Army Corps starts Lake Okeechobee discharges to St. Lucie, Caloosahatchee rivers

Lake Okeechobee discharges to the St. Lucie and Caloosahatchee rivers started about 3:30 p.m. Wednesday, federal officials announced about an hour before.

The St. Lucie River will get about 1.16 billion gallons a day and the Caloosahatchee River will get about 2.59 billion gallons a day, said Col. Andrew Kelly, the Army Corps of Engineers commander for Florida.

The discharges could last "close to a month," Kelly said, but wouldn't be more specific. 

"It all depends on the weather, how much rain we get and how much water flows into the lake," Kelly said. "The goal is to stabilize the rate of the rise in the lake, and if we can, turn it. ... If in a month the lake level has peaked and it's starting to come down, I would be very comfortable (stopping the discharges)."

The South Florida rainy season and the hurricane season are still underway, Kelly noted, but added he was committed to "reduce or stop the flows as soon as we can."

Lake Okeechobee level

The discharges are intended to prevent breaches in the Herbert Hoover Dike around the quickly rising lake, and prevent the catastrophic flooding that could result.

On the east coast, the water will be a mixture of Lake O water and stormwater runoff, mostly from farmland in western Martin County, discharged into the C-44 Canal and through the St. Lucie Lock and Dam.

The lake has risen about 1 foot, 4 inches in the last 30 days, and has been rising an average half-inch a day over the last week, to an elevation Wednesday of 16 feet, 2½ inches above sea level.

Ed Killer column:Four reasons why Lake O discharges are unnecessary

The Corps wants to try to limit the lake rise no more than 16 feet, 6 inches, said John Maehl, Martin County director of environmental restoration, who was on a phone-in meeting with Corps officials before Kelly made the discharge announcement.

"They know they can't lower the lake with discharges," Maehl said. "But they can slow the ascent."

Hurricane season

In fact, the combined discharges to the St. Lucie and Caloosahatchee rivers would drop the lake about a ¼-inch a day, about half the daily rise.

Florida's weather is "transitioning into the dry season," said Kevin Rodriguez, a meteorologist at the National Weather Service in Melbourne. "We're not there yet, but we're getting close."

Forecasts through the end of October, when the dry season should kick in, call for continued chances of rain, Rodriguez said, "but lighter, more transient rain than the daylong deluges we've seen recently."

The tropics are "quiet," Rodriguez said, with no significant weather systems heading toward Florida.

Hurricane season runs through the end of November, Rodriguez said, "and I'm pretty sure one or two more systems will develop by then. What they might do, if they might head our way, we really don't know."

River salinity

A month of discharges would put 34.8 billion gallons of nutrient-polluted freshwater in the St. Lucie River estuary, which is normally a brackish mix off fresh and salty water.

Runoff from recent heavy rains already has dropped salinity in the estuary to nearly nothing. Salinity in the river's South Fork near the Palm City Bridge was 0.59 parts per thousand late Wednesday morning. A healthy estuary has salinity levels between 15 and 25 parts per thousand.

Lack of salinity can kill oysters and seagrass, important parts of the estuarine ecology.

More: Seagrass starting to revive along Indian River Lagoon

"The salinity levels in the St. Lucie estuary look like a flat line on a hospital patient's monitor," said Mark Perry, executive director of the Florida Oceanographic Society in Stuart. "We're already so saturated with freshwater that adding more from Lake Okeechobee would blow us away."

The nonprofit's most recent weekly water quality report gave the St. Lucie River estuary an overall "D" grade, with the river's South Fork and the main branch along the Stuart waterfront getting "F" grades, primarily for poor visibility and nearly nonexistent salinity.

More: Check out Florida Oceanographic's weekly water quality reports

Algal blooms

On the plus side, the lake has relatively little cyanobacteria, commonly called "blue-green algae." During some previous discharge events — particularly in 2013, 2016 and 2018 — water sent to the estuaries was laden with algae.

The massive blooms that resulted were too toxic to touch and made the air surrounding them hazardous to breathe.

The current algae conditions on Lake O are "pretty decent," Kelly said. "This has not been a bad algae year on the lake. "

A satellite image taken Tuesday showed low to moderate levels of blue-green algae mostly in the central part of Lake O, although one bloom stretched east to within a few miles of the Port Mayaca Lock and Dam, where lake water is released toward the St. Lucie River.

More: Lake O discharges, not septic tanks, cause massive algae blooms

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.