

Carbonate rock

(limestone/dolomite)

Limestone near or at land

surface; solution sinkholes are prevalent.

Large volumes of water

move through the

Upper Floridan aquifer.

When a sinkhole breaches

the confining unit, water can

move into the Upper

Floridan aquifer.

Ground water is recharged in the

upland areas.

Upper Floridan aquifer

Intermediate confining unit

Surficial aquifer
Wetland Hydrogeologic Setting 15

(Sinclair and others, 1985; Tihansky, 1999). These sand-filled 

columns may increase the potential for leakage beneath 

wetlands if the underlying clay layer is substantially disrupted, 

and especially if water levels are relatively low in the underlying aquifers. Alternatively, the presence of organic-rich 

wetland sediments may impede leakage. Because of the long 

history of karstification in Florida, sinkholes exist in all stages 

of development, from ancient stable depressions formed during 

lower sea level stands to depressions formed recently.

The geologic framework of the study area is characterized 

by a thick sequence of Miocene to Eocene carbonate rock that 

is overlain by sand and clay sediments of Pliocene to Holocene 

age. The stratigraphic units, from oldest to youngest (deepest 

to shallowest), include the Avon Park Formation (Eocene), 

Ocala Limestone (Eocene), Suwannee Limestone (Oligocene), 

and Tampa Member of the Arcadia Formation of the Hawthorn 

Group (Miocene) (Miller, 1986; Metz and Sacks, 2002). 

Undifferentiated deposits of the Hawthorn Group and undifferentiated surficial deposits overlie the Tampa Member of the 

Hawthorn Group, except in the Green Swamp region where 

the Tampa Member and the Suwannee Limestone have been 

eroded (Tibbals and Grubbs, 1982). 

A dense, plastic clay layer typically overlies the limestone 

below the study wetlands and is contained within the Miocene 

and Pliocene-age sediments of the Hawthorn Group. This layer 

is variable in extent, thickness, and permeability throughout 

the study area (Buono and others, 1979). The clay can be tan, 

greenish-gray, or blue-gray in color and can contain varying 

amounts of sand, phosphate grains, carbonate mud, and highly 

weathered limestone nodules (Sinclair, 1974). Clay minerals 

in the Hawthorn Group can contain potassium, radium, and 

radionuclides (Carr and Alverson, 1959). The radiogenic sediments in the Hawthorn Group yield elevated gamma radiation 

signatures that are used to identify the Group in borehole 

geophysical logs (Carr and Alverson, 1959; Scott, 1988).

The three principal hydrogeologic units in the study area, 

in descending order, are the surficial aquifer system, intermediate confining unit, and Upper Floridan aquifer. The surficial 

aquifer system is a permeable hydrogeologic unit contiguous 

with the land surface. It principally consists of unconsolidated 

to poorly indurated clastic deposits of sand and clayey sand 

(Southeastern Geological Society, 1986). Commonly, this 

unit is termed the surficial aquifer system where more than 

one permeable zone is present or where the deposits are 

interbedded. In this report, the deposits are considered to form 

a single homogeneous aquifer (Metz and Sacks, 2002), and 

are referred to as the surficial aquifer. Recharge to the water 

table by rainfall infiltration is relatively rapid because the 

surface soils are generally permeable and the water table is 

close to land surface. Although water recharged to the surficial 

aquifer can move laterally along short flow paths to points of 

discharge, most leaks downward into the underlying Upper 

Floridan aquifer.

The intermediate confining unit is a nonwater-yielding 

strata of undifferentiated deposits within the clay-rich 

Hawthorn Group (Metz and Sacks, 2002). The unit consists 

of dense, marine green-gray plastic clay that contains varying 

amounts of sand, chert, phosphate, organic material, and 

carbonate mud (Sinclair, 1974). The clay unit is variable in its 

extent and thickness throughout the study area. Although the 

intermediate confining unit impedes downward flow between 

the surficial aquifer and Upper Floridan aquifer in some areas, 

the hydraulic connection between the surficial and Upper 

Floridan aquifers is increased where the intermediate confining 

unit is thin or breached by sinkholes. The Upper Floridan 

aquifer is the primary source of water supply in the study area. 

The limestone and dolomites of the Upper Floridan aquifer 

contain many solution-enlarged fractures and typically yield 

large quantities of ground water to public and private wells 

(Metz and Sacks, 2002). 

Hydrogeologic Methods

The stratigraphy of the wetland basins was interpreted 

from existing geologic and borehole geophysical logs, grainsize analysis, and from the descriptions of well cuttings from 

more than 100 wells drilled for the study. Table 3 describes the 

construction and location of the wells used in the study, along 

with well index numbers and a summary of data collected at 

each well. The index numbers are provided to cross reference 

the wells shown in the maps of wetland basins and in the 

hydrogeologic sections of the eight wetlands with table 3. No 

new wells were drilled at the two most remote wetlands, 

namely, GS Natural Marsh and GS Natural Cypress; therefore, 

interpretation of stratigraphy and ground-water flow patterns 

in these two basins is limited.

Drilling a monitoring well for the study
16 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Table 3. Well characteristics and data collected for wells used in the study. 

[USGS, U.S. Geological Survey; Hydrogeologic unit: ICU, intermediate confining unit; SA, surfical aquifer; UFA, Upper Floridan aquifer; 

Data summary: CWR, continuous water-level recorder; GSA, grain-size analysis; QW, water quality; WL, periodic water level; --, unknown 

well or casing depth]

Well

index number

USGS well

identification number Well name

Well

depth1

(feet)

Casing 

depth1

(feet)

Hydrogeologic 

unit

Data summary

1 282201082280401 Crossbar Duck PD LNE 7 4 SA GSA,QW,WL

2 282201082280701 Crossbar Duck PD LNW 14 9 SA QW,WL

3 282157082280201 Crossbar Duck PD LSE 13 9 SA GSA,QW,WL

4 282158082280601 Crossbar Duck PD LSW 11 7 SA GSA,QW,WL

5 282202082280401 Crossbar Duck PD MNE 13 9 SA GSA,QW,WL

6 282202082280801 Crossbar Duck PD MNW 14 10 SA GSA,QW,WL

7 282156082280201 Crossbar Duck PD MSE 20 16 SA GSA,QW,WL

8 282157082280701 Crossbar Duck PD MSW 15 11 SA GSA,QW,WL

9 282203082280401 Crossbar Duck PD UNE 19 15 SA QW,WL

10 282203082280901 Crossbar Duck PD UNW 14 10 SA GSA,QW,WL

11 282157082280801 Crossbar Duck PD USW 21 17 SA GSA,QW,WL

12 282202082280301 Crossbar Duck PD FLRD 2 138 77 UFA CWR,WL

13 282154082280401 Crossbar A-2 Deep 3 700 152 UFA WL

14 282154082280402 Crossbar A-2 Shallow 3 (USE) 23 19 SA QW,WL

15 282157082280301 Crossbar Duck PD Aug 5 -- -- UFA QW

15a 282159082280301 Crossbar Duck PD Center 1 1 SA WL

16 281641082235101 Cypress Creek W-19 B Center 7 -- SA WL

17 281640082235201 Cypress Creek W-19 H 11 7 SA QW,WL

18 281643082234901 Cypress Creek W-19 I 11 6 SA QW,WL

19 281639082235201 Cypress Creek W-19 J 13 8 SA QW,WL

20 281641082235401 Cypress Creek W-19 K 17 12 ICU CWR,WL

21 281642082235401 Cypress Creek W-19 K2 10 6 SA QW,WL

22 281641082235501 Cypress Creek W-19 L 17 12 SA GSA,QW,WL

23 281644082234701 Cypress Creek W-19 M 7 2 SA GSA,QW,WL

24 281644082235601 Cypress Creek W-19 N 13 8 SA QW,WL

25 281645082234901 Cypress Creek W-19 O 9 4 SA QW,WL

26 281645082235101 Cypress Creek W-19 Q 8 4 ICU QW,WL

27 281642082235001 Cypress Creek W-19 P 7 3 SA QW,WL

28 281642082235501 Cypress Creek W-19 FLRD 2 117 80 UFA CWR,WL

28a 281641082235301 Cypress Creek W-19 W 6 2 SA WL

29 281758082231701 Cypress Creek W-29 B1CTR 4 9 0 SA GSA,QW,WL

30 281758082231601 Cypress Creek W-29 B1LNE 10 6 SA GSA.WL

31 281759082231801 Cypress Creek W-29 B1LNW 7 3 SA GSA.WL

32 281758082231602 Cypress Creek W-29 B1LSE 8 4 SA GSA.WL
Wetland Hydrogeologic Setting 17

Well

index number

USGS well

identification number Well name

Well

depth1

(feet)

Casing 

depth1

(feet)

Hydrogeologic 

unit

Data summary

33 281758082231702 Cypress Creek W-29 B1LSW 10 6 SA GSA.WL

34 281759082231601 Cypress Creek W-29 B1MNE 11 7 SA QW,WL

34a 281759082231802 Cypress Creek W-29 Ext 4 (B1MNW) 9 -- SA WL

35 281758082231501 Cypress Creek W-29 B1MSE 8 4 SA QW,WL

36 281757082231801 Cypress Creek W-29 B1MSW 11 7 SA GSA,QW,WL

37 281800082231901 Cypress Creek W-29 B1UNW 15 11 SA GSA.WL

38 281754082231301 Cypress Creek W-29 B2CTR 5 1 SA GSA.WL

39 281754082231302 Cypress Creek W-29 B2CTRDP 11 8 SA GSA.WL

40 281755082231301 Cypress Creek W-29 B2LNE 8 4 SA GSA,QW,WL

41 281755082231401 Cypress Creek W-29 B2LNW 7 3 SA GSA.WL

42 281754082231201 Cypress Creek W-29 B2LSE 10 6 SA GSA,QW,WL

43 281753082231401 Cypress Creek W-29 B2LSW 9 5 SA GSA.WL

44 281756082231201 Cypress Creek W-29 B2MNE 12 8 SA GSA.QW,WL

45 281755082231601 Cypress Creek W-29 B2MNW 9 5 SA GSA.WL

46 281753082231201 Cypress Creek W-29 B2MS 10 6 SA GSA.WL

47 281754082231202 Cypress Creek W-29 B2MSE 17 13 SA QW,WL

48 281753082231402 Cypress Creek W-29 B2MSW 18 14 SA QW,WL

49 281757082231201 Cypress Creek W-29 B2UNE 14 10 SA GSA.WL

50 281756082231601 Cypress Creek W-29 B2UNW 10 6 SA GSA.WL

51 281750082231501 Cypress Creek W-29 B2USW 5 1 SA WL

52 281759082231901 Cypress Creek W-29 FLRD 2 136 59 UFA CWR,WL

53 281810082223101 Cypress Creek W34 INT2 4 10 -- SA WL

54 281813082224001 Cypress Creek W-03 DO Creek 4 3 -- SA WL

55 281814082223801 Cypress Creek W-03 UFA 2 151 20 UFA WL

56 281812082233801 Cypress Creek W-03 Augmentation 5 -- -- UFA QW

57 281817082224201 Cypress Creek W-04 INT 4 6 -- SA WL

58 281809082224403 Cypress Creek Shallow E-106 14 -- SA WL

59 281817082223801 Cypress Creek BIO-1 2 15 2 SA WL

60 281816082225301 Cypress Creek BIO-2 2 21 5 SA WL

61 281804082224201 Cypress Creek BIO-3 2 16 2 SA WL

62 281813082224202 Cypress Creek C2-S 19 2 SA WL

64 281804082224202 Cypress Creek CCWFFUP 2 5 2 SA WL

65 281805082224201 Cypress Creek CCWFWTLD 2 7 2 SA WL

66 281817082223802 Cypress Creek CCWF E UPL 2 12 2 SA WL

67 281801082225201 Cypress Creek E107S 4 20 15 SA WL

68 281813082224501 Cypress Creek T1-A 2 12 2 SA WL

69 281816082224701 Cypress Creek T1-B 2 12 2 SA WL

70 281817082225001 Cypress Creek T1-C 2 11 2 SA WL
18 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Well

index number

USGS well

identification number Well name

Well

depth1

(feet)

Casing 

depth1

(feet)

Hydrogeologic 

unit

Data summary

71 281819082225401 Cypress Creek T1-D2 12 5 SA WL

72 281821082225701 Cypress Creek T1-F 2 12 2 SA WL

73 281824082230101 Cypress Creek T1-H 2 11 2 SA WL

74 281817082225401 Cypress Creek W-05 No. 1 2 10 2 SA CWR,QW,WL

75 281817082225101 Cypress Creek W-05 No. 2 2 23 3 SA CWR,QW,WL

76 281821082225301 Cypress Creek W-05 No. 3 2 8 2 SA QW,WL

77 281822082225901 Cypress Creek W-05 No. 4 2 8 2 SA QW,WL

78 281821082225601 Cypress Creek W-05 No. 5 2 6 3 SA QW,WL

79 281816082225701 Cypress Creek W-05 No. 6 2 14 2 SA QW,WL

80 281818082225501 Cypress Creek W-05 Center 4 8 -- SA CWR,WL

81 281820082225001 Cypress Creek W-05 Aug. 5 -- -- UFA QW

82 281821082225302 Cypress Creek W-05 FLRD 2 125 60 UFA CWR,WL

83 282446081574201 Green Swamp Cypress 5 Upland 2 14 -- SA WL

84 282447081574001 Green Swamp Cypress 5 Center 15 3 SA WL

85 282118082010301 Green Swamp Marsh UPL 2 9 1 SA WL

86 282118082010401 Green Swamp Marsh FLRD 2 122 44 UFA WL

87 282116082010201 Green Swamp Marsh Center 6 1 SA CWR,WL

88 280849082134101 Hillsborough River ST PK CTR 9 0 SA CWR,GSA,QW,WL

89 280851082134001 Hillsborough River ST PK LN 12 8 SA GSA,QW,WL

90 280850082134301 Hillsborough River ST PK LNW 11 7 SA GSA,QW,WL

91 280849082134001 Hillsborough River ST PK LSE 13 9 SA GSA,QW,WL

92 280847082134301 Hillsborough River ST PK LSW 14 10 SA GSA,QW,WL

93 280854082134201 Hillsborough River ST PK UN 14 10 SA GSA,QW,WL

94 280852082134301 Hillsborough River ST PK UNW 16 12 SA GSA,QW,WL

95 280847082134001 Hillsborough River ST PK USE 11 7 SA GSA,QW,WL

96 280846082134501 Hillsborough River ST PK USW 14 10 SA GSA,QW,WL

97 280849082134401 Hillsborough River ST PK UW 16 12 SA GSA,QW,WL

98 280852082135601 Hillsborough ST PK Parking Lot DP 2 76 62 UFA CWR,QW,WL

99 280852082135602 Hillsborough ST PK Parking Lot SH 2 24 20 SA QW,WL

100 280846082134601 Hillsborough ST PK Boys Camp DP 2 74 62 UFA QW,WL

101 280846082134602 Hillsborough ST PK Boys Camp SH 2 18 15 SA QW,WL

102 281500082351101 Starkey S-10 FLRD Production 4 750 165 UFA QW

103 281454082345801 Starkey S-63 LMSE 14 10 SA WL

104 281456082345901 Starkey S-63 LNE HTRN 16 12 ICU QW,WL

105 281456082345902 Starkey S-63 LNE 6 2 SA GSA,QW,WL

106 281456082350101 Starkey S-63 LNW 18 14 SA QW,WL

107 281456082350102 Starkey S-63 LNW No. 2 10 6 SA QW,WL

108 281455082345801 Starkey S-63 LSE 14 10 SA QW,WL
Wetland Hydrogeologic Setting 19

Well

index number

USGS well

identification number Well name

Well

depth1

(feet)

Casing 

depth1

(feet)

Hydrogeologic 

unit

Data summary

109 281454082350001 Starkey S-63 LSW 14 10 SA QW,WL

110 281457082345802 Starkey S-63 MNE 18 14 SA QW,WL

111 281457082350201 Starkey S-63 MNW HTRN 22 18 ICU QW,WL

112 281457082350202 Starkey S-63 MNW No. 2 11 7 SA QW,WL

113 281453082350101 Starkey S-63 MSW HTRN 22 18 ICU GSA.QW,WL

114 281453082350102 Starkey S-63 MSW NRSD 9 5 SA QW,WL

115 281453082345701 Starkey S-63 UMSE 11 7 SA QW,WL

116 281457082345801 Starkey S-63 UNE 16 12 SA QW,WL

117 281457082350401 Starkey S-63 UNW HTRN 21 17 SA QW,WL

118 281457082350402 Starkey S-63 UNW No.2 NRSD 12 8 SA WL

119 281452082345501 Starkey S-63 USE 19 15 SA QW,WL

120 281452082350301 Starkey S-63 USW HTRN 22 18 ICU QW,WL

121 281452082350302 Starkey S-63 USW NRSD 10 6 SA QW,WL

122 281452082350303 Starkey S-63 FLRD 2 130 80 UFA CWR,WL

122a 281455082350001 Starkey S-63 Center 4 0 SA CWR,WL

123 281415082342401 Starkey S-68 LE 14 10 SA QW,WL

124 281419082342601 Starkey S-68 LNE 14 10 SA QW,WL

125 281420082343101 Starkey S-68 LNW 14 10 SA QW,WL

126 281414082342701 Starkey S-68 LSE 12 8 SA QW,WL

127 281417082343201 Starkey S-68 LW 13 9 SA QW,WL

128 281413082342801 Starkey S-68 MSE HTRN 18 14 ICU GSA,WL

129 281413082342802 Starkey S-68 MSE NRSD 7 3 SA QW,WL

130 281417082343301 Starkey S-68 MW 13 9 SA QW,WL

131 281422082342701 Starkey S-68 UNE 14 10 SA QW,WL

132 281421082343101 Starkey S-68 UNW 14 10 SA GSA,QW,WL

133 281410082342701 Starkey S-68 USE HTRN 21 17 ICU QW,WL

134 281410082342702 Starkey S-68 USE NRSD 9 4 SA QW,WL

135 281417082343601 Starkey S-68 UW HTRN 18 14 ICU QW,WL

136 281417082343602 Starkey S-68 UW NRSD 11 7 SA QW,WL

137 281421082343102 Starkey S-68 FLRD 2 130 80 UFA WL

138 281418082343001 Starkey S-68 Center 4 4 SA WL

1

Depth values are in feet below land surface.

2

Southwest Florida Water Management District well.

3

Pinellas County well.

4

Tampa Bay Water well.

5

Tampa Bay Water augmentation outflow from well-field production pipeline.
20 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Stratigraphy below the wetlands was reconstructed using 

information from bathymetry surveys (Haag and others, 2005) 

and from cores collected using a vibracore device (Lanesky 

and others, 1979). Stratigraphic data also were collected and 

interpreted using a multi-sensor down-core scanner (Gunn and 

Best, 1998), point measurements of the wetland soft-sediment 

thicknesses (Brenner and Whitmore, 1999), and groundpenetrating radar (GPR) (Barr, 1993; Kruse and others, 2006). 

The thickness of the organic-rich sediment in each wetland 

was measured by probing the sediments with a calibrated 

metal rod, following an approach used for shallow lakes in 

Florida (Brenner and Whitmore, 1999). Sediment thickness 

was measured at multiple points along at least one cross 

section through each of the 10 wetlands, and at additional 

points in several other wetlands.

The stratigraphic data beneath the wetlands were 

generally collected within 15 ft of land surface. Geologic 

samples were collected using a vibracore device at the five 

marshes (fig. 9). At the cypress wetlands, samples were 

obtained using a hand auger or a small rotary drill rig (fig. 10). 

The vibracores generated the most intact profile of the shallow 

stratigraphy; however, the maximum core length was either 

about 13 ft or to the depth of the first substantial clay layer. 

The coring device, powered by an air compressor, vibrated a 

3-in. diameter aluminum core barrel into the wetland bottom 

(Lanesky and others, 1979). 

Cores from three of the marshes were analyzed 

for changes in selected sediment properties with depth. 

A GeotekTM multi-sensor scanner was used for down-core 

logging of saturated bulk density, also called gamma bulk 

density because it is determined by measuring the attenuation of gamma radiation from a Cesium-137 (137Cs) source 

(J.M. Jaeger, University of Florida, written commun., 2003). 

Following the logging, cores were split and the sediments 

were photographed, described, and subsampled at 2-cm 

intervals for further analyses. Freeze-dried sediment samples 

were analyzed for radium-226 (226Ra) activity as well as other 

associated radioisotopic activity using a gamma counter with 

an intrinsic low-energy germanium detector (J.M. Jaeger, 

University of Florida, written commun., 2003). Sediment grain 

sizes, or the relative mass percentages of sand, silt and clay, 

were analyzed to a depth of 19.7 in. (50 cm) in each core using 

the methods of Galehouse (1971). 

In addition to vertical profiles of 226Ra activity in 

sediment cores from the three marshes, 226Ra activity also 

was measured in surface sediment grab samples taken from 

the 10 wetlands, as well as in surface water and augmentation 

water at selected wetlands. Samples for 226Ra analysis were 

collected from the marsh wetlands in July 2002. A single 

1-L subsurface grab water sample and a single 500-mL 

sediment sample were collected from inundated areas near the 

perimeter of each marsh in less than 6 in. of water (excluding 

W‐29 Impaired Marsh, which was dry). A 1-L sample 

of augmentation water was collected at each of the two 

augmented marshes. In May 2004, a second set of sediment 

samples was collected at all 10 wetlands for 226Ra analysis. 

Three sediment samples were collected at widely spaced 

locations in each wetland where the water depth was 6 in. or 

less. The water and sediment samples were collected using 

standard USGS methods described in Wilde and others (1998).

Water and sediment samples were analyzed through 

the USGS National Water Quality Laboratory (NWQL) in 

Lakewood, Colorado. The 226Ra activity was reported for 

each sample, along with the minimum detectable concentration (MDC), and the combined standard uncertainty (CSU). 

The MDC at the time of analysis for 226Ra activity was 

1.8 dpm/g for sediment samples and 0.09 dpm/L for water 

samples. The uncertainty associated with the 226Ra activity is 

1 standard deviation of the CSU for 226Ra determined by alpha 

spectrometry. The uncertainty terms for the 226Ra samples in 

this study were generally smaller than the measured values 

(16 – 53 percent of the measured values). Further explanations 

of these terms are found in Focazio and others (2001).

The GPR surveys were made at three wetlands 

(W‐29 Impaired Marsh, Duck Pond Augmented Marsh, and 

S‐63 Augmented Cypress) to provide evidence of karst subsidence in wetland basins. The surface-geophysical technique can 

profile the top of subsurface clay layers, identifying areas where 

the clays are deformed downward or breached by subsidence 

into sinkholes (Wilson and Garmen, 2002). Geophysical 

surveys included data collected over flooded wetlands (W‐29 

Impaired Marsh and Duck Pond Augmented Marsh) and across 

land. All GPR surveys were performed using a PulseEKKO 

100TM system and in the manner of Barr (1993). The depth of 

reflected signals was correlated with geologic data at known 

reference points.

Ground-water levels were measured biweekly over 

varying time frames in a total of 118 surficial aquifer, 

9 intermediate confining unit, and 11 Upper Floridan aquifer 

wells (table 3). At most of the wetlands, upland surficial 

aquifer wells were drilled at varying distances from the 

wetland perimeter to monitor the surrounding water table. 

One or more wells located near the center of each wetland 

were used to monitor either wetland stage during flooded 

periods, or the ground-water level as it receded below the land 

surface during dry periods. Because W‐29 Impaired Marsh 

was frequently dry, numerous wells were drilled inside the 

perimeter of this wetland to map the underlying water table. 

The potentiometric level of the Upper Floridan aquifer also 

was monitored in the vicinity of each wetland. Water levels 

were recorded continuously at six Upper Floridan aquifer 

monitoring well locations, and biweekly in others (table 3). 

Upper Floridan aquifer water levels were then compared 

to the overlying surficial aquifer and wetland water levels. 

Continuous water-level monitoring for this study was done 

with submersible pressure transducers according to standard 

methods described in Freeman and others (2004). Biweekly 

ground-water levels and other hydrologic data for the wetlands 

are available online from the USGS National Water Information 

System database at http://waterdata.usgs.gov/fl/nwis/gw

(U.S. Geological Survey, 2007). 
Wetland Hydrogeologic Setting 21

Basin Stratigraphy

The wetlands showed no distinctive differences in basin 

stratigraphy that could be linked to the wetland type (marsh or 

cypress) or to the hydrologic conditions of the three wetland 

groups (natural, impaired, or augmented). For example, the 

unconsolidated surficial deposits surrounding the wetlands ranged 

from 20 to 40 ft thick and were mostly similar in composition 

(figs. 11-18). Surficial deposits typically were composed of an 

uppermost fine- to medium-grained sand unit, a sequence of 

clayey sand, and a lower sequence of sandy clay. The sand is 

white to buff colored near the surface and contains a mixture 

of dark organic matter and silt. Based on grain-size analysis, 

Duck Pond Augmented Marsh and W‐29 Impaired Marsh had 

the highest sand content in their surrounding surficial deposits. 

The clay content increased with depth below the sand and organic 

layer, creating a sequence of clayey sand. In some instances, iron 

staining and small limestone nodules were noted in this middle 

sequence (W‐29 Impaired Marsh, W‐3 Augmented Marsh, Duck 

Pond Augmented Marsh, W‐19 Impaired Cypress, 63 Augmented 

Cypress, S‐68 Natural Cypress). A unit of sandy clay exists below 

the clayey sand sequence.

The description of the intermediate confining unit taken from 

drilling logs indicates it is variable in thickness, composition, and 

permeability throughout the 10 wetland basins. The thickness of 

the intermediate confining unit ranges from 5 ft at HRSP Natural 

Marsh (in areas where it is present) to 30 ft near W‐19 Impaired 

Cypress. A grain-size analysis of samples from four of the basins 

where the intermediate confining unit is present indicates the clay 

fraction ranges from 30 to 80 percent.

The top of the limestone (and Upper Floridan aquifer) at 

the 10 wetland basins is relatively shallow and of irregular depth 

due to erosion. The limestone was encountered during drilling 

at depths ranging from 18 ft (W‐5 Augmented Cypress) to 40 ft 

below land surface (W‐19 Impaired Cypress). Historical geologic 

logs from wells near many of the wetlands indicate that sand and 

clay were encountered within the limestone unit far below the 

typical depth range of mantle deposits; for example, at 80 ft below 

land surface near S‐68 Natural Cypress and S‐63 Augmented 

Cypress, implicating potential sinkhole formation.

The HRSP Natural Marsh wetland, located along the 

Hillsborough River, is the only wetland in this study that currently 

is located in a regional ground-water discharge area. Large 

volumes of ground water seep upward from the Upper Floridan 

aquifer toward land surface in this area (Wolansky and Thompson, 

1987). For example, a second magnitude spring (Crystal Springs) 

that discharges about 40 Mgal/d to the Hillsborough River is 

located about 6 mi northeast of HRSP Natural Marsh. Because of 

erosional processes in the vicinity of the Hillsborough River, the 

geology varies substantially and is characterized by an irregular 

weathered limestone surface and a thin to nonexistent intermediate 

confining unit (Trommer and others, 2007). Historical geologic 

logs and those from wells drilled during this study indicate 

substantial variability in the geology at HRSP. These logs indicate 

limestone at land surface near the river, as well as limestone 

deposits at a depth of 50 ft below land surface within the HRSP 

Natural Marsh basin.

The surficial deposits surrounding HRSP Natural Marsh 

differ in composition from the other wetlands and are composed 

of an upper fine sand unit underlain by a sandy clay, underlain 

by a sequence of white, medium-grained quartz sands, overlying 

a blue-green clay unit. Grain-size analyses indicate the surficial 

sediments around this wetland contain the highest percentage of 

clay (10-80 percent) of all the study wetlands. The mineralogy of 

the uppermost 20 ft of sediment indicated a high percentage of 

calcium carbonate (CaCO3) (10 to 60 percent) within the shallow 

mantle deposits. The shallow ground-water chemistry, sampled 

in wells less than 20 ft deep, indicated a substantial enrichment of 

calcium carbonate in the surficial aquifer.

Sub-Wetland Stratigraphy

Stratigraphy was examined to a depth of about 15 ft below 

the wetlands. All wetlands investigated share a common shallow 

stratigraphic sequence. An organic-rich wetland sediment layer is 

underlain by a sequence of sand and silt, underlain by a sandy-clay 

layer. However, differences in the nature of these layers distinguish 

one wetland from another. In particular, the wetlands differ in the 

(1) degree to which karst subsidence features are evident in the 

wetland basin, (2) thickness and composition of the organic-rich 

bottom sediments, (3) relative proportion of mud (silt and clay) 

in the shallow sediments, (4) 226Ra enrichment in the sediments, 

(5) presence or absence of an iron hardpan in the underlying sand 

layers, and (6) depth of the intermediate confining unit below 

the wetland.

The organic-rich wetland sediments are composed of 

varying amounts of grayish-brown organic material, sand, and 

mud (silt and clay). The organic material varies in consistency 

from a fibrous, matted, turf-like material to a plastic, mud-like 

slime, resembling an early description of peat deposits in Florida 

marshes provided by Davis (1946). Organic sediment is thickest 

in the deepest areas of the wetlands and thinnest near the margins. 

The maximum sediment depth was similar in 8 of the 10 wetlands, 

ranging from 2.1 to 3.3 ft below land surface, and averaging 

3.2 ft in thickness. The maximum sediment thickness was more 

than double this average in the two augmented marshes, namely, 

Duck Pond Marsh and W‐3 Marsh (6.8 ft and 7.4 ft, respectively) 

(figs. 12 and 13).

The thicker sediment encountered in the two augmented 

marshes is probably a consequence of ground-water augmentation. Both marshes are continually augmented, and have never 

been dry completely during their augmentation history. Instead, 

augmentation has maintained flooding over at least 40-60 percent 

of the marsh surface area. In contrast, the two augmented cypress 

wetlands, where the maximum sediment thickness was similar to 

the unaugmented wetlands, have each been dry during part of their 

augmentation history. The augmented cypress wetlands have been 

less than 20 percent flooded or completely dry during more than 

30 percent of their respective periods of record. Further information about wetland flooding characteristics is provided in the 

section titled Wetland Flooding Characteristics.
22 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida 28°21'15"N

0 1,000 FEET

0 75 150 METERS 0 300 METERS

0 250 500 FEET

150 METERS

0 250 500 FEET

0 75

0 500 FEET

0 150 METERS

150 METERS

0 250 500 FEET

0 75

82°28’10"W 82°28'00"W

28°22'00"N

82°1'10"W 82°1'0"W

82°22'40"W

82°13'50"W

28°08’45"N

82°22'30"W

82°13'40"W

28°18’00"N

28°18'15"N

X’

X

Z’

9

8

7

6 5

4

3

2 1

15

12

11

10

Z

13 14

Y

Y’

87

86 85

GPR LINE

(refers to figure 22)

99

98

97

96

95

94

93

92

91

90

89

88

101

100

X

X’

69

68

66

65

64

62

61

59

58

57

55

54

53

X

X’

56

(A) Duck Pond Augmented Marsh (B) W-3 Augmented Marsh

(C) HRSP Natural Marsh (D) GS Natural Marsh

CC-2

CC-11

106D

(E) W-29 Impaired Marsh

52

51

50

49

48 46

45

44

43

41

38

37

36

35

34

30

Z

Z’

GPR LINE

29 (refers to figure 22)

42

33 32

47

X

X’

31

39

34a

40

82°23'20"W 82°23'10"W

Hillsborough River

TW-17

CB-4

15a

87

EXPLANATION

Note: Wells A1 shallow and deep are 900 feet beyond southern extent of map (A).

Wells C3 and E107D are 280 and 580 feet, respectively, beyond southern extent of map (B).

Well C1 is 525 feet beyond northern extent of map (B).

WETLAND– Source: Fish and

Wildlife Service, National

Wetlands Inventory polygon

data, March, 2004; Universal

Transverse Mercator Projection,

Zone 17

STUDY WETLAND BOUNDARY

LOCATION OF GEOLOGIC

SECTION–Shown in figures 11-14

GROUND-PENETRATING RADAR

(GPR) LINE–Shown in figure 22

OBSERVATION WELL AND

INDEX NUMBER– Number

refers to table 3

DATA POINT FOR SEDIMENT

SURVEY

SURFACE-WATER GAGE

RADIOISOTOPIC CORES

RAINFALL MEASUREMENT

SITE

VIBRACORES

PRODUCTION WELL

Figure 9. Location of data-collection sites for the marsh wetlands.
Wetland Hydrogeologic Setting 23

0 500 FEET

0 150 METERS

82°34'40"W 82°34'20"W

28°14'15"N

300 METERS

0 500 1,000 FEET

0 150

82°35'00"W

28°14'55"N

0 500 FEET

0 150 METERS

82°23'10"W 82°22'50"W

28°18'10"N 28°18'30"N

300 METERS

0 500 1,000 FEET

0 150

81°57'40"W

28°24’45"N

0 500 FEET

0 152 METERS

82°23'50"W

28°16’45"N

87

EXPLANATION

(E) W-19 Impaired Cypress

Well CC 9 is located 350 feet beyond

eastern extent of map

84

83

28

27

26

25

24

23

22

21

20

19

18

17

16

X

X’

28a

CC-10

(D) S-68 Natural Cypress

(A) W-5 Augmented Cypress (B) S-63 Augmented Cypress

(C) GS Natural Cypress

82

81

79

78

77

76

74 75

73

72

71

70

69

68

62

60

58

57

54

80

81

CC-2

Cypress Creek

X’

137

136

135

134

133

132

131

130

129

128

127

126

125 124

123

138

X’

X

Cross

Cypress

Branch

122 121

120

119

118

117 116

115 114

113

112

111 110

109

108

107

106

105

103

GPR LINE

(refers to figure 22)

102

104 Z

Z’

122a

X

X’

Anclote River

X

CC-1

WETLAND–Source: Fish and

Wildlife Service, National

Wetlands Inventory polygon

data, March, 2004; Universal

Transverse Mercator Projection,

Zone 17

STUDY WETLAND BOUNDARY

LOCATION OF GEOLOGIC

SECTION–Shown in

figures 15-18

GROUND-PENETRATING

RADAR (GPR) LINE–Shown in

figure 22

OBSERVATION WELL AND

INDEX NUMBER– Number

refers to table 3

DATA POINT FOR SEDIMENT

SURVEY

SURFACE-WATER GAGE

RADIOISOTOPIC CORES

RAINFALL MEASUREMENT

SITE

HAND-AUGERED CORES

PRODUCTION WELL

Figure 10. Location of data-collection sites for the cypress wetlands.
24 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 11. Generalized hydrogeologic section and vertical head distribution for HRSP Natural Marsh at Hillsborough River State Park.

HILLSBOROUGH RIVER STATE PARK NATURAL MARSH

May 30, 2002

0 100 200 300 FEET

USGS Children’s Camp 51-FT FLRD

39.09

39

93

38.24

94

39.06

38.6

89

88

44.61

96

38.96

39.13 39.18

100, Depth 74 feet, casing 62 feet

92

101

44 43

42 41 40

X X’

FEET FEET ELEVATION ABOVE NGVD 29

60

50

40

30

20

10

0

EXPLANATION

39

39.18

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA

VIBRACORE

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE

EQUIPOTENTIAL LINE – Contour interval 1 foot. Dashed

where inferred

INFERRED GEOLOGIC CONTACT – Altitude of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

92

92

ELEVATION ABOVE NGVD 29

60

50

40

30

20

10

0

92

44.61

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER
Wetland Hydrogeologic Setting 25

Figure 12. Generalized hydrogeologic section and vertical head distribution for Duck Pond Augmented Marsh at Cross Bar Well Field.

DUCK POND AUGMENTED MARSH, CROSS BAR WELL FIELD

May 30, 2002

0 200 400 600 FEET

X X’

FEET FEET

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

50.65

2

ELEVATION ABOVE NGVD 29

80

70

60

50

40

30

20

A1- Deep well (no water level),

Depth 700 , cased 155 feet feet

A-1 Shallow

53.84

Geologic interpretation

based on

ground-penetrating radar

52.70

62

68

60

56

54

66

64

53

7

14

3

6

10

54.82

60.18

63.56

60.56

56.97 68.12

64.37

TW-17 soil bore log, 80 (plugged) feet

CB-4 production well

Depth 705 , cased 155 feet feet

12, Depth 138 feet, cased 77 feet

13, Depth 700 feet, cased 152 feet

EXPLANATION

64

54.82

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

VIBRACORE

INDICATES WELL WAS PROJECTED ONTO

SECTION

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 1 and 2 feet.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

14

14

58

58

60

*

*

*

*

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER

68.12

15a
26 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 13. Generalized hydrogeologic section and vertical head distribution for W-3 Augmented Marsh at Cypress Creek Well Field. E-106D, depth 1,290 feet, casing 285 feet (well plugged)

54.20

?

?

C-3 production, depth 700 feet

casing 81 feet

W-3 AUGMENTED MARSH, CYPRESS CREEK WELL FIELD

September 5, 2002 E-107D, depth 700 feet, casing 85 feet

57

65

58

64

61

66.84

70.34

(DRY)

(DRY)

58.63

61.33

70

68

66

64

62

60

58

56

55, Depth 125 feet, casing 75 feet

C-1 production, depth 700 feet, casing 80 feet

X X’

FEET FEET

EXPLANATION

64

61.54

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

VIBRACORE

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 1 and 2 feet.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

58

58

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

69

67

65

63

61

59

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

0 200 400 600 FEET

70.34

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER
Wetland Hydrogeologic Setting 27

Figure 14. Generalized hydrogeologic section and vertical head distribution for W-29 Impaired Marsh at Cypress Creek Well Field.

0 100 200 FEET

X X’

FEET FEET

W-29 IMPAIRED MARSH, CYPRESS CREEK WELL FIELD

May 16, 2002

Geologic interpretation based on ground-penetrating radar

58 54 50 46 42

65 64

63

60

59

61

62

63.03 62.90 63.12 63.21

62.25

62.68 60.95 65.97

35

29

32

31

52,

34a

Depth 136 feet,

cased 59 feet

42

47

39

EXPLANATION

64

63.21

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA–

Unnumbered wells are property of Tampa

Bay Water

VIBRACORE

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 1 and 4 feet.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

35

35

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER

40.52
28 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 15. Generalized hydrogeologic section and vertical head distribution for S-68 Natural Cypress at Starkey Well Field.

35.09

S-68 NATURAL CYPRESS, STARKEY WELL FIELD

May 26, 2004

35.01

42.18

41.84

40.87

42.62

40.94

41.30

134

133

42

38 36

34

40

ELEVATION ABOVE AND BELOW NGVD 29

300 FEET

EXPLANATION

34

42.18

50

40

30

20

10

0

10

0 100 200

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 1 and 2 feet.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

126

126

128

129

126

138

137,

132

125

Depth 118 feet, casing 81 feet

ELEVATION ABOVE AND BELOW NGVD 29

50

40

30

20

10

0

10

41

X X’

FEET FEET

42.62

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER

33.84
Wetland Hydrogeologic Setting 29

Figure 16. Generalized hydrogeologic section and vertical head distribution for S-63 Augmented Cypress at Starkey Well Field.

S-63 AUGMENTED CYPRESS, STARKEY WELL FIELD

June 9, 2004

GPR line GPR line

Geologic interpretation based on ground-penetrating radar (GPR)

ELEVATION ABOVE AND BELOW NGVD 29

ELEVATION ABOVE AND BELOW NGVD 29

38.15

36.88

38.27

38.86

32.50

32.50 33.19

35.21

41.75

38.95

35.60

121

113

114

109

104

105

110

116

122a

122, Depth 130 feet, casing 80 feet

40

37

36

38

41

33

39

35 34

0 100 200 300 FEET

EXPLANATION

33

35.93

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 1 foot. Dashed

where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

114

114

FEET

120

50

40

30

20

10

0

10

50

40

30

20

10

0

10

X

FEET

X’

41.75

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER
30 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 17. Generalized hydrogeologic section and vertical head distribution for W-5 Augmented Cypress at Cypress Creek Well Field. CC-2 production well depth 700 feet, casing 118 feet

ELEVATION ABOVE NGVD 29

73

67.18

67.47

65.18

70.70

66.49

Cypr

65.43 65.81

ess Creek

67

W-04

W-5 AUGMENTED CYPRESS, CYPRESS CREEK WELL FIELD

May 22, 2004, during augmentation experiment of W-05

66.32

X

77

72

78

74

75

70

68

67.21

80

66.28

X’

66

67.01

65.5 65.5

65

64

70

66

68

0 200 400 600 FEET

80

70

60

50

40

30

20

80

70

60

50

40

30

20

ELEVATION ABOVE NGVD 29

69

62

EXPLANATION

63

66.49

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

INDICATES WELL WAS PROJECTED ONTO

SECTION

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE

EQUIPOTENTIAL LINE – Contour interval 0.5 and 1 foot.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

78

72 78

FEET FEET 82

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER

70.70

*

*

*

63.39
Wetland Hydrogeologic Setting 31

Figure 18. Generalized hydrogeologic section and vertical head distribution for W-19 Impaired Cypress at Cypress Creek Well Field.

W-19 IMPAIRED CYPRESS, CYPRESS CREEK WELL FIELD

May 18, 2004

56.32

56.29

64

63

ELEVATION ABOVE NGVD 29

300 FEET

23

22

21

60.84

60.26

64.69

EXPLANATION

63

65.06

X X’

61

62 58

57

59

56

55

54

58.60 28a

16

60

60.5

60.5

FEET FEET ELEVATION ABOVE NGVD 29

80

70

60

50

40

30

20

10

28

Cypress Creek Production well 10

Depth 700 feet, casing 84 feet

Cypress Creek Production well 9

Depth 710 feet, casing 162 feet

0 100 200

80

70

60

50

40

30

20

10

WETLAND SEDIMENT

SAND AND ORGANICS

SAND WITH INCREASING CLAY CONTENT

WITH DEPTH

SAND, CLAY, AND CARBONATE MUD

LIMESTONE

GRAIN-SIZE ANALYSIS

DEEP-WELL GEOLOGIC CONTROL DATA –

Unnumbered wells are property of Tampa

Bay Water

WELL WITH NUMBER AND HYDRAULIC HEAD VALUE –

Green line indicates geologic control data. Gray box is

screened interval for well. Red well number ( ) refers

to index number in table 3. Black number is head value

in feet above NGVD 29.

WATER TABLE – Dashed where inferred

EQUIPOTENTIAL LINE – Contour interval 0.5 and 1 foot.

Dashed where inferred

INFERRED GEOLOGIC CONTACT – Elevation of geologic

contact is representative of typical karst stratigraphy

rather than site specific data

GROUND-WATER FLOW DIRECTION

WETLAND STAGE

23

23

18

60.84

SURFICIAL

AQUIFER

INTERMEDIATE

CONFINING UNIT

UPPER FLORIDAN

AQUIFER

53.61
32 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

The W‐29 Impaired Marsh wetland showed evidence of 

organic sediment loss, probably as a consequence of prolonged 

dry conditions in the wetland. Recurring exposure to the air 

oxidizes the organic matter in wetland sediments, limiting or 

greatly slowing their accumulation rate (Mitsch and Gosselink, 

2000). Dry conditions prevailed at W‐29 Impaired Marsh 

during the 16 years prior to this study, exposing wetland 

sediments over the majority of the wetland area to oxidation. 

The maximum sediment depth measured in W‐29 Impaired 

Marsh (2.5 ft) was similar to the maximums recorded in the 

natural marshes, but was measured at an isolated deep point 

near the staff gage (fig. 14). The remaining point measurements indicate much thinner sediment depths in other areas. 

Furthermore, the median sediment thickness for all points 

measured in W‐29 Impaired Marsh was 0.4 ft—the smallest 

median value of any study wetland and about one-third of 

the median value for the wetland having the next thinnest 

sediments (HRSP Natural Marsh).

adherence of settling clay particles (Mitsch and Gosselink, 

2000). In contrast, the surface sediments taken from a historically drier area of W‐29 Impaired Marsh are much sandier 

(fig. 19B). The upper 1.6 ft (0.5 m) of this core has a much 

higher bulk density and less organic matter, and the percentages of clay and silt are markedly lower than those measured 

in the GS Natural Marsh. A core taken from a perpetually 

flooded area of W‐3 Augmented Marsh has dark organic-rich 

sediment at a depth of 6.6 ft (2 m). Because the sand content 

increases substantially below a depth of about 1.6 ft (0.5 m), 

the gamma bulk density values are only slightly lower than 

values in the underlying sand despite the black organic appearance of the sediment. For all four cores described here, the 

gamma bulk density values below about 1.6 ft (0.5 m) depth 

are between 1.6 and 2.0 g/cm3.

Vibracores from Duck Pond Augmented Marsh, 

W‐3 Augmented Marsh, and W‐29 Impaired Marsh show iron 

staining in the sandy zones that occurs below the shallow 

organic-rich sediments, suggesting available oxygen in the 

water leaking out of the wetland. Similar iron staining is 

absent in the core from GS Natural Marsh. Vibracores encountered the clay intermediate confining unit below several of the 

wetlands. The clay has a green-gray color and a dense plastic 

consistency that is characteristic of the Hawthorn Group 

(Sinclair, 1974; Scott, 1988). Because the vibracore device 

could not penetrate the dense clay layer, only the depth to the 

layer was established. A clay layer was encountered below the 

following wetlands: W‐3 Augmented Marsh, W‐5 Augmented 

Cypress (well 74, by drilling), HRSP Natural Marsh, and GS 

Natural Marsh. The presence of a clay layer at a shallow depth 

beneath at least some part of these wetlands may indicate 

better confinement than at wetlands where the clay layer is 

either deeper or entirely absent. The vibracore device did 

not encounter the clay layer beneath W‐29 Impaired Marsh, 

and vibracores were not collected at the four other cypress 

wetlands. Consequently, the depth of the confining unit 

directly below these wetlands could not be determined.

Radium-226

Collectively, 226Ra activity in shallow sediment samples 

and in water samples from both unaugmented and augmented 

wetlands was relatively low. In shallow sediment samples, 

average 226Ra activities were 0.16-0.56 dpm/g at unaugmented 

sites and 0.14-0.77 dpm/g at augmented sites. The augmentation water supplied to the two augmented marshes had

226Ra activities typical of Upper Floridan aquifer ground 

water in the area, ranging from 1.5 to 2.7 dpm/L. These

226Ra activities were similar to the 226Ra activity in ground 

water (0.82-3.26 dpm/L) from wells used to augment four 

nearby lakes (Brenner and others, 2006). As a result of the 

augmentation in the present study, 226Ra activity in the surface 

water of the two augmented marshes (1.1-2.1 dpm/L) was 

higher than in the two natural marshes (0.2-0.4 dpm/L).

Vibracores are used to describe the 

stratigraphy below marsh wetlands

Differences between the organic sediment profiles 

seen in vibracores taken from the three marshes probably 

also correlate to different durations of flooding and drying. 

Gamma bulk density provided a proxy for organic content 

in sediment cores. Increased organic content reduces the 

bulk density of soils compared to purely mineral or sandy 

soils. The bulk density of an organic soil is generally 0.2 to 

0.3 g/cm3, whereas values for unlithified sands generally 

range from 1.5 to 1.8 g/cm3 (Mitsch and Gosselink, 2000). 

Bulk density data from the sediment core from GS Natural 

Marsh indicated the maximum organic matter content is near 

the land surface (fig. 19A). The maximum clay content also is 

near land surface, and both clay and organic matter decrease 

sharply with depth. Clay and organic matter can accumulate in low-energy aquatic environments such as wetlands, 

where fragments of organic matter may act as a substrate for 
Wetland Hydrogeologic Setting 33

Figure 19. Vertical profiles of bulk gamma density and grain size in sediment cores from (A) GS Natural Marsh and (B) W-29 

Impaired Marsh.

DEPTH OF CORE, IN FEET

DEPTH OF CORE, IN FEET

Clay

Silt

Sand

Bulk Gamma Density

MASS PERCENT

0.2 0.4 0.6 0.8

0.0 0.5 1.0 1.5 2.0 2.5

DEPTH OF CORE, IN CENTIMETERS

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

0.0 0.5 1.0 1.5 2.0

0 1.0

-0.5

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

EXPLANATION

(A) GS Natural Marsh (B) W-29 Impaired Marsh

MASS PERCENT

0 0.2 0.4 0.6 0.8 1.0

DEPTH OF CORE, IN CENTIMETERS

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

GAMMA BULK DENSITY, IN

GRAMS PER CUBIC CENTIMETER

GAMMA BULK DENSITY, IN

GRAMS PER CUBIC CENTIMETER
34 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 20. Average, minimum, and maximum radium-226 activity 

from surface sediment samples collected in July 2002 and 

May 2004.

Figure 21. Vertical profiles of radium-226 activity in sediment 

cores taken from (A) W-3 Augmented Marsh, (B) W-29 Impaired 

Marsh #1, (C) W-29 Impaired Marsh #2, and (D) GS Natural Marsh.

