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Lake Okeechobee Surface 

Water Improvement and 

Management (SWIM) Plan 

Planning Document

July 2002 Draft

prepared by

 South Florida Water Management District

 West Palm Beach, Florida

Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

i

EXECUTIVE SUMMARY

This document provides an overview of the activities and accomplishments that

have been directed towards the restoration of Lake Okeechobee since adoption of the

Surface Water Improvement and Management (SWIM) Plan - Update for Lake

Okeechobee (SFWMD, 1997a). This update also describes the current and proposed

activities through 2000.

Lake Okeechobee and its watershed are key components of South Florida's

Kissimmee-Okeechobee-Everglades ecosystem, which extends from the headwaters of the

Kissimmee River in the north to Florida Bay in the south. The lake provides a number of

ecological and societal values. It is home to one of the nation's prized bass and speckled

perch fisheries, as well as an economically important commercial fishery. At the same

time, it provides habitat for a wide variety of wading birds, migratory waterfowl, and the

federally-endangered Everglades Snail Kite. Lake Okeechobee is also a source of drinking

water for cities and towns along the lake, and can be a backup water supply for the

communities of the lower east coast of Florida. The lake also supplies irrigation water for

the expansive Everglades Agricultural Area, and is a critical supplemental water supply

for the Everglades. 

The Lake Okeechobee SWIM planning area has been defined as the major basins

that are direct tributaries to the lake, including those basins that are hydrologically

upstream and/or from which water is presently released or pumped into the lake on a

regular basis. Although the Lake Okeechobee SWIM planning area generally excludes

basins that are hydrologically downstream and act primarily as receiving basins for water

supply (Caloosahatchee and St. Lucie River), the conveyance of flood control discharges

and the resulting potential associated environmental impacts make these basins a

component of this plan.

The SWIM Act (Section 373.451-.459, Florida Statutes, [F.S.]), adopted by the

Florida Legislature in 1987, requires water management districts, in conjunction with

other state agencies and local governments, to prepare SWIM Plans for priority water

bodies, including Lake Okeechobee. The SWIM Act requires that the plans describe

strategies and potential programs for restoring or protecting the water body to Class III

standards or better for recreation, propagation and maintenance of a healthy, wellbalanced population of fish and wildlife. The plan must include a listing of studies that are

being or have been prepared for the water body; a description of the research and

feasibility studies that will be performed to determine the particular strategy or strategies

to restore or protect the water body; a description of the measures needed to manage and

maintain the water body once it has been restored and to prevent future degradation; a

schedule for restoration and protection of the water body; and an estimate of the funding

needed to carry out the restoration or protection strategies. 

The SWIM Act sets forth a specific process for the preparation, review, and

approval of SWIM Plans. It requires the South Florida Water Management District
ii

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

(SFWMD or District) to develop SWIM plans in cooperation with the Florida Department

of Environmental Protection (FDEP) and other agencies. Pursuant to Section 373.455,

F.S., the District submits a draft plan to the FDEP and other agencies. The FDEP reviews

the cost of the SWIM Plan, funding availability, and the likelihood that the plan will

significantly improve or protect water quality and associated natural resources. If the

FDEP determines that a SWIM plan does not meet minimum plan requirements, it shall

recommend to the District modifications or additions to the plan pursuant to Section

373.456(1), F.S. Other agencies review the plan for its effects on the resources within their

respective jurisdictions and make recommendations.

SWIM plans must be consistent with state water policy as outlined in Chapter

62-40, Florida Administrative Code (F.A.C), and to otherwise provide guidance to the

FDEP and the water management districts in the development and preparation of water

management programs, rules, and plans. Chapter 62-40.432 requires the water

management districts to develop pollution load reduction goals (PLRGs) for SWIM water

bodies. The PLRG developed for Lake Okeechobee was a 40 percent reduction in

phosphorus loading from the watershed, based on the conditions that existed from 1973 to

1979 (Federico et al., 1981), with an expected downstream benefit of maintaining the

trophic state and the biological integrity of the lake. To assist in achieving this goal, total

phosphorus concentrations in runoff leaving land parcels were limited by the Lake

Okeechobee Works of the District (WOD) Rule. The total phosphorus concentration

targets range from 0.18 to 1.2 milligrams per liter (mg/l). 

The federal Clean Water Act (Title 33, Chapter 26, Subchapter III, Section

1313(d)), requires that each state develop total maximum daily loads (TMDLs) for each

water-quality-limited segment reported. A TMDL reflects the total pollutant loading, from

all contributing sources, that a water segment can receive without exceeding its capacity to

assimilate the pollutant loads and still meet applicable water quality standards. The

phosphorus TMDL established for Lake Okeechobee is 140 metric tons (based on a 5-year

rolling average) to achieve an in-lake target phosphorus concentration of 40 parts per

billion in the pelagic zone of the lake (FDEP 2000). The restoration target was determined

using computer models developed based on past research performed by the SFWMD

using SWIM funds. This target will support a healthy lake system, restore the designated

uses of Lake Okeechobee, and allow the lake to meet applicable water quality standards.

The 1997 SWIM plan update reported that phosphorus load reductions had

occurred, but the 40 percent reduction in loads was not achieved. It recommended the

implementation of programs and projects to improve the lake and watershed water quality

situation. The status of these programs and projects are summarized in this update. Even

with the implementation of these programs and projects, nutrient loads to Lake

Okeechobee have not decreased significantly. The highest inflow phosphorus

concentrations continue to be found in the S-154 and S-191 basins where dairies are

abundant and the majority of the out-of-compliance WOD sites are found. Phosphorus

loading is far in excess of the amount considered for a healthy Lake Okeechobee

ecosystem and current model data predict that it may take decades before in-lake

phosphorus concentrations will respond to reduced external loads. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

iii

Several major accomplishments have been made in the restoration effort since the

publication of the last SWIM plan update in 1997. One of the most important restoration

actions was the Lake Okeechobee Managed Recession Operation. During six years prior

to 2000, high water levels in the lake (associated with a prolonged wet period) destroyed

nearly all of the lake’s submerged plant beds and caused extremely poor water quality. The

lake’s prize bass fishery was on the brink of ecological collapse. A period of low water

levels (less than 13 feet, lasting for at least 8 weeks) was required to allow recovery of the

biological communities. In April and May 2000, approximately one foot of water was

released from Lake Okeechobee. Coincident with that, another one foot of water left the

lake for normal water supply deliveries to agriculture and other uses, and one foot left the

lake by direct evaporation into the atmosphere. Taken together the lake dropped by

approximately 3 feet between April and July. As a result of the low water levels, Lake

Okeechobee quickly recovered from its previously stressed condition. Over 45,000 acres

of new submerged plant beds grew during the summer and fall and the lake’s nearshore

bulrush community (prime bass habitat) expanded. The low water levels also allowed

coordinating state and federal agencies to carry out controlled fires that have killed tens of

thousands of acres of exotic plants that were taking over valuable wildlife habitat.

A new regulation schedule for the lake was formally adopted by the United States

Army Corps of Engineers (USACE) in July 2000. This schedule, the Water Supply and

Environment (WSE) schedule uses climate forecasting to determine the volumes of water

to release from the lake under flood control circumstances, and has the potential to provide

environmental benefits for the lake and downstream systems while not sacrificing water

supply. The extent of the benefits will depend in part on specific adaptive management

protocols that are presently being developed by the District.

Restoration efforts for Lake Okeechobee were recently advanced with the passing

of the Water Resources Development Act of 2000 (WRDA 2000). The WRDA 2000

authorizes the Comprehensive Everglades Restoration Plan (CERP). The CERP is

expected to have substantial effects on the lake's hydropattern. It is expected to reduce the

number of extreme high and low events and increase the occurrence of ecologically

beneficial spring recession events. The act also authorizes projects that will reduce

nutrient loads to the lake. These components include regional stormwater treatment areas,

reclamation of isolated wetlands, and regional water storage facilities, such as aquifer

storage and recovery wells and reservoirs. 

The enactment of the Lake Okeechobee Protection Act (LOPA) (Section 373.4595,

F.S.) in 2000 also advanced restoration efforts. This act provides an umbrella that captures

many lake restoration efforts. It will significantly enhance mandates restoring and

protecting the lake using a phased, watershed-based approach to reduce phosphorus

loading to the lake and downstream receiving waters. Fulfilling this act will require a great

deal of cooperation among government agencies and the public. To facilitate the execution

of the Lake Okeechobee Protection Plan, an interagency committee was formed with

individuals from the FDEP, the Florida Department of Agriculture and Consumer

Services, and the SFWMD. The agencies are currently planning and implementing

numerous management activities in the watershed to reduce phosphorus loading to the

lake. These include the construction of surface water storage reservoirs and stormwater
iv

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

treatment areas; the restoration of isolated wetlands the development and implementation

of best management practices to control nonpoint sources of pollution; the continuation of

research and monitoring to ensure the projects are designed and implemented to optimize

success; the removal of phosphorus-rich sediment from tributaries to Lake Okeechobee;

and the implementation of a sediment management feasibility study to determine whether

or not it is feasible to reduce internal loading from the lake sediments. More current

information regarding the status of the LOPA activities can be found in the Lake

Okeechobee Protection Program Annual Report to the Legislature (SFWMD, 2001a,

2001b).

This update of the Lake Okeechobee SWIM Plan has set goals for the Lake

Okeechobee SWIM planning area in the areas of water quality; environmental resources;

flood protection and water supply; recreation, navigation, and public involvement; and

intergovernmental coordination. Objectives have been developed to accomplish these

goals. Programs and projects are being developed and will be implemented to achieve

these objectives. The goals and objectives, as well as some of the programs and projects

are summarized below.

Phosphorus Load Reduction in the Tributaries

In an effort to meet the proposed TMDL target and in-lake phosphorus

concentration of 40 parts per billion and achieve a phosphorus load of 140 tons per year,

over-target phosphorus loading must continue to be reduced. The expanded WOD

program, the new Lake Okeechobee Protection Plan, and other new programs and projects

are being implemented to achieve the inflow target are summarized in Chapter 2 and

itemized below:

• Best available technologies to significantly reduce the export of

phosphorus from dairy operations into tributaries and Lake

Okeechobee 

• Reservoir-assisted stormwater treatment areas

• Critical restoration projects

• Isolated wetlands restoration

• Natural resource economic analysis of a wide range of phosphorus

control alternatives, using full-cost accounting practices

• Sediment removal technologies in the tributaries

• Research and modeling efforts to determine source of loads and

methods to reduce them
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

v

Reduction of Nonnutrient Pollutant Loads

To reduce the nonnutrient pollutant loads, Class I Water Quality Standards (potable

water supplies) must be achieved within Lake Okeechobee and Class III Water Quality

Standards must be achieved within the lake tributaries. To achieve the in-lake reduction,

the following initiatives are planned, and are detailed in Chapter 3:

• The District will continue monitoring to ensure the water quality

requirements of the Lake Okeechobee Operating Permit are fulfilled. 

• Both the District’s monthly water quality monitoring program and its

organics and pesticide monitoring program will be modified to focus

resources on parameters that are known to have potential sources in the

watershed. 

• The applicability of additional management strategies for canals and

marinas will be determined. 

Reduction of In-Lake Nutrients

Due to an overabundance of nutrients in Lake Okeechobee, a process known as

eutrophication, large algal blooms have periodically formed in Lake Okeechobee. Algal

blooms are cause for concern because they may contain toxins that affect fish and wildlife;

they create taste and odor problems for drinking water; and when they die off and degrade,

oxygen is removed from the water column and waste products (e.g., ammonia)

accumulate, causing fish kills and the death of other aquatic life. Lake users also find these

blooms unsightly, reducing their enjoyment of the resource. 

In-lake phosphorus must be reduced to a attain a more natural, lower frequency of

potentially harmful algal blooms. To achieve this goal the SFWMD will do the following:

• Evaluate the feasibility of removing phosphorus-rich sediments from

the lake

• Evaluate the feasibility of chemical treatment of lake sediments to

“inactivate” the phosphorus

• Identify lake stage management options that would facilitate greater

coverage of submerged plants, and thus, greater phosphorus uptake

• Complete research and model development necessary to guide the most

effective phosphorus reduction efforts, as called for in the Lake

Okeechobee Protection Plan

Environmental Resources

Another goal of the Lake Okeechobee SWIM Program is to protect and enhance

the lake’s environmental resources. These resources include biological diversity,

ecological functions, and the distribution and abundance of native plants and animals. The

following objectives have been set to fulfill the environmental resource goal:
vi

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

• Identification of a range of water levels that will allow for a healthy

community of submerged and emergent native plants and the

communities of fish and wildlife that they support

• Identification and implementation of effective programs to control

exotic plants, including melaleuca and torpedograss

• Various in-lake habitat restoration projects carried out jointly with the

Florida Fish and Wildlife Conservation Commission (FWC)

Given the amount of public dollars that are being spent on the restoration of Lake

Okeechobee, it is critical that we be able to track changes in the health of the ecosystem

both for 1) documentation of success, and 2) feedback to managers so that, if necessary,

management strategies can be modified. This “adaptive assessment” strategy mirrors the

approach being used in the CERP, and it includes long-term monitoring of a

comprehensive set of ecological performance measures in the lake. These performance

measures include submerged and emergent plants; plankton and macro algae; benthic

invertebrates; and fish. The program involves coordinated efforts between the District and

the FWC.

Preserving and enhancing critical habitats or areas to protect sensitive

communities and/or rare, threatened, or endangered species is another of the

environmental resource objectives for Lake Okeechobee. To fulfill this objective, the

District will continue restoration evaluation efforts under the Kissimmee River

Restoration Project and will coordinate with state and federal agencies to complete the

implementation of the South Florida Multispecies Recovery Plan in conjunction with the

CERP.

The long-term goal, under the CERP, is to have hydrologic conditions that include

fewer extreme high water level events in the lake and fewer damaging discharges to the

estuaries. In the interim, until the CERP is completed, we aim to minimize (to the extent

possible with the existing system) those impacts by careful use of the WSE schedule,

including adaptive management protocols that are driven by the needs of downstream

systems for fresh and salt water. Those needs have been identified by an ongoing program

of research, largely funded with SWIM dollars.

Flood Control and Water Supply

The flood control and water supply goals for the Lake Okeechobee SWIM

planning area are as follows:

• Ensure adequate flood protection to local communities and agriculture

around the lake

• Provide a balance between the competing objectives of flood

protection, water supply, and protection of the lake’s marsh zone and

downstream estuaries
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

vii

• Maintain an adequate quantity of water in Lake Okeechobee to

supplement downstream environmental needs and reasonablebeneficial use requirements

The District will fulfill two objectives to ensure adequate flood protection for the

Lake Okeechobee SWIM planning area. The first objective is to ensure design capacity of

the Central and Southern Florida Project is met. The second objective is to continue

reducing the Everglades Agricultural Area’s dependency on the lake and the water

conservation areas for flood control. The District will also assist local governments in

addressing flood protection in their comprehensive plans. 

As the local sponsor of the CERP and the Lake Okeechobee regulation schedule,

the District must provide a balance between the competing objectives of flood protection,

water supply, and protection of the lake’s marsh zone and downstream estuaries. To

maximize the extent to which this balance is achieved prior to completion of the CERP,

District and other agency scientists are working with operations specialists to identify

environmental “triggers” that can be used in the process of the WSE regulation schedule

for determining amounts of water to release from the lake under flood control conditions.

Information from the long-term ecological assessment program, described above, will be

supportive of this process, by providing information on ecological status of the lake at any

given time. As noted, information on declining lake health was a major driving force for

the Lake Okeechobee Managed Recession Operation in 2000. Results from ongoing

experimental research with the lake's submerged plant communities is also defining a

“stage envelope” necessary to support this important resource, much like the “salinity

envelope” that was recently developed for the St. Lucie Estuary to protect its biota. This

information will be core to the scientific input in support of water release triggers under

WSE.

The District must ensure Lake Okeechobee has an adequate quantity of water to

supplement downstream environmental, urban, and agricultural needs, and to recharge the

coastal aquifer. To determine the overall water supply demand that will be made on the

lake, the urban and agricultural water supply needs must be updated regularly and the

environmental water needs for the downstream environment, as well as the role of Lake

Okeechobee in meeting them, must be determined. Also, water supply demands need to be

reduced. The District has developed and is implementing programs and projects that will

reduce some of these demands including implementing and improving the Lake

Okeechobee Supply-Side Management Plan (Hall, 1991). 

Recreation

The District’s goal for recreation within the Lake Okeechobee SWIM planning

area is to attain recreational opportunities that meet public demand and are consistent with

other SWIM goals. The District is achieving this goal by managing Lake Okeechobee in

an effort to optimize opportunities for growth of native vegetation and enhance the health

of the lake’s fisheries and associated recreational opportunities such as sport fishing,

boating, ecotourism, and tournaments.
viii

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Navigation 

The Lake Okeechobee SWIM goals for navigation are to assist the USACE in

maintaining navigability for commercial and recreational uses within Lake Okeechobee,

the Lake Okeechobee Waterway, and recreational uses within the Kissimmee River. These

goals are achieved by maintaining water storage in Lake Okeechobee, maintaining

navigation locks and structures, and controlling aquatic weeds. With the restoration of the

Kissimmee River under way, special consideration must be given to the changing

navigation conditions that are occurring on the river with the removal of structures and

locks, and the resulting low water conditions.

Public Involvement and Intergovernmental Coordination

The public involvement and intergovernmental coordination goals for the Lake

Okeechobee SWIM planning area are to prepare and implement an effective public

awareness program and an effective intergovernmental awareness and involvement

program. These programs will encourage public participation in the Lake Okeechobee

SWIM planning process.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Table of Contents

ix

TABLE OF CONTENTS

Executive Summary i

List of Tables xi

List of Figures xiii

Acronyms and Abbreviations xvii

Chapter 1: Introduction, Basin Description, and Inventory 1

Introduction..............................................................................................................1

Basin Description and Inventory .............................................................................9

Boundaries and Subbasins .....................................................................................13

Point and Nonpoint Pollution Sources...................................................................15

Land Use ................................................................................................................18

Chapter 2: Watershed and Tributary Water Quality 21

Goals, Objectives, and Strategies ..........................................................................21

Phosphorus Loads and Targets by Basin ...............................................................24

Watershed Regulatory Programs ...........................................................................28

Comprehensive Everglades Restoration Plan ........................................................32

Current Management Programs .............................................................................33

Lake Okeechobee Protection Program and Permits ..............................................39

Class I, III, and IV Standards.................................................................................50

Chapter 3: In-Lake Water Quality 67

Goals, Objectives, and Strategies ..........................................................................67

Nutrients.................................................................................................................69

Water Quality Budgets...........................................................................................77

Models ...................................................................................................................82

Sediment Assessment ............................................................................................94

Class I Water Quality Parameters..........................................................................96
x

Table of Contents Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Chapter 4: Environmental Resources 101

Goals, Objectives, and Strategies ........................................................................105

Ecological Impacts of Water Level Variation .....................................................107

Ecological Impacts of Nutrients ..........................................................................119

Ecological Impacts of Exotic Species..................................................................126

Long-Term Ecological Assessment .....................................................................128

Lake Okeechobee’s Role in the Regional Ecosystem .........................................131

Chapter 5: Flood Control and Water Supply 141

Goals, Objectives, and Strategies ........................................................................141

Flood Control.......................................................................................................144

Water Supply .......................................................................................................148

Chapter 6: Recreation 151

Goals, Objectives, and Strategies ........................................................................152

Recreational Activities.........................................................................................152

Summary of Recreation Issues ............................................................................155

Ongoing Activities...............................................................................................156

Chapter 7: Navigation 161

Goals, Objectives, and Strategies ........................................................................161

Navigation Lock Structures .................................................................................162

Summary of Navigation Issues ............................................................................163

Chapter 8: Public Involvement and Intergovernmental Coordination167

Goals, Objectives, and Strategies ........................................................................168

Review of Current Projects..................................................................................170

Chapter 9: Budget 173

References 183

Glossary 195
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT List of Tables

xi

LIST OF TABLES

Table 1-1. County census totals and the percentage increase in the Lake Okeechobee 

SWIM planning area........................................................................................8

Table 1-2. Permits in the Lake Okeechobee planning area ............................................16

Table 1-3. Lake Okeechobee basin land use summary...................................................17

Table 2-1. Phosphorus (P) loads and targets by basin in the Lake Okeechobee watershed 

for 1990-1994 ................................................................................................26

Table 2-2. Phosphorus (P) loads and targets by basin in the Lake Okeechobee watershed 

for 1995-2000 ................................................................................................27

Table 2-3. Works of the District permits required for various land uses........................30

Table 2-4. The percentage of instances that Class I and III criteria was exceeded for 

tributary samples taken during inflow periods to Lake Okeechobeea...........53

Table 2-5. The percentage of instances that the Class I, III, and IV criteria was exceeded 

for tributary samples taken during periods of no inflow to Lake

Okeechobeeb..................................................................................................56

Table 2-6. Results of fecal and total coliform measurements taken in lake okeechobee 

tributaries and in-lake stations from October 1993 to September 1994cd.....63

Table 3-1. Water budget for Lake Okeechobee..............................................................78

Table 3-2. Lake Okeechobee phosphorus (P) budget in tons .........................................79

Table 3-3. Lake Okeechobee nitrogen (N) budget in tons..............................................81

Table 3-4. Percentage of instances that Class I criteria were exceeded within Lake 

Okeechobeea ..................................................................................................97

Table 4-1. List of the ecological performance measures associated with the Lake 

Okeechobee Conceptual Ecosystem Model, arranged according to the four 

major attributes............................................................................................131

Table 4-2. The federally-listed endangered and threatened species of South Florida..133

Table 6-1. Public recreation sites in the Lake Okeechobee SWIM planning area .......153

Table 7-1. Navigation lock structures on the federal project........................................163
xii

List of Tables Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT List of Figures

xiii

LIST OF FIGURES

Figure 1-1. Review process for the Lake Okeechobee SWIM plan updates ....................3

Figure 1-2. Lake Okeechobee SWIM planning area.........................................................5

Figure 1-3. Land use within the Lake Okeechobee SWIM planning area......................19

Figure 2-1. Comparison of the modified Vollenweider model total phosphorus 

predictions to observed data for 1973 to 1979 .............................................24

Figure 2-2. The drainage basins that contribute nutrient enriched runoff to Lake 

Okeechobee ..................................................................................................25

Figure 2-3. The tributary stations samples were collected from to determine compliance 

with Class I, III, and IV Standards...............................................................51

Figure 3-1. Lake Okeechobee annual average total phosphorus mean of stations L001 to 

L008 .............................................................................................................69

Figure 3-2. Annual phosphorus loads to Lake Okeechobee ...........................................70

Figure 3-3. Phosphorus sediment concentrations (in parts per thousand) within Lake 

Okeechobee in 1988 and 1998 .....................................................................70

Figure 3-4. Yearly mean phosphorus versus lake stage at the nearshore and open water 

stations for 1986 to 2000..............................................................................71

Figure 3-5. Phosphorus water column concentrations in Lake Okeechobee during 

October and November 1999 .......................................................................72

Figure 3-6. Annual nitrogen loads to Lake Okeechobee ................................................73

Figure 3-7. Annual average nitrogen concentrations in Lake Okeechobee ....................73

Figure 3-8. Average annual ratio of total phosphorus to total nitrogen..........................74

Figure 3-9. Average annual ratio of soluble nitrogen to phosphorus..............................74

Figure 3-10. Average annual chlorophyll a concentration in Lake Okeechobee..............75

Figure 3-11. Cumulative percent of chlorophyll a samples classified as a bloom condition 

(chlorophyll a > 40 ppb) at a) nearshore stations and b) open water

stations..........................................................................................................76

Figure 3-12. Changes in total phosphorus (P) and dissolved reactive phosphorus (DRP) 

amounts at over 100 locations in Lake Okeechobee between 1988

and 1998. ......................................................................................................80

Figure 3-13. Actual and target loads of phosphorus to Lake Okeechobee a) annually and 

b) as a five-year rolling average...................................................................82

Figure 3-14. Five-year rolling average of a) tons of phosphorus above target and b) inflow 

to Lake Okeechobee.....................................................................................83

Figure 3-15. Five-year rolling average of phosphorus concentrations in inflows to Lake 

Okeechobee ..................................................................................................84
xiv

List of Figures Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Figure 3-16. Comparison of the modified Vollenweider model total phosphorus 

predictions to observed data for 1973 to 2000 .............................................84

Figure 3-17. Comparison of a simple mass balance model total phosphorus predictions to 

observed data for 1973 to 2000....................................................................85

Figure 3-18. Comparison of total phosphorus predictions from a simple mass balance 

model, which includes a submerged aquatic vegetation component, to 

observed data for 1973 to 2000....................................................................86

Figure 4. A diagram of the Lake Okeechobee Water Quality Model..........................87

Figure 5. Simulations of the Lake Okeechobee Water Quality Model under pre-1910 

conditions to determine the maximum phosphorus inflow concentration that 

can be absorbed by the sediments without increasing phosphorus 

concentrations in the water column..............................................................88

Figure 6. Predictions of in-lake phosphorus concentrations under different inflow

loads .............................................................................................................89

Figure 3-1. Lake Okeechobee hydrodynamic sediment transport model predictions of 

wave height on January 21, 2000.................................................................91

Figure 3-2. Lake Okeechobee hydrodynamic sediment transport model predictions of 

surface currents and sediment concentrations on January 21, 2000 ............92

Figure 3-3. Lake Okeechobee hydrodynamic sediment transport model predictions of 

bottom currents and sediment concentrations on January 21, 2000.............93

Figure 3-4. Locations within Lake Okeechobee where DDD p,p’ was detected in samples 

taken in 1998 ................................................................................................94

Figure 3-5. Locations within Lake Okeechobee where DDE p,p’ was detected in samples 

taken in 1998 ................................................................................................95

Figure 4-1. Hydrologic and morphological conditions of Lake Okeechobee before human 

impacts (PAST), during the last 40 years (PRESENT), and anticipated when 

the CERP is completed (FUTURE) ...........................................................102

Figure 4-2. Maps of Lake Okeechobee showing the area of littoral zone that is inundated 

with water under a variety of lake stage elevations ...................................108

Figure 4-3. Areas of Lake Okeechobee that support distinct primary producer 

assemblages, determined largely as a function of water depth ..................109

Figure 5. Four dominant vegetation communities in Lake Okeechobee’s littoral zone 

based on 1996 aerial photographs ..............................................................110

Figure 4-1. Plot of monthly averaged water levels in Lake Okeechobee from 1973 to 

2000............................................................................................................111

Figure 5. The spatial extent of bulrush along a 14-kilometer region of the littoral zone 

in 1992 versus 1999....................................................................................112

Figure 6. Results of a yearly program (in this case the summer of 2000) that maps the 

distribution of submerged aquatic vegetation in Lake Okeechobee. .........113
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT List of Figures

xv

Figure 7. Total amounts of biomass accrual during a controlled experiment that 

exposed torpedograss to various water depths: a. biomass accrual for plant 

fragments attached to the sediment surface, and b. biomass accrual of 

established plants subjected to the same range of depth treatments ..........117

Figure 8. Total phosphorus concentrations measured during a controlled mesocosm 

experiment in the littoral zone after adding various amounts of phosphorus 

over a 28-day period...................................................................................122

Figure 9. A Conceptual model of algal bloom dynamics in shallow eutrophic

lakes............................................................................................................124

Figure 10. An ecosystem conceptual model for Lake Okeechobee, developed for the 

adaptive assessment process of the CERP. ................................................130

Figure 5-1. The Run 25 Lake Okeechobee regulation schedule ...................................146

Figure 5-2. The WSE regulation schedule....................................................................148

Figure 6-1. The Kissimmee River section of the Florida National Scenic Trail ..........157

Figure 6-2. The Lake Okeechobee section of the Florida National Scenic Trail..........158

Figure 7-1. Navigation of the Kissimmee River during Phase I construction of the 

Kissimmee River Restoration Project ........................................................165
xvi

List of Figures Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Acronyms and Abbreviations

xvii

ACRONYMS AND ABBREVIATIONS

oC degrees Celsius

ASR aquifer storage and recovery

BAT best available technologies

BMP best management practice

C&SF Central and Southern Florida

CaCO3 calcium carbonate

CDS continuous deflective separation

CERP Comprehensive Everglades Restoration Plan

cfs cubic feet per second

DDD, p,p’ dichlor diphenyl dichlor

DDE, p,p’ dichlor diphenyl ethylene

DDT dichlor diphenyl trichlor

District South Florida Water Management District

EAA Everglades Agricultural Area

EAAMOD Everglades Agricultural Area Model

EPD Everglades Protection District

F.A.C. Florida Administrative Code

FDACS Florida Department of Agriculture and Consumer Services

FDCA Florida Department of Community Affairs

FDEP Florida Department of Environmental Protection

FDOT Florida Department of Transportation

FHANTM Field Hydrologic and Nutrient Transport Model

FTA Florida Trail Association

F.S. Florida Statutes

FWC Florida Fish and Wildlife Conservation Commission

GIS geographic information system

ha hectare

HIA high-intensity use area

IFAS Institute of Food and Agricultural Sciences

kg kilogram
xviii

Acronyms and Abbreviations Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

km kilometer

LEC Lower East Coast

LOADSS Lake Okeechobee Agricultural Decision Support System

LOHSTM Lake Okeechobee Hydrodynamic and Sediment Transport Model

LOPA Lake Okeechobee Protection Act

MFL minimum flows and levels

mgd million gallons per day

mg/l milligrams per liter

NGVD National Geodetic Vertical Datum

NPDES National Pollution Discharge Elimination System

NRCS Natural Resources Conservation Service

PAM permit addendum modification

PCA phosphorus control alternatives

PLRG pollution load reduction goals

ppb parts per billion

ppm parts per million

ppt parts per thousand

RCRC Resource Conservation and Recovery Act

Restudy Central and Southern Florida Project Comprehensive Review Study

SFWMD South Florida Water Management District

SOR Save Our Rivers

STA stormwater treatment area

SWIM Surface Water Improvement and Management

TMDL total maximum daily loads

TST tributary sediment trap

μg/l micrograms per liter

USACE United States Army Corps of Engineers

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

USGS United States Geological Survey

WCA water conservation area

WMA wildlife management area

WOD Works of the District
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Acronyms and Abbreviations

xix

WSE Water Supply and Environmental
xx

Acronyms and Abbreviations Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

i

EXECUTIVE SUMMARY

This document provides an overview of the activities and accomplishments that

have been directed towards the restoration of Lake Okeechobee since adoption of the

Surface Water Improvement and Management (SWIM) Plan - Update for Lake

Okeechobee (SFWMD, 1997a). This update also describes the current and proposed

activities through 2000.

Lake Okeechobee and its watershed are key components of South Florida's

Kissimmee-Okeechobee-Everglades ecosystem, which extends from the headwaters of the

Kissimmee River in the north to Florida Bay in the south. The lake provides a number of

ecological and societal values. It is home to one of the nation's prized bass and speckled

perch fisheries, as well as an economically important commercial fishery. At the same

time, it provides habitat for a wide variety of wading birds, migratory waterfowl, and the

federally-endangered Everglades Snail Kite. Lake Okeechobee is also a source of drinking

water for cities and towns along the lake, and can be a backup water supply for the

communities of the lower east coast of Florida. The lake also supplies irrigation water for

the expansive Everglades Agricultural Area, and is a critical supplemental water supply

for the Everglades. 

The Lake Okeechobee SWIM planning area has been defined as the major basins

that are direct tributaries to the lake, including those basins that are hydrologically

upstream and/or from which water is presently released or pumped into the lake on a

regular basis. Although the Lake Okeechobee SWIM planning area generally excludes

basins that are hydrologically downstream and act primarily as receiving basins for water

supply (Caloosahatchee and St. Lucie River), the conveyance of flood control discharges

and the resulting potential associated environmental impacts make these basins a

component of this plan.

The SWIM Act (Section 373.451-.459, Florida Statutes, [F.S.]), adopted by the

Florida Legislature in 1987, requires water management districts, in conjunction with

other state agencies and local governments, to prepare SWIM Plans for priority water

bodies, including Lake Okeechobee. The SWIM Act requires that the plans describe

strategies and potential programs for restoring or protecting the water body to Class III

standards or better for recreation, propagation and maintenance of a healthy, wellbalanced population of fish and wildlife. The plan must include a listing of studies that are

being or have been prepared for the water body; a description of the research and

feasibility studies that will be performed to determine the particular strategy or strategies

to restore or protect the water body; a description of the measures needed to manage and

maintain the water body once it has been restored and to prevent future degradation; a

schedule for restoration and protection of the water body; and an estimate of the funding

needed to carry out the restoration or protection strategies. 

The SWIM Act sets forth a specific process for the preparation, review, and

approval of SWIM Plans. It requires the South Florida Water Management District
ii

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

(SFWMD or District) to develop SWIM plans in cooperation with the Florida Department

of Environmental Protection (FDEP) and other agencies. Pursuant to Section 373.455,

F.S., the District submits a draft plan to the FDEP and other agencies. The FDEP reviews

the cost of the SWIM Plan, funding availability, and the likelihood that the plan will

significantly improve or protect water quality and associated natural resources. If the

FDEP determines that a SWIM plan does not meet minimum plan requirements, it shall

recommend to the District modifications or additions to the plan pursuant to Section

373.456(1), F.S. Other agencies review the plan for its effects on the resources within their

respective jurisdictions and make recommendations.

SWIM plans must be consistent with state water policy as outlined in Chapter

62-40, Florida Administrative Code (F.A.C), and to otherwise provide guidance to the

FDEP and the water management districts in the development and preparation of water

management programs, rules, and plans. Chapter 62-40.432 requires the water

management districts to develop pollution load reduction goals (PLRGs) for SWIM water

bodies. The PLRG developed for Lake Okeechobee was a 40 percent reduction in

phosphorus loading from the watershed, based on the conditions that existed from 1973 to

1979 (Federico et al., 1981), with an expected downstream benefit of maintaining the

trophic state and the biological integrity of the lake. To assist in achieving this goal, total

phosphorus concentrations in runoff leaving land parcels were limited by the Lake

Okeechobee Works of the District (WOD) Rule. The total phosphorus concentration

targets range from 0.18 to 1.2 milligrams per liter (mg/l). 

The federal Clean Water Act (Title 33, Chapter 26, Subchapter III, Section

1313(d)), requires that each state develop total maximum daily loads (TMDLs) for each

water-quality-limited segment reported. A TMDL reflects the total pollutant loading, from

all contributing sources, that a water segment can receive without exceeding its capacity to

assimilate the pollutant loads and still meet applicable water quality standards. The

phosphorus TMDL established for Lake Okeechobee is 140 metric tons (based on a 5-year

rolling average) to achieve an in-lake target phosphorus concentration of 40 parts per

billion in the pelagic zone of the lake (FDEP 2000). The restoration target was determined

using computer models developed based on past research performed by the SFWMD

using SWIM funds. This target will support a healthy lake system, restore the designated

uses of Lake Okeechobee, and allow the lake to meet applicable water quality standards.

The 1997 SWIM plan update reported that phosphorus load reductions had

occurred, but the 40 percent reduction in loads was not achieved. It recommended the

implementation of programs and projects to improve the lake and watershed water quality

situation. The status of these programs and projects are summarized in this update. Even

with the implementation of these programs and projects, nutrient loads to Lake

Okeechobee have not decreased significantly. The highest inflow phosphorus

concentrations continue to be found in the S-154 and S-191 basins where dairies are

abundant and the majority of the out-of-compliance WOD sites are found. Phosphorus

loading is far in excess of the amount considered for a healthy Lake Okeechobee

ecosystem and current model data predict that it may take decades before in-lake

phosphorus concentrations will respond to reduced external loads. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

iii

Several major accomplishments have been made in the restoration effort since the

publication of the last SWIM plan update in 1997. One of the most important restoration

actions was the Lake Okeechobee Managed Recession Operation. During six years prior

to 2000, high water levels in the lake (associated with a prolonged wet period) destroyed

nearly all of the lake’s submerged plant beds and caused extremely poor water quality. The

lake’s prize bass fishery was on the brink of ecological collapse. A period of low water

levels (less than 13 feet, lasting for at least 8 weeks) was required to allow recovery of the

biological communities. In April and May 2000, approximately one foot of water was

released from Lake Okeechobee. Coincident with that, another one foot of water left the

lake for normal water supply deliveries to agriculture and other uses, and one foot left the

lake by direct evaporation into the atmosphere. Taken together the lake dropped by

approximately 3 feet between April and July. As a result of the low water levels, Lake

Okeechobee quickly recovered from its previously stressed condition. Over 45,000 acres

of new submerged plant beds grew during the summer and fall and the lake’s nearshore

bulrush community (prime bass habitat) expanded. The low water levels also allowed

coordinating state and federal agencies to carry out controlled fires that have killed tens of

thousands of acres of exotic plants that were taking over valuable wildlife habitat.

A new regulation schedule for the lake was formally adopted by the United States

Army Corps of Engineers (USACE) in July 2000. This schedule, the Water Supply and

Environment (WSE) schedule uses climate forecasting to determine the volumes of water

to release from the lake under flood control circumstances, and has the potential to provide

environmental benefits for the lake and downstream systems while not sacrificing water

supply. The extent of the benefits will depend in part on specific adaptive management

protocols that are presently being developed by the District.

Restoration efforts for Lake Okeechobee were recently advanced with the passing

of the Water Resources Development Act of 2000 (WRDA 2000). The WRDA 2000

authorizes the Comprehensive Everglades Restoration Plan (CERP). The CERP is

expected to have substantial effects on the lake's hydropattern. It is expected to reduce the

number of extreme high and low events and increase the occurrence of ecologically

beneficial spring recession events. The act also authorizes projects that will reduce

nutrient loads to the lake. These components include regional stormwater treatment areas,

reclamation of isolated wetlands, and regional water storage facilities, such as aquifer

storage and recovery wells and reservoirs. 

The enactment of the Lake Okeechobee Protection Act (LOPA) (Section 373.4595,

F.S.) in 2000 also advanced restoration efforts. This act provides an umbrella that captures

many lake restoration efforts. It will significantly enhance mandates restoring and

protecting the lake using a phased, watershed-based approach to reduce phosphorus

loading to the lake and downstream receiving waters. Fulfilling this act will require a great

deal of cooperation among government agencies and the public. To facilitate the execution

of the Lake Okeechobee Protection Plan, an interagency committee was formed with

individuals from the FDEP, the Florida Department of Agriculture and Consumer

Services, and the SFWMD. The agencies are currently planning and implementing

numerous management activities in the watershed to reduce phosphorus loading to the

lake. These include the construction of surface water storage reservoirs and stormwater
iv

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

treatment areas; the restoration of isolated wetlands the development and implementation

of best management practices to control nonpoint sources of pollution; the continuation of

research and monitoring to ensure the projects are designed and implemented to optimize

success; the removal of phosphorus-rich sediment from tributaries to Lake Okeechobee;

and the implementation of a sediment management feasibility study to determine whether

or not it is feasible to reduce internal loading from the lake sediments. More current

information regarding the status of the LOPA activities can be found in the Lake

Okeechobee Protection Program Annual Report to the Legislature (SFWMD, 2001a,

2001b).

This update of the Lake Okeechobee SWIM Plan has set goals for the Lake

Okeechobee SWIM planning area in the areas of water quality; environmental resources;

flood protection and water supply; recreation, navigation, and public involvement; and

intergovernmental coordination. Objectives have been developed to accomplish these

goals. Programs and projects are being developed and will be implemented to achieve

these objectives. The goals and objectives, as well as some of the programs and projects

are summarized below.

Phosphorus Load Reduction in the Tributaries

In an effort to meet the proposed TMDL target and in-lake phosphorus

concentration of 40 parts per billion and achieve a phosphorus load of 140 tons per year,

over-target phosphorus loading must continue to be reduced. The expanded WOD

program, the new Lake Okeechobee Protection Plan, and other new programs and projects

are being implemented to achieve the inflow target are summarized in Chapter 2 and

itemized below:

• Best available technologies to significantly reduce the export of

phosphorus from dairy operations into tributaries and Lake

Okeechobee 

• Reservoir-assisted stormwater treatment areas

• Critical restoration projects

• Isolated wetlands restoration

• Natural resource economic analysis of a wide range of phosphorus

control alternatives, using full-cost accounting practices

• Sediment removal technologies in the tributaries

• Research and modeling efforts to determine source of loads and

methods to reduce them
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

v

Reduction of Nonnutrient Pollutant Loads

To reduce the nonnutrient pollutant loads, Class I Water Quality Standards (potable

water supplies) must be achieved within Lake Okeechobee and Class III Water Quality

Standards must be achieved within the lake tributaries. To achieve the in-lake reduction,

the following initiatives are planned, and are detailed in Chapter 3:

• The District will continue monitoring to ensure the water quality

requirements of the Lake Okeechobee Operating Permit are fulfilled. 

• Both the District’s monthly water quality monitoring program and its

organics and pesticide monitoring program will be modified to focus

resources on parameters that are known to have potential sources in the

watershed. 

• The applicability of additional management strategies for canals and

marinas will be determined. 

Reduction of In-Lake Nutrients

Due to an overabundance of nutrients in Lake Okeechobee, a process known as

eutrophication, large algal blooms have periodically formed in Lake Okeechobee. Algal

blooms are cause for concern because they may contain toxins that affect fish and wildlife;

they create taste and odor problems for drinking water; and when they die off and degrade,

oxygen is removed from the water column and waste products (e.g., ammonia)

accumulate, causing fish kills and the death of other aquatic life. Lake users also find these

blooms unsightly, reducing their enjoyment of the resource. 

In-lake phosphorus must be reduced to a attain a more natural, lower frequency of

potentially harmful algal blooms. To achieve this goal the SFWMD will do the following:

• Evaluate the feasibility of removing phosphorus-rich sediments from

the lake

• Evaluate the feasibility of chemical treatment of lake sediments to

“inactivate” the phosphorus

• Identify lake stage management options that would facilitate greater

coverage of submerged plants, and thus, greater phosphorus uptake

• Complete research and model development necessary to guide the most

effective phosphorus reduction efforts, as called for in the Lake

Okeechobee Protection Plan

Environmental Resources

Another goal of the Lake Okeechobee SWIM Program is to protect and enhance

the lake’s environmental resources. These resources include biological diversity,

ecological functions, and the distribution and abundance of native plants and animals. The

following objectives have been set to fulfill the environmental resource goal:
vi

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

• Identification of a range of water levels that will allow for a healthy

community of submerged and emergent native plants and the

communities of fish and wildlife that they support

• Identification and implementation of effective programs to control

exotic plants, including melaleuca and torpedograss

• Various in-lake habitat restoration projects carried out jointly with the

Florida Fish and Wildlife Conservation Commission (FWC)

Given the amount of public dollars that are being spent on the restoration of Lake

Okeechobee, it is critical that we be able to track changes in the health of the ecosystem

both for 1) documentation of success, and 2) feedback to managers so that, if necessary,

management strategies can be modified. This “adaptive assessment” strategy mirrors the

approach being used in the CERP, and it includes long-term monitoring of a

comprehensive set of ecological performance measures in the lake. These performance

measures include submerged and emergent plants; plankton and macro algae; benthic

invertebrates; and fish. The program involves coordinated efforts between the District and

the FWC.

Preserving and enhancing critical habitats or areas to protect sensitive

communities and/or rare, threatened, or endangered species is another of the

environmental resource objectives for Lake Okeechobee. To fulfill this objective, the

District will continue restoration evaluation efforts under the Kissimmee River

Restoration Project and will coordinate with state and federal agencies to complete the

implementation of the South Florida Multispecies Recovery Plan in conjunction with the

CERP.

The long-term goal, under the CERP, is to have hydrologic conditions that include

fewer extreme high water level events in the lake and fewer damaging discharges to the

estuaries. In the interim, until the CERP is completed, we aim to minimize (to the extent

possible with the existing system) those impacts by careful use of the WSE schedule,

including adaptive management protocols that are driven by the needs of downstream

systems for fresh and salt water. Those needs have been identified by an ongoing program

of research, largely funded with SWIM dollars.

Flood Control and Water Supply

The flood control and water supply goals for the Lake Okeechobee SWIM

planning area are as follows:

• Ensure adequate flood protection to local communities and agriculture

around the lake

• Provide a balance between the competing objectives of flood

protection, water supply, and protection of the lake’s marsh zone and

downstream estuaries
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Executive Summary

vii

• Maintain an adequate quantity of water in Lake Okeechobee to

supplement downstream environmental needs and reasonablebeneficial use requirements

The District will fulfill two objectives to ensure adequate flood protection for the

Lake Okeechobee SWIM planning area. The first objective is to ensure design capacity of

the Central and Southern Florida Project is met. The second objective is to continue

reducing the Everglades Agricultural Area’s dependency on the lake and the water

conservation areas for flood control. The District will also assist local governments in

addressing flood protection in their comprehensive plans. 

As the local sponsor of the CERP and the Lake Okeechobee regulation schedule,

the District must provide a balance between the competing objectives of flood protection,

water supply, and protection of the lake’s marsh zone and downstream estuaries. To

maximize the extent to which this balance is achieved prior to completion of the CERP,

District and other agency scientists are working with operations specialists to identify

environmental “triggers” that can be used in the process of the WSE regulation schedule

for determining amounts of water to release from the lake under flood control conditions.

Information from the long-term ecological assessment program, described above, will be

supportive of this process, by providing information on ecological status of the lake at any

given time. As noted, information on declining lake health was a major driving force for

the Lake Okeechobee Managed Recession Operation in 2000. Results from ongoing

experimental research with the lake's submerged plant communities is also defining a

“stage envelope” necessary to support this important resource, much like the “salinity

envelope” that was recently developed for the St. Lucie Estuary to protect its biota. This

information will be core to the scientific input in support of water release triggers under

WSE.

The District must ensure Lake Okeechobee has an adequate quantity of water to

supplement downstream environmental, urban, and agricultural needs, and to recharge the

coastal aquifer. To determine the overall water supply demand that will be made on the

lake, the urban and agricultural water supply needs must be updated regularly and the

environmental water needs for the downstream environment, as well as the role of Lake

Okeechobee in meeting them, must be determined. Also, water supply demands need to be

reduced. The District has developed and is implementing programs and projects that will

reduce some of these demands including implementing and improving the Lake

Okeechobee Supply-Side Management Plan (Hall, 1991). 

Recreation

The District’s goal for recreation within the Lake Okeechobee SWIM planning

area is to attain recreational opportunities that meet public demand and are consistent with

other SWIM goals. The District is achieving this goal by managing Lake Okeechobee in

an effort to optimize opportunities for growth of native vegetation and enhance the health

of the lake’s fisheries and associated recreational opportunities such as sport fishing,

boating, ecotourism, and tournaments.
viii

Executive Summary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Navigation 

The Lake Okeechobee SWIM goals for navigation are to assist the USACE in

maintaining navigability for commercial and recreational uses within Lake Okeechobee,

the Lake Okeechobee Waterway, and recreational uses within the Kissimmee River. These

goals are achieved by maintaining water storage in Lake Okeechobee, maintaining

navigation locks and structures, and controlling aquatic weeds. With the restoration of the

Kissimmee River under way, special consideration must be given to the changing

navigation conditions that are occurring on the river with the removal of structures and

locks, and the resulting low water conditions.

Public Involvement and Intergovernmental Coordination

The public involvement and intergovernmental coordination goals for the Lake

Okeechobee SWIM planning area are to prepare and implement an effective public

awareness program and an effective intergovernmental awareness and involvement

program. These programs will encourage public participation in the Lake Okeechobee

SWIM planning process.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

1

Chapter 1

INTRODUCTION, BASIN DESCRIPTION, AND 

INVENTORY

A. INTRODUCTION

This update provides an overview of the activities and accomplishments achieved

since adoption of the Surface Water Improvement and Management (SWIM) Plan - Update

for Lake Okeechobee (SFWMD, 1997a) on August 8, 1997. The highlights of any projects

completed since the 1997 SWIM plan update are provided, as well as current and

proposed activities for the short- and long-term.

The structure of this plan includes the issues, goals, objectives, and strategies that

provide the framework around which the South Florida Water Management District

(SFWMD or District) initiates or continues programs to protect the lake. The goals

provide the general direction for developing cohesive management strategies, the

objectives describe more specific approaches towards achieving a particular goal, and the

strategies provide the detail needed to accomplish an objective. For each strategy, progress

and projects are being developed and implemented. Each chapter is developed with three

components: 1) the issues and the strategies developed to address these issues; 2) the

present condition as it exists in the watershed or the lake; and 3) a summary of the

progress to date on each program or project. 

A1. SWIM Plan Requirements and Planning Process

A1a. Plan Requirements

The SWIM Act (Section 373.451-.459, Florida Statutes [F.S.]) was adopted by the

Florida Legislature in 1987. This law requires that water management districts, in

conjunction with other state agencies and local governments, prepare SWIM plans for

priority water bodies as identified by the SWIM Act. The 1987 legislation required the

District to develop plans for Lake Okeechobee, the Indian River Lagoon, and Biscayne

Bay. The SWIM Act required that the plans demonstrate strategies and programs to

address the following central concerns:

• Point and nonpoint source pollution (Section 373.451(4)(a), Florida

Statutes [F.S.])

• Destruction of natural systems (Section 373.451(4)(b), F.S.)

• Correction and prevention of surface water problems (Section

373.451(5), F.S.)

• Research for better management of surface waters and associated

natural systems (Section 373.451(7), F.S.)
2

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

SWIM legislation also specifies the minimum requirements for the plans contents

(Section 373.453(2) F.S.). These requirements are described in the Surface Water

Improvement and Management Review Procedures Manual (FDER, 1990). 

The required descriptions of the water body, point and nonpoint sources of

pollution, land uses, and agency jurisdictions are provided later in this chapter and in the

appendices. The remaining requirements that describe strategies for restoring and

protecting water quality, including the current condition and future plans for restoring the

water body, are presented within the individual plan chapters (Chapters 2 through 8).

The Florida Department of Environmental Protection (FDEP) is required by

Section 373.456, F.S., to review each SWIM plan for consistency with state water policy

as outlined in Chapter 62-40, Florida Administrative Code (F.A.C). Chapter 62-40 is

intended to clarify state water policy as expressed in Chapters 187, 373, and 403, F.S., and

to otherwise provide guidance to the FDEP and the water management districts in the

development and preparation of water management programs, rules, and plans. The intent

of Chapter 62-40 is as follows: “The waters of the state are among its basic resources.

Such waters should be managed to conserve and protect natural resources and scenic

beauty and to realize the full beneficial use of the resource.” Therefore, Chapter 62-40

provides the basis for the FDEP's review of all water management district SWIM planning

documents with respect to meeting state water policy requirements. SWIM legislation is

provided in Appendix A of this plan.

