USGS Fact Sheet FS-032-98

large areas including much of Everglades National

Park, Big Cypress National Preserve, and several

water conservation areas and other public lands.

Figure 1. The Southern Florida NAWQA study

unit.

G u l f o f M e x i c o

A t l a n t i c O c e a n

N

STUDY-UNIT

BOUNDARY

Everglades Agricultural Area

West

Palm

Beach

Miami

Homestead

Big Cypress National Preserve

EXPLANATION

Everglades National Park

Immokalee

BROWARD

LEE HENDRY

CHARLOTTE

DE SOTO

HARDEE MANATEE

SARASOTA

OSCEOLA

ORANGE

HIGHLANDS

HILLSBOROUGH

OKEECHOBEE MARTIN Lake

Okeechobee

COLLIER

DADE

Florida Bay

MONROE

POLK

ST LUCIE

INDIAN

RIVER

GLADES

PALM

BEACH

0 25 50 Miles

0 25 50 Kilometers

INTRODUCTION

Population growth and activities

in the south Florida area over the past

40 years have resulted in increased

water use, changes in the distribution

and timing of flow, and deterioration of

water quality. These changes threaten

both the remaining natural ecosystem

and the growing human population.

Wetlands and shallow waters in the

region are sensitive to increased nutrient and contaminant inputs that are

often associated with wastewater

discharges and stormwater runoff.

Discharges and runoff reaching the

coast through canals can adversely

affect south Florida’s estuaries and

bays. The Biscayne aquifer in southeastern Florida, the sole source of

drinking water for nearly 3.4 million

people, is at risk of contamination

because of its shallow depth, highporosity, and location beneath an area

of intense urbanization.

Recent consensus has been

reached among Federal and State

agencies and environmental groups

that the south Florida ecosystem, and

the Everglades in particular, should be

protected and restored, to the extent

possible, to its predevelopment condition. Protection and restoration will

require a thorough understanding of

the distribution, amount, and quality

of water in the area and the human and

natural processes that affect the water.

The U.S. Geological Survey is providing scientific information that will contribute to the protection and restoration

effort through such programs as

NAWQA and the South Florida

Ecosystem Initiative.

This report provides information on sources of wastewater

discharge and runoff within the

Southern Florida (SOFL) NAWQA

study area (fig. 1). This information

can be used in evaluating the potential effects of wastewater on

water quality of the region.

SOUTHERN

FLORIDA NAWQA

STUDY UNIT

 The Southern Florida

NAWQA study unit encompasses an area of about

19,500 square miles in southern and central Florida (fig. 1).

Within the study unit are areas

of agricultural and urban

development, phosphate mining, islands (keys), and wetlands (marshes and swamps).

Agriculture is widespread, but

it is most intensive in the

Everglades Agricultural Area

(EAA), south of Lake

Okeechobee, and in western

Dade County. Nearly 5.8 million people resided in the

study unit in 1990, in addition

to several million visitors and

seasonal residents. Most

people live near the coast of

the Atlantic Ocean and the

Gulf of Mexico where the population has increased 100 percent in the 20 years from 1970

and 1990. Phosphate mining is

predominantly in the

Peace River Basin mostly in

DeSoto, Hardee, and Manatee

Counties. Wetlands cover

Water-Quality Assessment of Southern Florida—

Wastewater Discharges and Runoff

Nearly 800 million gallons per day of treated wastewater was discharged in the

Southern Florida National Water-Quality Assessment (NAWQA) study unit in 1990, most

to the Atlantic Ocean (44 percent) and to deep, saline aquifers (25 percent). About 9 percent was discharged to fresh surface waters and about 22 percent to shallow ground

water, of which septic tanks accounted for 9 percent. Runoff from agricultural and urban

lands, though not directly measured, is a large source of wastewater in southern Florida.