Augmenting lakes with ground water has been shown 

to elevate the 226Ra activity in the lake sediment and 

lake water (Brenner and others, 1997; Smoak and Krest, 

2006). The results of the present study, however, indicate 

that the 226Ra activities in the surface sediment samples 

were similar in augmented and unaugmented wetlands 

(fig. 20). Radium-226 activities in sediment from natural 

and impaired wetlands ranged from about 0.1 to 1.2 dpm/g, 

and most activity levels were less than 0.3 dpm/g (fig. 20). 

In the augmented wetlands, 226Ra activities in the sediment 

ranged from 0.1 to 1.4 dpm/g. The augmented wetlands 

generally appeared to have higher 226Ra activity, although 

non-parametric statistical tests indicated no significant difference (p = 0.06). The wetland with the lowest average 226Ra 

activity in the surface sediment was S‐68 Natural Cypress 

(average 0.2 dpm/g), whereas the site with the highest 226Ra 

activity was the nearby S‐63 Augmented Cypress (average 

0.8 dpm/g). These sites are about 1 mi apart, and have the 

most similar geology of any of the augmented/natural wetland 

pairs. Based on these observations, the difference in sediment 

226Ra activity is probably related to augmentation practices.

Sediments cores taken from ground-water-augmented 

lakes indicate recent enrichment of 226Ra, and 226Ra levels 

in shallow sediment 0 to 4 cm (0-1.6 in.) deep were an order 

of magnitude greater than the deeper background values 

(Brenner and others, 2006). However, vertical profiles 

of 226Ra activity in sediment cores from one augmented 

marsh and two unaugmented marshes in the present study 

provided little or no evidence of this effect (J.M. Jaeger 

and L.M. Mertz, University of Florida, written commun., 

2003). Radium-226 activities in the surface sediments of 

the cores ranged from less than 1 to about 4 dpm/g (fig. 21). 

GS Natural Marsh had the highest 226Ra activity at the 

sediment surface (4.3 dpm/g), which was probably due to the 

presence of radiogenic clays of the Hawthorn Group near the 

surface (fig. 21D). The next highest 226Ra activity was in the 

core from W‐3 Augmented Marsh (3.9 dpm/g). Peak values 

in the core (fig. 21A) were substantially greater than the 

average of the surface sediment samples (fig. 20), although 

226Ra activity in surface samples resembled values deeper in 

the core. The cores from W‐29 Impaired Marsh showed low 

226Ra activities and little change with depth (fig. 21B-C).

The 226Ra activity measured in sediments of natural, 

impaired, and augmented wetlands in this study were similar 

in magnitude to those reported for other natural wetlands 

in central Florida (about 0.4 dpm/g) (Brenner and others, 

2004). The values were considerably lower, however, than 

those measured in many augmented lakes in central Florida 

(Brenner and others, 2000; 2004). Concern about the accumulation of 226Ra in lake sediments and biota (DeArmond 

and others, 2006; Smoak and Krest, 2006; Brenner and 

others, 2007) has resulted in closer scrutiny of the practice 

of augmenting lakes with water from the Upper Floridan 

aquifer. Results from this study indicate that 226Ra activity 

is low in sediments beneath the augmented wetlands, and is 

considerably lower than the U.S. Environmental Protection 

HRSP Natural

Marsh

GS Natural

Cypress

GS Natural

Marsh

S-63 Augmented

Cypress

W-5 Augmented

Cypress

Duck Pond

Augmented Marsh

W-3 Augmented

Marsh

W-19 Impaired

Cypress

W-29 Impaired

Marsh

S-68 Natural

Cypress

RADIUM-226 ACTIVITY (DPM/G)

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Maximum

Minimum

Average

(A)

(B)

(C)

(D)

Hawthorn Group

0 2 4 0 2 0 2

0 2 4 6 8 10

0

50

100

150

200

250

300

350

0

50

100

150

DEPTH BELOW TOP OF SEDIMENT CORE, IN CENTIMETERS

SEDIMENT RADIUM-226 ACTIVITY, IN

DISINTEGRATIONS PER MINUTE

PER GRAM (DPM/G)
Wetland Hydrogeologic Setting 35

Agency action level of 11 dpm/g (5 pCi/g) above background levels (U.S. Environmental Protection Agency, 

1999; Hazardous Substance and Waste Management 

Research, Inc., 2000).

There is concern in central Florida that 226Ra in water 

and sediment may enter the food chain and bioaccumulate in 

aquatic organisms (Brenner and others, 2007). Mussels in lakes 

receiving ground-water augmentation have been shown to 

bioaccumulate 226Ra at rates many orders of magnitude greater 

than those for lake sediments (Brenner and others, 2007). 

Over a 2-3 month study period, these mussels (primarily the 

unionid mussel Elliptio buckleyi) accumulated 226Ra relatively 

rapidly in their soft tissues, and larger mussels showed greater 

226Ra activity than smaller mussels. These large, long-lived 

mussels were not found in the augmented wetlands, probably 

because the wetlands are not as hydrologically stable as lakes, 

and may dry out completely during some years. Augmented 

wetlands in the present study do harbor filter-feeding bivalves 

in the Family Sphaeriidae, but these small mussels have much 

shorter life spans, typically 1 year or less, and they do not 

build up large amounts of soft tissue because they are adapted 

to devote resources toward rapid and early reproduction 

rather than attaining a large body size. Therefore, although no 

tissue samples were analyzed from Sphaeriidae in this study, 

it is expected that bioaccumulation of 226Ra activity in these 

mussels would be substantially less than that reported for the 

large mussels living in augmented lakes. 

Several factors could contribute to the lower 226Ra activity 

observed in augmented wetlands compared to augmented lakes. 

Factors generally affecting the amount of 226Ra adsorbed to 

recent sediments include: (1) 226Ra activity in the augmentation 

water, (2) water residence time in the wetland, (3) the proportional contribution of ground water to the water budget of the 

wetland (Brenner and others, 2006), (4) the organic matter 

content of the sediment (DeArmond and others, 2006), and 

(5) cycling between wet and dry wetland soil conditions. Some 

factors are comparable in both wetlands and lakes, whereas 

others favor 226Ra accumulation in wetlands, suggesting other 

considerations (Mark Brenner, University of Florida, written 

commun., 2007). For one, the apparent levels of 226Ra activity 

per gram of dry weight could be “diluted” in the sediment of 

augmented wetlands by greater primary productivity and faster 

sediment deposition rates in augmented wetlands compared 

to augmented lakes. In addition, lake sediment may contain 

smaller particles (including algae), which are preferential 

binding sites for 226Ra. Wetlands may tend to have larger 

particle sizes, contributed from coarse plant material, with 

less surface area for binding. It is also possible the 226Ra 

could remain in solution because of the shorter residence time 

of augmentation water in wetlands compared to lakes, and 

could be washing out of the wetlands either by overflow or by 

downward leakage.

Cycling between wet and dry conditions also could lower 

the 226Ra activity in the surficial sediments of augmented 

wetlands compared to those of augmented lakes 226Ra is only 

slightly particle reactive and is susceptible to desorption from 

inorganic particles under changing Eh and pH conditions 

(Frissel and Koster, 1990). Cycling between wet and dry 

wetland soil conditions alters the Eh/pH conditions, which 

controls the distribution of 226Ra between the particulate and 

dissolved phases. This inherent cycling could limit the 226Ra 

accumulation in augmented wetlands that periodically dry out.

Evidence of Karst Features in Wetland Basins

The circular shape of most of the wetlands in this study 

is similar to the general shape of many lakes in the study area, 

which is consistent with sinkhole formation (Sinclair and 

others, 1985; Metz and Sacks, 2002). Depressional features in 

the bottom of the wetlands provide further evidence of karstification in the study area. The small circular depressions along 

the wetland bottom range in depth from 1.07 ft at GS Natural 

Marsh to 8.13 ft below the wetland perimeter at Duck Pond 

Augmented Marsh (app. 3). The deepest areas of these depressions may overlie sand columns or “piping features” created 

by localized subsidence beneath the wetlands. Duck Pond 

Augmented Marsh had the deepest depression in the wetland 

bottom, and this may be a factor affecting its leakage rate. 

Analysis of GPR data at three wetlands (W‐29 Impaired 

Marsh, Duck Pond Augmented Marsh, and S‐63 Augmented 

Cypress) revealed well-defined reflectors in areas of the 

basins where the lateral bedding within the surficial deposits 

was intact. In other areas of the record, discontinuous reflectors and dipping reflectors indicate that the surficial deposits 

have been disrupted by karst subsidence (fig. 22). The most 

notable geologic features beneath W‐29 Impaired Marsh and 

Duck Pond Augmented Marsh are the steeply dipping reflectors that indicate subsidence in the underlying layers and 

may signify sinkhole activity (fig. 22). For W‐29 Impaired 

Marsh, the bathymetry indicates the wetland has two distinct 

basins (Haag and others, 2005), which suggests that multiple 

sinkholes form the wetland. The GPR data indicate that the 

southern basin of W‐29 Impaired Marsh has a more intact clay 

layer than the northern basin, which shows a more intact sandy 

layer and thus a higher permeability zone (fig. 22A). The GPR 

data for Duck Pond Augmented Marsh show a reflection-free 

or attenuated zone near the center, which is surrounded by 

steeply dipping reflectors on both sides of the wetland bottom 

(fig. 22B). These steeply dipping reflectors indicate subsidence 

or sinkhole activity. The reflection-free zone in the middle is 

probably interference caused by gases in the thick, organic 

sediments (fig. 22B).

Smaller infilled or buried sinkholes not evident as 

depressions in the land surface were found to be abundant in 

the GPR record, along with possible piping features where 

reflective layers in the surficial deposits are disrupted or are 

deformed downward by karst subsidence (fig. 22C-D). In these 

areas, the surficial aquifer has the potential to leak faster to the 

underlying Upper Floridan aquifer, creating a depression in the 

water table despite a level or inclining land surface (Lee, 1996).
36 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

02468

10121416182022

0

ACE DEPTH, IN FEET BELOW LAND SURF

Y (B) DUCK POND AUGMENTED MARSH, CROSS BAR WELL FIELD

VEL TIME, IN MILLISECONDS TRA AY TWO-W

DATA INTERFERENCE

POSSIBLE SUBSIDENCE

FEATURE; DIPPING BED

WETLAND

BOTTOM

WETLAND WATER SURFACE

DISTANCE, IN FEET

1

10

POSSIBLE PIPING

FEATURE

WATER-TABLE

CLAY LAYER

LAND SURFACE

WELL CONTROL POINT

AND WELL NUMBER

(D) DUCK POND AUGMENTED MARSH BASIN, CROSS BAR WELL FIELD

020406080100120140160180200220

Y’

100 200 300 380

02468

10121416182022

0

ACE DEPTH, IN FEET BELOW LAND SURF

Z

DISTANCE, IN FEET

020406080100120140160180200220

Z’

100 190

VEL TIME, IN MILLISECONDS TRA AY TWO-W

(A) W-29 IMPAIRED MARSH, CYPRESS CREEK WELL FIELD

(C) S-63 AUGMENTED CYPRESS BASIN, STARKEY WELL FIELD

02468

10121416182022

0

ACE DEPTH, IN FEET BELOW LAND SURF

Z

VEL TIME, IN MILLISECONDS TRA AY TWO-W

DISTANCE, IN FEET

020406080100120140160180200220

Z’

100 200 300 330

02468

10121416182022

ACE DEPTH, IN FEET BELOW LAND SURF

Z

DISTANCE, IN FEET

020406080100120140160180200220

Z’

VEL TIME, IN MILLISECONDS TRA AY TWO-W

43 38 40

44

WELL CONTROL POINT AND WELL NUMBER

CLAY

LAYER

WATER

SURFACE

WETLAND

BOTTOM

DISRUPTION

OF THE

SURFICIAL

DEPOSITS

DISRUPTION

OF THE

SURFICIAL

DEPOSITS

110 105 116

DISRUPTIONS

IN THE SURFICIAL

DEPOSITS

CLAY

LAYER

CLAY

LAYER

WATER-TABLE

LAND SURFACE WELL CONTROL POINT

AND WELL NUMBER

180 0 100 190 180

WELL CONTROL POINT AND WELL NUMBER

Figure 22. Ground-penetrating radar profiles with interpreted geologic features below (A) W-29 Impaired Marsh, (B) Duck Pond Augmented Marsh, (C) S-63 Augmented Cypress basin, and (D) Duck Pond Augmented Marsh basin. (Locations of ground-penetrating radar transects are shown in figures 9 and 10.)
Wetland Hydrogeologic Setting 37

Ground-Water Flow Patterns in Wetland Basins

Mapping ground-water flow patterns around wetlands 

over time reveals the changeable interactions between wetlands 

and their underlying aquifers, as demonstrated by studies of 

the prairie potholes of North Dakota (Winter and Rosenberry, 

1995). In the present study, ground-water flow patterns around 

two natural wetlands are characterized and compared to the 

ground-water flow patterns around four augmented wetlands 

and two impaired wetlands. Commonly observed flow patterns 

are presented from two perspectives—by contouring the watertable elevations around the wetlands, and by contouring the 

vertical distribution of hydraulic head between the wetland 

stage, water table, and potentiometric level in the Upper 

Floridan aquifer. Time-series graphs of wetland stage and 

selected ground-water levels in each basin are used to show 

how the relation between wetland water levels and groundwater levels fluctuate seasonally, and how typical ground-water 

flow patterns could be altered during seasonal extremes.

Wetlands, like lakes, can experience either recharge, 

discharge, or flow through with respect to the surrounding 

ground water (Winter and others, 1998). For instance, 

several marshes in the ridge areas of central Florida were 

found to be in flow-through settings (Knowles and others, 

2005). The wetlands in this study, whether they were natural, 

impaired, or augmented, routinely recharged the underlying 

aquifer. The water levels in wetlands typically were higher than 

the water-table altitude in the surficial aquifer, causing water 

to leak into and recharge the aquifer (fig. 23A). Only one of 

the eight wetlands (W‐19 Impaired Cypress) in which groundwater flow paths were established experienced persistent flowthrough conditions (fig. 23B). During the wettest conditions of 

the study, however, several marsh and cypress wetlands briefly 

switched from a recharge condition to a flow-through condition. When this occurred, the areas of ground-water flow into 

the wetland often mirrored areas of surface-water inflow.

Augmented wetlands experienced the most extreme 

recharge conditions because their stages were highest above 

the background ground-water levels. The two augmented 

marshes were perched on top of steep, conical, ground-water 

mounds that radiated out from the wetland perimeter as much 

as 500 ft (fig. 24A-B). During May 2002, the ground-water 

mound below Duck Pond Augmented Marsh was about 15 ft 

high. The water-table contours encircling the wetland dropped 

from the wetland water level to an elevation slightly above 

the potentiometric surface of the Upper Floridan aquifer 

(fig. 12), indicating that wetland leakage was recharging the 

surficial aquifer below the wetland. The intermediate confining 

unit slowed the vertical flow between the wetland and Upper 

Floridan aquifer, causing the base of the recharge mound to 

spread outward over the top of the confining clays until it 

blanketed an area large enough to transmit flow at the augmentation rate. The size of the mound stayed relatively consistent 

year-round because the wetland water level and Upper Floridan 

aquifer potentiometric surface tracked each other seasonally 

(fig. 25A). The recharge mound covered about 40 acres during 

(A)

(B)

EXPLANATION

WATER TABLE

GROUND-WATER FLOW PATH

Figure 23. Conceptualized interactions of wetlands with 

(A) ground-water recharge and (B) ground-water flow through. 

(Modified from Winter and others, 1998.)
38 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 24. Ground-water flow patterns around the marsh wetlands during representative dry-season conditions. Wetter conditions 

are shown at W-3 Augmented Marsh, because monitoring wells were dry during the dry season.

82°28’10"W 82°28'00"W

28°22'00"N

82°23'20"W 82°23'10"W

28°18’00"N

82°22'40"W

28°18'15"N

82°13'50"W

28°08’45"N

82°22'30"W

82°13'40"W

150 METERS

0 250 500 FEET

0 75

0 1,000 FEET

0 300 METERS

150 METERS

0 250 500 FEET

0 75

0 500 FEET

0 150 METERS

(A) Duck Pond Augmented Marsh, May 30, 2002 (B) W-3 Augmented Marsh, September 5, 2002

61.13

EXPLANATION

(C) HRSP Natural Marsh, May 30, 2002 (D) W-29 Impaired Marsh, May 24, 2001

FLOODED AREA–Blue number is

wetland stage

WETLAND

STUDY WETLAND BOUNDARY

WATER-TABLE CONTOUR–in feet

above NGVD of 1929. Contour

interval 0.5 and 1 feet. Dashed

where inferred

GROUND-WATER FLOW DIRECTION

OBSERVATION WELLS

SURFACE-WATER GAGE

- - Number is

elevation of water level in feet above

NGVD 29

60

62.42

58.98 60.18

64.37

66.44

63.64

61.49

63.56

60.56

56.97

65.21

54.82

68.12

54

56

58

62

60

64

68

67

69

64

62

60 59

61

63

66

68

70

58.63

70.34

65.18

61.33 65.87

55

57

59

61

63

40

38

39

37

38.6

38.9

38.82

38.96

40.22

38.24

39.18

40.33

39.06

36.17

39.13

41

42

43

44

62

61.5

61

62.00

61.5

62.10 61.72

61.13

61.59

61.17

60.98

61.34

61.79

61.62

60.95

61.23

61.79

61.61

44.61

44.61

Hillsborough River

65

66.84

66
Wetland Hydrogeologic Setting 39

Figure 25. Wetland stage and ground-water levels in selected surficial and Upper Floridan aquifer wells in the marsh 

wetland basins.

88

100

93

Well index no.

Well index no.

Well index no.

HRSP Natural Marsh

GS Natural Marsh

Well index no. 86

Well index no. 57

W-3 Augmented Marsh

Well index no. 2

Well index no. 12

Well index no. 6

Duck Pond Augmented Marsh

Well index no. 10

Well index no. 101

W-29 Impaired Marsh

Well index no. 47

Well index no. 38

Well index no. 52

Well index no. 51

WATER LEVEL, IN FEET ABOVE NGVD 29

(E) W-29 IMPAIRED MARSH BASIN

75

70

65

60

55

50

45

40

35

30

WATER LEVEL, IN FEET ABOVE NGVD 29

2001

55

50

45

40

35

30

25

75

70

65

60

55

50

45

WATER LEVEL, IN FEET ABOVE NGVD 29

WATER LEVEL, IN FEET ABOVE NGVD 29

M

2000 2001 2002

J J A S O N D M J F MA J J A S O N D

105

100

95

90

85

80

75

75

70

65

60

55

50

45

40

WATER LEVEL, IN FEET ABOVE NGVD 29

(A) DUCK POND AUGMENTED MARSH BASIN (B) W-3 AUGMENTED MARSH BASIN

(C) HRSP NATURAL MARSH BASIN (D) GS NATURAL MARSH BASIN

2000 2002 2003 2004

F A J A O D J F A A O D J F A A O D J F A A O D J F A

2000 2001 2002 2003 2004

F A J A O D J F A A O D J F A A O D J F A A O D J F A

A J F M AM J J A S O N

M

2000 2001 2002

M A J J A S O N D M J F MA J J A S O N D J F M AM J J A S O N

2000 2001 2002

A J J A S O N D M J F MA J J A S O N D J F M AM J J A S O N

Well index no. 85

Well index no. 55

EXPLANATION

WATER LEVELS FOR:

Marsh or cypress wetland

Surficial aquifer

Upper Floridan aquifer

86 WELL INDEX NUMBER – Refers to

table 3 for well description

and figure 9 for locations
40 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

May 2002, including the 5.2-acre wetland area. The roughly 

symmetrical mound had a steeper slope in the direction of 

the nearest production well, located southeast of the marsh 

(figs. 24A and 7). Similar water-table mounds have been 

documented below augmented lakes in the northern Tampa 

Bay region, although their sizes were considerably greater 

(Metz and Sacks, 2002).

At W‐3 Augmented Marsh, the water-table mound 

had a total height of about 12 to 13 ft during September 

2002 (fig. 24B), with the steepest slope in the direction of the 

ground-water production well located south of the wetland. 

The surficial aquifer is probably dewatered near the production 

well, causing the level of the water table to approach the head 

of the Upper Floridan aquifer (fig. 13). In September 2002, the 

mound at W‐3 Augmented Marsh was about 52 acres in size, 

including the 7.4-acre wetland area, but unlike Duck Pond 

Augmented Marsh, the shape and size of the mound changed 

substantially over time. The Upper Floridan aquifer levels at 

W‐3 Augmented Marsh changed by more than 15 ft during the 

study period. There were corresponding changes in the water 

table, but little change in wetland stage (fig. 25B). As a result, 

when the Upper Floridan aquifer level was lowest (in spring 

2001), the water table fell below the monitoring well depths 

and could not be mapped. Under these conditions, a steeper 

mound with a smaller footprint probably existed under the 

wetland, and more leakage probably flowed straight downward 

instead of radially outward from the wetland.

A compact and steep recharge mound also was observed 

below HRSP Natural Marsh in May 2002 (fig. 24C). The 5-ft 

mound created only a slightly larger footprint than the wetland 

flooded area. The base of the mound did not expand outward 

as it approached the water level in the Upper Floridan aquifer, 

probably due to the lack of confining clays overlying the 

limestone of the Upper Floridan aquifer in the basin (fig. 11). 

During the dry seasons, such as in late May and early June 

of 2001 and 2002, the potentiometric surface of the Upper 

Floridan aquifer, which also constitutes the water table in this 

basin, dropped well below the wetland stage, causing wetland 

water levels to decline (fig. 25C). In contrast, during the late 

summer and early fall of 2001 and 2002, the Upper Floridan 

aquifer head approached land surface, rising above the wetland 

bottom elevation in 2001. The HRSP Natural Marsh became a 

flow-through wetland during the wet seasons of 2001 and 2002. 

Ground-water levels toward the southeast rose higher than the 

wetland, whereas those toward the northwest were lower (wells 

91 and 95), creating a flow-through setting for the wetland and 

effectively making the basin part of the regional ground-water 

flow pattern toward the Hillsborough River (Wolansky and 

Thompson, 1987) (fig. 9C).

A recharge mound also was present in the water 

table beneath W‐29 Impaired Marsh, even though the wetland 

was dry and the peak of the recharge mound was several feet 

below the wetland bottom (fig. 24D). Although rainfall and 

runoff were insufficient to flood W‐29 Impaired Marsh for 

more than several months during the first 2 years of the study, 

recharge still created a water table mound beneath the wetland 

(fig. 14). Water levels in the Upper Floridan aquifer were much 

lower than those in the surficial aquifer (fig. 25E); however, the 

surficial aquifer was not dewatered during the lowest waterlevel conditions, suggesting restricted flow across the intermediate confining unit. Persistent flooding in W‐29 Impaired 

Marsh occurred only after mid-2002, after water levels in the 

Upper Floridan and surficial aquifers had risen substantially.

The two augmented cypress wetlands had smaller, lower 

recharge mounds compared to the two augmented marshes 

because the regional water table had risen closer to land surface 

during the cypress study period. In May–June 2004, stage in 

the augmented cypress wetlands S‐63 and W‐5 was only 3 to 

5 ft higher than the background water table, and the recharge 

mounds radiated outward about 200 ft from the water’s edge 

(fig. 26A-B). The water-table mound was even lower around 

S‐68 Natural Cypress (fig. 26D).

The pattern of ground-water flow around W‐19 Impaired 

Cypress reflected the geologic setting of the wetland basin and 

the effect of ground-water pumping from a nearby production 

well (fig. 26C). Most of the time, ground-water inflow occurred 

on the eastern side of the wetland through an area where the 

surficial deposits contain more clay and the Upper Floridan 

aquifer is better confined compared to the western side. This 

observation is supported by lithologic and grain size analyses 

of two geologic cores (29 and 17 ft deep) on the eastern side of 

W‐19 Impaired Cypress, and two index wells (22 and 23) on 

the western side (table 3). Wetland water leaked outward from 

the western side where the surficial deposits are sandier and 

the clay confining unit appears to be discontinuous (fig. 26D). 

Pumping from a production well lowered surficial aquifer 

and Upper Floridan aquifer heads on the western side of the 

wetland, and also induced outflow from the wetland (fig. 18). 

During May 2004, a seasonal minimum in water-table elevation 

briefly caused potential for outflow along the eastern perimeter 

of the wetland, putting the entire wetland in a ground-water 

recharge setting.

Although the most commonly observed ground-water 

interaction displayed by the wetlands was one of ground-water 

recharge, all four natural wetlands had the potential to receive 

ground-water inflow from the surficial aquifer during brief 

periods. The water-table elevation in areas adjacent to the 

natural marshes rose above the wetland stage briefly during 

the summers of 2001 and 2002 (fig. 25C-D), and at the natural 

cypress wetlands during the summer of 2003 (fig. 27C-D). 

The pattern suggests that the natural wetlands may receive 

some ground-water inflow during high rainfall periods. 

Ground-water inflow conditions never occurred at the four 

augmented wetlands, even during the wettest periods of the 

study, but did occur at W‐29 Impaired Marsh in February 

2003 and April 2004 (fig. 25E). Water tables were high in the 

wetland basins when the Upper Floridan aquifer head also was 

high and the difference between the wetland stage and Upper 

Floridan aquifer head was minimal (figs. 25 and 27). The head 

differences between the wetlands and the Upper Floridan 

aquifer differed in the three groups of wetlands over time, and 

substantially affected wetland leakage losses.
Wetland Hydrogeologic Setting 41

Figure 26. Ground-water flow patterns around cypress wetlands during representative dry-season conditions.

61.13

EXPLANATION

FLOODED AREA–Blue number is

wetland stage

WETLAND

STUDY WETLAND BOUNDARY

WATER-TABLE CONTOUR–in feet

above NGVD of 1929. Contour

interval 0.5 and 1 feet. Dashed

where inferred

GROUND-WATER FLOW DIRECTION

OBSERVATION WELLS

SURFACE-WATER GAGE

- - Number is

altitude of water level in feet above

NGVD of 1929

60

44.62

(B) S-63 Augmented Cypress on Starkey Well Field

June 23, 2004

300 METERS

0 500 1,000 FEET

0 150

82°23'10"W 82°22'50"W

28°18'10"N 28°18'30"N

(A) W-5 Augmented Cypress on Cypress Creek Well Field

May 22, 2004

67.21

67.18

67.47

66.28

65.43

65.18

65.11

68.15

70

69

68

67

70.70

66

66

66.11

67

66.31

65.93

(C) W-19 Impaired Cypress on Cypress Creek Well Field

May, 18, 2004

82°34'40"W 82°34'20"W

28°14'15"N

(D) S-68 Natural Cypress on

May 26, 2004

Starkey Well Field

42.62

39.02

40.94

41.36

41.85

42.17

Dry

42

39.59 40.10

40.67

39.71

39.96

36.69

37.05 36.85

82°35'00"W

28°14'55"N

0 500 FEET

35.72

39.59

41.78

41.03

82°23'50"W

28°16'45"N

56.4

60.84

55.88

56.29

60.52

64.69

56.99

56.32

57.44

60.26

58.60

65.81

0 150 METERS

39

37

38

36

40

41

63

64

61 62

60

57

58 59

56

58.02

61.17

39.83

40.80

42.06

41.30

42.18

41.35

300 METERS

0 500 1,000 FEET

0 150

0 500 FEET

0 150 METERS

Cypress Creek

Cross Cypress

Branch

Anclote River

40

41

39
42 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 27. Wetland stage and ground-water levels in selected surficial and Upper Floridan aquifer wells in the cypress 

wetland basins.

WATER LEVEL, IN FEET ABOVE NGVD 29

2002 2003 2004

(E) W-19 IMPAIRED CYPRESS BASIN

J J A S O N D M J F M A J J A S O N D M J F M A J J A

75

70

65

60

55

50

45

WATER LEVEL, IN FEET ABOVE NGVD 29

2002 2003 2004

J J A S O N D M J F M A J J A S O N D M J F M A J J A

55

50

45

40

35

30

25

2002 2003 2004

J J A S O N D M J F M A J J A S O N D M J F M A J J A

85

80

75

70

65

60

55

WATER LEVEL, IN FEET ABOVE NGVD 29

WATER LEVEL, IN FEET ABOVE NGVD 29

2002 2003 2004

J J A S O N D M J F M A J J A S O N D M J F M A J J A

115

110

105

100

95

90

85

2002 2003 2004

J J A S O N D M J F M A J J A S O N D M J F M A J J A

55

50

45

40

35

30

25

WATER LEVEL, IN FEET ABOVE NGVD 29

GS Natural Cypress

Well index no. 83

W-19 Impaired Cypress

Well index no. 23

Well index no. 17

S-63 Augmented Cypress

Well index no. 122

Well index no. 109

Well index no. 20

Duration of

augmentation

experiment

W-5 Augmented Cypress

Well index

no. 60

Well index no. 74

S-68 Natural Cypress

Well index no. 137

Well index no. 132

(A) W-5 AUGMENTED CYPRESS BASIN (B) S-63 AUGMENTED CYPRESS BASIN

(C) S-68 NATURAL CYPRESS BASIN (D) GS NATURAL CYPRESS BASIN

Well index no.135

Well index no. 125

Well index no. 82

Well index no. 104

Well index no. 84

Well index no. 28

EXPLANATION

WATER LEVELS FOR:

Marsh or cypress wetland

Surficial aquifer

Intermediate confining unit

Upper Floridan aquifer

17 WELL INDEX NUMBER – Refers to

table 3 for well description

and figure 10 for locations
Wetland Hydrogeologic Setting 43

Overview of Wetland Hydrogeologic Settings

Isolated wetlands are one of the dominant landforms in 

the low-lying areas north of Tampa Bay. The geologic setting 

of these wetlands, and the depth and direction of ground 

water flowing below their basins, directly affect their rate of 

ground-water exchange and indirectly affect the runoff they 

receive from the surrounding upland areas. The wetlands in this 

study showed no distinctive differences in basin stratigraphy 

that could be linked to the wetland type (marsh or cypress) or to 

the hydrologic conditions of the three wetland groups (natural, 

impaired, or augmented). All investigated wetlands shared 

a common stratigraphic sequence, whereby an organic-rich 

wetland sediment layer was underlain by a sequence of sand and 

silt, and then by a sandy clay layer. However, differences in the 

thickness and composition of these stratigraphic layers distinguished one wetland from another. The thicker sediment encountered in the two augmented marshes is probably a consequence 

of augmentation. The W‐29 Impaired Marsh showed evidence of 

organic sediment loss, probably as a consequence of prolonged 

dry conditions in the wetland. 

Analysis of GPR data at three wetlands (W‐29 Impaired 

Marsh, Duck Pond Augmented Marsh, and S‐63 Augmented 

Cypress) indicated well-defined reflectors in areas of the 

basins where the lateral bedding within the surficial deposits 

was intact. In other areas of the record, discontinuous 

reflectors and dipping reflectors suggest that the surficial 

deposits have been disrupted by karst subsidence. The most 

notable geologic features beneath W‐29 Impaired Marsh and 

Duck Pond Augmented Marsh are the steeply/dipping reflectors that indicate subsidence in the underlying layers and 

signify sinkhole activity. Smaller infilled or buried sinkholes 

not evident as depressions in the land surface were found to 

be abundant in the GPR record, along with possible piping 

features where reflective layers in the surficial deposits are 

disrupted or are deformed downward due to karst subsidence. 

In these areas, the surficial aquifer has the potential to leak 

faster to the underlying Upper Floridan aquifer, causing a low 

in the water table despite a level or rising land surface.

The wetlands in this study, whether they were natural, 

impaired, or augmented, routinely recharged the underlying aquifer. The water levels in wetlands typically were 

higher than the water-table elevation in the surficial aquifer, 

causing water to leak into and recharge the aquifer. None 

of the wetlands were observed in a discharge setting, where 

wetland water levels are lower than the encircling water table. 

Only one of the eight wetlands where ground-water flow paths 

were established was persistently in a flow-through setting. 

However, during the wettest conditions of the study, several 

marsh and cypress wetlands briefly alternated from a recharge 

condition to a flow-through condition. When this occurred, 

the areas of ground-water flow into the wetland often mirrored 

areas of surface-water inflow.

Recharge mounds were observed below all the wetlands. 

The recharge mounds were generally compact and steep at the 

natural wetlands, often with a footprint only slightly larger 

than the wetland flooded area. A recharge mound was even 

present beneath W‐29 Impaired Marsh, despite the fact that the 

wetland was usually dry and rainfall was insufficient to flood 

the wetland for more than a few months. Augmented wetlands 

had the most extreme recharge settings. The two augmented 

marshes were perched on top of steep, conical, ground-water 

mounds that radiated out from the wetland perimeter as much 

as 500 ft. During May 2002, the ground-water mound below 

Duck Pond Augmented Marsh was about 15 ft high and 

covered about 40 acres, including the 5-acre wetland area. 

The concentric water-table contours encircling the wetland 

dropped from the wetland water level to an elevation slightly 

above the potentiometric surface of the Upper Florida aquifer, 

indicating that wetland leakage had recharged the surficial 

aquifer below the wetland. The two augmented cypress 

wetlands had smaller, lower recharge mounds compared to the 

two augmented marshes because the regional water table was 

closer to the land surface during the latter part of the project 

when the cypress wetlands were studied.

Thick organic sediment in an 

augmented wetland

Although augmenting lakes with ground water has been 

shown to elevate the 226Ra activity in the lake water and sediment, results of the present study indicate that the 226Ra activities 

in the surface sediment samples were similar in augmented and 

unaugmented wetlands. The 226Ra activities measured in sediments of natural, impaired, and augmented wetlands in this study 

were similar in magnitude to those reported for other natural 

wetlands in central Florida, and they were considerably lower 

than activities measured in many augmented lakes in central 

Florida. Factors that could contribute to the lower 226Ra activity 

observed in augmented wetlands compared to augmented lakes 

include the 226Ra activity in the augmentation water, short water 

residence time in the wetland, proportional contribution of the 

augmentation water to the water budget of the wetland, organic 

matter content of the wetland sediment, and cycling between wet 

and dry wetland soil conditions.
44 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
The water-budget approach was used in this study primarily to 

quantify ground-water interactions with the wetlands. The approach was 

adapted from studies designed to quantify the interaction of ground water 

with lakes in mantled karst terrain (Sacks and others, 1992; Lee, 1996; 

Lee and Swancar, 1997; Swancar and Lee, 2003). The lake water-budget 

studies typically shared four traits: (1) terms in the water-budget equation 

were defined at the weekly or monthly timescale over a year or more; 

(2) lake evaporation was quantified independently; (3) net ground-water 

exchange was derived as a residual term to the water-budget equation; 

and (4) detailed hydrogeologic descriptions of the lake basin, including 

aquifer geochemistry, were used to help interpret the timing and magnitude of ground-water exchanges. The water-budget approach used for the 

wetlands in this study is analogous, except that evaporation was estimated 

instead of measured, and wetland water-budget components were analyzed 

at the daily timescale instead of being summed over weekly or monthly 

time periods. 

The water-budget analysis quantifies all of the water exchanges with 

a wetland volumetrically, and compares these exchanges to the measured 

change in the wetland water volume. The wetland volume change is 

computed using daily stage data and wetland bathymetric data. Describing 

all flows volumetrically was required to (1) compare wetland groups in 

this study, because augmentation inflows were volumetric, not areal flux 

rates; and (2) quantify runoff into wetlands. Bathymetric data for wetlands 

often are not available, and stage changes alone are used to evaluate 

the water budget of wetlands. This approach is valid only if all water 

exchanges of interest are areal fluxes (for example, rainfall, evaporation, 

or leakage), or if the size of the flooded area remains constant despite 

changes in stage, as can occur in artificial retention ponds (for example, 

Choi and Harvey, 2000). Stage changes alone were used to describe the 

earliest water budgets created for isolated wetlands in the United States, 

Wetland Water Budgets
46 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

such as the prairie pothole wetland in North Dakota during the 

1960s (Shjeflo, 1968; Eisenlohr, 1972), and the earliest water 

budgets created for isolated wetlands in the mantled karst 

terrain in Florida (Heimburg, 1976; 1984).

Methods of Computation

For a wetland not connected by streams to other 

surface-water bodies, the change in the water volume over an 

interval of time equals the difference between the inflow and 

outflow volumes:

∆S = P – ET + A + R + Gi – L [L3], (1)

where: 

∆S is change in wetland volume, 

P is precipitation, 

ET is evapotranspiration, 

A is augmentation water added to the wetland, 

R is runoff into the wetland, 

Gi is ground-water inflow, and

L is leakage—the wetland water that leaks out to the 

underlying ground water. 

All terms in equation 1 are expressed in units of volume and 

are quantified daily.

Four of the terms in equation 1 (∆S, P, ET, A) were 

directly quantified using the methods described in this section. 

These four terms were used to compute a residual term equal 

to the difference between the two dominant unknown terms, 

namely, R and L:

Residual Term = R - L ± eResidual Term

= ∆S - P + ET - A. (2)

Ground-water inflow, Gi, is not included in the residual term 

because it probably makes a negligible contribution to the 

wetlands during their water-budget periods. The water quality 

of the wetlands and ground-water flow patterns around 

them support this assumption at all of the wetlands except 

W‐19 Impaired Cypress, where some ground-water inflow 

is interpreted to occur, although at a daily rate that is small 

compared to other budget terms. The residual term has an 

associated error or uncertainty (eResidual Term ) that is derived 

from the various measurement errors present in the directly 

quantified terms on the right hand side of equation 2. 

The residual term computed from the water-budget 

equation can be either positive or negative, depending 

primarily upon whether the runoff (R) or the leakage 

(L) predominates. For unaugmented wetlands in this study, 

the majority of the water-budget days with a negative residual 

value had no rainfall to generate runoff (table 4). Negative 

residual values on these days, therefore, were interpreted to 

represent gross leakage. Similarly, because most days with 

a positive residual term were days with rainfall, the positive 

residual values were equated with runoff. Wetland leakage does 

occur on days when runoff generates a positive residual value 

and, therefore, the runoff estimate is actually the difference 

between runoff and leakage, or a net runoff estimate, meaning 

the positive residuals underestimate the runoff. For this reason, 

the large daily leakage rates of augmented wetlands can mask 

smaller runoff events by generating a negative residual term, 

even on days when runoff may have occurred. Positive residual 

values may be generated for augmented wetlands, although 

only for days when large rainfall events create enough runoff to 

exceed leakage.

A positive or negative residual value also could be an 

artifact of residual error that is greater than the L and R terms. 

Although the actual error is unknown, the maximum probable 

uncertainty in the residual term can be estimated by adding 

together (as a root mean square) the errors ascribed to each of 

the directly quantified terms of the water-budget components 

in equation 2 (Ramette, 1981; Winter, 1981; Lee and Swancar, 

1997). This cumulative error can itself be positive or negative, functionally adding to or subtracting from the runoff and 

leakage. When the residual error is large, it masks the hydrologic information contained in the residual term, making the 

term physically meaningless for interpreting runoff or leakage. 

In this analysis, the uncertainty in the residual term 

is acknowledged but is not estimated using the maximum 

probable error approach. Error estimates were not available for 

the daily values of the water-budget components, and the use 

of conservatively large error estimates can discourage further 

examination of the residual values and their potentially valuable physical information (Lee and Swancar, 1997). Instead, 

the size of error and, conversely, the physical importance of 

the residual term were checked by correlating the population 

of daily residual values to external environmental variables. 

The positive water-budget residuals considered to reflect runoff 

were examined in relation to rainfall. The negative waterbudget residuals considered to reflect leakage were examined 

for correlation to head values in the underlying Upper Floridan 

aquifer. If the residual terms were significantly correlated to 

an independently measured physical variable, then their values 

were assumed to retain physical meaning despite residual 

errors, and the errors were concluded to be, on average, 

substantially smaller than the residual values. 

The daily volume of leakage from each wetland was 

expressed as a linear flux rate in inches per day by dividing 

it by the average size of the flooded area in the wetland on 

that day. In this way, the linear leakage rates from each of 

the wetlands (or at an individual wetland over time) could be 

compared without regard to the size of the respective flooded 

areas. Collectively, the daily linear leakage rates calculated 

for each wetland were viewed as a sample population with 

statistical properties that could be compared among wetlands.

The median value of the daily leakage rate was compared for 

the 10 wetlands, and the first and third quartiles were interpreted to be plausible ranges for the daily leakage of a given 

wetland. Leakage values that fell outside the first and third 

quartiles were considered less physically representative and 

possibly artifacts of residual error.
Wetland Water Budgets 47

The box plots used for descriptive analysis of linear 

leakage rates include a vertical box that represents the 

25th through the 75th percentiles of the data (50 percent of 

the data), and a horizontal line or symbol that represents 

the median of the data (that is, the middle observation). 

The height of the box from top to bottom is a representation 

of how much variability or “spread” is present in the data. 

The length of this spread is called the interquartile range. 

The long lines extending from the boxes are called “whiskers.” The whiskers extend up to 1.5 times the interquartile 

range, indicating the spread of additional data beyond 

the 25th and the 75th percentiles. If data do not extend to 

or beyond 1.5 times the interquartile range, the whiskers 

extend to the outermost upper and lower data points from 

the median. Stars and open circles are “outlier” data points 

beyond the 1.5 and 3.0 interquartile ranges, respectively.

A subset of the daily data collected at each wetland 

was used for the water-budget analysis (table 4). Days 

were eliminated if the (1) wetland was flooded beyond the 

wetland perimeter, making the change in volume unquantifiable; (2) wetland was dry; or (3) flooded area was less than 

0.06 acres (about 2,600 ft2), making it difficult to accurately 

describe the change in volume term (∆S). Additional days 

were lost if augmentation flow rates were not available 

(163 days for S‐63 Augmented Cypress), or if equipment or power failures resulted in missing data. Between 

225 and 687 daily residual values were available for 9 of 

the 10 wetlands (table 4). At W‐3 Augmented Marsh, the 

location of the stage recorder within the wetland limited the 

population of interpretable water-budget days to the 47 days 

with the highest stage. 

Table 4. Water-budget characteristics and selected flux rates for the study wetlands.

[NGW, net ground-water; in/d, inches per day]

Waterbudget 

characteristics

Natural Augmented Impaired

GS Natural 

Marsh

HRSP 

Natural 

Marsh

GS 

Natural 

Cypress

S-68 

Natural 

Cypress

Duck 

Pond 

Augmented 

Marsh

W-3 

Augmented 

Marsh

S-63 

Augmented 

Cypress

W-5 

Augmented 

Cypress

W-29 

Impaired 

Marsh

W-19 

Impaired 

Cypress

Dates of hydrologic data 

collection

12/11/00-

10/02/02

12/12/00-

04/05/04

11/22/02-

08/01/04

12/11/02-

08/04/04

12/08/00-

10/14/02

12/07/00-

10/09/02

11/05/02-

08/04/04

10/11/02-

07/27/04

12/07/00-

07/01/04

08/23/02-

07/26/04

Total data collection days 661 1,211 619 602 676 672 638 656 1,303 704

Total water budget days 295 607 225 452 635 47 463 333 687 460

Dry days 171 31 59 10 0 0 76 911 484 24

Overflow days 133 227 265 120 0 0 21 1962 121 99

Positive NGW days 

“Runoff Days”

123 211 413 121 0 0 34 41 173 93

Negative NGW days 

“Leakage Days”

172 396 184 331 635 47 429 292 514 367

Leakage rate, median, in/d 0.07 0.11 0.26 0.14 2.0 0.6 1.17 0.40 0.09 0.18

Leakage rate, mean, in/d 0.10 0.16 0.28 0.16 2.2 0.71 1.27 0.56 0.13 0.22

Rainfall sum for leakage 

days, inches

3.22 20.86 2.62 4.55 87.04 17.48 28.9 13.11 13.72 7.79

Rainfall sum for runoff 

days, inches

31.50 67.52 17.45 41.08 0 0 30.59 22.25 96.92 39.89

1

Dry days at W-5 Augmented Cypress were part of an augmentation experiment. 

2

Overflow occurs at W-5 Augmented Cypress when the wetland stage exceeds a road cut elevation at 71.20 ft above NGVD 29. At all other sites, it occurs 

when the elevation exceeds the wetland perimeter. 

3

The number of “Runoff Days” appears low at GS Natural Cypress because the water budget (and runoff) could not be computed for the numerous 

“overflow” days when the wetland was overflowing its perimeter, despite the fact that the potential for runoff was high.
48 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Rainfall and Evapotranspiration

At each wetland, rainfall was measured hourly to the nearest 

0.01 in., using 6-in.-diameter rain gages (Texas Electronics, 

Inc.) with automated tipping-buckets, and cumulative rainfall 

was measured every 2 weeks in 4-in.-diameter storage rain 

gages. The rainfall totals at the different sites are summarized in 

appendixes 1 and 2. The tipping-bucket gages consistently overreported rainfall by several percent and were corrected using 

the storage rain gage observations. At the five cypress wetlands, 

rainfall under the tree canopy was measured using both tippingbucket and storage rain gages. Rainfall outside the wetland tree 

canopy was measured with a storage rain gage. The biweekly 

rainfall totals under the canopy were consistently lower, ranging 

from 85 to 95 percent of the rainfall totals outside the canopy 

(app. 3). Rainfall measured under the canopy was used in water 

budgets for the cypress wetlands.

lysimeters to record evapotranspiration losses from three marshes 

in the Upper St. Johns River Basin in east-central Florida from 

May 1996 through December 1999.

Daily evapotranspiration from the cypress wetlands was 

based on work by Sumner (2001). The study used tower-mounted 

instruments above the tree canopy, and the energy-budget variant 

of the eddy correlation method, to describe evapotranspiration 

from an extensive area of cypress wetland with fragmented areas 

of pine-forested upland in east-central Florida. Cypress wetland 

evapotranspiration estimates used in the current study were 

based on daily, and daily maximum, unburned evapotranspiration rates obtained from D.M. Sumner (U.S. Geological Survey, 

written commun., 2005). Daily values were summed to create 

monthly totals (app. 4). The annual cypress evapotranspiration 

rate of 38.19 in/yr (970 mm/yr) estimated by Bidlake and others 

(1996) in a similarly instrumented study in west-central Florida 

compares closely with the annual total of 37.80 in/yr (960 mm/

yr) determined by Sumner (2001). Measured evapotranspiration 

rates in Sumner (2001) declined during spring months when 

wetlands were dry. Because evapotranspiration was needed only 

for flooded cypress wetlands in this study, values for the dryseason months of May and June were adjusted slightly upward.

Synthetic daily evapotranspiration values were created by 

assigning the monthly average daily value to the middle day of 

each month and interpolating the values for intervening days. 

Although the actual daily variability in evapotranspiration is 

lost, the information that is preserved provides the water budget 

with a daily evapotranspiration signal of appropriate magnitude 

to minimize the error in the largest number of residual values. 

The validity of using synthetic evapotranspiration in an annual 

sine curve to minimize budget errors has gained credibility in 

recent water budget studies and rainfall-runoff models (Oudin 

and others, 2005; Sumner, 2006).

Marsh and cypress wetland evapotranspiration rates for 

this study were lower than the open-water evaporation rate for 

Lake Starr, a lake in central Florida with 10 years of continuous, 

energy-budget evaporation estimates, the longest for any lake in 

the southeastern United States (Swancar and Lee, 2003; Swancar, 

2006). The monthly Lake Starr evaporation rates shown in 

appendix 4 are averages for a 4-year period from 1997 to 2000. 

Wetland Stage, Volume, and Area

Bathymetric survey results described in Haag and others 

(2005) were used to determine the water volume and flooded 

area in each wetland for a given stage value. The daily volume 

and flooded area were interpolated to the nearest 0.01 ft of stage. 

Volume and area were computed at midnight of each day, and the 

daily volumes of evapotranspiration and rainfall were computed 

by multiplying the linear flux rate of these terms by the daily 

average size of the flooded area of the wetland. The daily change 

in wetland volume was the forward difference between successive midnight volumes.

The daily augmentation volumes at the four augmented 

wetlands were provided by Tampa Bay Water and were typically 

rounded to the nearest 10,000 gal (0.01 Mgal/d) (Chris Shea, 

Tampa Bay Water, written commun., 2004).

Beneath the tree canopy in a cypress wetland

Because evapotranspiration was not measured at the study 

wetlands, a synthetic daily time series was created based on 

published weekly to monthly wetland evapotranspiration data in 

Florida. Evapotranspiration losses from marshes were based on 

three comprehensive field studies of marshes in Florida (Abtew, 

1996; German, 2000; and Mao and others, 2002). Monthly 

average marsh evapotranspiration was derived by averaging all 

of the published evapotranspiration values for a given month 

(app. 4). German (2000) used the Bowen-ratio/energy-budget 

method to compute annual evapotranspiration from seven marsh 

sites distributed in the Everglades area of southern Florida during 

2 years. The monthly average evapotranspiration for all seven 

sites for 1996 and 1997 was used in this study (E.R. German, 

U.S. Geological Survey, written commun., 2005). Monthly 

evapotranspiration from a cattail marsh in southern Florida for 

1993 and 1994 was measured by Abtew (1996) using continuously saturated lysimeters. Mao and others (2002) also used 
Wetland Water Budgets 49

Wetland Leakage

Wetland linear leakage rates varied nearly thirtyfold 

among the 10 sites (fig. 28). GS Natural Marsh had the lowest 

median leakage rate (0.07 in/d). Duck Pond Augmented 

Marsh had the greatest median leakage rate (2.00 in/d), with 

an interquartile range of 1.74 to 2.74 in/d (table 5). The four 

natural wetlands and two impaired wetlands shared similarly 

low leakage rates, ranging from 0.07 to 0.26 in/d.

