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What the Rainy Season and La Niña Mean this Year for SWFL

June 25, 2024
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Afternoon rains have made their return to Southwest Florida, offering relief from the sweltering heat that builds up throughout the day during summer in our subtropical climate. 

With the expected shift in the coming months into a La Niña weather pattern, less wind shear in tropical waters makes the formation of large and powerful hurricanes more likely. This shift, along with warming waters in the Gulf and Atlantic, sets the expectation for a season filled with heavy precipitation, a heightened lake stage, and increased basin runoff to the estuary. 

“Increased rainfall has wide-reaching effects on Florida’s ecology, including the health of Lake Okeechobee and the Caloosahatchee River and Estuary,” said SCCF Policy Associate Allie Pecenka.  

Fed by multiple major tributaries, Lake Okeechobee collects runoff from rainfall quickly. This rainfall can be filled with nutrients that make harmful algal blooms on Lake Okeechobee more likely. In addition, if the amount of precipitation is greater than the amount of water lost from the lake through evapotranspiration, it raises the water level in the lake. 

“If the lake stage increases too quickly — due to extended rains, cloud cover, or large storm systems moving over the lake — releases may become necessary,” Pecenka said. “In the event that regulatory releases must be made to the coast while a bloom is active, freshwater laden with cyanobacteria (or blue-green algae) could be transported into our coastal communities and ecosystems.”

Once in our estuary, blue-green algae blooms eventually die from saltwater exposure, leaving nutrients from the bloom available for uptake by other organisms, such as Karenia brevis, which causes red tide.  

“Under the new Lake Okeechobee System Operating Manual (LOSOM), expected to be fully operational in the coming months, these impacts could be lessened, but the timing of any needed releases will still play a major factor in the impacts felt on our coasts,” Pecenka said. 

Even without lake releases, heightened basin runoff from rainfall in areas surrounding the Caloosahatchee River and Estuary can also lead to harmful algal blooms within river canals, and increased water flows can have damaging impacts to the salinity in the estuary.

“Thanks to the work of the U.S. Army Corps of Engineers and stakeholders over the winter, the lake currently has some capacity to absorb rainy season impacts, but it will remain a balancing act until the storms are passed,” Pecenka said. 


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