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The Caloosahatchee River is the largest river in Southwest Florida and stretches from Lake Okeechobee to the Gulf of Mexico. Chad Gillis/News-Press

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What's been described as a dark wall of freshwater is moving miles into the Gulf of Mexico, and that plume could grow larger through the weekend as a tropical disturbance moves into the area. 

The National Weather Service issued a flood watch for Lee County this weekend, which will only add to the damage the Caloosahatchee River and its estuary have experienced this year. 

The combination of heavy rainfall, stormwater runoff and Lake Okeechobee releases have driven freshwater miles into the Gulf of Mexico and has made the Caloosahatchee estuary virtually disappear. 

"You can see the movement of dark water through the passes: Boca Grande, Blind Pass," said John Cassani, with the watchdog group Calusa Waterkeeper. "You can see the dark water moving out into the Gulf and now it looks like it’s miles offshore."

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There's still water in the river, but the critters that form that base of the once-productive estuary – creatures such as oysters, crabs and baitfish – are dying off or simply leaving the area due to a lack of salinity. 

The critical mixture of salt and freshwater, or brackish water is supposed to reach up to the Franklin Lock and Dam in the Olga area, but those water conditions are now offshore in the Gulf of Mexico. 

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Fish are also dying due to a lack of oxygen in the water. Called hypoxia, the lack of oxygen is also stretching into the Gulf. 

"I think this is the lowest reading we’ve gotten," said Rick Bartleson, a water quality scientist at the Sanibel-Captiva Conservation Foundation on Sanibel. "Oxygen doesn’t get down from the surface to the bottom because the water is not mixing. It’s like oil and water. The freshwater just sits mainly on the saltier, denser water." 

The station Bartleson took his most recent measures from is about a mile off Fort Myers Beach. 

He said the freshwater extends about 8 feet below the surface, blocking oxygen that would normally mix with the saltwater. 

Flows at the Franklin Lock and Dam have been as high as 10,000 cubic feet per second, or more than 6 billion gallons per day, in recent weeks, which is three times the amount of freshwater required to damage the estuary. 

Those flows aren't expected to subside anytime soon. Lake Okeechobee's surface is more than 16 feet above sea level, and the lake can rise several feet if enough rain falls in the right places. 

Army Corps of Engineers protocols say the surface of the lake should be kept between 12.5 and 15.5 feet above sea level to protected tens of thousands of lives living south of the lake while also providing drinking water for millions of Floridians and large farming operations. 

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The Corps stopped releases after Hurricane Irma hit but soon resumed them to help drain the lake. 

The News-Press reached out to the Army Corps several times this week, but the agency did not respond to phone calls or return messages. 

Records obtained by The News-Press say the Army Corps will meet again on Tuesday to discuss water releases. 

"It's not all about releases but that's a big part of it," Cassani said of problems in the estuary. "We've basically altered the salinity gradient so that there's really not a salinity gradient (in the estuary)." 

Connect with this reporter: Chad Gillis on Twitter

 

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