JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
DECEMBER
AMERICAN WATER RESOURCES ASSOCIATION
2004
WATER QUALITY CHARACTERISTICS OF STORM WATER
FROM MAJOR LAND USES IN SOUTH FLORIDA1
Gregory A. Graves, Yongshan Wan, and Dana L. Fike2
ABSTRACT: Starting in 1998, a study was conducted to characterize storm water quality from predominant land use types in a
coastal watershed along the south central coast of Florida, namely
citrus, pasture, urban, natural wetland, row crop, dairy, and golf
courses. Sixty-three sampling sites were located at strategic points
on drainage conveyances for each of seven specific land use areas.
Runoff samples were collected following storm events that met
defined rainfall criteria for a period of 30 months. Nitrogen (N),
phosphorus (P), heavy metals, pesticides, and other water quality
parameters were determined, and the results were analyzed to
compare and characterize land uses as relative sources for these
constituents in runoff. Results showed that runoff from most land
use types had low dissolved oxygen concentration and that sediment and nutrient concentrations were closely related to land use,
particularly to the amount of fertilizer applied in each land use.
Among the eight heavy metals tested, copper was the most frequently detected and was mostly associated with runoff from citrus
and golf course land uses. High levels of arsenic were also detected
in golf course runoff. The most frequently detected pesticide was
simazine from citrus. The information and methodologies presented
may facilitate pollution source characterization and ecological
restoration efforts.
(KEY TERMS: nonpoint source pollution; water quality; nutrients;
heavy metals; pesticides; St. Lucie Estuary.)
Graves, Gregory A., Yongshan Wan, and Dana L. Fike, 2004. Water Quality
Characteristics of Storm Water From Major Land Uses in South Florida. Journal
of the American Water Resources Association (JAWRA) 40(6):1405-1419.
INTRODUCTION
Land use and management have been shown to
influence the quality and quantity of storm water
runoff, which in turn affects nonpoint source pollution
at both regional and national scales (e.g., Osborne
and Wiley, 1988; Dauer et al., 2000). This problem is
particularly pronounced in coastal states, where more
than 60 percent of the coastal rivers, estuaries, and
bays are moderately to severely degraded by pollution
from urban and agricultural storm runoff and other
sources (National Research Council, 2000). In addition to the input of nutrients and suspended matter to
coastal water bodies from storm water runoff, heavy
metals and pesticides may exacerbate water quality
problems. Many of these contaminants are extremely
toxic to marine organisms and, at elevated concentrations, can adversely affect the structure and function
of biotic communities (Pait et al., 1992; Kennish,
1999).
The Indian River Lagoon (IRL) on the southeast
coast of Florida (Figure 1) has been considered one of
the most biologically diverse ecosystems in North
America (Swain et al., 1995). The St. Lucie Estuary
(SLE) is the largest tributary to the southern IRL and
was a freshwater body until the St. Lucie Inlet was
constructed the late 1800s. The health of these estuaries depends partly on the quantity, quality, timing,
and distribution of storm water runoff. Historically,
the area supported extensive areas of ridges, sloughs,
pine flatwoods, upland scrub, wetland flats, cypress
ponds, and savannas. Drainage of these areas was
afforded by wetland-to-wetland flow into two major
meandering streams and percolation into ground
water. Waters thus entered the estuary relatively
slowly and contained few nutrients.
Over the past 100 years, land use and drainage
patterns in the watersheds have undergone substantial changes as a result of the construction of a
1Paper No. 03194 of the Journal of the American Water Resources Association (JAWRA) (Copyright © 2004). Discussions are open until
June 1, 2005.
2Respectively, Environmental Manager, Florida Department of Environmental Protection, 1801 S.E. Hillmoor Drive, Suite C-204, Port St.
Lucie, Florida 34952; Senior Supervising Engineer, South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, Florida 33406; and Environmental Specialist, Florida Department of Environmental Protection, 1801 S.E. Hillmoor Drive, Suite C-204, Port St.
Lucie, Florida 34952 (E-Mail/Graves: [email protected]).
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Figure 1. Study Area Watershed.
ing increase in loads of nutrients and other pollutants
(USACE and SFWMD, 2001). Major stresses to the
system include frequent low dissolved oxygen events
and light limitation due to turbidity from resuspension of fine-grain sediments and high level of humic
substances from freshwater inflows (Chamberlain and
Hayward, 1996). Nutrient concentrations in the SLE
have been consistently high in recent years (Chamberlain and Hayward, 1996; Doering, 1996). Sediments in the SLE have been shown to contain heavy
metals at levels potentially harmful to fish and benthic macroinvertebrate communities (Haunert, 1988;
MacDonald et al., 1996; Thompson et al., 2001). Water
column monitoring of the SLE has detected pesticides
and copper in concentrations that periodically exceed
Florida’s water quality criteria (Graves and Strom,
1995; Graves et al., 2002). The impacts of these
changes on the SLE ecosystem have been dramatic.
Excess concentrations of nutrients (especially N and
P) relative to undisturbed or natural conditions and
network of primary, secondary, and tertiary canals.
The large primary South Florida Water Management
District (SFWMD) canals C-44 (completed in 1924
and enlarged to its current size in 1949) and C-23,
C-24, and C-25 canals (completed circa 1961) were
constructed by the U.S. Army Corps of Engineers
(USACE) under the auspices of the original Central
and South Florida Project (Figure 1). These canals
drained many historic wetlands, lowered ground
water tables, and allowed widespread agricultural
and urban development of the watershed. Because
most soils in the watershed (flatwoods soils, mainly
Alfisols and Spodozols) are sandy and have low water
and nutrient holding capacities, frequent applications
of fertilizers and pesticides as well as management
operations to affect rapid drainage are ubiquitous
practices on managed agricultural and urban lands.
An unanticipated result of canal construction was an
approximately eightfold increase in the quantity of
storm water delivered to the coast, with a correspondJAWRA
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WATER QUALITY CHARACTERISTICS OF STORM WATER FROM MAJOR LAND USES IN SOUTH FLORIDA
exacerbated by human activities foster progressive
organic enrichment, eventually leading to accelerated
phytoplankton production and biomass accumulation
that in turn are followed by changes in food webs
(Kennish, 1999; Livingston, 2001). Algal blooms have
occurred in the SLE during recent years when runoff
volume is high. In addition, increased accumulation of
unconsolidated, contaminated sediments in SLE has
nearly eliminated the oyster and seagrass beds
(Chamberlain and Hayward, 1996; Doering, 1996).