Among the six unaugmented wetlands, the three marshes 

leaked more slowly than the three cypress wetlands. This 

finding is not attributable to the different evapotranspiration rates used for the two wetland types, because when the 

lower cypress evapotranspiration rates were assumed for both 

wetland types, the three marshes still leaked, on average, at 

about half the rate of the three cypress wetlands (table 5). In 

addition, climate differences during the marsh and cypress 

wetland water-budget periods support this result. Marsh 

leakage rates were slower than cypress leakage rates even 

though the lower ground-water conditions during the marsh 

water-budget period theoretically should have favored faster 

leakage rates.

The augmented wetlands had the widest range in linear 

leakage rates, and these rates were not related to wetland type; 

that is, the two augmented cypress wetlands did not leak faster 

than the two augmented marshes. Differences in leakage 

rates, however, suggested differences in hydrogeologic 

conditions at the individual wetlands. For example, the two 

augmented wetlands located within the Cypress Creek Well 

Field (W‐3 Augmented Marsh and W‐5 Augmented Cypress), 

leaked at rates equal to about 20 to 50 percent of the rates of 

S‐63 Augmented Cypress and Duck Pond Augmented Marsh. 

Wetland leakage rates can change through time 

depending on rainfall and ground-water levels, and 

natural or augmentation-related changes in wetland stage. 

The changing ground-water head gradients surrounding 

the wetland interact with the hydraulic conductivity of the 

underlying sediments to determine the magnitude and direction of leakage flow. For example, as a group, augmented 

wetlands are expected to leak more than natural or impaired 

wetlands because the vertical head differences that drive 

leakage become amplified when ground-water levels are 

lowered by well-field pumping and wetland stage is raised 

through augmentation. But are augmented wetlands intrinsically leakier than their natural wetland counterparts? To 

address this question, wetland leakage rates were analyzed 

further to distinguish the effects of downward head conditions and hydraulic conductivity on the leakage rate of 

individual wetlands.

Table 5. Wetland leakage rate statistics.

[in/d, inches per day. Leakage rates in parentheses were computed using the 

same evapotranspiration rates for all wetlands. Results reveal higher leakage 

loss rates in the unaugmented cypress wetlands compared to the marsh 

wetlands whether evapotranspiration in marshes is set to be either equal to or 

greater than in cypress wetlands]

Wetland

group 

and/or 

type

Wetland 

name 

Leakage 

rate, median

(in/d)

Leakage 

rate, 1st 

quartile

 (in/d)

Leakage 

rate, 3rd 

quartile

(in/d)

Augmented

Duck Pond Augmented 

Marsh

2.00 1.74 2.74

S-63 Augmented 

Cypress

1.17 0.67 1. 68

W-3 Augmented Marsh 0.67 0.49 0.96

W-5 Augmented Cypress 0.40 0.23 0.67

Unaugmented

Marsh

GS Natural Marsh 0.07 (0.06) 0.03 0.13

HRSP Natural Marsh 0.11 (0.09) .05 0.24

W-29 Impaired Marsh 0.09 (0.07) 0.04 0.16

Cypress 

GS Natural Cypress 0.26 (0.22) 0.17 0.37

S-68 Natural Cypress 0.14 (0.11) 0.06 0.22

W-19 Impaired Cypress 0.18 (0.16) 0.12 0.28 Figure 28. Daily linear leakage rates in the study 

wetlands.

LINEAR LEAKAGE RATE, INCHES PER DAY 4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

7.33 8.24

DUCK POND AUGMENTED MARSH

W-3 AUGMENTED MARSH

GS NATURAL MARSH

HRSP NATURAL MARSH

W-29 IMPAIRED MARSH

S-68 NATURAL CYPRESS

W-5 AUGMENTED CYPRESS

S-63 AUGMENTED CYPRESS

W-19 IMPAIRED CYPRESS

GS NATURAL CYPRESS

Median

25-75 percent

Minimum-Maximim
50 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Effect of Downward Head Differences on 

Wetland Leakage

To compare the effect of hydrogeologic conditions on 

leakage estimates, the vertical, or downward, head difference between each wetland and the underlying aquifer was 

evaluated. The downward head difference, dh, provides the 

potential for vertical flow, and is part of the Darcy formula for 

one-dimensional, laminar ground-water flow (Bear, 1979)

Qv = Kv*A(dh/dz), (3)

where:

Qv is the volumetric flow rate in the vertical direction 

or leakage [L3/T];

Kv is the vertical hydraulic conductivity of the 

geologic material the leakage flows through;

A is the projected area perpendicular to the flow 

[L2], which is assumed to equal the flooded area 

of the wetland; and

dh/dz is a dimensionless vertical head gradient.

All leakage is assumed to exit the wetland vertically, through 

a projected area equal to the flooded area of the wetland.

The daily linear leakage rate, qv, is the volumetric 

leakage rate divided by the daily average flooded area.

qv = Qv/A = Kv(dh/dz) [L/T]. (4)

In these wetlands, the vertical head difference, dh, is 

equal to wetland stage minus the Upper Floridan aquifer 

head. The head difference occurs across the vertical interval, 

dz, equal to the vertical distance between the wetland bottom 

and the top of the persistent limestone of the Upper Floridan 

aquifer. Head differences at 9 of the 10 wetlands were calculated using biweekly measurements of wetland stage and the 

head in an adjacent Upper Floridan aquifer well. GS Natural 

Cypress lacked an Upper Floridan well and was, therefore, 

excluded from the analysis.

Wetlands with the greatest leakage rates were not 

necessarily those with the greatest downward head difference during their water budgets, as shown by a comparison 

of figures 28 and 29. Although W‐3 Augmented Marsh 

experienced the largest head difference, it leaked more slowly 

than the two fastest leaking wetlands, Duck Pond Augmented 

Marsh and S‐63 Augmented Cypress. W‐29 Impaired Marsh, 

which like W‐3 Augmented Marsh experienced large downward head differences and also was on Cypress Creek Well 

Field, had the second to lowest leakage rate. Head differences 

in the nine wetlands also were not clearly distinguished by 

wetland group or type. For example, head differences at the 

two natural marshes were among the lowest, as might be 

expected. Head differences at W‐19 Impaired Cypress and 

W‐5 Augmented Cypress, however, were both comparable 

in magnitude to those of the natural wetlands (fig. 29). 

The typically greater head differences at the augmented 

wetlands reveal two aspects of their condition. First, the potentiometric level of the Upper Floridan aquifer can range farther 

below these wetlands due to well-field pumping than it ranges 

at the natural wetlands. Second, the water budget could be 

calculated throughout the dry season because these wetlands 

are augmented, whereas unaugmented wetlands would become 

dry as ground-water levels declined.

The contrast in head differences at wetland groups 

becomes more evident when comparisons are based on the 

entire data-collection time period, rather than the subset of 

days used for calculating the wetland water-budgets. To do 

this, a surrogate for the hydraulic head difference was calculated using the bottom elevation of the wetland instead of 

wetland stage, reflecting the physical distance of the potentiometric surface below the wetland bottom. Because wetlands 

are typically shallow, the elevation difference computed using 

the wetland bottom elevation is generally only several feet less 

than the head difference derived using wetland stage when the 

wetland is flooded.

Figure 29. Downward head differences at each wetland during 

its water-budget period. Head difference is between wetland 

stage and the head of the Upper Floridan aquifer.

30

25

20

15

10

5

0

-5

HEAD DIFFERENCE, IN FEET

DUCK POND AUGMENTED MARSH

W-3 AUGMENTED MARSH

GS NATURAL MARSH

HRSP NATURAL MARSH

W-29 IMPAIRED MARSH

S-68 NATURAL CYPRESS

W-5 AUGMENTED CYPRESS

S-63 AUGMENTED CYPRESS

W-19 IMPAIRED CYPRESS

Median

25-75 percent

Minimum-Maximim
Wetland Water Budgets 51

The elevation difference between the bottom of the 

wetland and the potentiometric surface of the Upper Floridan 

aquifer at W‐29 Impaired Marsh contrasted sharply during 

the marsh and cypress data-collection periods, and revealed 

the importance of head conditions in underlying aquifers to 

wetland flooding (fig. 30). During the nearly 2-year marsh 

data-collection period, with rainfall slightly below average, 

the potentiometric surface was a median distance of 24.36 ft 

below the bottom of W‐29 Impaired Marsh while the 

interquartile range was 18.41 to 28.75 ft below the wetland 

(fig. 30A). Above average rainfall and pumping reductions 

during the cypress data-collection period raised the potentiometric surface to a median distance of only 3.39 ft below the 

bottom of W‐29 Impaired Marsh, with an interquartile range 

of 1.10 to 5.53 ft. During this period, W‐29 Impaired Marsh 

exhibited a characteristic seen only at the natural marshes 

during the previous marsh period—the potentiometric surface 

briefly rose above the wetland bottom, and the elevation 

difference became negative (fig. 30A).

If only those days when W‐29 Impaired Marsh was 

inundated and the water budget could be calculated (“waterbudget days”) are examined, the median distance between the 

wetland bottom and the potentiometric surface in the Upper 

Floridan aquifer was 5.35 ft, with an interquartile range from 

2.52 to 10.59 ft (fig. 30A). This range overlaps the lower 

values observed during the marsh period, but more closely 

resembles the range and median value occurring during the 

cypress period. There is one exception: the water-budget days 

do not include any days when the potentiometric surface of the 

Upper Floridan aquifer was above the wetland bottom elevation because, when these conditions occurred, the wetland was 

overflowing its perimeter and the water budget could not be 

calculated (fig. 30A). 

Figure 30. Elevation differences between the bottom of the wetland and the head in the Upper Floridan aquifer at (A) W-29 Impaired 

Marsh for three time periods, (B) marshes from December 2000 through September 2002, and (C) cypress wetlands from November 

2002 through July 2004.

DUCK POND

AUGMENTED

MARSH W-3

AUGMENTED

MARSH

W-29

IMPAIRED

MARSH

GS NATURAL

MARSH HRSP

NATURAL

MARSH

MARSHES CYPRESS WETLANDS

W-29

IMPAIRED

MARSH

S-68

NATURAL

CYPRESS

W-5

AUGMENTED

CYPRESS S-63

AUGMENTED

CYPRESS

W-19

IMPAIRED

CYPRESS

35

30

25

20

15

10

5

0

-5

WATER-BUDGET

DAYS

MARSH

PERIOD

CYPRESS

PERIOD

DIFFERENCE, IN FEET ELEVATION

ELEVATION DIFFERENCE, IN FEET DIFFERENCE, IN FEET ELEVATION

W-29 IMPAIRED MARSH

35

30

25

20

15

10

5

0

-5

(A)

(B) (C) 35

30

25

20

15

10

5

0

-5

EXPLANATION

Median

25-75 percent

Minimum-Maximum

Zero elevation difference indicates the

head in the Upper Floridan aquifer is at

the elevation of the wetland bottom.

(Negative values indicate the head in

the Upper Floridan aquifer is above the

wetland bottom)
52 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

During the marsh data-collection period, the 

potentiometric surface of the Upper Floridan aquifer was 

substantially closer to the bottom elevations of the two natural 

marshes than to the bottom elevations of the impaired and 

augmented marshes (fig. 30B). The median elevation differences in GS Natural Marsh and HRSP Natural Marsh were 

1.78 and 3.42 ft, respectively, and the interquartile range at 

both sites was between 1.00 and 5.41 ft. The potentiometric 

surface of the Upper Floridan aquifer also was occasionally 

above the bottom of each of the natural wetlands. In contrast, 

the median distance of the potentiometric surface below W‐3 

Augmented Marsh was large (17.94 ft), and similar in magnitude to the median value at W‐29 Impaired Marsh (24.37 ft), 

probably because both are located on the same well field 

and are subject to similar ground-water pumping regimes. 

The median distance of the potentiometric surface below 

Duck Pond Augmented Marsh is less (8.57 ft), in part because 

the marsh is substantially deeper than the other two marshes 

(fig. 30B). 

With pumping reductions and above average rainfall 

during 2002-04, the surrogate head differences in the natural, 

impaired, and augmented cypress wetlands, as well as 

W‐29 Impaired Marsh, resembled those measured earlier in 

the two natural marshes (compare fig. 30B with fig. 30C). 

The potentiometric surface of the Upper Floridan aquifer 

was a median distance of between 0.61 ft. and 3.40 ft below 

W‐5 Augmented Cypress, W‐19 Impaired Cypress, and 

W‐29 Impaired Marsh, while the interquartile range was 

-0.34 to 5.53 ft. All three wetlands showed negative surrogate 

head differences at their minimum values, or within the lower 

quartile at W‐19 Impaired Cypress. The potentiometric surface 

remained a greater distance below the two wetlands located on 

the Starkey Well Field where ground-water pumping had not 

been reduced. The median elevation difference at the natural 

wetland S‐68 Natural Cypress (4.80 ft) was slightly less than 

the median at S‐63 Augmented Cypress (6.63 ft), and the interquartile range was smaller. The potentiometric surface of the 

Upper Floridan aquifer was never above the bottom elevation 

of either wetland.

Effect of Hydraulic Conductivity on Wetland 

Leakage

Wetland leakage rates also are proportional to the 

vertical hydraulic conductivity (Kv), a constant and intrinsic 

property of the geologic material beneath a wetland. By 

assuming that all of the wetland leakage flowed vertically, 

the Darcy formula was used to derive a vertical leakance 

coefficient below each of the wetlands. Leakance, expressed 

as Kv/b (1/day), is a term used to describe the properties of a 

semipervious layer of thickness b capping a leaky confined 

aquifer (Anderson and Woessner, 1992). The property usually 

applies to a confining bed, or semipervious layer, because the 

layer with the lowest hydraulic conductivity tends to dictate 

the flow rate through the entire geologic interval. In this 

study, the precise stratigraphy beneath the wetlands was 

not known and the vertical thickness of the clastic deposits 

separating the bottom of each wetland from the top of the 

transmissive limestone was comparable (typically 20-40 ft); 

therefore, the entire thickness, dz, was equated to b and leakance was derived by rearranging equation 4 as follows:

 qv/(dh) = Kv /dz [T -1]. (5) 

A population of leakance coefficients was derived 

for each wetland by solving equation 5 using daily linear 

leakage rates, (qv), and daily vertical head differences (dh). 

The statistical properties of these populations of leakance 

coefficients should reflect the constant and intrinsic properties 

of the subsurface beneath the wetlands. Daily average Upper 

Floridan aquifer head values were computed from hourly 

readings at Duck Pond Augmented Marsh, W‐5 Augmented 

Cypress, W‐19 Impaired Cypress, W‐29 Impaired Marsh, and 

S‐68 Natural Cypress. Daily aquifer levels were interpolated 

from biweekly measurements at HRSP Natural Marsh, 

W‐3 Augmented Marsh, S‐68 Natural Cypress, and GS Natural 

Marsh. The number of daily leakance coefficient estimates 

at each site ranged from 48 (W‐3 Augmented Marsh) to 

418 (W‐29 Impaired Marsh).

 Based on the median and interquartile range of the 

leakance coefficient estimate, S‐63 Augmented Cypress on 

Starkey Well Field has the leakiest geologic setting of all the 

wetlands (fig. 31). Duck Pond Augmented Marsh has a lower 

leakance coefficient, but a faster linear leakage rate than 

S‐63 Augmented Cypress because it was subjected to larger 

downward head differences. S‐63 Augmented Cypress is about 

4,000 ft northwest of S‐68 Natural Cypress, a natural cypress 

wetland with one of the lowest leakance coefficients in the 

study. Although S‐68 Natural Cypress was subjected to downward head differences similar to those at S‐63 Augmented 

Cypress, it maintained a flooding pattern most similar to 

those of the natural wetlands, probably because of its lowpermeability setting.

A comparative analysis of wetland leakage rates 

alone would have been misleading. During the cypress 

water-budget period, the downward head differences at 

both W‐5 Augmented Cypress and W‐19 Impaired Cypress 

resembled those in the natural wetlands (fig. 30B-C). As a 

result, the leakage rate for W‐19 Impaired Cypress was one of 

the slowest, and the leakage rate for W‐5 Augmented Cypress 

was the slowest for the augmented wetlands (fig. 28). These 

two wetlands, however, have leakance coefficients that 

fall in a high-intermediate range, less than the two leakiest 

wetlands, but substantially greater than the values in the 

remaining five wetlands (fig. 31). The leakance coefficients 

for W‐5 Augmented Cypress and W‐19 Impaired Cypress 

indicate the vulnerability of these two wetlands to larger 

leakage rates when head differences are larger than those 

observed during this study. This vulnerability explains 

the augmented and impaired status, respectively, of these 

two wetlands. 
Wetland Water Budgets 53

The comparison of leakance coefficients reinforces 

the conclusion that the marshes occupied less leaky settings 

than the cypress wetlands. The five wetlands with the lowest 

leakance values include all four of the shallow marshes (even 

W‐3 Augmented Marsh), even though the marshes were 

located in three different parts of the study area. Duck Pond 

Augmented Marsh, the deepest wetland with the greatest 

potential for lateral flow, was the only exception (fig. 12). 

The results indicate that the relatively fast leakage rate 

observed in W‐3 Augmented Marsh during this study was due 

more to the large downward head differences it experienced 

than to a highly conductive setting. The distinction between 

marshes and cypress wetlands also was evident in neighboring 

wetlands for the two marshes and two cypress wetlands within 

Cypress Creek Well Field (fig. 31).

By assuming that vertical leakage always predominates 

over lateral leakage, both physical processes become incorporated in the vertical leakance coefficient. At each wetland, 

some leakage flows laterally away from the flooded perimeter, 

propelled by the slope in the surrounding water table and by 

the horizontal hydraulic conductivity of the surficial aquifer. 

The vertical exaggeration used in the hydrogeologic sections 

(figs. 11-18) exaggerates the appearance of horizontal flow 

near the wetlands. In fact, the wetlands are expansive, shallow 

features. Their large horizontal dimensions are typically 

exposed to vertical head gradients that far exceed the watertable slope. For this reason, horizontal leakage losses are 

considered negligible compared to vertical leakage losses. 

Case Studies of Wetland Leakage

Leakage rates from all 10 wetlands were affected by a 

range of physical and environmental conditions. The effects 

of these conditions on wetland leakage, however, are easiest 

to show using the water-budget results for the augmented 

wetlands, rather than corresponding results for natural and 

impaired wetlands. Augmented wetlands leaked the most, 

making daily leakage values less subject to residual error and 

more robust for statistical analysis. In addition, they typically did not flood beyond the wetland perimeter during the 

wettest season or dry up during the driest season, although 

S‐63 Augmented Cypress is a notable exception. As a result, 

the water budgets of augmented wetlands could be calculated 

for the greatest number of days per year, and for the greatest 

range in seasonal ground-water levels. This permitted 

detailed analyses of regression relations between leakage 

losses and environmental variables such as head in the Upper 

Floridan aquifer.

In the following three case studies, processes affecting 

wetland leakage rates are examined at three augmented 

wetlands: Duck Pond Augmented Marsh, S‐63 Augmented 

Cypress, and W‐5 Augmented Cypress. The three case studies 

examine, respectively, the relation between linear leakage 

rate and three factors: (1) head in the Upper Floridan aquifer; 

(2) size of the flooded area in the wetland; and (3) the effect 

of unsteady/unsaturated flow conditions when a dry wetland 

is initially augmented.

Duck Pond Augmented Marsh

Duck Pond Augmented Marsh provided the most 

continuous water-budget record of the 10 wetlands, and 

the most direct evidence of Upper Floridan aquifer head 

effects on wetland leakage rates. More than 90 percent of 

the 21-month water-budget period produced usable daily 

residual values, and all residual values were leakage (table 4). 

The nearly continuous record of daily leakage provided the 

opportunity to describe an annual wetland water budget for 

2001. At Duck Pond Augmented Marsh, the magnitudes of 

augmentation and leakage overshadow all other water-budget 

components (fig. 32). The annual volume of augmentation 

was equal to 65.52 vertical ft of water, covering an annual 

average flooded area of 2.87 acres. The annual leakage 

volume was only slightly less at 64.49 ft/yr, indicating the 

majority of the augmentation water (98 percent) exits the 

wetland as leakage. Annual rainfall and evaporation volumes, 

in comparison, totaled 4.36 and 3.95 ft/yr, respectively. 

Because the daily augmentation volume was relatively 

constant at Duck Pond Augmented Marsh, the daily leakage 

volume was relatively constant. However, the velocity of 

the leakage exiting the marsh, reflected in the linear leakage 

rate, was not constant. Instead, the leakage velocity accelerated and decelerated with fluctuations in the potentiometric 

surface of the Upper Floridan aquifer.

Figure 31. Leakance values below the study wetlands.

Median

25-75 percent

Non-Outlier Range

0.030

0.025

0.020

0.015

0.010

0.005

0

LEAKANCE, DAY-1

DUCK POND AUGMENTED MARSH

W-3 AUGMENTED MARSH

GS NATURAL MARSH

HRSP NATURAL MARSH

W-29 IMPAIRED MARSH

S-68 NATURAL CYPRESS

W-5 AUGMENTED CYPRESS

S-63 AUGMENTED CYPRESS

W-19 IMPAIRED CYPRESS
54 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 32. Annual water budget for Duck Pond 

Augmented Marsh in 2001. Volume is shown as height of 

water above the annual average flooded area.

Figure 33. Daily water-budget residual for Duck Pond 

Augmented Marsh and head in the Upper Floridan aquifer 

during December 2000 through September 2002. Gaps 

reflect missing data. Negative residual values represent 

leakage.

Figure 34. Daily average head in the Upper Floridan 

aquifer in relation to daily linear leakage rate from Duck 

Pond Augmented Marsh.

Dry conditions at S-63 Augmented Cypress 

wetland when augmentation stopped

Daily linear leakage from Duck Pond Augmented Marsh 

varied by a factor of 2 during the water-budget period, ranging 

from a minimum of about 1.7 in/d in September of both 

2001 and 2002 to a maximum of 3.7 in/d in April of 2001, and 

its magnitude closely tracked the head in the Upper Floridan 

aquifer (fig. 33). Daily leakage rates were correlated with the 

average head in the Upper Florida aquifer for the same day 

(R2 = 0.63, confidence interval 95 percent), indicating that 

leakage from Duck Pond Augmented Marsh responds rapidly 

to head changes in the Upper Floridan aquifer (fig. 34). 

The statistically significant relation between the heads 

measured in the Upper Floridan aquifer, and leakage derived 

as a residual term to the water-budget equation, validates the 

physical significance of the daily residual term. The relation 

also shows that the rate of leakage loss could be reduced by 

raising the Upper Floridan aquifer level near the wetland. 

S-63 Augmented Cypress

Unlike the continuous leakage seen at Duck Pond 

Augmented Marsh, S‐63 Augmented Cypress wetland periodically dried out and rewetted, and had more than 30 days with 

runoff (table 4 and fig. 35). These variations caused additional 

processes to affect leakage rates at S‐63 Augmented Cypress. 

The water budget still generated more than 420 linear leakage 

values that correlated with the head in the nearby Upper 

Floridan aquifer well, although at a lower R2 value (0.44) than 

Duck Pond Augmented Marsh (fig. 36). The maximum linear 

leakage rate at S‐63 Augmented Cypress was typically around 

3 in/d, similar to the maximum linear leakage rate at Duck 

Pond Augmented Marsh. However, exceptionally high linear 

leakage rates were evident in S‐63 Augmented Cypress when 

the wetland was drying out or rewetting.

0

10

20

30

40

50

60

70

Duck Pond Augmented Marsh Water Budget 2001 AUGMENTATION LEAKAGE EVAPOTRANSPIRATION CHANGE IN STORAGE RAIN

HEIGHT OF 

WATER THE ANNUAL

AVERAGE FLOODED AREA, IN FEET

OVER

OUTFLOW

INFLOW

60

58

56

54

52

50

48 0

DAILY AVERAGE HEAD IN THE UPPER

FLORIDAN AQUIFER, IN FEET ABOVE NGVD 29

LINEAR LEAKAGE RATE, IN INCHES PER DAY

R2=0.63

1 2 3 4

0

-1

-2

-3

-4

64

60

56

52

48

HEAD IN THE UPPER FLORIDAN

AQUIFER, IN FEET ABOVE NGVD 29

WATER-BUDGET RESIDUAL,

IN INCHES PER DAY

Upper Floridan aquifer head

J F M A M J J A S O N D

2001

D

2000

J F M A M J J A S

2002
Wetland Water Budgets 55

Figure 35. Daily rainfall, daily water-budget residual, 

and head in the Upper Floridan aquifer at S-63 

Augmented Cypress wetland during November 2002 

through July 2004. Data are missing when the wetland 

was dry or flooded beyond its perimeter. Positive and 

negative residual values represent runoff and leakage, 

respectively.

Figure 36. Daily average head in the Upper Floridan 

aquifer in relation to daily linear leakage rate at S-63 

Augmented Cypress wetland. Four leakage values 

greater than 3.5 in/d are omitted from the regression 

relation.

On repeated occasions when S‐63 Augmented Cypress 

dried out, linear leakage rates increased exponentially in the 

last few days before the wetland became dry. Similarly, when 

S‐63 Augmented Cypress rewetted after having been dry, the 

initial linear leakage rate was highest and decreased exponentially during the next few days. For example, S‐63 Augmented 

Cypress dried up on four occasions, each lasting one to 

several weeks. Each time, in the final days before completely 

drying or in the first days of being rewetted, the daily linear 

leakage rate peaked at from 4 to 7 in/d, substantially higher 

than the typical background leakage rates of 1 to 2 in/d 

(fig. 35). The peaks in the linear leakage rate were not proportional to changes in the Upper Floridan aquifer, suggesting 

that processes other than saturated, vertical ground-water flow 

were important.

The apparent increase in linear leakage rate could, in 

part, reflect increased lateral leakage along the perimeter of 

the flooded area. During drying periods, as the flooded area 

shrinks and the surrounding water table drops, the slope of the 

wetland water-table mound increases, and as a result, lateral 

leakage also increases. At the same time, the decrease in 

flooded area increases the perimeter-to-area ratio, increasing 

the relative importance of lateral flow to vertical flow 

(Millar, 1971). If the water-table slope reaches a maximum 

and the flooded area reaches a minimum immediately before 

S‐63 Augmented Cypress wetland dries out, or immediately 

after it rewets, the resulting increase in the lateral leakage 

could be interpreted as increased vertical leakage.

Increases in the linear leakage rate as the flooded area 

contracts also could be due to more permeable geologic 

material below the deepest region of the wetland. The deepest 

region of the wetland, and therefore, the last area to dry up or 

first to rewet, could overlie a collapse feature breaching the 

confining unit of the Upper Floridan aquifer—an association 

documented in Florida lakes (Tihansky and others, 1996). If 

this is the case, the linear leakage rate would increase when 

only this lowest region is flooded.

Finally, the rise in linear leakage rates could reflect a 

shift from saturated flow to infiltration into unsaturated soil. 

Evidence for this process can be found during an 8-day period 

in late December 2003, when S‐63 Augmented Cypress 

alternated between flooded and dry conditions every day 

(discussed later). Augmentation flow to S‐63 Augmented 

Cypress was sufficient to flood only the deepest area of the 

wetland for 4 to 14 hours each day. When inflow was turned 

off, the wetland rapidly dried up and the water table dropped 

below the wetland bottom. Linear leakage rates from the 

small area that flooded were exceptionally high. Hourly water 

budgets were used to estimate the hourly linear leakage rates 

during these 8 days. The median leakage rate was 0.9 in/hr 

with a range of 0.48 to 1.2 in/hr across a median flooded area 

of 0.18 acre. This is comparable to a daily linear leakage 

rate of about 21 in/d. When computed with the daily water 

budget, the highest daily value of leakage for S‐63 Augmented 

Cypress was 7.3 in/d occurring on the second day of flooding 

after it had been dry for a month and a half during April-May 

2004 (fig. 35). (The change in volume from the initial dry 

condition cannot be computed for the first day.) The higher 

linear leakage rates on an hourly basis most likely reflect 

infiltration into unsaturated soil, and this rate becomes attenuated as pore spaces in the soil fill and infiltration transitions to 

saturated ground-water flow.

At S‐63 Augmented Cypress, days with positive residual 

values (runoff) generally coincided with rainfall days when the 

potentiometric level of the Upper Floridan aquifer was high 

(fig. 35). They also coincided with periods when the water 

4

2

0

-2

-4

-6

-8

45

40

35

30

WATER-BUDGET RESIDUAL,

IN INCHES PER DAY

HEAD IN THE UPPER FLORIDAN

AQUIFER, IN FEET ABOVE NGVD 29

Upper Floridan aquifer

heads

Dry periods

Wetland flooded

beyond perimeter Runoff

events

2002

N D J F M A M J J A S O N D J F M A M J J

2003 2004

3

2

1

0

RAINFALL, IN

INCHES PER DAY

DAILY AVERAGE HEAD IN THE UPPER

FLORIDAN AQUIFER, IN FEET ABOVE NGVD 29

LINEAR LEAKAGE RATE, IN INCHES PER DAY

40

38

36

34

32

300

R2=0.44

1 2 3 4 5
56 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

table on the north-northeast side of the wetland was higher 

than wetland stage, creating the potential for S‐63 Augmented 

Cypress to receive lateral ground-water inflow. Most days 

with rainfall did not generate a positive residual term, and 

ground-water inflow was not large enough to generate a positive water-budget residual on days without rainfall (fig. 35). 

The elevated water table and potentiometric surface apparently predisposed the wetland to receive substantial runoff, as 

indicated by the positive residual terms on days with rainfall. 

These “runoff days” typically appeared as solitary events 

on days with rainfall, and were surrounded by days with net 

leakage.

W-5 Augmented Cypress

An augmented wetland would mimic the hydrology 

of natural wetlands more closely if it dried up periodically 

rather than being perpetually flooded, and would gain several 

ecological benefits. Drying reduces the thickness of accumulated 

organic sediments in the bottom of wetlands by allowing sediments to oxidize and consolidate. In addition, the regeneration 

of cypress is enhanced because cypress seedlings can germinate 

only in dry conditions (Demaree, 1932). In addition to ecological 

benefits, allowing certain augmented wetlands to dry out could 

potentially conserve water. Although periodic drying is recommended in regulatory permits (for example, once every 5 years 

at Duck Pond Augmented Marsh), none of the augmented 

wetlands in this study have been intentionally allowed to dry up. 

No standard method currently exists for drying and rewetting 

augmented wetlands, and additional monitoring and other assistance would be needed to implement such a regime. Moreover, 

the potential exists that rewetting a dry wetland would require 

an unacceptably large volume of augmentation water compared 

to maintaining an existing flooded area. Specifically, rewetting 

an impaired wetland involves first mounding the water table to 

land surface, then flooding the wetland. Field experiments are 

needed to quantify the amount of water and time rewetting 

actually requires. These experiments could be used to determine 

the feasibility of increasing the similarity of flooding patterns in 

augmented and natural wetlands. 

Several of these uncertainties were explored using the 

water-budget analysis of W‐5 Augmented Cypress. In addition to 

the regular water-budget period, leakage losses were quantified 

during a controlled experiment to rewet the wetland. During the 

late spring of 2004, W‐5 Augmented Cypress was allowed to 

dry out by not augmenting the wetland for 79 days. The wetland 

was completely dry for the last 40 days, and during this time 

the water table declined about 4.5 ft below the wetland bottom. 

Augmentation water then was added in a prescribed manner 

for 22 days, from May 10 until June 1, 2004. The augmentation flow rate and ground-water levels around the wetland 

were monitored twice a day, and wetland stage was monitored 

continuously. The prescribed augmentation rates flooded 

two different areas used to calculate leakage. First, 1.3 acres 

(flooded area 1) were flooded to an elevation of 70.65 ± 0.02 ft. 

The flooded area was then increased to 2.3 acres (flooded area 2) 

at an elevation of 70.75 ± 0.02 ft. No substantial rain fell during 

this period, and water budgets were calculated daily.

Augmentation of W‐5 Augmented Cypress quickly 

reestablished flooding conditions. About 12 hours after augmentation flow was started, the water table below the deepest area of 

W‐5 Augmented Cypress was mounded to the land surface, and 

a small pond formed. Thereafter, the size of the pond increased 

along with the size of the water-table mound (fig. 37A-B). 

About 5 days of augmentation were required to reach the first 

of the two prescribed flooded areas (fig. 38). After 11 days of 

augmentation, a recharge mound radiated out about 150 ft from 

the flooded area, engulfing part of a water-table trough that had 

been below the southeast corner of W‐5 Augmented Cypress 

when the wetland was dry (fig. 37B).

As the mound became established, the augmentation 

volume required to maintain the first flooded area steadily 

declined and leveled off at about 6,000 ft3/d (fig. 38). The time 

required to form the water-table mound is evident in the 

response of individual wells that were located closest to the 

wetland. Before augmentation began on May 10, water levels 

in all of the shallow wells were dropping at the same rate as the 

head in the Upper Floridan aquifer well (fig. 39). Afterwards, the 

ground-water levels in wells closest to the edge of the flooded 

area rose first (well index numbers 71, 74, 78, figs. 37 and 39). 

After 22 days of augmentation, the mound had reached its full 

height at wells 71 and 74, but was continuing to rise at well 

78. The mound extended outward to wells 75, 76, and 77, but 

instead of raising the water table at these wells, the recharge 

slowed the decline of the water table compared to the Upper 

Floridan aquifer level (fig. 39). During the first 4 or 5 days 

of rewetting, as the recharge mound grew in size and flooded 

area expanded to the first target area, the daily linear leakage 

rate declined exponentially, dropping from 8.24 in/d to a rate 

between 1.0 and 1.5 in/d. When the flooded area was increased 

in size to the second target area, the linear leakage rate declined 

again, reaching a rate between 0.5 and 1.0 in/d (fig. 40).

The rapid response of W‐5 Augmented Cypress to 

augmentation was due in part to the high augmentation flow 

rate. The maximum daily rate of augmentation flow into 

W‐5 Augmented Cypress was about 11,200 ft3/d (1.9 acre-ft/d), 

and thus the water deliverable in a day was 40 percent of the 

total wetland volume (as listed in app. 9 of Haag and others, 

2005). At Duck Pond Augmented Marsh, by comparison, the 

normal daily augmentation rate was about 3.6 percent of the 

total volume of the wetland. This small daily rate would require 

far more time to refill Duck Pond, and could potentially prevent 

successful refilling under certain conditions. 

Drying out and refilling W‐5 Augmented Cypress was 

feasible for ground-water conditions similar to the case 

study, and has the potential to conserve augmentation water. 

Refilling W‐5 Augmented Cypress to the first flooded area 

and establishing a steady rate of augmentation took about 

10.5 days and required 93,430 ft3 of water. This was about 

30,000 ft3 more water than would have been needed for uninterrupted augmentation of the wetland for the same 10.5 days 
Wetland Water Budgets 57

(at 6,000 ft3/d). This 30,000 ft3 “investment” of water could 

have been recouped during a 5-day period with no augmentation. If additional days without augmentation conserved water 

at the same 6,000 ft3/d maintenance rate, then not augmenting 

W‐5 Augmented Cypress for the 79-day period of this experiment conserved about 440,000 ft3/d, or 10.10 acre-ft, of water. 

The water conserved during the dry phase could be viewed 

as reserve to be used if needed in W‐5 Augmented Cypress 

wetland at some later time period, for example, to achieve the 

ecological benefits of seasonal maximum water levels.

Additional augmentation experiments and numerical 

ground-water flow modeling studies could be used to understand the ground-water conditions and augmentation rates that 

are optimal for drying down and refilling augmented wetlands 

most strategically, and similarly to natural wetlands. For 

example, the augmentation experiment of W‐5 Augmented 

Cypress wetland took place in May 2004 when the potentiometric surface of the Upper Floridan aquifer was higher than 

in previous years (fig. 27A). Additional augmentation volume 

and time would have been required to refill W‐5 Augmented 

Cypress for the lower ground-water conditions that prevailed 

at Cypress Creek Well Field during 2001 and much of 2002 

(for example, fig. 25E). 

Augmentation water flooding W-5 

Augmented Cypress Wetland

Figure 37. Water-table configuration at W-5 Augmented Cypress 

wetland (A) on May 10, 2004 before augmentation, and (B) on 

June 1, 2004 after 23 days of augmentation.

66.5

66

65.5

65

65.5

65

66

67

68

69

70 70.75

68

66

66.5

67.5

67

66.5

67

300 METERS

500 1,000 FEET

0 100

0

74

71

78

77

75

Floridan 82

76

Center

80

Floridan 82

76

71

74

77

78

75

Center

80

79

200

(A) Water table before augmentation

(B) Water table after augmentation

W-5 AUGMENTED CYPRESS

EXPLANATION

300 METERS

500 1,000 FEET

0 100

0

200

66

75

FLOODED AREA

WETLAND AREA

WATER-TABLE CONTOUR – Contour interval

1 and 0.5 feet, datum NGVD 29. Hachures

indicate depression

WELL LOCATION AND INDEX NUMBER – Number

refers to table 3
58 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 38 (top). Daily augmentation volume 

and flooded area in W-5 Augmented 

Cypress wetland during the augmentation 

experiment.

Figure 39 (middle). Response of the water 

table below W-5 Augmented Cypress 

wetland to augmentation. Well index 

numbers refer to table 3 and figure 37.

Figure 40 (bottom). Daily linear leakage 

rate and flooded area in W-5 Augmented 

Cypress wetland during the augmentation 

experiment.

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

Daily augmentation volume

Daily average flooded area

F

F

looded area 1

looded area 2

DAILY AUGMENTATION VOLUME, IN CUBIC FEET

FLOODED AREA, IN ACRES

5/10/2004

5/12/2004

5/14/2004

5/16/2004

5/18/2004

5/20/2004

5/22/2004

5/24/2004

5/26/2004

5/28/2004

5/30/2004

6/1/2004

72

70

68

66

64

62

MAY 3

MAY 7

MAY 11

MAY 15

MAY 19

MAY 23

MAY 27

MAY 31

JUNE 4

ELEVATION, IN FEET ABOVE NGVD 29

#80 (W-5 Center Well)

#74 #78

#75 #77

#76

#71

Augmentation

begins

Wetland bottom elevation

Water levels

before

augmentation

#82 (Upper Floridan aquifer)

9.0

7.5

6.0

4.5

3.0

1.5

0

3.0

2.5

2.0

1.5

1.0

0.5

0

DAILY LINEAR LEAKAGE RATE, IN INCHES PER DAY

FLOODED AREA, IN ACRES

5/11/2004

5/13/2004

5/15/2004

5/17/2004

5/19/2004

5/21/2004

5/23/2004

5/25/2004

5/27/2004

5/29/2004

5/31/2004

Daily linear leakage rate

Daily average flooded area

Flooded area 1

Flooded area 2

6/1/2004
Wetland Water Budgets 59

Runoff to Wetlands

Daily water-budget results provided insight into the 

importance of runoff on the hydrology of isolated wetlands. 

Runoff here refers to the rainfall that flows off of the surrounding 

upland and into the wetland, rather than water flowing out of 

the wetland. At 8 out of the 10 wetlands, some fraction of the 

water-budget days produced positive residual terms that were 

representative of runoff. Most, but not all, days with a positive 

residual term also had rainfall, whereas most days with a negative residual term did not (table 4). At S‐68 Natural Cypress, for 

example, the 331 days that had negative residual values (equated 

to leakage) experienced a total of only 4.55 in. of rainfall, 

whereas the 121 days with positive residual values interpreted 

as runoff experienced 41.08 in. of rainfall (table 4). The positive 

residual values, which may at times include a small amount of 

ground-water inflow, represent the daily runoff volumes to the 

wetland that exceeded the daily leakage loss.

The two augmented cypress wetlands had far fewer days 

with positive residual values than the unaugmented wetlands. In 

addition, at augmented wetlands, a “runoff day” was associated 

with more rainfall than the runoff days computed for natural 

wetlands (table 4). This result probably reflects the greater 

amount of rainfall required to generate runoff at wetlands where 

the water table was both lowered by pumping and lower than the 

wetland water level. Moreover, at augmented sites, only days 

with substantial rainfall would generate enough runoff and other 

inflow to exceed the typically large leakage losses and generate 

a positive residual term (eq. 2). For example, no positive residual 

terms occurred at either of the augmented marshes. Days with 

no rainfall, but with apparent runoff (positive residual term) had 

an irregular distribution in the record and the associated runoff 

amounts were small. These small positive residuals are considered to be an artifact of measurement errors.

The contribution of runoff to isolated wetlands also was 

evident in the relation between daily rainfall volume and the 

daily change in wetland volume. Absent other effects, the 

increase in wetland volume on a day with rainfall should equal 

the daily rainfall volume, creating a 1:1 ratio between the 

variables. At the six unaugmented wetlands, the slope of the 

regression line relating these variables was substantially greater 

than 1 (table 6). For example, at S‐68 Natural Cypress, the 

best-fit line indicated the change in daily wetland volume was 

1.74 times the daily rainfall volume. At other wetlands, slopes 

were 1.26 and 1.33 at HRSP Natural Marsh and W‐29 Impaired 

Marsh, respectively, and 2.45 at W‐19 Impaired Cypress 

(table 6). Slopes were greater in the cypress wetlands than the 

marshes, probably because the higher rainfall and ground-water 

levels during the cypress period enhanced runoff. W‐19 Impaired 

Cypress had the highest runoff ratio of all the cypress wetlands, 

perhaps because its ground-water flow-through setting favored 

runoff because the water table was above the wetland stage and 

closer to land surface on one side of the wetland (Hernandez and 

others, 2003).

Runoff was a substantial part of the hydrologic budget of all 

of the unaugmented wetlands and at least two of the augmented 

wetlands. The runoff at each wetland (during runoff days only) 

was compared to the direct rainfall received on those days to 

help determine the relative importance of the two processes. 

At the unaugmented (natural and impaired) marshes, runoff 

contributed additional water equal to 45 to 80 percent of the 

rainfall volume entering the wetland (table 7). At the natural 

Table 6. Regression results relating the daily rainfall volume to the 

daily change in wetland volume at the unaugmented wetlands.

[Results are limited to days when wetland stage was below the wetland 

perimeter. Days with streamflows into wetlands were not included in the 

analysis but would be expected to greatly increase the slope between rainfall 

volume and change in wetland volume. Slope of the best fit line relating 

daily rainfall volume to daily change in wetland volume for the unaugmented 

wetlands. Correlation coefficient is R2 value of a best fit line through the data 

with non-zero intercept]

Wetland

group and/

or type

Wetland name Slope1 Correlation 

coefficient

Unaugmented 

Marsh

GS Natural Marsh 1.49 0.95

HRSP Natural Marsh 1.26 0.90

W-29 Impaired Marsh 1.33 0.94

Cypress 

GS Natural Cypress 1.90 0.80

S-68 Natural Cypress 1.74 0.89

W-19 Impaired Cypress 2.45 0.77

1

Slopes exceed 1.0 due to the contribution of runoff to the wetland volume. 

Table 7. The volume ratio of runoff to rainfall in the study wetlands.

Wetland

group and 

type

Wetland 

name 

Volume ratio 

of runoff 

to rainfall

Augmented

Duck Pond Augmented Marsh No data

W-3 Augmented Marsh No data

S-63 Augmented Cypress 0.67

W-5 Augmented Cypress 0.96

Unaugmented

Marsh

GS Natural Marsh 0.80

HRSP Natural Marsh 0.69

W-29 Impaired Marsh 0.45

Cypress 

GS Natural Cypress 1.14

S-68 Natural Cypress 1.05

W-19 Impaired Cypress 1.82
60 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

and impaired cypress wetlands, the runoff volume exceeded 

rainfall. The difference between the marsh and cypress 

wetland volume ratios probably reflects the preferential runoff 

conditions during the wetter cypress period. Estimates of the 

runoff contribution to both the marsh and cypress wetlands are 

conservative, because the positive residual term representing 

runoff has been reduced by the leakage losses. However, 

runoff was an important part of the water budget for both 

wetland types (table 7).

The water budgets of the isolated wetlands provide a 

conservative estimate of the importance of runoff processes 

because they quantify runoff only until the wetland stage 

reaches the wetland perimeter. As wetland stage rises above 

the perimeter, and water-table elevations in the upland areas 

approach land surface, less rainfall would be expected to 

infiltrate in the surrounding basin, and the relative contribution of runoff from rainfall would increase. In this analysis, 

for example, water-budget calculations for all of the cypress 

wetlands were interrupted when the wetlands flooded beyond 

their perimeters. All five cypress wetlands generated an 

outflow stream during parts of the study, and all except 

W‐5 Augmented Cypress received stream inflow from a 

neighboring wetland. 

The transition from isolated cypress wetlands into a chain 

of streaming wetlands is the culmination of the wet season 

response for cypress-pine flatwood wetlands in Florida (Ewel 

and Odum, 1984). This transition does not occur every year, 

however, and its frequency as well as the requisite climate and 

ground-water conditions for it to occur are not well described. 

When this condition does occur, cumulative runoff from the 

linked basins can be estimated by gaging streamflow at a 

downstream location in the watershed (Sun and others, 2002). 

No instrumentation is in place to gage the periodic outflows 

from the basins containing the 10 isolated wetlands in this 

study. Gaging these flows would greatly improve current 

understanding of runoff processes in wetland basins.

The size of the catchment generating runoff to wetlands 

varies in different geologic settings (Riekerk and Korhnak, 

1992, 2000; O’Driscoll and Parizek, 2003) and for different 

rainfall and antecedent soil moisture conditions (Gerla, 1992; 

Hernandez and others, 2003). Riekerk and Korhnak (2000) 

estimated it to be 2 to 3 times larger than the vegetative 

wetland area of cypress wetlands in north-central Florida. 

Typical catchment sizes for isolated wetlands in the mantled 

karst terrain of Florida are not well understood; however, 

runoff results of this study were used to infer their minimum 

sizes. For the runoff and rainfall contributions to an isolated 

wetland to be equal, for example, the catchment would need to 

be equivalent in size to the flooded area, and all of the rainfall 

on the catchment would have to run off. If perfectly efficient 

at generating runoff, the catchment for a geometrically circular 

wetland with 2 acres of flooded area would extend into the 

uplands about 70 ft. If the runoff efficiency were 25 percent, 

with 75 percent lost to infiltration, the catchment would 

need to be four times the size of the flooded area, and the 

catchment radius would extend onshore about 205 ft. These 

radial distances, or other ones determined using different 

assumptions, are conceptualized, but emphasize the linkage 

between wetlands and the surrounding uplands contributing 

runoff to each wetland (Taylor and others, 2007). 

All of the wetlands in this study were surrounded by 

relatively undisturbed uplands. For wetlands outside well 

fields, parks, and wildlife management areas, however, 

land-use changes are common within the distances described 

here. For example, 30 ft is the recommended setback distance 

to buffer wetlands from land development in Hillsborough 

County (Hillsborough County Environmental Protection 

Commission, 2006), whereas Florida State law requires a 

buffer with a minimum width of 15 ft and average width of 

25 ft (Florida Legislature, 2007). Further research is needed to 

establish a scientific basis for decisions related to the creation 

and maintenance of buffer zones. Runoff estimates in this 

study reinforce the importance of preserving the linkages 

between wetlands and surrounding uplands to sustain natural 

wetland hydrology. 

Overview of Wetland Water Budgets

The wetland water-budget approach, which is based 

on a population of daily residual values, permits a comparative analysis of leakage from different types and groups of 

wetlands. Linear leakage rates were shown to be time dependent upon the climate and hydrogeologic conditions during 

the water-budget period. Combining wetland leakage rates 

with the vertical head differences at each wetland was pivotal 

to understanding leakage losses from these wetlands, and 

results indicate it may be fundamental to properly interpreting 

water budgets for other wetlands in the mantled karst terrain 

of Florida.

Median linear leakage rates for the six unaugmented 

wetlands ranged from 0.07 to 0.26 in/d, and were similar to 

the average daily leakage rates calculated for unaugmented 

lakes in central Florida. Sacks and others (1998) described 

leakage losses, ranging from 0.046 to 0.23 in/d (17-85 in/yr) 

in 10 lakes in ridge areas of central Florida, using an approach 

that combined water and isotope mass-balances. Lake leakage 

rates toward the lower end of this range, 0.048 to 0.079 in/d 

(17.5-29 in/yr), were computed for Lake Lucerne and Lake 

Starr, two lake basins in central Florida analyzed using water 

budgets and numerical ground-water flow modeling (Lee and 

Swancar, 1997; Swancar and Lee, 2003). 

The four augmented wetlands resembled augmented 

lakes in central Florida by displaying higher leakage rates 

and a wider range of leakage rates than their unaugmented 

counterparts. For example, Round Lake, an augmented 

11-acre lake adjacent to a municipal well field in Hillsborough 

County, had an average daily leakage rate of 0.5 in/d (182 

in/yr average, 153-225 in/yr range) (Metz and Sacks, 2002), a 

rate comparable to the lowest leakage rates in the augmented 

wetlands. The greatest wetland leakage rate measured in this 

study at Duck Pond Augmented Marsh was about 5 times 
Wetland Water Budgets 61

greater than the lowest leakage rate. In contrast, leakage from 

Triangle Lake and Monsee Pond, two augmented lakes located 

near Cross Bar Ranch Well Field, were 2 and 17 times greater, 

respectively, than the leakage rate computed for augmented 

Round Lake (Biological Research Associates, Inc., and SDI 

Environmental Services, Inc., 2001).

