Another change in plans for Lake O project: Sediment study postponed

November 12, 2021
By Staff Report

The U.S. Army Corps of Engineers Jacksonville District will delay the previously announced sediment study scheduled for Nov. 9 after heavy rains across Florida led to heavier local basin runoff in the Caloosahatchee River Estuary than originally forecast.

The new date has not been finalized for the one-day deviation from the Lake Okeechobee Regulation Schedule that is part of an ongoing sediment study by the South Florida Water Management District and the U.S. Geological Survey to find ways to predict sediment and nutrient transportation from the lake to the estuaries.

Heavy rainfall across the state resulted in Lake Okeechobee rising from 15.83 feet on November 4 to 16.02 feet on November 7, a rise of more than two inches in three days. With local basin runoff in the Caloosahatchee River Estuary at times exceeding the current 2,000 cubic feet per second target for ecological releases, additional releases for this study would likely have led to releases in excess of the ecological envelope that is best for the health of the estuary.

“This is a very important study, but our partners at SFWMD and USGS asked to postpone the releases required for the research while the system deals with the water from this recent storm,” said Col. James Booth, commander of the Jacksonville District. “We still have several weeks left in hurricane season, and even normal storms can quickly change how we manage the lake. For now we are in a pretty good place on Lake Okeechobee and don’t anticipate any immediate releases beyond the current schedule.” 

The original plan was to execute two directives on November 6 – the first was an initial change from the current 1,000 cubic feet per second (cfs) to the Caloosahatchee Estuary to 2,000 cfs to support estuary ecology. The second was a one-day deviation that was scheduled to begin November 9 as part of the ongoing sediment study.

The deviation to the Lake Okeechobee Regulation Schedule that was scheduled is part of the ongoing study by the SFWMD and USGS to find ways to predict sediment and nutrients transportation from the lake to the estuaries. 

The deviation will allow up to 6,000 cubic feet per second (cfs) flow for short periods of time for up to eight hours at the Julian Keen Jr. Lock and Dam (S-77). USACE executed a similar deviation in April to support the same study. 

While the deviation allows for up 6,000 cfs releases in short durations, it is expected that the daily average flows will be closer to 1,600 cfs at S-77. Downstream flows at W.P. Franklin Lock and Dam (S-79) are expected to be elevated due to these releases for Nov. 9. The maximum effect of these releases on Lake Okeechobee stage is less than ¼ inch. 

In a press release USACE said they are not aware of any FDEP test results of algae found at or near S-77 or along the C-43 in the recent weeks, but any more sampling and observations of algae will be taken into consideration. When the sediment study is finally executed, the deviation will allow up to 6,000 cubic feet per second (cfs) flow for short periods of time for up to eight hours at the Julian Keen Jr. Lock and Dam (S-77). USACE executed a similar deviation in April to support the same study. 

There are no plans to release lake water from the St. Lucie Lock and Dam (S-80) at this point. 

“Right now, the lake is in a good position, and after talking with stakeholders, we believe these releases will help maintain salinity levels in the estuary as dry season rain patterns reduce fresh water flows,” said Lt. Col. Todd Polk, Jacksonville District Deputy Commander for South Florida. “These flows also have the potential to kick start dry season lake recession that will help get the lake back into its ecological band.”

While the deviation allows for up 6,000 cfs releases in short durations, it is expected that the daily average flows will be closer to 1,600 cfs at S-77. Downstream flows at W.P. Franklin Lock and Dam (S-79) are expected to be elevated due to these releases for Nov. 9. The maximum effect of these releases on Lake Okeechobee stage is less than ¼ inch.