A water-quality assessment began in 1994 in southern Florida as part of a

national study. The study design for data collection during the intensive

phase of the study (1996-98) is described for each of the major components

(surface water, ground water, and aquatic biology) used to assess regional

water quality. The data will be evaluated to address national, regional, and

local water-quality concerns.

National Water-Quality Assessment Program:

Study Design for Data Collection in the Southern Florida Study Unit, 1996-98

WHAT IS THE NAWQA PROGRAM?

In 1991, the U.S. Geological Survey (USGS) initiated a 

full-scale National Water-Quality Assessment (NAWQA) 

Program. The three major objectives of the NAWQA 

Program are to (1) provide a consistent description of 

current water-quality conditions for a large part of the 

Nation’s water resources, (2) describe how water quality is 

changing over time, and (3) explain the natural and human 

factors that may affect observed water-quality conditions.

The NAWQA Program is functionally organized into 

59 study units and a National Synthesis Team. The study 

units represent the diversity of geography, land use, water 

resources, and water use of the Nation. Intensive assessment activities in each of the study units are conducted on a 

rotational rather than a continuous basis. Three years of 

intensive data collection are followed by a 6-year period of 

reduced data collection. The intensive phase of data collection in the Southern Florida (SOFL) NAWQA study unit 

began in October 1995 and continued until 

September 1998.

WHAT MAKES THE HYDROLOGIC SYSTEM IN 

SOUTHERN FLORIDA UNIQUE?

Compared with much of the United States, the hydrologic system of southern Florida is unique in many ways. 

The land is very flat, and surface waters are either distributed over large wetlands such as the Everglades and the Big 

Cypress Swamp or are confined in a highly controlled system of canals. Most of the large rivers have been channelized and flows are managed with control structures; the 

smaller rivers are primarily tidally affected coastal streams. 

Water moves rapidly between the surface and shallow 

ground water, depending on water-level gradients, so that 

the source of the water is difficult to distinguish. Because 

of the low relief and manipulation of flow, drainage basins 

are difficult to define.

The hydrologic 

system is also unique 

for political reasons. 

More than 5 million 

people live along the coast in close proximity to the wilderness wetlands of Everglades National Park, Big Cypress 

National Preserve, and other public lands. The warm climate that encourages people to live in the region also supports intense agricultural development. Competing 

interests --- wilderness protection, urban expansion, and 

agricultural development --- vie for available water 

resources. In this arena of competing water-resource 

demands, the largest environmental restoration effort in the 

world is underway: the protection and restoration of the 

Florida Everglades.

HOW IS SOFL NAWQA DATA

COLLECTION DESIGNED?

The SOFL NAWQA study unit encompasses about 

19,500 square miles. The study unit contains large areas of 

intensive agricultural development, rangeland, and pasture 

land; has vast areas of wetlands, mostly in public ownership 

or under public control; and includes a large urban complex 

of about 4.5 million people. The natural systems in the study 

unit have been greatly altered by drainage, development, 

and water management, and water resources of the region 

have been significantly degraded.

Data collection is designed to address local, regional, 

and national water-quality concerns. Major water-quality 

issues of concern were identified in 1994 through the 

assistance of a local liaison committee of governmental 

officials, lay people, and others with an interest in water 

resources in southern Florida. The most important waterquality issues identified are nutrient enrichment, pesticide 

contamination, mercury contamination, habitat 

disturbance, and contamination of the Biscayne aquifer.

ALABAMA GEORGIA

FLORIDA

Southern

Florida

NAWQA

Study Unit

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-061-98

July 1998
habitat disturbance are often most susceptible to invasion 

by exotic species. Changes in plant and animal community 

composition have occurred in southern Florida; however, 

the factors influencing these changes are not well understood.

Contamination of the Biscayne aquifer -- The Biscayne 

aquifer is the sole source of drinking water for about 3.6 

million people living along the southeastern coast of the 

study unit. Ground water in the aquifer is vulnerable to 

contamination from surface sources, because high aquifer 

permeability allows rapid infiltration of surface waters. 

Contaminants of greatest concern include nitrate, pesticides, and volatile organic compounds.

Each of these water-quality concerns is evaluated with 

regard to the contribution that the SOFL NAWQA project 

makes to both regional management needs and national 

NAWQA Program goals. Collection of data during 1996-

98 to meet these needs and goals is summarized in the following tables for the categories of surface water, ground 

water, and aquatic biology.