Leakance coefficients derived for the study wetlands 

indicate that marshes generally were underlain by less 

conductive geologic material than cypress wetlands. 

The slower leakage from the unaugmented marshes compared 

to unaugmented cypress wetlands was consistent with the 

flooding and geochemical evidence described later for the 

two wetland types. The result could be an artifact of the small 

sample size. If not, however, the mechanism responsible for 

this fundamental difference is unclear. One possibility is that 

the roots of cypress trees may penetrate and disrupt the lower 

permeability, clay-rich layers below cypress wetlands making 

cypress wetlands leakier than marshes. 

The distance of the potentiometric surface of the Upper 

Floridan aquifer below the wetland bottom was indicative 

of the hydrologic status of the wetland. The potentiometric 

surface of the Upper Floridan aquifer was generally within 

5 ft of the bottom elevation of the two natural marshes in this 

study, and was higher than the bottom elevation during some 

period each year. In contrast, the potentiometric surface ranged 

from about 8 to 30 ft below the impaired and augmented 

marshes and never approached the bottom elevation of the 

wetlands. If the proximity of the potentiometric surface to the 

bottom of the natural marshes is a characteristic of natural 

conditions in this area, then the two impaired wetlands and 

one augmented wetland on the Cypress Creek Well Field 

experienced natural ground-water conditions during the 

wet 2003-04 study period when well-field pumping was 

greatly reduced. Ground-water pumping was not reduced at 

Starkey Well Field during the same period, and probably for 

this reason the characteristic distance was exceeded at the 

natural wetland on this well field. The median potentiometric 

surface was typically within 7 ft of the bottom of S‐68 Natural 

Cypress, and never rose above the wetland bottom.

The water-budget approach used in this study, which 

quantified the daily change in wetland volume and area, 

provided a means to evaluate the minimum runoff to the 

isolated wetlands. At a minimum, runoff contributed from 

half (45 percent) to twice (182 percent) as much water as 

direct rainfall at individual wetlands, and indicated the scale 

of the surrounding catchment. When the isolated wetlands 

in this study began to connect with neighboring wetlands 

through outflow streams, however, runoff processes could not 

be quantified for the expanded watershed. Quantifying these 

ephemeral stream flows would further the understanding of 

the hydrology of isolated wetlands as well as the hydrology 

of downgradient rivers that receive the outflow from 

these watersheds. 
62 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
Surface water in the isolated wetlands of west-central Florida is 

composed of rainfall, surface runoff, and ground-water inflow from the 

surficial aquifer. The hydrologic setting and interactions between ground 

water and surface water influence water quality in the wetlands, as well 

as ground-water geochemistry near the wetlands (LaBaugh and others, 

1987). When anthropogenic activities such as ground-water withdrawal 

and wetland augmentation are superimposed on the landscape, the 

direction and rate of surface- and ground-water movement are altered. 

Consequently, wetland water quality and the geochemistry of wetland 

basins may change measurably. These changes affect the biota in 

wetlands, and they also can be used to describe and predict ground-water 

flow patterns in wetland basins.

Water-Quality and Geochemical Methods

Surface-water samples (1.3-L subsurface grab samples) were 

collected at three widely spaced locations in each of the 10 wetlands 

quarterly if the wetlands were not dry. The grab samples from each 

wetland were composited into a 4-L container and chilled. Composited 

water samples were processed using standard USGS methods described 

in Wilde and others (1998), and sent to the USGS Water Quality 

Laboratory in Ocala, Florida, for analysis of major ions and nutrients. 

Quality-assurance samples were collected for about 10 percent of the 

samples, including duplicate samples and field-blank samples. Field 

properties (water temperature, pH, specific conductance, and dissolved 

oxygen concentration) were measured using standard USGS methods at 

the same three locations on each sampling date with a multiparameter 

probe and stirring assembly. Ground-water samples were collected in 

seven wetland basins to describe chemical characteristics in the shallow 

ground water surrounding the wetlands. These water-quality data were 

Wetland Water Quality and Geochemistry of Wetland 

Basins
64 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

then used to help determine ground-water flow patterns in the 

basins surrounding the wetlands. Ground water was sampled 

semiannually (during wet and dry periods) from 6 to 12 

selected monitoring wells in the surficial aquifer around each 

wetland. Marshes were sampled during 2000-02, and cypress 

wetlands were sampled during 2003-04 (fig. 2). In addition, 

water from the Upper Floridan aquifer used to augment 

wetlands was sampled concurrently. 

Standard USGS protocols were used to collect groundwater and quality-assurance samples (Wilde and others, 1998). 

Surficial aquifer samples were collected using a peristaltic 

pump. Three casing volumes were removed from each 

monitoring well, and after field properties (temperature, pH, 

dissolved oxygen, and specific conductance) stabilized, the 

water sample was collected. For low-yield wells, the wells were 

pumped dry and then sampled the following day. Augmentation 

water was collected as a grab sample from the augmentation 

outflow pipe. The USGS laboratory in Ocala, Florida, analyzed 

ground-water samples for concentrations of major ions and 

nutrients. Results for surface and ground water are available in 

the USGS water data reports for southwest Florida (Kane and 

Fletcher, 2002; Kane and others, 2003; Kane, 2004a,b) and 

from the USGS National Water Information System (NWIS) 

database at http://waterdata.usgs.gov/nwis.

Differences between water-quality parameters for different 

groups and types of wetlands were described statistically using 

the Wilcoxon-Mann-Whitney two-sided test and visually using 

box plots. The Wilcoxon-Mann-Whitney test was chosen for 

statistical analysis because most water-quality parameters were 

not normally distributed, and this non-parametric test does 

not assume that the data are drawn from a given probability 

distribution. For the calculation of median concentrations of 

the various forms of nitrogen and phosphorus, values below the 

reporting limits were set to the reporting limit.

Stable isotope samples were used to help determine flow 

patterns in the wetland basins. In March 2004, all wetland 

surface waters were sampled for the stable isotopes deuterium 

(

2

H or D) and oxygen-18 (18O). Unfiltered water samples were 

collected in glass bottles with polyseal caps for isotope analysis. Ground-water samples for analysis of the stable isotopes 

deuterium and 18O were collected at two wetland basins. All 

isotope samples were analyzed by the USGS Stable Isotope 

Laboratory in Reston, Virginia (isotope information available at http://isotopes.usgs.gov/). Stable isotope abundance 

is expressed as the ratio of the two isotopes in the sample 

(

2

H/1H or 18O/16O) compared to the same ratio in an international standard, using the delta notation (δ) as the unit of 

measurement (parts per thousand, or per mil) (Sacks, 2002).

Water-Quality Constituents

In this study, water-quality constituents of interest in the 

wetlands include pH, specific conductance, major ions, alkalinity, dissolved organic carbon, nutrients, and stable isotopes. 

These constituents are of interest either because they affect the 

biotic community, or because they can be used to indicate the 

direction and magnitude of surface- and ground-water flow in 

the wetland basins. Radium-226 also was analyzed in water 

and sediments at the wetlands (226Ra results are summarized 

in the Wetland Hydrogeologic Setting section of the report). 

Water-quality comparisons primarily are made between groups 

of wetlands (natural, impaired, and augmented), although 

some comparison are made between types of wetlands 

(marshes and cypress). For some comparisons, natural and 

impaired wetlands were grouped together as “unaugmented 

wetlands,” and collectively compared to augmented wetlands.

Field Properties and Major Ions

The six natural and impaired marsh and cypress wetlands 

in this study receive the majority of their hydrologic input 

from rainfall and runoff from undisturbed uplands. Water 

in these wetlands is dilute and poorly buffered (fig. 41). 

The median specific conductance in these six wetlands was 

45 μS/cm, median acid neutralizing capacity (ANC) was 

1.2 mg/L as calcium carbonate, and the pH was relatively low 

(median 4.5, table 8). The low pH originates, in part, from 

humic substances released by the slow decomposition of plant 

material, and wetland water typically is stained by organic 

compounds. Median concentrations of all major ions were low, 

typically less than 5 mg/L. Water quality in W‐29 Impaired 

Marsh was similar to that of the four natural wetlands. 

W‐19 Impaired Cypress, however, had a somewhat higher 

median pH (6.0), calcium concentration (12.0 mg/L) and ANC 

(18 mg/L as calcium carbonate) than the four natural wetlands. 

Although rainfall water quality was not assessed in this study, 

studies in north-central Florida (Riekerk and Korhnak, 1992) 

indicate that rainfall pH averaged 4.8 over an 11-year period. 

Therefore, pH at the natural sites and W‐29 Impaired Marsh 

was similar to that of rainfall. The higher pH at W‐19 Impaired 

Cypress may indicate ground-water inflow to the wetland.

The range of water quality in the natural wetlands in 

this study is similar to water quality reported for natural 

wetlands in other studies in west-central Florida (Dierberg and 

Brezonik, 1984; Berryman and Hennigar, Inc., 1995; 2000). 

Mitsch (1984) and Dierberg and Brezonik (1984) reported 

consistently low pH, low concentrations of cations, low 

alkalinity, and low concentrations of nutrients in short- and 

long-term studies of cypress domes in central Florida.

Augmentation water applied to study wetlands is drawn 

from the Upper Floridan aquifer, which is composed primarily 

of calcite and dolomite. As a consequence, augmented marsh 

and cypress wetlands in this study had a higher median 

specific conductance (346 μS/cm) and pH (7.5) than natural 

and impaired wetlands of either type (table 8). Major ions in 

augmented wetlands were calcium (median 62.8 mg/L) and 

bicarbonate (median 205 mg/L). Major ion concentrations 

and ANC (median 172.5 mg/L as calcium carbonate) also 

were much higher in augmented wetlands than in natural and 

impaired wetlands (fig. 41). These changes in water quality 

related to augmentation are similar to those reported by 

Cooney and Allen (2006) for augmented lakes.
Wetland Water Quality and Geochemistry of Wetland Basins 65

Concentrations of all major ions (including calcium, 

magnesium, potassium, and sulfate), specific conductance, and 

pH were higher in augmented wetlands than in unaugmented 

wetlands (fig. 42); these differences were statistically significant (p < 0.01) based on the Wilcoxon-Mann-Whitney test. 

The higher values in the augmented wetlands are characteristic 

of the augmentation source water from the Upper Floridan 

aquifer. Dissolved oxygen concentrations typically were 

higher in the augmented wetlands, and this difference also was 

statistically significant (p = 0.01). Higher dissolved oxygen 

concentrations may be an artifact of water delivery because 

when augmentation water is added to the wetlands, the position of the augmentation pipe above the water surface and the 

subsequent turbulence results in mixing of air with the water. 

In addition, the residence time of water in the augmented 

wetlands is expected to be less than in unaugmented wetlands, 

and the resulting flushing effect may allow less time for the 

accumulation of water rich in organic compounds that can 

subsequently deplete dissolved oxygen. Dissolved organic 

carbon, iron, and organic nitrogen concentrations were all 

lower in augmented wetlands than in unaugmented wetlands 

(fig. 42) by amounts that were statistically significant 

(p < 0.01). This also is likely due to the low residence times 

of these constituents in the augmented wetlands, as well as 

low respective concentrations in the augmentation water. 

Differences in temperature and ammonia, nitrite plus nitrate, 

and total phosphorous concentrations were not statistically 

significant (p > 0.10 in all cases) between the augmented and 

unaugmented wetlands.

There were no significant differences (p > 0.20 in all 

cases) in major ion concentrations or most field properties 

between wetland types; specifically, between unaugmented 

marsh and cypress wetlands, or between augmented marsh and 

cypress wetlands. These results indicate that the water source, 

rather than the vegetation type, may be the most important 

factor influencing these aspects of wetland water quality. 

Average surface-water temperatures were significantly 

different (p = 0.007) between marshes and cypress wetlands. 

Marsh temperatures typically were higher, most likely because 

marshes are open to sunlight with no tree canopy. Light penetration in forested (cypress) wetlands is much lower (Dierberg 

and Brezonik, 1984). Although field properties in marsh 

wetlands were collected during different years (2000-02) than 

the field properties in cypress wetlands (2002-04), the mean 

sample collection time in marsh wetlands (12:29 p.m.) was 

close to the mean sample collection time in cypress wetlands 

(12:32 p.m.), indicating that time of day was not the cause of 

different average temperatures. Battle and Golladay (2001) 

also reported lower water temperatures in cypress wetlands 

compared to marsh wetlands. 

Specific conductance, chloride, and sodium 

concentrations were higher in unaugmented wetlands in 

the dry season compared to the wet season (data available 

at http://waterdata.usgs.gov/nwis). This pattern indicates 

evaporative concentration in the dry season and dilution by 

rainwater in the wet season. Augmented wetlands generally 

Figure 41. Stiff diagrams for surface water in marsh and 

cypress wetlands.

W-5 Augmented Cypress

MEDIAN WETLAND

SURFACE-WATER CHEMISTRY

0

Milliequivalents per liter Cations Anions

5 5

Chloride

Bicarbonate

Sulfate

Sodium and Potassium

Calcium

Magnesium

GS Natural Marsh

S-63 Augmented Cypress

W-3 Augmented Marsh

W-19 Impaired Cypress

Duck Pond Augmented Marsh

S-68 Natural Cypress

GS Natural Cypress

W-29 Impaired Marsh

HRSP Natural Marsh
66 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Table 8. Range and median water quality for surface water in wetlands. [All units in milligrams per liter unless noted; μS/cm, microsiemens per centimeter at 25 degrees Celsius; Min., minimum value; Max., maximum value; Med., median value; ANC, acid neutralizing capacity; CaCO3, calcium carbonate; N, nitrogen; P, phosphorus; <, less than] Wetland name and number of samples Field specific conductance 

(μS/cm)

Field pH

(standard units)

Calcium,

dissolved

Magnesium,

dissolved

Sodium,

dissolved

Potassium,

dissolved

Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med.

GS Natural Marsh 7 36.0 85.0 45.0 3.9 5.5 4.5 1.4 3.6 2.1 0.6 1.3 0.9 2.2 5.7 2.8 0.2 2.2 0.4HRSP Natural Marsh 9 32.0 75.7 37.3 4.4 5.7 4.8 1.4 6.6 3.3 0.7 1.1 0.8 1.3 6.2 2.4 <0.1 2.9 0.3W-29 Impaired Marsh 3 43.0 67.0 65.0 4.1 5.1 4.4 1.1 5.1 4.1 0.6 2.5 2.1 1.9 3.7 2.0 0.2 1.4 0.2Duck Pond Augmented Marsh 10 240 346 292 7.0 8.0 7.3 42.0 66.3 54.0 2.0 2.5 2.3 2.8 4.1 3.6 0.3 0.9 0.4W-3 Augmented Marsh 8 331 499 433 7.1 7.8 7.4 51.8 85.7 73.5 5.0 8.6 7.0 4.5 5.1 4.7 0.6 2.0 0.7GS Natural Cypress 4 33.3 94.9 51.0 4.1 4.4 4.2 1.3 4.1 1.6 0.6 1.9 0.7 1.3 6.4 2.9 <0.1 0.2 0.2S-68 Natural Cypress 7 29.8 69.8 53.0 4.2 4.8 4.5 0.8 3.7 1.6 0.4 1.1 0.8 <0.1 0.8 0.3 1.4 5.3 4.3W-19 Impaired Cypress 6 45.8 101 59.2 5.7 6.5 6.0 8.6 15.0 12.0 0.8 1.5 0.9 0.9 3.9 1.4 0.2 1.1 0.3S-63 Augmented Cypress 8 47.9 473 464 6.7 7.7 7.5 8.0 86.0 83.0 0.7 5.5 5.3 1.0 5.9 5.8 0.4 1.8 0.9W-5 Augmented Cypress 5 109 494 325 6.5 7.6 7.4 20.0 85.0 57.0 2.0 8.3 5.3 1.6 4.8 3.6 0.6 0.8 0.6

Wetland name

and number 

of samples

Chloride,

Dissolved

Sulfate, 

Dissolved

ANC, total,

as CaCO3

Total nitrogen,

dissolved as N

Total phosphorus,

dissolved as P

Dissolved 

organic carbon

Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med.

GS Natural Marsh 7 3.1 9.3 4.2 <0.2 1.0 0.3 0.2 3.8 1.5 1.7 3.5 2.2 <0.008 0.014 0.008 24.7 50.3 37.0HRSP Natural Marsh 9 1.8 9.0 3.3 <0.2 1.0 0.4 0.0 5.3 2.0 1.1 2.9 1.8 <0.008 0.023 0.011 23.0 45.0 38.0W-29 Impaired Marsh 3 2.9 6.9 3.2 0.3 9.4 7.1 0.0 3.0 0.0 2.1 3.9 2.8 <0.008 0.022 0.012 30.0 41.0 39.0Duck Pond Augmented Marsh 10 5.0 7.1 6.2 0.8 2.4 1.4 111.0 173.8 138.5 0.2 0.5 0.3 <0.008 0.020 0.005 2.3 6.8 4.4W-3 Augmented Marsh 8 7.9 10.0 8.2 4.6 31.0 7.7 152.8 212.3 201.0 0.2 0.5 0.2 0.017 0.030 0.026 2.2 7.2 3.8GS Natural Cypress 4 1.8 12.0 4.1 <0.2 0.6 0.3 0.0 1.5 0.0 1.0 2.2 1.2 <0.008 0.018 0.012 28.0 71.0 39.0S-68 Natural Cypress 7 3.0 13.0 8.8 0.3 2.1 0.6 0.0 2.7 0.0 0.5 2.8 0.9 <0.008 0.020 0.004 14.0 49.0 24.0W-19 Impaired Cypress 6 1.8 11.0 3.1 0.7 1.3 0.9 13.5 23.8 18.0 0.7 3.0 1.2 0.011 0.112 0.020 24.0 49.0 31.0S-63 Augmented Cypress 8 1.4 8.6 8.5 1.3 4.3 2.0 6.9 237.5 214.5 0.2 0.5 0.3 <0.008 0.026 0.012 3.8 11.0 4.6W-5 Augmented Cypress 5 2.2 8.3 6.9 3.6 34.0 9.4 24.7 196.8 144.8 0.2 1.0 0.5 <0.008 0.037 0.020 2.3 32.0 12.0
Wetland Water Quality and Geochemistry of Wetland Basins 67

MAXIMUM VALUE

75 PERCENT

MEDIAN VALUE

25 PERCENT

MINIMUM VALUE

7.5

6.5

5.5

4.5

3.5

2.5

1.5

0.5

SODIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

POTASSIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

EXPLANATION

14

12

10

8

6

4

2

0

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

AUGMENTED

UNAUGMENTED

SULFATE CONCENTRATION,

IN MILLIGRAMS PER LITER

MAGNESIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

45

40

35

30

25

20

15

10

5

0

4.0

3.0

2.0

1.0

0

12

10

8

6

4

2

0

CALCIUM CONCENTRATION,

IN MILLIGRAMS PER LITER

120

100

80

60

40

20

0

ALKALINITY, IN MILLIGRAMS

PER LITER AS CaCO3

280

240

200

160

120

80

40

0

IRON CONCENTRATION,

IN MICROGRAMS PER LITER

2,000

1,800

1,600

1,400

1,200

1,000

800

600

400

200

0

AUGMENTED

UNAUGMENTED

AUGMENTED

UNAUGMENTED

AUGMENTED

UNAUGMENTED

AUGMENTED

UNAUGMENTED

8.5

7.5

6.5

5.5

4.5

3.5

pH

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

16

12

8

4

0

90

80

70

60

50

40

30

20

10

0

600

500

400

300

200

100

0

0.024

0.020

0.016

0.012

0.008

0.004

0

0.10

0.09

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0

DISSOLVED OXYGEN,

IN MILLIGRAMS PER LITER

DISSOLVED ORGANIC CARBON,

IN MILLIGRAMS PER LITER

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER

TOTAL ORGANIC NITROGEN

CONCENTRATION, IN MILLIGRAMS

PER LITER

ORTHOPHOSPHATE CONCENTRATION,

IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS PER LITER

NITRITE CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 42. Box plots of field properties and chemical 

constituents in surface waters of augmented and 

unaugmented (natural and impaired) wetlands.
68 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

showed little seasonal variation in chemical composition. 

However, during one wet period (June 2003), the augmented 

cypress wetlands were diluted considerably by rainwater and 

concentrations of many constituents were similar to those in 

the unaugmented wetlands.

Greater concentrations of iron in unaugmented cypress 

(254-724 mg/L) and marsh (456-536 mg/L) wetlands 

compared to those in augmented wetlands (6-33 mg/L) were 

evident in this study (fig. 42). The higher iron concentrations 

in the unaugmented wetlands are attributed to low pH and the 

abundance of humic materials, both of which are known to 

increase the solubility of iron (Dierberg and Brezonik, 1984).

Nutrients and Dissolved Organic Carbon

Nutrients, including the various forms of nitrogen and 

phosphorus as well as dissolved organic carbon, are important 

constituents in freshwater wetlands because they can influence the growth of algae and aquatic plants. Concentrations 

of several nutrients were significantly different (p < 0.05) 

when natural and impaired marsh and cypress wetlands were 

compared. Organic nitrogen concentrations were higher in 

marshes than in cypress wetlands, whereas orthophosphate 

concentrations were significantly lower in marshes than 

cypress wetlands.

Differences in nutrient concentrations among the groups 

of wetlands in this study were smaller than differences in 

concentrations of some of the major ions, such as calcium or 

bicarbonate. In natural wetlands, the median concentration of 

total nitrogen was 0.9-2.2 mg/L, whereas the median concentration for augmented wetlands was 0.2-0.5 mg/L (table 8). 

Median concentrations of total nitrogen in the impaired 

wetlands ranged from 1.2 mg/L in W‐19 Impaired Cypress 

to 2.8 mg/L in W‐29 Impaired Marsh (table 8). Organic 

nitrogen was the predominant form of nitrogen in all three 

groups of wetlands, and was present in higher concentrations 

in natural and impaired wetlands than in augmented wetlands 

(fig. 42). Nitrate and nitrite concentrations were minimal in 

all wetlands (less than 0.1 mg/L) (fig. 42). Median ammonia 

nitrogen concentrations were similar in natural (0.019 mg/L) 

and augmented (0.022 mg/L) wetlands, and W‐29 Impaired 

Marsh had the highest ammonia nitrogen concentrations in 

the study (0.1 mg/L). Median total phosphorus concentrations were highest at W‐3 Augmented Marsh (0.026 mg/L), 

and concentrations ranged from less than 0.008-0.020 mg/L 

at the other augmented wetlands. Median total phosphorus 

concentrations were generally lower at the natural wetlands 

(less than 0.008-0.012 mg/L) (table 8). Median orthophosphate concentrations were lower at the unaugmented 

wetlands than at the augmented wetlands (fig. 42). Median 

dissolved organic carbon (DOC) concentrations were 

substantially higher in natural (24.0-39.0 mg/L) and impaired 

(31.0-39.0 mg/L) wetlands of both types than in augmented 

wetlands (3.8-12.0 mg/L), reflecting the typically low DOC 

concentrations in augmentation water from the Upper Floridan 

aquifer (fig. 43). 

Differences in concentrations of most nutrients were 

statistically significant between unaugmented and augmented 

wetlands. Organic nitrogen, nitrite, and dissolved organic 

carbon concentrations were all significantly higher in unaugmented wetlands compared to augmented wetlands (p < 0.05) 

(fig. 42). If natural and impaired wetlands were grouped 

together as unaugmented wetlands, then the total phosphorus 

concentration in these wetlands was not significantly different 

from augmented wetlands. However, when only natural and 

augmented wetlands are compared, total phosphorus concentrations were significantly different between these two groups 

of wetlands (table 8). Nitrate, orthophosphate, and total phosphorus concentrations were significantly higher in augmented 

wetlands than in unaugmented wetlands. Cooney and Allen 

(2006) also reported higher total phosphorus concentrations in 

augmented lakes compared to natural lakes. Higher orthophosphate concentrations in augmented wetlands are likely due 

to augmentation with water from the Upper Floridan aquifer 

that has been in contact with overlying Hawthorn Group 

deposits. Higher concentrations of organic nitrogen, DOC, 

and nitrite in natural wetlands may be due to accumulation 

from longer residence times and the absence of flushing found 

in augmented wetlands. Higher concentrations of nitrate in 

augmented wetlands could be attributable to shorter residence 

times and less time for denitrification to occur.

Decomposing leaves and other plant material 

contribute humic substances to wetlands
Wetland Water Quality and Geochemistry of Wetland Basins 69

The nitrogen to phosphorus (N/P) ratio is often used to 

characterize aquatic ecosystems. The N/P ratio in most natural 

and impaired wetlands in this study (median 74) was significantly 

higher than the N/P ratio in augmented wetlands (median 19) 

(fig. 44). The high N/P ratios at W‐29 Impaired Cypress are due 

to the high ammonia nitrogen concentrations (>0.5 mg/L as 

nitrogen) measured in water samples collected in the wetland. 

Plant communities in the natural wetlands may be phosphorus 

limited, a pattern reported by Bedford and others (1999) for a 

large proportion of North American wetlands. The lower N/P 

ratios in augmented wetlands are probably due to the higher 

concentrations of available phosphate in augmentation water.

Stable Isotopes

The stable isotopes deuterium and 18O can be used to 

develop an understanding of residence times of surface water in 

wetlands. When deuterium and 18O are part of a water molecule, 

it takes additional energy to break the bonds in that molecule 

as it moves through the water cycle. Thus, in the process of 

evaporation, the heavier isotopes become enriched in the residual 

wetland water. To qualitatively compare stable isotope data 

from the wetlands in this study, the assumption was made that 

all the wetlands were influenced by similar regional hydrologic 

conditions (for example, rainfall and evaporation rate). Using 

this simplification, an increased proportion of these heavy 

molecules in wetland water indicates an increased evaporation 

effect, and hence, longer residence time. The ratios of deuterium 

and 18O in rainwater in west-central Florida can be plotted and 

used to describe a local meteoric water line, which is similar 

to the global meteoric water line (fig. 45) (Craig, 1961; Sacks, 

2002). As wetland water evaporates, the relative proportions 

of deuterium and 18O shift away from the meteoric water line 

because of differences in the vapor pressures of the isotopes 

(Clark and Fritz, 1997). The farther along the evaporation trend 

line a water sample plots away from the meteoric line, the more 

extensive evaporation is relative to the water body volume. 

With this technique, isotopic evidence can be used to estimate 

how much of the surface water and shallow ground water in and 

around wetlands is of meteoric origin and how much is derived 

from deep ground water (Matheney and Gerla, 1996).

All wetland surface waters were sampled for deuterium 

and 18O in March 2004. The results describe a local evaporation 

trend line (fig. 45), and can be grouped according to wetland type 

(marsh or cypress). The natural marsh wetlands were the most 

isotopically enriched and, therefore, the farthest from the intercept 

of the evaporation trend line with the local meteoric water line. 

Deuterium and 18O values in natural cypress wetlands were closer 

to this intercept, indicating less evaporation relative to wetland 

volume and a shorter residence time than in the marshes. Marshes 

generally undergo more evaporation relative to their volume than 

cypress wetlands because they are more open and the evaporation rate is higher. Some marshes in this part of central Florida 

(particularly the deeper marshes) appear to be inundated a greater 

proportion of time than cypress wetlands; that is, their hydroperiod is longer than that of nearby cypress wetlands (CH2M Hill, 

1996). Those marshes may have a greater potential for evaporation and isotope enrichment than the nearby cypress wetlands.

Augmentation water is a substantial input to the water 

budget of augmented marsh and cypress wetlands because 

these wetlands would typically dry up without it. Augmentation 

waters were isotopically depleted compared to surface water 

in the wetlands (fig. 45). W‐3 Augmented Marsh was the most 

isotopically enriched augmented wetland, and plots far from its 

augmentation water (fig. 45). This indicates that either surface 

water in W‐3 Augmented Marsh has a longer residence time, 

or the marsh may leak less than the other augmented wetlands. 

The other augmented wetlands do not plot as far along the evaporation trend line (fig. 45). S‐63 Augmented Cypress and Duck 

Pond Augmented Marsh were the most isotopically depleted, 

indicating short residence times for water in these wetlands. Duck 

Pond Augmented Marsh was closest in isotopic composition to 

its augmentation source water (fig. 45), implying a minimal 

residence time because wetland water has little opportunity to 

become isotopically enriched through evaporation.

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0 10 20 30 40 50 60 70 80

DISSOLVED ORGANIC CARBON, IN MILLIGRAMS PER LITER

ORGANIC NITROGEN,

IN MILLIGRAMS PER LITER

Augmented wetlands

Natural and impaired cypress wetlands

Natural and impaired marsh wetlands

Figure 43. Organic nitrogen and dissolved organic carbon in wetland surface water.
70 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 44. Box plot of nitrogen to phosphorus ratio in wetland 

surface water.

Figure 45. Delta deuterium and delta 18O in wetland surface 

water and augmentation water.

Basin Geochemistry

The difference in water chemistry between the surficial 

aquifer, Upper Floridan aquifer, and wetland surface water 

was useful for determining ground-water flow patterns and the 

influence of augmentation on basin water quality. For example, 

the surficial aquifer consists mostly of quartz, which is relatively 

insoluble and is recharged by dilute rainwater and wetland 

leakage; therefore, water in this aquifer is not highly mineralized. The Upper Floridan aquifer is more mineralized than the 

surficial aquifer because of the dissolution of calcite and a longer 

residence time, which enriches the water in calcium bicarbonate. 

The surface-water chemistry of the natural and impaired 

wetlands is dilute, indicating recharge by rainwater, whereas 

the water chemistry of the augmented wetlands reflects the 

calcium-bicarbonate waters of the Upper Floridan aquifer. These 

variations in water chemistry between the two aquifers and the 

natural, impaired, and augmented wetlands provide insight into 

the multiple flow processes occurring around the wetlands.

Field Properties and Major Ions

Stiff diagrams were used to compare the wetland surfacewater chemistry with the surrounding shallow ground-water 

chemistry, as well as to compare ground-water chemistry among 

wetland types (fig. 46). Ground-water samples from wells that 

had the lowest and highest ionic strength were used to show 

the variability of surficial aquifer water chemistry around 

each of the seven study wetlands where wells were located. 

Because the seasonal variability of wetland surface-water 

chemistry was minimal, median values were used to compare 

surface-water chemistry with the high and low ionic strength 

ground-water chemistry.

S‐68 Natural Cypress and W‐29 Impaired Marsh had the 

lowest ionic strength ground water surrounding the wetlands 

(fig. 46B and C, respectively). The ions that typically dominated 

the shallow ground water at these sites were dilute concentrations of sodium, chloride, and sulfate. Median values for 

field properties such as pH (4.3-4.5), specific conductance 

(77-144 μS/cm), and alkalinity (1-4.4 mg/L ANC, total, as 

calcium carbonate) were all relatively low (table 9). Ground 

water in these areas is influenced by the low ionic strength input 

from wetland leakage and by recharge from overland flow

and rainwater.

HRSP Natural Marsh and W‐19 Impaired Cypress had 

the most variable water quality in shallow ground water 

surrounding the wetlands, as indicated by minimum and 

maximum values for pH (4.9-7.7), specific conductance 

(101-814 μS/cm), and alkalinity (6.8-401 mg/L ANC, total, as 

calcium carbonate) (table 9). Shallow ground-water chemistry 

for these two sites ranged from low to high ionic strength, and 

reflects the influence of different source waters. The near-shore 

well HRSP LSE has the lowest conductivity, because it is 

influenced by leakage from wetland surface water that has low 

ionic strength (fig. 46A). The higher conductivity ground water 

in wells HRSP USW and W19 L is influenced by the upwelling 

of calcium-bicarbonate enriched water from the Upper Floridan 

aquifer (fig. 46A and D, respectively).

Augmentation altered the shallow ground-water chemistry around the augmented wetlands. Shallow ground water 

surrounding S‐63 Augmented Cypress, Duck Pond Augmented 

Marsh, and W‐5 Augmented Cypress is dominated by relatively 

high ionic strength water enriched in calcium and bicarbonate 

ions. In nearshore wells surrounding these augmented wetlands, 

the following field property maximums indicate the influence 

of the augmentation water: pH (6.5-7.5), specific conductance 

Maximum

75 percent

Median

25 percent

Minimum

500

400

300

200

100

0

NITROGEN/PHOSPHORUS RATIO

GS Natural

Marsh

HRSP Natural

Marsh

GS Natural

Cypress

S-68 Natural

Cypress

W-29 Impaired

Marsh

W-19 Impaired

Cypress

Duck Pond Augmented

Marsh

W-3 Augmented

Marsh

S-63 Augmented

Cypress

W-5 Augmented

Cypress

-4 -3 -2 -1

DELTA DEUTERIUM,

IN PARTS PER THOUSAND

Local evaporation trend

line (Sacks, 2002)

Local meteoric water

line (Sacks, 2002)

0 1 2 3 4

Duck Pond

Augmented Marsh

DELTA O, IN PARTS PER THOUSAND 18

30

25

20

15

10

5

0

-5

-10

-15

-20

W-3 Augmented Marsh

S-63

Augmented

Cypress

Natural and impaired marshes

Natural and impaired cypress wetlands

Augmented marsh

Augmented cypress

Augmentation water

EXPLANATION
Wetland Water Quality and Geochemistry of Wetland Basins 71

Figure 46. Stiff diagrams for surface water and shallow ground water at selected wetlands.

GROUND-WATER FLOW RELATIVE TO THE

WETLAND

WELL NAME AND INDEX NUMBER – Refer

to index number in table 3

MEDIAN WETLAND

SURFACE-WATER CHEMISTRY

LOWEST IONIC STRENGTH

SHALLOW GROUND WATER

HIGHEST IONIC STRENGTH

SHALLOW GROUND WATER

S-68 LW (127)

W-29 B1MNE (34) W-29 IMPAIRED MARSH

W-56 (79)

S-63 AUGMENTED CYPRESS

W-5 AUGMENTED CYPRESS

W-29 B2LNE (40)

W-51 (74)

S-63 MNW (111) S-63 LNW (107)

W-19 I (18) W-19 IMPAIRED CYPRESS W-19 L (22)

HRSP LSE (91) HRSP NATURAL MARSH HRSP USW (96)

Milliequivalents per liter Cations Anions

10 5 5 10

EXPLANATION

0

W-56 (79) W-51 (74)

prior to augmentation experiment

W-5 AUGMENTED CYPRESS

after augmentation experiment

prior to augmentation experiment

after augmentation experiment

5 0 5

Milliequivalents per liter

10

Cations

10

A

B

C

D

E

F

G

H

S-68 LNW (125) S-68 NATURAL CYPRESS

Anions

DUCK POND UNW (10) DUCK POND AUGMENTED MARSH DUCK POND LSW (4)

W-56 (79)

Milliequivalents per liter Cations Anions

10 5 0 5 10

Chloride

Calcium

Magnesium

Bicarbonate

Sulfate

Sodium and Potassium

(431-765 μS/cm), and alkalinity (220-407 mg/L ANC, total, 

as calcium carbonate) (table 9). Because the augmented 

water levels are typically higher than the adjacent 

water table, lateral leakage results in elevated calcium 

and bicarbonate concentrations in the surficial aquifer. 

Calcium and bicarbonate concentrations in the ground water, 

however, progressively decreased with distance away from 

the augmented wetlands (fig. 46). Similar patterns in water 

chemistry were observed in the surficial aquifer in northwest 

Hillsborough County near Round Lake, which also was 

augmented with water from the Upper Floridan aquifer (Metz 

and Sacks, 2002).

Calcium and bicarbonate concentrations in the surficial 

aquifer decreased more rapidly with increasing distance 

from the wetland at S‐63 Augmented Cypress compared to 

at Duck Pond Augmented Marsh. For example, a decrease in 

calcium and bicarbonate concentrations of similar magnitude 

was apparent in water taken from the S‐63 MNW and Duck 

Pond UNW wells, which are about 125 and 250 ft from the 

wetland perimeter, respectively (fig. 46E and F). The more 

abrupt decrease at S‐63 Augmented Cypress may be related to 

subsurface geologic features that create more direct downward 

ground-water flow at that site, and, by comparison, more lateral 

movement of ground water at Duck Pond Augmented Marsh.
72 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Table 9. Range and median water quality for ground water in wetland basins. [All units in milligrams per liter unless noted; μS/cm, microsiemens per centimeter at 25 degrees Celsius; E, estimated; Min., minimum value; Max., maximum value; Med., median value; ANC, acid neutralizing capacity; CaCO3, calcium carbonate; N, nitrogen; NH4

+, ammonium; NO2

–, nitrite; NO3

–, Nitrate; <, less than]

Wetland name 

and number 

of samples

Field specific conductance (μS/cm) Field pH (standard units) Dissolved oxygen Calcium, dissolved Magnesium, dissolved

Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med.

HRSP Natural Marsh 30 101 837 433 4.9 7.7 6.7 0.3 6.0 1.5 8.4 147 81 0.5 4.3 1.2W-29 Impaired Marsh 16 60 279 144 4.0 5.5 4.3 0.5 4.0 1.0 2.7 30 9.5 0.55 9.4 1.4Duck Pond Augmented Marsh 34 55 431 156 4.5 7.0 6.1 0.7 6.0 1.7 0.57 83 20 1.1 3.4 2.2S-68 Natural Cypress 29 51 633 77 4.2 7.2 4.5 0.7 3.6 1.1 1.2 116 2.4 0.29 6.4 1.2W-19 Impaired Cypress 10 145 763 372 5.0 7.2 6.4 0.6 4.4 0.9 7.0 148 66 1.4 9.5 4.0S-63 Augmented Cypress 30 58 671 116 4.5 7.1 5.6 0.3 1.9 0.9 2.3 122 11 0.61 8.9 1.3W-5 Augmented Cypress1 6 207 767 564 5.8 6.5 6.4 0.53 2.0 1.3 36 164 94 3.3 13 7.3W-5 Augmented Cypress2 6 283 765 474 5.9 7.5 6.3 0.7 3.6 1.0 49 140 83 4.1 15 6.5

Wetland name

and number 

of samples

Sodium,

dissolved

Potassium,

dissolved

Chloride,

dissolved

Sulfate, 

dissolved

ANC, total,

as CaCO3

Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med.

HRSP Natural Marsh 30 1.1 26 7.8 <0.1 1.2 0.1 0.2 43 13 0.2 60 18 12.7 299 179W-29 Impaired Marsh 16 0.7 3.9 2.0 0.3 0.7 0.6 1.4 8.0 3.9 8.4 93 18 0.1 18 4.3Duck Pond Augmented Marsh 34 1.6 4.4 3.5 <0.1 3.6 0.4 2.7 9.0 6.1 0.2 8.8 1.6 0 220 85S-68 Natural Cypress 29 1.5 12 5.3 <0.1 1.1 0.1 3.5 18 8.7 0.3 27 7.3 0 328 1W-19 Impaired Cypress 10 1.0 15 9.2 <0.1 0.5 0.2 1.3 40 11 0.2 40 3.2 6.8 401 197S-63 Augmented Cypress 30 2.8 19 5.9 <0.1 1.1 0.3 3.2 21 8.5 0.2 14 3.4 0 316 23W-5 Augmented Cypress1 6 2.4 14 4.3 <0.1 0.4 0.3 0.5 17 6.6 1.5 6.1 2.4 95 407 236W-5 Augmented Cypress2 6 2.4 14 5.3 <0.1 0.4 0.2 0.5 20 7.2 1.0 53 4.2 137 392 208

Wetland name

and number 

of samples

Organic Nitrogen,

dissolved as N

Ammonium (NH4

+),

dissolved as N

Nitrite (NO2

–), 

dissolved as N

Nitrate (NO3

–), 

dissolved as N

Dissolved 

organic carbon

Min. Max. Med. Min. Max. Med. Min. Max. Med. Min. Max. Med. Min Max Med

HRSP Natural Marsh 30 0.10 2.7 0.19 <0.002 0.11 0.01 <0.001 0.01 0.001 <0.001 2.3 0.001 1.3 40 3.0W-29 Impaired Marsh 16 0.30 1.61 0.74 0.007 0.89 0.08 E0.001 0.011 0.006 0.01 17.9 4.29 5.7 23 8.6Duck Pond Augmented Marsh 34 0.18 1.26 0.40 <0.002 2.0 0.12 <0.001 0.01 0.001 <0.001 7.54 0.002 1.2 29 8.6S-68 Natural Cypress 29 0.11 0.90 0.30 0.006 1.1 0.19 <0.001 0.006 0.002 <0.001 0.005 0.002 3.1 29 12W-19 Impaired Cypress 10 0.11 0.64 0.22 0.005 1.7 0.04 <0.001 0.004 0.001 <0.001 0.007 0.002 0.9 23 5.2S-63 Augmented Cypress 30 0.13 1.21 0.32 0.01 0.40 0.06 <0.001 0.004 0.001 <0.001 0.008 0.001 5.2 47 15W-5 Augmented Cypress1 6 0.16 1.51 0.66 0.01 0.32 0.05 <0.001 0.005 0.003 <0.001 0.001 0.001 5.3 44 22W-5 Augmented Cypress2 6 0.16 1.37 0.57 0.01 0.16 0.03 <0.001 0.005 0.003 <0.001 0.055 0.001 5.4 34 17

1 Before augmentation. 2After augmentation.
Wetland Water Quality and Geochemistry of Wetland Basins 73

Nutrients and Dissolved Organic Carbon

Dissolved nitrogen occurs in various forms in ground 

water such as organic nitrogen, ammonium cations (NH4

+), 

and nitrite and nitrate anions (NO2

-

 and NO3

-

) (Hem, 1985). 

The extent and type of nitrogen cycling reactions can determine which form of nitrogen is most prevalent in ground 

water surrounding the wetlands. For example, under aerobic 

conditions, oxidation of organic nitrogen (nitrification) by 

soil bacteria results in the successive conversion to ammonium, followed by nitrite, then nitrate anions. Nitrification 

processes typically occur above the water table in the soil zone 

where oxygen and organic matter are abundant (Freeze and 

Cherry, 1979).

The organic-rich soils surrounding the wetlands are 

reflected in the dominance of organic nitrogen over other 

nitrogen species in ground water (table 9). Organic nitrogen 

was the dominant form of nitrogen present in 71 percent of 

the shallow ground-water samples. Concentrations of organic 

nitrogen ranged from 0.10 to 2.7 mg/L, with a median of 

0.31 mg/L (table 9). When ammonium ion was the dominant form of nitrogen (17 percent of samples), concentrations ranged from 0.17 to 2 mg/L, with a median value of 

0.54 mg/L. When nitrate was the dominant form of nitrogen 

(12 percent of samples), concentrations ranged from 0.49 to 

18 mg/L, with a median value of 10 mg/L.

The ground water underlying W‐29 Impaired Marsh 

had the highest nitrate concentration of all the wetlands 

sampled. During the winter of 2001 at W‐29 Impaired 

Marsh, nitrate concentration ranged from 1 to 18 mg/L and 

the median value was 9 mg/L. A reduction in the nitrate 

concentration was observed in subsequent sampling during 

the spring of 2002 when nitrate concentrations ranged from 

0.01 to 7 mg/L, with a median value of 4 mg/L. Unlike the 

other wetlands, W‐29 Impaired Marsh was the only wetland 

where the majority of wells were located within the wetland 

rather than outside the wetland perimeter. Specifically, these 

wells were situated where partially decomposed plant material accumulates, resulting in a high organic content in the 

wetland bottom.

The DOC data also were used to determine groundwater/surface-water interactions between wetlands and the 

surrounding aquifer (table 9). Decomposition of plant material 

produces organic matter that is rich in carbon and is soluble 

in ground water. The most common category of soil-derived 

organic matter is humic matter, which imparts a dark color 

to the soil and wetland water. The typical range of DOC in 

ground water is <0.2 to 10 mg/L, although in certain environments such as wetlands, DOC concentrations can be much 

higher (Wassenaar, 1990).

A total of 60 percent of the shallow ground-water 

samples from the wetland basins had DOC concentrations 

less than 10 mg/L, and 40 percent ranged from 11 to 47 mg/L. 

These higher DOC concentrations in ground water were 

associated with samples obtained from all wetland types 

(augmented, natural, impaired marsh, and cypress wetlands). 

However, S‐63 Augmented Cypress, S‐68 Natural Cypress, 

and W‐5 Augmented Cypress had the greatest number of wells 

surrounding the wetlands with elevated DOC concentrations. 

These elevated concentrations may be related to the relatively 

high tannin content of soils associated with cypress wetlands.

Stable Isotopes

The naturally occurring stable isotopes deuterium 

and 18O were used to help understand ground-water flow 

paths around the two augmented cypress wetlands and the 

S‐68 Natural Cypress wetland. As residence time increases, 

evaporation causes wetland water to become enriched in 

heavier isotopes, leaving the water with a higher δ value (the 

isotopic composition in delta notation) than rainwater. In 

the shallow ground water, however, less evaporation occurs 

and isotopes are relatively less enriched, or have a lower 

δ value. The relative enrichment (in surface water) or lack of 

enrichment (in ground water) of these isotopes can be used 

to help determine flow paths between the wetlands and the 

surrounding ground-water flow system. For example, isotopically enriched ground water (with a higher δ value) near a 

wetland can indicate areas of wetland leakage, because of the 

enrichment in isotopes from the surface water.

Isotopes were sampled in the ground water surrounding 

W‐5 Augmented Cypress during a period when the wetland 

was not augmented for 79 days. The wetland was dry when 

the samples were collected, although a ground-water mound 

existed underneath the wetland. Analysis results indicate 

that some of the wells sampled (W‐5 wells 2, 3, and 6) plot 

near the lower end of evaporation trend line, which indicates minimal wetland leakage to the ground-water system 

(fig. 47A). Two wells (W‐5 wells 4 and 5) west of the wetland, 

however, did show evidence of wetland leakage, as indicated 

by the enrichment in heavier isotopes. Based on the isotopic 

analysis, the direction of ground-water flow was inferred to be 

westward, toward nearby Cypress Creek.

The wells were sampled again for isotopes about 

1 month after augmentation had resumed at W‐5 Augmented 

Cypress. Sample analyses indicate that ground-water 

flow paths were altered by the augmentation. Most of the 

ground water sampled showed isotopic signatures similar 

to those of the augmentation water. This is especially true 

for W‐5 Augmented Cypress wells 1 and 2 (index wells 

74 and 75) southeast of the wetland (fig. 47B). A karst subsidence feature may lower the water table and increase wetland 

leakage toward this area (fig. 37).

Isotopic data also were compared between an augmented 

wetland (S‐63 Augmented Cypress) and a nearby natural 

wetland (S‐68 Natural Cypress) to understand the differences 

between ground-water flow patterns around the two wetlands. 

For S‐63 Augmented Cypress, the isotopic signatures for 

surface water, augmentation water, and the S‐63 LSE well 

were similar (fig. 47C). The wetland leakage is directed to 

the east toward this well, which is located near areas of karst 

subsidence. The similarity in the isotopic signatures of surface 
74 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 47. Delta deuterium and delta 18O in wetland surface water, shallow ground water, and augmentation water from the 

Upper Floridan aquifer at W-5 Augmented Cypress, S-63 Augmented Cypress, and S-68 Natural Cypress.

LOCAL METEORIC WATER LINE (Sacks, 2002)

LOCAL EVAPORATION TREND LINE (Sacks, 2002)

SHALLOW GROUND WATER WELL AND

NUMBER—Parenthetic number refers to index

number in table 3

WETLAND SURFACE WATER

AUGMENTATION FROM THE UPPER FLORIDAN

AQUIFER

-3

DELTA DEUTERIUM, IN PER MIL

5

0

-5

-10

-15

-20

DELTA O, IN PER MIL 18

W-5 no. 1 well (74)

W-5 no. 2

well (75)

USE well (119)

LNW well (125)

UNW well

(132)

EXPLANATION

MNW well

(111)

LSE well

(108)

W-5 no. 6 well (79)

W-5 no. 3

well (76)

W-5 no. 2 well (75)

W-5 no. 4 well (77)

W-5 no. 5

well (78)

W-5 no. 3 well (76)

W-5 no. 5

well (78)

W-5 no. 6

well (79)

W-5 no. 4

well (77)

LNW#2 well

(107)

UNW well (133)

MNW well (111)

UMSE well (115)

LSW well (109)

LNE well

(105)

USE well (119)

MSW well (114)

LSE well (108)

UNE well (116)

(A) W-5 Augmented Cypress prior to augmentation

experiment

-4 -2 -1 0 1 -3

5

0

-5

-10

-15

-20

-4 -2 -1 0 1

(B) W-5 Augmented Cypress after augmentation

experiment

-3

5

0

-5

-10

-15

-20

(C) S-63 Augmented Cypress

-4 -2 -1 0 1 -3

5

0

-5

-10

-15

-20

-4 -2 -1 0 1

(D) S-68 Natural Cypress

DELTA DEUTERIUM, IN PER MIL

DELTA O, IN PER MIL 18
Wetland Water Quality and Geochemistry of Wetland Basins 75

water, augmentation water, and shallow ground water also 

may indicate the wetland is augmented, in part, by recirculated 

wetland water that has returned to the Upper Floridan aquifer. 

