October 17, 2017
Lake O releases will continue, along with damage to Caloosahatchee River estuary
By: Chad Gillis
Water is flowing from Lake Okeechobee to the Caloosahatchee River as fast as gravity will allow, and the extreme freshwater releases are expected to continue for several weeks.
The surface of Lake Okeechobee was 17.2 feet above sea level Tuesday, and Army Corps of Engineer protocols say the lake should be kept below 15.5 feet above sea level or below to protect tens of thousands of residents and massive farm lands south of the lake.
How fast will the lake recede?
"As a rule of thumb during dry season (which starts Nov. 1) a half-a-foot a month is a very reasonable recession rate," said John Campbell, with the Army Corps' Jacksonville office. "Sometimes it will get up to three-quarters (of a foot), but it takes quite a while to get water off Lake Okeechobee."
Campbell said the Corps will likely ease the releases before the lake gets to 15.5 feet as long as there are no more impacts from hurricanes, tropical storms or other large rain events.
"But we need to get it lower than it is today," Campbell said. "As long as we’re doing daily inspections on the dike, it’s not responsible to shut down releases."
The flow rate at the Franklin Lock and Dam was above 10,000 cubic feet per second (about 6.5 billion gallons a day) Tuesday and has been as high as 28,000 cubic feet since Hurricane Irma made landfall on Sept. 10.
About 70 percent of the water flowing through the lock is from Lake Okeechobee at this point, although as much as 21,000 cubic feet per second came from the river's watershed in the aftermath of Irma.
These high volumes over an extended period of time can cause seagrass and oyster bed deaths as well as fish kills and bacteria and algae outbreaks.
"I think we’re past that threshold where damage has become an ongoing thing," said John Cassani, with Calusa Waterkeeper. "You start crunching the numbers and it’s an enormous impact. We’re not just changing salinity."
The nutrient loads and other pollutants, he said, "are going to not just the estuaries, but also nearshore waters and the Gulf of Mexico."
If that weren't enough stress on the estuary, an algae bloom may be on the horizon due to the volume of nutrients flowing to the coast, Cassani and others worry.
A mixture of fresh and saltwater are needed to create an estuary, areas that serve as the birthing grounds for the base of the marine food chain.
The Caloosahatchee River estuary is practically non-existent right now because freshwater flows are pushing plumes of water several miles into the Gulf of Mexico.
It's an unnatural process that started about a century ago, when the Caloosahatchee and St. Lucie rivers were connected to Lake Okeechobee to drain the historic Everglades for development and farming.
Today the Caloosahatchee often needs water from Lake Okeechobee because the watershed has been developed.
Water that once sat on the landscape and slowly rolled into the river during the dry season is now sent to the Gulf as fast as possible. Lake water is needed during extremely dry times to mimic those historic conditions.
But these days there's too much water. Harm to the estuary starts once levels reach 2,800 cubic feet per second and above.
The longer the duration of the releases and storm water runoff, the higher the impacts to the base of the marine food chain.
"This is kind of like a triple whammy because you have at tremendous amount of freshwater so you don’t really have an estuary mixing zone," said Rae Ann Wessel, with the Sanibel-Captiva Conservation Foundation. "When we have this very high colored water with dissolved nutrients in it, it obstructs light from getting to the oxygen producers in the water column and you’re compounding the problem. The duration is the other whammy and we're not talking about several hours or even days, this could be weeks to months."
Campbell said there's no timetable for when releases will ease.
"It depends on how much rain continues to fall," he said. "It turned dry very, very quickly post (Hurricane) Matthew to a fairly significant drought for several months, so that has not occurred through the post Irma time frame. We’ve had fairly frequent rain events (since Irma)."