To address these issues, the Florida Legislature
designated the SLE as a Surface Water Improvement
and Management (SWIM) priority water body, requiring that a pollutant load reduction goal be established
for the SLE. This effort is continued through the current SLE/IRL ecosystem restoration plan undertaken
by the SFWMD and the USACE through the Comprehensive Everglades Restoration Plan (USACE and
SFWMD, 2001). This restoration plan aims to
reestablish an appropriate salinity regime and
improve water quality conditions in the estuary
through construction of large regional reservoirs and
storm water treatment areas (STAs), as well as rehydration of large tracts of former wetlands. It is the
intention that the ecological improvements afforded
by these large scale efforts will be complemented by
effective agricultural and urban best management
practice (BMP) programs to fully meet designated
uses of the SLE as determined by Florida Department
of Environmental Protection (FDEP) rule.
The major objective of this study was to conduct a
systematic analysis of water quality of storm event
runoff emanating from major land use types in the
watershed to support the SWIM program and water
quality evaluations in the SLE/IRL ecosystem
restoration plan. Another goal of this study was to
ascribe problem pollutants, especially pesticides and
heavy metals that are toxic to estuarine biota, to specific sources in the watershed. The collected data were
also useful for SFWMD’s ongoing watershed water
quality model development effort (Wan et al., 2003), in
which water quality prediction is based primarily on
the land use types and associated management practices. The model, in turn, will be employed to evaluate
watershed management, BMPs, and restoration alternatives.
Basins 4, 5, and 6 (Figure 1). Drainage is afforded by
an interconnected web of ditches and tertiary, secondary, and large primary canals. This system not
only affords flood protection through rapid transport
of rain water through the drainage network but also
has acted to lower ground water levels, which has
made otherwise untenable land available for urban
and agricultural expansion.
Land use in the watershed is predominantly citrus
agriculture, cattle pasture, urban, and isolated wetland, accounting for about 25, 23, 16, and 13 percent
of the total land area, respectively. The remaining
land is mostly forest, other agricultural lands such as
row crops and plant nurseries, rangelands, transportation, and water. About 74 percent of urban land
is developed for residential use. Most soils in the
watershed are characterized by a shallow hardpan
that acts as a confining layer for flow, which can
increase lateral movement of pollutants to adjacent
surface drainage canals. Annual rainfall in the area
averages about 1,300 mm, of which about 20 to 40
percent becomes storm water runoff depending on
land use types. Due to high ground water tables and
the sandy nature of the soils, most runoff is delivered
through the canal network as subsurface or returned
flows. During the dry season, water in major canals
including the C-23, C-24, and C-44 is retained for
regional water supply purposes unless the canal stage
reaches a critical level for discharge during a storm
event. Baseflow in natural streams including the
North Fork and South Fork of the St. Lucie River is
low due to the flat terrain in the area. These two natural rivers are tidally influenced and provide a valuable nursery site of oligohaline biota.
Agricultural irrigation is typically accomplished by
direct withdrawal from the ubiquitous nearby primary or secondary canals. When large volumes of surface
water are being utilized, tertiary drainage canals and
ditches may become water supply conduits such that
flow direction is reversed by active pumping. During
the dry season, agricultural areas that do not have
access to reservoirs may instead depend on ground
water for irrigation. Urban areas rely almost entirely
on ground water sources.
MATERIALS AND METHODS
DESCRIPTION OF STUDY AREA
Identification of Land Use and Sampling Sites
The 2,200 square kilometer IRL/SLE watershed is
relatively flat, rising from sea level at the coast to less
than 25 meters inland. The watershed draining to the
St. Lucie Estuary consists of nine drainage basins:
North Fork, South Fork, C-24, C-23, C-44, S-153, and
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Sample collection sites were selected such that the
upstream land use reflected a single land use type.
Site location was initially identified using SFWMD’s
1995 geographical information system (GIS) base land
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use data shape file. Maps detailing specific citrus irrigation types were provided by the U.S. Department of
Agriculture (USDA) and were used to locate sampling
sites in citrus grove areas with four different irrigation methods (USDA, 1993). Land use of all sampling
sites gleaned from maps was subsequently ground
truthed. No sites were located on primary canals, and
to the extent possible, sites on secondary canals were
avoided. Although desirable, it was not possible to
locate a sufficient number of sampling sites that did
not intrude on private property. Access to some sites
was made possible by written agreements between
landowners and FDEP that stipulated the owners’
anonymity, while access to others required obtaining
court ordered inspection warrants pursuant to Sections 403.091 and 403.858 of the Florida Administrative Code (FAC). Accordingly, in respect of the
interests of the landowners involved, the exact location of sampling sites is withheld.
A total of 63 sampling sites were identified, representing the major land use types in the watershed
(Table 1). Drainage areas ranged from 0.04 (ornamental nursery) to 45.5 km2 (pastureland). Because most
of the managed lands have drainage canals in the
watershed, it was possible to select all sampling sites
(although difficult as indicated by logging more than
2,700 km of travel to identify and verify such sites)
such that the storm water being sampled was representative of a single land use. The 24 citrus sites represented four irrigation types, namely one overhead
irrigated, five drip irrigated, nine flood irrigated, and
eight jet irrigated groves. Currently, citrus irrigation
in the watersheds is in the process of converting traditional flood irrigation into drip irrigation. The
urban sites had five in residential areas and three in
commercial and industrial areas. Although classified
as an urban land use, eight sites in a separate set
were located to characterize golf course runoff due to
its perceived unique fertilization and irrigation needs.
Four row crop and one dairy site also were located
(there was only one dairy in the basin). Three sites
were located to characterize runoff from “residual”
application where sewage sludge had been applied as
a supplemental fertilizer; however, these were in differing land use categories (a pasture, a sod farm, and
a sugarcane field).
Sampling and Analytical Protocol
The ideal sampling protocol would be to install
autosamplers at each of the sampling sites, but the
cost involved would be prohibitive. As a feasible alternative, grab samples were collected in accordance
with the storm water sampling guidelines proposed
by Timpe et al. (1996). These guidelines required collection of samples within 24 hours following a “qualified rain event,” defined as one preceded by at least
72 hours of no rain and in which the amount of rain
in inches was between the 25th and 75th percentile of
historic rainfall amounts for the basin. Thirty-one
years of rainfall data at rain gages located throughout
the study area were examined, and the rainfall criteria were determined to be a rain event that delivered
between 18 and 38 mm of rain in a widespread pattern across most of the basin. Rainfall events that
affected only a small portion of the study area were
not sampled. Multiple analytes required the use of
multiple sample containers (one set of these containers was filled at each sampling site following each
qualifying rain event). The total sampling period lasted for 30 months, from January 1998 through July
2000.
