Lake level rising, no algal blooms reported

Recent rainfall has caused Lake Okeechobee to rise. While the lake has “potential” for blue green algal blooms, there were no reports of algal blooms last week. Florida Department of Environmental Protection (FDEP) tests of water in Lake Okeechobee found no toxins or barely detectable low levels (within the standard allowed for drinking water.)

The lake rose more than half a foot over the past week. On Aug. 12, the lake level was 12.3 feet above sea level; on Aug. 19, the lake level was 12.99 feet. By Aug. 20, the lake level was 13.06 feet. The rise in lake level made it possible for the South Florida Water Management District to safely resume use of the navigation locks on the north end of the lake, which had been closed much of the summer due to the low lake level.

No water from the lake flowed into the Caloosahatchee River last week. Flow at the Moore Haven lock was zero. Flow at the Franklin Lock to the Caloosahatchee estuaries averaged 7,139 cubic feet per second (cfs), all from local basin runoff. Flows above 2,800 cfs are considered damaging to the estuaries’ salinity levels.

On the east side of the lake, water backflowed into the lake from the St. Lucie Canal at an average of 384 cfs. No water has flowed from the lake into the St. Lucie since March. Water has been backflowing from the St. Lucie Canal into the lake this summer. The St. Lucie Canal is maintained at a level of 14 to 14.5 feet above sea level. When the lake level is lower than the St. Lucie Canal, if the Port Mayaca water control structures are open, the canal water backflows into the lake. This summer, the corps has protected the St. Lucie estuary from excess freshwater and nutrient load from the basin runoff by backflowing the nutrient laden water into Lake Okeechobee. (On average, phosphorus levels in the St. Lucie canal basin are about double the average levels in Lake Okeechobee.)

According to the FDEP report, statewide, for the period Aug. 9 – 15, there were 20 reported site visits, with all 20 site visits resulting in samples collected.
Algal bloom conditions were observed by the samplers at only nine of those sites statewide.

National Oceanic and Atmospheric Administration imagery for Lake Okeechobee continues to indicate the lake has “medium bloom potential,” with some concentrations of algae in the water column of approximately 20% of the northeastern portion of the lake.

NOAA imagery of St. Lucie and Caloosahatchee estuaries has been obscured by cloud cover, but there have not been any reports of blooms.

South Florida Water Management District collected samples at the Franklin Lock on the Caloosahatchee River and the Port Mayaca Lock structures on Aug. 12. No algae was visible at the Franklin Lock structure, but patches of algae were visible in the water column at Port Mayaca at the time of sampling. No toxins were detected at the Franklin Lock structure and only trace levels of microcystins (0.39 parts per billion) were detected at the Port Mayaca structure.

On Aug. 15, FDEP visited two locations on Lake Okeechobee (Lake O North, and Lake O West, sample results pending) and did not observe any algal blooms; however, the conditions were rough, and the water was well mixed. The South Florida Water Management District will be perform sampling on Lake Okeechobee next week in areas with the highest bloom potential.

The Environmental Protection Agency considers toxin levels under 1 part per billion (ppb) to be safe for drinking water and levels of 8 ppb safe for recreational contact.

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