Lower lake level helpful this year, but not every year

Dr. Paul Gray of Florida Audubon chose his words carefully at the June 7 meeting of the County Coalition for the Responsible Management of Lake Okeechobee, the Caloosahatchee and St. Lucie Estuaries and the Lake Worth Lagoon.

This year, he explained, the low lake level is good for the overall ecological health of the lake. This year, with the water less than 11 feet above sea level, aquatic vegetation is recovering and that vegetation will provide spawning areas for fish.

Dr. Gray added that he does not support the idea of attempting to lower the Big O to less than 11 feet above sea level every year.

“In a normal year we would not want that to happen, but this is not a normal year,” said Dr. Gray.

He said due to a series of high water years and the churning of the lake by Hurricane Irma, the submerged aquatic plant community is virtually wiped out right now.

“In a normal year we really don’t need the lake to go below 12 feet,” said Dr. Gray. “This year, it helps recover that plant community. We’re taking our medicine right now.”

Dr. Gray said the low lake level is hurting navigation, and it has also meant there are no wading birds nesting on the lake this year.
“Once the aquatic vegetation comes back, the fish will come back,” he said.

Dr. Gray said in addition to the lower lake levels which promote restoration of the aquatic vegetation in the lake, they need projects to remove some of the dead vegetation left stacked on the lake shore by Hurricane Irma.

This year, the fact that the lake level fell below 11 feet is good for the lake, he said. But that would not be good for the lake every year, he stressed.

The U.S. Army Corps of Engineers is in the process of reviewing the Lake Okeechobee System Operating Manual. Currently the corps tries to keep the lake between 12.5 feet and 15.5 feet, following the schedule set forth in the Lake Okeechobee Regulation Schedule, which went into effect in 2008. Some politicians have advocated attempting to bring the level of the lake down to 10.5 feet every year before the start of the rainy season.

At the Friday meeting, Dr. Gray made it clear he does not support the idea of lowering the lake below 11 feet every year.

Lt. Col. Reynolds explained that based on the water averages for 2008-2018, about 2,246,000 acre feet of water flowed into the lake from the north per year, or about 5 feet on Lake Okeechobee; about 1,680,000 acre feet of water entered the lake from direct rainfall, about 3.77 feet on Lake Okeechobee. That means, on average for the past 10 years, about enough water has entered the lake to raise the lake by 8.77 feet each year.

Most of the water that leaves the lake does so through evaporation into the air and percolation into the aquifer. On average, based on the past 10 years of data, about 5 feet of water have left the lake through evaporation and seepage; about 1.5 feet of water have been sent south; about 0.65 ft. west to the St. Lucie; and about 1.6 ft. east to the Caloosahatchee. Water from the lake is sent south every year during the dry season and during the wet season if there is capacity in the water conservation areas. The Caloosahatchee River receives flow in the dry season every year to prevent saltwater intrusion into the waterway. Both the Caloosahatchee and the St. Lucie may receive lake releases during the wet season in years this is required due to the excess of inflow into the lake.

NOTE: This 10-year average includes significantly wetter years than the 2005 Audubon study which found about 7 feet of water entering the lake on average per year. That study also estimated about 5 feet of water left the lake through evaporation and seepage. This indicates the amount of water leaving the lake from evaporation into the air and percolation in the earth is about the same — enough water to lower the lake level by 5 feet — even in years when there is less rainfall.

Lt. Col. Reynolds explained that the goal of the Comprehensive Everglades Restoration Plan is to increase storage throughout the system and increase the flow south so that no water is sent east to the St. Lucie, more water is sent south and the Caloosahatchee River receives the amount of freshwater flow that it needs.

Mark Perry of Florida Oceanographic Society said more attention should be given to the Lake Okeechobee Watershed Project, which is supposed to attenuate the flow into the lake. He said when dealing with the quality and quantity of the freshwater flow to and from the lake “that timing is always left out of that equation.

“If we could slow that down and attenuate that flow from the north, it needs to continue to flow south during the dry season,” he said.

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