Lake O sediment study releases scheduled for April 20-21

U.S. Army Corps of Engineers Jacksonville District
Published April 19, 2021

The U.S. Army Corps of Engineers (USACE) Jacksonville District will execute a temporary, minor deviation to the Lake Okeechobee Regulation Schedule April 20 and 21 as part of the ongoing study by the South Florida Water Management District (SFWMD) and U.S. Geological Survey (USGS) to find ways to indirectly measure sediment and nutrients transported from the lake to the estuaries.

The deviation will allow up to 5,000 cubic feet per second (cfs) flow from structures for short periods of time for up to 8 hours on April 20 at the Moore Haven Lock and Dam (S-77) and April 21 at the Port Mayaca Lock and Dam (S-308).

USACE executed a similar deviation in February to support the same study and expects to do so again in May. This study will help develop a better understanding of how different release schedules may influence nutrient/sediment loading to the estuaries.

While the deviation allows for up 5,000 cfs releases in short bursts, it is expected that the flows will be closer to 500 cfs. Weather permitting, USACE will attempt to draw down the St. Lucie Canal (C-44) prior to the test to minimize the potential for opening the St. Lucie Lock and Dam (S-80). There is still a possibility that the S-80 may be opened to accommodate the increased water resulting from the testing or to maintain canal levels from local runoff in the case of heavy rains in the basin. The maximum effect of these releases on Lake Okeechobee stage is less than ½ inch.

“We are excited to find out what USGS and SFWMD learn from this study as they work to better understand the flow of sediment from the lake and into the estuaries,” said Col. Andrew Kelly, Jacksonville District commander. “Finding alternative methods to measure how much sediment moves from the lake into the estuaries is important as we attempt to better understand the system and its impacts on coastal communities.”

USACE is aware of FDEP test results of algae found on the lake side of the S-308 that contained microcystin at 22 parts per billion, which is above the levels the Environmental Protection Agency recommends for recreational use. Every effort will be made to reduce the need to open the S-80 during the eight-hour period when water may be released from S-308 . The maximum possible impact on the lake level is expected to be less than ½ inch.

Jim Yocum

Release no. 21-030