N

Contaminants in fish tissue sampling sites

Cooperative sampling sites

Nutrient/pesticide and

algae synoptic sampling sites

Intensive pesticide sampling sites

Water chemistry, bottom sediment, aquatic biology,

sediment toxicity, process studies, and storm sampling sites

Lake

Okeechobee

Water Conservation Areas 1-3

Big Cypress National Preserve

Everglades National Park

Urban land-use

survey

Lake

Okeechobee

Tamiami Trail

Canal

Study unit

survey

Ground water

and surface water

synoptic survey

Agricultural

land-use survey

Study components used

to assess water quality 

and aquatic biology in

the SOFL Study Unit

GROUND WATER SAMPLING

SURFACE WATER AND

AQUATIC BIOLOGY SAMPLING

Nutrient enrichment -- Nutrient runoff from agricultural 

fertilizers, cattle lands, and urban sources adversely affects 

wetlands in southern Florida. The Everglades ecosystem, 

which developed and persists only under low-nutrient 

conditions, is vulnerable to nutrient enrichment, 

particularly by phosphorus.

Pesticide contamination -- Agricultural production of 

sugarcane, citrus, and vegetables involves the use of 

numerous insecticides, herbicides, and fungicides that 

subsequently may be transported into surface and ground 

waters. Urban activities are also a source of pesticides. The 

geochemical processes controlling the fate and transport of 

pesticides in water and sediment in southern Florida are not 

well understood. Moreover, the effects of these compounds 

on humans and the natural systems of southern Florida are 

largely unknown.

Mercury contamination -- Mercury has been found at 

alarmingly high levels in fish and wildlife in southern 

Florida and poses a threat to the health of wildlife and 

humans. However, the sources of mercury contamination 

and its pathways in the food chain are not well understood. 

Habitat disturbance -- Dredging, water diversion, and 

altered hydroperiod can adversely affect aquatic plant and 

animal communities. Aquatic ecosystems which undergo 
Study 

component Objectives Brief description andwater-quality parameters

Number 

of sites

Frequency 

during 

water year

Historical

data

available

SURFACE WATER

Bottomsediment 

survey

Determine presence of potentially 

toxic compounds in sediment at 

selected sites

Sample the depositional zone for pesticides, 

other synthetic organic compounds, and 

trace elements at water-chemistry sites

7 1

(1996) Some

Water

chemistry 

sites

Describe concentrations and loads 

of major ions and nutrients at 

selected sites

Sample near continuous streamflow sites for 

major ions, nutrients, organic carbon, and 

suspended sediment

7

2-6 in 1996

12-31 in 1997

12 in 1998

 Data at 

some sites

Cooperative

sampling

program

Assess the influence of

sampling method and location

on water quality

Sample water-chemistry sites on the same 

day as the SFWMD using both USGS 

methods and SFWMD methods

5

2-6 in 1996

12-31 in 1997

12 in 1998

None

Storm 

sampling

Assess effects of runoff during 

high-flow conditions on surfacewater quality

Sample water-chemistry sites during highflow conditions for major ions, nutrients, 

organic carbon, and suspended sediment

Variable

variable

(1997 and 

1998)

Some

Nutrient/

pesticide 

synoptic 

studies 

Determine the concentration of 

nutrients and pesticides across 

southern end of study unit during 

high and low flow

Sample sites along the Tamiami Trail Canal 

during low flow (June) and high flow 

(August) for major ions, mercury, nutrients, 

organic carbon, and pesticides

30

3

(Aug. 1996)

(June & Aug. 

1997)

Limited

Process 

studies

Describe processes controlling the 

degradation and biological 

availability of pesticides

Deploy and collect semipermeable 

membrane devices at selected sites. Collect 

water and bottom-sediment samples 

Variable 4

(1997-98)

Undetermined

Intensive 

pesticide

sampling

Determine seasonal variation in 

the occurrence and concentrations of nutrients and pesticides at 

water-chemistry sites

Sample water-chemistry sites which are 

located in specified agricultural land-use 

areas (citrus, sugarcane, and vegetables) for 

nutrients and pesticides

3

2 in 1996; 

weekly/

biweekly in 

1997;

monthly in 1998

Some

GROUND WATER

Urban 

land-use 

survey

Describe water quality in a residential and light commercial landuse area in a shallow aquifer susceptible to contaminationSample new and existing wells for major 

ions, nutrients, organic carbon, pesticides, 

radionuclides, trace elements, and volatile 

organic compounds (VOCs)

38 wells 1

(1997) Some

Ground water

and surface 

water

synoptic 

survey

Determine which water-quality 

constituents are transported 

through shallow ground water 

into surface water in an agricultural land-use area 

Sample shallow wells and surface-water 

sites for major ions, nutrients, pesticides, 

and VOCs before and during a surfacewater release in a canal that drains agricultural land

7 wells;

9 

surfacewater 

sites

1-5

(1998) None

Agricultural

land-use 

survey

Describe the effects of citrus land 

use on water quality in a shallow 

aquifer 

Sample new wells for major ions, nutrients, 

pesticides, radionuclides, and trace 

elements

30 wells 1

(1998) Some

Study 

unit 

survey 

Describe overall water quality in 

the Biscayne aquifer, which is 

used for drinking-water supply

Sample existing wells for major ions, nutrients, organic carbon, pesticides, radionuclides, trace elements, and VOCs