Chapter 62-40.432 requires the water management districts to develop pollution

load reduction goals (PLRGs) for SWIM water bodies. PLRGs are defined as targeted

reductions in pollutant loadings to a water body needed to achieve watershed management

goals. Watershed management goals are defined as the goals that encompass any one or all

of the major water management district responsibilities: flood protection, water supply,

water quality, and environmental system protection and enhancement. The goals provide

the general direction for developing cohesive strategies to manage water resources within

a drainage basin, subbasin, or segment of a drainage basin or subbasin.

The PLRG developed for Lake Okeechobee is a 40 percent reduction in

phosphorus loading from the watershed, based on the conditions that existed from 1973 to

1979 (Federico et al., 1981). This percent reduction was expected to maintain the trophic

state and the biological integrity of the lake. Early reports clearly indicated that

phosphorus was a major contributor to accelerated eutrophication of Lake Okeechobee

(Davis and Marshall, 1975; Federico et al., 1981; Joyner, 1972; Kissimmee-Okeechobee

Basin Report, 1972). Eutrophication was and remains a clear threat to the health of this

lake, and is the focus of the majority of projects designed to improve the condition of the

lake. Progress towards achieving the PLRG is evaluated by comparing a target five-year

rolling average of phosphorus loading to the lake, as specified in Federico et al. (1981) to

the actual calculated loading from the discharge structures. In 2001, a phosphorus total

maximum daily load (TMDL) of 140 tons per year was established for the lake in an effort

to achieve the in-lake phosphorus concentration of 40 micrograms per liter (μg/l)

(described in more detail in Chapters 2 and 3). The TMDL is more stringent than the
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

3

PLRG developed in 1981 (Federico et al., 1981), and it incorporates the recognition of the

capacity of the lake to continue to assimilate phosphorus.

A1b. Review and Approval Process

The SWIM Act sets forth a specific process for the preparation, review, and

approval of SWIM Plans (Figures 1-1). It requires the District to develop SWIM plans in

cooperation with the FDEP and other agencies. The review process is initiated when the

District submits the draft plan to the FDEP and other agencies for a 45-day agency review

period (Section 373.455, F.S.). Other agencies review the plan for its effects on the

resources within their respective jurisdictions and make recommendations. These agencies

include the FDEP, the Florida Department of Agriculture and Consumer Services

(FDACS), the Florida Department of Community Affairs (FDCA), Florida Fish and

Wildlife Conservation Service (FWC), and local governments. After the 45- day review

period, the District has 15 days to prepare a response and present the agencies positions to

the Governing Board of the District.

Review criteria include cost, funding availability, and the likelihood that the plan

will significantly improve or protect water quality and associated natural resources. If the

FDEP determines that a SWIM plan does not meet minimum plan requirements, the FDEP

shall recommend to the District modifications or additions to the plan pursuant to Section

373.456(1), F.S.

The first draft of the 2002 Lake Okeechobee SWIM Plan Update was presented to

the District's Governing Board on _________, 2002. At this meeting, the Governing

Board was presented an overview of the plan and gave approval to initiate the public

participation process. On ________ and ___________, public meetings were held in

 

Public Meetings

Okeechobee 

Clewiston

Governing Board 

Workshop 

Discuss First Draft of 

Plan 

Final Draft Submitted for 

373.455, F.S., Review 

(45 Days) 

FDEP, FDACS, FDCA, FWC, 

Local Governments 

SFWMD Review of Agency Comments

Final Draft 

Approved by 

SFWMD 

Governing Board

Final Draft SWIM Plan 

Adopted by SFWMD 

Governing Board

Approved Final Draft 

373.456, F.S., 

Consistency Review 

(30 days) 

Figure 1-1. Review process for the Lake Okeechobee SWIM plan updates
4

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Okeechobee and Clewiston, respectively, to discuss the update. Comments received as a

result of these meetings are assembled in the appendices. 

A final draft was approved by the Governing Board on ___________. The plan

was then transmitted to the FDEP to ensure consistency with the State Water Policy and

the State Comprehensive Plan, pursuant to Section 373.456, F.S.

The FDEP found the plan update consistent with the State Water Policy (Chapter

62-40, F.A.C.) and the State Comprehensive Plan (Chapter 187, F.S.) on ___________.

The approved plan became effective on _________, with public notice in the Florida

Administrative Weekly.

A2. Relationship to Other Planning Efforts

Lake Okeechobee is a key component of South Florida's Kissimmee-OkeechobeeEverglades surface water hydrologic and ecological system. The system begins in Central

Florida near Orlando, extends southward through the Kissimmee Chain of Lakes, the

Kissimmee River, Lake Okeechobee, and continues southward through the Everglades

into Florida Bay. In addition, through man-made canals, Lake Okeechobee is connected to

the St. Lucie and Caloosahatchee estuaries. The SWIM Act Priority Water Body List

identified one portion of this system, Lake Okeechobee, as an area of immediate high

priority. The District realized that this piece of the Kissimmee-Okeechobee-Everglades

system could not be looked at in isolation from the rest of the system, but did not believe

that the planning and research resources of the District were adequate to address this entire

system within a single SWIM plan. The Kissimmee-Okeechobee-Everglades area was

divided, based on hydrologic features, into SWIM planning areas.

Boundaries of SWIM planning areas were determined by taking the receiving

water body (in this case Lake Okeechobee) and including the tributary basins that deliver

water into the lake. Thus, the Lake Okeechobee SWIM planning area (Figure 1-2)

includes such major inflow basins as the Kissimmee River, canals downstream from Lake

Istokpoga, Fisheating Creek, various basins that pump water directly into the lake for

routine drainage purposes, the St. Lucie Canal, and the Taylor Creek/Nubbin Slough

basin. 

The basin boundaries of the Lake Okeechobee SWIM planning area overlap with

those of the Everglades Protection Area and the Indian River Lagoon. This overlap occurs

for a variety of reasons, primarily because Lake Okeechobee is a major source of inflow

water for the Everglades region and, when the C-44 Canal is below 14.5 feet, for the

Indian River Lagoon. Water use demands and flood protection requirements within the

Everglades influence water supply, water quality, and lake water level issues within the

Lake Okeechobee SWIM planning area. 

This plan update includes descriptions of two projects associated with the

Everglades Forever Act. The first project required the Chapter 298 Special Drainage

Districts discharging into Lake Okeechobee to complete conveyance system modifications
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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Figure 1-2. Lake Okeechobee SWIM planning area
6

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

sufficient to redirect 80 percent of their runoff to the District's primary canal system for

subsequent treatment in stormwater treatment areas (STAs) (Section 373.4592(4)(a)8,

F.S.). The second project required the FDEP and the SFWMD to request the United States

Army Corps of Engineers (USACE) to evaluate Lake Okeechobee regulatory releases

(Section 373.4592(4)(b)4, F.S.). This evaluation resulted in the adoption of the Water

Supply and Environmental (WSE) regulation schedule. This schedule facilitates the

releases of water into the Everglades Protection Area in order to further improve lake

hydroperiod restoration and reduce harmful discharges to the estuaries and wasteful

discharges to tide.

It is critical to the SWIM process that the related plans are consistent and that these

plans be coordinated with other SWIM planning efforts currently under way in South

Florida (e.g., Indian River Lagoon and Biscayne Bay SWIM Plans, Kissimmee River

Restoration, regional water supply plans, and the Everglades Program).

A3. Agency Jurisdictions and Institutional Authorizations

A3a. Federal

Federal jurisdiction of Lake Okeechobee involves the regulatory responsibilities of

the USACE, the United States Environmental Protection Agency (USEPA), and the

United States Fish and Wildlife Service (USFWS). The USACE is responsible for

prescribing the operational criteria and regulation schedules for the Central and Southern

Florida (C&SF) Project. Its primary regulatory functions include operation and

maintenance of the levee and major outlet works, dredge and fill permitting, maintaining

navigable United States waters, cleanup of pollution spills, and the protection of

endangered species. The USEPA is responsible for protection of the environmental

resources of Lake Okeechobee. The USEPA has oversight responsibility for Florida’s

National Pollutant Discharge Elimination System (NPDES) and Resource Conservation

and Recovery Act (RCRC) (also known as the Solid Waste Disposal Act). The USFWS is

responsible for conserving, protecting, and enhancing fish and wildlife communities and

their habitats in Lake Okeechobee. Several other federal agencies also contribute to

management and data collection in Lake Okeechobee. These include the United States

Geological Survey (USGS), the United States Forest Service, the National Weather

Service, the United States Department of Agriculture, and the Department of the Interior.

A3b. Comprehensive Everglades Restoration Plan

The USACE and the SFWMD conducted a feasibility review of the C&SF Project

and presented their recommendations in the Central and Southern Florida Project

Comprehensive Review Study, Final Integrated Feasibility Report and Programmatic

Environmental Impact Statement (USACE and SFWMD, 1999). These recommendations

will be implemented through the Comprehensive Everglades Restoration Plan (CERP).

The primary purpose of the CERP is the restoration of South Florida’s ecosystem

including the Everglades. It also provides for the other water-related needs of the region

including urban and agricultural water supply and flood protection. The CERP will
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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accomplish this by storing most of the water currently discharged to the ocean, improving

the quality of water discharged into the ecosystem, and removing over 240 miles of

internal levees in the Everglades. Most CERP projects will be implemented by 2020, but

several will not be completed until 2050.

The basic approach of CERP is to capture most of the 1.7 billion gallons of water

per day that on average flows to the ocean. The water will be stored in surface and

underground storage areas until it is needed to supply the natural system as well as urban

and agricultural needs. The timing and distribution of water flows to the ecosystem will be

modified to more closely approximate predrainage patterns. Wetlands-based STAs will be

built to improve quality discharges to the natural system. Seepage management will be

initiated to reduce unwanted water loss. Wastewater will be reclaimed and reused. Flows

will be redirected westward to the Water Conservation Areas (WCAs), Everglades

National Park, and northeastern Shark River Slough. The three features to reduce seepage

are 1) addition of impervious barriers to the levees to block loss of water; 2) installation of

pumps near levees to redirect water back into the Everglades; and 3) hold water levels

higher in undeveloped areas between the Everglades and Palm Beach, Broward, and

Miami-Dade counties. Operational changes in water delivery schedules will be made in

some areas to alleviate extreme fluctuations. Lake Okeechobee water levels are being

modified to improve the health of the lake. In other areas, a rainfall-driven operational

plan will enhance the timing of water flows (Chapter 5).

A3c. State

Many state agencies are involved with both the management and regulation of

activities in Lake Okeechobee. The FDEP and the FWC are leading state agencies in the

protection and management of the lake. Their jurisdictions include the protection of water

quality, wetland resources, fisheries, and wildlife resources of Lake Okeechobee. The

FDEP issues National Pollutant Discharge Elimination System permits for point source

discharges. Other state agencies that have a role in managing the lake include the Florida

Department of Health and Rehabilitative Service, the FDCA, the FDACS, and the Florida

Department of Transportation (FDOT). The SFWMD’s Water Resource Advisory

Committee, a multiagency/multiuser group, also provides input to issues associated with

the lake and its watershed.

A3d. Regional

At the regional level, the SFWMD and four regional planning councils have

jurisdiction within the Lake Okeechobee SWIM planning area. The District’s authority is

to manage and protect the water resources in a 16-county region that includes the Lake

Okeechobee SWIM planning area. Regional planning council jurisdictions are assigned by

county. Palm Beach, St. Lucie, Indian River, and Martin counties are within the Treasure

Coast Regional Planning Council. The Southwest Florida Regional Planning Council has

jurisdiction within Glades and Hendry counties. The Central Florida Regional Planning

Council has jurisdiction within Okeechobee and Highlands counties. The East Central

Florida Regional Planning Council has jurisdiction within Polk and Osceola counties.

Regional planning councils have responsibilities to develop regional comprehensive
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Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

policy plans for protection of water resources within the Lake Okeechobee SWIM

planning area, provide assistance to local governments on related issues, and determine

impacts of proposed development on the lake and other related resources. The regional

planning councils have all adopted regional policy plans that include goals and policies

designed to aid in the protection of all surface and ground waters in the region, including

Lake Okeechobee and its tributaries. The regional planning councils also provide

technical assistance to local governments and evaluate anticipated impacts from

Developments of Regional Impact on regional resources, such as Lake Okeechobee.

A3e. Local

The local governments have the authority to control land use in the Lake

Okeechobee watershed through their comprehensive plans and land development

regulations. They also have authority to regulate water quality and nuisances. Sectors that

exist at the local government level include planning, building, zoning, and regulatory

departments; water and sewer utilities; city and police departments; and soil and water

conservation districts. The various counties and municipalities have developed

comprehensive plans that guide the future development and preservation of local

resources. Recent (2000) census figures are provided in Table 1-1. 

A4. Goals

The goals for each part of this update are summarized below:

• Water Quality - Reduce pollutant loads from the watershed and reduce

in-lake nutrients that stimulate algal blooms and ensure that the lake

can support and sustain a healthy, natural ecosystem

Table 1-1. County census totals and the percentage increase in the Lake Okeechobee SWIM 

planning area

County

2000

Population

Percent Increase

(since 1997 SWIM 

Plan update)

Hendry 36,210 22

Highlands 87,366 15

Glades 10,576 38

Martin 126,731 12

Okeechobee 35,910 16

Osceola 172,493 24

Palm Beach 1,131,184 14

Polk 483,924 10

St. Lucie 192,695 10
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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• Environmental Resources - Protect and enhance the environmental

resources of Lake Okeechobee, and enhance the lake's functional role

in the regional aquatic ecosystem

• Water Supply/Flood Protection - Maintain an adequate quantity and

quality of water in Lake Okeechobee to supplement downstream

environmental needs and to meet reasonable and beneficial use

requirements while ensuring adequate flood protection to local

communities and agriculture around the lake

• Recreation - Attain recreational opportunities that meet public demand

and are consistent with other SWIM goals

• Navigation - Assist in maintaining navigability within the federallyoperated navigation projects in the Lake Okeechobee planning area

(Kissimmee River and Okeechobee Waterway, including the

Caloosahatchee River and the St. Lucie Canal)

• Public Involvement and Intergovernmental Coordination - Prepare

and implement effective public and intergovernmental awareness

programs and encourage public participation in the Lake Okeechobee

SWIM planning process

B. BASIN DESCRIPTION AND INVENTORY

Lake Okeechobee and its watershed are key components of South Florida's

Kissimmee-Okeechobee-Everglades ecosystem, which extends from the headwaters of the

Kissimmee River in the north to Florida Bay in the south. The lake is the second largest

freshwater body located wholly within the continental United States. It provides a number

of ecological and societal values. It is home to one of the nation's prized bass and speckled

perch fisheries, as well as an economically important commercial fishery. At the same

time, it provides habitat for a wide variety of wading birds, migratory waterfowl, and the

federally-endangered Everglades Snail Kite. Lake Okeechobee also is a source of drinking

water for lakeside cities and towns, and can be a backup water supply for the communities

of the lower east coast of Florida. The lake also supplies irrigation water for the expansive

Everglades Agricultural Area (EAA), and is a critical supplemental water supply for the

Everglades. Given these often-competing demands on the lake, management of the water

resource is a major challenge. 

B1. History

Geological survey data indicate that Lake Okeechobee was formed about 6,000

years ago, when ocean waters receded and water was left standing in a shallow depression

in what today is known as the State of Florida (Gleason and Stone, 1975). The original

lake probably was saline (salty), but over time the salt water was replaced by fresh water

from rainfall. The expansive lake that resulted from this process was named Okeechobee,

which means “big water” in the Seminole Tribe language. The lake had a large littoral

(wetland) zone that extended from the Kissimmee River to the Florida Everglades, and a
10

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

pelagic (open water) zone that was much larger and probably as much as 3 feet deeper

than that observed today. During periods of high rainfall, the littoral zone expanded far to

the west, and the lake was a direct source of water to the Everglades by way of broad

sheetflow and blind stream channels passing out of the lake’s southern end. Results of

sediment surveys, including paleolimnological (past lake history) analyses indicate that

sediments of the lake were primarily comprised of sand. The nearshore regions of the lake

probably supported dense beds of submerged plants and nesting and feeding habitat for

fish and wildlife (Steinman, 2001). 

B2. Human Impacts

The following major issues have been identified as most critical for restoration of

the Lake Okeechobee ecosystem: 

• External loads of phosphorus to the lake must be substantially reduced. 

• Internal loading of phosphorus from the lake sediments must also be

reduced, if feasible, or responses to external load reduction will be

considerably delayed. 

• Extremely high and low water levels must be dramatically reduced in

their frequency and duration. 

• The rapid expansion of exotic plants in the lake’s littoral zone must be

stopped.

B2a. Excessive Nutrient Inputs

During the Twentieth Century, much of the land around Lake Okeechobee was

converted to agricultural use. To the north, dairy farms and beef cattle ranching became

the major land uses, while to the south, sugarcane and vegetable farming increased

rapidly. These land use changes resulted in a large increase in the rate of nutrient (nitrogen

and phosphorus) inputs to the lake, and detrimental changes occurred in the lake’s water

quality. Nitrogen inputs were particularly high from the south. These nitrogen inputs were

significantly reduced after the late 1970s when an interim action plan (SFWMD 1979)

prohibited pumping of agricultural water into the lake from the south except under

situations where farmlands would otherwise be flooded. Phosphorus inputs from the

northern watershed increased dramatically, and can be traced primarily to the animal

agricultural activities in that watershed. Loads (concentration times flow) of total

phosphorus to the open water region of the lake nearly tripled between the early 1970s and

mid-1980s, and coincident with this trend, the concentration of phosphorus in the lake

itself increased from below 40 to over 100 parts per billion (ppb). Blooms of blue-green

algae became more common, with particularly large blooms covering more than 40

percent of the lake surface in the 1980s. A number of programs have been implemented

and others are under development to substantially reduce phosphorus loads to Lake

Okeechobee (Havens et al., 1996a). 

During the early 1990s, scientists discovered that one of the greatest challenges in

reversing harmful trends caused by excessive phosphorus may be in controlling sources
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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internal to the lake. Because high phosphorus loads have occurred for over 60 years, more

than 30,000 tons of phosphorus has accumulated at the bottom of the lake, in the form of

soft organic mud (Olila and Reddy, 1993; Steinman et al., 1999). Because of the lake's

shallow depth (averaging just 2.3 meters or 9.0 feet), this mud is mixed into the water

column every time strong winds blow across the lake’s surface. This keeps the phosphorus

concentration in the water column high. When the turbid water (water clouded by

sediments from the lake bottom) is transported to the nearshore region, it prevents

submerged plant beds from getting the light they need to grow. Phosphorus in the water

also may stimulate the growth of cattails along the edge of the littoral zone. 

Because so much phosphorus is being stored within the lake's sediment, internal

loads of phosphorus (from sediment to water) now equal external loads (coming from the

watershed to the lake). Given this condition, the lake's recovery will be severely delayed.

Even when external loads are dramatically reduced, the lake's sediments act as a

phosphorus reservoir and continue to release phosphorous into the water column of the

lake. Some combination of sediment removal and external load reduction may be needed

to achieve recovery of Lake Okeechobee in a relatively short (decades) time frame.

B2b. Hydrologic Modifications

Other changes in South Florida have had severe impacts on Lake Okeechobee. In

the 1890s, Hamilton Disston constructed a canal connecting Lake Okeechobee with Lake

Hicpochee, the headwaters of the Caloosahatchee River. This provided the lake’s first

outlet to tidewater via the Caloosahatchee River. In the early 1900s, the Everglades

Drainage District constructed several other canals that impacted Lake Okeechobee. The

St. Lucie, Hillsboro, North New River, West Palm Beach, and Miami canals were

constructed to deliver water from the lake to tide. These canals provided slow, continuous

drainage from Lake Okeechobee and the Everglades. The goal was to drain the northern

Everglades for agriculture.

Small towns arose in this region, some very close to the lake. A small muck levee

was constructed along the southern shore of the lake to protect those towns and farms. In

the 1920s, two major hurricanes struck South Florida. One of them generated a storm

surge in the lake that flooded coastal areas and hundreds of acres to the south and killed

approximately two thousand people. To prevent this kind of devastation from recurring,

the state asked the United States Congress for help. In 1931, Congress directed the

USACE to lead efforts to prevent future tragedies of that scale. One of the first features the

USACE constructed was the Herbert Hoover Dike, an earthen levee that consisted of

sections along the north and south shoreline. This was the first project for flood protection

in Florida by the USACE. One of the major impacts of the dike on Lake Okeechobee was

to restrict the littoral zone to a much smaller region, along the western and southern

shorelines. When water levels in the lake become very high, this reduced littoral zone can

no longer expand outward. Instead, it is flooded with deeper and deeper water. 

In 1948, Congress authorized the USACE to implement a comprehensive water

resources project, the Central and Southern Florida Project for Flood Control and other

purposes. This project is now referred to as the C&SF Project. As a result of the system of
12

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

canals and levees built by the USACE, all discharges into (except Fisheating Creek) and

out of the lake are now artificially controlled. 

The 1948 authorization required that the SFWMD operate and maintain all

components of the C&SF Project, except the main outlets of Lake Okeechobee and the

WCAs, in accordance with rules prescribed by the Secretary of the Army. As a result, the

USACE establishes the regulation schedule for Lake Okeechobee that defines the

operating rules required to meet the authorized project purposes. The regulation schedule

was designed to provide floodwater storage capacity during the wet season, and to

supplement water supply during the dry season. Because of recent increases in rainfall, the

lake has experienced frequent and prolonged high water levels that have been extremely

damaging to both the lake and to downstream ecosystems. These high water levels led to

drastic declines in the lake's submerged plant beds. Also, scientists at the FWC have

recently suggested that juvenile age classes of important sport fish (such as bass) have

substantially declined (FWC unpublished data). 

When lake levels were particularly high, large flood control discharges of fresh

water are sent through canals to the St. Lucie and Caloosahatchee estuaries, where they

had severe impacts on estuarine organisms. A new lake regulation schedule, the WSE

schedule, that will attempt to reduce the occurrence of extreme high water events by using

climate forecasting, was implemented in July 2000, and is discussed in detail in Chapter

5. 

Extremely low water levels during the dry season can threaten the lake's ecological

health by allowing certain exotic plants that have invaded the littoral zone to rapidly

expand. Alternatively, low lake levels can facilitate exotic control programs, such as fire

and herbicide treatments that occurred during the 2000 managed recession. Low water

levels may become a greater concern in the future when a greater water supply is needed

for both Everglades restoration and the growing human population of South Florida. 

B2c. Exotic Plants and Animals

A large percentage of the native plant habitat in the lake’s littoral zone (about 20

percent or over 20,000 acres) has been overtaken by exotic plants, most notably melaleuca

and torpedograss. Melaleuca is a native tree of Australia and torpedograss is a pasture

grass native to Europe. Both were planted intentionally in the vicinity of the lake, and both

rapidly colonized the littoral zone. The SFWMD and other agencies are actively engaged

in a program to eradicate melaleuca from South Florida using herbicide and biological

control agents. The spread of melaleuca and torpedograss has been documented to be

increased by low lake stage. Work is in progress to better quantify this linkage, which is

critical to the development of lake operating protocol under CERP as well as to the

success of ongoing exotic control efforts. District scientists identified an improved control

program for torpedograss in the late 1990s and it was implemented in 2000-2001.

Widespread control is expected to take many years. The lake also contains exotic animals,

including an asiatic clam and fish, but their negative impacts have not been well

documented. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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C. BOUNDARIES AND SUBBASINS

The Lake Okeechobee SWIM planning area (Figure 1-2) has been defined as the

major basins that are direct tributaries to the lake, including those basins that are

hydrologically upstream and/or from which water is presently released or pumped into the

lake on a regular basis. Water from several tributaries drains into the lake through the

Kissimmee River (C-38), including the S-65 series of basins, the S-84 basin, and the

S-154 basin. The S-133 basin also drains into the lake from the north. The Taylor

Creek\Nubbin Slough basin and the S-135 drain into the lake from the northeast. The

following basins drain into the lake from the northwest: Arbuckle Creek, Istokpoga, C-41,

S-65E, C-40, S-84, L-48, L-49, and S-131. Water from the S-135 and C-44 basins drain

into the lake through the St. Lucie Canal when lake stage permits. Basins that drain from

the EAA into the lake include the S-4 and Chapter 298 Special Drainage Districts, and

Agricultural Lease #3420. The Chapter 298 Special Drainage Districts include the East

Beach Water Control District, the East Shore Drainage District, the South Shore Drainage

District, the Industrial Canal, the South Florida Conservancy (S-236), and 715 Farms.

Additionally, water from the S-2 and S-3 basins is backpumped into the lake

during flood or emergency water conditions. The Fisheating Creek basin drains into the

lake from the western shore while the East Caloosahatchee basin drains into the lake from

the west only during extreme conditions (i.e., when the lake level drops to 11.5 feet). A

detailed discussion of these basins, including their associated water quality issues, can be

found in the Interim Lake Okeechobee Surface Water Improvement and Management Plan

(SFWMD, 1989a) and a detailed map can be found in Figure 2-2 in Chapter 2. 

C1. Kissimmee River Restoration

The Kissimmee River Restoration Project will recreate floodplain habitat for use

by more than 320 fish and wildlife species and enhance the Kissimmee-OkeechobeeEverglades system. A detailed background of the Kissimmee River channelization is

provided in the Surface Water Improvement and Management Plan - Update for Lake

Okeechobee (SFWMD, 1997a). The restoration is planned in phases, over a 15-year

period, to allow incremental funding of construction and land acquisition. The project

includes three major components: 

• Twenty-two continuous, linear miles of the C-38 canal will be

backfilled and the adjacent floodplain land will be acquired. This

component includes the removal of two of the structures along the

canal (S65-B and S65-C), degradation of levees in the floodplain, and

reconstruction of approximately nine miles of river channel.

• The headwaters will be revitalized. The primary focus of this

component is the storage/release of water from the upper basin lakes to

the Kissimmee River, including expansion of canals connecting Lakes

Kissimmee, Hatchineha, and Cypress, improving the structure at the

outlet of Lake Kissimmee (S65), and land acquisition to allow
14

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

additional water storage capacity in Lake Kissimmee, Lake

Hatchineha, Lake Cypress, and Tiger Lake. 

• A Comprehensive Ecological Evaluation Program will be designed to

evaluate the success of the project in meeting the established

restoration goals, to provide for continuous, scientifically-informed

fine-tuning of the reconstruction, and adaptive management of the

recovering and restored ecosystem. 

The State of Florida and the USACE have entered into a partnership to implement

the Kissimmee River Restoration Plan with the SFWMD acting as the local sponsor of this

project with a 50-50 cost share arrangement. The SFWMD and the state have already

acquired much of the 85,000 acres required for restoration. In February 2001, the first of

four phases of the restoration was essentially completed. Seven miles of the C-38 canal

backfilled, 1.5 miles of new river channel were constructed, and 15 miles of the historic

Kissimmee River were reconnected. 

C2. Everglades Restoration

Enactment of the 1994 Everglades Forever Act established both interim and longterm water quality goals to achieve restoration and protection of the Everglades Protection

Area, which includes the three WCAs and Everglades National Park. To achieve interim

goals, activities are now under way to reduce phosphorus concentrations to a long-term

average of 50 ppb. These activities includes the Everglades Construction Project and the

EAA Best Management Practices (BMP) Program (SFWMD, 2000a).

C2a. Everglades Construction Project

The Everglades Construction Project is the first major step in Everglades

restoration. The project is mandated in the Everglades Forever Act (Section

373.4592(4)(a), F.S.) and Phase I of six STAs. When fully constructed, these large (47,655

acres) constructed wetlands will receive nearly 1.4 million acre-feet per year of

stormwater runoff from the EAA and adjacent watersheds, and regulatory releases from

Lake Okeechobee. Treated water discharged from the STAs will be directed to the

Everglades Protection Area to improve water flow, timing, quantity, and quality.

Additional treatment will be required before water is discharged to the Everglades to meet

all state water quality standards. Land acquisition began in 1994 and was completed in

2001. Construction began in 1997 and the last of the STAs will be complete in October

2003. The District is the primary agency responsible for the design, land acquisition,

construction, operation, and maintenance of the Everglades Construction Project. The

USACE has been authorized by federal law to construct one of the STAs. The USACE

also participated in producing a programmatic environmental impact statement for the

project and issued the federal construction permit in 1997. The FDEP is providing

technical support and is responsible for the majority of state construction and operating

permits (SFWMD, 2000a). 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

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C2b. Everglades Stormwater Program

The Everglades Stormwater Program will improve water quality in basins not

addressed by the Everglades Construction Project through monitoring, regulation, and

cooperative resource management. The Everglades Stormwater Program identified

strategies for complying with water quality standards. The EAA BMP Program is

administered under the Everglades Stormwater Program, with the intent of continuing to

reduce phosphorus loads from the EAA. The main BMPs include efficient fertilizer

application, control of erosion and sediment, and effective stormwater pumping operations

(SFWMD, 2000a).

D. POINT AND NONPOINT POLLUTION SOURCES

The vast majority of nutrient loading to the lake comes from nonpoint sources,

with only minor contributions from point sources. Sections 373.451- 373.4595, F.S., and

Chapter 62-43, F.A.C., require that SWIM plans include the identification of point and

nonpoint sources of pollution in the planning area. Table 1-2 is a summary of industrial

and domestic wastewater, dairies, Works of the District (WOD), and surface water

permits, and waste disposal sites. 

D1. Point Sources

Point sources of pollution are defined as discharges to surface and ground waters

where discrete measures of water flow and water quality can be taken. In the Lake

Okeechobee SWIM planning area, domestic wastewater treatment and industrial waste

facility discharges are considered point sources.

Currently, 69 industrial waste facilities are permitted in the Lake Okeechobee

SWIM planning area. The permitted facilities consist mostly of dairy operations and

power plants. Most of these facilities use land application (on-site ponds and/or irrigation)

for disposal.

Currently, 121 domestic wastewater treatment facilities are permitted by the FDEP

in the Lake Okeechobee SWIM planning area, with approved capacities between 0.005

million gallons per day (mgd) to 3.00 mgd. Most of these facilities reuse this water,

disposing of the reclaimed water by land applications, such as percolation ponds, drain

fields, and/or irrigation. Three of the facilities use deep well injection for effluent disposal,

while one, the Avon Park Correctional Institute in Polk County, uses a surface water

discharge. All facilities are required, at a minimum, to provide secondary level treatment

and basic level disinfection prior to disposal into ground water. Disinfection is not

required for deep well injection.

Domestic wastewater and industrial waste facilities in the planning area are

regulated by the FDEP. However, in Palm Beach County, regulation of domestic

wastewater facilities with a capacity less than 0.50 mgd has been delegated to Palm Beach

County Health and Rehabilitative Services. In addition to approval by these agencies,
16

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

surface water discharges also require a National Pollutant Discharge Elimination System

permit. This permitting program, previously administered by the USEPA, was delegated to

the state in 1995. Surface water discharge permits include water quality-based or

technical-based effluent limits. Specific effluent limits are based on the presumption that

the assimilative capacity of the receiving water is sufficient to handle these additional

pollutant loads. 

D2. Nonpoint Sources

Nonpoint source pollution is associated with land use activities that do not have a

single discrete discharge point. Nonpoint sources are driven by rainfall and runoff, and are

the dominant pollution sources in the Lake Okeechobee watershed. These pollution

sources are delineated into rural and urban. Rural nonpoint sources include stormwater

runoff and are associated with agricultural activities. Stormwater runoff from these

activities carries pollutants such as phosphorus from fertilizers, pesticides, and other

Table 1-2. Permits in the Lake Okeechobee planning area

Permit Type

Permitting

Agency

Permit

Activity General Description Information Provided

Total

Number

Point Sources

Industrial 

Wastewater

FDEP Industrial 

treatment

systems

Listing of permitted 

industrial waste facilities 

within the Lake 

Okeechobee basin

-Facility name

-Facility location with latitude/

longitude

-Rated capacity

69

Domestic 

Wastewater

FDEP

Palm Beach 

County Health 

and 

Rehabilitative 

Services

Private and 

municipal 

wastewater 

facilities

Listing of permitted 

domestic wastewater 

facilities within the Lake 

Okeechobee basin

-Facility name

-FDEP identification number

-Facility location

-Rated capacity

-Disposal method

121

Dairies FDEP Dairy farm BMPs Listing of those dairy 

farms that have begun 

the permitting process

-Number of cows

-BMP system specifications

-Percent BMPs completed

26

Nonpoint Sources

Works Of the 

District (WOD) 

Permits

SFWMD Agricultural, 

industrial, 

commercial, and 

nonpoint source 

BMPs

Listing of SWIM Permits 

within the Lake 

Okeechobee basin

-Permit number

-Location and project size

-Location of water quality 

monitoring sites

-Listing of water quality data

-Land use

-Basin BMPs specifications

-Tracking of sites that exceed 

SWIM phosphorus limits

721

Surface Water 

Management

SFWMD Stormwater 

management 

systems

Listing of SWIM permits 

within the Lake 

Okeechobee basin

-Permit number

-Permittee

-Location

-Receiving body

-Type of facilities

-Rate of discharge

-Project size

470

Waste 

Disposal Sites

FDEP Landfills Listing of waste disposal 

sites within the Lake 

Okeechobee basin

-Site name

-Location

-Status class

16
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

17

agricultural chemicals. Urban nonpoint sources are also primarily conveyed by

stormwater and contain pollutants associated with urban land uses. The sources of these

pollutants range from those transported by direct precipitation, to pollutants resulting from

automobile tire wear, and construction activities.

Agricultural activities surrounding the lake are the principal land uses in the area

and are responsible for discharging large quantities of nutrients to the waters within the

watershed through stormwater runoff (Anderson and Flaig, 1995). More than 60 percent

of the Lake Okeechobee watershed is used for agriculture (Table 1-3). 

Table 1-3. Lake Okeechobee basin land use summary

Land Use Subcategory

(Level 3)

Lake Okeechobee 

Basin

Total Acreage

Percent of Basin 

Land Use

Aquaculture 409 <1%

Barren Land 15,528 <1%

Citrus Groves 56,690 3%

Dairies 12,871 <1%

Fallow Crop Land 4,340 <1%

Field Crops 10,247 <1%

Field Crops – Sugarcane 225,876 12%

Floriculture 21 <1%

Fruit Orchards 933 <1%

Forested Uplands 171,686 9%

Horse Farms 980 <1%

Improved Pasture 445,119 24%

Ornamentals 182 <1%

Other 406 <1%

Other Groves 72 <1%

Rangeland 124,252 6%

Row Crops 12,173 <1%

Sod Farms 2,324 <1%

Transportation, Communication, and Utilities 11,415 <1%

Tree Nurseries 2,241 <1%

Unimproved Pasture 76,181 4%

Urban and Built-Up 55,166 3%

Water Bodies 314,662 17%

Wetlands 318,479 17%

Woodland Pasture 9,725 <1%

TOTAL 1,871,978

SUMMARY

Agriculture 62%

Urban 3%

Wetlands/Water 34%

Other <1%
18

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

E. LAND USE

E1. Land Use/Land Cover Categories

The continuous population influx and agricultural growth in South Florida causes

rapid changes in land use. Therefore, periodic land use/land cover mapping is performed

every five years to monitor these dynamic changes in land use. The District has updated

the aerial photography (1:40,000) first performed in 1994-1995 by the USGS’ National

High Altitude Photography and National Aerial Photography Program. The existing land

use/land cover conditions have been classified utilizing the FDOT Florida Land Use and

Cover Classification System. The system is a four-tiered hierarchal, alphanumeric, land

use/land cover coding system that standardizes mapping across the State of Florida. Level

I is the most general classification level with categories for agriculture, barren land,

forested uplands, rangeland, urban, water, and wetlands. Levels II - IV are subcategories

with increasing levels of detail. Land use data are presented in Table 1-3 and Figure 1-3

and has been updated from the previous Lake Okeechobee SWIM plan update (SFWMD,

1997a). Table 1-3 uses Level III subcategories. 

E2. Land Use Impacts on Water Quality

Impacts on water quality are a direct function of intensity of land use. Land use

intensity in the Lake Okeechobee watershed has traditionally been low. Ranching, dairy

farming, and vegetable farming are the most intensive land uses in the basin that

contribute to nutrient (phosphorus and nitrogen) loading to the lake. Nutrients, primarily

phosphorus, have been imported into the watershed as animal feed and fertilizer that are

used to support improved pastures and dairy operations. A high correlation has been

shown to exist between phosphorus imports and phosphorus load to the lake. Wetlands

along the flow path to the lake have been demonstrated to reduce phosphorus loading

(Boggess et al., 1995), although many wetlands have been ditched to drain the land for

improved pasture, reducing their capacity to retain water and phosphorus.

Urban land uses within the Lake Okeechobee watershed contribute to nonpoint

pollution that enters the lake. Stormwater from these areas, which cover approximately 3

percent of the watershed, may contribute dissolved solids, nutrients, and heavy metals

(Whalen and Cullum, 1988). These materials enter in runoff from lawns and impervious

areas such as parking lots, and through on-site wastewater disposal systems. Based on the

values from the S-127 and S-133 basins for the 1995-1999 reporting period, the urban

contribution of phosphorus to Lake Okeechobee is less than 0.5 percent of the total load,

with the balance of the load being contributed from agricultural sources (Chapter 2). 

Stormwater and shallow ground water from agricultural land use may contain

pollutants associated with the application of fertilizers, pesticides, and herbicides. Areas

north of the lake are used for dairy and cattle farming, whereas areas south of the lake are

used for sugarcane, rice, winter vegetables, and sod farming. The major concern is the

large amount of primary nutrients (phosphorus and nitrogen) that are discharged to the

lake as surface water runoff from these areas. Although trace amounts of organics and
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 1: Introduction, Basin Description, and Inventory

19

Figure 1-3. Land use within the Lake Okeechobee SWIM planning area
20

Chapter 1: Introduction, Basin Description, and Inventory Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

trace elements had been detected within the basin (Pfeuffer, 1985, 1988), no major

problems existed in the watershed or in the lake itself. A review of 27 years (1973-2000)

of data indicated that the water quality associated with major inflows has not substantially

impaired the designated uses of the lake. The instances of trace metal criteria being

exceeded are most likely to be due to anthropogenic sources, such as agricultural uses of

sludge, fertilizers, and pesticides. Numerous tributary total and fecal coliform

measurements were above the criteria during a year of intensive study (Ogburn et al.,

1996).
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

21

Chapter 2

WATERSHED AND TRIBUTARY WATER QUALITY

The Lake Okeechobee watershed is dominated by agriculture, which contributes

nutrients and other pollutants that have impacted the ecological condition of Lake

Okeechobee. Phosphorus is of particular concern in this system because it has been

identified as the key element that contributes to the eutrophication of the lake (Davis and

Marshall, 1975; Federico et al., 1981; Joyner 1972; Kissimmee-Okeechobee Basin

Report, 1972). To restore the ecological condition of Lake Okeechobee, a 40 percent

phosphorus load reduction goal was developed based on data collected from 1973 to 1979

(Federico et al., 1981). The SWIM Act (Section 373.451-.459, F.S.) was passed in 1987

requiring that a program be established to reduce phosphorus loads to Lake Okeechobee

by this amount. 

The Interim Lake Okeechobee SWIM Plan (SFWMD, 1989a) set forth a

recommended approach for meeting the 40 percent phosphorus reduction goal. According

to the plan, all tributary inflows to the lake were required to meet the 0.18 milligrams per

liter (mg/l) (180 ppb) performance limitation for total phosphorus or maintain their 1989

discharge concentration, whichever was less. Basins that exceeded the 0.18 mg/l

limitation were required to reduce their phosphorus concentrations and achieve

compliance by July 1992. 

Strategies have been developed to reach these reduction loading goals. These

include continuing to implement the Works of the District (WOD) Program, implementing

the CERP, developing BMPs for agriculture, continuing to model load reduction

scenarios, and implementation of the Lake Okeechobee Protection Program and Permits

(Section 373.4595(3)-(4), F.S.). 

Strategies have also been developed to achieve State Class I Water Quality

Standards within Lake Okeechobee and Class III Water Quality Standards within the

lake’s tributaries. These standards are set forth in Chapter 62-302.530, F.A.C.

A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Reduce pollutant loads from the watershed to protect 

aquatic life and water quality in Lake Okeechobee

Objective 1: Bring the overtarget basins down to their phosphorus

loading targets

Strategy 1: Continue to implement the WOD Program and

develop nutrient management plans for out-of-compliance parcels
22

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Strategy 2: Implement the CERP initiatives to reduce the loads to

the lake through reservoir-assisted stormwater treatment areas

Strategy 3: Develop BMPs for agriculture and continue modeling

load reduction scenarios

Objective 2: Develop and implement the components of the Lake

Okeechobee Protection Program and Permits to meet the TMDL target by

2015

Strategy 1: Identify any health or environmental problems

associated with spreading wastewater residuals and chicken manure

on land

Strategy 2: Institute best available technologies (BATs) on

selected dairies to significantly reduce the export of phosphorus

into Lake Okeechobee tributaries

Strategy 3: Implement a nonregulatory, landowner-based

initiative for on-site retention of phosphorus and water through the

Lake Okeechobee Water Retention/Phosphorus Removal Critical

Restoration Project

Strategy 4: Restore or create isolated wetlands in association with

the implementation of BMPs to reduce the phosphorus loading

from beef cattle operations and other land uses in the watershed

Strategy 5: Implement the Phosphorus Source Control Grant

Program to fund load reduction projects proposed by applicants

Strategy 6: Evaluate two methods of sediment removal

technologies selected as part of the sediment removal project under

way in Lettuce Creek

Strategy 7: Conduct an economic analysis of all feasible on-farm

and regional phosphorus control alternatives to reduce phosphorus

loads to the recommended levels

Objective 3: Achieve State Class I Water Quality Standards (Chapter

62-302, F.A.C.) within Lake Okeechobee, and Class III Water Quality

Standards within the lake’s tributaries

Strategy 1: Support the development and implementation of a

comprehensive plan to address the occurrence of Class I/Class III

water quality criteria being exceeded within Lake Okeechobee and

its tributaries to fulfill the requirements of the Lake Okeechobee

Operating Permit
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

23

Strategy 2: Establish additional monitoring of biological

conditions and trace metals during inflow conditions to document

whether the inflows from tributaries to Lake Okeechobee meet the

standards of their designated usage class

Strategy 3: Establish monitoring to determine the significance of

and the potential causes of low dissolved oxygen in inflows from

tributaries to the lake before management strategies are evaluated

Strategy 4: Sample the tributaries for total dissolved solids on a

regular basis, since Class I criterion for total dissolved solids was

exceeded over 25 percent of the time in inflows from the tributaries

to Lake Okeechobee

Strategy 5: Modify the District's monthly monitoring program to

include iron analysis to facilitate a more conclusive assessment of

the potential need for management measures to control trace metals

within the tributaries

Strategy 6: Reduce the list of organic parameters from the

supplemental monitoring program to focus on compounds that are

known to have potential sources in the watershed, such as

pesticides, herbicides, and petroleum hydrocarbons

Strategy 7: Recommend quarterly sampling for organics, with the

schedule being based on seasonal uses of agricultural chemicals

and/or periods of inflow to the lake

Strategy 8: Conduct a survey to establish the extent and source of

total and fecal coliforms that exceed the criteria

Strategy 9: Determine the applicability of additional management

strategies for the following: 1) canals, using sediment removal and

constructed wetlands, 2) marinas, using liquid waste management

and boat maintenance control measures, and 3) establishing

alternative, more appropriate, criterion for some parameters in

order to prevent Class I/Class III water quality criteria for the

tributaries from being exceeded 
24

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

B. PHOSPHORUS LOADS AND TARGETS BY BASIN

The SFWMD Technical Publication 81-2 (Federico et al., 1981) developed a 40

percent phosphorus load reduction goal based on a modified Vollenweider model. This

model, developed for Lake Okeechobee using data from 1973 to 1979, predicts the in-lake

phosphorus concentration based on external loads, external flow, and turnover time (i.e.,

the amount of time it would take the lake to empty based solely on surface outflows). The

agreement between model prediction and yearly average observed data was quite good for

the 1973 to 1979 (Figure 2-1). 

Given that the target in-lake phosphorus concentration and the TMDL is 40 ppb,

the model can be rewritten to determine the phosphorus loads that would reach that target

concentration. This loading goal, which averaged 397 tons per year, was used to set the

criterion for each basin (Figure 2-2) by determining the flow-weighted average

concentration of phosphorus that would result in 397 tons or less entering the lake. This

value was 180 ppb at each inflow point. Thus, the 1989 Interim Lake Okeechobee SWIM

Plan (SFWMD, 1989a) required that all tributary inflows to the lake should meet the 180

ppb performance limitation for total phosphorus or maintain their 1989 discharge

concentration, whichever was less. 

Targets are developed for each basin based on average annual, flow-weighted total

phosphorus concentrations. These targets are adjusted for variations in discharge. To

calculate the observed load from each basin, the observed concentration is multiplied by

flow. Excess phosphorus loads are calculated as the difference between the observed and

target loads. The phosphorus loads and targets for each basin for 1990 to 1994 and 1995 to

2000 are presented in Tables 2-1 and 2-2, respectively.

0

10

20

30

40

50

60

70

80

90

100

1973 1974 1975 1976 1977 1978 1979

 Total Phosphorus (ppb) 

Observed

Predicted

Figure 2-1. Comparison of the modified Vollenweider model total phosphorus predictions to

observed data for 1973 to 1979
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

25

Collectively, the flow-weighted mean concentration from controllable sources of

these tributaries for the five-year period following full implementation of BMPs (1990

through 1994) was 243 ppb (Table 2-1). During this period, 19 basins were at least 10

percent above their target loads, and 8 basins were at least 10 percent below their target

loads. The other 2 basins were within plus or minus 10 percent of their target loads. The

excess loading was 140 tons per year based on target loads for each basin. The S65 basins

(A through E) were not separated from each other because the measurements at these

structures do not capture the seepage and bypass flows, which are significant. To

determine the basin loads from S65A through S65E, the discharge out of S65 (Lake

Kissimmee) was subtracted from the discharge from S65E. The resultant is assumed to be

the contributions of flow and load from the S65A through S65E basins. 

S-65A

S-65B

S-65C S-65D

C-41A S-154

FISHEATINGCREEK

S-65E

C-41

S-133

C-40

S-154C

L-59E

LAKE OKEECHOBEE

S-135

L-59W L-48

L-60E

L-61E

L-49

L-60W

L-61WS-131

S-191

NICODEMUS SLOUGH

Figure 2-2. The drainage basins that contribute nutrient enriched runoff to

Lake Okeechobee
26

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Table 2-1. Phosphorus (P) loads and targets by basin in the Lake Okeechobee watershed for 1990-1994

Basin

Area

(square 

miles)

Target 

Total

P

(ppb)

1990-1994

Discharge

(acre-feet)

Target 

Load

(tons/

year)

FlowWeighted 

Total P 

(ppb)

Average 

(tons/

year)

Over/

Under

(tons/

year)

Percent 

Over/

Under 

Target

Controllable Sources

715 Farms (Culvert 12A) 4 180 9,293 2.3 147 1.9 -0.4 -18%

C-40 Basin (S-72) 87 180 23,096 5.6 415 13.0 7.3 130%

C-41 Basin (S-71) 176 180 52,956 12.9 417 30.0 16.9 131%

S-84 Basin (C41A) 180 100 47,478 6.4 143 9.2 2.7 42%

S-308C (St. Lucie-C-44) 190 180 89,043 21.7 152 18.4 -3.3 -15%

East Beach DD (Culvert 10) 10 180 7,973 1.9 508 5.5 3.6 182%

East Shore DD (Culvert 12) 13 130 11,958 2.1 191 3.1 1.0 47%

Fisheating Creek 462 180 178,676 43.6 161 38.9 -4.7 -11%

Industrial Canal 23 180 22,210 5.4 110 3.3 -2.1 -39%

L-48 Basin (S-127) 32 180 13,267 3.2 246 4.4 1.2 37%

L-49 Basin (S-129) 19 180 8,595 2.1 133 1.6 -0.5 -26%

L-59E 15 160 4,512 1.2 245 1.5 0.6 49%

L-59W 15 160 5,867 1.6 163 1.3 0.0 2%

L-60E 6 100 877 0.1 194 0.2 0.1 55%

L-60W 6 100 298 0.1 247 0.1 0.0 36%

L-61E 22 90 4,805 0.7 153 1.0 0.5 63%

L-61W 22 90 7,308 1.1 101 1.0 0.1 12%

Taylor Creek/Nubbin Slough (S-191) 188 180 108,825 26.6 609 90.0 63.6 239%

S-131 Basin 11 150 7,965 1.6 103 1.1 -0.5 -31%

S-133 Basin 40 180 24,248 5.9 253 8.3 2.4 40%

S-135 Basin 28 160 21,557 4.7 98 2.9 -1.8 -39%

S-154 Basin 37 180 19,550 4.8 728 19.3 14.6 306%

S-2 166 160 31,424 6.8 231 9.8 3.0 44%

S-3 101 150 5,904 1.2 179 1.4 0.2 19%

S-4 66 180 17,766 4.3 175 4.2 -0.1 -3%

S-65A, B, C, D, E 749 113 265,192 55.9 257 92.4 35.6 64%

South Florida Conservancy DD (S-236) 15 90 3,407 0.4 116 0.5 0.1 29%

South Shore/South Bay DD (Culvert 4A) 7 80 7,195 0.8 113 1.21 0.4 54%

Nicodemus Slough (Culvert 5) 28 60 2,503 0.3 59 0.2 -0.1 -22%

Controllable Totals 1,003,746 226 243 366 140 62%

Uncontrollable Sources

Rainfall - - 72.0

S-65 (Lake Kissimmee) - 733,505 38 39.3

Lake Istokpoga (S-68) - 183,872 29 7.2

S-5A Basin (S-352-West Palm Beach 

Canal) - 2,048 0

East Caloosahatchee (S-77) - 3,616 245 1.2

L-8 Basin (Culvert 10a) - 68,503 99 9.2

Uncontrollable Totals 991,544 129

Total Loading 1,995,291 495

Target Loading (concentration-based) 355 140 39%

Vollenweider Target 399 96 24%
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

27

Table 2-2. Phosphorus (P) loads and targets by basin in the Lake Okeechobee watershed for 1995-2000

Basin

Area

(square 

miles)

Target 

Total

P

(ppb)

1995-2000 Percent

Change 

Over/

Under 

Target

Discharge

(acre-feet)

Target 

Load

(tons/

year)

FlowWeighted 

Total P 

(ppb)

Average 

(tons/

year)

Over/

Under

(tons/

year)

Percent 

Over/

Under 

Target

Controllable Sources

715 Farms (Culvert 12A) 4 180 12,999 3.2 96 1.7 -1.5 -46.6% -28%

C-40 Basin (S-72) 87 180 13,558 3.3 508 9.4 6.0 182.0% 52%

C-41 Basin (S-71) 176 180 46,001 11.3 429 26.8 15.5 138.1% 7%

S-84 Basin (C41A) 180 100 57,298 7.8 149 11.6 3.9 49.5% 7%

S-308C (St. Lucie-C-44) 190 180 34,134 8.4 185 8.6 0.3 3.0% 18%

East Beach DD (Culvert 10) 10 180 13,206 3.2 644 11.6 8.3 257.9% 75%

East Shore DD (Culvert 12) 13 130 14,439 2.6 164 3.2 0.7 26.0% -21%

Fisheating Creek 462 180 210,576 51.5 178 50.9 -0.6 -1.2% 10%

Industrial Canal 23 180 20,672 5.1 103 2.9 -2.2 -43.1% -4%

L-48 Basin (S-127) 32 180 26,457 6.5 230 8.3 1.8 27.7% -9%

L-49 Basin (S-129) 19 180 14,630 3.6 91 1.8 -1.8 -49.3% -23%

L-59E 15 160

No data available

L-59W 15 160

L-60E 6 100

L-60W 6 100

L-61E 22 90

L-61W 22 90

Taylor Creek/Nubbins Slough (S-191) 188 180 97,154 23.8 651 86.0 62.2 261.7% 22%

S-131 Basin 11 150 9,180 1.9 115 1.4 -0.4 -23.3% 8%

S-133 Basin 40 180 23,924 5.9 182 5.9 0.1 1.0% -39%

S-135 Basin 28 160 22,845 5.0 116 3.6 -1.4 -27.4% 11%

S-154 Basin 37 180 26,602 6.5 826 29.9 23.4 358.9% 53%

S-2 166 160 29,235 6.4 197 7.8 1.5 22.9% -21%

S-3 101 150 11,568 2.4 213 3.4 1.0 42.1% 23%

S-4 66 180 33,801 8.3 215 9.9 1.6 19.6% 22%

S-65A, B, C, D, E 749 113 283,267 43.4 213 81.9 38.5 88.7% 25%

South Florida Conservancy DD (S236) 15 90 14,494 1.8 111 2.2 0.4 23.1% -6%

South Shore/South Bay DD (Culvert 

4A) 7 80 7,893 0.9 101 1.1 0.2 26.5% -27%

Nicodemus Slough (Culvert 5) 28 60

Controllable Totals 1,023,934 212 266 370 158 74.2% 12%

Uncontrollable Sources

Rainfall - - 72.0

S-65 (Lake Kissimmee) - 885,858 84 100.3

Lake Istokpoga (S-68) - 292,451 59 23.3

S-5A Basin (S-352-West Palm Beach 

Canal)

 - 18 248 0.0

East Caloosahatchee (S-77) - 342 244 0.1

L-8 Basin (Culvert 10a) - 52,953 97 6.9

Uncontrollable Totals 1,231,622 121 203

Total Loading 2,255,556 573

Target Loading (concentrationbased) 415 158 37.9% -2%

Vollenweider Target 371 201 54.3% 30%
28

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

The next six-year period, 1995 to 2000, the overall flow-weighted concentration

from controllable sources increased slightly to 266 ppb (Table 2-2). Ten basins had

concentrations at least 10 percent above their target and 6 basins had concentrations at

least 10 percent below. Discharges for the L59, L60, and L61 basins, and Nicodemus

Slough were not available for this period, and thus they were not included in this

calculation. However, in the 1990 to 1994 period, they accounted for only 5.1 tons of

phosphorus loads or less than 1.4 percent of the total. 

