WEST PALM BEACH — Water conditions in Lake Okeechobee showed improvement in March, according to a report given by Dr. Susan Gray, chief environmental scientist, at the South Florida Water Management District (SFWMD) Governing Board meeting on April 11.
The lake is dropping a little faster than they would like to see, she said.
During the dry season, “we like to see about half a foot a month recession,” she said. “Last month it dropped about three quarters of foot, a little fast for the lake.”
She said due to the low lake levels, they are not seeing wading bird nesting
“We saw an upsurge in wading bird forging in March when water was above 12 ft.,” she explained. But the birds are not nesting around the lake. If they don’t have sufficient water for protection of the nests from predators, the birds will not nest there she said.
She said birds may be feeding in Lake Okeechobee and nesting in other areas. “The question is how far is the flight, and do they use up too much energy going back and forth,” she explained.
She said when they look at bird populations, they consider the entire Everglades, including the Kissimmee River, Lake Okeechobee and the southern Everglades.
“We have performance goals for the greater Everglades that looks at how many nests and fledglings,” she explained.
“There was an incredible nesting success last year, the best we have seen in decades,” she said.
Dr. Gray said they are seeing regrowth of submerged aquatic vegetation (SAV) in Lake Okeechobee. The lower lake levels allow increased light penetration to the lake bottom, which encourages growth.
If it falls too low, the areas will dry out, and that SAV will be lost, she added.
The SAV provides habitat for fish and wildlife and is also important because it provides the lake’s natural filter system.
“This is important in terms for a healthy lake,” she said.
She said they are seeing growth of eel grass which is a good sign.
The potential for algae blooms on the lake is low based on the NOAA (National Oceanographic and Atmospheric Administration) images, she said. “These conditions wax and wane.”
She said SFWMD staff are on the lake at least twice a month testing water in 20-25 sampling areas.
She said once a year, SFWMD conducts an extensive lakewide map for SAV.
The lake needs highs and lows, she said. Dr. Gray said she supports the 12-to-15 ft. or 12.5-to-15.5 ft. schedule.
“I like to see it go down to 12 ft. as often as possible or slightly below that,” she explained. “I am a little cautious if it keeps dropping too much.
“When you start going way too low, you dry out those grasses, you expose the bottom and it oxidizes,” she said.
The lower lake levels have allowed FWC in cooperation with SFWMD and the U.S. Army Corps of Engineers to conducted some prescribed burns around the lake to burn off the dead vegetation.
Dr. Gray said salinity levels are currently good in both the St. Lucie and Caloosahatchee Estuaries.
In March, about 28 percent of the freshwater flow to the St. Lucie Estuary came from the Lake Okeechobee releases. Lake releases stopped March 12.
When the lake is 12 ft. or lower, it is not possible to release water from the lake to the St. Lucie because it is gravity flow
The Caloosahatchee Estuary needs freshwater flow from the lake during the dry season to prevent salinity levels from going too high. Dr. Gray explained that different parts of the estuary need different levels and that different plants and animals prefer different levels of salinity.
“The estuary has to have a range of salinities to be healthy,” she said. “Not all constituents of the estuary need the same salinity in the same spot.”
Salinity levels should also vary based on the time of year, she continued.
“Estuaries are not static systems. They are dynamic,” said Dr. Gray.
Spring is a critical time for estuaries, she continued.
“I think both March and April were fine,” she said, and still within the good conditions for the plants and animals that live within this region.”
Total Lake Okeechobee releases to Stormwater Treatment Areas (STAs) south of the Everglades Agricultural Area in water year 2019 (water released since May 1, 2018) totals 450,000 acre feet of water since May 1, 2018.
This is the second highest annual volume of lake releases treated to date
To put that in perspective, 450,000 acres equals 126 billion gallons of water or the equivalent of about 10.5 inches on Lake Okeechobee.
Right now, the only place to store excess water is in Lake Okeechobee, said SFWMD Executive Director Drew Bartlett. “We don’t have anywhere else to put it.”
Drew Bartlett said right now the place excess water is stored is in Lake Okechobee. “We’re going to be living with this imperfect system until we get a lot more storage in the system,” he said.