Table of Contents
EXECUTIVE SUM M ARY ....................................................................................................................................... iii
IN TR O D U C TIO N ....................................................................................................................................................... 1
EXTENT OF FLORIDA FRESHW ATER W ETLANDS .................................. ...........................................................1......
DESCRIPTION OF FLORIDA FRESHWATER W ETLANDS..................................................................................2
Wetland Vegetation................................................... ........................... 3
Wetlands Hydrogeomorphology........... ................................................................................. 3
PURPOSE OF STUDY .......................... .................... ....................................................... .. 3
M E TH O D S...................................................................................................................................................................4
D A TA SEA R C H ....................................................................................................................................................... . 4
P published, P eer-R review ed Literature.................................................... ...................................................4........
G ray L iterature.............................................. ................................................................................ . . .......... 5
Unpublished D ata......... ............................................................................. ........ .................. .. 5
N UTRIENT AND H YDROLOGY D ATABASE ...................................... ....................................................................6...
NUTRIENT D ATA SUMMARY AND SYNTHESIS.................................... .............................................................7......
W ETLAND H YDROLOGY SUMMARY AND SYNTHESIS.............................................................................. .................. 7
METHODOLOGY FOR ESTIMATING NUTRIENT LOADING FROM WETLANDS .............................................................. 7
R E SU L T S .....................................................................................................................................................................8
N ON-IM PACTED W ETLANDS.................................... ......................................................... ........................ 8
D epressional F rested W etlands........................................................................................................................ 8
B asin F rested W etlands.................................................................................................................................. 14
D epressional E m ergent W wetlands .............................................................................. .................................... 14
Basin Em ergent W etlands.................. .................................................................................... 14
IMPACTED W ETLANDS.................... ............................................................................ ................. 15
Depressional Forested Wetlands........... ................................................................................ 15
B asin F rested W etlands.................................................................................................................................. 16
D epressional E m ergent W wetlands .............................................................................. .................................... 16
Basin Emergent Wetlands................................................................................................. 17
NON-IMPACTED WETLANDS QUARTILES AND NUTRIENT CONCENTRATIONS ....................................................... 17
H YDRO-G RAPHS ........................................................................ ............................................. .................. 20
METHODOLOGY FOR ESTIMATING NUTRIENT LOADINGS FROM WETLANDS..........................................................23
D ata Input ..................................................................................... .................. 23
C calculation of D discharge Volum es ...................................................................................................................... 26
SAMPLE CALCULATION FOR ESTIMATING WETLAND LOADING..............................................................................28
DISCUSSION AND RECOMMENDATIONS ..................................................................................................... 29
D ATA U N CERTAIN TY .................................. ........................ ..............................................30
FUTURE RESEARCH.............ARCH .................................................................................................................................................. 30
R E FERE N C E S .......................................................................................................................................................... 32
APPENDIX A - REFERENCES WITH RELEVANT DATA INCLUDED IN ACCESS DATABASE,
NUTRIENT TABLES, OR HYDROGRAPH COLLECTION ........................................................................... 34
APPENDIX B - COLLECTED HYDROGRAPHS FOR FLORIDA WETLANDS .........................................39
APPENDIX C - WETLAND HYDROLOGY MODEL ...................................................................................... 63
This report summarizes a database of environmental parameters for isolated wetlands in Florida
with specific focus on nitrogen and phosphorus in the wetland water column and soils. This
database, the Florida Isolated Wetland Nutrient Database (FIWND) was assembled through a
comprehensive review of literature and available data sources, with a particular focus on
gathering all existing nitrogen and phosphorus water quality data for reference isolated wetlands
that have minimal impact from human disturbance, hereafter called non-impacted wetlands. Data
were also collected for impacted isolated wetlands, thereby providing a record of wetland water
and soil quality across the landscape (where recorded) and a basis for comparison with reference
The data indicate that water column nitrogen and phosphorus both show considerable natural
variation in non-impacted Florida wetlands. Total Kjeldahl Nitrogen (TKN) values for non-
impacted isolated wetlands ranged from a low of 0.002 mg N/L to a high of 6.0 mg N/L while
total phosphorus (TP) values ranged from a low of 0.002 mg P/L to 0.64 mg P/L. Impacted
wetlands generally showed much more variation in water column nutrient parameters, with a
TKN range from 0.450 mg N/L to 31.0 mg N/L and a TP range from 0.0035 mg P/L to 17.0 mg
P/L. Note that TKN values are reported, as opposed to total nitrogen (TN), due to the low
sample size of non-impacted (n = 3) and impacted (n = 21) TN data.
Using the 75th percentile (or third quartile) of nutrient concentrations as an indicator of
background nutrient concentrations during the wet season, isolated non-impacted wetlands water
column TKN concentrations were below 2.000 mg N/L for forested depressional wetlands, 2.200
mg N/L for emergent depressional wetlands, and 1.608 mg N/L for emergent basin wetlands.
Water column nitrate-nitrogen (NO3-N) and ammonia-nitrogen (NH3-N) 75th percentile values
were much lower. Background TP concentrations were below 0.085 mg P/L for forested
depressional wetlands, 0.041 mg P/L for emergent depressional wetlands, and 0.047 mg P/L for
emergent basin wetlands.
While the data show small differences in the range of soil nitrogen values between non-impacted
and impacted wetlands, a strong difference is found for phosphorus levels in non-impacted and
impacted wetlands. Background soil TN concentrations, based on the 75th percentile of non-
impacted wetlands, were 13.50 mg N/g soil for forested depressional wetlands, 12.35 mg N/g
soil for emergent depressional wetlands, and 30.35 mg N/g soil for emergent basin wetlands.
The 75th percentile soil TP concentrations were 0.408 mg P/g soil for forested depressional
wetlands, 0.260 mg P/g soil for emergent depressional wetlands, and 0.205 mg P/g soil for
emergent basin wetlands.
We have proposed a methodology for calculating runoff for isolated depressional and basin
wetlands for individual rainfall events. The methodology uses the US Department of Agriculture
Soil Conservation Service (now Natural Resources Conservation Service) runoff equation with
modified curve numbers (CNs) developed specifically for isolated wetlands. During the dry
season, we propose that runoff will only occur if the rainfall event is greater than the difference
between the wetland water level and the mean wet-season water level. Nutrient concentration
for runoff can then be calculated based on the FIWND values collected for this study. We
propose that 75th percentile nutrient concentrations are used for dry season calculations,
reflecting higher nutrient concentrations in lower water conditions. Further, the lower 25th
percentile nutrient concentrations should be used to calculate loading during the wet season, to
reflect the more dilute nutrient conditions in times of higher wetland water levels and therefore
dilution of nutrient concentrations.
Interpretive caution toward these results is warranted because much of the literature data were
collected during relatively short-term research studies focused on a small number of specific
sites. As well, reporting conventions across studies are quite idiosyncratic. A systematic
approach for sampling water quality of Florida's isolated wetlands is necessary for a robust,
regionally specific understanding of the natural condition of these systems and the role they play
in maintaining water quality across the natural and developed landscape matrix.
Wetlands are defined by the presence of hydric soils, hydrophytic vegetation, and characteristic
hydrology that provides saturation or inundation for a sufficient part of the growing season to
support hydric soils and hydrophytic vegetation. For the purposes of this review we refer to the
US Fish and Wildlife Service standard classification scheme for wetlands and deepwater habitats
(Cowardin et al. 1979). Our focus was on isolated palustrine forested and emergent wetlands.
Data were further divided into smaller depressional wetlands and larger basin wetlands. In this
review, the term isolated specifically refers to wetlands that generally lack a significant surface
water connection, though may connect to other wetlands or water bodies in times of above
average water levels, and are therefore considered to have surficial hydrologic isolation.
Further, the wetlands are considered geographically isolated owing to the surrounding land cover
being upland habitat (after Tiner 2003). Additional data for wetlands outside of Florida or for
other palustrine wetland types (e.g. strands, sloughs) were collected and entered in the database
when included in relevant data sets or otherwise available, but are not presented here.
A further focus of this review was on reference standard wetlands. That is, wetlands that
represent ecological integrity, the highest ecological condition, and that were generally free from
obvious and apparent anthropogenic influence. Hereafter, these reference standard wetlands are
described as non-impacted, to facilitate standard terminology throughout this document.
Additional data were collected for impacted wetlands, described as those influenced by
anthropogenic activities in the surrounding landscape (e.g. row crops, pasture, dairy farms,
residential development, highways). While the scope of work called for a specific review of
non-impacted, the inclusion of data from impacted wetlands provides a broader understanding of
the current state of wetland water and soil quality across the Florida landscape.
Extent of Florida Freshwater Wetlands
Wetlands once occurred on approximately 8.2 million ha throughout the state of Florida. Today
considerably less of the landscape is occupied by wetlands, with an estimate from 1996 of 4.6 million
ha of wetlands in Florida (Dahl 2005). Of these wetlands, approximately 90% are freshwater
wetlands (4.1 million ha) with 2.3 million ha of freshwater forested wetlands, 1.1 million ha of
freshwater emergent wetlands, 725,000 ha of freshwater shrub wetlands, and 98,000 ha of freshwater
ponds (Dahl 2005).
The US Fish and Wildlife Status and Trends report (Dahl 2005) does not specifically address
hydrologically isolated wetlands. The four broad types of freshwater wetlands include forested
wetlands (e.g. wet pine flatwoods, mixed hardwoods, river swamps, cypress domes, and hydric
hammocks), emergent wetlands (e.g. marsh, swale, slough, wet prairie, wet savanna, reed swamps,
glades), shrub wetlands (e.g. titi swamps, scrub cypress, dwarf cypress), and natural and manmade
freshwater ponds (Dahl 2005). The mean surface area of freshwater wetlands ranged from 7 ha for
forested wetlands, 4 ha for emergent wetlands, 3 ha for shrub wetlands, to 0.7 ha for freshwater
ponds (Dahl 2005).
Further, these wetland types are not equally abundant throughout Florida (Table 1). Lane (2000)
presented four Florida wetland regions derived from a spatial hydrological model: panhandle, north,
central, and south (Figure 1). In the panhandle region, Lane (2000) identified 90.1% of the
freshwater wetlands as forested with the remaining 10% divided between shrub (6.8%) and emergent
(3.2%) wetlands. In contrast, in the south region, 21.9% of the freshwater wetlands were forested,
with 17.3% shrub and 60.8% emergent shrub wetlands. In an earlier study, the Florida Department
of Community Affairs (1988) estimated that the ratio of forested to emergent wetlands in the Florida
panhandle was 10:1; whereas the ratio was 3:1 and 1:5 in central and south Florida, respectively (as
cited by Dahl 2005).
Table 1. Spatial distribution of palustrine wetland types in Florida (Lane 2000)
Vegetation Panhandle North Central South
Forested 90.1% 78.2% 49.8% 21.9%
Emergent 3.2% 13.3% 41.4% 60.8%
Shrub 6.8% 8.6% 8.7% 17.3%
)0 0 200 400 Kilometers
Figure 1. Florida wetland regions (Lane 2000)
Description of Florida Freshwater Wetlands
Distinct differences occur among Florida wetland types, though an overlap in flora and fauna
occurs. This review focused on geographically isolated depressional and basin, forested and
emergent wetlands. These geographically isolated wetlands belong to what Tiner (2003) calls
Coastal Plain ponds, cypress domes, gum ponds, or pocosin wetlands.
Forested wetlands include those wetlands characterized by woody species that are at least 6 m
tall or taller (Dahl 2005). Emergent wetlands, commonly called marshes, host rooted herbaceous
hydrophytes, with the exclusion of wetlands dominated by mosses and lichens (Dahl 2005). The
biomass turnover rate of emergent wetlands is typically an order of magnitude higher than
forested wetlands (Hopkinson 1992).
For the purposes of this review we have broadly grouped the data as depressional or basin
wetlands. Depressional wetlands often occur in relatively small watersheds and their water
budget is dependent on precipitation (Brinson 1993), making them hydrologically isolated from
surface water connectivity. While not strictly hydrologically isolated wetlands, basin wetlands
in this review were characterized as larger wetland systems often with a seasonal or semi-
permanent surface hydrologic connection to other wetlands or aquatic bodies, either as inflow or
outflow. Because basin wetlands can be nearly "completely surrounded by uplands," which
Tiner (2003) uses to define isolated wetlands, basin wetlands qualify as geographically isolated
wetlands for the purposes of this review. Brinson and Lee (1989) described basin wetlands as
having low hydrologic energy, long hydroperiods, low nutrient availability, low to moderate
temperature, low to high fire frequency, and low herbivory.