The excess loading for the 1995 to 2000 period was 158 tons per year based on the

flow and target concentrations for each basin (Table 2-2). This was a 2 percent decrease

compared to the 1990 to 1994 period (Table 2-1). However, based on the Vollenweider

model target, the excessive loading had increased by 30 percent compared to the 1990 to

1994 period. This is because the Vollenweider target includes both controlled and

noncontrolled loads contributing to Lake Okeechobee.

The highest inflow concentrations were found in the S-154 and S-191 basins,

where dairies are abundant and where the majority of the out-of-compliance WOD sites

that are out of compliance are located. These basins, along with the S65 basins, account

for most of the overtarget load, and, if they met their target concentrations, would

collectively bring overall loading to Lake Okeechobee very close to the target. These

basins currently receive intensive study, regulatory scrutiny, and are the focus of

remediation activities. These basins are also the focus of the landowner-based initiative

described later in this chapter. The Kissimmee River, which runs through the S65 basins,

is currently being restored. As of this writing, the S65B structure has been removed and

over seven miles of the C-38 canal has been plugged and fifteen miles of historic

Kissimmee River have been reconnected.

Comparing noncontrollable loads in the two periods shows a disturbing trend.

Subtracting out the atmospheric loads gives a noncontrollable load of 57 tons during the

1990 to 1994 period (Table 2-1), and 131 tons in the 1995 to 2000 period (Table 2-2).

This large increase of 1995 noncontrollable surface discharges can only partially be

explained by an increase in discharge. The flow-weighted average concentration of

discharge from Lake Istokpoga and Lake Kissimmee more than doubled over this time

period.

C. WATERSHED REGULATORY PROGRAMS

The Surface Water Improvement and Management (SWIM) Plan - Update for Lake

Okeechobee (SFWMD, 1997a) published in 1997 discussed several programs that had

already been implemented to achieve the phosphorus reduction in runoff from the

watershed. A brief description of these programs and their current status is provided in this

section.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

29

C1. Dairy Rule

In June 1987, the Florida Department of Environmental Regulation, now known as

the Florida Department of Environmental Protection (FDEP) enacted the Dairy Rule

(Chapter 62-670, F.A.C.). The Dairy Rule required that all dairy operations within the

Lake Okeechobee watershed and its tributaries implement BMPs for the purpose of

reducing phosphorus inputs to the lake. A total of 49 dairies, the majority located in the

Taylor Creek/Nubbins Slough and Lower Kissimmee River basins, came under

jurisdiction of the rule.

The Dairy Rule did not establish a specific off-site phosphorus discharge

concentration limitation, but required BMPs to be incorporated into the operation of

dairies. These BMPs needed to provide reasonable assurances that each dairy could meet

state water quality standards (Chapter 62-670, F.A.C.) and that acceptable phosphorus

levels in off-farm discharges would be achieved (Albers et al., 1991). Although the

Interim Lake Okeechobee SWIM Plan (SFWMD, 1989a) established a maximum

discharge limitation of 1.2 mg/l total phosphorus, the dairies were exempted from

permitting and enforcement under the WOD Program, since they were under the

jurisdiction of the Dairy Rule.

Implementation of dairy BMPs was completed at 30 dairies. Four of these dairies

have since closed, one of which was purchased by the District in 1994 with Save Our

Rivers (SOR) funds and one was purchased for use as a reservoir assisted stormwater

treatment area (RSTAS) that is part of a critical restoration project. Currently, only 26

dairies have operating permits of which 25 are active at this time. One dairy has

temporarily closed while maintaining the Dairy Rule permit in an active status with the

option of reopening at a later date. The FDEP continues to monitor the active dairies for

compliance with their Dairy Rule operating permits. Nineteen dairies participate in the

program.

C2. Works of the District/Regulation of Nondairy Land Uses

After the adoption of the Interim Lake Okeechobee SWIM Plan (SFWMD, 1989a),

Chapter 40E-61, F.A.C., was developed by the SFWMD with an effective date of

November 1989. The rule established criteria to ensure that use of, or connection to, a

WOD project or lands would be compatible with the SFWMD’s ability to carry out the

water quality objectives found in several SFWMD programs, including those stated in

Section 373.016, F.S.; Chapter 62-40, F.A.C.; and the SWIM Act as outlined in Sections

373.451 through 373.459, F.S., and Chapter 40E-61, F.A.C. This regulatory program

applies to all nondairy land uses and areas of dairies not covered by the Dairy Rule that

discharge to WOD projects or lands located within the Lake Okeechobee drainage basin. 

Works of the District projects include waterways, canals, water control structures,

rights-of-way, wetlands, remnant oxbows or slough, lakes, and streams that the District

owns or has the responsibility of managing. All land uses within the basin are subject to

this rule. However, the type of permit required depends on several factors: the type of land
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

use, the extent to which the use is a contributor of phosphorus to the lake, and the basin in

which the land is located. The deadlines for submittal of permit applications were

prioritized to bring the most problematic basins into compliance first. 

From January 1990 through March 2001, 721 permits were issued in the following

basins: S-191, S-154, S-127, C-38 Pool E, S-4, S-71, S-72, Industrial Canal, S-133,

Culvert 10 (East Beach Drainage District), C-38 Pool D, Culvert 12A (715 Farms),

Fisheating Creek, and S-154C. In all of the 14 priority basins, initial permitting of all

problematic parcels equal to or greater than five acres in size is complete. Administrative

maintenance of the permit files is an ongoing activity, as land use and ownership changes

require permit modifications and transfers.

In priority basins, individual permits were required for certain land uses and

general (Notice of Intent) permits were required for other land uses. All other basins

required a general (no Notice of Intent) permit. Provided in Table 2-3 is a simplified

overview of the various land uses and the type of permit required by the SFWMD. In the

basins north of the lake, the primary nondairy land uses are improved pasture for beef

cattle and agricultural uses such as sod production.

In the regulatory program, users of the WOD are required to meet specific off-site

phosphorus discharge concentration limitations. If the SFWMD monitoring data indicate

that the probability of the average annual off-site discharge concentration not being met is

greater than 50 percent, the affected landowner is required to take corrective measures to

bring discharges from the property into compliance with the rule. The SFWMD conducts a

two-pronged water quality monitoring program to identify high phosphorus source areas

within the basin and to distinguish between landowners who are in compliance and those

who are not. Routine biweekly water quality monitoring is conducted on permitted

parcels. At least one year of monitoring is required on all individual permits to document

compliance status. Unfortunately, due to limited resources it has not always been possible

to monitor all individual permits. In some cases monitoring conducted downstream of

several permit holders has been used to establish compliance. A nonroutine, site specific

surveillance monitoring program is also conducted throughout the basin to identify high

phosphorus source areas in both the priority and nonpriority basins. 

Table 2-3. Works of the District permits required for various land uses

General Permit

(Notice of Intent) Individual Permit

Urban stormwater

Golf courses

Sugarcane

Horse farms

Nurseries

Land spreading of sludge

Sod farms

Dairy land use not covered by Dairy 

Rule

Improved pasture

Vegetable farms/row crops

Heifer farms

Poultry farms

Hog farms

Goat farms
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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A formal notification of potential noncompliance is sent to owners of parcels

discharging surface waters with high phosphorus concentrations. Once noncompliance is

confirmed, a permittee is required to develop a nutrient management plan with an

implementation schedule. This plan is incorporated into their SWIM permit as a permit

addendum modification (PAM). If SWIM phosphorus limitations are not achieved within

one year of issuance of the PAM, additional BMPs and corrective actions may be required.

The effectiveness of identified corrective actions are evaluated using existing water

quality and soils data along with the field-scale Everglades Agricultural Area Model

(EAAMOD). This information is then documented in a formal technical assessment and

initiated through a consent agreement between the SFWMD and the landowner.

The following list includes BMPs incorporated into the nutrient management plans

for the WOD sites that are out of compliance:

• Remove residual phosphorus in soils in former high-intensity areas

(HIAs) through a nutrient management program of forage production

(sorghum, oats, and Bahia, Alicia Bermuda, and improved grasses)

with subsequent harvest and export

• Develop grassed buffer areas around existing areas where animals

congregate

• Minimize or eliminate the development of new animal congregating

areas by mobilizing shade, water, and feeding areas and placing these

areas away from tributaries in well drained, sandy areas

• Eliminate cattle from tributaries and develop rotational grazing

strategies that move cattle away from sensitive areas during the peak

rainfall periods

• Eliminate phosphorus fertilizer applications near tributaries

• Limit the overdrainage of wetland soils

• Restore wetlands that have been ditched or drained

• Reduce animal density (voluntary)

• Reduce phosphorus import in animal feeds

• Use soil amendments to improve soil binding capacity and enhance

availability of phosphorus for plant uptake

• Use the University of Florida’s Institute of Food and Agricultural

Sciences (IFAS) soil testing data and subsequent fertilizer application

recommendations to optimize plant growth and minimize nutrient

runoff

• Eliminate off-site discharge from areas that have a high density of

animals

• Scrape sediment and remove from the site or spread in upland areas

• Use a combination of chemical and biological treatment of hot spot

ditches
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

• When maintaining ditches, remove and spread sediments in upland

areas

• Drag and spread manure to reduce the accumulation of manure in high

traffic areas to distribute nutrients more evenly across the pastures

• Develop balanced phosphorus budgets as part of a nutrient

management plan

As of March 2001, the WOD noncompliance activity summary included 28 PAMs

and 8 Consent Agreements. Sixteen permittees that have initiated corrective actions have

achieved the SWIM phosphorus limitation for their respective land use. Fourteen of the

permittees that have developed corrective actions in accordance with their PAM have

since achieved their off-site phosphorus limitation. The remaining two permittees have

achieved compliance following the implementation of corrective actions called for in their

Consent Agreement. 

D. COMPREHENSIVE EVERGLADES RESTORATION 

PLAN

The Central and Southern Florida Project Comprehensive Review Study, Final

Integrated Feasibility Report and Programmatic Environmental Impact Statement

(USACE and SFWMD, 1999) recommended a comprehensive plan for the restoration,

protection, and preservation of the water resources of Central and South Florida, including

the Everglades ecosystem, while providing for the other water-related needs of the region.

The comprehensive review study, referred to as the Restudy, proposed project components

and determined their potential impacts on existing resources. The Florida Legislature

passed the Restudy Bill (Senate Bill 1672) in April 1999, and authorized the SFWMD to

be the local sponsor of these projects. The Restudy projects are being implemented

through the Comprehensive Everglades Restoration Plan (CERP). The CERP contains

over 60 major components that involve either structural or operational changes to the

existing C&SF Project. The basic approach of the plan is to capture most of the 1.7 billion

gallons of water per day that on average is discharged through project canals to the

Atlantic Ocean and the Gulf of Mexico and use it to supplement water supply and to

achieve the restoration of natural systems, including Lake Okeechobee and the

Everglades. Restoration of natural areas will be accomplished by restoring more natural

flows of water, improving water quality, and establishing more natural hydroperiods. 

Major features of the CERP that directly affect the Lake Okeechobee watershed

include the following: 

• Taylor Creek/Nubbin Slough Reservoir-Assisted Storage Treatment

Area: a 5,000-acre storage area with a 5,000-acre water treatment area

• North of Lake Okeechobee Storage Reservoir: a 17,500-acre storage

area with a 2,500-acre water treatment area

• Lake Okeechobee Water Quality Treatment facilities: a 1,775-acre

treatment area in the S-154 Basin; a 2,600-acre treatment area in the
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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S-65D Basin; and plugged drainage ditches that will result in the

restoration of 3,500 acres of wetlands

• Lake Okeechobee Tributary Sediment Control: capturing or removing

phosphorus-laden sediment in tributaries to prevent it from reaching

Lake Okeechobee

• Lake Okeechobee Aquifer Storage and Recovery (ASR): a series of

ASR wells around the lake with 1 billion gallons per day capacity to be

proceeded by pilot testing

E. CURRENT MANAGEMENT PROGRAMS

Effective phosphorus control strategies can only be successfully implemented if

we understand the source and fate of phosphorus in uplands, wetlands, and streams of the

watershed. To achieve this understanding, several research projects were conducted to

develop the understanding of the movement of phosphorus in the watershed. Completed

and ongoing research projects are described in this section. Key results presented here

have implications for the development of cost-effective and sustainable BMPs to reduce

phosphorus loads from the watershed into adjacent aquatic systems. 

E1. Phosphorus Budgets

Phosphorus is of particular concern in this system because it has been identified as

the key element that contributes to the eutrophication of the lake (Davis and Marshall,

1975; Federico et al., 1981). Early research indicated that phosphorus loads originated

from agricultural nonpoint sources, mainly beef cattle ranches and dairy farms (Boggess et

al. 1995). Based on data from 1985 to 1989, Boggess et al. (1995) estimated that the total

phosphorus import into 22 basins of the northern Lake Okeechobee watershed was

approximately 3,500 tons per year. The phosphorus import was primarily in the form of

pasture fertilizer and dairy feed. In addition, approximately 330 tons of phosphorus

entered the watershed in the form of rain. The total phosphorus export in milk, cows, and

crops was about 900 tons per year. In addition, about 330 tons of phosphorus reached the

lake per year. From these values, it was estimated that the net phosphorus import of 2,600

tons per year was retained in upland soils and the transport system (streams and wetlands).

This imbalance in import versus export continues to add to the build-up of phosphorus in

the northern Lake Okeechobee watershed. This has caused the concern that unless controls

are placed on importing phosphorus, attempts to restore Lake Okeechobee will be delayed

or fail altogether.

The study by Boggess et al. (1995) was based on phosphorus and materials budget

information collected ten years ago, which is prior to the implementation of many BMP

programs. Since then, land uses and associated management practices have changed

dramatically. A study is being conducted to update the phosphorus budget information,

taking into account many of the land management changes that have occurred in recent

years. This new phosphorus budget will use the most recent phosphorus import and export

data available, as well as examine phosphorus sources that were not explored previously,
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

such as sludge application, poultry manure, on-site septic systems, and phosphorus

discharges via subsurface flow. This study also includes analyzing possible relationships

between net phosphorus imports and basin characteristics (land use type, soil type, stream

type, etc.) for each basin, identifying basin characteristics that affect net phosphorus

imports and storage, and developing a graphical user interface to view input data (farms,

drainage basins, hydrographic features, land uses, and soil types) and phosphorus budget

results (import and export) using ArcViewTM, a geographic information system. The

updated phosphorus budget information will be available in March 2002. The final report

and the graphical user interface are due in April 2002. Based on this information, we will

determine how much the net import of phosphorus to the watershed has changed over the

past decade, and what sources are particularly problematic. Then, we can target those

problem sources and determine effective means to control them. 

E2. Phosphorus Assimilation

The WOD Rule limits total phosphorus concentrations in runoff leaving land

parcels (SFWMD, 1989a). The total phosphorus concentration limitations range from 0.18

to 1.2 mg/l. These limitations were developed based on estimated phosphorus assimilation

in channels and wetlands along measured flow paths. A first order exponential decay

function was used to describe phosphorus assimilation with flow travel distance in

channels and wetlands (SFWMD, 1989a). However, the assimilation of phosphorus is

actually influenced by diverse physical, chemical, and biological factors. These factors

include phosphorus sorption/desorption by sediments, water flow rate and travel length,

and phosphorus uptake by vegetation. If phosphorus load estimates from the watershed are

to improve, it will be necessary to develop better phosphorus retention/assimilation

algorithms for describing phosphorus transport dynamics. These algorithms are critical to

watershed nutrient management.

A second order exponential decay function was used in the updated Lake

Okeechobee Agricultural Decision Support System (LOADSS) model. The function

included a temporal adjustment of flow rate on an annual scale (SWET, 1999). To take

into account of additional biogeochemical processes within various flow conveyance

systems (e.g., overland, channels, natural streams, and wetlands), a study was conducted

recently to enhance the existing algorithm used in the LOADSS model. After examining

the available data, the contractor concluded that the data resources for the Lake

Okeechobee watershed are insufficient to advance the current phosphorus assimilation

algorithm. Therefore, the focus of future studies should be gathering the necessary data to

properly quantify the phosphorus assimilation in specific water conveyance systems. 

E3. Potential Phosphorus Load Reduction from Nondairy 

Out-of-Compliance Sites and Dairy Hot Spots

E3a. Beef Cattle Waste

Cattle waste from the basins north of Lake Okeechobee has been identified as a

source of phosphorus contributing to the accelerated eutrophication of the lake. The WOD
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program issues permits and monitors phosphorus concentrations in surface runoff from

nondairy land parcels that are 0.5 acres or greater in size. A site is considered out of

compliance if the average total phosphorous concentration in the runoff within a 12-month

period exceeds the regulatory standard for the site. Pasture sites with excess phosphorus

discharge are potential targets for corrective management actions designed to reduce

phosphorus loads.

Zhang et al. (2001) indicates that, from October 1998 to September 1999, 77 outof-compliance sites discharged an estimated 51 tons of phosphorous on an average annual

basis, of which an estimated 24 tons per year reached Lake Okeechobee. The remaining

estimated 27 tons of phosphorus load were retained by streams and wetlands. An

estimated 16 tons of phosphorus load reduction per year would be expected if phosphorus

concentrations in runoff from these sites do not exceed the discharge limits. If the land

uses were changed to native range land with an off-site annual total phosphorus areal

loading rate of 0.102 pound per acre, an estimated 23 tons of phosphorus load reduction

would be expected on an average annual basis from these out-of-compliance sites.

Of the 77 out-of-compliance sites, 12 sites had a phosphorus loading rate greater

than 2.5 pounds per acre. These sites were recommended to be placed on the priority list

for the Lake Okeechobee Water Retention/Phosphorus Removal Critical Restoration

Project. Ongoing research is being conducted by the District to identify remedies and

associated costs for these sites and to evaluate the cost-effectiveness of strategies for

reducing phosphorus loads.

E3b. Dairy Waste

Dairy waste from the northern Lake Okeechobee watershed has been identified as

a source of phosphorus contributing to the accelerated eutrophication of Lake Okeechobee

(Ray and Zhang, 2001). Sites were identified as priority sites if the average total

phosphorus concentration in runoff exceeded regulatory site limitations from October

1998 to September 1999. These sites are located at both active and former dairies. The

phosphorus discharge limit for active dairy sites is 1.2 mg/l. The discharge limitations for

former dairy sites vary based on current land use and must not exceed 1.2 mg/l. Twentyone priority sites were identified within the northern Lake Okeechobee watershed. These

sites produce an estimated 18.1 tons of phosphorus load annually, of which an average of

9.5 tons of phosphorus load reaches the lake on an annual basis. The remaining 8.6 tons of

phosphorus load were retained/assimilated by streams and wetlands in the discharge

transport system between the sites and the lake. If none of the sites were to exceed the 1.2

mg/l phosphorous runoff concentration, off-site loads would be reduced by an estimated

10.7 tons, with the loads to the lake reduced by 5.8 tons. Furthermore, if all dairy sites

were converted to improved pasture with a discharge concentration limitation of 0.35 mg/

l, off-site loads would be reduced by an estimated 15.7 tons and loads to the lake would be

reduced by 8.3 tons. 

These load estimates do not include the outer pastures associated with the dairies.

In 1999, three monitoring stations were added to the discharge points of the dairy pastures.

This information will be used to calibrate a computer simulation model that will estimate
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

the phosphorous load from all dairy pastures. This information will be included in the

updated study. Due to the 2000 drought, not enough samples were collected to complete

this study by the original target date of December 2001. The study will be extended until

an adequate number of samples have been collected and analyzed.

E4. Modeling Efforts

To determine the effectiveness of individual BMPs, a systematic methodology for

cross-comparison of alternative strategies for phosphorus load reduction, including fieldscale, farm-scale, or basin-scale phosphorus reduction practices, needed to be developed.

The need to evaluate practices at different scales resulted in the development of field- and

basin-scale computer models. Projects include development and application of the

following models: (1) the EAA model upgrade; (2) the next generation field-scale

Nonpoint Source Pollution Model; (3) the next generation Watershed Phosphorus

Transport Model; and (4) the Lake Okeechobee Agricultural Decision Support System.

General overviews and applications of each project are presented below.

E4a. EAA Model Upgrade

A field hydrologic and nutrient transport model (FHANTM) (Tremwel and

Campbell, 1992), has been used in the Lake Okeechobee watershed as a tool to evaluate

the effectiveness of BMPs implemented on parcels out of compliance with the WOD

phosphorus discharge concentration limitations (Gornak and Zhang, 1999). Unfortunately,

FHANTM does not handle the phosphorus soil interaction well. Zhang and Gornak (1999)

evaluated three field-scale models, FHANTM, FHANTM 2.0, and the EAA Model

(EAAMOD), to determine which was best suited for use in the WOD program. It was

concluded that none of the models were sufficient, but that EAAMOD had the most

potential. Therefore, EAAMOD was upgraded in 2000 for use in the Lake Okeechobee

WOD program. 

In addition to upgrading the field-scale version of EAAMOD, the field-scale

model is to be integrated into a farm-scale model (EAAMOD WAMView). A field-scale

model evaluates the land use from one pasture. The advantage of the farm-scale model is

that an entire farm can be simulated at one time rather than simulating the fields

individually. Final adjustments to the farm-scale model are being made at this time. 

E4b. Nonpoint Source Pollution Model

Runoff from fields in the Lake Okeechobee watershed is a major source of

phosphorus entering the lake. The ability to estimate edge-of-field phosphorus loads and

potential load reductions due to BMPs is important to programs whose goal is to limit the

amount of phosphorus entering the lake. Examples of such programs are WOD, isolated

wetland restoration, and reservoir-assisted STAs. The Nonpoint Source Pollution Model

estimates the impacts that land use practices and BMPs have on reducing phosphorus

loads leaving a field. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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The Nonpoint Source Pollution Model has hydrology and nutrient transport

components and a graphical user interface. The hydrology component computes overland

and ground water flows leaving a field. The nutrient transport component computes

phosphorus concentrations in these flows, and can be expanded to include nitrogen should

the need arise. The graphical user interface facilitates use of the model by automating

many modeling functions including input data preparation, model execution, and output

analysis. The Nonpoint Source Pollution Model also will be a component of the basinscale Phosphorus Transport Model. 

E4c. Phosphorus Transport Model

The Phosphorus Transport Model was originally developed and applied to the

Taylor Creek basin (Zhang et al., 1996). It gave close estimates of flow and phosphorus

loading on a seasonal basis. The next generation of the Phosphorus Transport Model

operates on a daily time step and it contains two submodels: a field-scale submodel and a

channel system submodel. The field-scale submodel will simulate phosphorus loads

leaving individual fields in a watershed and is being developed by the Next Generation

Field-Scale Nonpoint Source Pollution Model project. The channel system submodel will

receive runoff and phosphorus loads leaving fields as input and simulate phosphorus

transport and removal by streams, canals, and wetlands. The channel system submodel

will have a hydrology component to simulate water movement, and a transport component

to simulate phosphorus transport and removal. Also, a graphical user interface will be

developed to facilitate model use by automating many modeling functions, including input

data preparation, model execution, and output analysis. The Phosphorus Transport Model

can be used to evaluate the effectiveness of BMPs on reducing phosphorus loads from the

watershed to the lake. The final product is due in July 2003.

E4d. Lake Okeechobee Agriculture Decision Support System

The Lake Okeechobee Agriculture Decision Support System (LOADSS) is a tool

based on a geographic information system that evaluates the effects of different land use

practices on reducing phosphorus loads and the economic impact of these practices on the

surrounding area (Negahban et al., 1995). LOADSS was originally developed with data

collected before 1987. The model was updated in 1997 with 1995 conditions (SWET,

1999).

The updated LOADSS model contains the most current land use data and

economic information. Land parcel boundaries developed for the WOD rule also were

incorporated into the LOADSS database. The update created a new database allowing

users to conduct a phosphorus loading analysis at a finer spatial scale. The updated

economics database included the cost of converting one land use to another. Within

LOADSS, a land use and phosphorus management plan can be developed using a menudriven user interface. The updated LOADSS model allows the District to evaluate what-if

scenarios and determine the effectiveness of phosphorous control practices on reducing

phosphorus loads to the lake.
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

E5. Optimization of BMPs for Beef Cattle Ranching in the Lake 

Okeechobee Basin

Research on optimizing BMPs for beef cattle ranching in the Lake Okeechobee

basin was initiated in 1996 to reduce nonpoint sources of phosphorus pollution for beef

cattle and contribute to modeling efforts for load reduction scenarios. The project is being

implemented in several phases, and it is expected to be concluded in 2005. The first phase

examines cattle stocking density BMPs.

This project was established within the broader context of a Memorandum of

Understanding among the SFWMD, Archbold Expeditions’ MacArthur Agro-Ecology

Research Center, the IFAS, and the Florida Cattleman’s Association. The program was

established at MacArthur Agro-Ecology Research Center, a 4,170-hectare cattle ranch

operated by Archbold Expeditions in the C-41 basin along Harney Pond Canal. In addition

to financial support from the SFWMD, the cattle stocking rate project has received

funding from Archbold Biological Station, the IFAS, the FDEP/USEPA 319 funds, and the

United States Department of Agriculture’s Natural Resources Conservation Service

(NRCS) and the National Research Initiative to support a multifaceted project to examine

the ecology and economics of sustainable cow-calf operations and control of phosphorus

in surface runoff.

The most significant finding of the project to date is that surface water phosphorus

concentrations and total phosphorus loads were significantly greater from the improved

pastures than from the semi-native pastures. Total phosphorus concentrations and loads

were five times higher on the improved pastures than on the semi-native pastures. This

difference could be an artifact of prior land use history, since the improved pastures used

in the study received phosphorus inputs for many years up until 1986. The semi-native

pastures, by contrast, were never fertilized. Additionally, a notable difference was

observed in the proportion of ortho-phosphorus in the runoff from the two pasture types.

The ratio of ortho-phosphorus to total phosphorus was 0.74 in the improved pastures and

0.23 in the semi-native pastures. The improved pastures not only exported more

phosphorus but they also exported a more biologically available form of phosphorus.

Soil phosphorus test results were consistent with the surface water phosphorus

data from the pastures. The high phosphorus content in the improved pasture runoff water

was matched by correspondingly high water soluble phosphorus concentrations in the

improved pasture soils, which were greatest in the upper 5 centimeters of the soil. Links

between soil phosphorus pools and surface water concentrations warrant further

investigation. 

This project is scheduled to continue through 2005. Statistical differences resulting

from the different stocking rates are not expected to be evident this early in the project.

The stocking density treatments need to be continued for at least two more years before

assessing whether the cattle stocking densities being tested have an appreciable effect on

nutrient concentrations or loads in surface runoff. In addition to continuing the study to

obtain statistical differences in stocking rates, variability in annual rainfall necessitates
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

39

that the project be continued to capture the range of loading scenarios likely to be

encountered from beef cattle pastures in the basin. 

E6. Star Grass Experiment

Rechcigl et al. (1990) and Rechcigl and Bottcher (1992) showed that fertilization

of Bahia grass can contribute to phosphorus in runoff because the Bahia grass does not

require additional phosphorus. As a result of those studies, which were funded by the

SFWMD, the IFAS reduced the phosphorus fertilization requirement for Bahia grass to

zero for South Florida. This was a win-win scenario for the ranchers and Lake

Okeechobee. Ranchers will not need to pay for costly phosphorus fertilizer that is not

needed and less phosphorus is imported to the Lake Okeechobee watershed.

As a follow up to the Bahia grass study, the IFAS suggested that phosphorus

fertilization recommendations for other pasture grasses may also be reduced. A major

field and laboratory experiment was initiated in 1998 to evaluate the optimum phosphorus

fertilization requirements for star grass and to evaluate the use of limestone and gypsum

soil amendments to reduce the mobility of phosphorus. This study is being conducted by

IFAS on the Williamson Ranch in Okeechobee County. 

Two years of data have been collected from samples of runoff and ground water

from field plots and samples of leachate from soil columns in the laboratory. Preliminary

data indicate that both calcium limestone and gypsum may retard phosphorus movement

in ground water but not in surface water. The initial data also indicate that the phosphorus

fertilization recommendations for star grass may be reduced. Unfortunately, due to the

drought conditions in 2000, only two small runoff events occurred. 

One field and educational day has been conducted to present the preliminary

results of the experiment to the local ranchers. Two more field and educational days are

scheduled to be conducted over the next two years. The final report is due in September

2002. An IFAS extension publication will also be produced to provide ranchers with the

results of the study.

F. LAKE OKEECHOBEE PROTECTION PROGRAM AND 

PERMITS

The Florida Legislature passed the Lake Okeechobee Protection Program,

amending Section 373.4595(3), F.S., during the 2000 session. This law establishes a

comprehensive long-term program to restore and protect Lake Okeechobee and its

downstream receiving waters. The legislature also appropriated $38.5 million dollars to

expedite the restoration of Lake Okeechobee. It requires significant involvement and

cooperation between the FDEP, the FDACS, the SFWMD, the IFAS, and the NRCS to

implement the program. The legislation is similar in scope and approach to the Everglades

Forever Act, involving major new programs in planning, construction of major public

treatment projects, and new BMP and permitting requirements, though it does not include
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

dedicated funding. It establishes the Lake Okeechobee Protection Program and authorizes

Lake Okeechobee Protection Permits (Section 373.4595(4), F.S.).

F1. Overview of the Lake Okeechobee Protection Program

The Lake Okeechobee Protection Program contains several components:

Lake Okeechobee Protection Plan. By January 1, 2004, the SFWMD, in

cooperation with the FDEP and the FDACS, is to complete the Lake Okeechobee

Protection Plan. This plan will determine how water quality standards, particularly for

phosphorus, will be met in Lake Okeechobee and its downstream receiving waters. The

plan include a combination of source controls (e.g., BMPs) and treatment facilities that

will be constructed by the District and its partners. It may also determine how sediments

within the lake will be managed. The components of this plan are discussed later in this

chapter.

Lake Okeechobee Watershed Phosphorus Control Program. The Lake

Okeechobee Watershed Phosphorus Control Program includes both agricultural and

nonagricultural BMP projects. In February 2001, the FDEP, the FDACS, and the SFWMD

entered into an interagency agreement to address how to implement the programs and

coordinate with existing regulatory programs (e.g., WOD and Everglades restoration

programs). According to the agreement, the FDACS will be responsible for establishing

BMPs for agriculture. If water quality problems persist on farms where BMPs have been

implemented, the FDACS shall reevaluate the BMPs and make appropriate changes to the

rule to adopt additional BMPs. Development of nonagricultural nonpoint source BMPs

will be the responsibility of the FDEP. The FDEP shall initially focus on the priority

basins, and will deal with appropriate nutrient applications rates for soil amendments,

monitoring to assess the effectiveness of BMPs including domestic wastewater systems,

land application of animal residuals, and alternative nutrient reduction technologies. 

Lake Okeechobee Construction Project. The Lake Okeechobee Construction

Project will be implemented in two phases. In Phase 1, a series of projects will be

constructed that are focused in the priority basins (S-191, S-154, S-65D, and S-65E) and

are consistent with the Lake Okeechobee Issue Team’s Action Plan (Harvey and Havens

1999). These include construction of two pilot STAs and the restoration of several isolated

wetlands as part of the Lake Okeechobee Critical Project, a joint program between the

SFWMD and the USACE, a sediment removal pilot project in a tributary draining into

Lake Okeechobee, and design work on a large-scale STA in the S-191 basin. In Phase 2,

the District, in cooperation with the other agencies, will develop an implementation plan

for the construction of additional facilities to further reduce phosphorus loading

throughout the watershed. 

Lake Okeechobee Research and Water Quality Monitoring Program. The

SFWMD, in cooperation with the FDEP and the FDACS, is to complete an extensive

research and monitoring program that will provide the necessary information for the Lake

Okeechobee Protection Plan. A water quality baseline for total phosphorus will be
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

41

conducted to record existing conditions. Monitoring will be conducted for long-term

ecological changes and for compliance with water quality standards. Other specifically

identified components include 1) development of a Lake Okeechobee water quality

model, 2) determination of phosphorus sources within the watershed, 3) assessment of

phosphorus sources from the Upper Kissimmee Chain-of-Lakes and Lake Istokpoga, 4)

assessment of water management practices within the watershed, and 5) evaluation of the

feasibility of alternative nutrient reduction technologies.

Exotic Species Control Plan. The District, with cooperation from the FDEP and

the FDACS, has identified the exotic species within the Lake Okeechobee watershed. The

Exotic Species Control Plan was developed to protect the native flora and fauna from the

invasion of exotic species.

Lake Okeechobee Internal Phosphorus Management Program. By July 1,

2003, the District, in cooperation with the FDEP and the FDACS, is to complete a

feasibility study to determine it if is reasonable to manage phosphorus-laden sediments in

the lake. If feasible, the District will establish the Lake Okeechobee Internal Phosphorus

Management Program. Through this program the District will pursue the design, funding,

and permitting for implementing sediment management methods. 

Annual Progress Report. The District is to submit an annual progress report on

the implementation of the Lake Okeechobee Protection Program to the Governor of

Florida and the Florida Legislature. The second one will be submitted on January 1, 2002.

F2. Overview of the Lake Okeechobee Protection Permits

The Lake Okeechobee Protection Permits contains several components:

Existing Structures. All structures discharging into Lake Okeechobee are to have

an FDEP permit, and discharges from the SFWMD structures are to achieve state water

quality standards by January 1, 2015. The SFWMD is not to divert waters to the St. Lucie

River, Caloosahatchee River, or the Everglades, in such a way that state water quality

standards are violated, unless the SFWMD declares an emergency and FDEP concurs

(existing law retained).

Lake Okeechobee Construction Project Facilities. The SFWMD is to obtain

permits from the FDEP for the Lake Okeechobee Construction Project. The design

objective is to meet the 40 ppb target for phosphorus by 2015, unless the TMDL for the

water body is different. 

F3. Lake Okeechobee Watershed Phosphorus Control Program

Several projects are being conducted within the Lake Okeechobee Watershed

Phosphorus Control Program. They include the previously mentioned star grass

experiment to determine the appropriate application rates for soil amendments; a study on

the land application of residuals and chicken manure; a project to identify, select, monitor,
42

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

and implement best available technologies (BATs) for dairies; isolated wetland

restoration; and the Phosphorus Source Control Grant Program.

F3a. Land Application of Residuals and Chicken Manure

Although dairy farming and beef cattle ranching are often cited as the main source

of phosphorus input to the lake, the contribution from other sources outside the watershed,

such as the land application of sewage sludge (residuals) and chicken manure, also

contribute phosphorus to the lake. In Florida, 66 percent of the residuals are applied to

land (FDEP, 1997). In 1998, residuals and chicken manure contributed 1,259 dry tons of

phosphorus loading to the Lake Okeechobee watershed (FDEP, 1999). 

Beneficial use of residuals and chicken manure via land application is usually

limited by nitrogen considerations. Customarily, residuals application rates are based on

nitrogen needs of the crop. This practice often results in phosphorus inputs that far exceed

the amounts required for normal growth. Addition of phosphorus beyond plant utilization

is a waste of a nutrient resource, and in areas of sandy soils, could pose an environmental

liability. To reduce phosphorus runoff, the FDEP has initiated a phosphorus rule in the

basin, limiting residual application to the phosphorus requirement of the crop versus the

nitrogen requirement.

Soils in the Lake Okeechobee watershed present a unique situation for

management of phosphorus in applied wastes due to a fluctuating water table and

predominantly sandy soils with low phosphorus retention capacity. These conditions

promote transport of phosphorus via surface runoff and subsurface lateral seepage to

streams and canals, which can lead to eutrophication of surface waters.

Water treatment residuals containing aluminum are frequently disposed in

landfills. During land application, addition of aluminum to wastewater residuals and

chicken manure may bind excess phosphorus, thereby minimizing the threat to surface

waters. 

The Lake Okeechobee Action Plan (Harvey and Havens, 1999) recommends

enhanced source control as a factor in evaluation of the watershed phosphorus loading

issue. In addition, the Lake Okeechobee Protection Act (Section 373.4595, F.S.) requires

entities within the Lake Okeechobee watershed to develop conservation or nutrient

management plans that limit domestic wastewater residual application, based upon

phosphorus loading.

In support of these directives, the District and the FDEP initiated a project that will

help ensure that associated nutrient management plans are based on sound science. The

results from this study will identify any environmental and health problems associated

with use of residuals and chicken manure in the watershed. Results will include

recommendations regarding judicious applications of residuals and chicken manure and

their establishment as a BMP for landowners in the watershed. At the time of this writing,

the laboratory characterization of the waste materials and construction of the field study is
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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currently under way. Monitoring activities are scheduled to commence in 2002. The final

report is due by the end of 2003.

F3b. Dairy Best Available Technologies

In the previous Lake Okeechobee SWIM Plan (1997) it was noted that numerous

dairies have runoff with total phosphorus concentrations in excess of 1,000 ppb, and that

current monitoring data show some sites have concentrations above 7,000 ppb. At the

present time, many of the 20 active dairies within the priority basins have phosphorus

discharge concentrations in excess of the 1,200 ppb limit identified in the WOD Program

(Chapter 40E-61, F.A.C.). Given the current level of water quality in the runoff from the

Lake Okeechobee watershed, a comprehensive project is being undertaken to identify,

select, and implement best available technologies (BATs) that will significantly reduce the

export of phosphorus from dairy operations into tributaries and Lake Okeechobee. 

The objectives of this project will be to identify, select, monitor, and implement

BATs that will significantly reduce the export of phosphorus from dairy operations into

Lake Okeechobee and its tributaries. Various alternatives will be evaluated to determine

the best comprehensive system of technologies that will address the multiple dairy farm

components (HIAs, waste management system, pastures, etc.). Selection of technologies

for implementation will be accomplished by an objective methodology that allows for

review and input by a multiagency team composed of the FDEP, the FDACs, the NRCS,

the SFWMD, and stakeholders. This project will address, at a minimum, the following

issues:

• Engineering feasibility of proposed alternatives 

• Short- and long-term costs (e.g., capital, start-up, cost per kilograms

phosphorus removed, operation and maintenance) including potential

revenue sources to offset project costs

• Feasibility of each alternative relative to obtaining a water quality goal

of 40 ppb (Note that a numeric goal is necessary for the comparison of

alternatives. A goal of 40 ppb has been selected for this project based

on the most recent regulatory requirements for the watershed and to

reduce the harmful ecological impacts to the lake and downstream

regional water resources. If this goal is not attainable, the selected

consultant will identify the level of phosphorus reduction that is

technically and economically practicable.)

• Process start-up time and a time line to achieve desired treatment goals

• Socioeconomic implications (i.e., economic impacts, cultural

resources, social benefit/cost factors, etc.)

• Legal and permitting issues

• Coordination with other agencies to avoid duplication of efforts

• Opportunities for partnerships with the private sector
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

It is recognized that in a comprehensive approach to reducing phosphorus export

from dairies, different scenarios may be required for individual dairy phosphorus

reduction plans. For example, one dairy’s phosphorus export problem may be primarily

due to limitations in its existing waste management system, while another dairy’s

problems may have arisen as a result of residual phosphorus accumulation in its outer

pasture areas. Phosphorus reduction might be accomplished on each of these dairies using

different technologies or combinations of those technologies. For this reason, a

comprehensive nutrient management plan is being developed for each of the three dairies

participating in this project prior to selecting appropriate technologies. Each dairy

phosphorus reduction scenario is likely to affect project costs, the nature and magnitude of

phosphorus export, and/or other important considerations.

A specific set of goals and performance measures for each of the alternatives have

been developed through this project. Each technology will be evaluated against the

performance measures to identify all feasible alternatives for reducing phosphorus exports

from the dairies. All of the potential impacts (environmental, socioeconomic, etc.) of each

alternative will also be identified. Information regarding the technologies that are selected

for implementation on the three dairies participating in this project will be disseminated to

the other dairies and ranches in the watershed. The assessment phase of the project was

completed in 2001. The Governing Board approved the project proceeding into the

implementation phase. Installation of a water quality monitoring network has been

initiated and design and construction of the technology will follow thereafter.

F3c. Lake Okeechobee Water Retention/Phosphorus Removal Critical 

Restoration Project

In 1996, the South Florida Ecosystem Restoration Working Group initiated critical

restoration projects to be implemented under the USACE’s authority provided in Section

528 of the 1996 Water Resources Development Act. In 1998, the USACE and the

SFWMD proposed the Lake Okeechobee Water Retention/Phosphorus Removal Critical

Restoration Project to the working group. The working group ranked this project number

ten on the list of critical restoration projects. A cooperation agreement for this project was

signed on January 7, 2000. The project was estimated to cost $16,360,000. The SFWMD

is the local sponsor of the project, which will be cost shared between with the USACE and

the SFWMD. 

The initial vision of this project was to increase regional water storage north of

Lake Okeechobee through wetland restoration/creation on lands volunteered by private

landowners. Approximately 45 percent of the wetlands in the Lake Okeechobee watershed

have been ditched in order to speed their drainage. By simply plugging the drainage

outlets, the surface runoff would still drain as usual, but the wetlands would once again

serve as on-site water storage areas. The secondary and tertiary benefits would include

reducing phosphorus in surface runoff and enhancing wildlife habitat, respectively. 

The proposed project sites are located throughout the northern Lake Okeechobee

watershed in the following basins: S-65D and S-84, along the Lower Kissimmee River;

S-154, and Taylor Creek/Nubbin Slough (S-191). Initially two pilot STAs and 10 small-
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

45

scale restoration/ creation projects were planned. Those numbers are subject to change.

An expanded effort for this critical project is being considered that would include all Lake

Okeechobee subbasins in the northern part of the watershed that are contributing nutrients

and other pollutants to the lake.

The first STA is located on Taylor Creek. It is a 193-acre site that was acquired

from Grassy Island Ranch. The District, in conjunction with the USGS is conducting

preconstruction monitoring that to determine the efficacy of the STA. This monitoring will

continue after construction is complete. A second STA, approximately 1,000 acres in size,

will be constructed adjacent to Nubbin Slough at the New Palm/Newcomer Dairy property

acquired by the District through the Save Our Rivers Program. The USACE is designing

and will construct both STAs.

For the small-scale sites, the SFWMD is designing and constructing modifications

to improve stormwater retention, restore wetlands, and improve quality of discharge

water. Components of the proposed modifications include plugging drainage ditches and

installation of riser culverts in existing drainage ditches to retain water in currently

overdrained historic wetlands. Some of the sites involve expansion of existing water

storage ponds or creation of new impoundments. The sites will remain in private

ownership and proposed project areas will require flowage easements with the

landowners.

F3d. Isolated Wetland Restoration and Creation Program

Historically, isolated wetlands covered a significant percent of land area in the

Lake Okeechobee watershed, capturing stormwater runoff and helping to retain

phosphorus in the watershed. However, in the 1960s, many of these wetlands were drained

to put more land into agricultural production, and in the process, have allowed more

phosphorus to reach Lake Okeechobee. As a consequence, the elimination of wetlands has

contributed to the accelerated eutrophication of Lake Okeechobee. 

Restoration of ditched natural wetlands and the creation of new wetlands as filter

marshes is one of the potential mechanisms for reducing phosphorus loading to Lake

Okeechobee. One of the programs currently under way to restore and create new wetlands

in the Lake Okeechobee watershed is the Lake Okeechobee Isolated Wetland Restoration

and Creation Program. 

The Lake Okeechobee Isolated Wetland Restoration and Creation Program is a

voluntary landowner cost-sharing program that will be conducted from October 2000 to

September 2003. This program offers landowners the opportunity to restore isolated

wetlands that have previously been ditched, drained, and converted to agricultural uses.

The SFWMD is administering the program with the cooperation of a multiagency team

that includes the FDACs, the FDEP, the NRCS, the USFWS, and the IFAS. As of April

2002, eleven landowners had signed up for the program and design and construction had

begun on two of the sites.
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

F3e. Phosphorus Source Control Grant Program

The goal of the Lake Okeechobee Phosphorus Source Control Grant Program is to

identify, fund, and implement projects that reduce external phosphorus loads from the

Lake Okeechobee watershed. The SFWMD is administering the program, but an

interagency team that includes the FDEP, the FDAC, the NRCS, and the IFAS participated

in the program coordination and selection of projects.

The program has two major components: 1) grant and 2) engineering oversight.

The grant component is comprised of two separate funding releases and will be

administered in four phases: 1) Project Selection 2) Implementation and Reporting, 3)

Operation and Maintenance, and 4) Monitoring and Reporting. Under the engineering

oversight component, the District will contract an engineering firm to verify that

implementation of funded projects is performed in accordance with the funding agreement

and grant application. The project selection phase has been completed for both funding

releases.

F4. Lake Okeechobee Tributary Sediment Removal 

Demonstration Project

In 1997, the District sponsored a study to determine the relative magnitude of

phosphorus content and transport potential of sediment from various tributaries in the

northern portion of the Lake Okeechobee watershed that convey stormwater runoff to the

lake and to analyze feasible management alternatives for source removal and control. That

study, completed by Mock Roos and Associates (1997) concluded that sediment removal

would reduce phosphorus loads to Lake Okeechobee. The total phosphorus reduction will

be limited by a fraction of particulate phosphorus in the tributary bed load, which is about

25 percent. It was estimated between 5 to 25 percent of the particulate phosphorus

entering the lake could be eliminated by direct sediment removal. 

The Lake Okeechobee Tributary Sediment Removal Demonstration Project was

developed in 1999 and is ongoing. It is a multiphase project. Project design and permitting

has been completed and construction has begun. The project will be completed by October

1, 2003.

 The project has been designed to demonstrate the phosphorus reduction benefits

realized by tributary sediment removal. Before expanding sediment removal to other

tributaries, this activity must be demonstrated to be technically feasible and economically

viable. If the project demonstrates that either of the tested technologies can successfully

trap sediments, the technology will be utilized in other tributaries by the District and/or

private property owners. The specific objectives of the study are as follows:

• To determine if particulate phosphorus loading to Lake Okeechobee

from the Lettuce Creek drainage basin may be reduced using either of

two sediment removal technologies
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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• To demonstrate the feasibility of sediment removal in a tributary as a

method to reduce phosphorus loading to the lake

• To perform a detailed assessment of effectiveness of these two

technologies and their economic viability

The two sediment removal technologies that will be tested in this demonstration

project are a continuous deflective separation (CDS) unit and a tributary sediment trap

(TST). They were selected based on the following criteria:

• According to current literature, these technologies are effective in

reducing particulate phosphorus loading.

• These technologies can be applied in open channel flow condition and

have a high treatment capacity.

• These technologies are on the lower end of cost for treatment facilities.

• The treatment facilities can be easily maintained. 

The CDS unit is a patented process for removal of bedding and suspended solids. It

was developed in Australia by CDS Technologies, Ltd., and is manufactured in the United

States by CDS Technologies, Inc. The CDS unit works by trapping pollutants using a

separation screen. Stormwater runoff discharges into the center chamber of the CDS unit

and then passes through a separation screen to an outer chamber prior to discharging

downstream. Gross pollutants are trapped in a sump area located below the separation

screen. 