U.S. Department of the Interior

U.S. Geological Survey

1

ALABAMA GEORGIA

FLORIDA

Southern

Florida

NAWQA

Study Unit

National Water-Quality Assessment Program
5%

44%

25%

13%

9%

4%

WASTEWATER DISCHARGES

TO SURFACE WATER

[Totaled more than 787 million gallons per day in 1990, %, percent]

Domestic discharge to saline

water

Domestic discharge to injection

wells or boreholes

Septic tank discharge to drain

fields

Domestic discharge to freshwater

Domestic discharge to drain field,

percolation ponds, spray fields,

and reuse systems

Industrial discharge to freshwater

TO SUBSURFACE/GROUND WATER

WASTEWATER

 Wastewater is generated from

human activities. It includes (1) discharge from domestic (municipal) and

industrial treatment plants and septic

tanks, and (2) runoff from agricultural

lands, urban areas, and landfills. The

water from wastewater facilities is

treated before release, and then it is discharged to streams, shallow boreholes, or

deeper injection wells. In 1990, treated

wastewater discharged from domestic and

industrial facilities and septic tanks in the

study unit totaled more than 787 million

gallons per day (Mgal/d) (Marella, 1994).

Nearly 413 Mgal/d, or 53 percent of the

treated wastewater, was discharged to surface-water bodies (fig. 2) with more than

three-quarters of this total (344 Mgal/d)

being discharged to the Atlantic Ocean.

The remaining 47 percent of the treated

wastewater was discharged to the subsurface, with more than two-thirds

(196 Mgal/d) being discharged into deep

nonpotable aquifers through injection

wells (fig. 2). Although the discharged

wastewater is regulated in both quantity

and quality, it can adversely affect water

quality of the receiving water bodies, particularly if they have restricted circulation

or a limited capacity for dilution. In the

Florida Keys, for example, there is concern that wastewater from some 240 small

package treatment plants seeping from

shallow injection wells into marine waters

may be adversely affecting the very sensitive coral reefs and other near-shore communities (Shinn and others, 1994).

Agricultural and urban runoff are

major nonpoint sources of nutrients and

contaminants to southern Florida waters.

Because runoff is from nonpoint sources,

it is difficult to quantify; instead, for this

study the areal extent of agricultural and

urban land uses was used as an indicator

of the effect of runoff on southern Florida.

The nutrients and contaminants come

from fertilizers, pesticides, manure, and

urban waste. Fertilizer and manure dominate nutrient inputs to the southern

Florida basins; wastewater treatment

plant inputs are insignificant in comparison (Haag and others, 1996). In the northern Everglades, agricultural runoff of

nutrients has resulted in overenrichment

and ecological disruption of wetlands,

and there is concern that these adverse

effects will become visible in the southern

Everglades, including the Everglades

National Park (McPherson and Halley,

1997). Long-term data already show that

changes in water quality in the southern

or dispose of wastewater derived principally from residential dwellings, business,

or commercial buildings, institutions, and

some industrial facilities (Marella, 1994).

Data were collected for the 350 facilities

that had a capacity of greater than

0.01 Mgal/d. Discharge from these

350 facilities, which served 72 percent of

the population (4.2 million), accounted for

nearly 99 percent of the treated domestic

wastewater discharged during 1990. Discharge from the remaining 1,150 smaller

facilities totaled about 10 Mgal/d

(estimated by assuming a maximum

discharge of 0.009 Mgal/d per system).

These smaller domestic wastewater facilities, together with septic tanks, served the

remaining 28 percent of the population

(1.6 million).

Discharge of treated wastewater

from the domestic wastewater facilities in

1990 totaled 682 Mgal/d, of which

approximately 57 percent (390 Mgal/d)

Everglades have occurred; specific conductance and major ion concentrations

have increased in the Shark River Slough

(Flora and Rosendahl, 1982). Continued

residential development along the southeastern coast and the Florida Keys also

will intensify problems in coastal waters

as a result of increased stormwater runoff,

septic tank and disposal well leachate, and

inputs of nutrients and heavy metals from

marinas and live-aboard vessels. Landfills

are also a water-quality concern, as contaminants can leach into the ground and

surface waters and adversely affect local

water quality.