Purpose of Study
This review was conducted in response to a request for a literature review to summarize and
synthesize available scientific information regarding background nutrient concentrations and
hydrology for Florida isolated wetlands. This review synthesizes information in order to define
background conditions for non-impacted wetlands (i.e. natural, minimally impaired, reference
standard wetlands) and impacted wetlands (i.e. wetlands surrounded by human land use
activities) for the proposed Statewide Stormwater Treatment Rule. The available literature,
including published, peer reviewed documents and gray literature reports, has been used to
document nutrient concentrations, particularly nitrogen and phosphorus, and to summarize the
existing information on wetland hydrology (i.e. depth, duration, flood frequency).
Wetland hydrology is generally considered the single most influential determinant of wetland
condition (e.g. Duever et al. 1986; Mitsch and Gosselink 2007). Long term monitoring records
of wetland hydrology are generally absent from wetland studies and what data are available
generally span five growing seasons or less and are thus considerably dependent on short term
weather conditions as opposed to long term climactic averages. An acceptable integration of
wetland hydrology reflecting long term climatic averages is difficult to predict; however,
understanding wetland hydrology is critical to developing realistic estimates of stormwater
loading from wetlands.
As guidance for public policy, the wetland literature review presents what is known about
nutrient concentrations and hydrology, the information gaps that inject substantial uncertainty,
and suggested research to address these gaps.
The primary objective of this scope was to develop a synthetic database on concentrations of
water column nitrogen and phosphorus in isolated wetlands in order to provide usable scientific
information as input to the development of the Statewide Stormwater Treatment Rule for
Florida. To accomplish this objective, the project team reviewed available scientific literature on
wetland nutrient concentrations, focusing on nitrogen and phosphorus, and hydrology. To reflect
differences between wetland types and the spatial differences in ecological drivers across
Florida, the review considered differences by wetland vegetation (e.g., forested, emergent),
wetland hydrogeomorphology (e.g., depressional, basin), and wetland region (e.g., panhandle,
north, central, south). A secondary objective of this scope was the development of a stormwater
loading model that can be used to predict the nutrient load in runoff from isolated wetlands.
Several sources of literature were consulted including the published, peer-reviewed literature;
gray literature from academic and institutional literature, consulting reports, and city, county,
state, and federal agencies; and unpublished data sets.
Published, Peer-Reviewed Literature
A comprehensive search of the UF library system was conducted using relevant key word
searches: ammonia, basin, cypress, depressional, emergent, Florida, forested, hydrology,
hydroperiod, isolated, nitrate, nitrite, nitrogen, nutrients, phosphate, phosphorus, and/or wetland.
The search included nine ecological databases: Academic Search Premier, AGRICOLA (CSA),
Biological and Agricultural Index Plus, BIOSIS Previews, CAB Abstracts, Ecology Abstracts,
OmniFile Full Text Mega, Science Citation Index, and Wildlife & Ecology Studies Worldwide.
Academic Search Premier, as the largest academic multi-disciplinary database, includes nearly
4,700 publications, with more than 3,600 from peer-reviewed journals. AGRICOLA (CSA) is a
bibliographic database including listings for journal articles, monographs, proceedings, theses,
patents, translations, audiovisual materials, computer software, and technical reports pertaining
to all aspects of agriculture. Biological and Agricultural Index Plus includes resources in biology
and agriculture, with some content from peer-reviewed journals. BIOSIS Previews provides the
largest collection of biological sciences records world-wide from over 6000 book chapters, book
reviews, journals, meetings, review articles, software, and U.S. patents. CAB Abstracts presents
international research and development materials in the fields of agriculture, animal health,
forestry, human health, human nutrition, and management and conservation of natural resources.
Ecology Abstracts provides a search in current ecology research. Wilson OmniFile Full Text,
Mega Edition provides resources from six of Wilson's full-text databases as a single multi-
disciplinary database. Science Citation Index Expanded provides a search in 5,900 major
journals across 150 scientific disciplines and includes all cited references captured from indexed
articles. Wildlife & Ecology Studies Worldwide includes over 650,000 bibliographic records and
is the largest index for materials on wild mammals, birds, reptiles, and amphibians.
A search for gray literature data sources included the University of Florida's Howard T. Odum
Center for Wetlands library, which includes student theses and dissertations, internal project
reports, and reports from agencies including the Florida Department of Environmental
Protection, National Park Service, Water Management Districts (i.e., South Florida Water
Management District, Southwest Florida Water Management District, and St. Johns River Water
Management District), and some additional agency or consulting firm reports for individual
projects. As a part of the search process, agency websites were searched for appropriate reports
and materials (e.g., Sarasota County Water Atlas
http://www.sarasota.wateratlas.usf.edu/Default.aspx, South Florida Water Management District
http://www.sfwmd.gov/), Southwest Florida Water Management District
http://www.swfwmd.state.fl.us/, St. Johns River Water Management District
http://sjr.state.fl.us/publications.html, United States Geological Survey
Many different avenues were explored for gathering unpublished wetland data including face-to-
face meetings, phone calls, and email communication. The following individuals provided data,
either as unpublished data sets or as published reports or journal articles: Mark Clark, University
of Florida Department of Soil and Water Science, USEPA coastal plain database and Kissimmee
soil phosphorus data; Katherine Ewel, University of Florida, unpublished reports; Boyd
Gunsalus, South Florida Water Management District (SFWMD), repeat water measures for
wetlands in south Florida; Joe Hand, Florida Department of Environmental Protection (FDEP),
water quality data for eight wetlands; Steve Kintner, Director of Volusia County Environmental
Management Division, provided USGS study, Knowles (2005); Ray Miller, Don Medellen, and
Mike Lopushinsky, SFWMD, Jonathan Dickenson State Park hydrology data; Kim O'Dell,
Orlando Diaz, and Benita Whelan, SFWMD, Okeechobee (research report); Todd Osbourne,
University of Florida, Okeechobee basin, pasture study; Ted Rochow, SWFWMD (Green
Swamp hydrology); Brian Gentry, Palm Beach County.
The following individuals, agencies, or organizations were contacted but did not have applicable
data for this review: Patrick Bohlen, Buck Island Ranch; Tom DeBusk, consultant with DB
Environmental; Mike Duever, SFWMD; Bob Epting, Sonny Hall, and Marc Minno, SJRWMD;
Larry Kohrnack, University of Florida; Mike Owen, Fakahatchee Strand State Preserve; Pete
Wallace; Karen Bickford, TMDL Director, Lee County Natural Resources; Julie Bortles,
Environmental Program Supervisor, Orange County Environmental Protection Division; Aisa
Ceric, Palmer Kinser, Vicki Toge, SJRWMD; Charlie Hunsicker, Director, Manatee County
Natural Resources Department; Bob Knight, Wetland Solutions, Inc.; Robert Kollinger, Polk
County Natural Resources and Drainage; Gordon A. Leslie, Hillsborough County,
Environmental Protection Commission; Gary Maidhof, Citrus County; Randy Mathews,
Coordinator, Osceola County Environmental Lands Conservation Program; Brian McMahon,
EWR, Inc.; Caprecid Oliver, St. Lucie County Environmental Resources Department; John
Ryan, Environmental Supervisor, Sarasota County Water Resources; Kirk Stage, Water and Air
Resources, Inc.; St. Marks and St. Vincent National Wildlife Refuge; Walter Wood, Lake
County Environmental Utilities. Additional sources that led to duplicate data or data not
relevant to this review included HGM Depressional Guidebook reference sites by the US Army
Corps of Engineers; Disney Wilderness Preserve; Minimum Flows and Levels work; TMDL
work; Tampa Bay Water well fields; and Withlacoochee State Forest.
Nutrient and Hydrology Database
As this is a review of available data and not a project with systematic data collection, entry
points took variable formats. The Florida Isolated Wetland Nutrient Database (FIWND)
developed in Microsoft Access was designed so that each row represented a data entry point.
This may include data from an individual wetland from a single sampling event or the mean,
standard deviation, standard error, or range for a given wetland or group of wetlands. Each row
was assigned a unique, non-repeating, automatically assigned Contact ID number in the first
column. In total there were 138 columns in the data base, though no data entry point (row) had
data for every column. In addition to the unique Contact ID column there were 20 study
description columns, 4 data source or citation columns, 49 water quality columns, 24 water or
nutrient budget columns, and 40 soil quality columns.
Study description columns included: Wetland Name, One or More (e.g., ranges, mean, single
wetland), Reference Wetland, Wetland Vegetation, Wetland Type, Sample Size, Area, Nearby
City/Town, State, Region, County, Water Management District, Surrounding Land Use, Land
Use Detail, Study Time Frame, Sample Frequency, Characteristic Hydrology, Hydroperiod,
Hydrologic Alteration, and Characteristic Vegetation.
Columns specific to the data source and citation included: Data Source (e.g., author, year), Data
Certainty, Applicability, and Other Comments.
Water quality columns included: Color, Dissolved Oxygen, pH, Temperature, Conductivity,
Turbidity, Nitrate-Nitrogen (NO3), Nitrite-Nitrogen (NO2), Ammonia-Nitrogen (NH3), Organic
Nitrogen, Total Kjeldahl Nitrogen (TKN), Total Nitrogen (TN), Ortho-P, Soluble Reactive
Phosphorus, Organic Phosphorus, Total Dissolved Phosphorus, Total Phosphorus (TP),
Oxidation Reduction Potential, Secchi Depth, BOD, Suspended Solids, Dissolved Solids,
Chloride, Flouride, Sulfate, Hydrogen Sulfide, Alkalinity, Hardness, Magnesium, Calcium,
Potassium, Sodium, Iron, Manganese, Chlorophyll a, Silicon, Inorganic Carbon, Organic
Carbon, Bicarbonate, Caffeine, Fecal Coliform, Total Coliform, Enterococci, Oil and Grease,
Copper, Zinc, Cadmium, Lead, and Mercury.
Columns specific to water and/or nutrient budgets included: Rainfall, Transpiration,
Evaporation, Total Water Loss, Inflow TN, Surface Runoff TN, Bulk Precipitation TN, Nitrogen
Fixation, Infiltration TN, Denitrification, Surface Outflow TN, Sediment Deposition TN,
Cypress Uptake TN, Above Ground Biomass TN, Below Ground Storage TN, Inflow TP,
Surface Runoff TP, Bulk Precipitation TP, Infiltration TP, Surface Overflow TP, Sediment
Deposition TP, Cypress Uptake TP, Above Ground Biomass TP, and Below Ground Storage TP.
Soil physical and chemical columns included: Core Depth, Temperature, pH, Redox Potential,
%Moisture, Bulk Density, Organic Matter, %Organic Matter, %Loss on Ignition, Soluble
Reactive Phosphorus, Total Phosphorus (TP), Nitrate-Nitrogen (NO3), Nitrite-Nitrogen (NO2),
Ammonia-Nitrogen (NH3), Total Kjeldahl Nitrogen (TKN), Total Nitrogen (TN), Total Carbon,
Carbon/Nitrogen Ratio, Nitrogen/Phosphorus Ratio, Carbon/Phosphorus Ratio, Microbial
Biomass Carbon, Microbial Biomass Nitrogen, Nitrogen Mineralization Rate, Annual Nitrogen
Mineralization, Denitrification Rate, Annual Denitrification, Calcium, Magnesium, Potassium,
Calcium/Potassium Ratio, Calcium/Magnesium Ratio, Milliequivalent of Cations, Iron,
Aluminum, Sodium, Hydrogen, Cation Exchange Capacity, Cadmium, Copper, Manganese,
Lead, and Zinc.
Nutrient Data Summary and Synthesis
Due to the inherently variable nature of review data, advanced statistical analyses were
inappropriate. Summary tables were constructed to specifically address ranges in nutrient
concentration in the water column and soils of reference and impact, forested and emergent,
depressional and basin wetlands. A graphical presentation of water column NO3, NH3, TKN,
and TP and soil TN and TP was developed using box plots in Minitab v.15 (�2007 Minitab,
Inc.). Wetland categories having three or fewer data entries were omitted from graphical
Wetland Hydrology Summary and Synthesis
In an attempt to summarize available data on frequency and depth of flooding, figures showing
temporal water level variations for Florida wetlands were compiled. Hydrographs were
interpreted to provide a general overview of minimum and maximum flooding depth, an
estimation of flooding duration, and an overview of months with standing water.