The use of a tributary sediment trap (TST) is recommended by the Guidebook of

Sediment Control Best Management Practices (SFWMD, 1999a). The principle of

sediment removal using a sediment trap is similar to a settling basin/water detention area.

An artificial or natural water detention area in which water flow velocities are lowered,

relative to inflows, to facilitate the settling of suspended solids. However, a trap contains a

deepened section in addition to a widened section. Water velocities are suddenly slowed

down by a porous barrier or baffle in a settling basin/trap, which allows sediment to settle

into a collection area. 

The project is being conducted at the site where Lettuce Creek discharges to the

SFWMD conveyance system. Lettuce Creek is within the Nubbins Slough basin, which is

located northeast of Lake Okeechobee. It discharges through the L-63S Canal and is one

of the major sources of phosphorus load discharging into Lake Okeechobee. Lettuce

Creek was selected for this sediment removal demonstration because it has the following

characteristics: 

• Continuous flow

• No upstream water control structures

• Relatively high sediment phosphorus content and particulate

phosphorus concentrations

• Erosive soil
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Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

• Relatively high sediment transport rate

• Diversified land uses in the drainage basin

• High period of record and 12-month rolling average phosphorus

concentration among the tributaries according to the data reported in

the Tributary Water Quality Monthly Report. 

• Both a CDS unit and a TST will be installed at the discharge site of

Lettuce Creek. By installing both the CDS unit and the TST at one site,

their performance on phosphorus removal can be compared. 

The project will be conducted in three phases. Phase I includes the development of

a work plan, land surveys, data collection and computation for engineering design, project

engineering design, development of a quality assurance project plan, and project

permitting. During Phase II, the CDS unit and the TST will both be constructed and

installed, and monitoring instruments will be calibrated. In Phase III, the monitoring

network implemented in Phase II will be operated and maintained for 12 months.

After 12 months of monitoring, the selected contractor will analyze monitoring

data to determine whether either sediment removal technology should be applied to other

tributaries. Data from the monitoring network will provide an understanding of

phosphorus movement through the tributary system and sediment removal mechanisms.

The total cost of construction, maintenance fees, and cost per unit phosphorus removal of

each technology will be analyzed to determine if these technologies are technically and

economically effective and which technology is the most cost-effective. 

F5. Natural Resource Analysis of Lake Okeechobee 

Phosphorus Management Strategies

The Lake Okeechobee Protection Act (373.4595, F.S.) establishes extensive and

comprehensive requirements for surface water improvements and management within

Lake Okeechobee and its watershed. Cost-effectiveness in reducing phosphorus is an

implicit part of the overall legislation, and it is explicitly referred to in various activities.

This project will provide the framework and detailed information for comparing the costeffectiveness of various phosphorus reduction treatments.

The purpose of this project is to provide an environmental (or natural resource)

economic analysis of the alternative phosphorus management strategies that have been

used, or are being considered, in the Lake Okeechobee watershed. Natural resources

valuation principles will be utilized and will include the determination of the economic

impacts to the surrounding communities that each of the strategies could present.

Alternative phosphorus management strategies (beyond the Dairy Rule BMPs) are being

examined to further reduce external nutrient loads to the lake in an effort to achieve the inlake target phosphorus concentration of 40 ppb. Some of the phosphorus control strategies

currently under consideration, or partially implemented, include implementation of the

Dairy Rule, WOD regulation of nondairy land uses, confinement dairies, land acquisition

with restrictions, reservoir-assisted STAs, implementation of BATs, implementation of
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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enhanced BMPs, implementation of projects under the Phosphorus Source Control Grant

Program, reclamation or creation of isolated wetlands to capture phosphorus and attenuate

flows, use of residual and animal manure from outside the basin, removal of sediments in

tributaries, and regional treatment systems. 

Hazen and Sawyer Consultants (1995) determined the direct economic impacts to

Okeechobee County and the region from the implementation of the Lake Okeechobee

water quality programs that included the Dairy Rule, the Dairy Buy-Out Program, and the

WOD Program. The Dairy Rule provides for the collection, storage, and land application

of waste and nutrient-laden runoff HIAs surrounding and including the milking barns.

However, the positive impacts from improved water quality conditions of Lake

Okeechobee due to the water quality programs, such as increased sales, income, and

employment related to Okeechobee’s tourism industry, were not included in their

economic impact evaluation. During the 1988 to 1993 study period analyzed by Hazen

and Sawyer Consultants (1995), many of the dairies and landowners were constructing the

production modifications needed to comply with the water quality programs, while other

dairies were ceasing operation under the Dairy Buy-Out Program. Because the

requirements under the water quality programs were not fully implemented until 1993, the

full potential of the expected reductions in phosphorus loads into Lake Okeechobee did

not take place until after the study period. This current project will continue where the

efforts ended in the 1995 analysis, and will now include a full cost accounting of ten

phosphorus control alternatives (PCAs) to further reduce the amount of phosphorus

entering Lake Okeechobee. 

The PCAs were chosen based on three criteria:

• Sufficient information is or will be available to allow for an adequate

evaluation of benefits and costs associated with the PCA.

• The PCAs have the potential to successfully reduce phosphorus loading

to Lake Okeechobee.

• The PCAs are being considered in planning programs.

Benefits and costs of each alternative to the District, to landowners, and to the

regional economy will be described and quantified. The following PCAs were selected

according to the above criteria:

1. Chemical treatment of runoff at the edge of property

2. Wetland treatment of runoff at the edge of property

3. Nonstructural management at the land parcel level

4. Optimization of Dairy Rule design or use of alternative waste

management technologies

5. Enhanced cow-calf BMPs

6. Alternative land uses – convert dairy, citrus, field crop, and row crops

to land uses such as wetlands, natural areas, cow-calf operations, and

forage production
50

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

7. Reservoir-assisted STAs

8. System able to receive supplemental water from the lake

9. Tributary sediment removal

10. Terminal large-scale water treatment facilities

This study will identify benefits and costs of each PCA using a full cost accounting

approach, which attempts to identify and quantify the social benefits and costs resulting

from a policy decision. Decades of research into phosphorus reduction strategies in the

Lake Okeechobee Basin and the EAA, and many current and new research and planning

projects, will provide a wealth of data that may be used to provide an economic evaluation

of alternatives. 

The benefits and costs of the PCAs will be measured relative to baseline

conditions that represent current management practices of landowners, to the extent that

the available information will allow. This study will also consider the costs per unit of

phosphorus reduction associated with a range of phosphorus input and output levels for

those PCAs that can be effectively implemented at different scales.

A Computerized Alternatives Evaluation/Full Cost Accounting Model will be

developed to allow for updating as new data and information become available. The

benefit-cost analysis will be used in conjunction with a model that uses evaluation criteria

to measure the relative benefits and costs of the alternative and will provide a ranking of

alternatives based on the magnitude of itemized benefits and costs. This will allow the

District to add and evaluate additional PCAs in the future.

K. CLASS I, III, AND IV STANDARDS

Historical (1988 to 2000) tributary inflow water quality data were evaluated to

determine the level of compliance with numeric state water quality standards (Chapter

62-302.530, F.A.C.). Sample locations included 33 tributary stations located at all water

control structures maintained by the SFWMD and the USACE; locations along the

Kissimmee River, Taylor Creek/Nubbins Slough, Harney Pond and Indian Prairie canals,

and Fisheating Creek; and all Everglades Protection District structures that drain into the

lake through pump stations or culverts including the four Chapter 298 Districts and

Closter Farms (Figure 2-3). In addition, in 1992, more than 60 previously unsampled

water quality and biological parameters were collected during a 12-month monitoring

program at the same 42 stations mentioned above (Ogburn et al., 1996). 

The classification of tributary waters varies. For example, S308C and S77 waters

must meet Class I (potable water supplies) criteria no matter if they are flowing into the

lake or not. CULV10 and CULV10A waters flowing into the lake must meet Class I

standards, but if water is not flowing into the lake, the water needs to meet only Class IV

and Class III standards, respectively. Industrial Canal must meet Class III standards

whether water is flowing into the lake or not. The observations were thus separated into

inflow (Table 2-4) or no inflow (Table 2-5) to the lake, and then subdivided by the
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

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Figure 2-3. The tributary stations samples were collected from to determine compliance with

Class I, III, and IV Standards
52

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

standards that each station must meet. Observations for each class parameter were

summed to determine the overall percent noncompliance for each given parameter. 

All values for each contaminant were summed and the percentage of instances that

the criterion was exceeded was calculated for each class. An evaluation of these data from

the 13-year period of 1988 to 2000 indicated that major inflows generally comply with

applicable state water quality criteria with the exception of dissolved oxygen, iron, and

conductivity (Table 2-4). Water quality criteria for most monitored parameters were

exceeded in less than 25 percent of the measurements at specific locations. The criteria for

arsenic, trace metals (cadmium, copper, lead, mercury, and zinc) and organic contaminants

were rarely exceeded in the lake inflows. For most tributaries, fewer than 20 trace metal

samples were taken over the 13-year period while waters were flowing into the lake. Due

to this small sample size, the percentage of instances that criterion was exceeded was not

calculated for these contaminants. Based on the number of times the criteria were

exceeded, water quality associated with inflows has not substantively impaired the

designated uses of the lake. However, additional monitoring of biological conditions and

trace metals during inflow conditions may be warranted to document whether the inflows

meet their designated use. 

Parameters that widely or frequently exceeded the criteria included alkalinity,

chloride, dissolved oxygen, conductivity, and iron. Pesticide criteria were infrequently

exceeded during the quarterly sampling in the supplemental monitoring program (Ogburn

et al., 1996), but pesticides and other organics are included in this evaluation despite the

very limited database, and because of their potential for ecological impacts. 

K1. pH

The Class I, III, and IV criteria for pH include minimum (6.0) and maximum (8.5)

values, unless natural background conditions are documented to be lower or higher. The

criteria were developed primarily to protect aquatic life. More than 10 percent of the

samples at the Fisheating Creek station (FECSR78) exceeded the criteria during periods of

inflow (Table 2-4). These samples had many low pH values, which appeared to be

associated with naturally occurring humic and fulvic acids from wetlands in the Fisheating

Creek drainage basin. 

K2. Alkalinity

The criteria for alkalinity require a minimum value of 20 ppm as calcium

carbonate (CaCO3) for Class I and III waters, while no minimum and a maximum of 600

ppm is required for Class IV waters. Alkalinity buffers pH changes, and the bicarbonate

and carbonate that contribute to alkalinity can complex some trace metals and reduce their

potential toxicity to aquatic organisms. Low alkalinity can inhibit shell formation by

aquatic snails and other mollusks.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

53

Table 2-4. The percentage of instances that Class I and III criteria was exceeded for tributary samples taken 

during inflow periods to Lake Okeechobeea

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

Class I

CULV10 0.0 2.0 74.5 52.1 84.8 ND 22.9 33.3 2.2 ND ND ND ND ND ND ND

45 49 47 48 46 7 48 48 45 12 12 11 11 11 11 11

CULV10A 3.5 2.2 19.5 11.1 89.4 ND 3.4 7.0 0.0 65.4 0.0 0.0 0.0 0.0 0.0 0.0

86 90 87 90 85 17 89 86 87 26 26 24 23 24 24 23

CULV12 0.0 2.8 34.3 11.1 82.4 ND 5.6 13.9 5.6 ND ND ND ND ND ND ND

34 36 35 36 34 7 36 36 36 10 10 9 9 9 9 10

CULV12A 1.0 0.0 86.1 80.6 86.9 ND 1.9 16.3 0.0 19.2 0.0 4.0 0.0 0.0 0.0 0.0

101 103 101 103 99 17 104 104 97 26 26 25 25 25 25 25

CULV4A 0.0 1.6 71.2 9.7 96.6 ND 1.7 13.6 1.9 ND ND ND ND ND ND ND

59 61 59 62 59 6 60 59 54 9 9 8 8 8 8 10

CULV5 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND

12 14 13 14 12 2 14 14 14 4 4 4 4 4 4 4

FECSR78 15.8 72.1 23.4 0.0 55.2 0.0 0.0 1.1 0.0 91.1 0.0 7.1 0.0 11.9 2.4 0.0

183 190 184 189 181 27 186 189 172 45 44 42 42 42 42 41

HGS5 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND

2 3 2 3 21 3 3 31111111

S127 0.0 0.0 11.9 14.9 65.7 ND 0.0 1.5 0.0 ND ND ND ND ND ND ND

67 68 67 67 67 10 67 67 63 15 15 13 13 13 13 15

S129 0.0 0.0 0.0 0.0 50.0 ND 0.0 1.9 0.0 ND ND ND ND ND ND ND

50 53 50 53 48 7 53 52 45 11 11 10 10 10 10 11

S131 1.9 0.0 0.0 0.0 51.9 ND 0.0 1.9 0.0 ND ND ND ND ND ND ND

53 55 54 55 52 8 55 53 44 11 11 11 11 11 11 11

S133 0.0 0.0 2.3 0.0 65.9 ND 0.0 0.0 0.0 ND ND ND ND ND ND ND

44 45 44 45 44 7 44 45 45 11 12 12 12 12 12 11

a. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage 

the criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

Criterion has not been established
54

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

S135 0.0 2.3 0.0 0.0 38.1 ND 0.0 2.3 0.0 ND ND ND ND ND ND ND

42 43 42 43 42 7 43 43 38 8 8 8 8 8 8 8

S191 2.6 3.4 19.4 1.9 68.5 ND 0.9 4.7 0.0 86.2 0.0 0.0 3.7 0.0 3.6 0.0

386 178 377 376 371 17 212 403 397 29 29 28 27 28 28 28

S2 0.0 2.3 31.6 0.0 98.2 ND 15.2 15.2 0.0 ND ND ND ND ND ND ND

57 43 57 48 56 7 46 66 52 9 9 9 9 9 9 7

S236 0.0 0.0 79.2 68.0 87.5 ND 3.8 11.5 0.0 ND ND ND ND ND ND ND

24 26 24 25 24 5 26 26 25 7 7 7 7 7 7 7

S3 0.0 0.0 17.1 10.3 100.0 ND 0.0 18.0 0.0 ND ND ND ND ND ND ND

41 24 41 29 41 7 30 50 37 8 8 8 8 8 8 8

S308C 0.0 0.0 2.7 0.0 41.7 ND 8.6 2.8 0.0 ND ND ND ND ND ND ND

36 36 37 36 36 5 35 36 34 9 9 9 9 9 9 9

S4 0.0 4.0 0.0 0.0 70.8 ND 0.0 0.0 0.0 ND ND ND ND ND ND ND

24 25 24 25 24 1 24 24 23 4 4 4 4 4 4 4

S77 ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND

2 2 2 2 20 2 2 20000000

Class I Total 3.3 13.2 27.0 12.3 71.2 44.8 2.7 7.4 0.3 52.9 0.0 1.6 0.4 2.1 0.8 0.0

1,348 1,144 1,347 1,349 1,325 165 1,177 1,406 1,313 255 255 243 241 243 243 244

Class III

C38W 4.9 0.0 97.5 43.4 7.8 2.3 0.0 0.0 11.9 0.0 0.0 0.0 0.0

123 130 119 122 129 128 44 44 42 41 42 42 39

INDUSCAN 0.0 0.0 19.0 55.2 5.5 3.5 ND ND ND ND ND ND ND

58 57 58 58 55 57 12 12 10 10 10 10 12

L59E 0.0 9.1 54.5 100.0 0.0 9.5 ND ND ND ND ND ND ND

20 22 22 20 21 21 3333333

Table 2-4. The percentage of instances that Class I and III criteria was exceeded for tributary samples taken 

during inflow periods to Lake Okeechobeea (continued) 

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

a. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage 

the criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

Criterion has not been established
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

55

L59W 4.5 2.6 8.1 65.8 0.0 2.7 0.0 0.0 6.9 0.0 0.0 0.0 0.0

111 115 111 111 113 111 31 31 29 28 29 29 31

L60E 5.0 4.8 8.0 56.6 0.0 1.0 3.6 0.0 3.7 0.0 0.0 0.0 0.0

101 104 100 99 103 101 28 28 27 26 27 27 25

L60W 3.4 0.0 5.2 64.9 0.0 1.7 ND ND ND ND ND ND ND

58 60 58 57 59 58 16 16 13 13 14 13 13

L61E ND ND ND ND ND ND ND ND ND ND ND ND ND

16 16 16 16 16 16 7666666

L61W 4.7 1.5 18.8 82.8 0.0 1.6 14.3 0.0 ND ND ND ND ND

64 65 64 64 63 63 21 21 19 19 19 19 19

S154 2.8 5.2 21.4 69.4 0.0 5.1 ND ND ND ND ND ND ND

181 96 173 173 109 196 15 15 14 14 14 14 14

S154C 1.7 0.0 96.7 77.3 0.0 2.2 2.8 0.0 2.9 0.0 0.0 0.0 0.0

180 188 182 181 188 183 36 35 34 34 34 34 33

S65E 5.2 10.7 1.5 39.4 0.0 3.4 1.4 0.0 3.6 1.8 5.5 0.0 0.0

542 366 521 520 431 590 281 59 55 55 55 55 56

S71 4.6 14.5 9.0 69.5 0.0 4.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0

174 186 177 174 184 182 34 34 32 32 32 32 29

S72 0.0 4.9 13.8 82.3 0.0 2.5 ND ND ND ND ND ND ND

80 82 80 79 79 80 19 19 18 18 18 18 18

S84 4.1 36.2 12.2 26.7 0.0 3.1 0.0 0.0 14.8 3.7 14.8 0.0 0.0

271 138 270 270 135 293 29 29 27 27 27 27 27

Class III 

Total

3.9 8.4 23.2 54.1 0.8 3.2 3.8 0.0 4.9 0.6 2.7 0.3 0.0

1,979 1,625 1,951 1,944 1,685 2,079 576 352 329 326 330 329 325

Table 2-4. The percentage of instances that Class I and III criteria was exceeded for tributary samples taken 

during inflow periods to Lake Okeechobeea (continued) 

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

a. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage 

the criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

Criterion has not been established
56

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Table 2-5. The percentage of instances that the Class I, III, and IV criteria was exceeded for tributary samples 

taken during periods of no inflow to Lake Okeechobeeb

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

Class I

S308C 3.8 0.6 2.5 0.0 12.0 0.0 17.0 0.0 0.0 87.9 0.0 0.0 0.0 9.7 0.0 0.0

158 159 159 158 158 24 159 153 147 33 33 31 30 31 31 31

S77 2.5 3.0 3.0 0.0 44.7 0.0 1.0 2.6 0.0 15.2 0.0 0.0 0.0 0.0 2.2 0.0

200 198 200 200 197 28 200 196 195 46 47 45 45 45 45 44

Total

Class I

3.1 2.0 2.8 0.0 30.1 0.0 8.1 1.4 0.0 45.6 0.0 0.0 0.0 3.9 1.3 0.0

358 357 359 358 355 52 359 349 342 79 80 76 75 76 76 75

Class III

C38W ND ND ND ND ND ND ND ND ND ND ND ND ND

13 13 10 12 13 13 1111111

CULV10A 1.9 0.0 5.8 25.0 13.5 1.1 38.1 0.0 5.0 0.0 5.0 0.0 ND

104 96 103 104 96 90 21 20 20 20 20 20 17

CULV5 6.5 2.4 19.4 87.0 2.4 0.8 9.8 0.0 5.3 0.0 2.6 0.0 0.0

124 126 124 123 125 125 41 40 38 38 38 38 37

FECSR78 ND ND ND ND ND ND ND ND ND ND ND ND ND

777 7 7 7 4444444

HGS5 2.7 0.5 15.4 28.2 22.3 7.6 28.6 0.0 0.0 0.0 0.0 0.0 0.0

294 221 293 291 220 223 49 48 46 46 46 46 48

INDUSCAN 1.9 0.9 21.0 38.8 0.0 4.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0

104 106 105 103 109 109 31 30 30 30 30 30 29

L59E 4.0 0.9 45.6 72.5 1.9 7.4 7.7 0.0 8.1 2.8 0.0 2.7 0.0

101 109 103 102 108 108 39 39 37 36 37 37 35

L59W 0.0 1.9 12.5 46.8 0.0 5.7 ND ND ND ND ND ND ND

48 53 48 47 52 53 14 14 14 14 14 14 14

L60E 3.6 1.7 8.8 48.2 0.0 0.0 ND ND ND ND ND ND ND

55 60 57 56 60 59 19 19 18 18 18 18 18

b. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage the

criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

No criterion has been established
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

57

L60W 8.6 7.0 5.3 59.6 0.0 6.0 3.6 0.0 0.0 0.0 3.6 3.6 0.0

93 100 95 94 99 100 28 28 28 28 28 28 25

L61E 2.5 4.7 9.8 50.0 0.8 1.6 0.0 0.0 3.0 0.0 3.0 0.0 0.0

122 128 123 122 126 127 35 35 33 33 33 33 31

L61W 1.5 1.5 4.5 60.6 1.5 1.5 ND ND ND ND ND ND ND

65 67 66 66 67 67 19 18 18 18 18 18 17

S127 3.3 0.8 17.9 38.5 0.8 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0

122 127 123 122 127 127 34 33 33 32 33 33 29

S129 0.0 0.0 2.6 23.5 0.0 1.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

115 120 116 115 120 121 35 35 34 34 34 34 31

S131 4.0 0.0 0.0 28.8 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0

125 128 125 125 126 128 39 38 36 36 36 36 34

S133 0.0 0.8 1.6 51.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.0 0.0

121 127 122 119 126 124 36 35 33 32 33 33 32

S135 3.2 1.5 0.0 30.6 0.8 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0

124 132 126 124 131 130 40 40 38 37 38 38 37

S154 2.2 1.5 22.6 45.3 0.9 3.4 81.3 0.0 6.5 0.0 0.0 0.0 0.0

365 200 350 349 226 387 32 31 31 31 31 31 28

S154C 0.0 0.0 89.5 92.1 0.0 2.4 ND ND ND ND ND ND ND

38 41 38 38 41 41 12 12 11 10 11 11 12

S191 3.3 0.7 24.0 32.4 1.6 3.3 0.0 0.0 0.0 0.0 0.0 5.0 0.0

304 148 296 296 183 337 23 21 20 20 20 20 21

S2 0.6 0.0 31.4 37.1 3.6 8.4 2.4 0.0 0.0 0.0 0.0 0.0 0.0

171 171 172 170 168 166 42 44 42 42 42 42 41

S3 2.8 1.1 30.6 28.2 1.7 4.6 2.3 0.0 2.4 0.0 0.0 0.0 0.0

180 179 180 177 178 175 44 44 42 42 42 42 42

Table 2-5. The percentage of instances that the Class I, III, and IV criteria was exceeded for tributary samples 

taken during periods of no inflow to Lake Okeechobeeb (continued) 

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

b. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage the

criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

No criterion has been established
58

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

S4 1.5 0.0 12.5 25.4 0.0 5.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0

136 143 136 134 143 141 46 45 43 43 43 43 41

S65E 1.6 1.9 0.0 18.2 0.0 1.3 0.0 ND ND ND ND ND ND

62 52 56 55 66 75 35 4 3 3 3 3 3

S71 5.3 4.1 7.4 45.7 1.0 1.0 ND ND ND ND ND ND ND

94 98 94 94 98 96 15 14 14 14 14 14 14

S72 3.1 4.0 9.3 43.8 0.0 1.0 0.0 0.0 3.4 0.0 3.4 0.0 0.0

96 101 97 96 101 100 30 30 29 28 29 29 28

S84 2.0 18.8 11.1 13.2 0.0 2.9 ND ND ND ND ND ND ND

198 101 199 197 100 208 19 19 19 18 19 19 14

Total

Class IIl

2.8 2.0 16.6 39.2 3.0 3.4 7.9 0.0 1.8 0.3 1.0 0.7 0.1

3,381 2,954 3,364 3,338 3,016 3,437 783 741 715 708 715 715 683

Class IV

CULV10 1.7 0.0 37.8 34.2 1.6 0.0 0.0 0.0 0.0 0.0 0.0

120 124 119 117 125 37 36 36 36 36 36

CULV12 4.0 0.0 27.2 20.3 0.8 0.0 0.0 0.0 0.0 0.0 0.0

126 134 125 123 132 39 38 38 38 38 37

CULV12A 1.4 0.0 45.1 55.7 1.4 0.0 0.0 0.0 0.0 0.0 ND

71 74 71 70 73 21 20 20 20 20 19

CULV4A 0.0 0.0 23.2 29.7 2.7 0.0 0.0 0.0 0.0 0.0 0.0

112 114 112 111 113 36 35 35 35 35 34

S236 0.8 0.0 61.1 33.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0

126 131 126 125 131 39 38 38 38 38 34

Total

Class IV

1.6 0.0 38.7 32.8 1.2 0.0 0.0 0.0 0.0 0.0 0.0

555 577 553 546 574 172 167 167 167 167 160

Table 2-5. The percentage of instances that the Class I, III, and IV criteria was exceeded for tributary samples 

taken during periods of no inflow to Lake Okeechobeeb (continued) 

STATION

pHAlkalinityConductivityChlorideDissolved OxygenTotal Dissolved SolidsTurbidity Un-ionized AmmoniaNitrateIronArsenicCadmiumCopperLeadZincMercury

b. The upper number in each cell indicates the number of samples collected, while the lower number represents the percentage the

criterion was exceeded. The key below explains the color coding

25% or more of samples exceed criterion

Between 10% and 25% of samples exceed criterion

Less than 10% of samples exceed criterion

ND Not determined

No criterion has been established
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

59

During inflow conditions, low alkalinity criteria were exceeded in more than 25

percent of samples at FECSR78 (Fisheating Creek) and S84, and were exceeded in more

than 10 percent of the samples at S65E and S71 (Table 2-4). Low alkalinity values were

directly associated with low pH. Low alkalinity appears to be a natural condition in the

inflow systems where it was documented. Since alkalinity within the lake very rarely was

below the minimum value and no samples exceeded the maximum value, the instances of

low alkalinity in these tributaries has not contributed to any degradation of the lake.

K3. Chloride

The Class I chloride criterion (250 ppm) is based on drinking water concerns, as

high levels of chloride can give drinking water a salty taste. Class III and IV criteria have

not been established for chloride. The chloride criterion was not exceeded during no

inflow condition (Table 2-5), but was exceeded during inflow conditions more than 25

percent of the time at three stations (CULV10, CULV12A, and S236), and exceeded more

than 10 percent of the time at four other stations (CULV10A, CULV12, S127, and S3)

(Table 2-4). 

Five of the stations with chloride criterion violations are located along the

southeastern shore of the lake (Figure 2-3). Shallow ground water along the southeastern

shore of the lake is affected by chloride and other salts that remain from the Pleistocene

Era, when much of Florida was covered by shallow seas (Schroeder et al., 1954).

Therefore, the inflows with high chloride concentrations appear to be related to ground

water seepage into the canals, and they do not appear to impact the use of the lake as a

source of drinking water. 

K4. Dissolved Oxygen

Adequate levels of dissolved oxygen are necessary for aquatic animals to respire.

The Class I and III criteria require a minimum of 5.0 ppm, and the Class IV minimum is

3.0 ppm during inflow conditions. The Class I and III criteria for dissolved oxygen were

exceeded in more than 25 percent of the samples in all of the stations with 20 or more

samples (Table 2-4). During no inflow conditions, the criteria were exceeded 25 percent

of the time at all but 5 stations with 20 or more samples. At these 5 stations, the criteria

were exceeded 10 percent of the time.

Many of the inflow stations showed a greater tendency for the dissolved oxygen

criteria to be exceeded when water was flowing toward the lake, as opposed to when water

was not flowing towards the lake, especially for stations at the southern end of the lake

(Figure 2-3 and Tables 2-4 and 2-5). This may be due to seepage of ground water with

low dissolved oxygen concentrations into canals during pumping events. Canal water

levels can be drawn down faster than ground water levels by pumping at control structures

causing ground water to seep into the canals. Ground water typically has low dissolved

oxygen levels that tend to reduce the dissolved oxygen levels in the canals. However, no

studies have been conducted to document whether seepage into canals has a significant

impact on surface water dissolved oxygen concentrations during pump events.
60

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Dissolved oxygen fluctuates naturally in water bodies because of many physical

and biological factors. The data collected on dissolved oxygen is done on a snapshot basis,

and the time of sampling can have an impact on the values. Dissolved oxygen values

during extended periods of no inflow at a structure can also play a role. Chronically low

dissolved oxygen values can be the result of anthropogenic influences, but they can also

be a natural characteristic of wetlands and other low energy systems. Schwartz (1985)

concluded that the low dissolved oxygen values in Taylor Creek/Nubbins Slough,

Fisheating Creek, and the Kissimmee River systems were due to drainage from extensive

wetlands systems in their basins. Loading of oxygen-demanding substances and ground

water seepage into the drainage systems around the lake also may contribute to the low

dissolved oxygen values documented in the inflows. In-lake criteria were exceeded less

than two percent of the time at all locations (Table 3-4 in Chapter 3), thus they are of no

great concern. However, additional monitoring may be needed to determine the

significance of the potential causes of low dissolved oxygen before management strategies

are evaluated. 

K5. Total Dissolved Solids

The Class I criterion for total dissolved solids is no greater than 500 ppm on a

monthly averaged basis or not greater than 1,000 ppb at any time. No Class III or IV

criteria for total dissolved solids have been established. During periods of no inflow, the

Class I criterion for total dissolved solids was not exceeded (Table 2-5). During periods of

inflow to the lake, less than 20 samples were taken for each tributary, with the exception

of FECSR78, so the percentage of instances that the criterion was exceeded could not be

calculated. However, a summation of all of the observations show that the Class I criterion

was exceeded over 45 percent of the time (Table 2-4). Based on this finding it is

recommended that the tributaries be sampled on a regular basis for total dissolved solids.

K6. Turbidity

Turbidity is evaluated with respect to background values. The criterion allows a

maximum of 29 nephelometric turbidity units (NTUs) above background. Background

turbidity for each station was assumed to be the median (i.e., 50 percent of the samples are

less than and 50 percent of the samples are greater than the median value). More than 10

percent of the samples taken at two stations during inflow conditions (CULV10 and S2)

and three other stations during no inflow conditions (S308C, CULV10A, and HGS5)

exceeded the criterion (Tables 2-4 and 2-5). Watershed management strategies may

reduce sediment loading and turbidity levels in canals. 

K7. Un-ionized Ammonia

Aqueous ammonia can be present as un-ionized ammonia and as ammonium ion.

Un-ionized ammonia is the form that is toxic to some aquatic organisms. The criterion

allows up to 0.02 ppm un-ionized ammonia to be present in the water. The proportion of

un-ionized ammonia increases with increasing pH and temperature. The un-ionized

ammonia criteria was exceeded at many tributary stations, but these instances were
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

61

generally infrequent. During no inflow conditions no station had more than 10 percent of

samples exceeding the criterion (Table 2-5). During inflow conditions one station

(CULV10) exceeded the criterion in more than 25 percent of the samples and six stations

(CULV12, CULV12A, CULV4A, S2, S236, and S3) exceeded the criterion in more than

10 percent of the samples (Table 2-4). These high levels are most likely related to

anthropogenic sources of nitrogen, such as land spreading of sludge and/or agricultural

fertilizers.

K8. Iron

The Class I, III, and IV standards for iron are 0.3, 1.0, and 1.0 ppm, respectively,

During inflow periods, only 4 stations that are required to meet Class I standards for iron

(CULV10A, CULV12A, FECSR78, and S191) had been sampled 20 or more times (Table

2-4). CULV12A exceeded the criterion more than 10 percent of the time while the three

others exceeded Class I criterion more than 25 percent of the time. Only one station

required to meet Class III standards during inflow periods, L61W, exceeded this standard

more than 10 percent if the time (Table 2-4). 

During no inflow periods, both stations (S308C and S77) that are required to meet

Class I standards exceeded the criterion for iron. S308C exceeded the Class I standard

more than 25 percent of the time and S77 more than ten percent of the time (Table 2-5).

Class III standards were exceeded more than 25 percent of the time at three stations:

CULV10A, HGS5, and S154.

K9. Arsenic and Trace Metals (Cadmium, Copper, Lead, Zinc, 

and Mercury

The Class I criterion for arsenic is 50 ppb. The Class I criteria for cadmium,

copper, lead, and zinc are calculated as a function of water hardness, and, therefore, do not

have specific values. The historical database generally had less than 40 observations each

for arsenic, cadmium, copper, lead, mercury, and zinc for each tributary for both periods of

inflow or no inflow to the lake (Tables 2-4 and 2-5). Because of the small sample size

(less than 20), the percentage that the criteria were exceeded were not determined at a

number of tributaries. However, when data for each metal was summed for each class, the

number of samples exceeding the criteria for periods of inflow was less than 10 percent

for both Class I and Class III criteria (Table 2-4). The criteria for arsenic were not

exceeded in either class.

Most likely, the trace metal criteria is being exceeded due to anthropogenic

activities and sources such as agricultural uses of sludge, fertilizers, and pesticides;

burning of fossil fuels and wastes; and gasoline additives. The limited amount of trace

metal data makes it difficult to determine if management strategies need to be

implemented to reduce trace metal concentrations. The District’s monthly monitoring

program should be modified to include trace metals to facilitate a more conclusive

assessment of the potential need for management measures to control trace metals within

the tributaries.
62

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

K10. Organics and Pesticides

Pesticides and herbicides could be found in inflow samples because of the

dominance of agricultural land uses in much of the Lake Okeechobee basin. During 1993

and 1994, CULV10 was the only location with detectable levels of pesticides (Ogburn et

al., 1996). During two quarterly sampling events, concentrations of dieldrin and dichlor

diphenyl trichlor (DDT) exceeded criteria in samples taken at CULV10. One instance of

the toxaphene criteria being exceeded was documented at CULV10. At CULV10A, the

polycyclic aromatic hydrocarbon criterion (2-methyl naphthalene) was exceeded once.

The results indicated that pesticides and other organic contaminants do not

chronically exceed the criteria. These results are also supported by the sediment sampling

analysis that showed only dichlor diphenyl dichlor (DDD-p,p') and dichlor diphenyl

ethylene (DDE-p,p') were above the detection limit in seven and nine of the 31 samples

taken, respectively. For the tributaries, these parameters were only sampled four times at

each station, and the seasonal application of pesticides and variations in transport to

surface waters based on rainfall patterns could have affected the likelihood of detecting

organic contaminants. Therefore, additional organic monitoring may be needed in

conjunction with the District’s existing monitoring program to allow conclusions to be

made regarding the instances of the criteria being exceeded for pesticides, herbicides, and

other organic contaminants. The list of organic parameters from the supplemental

monitoring program should be reduced to focus on compounds that are known to have

potential sources in the watershed, such as pesticides, herbicides, and petroleum

hydrocarbons. Quarterly sampling for organics was recommended, and the schedule

within each quarter should be based on seasonal uses of agricultural chemicals and/or

periods of inflow to the lake.

K11. Coliforms

Ogburn et al. (1996) also measured total and fecal coliforms at the tributaries

throughout a year and found instances of criteria for both being exceeded (Table 2-6). Of

the 87 fecal coliform measurements taken during inflow conditions, 22 were above the

criteria. However, only 9 of the 84 measurements of total coliforms were above the criteria

during inflow conditions. It is recommended that a routine monitoring for fecal and total

coliforms be initiated in the District's monitoring program. 

K12. Recommended Class I and III Management Strategies for 

Tributaries 

Based on existing land uses and water quality conditions in the Lake Okeechobee

basin, several strategies for canals and marinas may be applicable to the lake inflows:

• Canals - Oxygen injection, air injection, sediment removal, and

constructed wetlands

• Marinas - Liquid waste management and boat maintenance control

measures
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

63

Table 2-6. Results of fecal and total coliform measurements taken in lake okeechobee tributaries 

and in-lake stations from October 1993 to September 1994cd

Station

Fecal Coliforms Total Coliforms

Inflow No Inflow Inflow No Inflow

Class I Class III Class I Class III Class I and III Class I and III

Number of Times

Criterion Exceeded

Number of 

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

CULV10 2 2 . . . . . .12 . .

CULV10A 0 4 . . . .15 0 4 3 5

CULV12 1 2 . . . . . .02 . .

CULV12A 4 4 . . . . . .34 . .

CULV4A 2 2 . . . . . .12 . .

CULV5 . 0 . . . . 1 12 . 0 0 12

FECSR7816 . . . .16 0 6 1 6

HGS5 1 3 26 0 3 2 6

INDUSCAN . .34 . .08 0 4 2 8

L001 . . . . 0 12 . . . . 1 12

L002 . . . . 0 12 . . . . 1 12

L003 . . . . 0 12 . . . . 0 12

L004 . . . . 0 12 . . . . 1 12

L005 . . . . 0 12 . . . . 0 12

L006 . . . . 0 12 . . . . 0 12

L007 . . . . 0 12 . . . . 0 12

L59E . .01 . . 3 11 0 1 2 11

L59W . . 0 11 . . 0 1 1 10 0 1

L60E . .16 . .06 1 5 0 6

L60W . . 1 10 . .02 1 9 0 2

L61E . . .0 . . 0 12 . 0 2 11

L61W . . .0 . . 3 12 . 0 0 12

LZ2 . . . . 0 12 . . . . 1 12

LZ30 . . . . 0 12 . . . . 1 12

S127 0 1 . . . . 0 11 0 1 1 11

S129 1 2 . . . . 0 10 0 2 1 9

S131 1 1 . . . . 1 11 0 1 0 11

S133 0 1 . . . . 0 11 0 1 0 11

S135 0 2 . . . .08 0 2 1 8

S154 . . .0 . . 1 12 . 0 0 12

S154C . . 1 12 . . . 0 1 12 . 0

S191 1 1 . . . . 0 11 0 1 0 11

S2 0 1 . . . . 1 11 0 1 1 11

c. Source = Ogburn et al., 1996

d. The key to the shading is as follows:

In-lake samples Class I no inflow criterion only

Standard does not apply for this station and category
64

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

• Administrative - Mixing zones and site-specific alternative criteria

In addition, constructed wetlands may be appropriate for most land uses, assuming

the availability of land. Alternative criteria could also potentially be established for some

parameters in order to prevent the water quality criteria from being exceeded. 

K12a.Strategies for Canals

Three techniques have been developed for increasing dissolved oxygen in

discharges from dams: oxygen injection, air injection, and the construction of spillways

and weirs. Oxygen injection involves the use of pure oxygen to increase levels of

dissolved oxygen in reservoirs. It could potentially be used to increase dissolved oxygen

concentrations in the systems that drain to the lake. Air injection is similar to oxygen

injection, but atmospheric air or compressed air is used to increase the dissolved oxygen

concentration of the water body. It requires a compressor or other source of air, a diffuser

system to distribute the air, and a pipe to deliver the air to the diffusers. Air injection may

not be effective for large volume, intermittent flood control flows to the lake. Spillways

and weirs could be constructed at the downstream sides of control structures to enhance

aeration of water as it flowed over the structures. These techniques could potentially be

S236 1 1 . . . . . .01 . .

S3 . 0 . . . . 0 12 . . 1 12

S308C 1 5 . .06 . .0506

S4 . 0 . . . . 1 12 . . 1 12

S65E . .01 . . 0 11 0 1 0 11

S71 . .01 . . 0 11 0 1 0 10

S72 . .02 . . 2 10 0 2 1 9

S77 . 0 . .08 . . .008

S84 . .01 . . 0 11 0 1 0 11

TOTAL 16 38 6 49 0 122 17 233 9 84 24 351

Table 2-6. Results of fecal and total coliform measurements taken in lake okeechobee tributaries 

and in-lake stations from October 1993 to September 1994cd (continued) 

Station

Fecal Coliforms Total Coliforms

Inflow No Inflow Inflow No Inflow

Class I Class III Class I Class III Class I and III Class I and III

Number of Times

Criterion Exceeded

Number of 

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

Number of Times

Criterion Exceeded

Number of

Samples

c. Source = Ogburn et al., 1996

d. The key to the shading is as follows:

In-lake samples Class I no inflow criterion only

Standard does not apply for this station and category
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 2: Watershed and Tributary Water Quality

65

applicable to the canals and pumped water control structures that are commonly used to

control surface water movement in the Lake Okeechobee watershed. In addition, sediment

removal from canals and constructed wetlands provide management alternatives that

could potentially be used for many land use categories in the watershed. 

K12b.Marina Operation Strategies

Marina and boat operations, such as disposal of liquid wastes, and boat

maintenance and cleaning can generate surface water pollution. Management strategies

that could potentially be applicable to marinas on the lake include liquid waste

management and boat maintenance control measures. Liquid waste management involves

providing appropriate facilities at marinas for disposal of liquid wastes, such as oil, waste

gasoline, solvents, antifreeze, and paints. Boat maintenance control measures include

providing designated areas for boat maintenance and repairs, and requiring their use for

those activities. It also calls for regular cleaning of the maintenance areas to remove trash,

sandings, paint chips, etc. The goal is to reduce the amount of solid wastes that are

introduced to surface waters.

Marinas and associated camping areas that have direct runoff into the lake from

paved areas should develop and implement stormwater treatment systems. This would

reduce the wastes associated with these recreation activities.

K12c.Administrative Measures 

Chapter 62, F.A.C., includes provisions that allow for relief from water quality

criteria under certain circumstances, such as site-specific alternative criteria and mixing

zones. These alternatives differ from the management strategies described previously,

because the administrative measures prevents criteria from being exceeded without

improving water quality conditions. Administrative relief measures would likely be

viewed by FDEP as acceptable only after thorough demonstration that other alternatives to

improve water quality conditions are not feasible due to technical or financial limitations.

Surface water quality regulations contained in Chapter 62-302.530, F.A.C.,

provide for the establishment of site-specific alternative criteria in certain cases when a

water body does not meet applicable criteria due to natural conditions or man-induced

conditions that cannot be controlled or abated. In addition, the general criteria for surface

waters (Chapter 62-302.520, F.A.C.) allow for establishment of alternative dissolved

oxygen criteria using the same provisions included in 62-302.800, F.A.C. Site-specific

alternative criteria may be approved for specific parameters in all or part of a surface

water body. 

A mixing zone may be granted to allow alternative criteria for specific parameters

within the zone of mixing, provided the applicable criteria are met at the edge of the

mixing zone. Chapter 62-4.244, F.A.C., describes the conditions under which a mixing

zone may be requested, the criteria used by FDEP to evaluate requests for mixing zones,

and the limitations that apply to mixing zones. No mixing zone or combination of mixing

zones is allowed to significantly impact the designated uses of the receiving body of water.
66

Chapter 2: Watershed and Tributary Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

A separate mixing zone must be defined for each parameter, and a mixing zone cannot

include a nursery area for aquatic biota. Mixing zone dimensions are determined by

modeling, using anticipated concentrations of the specific parameter in the receiving water

body. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

67

Chapter 3

IN-LAKE WATER QUALITY

In the mid-1980s Lake Okeechobee experienced a number of very large algal

blooms (Jones, 1987). These blooms were attributed in part to an overabundance of

nutrients, a process known as eutrophication. Algal blooms are cause for concern because

they may contain toxins that affect fish and wildlife; they create taste and odor problems

for drinking water; and when they die off and degrade, oxygen is removed from the water

column causing fish kills and the death of other aquatic life. Lake users also find these

blooms unsightly, reducing their enjoyment of the resource.

The 40 percent phosphorus load reduction goal developed to restore the ecological

condition of Lake Okeechobee resulted in a decline in the phosphorus load to the lake

from the tributaries, but no reduction of phosphorus occurred within the lake. This was

attributed in part to the huge amount of phosphorus that has accumulated over decades in

sediments within the lake preventing the phosphorus concentration in the water column

from declining.

Along with discussing nutrients, this chapter also discusses Class I water quality

parameters within the lake, but no objectives or strategies are presented or discussed here.

The in-lake and tributaries strategies directed towards reducing nonnutrient pollutants are

combined. They are discussed in Chapter 2.

A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Reduce in-lake nutrients to attain a more natural (lower) 

frequency of potentially harmful algal blooms

Objective 1: Determine the economic, engineering, and ecological

feasibility of reducing internal phosphorus loading from lake sediments

Strategy 1: Determine the feasibility of removing the mud

sediments from the lake’s pelagic region

Strategy 2: Determine the feasibility of chemical treatment of

mud sediments in the lake’s pelagic region in order to “inactivate”

soluble (biologically available) phosphorus

Objective 2: Quantify rates of internal nutrient loading from lake sediments so

that accurate predictions can be made about the timing and extent of lake

responses to potential management actions, such as sediment removal
68

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Strategy 1: Quantify the location, mobility, and phosphorus

content and efflux of lake sediments

Strategy 2: Continue the development and application of the Lake

Okeechobee Water Quality Model and the Lake Okeechobee

Hydrodynamic Transport Model to determine the feasibility of

managing sediments for the reduction of internal loads

Objective 3: Reduce uncertainty about in-lake sources, sinks, and cycling of

nitrogen and phosphorus using research and modeling approaches

Strategy 1: Perform in-lake and laboratory studies to measure

aspects of the phosphorus cycle where a high level of uncertainty

currently exists

Strategy 2: Perform in-lake and laboratory studies to measure

major aspects of the nitrogen cycle

Objective 4: Quantify trends in limnetic and marsh zone water quality and

progress towards established lake enhancement goals

Strategy 1: Incorporate water quality data into a comprehensive

plan for assessing trends in long-term ecological data that may

serve as measures of management activities and success

Objective 5: Determine the impact of submerged aquatic vegetation on lake

water quality

Strategy 1: Further monitoring and comparisons with previous

years will need to be conducted to determine if lowering the lake

levels during the managed recession during the spring of 2000 has

had an impact on the water quality of the lake

Strategy 2: Conduct empirical and modeling studies to determine

the impact submerged aquatic vegetation has on the water quality of

the lake

Objective 6: Determine the feasibility of an internal phosphorus management

program to meet the phosphorus TMDL target of 140 tons per year and achieve an

in-lake phosphorus concentration of 40 ppm in the pelagic zone of the lake

Strategy 1: Demonstrate the feasibility and cost-effectiveness of

removing the phosphorus laden mud using innovative dredging,

material processing, and water treatment technologies.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

69

B. NUTRIENTS

B1. Phosphorus

Phosphorus is of particular concern in this system because it is an essential

element that contributes to eutrophication in Lake Okeechobee (Davis and Marshall,

1975; Federico et al., 1981; Joyner, 1972; Kissimmee-Okeechobee Basin Report, 1972).

Phosphorus within the lake's water column increased dramatically from 40 ppb in the

early 1970s to 145 ppb in 2000 (Figure 3-1). 

A phosphorus load reduction goal was developed to restore the ecological

condition of Lake Okeechobee. This goal requires a 40 percent reduction in phosphorus

loading to the lake, based on the data collected from 1973 to 1979 (Federico et al., 1981).

Tributary phosphorus limitations were based upon reaching an in-lake phosphorus

concentration of 40 ppb by July 1992 as recommended by a modification of the

Vollenweider (1976) nutrient loading model, described in SFWMD Technical Publication

81-2 (Federico et al., 1981). As controls within the basins surrounding Lake Okeechobee

increased, a noticeable decline in the phosphorus load to the lake occurred from 1983 to

1993 (Figure 3-2). Despite this load reduction, no reduction of phosphorus occurred

within the lake (Figure 3-1). This in part was attributed to the huge amount of phosphorus

that has accumulated over decades in sediments within this shallow lake (Figure 3-3). As

the external loads have declined, internal loads from the sediments have become more

significant, acting as a buffer to the system and preventing the phosphorus concentration

in the water column from declining. 

0

20

40

60

80

100

120

140

160

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus (ppb)

Figure 3-1. Lake Okeechobee annual average total phosphorus mean of stations L001 to

L008
70

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

100

300

500

700

900

1,100

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Phosphorus Loads (ton

s

Figure 3-2. Annual phosphorus loads to Lake Okeechobee

Figure 3-3. Phosphorus sediment concentrations (in parts per thousand) within Lake

Okeechobee in 1988 and 1998
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

71

Part of the total phosphorus increase may be attributed to lake levels. A

relationship exists between lake levels and phosphorus within the western nearshore

region of the lake, which has been sampled since 1986 (Figure 3-4). At low stages, total

phosphorus at the nearshore region is much less than in the open water region. At high

stages, the values overlap. This indicates that at high stages the open water and nearshore

areas mix rather well, with the phosphorus laden waters from the open water moving into

the shallower nearshore regions. A general exception to this relationship occurred in 2000

when the annual average stage did not reflect the large change in water levels from 16.16

on January 1, 2000, to 11.31 on December 31, 2000. These high values for both open

water and nearshore were also influenced by Hurricane Irene in 1999 and another major

storm in April 2000.

An example of this mixing is provided by spatial phosphorus maps for the periods

before and after Hurricane Irene passed over the lake in November 1999 (Figure 3-5). In

October, total phosphorus in most areas of the lake was less than 120 ppb, with values

exceeding 100 ppb in the south central, northwestern, and western regions. In November,

almost the entire lake was above 160 ppb and the majority of the open water region (about

30 percent of the lake) was at 200 ppb. 

When the lake stage is lower, the water movement into and out of the nearshore

region is more restricted. In addition, because of the shallow water column, more light

reaches the bottom sediments stimulating the growth of submergent aquatic vegetation.

The growth of these plants not only reduces the amount of material being resuspended

from the sediments, but also takes up existing phosphorus in the water column reducing

water column phosphorus concentrations.

Figure 3-4. Yearly mean phosphorus versus lake stage at the nearshore and open water

stations for 1986 to 2000

y = 3.255x + 50.066

R2

 = 0.0711

p > 0.1

y = 10.064x - 84.805

R2

 = 0.362

P < 0.05

0

20

40

60

80

100

120

140

11 12 13 14 15 16 17

Stage (feet NGVD)

Total Phosphorus (ppb)

Open Water 2000 Nearshore 2000 Nearshore Open Water
72

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

In current years, the lake stage has been very high, reducing the amount of

submerged aquatic vegetation and increasing the amount of phosphorus that remains in the

water column. Because submerged aquatic vegetation is important to the health of fish,

birds, and other aquatic life, the District implemented a plan to reduce the lake stage from

over 15 feet to 13 feet, beginning May 1, 2000. Because of the continued dry conditions,

the lake stage fell to below 12 feet in June 2000. Monitoring of submerged aquatic

vegetation has shown an increase in plants in the southern end of the lake and in some

areas along the western shore (Figure 6 in Chapter 4). Water clarity has also increased in

these areas and preliminary data show that phosphorus levels have declined significantly

in the nearshore areas.

