JACKSONVILLE – The U.S. Army Corps of Engineers will stop sending water from Lake Okeechobee to the St. Lucie and will decrease flow to the Caloosahatchee to the beneficial flow of 1,000 cfs, starting April 10.
Lake Okeechobee was 14.19 feet above sea level on Friday, a quarter of a foot lower than last week, almost 1 foot lower than 30 days ago, and 2.5 feet higher than this day last year, Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District, explained in an April 9 media call.
With the exception of evaporation, most of the water leaving the lake is going south, he said.
“We have put an end to the harmful algal bloom (HAB) deviation,” said Kelly. The deviation allows the corps to release water east and west when there are no HABs on the lake, in order to reduce the chance lake releases will be required in the hotter summer months when HABs are more common. He said due to the recession rate of the lake, the deviation is no longer needed. The algal potential on the lake remains low, Kelly explained.
“What we’re seeing is pretty normal for this time of year, not setting off any alarm bells,” he said. Algae and cyanobacteria (sometimes called blue green algae) is a natural part of the ecosystem. Algae and cyanobacteria are always in the lake, even when the microscopic organisms are not visible to the human eye.
Kelly said as the wet season starts, Florida Department of Environmental Protection and the South Florida Water Management District will probably increase the algae monitoring as they did last wet season. He said the algae task force, scientists, and academic institutions are trying to get a better understanding of the science of algae and working to develop tools to better predict what sometimes causes cyanobacteria to produce toxins.
“Nature has taken over. We’re basically done with the HAB deviation,” he added.
Kelly said the corps is working with the scientists who study the Caloosahatchee River to maintain the optimal freshwater flow to the estuaries. During the dry season the river needs some freshwater from the lake to keep salinity levels in balance. Flows below 450 cfs (measured at the Franklin Lock) are considered harmful as the salinity levels in the estuaries are too high. Flows higher than 2,800 cfs are also considered harmful because the salinity levels drop too low. The ideal salinity levels vary for different parts of the estuaries. “We will work with the scientists to give the Caloosahatchee the freshwater it needs to stay healthy,” said Kelly.
“We are happy the lake is getting lower. We anticipate still somewhere in the 13 to 13.5 ft range when the rainy season starts,” said Kelly. The corps may use HAB deviations to release water later in the year – if there are no HABs on the lake – to prevent the need for releases in the fall.
South of Lake O, freshwater is moving to the stormwater treatment areas (STAs) and through the system to Florida Bay, he said.
“This year we got 2 million acre feet of water out of the Water Conservation Areas (WCAs) and about 1.8 million acre feet to Everglades National Park,” he explained.
“We are seeing good signs our operating plan and our deliveries to Florida Bay are working very well. Unlike last year where salinities were getting higher than desired in Florida Bay, we’re seeing much better effects on Florida Bay,” Kelly said.
System-wide, it’s going to be a great year for wading birds, he predicted, noting the environmental indicators are looking good.
“What we’re seeing on the ground is increasing availability of sending water south,” said Kelly. “We’re going to send as much water as we can to the south. That’s going to be the main tool that we use to drive the lake down before rainy season starts.
For the seven day average ending Friday, about 2,248 cfs moved south from the lake. Some of that water is used for agricultural irrigation and urban water supply. Some water goes to the Stormwater Treatment Areas (STAs) to be cleaned before it is sent south to Everglades National Park. Kelly said on Friday about 1,150 cfs of clean freshwater was moving under the Tamiami Trail to Everglades National Park.
Kelly said the recession rate matters because they try to keep the lake from dropping too quickly to protect the ecosystem for the endangered species that live in the lake’s marshes. A slow recession of lake level is natural during the dry season.
For example, Everglades Snail Kites nest at the water line, Kelly said. They like their nests there right on the water. “If they build the nest and the water recedes, they are left high and dry,” and their nests are more vulnerable to predators, he explained.
The advanced releases began in February as part of a planned deviation approved in September 2020 to reduce the risk of lake releases when harmful algal blooms are more likely to be present this summer. The deviation released about 91,000 more acre feet of water from the lake than would have normally been released under the Lake Okeechobee Regulation Schedule (LORS).
Use of the deviation was limited by a requirement to maintain a recession rate of no more than 0.5 feet per month to avoid harm to nesting birds.
USACE operators continue to monitor for algae at Corps of Engineer structures and facilities and report any visible algae to Florida Department of Environmental Protection for testing.