This recirculation pattern also was evident in isotopic data 

from lakes augmented with ground water from the Upper 

Floridan aquifer (Metz and Sacks, 2002). Two other wells 

(S‐63 LNW 2 and S‐63 USE) also show the influence of 

wetland leakage but not as clearly as the LSE well (fig. 47C).

Isotopic data for six out of eight S‐68 Natural Cypress 

wells plot near the lower end of the evaporation trend line, 

which indicates minimal wetland leakage to the groundwater system (fig. 47D). Samples were collected during the 

dry season when water levels were low in the wetland and 

the surrounding ground-water system. Two wells (LNW 

and UNW) northwest of S‐68 Natural Cypress did show 

evidence of wetland leakage as indicated by the enrichment 

in heavier isotopes. This result implied that ground water was 

flowing to the northwest and generally toward nearby Cross 

Cypress Branch.

Overview of Water Quality and Geochemistry

Water quality in the unaugmented wetlands is similar 

to that of the rainwater from which it is primarily derived—

dilute, acidic, poorly buffered, and lacking in nutrients. 

Augmented wetlands had higher major ion concentrations, 

specific conductance, pH, and alkalinity, reflecting the 

chemistry of the Upper Floridan aquifer, which is the source 

of the augmentation water. Dissolved organic carbon, iron, and 

organic nitrogen concentrations were lower in augmented than 

in unaugmented wetlands, most likely due to the low residence 

time as well as the low concentrations in augmentation water. 

Differences in temperature, and ammonia, nitrite plus nitrate, 

and total phosphorus concentrations were not significantly 

different between augmented and unaugmented wetlands. 

Specific conductance, chloride, and sodium concentrations 

were higher in unaugmented wetlands in the dry season than 

in the wet season, because they are influenced by evaporative concentration and dilution, respectively, but augmented 

wetlands generally showed little seasonal variation in 

chemical composition. 

Major ion concentrations and most field properties were 

similar between marsh and cypress wetlands of the same type; 

that is, between unaugmented marsh and cypress wetlands, or 

between augmented marsh and cypress wetlands. These results 

indicate that the water source, and not the vegetation type, 

may be the most important factor influencing these aspects 

of wetland water quality. However, water temperatures in 

marshes of all types tended to be higher than water temperatures in cypress wetlands, because tree cover in cypress 

wetlands limits light penetration. Because they are more 

open systems, marshes undergo more evaporation relative to 

their volume than cypress wetlands, as indicated by analysis 

of stable isotopes. Stable isotope ratios indicate that cypress 

wetlands may have shorter residence times compared to 

marsh wetlands. The two augmented cypress wetlands had the 

shortest residence times of all the wetlands in the study, based 

on analysis of stable isotopes. 

Wetland leakage influenced the shallow ground-water 

quality near the augmented and unaugmented wetlands. 

Unaugmented wetlands S‐68 Natural Cypress and 

W‐29 Impaired Marsh had low ionic strength ground water 

surrounding the wetlands, because the surficial aquifer in their 

basins is influenced primarily by wetland leakage and recharge 

from rainwater. In contrast, leakage from HRSP Natural Marsh 

diluted the carbonate-rich ground water that characterizes the 

surficial aquifer in this area. In W‐19 Impaired Cypress basin, 

the influence of shallow ground water with a relatively high 

ionic strength periodically dominated the low ionic strength 

wetland surface water that leaked into the surrounding basin.

When wetlands are augmented with calcium-bicarbonate 

enriched water from the Upper Floridan aquifer, the 

surrounding ground-water chemistry is altered. Shallow 

ground water surrounding the augmented marsh and 

cypress wetlands was dominated by high ionic strength 

water derived from lateral outflow and downward leakage 

from the augmented wetlands. However, calcium and 

bicarbonate concentrations in shallow ground water progressively decreased with distance away from augmented 

wetlands, and the rates of decrease are related to subsurface 

geologic features.

The influence of wetland water chemistry on the 

shallow ground water in wetland basins is also evident in 

other constituents. The organic rich soils surrounding the 

wetlands and covering the wetland bottom are reflected by 

the dominance of organic nitrogen over other nitrogen species 

in the shallow ground water. Higher DOC concentrations in 

shallow ground water near the wetlands are derived from the 

decomposition of wetland vegetation, and are associated with 

all wetland types and groups.
76 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
The flooding patterns of wetlands over time can provide a more 

informative and useful indication of their hydrologic and ecological 

condition than water levels alone (Haag and others, 2005; Lee and 

Haag, 2006). In the northern Tampa Bay area, for example, wetland 

water levels are routinely monitored in several hundred wetlands. 

The hydrologic condition and regulatory status of a subset of these 

wetlands is determined by comparing their measured water levels to a 

minimum target water level established for each wetland (Southwest 

Florida Water Management District, 1999b). The benefit of this 

approach can be increased by combining wetland water levels with 

bathymetric mapping results to determine how much of the total 

wetland area is being flooded over time. The size of the flooded area, 

when expressed as a percentage of a total wetland area, is a quantitative 

measure that is independent of the size of the wetland and is directly 

comparable to other wetlands. Describing the size of the flooded areas 

of wetlands provides a “landscape perspective” to wetland assessment and allows wetlands to be described collectively as a regional 

surface-water resource (Lee and Haag, 2006).

The flooded areas of 10 wetlands were examined in detail over 

the data-collection period, and then over a longer “historical” period 

of up to 16 years using historical stage data. Short-term variability in 

the size of the flooded area is examined by describing and comparing 

the weekly average flooded areas in the 10 wetlands over several 

years. Stage data routinely collected over the past 8-16 years are then 

used with bathymetric data to describe the historical average flooding 

characteristics of the 10 wetlands. Finally, the seasonal flooding 

regime of each wetland is characterized using the historical monthly 

average flooded area. The results of each approach are compared for 

the natural, augmented, and impaired groups of wetlands, and for the 

marsh and cypress wetland types.

Wetland Flooding Characteristics
78 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Methods of Flooded Area Determination

Bathymetric maps of the 10 wetlands were used to 

determine the size of the inundated area and the water volume 

stored in the study wetlands over a range of stage values. 

The elevation of land surface was surveyed at numerous locations across the wetland, and digital interpolation and contouring 

routines were used to delineate the outline of the flooded area at 

different values of wetland stage. Bathymetric maps and curves 

defining the relation between stage and area, and stage and 

volume, were published in Haag and others (2005). The wetland 

perimeter was delineated using biological indicators or hydric 

soil indicators.

With the exception of W‐3 Augmented Marsh, stage in 

each wetland (reported in feet above NGVD 29) was continuously monitored at a center well located in the deepest part of 

the wetland (table 3). The well casing was slotted above and 

below the ground surface. Consequently, the pressure transducer 

measured stage or ground-water level if the water level was 

above or below the wetland bottom, respectively. 

Bathymetry data and hourly values of wetland stage were 

used to compute the daily and weekly average flooded areas in 

the wetlands. Flooded areas for each wetland were expressed 

as a percentage of the total area of the wetland. Daily stage 

equaled the 12 a.m. stage reading at each site. Continuously 

recorded measurements were checked in the field every 

2 weeks for quality assurance. During site visits, a staff gage 

was read by USGS personnel when wetlands were flooded, 

and the water level was measured in the center well whether 

the wetland was flooded or not. Wetland water-level data for 

this study are available online from the USGS National Water 

Information System database at http://waterdata.usgs.gov/fl/nwis

(U.S. Geological Survey, 2007). 

At W‐3 Augmented Marsh, wetland stage was not 

monitored in the deepest part of the wetland, but instead, closer 

to the perimeter near the historical staff gage. As a result, 

continuous water levels measured in the center well fell slightly 

below land surface when deeper areas of the wetland were still 

inundated. When this occurred, wetland stage was estimated from 

the ground-water levels in the center well. Because the water 

table sloped away from the flooded area of W‐3 Augmented 

Marsh, using the ground-water levels probably slightly underestimates wetland stage and, therefore, the size of the flooded 

area, particularly during the driest periods. This approximation 

however, was considered to have a small affect on the interpretation of the percentage of total wetland area flooded weekly.

The historical stage data used to analyze the flooded area 

in three of the four natural wetlands (GS Natural Marsh, GS 

Natural Cypress, and HRSP Natural Marsh) were collected by 

the Southwest Florida Water Management District (Michael 

Hancock, Southwest Florida Water Management District, written 

commun., 2003). The earliest water-level readings were made 

once or twice a month from staff gages. More recent daily readings were collected by continuous recorders. Historical data at the 

remaining seven wetlands were collected by Tampa Bay Water, 

typically every 2 weeks (Tampa Bay Water, 2000) (table 10).

The saturated soil moisture content in the uppermost foot 

of soil was monitored in the deepest areas of W‐29 Impaired 

Marsh and HRSP Natural Marsh for about 9 months using a 

variant of the time-domain reflectometry approach developed by 

Topp and others (1980). Measurements were made using CS 615 

water content reflectometers with 15-min output to CR10X data 

loggers (Campbell Scientific, Inc., 1996).

Changes in Extent of Flooded Area

Because most isolated freshwater wetlands are shallow, 

the size of their flooded areas changes rapidly when surfacewater levels change. The timing and extent of these changes 

on a yearly or daily basis are not well described in the wetland 

literature, yet understanding the rate of change is informative for studies of both wetland ecology and hydrology. For 

example, monthly measurements of stage may be adequate to 

describe the average annual stage and flooded area in a wetland 

over a long-term period (Shaffer and others, 2000). However, 

monthly measurements of wetland stage can introduce sizeable errors in estimates of monthly average flooded areas, and 

under-represent extremes, such as dry or bank-full conditions, 

that can exist briefly and be missed in monthly or biweekly 

sampling. Accurately documenting extremes, especially the 

length of time that a target water level is exceeded, can require 

more frequent (daily) data collection (Shaffer and others, 2000). 

The weekly flooding regime, based on daily measurements, 

is described herein and compared in natural, augmented, and 

impaired wetland groups. Marshes and cypress wetlands types 

are discussed separately because the two types of wetlands were 

studied sequentially, not concurrently, and rainfall conditions 

differed substantially between the two data-collection periods. 

Periodic water-level readings are made 

from staff gages
Wetland Flooding Characteristics 79

Marshes

The flooded areas of the natural marshes changed 

similarly despite the approximately 20-mi distance between 

their locations within the northern Tampa Bay area 

(fig. 48A-B). The size of the flooded areas at both sites 

changed substantially on a week-to-week basis, and ranged 

from 0 percent (dry) to greater than 100 percent of the total 

wetland area. Flooded area size was relatively constant at each 

marsh for only a small part of the 21-month study period. 

If surface-area fluctuations within a ±10 percent range are 

considered constant, then the weekly average flooded area was 

nearly constant at HRSP Natural Marsh for about 17 weeks 

in the winter and early spring of 2002 (fig. 48A-B). Although 

flooding beyond the wetland perimeter inundated 100 percent 

of the marsh area, the condition was not static because the size 

of the flooded area beyond the perimeter changed.

The flooded areas of the two augmented marshes were 

relatively constant compared to the natural marshes, with 

less weekly variation and less overall range in flooded area 

(fig. 48C-D). The augmented marshes remained flooded 

during both dry seasons (roughly April and May of 2002 and 

2003), while the natural marshes dried out. Water levels in 

W‐3 Augmented Marsh varied the least of all marshes because 

the switch controlling the flow of augmentation water operated 

within a narrow range of stage. When the wetland water level 

dropped below a fixed level, a float switch opened a pipeline 

valve, adding augmentation water until the stage recovered and 

the switch turned off flow. Flow rates into W‐3 Augmented 

Marsh were always sufficiently large to replace the daily water 

losses due to evapotranspiration and leakage. As a result, the 

effects of seasonal differences in climate and leakage were not 

evident in the wetland water levels, and 50 to 70 percent of 

the total wetland surface area stayed inundated throughout the 

21-month study period (fig. 48C).

The flooded area of Duck Pond Augmented Marsh 

contracted and expanded more than W‐3 Augmented 

Marsh during the study (fig. 48D). The daily augmentation flow to Duck Pond Augmented Marsh was relatively 

constant for nearly 2 years (mean = 23,420 ft3/d, standard 

deviation = 1,912 ft3/d). During the drier spring months, 

augmentation did not offset the daily losses due to evaporation 

and leakage, and flooded area became smaller. During the 

wetter summers, stage and flooded area increased because of 

greater rainfall and slower leakage as a result of rising groundwater levels (fig. 48D).

Table 10. Description of stage data used for the historical flooding analyses.

[SWFWMD, Southwest Florida Water Management District; HRSP, Hillsborough River State Park; GS, Green Swamp Wildlife 

Management Area] Group

Wetland Starting

year

Historical 

period

(years)

Measurement frequency Data source

Natural

GS Natural Cypress 1988 16 Daily (Jan 1988–Dec 2003) SWFWMD

S-68 Natural Cypress 1989 15 Monthly (Jan 1989–Jun 2003) 

Biweekly (Jul 2003–Dec 2003)

Tampa Bay Water

HRSP Natural Marsh 1988 16 Monthly (Jan 1988–Oct 1994)

Daily (Sep 1994–Dec 2003)

SWFWMD

GS Natural Marsh 1996 8 Daily (Jan 1996–Dec 2003) SWFWMD

Augmented

Duck Pond Augmented Marsh 1988 16 Monthly (Jan 1988–Sep 1996)

Biweekly (Oct 1996–Dec 2003)

Tampa Bay Water

W-5 Augmented Cypress 1988 16 Monthly (Jan 1988–May 1994)

Biweekly (Jun 1994–Dec 2003)

Tampa Bay Water

W-3 Augmented Marsh 1995 9 Biweekly (Jan 1995–Dec 2003) Tampa Bay Water

S-63 Augmented Cypress 1991 13 Monthly (Jan 1991–Oct 1994)

Biweekly (Nov 1994–Dec 2003)

Tampa Bay Water

Impaired

W-29 Impaired Marsh 1989 15 Monthly (Jan 1989–Oct 1994)

Biweekly (Nov 1994–Dec 2003)

Tampa Bay Water

W-19 Impaired Cypress 1989 15 Monthly (Jan 1989–Oct 1994)

Biweekly (Nov 1994–Dec 2003)

Tampa Bay Water
80 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

HRSP Natural Marsh

100

90

80

70

60

50

40

30

20

10

0

FLOODED AREA, IN PERCENT OF TOTAL WETLAND AREA

GS Natural Marsh

W-29 Impaired Marsh

WEEK

12/12/2000

1/30/20013/20/2001

5/8/2001

6/26/20018/14/200110/2/2001

11/20/2001

1/8/2002

2/26/20024/16/2002

6/4/2002

7/23/20029/10/2002

WEEK

(B)

(A)

W-3 Augmented Marsh

(E)

Duck Pond Augmented Marsh

(C)

(D)

12/12/2000

1/30/20013/20/2001

5/8/2001

6/26/20018/14/200110/2/2001

11/20/2001

1/8/2002

2/26/20024/16/2002

6/4/2002

7/23/20029/10/2002

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

Figure 48. Percentage of the total wetland 

area flooded on average each week in the 

natural, augmented, and impaired marshes 

from December 12, 2000 to September 30, 

2002. Flooded areas beyond 100 percent 

are not shown.

During the same 21-month time period, W‐29 Impaired 

Marsh was usually dry, and periodic flooding inundated 

substantially less area than in the natural marshes (fig. 48E). 

The flooded area inundated 50 percent of the marsh vegetated 

area for 2 weeks during the rainy summer season of 2001 

(July–September). The marsh dried up over the next 5 weeks and 

remained dry until the following summer when flooding covered 

60 percent of the total wetland area. W‐29 Impaired Marsh 

flooded less than the natural marshes, in part because it received 

about 7.5 to 10 in/yr less rainfall during 2001 than the two natural 

marshes (fig. 5). However, it probably flooded less than the 

natural marshes would have with the same amount of rainfall 

because the drier soil conditions at W‐29 Impaired Marsh favored 

infiltration over runoff.

W‐29 Impaired Marsh experienced drier soil conditions than 

HRSP Natural Marsh because the water table of the impaired 

marsh was lower than that of the natural marsh (fig. 49). The soils 

were composed of similar organic-rich sands in both locations. 

During the first 6 months of the study period (prior to May 2002) 

HRSP Natural Marsh was flooded and W‐29 Impaired Marsh was 

dry. The two sites could be directly compared when they both 

dried out for 2 months starting in May 2002 (fig. 49).

At W‐29 Impaired Marsh, the soil moisture content in 

the uppermost foot of soil dropped steeply when the water 

table fell from 1 to 2 ft below the wetland bottom, and then 

dropped steadily with increasing depth (fig. 50). When the 

water-table depth was between 1 and 2 ft, soil moisture 

remained between 0.8 and 0.4 cm3/cm3. A similar relation 
Wetland Flooding Characteristics 81

Cypress Wetlands

Weekly flooding patterns in the natural cypress wetlands 

resembled those of the natural marshes in several respects 

(figs. 48A-B and 51A-B). The natural cypress wetlands 

were nearly full a greater percentage of time than the natural 

marshes because of the wetter climate conditions during 

the cypress monitoring period, particularly in December 

2002. Both natural cypress wetlands remained flooded in 

2003 during late spring, which is usually dry. Following what 

is probably more typical behavior, both wetlands dried out 

during late spring in 2004, and within a few months were 

100 percent flooded by summer rainfall. Because of the 

above-average rainfall and reduced ground-water pumping on 

Cypress Creek Well Field, flooding in W‐19 Impaired Cypress 

was not diminished, but instead resembled flooding in the 

natural cypress wetlands.

The two augmented cypress wetlands did not 

maintain stable flooded areas like the augmented marshes, 

mostly because of changes in the augmentation regimes 

(figs. 48C-D and 51C-D). Instead, flooded area changed 

substantially on a weekly basis at the augmented cypress 

wetlands, which ranged from 0 to 100 percent full. The typical 

augmentation regime in both wetlands called for stage to 

be augmented to a minimum level in both wetlands, and 

augmentation to be shut off if stage rose above a maximum 

target level. However, unplanned extremes in the flooded area 

occurred at both sites.

Most of W‐5 Augmented Cypress flooded in December 

2002 and again in June 2003 because rainfall was well above 

average and augmentation never shut off due to an open flow 

valve. The resulting augmentation rate of about 5,270 ft3/d 

combined with above-average rainfall raised the water level 

above the elevation of a roadside ditch intersecting the 

wetland perimeter (Haag and others, 2005). As a consequence, 

flooding in W‐5 Augmented Cypress resembled the natural 

cypress sites until August 2003, when the augmentation pipeline was manually shut off. With no augmentation, the flooded 

area declined quickly and W‐5 Augmented Cypress dried out 

in 3 months, remaining dry except during two short episodes 

of augmentation (January to March of 2004 and mid-May to 

early June 2004) (fig. 51C). Flooding between May and June 

2004 resulted from the controlled augmentation experiment 

discussed earlier. 

At S‐63 Augmented Cypress, the augmentation was 

designed to follow a regime of target stages that would be 

lowered step-wise during the drier months and raised during 

the wet season (with a total stage range of 0.85 ft) in an effort 

to resemble natural seasonal variation. The actual regime was 

more variable. The weekly flooded area at S‐63 Augmented 

Cypress wetland changed more abruptly than any other 

wetland studied, generally existing in one of three conditions: 0 percent flooded, about 50 percent flooded, or 80 to 

100 percent flooded (fig. 51D). Dry conditions occurred 

when augmentation stopped due to mechanical problems, or 

when the daily augmentation flow was too low to maintain 

11/1/2001

12/1/2001

1/1/2002

2/1/2002

3/1/2002

4/1/2002

5/1/2002

6/1/2002

7/1/2002

8/1/2002

9/1/2002

DAILY AVERAGE SOIL MOISTURE

CONTENT, IN CUBIC CENTIMETER

PER CUBIC CENTIMETER

1.0

0.8

0.6

0.4

0.2

0

HRSP natural marsh

Standing water in HRSP

W-29 impaired marsh

Dry season

difference in

soil moisture

content

DAILY AVERAGE SOIL MOISTURE CONTENT,

IN CUBIC CENTIMETER PER CUBIC CENTIMETER

0

-1

0

1

2

3

4

5

6 0.2 0.4 0.6 0.8 1.0

DEPTH OF 

WATER TABLE BELOW

WETLAND BOTTOM, IN FEET

W-29 IMPAIRED MARSH

Land surface

Figure 49. Soil moisture content in HRSP Natural 

Marsh and W-29 Impaired Marsh during the same 

time period. Soil moisture values of 0.8 or greater 

indicate water is at or above land surface.

Figure 50. The relation between daily average 

soil moisture in the top one foot of soil and 

the daily average water-table depth below 

W-29 Impaired Marsh.

was observed between the water-table depth and soil moisture content at HRSP Natural Marsh. Because the water 

table was never more than 1.75 ft below HRSP Natural Marsh, 

however, soil moisture content remained above 0.4 cm3/cm3

(fig. 49). During this same time, the water table dropped to 

about 5 ft below the deepest part of W‐29 Impaired Marsh, 

and soil moisture fell below 0.2 cm3/cm3. Because the water 

table slopes away from W‐29 Impaired Marsh, the higher areas 

of the wetland bottom are farther above the water table and 

presumably were even drier.
82 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

S-68 Natural Cypress

100

90

80

70

60

50

40

30

20

10

0

W-19 Impaired Cypress

GS Natural Cypress

W-5 Augmented Cypress

S-63 Augmented Cypress 12/11/2002 1/29/2003 3/19/2003 5/7/2003 6/25/2003 8/13/2003

10/1/2003

11/19/2003

1/7/2004

2/25/20044/14/2004

6/2/2004

7/21/2004

12/11/2002

1/29/20033/19/2003

5/7/2003

6/25/20038/13/200310/1/2003

11/19/2003

1/7/2004

2/25/20044/14/2004

6/2/2004

7/21/2004

(A)

(B)

(C)

(D)

(E)

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

FLOODED AREA, IN PERCENT OF TOTAL WETLAND AREA

WEEK

WEEK

Figure 51. Percentage of the total wetland area 

flooded on average each week in the natural, 

augmented, and impaired cypress wetlands 

from December 11, 2002 to July 27, 2004. 

Flooded areas beyond 100 percent of the total 

wetland area are not shown.

Figure 52. Hourly variation in flooded area at S-63 Augmented Cypress from December 24, 2003 

to December 31, 2003.

FLOODED AREA, IN

PERCENT OF

TOTAL AREA

50

40

30

20

10

0

S-63 Augmented Cypress

12/23/2003,

MIDNIGHT

12/24/2003,

MIDNIGHT

12/25/2003,

MIDNIGHT

12/26/2003,

MIDNIGHT

12/27/2003,

MIDNIGHT

12/28/2003,

MIDNIGHT

12/29/2003,

MIDNIGHT

12/30/2003,

MIDNIGHT

12/31/2003,

MIDNIGHT
Wetland Flooding Characteristics 83

flooding. In contrast, large daily rainfall events combined 

with augmentation flooded an area between 80 to 100 percent. 

Augmentation in the absence of substantial rainfall resulted in 

flooding of about 50 percent of the total wetland area.

During certain times of the year, the flooded area 

at S‐63 Augmented Cypress changed on an hourly basis. 

The daily 12 a.m. stage readings indicated that the wetland 

was completely dry for several weeks in late December 

2003 (and April-May 2004). Hourly readings, however, 

showed that augmentation inundated as much as 45 percent of 

the total area during the day, but the water quickly leaked out 

when augmentation stopped, generally leaving the wetland dry 

by midnight (fig. 52). This hourly variation in flooded area 

occurred on repeated occasions during the relatively wet study 

years, and thus, has probably also occurred in other years.

Comparison of Recent and Historical Flooded 

Area Duration Distributions

Tracking wetland flooded area through time yields a 

time series that can be summarized statistically and compared 

to other wetlands. Alternatively, flooding statistics for an 

individual wetland can be compared for different time periods. 

Statistically derived flooded-area duration distributions, 

referred to as flooded-area frequency distributions in Haag 

and others (2005), are used to compare the overall character 

of flooding at the different wetlands. Flooded-area duration 

distributions show the percentages of time that the boundary 

of the flooded area was within different 20-percent intervals 

of the total wetland area (fig. 53). The amount of time spent 

with the boundary of the flooded area in each 20-percent 

interval can be summed to compute the cumulative duration 

of flooding for different areas in the wetland, and can provide 

hydrologic evidence to support observed changes in the 

vegetation (Haag and Lee, 2006).

Flooded-area duration distributions were used to 

characterize the wetland flooding behavior over two time 

periods. For each wetland, the “recent” period covers the study 

period, which ranged in length from 1.7 years to 4 years at the 

10 wetlands (table 4). The “historical” period for each wetland 

begins earlier and extends through the study period (table 10). 

For seven of the wetlands, 15 or 16 years of stage data were 

used. For the other three wetlands, between 8 and 13 years 

of stage data were available. A modified bathymetric map 

of each wetland indicates the shape and size of the flooded 

area for each 20-percent increment of the total wetland area. 

The flooded-area contours were derived from the original 

wetland bathymetric data (app. 5).

The interpretation of long-term average flooding behavior 

can be affected by the length of the historical time period 

used. In this analysis, the annual average rainfall and wellfield pumping were similar over the 8- and 16-year historical 

periods considered. Except during 2003, ground-water withdrawals from the well fields were relatively consistent over 

the shortest and longest historical time periods. From 1988 to 

2002, the monthly average ground-water pumping from the 

11 municipal well fields ranged from 131 to 165 Mgal/d and 

averaged 145 Mgal/d (fig. 6); from 1996 to 2002, it averaged 

149 Mgal/d. In 2003, the final year of the “historical” analysis, 

ground-water withdrawals dropped steeply to 79 Mgal/d. 

Although annual rainfall fluctuated widely over the 16-year 

period, the regional average annual rainfall for the period from 

1988 to 2003 was about average (52.56 in., as noted earlier), 

and was similar to the average rainfall of the first and second 

halves of this period (52.62 in. for 1988-95, and 52.50 in. 

for 1996-2003).

For the recent time period, the flooded-area duration 

distributions were computed from USGS daily values of stage, 

yielding 365 observations of wetland area per year. Historical 

flooded-area duration distributions were based on monthly 

average estimates of wetland area, or 12 observations per 

year, for 8 to 16 years. Monthly averages, in turn, were based 

on the number of evenly spaced observations of stage available each month from agency databases. Stage data collected 

by other agencies were adjusted with small offsets where 

necessary to coincide with USGS elevations (table 2, Haag 

and others, 2005). 

Figure 53. Conceptualized wetland showing the boundary of 

the flooded area located in different 20-percent intervals of the 

total wetland area.

100 percent

wetland

area

EXPLANATION

80

BOUNDARY OF THE FLOODED AREA

AREA CONTOUR – showing the location

of each 20-percent interval of the

total wetland area
84 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Natural Wetlands

The historical flooded-area duration of the four natural 

wetlands provided preliminary insights into the flooding characteristics of natural wetlands in this region of Florida. Either 15 or 

16 years of data were analyzed for three of the natural wetlands. 

The fourth natural wetland, GS Natural Marsh, had the shortest 

record, with only 8 years of data available (table 10). 

The historical flooded-area duration distributions for the 

two natural cypress wetlands had two discernible features. In GS 

Natural Cypress wetland, the largest percentages of time were 

spent with the boundary of the flooded area in two contrasting 

flooded area intervals—one in which 81 to 100 percent of the 

wetland area was flooded, and the other in which 0 to 20 percent 

was flooded (fig. 54A). These contrasting conditions could 

reflect the wetland response to the annually occurring wet and 

dry seasons. GS Natural Cypress was mostly dry more often than 

mostly wet, with 0 to 20 percent flooded about 52 percent of the 

time, and more than 81 percent flooded about 29 percent of the 

time (fig. 54A). The pattern was similar but less pronounced at 

S‐68 Natural Cypress, which was 21 to 40 percent flooded during 

the greatest percentage of the historical period (37 percent), and 

81 to 100 percent flooded during the second greatest percentage 

of the period (29 percent) (fig. 54B, table 11).

The natural cypress wetlands were 81 to 100 percent 

flooded more often during the recent period than the historical 

period. Specifically, the natural cypress wetlands were 

between 81 and 100 percent flooded during more than half of 

the recent period (fig. 54A-B). 

The HRSP Natural Marsh wetland had the same 16-year 

historical period as the natural cypress wetlands. Unlike its 

cypress counterparts, however, HRSP Natural Marsh was 

0 to 20 percent flooded during the smallest percentage of the 

period (fig. 55A). The duration of flooding at this wetland for 

the historical period was relatively evenly divided over the 

other 20-percent increments of the total area.

The HRSP Natural Marsh wetland was drier during the 

recent period than the historical period. Compared to the 

historical period, a smaller percentage of time was spent 61 to 

100 percent flooded during the recent period, and a substantially larger percentage of time was spent 0 to 20 percent 

flooded (fig. 55A).

The 8-year historical data period for GS Natural Marsh 

was about half as long as the historical period for HRSP 

Natural Marsh. GS Natural Marsh was 81 to 100 percent 

flooded the greatest percentage of the historical period 

(about 45 percent), and was 0 to 20 percent flooded less than 

20 percent of the period (fig. 55B).

A cypress wetland when the flooded area is small

Photograph provided by M. Hancock, SWFWMD
Wetland Flooding Characteristics 85

50 METERS

0 150 FEET

0

25 METERS

0 100 FEET

0

FLOODED AREA, IN PERCENT OF TOTAL

WETLAND AREA

0-20

21-40

41-60

61-80

81-100

WETLAND PERIMETER AT 100 PERCENT

INUNDATION

CONTOUR LINE

VEGETATION PLOTS

DEEPEST POINT

STAFF LOCATION

Historical (1988-2003) Historical (1989-2003)

Recent (12/11/02-7/27/04)

100

80

60

40

20

0

100

80

60

40

20

0

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TIME

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TOTAL WETLAND

AREA INUNDATED

PERCENTAGE OF TIME

100

80

60

40

20

0

100

80

60

40

20

0

GS Natural Cypress S-68 Natural Cypress

PERCENTAGE OF TOTAL WETLAND

AREA INUNDATED

EXPLANATION

(A) (B)

Recent (12/11/2002-7/27/2004)

Figure 54. The recent and historical flooded-area duration distributions and maps showing the shapes of these 

flooded areas in (A) GS Natural Cypress and (B) S-68 Natural Cypress.
86 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

25 METERS

0 100 FEET

0

0 25 METERS

0 100 FEET

HRSP Natural Marsh

Historical (1988-2003)

More recent (12/12/00-8/11/03)

Historical (1996-2003)

GS Natural Marsh

PERCENTAGE OF TIME

100

80

60

40

20

0

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

0-20

21-40

41-60

61-80

81-100

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TOTAL WETLAND

AREA INUNDATED

PERCENTAGE OF TIME

Recent (12/12/00-9/30/02) Recent (12/12/00-9/30/02)

FLOODED AREA, IN PERCENT OF TOTAL

WETLAND AREA

0-20

21-40

41-60

61-80

81-100

WETLAND PERIMETER AT 100 PERCENT

INUNDATION

CONTOUR LINE

VEGETATION PLOTS

DEEPEST POINT

STAFF LOCATION

EXPLANATION

(A) (B)

Figure 55. The recent and historical flooded-area duration distributions and maps showing the shapes of 

these flooded areas in (A) HRSP Natural Marsh and (B) GS Natural Marsh.
Wetland Flooding Characteristics 87

Augmented Wetlands

During the historical period, between 41 to 80 percent of 

the total area of three of the four augmented wetlands typically was flooded, and relatively little time was spent with 

the flooded extent in either the driest or wettest area intervals 

(figs. 56 and 57A). For example, Duck Pond Augmented 

Marsh was 41 to 100 percent flooded over 95 percent of the 

historical period (fig. 56A). Similarly, W‐3 Augmented Marsh 

was 61 to 80 percent flooded over 60 percent of the historical 

period (fig. 56B). The wetland was 81 to 100 percent flooded 

only 7 percent of the historical period, and less than 61 percent 

flooded only 30 percent of the period. The staff gage location 

at this wetland required consolidating all observations in the 

interval between 0 and 60 percent of the total area; however, 

many of these observations were probably just less than 

60 percent. W‐5 Augmented Cypress was rarely more than 

60 percent flooded during the historical period (fig. 57A).

In contrast, S‐63 Augmented Cypress wetland showed 

a historical flooded-area duration distribution with flooding 

in each of the area intervals, with the greatest percentage 

in the 0 to 20 percent interval (fig. 57B). The flooded area 

of S‐63 Augmented Cypress was more variable over time 

than any other wetland studied, potentially making the 

historical biweekly staff gage readings less representative of 

monthly average conditions than at other sites. Nevertheless, 

the historical flooded-area duration distribution for 

S‐63 Augmented Cypress shared characteristics observed at 

the natural and impaired cypress wetlands. S‐63 Augmented 

Cypress resembled the natural cypress wetlands because it 

was 0 to 20 percent flooded about 40 percent of the historical 

period. However, it resembled the impaired sites by spending 

a relatively small percentage of the period with flooding over 

61 to 100 percent of the total area (fig. 57B and table 11).

The flooded-area duration distributions in the augmented 

cypress wetlands were wetter for the recent period than 

the historical period. S‐63 Augmented Cypress was 41 to 

60 percent flooded during nearly half of the recent period, 

and 80 to 100 percent flooded about twice as often as it was 

historically (fig. 57B). Similarly, W‐5 Augmented Cypress was 

61 to 100 percent flooded a greater percentage of time in the 

recent period than the historical period. Intentionally drying 

out W‐5 Augmented Cypress for a rewetting experiment 

increased the percentage of time it was 0 to 20 percent flooded 

during the recent period (fig. 57A).

Impaired Wetlands

W‐29 Impaired Marsh was largely dry more often 

during the historical period than both of the natural marshes 

(figs. 55 and 58A). W‐29 Impaired Marsh was 0 to 40 percent 

flooded 71 percent of the historical period (table 11), and was 

probably dry during much of this time. Because of its relatively high position, however, the historical staff gage could 

not be used to determine flooding extent when the wetland 

was less than 40 percent flooded (fig. 58A). W‐29 Impaired 

Marsh was 81 to 100 percent full about 10 percent of the 

historical period compared to 22 percent for HRSP Natural 

Marsh, and nearly 50 percent of the time in GS Natural Marsh 

(compare fig. 58A with fig. 55A-B). 

Two flooded-area duration graphs are used to reflect 

the recent conditions at W‐29 Impaired Marsh because data 

were collected at the site during the marsh and cypress 

data-collection periods. Flooding conditions during the 

marsh period resembled the historical conditions, with 0 to 

20 percent flooding over 80 percent of the time (fig. 58A). 

Much of this time, the wetland was dry; moreover, the recent 

conditions were drier than the historical conditions, with no 

flooding occurring in the area intervals above 60 percent. 

During the wetter cypress period when well-field 

pumping was reduced, the hydrologic conditions at 

W‐29 Impaired Marsh were nearly the opposite of conditions 

during the historical and marsh periods. The wetland was 80 to 

100 percent full over 70 percent of the time, and never less 

than 21 percent full. The flooded-area duration distribution 

of W‐29 Impaired Marsh during the later recent period did 

not indicate impairment, but resembled the recent flooding 

conditions in the two natural cypress wetlands.

Recent flooding at W‐19 Impaired Cypress also 

resembled recent flooding at the natural cypress wetlands. 

However, the impaired condition of the wetland was evident 

in the 16-year historical flooded-area duration distribution. W‐19 Impaired Cypress was 0 to 20 percent flooded 

60 percent of the historical period (fig. 58B), and was 

completely dry (0 percent flooding over a monthly averaged 

time period) almost 50 percent of that time. By comparison, 

GS Natural Cypress was 0 to 20 percent flooded during 

Table 11. Percentage of the historical time each wetland area 

interval was flooded.

[Outlined cells are combined area intervals]

Wetland

Area interval

(percentage of total area)

0-20 21-40 41-60 61-80 81-100

GS Natural Cypress 52 7 4 8 29

S-68 Natural Cypress 7 37 10 17 29

HRSP Natural Marsh 13 20 28 17 22

GS Natural Marsh 18 6 6 22 48

W-5 Augmented Cypress 19 27 42 6 6

S-63 Augmented Cypress 37 17 21 14 11

Duck Pond Augmented 

Marsh 0 2 23 39 35

W-3 Augmented Marsh 31 62 7

W-19 Impaired Cypress 60 7 10 8 15

W-29 Impaired Marsh 71 8 11 10
88 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 56. The recent and historical flooded-area duration distributions and maps showing the shapes of 

these flooded areas in (A) Duck Pond Augmented Marsh and (B) W-3 Augmented Marsh.

(A) (B)

50 METERS

150 FEET

0 50 METERS

0 150 FEET

0

0

Historical (1988-2003) Historical (1995-2003)

Recent (12/12/00-9/30/02) Recent (12/12/00-9/30/02)

100

80

60

40

20

0

100

80

60

40

20

0

0-60

61-80

81-100

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

PERCENTAGE OF TIME

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

PERCENTAGE OF TIME

100

80

60

40

20

0

100

80

60

40

20

0

EXPLANATION

Duck Pond Augmented Marsh W-3 Augmented Marsh

0-60

WETLAND PERIMETER AT 100

PERCENT INUNDATION

CONTOUR LINE

VEGETATION PLOTS

DEEPEST POINT

STAFF LOCATION

FLOODED AREA, IN PERCENT

OF TOTAL WETLAND AREA

0-20

21-40

41-60

61-80

81-100
Wetland Flooding Characteristics 89

Figure 57. The recent and historical flooded-area duration distributions and maps showing the shapes of these 

flooded areas in (A) W-5 Augmented Cypress and (B) S-63 Augmented Cypress.

FLOODED AREA, IN PERCENT OF TOTAL

WETLAND AREA

0-20

21-40

41-60

61-80

81-100

WETLAND PERIMETER AT 100 PERCENT

INUNDATION

CONTOUR LINE

VEGETATION PLOTS

DEEPEST POINT

STAFF LOCATION

OUTFLOW

EXPLANATION

Historical (1991-2003)

Recent (12/11/02-7/27/04)

25 METERS

0 100 FEET

0

100

80

60

40

20

0

100

80

60

40

20

0

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

PERCENTAGE OF TIME

(B) S-63 Augmented Cypress

50 METERS

0 150 FEET

0

Historical (1988-2003) 0-20 21-40 41-60

61-80

81-100

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

PERCENTAGE OF TIME

100

80

60

40

20

0

100

80

60

40

20

0

W-5 Augmented Cypress

Recent (12/11/02-7/27/04)

(A)
90 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Figure 58. The recent and historical flooded-area duration distributions and maps showing the shapes

of these flooded areas in (A) W-29 Impaired Marsh and (B) W-19 Impaired Cypress.

50 METERS

150 FEET

0

0

50 METERS

0 150 FEET

0

PERCENTAGE OF TIME

Recent - Marsh Period

(12/12/00-9/30/02)

100

80

60

40

20

0

Recent - Cypress Period

( 12/10/02-6/28/04)

Historical (1989-2003)

Recent (12/11/02-7/27/04)

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

Historical (1989-2003) 41-60

61-80

81-100

0-40

0-20

21-40

41-60

61-80

81-100

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

0-20

21-40

41-60

61-80

81-100

PERCENTAGE OF TOTAL

AREA INUNDATED

WETLAND

PERCENTAGE OF TIME

W-29 Impaired Marsh W-19 Impaired Cypress

FLOODED AREA, IN PERCENT OF TOTAL

WETLAND AREA

41-60

61-80

81-100

WETLAND PERIMETER AT 100

PERCENT INUNDATION

CONTOUR LINE

VEGETATION PLOTS

DEEPEST POINT

STAFF LOCATION–Recent

STAFF LOCATION–Historic

EXPLANATION

(A) (B)

0-20

0-40

21-40

Figure 58. The recent and historical floodedarea duration distributions and maps 

showing the shapes of these flooded areas 

in (A) W-29 Impaired Marsh and (B) W-19 

Impaired Cypress.
Wetland Flooding Characteristics 91

52 percent of the same period (fig. 54A), but was completely 

dry only 30 percent of the time. S‐68 Natural Cypress, in 

contrast, was 21 to 40 percent flooded nearly 40 percent of 

its historical period (fig. 54B), but was completely dry only 

5 percent of that time. In addition to being completely dry 

substantially more often than the natural cypress wetlands, 

W‐19 Impaired Cypress was 81 to 100 percent flooded only 

about half as often (table 11).

Seasonal Average Flooding Patterns

To assess seasonal flooding patterns, historical stage data 

from each wetland were used to reconstruct their monthly 

average flooded areas during an average year. The historical, 

monthly average flooded area, expressed as a percentage of 

the total wetland area, was computed by averaging all available values of the monthly mean flooded areas for a chosen 

month. Averaging emphasizes the central tendency of the data 

and deemphasizes the extremes.

The monthly average flooded area patterns for the 

natural, augmented, and impaired wetlands show characteristic traits by group (fig. 59A-I). The natural wetlands 

show the greatest variation in monthly average flooded area. 

The smallest monthly average flooded area consistently 

occurred in June and the largest in September or October 

(fig. 59 A-D). The greatest monthly average flooded area 

percentage was typically 40 to 60 percent greater than the 

smallest flooded area percentage. The minimum monthly 

average flooded area was about 15 percent of the total wetland 

area at GS Natural Cypress wetland and around 30 percent 

of the total wetland area in the three other natural wetlands. 

The maximum monthly average flooded area in the natural 

sites ranged from about 60 percent of the total wetland area in 

GS Natural Cypress wetland to about 75 percent of the total 

wetland area for the two other natural wetlands that shared 

the same historical time period. The natural marsh with the 

shorter period of record (GS Natural Marsh) had a maximum 

monthly flooded area that averaged just over 90 percent 

of the total wetland area during August, September, and 

October (fig. 59B).

The monthly average flooded area in the impaired 

wetlands showed a seasonal pattern similar to the natural 

wetland patterns, but with substantially less area flooded 

during each month of the year, and a smaller range between 

the minimum and maximum flooded areas (fig. 59E-F). 

Photograph provided by M. Hancock, SWFWMD

Seasonal changes in flooding patterns affect habitat for 

sandhill cranes and other wildlife
92 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

For example, at W‐19 Impaired Cypress the minimum 

monthly average flooded area was 7 percent of the total 

wetland area and the maximum was 45 percent (fig. 59F). 

At W‐29 Impaired Marsh, the monthly average flooded area 

over the historical period was always less than 40 percent of 

the total area (fig. 59E). For this reason, the monthly average 

flooded areas at this site were inferred using ground-water 

levels measured by Tampa Bay Water in a well next to the 

historical staff gage.

The monthly average flooded areas in the augmented 

wetlands varied less than those in the natural wetlands 

(fig. 59G-I). The augmented wetlands did have a minimum 

monthly average flooded area, typically in April or May, and 

a maximum between September and December; however, 

the average difference between the annual minimums and 

maximums was the smallest of all three wetland groups. 

Of the augmented wetlands, the most evident seasonality in 

flooded area occurred in S‐63 Augmented Cypress, where 

augmentation rates were designed to target different water 

levels during the year in an effort to impose a more natural 

cycle. The resulting pattern shows slightly more seasonality 

than W‐5 Augmented Cypress (fig. 59H-I). However, the 

minimum monthly average flooded area occurred in April at 

S‐63 Augmented Cypress, as opposed to June in the natural 

wetlands. Both augmented cypress wetlands maintained 

smaller monthly average flooded areas compared to the natural 

wetlands. The minimum monthly average flooded areas for 

the two augmented cypress wetlands were similar to those of 

the natural wetlands, averaging 20 to 30 percent of the total 

wetland area, although the maximum monthly average flooded 

areas were substantially less.

The monthly average flooding pattern at Duck Pond 

Augmented Marsh was the least similar to the flooding 

patterns of the natural wetland sites. At Duck Pond Augmented 

Marsh, the minimum monthly average flooded area was about 

60 percent of the total wetland area and the maximum was 

about 80 percent. A similar seasonal analysis was not possible 

for W‐3 Augmented Marsh because areas below 60 percent of 

the total wetland area could not be differentiated in the historical data. However, a consistently large flooded area probably 

was maintained throughout the year at W‐3 Augmented Marsh, 

as suggested by flooding results for the recent time period.

Figure 59. Historical monthly average flooded area in the study wetlands.

FLOODED AREA (PERCENT OF TOTAL WETLAND AREA)

Duck Pond Augmented Marsh (1988-2003) 100

80

60

40

20

0

GS Natural Cypress (1988-2003)

GS Natural Marsh (1996-2003)

S-68 Natural Cypress (1989-2003)

HRSP Natural Marsh (1988-2003)

W-29 Impaired Marsh (1989-2003)

W-19 Impaired Cypress (1989-2003) W-5 Augmented Cypress (1988-2003) JAN FEB MAR APR MAY JUN JUL AUG SEP

OCT

NOV

DEC

S-63 Augmented Cypress (1991-2003) 100

80

60

40

20

0

100

80

60

40

20

0

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

(B)

(A)

(C)

(D)

(E)

(G)

(F) (I)

(H)
Wetland Flooding Characteristics 93

Overview of Flooding Characteristics

Flooded area, when expressed as a percentage of total area, 

is an informative measure for describing and comparing the 

hydrologic condition of isolated wetlands in a region regardless 

of their size. Wetland conditions can be compared concurrently, and abundant historical stage data for wetlands can be 

synthesized into a comparable hydrologic indicator. The flooding 

patterns in the study wetlands were examined over three different 

timeframes. Although a relatively small number of wetlands 

were used in this study, results revealed similarities within the 

three hydrologic groups associated with the wetlands, and to a 

lesser extent, the two wetland types.

In the natural wetlands, the weekly average size of the 

flooded areas changed relatively rapidly and displayed shortlived extremes. Stage observations are currently made once 

every 2 weeks in about 480 wetlands in west-central Florida 

(Tampa Bay Water, 2000). Results from this study indicate that 

biweekly measurements would miss much of the variability 

captured by averaging daily values. Biweekly observations may 

provide sufficient measurement frequency for some regulatory 

purposes, however, such as estimating the annual and monthly 

average water levels over multiple years. Daily stage data 

collected at natural wetlands in west-central Florida by the 

SWFWMD could be used to check this conclusion.

The flooding behaviors in natural wetlands were 

sufficiently similar to characterize them as a group. For example, 

natural wetlands showed similar patterns in the percentages of 

their total areas that were flooded over similar time periods. 

Although there were differences for individual weeks, overall, 

the natural wetlands were similar to one another in the timing 

and magnitude of total wetland area inundated during a given 

year. These similarities may indicate that shared rainfall conditions determined the weekly flooding patterns in the four natural 

wetlands as much, or more than, differences in their physical 

settings. For this reason, the “natural” flooding pattern observed 

for the first 2 years of the study, when rainfall was about average, 

was distinctly different than the “natural” pattern observed for 

the next 2 years when rainfall was above average.

Natural wetlands also showed certain characteristic 

flooding patterns over the historical period that contrasted with 

the impaired and augmented wetlands. Comparing all of the 

wetlands for the same 8-year period, the two natural cypress 

wetlands had about half of their total areas flooded about 45 

percent of the time (41 and 51 percent, table 12). During the 

same period, water covered more than half of the two natural 

marshes about 70 percent of the time. Therefore, the upper 

halves of the marsh wetland areas were flooded more often than 

the upper halves of the cypress wetlands. Some marshes are 

recognized as having, on average, longer periods of inundation 

than cypress wetlands (CH2M HILL, 1996). The average duration of inundation, however, is defined at the location of the staff 

gage, typically in the deepest part of the wetland. In the current 

study, the duration of flooding in the deepest part of the natural 

marsh and cypress wetlands was fairly similar, averaging 

about 11.4 and 9.4 months per year, respectively (table 13). 

Table 12. The percentage of time that more than half 

of the total wetland area was flooded, based on stage 

data from 1996 to 2003.

Wetland Percentage of 

time

 GS Natural Cypress 41

 S-68 Natural Cypress 51

 HRSP Natural Marsh 67

 GS Natural Marsh 71

 W-5 Augmented Cypress 31

 S-63 Augmented Cypress 33

 Duck Pond Augmented Marsh 81

 W-3 Augmented Marsh1 69

 W-19 Impaired Cypress 32

 W-29 Impaired Marsh 33

1Percentage of time more than 60 percent of the wetland 

area was flooded.

Table 13. Average duration of flooding at deepest 

point in wetland, in months per year, based on stage 

data from 1996 to 2003. 

Wetland Duration, in 

months per year

 GS Natural Cypress 7.9

 S-68 Natural Cypress 10.8

 HRSP Natural Marsh 11.9

 GS Natural Marsh 10.9

 W-5 Augmented Cypress 12

 S-63 Augmented Cypress 10.9

 Duck Pond Augmented Marsh 12

 W-3 Augmented Marsh 12

 W-19 Impaired Cypress 6.5

 W-29 Impaired Marsh 5.1
94 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Comparing the flooding duration that occurs nearer the 

wetland margins, in addition to the deepest part of the wetland, 

may provide a more telling hydrologic difference. Ultimately, 

describing historic flooding patterns in a larger population of 

natural marsh and cypress wetlands will help clarify differences between these two types of wetlands.