Methodology for Estimating Nutrient Loading from Wetlands
To fulfill the second objective of this project, we developed a method to predict nutrient loading,
specifically nitrogen and phosphorus, to downstream systems in runoff from isolated wetlands.
The method assumes that nutrient loading is from wetland surface runoff and that no
contributions from groundwater seepage from the wetland to receiving water bodies are
considered. Further, the method differentiates between two seasons, a wet season (growing
season, June - October) and dry season (dormant season; November - May) and the
corresponding antecedent soil moisture conditions. The method is based on a Soil Conservation
Service (SCS) curve number (CN) (USDA 1985) and accounts for differences in background
concentrations of water column phosphorus and nitrogen in two broad hydrogeomorphic classes
(depressional and basin wetlands) and two vegetation types (forested and emergent). Wetland
types not included in this project are those with direct permanent hydrologic exchanges with
downstream water bodies (e.g. lake border swamps, riparian and floodplain wetlands). The
assumption is that these latter types of wetlands are intimately connected to the receiving water
bodies, and therefore their water quality is the same as the neighboring water body.
A complete list of the published peer-reviewed and gray literature references used to build the
Florida Isolated Wetland Nutrient Database (FIWND) and compilation of hydrographs is
presented in Appendix A. Dates of sample collection for entries in the database for nutrient
concentrations range from 1973-2008.
The FIWND database contained 372 entries for non-impacted wetlands in Florida. These entries
break down into the following categories for isolated wetlands: 1) 142 depressional forested
wetlands (-38%); 2) 3 basin forested wetlands (<1%); 3) 75 depressional emergent wetlands
(-20%); 4) 20 basin emergent wetlands (-5%); and 5) 32 entries for non-impacted wetlands in
which there was no identifying vegetation and/or geomorphic description available (-9%). The
database also contains 3 entries for non-impacted strand wetlands (<1%) and 97 entries for non-
impacted floodplain wetlands (-26%). An additional 304 entries are for non-impacted wetlands
in southeastern states outside of Florida and 15 entries are for non-impacted wetlands in the state
of Indiana. Because historical data on non-impacted wetlands generally are in short supply, non-
isolated wetlands in Florida and isolated wetlands outside of Florida were included in the
database as a matter of course when located during the literature review process, though the
search for these additional wetland types was in no way exhaustive.
There was location information at the level of Florida regions (i.e. panhandle, north, central, and
south) for 186 isolated non-impacted wetlands in the database. Of these, 25 (-13%) were in the
panhandle, 64 were in north Florida (-34%), 41 were in central Florida (-22%), and 56 were in
south Florida (-30%). Some additional entries were originally categorized at the coarser scale of
USEPA regions and do not contain sufficient auxiliary information for categorization by Florida
Depressional Forested Wetlands
A relatively large number of data points were found for the parameters of water column NO3,
NH3, TKN, and TP concentrations in non-impacted depressional forested wetlands (Tables 2 &
3). With the exception of TN, which only has two entries, all dissolved nitrogen parameters
showed a lower bound that approached the common analytical detection limit (-0.002 mg N/L)
(Figures 2 & 3). The range for TKN showed a relatively normal distribution up to an upper range
of 5.6 mg N/L, while the upper values for both NO3 (1.9 mg N/L) and NH3 (1.7 mg N/L) were
far outliers associated with one datum entry (Figure 2). Most values for TP were below 0.05
mg/L, although there were several outliers up to an upper value of 0.64 mg P/L (Figure 3). Direct
interaction with highly phosphatic clays of the Hawthorne layer likely explained the very high
phosphorus values found in some non-impacted forested depressional wetlands.
Soil nutrient ranges in reference forested depressional wetlands were shown in Tables 4 & 5 and
graphically presented in Figure 4. Soil nitrogen concentrations ranged from 1.68 mg N/g to
14.45 mg N/g as measured by TKN and 2.2 mg N/g to 17.7 mg N/g of TN. Soil phosphorus
concentrations showed greater variability, which also was almost certainly a function of some
wetland soils having direct interaction with phosphate rich Hawthorne clays. The range of SRP
(0.0022 mg P/g - 4.296 mg P/g) spanned across three orders of magnitude and TP values
spanned approximately two orders of magnitude (0.02 mg P/g - 1.51 mg P/g).
Table 2. Ranges of water column dissolved nitrogen parameters
NO3-N (mg N/L) NH3-N (mg N/L) TKN (mg N/L) TN (mg N/L)
0.002 -1.9 0.002 -1.7 0.002 -5.6 1.6 -1.67
(79 entries) (66 entries) (82 entries) (2 entries)
Basinforested 0.004 -0.09 0.01 -0.095 0.62 -0.98 0.94
(3 entries) (3 entries) (3 entries) (1 entry)
0.002 - 0.047 0.005 -2.6 0.41 -6.0 N.A.
Depressional emergent (49 entries) (29 entries) (49 entries) (0 entries)
0.007 - 0.117 0.06 -1.2 0.92 -1.77 N.A.
Basin emergent (9 entries) (9 entries) (4 entries) (0 entries)
0.002 -0.63 0.002 -12.6 0.45 -31.0 1.2 -17.1
(124 entries) (125 entries) (126 entries) (9 entries)
0.06-0.13 0.01 -0.03 0.62- 1.3 0.1- 1.33
(6 entries) (6 entries) (7 entries) (7 entries)
0.004 - 0.016 0.136 1.45 -14.36 N.A.
Depressional emergent (17 entries) (1 entry) (16 entries) (0 entries)
0.04 -0.1 0.02 -0.51 0.57 -3.9 0.57 -1.50
Basin emergent (6 entries) (6 entries) (6 entries) (5 entries)
Table 3. Ranges of water column phosphorus parameters
Ortho-P (mg P/L) SRP (mg P/L) Organic P (mg P/L) TP (mg P/L)
0.0008 - 0.48 Non-detect 0.02 -0.12 0.002 -0.64
(7 entries) (1 entry) (2 entries) (82 entries)
Basin forested 0.003 - 0.006 N.A. 0.01 0.009 -0.01
(2 entries) (0 entries) (1 entry) (3 entries)
N.A. N.A. N.A. 0.0069 - 0.12
Depressional emergent (0 entries) (0 entries) (0 entries) (49 entries)
0.002 - 0.035 N.A. N.A. 0.007 -0.08
Basin emergent (8 entries) (0 entries) (0 entries) (5 entries)
0.05 -10.46 0.03 -0.05 0.18 -2.10 0.0049 - 17.0
(19 entries) (2 entries) (7 entries) (150 entries)
N.A. N.A. 0.003 -0.01 0.01 -0.05
(0 entries) (0 entries) (6 entries) (7 entries)
N.A. 0.016 -1.96 N.A. 0.0035 -7.98
(0 entries) (3 entries) (0 entries) (117 entries)
0.25 0.09 N.A. 0.029 -0.57
Basin emergent (5 entries) (1 entry) (0 entries) (7 entries)
Table 4. Ranges for soil nitrogen parameters
NO3-N NH3-N TKN TN
(mg N/g soil) (mg N/g soil) (mg N/g soil) (mg N/g soil)
Depressional forested N.A. N.A. 1.68- 14.45 2.2 -17.7
(0 entries) (0 entries) (37 entries) (25 entries)
Basin foster N.A. N.A. N.A. N.A.
(0 entries) (0 entries) (0 entries) (0 entries)
N.A. N.A. N.A. 0.002 -34.2
Depressional emergent (0 entries) (0 entries) (0 entries) (44 entries)
0.00026 -0.190 0.0253 -0.15 N.A. 20-35.1
Basin emergent ( 4 entries) (12 entries) (0 entries) (12 entries)
Depressional forested N.A. N.A. 0.51 -16.63 1.2 -21.0
(0 entries) (0 entries) (83 entries) (50 entries)
Basin foster N.A. N.A. N.A. 0.36-3.54
(0 entries) (0 entries) (0 entries) (8 entries)
N.A. N.A. N.A. 1.1 -43.3
Depressional emergent (0 entries) (0 entries) (0 entries) (49 entries)
N.A. 0.0963 N.A. 0.619 -46
Basin emergent (0 entries) (1 entry) (0 entries) (12 entries)
Table 5. Ranges
for soil phosphorus parameters
SRP (m2 P/2 soil) Total P (m2 P/2 soil)
0.0022 - 4.296
0.00072 - 0.033
0.00045 - 0.023
0.1217 - 3.54
0.0001 - 0.0235
0.048 - 0.270
0.0439 - 7.53
0.01463 - 0.225
0.00187 - 4.32
0.046 - 2.67
II I I I I I I
R I R I R I R I
Forested Emergent Forested Emergent
Figure 4. Soil nutrient concentrations: a) total nitrogen (TN) and b) total phosphorus (TP)
for R (non-impacted or reference, no fill) or I (impact, gray fill); forested and
emergent; depressional and basin wetlands. Boxes represent the first through third
quartiles; horizontal interior line represents the median; vertical whickers
represent data range; asterisks represent outliers. Extreme outliers are not shown
due to scaling constraints.
Basin Forested Wetlands
Limited water quality data were located for non-impacted basin forested wetlands. Nitrate values
ranged from 0.004 mg N/L to 0.09 mg N/L, ammonia ranged from 0.01 mg N/L to 0.095 mg
N/L, and TKN ranged from 0.62 mg N/L to 0.98 mg N/L in three entries (Table 2). Ortho-P
ranged from 0.003 - 0.006 mg P/L in two samples, and TP ranged from 0.009 - 0.01 mg P/L in
three entries (Table 3). No soil N or P data were located for non-impacted basin forested
wetlands (Tables 4 & 5; Figure 4).
Depressional Emergent Wetlands
A fair number of data points were found for the parameters of water column NO3-N, NH3-N,
TKN (Table 2), and TP (Table 3) concentrations in non-impacted depressional emergent
wetlands. NO3-N values ranged from a lower bound near the common detection limit (0.002 mg
N/L) to an upper bound of 0.047 mg N/L; NH3-N data values showed a considerably wider
range from a low of 0.005 mg N/L to an outlier value of 2.6 mg N/L (Table 2; Figure 2). TKN
varied across an order of magnitude, from a low of 0.41 mg N/L to a high of 6.0 mg N/L in non-
impacted depressional emergent wetlands (Table 2; Figure 3). Water column TP varied across
two orders of magnitude, from a low of 0.0069 mg P/L to a high of 0.12 mg P/L (Table 3; Figure
Soil nitrogen values in non-impacted depressional emergent wetlands showed considerable
variation, with TN having an extreme lower end of 0.002 mg N/g and a high value of 34.2 mg
N/g (Table 4; Figure 4). Soil phosphorus also varied considerably, with a low TP value of
0.00468 mg P/g to a high of 1.01 mg P/g (Table 5; Figure 4). While variability in both water
column and soil phosphorus was likely a function of some wetlands having interaction with
phosphate-rich Hawthorne clays, the source of variability in nitrogen among non-impacted
depressional emergent wetlands was somewhat less clear.
Basin Emergent Wetlands
Few data points for water column nitrogen and phosphorus were found for non-impacted basin
emergent wetlands (Tables 2 & 3). Ranges for both NO3-N (0.007 - 0.117 mg N/L) and NH3-N
(0.06 -1.2 mg N/L) spanned across one and a half orders of magnitude in nine data entries, while
TKN showed a much narrower range (0.92 mg N/L - 1.77 mg N/L) in four data entries (Table 2;
Figures 2 & 3). Ranges for Ortho-P (0.002 mg P/L - 0.035 mg P/L) and TP (0.007 mg P/L - 0.08
mg P/L) both spanned across approximately one order of magnitude among eight data entries
(Table 3; Figure 3).
