OKEECHOBEE — How low will Lake Okeechobee go this year?
On Saturday, May 2, the U.S. Army Corps of Engineers Jacksonville District increased flows from the W.P. Franklin Lock and Dam (S-79) to the Caloosahatchee estuary at a seven-day average rate of 650 cubic feet per second (cfs) for the benefit of the estuary.
Lake Okeechobee is a vast but very shallow lake. On Monday, May 11, the official lake level (measured by the U.S. Army Corps of Engineers) was 11.17 feet above sea level. The level above sea level is not the depth of the lake. The bottom of the freshwater lake is above sea level.
Fishermen know when the lake level falls below 12 feet, they have to be careful. When the lake is this low, those who aren’t familiar with the Big O could damage their boats. The fishing is good, according to reports from those who have ventured out, but this is the time of year to go with someone who really knows the lake.
At the Clif Betts Jr. Memorial Lakeside Recreation Area (previously named Jaycee Park and commonly known as Lock 7), the area under the pier has dried out to the extent that not only has grass grown past the third set of pylons under the pier, but the area under the pier is also so dry that the county maintenance department was able mow the grass.
The low lake level means three locks on the northern end of the lake are closed to boat traffic due to safety concerns. Injury and lock damage could occur when boats pass through these structures when lake levels are outside of designated safety limits.
Currently, the S-193 boat lock at Taylor Creek in Okeechobee County is open on Saturdays and Sundays between 5:30 a.m. and 10:30 p.m. The S-193 lock will close entirely if Lake Okeechobee goes below 11 feet. Locks will resume normal operations when the lake is at least 12.5 feet.
Scientists have agreed the most beneficial levels for the lake’s ecology are the range of 12 feet to 15 feet. Nature designed the lake to rise slowly in the wet season and fall slowly in the dry season. The Central and South Florida Flood Control Project changed the whole system. Now, when there is heavy rainfall in the area north of the lake, instead of slowly sheetflowing into the lake over many months, it flows rapidly into the Big O. When the water rises faster than the submerged aquatic vegetation (SAV) can grow, it can damage or even kill the SAV.
That happened after Hurricane Irma. The hurricane churned up the lake, ripping out vegetation and leaving the water muddy. The flood waters draining from the north (Orlando south) made the situation worse.
To help the SAV recover, the U.S. Army Corps of Engineers decided to release more water during the 2018-2019 dry season. They sent extra water to the Caloosahatchee River throughout the dry season and released water to the St. Lucie River for six weeks in February and March 2019. This extra water sent to tide (in addition to the 457 cubic feet per second the South Florida Water Management District already allocates to the Caloosahatchee during the dry season) added up to about 1 foot of water on Lake Okeechobee. When the lake fell below 11 feet in June 2019, water managers were not concerned. They expected the 2019 wet season to bring the lake level back up to 15 feet. That didn’t happen.
The lake started the 2019-2020 dry season at 13.38 feet. While those who depend on the lake for water supply were concerned, some coastal residents wanted it even lower. When the corps announced plans to manage the already low lake to maximize water supply, the City of Stuart threatened to sue. They wanted the corps to release more water to push the lake lower. Congressman Brian Mast has pushed for the corps to lower the lake to 10.5 feet by the start of June every year in order to provide more capacity for runoff from summer rains, and to lessen the need for wet season discharges to the St. Lucie Canal.
For the seven-day period ending May 12, the corps released an average of 530 cubic feet per second (cfs) of water from Lake Okeechobee to the Caloosahatchee River at Moore Haven. No lake water has been released to the St. Lucie River since March 2019. On May 12, water from the St. Lucie Canal was backflowing in to the lake at a rate of 19 cfs. When the level in the lake is lower than the level in the St. Lucie (C-44) Canal, runoff from that basin backflows into the lake. If the canal level falls too low, the corps sometimes sends lake water into the C-44 Canal to keep the canal higher for navigation. However, the St. Lucie Lock is closed at these times.
Over the weekend, the corps advised that if the area received the predicted rainstorm, some water from the C-44 basin might be released through the St. Lucie Lock. This corps advisory led to confusion by coastal media and it was inaccurately reported that lake water might be released. The corps press release was clear that no water from Lake Okeechobee would be sent to the St. Lucie River. Had the anticipated storm dropped heavy rainfall, water from local basin runoff — not from Lake Okeechobee — would have been released through the St. Lucie Lock. The expected rainfall did not happen. There was zero flow through the St. Lucie Lock for the past seven days.
Algae blooms sampled
The National Oceanic and Atmospheric Administration (NOAA) satellite image from May 11 shows low potential for algae blooms in Lake Okeechobee.
Some algae has been observed in the lake in recent weeks. Both the South Florida Water Management District (SFWMD) and the St. Johns River Water Management District (SJRWMD) began their enhanced algal bloom monitoring in May, with additional routine monitoring stations being visited and sampled for algal identification, cyanotoxins, chlorophyll a and nutrients twice a month in addition to algal bloom response sampling.
On May 5, a sample taken on the northeast shore near the Okeechobee County line indicated the presence of Microcystis aeruginosa with a microcystins level of 2.5 micrograms per liter. Also on May 5, a sample taken near the point in the lake where the Okeechobee, Glades, Hendry, Palm Beach and Martin County lines meet, found mixed algae with no dominant species. No toxins were detected.
On May 6, a surface grab in Pelican Bay had Microcystis aeruginosa as the dominant species and a microcystins level of 2.6 micrograms per liter. Also on May 6, a sample of algae suspended in the water column about 8 miles offshore contained Microcystis aeruginosa as the dominant species and a microcystins level of 6.8 micrograms per liter. That same day, a sample of algae suspended in the water about 10 miles north of Clewiston had Microcystis aeruginosa as the dominant species and a microcystins level of 0.53 micrograms per liter. That same day, a test on blue-green algae suspended in the water column at the south end of the lake had Microcystis aeruginosa as the dominant species and a microcystins level of 1.5 micrograms per liter.
On May 5, Lee County staff collected a sample on the Caloosahatchee River at the Franklin Lock. The sample was dominated by Microcystis aeruginosa and had trace levels at 0.36 migrams per liter total microcystins detected.
The World Health Organization considers levels up to 8 micrograms per liter safe for human recreational contact.