B2. Nitrogen

Nitrogen is another nutrient that contributes to eutrophication of waters. One

management action put into place in 1979 to help reduce nitrogen loads to the lake was the

Interim Action Plan (SFWMD, 1979). This plan reduced nutrient loads to Lake

Okeechobee from the EAA - Everglades Protection District (EPD) (Figure 3-6). The plan

diverted as much nutrient-rich water away from the lake as possible and directed it

southward towards the WCAs, while maintaining an adequate level of flood protection in

the EAA-EPD. The Interim Action Plan has been successful in reducing the amount of

nutrients that would have otherwise been pumped into the lake, and has exceeded its

original goal of a 90 percent reduction in nitrogen loading from the EAA-EPD. An

additional benefit has been the reduced phosphorus loading to the lake. Currently planned

Everglades restoration activities will allow for the diversion of some nutrient-rich waters

to STAs, which should further reduce backpumping from the EAA into the lake. 

Figure 3-5. Phosphorus water column concentrations in Lake Okeechobee during October

and November 1999
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

73

The response of in-lake nitrogen to the reduction of nitrogen loads was dramatic

(Figure 3-7). Lake water concentrations of total nitrogen prior to the Interim Action Plan

had increased from 1,500 to 3,000 ppm. After the Interim Action Plan and several BMPs

were implemented, total nitrogen concentrations in lake water returned to the 1,500 ppm

level. Total nitrogen concentrations have remained close to this value ever since. Because

total nitrogen declined while total phosphorus did not, the lake water total nitrogen:total

phosphorus ratios declined from near 35:1 in the 1970s to about 15:1 in the mid-1990s

(Figure 3-8). The ratio of soluble nitrogen:phosphorus (soluble nutrients are those readily

available for uptake by algae) displayed a similar decline and currently ranges between

4.5:1 to 6:1 (Figure 3-9). According to Smith et al. (1995a) the lower ratios of total

nitrogen:total phosphorus and soluble nitrogen:phosphorus have made the water column

of Lake Okeechobee more favorable for the proliferation of nitrogen-fixing blue-green

algae. 

5,000

6,000

7,000

8,000

9,000

10,000

11,000

12,000

13,000

14,000

15,000

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Nitrogen Load (tons)

Figure 3-6. Annual nitrogen loads to Lake Okeechobee

0

500

1,000

1,500

2,000

2,500

3,000

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Nitrogen (ppb)

Figure 3-7. Annual average nitrogen concentrations in Lake Okeechobee
74

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Most lake algae are limited by phosphorus, but the years of excessive phosphorus

loads and the successful reduction of nitrogen loads to the lake has resulted in Lake

Okeechobee becoming secondarily nitrogen limited. To restore the ecological balance in

the lake, phosphorus must become the limiting nutrient again. 

0

5

10

15

20

25

30

35

40

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Nitrogen:Total Phosphorus

Ratio

Figure 3-8. Average annual ratio of total phosphorus to total nitrogen

0

2

4

6

8

10

12

14

16

18

20

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Soluble Nitrogen:Phosphorus Ratio

Figure 3-9. Average annual ratio of soluble nitrogen to phosphorus
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

75

B3. Chlorophyll a and Algal Blooms

From 1974 to 1977, while external nutrient loads and lake water nutrient

concentrations were increasing, chlorophyll a did not display any significant upward or

downward trend (Figure 3-10). Chlorophyll a was not measured from 1977 until the end

of 1980. From 1981 to 1992, while nitrogen concentrations declined and phosphorus

concentrations remained high but stable, chlorophyll a increased significantly, from less

than 20 to over 25 ppb. Since 1992, chlorophyll a has remained between 20 and 28 ppb.

Havens (1995) studied the increase from 1981 to 1992, and proposed four explanations

that could be tested in future research and/or modeling efforts: 1) phytoplankton growth

was stimulated by the 3 degrees Celsius (oC) rise in water temperatures that occurred

during the 12-year period; (b) growth was stimulated by greater underwater light

penetration that was caused by the 15 percent decline in average wind velocities (windgenerated waves resuspend bottom sediments, reducing light penetration) during the 12-

year period; (c) the 50 percent decline in total nitrogen:total phosphorus and soluble

nitrogen:phosporus ratios favored dominance by nitrogen-fixing blue-green algae, and

many of these species have the ability to float and, therefore, may be sampled more

readily; and (d) a greater dominance by large filaments of blue-green algae has led to less

grazing impacts on the algal biomass by zooplankton. Regardless of the cause, it appears

that excessive nutrient loading has established conditions favorable for phytoplankton

growth and the ultimate growth rates are now a function of less predictable meteorological

or biological factors. This situation has been observed in other nutrient stressed lakes

(Gophen, 1994).

0

5

10

15

20

25

30

35

40

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Chlorophyll a (ppb)

Figure 3-10. Average annual chlorophyll a concentration in Lake Okeechobee
76

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

The occurrence of algal blooms when the chlorophyll a concentration is greater

than 40 ppb has increased over time as well (Havens et al., 1995a). A large amount of this

increase occurs when the phosphorus concentrations in the nearshore region exceed 40

ppb (Walker and Havens, 1995) (Figure 3-11a). In the open water region a similar

relationship exists, but at higher total phosphorus concentrations the number of blooms

declines, because higher phosphorus levels also occur from sediment resuspension, and

this resuspended sediment reduces light penetration into the water column preventing

algal growth (James and Havens, 1996) (Figure 3-11b). 

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

2030405060708090

100110120130140150160170180190200210

Tota l P hosphorus (ppb)

Cum ula tive Pe rce

of sa m ple s

0%

5%

10%

15%

20%

25%

102030405060708090

100110120130140150160170180200210

Tota l P hosphorus (ppb)

Cum ula tive Pe rce

of sa m ple s

Figure 3-11. Cumulative percent of chlorophyll a samples classified as a bloom condition

(chlorophyll a > 40 ppb) at a) nearshore stations and b) open water stations.

b.

a.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

77

C. WATER QUALITY BUDGETS

Water and nutrient budgets were updated based on the method used by James et al.

(1995a). This includes summing 31 major inflows and 7 outflows; and estimating volume

and area with stage per volume and stage per area curves on a monthly basis. These

monthly values were summed or averaged for each year to produce a yearly budget.

Atmospheric deposition was based on a constant 72 tons per year. Deposition to the

sediments was estimated as the difference between the mass of material in December and

January of the same year plus loads into the lake minus loads out of the lake.

C1. Water Budget

Although Lake Okeechobee is the largest lake by area (approximately 650 square

miles, 1,730 square kilometers) in the southeastern United States, it is also very shallow

with an average depth just over eight feet (Table 3-1). Because of the large surface area

with respect to volume, a large percentage of the water evaporates within a year. Outflows

from the lake are determined by a regulation schedule (see Chapter 5), which allows a

certain amount of flow when stage exceeds a value determined by the time of year. The

objective of this regulation schedule is to maintain high water levels at the beginning of

the dry season (November) to aid water supply, and to maintain lower water levels at the

beginning of the wet season (May) for flood control. Based on surface outflows only, the

turnover time for the lake averages almost three years, if evaporation is included, this

average decreases to one year. On average, evaporation accounts for more water loss than

does surface outflow. 

C2. Phosphorus Budget

Phosphorus loads to the lake have declined from highs in the mid-1980s of over

600 tons to lows in the early 1990s of less than 500 tons (Table 3-2). The loads in the late

1990s have increased as South Florida experienced three very wet years (1994, 1995, and

1998). This was followed by a very dry year (2000), that contributed the least amount of

phosphorus to the lake on record (215 tons). Because phosphorus is conservative in lakes

(it does not have a gaseous form), budgets estimate that on average 368 tons of

phosphorus per year is deposited in lake sediments (net deposition). The proportion of

phosphorus in the lake water column that settles into the sediment has been declining over

time to current levels near zero. This decline is important in the regulation of phosphorus

limits to the lake (see Models discussion below). It also demonstrates that despite some

external load reductions, phosphorus concentrations in the lake have increased. A

comparison of current (1998) and past (1988) sediment phosphorus concentrations

indicate that although total phosphorus in the sediments has not increased, the amount of

dissolved phosphorus has increased (Figure 3-12) (Fisher et al., 2001). This indicates that

the ability of sediments to absorb phosphorus has declined. Current predictions of water

quality models show that it will take decades before in-lake total phosphorus

concentrations respond to reduced external loads. 
78

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Table 3-1. Water budget for Lake Okeechobee

YearLake Area(1,000s of acres)AverageDepth(feet)

Lake VolumeChange inLake VolumeInflowRainfallOutflowEvaporationError

Percent Error

TurnoverwithoutEvaporationTurnoverwithEvaporation

(1,000s of acre-feet) (years)

1973 409 7.9 3,238 692 2,437 1,554 618 2,209 -472 -14.6 5.24 1.15

1974 418 8.2 3,443 204 2,940 1,630 1,842 2,357 -166 -4.8 1.87 0.82

1975 416 7.8 3,247 -450 1,534 1,474 878 2,329 -252 -7.8 3.70 1.01

1976 420 7.9 3,299 210 1,942 1,350 1,528 2,298 744 22.6 2.16 0.86

1977 423 7.8 3,320 115 1,304 1,742 616 2,572 257 7.7 5.39 1.04

1978 445 9.4 4,174 1091 2,630 1,784 675 2,580 -69 -1.7 6.18 1.28

1979 445 10.0 4,451 276 2,969 1,639 1,958 2,697 324 7.3 2.27 0.96

1980 444 9.4 4,161 -1601 986 1,454 1,455 2,623 37 0.9 2.86 1.02

1981 361 7.2 2,583 -1086 822 1,097 762 2,189 -54 -2.1 3.39 0.88

1982 394 8.9 3,524 2539 3,135 1,792 576 2,291 480 13.6 6.12 1.23

1983 445 10.3 4,600 -214 2,997 1,977 2,703 2,628 143 3.1 1.70 0.86

1984 445 9.9 4,398 -641 1,931 1,649 1,909 2,771 458 10.4 2.30 0.94

1985 417 7.9 3,290 -590 1,284 1,475 1,054 2,523 228 6.9 3.12 0.92

1986 438 8.2 3,606 372 1,466 1,688 582 2,670 471 13.1 6.20 1.11

1987 442 8.7 3,843 619 2,219 1,551 860 2,682 391 10.2 4.47 1.08

1988 445 9.5 4,212 -743 1,512 1,477 1,225 2,737 229 5.4 3.44 1.06

1989 387 7.5 2,908 -896 1,283 1,453 1,317 2,376 61 2.1 2.21 0.79

1990 365 7.3 2,666 23 1,351 1,394 625 2,122 24 0.9 4.27 0.97

1991 415 8.6 3,568 1532 2,199 1,793 316 2,334 189 5.3 11.29 1.35

1992 445 9.4 4,196 -31 1,663 1,706 1,234 2,366 199 4.7 3.40 1.17

1993 443 8.7 3,870 -792 1,613 1,556 1,893 2,372 305 7.9 2.04 0.91

1994 443 9.1 4,050 1504 3,155 2,131 1,566 2,517 301 7.4 2.59 0.99

1995 445 10.4 4,626 -539 3,527 2,005 3,806 2,642 378 8.2 1.22 0.72

1996 445 9.3 4,124 -952 1,271 1,519 1,394 2,857 508 12.3 2.96 0.97

1997 435 8.3 3,631 1224 2,284 1,809 589 2,527 247 6.8 6.16 1.17

1998 445 10.1 4,504 -245 3,619 1,809 3,373 2,713 413 9.2 1.34 0.74

1999 443 9.4 4,169 -36 2,169 1,840 1,496 2,582 33 0.8 2.79 1.02

2000 396 8.1 3,197 -2090 679 1,258 1,480 2,379 -167 -5.2 2.16 0.83

Average 426 8.8 3,746 -18 2,033 1,629 1,369 2,498 187 4.7 2.74 0.97
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

79

Table 3-2. Lake Okeechobee phosphorus (P) budget in tons

Year

Lake 

P 

Mass

Net 

Change 

in Lake 

Content

Surface 

P Load 

In

Atmospheric 

Deposition

Total 

P 

Load 

In

Total 

P 

Load 

Out

Net 

Deposition

Proportion of 

Lake Content

Deposited into 

Sediments

Proportion of 

In Load

Deposited into 

Sediments

1973 238 -171 478 72 550 51 670 2.81 1.22

1974 228 74 813 72 885 227 584 2.56 0.66

1975 234 -76 327 72 399 66 409 1.75 1.02

1976 258 99 444 72 516 286 131 0.51 0.25

1977 264 -54 367 72 439 66 427 1.62 0.97

1978 394 54 670 72 742 96 592 1.50 0.80

1979 556 152 993 72 1065 224 690 1.24 0.65

1980 530 -372 215 72 287 145 514 0.97 1.79

1981 305 -222 363 72 434 79 578 1.90 1.33

1982 384 433 891 72 963 95 435 1.13 0.45

1983 581 -139 656 72 728 428 439 0.76 0.60

1984 615 -335 627 72 699 362 672 1.09 0.96

1985 368 -227 396 72 468 125 570 1.55 1.22

1986 313 31 503 72 575 59 485 1.55 0.84

1987 572 40 509 72 581 112 429 0.75 0.74

1988 647 -287 384 72 456 183 560 0.87 1.23

1989 362 365 350 72 422 186 -129 -0.36 -0.31

1990 385 31 397 72 469 85 353 0.92 0.75

1991 402 64 452 72 524 44 416 1.03 0.79

1992 494 -240 390 72 462 116 586 1.19 1.27

1993 475 139 285 72 357 233 -16 -0.03 -0.05

1994 505 270 594 72 666 180 216 0.43 0.32

1995 633 246 708 72 780 387 148 0.23 0.19

1996 680 -96 177 72 250 205 141 0.21 0.57

1997 491 409 471 72 543 86 48 0.10 0.09

1998 732 -239 815 72 887 569 557 0.76 0.63

1999 658 681 689 72 761 259 -180 -0.27 -0.24

2000 659 -94 143 72 215 322 -13 -0.02 -0.06

Average 463 19 504 72 576 188 368 0.80 0.64
80

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

C3. Nitrogen Budget

Nitrogen loading rates have averaged over 8,900 tons per year, with an output

mass of about 3,500 tons per year (Table 3-3). In terms of historical trends, the rate of

nitrogen loading increased significantly through the early 1980s, and then declined rapidly

through the early 1990s, which is attributed to the decline in backpumping from the EAAEPD (Figure 3-6) (James et al., 1995a). 

The mass-balance budget also shows that the lake acts as a sink for nitrogen, with

62 percent of the nitrogen introduced into the lake being retained on an average annual

basis (Figure 3-6). Much of this may be lost to the atmosphere as N2 gas, from the process

of denitrification. Denitrification may be very important to the overall nitrogen cycle of

Lake Okeechobee. However, as is also the case for other bacterially-mediated

transformations of nitrogen in Lake Okeechobee, it has not been directly measured, and

represents an area for future study. 

Increased = 41

Decreased = 5

Decreased = 33

Increased = 9

Decreased = 52

Increased = 8

Decreased = 9

Increased = 73

Figure 3-12. Changes in total phosphorus (P) and dissolved reactive phosphorus (DRP)

amounts at over 100 locations in Lake Okeechobee between 1988 and 1998.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

81

Table 3-3. Lake Okeechobee nitrogen (N) budget in tons

Year

Lake 

N 

Mass

Net 

Change 

in Lake 

Content

Surface 

N Load 

In

Atmospheric 

Deposition

Total 

N 

Load 

In

Total 

N 

Load 

Out

Net 

Deposition

Proportion of 

Lake Content 

Assimilated

Proportion 

of Loads 

Assimilated 

by Lake

1973 6,781 2,116 6,827 3,669 10,496 1,592 6,789 1.00 0.65

1974 7,342 -1,421 8,695 3,669 12,365 4,170 9,615 1.31 0.78

1975 6,248 2,498 5,321 3,669 8,990 1,781 4,711 0.75 0.52

1976 8,880 4,398 5,492 3,669 9,161 4,752 10 0.00 0.00

1977 7,850 -6,013 6,042 3,669 9,711 1,871 13,853 1.76 1.43

1978 10,355 1,011 8,389 3,669 12,058 2,211 8,837 0.85 0.73

1979 11,695 2,157 8,325 3,669 11,994 6,194 3,643 0.31 0.30

1980 13,469 -954 3,279 3,669 6,948 4,544 3,358 0.25 0.48

1981 8,993 -6,478 5,694 3,669 9,363 2,755 13,086 1.46 1.40

1982 8,690 3,692 9,475 3,669 13,144 1,788 7,664 0.88 0.58

1983 9,692 4,815 6,792 3,669 10,461 6,581 -935 -0.10 -0.09

1984 9,345 -5,615 4,332 3,669 8,001 5,204 8,413 0.90 1.05

1985 7,028 -1,519 4,320 3,669 7,989 2,727 6,781 0.96 0.85

1986 7,652 433 3,805 3,669 7,474 1,627 5,414 0.71 0.72

1987 9,543 -3,819 5,304 3,669 8,973 2,551 10,242 1.07 1.14

1988 8,829 -2,244 3,261 3,669 6,930 2,985 6,188 0.70 0.89

1989 6,131 2,352 3,418 3,669 7,087 3,290 1,446 0.24 0.20

1990 5,794 155 2,710 3,669 6,379 1,442 4,783 0.83 0.75

1991 6,447 1,765 4,630 3,669 8,299 761 5,773 0.90 0.70

1992 7,645 -2,050 3,641 3,669 7,310 2,665 6,695 0.88 0.92

1993 7,421 1,877 2,981 3,669 6,650 5,759 -986 -0.13 -0.15

1994 8,513 3,046 5,841 3,669 9,510 3,761 2,703 0.32 0.28

1995 8,610 -925 6,585 3,669 10,254 8,373 2,806 0.33 0.27

1996 9,014 1,861 2,453 3,669 6,122 2,822 1,439 0.16 0.24

1997 7,817 2,690 5,023 3,669 8,692 1,634 4,368 0.56 0.50

1998 9,364 -3,397 7,772 3,669 11,441 7,837 7,000 0.75 0.61

1999 8,237 4,702 5,137 3,669 8,806 3,474 630 0.08 0.07

2000 7,804 -931 1,646 3,669 5,315 4,442 1,805 0.23 0.34

Average 8,400 150 5,257 3,669 8,926 3,557 5,219 0.62 0.58
82

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

D. MODELS

Results from the modified Vollenweider Model show that the target phosphorus

load and the observed phosphorus load vary from year-to-year (Figure 3-13a). The target

has been met in only one year (1991). 

To reduce the variability of the observed and target loads while maintaining the

overall trend, a five-year moving average is calculated. This is done by creating a fiveyear window and averaging all years within that window. As the window progresses

forward, or rolls, in time the oldest years are dropped and newer years are added. This

five-year average shows some declines in the loads to the lake (Figure 3-13b). This

decline is more dramatic when observed as the amount of phosphorus that the observed

load exceeded the target load (Figure 3-14a). The amount of excessive load declined in

the 1980s and 1990s, but has increased since 1995. This can be attributed in part to the

number of wet years in the late 1990s that have increased the overall flow to the lake

(Figure 3-14b). However, inflow concentrations weighted for flow have also increased in

the past few years (Figure 3-15). 

Figure 3-13. Actual and target loads of phosphorus to Lake Okeechobee a) annually and b) as a

five-year rolling average

0

200

400

600

800

1,000

1,200

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus Loa

d

in Tons per Year

Observed Load

Target Load

a.

0

200

400

600

800

1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus Loa

d

Tons per Year

Observed Load

Target Load

b.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

83

Figure 3-14. Five-year rolling average of a) tons of phosphorus above target and b) inflow to

Lake Okeechobee

0

50

100

150

200

250

300

350

72-7675-7978-8281-8584-8887-9190-9493-9796-00

Years

Tons of Phosphorus Above 

Target

a.

1,000

1,500

2,000

2,500

3,000

72-7675-7978-8281-8584-8887-9190-9493-9796-00

Years

Inflow Thousands of Acre-ft

b.
84

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

After 1986, the modified Vollenweider model consistently under predicted the

observed value of total phosphorus in the lake (Figure 3-16). Havens and James (1997)

suggested that this model ignored the large load sediments contributed to the water

column of the lake. These sediments can potentially produce an internal load comparable

to the external loads of the lake (Moore et al., 1998). Other models have been proposed

that will estimate total phosphorus within the lake, including representations of sediments.

Models that assume a constant settling rate of phosphorus from the water column to the

100

150

200

250

72-7675-7978-8281-8584-8887-9190-9493-9796-00

Years

Inflow Concentration

(ppb)

Figure 3-15. Five-year rolling average of phosphorus concentrations in inflows to Lake

Okeechobee

0

20

40

60

80

100

120

140

160

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus

(ppb)

Observed

Predicted

Figure 3-16. Comparison of the modified Vollenweider model total phosphorus predictions to

observed data for 1973 to 2000
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

85

sediments overpredict total phosphorus in the 1970s but predict current phosphorus values

well (Figure 3-17). To predict the historical record of the lake well, these models have to

change the net settling rate over time. 

A number of hypotheses have been suggested to account for the decrease in net

settling. The first relates to lake levels and wind. Lakewide total phosphorus

concentrations are strongly correlated with water levels (Canfield and Hoyer, 1988;

Havens, 1997) and wind (Maceina and Soballe, 1990). Several mechanisms have been

proposed to explain the relationship, including 1) flooding of marsh vegetation and

subsequent phosphorus release from dying plants; 2) enhanced water column stability

when water levels are high, leading to low oxygen conditions and subsequent soluble

phosphorus release from sediments; and 3) the reduction of submerged aquatic vegetation

under high lake level conditions that remove and retain phosphorus from the water

column. 

The first two hypothesis were tested during the 1980s and 1990s. Considerable

research was directed at the marsh flooding process in the late 1980s, and the general

conclusion was that the marsh zone is generally hydrologically uncoupled from the

limnetic zone, but when water exchange does occur, the marsh zone is a strong sink for

phosphorus (Sheng and Lee, 1991; Dierberg, 1992; Harris et al., 1995). Research efforts

began in the summer of 1996 to determine if a relationship exists between dissolved

oxygen and soluble reactive phosphorus in the water column of the lake. Three years of

daily dissolved oxygen and weekly to biweekly soluble reactive phosphorus data do not

indicate any relationship. 

The third hypothesis on the relationship between in-lake phosphorus and water

levels, the impact of the reduction of submerged aquatic vegetation, has been more

recently tested. When the lake stage is lower, more light reaches the bottom sediments

stimulating the growth of submergent aquatic vegetation. The growth of these plants not

only reduces the amount of material being resuspended from the sediments, but also take

0

20

40

60

80

100

120

140

160

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus (ppb)

Observed

Predicted

Figure 3-17. Comparison of a simple mass balance model total phosphorus predictions to

observed data for 1973 to 2000
86

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

up existing phosphorus, reducing the overall phosphorus concentration in the water

column. The current effort to lower the lake levels has provided an opportunity to test this

hypothesis. Forty locations where submerged aquatic vegetation has been observed in the

past were visited in April 2000 and submerged aquatic vegetation was found at only two

of the sites. At this time the lake stage was over 14.5 feet National Geodetic Vertical

Datum (NGVD). By the end of September, 2000, a mapping program found over 43,000

acres of submerged aquatic vegetation in the lake (see Chapter 4). In April 2000, the

lowest total phosphorus concentration measured in the lake was 126 ppb at the Palm Out

station. As of this writing, the highest total phosphorus value measured in the lake was 58

ppb in May 2000 at L006. These May values do not include the central L001 to L005

stations. However, the values that were observed were much less than any values obtained

in April. In previous years, total phosphorus drops noticeable from April to May, but this

decline was not as dramatic in 1998 or 1999 as it was in 2000. Further monitoring and

comparisons to previous years will determine if the recession truly has had an impact on

the water quality of the lake.

A simple model that handles this relationship between submerged aquatic

vegetation and lake levels adequately predicted yearly total phosphorus values for Lake

Okeechobee (Figure 3-18). The simulation included data from the 1970s. These model

results do not prove that submerged aquatic vegetation has or has had a large impact on the

water quality of Lake Okeechobee. However, it does suggest that further empirical and

modeling studies regarding these relationships should be conducted.

0

20

40

60

80

100

120

140

160

1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

Total Phosphorus (ppb)

Observed

Predicted

Figure 3-18. Comparison of total phosphorus predictions from a simple mass balance model,

which includes a submerged aquatic vegetation component, to observed data for

1973 to 2000
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

87

D1. Total Maximum Daily Load and Water Quality Models

On December 31, 1999, the USEPA set a phosphorus TMDL for Lake Okeechobee

of 0.05 ppm or 50 ppb for the waters flowing into the lake. This is much less than the

current SWIM target and is based on the Lake Okeechobee Water Quality Model, a more

sophisticated water quality model that includes the impact of sediments. The Lake

Okeechobee Water Quality Model was developed by SFWMD staff using a modified

version of the Water Analysis Simulation Package that is currently supported by the

USEPA. This model simulates the oxygen, phosphorus, nitrogen, and silica cycles within

the lake; suspended solids; and three algal groups: diatoms, greens, and cyanobacteria

(Figure 4). The model was developed to answer two questions: 1) how will Lake

Okeechobee respond to decreased phosphorus loads? and 2) under what conditions will

algal blooms occur? This model includes sediment water interactions and has been

calibrated and verified to monthly data observed from 1983 to 1996. 

The USEPA used this model to determine what inflow loads the lake could

assimilate, given lake conditions prior to the 1900s. They ran a number of scenarios and

determined that at an inflow concentration of 84 ppb, the sediment concentration did not

change (Figure 5). The USEPA then went further by taking a number of loading

conditions and, based on current lake and sediment conditions, determined the amount of

Loads and 

Flows

Temperature Solar 

Radiation

Sediment 

Resuspension

Sediment

Dissolved

Oxygen

Carbonaceous 

Biological 

Oxygen 

Demand

Nitrate Ammonium

and 

Nitrite

Inorganic 

Suspended 

Solids

Dissolved 

Reactive 

Phosphorus

Dissolved

Silica

Organic 

Nitrogen

Particulate

Silica

Cyanobacteria

Diatoms

Green Algae

Organic 

Phosphorus

Labile

Dissolved

Moderately 

Labile

Nonreactive

Figure 4. A diagram of the Lake Okeechobee Water Quality Model (USEPA, 2000)
88

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

time it would take to reach the in-lake target goal of 40 ppb. The USEPA determined that a

target value of 50 ppb in the inflow, which on average is a phosphorus load of 218 tons per

year, was an adequate TMDL to reach the target in a reasonable time frame, and to meet a

minimum margin of safety criteria. The model predicts that the majority of the in-lake

reduction response will occur in the first 20 to 30 years, so that despite the long period of

time it will take to reach the target, the in-lake concentration will be reduced significantly

in a reasonably short period of time (Figure 6). 

Two concerns about the use of this model exist. The first is that the model does not

adequately predict the observed data from the 1970s (Figure 3-17). This is a problem of

all mass balance models used to this point that assume a constant settling rate throughout

the observed history. As described above, some mechanism must be found to explain a

change in this settling rate. One possibility is the relationship between lake levels and

submerged aquatic vegetation. For the Lake Okeechobee Water Quality Model to handle

the submerged aquatic vegetation, three things are needed: 1) the model must be enhanced

to include a submerged aquatic vegetation component; 2) the model must work on a

spatially-segmented scale to represent shallow areas where submerged aquatic vegetation

can grow; and 3) deeper areas where mud sediments exist and the hydrodynamics of the

lake between the grids must be specified by the Lake Okeechobee Hydrodynamic

Sediment Transport Model. The second concern is that the predictions of the model

contain a large amount of uncertainty. This uncertainty is being quantified through a study

that will determine the range of potential values in each model parameter, and determine

the possible range of outcomes if these parameter values are changed within the range of

acceptable values (SFWMD Contract C-10668). 

85

86

87

88

89

90

91

92

0 50 100 150 200 250 300 350

80 ppb Inflow 84 ppb Inflow 85 ppb Inflow

Total Phosphorus Sediment (mg/L)

Year

Figure 5. Simulations of the Lake Okeechobee Water Quality Model under pre-1910 conditions

to determine the maximum phosphorus inflow concentration that can be absorbed by

the sediments without increasing phosphorus concentrations in the water column

(USEPA, 2000)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

89

In 2000, the FDEP assembled a TMDL Technical Advisory Committee to develop

its own phosphorus TMDL for Lake Okeechobee. They have investigated a number of

simple mass balance and empirical models, as well as the Lake Okeechobee Water Quality

Model. The TMDLs determined from each of these models were very similar to one

another and were similar to the USEPA proposed TMDL. The final TMDL accepted was

140 metric tons or approximately 40 ppb in inflow waters (FDEP, 2001). The only

difference may be the amount of atmospheric deposition assumed. The Lake Okeechobee

Water Quality Model assumed a deposition of 72 tons per year, which is the same value

used in the determination of phosphorus budgets to the lake in this SWIM plan. However,

because of the tremendous uncertainty in measurements of atmospheric deposition (Ahn

and James, 1999, 2000) and the reduction of atmospheric deposition over large bodies of

water, the Lake Okeechobee TMDL Technical Advisory Committee recommended using

an atmospheric load less than half of the current estimate. Further research on atmospheric

deposition in South Florida is currently under way (SFWMD Contract C-10740).

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250 300 350

250Tons (70 ppb) 

Total Phosphorus (mg/L)

 70 Tons (0 ppb) 

275Tons (80 ppb) 

173Tons (40 ppb) 198 Tons (50 ppb) 

224Tons (60 ppb) 

Year

Figure 6. Predictions of in-lake phosphorus concentrations under different inflow loads 

(USEPA, 2000)
90

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

D2. Hydrodynamic and Sediment Transport Model 

The Lake Okeechobee Hydrodynamic and Sediment Transport Model (Jin et al.,

2000a) simulates hydrodynamic and sediment transport processes in Lake Okeechobee. It

also provides detailed long-term information regarding circulation patterns, sediment

distribution, and sediment resuspension/deposition under different hydrological and manmade conditions (e.g., high/low lake stages, storm events/hurricanes, and sediment

removal/dredging). These results can be used in a spatially-segmented water quality

model to predict the impacts of sediment resuspension and movement of nutrients on both

nearshore and pelagic areas of Lake Okeechobee.

Wind influences both lake circulation and sediment resuspension. The circulation

patterns vary with wind velocity and water depth. Wind also affects sediment resuspension

through the production of waves. Wave height is determined by both wind velocity and

fetch, which is the length of exposed water surface in the direction that the wind blows. In

general, the larger the wind velocity and fetch, the larger the wave height and wave period.

Due to shallow depths in the lake, energy generated by wind is directly transmitted

through the water column to the lake bottom. If the transmitted energy exceeds the

sediment's critical shear stress, resuspension occurs (Jin and Ji, 2000). The bottom stresses

resulting from wind generated surface waves are the major causes of sediment

resuspension and transport in Lake Okeechobee (Jin and Wang, 1998). 

An example of these relationships is demonstrated for January 21, 2000. On this

date, the wind was blowing in the southeastern direction at 6 miles per second, and the

lake had a significant wave height of over 70 centimeters in the deepwater areas

(Figure 3-1). Simulated circulation patterns in the top and bottom layers on this day were

very similar (Figures 3-2 and 3-3). Sediment concentrations exceeding 200 ppm were

predicted in the central region of the lake. The resuspension of sediment is strongly

associated with significant wave height, and the transport of the suspended sediment in the

lake is totally driven by the currents. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

91

Figure 3-1. Lake Okeechobee hydrodynamic sediment transport model

predictions of wave height on January 21, 2000
92

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Figure 3-2. Lake Okeechobee hydrodynamic sediment transport model predictions of surface

currents and sediment concentrations on January 21, 2000
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

93

Figure 3-3. Lake Okeechobee hydrodynamic sediment transport model predictions of bottom

currents and sediment concentrations on January 21, 2000
94

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

E. SEDIMENT ASSESSMENT

In 1998, as part of the Sediment Remapping Study (Reddy, 1998), 31 sediment

samples were taken from the lake and measured by the FDEP's Central Laboratory for a

series of herbicides, pesticides, and their breakdown products. Of the 64 organics

measured, only two, DDD, p, p’ and DDE, p, p’, were detected (Figures 3-4 and 3-5).

These organics are breakdown products of DDT, a toxic and persistent chemical widely

used for agricultural pest control in the United States from the 1940s to the 1960s. DDD,

p, p’ and DDE, p, p’ were found in seven and nine of the 31 samples, respectively. The

amounts detected were above the minimum detection value for the analytical procedure,

but were below an amount that could be accurately measured. The Development and

Evaluation of Sediment Quality Assessment Guidelines (MacDonald, 1994) lists the

threshold and probable effect levels of these organics as 1.2 and 7.8 ppb for DDD p,p’, and

2.1 and 374 ppb for DDE p,p’, respectively. Thus, the amount of DDD, p, p’ and DDE, p,

p’ in the sediments of Lake Okeechobee are a cause for some concern as the measured

values exceeded the threshold levels, but for the most part they did not exceed the

probable effect levels. 

No Sample

Below Detection Limit

5 to 12 ppb

0 20 40 60

kilometers

Figure 3-4. Locations within Lake Okeechobee where DDD p,p’ was detected in samples taken

in 1998
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

95

E1. Lake Okeechobee Sediment Management Feasibility Study

At present, more than 51,600 metric tons of phosphorus is in the mud sediments of

Lake Okeechobee. This sediment material, which appears to have accumulated in the lake

during the last 150 years (Brezonik and Engstrom, 2001), frequently is resuspended into

the water column by wind and waves (Maciena and Søballe, 1990). When this occurs,

phosphorus is transported into the water column (internal loading) at a magnitude

approximately equal to external loading from the watershed (Moore et al., 1998). Due to

this high internal loading, the lake may not respond to reductions in external phosphorus

inputs (Steinman et al., 1999). This situation is typical of shallow, nutrient-enriched lakes

(Sas, 1989), which generally require in-lake restoration measures to achieve recovery

(Moss et al., 1999).

Under direction of the South Florida Ecosystem Restoration Working Group, a

multiagency team, known as the Lake Okeechobee Issue Team, developed an action plan

for the rehabilitation of Lake Okeechobee. To ensure recovery of Lake Okeechobee from

cultural eutrophication, the action plan recommended removal of all or part of the mud

0 20 40 60

kilometers

No Sample

Below Detection Limit

2.5 to 15 ppb

Figure 3-5. Locations within Lake Okeechobee where DDE p,p’ was detected in samples taken

in 1998
96

Chapter 3: In-Lake Water Quality Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

sediments, to the maximum extent practicable, in order to substantially reduce internal

phosphorus loading. If the sediments are removed, they must be processed and disposed of

in such a way that will not contribute phosphorus to the lake or other regional water

resources. The mud in Lake Okeechobee covers an area greater than 80,000 hectares and

has a volume of approximately 200 million cubic meters. This amount of material is an

order of magnitude greater than has ever been removed from any lake in the world (Cooke

et al., 1993). 

Given these issues, a comprehensive feasibility study must be conducted to

provide detailed information regarding the benefits, potential concerns, and costs

associated with alternatives for addressing the internal phosphorus loading issue.

Therefore, the objective of the Lake Okeechobee Sediment Management Feasibility Study

is to analyze various alternatives in order to determine the best method of sediment

treatment that will reduce internal phosphorus loading in Lake Okeechobee. Feasibility

study goals will be achieved using an objective methodology that allows for review and

input by experts and stakeholders throughout the study process. The final deliverables

from this study, which are expected in October 2003, will be used in conjunction with a

multiple criteria decision process and public/interagency input in order to make final

recommendations to the Governing Board of the SFWMD.

E2. Lake Okeechobee Pilot Dredging Project

In 2000, when the District began the Lake Okeechobee Sediment Management

Feasibility Study, the objective was to analyze various alternatives in order to determine

the best method of sediment treatment that will reduce internal phosphorus loading in

Lake Okeechobee. One of the sediment treatment alternatives under consideration is

dredging. However, the fluid characteristics of the sediment, the large area of its coverage,

the shallow depth of sediment, and the environmental sensitivity of Lake Okeechobee will

present a very considerable challenge for dredging. The use of conventional dredging

technologies for this project may not suffice and more advanced technologies need to be

evaluated.

In the fall of 2000, the District initiated a contract to conduct a pilot dredging

project in Lake Okeechobee. The project is scheduled to begin in March 2002. It will

demonstrate the feasibility and cost-effectiveness of removing the phosphorus laden mud

layer using innovative dredging, material processing, and water treatment technologies.

Permit applications have been developed and are under review, prior to submittal to the

appropriate agencies. The results of this project also will provide essential information for

input to the Sediment Management Feasibility Study that is being conducted concurrently

under a separate District contract.

F. CLASS I WATER QUALITY PARAMETERS

An evaluation of the District's water quality and biological monitoring data,

collected at ten open water stations during the period beginning in 1972 and ending in

1991, have been reported (CH2M Hill, 1995; Ogburn et al., 1996). Since then, additional
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

97

data have been collected and added to update this report. Because Lake Okeechobee is

classified as a drinking water source in Chapter 62-302.400, F.A.C., in-lake conditions

were compared to Class I standards. Observed data from 1988 to 2000 were compared to

Class I criteria (effective Dec. 26, 1996) (Chapter 62-302.530, F.A.C.). The results of this

comparison are presented in Table 3-4. The evaluation considered both the frequency and

the magnitude of the instances in which the criteria were exceeded.

Table 3-4. Percentage of instances that Class I criteria were exceeded within Lake Okeechobeea

STATIONpHAlkalinityConductivityChlorideDissolvedOxygenTotal DissolvedSolidsTurbidity Un-IonizedAmmoniaNitrateIronArsenicCadmiumCooperLeadZincMercury

L001 23.1 1.0 1.5 0.0 0.0 0.0 3.5 0.0 0.0 63.3 0.0 2.9 0.0 0.0 0.0 0.0

195 201 196 197 194 2 201 191 178 49 37 34 34 34 34 34

L002 17.7 0.0 0.0 0.0 0.0 0.0 6.2 2.0 0.0 66.7 0.0 0.0 0.0 0.0 0.0 0.0

 232 205 234 203 232 2 258 255 226 48 36 33 33 33 33 33

L003 4.6 0.0 0.0 0.0 0.5 0.0 13.4 0.0 0.0 87.2 0.0 0.0 0.0 0.0 0.0 0.0

 195 202 196 198 195 2 202 193 180 47 36 33 33 33 33 29

L004 2.6 0.0 0.0 0.0 0.0 0.0 14.9 0.0 0.0 87.5 0.0 3.0 0.0 0.0 0.0 0.0

 194 201 195 195 193 2 201 191 177 48 36 33 33 33 33 31

L005 43.2 0.0 0.4 0.0 0.4 0.0 7.4 0.4 0.0 44.7 0.0 0.0 0.0 3.1 0.0 0.0

 227 202 228 199 225 2 258 251 220 47 36 32 32 32 32 33

L006 5.0 0.5 0.0 0.0 0.0 0.0 16.9 0.0 0.0 75.5 0.0 0.0 0.0 0.0 0.0 0.0

 239 206 241 205 238 3 248 247 229 49 37 35 35 35 35 30

L007 14.9 0.0 0.0 0.0 0.0 0.0 8.7 0.0 0.0 49.0 0.0 0.0 0.0 0.0 0.0 0.0

 201 208 202 206 199 3 207 204 193 49 37 35 35 35 35 30

L008 14.4 0.0 0.0 0.0 0.5 0.0 18.8 0.0 0.0 79.6 0.0 0.0 0.0 0.0 0.0 0.0

 188 197 189 191 187 2 197 186 171 49 37 34 34 34 34 34

LZ2 42.6 0.0 2.2 0.0 0.0 0.0 2.0 0.0 0.0 39.1 0.0 0.0 0.0 0.0 0.0 0.0

 94 97 93 96 96 0 98 90 76 23 23 20 20 20 20 23

LZ30 18.6 0.6 0.6 0.0 1.2 0.0 11.9 0.6 0.0 52.4 0.0 3.0 0.0 0.0 0.0 0.0

 172 179 174 178 171 3 177 177 164 42 35 33 33 33 33 27

Total 17.5 0.2 0.4 0.0 0.3 0.0 10.7 0.4 0.0 66.1 0.0 0.9 0.0 0.3 0.0 0.0

1,937 1,898 1,948 1,868 1,930 21 2,047 1,985 1,814 451 350 322 322 322 322 304

a. The upper number in each cell indicates the number of samples collected, while the lower number represents the 

percentage the criteria was exceeded. The key below explains the color coding

25% or more of samples exceed criteria

Between 10% and 25% of samples exceed criteria

Less than 10% of samples exceed criteria

ND Not determined

No criteria has been established
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Results of the study indicate that Class I criteria for iron is exceeded at all stations

in more than 25 percent of the samples (Table 3-4). The Class I criteria were exceeded for

pH at five stations in more than 10 percent of the samples and two stations in more than 25

percent of the samples. Turbidity exceeded the Class I standard at five stations in more

than 10 percent of the samples. The mechanisms, most of which are natural, that caused

the criteria to be exceeded are discussed below. 

F1. pH

The Class I criteria for pH include minimum (6.0) and maximum (8.5) values. The

in-lake stations had between 94 and 239 observations for this parameter. The incidence of

criteria being exceeded ranged from 2.6 percent at L004 in the eastern central region of the

lake to nearly 43.2 percent at L005 in the central western region of the lake. All but one of

the instances were values above the maximum criterion of 8.5, and were likely caused by

algal photosynthesis. Since the average pH for the lake is 8.1, pH measurements over 8.5

are rather common and do not truly represent degraded conditions of the lake.

F2. Alkalinity

The Class I criterion for alkalinity requires a minimum value of 20 ppm calcium

carbonate (CaCO3). Of the 1,898 observations, only four were less than the minimum, and

these occurred at one station twice and at four other stations once. 

F3. Dissolved Oxygen

The Class I criterion for dissolved oxygen requires a minimum value of 5 ppm.

The in-lake stations had between 96 and 238 measurements for this parameter. Four

stations had one or two measurements below the minimum. These low values were

probably caused by decomposition of algae and plants.

F4. Turbidity

The Class I criterion for turbidity is 29 nephelometric turbidity units (NTUs)

above background. The background value for each station was determined as the median

value; half of all values are lower and half of the values are higher than the median value.

This criterion was exceeded at all stations for 2.0 percent to 18.8 percent of all

observations. These instances are related to the shallow nature of the lake and wind-driven

resuspension of mud bottom sediments.

F5. Un-ionized Ammonia

The Class I criterion for un-ionized ammonia is 20 ppb. Between 90 and 255 total

observations were made at each of the in-lake stations and only one to five observations at

three stations exceeded the criterion. This is considerably lower than the frequency on

observed in inflow water. The ability of algae and bacteria to use ammonia as a nitrogen
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 3: In-Lake Water Quality

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source appears to minimize the potential for the un-ionized ammonia criterion to be

exceeded in the lake.

F6. Iron

The Class I criterion for iron is 0.3 ppm, which will prevent discoloration and

staining by domestic water supplies. This criterion was exceeded at all of the in-lake

stations. The percent of times the criterion was exceeded ranged from 39.1 to 87.5 percent

of the observations. This amount of iron within the water could affect drinking water

quality, perhaps causing objectionable taste and staining of dishes and clothes. The

widespread distribution of high iron concentrations in the lake and inflows indicates that

this is a natural condition. The most likely source is local soils.

F7. Arsenic, Cadmium, Copper, Lead, and Zinc

The Class I criteria for arsenic is 50 ppb. The Class I criteria for cadmium, copper,

lead, and zinc are calculated as a function of water hardness, and, therefore, do not have

specific values. Very few observations have been made for these five parameters

(generally less than 40 per station for the 12-year period), and the criteria were rarely

exceeded. No stations exceeded the criteria for arsenic, copper, or zinc. Three stations

exceeded the criterion for cadmium once and another for lead once. 

F8. Mercury

All mercury data, with the exception of three samples, were reported as “below

detection limit.” Any observation above the detection limit, was flagged as not meeting

the quality assurance/quality control (QA/QC) standard for precision or accuracy. Since

the minimal detection limit for mercury analysis (0.02 ppb) was above the Class I criterion

of 0.012 ppb, no meaningful evaluation of compliance is possible.

F9. Other Class I Criteria

Other aspects of water quality, including pesticides, polychlorinated biphenyls

(PCBs), biological integrity, and total coliforms, were not measured at the in-lake stations,

and as such, represent an area where information is needed. It is also important that

compliance with other Class I criteria be assessed, since conditions in the lake may change

from year-to-year. Although a couple of total dissolved solids samples were taken at each

station, the numbers are so small that no meaningful evaluation is possible. Thus, it is

recommended that more samples be analyzed for dissolved solids.
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Chapter 4

ENVIRONMENTAL RESOURCES

Lake Okeechobee is the central component of a large interconnected aquatic

ecosystem in South Florida that extends from the headwaters of the Kissimmee River to

Florida Bay. Prior to intensive human development in South Florida, the hydrology of

Lake Okeechobee was coupled directly to that of the meandering Kissimmee River and its

marsh ecosystem in the north, and to the great expanse of Everglades marsh in the south

(Figure 4-1, PAST). During periods of high rainfall, lake water levels may have exceeded

20 feet NGVD and water exited the lake at its southern end into a number of blind river

channels and as overland sheetflow into the Everglades sawgrass community. 

After two major hurricanes and associated floods killed over 2,000 people in the

1920s, the USACE constructed a system of gates, dikes, pumps, and canals around Lake

Okeechobee and throughout South Florida. This effort, the C&SF Project, was completed

in the mid-1960s and today the lake is entirely surrounded by an earthen dike. All water

inflows, except Fisheating Creek to the west, and outflows are controlled. Maximal water

levels in the lake are regulated and the natural connections between the lake and the

Everglades marsh have been lost. 

Lake Okeechobee is now smaller than under natural conditions, and water levels

are lower (Figure 4-1, PRESENT). The littoral zone occupies about 25 percent of the

lake's surface along the southern and western shores and it occurs in a region that was

once under water. As a result of the dike, the littoral zone is uncoupled from land that once

supported a much larger marsh to the west. That land now supports agricultural crops.

Despite lower water levels from a historical perspective, flooding in the littoral zone in

recent years has resulted in serious impacts. Because the dike prevents the gradual

outward expansion of marsh habitat that normally may have occurred, additional water

(greater than 15 feet NGVD) in the lake results in deeper flooding of the littoral zone.

Likewise, under extreme low water level conditions (less than 11 feet NGVD) nearly the

entire littoral zone is dry and unavailable as habitat for fish and other wildlife. This occurs

because a relatively sharp depth gradient occurs at the interface between this region of the

lake and the adjacent pelagic (open water) zone. 

When the water level in Lake Okeechobee increases above a seasonally variable

maximum (the lake stage that triggers discharge decisions on any given date based on a

USACE regulation schedule), discharges can occur through canals connected to estuaries

on the east and west coast of Florida. As a result of past discharges, the estuarine

ecosystems have experienced unnaturally large inputs of fresh water following periods of

high rainfall in the Lake Okeechobee watershed, and estuarine fish, shellfish, plants, and

other biota have been impacted.
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Figure 4-1. Hydrologic and morphological conditions of Lake Okeechobee before human

impacts (PAST), during the last 40 years (PRESENT), and anticipated when the

CERP is completed (FUTURE)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

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A number of management efforts have been directed at the issues associated with

littoral zone flooding, drying, and high freshwater discharges to the estuaries:

• The WSE schedule, a lake regulation schedule that uses climate

forecasting, was developed and adopted late in the summer of 2000.

This schedule allows proactive discharges of water from the lake to

minimize damage to the littoral zone and the estuaries during periods of

high rainfall as well as conservation of water in the lake when dry

conditions are predicted.

• Minimum water level criteria for the lake were developed as required

by state law.

• An emergency lake recession operation was carried out in the spring of

2000 to provide a period of lake levels below 13 feet NGVD so that

submerged plant beds could recover from damaging high water levels

that occurred in between 1994 and 1999.

• A set of adaptive management protocols are under development to help

the District and the USACE take full advantage of the flexibility in the

WSE schedule, in order to maximize benefits of the lake for its multiple

uses.

Lake Okeechobee once played a critical role in supplying fresh water to the

Everglades marsh. As a result of the C&SF Project and the other human developments in

South Florida, this water supply has been greatly reduced, and may in part be the cause of

ecological imbalance in the Everglades ecosystem. The USACE and the SFWMD

launched a regional restoration project, the CERP, in 2000. This project involves major

changes both in the infrastructure and operation of the C&SF system. It is designed to

restore a more natural flow of water within the boundaries of the ecosystem, while

providing the flood protection and water supply that will be required by South Florida's

growing human population. The regional project is expected to result in substantial

ecological benefits to Lake Okeechobee, as a result of a less extreme variability in lake

stages (Figure 4-1, FUTURE). A key part of CERP is a process called adaptive

assessment, which involves applied science and monitoring of a suite of ecological

performance measures. The results of that science and monitoring will be used to evaluate

the benefits of the CERP as it unfolds, and as the basis for recommending modifications to

the plan where they are necessary. Adaptive assessment also includes cause-and-effect

ecological research and modeling aimed at reducing the uncertainty of management

decisions. Using SWIM funds, assessments have been initiated prior to the CERP and

provide a sound scientific basis for the lake component of the restoration program. Some

areas of uncertainty still exist and are reflected in the objectives and strategies of this

SWIM plan update.

In addition to altered hydrology, Lake Okeechobee has been impacted by

excessive inputs of nutrients, in particular phosphorus (described in detail in Chapter 2

and Chapter 3). These phosphorus inputs, originating primarily from agricultural

activities in the lake's northern watershed, have led to increases in lake water nutrient

concentrations, more frequent algal blooms, and dominance by algal and animal species
104

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

that are tolerant of eutrophic conditions (Warren et al, 1995; Havens et al., 1996a). These

trends and their possible reversal due to management programs have the potential to

dramatically affect the values of the ecosystem for humans and wildlife. 

A third human-related impact on Lake Okeechobee is the introduction and

proliferation of exotic species. To date, the most significant impacts have been associated

with two exotic plants: Melaleuca quinquenervia (melaleuca) and Panicum repens

(torpedograss). 

