C-44 backflow feeds algae bloom in Lake O

LAKE OKEECHOBEE — Lake Okeechobee area anglers, water managers and environmentalists are keeping a careful watch on algae blooms in the big lake.

National Oceanic and Atmospheric Administration (NOAA) satellite imagery from the week of June 10 shows algae bloom potential in about 60 percent of Lake Okeechobee, with the highest bloom potential on the east side of the lake. (More recent satellite images were obscured by cloud cover.)

At the June 11 meeting of the South Florida Water Management District board, Jacqui Thurlow-Lippisch said she flew recently over the lake and noted a visible algae bloom on the east side. She said there has been a heavy backflow into the lake from the C-44 Canal on the east side of the lake. The freshwater from basin runoff would have been detrimental to the St. Lucie River had it been released east through the St. Lucie Lock, she said. While the nutrient load from the C-44 backflow contributes to the excess nutrient load in the lake, Lake O is already eutrophic, she said. (The C-44 basin runoff is about twice as high in phosphorus as is the lake water on average, according to SFWMD data.)

Water from the C-44 (also known as the St. Lucie Canal) can flow east to the St. Lucie River through the St. Lucie Lock and Dam or back flow west into Lake Okeechobee at Port Mayaca.

For more than a year, with the exception of some small releases to maintain the water level in the canal for navigation, no lake water has flowed into the C-44 Canal.

“Except for some small flows required for maintenance and when boats lock through, the St. Lucie Lock and Dam has been basically closed since March of 2019,” stated Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District, in a June 9 press release. “When we needed to manage levels in the St. Lucie Canal for navigation and flood control, the water went back into the lake through Port Mayaca rather than into the St. Lucie Estuary.”

The corps estimates more than 58,000 acre-feet (about 19 billion gallons) backflowed into Lake Okeechobee through Port Mayaca Lock and Dam (S-308) since March 2019.

“The possibility for opening the S-80 (St. Lucie Lock) to handle rain in the C-44 watershed, while not imminent, grows as the lake level goes up and wet season rains continue to take up storage capacity in South Florida,” said Col. Kelly. “Depending on winds and lake levels, flowing water through Port Mayaca becomes less effective in managing canal levels for flood control.”

The rainy season started in mid-May, according to the water conditions report provided by John Mitnik at the June 11 SFWMD meeting.

On the west side of the lake, since the rains started very little water has been released at Moore Haven. Most of the flow at the Franklin Lock on the Caloosahatchee River is from basin runoff. On June 16, the flow at Moore Haven was zero; the average for the week was 71 cubic feet per second (cfs). On June 16, the backflow into the lake from the C-44 Canal at Port Mayaca was 259 cubic feet per second. The average for the week was 390 cfs.

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