Differences in flooding characteristics between the 

natural, augmented, and impaired wetlands are consequences 

of external factors such as rainfall, physical and geologic 

settings, augmentation, changes in runoff, and ground-water 

withdrawals. Flooding in the natural wetlands can be used 

as an indicator of typical hydrologic conditions to help 

determine (1) what percentage of the total area of an impaired 

wetland is no longer flooded like a natural wetland, (2) what 

percentage of the augmented wetland continues to be flooded 

like a natural wetland, and (3) how long altered conditions 

have existed.

Only the inner 40 to 60 percent of the total area of 

impaired wetlands was flooded with a frequency comparable 

to that of the natural wetlands. The outer 40 to 60 percent of 

the total wetland area, nearer the wetland perimeter, flooded 

much less frequently, and approached a hydrologic status 

comparable to the adjacent upland area. The effects of the 

altered hydrology on the vegetation at the impaired wetlands 

are well documented, and include the encroachment of pine 

trees into W‐29 Impaired Marsh (Berryman and Hennigar Inc., 

2000; Haag and others, 2005) and cypress tree mortality in 

W‐19 Impaired Cypress (Reynolds, Smith & Hills, Inc., 2001; 

Haag and others, 2005).

Neither of the impaired wetlands is considered to be 

as severely affected by ground-water withdrawals as the 

augmented wetlands were prior to mitigation. Three of the 

four augmented wetlands were considered affected as early as 

the late 1970s. Ground-water withdrawals at Cross Bar Well 

Field began in 1980, and effects were reported at Duck Pond 

Marsh soon thereafter. Three of the four augmented wetlands 

in this study are within several hundred feet of production 

wells (W‐3 Augmented Marsh, Duck Pond Augmented Marsh, 

and S‐63 Augmented Cypress), and all four are subject to 

ground-water drawdown effects that lower the elevation of 

the surrounding water table several feet below the wetland 

bottom. Therefore, without augmentation, the four augmented 

wetlands probably would have had little or no area with 

flooding comparable to that of a natural wetland. 

Augmentation has most likely prevented a complete 

loss of flooded area at the four augmented wetlands, both 

for the historical time period used in these analyses, and for 

the entire period for which augmentation has been practiced, 

namely: 1978-present at W‐5 Augmented Cypress, 1979-

present at W‐3 Augmented Marsh, 1987-present at Duck Pond 

Augmented Marsh, and 1990-present at S‐63 Augmented 

Cypress. Augmentation has imposed routine inundation 

(defined as inundation for at least 30 percent of the time) over 

a substantial area of each of these wetlands. For the historical 

periods given in table 10, augmentation of Duck Pond 

Augmented Marsh increased the routinely inundated area from 

perhaps as little as 0 percent to between 81 and 100 percent of 

the total wetland area. It maintained a permanent pond over 

40 to 60 percent of the total area, and a viable marsh fringe 

in the remaining 40 percent of the area. At W‐5 Augmented 

Cypress, augmentation sustained routine inundation of 40 to 

60 percent of the total wetland area. The remaining 40 percent 

of the area of W‐5 Augmented Cypress flooded less frequently 

than either of the impaired wetlands. Augmentation increased 

the routinely inundated area in W‐3 Augmented Marsh from 

perhaps 0 to 20 percent of the total wetland area to 61 to 

80 percent of the total area. The remaining 20 percent of the 

wetland area (81-100 percent interval) flooded much less often 

than the natural wetlands.

At S‐63 Augmented Cypress, the wetland surface area 

routinely inundated by augmentation is more difficult to 

characterize. Historically, the 0 to 20 percent area interval 

of S‐63 Augmented Cypress was flooded much more often 

than any other interval. The 81 to 100 percent interval was 

flooded only 11 percent of the historical time compared 

to about 30 percent in both natural cypress wetlands. 

At S‐63 Augmented Cypress, the cumulative duration of 

flooding approached the natural level in the area interval 

between either 61 to 80 percent of the total area (cumulative 

flooding 25 percent of the time) or 41 to 60 percent of the total 

area (cumulative flooding 46 percent of the time) (table 11). In 

the area of S‐63 Augmented Cypress that was routinely inundated, the timing of dry and flooded periods may have differed 

widely from that of natural wetlands. Based on the weekly 

flooded area estimates, S‐63 Augmented Cypress displayed 

the least seasonality and continuity in size of the flooded area 

during successive weeks of any of the study wetlands.

The duration of dry conditions also differed substantially 

in the three wetland groups. For the 8 years from 1996 to 

2003, the natural wetlands all dried out at their deepest points. 

On average, dry conditions in the natural wetlands lasted 

3 days per year at HRSP Natural Marsh, about 1 month per 

year at S‐68 Natural Cypress and GS Natural Marsh, and 

4 months per year at GS Natural Cypress. In contrast, the 

impaired wetlands were dry 5.5 to almost 7 months per year 

at the deepest point (table 13). Except for S‐63 Augmented 

Cypress, the augmented wetlands never dried out at their 

deepest points over this time period.

Wetland flooding characteristics relate in various ways to 

all of the other sections of the report. Differences in flooding 

behavior have a pronounced and immediate effect on wetland 

water quality, vegetation, and ecology, and can be interpreted 

along with measurements of ecosystem function. Moreover, 

flooding characteristics have a direct and substantial affect on 

ground-water flow patterns and the wetland water budget.
Ecological patterns in wetlands reflect complex and dynamic 

interactions between physical and biological factors (Mitsch and 

Gosselink, 2000). The ecological comparison of natural, impaired, and 

augmented marsh and cypress wetlands in this study focuses primarily on 

the periphyton, wetland vegetation, and macroinvertebrate communities 

found in each. Differences in species composition, relative abundance, 

and biomass were used to compare and contrast community structure at 

the sites. 

Methods of Ecological Data Collection and Interpretation

Ecological data were collected quarterly and semiannually in marsh 

and cypress wetlands using similar methods regardless of wetland type. 

The ecological sampling was primarily designed to facilitate comparisons 

among the groups of marsh wetlands (natural, impaired, and augmented), 

and among the groups of cypress wetlands. Data analysis involved a 

combination of descriptive and statistical methods. As noted earlier, all 

data and interpretive results for this section are reported in metric units. 

English units are only shown if they were the original unit of measure. 

Periphyton

The periphyton community was assessed in each of the 

10 wetlands using an artificial substrate sampler fitted with glass 

slides (25 x 76 mm). Periphyton growing on glass slides was collected 

as a surrogate for the periphyton typically found on wetland plant and 

sediment surfaces because this collection method provided consistent 

periphyton samples in all 10 wetlands (Stevenson and others, 1996). 

To determine community composition and periphyton biomass, 

samples were collected quarterly at the marsh wetlands during 

Wetland Ecology
96 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

2000-02, and at the cypress wetlands during 2002-04. 

A synoptic sampling of periphyton biomass and chlorophyll-a

at all wetlands also occurred during September–October 2003.

The periphyton sampler (Wildco TM) was tethered to the 

staff gage at each wetland and floated at the water surface, 

so that the glass slides were immersed just below the water 

surface. Samplers remained deployed in the wetlands for 

15 to 30 days. Each sampler was retrieved at the end of the 

sampling interval, placed in a plastic bag, and transported to 

the laboratory in a chilled cooler.

Two glass slides from each sampler were scraped with 

a single-edge razor blade and the algal material was mixed 

with a small aliquot of water and filtered onto glass fiber 

filters and frozen. Frozen samples were analyzed for biomass 

(ash-free dry mass) and chlorophyll-a concentration at the 

USGS Water Quality Laboratory in Ocala, Florida. Although 

glass slides were left in the field for 15 to 30 days, the biomass 

and chlorophyll-a data were normalized to a 21-day period for 

the purpose of comparison. Two additional glass slides were 

scraped, and the algal material was placed in a glass vial and 

preserved with 3 to 5 percent formalin. Preserved samples 

were shipped to Michigan State University in Ann Arbor, 

MI and analyzed to determine the composition of the algal 

community. Laboratory analysis methods are described in 

Stevenson and others (2002).

Wetland Vegetation

Vegetation sampling was designed to facilitate 

comparisons among the groups (natural, impaired, and 

augmented) of marsh wetlands, and among the groups of 

cypress wetlands. Differences in vegetation between marsh 

and cypress wetlands within groups were not of primary 

interest. The species composition and relative abundance of 

vegetation in all 10 wetlands were assessed in fixed plots in 

May and October 2002, May and October 2003, and May 

2004. At each wetland site, three 1-m2 vegetation plots 

were established and maintained for the duration of the 

study (app. 5). Vegetation plots were defined as transitional, 

intermediate, or deep, based on their elevation relative to the 

elevation at the wetland perimeter (Haag and others, 2005). 

Transitional plots were located 3 to 6 in. (7.6-15.2 cm) 

below the seasonal high water elevation, which corresponds 

to the elevation of the wetland perimeter. Deep plots were 

located near a point of lowest elevation (maximum water 

depth) at each wetland. Intermediate plots were located at an 

elevation half-way between the elevation of the deep plots 

and the elevation of the transitional plots. 

 All emergent plants in the 1-m2 plots were identified 

to species, and their percent cover was estimated visually. No plants were removed, with the exception of an 

occasional specimen for species verification. Additional 

estimates of the relative abundance of herbaceous vegetation were made quarterly when macroinvertebrate and 

periphyton samples were collected in marsh wetlands during 

July 2000–July 2002 and in cypress wetlands during July 

2002–July 2004. All plants were identified in 0.25 m2 plots 

in water depths of about 15 to 30 cm, at elevations similar to 

those of the intermediate plots.

Verification of species identification, when necessary, 

was provided by the University of South Florida Herbarium 

in Tampa, Florida. Plant names used herein follow 

Wunderlin (1998). Wetland plants were assigned a status 

based on the Florida Vegetative Index (Florida Department 

of Environmental Protection, 2004) or the Atlas of Florida 

Vascular Plants (Wunderlin and Hansen, 2004). Any plant 

not specifically listed in the index is considered an upland 

plant with the exception of vines and aquatic plants. Aquatic 

plants are those, including the roots, that (1) typically float 

on water or require water for their entire structural support; 

or (2) desiccate outside of water (Florida Department of 

State, 1994). The three wetland plant indicator categories

(obligate wetland species, facultative wet wetland species 

and facultative wetland species) are defined according to 

Federal guidelines (Reed, 1988). Specifically, an obligate 

species is present in wetlands greater than 99 percent of the 

time, a facultative wet species is present in wetlands 67 to 

99 percent of the time, and a facultative species is present 

in wetlands 34 to 66 percent of the time. Although both 

obligate and facultative wet species are widely recognized 

as useful indicators of wetlands, facultative species can be 

dominant plants in uplands as well as in wetlands and, therefore, are not considered to be reliable indicators of wetlands.

The species composition of vegetation in marsh and 

cypress wetlands was compared using Jaccard’s Similarity 

Index (Jongman and others, 1995). Jaccard’s Index is 

a qualitative measure of similarity that expresses the 

percentage of species shared in common by two wetland 

Vegetation assessment in a deep plot at a marsh wetland
Wetland Ecology 97

communities. Data were grouped by plot elevation so that 

vegetation comparisons among the 10 wetlands were made 

between transitional plots, intermediate plots, or deep plots. 

The biomass of vegetation in marsh wetlands was 

estimated quarterly during 2000-02. A 0.25-m2 frame was 

placed on the wetland bottom at three widely separated 

locations in each marsh wetland on each sampling date. 

The frame was placed in water at depths less than about 

0.3 m to facilitate sample collection. The relative proportions of the five dominant plant species in each frame were 

recorded based on visual estimates. Plants were clipped at 

their base at the sediment surface and all plant biomass in 

the frame was placed in a plastic bag and returned to the 

laboratory. Plants were dried in an oven on aluminum foil 

at 105 oC for 24 to 72 hours until a constant weight was 

obtained. Dried plants were weighed to the nearest gram. 

Plant biomass data are reported as dry weight in grams 

per square meter. The estimates of plant biomass were 

restricted to herbaceous vegetation growing in water depths 

of about 0.3 m; therefore, they are not representative of 

plant biomass in the entire wetland. Samples from the five 

marsh wetlands, however, can be compared because they all 

were collected at similar water depths and during the same 

time period.

Tree density was estimated in cypress wetlands during 

2002. At each cypress wetland, five “reference” trees were 

chosen at five locations widely spaced throughout the 

wetland where water depth did not exceed 1 m. All cypress 

trees within a radius of 3.05 m from the reference trees 

were measured to determine tree diameter at breast height. 

The density of cypress trees at these locations was used to 

estimate the total number of cypress trees per acre in each of 

the five cypress wetlands and to compare the relative size of 

cypress trees in each wetland. The occurrence of fallen and 

leaning trees also was recorded.

Macroinvertebrates

Macroinvertebrates were sampled quarterly in the 

10 wetlands in this study. A standard D-frame aquatic dip 

net about 30 cm wide with a mesh size of 0.5 mm was 

used to collect macroinvertebrate samples at three widely 

spaced locations in each marsh and cypress wetland on 

each sampling date. Samples were collected at water depths 

of 0.25 to 0.75 m at all wetlands to facilitate comparisons. Dip-net sweeps are an effective sampling method 

for wetland macroinvertebrates (Cheal and others, 1993; 

Rader and Richardson, 1994), although dip-net samples 

may underestimate the abundance of small-bodied taxa 

(Kratzer and Batzer, 2007). One distinct advantage of 

using the dip-net method for this study was that it could 

be used in all 10 wetlands regardless of wetland group or 

type. The net was used to sweep an area about 1-m long, so 

that the total area swept by the net was about 0.33 m2. All 

material in one dip-net sweep was placed in one or more 1-L 

containers, preserved with 10-percent buffered formalin, 

and transported to the laboratory for analysis. A solution of 

rose bengal (100 mg/L) was added to stain the macroinvertebrates in the preserved samples at least 48 hours before 

samples were sorted to facilitate separation of biota from 

detritus and sediment.

The formalin preservative was then decanted, and each 

sample was rinsed with water to remove residual formalin. 

Each sample was then spread out in a shallow gridded pan 

and examined at 1.75X magnification. All organisms were 

removed and stored in 70-percent ethanol until they could 

be identified. Non-insect macroinvertebrates were usually 

identified to order, and insects were identified to the lowest 

practical taxonomic level, usually to genus. (Diptera were 

identified to family.) References used for macroinvertebrate 

identification included Heard (1979), Merritt and Cummins 

(1984), Berner and Pescador (1988), Pennak (1989), 

Daigle (1991), Epler (1996), Thorp and Covich (1996), 

Rasmussen and Pescador (2002), Richardson (2003), and 

Thompson (2004). After identification, macroinvertebrates 

were dried in an oven at 100 oC for 24 to 48 hours, cooled, 

and weighed to obtain biomass estimates for each sample. 

Macroinvertebrate biomass data are reported as dry weight 

per square meter. Fish collected in dip-net samples were 

identified using Burgess (2004).

Several commonly used measures of community 

composition (metrics) were used for comparison of macroinvertebrates among the groups of marsh wetlands and 

among the groups of cypress wetlands, including mean taxa 

richness (the number of macroinvertebrate taxa per square 

meter), density (the number of macroinvertebrate organisms 

per square meter), biomass (the dry weight of macroinvertebrates per square meter), proportion of total Diptera and 

Chironomidae, and distribution of macroinvertebrate taxa 

among functional feeding groups (Merritt and others, 1996). 

Shannon diversity (Krebs, 1999), which incorporates both 

the number of species (richness) and the number of individuals in each species (evenness), also was calculated for each 

wetland. Each of these metrics describes different aspects of 

the macroinvertebrate community, and when used together, 

they can provide a basis for comparing and contrasting sites.

During early field reconnaissance, macroinvertebrates 

were collected in the 0.2- to 0.4-m-deep areas of each 

wetland with a 5-cm-diameter aluminum coring device, but 

a variety of factors made it difficult to obtain consistent 

10-cm-long cores. Fibrous plant material hindered penetration of the core sampler at natural and impaired marsh sites, 

and the partially cut plant fragments hindered core retention. Tree roots prevented core penetration at natural and 

impaired cypress sites. Flocculent core samples could be 

collected at the augmented marsh and cypress sites, although 

there were few macroinvertebrates present (perhaps because 

of anoxic conditions in those thick sediments) and those 

organisms that were identified (Oligochaeta, Diptera larvae) 

were often in fragments. Because comparable semi-quantitative sediment core samples could not be collected at all 

sites, collection of sediment samples was discontinued.
98 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Periphyton

Periphyton, also known as attached algae, grows in 

freshwater wetlands on all available substrates during periods 

of sustained inundation in response to nutrients and other 

water-quality constituents, and other physical and biochemical 

factors. Periphyton has a long history of use in the assessment 

of aquatic habitats. Specifically, the species composition 

of periphyton communities has been linked to a variety of 

water-quality constituents including pH, conductivity, nitrates, 

phosphorus, and others. Few studies have characterized algae 

in freshwater wetlands despite the widespread abundance 

of these wetlands (Goldsborough and Robinson, 1996), 

and wetland periphyton research in Florida has generally 

focused on the Everglades and surrounding areas (Lane and 

Brown, 2007). 

Biomass and Chlorophyll-a

The median biomass of periphyton was lower in 

natural marshes (3.4-3.8 mg/m2) than in augmented marshes 

(5.6-5.9 mg/m2) in this study (table 14). The median periphyton biomass was lowest at W‐29 Impaired Marsh (1.1 mg/m2) 

compared to the other nine wetlands in the study. The median 

periphyton biomass also was lower at the natural cypress 

(1.3- 2.3 mg/m2) and impaired cypress (1.9 mg/m2) wetlands 

than at the augmented cypress (5.0-6.7 mg/m2) wetlands.

A synoptic sampling of periphyton biomass and 

chlorophyll-a in all wetlands during September–October 

2003 (table 15) also indicated that augmented marsh and 

cypress wetlands had higher periphyton biomass than 

natural wetlands. The median periphyton biomass was 

similar in natural and impaired cypress wetlands (2.20 and 

2.64 mg/m2, respectively), and augmented cypress wetlands 

had a substantially higher periphyton biomass (6.15 mg/m2). 

Chlorophyll-a concentrations in periphyton were higher in 

the augmented marshes (2.70 μg/cm2) than in the natural 

(1.47 μg/cm2) or impaired marshes (0.27 μg/cm2). Similarly, 

concentrations of chlorophyll-a were higher in the augmented 

cypress (5.68 μg/cm2) than in the natural (0.55 μg/cm2) or the 

impaired (1.76 μg/cm2) cypress wetlands.

Table 14. Median biomass of periphyton samples collected in 

study wetlands, 2002-04.

[mg/m2, milligrams per square meter]

Wetland Number of 

samples

Periphyton biomass (mg/m2)

Median Minimum Maximum

Green Swamp Natural 

Marsh 10 3.8 0.7 10.7

HRSP Natural Marsh 8 3.4 0.6 10.1

W-29 Impaired Marsh 5 1.1 0.5 2.3

Duck Pond Augmented 

Marsh 8 5.6 2.0 15.9

W-3 Augmented Marsh 8 5.9 0.5 15.2

Green Swamp Natural 

Cypress 9 1.3 0.6 5.0

S-68 Natural Cypress 6 2.3 0.3 5.3

W-19 Impaired Cypress 9 1.9 0.4 6.5

S-63 Augmented 

Cypress 6 6.7 1.6 23.3

W-5 Augmented 

Cypress 5 5.0 1.3 11.8

Table 15. Median biomass and chlorophyll-a of periphyton 

samples collected in study wetlands during September–October 

2003.

[mg/m2, milligrams per square meter; μg/cm2, micrograms per square 

centimeter]

Wetland Number of 

samples

Biomass,

(mg/m2)

Chlorophyll-a,

(μg/cm2)

Natural marshes 6 4.40 1.47

Impaired marsh 4 2.29 0.27

Augmented marshes 4 6.60 2.70

Natural cypress 6 2.20 0.55

Impaired cypress 4 2.64 1.76

Augmented cypress 6 6.15 5.68

Periphyton biomass on glass-slide samplers was higher

in augmented wetlands than in natural wetlands
Wetland Ecology 99

green algae and acid-loving diatoms. Wetlands supplied with 

ground water, which has a higher pH and mineral content, 

would be expected to contain more blue-green algae and 

diatoms that prefer alkaline waters.

When algae in this study were compared on the basis of 

biovolume, green algae were the predominant group at natural 

marsh and cypress wetlands, as well as augmented marshes 

(fig. 60). Desmids were more abundant at the unaugmented 

wetlands, with the exception of S‐63 Augmented Cypress. 

Diatoms also were an important part of the total biovolume 

of algae at all wetlands except the unaugmented marshes. 

Filamentous and colonial bluegreen algae were present at low 

densities in most of the wetlands. 

In studies of Everglades wetlands, desmids were more 

common at sites with low calcium carbonate and nutrient 

concentrations, whereas green algae and diatoms were more 

common at sites with moderate calcium carbonate and phosphorus concentrations (Browder and others, 1994). Similar 

patterns of algae abundance were not evident in the present 

study. One drawback of using algae as indicators of wetland 

condition is that they exhibit seasonal variation that may 

overshadow differences caused by other environmental factors 

(Stevenson and others, 1996).

Figure 60. Relative abundance of dominant algal groups in marsh and cypress wetlands.

There are few studies of periphyton communities in 

Florida wetlands other than the Everglades (Lane and Brown, 

2007). Goldsborough and Robinson (1996) tabulated results 

of biomass and chlorophyll-a data from a number of studies 

of freshwater wetlands, and the reported ranges for these algal 

community measures are broad. The range for chlorophyll-a

reported in the present study (0.67-5.54 μg/cm2), however, 

is within the broad ranges included in that summary paper 

(0.1-7.9 μg/cm2). Moreover, the range for periphyton biomass 

reported in the present study (1.57-2.07 mg/cm2) (data not 

shown) also is within the ranges reported in Goldsborough and 

Robinson (1996) (0.1-45 mg/cm2).

Community Composition

The most abundant periphyton groups in most freshwater 

habitats are blue-green algae (Cyanophyta), green algae 

(Chlorophyta), diatoms (Bacillariophyta), and red algae 

(Rhodophyta), although other algal groups may be present 

(Stevenson and others, 1996). In general, wetlands supplied by 

rainwater, which has a low ionic content and low pH, would 

be expected to support a periphyton community dominated by 

Unicellular green algae

Filamentous green algae

Filamentous bluegreen algae

Euglenophytes

Diatoms

Desmids

Colonial green algae

Colonial bluegreen algae

100

80

60

40

20

0

GS

NATURAL

MARSH

HRSP

NATURAL

MARSH

W-29

IMPAIRED

MARSH

GS

NATURAL

CYPRESS

S-68

NATURAL

CYPRESS

W-19

IMPAIRED

CYPRESS

DUCK POND

AUGMENTED

MARSH

W-3

AUGMENTED

MARSH

S-63

AUGMENTED

CYPRESS

W-5

AUGMENTED

CYPRESS

EXPLANATION

ABUNDANCE, IN PERCENT OF TOTAL
100 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Diatoms are an important component of periphyton, and 

assessments of the diatom community can be used to compare 

wetlands because diatoms are relatively easy to identify and 

data are available that describe their ecological preferences 

(Lane and Brown, 2007). Diatom species richness was similar 

at the natural marshes (26.0) and S‐68 Natural Cypress (27.0), 

but much lower at GS Natural Cypress (16.0) (table 16). 

The species richness was 21.0 at the two augmented cypress 

wetlands. The highest diatom species richness was found at 

W‐29 Impaired Marsh (29.0), and the lowest value was found 

at W‐19 Impaired Cypress (15.0).

A study of diatoms in 50 forested wetlands throughout 

Florida indicated that species richness averaged 19.0 at “reference” (undisturbed) sites and at sites influenced by agriculture 

(Reiss and Brown, 2005). Wetlands in urban settings in that 

study had higher diatom species richness (22.0). A parallel 

assessment of 70 marsh wetlands indicated a mean species 

richness of 18.4, with no difference in species richness 

observed between reference marshes and marshes that had 

experienced effects from agriculture or urban development 

(Lane and others, 2003).

Several species of diatoms were more abundant at natural 

and impaired sites in the present study than at augmented sites 

(table 16), including Eunotia nagelii, Eunotia incisa, Frustulia 

rhomboides, and Pinnularia subcapitata. Other taxa were 

more abundant at augmented sites than at the unaugmented 

sites, including species of Gomphonema and Nitzchia.

In the study of Florida forested wetlands by Reiss 

and Brown (2005), five diatom species were identified in 

50 percent or more of the forested wetlands sampled. Four 

of those five species were found in the natural cypress 

wetlands in the present study, and all five species were found 

at W‐19 Impaired Cypress. Only two of the species were 

found at the augmented cypress wetlands in the present study. 

Reiss and Brown (2005) also established lists of tolerant 

and intolerant diatom species for the set of Florida forested 

wetlands they sampled. Of those species listed as tolerant, 

only one species (Navicula minima) was identified at the 

cypress wetlands in the present study, where it was found in 

low numbers at most sites. Of the species listed by Reiss and 

Brown (2005) as intolerant or sensitive, Eunotia naegelii was 

found at the GS Natural Cypress, but not at the augmented or 

Table 16. Median diatom species richness and most abundant diatom species in study wetlands.

Wetland name

Median diatom

species richness 

(range)

Most abundant diatom species

GS Natural Marsh 26

(16–38)

Cocconeis 

placentula 

euglypta

Eunotia

incisa

Eunotia

 naegelii

Frustulia 

rhomboides

Pinnularia 

subcapitata

HRSP Natural Marsh 26

(20–48)

Acnanthes

exigua

Eunotia

incisa

Eunotia

 naegelii

Fragilaria 

brevistriata

Gomphonema 

gracile

GS Natural Cypress 16

(10–39)

Acnanthes

exigua

Eunotia

incisa

Eunotia

 naegelii

Pinularia

braunii

amphicephala

Pinnularia 

subcapitata

S-68 Natural Cypress 27

(21–47)

Eunotia

 naegelii

Eunotia

paludosa

Eunotia

septentrionalis

Frustulia 

rhomboides

Pinnularia 

subcapitata

W-19 Impaired Cypress 15

(10–26)

Eunotia

incisa

Eunotia

rhomboidea

Frustulia 

rhomboides

crassinerva

Gomphonema

affine

Navicula

minima

W-29 Impaired Marsh 29

(8–34)

Acnanthes

exigua

Eunotia

 naegelii

Frustulia

brevis

Frustulia 

rhomboides

Pinnularia 

subcapitata

Duck Pond Augmented Marsh 29

(14–51)

Cymbella

 laevis

Eunotia

 naegelii

Fragilaria 

brevistriata

Frustulia 

rhomboides

Nitzschia

 paleacea

W-3 Augmented Marsh 22

(12–31)

Cymbella

 laevis

Gomphonema 

parvulum

Fragilaria 

brevistriata

Nitzschia 

archibaldii

Pinnularia 

subcapitata

S-63 Augmented Cypress 21

(17–28)

Gomphonema 

angustum

Gomphonema 

gracile

Navicula

minima

Nitzschia 

amphibia

Sellaphora 

pupula

W-5 Augmented Cypress 21

(8–34)

Acnanthes

biasolettiana

Cocconeis 

placentula euglypta

Cocconeis

placentula 

lineata

Gomphonema 

parvulum

Gomphonema

 pseudotenellum
Wetland Ecology 101

Diatom species have varying sensitivity to changes in 

water-quality properties, including pH and nutrients. The Van 

Dam Ecological Indicator values for diatom species are among 

the most complete references for assessing various environmental 

conditions (Van Dam and others, 1994). Several of these indices 

were used to characterize the sites in the present study, including 

the following:

•	 pH Index—Diatoms are sensitive to pH and the index 

value, which ranges from 1 to 5, indicates acidic to 

alkaline conditions, respectively.

•	 Trophic State Index—Diatoms are sensitive to nutrient 

concentrations and the index values, which range from 

1 to 6, indicate an increasing proportion of diatoms 

tolerant to elevated nutrient concentrations.

•	 Index of Nitrogen Uptake Metabolism—Diatoms vary in 

nitrogen uptake ability and the indicator values, which 

range from 1 to 4, increase with organic enrichment.

Van Dam Ecological Indicator values were calculated 

for diatom samples collected at the 10 wetlands in the present 

study (table 17). The pH index values indicate the prevalence of 

diatoms preferring more acidic conditions at the natural wetlands, 

whereas diatoms at the augmented wetlands were typical of a 

more alkaline pH. The trophic index values were consistently 

lower at the natural (1.38-2.61) and impaired (1.98-2.03) 

wetlands than at the augmented wetlands (4.00-4.77). Similarly, 

nitrogen index values were lower at the natural (1.10-1.41) and 

impaired (1.34-1.73) wetlands than at the augmented wetlands 

(1.67-2.23). These patterns of indicator values indicate that the 

diatom communities at augmented sites include species that may 

be able to take advantage of the nutrients released by the partially 

decomposed organic material that accumulates in these wetlands.

The diatom Gomphonema 

gracile was found 

widely in augmented marshes

impaired cypress wetlands. Frustulia rhomboides and Eunotia 

rhomboidea and were common at the natural and impaired 

cypress wetlands, respectively, but not at the augmented 

cypress wetlands (table 16). The higher specific conductances 

prevailing at augmented cypress wetlands may explain the 

absence of these species at augmented sites compared to 

natural sites, which have much lower specific conductances. 

For example, in river habitats the optimum specific conductance for these three diatom species is low (65-90 μS/cm) 

(Potopova and Charles, 2003). 

Studies at 70 Florida marsh wetlands also indicated that 

species in the genera Anomoeoneis, Eunotia, and Frustulia

were generally found to be sensitive to human disturbances 

(Lane and others, 2003). Eunotia naegelli, Eunotia rhomboidea, and Frustulia rhomboides were indicative of reference 

sites (Lane and others, 2003). Although these three species 

were commonly found at the natural and impaired marshes 

in the present study, they were not widely found at the 

augmented marshes. Species of Gomphonema, Navicula, and 

Nitzchia were found to be indicative of disturbed conditions 

in marsh wetlands by Lane and others (2003). In the present 

study Gomphonema gracile, Navicula minima, Nitzchia 

amphibia, and Nitzchia paleacea were found widely in the 

augmented marshes, but were not common in the natural 

marshes. For example, the species Navicula minima has an 

optimum specific conductance of 319 μS/cm in river habitats, and a range of 140-729 μS/cm (Potopova and Charles, 

2003), indicating that it would not be expected in high 

numbers in natural wetlands with their characteristically low 

specific conductances.

Photograph provided by R.J. Stevenson, 

Michigan State University

Table 17. Van Dam Ecological Indicator values (Van Dam and 

others, 1994) for diatoms in study wetlands. 

Wetland name

Van Dam 

Trophic Index

mean value

Van Dam 

Nitrogen 

Index

mean value

Van Dam

pH Index

mean value

GS Natural Marsh 2.21 1.41 2.41

HRSP Natural Marsh 2.61 1.38 2.59

W-29 Impaired Marsh 2.03 1.73 2.21

GS Natural Cypress 1.90 1.27 2.28

S-68 Natural Cypress 1.38 1.10 2.02

W-19 Impaired Cypress 1.98 1.34 2.36

Duck Pond Augmented Marsh 4.00 1.67 3.25

W-3 Augmented Marsh 4.55 1.97 3.41

S-63 Augmented Cypress 4.42 2.23 3.62

W-5 Augmented Cypress 4.77 2.00 3.92
102 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Table 18. Jaccard’s Similarity Index matrices (using all species greater than 1 percent of abundance) for vegetation in fixed 

plots in marsh wetlands, 2000-04.

[Colors indicate wetland group: green, natural; brown, impaired; blue, augmented; numbers indicate total number of plant species at each site; 

%, percent] Deep plots

GS Natural 

Marsh

HRSP Natural 

Marsh

W-29 Impaired 

Marsh

Duck Pond 

Augmented Marsh

W-3 Augmented 

Marsh

GS Natural Marsh 4 species 40% 14% 0% 0%

HRSP Natural Marsh 3 species 17% 0% 20%

W-29 Impaired Marsh 4 species 0% 20%

Duck Pond Augmented Marsh 6 species 13%

W-3 Augmented Marsh 3 species

Intermediate plots

GS Natural 

Marsh

HRSP Natural 

Marsh

W-29 Impaired 

Marsh

Duck Pond 

Augmented Marsh

W-3 Augmented 

Marsh

GS Natural Marsh 8 species 6% 11% 5% 8%

HRSP Natural Marsh 11 species 10% 9% 6%

W-29 Impaired Marsh 12 species 14% 6%

Duck Pond Augmented Marsh 13 species 27%

W-3 Augmented Marsh 6 species

Transitional plots

GS Natural 

Marsh

HRSP Natural 

Marsh

W-29 Impaired 

Marsh

Duck Pond 

Augmented Marsh

W-3 Augmented 

Marsh

GS Natural Marsh 9 species 19% 20% 11% 11%

HRSP Natural Marsh 10 species 23% 16% 16%

W-29 Impaired Marsh 6 species 20% 13%

Duck Pond Augmented Marsh 12 species 9%

W-3 Augmented Marsh 12 species

Wetland Vegetation

Differences in the relative abundance of aquatic 

plants and woody vegetation in wetlands are attributable to 

differences in a number of abiotic factors, including the 

areal extent of flooding, flood duration, water depth, and 

nutrient availability.

Comparison of Vegetation Communities

When vegetation in marsh wetlands was compared in deep 

plots, the greatest Jaccard’s Similarity Index value (40 percent) was 

found between the two natural marshes where Panicum hemitomon and Pontederia cordata were found, followed by 20-percent 

similarity at W‐29 Impaired Marsh and W‐3 Augmented Marsh, 

where Panicum hemitomon and Nymphaea odorata were found 

(table 18). Deep plots at GS Natural Marsh and HRSP Natural 

Marsh were flooded more than 65 and 71 percent of the year, 

respectively, during the recent period in the study (table 19). 

Vegetation in Duck Pond Augmented Marsh was not similar 

to that of any other marsh site (table 18), with the exception of 

W‐3 Augmented Marsh, which shared a single plant species 

(Sagittaria latifolia). The deep plots at Duck Pond Augmented 

Marsh were flooded 100 percent of the time during the recent 

period, and to a much greater depth than any of the other sites 

(table 19). Deep plots at W‐3 Augmented Marsh were flooded 

more than 61 percent of the time. Overall, the number of aquatic 

plant species in deep plots was low at the five marsh sites, and 

therefore, the number of shared species also was low.

Although intermediate plots at the marsh sites contained 

more vegetation species than deep plots, Jaccard’s Similarity Index 

was generally low between sites. One exception was between 

the augmented marshes (27 percent), where the four shared 

species were Leersia hexandra, Panicum hemitomon, Sagittaria 

latifolia (all obligate plants), and the vine Berschemia scandens. 

Intermediate plots at Duck Pond Augmented Marsh were flooded 

91 percent of the time, and at W‐3 Augmented Marsh 61 percent of 

the time (table 19). 
Wetland Ecology 103

Transition plots at the marsh sites also had relatively 

more vegetation species than deep plots, although the amount 

of time that these plots were flooded during the recent 

period varied from 0 percent at W‐3 Augmented Marsh to a 

maximum of 31 to 53 percent of the time at the two natural 

marsh wetlands (table 19). The greatest observed similarities 

between transitional plots were among the natural and 

impaired sites, where shared species included several facultative species (Amphicarpum muhlenbergianum, Andropogon 

virginicus, Lachnanthes caroliana), and the obligate species 

Panicum hemitomon. 

When vegetation in cypress wetlands was compared, 

the greatest Jaccard’s Similarity Index among deep plots 

(14 percent) was between S‐68 Natural Cypress and 

S‐63 Augmented Cypress (table 20). The shared species were 

Panicum hemitomon and Rhynchospora corniculata (both 

obligate). Deep plots at these two sites were flooded more 

than 96 and 86 percent of the time, respectively. Jaccard’s 

Similarities were also low among intermediate plots, although 

S‐63 Augmented Cypress shared two species each with 

W‐19 Impaired Cypress (Acer rubrum and Myrica cerifera) and 

W‐5 Augmented Cypress (Rhynchospora mileacea and Lycopus 

rubellus) (table 20). Intermediate plots at W‐5 Augmented 

Cypress were flooded more then 62 percent of the time. 

Transition plots at the cypress wetlands had minimal Similarity 

Indices (table 20). S‐68 Natural Cypress and S‐63 Augmented 

Cypress shared three species: Amphicarpum muhlenbergianum

(facultative wet), Andropogon virginicus (facultative), and 

Aristida strict var. beyrichiana (facultative). Transitional 

plots at these sites were flooded 52 and 30 percent of the 

time, respectively.

W‐29 Impaired Marsh is of particular interest because 

it illustrates the possible effects of changes in ground-water 

pumping and rainfall on wetland vegetation. The flooding 

characteristics and percentages of time that plots were inundated were substantially different at W‐29 Impaired Marsh 

during 2000-02, when rainfall was about average, than during 

2002-04 when rainfall was above average and ground-water 

pumping had decreased (table 21). During the average rainfall 

period, deep plots at W‐29 were more similar to the deep plots at 

the natural marshes than those at the augmented marshes. These 

differences did not extend to the intermediate or transition plots. 

The influence of this difference in rainfall and groundwater pumping over time is also evident for Jaccard’s Similarity 

Indices among plots at individual wetlands during the two 

periods (table 21). Within each marsh, the vegetation in the 

deep and intermediate plots generally was more similar over 

time (comparing the average period and the wetter period) at 

the augmented wetlands than at the natural wetlands because 

water levels were not controlled as much by rainfall and 

pumping, but were kept relatively constant throughout the 

entire 4-year period. This pattern was not consistent at the 

natural and augmented cypress wetlands. The lowest similarities 

over time were at W‐29 Impaired Marsh (16-33 percent) and 

at W‐19 Impaired Cypress (0-33 percent), because these two 

wetlands were most vulnerable to ground-water pumping and 

rainfall variation. 

Use of the Jaccard’s Similarity Index to establish similarity 

between vegetation communities in the wetlands in this study 

was limited by the fact that the most abundant species were 

rarely the same between individual wetlands. Initially, the 

Jaccard’s Similarity Indices were calculated using only the 

abundant (common) species because many previous qualitative 

wetland assessments used relative abundance of common plant 

species to characterize the wetlands (Jongman and others, 

1995). Among the pairs of marsh wetlands compared using 

only abundant species, however, most of the pairs of marsh 

wetlands in the current study shared only one or two plant 

species. The index was even less useful for comparing cypress 

wetlands, where there are few herbaceous plant species in the 

deep and intermediate plots. The majority of pairs of cypress 

wetlands compared using the index shared only one species 

(pond cypress), and 7 of the 10 possible cypress wetland 

comparisons would have had no species in common if pond 

cypress trees had not been included in the calculations.

Table 19. The percentage of time that fixed vegetation plots were 

flooded during the recent period (2000–02 or 2002–04), based on 

stage data and bathymetry. 

 [>, greater than]

Wetland name (and data 

collection period)

Percentage of time flooded

Deep

plots

Intermediate

plots

Transitional

plots

GS Natural Marsh (2000–02) >65 65 31

HRSP Natural Marsh (2000–04) >71 71 53

W-29 Impaired Marsh (2000–021) >18 12 0

W-29 Impaired Marsh (2002–042) >99 99 67

Duck Pond Augmented Marsh 

(2000–04) 100 91 5

W-3 Augmented Marsh (2000–02) >61 61 0

GS Natural Cypress (2002–04) >77 77 62

S-68 Natural Cypress (2002–04) >96 80 52

W-19 Impaired Cypress (2002–04) >93 93 61

S-63 Augmented Cypress 

(2002–04) >86 >86 30

W-5 Augmented Cypress 

(2002–04) >62 >62 55

1 Period of average rainfall and ground-water pumping.

2 Period of above-average rainfall and reduced ground-water pumping.
104 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Table 20. Jaccard’s Similarity Index matrices (using all species greater than 1 percent of abundance) for vegetation in 

fixed plots in cypress wetlands, 2000-04.

[Colors indicate wetland group: green, natural; brown, impaired; blue, augmented; numbers indicate total number of plant species in plots; 

%, percent] Deep plots

GS Natural 

Cypress

S-68 Natural 

Cypress

W-19 Impaired 

Cypress

S-63 Augmented 

Cypress

W-5 Augmented 

Cypress

GS Natural Cypress 1 species 0% 0% 0% 0%

S-68 Natural Cypress 3 species 0% 14% 0%

W-19 Impaired Cypress 6 species 0% 0%

S-63 Augmented Cypress 11 species 0%

W-5 Augmented Cypress 1 species

Intermediate plots

GS Natural 

Cypress

S-68 Natural 

Cypress

W-19 Impaired 

Cypress

S-63 Augmented 

Cypress

W-5 Augmented 

Cypress

GS Natural Cypress 4 species 0% 0% 7% 0%

S-68 Natural Cypress 9 species 0% 5% 0%

W-19 Impaired Cypress 8 species 18% 0%

S-63 Augmented Cypress 11 species 13%

W-5 Augmented Cypress 7 species

Transitional plots

GS Natural 

Cypress

S-68 Natural 

Cypress

W-19 Impaired 

Cypress

S-63 Augmented 

Cypress

W-5 Augmented 

Cypress

GS Natural Cypress 9 species 6% 7% 0% 0%

S-68 Natural Cypress 10 species 7% 14% 0%

W-19 Impaired Cypress 6 species 0% 7%

S-63 Augmented Cypress 14 species 5%

W-5 Augmented Cypress 9 species

When the species richness data from fixed plots sampled 

semiannually were combined with the data from random plots 

sampled quarterly, mean species richness also was generally 

lower in natural marshes (17-21) and natural cypress wetlands 

(14-20) than in augmented marshes (23-29) and augmented 

cypress wetlands (18-24) (tables 22 and 23). Species richness 

at W‐29 Impaired Marsh (15) was lower than at the natural 

marshes, but at W‐19 Impaired Cypress species richness 

(17) was similar to that of the natural cypress.

Sampling randomly located plots at the marshes 

improved the estimates of species richness by 31-40 percent at 

the natural marshes and by 32-53 percent at the augmented 

marshes. The addition of random plots improved those 

Species Richness

Species richness is a commonly used measure of 

community composition in ecological studies, and is simply a 

count of the number of different species in a sample or group 

of samples. In the fixed vegetation plots sampled semiannually in this study, the mean species richness of plants at the 

natural marshes (17) and the natural cypress wetlands (16) was 

slightly lower than the mean species richness at the augmented 

marsh wetlands (19) and the augmented cypress wetlands 

(19). Mean species richness also was lower at W‐29 Impaired 

Marsh (14) and at W‐19 Impaired Cypress (16) than at the 

augmented wetlands. 
Wetland Ecology 105

estimates by only 18-27 percent at the natural cypress 

wetlands and by 13-14 percent at the augmented cypress 

wetlands. Overall, the greatest number of species at wetlands 

in this study was found at two of the augmented wetlands. 

At Duck Pond Augmented Marsh, which had 29 species, more 

than half of the total wetland area was flooded 81 percent 

of the time (table 12), enabling many obligate species to 

remain established. In contrast, at S‐63 Augmented Cypress, 

which had 24 species, more than half of the total wetland 

area was flooded only 33 percent of the time. Moreover, 

S‐63 Augmented Cypress had a flooded area that fluctuated rapidly and frequently during the study, and was often 

completely dry. The frequency and extent of fluctuations in the 

hydrograph and the extent of flooded area at S‐63 Augmented 

Cypress likely contributed to the unusually high density and 

species richness of emergent species at this site. 

Species richness in wetlands is influenced by many 

factors. Studies of wetlands that are shallow depressions 

indicate that species composition can vary considerably 

over time, and also vary spatially within the same wetland 

(Swanson and others, 2003). The importance of hydrologic 

conditions to species richness has been observed in studies 

of natural wetlands. Studies of emergent wetlands in the 

northwestern United States (Magee and Kentula, 2005) found 

that the richest assemblages of plants were present in wetlands 

with relatively low water-level variability. Wetland size also 

is an important influence on species richness. A study of 

58 large marsh and swamp wetlands in southeastern Ontario, 

Canada, indicated that plant species richness was positively 

correlated with wetland area (Houlahan and others, 2006). 

About 20 percent of all the species identified in that study 

were found in only one wetland. This observation agrees with 

the relatively low similarity indices obtained for wetland plant 

species comparisons in the present study. Furthermore, 49 of 

the 58 wetlands in the Ontario study contained at least one 

species unique to that wetland. Those results suggest that no 

single wetland, regardless of size, can conserve the landscape 

diversity of aquatic plants, and that small wetlands may be 

critically important for the conservation of rare species. 

Relative Abundance of Wetland Plants by 

Indicator Category

The relative abundance of wetland plant species in 

various indicator categories (obligate, facultative wet, facultative, facultative upland, upland, and undetermined) (Florida 

Department of Environmental Protection, 2004) differed among 

some of the wetland groups in this study (fig. 61). The natural 

and impaired marshes had a somewhat higher percentage 

(52-53 percent) of obligate species than W‐3 Augmented Marsh 

(38 percent), but the percentage was similar to Duck Pond 

Augmented Marsh. Natural marshes had a higher percentage of 

facultative wet species than Duck Pond Augmented Marsh but 

a similar percentage to W-3 Augmented Marsh. The impaired 

marsh, however, had a much lower percentage of facultative wet 

species (7 percent). Natural and augmented marshes had similar 

percentages of facultative species (14 percent and 15 percent, 

respectively), whereas W‐29 Impaired Marsh had twice as many 

facultative species (33 percent).

The natural cypress and the augmented cypress 

wetlands did not differ in their percentage of obligate plant 

species (39 percent and 40 percent, respectively), whereas 

W‐19 Impaired Cypress had only 29 percent obligate 

species. Natural and augmented cypress wetlands also had 

the same percentage of facultative wet species (27 percent), 

Table 21. Jaccard’s Similarity Index comparing vegetation in 

fixed plots sampled during 2000-02 (the period of average rainfall) 

with vegetation in fixed plots sampled during 2002-04 (the period 

of above-average rainfall and reduced ground-water pumping). 

Wetland name 

Jaccard’s Similarity Index (percent)

Deep

plots

Intermediate

plots

Transitional

plots

GS Natural Marsh 25 38 56

HRSP Natural Marsh 67 30 40

W-29 Impaired Marsh 25 33 16

Duck Pond Augmented Marsh 83 50 33

W-3 Augmented Marsh 100 50 50

GS Natural Cypress 100 50 55

S-68 Natural Cypress 67 44 90

W-19 Impaired Cypress 17 0 33

S-63 Augmented Cypress 45 64 33

W-5 Augmented Cypress 100 29 67

High density of emergent vegetation at S-63 

Augmented Cypress wetland
106 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Table 22. Plant species in fixed and randomly located plots in marsh wetlands.