Samples were only collected from sites where water
was visually determined to be flowing, and only when
that direction of flow was indicative of runoff (e.g., not
when reversed flow due to irrigation pumping was
encountered). During such an event, water temperature, dissolved oxygen (DO) concentration, pH, and
conductivity were measured on site in the field. New,
TABLE 1. Land Use Acreage, Percentage of Land Use Within the
Watershed, and Number of Sampling Sites Per Land Use.
Land Use Category
Area in the
Watersheds (ha)
Citrus
Pasture
Urban – General
Urban – Golf Course
Wetland
Row crops
Dairy
Residuals (sludge disposal/application sites)
49,655
46,576
31,943
1,274
26,176
4,437
0,557
4,359
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Percentage of Total
Watershed Area
25
23
16
0.6
13
2.2
0.3
2.1
Number of
Sample Site
24
11
8
8
4
4
1
3
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WATER QUALITY CHARACTERISTICS OF STORM WATER FROM MAJOR LAND USES IN SOUTH FLORIDA
unused sampling containers were used to collect
water for pesticides and heavy metal analyses. Sterile
single-service Whirlpak® bags were used to collect
samples for fecal coliform bacteriological analysis. All
other containers were washed with 1:3 diluted
hydrochloric acid and then thoroughly rinsed with
deionized water. All sample bottles were prelabeled,
and sets of bottles for each site were sealed in individual labeled plastic bags under controlled laboratory
conditions. All necessary sample bottles, paperwork,
and field equipment were assembled and organized
ahead of time to facilitate rapid deployment during
the typically adverse conditions associated with rain
event sampling.
For each site sampled, new disposable latex gloves
were worn to handle sample collection and preservation. During sampling, the sampling bottle was
removed individually from the plastic bags and
immersed unopened in the flowing water. Canals
were relatively small enough that with adequate flow
they were considered well mixed. The cap was then
removed and the bottle filled, with the mouth of the
bottle submerged below the surface of the water and
oriented into the flow of water. Where hand filling
was impractical, a “bottle on a stick” apparatus was
used in a similar fashion to ensure sample integrity.
New containers for fecal coliform, metals, and pesticide analyses were filled without rinsing. Reused acid
cleaned containers were rinsed twice with storm
water prior to filling. Samples for nutrient analyses
were preserved by the addition of 0.5 mL concentrated sulfuric acid per 250 mL sample. Samples for
metal analysis were preserved by the addition of 2 mL
of trace metal grade concentrated nitric acid directly
from the reagent container into the sample bottle to
preclude potential contamination. Deionized water
blanks were prepared and analyzed for each sampling
event and for each set of analytes to check for contamination and preservative purity.
Samples collected for pesticide analysis were analyzed for organochlorine pesticides as detected by gas
chromatograph/electron capture detector (FDEP Standard Operating Procedure GC-011-5 based on USEPA
Method 608, 617, and 1656) and organonitrogen
and phosphorus pesticides as detected by gas chromatograph/nitrogen-phosphorus detector (FDEP
Standard Operating Procedure GC-012-3 based on
USEPA Methods 614, 619, 622, 633, and 507). Pesticide detection limits employed were as low as practical and appropriate to the study. Samples collected for
metal analysis were analyzed for total arsenic (As),
cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb),
manganese (Mn), nickel (Ni), and zinc (Zn). Samples
collected for nutrient analysis were analyzed for total
phosphorus (TP), total nitrogen (TN), organic N, inorganic N, ammonia (NH3-N), and nitrate plus nitrite
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
(NO 2+3 -N). Other parameters analyzed included
five-day biological oxygen demand (BOD5), color, turbidity, total suspended solids (TSS), and hardness. All
analyses were performed using standard, approved
analytical techniques (FDEP, 1992; APHA, 1998). All
analytical runs included analysis of spikes and duplicates at a frequency of 10 percent. Pesticide and
metal analyses were performed at the FDEP Central
Laboratory in Tallahassee. All other analyses were
performed at FDEP’s Southeast District Laboratory in
Port St. Lucie. Both laboratories are certified by the
State of Florida and have rigorous quality assurance
programs.
Statistical Analysis
The criterion of significance for all tests was p ≤
0.05. Differences among groups were identified using
the nonparametric Kruskal-Wallis test. Practical significance of pairwise differences was determined by
evaluating confidence intervals from Fisher’s least
significant difference procedure applied to ranked
data. Correlations were examined using Spearman’s
rank correlation procedure. Comparisons between citrus and other categories are based on the complete set
of citrus data collected. Statistical analyses of differences among citrus irrigation types were performed
on a subset of data not including data from the single
overhead irrigation land use type. All references to
values within the body of the manuscript refer to values computed from raw data.
RESULTS AND DISCUSSION
Dissolved Oxygen
Frequent low dissolved oxygen conditions as a consequence of runoff events from the watershed are one
of the major stresses to the SLE system (Chamberlain
and Hayward, 1996). Figure 2 depicts DO concentration in storm water from major land use types. Due to
the limited number of samples taken from the dairy
site, dairy data are not shown in this figure. For each
land use, DO concentrations ranged from less than 2
to about 10 mg L-1, with about 70 percent of the samples below 5.0 mg L -1, the Florida State Class III
water quality standard. The mean DO concentration
of wetland runoff was higher than from other land
use types and statistically higher than all but row
crop. The higher DO concentration in wetland runoff
may be related partly to wind driven mixing in open
wetland, while runoff from other land use types was
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and oxygen production may be interspersed with collapse and oxygen consumption not only on a diel basis
but also longer term as conditions may shift from
favorable to unfavorable (e.g., periodic flow induced
turbidity cutting off light penetration). In addition,
low DO concentration in runoff may also be affected
by canal morphology, which may inhibit wind induced
mixing; low ratio of surface area to cross sectional
area, which may hinder reaeration of the water column; and sediment oxygen demand from decomposing
vegetative matter.
directly collected in tertiary canals where wind action
would have less influence. In addition, submerged
aquatic vegetation in a wetland releases oxygen during photosynthesis processes and thereby increases
DO in the water column. The dissolved oxygen
concentration from citrus, golf, and pasture was significantly lower than row crop or urban land uses.