Soil NO3-N values showed a high level of variation in four entries, from a low of 0.00026 mg
N/g to 0.190 mg N/g (Table 4). Soil NH3-N ranged across an order of magnitude from 0.0253 mg
N/g to 0.15 mg N/g in 12 entries, while soil TN showed a narrow range from 20 mg N/g to 35.1
g N/g for the same 12 entries (Table 4; Figure 4). Soil SRP ranged from 0.00045 mg P/g to 0.023
mg P/g, while soil TP ranged from 0.048 mg P/g to 0.270 mg P/g (Table 5; Figure 4).
The FIWND database contained 918 entries for wetlands in Florida that have some degree of
impact by human land use disturbance. These entries break down into the following categories
for isolated wetlands: 1) 291 depressional forested wetlands (-32%); 2) 7 forested basin
wetlands (<1%); 3) 455 depressional emergent wetlands (-49%); 4) 48 basin emergent wetlands
(-5%); and 5) 35 entries in which there was no identifying vegetation and/or geomorphic
description available (-4%). The database also contained 34 entries for impacted strand wetlands
(-4%) and 48 entries for impacted floodplain wetlands (-5%). An additional 229 entries are for
impacted isolated wetlands in southeastern states outside of Florida and 60 entries are for
impacted wetlands in the state of Indiana.
There was location information at the level of Florida regions for 701 isolated wetlands with
human impact in the database. Of these, 44 (-6%) were in the panhandle, 64 were in north
Florida (-14%), 562 were in central Florida (-76%), and 31 were in south Florida (-4%).
Remaining entries were originally categorized at the coarser scale of USEPA regions and do not
contain sufficient auxiliary information for categorization by Florida region.
Depressional Forested Wetlands
A relatively large number of data points were found for the parameters of water column NO3-N,
NH3-N, TKN, and TP concentrations in impacted depressional forested wetlands (Tables 2 & 3).
Similar to non-impacted systems, dissolved nitrogen and NH3-N parameters showed a lower
bound in impacted depressional forested wetlands at the common analytical detection limit of
0.002 mg N/L. In contrast to non-impacted systems, the lower TKN bound of 0.45 mg N/L was
much higher than the common analytical detection limit, and the box plot in Figure 3 shows the
somewhat higher 75th percentile range for TKN in impacted forested depressional wetlands.
Interestingly, the highest value for NO3-N (0.63 mg N/L) in impacted depressional forested
wetlands is considerably lower than the high outlier value of 1.9 mg N/L found in the non-
impacted depressional forested wetland data, and the 75th percentile (third quartile) ranges for
NO3-N in non-impacted and impacted systems were relatively similar (Figure 2). In contrast, the
upper bound of 12.6 mg N/L for NH3-N found in impacted depressional forested wetland
systems was considerably higher than the 1.7 mg N/L shown in non-impacted depressional
forested wetland systems (Figure 2), as is the upper bound of 31.0 mg N/L for TKN (5.6 mg N/L
in non-impacted) (Figure 3). These upper NH3-N and TKN nitrogen values represented severe
nitrogen contamination in these isolated wetlands, and the extent of such contamination
throughout the database was apparent in the 75th percentile ranges (Figure 2).
The lower TP bound of 0.0049 mg P/L in impacted systems was somewhat higher than the lower
TP bound of 0.002 mg P/L found in non-impacted systems. Extremely high ortho-P values of
10.46 mg P/L and TP values of 17.0 mg P/L (Table 5) likely represented severe phosphorus
contamination of wetlands associated with agricultural operations. The much higher 75th
percentile (third quartile) range of TP in impacted depressional forested wetlands was clear
Tables 4 & 5 shows soil nutrient ranges in impacted forested depressional wetlands. Soil
nitrogen concentrations ranged from 0.51 mg N/g to 16.63 mg N/g as measured by TKN and 1.2
mg N/g to 21.0 mg N/g of TN, neither of which differ dramatically from the ranges found in non-
impacted systems (Table 4; Figure 4). Like with non-impacted wetland systems, impacted
wetland systems soil phosphorus concentrations showed greater variability. The range of soil
SRP (0.00137 mg P/g - 1.497 mg P/g) spanned across three orders of magnitude, although,
interestingly, the high soil SRP value was considerably lower than the high value of 4.296 mg
P/g found in non-impacted systems (Table 5). TP values spanned well over two orders of
magnitude (0.0439 mg P/g - 7.53 mg P/g), with the high value several times larger than the
highest value (1.51 mg P/g) found in non-impacted systems. While soil phosphorus levels in
impacted forested depressional systems also may have considerable natural variation due to
interaction with phosphatic clays, the much higher 75th percentile (third quartile) range for soil
TP in impacted systems is suggestive of anthropogenic enrichment.
Basin Forested Wetlands
Limited amounts of water quality data were identified for impacted basin forested wetlands.
Nitrate values ranged from 0.06 mg N/L to 0.13 mg N/L and ammonia ranged from 0.01 mg N/L
to 0.03 mg N/L for six entries. TKN ranged from 0.62 mg N/L to 1.3 mg N/L across seven
entries (Table 2). Organic P ranged from 0.003 - 0.01 mg P/L in six entries, and TP ranged from
0.01 - 0.05 mg P/L in seven entries (Table 3).
Limited amounts of soil TN and TP data were collected for impacted basin forested wetlands
(Tables 4 & 5). TN values ranged from 0.36 mg N/g to 3.54 mg N/g, while TP ranged from
0.01463 mg P/g to 0.225 mg P/g. Due to the limited amount of water quality and soil nutrient
data for non-impacted and impacted basin forested wetlands it is premature to make detailed
comparisons of the findings at this time.
Depressional Emergent Wetlands
Database entries for impacted depressional emergent wetlands showed a clear phosphorus bias.
While there were large numbers of data points for water column TP (117 entries; Table 3) and
soil TP (423 entries; Table 5), there were a little less than 20 entries for both water nitrate and
water TKN (Table 2) and a little under 50 entries for soil TN (Table 4).
Nitrate values ranged from a lower bound of 0.004 mg N/L to an upper bound of 0.016 mg N/L.
Interestingly, the higher bound for nitrate at impacted sites was somewhat lower than the 0.047
mg N/L found at non-impacted sites, although the small number of data points makes this result
difficult to interpret. TKN varied across an order of magnitude in impacted depressional
emergent wetlands, from a low of 1.45 mg N/L to 14.36 mg N/L. This range was considerably
higher than the TKN range of 0.41 mg N/L to 6.0 mg N/L found in non-impacted systems, and
the higher values showed up clearly in the 75th percentile (third quartile) range (Figure 2). TP
varied across three and a half orders of magnitude in impacted depressional emergent wetlands,
from a low of 0.046 mg P/L to a high of 7.98 mg P/L. The much higher 75th percentile (third
quartile) range for impacted sites showed up clearly in the box plot in Figure 3. The high end of
this range almost certainly was a function of extreme anthropogenic enrichment.
Soil nitrogen values in non-impacted depressional emergent wetlands showed quite a bit of
variation, with TN having an extreme lower end of 1.1 mg N/g and a high value of 43.3 mg N/g.
However, the high end of the TN range was not markedly higher than the high value of 34.2 mg
N/g found in reference systems, and box plots were not dramatically different for soil TN in non-
impacted and impacted sites (Figure 4). Soil phosphorus also varied considerably, with SRP
ranging from 0.00137 mg P/g to 1.497 mg P/g and TP ranging from a low value of 0.00187 mg
P/g to a high of 4.32 mg P/g. While some natural variability through Hawthorne interaction was
certainly possible, the high ends of soil P values were most likely a function of anthropogenic
enrichment from land use in the watershed. The 75th percentile (third quartile) box plot range for
soil TP was marginally higher in impacted sites (Figure 4).
Basin Emergent Wetlands
Limited water column nitrogen and phosphorus data were located for impacted basin emergent
wetlands (Tables 2 & 3). Ranges were 0.04 mg N/L to 0.1 mg N/L for NO3-N, 0.02 mg N/L to
0.51 mg N/L for NH3-N, 0.57 mg N/L to 3.9 mg N/L for TKN, and 0.57 mg N/L to 1.5 mg N/L
for TN. The range for TP in impacted basin emergent wetlands was 0.029 mg P/L to 0.57 mg
P/L. Interpretation of box plot ranges was somewhat tenuous, however, due to the small number
of data points (Figures 2 & 3).
Soil TN in impacted basin emergent wetlands ranged greatly from an outlier low of 0.619 mg
N/g to 46 g N/g across 12 entries (Table 4). Twelve entries for soil SRP showed a range from
0.1217 mg P/g to 3.54 mg P/g. Soil TP showed a considerable range of values from 0.00187 mg
P/g to 2.67 mg P/g (Table 5). Much of soil P sampling in impacted basin emergent wetlands was
performed for the express purpose of better understanding P transport in enriched areas, and thus
it is fairly safe to conclude that the high end of the P soil ranges in these systems was a direct
function of anthropogenic activities (Figure 4).
Non-Impacted Wetlands Quartiles and Nutrient Concentrations
Partitioning the non-impacted wetlands data into quartiles allowed a better focus on the reference
standard condition in the Florida landscape (Figure 5). The Florida Department of
Environmental Protection (FDEP) has used such an approach when determining thresholds for
metric scoring for bioassessment work on lakes and streams (e.g. Barbour et al. 1996) as have
other states (e.g. Royer et al. 2001). In some instances, values below the 75th percentile (3rd
quartile) have been considered representative of the reference standard condition (for values that
increase with human disturbances or impacts). Actual quartile values were presented in Table 6.
Forested Depresional Emergent Deprional Emergent Basin
Forested Depressional Emergent Depressional Enmergent Basin
Figure 5. Non-impacted wetland nutrient concentrations: a) water column nitrate-N, b) water column ammonia-N, c) water
column TKN, d) water column TP, e) soil TN, and f) soil TP for forested depressional, emergent depressional, and
emergent basin wetlands. Boxes represent the first through third quartiles; horizontal interior line represents
median; vertical whickers represent data range; asterisks represent outliers. Extreme outliers were not shown.
Table 6. Non-impacted wetland water column and soil nutrient data
Forested Emergent Emergent
Depressional Depressional Basin
Nitrate-N (mg N/L)
25th Percentile 0.002 0.002 0.011
Median 0.005 0.006 0.024
75th Percentile 0.020 0.010 0.038
Ammonia-N (mg N/L)
25th Percentile 0.018 0.016 0.111
Median 0.024 0.020 0.160
75th Percentile 0.050 0.033 0.230
TKN (mg N/L)
25th Percentile 1.085 1.123 0.960
Median 1.450 1.694 1.100
75th Percentile 2.000 2.200 1.608
TP (mg P/L)
25th Percentile 0.027 0.016 0.009
Median 0.044 0.026 0.012
75th Percentile 0.085 0.041 0.047
TN (mg N/g)
25th Percentile 4.300 2.200 25.525
Median 7.400 4.950 27.350
75th Percentile 13.500 12.350 30.350
TP (mg P/g)
25th Percentile 0.205 0.048 0.100
Median 0.290 0.098 0.158
75th Percentile 0.408 0.260 0.205
Twenty-four figures taken from published reports or peer-reviewed documents were collected
showing temporal water level variations for Florida wetlands (Appendix B). Some figures
provided data for more than one wetland, and these were summarized for non-impacted and
impacted wetlands (Tables 7 & 8). These hydrographs were interpreted to provide a general
overview of minimum and maximum flooding depth, an estimation of flooding duration, and an
overview of months with standing water. Note that interpretation was solely based on visual
determinations from published figures, as raw data were typically unavailable.
Hydrographs were interpreted for 21 non-impacted wetlands and 20 impacted wetland systems,
though some individual wetlands may be included in more than one row in Tables 7 & 8. For
example, the non-impacted depressional forested wetland labeled Austin Cary was listed three
times in Table 7 for three separate studies representing the same physical wetland. Similarly, the
impacted wetland Sewage or Sewage Dome was listed in two separate rows in Table 8,
representing data collected at the same physical wetland for two overlapping time periods, from
January 1976 to January 1977 (Brown 1981) and from July 1974 to December 1977 (Dierberg
and Brezonik 1983).
In total, 21 hydrographs for non-impacted Florida wetlands were interpreted, including
hydrographs for 11 depressional forested wetlands, four depressional emergent wetlands, one
mixed vegetation wetland, and five wetlands described as seasonally connected, larger wetland
systems. Non-impacted depressional forested wetlands had a range in maximum flooding depth
from 0.45-2.2 m with a range of length of flooding duration spanning 155-365 days/year (Table
7). Non-impacted depressional emergent wetlands had a higher range of maximum flooding
depth from 0.5-3.3 m with flooding duration ranging from 305-365 days/year.
