Corps: Lake Okeechobee could rise 10 inches from Tropical Storm Eta

Posted 11/6/20

Lake Okeechobee could rise as much as 10 inches if Tropical Storm Eta does not turn farther west...

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Corps: Lake Okeechobee could rise 10 inches from Tropical Storm Eta


JACKSONVILLE — Lake Okeechobee could rise as much as 10 inches if Tropical Storm Eta does not turn farther west, according to information shared by U.S. Army Corps of Engineers Jacksonville Commander Col. Andrew Kelly in a Nov. 6 media briefing. He said the corps expects significant rainfall directly into the lake as well as south of the lake.

Last week, Kelly indicated the corps was planning to phase out releases of lake water to the east and west, but Eta changed that plan. On Nov. 6, Lake Okeechobee was at 16.10 feet above sea level. The Lake Okeechobee Regulation Schedule (LORS) sets 15.5 feet as the target high lake level and 12.5 feet as the target low lake level.

“We have done a pretty good job overall of stemming the rise of Lake Okeechobee,” said Kelly, “and then Eta came.”

“The decision this week was predominantly based on what we anticipate the effects of Eta (will be) right now,” he continued. “We are looking at the potential for up to 10 inches of rain in the southern end of the system and up to about a 10-inch rise on Lake Okeechobee, depending on where the precipitation lands and whether Eta takes an expected turn to the west,” he said.

With that in mind, the corps will continue to release water from the lake at an average 4,000 cubic feet per second (cfs) at Moore Haven, and will continue — as much as possible — to release water through the St. Lucie Lock at an average rate of 1,800 cfs.

Water released through the St. Lucie Lock is a mixture of lake water and local basin runoff. The St. Lucie Lock is 23.9 miles from Port Mayaca, where the St. Lucie Canal connects to Lake Okeechobee. Releases started on Oct. 14. For the first week, the seven day average at Port Mayaca was only 331 cfs. For the second week of releases, the average flow at Port Mayaca was 906 cfs. For the third week (through Nov. 4), the average flow at Port Mayaca was 1,252 cfs. On Nov. 5, flow at Port Mayaca averaged 1,265 cfs.

Col. Kelly said that, due to the tides and local basin runoff, “the likelihood for reaching that 1,800 cfs at St. Lucie is probably not going to happen.

“We will manage the C-44 (St. Lucie) Canal appropriately,” he explained. “We will likely shut down S-308 (the Port Mayaca Lock) and not send additional water that will exacerbate any basin runoff.”

He said the operators on the C-44 Canal “do what they do best” to keep the canal levels low enough to prevent flooding in the local basin.

“The lake releases take a back seat,” Kelly explained. “We do not force water out of the lake when the canal is high. They’ve got to work the canal to manage flood control.”

The colonel said depending on how much rain Eta dumps and where, they may also adjust releases to the Caloosahatchee. “We will have to play that one by ear,” he added.

South of the lake, the corps and South Florida Water Management District are taking measures to try to move water out of the system with the expectation of significant rainfall coming from Eta, he said. No water from the lake will released south as they try to lower the levels in the water conservation areas (WCAs), with particular concern for WCA-3A, which is already more than a foot above its regulation schedule, he explained.

Earlier this week, the corps executed an emergency deviation to open some structures on southwestern side of WCA-3A in an effort to get additional water out. Due to flood control problems in other areas, they could not move as much water as they would like, he added. The S-12 gates were supposed to close on Nov. 1 (to protect the nesting grounds of the Cape Sable seaside sparrow), and the deviation allowed the corps to keep moving water under the Tamiami Trail.

“Every single drop of water we can get out of there is good right now,” Kelly said. “It’s just really high right now and has been for a while.” He said they will continue to flow water from 3-A to allow area south of the lake to dry out prior to the rainfall event.

He said decisions will be made based on current conditions and forecasts as the tropical storm approaches.

“We’ll know Monday, Tuesday or Wednesday what the rainfall impact is,” he said. “We currently expect some significant fall directly over the lake.” Rainfall north of the lake could also cause the lake to rise.

“If we get a 5- to 10-inch rise in Lake Okeechobee, this release schedule could extend for another month,” said Kelly, adding it is “way too soon” to make a decision on that.

“If we get a full 10-inch rise, we will ramp up (releases) as it gets closer to the 17-foot level,” he explained. As the lake rises, the corps also increases dike inspections.

“We are doing routine inspections with no indicators of any problems right now,” he said. “Once lake gets closer to 17 feet, we increase that out of an abundance of caution.”

He said the dike repairs, scheduled for completion in 2022, have made the dike safer. “We learned from the potential of Dorian that all of the repairs and all of the rehabilitation that have been going for the dike for years have helped,” he said. Large culvert structures have been completed. A significant amount of the cutoff wall is now done. He explained that evacuations of communities south of the lake in anticipation of storms in previous years had to do with wind speeds.

“A lot of what happens on Lake Okeechobee is based on wind,” he said. Because the big lake is shallow, wind can push the water from one end to the other, stacking it up against the dike. “The lake kind of sloshes very significantly due to its shallowness,” he said.

“If this becomes a non-event, we could very, very easily and very, very quickly switch back to our original plan to try to reduce the discharges,” Kelly said. The decision will probably come on Tuesday or Wednesday, unless Eta becomes “a non-event.”

He said the dry season strategy will depend on the lake level when the dry season starts.

“Certainly we won’t start the dry season where we started the dry season last year, where we were in full on conservation mode,” he explained.

“When we are officially out of an active hurricane season in the Atlantic and in the Gulf, we will switch and decide how to manage in the dry season,” Kelly said. “We have to figure out a long-term solution of how to manage the dry season. We will end the releases as soon as we can.”

He said the effects of Eta, “and whether we are sitting closer to 17 or closer to 16, will have an effect on our strategy out of the gate.”

There have been no concerns so far about algae in the lake releases, he said. The wind, rain and cloud cover and the cooler temperatures have reduced the algae bloom potential on the lake. He said Florida Department of Environmental Protection has ramped up additional monitoring on both sides of the lake since the releases started. He said they have mitigating strategies ready should algae be detected, but so far they have not needed mitigation.

If the western basin gets significantly more rainfall that expected, flow at Moore Haven could be adjusted as well, Kelly stated.

“We’re in a close fight as far as getting to the end of the wet season, getting to the end of the hurricane season,” he said.

eta, storm, lake okeechobee, water levels