WATER QUALITY IN BIG CYPRESS NATIONAL PRESERVE AND 

EVERGLADES NATIONAL PARK, 1960-2000

Water quality varies spatially across the region because of natural variations in geology, 

hydrology, and vegetation and because of differences in water management and land use. 

Although water quality in Big Cypress National Preserve and Everglades National Park is 

generally good, major physical alteration of the landscape and associated watermanagement practices in the watershed have altered its quality.

INTRODUCTION

The extreme southern tip of the Florida Peninsula is an 

extensive subtropical wetland that includes the Everglades, 

the Big Cypress Swamp, and the coastal mangrove forests. 

The Everglades is a wide, flat expanse of grasslands and 

tree islands that historically served as the primary drainage 

path for runoff from water overflowing the southern bank 

of Lake Okeechobee as well as from direct rainfall. The Big 

Cypress Swamp to the west of the Everglades is characterized by cypress domes, elongated bands of cypress trees 

(strands), and meandering marshy areas (sloughs). Water in 

both the Everglades and the Big Cypress Swamp, drains 

south and southwest toward Florida Bay and the Gulf of 

Mexico.

Major physical alteration of the landscape and associated water-management practices, including canal and 

levee construction, agriculture and residential development, 

as well as operation of pumps and flood gates in the 1900s, 

have altered the volume, timing, distribution, and quality of 

surface water in this system. Everglades National Park 

(EVER, established in 1947) and the Big Cypress National 

Preserve (BICY, established 1974) were both created by 

Congress to preserve and protect large areas of the south 

Florida ecosystem that had remained relatively intact and 

free of agricultural and urban development. Because they 

are located at the downgradient end of the altered system, 

however, both areas are subject to effects of upstream 

water-management practices. Waters in BICY and EVER 

are currently designated by the State of Florida as Outstanding Florida Waters and Outstanding Natural Resource 

Waters, respectively, and therefore must be monitored and 

protected.

Water-quality analyses and studies have been conducted in EVER for more than four decades, with studies 

increasing in number and scope in recent years. The most 

extensive water-quality database is maintained by the South 

Florida Water Management District (SFWMD). Waterquality data collection and studies in BICY are less numerous, but extend back to the early 1970s when the proposed 

Big Cypress “Jetport” triggered a flurry of environmental 

investigations.

The National Park Service (NPS) maintains hydrologic 

monitoring stations to measure water levels (stage) and 

water quality in BICY and EVER (fig. 1)

Everglades

National

Park

Gulf of Mexico

Florida Bay

0 5 MILES

Everglades

Agricultural Area

L28N

Miami Canal

New River

Canal

Interceptor

Canal

L28

North

West

Feeder

Feeder

A12

S190

S140 A1 A2

A3

A13

A14

A4

P37

TSB

P35

P34

P36

P33

A9

A B

AB C D

A5

S344

S343

S12s S333

S332

Taylor

Slough

Shark

River

Slough

EP

L67 Ext

L28

L67 A

Barron River Canal

L67 C

75

A5

C-111

S332

L28

STATION Location

and number

CONTROL

STRUCTURE

Location and number

LEVY Location

and number

−

−

−

EXPLANATION

Alligator Alley

Ponce de

Leon Bay

Whitewater

Bay

40 Mile

Bend

Tamiami Trail 41

BR105

(A6)

Monroe

Turner

River

NP201 NE1

S177

S18C

Big Cypress

National Preserve

L31

Water Conservation Area 3A

US41

LOCATION OF

STUDY AREA

Florida

Figure 1. Big Cypress National Preserve and Everglades 

National Park with major features and sampling sites.

. Data collected at 
these stations provide a historical baseline (beginning as 

early as 1959) for assessing hydrologic conditions and 

making a wide range of management decisions. In this current study, we assessed selected water-quality data collected between 1959 and 2000 at these stations and at 

nearby canal sites to define baseline conditions and to identify long-term trends.

METHODS AND APPROACH

• Data used in this study were primarily from the SFWMD, 

the U.S. Geological Survey (USGS) and the NPS. Concentrations of pesticides and other toxic organics in water 

and sediment were determined at selected sites in BICY 

and EVER, using data collected at various intervals.

• For trend analysis, we focused on specific conductance, 

chloride, sulfate, total phosphorus, and total nitrogen from 

sites having the longest periods of water-quality record.