[Bold type indicates abundant species (more than 10 percent of the plant community). Species type: FAC, facultative; FACW, facultative wet; FACU, facultative upland; OBL, obligate; --, not classified]

GS Natural Marsh 

(17 species)

HRSP Natural Marsh 

(21 species)

W-29 Impaired Marsh 

(15 species)

Duck Pond Augmented Marsh 

(29 species)

W-3 Augmented Marsh 

(23 species)

Species name Type Species name Type Species name Type Species name Type Species name Type

Amphicarpum muhlenbergianum FACW Amphicarpum muhlenbergianum FACW Amphicarpum muhlenber­ gianum FACW Ampelopsis arborea FAC Amphicarpum muhlenbergianum FACWAndropogon virginicus FAC Andropogon virginicus FAC Andropogon virginicus FAC Amphicarpum muhlenbergianum FACW Andropogon glomeratus var. pumilus --Carex joorii FACW Erigeron quercifolius FAC Conyza canadensis FACU Andropogon glomeratus 

var. pumilus

 -- Berchemia scandens FACW

Carex verrucosa FACW Juncus maiginatus FACW Eupatorium capillifolium FAC Andropogon virginicus FAC Callicarpa americana FACUEriocaulon compressum OBL Lacnanthes caroliana FAC Euthamia caroliniana FAC Aristida palustris OBL Carex joorii FACWLachnanthes caroliana FAC Leersia hexandra OBL Hypericum fasciculatum OBL Centella asiatica FACW Hydrocotyle umbellata FACWPanicum hemitomon OBL Ludwigia linearis OBL Lachnanthes caroliana FAC Chara sp. -- Leersia hexandra OBLPolygala lutea FACW Nymphaea odorata OBL Nymphaea odorata OBL Cyperus haspan OBL Ludwigia repens OBLPolygala rugellei FACW Oxypolis filiformis OBL Panicum hemitomon OBL Eleocharis equisetoides OBL Mikania scandens FACWPontederia cordata OBL Panicum hemitomon OBL Paspalum setaceum FAC Eleocharis vivipara OBL Myrica cerifera FACProserpinaca pectinata OBL Panicum verrucosum FACW Rhynchospora microcarpa OBL Erigeron quercifolius FAC Nymphaea odorata OBLRhynchospora cephalantha OBL Panicum virgatum FACW Saccharum baldwinii OBL Fuirena squarrosa OBL Panicum hemitomon OBLRhynchospora fascicularis FACW Pluchea rosea FACW Sagittaria graminea OBL Hydrocotyle umbellata FACW Pontederia cordata OBLSaccharum giganteum OBL Polygala lutea FACW Utricularia purpurea OBL Juncus marginatus FACW Pteridium aquilinum --Sagittaria graminea OBL Polygonum 

 hydropiperoides

OBL Xyris fimbriata OBL Juncus megacephalus OBL Ptilimnium 

 capillaceum

FACW

Utricularia purpurea OBL Pontederia cordata OBL Leersia hexandra OBL Quercus laurifolia FACWXyris fimbriata OBL Proserpinaca pectinata OBL Ludwigia microcarpa OBL Rubus cuneifolius FAC

Rhynchospora inundata OBL Mikania scandens FACW Sagittaria latifolia OBLSagittaria graminea OBL Nuphar advena OBL Salix caroliniana OBLScleria baldwinii FACW Nymphoides aquatica OBL Serenoa repens FACUUtricularia foliosa OBL Panicum hemitomon OBL Smilax bona-nox FAC

Panicum rigidulum FACW Typha latifolia OBLPhyla nodiflora FAC Xyris fimbriata OBLPontederia cordata OBLProserpinaca palustris OBLRhynchospora colorata FACWRhynchospora microcarpa OBLSagittaria latifolia OBLSetaria parviflora FAC
Wetland Ecology 107

Table 23. Plant species in fixed and randomly located plots in cypress wetlands.[Bold type indicates abundant species (more than 10 percent of the plant community). Species type: FAC, facultative; FACW, facultative wet; FACU, facultative upland; OBL, obligate; --, not classified]

GS Natural Cypress 

(14 species)

S-68 Natural Cypress 

(20 species)

W-19 Impaired Cypress 

(17 species)

S-63 Augmented Cypress 

(24 species)

W-5 Augmented Cypress 

(18 species)

Species name Type Species name Type Species name Type Species name Type Species name Type

Cephalanthus occidentalis OBL Amphicarpum muhlenbergianum FACW Acer rubrum FACW Acer rubrum FACW Callicarpa americana FACUIlex cassine OBL Andropogon virginicus FAC Carex longii FACW Amphicarpum muhlenbergianum FACW Dichanthelium commutatum FACLachnanthes caroliana FAC Andropogon virginicus var. 

glaucus

FAC Carex verrucosa FACW Andropogon virginicus FAC Erechtites hieracifolia FAC

Ludwigia lanceolata OBL Aristida condensata -- Dichanthelium ensifolium 

var. unciphyllum

FAC Aristida stricta var. 

beyrichiana

FAC Lycopus rubellus OBL

Lyonia lucida FACW Aristida palustris OBL Dichanthelium sp. -- Aster elliottii OBL Melothria pendula FACWOsmunda cinnamomea FACW Aristida stricta var. beyrichiana FAC Habenaria floribunda FACW Blechnum serrulatum FACW Oplismenus hirtellus FACSagittaria graminea OBL Coelorachis rugosa FACW Lemna obscura OBL Coelorachis rugosa FACW Panicum anceps FACSerenoa repens FACU Dichanthelium ensifolium 

var. unciphyllum

FAC Melothria pendula FACW Cyperus distinctus OBL Panicum rigidulum FACW

Smilax laurifolia FACW Dichanthelium erectifolium OBL Mikania scandens FACW Ludwigia repens OBL Polygonum hydropiperoides OBLTaxodium ascendens OBL Eupatorium capillifolium FAC Myrica cerifera FAC Lycopus rubellus OBL Quercus laurifolia FACWToxicodendron radicans FAC Hypericum fasciculatum OBL Paspalum repens OBL Mikania scandens FACW Rhynchospora corniculata OBLVitis rotundifolia FAC Hypericum myrtifolium FACW Ptilimnium capillaceum FACW Myrica cerifera FAC Rhynchospora miliacea OBLWoodwardia virginica FACW Ilex glabra FACW Serenoa repens FACU Panicum hemitomon OBL Riccia fluitans --Xyris fimbriata OBL Lachnanthes caroliana FAC Taxodium ascendens OBL Panicum rigidulum FACW Sagittaria graminea OBL

Panicum hemitomon(A) OBL Toxicodendron radicans FAC Persea palustris OBL Serenoa repens FACUPluchea rosea FACW Utricularia foliosa OBL Pluchea odorata FACW Smilax bona-nox FACRhynchospora corniculata OBL Utricularia inflata OBL Rhynchospora corniculata OBL Taxodium ascendens OBLSerenoa repens FACU Rhynchospora microcarpa OBL Thelypteris palustris FACWTaxodium ascendens OBL Rhynchospora miliacea OBLUtricularia purpurea OBL Rubus cuneifolius FAC

Saccharum baldwinii OBLSerenoa repens FACUTaxodium ascendens OBLWoodwardia virginica FACW
108 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

but W‐19 Impaired Cypress had more facultative wet species 

(41 percent). Natural cypress and augmented cypress wetlands 

had similar percentages of facultative species (25 and 22 percent, 

respectively), and the W‐19 Impaired Cypress had 18 percent 

facultative species.

The proportion of facultative upland and undetermined 

plant species varied somewhat among sites, and no patterns were 

evident. Although facultative upland plants are rarely found in 

wetlands, they may be present at the wetland edge or in areas 

with a higher elevation within a wetland, such as on hummocks. 

Sample plots in the natural marshes had no facultative upland or 

undetermined species, whereas they constituted 0 to 9 percent of 

the plants in augmented marshes and 7 percent of the plants in 

W‐29 Impaired Marsh. The percentage of facultative upland and 

undetermined species averaged 6 percent at the natural cypress 

wetlands, ranged from 4 to 11 percent at the augmented cypress 

wetlands, and was 6 percent at W‐19 Impaired Cypress.

It is widely accepted that the relative abundance of plants 

in different indicator categories is not a precise descriptor of 

wetland hydrologic conditions. For example, although many 

obligate wetland species are found in permanently or semipermanently flooded wetlands, a number of obligate species 

also are present in wetlands that are temporarily or seasonally 

flooded. In a given wetland, a high proportion of facultative 

plant species indicates relatively dry conditions during the most 

recent growing season (Adamus and others, 1991). Further quantitative studies are needed before plant indicator status can be 

used as stand-alone evidence of short- or long-term hydrologic 

conditions. One such study is underway in the northern Tampa 

Bay area to determine the frequency at which individual wetland 

plant species are found at measured depths in cypress wetlands 

(GPI Southeast, Inc., 2006). Tampa Bay Water and SWFWMD 

also are applying a regional annual Wetland Assessment 

Procedure to describe the occurrence of wetland plants by 

indicator status, and the associated changes in wetland hydrology 

Figure 61. Relative abundance of obligate, facultative wet, facultative, and facultative upland plants in marsh and cypress wetlands.

DUCK POND

AUGMENTED

MARSH

100

90

80

70

60

50

40

30

20

10

0 GS

NATURAL

MARSH

W-29

IMPAIRED

MARSH

W-3

AUGMENTED

MARSH

PLANT TYPE, IN PERCENT OF TOTAL

GS

NATURAL

CYPRESS

W-19

IMPAIRED

CYPRESS

S-63

AUGMENTED

HRSP CYPRESS

NATURAL

MARSH

W-5

AUGMENTED

CYPRESS

S-68

NATURAL

CYPRESS

EXPLANATION

OBLIGATE

FACULTATIVE WET

FACULTATIVE

FACULTATIVE UPLAND

UNDETERMINED
Wetland Ecology 109

over time (Southwest Florida Water Management District and 

Tampa Bay Water, 2005). These detailed data will be useful 

in future assessments of wetland plant distribution, zonation 

patterns, and plant tolerance to changing wetland hydrology. 

Plant Biomass in Marshes

Estimates of plant biomass in marshes (expressed as dry 

weight per square meter) were restricted to herbaceous vegetation growing in water depths of about 0.3 m and, therefore, are 

not representative of plant biomass throughout each wetland. 

Samples from the five marsh wetlands can be compared, 

however, because they were collected at similar water depths and 

during the same time periods. Duck Pond Augmented Marsh and 

W‐3 Augmented Marsh had higher average vegetation biomass 

(717 g/m2 and 581 g/m2, respectively) than GS Natural Marsh 

and HRSP Natural Marsh (308 and 452 g/m2, respectively) 

(table 24). Vegetation biomass at W‐29 Impaired Marsh 

(384 g/m2) was within the range of values for the natural 

marshes. The higher biomass of herbaceous vegetation in 

augmented marsh wetlands may be related to the higher concentrations of phosphorus made available as accumulated dead 

plant material slowly decays. For example, concentrations of 

total phosphorus were substantially higher in W‐3 Augmented 

Marsh (median 0.03 mg/L) than in the natural and impaired 

marshes (median 0.01 mg/L). In Duck Pond Augmented Marsh, 

however, the median concentration of total phosphorus was only 

0.01 mg/L; at this site, the high leakance rate may prevent phosphorus accumulation. Natural wetlands in this study appeared to 

be phosphorus limited, based on the high nitrogen-to-phosphorus 

ratios found in their surface waters (fig. 44).

Tree Density and Size in Cypress Wetlands

The mean density of cypress trees in the two natural 

cypress wetlands (2,985 trees/ha) was more than 25 percent 

greater than in the two augmented wetlands (2,322 trees/ha) and 

W‐19 Impaired Cypress (2,226 trees/ha). The mean percentages 

of fallen trees, dead trees, and stumps were substantially smaller 

in the two natural wetlands (10.1 percent) than in the two 

augmented wetlands (28.0 percent) or W‐19 Impaired Cypress 

(34.6 percent). Persistent dry conditions in W‐19 Impaired 

Cypress and in the augmented wetlands prior to augmentation 

are the presumed reason for the relatively high number of dead 

trees at these sites. 

The 10.5-cm mean diameter of cypress trees in the 

natural wetlands was smaller than the 12.5-cm diameter in the 

augmented wetlands, and 17.6-cm diameter in the impaired 

wetland. The larger mean diameter and lower mean density of 

trees in augmented and impaired wetlands may be the cumulative result of years of failed seed germination and poor seedling 

survival, resulting in an absence of young trees. Cypress can 

only germinate on dry land (Demaree, 1932). Moreover, the 

regeneration of Taxodium spp. requires a sequence of hydrologic 

conditions unlikely to exist under altered hydrologic regimes 

prevalent in augmented wetlands or impaired wetlands, specifically, prolonged flooding, followed by drawdown, quickly 

followed by moderate water levels (Dickson and Broyer, 

1972; Deghi, 1984). A greater cypress tree growth rate at 

S‐63 Augmented Cypress, compared to unaugmented wetlands, 

was observed when Tampa Bay Water staff was monitoring 

the wetland in the mid-1990s (Chris Shea, Tampa Bay Water, 

written commun., 2007). The availability of nutrients released by 

partially decayed wetland vegetation may contribute to enhanced 

tree growth.

Effects of Environmental Stressors on Wetland 

Plant Communities

Numerous environmental stressors related to human 

activities, including physical disturbance, nutrient enrichment, 

and disturbance to the hydrologic regime resulting in desiccation, 

excessive inundation, and increased or decreased hydroperiod, 

have been associated with an increase or decrease in abundance 

of some plants species in wetlands (Wilcox, 1995; Shay and 

others, 1999; Kowalski and Wilcox, 2003). Doherty and others 

(2000a) surveyed wetland studies in Florida and developed 

lists of “tolerant” and “intolerant” plant taxa that decreased 

or increased, respectively, in response to numerous stressors. 

The relative abundance of these plant species, therefore, could 

be used to indicate the amount of overall disturbance from 

environmental stressors that has occurred in Florida wetlands. 

In the present study, there was a relatively higher percentage 

of intolerant species and a lower percentage of tolerant species 

at natural marsh and cypress wetlands compared to augmented 

and impaired wetlands (fig. 62). At augmented marsh and 

cypress wetlands there were relatively more tolerant species than 

intolerant species (table 25). However, the overall differences 

were small and could not be used to reliably distinguish natural 

from augmented sites.

Although the amount of physical disturbance in the vicinity 

of wetlands in this study varied, areas surrounding natural 

wetlands generally were the least disturbed. The natural marsh 

and cypress wetlands are surrounded by flatwoods or unmanaged 

pine flatwoods. Some wetlands on well fields are near paved 

roads, which can change the pattern of surface-water flow and 

decrease runoff to the wetlands. At W‐5 Augmented Cypress, 

an unpaved road breached the wetland perimeter and increased 

runoff from the wetland. At Duck Pond Augmented Marsh, the 

Table 24. Biomass of vegetation in marsh wetlands.

[Min., minimum value; Max., maximum value]

Wetland name Number of 

samples

Plant biomass, in grams of

dry weight per square meter

Mean Min. Max.

Green Swamp Natural Marsh 19 308 248 372

HRSP Natural Marsh 19 452 244 548

W-29 Impaired Marsh 9 384 332 427

Duck Pond Augmented Marsh 19 717 619 856

W-3 Augmented Marsh 21 581 397 800
110 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

area directly adjacent to the wetland edge is regularly mowed, 

and the area adjacent to that is an agriculturally managed 

pine plantation. The widespread practice of clearing the areas 

surrounding wetlands prior to agricultural and urban land use 

facilitates the invasion of wetlands by weedy (tolerant) plant 

species (Rochow, 1998; Angeler and Garcia, 2005). Habitat 

fragmentation and physical disturbance also tend to favor plant 

species that can disperse their seeds widely, such as Typha sp., 

Salix caroliniana, and Eupatorium capillifolium. These particular species were found at the augmented and impaired marshes 

in the present study. Land clearing within 250 m of the edge 

of wetlands in southeastern Ontario, Canada, was shown to 

interfere with critical seed sources (Houlahan and others, 2006). 

That study suggested that wetlands cannot be managed in isolation from their surrounding uplands or other adjacent wetlands 

without impairing germination and growth of indigenous plant 

species. 

One of the changes associated with reduced hydroperiod 

and lower water levels is a reduction in the size of the wetland 

flooded area (Mortellaro and others, 1995). Differences in 

wetland topography, exemplified by Duck Pond Augmented 

Marsh and S‐63 Augmented Cypress, can lead to substantially 

different effects on the size of wetland flooded area when 

wetland water levels are reduced. Even slight water-level 

reductions (as measured at the staff gage) at S‐63 Augmented 

Cypress may eliminate large areas of flooding and the associated aquatic plant habitat, whereas water-level reductions of a 

similar magnitude at Duck Pond Augmented Marsh resulted in 

little change in the flooded area and aquatic plant habitat along 

the wetland edge. The reduction in wetland flooded area can 

increase distances between wetlands, fragmenting the aquatic 

habitats available to wetland plants. 

Wetland plants may not be useful as sole indicators of 

changes in the hydrologic regime (Tiner, 1991), but may 

be relied upon with more success when used in conjunction with measurement of physical characteristics including 

flood frequency and flood duration (Haag and others, 2005). 

The Wetland Assessment Procedure used by SWFWMD and 

Tampa Bay Water (2005) relates changes in wetland plant 

distribution to changes in wetland hydrologic regime on a yearly 

basis, and ultimately over longer time periods. Magee and 

Kentula (2005) studied emergent wetlands in the northwestern 

United States and found that large increases in annual water 

depth will likely exclude many emergent marsh species and 

favor aquatic assemblages more typically found in permanently 

flooded ponds. However, Kirkman and others (1999) discuss the 

difficulty of extracting useful metrics from depression wetlands 

for which normal hydrologic variability is great, because some 

plant species can withstand intense hydrologic stress and many 

species are adapted to a wide variety of hydrologic conditions.

In addition to sensitivity to physical disturbance, some 

wetland plants have varying tolerance to changes in water 

quality. In studies of lakes in Florida, for example, a number 

of wetland plants were found in lakes with low phosphorus 

concentrations, but not in lakes with higher concentrations 

(Doherty and others, 2000a). Several of the plant taxa found 

in that study (Eriocaulon spp., Hypericum spp., Lacnanthes 

caroliniana, Utricularia purpurea, and Xyris spp.) were 

found only in unaugmented wetlands in the current study. 

The natural and impaired wetlands derive their phosphorus 

from rainfall, and therefore, have relatively low phosphorus 

concentrations. Several wetland plant species also have 

been associated with low nitrogen concentrations in lakes, 

including Eriocaulon spp., Hypericum spp., Leersia hexandra, 

and Xyris spp. These species were found at several of the 

natural and impaired wetlands in the present study, although 

total nitrogen was relatively higher at those sites than at the 

augmented sites. Craft and others (1995) reported increased 

growth of Chara spp. in wetlands with moderate phosphorus 

enrichment, and evidence of replacement of Utricularia spp. 

by Chara at those sites. Duck Pond Augmented Marsh, which 

had a relatively low total phosphorus concentration, was 

the only site in the study containing Chara spp.; conversely, 

Utricularia was not found at this site. Chara spp. thrive in 

the presence of high calcium concentrations such as those 

found at Duck Pond Augmented Marsh. Houlahan and others 

(2006) found a strong negative correlation between nutrient 

concentrations and plant species richness, whereby eutrophication of wetlands led to reduced species richness. However, the 

range of nutrient concentrations in the wetlands in the present 

study cannot be characterized as eutrophic. Cattails (Typha

spp.) have been observed to have a competitive advantage at 

sites with elevated nutrient concentrations and high rates of 

silt accumulation (Wilcox and others, 1984). W‐3 Augmented 

Marsh is one of the two sites in this study where cattails were 

established, and this site had the highest phosphorus concentration as well as the thickest accumulation of soft sediments. 

Newman and others (1998) found that the combination of 

elevated nutrients and increased water depth favors the growth 

of cattail in the Everglades.

The higher pH of augmentation water may alter 

vegetation community in augmented wetlands compared to 

natural wetlands. For example, Eriocaulon spp., Lacnanthes 

caroliniana, Utricularia purpurea, and Xyris spp. were found in 

Figure 62. Number of tolerant and intolerant plant species 

at natural, impaired, and augmented wetlands.

14

12

10

8

6

4

2

0

NUMBER OF SPECIES

NATURAL

WETLANDS

AUGMENTED

WETLANDS

IMPAIRED

WETLANDS

Intolerant species

Tolerant species
Wetland Ecology 111

the present study at natural marsh and cypress wetlands, where 

the pH is low (4.2-4.8), but not at augmented sites where the pH 

typically is above 7.0. Conversely, Mikania scandens, Sagittaria 

latifolia, and Typha spp. were found at the augmented marshes. 

These are species that tend to be found in Florida lakes at 

relatively high values of pH (Doherty and others, 2000a).

It is difficult to distinguish between the natural variability 

of plant communities in the 10 wetlands in the present study 

and plant responses to hydrologic changes associated with 

augmentation, even though wetland plants are sensitive to 

hydrologic change (Wilcox, 1995) and have been used to assess 

conditions in wetlands in the northern Tampa Bay area (Rochow, 

1994). In part, this may be due to the small number of wetlands 

in each group and of each type in this study, and the relatively 

short duration of the assessment period. The number of shared 

vegetation species in fixed plots at comparable locations in the 

hydrologic gradient was relatively low among the same type 

of wetlands (marsh or cypress) in the same group (natural or 

augmented), and therefore, similarity indices were not useful in 

determining differences among wetland groups. 

Table 25. Wetland plants that tend to decrease or increase in abundance with disturbance.

[Data are from Doherty and others, 2000; A, abundant; P, present]

Species name

GS

Natural

Marsh

HRSP

Natural

Marsh

GS

Natural

Cypress

S-68

Natural

Cypress

W-29

Impaired

Marsh

W-19

Impaired

Cypress

Duck

Pond

Augmented

Marsh

W-3

Augmented

Marsh

S-63

Augmented

Cypress

W-5

Augmented 

Cypress

Plant taxa that typically decrease in abundance with disturbance

Bacopa caroliniana

Eleocharis (not E. baldwinii) A

Eriocaulon A

Hypericum fasciculatum A A

Juncus repens

Nymphaea A A

Nymphoides aquatica A

Polygala

Pontederia cordata A A

Rhynchospora corniculata, R. inundata A A A A

Sagittaria A A P A A A A

Sphagnum A

Utricularia inflata, U. purpurea A A A A

Xyris fimbriata A P A A

Plant taxa that typically increase in abundance with disturbance

Amphicarpum A A P A A P P

Andropogon P A A A A P A

Axonopus 

Blechnum A

Erianthus

Eupatorium P A

Euthamia minor A

Lycopus A P

Paederia

Paspalum notatum

Pinus spp.

Rubus spp. P

Smilax spp., S. glauca P P P

Woodwardia A P
112 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Macroinvertebrates

The composition of macroinvertebrate communities 

reflects the biological conditions in wetlands at the 

most fundamental level (Doherty and others, 2000a). 

Macroinvertebrates are a trophic link between primary 

producers, plant-derived detritus, and higher trophic levels 

such as fish, amphibians, and waterfowl. Because of these 

food-web linkages, the taxa richness and abundance of 

macroinvertebrates, and the relative abundance of selected 

taxonomic groups, have been used to indicate overall aquatic 

ecosystem condition. Macroinvertebrates in depression 

wetlands are found along a continuum of abiotic conditions. 

The tolerances of macroinvertebrates to changing water depth 

and water quality vary between and among taxonomic groups.

Marsh Macroinvertebrate Communities

The macroinvertebrate taxonomic groups (Order: Family) 

found with the greatest frequency in the two natural marsh 

wetlands were mayflies (Ephemeroptera: Baetidae), dragonflies and damselflies (Odonata: Coenagrionidae, Aeschnidae, 

Libellulidae), true bugs (Hemiptera: Belastomatidae, 

Notonectidae), beetles (Coleoptera: Dytiscidae, Haliplidae), 

and true flies (Diptera: Chironomidae) (tables 26, 27). 

Numerically, the most abundant families were Cambaridae, 

Chaoboridae, Chironomidae, Dytiscidae, and Libellulidae. 

Crayfish (Procambarus) were found in about 24 percent of 

samples in GS Natural Marsh and in 90 percent of the samples 

at HRSP Natural Marsh (table 27). Mean taxa richness was 

15.4 taxa/m2 at GS Natural Marsh and 19.9 taxa/m2 at HRSP 

Natural Marsh (fig. 63C). The higher taxa richness at HRSP 

Natural Marsh primarily was attributable to more species of 

Odonata at this site. Twenty families of macroinvertebrates 

were collected at GS Natural Marsh and 18 families were 

collected at HRSP Natural Marsh (table 26). Shannon diversity 

was similar at the two natural marshes (1.40-1.51) (fig. 64). 

Macroinvertebrate biomass also was similar at the two natural 

marshes, but mean macroinvertebrate density (primarily of 

Diptera in the family Chaoboridae) was substantially higher 

at HRSP Natural Marsh (173.4 individuals/m2) than at GS 

Natural Marsh (73.1 individuals/m2) (fig. 63A-B).

Hemiptera and Coleoptera were less abundant at 

W‐29 Impaired Marsh than in the natural marshes (table 27). 

The freshwater shrimp Palaemonetes paludosus was present 

in 100 percent of samples from this site (table 27) at a relatively high mean density (35.3 individuals/m2). Taxa richness 

(19.0 taxa/m2) at W‐29 Impaired Marsh was similar to HRSP 

Natural Marsh (fig. 63C), although only 10 families of macroinvertebrates were collected at this site (table 26). Shannon 

diversity was much lower (1.00) than at the natural marshes 

(fig. 64), primarily because the macroinvertebrate density 

was much higher (greater than 450 individuals/m2) (fig. 63B). 

Diptera (Chironomidae and Chaoboridae) contributed most 

to the higher densities of macroinvertebrates (table 27), but 

Figure 63. Biomass, density, and taxa richness of 

macroinvertebrates in marsh wetlands.

(A) MACROINVERTEBRATE BIOMASS

GS

Marsh

HRSP

Marsh

W-29

Marsh

Duck Pond

Marsh

W-3

Marsh

10,000

1,000

100

10

1

Impaired

Marsh

MEAN DRY WEIGHT, IN MILLIGRAMS

PER SQUARE METER

Augmented

Marsh

Natural

Marshes

(B) MACROINVERTEBRATE DENSITY

600

500

400

300

200

100

0

MEAN DENSITY

PER SQUARE METER

Impaired

Marsh

Augmented

Marshes

Natural

Marshes

GS

Marsh

HRSP

Marsh

W-29

Marsh

Duck Pond

Marsh

W-3

Marsh

(C) MACROINVERTEBRATE TAXA RICHNESS

MEAN NUMBER OF TAXA

PER SQUARE METER

Impaired

Marsh

Augmented

Marshes

Natural

Marshes

30

25

20

15

10

5

0

GS

Marsh

HRSP

Marsh W-29

Marsh

Duck Pond

Marsh

W-3

Marsh
Wetland Ecology 113

Figure 64. Shannon diversity of macroinvertebrates in marsh and cypress wetlands.

Table 26. Summary of macroinvertebrate community assessment.

[mg, milligrams; m2, square meter; Coleoptera families in lime green; Crustacea families in black; Decapoda families in red; Diptera families 

in dark green; Ephemeroptera families in pink; Gastropoda families in blue; Odonata families in orange]

Wetland name

(and number of samples)

Total

number 

of 

families

Most abundant families

Mean

biomass

(mg/m2)

Mean 

taxa

richness

Mean 

density

(individuals/

m2)

Mean 

Shannon 

diversity

GS Natural Marsh (21) 20 Cambaridae, Chironomidae, 

Dytiscidae, Libellulidae 529.1 15.4 73.1 1.51

HRSP Natural Marsh (21) 18 Cambaridae, Chaoboridae,

Chironomidae, Libellulidae 787.7 19.9 173 1.40

W-29 Impaired Marsh (9) 10 Baetidae, Chaoboridae, Chironomidae, 

Palaemonidae 134.1 19.0 450 0.99

Duck Pond Augmented Marsh (21) 23 Baetidae, Caenidae, Chironomidae, 

Planorbidae 543 24.0 148 1.29

W-3 Augmented Marsh (21) 16 Ampullariidae, Chironomidae, 

Physidae, Planorbidae 9,593 11.9 35.0 1.49

GS Natural Cypress (21) 13 Baetidae, Cambaridae, Chaoboridae, 

Chironomidae 606 13.0 82.7 1.16

S-68 Natural Cypress (21) 14 Caenidae, Cambaridae, Chironomidae, 

Coenagrionidae 65.6 14.5 55.6 1.52

W-19 Impaired Cypress (18) 17 Baetidae, Chironomidae Coenagrionidae, 

Hyalellidae 253.5 20.5 135.7 1.61

S-63 Augmented Cypress (21) 22 Baetidae, Chironomidae Coenagrionidae, 

Physidae 302 20.5 129.3 1.76

W-5 Augmented Cypress (18) 20 Baetidae, Chironomidae, Coenagrionidae, 

Hyalellidae 244.7 21.2 553.3 0.71

2.0

1.5

1.0

0.5

0

GS

NATURAL

MARSH

SHANNON DIVERSITY INDEX

W-29

IMPAIRED

MARSH

W-19

IMPAIRED

CYPRESS

S-63

AUGMENTED

CYPRESS

GS

NATURAL

CYPRESS

S-68

NATURAL

CYPRESS

W-5

AUGMENTED

CYPRESS

HRSP

NATURAL

MARSH

DUCK

POND

AUGMENTED

MARSH

W-3

AUGMENTED

MARSH
114 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Table 27. Mean density, frequency of occurrence, and functional feeding group classification of macroinvertebrates in marsh wetlands. [m2, square meter; SD, standard deviation; C, collector-gatherer; F, filtering collector; G, generalist; H, herbivore; P, predator; S, scraper; SH, shredder; sp., species; *, multiple feeding groups] Macroinvertebrate taxonomy and feeding group classification GS Natural Marsh (21 samples) HRSP Natural Marsh (21 samples) W-29 Impaired Marsh (9 samples) Duck Pond Augmented Marsh (21 samples) W-3 Augmented Marsh (15 samples)

Mean density 

per m2 ± SD

Occurrence 

frequency

 (percent)

 Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ±SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Hirudinea PCrustacea

Amphipoda

Hyalellidae

Hyalella azteca S 0.4 ± 1.4 9.5

Decapoda

Cambaridae

Procambarus alleni

G 2.6 ± 6.1 23.8 11.9 ± 12.6 90.5 0.7 ± 1.3 23.8

Palaemonidae

Palaemonetes paludosus SH 35.3 ± 38.4 100

Insecta

Ephemeroptera

Baetidae

Callibaetis floridanus

C 0.1 ± 0.7 4.8 3.6 ± 4.2 52.4 7.3 ± 12.6 33.3 20.4 ± 32.3 42.9 0.4 ± 1.4 9.5

Caenidae

Caenis diminuta

C 14.3 ± 31.9 33.3

Odonata

Lestidae

Lestes disjusctivus P 5.9 ± 15.0 14.3

Coenagrionidae

Enallagma civale P 1.3 ± 3.6 14.3 2.7 ± 4.6 33.3Enallagma dubium PEnallagma pallidum P 0.4 ± 2.0 4.8 0.7 ± 1.3 22.2 2.3 ± 4.5 28.6Enallagma sp. P 0.1 ± 0.7 4.8 0.3 ± 1.3 4.8Ishnura posita P 3.3 ± 5.4 33.3
Wetland Ecology 115

Macroinvertebrate taxonomy 

and feeding group classification

GS Natural 

Marsh 

(21 samples)

HRSP Natural 

Marsh 

(21 samples)

W-29 Impaired 

Marsh 

(9 samples)

Duck Pond 

Augmented Marsh 

(21 samples)

W-3 Augmented

Marsh 

(15 samples)

Mean density 

per m

2

 ± SD

Occurrence 

frequency

 (percent)

 Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ±SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Ishnura sp. P

Aeschnidae

Anax juniusAnax longipes P 1.7 ± 2.9 33.3 0.3 ± 0.9 9.5 3.0 ± 3.0 66.7Coryphaeschna adnexa P 0.1 ± 0.7 4.8 0.4 ± 1.4 9.5Gomphaeschna antilope P ` 23.8 0.3 ± 0.9 9.5

Libellulidae

Libellula auripennis P 3.3 ± 5.0 42.9 1.0 ± 2.9 14.3 0.7 ± 1.3 22.2Libellula semifasciata P 7.1 ± 8.8 52.4 1.3 ± 3.0 22.2Erythemis simplicolis P 3.0 ± 13.1 9.5 0.6 ± 1.5 14.3 0.4 ± 1.4 9.5Pachydiplax longipennis P 2.0 ± 4.3 19.0Tramea Carolina P 2.9 ± 6.7 19.0 0.1 ± 0.7 4.8

Hemiptera

Belastomatidae

Belastoma sp. P 1.7 ± 3.4 28.6 2.7 ± 4.2 38.1 0.4 ± 1.1 14.3 0.3 ± 1.3 4.8Lethocerus sp. P 0.1 ± 0.7 4.8

Corixidae

Trichocorixa sp. P 0.6 ± 1.8 9.5

Gerridae

Gerris sp. P

Naucoridae

Pelocoris sp. P 0.1 ± 0.7 4.8 0.7 ± 2.0 11.1 2.0 ± 3.9 23.8

Nepidae

Ranatra sp. P 0.4 ± 1.1 14.3 0.3 ± 0.9 9.5 0.4 ± 2.0 4.8

Notonectidae

Buenoa sp. P 0.3 ± 0.9 9.5 3.1 ± 7.9 33.3Notonecta sp. P 2.6 ± 3.7 42.9
116 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Macroinvertebrate taxonomy and feeding group classification GS Natural Marsh (21 samples) HRSP Natural Marsh (21 samples) W-29 Impaired Marsh (9 samples) Duck Pond Augmented Marsh (21 samples) W-3 Augmented Marsh (15 samples)

Mean density 

per m2 ± SD

Occurrence 

frequency

 (percent)

 Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ±SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Veliidae

Microvelia sp. P

Megaloptera

Corydalidae

Chauliodes sp. P

Sialidae

Sialis sp. P

Coleoptera

Chrysomelidae

Disonycha sp.

H 0.7 ± 3.3 4.8

Curculionidae

Onychylis sp.

H 0.3 ± 1.3 4.8 0.3 + 0.9 9.5 1.7 ± 3.7 23.8

Dytiscidae

Celina sp. P 0.1 ± 0.7 4.8Copelatus sp. P 0.1 + 0.7 4.8Coptotomus interogatus P 4.3 ± 10.2 23.8 0.3 ± 1.3 4.8Cybister fimbriolatus P 4.9 ± 6.9 47.6 1.1 ± 2.0 28.6 1.9 ± 2.6 42.9Hydaticus bimarginatus P 2.0 ± 3.0 38.1 0.3 ± 1.3 4.8 5.7 ± 8.9 55.6 2.3 ± 6.4 19.0 0.1 ± 0.7 4.8Hydroporus sp. PLaccophilus proximus P 0.9 ± 2.4 14.3 0.3 ± 0.9 9.5Thermonectes basillaris P 0.1 ± 0.7 4.8

Elmidae

Stenelmis sp.

C 0.1 ± 0.7 4.8

Haliplidae

Peltodytes sp.

H 0.7 ± 1.3 23.8 1.0 ± 2.7 19.0 0.4 ± 1.4 9.5

Hydrophilidae

Berosus sp. P 0.3 ± 1.3 4.8
Wetland Ecology 117

Macroinvertebrate taxonomy 

and feeding group classification

GS Natural 

Marsh 

(21 samples)

HRSP Natural 

Marsh 

(21 samples)

W-29 Impaired 

Marsh 

(9 samples)

Duck Pond 

Augmented Marsh 

(21 samples)

W-3 Augmented

Marsh 

(15 samples)

Mean density 

per m

2

 ± SD

Occurrence 

frequency

 (percent)

 Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ±SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m

2

 ± SD

Occurrence 

frequency 

(percent)

Enochrus sp. P 1.0 ± 2.0 23.8Hydrobiomorpha casata P 1.7 ± 5.0 14.3 0.3 ± 1.3 4.8Hydrochara sp. PTropisternus lateralis P 0.6 ± 1.5 14.3Hydrophilus triangularis P

Noteridae

Mesonoterus addendus P 0.7 ± 2.3 9.5Pronoterus semipunctatus P 0.1 ± 0.7 4.8 0.3 ± 0.9 9.5Suphisellus gibbulus P 1.3 ± 2.4 28.6

Ptilodactylidae

Anchytarsus bicolor H 0.9 ± 1.9 19.0

Scirtidae/Helodidae

Prinocyphon sp. C 0.1 ± 0.7 4.8 0.4 ± 1.1 14.3

Trichoptera

Hydropsychidae

Potamyia sp. F 2.3 ± 6.1 23.8

Hydroptilidae

Oxytheria sp. H 0.1 ± 0.7 4.8

Lepidoptera

Pyralidae H 0.1 ± 0.7 4.8

Diptera

Ceratopogonidae P 1.6 ± 7.2 4.8 2.7 ± 4.1 44.4 0.9 ± 2.9 9.5Chaoboridae P 0.1 ± 0.7 4.8 106.0 ± 248.6 42.9 63.0 ± 59.8 100.0 1.6 ± 5.5 9.5Chironomidae * 40.7 ± 70.8 71.4 12.6 ± 25.7 33.3 341.7 ± 314.6 100.0 59.0 ± 74.8 100.0 4.1 ± 17.0 14.3Culicidae FDixidae CSciomyzidae P
118 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Macroinvertebrate taxonomy and feeding group classification GS Natural Marsh (21 samples) HRSP Natural Marsh (21 samples) W-29 Impaired Marsh (9 samples) Duck Pond Augmented Marsh (21 samples) W-3 Augmented Marsh (15 samples)

Mean density 

per m2 ± SD

Occurrence 

frequency

 (percent)

 Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ±SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Mean density 

per m2 ± SD

Occurrence 

frequency 

(percent)

Stratiomyidae

C 1.1 ± 4.6 9.5

Tabanidae P 0.1 ± 0.7 4.8Tanyderidae

C

Tipulidae

C 0.3 ± 1.3 4.8

Mollusca

Gastropoda

Ampullariidae

Pomacea paludosa S 4.6 ± 6.5 66.7

Ancyllidae

Laevapex fiscus S 1.4 ± 4.1 19.0

Lymnaeidae

Fossoria cubensis S 2.3 ± 4.5 23.8 2.4 ± 3.6 42.9

Physidae

Hatia cubensis S 11.9 ± 19.2 57.1 5.0 ± 8.6 38.1

Planorbidae

Gyraulus parvus S 13.7 ± 29.7 28.6 0.3 ± 0.9 9.5Micromenetus dilatus S 1.1 ± 2.4 23.8Planorbella druryi S 2.3 ± 4.0 33.3 1.9 ± 4.6 19.0Planorbella scalaris S 3.1 ± 5.0 42.9Planorbella trivolvus S 0.3 ± 0.9 9.5 7.3 ± 7.3 71.4

Viviparidae

Viviparous georgianus S 0.7 ± 2.3 9.5

Bivalvia

Sphaeriidae

Musculium lacustre F 0.1 ± 0.7 4.8
Wetland Ecology 119

At W‐19 Impaired Cypress, taxa with a high frequency 

of occurrence included amphipods (Amphipoda: Hyalellidae), 

mayflies (Ephemeroptera: Baetidae), damselflies (Odonata: 

Coenagrionidae), and true flies (Diptera: Chironomidae) 

(table 28). A total of 17 families of macroinvertebrates 

were collected (table 26). Taxa richness (20.5 taxa/m2), 

mean density (135.7 individuals/m2), and mean biomass 

(253.5 mg/m2 ) of macroinvertebrates at W‐19 Impaired 

Cypress were all substantially higher than at either of the 

natural cypress wetlands (fig. 65), whereas Shannon diversity 

(1.61) was similar to that of S‐68 Natural Cypress (fig. 64).

In both of the augmented cypress wetlands, taxa with a 

high frequency of occurrence included crayfish (Decapoda: 

Cambaridae), mayflies (Ephemeroptera: Baetidae), 

damselflies (Odonata: Coenagrionidae), and true flies 

(Diptera: Chironomidae) (table 28). At S‐63 Augmented 

Cypress, snails (Gastropoda: Physidae) were also abundant, whereas at W‐5 Augmented Cypress, amphipods 

(Amphipoda: Hyalellidae) were found in more than 

75 percent of the samples and were extremely abundant (mean 

density 428 individuals/m2) (table 28). Mean taxa richness 

and the number of macroinvertebrate families collected were 

substantially higher at both augmented cypress wetlands 

compared to the natural cypress wetlands (fig. 65C and 

table 26). The relatively even distribution of individuals in 

taxonomic groups at S‐63 Augmented Cypress resulted in the 

highest Shannon diversity value (1.76) in the study (fig. 64). 

In contrast, because of the abundance of amphipods, Shannon 

diversity was much lower at W‐5 Augmented Cypress than at 

the other wetlands (fig. 64). Mean macroinvertebrate biomass 

was similar between S‐63 Augmented Cypress (302 mg/m2) 

and W‐5 Augmented Cypress (244.7 mg/m2) (fig. 65A), but 

because amphipods had a high frequency of occurrence and 

were abundant at W‐5 Augmented Cypress, the mean density 

of macroinvertebrates at that site was substantially higher than 

at S‐63 Augmented Cypress.

Functional Feeding Groups

As noted earlier, macroinvertebrates are a trophic link 

between primary producers and plant-derived detritus, and the 

higher trophic levels in the food web such as fish, amphibians, and waterfowl. The distribution of macroinvertebrates in 

functional feeding groups in wetlands reflects these linkages 

between food resources and how organisms take advantage of 

them (Merritt and Cummins, 1984; Merritt and others, 1996; 

Merritt and others, 1999). The macroinvertebrates collected 

from the 10 wetlands in the present study can be grouped into 

several major functional feeding groups, including generalists, 

predators, herbivores, collector-gatherers, filtering collectors, 

scrapers, and shredders (tables 27 and 28). The proportion of 

taxa in each of these feeding groups varied among natural, 

impaired, and augmented wetlands (fig. 66).

Predator taxa were abundant in all study wetlands, 

both in number of taxa and number of individuals (tables 

27 and 28). Batzer and Wissinger (1996) also reported that 

because these organisms are small, the macroinvertebrate 

biomass at W‐29 Impaired Marsh (134.1 mg/m2) was substantially lower than at either of the natural marshes (fig. 64A).

At W‐3 Augmented Marsh, 16 families of macroinvertebrates were collected (table 26), but only glass shrimp 

(Paleomonetes paludosus), true flies (Diptera: Chaoboridae, 

Chironomidae), and snails (Gastropoda: Ampullariidae, 

Physidae, Planorbidae) were abundant (table 27). Dragonflies 

and damselflies (Odonata) were notably absent at 

W‐3 Augmented Marsh compared to the natural and impaired 

marshes, with only one species collected (table 27). Mean taxa 

richness was lowest at W‐3 Augmented Marsh (11.9 taxa/m2), 

and W‐3 Augmented Marsh also had a much lower mean density 

of macroinvertebrates (35.0 individuals/m2) than any of the other 

marshes (fig. 63B-C). However, because snails were abundant, 

the biomass at W‐3 Augmented Marsh was much higher 

(9,600 mg/m2) than at any other wetland (fig. 63A). Shannon 

diversity at W‐3 Augmented Marsh (1.49) was similar to the 

natural marshes (fig. 64), in part because of the large number of 

snail species.

The macroinvertebrate community at Duck Pond 

Augmented Marsh was more similar to the natural marshes 

than to W‐3 Augmented Marsh. Mayflies (Ephemeroptera: 

Baetidae, Caenidae), true flies (Diptera: Chironomidae), and 

snails (Gastropoda: Planorbidae) were abundant at Duck Pond 

Augmented Marsh (table 26), and mean taxa richness was higher 

(24.0 taxa/m2) than any of the other marshes (fig. 63C). Twentythree families of macroinvertebrates were collected at Duck 

Pond Augmented Marsh (table 26), and Shannon diversity was 

1.29 (fig. 64). The mean biomass of macroinvertebrates at Duck 

Pond Augmented Marsh (543 mg/m2) was similar to GS Natural 

Marsh, and mean macroinvertebrate density (148.3 individuals/

m2) was similar to HRSP Natural Marsh (fig. 63A-B).

Cypress Macroinvertebrate Communities

In the two natural cypress wetlands, crayfish (Decapoda: 

Cambaridae) were found in about 50 percent of the 

samples (table 28). Other taxa with a high frequency of 

occurrence included mayflies (Ephemeroptera: Baetidae, 

Caenidae), damselflies (Odonata: Coenagrionidae), beetles 

(Coleoptera: Dytiscidae), and true flies (Diptera: Chaoboridae, 

Chironomidae) (table 28). There were 13 families of 

macroinvertebrates collected at GS Natural Cypress and 

14 families at S‐68 Natural Cypress (table 26), and taxa 

richness also was similar (13.0 and 14.5 taxa/m2, respectively) 

(fig. 65C). Shannon diversity was 1.16 at GS Natural Cypress 

and 1.52 at S‐68 Natural Cypress (fig. 64). Macroinvertebrate 

biomass was much higher at GS Natural Cypress (606 mg/m2) 

than at S‐68 Natural Cypress (65.6 mg/m2) (fig. 65A), because 

of the presence of several large crayfish (Decapoda) and dragonflies (Odonata: Aeschnidae) (table 28). However, macroinvertebrate density was relatively low in both natural cypress 

wetlands (82.7 and 55.6 individuals/m2) (table 26; fig. 65B).
120 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Damselflies. such as Enallagma sp., 

are abundant macroinvertebrate 

predators in wetlands

predatory insects were abundant in seasonally flooded 

marshes. Collector-gatherers also are an important feeding 

group in marsh and cypress wetlands, as indicated by the 

relatively high densities (3-20 individuals/m2) of mayfly 

nymphs (Callibaetis floridanus and Caenis diminuta), 

which were found at all sites in the study. Herbivore taxa 

were more numerous at GS Natural Cypress and Duck Pond 

Augmented Marsh than at the other sites, but in general were 

low in frequency of occurrence (5-25 percent of samples) 

and density (generally less than 2 individuals/m2) at all sites 

(tables 27 and 28). Haack and others (1989) reported that 

many wetland plants contain secondary compounds that 

inhibit herbivory by insects. Moreover, the low pH of natural 

wetlands can slow down the microbial mineralization that 

conditions leave and makes them more palatable to herbivores. Collectively, these factors may limit the number of 

herbivores found in isolated wetlands.

Shredders were largely absent in both marsh and cypress 

wetlands in the present study, although there were a few 

Tipulidae (Diptera) collected in the impaired and augmented 

cypress wetlands and at W‐3 Augmented Marsh. Although 

some members of this Diptera family are shredders, the specimens were not identified below the family level, and thus, 

were conservatively grouped as collector-gatherers. Batzer 

and others (2005) reported that shredders are largely absent in 

many southern forested wetlands, including forested wetlands 

in northern Florida (Haack and others, 1989). Although typically classified as a generalist, the glass shrimp Paleomonetes 

paludosus, was categorized as a facultative shredder in studies 

Figure 65. Biomass, density, and taxa richness of 

macroinvertebrates in cypress wetlands.

Photograph provided by D. Denson, Florida 

Department of Environmental Protection

(A) MACROINVERTEBRATE BIOMASS

GS

Cypress

S-68

Cypress

W-19

Cypress

S-63

Cypress

W-5

Cypress

10,000

1,000

100

10

1

Impaired

Cypress

MEAN DRY WEIGHT, IN MILLIGRAMS

PER SQUARE METER

Augmented

Cypress

Natural

Cypress

(B) MACROINVERTEBRATE DENSITY

600

500

400

300

200

100

0

MEAN DENSITY

PER SQUARE METER

Impaired

Cypress

Augmented

Cypress

Natural

Cypress

GS

Cypress S-68

Cypress

W-19

Cypress

S-63

Cypress

W-5

Cypress

(C) MACROINVERTEBRATE TAXA RICHNESS

MEAN NUMBER OF TAXA

PER SQUARE METER

Impaired

Cypress

Augmented

Cypress

Natural

Cypress

GS

Cypress

S-68

Cypress

W-19

Cypress

S-63

Cypress

W-5

Cypress

30

25

20

15

10

5

0
Wetland Ecology 121

Figure 66. Proportion of macroinvertebrate functional feeding groups (determined by 

number of taxa) in (A) marsh wetlands and (B) cypress wetlands.

W-3 AUGMENTED MARSH

W-29 IMPAIRED MARSH

GS NATURAL MARSH HRSP NATURAL MARSH

DUCK POND AUGMENTED MARSH

(A)

W-5 AUGMENTED CYPRESS

W-19 IMPAIRED CYPRESS

S-63 AUGMENTED CYPRESS

GS NATURAL CYPRESS S-68 NATURAL CYPRESS

(B)

EXPLANATION

Collector

gatherers

Filter gatherers

Multiple groups

(Chironomidae)

Herbivores

Predators

Scrapers

Generalists

Shredders
122 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Table 28. Mean density, frequency of occurrence, and functional feeding group classification of macroinvertebrates in cypress wetlands. [m2, square meter; SD, standard deviation; C, collector-gatherer; F, filtering collector; G, generalist; H, herbivore; P, predator; S, scraper; SH, shredder; sp., species; *, multiple feeding groups] Macroinvertebrate taxonomy and feeding group classification GS Natural Cypress (21 samples) S-68 Natural Cypress (18 samples) W-19 Impaired Cypress (18 samples) S-63 Augmented Cypress (18 samples) W-5 Augmented Cypress (18 samples)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Hirudinea P 0.2 ± 0.7 5.6 0.2 ± 0.7 5.6Crustacea

Amphipoda

Hyalellidae

Hyalella azteca 

G 48.3 ± 57.1 72.2 428.0 ± 528.0 77.8

Decapoda

Cambaridae

Procambarus alleni 

G 3.4 ± 3.9 52.4 2.5 ± 3.5 50.0 2.8 ± 3.8 44.4 1.5 ± 2/6 33.3

Palaemonidae

Palaemonetes paludosus SH

Insecta

Ephemeroptera

Baetidae

Callibaetis floridanus

C 6.3 ± 6.9 61.9 2.2 ± 4.9 27.8 9.2 ± 8.1 100.0 15.0 ± 28.1 66.7 8.3 ± 11.4 61.1

Caenidae

Caenis diminuta

C 3.3 ± 5.8 38.9 0.2 ± 0.7 5.6 1.7 ± 3.1 27.8

Odonata

Lestidae

Lestes disjusctivus P

Coenagrionidae

Enallagma civale P 4.3 ± 6.1 50.0 8.3 ± 31.7 16.7Enallagma dubium P 1.3 ± 4.4 11.1 0.3 ± 1.4 5.6 5.2 ± 7.2 50.0 1.3 ± 4.4 11.1Enallagma pallidum P 4.3 ± 8.8 44.4 3.0 ± 5.1 38.9 12.3 ± 34.0 38.9Enallagma sp. P 0.8 ± 2.0 16.7 0.3 ± 1.0 11.1
Wetland Ecology 123

Macroinvertebrate taxonomy 

and feeding group classification

GS Natural

Cypress 

(21 samples)

S-68 Natural

Cypress 

(18 samples)

W-19 Impaired

Cypress 

(18 samples)

S-63 Augmented 

Cypress 

(18 samples)

W-5 Augmented

Cypress 

(18 samples)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Ishnura posita P 2.3 ± 4.6 27.8 4.2 ± 6.1 44.4 2.8 ± 5.6 27.8 11.3 ± 35.0 38.9Ishnura sp. P

Aeschnidae

Anax junius P 1.3 ± 2.8 23.8 0.8 ± 1.7 22.2Anax longipes PCoryphaeschna adnexa P 0.5 ± 1.2 16.7Gomphaeschna antilope P

Libellulidae

Libellula auripennis PLibellula semifasciata P 2.9 ± 7.1 42.9 1.0 ± 2.3 16.7 1.5 ± 3.1 22.2 4.5 ± 7.2 38.9Erythemis simplicolis P 3.0 ± 12.0 11.1 0.3 ± 1.0 11.1Pachydiplax longipennis P 1.8 ± 4.0 27.8 2.2 ± 3.5 38.9 4.8 ± 10.9 27.8 1.2 ± 2.9 22.2Tramea carolina P

Hemiptera

Belastomatidae

Belastoma sp. P 0.5 ± 1.2 16.7Lethocerus sp. P

Corixidae

Trichocorixa sp. P 0.9 ± 2.4 14.3

Gerridae

Gerris sp. P 0.3 ± 1.0 11.1

Naucoridae

Pelocoris sp. P

Nepidae

Ranatra sp. P 0.3 ± 0.9 9.5 0.2 ± 0.7 5.6 0.3 ± 1.0 11.1 0.3 ± 1.0 11.1

Notonectidae

Buenoa sp. P
124 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Macroinvertebrate taxonomy and feeding group classification GS Natural Cypress (21 samples) S-68 Natural Cypress (18 samples) W-19 Impaired Cypress (18 samples) S-63 Augmented Cypress (18 samples) W-5 Augmented Cypress (18 samples)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Notonecta sp. P

Veliidae

Microvelia sp. P 1.3 ± 2.4 27.8

Megaloptera

Corydalidae

Chauliodes sp. P 0.7 ± 1.6 16.7 0.3 ± 1.0 11.1

Sialidae

Sialis sp. 1.5 ± 5.7 11.1 0.5 ± 1.5 11.1

Coleoptera

Chrysomelidae

Disonycha sp.

