SANIBEL-CAPTIVA CONSERVATION FOUNDATION

Spring is a time of change, as birds begin their migrations and estuarine species start their spawn. Important changes also happen in the Caloosahatchee River and Estuary as waters begin to warm and the wet season looms on the horizon.

In Southwest Florida, seasonal water quality is strongly tied to the health and management of Lake Okeechobee, which was artificially connected to the Caloosahatchee River and Estuary in the 1800s.

When the lake gets too high, the Caloosahatchee — and the St. Lucie Estuary to the east — often receives large releases of water from the lake, which can harm the ecosystem.

This year, much of February and March included high-volume, damaging water releases from the lake to the Caloosahatchee, and the U.S. Army Corps of Engineers recently announced that a reduced flow volume of 2,000 cubic feet per second (weekly average) will be sent west through the end of the dry season, barring significant changes in conditions.

WHY THE COASTS RECEIVE LAKE WATER

SANIBEL-CAPTIVA CONSERVATION FOUNDATION

“Lake Okeechobee is a highly managed system. Its height is controlled by the U.S. Army Corps of Engineers using the Herbert Hoover Dike and a system of locks, canals, and dams,” Sanibel-Captiva Conservation Foundation Environmental Policy Director Matt DePaolis said. “The lake serves as a storage reservoir for the agriculture interests south of the lake, guaranteeing the industrial sugar production has as much water as it wants. To ensure there’s enough water in even the driest years, it’s necessary to keep the water in the lake much higher than it ever was naturally.”

But an overly full lake during rainy season quickly turns into a flood risk for surrounding communities. Additionally, high lake levels prevent light from reaching the submerged aquatic vegetation in the lake, hindering their growth and preventing essential filtration to the ecosystem.

So when the lake is deemed too high, the Corps releases water out of the lake, primarily to the east and west coasts via the St. Lucie and Caloosahatchee estuaries.

This lake water is polluted with nitrogen and phosphorous and can contribute to harmful algal blooms in the estuaries — sometimes directly, DePaolis said. At certain volumes, the influx of freshwater into brackish — partly salty — water can also lower salinity levels in the estuaries, which can negatively impact oysters, tapegrass and other organisms.

“Deciding when, where and how much Lake Okeechobee water to release is a nuanced decision-making process involving input from diverse stakeholders,” Policy Associate Allie Pecenka said. “SCCF and other members of the Southwest Florida community offer analysis and feedback during the Corps’ stakeholder-engagement process, including science-based recommendations for conditions under which the Caloosahatchee estuary would remain healthiest.”

IAN BEGAN TREND OF OVERLY FULL LAKE

Following Hurricanes Ian and Nicole in the fall of 2022, Lake Okeechobee was filled nearly to capacity, and levels remained high for much of 2023. When a strong El Nino event was forecast for 2023-24 — which often means a wetter-than-normal dry season — the SCCF began advocating for the Corps to continue lowering the lake in anticipation of it rising further.

“From June through October, frequent rains and watershed runoff can compound Lake Okeechobee releases, introducing an abundance of excess nutrients into the Caloosahatchee and Gulf of Mexico and harming our wildlife, our communities, and our economies,” Pecenka said. “This is why SCCF begins asking the Corps to send releases during the dry season, when our estuary is less vulnerable to impacts from receiving flows.”

As predicted, high levels of precipitation during the dry season this year further increased the height of Lake Okeechobee — and the Corps’ requirement to lower it.

2024 RELEASES AND CURRENT STATUS

In mid-February, the Corps decided to start lowering the lake before the wet season by releasing water to both coasts. The Caloosahatchee has received flows of varying measures from the lake since Feb. 17, with a few brief pauses aimed to allow salinities in the estuaries to recover and reduce the stress on oyster populations prior to spawning.

“Local oyster communities are particularly vulnerable during spawning season in the spring, and the impacts to a disrupted spawning season can span generationally for this highly important species,” Pecenka said.

SCCF’s policy department, informed by data from its Marine Laboratory, continually engages with the Corps and other stakeholders to express concerns for the health of local ecosystems in the event the Caloosahatchee receives large, long-duration releases.

On April 6, the Corps resumed minimal releases to the Caloosahatchee — an average of 650 cubic feet per second — to reduce stagnant conditions conducive to blue-green algal blooms. Beginning on April 13, the releases increased to a weekly average of 2,000 cubic feet per second through the rest of the dry season.

While the SCCF is supportive of the current release schedule, we remain concerned with the high lake stage and the potential for high-volume releases this summer and fall. We ask the Corps to remain reactive to changing conditions and adjust flows as needed to support the ecological health of the system.