• For trend analysis, we used the USGS computerized statistical program, S-ESTREND, including the uncensored 

seasonal Kendall test for specific conductance, chloride, 

and total nitrogen, and the Tobit regression test for sulfate 

and total phosphorus (which have numerous “less-than” 

values).

• For evaluation of spatial patterns of selected constituents, 

we plotted median concentrations at sites for a 10-year 

baseline period (1991-2000).

RESULTS AND DISCUSSION

Seasonal changes in water levels and flows in the 

BICY and EVER affect water quality. As water levels and 

flows decline during the dry season, physical, geochemical, 

and biological processes increase the breakdown of organic 

materials and the build-up of organic waste, nutrients, and 

other constituents in the remaining surface water. For 

example, during much of the year, concentrations of total 

phosphorus in the marsh usually are less than 0.01 milligrams per liter (mg/L). During the dry season, however, 

concentrations sometimes rise briefly above this value and 

occasionally, under drought conditions, exceed 0.1 mg/L 

(fig. 2). 

DETECTIONS ( ) LESS-THAN

VALUES ( )

GAGE HEIGHT

1

3

4

5

6

7

8

GAGE HEIGHT, IN FEET

2

TOTAL PHOSPHPHORUS,

IN MILLIGRAMS PER LITER 0.1

1972

YEARS

1975 1980 1985 1990 1995 2000 0

0.2

0.3

0.4

0.5

0.7

0.6

P-33

Figure 2. Concentrations of total phosphorus, in milligrams per 

liter, and water level at station P-33, 1959-2000.

Water quality in BICY and EVER 

is affected by long-term changes 

in water levels, flows, water 

management, and upstream land 

Long-term changes in water levels, flows, water 

management, and upstream land use can affect water 

quality in the BICY and EVER, based on analysis of 

available data (1959-2000). Specific conductance and 

concentrations of chloride increased in Taylor Slough and 

Shark River Slough in the 1980s and early 1990s. For 

example, chloride concentrations more than doubled at 

both sites from 1960 to 1990 (fig. 3), primarily due to canal 

transport of high dissolved-solids water into the sloughs. 

0

20

40

60

90

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

10

30

50

70

80 A Taylor Slough Bridge

B P33

YEAR

0

CHLORIDE CONCENTRATION,

IN MILLIGRAMS PER LITER

1960 1970 1980 1990 2000

50

100

150

Figure 3. Chloride concentrations and loess smooth line at 

Taylor Slough Bridge (TSB) and P-33, 1959-2000. At the 

95-percent confidence level, uncensored seasonal Kendall 

test with stage adjustment at TBS gave significant upward 

trends for 1966-2000, 1966-1993, and 1983-1993, no significant trend for 1993-2000 and 1966-1983; and at P-33 significant upward trends for 1959-2000, 1959-82, no trend for 

1982-93, and a significant downward trend for 1993-2000.

Trends in sulfate and total phosphorus during the period are 

likely attributed, at least in part, to high percentages of lessthan and zero values combined with changes in reporting 
levels over the period of record. High spikes in nutrient 

concentrations were evident during dry periods (figs. 2, 4), 

5

7

9

GAGE HEIGHT, IN FEET

6

8

10

1996

FMAMJ JASOND

1997

FMAMJ JASOND FMAMJ JASOND J

1998

0

100

200

300

400

500

SULFATE (X 100), AND

TOTAL PHOSPHORUS (X 1,000)

IN MILLIGRAMS PER LITER

J J

SULFATE TOTAL

PHOSPHORUS

GAGE

HEIGHT

Bridge 105

Figure 4. Water level at Bridge 105 on the Tamiami Trail and 

concentrations of sulfate (have been multiplied times100) and 

total phosphorus (have been multiplied times 1,000) for January 

1996-January 1999.

and were attributed to either increased canal inflows of 

nutrient-rich water relative to marsh inflows, increased 

nutrient releases from breakdown of organic bottom sediment, or increased build-up of nutrient waste from concentrations of aquatic biota and wildlife in remaining ponds. 

Long-term changes in water quality are less pronounced in 

western EVER and BICY, however, seasonal and droughtrelated changes are evident. 

