South Florida Ecosystem Restoration Working Group

Annual Report 1996


Part IV. 1996 SUBREGION ACCOMPLISHMENTS, INITIATIVES AND 1997 GOALS


SUBREGION II:
LAKE OKEECHOBEE

[1996 Accomplishments] [1996 Initiatives] [1997 Goals]


a. Ecosystem Problems and Restoration Objectives

Ecosystem problems in Lake Okeechobee result primarily from nutrient runoff from ranching, dairy and agricultural lands and invasion of exotic plants.

Nutrient enrichment has caused major alterations in the ecology of the Lake. For example, increases have occurred in the populations of blue-green algae and pollution-tolerant benthic animals. Alteration of native littoral zone plant communities are linked to exotic plant invasions and/or unnatural lake levels. Melaleuca, for example, now covers thousands of acres of marshland. Proliferation of various exotic species demands on-going remedial actions as well as research to improve control technologies.

Special attention is focused upon reducing excessive nutrient loading from the agricultural areas north of the Lake. Since the 1 970s, agricultural activities, including dairying and beef cattle ranching, have been recognized as sources of excessive phosphorus loading to the Lake and the probable cause of accelerated eutrophication. There have been major efforts to reduce phosphorus loads from agriculture, and significant progress has been made, particularly in reducing runoff from most dairy operations. However, much work remains to be done.

An independent evaluation to identify sources and cleanup options for certain dairies has been initiated. Additionally, under a cooperative program with the University of Florida and Archbold Biological Station, research is being conducted to identify and optimize beef cattle ranching practices that will reduce nutrient loads in stormwater runoff. The long-term goal of this project is to implement effective BMPs on beef cattle ranches. Research is also being conducted to quantify the amount of phosphorus load reduction that might be achieved by the removal of contaminated sediments from ditches and canals in the watershed.

The restoration of more natural flows from the lake into the Everglades and other parts of the natural system, including a reduction of the flow of water to the east and west coast estuaries, is critical to success. Success in these efforts would provide significant ecological and commercial benefits far beyond the shores of Lake Okeechobee.

Program costs associated with Lake Okeechobee ecosystem restoration through the year 2001 will be for research, feasibility studies, and model development. The results of planned research may lead to construction efforts in later years.

RESTORATION OBJECTIVES:

b. 1996 Accomplishments

Lake Okeechobee Regulation Schedule Review

Developed environmental performance measures for key environmental communities that are dependent on Lake Okeechobee, including the lake's littoral zone, the Caloosahatchee and St. Lucie Estuaries, and the Everglades. These performance measures are being used to evaluate modeling efforts of alternative lake schedules to prevent significant harm to the plant and animal communities.

Established minimum water level criteria for Lake Okeechobee in order to prevent significant harm to the lake's plant and animal communities under conditions of increased demands for water delivery from the lake.

Completed vegetation maps for a large portion of the Lake Okeechobee littoral zone. These maps will be used to document the current distribution of native and exotic plants, and can be compared with past and future maps to quantify changes in the littoral vegetation community.

Improved water quality and hydrodynamic models for Lake Okeechobee. These models will be used to predict lake responses to nutrient load reductions and changes in water level regulation.

Nutrient Loading

Completed a "Special Report on Phosphorus Loading to Lake Okeechobee". This synoptic report portrays the most current estimates of phosphorus loading to Lake Okeechobee, and highlights strategies for reducing phosphorus in the lake.

Completed experimental studies to 20 quantify how pristine, nutrient-poor communities in the Lake Okeechobee littoral zone respond to increased inputs of phosphorus and nitrogen. The results of this research will allow us to better understand and predict the impacts of nutrient-rich water incursion into the marsh community.

Development of Best Management Practices

Completed construction of field-scale experimental beef cattle pasture arrays at the Buck Island Ranch. This facility is now being used for research to optimize cattle stocking densities, forage crop fertilization rates, and grazing schemes to minimize phosphorus runoff from beef cattle ranches.

Eradication of Invasive Exotics

Performed large-scale experimental pilot studies to evaluate the effectiveness of herbicides and surfactant chemicals for controlling torpedo grass in the Lake Okeechobee littoral zone. Preliminary results indicate that in some areas, a single aerial herbicide treatment can yield long term control. However, replicate treatments in a second study area were not as successful. Treatment optimization tests are continuing.

Killed 3.2 million melaleuca trees by manual herbicide treatment and over 1.3 million seedlings were hand-pulled within the Lake Okeechobee littoral zone. This brings the total melaleuca kill in Lake Okeechobee since 1993 to 8.6 million trees and 9.5 million seedlings. In addition, approximately 407 acres of dense melaleuca stands were killed through aerial herbicide treatment during 1996.

Herbert Hoover Dike Seepage and Stability Study

Completed dam break analysis and inundation mapping to determine extent of potential damage associated with a failure of Herbert Hoover Dike.

Completed collection and performed analysis of subsurface geotechnical data.

Water Management

Implemented a Water Rights Compact providing for water quality, water supply, and flood control improvements for the Seminole Big Cypress and Brighton Reservations.

c. 1996 Initiatives

Involving the Public

Began an interagency effort to promote more sustainable, diverse and prosperous economies among the communities surrounding Lake Okeechobee.

Lake Okeechobee Regulation Schedule Review

Initiated cooperative research between scientists of federal, state and regional agencies to quantify animal utilization of various aquatic plant communities in the Lake Okeechobee littoral zone. This information will be used for predicting the impacts of water level-related changes in vegetation on fish, birds and other animals in the lake.

Herbert Hoover Dike Seepage and Stability Study

Initiated an interagency effort to better evaluate the impacts of the regulation schedule on agricultural water supply.

During 1996, approximately five million melaleuca trees were killed by individual treatment of adult trees with herbicide and by manually uprooting seedlings. These techniques are extremely labor intensive and costly, which is why the introduction of more natural biological controls (e.g., insects) is so important to the future of melaleuca elimination. Eradication techniques

d. 1997 Goals

Involving the Public

Continue an interagency effort to promote more sustainable, diverse and prosperous economies among the communities surrounding Lake Okeechobee.

Herbert Hoover Dike Seepage and Stability Study

Complete the evaluation of existing structural integrity of Herbert Hoover Dike during extreme flood conditions.

Evaluate alternative methods for improving the structural integrity of the dike to meet current safety design criteria.

Lake Okeechobee Regulation Schedule Review

Complete vegetation maps of the Lake Okeechobee littoral zone.

Complete an interagency agreement and initiate work to gather information to support the environmental evaluation of alternative regulation schedules.

Eradication of Invasive Exotics

Complete assessment of herbicides for control of torpedo grass in the littoral zone of Lake Okeechobee.

Water Management

Develop water quality standards for Seminole Brighton Reservation.

Design and implement a field-level BMP project for all land uses on the Seminole Brighton Reservation.

Design and construct a comprehensive surface water management system for the Seminole Brighton Reservation.

Develop a comprehensive monitoring program for surface water systems on the Seminole Brighton Reservation.

Spray crews utilize EPA approved herbicides to control aquatic vegetation Spraying

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