Corps adjusts lake flow to support algae research

JACKSONVILLE — The U.S. Army Corps of Engineers Jacksonville District has announced a change in the Lake Okeechobee release schedule for eight days in order to provide flow needed for scientific research into harmful algal blooms (HABs).

On July 13, the corps officially cut the flow to the Caloosahatchee from Lake Okeechobee to 0 cubic feet per second. Prior to that change, the schedule called for a flow of 450 cfs, measured at the Franklin Lock, to ensure sufficient flow into the river to prevent saltwater intrusion. However, since the start of the rainy season, very little water has flowed from the lake to the Caloosahatchee River through the lock at Moore Haven because there was more than enough local basin runoff to provide more than 450 cfs at the Franklin Lock.

The Franklin Lock is 43.4 miles from the Moore Haven lock, so the water flowing through the Franklin Lock is a mixture of lake water and basin runoff that flows directly into the river. For the seven-day period ending July 15, with no flow coming from Lake Okeechobee, the flow at the Franklin Lock averaged 2,516 cfs.

Starting Wednesday, July 17, the corps will increase target flows from Lake Okeechobee to 200 cubic feet per second (cfs) at Moore Haven Lock and Dam (S-77) for eight hours daily over a period of 10 days. The adjustment will provide the flow required to support USACE’s Engineer Research and Development Center (ERDC) HABITATS pilot-scale demonstration project upstream of the structure at Moore Haven.

“The Corps’ Engineer Research and Development Center is doing the important scientific research that’s required to help us understand the dynamics of algal communities,” said Col. Andrew Kelly, Jacksonville District commander. “We hope the research that the corps is working on right now, in partnership with other scientists and experts, will provide the answers we need to help us find solutions to deal with HABs nationwide, and even worldwide.”

The research at Moore Haven will assess the performance and scalability of a new system for removing and disposing of blue-green algae from large water bodies to reduce the potential environmental and economic impacts of HABs on ecosystems and communities.

The U.S. Army Corps of Engineers Engineer Research and Development Center (ERDC) received $2.3 million to undertake multiple activities this year, aimed at detecting, treating, and removing harmful algal blooms. Activities currently underway include basic scientific research on algae community dynamics and genomics, testing of algae treatments and demonstration of algal removal systems.

With the exception of the period from Feb. 23 to March 22, flow from Lake Okeechobee to the Caloosahatchee River was at levels that benefit the river. Without freshwater flow from the lake during the dry season, the river suffers from saltwater intrusion. Lee County officials have asked for flows up to 1,000 cfs, measured at the Franklin Lock to maintain optimal salinity levels in the Caloosahatchee estuaries.

From Feb. 23 to March 22, flow to the Caloosahatchee was 1,800 cfs, measured at the Franklin Lock, as the corps responded to a request from Florida Gov. Ron DeSantis to lower the lake level during the dry season in order to have more capacity available in the lake at the start of the wet season.

Likewise, to the east, there was no flow to the St. Lucie Canal from the start of the wet season until Feb. 23. From Feb. 23 to March 15, flow from the lake to the St. Lucie was 500 cfs, measured at the St. Lucie Lock, which is 23.9 miles from Port Mayaca. Flow from March 15 to March 30, also measured at the St. Lucie Lock averaged 250 cfs. Some flow measured at the St. Lucie Lock is from local basin runoff that drains into the St. Lucie Canal.

Since March 30, there has been no flow from the lake to the St. Lucie Canal. Until the middle of June, the gates at Port Mayaca were open, allowing some water from the St. Lucie basin to backflow into Lake Okeechobee if there were sufficient rains to create basin runoff. The flow at that structure is gravity fed, and when the lake level is low, water can backflow into the lake. The same thing happens at the water control structure near Clewiston due to the natural land elevation at Clewiston. The backflow at both structures is minimal, especially compared to the capacity of the big lake.

No water from Lake Okeechobee has flowed into the St. Lucie Canal since March 30. For the seven-day period ending July 15, the average flow through the St. Lucie Lock was 214 cfs, all from local basin runoff.
Tuesday’s lake level was 11.47 feet above sea level.

Algal blooms tested
Over the past week, Florida Department of Environmental Regulation tested algal blooms on Lake Okeechobee.
• On July 10, FDEP tested an undefined algal bloom in Lake Okeechobee in Palm Beach County, about 10 miles northwest of Belle Glade. Dominant taxon was Microcystis aeruginosa. Toxin level was 2.1 micrograms per liter. That same day, a test of a streaky surface bloom about two miles southwest of the first area tested had toxin levels of 19 micrograms per liter.
• On July 10, a windblown algal bloom which was dominate for Microcystis aeruginosa was sampled inside the wing structures of the Port Mayaca Lock. Toxin levels were barely detectable at 0.44 micrograms per liter. On July 15, FDEP checked the same area and found no algae.

For more information on water level and flows data for Lake Okeechobee, visit the corps’ water management website at saj.usace.army.mil/Missions/CivilWorks/WaterManagement.aspx.

Publisher/Editor Katrina Elsken can be reached at kelsken@newszap.com

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