Twenty hydrographs for impacted Florida wetlands were interpreted, including 10 depressional
forested wetlands, three larger connected forested wetlands, six depressional emergent wetlands,
and a single basin emergent wetland. Impacted depressional forested wetlands had a lower range
in maximum flooding depth from 0.25-1.10 m and a longer range of flooding duration from 263-
365 days/year (Table 8). Three of the north region non-impacted wetlands and four of the north
region impacted wetlands had standing water each month during the period of record. The
impacted depressional emergent wetlands had a lower maximum flooding height of 0.13-0.45 m
and fewer days flooded from 56-228 days/year. A single hydrograph was available for one
impacted emergent basin wetland, which had standing water 365 day/year.
Table 7. Interpretation of hydrographs for non-impacted Florida wetlands. All values are approximations based on visual
interpretation of published figures.
Min Max Flooding Data Data Months with Standing Water
Wetland Depth Depth Duration Start End
Type Region Name (m) (m) (days) Date Date J F M A M J J A S O N D Data Source
Central Forested 0.00 0.80 316 Jan-1981 Dec-03 x x x x x x x x x Bardi et al. 2005
Central GI 0.00 0.80 345 May-89 Apr-99 x x x x x x x x x Carret al. 2006
S North Large Dome 0.20 0.63 365 Jan-76 Jan-77 x x x x x x x x x x x x Brown 1981
I North Control 0.00 0.59 350 Jan-94 May-96 x xx x x x x x x Casey and Ewel 1998
North Austin Cary 0.00 0.75 350 Jan-74 Jun-79 x x x x x x x x Dierberg 1980
S North Austin Cary 0.00 0.75 340 Jan-74 Jun-79 x x x x x x x x x Dierberg andBrezonik 1983
" North Large 1.00 2.20 365 Mar-82 Mar-83 x x x x x x x x x x x x Ewel 1990
S North Medium 0.80 1.25 365 Mar-82 Mar-83 x x x x x x x x x x x x Ewel 1990
North Small 0.00 1.00 350 Mar-82 Mar-83 x x x x x x x x x x Ewel 1990
North Austin Cary 0.00 0.50 155 Mar-74 Dec-74 x x x x x x x x Mitsch 1984
North C Wetland 0.00 0.45 295 Jan-92 Dec-96 x x x x Sun et al. 2000
Central Herbaceous 0.00 0.50 320 Jan-94 Dec-03 x x x x x x x x x Bardi et al. 2005
* Central Large Unk 3.30 365 Sep-01 Jun-03 - - - - - - - - - - - - Knowles et al. 2005
g Central Small Unk 1.80 305 Sep-01 Jun-03 - - - - - - - - - - - - Knowles et al. 2005
North Wetland 0.00 0.50 Unk May-99 Nov-99 - - - - - x x x x x x - Wise et al. 2000
Central Wetlands Unk Unk Unk Apr-85 Sep-86 - - - - - - - - - - - - CH2MHILL 1987
" South Flatwoods 0.00 0.20 47 Unk Unk x Duever et al. 1986
a South Swamp 0.00 1.00 226 Unk Unk x x x x x x x Dueveretal. 1986
South Marsh 0.00 0.50 153 Unk Unk x x x x x x Dueveretal. 1986
North Prairie 0.00 0.70 Unk Jan-81 Dec-91 - - - - - - - - - - - - Clough 1992
North Prairie 0.00 0.27 61 Mar-90 Feb-91 x x x Clough 1992
(x) signifies standing water was reported; () empty space signifies no standing water was reported (-) signifies no data were available.
Table 8. Interpretation of hydrographs for impacted Florida wetlands. All values are approximations based on visual interpretation of
Min Max Flooding Data Data Months with Standing Water
Depth Depth Duration Start End
Type Region Wetland Name (m) (m) (days) Date Date J F M A M J J A S O N D Data Source
North Small Domel 0.00 0.60 263 Jan-76 Jan-77 x x x x x x x x Brown 1981
North Small Dome2 0.00 0.52 287 Jan-76 Jan-77 x x x x x x Brown 1981
" North Sewage Dome 0.65 0.73 365 Jan-76 Jan-77 x x x x x x x x x x x x Brown 1981
North Bermed Dome 0.00 0.25 358 Jan-76 Jan-77 x x x x x x x x x x Brown 1981
North Pasture 0.00 0.25 359 Jan-76 Jan-77 x x x x x x x x Brown 1981
o North Sewage 0.35 1.10 365 Jul-74 Dec-77 x x x x x x x x x x x x Dierberg and Brezonik 1983
| North Swamp Harvest 0.00 0.85 358 Jan-94 May-96 x x x x x x x x x x Casey and Ewel 1998
North Swamp+ Upland 0.00 0.60 350 Jan-94 May-96 x x x x x x x x x Casey and Ewel 1998
SNorth W Wetland 0.00 0.65 301 Jan-92 Dec-96 x x x x x x x x x x x x Sun et al. 2000
North ALL Wetland 0.00 0.50 331 Jan-92 Dec-96 x x x x x x x x x x x x Sun etal. 2000
" North K 0.00 2.30 319 Jan-93 Dec-96 x x x x x x x Riekerk and Korhnak 2000
North N 0.00 1.20 319 Jan-93 Dec-96 x x x x x x x RiekerkandKorhnak2000
North C 0.00 1.60 293 Jan-93 Dec-96 x x x x x x Riekerk and Korhnak 2000
Central Improved 0.00 0.45 228 01 Mar-02 x x x x x x x Bohlen and Gathumbi 2007
. Central Semi-Native 0.00 0.30 154 01 Mar-02 x x x x Bohlen and Gathumbi 2007
Central Improved 0.00 0.45 225 Sep-00 Apr-03 x x x x x Gathumbi et al. 2005
W Central Seminative 0.00 0.35 180 Sep-00 Apr-03 x x x Gathumbi et al. 2005
Central Improved 0.00 0.33 76 Jul-00 Jul-01 x x x Steinman et al. 2003
Central Semi-Improved 0.00 0.13 56 Jul-00 Jul-01 x x Steinman et al. 2003
Central Boggy Marsh Unk Unk 365 Sep-01 Jun-03 - - - - - - - - - - - - Knowles et al. 2005
(x) signifies standing water was reported; () empty space signifies no standing water was reported (-) signifies no data were available.
Methodology for Estimating Nutrient Loadings from Wetlands
Since it is unclear how nutrient loads are to be calculated for redevelopment and post-
development loading analysis within the new Statewide Stormwater Treatment Rule, this
methodology is designed to be used for individual rainfall events. With some relatively broad
assumptions and the use of a Microsoft Excel� spread sheet model (Appendix C), daily rainfall
data can be used to determine annual discharge volumes. The methodology uses the USDA SCS
(1972) runoff equation:
Q = (P-0.2S)2 / (P + 0.8S) (Eq. 1)
S =(1000/CN) - 10 (Eq. 2)
Q = amount of runoff (inches),
P = precipitation (inches),
S = maximum potential retention (inches), and
CN = Curve Number (integer between 0 and 100).
Land Cover by Wetland Type
Florida land use and land cover have been classified through the Florida Land Use, Cover and
Forms Classification System (FLUCCS) developed by the Florida Department of Transportation
(FDOT 1999). For this project, wetlands were included with assigned FLUCCS codes 610
Wetland Hardwood Forests, 620 Wetland Coniferous Forests, 630 Wetland Forested Mixed, and
641 Freshwater Marshes (Table 9).
Table 9. Isolated wetland FLUCCS codes (FDOT 1999)
Wetlands Classification FLUCCS Codes
Depressional forested 610, 620, 630
Basin forested 610, 620, 630
Depressional emergent 641
Basin emergent 641
Suspected differences in background concentrations of nitrogen and phosphorus in Florida
wetlands necessitated classifying wetlands based on a simplified hydrogeomorphic classification
system (i.e. depressional or basin), dominant vegetation type (i.e. forested or emergent) and
further separated as non-impacted and impacted wetlands. Wetlands that were equal to or less
than approximately 2.5 hectare in size, often occurring in relatively small watersheds, were
classified as depressional wetlands. The water budget of depressional wetland has been
described as being dependent primarily on precipitation (Brinson 1993), making them
hydrologically isolated from surface water connectivity. Basin wetlands were described as
larger in size, characterized with a larger contributing watershed, and having a seasonal or semi-
permanent surface hydrologic connection to other wetlands or aquatic bodies. Non-impacted
wetlands were those in primarily natural setting, surrounded by natural lands and having no
obvious hydrologic alterations. Impacted wetlands were those wetlands having at least 25% of
their adjacent land area in agricultural or urban uses. Impacted wetlands were further divided
into those that were in landscapes with lowered water tables (i.e. dryer than normal) and those
that were receiving higher than normal runoff inputs (i.e. wetter than normal). Determination of
these hydrologic conditions required a degree of best scientific judgment, but we believe that it
was necessary to take into consideration the hydrologic alterations that occur in impacted
wetlands. In some cases, wetlands are drained that will require more rainfall to induce runoff,
while in other cases, where wetlands are receiving higher than normal runoff from adjacent
lands, smaller rainfall events are required to induce runoff.
Determination of Hydrologic Soil Groups
The Natural Resources Conservations Service's Soil Survey Geographic Data Base (SSURGO)
classifies wetland soils based on hydrologic soil groups (HSG) (USDA SCS 1972; USDA NRCS
2009). With soil groups running a gradient from Group A soils, with more than 90% sand or
gravel, having low runoff potential when thoroughly wet to Group D soils, with less than 50%
sand, having high runoff potential when thoroughly wet (NRCS 2009).
The average Curve Numbers (CN) for wetlands hydrologic soil groups were taken from a recent
study on pollution load reduction goals for the Newnans Lake watershed in north central Florida
(Di et al. 2009) (Table 10). The CNs for wetlands and other land uses were developed based on
average antecedent moisture conditions (AMC) II (Di et al. 2009). AMC II CNs reflect average
Table 10. Wetland Curve Numbers (CN) for soil hydrologic groups (Di et al. 2009)
Hydrologic Soil Group
A B C D
AMC II Wetland CNs 49 65 72 80
Antecedent Moisture Conditions (AMC)
Because of the variable hydrologic conditions in isolated wetlands driven by the large influence
of precipitation events and the natural inter-annual variability in wetland water levels, CNs must
be adjusted based on antecedent moisture conditions (AMC), a short-term adjustment factor for
the preceding 5-days rainfall, and seasonal adjustments, a longer-term adjustment factor
reflecting the dry or wet season water levels. AMC II CNs for wetlands are given above in
Table 10; however, NRCS (2009) recognizes three AMC classes: AMC I (drier than average
condition), AMC II (average condition), and AMC III (wetter than average condition) using
rainfall event and season.
Table 11 lists average dry and wet season water levels in non-impacted and impacted
depressional and basin wetlands in Florida. These water levels are derived from the Wetland
Hydrology Model simulation results (Appendix C). Using these data, reasonable water level
impacted depressional wetlands with a current dry season water level of 8 inches and a mean wet
season water level of 20 inches (Table 11), a dry-season rainfall event of greater than 12 inches
would be required to produce run-off from the given wetland.
Then, using data for event mean concentrations (Table 14), runoff volumes of TKN and TP can
be calculated when the wetland surface area is known. Values for event mean concentrations
reflect background nutrient concentrations for isolated wetlands as determined from the FIWND
database developed for this project. We propose that 75th percentile nutrient concentrations are
used for dry season calculations, reflecting higher nutrient concentrations in lower water
conditions. Further, the lower 25th percentile nutrient concentrations should be used to calculate
loading during the wet season, to reflect the more dilute nutrient conditions in times of higher
wetland water levels. Note that nitrogen nutrient concentrations are available for TKN, as
opposed to TN. TKN values should be lower than TN values for wetlands, as TKN measurement
does not account for nitrate (NO3-N) or nitrite (N02-N) in the water column. At this time, a
sufficient quantity of water column TN values was not available for estimating nutrient loading
from Florida isolated wetlands.