Domestic Wastewater

Discharges

An estimated 1,500 domestic wastewater facilities within the SOFL study

unit were regulated by the Florida

Department of Environmental Protection

(FDEP) in 1990. These facilities receive

2

Figure 2. Wastewater discharged by source and destination in the southern

Florida study unit, 1990.

Domestic wastewater facility, Dade County. (Photo courtesy of the

Florida Department of Environmental Protection.)
Table 1. Wastewater discharged by county in Southern Florida

NAWQA study unit, 1990

[Values in million gallons per day. Modified from Marella, 1994]

Domestic Industrial Septic

tanks

Total

discharged

Broward 171.02 0 7.80 178.82

Charlotte* 4.75 0 3.75 8.50

Collier 16.41 0 2.61 19.02

Dade 283.36 0 15.73 299.09

DeSoto 1.10 0 0.87 1.97

Glades 0.05 0 0.56 0.61

Hardee 1.11 0 0.60 1.71

Hendry 2.14 8.55 0.71 11.40

Highlands 2.44 0 3.03 5.47

Hillsborough* 0 0 0 0

Lee 29.11 0 7.35 36.46

Manatee* 0 0 0.16 0.16

Martin* 4.49 0.27 2.98 7.74

Monroe 9.45 0 2.97 12.42

Okeechobee* 0.38 0 1.40 1.78

Orange* 34.05 0 1.89 35.94

Osceola* 10.22 0 1.86 12.08

Palm Beach 84.29 1.18 6.84 92.31

Polk* 24.30 21.96 8.12 54.38

St. Lucie* 2.50 0 3.19 5.69

Sarasota* 1.45 0 0.55 2.00

Totals 682.22 31.96 72.97 787.15

was discharged to surface water and

43 percent (292 Mgal/d) to ground water.

The Atlantic Ocean received 88 percent of

the surface-water discharges; deep nonpotable aquifers received 67 percent of the

ground-water discharge through injection

wells. Land application systems (drain

fields, percolation ponds, spray fields,

shallow wells, and reuse irrigation systems) accounted for the remaining wastewater released to the ground. Broward

and Dade Counties accounted for twothirds (454 Mgal/d) of the study unit’s

domestic discharge in 1990 (table 1).

Within these study areas, 41 domestic

wastewater facilities discharged more

than 1 Mgal/d each (fig. 3), totaling

80 percent of the discharge produced in

1990.

Industrial Wastewater

Discharges

According to the FDEP, industrial

wastewater facilities are those that produce, treat, or dispose of wastewater not

otherwise defined primarily as domestic

wastewater, including the runoff and

leachate from areas that receive contaminants associated with industrial or commercial storage, handling, or processing

(Marella, 1994). Nearly all of the 18 facilities in the study area have a capacity of

more than 0.04 Mgal/d, but

often discharge well below

their capacities, discharge

only seasonally, or do not discharge at all during a given

year. This is particularly true

for food processing plants and mining

operations within the study unit, as many

of these facilities only operate seasonally.

Discharge of treated wastewater from the

18 industrial wastewater facilities totaled

nearly 32 Mgal/d in 1990. Additionally,

an undetermined amount of untreated

water was discharged from mining operations (from dewatering or stormwater

retention). Nearly all (99.9 percent) of

the industrial wastewater was discharged

to surface water. Most of the industrial

operations within the study unit dispose

of their wastewater through domestic

facilities (municipal sewer). As regulations increase regarding the quality and

quantity of wastewater discharges

allowed in Florida, it has become more

cost effective for industrial water users to

discharge their wastewater to domestic

facilities for treatment and disposal,

rather than treating it themselves. Additionally, industrial users recycle more

water than in the past. As a result,

discharge of industrial wastewater in

southern Florida decreased about

33 percent from 1985 to 1990.

