LAKE OKEECHOBEE – Is the dry season over?
After weeks of gradual recession during the dry season, Lake Okeechobee’s level went up last week thanks to heavy rainfall in the Lake Okeechobee watershed.
It’s too soon to tell what may happen in the month of May, according to Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District.
The Big O was 14.25 feet above sea level on April 22.
The switch from recession to rising water levels is the reason the corps will increase releases from the Lake to the Caloosahatchee River from 1,000 cubic feet per second to 2,000 cfs starting Saturday, April 24.
The Caloosahatchee River needs some freshwater flow from the lake in the dry season. Flows below 450 cfs are deemed harmful because the salinity levels rise too high. Flows above 2,800 cfs are considered harmful because the salinity levels drop too low.
Rainfall in the Caloosahatchee basin could result in higher releases than the 2,000 cfs target to the Caloosahatchee River, due to local basin runoff. The Franklin Lock is 43.4 miles from the Moore Haven Lock, where water from the lake enters the river. If there is enough basin runoff for flow to meet the target flow at the Franklin Lock, no lake water is released at Moore Haven.
For example, for daily average for April 21, there was no flow from the lake at Moore Haven, but flow at the Franklin Lock was 1,911 cfs -- all from local basin runoff. For the seven day period ending April 22, the average flow from the lake at Moore Haven was 683 cfs and the flow at the Franklin Lock was 1,132 cfs.
No water will be released at Port Mayaca to the St. Lucie Canal.
“We were seeing a recession week of close to a foot per month,” Kelly explained. Rainfall over the past two weeks has stopped the recession and caused the lake level to creep upward.
The lake is 2.8 feet higher than it was this time last year, he said.
“May is one of the toughest months in terms of prediction,” Kelly continued. Historically, some years the rainy season has started in May. “It is not unlikely we may have seen the lowest point on the lake this year.
“May is a huge wild card.
“We have to anticipate altering operations,” said the colonel. He will hold weekly media briefings starting next week.
Even with the rise in the lake, the corps is still using operational flexibility to balance the needs of the whole system. Under current conditions, the Lake Okeechobee Operation Schedule (LORS) calls for releases 3,000 cfs to the Caloosahatchee and 1,170 cfs to the St. Lucie. “We’re increasing flow to the Caloosahatchee to 2,000 cfs and holding zero to the St. Lucie,” said Kelly.
“We are hoping for greater recession rates,” he explained.
“We remain focused on the lake level, and the lake level is certainly higher than we would like it to be,” Kelly said. “We would definitely like to see the lake lower than 14 feet by the time the hurricane season starts in earnest.
“Hopefully Mother Nature supports that effort,” he said.
“If the lake is higher than we want it to be, that will put us in a position where we need to do lake releases earlier in the season,” Kelly continued.
“I anticipate, depending on where the lake ends up when the rainy season kicks into full gear, releases earlier in the season than we did last year,” Kelly said.
Meanwhile, the corps is increasing flow south as much as possible.
They are also monitoring potential algal blooms. Florida Department of Environmental Protection (FDEP) will increase monitoring of the lake for algae as they did last summer.
Kelly said they have seen a few small pockets of algae in places where the water is still such as the water control structure at Port Mayaca. Microcystis aeruginosa was the dominant cynaobacteria in the sample taken April 19. The microcystin toxin level in the sample was 120 micrograms per liter. The World Health Organization considers levels above 8 micrograms per liter to unsafe for human recreational contact (swimming).
“When we look at the lake holistically, it still does not look like there is any significant lake coverage,” said Kelly. The satellite imagery from the National Oceanic and Atmospheric Administration (NOAA) is still looking good, he continued.
“Florida Department of Health has initiated some signage identifying algae risks in some areas,” he said.
Pockets of algae and/or cyanobacteria (sometimes called blue green algae) are normal for this time of year, he said. “We are paying close attention.”