Figure 2. Whisker Box Plot of DO Concentration in Storm Water
From Major Land Use Types. Mean and median concentrations
are shown as solid and dotted lines, respectively, within the
box. The number of samples is 105 for citrus, 27 golf course,
47 pasture, 112 urban, 40 wetland, and 18 residual.
Figure 3. BOD5 Distribution of 176 Storm Water Samples,
Including 56 from Citrus, 8 Dairy, 26 Golf Course, 27 Pasture,
12 Residual, 13 Row Crop, 30 Urban, and 17 Wetland.
There were no significant differences for BOD 5
among land use types (p = 0.12). Variations in DO
concentrations in runoff among the major land use
types could not be explained by correlation with BOD5
(p = 0.21), which suggests that factors other than
BOD influenced DO in water. In general, BOD5 was
low, with 80 percent less than 3 mg L-1, indicating
that materials being washed off from the land during
significant rain events are to a great extent refractory
and not amenable to further oxidation (Figure 3).
Since the difference between means was around 1 mg
L-1, on the order of analytical reproducibility, analysis
for BOD was discontinued in the latter part of the
study to reduce costs. Statistical analyses conducted
to determine correlation between DO concentration
and the various factors measured, including time of
sample collection, indicated that water temperature,
water color, TP, and TN were significantly correlated
(all p < 0.01). This suggests that the storm water with
low DO concentrations might be partly due to mixing
with warmer water (which has a lower dissolved oxygen saturation point) that remained stagnant in the
canal prior to the rainfall event and partly due to
enhanced primary productivity due to elevated nutrient concentrations. Presumably, periods of growth
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Sediment, Turbidity, and Color
Turbidity and TSS were significantly correlated
with concentrations of all nutrient species, all heavy
metals, and, of the nine pesticides detected, simazine.
Figure 4 shows plots of color, turbidity, and TSS of
runoff from major land use types, and significant differences among land uses for turbidity are presented
in Figure 5. Because water turbidity is directly caused
by the presence of suspended matter, such as clay,
silt, or plankton, the overall patterns of turbidity and
TSS concentrations in runoff from the land use types
were similar. The data were mostly skewed, with
some extremely high events driving the means much
higher than the medians. Wetland runoff was significantly less turbid (mean = 4.1 NTU) than all other
land use types and contained less sediment (mean
TSS = 3.4 mg L-1) than runoff from citrus, golf, and
row crop land use types, reflecting the filtering effect
of wetland vegetation (Kadlec and Knight, 1996).
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Urban runoff had the second lowest turbidity (mean =
5.3 NTU) and TSS concentration (mean TSS = 5.1 mg
L-1), likely due to the fact that most of the urban samples were residential, with suspended sediment
trapped and stabilized by lawns and vegetated
swales. Turbidity and TSS concentration in residual
runoff was similar to those in urban runoff. Total suspended solids and turbidity in urban and residential
runoff were statistically lower than that measured in
runoff from citrus, golf, pasture, and row crop land
uses. No significant differences were detected for
mean TSS concentration in runoff among citrus, pasture, golf course, and row crop land uses. However,
turbidity in samples of runoff from row crop was significantly higher than citrus and residual, albeit citrus and row crop both have furrows in the field. Row
crop runoff had the highest mean turbidity (16.2
NTU) and TSS concentration (16.4 mg L-1). This was
likely a result of furrows between row crop planting
mounds typically left unvegetated, while furrows
between citrus tree rows are vegetated, at least in
those groves using BMPs (Boman et al., 2000).
Color in runoff from pasture, residual, and wetland
runoff was significantly higher than citrus and urban
land uses, although not significantly different from
golf or row crop. In general, mean water color of pasture and wetland runoff was the highest (227 and 235
Pt-Co units, respectively) followed by residual runoff
(173 Pt-Co units). Water flowing through typically
dense wetland vegetation or slowly over grasses within pasture and residual land uses would presumably
leach more humic and tannic acids and thus produce
more color compared to more rapid runoff from other
land use types or where grasses were more heavily
managed (i.e., golf course). Among the subcategories
of citrus, flood irrigated groves had higher water color
than groves that employed jet irrigation. Regression
analyses of the data indicated that change in TSS
concentration in storm water runoff explains about 65
percent of the variation in turbidity (f = 621.4, p <
0.001) but only 7 percent of variation in color (f =
24.7, p < 0.001) (Figure 6). This suggests that runoff
color in the watershed was mostly induced by the
amount of dissolved humus and peat (from vegetative
decay) in water, while water turbidity was directly
caused by the presence of suspended matter such as
clay, silt, or plankton.
concentrations in dairy runoff and those of all others
were extremely large, typically an order of magnitude
or greater. Dairy farms have been identified as
sources of large loads of nutrients in South Florida
(Ray and Zhang, 2001).
Figure 4. Whisker Box Plots of Color, Turbidity, and TSS
Concentration of Storm Water from Major Land Use
Types. Mean and median concentrations are shown as
solid and dotted lines, respectively, within the box.
The number of samples is 127 from Citrus,
52 Pasture, 27 Golf Course, 20 Row Crop,
107 Urban, 20 Residual, and 30 Wetland.
Nutrients
On average, organic N comprises 70 to 95 percent
of the total N. Except for row crop runoff, nitrate and
nitrite are present in relatively low concentrations
and constitute around half or less of the total inorganic N concentration. Inorganic nitrogen constitutes
about 5 percent of the total nitrogen in storm water
The mean and median concentration of N and P are
summarized in Table 2. The results of pairwised
comparisons are shown in Figure 5. Boxplots of nutrient data are presented in Figure 7. Among all the
land use types, the differences between N and P
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Figure 5. Significant Differences of Nutrient Concentrations in Runoff From Select Land Use Categories.
Columns are compared against rows, where a “+” denotes column significantly greater than row,
and “-” denotes column significantly less than row. Blanks indicate difference not significant.
from wetland, while runoff from pasture and urban
contains about twice that amount (means of 10 percent and 11 percent, respectively). However, the fraction of inorganic nitrogen comprising the total
nitrogen concentration from citrus, golf, and residual
land uses was around 18 percent, while the mean
fraction from row crop was 29 percent. This indicates
that an increasing scale exists among land uses based
on their propensity to release nitrogen in its most soluble, readily assimilated form. This in turn has implications for receiving waters when those are estuaries,
as the latter are typically N-limited systems (Kennish, 1999).