Melaleuca is an Australian tree that was first introduced into South Florida in the

early 1900s. Since that time it has rapidly invaded many natural areas in the region,

creating dense monocultures that displace native plant communities and alter wildlife

value of the habitat. Melaleuca originally was planted in Lake Okeechobee by the USACE

in the late 1930s and early 1940s. These fast growing trees were planted on low-lying

islands on the side of the levee facing the lake to protect the levee system from wind and

wave erosion. Melaleuca has since spread to cover thousands of hectares of the lake's

littoral zone. 

Torpedograss is native to Europe, but now occurs in Australia, Asia, Africa, and

North America. Torpedograss was introduced into Florida in the 1920s. It gained

popularity as a cattle foraging grass in the 1950s and was planted in every county in South

Florida. Torpedograss was introduced into the lake in the 1940s and since then it has

expanded to more than 6,000 hectares (ha) in the northern and western littoral zone.

The District has been carrying out an effective program to eradicate melaleuca,

and is beginning to implement a program, in cooperation with the FDEP, to control

torpedograss. Until now, torpedograss has spread unchecked in the lake's littoral zone,

displacing valuable native plant communities. Scientists at the District have worked

closely with managers to identify the optimal treatment methods for killing the invasive

grass. Present efforts are using a combination of controlled fire and the contact herbicide

Arsenal®. During 2000-2001, the coordinating agencies treated several thousand acres of

torpedograss in this manner. A much larger area of the littoral zone will be treated in

future years. Because Arsenal® is a nonselective herbicide, one issue of concern is how to

achieve good control of torpedograss while allowing native plants to recolonize treated

sites. A major focus of exotic plant research in the near future will be in screening

alternative herbicides that can more selectively control torpedograss, and in evaluating the

potential for use of biocontrol agents against this exotic plant. 

The Lake Okeechobee Protection Act (Section 373.4595, F.S.) calls for the

identification of exotic plants and animals that occur in the lake and watershed that

threaten native flora and fauna, and, where necessary, the development of control

measures. This may result in an expansion of exotic control programs beyond their present

scope.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

105

A. GOALS, OBJECTIVES, AND STRATEGIES

Management goals and objectives developed for Lake Okeechobee include

provisions for protecting and enhancing the environmental resources of the lake itself, and

for enhancing the functional role of the lake in the regional ecosystem. The regional

system includes the St. Lucie and Caloosahatchee estuaries, the Kissimmee River, and the

Florida Everglades. 

In regard to the lake resources, a multifaceted approach is used to provide the most

scientifically rigorous and relevant information to decision makers. It involves three

fundamental and interrelated components: 

• A systematic program of long-term ecological assessment is designed

to provide the information necessary to evaluate specific “performance

measures.” These performance measures are used to judge the success

of lake restoration projects carried out under the CERP and the Lake

Okeechobee Protection Act (Section 373.4595, F.S.) mandates. They

also provide the scientific basis for making changes in the restoration

projects if they are not having the expected effects on the ecosystem

(this is the underlying concept of adaptive assessment).

• Issue-oriented experimental research is carried out to address major

questions related to management of the resource. Examples include the

identification of an optimal lake stage “envelope” for maintaining

healthy submerged plant beds, identifying selective herbicides that can

effectively kill torpedograss while not harming native plants,

quantifying the role that plants and animals play in controlling the

lake’s phosphorus assimilation, and evaluating how higher trophic

levels (e.g., fish and wading birds) respond to reduced nutrient loads

and/or changes in hydrology. 

• Predictive models are being developed and applied to address specific

management issues. Examples include the use of a lake water quality

model for setting a TMDL for phosphorus; use of a lake sediment

transport model for identifying the optimal location(s) for lake

sediment dredging; and use of a next generation, hydrodynamic, water

quality model for predicting effects of CERP project elements on lake

water quality, submerged plant distribution and abundance, and

phosphorus transport into the littoral zone.
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Goal 1: Protect and enhance the environmental resources of 

Lake Okeechobee, in terms of biological diversity, 

ecological functions, and the distribution and abundance 

of native plants and animals

Objective 1: Quantify how variations in lake water level affect the

environmental resources, and use this information to set appropriate lake

management goals

Strategy 1: Quantify relationships between lake water levels and

the germination, growth, and spatial distribution of submerged and

emergent aquatic plants, and use this information to identify ranges

of lake water levels that are optimal for the native plant

communities

Strategy 2: Develop and use models to predict how different

management actions (e.g., different ranges of water levels under the

CERP) will affect the distribution and abundance of native plant

communities

Strategy 3: Quantify the relationship between lake water levels

and the germination, growth, and spatial distribution of nuisance

and exotic plants and use this information to identify conditions

that will minimize their rates of expansion

Strategy 4: Identify wildlife uses (i.e., foraging and nesting) of

native versus exotic plant communities in the lake, and use this

information to identify the wildlife benefits that might be realized

by different scales of exotic plant control

Strategy 5: Identify the cause-and-effect links between lake water

levels, nutrient transport among the lake's major zones (pelagic,

nearshore, and littoral), and the impacts of nutrients on the lake's

biological communities

Objective 2: Develop a predictive understanding of nutrient dynamics in

the lake ecosystem, and use this information in support of the CERP and

TMDL development process

Strategy 1: Quantify the biological processes that affect

phosphorus dynamics in the pelagic, nearshore, and littoral zones 

Strategy 2: Enhance existing lake models to account for

important biological processes, and expand the capability of the

models to predict responses of major producer communities

(phytoplankton, periphyton, and vascular plants) to changes in

external and internal nutrient loading
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

107

Strategy 3: Quantify major links in the lake's food web and use

this information in concert with model output to predict effects of

nutrient load reduction on fish, birds, alligators, and other important

animals in the ecosystem

Objective 3: Identify exotic species that threaten native plants and

animals in the lake and develop and implement programs for their control

Strategy 1: Quantify the distribution and abundance of exotic

plants in the lake, identify any significant trends in their expansion

over time, and evaluate their impacts on native plants and animals

and/or water quality

Strategy 2: Quantify the distribution and abundance of exotic

animals in the lake, identify any significant trends in their

expansion over time, and evaluate their impacts on native plants

and animals and/or water quality

Strategy 3: Develop and implement effective measures to control

exotic species that threaten native plants and animals and/or water

quality, focusing these efforts on the control of torpedograss for the

next three years

Objective 4: Quantify long-term trends in the lake's ecological values

Strategy 1: Develop and implement a program of long-term

ecological assessment that is consistent with the ecological

attributes and performance measures identified in the Lake

Okeechobee Conceptual Model (Havens, 2000) and the CERP

Strategy 2: Develop and maintain a georeferenced database for

the long-term ecological assessment program being developed,

including a user-friendly graphical user interface, comprehensive

meta data files, and links to the internet

B. ECOLOGICAL IMPACTS OF WATER LEVEL 

VARIATION

Lake Okeechobee is completely encircled by a dike that eliminates natural

connections between the lake and vast marsh ecosystems that once occurred to the north,

west, and south (Aumen, 1995; Havens et al., 1996a). Because the littoral zone is

constrained to a region inside the dike, recent (1994 to 2001) variations in water level

(from greater than 18 to less than 10 feet NGVD) have caused complete submersion and

exposure of the littoral community (Figure 4-2). A long lasting (1994 to 2000) period of

high water levels in particular resulted in a number of harmful impacts on native plants

and animals. The lake's emergent and submerged plant communities provide habitat for
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Figure 4-2. Maps of Lake Okeechobee showing the area of littoral zone that is inundated with

water under a variety of lake stage elevations
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

109

fish (Fox et al., 1993), wading birds (Smith and Callopy, 1995; Smith et al., 1995a), and

federally-endangered species like the Everglades snail kite (Bennetts and Kitchens, 1997).

Therefore, it is important that resource managers understand clearly how changes in water

levels affect the lake ecosystem, so that actions can be taken to minimize harm. As better

information becomes available, it can be used to modify existing rules and/or proposed

operational criteria, so that they provide the necessary conditions for protecting the

ecosystem. A rigorous program of scientific research, monitoring, and modeling provides

the foundation for these efforts.

B1. Effects of Water Level on Native Plant Communities

Two distinct regions of the

lake support native plants (Figure 4-

3) and these generally are

considered separately when studying

the effects of water level. The littoral

zone is a large region of emergent,

submerged, and floating-leaf plants

that occurs along the lake's western

side and on islands in the southern

region. The littoral zone supports

more than 50 native plant species,

whose distribution can be largely

explained by hydroperiod

(Richardson et al., 1995). Some

species, such as Eleocharis cellulosa

(spikerush), Typha spp. (cattail), and

Nelumbo spp. (water lily) occur

where there is a long (greater than

95 percent) hydroperiod. Other

species, such as Spartina bakeri

(sand cordgrass) are restricted to

shorter (less than 80 percent)

hydroperiod littoral regions. A

number of approaches are being

used to further evaluate the

hydroperiod requirements of native

littoral plant species, and allow

predictions of how the community

will respond to changes in lake stage

operations. District scientists maintain GIS maps of the vegetation and correlate these with

antecedent hydroperiod conditions. The entire littoral zone is photographed at five-year

intervals with 1:24,000 aerial photography, and from this information GIS maps are made

for dominant species of native plants (Figure 5). A complete littoral zone vegetation map

is constructed approximately once each decade, unless some event occurs to change the

large-scale distribution of plants (e.g., in 1989 and 2000-2001 fires burned most of the

Figure 4-3. Areas of Lake Okeechobee that support

distinct primary producer assemblages,

determined largely as a function of water

depth
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Figure 5. Four dominant vegetation communities in Lake Okeechobee’s littoral zone based on

1996 aerial photographs 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

111

littoral plant community). The utility of new technologies (e.g., hyperspectral remote

sensing) also will be evaluated, as they become available. More focused experimental

studies also are being done to identify the optimal hydroperiod for particularly important

species. For example, research is being done in partnership with the USACE Waterways

Experiment Station to quantify the optimal hydroperiod for spikerush, a critical foraging

habitat for snail kites.

The second region of Lake Okeechobee where vascular plants can occur is the

nearshore zone (Figure 4-3), which occurs at a lower elevation (deeper water),

immediately adjacent to the littoral zone. The nearshore zone can support beds of

Potamogeton illinoensis (peppergrass) and Vallisneria americana (eelgrass). It also

includes areas at the southern end of the lake with “lawns” of a branched macro alga

(Chara) and a narrow band of Scirpus californicus (giant bulrush) running parallel to the

western lakeshore. Bulrush provides important habitat for sport fish (Furse and Fox, 1994)

and it may act as a wave barrier to protect submerged plant beds that develop behind it.

Plants in the nearshore zone were severely impacted in the late 1990s when water levels in

the lake frequently were in excess of 16 feet NGVD and never fell below 13 feet NGVD

for a long duration. In 1998, a record high water level of 18.4 feet NGVD occurred.

(Figure 4-1). The ecological impacts caused by high water levels are still being studied.

Some effects are documented in 1) a study of Chara performed by Steinman et al. (1997),

showing that abundance of this species declined to near zero when high lake stages

occurred; and 2) remote sensing of bulrush conducted by Hanlon and Brady (2000),

indicating that possibly a large part of former coverage was lost during the high water

years (Figure 5). Studies of Chara and bulrush are ongoing, and they will continue to

provide information regarding the impacts of water level on the nearshore plant

community.

8

10

12

14

16

18

20

1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001

Stage (ft NGVD)

Figure 4-1. Plot of monthly averaged water levels in Lake Okeechobee from 1973 to 2000
112

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

The District also initiated a program dealing with submerged vascular plant beds in

the spring of 1999. On a quarterly basis (or more often) the dry weight biomass (the

amount of living matter) and species composition of submerged plants is evaluated at 42

stations in the nearshore zone. The stations represent a subset of sites that were sampled in

the Lake Okeechobee Ecosystem Study (Zimba et al., 1995) in the late 1980s and early

1990s. This allows for a comparison of historical data. In District surveys conducted in

1999, plants were found at just seven of the 42 sites, whereas in 1989 and 1990, plants

were found at all of the locations because water levels were considerably lower (12 to 13

feet NGVD). Lower water corresponds with more light reaching the lake bottom and

increased plant growth. In contrast, the years between 1994 and 1999 were characterized

by deep (up to 18 feet NGVD) and turbid water, with potential scouring of submerged

plant beds also occurring due to wind and wave action (Havens et al., 2001). Several

months after a managed recession operation lowered water levels to near 12 feet NGVD in

the spring of 2000, submerged plants increased rapidly in the lake, and by October 2000,

were found at nearly all of the surveyed sites. In tandem with measurements of plants at

the 42 stations, District staff are evaluating the biomass and composition of periphyton

(attached algae) and selected macro invertebrates, both of which play important roles in

the food web that supports fish and bird populations.

Figure 5. The spatial extent of bulrush along a 14-kilometer region of the littoral zone in 1992

versus 1999. The total number of acres was substantially reduced in 1999, although

the plants still occurred in the same elevation contour of the lake.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

113

In addition to the quarterly surveys, the District is now carrying out annual

mapping of the submerged plant community at the end of the summer growing season

(September-October). In this program, which started in 2000, the entire nearshore region

was originally mapped in GIS as a 500 x 500-meter regular grid. Coordinates of all grid

cells are loaded into a field global positioning satellite unit and scientists collect triplicate

samples of submerged plants at every georeferenced site (more than 1,800 sites were

sampled in 2000). Due to the large number of sampling sites, records are taken only of

sediment type, water depth, transparency, and the presence or absence of each plant

species. This study provides output in the form of GIS maps of the attributes evaluated.

Starting in 2001, the spatial resolution was reduced to 1,000 meters by 1,000 meters to

make the program more cost-effective and permit a complete sampling in just one month’s

time. These new maps still provide a very high degree of spatial resolution.

In 2000, it was documented that the lake supported approximately 18,000 ha

(total) of submerged plants (Figure 6), as compared to a FWC estimate of 1,200 ha in

Figure 6. Results of a yearly program (in this case the summer of 2000) that maps the

distribution of submerged aquatic vegetation in Lake Okeechobee. Sampling was

conducted in all grid cells shown on this map, working from the shoreline outward

until at least two contiguous cells were found without plants. The total area of

plants then was determined with GIS.

All Species - Total Area

17,750 Hectares
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1999. The total submerged native plant coverage is one of the priority ecological

performance measures of the CERP and is included as one of the 15 key regional

performance measures in a yearly report card to the United States Congress. The output

from this project will also be used in the calibration and validation of predictive models

that will also draw on information obtained in ongoing cause-and-effect research to

identify submerged plant responses to variations in water depth and sediment type. This

overall program is patterned after a successful project to reestablish the submerged aquatic

vegetation in Chesapeake Bay (USEPA, 1992).

B2. Effects of Water Level on Exotic and Nuisance Plants

The littoral and nearshore zones of Lake Okeechobee also support high densities

of exotic invasive and native nuisance plants. Exotic invasive plants are nonnative species

that tend to outcompete native species and become quickly established, especially in areas

of disturbance or where the normal hydroperiod has been altered. Native nuisance plants

are native plants that spread rapidly under disturbed conditions and displace more

desirable plant communities. In the nearshore zone, the principal exotics are Hydrilla

verticillata (Hydrilla), Eichhornia crassipes (water hyacinth), and Pistia stratiotes (water

lettuce). Hydrilla, a plant that provides valuable fisheries habitat (Furse and Fox, 1994),

once covered nearly 5,000 ha in the lake (Zimba et al., 1995), but today has been nearly

eliminated, perhaps by high water levels in the late 1990s. Its distribution and abundance

will be assessed as part of a submerged aquatic vegetation program described above.

Water hyacinth and lettuce are controlled by contact herbicide application in a program

carried out by the USACE. Effects of water depth on these species have not been

elucidated, although the results of a recent investigation by Grimshaw (2000) indicate that

the plants may become more widely distributed when lake water levels are high. 

In the littoral zone, the principal exotic and nuisance plants of concern are

melaleuca, torpedograss, and cattail. Based on a GIS map constructed in 1996, these

species occupied 1,200, 6,800, and 9,200 ha, respectively. These species occupied only

360, 0, and 7,900 ha, respectively, when a similar mapping effort was carried out in the

early 1970s (Pesnell and Brown, 1977). 

B2a. Melaleuca

In addition to the GIS mapping that has been done to quantify the total area

covered by melaleuca, experimental research has evaluated the potential impacts of water

depth on melaleuca invasion and expansion. Lockhart (1995) quantified the germination

and growth of melaleuca under a variety of water depths inside large replicated outdoor

tanks. She documented that low water levels that expose the soil are necessary for the

initial germination of melaleuca seeds, but once established, young plants can grow

rapidly under either exposed or flooded conditions. Field observations following a drought

and low lake stage (less than 11 feet NGVD in 1989-1990) are consistent with this

conclusion. After large regions of the littoral zone were exposed, small melaleuca saplings

were found over a wide area where they previously did not occur. The plants persisted

after water levels increased.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

115

As a result of an ongoing program to eradicate melaleuca from the lake (described

in greater detail later in this report), nearly the entire 1,200 ha of that exotic plant's

coverage now is characterized as dead. Because large seed sources may remain outside the

lake, some level of maintenance control of melaleuca may need to occur even where the

resident lake population has been eliminated. The magnitude of this effort may largely be

a function of lake stage operations, which will determine the availability of sites for

successful seed germination. During the 2000-2001 drought, with lake stages falling

below 10 feet NGVD and the entire littoral zone exposed, widespread germination of

melaleuca certainly was possible, and is being closely monitored so that appropriate

actions can be taken.

B2b. Torpedograss

Probably the greatest existing threat to the native littoral vegetation in Lake

Okeechobee is torpedograss, which has recently been expanding at a rapid rate and has

displaced important native plant species such as spikerush and Rhynchospora tracyi

(beakrush). As discussed below, District scientists performed research in the late 1990s

that identified a method using fire and herbicide to kill torpedograss in heavily infested

areas. Research also is being done to assess how environmental conditions affect this

plant’s ability to expand into native communities. That work has largely been driven by a

need to provide a solid scientific basis for the District’s proposed minimum flows and

levels (MFL) criterion for the lake and other regional ecosystems.

 The results to date indicate that hydroperiod is a major factor affecting rate of

torpedograss expansion. Observational data indicate that torpedograss occurs primarily

above the 13 feet NGVD elevation contour in the lake, where water depths generally are

shallow and the hydroperiod is below 75 percent (Richardson et al., 1995). During a

period of relatively low water levels in the summer of 1997, District scientists observed

that torpedograss expanded into regions of the littoral zone where it previously did not

occur, and that these regions had their soils exposed during the event. District staff is

conducting a long-term assessment program at three different spatial scales to monitor

further expansion:

• Three one-square kilometer reference plots are being photographed

(1:4,800 scale infrared photographs) annually, and changes in

torpedograss coverage from one year to the next are being quantified

with GIS technology. The reference plots encompass a gradient from

long (over 90 percent) to short (below 75 percent) hydroperiod. 

• The exact locations of several torpedograss fronts and the interfaces of

its expansion into native plant communities are mapped biannually

using GPS.

• The density of torpedograss and spikerush stems are being measured

inside a number of fixed one-square meter reference cells, where both

plants occur. These cells have variable densities ranging from

approximately 50 percent torpedograss and 50 percent spikerush at a

short hydroperiod site to near 100 percent spikerush at a long

hydroperiod site. 
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In a recent evaluation of data from the second method (the torpedograss fronts), it

was documented that forward expansion rate increased coincident with low lake stages in

2000-2001, as compared to earlier years with higher stage. In addition to these field

observations and remote sensing, staff recently has collaborated with scientists from the

USACE Waterways Experiment Station in a set of controlled experiments to establish

cause-and-effect links between water level and torpedograss expansion. The research

examined the ability of torpedograss plant fragments to become established in lake

sediments flooded to various depths. Biologists believe that fragments (sections of roots

and/or stems that break off from a mature plant) are the main vector for expansion in this

plant species. In the experiments, Smart et al. (2000) confirmed that when fragments were

placed into water with a depth greater than 25 centimeters, they could not establish roots

or aboveground biomass. However, when established plants were placed into a similar

gradient of water depths, they were able to maintain a high biomass production even when

flooded to 125 centimeters (Figure 7). These results suggest that standing water might

prevent torpedograss from invading new areas of the littoral zone, but that once the plant

becomes established, it cannot effectively be controlled by lake stage operations. Followup studies, planned for 2001-2003, will evaluate whether water depth affects the ability of

fragments to invade existing stands of native plants (at natural densities), and also will

attempt to confirm the notion that propagation by seeds is not an important vehicle for

invasion by this exotic grass.

B2c. Cattail

Although cattail is a native species in Lake Okeechobee, its expansion is a concern

because it spreads rapidly, displaces other more beneficial native plants, and it provides

poor habitat relative to the species that it replaces (including spikerush and sawgrass). As

a result of the dense growth form of cattail and its accumulated dead thatch material, little

light penetrates the canopy. This results in low oxygen conditions in the water because

microbial activity far exceeds the low rates of primary production by periphytic algae

(Grimshaw et al., 1997). In Lake Okeechobee, high water levels may indirectly cause the

spread of cattail. Expansion has been most pronounced at the pelagic-littoral interface and

along the edges of boat trails leading into the interior littoral zone. These are areas that

likely receive the greatest inputs of phosphorus from the pelagic zone when lake stage is

high. The reduced occurrence of high lake stage events once CERP is completed, and the

reduced concentrations of phosphorus in the lake water due to CERP and Lake

Okeechobee Protection Program activities might result in reduced rates of cattail

expansion. However, this is many years in the future. In the short term, research has

shown (Aumen and Wetzel, 1995) that one effective approach for reducing the rate of

cattail expansion may be prescribed fires. When flooding occurs shortly after a fire, the

recovery of cattail appears to be low. Even if this does not occur, fire can remove large

amounts of dead thatch material and allow for a greater light penetration inside recovering

cattail stands.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

117

Figure 7. Total amounts of biomass accrual during a controlled experiment that exposed

torpedograss to various water depths: a. biomass accrual for plant fragments

attached to the sediment surface, and b. biomass accrual of established plants

subjected to the same range of depth treatments (Smith et al., 2002)

0

50

100

150

200

250

300

350

400

-5 0 15 25 50 75 100 125

Planting Depth (centimeters)

Biomass (grams)

Below ground

Above ground

a. Fragments

0

50

100

150

200

250

300

350

400

Initial -5 0 25 50 75 100 125

Planting Depth (centimeters)

Biomass (grams)

Below ground

Above ground

b. Established
118

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

B3. Wildlife Use of Native and Exotic Plant Communities

Hundreds of species of animals including birds, fish, mammals, amphibians,

reptiles, and invertebrates utilize the plant communities found in Lake Okeechobee's

littoral zone for nesting, foraging, feeding, and shelter (Chick and McIvor, 1994; Aumen

and Wetzel, 1995; Havens et al., 1996b). The rapid expansion of exotic vegetation

throughout many areas of the littoral zone, and the resulting loss of tens of thousands of

hectares of native plant communities has raised concerns that the habitat quality of the

ecosystem has been degraded. However, the quantitative data supporting this view is

limited. In order to protect and enhance valuable wildlife habitat, a thorough evaluation of

wildlife species diversity and habitat use of both exotic and native plant communities

should be conducted. A longer-term assessment of the distribution and abundance of key

animal species, as described in the Ecological Impacts of Exotic Species section, is also

needed. In the five-year Lake Okeechobee Ecosystem Study (1988-1992), wading bird use

of distinct vegetation types was considered by University of Florida scientists, and it was

documented that certain native vegetation (e.g., willow) offers optimal nesting or foraging

habitat (Smith and Callopy, 1995; Smith et al., 1995a). In another study, scientists at the

Florida Game and Fresh Water Fish Commission (now called the Florida Fish and

Wildlife Conservation Commission) documented that peppergrass, eelgrass, and bulrush

provide good habitat for sport fish (Furse and Fox, 1994). A particularly high biomass of

fish occurred in hydrilla, a submerged aquatic exotic.

The USACE recently completed a survey of reptiles and birds in spikerush,

torpedograss, and cattail habitats of the lake. However, due to problems with sampling

during high water periods, the short-term nature of the study (two years), and the location

of survey quadrants in sites that were not characteristic of the larger habitats, the results

are inconclusive (USACE, 1999a). A more comprehensive study is needed in order to

quantitatively assess the habitat value of native and exotic plant communities and make

predictions about how hydroperiod-related changes in plant community structure will

affect important populations of animals in the ecosystem.

B4. Links between Water Levels and Nutrient Transport

It is difficult to separate out the effects of water levels from those caused by

excessive nutrients in Lake Okeechobee, because the two factors are strongly interrelated.

Therefore, some mention of nutrients is appropriate under this section of the plan,

although the issue is described in Chapter 3. High water levels have been shown to result

in greater amounts of phosphorus in the water column, especially the ecologically

important nearshore zone. This issue is described in the Lake Okeechobee Action Plan

(Harvey and Havens, 1999) and documented in peer reviewed literature (Canfield and

Hoyer, 1988; Havens, 1997). The possible mechanisms also have been described. These

mechanisms include 1) higher water levels allow for greater transport of phosphorus-rich

sediment material from midlake to the nearshore zone (Maceina, 1993); and 2) higher

water levels favor dominance of phytoplankton over plants and this allows more of the

phosphorus to remain in the water column (Phlips et al., 1993a). As a result of these

processes, it also has been observed that when water levels remain relatively low (14 to 15
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

119

feet NGVD annual average) the lake has distinct ecological zones (Phlips et al., 1993b).

This includes a relatively nutrient-poor nearshore region where light penetration in the

water column is high and where nutrients limit the growth of phytoplankton; and a

nutrient-rich, turbid, central region where light is most often the limiting factor. When

water levels are higher (as in recent years), conditions are more homogeneous, with high

concentrations of nutrients in both the nearshore and midlake regions and high lakewide

turbidity. 

At very high water levels (greater than 17 feet NGVD) phosphorus-rich pelagic

water is transported into the interior littoral zone, where it may bring about changes in the

abundance and composition of periphyton and perhaps stimulate the spread of cattail. The

impacts on periphyton have been considered with controlled mesocosm experiments

(Havens et al., 1997) and are being further evaluated in a long-term research project on

periphyton status along a natural elevation gradient in the littoral zone. In addition, an

existing model of lake water circulation and transport is being modified to include a water

quality component. Once this is done, the model can be used to predict how different lake

operation schedules might affect phosphorus and other chemical transport into the littoral

zone. When coupled with results from scientific investigations of the littoral food web it

will be possible to make predictions of impacts at higher trophic levels.

C. ECOLOGICAL IMPACTS OF NUTRIENTS

The biological communities of Lake Okeechobee have been dramatically impacted

by excessive inputs of phosphorus and nitrogen (Havens et al., 1996a). The composition

of benthic macro invertebrates has shifted toward pollution-tolerant species (Warren et al.,

1995). The biomass of cyanobacteria (blue-green algae) has increased relative to diatoms

and other algal groups (Cichra et al., 1995), and algal blooms have become more frequent

(Havens et al., 1995a). The blooms are linked with high phosphorus concentrations,

especially in the nearshore region (Walker and Havens, 1995; Havens and Walker, 2001).

Because of the long history of excessive nutrient inputs, the lake's mud sediments also

have accumulated large quantities of phosphorus (greater than 30,000 metric tons in the

upper 10 centimeters) and sediment-to-water fluxes of phosphorus exceed the external

inputs on an annual basis (Olila and Reddy, 1993). Because dissolved phosphorus

concentrations often exceed the requirements of the algae, their growth rates generally are

limited by other factors, in particular light and nitrogen (Aldridge et al., 1995; Phlips et al.,

1997). The high frequency of nitrogen limitation has favored dominance by

cyanobacteria, including species that form surface blooms (Smith et al., 1995a; Havens et

al., 1998).

As a result of these harmful impacts, considerable efforts have been made to

reduce the external phosphorus loading to Lake Okeechobee (Steinman et al., 1998) and

lake managers continue to explore new approaches for further reducing the loads, both

external and internal to the lake ecosystem. Because the management actions can have

dramatic economic and ecological effects (Havens et al., 1996a), it is critical that they

have a solid foundation in science and engineering. In regard to ecological responses,

good information now exists regarding certain ecosystem properties, such as phosphorus
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

geochemistry in the pelagic region (Reddy et al., 1995; Moore et al., 1998), but other

potentially important aspects of phosphorus dynamics are not fully understood. In the

following section, the focus is on the potential role that plants and animals may play in the

lake's phosphorus dynamics. Other aspects are considered in Chapter 3 of this plan.

C1. Biological Processes Affecting Phosphorus Dynamics

The recently completed Lake Okeechobee Phosphorus Dynamics Study (Reddy et

al., 1995) and other research projects conducted on this and other shallow eutrophic lakes,

show evidence that biological interactions play an important role in the internal cycling of

phosphorus. Important biological interactions may include, but are not limited to, the

following: 1) competition for dissolved phosphorus among phytoplankton, periphyton,

and vascular plants in the nearshore zone; 2) suppression of wind-driven sediment

resuspension by benthic plant assemblages in that same lake region; 3) bioturbation of

pelagic mud sediments by macro invertebrates and fish; 4) uptake and sedimentation of

phosphorus in the plankton; and 5) vertical migration of bloom-forming cyanobacteria.

The extent to which these processes occur may affect the lake's capacity to assimilate

phosphorus (i.e., remove it from the water column into sediment storage). As such, the

biological processes are directly related to the establishment of appropriate phosphorus

loading targets such as the TMDL. Because the FDEP has proposed that the lake’s

phosphorus TMDL be “revisited” at five-year intervals and possibly modified as more

information becomes available about the ecosystem, understanding the role of biota in the

phosphorus cycle is critical. Havens and Schelske (2001), for example, note that some of

the changes that are expected to occur in a recovering lake (reduced cyanobacteria

dominance, increased submerged plants, changes in benthic macro invertebrate species)

might increase the lake’s phosphorus assimilation, and allow for attainment of the in-lake

phosphorus goal of 40 μg/l at a higher rate of external loading than presently is

anticipated. Walker and Havens (2001) also note that a better understanding of how

particular concentrations of phosphorus affect plant and animal communities is needed so

that the in-lake phosphorus goal can have a more holistic foundation, rather than being set

only on the basis of algal blooms, as presently is the case.

C1a. Competition for Phosphorus

Both observational (Scheffer et al., 1994) and experimental (Confer, 1972;

Hansson, 1990) studies have revealed competitive interactions between phytoplankton

and benthic producers in shallow lakes. Most of the published research deals with

temperate lakes, but recent studies indicate that similar interactions occur in the nearshore

zone of subtropical Lake Okeechobee. Phlips et al. (1993a) was the first to suggest that

this was the case, when they documented that a midsummer low in phytoplankton biomass

corresponded with maximal biomass of epiphtyon and submerged plants. Havens et al.

(1996c) performed in situ nutrient-addition studies in the nearshore zone and found that

the phytoplankton and periphyton were limited by the same nutrients (most often nitrogen

and phosphorus colimitation), confirming the potential for nutrient competition. Most

recently, Hwang et al. (1998) documented that conditions in the nearshore zone could

favor phosphate uptake by either phytoplankton (during deep water periods with poor
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

121

transparency) or periphyton (during shallow periods with high transparency). Data

collected during the recent lake recession operation, wherein the lake stage dropped to

near 12 feet NGVD in the summer of 2000, are supportive of the role that plants can play

in controlling water column phosphorus. Prior to the recession operation, when lake stage

was near 15 feet NGVD, nearshore waters were turbid, devoid of plants, and had total

phosphorus in excess of 100 μg/l. Within weeks of attaining the low stage level in the

spring of 2000, nearshore areas developed clear water, vast lawns of submerged plants

(primarily Chara spp.), and total phosphorus concentrations below 30 μg/l.

Nutrient dynamics in the central pelagic region are less complex, because the

greater water depth and reduced light penetration are not suitable for benthic plant and

periphyton communities. In the littoral zone, the greatest quantities of phosphorus occur in

the periphyton community, because high transparencies occur regardless of lake stage

(Havens et al., 2000). This periphyton has a tremendous capacity to remove phosphorus

from the water column, as documented in controlled mesocosm studies by Havens et al.

(1997). After adding 800 μg/l of soluble phosphorus to enclosures over a period of 28

days, water column phosphorus concentrations remained below 30 μg/l. At the same time,

concentrations of phosphorus in periphyton tissues increased significantly (Figure 8).

These results do not mean that phosphorus inputs cannot have negative effects on the

indigenous community. In the same study, the authors observed dramatic changes in the

taxonomic composition of periphyton after weeks of high nutrient loading. Similar to what

has been observed in the Florida Everglades (McCormick et al., 1996), the periphyton

shifted toward dominance by large filamentous green algae that are not a good food

resource for invertebrate grazers. 

Havens et al. (1997) noted that the littoral periphyton in Lake Okeechobee was

colimited by nitrogen and phosphorus, rather than by phosphorus alone as it is in the

pristine central Everglades. They hypothesized that the littoral periphyton community has

been impacted by phosphorus inputs to that region that occur during periods of high water

level. Ongoing research is being done to confirm the validity of this hypothesis. This

includes a multiyear study of periphyton taxonomic structure and nutrient limitation along

transects where water moves into the littoral zone. During periods of high stage we expect

to see a shift towards taxa more indicative of eutrophic conditions, especially at sites

closest to the open water zone. When combined with results of controlled mesocosm

studies, this information can be used to calibrate models to predict how the littoral

community will benefit from reduced phosphorus transport associated with new CERP

lake stage operations and lowered external phosphorus loads. 

C1b. Sediment Stabilization

The large reservoir of phosphorus stored in the sediments of Lake Okeechobee can

serve as a net source of phosphorus to the water column via resuspension and diffusion

(Olila and Reddy, 1993). However, in nearshore areas, benthic plants can reduce this

resuspension because their roots physically bind sediments and their morphology presents

a physical barrier to shearing stress on the sediment surface. Plants also can change the pH

and dissolved oxygen status of surrounding water and this can affect diffusive phosphorus

transport. If sediment stabilization ever does come into play, it most likely would be
122

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT a. Water Column Phosphorus

0

800600400200

0 100 200 300 400 500 600 700 800

Phosphorus Added (

μg/l)

g/l) μ Phosphorus Measured (

b. Surface Mat Phosphorus

0

800600400200

0 100 200 300 400 500 600 700 800

Phosphorus Added (

μg/l)

Phosphorus Measured (mg/kg)

c. Epiphyton Phosphorus

0

500

200015001000

0 200 400 600 800

Phosphorus Added (

μg/l)

Phosphorus Measured (mg/kg)

d. Metaphyton Phosphorus

0

800600400200

0 200 400 600 800

Phosphorus Added (

μg/l) 

Phosphorus Measured (mg/l) 

Figure 8. Total phosphorus concentrations measured during a controlled mesocosm experiment

in the littoral zone after adding various amounts of phosphorus over a 28-day period :

a. water column concentrations, b. surface algal mat concentrations, c. epiphyton

concentrations, and d. metaphyton concentrations (Havens et al., 1997)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

123

during years with very low water levels, when submerged plants can extend for several

kilometers offshore (Zimba et al., 1995). In the late 1990s, following several years of high

water level, submerged plants were restricted to areas just adjacent to the littoral zone and

their role in affecting sediment-water phosphorus exchanges probably was minimal.

However, as indicated above, submerged plants increased dramatically in the summer of

2000 when lake stage was lowered, and were concomitant decreases in phosphorus and

suspended materials were recorded in the water column of the nearshore region. In the

longer term, a considerably lower water level regime is anticipated under the CERP.

Research and modeling are needed to predict the impacts of more widespread plant

growth on water column total phosphorus, because the effects noted above might

determine, in part, a more appropriate long-term phosphorus TMDL than has recently

been proposed.

C1c. Sedimentation of Phosphorus in Plankton

One of the main loss processes for phosphorus from the water column of lakes is

settling of phytoplankton cells, zooplankton, and zooplankton fecal pellets. The Lake

Okeechobee Water Quality Model estimates sedimentation rate based on

paleolimnological data from lake sediment cores (Brezonik and Engstrom, 1998). Given

that it represents an important loss process in that model, more direct measurements of

these rates and how they vary with environmental conditions (e.g., wind, current) are

needed. Furthermore, it is important to determine how the net settling rate is affected by

the taxonomic composition of the plankton. Present sedimentation rates may be low as a

result of dominance by small species of cyanobacteria, but the rates could increase

substantially if diatoms become dominant (Havens and Schelske, 2001), as they did in the

mid-1970s (Marshall et al., 1977). Anticipated benefits of meeting the TMDL include

reduced in-lake total phosphorus concentrations, an increased frequency of phosphorus

limitation, and a decline in cyanobacteria relative to diatoms. The increased settling rate of

diatoms relative to cyanobacteria could result in a greater net assimilative capacity of the

lake for phosphorus. Furthermore, under phosphorus deficient conditions, a greater

portion of the water column total phosphorus is expected to occur in algal cells (as

opposed to the soluble phase) and this could further contribute to sedimentation (Havens

and Schelske, 2001). The extent to which algal cells are grazed by zooplankton and

subsequently repackaged into larger, more readily settled, particles also may change.

These processes may have a direct bearing on the lake TMDL, and as such, need to be

supported by quantitative scientific information.

C1d. Bioturbation

The burrowing and feeding activities of benthic invertebrates and fish can recycle

nutrients from lake sediments to the overlying water column, and in shallow eutrophic

lakes these fluxes can account for a large fraction in the lake's internal phosphorus load

(Schaus et al., 1997). In Lake Okeechobee, sediments of the central pelagic zone contain

high densities of oligochaete worms, and Van Rees et al. (1996) reported that their

activities resulted in sediment to water phosphorus fluxes that were two to 15 times

greater than in sediments without the animals. Research still is needed to determine how

these phosphorus flux rates compare to those occurring when the lake's invertebrate
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

community is dominated by chironomids and other taxa less indicative of polluted

conditions. We also have no information about the role of fish bioturbation in this lake.

Because the fish assemblage contains a high density of gizzard shad (Dorosoma

cepedianum), which is known to recycle large quantities of sediment phosphorus in other

shallow lakes (Vanni, 1996), this process merits evaluation. The information is

particularly important in the context of setting a TMDL for phosphorus because, under

conditions of reduced external loading, changes in both the benthic invertebrate and

fisheries communities may occur. Reductions in the relative biomass of oligochaetes and

gizzard shad could be expected to contribute to reduced internal loading and increased net

phosphorus assimilative capacity (Havens and Schelske, 2001).

C1e. Cyanobacteria Vertical Migration and Nutrient Utilization

Vertical migration of cyanobacteria from the lake sediments to near the surface of

the water column may be a another important pathway for phosphorus transport in Lake

Okeechobee, as it is in other shallow lakes (Takamura et al., 1992). Based on multivariate

statistical analysis of phytoplankton and water quality data collected in the Lake

Okeechobee Ecosystem Study, Havens et al. (1998) developed a conceptual model of algal

bloom dynamics for the lake (Figure 9). Blooms are triggered during prolonged calm

periods when two events may occur: 1) an anoxic (greatly deficient in oxygen) or hypoxic

(deficiency of oxygen reaching animal plant tissues) layer develops at the sediment-water

interface, allowing soluble phosphorus to enter the water column where it can be taken up

(a) Turbid Conditions (b) Calm Conditions

Wind mixing and

no sustained vertical

heterogeneity of

algal biomass

Light Light

Lyngbya,

Oscillatoria,

other nonnitrogen-fixers

adapted to

low irradiance

Carbon 

Dioxide

(CO2)

Phosphate

Dissolved

Inorganic

Nitrogen

Cynobacteria

Cynobacteria

BLOOM

Anabaena,

Microcystis,

other nitrogen-fixers

that require

high irradiance

Stable water

column,

vertical migration,

sustained

surface biomass

maximum

Phosphate

Nirogen

(as N2)

Carbon 

Dioxide

(CO2)

Dissolved

Inorganic

Nitrogen

Figure 9. A Conceptual model of algal bloom dynamics in shallow eutrophic lakes (Havens

et al., 1998)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

125

by cyanobacteria colonies; and 2) bloom-forming cyanobacterial species (e.g., Anabaena

and Microcystis) that require high light levels for optimal growth migrate to the water

surface, forming the visible surface blooms that have been such a major concern in this

shallow lake. Because the cyanobacteria can obtain nitrogen and carbon from atmospheric

sources, they are essentially unlimited in their growth during such calm periods. This

model still needs to be validated by results from controlled experiments. In particular, the

rates of upward phosphorus transport should be quantified and the vertical migration

process incorporated into lake water quality models.

Under most circumstances, the phytoplankton in Lake Okeechobee is more limited

by nitrogen than phosphorus (Aldridge et al., 1995), and, therefore, an understanding of

nitrogen cycling also is necessary for accurate predictions of lake responses to changes in

external nutrient loading. At this time we know very little about nitrogen dynamics in

subtropical lakes. Only two processes, planktonic nitrogen fixation (Phlips and Ihnat,

1995) and denitrification (Messer et al., 1979), have been directly measured in Lake

Okeechobee, the latter being studied over 15 years ago, when nutrient concentrations were

much lower than at present. No studies have been conducted to measure rates of

nitrification or mineralization, yet these processes are included in the water quality model

that is used to predict algal responses to external load reductions (James et al., 1997). The

water quality model uses parameter values taken from the published literature on

temperate lakes, and these rates may not be applicable for subtropical Lake Okeechobee.

A pilot study in the summer of 1996 (Gu et al., 1997) provided some information

concerning planktonic algal uptake rates for nitrate, nitrite, ammonia, urea, and N2 (the

various dissolved forms of this nutrient), but additional studies of a broader scale are

needed to fill this information gap.

C2. Development and Application of Predictive Models

The use of models for predicting lake responses to management actions is

described in detail in Chapter 3 of this plan. Here, the focus is on incorporating additional

aspects of the lake biology into the models and on extrapolating model predictions to

higher trophic levels. The lake water quality model presently in use is based on the

USEPA Water Quality Analysis Simulation Package (WASP). However, the Lake

Okeechobee Water Quality Model has been modified to 1) make predictions regarding the

biomass of three algal groups, diatoms, chlorophytes, and cyanobacteria; 2) include the

silica cycle; 3) consider five ecologically distinct regions of the lake; and 4) allow linkage

with a three-dimensional hydrodynamic model and a sediment transport model (James et

al., 1997). Sensitivity analysis indicates that model refinement should include better (lakespecific) information about algal settling rates, as noted above. Furthermore, the model

appears to be lacking some of the processes that vary with lake stage and drive the

observed linkage between water levels and phosphorus assimilation. Preliminary work

with a relatively simple phosphorus model (based on the Stella modeling platform)

suggests that by including submerged aquatic vegetation related processes in the model,

long-term predictions of lake response to CERP could be substantially improved. This will

be one focus of model refinement during the next three years. The work will largely

depend on the results of observational and experimental submerged plant research being
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

done by District scientists. To effectively use a model that includes a vegetation

component, however, it will be necessary to modify the Lake Okeechobee Hydrodynamic

Model to include water quality and light attenuation components, and then link this

model’s output with the Stella model of submerged vegetation. This linked model could

produce maps showing submerged vegetation distribution under different lake stage or

nutrient loading scenarios, and as such, become a valuable tool for managers. The model

also could address effects of water and nutrient input to the littoral zone, by making use of

results from controlled experiments to identify how the littoral landscape (plants and

animals) responds to different depth and nutrient input conditions. This is a long-term goal

beyond the three-year horizon of this SWIM planning document, but model development

and experimental data collection in the next three years can provide much of the

information needed to achieve that goal.

C3. Nutrients and the Lake Food Web

It has been recognized for some time that the lake's commercial fishery has great

economic value, perhaps in excess of $300 million (Furse and Fox, 1994). The lake also

plays a critical role as a habitat for migratory waterfowl, wading birds, alligators,

federally-endangered Everglades snail kites, and numerous other amphibians, reptiles, and

mammals (Smith et al., 1995a; Bennetts and Kitchens, 1997; USACE, 1999a). Despite

this fact, our understanding of the lake food web is quite rudimentary, having been

investigated only in a preliminary manner based on gut analyses of selected taxa and

published feeding relationships from other lakes (Havens et al., 1996b). More recently, the

fisheries food web was studied at one littoral site, two nearshore sites, and two pelagic

sites using stable nitrogen and carbon isotope analysis (Fry et al., 1999). Based on this

study, it was documented that certain fish species migrate between the littoral and pelagic

zones, and that stable isotope analysis is an effective tool for exploring food web structure

at a finer spatial and temporal scale than is possible with gut analysis. Additional food web

data, regarding the linkages between animals and plant habitat and water depth, and

results of other experimental studies will be needed to make accurate predictions of fish,

bird, and other animal responses to changes in water depth and nutrient loading associated

with CERP and TMDL compliance. 

D. ECOLOGICAL IMPACTS OF EXOTIC SPECIES

At least 14 species of exotic plants and a number of exotic animals are found in the

littoral and nearshore zones of Lake Okeechobee. Five of the exotic plants are considered

a threat to the ecosystem due to their rapid expansion into areas once occupied by native

plants. Melaleuca and torpedograss occur in higher elevation regions of the littoral zone.

Water hyacinth, water lettuce, and hydrilla occur in the nearshore areas where there

normally is year-round standing water. The District, the FDEP, and the USACE have

active programs to control all of these plants except hydrilla. The most recently activated

program is the one targeting torpedograss. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

127

D1. Exotic Plant Assessment and Control 

As noted previously in the Ecological Impacts of Water Level Variation section

on page 107, a number of different approaches are being used to monitor and assess yearto-year changes in exotic plant distribution and programs have been established for exotic

control. The primary focus has been on melaleuca and torpedograss because of their rapid

invasion of large regions of the littoral zone. 

Prior to melaleuca treatment, Lake Okeechobee had two main areas of infestation

by that exotic tree. The first area encompassed the original plantings along the Herbert

Hoover Dike and rim canal tree islands. Large, mature, extremely dense monocultures of

melaleuca covered nearly 1,200 ha at those sites. The second main area of infestation

included the shallow marsh region of the lake where trees spread towards the lake from

the original plantings. Melaleuca infestations in the marsh typically consisted of outlier

trees and heads of varying ages scattered over an area of approximately 10,000 ha. As a

result of aggressive management program using herbicide and biological agents the

coverage of live melaleuca has been dramatically reduced in the lake.

Torpedograss has invaded over 6,000 ha of the littoral zone and it is continuing to

invade new areas adding further stress to the ecosystem. The plant occurs primarily in the

northwestern region of the lake and around the perimeter of Moonshine Bay, just to the

south of Fisheating Bay (Figure 5). As described in detail above, a number of studies are

ongoing to evaluate rates of torpedograss expansion in different regions of the littoral

zone, and preliminary studies have been done to characterize how torpedograss degrades

the quality of wildlife habitat. Additional research is needed in this area. As indicated

above, however, a primary focus of research in the near future will be on identification of

more effective and selective control methods.

Starting in 2000, the District and FDEP began a large-scale, multiyear program to

eradicate torpedograss from the lake’s littoral zone. The method being used at this time is

a combination of controlled fire to burn away the accumulated biomass, followed by

application of the contact herbicide Arsenal® to the subsequent torpedograss regrowth.

This method was shown to provide long-term control of torpedograss in field-scale

experiments carried out by District and University of Florida scientists. However, the

nonselective nature of Arsenal® and the fact that similar applications sometimes had very

different long-term effects raised concern about a need for additional herbicide screening.

A high priority in 2000-2002 will be to identify herbicides that can provide consistent

long-term torpedograss control, while at the same time allowing native plant species to

recolonize treated areas. Research also is needed to determine what environmental

conditions (e.g., wet versus dry, presence versus absence of periphyton algae) allow for

the most effective long-term control. The District also proposes to carry out preliminary

(literature-based) evaluations of whether potential biocontrol agents exist for

torpedograss. If this yields positive results, then a recommendation could be made for

more intensive investigation using the state’s new Invasive Exotic Aquatic Plant

Quarantine facility. This line of research was identified as a high priority in the Lake

Okeechobee Action Plan (Harvey and Havens, 1999).
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

D2. Identification of Exotic Animals and Their Ecological Impacts

Although a number of exotic animals are known to occur in the lake, their

distribution, abundance, and ecological impacts have been little studied. This does not

necessarily mean that those impacts are small. For example, scientists at the FWC have

suggested that blue tilapia (Tilapia aurea) may displace bluegill (Lepomis macrochirus), a

commercially important fish in the lake, because the two species have similar diet habits

and nesting preferences. Also, the Asiatic clam corbicula (Corbicula fluminea) has a high

particle filtering rate and the potential to significantly reduce the biomass of

phytoplankton (Cohen et al., 1984). Large micro crustaceans such as Daphnia lumholtzii,

which invaded the lake in the early to mid-1990s (Havens and East, 1997; East et al.,

1999), might significantly alter energy transfer from algae to fish in the lake's food web. A

complete census of exotic animals in the lake and evaluations of both their rates of

population change over time and their impacts on native species are needed.

E. LONG-TERM ECOLOGICAL ASSESSMENT

As a part of the CERP, the District, the USACE, and other cooperating agencies

are developing plans for long-term assessment of ecological responses to the regional

restoration project. The first objective of this effort is to quantify benefits in terms of a set

of ecological performance measures (e.g., a reduction in algal bloom frequency or a

decrease in the total number of acres of cattail). The second objective is to provide

feedback that might lead to changes in CERP project construction and/or operations. The

latter would occur if unexpected and undesired changes were occurring in the ecosystem

as the project moved forward. This is the concept of adaptive assessment. The Lake

Okeechobee Protection Act (Section 373.4595, F.S.) also mandates that long-term

monitoring be done to assess responses of the lake ecosystem to management actions.

Prior to these regional programs and legislative mandates, the District had

implemented long-term monitoring of a number of ecological attributes considered to be

important indicators of ecosystem stress from nutrients, water levels, and exotic species

expansion. At this time the District's program on Lake Okeechobee includes the following

elements:

• Littoral vegetation mapping carried out at various scales of spatial and

temporal resolution to determine historical changes in the distribution

and abundance of native and exotic plants

• Quarterly sampling of submerged plants at 42 locations in the lake's

nearshore zone

• Yearly mapping of submerged plants to determine total aerial extent at

the end of each summer growing season

• Quarterly sampling of attached algae at several nearshore (south, west,

and north) and littoral zone locations (along a depth gradient)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

129

• Monthly sampling of plankton abundance, taxonomic composition,

primary productivity, and nutrient limitation at five locations

corresponding to distinct ecological zones in the open lake

• Quarterly sampling of macro invertebrates associated with bulrush

communities in the nearshore region

In addition to the District's programs on the lake, the FWC carries out surveys of

benthic invertebrate communities, larval fish, and adult sport fish populations on a

periodic basis.

