Posted on April 22, 2021
Lake Okeechobee discharges will resume in short bursts over two days this week so government scientists can study the flow of sediment that pollutes coastal estuaries.
Tuesday’s release from the Moore Haven Lock & Dam to the Caloosahatchee River does not concern the Treasure Coast, but Wednesday’s release from the Port Mayaca Lock & Dam does because of highly toxic algae documented there in the past week.
If the Army Corps of Engineers has to open the St. Lucie Lock & Dam during the study, the algae could make its way from the lake to the C-44 Canal to the St. Lucie River.
To minimize the potential of that happening, the Corps will try to lower the level in the C-44 Canal, according to a news release the agency issued Monday.
The cyanobacteria, more commonly called blue-green algae, contained 22 parts per billion of a toxin called microcystin on April 12, according to the Florida Department of Environmental Protection. At 8 parts per billion makes water dangerous to touch, ingest or inhale for people, pets and wildlife, according to the Environmental Protection Agency.
Microcystin has been linked to neurological diseases such as Alzheimer’s, Parkinson’s and Lou Gehrig’s.
The Corps said it expects to release 500 cubic feet per second of Lake O water from the Port Mayaca floodgates, but could release as much as 5,000 cubic feet per second. TCPalm cannot convert those amounts into layman’s terms without knowing the volume, duration and frequency of the short bursts.
The Corps conducted similar short-burst discharges for the sediment study in February and plans to again in May.
“Every effort will be made to reduce the need to open the S-80 [St. Lucie Lock & Dam],” the Corps’ news release states. “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.”
Who is conducting the sediment study and why?
The sediment study is being conducted by the U.S. Geological Survey and the South Florida Water Management District; the latter ponied up $1 million through 2024.
They will study how much sediment is carried in discharged lake water by varying the volume and duration to see if there’s an optimal scenario to reduce sediment-loading.
They will not study what pollutes the sediment or where it comes from. Most of it comes from nutrients in fertilizers, such as nitrogen and phosphorus in farm and urban stormwater runoff, that feed toxic algae blooms in the coastal estuaries.
Since 2009, nearly 226,000 tons of sediment have moved from the lake to the Caloosahatchee and St. Lucie estuaries, according to Mark Perry, executive director of the Florida Oceanographic Society, a research and education nonprofit in Stuart.
“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, the Corps’ Florida 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.”
The discharges will reduce Lake O’s level by less than a ½ inch, the Corps said.
The lake’s level was 14 feet, 2 inches above sea level Monday, 1 foot, 7 inches more than the 12½ feet the Corps wants it at by June 1 to make room for heavy summer rains.