Among all land use types, wetland runoff had the
lowest concentrations in TP and inorganic N, indicating the nutrient assimilation capacity of a wetland.
The TN concentration in wetland runoff was not the
lowest in runoff from the different land uses, primarily due to plant detritus contributing to dissolved
organic N in wetland storm water. The high organic N
concentration in wetland runoff also was consistent
with the fact that wetland storm water treatment
areas in South Florida have lower removal efficiencies
for TN than for TP (SFWMD and FDEP, 2004). The
low inorganic N concentration in wetland runoff was
due to the near absence of nitrate-nitrite N relative
to ammonia N. The low nitrate-nitrite N concentrations result from processes conducive to denitrification in wetlands (Hammer and Bastian, 1989)
whereby nitrate is directly and rapidly denitrified
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while ammonia must first undergo oxidation as a precursor to denitrification. This lends credence to the
idea that in those instances where constructed wetlands may be employed for nitrogen removal, conditions amenable to facilitating oxidation of nitrogen to
the nitrate form are desirable. The nutrient cycling
inherent to wetlands characterizes the water quality
advantages that may be obtained by restoring degraded wetlands or constructing wetlands for water quality treatment.
Total phosphorus concentrations in urban runoff
was less than any other land use except wetland,
which was statistically less. Total nitrogen in urban
runoff was less than any other except wetland and
residual, which were not statistically different (Figure
5). Figure 8 shows the distribution of TN and TP concentrations in runoff from citrus, pasture, and urban
lands that have the highest acreage in the watershed
and thus contribute most of the storm water runoff
entering the estuaries. The majority of samples from
urban land had concentrations that were less than
half that observed in citrus and pasture. The lower
concentrations were probably due to the fact that 100
out of 116 of the urban samples were collected in residential areas, where grassed swales may enhance
nutrient removal as documented and recommended
by Livingston et al. (1988).
Differences in TN and TP concentrations in runoff
from pasture and citrus (which together constitute
nearly half the acreage within the study area) were
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not significantly different. However, differences were
significant between these two land uses when inorganic and organic N fractions were examined (Figure
5). The ratio of inorganic N to TN concentration in
pasture runoff was significantly lower than that from
citrus, and the ratio of organic N was significantly
higher. These differences in inorganic N and organic
N in runoff from citrus and pasture were presumably
a result of the type of fertilization used on these land
uses. High levels of chemical fertilization are applied
to citrus (in one typical formulation, the inorganic N
accounts for 89 percent of the total N applied), while
the nitrogen source in pasture is mainly from cattle
wastes in which about 99.9 percent of the nitrogen is
in the organic form (del Rosario et al., 2002). The recommended fertilization rates for citrus are 134 to 224
kg N ha-1 y-1 and about 60 kg P-1 ha-1 y-1, respectively
(Tucker et al., 1995). Nitrogen and P removal via harvested produce is much less than what was applied,
and about 50 percent of applied N and P fertilizers
are subject to potential runoff losses (Lorenz and
Maynard, 1980). The application and high rates of fertilizer loss probably account for the relatively high
inorganic N concentrations in citrus runoff.
Among the four irrigation methods of citrus land
use, there were no significant differences in concentrations of inorganic N, NH 3-N, and NO 3+NO 3-N.
Mean organic N concentrations in runoff from flood
irrigated citrus (1.5 mg L-1) were, however, significantly greater than those where drip or jet irrigation
methods were employed (0.9 and 1.0 mg L-1, respectively). This resulted in equivalent differences among
irrigation types for TN. These differences in organic N
and TN may be attributed to the hydraulics of the
irrigation methods. Drip and jet irrigation involve
slow release of water in contrast to flood irrigation, in
which water is frequently being “turned over” within
the internal ditch and canal systems and can suspend
plant detritus (containing organic N) that is commonly deposited at the bottom of canals in South Florida.
Similarly, the mean TP concentration in runoff from
the flood irrigated grove (0.48 mg L-1) was substantially greater than in runoff from drip irrigated and
jet irrigated sites (i.e., 0.21 and 0.29 mg L-1, respectively). A statistically significant difference was present only between flood and the drip irrigated sites.
The influence of fertilization on runoff N and P concentrations was also apparent for other land uses
(Table 2 and Figures 5 and 7). Total phosphorus concentration in runoff from row crop land use was significantly higher than other land uses. Total nitrogen
concentrations in runoff from golf were significantly
higher than any land use other than row crop (differences between golf and row crop were not significant).
This to some degree reflects heavy fertilization
required for row crops and golf courses. Typically,
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
vegetables in South Florida are double cropped with
per crop N and P applications in excess of 224 kg N
ha-1 and 74 kg P ha-1 (448 kg N ha-1 y-1 and 148 kg P
ha-1 y-1), respectively. Fertilizer recommendations for
potting foliage plants range from 1,000 to 2,700 kg
ha-1 y-1 for N and 150 to 410 kg ha-1 y-1 for P depending on the species grown (Joiner et al., 1981). For
Florida turf grasses, a yearly fertilization program
usually includes a combination of one or two applications of multiple nutrient fertilization and several
supplemental applications of N (e.g., use of fertilizer
formulations such as 38-0-0 urea formaldehyde),
totaling about 200 to 250 kg N ha -1 y -1 (Sartain,
2000). Total phosphorous concentration in golf course
runoff was mid-range, similar to that in runoff from
residual and pastureland land uses. Phosphorus fertilization rates in the study area are much less than
N application rates and are not always required.
Application of effective best management practices for
nutrient management can reduce loading from these
highly fertilized lands.
Figure 6. Regression of Water Turbidity and Color With
TSS Concentration of Storm Water Samples.
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GRAVES, WAN, AND FIKE
TABLE 2. Mean and Median Nutrient Concentrations in Storm Water
Runoff From Eight Land Use Types Sampled in the Study Area.