Table 14. Isolated wetland nutrient concentrations
Forested Forested Emergent Emergent
Wetland Type --�
Depressional Basin Depressional Basin
TKN (mg N/L)
Sample Size (n) 82 3 49 4
25th Percentile 1.085 0.620 1.123 0.960
Median 1.450 0.920 1.694 1.100
75th Percentile 2.000 0.980 2.200 1.608
TP (mg P/L)
Sample Size (n) 82 3 49 5
25th Percentile 0.027 0.009 0.016 0.009
Median 0.044 0.010 0.026 0.012
75th Percentile 0.085 0.010 0.041 0.047
TKN (mg N/L)
Sample Size (n) 126 7 16 6
25th Percentile 1.177 0.820 2.233 0.893
Median 1.600 0.980 2.956 1.100
75th Percentile 2.770 1.120 4.789 2.100
TP (mg P/L)
Sample Size (n) 150 7 117 7
25th Percentile 0.080 0.010 0.073 0.120
Median 0.186 0.010 0.250 0.130
75th Percentile 0.669 0.030 0.769 0.230
Sample Calculation for Estimating Wetland Loading
As a sample calculation, a non-impacted depressional emergent wetland has a surface area of 1
acre, soils classified within hydrologic soils Group D, and normal antecedent moisture
conditions (AMC II) during the wet season. If a rainfall event produced 3 inches of rain, what is
the estimated nutrient loading from the wetland runoff?
First, defining the variables, we see:
Q amount of runoff (inches) = (P - 0.2S)2 / (P + 0.8S) = (3 - (0.2*2.5))2 / (3 + (0.8*2.5)) =
P = amount of precipitation (inches) = 3 inches
CN (AMC II, Hydrologic soil Group D) = 80
S = maximum potential retention (inches) = (1000/CN) - 10 = (1000/80) - 10 = 2.5 inches
Unit conversions: 1 acre = 43,560 ft2
1 cubic meter = 35.315 cubic foot = 1000 liter
Applying the calculated amount of runoff of 1.25 inches of water over a surface area of 1 ac, the
volume of the wetland runoff is 128,486 liters. Using the 25th percentile values for TKN (1.085
mg N/L) and TP (0.027 mg P/L) concentrations (Table 14), the estimated load to the downstream
environment from the wetland runoff is 139.41 g N and 3.47 g P. Note that if the same 3 inch
rainfall event occurred in the dry season, runoff would not occur from this wetland unless the
current water level (at the time of calculation) in the wetland was within 3 inches or higher of the
mean wet season water level of 20 inches for non-impacted depressional wetlands.
DISCUSSION AND RECOMMENDATIONS
Because wetlands are not normally thought of as contributing nutrient loads in stormwater runoff
and as a consequence they are often left out of calculations or included as sinks for stormwaters
and nutrients, some explanation of this relatively complex approach to calculating runoff from
wetlands is in order. We consider several things in this discussion: types of wetlands that can
generate runoff, the assumptions necessary to generate runoff, and the effects of altered
hydroperiod and depths of inundation on runoff generation.
It is important to note that we have not included all types of wetlands in this review and
especially in the modeling methodology. Wetlands that are directly connected to water bodies
and that share surface waters, such as lake fringe and riverine floodplain swamps, are receiving
bodies, and therefore should not be considered contributors of stormwater or associated nutrients
to the adjacent open water. By eliminating lake fringe and riverine floodplain swamps from this
evaluation of stormwater contributions, we are left identifying the contributions from isolated
depressional and basin wetlands that are common throughout the low topographic relief areas of
the Florida landscape. We turn next to the assumptions necessary to include these wetlands as
generators of stormwater runoff and nutrients to receiving water bodies.
Isolated depressional and basin wetlands are typically considered nutrient sinks (e.g. Howard-
Williams 1985), since they are most frequently found in low areas of the landscape. When there
is surface runoff from upland areas, it usually finds its way to these wetlands, thus driving their
seasonally dynamic hydrology. Only after these wetlands reach their maximum storage capacity
does water runoff (from these wetlands) towards lower elevations. Thus, any methodology used
to predict stormwater runoff from isolated wetlands must take into account the storage function
of these wetlands. During the dry season much larger rainfall events are necessary before there
is wetland runoff, and in contrast, during the wet season much smaller events will generate
wetland runoff. Our methodology recognizes these facts and adjusts curve numbers (CNs) to
take into consideration these different hydrologic realities.
Not all wetlands are untouched by human activities. That is to say, the hydrologic characteristics
of landscapes can be altered by such things as groundwater pumping or ditching that results in
dryer than normal conditions in a particular wetland. By the same token, hydrologic alteration to
surrounding uplands that increases runoff or impounds water can cause wetter than normal
situations. In either case, the potential for runoff from a wetland is altered. In the first case,
dryer than normal conditions mean lower than normal water levels in the wetland and larger
rainfall events in both the dry and wet season to produce wetland runoff In the second case the
opposite is true. We have taken these potential conditions into consideration in this
methodology and have made allowances for their incorporation.
In all, we have addressed the main controlling factors that affect wetland stormwater runoff with
this methodology. It recognizes four different types of wetlands, in altered and unaltered
landscapes, and the different potential for runoff generation between Florida's wet and dry
In comparison to a recent study addressing pollutant loads in the hypereutrophic Newnan's Lake
watershed in north central Florida, Di et al. (2009) estimated mean nutrient loading from
wetlands and aquatic bodies of 1.680 mg/L TN and 0.173 mg/L TP from 1995-1998. Nutrient
concentrations for isolated wetlands throughout Florida in this project were similar for the 75th
percentile of non-impacted wetlands at 0.980-2.200 mg/L TKN (though note the different
nitrogen form and range for multiple wetland types) and lower for the 75th percentile of non-
impacted wetlands at 0.010-0.085 mg/L TP, and similar for the 75th percentile of impacted
wetlands at 1.120-4.789 mg/L TKN and 0.030-0.769 mg/L TP.
One of the key findings of this project is that there has been very little systematic collection of
water quality data for isolated wetlands in Florida. Much of the literature data were collected
during relatively short-term research studies focused on a small number of specific sites. This
site bias makes it quite uncertain as to whether the nutrient ranges reported accurately reflect the
distribution found in isolated wetlands throughout the state. Amplifying this uncertainty is the
fact that there is wide divergence in reporting conventions and sampling regimes among different
studies and wetland sites. For example, a number of studies only report the mean values and
standard deviations from a series of sampling events over time, while others have raw data
available. A similar problem is that several wetland sites have more than 50 data points sampled
over several years, while others only have data for one discrete sampling date. Such
idiosyncrasies make it inherently difficult to make robust and confident generalizations from the
given data. Differences in field collection and laboratory analytic methods among studies are a
final source of uncertainty that should also be noted. However, such data quality concerns likely
are minor, as most data come from highly reliable sources such as government reports, peer
reviewed literature, and doctoral dissertations.
While the comprehensive cataloguing of archival nutrient data from isolated wetlands is a step
forward in understanding the natural condition of these systems and evaluating their nutrient
treatment capacity, it is also quite clear that a more systematic sampling effort would greatly
benefit ongoing efforts to develop a Statewide Stormwater Treatment Rule and otherwise protect
One possible approach for reaching a broad range of isolated wetland systems across the state
would be to add a water chemistry sampling component to some percentage of wetlands that will
be evaluated through the US Environmental Protection Agency's National Wetland Condition
Assessment (NWCA) program scheduled to begin in 2011. The NWCA is developing a
probabilistic method for site selection, and it stands to reason that a random sub-selection of
these could be used for collection of water chemistry as a complement to the other site condition
assessments that will be performed. The NWCA is currently debating what parameters will be
included in sample design, and it is the understanding of the authors that to date it is likely soil
chemical and physical measures will be collected but water measures will not.
Another approach for acquiring more data for the isolated wetlands database would be to include
regular water chemistry sampling at wetlands in well-fields that are already being monitored for
hydrologic impacts from groundwater draw-downs. Because both the NWCA and well-field
monitoring programs are existing programs, start up costs to add water quality sampling as a
regular monitoring component should be minimal.
A final thought for future research priorities is that isolated wetlands in the panhandle region are
very under-studied in comparison to other regions of the state. Given the low population density
and large natural areas in much of the panhandle, the region seems ideal for targeted sampling of
reference isolated wetland types, particularly as development pressure increases. Additional
research of wetlands in the panhandle region would also have the benefit of making it clearer as
to how these systems are similar to, and in what ways they differ from, peninsular wetland types.
Such information will be invaluable for adaptive watershed management as development
pressure continues to increase in the panhandle region over the next decades.
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Appendix B - Collected Hydrographs for Florida Wetlands
Centiral Reioi DepreS~innal Forested Welland
99 19 '116 1 s, 344
Centiral Reg~ioni DeprxsioiuiI Herbaceo us "'edand
50 1S 24 -2P 1944M
Data from SWFWMD 1994-2003. Data from SWFWMD 1981-2003.
Figure B-1. Figure from Bardi et al. (2005), data compiled from the Southwest Florida Water
Management District (SWFWMD) from 1994-2003 for a reference standard central Florida
depressional herbaceous wetland (left) and 1981-2003 for a reference standard central Florida
depressional forested wetland (right).
- 5-dad D.-
29 -, 0_
Figure B-4. Figure 2 from Carr et al. (2006). Original caption reads: "Water surface elevation
(points and solid line) for median water surface elevation (dashed line) for cypress dome GI in
Lake County, Florida from May 1989 through April 1999. Mean monthly rainfall totals (bars)
for 55 stations in Pasco County, Florida are also shown."
40 - -0- Swamp + upland harvest
0 ha Harvest
1994 1995 1996
Figure B-5. Figure 3 from Casey and Ewel (1998). Original caption reads: "Monthly mean
standing water depth in three groups of cypress swamps. Before April 1994, none of the nine
swamps had been harvested. After May 1994, the nine swamps were divided into three
treatments: control, swamp harvest, and swamp+upland harvest with three swamps per
M A M J J A S O N D J F M A M J J A S 0
Figure B-6. Figure 3-1 from CH2MHILL (1987). 'Standard Elevation' line represents the elevation 0.33 m (1 ft) below the upland
elevation; it does not represent the soil surface. Original caption reads: "Hydrograph of 23 unditched study wetlands."
1 1 + +1 SE
0 S~O -1 SE
Figure B-7. Figure 3-2 from CH2MHILL (1987). 'Standard Elevation' line represents the elevation 0.33 m (1 ft) below the upland
elevation; it does not represent the soil surface. Original caption reads: "Average hydrograph of ditched versus unditched study
-5 + Study Weand 20
0 Study Wedand 22 , '
A Study Wetano 27
X Study Weland 2
-8- I-I- I - I II I I I I
F M A M J J A S 0 N D J F M A M J J A SO
Figure B-8. Figure 3-3 from CH2MHILL (1987). 'Standard Elevation' line represents the elevation 0.33 m (1 ft) below the upland
elevation; it does not represent the soil surface. Original caption reads: "Hydrograph of hydrologically altered study wetlands."
181 '82 '83 '84 '85 '86 '87 '88 '89 '90 '91
Figure B-9. Figure 3-2 from Clough (1992). Data represent yearly fluctuations for a wet prairie. Original caption reads: "Mean,
maximum, and minimum annual stage at Hopkins Prairie from 1981 to 1991 (data from St. Johns River Water Management District)."
M A M J J A S O N D J F M AM J
J A S O N D
Figure B-10. Figure 3-3 from Clough (1992). Data represent yearly fluctuations for a wet prairie. Original caption reads: "Mean,
monthly water level at Hopkins Prairie from March 1990 to December 1991."
A J 0 J A J 0 J A J 0 J J-0 J A J 0 J
1974 1975 1976 1977 978
Figure B-l 1. Figure 4-2 from Dierberg (1980). Original caption reads: "Monthly variations in
the depth of standing water at the center of Austin Cary cypress dome."
SAUSTIN CARY DOME
?4 1485( 1F I ^ A M J j A S 0 N D F MAM A S N
J 151.10 ,-7 -- -7-7
5 AUSTIN CARY DOME
148.60 F M A M J J A S 0 N 0 J F M A M A S 0 N
151.'!0 I-ITI i-II--- I1 I I I I I
AUSTIN CARY DOME
I 197 97
j F M A M J A S 0 N D JJ
Figure B-12. Figure 7-6 from Dierberg (1980). Original caption reads: "Water level fluctuations
in the surface waters of the center of Austin Cary natural dome from 1974 to 1979."
