JACKSONVILLE – Releases from lake Okeechobee to the Caloosahatchee River will increase from 1,000 cubic feet per second (cfs) to 2,000 cfs starting on or around Feb. 6, according to Commander of the U.S. Army Corps of Engineers Jacksonville District Col. Andrew Kelly.
On Thursday, Lake Okeechobee was 15.57 feet, Kelly explained in a media conference call. The ecologically optimal range for the big lake varies from 12.5 feet at the start of the wet season (around June 1) to 15.5 feet at the start of the dry season (around Dec 1).
“We’re pivoting from a recovery into our dry season strategy,” he said.
“Utilizing the HAB (Harmful Algal Bloom) deviation, we are going to start the dry season a little bit aggressive,” he said. The HAB deviation allows the corps to release lake water in the colder months when there is less risk of HABs in order to reduce the need for releases in the summer months with the HAB risk is higher.
“We are in a situation where the lake is still high,” he said. Kelly explained this is the second highest the lake level has been at this time of year since the Lake Okeechobee Regulation Schedule was implemented in 2008.
He said without action now, the lake will be higher than desirable – in the 14 to 15 feet range – when the wet season starts.
Since 2008, there have been wet season lake releases to the coastal estuaries every year the lake was above 14 feet on June 1.
“We’ll start by pushing a little bit more water to the west at about 2,000 cfs to the Caloosahatchee starting on or about Feb. 6,” Kelly said. He said between now and Feb. 6, corps officials will work with estuary scientists to make sure they get the pulse releases right. The 2,000 cfs releases, which will be measured at the Franklin Lock, will include local basin runoff mixed with lake water. The lake water enters the Caloosahatchee at the Moore Haven Lock, which is 43.4 miles from Franklin Lock.
Kelly said they will also push lake water south if they can.
He said they hope the predicted La Niña will mean the dry season will be drier than average which would increase evapotranspiration from the lake into the atmosphere. Evapotranspiration is the combination evaporation of water into the air from the surface and transpiration of water into the air by plants.
The whole system is full, but the water levels are starting to recede, Kelly said. “At this point, we’re pretty mindful of the recession rates throughout the entire season from the Kissimmee to the lake to the Everglades.”
Kelly said 2,000 cfs is at the high end of the good range for the Caloosahatchee River. The Caloosahatchee needs freshwater releases from Lake Okeechobee during the dry season to maintain optimal salinity rates in the estuaries. Flows below 450 cfs (measured at the Franklin Lock) are considered harmful as the salinity levels in the estuaries are too high. Flows higher than 2,800 cfs are also considered harmful because the salinity levels drop too low. The “Goldilocks” just-right freshwater flow at the Franklin Lock advocated by estuary scientists is around 1,000 cfs.
“Typically for this time of year, we’ve been pushing about 1,000 cfs,” said Kelly.
The increase from 1,000 cfs to 2,000 is about 538 million gallons per day or about 3.76 billion gallons per week. One inch on Lake Okeechobee is about 12 billion gallons of water, so the additional flow to the Caloosahatchee over three weeks would represent a little less than an inch on Lake Okeechobee.
Kelly said a lot, as usual, depends on Mother Nature.
“Right now we are just trying to predict the climate months in advance which is always exceptionally challenging,” he said.
“If Mother Nature supports us with a little drier season than normal, we hope to be at a better place when hurricane season starts," he said. The goal in all of this is getting the recession rate right to better prepare for hurricane season. Mother Nature cooperating means no huge deluge of rain in the February/March time frame, he added. “If all of that works, we’ll see an increase in evapotranspiration.”
He said they hope to avoid high volume releases at the end of the summer when it is hot and there is more potential for algal blooms.
South of the lake, the water conservation areas (WCAs) are still above schedule, but the recession rates are good, Kelly said. He said this week they are ending the deviation which allowed them to release water from WCA-3A under the Tamiami Trail. Without the deviation, flow through those structures under the trail would have been closed to protect the nesting grounds of the Cape Sable Seaside Sparrow.
WCA-3A is still half a foot high, he said, but the trend lines are good. “It’s coming down pretty quick.” He said 56% of the tree islands in WCA-3A are still inundated with water. “Because of (Tropical Storm) Eta, they have been inundated much more than is preferable,” he said. “With the recession right now more and more tree islands are getting out of the inundation.”
“The steps we are taking right now and being aggressive in February creates a better likelihood we will be in a better place,” he said. When the lake is high at the start of hurricane season, it becomes more likely the corps will be forced to release water from the lake later in the wet season. “Without our help, without aggressive action, it’s likely it will be around the 14 foot range,” he said.
In related matters, Kelly said construction on the Everglades Agricultural Area (EAA) reservoir is on track and they hope to award the first construction contract by the end of the calendar year.
Work also continues on the Lake Okeechobee System Operating Manual (LOSOM), which will replace LORS when the dike repairs are finished in 2022. Kelly said there has been tremendous stakeholder input on LOSOM. They have the options narrowed down to 13 plans which they will run through extensive computer modeling.
“We are shifting gears and looking forward to a new system operating manual in 2022,” he said.