Land Use
No. of
Samples
Citrus
Pasture
Urban
Golf Course
Wetland
Row crop
Residual
Dairy
127
53
115
28
30
20
21
8
Total P
(mg L-1)
Mean Median
Total N
(mg L-1)
Mean Median
0.29
0.29
0.22
0.24
0.02
0.63
0.26
12.54
1.37
1.46
1.07
1.62
1.18
1.88
1.09
38.9
0.16
0.22
0.09
0.19
0.01
0.45
0.20
8.86
Organic N
(mg L-1)
Mean Median
1.23
1.09
0.82
1.51
0.94
1.31
0.87
24.6
1.11
1.32
0.92
1.27
1.10
1.14
0.87
9.98
1.05
0.94
0.72
1.22
0.99
0.97
0.81
7.39
Inorganic N
(mg L-1)
Mean Median
NH3-N
(mg L-1)
Mean Median
0.26
0.15
0.13
0.32
0.14
0.77
0.21
28.9
0.13
0.11
0.06
0.20
0.14
0.20
0.09
28.5
0.13
0.08
0.05
0.22
0.02
0.33
0.14
11.5
0.06
0.06
0.03
0.10
0.02
0.04
0.05
11.0
NOx-N
(mg L-1)
Mean Median
0.14
0.03
0.07
0.12
0.00
0.57
0.11
0.39
0.04
0.01
0.01
0.07
0.00
0.27
0.05
0.03
Figure 7. Box Plots of Nutrient Data for
Selected Land Uses. Concentrations
are natural logarithms.
Heavy Metals
highest concentrations of As were also found in samples taken from golf course runoff. The high As concentrations in golf course runoff was likely an
indication of the use of herbicides containing As compounds on some golf courses in the study area (Ma et
al., 2000). Arsenic was detected in some runoff samples from other land use types including urban and
row crop, but most of these were below 10 mg L-1.
Haunert (1988) and Thompson et al. (2001) indicated
that As concentrations were above threshold effects
levels (TELs in MacDonald et al., 1996) in 94 percent
The storm water heavy metal concentrations from
different land use types (Table 3) were compared with
Florida’s water quality standards for heavy metals in
freshwater (Rule 62-302.530, FAC). Only As and Cu of
the eight heavy metals tested were detected above
the applicable standards. Only one golf course runoff sample was found to contain a concentration
above the As standard (50 mg L-1); however, the nine
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JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
WATER QUALITY CHARACTERISTICS OF STORM WATER FROM MAJOR LAND USES IN SOUTH FLORIDA
and 14 percent, respectively, of the SLE sediment
samples analyzed.
Copper was at detectable concentrations in most of
the samples analyzed during this study. Nine golf
course samples, 5 citrus samples, and 1 row crop sample contained Cu above Florida’s hardness based
water quality standard. These elevated Cu concentrations are believed to be related to the wide use of several forms of Cu as fungicides for Florida citrus
(Butler et al., 1998b; Aerts and Nesheim, 2000) and
tomatoes (Butler et al., 1998a) and direct application
of copper sulfate as an algicide or herbicide in golf
courses to control algae or weed growth in lakes and
ponds (Eisler, 1997). Monitoring studies of SLE sediments by Haunert (1988) and Thompson et al. (2001)
found concentrations of copper to be above threshold
effects levels (TELs in MacDonald et al., 1996) in 90
percent and 93 percent, respectively, of the samples
analyzed. The Florida estuarine/marine Cu criterion
is set at 2.9 mg L-1. From 1995 through 2002 FDEP
collected 89 samples from SLE, 42 of which (47 percent) exceeded this criterion (FDEP, 2003). This 1995
through 2002 study by FDEP resulted in the SLE
being identified as a “verified impaired” water body
under Florida’s Impaired Water Rule (Rule 62-303,
FAC), requiring the segments of the estuary so identified for total maximum daily load (TMDL) development to abate copper loss to the environment.
The concentration of Zn in two samples exceeded
Florida’s water quality standard and were both associated with row crop, where zinc containing preplant
supplements may be employed to stimulate cell formation and shoot growth. The concentration of Pb
exceeded Florida’s standard in one sample from urban
Figure 8. TN and TP Concentration Distribution of Storm Water
Runoff From Citrus, Pasture, and Urban Lands.
TABLE 3. Heavy Metal Analysis Results Summarizing 196 Water Samples Including 99 from Citrus,
34 Urban, 22 Row Crop, 21 Golf Course, 17 Pasture, 10 Residual, and 2 Wetland Land Uses.
Maximum
Concentration
Detected
(mg L-1)
No. of
Samples
Exceeding
the Florida
Criteria
Heavy
Metal
Detection
Limit
(mg L-1)
No. of
Samples
Detected
Florida
Fresh Water
Criteria
(mg L-1)
As
Mn
Cd
Cr
Cu
3.00
0.25
0.30
1.00
2.00
024
196
001
008
141
50
1003
25 to 400
66.5 to 644
3.62 to 38.66
72.1
865.0
0.44
6.6
77.4
01
NA
None
None
15
Pb
Ni
Zn
2.00
2.00
1.80
004
075
052
0.545 to 18.6
48.8 to 509.4
32.7 to 343.1
7.1
18.2
119.0
01
None
02
Land Use
Above
Florida
Criteria
Golf Course
NA
None
None
Golf Course, Citrus,
Row Crop
Urban
None
Row Crop
Other
Detected
Land Use
Urban
All
Pasture
Urban, Citrus
Urban
Citrus, Row Crop
Citrus, Row Crop, Urban
Citrus, Urban
Notes:
1. Except for As and Mn, numerical standards for heavy metals are based on an exponential relationship between hardness (e.g., Cdmax =
e(0.7852[lnH]-3.49), where H is hardness in mg L-1). Maximum and minimum hardness values for computing allowable metal concentrations
are specified in rule (FAC 62-302.530), namely 25 and 400 mg L-1 calcium/magnesium hardness, respectively. Ranges provided for allowable concentrations reflect these limits on hardness.
2. Standard for Mn is for drinking water, which is not applicable to surface water samples.
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
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Herbicide
Simazine
*Ratings are based on Pait et al. (1992) except for Bromacil, Metalaxyl, and Ethion of which the ratings were estimated from Cornell University (1993) and USEPA (1998).