At any given time the information obtained from the Ecological Assessment

Program will allow us to evaluate changes in the lake, and contrast these with past

management efforts or societal and natural disturbances in the watershed. The existing

Ecological Assessment Program will be integrated with the larger CERP adaptive

assessment process, which is based on an ecological conceptual model developed by

experts from various state and federal agencies. The lake model (Figure 10) is presented

in a format that is consistent with models of other South Florida ecosystem regions. It

indicates seven major stressors (ovals) that impact the four identified values (pentagons)

of the system by way of a number of pathways (diamonds and arrows). The Lake

Okeechobee Ecosystem Conceptual Model (Havens, 2000) is largely based on the results

of scientific research conducted on the lake in the last decade and summarized in this and

previous SWIM plans (SFWMD, 1989a, 1993, 1997a). Research and modeling needs

identified in the present plan update are consistent with areas of uncertainty in the

conceptual model. The model also is directly linked with quantitative performance

measures (Table 4-1) that are used to judge program success. Annual reports of key

performance measures will be submitted by the CERP program to the State of Florida and

the federal government. The information obtained in the program also will be used in a

report to the Florida Legislature mandated by the Lake Okeechobee Protection Act

(373.4595, F.S.). 

E1. Ecological Assessment Database

The information obtained in the long-term ecological monitoring program, as well

as in other research efforts on the lake, must be maintained in a standardized

georeferenced format that is readily accessible to scientists and managers. In recent years,

a database has been developed to store information collected in the Lake Okeechobee

Ecosystem Study. The database contains a first-generation user interface that now is under

development. Work also is under way to link the tabular data with spatial data that reside

in Arc Info coverages. Also, the data libraries need to be integrated with the District's

research web site so users outside the agency can readily access both raw data and

summary information. 
130

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT More resuspended sediments Extremes in high lake stage Extremes in low lake stage Exotic & nuisance plants Exotic animals Elevated levels of phosphorus (P) Elevated levels of nitrogen & Class I / III chemicals Waste water discharged from agricultural, urban, and residential areas; C&SF Project Increased mud sediments due to nutrient inputs, wind waves, and operation of the C&SF Project Rainfall, evapotranspiration, water supply deliveries out of the lake, operation of the C&SF Project Accidental and purposeful introductions of exotic species More blue-green blooms Greater turbidity, less light Greater wave energy & flooding of marsh More by-products of algal decay Greater BOD, anoxia, Increased P release deposition of organics Reduced growth of SAV More sediment & P in nearshore & Greater littoral horizontal mixing Dense growth low dissolved oxygen Loss of habitat for birds & alligators Formation of nearshore “berm” Impacts on benthic inverts. More frequent fires Lake water quality Fish & aquatic fauna Snail kite wading birds & alligators Native vegetation mosaic Control programs with herbicide, fire, and biological agents Water Quality Performance Measures Fish / Fauna Performance Measures Vegetation Performance Measures Megafauna Performance Measures Benefits SAV, bulrush, other plants Reduced sediment stability More upward P transport Reduced P uptake from water Reduced net P loss to sediment Loss of forage base (small fish, inverts) Damage to nearshore emergent plants Displace beneficial native plants Lost habitat for fish & aquatic biota Benefits to native emergent plants Possible effects on fish migration

Figure 10. An ecosystem conceptual model for Lake Okeechobee, developed for the adaptive

assessment process of the CERP. The model shows linkages between sources

(rectangles), stressors (ellipses), ecological processes (diamonds), attributes

(pentagons), and performance measures (parallelograms). Note: SAV = submerged

aquatic vegetation and BOD = biochemical oxygen demand
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

131

F. LAKE OKEECHOBEE’S ROLE IN THE REGIONAL 

ECOSYSTEM

F1. Protection and Management of Rare, Threatened, and 

Endangered Species

The South Florida Multispecies Recovery Plan (USFWS, 1999) was developed to

facilitate implementation of an ecosystem approach to fish and wildlife conservation. The

multifaceted intent of the plan was to assist governmental entities, Indian tribes, nonprofit

organizations, and others to protect threatened and endangered species through the

acquisition of lands for habitat conservation planning, public outreach, and information

exchange among South Florida working groups. 

The South Florida Multispecies Recovery Plan was prepared to fulfill two

initiatives of the South Florida Ecosystem Restoration Plan: 1) restore and maintain the

biodiversity of native plants and animals in the upland, wetland, estuarine, and marine

communities; and 2) recover threatened and endangered species. These initiatives will be

completed in conjunction with the remaining South Florida ecosystem restoration

objectives that comprise the major components of CERP. All the projects associated with

Table 4-1. List of the ecological performance measures associated with the Lake Okeechobee 

Conceptual Ecosystem Model, arranged according to the four major attributesa

Lake Water Quality

• Total phosphorus concentration

• Total nitrogen:phosphorus ratio

• Algal bloom frequency

• Diatom:cyanobacteria biomass ratio

• Nitrogen versus phosphorus limitation

• Water clarity as Secchi depth

• External phosphorus loading rate

• Net lake phosphorus assimilation

• Sediment deposition rate

Fish and Aquatic Fauna

• Population density and age structure of selected taxa that represent major trophic guilds (piscivores, planktivores, 

omnivores, and benthivores)

• Abundance of selected pollution-tolerant and “desired” taxa in pelagic and littoral zones

Native Vegetation Mosaic

• Spatial extent of exotic plants in the littoral zone

• Diverse landscape of native plants in the littoral zone

• Continuous stands of willow and/or pond apple

• Spatial extent of continuous bulrush stands

• Spatial extent of submerged vascular plants

• Spatial extent of shoreline organic berm

Snail Kite, Wading Birds, and Waterfowl

• Number of Snail Kite nests within the lake proper

• Frequency of large feeding colonies of wading birds in the lake during winter/ spring

• Number of nests of great egret, white ibis, snowy egret, and heron

• Frequency of large feeding colonies of water fowl in the lake during winter/spring

a. Source: Havens, 2000
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Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

the restoration of South Florida will have substantial effects on fish and wildlife resources

in South Florida (USFWS, 1999). The success or failure of many of the projects could

determine the status of other species accordingly. 

Over 600 species in the South Florida region are considered rare or imperiled

(USFWS, 1999) and 72 species are either federally-listed or protected from take (Table 4-

2). These species include 8 mammals, 13 birds, 10 reptiles, 2 invertebrates, and 35 plants.

Most of these species are listed as threatened or endangered by the federal government.

The mountain lion, peregrine falcon, and American alligator are not biologically

threatened or endangered, but are afforded protection from “take” because they are

physically similar in appearance to listed species (USFWS, 1999). Also included in the

list, but not federally-listed, are the whooping crane, which is considered an experimental

population, and Johnson’s sea grass, which is under the jurisdiction of the National Marine

Fisheries Service. 

The South Florida Multispecies Recovery Plan set the following criteria for the

classification of species, all of which are based on stochastic modeling:

• Recovered - The species has a 95 percent probability (+/- 0.05 percent)

of persisting for at least 100 years and it is assumed threats to the

species have been eliminated or ameliorated and the species has met all

other recovery criteria.

• Threatened - The species has a 20 to 90 percent probability of

persisting for 100 years, regardless of other criteria.

• Endangered - The species has less than a 20 percent probability of

persisting for 100 years, regardless of other criteria. This classification

assumes a critical situation.

Recovery objectives for all 68 species, as well as the restoration of 23 habitats, are

included in the plan, as well as specific habitat requirements. Loss of habitat through land

use conversions, wetland drainage, hydrology alterations, and water quality degradation

are often limiting factors for many species. At least 17 of the 68 species included in the

recovery plan are dependant upon implementation of the CERP components for survival

and recovery, and possibly many others will also benefit significantly as a result.

F2. Kissimmee River Restoration

An important component of the lake’s regional ecosystem is the Kissimmee River

drainage basin. The Kissimmee River drainage basin accounts for approximately 31

percent of surface water inflows to the lake (Aumen, 1995), and can have a significant

impact on the lake ecosystem. Prior to channelization in the 1960s, the Kissimmee River

meandered 166 kilometers (km) through a complex of 18,000 ha of floodplain wetlands.

The river-floodplain ecosystem supported diverse and productive fish and wildlife

communities regulated by basin hydrology and channel geomorphology (Toth et al.,

1995). Channelization of the river for flood control severely impacted the biological

resources of the basin and diminished the ecological integrity of the ecosystem (Koebel,

1995).
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

133

Table 4-2. The federally-listed endangered and threatened species of South Florida

Common Name Scientific Name Statusb

Mammals

Florida panther Puma concolor coryi E

Mountain lion Puma concolor T (S/A)

Key deer Odocoileus virginianus clavium E

Key Largo cotton mouse Peromyscus gossypinus allapaticola E

Key Largo woodrat Neotomafloridana smalli E

Lower Keys rabbit Sylvilagus palustris hefneri E

Rice rat (silver rice rat) Oryzomys palustris natator (0. argentatus) E (CH)

Southeastern beach mouse Peromyscus polionotus niveiventris T

West Indian manatee Trichechus manatus E (CH)

BIRDS

Audubon's crested caracara Polyborus plancus audubonii T

Bachman's warbler Vermivora bachmanii E

Bald eagle Haliaeetus leucocephalus T

Cape Sable seaside sparrow Ammodramus (Ammospiza) maritimus mirabilis E (CH)

Everglade snail kite Rostrhamus sociabilis plumbeus E (CH)

Florida grasshopper sparrow Ammodramus savannarum floridanus E

Florida scrub jay Aphelocoma coerulescens T

Ivory-billed woodpecker Campephilus principalis E

Kirtland's warbler Dendroica kirtlandii E

Peregrine falcon Falco peregrinus E (S/A)

Piping plover Charadrius melodus T

Red-cockaded woodpecker Picoides (Dendrocopos) borealis E

Roseate tem Stema dougallii dougallii T

Whooping crane Grus americans XN

Wood stork Mycteria americans E

Reptiles

American crocodile Crocodylus acutus E (CH)

American alligator Alligator mississippiensis T (S/A)

Atlantic salt marsh snake Nerodia clarkii (lasciata) taeniata T

Bluetail (blue-tailed) mole skink Eumeces egregius lividus T

Eastem indigo snake Drymarchon corai's couperi T

Green sea turtle Chelonia mydas (including agassizi) E (CH)

Hawksbill sea turtle Eretmochelys imbricate E (CH)

Kemp's (Atlantic) ridley sea turtle Lepidochelys empii E

Leatherback sea turtle Dennochelys coriacea E (CH)

Loggerhead sea turtle Caretta caretta T

Sand skink Neoseps reynoldsi T

Invertebrates

a. Source: USFWS, 1999

b. Key:

R = Recovered

T = Threatened

E = Endangered

S/A = Endangered or threatened by similarity of appearance

CH = Critical habitat

XN = Nonessential experimental population

NMFS = under the jurisdiction of the National Marine Fisheries 

Service
134

Chapter 4: Environmental Resources Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Schaus swallowtail butterfly Heraclides (Papilo) aristodemus ponceanus E

Stock Island tree snail Orthalicus reses (not including nesodryas) T

Plants

Avon Park harebells Crotalaria avonensis E

Beach jacquemontia Jacquemontia reclinata E

Beautiful pawpaw Deeringothamnus pulchellus E

Britton's beargrass Nolina brittoniana E

Carter's mustard Warea carteri E

Crenulate lead-plant Amorpha crenulata E

Deltoid spurge Chamaesyce(Euphorbia) deltoidea spp. deltoidea E

Florida bonamia Bonamia grandiflora T

Florida golden aster Chrysopsis (Heterotheca) floridana E

Florida perforate cladonia Cladonia perforate E

Florida ziziphus Ziziphus celata E

Four-petal pawpaw Asimina tetramera E

Fragrant prickly-apple Cereus eriophorus var. fragrans E

Garber's spurge Chamaesyce(Euphorbia) garberi T

Garrett's mint Dicerandra christmanii E

Highlands scrub hypericim Hypericum cumulicola E

Johnson’s seagrass Halophila johnsonii NMFS

Key tree-cactus Pilosocereus (Cereus) robinii E

Lakela's mint Dicerandra immaculate E

Lewton's polygala Polygala lewtonii E

Okeechobee gourd Cucurbita okeechobeensis spp. okeechobeensis E

Papery whitlow-wort Paronychia chartacea (Nyachia pulvinata) T

Pigeon wings Clitoriafragrans T

Pygmy fringe-tree Chionanthus pygmaeus E

Sandlace Polygonella myriophylla E

Scrub blazing star Liatris ohlingerae E

Scrub buckwheat Eriogonum longifolium var. gnaphalifolium T

Scrub lupine Lupinus aridorum E

Scrub mint Dicerandrafrutescens E

Scrub plum Prunus geniculata E

Short-leaved rosemary Conradina brevifolia E

Small's milkpea Galactia smallii E

Snakeroot Eryngium cuneifolium E

Tiny polygala Polygala smallii E

Wide-leaf warea Warea amplexifolia E

Wireweed Polygonella basiramia (ciliata var. b.) E

Table 4-2. The federally-listed endangered and threatened species of South Florida

Common Name Scientific Name Statusb

a. Source: USFWS, 1999

b. Key:

R = Recovered

T = Threatened

E = Endangered

S/A = Endangered or threatened by similarity of appearance

CH = Critical habitat

XN = Nonessential experimental population

NMFS = under the jurisdiction of the National Marine Fisheries 

Service
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

135

The Kissimmee River Restoration Project includes the continuous backfilling of

35 km (22 miles) of canal, acquisition of adjacent floodplain lands, removal of two water

control structures (S65-B and S65-C), degrading existing floodplain levees, and

reconstructing approximately 14 km (9 miles) of river channel. The project also includes

modification of the upper Kissimmee River basin water regulation schedule. This will be

accomplished by expanding the C-36 and C-37 canals, which connect Lakes Cypress,

Hatchineha, and Kissimmee; land acquisition to allow additional water storage in these

three lakes and Tiger Lake; and enlarging structure S65 at the outlet of Lake Kissimmee.

While the upper basin component provides the necessary flows critical for restoration of

the lower basin river-floodplain ecosystem, more naturally fluctuating lake levels also will

enhance the marsh zones within these lakes and provide improved fish and wildlife

habitat. 

In order to assess restoration success, a Comprehensive Restoration Evaluation

Program has been developed. This program takes an ecosystem perspective and includes

hydrological, physical, chemical, structural, and functional attributes of the system that

will best elicit restoration response by all biological communities including river channel

and floodplain vegetation, aquatic invertebrates, fishes, wading birds, waterfowl,

amphibians, and reptiles (Karr et al., 1991; Koebel, 1995). Postrestoration community

structure characteristics and functional attributes will be compared to baseline conditions

and, whenever possible, specific historically-based expectations for restoration to

determine if communities have changed, if the changes are in the direction and magnitude

desired, and whether restoration goals have been achieved. 

Phase I of restoration construction (Koebel, 1995) resulted in over 12 km (7.5

miles) of backfilled canal. Approximately 2.4 km (1.5 miles) of new river channel have

been excavated, with a total of 24 km (15 miles) of historic Kissimmee River reconnected.

In addition to backfilling, most floodplain levees in Pool C have been degraded and the

S65-B structure has been removed. Within the upper Kissimmee River basin, expansion of

the C-37 Canals is expected to be completed in 2003. 

F3. Environmental Impacts on South Florida Estuaries

Estuaries surround the District’s boundaries and serve several, often-conflicting

societal uses. They support commercial and recreational fisheries, comprise important

waterways for commercial shipping and recreational boating, and often receive processed

industrial and municipal wastes. In addition, estuaries provide flood protection, draining

rainfall runoff from urban and agricultural land. Estuaries are important nursery grounds

for many commercially-important fish species (SFWMD, 2000b), and contribute

significantly to Florida’s economy, quality of life, and environmental well being. Water

quality characteristics, in addition to salinity patterns, affect community structure and food

web organization in coastal systems (Myer and Ewel, 1990). 

Changes in freshwater inflow patterns (i.e., Lake Okeechobee releases) have

threatened and/or resulted in the loss of critical estuarine habitats and biological

communities within District estuaries. The estuarine environment is sensitive to
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freshwater releases, and disruption of the volume, distribution, circulation, and temporal

patterns of freshwater discharges could place severe stress on the entire ecosystem.

The District’s overall goal for the upper east coast and lower west coast estuaries,

as presented in the Estuary Research Plan (SFWMD, 1998) is to protect, enhance, and

rehabilitate estuarine ecosystems. This research plan employs a resource-based approach,

that 1) identifies issue-specific management objectives and 2) provides a framework for

the integrated research required to meet these objectives in each estuarine system. The

first objective seeks to establish the optimum quantity of freshwater inflow for individual

estuaries. The research-management link occurs through the development and

implementation of CERP and regional water supply plans that incorporate MFLs and

PLRGs, which depend, in part, on research that identifies estuarine inflow targets as

criteria for allocating water from the connected watershed and retention facilities (e.g.,

Lake Okeechobee, reservoirs, and ASR systems).

F3a. Caloosahatchee Estuary

The Caloosahatchee River (C-43 Canal) bisects the Caloosahatchee watershed and

functions as a primary canal that conveys stormwater runoff and regulatory releases from

Lake Okeechobee, provides navigation for large boats along the Okeechobee Waterway,

and provides recreational opportunities for boating, fishing, and wildlife observation. The

estuary provides foraging areas and wetland habitat for a large number of Florida’s rare,

endangered, and threatened species (SFWMD, 2000b).

Section 373.042, F.S., requires the water management districts to establish MFL

criteria for surface water and aquifers within their jurisdiction. The minimum flow is

defined as the “...limit at which further withdrawals would be significantly harmful to the

water resources or ecology of the area.” The minimum surface water level is defined as the

“level of surface water at which further withdrawals would be significantly harmful to the

water resources of the area.” For purposes of establishing MFLs, significant harm is

defined as loss of water resource functions that take multiple years to recover that result

from a change in surface water or ground water hydrology. Through the development of

the Lower East Coast Regional Water Supply Plan (SFWMD, 2000c), the Lower West

Coast Water Supply Plan (SFWMD, 2000d), and the Caloosahatchee Water Management

Plan (SFWMD, 2000e), and concurrent staff research and analysis, a methodology and

technical basis for establishment of the MFL criteria for the Caloosahatchee Estuary was

developed (SFWMD, 2000b).

The proposed Caloosahatchee Estuary MFL criteria is based on maintaining

freshwater base flows to the upper reaches of the Caloosahatchee Estuary, which will

prevent excessive salinity levels in the estuary from causing significant harm to

submerged aquatic vegetation and fish and invertebrate communities. Research data were

used to relate freshwater flow rates to salinity distributions along the Caloosahatchee

River and to correlate biological community responses to varying salinity conditions.

These relationships were established for submerged aquatic vegetation, fish, and

invertebrates with major emphasis on the salinity requirements of the freshwater grass,

Vallisneria amerciana, commonly known as tape grass or eelgrass (SFWMD, 2000b).
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Tape grass is one of the dominant submerged aquatic plants in the upper Caloosahatchee

Estuary, and occurs in well-defined beds in shallow waters. Vallisneria americana has

been identified as important habitat for a variety of freshwater and estuarine invertebrate

and vertebrate species, including some commercially and recreationally important fish

(Bortone and Turpin, 1998). It can also be a food source for the Florida manatee

(SFWMD, 2000b). 

Excessive freshwater inflows to the estuary result in imbalances beyond the

tolerances of estuarine organisms, while estuarine biota adapt to, and depend on, natural

seasonal salinity fluctuations. Retaining water within upland basins for water supply

purposes can reduce inflows into the estuary and promote excessive salinities. Conversely,

the inflow of large quantities of water into the estuary due to flood control activities can

significantly reduce salinities and introduce stormwater contaminants (SFWMD, 2000b).

In order to make informed management decisions, research is being conducted by the

District and others to investigate the in situ influence of freshwater inflow and salinity on

tape grass to determine if freshwater inflow requirements are needed to permit a healthy,

thriving ecosystem in the upper reaches of the Caloosahatchee Estuary. In addition,

mapping of submerged aquatic vegetation on the basis of distribution and proximity to

significant freshwater input on spatial and temporal variations in biotic communities, will

provide seasonal fluctuations of submerged aquatic vegetation in the lower parts of the

Caloosahatchee estuary, San Carlos Bay, and Pine Island Sound (SFWMD, 2000b). 

The valued ecosystem component approach applied to the Caloosahatchee River

and Estuary was developed by the USEPA as part of the National Estuary Program.

Vallisneria was selected as the valued ecosystem component of choice because it requires

a number of the primary water resource functions that need protection during low flow

periods. The District has published several studies using this resource-based approach to

define a preliminary estimate of optimum freshwater flows that should be delivered to the

Caloosahatchee Estuary (Chamberain et al., 1995, Chamberlain and Doering, 1998a,

1998b). Among the conclusions is that a minimum inflow of 300 cfs will not be harmful to

Vallisneria communities and other estuarine biota, however, inflows greater than 2,500 to

3,000 cfs will be detrimental to these communities anytime of the year. A distribution of

inflows that has the greatest frequency of falling within the range of 300 to less that 1,500

cfs, with a peak flow range of 300 to 800 cfs, should be generally beneficial to all biota

evaluated. The greatest priority should be given to making the desired delivery in

February to ensure that optimum conditions are available in the spring and the required

salinity regime has been established for Vallisneria when it is most needed (SFWMD,

2000b).

The health of the estuary is an indicator of the health of the watershed. The loss of

important habitat functions, such as young fish nurseries and good water quality, as a

result of reduced dry season flows and increased salinity, have the potential to result in

some level of harm to the submerged aquatic vegetation communities and their associated

fauna within the Caloosahatchee Estuary (SFWMD, 2000b). 

Once the CERP facilities are operational, the optimal flow requirements for the

Caloosahatchee Estuary will be realized, but the estuary has a high probability of
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experiencing significant harm due to the lack of sufficient freshwater flows before the

structural solutions that are part of the CERP are completed. In the interim basis, the

proposed minimum flow should help to eliminate, or greatly reduce, the need to make

short-term, high volume releases in the dry season. High volume releases over short time

periods, and limiting boat lockages through the water control structures, are common

practices during the dry season to protect municipal water supply from salt water and/or

undesirable algae blooms (SFWMD, 2000b). District staff have identified short-term and

long-term approaches to implementing the proposed MFL criteria and protecting the

resource from significant harm.

F3b. St. Lucie Estuary

Historically, the amount of salt water entering the St. Lucie Estuary varies due to

the constantly changing nature of the inlets along the barrier island. As a result of

increased settlements along the coast and in the western portion of the counties, the

amount, quality, and timing of fresh water entering the system have been drastically

altered. The area, which originally drained slowly by overland flow into the St. Lucie

Estuary, increased in size, and the drainage increased in velocity and amount.

Salinity is one of the more crucial abiotic factors influencing the distribution of

organisms in estuaries. Numerous studies have found that estuary flora and fauna tend to

fall into general groups based on their reactions and tolerances to salinity, and are

classified as such. While organisms are usually found in one of the classification

categories, they can become stressed with systems that move from one category to another

with varying conditions (Woodward-Clyde Consultants, 1998). 

Some estuarine species, such as the eastern oyster, Crassosterea virginica, have

been negatively impacted by the change in flow patterns. Although much is known about

Crassastrea virginica from other estuarine systems, the St. Lucie Estuary oysters have not

been studied. The wide and varied fluctuation of salinity from stormwater runoff and Lake

Okeechobee releases do not allow the current system to maintain a stable population.

Oyster growth, development, and reproduction depends on the depth of water, the

substrate type, salinity, currents, dissolved oxygen, temperature, pH, amount of suspended

solids, and availability of food sources. Similar to most sessile estuarine animals,

Crassostrea virginica is anatomically and physiologically well adapted to a wide range of

temperatures, salinities, and dissolved oxygen levels, and capable of surviving

environmental extremes as long as the conditions do not continue for extended periods of

time.

The American oyster is an almost exclusively estuarine bivalve mollusk with both

economic and ecological importance (Livingston, 1990). Declines in the oyster harvest are

attributable to reduced production due to habitat loss, disease, and especially extensive

closures of the fishery because of contamination by coliform bacteria from inadequately

treated salinity wastewater discharges. The ecological significance of the oyster is 1) as a

filter-feeding, primary consumer; 2) as a creator of hard, reef-like substrates forming a

habitat for other organisms; and 3) as prey for numerous consumers. Because they are

sessile throughout most of the life cycle, oysters have adapted to a wide range of
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 4: Environmental Resources

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environmental conditions and can withstand substantial variations in these factors. Efforts

are under way to evaluate the overall health, survival, and reproduction of the eastern

oyster in the St. Lucie Estuary. Research evaluating this species is important in

determining water management practices since the District considers the oyster a valued

ecosystem component (IFAS, 2000). 

Few references have been published on submerged aquatic vegetation and oyster

distributions in the St. Lucie Estuary. Woodward-Clyde Consultants (1998) produced a

literature review of both submerged aquatic vegetation and oysters and, aside from one

survey completed in 1960, most of the information has been anecdotal in nature and

consisted of verbal communications from local sources with intimate knowledge. The

literature review concluded that all of the submerged aquatic vegetation species evaluated

(turtle grass, manatee grass, wild celery, and sago pond) may tolerate moderate current or

wave action, while other species have low or unknown tolerances to moderate currents.

Appearance of significant natural ranges of all of the true sea grasses appear to be

restricted to a range of salinities from about 22 parts per thousand (ppt) to 36 ppt in natural

environments (Woodward-Clyde, 1998). The reviewed literature indicates that all of the

sea grasses examined have some short-term (i.e., one to three days) low salinity tolerance

near 10 ppt and short-term high salinity tolerance between 50 and 70 ppt. The distribution

of these species in salinities of about 20 ppt appears to be due to the competitive abilities

of each species and to other environmental factors, rather than to individual salinity

tolerances of each species (Woodward-Clyde, 1998).

Based on existing low flow conditions in the St. Lucie Estuary, it appears that even

with minimal freshwater discharge, the salinity range for turtle grass, manatee grass,

paddle grass, and Johnson’s sea grass, would be too low for these species anywhere but in

the lower estuary. Shoal grass and star grass both appear to tolerate some lower salinities,

down to five to 10 ppt on a casual basis, and possibly lower for short periods (less than

three days) (Woodward-Clyde, 1998). The adaptability of the submerged aquatic

vegetation for the St. Lucie Estuary appears to be similar to the current and historical

conditions indicating that possibly the alteration of the salinity regime in the estuary may

not significantly alter the distribution limits of the species from those currently seen. One

possible effect could be more permanent, denser areas of submerged aquatic vegetation

(Woodward-Clyde, 1998). 

Light availability may be the greatest limitation to submerged aquatic vegetation

beds in the St. Lucie Estuary. Period of record data suggest that the establishment of sea

grass beds may be limited to a very small portion of the estuary unless water clarity is

significantly improved, and possibly only brackish water species may adapt to the amount

of light available (Woodward-Clyde, 1998).

F3c. Current Status

An update to the Indian River Lagoon SWIM Plan will include developing interim

PLRGs in the St. Lucie Estuary and the southern Indian River Lagoon for nutrients, fresh

water, and total suspended solids. The District has initiated storm event monitoring in the

St. Lucie Estuary to assist in the PLRG effort. Several Indian River Lagoon SWIM
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stormwater retrofit projects are under way in Martin and St. Lucie Counties that will

reduce both the peak flows and sediment loading, and will enhance the water quality of

stormwater runoff entering the Indian River Lagoon and the St. Lucie Estuary. Efforts also

include habitat restoration and enhancement as well as environmental education projects. 

Other efforts for the St. Lucie River watershed include projects reviewed and

approved in July 1999 by the St. Lucie River Issue Team for implementation within the

next five years. In Fiscal Year 19991, $7.5 million was allocated by the State of Florida

with the intention of accelerating the progress of water quantity, quality, and timing

improvements through implementation projects in the St. Lucie River and Estuary. The

highest ranked projects submitted were funded and are currently under way. For Fiscal

Year 2000, the state has set aside $10 million to continue funding St. Lucie Estuary

projects that were submitted for review by both the St. Lucie River Issue Team and the

newly created Florida Water Advisory Panel. 

1. The District’s fiscal year begins on October 1 and ends on the following September 30. Fiscal Year

1999 began on October 1, 1999, and ended on September 30, 2000.
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Chapter 5

FLOOD CONTROL AND WATER SUPPLY

Lake Okeechobee is regulated for flood control and water supply purposes and is

the heart of South Florida’s water management system. During the wet season (June

through November), lake levels are regulated to reduce potential flood damages by storing

enormous volumes of water. Conversely, during the dry months (December through May),

stored water is released to support the Everglades system and to provide water supply to

South Florida’s municipal and industrial users, and agricultural irrigation (Miller, 1999).

Since the first attempts to protect agriculture, by lowering lake levels and the construction

of canals and dikes, several efforts have been undertaken to serve the multipurpose uses

that the lake provides now. The subsequent efforts were summarized in Table 14 of the

Surface Water Improvement and Management (SWIM) Plan - Update for Lake

Okeechobee (SFWMD, 1997a). 

A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Ensure adequate flood protection to local communities 

and agriculture around the lake

Objective 1: Upgrade the efficiency and stability of flood control

facilities within the Lake Okeechobee basin and provide for the

maintenance and control of aquatic weeds to ensure project design capacity

is met for inflow and discharge canals and structures

Strategy 1: Support the Hoover Dike Major Rehabilitation Project

being implemented by the USACE

Strategy 2: Maintain design flow and conveyance capacities of

the flood control system by continuing the aquatic weed

maintenance at inflow/discharge structures and canals, consistent

with other lake management objectives

Strategy 3: Assist local governments in their comprehensive

planning process to address local flood protection needs, consistent

with water quality and environmental resource objectives

Objective 2: Reduce the EAA’s dependency on the lake for flood control

as much as practical 

Strategy 1: Maintain present reductions in the use of the S-2 and

S-3 pumps for flood protection in the S-2 and S-3 basins 
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Goal 2: Provide a balance between the competing objectives of 

flood protection, water supply, and protection of the 

lake’s marsh zone and downstream estuaries

Objective 1: As the local sponsor, work actively with the USACE and

state agencies in the implementation of the WSE Lake Okeechobee

regulation schedule

Strategy 1: Coordinate meetings/facilities and participate in

presentations of the Lake Okeechobee WSE regulation schedule

and adaptive protocols

Strategy 2: Provide updated vegetation maps from the Lake

Okeechobee marsh zone (updated regularly)

Objective 2: Work as the local sponsor with the USACE to implement the

CERP

Strategy 1: Cooperate with the USACE on developing new

biological data for the major vegetation communities in the marsh

zone of Lake Okeechobee

Strategy 2: Collect additional data from the marsh zone of Lake

Okeechobee that evaluates the effect of lake stage on the vegetation

communities (ongoing)

Goal 3: Maintain an adequate quantity of water in Lake 

Okeechobee to supplement downstream environmental 

needs and reasonable-beneficial use requirements

Objective 1: Provide water deliveries for use by agriculture and urban

communities around the lake and to recharge the coastal aquifer

Strategy 1: Define urban and agricultural water supply needs of

users that utilize Lake Okeechobee

Strategy 2: Continue to implement the current Lake Okeechobee

Supply-Side Management Plan (Hall, 1991) for allocation of water

deliveries to the EAA during a declared water shortage as described

in the Staff Manual for the Management of Water Shortages

(SFWMD, 1987)

Objective 2: Provide water supply for supplementing environmental

needs through the implementation of the Lower East Coast Regional Water

Supply Plan (SFWMD, 2000c)
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Strategy 1: Establish environmental water needs for Lake

Okeechobee, the St. Lucie and Caloosahatchee Estuaries, the

WCAs, and Everglades National Park for the protection of natural

vegetation; fish and wildlife habitat; and rare, threatened, and

endangered species

Strategy 2: Define the role of Lake Okeechobee in meeting the

water needs of the downstream environment

Strategy 3: Develop a flexible framework for managing the

operation of the lake at stages below regulation, including the

modification of the Lake Okeechobee Supply-Side Management

Plan (Hall, 1991)

Objective 3: Reduce dependency on Lake Okeechobee as a water supply

for downstream users through implementation of demand management and

water conservation techniques and development of alternative sources of

water supply

Strategy 1: Require that permitted users within the Lake

Okeechobee Service Area develop and implement water demand

management strategies

Objective 4: Augment water supply from Lake Okeechobee consistent

with environmental objectives

Strategy 1: Investigate methods for development of additional

sources of water to the lake that would not adversely effect its

trophic state, marsh zone, or downstream estuaries

Strategy 2: Investigate and research alternative (nonlake) options

for supplying agricultural and public water supply demands (e.g.,

wastewater reuse, industrial and agricultural recycling, alternate

surface water storage facilities, ASR, and desalination

technologies)

Strategy 3: Investigate and promote the use of optimization

technology on the operation and location of coastal wellfields in

order to reduce the potential of saltwater intrusion and, therefore,

demands on Lake Okeechobee

Strategy 4: As water use permits within the Lake Okeechobee

Service Area come up for renewal, examine and, if necessary,

revise them to insure consistency with the Lake Okeechobee water

budget, applicable SWIM and water supply plans, modified

regulation schedule, and any other identified natural resource

management needs of the lake.
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B. FLOOD CONTROL

Flood control protects life and property adjacent to Lake Okeechobee. It is

achieved in two ways. First, levees completely encircle the lake except where it connects

to high ground on either side of Fisheating Creek. Second, lake stage (water level) is

monitored daily by the USACE and the SFWMD, and this information is evaluated

according to the lake regulation schedule (described in the Regulation Schedule section

on page 5-146). The general concept is to ensure that sufficient storage capacity is

available for basin runoff and rainfall. Therefore, the regulation schedule is at its lowest

point before the start of the rainy season on June 1 of each year. The regulation schedule

must maintain levels in the lake that are safe in the event of hurricane wind and wave

action. Although intense rainfalls amounting to four inches or more are common in

Florida, serious flooding usually is the result of prolonged heavy seasonal rainfall

aggravated by tropical storm or hurricane rains.

B1. Flood Control Canals and the Hoover Dike

B1a. Canals

The two major lake outlets, the Caloosahatchee River and St. Lucie Canal, and

four smaller agricultural canals, the West Palm Beach, North New River, Hillsboro, and

Miami canals, provide relief for the lake when water levels reach certain elevations

designated by the operational schedule.

The Caloosahatchee River flows westward to the city of Fort Myers, through the

Caloosahatchee Estuary, and then into the Gulf of Mexico. The St. Lucie River mimics the

same model on the east coast of Florida; water flows through the canal to the city of Stuart

and then to the St. Lucie Estuary before entering the Atlantic Ocean. During droughts,

when water levels are exceedingly low, releases are restricted to conserve water according

to the Lake Okeechobee Supply-Side Management Plan (Hall, 1991). The resulting

fluctuations in lake levels have been about twice the historical range (Miller, 1999). 

B1b. Herbert Hoover Dike

The Herbert Hoover Dike is the earthen embankment system located along the

perimeter of Lake Okeechobee. Components of the dike system have been constructed

intermittently since the early 1900s, and the lake is now almost encircled by the dike

system, with the exception of two portions around the Fisheating Creek inflow where the

levees meet higher ground. The existing embankments total approximately 142 miles in

length with typical elevations of 25 feet above adjacent land elevations. In addition to the

earthen embankment, the dike system also includes numerous water control structures

along its length. 

In March 1999, the USACE completed the Herbert Hoover Dike Major

Rehabilitation Evaluation Report (USACE, 1999b), which documented approximately 10

years worth of levee seepage and stability studies. The Jacksonville District of the USACE
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145

indicated that seepage and piping problems do exist, and the severity of those problems

warranted immediate repair measures. Analysis of dike reliability indicated that portions

of the dike exhibit unacceptable risks of failure at certain water levels. The USACE is

proposing a solution that involves the construction of a seepage berm, with a relief trench

and drainage system, along the land side tow of the dike. It will serve as an

environmentally-friendly filter that lets the water through without allowing the dike

material to pass through with it. 

The USACE’s analysis and conclusions have been supported by an engineering

consulting firm hired by the USACE and a panel of experts (USACE 1999b). The

USACE’s rehabilitation is expected to cost a total of $160 million dollars to construct.

Reach 1, which runs for 22 miles along the southeastern shore, is the highest priority for

rehabilitation. The most recent cost estimate for the Reach 1 repair is $78 million. The

District has been asked to participate as a local sponsor of the rehabilitation project and

share the costs. 

B1c. Backpumping

While eight pumping stations provide flood protection to basins surrounding the

lake, only two of the them are considered backpumping stations: S-2 and S-3. The vast

majority of pumping events at S-2 and S-3 have been in support of flood control

operations. Backpumping for water supply is used to move runoff from the EAA into Lake

Okeechobee for storage and later use to meet demands. Only rarely has backpumping for

water supply been used, and historically only used in conjunction with serious droughts

that occurred in 1981, 1985, 1989 (Tommy Stroud, 2000, personal communication) and

then again in 2001.

The Interim Action Plan (SFWMD 1979), instituted in 1979, was established to

reduce phosphorus loading to Lake Okeechobee by diverting a significant portion of EAA

runoff south toward the WCAs. The change resulted in an estimated 90 percent reduction

of water pumped into the lake from S-2 (between South Bay and Belle Glade) and S-3

(between South Bay and Clewiston). The Interim Action Plan required improved

conveyance capacity in EAA canals to move more water south. 

B1d. Bolles and Cross Canals Improvements

The need for the improvement of the Bolles and Cross canals was identified in all

previous Lake Okeechobee SWIM Plans (SFWMD 1989a, 1993, 1997a). Improvements

to these canals would allow better movement of water during local storm events and

should result in a decrease in intermittent backpumping to the lake. As part of the CERP,

the USACE prepared a general reevaluation report and an project environmental impact

statement on improvements to the Bolles Canal. At this time, these canals will be

incorporated into the EAA Reservoir Project.
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B2. Regulation Schedule

B2a. Historical Regulation Schedules

The C&SF Project originated during a time when flood control, water supply, and

land development through drainage, were the primary objectives, and where

environmental issues were not a prominent concern. The Lake Okeechobee regulation

schedule determines the timing and quantity of water that needs to be released from the

lake when the stage exceeds a certain level, which varies according to season. The most

recent lake regulation schedule (Run 25) allowed the lake to peak at 16.75 feet NGVD on

September 30. The water stored in the lake is intended for water supply during the dry

season. A detailed summary of Run 25 is contained in the Surface Water Improvement and

Management (SWIM) Plan - Update for Lake Okeechobee (SFWMD, 1997a).

In 1965, the lake regulation schedule was modified to allow greater storage during

the wet season. This was in response to the dry conditions of the early 1960s. After the

summer and fall of 1965, a new schedule was developed to help deliver water to

Everglades National Park. In May 1992, an alternative lake regulation schedule, Run 25,

was put into effect for a two-year period, (Figure 5-1) (SFWMD, 1989). The Run 25

Figure 5-1. The Run 25 Lake Okeechobee regulation schedule
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147

schedule ranged from 15.60 to 16.75 feet National Geodetic Vertical Datum (NGVD),

with multiple operation zones that varied flood releases over a wide range before reaching

maximum release rates. The purpose of this regulation schedule was to reduce damaging

flows to the St. Lucie and Caloosahatchee Estuaries without sacrificing the flood control

or water supply benefits derived from the lake. Run 25 was approved for implementation

in December 1994, and was considered interim (as are all regulation schedules) because

the Flood Control Act of 1968 authorized an additional four feet of water supply space in

the lake.

B2b. Current Regulation Schedule

Until such time as more permanent solutions to the environmental restoration

efforts under CERP are instituted, the Lake Okeechobee Regulation Schedule Study is

being implemented to improve the environmental health of the major ecosystems that are

currently declining. The Lake Okeechobee Regulation Schedule Study was initiated in an

effort to optimize the Run 25 regulation schedule for environmental benefits at little or no

impact to the competing purposes of flood control and water supply (USACE, 1999c). The

Lake Okeechobee Regulation Schedule Study considered four alternative regulation

schedules: 22AZE, HSM, Corps 2010, and WSE. An economic study was conducted to

determine the net regional and national benefits for the various alternatives.

The study determined the WSE schedule (Figure 5-2) represented the best

operational compromise to improve the environmental health of the major South Florida

ecosystems. Implementation of the WSE lake regulation schedule was determined to not

adversely impact water supply, flood control, or existing local or regional economies, and

may possibly enhance them through an improved and more sustainable natural ecosystem

and the tourism and small business revenue it is expected to generate (USACE, 1999c).

The WSE schedule appears to provide substantial benefits for the lake littoral zone and

marsh. High lake stages, and regulatory discharges to the St. Lucie Estuary, which have

plagued the lake, will be reduced under the WSE. Conditions within the Caloosahatchee

system are not expected to substantially improve under WSE, or with any of the other

alternatives. Flows currently conveyed through the EAA in existing canals will continue

under the WSE schedule without effecting current land use or wetlands. WCA-2A and

WCA-3A will receive some additional flow, but is not expected to significantly affect

regional hydroperiods or existing land or recreational uses. 

This new schedule is the first to incorporate climatological forecasting technology

as part of the water management decisionmaking process for Lake Okeechobee (USACE,

1999c). A key feature of the WSE schedule is the lower operational zone, Zone D

(Figure 5-2), which allows the flexibility to deliver water to the Everglades during lower

lake stages. The WSE schedule allows dry season discharges to the estuaries to be

gradually increased as necessary to control water levels, and allows more water to be kept

in the regional system for water supply and hydroperiod restoration (USACE, 1999c). 

The District’s Governing Board approved the WSE schedule in July 2000. It was

implemented incorporating the most up-to-date technical knowledge and tools currently

available. 
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C. WATER SUPPLY

In 1997, the District merged its Lower East Coast (LEC) regional water supply

analysis of major water storage facilities into the Restudy process. This was a multiyear

planning effort with a 2050 planning horizon. Analytical tools, evaluation techniques, and

storage projects used in the LEC regional water supply planning efforts completed from

1992 to 1997 were refined for the Restudy analyses. Technical analyses of the LEC

planning area’s future water needs, and the availability of water supplies, indicate that

extensive actions are required to ensure that a sustainable water supply is available to

fulfill future urban, agricultural, and natural systems water needs. The Lower East Coast

Regional Water Supply Plan (SFWMD 2000e) presents the recommended actions to meet

the needs, providing the projects recommended in the Restudy are built on schedule.

Otherwise, the region will face increased water shortages and environmental decline. The

recommendations made by the Restudy are being implemented through the CERP.

Figure 5-2. The WSE regulation schedule
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149

C1. Water Supply Demand Estimates

The LEC planning area is expected to experience substantial growth between now

and 2020, increasing by almost 58 percent form 1995. Most of the increase in population

will occur in the coastal areas, which is projected to have almost seven million residents in

2020 (SFWMD 2000c). This growth will create additional water demands for potable and

irrigation water. The overall water demands of consumptive users is projected to increase

by 20 percent (SFMWD 2000c). 

C2. Determination of Natural Areas Water Supply Needs

Implementation of the Lower East Coast Regional Water Supply Plan (SFWMD,

2000c) with its various regional water supply development projects will result in a number

of major environmental benefits to South Florida’s natural areas. Lake Okeechobee and

the St. Lucie and Caloosahatchee Estuaries will show major improvements by 2010. They

should meet their respective planning targets by 2015, due to the implementation of the

WSE schedule for the lake and the construction of regional water supply reservoirs within

the C-43 and C-44 basins. Construction and operation of the regional storage projects

north of the lake greatly reduces the need to 1) make large releases of fresh water to the St.

Lucie and Caloosahatchee Estuaries and Lake Worth Lagoon during high rainfall years;

and 2) meet low flow criteria proposed to protect these ecosystems during dry periods

(SFWMD, 1999b, 2000b)

C3. Supply-Side Management Plan

When water levels decline in Lake Okeechobee, the Lake Okeechobee Supply-Side

Management Plan (Hall, 1991) becomes activated and water use may be restricted

according to the District’s Water Shortage Plan (SFWMD, 1987). This plan provides for

phased restrictions on water use that are designed to protect the resource from incurring

significant harm. When drought conditions are of sufficient magnitude that water

resources begin to experience harm, the District’s Governing Board may require

restrictions on operational deliveries and water uses, pursuant to the Water Shortage Rule

40E-21, F.A.C. (SFWMD 2000c). To meet the existing and future demands on Lake

Okeechobee, the stage that triggers supply-side management was lowered by

approximately one-half foot. The end of the dry season (May 31) stage target was also

reduced from 11.0 to 10.5 feet NGVD.

C4. Water Conservation Strategies

As a result of the implementation of the Water Supply Policy Document and the

regional water supply plan recommendations, many conservation-oriented changes have

been incorporated into the District's Basis of Review for consumptive water use permit

applications. Mandatory water conservation measures incorporated into the District's

Basis of Review for water use permit applications include water conservation plans for

public water supply utilities, and landscape and golf course irrigation projects. Water

conservation elements for public water supply include irrigation ordinances, Xeriscape®
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criteria, ultra-low volume plumbing fixtures, conservation-based rate structures, leak

detection programs, and reclaimed water reuse feasibility studies. For agricultural

projects, the Basis of Review provides mandatory irrigation efficiency standards and

requires agricultural demand management measures including monitoring and reporting of

water use.

C5. Water Supply Alternatives

Continued use of the traditional source of public water, the Surficial Aquifer

System, can be expanded by incorporating proposed water resource development projects

and more efficient use of regional and local water supplies, especially within the coastal

areas (SFWMD 2000c and d). Providing additional management of historical sources and

through conservation and storage of water, the following options have been identified to

make additional water available:

• Conservation

• Surficial Aquifer System

• Floridan aquifer

• Reclaimed water

• Seawater

• ASR

• Reservoirs

• Surface water

The Floridan aquifer appears to be a promising source of additional potable water

in areas with limited access to regional supplies, without complete knowledge of longterm water quality impacts. Several public water utilities already use reverse osmosis

technology to remove salt from saline Floridan aquifer water.

C6. L-8 Diversion

The Lake Okeechobee Technical Advisory Council recommended the L-8

Diversion Project (LOTAC, 1988). This project has since been incorporated into the

Everglades Protection Project. The conceptual design for the Everglades Protection

Project included plans for the L-8 diversion works being operated to direct runoff from the

northern L-8 basin. The water source is primarily from the Dupuis Reserve and the J.W.

Corbett Wildlife Management Area (WMA), and will be directed to Lake Okeechobee via

the S-76 control structure, Culvert 10A, and the new S-309 pump station that will be

constructed. Analysis of phosphorus loading using the modified Vollenweider model

(Vollenweider, 1976) indicates that the long-term loading target is slightly more

achievable with this added source of clean water.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 6: Recreation

151

Chapter 6

RECREATION

The Lake Okeechobee SWIM planning area has three major recreational areas:

Lake Okeechobee, the Okeechobee Waterway, and the Kissimmee River. Lake

Okeechobee is the largest recreational resource of the region. The lake has one of the most

productive freshwater sports fisheries in North America and is an important winter

waterfowl observation and hunting area. The extensive littoral zone on the western,

undiked side of the lake provides critical habitat for the lake’s popular sport fishery. The

associated waterways and shoreline provide a wide variety of water-based recreation

activities for local residents and out-of-state visitors, including boating, picnicking,

sightseeing, camping, swimming, hunting, airboating, hiking, biking, and horseback

riding. 

Lake Okeechobee experienced six years of inordinately high water levels during

the mid-1990s. These high water levels have caused damage to the native plant

populations in the lake and have the potential to threaten the fisheries. The Lake

Okeechobee Recession was approved by the SFWMD Governing Board by resolution in

2000 was designed to bring Lake Okeechobee to a target level of 13 feet NGVD for a

period of six to eight weeks in order for suspended sediments in the lake’s water column to

settle out allowing sunlight to reach seed beds in the lake’s bottom. Although signs of new

life in Lake Okeechobee were slower than expected, many areas showed recovery. The

northern portion of the lake remains an area of concern.

The Okeechobee Waterway, which stretches 152 miles from Fort Myers to Stuart,

links the Gulf and Atlantic coasts of Florida with the lake via the Caloosahatchee River

and St. Lucie Canal. The waterway has been used for decades by the Kissimmee Boat-ACade in its oceangoing trips. 

Phase 1 of the Kissimmee River Restoration Project is completed and has had an

effect on recreational activities. Although lands acquired for this restoration effort have

provided greater opportunities for users such as hiking, hunting, and camping, navigation

of larger boats on the restored section of the river is limited and navigation through the

entire length of river will be blocked intermittently during many phases of restoration

construction.

The major challenge addressed by this chapter is to manage Lake Okeechobee in

order to optimize opportunities for growth of native vegetation to enhance the health of

the lake’s fisheries. This challenge will be addressed by using the newly approved WSE

regulation schedule for Lake Okeechobee and by working closely with other state and

federal agencies to avoid, to the greatest extent possible, extended high water levels in the

future.
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A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Attain recreational opportunities that meet public 

demand and are consistent with other SWIM goals

Objective 1: Develop and support recreational opportunities within the

Lake Okeechobee SWIM planning area to the maximum extent possible

considering the environmental sensitivity and suitability of the area

Strategy 1: Assist communities along Lake Okeechobee in

developing recreational opportunities such as fishing, hunting,

camping, hiking, boating, canoeing, bicycling, birding, sailing,

ecotourism, and other related outdoor activities

Strategy 2: Continue recreational development of appropriate

lands owned by the SFWMD and supporting development of other

lands within the Lake Okeechobee SWIM planning area as

segments of the Florida National Scenic Trail

B. RECREATIONAL ACTIVITIES

The SFWMD and USACE have published several pamphlets of recreational

facilities in Lake Okeechobee and the Okeechobee Waterway, as well as SFWMD land

management areas along the Kissimmee River. These have been combined to produce a

comprehensive list of recreation sites and their respective activities/public uses in the

Lake Okeechobee SWIM planning area (Table 6-1). The recreation sites are listed by

county, except for the 27 management areas listed under the Kissimmee River Land

Management Areas, which include properties acquired by the District for the restoration

of the Kissimmee River. In addition to these public recreation sites and land management

areas, numerous private fish camps, marinas, boat tour, and sightseeing facilities are

located near access points to the lake. Additional recreational information is available

from federal and state agencies, chambers of commerce, tourism development councils,

and the SFWMD’s Okeechobee Service Center.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 6: Recreation

153

Table 6-1. Public recreation sites in the Lake Okeechobee SWIM planning area

Recreation Site

Recreational Activitiesa

Boating Fishing Picnic Camping Hunting Biking Hiking

Horse

Back

Martin County

Port Mayaca Recreational Area X X (X) A A

Port Mayaca Wayside Park X

Chancey Bay Access Area X X (X) A A

Indiantown Marina X X X

DuPuis Reserve X X X X X X X X

St. Lucie Lock and Dam X X X X

Phipps Martin County Park X X X X X X

Okeechobee County

Henry Creek Lock Access Area X X

Nubbin Slough Access Area X X X

Taylor Creek Access Area X X A A

Okeechobee (Lock 7/Wayside) X X X A A

C. Scott Driver, Jr. Recreation 

Area 

X X

Okee-Tantie Recreation Area X X X X A A

Glades County

Buckhead Ridge X X

Indian Prairie Canal Access 

Area

X X (X) X A A

Bare Beach Access Area X X X A A

Harney Pond Canal Access 

Area

X XX A A

Fisheating Creek Access Area X X X

Nicodemus Slough U U U U

Sportsman's Village Access 

Area

X XX

Moore Haven West (Moore 

Haven Recreational Village)

X XX X A A

Moore Haven East (Alvin Ward 

Park)

X XX A A

Ortona Lock and Dam (North) X X X

Ortona Lock and Dam (South) X X X

Hendry County

Clewiston Recreation Area X X X A A

COE, Clewiston

Port Labelle Marina X

Belle Hatchee Marina X

Barron Park X

Labelle Access Area X X

Labelle Lions Park X

Lee County

Alva Access Area X

a. Key

X = Activity allowed at site.