Figure 3. Active domestic wastewater treatment

facilities that discharged more than 1 Mgal/d in

1990.

Fresh

Surface water disposal

Surface/Ground water disposal

Wastewater facilities with discharge

more than 1 million gallons

per day in 1990:

Saline

Drain field, Injection well

 percolation ponds,

 spray field, and

 reuse systems

G u l f o f M e x i c o

A t l a n t i c O c e a n

N

EXPLANATION

STUDY-UNIT

BOUNDARY

0 25 50 Miles

0 25 50 Kilometers

 

Wastewater Discharges from

Septic Tanks

 The use of septic tanks is common

throughout the NAWQA study unit.

Septic tanks are mostly used for individual households or small commercial

establishments (churches, convenience

stores, small motels, restaurants, and

campgrounds) that are in rural or remote

areas, or in urban areas that are not served

by a domestic wastewater facility. Water

from septic tanks is generally released to

the ground through a subsurface drain

field (sometimes referred to as an absorption field) after natural biological treatment. In 1990, more than half a million

(550,000) septic tanks were in use within

the study unit (U.S. Bureau of Census,

1993). Concentrations of septic tanks are

common in highly suburbanized counties,

where housing growth often occurs in

unincorporated areas immediately adjacent to city limit (Marella, 1994). In many

cases, these areas are not served by

domestic wastewater facilities. Charlotte

and Dade Counties have a density of

septic tanks greater than 50 per square

mile (Marella, 1994). However, the actual

density of the septic tanks in areas not

served by domestic wastewater facilities

3

* Only part of county is within the study unit.
is greater. For example, about 55 percent

of the land in Dade County is in fresh or

saltwater marshlands, and is generally

uninhabitable (Field and others, 1991).

The density of septic tanks in the inhabitable areas would be about 130 tanks per

square mile, but it is even greater because

most of the inhabited areas are served by

a domestic wastewater facility.

Based on an average discharge of

55 gal/d (gallons per day) per person

(Tchobanoglous, 1991) and 2.46 people

per household (Smith and Cody, 1992),

estimated water released from each septic

tank is about 135 gal/d. Discharge from

the nearly 550,000 septic tanks in the

study unit for 1990 is about 73 Mgal/d.

Most of the effluent is released to the subsurface through on-site subsurface drain

fields or boreholes that allow the water

from the tank to percolate into the ground

(usually into the surficial aquifers) and

either transpire to the atmosphere through

surface vegetation or add to the flow of

shallow ground water. Dade County,

with nearly 116,300 septic tanks, had

estimated releases of nearly 16 Mgal/d in

1990. The number and density of septic

tanks can have important effects on water

quality; waste generated from each tank

can add high levels of nitrogen (nearly

24 pounds per year) and phosphorus

(9 pounds per year) to the surficial aquifer

and adjacent surface water (Tchobanoglous, 1991).

Agricultural Wastewater

Runoff

One of the most intense areas of agricultural production in the United States is

the Everglades Agricultural Area, located

Figure 4. Agricultural and urban land use and

active landfills in the study unit, 1995. (Modified

from South Florida Water Management District

and Southwest Florida Water Management District

digital data, 1988-90.)

G u l f o f M e x i c o

A t l a n t i c O c e a n

N

STUDY-UNIT

BOUNDARY

Urban or built-up land

Agricultural land

Active landfills

Land-use parcels greater

than or equal to 1 square mile

EXPLANATION

0 25 50 Miles

0 25 50 Kilometers

Citrus production is predominantly

in the Coastal Flatwoods (Indian River,

Martin, and St.Lucie Counties) and on the

Lake Wales Ridge (Highlands and Polk

Counties). Nearly 641,000 acres of citrus

4

Installation of septic tank and drain

field in southern Florida.

south of Lake Okeechobee

(fig. 1). Within the EAA,

about 400,000 acres of

sugarcane (Florida Agricultural Statistics Service, 1991)

and nearly 100,000 acres of

various vegetable (truck)

crops are grown (fig. 4).