53
12
44
1
0.05
Moderate
Weak
Herbicide
Bromacil
Very low
Insecticide
Insecticide
Insecticide
Insecticide
Insecticide
Fungicide
Herbicide
Chlorpyrifos ethyl
Diazinon
Endosulfan
Ethion
Malathion
Metalaxyl
Atrazine
Very low
Weak
Moderate
0.3
1,400
22
0
63
Citrus
Urban
Row Crop
Citrus
Citrus
Citrus
Citrus, Urban,
and Golf Course
Citrus and
Row Crop
Citrus, Row Crop
Golf Course,
Pasture
0.98
0.12
0.086
0.068 to 2.7
0.82
1.3
0.85
1
1
1
4
1
0
0
1
1
2
4
1
1
22
0.00175
0.01
0.056
0.003
0.1
299
2
0.1
0.1
0.01
0.05
0.15
0.6
0.05
Moderate
Moderate
Low
High
Low
Moderate
Moderate
Very Strong
Strong
Very strong
Very strong
Moderate
Weak
Weak
Pesticide
Type
Pesticide
High
Moderate
Extremely high
Very high
Low
Low
Very Low
No. of
Samples
Maximum
No. of
Exceeding Concentration
Samples the Florida
Detected
Detected*
Criteria
(mg L-1)
Florida
Chronic
Toxicity
Standard
(mg L-1)
Rating in
Detection
Persistence
Limit in
in Aquatic
Water
Environment (mg L-1)
Rating in
Affinity to
Soil or
Sediment
Pesticide monitoring results are summarized in
Table 4. Detected pesticides included five insecticides
(chlorpyrifos ethyl, diazinon, endosulfan, ethion, and
malathion), three herbicides (atrazine, bromacil, and
simazine), and one fungicide (metalaxyl). Concentrations were evaluated using FDEP’s Class III pesticides criteria established based on one-twentieth of
the concentration “lethal to 50 percent of the test
organisms in 96-hours … for a species significant to
the indigenous aquatic community” (Rule 62-302.200,
FAC). However, some sampling sites from “secondary
and tertiary canals wholly within agricultural areas”
and as otherwise defined in Rule 62-302.400(12)(a),
FAC, may be classified as Class IV waters, where
numeric pesticide criteria are not applicable.
Of the nine pesticides detected, six were measured
at concentrations above their corresponding Class III
State criteria, namely chlorpyrifos, diazinon, endosulfan, ethion, malathion, and simazine. Chlorpyrifos (as
chlorpyrifos ethyl) was detected in a citrus sample at
a concentration of 0.98 mg L-1, 560 times higher than
the state criterion of 0.00175 mg L-1. Chlorpyrifos is
one of the most widely used insecticides in South
Rating in
Toxicity to
Estuarine
Biota*
Pesticides
TABLE 4. Pesticide Analysis Results Summarizing 79 Runoff Samples of Which 39 Were From Citrus, 13 Urban, 11 Golf Course,
8 Row Crop, 4 Residual, 3 Pasture, and 1 Wetland Land Uses. Florida chronic toxicity standard is provided for comparison.
land use, presumably an artifact of the use of leaded
fuels and the prevalence of roadways in urban areas.
Manganese was detected in all samples. As a result of
the low toxicity of Mn in aquatic environments Florida does not have a standard for Mn in surface water;
Florida’s criterion of 100 mg L-1 Mn is applicable only
for drinking water sources. Row crop runoff had a
mean Mn concentration an order of magnitude higher
than runoff from other land use types, with the highest levels observed up to 865 mg L-1. The highest Mn
concentration observed for nonrow crop land use was
102 mg L-1 from citrus. This may reflect the heavy
fertilizations required, as Mn supplements may be
indicated for crops grown on the alkaline soils common in South Florida. Manganese in runoff may also
be an artifact of naturally occurring Mn in soil, since
Mn concentration, like the other heavy metals analyzed, was correlated to TSS and turbidity, and the
general crustal abundance of Mn is on the order of
950 mg kg-1. No concentration of Ni, Cr, or Cd exceeded Florida’s standards. Nickel was detected in samples from citrus, row crop, and urban land uses;
potential Ni sources include fertilizers, which may
contain Ni as an essential nutrient additive (Eisler,
1997). Chromium was detected in water samples from
urban and citrus areas; sources of chromium include
wear of machinery and contaminants in fertilizer.
Cadmium was only detected in one sample from a
pasture area.
Land Use
Detected
GRAVES, WAN, AND FIKE
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
WATER QUALITY CHARACTERISTICS OF STORM WATER FROM MAJOR LAND USES IN SOUTH FLORIDA
Florida (Miles and Pfeuffer, 1997) and is primarily
used in urban areas and golf courses, although this
detection was found in citrus runoff. Endosulfan was
detected twice in row crop runoff at concentrations of
0.029 and 0.086 mg/L (the latter value exceeded the
State criterion of 0.056 mg L-1). This insecticide has
been applied solely for vegetables in South Florida
and has become a pollutant of concern in Florida Bay
(Scott et al., 2002). Ethion, used primarily in citrus,
was detected four times in citrus runoff. The detected
concentrations ranged from 0.068 to 2.7 mg L-1, all of
which exceeded the State criterion of 0.003 mg L-1.
Because ethion is highly toxic to aquatic organisms, is
prone to runoff, and possesses a relatively long halflife, the U.S. Environmental Protection Agency
(USEPA, 2002) recently issued an order canceling the
registration of ethion for use in the watershed. The
State criteria of chlorpyrifos and ethion are much
lower than the detection limits of this study, implying
that some of the undetected samples might also contain these compounds in concentrations above the criteria. Diazinon, moderately toxic to estuarine biota,
was detected in a residential runoff sample at 0.12 mg
L-1, exceeding Florida’s criterion of 0.01 mg L-1. This
pesticide is commonly applied to urban residential
lawns and has been detected in urban areas of other
states (e.g., Crawford, 2001). Malathion was detected
in a citrus runoff sample at a concentration level (0.82
mg L-1) more than eight times Florida’s malathion criterion of 0.1 mg L-1.
The most frequently detected pesticides in this
study were three herbicides – atrazine, simazine, and
bromacil – as was previously documented by Miles
and Pfeuffer (1997) during their study of pesticides in
the primary canals of South Florida. Atrazine was at
detectable concentrations in 22 of the 79 samples collected, with the highest observed concentration (0.85
mg L-1) from urban land use. Atrazine was not detected in pasture, row crop, or wetland runoff samples.
