Heavy rainfall predicted south of Lake O this weekend

Posted 3/22/24

With as much as 7 inches of rain expected south of Lake Okeechobee this weekend the “dry” season...

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Heavy rainfall predicted south of Lake O this weekend


With as much as 7 inches of rain expected south of Lake Okeechobee this weekend the “dry” season continues to be very wet for the Central Everglades.

That’s bad news for the Water Conservation Areas (WCAs), which are already above schedule. The WCAs are south of the Everglades Agricultural Area, which is south of Lake Okeechobee. The EAA Stormwater Treatment Areas (STAs), which flow into the WCAs, are within the EAA.

Meanwhile, the S-12 A and B water control structures that allow flow south from Water Conservation Area (WCA) 3A under the Tamiami Trail are scheduled to be closed at the end of March.

In a March 22 media conference call, Major Cory Bell, deputy commander for the U.S. Army Corps of Engineers (USACE) Jacksonville District, said USACE started releases from Lake Okeechobee on Feb. 17, with up to 4,000 cubic feet of water released west through the Julian Keen Jr. Lock at Moore Haven and up to 1,800 cfs releases to the St. Lucie River through the St. Lucie Lock.   As much water as the system can take is also released south, but heavy rainfall south of the lake has taken up much of the capacity in the STAs and WCAs. Flow south is also blocked by the East Coast Protection Levee and the Tamiami Trail. 

Lake Okeechobee has been high since 2022, when USACE and South Florida Water Management District, used massive pumps to speed water down the Kissimmee Chain of Lakes into the Kissimmee River and Lake Okeechobee, saving about 10,000 homes in the Orlando/Kissimmee area from flooding from Hurricane Ian. This caused Lake O to rise several feet. Although the Lake Okeechobee Regulation Schedule of 2008 (LORS-08) called for lake releases east and west during the 2022-2023 dry season, the USACE opted to prioritize the health of the coastal estuaries and use the “operational flexibility” in the schedule to “bank” about 2 feet of extra water in the Big O. They limited releases to the beneficial freshwater flow the Caloosahatchee River needs in the dry season.

A normal dry season lowers the lake about 3 feet via evapotranspiration (a combination of evaporation and plant transpiration) and flow south for irrigation and coastal water supply. The rainy El Nino “dry” season this year has kept the lake level up due to continued rainfall into the lake, lower than normal evapotranspiration due to cloudy weather and less need for water supply south of Lake O as direct rainfall has kept the crops watered and the urban water supply areas filled.

The coastal releases east and west which began Feb. 17 helped start the lake’s recession, Bell said.

“Water levels must come down before the start of the wet season for both the ecology of the lake and safety of the citizens,” Bell explained.

Bell said the lake releases, which lower the salinity levels in the Caloosahatchee and St. Lucie estuaries, are stressful to the estuaries. To protect the salinity levels in the estuaries, USACE plans to pause lake releases for a two-week rest period starting March 29.

Due to the Endangered Species Act, the S-12 A and B water control structures are usually closed nine months of the year to protect the nesting grounds of a subpopulation of the Cape Sable Seaside Sparrow. This year, USACE received a deviation that allowed them to keep the water flowing under the Tamiami Trail longer. That deviation ends at the end of the month.

On the media call, a reporter asked: With the lake already high, could it handle the flow from another Hurricane Ian?

“That’s a loaded question. Hurricane prediction is hard,” countered Bell.

“We cannot control Mother Nature,” he said. “ We continue to focus on moving water throughout the interconnected system.”

On March 22, Lake O was 15.55 feet above sea level. The lake’s ecological envelope ranges from 12 feet to 15.5 feet. Ideally, the lake should be 12 feet or below at the start of the wet season in June and around 15.5 feet at the start of the dry season in November. On average, Lake O receives enough flow to rise 3 to 4 feet during the wet season (between June and November), even without a major hurricane.

The Herbert Hoover Dike, which surrounds Lake Okeechobee, was built for flood control after thousands of people died in the hurricanes of 1926 and 1928. When the lake is at 15.5 feet, the marshes around the edges of the dike are inundated with water. As the lake level rises, the water stacks up on the side of the dike. Water levels above 15.5 feet are damaging to the lake’s ecology.

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