S-707 .. .... . . "I-r-- .--- - - , -
SSewage-e a r nturald dome
b0 197 174 1S 1976 977 1978 1979
JF JASONOJFMAMJJASONOJFMAMJJASONOJ FMAM J JASOND
Figure B-13. Figure 1 from Dierberg and Brezonik (1983). Austin Cary natural dome (top) is a reference standard wetland; Sewage-
enriched dome (bottom) is an impacted wetland. Original caption reads: "Water level fluctuations in the surface water at the centres
of Austin Cary natural (1974-1979) and sewage-enriched (1974-1977) domes. Data collected by K. Heimburg."
+2 - Hydroperiod (time of inundation)
Cypress Swamp (8 months) .i.
Marsh (6 months) - - -
Hydric Pine Flatwoods (2 months) ****....***
Water " - Ground Level .
(Meters) - . -
I I %I I t I I I I I
-2 - - .
O N D J F M A M J J A S
Figure B-14. Figure 7-6 from LWCWSP, summarized from Duever et al. (1986). Original
caption reads: "Hydrographs and hydroperiod ranges for three different south Florida vegetation
types (Duever et al., 1986)."
"0 I T5 r"L A "U. A G
2 100 d, 4!4h
A M J J A S O N D J F M
Figure B-15. Figure 5 from Ewel (1990). Original Caption reads: "Typical hydrographs
recorded in the centers of nine swamps in central Florida (Ewel and Wickenheiser 1988). Water
levels and depths of water above ground in each basin. Small swamps are less than 1 ha,
medium swamps are 1-2 ha, and large swamps are more than 5 ha." Taken from Ewel and
Wickenheiser (1988), caption: "Biweekly changes in water level (March 1982-March 1983) in
the nine study sites."
- 40 v memiauve
|20 -VV vv
ASONDJ FMAMJ JASONDJ FMAMJ JASONDJ FMAMJ
September 2000 - April 2003
Figure B-16. Figure 1 from Gathumbi et al. (2005). Original caption reads: "Mean monthly
water depth measured in improved pasture and seminative pasture wetlands (September 2000 to
May 2003) illustrating the seasonal fluctuation of both water depth and hydroperiod in these
wetland systems (modified from Steinman et al. 2003)."
I I I I I I I I I R I
-60 - -*- VERTICAL HEAD DIFFERENCE FOR BOGGY MARSH SOUTH TRANSECT (AVERAGE = 1.67 FEET)
-70 --*- VERTICAL HEAD DIFFERENCE FOR BOGGY MARSH EAST TRANSECT (AVERAGE = 1.49 FEET)
- -.- VERTICAL HEAD DIFFERENCE FOR BOGGY MARSH WEST TRANSECT (AVERAGE = 1.51 FEET)
-8 - VERTICAL HEAD DIFFERENCE FOR BOGGY MARSH (AVERAGE = 1.50 FEET)
-90 - --- BOGGY MARSH WATER-SURFACE ELEVATION
100 I I I I I I I I I I I I I - I
DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE
2001 2002 2003
Figure B-19. Figure 32 from Knowles et al. (2005). Original caption reads: "Potential for exchange (vertical) between ground water
and Boggy Marsh, Hilochee Wildlife Management Area."
l* * *
. - a',
', !- e l W/
I I I I I I I I
9. \ 0-
MAk APR. IAY JUNE JULY A 3. OC. NOV. DEC.
Figure B-20. Figure 3.1 from Mitsch (1984). Original caption reads: "Annual pattern of water
level, pH, phosphorus, and nitrogen in the Austin Cary cypress dome pond."
A. WATER LEVEL DEPTH
- - .-.- . . . _ . .. . . . . _ .. . . . .
I | I., I
J FA J AOD F J AODFA JAODFAJ AOD
1993 1994 1'995 1996
--m- K -- N --- C
Figure B-21. Figure 6A from Riekerk and Korhnak (2000). Original caption reads: "A)
Monthly wetland water-level depths." Three wetlands are depicted: K, N, and C.
- 40 --- II111P.ILUV\U
E v .... v semi-improved
7/1/00 11/1/00 3/1/01 7/1/01 11/1/01 3/1/02
Figure B-22. Figure 1 from Steinman et al. (2003). Original caption reads: "Mean water depth
in wetlands from improved and semi-native pastures revealing the seasonal nature of these
systems. Data presented in this paper correspond only to the July through October 2001 period."
I 3I I
.LL W andl
Figure B-23. Figure 1 from Sun et al. (2000). Original caption reads: "Daily water-level
dynamics in three cypress wetlands during 1992-1996; the arrow indicates harvesting treatment
I Rainfall -- Groundwater - Surface Water
I I I I 3.6
Figure B-24. Figure 3 from Wise et al. (2000). Original caption reads: "Long-term monitoring
data including study period."
Appendix C - Wetland Hydrology Model
Mark T. Brown
Department of Environmental Engineering Sciences and
Center for Wetlands
University of Florida
Gainesville, FL 32611
DESCRIPTION of the MODEL
Given in Figure C-1 is a systems diagram of the wetland hydrology model. For a complete
description of the symbols and resulting mathematics see Odum (1983). The systems diagram is
a method of writing differential equations since each symbol is rigorously defined with explicit
mathematical meaning. Differential equations are written directly from the diagram and
programmed as difference equations in EXCEL.
Storages of water include surface water, soil water (as the interstitial waters in organic soils of
the wetland), and groundwater. Inputs to surface water include rainfall (J2.1), runoff from
surrounding lands (called runin [J2.2]), and "exchange" with soil water (J4.1). Surface outflow
from the wetland (J4.2) occurs when surface water elevation exceeds the elevation of the
wetland's outer edge. Evapotranspiration (J3) includes evaporation from surface water (J3.2) and
transpiration (J3.1). Ground water exchange with soil water (J5.1) is driven by ground water
elevation, which results from exchange with ground waters outside the system boundary (J5.2).
Numbered pathways in the diagram refer to corresponding line items in Table 1.
The water balance equations for each water storage are as follows:
Surface water = J2.1+ J2.2 - J3.2 - J4.1 - J4.2 (1)
Soil water = J4.1 - J3.1 - J5.1 (2)
Ground water = +/- J5.1 (3)
Rainfall is programmed as daily events from any climate data set. Runoff from surrounding
lands depends on slope and conditions of the watershed, and is programmed by adjusting rate
coefficients. Water level within the wetland is controlled by inflows of rain and surface run-in ,
and outflows of transpiration (exchange with soil water), evaporation, and surface outflow.
Since vegetation is rooted in soils, and transpired water is "extracted" from the soil (not the
water column) a storage of soil water is included in the model. The amount of soil water is
controlled by input from surface water and outflows via transpiration and seepage. Infiltration to
surficial aquifer (ground water) is calculated as follows:
Igw = K*A*dH/dL (4)
A =Area of wetland
dL = 50 meters
Evapotranspiration is calculated using a Hargreaves model as follows:
ET= 0.0135(Ts + 17.78)Rs (5)
(585.5 - 0.55 Ts)
ET = Evapotranspiration (mm/day)
Ts = Mean Temperature (C 0)
Rs = incident solar radiation (MJ/m2/day or Langleys/m2/day)
A = coefficient (a = 10 when Rs is expressed as Lengleys/day, or a = 238.8 when Rs
is expressed as MJ/m2/day.
Surface outflow from the wetland occurs through a rectangular weir set at 0.5 meters above the
wetland bottom. The following equation is used to calculate the discharge when water level is
greater than 0.5 meters. (Q=1.21 LH15 )
Q = discharge in m3/day D
L = the length of weir in meters
H = head on the weir in meters
Table C-1 lists each of the pathways and storage within the wetland and the initial or
programmed values for each. From these data rate coefficients for each pathway in the model
Output from the model is displayed on the computer screen during each simulation run. The
output shows a yearly hydrograph and also a maximum water level plotted against a section view
through the wetland and adjacent upland.
Sensitivity analysis, calibration, and validation of the model was done using data from
previously studied wetland systems (see Odum and Ewel, 1974, 1975, 1976, 1978, 1980, 1986;
Heimburg and Wang, 1976 and Heimburg, 1986) and data collected from field measurements at
the Lake County site.
Sensitivity analysis was conducted by evaluating the effect on model output of varying input
parameters and flow pathway coefficients. Results obtained when parameters were increased
and decreased by as much as 100% from programmed values were compared with expected
model behavior (ie if an increase in a parameter should cause an increase in a flow or storage,
the resulting behavior was compared with the expected result).
The model was calibrated against a data set for a cypress wetland in north central Florida
(Heimberg and Wang, 1976). Total flows into and out of the simulated wetland were compared
to measured parameters in the cypress wetland. Predicted water levels that were generated by the
model were compared to measured water levels. In the absence of long term water level data for
the Lake County site, the elevations of lichen lines and cypress knees were used as indicators of
depth of inundation (Brown and Doherty, 2000).
Rate coefficients and input parameters were adjusted based on results of the sensitivity analysis
during calibration until a good fit between measured values for the cypress wetland and the
simulation model was obtained. Of primary concern was the total flows into and out of the
surface wetland (rainfall, runin, ET, and seepage). The goal of calibration was to obtain
simulation results for total flows within 5% of the measured values.
Water levels in the wetland were simulated for the base condition using actual precipitation for
an average rainfall year. The base condition was 0% impervious surface, 1% watershed slope,
four to one watershed to wetland ratio (4 hectares of watershed to 1 hectare of wetland),
watershed soil hydrologic group "C", wetland water depth of 0.53 meters (1.75 feet), and an
average rainfall year.
The model was then simulated for varying conditions and rainfall events to evaluate the area of
upland immediately adjacent to the wetland that would be inundated. First different storm
events were simulated during the rainy season by introducing a five, 10, 25, 50, and 100 year
storm event on the 190th day of the year. Second, the percent impervious surface was increased
in 10% increments to 50% to simulate development of the watershed.
Table C-1. Flows for Wetlands Model
Flow Name Description Footnote
Programmed daily from
Programmed daily from
Function of surrounding
Sum of evaporation and
Function of sunlight and
and net production of veg.
Function of sunlight and area
Programmed based on ET,
J4.2 Surface water Calculated output 8.
J5.1 Seepage Function of soil trasnmissivity 9.
and head of surface water
J5.2 Groundwater Programmed 10.
Footnotes to Table 1.
1. J1 - Sunlight. Average monthly solar radiation at Gainesville, Florida (Dohrenwend, 1978),
based on a 20-year record from 1955 to 1975. Daily solar radiation calculated by fitting a
sine function to average monthly radiation as follows:
Jan. - 8480 langleys
Feb. - 9945
Mar. - 13703
Apr. - 16307
May - 17404
Jun. - 15553
Jul. - 14999
Aug. - 15619
Sep. - 13305
Oct. - 12061
Nov. - 10009
Dec. - 8765
2. J2.1 - Rainfall. Rainfall directly on wetland area. Programmed daily from NOAA data.
3. J2.2 - Runin. Daily runin from surrounding watershed. Calculated from rainfall (NOAA
data), soil moisture conditions (programmed minimum event for runoff), percent
imperviousness, area of contributing watershed, and slope of watershed.
4. J3 - Evapotranspiration. Sum of Transpiration and Evaporation. Used measured
evapotranspiration values (Heimberg and Wang, 1976) for calibration as follows:
5. J3.1 - Transpiration. Transpiration of wetland calculated as average water use per
increment of net production normalized to fit a growth curve for the growing season based on
solar insolation. Water use was taken as 1775 g H20/g carbohydrate, average GPP is
between 5.6 and 7.9 gC/m2 day 1 (depending on wetland type), and 30 g H20 per 12 g
Carbon fixed (Brown, 1978).
6. J3.2- Evaporation. Evaporation determined as difference between measured values of
evapotranspiration (Heimberg and Wang, 1976) and calculated transpiration during the
growing season. Evaporation during the dormant season is and equal to daily measured ET.
7. J4.1 - Surface / soil water interchange. Calculated rate. When there is surface water in the
wetland, interchange equals sum of transpiration, and seepage. When there is no surface
water the rate is equal to transpiration
8. J4.2 - Surface outflow. Surface water outflow from wetland is programmed to occur when
water levels are greater than elevation of wetland edge. If there is no positive outfall, water
levels increase in surrounding upland landscape.
