Lake’s ecology depends on water levels 12 to 15.5 feet

Water levels too high damage the lake’s marshes; frequent low water also damaging

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LAKE OKEECHOBEE —Lake Okeechobee’s health relies on balance once provided by Mother Nature. The lake’s ecosystem needs natural lows — but not too low — in the dry season and natural high levels — but not too high — in the wet season. With Lake Okeechobee above 16 feet, concerns rise not only for the security of the Herbert Hoover Dike, the earthen berm that encircles the second largest freshwater lake within the continental United States, but also for the health of the lake itself.

In the Audubon publication “Lake Okeechobee and the Northern Estuaries: The High Cost of High Water,” Dr. Paul Gray explained: “Lake Okeechobee is a paradise of biodiversity. Wetland communities fill almost one-third of the lake, providing prime habitat for Everglade snail kites, a variety of wading birds, ducks, game fish and other species. Water levels between 12.5 and 15.5 feet protect these important resources.

“The lake’s thrilling biodiversity and abundance of life cannot thrive when water levels are too high. When water levels rise to 16 feet, the 50,000-acre (75-square-mile) submerged marsh is in deep enough water that plants begin to die. Plant die-offs harm fisheries and increased turbidity makes lake water dirtier. Prolonged deep water also eliminates the wildlife-rich wet prairie communities that wading birds and waterfowl need for foraging. Once plant communities are lost, habitat for fish spawning and feeding is lost, creating a domino effect on the lake’s food chain. Rapidly rising water also drowns alligator and bird nests, including those of Everglade snail kites — an Audubon priority species.”

Gray also points out that while repairs to Herbert Hoover Dike are important to the safety of those who live south of the Big O, even after repairs are made, highs above 15.5 feet are harmful to the lake’s ecology. “Even after the U.S. Army Corps of Engineers completes the ongoing HHD repairs, consistently holding more water in the lake will damage fragile ecological resources and create significant safety concerns. The ability to store considerably more water outside of the lake is the key to easing high water levels and meeting dry season needs. Repairing the HHD alone cannot prevent or substantially reduce discharges from Lake Okeechobee to the St. Lucie and Caloosahatchee estuaries,” he wrote.

Why not keep the lake lower?
Just as high levels are damaging to the lake’s ecology, low levels can also cause harm. “A Brief History of Lake Okeechobee Ecosystem,” also by Dr. Paul Gray, explains: “Just as holding the lake too high can have devastating impacts, drawdowns or lake schedules that drop water levels too low, for too long, or too often are harmful. To identify and prevent damaging low water events, the South Florida Water Management District established a Minimum Flow and Level (MFL) that identifies the minimum level of water that is needed to protect the health of Lake Okeechobee. The lake’s MFL states that if it drops below 11 feet for more than 80 days, more often than once every six years, then “significant harm” occurs. Significant harm is defined as “harm that requires multiple years for the water resource to recover.”

“Significant harm can typically be seen in four ways: First, marsh-wide population crashes occur in wetland-dependent species such as Florida apple snails, frogs, aquatic snakes, turtles, round-tailed muskrats and similar species. Second, massive evacuations of wildlife can take place. Many species leave but may not find suitable habitat elsewhere.

This was demonstrated by the Everglade snail kite, which suffered 50% population losses during the droughts of 2001 and 2007-08 when the lake habitat was too dry to be suitable for kites. Third, permanent subsidence and loss of organic soils occurs on the south end of the lake. Finally, fish, alligator and aquatic invertebrates lose reproductive capacity when marsh breeding areas are completely dry. As the MFL designation recognizes, it can take years to recover from these types of harm.”

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