30 wells 1

(1998) Some

AQUATIC BIOLOGY

Contaminants

in fish tissue

Determine the presence of 

contaminants that can 

accumulate in fish tissue

Collect largemouth bass and Florida gar at a 

large number of sites. Sample composites of 

whole fish for organic compounds and fish 

livers for trace elements

16 1

(1996) Limited

Sediment

toxicity 

testing

Evaluate potential toxicity of bed 

sediment at the water-chemistry 

sites

Collect bed sediment samples and evaluate 

their potential toxicity using ASTM methods and Hyallela azteca

7 1

(1996) None

Aquatic 

biology

Assess biological communities 

and stream habitat at the basic 

fixed sites 

Quantitatively sample fish, macroinvertebrates, and algae near water-chemistry sites. 

Quantitatively describe stream habitat for 

these organisms

7

3,

1 per year

(1996-98)

Limited

Algae

synoptic

studies

Determine the influence of nutrients on the algal community along 

a nutrient gradient in the southern 

part of the basin

Collect algae using artificial substrate samplers at sites across the Tamiami Trail Canal 10-13

3

(June, Aug., 

Nov., 1997)

None
Hydrologic data and other information 

related to the Southern Florida 

NAWQA project can be obtained from:

Project Chief

Southern Florida

NAWQA Study

U.S. Geological Survey

4710 Eisenhower Blvd.

Suite B5 

Tampa, FL 33634

http://srv3sfltpa.er.usgs.gov

Southern Florida NAWQA

SUGGESTIONS FOR FURTHER READING

Gerould, Sarah, and Higer, Aaron, 1995, South Florida Ecosystem Program of the U.S. Geological Survey: U.S. Geological 

Survey Fact Sheet FS-134-95, 2 p.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design of the 

National Water-Quality Assessment Program: Occurrence 

and distribution of water-quality conditions: U.S. Geological 

Survey Circular 1112, 33 p.

Haag, K.H., 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 groundwater quality and ecology: U.S. Geological Survey WaterResources Investigations Report 96-4177, 42 p.

Haag, K.H., and McPherson, B.F., 1997, Organochlorine pesticides and PCBs in southern Florida fishes: Then and now: 

U.S. Geological Survey Fact Sheet FS-110-97, 4 p.

Marella, R.L., 1998, Water quality assessment of southern 

Florida--wastewater discharges and agricultural and urban 

runoff: U.S. Geological Survey Fact Sheet FS-032-98, 6 p.

McPherson, B.F., 1994, National Water-Quality 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. 

HOW CAN THE NAWQA PROGRAM 

CONTRIBUTE TO WATER-RESOURCE 

MANAGEMENT IN SOUTHERN FLORIDA?

The SOFL NAWQA study is one of many efforts 

underway to provide scientific information about the southern Florida ecosystem. The need for scientific information 

stems from a variety of political interests and goals that 

include the protection and restoration of the Everglades and 

the southern Florida environment. The State of Florida 

passed the Everglades Forever Act in 1994, thereby establishing a comprehensive program to restore parts of the 

remnant Everglades. A coalition of Federal, State, and local 

agencies and Indian tribes organized under the “South Florida Ecosystem Restoration Task Force” guides restoration.

The Restoration Task Force through its South Florida 

Working Group includes a Science Coordinating Team 

which develops the scientific questions that need answers 

for management decisions regarding restoration. Many 

agencies and organizations are actively studying and monitoring environmental conditions in the region, including the 

U.S. Environmental Protection Agency, National Oceanographic and Atmospheric Administration, National Park 

Service, U.S. Army Corps of Engineers, U.S. Fish and 

Wildlife Service, South Florida Water Management District (SFWMD), Florida Department of Environmental Protection, Florida Department of Agriculture and Consumer 

Services, Florida Game and Freshwater Fish Commission, 

the Miccosukee Tribe of Indians of Florida, the Seminole 

Tribe of Indians of Florida, the University of Miami, Florida International University, and others. These parties are 

carrying out studies to meet needs defined by the Task 

Force and to meet their own programmatic requirements. 

Some studies are directed at specific restoration activities, 

such as the SFWMD’s Everglades Nutrient Removal 

Project that evaluates the uptake of phosphorus by marshlands. Other activities are more general in nature, such as 

SFWMD’s monitoring of water quality across the region. 

The USGS is actively contributing scientific information about southern Florida under three of its programs: the 

Federal-State Cooperative Program, the Ecosystem Initiative, and the NAWQA Program. Each of these programs 

complements the others and helps develop a better understanding of the southern Florida environment -- essential 

for successful restoration. The challenge to the NAWQA 

Program is to provide useful information that contributes to 

the restoration of the southern Florida ecosystem, meets 

USGS programmatic requirements, and does not duplicate 

ongoing data-collection efforts in the region.

—by K.H. Haag, B.A. Bernard, L.A. Bradner, 

D.S. McCulloch, B.F. McPherson, and R.L. Miller