9. Js.1 - Seepage. Rate is a function of the height of water in wetland and height of
groundwater outside the wetland. Rate equation was simplified from an empirically derived
equation (Heimberg and Wang, 1976)
10. J5.2 - Groundwater exchange. Programmed rate constant based on transmissivity.
Generally the flow is considered groundwater recharge (ie waterflow is away from the
wetland). Wetland can be programmed to be experience groundwater discharge if
surrounding groundwater elevation is higher than water levels in the wetland.
J5.1 Gd. Water Flow
M.T. Brown 06/09
Figure C-1. Wetland Hydrology Model.
Appendix C Literature Cited
Brown, MT, RE Tighe, eds (1990) Development of Techniques and Guidelines for Reclamation
of Phosphate Mined Lands as Diverse Landscapes and Complete Hydrologic Units. Final
Report to Florida Institute of Phosphate Research. Gainesville, FL: Center for Wetlands,
University of Florida
Brown, SL (1978) A Comparison of Cypress Ecosystems in the Landscape of Florida. Ph.D
Dissertation. Gainesville, Florida: Center for Wetlands, Univ. FL. p. 570.
Dohrenwend, RE (1978) The Climate of Alachua County, Florida. Gainesville, Florida: Bulletin
796, I.F.A.S., University of Florida
Heimburg, K (1986) Hydrology of North Central Florida Cypress Domes. In HT Odum and KC
Ewel (eds) Cypress Swamps. University Presses of Florida, Gainesville FL. 472 pp.
Heimburg, K, F Wang (1976) Hydrological Budget Model. In HT Odum and KC Ewel (eds):
Cypress Wetlands for Water Management Recycling and Conservation (3rd annual
report). Gainesville, FL: Center for Wetlands, Univ. of FL. p. 68.
Odum, HT (1983) Systems Ecology. New York: McGraw Hill, p. 644.
Odum, HT, KC Ewel (1974) Cypress Wetlands for Water Management, Recycling and
Conservation. First Annual Report. Gainesville, Florida: Center for Wetlands, Univ. of
FL. p. 947.
Odum, HT, KC Ewel (1975) Cypress Wetlands for Water Management, Recycling and
Conservation. Second Annual Report. Gainesville, Florida: Center for Wetlands, Univ.
ofFL. p. 817.
Odum, HT, KC Ewel (1976) Cypress Wetlands for Water Management, Recycling and
Conservation. Third Annual Report. Gainesville, Florida: Center for Wetlands, Univ. of
FL. p. 879.
Odum, HT, KC Ewel (1978) Cypress Wetlands for Water Management, Recycling and
Conservation. Fourth Annual Report. Gainesville, Florida: Center for Wetlands, Univ. of
FL. p. 945.
Odum, HT, KC Ewel (1980) Cypress Wetlands for Water Management, Recycling and
Conservation. Fifth and Final Report. Gainesville, Florida: Center for Wetlands, Univ. of
FL. p. 284.
HT Odum KC Ewel, eds (1986) Cypress Swamps. University Presses of Florida, Gainesville
FL. 472 pp.
Summary of the Available Literature on Nutrient Concentrations
and Hydrology for Florida Isolated Wetlands
Prepared under DEP Contract WM942 and submitted to the Bureau of Watershed Restoration,
Florida Department of Environmental Protection, Tallahassee, Florida
Kelly Chinners Reiss, Jason Evans, Mark T. Brown
Howard T. Odum Center for Wetlands
Department of Environmental Engineering Sciences, University of Florida
100 Phelps Lab, Museum Rd. P.O. Box 116350
Gainesville, FL 32611-6350
3 September 2009
R I R I
R I R I
Figure 2. Water column nutrient concentrations: a) nitrate-nitrogen (N03-N) and b)
ammonia-nitrogen (NH3-N) for R (non-impacted or reference, no fill) or I
(impacted, gray fill); forested and emergent; depressional and basin wetlands.
Boxes represent the first through third quartiles; horizontal interior line represents
the median; vertical whiskers represent data range; asterisks represent outliers.
Extreme outliers are not shown due to scaling constraints.
R I R I R I R I
Forested Emergent Forested Emergent
Figure 3. Water column nutrient concentrations: a) Total Kjeldahl Nitrogen (TKN), and
b) total phosphorus (TP) for R (non-impacted or reference, no fill) or I (impacted,
gray fill); forested and emergent; depressional and basin wetlands. Boxes represent
the first through third quartiles; horizontal interior line represents the median;
vertical whiskers represent data range; asterisks represent outliers. Extreme
outliers are not shown due to scaling constraints.
ranges for isolated wetlands in the dry and wet season under AMC adjustment factors I-III are
determined based on the rainfall quantity (over a 5-day period) required to cause outflow from
the wetland during dry and wet seasons (Table 12). The variability in dry and wet season water
levels, antecedent weather conditions, and hydrologic soil unit influence the wetland adjusted
CNs (Table 13). The average depths of water in each of the wetland types given in Table 11 were
derived based on the simulation model given in Appendix C. Dry and wet initial conditions
were set for each simulation and then average water levels were calculated for wet and dry
seasons using an average rainfall year for north central Florida. To determine the rainfall
necessary to cause runoff during wet and dry seasons and thus AMC adjustment factors in Table
12, again the model was used. In this case, rainfall events were increased during a period of 5
days until runoff occurred in the dry and wet season. The values were rounded to the nearest
half inch. Rainfall amounts less than this value were equivalent to the AMC I events. AMC III
events were determined in much the same way except the event sizes were increased until nearly
all rainfall became runoff within the first 24 ours following the event. Rainfall events larger than
this number were considered AMC III events and those between AMC I and AMC III were
considered AMC II events. The adjustment factors in Table 13 are estimates based on best
Table 11. Dry and wet season water levels (inches) in isolated wetlands
Wetland Type Water Level - Dry Season Water Level - Wet Season
Depressional 6 20
Basin 10 24
Depressional 7 22
Basin 14 27
Table 12. Isolated wetland water level ranges by AMC adjustment factors for dry and wet
Dry Season (inches) Wet Season (inches)
Non-Impacted Depressional Wetlands
AMC I Less than 5 Less than 0.5
AMC II 5.0 to 10.0 0.5 to 1.0
AMC III Over 10.0 Over 1.0
Non-Impacted Basin Wetlands
AMC I Less than 1.5 Less than 0.1
AMC II 1.5 to 2.5 0.1 to 0.5
AMC III Over 2.5 Over 0.5
Impacted Depressional Wetlands (Dryer than normal)
AMC I Less than 7 Less than 1.0
AMC II 7.0 -12.0 1.0- 1.5
AMC III Over 12 Over 1.5
Impacted Basin Wetlands (Dryer than normal)
AMC I Less than 3.0 Less thanl.5
AMC II 3.0 to 5.0 1.5 -2.5
AMC III Over 5.0 Over 2.5
Impacted Depressional Wetlands (Wetter than normal)
AMC I Less than 3 - None -
AMC II 3.0 to 5.0 Less than 0.5
AMC III Over 5.0 Over 0.5
Impacted Basin Wetlands (Wetter than normal)
AMC I Less than 1.0 - None -
AMC II 1.0 -2.0 Less than 0.1
AMC III Over 2.0 Over 0.1
Table 13. Adjusted wetland Curve Numbers (CNs)
AMC I AMC II AMC III
Hydrologic Soil Group CN CN CN
A 32 49 60
B 45 65 75
C 52 72 81
D 63 80 88
Calculation of Discharge Volumes
Using equations 1 and 2 above, the runoff volume for a rainfall event can be calculated using the
adjusted wetland CNs (Table 13). During the dry season, we propose that runoff will only occur
if the rainfall event is greater than the difference between the wetland water level and the mean
wet-season water level for depressional and basin wetlands (Table 11). For example, for a non-
v v semi-native
Measurement date (m/d/yy)
Figure B-2. Figure 1 from Bohlen and Gathumbi (2007). Original caption reads: "Average
water depth and hydroperiod in wetlands in improved (solid line) and semi-native (dotted line)
pastures from July 2000 through March 2002."
0.50 DOME Z . -
t,- /BERMED DOME
D / I
< [ /-PASTURE DOME
O. 25 .... , ..... / / . - ,-
JAN FE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
,-FLOODPLAIN FOREST /
', e,/, SCRUB CYPRESS /
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Figure B-3. Figure 2 from Brown (1981). The Large Dome in (a) is considered a reference
standard depressional forested wetland. Small Dome 1 and Small Dome 2 in (a) and Sewage
Dome, Bermed Dome, and Pasture Dome in (b) are impacted depressional forested wetlands.
Original caption reads: "The annual fluctuation of surface water levels. Records are from
December 1976 to December 1977 for the scrub cypress forest (Flohrscutz 1978) and from
January 1976 to January 1977 for the other sites. Data for Sewage Dome and Large Dome were
obtained from K. Heimburg (personal communication)."
RAINFALL= 14.10 INCHES -
(SEPT. - DEC. 2001)
- TROPICAL STORM
RAINFALL = 89.78 INCHES
WETLAND EVAPORATION = 58.5
ES W RAINFALL = 16.95 INCHES - -
8 INCHES WETLAND EVAPORATION = 24.21 INCHES
(JAN, 1 - JUNE 11, 2003)
F BOGGY MARSH
FLOOD-RELIEF DRAIN OPEN
I A~~ ~ &AAA..
S----'- "---~-- *� � - FREEZE-PROTECTION
I I I 11 1 " I li I I I I I
SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT, NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE
2001 2002 2003
Figure B-17. Figure 19 from Knowles et al. (2005). Original caption reads: "Daily water levels, cumulative rainfall, and cumulative
wetland evaporation for the Boggy Marsh site, Hilochee Wildlife Management Area (station numbers refer to figure 5 and table 1)."
WETLAND-PERIMETER WELL (STATION 12)
--- BOGGY MARSH (STATION 4)
- MID-RIDGE WELL (STATION14)
RIDGE WELL (STATION 16)
-- UPPER FLORIDAN AQUIFER WELL (STATION 17)
- DAILY CUMULATIVE RAINFALL (STATIONS 18 AND 19)
- DAILY CUMULATIVE WETLAND EVAPORATION
. 32 1 l 1 1 1 1 l lll l l l l 140
S31 - RAFALL=2INCHES RAINFALL = 90.56 INCHES -___
LL 30 - (SEPT - DEC. 2001 WETLAND EVAPORATION =58,97 INCHES 130
29 - (2t002
- 120 0
a 28 - WETLAND PERIMETER WELL (STATION 34) 2_ Q
0 27 - -LARGE WETLAND (STATION 35) RAINFALL= 23.71 INCHES - 110>
> 26 - MID-RIDGE WELL (STATION 41) WETLAND EVAPORATION = 25.65 INCHES _ W
25 RIDGE WELL (STATION 48) (JAN.1 - JUNE 11, 2003) - 100
S24 --- LOWER SURFICIAL AQUIFER SYSTEM WELL (STATION 62) -
(ESTIMATE OF UPPER FLORIDAN AQUIFER WATER LEVEL) STORMWATER APPLICATIONS - 90
23 - UPPER FLORIDAN AQUIFER WELL STATION 63) ONTO ---ADJACENT --
< 22 - DAILY CUMULATIVE RAINFALL (STATIONS 57 AND 58) TO PROPERTY - 80
21 - DAILY CUMULATIVE WETLAND EVAPORATION STATION 59) I - 7 0
20- , 70<0
18 - GABRIELLE -, . E- -- - AA - 60
WETLAND PERIMETER WELL A
17 - STATION 34-
S16- BECAME SUBMERGED --
3 15 - _ , -40O
..14 - -
W 13- - 30O
- 10 , -- 10
S 9 -- " ESTIMATED -
8 I I I I I I I I INj I I I I I I I 0 O
SEPT. OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT OCT. NOV DEC JAN. FEB. MAR. APR. MAY JUNE
2001 2002 2003
Figure B-18. Figure 20 from Knowles et al. (2005). Original caption reads: "Daily water levels, cumulative rainfall, and cumulative
wetland evaporation for the large wetland, Lyonia Preserve (station numbers refer to figure 6 and table 1)."