Current lake schedule is optimal for lake’s health

OKEECHOBEE — Repairs to the aging Herbert Hoover Dike are critical for the safety of those who live south of the Big O, but changing the lake schedule when repairs are complete would be harmful to the lake, which is the heart of the Everglades, according to a study published in April 2017 by Paul Gray, Ph.D., of Audubon Florida.

The lake needs seasonal periods of high water and low water to maintain the health of the ecosystem. But water above 16 ft. even for short periods is damaging, as are prolonged periods of low water.

Data from the past 65 years show that levels above 16 ft. are damaging to the marshes, the birds and the fishers, according to the study.

“When Okeechobee levels rise above 16 feet, even for short periods of time, environmental degradation results. When lake management schedules persistently hold water levels higher than 16 feet, the damages are compounded,” Dr. Gray wrote.

A deeper lake is also a dirtier lake, Dr. Gray wrote. “At levels above about 15.5 feet, nutrient rich water from the middle of the lake flows into the marsh, degrades water quality, shades out desirable plant communities and encourages noxious plants such as cattails to expand.

“Conversely, low phosphorus levels in the lake occurred after a multi-year period of relatively low water conditions.”

Phosphorus levels in the lake vary with higher phosphorus in the center of the lake and lower levels in the marshes around the edge.

“Originally, Lake Okeechobee was larger and deeper than today but this has been forever changed by the modern water management system. Any future lake management scenarios must consider impacts to the lake and competing needs outside of the lake,” he wrote.

Construction of the Herbert Hoover Dike reduced the lake’s footprint by about one-third, according to U.S. Army Corps of Engineer records. In order to maintain a marshy area around the edges of the lake, the water levels must be kept below 16 ft.

From 1951 to 1978, the regulation schedule for the lake has a high level objective of 15.5 ft., roughly the same level as the highest ground elevations within the Herbert Hoover Dike. Water levels of 15.5 ft. flood the entire marsh that surrounds Lake Okeechobee. During the dry season, the water levels fell, allowing portions of the marsh to dry out. “This period was considered one of marsh plant diversity and health,” Dr. Gray wrote. “Everglade Snail Kites and wading birds nested in the lake in abundance, wintering waterfowl were abundant, and the fishery was productive.” The lowest level during this time period was in 1956 when the lake fell to 10.14 ft.

From 1978-1992, the lake regulation schedule was changed to 15.5 to 18.5 ft.

This extended period of high water created an ecological emergency, Dr. Gray wrote. The state-convened Lake Okeechobee Littoral Zone Technical Advisory Group’s 1988 report found problems including loss of wading bird habitat, decline in willow, and loss of moist soil annual plant production. That advisory group recommended lowering the lake level to improve fish and wildlife habitat in the littoral zone (the marshy areas around the lake).

From 1992 to 2000, more harm to the lake resulted from high water levels maintained above 15.5 ft., Dr. Gray continued. The Corps adopted a new schedule in 1992, designed to keep the lake between 15.65 and 16.75 ft. This did not allow the marshy areas to dry out – except during droughts – and by 2000, the result was the loss of most of the wading bird nesting areas inside the dike and a “crash” of the fisheries. In addition, dead plants in the outer marsh edges formed a large organic berm.

From 2000 to 2008, the Corps adopted a new schedule that allowed the lake to drop lower than previous schedules but still allowed high lake levels, the report continues. High water events over 17 ft. in 2003, 2004 and 2005 created serious environmental problems within the lake, including the loss of about 45,000 acres of plant communities. This damaged the spawning areas for fish, allowing no cover for the small fish. The Speckled Perch (black crappie) fishery crashed and would not recover for almost a decade.

A new lake schedule was adopted in 2008, with the goal of keeping the lake level below 16 ft. most of the time. “Lower levels were adopted partly to ensure the safety of the HHD, but also in recognition of the repetitive harmful impacts that had occurred from higher Lake levels,” Dr. Gray continued.

“The 2015 South Florida Ecosystem Report details that in the 6 years since the adoption of LORS, there had been substantial recovery of submerged aquatic vegetation, bass and crappie fisheries, wading bird and Everglade Snail Kite breeding and feeding and other biological improvements in the lake. The famous FLW Bass Tournament on Lake Okeechobee in 2011 saw the three heaviest stringers of bass ever caught in the history of the tournament.”

In 2016, an unusually wet dry season pushed the lake above 16 ft., despite water managers efforts to keep the lake lower. Data from the periods in which the lake was above 16 ft. shows even short periods of high water are damaging to the marshes, with a loss of 23 sq. miles of plant communities during that time. Wading bird nesting in 2016 was 49 percent below the 10-year average.

Dr. Gray concluded that lake levels in the 12.5-15.5 foot range are ideal for thriving plant and wildlife communities.

“When the lake rises above 16 feet, harm begins, and accelerates if levels continue to rise,” he wrote.

“Lake Okeechobee is one of the great natural resources of our nation. Its bass fishery is world famous, its black crappie fishery can yield more fish than the rest of Florida combined. It is critical for the endangered Everglade Snail Kite, is a migratory stopover for millions of birds, and hosts a significant percent of wading bird nesting in the state.

Any future decisions about Lake Okeechobee’s water levels must carefully consider the impacts of holding too much or too little water in the lake,” he concluded.

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