Lake Okeechobee level drops, but will rise again in wake of Tropical Storm Eta

How could Lake Okeechobee's elevation drop over the weekend despite Tropical Storm Eta's pass across Florida?

Just wait, said Paul Gray, Florida Audubon Society's Lake O expert.

Lake O's elevation above sea level fell about half an inch over the weekend to 16 feet, 1¼ inches Monday morning.

Rain that fell in the watershed north of Lake O — up to 3 to 4 inches in some places — will be running into the lake for the next few days, Gray said Monday.

"Look for the lake to go back up," he said, and look for discharges to the St. Lucie and Caloosahatchee rivers to continue "for the next two weeks, maybe longer."

The threat of heavy rain from Eta was the reason the Army Corps of Engineers announced Friday discharges from the lake would continue.

More: Eta expected to become hurricane in warm Gulf water

The threat isn't over, as Eta is forecast to spin around in the Gulf of Mexico and head back to Florida. But there's still a lot of uncertainty about what the storm will do, said Jessie Smith, a meteorologist at the National Weather Service in Melbourne.

"The predicted landfall late this week could be anywhere from Sarasota to Pensacola," Smith said.

Eta is expected to bring an inch to an inch and a half of rain immediately north of the lake over the next seven days, Smith said. If its projected path veers to the south and closer to Lake O, it could mean even more water in Lake O.

"Let's not even talk about that," Gray said. "It's just generally bad news."

Damage done

Since Lake O discharges began Oct. 14, about 20.6 billion gallons of water has poured through the St. Lucie Lock and Dam into the St. Lucie River. About 14.4 billion gallons of that has been from Lake O.

The discharged water hasn't contained cyanobacteria, commonly called blue-green algae, and no blooms have been reported in the St. Lucie estuary at Stuart.

That wasn't the case in 2013, 2016 and 2018, when massive discharges caused widespread toxic algae blooms.

More: Scientists concerned about chemicals used to kill algae

Even algae-free water from the lake has exacerbated poor conditions in the estuary and caused environmental damage because it lowers salinity needed by key marine plants, such as seagrass, and animals, such as oysters.

Oysters, which thrive on a mix of fresh and salty water, were barely hanging on in late summer as heavy rains filled the estuary with freshwater. The discharges wiped out what little salinity was left, said Mark Perry, executive director of the Florida Oceanographic Society in Stuart.

"Right now, oysters are out there dying," Perry said. "They can only take about 28 days of water with little or no salinity."

Tuesday marks 28 days since the lake discharges started.

"Actually, the water was almost entirely fresh, no salinity, before the discharges started," Perry said, referring to stormwater runoff that flooded areas of south Martin County in early October, "so we're well past that 28-day threshold now."

More:Study says oysters can't handle Lake Okeechobee discharges

Tyler Treadway is an environment reporter who specializes in issues facing the Indian River Lagoon. Support his work on TCPalm.com.  Contact him at 772-221-4219 and tyler.treadway@tcpalm.com.