Florida rainy season raises interest in Lake Okeechobee water management

JACKSONVILLE, FL, UNITED STATES

06.09.2020

Story by James Yocum 

U.S. Army Corps of Engineers, Jacksonville District

There appears to be little doubt that rainy season has begun in Florida. Heavy downpours in Mid-May combined with the historically early formation of the third tropical storm of the hurricane season have clearly pointed to the end of the dry season.
But weather is not the only sign of change. Observant local residents have noticed several water control structures in south Florida are open and operating to provide flood control after being shut down following last year's wet season.
And while those heavy rains in May raised levels in Lake Okeechobee, the drier than usual March left the lake with enough capacity to avoid the need for imminent planned releases to the estuaries. In fact, rather than send water to the St. Lucie Estuary, for the past year Lake Okeechobee has taken in vastly more basin runoff from the St. Lucie Canal (C-44) than the small amount that has been allowed to flow through the St. Lucie Lock and Dam (S-80).
“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,” said Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District. “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, roughly 19 billion gallons, flowed into Lake Okeechobee through Port Mayaca Lock and Dam (S-308) since March 2019. For comparison, the Indian River Lagoon-South C-44 Reservoir that is under construction will hold about 50,000 acre feet of water, and the already operational A-1 Flow Equalization Basin holds around 60,000 acre feet.
At some point, the lake will no longer be able to take water from the St. Lucie canal, Kelly said.
“The possibility for opening the S-80 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 Kelly. “Depending on winds and lake levels, flowing water through Port Mayaca becomes less effective in managing canal levels for flood control.”
On the West Coast, the Corps is still operating under the plan to send a minimum 7-day average rate of 650 cubic feet per second (cfs) to the Caloosahatchee estuary, though Lake Okeechobee water has been less and less necessary as the wet season began to provide rain to the area.
“Rainfall in the local basins has provided enough water to the Caloosahatchee Estuary in the past two weeks,” Kelly said. “We are still ready to provide fresh water releases from the lake when necessary, but, at this point, nature is providing enough water without help from us.”
The Corps continues to monitor algal bloom conditions by tracking reports from its partners at the Florida Department of Environmental Protection (FDEP) on bloom potential and sampling results. While bloom potential has been consistently lower on satellite images than what was visible in 2019 and years before, some of that is due to winds and rain over the lake that can temporarily reduce the bloom potential.
“We have seen and reported algae blooms at several of our structures over the past few weeks, and as recently as June 1 when the FDEP tested samples from both Moore Haven and Port Mayaca without observing any cyanotoxins,” Kelly said. “We continue to monitor this closely, because we realize that a few sunny days with less wind can quickly change the bloom conditions on the lake and at our structures.”
Later testing of samples from elsewhere in the lake did show some microcystin. At Culvert 10A, a sample taken June 3 had 27 parts per billion, and on the same day, a sample from the center of the lake showed 8 parts per billion.
The most recent weekly update report from FDEP, for the week ending June 4, shows light to moderate bloom potential on 15 percent of Lake Okeechobee. Clouds partially obscured parts of the Caloosahatchee and St. Lucie rivers and estuaries, but the areas that were visible showed no observable bloom activity. Corps personnel continue to report intermittent visible blooms at all lock structures along the Okeechobee Waterway to FDEP daily.
Visit www.saj.usace.army.mil/Algae/ for more information on algae reports near Jacksonville District facilities.

• Date Taken: 06.09.2020
• Date Posted: 06.10.2020 11:59
• Story ID: 371817
• Location: JACKSONVILLE, FL, US