(X) = Activity proposed at site.

A = Access to Florida National Scenic Trail on Hoover Dike.

U = Uses will be allowed once the proposed construction contract is completed.
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W.P. Franklin Lock and Dam 

North

XX X

W.P. Franklin Lock and Dam 

South

X X

Palm Beach County

John Stretch Park X X X A A

South Bay Access Area X X X A A

Belle Glade Recreation Area X X X X A A

Rardin Park X X X A A

Bacom Point X X A A

Pahokee Marina and 

Campground

X XX X A A

Canal Point Lions Club Park X X X A A

Kissimmee River Land Management Areas

KICCO X X X X X X

No Name Slough X X X X X

Boney Marsh X X X X X X

Bluff Hammock I X X X X X X

Bluff Hammock II X X X X X

Starvation Slough X X X

Oak Creek X X X X

Hickory Hammock X X X X X X X

Turkey Hammock X X X

Cornwell Marsh East X X X X X X X

Cornwell Marsh West X X X X X X X X

Micco Landing X X X X X

Chandler Slough - 1 X X X X X

Chandler Slough - 2 X X X X

Pearce Homestead

Seaboard Marsh North X X X X X

Seaboard Marsh South X X X X X

River Acres II X

Yates Marsh X X X X X X

Telex Marsh X X X X X X

Platt’s Bluff X X X X X

Daughtry Cutoff X X X X X

Maple River X X X X X

70 N Marsh X X X X X

S-65E Impoundment X X X X X X

M-2 Marsh

(Part of Paradise Run)

X XX X X X

Mims Island

(Part of Paradise Run)

XX X X X

Table 6-1. Public recreation sites in the Lake Okeechobee SWIM planning area

Recreation Site

Recreational Activitiesa

Boating Fishing Picnic Camping Hunting Biking Hiking

Horse

Back

a. Key

X = Activity allowed at site.

(X) = Activity proposed at site.

A = Access to Florida National Scenic Trail on Hoover Dike.

U = Uses will be allowed once the proposed construction contract is completed.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 6: Recreation

155

C. SUMMARY OF RECREATION ISSUES

C1. Lake Okeechobee and Okeechobee Waterway

The Lake Okeechobee and Okeechobee Waterway Master Plan (USACE, 1986)

identified factors influencing public use, including the existing conditions of the project’s

recreation resources and requirements needed to meet future demands. The main factor

identified was a deficiency of supporting facilities at several areas heavily used for both

boat and bank recreational fishing. Crowding at boat launching areas is exacerbated

during the busy winter months and during times when the areas are also being used for

waterfowl hunting. Also, additional launch ramps are needed to meet the increasing

demands for access to the rim canal and Lake Okeechobee. Access to the lake is also

affected by water levels and maintenance of boat trails (see Chapter 7, which addresses

navigation). Other deficiencies were identified for campsites, hiking and bicycling trails,

and picnicking facilities. 

In 1996, recreation levels at Lake Okeechobee were estimated at 64,503,500

visitor hours (Miller, 1999) and fishing and boating pressure continues to increase,

particularly in the bay areas and littoral zone, where recreational fishing is concentrated.

Therefore, it is critical to maintain adequate recreation facilities and meet future projected

needs.

Many impediments prevent the building of additional facilities. The USACE may

not develop or enhance recreational facilities without a cost-sharing sponsor, except those

justified to serve other project purposes or for public health and safety (USACE, 1986).

Interviews with staff at the FWC reveal that a number of problems are encountered in

building boat launch ramps. These include the FWC’s priorities to repair over 200 existing

ramps built throughout the state since 1960, the difficulties involved in meeting funding

guidelines, and complications that arise when formal written agreements are required

between multiple parties, including federal, state, local, and private interests. 

C2. Kissimmee River

The Environmental Restoration of the Kissimmee River Feasibility Report and

Environmental Impact Statement (USACE, 1991) identifies impacts to recreation and

navigation resulting from restoration of the Kissimmee River. While acquisition of lands

along the Kissimmee River have created additional recreational opportunities, including

extension of the Florida National Scenic Trail (see the Florida National and Lake

Okeechobee Scenic Trails section below), impacts on general boating and recreational

boating are anticipated as construction of the river restoration project is completed. Larger

houseboats and other deep draft vessels are not able to navigate within the restored

reaches of the river, and water sports, such as water skiing, will be limited to those reaches

not included in restoration. This loss will be offset in part by opportunities for canoeists

and fishermen using smaller boats. Fishing success on the restored river is expected to

increase over the long term. Navigation issues arising from the Kissimmee River

Restoration Project are further discussed in Chapter 7.
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Chapter 6: Recreation Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

D. ONGOING ACTIVITIES

D1. Greater Lake Okeechobee Tourism Alliance

In recognition of the ecotourism potential of the region, the Greater Lake

Okeechobee Tourism Alliance was formed in 1993 to promote a regional identity focusing

on the natural scenic beauty and cultural heritage of the area. The Greater Lake

Okeechobee Tourism Alliance, which is an arm of the Florida' Heartland Rural Economic

Development Initiative, has been active in promoting hiking and bicycling around the

Lake Okeechobee Scenic Trail and other areas of the Florida National Scenic Trail. The

alliance recently published a tourism pamphlet for the eight-county region served by the

group.

The District participated in regional detailed design workshops that provided a

forum for communities around Lake Okeechobee to develop master plans that share a

common vision. This was a joint effort by the District, local governments, regional

planning councils, and groups such as Greater Lake Okeechobee Tourism Alliance and the

Conservation Fund. The concept was to ensure that community master plans are integrated

with regional economic and environmental goals. Recreational development was an

important component of these workshops.

Annual events on the Herbert Hoover Dike include the Big-O-Go and Big-O-Hike

sponsored by the Greater Lake Okeechobee Tourism Alliance and the FTA (FTA). Trail

organizers from both groups have been a catalyst for trail development and are

instrumental in promoting tourism in the region. The Big-O-Go is a 120-mile, four-day

mountain bike marathon that was first held in November 1994. Due to its success and the

success of the Big-O-Hike, a nine-day hiking event that has taken place every November

since 1992, these events are anticipated to draw more participants in coming years. Both

events promote economic growth to the region and have gained the cooperation and

enthusiasm of communities around the lake. 

D2. Florida National and Lake Okeechobee Scenic Trails

The Florida National Scenic Trail is one of eight national scenic trails in the

country. When completed, the trail will meander 1,300 miles through Florida from the

Gulf Island Seashore of the Panhandle to the Big Cypress National Preserve. Development

and maintenance of the Florida National Scenic Trail is being led by the FTA in

cooperation with numerous public and private agencies, organizations, and individuals.

Portions of the trail are within the Lake Okeechobee SWIM planning area (Figures 6-1

and 6-2). The trail has and will continue to provide new recreational opportunities along

the Kissimmee River and around Lake Okeechobee. Potential recreational opportunities

include fishing, hunting, camping, hiking, bicycling, canoeing, and birding. Additional

opportunities include connecting the trail to surrounding communities and providing

equestrian access in limited areas. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 6: Recreation

157

Figure 6-1. The Kissimmee River section of the Florida National Scenic Trail (WMA = Wildlife

Management Area; FTA = Florida Trail Association; SOR = Save Our Rivers)
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Chapter 6: Recreation Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Figure 6-2. The Lake Okeechobee section of the Florida National Scenic Trail 

(WMA = Wildlife Management Area; FTA = Florida Trail Association; SOR = Save

Our Rivers)
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 6: Recreation

159

Once they reach the Hoover Dike at Clewiston, hikers heading north from Big

Cypress have the choice of walking around the east or west sides of Lake Okeechobee.

Scenic views of the lake and the adjacent agricultural lands are afforded from the trail at

Clewiston, Lake Harbor, South Bay, Pahokee, and on Torrey Island west of Belle Glade.

D3. Florida Cracker Trail

The Florida Cracker Trail is a historic east-west route that Florida cattlemen

followed each spring until the 1930s. The trail passes through Manatee, Hardee,

Highlands, Okeechobee, and St. Lucie Counties. Each year since 1988, the historical

return trip of the cattle drive has been reenacted. The Florida Legislature named and

recognized the Florida Cracker Trail in 1986, and the trail is officially designated on

FDOT maps. 

D4. Fishing Tournaments

The FWC estimates over 250,000 angler hours are dedicated to fishing

tournaments on Lake Okeechobee annually. This accounts for 25 percent of all statewide

tournament activity. Based on their reservation numbers, Okee-Tantie Park in Okeechobee

hosted 50 tournaments in 1994. Other popular tournament sites are Roland Martin's

Marina, Anglers Inn, Harney Pond, the Indian Prairie Canal, and the city ramps in

Clewiston, Moore Haven, Lakeport, and Belle Glade. Combined, these sites probably host

the same number of tournaments as Okee-Tantie.

D5. Boating Events

The Kissimmee Boat-A-Cade, formed in 1947, uses the Kissimmee Waterway for

three annual boating trips from the city of Kissimmee through Lake Okeechobee. From

Lake Okeechobee, the boats proceed to either the east or west coast through the

Okeechobee Waterway, depending upon their destination. A total of about 300 boats

participate annually in the Kissimmee Boat-A-Cade. Boat sizes range from 18 to 40 feet.

In the past, the Boat-A-Cade has also made trips to the Florida Keys and Charleston,

South Carolina. 
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Chapter 6: Recreation Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 7: Navigation

161

Chapter 7

NAVIGATION

Lake Okeechobee, the Okeechobee Waterway, and the Kissimmee River have

undergone a century of development for navigation. Construction has been accomplished

by both private individuals and public agencies. The development phases of the federal

navigation project is described in more detail in the Lake Okeechobee and Okeechobee

Waterway Master Plan (USACE, 1986) and Environmental Restoration of the Kissimmee

River: Feasibility Report and Environmental Impact Statement (1991).

The development of the Okeechobee Waterway began in the 1800s with dredging

that opened 360 contiguous miles of navigable waterway connecting the Caloosahatchee

River, Lake Okeechobee, and the Kissimmee River. Dredging of the St. Lucie River began

in the early 1900s, connecting the lake with the Atlantic Ocean. In 1930, the federal

government adopted the Okeechobee Waterway as a federal navigation project with due

consideration to be given to flood control (USACE, 1986). The navigation channel has an

authorized project depth of 8 feet based upon a Lake Okeechobee stage of 12.56 feet

NGVD. The Kissimmee River has an authorized navigation project depth of 3 feet at

ordinary stage of the river (USACE, 1991).

In addition to the federal navigation project, about 31 miles of historic boat trails

are located in the marsh zone of Lake Okeechobee. These trails are used primarily for

recreational fishing. The USACE maintains these historic boat trails to provide safe harbor

for recreational boaters during inclement weather. Numerous unplanned recreational boat

trails have also been developed and maintained by continual boat use. No one is

responsible for maintaining these unplanned boat trails.

The major challenge addressed by this chapter is to increase public access to the

lake in order to enhance recreational uses including fishing, boating, and wildlife

observation. This challenge will be addressed by the SFWMD by supporting the Lake

Okeechobee Scenic Trail development and continuing to work with ecotourism groups.

A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Maintain navigability for commercial and recreational 

uses within Lake Okeechobee and the Lake Okeechobee 

Waterway

Objective 1: Provide assistance to maintain navigation within the federallyoperated navigation project encompassed by Lake Okeechobee and the

Okeechobee Waterway

Strategy 1: Consistent with water supply and environmental

objectives, maintain water storage in Lake Okeechobee to ensure
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Chapter 7: Navigation Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

reasonable access to marinas and commercial and recreational

channels

Strategy 2: Support the USACE’s efforts to control aquatic weeds

on the Okeechobee Waterway and on the recreational boat trail

system to levels that do not unreasonably impede recreational

access consistent with the approved Lake Okeechobee Aquatic

Plant Management Plan

Strategy 3: Maintain designated navigation locks and structures for

the federal navigation project

Strategy 4: Support the USACE’s efforts to maintain and enhance

navigation within the Okeechobee Waterway

Goal 2: Maintain navigability for recreational uses within the 

Kissimmee River

Objective 1: Provide assistance to maintain recreational navigation within

the Kissimmee River

Strategy 1: Support the USACE’s efforts to maintain recreational

navigation within the Kissimmee River consistent with the

Kissimmee River Restoration Project

Strategy 2: Control aquatic weeds on the Kissimmee River to levels

that do not unreasonably impede recreational access consistent with

the approved Kissimmee River Aquatic Plant Management Plan 

B. NAVIGATION LOCK STRUCTURES

Navigation lock structures on Lake Okeechobee, the Okeechobee Waterway, and

the Kissimmee River are managed by the USACE or the SFWMD (Table 7-1). The

USACE maintains five navigation boat locks on the Okeechobee Waterway. Boaters on

the Okeechobee Waterway may take two distinct routes across Lake Okeechobee from the

Port Mayaca Lock to the Moore Haven Lock. One is a 39-mile long open water crossing

while the other, known as the Rim Canal, follows 50 miles along the southern shore.

All locks, other than those located in the Okeechobee Waterway, have been turned

over to the SFWMD for operation and maintenance. This leaves the Franklin, Ortona,

Moore Haven, Port Mayaca, and St. Lucie locks under the jurisdiction and regular

operation and maintenance of the USACE. In the event of a hurricane, jurisdiction of all

locks on Lake Okeechobee reverts to the USACE. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 7: Navigation

163

C. SUMMARY OF NAVIGATION ISSUES

C1. Lake Okeechobee and the Okeechobee Waterway

Boating access to Lake Okeechobee is affected by water levels. At lake stages

below 12.56 feet NGVD, the authorized project depth cannot be maintained. During

periods of low lake level, navigational access to much of the fishing area is reduced.

Conservation measures may be imposed which restrict discharges from the lake including

limitations by the USACE on the frequency of lockage operation. The USACE is the lead

agency in assuring and maintaining navigability in the lake. 

In addition to the issues of adequate depth and unimpaired structural operations,

travel impediment due to aquatic weed infestations is also an issue. This is of concern both

within the Okeechobee Waterway and within the numerous boat trails and within the Rim

Canal where recreational uses might be adversely impacted. The Rim Canal and boat trails

also become inaccessible during low water periods. The USACE administers an Aquatic

Weed Control Program. 

Table 7-1. Navigation lock structures on the federal projecta

Lock

Managing 

Agency

 Water Body/

Waterway

Width/

Length 

(feet)

Hours of 

Operation

St. Lucie Lock (S-80) USACE St. Lucie Canal 50/250 6AM-10PM 

Port Mayaca Lock (S-308B) USACE St. Lucie Canal/

Lake Okeechobee

56/400 6AM-10PM

Clewiston Lock (S-310) SFWMD Lake Okeechobee 50/60 5:30AM-8PMb

Moore Haven Lock (S-77) USACE Caloosahatchee/

Lake Okeechobee

50/250 6AM-10PM

Fisheating Creek Lock (S-131) SFWMD Lake Okeechobee 15/50 5:30AM-8PMb

Buckhead Ridge Lock (S-127) SFWMD Lake Okeechobee 15/50 5:30AM-8PMb

Taylor Creek Lock (S-193) SFWMD Lake Okeechobee 50/60 5:30AM-8PMb

Henry Creek Lock (G-36) SFWMD Lake Okeechobee 15/50 5:30AM-8PMb

Chancey Bay Lock (S-135) SFWMD Lake Okeechobee 15/50 5:30AM-8PMb

Ortona Lock (S-78) USACE Caloosahatchee 50/250 6AM-10PM

W.P. Franklin Lock (S-79) USACE Caloosahatchee 56/400 6AM-10PM

S-61 SFWMD Kissimmee River 30/90 7AM-6PMc

S-65 SFWMD Kissimmee River 30/90 7AM-6PMc.

S-65A SFWMD Kissimmee River 30/90 8AM-5PMc.

S-65C SFWMD Kissimmee River 30/90 8AM-5PMc.

S-65D SFWMD Kissimmee River 30/90 8AM-5PMc.

S-65E SFWMD Kissimmee River 30/90 7AM-6PMc.

a. Source: USACE, 1986 and SFWMD Contract C-4209, August 17, 1993

b. Open until 9:00 PM from May 1 to September 30

c. Weekend hours for all Kissimmee River locks: March 1-October 31, 5:30AM-7:30PM; November 1-February 

28, 5:30AM-6:30PM
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Chapter 7: Navigation Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

The Okeechobee Waterway has had an authorized federal navigation depth of 8

feet since the 1930s. In the 1960s, the Caloosahatchee (C-43) and St. Lucie (C-44) Rivers

were widened and deepened as part of the C&SF Project to accommodate flood releases

from Lake Okeechobee. The authorized flood control channel depth of 26 feet is greater

than the navigation channel depth the USACE is required to maintain. Therefore, the

Okeechobee Waterway has not needed to be dredged for navigation, except for in the St.

Lucie Inlet area, where the Okeechobee Waterway intersects with the Intracoastal

Waterway. Navigational dredging of the St. Lucie River downstream of S-80 is the

responsibility of the Florida Inland Navigation District. The St. Lucie Inlet area was last

dredged in 1980, and the area is in need of dredging again.

C2. Kissimmee River

Since 1902, the Kissimmee River (C-38) has had an authorized navigation depth of

3 feet. The actual channel depth is greater than the authorized channel depth the USACE is

required to maintain, because the C&SF Project channelized the river into a 30-foot deep

canal for flood protection. Presently, the size of the navigation locks, which provide a

minimum depth of five feet, limit the size of boats in the C-38 Canal (USACE, 1991). In

addition, the five bridges crossing the Kissimmee River, with vertical clearances ranging

from 12 to 20 feet, may restrict the height of boats.

Channelization of the Kissimmee River resulted in destruction of wetlands and

other riverine habitats. As a result, in 1992, the USACE and SFWMD agreed to a plan that

includes backfilling 22 miles of the channel and removing the S-65B and S-65C locks.

The S-65B navigation lock was removed in 2000 during the first phase of restoration.

During Phase I of the restoration construction, navigation along the Kissimmee River has

been restricted from north to south, although most of the original river remains open to

recreational use both north of the construction project and south of the project (Figure 7-

1). Further restrictions to north-south navigation along the river will happen as navigation

locks are taken out of service for major overhauls. After the Kissimmee River Restoration

Project is completed, the restored river will meet the authorized navigation depth of 3 feet

during normal flow conditions. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 7: Navigation

165

Figure 7-1. Navigation of the Kissimmee River during Phase I construction of the Kissimmee

River Restoration Project
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Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 8: Public Involvement and Intergovernmental 

167

Chapter 8

PUBLIC INVOLVEMENT AND 

INTERGOVERNMENTAL COORDINATION

The condition of the lake and the status of District management efforts

traditionally have been routinely reported to the public as part of the agency’s ongoing

public communication effort. The Surface Water Improvement and Management (SWIM)

Plan - Update for Lake Okeechobee (SFWMD, 1997a) established a specific public

information goal to provide citizens with information concerning Lake Okeechobee water

resource management issues and to implement an effective public awareness and

participation project.

In addition, the SWIM Act requires the District to coordinate with other public

agencies as part of the process of preparing, reviewing, and approving Lake Okeechobee

SWIM plan updates (Sections 373.453 and 373.455, F.S.). The development of a Public

Participation Program and an Intergovernmental Coordination Program will promote the

involvement of the public and other agencies in the SWIM planning process.

This chapter presents goals, objectives, and strategies that have been used to

develop the public information and participation program to inform the residents of South

Florida about Lake Okeechobee water resource issues, and provide opportunities for the

public to participate in the Lake Okeechobee SWIM planning process. The addition of a

dedicated, organized approach for keeping local government staff members and elected

officials up to date on Lake Okeechobee SWIM issues has led to more active local

government involvement and enhanced public communication.

The methods for developing and disseminating information that describes the

characteristics of the lake ecosystem, conveys a sense of the lake’s environmental

sensitivity, and demonstrates Lake Okeechobee’s prominence in the Kissimmee-Lake

Okeechobee-Everglades ecosystem are as follows:

• Foster a greater understanding of Lake Okeechobee’s role in meeting

the water supply and flood protection needs of South Florida

• Develop an understanding of human demands and impacts on Lake

Okeechobee 

• Enlist public support for Lake Okeechobee restoration and preservation

efforts

• Promote an understanding of and consistency with Lake Okeechobee

SWIM goals in other related efforts such as the CERP

The Public Participation and Intergovernmental Coordination programs are

designed to do the following:
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• Advise the public; county, state, and federal government agency staff;

and elected officials of the nature and scope of Lake Okeechobee

SWIM planning efforts

• Keep open the lines of communication between the public and agency

planners, listen to the needs and the views of the public, and identify

and respond to interested individuals, special interest groups, elected

officials and agencies

• Make available for agency and public review and comment all plans,

reports, data analyses, interpretations, and other information

• Facilitate interagency coordination in the development and

implementation of action plans to achieve common water resource

goals and objectives

• Allow for facilitated public input into the planning process for future

Lake Okeechobee restoration and preservation efforts

The major challenge addressed by this chapter is to foster a greater understanding

of Lake Okeechobee restoration and preservation efforts and enlist public support for

meeting established goals. This challenge will be addressed by enhancing public, local

government, and interagency coordination including discussions on problem solving and

minimizing economic impacts; and by assisting local governments with the incorporation

of SWIM considerations into local comprehensive plans. 

A. GOALS, OBJECTIVES, AND STRATEGIES

Goal 1: Prepare and implement an effective public awareness 

program

Objective 1: Develop and distribute materials that inform the general

public about the features of the Lake Okeechobee ecosystem, including its

physical, chemical, and hydrologic features; water quality and sediment

characteristics; tributary basins; biological resources; recreational

resources; and the role of Lake Okeechobee in the Kissimmee-Lake

Okeechobee-Everglades ecosystem

Strategy 1: Within existing SFWMD public information projects,

generate and distribute information to explain the lake's capacity to

address the flood protection, water supply, and environmental

resource needs of South Florida and, more specifically, within the

Lake Okeechobee SWIM planning area

Strategy 2: Prepare a public communications plan that will reflect

major milestones in Lake Okeechobee research and the SWIM

planning process that will 1) focus on the actual issues and
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 8: Public Involvement and Intergovernmental 

169

information that will be conveyed to various target audiences and

2) specify the appropriate communication vehicle(s)

Goal 2: Encourage public participation in the Lake Okeechobee 

SWIM planning process

Objective 1: Create new opportunities for residents, scientists, business

and commercial concerns, environmental groups, the regulated community,

recreational users, and other special interest groups to participate in the

development of lake management strategies emphasizing participation by

local populations and affected parties within the Lake Okeechobee SWIM

planning area 

Strategy 1: Develop a public participation and intergovernmental

coordination process to support Lake Okeechobee SWIM plan

development and implementation of lake restoration, preservation,

and management strategies

Strategy 2: Establish a Florida yards and neighbors project, in

which volunteers are solicited from the community to implement

water conservation, environmental enhancements, and reduced

nutrient inputs from their own yards

Goal 3: Prepare and implement an effective intergovernmental 

awareness and involvement program

Objective 1: Develop an intergovernmental participation and

coordination process to focus on intergovernmental involvement through

scheduling and pursuing an active outreach program to involve all local,

state, and federal entities with interest in issues related to Lake

Okeechobee.

Strategy 1: Prepare an intergovernmental involvement plan, that

reflects major milestones in Lake Okeechobee research, supports

Lake Okeechobee SWIM Plan development, and the

implementation of lake management strategies

Strategy 2: Schedule and pursue an active outreach program to

involve all local, state, and federal entities with interest in issues

related to Lake Okeechobee

Objective 2: Develop and coordinate workshops and meetings that

inform appropriate government staff members and elected officials about

the features of the Lake Okeechobee ecosystem, its physical, chemical, and

hydrologic features; water quality and sediment characteristics; tributary
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basins; biological resources; recreational resources; and the role of Lake

Okeechobee in the Kissimmee-Lake Okeechobee-Everglades ecosystem

Strategy 1: Develop and coordinate workshops and meetings that

inform appropriate government staff members and elected officials

regarding current and proposed restoration projects on Lake

Okeechobee

Strategy 2: Maintain communication with local government staff

members and elected officials about current and proposed policy

regarding the Lake Okeechobee ecosystem by involving agency

staff members in regular local meetings and workshops

Objective 3: Create methods for appropriate local government staff

members and elected officials to better participate in the interagency

process that results in public policy regarding the operation and

management of Lake Okeechobee, and to link Lake Okeechobee SWIM

projects with other interagency efforts

Strategy 1: Use the Okeechobee Service Center as a

clearinghouse for all lower Kissimmee Basin/Lake Okeechobee

projects so staff members can better coordinate all system-related

projects

Strategy 2: Use the Okeechobee Service Center as a resource/

facilitator so that interagency and multigovernmental projects can

be housed and/or coordinated locally

B. REVIEW OF CURRENT PROJECTS

B1. Lake Okeechobee-Closer Look

The SFWMD publishes a document titled Lake Okeechobee-Closer Look. It was

originally designed to accompany an informational natural history seminar on the lake,

From Algae to Alligators: The Nature of Lake Okeechobee, that was presented in 1995.

The document explores Lake Okeechobee, discussing its past, present, and future in the

context of man’s impacts on the lake. An 8-page edition of this document was published in

March 1995 and July 1997 (SFWMD, 1995, 1997b), and updated in November 2000

(SFWMD, 2000g). Most recently, it has been issued as a companion publication with this

update. 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Chapter 8: Public Involvement and Intergovernmental 

171

B2. Media Coordination

The District has established a weekly newspaper column, Water Works, that

frequently includes information specific to Lake Okeechobee restoration. It also keeps

readers informed about upcoming meetings and invites public participation. 

Media tours of Lake Okeechobee have been implemented. The purpose of these

tours was to highlight the volunteer tree planting efforts of District staff and to showcase

successes with Lake Okeechobee recession initiatives.

B3. Proposed Media Coordination Project

The District proposes to design and implement a water media leadership project

for state, local, and national editors and reporters, who frequently report on the

environmental and water management issues of South Florida. Similar to other leadership

projects, participants in this leadership course will have an opportunity for field trips and

in-depth exposure to the competing demands on water resources in South Florida, as well

as an opportunity to learn about process and decision making from an agency perspective.

B4. Proposed Public and Intergovernmental Coordination 

Communications Plan

The District has begun developing a public and intergovernmental coordination

communications plan. The communications plan will include, but may not be limited to, a

series of articles summarizing SFWMD research efforts and publications pertaining to

Lake Okeechobee undertaken since 1989. The project will explain how SFWMD research

projects define and measure the extent of resource problems and contribute toward the

development of management strategies. The project will develop a reporting mechanism

that tracks the progress of the regulatory programs in reducing the phosphorus loading to

the lake, as well as the status of implementation of Lake Okeechobee Protection Act

(Section 373.4595 F.S.) measures, which include the implementation of the Dairy Rule

and the Works of the District Rule, and development and implementation of TMDLs and

BMPs.

Special emphasis will be given to reporting to the public the status of Lake

Okeechobee Protection Plan restoration efforts. Program updates will communicate the

effectiveness of efforts to date, including discussions of current progress, definitions of

problems, results achieved to date, and an indication of whether objectives have been met.

If management projects will not be proceeding as planned, efforts will be made to explain

why they are being discontinued, deferred, or redirected. Program updates will also

describe SFWMD efforts to coordinate SWIM planning activities with other agencies that

share similar resource goals and objective and provide information concerning funding

sources and project budgets. 
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As much as possible, public communication efforts will be coordinated with other

Lake Okeechobee restoration efforts. Meetings with the public will include presentations

on multiple projects and initiatives when possible.

B5. Proposed Intergovernmental and Public Participation Project

An intergovernmental and public participation project will generate methods to

advise the public and elected officials of the nature and scope of the Lake Okeechobee

SWIM planning efforts, maintain open lines of communication between the public and

agency planners, listen to the needs and the views of the public, and identify and respond

to interested individuals, special interest groups, and other agencies. Facilitated

discussions on SWIM plan development will be held utilizing representatives from a wide

variety of interests. Results of the facilitated discussions will be considered during

development of future SWIM plan updates. 

The participation project will identify key research efforts for public review and

assessment and prepare to report the results of those research efforts as early as possible.

Issue papers may be prepared to inform target audiences and to frame discussions with

agency planners. Methods of soliciting technical review and comment will be created and

implemented. The project will be prepared to communicate the revised status of research

efforts and subsequent impacts on the SWIM planning process.

The project will create avenues for the public to review the status and address the

effectiveness of SWIM resource management efforts. Communities, special interest

groups, and others affected by resource management projects will be identified and the

role of external parties in the development of management goals, objectives, and strategies

will be defined. The project will provide for the development of a process to communicate

with and solicit input from these targeted groups on the impact of lake management

strategies. Subsequent revisions to management goals and objectives will be documented.

The project will provide opportunities for other public agencies to participate in

the development and implementation of management projects. Potential activities include,

but are not limited to, participation in issue-specific task forces or advisory groups; local

meetings or workshops; cosponsorship of studies to evaluate management alternatives;

contribution of funding or in-kind services for demonstration projects; and cost sharing

the implementation of management projects.
Lake Okeechobee SWIM Plan – April 4, 2002 DRAFT Chapter 9: Budget

173

Chapter 9

BUDGET

The following table identifies the 1998-2000, 2001 and 2002 budgets for Lake 

Okeechobee projects. The project budgets are sorted by goals and objectives from 

Chapters 2, 3, and 4. Efforts were made to include all SFWMD contributions (contract 

funds and staff time), as well as the funds appropriated to the SFWMD from the state. 

Federal contributions, such as the 50:50 Army Corps of Engineers cost-share match for 

the Critical Projects have not been included. 

The sources of this information include current District reports and internal 

budget line item amounts associated with Lake Okeechobee research, planning, and 

monitoring projects. Certain goals, objectives and several strategies do not have separate, 

identifiable projects associated with them at this time and therefore are not listed in the 

budget matrix.
Table 9-1. Ongoing and new Lake Okeechobee SWIM related projects and funding levels 

(funds are ad valorem unless otherwise noted).

SWIM PLAN GOALS, OBJECTIVES AND PROJECTS FUNDING PERIOD

1998-2000 2001 2002

WATERSHED AND TRIBUTARY WATER QUALITY $ $ $

GOAL: Reduce pollutant loads from the watershed to protect aquatic life and 

water quality in Lake Okeechobee TOTAL 15,656,130 3,753,336

Objective 1: Bring the overtarget basins down to their phosphorus loading targets SUBTOTAL 805,973 1,775,398

(Strategies 1-3)

Works of the District monitoring - TP

Lab Analysis/testing 18,906

Backpumping 23,000

Works of the District applications

Dairy water quality monitoring 153,195

Watershed water quality monitoring 69,688

Inflow water quality monitoring 101,191

Water quality data anlysis/reporting 381,254

Buck Island beef cattle ranch study analysis 102,000

Beef Cattle Management Practice Research

Buck Island Ranch, beef cattle BMP study 150,000 158,516

Watershed projects

Lake and watershed GIS development 190,000 209,867

Model uncertaintly 15,900

Watershed Modeling Graphical User Interface (GUI) 51,000

Watershed P budget 48,273 169,812

Lakewide P budget 119,800 76,211

TMDL support 25,000

Watershed P dynamics/ model development 57,724 56,014

Model applications & watershed P budget analysis 199,276 173,625

Modeling applications related to permit applications and CERP 31,119

* State-appropriated funding

* * EPA/DEP partial funding
SWIM PLAN GOALS, OBJECTIVES AND PROJECTS FUNDING PERIOD

1998-2000 2001 2002

$ $ $

Objective 2: Implement the components of the Lake Okeechobee Protection Program 

and Permits to meet the TMDL target by 2015 (Strategies 1-8) SUBTOTAL 14,444,157 1,659,200

Dairy Best Available Technologies 1,644,500 427,750

* Isolated wetland restoration program 4,500,000

* LO cow-calf BMPs 225,000

* LO wetland research 350,000

LO Regulation Schedule 21,392

* * Tributary sediment removal study 319,985 67,199

Natural Resources Economics Study 70,000 80,000

* P Source Control Grant Program 7,500,000

Mandated reports 58,140 52,626

* LO program planning and reporting 15,000 242,732

SWIM Plan 58,140 13,893

* * Residuals study 257,000 200,000

Objective 3: Achieve State Class 1 Water Quality Standards (Chapter 60-302, F.A.C.) 

within Lake Okeechobee and Class III Water Quality Standards within the 

Lake's tributaries (Strategies 1-9) SUBTOTAL 917,000 203,000 159,369

Nutrient budget calculations and water quality analysis 917,000 203,000 159,369

* State-appropriated funding

* * EPA/DEP partial funding
SWIM PLAN GOALS, OBJECTIVES AND PROJECTS FUNDING PERIOD

1998-2000 2001 2002

IN LAKE WATER QUALITY $ $ $

GOAL: Reduce in-lake nutrients to attain a more natural (lower) frequency of 

potentially harmful algal blooms TOTAL 1,200,000 896,000 3,973,608

Objective 1: Determine the economic, engineering, and ecological feasibility of 

reducing internal phosphorus loading from lake sediments Strategies 1-2 SUBTOTAL 1,092,060

Lake pilot dredging project 648,300

* * Lake sediment management study 403,760

* Confined disposal facility management 40,000

Objective 2: Quantify rates of internal nutrient loading from lake sediments so that 

accurate predictions can be made about the timing and extent of lake 

responses to potential management actions such as sediment removal 

(Strategies 1-2) SUBTOTAL 487,000 1,013,387

Sediment P release 16,000 16,000

Sediment P dynamics 71,000 186,698

Sediment P dynamics study 179,600

Lake water quality and hydrodynamic modeling 179,000 95,917

Spatial scale hydrodynamic & water quality model 58,000 269,290

Hydrodynamic and water quality data during hurricane season 185,965

Model update and maintenance 179,000 95,917

Objective 3: Reduce uncertainty about in-lake sources, sinks, and cycling of nitrogen 

and phosphorus using research and modeling approaches (Strategies 1-2) SUBTOTAL 1,200,000 274,000 1,474,000

In-lake research: nutrient impacts 1,200,000 274,000 1,474,000

Objective 4. Quantify trends in limnetic and marsh zone water quality and progress 

towards established lake enhancement goals (Strategy 1) SUBTOTAL 0 261,364

Lake Water Quality Monitoring 224,576

Long-term water quality trends evaluation 36,788

Objective 5: Determine the impact of submerged aquatic vegetation on lake water 

quality (Strategies 1-2) SUBTOTAL 135,000 132,797

Submerged plant assessment 73,000 72,435

Littoral vegetation assessment 62,000 60,362

* State-appropriated funding

* * EPA/DEP partial funding
SWIM PLAN GOALS, OBJECTIVES AND PROJECTS FUNDING PERIOD

1998-2000 2001 2002

ENVIRONMENTAL RESOURCES $ $ $

GOAL: Protect and enhance the environmental resources of Lake Okeechobee, in

terms of biological diversity, ecological functions, and the distribution and 

abundance of native plants and animals TOTAL 615,354 1,312,996

Objective 1: Quantify how variations in lake water level affect the environmental 

resources, and use this information to set appropriate lake management 

goals (Strategies 1-5) SUBTOTAL 86,000 102,435

Water level impacts

Torpedo grass vs. depth 67,000 30,000

Plankton algal bloom assess. 19,000 72,435

Objective 2: Develop a predictive understanding of nutrient dynamics in the lake 

ecosystem, and use this information in support of the CERP and TMDL 

process (Strategies 1-3) SUBTOTAL 0 419,000

Predictive modeling 419,000

Objective 3: Identify exotic species that threaten native plants and animals in the lake 

and develop and implement programs for their control (Strategies 1-3) SUBTOTAL 214,354 408,965

In lake research/exotic plants 137,000 218,160

Torpedo grass eradication 140,805

Exotic plant assessment 77,354 20,000

LO torpedograss seed bank 30,000

Objective 4: Quantify long-term trends in the lake’s ecological values (Strategies 1-2) SUBTOTAL 315,000 382,596

Submerged veg research/mapping 161,000 208,689

In lake ecological trend assessment 154,000 173,907

PERIOD TOTAL FOR ALL GOALS AND OBJECTIVES 2,117,000 16,964,484 8,880,571

GRAND TOTAL FOR ALL GOALS AND OBJECTIVES 27,962,055

* State-appropriated funding

* * EPA/DEP partial funding
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Glossary

195

GLOSSARY

Acre-Foot The volume of water that would cover one acre to a depth of one foot; 43,560

cubic feet; 1,233.5 cubic meters; 325,872 gallons.

Algal Bloom Rapid growth of algae on the surface of lakes, streams, or ponds; stimulated

by nutrient enrichment. 

Aquifer A portion of a geologic formation or formations that yield water in sufficient

quantities to be a supply source.

Backpumping The practice of pumping water that is leaving the area back into a surface

water reservoir.

Basin (Surface Water) A tract of land drained by a surface water body or its tributaries.

Best Management Practices (BMPs) Agricultural management activities designed to

achieve an important goal, such as reducing farm runoff, or optimizing water use.

Biomass The amount of living matter, as in a unit area or volume of habitat.

Bioturbation The recycling of nutrients from lake sediments to the overlying water

column caused by the burrowing and feeding activities of benthic invertebrates and fish.

Central and Southern Florida Project Comprehensive Review Study (Restudy) A

five-year study effort that looked at modifying the current C&SF Project to restore the

Kissimmee-Lake Okeechobee-Everglades and South Florida ecosystem while providing

for the other water related needs of the region. The study concluded with the

Comprehensive Plan being presented to Congress on July 1, 1999. The recommendations

made within the Restudy, that is, structural and operational modifications to the C&SF

Project, are being further refined and will be implemented in the Comprehensive

Everglades Restoration Plan (CERP).

Central and Southern Florida (C&SF) Project A complete system of canals, storage

areas, and water control structures spanning the area from Lake Okeechobee to both the

east and west coasts, and from Orlando south to the Everglades. It was designed and

constructed during the 1950s by the United States Army Corps of Engineers (USACE) to

provide flood control and improve navigation and recreation.

Chapter 298 Special Drainage Districts East Beach Water Control District, East Shore

Drainage District, South Shore Drainage District, the Industrial Canal, South Florida

Conservancy [S-236], and 715 Farms.

Chironomids Any of a family (Chironomidae) of midges that lack piercing

mouthparts.
196

Glossary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Chlorophytes

Class I through V Surface Water Quality Standards As defined by Chapter 62-

302.400, F.A.C., all surface waters in Florida have been classified according to designated

use as follows:

• Class IPotable water supplies

• Class IIShellfish propagation or harvesting

• Class IIIRecreation, propagation, and maintenance of a healthy, wellbalanced population of fish and wildlife

• Class IVAgricultural water supplies

• Class VNavigation, utility, and industrial use

Comprehensive Everglades Restoration Plan (CERP) The implementation of

recommendations made within the Restudy, that is structural and operational

modifications to the C&SF Project are being further refined and will be implemented

through this plan.

Consumptive Use Use that reduces an amount of water in the source from which it is

withdrawn.

Consumptive Use Permit A permit issued by the SFWMD allowing utilities to withdraw

ground water for consumptive use.

Control Structure A man-made structure designed to regulate the level/flow of water in a

canal (e.g., weirs, dams).

Cynobacteria Blue-green algae.

Denitrification Reduction of nitrates or nitrites commonly by bacteria (as in soil) that

usually results in the escape of nitrogen into the air.

Diatom Any of a class (Bacillariophyceae) of minute planktonic unicellular or

colonial algae with silicified skeletons.

Epiphyton Plants that derive their moisture and nutrients from the air and rain and usually

grow on other plants

Estuary A water passage where the ocean or sea meets a river.

Eutrophication The gradual increase in nutrients in a body of water. Natural

eutrophication is a gradual process, but human activities may greatly accelerate the

process.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Glossary

197

Everglades Agricultural Area (EAA) The area of histosols (muck) predominantly to the

southeast of Lake Okeechobee that is used for agricultural production.

Everglades Construction Project The foundation for the largest ecosystem restoration

program in the history of Florida. It is composed of 12 interrelated construction projects

located between Lake Okeechobee and the Everglades, including over 47,000 acres of

stormwater treatment areas (STAs).

Everglades Protection Area This area is comprised of the Water Conservation Areas and

Everglades National Park.

Everglades Stormwater Program A program to ensure that water quality standards are

met at all structures not included in the Everglades Construction Project.

Exotic Invasive Plant Species A nonnative species that tends to outcompete native

species and become quickly established, especially in areas of disturbance or where the

normal hydroperiod has been altered.

Food Web The totality of interacting food chains in an ecological community.

Fiscal Year The South Florida Water Management District’s fiscal year begins on October

1 and ends on September 30 the following year.

Geographic Informations Systems (GIS) Mapping The abstract representation of

natural (or cultural) features of a landscape into a digital database, geographic information

system.

Governing Board Governing Board of the South Florida Water Management District.

Ground Water Water beneath the surface of the ground, whether or not flowing through

known and definite channels.

Hectare A unit of measure in the metric system equal to 10,000 square meters (2.47

acres).

Hydroperiod The frequency and duration of inundation or saturation of an ecosystem. In

the context of characterizing wetlands, the term hydroperiod describes that length of time

during the year that the substrate is either saturated or covered with water.

Institute of Food and Agricultural Sciences (IFAS) The agricultural branch of the

University of Florida that performs research, education, and extension.

Indian River Lagoon Extending for 156 miles from north of Cape Canaveral to Stuart

along the east coast of Florida, this lagoon is America’s most diverse estuary, home to

more than 4,000 plant and animal species.
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Glossary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Lagoon A body of water separated from the ocean by barrier islands, with limited

exchange with the ocean through inlets. 

Lake Okeechobee This lake measures 730 square miles and is the second largest

freshwater lake wholly within the United States.

Lake Okeechobee SWIM Planning Area The major basins that are direct tributaries to

Lake Okeechobee, including those basins that are hydrologically upstream and/or from

which water is presently released or pumped into the lake on a regular basis.

Levee An embankment to prevent flooding, or a continuous dike or ridge for confining the

irrigation areas of land to be flooded.

Littoral Of, relating to, situated, or growing on or near a shore.

Load Concentration times flow.

Marsh A frequently or continually inundated wetland characterized by emergent

herbaceous vegetation adapted to saturated soil conditions.

Mesocosm An experimental approach to quantify the responses of a whole plant and

animal community.

Metaphyton

microgram One millionth of a gram

Minimum Flows and Levels (MFL) The point at which further withdrawals would cause

significant harm to water resources.

National Geodetic Vertical Datum (NGVD) A nationally established references for

elevation data.

Native Nuisance Species Native plant species that spread rapidly under disturbed

conditions and displace more desirable plant communities.

Nitrification The oxidation (as by bacteria) of ammonium salts to nitrites and the

further oxidation of nitrites to nitrates.

Nitrogen Fixation The metabolic assimilation of atmospheric nitrogen into ammonia by

soil microorganisms and especially rhizobia.

Nonpoint source Source originating over broad areas, such as areas of fertilizer and

pesticide application or leaking sewer systems, rather than from discrete points.

Nutrient Cycle The cyclic conversions of nutrients from one form to another within the

biological communities. A simple example of such a cycle would be the production and
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Glossary

199

release of molecular oxygen (O2) from water (H2O) during photosynthesis by plants and

the subsequent reduction of atmospheric oxygen to water by the respiratory metabolism of

other biota. The cycle of nitrogen is much more complex, with the nitrogen atom

undergoing several changes in oxidation state (N2, NO3-, R-NH2, and NH4, among others)

during the cycling of this element through the biological community, and into the air,

water, or soil, and back.

Oligochaetes Any of a class or order (Oligochaeta) of hermaphroditic terrestrial or

aquatic annelids (as an earthworm) that lack a specialized head

Pelagic Zone Open water zone.

Performance Measure Performance measures quantify how well or how poorly an

alternative meets a specific objective. Good performance measures are quantifiable, have

a specific target, indicate when a target has been reached, and measure the degree to which

the goal has been met.

Periphyton Organisms (as some algae) that live attached to underwater surfaces

Phytoplankton The floating, usually minute, plant life of a body of water.

Point Source Any discernible, confined and discrete conveyance from which pollutants

are or may be discharged, including, but not limited to, any pipe, ditch, channel, tunnel,

conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding

operation, or vessel or other floating craft. This term does not include agricultural

stormwater discharges and return flows from irrigated agriculture.

Pollution Load Reduction Goals (PLRGs) Targeted reductions in pollutant loadings to a

water body needed to achieve watershed management goals.

Public Water Supply Demand All potable water supplied by regional water treatment

facilities with pumpage of 0.5 million gallons per day (mgd) or more to all customers, not

just residential.

Reasonable-Beneficial Use Use of water in such quantity as is necessary for economic

and efficient utilization for a purpose and in a manner that is both reasonable and

consistent with the public interest.

Regional Water Supply Plan Detailed water supply plan developed by the District under

Section 373.0361, F.S.

Reservoir A man-made or natural lake where water is stored.

Rolling Average The arithmetic average of a sequence of data within a data set moved

and calculated sequentially to smooth the data and reveal trends (e.g., five-year rolling

total phosphorus concentrations).
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Glossary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Saline Water Water with a chloride concentration greater than 250 milligrams per liter.

The term saline water includes brackish water and seawater.

Saltwater Water Intrusion This occurs when more dense saline water moves laterally

inland from the seacoast, or moves vertically upward, to replace fresher water in an

aquifer.

Seawater Water which has a chloride concentration equal to or greater than 19,000

milligrams per liter.

Sedimentation The action or process of forming or depositing sediment.

Significant Harm (Term will be defined during proposed rule development process) An

adverse impact to water resources or the environment, relating to an established minimum

flow or level for a water body; generally temporary but not necessarily short-lived,

especially when the period of recovery from the adverse impact exceeds several months to

several years in duration; more intense than harm, but less intense than serious harm. 

Slough A channel in which water moves sluggishly, or a place of deep muck, mud, or

mire. Sloughs are wetland habitats that serve as channels for water draining off

surrounding uplands and/or wetlands.

Stage The elevation of the surface of a surface water body.

Stormwater Surface water resulting from rainfall that does not percolate into the ground

or evaporate.

Stormwater Treatment Area (STA) A system of large treatment wetlands that use

naturally occurring biological processes to reduce the levels of phosphorus from

agricultural runoff prior to it being released to the Everglades. 

Supply-Side Management The conservation of water in Lake Okeechobee to ensure that

water demands are met while reducing the risk of serious or significant harm to natural

systems.

Surface Water Water that flows, falls, or collects above the surface of the earth.

Surficial Aquifer System The major source of water in the LEC planning area. It is

unconfined, consisting of varying amounts of limestone and sediments that extend from

the land surface to the top of an intermediate confining unit.

Total Maximum Daily Load (TMDL) The level of loading to a body of water that will

protect uses and maintain compliance with water quality standards (defined in the Clean

Water Act [Title 33, Chapter 26, Subchapter III, Section 1313(d)]).

Trophic Level One of the hierarchical strata of a food web characterized by

organisms which are the same number of steps removed from the primary producers 
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT Glossary

201

Turbidity The measure of suspended material in a liquid.

Vertical Migration The vertical movement of oil, gas, contaminants, water, or other

liquids through porous and permeable rock.

Wastewater The combination of liquid and waterborne discharges from residences,

commercial buildings, industrial plants and institutions together with any ground water,

surface runoff, or leachate that may be present.

Water Conservation Reducing the demand for water through activities that alter water

use practices, e.g., improving efficiency in water use, reducing losses of water, and

reducing waste of water.

Water Conservation Areas (WCAs) That part of the original Everglades ecosystem that

is now diked and hydrologically controlled for flood control and water supply purposes.

These are located in the western portions of Miami-Dade, Broward, and Palm Beach

Counties, and preserve a total of 1,337 square miles, or about 50 percent of the original

Everglades.

Water Budget An accounting of total water use or projected water use for a given

location or activity.

Watershed The drainage area from which all surface water drains to a common receiving

water body system.

Watershed Management Goals Goals that encompass any one or all of the major water

management district responsibilities: flood protection, water supply, water quality, and

environmental system protection and enhancement. The goals provide the general

direction for developing cohesive strategies to manage water resources within a drainage

basin, subbasin, or segment of a drainage basin or subbasin.

Water Shortage Declaration Water shortage declarations can be made by the District’s

Governing Board pursuant to Rule 40E-21.231, F.A.C., which states “If ...there is a

possibility that insufficient water will be available within a source class to meet the

estimated present and anticipated user demands from that source, or to protect the water

resource from serious harm, the Governing Board may declare a water shortage for the

affected source class.” A gradual progression in severity of restriction is implemented

through increasing phases. Once declared, the District is required to notify permitted users

by mail of the restrictions and to publish restrictions in area newspapers.

Wetlands Areas that are inundated or saturated by surface or ground water at a frequency

and duration sufficient to support a prevalence of vegetation typically adapted for life in

saturated soil conditions.

XeriscapeTM Landscaping that involves seven principles: proper planning and design;

soil analysis and improvement; practical turf areas; appropriate plant selection; efficient

irrigation; mulching; and appropriate maintenance.
202

Glossary Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT

Zooplankton The passively floating or weakly swimming, usually minute, animal life of

a body of water.
Lake Okeechobee SWIM Plan - June 21, 2002 DRAFT References

183

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