Median concentrations of total phosphorus generally are higher in BICY (most 

median values, 1991-2000, were greater than 0.015 mg/L) than in EVER 

(median values, 1991-2000, were less than 0.01 mg/L), probably because of 

higher phosphorus content in natural sources, such as shallow soils, rocks, and 

ground water in the Big Cypress region compared to the Everglades region.

Water quality varies spatially across the region 

because of natural variations in geology, hydrology, and 

vegetation and because of differences in water management 

and land use. Nutrient concentrations are relatively low in 

BICY and EVER compared to concentrations in parts of 

the northern Everglades, which are near agricultural and 

urban lands. Median concentrations of total phosphorus 

(fig. 5) generally are higher in BICY (most median values, 

1991-2000, were greater than 0.015 mg/L) than in EVER 

(median values, 1991-2000, less than 0.01 mg/L), probably 

because of higher phosphorus concentrations in natural 

sources, such as shallow soils, rocks, and ground water in 

the Big Cypress Swamp region, compared to the Everglades region. 

Everglades

National

Park

Gulf of Mexico

Florida Bay

0 5 MILES

Miami Canal

L28N

New River

Canal

Interceptor

Canal

L28

North

West Feeder

Feeder

P35

Taylor

Slough

Shark

River

Slough

L67 Ext

L28

L67 A

Barron River Canal

L67 C

75

C-111

Alligator Alley

Whitewater

Bay

40 Mile

Bend

Tamiami Trail 41

BR105

(A6)

Monroe

Turner

River

Big Cypress

National Preserve

L31

Water

Conservation

Area 3A

US41

(0.007)

P36

(0.006)

P33

P34 (0.005)

(0.005)

P37

(0.001)

TSB

(0.004)

S332

(0.007)

EP

(0.004)

S18C

(0.007)

S177

(0.007)

NE1

(0.007) NP201

(0.004)

S333

(0.011)

(0.010)

A9

(0.016)

(0.019)

A4

(0.010)

A5

(0.018)

(0.008)

S12A

(0.01)

S12D

A14

(0.009)

A13

(0.012)

A3

(0.009)

A12

(0.016)

A2

A1

(0.018)

S190

(0.05)

L28

EXPLANATION

STATION Location

and number. Red

bar and number in

parenthesis

represent median

total phosphorus

concentration in

milligrams per liter

LEVY Location

and number

−

−

P34

(0.005)

(0.016)

Figure 5. Median concentrations of total phosphorus at the Big 

Cypress National Preserve and Everglades National Park sites 

and nearby canal sites, 1991-2000.

Concentrations of chloride and sulfate 

(fig. 6), are higher in EVER (most median values in Shark 

River Slough, 1991-2000, were greater than 2 mg/L of 

sulfate and 50 mg/L of chloride), than in BICY (median 

values, 1991-2000, were less than 1 mg/L of sulfate and at 

most sites, less than 20 mg/L of chloride). This difference 

is probably because of the canal transport system, which 

conveys more water from an agricultural source into EVER 

than into BICY.

Trace elements and contaminants such as pesticides 

and other toxic organics are in relatively low concentrations in BICY and EVER compared to concentrations in 

parts of the northern Everglades, near agricultural and 

urban sources. Atrazine was the only pesticide found in 

water that exceeded the aquatic-life criterion in less than 1 

percent (2 out of 304) of the samples (table 1). In canal bed 

sediments, however, the pesticides heptachlor expoxide, 

lindane, and p,p′-DDE exceeded criteria in 1, 2, and 16 percent of the samples, respectively. 
Table 1. Most frequently detected pesticides and other organics in water for the period of record (1966-2000) at selected sites in and 

near Everglades National Park and the Big Cypress National Preserve

[μg/L, micrograms per liter]