Surface water is the primary

source of water for irrigation.

Most of the water

originates from Lake

Okeechobee and is diverted

through canals or ditches,

where it is pumped or

gravity fed onto fields.

Most of the sugarcane is irrigated by subsurface flood

systems where the water is

used to maintain a high water

table in the fields. Excess

irrigation water is returned to

the canals. An estimated

813 Mgal/d of surface water

was withdrawn or diverted to

irrigate sugarcane in 1990

(Marella, 1992), with an

unknown percentage of this

water returned to the hydrologic system. Vegetable irrigation occurs through either

similar subsurface irrigation

systems or from traveling

guns or portable systems

with overhead sprinklers.

Excess water also is returned to surface

water sources. Other areas of vegetable

production are located near Homestead, in

Dade County, and Immokalee, in Collier

County (figs. 1 and 4).

Agricultural discharge in southern Florida. (Photo courtesy of

South Florida Water Management District.)
was in the study unit in 1990, of which

most was irrigated. Citrus acreage

increased nearly 118,000 acres from 1980

to 1990, primarily in Charlotte, Collier,

Hendry, and Lee Counties (Florida Agricultural Statistics Service, 1994). Most of

the crops in the study unit are cultivated

on sandy soils, which have a very low

water-holding capacity, or on muck land

with a high water-holding capacity. Runoff from these agricultural activities can

be significant, especially during rainy

seasons when the soil is saturated.

 Some of the largest dairy and cattle

operations in the United States are in

southern Florida. Overall, 70,000 dairy

cows and nearly 600,000 beef cows were

within the study unit in 1990, and an estimated 250,000 acres of improved pasture

was used for grazing in 1992 (U.S.

Bureau of Census, 1994). Okeechobee

County had more than 45,000 dairy cows

and 81,000 beef cows in 1990 (Florida

Agricultural Statistics Service, 1992).

High nutrient concentrations are attributed

to runoff from improved pasture and dairy

operations in some areas of southern

Florida (Haag and others, 1996).

Urban Wastewater Runoff

Urban development in southern Florida

is concentrated near the Atlantic and gulf

coasts (fig. 4). The 100-mile stretch of

coastline between Miami and West Palm

Beach is the largest, most highly urbanized

region. In this urbanized region, thousands

of acres are covered with impervious parking lots, roads, or buildings that inhibit the

percolation of rainfall. The stormwater that

collects in retention ponds, canals, or ditches

often contains bacteria, viruses, oil and

grease, toxic metals, nutrients, and pesticides. These contaminants seep into the

ground from ponds, canals, and ditches and

adversely affect public water supplies, or

they are discharged from canals into lakes

and bays, degrading these waters (Klein and

others, 1975).

Wastewater Runoff from

Landfills

Landfills are a source of nonpoint

pollutants associated with urban areas.

Contaminants from landfills leach into the

ground and surface waters, adversely

affecting water quality. There are approximately 40 active landfills in the study unit

that receive an average of 20 or more tons

of solid waste per day (fig. 4). Unregulated dumping also occurs in southern

Florida.

5

Urban development in southern Florida.

Public supply water source in Palm Beach County.

Livestock grazing in southern Florida.

Drainage canal in St. Lucie County.
Haag, K.M., Miller, R.L., Bradner, L.A., and

McCulloch, D.S., 1996, Water-quality

assessment of southern Florida: An

overview of available information on

surface- and ground-water quality and

ecology: U.S. Geological Survey

Water-Resources Investigations Report

96-4177, 42 p.

 Klein, Howard, Armbruster, J.T., McPherson,

B.F., and Freiberger, H.J., 1975, Water

and the south Florida environment: U.S.

Geological Survey Water-Resources

Investigations Report 214-75, 165 p.

Marella, R.L., 1992, Water withdrawals, use

and trends in Florida, 1990: U.S.