No samples exceeded the calculated (2 mg L-1) Florida
atrazine criterion. Bromacil was also detected in 22
samples but only in row crop and citrus runoff. No
samples exceeded the calculated bromacil water criterion (1,400 mg L-1). Simazine was detected in 44 samples, including all 39 samples of citrus runoff, and
12 of these were above the calculated criterion (1.0 mg
L-1). Four of the row crop samples, one golf course
sample, and one pasture sample also contained
detectable concentrations of simazine. Simazine was
the only pesticide whose concentration correlated
with TSS and turbidity, and it has been routinely
detected in the SLE, at concentrations as high as 0.98
mg L-1 (FDEP, 1999). The fungicide metalaxyl was
detected in only one citrus runoff sample at a concentration of 1.3 mg L-1, below Florida’s calculated criterion of 299 mg L-1. The presence of a mixture of these
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
pesticides in the primary tributaries has resulted in
at least one well documented large fish kill (Graves
and Strom, 1995).
SUMMARY AND CONCLUSIONS
This study examined storm water quality from
dominant land use types in the St. Lucie Estuary
watershed. Runoff samples were collected from lands
used for citrus, pasture, urban, natural wetland, row
crops, and golf courses following storm events that
met defined rainfall criteria for a period of 30 months
starting in January 1998. Storm water runoff from
most land use types had low DO concentration, with
the means ranging from about 3 to 6 mg L-1. The low
DO concentration in runoff appeared not related to
oxygen demands contained within the water but
rather may be caused by some combination of canal
morphology, sediment demand, high water temperature, and instream processes exacerbated by high
nutrient loads. Water color was high (over 200) in
runoff from land with dense vegetations such as wetland and pasture where humic and tannic acids are
readily available to be washed off during a rainfall
event. Water color was not correlated with turbidity.
Sediment and nutrient concentrations were closely
related to land use or land management. Except for
the sole dairy farm monitored in this study, row crop
runoff had the highest N, P, and TSS concentrations
due to the significant amount of fertilizers applied
and frequent irrigation and drainage needed. Nutrient and sediment concentrations in citrus runoff were
also high, and flood irrigation method typically resulted in higher nutrient and sediment concentrations
than other irrigation methods. With the high runoff
rate associated with flood irrigation in citrus and vast
citrus acreage in the watershed, the conversion of
flood irrigation into micro jet method and the ongoing
BMP program (Boman et al., 2000) are the start of a
nutrient and sediment loading reduction effort. The
water leaving urban/residential land, except for golf
courses, was intermediary in quality, being somewhat
better than water from agricultural land use but
worse than wetlands. Nutrient and TSS concentrations in golf course runoff were higher than runoff
from other urban land uses and were similar to those
from some agricultural land uses. In wetlands, almost
all of the readily bioavailable inorganic N was in the
reduced ammonia form, an indication of the ability of
wetlands to remove nitrate N through assimilation
and denitrification. This has clear implications in
designing treatment wetlands or other areas where
the aim is to minimize threats to estuarine resources:
areas should be provided within the treatment
1417
JAWRA
GRAVES, WAN, AND FIKE
scenario to facilitate nitrification of runoff prior to its
passage through vegetated wetland areas.
Among the eight heavy metals tested, Cu was
detected widely and 15 samples contained levels
exceeding the Florida freshwater standard. Due to its
toxicity to estuarine environments, abatement of the
discharge of Cu is recommended. The land use
exhibiting the highest potential for release of Cu in
storm water was golf course, followed by citrus and
row crop. High levels of As were also detected in golf
course runoff, and one exceeded the Florida freshwater standard. Existing BMPs for these land use types
should be reviewed and potentially amended to
address these problems, which can result in long term
environmental harm. Use restrictions for Cu and As
in this and similar watersheds may be advisable.
Other metal releases were associated with various
land use types, but concentrations were relatively low.
The most frequently detected pesticide was
simazine (44 out of 79 samples), including all 39 citrus runoff samples, of which 12 were at concentrations above the calculated Florida pesticide criterion
(1.0 mg L-1). A few detections of chlorpyrifos (once in
citrus runoff), endosulfan (twice in row crop runoff),
ethion (four times in citrus runoff), and diazinon (once
in urban runoff) were found at concentrations toxic to
estuarine biota. These few high insecticide concentration detections were likely the result of misuse,
overuse, or bad timing (having mistakenly applied the
chemical only to have it wash away in a subsequent
heavy storm). Growers and golf course caretakers in
the basin should carefully adhere to BMP guidelines
and pesticide labeling requirements. New BMPs may
also need to be developed, especially for golf courses
in light of the significant number of golf courses currently in place within the study area and the likely
increase as the watersheds are further developed.
Since all of the nutrient species, the heavy metals,
and the most commonly detected pesticide, simazine,
were correlated with turbidity and TSS, efforts directed toward better reducing losses of suspended matter
during storms may yield valuable environmental benefits.
LITERATURE CITED
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Department, Cooperative Extension Service, Institute of Food
and Agricultural Sciences, Gainesville, Florida.
APHA (American Public Health Association), 1998. Standard
Methods for the Examination of Water and Wastewater (20th
Edition). American Public Health Association, Washington, D.C.
Boman, B., C. Wilson, and J. Hebb (Editors), 2000. Water Quality/Quantity BMPs for Indian River Area Citrus Groves. University of Florida, Institute of Food and Agriculture, Indian River
Research and Education Center, Fort Pierce, Florida.
Butler, A.G. Hornsby, W.M. Stall, F.A. Johnson, J.W. Noling, and
T.A. Kucharek, 1998a. Managing Pesticides for Tomato Production and Water Quality Production. Circular 1010, University of
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Butler, A.G. Hornsby, D.P. Tucker, J.L. Knapp, and J.W. Noling,
1998b. Managing Pesticides for Citrus Production and Water
Quality Protection. Circular 974, University of Florida Soil and
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Institute of Food and Agricultural Sciences, Gainesville, Florida.
Chamberlain, R. and D. Hayward, 1996. Evaluation of Water Quality and Monitoring in the St. Lucie Estuary, Florida. Water
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ACKNOWLEDGMENTS
The authors would like to recognize Tom White, FDEP
Southeast District Laboratory Manager, who performed all of the
nutrient analyses for this study single-handedly; and Bruce Peery,
Doug Strom, and Jeff Christian, who braved downpour and lightning to make this work possible.
JAWRA
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WATER QUALITY CHARACTERISTICS OF STORM WATER FROM MAJOR LAND USES IN SOUTH FLORIDA
Graves, G.A., M.A. Thompson, and D. Fike, 2002. St. Lucie River
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