Constituent

Number of

detections 

by

compounds

Number of

determinations

by compounds

Detections

per

determination

Highest

measured

concentration

Lowest

measured

concentration

Aquatic

life

criteria

Number 

of

exceedances

Class III

criteria,

fresh 

waters

Atrazine, unfiltered, μg/L 116 304 0.382 13.2 0.01 1.8 2

Atrazine, filtered, μg/L 90 99 0.909 0.87 0.00347 1.8 0

Metolachlor, filtered, μg/L 83 99 0.838 0.0635 0.0036 7.8 

Deethylatrazine, filtered, μg/L 73 99 0.737 0.0225 0.00107

Tebuthiuron, filtered, μg/L 61 99 0.616 0.0494 0.0027 1.6 0

Endosulfan sulfate, unfiltered, μg/L 43 374 0.115 0.45 0.0033

EPTC, filtered, μg/L 29 99 0.293 0.0148 0.00081

2,6-Diethylaniline, filtered, μg/L 23 99 0.232 0.0054 0.00098

Simazine, filtered, μg/L 20 99 0.202 0.0979 0.00361 10 0

Chlorpyrifos, filtered, μg/L 19 99 0.192 0.0234 0.00249

Endosulfan I, unfiltered, μg/L 17 55 0.309 0.05 0.001 0 0.056

Malathion, filtered, μg/L 16 99 0.162 0.0837 0.00324 0.1 0 0.1

Hexazinone, unfiltered, μg/L 15 153 0.098 0.031 0.019

A4

Everglades

National

Park

Gulf of Mexico

Florida Bay

L28N

Miami Canal

New River

Canal

Interceptor

Canal

L28

North

West Feeder

Feeder

P35

Taylor

Slough

Shark

River

Slough

L67 Ext

L28

L67 A

Barron River Canal

L67 C

75

C-111

Alligator Alley

Whitewater

Bay

40 Mile

Bend

Tamiami Trail 41

BR105

(A6)

Monroe

Turner

River

Big Cypress

National Preserve

L31

Water

Conservation

Area 3A

US41

(2)

P36

(3)

P33

P34 (5)

(0.0)

P37

(0.0)

TSB

(2)

S332

(4)

EP

(10)

S18C

(12)

S177

(4)

NE1

NP201 (2) (5)

S333

(10)

(0.4)

A9

(0.0)

(0.1)

A4

(0.8)

A5

(0.0)

(0.0)

S12A

S12D

A14

(0.0)

A13

(0.0)

A3

(0.0)

A12

(0.3)

A2

(0.4)

A1

(0.3)

S190

(10)

L28

EXPLANATION

STATION Location

and number. Red

bar and number in

parenthesis represent

median sulfate

concentration in

milligrams per liter

LEVY Location

and number

−

−

P35

(2)

Sulfate Chloride

Everglades

National

Park

Gulf of Mexico

Florida Bay

L28N

Miami Canal

New River

Canal

Interceptor

Canal

L28

North

West Feeder

Feeder

Taylor

Slough

Shark

River

Slough

L67 Ext

L28

L67 A

Barron River Canal

L67 C

75

C-111

Alligator Alley

Whitewater

Bay

40 Mile

Bend

Tamiami Trail 41

Monroe

Turner

River

Big Cypress

National Preserve

L31

Water

Conservation

Area 3A

0 5 MILES

P35

(65)

P36

(63)

P33

(63) P34

(18)

P37

(25)

TSB

(37)

S332

(38)

EP

(80)

S18C

(39)

S177

(36)

NE1

(65)

NP201

(51)

S333

(68)

US41

(16)

A9

(14)

BR105

(A6)

(13)

(22)

A5

(9)

S12A

(17)

S12D

(67)

A14

(21)

A13

(13)

A3

(24)

A12 A2 (9) (26)

A1

(53)

S190

(39)

L28

EXPLANATION

STATION-Location

and number. Red

bar and number in

parenthesis represent

median chloride

concentration in

milligrams per liter

LEVY-Location

and number

P34

(18)

0 5 MILES

Figure 6. Median concentrations of sulfate and chloride at the Big Cypress National Preserve and Everglades National Park sites and 

nearby canal sites, 1991-2000.

For more information, please contact:

U.S. Geological Survey

Florida Integrated Science Centers

2010 Levy Avenue

Tallahassee, Florida 32310

The data on which this factsheet is based are available at the SOFIA 

website http://sofia.usgs.gov/exchange/rmiller. The report on which the 

factsheet is based is available at the SOFIA web site, and at 

http://pubs.water.usgs.gov/wri034249/

Authors: Benjamin F. McPherson, and Ronald L. Miller, U.S. Geological Survey, Tampa, Florida; 

Robert Sobczak, and Christine Clark, National Park Service, Ochopee, Florida

U.S. Geological Survey Fact Sheet FS-097-03