Geological Survey Water-Resources

Investigations Report 92-4140, 38 p.

——— 1994, Estimated discharge of treated

wastewater in Florida, 1990: U.S. Geological Survey Open-File Report 93-364,

53 p.

McPherson, B.F., 1994, National waterquality assessment program--Southern

Florida: U.S. Geological Survey OpenFile Report 94-57, 2 p.

McPherson, B.F., and Halley, Robert, 1997,

The south Florida environment--A

region under stress: U.S. Geological

Survey Circular 1134, 61 p.

McPherson, B.F., Higer, A.L., Gerould, Sarah,

and Kantrowitz, I.H., 1995, South

Florida ecosystem program of the U.S.

Geological Survey: U.S. Geological

Survey Fact Sheet FS-134-95, 4 p.

Shinn, E.A., Reese, R.S., and Reich, C.D.,

1994, Fate and pathways of injectionwell effluent in the Florida Keys: U.S.

Geological Survey Open-File Report

94-276, 121 p.

Smith, S.K., and Cody, Scott, 1992, Number

of households and average household

size in Florida, April 1991: University of

Florida, Bureau of Economic and Business Research, v. 25, no. 2, bull. 100, 4 p.

Tchobanoglous, George, 1991, Wastewater

engineering, treatment, disposal, and

use: Metcalf and Eddy, Inc., 3rd ed.,

1334 p.

U.S. Bureau of Census, 1993, 1990 Census of

housing, detailed housing characteristics;

Florida: Washington, D.C., U.S. Department of Commerce, Bureau of the

Census, Ch-2-11, 793 p.

——— 1994, 1992 Census of agriculture;

Florida state and county data: Washington D.C., U.S. Department of Commerce, Bureau of the Census, geographic

area series, v. 1, pt. 9, 439 p.

—by Richard L. Marella

REFERENCES

Field, D.W., Reyer, A.J., Genovese, P.V., and

Shearer, B.D., 1991, Coastal wetlands of

the United States: Asheville, N.C., U.S.

Department of Commerce, National

Oceanic and Atmospheric Administration, National Ocean Service, Office of

Oceanography and Marine Assessment,

Ocean Assessments Division, Strategic

Assessment Branch, 59 p.

Flora, M.D., and Rosendahl, P.C., 1982, An

analysis of surface water nutrient concentrations in the Shark River Slough,

1972-1980: Homestead, South Florida

Research Center Report T-653, 40 p.

Florida Agricultural Statistics Service, 1991,

Field crops summary 1990: Orlando,

Florida Department of Agriculture and

Consumer Services, Agricultural Statistics Service, 19 p.

——— 1992, Livestock, dairy, and poultry

summary 1991: Orlando, Florida Department of Agriculture and Consumer

Services, Agricultural Statistics Service,

84 p.

——— 1994, Commercial citrus inventory

1994: Orlando, Florida Department of

Agriculture and Consumer Services,

Agricultural Statistics Service, 109 p.

For additional copies of this report, please write to:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

For more information, please contact:

Benjamin F. McPherson, Project Chief

Southern Florida Study Unit

U.S. Geological Survey

4710 Eisenhower Blvd., Suite B-5

Tampa, Florida 33634-6381

Telephone: 813-884-9336 FAX - 813-889-9811

6

THE NATIONAL WATER-QUALITY ASSESSMENT (NAWQA) PROGRAM

In 1991, the U.S. Geological Survey began the NAWQA Program to describe the status of, and trends in, the quality of the

Nation’s surface- and ground-water resources, and to identify the natural and human factors that affect the quality of these

resources. The NAWQA Program is designed to produce water-quality information that is useful to policymakers and

managers at Federal, State, and local levels. The Southern Florida study is one of 60 active or proposed studies nationwide,

which represent 60 to 70 percent of the Nation’s water use and population served by public water supplies.

USGS Fact Sheet FS-032-98