H 0.4 ± 1.4 9.5

Curculionidae

Onychylis sp.

H 0.4 ± 1.4 9.5 0.3 ± 0.9 9.5

Dytiscidae

Celina sp. PCopelatus sp. PCoptotomus interogatus PCybister fimbriolatus P 1.1 ± 2.0 28.6 0.7 ± 1.3 22.2Hydaticus bimarginatus P 0.2 ± 0.7 5.6Hydroporus sp. PLaccophilus proximus PThermonectes basillaris P 0.6 ± 1.5 14.3

Elmidae

Stenelmis sp. 

C 1.3 ± 5.9 4.8

Haliplidae

Peltodytes sp. 

H

Hydrophilidae
Wetland Ecology 125

Macroinvertebrate taxonomy 

and feeding group classification

GS Natural

Cypress 

(21 samples)

S-68 Natural

Cypress 

(18 samples)

W-19 Impaired

Cypress 

(18 samples)

S-63 Augmented 

Cypress 

(18 samples)

W-5 Augmented

Cypress 

(18 samples)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m

2

 ± SD

Occurrence 

frequency

(percent)

Berosus sp. CEnochrus sp. CHydrobiomorpha casata C 0.5 ± 1.5 11.1Hydrochara sp. C 0.5 ± 1.2 16.7Tropisternus lateralis CHydrophilus triangularis C 2.7 ± 4.7 38.9

Noteridae

Mesonoterus addendus P 0.7 ± 1.9 14.3 0.8 ± 2.5 11.1 0.5 ± 1.5 11.1Pronoterus semipunctatus P 1.0 ± 2.3 16.7Suphisellus gibbulus P 0.4 ± 1.4 9.5

Ptilodactylidae

Anchytarsus bicolor H

Scirtidae/Helodidae

Prinocyphon sp. C 1.2 ± 2.9 16.7

Trichoptera

Hydropsychidae

Potamyia sp. F

Hydroptilidae

Oxytheria sp. H 0.9 ± 2.4 14.3

Lepidoptera

Pyralidae H 0.3 ± 1.0 11.1

Diptera

Ceratopogonidae P 8.0 ± 18.0 38.9 9.3 ± 22.9 33.3 3.8 ± 6.7 44.4Chaoboridae P 11.3 ± 21.7 57.1 1.5 ± 2.8 27.8 2.7 ± 7.8 27.8 3.3 ± 9.9 16.7Chironomidae * 51.7 ± 63.3 85.7 28.2 ± 32.5 83.3 43.3 ± 46.5 88.9 38.8 ± 46.9 72.2 64.3 ± 89.5 100.0Culicidae F 6.3 ± 13.0 44.4Dixidae C 0.2 ± 0.7 5.6
126 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida Macroinvertebrate taxonomy and feeding group classification GS Natural Cypress (21 samples) S-68 Natural Cypress (18 samples) W-19 Impaired Cypress (18 samples) S-63 Augmented Cypress (18 samples) W-5 Augmented Cypress (18 samples)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Mean density

per m2 ± SD

Occurrence 

frequency

(percent)

Sciomyzidae P 0.2 ± 0.7 5.6 0.5 ± 1.5 11.1Stratiomyidae

C 0.3 ± 1.0 11.1

Tabanidae P 0.2 ± 0.7 5.6 0.8 ± 1.7 22.2Tanyderidae

C 0.2 ± 0.7 5.6 0.2 ± 0.7 5.6

Tipulidae

C 1.3 ± 2.8 22.2 0.5 ± 1.2 16.7 0.7 ± 1.6 16.7

Mollusca

Gastropoda

Ampullariidae

Pomacea paludosa S

Ancyllidae

Laevapex fiscus S 5.2 ± 21.9 5.6 0.8 ± 2.0 16.7

Lymnaeidae

Fossoria cubensis S 4.5 ± 5.8 55.6

Physidae

Hatia cubensis S 20.8 ± 37.8 66.7

Planorbidae

Gyraulus parvus S 4.2 ± 10.1 16.7Micromenetus dilatus SPlanorbella druryi SPlanorbella scalaris SPlanorbella trivolvus S 1.3 ± 3.1 22.2

Viviparidae

Viviparous georgianus S

Bivalvia

Sphaeriidae

Musculium lacustre F 0.7 ± 1.6 16.7
Wetland Ecology 127

in the Kissimmee River basin (Merritt and others, 1999) and 

in the present study. Paleomonetes paludosus was only found 

in high numbers at W‐29 Impaired Marsh in the present study. 

During the early part of the study, dead leaves from maidencane were plentiful at the site, providing an abundant potential 

food for this species. Beck and Cowell (1976) studied stomach 

contents of Paleomonetes paludosus and found abundant 

vascular plant material, along with large amounts of algae, 

indicating that this species may function as a shredder at other 

sites as well.

Like shredders, scrapers also are underrepresented in 

many southern wetlands (Haack and others, 1989; Batzer and 

others, 2005). Scrapers were represented in the present study 

principally by the abundant gastropods (snails) found at all four 

of the augmented sites (tables 27 and 28). Snails were not found 

at any of the natural (unaugmented) wetlands because calcium 

carbonate concentrations in the acidic surface waters were too 

low for shell formation. The number of species, frequency 

of occurrence, and density of snails in the present study were 

greater at the augmented marsh sites than the augmented cypress 

sites (tables 27 and 28). At W‐5 Augmented Cypress, the 

amphipod Hyalella azteca was an abundant facultative scraper 

species (Merritt and others, 1999) that may thrive by scraping 

attached algae from the abundant Riccia mats where it was 

collected. These floating mats of vegetation not only provided a 

substrate for attachment of Hyalella, but also may have indirectly 

provided a food source as a surface for algal growth. Amphipods 

were also moderately abundant at W‐19 Impaired Cypress, and 

submersed aquatic vegetation (Utricularia spp.) was present 

at this site as a substrate for these macroinvertebrates. Kushlan 

and Kushlan (1980) reported that amphipods were abundant at 

wetland sites where they were secure from predation, especially 

within vegetation mats. The occurrence of Hyalella azteca, 

however, may be limited by pH and available substrate. This 

species prefers neutral pH conditions and is not common in 

areas with a pH below 5.8 (Grapentine and Rosenberg, 1992); 

therefore, its abundance at W‐5 Augmented Cypress (median 

pH 7.4) and W‐19 Impaired Cypress (median pH 6.0) would be 

expected. The absence of Hyalella azteca at sites with circumneutral pH and abundant submersed aquatic vegetation, such as 

at the augmented marshes, cannot be explained on the basis of 

these factors alone.

Chironomidae (Diptera) were not identified below the 

family level in the present study. Consequently, the distribution of individuals in this family among functional feeding 

groups at the study wetlands could not determined.

Macroinvertebrates as Ecological Indicators in 

Wetlands

Macroinvertebrates can be used as biotic indicators of 

ecological condition in wetlands because they generally have 

well-understood life histories, established ecological requirements, a varying degree of sensitivity to stress, and are easily 

identified (Angeler and Garcia, 2005). Macroinvertebrate 

ecological indicators are widely used in the United States 

to monitor the effects of human-related stressors, including 

nutrient enrichment, contamination by metals, acidification 

related to mining, salinization, sedimentation, and vegetation removal (U.S. Environmental Protection Agency, 1990; 

2001). Doherty and others (2000a) produced a comprehensive 

compilation of literature describing how specific stressors in 

inland freshwater wetlands of Florida may affect macroinvertebrate species assemblages. The University of Florida, 

under contract with the Florida Department of Environmental 

Protection, developed a series of wetland bioassessment documents to standardize methods and advance the understanding 

of wetlands in the State (Doherty and others, 2000b; Lane, 

2000; Lane and others, 2003; Reiss and Brown, 2005). Those 

efforts include the development of a Wetland Condition Index 

(which incorporates macroinvertebrates) for isolated depression 

forested and herbaceous wetlands throughout Florida.

Ephemeroptera (mayflies) have been used as indicator 

species in some parts of the United States, and their absence 

is often interpreted as an indication of unfavorable environmental conditions. However, Ephemeroptera were found 

at all wetlands in this study, and both of the genera found 

(Callibaetis and Caenis) are common inhabitants of natural 

Florida wetlands that dry out seasonally (Berner and Pescador, 

1988), including Everglades marshes (Rader, 1994). Moreover, 

they may be ideally adapted to these habitats because they are 

(1) tolerant of low oxygen conditions and low pH; (2) have 

short development times; and (3) produce multiple generations each year, allowing continuous recolonization if water is 

present. Caenis spp. and Libellula spp. (Odonata) are considered to be indicative of permanent standing water in Florida 

(Doherty and others, 2000b). In the present study, Caenis

spp. were not found in the impaired wetlands, where water is 

intermittent, although Libellula spp. were found. 

The numerical proportions of Diptera and Chironomidae 

(a family within Diptera) in macroinvertebrate communities have been used to describe and compare wetlands. 

Communities of Diptera with great similarity in species 

composition have been found in both natural and created 

flatwoods marshes in Florida that differ in their environmental 

conditions (Crisman and others, 1997; Evans and others, 

1999), most likely because many species of aquatic Diptera 

tolerate a wide range of environmental conditions. In the 

present study, the mean proportion of Diptera to all other 

macroinvertebrates was substantially lower in W‐3 Augmented 

Marsh (17 percent) and W‐5 Augmented Cypress wetland 

(13 percent) than in any of the natural marshes (mean value 

67 percent) or any of the natural cypress wetlands (mean value 

64 percent) (fig. 67). At Duck Pond Augmented Marsh and 

S‐63 Augmented Cypress, Diptera made up about 40 percent 

of the total macroinvertebrate abundance. Diptera constituted 

87 percent of the total invertebrate community at W‐29 Impaired 

Marsh, and 45 percent at W‐19 Impaired Cypress. Within the 

order Diptera, individuals in the families Chironomidae (fig. 67), 

Chaoboridae, and Ceratopogonidae contributed most to the 

overall abundance of this insect order. In natural forested pond 
128 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

wetlands in Massachusetts (Brooks, 2000), Chironomidae also 

were dominant and their numerical dominance was greater in 

shorter hydroperiod wetlands. In longer hydroperiod wetlands in 

Massachusetts, the taxa richness of the entire macroinvertebrate 

community was greater, diminishing the relative importance of a 

single family such as Chironomidae.

The natural variability of macroinvertebrate communities 

in marsh and cypress wetlands in the present study was high, and 

may exceed the differences attributable to augmentation for many 

of the community metrics that were used in this study. Similarly 

high levels of inter-site and temporal variability in total density 

and taxa richness of macroinvertebrates also have been reported 

in other isolated wetlands in Florida and throughout the Southeast 

(Cowell and Vodopich, 1981; Leslie and others, 1997, 1999; 

Kratzer and Batzer, 2007). For each wetland type in the present 

study the two augmented wetlands did not resemble one another, 

although they also were often different from the natural wetlands 

of the same type. For example, taxa richness and the number of 

macroinvertebrate families collected were higher at Duck Pond 

Augmented Marsh than at the natural marshes, but were much 

lower at W‐3 Augmented Marsh. These differences in the macroinvertebrate communities between the two augmented marshes 

probably reflected their dissimilar bathymetry and water depths. 

Likewise, mean macroinvertebrate density was similar in the two 

natural cypress wetlands, but was four times higher in one of the 

augmented cypress wetlands (W‐5) than in the other (S-63). 

Taxa richness in the unaugmented marsh (15-20 taxa) 

and cypress wetlands (13-20 taxa) in the present study was 

similar to reported taxa richness in natural marsh wetlands 

(14-17 taxa) and natural cypress wetlands (8-12 taxa) in 

Martin and St. Lucie Counties in southeastern Florida (Smock, 

1995). The mean number of families (13-17) and the macroinvertebrate density (56-136 individuals/m2) in unaugmented 

cypress wetlands in the present study were somewhat lower 

than the number of families (12-27) and the invertebrate 

density (39-1,245 individuals/m2) reported by Haack and 

others (1989) in a forested wetland in northern Florida, 

although the northern Florida wetland was a flow-through 

system instead of an isolated wetland. Leslie and others 

(1997; 1999) also reported higher densities of macroinvertebrates (1,127-5,320 individuals/ m2) in pond cypress wetlands 

near Gainesville, Florida, than those found in the present 

study. Taxa richness in shallow, acidic, nutrient-rich Carolina 

bay marshes of the southeastern United States (Taylor and 

others, 1999) was much higher (>100 taxa) than taxa richness 

in marshes in the present study. 

In the present study, unaugmented marshes had higher 

mean macroinvertebrate density (73-450 individuals/m2) and 

taxa richness (15-20 taxa) than unaugmented cypress wetlands 

(56-136 individuals/ m2; 13-20 taxa). A similar pattern of 

macroinvertebrate density and taxa richness was reported 

in natural limesink marsh and cypress wetlands in Georgia 

(Gollady and others, 1999; Battle and Golladay, 2001). Battle 

and Golladay (2001) suggest that the dense emergent vegetation and associated periphyton in the Georgia marshes provide 

more food resources and greater habitat availability for 

macroinvertebrates than in the forested wetlands. 

Few studies have compared macroinvertebrates between 

augmented and natural wetlands. Data from an augmented 

cypress wetland in northern Florida (MacMahan and Davis, 

1984) indicate that there is an overall decrease in species 

richness, number of individuals, and biomass of arthropods 

compared to the control (nonaugmented) wetland. A study by 

Berryman and Hennigar, Inc. (2000) compared 11 natural and 

augmented marsh and cypress wetlands in the northern Tampa 

Bay area, and found that the greatest number of macroinvertebrate species were found at a natural marsh and at an augmented 

marsh (W‐3 Augmented Marsh), and the fewest number of 

Figure 67. Abundance of Chironomidae, all Diptera, and all macroinvertebrates in marsh and cypress wetlands.

600

500

400

300

200

100

0

ABUNDANCE PER SQUARE METER

Chironomidae

All Diptera

All macroinvertebrates

GS

NATURAL

MARSH

HRSP

NATURAL

MARSH

W-29

IMPAIRED

MARSH

DUCK

POND

AUGMENTED

MARSH

W-3

AUGMENTED

MARSH

GS

NATURAL

CYPRESS

S-68

NATURAL

CYPRESS

W-19

IMPAIRED

CYPRESS

S-63

AUGMENTED

CYPRESS

W-5

AUGMENTED

CYPRESS
Wetland Ecology 129

species were found at several augmented cypress wetlands. 

Species diversity was highest in a natural marsh (2.6) and 

S‐63 Augmented Cypress (2.1), and lowest (0.4-0.6) at other 

augmented cypress sites in that study. No relations between 

macroinvertebrate abundance and wetland augmentation were 

found in that study.

Although macroinvertebrates have been reported to 

respond to changes in wetland hydroperiod (Batzer and others, 

1999), differences in macroinvertebrate communities among 

different hydrologic groups were not apparent in the current 

study. Schneider (1999) reported that as the duration of standing 

water increased in vegetated ponds, macroinvertebrate taxa 

richness also increased, and invertebrate communities were 

most similar in ponds with similar hydroperiods. Short-duration 

ponds were the most variable in invertebrate community 

composition, and ponds with the longest flood duration were the 

least variable (Schneider, 1999). Small pond-cypress swamps in 

northern Florida are characterized by unpredictable changes in 

invertebrate abundance (Leslie and others, 1999), and variable 

patterns of drying and rewetting may be responsible for the lack 

of predictability in invertebrate populations in these wetlands. In 

natural limesink wetlands in southwest Georgia (Golladay and 

others, 1999), extended inundation at some sites caused shortterm reductions in macroinvertebrate populations.

Because of the naturally occurring differences in 

macroinvertebrate density, diversity, and taxa richness within 

wetland types, a greater number of augmented and natural 

wetlands of each type are needed than in the present study 

before reliable conclusions can be made about the hydrologic 

effects of augmentation on ecologic conditions. Differences 

related to water quality, such as the presence or absence of 

gastropods and mollusks, were clearly evident in the current 

study, even with the small sample size used.

Tadpoles were collected incidentally in dip-net 

samples in the two cypress wetlands at Starkey Well Field 

(S‐63 Augmented Cypress and S‐68 Natural Cypress), as well as 

in all of the unaugmented and augmented marsh wetlands in the 

present study (table 29). Tadpoles were not collected in dip-net 

samples in GS Natural Cypress, W‐5 Augmented Cypress, 

and W‐19 Impaired Cypress. Hydroperiod has been found to 

regulate amphibian reproductive success in several wetlands 

near the study wetlands in the Starkey Well Field (Mushinsky 

and others, 2004), and the capture rate and species richness of 

larval frogs was higher in wetlands with longer hydroperiods. 

Most amphibians actually require small, ephemeral, fish-free 

wetlands to successfully reproduce (Sexton and Phillips, 1986; 

Brooks, 2000). In wetlands in the Morris Bridge Well Field, 

Guzy and others (2006) found no significant relation between 

the number of tadpole species and wetland hydroperiod, 

although the density of tadpoles was higher in wetlands unaffected by ground-water pumping than in any of the wetlands 

with hydroperiods shortened by ground-water pumping. A more 

systematic estimate of larval frog density and distribution would 

be required to determine correlations with flooding frequency 

and flooded extent in wetlands from the present study.

Fish also were collected incidentally in some dip-net 

samples in the present study (table 29). The presence of fish 

in wetlands requires either perennial standing water, small 

refugia in localized depressions, or seasonal interconnections 

to adjacent surface-water bodies. Fish were collected in GS 

Natural Marsh and both the augmented marshes, but not in 

HRSP Natural Marsh or W‐29 Impaired Marsh. Because 

the natural and impaired marshes dry out periodically, fish 

populations disappear during those times, and opportunities for 

recolonization are limited to periods when these wetlands are 

connected to nearby water bodies (Euliss and others, 1999). GS 

Natural Marsh did have a wet-season connection to a nearby 

perennially flooded borrow pit, whereas W‐29 Impaired Marsh 

and HRSP Natural Marsh had no such connection or source 

for fish recolonization. In the cypress wetlands, no fish were 

collected in GS Natural Cypress and W‐19 Impaired Cypress. 

S‐68 Natural Cypress and S‐63 Augmented Cypress, which 

had fish present, both can have surface-water connections to 

nearby Cross Cypress Branch during periods of high rainfall, 

providing a seasonal source for fish recolonization. Similarly, 

W‐5 Augmented Cypress is connected by surface flow during 

wet periods to the Cypress Creek system. 

Studies have linked minimum wetland size, the presence 

of buffer areas, and proximity to other wetlands to the 

stability of wetland faunal communities (Amezaga and others, 

2002), including birds (Haig and others, 1998), amphibians 

and reptiles (Semlitsch and Bodie, 2003), fish (Matthews, 

1998), and macroinvertebrates (Bried and Ervin, 2006). 

Table 29. Occurrence of fish and larval amphibians (tadpoles) in 

study wetlands. 

Wetland name Jordanella

floridae

Fundulus 

seminolis

Heterandria 

formosa

Gambusia 

holbrooki Tadpoles

GS Natural 

Marsh x x

HRSP Natural 

Marsh x

W-29 Impaired 

Marsh x

Duck Pond 

Augmented 

Marsh

x x x x

W-3 Augmented 

Marsh x x x x

GS Natural 

Cypress

S-68 Natural 

Cypress x x

W-19 Impaired 

Cypress

S-63 Augmented 

Cypress x x

W-5 Augmented 

Cypress x
130 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Habitat fragmentation of wetlands is a growing phenomenon, 

whereby a few wetlands are preserved but the landscape 

mosaic overall has fewer total wetlands. The more isolated a 

wetland is, the smaller the opportunity for near-by wetlands 

to serve as refugia or as sources of new colonization for all 

types of biota. Many groups of wetland organisms use the 

surrounding uplands for forage area and for completion of 

essential life-history stages. Disturbance in the upland area 

surrounding a wetland can interrupt these important processes. 

Further studies are needed to establish a scientific foundation 

for decisions related to the creation and maintenance of protective ecological buffers (Environmental Protection Commission 

of Hillsborough County, 2006; Taylor and others, 2007).

Wissinger (1999), in a synthesis of studies on macroinvertebrates in North American wetlands, cites hydroperiod, 

dissolved oxygen, salinity, pH, suspended sediment, and 

nutrient levels as the factors most often found to influence 

invertebrate abundance and community composition. Of these 

factors, only pH and hydroperiod were sufficiently different 

between natural and augmented wetlands in the present study 

to have a measurable influence on invertebrate communities. 

Wissinger (1999) noted that because hydroperiod can have 

many indirect effects (presence of predators, nutrient availability, vegetation heterogeneity, and water chemistry) it is 

generally difficult to separate the direct effects (drying and 

inundation) from those indirect effects. The ability of many 

macroinvertebrates to reproduce under a variety of conditions, 

colonize either from the air or by way of overland connections, and facultatively feed at different trophic levels indicates 

that ecosystem integrity in wetlands can be maintained across 

a range of conditions, and that invertebrate communities can 

be heterogeneous between sites, yet functionally similar and 

ecologically intact. 

Overview of Wetland Ecology

Because the algae making up the periphyton community 

have short life cycles and respond rapidly to changing conditions, they are less influenced by water depth and hydrologic 

regime than are wetland vegetation and macroinvertebrates. 

If water disappears from a wetland, the periphyton ceases to 

grow and may enter a desiccated (dried) resting stage, often 

settling and accumulating in the moist bottom sediments 

(Stevenson and others, 1996). Many algae are adapted to 

pulsed hydroperiods and, depending on the extent and duration 

of dry periods, can recolonize rapidly from desiccated cells. 

Drawdown of water levels, either naturally or due to anthropogenic activities, concentrates dissolved nutrients that can 

stimulate subsequent periphyton growth when water returns. 

Reflooding can also mobilize previously unavailable nutrients 

from oxidized organic material in the wetland basin.

Overall, periphyton biomass was greater in augmented 

wetlands than in natural and impaired wetlands of both types 

in this study. Median concentrations of nutrients (nitrogen and 

phosphorus) in the study wetlands did not exceed threshold 

concentrations that typically indicate nutrient enrichment in 

wetlands and, therefore, patterns of periphyton abundance 

related to nutrients could not be determined in the study. 

Diatom species abundance and distribution in the present 

study were related to differences in specific conductance, pH, 

and possibly to nutrients in the accumulated organic material. 

In studies of prairie wetlands (Mayer and Galatowisch, 1999), 

the high degree of natural variability in diatoms among sites 

made them a poor indicator of human activities.

Plant species richness was higher in augmented wetlands 

than in natural and impaired wetlands. Changes in flooding 

characteristics or water quality may have facilitated the 

establishment of additional plant species at individual sites. 

Plant biomass was higher in augmented marshes than in 

natural and impaired marshes. These differences were not 

related to measured nutrient concentrations, but may be related 

to nutrients released by decaying plant material and quickly 

absorbed by vegetation, promoting plant growth. Tree density 

was lower and the percentage of fallen and dead trees was 

higher in augmented and impaired cypress wetlands than in 

natural cypress wetlands, most likely because extended dry 

conditions prior to augmentation accelerated tree fall and 

altered hydrology, preventing germination of new trees.

The natural variability of macroinvertebrate communities 

in marsh and cypress wetlands was high and may exceed any 

differences attributable to augmentation for many community 

metrics used in this study. Similarly high levels of inter-site 

and temporal variability in total density and taxa richness 

of macroinvertebrates have been reported in other isolated 

wetlands in Florida and throughout the southeastern United 

States. Regarding wetland types, unaugmented marshes generally had higher macroinvertebrate density and taxa richness 

than unaugmented cypress wetlands. Generalizations about 

wetland hydrologic groups were more difficult to determine 

because there were few similarities in macroinvertebrate 

communities between the two augmented marshes, and also 

between the two augmented cypress wetlands. Because of 

the naturally occurring differences in macroinvertebrate 

density, diversity, and taxa richness between wetland types, 

a greater number of augmented and natural wetlands of each 

type are needed for consideration than in the present study 

before reliable conclusions can be made about the hydrologic 

effects of augmentation. Differences related to water quality, 

such as the presence or absence of gastropods and mollusks, 

were clearly evident in the current study, even with the small 

sample size used.
Understanding isolated wetlands over the spectrum of prevailing 

hydrologic conditions in west-central Florida required the development of 

sampling and analysis techniques that could be applied equivalently to two 

different types of wetlands (marsh and cypress) in three wetland groups with 

widely differing hydrologic regimes (natural, impaired, and augmented). 

Comparisons of wetland hydrology, water quality, and ecology indicated 

intrinsic differences between marshes and cypress wetlands in this study, as 

well as between natural wetlands and wetlands affected by environmental 

stresses including impaired water levels and ground-water augmentation. Results were used to characterize the hydrologic behavior of natural 

wetlands and then compare this behavior to wetlands affected by long-term 

ground-water withdrawals from large municipal well fields.

Collectively, five comparisons were considered. Natural marshes were 

compared to natural cypress wetlands to highlight possible hydrologic 

differences between the two wetland types. Augmented wetlands were 

compared to natural wetlands to infer the long-term consequences of 

augmentation. Impaired wetlands were compared to natural wetlands to 

assess the degree of impairment, and then compared to augmented wetlands 

to infer the extent of mitigation that was achieved. Recent and historical 

flooding conditions in each wetland group were compared to infer the 

effects of ground-water pumping and rainfall over time. Finally, the amount 

of water required to steadily augment a wetland was compared to the 

amount needed to refill it from dry conditions. Ecological comparisons of 

the wetlands based upon surveys of periphyton, vegetation, and macroinvertebrates were then used to explore the effect of these physical differences 

on wetland condition. In addition to being used for comparisons, the results 

from these 10 wetlands expand the available knowledge about isolated 

wetlands in general by documenting in detail the wetland flooding characteristics, wetland geologic framework and geochemistry, ground-water flow 

patterns around wetlands, and wetland water budgets. 

Summary and Conclusions
132 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Augmentation has maintained some of the functional 

capacity of the four augmented wetlands located within the 

well fields during the augmentation period (which began in 

the early 1980s). Without augmentation, the four augmented 

wetlands would have been dry during the majority of this period. 

The historical flooding pattern of W‐29 Impaired Marsh illustrated the most optimistic flooding regime that could have been 

expected in the absence of augmentation: 20 percent or less of 

the total wetland area was inundated for most of the time, and 

entirely dry conditions prevailed for as much as 80 percent of 

the time. In addition, the soil moisture comparisons at the natural 

and impaired marshes, together with the hydrogeologic sections 

of the augmented wetlands, indicate that without augmentation, 

the water table would have been too deep below the wetlands to 

provide the soil moisture conditions necessary for aquatic algae, 

wetland plants, and freshwater macroinvertebrates to survive. 

Wetland plants would likely have been replaced with upland 

vegetation, as occurred at W‐29 Impaired Marsh where slash 

pines became established throughout the marsh during prolonged 

dry conditions (Haag and others, 2005). Cypress tree mortality 

would have been widespread, as was evident in W‐19 Impaired 

Cypress. Moreover, because both of the impaired wetlands were 

affected less severely by ground-water withdrawals than the 

four augmented wetlands prior to their augmentation, even more 

severe deterioration could have been expected.

The wetlands augmented with ground water are 

ecologically similar to the natural wetlands in many respects. 

Most of the biotic community measures in the augmented 

wetlands, including relative species abundance, taxa richness, and Shannon diversity were within the existing range 

for natural wetlands of the same type. The distribution of 

wetland periphyton species was related to pH and specific 

conductance, and differences related to nutrient concentrations were not distinct. Biomass of herbaceous vegetation 

was higher in augmented wetlands than in unaugmented 

wetlands, and may be related to availability of nutrients 

released from the accumulated partially decayed vegetation. 

The relative abundance of plant types (obligate, facultative 

wet, and facultative) was not substantially different among 

wetland groups, most likely because many of these plants 

have broad tolerances for water depth and grow across a 

gradient of hydrologic conditions. The occurrence of snails 

and mussels was confined to augmented sites where the 

concentration of calcium carbonate was sufficient for shell 

formation. With the exception of W‐3 Augmented Marsh 

(where snails were abundant), the biomass and density of 

macroinvertebrates at augmented sites was within the range 

found at natural and impaired sites. 

The hydrology of augmented wetlands differed from the 

natural wetlands in several fundamental aspects, including 

the size of the flooded areas, residence times of water in the 

wetlands, leakage rates, the magnitude of runoff, and the 

water-table configuration. The relatively constant flooded 

area in three of the four augmented wetlands was well within 

the wetland perimeter, leaving the remainder of the wetland 

bottom subject to invasion by upland vegetation. Perennial 

standing water in augmented wetlands, however, increased 

their primary productivity compared to natural wetlands, as 

indicated by the higher vegetation and periphyton biomass. 

This greater primary productivity, combined with infrequent 

drying, probably accelerated the accumulation of organic 

material in all but S‐63 Augmented Cypress, which repeatedly dried out. Radium-226 activities were not substantially 

elevated in the bottom sediment of augmented wetlands 

compared to natural wetlands.

Although augmentation practices could be refined to 

more closely mimic the flooded-area behavior of natural 

wetlands, the quantitative information needed to design a 

reliable system for doing this is lacking. The information 

described in the comparative analyses moves this goal closer 

by detailing the quantities and fate of the water flowing 

through augmented wetlands. Knowledge about the leakage 

quantities from a variety of augmented wetlands, the size 

of the recharge mounds, the change in the flooded area 

associated with changes in wetland stage, and the change in 

leakage quantities with changing levels in the Upper Floridan 

aquifer, can be used to size augmentation pipelines and 

allocate augmentation volume amounts during the year. For 

example, the augmentation experiment at W‐5 Augmented 

Cypress demonstrated that, if pipelines are sized adequately, 

it is feasible to allow an augmented wetland to dry out 

Isolated freshwater wetlands act as surface-water storage 

features in the landscape

Photograph provided by M. Hancock, SWFWMD
Summary and Conclusions 133

completely for several weeks or months and to refill the 

wetland within several days. Drying provides ecological 

benefits because it allows organic material to dry, oxidize, 

and compact. Moreover, drying and refilling this wetland 

saved a substantial volume of water compared to uninterrupted augmentation over the same time period. 

Having improved methods for comparing the hydrologic 

condition of natural and impaired wetlands will provide 

better evidence for defining wetland impairment and for 

refining mitigation goals for wetlands. For example, in 

addition to the current policy of augmenting wetland water 

levels to a minimum elevation, augmentation could be 

used to flood a minimum percentage of the total wetland 

area. The minimum percentage of inundated wetland area 

during both short and long time periods could be inferred 

by the recent and historical flooded-area duration of natural 

wetlands in the same region. Similarly, as a survey tool, 

impairment may be indicated if the distance of the potentiometric surface of the Upper Floridan aquifer below a wetland 

remains consistently outside the range observed in natural 

wetlands in the same region. Study results also indicate that 

preserving the greatest wetland area for a given amount of 

augmentation water may not always equate to conserving 

the largest number of individual wetlands. The augmentation experiment and water-budget results showed that 

linear leakage rates typically decreased as the size of the 

flooded area increased. This finding suggests, for example, 

that expanding the flooded area in an existing augmented 

wetland could be an efficient way to compensate for the 

loss of flooded area in wetlands that cannot effectively 

be rehydrated. Overall, augmentation may be required in 

fewer wetlands in the coming decade than the previous two 

decades, because the reduced ground-water pumping that 

was initiated in 2003 will raise potentiometric levels at the 

well fields, increasing wetland water levels and flooded 

area in numerous impaired and augmented wetlands. Less 

augmentation water would then be required to maintain 

augmented wetlands at their desired levels, especially at 

the leakiest sites such as Duck Pond Augmented Marsh and 

S‐63 Augmented Cypress, where daily leakage rates were 

inversely correlated to Upper Floridan aquifer water levels.

Comparing wetland types indicated possible differences 

in geologic setting between marsh and cypress wetlands in 

this study. Considered collectively, the geologic material 

below marshes had lower leakance values than most cypress 

wetlands (with the exception of Duck Pond Augmented 

Marsh), indicating that marshes may occupy depressions with 

less permeable bed material than cypress wetlands. The two 

natural marshes leaked more slowly than the two natural 

cypress wetlands. The isotopic signature of water in marshes 

showed greater evidence of evapoconcentration than cypress 

wetlands, possibly because of higher evaporation rates and 

longer water residence times in marshes. The duration of 

flooding at the deepest point in natural marshes and natural 

cypress wetlands was similar, although more than half of 

the surface area of marshes was flooded more often than at 

cypress wetlands. Historically, natural cypress wetlands tended 

to exhibit extremes in the size of the flooded area, either 

nearly full or nearly dry, more often than the natural marshes.

The study results consistently showed that the isolated 

freshwater wetlands in this study act as surface-water storage 

features that receive rainfall and runoff from upland areas 

and slowly release this water as ground-water recharge to the 

surficial and Upper Floridan aquifers. Recharge mounds were 

mapped for 8 of the 10 wetlands using hydrogeologic data, 

and the recharge water altered the geochemistry of the surficial 

aquifer around and below the wetlands. Leakage rates below 

wetlands varied by a factor of 30, with augmented wetlands 

leaking fastest. In addition to increasing wetland leakage rates, 

ground-water withdrawals also reduce runoff to wetlands, which 

is an additional consequence of concern. 

Runoff constituted a substantial component of wetland 

water budgets, even before it began generating stream flow 

between wetlands. Wetland hydrology evaluated from an overall 

watershed perspective is considered a priority for future studies. 

Data are needed to quantify the water stored in wetlands, the 

water flowing between individual wetlands during the wettest 

periods, and the accumulated flow exiting the watershed. 

Because isolated wetlands frequently act as headwaters to rivers, 

quantifying wetland hydrology on the watershed scale will 

expand the current understanding of both of these surface-water 

resources in Florida.
134 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
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144 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
Glossary 145

Glossary

aquatic — Living or growing in or on water.

aquifer — A geologic formation, group of formations, 

or part of a formation that contains sufficient saturated 

permeable material to yield significant quantities of water 

to wetlands, springs, and wells.

biomass — The amount of living plant or animal matter 

present in a particular habitat, usually expressed as 

weight-per-unit area.

confining unit — A body of impermeable or distinctly 

less permeable material stratigraphically adjacent to one or 

more aquifers that restricts the movement of water into and 

out of aquifers.

cypress wetland — A poorly drained to permanently wet 

depression dominated by cypress trees. 

discharge area — An area that has surface-water levels 

that are lower than the surrounding water table, leading to 

an inflow of ground water.

emergent plants — Erect, rooted, herbaceous plants that 

may be temporarily to permanently flooded at the base, 

but that do not tolerate the prolonged inundation of the 

entire plant.

evapotranspiration — A process in which water is 

discharged to the atmosphere as a result of (1) evaporation from the soil and surface-water bodies, and (2) plant 

transpiration.

flood duration — The amount of time that a wetland or 

part of a wetland contains water.

flood frequency — The average number of times 

that a wetland or part of a wetland is flooded during a 

given period.

functional capacity — The ability of a wetland to carry 

out natural processes such as nutrient processing, water 

retention, and aquatic plant succession. 

hydraulic head — The elevation above a common datum 

to which water rises in a tightly cased well. Synonymous 

with head.

hydrogeomorphic class (HGM) — Wetland classification system based on type of hydrologic conditions, local 

geomorphology, and climate.

hydroperiod — The seasonal pattern of the water level in 

a wetland.

isolated wetlands — Wetlands with no apparent surfacewater connection to streams, rivers, estuaries, or the ocean.

karst — A region underlain by limestone that contains 

solution cavities and where the physical features of the land 

surface include large and small depressions.

marsh — A frequently to continually wet depression characterized by emergent herbaceous vegetation without trees.

overland flow — Nonchannelized sheet flow of surface 

water that usually occurs during and immediately 

following rainfall.

permeability — The capacity of soil or rock to conduct 

water flow.

potentiometric surface — The surface that represents the 

level to which water will rise in a tightly cased (sealed) well. 

runoff — Nonchannelized surface-water flow.

seasonally flooded — Wetlands that are flooded for 

extended periods during the growing season and dry by the 

end of the growing season.

species richness — A count of the number of different 

species in a sample or group of samples.

stage — Wetland water level, in feet above a common 

datum.

swamp — A wetland dominated by trees or shrubs.

taxa richness — A count of the number of different taxa 

in a sample or group of samples. Used when identification 

to species is not possible. A taxon is a level of identification 

above the species level, such as genus.

well field — An area developed by a local or regional water 

authority where ground water is withdrawn from the aquifer 

and sent to a treatment and distribution system.

wetlands — Ecosystems characterized by the presence of 

shallow water or flooded soils for part of the growing season, 

plants adapted to a wet environment, and soil indicators of 

flooding (hydric soils).

wetland augmentation — The addition of water from an 

external source to increase the water level in a wetland.

wetland plant indicator categories:

obligate — Found in wetlands more than 99 percent of 

the time.

facultative wet — Found in wetlands 67 to 99 percent of 

the time.

facultative — Found in wetlands 34 to 66 percent of 

the time.
146 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida
Appendixes 147

Appendix 1. Monthly rainfall at the marsh wetlands.

W-29 IMPAIRED MARSH 20

16

12

8

4

0 D J F M A M J J A S O N D

2001 2002 2003 2004

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J

0.19

2.76

0.75

4.60

0.03

0.14

10.02

10.16

6.14

8.70

0.46

0.22

0.77

3.22

3.29

0.84

4.66

1.17

10.32

8.55

6.82

4.36

2.66

13.54

0.31

5.64

5.78

2.87

2.18

15.51

7.70

13.49

8.03

2.27

2.05

9.17

1.55

3.83

4.44

0.76

2.08

0.50

11.35

HRSP NATURAL MARSH

J F M A M J J A S O N D

2001 2002 2003 2004

J F M A M J J A S O N D J F M A M J J A S O N D J F M

20

16

12

8

4

0

1.24

0.57

7.21

0.05

1.47

9.13

8.89

8.25

13.46

1.40

0.20

0.51

2.64

2.86

1.62

2.15

3.10

10.41

6.54

7.98

5.04

5.16

2.10

13.27

0.10

2.58

4.69

1.82

1.83

14.52

5.90

6.28

2.53

1.72

1.19

1.77

4.65

1.39

4.44

W- 3 AUGMENTED MARSH

D J F M A M J J A S O N D

2001 2002

J F M A M J J A S

20

16

12

8

4

0

2.63

0.74

4.80

0.10

0.20

11.39

11.45

6.61

8.37

0.36

0.25

0.93

3.42

3.42

0.89

0.20

5.29

1.16

10.19

8.34

8.34

6.05

GREEN SWAMP NATURAL MARSH

J F M A M J J A S O N D

2001 2002

J F M A M J J A S

20

16

12

8

4

0

2.79

0.65

6.34

0.01

1.66

10.73

7.31

7.50

14.83

1.31

0.85

0.66

3.20

2.64

1.17

1.70

1.76

9.94

8.37

10.53

4.58

DUCK POND AUGMENTED MARSH

D J F M A M J J A S O N D

2001 2002

J F M A M J J A S

20

16

12

8

4

0

3.21

0.72

4.45

0.00

0.02

13.16

12.25

6.28

9.62

0.62

0.45

0.64

3.40

1.86

1.02

1.68

2.83

1.56

10.14

10.60

7.67

5.42

MONTHLY RAINFALL, IN INCHES

REGIONAL MONTHLY AVERAGE

RAINFALL (1895-2004) for

Division 3 Florida

NOAA

data

EXPLANATION

MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES

MARSH DATA

COLLECTION PERIOD

CYPRESS DATA

COLLECTION PERIOD

MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES
148 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Appendix 2. Monthly rainfall inside the canopy at the cypress wetlands.

W-19 IMPAIRED CYPRESS

0.15

4.71

5.56

1.71

1.38 17.90

5.84

11.74

6.33

1.12

1.65

1.34

3.68

4.32

0.66

1.61

0.46

12.20

J F M A M J J A S O N D J F M A M J

2003 2004

20

16

12

8

4

0

S-68 NATURAL CYPRESS

J F M A M J J A S O N D J F M A M J

2003 2004

0.05

4.26

2.78

3.35

1.47

14.73

3.16

13.28

3.51

1.80

1.13

1.56

4.58

5.18

1.05

3.78

2.21

10.36

20

16

12

8

4

0

W-5 AUGMENTED CYPRESS 20

16

12

8

4

0 N D

2002

J F M A M J J A S O N D J F M A M J

2003 2004

2.55

10.89

0.25

5.38

5.35

3.08

2.10

12.51

6.78

9.75

7.82

1.82

1.78

1.36

3.39

4.05

0.80

1.81

0.56

9.41

S-63 AUGMENTED CYPRESS

J F M A M J J A S O N D J F M A M J

2003 2004

0.03

4.05

3.21

3.60

1.40

12.95

4.60

14.39

3.52

1.74

1.87

1.42

4.35

5.17

0.93

3.68

2.52

10.80

20

16

12

8

4

0

GS NATURAL CYPRESS

D

2002

J F M A M J J A S O N D J F M A M J

2003 2004

11.69

0.13

2.82

6.31

3.84

2.07

13.19

8.21

10.66

4.01

1.04

0.58

0.92

2.73

1.48

0.76

6.53

2.64

6.82

20

16

12

8

4

0

CYPRESS DATA

COLLECTION PERIOD

MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES MONTHLY RAINFALL, IN INCHES

EXPLANATION

REGIONAL MONTHLY AVERAGE

RAINFALL (1895-2004) for

Division 3 Florida

NOAA

data
Appendixes 149

Appendix 3. Relation between rainfall measurements inside and outside of the tree canopy at the 

cypress wetlands.

8

6

4

2

0

0 2 4 6 8

W-19 Impaired cypress

8

6

4

2

0

0 2 4 6 8

S-63 Augmented cypress

8

6

4

2

0

0 2 4 6 8

S-68 Natural cypress

8

6

4

2

0

0 2 4 6 8 9

GS Natural cypress

0 2 4 6 8 10 12

12

10

8

6

4

2

0

W-5 Augmented cypress

RAIN BENEATH TREE CANOPY, IN INCHES

RAIN OUTSIDE TREE CANOPY, IN INCHES

slope R2 n

GS Natural Cypress 0.84 0.99 39

S-63 Augmented Cypress 0.90 0.99 41

S-68 Natural Cypress 0.91 0.99 39

W-5 Augmented Cypress 0.85 0.99 42

W-19 Impaired Cypress 0.96 0.98 35

Wetland

Regression statistics for rainfall at each

cypress wetland

[R = coefficient of variation,

n= number of values]

2
150 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

Appendix 4. Evapotranspiration (ET) estimates for marsh and cypress wetlands.

0.30

0.25

0.20

0.15

0.10

0.05

0

Central Florida marshes, lysimeter, Mao and others (2002)

South Florida marshes, lysimeter, Abtew (1996)

Everglades marshes, energy-budget method, German (2000)

Synthetic daily marsh wetland ET, in/d (Annual total ET is 48.35 in)

EVAPOTRANSPIRATION RATE,

IN INCHES PER DAY

JAN

EXPLANATION

(A) Marshes

FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC

Monthly average daily energy budget rate, Lake Starr (Swancar, 2006)

Lake Starr daily evaporation interpolated from monthly average (Annual Total ET is 57.29 in)

Synthetic daily cypress wetland ET

Synthetic daily marsh ET

Plus and minus 25 percent of the evaporation rate

JAN

EXPLANATION

(C) Lake Starr Evaporation and

marsh and cypress wetland ET

FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0

EVAPOTRANSPIRATION RATE,

IN INCHES PER DAY Central Florida cypress wetland average ET, energy-budget, Sumner (2001)

Central Florida cypress wetland maximum daily ET, energy-budget, Sumner (2001)

Synthetic daily cypress wetland ET, in/d (Annual total ET is 40.63 in)

JAN

EXPLANATION

(B) Cypress wetlands

FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC

0.30

0.25

0.20

0.15

0.10

0.05

0

EVAPOTRANSPIRATION RATE,

IN INCHES PER DAY
0

1

2

W-29 Marsh

50 METERS

150 FEET

(E)

0

0

BATHYMETRIC CONTOURS – Depth in feet below wetland

perimeter elevation of 69.92 feet above NGVD 29.

Interval is 0.5 foot

8.13

0

2

4

6

Duck Pond Marsh

0 50 METERS

0 150 FEET

BATHYMETRIC CONTOURS – Depth in feet

below wetland perimeter elevation of 70.48

feet above NGVD 29. Interval is 1 foot

BATHYMETRIC CONTOURS – Depth in feet

below wetland perimeter elevation of 93.30

feet above NGVD 29. Interval is 0.2 foot

0

1

1

0.5

1

1.5

1.5

1.5

Hillsborough River State Park Marsh

(B)

25 METERS

0 100 FEET

0

0.5

BATHYMETRIC CONTOURS – Depth in feet

below wetland perimeter elevation of 46.35

feet above NGVD 29. Interval is 0.5 foot

5.44

0

1 2

0

2.5

W-03 Marsh

0 50 METERS

0 150 FEET

BATHYMETRIC CONTOURS – Depth in feet

below wetland perimeter elevation of 72.44

feet above NGVD 29. Interval is 0.5 foot

EXPLANATION

VEGETATION PLOTS

DEEPEST POINT – Showing depth in feet below wetland

perimeter

STAFF LOCATION

DIRT ROADWAY – Elevation higher than wetland perimeter

elevation

elevation

1.07

0 25 METERS

0 100 FEET

(D)

0

0

1.0

0.4

0.8

0.8 1.0

Green Swamp Marsh

(A)

(C)

2.65

2.76

Appendixes 151

Appendix 5. Bathymetric maps for the 10 study wetlands 

showing location of vegetation plots (modified from 

Haag and others, 2005).
152 Comparative Hydrology, Water Quality, and Ecology of Selected Natural and Augmented Freshwater Wetlands, Florida

0

50 METERS

0 150 FEET

0

25 METERS

0 100 FEET

0

50 METERS

0 150 FEET

0

1.55

1

S-68 Cypress

(H)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 43.66 feet above

NGVD 29. Interval is 0.5 foot

0

1 W-05 Cypress

50 METERS

150 FEET

(J)

VEGETATION PLOTS

DEEPEST POINT – Showing depth in feet below wetland

perimeter

STAFF LOCATION

DIRT ROADWAY – Elevation higher than wetland

perimeter elevation

WETLAND OUTFLOW – To roadside ditch at approximate

elevation of 71.0 feet above NGVD 29

elevation

0

0

EXPLANATION

2.11

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 98.56 feet above

NGVD 29. Interval is 0.5 foot

1.69

0

1

0 25 METERS

0 100 FEET

(F)

Green Swamp Cypress

1.47

0

1

S-63 Cypress (G)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 42.32 feet above

NGVD 29. Interval is 0.5 foot

2.70

0

1

2

W-19 Cypress

(I)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 63.23 feet above

NGVD 29. Interval is 0.5 foot

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 71.47 feet above

NGVD 29. Interval is 0.5 foot

Appendix 5. Bathymetric maps for the 10 study wetlands 

showing location of vegetation plots (modified from 

Haag and others, 2005).—Continued